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Sample records for asynchronous cdma systems

  1. A Novel Multiuser Detector for Asynchronous CDMA System

    Institute of Scientific and Technical Information of China (English)

    LIANGXint; SHANGYong; LIANGQinglin; XIANGHaige

    2004-01-01

    The decorrelating and the MMSE (Minimum mean square error) multiuser detector for asynchronous CDMA (Code devision multiple access) system are ideally anticausal infinite memory-length detectors. Asa result~ in practice they have to be approximately implemented with finite-memory structure, and the process delay in detection is unavoidable. Based on the analysis of a new signal model for asynchronous system, a novel multiuser detector for asynchronous CDMA system is proposed in this paper~ which is termed as DF-IC-MMSE (Decision ,feedback interference cancellation-MMSE) detector. It's the detection statistics that makes the DF-IC-MMSE-detector basically different from other traditional ones. The DF-IC-MMSE detector can be ideally implemented with Causal finite memory-length structure, and cause no delay in symbol detection. Simulations show that the performance of DF-IC-MMSE detector is almost identical to that of the ideal MMSE detector.

  2. AN IMPROVED DOA ESTIMATION ALGORITHM FOR ASYNCHRONOUS MULTIPATH CDMA SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Yang Wei; Chen Junshi; Tan Zhenhui; Takis Mathiopoulos

    2006-01-01

    This paper proposes an improved Direction Of Arrival(DOA) estimation algorithm for asynchronous multipath Code Division Multiple Access(CDMA) system. The algorithm is based on the correlation matrices of outputs of decorrelator, which is a Multi-User Detection(MUD) approach, one of the key techniques for CDMA system. Through decorrelating processing, the desired user's mulipath signals can be resolved and all the other resolved multipath signal interference is eliminated. So the proposed algorithm is expected to perform much better than algorithm such as that based directly on the Matched Filter(MF) bank outputs. Simulation results confirm this. While the improved algorithm performs better and better as Signal-to-Noise Ratio(SNR)increases, the performance of algorithm based directly on the MF bank outputs can not be improved.

  3. Computationally Efficient Blind Code Synchronization for Asynchronous DS-CDMA Systems with Adaptive Antenna Arrays

    Directory of Open Access Journals (Sweden)

    Chia-Chang Hu

    2005-04-01

    Full Text Available A novel space-time adaptive near-far robust code-synchronization array detector for asynchronous DS-CDMA systems is developed in this paper. There are the same basic requirements that are needed by the conventional matched filter of an asynchronous DS-CDMA system. For the real-time applicability, a computationally efficient architecture of the proposed detector is developed that is based on the concept of the multistage Wiener filter (MWF of Goldstein and Reed. This multistage technique results in a self-synchronizing detection criterion that requires no inversion or eigendecomposition of a covariance matrix. As a consequence, this detector achieves a complexity that is only a linear function of the size of antenna array (J, the rank of the MWF (M, the system processing gain (N, and the number of samples in a chip interval (S, that is, 𝒪(JMNS. The complexity of the equivalent detector based on the minimum mean-squared error (MMSE or the subspace-based eigenstructure analysis is a function of 𝒪((JNS3. Moreover, this multistage scheme provides a rapid adaptive convergence under limited observation-data support. Simulations are conducted to evaluate the performance and convergence behavior of the proposed detector with the size of the J-element antenna array, the amount of the L-sample support, and the rank of the M-stage MWF. The performance advantage of the proposed detector over other DS-CDMA detectors is investigated as well.

  4. Iterative Multiuser Receiver Based on Factor Graph for Asynchronous Coded CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Factor