WorldWideScience

Sample records for collaborative spectrum sensing

  1. Coalition Formation Games for Collaborative Spectrum Sensing

    CERN Document Server

    Saad, Walid; Basar, Tamer; Debbah, Merouane; Hjørungnes, Are

    2010-01-01

    Collaborative Spectrum Sensing (CSS) between secondary users (SUs) in cognitive networks exhibits an inherent tradeoff between minimizing the probability of missing the detection of the primary user (PU) and maintaining a reasonable false alarm probability (e.g., for maintaining a good spectrum utilization). In this paper, we study the impact of this tradeoff on the network structure and the cooperative incentives of the SUs that seek to cooperate for improving their detection performance. We model the CSS problem as a non-transferable coalitional game, and we propose distributed algorithms for coalition formation. First, we construct a distributed coalition formation (CF) algorithm that allows the SUs to self-organize into disjoint coalitions while accounting for the CSS tradeoff. Then, the CF algorithm is complemented with a coalitional voting game for enabling distributed coalition formation with detection probability guarantees (CF-PD) when required by the PU. The CF-PD algorithm allows the SUs to form mi...

  2. Mitigating Entropy Selfishness in Distributed Collaborative Spectrum Sensing

    CERN Document Server

    Li, Shuai; Gao, Zhaoyu; Guan, Xinping

    2011-01-01

    Collaborative spectrum sensing has been recognized as a promising approach to improve the sensing performance via exploiting the spatial diversity of the CR users. Such kind of cooperation, however, might be easily disrupted by the selfish users, especially for the distributed collaborative sensing. In this study, we identify a new kind of selfish behavior in collaborative sensing. Specifically, the selfish user could pretend to be an honest one by claiming a duplicated or slightly modified sensing report from others as a new one. This selfish behavior may significantly reduce the spatial diversity of the sensing reports and thus degrade the performance of collaborative spectrum sensing. We denote such a selfishness issue as Entropy Selfishness. Since it represents a challenge to decide whether a sensing report is a fresh one, entropy selfishness makes the existing incentive schemes designed for conventional wireless networks (e.g., mobile ad hoc networks) unsuitable for Cognitive Radio Networks (CRNs). To th...

  3. Attack Prevention for Collaborative Spectrum Sensing in Cognitive Radio Networks

    CERN Document Server

    Duan, Lingjie; Huang, Jianwei; Shin, Kang G

    2011-01-01

    Collaborative spectrum sensing can significantly improve the detection performance of secondary unlicensed users (SUs). However, the performance of collaborative sensing is vulnerable to sensing data falsification attacks, where malicious SUs (attackers) submit manipulated sensing reports to mislead the fusion center's decision on spectrum occupancy. Moreover, attackers may not follow the fusion center's decision regarding their spectrum access. This paper considers a challenging attack scenario where multiple rational attackers overhear all honest SUs' sensing reports and cooperatively maximize attackers' aggregate spectrum utilization. We show that, without attack-prevention mechanisms, honest SUs are unable to transmit over the licensed spectrum, and they may further be penalized by the primary user for collisions due to attackers' aggressive transmissions. To prevent such attacks, we propose two novel attack-prevention mechanisms with direct and indirect punishments. The key idea is to identify collisions...

  4. Generalized mean detector for collaborative spectrum sensing

    KAUST Repository

    Shakir, Muhammad Zeeshan

    2013-04-01

    In this paper, a unified generalized eigenvalue based spectrum sensing framework referred to as Generalized mean detector (GMD) has been introduced. The generalization of the detectors namely (i) the eigenvalue ratio detector (ERD) involving the ratio of the largest and the smallest eigenvalues; (ii) the Geometric mean detector (GEMD) involving the ratio of the largest eigenvalue and the geometric mean of the eigenvalues and (iii) the Arithmetic mean detector (ARMD) involving the ratio of the largest and the arithmetic mean of the eigenvalues is explored. The foundation of the proposed unified framework is based on the calculation of exact analytical moments of the random variables of test statistics of the respective detectors. In this context, we approximate the probability density function (PDF) of the test statistics of the respective detectors by Gaussian/Gamma PDF using the moment matching method. Finally, we derive closed-form expressions to calculate the decision threshold of the eigenvalue based detectors by exchanging the derived exact moments of the random variables of test statistics with the moments of the Gaussian/Gamma distribution function. The performance of the eigenvalue based detectors is compared with the traditional detectors such as energy detector (ED) and cyclostationary detector (CSD) and validate the importance of the eigenvalue based detectors particularly over realistic wireless cognitive environments. Analytical and simulation results show that the GEMD and the ARMD yields considerable performance advantage in realistic spectrum sensing scenarios. Moreover, our results based on proposed simple and tractable approximation approaches are in perfect agreement with the empirical results. © 1972-2012 IEEE.

  5. Throughput optimization for dual collaborative spectrum sensing with dynamic scheduling

    Science.gov (United States)

    Cui, Cuimei; Yang, Dezhi

    2017-07-01

    Cognitive radio technology is envisaged to alleviate both spectrum inefficiency and spectrum scarcity problems by exploiting the existing licensed spectrum opportunistically. However, cognitive radio ad hoc networks (CRAHNs) impose unique challenges due to the high dynamic scheduling in the available spectrum, diverse quality of service (QOS) requirements, as well as hidden terminals and shadow fading issues in a harsh radio environment. To solve these problems, this paper proposes a dynamic and variable time-division multiple-access scheduling mechanism (DV-TDMA) incorporated with dual collaborative spectrum sensing scheme for CRAHNs. This study involves the cross-layered cooperation between the Physical (PHY) layer and Medium Access Control (MAC) layer under the consideration of average sensing time, sensing accuracy and the average throughput of cognitive radio users (CRs). Moreover, multiple-objective optimization algorithm is proposed to maximize the average throughput of CRs while still meeting QOS requirements on sensing time and detection error. Finally, performance evaluation is conducted through simulations, and the simulation results reveal that this optimization algorithm can significantly improve throughput and sensing accuracy and reduce average sensing time.

  6. A SPARSITY AND COMPRESSION RATIO JOINT ADJUSTMENT METHOD FOR COLLABORATIVE SPECTRUM SENSING

    Institute of Scientific and Technical Information of China (English)

    Chi Jingxiu; Zhang Jianwu; Xu Xiaorong

    2012-01-01

    Spectrum sensing is the fundamental task for Cognitive Radio (CR).To overcome the challenge of high sampling rate in traditional spectral estimation methods,Compressed Sensing (CS) theory is developed.A sparsity and compression ratio joint adjustment algorithm for compressed spectrum sensing in CR network is investigated,with the hypothesis that the sparsity level is unknown as priori knowledge at CR terminals.As perfect spectrum reconstruction is not necessarily required during spectrum detection process,the proposed algorithm only performs a rough estimate of sparsity level.Meanwhile,in order to further reduce the sensing measurement,different compression ratios for CR terminals with varying Signal-to-Noise Ratio (SNR) are considered.The proposed algorithm,which optimizes the compression ratio as well as the estimated sparsity level,can greatly reduce the sensing measurement without degrading the detection performance.It also requires less steps of iteration for convergence.Corroborating simulation results are presented to testify the effectiveness of the proposed algorithm for collaborative spectrum sensing.

  7. Energy-Based Collaborative Spectrum Sensing for Cognitive UWB Impulse Radio

    Institute of Scientific and Technical Information of China (English)

    Wei-Chiang Wu; Chun-Te Wu

    2015-01-01

    This paper focuses on the issue of collaborative spectrum sensing in cognitive ultra wideband (CUWB) impulse radio. We employ energy-based signal detection method and apply the Neyman-Pearson (NP) decision rule to determine the optimum threshold. Two cooperative spectrum sensing schemes are developed in this paper. The decision fusion scheme is based on hard decision, in which each cooperating cognitive user (CU) sends its own local decision to the fusion center (FC). The FC then makes a final decision according to the majority voting rule. Alternatively, the data fusion scheme is based on soft decision, in which each local CU sends its observed value directly to the FC. The FC combines these values, compares to a threshold and then makes the final decision. The performances of both schemes are studied by using analytical tools and computer simulations. The receiver operating characteristics (ROC), which reveal the probability of detection versus false-alarm curve, are employed to evaluate the system performance under different scenarios.Simulation results demonstrate that the data fusion scheme outperforms the decision fusion scheme and verify that the collaborative spectrum sensing has practical importance in CUWB networks.

  8. Collaborative spectrum sensing based on the ratio between largest eigenvalue and Geometric mean of eigenvalues

    KAUST Repository

    Shakir, Muhammad

    2011-12-01

    In this paper, we introduce a new detector referred to as Geometric mean detector (GEMD) which is based on the ratio of the largest eigenvalue to the Geometric mean of the eigenvalues for collaborative spectrum sensing. The decision threshold has been derived by employing Gaussian approximation approach. In this approach, the two random variables, i.e. The largest eigenvalue and the Geometric mean of the eigenvalues are considered as independent Gaussian random variables such that their cumulative distribution functions (CDFs) are approximated by a univariate Gaussian distribution function for any number of cooperating secondary users and received samples. The approximation approach is based on the calculation of exact analytical moments of the largest eigenvalue and the Geometric mean of the eigenvalues of the received covariance matrix. The decision threshold has been calculated by exploiting the CDF of the ratio of two Gaussian distributed random variables. In this context, we exchange the analytical moments of the two random variables with the moments of the Gaussian distribution function. The performance of the detector is compared with the performance of the energy detector and eigenvalue ratio detector. Analytical and simulation results show that our newly proposed detector yields considerable performance advantage in realistic spectrum sensing scenarios. Moreover, our results based on proposed approximation approach are in perfect agreement with the empirical results. © 2011 IEEE.

  9. Toward Collaboration Sensing

    Science.gov (United States)

    Schneider, Bertrand; Pea, Roy

    2014-01-01

    We describe preliminary applications of network analysis techniques to eye-tracking data collected during a collaborative learning activity. This paper makes three contributions: first, we visualize collaborative eye-tracking data as networks, where the nodes of the graph represent fixations and edges represent saccades. We found that those…

  10. Generalized eigenvalue based spectrum sensing

    KAUST Repository

    Shakir, Muhammad

    2012-01-01

    Spectrum sensing is one of the fundamental components in cognitive radio networks. In this chapter, a generalized spectrum sensing framework which is referred to as Generalized Mean Detector (GMD) has been introduced. In this context, we generalize the detectors based on the eigenvalues of the received signal covariance matrix and transform the eigenvalue based spectrum sensing detectors namely: (i) the Eigenvalue Ratio Detector (ERD) and two newly proposed detectors which are referred to as (ii) the GEometric Mean Detector (GEMD) and (iii) the ARithmetic Mean Detector (ARMD) into an unified framework of generalize spectrum sensing. The foundation of the proposed framework is based on the calculation of exact analytical moments of the random variables of the decision threshold of the respective detectors. The decision threshold has been calculated in a closed form which is based on the approximation of Cumulative Distribution Functions (CDFs) of the respective test statistics. In this context, we exchange the analytical moments of the two random variables of the respective test statistics with the moments of the Gaussian (or Gamma) distribution function. The performance of the eigenvalue based detectors is compared with the several traditional detectors including the energy detector (ED) to validate the importance of the eigenvalue based detectors and the performance of the GEMD and the ARMD particularly in realistic wireless cognitive radio network. Analytical and simulation results show that the newly proposed detectors yields considerable performance advantage in realistic spectrum sensing scenarios. Moreover, the presented results based on proposed approximation approaches are in perfect agreement with the empirical results. © 2012 Springer Science+Business Media Dordrecht.

  11. Cooperative Distributed Sequential Spectrum Sensing

    CERN Document Server

    S, Jithin K; Gopalarathnam, Raghav

    2010-01-01

    We consider cooperative spectrum sensing for cognitive radios. We develop an energy efficient detector with low detection delay using sequential hypothesis testing. Sequential Probability Ratio Test (SPRT) is used at both the local nodes and the fusion center. We also analyse the performance of this algorithm and compare with the simulations. Modelling uncertainties in the distribution parameters are considered. Slow fading with and without perfect channel state information at the cognitive radios is taken into account.

  12. Collaboration and Coordination in Secondary Networks for Opportunistic Spectrum Access

    CERN Document Server

    Jouini, Wassim; Bononi, Luciano; Moy, Christophe

    2012-01-01

    In this paper, we address the general case of a coordinated secondary network willing to exploit communication opportunities left vacant by a licensed primary network. Since secondary users (SU) usually have no prior knowledge on the environment, they need to learn the availability of each channel through sensing techniques, which however can be prone to detection errors. We argue that cooperation among secondary users can enable efficient learning and coordination mechanisms in order to maximize the spectrum exploitation by SUs, while minimizing the impact on the primary network. To this goal, we provide three novel contributions in this paper. First, we formulate the spectrum selection in secondary networks as an instance of the Multi-Armed Bandit (MAB) problem, and we extend the analysis to the collaboration learning case, in which each SU learns the spectrum occupation, and shares this information with other SUs. We show that collaboration among SUs can mitigate the impact of sensing errors on system perf...

  13. Dynamic Spectrum Detection Via Compressive Sensing

    Directory of Open Access Journals (Sweden)

    Michael Odeyomi

    2012-04-01

    Full Text Available Spectrum congestion is a major concern in both military and commercial wireless networks. To support growing demand for ubiquitous spectrum usage, Cognitive Radio is a new paradigm in wireless communication that can be used to exploit unused part of the spectrum by dynamically adjusting its operating parameters. While cognitive radio technology is a promising solution to the spectral congestion problem, efficient methods for detecting white spaces in wideband radio spectrum remain a challenge. Conventional methods of detection are forced to use the high sampling rate requirement of Nyquist criterion. In this paper, the feasibility and efficacy of using compressive sensing (CS algorithms inconjunction with Haar wavelet for identifying spectrum holes in the wideband spectrum is explored. Compressive sensing is an emerging theory that shows that it’s possible to achieve good reconstruction, at sampling rates lower than that specified by Nyquist. CS approach is robust in AWGN and fading channel.

  14. MTO: Sensing Across the Spectrum

    Science.gov (United States)

    2009-03-04

    ME MS LNA LNA MEMS B P F 1600 B P F 800 t e x t LO 820/1620 Log A mp 650-1000 Example ASP Architecture On the Horizon: Antennas Challenges • Chu...for Absolute Reference (COUGAR) Lal Fiber optic resonator gyroscope architecture for ultra-high precision rotation sensing Chip-Scale Atomic Clock...Covert sensing with bionic platforms • Underwater surveillance/SONAR Approved for Public Release, Distribution Unlimited Recent Accomplishments

  15. Sensing in the Collaborative Internet of Things

    Directory of Open Access Journals (Sweden)

    João B. Borges Neto

    2015-03-01

    Full Text Available We are entering a new era of computing technology, the era of Internet of Things (IoT. An important element for this popularization is the large use of off-the-shelf sensors. Most of those sensors will be deployed by different owners, generally common users, creating what we call the Collaborative IoT. This collaborative IoT helps to increase considerably the amount and availability of collected data for different purposes, creating new interesting opportunities, but also several challenges. For example, it is very challenging to search for and select a desired sensor or a group of sensors when there is no description about the provided sensed data or when it is imprecise. Given that, in this work we characterize the properties of the sensed data in the Internet of Things, mainly the sensed data contributed by several sources, including sensors from common users. We conclude that, in order to safely use data available in the IoT, we need a filtering process to increase the data reliability. In this direction, we propose a new simple and powerful approach that helps to select reliable sensors. We tested our method for different types of sensed data, and the results reveal the effectiveness in the correct selection of sensor data.

  16. Sensing in the collaborative Internet of Things.

    Science.gov (United States)

    Borges Neto, João B; Silva, Thiago H; Assunção, Renato Martins; Mini, Raquel A F; Loureiro, Antonio A F

    2015-03-19

    We are entering a new era of computing technology, the era of Internet of Things (IoT). An important element for this popularization is the large use of off-the-shelf sensors. Most of those sensors will be deployed by different owners, generally common users, creating what we call the Collaborative IoT. This collaborative IoT helps to increase considerably the amount and availability of collected data for different purposes, creating new interesting opportunities, but also several challenges. For example, it is very challenging to search for and select a desired sensor or a group of sensors when there is no description about the provided sensed data or when it is imprecise. Given that, in this work we characterize the properties of the sensed data in the Internet of Things, mainly the sensed data contributed by several sources, including sensors from common users. We conclude that, in order to safely use data available in the IoT, we need a filtering process to increase the data reliability. In this direction, we propose a new simple and powerful approach that helps to select reliable sensors. We tested our method for different types of sensed data, and the results reveal the effectiveness in the correct selection of sensor data.

  17. Spectrum handoff algorithm with imperfect spectrum sensing incognitive radio networks

    Science.gov (United States)

    Ma, Bin; Bao, Xiao-min; Xie, Xian-zhong

    2016-10-01

    To guarantee the quality of service of licensed users, the unlicensed users must vacate the occupied channel by spectrum handoff if licensed users appear in the licensed spectrum. However, spectrum sensing with false alarm and missed detection may lead to more inaccuracy problems when unlicensed users perform spectrum handoff. To improve the problems mentioned before, we utilize PRP M/G/1 queuing network model to propose a spectrum handoff algorithm with error data retransmission mechanism and analyze its performance by transmission delay and extended data delivery time. In addition, we discuss the relationship between false alarm probability, extended data delivery time and user traffic load and verify the effectiveness of the proposed algorithm.

  18. Evolutionary Game Theory-Based Collaborative Sensing Model in Emergency CRAHNs

    Directory of Open Access Journals (Sweden)

    Sasirekha GVK

    2012-01-01

    Full Text Available Game theory has been a tool of choice for modeling dynamic interactions between autonomous systems. Cognitive radio ad hoc networks (CRAHNs constituted of autonomous wireless nodes are a natural fit for game theory-based modeling. The game theory-based model is particularly suitable for “collaborative spectrum sensing” where each cognitive radio senses the spectrum and shares the results with other nodes such that the targeted sensing accuracy is achieved. Spectrum sensing in CRAHNs, especially when used in emergency scenarios such as disaster management and military applications, needs to be not only accurate and resource efficient, but also adaptive to the changing number of users as well as signal-to-noise ratios. In addition, spectrum sensing mechanism must also be proactive, fair, and tolerant to security attacks. Existing work in collaborative spectrum sensing has mostly been confined to resource efficiency in static systems using request-based reactive sensing resulting in high latencies. In this paper, evolutionary game theory (EGT is used to model the behavior of the emergency CRAHNS, providing an efficient model for collaborative spectrum sensing. The resulting implementation model is adaptive to the changes in its environment such as signal-to-noise ratio and number of users in the network. The analytical and simulation models presented validate the system design and the desired performance.

  19. Sensing Task Allocation for Heterogeneous Channels in Cooperative Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    Qihui Wu

    2010-12-01

    Full Text Available In the traditional centralized cooperative spectrum sensing, all secondary users sense the same channel. But, for a given channel, there exists detection performance diversity among all the users, due to the different signal-fading process. Involving the user with poor performance in cooperative sensing will not only deteriorate the detection correctness but also waste the sensing time. In the heterogeneous channels, the problem is even severe. A novel idea is to allocate the secondary users to sense different channels. We analyze the allocation problem before formulate it to be an optimization problem, which is a NP-hard problem. Then we propose the declined complexity algorithm in equal secondary user case and the two-hierarchy approach algorithm in unequal case. With the simulation, we verify the near optimality of the proposed algorithms and the advantage of the task allocation.

  20. Remote sensing with laser spectrum radar

    Science.gov (United States)

    Wang, Tianhe; Zhou, Tao; Jia, Xiaodong

    2016-10-01

    The unmanned airborne (UAV) laser spectrum radar has played a leading role in remote sensing because the transmitter and the receiver are together at laser spectrum radar. The advantages of the integrated transceiver laser spectrum radar is that it can be used in the oil and gas pipeline leak detection patrol line which needs the non-contact reflective detection. The UAV laser spectrum radar can patrol the line and specially detect the swept the area are now in no man's land because most of the oil and gas pipelines are in no man's land. It can save labor costs compared to the manned aircraft and ensure the safety of the pilots. The UAV laser spectrum radar can be also applied in the post disaster relief which detects the gas composition before the firefighters entering the scene of the rescue.

  1. Compressive Wideband Spectrum Sensing for Fixed Frequency Spectrum Allocation

    CERN Document Server

    Liu, Yipeng

    2010-01-01

    Too high sampling rate is the bottleneck to wideband spectrum sensing for cognitive radio (CR). As the survey shows that the sensed signal has a sparse representation in frequency domain in the mass, compressed sensing (CS) can be used to transfer the sampling burden to the digital signal processor. An analog to information converter (AIC) can randomly sample the received signal with sub-Nyquist rate to obtained the random measurements. Considering that the static frequency spectrum allocation of primary radios means the bounds between different primary radios is known in advance, here we incorporate information of the spectrum boundaries between different primary user as a priori information to obtain a mixed l2/l1 norm denoising operator (MNDO). In the MNDO, the estimated power spectrum density (PSD) vector is divided into block sections with bounds corresponding different allocated primary radios. Different from previous standard l1-norm constraint on the whole PSD vector, a sum of the l2 norm of each sect...

  2. Implementation of Cooperative Spectrum Sensing Algorithm using Raspberry Pi

    Directory of Open Access Journals (Sweden)

    Ammar Ahmed Khan

    2016-12-01

    Full Text Available A novel cooperative spectrum sensing algorithm is implemented and analyzed using Raspberry Pi. In the proposed setup, Nokia cell phone is used as a spectrum sensing device while Raspberry Pi functions as a FC device to collect sensing results from local sensing devices. The investigation results of the proposed setup show significant improvement in detection performance as compared to local spectrum sensing techniques. Furthermore, results show a successful communication between sensing nodes and FC.

  3. Decentralized asset management for collaborative sensing

    Science.gov (United States)

    Malhotra, Raj P.; Pribilski, Michael J.; Toole, Patrick A.; Agate, Craig

    2017-05-01

    There has been increased impetus to leverage Small Unmanned Aerial Systems (SUAS) for collaborative sensing applications in which many platforms work together to provide critical situation awareness in dynamic environments. Such applications require critical sensor observations to be made at the right place and time to facilitate the detection, tracking, and classification of ground-based objects. This further requires rapid response to real-world events and the balancing of multiple, competing mission objectives. In this context, human operators become overwhelmed with management of many platforms. Further, current automated planning paradigms tend to be centralized and don't scale up well to many collaborating platforms. We introduce a decentralized approach based upon information-theory and distributed fusion which enable us to scale up to large numbers of collaborating Small Unmanned Aerial Systems (SUAS) platforms. This is exercised against a military application involving the autonomous detection, tracking, and classification of critical mobile targets. We further show that, based upon monte-carlo simulation results, our decentralized approach out-performs more static management strategies employed by human operators and achieves similar results to a centralized approach while being scalable and robust to degradation of communication. Finally, we describe the limitations of our approach and future directions for our research.

  4. Compressive Sensing for Spread Spectrum Receivers

    DEFF Research Database (Denmark)

    Fyhn, Karsten; Jensen, Tobias Lindstrøm; Larsen, Torben

    2013-01-01

    With the advent of ubiquitous computing there are two design parameters of wireless communication devices that become very important: power efficiency and production cost. Compressive sensing enables the receiver in such devices to sample below the Shannon-Nyquist sampling rate, which may lead...... to a decrease in the two design parameters. This paper investigates the use of Compressive Sensing (CS) in a general Code Division Multiple Access (CDMA) receiver. We show that when using spread spectrum codes in the signal domain, the CS measurement matrix may be simplified. This measurement scheme, named...... Compressive Spread Spectrum (CSS), allows for a simple, effective receiver design. Furthermore, we numerically evaluate the proposed receiver in terms of bit error rate under different signal to noise ratio conditions and compare it with other receiver structures. These numerical experiments show that though...

  5. Spectrum Sensing and Primary User Localization in Cognitive Radio Networks via Sparsity

    Directory of Open Access Journals (Sweden)

    Lanchao Liu

    2016-01-01

    Full Text Available The theory of compressive sensing (CS has been employed to detect available spectrum resource in cognitive radio (CR networks recently. Capitalizing on the spectrum resource underutilization and spatial sparsity of primary user (PU locations, CS enables the identification of the unused spectrum bands and PU locations at a low sampling rate. Although CS has been studied in the cooperative spectrum sensing mechanism in which CR nodes work collaboratively to accomplish the spectrum sensing and PU localization task, many important issues remain unsettled. Does the designed compressive spectrum sensing mechanism satisfy the Restricted Isometry Property, which guarantees a successful recovery of the original sparse signal? Can the spectrum sensing results help the localization of PUs? What are the characteristics of localization errors? To answer those questions, we try to justify the applicability of the CS theory to the compressive spectrum sensing framework in this paper, and propose a design of PU localization utilizing the spectrum usage information. The localization error is analyzed by the Cramér-Rao lower bound, which can be exploited to improve the localization performance. Detail analysis and simulations are presented to support the claims and demonstrate the efficacy and efficiency of the proposed mechanism.

  6. Digital FMCW for ultrawideband spectrum sensing

    Science.gov (United States)

    Cheema, A. A.; Salous, S.

    2016-08-01

    An ultrawideband digital frequency-modulated continuous wave sensing engine is proposed as an alternative technique for cognitive radio applications. A dual-band demonstrator capable of sensing 750 MHz bandwidth in 204.8 µs is presented. Its performance is illustrated from both bench tests and from real-time measurements of the GSM 900 band and the 2.4 GHz wireless local area network (WLAN) band. The measured sensitivity and noise figure values are -90 dBm for a signal-to-noise ratio margin of at least 10 dB and ~13-14 dB, respectively. Data were collected over 24 h and were analyzed by using the energy detection method. The obtained results show the time variability of occupancy, and considerable sections of the spectrum are unoccupied. In addition, unlike the cyclic temporal variations of spectrum occupancy in the GSM 900 band, the detected variations in the 2.4 GHz WLAN band have an impulsive nature.

  7. Dynamic Digital Channelizer Based on Spectrum Sensing.

    Science.gov (United States)

    Hu, Junpeng; Zuo, Zhen; Huang, Zhiping; Dong, Zhi

    2015-01-01

    The ability to efficiently channelize a received signal with dynamic sub-channel bandwidths is a key requirement of software defined radio (SDR) systems. The digital channelizer, which is used to split the received signal into a number of sub-channels, plays an important role in SDR systems. In this paper, a design of dynamic digital channelizer is presented. The proposed method is novel in that it employs a cosine modulated filter bank (CMFB) to divide the received signal into multiple frequency sub-bands and a spectrum sensing technique, which is mostly used in cognitive radio, is introduced to detect the presence of signal of each sub-band. The method of spectrum sensing is carried out based on the eigenvalues of covariance matrix of received signal. The ratio of maximum-minimum eigenvalue of each sub-band is vulnerable to noise fluctuation. This paper suggests an optimized method to calculate the ratio of maximum-minimum eigenvalue. The simulation results imply that the design of digital channelizer can effectively separate the received signal with dynamically changeable sub-channel signals.

  8. Spectrum Sensing for Cognitive Radio Based on Multiple Antennas

    DEFF Research Database (Denmark)

    Nguyen, Huan Cong; De Carvalho, Elisabeth; Prasad, Ramjee

    2012-01-01

    Spectrum sensing is a key component for enabling the cognitive radio paradigm. In this paper, we propose a novel totally-blind spectrum sensing technique for cognitive radio device equipped with multiple antennas, namely the Space Frequency Cross Product Sensing (SFCPS) algorithm. Existing...

  9. A novel weighed cooperative bandwidth spectrum sensing for spectrum occupancy of cognitive radio network

    Institute of Scientific and Technical Information of China (English)

    刘鑫; 陈琨奇; 闫钧华

    2016-01-01

    In cognitive radio network (CRN), a secondary user (SU) may utilize the spectrum resource of the primary user (PU) and avoid causing harmful interference to the primary network (PN) via spectrum sensing. In the traditional time spectrum sensing, the SU cannot detect the PU’s presence during its transmission, thus increasing interference to the PN. In this work, a novel weighed cooperative bandwidth spectrum sensing method is proposed, which allows multiple SUs to use part of the bandwidth to perform cooperative spectrum sensing throughout the whole frame in order to detect the PU’s reappearance in time. The SU’s spectrum efficiency is maximized by jointly optimizing sensing bandwidth proportion, number of cooperative SUs and detection probability, subject to the constraints on the SU’s interference and the false alarm probability. Simulation results show significant decrease on the interference and improvement on the spectrum efficiency using the proposed weighed cooperative bandwidth spectrum sensing method.

  10. Hard Decision Fusion based Cooperative Spectrum Sensing in Cognitive Radio System

    Directory of Open Access Journals (Sweden)

    N. Armi N.M. Saad

    2013-09-01

    Full Text Available Cooperative spectrum sensing was proposed to combat fading, noise uncertainty, shadowing, and even hidden node problem due to primary users (PUs activity that is not spatially localized. It improves the probability of detection by collaborating to detect PUs signal in cognitive radio (CR system as well. This paper studies cooperative spectrum sensing and signal detection in CR system by implementing hard decision combining in data fusion centre. Through computer simulation, we evaluate the performances of cooperative spectrum sensing and signal detection by employing OR and AND rules as decision combining. Energy detector is used to observe the presence of primary user (PU signal. Those results are compared to non-cooperative signal detection for evaluation. They show that cooperative technique has better performance than non-cooperative. Moreover, signal to noise ratio (SNR with greater than or equal 10 dB and 15 collaborated users in CR system has optimal value for probability of detection.

  11. Adaptive Counting Rule for Cooperative Spectrum Sensing Under Correlated Environments

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Prasad, Neeli R.

    2012-01-01

    Spectrum sensing is the cognitive radio mechanism that enables spectrum awareness. It has been shown in the literature that spectrum sensing performance can be greatly improved through the use of cooperative sensing schemes. This paper considers and proposes a data fusion based cooperative spectrum...... sensing scheme based on data fusion, where an adaptive counting rule is used to implement the data fusion. The proposed scheme is evaluated against other common counting rules (e.g. 1-out-of-c and c-out-of-c) found in the literature and the optimum counting rule, while under different correlation...

  12. ADAPTIVE COUNTING RULE FOR COOPERATIVE SPECTRUM SENSING UNDER CORRELATED ENVIRONMENTS

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Prasad, Neeli R.

    2010-01-01

    Spectrum sensing is the Cognitive Radio mechanism that enables spectrum awareness. Spectrum sensing detection performance can be greatly improved, through the use of cooperative sensing schemes. This paper considers and proposes a cooperative spectrum sensing scheme, which implements an adaptive...... counting rule to perform the data fusion. The proposed scheme is evaluated against other common counting rules (e.g. 1-out-of-n and n-out-of-n) and the optimum counting rule, under different correlation conditions. The impact of correlation on the performance of the data fusion schemes, based on counting...

  13. Analytical Model Analysis Of Distributed Cooperative Spectrum Sensing Method

    Directory of Open Access Journals (Sweden)

    Ravi Prakash Shukla

    2012-05-01

    Full Text Available Spectrum sensing is a key function of cognitive radio to prevent the harmful interference with licensed users and identify the available spectrum for improving the spectrum’s utilization. Various methods for spectrum sensing control, such as deciding which sensors should perform sensing simultaneously and finding the appropriate trade-off between probability of misdetection and false alarm rate, are described. However, detection performance in practice is often compromised with multipath fading, shadowing and receiver uncertainty issues. To mitigate the impact of these issues, cooperative spectrum sensing has been shown to be an effective method to improve the detection performance by exploiting spatial diversity.

  14. Cooperative Spectrum Sensing over Non-Identical Nakagami Fading Channels

    KAUST Repository

    Rao, Anlei

    2012-09-08

    Previous works in cooperative spectrum sensing assumed that the channels for sensing and reporting are independent identical distributed (i.i.d). A more practical and appropriate assumption, however, should be that the sensing channels and reporting channels are independent but not necessarily identically distributed (i.n.i.d). In this paper, we derive the false-alarm probability and the detection probability of cooperative spectrum sensing with energy fusion over i.n.i.d Nakagami fading channels. Selected numerical results show that cooperative spectrum sensing still gives considerably better performance results even over i.n.i.d fading channels.

  15. Epoch-based Application Collaboration for Sensing Data Analysis

    Institute of Scientific and Technical Information of China (English)

    HU Kan; LIU Yun-sheng; WEN Bing

    2008-01-01

    The application collaboration was addressed to provide energy-efficient data services for distributed sensing applications to collaboratively interacting to achieve a desired global objective not detectable by any single cluster. An epoch-based transaction model was proposed by using the concept of sphere of control (SoC), and a collaborative sensing application can be dynamically formed as a nested architecture composed of time-synchronized applications. By loosening the rigid constraints of ACID to adapt the requirements of sensor networks, the submission, rollback and consistency rules ware educed and a two-phrase submission protocol was designed. Finally, it was illustrated that the model is capable of providing an adaptive formal template for sensing application collaboration. Our performance evaluations show that by applying the two-phrase submission protocol, we can significantly improve the number of reported answers and response time, raise resource utilization, and reduce the energyconsumption and data loss.

  16. Multislot Simultaneous Spectrum Sensing and Energy Harvesting in Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Xin Liu

    2016-07-01

    Full Text Available In cognitive radio (CR, the spectrum sensing of the primary user (PU may consume some electrical power from the battery capacity of the secondary user (SU, resulting in a decrease in the transmission power of the SU. In this paper, a multislot simultaneous spectrum sensing and energy harvesting model is proposed, which uses the harvested radio frequency (RF energy of the PU signal to supply the spectrum sensing. In the proposed model, the sensing duration is divided into multiple sensing slots consisting of one local-sensing subslot and one energy-harvesting subslot. If the PU is detected to be present in the local-sensing subslot, the SU will harvest RF energy of the PU signal in the energy-harvesting slot, otherwise, the SU will continue spectrum sensing. The global decision on the presence of the PU is obtained through combining local sensing results from all the sensing slots by adopting “Or-logic Rule”. A joint optimization problem of sensing time and time splitter factor is proposed to maximize the throughput of the SU under the constraints of probabilities of false alarm and detection and energy harvesting. The simulation results have shown that the proposed model can clearly improve the maximal throughput of the SU compared to the traditional sensing-throughput tradeoff model.

  17. Throughput Optimization via Cooperative Spectrum Sensing with Novel Frame Structure

    Directory of Open Access Journals (Sweden)

    Hang Hu

    2013-01-01

    Full Text Available In cognitive radio (CR networks, cooperation can greatly improve the performance of spectrum sensing. In this paper, we propose a novel cooperative spectrum sensing (CSS frame structure in which CR users conduct spectrum sensing and data transmission concurrently over two different parts of the primary user (PU spectrum band. Energy detection sensing scheme is used to prove that there exists an optimal sensing bandwidth which yields the highest throughput for the CR network. Thus, we focus on the optimal sensing settings of the proposed sensing scheme in order to maximize the throughput of the CR network under the conditions of sufficient protection to PUs and required bandwidth for potential CR user data transmission. Some algorithms are also derived to jointly optimize the sensing bandwidth and the final decision threshold. Our simulation results show that optimizing the sensing bandwidth and the final decision threshold together will further increase the throughput of the CR network as compared to that which only optimizes the sensing bandwidth or the final decision threshold.

  18. Detection efficiency of cooperative spectrum sensing in cognitive radio network

    Institute of Scientific and Technical Information of China (English)

    CHEN Xing; BIE Zhi-song; WU Wei-ling

    2008-01-01

    Sensing the spectrum in a reliable and efficient manner is crucial to cognitive radio. To combat the channel fading suffered by the single radio, cooperative spectrum sensing is employed, to associate the detection of multiple radios. In this article, the optimization problem of detection efficiency under the constraint of detection probability is investigated, and an algorithm to evaluate the required radio number and sensing time for maximal detection efficiency is presented. To show the effect of cooperation on the detection efficiency, the proposed algorithm is applied to cooperative sensing using the spectral correlation detector under the Rayleigh flat fading channel.

  19. Compressed Measurements Based Spectrum Sensing for Wideband Cognitive Radio Systems

    Directory of Open Access Journals (Sweden)

    Taha A. Khalaf

    2015-01-01

    Full Text Available Spectrum sensing is the most important component in the cognitive radio (CR technology. Spectrum sensing has considerable technical challenges, especially in wideband systems where higher sampling rates are required which increases the complexity and the power consumption of the hardware circuits. Compressive sensing (CS is successfully deployed to solve this problem. Although CS solves the higher sampling rate problem, it does not reduce complexity to a large extent. Spectrum sensing via CS technique is performed in three steps: sensing compressed measurements, reconstructing the Nyquist rate signal, and performing spectrum sensing on the reconstructed signal. Compressed detectors perform spectrum sensing from the compressed measurements skipping the reconstruction step which is the most complex step in CS. In this paper, we propose a novel compressed detector using energy detection technique on compressed measurements sensed by the discrete cosine transform (DCT matrix. The proposed algorithm not only reduces the computational complexity but also provides a better performance than the traditional energy detector and the traditional compressed detector in terms of the receiver operating characteristics. We also derive closed form expressions for the false alarm and detection probabilities. Numerical results show that the analytical expressions coincide with the exact probabilities obtained from simulations.

  20. Novel Cooperative Spectrum Sensing Methods And Their Limitations

    DEFF Research Database (Denmark)

    Kiilerich Pratas, Nuno

    2012-01-01

    The rapid growth of services offered through wireless communication has as consequence an increase on the demand for electromagnetic radio frequency spectrum, which is a scarce resource, mainly assigned to license holders on a long-term basis for large geographical regions, causing a large portion...... of the spectrum to remain unused for a significant percentage of the time. A new paradigm -- to overcome this apparent spectrum shortage -- that consists of radio devices with the ability to adapt to their spectral environment and are therefore able to make use of the available spectrum in an opportunistic manner...... was put forward, i.e. the Cognitive Radio paradigm. Spectrum sensing is the key mechanism in enabling spectrum awareness in Cognitive Radio. The performance of the spectrum sensing depends on the local channel conditions, such as the multipath, shadowing and the receiver uncertainty issues...

  1. Cooperative spectrum sensing and Detection efficiency in cognitive radio network

    Directory of Open Access Journals (Sweden)

    Nishant Dev Khaira

    2012-01-01

    Full Text Available —Spectrum sensing is required for better utilization of spectrum and preventing interference with licensed users. However, detection performance in practice is often compromised with multipath fading, shadowing and receiver uncertainty issues. To mitigate the impact of these issues, cooperative spectrum sensing has been shown to be an effective method to improve the detection performance by exploiting spatial diversity. While cooperative gain such as improved detection performance and relaxed sensitivity requirement can be obtained, cooperative sensing can incur cooperation overhead. The overhead refers to any extra sensing time, delay, energy, and operations devoted to cooperative sensing and any performance degradation caused by cooperative sensing. Specifically, the cooperation method is analyzed by the fundamental components called the elements of cooperative sensing, including cooperation models, sensing techniques, hypothesis testing, data fusion, control channel and reporting, user selection, and knowledge base. To combat the channel fading suffered by the single radio, cooperative spectrum sensing is employed, to associate the detection of multiple radios. In this article, the optimization problem of detection efficiency under the constraint of detection probability is investigated.

  2. Blind Spectrum Sensing by Information Theoretic Criteria for Cognitive Radios

    CERN Document Server

    Wang, Rui

    2010-01-01

    Spectrum sensing is a fundamental and critical issue for opportunistic spectrum access in cognitive radio networks. Among the many spectrum sensing methods, the information theoretic criteria (ITC) based method is a promising blind method which can reliably detect the primary users while requiring little prior information. In this paper, we provide an intensive treatment on the ITC sensing method. To this end, we first introduce a new over-determined channel model constructed by applying multiple antennas or over sampling at the secondary user in order to make the ITC applicable. Then, a simplified ITC sensing algorithm is introduced, which needs to compute and compare only two decision values. Compared with the original ITC sensing algorithm, the simplified algorithm significantly reduces the computational complexity without losing any performance. Applying the recent advances in random matrix theory, we then derive closed-form expressions to tightly approximate both the probability of false alarm and probab...

  3. Cyclostationary Beacon for Assisting Spectrum Sensing in Opportunistic Spectrum Access

    Directory of Open Access Journals (Sweden)

    Thomas Kaiser

    2011-03-01

    Full Text Available Cognitive radio is a promising solution to the problem of spectrum scarcity by means of allowing secondary radio networks access the spectrum opportunistically. One of the most important issues in cognitive radio is how to detect existing over-the-air signals reliably. Not a few literatures have reported that signals could be detected via their inherent or embedded properties. However, this approach may not be reliable and flexible enough for all kinds of signals with different modulation types. In this paper, we propose a type of multitone beacon signal carrying cyclostationary signatures, which is able to enhance the reliability and efficiency of signal detection at low cost of spectrum overhead. This beacon not only can indicate the presence or absence of user signal but also can reveal some other information helpful to opportunistic spectrum access through the information bits carried on its cyclostationary signatures. It could be applied to device/network identification, indication of spectrum allocation and spectrum rendezvous, both for primary and secondary users. Based on our previous work reported in [1], the generation and detection algorithm of the beacon signal are extended with improved spectral efficiency. Performance is discussed with both computer simulation and testbed validation.

  4. RF spectrum sensing in CMOS exploiting crosscorrelation

    NARCIS (Netherlands)

    Oude Alink, Mark Stefan

    2013-01-01

    The introduction of new wireless services, the demand for higher datarates, and higher traffic volumes call for a more efficient use of the RF spectrum than what is currently possible with static frequency allocation. Dynamic spectrum access offers a more efficient use by allowing unlicensed users t

  5. SPECTRUM SENSING IN COGNITIVE RADIO NETWORKS: QOS CONSIDERATIONS

    Directory of Open Access Journals (Sweden)

    Nabil Giweli

    2015-12-01

    Full Text Available The rapidly growing number of wireless communication devices has led to massive increases in radio traffic density, resulting in a noticeable shortage of available spectrum. To address this shortage, the Cognitive Radio (CR technology offers promising solutions that aim to improve the spectrum utilization. The operation of CR relies on detecting the so-called spectrum holes, the frequency bands that remain unoccupied by their licensed operators. The unlicensed users are then allowed to communicate using these spectrum holes. As such, the performance of CR is highly dependent on the employed spectrum sensing methods. Several sensing methods are already available. However, no individual method can accommodate all potential CR operation scenarios. Hence, it is fair to ascertain that the performance of a CR device can be improved if it is capable of supporting several sensing methods. It should obviously also be able to select the most suitable method. In this paper, several spectrum sensing methods are compared and analyzed, aiming to identify their advantages and shortcomings in different CR operating conditions. Furthermore, it identifies the features that need to be considered while selecting a suitable sensing method from the catalog of available methods.

  6. Spread spectrum compressed sensing MRI using chirp radio frequency pulses

    CERN Document Server

    Qu, Xiaobo; Zhuang, Xiaoxing; Yan, Zhiyu; Guo, Di; Chen, Zhong

    2013-01-01

    Compressed sensing has shown great potential in reducing data acquisition time in magnetic resonance imaging (MRI). Recently, a spread spectrum compressed sensing MRI method modulates an image with a quadratic phase. It performs better than the conventional compressed sensing MRI with variable density sampling, since the coherence between the sensing and sparsity bases are reduced. However, spread spectrum in that method is implemented via a shim coil which limits its modulation intensity and is not convenient to operate. In this letter, we propose to apply chirp (linear frequency-swept) radio frequency pulses to easily control the spread spectrum. To accelerate the image reconstruction, an alternating direction algorithm is modified by exploiting the complex orthogonality of the quadratic phase encoding. Reconstruction on the acquired data demonstrates that more image features are preserved using the proposed approach than those of conventional CS-MRI.

  7. PERFORMANCE OPTIMIZATION OF COGNITIVE RADIO WITH WIDEBAND SPECTRUM SENSING

    Directory of Open Access Journals (Sweden)

    E. Saraniya

    2014-09-01

    Full Text Available Cognitive radio (CR technology allows the unlicensed user to access the licensed spectrum bands. Spectrum sensing is an essential function in cognitive radio to detect the spectrum holes and opportunistically use the underutilized frequency bands without causing interference to primary user (PU. In this paper we are maximizing the throughput capacity of cognitive radio user and hence the performance of spectrum sensing and protection to licensed user improves over a wideband spectrum sensing band. The simulation of cognitive radio is done by analyzing the performance of energy detector spectrum sensing technique to detect primary user and to formulate the optimization using multiband joint detection method (MJD to achieve suitable trade- off between secondary user access and primary user network. The main aim of this paper is to maximize the probability of detection and to decrease the probabilities of miss detection and false alarm. To maximize the throughput it requires minimizing the throughput loss caused by miss detection and the significant reduction in probability of false alarm helps in achieving the spectral efficiency from the secondary user’s perspective. The simulation results show that the performance increases with the MJD method.

  8. Sensing Super-Position: Human Sensing Beyond the Visual Spectrum

    Science.gov (United States)

    Maluf, David A.; Schipper, John F.

    2007-01-01

    The coming decade of fast, cheap and miniaturized electronics and sensory devices opens new pathways for the development of sophisticated equipment to overcome limitations of the human senses. This paper addresses the technical feasibility of augmenting human vision through Sensing Super-position by mixing natural Human sensing. The current implementation of the device translates visual and other passive or active sensory instruments into sounds, which become relevant when the visual resolution is insufficient for very difficult and particular sensing tasks. A successful Sensing Super-position meets many human and pilot vehicle system requirements. The system can be further developed into cheap, portable, and low power taking into account the limited capabilities of the human user as well as the typical characteristics of his dynamic environment. The system operates in real time, giving the desired information for the particular augmented sensing tasks. The Sensing Super-position device increases the image resolution perception and is obtained via an auditory representation as well as the visual representation. Auditory mapping is performed to distribute an image in time. The three-dimensional spatial brightness and multi-spectral maps of a sensed image are processed using real-time image processing techniques (e.g. histogram normalization) and transformed into a two-dimensional map of an audio signal as a function of frequency and time. This paper details the approach of developing Sensing Super-position systems as a way to augment the human vision system by exploiting the capabilities of Lie human hearing system as an additional neural input. The human hearing system is capable of learning to process and interpret extremely complicated and rapidly changing auditory patterns. The known capabilities of the human hearing system to learn and understand complicated auditory patterns provided the basic motivation for developing an image-to-sound mapping system. The

  9. A Secure Distributed Spectrum Sensing Scheme in Cognitive Radio

    Science.gov (United States)

    Nhan, Nguyen-Thanh; Koo, Insoo

    Distributed spectrum sensing provides an improvement for primary user detection but leads a new security threat into CR system. The spectrum sensing data falsification malicious users can decrease the cooperative sensing performance. In this paper, we propose a distributed scheme in which the presence and absence hypotheses distribution of primary signal is estimated based on past sensing received power data by robust statistics, and the data fusion are performed according to estimated parameters by Dempster-Shafer theory of evidence. Our scheme can achive a powerful capability of malicious user elimination due to the abnormality of the distribution of malicious users compared with that of other legitimate users. In addition, the performance of our data fusion scheme is enhanced by supplemented nodes’ reliability weight.

  10. Compressed wideband spectrum sensing based on discrete cosine transform.

    Science.gov (United States)

    Wang, Yulin; Zhang, Gengxin

    2014-01-01

    Discrete cosine transform (DCT) is a special type of transform which is widely used for compression of speech and image. However, its use for spectrum sensing has not yet received widespread attention. This paper aims to alleviate the sampling requirements of wideband spectrum sensing by utilizing the compressive sampling (CS) principle and exploiting the unique sparsity structure in the DCT domain. Compared with discrete Fourier transform (DFT), wideband communication signal has much sparser representation and easier implementation in DCT domain. Simulation result shows that the proposed DCT-CSS scheme outperforms the conventional DFT-CSS scheme in terms of MSE of reconstruction signal, detection probability, and computational complexity.

  11. Compressed Wideband Spectrum Sensing Based on Discrete Cosine Transform

    Directory of Open Access Journals (Sweden)

    Yulin Wang

    2014-01-01

    Full Text Available Discrete cosine transform (DCT is a special type of transform which is widely used for compression of speech and image. However, its use for spectrum sensing has not yet received widespread attention. This paper aims to alleviate the sampling requirements of wideband spectrum sensing by utilizing the compressive sampling (CS principle and exploiting the unique sparsity structure in the DCT domain. Compared with discrete Fourier transform (DFT, wideband communication signal has much sparser representation and easier implementation in DCT domain. Simulation result shows that the proposed DCT-CSS scheme outperforms the conventional DFT-CSS scheme in terms of MSE of reconstruction signal, detection probability, and computational complexity.

  12. Upper bounds for Neyman-Pearson cooperative spectrum sensing

    KAUST Repository

    Zahabi, Sayed Jalal

    2011-06-01

    We consider a cooperative spectrum sensing scenario where the local sensors at the secondary users are viewed as one-level quantizers, and the quantized data are to be fused under Neyman-Pearson (N-P) criterion. We demonstrate how the N-P fusion results in a randomized test, which represents the total performance of our spectrum sensing scheme. We further introduce an upper performance bound for the overall primary user signal detection. An analytical procedure towards the upper bound and its relevant quantization setup at the local sensors are proposed and examined through simulations. © 2011 IEEE.

  13. Novel Spectrum Sensing Algorithms for OFDM Cognitive Radio Networks.

    Science.gov (United States)

    Shi, Zhenguo; Wu, Zhilu; Yin, Zhendong; Cheng, Qingqing

    2015-06-15

    Spectrum sensing technology plays an increasingly important role in cognitive radio networks. Consequently, several spectrum sensing algorithms have been proposed in the literature. In this paper, we present a new spectrum sensing algorithm "Differential Characteristics-Based OFDM (DC-OFDM)" for detecting OFDM signal on account of differential characteristics. We put the primary value on channel gain θ around zero to detect the presence of primary user. Furthermore, utilizing the same method of differential operation, we improve two traditional OFDM sensing algorithms (cyclic prefix and pilot tones detecting algorithms), and propose a "Differential Characteristics-Based Cyclic Prefix (DC-CP)" detector and a "Differential Characteristics-Based Pilot Tones (DC-PT)" detector, respectively. DC-CP detector is based on auto-correlation vector to sense the spectrum, while the DC-PT detector takes the frequency-domain cross-correlation of PT as the test statistic to detect the primary user. Moreover, the distributions of the test statistics of the three proposed methods have been derived. Simulation results illustrate that all of the three proposed methods can achieve good performance under low signal to noise ratio (SNR) with the presence of timing delay. Specifically, the DC-OFDM detector gets the best performance among the presented detectors. Moreover, both of the DC-CP and DC-PT detector achieve significant improvements compared with their corresponding original detectors.

  14. Multiantenna spectrum sensing for cognitive radio: overcoming noise uncertainty

    OpenAIRE

    López Valcarce, Roberto; Vázquez Vilar, Gonzalo; Sala Álvarez, José

    2010-01-01

    Spectrum sensing is a key ingredient of the dynamic spectrum access paradigm, but it needs powerful detectors operating at SNRs well below the decodability levels of primary signals. Noise uncertainty poses a significant challenge to the development of such schemes, requiring some degree of diversity (spatial, temporal, or in distribution) for identifiability of the noise level. Multiantenna detectors exploit spatial independence of receiver thermal noise. We review this ...

  15. MOSDEN: A Scalable Mobile Collaborative Platform for Opportunistic Sensing Applications

    Directory of Open Access Journals (Sweden)

    Prem Prakash Jayaraman

    2014-05-01

    Full Text Available Mobile smartphones along with embedded sensors have become an efficient enabler for various mobile applications including opportunistic sensing. The hi-tech advances in smartphones are opening up a world of possibilities. This paper proposes a mobile collaborative platform called MOSDEN that enables and supports opportunistic sensing at run time. MOSDEN captures and shares sensor data acrossmultiple apps, smartphones and users. MOSDEN supports the emerging trend of separating sensors from application-specific processing, storing and sharing. MOSDEN promotes reuse and re-purposing of sensor data hence reducing the efforts in developing novel opportunistic sensing applications. MOSDEN has been implemented on Android-based smartphones and tablets. Experimental evaluations validate the scalability and energy efficiency of MOSDEN and its suitability towards real world applications. The results of evaluation and lessons learned are presented and discussed in this paper.

  16. Cooperative Sequential Spectrum Sensing Based on Level-triggered Sampling

    CERN Document Server

    Yilmaz, Yasin; Wang, Xiaodong

    2011-01-01

    We propose a new framework for cooperative spectrum sensing in cognitive radio networks, that is based on a novel class of non-uniform samplers, called the event-triggered samplers, and sequential detection. In the proposed scheme, each secondary user computes its local sensing decision statistic based on its own channel output; and whenever such decision statistic crosses certain predefined threshold values, the secondary user will send one (or several) bit of information to the fusion center. The fusion center asynchronously receives the bits from different secondary users and updates the global sensing decision statistic to perform a sequential probability ratio test (SPRT), to reach a sensing decision. We provide an asymptotic analysis for the above scheme, and under different conditions, we compare it against the cooperative sensing scheme that is based on traditional uniform sampling and sequential detection. Simulation results show that the proposed scheme, using even 1 bit, can outperform its uniform ...

  17. ENERGY EFFICIENT COOPERATIVE SPECTRUM SENSING IN COGNITIVE RADIO

    Directory of Open Access Journals (Sweden)

    Ramzi Saifan

    2016-03-01

    Full Text Available Sensing in cognitive radio (CR protects the primary user (PU from bad interference. Therefore, it is assumed to be a requirement. However, sensing has two main challenges; first the CR is required to sense the PU under very low signal to noise ratios which will take longer sensing time, and second, some CR nodes may suffer from deep fading and shadowing effects. Cooperative spectrum sensing (CSS is supposed to solve these challenges. However, CSS adds extra energy consumption due to CRs send the sensing result to the fusion center and receive the final decision from the fusion center. This is in addition to the sensing energy itself. Therefore, CSS may consume considerable energy out of the battery of the CR node. Therefore in this paper, we try to find jointly the sensing time required from each CR node and the number of CR nodes who should perform sensing such that the energy and energy efficiency (i.e., ratio of throughput to energy consumed are optimized. Simulation results show that the joint optimization achieves better in terms of energy efficiency than other approaches that perform separate optimization.

  18. Cooperative Spectrum Sensing and Localization in Cognitive Radio Systems Using Compressed Sensing

    Directory of Open Access Journals (Sweden)

    Wael Guibène

    2013-01-01

    Full Text Available We propose to fuse two main enabling features in cognitive radio systems (CRS: spectrum sensing and location awareness in a single compressed sensing based formalism. In this way, we exploit sparse characteristics of primary units to be detected, both in terms of spectrum used and location occupied. The compressed sensing approach also allows to overcome hardware limitations, in terms of the incapacity to acquire measurements and signals at the Nyquist rate when the spectrum to be scanned is large. Simulation results for realistic network topologies and different compressed sensing reconstruction algorithms testify to the performance and the feasibility of the proposed technique to enable in a single formalism the two main features of cognitive sensor networks.

  19. The Solar Spectrum: An Atmospheric Remote Sensing Perspective

    Science.gov (United States)

    Toon, Geoff

    2013-01-01

    The solar spectrum not only contains information about the composition and structure of the sun, it also provides a bright and stable continuum source for earth remote sensing (atmosphere and surface). Many types of remote sensors use solar radiation. While high-resolution spaceborne sensors (e.g. ACE) can largely remove the effects of the solar spectrum by exo-atmospheric calibration, this isn't an option for sub-orbital sensors, such as the FTIR spectrometers used in the NDACC and TCCON networks. In this case the solar contribution must be explicitly included in the spectral analysis. In this talk the methods used to derive the solar spectrum are presented, and the underlying solar physics are discussed. Implication for remote sensing are described.

  20. On the Performance of Cooperative Spectrum Sensing under Quantization

    CERN Document Server

    Han, Weijia; Li, Zan; Zhang, Yan; Liu, Qin

    2011-01-01

    In cognitive radio, the cooperative spectrum sensing (CSS) plays a key role in determining the performance of secondary networks. However, there have not been feasible approaches that can analytically calculate the performance of CSS with regard to the multi-level quantization. In this paper, we not only show the cooperative false alarm probability and cooperative detection probability impacted by quantization, but also formulate them by two closed form expressions. These two expressions enable the calculation of cooperative false alarm probability and cooperative detection probability tractable efficiently, and provide a feasible approach for optimization of sensing performance. Additionally, to facilitate this calculation, we derive Normal approximation for evaluating the sensing performance conveniently. Furthermore, two optimization methods are proposed to achieve the high sensing performance under quantization.

  1. Wideband Spectrum Sensing at Sub-Nyquist Rates

    CERN Document Server

    Mishali, Moshe

    2010-01-01

    We present a mixed analog-digital spectrum sensing method that is especially suited to the typical wideband setting of cognitive radio (CR). The advantages of our system with respect to current architectures are threefold. First, our analog front-end is fixed and does not involve scanning hardware. Second, both the analog-to-digital conversion (ADC) and the digital signal processing (DSP) rates are substantially below Nyquist. Finally, the sensing resources are shared with the reception path of the CR, so that the lowrate streaming samples can be used for communication purposes of the device, besides the sensing functionality they provide. Combining these advantages leads to a real time map of the spectrum with minimal use of mobile resources. Our approach is based on the modulated wideband converter (MWC) system, which samples sparse wideband inputs at sub-Nyquist rates. We report on results of hardware experiments, conducted on an MWC prototype circuit, which affirm fast and accurate spectrum sensing in par...

  2. Spectrum Sensing in the Presence of Multiple Primary Users

    CERN Document Server

    Wei, Lu

    2012-01-01

    We consider multi-antenna cooperative spectrum sensing in cognitive radio networks, when there may be multiple primary users. A detector based on the spherical test is analyzed in such a scenario. Based on the moments of the distributions involved, simple and accurate analytical formulae for the key performance metrics of the detector are derived. The false alarm and the detection probabilities, as well as the detection threshold and Receiver Operation Characteristics are available in closed form. Simulations are provided to verify the accuracy of the derived results, and to compare with other detectors in realistic sensing scenarios.

  3. Locally Best Invariant Test for Multiple Primary User Spectrum Sensing

    CERN Document Server

    Wei, Lu; Tirkkonen, Olav

    2012-01-01

    We consider multi-antenna cooperative spectrum sensing in cognitive radio networks, when there may be multiple primary users. A noise-uncertainty-free detector that is optimal in the low signal to noise ratio regime is analyzed in such a scenario. Specifically, we derive the exact moments of the test statistics involved, which lead to simple and accurate analytical formulae for the false alarm probability and the decision threshold. Simulations are provided to examine the accuracy of the derived results, and to compare with other detectors in realistic sensing scenarios.

  4. A Spectrum Sensing Network for Cognitive PMSE Systems

    Science.gov (United States)

    Brendel, Johannes; Riess, Steffen; Stoeckle, Andreas; Rummel, Rafael; Fischer, Georg

    2012-09-01

    This article is about a Spectrum Sensing Network (SSN) which generates an accurate radio environment map (e.g. power over frequency, time, and location) from a given application area. It is intended to be used in combination with cognitive Program Making and Special Events (PMSE) devices (e.g. wireless microphones) to improve their operation reliability. The SSN consists of a distributed network of multiple scanning radio receivers and a central data management and storage unit. The parts of the SSN are presented in detail and the advantages and use cases of such a sensing network structure will be outlined.

  5. Energy-Efficient Collaborative Outdoor Localization for Participatory Sensing.

    Science.gov (United States)

    Wang, Wendong; Xi, Teng; Ngai, Edith C-H; Song, Zheng

    2016-05-25

    Location information is a key element of participatory sensing. Many mobile and sensing applications require location information to provide better recommendations, object search and trip planning. However, continuous GPS positioning consumes much energy, which may drain the battery of mobile devices quickly. Although WiFi and cell tower positioning are alternatives, they provide lower accuracy compared to GPS. This paper solves the above problem by proposing a novel localization scheme through the collaboration of multiple mobile devices to reduce energy consumption and provide accurate positioning. Under our scheme, the mobile devices are divided into three groups, namely the broadcaster group, the location information receiver group and the normal participant group. Only the broadcaster group and the normal participant group use their GPS. The location information receiver group, on the other hand, makes use of the locations broadcast by the broadcaster group to estimate their locations. We formulate the broadcaster set selection problem and propose two novel algorithms to minimize the energy consumption in collaborative localization. Simulations with real traces show that our proposed solution can save up to 68% of the energy of all of the participants and provide more accurate locations than WiFi and cellular network positioning.

  6. Energy-Efficient Collaborative Outdoor Localization for Participatory Sensing

    Directory of Open Access Journals (Sweden)

    Wendong Wang

    2016-05-01

    Full Text Available Location information is a key element of participatory sensing. Many mobile and sensing applications require location information to provide better recommendations, object search and trip planning. However, continuous GPS positioning consumes much energy, which may drain the battery of mobile devices quickly. Although WiFi and cell tower positioning are alternatives, they provide lower accuracy compared to GPS. This paper solves the above problem by proposing a novel localization scheme through the collaboration of multiple mobile devices to reduce energy consumption and provide accurate positioning. Under our scheme, the mobile devices are divided into three groups, namely the broadcaster group, the location information receiver group and the normal participant group. Only the broadcaster group and the normal participant group use their GPS. The location information receiver group, on the other hand, makes use of the locations broadcast by the broadcaster group to estimate their locations. We formulate the broadcaster set selection problem and propose two novel algorithms to minimize the energy consumption in collaborative localization. Simulations with real traces show that our proposed solution can save up to 68% of the energy of all of the participants and provide more accurate locations than WiFi and cellular network positioning.

  7. OTHR Spectrum Reconstruction of Maneuvering Target with Compressive Sensing

    Directory of Open Access Journals (Sweden)

    Yinghui Quan

    2014-01-01

    Full Text Available High-frequency (HF over-the-horizon radar (OTHR works in a very complicated electromagnetic environment. It usually suffers performance degradation caused by transient interference. In this paper, we study the transient interference excision and full spectrum reconstruction of maneuvering targets. The segmental subspace projection (SP approach is applied to suppress the clutter and locate the transient interference. After interference excision, the spectrum is reconstructed from incomplete measurements via compressive sensing (CS by using a redundant Fourier-chirp dictionary. An improved orthogonal matching pursuit (IOMP algorithm is developed to solve the sparse decomposition optimization. Experimental results demonstrate the effectiveness of the proposed methods.

  8. Cooperative Wideband Spectrum Sensing for the Centralized Cognitive Radio Network

    CERN Document Server

    Zhang, Peng

    2011-01-01

    Various primary user (PU) radios have been allocated into fixed frequency bands in the whole spectrum. A cognitive radio network (CRN) should be able to perform the wideband spectrum sensing (WSS) to detect temporarily unoccupied frequency bands. We summarize four occupancy features for the frequency bands. 1. The occupancy is sparse; 2. The frequency band allocation information is fixed and common; 3. There are three categories for the frequency band usages; 4. The occupied frequency bands are common in the CRN. For the first time, we consider all features as the prior knowledge in the compressed sensing based cooperative WSS (CWSS) algorithm design for a centralized CRN. We propose a modified orthogonal matching pursuit (Mod-OMP) algorithm and a modified simultaneous orthogonal matching pursuit (Mod-SOMP) algorithm for the CWSS. We compare the CWSS performance of Mod-OMP/Mod-SOMP with the original OMP/SOMP and show the performance improvements.

  9. Spectrum Sensing in Cognitive Radio Networks: Performance Evaluation and Optimization

    CERN Document Server

    Xiong, Gang; Yener, Aylin

    2012-01-01

    This paper studies cooperative spectrum sensing in cognitive radio networks where secondary users collect local energy statistics and report their findings to a secondary base station, i.e., a fusion center. First, the average error probability is quantitively analyzed to capture the dynamic nature of both observation and fusion channels, assuming fixed amplifier gains for relaying local statistics to the fusion center. Second, the system level overhead of cooperative spectrum sensing is addressed by considering both the local processing cost and the transmission cost. Local processing cost incorporates the overhead of sample collection and energy calculation that must be conducted by each secondary user; the transmission cost accounts for the overhead of forwarding the energy statistic computed at each secondary user to the fusion center. Results show that when jointly designing the number of collected energy samples and transmission amplifier gains, only one secondary user needs to be actively engaged in sp...

  10. Sensing Technologies for Autism Spectrum Disorder Screening and Intervention

    OpenAIRE

    John-John Cabibihan; Hifza Javed; Mohammed Aldosari; Frazier, Thomas W.; Haitham Elbashir

    2016-01-01

    This paper reviews the state-of-the-art in sensing technologies that are relevant for Autism Spectrum Disorder (ASD) screening and therapy. This disorder is characterized by difficulties in social communication, social interactions, and repetitive behaviors. It is diagnosed during the first three years of life. Early and intensive interventions have been shown to improve the developmental trajectory of the affected children. The earlier the diagnosis, the sooner the intervention therapy can b...

  11. Energy detection for spectrum sensing in cognitive radio

    CERN Document Server

    Atapattu, Saman; Jiang, Hai

    2014-01-01

    This Springer Brief focuses on the current state-of-the-art research on spectrum sensing by using energy detection, a low-complexity and low-cost technique. It includes a comprehensive summary of recent research, fundamental theories, possible architectures, useful performance measurements of energy detection and applications of energy detection. Concise, practical chapters explore conventional energy detectors, alternative forms of energy detectors, performance measurements, diversity techniques and cooperative networks. The careful analysis enables reader to identify the most efficient techn

  12. 47 CFR 15.717 - TVBDs that rely on spectrum sensing.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false TVBDs that rely on spectrum sensing. 15.717... Television Band Devices § 15.717 TVBDs that rely on spectrum sensing. (a) Parties may submit applications for certification of TVBDs that rely solely on spectrum sensing to identify available channels. Devices authorized...

  13. Eigenvalue based Spectrum Sensing Algorithms for Cognitive Radio

    CERN Document Server

    Zeng, Yonghong

    2008-01-01

    Spectrum sensing is a fundamental component is a cognitive radio. In this paper, we propose new sensing methods based on the eigenvalues of the covariance matrix of signals received at the secondary users. In particular, two sensing algorithms are suggested, one is based on the ratio of the maximum eigenvalue to minimum eigenvalue; the other is based on the ratio of the average eigenvalue to minimum eigenvalue. Using some latest random matrix theories (RMT), we quantify the distributions of these ratios and derive the probabilities of false alarm and probabilities of detection for the proposed algorithms. We also find the thresholds of the methods for a given probability of false alarm. The proposed methods overcome the noise uncertainty problem, and can even perform better than the ideal energy detection when the signals to be detected are highly correlated. The methods can be used for various signal detection applications without requiring the knowledge of signal, channel and noise power. Simulations based ...

  14. Optimality of Multichannel Myopic Sensing in the Presence of Sensing Error for Opportunistic Spectrum Access

    Directory of Open Access Journals (Sweden)

    Xiaofeng Jiang

    2013-01-01

    Full Text Available The optimization problem for the performance of opportunistic spectrum access is considered in this study. A user, with the limited sensing capacity, has opportunistic access to a communication system with multiple channels. The user can only choose several channels to sense and decides whether to access these channels based on the sensing information in each time slot. Meanwhile, the presence of sensing error is considered. A reward is obtained when the user accesses a channel. The objective is to maximize the expected (discounted or average reward accrued over an infinite horizon. This problem can be formulated as a partially observable Markov decision process. This study shows the optimality of the simple and robust myopic policy which focuses on maximizing the immediate reward. The results show that the myopic policy is optimal in the case of practical interest.

  15. On Spectrum Sensing for TV White Space in China

    Directory of Open Access Journals (Sweden)

    Christian Kocks

    2012-01-01

    Full Text Available In the field of wireless communications the idea of cognitive radio is of utmost interest. Due to its advantageous propagation properties, the TV white space can be considered to become the first commercial application of cognitive radio. It allows the usage of secondary communication systems at non-occupied frequency bands. Within this paper, spectrum sensing algorithms are introduced for the three predominant Chinese TV standards DTMB, CMMB, and PAL-D/K. A prototype platform is presented and its underlying architecture based on a combination of DSP and FPGA is illustrated including the setup of the cognitive radio application. Furthermore, the performance of the sensing algorithms implemented on the prototype platform is shown in comparison to simulation results.

  16. Collaborative cultures in education: sense of community of teachers and student teachers

    NARCIS (Netherlands)

    Admiraal, W.; Brouwer, P.; Dobber, M.; Lockhorst, D.; Vandyck, I.

    2011-01-01

    Teacher communities create excellent conditions for teacher learning implying a sustainable form of teacher collaboration and collaborative learning. Sense of community of both teachers in secondary schools and student teachers was related to the perception of a collaborative group culture. Various

  17. A Review on Spectrum Sensing for Cognitive Radio: Challenges and Solutions

    Directory of Open Access Journals (Sweden)

    Zeng Yonghong

    2010-01-01

    Full Text Available Cognitive radio is widely expected to be the next Big Bang in wireless communications. Spectrum sensing, that is, detecting the presence of the primary users in a licensed spectrum, is a fundamental problem for cognitive radio. As a result, spectrum sensing has reborn as a very active research area in recent years despite its long history. In this paper, spectrum sensing techniques from the optimal likelihood ratio test to energy detection, matched filtering detection, cyclostationary detection, eigenvalue-based sensing, joint space-time sensing, and robust sensing methods are reviewed. Cooperative spectrum sensing with multiple receivers is also discussed. Special attention is paid to sensing methods that need little prior information on the source signal and the propagation channel. Practical challenges such as noise power uncertainty are discussed and possible solutions are provided. Theoretical analysis on the test statistic distribution and threshold setting is also investigated.

  18. Spectrum Sensing For Cognitive Radios Through Differential Entropy

    Directory of Open Access Journals (Sweden)

    Sanjeev Gurugopinath

    2016-04-01

    Full Text Available In this work, we present a novel Goodness-of-Fit Test driven by differential entropy for spectrum sensing in cognitive radios, under three different noise models – Gaussian, Laplacian and mixture of Gaussians. We analyze the proposed detector under Gaussian noise which models the worst-case. We then analyze by considering the Laplacian noise process which has tails heavier than that of the Gaussian. We generalize the analysis considering the noise to be a mixture of Gaussians, which is often the case with noise and interference in communication systems. We analyze the performance under each of these cases for a large class of practically relevant fading channel models and primary signal models, with emphasis on low Signal-to-Noise ratio regimes. Towards this end, we derive closed form expressions for the distribution of the test statistic under the null hypothesis and the detection threshold that satisfies a constraint on the probability of false-alarm. Through Monte Carlo simulations, we demonstrate that our detection strategy outperforms an existing spectrum sensing technique based on order statistics.

  19. Broadband Cooperative Spectrum Sensing Based on Distributed Modulated Wideband Converter

    Directory of Open Access Journals (Sweden)

    Ziyong Xu

    2016-09-01

    Full Text Available The modulated wideband converter (MWC is a kind of sub-Nyquist sampling system which is developed from compressed sensing theory. It accomplishes highly accurate broadband sparse signal recovery by multichannel sub-Nyquist sampling sequences. However, when the number of sparse sub-bands becomes large, the amount of sampling channels increases proportionally. Besides, it is very hard to adjust the number of sampling channels when the sparsity changes, because its undersampling board is designed by a given sparsity. Such hardware cost and inconvenience are unacceptable in practical applications. This paper proposes a distributed modulated wideband converter (DMWC scheme innovatively, which regards one sensor node as one sampling channel and combines MWC technology with a broadband cooperative spectrum sensing network perfectly. Being different from the MWC scheme, DMWC takes phase shift and transmission loss into account in the input terminal, which are unavoidable in practical application. Our scheme is not only able to recover the support of broadband sparse signals quickly and accurately, but also reduces the hardware cost of the single node drastically. Theoretical analysis and numerical simulations show that phase shift has no influence on the recovery of frequency support, but transmission loss degrades the recovery performance to a different extent. Nevertheless, we can increase the amount of cooperative nodes and select satisfactory nodes by a different transmission distance to improve the recovery performance. Furthermore, we can adjust the amount of cooperative nodes flexibly when the sparsity changes. It indicates DMWC is extremely effective in the broadband cooperative spectrum sensing network.

  20. Energy Efficient Spectrum Sensing for State Estimation over A Wireless Channel

    OpenAIRE

    Cao, Xianghui; Zhou, Xiangwei; Cheng, Yu

    2014-01-01

    The performance of remote estimation over wireless channel is strongly affected by sensor data losses due to interference. Although the impact of interference can be alleviated by performing spectrum sensing and then transmitting only when the channel is clear, the introduction of spectrum sensing also incurs extra energy expenditure. In this paper, we investigate the problem of energy efficient spectrum sensing for state estimation of a general linear dynamic system, and formulate an optimiz...

  1. On the Performance of Spectrum Sensing Algorithms using Multiple Antennas

    CERN Document Server

    Liang, Ying-Chang; Zeng, Yonghong

    2010-01-01

    In recent years, some spectrum sensing algorithms using multiple antennas, such as the eigenvalue based detection (EBD), have attracted a lot of attention. In this paper, we are interested in deriving the asymptotic distributions of the test statistics of the EBD algorithms. Two EBD algorithms using sample covariance matrices are considered: maximum eigenvalue detection (MED) and condition number detection (CND). The earlier studies usually assume that the number of antennas (K) and the number of samples (N) are both large, thus random matrix theory (RMT) can be used to derive the asymptotic distributions of the maximum and minimum eigenvalues of the sample covariance matrices. While assuming the number of antennas being large simplifies the derivations, in practice, the number of antennas equipped at a single secondary user is usually small, say 2 or 3, and once designed, this antenna number is fixed. Thus in this paper, our objective is to derive the asymptotic distributions of the eigenvalues and condition...

  2. Matched Filter Based Spectrum Sensing on Cognitive Radio for OFDM WLANs

    Directory of Open Access Journals (Sweden)

    R.Saravanan

    2013-02-01

    Full Text Available For the unlicensed users to use the licensed spectrum, unused frequency bands called white spaces need to be detected. Cognitive radio does this task by dynamic spectrum access. This requires intelligent spectrum sensing techniques. In this paper such unused spectrum for OFDM WLAN (IEEE 802.11a is predicted by exploring the signals presence in minimum time using matched filter based detection incorporating optimal threshold selection, thereby increasing the sensing accuracy andinterference reduction of secondary network.

  3. Energy-Efficient Spectrum Sensing for Cognitive Radio Networks

    NARCIS (Netherlands)

    Maleki, S.

    2013-01-01

    Dynamic spectrum access employing cognitive radios has been proposed, in order to opportunistically use underutilized spectrum portions of a heavily licensed electromagnetic spectrum. Cognitive radios opportunistically share the spectrum, while avoiding any harmful interference to the primary licens

  4. Energy-Efficient Spectrum Sensing for Cognitive Radio Networks

    NARCIS (Netherlands)

    Maleki, S.

    2013-01-01

    Dynamic spectrum access employing cognitive radios has been proposed, in order to opportunistically use underutilized spectrum portions of a heavily licensed electromagnetic spectrum. Cognitive radios opportunistically share the spectrum, while avoiding any harmful interference to the primary licens

  5. Sensing Technologies for Autism Spectrum Disorder Screening and Intervention.

    Science.gov (United States)

    Cabibihan, John-John; Javed, Hifza; Aldosari, Mohammed; Frazier, Thomas W; Elbashir, Haitham

    2016-12-27

    This paper reviews the state-of-the-art in sensing technologies that are relevant for Autism Spectrum Disorder (ASD) screening and therapy. This disorder is characterized by difficulties in social communication, social interactions, and repetitive behaviors. It is diagnosed during the first three years of life. Early and intensive interventions have been shown to improve the developmental trajectory of the affected children. The earlier the diagnosis, the sooner the intervention therapy can begin, thus, making early diagnosis an important research goal. Technological innovations have tremendous potential to assist with early diagnosis and improve intervention programs. The need for careful and methodological evaluation of such emerging technologies becomes important in order to assist not only the therapists and clinicians in their selection of suitable tools, but to also guide the developers of the technologies in improving hardware and software. In this paper, we survey the literatures on sensing technologies for ASD and we categorize them into eye trackers, movement trackers, electrodermal activity monitors, tactile sensors, vocal prosody and speech detectors, and sleep quality assessment devices. We assess their effectiveness and study their limitations. We also examine the challenges faced by this growing field that need to be addressed before these technologies can perform up to their theoretical potential.

  6. Sensing Technologies for Autism Spectrum Disorder Screening and Intervention

    Directory of Open Access Journals (Sweden)

    John-John Cabibihan

    2016-12-01

    Full Text Available This paper reviews the state-of-the-art in sensing technologies that are relevant for Autism Spectrum Disorder (ASD screening and therapy. This disorder is characterized by difficulties in social communication, social interactions, and repetitive behaviors. It is diagnosed during the first three years of life. Early and intensive interventions have been shown to improve the developmental trajectory of the affected children. The earlier the diagnosis, the sooner the intervention therapy can begin, thus, making early diagnosis an important research goal. Technological innovations have tremendous potential to assist with early diagnosis and improve intervention programs. The need for careful and methodological evaluation of such emerging technologies becomes important in order to assist not only the therapists and clinicians in their selection of suitable tools, but to also guide the developers of the technologies in improving hardware and software. In this paper, we survey the literatures on sensing technologies for ASD and we categorize them into eye trackers, movement trackers, electrodermal activity monitors, tactile sensors, vocal prosody and speech detectors, and sleep quality assessment devices. We assess their effectiveness and study their limitations. We also examine the challenges faced by this growing field that need to be addressed before these technologies can perform up to their theoretical potential.

  7. Higher-Order Cyclostationarity Detection for Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    Julien Renard

    2010-01-01

    Full Text Available Recent years have shown a growing interest in the concept of Cognitive Radios (CRs, able to access portions of the electromagnetic spectrum in an opportunistic operating way. Such systems require efficient detectors able to work in low Signal-to-Noise Ratio (SNR environments, with little or no information about the signals they are trying to detect. Energy detectors are widely used to perform such blind detection tasks, but quickly reach the so-called SNR wall below which detection becomes impossible Tandra (2005. Cyclostationarity detectors are an interesting alternative to energy detectors, as they exploit hidden periodicities present in man-made signals, but absent in noise. Such detectors use quadratic transformations of the signals to extract the hidden sine-waves. While most of the literature focuses on the second-order transformations of the signals, we investigate the potential of higher-order transformations of the signals. Using the theory of Higher-Order Cyclostationarity (HOCS, we derive a fourth-order detector that performs similarly to the second-order ones to detect linearly modulated signals, at SNR around 0 dB, which may be used if the signals of interest do not exhibit second-order cyclostationarity. More generally this paper reviews the relevant aspects of the cyclostationary and HOCS theory, and shows their potential for spectrum sensing.

  8. Dynamic control approaches of spectrum sensing in multi-band cognitive radio networks

    Institute of Scientific and Technical Information of China (English)

    AN Chun-yan; JI Hong; SI Peng-bo; MAO Xu

    2010-01-01

    In this paper,the dynamic control approaches for spectrum sensing are proposed,based on the theory that prediction is synonymous with data compression in computational learning. Firstly,a spectrum sensing sequence prediction scheme is proposed to reduce the spectrum sensing time and improve the throughput of secondary users. We use Ziv-Lempel data compression algorithm to design the prediction scheme,where spectrum band usage history is utilized. In addition,an iterative algorithm to find out the optimal number of spectrum bands allowed to sense is proposed,with the aim of maximizing the expected net reward of each secondary user in each time slot. Finally,extensive simulation results are shown to demonstrate the effectiveness of the proposed dynamic control approaches of spectrum sensing.

  9. Cooperative spectrum sensing schemes with the interference constraint in cognitive radio networks.

    Science.gov (United States)

    Do, Tri-Nhu; An, Beongku

    2014-05-05

    In this paper, we propose cooperative spectrum sensing schemes, called decode-and-forward cooperative spectrum sensing (DF-CSS) scheme and amplify-and-forward cooperative spectrum sensing (AF-CSS) scheme, in cognitive radio networks. The main goals and features of the proposed cooperative spectrum sensing schemes are as follows: first, we solve the problem of high demand for bandwidth in a soft decision scheme using in our proposed schemes. Furthermore, the impact of transmission power of relaying users which is determined by the interference constraint on sensing performance of cooperative spectrum sensing schemes is also investigated. Second, we analyze the sensing performance of our proposed cooperative spectrum sensing schemes in terms of detection probability and interference probability, respectively. We take into account the interference caused by secondary user (SU) to primary user (PU) in the case that the transmission power of the relaying users exceeds a predefined interference constraint assigned by the primary user. The simulation results show that in cooperative spectrum sensing schemes the total sensing performance depends not only on the interference tolerance level, but also on the relay protocols used. We also prove that high transmission power of relaying users increases the interference between the secondary networks and the primary network.

  10. The Effect of Online Collaboration on Adolescent Sense of Community in Eighth-Grade Physical Science

    Science.gov (United States)

    Wendt, Jillian L.; Rockinson-Szapkiw, Amanda J.

    2015-01-01

    Using a quasi-experimental, nonequivalent pretest/posttest control group design, the researchers examined the effects of online collaborative learning on eighth-grade student's sense of community in a physical science class. For a 9-week period, students in the control group participated in collaborative activities in a face-to-face learning…

  11. The Effect of Online Collaboration on Adolescent Sense of Community in Eighth-Grade Physical Science

    Science.gov (United States)

    Wendt, Jillian L.; Rockinson-Szapkiw, Amanda J.

    2015-01-01

    Using a quasi-experimental, nonequivalent pretest/posttest control group design, the researchers examined the effects of online collaborative learning on eighth-grade student's sense of community in a physical science class. For a 9-week period, students in the control group participated in collaborative activities in a face-to-face learning…

  12. Achievable Outage Rates In Cognitive Radio Networks under Imperfect Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    N. Tafaghodi Khajavi

    2012-06-01

    Full Text Available In this paper, we aim at deriving the outage rates achieved by the primary user due spectrum sensing in a cognitive radio network, that we call sensing-induced primary outage rates. To reach this goal, in the first step, instead of classical spectrum sensing techniques that evaluate sensing performance only based on correct detection of the presence of the primary user’s signal, we propose a modified framework that also takes into account the correct detection of the absence of primary user’s signal for spectrum sensing performance evaluation. In a second step, we derive the information rates achieved by the coexistence of a primary and a cognitive network. In the last step, assuming slow fading sensing channels, we derive the sensing-induced primary outage rates, i.e., outage rates achieved by the primary network in the presence of a CR with imperfect spectrum sensing, characterized by a given miss-detection probability. Numerical results show that the proposed spectrum sensing outperforms conventional spectrum sensing techniques in terms of primary signal outage rates and total achievable throughputs, without any increase in the cognitive radio complexity.

  13. Decentralized cooperative spectrum sensing for ad-hoc disaster relief network clusters

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Prasad, Neeli R.

    2010-01-01

    Disaster relief networks need to be highly adaptable and resilient in order to encompass the emergency service demands. Cognitive Radio enhanced ad-hoc architecture have been put forward as candidate to enable such networks. Spectrum sensing, the cornerstone of the Cognitive Radio paradigm, has...... been the target of intensive research, of which the main common conclusion was that the achievable spectrum sensing accuracy can be greatly enhanced through the use of cooperative sensing schemes. When considering applying Cognitive Radio to ad-hoc disaster relief networks, the use of spectrum sensing...

  14. Centralized cooperative spectrum sensing for ad-hoc disaster relief network clusters

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Prasad, Neeli R.

    2010-01-01

    Disaster relief networks have to be highly adaptable and resilient. Cognitive radio enhanced ad-hoc architecture have been put forward as a candidate to enable such networks. Spectrum sensing is the cornerstone of the cognitive radio paradigm, and it has been the target of intensive research....... The main common conclusion was that the achievable spectrum sensing accuracy can be greatly enhanced through the use of cooperative sensing schemes. When considering applying Cognitive Radio to ad-hoc disaster relief networks, spectrum sensing cooperative schemes are paramount. A centralized cluster...

  15. Kinerja Spectrum Sensing Dengan Metode Cyclostationary Feature Detector Pada Radio Kognitif

    Directory of Open Access Journals (Sweden)

    HENDRY CAHYO

    2017-06-01

    Full Text Available   Abstrak Perkembangan dalam dunia telekomunikasi nirkabel terutama spektrum frekuensi adalah hal yang perlu mendapatkan perhatian penting. Spektrum frekuensi merupakan sumber daya yang terbatas, penggunaannya harus dilakukan secara efisien dan se-maksimal mungkin. Penelitian ini membahas teknik spectrum sensing pada radio kognitif untuk menghadapi masalah keterbatasan penggunaan spektrum frekuensi. Radio kognitif merupakan sistem radio cerdas yang bisa mengatur parameternya seperti frekuensi kerja, daya pancar, dan skema modulasi secara optimal dalam melakukan proses komunikasi. Spectrum sensing merupakan teknik untuk memaksimalkan penggunaan spektrum frekuensi. Penelitian ini membandingkan kinerja metode cyclostationary feature detection dan metode energy detection pada teknik spectrum sensing menggunakan software matlab sehingga dapat diketahui bahwa kinerja cyclostationary feature detection untuk nilai Pd = 0,85 lebih handal sebesar 0,2 untuk fungsi probability of false dan lebih handal sebesar 2 dB untuk fungsi signal to noise ratio daripada energy detection. Kata kunci: radio kognitif, spectrum sensing, cyclostationary feature detection, energy detection, probability of false alarm.   Abstract Developments in the world of wireless telecommunications specially frequency spectrum is an important thing to get attention. Frequency spectrum is afinite resource, its use must be efficiently and as maximum as possible. This study discuss the technique of spectrum sensing in cognitive radio to faces the problem using restrictiveness of frequency spectrum. Cognitive radio is a smart radio system that can adjust its parameters like work frequency, emission power, and modulation scheme are optimal in the communication process. Spectrum sensing is a technique to maximize the use of the frequency spectrum. This study compared performance of cyclostationary feature detection methodh with energy detection methodh in spectrum sensing technique using

  16. Total Variation Minimization Based Compressive Wideband Spectrum Sensing for Cognitive Radios

    CERN Document Server

    Liu, Yipeng

    2011-01-01

    Wideband spectrum sensing is a critical component of a functioning cognitive radio system. Its major challenge is the too high sampling rate requirement. Compressive sensing (CS) promises to be able to deal with it. Nearly all the current CS based compressive wideband spectrum sensing methods exploit only the frequency sparsity to perform. Motivated by the achievement of a fast and robust detection of the wideband spectrum change, total variation mnimization is incorporated to exploit the temporal and frequency structure information to enhance the sparse level. As a sparser vector is obtained, the spectrum sensing period would be shorten and sensing accuracy would be enhanced. Both theoretical evaluation and numerical experiments can demonstrate the performance improvement.

  17. Collaborative Smartphone Sensing using Overlapping Coalition Formation Games

    OpenAIRE

    Di, Boya; Wang, Tianyu; Song, Lingyang; Han, Zhu

    2016-01-01

    With the rapid growth of sensor technology, smartphone sensing has become an effective approach to improve the quality of smartphone applications. However, due to time-varying wireless channels and lack of incentives for the users to participate, the quality and quantity of the data uploaded by the smartphone users are not always satisfying. In this paper, we consider a smartphone sensing system in which a platform publicizes multiple tasks, and the smartphone users choose a set of tasks to p...

  18. Coalitional Games in Partition Form for Joint Spectrum Sensing and Access in Cognitive Radio Networks

    CERN Document Server

    Saad, Walid; Zheng, Rong; Hjørungnes, Are; Başar, Tamer; Poor, H Vincent

    2012-01-01

    Unlicensed secondary users (SUs) in cognitive radio networks are subject to an inherent tradeoff between spectrum sensing and spectrum access. Although each SU has an incentive to sense the primary user (PU) channels for locating spectrum holes, this exploration of the spectrum can come at the expense of a shorter transmission time, and, hence, a possibly smaller capacity for data transmission. This paper investigates the impact of this tradeoff on the cooperative strategies of a network of SUs that seek to cooperate in order to improve their view of the spectrum (sensing), reduce the possibility of interference among each other, and improve their transmission capacity (access). The problem is modeled as a coalitional game in partition form and an algorithm for coalition formation is proposed. Using the proposed algorithm, the SUs can make individual distributed decisions to join or leave a coalition while maximizing their utilities which capture the average time spent for sensing as well as the capacity achi...

  19. A Multi-Perspective Collaborative on Teacher Learning for Teachers of Students with Autism Spectrum Disorder

    Science.gov (United States)

    West, Elizabeth A.; Jones, Phyllis; Chambers, Dianne; Whitehurst, Teresa

    2012-01-01

    The purpose of this multi-perspective collaborative research activity was to analyze moments of teacher learning as perceived by a group of teachers who educate students with the label of Autism Spectrum Disorder (ASD). The researchers in this project acknowledge the value of hearing teachers' perspectives on what works for them in their…

  20. A Modified Energy Detection Based Spectrum Sensing Algorithm for Green Cognitive Radio Communication

    Directory of Open Access Journals (Sweden)

    Sidra Rajput

    2015-10-01

    Full Text Available Spectrum Sensing is the first and fundamental function of Cognitive Cycle which plays a vital role in the success of CRs (Cognitive Radios. Spectrum Sensing indicate the presence and absence of PUs (Primary Users in RF (Radio Frequency spectrum occupancy measurements. In order to correctly determine the presence and absence of Primary Users, the algorithms in practice include complex mathematics which increases the computational complexity of the algorithm, thus shifted the CRs to operate as ?green? communication systems. In this paper, an energy efficient and computationally less complex, energy detection based Spectrum Sensing algorithm have been proposed. The design goals of the proposed algorithm are to save the processing and sensing energies. At first, by using less MAC (Multiply and Accumulate operation, it saves the processing energy needed to determine the presence and absence of PUs. Secondly, it saves the sensing energy by providing a way to find lowest possible sensing time at which spectrum is to be sensed. Two scenarios have been defined for testing the proposed algorithm i.e. simulate detection capability of Primary Users in ideal and noisy scenarios. Detection of PUs in both of these scenarios have been compared to obtain the probability of detection. Energy Efficiency of the proposed algorithm has been proved by making performance comparison between the proposed (less complex algorithm and the legacy energy detection algorithm. With reduced complexity, the proposed spectrum sensing algorithm can be considered under the paradigm of Green Cognitive Radio Communication

  1. Optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing in cognitive radio network

    Institute of Scientific and Technical Information of China (English)

    刘鑫; 仲伟志; 陈琨奇

    2015-01-01

    In order to improve the throughput of cognitive radio (CR), optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing was investigated in a CR network that includes multiple users and one fusion center. The frame structure of cooperative spectrum sensing was divided into multiple transmission time slots and one sensing time slot consisting of local energy detection and cooperative overhead. An optimization problem was formulated to maximize the throughput of CR network, subject to the constraints of both false alarm probability and detection probability. A joint optimization algorithm of sensing time and number of users was proposed to solve this optimization problem with low time complexity. An allocation algorithm of cooperative users was proposed to preferentially allocate the users to the channels with high utilization probability. The simulation results show that the significant improvement on the throughput can be achieved through the proposed joint optimization and allocation algorithms.

  2. Efficient Wideband Spectrum Sensing with Maximal Spectral Efficiency for LEO Mobile Satellite Systems

    Directory of Open Access Journals (Sweden)

    Feilong Li

    2017-01-01

    Full Text Available The usable satellite spectrum is becoming scarce due to static spectrum allocation policies. Cognitive radio approaches have already demonstrated their potential towards spectral efficiency for providing more spectrum access opportunities to secondary user (SU with sufficient protection to licensed primary user (PU. Hence, recent scientific literature has been focused on the tradeoff between spectrum reuse and PU protection within narrowband spectrum sensing (SS in terrestrial wireless sensing networks. However, those narrowband SS techniques investigated in the context of terrestrial CR may not be applicable for detecting wideband satellite signals. In this paper, we mainly investigate the problem of joint designing sensing time and hard fusion scheme to maximize SU spectral efficiency in the scenario of low earth orbit (LEO mobile satellite services based on wideband spectrum sensing. Compressed detection model is established to prove that there indeed exists one optimal sensing time achieving maximal spectral efficiency. Moreover, we propose novel wideband cooperative spectrum sensing (CSS framework where each SU reporting duration can be utilized for its following SU sensing. The sensing performance benefits from the novel CSS framework because the equivalent sensing time is extended by making full use of reporting slot. Furthermore, in respect of time-varying channel, the spatiotemporal CSS (ST-CSS is presented to attain space and time diversity gain simultaneously under hard decision fusion rule. Computer simulations show that the optimal sensing settings algorithm of joint optimization of sensing time, hard fusion rule and scheduling strategy achieves significant improvement in spectral efficiency. Additionally, the novel ST-CSS scheme performs much higher spectral efficiency than that of general CSS framework.

  3. Efficient Wideband Spectrum Sensing with Maximal Spectral Efficiency for LEO Mobile Satellite Systems

    Science.gov (United States)

    Li, Feilong; Li, Zhiqiang; Li, Guangxia; Dong, Feihong; Zhang, Wei

    2017-01-01

    The usable satellite spectrum is becoming scarce due to static spectrum allocation policies. Cognitive radio approaches have already demonstrated their potential towards spectral efficiency for providing more spectrum access opportunities to secondary user (SU) with sufficient protection to licensed primary user (PU). Hence, recent scientific literature has been focused on the tradeoff between spectrum reuse and PU protection within narrowband spectrum sensing (SS) in terrestrial wireless sensing networks. However, those narrowband SS techniques investigated in the context of terrestrial CR may not be applicable for detecting wideband satellite signals. In this paper, we mainly investigate the problem of joint designing sensing time and hard fusion scheme to maximize SU spectral efficiency in the scenario of low earth orbit (LEO) mobile satellite services based on wideband spectrum sensing. Compressed detection model is established to prove that there indeed exists one optimal sensing time achieving maximal spectral efficiency. Moreover, we propose novel wideband cooperative spectrum sensing (CSS) framework where each SU reporting duration can be utilized for its following SU sensing. The sensing performance benefits from the novel CSS framework because the equivalent sensing time is extended by making full use of reporting slot. Furthermore, in respect of time-varying channel, the spatiotemporal CSS (ST-CSS) is presented to attain space and time diversity gain simultaneously under hard decision fusion rule. Computer simulations show that the optimal sensing settings algorithm of joint optimization of sensing time, hard fusion rule and scheduling strategy achieves significant improvement in spectral efficiency. Additionally, the novel ST-CSS scheme performs much higher spectral efficiency than that of general CSS framework. PMID:28117712

  4. Efficient Wideband Spectrum Sensing with Maximal Spectral Efficiency for LEO Mobile Satellite Systems.

    Science.gov (United States)

    Li, Feilong; Li, Zhiqiang; Li, Guangxia; Dong, Feihong; Zhang, Wei

    2017-01-21

    The usable satellite spectrum is becoming scarce due to static spectrum allocation policies. Cognitive radio approaches have already demonstrated their potential towards spectral efficiency for providing more spectrum access opportunities to secondary user (SU) with sufficient protection to licensed primary user (PU). Hence, recent scientific literature has been focused on the tradeoff between spectrum reuse and PU protection within narrowband spectrum sensing (SS) in terrestrial wireless sensing networks. However, those narrowband SS techniques investigated in the context of terrestrial CR may not be applicable for detecting wideband satellite signals. In this paper, we mainly investigate the problem of joint designing sensing time and hard fusion scheme to maximize SU spectral efficiency in the scenario of low earth orbit (LEO) mobile satellite services based on wideband spectrum sensing. Compressed detection model is established to prove that there indeed exists one optimal sensing time achieving maximal spectral efficiency. Moreover, we propose novel wideband cooperative spectrum sensing (CSS) framework where each SU reporting duration can be utilized for its following SU sensing. The sensing performance benefits from the novel CSS framework because the equivalent sensing time is extended by making full use of reporting slot. Furthermore, in respect of time-varying channel, the spatiotemporal CSS (ST-CSS) is presented to attain space and time diversity gain simultaneously under hard decision fusion rule. Computer simulations show that the optimal sensing settings algorithm of joint optimization of sensing time, hard fusion rule and scheduling strategy achieves significant improvement in spectral efficiency. Additionally, the novel ST-CSS scheme performs much higher spectral efficiency than that of general CSS framework.

  5. Performance of Cooperative Spectrum Sensing over Non-Identical Fading Environments

    KAUST Repository

    Rao, Anlei

    2012-09-08

    Different from previous works in cooperative spec- trum sensing that assumed the sensing channels independent identically distributed (i.i.d.), we investigate in this paper the independent but not identically distributed (i.n.i.d.) situations. In particular, we derive the false-alarm probability and the detection probability of cooperative spectrum sensing with the scheme of energy fusion over i.n.i.d. Rayleigh, Nakagami, and Rician fading channels. From the selected numerical results, we can see that cooperative spectrum sensing still gives considerably better performance even over i.n.i.d. fading environments.

  6. The Effect of Online Collaboration on Adolescent Sense of Community in Eighth-Grade Physical Science

    Science.gov (United States)

    Wendt, Jillian L.; Rockinson-Szapkiw, Amanda J.

    2015-10-01

    Using a quasi-experimental, nonequivalent pretest/posttest control group design, the researchers examined the effects of online collaborative learning on eighth-grade student's sense of community in a physical science class. For a 9-week period, students in the control group participated in collaborative activities in a face-to-face learning environment, whereas students in the experimental group participated in online collaborative activities using the Edmodo educational platform in a hybrid learning environment. Students completed the Classroom Community Scale survey as a pretest and posttest. Results indicated that the students who participated in the face-to-face classroom had higher overall sense of community and learning community than students who participated in collaborative activities in the online environment. Results and implications are discussed and suggestions for future research are provided.

  7. Industrial Internet of Things-Based Collaborative Sensing Intelligence: Framework and Research Challenges.

    Science.gov (United States)

    Chen, Yuanfang; Lee, Gyu Myoung; Shu, Lei; Crespi, Noel

    2016-02-06

    The development of an efficient and cost-effective solution to solve a complex problem (e.g., dynamic detection of toxic gases) is an important research issue in the industrial applications of the Internet of Things (IoT). An industrial intelligent ecosystem enables the collection of massive data from the various devices (e.g., sensor-embedded wireless devices) dynamically collaborating with humans. Effectively collaborative analytics based on the collected massive data from humans and devices is quite essential to improve the efficiency of industrial production/service. In this study, we propose a collaborative sensing intelligence (CSI) framework, combining collaborative intelligence and industrial sensing intelligence. The proposed CSI facilitates the cooperativity of analytics with integrating massive spatio-temporal data from different sources and time points. To deploy the CSI for achieving intelligent and efficient industrial production/service, the key challenges and open issues are discussed, as well.

  8. Industrial Internet of Things-Based Collaborative Sensing Intelligence: Framework and Research Challenges

    Directory of Open Access Journals (Sweden)

    Yuanfang Chen

    2016-02-01

    Full Text Available The development of an efficient and cost-effective solution to solve a complex problem (e.g., dynamic detection of toxic gases is an important research issue in the industrial applications of the Internet of Things (IoT. An industrial intelligent ecosystem enables the collection of massive data from the various devices (e.g., sensor-embedded wireless devices dynamically collaborating with humans. Effectively collaborative analytics based on the collected massive data from humans and devices is quite essential to improve the efficiency of industrial production/service. In this study, we propose a collaborative sensing intelligence (CSI framework, combining collaborative intelligence and industrial sensing intelligence. The proposed CSI facilitates the cooperativity of analytics with integrating massive spatio-temporal data from different sources and time points. To deploy the CSI for achieving intelligent and efficient industrial production/service, the key challenges and open issues are discussed, as well.

  9. Full-Duplex Cooperative Sensing for Spectrum-Heterogeneous Cognitive Radio Networks.

    Science.gov (United States)

    Liu, Peng; Qi, Wangdong; Yuan, En; Wei, Li; Zhao, Yuexin

    2017-08-02

    In cognitive radio networks (CRNs), spectrum sensing is critical for guaranteeing that the opportunistic spectrum access by secondary users (SUs) will not interrupt legitimate primary users (PUs). The application of full-duplex radio to spectrum sensing enables SU to carry out sensing and transmission simultaneously, improving both spectrum awareness and CRN throughput. However, the issue of spectrum sensing with full-duplex radios deployed in heterogeneous environments, where SUs may observe different spectrum activities, has not been addressed. In this paper, we give a first look into this problem and develop a light-weight cooperative sensing framework called PaCoSIF, which involves only a pairwise SU transmitter (SU-Tx) and its receiver (SU-Rx) in cooperation. A dedicated control channel is not required for pairwise cooperative sensing with instantaneous feedback (PaCoSIF) because sensing results are collected and fused via the reverse channel provided by full-duplex radios. We present a detailed protocol description to illustrate how PaCoSIF works. However, it is a challenge to optimize the sensing performance of PaCoSIF since the two sensors suffer from spectrum heterogeneity and different kinds of interference. Our goal is to minimize the false alarm rate of PaCoSIF given the bound on the missed detection rate by adaptively adjusting the detection threshold of each sensor. We derive an expression for the optimal threshold using the Lagrange method and propose a fast binary-searching algorithm to solve it numerically. Simulations show that, with perfect signal-to-interference-and-noise-ratio (SINR) information, PaCoSIF could decrease the false alarm rate and boost CRN throughput significantly against conventional cooperative sensing when SUs are deployed in spectrum-heterogeneous environments. Finally, the impact of SINR error upon the performance of PaCoSIF is evaluated via extensive simulations.

  10. Current Trends and Research Challenges in Spectrum-Sensing for Cognitive Radios

    Directory of Open Access Journals (Sweden)

    Roopali Garg

    2016-07-01

    Full Text Available The ever increasing demand of wireless communication systems has led to search of suitable spectrum bands for transmission of data. The research in the past has revealed that radio spectrum is under-utilized in most of the scenarios. This prompted the scientist to seek a solution to utilize the spectrum efficiently. Cognitive Radios provided an answer to the problem by sensing the idle (licensed bands and allowing (secondary users to transmit in these idle spaces. Spectrum sensing forms the main block of cognition cycle. This paper reviews the current trends in research in the domain of spectrum sensing. The author describes the type of channel being modelled, diversity combining schemes used, optimal algorithms applied at fusion centre, spectrum sensing techniques employed. Further, the research challenges are discussed. It is presented that various attributes like sensing time, throughput, rate reliability, optimum cooperative users, sensing frequency etc. needs to be addressed. A trade-off needs to be established to optimize two opposing parameters like sensing and throughput.

  11. Collaborative Sense-Making in Print and Digital Text Environments

    Science.gov (United States)

    Davis, Dennis S.; Neitzel, Carin

    2012-01-01

    This study describes the sense-making behaviors of sixth- and seventh-grade students (n = 46 dyads) as they read and discussed expository articles in print and digital formats. Most dyads approached the digital text as if it were static and linear, despite the availability of hyperlinks. Reading through (or covering) the text was the most commonly…

  12. Research of Adaptive Resolution Spectrum Sensing Method Based on Discrete Wavelet Packet Transform

    Directory of Open Access Journals (Sweden)

    Wei Naiqi

    2013-09-01

    Full Text Available Spectrum sensing is the precondition of the realization of cognitive radio. In order to achieve efficient multi-resolution spectrum sensing, and find the available spectrum hole quickly, it proposes a variable resolution adaptive frequency spectrum energy sensing method based on discrete wavelet packet transform (DWPT. The method applied hierarchical decomposition and threshold denoising characteristic of wavelet packet transform, and solved the problem of subband sort disorder in wavelet packet decomposition process; it can eliminate the influence of uncertainty noise on detection performance, effectively. It also can reduce the computational complexity according to demand of selection resolution and perception band. The simulation results and its analysis show that the proposed method has advantages of high precision, simple arithmetic and fine flexibility, etc. The method is adapted to fast sensing in the cognitive radio environment.  

  13. Cluster-based spectrum sensing for cognitive radios with imperfect channel to cluster-head

    KAUST Repository

    Ben Ghorbel, Mahdi

    2012-04-01

    Spectrum sensing is considered as the first and main step for cognitive radio systems to achieve an efficient use of spectrum. Cooperation and clustering among cognitive radio users are two techniques that can be employed with spectrum sensing in order to improve the sensing performance by reducing miss-detection and false alarm. In this paper, within the framework of a clustering-based cooperative spectrum sensing scheme, we study the effect of errors in transmitting the local decisions from the secondary users to the cluster heads (or the fusion center), while considering non-identical channel conditions between the secondary users. Closed-form expressions for the global probabilities of detection and false alarm at the cluster head are derived. © 2012 IEEE.

  14. Spectrum sensing and resource allocation for multicarrier cognitive radio systems under interference and power constraints

    Science.gov (United States)

    Dikmese, Sener; Srinivasan, Sudharsan; Shaat, Musbah; Bader, Faouzi; Renfors, Markku

    2014-12-01

    Multicarrier waveforms have been commonly recognized as strong candidates for cognitive radio. In this paper, we study the dynamics of spectrum sensing and spectrum allocation functions in cognitive radio context using very practical signal models for the primary users (PUs), including the effects of power amplifier nonlinearities. We start by sensing the spectrum with energy detection-based wideband multichannel spectrum sensing algorithm and continue by investigating optimal resource allocation methods. Along the way, we examine the effects of spectral regrowth due to the inevitable power amplifier nonlinearities of the PU transmitters. The signal model includes frequency selective block-fading channel models for both secondary and primary transmissions. Filter bank-based wideband spectrum sensing techniques are applied for detecting spectral holes and filter bank-based multicarrier (FBMC) modulation is selected for transmission as an alternative multicarrier waveform to avoid the disadvantage of limited spectral containment of orthogonal frequency-division multiplexing (OFDM)-based multicarrier systems. The optimization technique used for the resource allocation approach considered in this study utilizes the information obtained through spectrum sensing and knowledge of spectrum leakage effects of the underlying waveforms, including a practical power amplifier model for the PU transmitter. This study utilizes a computationally efficient algorithm to maximize the SU link capacity with power and interference constraints. It is seen that the SU transmission capacity depends critically on the spectral containment of the PU waveform, and these effects are quantified in a case study using an 802.11-g WLAN scenario.

  15. Soft cooperative spectrum sensing performance under imperfect and non identical reporting channels

    KAUST Repository

    Ben Ghorbel, Mahdi

    2015-02-01

    Cooperation among cognitive radio users improves the spectrum sensing performance by combining local decisions measured over independent sensing channels, allowing reduction of miss-detection and false alarm probabilities. While most of the works in cooperative spectrum sensing techniques assume perfect channels between the cooperating users, this paper studies the effect of imperfect channels when local users report their sensed information to the fusion center. Cooperative detection and false-alarm probabilities are derived for a general scheme of imperfect reporting channels under non necessarily identical sensing and reporting channels. Numerical simulations show that imperfect reporting channels should be considered to optimize the cooperative sensing in terms of consumed energy and probability of error.

  16. Universal and efficient compressed sensing by spread spectrum and application to realistic Fourier imaging techniques

    CERN Document Server

    Puy, Gilles; Gribonval, Rémi; Wiaux, Yves

    2011-01-01

    We advocate a compressed sensing strategy that consists of multiplying the signal of interest by a wide bandwidth modulation before projection onto randomly selected vectors of an orthonormal basis. Firstly, in a digital setting with random modulation, considering a whole class of sensing bases including the Fourier basis, we prove that the technique is universal in the sense that the required number of measurements for accurate recovery is optimal and independent of the sparsity basis. This universality stems from a drastic decrease of coherence between the sparsity and the sensing bases, which for a Fourier sensing basis relates to a spread of the original signal spectrum by the modulation (hence the name "spread spectrum"). The approach is also efficient as sensing matrices with fast matrix multiplication algorithms can be used, in particular in the case of Fourier measurements. Secondly, these results are confirmed by a numerical analysis of the phase transition of the l1- minimization problem. Finally, w...

  17. System Capacity Limits Introduced by Data Fusion on Cooperative Spectrum Sensing under Correlated Environments

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Prasad, Neeli R.

    2010-01-01

    Spectrum sensing, the cornerstone of the Cognitive Radio paradigm, has been the focus of intensive research, from which the main conclusion was that its performance can be greatly enhanced through the use of cooperative sensing schemes. Nevertheless, if a proper design of the cooperative scheme i...

  18. Capacity limits introduced by data fusion on cooperative spectrum sensing under correlated environments

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Rodrigues, Antonio

    2010-01-01

    scenarios encompassing different degree of environment correlation between the cluster nodes, number of cluster nodes and sensed channel occupation statistics. Through this study we motivate that to maximize the perceived capacity by the cooperative spectrum sensing, the use of data fusion needs...

  19. Sense of Belonging and Life Transitions for Two Females with Autism Spectrum Disorder in Finland

    Science.gov (United States)

    Pesonen, Henri V.; Kontu, Elina K.; Pirttimaa, Raija A.

    2015-01-01

    Sense of belonging refers to the degree to which individuals feel included, accepted, and supported by others in a variety of social settings. This study, based on the narratives of two females (ages 26 and 29) with Autism Spectrum Disorder (ASD), examines sense of belonging and various life transition issues that may appear throughout childhood,…

  20. Sense of Belonging and Life Transitions for Two Females with Autism Spectrum Disorder in Finland

    Science.gov (United States)

    Pesonen, Henri V.; Kontu, Elina K.; Pirttimaa, Raija A.

    2015-01-01

    Sense of belonging refers to the degree to which individuals feel included, accepted, and supported by others in a variety of social settings. This study, based on the narratives of two females (ages 26 and 29) with Autism Spectrum Disorder (ASD), examines sense of belonging and various life transition issues that may appear throughout childhood,…

  1. The Effect of Online Collaborative Learning on Middle School Student Science Literacy and Sense of Community

    Science.gov (United States)

    Wendt, Jillian Leigh

    2013-01-01

    This study examines the effects of online collaborative learning on middle school students' science literacy and sense of community. A quantitative, quasi-experimental pretest/posttest control group design was used. Following IRB approval and district superintendent approval, students at a public middle school in central Virginia completed a…

  2. Collaborative autonomous sensing with Bayesians in the loop

    Science.gov (United States)

    Ahmed, Nisar

    2016-10-01

    There is a strong push to develop intelligent unmanned autonomy that complements human reasoning for applications as diverse as wilderness search and rescue, military surveillance, and robotic space exploration. More than just replacing humans for `dull, dirty and dangerous' work, autonomous agents are expected to cope with a whole host of uncertainties while working closely together with humans in new situations. The robotics revolution firmly established the primacy of Bayesian algorithms for tackling challenging perception, learning and decision-making problems. Since the next frontier of autonomy demands the ability to gather information across stretches of time and space that are beyond the reach of a single autonomous agent, the next generation of Bayesian algorithms must capitalize on opportunities to draw upon the sensing and perception abilities of humans-in/on-the-loop. This work summarizes our recent research toward harnessing `human sensors' for information gathering tasks. The basic idea behind is to allow human end users (i.e. non-experts in robotics, statistics, machine learning, etc.) to directly `talk to' the information fusion engine and perceptual processes aboard any autonomous agent. Our approach is grounded in rigorous Bayesian modeling and fusion of flexible semantic information derived from user-friendly interfaces, such as natural language chat and locative hand-drawn sketches. This naturally enables `plug and play' human sensing with existing probabilistic algorithms for planning and perception, and has been successfully demonstrated with human-robot teams in target localization applications.

  3. Performance Analysis of Cognitive Radio for Wi-Fi Signals Using Cyclostationary Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    Mandeep Singh

    2014-08-01

    Full Text Available The need for radio spectrum usage is increasing day by day with recent advancements in wireless system. But there is limited amount of spectrum available. So that for solving this problem Cognitive Radio (CR is used for purpose of the spectrum utilization properly. Basically the Licensed users use the licensed bands but the unlicensed users should always check spectrum with the help of CR technology. The main aim of cognitive radio is to sense the spectrum continuously. In this paper, we have provided the proposal that how the capacity of the system can be increased by reuse the unused licensed band by simulating a Cognitive radio system. The secondary users can occupy free space (spectrum holes and also licensed bands by continuously monitoring the spectrum. The requirements of cognitive radio systems will be investigated by considering spectrum sensing techniques. To achieve this, a Cyclostationary Spectrum Sensing technique is studied and applied to detect OFDM signals in a noisy environment. The results are obtained for the applications employed in high frequency, such as, Wi-Fi.

  4. Suggestions for Formulating Collaborative Remote Sensing Emergency Plan Based on Case Studies

    Science.gov (United States)

    Liu, B.; Wang, F.; Zheng, X.; Qi, M.

    2017-09-01

    With the rapid development of the Remote Sensing (RS) technology, Remote Sensing Services for Emergency Monitoring (RSSEM) are playing a more and more important role in the field of emergency management, where the collaborative RS approaches (including such as Space-Air-Ground platforms) can provide the decision-makers a quick access to the detailed, real-time information about the emergencies. However, there are still some problems in the current mechanism of RSSEM, for example, the inappropriate choices of the collaborative RS approaches, the miscellaneous procedures and so on. It is urgent to formulate a collaborative RS emergency plan for regulating the applications of the RS monitoring approaches in order to be well prepared for the emergency management. In our studies, creating a good collaborative RS emergency plan is the main research objective. This paper is divided into four parts. The Part Ⅰ gives a brief introduction about the research background. The Part Ⅱ investigates four case studies to analyze the applications of the RS technologies under the guidance of the available RS related emergency plans, and then points out the existing problems in the mechanism of the RSSEM. The Part Ⅲ proposes our suggestions for formulating the collaborative RS emergency plan to explore the countermeasures of the problems pointed out in the Part Ⅱ. The last part concludes this paper and discusses the future work of the collaborative RS emergency plan.

  5. A Robust FLOM Based Spectrum Sensing Scheme under Middleton Class A Noise in IoT

    Directory of Open Access Journals (Sweden)

    Enwei Xu

    2017-01-01

    Full Text Available Accessibility to remote users in dynamic environment, high spectrum utilization, and no spectrum purchase make Cognitive Radio (CR a feasible solution of wireless communications in the Internet of Things (IoT. Reliable spectrum sensing becomes the prerequisite for the establishment of communication between IoT-capable objects. Considering the application environment, spectrum sensing not only has to cope with man-made impulsive noises but also needs to overcome noise fluctuations. In this paper, we study the Fractional Lower Order Moments (FLOM based spectrum sensing method under Middleton Class A noise and incorporate a Noise Power Estimation (NPE module into the sensing system to deal with the issue of noise uncertainty. Moreover, the NPE process does not need noise-only samples. The analytical expressions of the probabilities of detection and the probability of false alarm are derived. The impact on sensing performance of the parameters of the NPE module is also analyzed. The theoretical analysis and simulation results show that our proposed sensing method achieves a satisfactory performance at low SNR.

  6. Coalitional Games in Partition Form for Joint Spectrum Sensing and Access in Cognitive Radio Networks

    Science.gov (United States)

    Saad, Walid; Han, Zhu; Zheng, Rong; Hjorungnes, Are; Basar, Tamer; Poor, H. Vincent

    2012-04-01

    Unlicensed secondary users (SUs) in cognitive radio networks are subject to an inherent tradeoff between spectrum sensing and spectrum access. Although each SU has an incentive to sense the primary user (PU) channels for locating spectrum holes, this exploration of the spectrum can come at the expense of a shorter transmission time, and, hence, a possibly smaller capacity for data transmission. This paper investigates the impact of this tradeoff on the cooperative strategies of a network of SUs that seek to cooperate in order to improve their view of the spectrum (sensing), reduce the possibility of interference among each other, and improve their transmission capacity (access). The problem is modeled as a coalitional game in partition form and an algorithm for coalition formation is proposed. Using the proposed algorithm, the SUs can make individual distributed decisions to join or leave a coalition while maximizing their utilities which capture the average time spent for sensing as well as the capacity achieved while accessing the spectrum. It is shown that, by using the proposed algorithm, the SUs can self-organize into a network partition composed of disjoint coalitions, with the members of each coalition cooperating to jointly optimize their sensing and access performance. Simulation results show the performance improvement that the proposed algorithm yields with respect to the non-cooperative case. The results also show how the algorithm allows the SUs to self-adapt to changes in the environment such as the change in the traffic of the PUs, or slow mobility.

  7. Spread Spectrum Based Energy Efficient Collaborative Communication in Wireless Sensor Networks.

    Science.gov (United States)

    Ghani, Anwar; Naqvi, Husnain; Sher, Muhammad; Khan, Muazzam Ali; Khan, Imran; Irshad, Azeem

    2016-01-01

    Wireless sensor networks consist of resource limited devices. Most crucial of these resources is battery life, as in most applications like battle field or volcanic area monitoring, it is often impossible to replace or recharge the power source. This article presents an energy efficient collaborative communication system based on spread spectrum to achieve energy efficiency as well as immunity against jamming, natural interference, noise suppression and universal frequency reuse. Performance of the proposed system is evaluated using the received signal power, bit error rate (BER) and energy consumption. The results show a direct proportionality between the power gain and the number of collaborative nodes as well as BER and signal-to-noise ratio (Eb/N0). The analytical and simulation results of the proposed system are compared with SISO system. The comparison reveals that SISO perform better than collaborative communication in case of small distances whereas collaborative communication performs better than SISO in case of long distances. On the basis of these results it is safe to conclude that collaborative communication in wireless sensor networks using wideband systems improves the life time of nodes in the networks thereby prolonging the network's life time.

  8. Optimal Entropy-Based Cooperative Spectrum Sensing for Maritime Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Waleed Ejaz

    2013-11-01

    Full Text Available Maritime cognitive radio networks (MCRNs have recently been proposed for opportunistic utilization of the licensed band. Spectrum sensing is one of the key issues for the successful deployment of the MCRNs. The maritime environment is unique in terms of radio wave propagation over water, surface reflection and wave occlusions. In order to deal with the challenging maritime environment, we proposed an optimal entropy-based cooperative spectrum sensing. As the results of spectrum sensing are sensitive to the number of samples in an entropy-based local detection scheme, we first calculated the optimal number of samples. Next, a cooperative spectrum sensing scheme considering the conditions of the sea environment is proposed. Finally, the throughput optimization of the m-out-of-n rule is considered. Results revealed that although the existing schemes work well for the lower sea states, they fail to perform at higher sea states. Moreover, simulation results also indicated the robustness of the entropy-based scheme and the proposed cooperative spectrum sensing scheme at higher sea states in comparison with the traditional energy detector.

  9. Removing non-stationary noise in spectrum sensing using matrix factorization

    Science.gov (United States)

    van Bloem, Jan-Willem; Schiphorst, Roel; Slump, Cornelis H.

    2013-12-01

    Spectrum sensing is key to many applications like dynamic spectrum access (DSA) systems or telecom regulators who need to measure utilization of frequency bands. The International Telecommunication Union (ITU) recommends a 10 dB threshold above the noise to decide whether a channel is occupied or not. However, radio frequency (RF) receiver front-ends are non-ideal. This means that the obtained data is distorted with noise and imperfections from the analog front-end. As part of the front-end the automatic gain control (AGC) circuitry mainly affects the sensing performance as strong adjacent signals lift the noise level. To enhance the performance of spectrum sensing significantly we focus in this article on techniques to remove the noise caused by the AGC from the sensing data. In order to do this we have applied matrix factorization techniques, i.e., SVD (singular value decomposition) and NMF (non-negative matrix factorization), which enables signal space analysis. In addition, we use live measurement results to verify the performance and to remove the effects of the AGC from the sensing data using above mentioned techniques, i.e., applied on block-wise available spectrum data. In this article it is shown that the occupancy in the industrial, scientific and medical (ISM) band, obtained by using energy detection (ITU recommended threshold), can be an overestimation of spectrum usage by 60%.

  10. TESTBED IMPLEMENTATION OF MULTI DIMENSIONAL SPECTRUM SENSING SCHEMES FOR COGNITIVE RADIO

    Directory of Open Access Journals (Sweden)

    Deepa N Reddy

    2016-06-01

    Full Text Available Cognitive Radio (CR is a promising technology to exploit the underutilized spectrum. Spectrum sensing is one of the most important components for the establishment of cognitive radio system. Spectrum sensing allows the secondary users (SUs to detect the presence of the primary users (PUs. The aim of this work is to create a CR environment to study the spectrum sensing methods using Universal software radio Peripheral (USRP boards. In this paper a novel method of estimation of spectrum opportunities in multiple dimensions especially the space and the angle dimensions are carried out on USRP boards. This paper typically provides the experimental results carried out in an indoor wireless environment. To enhance the sensing performance the space dimension is firstly studied using spatial diversity of the cooperative SUs. Secondly the receiver diversity is analyzed using multiple antennas to enhance the error performance of the wireless system. The spectrum usage is also determined in the angle dimension by investigating the direction of the dominant signals using MUSIC algorithm.

  11. Wideband spectrum sensing order for cognitive radios with sensing errors and channel SNR probing uncertainty

    KAUST Repository

    Hamza, Doha R.

    2013-04-01

    A secondary user (SU) seeks to transmit by sequentially sensing statistically independent primary user (PU) channels. If a channel is sensed free, it is probed to estimate the signal-to-noise ratio between the SU transmitter-receiver pair over the channel. We jointly optimize the channel sensing time, the sensing decision threshold, the channel probing time, together with the channel sensing order under imperfect synchronization between the PU and the SU. The sensing and probing times and the decision threshold are assumed to be the same for all channels. We maximize a utility function related to the SU throughput under the constraint that the collision probability with the PU is kept below a certain value and taking sensing errors into account. We illustrate the optimal policy and the variation of SU throughput with various system parameters. © 2012 IEEE.

  12. Green Cooperative Spectrum Sensing and Scheduling in Heterogeneous Cognitive Radio Networks

    KAUST Repository

    Celik, Abdulkadir

    2016-09-12

    In this paper, we consider heterogeneous cognitive radio networks (CRNs) comprising primary channels (PCs) with heterogeneous characteristics and secondary users (SUs) with various sensing and reporting qualities for different PCs. We first define the opportunity as the achievable total data rate and its cost as the energy consumption caused from sensing, reporting, and channel switching operations and formulate a joint spectrum discovery and energy efficiency objective to minimize the energy spent per unit of data rate. Then, a mixed integer nonlinear programming problem is formulated to determine: 1) the optimal subset of PCs to be scheduled for sensing; 2) the SU assignment set for each scheduled PC; and 3) sensing durations and detection thresholds of each SU on PCs it is assigned to sense. Thereafter, an equivalent convex framework is developed for specific instances of the above combinatorial problem. For comparison, optimal detection and sensing thresholds are also derived analytically under the homogeneity assumption. Based on these, a prioritized ordering heuristic is developed to order channels under the spectrum, energy, and spectrum-energy limited regimes. After that, a scheduling and assignment heuristic is proposed and is shown to perform very close to the exhaustive optimal solution. Finally, the behavior of the CRN is numerically analyzed under these regimes with respect to different numbers of SUs, PCs, and sensing qualities.

  13. Collaborative mobile sensing and computing for civil infrastructure condition assessment: framework and applications

    Science.gov (United States)

    Chen, Jianfei; Chen, ZhiQiang

    2012-04-01

    Multi-function sensing and imaging devices, GPS, communication and computing devices are being ubiquitously used in field by engineers in civil engineering and emergence response practice. Field engineers, however, still have difficulty to balance between ever-increasing data collection demand and capacity of real-time data processing and knowledge sharing. In addition, field engineers usually work collaboratively in a geospatially large area; however, the existing sensing and computing modalities used in the field are not designed to accommodate this condition. In this paper, we present a solution framework of collaborative mobile sensing and computing (CMSC) for civil infrastructure condition assessment, with the Android-based mobile devices as the basic nodes in the framework with a potential of adding other auxiliary imaging and sensing devices into the network. Difficulties in mixed C++ and Java code programming that are critical to realize the framework are discussed. With a few prototypes illustrated in this paper, we envisage that the proposed CMSC framework will enable seamless integration of sensing, imaging, real-time processing and knowledge discovery in future engineers-centered field reconnaissances and civil infrastructure condition assessment.

  14. Spectrum Sensing Based on Censored Observations in Time-Varying Channels using AR-1 Model

    Directory of Open Access Journals (Sweden)

    Dhaval K Patel

    2015-01-01

    Full Text Available Non-parametric sensing algorithms are preferred in cognitive radio. In this paper, spectrum sensing method based on censored observations is proposed. We evaluate the performance of Censored Anderson-Darling (CAD sensing method in time-varying and flat-fading channel using Monte Carlo simulations. We have shown the performance of the CAD sensing in terms of receiver operating characteristic (ROC. The considered channel is modeled by Gaussian variables and characterized by a first ordered autoregressive process ($AR1$. It is shown that the proposed method outperforms prevailing techniques such as the Energy detection (ED sensing and  Order-statistic (OS based sensing in time-varying channel at lower signal to noise ratio.

  15. Mitigating RF Front-End Nonlinearity of Sensor Nodes to Enhance Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    Lin Hu

    2016-11-01

    Full Text Available The cognitive radio wireless sensor network (CR-WSN has gained worldwide attention in recent years for its potential applications. Reliable spectrum sensing is the premise for opportunistic access to sensor nodes. However, as a result of the radio frequency (RF front-end nonlinearity of sensor nodes, distortion products can easily degrade the spectrum sensing performance by causing false alarms and degrading the detection probability. Given the limitations of the widely-used adaptive interference cancellation (AIC algorithm, this paper develops several details to avoid these limitations and form a new mitigation architecture to alleviate nonlinear distortions. To demonstrate the efficiency of the proposed algorithm, verification tests for both simulations and actual RF front-end measurements are presented and discussed. The obtained results show that distortions can be suppressed significantly, thus improving the reliability of spectrum sensing. Moreover, compared to AIC, the proposed algorithm clearly shows better performance, especially at the band edges of the interferer signal.

  16. Mitigating RF Front-End Nonlinearity of Sensor Nodes to Enhance Spectrum Sensing.

    Science.gov (United States)

    Hu, Lin; Ma, Hong; Zhang, Hua; Zhao, Wen

    2016-11-25

    The cognitive radio wireless sensor network (CR-WSN) has gained worldwide attention in recent years for its potential applications. Reliable spectrum sensing is the premise for opportunistic access to sensor nodes. However, as a result of the radio frequency (RF) front-end nonlinearity of sensor nodes, distortion products can easily degrade the spectrum sensing performance by causing false alarms and degrading the detection probability. Given the limitations of the widely-used adaptive interference cancellation (AIC) algorithm, this paper develops several details to avoid these limitations and form a new mitigation architecture to alleviate nonlinear distortions. To demonstrate the efficiency of the proposed algorithm, verification tests for both simulations and actual RF front-end measurements are presented and discussed. The obtained results show that distortions can be suppressed significantly, thus improving the reliability of spectrum sensing. Moreover, compared to AIC, the proposed algorithm clearly shows better performance, especially at the band edges of the interferer signal.

  17. Distributed Cooperative Spectrum Sensing in Mobile Ad Hoc Networks with Cognitive Radios

    CERN Document Server

    Yu, F Richard; Huang, Minyi; Mason, Peter; Li, Zhiqiang

    2011-01-01

    In cognitive radio mobile ad hoc networks (CR-MANETs), secondary users can cooperatively sense the spectrum to detect the presence of primary users. In this chapter, we propose a fully distributed and scalable cooperative spectrum sensing scheme based on recent advances in consensus algorithms. In the proposed scheme, the secondary users can maintain coordination based on only local information exchange without a centralized common receiver. We use the consensus of secondary users to make the final decision. The proposed scheme is essentially based on recent advances in consensus algorithms that have taken inspiration from complex natural phenomena including flocking of birds, schooling of fish, swarming of ants and honeybees. Unlike the existing cooperative spectrum sensing schemes, there is no need for a centralized receiver in the proposed schemes, which make them suitable in distributed CR-MANETs. Simulation results show that the proposed consensus schemes can have significant lower missing detection prob...

  18. Spectrum sensing algorithm based on autocorrelation energy in cognitive radio networks

    Science.gov (United States)

    Ren, Shengwei; Zhang, Li; Zhang, Shibing

    2016-10-01

    Cognitive radio networks have wide applications in the smart home, personal communications and other wireless communication. Spectrum sensing is the main challenge in cognitive radios. This paper proposes a new spectrum sensing algorithm which is based on the autocorrelation energy of signal received. By taking the autocorrelation energy of the received signal as the statistics of spectrum sensing, the effect of the channel noise on the detection performance is reduced. Simulation results show that the algorithm is effective and performs well in low signal-to-noise ratio. Compared with the maximum generalized eigenvalue detection (MGED) algorithm, function of covariance matrix based detection (FMD) algorithm and autocorrelation-based detection (AD) algorithm, the proposed algorithm has 2 11 dB advantage.

  19. Analytical Simulation and Performance Optimization for Spectrum Sensing in Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Ayman A. El-Saleh

    2011-02-01

    Full Text Available Dynamic spectrum allocation (DSA solutions such as cognitive radio networks (CRNs have been proposed as a key technology to exploit the frequency segments that are spectrally underutilized. In this paper, the performance of cooperative CRNs has been analyzed under two different operational modes, namely, constant primary user protection (CPUP and constant secondary user spectrum usability (CSUSU. The CRN performance metrics have been selected to be the overall CRN capacity and the overall interference from CRN to the primary users under CPUP and CSUSU scenario, respectively. Computer simulations are invoked to evaluate the CRN performance with varying the sensing time as well as the number of cooperating users in the network and the observations have been presented. Finally, particle swarm ptimization algorithm has been used to jointly optimize the sensing time duration and cooperation level of spectrum sensing in CRNs. The simulation results show that the CRN performance can be noticeably improved by applying suitable optimization algorithms.

  20. Robust Cooperative Spectrum Sensing for Disaster Relief Networks in Correlated Environments

    CERN Document Server

    Pratas, Nuno; Prasad, Neeli Rashmi; Rodrigues, Antonio; Prasad, Ramjee

    2009-01-01

    Disaster relief networks are designed to be adaptable and resilient so to encompass the demands of the emergency service. Cognitive Radio enhanced ad-hoc architecture has been put forward as a candidate to enable such networks. Spectrum sensing, the cornerstone of the Cognitive Radio paradigm, has been the focus of intensive research, from which the main conclusion was that its performance can be greatly enhanced through the use of cooperative sensing schemes. To apply the Cognitive Radio paradigm to Ad-hoc disaster relief networks, the design of effective cooperative spectrum sensing schemes is essential. In this paper we propose a cluster based orchestration cooperative sensing scheme, which adapts to the cluster nodes surrounding radio environment state as well as to the degree of correlation observed between those nodes. The proposed scheme is given both in a centralized as well as in a decentralized approach. In the centralized approach, the cluster head controls and adapts the distribution of the cluste...

  1. Analytical and Learning-Based Spectrum Sensing Time Optimization in Cognitive Radio Systems

    CERN Document Server

    Ghadikolaei, Hossein Shokri; Nasiri-Kenari, Masoumeh

    2011-01-01

    Powerful spectrum sensing schemes enable cognitive radios (CRs) to find transmission opportunities in spectral resources allocated exclusively to the primary users. In this paper, maximizing the average throughput of a secondary user by optimizing its spectrum sensing time is formulated assuming that a prior knowledge of the presence and absence probabilities of the primary users is available. The energy consumed for finding a transmission opportunity is evaluated and a discussion on the impact of the number of the primary users on the secondary user throughput and consumed energy is presented. In order to avoid the challenges associated with the analytical method, as a second solution, a systematic neural network-based sensing time optimization approach is also proposed in this paper. The proposed adaptive scheme is able to find the optimum value of the channel sensing time without any prior knowledge or assumption about the wireless environment. The structure, performance, and cooperation of the artificial ...

  2. Goodness-of-fit based secure cooperative spectrum sensing for cognitive radio network.

    Science.gov (United States)

    Vu-Van, Hiep; Koo, Insoo

    2014-01-01

    Cognitive radio (CR) is a promising technology for improving usage of frequency band. Cognitive radio users (CUs) are allowed to use the bands without interference in operation of licensed users. Reliable sensing information about status of licensed band is a prerequirement for CR network. Cooperative spectrum sensing (CSS) is able to offer an improved sensing reliability compared to individual sensing. However, the sensing performance of CSS can be destroyed due to the appearance of some malicious users. In this paper, we propose a goodness-of-fit (GOF) based cooperative spectrum sensing scheme to detect the dissimilarity between sensing information of normal CUs and that of malicious users, and reject their harmful effect to CSS. The empirical CDF will be used in GOF test to determine the measured distance between distributions of observation sample set according to each hypothesis of licensed user signal. Further, the DS theory is used to combine results of multi-GOF tests. The simulation results demonstrate that the proposed scheme can protect the sensing process against the attack from malicious users.

  3. Generalized FMD Detection for Spectrum Sensing Under Low Signal-to-Noise Ratio

    CERN Document Server

    Lin, Feng; Hu, Zhen; Hou, Shujie; Browning, James P; Wicks, Michael C

    2012-01-01

    Spectrum sensing is a fundamental problem in cognitive radio. We propose a function of covariance matrix based detection algorithm for spectrum sensing in cognitive radio network. Monotonically increasing property of function of matrix involving trace operation is utilized as the cornerstone for this algorithm. The advantage of proposed algorithm is it works under extremely low signal-to-noise ratio, like lower than -30 dB with limited sample data. Theoretical analysis of threshold setting for the algorithm is discussed. A performance comparison between the proposed algorithm and other state-of-the-art methods is provided, by the simulation on captured digital television (DTV) signal.

  4. A Novel Algorithm for Cooperative Distributed Sequential Spectrum Sensing in Cognitive Radio

    CERN Document Server

    S, Jithin K

    2010-01-01

    This paper considers cooperative spectrum sensing in Cognitive Radios. In our previous work we have developed DualSPRT, a distributed algorithm for cooperative spectrum sensing using Sequential Probability Ratio Test (SPRT) at the Cognitive Radios as well as at the fusion center. This algorithm works well, but is not optimal. In this paper we propose an improved algorithm- SPRT-CSPRT, which is motivated from Cumulative Sum Procedures (CUSUM). We analyse it theoretically. We also modify this algorithm to handle uncertainties in SNR's and fading.

  5. A localized cooperative wideband spectrum sensing for dynamic access of TV bands using RF sensor networks

    KAUST Repository

    Mirza, Mohammed

    2011-07-01

    In this paper we address and simulate a Radio Frequency (RF) sensor network for a cooperative spectrum sensing and localization scheme. The proposed method integrates a Wavelet based Multi-Resolution Spectrum Sensing (MRSS), an N-bit hard combination technique for cooperative decision making and a Received Signal Strength (RSS) based localization algorithm to detect the availability of frequency bands and the location of the usable base station. We develop an N-bit hard combination technique and compare its performance to a traditionally used 2-bit hard combination for cooperative sensing. The key idea is to design a novel RF sensor network based cooperative wideband spectrum sensing and localization scheme by using a wavelet based Multi-Resolution Spectrum Sensing (MRSS) and Received Signal Strength (RSS) Localization techniques which were originally proposed for cognitive radio applications. The performance evaluations are also done to show the different detection accuracies for varying parameters such as number of sensor nodes, Signal to Noise Ratios (SNR) and number of averaged Power Spectral Densities (PSD). The proposed scheme improves the problems of shadowing, fading and noise. In addition, the RSS based localization technique was shown to be an acceptable means of estimating the position of the available transmitter. © 2011 IEEE.

  6. PERFORMANCE OF OPPORTUNISTIC SPECTRUM ACCESS WITH SENSING ERROR IN COGNITIVE RADIO AD HOC NETWORKS

    Directory of Open Access Journals (Sweden)

    N. ARMI

    2012-04-01

    Full Text Available Sensing in opportunistic spectrum access (OSA has a responsibility to detect the available channel by performing binary hypothesis as busy or idle states. If channel is busy, secondary user (SU cannot access and refrain from data transmission. SU is allowed to access when primary user (PU does not use it (idle states. However, channel is sensed on imperfect communication link. Fading, noise and any obstacles existed can cause sensing errors in PU signal detection. False alarm detects idle states as a busy channel while miss-identification detects busy states as an idle channel. False detection makes SU refrain from transmission and reduces number of bits transmitted. On the other hand, miss-identification causes SU collide to PU transmission. This paper study the performance of OSA based on the greedy approach with sensing errors by the restriction of maximum collision probability allowed (collision threshold by PU network. The throughput of SU and spectrum capacity metric is used to evaluate OSA performance and make comparisons to those ones without sensing error as function of number of slot based on the greedy approach. The relations between throughput and signal to noise ratio (SNR with different collision probability as well as false detection with different SNR are presented. According to the obtained results show that CR users can gain the reward from the previous slot for both of with and without sensing errors. It is indicated by the throughput improvement as slot number increases. However, sensing on imperfect channel with sensing errors can degrade the throughput performance. Subsequently, the throughput of SU and spectrum capacity improves by increasing maximum collision probability allowed by PU network as well. Due to frequent collision with PU, the throughput of SU and spectrum capacity decreases at certain value of collision threshold. Computer simulation is used to evaluate and validate these works.

  7. Kinerja Spectrum Sensing dengan Metode Matched Filter Detector pada Radio Kognitif

    Directory of Open Access Journals (Sweden)

    BAYU ANGGA

    2017-06-01

    Full Text Available Abstrak Evolusi sistem nirkabel dan teknologi saat ini telah membuat dampak besar pada masyarakat. Namun, disaat yang sama pengelolaan dan pemanfaatan kelangkaan spektrum tidak efisien. Radio kognitif adalah paradigma baru dalam merancang sistem komunikasi nirkabel yang bertujuan untuk meningkatkan pemanfaatan spektrum frekuensi radio (RF dan mengurangi seminimal mungkin kelangkaan spektrum. Spectrum sensing adalah langkah utama yang akan memungkinkan jaringan radio kognitif, yaitu untuk menentukan status spektrum dan aktivitas pengguna utama secara berkala, dengan menggunakan metode matched filter detector dan energy detector sebagai pembandingnya. Hasil dari kinerja spectrum sensing berdasarkan simulasi, menunjukan kinerja matched filter detector membutuhkan SNR = 15 dB untuk mencapai probability detection (Pd sebesar 100%, dengan probability false alarm sebesar 0,01, sedangkan energy detector hanya membutuhkan SNR = 14,2 dB. Secara keseluruhan untuk deteksi sinyal yang optimal kinerja matched filter detector tidak lebih baik dibanding kinerja energy detector. Kata kunci: spectrum sensing, radio kognitif, probability detection, matched filter detector, energy detector. Abstract The evolution of wireless systems and current technology has made a huge impact on society. However, at the same time the management and utilization of spectrum scarcity is not efficient. Cognitive Radio is a new paradigm in designing wireless communication system that aims to improve the utilization of the radio frequency spectrum (RF and reduce to a minimum the scarcity of spectrum. Spectrum sensing is a major step that will allow the cognitive radio networks, namely to determine the status of the spectrum and activity of the primary user at regular intervals, using the method of matched filter detector and energy detector as a comparison. The results of the performance spectrum sensing based on simulations, indicates the performance matched filter detector requires

  8. Secure cooperative spectrum sensing for the cognitive radio network using nonuniform reliability.

    Science.gov (United States)

    Usman, Muhammad; Koo, Insoo

    2014-01-01

    Both reliable detection of the primary signal in a noisy and fading environment and nullifying the effect of unauthorized users are important tasks in cognitive radio networks. To address these issues, we consider a cooperative spectrum sensing approach where each user is assigned nonuniform reliability based on the sensing performance. Users with poor channel or faulty sensor are assigned low reliability. The nonuniform reliabilities serve as identification tags and are used to isolate users with malicious behavior. We consider a link layer attack similar to the Byzantine attack, which falsifies the spectrum sensing data. Three different strategies are presented in this paper to ignore unreliable and malicious users in the network. Considering only reliable users for global decision improves sensing time and decreases collisions in the control channel. The fusion center uses the degree of reliability as a weighting factor to determine the global decision in scheme I. Schemes II and III consider the unreliability of users, which makes the computations even simpler. The proposed schemes reduce the number of sensing reports and increase the inference accuracy. The advantages of our proposed schemes over conventional cooperative spectrum sensing and the Chair-Varshney optimum rule are demonstrated through simulations.

  9. Energy-Based Cooperative Spectrum Sensing of SC-FDMA Systems

    Directory of Open Access Journals (Sweden)

    Fucheng Yang

    2014-07-01

    Full Text Available In this paper, we propose a frequency-hopping M-ary frequency-shift keying spectrum sensing network (FH/MFSK SSN for identifying the on/off states of the users supported by a single-carrier frequency-division multiple assess (SC-FDMA primary radio (PR system. Specifically, the spectrums of an uplink interleaved frequency-division multiple access (IFDMA PR system are monitored by a number of cognitive radio sensing nodes (CRSNs. These CRSNs distributedly detect the on/off states of users based on one of the three energy detection schemes. After the local spectrum sensing, the CRSNs transmit their detected states to a fusion centre (FC with the aid of FH/MFSK techniques. At the FC, the on/off states of the users supported the IFDMA PR system are finally classified according to either the conventional equal-gain combining (EGC scheme or the novel erasure-supported EGC (ES-EGC scheme. In this way, the on/off information about the spectrums occupied by an IFDMA PR systemcan be obtained, so that they can be exploited by a cognitive radio (CR system. For local spectrum sensing, in this paper, we consider four synchronisation scenarios concerning the synchronisation between the received IFDMA signals and the CRSNs. The performance of the FH/MFSK SSN associated with various schemes is investigated by simulations. Our studies show that the FH/MFSK SSN constitutes one of the highly reliable spectrum sensing schemes, which are capable of exploiting both the space diversity provided by local CRSNs and the frequency diversity provided by the subcarriers of IFDMA system.

  10. Studying an inexpensive wire discone antenna as a candidate for TVWS spectrum monitoring / sensing

    CSIR Research Space (South Africa)

    Lysko, AA

    2014-10-01

    Full Text Available -Petersburg, Russia, 8-10 October 2014 Studying an Inexpensive Wire Discone Antenna as a Candidate for TVWS Spectrum Monitoring / Sensing Albert A. Lysko1 , Andy Lee2, Arno Hart3, David L. Johnson4 1Meraka Institute Council for Scientific and Industrial Research...

  11. Spectrum sensing using single-radio switched-beam antenna systems

    DEFF Research Database (Denmark)

    Tsakalaki, Elpiniki; Wilcox, David; De Carvalho, Elisabeth

    2012-01-01

    The paper describes spectrum sensing using single-radio switched-beam arrays with reactance-loaded parasitic elements. At a given frequency, the antenna's loading conditions (reactive loads) are optimized for maximum average beamforming gain in the beampattern look direction. Circular permutations...

  12. Spectrum sensing using single-radio switched-beam antenna systems

    DEFF Research Database (Denmark)

    Tsakalaki, Elpiniki; Wilcox, David; De Carvalho, Elisabeth

    2012-01-01

    The paper describes spectrum sensing using single-radio switched-beam arrays with reactance-loaded parasitic elements. At a given frequency, the antenna's loading conditions (reactive loads) are optimized for maximum average beamforming gain in the beampattern look direction. Circular permutations...

  13. Remote sensing of water vapor within the solar spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Bartsch, B. [Univ. Hamburg (Germany). Meteorologisches Inst.; Bakan, S. [Max-Planck-Inst. fuer Meteorologie, Hamburg (Germany); Fischer, J. [Freie Univ. Berlin (Germany). Inst. fuer Weltraumwissenschaften

    1995-12-31

    Water vapor is the most important natural atmospheric greenhouse gas, influencing strongly solar and thermal infrared radiative transfer, and giving rise for clouds, which have strong influence on weather and climate. Therefore, much effort is devoted to remote sensing of atmospheric water vapor. The detection over water is well established, while the situation over land surfaces is worse. A new method is developed to derive the total atmospheric water vapor content over land surfaces even for higher aerosol contents with the aid of backscattered solar radiances. Numerous radiative transfer simulations with a matrix operator code of vertically backscattered solar radiance were carried out for different vertically stratified atmospheres. From the evaluation of these theoretical calculations it can be concluded that this technique allows the detection of total atmospheric water vapor content over land surfaces with an error of less than 10%. This result is important with regard to future measurements planned with the MERIS imaging spectrometer on board the European satellite ENVISAT, which will be launched in 1998. In addition to these theoretical calculations also various aircraft measurements of the backscattered radiances in the wavelength range from 600 to 1,650 nm were carried out. These measurements are done with the above mentioned OVID, a new multichannel array spectrometer of the Universities of Hamburg and Berlin. First comparisons of these airborne CCD measurements with calculated spectra are shown.

  14. OPTIMIZATION OF MULTIPLE-CHANNEL COOPERATIVE SPECTRUM SENSING WITH DATA FUSION RULE IN COGNITIVE RADIO NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Yu Huogen; Tang Wanbin; Li Shaoqian

    2012-01-01

    This paper focuses on multi-channel Cooperative Spectrum Sensing (CSS) where Secondary Users (SUs) are assigned to cooperatively sense multiple channels simultaneously.A multi-channel CSS optimization problem of joint spectrum sensing and SU assignment based on data fusion rule is formulated,which maximizes the total throughput of the Cognitive Radio Network (CRN) subject to the constraints of probabilities of detection and false alarm.To address the optimization problem,a Branch and Bound (BnB) algorithm and a greedy algorithm are proposed to obtain the optimal solutions.Simulation results are presented to demonstrate the effectiveness of our proposed algorithms and show that the throughput improvement is achieved through the joint design.It is also shown that the greedy algorithm with a low complexity achieves the comparable performance to the exhaustive algorithm.

  15. Robust Spectrum Sensing Demonstration Using a Low-Cost Front-End Receiver

    Directory of Open Access Journals (Sweden)

    Daniele Borio

    2015-01-01

    Full Text Available Spectrum Sensing (SS is an important function in Cognitive Radio (CR to detect primary users. The design of SS algorithms is one of the most challenging tasks in CR and requires innovative hardware and software solutions to enhance detection probability and minimize low false alarm probability. Although several SS algorithms have been developed in the specialized literature, limited work has been done to practically demonstrate the feasibility of this function on platforms with significant computational and hardware constraints. In this paper, SS is demonstrated using a low cost TV tuner as agile front-end for sensing a large portion of the Ultra-High Frequency (UHF spectrum. The problems encountered and the limitations imposed by the front-end are analysed along with the solutions adopted. Finally, the spectrum sensor developed is implemented on an Android device and SS implementation is demonstrated using a smartphone.

  16. Remote sensing of water vapor within the solar spectrum

    Science.gov (United States)

    Bartsch, Barbara; Bakan, Stephan; Fischer, Juergen

    1995-01-01

    Due to the great importance of atmospheric water vapor for weather and climate, much effort is devoted to remote sensing of atmospheric water vapor. The detection over water is well established, while the situation over land surface is worse. Therefore, a new method is developed to derive the total atmospheric water vapor content over land surfaces even for higher aerosol contents with the aid of backscattered solar radiances. Numerous radiative transfer simulations with a matrix operator code of vertically backscattered solar radiance were carried out for different vertically stratified atmospheres. The resolution of 1.7 nm in the wavelength range from 700 to 1050 nm was adopted to the resolution of our multichannel spectrometer OVID (Optical Visible and near Infrared Detector). Various atmospheric conditions were chosen, which were defined by variable input parameters of: (a) vertical profiles of temperature, pressure, and water vapor, (b) total water vapor content, (c) aerosols, (d) surface reflectance, and (e) sun zenith angle. Clouds were not taken into account. From the evaluation of these theoretical calculations it can be concluded that this technique allows the detection of total atmospheric water vapor content over land surfaces with an error of less than 10%. This result is important with regard to future measurements planed with the MERIS imaging spectrometer on board the european satellite ENVISAT, which will be launched in 1998. In addition to these theoretical calculations also various aircraft measurements of the backscattered radiances in the wavelength range from 600 to 1650 nm were carried out. These measurements are done with the above mentioned OVID, a new multichannel array spectrometer of the Universities of Hamburg and Berlin. First comparisons of these airborne CCD measurements with calculated spectra are shown.

  17. Generalized Block Sparse Constraint Based Compressive Wideband Spectrum Sensing for Cognitive Radio

    CERN Document Server

    Liu, Yipeng

    2010-01-01

    Wideband spectrum sensing detects the unused spectrum holes for dynamic spectrum access of cognitive radios. However the too high sampling rate is the challenge for application. As the survey shows that the monitoring primary signal has sparse representation in frequency domain, compressive sensing can be used to transfer the sampling burden to the digital signal processor. An analog to information converter can randomly sample the received signal with sub-Nyquist rate to obtain the random measurements. In the spectrum recovery, to match the practical situation, an improved block sparse signal model can be formulated in that the static frequency spectrum allocation of primary radios means the bounds between di?erent primary radios is known. The whole monitoring spectrum is divided sections of di?erent length in accordance with di?erent allocated primary radios. The minimization of the l2 norm can encourage the dense distribution locally, while the l1 norm of the l2 norms can give the sparse distribution of th...

  18. Equal gain combining for cooperative spectrum sensing in cognitive radio networks

    KAUST Repository

    Hamza, Doha R.

    2014-08-01

    Sensing with equal gain combining (SEGC), a novel cooperative spectrum sensing technique for cognitive radio networks, is proposed. Cognitive radios simultaneously transmit their sensing results to the fusion center (FC) over multipath fading reporting channels. The cognitive radios estimate the phases of the reporting channels and use those estimates for coherent combining of the sensing results at the FC. A global decision is made at the FC by comparing the received signal with a threshold. We obtain the global detection probabilities and secondary throughput exactly through a moment generating function approach. We verify our solution via system simulation and demonstrate that the Chernoff bound and central limit theory approximation are not tight. The cases of hard sensing and soft sensing are considered and we provide examples in which hard sensing is advantageous to soft sensing. We contrast the performance of SEGC with maximum ratio combining of the sensors\\' results and provide examples where the former is superior. Furthermore, we evaluate the performance of SEGC against existing orthogonal reporting techniques such as time division multiple access (TDMA). SEGC performance always dominates that of TDMA in terms of secondary throughput. We also study the impact of phase and synchronization errors and demonstrate the robustness of the SEGC technique against such imperfections. © 2002-2012 IEEE.

  19. Performance analysis of spectrum sensing with multiple status changes in primary user traffic

    KAUST Repository

    Tang, Liang

    2012-06-01

    In this letter, the impact of primary user traffic with multiple status changes on the spectrum sensing performance is analyzed. Closed-form expressions for the probabilities of false alarm and detection are derived. Numerical results show that the multiple status changes of the primary user cause considerable degradation in the sensing performance. This degradation depends on the number of changes, the primary user traffic model, the primary user traffic intensity and the signal-to-noise ratio of the received signal. Numerical results also show that the amount of degradation decreases when the number of changes increases, and converges to a minimum sensing performance due to the limited sensing period and primary holding time. © 2012 IEEE.

  20. A Cooperative Spectrum Sensing Scheme Based on Trust and Fuzzy Logic for Cognitive Radio Sensor Networks

    Directory of Open Access Journals (Sweden)

    Yonghua Wang

    2013-01-01

    Full Text Available This paper proposes a cooperative spectrum sensing scheme based on trust and fuzzy logic for Cognitive Radio Sensor Networks (CRSN. The CRSN nodes use the T-S fuzzy logic to make local decisions on the presence or absence of the primary users (PU signal, and then use a censoring method to only allow the relatively reliable decisions sent to the fusion center. Utilizing a trust evaluation scheme based on the factors such as local sensing difference, sensing location factors, and sensing channel conditions for each node. Combing the majority rule and the trust values of the nodes, the fusion center makes the final decision. Simulation results show that the proposed scheme could improve the detect probability effectively.

  1. Green collaboration in cognitive radio cellular networks with roaming and spectrum trading

    KAUST Repository

    Sboui, Lokman

    2015-08-30

    In this paper, we propose a new cognitive cellular network architecture based on the coexistence of primary and secondary networks, (PN) and (SN), respectively. The PN aims to minimize its energy consumption by switching off the maximum number of its BSs and offloading its users to the SN\\'s infrastructure to maintain its QoS. In return, the PN pays a roaming price and permits the SN to share or lease the spectrum at a certain price. We propose a low-complexity algorithm allowing the PN to minimize its energy consumption by selecting a suboptimal combination of active base stations. Our algorithm also optimizes the resource allocation of the SN to maximize its total sum-rate while respecting the minimal profit constraints for both networks. In the numerical results, we show that our proposed algorithm achieves close performances to the optimal exhaustive search algorithm. In addition, we investigate the impact of various system parameters in the collaboration decision.

  2. Energy Efficient Cooperative Spectrum Sensing in Cognitive Radio Networks Using Distributed Dynamic Load Balanced Clustering Scheme

    Directory of Open Access Journals (Sweden)

    Muthukkumar R.

    2016-07-01

    Full Text Available Cognitive Radio (CR is a promising and potential technique to enable secondary users (SUs or unlicenced users to exploit the unused spectrum resources effectively possessed by primary users (PUs or licenced users. The proven clustering approach is used to organize nodes in the network into the logical groups to attain energy efficiency, network scalability, and stability for improving the sensing accuracy in CR through cooperative spectrum sensing (CSS. In this paper, a distributed dynamic load balanced clustering (DDLBC algorithm is proposed. In this algorithm, each member in the cluster is to calculate the cooperative gain, residual energy, distance, and sensing cost from the neighboring clusters to perform the optimal decision. Each member in a cluster participates in selecting a cluster head (CH through cooperative gain, and residual energy that minimises network energy consumption and enhances the channel sensing. First, we form the number of clusters using the Markov decision process (MDP model to reduce the energy consumption in a network. In this algorithm, CR users effectively utilize the PUs reporting time slots of unavailability. The simulation results reveal that the clusters convergence, energy efficiency, and accuracy of channel sensing increased considerably by using the proposed algorithm.

  3. Hybrid Accuracy-Time Trade-off Solution for Spectrum Sensing in Cognitive Radio Networks

    DEFF Research Database (Denmark)

    Ivanov, Antoni Stefkov; Mihovska, Albena Dimitrova; Poulkov, Vladimir

    2017-01-01

    is then compared with the one acquired using the statistical method. Finally, an optimal balance between the sensing time and accuracy is obtained for the current environmental conditions using the derived closed form expression. The algorithm is implemented using the USRP and GNU Radio. Through simulation results......The rise of the cognitive radio systems as a concept for future networks has seen a great amount of scientific effort in the recent years. Appropriately, much attention is given to how the vital function of spectrum sensing should be executed. The cognitive radio device is required to be able...

  4. Multi-Touch Collaborative Gesture Recognition Based User Interfaces as Behavioral Interventions for Children with Autistic Spectrum Disorder: A Review

    Directory of Open Access Journals (Sweden)

    AHMED HASSAN

    2016-10-01

    Full Text Available This paper addresses UI (User Interface designing based on multi-touch collaborative gesture recognition meant for ASD (Autism Spectrum Disorder - affected children. The present user interfaces (in the context of behavioral interventions for Autism Spectrum disorder are investigated in detail. Thorough comparison has been made among various groups of these UIs. Advantages and limitations of these interfaces are discussed and future directions for the design of such interfaces are suggested.

  5. Coexistence and spectrum sensing of IEEE 802.11 systems for cognitive radio applications

    NARCIS (Netherlands)

    Bloem, van Johan Willem Hermanus

    2013-01-01

    Nowadays, a vast majority of the Wi-Fi systems operates in the 2.4 GHz ISM band that becomes more and more crowded due to the growing usage of Wi-Fi. On top of that, a growing number of non Wi-Fi technologies become active in this band as well. In this thesis the focus is on spectrum sensing and det

  6. Spectrum Feature Retrieval and Comparison of Remote Sensing Images Using Improved ISODATA Algorithm

    Institute of Scientific and Technical Information of China (English)

    刘磊; 敬忠良; 肖刚

    2004-01-01

    Due to the large quantities of data and high relativity of the spectra of remote sensing images, K-L transformation is used to eliminate the relativity. An improved ISODATA(Interative Self-Organizing Data Analysis Technique A) algorithm is used to extract the spectrum features of the images. The computation is greatly reduced and the dynamic arguments are realized. The comparison of features between two images is carried out, and good results are achieved in simulation.

  7. Evaluation of Kolmogorov - Smirnov Test and Energy Detector Techniques for Cooperative Spectrum Sensing in Real Channel Conditions

    Directory of Open Access Journals (Sweden)

    D. Lekomtcev

    2015-06-01

    Full Text Available The cognitive radio technology allows solving one of the main issues of current wireless communication technologies, namely a deficit of vacant spectrum. A dynamic spectrum access used in the cognitive radio networks (CRN gives an ability to access an unused spectrum in real time. Cooperative spectrum sensing is the most effective method for spectrum holes detecting. It combines sensing information of multiple cognitive radio users. In this paper, an experimental evaluation of spectrum sensing methods based on the Kolmogorov - Smirnov statistical test and Energy Detector using the Universal Software Radio Peripheral (USRP devices synchronized through a MIMO cable and with further processing in the GNU Radio and Matlab software are presented. Three hard decision fusion schemes are analyzed. Simulation comparison between these rules is presented via Receiver Operating Characteristic (ROC curves. The influence of real channel with interferences is compared in contrast to commonly assumed AWGN channel model of vacant channel noise.

  8. RF Spectrum Sensing Based on an Overdamped Nonlinear Oscillator Ring for Cognitive Radios

    Science.gov (United States)

    Tang, Zhi-Ling; Li, Si-Min; Yu, Li-Juan

    2016-01-01

    Existing spectrum-sensing techniques for cognitive radios require an analog-to-digital converter (ADC) to work at high dynamic range and a high sampling rate, resulting in high cost. Therefore, in this paper, a spectrum-sensing method based on a unidirectionally coupled, overdamped nonlinear oscillator ring is proposed. First, the numerical model of such a system is established based on the circuit of the nonlinear oscillator. Through numerical analysis of the model, the critical condition of the system’s starting oscillation is determined, and the simulation results of the system’s response to Gaussian white noise and periodic signal are presented. The results show that once the radio signal is input into the system, it starts oscillating when in the critical region, and the oscillating frequency of each element is fo/N, where fo is the frequency of the radio signal and N is the number of elements in the ring. The oscillation indicates that the spectrum resources at fo are occupied. At the same time, the sampling rate required for an ADC is reduced to the original value, 1/N. A prototypical circuit to verify the functionality of the system is designed, and the sensing bandwidth of the system is measured. PMID:27294928

  9. On the Impact of User Distribution on Cooperative Spectrum Sensing and Data Transmission with Multiuser Diversity

    KAUST Repository

    Rao, Anlei

    2011-07-01

    In this thesis, we investigate the independent but not identically distributed (i.n.i.d.) situations for spectrum sensing and data transmission. In particular, we derive the false-alarm probability and the detection probability of cooperative spectrum sensing with the scheme of energy fusion over i.n.i.d. Nakagami fading channels. Then, the performance of adaptive modulation with single-cell multiuser scheduling over i.n.i.d. Nakagami fading channels is analyzed. Closed-form expressions are derived for the average channel capacity, spectral efficiency, and bit-error-rate (BER) for both constant-power variable-rate and variable-power variable-rate uncoded M- ary quadrature amplitude modulation (M-QAM) schemes. In addition, we study the impact of time delay on the average BER of adaptive M-QAM. From the selected numerical results, we can see that cooperative spectrum sensing and multiuser diversity brings considerably better performance even over i.n.i.d. fading environments.

  10. Collaboration

    Science.gov (United States)

    King, Michelle L.

    2010-01-01

    This article explores collaboration between library media educators and regular classroom teachers. The article focuses on the context of the issue, positions on the issue, the impact of collaboration, and how to implement effective collaboration into the school system. Various books and professional journals are used to support conclusions…

  11. The effect of online collaborative learning on middle school student science literacy and sense of community

    Science.gov (United States)

    Wendt, Jillian Leigh

    This study examines the effects of online collaborative learning on middle school students' science literacy and sense of community. A quantitative, quasi-experimental pretest/posttest control group design was used. Following IRB approval and district superintendent approval, students at a public middle school in central Virginia completed a pretest consisting of the Misconceptions-Oriented Standards-Based Assessment Resources for Teachers (MOSART) Physical Science assessment and the Classroom Community Scale. Students in the control group received in-class assignments that were completed collaboratively in a face-to-face manner. Students in the experimental group received in-class assignments that were completed online collaboratively through the Edmodo educational platform. Both groups were members of intact, traditional face-to-face classrooms. The students were then post tested. Results pertaining to the MOSART assessment were statistically analyzed through ANCOVA analysis while results pertaining to the Classroom Community Scale were analyzed through MANOVA analysis. Results are reported and suggestions for future research are provided.

  12. Exact performance of cooperative spectrum sensing for cognitive radios with quantized information under imperfect reporting channels

    KAUST Repository

    Ben Ghorbel, Mahdi

    2013-09-01

    Spectrum sensing is the first and main step for cognitive radio systems to achieve an efficient use of the spectrum. Cooperation among cognitive radio users is a technique employed to improve the sensing performance by exploiting the diversity between the sensing channels to overcome the fading and shadowing effects which allows reduction of miss-detection and false alarm probabilities. Information can be exchanged between cooperating users in different formats from the binary hard information to the full soft information. Quantized information has shown its efficiency as a trade-off between binary hard and full soft for other cooperative schemes, in this paper, we investigate the use of quantized information between cooperating cognitive users. We derive closed-form expressions of the cooperative average false alarm and detection probabilities over fading channels for a generalized system model with not necessarily identical average sensing Signal-to-Noise Ratio (SNR) and imperfect reporting channels. Numerical simulations allow us to conclude a tradeoff between the quantization size and the reporting energy in order to achieve the optimal cooperative error probability. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.

  13. Energy/bandwidth-Saving Cooperative Spectrum Sensing for Two-hopWRAN

    Directory of Open Access Journals (Sweden)

    Ming-Tuo Zhou

    2014-07-01

    Full Text Available A two-hop wireless regional area network (WRAN providing monitoring services operating in Television White Space (TVWS, i.e., IEEE P802.22b, may employ a great number of subscriber customer-premises equipments (S-CPEs possibly without mains power supply, leading to requirement of cost-effective and power-saving design. This paper proposes a framework of cooperative spectrum sensing (CSS and an energy/bandwidth saving CSS scheme to P802.22b. In each round of sensing, S-CPEs with SNRs lower than a predefined threshold are excluded from reporting sensing results. Numerical results show that the fused missed-detection probability and false alarmprobability could remainmeeting sensing requirements, and the overall fused error probability changes very little. With 10 S-CPEs, it is possible to save more than 40% of the energy/bandwidth on a Rayleigh channel. The principle proposed can apply to other advanced sensing technologies capable of detecting primary signals with low average SNR.

  14. Temperature-induced spectrum response of volume grating as an effective strategy for holographic sensing in acrylamide polymer part I: sensing.

    Science.gov (United States)

    Liu, Hongpeng; Yu, Dan; Zhou, Ke; Mao, Dongyao; Liu, Langbo; Wang, Hui; Wang, Weibo; Song, Qinggong

    2016-12-10

    Temperature-induced diffraction spectrum responses of holographic gratings are characterized for exploring the temperature-sensing capability of a holographic sensor. Linear blue shift of peak wavelength and linear diffraction reduction are observed. It provides quantitative expressions for sensing applications. Inorganic nanoparticles are dispersed into the binder to improve sensing properties. Obvious improvement of sensing parameters, including wavelength shift and diffraction change, is confirmed. The sensitivity, response rate, and linear response region of holographic sensors are determined to evaluate sensing capacity. Influence of relative humidity on holographic sensing response is discussed. Expansion of humidity range provides a probability for extending the range of wavelength shift. Finally, the temperature response reversibility of a holographic sensor is evaluated. These experimental results can expand the practical application field of holographic sensing strategy and accelerate the development of holographic sensors.

  15. Secondary access based on sensing and primary ARQ feedback in spectrum sharing systems

    KAUST Repository

    Hamza, Doha R.

    2012-04-01

    In the context of primary/secondary spectrum sharing, we propose a randomized secondary access strategy with access probabilities that are a function of both the primary automatic repeat request (ARQ) feedback and the spectrum sensing outcome. The primary terminal operates in a time slotted fashion and is active only when it has a packet to send. The primary receiver can send a positive acknowledgment (ACK) when the received packet is decoded correctly. Lack of ARQ feedback is interpreted as erroneous reception or inactivity. We call this the explicit ACK scheme. The primary receiver may also send a negative acknowledgment (NACK) when the packet is received in error. Lack of ARQ feedback is interpreted as an ACK or no-transmission. This is called the explicit NACK scheme. Under both schemes, when the primary feedback is interpreted as a NACK, the secondary user assumes that there will be retransmission in the next slot and accesses the channel with a certain probability. When the primary feedback is interpreted as an ACK, the secondary user accesses the channel with either one of two probabilities based on the sensing outcome. Under these settings, we find the three optimal access probabilities via maximizing the secondary throughput given a constraint on the primary throughput. We compare the performance of the explicit ACK and explicit NACK schemes and contrast them with schemes based on either sensing or primary ARQ feedback only. © 2012 IEEE.

  16. Time domain averaging and correlation-based improved spectrum sensing method for cognitive radio

    Science.gov (United States)

    Li, Shenghong; Bi, Guoan

    2014-12-01

    Based on the combination of time domain averaging and correlation, we propose an effective time domain averaging and correlation-based spectrum sensing (TDA-C-SS) method used in very low signal-to-noise ratio (SNR) environments. With the assumption that the received signals from the primary users are deterministic, the proposed TDA-C-SS method processes the received samples by a time averaging operation to improve the SNR. Correlation operation is then performed with a correlation matrix to determine the existence of the primary signal in the received samples. The TDA-C-SS method does not need any prior information on the received samples and the associated noise power to achieve improved sensing performance. Simulation results are presented to show the effectiveness of the proposed TDA-C-SS method.

  17. Analyzing Chaos Systems and Fine Spectrum Sensing Using Detrended Fluctuation Analysis Algorithm

    Directory of Open Access Journals (Sweden)

    Javier S. González-Salas

    2016-01-01

    Full Text Available A numerical study that uses detrended fluctuation analysis (DFA algorithm of time series obtained from linear and nonlinear dynamical systems is presented. The DFA algorithm behavior toward periodic and chaotic signals is investigated and the effect of the time scale under analysis is discussed. The displayed results prove that the DFA algorithm response is invariant (stable performance to initial condition and chaotic system parameters. An initial idea of DFA algorithm implementation for fine spectrum sensing (SS is proposed under two-stage spectrum sensor approach with test statistics based on the scaling exponent value. The outcomes demonstrate a promising new SS technique that can alleviate several imperfections such as noise power uncertainty and spatial correlation between the adjacent antenna array elements.

  18. AN ADAPTIVE MEASUREMENT SCHEME BASED ON COMPRESSED SENSING FOR WIDEBAND SPECTRUM DETECTION IN COGNITIVE WSN

    Institute of Scientific and Technical Information of China (English)

    Xu Xiaorong; Zhang Jianwu; Huang Aiping; Jiang Bin

    2012-01-01

    An Adaptive Measurement Scheme (AMS) is investigated with Compressed Sensing (CS)theory in Cognitive Wireless Sensor Network (C-WSN).Local sensing information is collected via energy detection with Analog-to-Information Converter (AIC) at massive cognitive sensors,and sparse representation is considered with the exploration of spatial temporal correlation structure of detected signals.Adaptive measurement matrix is designed in AMS,which is based on maximum energy subset selection.Energy subset is calculated with sparse transformation of sensing information,and maximum energy subset is selected as the row vector of adaptive measurement matrix.In addition,the measurement matrix is constructed by orthogonalization of those selected row vectors,which also satisfies the Restricted Isometry Property (RIP) in CS theory.Orthogonal Matching Pursuit (OMP) reconstruction algorithm is implemented at sink node to recover original information.Simulation results are performed with the comparison of Random Measurement Scheme (RMS).It is revealed that,signal reconstruction effect based on AMS is superior to conventional RMS Gaussian measurement.Moreover,AMS has better detection performance than RMS at lower compression rate region,and it is suitable for large-scale C-WSN wideband spectrum sensing.

  19. Systematic analysis of geo-location and spectrum sensing as access methods to TV white space

    CSIR Research Space (South Africa)

    Mauwa, H

    2016-11-01

    Full Text Available -LOCATION AND SPECTRUM SENSING AS ACCESS METHODS TO TVWHITE SPACE H. Mauwa1, A. Bagula1, M. Zennaro2, E. Pietrosemoli2, A. Lysko3, T.X. Brown4 1ISAT Laboratory, Computer Science Department, University of The Western Cape (UWC), Private Bag X17, Bellville, 7535, South..., antenna parameters (radiation pat- tern, height above the ground), transmit power, times of op- eration, protection requirements, allowed WSD transmitter power, and other related parameters [6][7]. The database in- formation is used to predict which...

  20. A Hybrid Combination Scheme for Cooperative Spectrum Sensing in Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Changhua Yao

    2014-01-01

    Full Text Available We propose a novel hybrid combination scheme in cooperative spectrum sensing (CSS, which utilizes the diversity of reporting channels to achieve better throughput performance. Secondary users (SUs with good reporting channel quality transmit quantized local observation statistics to fusion center (FC, while others report their local decisions. FC makes the final decision by carrying out hybrid combination. We derive the closed-form expressions of throughput and detection performance as a function of the number of SUs which report local observation statistics. The simulation and numerical results show that the hybrid combination scheme can achieve better throughput performance than hard combination scheme and soft combination scheme.

  1. Laser Sensing of Vegetation Based on Dual Spectrum Measurements of Reflection Coefficients

    Directory of Open Access Journals (Sweden)

    M. L. Belov

    2017-01-01

    Full Text Available Currently, a promising trend in remote sensing of environment is to monitor the vegetative cover: evaluate the productivity of agricultural crops; evaluate the moisture content of soils and the state of ecosystems; provide mapping the sites of bogging, desertification, drought, etc.; control the phases of vegetation of crops, etc.Development of monitoring systems for remote detection of vegetation sites being under unfavorable conditions (low or high temperature, excess or lack of water, soil salinity, disease, etc. is of relevance. Optical methods are the most effective for this task. These methods are based on the physical features of reflection spectra in the visible and near infrared spectral range for vegetation under unfavorable conditions and vegetation under normal conditions.One of the options of optoelectronic equipment for monitoring vegetation condition is laser equipment that allows remote sensing of vegetation from the aircraft and mapping of vegetation sites with abnormal (inactive periods of vegetation reflection spectra with a high degree of spatial resolution.The paper deals with development of a promising dual-spectrum method for laser remote sensing of vegetation. Using the experimentally measured reflection spectra of different vegetation types, mathematical modeling of probability for appropriate detection and false alarms to solve a problem of detecting the vegetation under unfavorable conditions (with abnormal reflection spectra is performed based on the results of dual-spectrum measurements of the reflection coefficient.In mathematical modeling, the lidar system was supposed to provide sensing at wavelengths of 0.532 μm and 0.85 μm. The noise of the measurement was supposed to be normal with zero mean value and mean-square value of 1% -10%.It is shown that the method of laser sensing of vegetation condition based on the results of dual-spectrum measurement of the reflection coefficient at wavelengths of 0.532 μm and 0

  2. COLLABORATIVE PARENT COUNSELING in MUSIC THERAPY (CPCiMT) FOR PARENTS OF CHILDRN WITH AUTISM SPECTRUM DISORDER

    DEFF Research Database (Denmark)

    Gottfried, Tali

    Abstract Collaborative Parent Counseling in Music Therapy (PCiMT) for parents of children with Autism Spectrum Disorder is a clinical approach, in which the music therapist conducts both the individual MT sessions for the child as well as the counseling sessions for the parents. This practice...... is now being tested in my PhD research. Description Early parent-child relationship, represented commonly by reciprocal musical-wise interaction (Stern, 1985), is interrupted by organic impairments, sourced at the core of the Autism Spectrum Disorder (ASD). Parenting a child with ASD involves great...

  3. A collaborative smartphone sensing platform for detecting and tracking hostile drones

    Science.gov (United States)

    Boddhu, Sanjay K.; McCartney, Matt; Ceccopieri, Oliver; Williams, Robert L.

    2013-05-01

    based on multiple (geographically distributed) observation data points. This developed collaborative sensing platform has been field tested and proven to be effective in providing real-time alerting mechanism for the personnel in the field to avert or subdue the potential damages caused by the detected hostile drones.

  4. Collaboration.

    Science.gov (United States)

    McDonald, Meme; Pryor, Boori Monty

    2000-01-01

    Describes, in the words of two Australian authors (one Aboriginal and one European-Australian), how they work together when they write books together, and how their collaboration goes beyond the two of them. (SR)

  5. Cyclostationary Spectrum Collaborative Detection Based on Maximal-Ratio Combining%基于最大比合并的循环平稳频谱协作检测

    Institute of Scientific and Technical Information of China (English)

    陈新永; 杨瑞娟; 李晓柏; 谢超

    2013-01-01

    Multi-antenna spatial diversity and multi-users collaborative detection are key technologies for achieving the performances of spectrum detection in cognitive radio system.A spectrum sensing technique based on cyclostationary signatures for multi-antenna and multiple users is proposed.Each antenna receiver signal is combined according to maximal-ratio combining in the frequency domain,and the elementary spectrum verdict is made for the combined signals.The spectrum collaborative detection is performed according to the rule K/N for multiple users.The simulation results and analysis show that utilizing the cyclostationary signatures and the collaborative detection technique can improve the performances of spectrum sensing in cognitive radio system.%多天线空间分集和多用户协作检测是提高认知无线电频谱检测性能的2种关键技术,由此提出了基于循环平稳特征的多天线多用户频谱协作检测方法.首先接收器在频域按照最大比合并的方法合并各天线接收信号,对合并信号进行初步频谱判决.然后在多用户中按照K/N融合准则进一步做频谱协作检测.仿真分析表明,综合利用信号循环平稳特征和协作检测技术可有效改善认知无线电系统检测性能.

  6. Cognitive Radio Spectrum Sensing Algorithms based on Eigenvalue and Covariance methods

    Directory of Open Access Journals (Sweden)

    K.SESHU KUMAR

    2013-04-01

    Full Text Available Spectrum sensing method is the fundamental factor when we are working with cognitive radio systems. Main aim and fundamental problem of cognitive radio is to identify weather primary users in authorized or licensed spectrum is presented or not. Paper deals with a new scheme of sensing based on the eigenvalues concept. It contain signals of covariance matrix received by the secondary users. In this method we are suggested two algorithms of sensing, one algorithm established by the maximum to minimum eigenvalue ratio. Other algorithm focused on average to minimum eigenvalue ratio. These two are done by using random matrix theories (RMT, and also these RMT are latest and also produce some accurate results. Now we calculate the ratios of distributions and probabilities of detection (Pd and derive the probabilities of false alarm (Pfa for the proposed algorithms, and also finding thresholds values for given Pfa. This method will improve the problem of noise uncertainty, and also performance isimproved compare to energy detection when highly correlated signal is available. Paper also deals with another method is and also covariance methods. First one is statistical covariance method, it has different noise and received signal, and it is used for finding the primary users presence where there is only noise. These algorithms implemented by use of small number of received signal samples and processed to calculate the sample covariance matrix. By use of sample covariance matrix we are extracted two test statistics. Finally we compare these results and concluded that signal presence. These are used in many signal detection applications, and also do not need signal information, also noise power and channel. We did the Simulations based on two ways. First one is randomly generated signals. Other one is done by captured DTV signals taken from ATSV committee, these are broadcasting signals. These methods confirm and verifies the efficiency of the proposed

  7. Combined diversity and improved energy detection in cooperative spectrum sensing with faded reporting channels

    Directory of Open Access Journals (Sweden)

    Srinivas Nallagonda

    2016-04-01

    Full Text Available In this paper we evaluate the performance of cooperative spectrum sensing (CSS where each cognitive radio (CR employs an improved energy detector (IED with multiple antennas and uses selection combining (SC for detecting the primary user (PU in noisy and faded sensing (S channels. We derive an expression for the probability of false alarm and expressions for probability of missed detection in non-faded (AWGN and Rayleigh faded sensing environments in terms of cumulative distribution function (CDF. Each CR transmits its decision about PU via noisy and faded reporting (R channel to fusion center (FC. In this paper we assume that S-channels are noisy and Rayleigh faded while several cases of fading are considered for R-channels such as: (i Hoyt (or Nakagami-q, (ii Rayleigh, (iii Rician (or Nakagami-n, and (iv Weibull. A Binary Symmetric channel (BSC with a fixed error probability (r in the R-channel is also considered. The impact of fading in R-channel, S-channel and several network parameters such as IED parameter, normalized detection threshold, number of CRs, and number of antennas on missed detection and total error probability is assessed. The effects of Hoyt, Rician, and Weibull fading parameters on overall performance of IED-CSS are also highlighted.

  8. A soft-hard combination-based cooperative spectrum sensing scheme for cognitive radio networks.

    Science.gov (United States)

    Do, Nhu Tri; An, Beongku

    2015-02-13

    In this paper we propose a soft-hard combination scheme, called SHC scheme, for cooperative spectrum sensing in cognitive radio networks. The SHC scheme deploys a cluster based network in which Likelihood Ratio Test (LRT)-based soft combination is applied at each cluster, and weighted decision fusion rule-based hard combination is utilized at the fusion center. The novelties of the SHC scheme are as follows: the structure of the SHC scheme reduces the complexity of cooperative detection which is an inherent limitation of soft combination schemes. By using the LRT, we can detect primary signals in a low signal-to-noise ratio regime (around an average of -15 dB). In addition, the computational complexity of the LRT is reduced since we derive the closed-form expression of the probability density function of LRT value. The SHC scheme also takes into account the different effects of large scale fading on different users in the wide area network. The simulation results show that the SHC scheme not only provides the better sensing performance compared to the conventional hard combination schemes, but also reduces sensing overhead in terms of reporting time compared to the conventional soft combination scheme using the LRT.

  9. Outage Analysis of Spectrum-Sharing over M-Block Fading with Sensing Information

    KAUST Repository

    Alabbasi, Abdulrahman

    2016-07-13

    Future wireless technologies, such as, 5G, are expected to support real-time applications with high data throughput, e.g., holographic meetings. From a bandwidth perspective, cognitive radio is a promising technology to enhance the system’s throughput via sharing the licensed spectrum. From a delay perspective, it is well known that increasing the number of decoding blocks will improve the system robustness against errors, while increasing the delay. Therefore, optimally allocating the resources to determine the tradeoff of tuning the length of decoding blocks while sharing the spectrum is a critical challenge for future wireless systems. In this work, we minimize the targeted outage probability over the block-fading channels while utilizing the spectrum-sharing concept. The secondary user’s outage region and the corresponding optimal power are derived, over twoblocks and M-blocks fading channels. We propose two suboptimal power strategies and derive the associated asymptotic lower and upper bounds on the outage probability with tractable expressions. These bounds allow us to derive the exact diversity order of the secondary user’s outage probability. To further enhance the system’s performance, we also investigate the impact of including the sensing information on the outage problem. The outage problem is then solved via proposing an alternating optimization algorithm, which utilizes the verified strict quasiconvex structure of the problem. Selected numerical results are presented to characterize the system’s behavior and show the improvements of several sharing concepts.

  10. A Novel Wireless Power Transfer-Based Weighed Clustering Cooperative Spectrum Sensing Method for Cognitive Sensor Networks.

    Science.gov (United States)

    Liu, Xin

    2015-10-30

    In a cognitive sensor network (CSN), the wastage of sensing time and energy is a challenge to cooperative spectrum sensing, when the number of cooperative cognitive nodes (CNs) becomes very large. In this paper, a novel wireless power transfer (WPT)-based weighed clustering cooperative spectrum sensing model is proposed, which divides all the CNs into several clusters, and then selects the most favorable CNs as the cluster heads and allows the common CNs to transfer the received radio frequency (RF) energy of the primary node (PN) to the cluster heads, in order to supply the electrical energy needed for sensing and cooperation. A joint resource optimization is formulated to maximize the spectrum access probability of the CSN, through jointly allocating sensing time and clustering number. According to the resource optimization results, a clustering algorithm is proposed. The simulation results have shown that compared to the traditional model, the cluster heads of the proposed model can achieve more transmission power and there exists optimal sensing time and clustering number to maximize the spectrum access probability.

  11. Acousto-optic control of the LPG spectrum for sensing applications

    Science.gov (United States)

    Oliveira, Roberson A.; Possetti, Gustavo R. C.; Marques, Carlos A. F.; Neves, Paulo T., Jr.; Bavastri, Carlos A.; Kamikawachi, Ricardo C.; Fabris, José L.; Muller, Marcia; Nogueira, Rogério N.; Canning, John; Pohl, Alexandre A. P.

    2011-05-01

    Experimental and numerical demonstration of the acousto-optic effect applied in long period grating by means of flexural waves is presented. The interaction between acoustic and optical waves is modeled with help of the method of assumed modes, which delivers the strain field inside the grating and the transfer matrix method, which, given the strain field as input, calculate the resultant grating spectrum. The experimental and theoretical results are found to be in good agreement. The main effect of the bends in the grating is the break of degeneracy of the circular cladding modes, leading the attenuation band to be changed. Among all the applications of this methodology, it is important to mention the possibility of use as a tunable filter, laser cavity gain controller, switching device and transducer in sensing systems.

  12. Cooperative Spectrum Sensing Using Eigenvalue Fusion for OFDMA and Other Wideband Signals

    Directory of Open Access Journals (Sweden)

    Dayan A. Guimarães

    2013-01-01

    Full Text Available In this paper, we propose a new approach for the detection of OFDMA and other wideband signals in the context of centralized cooperative spectrum sensing for cognitive radio (CR applications. The approach is based on the eigenvalues of the received signal covariance matrix whose samples are in the frequency domain. Soft combining of the eigenvalues at the fusion center is the main novelty. This combining strategy is applied to variants of four test statistics for binary hypothesis test, namely: the eigenvalue-based generalized likelihood ratio test (GLRT, the maximum-minimum eigenvalue detection (MMED, the maximum eigenvalue detection (MED and the energy detection (ED. It is shown that the eigenvalue fusion can outperform schemes based on decision fusion and sample fusion. A tradeoff is also established between complexity and volume of data sent to the fusion center in all combining strategies.

  13. Microwave spectrum sensing based on photonic time stretch and compressive sampling.

    Science.gov (United States)

    Chi, Hao; Chen, Ying; Mei, Yuan; Jin, Xiaofeng; Zheng, Shilie; Zhang, Xianmin

    2013-01-15

    An approach to realizing microwave spectrum sensing based on photonic time stretch and compressive sampling is proposed. The time stretch system is used to slow down the input high-speed signal and the compressive sampling based on random demodulation can further decrease the sampling rate. A spectrally sparse signal in a wide bandwidth can be captured with a sampling rate far lower than the Nyquist rate thanks to both time stretch and compressive sampling. It is demonstrated that a system with a time stretch factor 5 and a compression factor 8 can be used to capture a signal with multiple tones in a 50 GHz bandwidth, which means a sampling rate 40 times lower than the Nyquist rate. In addition, the time stretch of the microwave signal largely decreases the data rate of random data sequence and therefore the speed of the mixer in the random demodulator.

  14. Distributed Spectrum Sensing with Sequential Ordered Transmissions to a Cognitive Fusion Center

    CERN Document Server

    Hesham, Laila; Nafie, Mohammed

    2011-01-01

    Cooperative spectrum sensing is a robust strategy that enhances the detection probability of primary licensed users. However, a large number of detectors reporting to a fusion center for a final decision causes significant delay and also presumes the availability of unreasonable communication resources at the disposal of a network searching for spectral opportunities. In this work, we employ the idea of sequential detection to obtain a quick, yet reliable, decision regarding primary activity. Local detectors take measurements, and only a few of them transmit the log likelihood ratios (LLR) to a fusion center in descending order of LLR magnitude. The fusion center runs a sequential test with a maximum imposed on the number of sensors that can report their LLR measurements. We calculate the detection thresholds using two methods. The first achieves the same probability of error as the optimal block detector. In the second, an objective function is constructed and decision thresholds are obtained via backward in...

  15. Cognitive communication and cooperative hetnet coexistence selected advances on spectrum sensing, learning, and security approaches

    CERN Document Server

    Bader, Faouzi

    2014-01-01

    This book, written by experts from universities and major industrial research laboratories, is devoted to the very hot topic of cognitive radio and networking for cooperative coexistence of heterogeneous wireless networks. Selected highly relevant advanced research is presented on spectrum sensing and progress toward the realization of accurate radio environment mapping, biomimetic learning for self-organizing networks, security threats (with a special focus on primary user emulation attack), and cognition as a tool for green next-generation networks. The research activities covered include work undertaken within the framework of the European COST Action IC0902, which is geared towards the definition of a European platform for cognitive radio and networks. Communications engineers, R&D engineers, researchers, and students will all benefit from this complete reference on recent advances in wireless communications and the design and implementation of cognitive radio systems and networks.

  16. A Decentralized Eigenvalue Computation Method for Spectrum Sensing Based on Average Consensus

    Science.gov (United States)

    Mohammadi, Jafar; Limmer, Steffen; Stańczak, Sławomir

    2016-07-01

    This paper considers eigenvalue estimation for the decentralized inference problem for spectrum sensing. We propose a decentralized eigenvalue computation algorithm based on the power method, which is referred to as generalized power method GPM; it is capable of estimating the eigenvalues of a given covariance matrix under certain conditions. Furthermore, we have developed a decentralized implementation of GPM by splitting the iterative operations into local and global computation tasks. The global tasks require data exchange to be performed among the nodes. For this task, we apply an average consensus algorithm to efficiently perform the global computations. As a special case, we consider a structured graph that is a tree with clusters of nodes at its leaves. For an accelerated distributed implementation, we propose to use computation over multiple access channel (CoMAC) as a building block of the algorithm. Numerical simulations are provided to illustrate the performance of the two algorithms.

  17. Exact Distributions of Finite Random Matrices and Their Applications to Spectrum Sensing.

    Science.gov (United States)

    Zhang, Wensheng; Wang, Cheng-Xiang; Tao, Xiaofeng; Patcharamaneepakorn, Piya

    2016-07-29

    The exact and simple distributions of finite random matrix theory (FRMT) are critically important for cognitive radio networks (CRNs). In this paper, we unify some existing distributions of the FRMT with the proposed coefficient matrices (vectors) and represent the distributions with the coefficient-based formulations. A coefficient reuse mechanism is studied, i.e., the same coefficient matrices (vectors) can be exploited to formulate different distributions. For instance, the same coefficient matrices can be used by the largest eigenvalue (LE) and the scaled largest eigenvalue (SLE); the same coefficient vectors can be used by the smallest eigenvalue (SE) and the Demmel condition number (DCN). A new and simple cumulative distribution function (CDF) of the DCN is also deduced. In particular, the dimension boundary between the infinite random matrix theory (IRMT) and the FRMT is initially defined. The dimension boundary provides a theoretical way to divide random matrices into infinite random matrices and finite random matrices. The FRMT-based spectrum sensing (SS) schemes are studied for CRNs. The SLE-based scheme can be considered as an asymptotically-optimal SS scheme when the dimension K is larger than two. Moreover, the standard condition number (SCN)-based scheme achieves the same sensing performance as the SLE-based scheme for dual covariance matrix K = 2 . The simulation results verify that the coefficient-based distributions can fit the empirical results very well, and the FRMT-based schemes outperform the IRMT-based schemes and the conventional SS schemes.

  18. Accelerated diffusion spectrum imaging via compressed sensing for the human connectome project

    Science.gov (United States)

    Lee, Namgyun; Wilkins, Bryce; Singh, Manbir

    2012-02-01

    Diffusion Spectrum Imaging (DSI) has been developed as a model-free approach to solving the so called multiple-fibers-per- voxel problem in diffusion MRI. However, inferring heterogeneous microstructures of an imaging voxel rapidly remains a challenge in DSI because of extensive sampling requirements in a Cartesian grid of q-space. In this study, we propose compressed sensing based diffusion spectrum imaging (CS-DSI) to significantly reduce the number of diffusion measurements required for accurate estimation of fiber orientations. This method reconstructs each diffusion propagator of an MR data set from 100 variable density undersampled diffusion measurements minimizing the l1-norm of the finite-differences (i.e.,anisotropic total variation) of the diffusion propagator. The proposed method is validated against a ground truth from synthetic data mimicking the FiberCup phantom, demonstrating the robustness of CS-DSI on accurately estimating underlying fiber orientations from noisy diffusion data. We demonstrate the effectiveness of our CS-DSI method on a human brain dataset acquired from a clinical scanner without specialized pulse sequences. Estimated ODFs from CS-DSI method are qualitatively compared to those from the full dataset (DSI203). Lastly, we demonstrate that streamline tractography based on our CS-DSI method has a comparable quality to conventional DSI203. This illustrates the feasibility of CS-DSI for reconstructing whole brain white-matter fiber tractography from clinical data acquired at imaging centers, including hospitals, for human brain connectivity studies.

  19. Multi-Objective Clustering Optimization for Multi-Channel Cooperative Spectrum Sensing in Heterogeneous Green CRNs

    KAUST Repository

    Celik, Abdulkadir

    2016-06-27

    In this paper, we address energy efficient (EE) cooperative spectrum sensing policies for large scale heterogeneous cognitive radio networks (CRNs) which consist of multiple primary channels and large number of secondary users (SUs) with heterogeneous sensing and reporting channel qualities. We approach this issue from macro and micro perspectives. Macro perspective groups SUs into clusters with the objectives: 1) total energy consumption minimization; 2) total throughput maximization; and 3) inter-cluster energy and throughput fairness. We adopt and demonstrate how to solve these using the nondominated sorting genetic algorithm-II. The micro perspective, on the other hand, operates as a sub-procedure on cluster formations decided by the macro perspective. For the micro perspectives, we first propose a procedure to select the cluster head (CH) which yields: 1) the best CH which gives the minimum total multi-hop error rate and 2) the optimal routing paths from SUs to the CH. Exploiting Poisson-Binomial distribution, a novel and generalized K-out-of-N voting rule is developed for heterogeneous CRNs to allow SUs to have different local detection performances. Then, a convex optimization framework is established to minimize the intra-cluster energy cost by jointly obtaining the optimal sensing durations and thresholds of feature detectors for the proposed voting rule. Likewise, instead of a common fixed sample size test, we developed a weighted sample size test for quantized soft decision fusion to obtain a more EE regime under heterogeneity. We have shown that the combination of proposed CH selection and cooperation schemes gives a superior performance in terms of energy efficiency and robustness against reporting error wall.

  20. A Sensing Error Aware MAC Protocol for Cognitive Radio Networks

    CERN Document Server

    Hu, Donglin

    2011-01-01

    Cognitive radios (CR) are intelligent radio devices that can sense the radio environment and adapt to changes in the radio environment. Spectrum sensing and spectrum access are the two key CR functions. In this paper, we present a spectrum sensing error aware MAC protocol for a CR network collocated with multiple primary networks. We explicitly consider both types of sensing errors in the CR MAC design, since such errors are inevitable for practical spectrum sensors and more important, such errors could have significant impact on the performance of the CR MAC protocol. Two spectrum sensing polices are presented, with which secondary users collaboratively sense the licensed channels. The sensing policies are then incorporated into p-Persistent CSMA to coordinate opportunistic spectrum access for CR network users. We present an analysis of the interference and throughput performance of the proposed CR MAC, and find the analysis highly accurate in our simulation studies. The proposed sensing error aware CR MAC p...

  1. Content-Based High-Resolution Remote Sensing Image Retrieval via Unsupervised Feature Learning and Collaborative Affinity Metric Fusion

    Directory of Open Access Journals (Sweden)

    Yansheng Li

    2016-08-01

    Full Text Available With the urgent demand for automatic management of large numbers of high-resolution remote sensing images, content-based high-resolution remote sensing image retrieval (CB-HRRS-IR has attracted much research interest. Accordingly, this paper proposes a novel high-resolution remote sensing image retrieval approach via multiple feature representation and collaborative affinity metric fusion (IRMFRCAMF. In IRMFRCAMF, we design four unsupervised convolutional neural networks with different layers to generate four types of unsupervised features from the fine level to the coarse level. In addition to these four types of unsupervised features, we also implement four traditional feature descriptors, including local binary pattern (LBP, gray level co-occurrence (GLCM, maximal response 8 (MR8, and scale-invariant feature transform (SIFT. In order to fully incorporate the complementary information among multiple features of one image and the mutual information across auxiliary images in the image dataset, this paper advocates collaborative affinity metric fusion to measure the similarity between images. The performance evaluation of high-resolution remote sensing image retrieval is implemented on two public datasets, the UC Merced (UCM dataset and the Wuhan University (WH dataset. Large numbers of experiments show that our proposed IRMFRCAMF can significantly outperform the state-of-the-art approaches.

  2. Spectrum

    DEFF Research Database (Denmark)

    Høgfeldt Hansen, Leif

    2016-01-01

    The publication functions as a proces description of the development and construction of an urban furniture SPECTRUM in the city of Gwangju, Republic of Korea. It is used as the cataloque for the exhibition of Spectrum.......The publication functions as a proces description of the development and construction of an urban furniture SPECTRUM in the city of Gwangju, Republic of Korea. It is used as the cataloque for the exhibition of Spectrum....

  3. A Novel Approach to Wideband Spectrum Compressive Sensing Based on DST for Frequency Availability in LEO Mobile Satellite Systems

    Directory of Open Access Journals (Sweden)

    Feilong Li

    2016-01-01

    Full Text Available In LEO mobile satellite network, the L/S frequency availability is an essential task for global communication but entails several major technical challenges: high sampling rate required for wideband sensing, limited power and computing resources for processing load, and frequency-selective wireless fading. This paper investigates the issue of frequency availability in LEO mobile satellite system, and a novel wideband spectrum compressed signal detection approach is proposed to obtain active primary users (PUs subbands and their locations that should be avoided during frequency allocation. We define the novel wideband spectrum compressed sensing method based on discrete sine transform (DST-WSCS, which significantly improves the performance of spectrum detection and recovery accuracy compared with conventional discrete Fourier transform based wideband spectrum compressed sensing scheme (DFT-WSCS. Additionally, with the help of intersatellite links (ISL, the scheme of multiple satellites cooperative sensing according to OR and MAJ decision fusion rules is presented to achieve spatial diversity against wireless fading. Finally, in-depth numerical simulations are performed to demonstrate the performance of the proposed scheme in aspect of signal detection probability, reconstruction precision, processing time, and so forth.

  4. Joint Resource Allocation of Spectrum Sensing and Energy Harvesting in an Energy-Harvesting-Based Cognitive Sensor Network.

    Science.gov (United States)

    Liu, Xin; Lu, Weidang; Ye, Liang; Li, Feng; Zou, Deyue

    2017-03-16

    The cognitive sensor (CS) can transmit data to the control center in the same spectrum that is licensed to the primary user (PU) when the absence of the PU is detected by spectrum sensing. However, the battery energy of the CS is limited due to its small size, deployment in atrocious environments and long-term working. In this paper, an energy-harvesting-based CS is described, which senses the PU together with collecting the radio frequency energy to supply data transmission. In order to improve the transmission performance of the CS, we have proposed the joint resource allocation of spectrum sensing and energy harvesting in the cases of a single energy-harvesting-based CS and an energy-harvesting-based cognitive sensor network (CSN), respectively. Based on the proposed frame structure, we have formulated the resource allocation as a class of joint optimization problems, which seek to maximize the transmission rate of the CS by jointly optimizing sensing time, harvesting time and the numbers of sensing nodes and harvesting nodes. Using the half searching method and the alternating direction optimization, we have achieved the sub-optimal solution by converting the joint optimization problem into several convex sub-optimization problems. The simulation results have indicated the predominance of the proposed energy-harvesting-based CS and CSN models.

  5. Cognitive Spectrum Efficient Multiple Access Technique using Relay Systems

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to increase the coverage of cellular systems by relay channels, relay stations and collaborate ra...

  6. Cognitive Spectrum Efficient Multiple Access Technique using Relay Systems

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to increase the coverage of cellular systems by relay channels, relay stations and collaborate...

  7. The Sense of Agency in Autism Spectrum Disorders: a Dissociation between Prospective and Retrospective Mechanisms?

    Directory of Open Access Journals (Sweden)

    Tiziana eZalla

    2015-09-01

    Full Text Available While a large number of studies have reported impairments in social and interpersonal abilities in individuals with autism spectrum disorder (ASD, relatively few studies have focused on self-related knowledge in this population. One of the processes implicated in the physical dimension of the Self is the sense of agency (SoA, i.e., the experience of initiating and controlling one’s own actions and producing desired changes in the world via these actions. So far, the few studies investigating SoA in ASD have reported contrasting results, with some showing spared, others impaired SoA. Here, we review the existing literature and suggest that the distinction between prospective and retrospective mechanisms of the SoA might help reconcile the existing findings. In the light of a multi-componential model of SoA, we propose the view that a specific impairment at the level of prospective mechanisms acting on internal agency signals (i.e., the intention, action selection, or command produced to achieve the goal may be responsible for the reduced SoA in ASD, along with spared retrospective mechanisms. Future research should shed light on the impact of abnormal SoA on social and self-related dysfunctions in ASD.

  8. Broad spectrum pro-quorum-sensing molecules as inhibitors of virulence in vibrios.

    Directory of Open Access Journals (Sweden)

    Wai-Leung Ng

    Full Text Available Quorum sensing (QS is a bacterial cell-cell communication process that relies on the production and detection of extracellular signal molecules called autoinducers. QS allows bacteria to perform collective activities. Vibrio cholerae, a pathogen that causes an acute disease, uses QS to repress virulence factor production and biofilm formation. Thus, molecules that activate QS in V. cholerae have the potential to control pathogenicity in this globally important bacterium. Using a whole-cell high-throughput screen, we identified eleven molecules that activate V. cholerae QS: eight molecules are receptor agonists and three molecules are antagonists of LuxO, the central NtrC-type response regulator that controls the global V. cholerae QS cascade. The LuxO inhibitors act by an uncompetitive mechanism by binding to the pre-formed LuxO-ATP complex to inhibit ATP hydrolysis. Genetic analyses suggest that the inhibitors bind in close proximity to the Walker B motif. The inhibitors display broad-spectrum capability in activation of QS in Vibrio species that employ LuxO. To the best of our knowledge, these are the first molecules identified that inhibit the ATPase activity of a NtrC-type response regulator. Our discovery supports the idea that exploiting pro-QS molecules is a promising strategy for the development of novel anti-infectives.

  9. Performance of Cooperative Eigenvalue Spectrum Sensing with a Realistic Receiver Model under Impulsive Noise

    Directory of Open Access Journals (Sweden)

    Dayan A. Guimarães

    2013-01-01

    Full Text Available In this paper we present a unified comparison of the performance of four detection techniques for centralized data-fusion cooperative spectrum sensing in cognitive radio networks under impulsive noise, namely, the eigenvalue-based generalized likelihood ratio test (GLRT, the maximum-minimum eigenvalue detection (MMED, the maximum eigenvalue detection (MED, and the energy detection (ED. We consider two system models: an implementation-oriented model that includes the most relevant signal processing tasks realized by a real cognitive radio receiver, and the theoretical model conventionally adopted in the literature. We show that under the implementation-oriented model, GLRT and MMED are quite robust under impulsive noise, whereas the performance of MED and ED is drastically degraded. We also show that performance under the conventional model can be too pessimistic if impulsive noise is present, whereas it can be too optimistic in the absence of this impairment. We also discuss the fact that impulsive noise is not such a severe problem when we take into account the more realistic implementation-oriented model.

  10. Multiobjective Optimization of Linear Cooperative Spectrum Sensing: Pareto Solutions and Refinement.

    Science.gov (United States)

    Yuan, Wei; You, Xinge; Xu, Jing; Leung, Henry; Zhang, Tianhang; Chen, Chun Lung Philip

    2016-01-01

    In linear cooperative spectrum sensing, the weights of secondary users and detection threshold should be optimally chosen to minimize missed detection probability and to maximize secondary network throughput. Since these two objectives are not completely compatible, we study this problem from the viewpoint of multiple-objective optimization. We aim to obtain a set of evenly distributed Pareto solutions. To this end, here, we introduce the normal constraint (NC) method to transform the problem into a set of single-objective optimization (SOO) problems. Each SOO problem usually results in a Pareto solution. However, NC does not provide any solution method to these SOO problems, nor any indication on the optimal number of Pareto solutions. Furthermore, NC has no preference over all Pareto solutions, while a designer may be only interested in some of them. In this paper, we employ a stochastic global optimization algorithm to solve the SOO problems, and then propose a simple method to determine the optimal number of Pareto solutions under a computational complexity constraint. In addition, we extend NC to refine the Pareto solutions and select the ones of interest. Finally, we verify the effectiveness and efficiency of the proposed methods through computer simulations.

  11. Resource-Efficient Fusion with Pre-Compensated Transmissions for Cooperative Spectrum Sensing

    Directory of Open Access Journals (Sweden)

    Dayan Adionel Guimarães

    2015-05-01

    Full Text Available Recently, a novel fusion scheme for cooperative spectrum sensing was proposed for saving resources in the control channel. Secondary users (SUs simultaneously report their decisions using binary modulations with the same carrier frequencies. The transmitted symbols add incoherently at the fusion centre (FC, leading to a larger set of symbols in which a subset is associated with the presence of the primary user (PU signal, and another subset is associated with the absence of such a signal. The decision criterion applied for discriminating these subsets works under the assumption that the channel gains are known at the FC. In this paper, we propose a new simultaneous transmission and decision scheme in which the task of channel estimation is shifted from the FC to the SUs, without the need for feeding-back of the estimates to the FC. The estimates are used at the SUs to pre-compensate for the reporting channel phase rotations and to partially compensate for the channel gains. This partial compensation is the result of signal clipping for peak-to-average power ratio (PAPR control. We show, analytically and with simulations, that this new scheme can produce large performance improvements, yet reduces the implementation complexity when compared with the original one.

  12. Autocrine Signaling and Quorum Sensing: Extreme Ends of a Common Spectrum.

    Science.gov (United States)

    Doğaner, Berkalp A; Yan, Lawrence K Q; Youk, Hyun

    2016-04-01

    'Secrete-and-sense cells' can communicate by secreting a signaling molecule while also producing a receptor that detects the molecule. The cell can potentially 'talk' to itself ('self-communication') or talk to neighboring cells with the same receptor ('neighbor communication'). The predominant forms of secrete-and-sense cells are self-communicating 'autocrine cells', which are largely found in animals, and neighbor-communicating 'quorum sensing cells', which are mostly associated with bacteria. While assumed to function independently of one another, recent studies have discovered quorum-sensing organs and autocrine-signaling microbes. Moreover, similar types of genetic circuit control many autocrine and quorum-sensing cells. Here, we outline these recent findings and explain how autocrine and quorum sensing are two sides of a many-sided 'dice' created by the versatile secrete-and-sense cell.

  13. Public-private collaborations and partnerships in stratified medicine: making sense of new interactions.

    Science.gov (United States)

    Chataway, Joanna; Fry, Caroline; Marjanovic, Sonja; Yaqub, Ohid

    2012-09-15

    The field of personalised or stratified medicine is evolving alongside the formation of a plethora of public/private partnerships and collaborations. These new institutional forms, or 'social technologies', are varied and emerge in response to several drivers, including the need to draw on a broader base of data inputs relating to genomics, patient behaviour and healthcare system differentiation. This paper discusses some of these drivers of partnerships and collaborations. Although the number of such partnerships is growing, their rationale and basis for collaboration remains unclear. Public-private collaborations are at the core of the set of new life sciences policies in the UK but there is little indication in the policy documents of clear boundaries for these partnerships. In part, this is due to the lack of empirical evidence at the system level for conceptualising what is still a relatively new approach. The collection of evidence in the form of broad evaluations, rather than tightly focused theoretical studies, is more likely to be related back to systems and be of more use for formulating policy rationales.

  14. Building a Research-Community Collaborative to Improve Community Care for Infants and Toddlers At-Risk for Autism Spectrum Disorders

    Science.gov (United States)

    Brookman-Frazee, Lauren; Stahmer, Aubyn C.; Lewis, Karyn; Feder, Joshua D.; Reed, Sarah

    2012-01-01

    This article describes the formation and initial outcomes of a research-community collaborative group that was developed based on community-based participatory research principles. The group includes a transdisciplinary team of practitioners, funding agency representatives, researchers, and families of children with autism spectrum disorders, who…

  15. Secure Cooperative Spectrum Sensing via a Novel User-Classification Scheme in Cognitive Radios for Future Communication Technologies

    Directory of Open Access Journals (Sweden)

    Muhammad Usman

    2015-05-01

    Full Text Available Future communication networks would be required to deliver data on a far greater scale than is known to us today, thus mandating the maximal utilization of the available radio spectrum using cognitive radios. In this paper, we have proposed a novel cooperative spectrum sensing approach for cognitive radios. In cooperative spectrum sensing, the fusion center relies on reports of the cognitive users to make a global decision. The global decision is obtained by assigning weights to the reports received from cognitive users. Computation of such weights requires prior information of the probability of detection and the probability of false alarms, which are not readily available in real scenarios. Further, the cognitive users are divided into reliable and unreliable categories based on their weighted energy by using some empirical threshold. In this paper, we propose a method to classify the cognitive users into reliable, neutral and unreliable categories without using any pre-defined or empirically-obtained threshold. Moreover, the computation of weights does not require the detection, or false alarm probabilities, or an estimate of these probabilities. Reliable cognitive users are assigned the highest weights; neutral cognitive users are assigned medium weights (less than the reliable and higher than the unreliable cognitive users’ weights; and unreliable users are assigned the least weights. We show the performance improvement of our proposed method through simulations by comparing it with the conventional cooperative spectrum sensing scheme through different metrics, like receiver operating characteristic (ROC curve and mean square error. For clarity, we also show the effect of malicious users on detection probability and false alarm probability individually through simulations.

  16. Partial Discharge Detection Using Low Cost RTL-SDR Model for Wideband Spectrum Sensing

    DEFF Research Database (Denmark)

    Mohamed, H.; Lazaridis, Pavlos; Upton, D.

    2016-01-01

    an optimal approach for PD signal analysis, and are very costly. In this paper an RTLSDR (Software Defined Radio) based spectrum analyser has been proposed in order to provide a potentially low cost solution for PD detection and monitoring. Initially, a portable spectrum analyser has been used for PD...

  17. Securing Consensus-Based Cooperative Spectrum Sensing Against Spectrum Sensing Data Falsification Attacks%抗SSDF攻击的一致性协作频谱感知方案

    Institute of Scientific and Technical Information of China (English)

    刘全; 高俊; 郭云玮; 刘思洋

    2011-01-01

    在分布式认知无线电网络中,一般很难找到合适的融合中心能够收集所有协作用户的感知信息,而且协作过程极可能遭到篡改感知数据(Spectrum Sensing Data Falsification,SSDF)攻击.鉴于此,该文提出了一种改进的一致性协作频谱感知方案.利用Metropolis迭代规则,各次用户仅依靠邻接点之间的局部信息交互即可实现感知协作,且无需网络的任何先验知识.为了抵抗潜在的三种SSDF攻击,该方案中引入了相应的抗攻击策略,使合法次用户能及时检测并拒绝恶意用户接入网络.仿真结果表明,改进方案能保证绝大多数合法次用户最终趋于状态一致,并分别做出正确决策;与现有的一致性方案相比,该方案能使协作感知在各种攻击场景中的稳健性明显增强.%In distributed cognitive radio networks (CRNs), a common fusion centre is always not available to collect the sensing results from all cooperative users,and the sensing cooperation is likely to be disrupted by spectrum sensing data falsification (SSDF) attacks. Allowing for these factors, this paper proposes a modified consensus-based scheme for decentralized cooperative spectrum sensing(CSS) .Utilizing the iteration rule based on Metropolis weight matrix,each secondary user (SU) can maintain cooperation with others only through the local information exchange in the neighborhood, without requiring any a priori knowledge of the whole network. To counter three potential attack models of SSDF, some anti-attack strategies are also introduced,by which the authentic Sus can identify and reject the malicious users quickly. As represented by the extensive simulation results, the proposed scheme can generally guarantee most authentic Sus to reach a consensus and make right decisions individually; also,it is proved to be much more robust against all potential SSDF attacks,compared with the existing consensus-based scheme.

  18. Sixteen years of Collaborative Learning through Active Sense-making in Physics (CLASP) at UC Davis

    CERN Document Server

    Potter, Wendell; West, Emily; Paul, Cassandra; Bowen, Mark; Weiss, Brenda

    2012-01-01

    The introductory physics series for bioscience students at the University of California, Davis is described. A central feature of the class is sense-making by the students during organized discussion/labs in which the students take part in peer-peer discussions, argumentation, and presentations of ideas. Differences in outcomes (MCAT scores and upper division GPAs) of students taking this class and students taking the standard physics series that this class supplanted are discussed.

  19. Channel Exploration and Exploitation with Imperfect Spectrum Sensing in Cognitive Radio Networks

    CERN Document Server

    Zhang, Zhou; Tan, Peng; Slevinsky, Jim

    2012-01-01

    In this paper, the problem of opportunistic channel sensing and access in cognitive radio networks when the sensing is imperfect and a secondary user has limited traffic to send at a time is investigated. Primary users' statistical information is assumed to be unknown, and therefore, a secondary user needs to learn the information online during channel sensing and access process, which means learning loss, also referred to as regret, is inevitable. In this research, the case when all potential channels can be sensed simultaneously is investigated first. The channel access process is modeled as a multi-armed bandit problem with side observation. And channel access rules are derived and theoretically proved to have asymptotically finite regret. Then the case when the secondary user can sense only a limited number of channels at a time is investigated. The channel sensing and access process is modeled as a bi-level multi-armed bandit problem. It is shown that any adaptive rule has at least logarithmic regret. Th...

  20. Attack-Tolerant Cooperative Spectrum Sensing Algorithm for Faded and Low-Power Primary User Signal Detection Over Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Mohammad Akbari

    2015-03-01

    Full Text Available Cognitive radio (CR is a novel scheme that is proposed recently to overcome the spectrum scarcity problem in wireless networks through dynamic spectrum access techniques. In this realm, detection of the legitimate users, called primary user (PU, is a primary mission that must be done carefully to prohibit causing any confliction. PU detection in low signal to noise ratio (SNR regime is one of the main challenges of CR users that measure the energy level of the PU for sensing the spectrum. This process will be more complicated when the SNR fluctuations due to wireless channel effects are taking into accounts. Another source of ambiguity is the false sensing data that might be reported by malfunctioning or malicious secondary nodes, the so called spectrum sensing data falsification attackers (SSDF. This paper utilizes the potential benefits of cooperative spectrum sensing method in a way that it can become applicable when the CR nodes encounter wireless channel uncertainty and (or some CR nodes that behave maliciously. To this end, the estimated PU-signal and channel statistics are employed to determine the likelihood of CR sensing reports in a MAP hypothesis test scheme for decision about channel occupancy. Also, in order to determine the trustworthiness of each CR-user's data and eliminate the effect of SSDF attackers, a computational trust evaluation algorithm is proposed that is based on the resolved likelihood of CR sensing reports

  1. Wideband Spectrum Sensing Based on MUSIC Algorithm%基于MUSIC算法的宽带频谱感知

    Institute of Scientific and Technical Information of China (English)

    赵知劲; 张鹏; 尚俊娜; 王海泉

    2012-01-01

    The estimation of the number of primary user's signal is a key issue for wideband spectrum sensing method based on MUSIC algorithm. To this end, this paper proposes an algorithm to estimate the number of the signals utilizing search matching algorithm with dynamic threshold. The orthogonal properties of signal subspace and noise subspace is used in this algorithm, which adjusts threshold constantly and searches the signal number that is the best matches with dimensions as the final estimate value. Simulation results show that the proposed algorithm has high accuracy at low Signal Noise Ratio{SNR) which greatly improves the performance of the wideband spectrum sensing.%利用MUSIC算法进行宽带频谱感知时,主用户信号个数估计是关键问题.为此,提出一种动态门限搜索匹配的信号个数估计算法.利用信号子空间和噪声子空间的正交性动态调整门限,搜索与预设维度最匹配的信号个数作为最终的估计值.仿真结果表明,在低信噪比的情况下,该算法能准确估计信号个数,提高宽带频谱感知性能.

  2. Navigating the "Research-to-Operations" Bridge of Death: Collaborative Transition of Remotely-Sensed Snow Data from Research into Operational Water Resources Forecasting

    Science.gov (United States)

    Miller, W. P.; Bender, S.; Painter, T. H.; Bernard, B.

    2016-12-01

    Water and resource management agencies can benefit from hydrologic forecasts during both flood and drought conditions. Improved predictions of seasonal snowmelt-driven runoff volume and timing can assist operational water managers with decision support and efficient resource management within the spring runoff season. Using operational models and forecasting systems, NOAA's Colorado Basin River Forecast Center (CBRFC) produces hydrologic forecasts for stakeholders and water management groups in the western United States. Collaborative incorporation of research-oriented remote sensing data into CBRFC operational models and systems is one route by which CBRFC forecasts can be improved, ultimately for the benefit of water managers. Successful navigation of research-oriented remote sensing products across the "research-to-operations"/R2O gap (also known as the "valley of death") to operational destinations requires dedicated personnel on both the research and operations sides, working in a highly collaborative environment. Since 2012, the operational CBRFC has collaborated with the research-oriented Jet Propulsion Laboratory (JPL) under funding from NASA to transition remotely-sensed snow data into CBRFC's operational models and forecasting systems. Two specific datasets from JPL, the MODIS Dust Radiative Forcing in Snow (MODDRFS) and the MODIS Snow Covered-Area and Grain size (MODSCAG) products, are used in CBRFC operations as of 2016. Over the past several years, JPL and CBRFC have worked together to analyze patterns in JPL's remote sensing snow datasets from the operational perspective of the CBRFC and to develop techniques to bridge the R2O gap. Retrospective and real-time analyses have yielded valuable insight into the remotely-sensed snow datasets themselves, CBRFC's operational systems, and the collaborative R2O process. Examples of research-oriented JPL snow data, as used in CBRFC operations, are described. A timeline of the collaboration, challenges

  3. Atmospheric correction of remote sensing imagery based on the surface spectrum's vector space

    Institute of Scientific and Technical Information of China (English)

    CHEN Chun; LIU ChengYu; ZHANG ShuQing

    2012-01-01

    Due to the atmosphere effect,the qualities of images decrease conspicuously,practically in the visible bands,in the processing of earth observation by the satellite-borne sensors.Thus,removing the atmosphere effects has become a key step to improve the qualities of images and to retrieve the actual reflectivity of surface features.An atmospheric correction approach,called ACVSS (Atmospheric Correction based Vector Space of Spectrum),is proposed here based on the vector space of the features'spectrum.The reflectance image of each band is retrieved first according to the radiative transfer equation,then the spectrum's vector space is constructed using the infrared bands,and finally the residual errors of the reflectance images in the visible bands are corrected based on the pixel position in the spectrum's vector space.The proposed methodology is verified through atmospheric correction on Landsat-7 ETM+ imagery.The experimental results show that our method is more accurate and the corrected image is more distinct,compared with those offered by current popular atmospheric correction software.

  4. Machine Learning-Aided, Robust Wideband Spectrum Sensing for Cognitive Radios

    Science.gov (United States)

    2015-06-12

    these sub-bands spanning several non-contiguous frequency ranges can be achieved using reconfigurable antennas [8]. Figure 1. The Spectrum of... Antenna Systems,” in Proc. International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS), Chiangmai, Thailand, pp. 1–6

  5. Study and Optimization of Cooperative Spectrum Sensing in OFDM Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Yingxue Li

    2012-11-01

    Full Text Available In this paper, a cooperative sensing algorithm for OFDM is proposed in this paper based on the performance analysis of ONPD algorithm, then the system weight vector is optimized and the closed form expression of optimal weight vector is obtained using the maximum improved deflection coefficient. Theoretical analysis and simulation results demonstrate the remarkable improvement of proposed algorithm on detection performance compared with the classical cooperation detection algorithm.

  6. A Novel Two-stage Entropy-based Robust Cooperative Spectrum Sensing Scheme with Two-bit Decision in Cognitive Radio

    CERN Document Server

    Zhao, Nan

    2011-01-01

    Spectrum sensing is a key problem in cognitive radio. However, traditional detectors become ineffective when noise uncertainty is severe. It is shown that the entropy of Gauss white noise is constant in the frequency domain, and a robust detector based on the entropy of spectrum amplitude was proposed. In this paper a novel detector is proposed based on the entropy of spectrum power density, and its performance is better than the previous scheme with less computational complexity. Furthermore, to improve the reliability of the detection, a two-stage entropy-based cooperative spectrum sensing scheme using two-bit decision is proposed, and simulation results show its superior performance with relatively low computational complexity.

  7. Broad Spectrum Anti-Quorum Sensing Activity of Tannin-Rich Crude Extracts of Indian Medicinal Plants

    Directory of Open Access Journals (Sweden)

    Varsha Shukla

    2016-01-01

    Full Text Available Quorum sensing (QS mechanisms have been demonstrated to have significance in expression of pathogenicity in infectious bacteria. In Gram negative bacteria the autoinducer molecules that mediate QS are acyl homoserine lactones (AHL and in Gram positive bacteria they are peptides called autoinducing peptides (AIP. A screening of tannin-rich medicinal plants was attempted to identify extracts that could interrupt the QS mechanisms in both Gram positive and Gram negative bacteria over a wide range of concentrations and therefore potentially be potent agents that could act as broad spectrum QS inhibitors. Six out of the twelve Indian medicinal plant extracts that were analyzed exhibited anti-QS activity in Chromobacterium violaceum 12472 and in S. aureus strain with agr:blaZ fusion over a broad range of subinhibitory concentrations, indicating that the extracts contain high concentration of molecules that can interfere with the QS mechanisms mediated by AHL as well as AIP.

  8. Implementation of an Optical-Wireless Network with Spectrum Sensing and Dynamic Resource Allocation Using Optically Controlled Reconfigurable Antennas

    Directory of Open Access Journals (Sweden)

    E. Raimundo-Neto

    2014-01-01

    Full Text Available This work proposes the concept and reports the implementation of an adaptive and cognitive radio over fiber architecture. It is aimed at dealing with the new demands for convergent networks by means of simultaneously providing the functionalities of multiband radiofrequency spectrum sensing, dynamic resource allocation, and centralized processing capability, as well as the use of optically controlled reconfigurable antennas and radio over fiber technology. The performance of this novel and innovative architecture has been evaluated in a geographically distributed optical-wireless network under real conditions and for different fiber lengths. Experimental results demonstrate reach extension of more than 40 times and an enhancement of more than 30 dB in the carrier to interference plus noise ratio parameter.

  9. Energy Efficiency and SINR Maximization Beamformers for Spectrum Sharing With Sensing Information

    KAUST Repository

    Alabbasi, Abdulrahman

    2014-09-01

    In this paper, we consider a cognitive radio multi-input-multi-output environment, in which we adapt our beamformer to maximize both energy efficiency (EE) and signal-to-interference-plus-noise ratio (SINR) metrics. Our design considers an underlaying communication using adaptive beamforming schemes combined with sensing information to achieve optimal energy-efficient systems. The proposed schemes maximize EE and SINR metrics subject to cognitive radio and quality-of-service constraints. The analysis of the proposed schemes is classified into two categories based on knowledge of the secondary-transmitter-to-primary-receiver channel. Since the optimizations of EE and SINR problems are not convex problems, we transform them into a standard semidefinite programming (SDP) form to guarantee that the optimal solutions are global. An analytical solution is provided for one scheme, while the second scheme is left in a standard SDP form. Selected numerical results are used to quantify the impact of the sensing information on the proposed schemes compared to the benchmark ones.

  10. A robust cooperative spectrum sensing scheme based on Dempster-Shafer theory and trustworthiness degree calculation in cognitive radio networks

    Science.gov (United States)

    Wang, Jinlong; Feng, Shuo; Wu, Qihui; Zheng, Xueqiang; Xu, Yuhua; Ding, Guoru

    2014-12-01

    Cognitive radio (CR) is a promising technology that brings about remarkable improvement in spectrum utilization. To tackle the hidden terminal problem, cooperative spectrum sensing (CSS) which benefits from the spatial diversity has been studied extensively. Since CSS is vulnerable to the attacks initiated by malicious secondary users (SUs), several secure CSS schemes based on Dempster-Shafer theory have been proposed. However, the existing works only utilize the current difference of SUs, such as the difference in SNR or similarity degree, to evaluate the trustworthiness of each SU. As the current difference is only one-sided and sometimes inaccurate, the statistical information contained in each SU's historical behavior should not be overlooked. In this article, we propose a robust CSS scheme based on Dempster-Shafer theory and trustworthiness degree calculation. It is carried out in four successive steps, which are basic probability assignment (BPA), trustworthiness degree calculation, selection and adjustment of BPA, and combination by Dempster-Shafer rule, respectively. Our proposed scheme evaluates the trustworthiness degree of SUs from both current difference aspect and historical behavior aspect and exploits Dempster-Shafer theory's potential to establish a `soft update' approach for the reputation value maintenance. It can not only differentiate malicious SUs from honest ones based on their historical behaviors but also reserve the current difference for each SU to achieve a better real-time performance. Abundant simulation results have validated that the proposed scheme outperforms the existing ones under the impact of different attack patterns and different number of malicious SUs.

  11. Recovery of a spectrum based on a compressive-sensing algorithm with weighted principal component analysis

    Science.gov (United States)

    Dafu, Shen; Leihong, Zhang; Dong, Liang; Bei, Li; Yi, Kang

    2017-07-01

    The purpose of this study is to improve the reconstruction precision and better copy the color of spectral image surfaces. A new spectral reflectance reconstruction algorithm based on an iterative threshold combined with weighted principal component space is presented in this paper, and the principal component with weighted visual features is the sparse basis. Different numbers of color cards are selected as the training samples, a multispectral image is the testing sample, and the color differences in the reconstructions are compared. The channel response value is obtained by a Mega Vision high-accuracy, multi-channel imaging system. The results show that spectral reconstruction based on weighted principal component space is superior in performance to that based on traditional principal component space. Therefore, the color difference obtained using the compressive-sensing algorithm with weighted principal component analysis is less than that obtained using the algorithm with traditional principal component analysis, and better reconstructed color consistency with human eye vision is achieved.

  12. Spectrum Sensing in relation to Distributed Antenna System for Coverage Predictions

    DEFF Research Database (Denmark)

    Kumar, Ambuj; Mihovska, Albena D.; Prasad, Ramjee

    2014-01-01

    (BTS)/Nodes at one location known as BTS hotel and the antennas are distributed all over target area by fiber optic network, is discussed. The very concept of splitting Base Station (BS) from its antenna system and putting it at one location (BS Hotel) and distributing antenna as nodes (Remote Unit......Distributed Antenna Systems (DAS) is one of the most promising ways of network deployment now-a-days. Mostly it is used in indoor environment for shopping areas and office locations. Here the Outdoor application of DAS, where multiple service providers can install their Base Transceiver Station...... technology adaptability, efficient energy usage etc. make O-DAS (Outdoor-DAS) network very lucrative. However, for an O-DAS network with large distribution of Remote Units, it is required to have complete knowledge of the spectrum environment at all the locations of remote unit for understanding actual...

  13. 基于软件无线电平台的频谱感知实验设计%Design of Spectrum Sensing Experiment Based on SDR Platform

    Institute of Scientific and Technical Information of China (English)

    王洪; 陈祝明; 郭睿刚

    2016-01-01

    频谱感知是感知无线电、动态频谱分配和电子侦听的核心,具有通用性的频谱感知实验可应用于相关的多门课程,在软件无线电平台上设计的频谱感知实验可编程重构,适用于较宽频段和多种信号。该文介绍了USRP与GNU Radio结合的软件无线电平台,讨论了频谱感知的基本原理,设计了基于能量检测的频谱感知实验,并以城市调频广播为例演示了频谱感知实验的过程和结果。%Spectrum sensing is the core of cognitive radio,dynamic spectrum distribution and electronic reconnaissance.Univer-sal experiment of spectrum sensing can be used in many relevant courses.Spectrum sensing experiment can be reconstructed by pro-gramming and be applicable to wide frequency range and signal diversity.This paper introduces the software platform with USRP and GNU Radio first.Then basic theory of spectrum sensing is discussed.We design experiments based on energy detection.Finally,fre-quency modulation broadcasting in city is chosen as an example to show the procedure and results of spectrum sensing.

  14. Remote Sensing of Snow in the Solar Spectrum: Experiments in the French Alps.

    Directory of Open Access Journals (Sweden)

    M. Fily

    2000-04-01

    Full Text Available Two experiments were perfonned irliApril and December 1992 in the French Alps using simultaneous relnote sensing and ground truth data. Snow grain site and soot content of samples collected in thefield were measured. The Landsat thematic mapper (TM sensor was used because it has a good spatial resolution, a middle infrared channel which is sensitive to grain size and a thermal infraredchannel. Firstj the reflectance data were compared with the theoretical results obtained from a bidirectional reflectance model. Then, some remote sehstng-derived snow parameters wbre comparediWith the outpllt ofa snow metamorphism model (CROCUS,viz., lower elevation of the snowcover, lhe surface grl1in size and the surface temperature. A digital elevation model was used to obtain thelocal incidenc:f angles and the elevation of each snow pixel. The pixels were then grouped according to CROCUS classification (range, elevation, slope, and orientation and the mean snow chart;cheracteristicsfor each class were .compared with the tROCUS results. The lower limit of snow and the surface grain size derived from TM data were compared favourably with the model results. Larger differences werefound for the temperature, because it varies rapidly and is very sensitive to shadowing by the snrrounding mountains and also because its remote measurement is dependent on atmospheric conditions.

  15. Sensing the Worst: Neurophenomenological Perspectives on Neutral Stimuli Misperception in Schizophrenia Spectrum

    Directory of Open Access Journals (Sweden)

    Mariateresa Sestito

    2017-06-01

    Full Text Available While investigating social cognitive impairments in schizophrenia, prominent evidence has been found that patients with schizophrenia show a tendency to misclassify neutral stimuli as negatively valenced. Within this population, patients presenting delusions are more prone to this phenomenon. In a previous study, Schizophrenia spectrum (SzSp patients rated positive, negative and neutral stimuli that were multimodally presented, while assessed with a checklist exploring anomalous subjective experiences and evaluated for positive and negative symptomatology. In the present work, we aimed to further explore the relationship between neutral stimuli misperception, anomalous experiences and positive/negative symptoms in SzSp patients. To this end, we adopted a dimensional approach by reconstructing from available data: (1 four a priori scales representing essential dimensions of SzSp experiential pathology following Parnas et al. (2005; and (2 five clinically meaningful factors to describe illness severity derived by Toomey et al. (1997. Results showed that although overall patients correctly recognized the target emotions, those who misinterpreted neutral auditory cues as negatively valenced also presented higher scores in Perplexity (PY, Bizarre Delusions (BD and Disorganization (Di dimensions. Moreover, a positive association between BD and both PY and Self-Disorder (SD dimensions emerged, suggesting that psychotic symptoms may be directly linked to patients’ subjectivity. In an attempt to comprehensively capture the multilayered neutral stimuli misperception phenomenon in SzSp, we aimed at bridging phenomenology and neurobiology by connecting the levels of molecular neurochemistry (i.e., altered dopaminergic neurotransmission, system neuroscience (aberrant salience of perceptual details and psychopathology (the chain involving hyper-reflexivity, self-disorders and the emergence of delusions.

  16. Collaborative Approaches to Increase the Utility of Spatial Data for the Wildfire Management Community Through NASA's Applied Remote Sensing Training Program

    Science.gov (United States)

    McCullum, A. J. K.; Schmidt, C.; Blevins, B.; Weber, K.; Schnase, J. L.; Carroll, M.; Prados, A. I.

    2015-12-01

    The utility of spatial data products and tools to assess risk and effectively manage wildfires has increased, highlighting the need for communicating information about these new capabilities to decision makers, resource managers, and community leaders. NASA's Applied Remote Sensing Training (ARSET) program works directly with agencies and policy makers to develop in-person and online training courses that teach end users how to access, visualize, and apply NASA Earth Science data in their profession. The expansion of ARSET into wildfire applications began in 2015 with a webinar and subsequent in-person training hosted in collaboration with Idaho State University's (ISU) GIS Training and Research Center (TReC). These trainings featured presentations from the USDA Forest Service's Remote Sensing Training and Applications Center, the Land Processes DAAC, Northwest Nazarene University, NASA Goddard Space Flight Center, and ISU's GIS TReC. The webinar focused on providing land managers, non-governmental organizations, and international management agencies with an overview of 1) remote sensing platforms for wildfire applications, 2) products for pre- and post-fire planning and assessment, 3) the use of terrain data, 4) new techniques and technologies such as Unmanned Aircraft Systems and the Soil Moisture Active Passive Mission (SMAP), and 5) the RECOVER Decision Support System. This training highlighted online tools that engage the wildfire community through collaborative monitoring and assessment efforts. Webinar attendance included 278 participants from 178 organizations in 42 countries and 33 US states. The majority of respondents (93%) from a post-webinar survey indicated they displayed improvement in their understanding of specific remote-sensing data products appropriate for their work needs. With collaborative efforts between federal, state, and local agencies and academic institutions, increased use of NASA Earth Observations may lead to improved near real

  17. Popular Content Distribution in CR-VANETs with Joint Spectrum Sensing and Channel Access using Coalitional Games

    Directory of Open Access Journals (Sweden)

    Tianyu Wang

    2014-07-01

    Full Text Available Driven by both safety concerns and commercial interests, popular content distribution (PCD, as one of the key services offered by vehicular networks, has recently received considerable attention. In this paper, we address the PCD problem in highway scenarios, in which a popular file is distributed to a group of onboard units (OBUs driving through an area of interest (AoI. Due to high speeds of vehicles and deep fading of vehicle-to-roadside (V2R channels, the OBUs may not finish downloading the entire file. Consequently, a peer-to-peer (p2p network should be constructed among the OBUs for completing the file delivery process. Here, we apply the cognitive radio technique for vehicle-to-vehicle communications and propose a cooperative approach based on coalition formation games, which jointly considers the spectrum sensing and channel access performance. Simulation results show that our approach presents a considerable performance improvement compared with the non-cooperative case.

  18. 一种信任度模糊分配的合作频谱感知算法%A Cooperative Spectrum Sensing Algorithm Based on Fuzzy Credibility

    Institute of Scientific and Technical Information of China (English)

    韩勇; 王放; 陈强; 王建新

    2011-01-01

    Due to multipath fading and shadow effect etc factors, single cognitive user can' t distinguish between the unused bands and license user' s signal in deep fade. Cooperative spectrum sensing uses information fusion technology to improve spectrum sensing performance by combining multi-cognitive users sensing results. Theory of evidence is an effective way of uncertainty reasoning, which has been used in cooperative spectrum sensing well. In this paper it integrates fuzzy set with theory of evidence and puts forward a cooperative spectrum sensing algorithm based on fuzzy credibility. Each cognitive user first makes local energy detection. Then it uses normal-shaped membership function as basic probability assignment which assigns credibility by cognitive user' s detection result. The fusion center receives all cognitive users' evidence and combines them by Dempster rule. At last the fusion center draws a conclusion. As simulation results shown, the cooperative spectrum sensing algorithm based on fuzzy credibility has a better sensing performance or algorithm complexity than existing cooperative spectrum sensing algorithm based on theory of evidence.%由于无线信道的多径衰落和阴影效应等因素,单个认知用户无法区分频段空闲还是授权用户的信号处于深度衰落中.合作频谱感知运用信息融合技术,通过融合多个认知用户的结果来提高频谱感知的性能.证据理论作为一种有效的不确定性推理方法,在合作频谱感知中已有较好的应用.本文将模糊集与证据理论相结合,提出一种信任度模糊分配的合作频谱感知算法.各个认知用户首先进行本地能量检测,然后使用正态形隶属函数进行基本概率赋值,根据认知用户的检测结果分配信任度.融合中心接收所有认知用户的证据,按照Dempster组合规则进行融合,最后进行判决.仿真结果表明,信任度模糊分配的合作频谱感知算法在感知性能上或者在算法

  19. Temperature-induced spectrum response of a volume grating as an effective strategy for holographic sensing in an acrylamide polymer part II: physical mechanism.

    Science.gov (United States)

    Liu, Hongpeng; Yu, Dan; Zhou, Ke; Mao, Dongyao; Liu, Langbo; Wang, Hui; Wang, Weibo; Song, Qinggong

    2016-12-10

    The temperature response mechanism of a diffraction spectrum in a holographic grating is characterized. Two possible major factors, changes in the refractive index and thermal expansion, are measured and analyzed to identify the sensing physical mechanism. Average refractive indices at various temperatures and relative humidity values are independently measured. Thermal optical coefficients of polymers are estimated quantitatively to evaluate the temperature response capability of the refractive index. Angle selectivity of multiplexing gratings is scanned at various temperatures to obtain magnitudes of Bragg angle detuning. The linear thermal expansion coefficients are extracted by the nonlinear fitting reading angle dependence of angle detuning. The significance of the thermal optical coefficient and the thermal expansion coefficient for holographic sensing is discussed. Finally, the primary factor for temperature-induced wavelength blueshift is analyzed theoretically.

  20. Non-uniform sampling and reconstruction of multi-band signals and its application in wideband spectrum sensing of cognitive radio

    CERN Document Server

    Rashidi, Moslem

    2010-01-01

    Sampling theories lie at the heart of signal processing devices and communication systems. To accommodate high operating rates while retaining low computational cost, efficient analog-to digital (ADC) converters must be developed. Many of limitations encountered in current converters are due to a traditional assumption that the sampling state needs to acquire the data at the Nyquist rate, corresponding to twice the signal bandwidth. In this thesis a method of sampling far below the Nyquist rate for sparse spectrum multiband signals is investigated. The method is called periodic non-uniform sampling, and it is useful in a variety of applications such as data converters, sensor array imaging and image compression. Firstly, a model for the sampling system in the frequency domain is prepared. It relates the Fourier transform of observed compressed samples with the unknown spectrum of the signal. Next, the reconstruction process based on the topic of compressed sensing is provided. We show that the sampling parame...

  1. Molecular genetic analysis of the calcium sensing receptor gene in patients clinically suspected to have familial hypocalciuric hypercalcemia: phenotypic variation and mutation spectrum in a Danish population

    DEFF Research Database (Denmark)

    Nissen, Peter H; Christensen, Signe E; Heickendorff, Lene

    2007-01-01

    hyperparathyroidism and is caused by inactivating mutations in the calcium sensing receptor (CASR) gene. OBJECTIVE: We sought to define the mutation spectrum of the CASR gene in a Danish FHH population and to establish genotype-phenotype relationships regarding the different mutations. DESIGN AND PARTICIPANTS...... calcium concentrations moderately above the upper reference limit, to calcium levels more than 20% above the upper reference limit. Furthermore, the mean plasma PTH concentration was within the normal range in eight of 11 studied mutations, but mild to moderately elevated in families with the mutations p...

  2. Tools and Techniques to Collaborate and Connect with At-Risk Climate Communities UsingSensors, Remote Sensing Data, and Media

    Science.gov (United States)

    Drapkin, J. K.; Ramamurthy, P.; Vant-Hull, B.; Yuen, K.; Glenn, A.; Jusino, C.; Corbin, C.; Schuerman, M.; Keefe, J.; Brooke, H.

    2016-12-01

    Those most at risk during heat waves and floods are often the socio-economically vulnerable. Yet very few studies exist of indoor temperatures during heat waves or of standing water events at the neighborhood level during extreme events. ISeeChange, a community weather and climate journal, is developing tools and testing techniques in a series of community pilots in Harlem and New Orleans to assess if a combination of citizen science, remote sensing, and journalism can bridge the gap. Our consortium of media (WNYC,Adapt NYC, ISeeChange), scientists (CUNY, CoCoRaHS, NASAJPL), and community partners (WE ACT for Environmental Justice, tenant, and neighborhood associations) are collaborating to engage with residents, report radio stories, as well as develop scientifically valuableinformation for decision-making. Community volunteers place temperature and humidity sensors inside residences (Harlem) or photograph standing water using specific methodologies (New Orleans). Sensordata, photographs, and text documenting the impacts of extreme weather on residents are posted on the ISeeChange platform via mobile app or community ambassadors and compared to other remote sensing data products (surface temperature, precipitation, subsidence) Preliminary results of the Harlem pilot show that indoor temperatures are far more stable than outdoor temperatures, so can be both cooler during the day but warmer at night; preliminary work on the New Orleans pilot is set to begin in fall 2016. A full analysis of the Harlem pilot will be presented along with preliminary results of the New Orleans pilot.

  3. Nonparametric Cooperative Spectrum Sensing Algorithm Based on Friedman Test%基于Friedman检验的非参数协作频谱感知方法

    Institute of Scientific and Technical Information of China (English)

    王炯滔; 金明; 李有明; 高洋

    2014-01-01

    Covariance matrix based spectrum sensing encounters performance degradation when there the antenna correlation is low. To overcome this drawback, a nonparametric cooperative spectrum sensing algorithm based on Friedman test is proposed. Distributed sensors possess the effect of space diversity, so that the signal power among the sensors at the same time may not be completely equal. Based on this feature, the spectrum sensing is realized by comparing signal powers among the sensors. For the nonparametric approach is adopted, the proposed algorithm is robust to noise uncertainty and is suitable for noise of any statistical distribution. The theoretical expression of decision threshold is also derived, which shows that the decision threshold has no relationship with the sample number. As a result, the threshold does not need to be reset when the sample number changes. Simulation results demonstrate the effectiveness of the algorithm.%协方差矩阵频谱感知方法在天线相关性低时感知性能较差,该文针对这一问题提出一种基于Friedman检验的非参数协作频谱感知方法。分布式放置的感知节点具有空间分集的特性,因此在同一时刻感知节点上的信号功率不完全相同。利用这一特点,提出通过比较各感知节点的信号功率水平来实现频谱感知。由于采用了非参数化表示,该方法对噪声不确定性稳定,且适用于任意统计分布的噪声。另外,推导了所提方法判决门限的理论表达式,结果显示判决门限与采样点数无关,因此在采样点数变化的情况下无需重新设置判决门限。仿真结果验证了上述理论分析的有效性。

  4. Novel signal separation algorithm based on compressed sensing for wideband spectrum sensing in cognitive radio networks%认知无线电网络中宽频谱的信号分离算法

    Institute of Scientific and Technical Information of China (English)

    吕守涛; 刘健

    2013-01-01

      在认知无线电网络中,认知用户随机接入宽带频谱进行数据传输,但是这样很容易受到恶意用户的干扰,这些恶意用户随意地接入共享频带进行信号传输,这些信号会干扰主用户和认知用户。为此,提出了一种基于压缩感知的信号分离方法。该方法可以很好地从宽带信号中分离出恶意用户信号。算法主要采用以下三个步骤:(1)所有认知用户采用压缩感知技术从宽带频谱中恢复各信号;(2)认知用户将分离的信号发送到融合中心,融合中心通过小波边缘检测的方法确定频谱边缘,并按照边缘特性将频谱分成若干频段;(3)融合中心根据具体特征对每个子频段进行信号分离。分析和仿真结果表明,这种新的基于压缩感知的宽频带信号分离方法能很好地从宽带信号中将含有恶意用户干扰的混合信号分离出来。%In cognitive radio networks, since cognitive terminals use the shared wideband frequency spectrum for data transmissions, they are susceptible to malicious denial-of-service attacks, where adversaries try to corrupt communication by actively transmitting interference signals. To address this issue, this paper proposes a novel signal separation algorithm based on compressed sensing, which can not only recover the entire spectrum but also separate mixed occupying signals. Specifically, the proposed algorithm is executed following three steps:(1)each cognitive terminal attempts to recover all signals over entire wideband spectrum employing compressed sensing technique;(2)all cognitive terminals send their recovered signals to the fusion center where wavelet edge detection method is adopted to locate spectrum edges of these signals and then divide the entire spectrum into several sub-bands;(3)the fusion center separates its received signals on each spectrum sub-band into different categories according to their features. Both analytical and

  5. A collaborative spectrum detection based on MTM with low complexity%一种基于多窗低复杂度的频谱检测算法

    Institute of Scientific and Technical Information of China (English)

    李莉; 黄立辉; 王沛; 张家凯

    2011-01-01

    频谱检测过程中的主用户识别是目前认知无线电研究的主要问题之一,根据Neyman-Pearson准则提出了一种改进的多窗频谱检测算法,得出认知无线电系统在多传感器环境下的最优门限公式,并确定了实际环境下需要传感器的最佳个数要求。实验仿真表明:在给定虚警概率PFA=0.1,信噪比SNR=0dB,多锥度(MTM)阶数K=4时,只需要4个传感器就能达到满足Neyman-Pearson准则的最佳检测性能;由于不需要进行奇异值分解(SVD),因此,相对于传统的多窗结合奇异值分解算法(MTM-SVD),算法的复杂度降低,提高了整个系统的工作效率。%The identification of the primary user is one of the most important issues in the spectrum sensing process for the cognitive radio networks.In the paper,a spectrum detecting algorithm is proposed based on the Neyman-Pearson criterion.The optimum threshold formula is obtained under multi-sensor environment.The optimal required number of the sensors is determined which is adapted to the signal to noise ratio(SNR) in every frequency bin.Simulation results indicate that under constraints of the false alarm probability PFA = 0.1,signal to noise ratio SNR=0 dB,number of tapes K=4,only four sensors are required to achieve the best detection performance under the Neyman-Pearson criterion.Secondly,because the improved algorithm does not require singular value decomposition(SVD) for denoising,the proposed algorithm also reduces the complexity of the system compared with traditional algorithm based on multitaper method with singular value decomposition(MTM-SVD).

  6. Single-channel spectrum sensing technique based on sub-nyquist sampling%基于Sub-Nyquist采样的单通道频谱感知技术

    Institute of Scientific and Technical Information of China (English)

    杨鹏; 樊昀; 黄知涛; 柳征; 姜文利

    2013-01-01

    宽带频谱感知技术在认知无线电中具有广泛的应用.基于时分的思想,将信号采集时间以固定长度的时间片进行划分,分别与不同的伪随机码信号相乘,经过低通滤波和sub-Nyquist采样,利用采样数据求出信号的频率支集.与已有的多通道频谱感知结构相比,本文用相对简单的单通道结构实现,同样能够利用低速率的采样点完成频谱感知.仿真实验结果表明,在信号的频率支集未知的情况下,该算法能够有效利用sub-Nyquist采样的数据实现频谱感知.%Spectrum sensing technique for wideband analog signals has been applied widely in cognitive radio.Based on the idea of time-division,this study was conducted with the following steps.Firstly,sampling time was divided into time slices which have fixed length.Secondly,the signal was multiplied by a bank of periodic waveforms which are modulated by pseudormdom number generators,and the product is low-pass filtered and sampled at sub-Nyquist rate.Finally,the samples were used to evaluate frequency support.Compared with the multi-channel structure,the single-channel structure proposed here is much simpler and has the ability to spectrum sensing with low-rate samples.Numerical simulations show that this algorithm can effectively use samples sampling at sub-Nyquist rate to finish the task of specmum sensing in scenarios that the spectral support is unknown in advance.

  7. Geomorphological diversity of Dong-Sha Atoll based on spectrum and texture analysis in high resolution remote sensing imagery

    Science.gov (United States)

    Chen, Jianyu; Mao, Zhihua; He, Xianqiang

    2009-01-01

    Coral reefs are complex marine ecosystems that are constructed and maintained by biological communities that thrive in tropical oceans. The Dong-Sha Atoll is located at the northern continental margin of the South China Sea. It has being abused by destructive activity of human being and natural event during recent decades. Remote sensing offers a powerful tool for studying coral reef geomorphology and is the most cost-effective approach for large-scale reef survey. In this paper, the high-resolution Quickbird2 imageries which covered the full atoll are used to categorize the current distribution of coral reefs geomorphological structure therein with the auxiliary SPOT5 and ASTER imageries. Spectral and texture analysis are used to distinguish the geomorphological diversity during data processing. The Gray Level Co-occurrence Matrices is adopted for texture feature extraction and atoll geomorphology mapping in the high-resolution pan-color image of Quickbird2. Quickbird2 is considered as the most appropriate image source for coral reefs studies. In the Dong-Sha Atoll, various dynamical geomorphologic units are developed according to wave energy zones. There the reef frame types are classified to 3 different types according as its diversity at the image. The radial structure system is the most characteristic and from high resolution imagery we can distinguish the discrepancy between them.

  8. The Collaborative Future

    Directory of Open Access Journals (Sweden)

    Thomas Marlowe

    2011-10-01

    Full Text Available Collaboration has become an important goal in modern ventures, across the spectrum of commercial, social, and intellectual activities, sometimes as a mediating factor, and sometimes as a driving, foundational principle. Research, development, social programs, and ongoing ventures of all sorts benefit from interactions between teams, groups, and organizations, across intellectual disciplines and across facets and features of the inquiry, product, entity, or activity under consideration. We present a survey of the state of collaboration and collaborative enterprise, in the context of papers and presentations at the International Symposium on Collaborative Enterprises 2011 (CENT 2011, and the extended papers appearing in this special issue.

  9. Improving Transportability of a Cognitive-Behavioral Treatment Intervention for Anxiety in Youth with Autism Spectrum Disorders: Results from a US-Canada Collaboration

    Science.gov (United States)

    Reaven, Judy; Blakeley-Smith, Audrey; Beattie, Tricia L.; Sullivan, April; Moody, Eric J.; Stern, Jessica A; Hepburn, Susan L.; Smith, Isabel M.

    2015-01-01

    Anxiety disorders frequently co-occur in youth with autism spectrum disorders. In addition to developing efficacious treatments for anxiety in children with autism spectrum disorders, it is important to examine the transportability of these treatments to real-world settings. Study aims were to (a) train clinicians to deliver Facing Your Fears:…

  10. Improving Transportability of a Cognitive-Behavioral Treatment Intervention for Anxiety in Youth with Autism Spectrum Disorders: Results from a US-Canada Collaboration

    Science.gov (United States)

    Reaven, Judy; Blakeley-Smith, Audrey; Beattie, Tricia L.; Sullivan, April; Moody, Eric J.; Stern, Jessica A; Hepburn, Susan L.; Smith, Isabel M.

    2015-01-01

    Anxiety disorders frequently co-occur in youth with autism spectrum disorders. In addition to developing efficacious treatments for anxiety in children with autism spectrum disorders, it is important to examine the transportability of these treatments to real-world settings. Study aims were to (a) train clinicians to deliver Facing Your Fears:…

  11. Cooperative Spectrum Sensing under Imperfect Decision Transmission%非理想决策传输条件下的协作频谱感知

    Institute of Scientific and Technical Information of China (English)

    刘全; 高俊; 陈乐生; 郭云玮

    2011-01-01

    The existing solutions of cooperative spectrum sensing ( CSS ) based on decision fusion are mostly built on the assumption of ideal decision transmission without considering any fading or noise corruption in common control channels. For this, the sensing channels and control channels are extend as Suzuki characteristics. A cooperation scheme is proposed under imperfect decision transmission model, in which a detector based on minimum error probability rule is used for decision estimation. The final decision combination is accomplished with K out of N rule. As demonstrated both by simulation, there is some performance deterioration in the proposed scheme, when compared with the ideal case that assumes error-free decision transmission. It is even inferior to the local sensing when the average signal to noise ratio of the control channels is very low. Further, the spatial correlation of shadowing effects is investigated. It is shown that the negative impacts of correlated shadowing on the CSS gets weaker with the increasing distance between each other of the secondary users.%现有的基于决策融合的协作频谱感知方案大多数都是以理想的通用控制信道为前提,没有考虑实际决策传输中也存在衰落及噪声干扰,对此,将感知信道和控制信道建模为Suzuki信道,提出一种基于最小错误概率决策估计和K/N决策融合的协作频谱感知方案.数值分析和仿真结果表明,非理想决策传输条件下的协作感知性能较理想条件下有一定恶化,在控制信道信噪比较低的情况下,其性能甚至不如本地感知.在此基础上,研究了阴影衰落的空间相关性对协作感知性能的影响.仿真结果显示,随着次用户之间距离的增大,阴影相关性的不利影响将逐渐减小.

  12. Collaboration 'Engineerability'

    NARCIS (Netherlands)

    Kolfschoten, Gwendolyn L.; de Vreede, Gert-Jan; Briggs, Robert O.; Sol, Henk G.

    2010-01-01

    Collaboration Engineering is an approach to create sustained collaboration support by designing collaborative work practices for high-value recurring tasks, and transferring those designs to practitioners to execute for themselves without ongoing support from collaboration professionals. A key assum

  13. 无线认知传感器网络的节能频谱感知策略%Energy-efficient spectrum sensing in wireless cognitive sensor networks

    Institute of Scientific and Technical Information of China (English)

    邹丹; 钟国辉; 屈代明; 曹洋

    2009-01-01

    Two energy-efficient strategies are proposed to reduce the energy consumed in the spectrum sensing procedure for wireless cognitive sensor networks. One involves using confidence voting algorithm to reduce the detection number, the other is based on Partially Observable Markov Decision Process (POMDP). Simulation results show that both algorithms can reduce the energy consumed in the detection efficiently, and the combination of the two algorithms can save more than 30% energy compared with the general algorithm with system detection reliability requirement guaranteed.%针对无线认知传感器网络频谱感知过程中的能耗,提出两种节能策略:①使用可信度投票算法来减少传输检测结果的节点个数;②使用基于部分可观测马尔可夫决策过程的检测算法来减少检测次数.仿真结果表明这两种算法均能有效减少检测能耗,而且组合使用时相比一般算法能节省不低于30%的能量,同时保证检测可靠度满足系统要求.

  14. Cooperative spectrum sensing technology based on SNR weighted%基于信噪比权值的合作频谱感知技术

    Institute of Scientific and Technical Information of China (English)

    王鹏; 许成谦

    2011-01-01

    According to the SNR of the cognitive users is different in the wirelss environment, a cooperative spectrum sensing method based on the SNR-weighted is proposed.Cognitive users receive the value of SNR according to the difference of distance fading factor between the cognitive users and the primary uscr, then evaluate the corresponding weight using recursive method Fusion center gives the final decisive result by weight fusion.Simulation results indicate tbat the algorithm can unprove the detection probability of the primary users.The detection performance is also better than that of the tradional hard decision method%根据无线环境中各个认知用户的信噪比不同,提出一种基于信噪比权值的合作频谱感知算法.认知用户根据与主用户之间路径衰落因子的不同,得出各自的信噪比值,再通过递归得到相应的权值.融合中心进行加权融合得出最终判决结果.仿真结果表明,这种算法可以提高对主用户的检测概率,其检测性能也优于传统的硬判决融合准则.

  15. Improving Collaborative Play between Children with Autism Spectrum Disorders and Their Siblings: The Effectiveness of a Robot-Mediated Intervention Based on Lego® Therapy

    Science.gov (United States)

    Huskens, Bibi; Palmen, Annemiek; Van der Werff, Marije; Lourens, Tino; Barakova, Emilia

    2015-01-01

    The aim of the study was to investigate the effectiveness of a brief robot-mediated intervention based on Lego® therapy on improving collaborative behaviors (i.e., interaction initiations, responses, and play together) between children with ASD and their siblings during play sessions, in a therapeutic setting. A concurrent multiple baseline design…

  16. Improving collaborative play between children with autism spectrum disorders and their siblings: The effectiveness of a robot-mediated intervention based on Lego® therapy

    NARCIS (Netherlands)

    Huskens, B.E.B.M.; Palmen, A.M.J.W.; Werff, M. van der; Lourens, T.; Barakova, E.I.

    2015-01-01

    The aim of the study was to investigate the effectiveness of a brief robot-mediated intervention based on Lego® therapy on improving collaborative behaviors (i.e., interaction initiations, responses, and play together) between children with ASD and their siblings during play sessions, in a therapeut

  17. 一种适用于认知超宽带的CUSUM频谱感知算法%Novel CUSUM spectrum sensing algorithm in cognitive UWB

    Institute of Scientific and Technical Information of China (English)

    宋晓鸥; 向新; 毕笃彦; 陈顺方

    2011-01-01

    A novel Cognitive UWB spectrum sensing algorithm is proposed and evaluated, which enables the detection of the low average SNR and low duty ratio signal with low complexity and small detection delay. An uniform probability density function of the low duty ratio received signal is constructed based on the characteristic of the UWB pulse signal. CUSUM test is introduced to implement the detection. Theoretical analysis indicates that the proposed algorithm is suitable for low duty ratio signal detection. Compared with the energy detection algorithm, the proposed algorithm conquers the SNR wall phenomenon, with superior detection delay performance. Furthermore, the theoretical analysis results are proved by simulations.%提出了一种新的认知超宽带频谱感知算法,该算法适合检测低平均信噪比、低占空比的超宽带脉冲信号,且具有复杂度低、检测延迟性能优越的特点.论文根据超宽带脉冲信号特性,给出形式统一的低占空比接收信号概率密度函数表达式,并采用累加和(CUSUM)算法实施检测.仿真结果表明,该算法对低占空比信号具有良好的适应性,有效克服了能量检测的信噪比门限效应,且检测延迟性能优越.

  18. Research on Variable Resolution Spectrum Sensing Method Based on DWPT%基于 DW PT 的可变分辨率频谱感知方法研究

    Institute of Scientific and Technical Information of China (English)

    韦乃棋; 陈自力; 朱安石; 张恒

    2014-01-01

    Spectrum sensing is the premise of cognitive radio realization .In order to implement effective multi-resolution spectrum sensing and find usable spectrum holes fleetly ,an adaptive variable resolution spectrum sensing method based on discrete wavelet packet transform (DWPT ) was proposed .By making use of the characteristics of hierarchical decomposition and threshold denoising of wavelet packet ,the problem of subba-nd sort chaos during wavelet packet decomposition was solved .The influence of nonstationary noise uncertain-ty was eliminated effectively .The sensing could be done according to the chosen resolution and spectrum bands ,which reduced the operation complexity .The simulation results and analysis show that the proposed method has advantages of high precision ,simple arithmetic and fine flexibility .The method is adapted to fast sensing cognitive radio environment .%频谱感知是认知无线电实现的前提。为实现高效多分辨率频谱感知,快速找到可用的频谱空洞,提出了一种基于离散小波包变换(DWPT )的可变分辨率自适应频谱能量检测法。该法利用小波包变换的分层分解和阈值去噪特性,解决了小波包分解过程中的子带排序混乱问题,有效消除了噪声不确定性对检测性能的影响,并可根据需求选择需要的分辨率和频带进行感知,降低了运算复杂度。仿真结果及其分析表明,所提出的方法具有检测精度高、算法简单、灵活性强等优点,适合用来对认知无线电频谱环境进行快速感知。

  19. Spectrum Sensing System Based on Array Duffing Oscillator Under Ultra-Low S NR%超低信噪比下基于阵列式Duffi ng振子的频谱感知系统

    Institute of Scientific and Technical Information of China (English)

    贾琼; 李兵兵

    2013-01-01

    快速、准确、有效的频谱检测算法是实现认知无线电的必要条件,文中主要研究了超低信噪比(小于-20 dB)环境下的频谱感知问题。首先,基于混沌动力学理论并结合频谱感知技术的特点,建立了具有强非线性特征的Duffing振子频谱感知模型。通过引入无量纲系数,实现了不同频率周期激振力作用下振子间的等效转换。然后,针对频谱检测的实际要求,提出了阵列式Duffing振子频谱感知方案。最后采用数值方法,重点分析了所述系统的检测性能。结果表明:在超低信噪比环境下,文中方法与传统的检测方法相比实现原理简单,且检测性能更好,更符合频谱感知技术的实际应用场合。%As a rapid,correct and efficient spectrum detection algorithm is necessary for cognitive radio,this paper mainly focuses on the spectrum sensing under ultra-low signal-to-noise ratio (SNR,less than -20 dB).In the in-vestigation,first,a Duffing oscillator spectrum sensing model with strong nonlinearity is established based on the theory of chaotic dynamics and the characteristics of spectrum sensing.Next,by introducing a dimensionless coeffi-cient as the transformation parameter of the system,the equivalence relationship between oscillators with different driving forces is derived.Then,a spectrum sensing approach based on the array Duffing oscillator is proposed to detect signals in a frequency band.Finally,the detection performance of the established model is numerically ana-lyzed.The results indicate that,as compared with the conventional spectrum detection methods,the proposed ap-proach is simpler to implement and is of higher detection performance.It is thus more applicable in practice.

  20. Reinforcement learning based sensing policy optimization for energy efficient cognitive radio networks

    CERN Document Server

    Oksanen, Jan; Koivunen, Visa

    2011-01-01

    This paper introduces a machine learning based collaborative multi band spectrum sensing policy for cognitive radios. The proposed sensing policy guides secondary users to focus the search of unused radio spectrum to those frequencies that persistently provide them high data rate. The proposed policy is based on machine learning, which makes it adaptive with the temporally and spatially varying radio spectrum. Furthermore, there is no need for dynamic modeling of the primary activity since it is implicitly learned over time. Energy efficiency is achieved by minimizing the number of assigned sensors per each subband under a constraint on miss detection probability. It is important to control the missed detections because they cause collisions with primary transmissions and lead to retransmissions at both the primary and secondary user. The minimization of the number of active sensors is formulated as a binary integer programming problem. Simulations show that the proposed machine learning based sensing policy ...

  1. Collaborative Support for Inclusion

    Science.gov (United States)

    Sanahuja-Gavaldà, Josep M.; Olmos-Rueda, Patricia; Morón-Velasco, Mar

    2016-01-01

    Nowadays, in Catalonia, students with autism spectrum disorders (ASD) are increasingly in regular schools although their presence, participation, learning and success are unequal. Barriers towards inclusion often depend on how to organise supporting at regular schools and the teachers' collaboration during this process. In this paper, the support…

  2. The Sound and the Sense: Exploring the Collaborative Construction of Free-Form Poetry in the Six-Year-Old Group

    Science.gov (United States)

    Pramling, Niklas

    2010-01-01

    An exploratory study into the collaborative activity of creating a poem in early years education is reported. A group of 6-year-old children and their teacher making free-form poetry are followed for three consecutive lessons. The analytical interest is wide in scope, from looking at the process in terms of the verbal actions of the children and…

  3. Environmental Remote Sensing for Natural Resources Management: A Workshop in Collaboration with Faculdade de Agronomia e Engenharia Florestal, Universidade Eduardo Mondlane

    Science.gov (United States)

    Washington-Allen, R. A.; Fatoyinbo, T. E.; Ribeiro, N. S.; Shugart, H. H.; Therrell, M. D.; Vaz, K. T.; von Schill, L.

    2006-12-01

    A workshop titled: Environmental Remote Sensing for Natural Resources Management was held from June 12 23, 2006 at Eduardo Mondlane University in Maputo Mozambique. The workshop was initiated through an invitation and pre-course evaluation form to interested NGOs, universities, and government organizations. The purpose of the workshop was to provide training to interested professionals, graduate students, faculty and researchers at Mozambican institutions on the research and practical uses of remote sensing for natural resource management. The course had 24 participants who were predominantly professionals in remote sensing and GIS from various NGOs, governmental and academic institutions in Mozambique. The course taught remote sensing from an ecological perspective, specifically the course focused on the application of new remote sensing technology [the Shuttle Radar Topography Mission (SRTM) C-band radar data] to carbon accounting research in Miombo woodlands and Mangrove forests. The 2-week course was free to participants and consisted of lectures, laboratories, and a field trip to the mangrove forests of Inhaca Island, Maputo. The field trip consisted of training in the use of forest inventory techniques in support of remote sensing studies. Specifically, the field workshop centered on use of Global Positioning Systems (GPS) and collection of forest inventory data on tree height, structure [leaf area index (LAI)], and productivity. Productivity studies were enhanced with the teaching of introductory dendrochronology including sample collection of tree rings from four different mangrove species. Students were provided with all course materials including a DVD that contained satellite data (e.g., Landsat and SRTM imagery), ancillary data, lectures, exercises, and remote sensing publications used in the course including a CD from the Environmental Protection Agency's Environmental Photographic Interpretation Center's (EPA-EPIC) program to teach remote sensing and

  4. 认知无线网络动态频谱感知决策安全协议框架研究%Research on security protocol framework of dynamic spectrum sensing in cognitive radio networks

    Institute of Scientific and Technical Information of China (English)

    高刃; 伍爵博; 唐龙

    2013-01-01

    对认知网络频谱感知安全研究现状进行了分析,提出了一个频谱感知决策安全协议框架.对认知无线网络模型中相关组件、符号进行了定义,并对其结构和安全性进行了详细描述.通过与相关方案比较,结果表明该协议框架能够用来抵御频谱感知所面临的潜在威胁,使之进行正确的频谱决策.%This paper analyzed the state of the art in spectrum sensing security of cognitive radio networks,and presented a security protocol framework of spectrum sensing.It gave the related definitions for cognitive radio network model and analyzed its structure and security.This paper carried out comparisons with other solutions.The results show that the proposed framework can be used to ward off the potential threat on spectnun sensing in order to make correct decision.

  5. Collaboration and E-collaboration

    DEFF Research Database (Denmark)

    Razmerita, Liana; Kirchner, Kathrin

    2015-01-01

    Understanding student’s perception of collaboration and how collaboration is supported by ICT is important for its efficient use in the classroom. This article aims to investigate how students perceive collaboration and how they use new technologies in collaborative group work. Furthermore, it tr...

  6. Grounding Service-Learning in the Digital Age: Exploring a Virtual Sense of Geographic Place through Online Collaborative Mapping and Mixed Media

    Science.gov (United States)

    Sandy, Marie G.; Franco, Zeno E.

    2014-01-01

    A sense of place has been an integral part of service-learning since the field's inception; it describes one's attachment to a particular geographic place and is often a precursor to engaging in action to care for localities and their inhabitants. But practicing service-learning in online environments requires reconsidering this core value. Should…

  7. Intensifying the Science, the Senses, and the Impact: A tale of Collaboration Between an Academic Research Lab and two Visual Artists

    Science.gov (United States)

    Tweedie, C. E.; Mazza Ramsay, F. D.; Samsel, F.

    2015-12-01

    Arguably, the majority of the scientific challenges being undertaken today have relevance to society - either for their direct influence on management, policy, or human-environmental wellbeing, or for a capacity to stretch the imagination and cause wonder about the natural world. For any scientific endeavor to achieve full impact and reach diverse audiences requires not only excellent science and a mastery of analytical approaches, but also creative messaging, visual appeal, and charismatic communication strategies using innovative media. Such qualities and challenges are encountered routinely by artists. As such, science has a lot to gain from learning, leveraging, and collaborating with the artistic community. In this paper, we detail the collaborative relationship that has developed between two visual artists and a research lab that is focused on ecosystem science, technological development, and education and outreach. We describe how our relationship was developed, the successes and challenges we have experienced, the lessons learned, and our future directions. We also present several guiding principles in the hope that other researchers may utilize to forge other successful collaborations between the science communities and creative industries.

  8. Survey on The Research of Spectrum Sensing Technologies Based on Random Matrix Theory%基于随机矩阵理论的频谱感知技术研究综述

    Institute of Scientific and Technical Information of China (English)

    王磊; 郑宝玉; 崔景伍

    2011-01-01

    Cognitive radio technology, which can improve the utilization rate of spectrum resources, has broad application prospect , and is likely to lead to another major revolution in the field of wireless communications. Spectrum sensing is the first step of cognitive radio technology, but its performance is far from the actual needs. Developed a truly practical application of high-performance spectrum sensing method has become an urgent problem to be solved. In recent years, a new theory closely related to wireless communications , random matrix theory ( RMT) , has been further applied to achieve a high performance in the field of spectrum sensing. New algorithms based on RMT and the latest research rusults, non-asymptotic random matrix theory (Non-Asymptotic RMT) , are expected to be the true high-performance sensing technology to practical applications. Therefore, the research on spectrum sensing technology based on random matrix theory has very important theoretical and practical value. This paper summarizes the development process of RMT in areas of cognitive radio spectrum sensing; introduces its basic principle, summed up its main characteristics, and prospects for further research.%认知无线电技术,可以提高频谱资源的利用率,应用前景广阔,极有可能引发无线通信领域的又一次重大变革.但频谱感知作为认知无线电技术的首要环节,其性能还远不能满足实际需要.研究出一种真正能够实际应用的高性能频谱感知方法已经成为一个亟待解决的问题.近年来,与无线通信领域密切相关的新理论——随机矩阵理论(RMT),在频谱感知领域得到了进一步的应用,实现了高性能频谱感知.且RMT最新研究成果——非渐近随机矩阵理论(Non-Asymptotic RMT)有望将这项高性能感知技术真正推向实际应用.因此,基于随机矩阵理论的频谱感知技术具有重要的研究价值.本文总结RMT在认知无线电频谱感知领域的发展历程

  9. 认知网络中基于演化博弈的频谱感知技术%Evolutionary Game for Cooperative Spectrum Sensing in Cognitive Radio Networks

    Institute of Scientific and Technical Information of China (English)

    陈亮; 纪红; 李屹; 李曦

    2012-01-01

    A new cooperative spectrum sensing scheme in cognitive radio networks based on evolutionary game is proposed to analyze the secondary users' transmission time and throughput, model the cooperative sensing as an evolutionary game, derive the dynamic procedure and optimal strategy for the secondary users, and develop a distributed learning algorithm as well. Analysis and simulation show that the proposed scheme guarantees sensing reliability without any performance loss and reduces the communication overhead significantly to achieve high throughput for secondary user in sensing cooperation.%提出了一种基于演化博弈理论的认知网络协作频谱感知方法.对协作频谱感知中次级用户的传输时间和吞吐量进行分析,建立协作感知的博弈模型并研究其动态演化特性,基于次级用户吞吐量最大化准则,得到相应纳什均衡解,在此基础上提出一种次级用户自适应分布式学习算法.理论分析和仿真结果表明,这种协作感知方法在保证检测性能的基础上,有效减少了协作通信开销,提高了次级用户吞吐量.

  10. A Survey on Spectrum Sensing Security Issues in Cognitive Radio Networks%认知无线电网络中频谱感知安全的研究进展

    Institute of Scientific and Technical Information of China (English)

    汪晓睿; 刘全

    2011-01-01

    频谱感知是认知无线电网络中的核心功能,它的引入可使次用户在不干扰主用户的前提下实现对授权频段的伺机接入,然而,同时也给网络带来了许多安全方面的新隐患.该文对频谱感知安全的最新研究进展进行了综述,针对物理层的伪装主用户攻击,分析了两种主流解决思路的可行性.针对链路层的篡改感知数据攻击,分别在信息融合式和分布式两种不同的感知场景下,归纳并比较了几种典型抗攻击策略的优劣.在此基础上,明确了下一步的主要研究方向.%In CRNs,spectrum sensing is the core functionality,and with the help of it, the secondary users are allowed to access the authorized spectrum bands in an opportunistic manner, without causing any interference to the primary users. However,it also brings in some new security threats. In this paper,the recent advances of security issues in CRNs are surveyed. For the primary user emulation attacks in the physical layer,the feasibility of two mainstream solutions is analyzed. For the spectrum sensing data falsification attacks in the link layer,the performances of several typical anti-attack strategies are summarized and compared,in the information-fusion-based CSS scenario and the decentralized CSS scenario,respectively. Furthermore,the main directions for the future research are viewed.

  11. Space-polarization Collaborative Suppression Method for Ionospheric Clutter in HFSWR

    Directory of Open Access Journals (Sweden)

    Yang Yunlong

    2016-12-01

    Full Text Available High Frequency Surface Wave Radar (HFSWR is able to receive surface target and low-flying aircraft echoes at a long-distance, but it suffers severely from ionospheric clutter. In this paper, a spacepolarization collaborative-based filter is introduced to mitigate ionospheric clutter. For parameter estimation on ionospheric clutter used for filters, a spatial parameter estimation algorithm based on compressive sensing is introduced to the DOA estimation of ionospheric clutter. In addition, a polarized parameter estimation algorithm based on statistical characteristics is proposed for ionospheric clutter in the range-Doppler spectrum. Higher estimation accuracy is achieved as a result of the range-Doppler spectrum; therefore, these two estimation algorithms enhance the performance of the space-polarization collaborative suppression method for ionospheric clutter. Experimental results of practical dual-polarized HFSWR data show the effectiveness of the two algorithms and the above mentioned filter for ionospheric clutter suppression.

  12. Collaborative experience

    DEFF Research Database (Denmark)

    Mortensen, Thomas Bøtker

    Literature review: Collaborative experience has been shown to have a positive effect on the collaborative outcome in general (Anand & Khanna, 2000; Kale, Dyer & Singh, 2002). Furthermore, it has been linked to the ability to exploit the network of the firm for learning (Powell, Koput and Smith...... experience was largest the higher the hypothesized ambiguity. Theoretically contribution: This research project aims at contributing to existing literature by arguing, that collaborative experience is a moderating variable which moderates the effects on collaborative outcome from the level of complexity......, that the largest effects from collaborative experience is from recent collaborative experience, since knowledge depreciates when it is not used. Methodologically contribution: The research project studies the dyad and aims at introducing, to this field of research, an established way of collecting data, a new...

  13. Working Collaboratively

    DEFF Research Database (Denmark)

    Holder, Anna; Lovett, George

    2009-01-01

    Working collaboratively is arguably an essential skill in architectural practice as the complexity of contemporary projects involves multiple agents in the conception, construction and use of architecture. This has been emphasised by recent government rhetoric. Mass collaboration has been...... identified as a transformative global force of the last decade, most notably in knowledge and information publishing, communication and creation. This paper presents a structured conversation on changing understandings of collaboration, and the realities of collaborative methodology in architectural work....... Ideas of the platforms and structures necessary to support ‘creative’ collaborations are advanced and tested, and a vocabulary of key terms is developed. The conversation extends to reflect on the role of the architecture profession in supporting or enabling collaboration in architectural works....

  14. Differential brain storm optimization algorithm and its application to spectrum sensing%差分头脑风暴算法及其在频谱感知中的应用

    Institute of Scientific and Technical Information of China (English)

    刁鸣; 王小兰; 高洪元

    2016-01-01

    为了有效求解连续优化问题,基于差分进化算法和头脑风暴优化算法的智能演进原理,提出一种新的全局搜索算法,即差分头脑风暴算法。通过4个经典的基准函数对该算法进行测试,并将该算法应用于频谱感知这个认知无线电领域的热点问题,提出基于差分头脑风暴的协作式频谱感知算法。使用差分头脑风暴算法、头脑风暴算法、混合蛙跳算法以及粒子群算法进行仿真对比。仿真结果表明,所提出的算法基于设计的创新方程,具有很强的全局收敛能力,能够显著改进头脑风暴算法的性能;基于差分头脑风暴的频谱感知检测概率比其他算法都高,且收敛速度比头脑风暴算法提高至少3倍。%In order to solve continuous optimization problems effectively, a novel global search method named differ⁃ential brain storm optimization ( DBSO) algorithm was proposed based on the intelligent evolutionary principles of brain storm optimization (BSO) algorithm and differential evolution (DE) algorithm. The proposed algorithm was tested with four classic benchmark functions, and applied to hot spectrum sensing issue in the domain of cognitive radio, and a cooperative spectrum sensing method was proposed based on DBSO algorithm. Comparison was conduc⁃ted between DBSO algorithm, BSO algorithm, shuffled frog leaping algorithm ( SFLA) and particle swarm optimiza⁃tion ( PSO) algorithm. The simulation results of the benchmark functions show that in terms of convergence preci⁃sion, the presented DBSO algorithm based on new creating equations outperforms other 3 intelligent algorithms;compared with these three intelligent spectrum sensing algorithms, the detection probability of DBSO is higher, and the convergence speed of the DBSO increases 3 times compared to BSO algorithm.

  15. Parameterized Performance Evaluation Method for Multi-resolution Spectrum Sensing (MRSS) Algorithm%多分辨率频谱感知算法性能的参数化评估方法

    Institute of Scientific and Technical Information of China (English)

    孙坤; 王萍; 李颖哲; 勾天杭

    2011-01-01

    多分辨率频谱感知算法是一种利用小波变换时频尺度可变特性,对宽带通信系统进行快速准确地感知的频谱感知算法。基于多分辨率频谱感知算法的特性,提出了一套频谱感知性能参数化评估方法,构建了基于OFDM信号的多分辨率频谱感知算法仿真平台。分别从小波函数基的选取、调制方式、扫描速率以及实际IQ失配问题的影响等角度,对OFDM宽带信号的感知性能进行了系统的仿真评估和分析,获得感知系统在不同参数设置时的检测概率和误检概率评估结果’为认知无线电系统的进一步设计实现与性能评估提供了重要依据。%Multi-Resolution Spectrum Sensing (MRSS) algorithm is a new algorithm for Cognitive Radio. It can take advantage of time-frequency variable-scale features of wavelet transform, to realize rapid and accurate spectrum sensing for broadband communications systems. Based on the characteristics of MRSS algorithm, a parametric evaluation method for its performance was proposed and OFDM based MRSS algorithm simulation platform was established. Simulation analysis was used to evaluate and analyze the performance of MRSS algorithm to OFDM signal from different angles which were wavelet function, modulation, I/Q gain mismatch and scan interval, and obtained the results of detection probability and false detection probability of the spectrum sensing system with different parameters. An important theoretical basis for the further design and implementation and performance evaluation of cognitive radio system was provided.

  16. Blogging to learn: becoming EFL academic writers through collaborative dialogues

    National Research Council Canada - National Science Library

    Sun, Yu-Chih; Chang, Yu-jung

    2012-01-01

    This study examines how blogs and their interactive and collaborative features help academically-advanced graduate students process academic writing knowledge and make sense of their writer identity...

  17. Conversational sensing

    Science.gov (United States)

    Preece, Alun; Gwilliams, Chris; Parizas, Christos; Pizzocaro, Diego; Bakdash, Jonathan Z.; Braines, Dave

    2014-05-01

    Recent developments in sensing technologies, mobile devices and context-aware user interfaces have made it pos- sible to represent information fusion and situational awareness for Intelligence, Surveillance and Reconnaissance (ISR) activities as a conversational process among actors at or near the tactical edges of a network. Motivated by use cases in the domain of Company Intelligence Support Team (CoIST) tasks, this paper presents an approach to information collection, fusion and sense-making based on the use of natural language (NL) and controlled nat- ural language (CNL) to support richer forms of human-machine interaction. The approach uses a conversational protocol to facilitate a ow of collaborative messages from NL to CNL and back again in support of interactions such as: turning eyewitness reports from human observers into actionable information (from both soldier and civilian sources); fusing information from humans and physical sensors (with associated quality metadata); and assisting human analysts to make the best use of available sensing assets in an area of interest (governed by man- agement and security policies). CNL is used as a common formal knowledge representation for both machine and human agents to support reasoning, semantic information fusion and generation of rationale for inferences, in ways that remain transparent to human users. Examples are provided of various alternative styles for user feedback, including NL, CNL and graphical feedback. A pilot experiment with human subjects shows that a prototype conversational agent is able to gather usable CNL information from untrained human subjects.

  18. Collaborative experience

    DEFF Research Database (Denmark)

    Mortensen, Thomas Bøtker

    sample of firms, an establish way of measuring the outcome of product development and a new way of measuring experience. Where the previous research in this field primarily uses secondary databases, this research project collects primary data by an online questionnaire to the NPD manager from one......, that the largest effects from collaborative experience is from recent collaborative experience, since knowledge depreciates when it is not used. Methodologically contribution: The research project studies the dyad and aims at introducing, to this field of research, an established way of collecting data, a new...... of the new product development as a performance measure. Finally, where previous research primarily has used the number of collaborations as a measure of collaborative experience, this research includes the recency in the measure of collaborative experience. Results: Since data has not yet been collected...

  19. Collaborative Prototyping

    DEFF Research Database (Denmark)

    Bogers, Marcel; Horst, Willem

    2014-01-01

    of the prototyping process, the actual prototype was used as a tool for communication or development, thus serving as a platform for the cross-fertilization of knowledge. In this way, collaborative prototyping leads to a better balance between functionality and usability; it translates usability problems into design......This paper presents an inductive study that shows how collaborative prototyping across functional, hierarchical, and organizational boundaries can improve the overall prototyping process. Our combined action research and case study approach provides new insights into how collaborative prototyping...... can provide a platform for prototype-driven problem solving in early new product development (NPD). Our findings have important implications for how to facilitate multistakeholder collaboration in prototyping and problem solving, and more generally for how to organize collaborative and open innovation...

  20. Collaborative Prototyping

    DEFF Research Database (Denmark)

    Bogers, Marcel; Horst, Willem

    2014-01-01

    This paper presents an inductive study that shows how collaborative prototyping across functional, hierarchical, and organizational boundaries can improve the overall prototyping process. Our combined action research and case study approach provides new insights into how collaborative prototyping...... constraints in involving the appropriate stakeholders at the right time. The paper specifically elaborates on the role of users in collaborative prototyping, which is important in order to cover all phases of the problem-solving cycle but triggers an interesting challenge due to the “reverse empathy...... can provide a platform for prototype-driven problem solving in early new product development (NPD). Our findings have important implications for how to facilitate multistakeholder collaboration in prototyping and problem solving, and more generally for how to organize collaborative and open innovation...

  1. Review on spectrum sensing and node coordination of cognitive radio network%认知无线网络频谱感知与节点协同问题综述

    Institute of Scientific and Technical Information of China (English)

    邓见光; 袁华强; 张剑; 潘晓衡; 王国华

    2011-01-01

    认知无线电是被公认的解决移动无线网络频谱资源短缺和频谱资源动态分配问题的最有效和最有潜力的技术。基于认知无线电技术目前在移动无线网络中的实际应用情况,详细分析了认知无线网络目前所存在的无线频谱资源感知、探测和接入机制以及多用户节点协同等问题,并综述了频谱资源分配算法和认知无线网络容量问题的最新研究进展,最后提出用博弈论来研究解决认知无线网络多用户协同问题中的用户自私行为。%Cognitive radio is recognized as the most effective and the most promising technology to solve the problems of the spectrum resource shortage and its dynamic allocation, which existe in the mobile wireless network. Based on the practical application of the cognitive radio in the mobile wireless network, a detailed analysis about the problems existed in the current cognitive radio network is given in this paper, which includes the sensing, detection and access mechanisms of the wireless spectrum and the coordination problem between multi-nodes. After that, summarize the latest development of the wireless spectrum allocation algorithm, and the problem of the cognitive radio network capacity. Finally, it is advised that the game theory can be adopted to study and solve the user' s selfish behavior in the coordination problem between multi-nodes of the cognitive radio network.

  2. Collaborative Economy

    DEFF Research Database (Denmark)

    and communities 13.Embedding social values in tourism management: Community currencies as laboratories of social entrepreneurship? Rita Cannas 14.Improvising Economy: Everyday encounters and tourism consumption Gunnar Thór Jóhannesson and Katrín Anna Lund 15.Community and connection: Exploring the outcomes......This book employs an interdisciplinary, cross-sectoral lens to explore the collaborative dynamics that are currently disrupting, re-creating and transforming the production and consumption of tourism. House swapping, ridesharing, voluntourism, couchsurfing, dinner hosting, social enterprise...... collaborative economy and tourism Dianne Dredge and Szilvia Gyimóthy PART I - Theoretical explorations 2.Definitions and mapping the landscape in the collaborative economy Szilvia Gyimóthy and Dianne Dredge 3.Business models of the collaborative economy Szilvia Gyimóthy 4.Responsibility and care...

  3. Collaborative tools

    Institute of Scientific and Technical Information of China (English)

    J. Manickam

    2007-01-01

    @@ A successful next generation fusion experiment, such as the International Thermonuclear Experimental Reactor (ITER) project, will need experimentalists, theorists, and computational scientists to collaborate efficiently, to understand the overwhelming amount of information from experiments, codes, and theory.

  4. Authority, Identity, and Collaborative Mathematics

    Science.gov (United States)

    Langer-Osuna, Jennifer M.

    2017-01-01

    The field of mathematics education research has seen a resurgence of interest in understanding collaborative learning because students in K-12 classrooms are increasingly expected to make sense of mathematics problems together. This Research Commentary argues for the importance of understanding student authority relations in collaborative…

  5. Collaborative Appropriation

    DEFF Research Database (Denmark)

    Muller, Michael; Neureiter, Katja; Verdezoto, Nervo;

    2016-01-01

    Previous workshops and papers have examined how individual users adopt and adapt technologies to meet their own local needs, by “completing design through use.” However, there has been little systematic study of how groups of people engage collaboratively in these activities. This workshop opens ...... a discussion for these under-studied forms of collaborative appropriation, using a broad range of perspectives including empirical data, design explorations, research, and critique....

  6. Cooperative cognitive radio networks the complete spectrum cycle

    CERN Document Server

    Ibnkahla, Mohamed

    2014-01-01

    PrefaceAcknowledgmentsAuthorIntroduction to Cognitive RadioIntroductionCognitive Radio FrameworkDefinition of Cognitive RadioFunctions of Cognitive Radio FrameworkTransceiver ArchitectureCritical Design ChallengesFunctions of the Spectrum Management ProcessParadigms of Cognitive RadioInterweave ParadigmUnderlay ParadigmOverlay ParadigmSummaryOrganization of This BookReferencesSpectrum SensingIntroductionSpectrum SensingMatched Filtering (Coherent Detector)Energy DetectorFeature DetectionComparisonDesign Trade-Off and ChallengesMultiband Spectrum SensingIntroductionSerial Spectrum Sensing Techn

  7. Collaborative Improvement

    DEFF Research Database (Denmark)

    Kaltoft, Rasmus

    The thesis data have been collected in the EU-sponsored project: Collaborative Improvement Tool for the Extended Manufacturing Enterprise, CO-IMPROVE. In this project four universities (Denmark, Ireland, Italy, and The Netherlands), two software vendors (Greece and Sweden) and three companies (De...... learn how to improve operations in (hopefully) a win-win like manner through collaboration.......The thesis data have been collected in the EU-sponsored project: Collaborative Improvement Tool for the Extended Manufacturing Enterprise, CO-IMPROVE. In this project four universities (Denmark, Ireland, Italy, and The Netherlands), two software vendors (Greece and Sweden) and three companies...... (Denmark, Italy and The Netherlands) each with three to five suppliers were involved. The CO-IMPROVE project and the thesis is based on “action research” and “action learning”. The main aim of the whole project is through actual involvement and actions make the researchers, companies and selected suppliers...

  8. Interprofessional Collaboration

    Directory of Open Access Journals (Sweden)

    Dawn Prentice

    2015-01-01

    Full Text Available In this hermeneutic phenomenological study, we examined the experience of interprofessional collaboration from the perspective of nursing and medical students. Seventeen medical and nursing students from two different universities participated in the study. We used guiding questions in face-to-face, conversational interviews to explore students’ experience and expectations of interprofessional collaboration within learning situations. Three themes emerged from the data: the great divide, learning means content, and breaking the ice. The findings suggest that the experience of interprofessional collaboration within learning events is influenced by the natural clustering of shared interests among students. Furthermore, the carry-forward of impressions about physician–nurse relationships prior to the educational programs and during clinical placements dominate the formation of new relationships and acquisition of new knowledge about roles, which might have implications for future practice.

  9. Collaborative Improvement

    DEFF Research Database (Denmark)

    Kaltoft, Rasmus

    -called Extended Manufacturing Enterprises (EMEs). In effect, the battlefield of competition is increasingly moving from the level of individual firms to that of EMEs. Consequently, new approaches must be developed not only to enhance the business performance of EMEs, but also, in particular, the inter-organisational......Many companies have gradually moved from vertically aligned operations to horizontally aligned operations, a change implying that co-ordination is shifting from the hierarchy to the market place with emphasis on collaboration with other companies. One form of collaboration with companies is so...

  10. Collaborative Design

    Science.gov (United States)

    Broderick, Debora

    2014-01-01

    This practitioner research study investigates the power of multimodal texts within a real-world context and argues that a participatory culture focused on literary arts offers marginalized high school students opportunities for collaborative design and authoring. Additionally, this article invites educators to rethink the at-risk label. This…

  11. A Fast and Low Complexity Algorithm of Wideband Spectrum Compressive Sensing%一种快速低复杂度宽带频谱压缩感知算法

    Institute of Scientific and Technical Information of China (English)

    任建新; 朱翠涛; 李中捷; 汪汉新

    2015-01-01

    This paper presents a kind of fast and low complexity linear Bregman algorithm and lists the specific implementation steps of the algorithm in order to improve the performance of the wideband spectrum sensing in doubly selective fading environment, which is used for the process of testing wideband compressed spectrum based on cyclic spectrum estimation. This algorithm aims at the flaw of redundant iterative computation in general linear Bregman algorithm. It can accelerate the convergence speed by adding auxiliary variables to estimate iterations of residual staying almost constant in linear Bregman algorithm and updating auxiliary variables to step out the process of redundant iteration. At the same time,it reduces the complexity of the algorithm. As a result,compared with general linear Bregman algorithm,the effect of compressive sampling reconstruction, the detection probability and convergence speed of the modified algorithm are improved in doubly selective fading environment.%为提高双选择性衰落环境下的宽带频谱感知性能,提出一种快速低复杂度线性Bregman算法。利用该算法可实现基于循环谱估计的宽带压缩频谱检测。针对一般线性Bregman算法存在冗余迭代计算的缺陷,通过增加辅助变量,估计线性Bregman算法中余量保持不变过程的迭代次数,更新辅助变量值,跳出冗余迭代的过程,从而加速算法的收敛速度,同时降低算法复杂度。实验结果表明,与一般线性Bregman算法相比,该算法在双选衰落环境下的压缩采样重构效果、检测概率和收敛速度性能均有所提高。

  12. Novel region division approach for joint space-time spectrum 2-dimensions sensing in cognitive radio%一种空时二维联合频谱感知区域划分方案

    Institute of Scientific and Technical Information of China (English)

    阮丽华; 李勇; 程伟

    2016-01-01

    Joint space-time sensing can effectively explore spectrum resources from 2-dimensions in cogni-tive radio networks.A novel region division approach is proposed to clarify the structure of the heterogeneous cognitive radio network.According to the application requirements of the IEEE 802.22 standard,the new ap-proach establishes a space-time robust sensing model.Primary user (PU)distribution region,protection region and secondary user (SU)sensing region are clearly defined.By restricting the outage probability of the primary user,closed-form bounds of three regions are obtained.Based on the transmission power of the PU and the maximum transmission power of the SU,the proposed approach can flexibly determine user distribution regions and the Overlay and Underlay access modes of the SU.Numerical and simulation results verify that the pro-posed approach can guarantee the communication quality of the PU,and exhibit more flexibility and efficiency in spatial spectrum resources allocation and access.%认知无线电空时二维联合频谱感知技术可以有效利用认知无线电网络的二维频谱资源,该文提出一种空时异构认知网络区域划分方案的设计方法。新的设计方法依据 IEEE 802.22标准和应用需求,建立了一种鲁棒性空时二维感知模型,并明确定义了认知无线电网络构架的主用户分布边界、保护边界和感知边界;基于认知用户对主用户通信中断概率的条件约束,严格推导出了3种边界条件的数学闭式解。采用新的设计方案,在保证主用户通信功率和认知用户最大允许通信功率的条件下,能够灵活确定主用户分区和认知用户的 Overlay 及Underlay 接入模式。理论分析和仿真结果表明,新的区域划分方案在保证主用户良好通信质量的前提下,能够实现认知用户在空间维度更有效的分配和接入可用频谱资源。

  13. 双树复小波特征融合的板材压缩感知协同检测与分选%Dual-tree complex wavelet feature fusion and wood board collaborative detection by compressed sensing

    Institute of Scientific and Technical Information of China (English)

    李超; 张怡卓; 于慧伶; 曹军

    2015-01-01

    提出一种对板材表面缺陷和纹理进行协同快速准确检测的算法. 根据双树复小波所特有的方向性和时移不变性,研究了板材表面图像的双树复小波特征提取及融合算法,对板材表面图像进行3级双树复小波分解得到40个特征向量,并通过遗传算法优选出23个关键特征,优选后的特征能够较为完整地表达板材图像的复杂信息并减小数据冗余. 最后采用压缩感知理论,将优选后的特征向量作为样本矩阵列,构造出训练样本数据字典,通过最小残差完成对板材表面信息的分类识别. 实验对木材表面存在的弦切纹、径切纹、活结和死结等4类柞木样本进行了检测,正确率分别为91. 8%、100%、96. 4%和91. 8%,该算法能够以95%的平均识别率完成板材表面缺陷、纹理的协同检测.%A quick and accurate collaborative classification method for wood defects and texture was pro-posed. As dual-tree complex wavelet has the advantages of approximate shift invariance and good direc-tional selectivity, dual-tree complex wavelet feature was extracted from wood board image and the fusion method was discussed. Three-level dual-tree complex wavelet decomposition was carried out to the surface image and 40 features were got, then genetic algorithm ( GA) was used for feature selection and 23 fea-tures were chosen. Feature fusion can better express the surface information and meanwhile heavily re-duce the data redundancy. Finally, wood surface classification was completed by using compressed sens-ing ( CS) , optimized dimensional feature vector was used as sample matrix and data dictionary of training samples was constructed, then, wood surface classification was completed by using least residual at last. Four types of Xylosma samples:radial texture, tangential texture, live knot and dead knot were used for experiment , the classification accuracy of the above four types were 91. 8%, 100%, 96. 4% and 91. 8%respectively

  14. Spectrum Sensing and TCP Cross-layer Design Based on Cognitive Radio%基于认知无线电的频谱感知及TCP跨层设计

    Institute of Scientific and Technical Information of China (English)

    林正红; 江虹; 殷明勇

    2014-01-01

    Most of the existing studies about TCP protocol in Cognitive Radio(CR) network assume that the Secondary User(SU)’s perception is perfect. These studies also do not consider the TCP protocol parameters and sensing time’s influence on the TCP performance. To solve the above problems, this paper proposes an improved TCP protocol which has the transmission pre-judgment ability based on the TCP Westwood(TCPW) protocol. It builds the cross-layer TCP throughput model on the basis of CR networks. Due to the perception errors of secondary user, its spectrum sensing and access problem is modeled as a Partial Observable Markov Decision Process(POMDP) which is then converted to belief state Markov Decision Process(MDP), with the Sarsa(λ) algorithm to achieve the solution of Belief State Markov Decision Process(BMDP) model. It can achieve the optimal sensing time while TCP throughput has the maximum value. Simulation results show that the TCP congestion window value obtains with this scheme is about 42%more than using the TCP Reno protocol, and is about 27%more than using the TCP Newreno protocol. The average throughput obtains with this scheme is about 5.7% higher than using TCP Reno, and is about 5.5%higher than using TCP Newreno. When the sensing time is 0.2 s, the resulting TCP average throughput is the maximum.%目前针对认知无线电网络中TCP协议的研究大多假设次用户的感知是完美的,且未综合考虑TCP协议参数和感知时间等因素对TCP性能的影响。针对上述问题,在TCP Westwood协议的基础上,提出一种基于传输预判的改进TCP协议,建立基于认知无线电网络的TCP吞吐量跨层模型。采用部分可观测马尔可夫决策过程对有感知误差的次用户频谱感知和接入过程进行建模,将其转换为信念状态马尔可夫决策过程,使用Sarsa(λ)算法对其进行求解,以在最大化TCP吞吐量的同时得到最优感知时间。仿真结果表明,与TCP Reno

  15. Improved algorithm based on Singular Value Decomposition in wideband spectrum sensing%基于奇异值分解的宽带频谱感知改进算法

    Institute of Scientific and Technical Information of China (English)

    王琨; 吴宗勇; 黄文芳

    2015-01-01

    对认知无线电中宽带频谱感知的信号检测问题进行研究,在信道位置和带宽随机分布的条件下,提出一种基于Hankel矩阵奇异值分解的改进算法完成宽带频谱的频率点奇异性检测并获得各子频段的起始频率和带宽,有效实现盲宽带频谱感知,同时利用提出的三种性能评价参数对该算法与多尺度小波变换算法进行了性能对比。通过实际接收微波信号及仿真OFDM信号感知实验验证,该算法有效抑制了噪声不确定性,滤除了伪奇异点,提高了宽带频谱感知性能。%The signal detection issue is investigated for wideband spectrum sensing in cognitive radio. Considering that channel position and bandwidth are randomly distributed, an improved singularity detection algorithm based on second-order component of hankel matrix Singular Value Decomposition is proposed for real-time detection of multiple signals. Applied to frequency points singularity detection in the entire frequency range, the start-end frequencies and the band-widths of each band can be obtained. On this basis, traditional multi-band detection in fixed channel is used to classify bands as occupied or vacant, so that it can efficiently accomplish wideband sensing, meanwhile. With the three new evalu-ated parameters, experimental results based on actual received microwave signal and emulational OFDM signal sustain that the proposed algorithm is better than multiresoluted wavelet in singularity detection.

  16. 基于贝叶斯准则的硬判决融合协同频谱感知最优化%Optimization for H-D information fused cooperative spectrum sensing based on Bayesian criterion

    Institute of Scientific and Technical Information of China (English)

    井俊; 徐友云; 马文峰

    2011-01-01

    将硬判决融合协同频谱感知描述为贝叶斯二元假设检验问题,本文考虑感知信息传输错误的可能性,以最小化半均判决风险(贝叶斯风险)为目标的最优本地判决和最优判决融合可分别归结为LRT(likelihood ratio test)问题,并证明基于能量检测的本地LRT与观测量的门限判决等价.当仅有本地判决结果可用时,融合中心通常假设本地观测量独立同分布,可证明此时的最优融合准则为N中取K的投票准则,并给出一种低复杂度的数值迭代算法来求解最优本地判决门限和投票融合门限.数值结果显示,大多数情况下最优N中取K的投票融合可被多数逻辑融合代替而几乎不增加判决风险.%H-D (Hard-Decision) information fused cooperative spectrum sensing can be formulated as a Bayesian binary hypothesis testing problem. With the sensing information transmission error probability included in the optimization for minimizing overall average decision risk (Bayes risk), the optimal local decision rule and the optimal decision fusion rule can be expressed as LRT (likelihood ratio test) problems, respectively. When only local decisions are available to the fusion center,independent and identically distributed local observations are usually assumed, and the optimal fusion rule is proved to be equal to a simple K out of N voting rule. A low-complexity iterative algorithm then can be constructed to pursue the optimal voting threshold and local decision threshold. Numerical results show that the optimal K out of N voting fusion can be replaced by majority logic fusion in most cases without additional decision risk.

  17. [Simulation of image multi-spectrum using field measured endmember spectrum].

    Science.gov (United States)

    Zhang, Ting; Ding, Jian-li; Wang, Fei

    2010-11-01

    The characteristic of landscape spectrum is the basic of application of remote sensing and plays an important role in quantitative analysis of remote sensing. However, in spectrum-based application of remote sensing, because the difference of measuring scale and instrument resolution yield serious error in spectral curve and reflectance for the same landscape, there exists difficulty in quantitative retrieval of special information extraction of remote sensing. Firstly, the imaging simulation principles of the optics image was described and proposed A method using field measured endmember spectrum with higher spectrum resolutions to simulate spectrum of Multi-spectrum images with lower spectrum resolution was proposed. In the present paper, the authors take the delta oasis of Weigan and Kuqa rivers ocated in the North of Tarim Basin as study area, and choose vegetation and soil as study object. At first, we accomplished the simulation from field measured endmember for multi-spectrum by using the spectral response function of AVNIR-2, and found the large correlation between simulated multi-spectrum and pixel spectrum of AVNIR-2 by using the statistical analyse. Finally, the authors set up the linear model to accomplish the quantitative transformation from edmember scale to pixel scale. The result of this study has the realistic meaning for the quantitative application of remote sensing.

  18. Collaborative Care

    OpenAIRE

    コラボレイティブケア研究科

    2005-01-01

    本書を著したHornbyは英国のソーシャルワーカーである。彼女は1983年に「Collaboration in social work(Journal of social work practice,1.1)」を発表し、ソーシャルワークでの職種間の連携の重要性について報告している。さらに1993年に発刊した本書では、同一機関内の人間関係 ...

  19. Timeline Collaboration

    DEFF Research Database (Denmark)

    Bohøj, Morten; Borchorst, Nikolaj Gandrup; Bouvin, Niels Olof

    2010-01-01

    This paper explores timelines as a web-based tool for collaboration between citizens and municipal caseworkers. The paper takes its outset in a case study of planning and control of parental leave; a process that may involve surprisingly many actors. As part of the case study, a web-based timeline......, CaseLine, was designed. This design crosses the boundaries between leisure and work, in ways that are different from what is often seen in current HCI. The timeline has several roles on these boundaries: It is a shared planning and visualization tool that may be used by parents and caseworkers alone......, and beyond this case....

  20. Using Collaborative Engineering to Inform Collaboration Engineering

    Science.gov (United States)

    Cooper, Lynne P.

    2012-01-01

    Collaboration is a critical competency for modern organizations as they struggle to compete in an increasingly complex, global environment. A large body of research on collaboration in the workplace focuses both on teams, investigating how groups use teamwork to perform their task work, and on the use of information systems to support team processes ("collaboration engineering"). This research essay presents collaboration from an engineering perspective ("collaborative engineering"). It uses examples from professional and student engineering teams to illustrate key differences in collaborative versus collaboration engineering and investigates how challenges in the former can inform opportunities for the latter.

  1. Using Collaborative Engineering to Inform Collaboration Engineering

    Science.gov (United States)

    Cooper, Lynne P.

    2012-01-01

    Collaboration is a critical competency for modern organizations as they struggle to compete in an increasingly complex, global environment. A large body of research on collaboration in the workplace focuses both on teams, investigating how groups use teamwork to perform their task work, and on the use of information systems to support team processes ("collaboration engineering"). This research essay presents collaboration from an engineering perspective ("collaborative engineering"). It uses examples from professional and student engineering teams to illustrate key differences in collaborative versus collaboration engineering and investigates how challenges in the former can inform opportunities for the latter.

  2. Collaborative Environments. Considerations Concerning Some Collaborative Systems

    Directory of Open Access Journals (Sweden)

    Mihaela I. MUNTEAN

    2009-01-01

    Full Text Available It is obvious, that all collaborative environments (workgroups, communities of practice, collaborative enterprises are based on knowledge and between collaboration and knowledge management there is a strong interdependence. The evolution of information systems in these collaborative environments led to the sudden necessity to adopt, for maintaining the virtual activities and processes, the latest technologies/systems, which are capable to support integrated collaboration in business services. In these environments, portal-based IT platforms will integrate multi-agent collaborative systems, collaborative tools, different enterprise applications and other useful information systems.

  3. Decision Analysis of Dynamic Spectrum Access Rules

    Energy Technology Data Exchange (ETDEWEB)

    Juan D. Deaton; Luiz A. DaSilva; Christian Wernz

    2011-12-01

    A current trend in spectrum regulation is to incorporate spectrum sharing through the design of spectrum access rules that support Dynamic Spectrum Access (DSA). This paper develops a decision-theoretic framework for regulators to assess the impacts of different decision rules on both primary and secondary operators. We analyze access rules based on sensing and exclusion areas, which in practice can be enforced through geolocation databases. Our results show that receiver-only sensing provides insufficient protection for primary and co-existing secondary users and overall low social welfare. On the other hand, using sensing information between the transmitter and receiver of a communication link, provides dramatic increases in system performance. The performance of using these link end points is relatively close to that of using many cooperative sensing nodes associated to the same access point and large link exclusion areas. These results are useful to regulators and network developers in understanding in developing rules for future DSA regulation.

  4. Resource management for energy and spectrum harvesting sensor networks

    CERN Document Server

    Zhang, Deyu; Zhou, Haibo; Shen, Xuemin (Sherman)

    2017-01-01

    This SpringerBrief offers a comprehensive review and in-depth discussion of the current research on resource management. The authors explain how to best utilize harvested energy and temporally available licensed spectrum. Throughout the brief, the primary focus is energy and spectrum harvesting sensor networks (ESHNs) including energy harvesting (EH)-powered spectrum sensing and dynamic spectrum access. To efficiently collect data through the available licensed spectrum, this brief examines the joint management of energy and spectrum. An EH-powered spectrum sensing and management scheme for Heterogeneous Spectrum Harvesting Sensor Networks (HSHSNs) is presented in this brief. The scheme dynamically schedules the data sensing and spectrum access of sensors in ESHSNs to optimize the network utility, while considering the stochastic nature of EH process, PU activities and channel conditions. This brief also provides useful insights for the practical resource management scheme design for ESHSNs and motivates a ne...

  5. Polymorphic collaboration in the global grid

    Science.gov (United States)

    McQuay, William K.

    2006-05-01

    Next generation collaborative systems must be able to represent the same information in different forms on a broad spectrum of devices and resources from low end personal digital assistants (PDA) to high performance computers (HPC). Users might be on a desktop then switch to a laptop and then to a PDA while accessing the global grid. The user preference profile for a collaboration session should be capable of moving with them as well as be automatically adjusted for the device type. Collaborative systems must be capable of representing the same information in many forms for different domains and on many devices and thus be polymorphic. Polymorphic collaboration will provide an ability for multiple heterogeneous resources (human to human, human to machine and machine to machine) to share information and activities, as well as the ability to regulate collaborative sessions based on client characteristics and needs; reuse user profiles, tool category choices, and settings in future collaboration session by same or different users; use intelligent agents to assist collaborative systems in learning user/resource preferences and behaviors, and autonomously derive optimal information to provide to users and decision makers. This paper discusses ongoing research in next generation collaborative environments with the goal of making electronic collaboration as easy to use as the telephone - collaboration at the touch of the screen.

  6. Conflictual Collaboration

    DEFF Research Database (Denmark)

    Busch-Jensen, Peter

    This paper focuses on conflicts as a useful and meaningful aspect of work and organizational theory, and I will discuss power relations as a phenomenon that relates to our handling of conflicts. Conflicts can be perceived negatively, as something to be avoided. However conflicts also offers...... important inclusive social elements that are important as well as appropriate to be aware of, not least because conflicts in a sense is an inevitable element of any form of social co-operation and practice. I will therefore argue that the problem is not the conflicts, but rather the tendency to consider...

  7. Collaborative Consumption

    DEFF Research Database (Denmark)

    Gjerdrum Pedersen, Esben Rahbek; Netter, Sarah

    2015-01-01

    Purpose – The purpose of this paper is to explore barriers and opportunities for business models based on the ideas of collaborative consumption within the fashion industry. Design/methodology/approach – The analysis is based on a multiple-case study of Scandinavian fashion libraries – a new......, clothes-sharing concept that has emerged as a fashion niche within the last decade. Findings – It is concluded that fashion libraries offers interesting perspectives, e.g. by allowing people to experiment with styles without having to pay the full cost and becoming a meeting place for young designers...... and end consumers. However, at present fashion libraries remain a small-scale phenomenon with difficulties reaching the mainstream market, not least due to limited financial and human resources as well as conventional fashion consumption patterns. Research limitations/implications – The study is limited...

  8. Collaborative Consumption

    DEFF Research Database (Denmark)

    Gjerdrum Pedersen, Esben Rahbek; Netter, Sarah

    Purpose: The purpose of this paper is to explore barriers and opportunities for business models based on the ideas of collaborative consumption within the fashion industry. Design/methodology/approach: The analysis is based on a multiple-­‐‑case study of Scandinavian fashion libraries – a new......, clothes-­‐‑sharing concept that has emerged as a fashion niche within the last decade. Findings: It is concluded that fashion libraries offers interesting perspectives, e.g. by allowing people to experiment with styles without having to pay the full cost and becoming a meeting place for young designers...... and end consumers. However, at present fashion libraries remain a small-­‐‑scale phenomenon with difficulties reaching the mainstream market, not least due to limited financial and human resources as well as conventional fashion consumption patterns. Research limitations/implications: The study is limited...

  9. Contested collaboration

    DEFF Research Database (Denmark)

    Sonnenwald, Diane H.

    1995-01-01

    support patterns of work activities, social groups, and personal beliefs. In these situations, design is fundamentally an interactive process that requires communication among users, designers, and developers. However, communication among these groups is often difficult although of paramount importance...... to design outcomes. Through a qualitative analysis of a house, expert system, and telecommunications network architecture and management system design situations, a descriptive model of design that characterizes communication among users, designers, and developers as they create an artifact was developed....... The model describes design phases, roles, themes, and intergroup communication networks as they evolve throughout the design process and characterizes design as a process of "contested collaboration". It is a first step towards a predictive design model that suggests strategies which may help participants...

  10. Technology collaboration

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Jacob [Halliburton (Brazil)

    2011-07-01

    The aim of this paper is to present Halliburton's Brazilian technology center. Halliburton has technology centers in the United States, Saudi Arabia, India, Singapore and Brazil, all of which aim at delivering accelerated innovation in the oil sector. The technology centers engage in research and development activities with the help of various universities and in collaboration with the customer or supplier. The Halliburton Brazil technology center provides its customers with timely research and development solutions for enhancing recovery and mitigating reservoir uncertainty; they are specialized in finding solutions for pre- and post-salt carbonate drilling and in the enhancement of production from mature fields. This presentation showcased the work carried out by the Halliburton Brazil technology center to help customers develop their deepwater field activities.

  11. Collaborative information seeking

    DEFF Research Database (Denmark)

    Hertzum, Morten

    2008-01-01

    , the activities involved in information seeking are often performed by varying subgroups of actors. Consequently, collaborative grounding is necessary to share information among collaborating actors and, thereby, establish and maintain the common ground necessary for their collaborative work. By focusing......Since common ground is pivotal to collaboration, this paper proposes to define collaborative information seeking as the combined activity of information seeking and collaborative grounding. While information-seeking activities are necessary for collaborating actors to acquire new information...... on the collaborative level, collaborative information seeking aims to avoid both individual reductionism and group reductionism, while at the same time recognizing that only some information and understanding need be shared....

  12. The use of technology in international collaboration

    DEFF Research Database (Denmark)

    Livonen, Mirja; Sonnenwald, Diane H.

    2000-01-01

    International collaboration is emerging as an essential function for organizations, playing an important role in organizational strategy, performance and knowledge management. Two case studies of international collaboration are discussed in this paper. Participants' perceptions and use of technol......International collaboration is emerging as an essential function for organizations, playing an important role in organizational strategy, performance and knowledge management. Two case studies of international collaboration are discussed in this paper. Participants' perceptions and use...... of technology to collaborate are examined from the perspective of sense of presence, participation, task type, productivity and ease of use. The data suggest that technology compatibility with cultural and work style preferences and technology infrastructure is more important than media richness, in contrast...

  13. A Survey on Dynamic Spectrum Access Techniques for Cognitive Radio

    CERN Document Server

    Garhwal, Anita

    2012-01-01

    Cognitive radio (CR) is a new paradigm that utilizes the available spectrum band. The key characteristic of CR system is to sense the electromagnetic environment to adapt their operation and dynamically vary its radio operating parameters. The technique of dynamically accessing the unused spectrum band is known as Dynamic Spectrum Access (DSA). The dynamic spectrum access technology helps to minimize unused spectrum bands. In this paper, main functions of Cognitive Radio (CR) i.e. spectrum sensing, spectrum management, spectrum mobility and spectrum sharing are discussed. Then DSA models are discussed along with different methods of DSA such as Command and Control, Exclusive-Use, Shared Use of Primary Licensed User and Commons method. Game-theoretic approach using Bertrand game model, Markovian Queuing Model for spectrum allocation in centralized architecture and Fuzzy logic based method are also discussed and result are shown.

  14. Hyperspectral remote sensing for terrestrial applications

    Science.gov (United States)

    Thenkabail, Prasad S.; Teluguntla, Pardhasaradhi G.; Murali Krishna Gumma,; Venkateswarlu Dheeravath,

    2015-01-01

    Remote sensing data are considered hyperspectral when the data are gathered from numerous wavebands, contiguously over an entire range of the spectrum (e.g., 400–2500 nm). Goetz (1992) defines hyperspectral remote sensing as “The acquisition of images in hundreds of registered, contiguous spectral bands such that for each picture element of an image it is possible to derive a complete reflectance spectrum.” However, Jensen (2004) defines hyperspectral remote sensing as “The simultaneous acquisition of images in many relatively narrow, contiguous and/or non contiguous spectral bands throughout the ultraviolet, visible, and infrared portions of the electromagnetic spectrum.

  15. In formation: Support for flexibility, mobility, collaboration, and coherence

    DEFF Research Database (Denmark)

    Büscher, Monika; Kramp, Gunnar; Krogh, Peter Gall

    2003-01-01

    This paper describes support for flexibility, mobility and collaboration in engaging with, and making sense of, information. Our focus lies on the transitions people make between different, dynamic configurations of digital and physical materials, technologies, people and spaces. The technologies...

  16. Oblivious Collaboration

    CERN Document Server

    Afek, Yehuda; Feige, Uriel; Gafni, Eli; Linial, Nati; Sudakov, Benny

    2011-01-01

    Communication is a crucial ingredient in every kind of collaborative work. But what is the least possible amount of communication required for a given task? We formalize this question by introducing a new framework for distributed computation, called {\\em oblivious protocols}. We investigate the power of this model by considering two concrete examples, the {\\em musical chairs} task $MC(n,m)$ and the well-known {\\em Renaming} problem. The $MC(n,m)$ game is played by $n$ players (processors) with $m$ chairs. Players can {\\em occupy} chairs, and the game terminates as soon as each player occupies a unique chair. Thus we say that player $P$ is {\\em in conflict} if some other player $Q$ is occupying the same chair, i.e., termination means there are no conflicts. By known results from distributed computing, if $m \\le 2n-2$, no strategy of the players can guarantee termination. However, there is a protocol with $m = 2n-1$ chairs that always terminates. Here we consider an oblivious protocol where in every time step ...

  17. Managing collaborative design

    NARCIS (Netherlands)

    Sebastian, R.

    2007-01-01

    Collaborative design has been emerging in building projects everywhere. The more complex a building project becomes, the closer and more intensive collaboration between the design actors is required. This research focuses on collaborative design in the conceptual architecture design phase,

  18. Properties of centralized cooperative sensing in cognitive radio networks

    Science.gov (United States)

    Skokowski, Paweł; Malon, Krzysztof; Łopatka, Jerzy

    2017-04-01

    Spectrum sensing is a functionality that enables network creation in the cognitive radio technology. Spectrum sensing is use for building the situation awareness knowledge for better use of radio resources and to adjust network parameters in case of jamming, interferences from legacy systems, decreasing link quality caused e.g. by nodes positions changes. This paper presents results from performed tests to compare cooperative centralized sensing versus local sensing. All tests were performed in created simulator developed in Matlab/Simulink environment.

  19. Collaborative Service Arrangements

    DEFF Research Database (Denmark)

    Winter, Søren; J. May, Peter

    2007-01-01

    in particular differs among collaborators. Our modeling of the influence of collaboration on perceived employment outcomes suggests that these impacts are relatively minor. They are greater when there is active involvement of municipal employment managers in fostering cooperative relationships...... with collaborators. In short, collaboration requires a healthy and active relationship to foster improved outcomes. These findings have implications for future research about collaborative service delivery concerning the measurement of collaboration, different bases for it, and potential impacts....

  20. Collaborative Service Arrangements

    DEFF Research Database (Denmark)

    J. May, Peter; Winter, Søren

    in particular differs among collaborators. Our modeling of the influence of collaboration on perceived employment outcomes suggests that these impacts are relatively minor. They are greater when there is active involvement of municipal employment managers in fostering cooperative relationships...... with collaborators. In short, collaboration requires a healthy and active relationship to foster improved outcomes. These findings have implications for future research about collaborative service delivery concerning the measurement of collaboration, different bases for it, and potential impacts....

  1. Collaborative Service Arrangements

    DEFF Research Database (Denmark)

    J. May, Peter; Winter, Søren

    While much of prior research on collaboration addresses the service delivery network as a whole, we address collaborative relationships between one type of organization—municipal employment services—and a range of governmental and non-governmental partners for employment services in Denmark...... with collaborators. In short, collaboration requires a healthy and active relationship to foster improved outcomes. These findings have implications for future research about collaborative service delivery concerning the measurement of collaboration, different bases for it, and potential impacts....

  2. Collaboration rules.

    Science.gov (United States)

    Evans, Philip; Wolf, Bob

    2005-01-01

    Corporate leaders seeking to boost growth, learning, and innovation may find the answer in a surprising place: the Linux open-source software community. Linux is developed by an essentially volunteer, self-organizing community of thousands of programmers. Most leaders would sell their grandmothers for workforces that collaborate as efficiently, frictionlessly, and creatively as the self-styled Linux hackers. But Linux is software, and software is hardly a model for mainstream business. The authors have, nonetheless, found surprising parallels between the anarchistic, caffeinated, hirsute world of Linux hackers and the disciplined, tea-sipping, clean-cut world of Toyota engineering. Specifically, Toyota and Linux operate by rules that blend the self-organizing advantages of markets with the low transaction costs of hierarchies. In place of markets' cash and contracts and hierarchies' authority are rules about how individuals and groups work together (with rigorous discipline); how they communicate (widely and with granularity); and how leaders guide them toward a common goal (through example). Those rules, augmented by simple communication technologies and a lack of legal barriers to sharing information, create rich common knowledge, the ability to organize teams modularly, extraordinary motivation, and high levels of trust, which radically lowers transaction costs. Low transaction costs, in turn, make it profitable for organizations to perform more and smaller transactions--and so increase the pace and flexibility typical of high-performance organizations. Once the system achieves critical mass, it feeds on itself. The larger the system, the more broadly shared the knowledge, language, and work style. The greater individuals' reputational capital, the louder the applause and the stronger the motivation. The success of Linux is evidence of the power of that virtuous circle. Toyota's success is evidence that it is also powerful in conventional companies.

  3. Collaborative outreach

    Science.gov (United States)

    Sanmarti-Vila, Lydia; García-Matos, Marta; Beduini, Federica; Carrasco, Silvia

    2016-09-01

    Many research projects and scientific initiatives multiple their impact and relevance through collaborations. It is the contact and exchange with others that often brings a scientist's work to the next level. The same happens with outreach: sharing activities, concepts, materials and knowhow may lead to greater impact, more innovative, inspirational ideas with enough potential to create pioneering outreach activities. A good example for this is the FP7 European project "GoPhoton!", an initiative of ECOP (European Centres of Outreach in Photonics) that ran through 2014 and 2015 and finished at the beginning of 2016 and was directed at the general public, young minds as well as current and future entrepreneurs. This project was based on the idea of sharing activities - which is at the core of ECOP's identity- already existing in other nodes (institutions within the project), or created within GoPhoton! The main concept was the effective leverage of local links such as the networks of educators and professionals in general, industrial clusters, museums, universities, governmental and non-governmental organizations, all from a Pan-European perspective possible through ECOP. This has resulted in over 200 events impacting over two million people. The sharing of activities across institutions that have different resources, facilities, and cultural environments is not straightforward. One of the biggest challenges for the consortium was to be able to extract the concept and identity of each activity, so that it could be realistically adapted to each local context. A crucial point was being able to effectively use the knowhow gained from a partner's activity, in a way that the essence of the activity remained untainted across the participating nodes, while still triggering innovation locally.

  4. Baryon spectrum and chiral dynamics

    CERN Document Server

    Glozman, L Ya

    1995-01-01

    New results on baryon structure and spectrum developed in collaboration with Dan Riska [1-4] are reported. The main idea is that beyond the chiral symmetry spontaneous breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks.

  5. Zellweger Spectrum

    Science.gov (United States)

    ... severe defect, resulting in essentially nonfunctional peroxisomes. This phenomenon produces the range of severity of the disorders. How is the Zellweger Spectrum Diagnosed? The distinctive shape of the head and face of a child born with one of the diseases of the ...

  6. Remote Sensing

    CERN Document Server

    Khorram, Siamak; Koch, Frank H; van der Wiele, Cynthia F

    2012-01-01

    Remote Sensing provides information on how remote sensing relates to the natural resources inventory, management, and monitoring, as well as environmental concerns. It explains the role of this new technology in current global challenges. "Remote Sensing" will discuss remotely sensed data application payloads and platforms, along with the methodologies involving image processing techniques as applied to remotely sensed data. This title provides information on image classification techniques and image registration, data integration, and data fusion techniques. How this technology applies to natural resources and environmental concerns will also be discussed.

  7. Comparison of RF spectrum prediction methods for dynamic spectrum access

    Science.gov (United States)

    Kovarskiy, Jacob A.; Martone, Anthony F.; Gallagher, Kyle A.; Sherbondy, Kelly D.; Narayanan, Ram M.

    2017-05-01

    Dynamic spectrum access (DSA) refers to the adaptive utilization of today's busy electromagnetic spectrum. Cognitive radio/radar technologies require DSA to intelligently transmit and receive information in changing environments. Predicting radio frequency (RF) activity reduces sensing time and energy consumption for identifying usable spectrum. Typical spectrum prediction methods involve modeling spectral statistics with Hidden Markov Models (HMM) or various neural network structures. HMMs describe the time-varying state probabilities of Markov processes as a dynamic Bayesian network. Neural Networks model biological brain neuron connections to perform a wide range of complex and often non-linear computations. This work compares HMM, Multilayer Perceptron (MLP), and Recurrent Neural Network (RNN) algorithms and their ability to perform RF channel state prediction. Monte Carlo simulations on both measured and simulated spectrum data evaluate the performance of these algorithms. Generalizing spectrum occupancy as an alternating renewal process allows Poisson random variables to generate simulated data while energy detection determines the occupancy state of measured RF spectrum data for testing. The results suggest that neural networks achieve better prediction accuracy and prove more adaptable to changing spectral statistics than HMMs given sufficient training data.

  8. CMOS RF Transceiver condiderations for Dynamic Spectrum Access

    NARCIS (Netherlands)

    Oude Alink, M.S.; Klumperink, E.A.M.; Kokkeler, A.B.J.; Smit, G.J.M.; Nauta, B.

    2012-01-01

    Cognitive Radio (CR), and in particular dynamic spectrum access (DSA), promises a much more efficient use of the spectrum by opportunistically using available frequencies. This asks for specific functionality, like spectrum sensing and frequency-agile transmission and reception. We will show that th

  9. Senses of the South

    Directory of Open Access Journals (Sweden)

    Géraldine Chouard

    2012-01-01

    Full Text Available Tell about the South. What it’s like there. What do they do there. Why do they live there. Why do they live at all. (Absalom, Absalom!, 142Exiled in the Massachusetts winter, Southerner Quentin Compson finds himself repeatedly assaulted by the uncomprehending inquisitiveness of his fellow students. As his roommate, a Canadian, collaborates with him telling fact from legend about the larger than life legendary figure of Thomas Sutpen, he tries to get a sense of the region:What is it? Somethin...

  10. Glucose Sensing

    CERN Document Server

    Geddes, Chris D

    2006-01-01

    Topics in Fluorescence Spectroscopy, Glucose Sensing is the eleventh volume in the popular series Topics in Fluorescence Spectroscopy, edited by Drs. Chris D. Geddes and Joseph R. Lakowicz. This volume incorporates authoritative analytical fluorescence-based glucose sensing reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. Glucose Sensing is an essential reference for any lab working in the analytical fluorescence glucose sensing field. All academics, bench scientists, and industry professionals wishing to take advantage of the latest and greatest in the continuously emerging field of glucose sensing, and diabetes care & management, will find this volume an invaluable resource. Topics in Fluorescence Spectroscopy Volume 11, Glucose Sensing Chapters include: Implantable Sensors for Interstitial Fluid Smart Tattoo Glucose Sensors Optical Enzyme-based Glucose Biosensors Plasmonic Glucose Sens...

  11. A Political History of U.S. Commercial Remote Sensing, 1984-2007: Conflict, Collaboration, and the Role of Knowledge in the High-Tech World of Earth Observation Satellites

    OpenAIRE

    Thompson, Kenneth Parker

    2007-01-01

    The political history of U.S. commercial remote sensing began in 1984 when the U.S. government first attempted to commercialize its civil earth observation satellite system â Landsat. Since then, the high technology of earth imaging satellite systems has generated intense debates and policy conflicts, primarily centered on U.S. government concerns over the national security and foreign policy implications of high-resolution commercial satellite systems. Conversely, proponents of commerc...

  12. Towards the collaborative hospital

    DEFF Research Database (Denmark)

    Prætorius, Thim; Hasle, Peter; Edwards, Kasper;

    2015-01-01

    of the collaborative hospital concern the creation of an appropriate balance between standardization and local autonomy, shared purpose centred around providing the best possible care, and use of enabling structures that sustain the new ways of collaborative work. The chapter builds on the theoretical framework...... for the collaborative hospital as new organizational form which is better equipped to respond to the challenges facing modern hospitals. The collaborative hospital is an ambidextrous organization that opens for pursuing both exploration and exploitation within the same organizational structure. The basic principles...... of the collaborative organization which is used for a discussion of theoretical and empirical aspects of the collaborative hospital....

  13. Remote Sensing.

    Science.gov (United States)

    Williams, Richard S., Jr.; Southworth, C. Scott

    1983-01-01

    The Landsat Program became the major event of 1982 in geological remote sensing with the successful launch of Landsat 4. Other 1982 remote sensing accomplishments, research, publications, (including a set of Landsat worldwide reference system index maps), and conferences are highlighted. (JN)

  14. How Barriers to Collaboration Prevent Progress in Demand for Knowledge

    DEFF Research Database (Denmark)

    Goduscheit, René Chester; Knudsen, Mette Præst

    2015-01-01

    This article analyses the challenging collaboration between small and medium-sized enterprises (SMEs) and knowledge institutions. The aim of the article is to shed light on the barriers, which hinder collaboration, and to investigate the particular role of research and technology organizations...... tendency to a mediating role of RTOs can be found among the SMEs' perception of university collaboration. Finally, the analysis shows that the knowledge institutions perceive the SMEs as very important collaboration partners, but the same sense of importance is not shared by the SMEs regarding...

  15. How Barriers to Collaboration Prevent Progress in Demand for Knowledge

    DEFF Research Database (Denmark)

    Goduscheit, René Chester; Knudsen, Mette Præst

    2015-01-01

    tendency to a mediating role of RTOs can be found among the SMEs' perception of university collaboration. Finally, the analysis shows that the knowledge institutions perceive the SMEs as very important collaboration partners, but the same sense of importance is not shared by the SMEs regarding......This article analyses the challenging collaboration between small and medium-sized enterprises (SMEs) and knowledge institutions. The aim of the article is to shed light on the barriers, which hinder collaboration, and to investigate the particular role of research and technology organizations...

  16. Make Sense?

    DEFF Research Database (Denmark)

    Gyrd-Jones, Richard; Törmälä, Minna

    Purpose: An important part of how we sense a brand is how we make sense of a brand. Sense-making is naturally strongly connected to how we cognize about the brand. But sense-making is concerned with multiple forms of knowledge that arise from our interpretation of the brand-related stimuli...... sense of brands is related to who people think they are in their context and this shapes what they enact and how they interpret the brand (Currie & Brown, 2003; Weick, Sutcliffe, & Obstfeld, 2005; Weick, 1993). Our subject of interest in this paper is how stakeholders interpret and ascribe meaning...... to the brand and how these meaning narratives play out over time to create meta-narratives that drive brand meaning co-creation. In this paper we focus on the concept of brand identity since it is at the level of identity that the brand creates meaning for individuals (Kapferer, 2012; Csaba & Bengtsson, 2006)....

  17. Fission Spectrum

    Science.gov (United States)

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  18. Using Remotely Sensed Data for Climate Change Mitigation and Adaptation: A Collaborative Effort Between the Climate Change Adaptation Science Investigators Workgroup (CASI), NASA Johnson Space Center, and Jacobs Technology

    Science.gov (United States)

    Jagge, Amy

    2016-01-01

    With ever changing landscapes and environmental conditions due to human induced climate change, adaptability is imperative for the long-term success of facilities and Federal agency missions. To mitigate the effects of climate change, indicators such as above-ground biomass change must be identified to establish a comprehensive monitoring effort. Researching the varying effects of climate change on ecosystems can provide a scientific framework that will help produce informative, strategic and tactical policies for environmental adaptation. As a proactive approach to climate change mitigation, NASA tasked the Climate Change Adaptation Science Investigators Workgroup (CASI) to provide climate change expertise and data to Center facility managers and planners in order to ensure sustainability based on predictive models and current research. Generation of historical datasets that will be used in an agency-wide effort to establish strategies for climate change mitigation and adaptation at NASA facilities is part of the CASI strategy. Using time series of historical remotely sensed data is well-established means of measuring change over time. CASI investigators have acquired multispectral and hyperspectral optical and LiDAR remotely sensed datasets from NASA Earth Observation Satellites (including the International Space Station), airborne sensors, and astronaut photography using hand held digital cameras to create a historical dataset for the Johnson Space Center, as well as the Houston and Galveston area. The raster imagery within each dataset has been georectified, and the multispectral and hyperspectral imagery has been atmospherically corrected. Using ArcGIS for Server, the CASI-Regional Remote Sensing data has been published as an image service, and can be visualized through a basic web mapping application. Future work will include a customized web mapping application created using a JavaScript Application Programming Interface (API), and inclusion of the CASI data

  19. Collaborative Contracting in Projects

    NARCIS (Netherlands)

    Suprapto, M.

    2016-01-01

    Project practitioners have increasingly recognized the importance of collaborative relationships to ensure successful executions of projects. However, the ability to sustain and consistenly drive real collaborative attitudes and behavior for achieving the desired outcomes remains of enduring practic

  20. Collaborative Contracting in Projects

    NARCIS (Netherlands)

    Suprapto, M.

    2016-01-01

    Project practitioners have increasingly recognized the importance of collaborative relationships to ensure successful executions of projects. However, the ability to sustain and consistenly drive real collaborative attitudes and behavior for achieving the desired outcomes remains of enduring

  1. Global Collaborative STEM Education

    Science.gov (United States)

    Meabh Kelly, Susan; Smith, Walter

    2016-04-01

    Global Collaborative STEM Education, as the name suggests, simultaneously supports two sets of knowledge and skills. The first set is STEM -- science, technology, engineering and math. The other set of content knowledge and skills is that of global collaboration. Successful global partnerships require awareness of one's own culture, the biases embedded within that culture, as well as developing awareness of the collaborators' culture. Workforce skills fostered include open-mindedness, perseverance when faced with obstacles, and resourceful use of technological "bridges" to facilitate and sustain communication. In respect for the 2016 GIFT Workshop focus, Global Collaborative STEM Education projects dedicated to astronomy research will be presented. The projects represent different benchmarks within the Global Collaborative STEM Education continuum, culminating in an astronomy research experience that fully reflects how the global STEM workforce collaborates. To facilitate wider engagement in Global Collaborative STEM Education, project summaries, classroom resources and contact information for established international collaborative astronomy research projects will be disseminated.

  2. Collaboration in Agricultural Education.

    Science.gov (United States)

    Peterson, Roland L.; And Others

    1995-01-01

    Theme articles discuss environment, food, agriculture, and renewal resources as they relate to science education, learning partnerships, collaboration in Kyrghyzstan, leadership development, opportunities for collaboration, networking, and the creation of a shared course between agribusiness and biology. (JOW)

  3. Collaboration in Agricultural Education.

    Science.gov (United States)

    Peterson, Roland L.; And Others

    1995-01-01

    Theme articles discuss environment, food, agriculture, and renewal resources as they relate to science education, learning partnerships, collaboration in Kyrghyzstan, leadership development, opportunities for collaboration, networking, and the creation of a shared course between agribusiness and biology. (JOW)

  4. Experiences of Collaborative Research

    Science.gov (United States)

    Kahneman, Daniel

    2003-01-01

    The author's personal history of the research that led to his recognition in economics is described, focusing on the process of collaboration and on the experience of controversy. The author's collaboration with Amos Tversky dealt with 3 major topics: judgment under uncertainty, decision making, and framing effects. A subsequent collaboration,…

  5. Trust repertoires for collaboration

    DEFF Research Database (Denmark)

    Fuglsang, Lars

    little about how such processes develop and how trust, understood as “confident positive expectations” (Lewicki et al. 1998) to collaborative activities, arises out of collaboration. The paper contributes by showing how trust and collaboration are intertwined. The main finding is that a facilitator can...

  6. Scheduling Heterogeneous Wireless Systems for Efficient Spectrum Access

    Directory of Open Access Journals (Sweden)

    Liao Shenghui

    2010-01-01

    Full Text Available The spectrum scarcity problem emerged in recent years, due to unbalanced utilization of RF (radio frequency bands in the current state of wireless spectrum allocations. Spectrum access scheduling addresses challenges arising from spectrum sharing by interleaving the channel access among multiple wireless systems in a TDMA fashion. Different from cognitive radio approaches which are opportunistic and noncollaborative in general, spectrum access scheduling proactively structures and interleaves the channel access pattern of heterogeneous wireless systems, using collaborative designs by implementing a crucial architectural component—the base stations on software defined radios (SDRs. We discuss our system design choices for spectrum sharing from multiple perspectives and then present the mechanisms for spectrum sharing and coexistence of GPRS+WiMAX and GPRS+WiFi as use cases, respectively. Simulations were carried out to prove that spectrum access scheduling is an alternative, feasible, and promising approach to the spectrum scarcity problem.

  7. Trust repertoires for collaboration

    DEFF Research Database (Denmark)

    Fuglsang, Lars

    This case study analyses the role of trust in a public private innovation network that involved a private consultancy company as a facilitator. We know that collaboration is a important for innovation, and that collaboration across organizational boundaries is not a trivial issue. But we know very...... little about how such processes develop and how trust, understood as “confident positive expectations” (Lewicki et al. 1998) to collaborative activities, arises out of collaboration. The paper contributes by showing how trust and collaboration are intertwined. The main finding is that a facilitator can...

  8. "Ritual Rhythms" - a collaborative WebDocumentary

    DEFF Research Database (Denmark)

    Møhl, Perle

    2014-01-01

    A collaborative web-based filmproject in 11 vignettes about the rituals and rhythms of daily life in various locations & settings in the city of Copenhagen. Created by Perle Møhl and the students on the 2014 courses in Visual Anthropology in Practice. We use the concepts of Ritual and Rhythm......, tuning in with all our senses to the details of daily life that often elude the attention of a wordy anthropology....

  9. Spectrum Trading for Efficient Spectrum Utilization

    Directory of Open Access Journals (Sweden)

    Cong Xiong

    2014-04-01

    Full Text Available The conventional command and control based spectrum management has led to substantial underutilization of some spectrum bands while severely crowding others due to the uneven and dynamic needs that vary over time and at different locations. Spectrum trading has emerged as a promising management approach to substantially improve spectrum utilization and user experience in wireless communications by taking advantage of market-based mechanisms. This article presents an overview of spectrum trading, including the fundamental characteristics of spectrum trading markets, the state-of-the-art techniques for modeling and resolving various spectrum trading issues, and trading based dynamic spectrum sharing and access. Moreover, some open issues in spectrum trading are identified for future research in this area.

  10. Bound muon decay spectrum in the leading logarithmic accuracy

    Science.gov (United States)

    Szafron, Robert; Czarnecki, Andrzej

    2016-09-01

    We compute the dominant, logarithmically enhanced radiative corrections to the electron spectrum in bound muon decay in the whole experimentally interesting range. The corrected spectrum fits well with the results from the TWIST Collaboration. The remaining theoretical error, dominated by the nuclear charge distribution, can be reduced in the muon-electron conversion searches by measuring the spectrum slightly below the new physics signal window.

  11. Project Learning and Virtual Collaboration

    DEFF Research Database (Denmark)

    Fibiger, Bo; Nielsen, Janni; Sorensen, Elsebeth

    2005-01-01

    on ICT and Learning. In addition, MIL provides a learning space where practice is under constant negotiation and reconstruction as an inherent, integrated part of the learning process. Consequently, we argue that MIL may be seen as an example of best practice in blended learning.......This paper will introduce a master program in ICT and Learning (MIL) and present some of the experiences we have gained so far. MIL is a result of a collaborative initiative taken by five Danish universities, and it is an accredited part-time 2-year master program. It is unique in the sense...... will be directed towards problems experienced by the students. From an analytical perspective, the paper will identify and discuss fundamental problems related to the organization, flexibility, and implementation of project pedagogy online. MIL is organized around ICT and Learning and the study theme focuses...

  12. Staging Collaborative Innovation Processes

    DEFF Research Database (Denmark)

    Pedersen, Signe; Clausen, Christian

    Organisations are currently challenged by demands for increased collaborative innovation internally as well as with external and new entities - e.g. across the value chain. The authors seek to develop new approaches to managing collaborative innovative processes in the context of open innovation...... and public private innovation partnerships. Based on a case study of a collaborative design process in a large electronics company the paper points to the key importance of staging and navigation of collaborative innovation process. Staging and navigation is presented as a combined activity: 1) to translate...

  13. The Solar Convection Spectrum

    Science.gov (United States)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  14. Investment and Pricing with Spectrum Uncertainty: A Cognitive Operator's Perspective

    OpenAIRE

    Duan, Lingjie; Huang, Jianwei; Shou, Biying

    2009-01-01

    This paper studies the optimal investment and pricing decisions of a cognitive mobile virtual network operator (C-MVNO) under spectrum supply uncertainty. Compared with a traditional MVNO who often leases spectrum via long-term contracts, a C-MVNO can acquire spectrum dynamically in short-term by both sensing the empty "spectrum holes" of licensed bands and dynamically leasing from the spectrum owner. As a result, a C-MVNO can make flexible investment and pricing decisions to match the curren...

  15. A novel spectrum sharing scheme for cognitive radios

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A novel approach, which combines spectrum adaptation and orthogonal frequency division multiplexing (OFDM), is proposed to share the licensed spectrum dynamically for cognitive radio systems. Given spectrum sensing and channel estimation information by the receiver, an improved model due to signal power thresholds is adopted to achieve spectrum adaptation for unlicensed users. In order to efficiently allocate the unlicensed signal power, a dynamic power allocation algorithm is also proposed. Simulation results indicate that the propositional scheme solves the partial interference problem of interference temperature model (ITM) and improves the spectrum utilization.

  16. Making Sense

    Science.gov (United States)

    Golding, Clinton

    2009-01-01

    In this article, the author provides a self-portrait of his intellectual life. He states that overall his approach to teaching and researching is about "making sense" where inadequate or incongruous conceptions fall into place or are transformed so they are congruous and adequate. In his teaching the author applies the methods of…

  17. Pervasive sensing

    Science.gov (United States)

    Nagel, David J.

    2000-11-01

    The coordinated exploitation of modern communication, micro- sensor and computer technologies makes it possible to give global reach to our senses. Web-cameras for vision, web- microphones for hearing and web-'noses' for smelling, plus the abilities to sense many factors we cannot ordinarily perceive, are either available or will be soon. Applications include (1) determination of weather and environmental conditions on dense grids or over large areas, (2) monitoring of energy usage in buildings, (3) sensing the condition of hardware in electrical power distribution and information systems, (4) improving process control and other manufacturing, (5) development of intelligent terrestrial, marine, aeronautical and space transportation systems, (6) managing the continuum of routine security monitoring, diverse crises and military actions, and (7) medicine, notably the monitoring of the physiology and living conditions of individuals. Some of the emerging capabilities, such as the ability to measure remotely the conditions inside of people in real time, raise interesting social concerns centered on privacy issues. Methods for sensor data fusion and designs for human-computer interfaces are both crucial for the full realization of the potential of pervasive sensing. Computer-generated virtual reality, augmented with real-time sensor data, should be an effective means for presenting information from distributed sensors.

  18. Image restoration using spectrum estimation

    Science.gov (United States)

    Na, Ki-Woon; Paik, Joon-Ki

    1994-09-01

    A stochastic approach to image restoration is proposed by using various spectrum estimation techniques. In order to estimate the original image from the knowledge of observed image, the minimum mean square error filter or Wiener filter is known to be optimum in the sense of minimizing the mean square error. The optimality of Wiener filter, however, holds only when the power spectra of the original image and noise are given in addition to the transfer function of the imaging system. In practice, the information of the original image is generally not available. In the present paper additive noise is assumed to be white with known variance and the Wiener filter is implemented using various estimation techniques for the original spectrum. The proposed method shows significant improvement over the conventional methods, such as the Wiener filter using constant signal-to-noise power ratio, particularly for images with low signal-to-noise ratio.

  19. Scientific sketching for collaborative VR visualization design.

    Science.gov (United States)

    Keefe, Daniel F; Acevedo, Daniel; Miles, Jadrian; Drury, Fritz; Swartz, Sharon M; Laidlaw, David H

    2008-01-01

    We present four studies investigating tools and methodologies for artist-scientist-technologist collaboration in designing multivariate, virtual reality (VR) visualizations. Design study 1 identifies the promise of 3D drawing-style interfaces for VR design and also establishes limitations of these tools with respect to precision and support for animation. Design study 2 explores animating artist-created visualization designs with scientific 3D fluid flow data. While results captured an accurate sense of flow that was advantageous as compared to the results of study 1, the potential for visual exploration using the design tools tested was limited. Design study 3 reveals the importance of a new 3D interface that overcomes the precision limitation found in study 1 while remaining accessible to artist collaborators. Drawing upon previous results, design study 4 engages collaborative teams in a design process that begins with traditional paper sketching and moves to animated, interactive, VR prototypes "sketched" by designers in VR using interactive 3D tools. Conclusions from these four studies identify important characteristics of effective artist-accessible VR visualization design tools and lead to a proposed formalized methodology for successful collaborative design that we expect to be useful in guiding future collaborations. We call this proposed methodology Scientific Sketching.

  20. Collaborative robotic team design and integration

    Science.gov (United States)

    Spofford, John R.; Anhalt, David J.; Herron, Jennifer B.; Lapin, Brett D.

    2000-07-01

    Teams of heterogeneous mobile robots are a key aspect of future unmanned systems for operations in complex and dynamic urban environments, such as that envisions by DARPA's Tactical Mobile Robotics program. Interactions among such team members enable a variety of mission roles beyond those achievable with single robots or homogeneous teams. Key technologies include docking for power and data transfer, marsupial transport and deployment, collaborative team user interface, cooperative obstacle negotiation, distributed sensing, and peer inspection. This paper describes recent results in the integration and evaluation of component technologies within a collaborative system design. Integration considerations include requirement definition, flexible design management, interface control, and incremental technology integration. Collaborative system requirements are derived from mission objectives and robotic roles, and impact system and individual robot design at several levels. Design management is a challenge in a dynamic environment, with rapid evolution of mission objectives and available technologies. The object-oriented system model approach employed includes both software and hardware object representations to enable on- the-fly system and robot reconfiguration. Controlled interfaces among robots include mechanical, behavioral, communications, and electrical parameters. Technologies are under development by several organizations within the TMR program community. The incremental integration and validation of these within the collaborative system architecture reduces development risk through frequent experimental evaluations. The TMR system configuration includes Packbot-Perceivers, Packbot- Effectors, and Throwbots. Surrogates for these robots are used to validate and refine designs for multi-robot interaction components. Collaborative capability results from recent experimental evaluations are presented.

  1. Advanced sensing techniques for cognitive radio

    CERN Document Server

    Zhao, Guodong; Li, Shaoqian

    2017-01-01

    This SpringerBrief investigates advanced sensing techniques to detect and estimate the primary receiver for cognitive radio systems. Along with a comprehensive overview of existing spectrum sensing techniques, this brief focuses on the design of new signal processing techniques, including the region-based sensing, jamming-based probing, and relay-based probing. The proposed sensing techniques aim to detect the nearby primary receiver and estimate the cross-channel gain between the cognitive transmitter and primary receiver. The performance of the proposed algorithms is evaluated by simulations in terms of several performance parameters, including detection probability, interference probability, and estimation error. The results show that the proposed sensing techniques can effectively sense the primary receiver and improve the cognitive transmission throughput. Researchers and postgraduate students in electrical engineering will find this an exceptional resource.

  2. Spectrum-Based and Collaborative Network Topology Analysis and Visualization

    Science.gov (United States)

    Hu, Xianlin

    2013-01-01

    Networks are of significant importance in many application domains, such as World Wide Web and social networks, which often embed rich topological information. Since network topology captures the organization of network nodes and links, studying network topology is very important to network analysis. In this dissertation, we study networks by…

  3. The Collaborative Leader.

    Science.gov (United States)

    Williams, Carolyn Grubbs

    1998-01-01

    Uses the Los Angeles Partners Advocating Student Success, an interinstitutional educational reform effort, as a case study in collaboration. Discusses the role of the president, and contends that collaboration provides community colleges with new opportunities to promote access and enhance the educational success of underserved students by…

  4. Collaboration in teacher teams

    NARCIS (Netherlands)

    Brouwer, P.

    2011-01-01

    In order to deal with innovations and the associated complexity of work, ongoing collaboration between teachers has become more important in secondary education. Teacher collaboration is one of the factors that contribute to the successful implementation of innovations in secondary schools. However,

  5. Corrections for collaborators

    NARCIS (Netherlands)

    NN,

    1953-01-01

    In the ”Directions and Hints” for collaborators in Flora Malesiana, which has been forwarded to all collaborators, two corrections should be made, viz: 1) p. 12; Omit the explanatory notes under Jamaica Plain, Mass., and Cambridge, Mass. 2) p. 13; Add as number 12a; Stockholm, Paleobotaniska Avdelni

  6. Enabling distributed collaborative science

    DEFF Research Database (Denmark)

    Hudson, T.; Sonnenwald, Diane H.; Maglaughlin, K.

    2000-01-01

    To enable collaboration over distance, a collaborative environment that uses a specialized scientific instrument called a nanoManipulator is evaluated. The nanoManipulator incorporates visualization and force feedback technology to allow scientists to see, feel, and modify biological samples being...... studied with an Atomic Force Microscope....

  7. Sensemaking in collaborative networks

    DEFF Research Database (Denmark)

    Peronard, Jean-Paul; Brix, Jacob

    2017-01-01

    be redesigned to strengthen the collaboration between companies. To enable this discussion we delve into the sensemaking literature and theory from loosely coupled systems. Our discussion leads to the development of the Balanced Activity System (BAS) model. The paper’s key contribution is the prescriptive BAS...... model that can be used strategically in collaborative networks to redesign or create new joint activities....

  8. Collaboration in teacher teams

    NARCIS (Netherlands)

    Brouwer, P.

    2011-01-01

    In order to deal with innovations and the associated complexity of work, ongoing collaboration between teachers has become more important in secondary education. Teacher collaboration is one of the factors that contribute to the successful implementation of innovations in secondary schools. However,

  9. Enabling distributed collaborative science

    DEFF Research Database (Denmark)

    Hudson, T.; Sonnenwald, Diane H.; Maglaughlin, K.

    2000-01-01

    To enable collaboration over distance, a collaborative environment that uses a specialized scientific instrument called a nanoManipulator is evaluated. The nanoManipulator incorporates visualization and force feedback technology to allow scientists to see, feel, and modify biological samples bein...

  10. Collaborative augmented reality environments

    DEFF Research Database (Denmark)

    Büscher, Monika; Christensen, Michael; Grønbæk, Kaj

    2000-01-01

    This paper describes Manufaktur, a prototype of a concept and infrastructure that goes beyond the classical CVE systems toward a collaborative augmented reality environment, where users? documents and objects appear as live representations in a 3D workspace. Manufaktur supports collaborative...

  11. Totally-blind Spectrum Sensing:A Joint Iterative Algorithm of Noise Estimation and Energy Detection%全盲频谱感知:噪声估计与能量检测联合迭代算法

    Institute of Scientific and Technical Information of China (English)

    劳子轩; 刘子扬; 彭涛; 王文博

    2013-01-01

      在目前能量检测的算法中,通常假设噪声水平是一个已知量,然而在实际应用中,环境噪声通常都是需要实际测量才能得到的。该文针对无法利用已知空闲频谱测量噪声功率的信号检测情况,提出了一种基于迭代的宽带频谱能量检测算法,能够针对先验信息全盲的宽带抽样信号进行有效检测。文中针对迭代算法进行了收敛性分析,当迭代初值选取合理时,算法可以稳定收敛。仿真结果表明,观测时长为20以上时,迭代算法就能有十分良好的性能。%In current energy detection algorithms, the environmental noise level is often assumed as prior information. However, it is a parameter which needs to be measured in practical application. In the situation of using the known free spectrum to measure noise power is impracticably, this paper proposes a novel broadband spectrum energy detection algorithm based on iteration which can make effective detection to the broadband sampling signal which prior information is total blind. This paper also demonstrates that when the initial value of the iterative algorithm is reasonable, the algorithm can get stable convergence. The simulation results show that the algorithm can obtain a very good performance if the length of time observation is more than 20.

  12. Nurse-patient collaboration

    DEFF Research Database (Denmark)

    Sørensen, Dorthe; Frederiksen, Kirsten; Groefte, Thorbjoern

    2013-01-01

    at three intensive care units and one general respiratory ward in Denmark. Results: Succeeding emerged as the nurses’ main concern in the nurse-patient collaboration during non-invasive ventilation treatment. Four collaborative typologies emerged as processing their main concern: (1) twofold oriented......Objectives: This paper provides a theoretical account of nurses’ collaboration with patients with chronic obstructive pulmonary disease during non-invasive ventilation treatment in hospital. Background: Despite strong evidence for the effect of non-invasive ventilation treatment, success remains...... a huge challenge. Nurse-patient collaboration may be vital for treatment tolerance and success. A better understanding of how nurses and patients collaborate during non-invasive ventilation may therefore contribute to improvement in treatment success. Design: A constant comparative classical grounded...

  13. Nurse–patient collaboration

    DEFF Research Database (Denmark)

    Sørensen, Dorthe; Frederiksen, Kirsten; Grøfte, Thorbjørn;

    2013-01-01

    Objectives: This paper provides a theoretical account of nurses’ collaboration with patients with chronic obstructive pulmonary disease during non-invasive ventilation treatment in hospital. Background: Despite strong evidence for the effect of non-invasive ventilation treatment, success remains...... a huge challenge. Nurse-patient collaboration may be vital for treatment tolerance and success. A better understanding of how nurses and patients collaborate during non-invasive ventilation may therefore contribute to improvement in treatment success. Design: A constant comparative classical grounded...... at three intensive care units and one general respiratory ward in Denmark. Results: Succeeding emerged as the nurses’ main concern in the nurse-patient collaboration during non-invasive ventilation treatment. Four collaborative typologies emerged as processing their main concern: (1) twofold oriented...

  14. On Coordinating Collaborative Objects

    CERN Document Server

    Imine, Abdessamad

    2010-01-01

    A collaborative object represents a data type (such as a text document) designed to be shared by a group of dispersed users. The Operational Transformation (OT) is a coordination approach used for supporting optimistic replication for these objects. It allows the users to concurrently update the shared data and exchange their updates in any order since the convergence of all replicas, i.e. the fact that all users view the same data, is ensured in all cases. However, designing algorithms for achieving convergence with the OT approach is a critical and challenging issue. In this paper, we propose a formal compositional method for specifying complex collaborative objects. The most important feature of our method is that designing an OT algorithm for the composed collaborative object can be done by reusing the OT algorithms of component collaborative objects. By using our method, we can start from correct small collaborative objects which are relatively easy to handle and incrementally combine them to build more ...

  15. OGC Collaborative Platform undercover

    Science.gov (United States)

    Buehler, G.; Arctur, D. K.; Bermudez, L. E.

    2012-12-01

    The mission of the Open Geospatial Consortium (OGC) is to serve as a global forum for the collaboration of developers and users of spatial data products and services, and to advance the development of international standards for geospatial interoperability. The OGC coordinates with over 400 institutions in the development of geospatial standards. OGC has a dedicated staff supported by a Collaborative Web Platform to enable sophisticated and successful coordination among its members. Since its origins in the early 1990s, the OGC Collaborative Web Platform has evolved organically to be the collaboration hub for standards development in the exchange of geospatial and related types of information, among a global network of thousands of technical, scientific and management professionals spanning numerous disparate application domains. This presentation describes the structure of this collaboration hub, the relationships enabled (both among and beyond OGC members), and how this network fits in a broader ecosystem of technology development and information standards organizations.

  16. Theoretical foundations for collaboration engineering

    NARCIS (Netherlands)

    Kolfschoten, G.L.

    2007-01-01

    Collaboration is often presented as the solution to numerous problems in business and society. However, collaboration is challenging, and collaboration support is not an off-the-shelf-product. This research offers theoretical foundations for Collaboration Engineering. Collaboration Engineering is an

  17. Exact CS Reconstruction Condition of Undersampled Spectrum-Sparse Signals

    Directory of Open Access Journals (Sweden)

    Ying Luo

    2013-01-01

    Full Text Available Compressive sensing (CS reconstruction of a spectrum-sparse signal from undersampled data is, in fact, an ill-posed problem. In this paper, we mathematically prove that, in certain cases, the exact CS reconstruction of a spectrum-sparse signal from undersampled data is impossible. Then we present the exact CS reconstruction condition of undersampled spectrum-sparse signals, which is valuable for digital signal compression.

  18. Latest Trends in Acoustic Sensing

    Directory of Open Access Journals (Sweden)

    Cinzia Caliendo

    2014-03-01

    Full Text Available Acoustics-based methods offer a powerful tool for sensing applications. Acoustic sensors can be applied in many fields ranging from materials characterization, structural health monitoring, acoustic imaging, defect characterization, etc., to name just a few. A proper selection of the acoustic wave frequency over a wide spectrum that extends from infrasound (<20 Hz up to ultrasound (in the GHz–band, together with a number of different propagating modes, including bulk longitudinal and shear waves, surface waves, plate modes, etc., allow acoustic tools to be successfully applied to the characterization of gaseous, solid and liquid environments. The purpose of this special issue is to provide an overview of the research trends in acoustic wave sensing through some cases that are representative of specific applications in different sensing fields.

  19. Compressive sensing based algorithms for electronic defence

    CERN Document Server

    Mishra, Amit Kumar

    2017-01-01

    This book details some of the major developments in the implementation of compressive sensing in radio applications for electronic defense and warfare communication use. It provides a comprehensive background to the subject and at the same time describes some novel algorithms. It also investigates application value and performance-related parameters of compressive sensing in scenarios such as direction finding, spectrum monitoring, detection, and classification.

  20. Social mapping for communal sensemaking and collaboration: the case of development informatics research in South Africa

    CSIR Research Space (South Africa)

    Van Biljon, J

    2017-05-01

    Full Text Available are well-understood. This work in progress paper proposes social mapping as an innovative way of making sense of the connections between Development Informatics researchers towards understanding the research landscape and behavioural collaboration patterns...

  1. Energy Efficiency Collaboratives

    Energy Technology Data Exchange (ETDEWEB)

    Li, Michael [US Department of Energy, Washington, DC (United States); Bryson, Joe [US Environmental Protection Agency, Washington, DC (United States)

    2015-09-01

    Collaboratives for energy efficiency have a long and successful history and are currently used, in some form, in more than half of the states. Historically, many state utility commissions have used some form of collaborative group process to resolve complex issues that emerge during a rate proceeding. Rather than debate the issues through the formality of a commission proceeding, disagreeing parties are sent to discuss issues in a less-formal setting and bring back resolutions to the commission. Energy efficiency collaboratives take this concept and apply it specifically to energy efficiency programs—often in anticipation of future issues as opposed to reacting to a present disagreement. Energy efficiency collaboratives can operate long term and can address the full suite of issues associated with designing, implementing, and improving energy efficiency programs. Collaboratives can be useful to gather stakeholder input on changing program budgets and program changes in response to performance or market shifts, as well as to provide continuity while regulators come and go, identify additional energy efficiency opportunities and innovations, assess the role of energy efficiency in new regulatory contexts, and draw on lessons learned and best practices from a diverse group. Details about specific collaboratives in the United States are in the appendix to this guide. Collectively, they demonstrate the value of collaborative stakeholder processes in producing successful energy efficiency programs.

  2. 基于特征值确定门限的协作MIMO频谱感知%Exact Threshold for Cooperative MIMO Spectrum Sensing Based on Random Matrix Theory

    Institute of Scientific and Technical Information of China (English)

    黄立辉; 李莉; 张静; 陈守坤

    2011-01-01

    To improve the effectiveness of eigenvalue-based detection in cognitive radio, the multi-cognitive-user MIMO circumstance is introduced, and a new exact threshold for frequency band sensing is proposeal based on random matrix theory.The advantages of MIMO technology is used to improve detection performance. Both theoretical analysis and the simulation results show that the new algorithm outperforms similar algorithms and classical energy detection techniques.%针对最新的基于特征值确定门限的检测方法,引入多认知用户MIMO环境,提出了基于特征值确定门限的协作MIMO频谱感知,充分利用了MIMO技术的优点来提高感知性能,利用随机矩阵理论推导出决策门限的准确表达式,改进了传统基于特征值算法需要大量协作用户的缺点.理论分析和仿真结果均表明,新的决策规则不仅减少了计算复杂性,整体性能也优于同类算法和典型的能量检测算法.

  3. Collaborative Learning in the Cloud

    DEFF Research Database (Denmark)

    Kirchner, Kathrin; Razmerita, Liana

    2015-01-01

    This present study aims to investigate how students perceive collaboration and identifies associated technologies used to collaborate. In particular we aim to address the following research questions: What are the factors that impact satisfaction with collaboration? How do these factors differ...... in different collaborative settings? Based on data from 75 students from Denmark and Germany, the article identifies collaborative practices and factors that impact positively and negatively satisfaction with collaboration....

  4. Collaborative Policy Innovation

    DEFF Research Database (Denmark)

    Sørensen, Eva; Boch Waldorff, Susanne

    2014-01-01

    Governments all over the Western world currently face wicked problems that call for policy innovation. A new strand of research in public innovation points to collaboration between public authorities and relevant and affected stakeholders as an important driver of public innovation. A case study...... and policy ideas produced in collaborative governance arenas are not diffused to the formal political institutions of representative democracy because the participating politicians only to a limited extent function as boundary spanners between the collaborative governance arena and the decision making arenas...

  5. Innovation and network collaboration

    DEFF Research Database (Denmark)

    Kesting, Peter; Müller, Sabine; Jørgensen, Frances

    2011-01-01

    Research suggests that small and medium-sized enterprises (SMEs) can benefit from network collaboration by enhancing opportunities for innovation. Managing the necessary collaboration to benefit from network participation may however be particularly challenging for SMEs due to their size...... and their inherent shortage of resources. In this paper, we propose that human resource management (HRM) practices may provide a means by which SMEs can increase their innovation capacity through network collaboration. Following a brief presentation of the relevant literature on networks, and innovation in networks...

  6. Collaboration in experiential therapy.

    Science.gov (United States)

    Berdondini, Lucia; Elliott, Robert; Shearer, Joan

    2012-02-01

    We offer a view of the nature and role of client-therapist collaboration in experiential psychotherapy, focusing on Gestalt and emotion-focused therapy (EFT). We distinguish between the necessary condition of mutual trust (the emotional bond between client and therapist) and effective collaboration (regarding the goals and tasks of therapy). Using a case study of experiential therapy for social anxiety, we illustrate how the development of collaboration can be both complex and pivotal for therapeutic success, and how it can involve client and therapist encountering one another through taking risks by openly and nonjudgementally disclosing difficult experiences in order to enrich and advance the work.

  7. Writing as collaborative inquiry

    DEFF Research Database (Denmark)

    Frølunde, Lisbeth; Pedersen, Christina Hee; Novak, Martin

    2015-01-01

    In our presentation we strive to disturb and unravel the romantic discourses of collaboration, dialogue and empowerment in relation to qualitative inquiry. For more than two years we (five Danish and Czech researchers) have been exploring the complex obstructions, difficulties and potentials...... involved in collaborative knowledge production across difference (including age, professional position, life situation, nation). We tell about our experiences with how collaboration can lead toward re-invention of our research practices and methods, as well as our own subjectivities, through involvement...

  8. Collaboration in Augmented Reality

    OpenAIRE

    Lukosch, S.; Billinghurst, M; Alem, L.; Kiyokawa, K.

    2015-01-01

    Augmented Reality (AR) is a technology that allows users to view and interact in real time with virtual images seamlessly superimposed over the real world. AR systems can be used to create unique collaborative experiences. For example, co-located users can see shared 3D virtual objects that they interact with, or a user can annotate the live video view of a remote worker, enabling them to collaborate at a distance. The overall goal is to augment the face-to-face collaborative experience, or t...

  9. Designing collaborative policy innovation

    DEFF Research Database (Denmark)

    Agger, Annika; Sørensen, Eva

    2014-01-01

    Recent approaches to enhancing public innovation suffer from two shortcomings: They overemphasize competition as a driver of innovation and overlook the fact that public sector innovation involves policy innovation as well as service innovation. Drawing on governance research and innovation theory......, the chapter investigates the extent to which and how collaboration between politicians and relevant stakeholders can spur the formulation, implementation and diffusion of new innovative policies. A case study of a process of collaborative policy innovation in a Danish municipality shows that collaborative...... policy arenas do contribute to policy innovation but also that the degree to which they do so depends on the institutional design of these arenas....

  10. Collaboration during visual search.

    Science.gov (United States)

    Malcolmson, Kelly A; Reynolds, Michael G; Smilek, Daniel

    2007-08-01

    Two experiments examine how collaboration influences visual search performance. Working with a partner or on their own, participants reported whether a target was present or absent in briefly presented search displays. We compared the search performance of individuals working together (collaborative pairs) with the pooled responses of the individuals working alone (nominal pairs). Collaborative pairs were less likely than nominal pairs to correctly detect a target and they were less likely to make false alarms. Signal detection analyses revealed that collaborative pairs were more sensitive to the presence of the target and had a more conservative response bias than the nominal pairs. This pattern was observed even when the presence of another individual was matched across pairs. The results are discussed in the context of task-sharing, social loafing and current theories of visual search.

  11. Configurable Project Collaboration Portal

    Data.gov (United States)

    National Aeronautics and Space Administration — SplashNote Systems is proposing to develop a more effective and innovative approach to project collaboration in distributed teams. The proposed system uniquely gives...

  12. Providers’ perspectives on collaboration

    Directory of Open Access Journals (Sweden)

    Patricia Bruner

    2011-08-01

    Full Text Available Objective: Changes in models of health care are required to better meet the needs of diverse, underserved patient populations. Collaboration among providers is one way to promote accessible, comprehensive and continuous care in healthcare organizations. This paper describes the quantitative findings from two time points that examined providers' views of collaboration among a sample of diverse personnel (e.g. clinical nurses, social workers, dental providers, mental health providers, clerical staff, medical assistants, public health staff, and administrators within a federally qualified nurse managed health care centre in the United States. Methods: The quantitative arm of a mixed-method study is presented in this paper. Two instruments, the Collaboration and Satisfaction About Care Decisions Scale and the University of the West of England Interprofessional Questionnaire (comprised of 4 subscales-Communication and Teamwork Scale, Interprofessional Learning Scale, Interprofessional Interaction Scale, and Interprofessional Relationships Scale were administered to providers at baseline and three to eight months following six same discipline focus group discussions on collaboration, in order to evaluate whether participating in the focus group discussions changed providers' views of collaboration. A summary of the focus group data which were published elsewhere is additionally summarized to help provide insight to the quantitative findings. Thirty-nine staff participated. Results: Paired t-tests revealed that only one scale out of the five, Collaboration and Satisfaction About Care Decisions Scale (33.97 at time one and 37.45 at time two, significantly and positively changed after the focus group discussion (p=0.046. Providers' views on collaboration ranged from positive to moderate views of collaboration; most measures revealed a non-significant improvement after the focus group discussions. Staff with some graduate school reported the greatest

  13. Drivers of Collaborative Advantage

    DEFF Research Database (Denmark)

    Weihe, Gudrid

    Drawing upon extant alliance literature, this article substantiates the argument that we need to look beyond mere structural and formative aspects of cooperation in order to fully understand the performance antecedents of public-private partnerships. Currently, scholarly work on operational...... processes and behavioural dimensions is practically non-existent. This article tries to remedy the current gap in the literature by reviewing research findings on interfirm collaboration (alliances). On that basis a conceptual framework for analyzing partnership processes is developed. Finally......, the antecedents of collaborative advantage are theoretically examined, and the organizational competences contributing to collaborative success are identified. The conclusion is that operational processes and social dynamics are vital drivers of collaborative advantage. Another significant conclusion...

  14. Indico: CERN Collaboration Hub

    CERN Document Server

    CERN. Geneva

    2012-01-01

    Indico development is also moving towards a broader collaboration where other institutes, hosting their own Indico instance, can contribute to the project in order make it a better and more complete tool.

  15. Collaborative software development

    NARCIS (Netherlands)

    Jonge, M. de; Visser, E.; Visser, J.M.W.

    2001-01-01

    We present an approach to collaborative software development where obtaining components and contributing components across organizational boundaries are explicit phases in the development process. A lightweight generative infrastructure supports this approach with an online package base, and several

  16. EPA Collaboration with Israel

    Science.gov (United States)

    The United States and Israel focus on scientific and technical collaboration to protect the environment, by exchanging scientific and technical information, arranging visits of scientific personnel, cooperating in scientific symposia and workshops, etc.

  17. Providers’ perspectives on collaboration

    Directory of Open Access Journals (Sweden)

    Patricia Bruner

    2011-08-01

    Full Text Available Objective: Changes in models of health care are required to better meet the needs of diverse, underserved patient populations. Collaboration among providers is one way to promote accessible, comprehensive and continuous care in healthcare organizations. This paper describes the quantitative findings from two time points that examined providers' views of collaboration among a sample of diverse personnel (e.g. clinical nurses, social workers, dental providers, mental health providers, clerical staff, medical assistants, public health staff, and administrators within a federally qualified nurse managed health care centre in the United States.Methods: The quantitative arm of a mixed-method study is presented in this paper. Two instruments, the Collaboration and Satisfaction About Care Decisions Scale and the University of the West of England Interprofessional Questionnaire (comprised of 4 subscales-Communication and Teamwork Scale, Interprofessional Learning Scale, Interprofessional Interaction Scale, and Interprofessional Relationships Scale were administered to providers at baseline and three to eight months following six same discipline focus group discussions on collaboration, in order to evaluate whether participating in the focus group discussions changed providers' views of collaboration. A summary of the focus group data which were published elsewhere is additionally summarized to help provide insight to the quantitative findings. Thirty-nine staff participated.Results: Paired t-tests revealed that only one scale out of the five, Collaboration and Satisfaction About Care Decisions Scale (33.97 at time one and 37.45 at time two, significantly and positively changed after the focus group discussion (p=0.046. Providers' views on collaboration ranged from positive to moderate views of collaboration; most measures revealed a non-significant improvement after the focus group discussions. Staff with some graduate school reported the greatest

  18. EPA Collaboration with Morocco

    Science.gov (United States)

    For the last four years, EPA has been collaborating with Morocco on environmental governance through the Middle East Partnership Initiative (MEPI). Initial work with Morocco focused on water pollution from the textile industry.

  19. CMS Collaboration Board Meeting

    CERN Multimedia

    Hoch, Michael

    2013-01-01

    The first CMS Collaboration Board meeting of the year (2013) provided an opportunity to thank Teresa Rodrigo, Matthias Kasemann and Randy Ruchti, the 2011-12 CB Chair, Deputy Chair and Secretary, respectively.

  20. HORIZON SENSING

    Energy Technology Data Exchange (ETDEWEB)

    Larry G. Stolarczyk

    2003-03-18

    With the aid of a DOE grant (No. DE-FC26-01NT41050), Stolar Research Corporation (Stolar) developed the Horizon Sensor (HS) to distinguish between the different layers of a coal seam. Mounted on mining machine cutter drums, HS units can detect or sense the horizon between the coal seam and the roof and floor rock, providing the opportunity to accurately mine the section of the seam most desired. HS also enables accurate cutting of minimum height if that is the operator's objective. Often when cutting is done out-of-seam, the head-positioning function facilitates a fixed mining height to minimize dilution. With this technology, miners can still be at a remote location, yet cut only the clean coal, resulting in a much more efficient overall process. The objectives of this project were to demonstrate the feasibility of horizon sensing on mining machines and demonstrate that Horizon Sensing can allow coal to be cut cleaner and more efficiently. Stolar's primary goal was to develop the Horizon Sensor (HS) into an enabling technology for full or partial automation or ''agile mining''. This technical innovation (R&D 100 Award Winner) is quickly demonstrating improvements in productivity and miner safety at several prominent coal mines in the United States. In addition, the HS system can enable the cutting of cleaner coal. Stolar has driven the HS program on the philosophy that cutting cleaner coal means burning cleaner coal. The sensor, located inches from the cutting bits, is based upon the physics principles of a Resonant Microstrip Patch Antenna (RMPA). When it is in proximity of the rock-coal interface, the RMPA impedance varies depending on the thickness of uncut coal. The impedance is measured by the computer-controlled electronics and then sent by radio waves to the mining machine. The worker at the machine can read the data via a Graphical User Interface, displaying a color-coded image of the coal being cut, and direct the machine

  1. Blogging to Learn: Becoming EFL Academic Writers through Collaborative Dialogues

    Science.gov (United States)

    Sun, Yu-Chih; Chang, Yu-jung

    2012-01-01

    This study examines how blogs and their interactive and collaborative features help academically-advanced graduate students process academic writing knowledge and make sense of their writer identity. Seven graduate students undertaking Master's level study in TESOL and Linguistics participated. The research questions are: (a) What kinds of…

  2. A Collaborative, Investigative Recombinant DNA Technology Course with Laboratory

    Science.gov (United States)

    Pezzementi, Leo; Johnson, Joy F.

    2002-01-01

    A recombinant DNA technology course was designed to promote contextual, collaborative, inquiry-based learning of science where students learn from one another and have a sense of ownership of their education. The class stressed group presentations and critical reading and discussion of scientific articles. The laboratory consisted of two research…

  3. Opposing incentives for collaboration

    DEFF Research Database (Denmark)

    Dorch, Bertil F.; Wien, Charlotte; Larsen, Asger Væring

    The Danish Bibliometric Research Indicator (BFI) is part of the performance-based model for the distribution of a special pool of baseline funding for universities and public research institutions in Denmark. BFI rewards the research publications published in the most recognized scientific journals...... collaboration is associated with a higher number of citations than single authorship which may present the author with two opposing incentives for research collaboration....

  4. Case Study in the Power of Collaboration: Planning Process for the Kansas Educational Leadership Institute

    Science.gov (United States)

    Devin, Mary

    2013-01-01

    This article reports on the collaborative efforts undertaken for systematic statewide support for the recruitment, development, and retention of quality leaders in schools and school districts in Kansas, USA. The author presents the case of a strong sense of "collaboration" that made the difference and stimulated movement from vision…

  5. Case Study in the Power of Collaboration: Planning Process for the Kansas Educational Leadership Institute

    Science.gov (United States)

    Devin, Mary

    2013-01-01

    This article reports on the collaborative efforts undertaken for systematic statewide support for the recruitment, development, and retention of quality leaders in schools and school districts in Kansas, USA. The author presents the case of a strong sense of "collaboration" that made the difference and stimulated movement from vision…

  6. The Perceptions of Participation in a Mobile Collaborative Learning among Pre-Service Teachers

    Science.gov (United States)

    Liu, Shih-Hsiung

    2016-01-01

    This study uses Facebook as a platform and arranges certain learning tasks to identify the feasibility of mobile collaborative learning for pre-service teachers. The pre-service teachers' sense of community and perceptions of collaborative learning are investigated. A total of 153 pre-service teachers volunteered to participate in an Intern Mobile…

  7. The Influences of Social Collaboration on Web 2.0 Self-Efficacy for Higher Education

    Science.gov (United States)

    Turky, Mohamed Abdullah

    2016-01-01

    The present study tries to research the relationship between Social Collaboration Activity and Web 2.0 Self-Efficacy for Higher Education student. It additionally looks to decide how Social Collaboration adds to the forecast of their sense Web 2.0 Self-Efficacy. The study reported in this paper was led to inspect the relationship Social…

  8. Joint collaborative technology experiment

    Science.gov (United States)

    Wills, Michael; Ciccimaro, Donny; Yee, See; Denewiler, Thomas; Stroumtsos, Nicholas; Messamore, John; Brown, Rodney; Skibba, Brian; Clapp, Daniel; Wit, Jeff; Shirts, Randy J.; Dion, Gary N.; Anselmo, Gary S.

    2009-05-01

    Use of unmanned systems is rapidly growing within the military and civilian sectors in a variety of roles including reconnaissance, surveillance, explosive ordinance disposal (EOD), and force-protection and perimeter security. As utilization of these systems grows at an ever increasing rate, the need for unmanned systems teaming and inter-system collaboration becomes apparent. Collaboration provides a means of enhancing individual system capabilities through relevant data exchange that contributes to cooperative behaviors between systems and enables new capabilities not possible if the systems operate independently. A collaborative networked approach to development holds the promise of adding mission capability while simultaneously reducing the workload of system operators. The Joint Collaborative Technology Experiment (JCTE) joins individual technology development efforts within the Air Force, Navy, and Army to demonstrate the potential benefits of interoperable multiple system collaboration in a force-protection application. JCTE participants are the Air Force Research Laboratory, Materials and Manufacturing Directorate, Airbase Technologies Division, Force Protection Branch (AFRL/RXQF); the Army Aviation and Missile Research, Development, and Engineering Center Software Engineering Directorate (AMRDEC SED); and the Space and Naval Warfare Systems Center - Pacific (SSC Pacific) Unmanned Systems Branch operating with funding provided by the Joint Ground Robotics Enterprise (JGRE). This paper will describe the efforts to date in system development by the three partner organizations, development of collaborative behaviors and experimentation in the force-protection application, results and lessons learned at a technical demonstration, simulation results, and a path forward for future work.

  9. Discriminative sensing techniques

    Science.gov (United States)

    Lewis, Keith

    2008-10-01

    The typical human vision system is able to discriminate between a million or so different colours, yet is able to do this with a chromatic sensor array that is fundamentally based on three different receptors, sensitive to light in the blue, green and red portions of the visible spectrum. Some biological organisms have extended capabilities, providing vision in the ultra-violet, whilst others, such as some species of mantis shrimp reportedly have sixteen different types of photo-receptors. In general the biological imaging sensor takes a minimalist approach to sensing its environment, whereas current optical engineering approaches follow a 'brute' force solution where the challenge of hyperspectral imaging is addressed by various schemes for spatial and spectral dispersion of radiation across existing detector arrays. This results in a problem for others to solve in the processing and communication of the generated hypercube of data. This paper explores the parallels between some of those biological systems and the various design concepts being developed for discriminative imaging, drawing on activity supported by the UK Electro-Magnetic Remote Sensing Defence Technology Centre (EMRS DTC).

  10. On the Operational Meaning of Broad-Spectrum Philosophy Methodology

    Directory of Open Access Journals (Sweden)

    Miao Yi

    2012-06-01

    Full Text Available This study analyze the Broad-spectrum Philosophy Methodology on the operational meaning, and discusses three relatively primary methods of Broad-spectrum Philosophy Methodologies. The methodology of Broad-spectrum philosophy cannot pursuit of accuracy of numerical sense, but it pursuits of the exact nature of the research questions, the accuracy of the sense of set theory and sums up the experience which we solve problems in real life and make it up to the generalized quantization and procedural level and thus the methodology of Broad-spectrum philosophy has a general guide and it is a broad operations research. We gets the results that along with deep exploration and development of Broad-spectrum Philosophy Methodology, its function as generalized operation research can be more powerful.

  11. Reminiscences, collaborations and reflections.

    Science.gov (United States)

    Akazawa, T

    1994-02-01

    This is a personal account by a semi old-timer who completed his official term as a professor of plant biochemistry at Nagoya University in Japan in 1992. My university student life began soon after the World War II (1948). I shared the hardships of many in my age group, in that life was difficult during my college years. I was fortunate to have the opportunity of studying in the USA on a Fulbright scholarship first at Purdue University (1955-1956), and then at the University of California, Berkeley (1956-1957). My graduate study and postdoctoral training in the new world were vitally refreshing and stimulating, which gave me the impetus for becoming a natural scientist associated with academic institutions. Consciously and subconsciously I was impressed by the friendly and liberal atmosphere surrounding young students as well as senior scholars in the United States. But more importantly, I was inspired by the critical and competitive minds prevailing among these people.The appointment as a biochemist at the International Rice Research Institute (IRRI) in the Philippines (1962-1964) was the real start of my professional career. The work was continued upon my return to Nagoya to become a staff member of the Research Institute for Biochemical Regulation (1964-1992). Throughout the years, my major research interest has covered photosynthesis as a whole, involving photosynthetic CO2-fixation (RuBisCO), carbohydrate metabolism, e.g. starch biosynthesis and breakdown (α-amylase), and metabolic regulation, which are interrelated in the basic metabolism of plant cells.I shall briefly describe in this article highlights from my studies and discoveries made and I shall also discuss their possible significance in plant metabolism, with the hope that it does not contradict my sense of humility: They are (a) discovery of ADPG in plants and its role in starch biosynthesis; (b) structure-function relationship of RuBisCO proteins, in particular on heterologous recombination of

  12. Collaborative Planetary GIS with JMARS

    Science.gov (United States)

    Dickenshied, S.; Christensen, P. R.; Edwards, C. S.; Prashad, L. C.; Anwar, S.; Engle, E.; Noss, D.; Jmars Development Team

    2010-12-01

    Traditional GIS tools have allowed users to work locally with their own datasets in their own computing environment. More recently, data providers have started offering online repositories of preprocessed data which helps minimize the learning curve required to access new datasets. The ideal collaborative GIS tool provides the functionality of a traditional GIS and easy access to preprocessed data repositories while also enabling users to contribute data, analysis, and ideas back into the very tools they're using. JMARS (Java Mission-planning and Analysis for Remote Sensing) is a suite of geospatial applications developed by the Mars Space Flight Facility at Arizona State University. This software is used for mission planning and scientific data analysis by several NASA missions, including Mars Odyssey, Mars Reconnaissance Orbiter, and the Lunar Reconnaissance Orbiter. It is used by scientists, researchers and students of all ages from more than 40 countries around the world. In addition to offering a rich set of global and regional maps and publicly released orbiter images, the JMARS software development team has been working on ways to encourage the creation of collaborative datasets. Bringing together users from diverse teams and backgrounds allows new features to be developed with an interest in making the application useful and accessible to as wide a potential audience as possible. Actively engaging the scientific community in development strategy and hands on tasks allows the creation of user driven data content that would not otherwise be possible. The first community generated dataset to result from this effort is a tool mapping peer-reviewed papers to the locations they relate to on Mars with links to ancillary data. This allows users of JMARS to browse to an area of interest and then quickly locate papers corresponding to that area. Alternately, users can search for published papers over a specified time interval and visually see what areas of Mars have

  13. Reputational Information and Strategic Collaboration

    DEFF Research Database (Denmark)

    Andersen, Poul Houman; Bendix, Henrik B.

    1998-01-01

    What types of information do decision-makers use when deciding on collaboration? What are the role of reputational information in relation to decisions on collaboration......What types of information do decision-makers use when deciding on collaboration? What are the role of reputational information in relation to decisions on collaboration...

  14. Study on spectral structure of quantum remote sensing

    Institute of Scientific and Technical Information of China (English)

    BI; Siwen; HAN; Jixia

    2006-01-01

    A study of the use of fine spectral structure in quantum remote sensing, including an expression, begins with a summary of present-day applications of spectrum remote sensing, which is followed by a theoretical discussion of the influence of electronic spin upon hydrogen-like atom energy levels and the calculation of spectral line in the absence of a circumstance field.

  15. Distributed Sensing and Processing Adaptive Collaboration Environment (D-SPACE)

    Science.gov (United States)

    2014-07-01

    we desire in learning the graph patterns from data. For the case of “ mega -example” training data, i.e., a single large data graph without...and browsing in databases using BANKS . In Data Engineering, 2002. Proceedings. 18th International Conference on (pp. 431-440). IEEE. Brocheler, M., A

  16. Making Sense of Ambiguity through Dialogue and Collaborative Action

    OpenAIRE

    Carroll, John Stephen

    2015-01-01

    This paper outlines the importance of ambiguity in organizations that manage hazardous operations in a rapidly changing environment. Three kinds of ambiguity are described: fundamental ambiguity in categories and labels for understanding what is happening; causal ambiguity for understanding cause–effect relationships that enable explanation, prediction, and intervention; and role ambiguity of agreeing on responsibilities. Examples of successful and unsuccessful ways that organizations deal wi...

  17. Is the Galactic Cosmic Ray Spectrum Constant in Time?

    CERN Document Server

    Eichler, David; Pohl, Martin

    2013-01-01

    The hypothesis is considered that the present Galactic cosmic ray spectrum is at present softer than its time average due to source intermittency. Measurements of muogenic nuclides underground could provide an independent measurement of the time averaged spectrum. Source intermittency could also account for the surprising low anisotropy reported by the IceCube collaboration. Predictions for Galactic emission of ultrahigh-energy quanta, such as UHE gamma rays and neutrinos, might be higher or lower than previously estimated.

  18. Infrastructure sensing.

    Science.gov (United States)

    Soga, Kenichi; Schooling, Jennifer

    2016-08-01

    Design, construction, maintenance and upgrading of civil engineering infrastructure requires fresh thinking to minimize use of materials, energy and labour. This can only be achieved by understanding the performance of the infrastructure, both during its construction and throughout its design life, through innovative monitoring. Advances in sensor systems offer intriguing possibilities to radically alter methods of condition assessment and monitoring of infrastructure. In this paper, it is hypothesized that the future of infrastructure relies on smarter information; the rich information obtained from embedded sensors within infrastructure will act as a catalyst for new design, construction, operation and maintenance processes for integrated infrastructure systems linked directly with user behaviour patterns. Some examples of emerging sensor technologies for infrastructure sensing are given. They include distributed fibre-optics sensors, computer vision, wireless sensor networks, low-power micro-electromechanical systems, energy harvesting and citizens as sensors.

  19. Sensing temperature.

    Science.gov (United States)

    Sengupta, Piali; Garrity, Paul

    2013-04-22

    Temperature is an omnipresent physical variable reflecting the rotational, vibrational and translational motion of matter, what Richard Feynman called the "jiggling" of atoms. Temperature varies across space and time, and this variation has dramatic effects on the physiology of living cells. It changes the rate and nature of chemical reactions, and it alters the configuration of the atoms that make up nucleic acids, proteins, lipids and other biomolecules, significantly affecting their activity. While life may have started in a "warm little pond", as Charles Darwin mused, the organisms that surround us today have only made it this far by devising sophisticated systems for sensing and responding to variations in temperature, and by using these systems in ways that allow them to persist and thrive in the face of thermal fluctuation.

  20. COLLABORATION BOARD (CB55)

    CERN Multimedia

    B. Cousins

    Open Access Publication Policy ATLAS had recently issued a short statement in support of open access publishing. The mood of the discussions in the December CMS Collaboration Board had appeared to be in favour and so it was being proposed that CMS issue the same statement as that made by ATLAS (the statement is attached to the agenda of this meeting). The Collaboration Board agreed. Election of the Chair of the Collaboration Board Following the agreement to shorten the terms of both the Spokesperson and the Collaboration Board Chair, and to introduce a longer overlap period between the election and the start of the term, the election for the next Collaboration Board Chair was due in December 2007. If the old standard schedule specified in the Constitution were adapted to this date, then the Board should be informed at the present meeting that the election was being prepared. However, it was felt that the experience of the previous year's election of the Spokesperson had shown that it would be desirable to...

  1. Additive Manufacturing Cloud via Peer-Robot Collaboration

    Directory of Open Access Journals (Sweden)

    Yuan Yao

    2016-05-01

    Full Text Available When building a 3D printing cloud manufacturing platform, self-sensing and collaboration on manufacturing resources present challenging problems. This paper proposes a peer-robot collaboration framework to deal with these issues. Each robot combines heterogeneous additive manufacturing hardware and software, acting as an intelligent agent. Through collaboration with other robots, it forms a dynamic and scalable integration manufacturing system. The entire distributed system is managed by rules that employ an internal rule engine, which supports rule conversion and conflict resolution. Two additive manufacturing service scenarios are designed to analyse the efficiency and scalability of the framework. Experiments show that the presented method performs well in tasks requiring large-scale access to resources and collaboration.

  2. Additive Manufacturing Cloud via Peer-robot Collaboration

    Directory of Open Access Journals (Sweden)

    Yuan Yao

    2016-05-01

    Full Text Available When building a 3D printing cloud manufacturing platform, self-sensing and collaboration on manufacturing resources present challenging problems. This paper proposes a peer-robot collaboration framework to deal with these issues. Each robot combines heterogeneous additive manufacturing hardware and software, acting as an intelligent agent. Through collaboration with other robots, it forms a dynamic and scalable integration manufacturing system. The entire distributed system is managed by rules that employ an internal rule engine, which supports rule conversion and conflict resolution. Two additive manufacturing service scenarios are designed to analyse the efficiency and scalability of the framework. Experiments show that the presented method performs well in tasks requiring large-scale access to resources and collaboration.

  3. Pride and Prejudice – Identity and Collaboration in Construction

    DEFF Research Database (Denmark)

    Thuesen, Christian

    2013-01-01

    Based on an 18 month ethnographic case study of a construction partnering project, the paper adopts practice based theory for understanding the identity formation and practices of collaboration in construction. Drawing upon practice based theory in general and actor network theory and communities...... practices – enabling and inhibiting collaboration. Pride and prejudice are thus central constitutive elements of present construction practices in the formation of identity and development of collaboration processes........ Overtime they learn to behave competently at the boundaries between professions forming their identity and a sense of belonging in relation to an institutionalized role and the realization of the physical building. In this process the actors develop “pride” in terms of authorship of the physical building...... and membership their profession. However another consequence of these learning processes is the development of prejudices. Prejudices are often viewed as a negative aspect of building processes as it hinders collaboration among the professions. Consequently prejudices is often seen as something which should...

  4. The collaboration imperative.

    Science.gov (United States)

    Nidumolu, Ram; Ellison, Jib; Whalen, John; Billman, Erin

    2014-04-01

    Addressing global sustainability challenges--including climate change, resource depletion, and ecosystem loss--is beyond the individual capabilities of even the largest companies. To tackle these threats, and unleash new value, companies and other stakeholders must collaborate in new ways that treat fragile and complex ecosystems as a whole. In this article, the authors draw on cases including the Latin American Water Funds Partnership, the Sustainable Apparel Coalition (led by Nike, Patagonia, and Walmart), and Action to Accelerate Recycling (a partnership between Alcoa, consumer packaged goods companies, and local governments, among others) to describe four new collaboration models that create shared value and address environmental protection across the value stream. Optimal collaborations focus on improving either business processes or outcomes. They start with a small group of key organizations, bring in project management expertise, link self-interest to shared interest, encourage productive competition, create quick wins, and, above all, build and maintain trust.

  5. Indico: A Collaboration Hub

    CERN Document Server

    Ferreira, P; Bossy, C; Gonzalez, J B; Pugh, M; Resco, A; Trzaskoma, J; Wachter, C

    2012-01-01

    Since 2009, the development of Indico has focused on usability, performance and new features, especially the ones related to meeting collaboration. Usability studies have resulted in the biggest change Indico has experienced up to now, a new web layout that makes user experience better. Performance improvements were also a key goal since 2010; the main features of Indico have been optimized remarkably. Along with usability and performance, new features have been added to Indico such as webchat integration, video services bookings, webcast and recording requests, designed to really reinforce Indico position as the main hub for all CERN collaboration services, and many others which aim is to complete the conference lifecycle management. Indico development is also moving towards a broader collaboration where other institutes, hosting their own Indico instance, can contribute to the project in order make it a better and more complete tool.

  6. Collaborative Economy and Tourism

    DEFF Research Database (Denmark)

    2017-01-01

    or spare capacity make it difficult to theorise. In this chapter, we lay the foundation for a social science approach to the exploration of the collaborative economy and its relationship with tourism. We argue that “collaborative” and “economy” should be conceptualised in a broad and inclusive manner......The digital collaborative economy is one of the most fascinating developments to have claimed our attention in the last decade. Not only does it defy clear definition, but its historical links back to non-monetised sharing and gift economies and its contemporary foundations in monetising idling...... in order to avoid narrow theorisations and blinkered accounts that focus only on digitally-mediated, monetised transactions. A balance between individual and collective dimensions of the collaborative economy is also necessary if we are to understand its societal implications....

  7. Innovation and network collaboration

    DEFF Research Database (Denmark)

    Kesting, Peter; Müller, Sabine; Jørgensen, Frances

    2011-01-01

    Research suggests that small and medium-sized enterprises (SMEs) can benefit from network collaboration by enhancing opportunities for innovation. Managing the necessary collaboration to benefit from network participation may however be particularly challenging for SMEs due to their size...... and their inherent shortage of resources. In this paper, we propose that human resource management (HRM) practices may provide a means by which SMEs can increase their innovation capacity through network collaboration. Following a brief presentation of the relevant literature on networks, and innovation in networks...... in particular, and HRM, we analyse and evaluate the potential applicability of existing models for supporting innovation in SMEs participating in networks. Finally, we propose several lines of inquiry arising from our analysis that provide directions for future research....

  8. Collaborative Economy and Tourism

    DEFF Research Database (Denmark)

    2017-01-01

    The digital collaborative economy is one of the most fascinating developments to have claimed our attention in the last decade. Not only does it defy clear definition, but its historical links back to non-monetised sharing and gift economies and its contemporary foundations in monetising idling...... or spare capacity make it difficult to theorise. In this chapter, we lay the foundation for a social science approach to the exploration of the collaborative economy and its relationship with tourism. We argue that “collaborative” and “economy” should be conceptualised in a broad and inclusive manner...... in order to avoid narrow theorisations and blinkered accounts that focus only on digitally-mediated, monetised transactions. A balance between individual and collective dimensions of the collaborative economy is also necessary if we are to understand its societal implications....

  9. Communication and collaboration technologies.

    Science.gov (United States)

    Cheeseman, Susan E

    2012-01-01

    This is the third in a series of columns exploring health information technology (HIT) in the neonatal intensive care unit (NICU). The first column provided background information on the implementation of information technology throughout the health care delivery system, as well as the requisite informatics competencies needed for nurses to fully engage in the digital era of health care. The second column focused on information and resources to master basic computer competencies described by the TIGER initiative (Technology Informatics Guiding Education Reform) as learning about computers, computer networks, and the transfer of data.1 This column will provide additional information related to basic computer competencies, focusing on communication and collaboration technologies. Computers and the Internet have transformed the way we communicate and collaborate. Electronic communication is the ability to exchange information through the use of computer equipment and software.2 Broadly defined, any technology that facilitates linking one or more individuals together is a collaborative tool. Collaboration using technology encompasses an extensive range of applications that enable groups of individuals to work together including e-mail, instant messaging (IM ), and several web applications collectively referred to as Web 2.0 technologies. The term Web 2.0 refers to web applications where users interact and collaborate with each other in a collective exchange of ideas generating content in a virtual community. Examples of Web 2.0 technologies include social networking sites, blogs, wikis, video sharing sites, and mashups. Many organizations are developing collaborative strategies and tools for employees to connect and interact using web-based social media technologies.3.

  10. Collaborating Across Borders

    Science.gov (United States)

    Flatten, Amy

    Physicists transcend national boundaries, ethnic differences, and scientific disciplines to address globally shared problems and questions. This talk will highlight how scientists have collaborated across borders - both geographic and scientific - to achieve ground-breaking discoveries through international scientific cooperation. The speaker also will address how international collaborations will be even more crucial for addressing future challenges faced by the physics community, such as building large-scale research facilities, strengthening scientific capacity in developing countries, fostering ''science for diplomacy'' in times of political tensions and other critical issues.

  11. Playful Collaboration (or Not)

    DEFF Research Database (Denmark)

    Bogers, Marcel; Sproedt, Henrik

    2011-01-01

    also be conducive to deep learning. As such, a game can engage different dimensions of learning and embed elements of active, collaborative, cooperative and problem-based learning. Building on this logic, we present an exploratory case study of the use of a particular board game in a class of a course......This paper explores how games and play, which are deeply rooted in human beings as a way to learn and interact, can be used to teach certain concepts and practices related to open collaborative innovation. We discuss how playing games can be a source of creativity, imagination and fun, while it can...

  12. Organizing for Asymmetric Collaboration

    DEFF Research Database (Denmark)

    Nielsen, Jørn Flohr; Sørensen, Henrik B.

      The vision of new organizational forms consists of less-organized networks and alliances between organizations, in which collaborative capabilities are assumed to be crucial (Miles et al., 2005). The path to such new forms may go through fragile cooperative efforts. Despite the good will of many...... complexity to already complex models, we claim that our approach has practical implications: it offers rather simple diagnostic cues to change agents that are coping with the barriers to management and collaboration among loosely coupled units....

  13. Sensing at the nanoscale

    Science.gov (United States)

    Demming, Anna; Hierold, Christofer

    2013-11-01

    properties are an important indicator for sensing. In search of a better understanding of these systems Zhang et al from Southern Illinois University inspect the role of Joule heating, exothermal reactions and heat dissipation in gas sensing using nanowires [7]. The mechanisms behind electrical chemical sensors are also further scrutinized in a kinetics study by Joan Ramon Morante from the University of Barcelona in Spain. 'In spite of the growing commercial success many basic issues remain still open and under discussion limiting the broad use of this technology,' he explains. He discusses surface chemical reaction kinetics and the experimental results for different representative gas molecules to gain an insight into the chemical to electrical transduction mechanisms taking place [8]. Perhaps one of the most persistent targets in sensing research is increasing the sensitivity. Gauging environmental health issues around the commercial use of nanomaterials places high demands on low-level detection and spurred a collaboration of researchers in the UK, Croatia and Canada to look into the use of particle-impact voltammetry for detecting nanoparticles in environmental media [9]. At the University of Illinois Urbana-Champaign in the US, researchers have applied wave transform analysis techniques to the oscillations of an atomic force microscopy cantilever and tailored a time-frequency-domain filter to identify the region of highest vibrational energy [10]. The approach allows them to improve the signal to noise ratio by a factor 32 on current high-performance devices. In addition, researchers in Korea report how doping NiO nanofibres can improve the sensitivity to a number of gases, including ethanol, where the response was enhanced by as much as a factor of 217.86 [11]. Biomedicine is one of the largest industries for the application of nanotechnology in sensing. Demonstrating the state of the art, researchers in China use silicon wafers decorated with gold nanoparticles for

  14. Compressive Sensing in Communication Systems

    DEFF Research Database (Denmark)

    Fyhn, Karsten

    2013-01-01

    Wireless communication is omnipresent today, but this development has led to frequency spectrum becoming a limited resource. Furthermore, wireless devices become more and more energy-limited, due to the demand for continual wireless communication of higher and higher amounts of information....... The need for cheaper, smarter and more energy efficient wireless devices is greater now than ever. This thesis addresses this problem and concerns the application of the recently developed sampling theory of compressive sensing in communication systems. Compressive sensing is the merging of signal...... acquisition and compression. It allows for sampling a signal with a rate below the bound dictated by the celebrated Shannon-Nyquist sampling theorem. In some communication systems this necessary minimum sample rate, dictated by the Shannon-Nyquist sampling theorem, is so high it is at the limit of what...

  15. Sensing with THz metamaterial absorbers

    CERN Document Server

    Cong, Longqing

    2014-01-01

    Metamaterial perfect absorbers from microwaves to optical part of the electromagnetic spectrum has been intensely studied for its ability to absorb electromagnetic radiation. Perfect absorption of light by metamaterials have opened up new opportunities for application oriented functionalities such as efficient sensors and emitters. We present an absorber based sensing scheme at the terahertz frequencies and discuss optimized designs to achieve high frequency and amplitude sensitivities. The major advantage of a perfect metamaterial absorber as a sensor is the sensitive shift in the absorber resonance frequency along with the sharp change in the amplitude of the resonance due to strong interaction of the analyte with the electric and the magnetic fields at resonant perfect absorption frequency. We compare the sensing performance of the perfect metamaterial absorber with its complementary structural design and planar metasurface with identical structure. The best FoM values obtained for the absorber sensor here...

  16. C3: A Collaborative Web Framework for NASA Earth Exchange

    Science.gov (United States)

    Foughty, E.; Fattarsi, C.; Hardoyo, C.; Kluck, D.; Wang, L.; Matthews, B.; Das, K.; Srivastava, A.; Votava, P.; Nemani, R. R.

    2010-12-01

    The NASA Earth Exchange (NEX) is a new collaboration platform for the Earth science community that provides a mechanism for scientific collaboration and knowledge sharing. NEX combines NASA advanced supercomputing resources, Earth system modeling, workflow management, NASA remote sensing data archives, and a collaborative communication platform to deliver a complete work environment in which users can explore and analyze large datasets, run modeling codes, collaborate on new or existing projects, and quickly share results among the Earth science communities. NEX is designed primarily for use by the NASA Earth science community to address scientific grand challenges. The NEX web portal component provides an on-line collaborative environment for sharing of Eearth science models, data, analysis tools and scientific results by researchers. In addition, the NEX portal also serves as a knowledge network that allows researchers to connect and collaborate based on the research they are involved in, specific geographic area of interest, field of study, etc. Features of the NEX web portal include: Member profiles, resource sharing (data sets, algorithms, models, publications), communication tools (commenting, messaging, social tagging), project tools (wikis, blogs) and more. The NEX web portal is built on the proven technologies and policies of DASHlink.arc.nasa.gov, (one of NASA's first science social media websites). The core component of the web portal is a C3 framework, which was built using Django and which is being deployed as a common framework for a number of collaborative sites throughout NASA.

  17. Signal Processing for Fibre-optic Distributed Sensing Techniques Employing Brillouin Scattering

    Institute of Scientific and Technical Information of China (English)

    XIAO Shang-hui; LI Li

    2009-01-01

    As fibre optic distributed scattering sensing systems are providing innovative solutions for the monitoring of large structures, Brillouin-based distributed scattering sensing techniques represent a new physical approach for structures health monitoring, which seems extremely promising and is receiving most attentions. This paper comprehensively presents some methods of signal interrogation for fibre optic Brillouin-based distributed scattering sensing technology, especially establishes an accurate Pseudo-Voigt model of Brillouin gain spectrum and gives some results on spectrum analysis and data processing.

  18. Dark tip-tilt sensing

    CERN Document Server

    Arcidiacono, Carmelo; Viotto, Valentina; Bergomi, Maria; Farinato, Jacopo; Magrin, Demetrio; Dima, Marco; Gullieuszik, Marco; Marafatto, Luca

    2016-01-01

    Dark wavefront sensing in its simplest and more crude form is a quad-cell with a round spot of dark ink acting as occulting disk at the center. This sensor exhibits fainter limiting magnitude than a conventional quad-cell, providing that the size of the occulting disk is slightly smaller than the size of the spot and smaller than the residual jitter movement in closed loop. We present simulations focusing a generic Adaptive Optics system using Natural Guide Stars to provide the tip-tilt signal. We consider a jitter spectrum of the residual correction including amplitudes exceeding the dark disk size.

  19. Collaborative form(s)

    DEFF Research Database (Denmark)

    Gunn, Wendy

    Gunn asks us to consider beauty as collaborative forms of action generated by moving between design by means of anthropology and anthropology by means of design. Specifically, she gives focus to play-like reflexions on practices of designing energy products, systems and infrastructure. Design...

  20. The Promise of Collaboration

    Science.gov (United States)

    Bauml, Michelle

    2016-01-01

    Whether a teacher loves it or dreads it, lesson planning is a crucial step in the teaching process. Done effectively, collaborative lesson planning--in which teachers work together to design lessons--leads to increased professional learning, higher job satisfaction for teachers, and better lesson plans. The process poses challenges for both…

  1. Learning Music from Collaboration

    Science.gov (United States)

    Sawyer, R. Keith

    2008-01-01

    I draw on two traditions of research: the social psychology of collaborative groups, and the ethnographic study of improvisational performance. I outline a general model of group creativity derived from these traditions. I show how the model can be used to better understand musical competence and performance, and I provide recommendations for how…

  2. The RD11 Collaboration

    CERN Multimedia

    CERN Audiovisual Unit

    1993-01-01

    Presentation of the RD11 Collaboration which is specialized in elaborating the second level trigger for the LHC. Also named EAST (Embedded Architectures for Second-level Triggering) in LHC Experiments.With John Strong, Rudy Bock, Werner Krischer, Gennaddi Klioutchnikov, Claudia Bondila, Iosif Legrand and Erwin Denes.

  3. Thematising Intercultural Collaboration

    DEFF Research Database (Denmark)

    Holmgreen, Lise-Lotte; Askehave, Inger

    2013-01-01

    Taking a critical discursive approach (Potter and Wetherell, 1987; Wetherell and Potter, 1988, 1992) to analysing interview data, the article discusses the possible implications of top and middle managers’ constructions of intercultural collaboration for the day-to-day workings of a Danish...

  4. Collaboration in Print

    DEFF Research Database (Denmark)

    Lund, Joachim

    2012-01-01

    During the Second World War, Germany's National Socialist regime mobilized German universities in order to support the war efforts through academic collaboration and a number of publications that were meant to legitimize Germany's territorial ambitions. The rector of the University of Kiel, Dr Paul...

  5. Collaboration Between Multistakeholder Standards

    DEFF Research Database (Denmark)

    Rasche, Andreas; Maclean, Camilla

    responsibility is unlikely to support a great variety of partly competing and overlapping standards. Increased collaboration between these standards would enhance both their impact and their adoption by firms. This report examines the nature, benefits, and shortcomings of existing multistakeholder standards...

  6. Collaborative Movie Annotation

    Science.gov (United States)

    Zad, Damon Daylamani; Agius, Harry

    In this paper, we focus on metadata for self-created movies like those found on YouTube and Google Video, the duration of which are increasing in line with falling upload restrictions. While simple tags may have been sufficient for most purposes for traditionally very short video footage that contains a relatively small amount of semantic content, this is not the case for movies of longer duration which embody more intricate semantics. Creating metadata is a time-consuming process that takes a great deal of individual effort; however, this effort can be greatly reduced by harnessing the power of Web 2.0 communities to create, update and maintain it. Consequently, we consider the annotation of movies within Web 2.0 environments, such that users create and share that metadata collaboratively and propose an architecture for collaborative movie annotation. This architecture arises from the results of an empirical experiment where metadata creation tools, YouTube and an MPEG-7 modelling tool, were used by users to create movie metadata. The next section discusses related work in the areas of collaborative retrieval and tagging. Then, we describe the experiments that were undertaken on a sample of 50 users. Next, the results are presented which provide some insight into how users interact with existing tools and systems for annotating movies. Based on these results, the paper then develops an architecture for collaborative movie annotation.

  7. Team Collaboration Software

    Science.gov (United States)

    Wang, Yeou-Fang; Schrock, Mitchell; Baldwin, John R.; Borden, Charles S.

    2010-01-01

    The Ground Resource Allocation and Planning Environment (GRAPE 1.0) is a Web-based, collaborative team environment based on the Microsoft SharePoint platform, which provides Deep Space Network (DSN) resource planners tools and services for sharing information and performing analysis.

  8. Playful Collaboration (Or Not)

    DEFF Research Database (Denmark)

    Bogers, Marcel; Sproedt, Henrik

    2012-01-01

    This article explores how playing games can be used to teach intangible social interaction across boundaries, in particular within open collaborative innovation. We present an exploratory case study of how students learned from playing a board game in a graduate course of the international...... imply several opportunities and challenges within education and beyond....

  9. Collaboration in Augmented Reality

    NARCIS (Netherlands)

    Lukosch, S.; Billinghurst, M.; Alem, L.; Kiyokawa, K.

    2015-01-01

    Augmented Reality (AR) is a technology that allows users to view and interact in real time with virtual images seamlessly superimposed over the real world. AR systems can be used to create unique collaborative experiences. For example, co-located users can see shared 3D virtual objects that they int

  10. Learning Music from Collaboration

    Science.gov (United States)

    Sawyer, R. Keith

    2008-01-01

    I draw on two traditions of research: the social psychology of collaborative groups, and the ethnographic study of improvisational performance. I outline a general model of group creativity derived from these traditions. I show how the model can be used to better understand musical competence and performance, and I provide recommendations for how…

  11. Collaboration in Augmented Reality

    NARCIS (Netherlands)

    Lukosch, S.; Billinghurst, M.; Alem, L.; Kiyokawa, K.

    2015-01-01

    Augmented Reality (AR) is a technology that allows users to view and interact in real time with virtual images seamlessly superimposed over the real world. AR systems can be used to create unique collaborative experiences. For example, co-located users can see shared 3D virtual objects that they int

  12. Intercultural Collaboration Stories

    DEFF Research Database (Denmark)

    Gertsen, Martine Cardel; Søderberg, Anne-Marie

    2011-01-01

    follows their recognizing new dimensions of their conflicts, eventually furthering their collaboration. We explain how Greimas's actantial model is valuable when mapping differences between and changes in the narrators’ projects, alliances and oppositions in the course of their interaction. Thus, we make...

  13. Driving collaborative improvement processes

    NARCIS (Netherlands)

    Middel, Rick; Gieskes, José; Fisscher, Olaf

    2002-01-01

    Continuous Improvement is a consolidated concept in theory and practice, mainly in the context of stand-alone companies. However, the battlefield of competition is increasingly moving from the level of individual firms to that of organisational settings based on loose company boundaries and collabor

  14. Driving collaborative improvement processes

    NARCIS (Netherlands)

    Middel, R.; Gieskes, J.; Fisscher, O.

    2005-01-01

    Continuous improvement is a consolidated concept in theory and practice, mainly in the context of stand-alone companies. However, the battlefield of competition is increasingly moving from the level of individual firms to that of organizational settings based on loose company boundaries and collabor

  15. Compact Microwave Fourier Spectrum Analyzer

    Science.gov (United States)

    Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry

    2009-01-01

    A compact photonic microwave Fourier spectrum analyzer [a Fourier-transform microwave spectrometer, (FTMWS)] with no moving parts has been proposed for use in remote sensing of weak, natural microwave emissions from the surfaces and atmospheres of planets to enable remote analysis and determination of chemical composition and abundances of critical molecular constituents in space. The instrument is based on a Bessel beam (light modes with non-zero angular momenta) fiber-optic elements. It features low power consumption, low mass, and high resolution, without a need for any cryogenics, beyond what is achievable by the current state-of-the-art in space instruments. The instrument can also be used in a wide-band scatterometer mode in active radar systems.

  16. Predicting the Demand for Spectrum Allocation through Auctions (PREPRINT)

    Science.gov (United States)

    2010-06-01

    part of new approach it is required to predict the customer needs . The customer needs will be predicted using automated collaborative filtering (ACF...the customer history, and bid for resources to meet customer needs . Dynamic spectrum allocation (DSA) using cognitive radios and DSA by auction

  17. Wireless Spectrum Research & Development Senior Steering Group's Testbed Information Portal

    Data.gov (United States)

    Networking and Information Technology Research and Development, Executive Office of the President — This application contains a list of Federal R&D sites that are available for public-private collaborative research efforts in the field of spectrum and wireless...

  18. Preservice Teachers' Learning among Students with Autism Spectrum Disorder

    Science.gov (United States)

    Power, Anne; Costley, Debra

    2014-01-01

    This article reports on a collaborative venture between Autism Spectrum Australia and the University of Western Sydney, New South Wales, Australia. The Social Club network was formed for children and adolescents to provide structured opportunities for positive peer interactions in safe, stimulating and nonjudgmental environments. The Social Clubs…

  19. Precise Determination of the Unperturbed B-8 Neutrino Spectrum

    NARCIS (Netherlands)

    Roger, T.; Buscher, J.; Bastin, B.; Kirsebom, O. S.; Raabe, R.; Alcorta, M.; Aysto, J.; Borge, M. J. G.; Carmona-Gallardo, M.; Cocolios, T. E.; Cruz, J.; Dendooven, P.; Fraile, L. M.; Fynbo, H. O. U.; Galaviz, D.; Gasques, L. R.; Giri, G. S.; Huyse, M.; Hyldegaard, S.; Jungmann, K.; Kruithof, W. L.; Lantz, M.; Perea, A.; Riisager, K.; Saastamoinen, A.; Santra, B.; Shidling, P. D.; Sohani, M.; Sorensen, A. J.; Tengblad, O.; Traykov, E.; van der Hoek, D. J.; Van Duppen, P.; Versolato, O. O.; Wilschut, H. W.

    2012-01-01

    A measurement of the final state distribution of the B-8 beta decay, obtained by implanting a 8B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jy

  20. Collaborations in Open Learning Environments

    NARCIS (Netherlands)

    Spoelstra, Howard

    2015-01-01

    This thesis researches automated services for professionals aiming at starting collaborative learning projects in open learning environments, such as MOOCs. It investigates the theoretical backgrounds of team formation for collaborative learning. Based on the outcomes, a model is developed describin

  1. Collaborations in Open Learning Environments

    NARCIS (Netherlands)

    Spoelstra, Howard

    2015-01-01

    This thesis researches automated services for professionals aiming at starting collaborative learning projects in open learning environments, such as MOOCs. It investigates the theoretical backgrounds of team formation for collaborative learning. Based on the outcomes, a model is developed

  2. Hybrid Collaborative Stereo Vision System for Mobile Robots Formation

    Directory of Open Access Journals (Sweden)

    Flavio Roberti

    2010-02-01

    Full Text Available This paper presents the use of a hybrid collaborative stereo vision system (3D-distributed visual sensing using different kinds of vision cameras for the autonomous navigation of a wheeled robot team. It is proposed a triangulation-based method for the 3D-posture computation of an unknown object by considering the collaborative hybrid stereo vision system, and this way to steer the robot team to a desired position relative to such object while maintaining a desired robot formation. Experimental results with real mobile robots are included to validate the proposed vision system.

  3. Harvesting the electromagnetic spectrum: from communications to renewables

    OpenAIRE

    Gremont, Boris

    2011-01-01

    The talk will give a unified perspective on one of the most precious commodities underpinning the globalised world: the electromagnetic spectrum. In particular, we will describe how electromagnetic waves have been used over the years to create the global village and the modern world as we know it. How waves can be used to help fight global warming will be discussed along with how waves and remote sensing help in saving lives. Finally, how can the electromagnetic spectrum be used to create the...

  4. The Brazilian Research Consortium on Obsessive-Compulsive Spectrum Disorders: recruitment, assessment instruments, methods for the development of multicenter collaborative studies and preliminary results Consórcio Brasileiro de Pesquisa em Transtornos do Espectro Obsessivo-Compulsivo: recrutamento, instrumentos de avaliação, métodos para o desenvolvimento de estudos colaborativos multicêntricos e resultados preliminares

    Directory of Open Access Journals (Sweden)

    Euripedes Constantino Miguel

    2008-09-01

    of 35 years, onset of obsessive-compulsive symptoms at 13 years of age, mild to moderate severity, mostly of symmetry, contamination/cleaning and comorbidity with depressive disorders. The Brazilian Research Consortium on Obsessive-Compulsive Spectrum Disorders has established an important network for standardized collaborative clinical research in obsessive-compulsive disorder and may pave the way to similar projects aimed at integrating other research groups in Brazil and throughout the world.OBJETIVO: Descrever o recrutamento de pacientes, instrumentos de avaliação, métodos para o desenvolvimento de estudos colaborativos multicêntricos e os resultados preliminares do Consórcio Brasileiro de Pesquisa em Transtornos do Espectro Obsessivo-Compulsivo, que inclui sete centros universitários. MÉTODO: Este estudo transversal incluiu entrevistas semi-estruturadas (dados sociodemográficos, histórico médico e psiquiátrico, curso da doença e diagnósticos psiquiátricos comórbidos e instrumentos que avaliam os sintomas do transtorno obsessivo-compulsivo (Escala para Sintomas Obsessivo-Compulsivos de Yale-Brown e Escala Dimensional para Sintomas Obsessivo-Compulsivos de Yale-Brown, sintomas depressivos (Inventário de Depressão de Beck, sintomas ansiosos (Inventário de Ansiedade de Beck, fenômenos sensoriais (Escala de Fenômenos Sensoriais da Universidade de São Paulo, juízo crítico (Escala de Avaliação de Crenças de Brown, tiques (Escala de Gravidade Global de Tiques de Yale e qualidade de vida (questionário genérico de avaliação de qualidade de vida, Medical Outcome Quality of Life Scale Short-form-36 e Escala de Avaliação Social. O treinamento dos avaliadores consistiu em assistir cinco entrevistas filmadas e entrevistar cinco pacientes junto com um pesquisador mais experiente, antes de entrevistar pacientes sozinhos. A confiabilidade entre todos os líderes de grupo para os instrumentos mais importantes (Structured Clinical Interview for DSM

  5. Composition of the ATLAS Collaboration

    CERN Document Server

    Pater, Joleen; The ATLAS collaboration

    2016-01-01

    The ATLAS collaboration consists of about 5,000 members from 178 institutes in 38 countries. About half of the members of the collaboration are scientific authors of the papers, and there are about 1,200 students in the collaboration. This note presents data showing aspects of the composition of the collaboration; in particular the relative fraction of women is described at several levels within the hierarchy of the ATLAS experiment.

  6. Social Software Engineering Development and Collaboration with Social Networking

    CERN Document Server

    Keyes, Jessica

    2011-01-01

    Although the precepts of software engineering have been around for decades, the field has failed to keep pace with rapid advancements in computer hardware and software. Modern systems that integrate multiple platforms and architectures, along with the collaborative nature of users who expect an instantaneous global reach via the Internet, require updated software engineering methods. Social Software Engineering: Development and Collaboration with Social Networking examines the field through the spectrum of the social activities that now compose it. Supplying an up-to-date look at this ever-evo

  7. International Scientific Collaboration of China: Collaborating Countries, Institutions and Individuals

    CERN Document Server

    Wang, Xianwen; Wang, Zhi; Peng, Lian; Wang, Chuanli

    2014-01-01

    Using bibliometric methods, we investigate China's international scientific collaboration from 3 levels of collaborating countries, institutions and individuals. We design a database in SQL Server, and make analysis of Chinese SCI papers based on the corresponding author field. We find that China's international scientific collaboration is focused on a handful of countries. Nearly 95% international co-authored papers are collaborated with only 20 countries, among which the USA account for more than 40% of all. Results also show that Chinese lineage in the international co-authorship is obvious, which means Chinese immigrant scientists are playing an important role in China's international scientific collaboration, especially in English-speaking countries.

  8. Security for ICT collaboration tools

    NARCIS (Netherlands)

    Broenink, E.G.; Kleinhuis, G.; Fransen, F.

    2011-01-01

    In order for collaboration tools to be productive in an operational setting, an information base that is shared across the collaborating parties is needed. Therefore, a lot of research is done for tooling to create such a common information base in a collaboration tool. However, security is often no

  9. Developing and Evaluating Collaborative Technologies

    Science.gov (United States)

    2005-11-01

    undertaking. This paper considers the topic of assessing collaborative technologies in the context of military logistics . A historical view of collaborative...research in military logistics is provided, as well as a discussion of current research aimed at developing a framework for assessing collaborative technologies.

  10. International collaborations through the internet

    DEFF Research Database (Denmark)

    Olson, Gary M.; David, Paul A.; Eksteen, Johan

    2007-01-01

    The past decade has seen remarkable advances in the availability of tools to support scientific collaboration at a distance. This is especially good news for international collaborations, where in the past constraints on collocation and travel have made such collaborations a major challenge. The ...

  11. Regulating Collaboration in Teacher Education

    Science.gov (United States)

    Dobber, Marjolein; Akkerman, Sanne F.; Verloop, Nico; Vermunt, Jan D.

    2014-01-01

    Collaboration in teacher education can be seen as a way to prepare student teachers for future social practices at school. When people collaborate with each other, they have to regulate their collaboration. In the Dutch teacher education programme that was investigated, student teachers were members of different types of groups, each of which had…

  12. Realities of Supply Chain Collaboration

    NARCIS (Netherlands)

    Kampstra, R.P.; Ashayeri, J.; Gattorna, J.

    2006-01-01

    Successful supply chain collaboration (SCC) practices are rather exceptional, yet collaboration is believed to be the single most pressing need in supply chain management.In this paper we discuss the realities of SCC, present prerequisites for the collaboration process, indicate where the process

  13. Security for ICT collaboration tools

    NARCIS (Netherlands)

    Broenink, E.G.; Kleinhuis, G.; Fransen, F.

    2010-01-01

    In order for collaboration tools to be productive in an operational setting, an information base that is shared across the collaborating parties is needed. Therefore, a lot of research is done for tooling to create such a common information base in a collaboration tool. However, security is often

  14. Task modeling for collaborative authoring

    NARCIS (Netherlands)

    Veer, van der Gerrit; Kulyk, Olga; Vyas, Dhaval; Kubbe, Onno; Ebert, Achim; Dittmar, A.; Forbrig, P.

    2011-01-01

    Motivation –Task analysis for designing modern collaborative work needs a more fine grained approach. Especially in a complex task domain, like collaborative scientific authoring, when there is a single overall goal that can only be accomplished only by collaboration between multiple roles, each req

  15. Collaboration in scientific practice

    DEFF Research Database (Denmark)

    Wagenknecht, Susann

    2014-01-01

    This monograph investigates the collaborative creation of scientific knowledge in research groups. To do so, I combine philosophical analysis with a first-hand comparative case study of two research groups in experimental science. Qualitative data are gained through observation and interviews......, and I combine empirical insights with existing approaches to knowledge creation in philosophy of science and social epistemology. On the basis of my empirically-grounded analysis I make several conceptual contributions. I study scientific collaboration as the interaction of scientists within research...... groups. Thereby, I argue that research groups and their role in scientific practice deserve more philosophical attention than they have hitherto received. In contemporary natural science, research groups are key to the formulation and corroboration of scientific knowledge claims prior...

  16. Collaborative Tax Regulation

    DEFF Research Database (Denmark)

    Boll, Karen

    2016-01-01

    their customer bases decline to commercially non-viable levels. The analysis is framed by public governance literature and argues that the regulation is an example of collaborative or interactive governance, because the tax administrators do not regulate non-compliance directly, but activate external...... stakeholders, i.e. the consumers, in the regulatory craft. The study is based on a qualitative methodology and draws on a unique case of regulation in the cleaning sector. This sector is at high risk of tax evasion and human exploitation of vulnerable workers operating in the informal economy. The article has...... implications for how tax practitioners think about collaborative and interactive regulatory initiatives. While the tax administration in the study sees the approach as effective, the analysis shows that there are a number of caveats in relation to regularity, public listing, costs and revenue focus...

  17. Collaborative Knowledge Production

    DEFF Research Database (Denmark)

    Olesen, Birgitte Ravn

    2014-01-01

    In this article, the author reflects on the conditions for working with collaborative research in current academic settings. On the basis of reflections on goals, challenges and results of earlier projects, the author looks into how economic and political shifts and transformations in work have...... changed the conditions for shared knowledge production with the institutionalization of neo-liberal discourse of the knowledge economy as managerial regimes. She questions if context-specific enactments of the discourse of participation can be handled, when neoliberal managerial regimes guide research...... activities and other working practices and the identities of academics and other professionals who are inscribed as subjects in these regimes. The conclusion is, that we have to look for cracks in the wall and insist on collaborative research because it is it the process of “being in relation that forms...

  18. Collaborative Tax Regulation

    DEFF Research Database (Denmark)

    Boll, Karen

    2016-01-01

    This article shows a new form of regulation within a tax administration where tax administrators abate tax evasion by nudging and motivating consumers to only purchase services from tax compliant businesses. This indirectly closes or forces tax evading businesses to change their practices, because...... their customer bases decline to commercially non-viable levels. The analysis is framed by public governance literature and argues that the regulation is an example of collaborative or interactive governance, because the tax administrators do not regulate non-compliance directly, but activate external...... implications for how tax practitioners think about collaborative and interactive regulatory initiatives. While the tax administration in the study sees the approach as effective, the analysis shows that there are a number of caveats in relation to regularity, public listing, costs and revenue focus...

  19. The Collaborative Heliophysics Observatory

    Science.gov (United States)

    Hurlburt, N.; Freeland, S.; Cheung, M.; Bose, P.

    2007-12-01

    The Collaborative Heliophysics Observatory (CHO) would provide a robust framework and enabling tools to fully utilize the VOs for scientific discovery and collaboration. Scientists across the realm of heliophysics would be able to create, use and share applications -- either as services using familiar tools or through intuitive workflows -- that orchestrate access to data across all virtual observatories. These applications can be shared freely knowing that proper recognition of data and processing components are acknowledged; that erroneous use of data is flagged; and that results from the analysis runs will in themselves be shared Ð all in a transparent and automatic fashion. In addition, the CHO would incorporate cross-VO models and tools to weave the various virtual observatories into a unified system. These provide starting points for interactions across the solar/heliospheric and heliospheric/magnetospheric boundaries.

  20. The Collaborative Economy

    DEFF Research Database (Denmark)

    Avital, Michel; Andersson, Magnus; Nickerson, Jeffrey

    2014-01-01

    An economy based on the exchange of capital, assets and services between individuals has grown significantly, spurred by proliferation of internet-based platforms that allow people to share underutilized resources and trade with reasonably low transaction costs. The movement toward this economy...... of “sharing” translates into market efficiencies that bear new products, reframe established services, have positive environmental effects, and may generate overall economic growth. This emerging paradigm, entitled the collaborative economy, is disruptive to the conventional company-driven economic paradigm...... as evidenced by the large number of peer-to-peer based services that have captured impressive market shares sectors ranging from transportation and hospitality to banking and risk capital. The panel explores economic, social, and technological implications of the collaborative economy, how digital technologies...

  1. Spatial Diversity Aware Data Fusion for Cooperative Spectrum Sensing

    DEFF Research Database (Denmark)

    Kiilerich Pratas, Nuno; Prasad, Neeli R.; Rodrigues, António;

    2012-01-01

    similar signal conditions are grouped by the fusion center in clusters and where the data fusion is then done separately at each cluster. The proposed algorithm uses the correlation between the binary decisions of the local detectors over an observation window to select the cluster where each local...... detector should go. It was observed that in the case where there is only one signal source, that the proposed algorithm is able to achieve the same level of performance when compared to the perfect clustering algorithm where full information about the signal conditions at each local detector is available....

  2. Compressive spectrum sensing of radar pulses based on photonic techniques.

    Science.gov (United States)

    Guo, Qiang; Liang, Yunhua; Chen, Minghua; Chen, Hongwei; Xie, Shizhong

    2015-02-23

    We present a photonic-assisted compressive sampling (CS) system which can acquire about 10(6) radar pulses per second spanning from 500 MHz to 5 GHz with a 520-MHz analog-to-digital converter (ADC). A rectangular pulse, a linear frequency modulated (LFM) pulse and a pulse stream is respectively reconstructed faithfully through this system with a sliding window-based recovery algorithm, demonstrating the feasibility of the proposed photonic-assisted CS system in spectral estimation for radar pulses.

  3. Diversity Techniques for Spectrum Sensing in Fading Environments (POSTPRINT)

    Science.gov (United States)

    2010-06-01

    Technical Library. Downloaded on June 24,2010 at 18:41:16 UTC from IEEE Xplore . Restrictions apply. DIVERSI 1 (3) show that most of the performance... IEEE Xplore . Restrictions apply. 2 For ease of notation, in the following we will drop the dependence of the decision statistic on the sample data...18:41:16 UTC from IEEE Xplore . Restrictions apply. 3 expansion. The argument of the Q-function in (13) can be rewritten as: ~ Rayleigh -Analysis

  4. ADAPTIVE COUNTING RULE FOR COOPERATIVE SPECTRUM SENSING UNDER CORRELATED ENVIRONMENTS

    DEFF Research Database (Denmark)

    Pratas, Nuno; Marchetti, Nicola; Prasad, Neeli R.;

    2010-01-01

    counting rule to perform the data fusion. The proposed scheme is evaluated against other common counting rules (e.g. 1-out-of-n and n-out-of-n) and the optimum counting rule, under different correlation conditions. The impact of correlation on the performance of the data fusion schemes, based on counting...

  5. Making Collaborative Innovation Accountable

    DEFF Research Database (Denmark)

    Sørensen, Eva

    The public sector is increasingly expected to be innovative, but the prize for a more innovative public sector might be that it becomes difficult to hold public authorities to account for their actions. The article explores the tensions between innovative and accountable governance, describes...... the foundation for these tensions in different accountability models, and suggest directions to take in analyzing the accountability of collaborative innovation processes....

  6. Collaborative Robotics Design Considerations

    Science.gov (United States)

    2004-05-06

    in Multirobot Systems," IEEE Transactions on Robotics and Automation, Vol. 18, No. 5, October 2002 [3] Batavia, P., "A Survey of Collaborative... Transactions on Robotics and Automation, Vol. 18, No.5, Oct. 2002, pp 781-795. [21]Scholtz, J.C., "Human-Robot Interactions: Creating Synergistic Cyber...Parker, L.E, eds., Kluwer Academic Publishers, 2002, pp 185-193. [20] Roumeliotis, S., Bekey, G.A., "Distributed Multirobot Localization," IEEE

  7. Collaborative Public Management and Collaborative Governance: Conceptual Similarities and Differences

    Directory of Open Access Journals (Sweden)

    Naim Kapucu

    2009-05-01

    Full Text Available There has been considerable interest among Public Administration scholars in collaborative public management and governance. However, there is a need for conceptual analysis of the two terms which share common aspects and differ essentially in scope and substance. We found that collaborative public management has a more local approach and focuses on the substance of collaboration practiced to solve societal problems and reach community goals at the organizational level. On the other hand, widely researched in management, political science, and public administration disciplines, collaborative governance has a global scope and focuses on both substance and process of collaboration in effectively solving societal problems with improved structures of nonhierarchical and decentralized institutions and mechanisms of citizen participation both through partnership projects and e-governance tools. The paper contributes to the better understanding of collaborative public management and collaborative governance with implications for both future research and practice.

  8. Cross-Cultural Collaboration - With Integrity

    Science.gov (United States)

    Maryboy, N. C.

    2015-12-01

    Cross-Cultural Collaboration - with Integrity This poster will show the value of cross-cultural collaboration, between scientific institutions and Indigenous ways of knowing, as practiced by the Indigenous Education Institute. Focus is on respect for diverse worldviews, integrity as process, and academic diversity and equity. Today, as never before, traditional ecological knowledge (TEK) is of vital importance as it speaks strongly to the significance of balance to create a healthy environment. Utilizing a lens of contemporary scientific perspective along with a traditional Indigenous perspective illuminates the complementary aspects of both ways of knowing and a greater sense of understanding the earth and sky than would be possible with one perspective alone. The poster will highlight several examples of successful cross-cultural collaborations. *Collaborative partnership with University of Washington, Tacoma, Symposium on Contemporary Native American Issues in Higher Education: Intersectionality of Native Language and Culture in Modern Society (Sharing Our Skies - Looking at the Stars Through Indigenous Eyes and Western Astronomy Lenses) *AST 201, Introduction to Indigenous Astronomy, Department of Physics and Astronomy, Northern Arizona University: a course that fulfills the Diversity Requirement for graduation *Native Universe: a National Science Foundation funded project, which honors Indigenous Voice in science museums to deepen our relationship with nature, vital in this time of climate change *MAVEN - Imagine Mars Through Indigenous Eyes: a NASA funded project which provides middle and high school curriculum delivered in science centers and Indigenous schools *Navajo Sky: modules and shows for planetariums, funded by NASA, that juxtapose Navajo and western astronomy concepts and context, highlighting place-based science

  9. Autism Spectrum Disorder (ASD)

    Science.gov (United States)

    ... Español (Spanish) Recommend on Facebook Tweet Share Compartir Autism spectrum disorder (ASD) is a developmental disability that can cause ... factors that may put children at risk for autism spectrum disorder (ASD) and other developmental disabilities. More E-mail ...

  10. The CMBR spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Stebbins, A.

    1997-05-01

    Here we give an introduction to the observed spectrum of the Cosmic Microwave Background Radiation (CMBR) and discuss what can be learned about it. Particular attention will be given to how Compton scattering can distort the spectrum of the CMBR. An incomplete bibliography of relevant papers is also provided.

  11. 5G Spectrum Sharing

    OpenAIRE

    Nekovee, Maziar; Rudd, Richard

    2017-01-01

    In this paper an overview is given of the current status of 5G industry standards, spectrum allocation and use cases, followed by initial investigations of new opportunities for spectrum sharing in 5G using cognitive radio techniques, considering both licensed and unlicensed scenarios. A particular attention is given to sharing millimeter-wave frequencies, which are of prominent importance for 5G.

  12. Fetal Alcohol Spectrum Disorder

    Science.gov (United States)

    Caley, Linda M.; Kramer, Charlotte; Robinson, Luther K.

    2005-01-01

    Fetal alcohol spectrum disorder (FASD) is a serious and widespread problem in this country. Positioned within the community with links to children, families, and healthcare systems, school nurses are a critical element in the prevention and treatment of those affected by fetal alcohol spectrum disorder. Although most school nurses are familiar…

  13. Collaborative exams: Cheating? Or learning?

    Science.gov (United States)

    Jang, Hyewon; Lasry, Nathaniel; Miller, Kelly; Mazur, Eric

    2017-03-01

    Virtually all human activity involves collaboration, and yet, collaboration during an examination is typically considered cheating. Collaborative assessments have not been widely adopted because of the perceived lack of individual accountability and the notion that collaboration during assessments simply causes propagation of correct answers. Hence, collaboration could help weaker students without providing much benefit to stronger students. In this paper, we examine student performance in open-ended, two-stage collaborative assessments comprised of an individually accountable round followed by an automatically scored, collaborative round. We show that collaboration entails more than just propagation of correct answers. We find greater rates of correct answers after collaboration for all students, including the strongest members of a team. We also find that half of teams that begin without a correct answer to propagate still obtain the correct answer in the collaborative round. Our findings, combined with the convenience of automatic feedback and grading of open-ended questions, provide a strong argument for adopting collaborative assessments as an integral part of education.

  14. Wave Reflection Coefficient Spectrum

    Institute of Scientific and Technical Information of China (English)

    俞聿修; 邵利民; 柳淑学

    2003-01-01

    The wave reflection coefficient frequency spectrum and directional spectrum for concrete face slope breakwaters and rubble mound breakwaters are investigated through physical model tests in the present study. The reflection coefficients of oblique irregular waves are analyzed by the Modified Two-Point Method (MTPM) proposed by the authors. The results show that the wave reflection coefficient decreases with increasing wave frequency and incident angle or decreasing structure slope. The reflection coefficient frequency spectrum and its variation with Iribarren number are given in this paper. The paper also suggests an empirical 3-dimensional reflection coefficient spectrum, i.e. reflection coefficient directional spectrum, which can be used to illustrate quantitatively the variation of reflection coefficient with the incident angle and the Iribarren number for oblique irregular waves.

  15. Strategies for improvement of spectrum capacity for WiMax cellular systems by Cognitive Radio Technology supported by Relay Stations

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to improve the wireless transmission by orthogonal OFDM-based communication and to increase the c...

  16. Strategies for improvement of spectrum capacity for WiMax cellular systems by Cognitive Radio Technology supported by Relay Stations

    DEFF Research Database (Denmark)

    Frederiksen, Flemming Bjerge; Prasad, Ramjee

    2007-01-01

    Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context will be presented and discussed in this paper. Ideas to improve the wireless transmission by orthogonal OFDM-based communication and to increase...

  17. Remote Sensing Information Science Research

    Science.gov (United States)

    Clarke, Keith C.; Scepan, Joseph; Hemphill, Jeffrey; Herold, Martin; Husak, Gregory; Kline, Karen; Knight, Kevin

    2002-01-01

    This document is the final report summarizing research conducted by the Remote Sensing Research Unit, Department of Geography, University of California, Santa Barbara under National Aeronautics and Space Administration Research Grant NAG5-10457. This document describes work performed during the period of 1 March 2001 thorough 30 September 2002. This report includes a survey of research proposed and performed within RSRU and the UCSB Geography Department during the past 25 years. A broad suite of RSRU research conducted under NAG5-10457 is also described under themes of Applied Research Activities and Information Science Research. This research includes: 1. NASA ESA Research Grant Performance Metrics Reporting. 2. Global Data Set Thematic Accuracy Analysis. 3. ISCGM/Global Map Project Support. 4. Cooperative International Activities. 5. User Model Study of Global Environmental Data Sets. 6. Global Spatial Data Infrastructure. 7. CIESIN Collaboration. 8. On the Value of Coordinating Landsat Operations. 10. The California Marine Protected Areas Database: Compilation and Accuracy Issues. 11. Assessing Landslide Hazard Over a 130-Year Period for La Conchita, California Remote Sensing and Spatial Metrics for Applied Urban Area Analysis, including: (1) IKONOS Data Processing for Urban Analysis. (2) Image Segmentation and Object Oriented Classification. (3) Spectral Properties of Urban Materials. (4) Spatial Scale in Urban Mapping. (5) Variable Scale Spatial and Temporal Urban Growth Signatures. (6) Interpretation and Verification of SLEUTH Modeling Results. (7) Spatial Land Cover Pattern Analysis for Representing Urban Land Use and Socioeconomic Structures. 12. Colorado River Flood Plain Remote Sensing Study Support. 13. African Rainfall Modeling and Assessment. 14. Remote Sensing and GIS Integration.

  18. Premorbid neurocognitive functioning in schizophrenia spectrum disorder

    DEFF Research Database (Denmark)

    Sørensen, Holger J; Mortensen, Erik L; Parnas, Josef;

    2006-01-01

    A prospective study based on the U.S. National Collaborative Perinatal Project and using the Wechsler Intelligence Scale for Children (WISC) found lower test scores for the Coding subtest in preschizophrenic children than in their unaffected siblings. Using data on cognitive functioning...... in adolescence, the aim of the present prospective study was to examine whether low scores on Coding is associated with the risk of developing schizophrenia spectrum disorders. The 12 subtests of the WISC were administered to 311 children and adolescents with a mean age of 15.1 years (range: 8 to 20 years...... in WISC IQ. Logistic regression analysis controlling for age at examination, gender, and social status yielded a significant, but relatively weak, association between low Coding test score and risk of schizophrenia spectrum disorder. For each unit increase in the Coding raw score, the adjusted odds ratio...

  19. Maximizing the utility of radio spectrum: Broadband spectrum measurements and occupancy model for use by cognitive radio

    Science.gov (United States)

    Petrin, Allen J.

    Radio spectrum is a vital national asset; proper management of this finite resource is essential to the operation and development of telecommunications, radio-navigation, radio astronomy, and passive remote sensing services. To maximize the utility of the radio spectrum, knowledge of its current usage is beneficial. As a result, several spectrum studies have been conducted in urban Atlanta, suburban Atlanta, and rural North Carolina. These studies improve upon past spectrum studies by resolving spectrum usage by nearly all its possible parameters: frequency, time, polarization, azimuth, and location type. The continuous frequency range from 400MHz to 7.2 GHz was measured with a custom-designed system. More than 8 billion spectrum measurements were taken over several months of observation. A multi-parameter spectrum usage detection method was developed and analyzed with data from the spectrum studies. This method was designed to exploit all the characteristics of spectral information that was available from the spectrum studies. Analysis of the spectrum studies showed significant levels of underuse. The level of spectrum usage in time and azimuthal space was determined to be only 6.5 % for the urban Atlanta, 5.3 % for suburban Atlanta, and 0.8 % for the rural North Carolina spectrum studies. Most of the frequencies measured never experienced usage. Interference was detected in several protected radio astronomy and sensitive radio navigation bands. A cognitive radio network architecture to share spectrum with fixed microwave systems was developed. The architecture uses a broker-based sharing method to control spectrum access and investigate interference issues.

  20. Towards a Design Theory for Collaborative Qualitative Data Analysis

    DEFF Research Database (Denmark)

    Nielsen, Peter Axel

    2016-01-01

    This position paper addresses how to develop a design theory to support the collaborative practice of qualitative data analysis. Qualitative researchers face several challenges in making sense of their empirical data and IS-support for this practice can be found in software applications such as N....... We use this as a stepping stone to discuss how to use a design theory to problematize existing applications and how to extend a design theory by abduction....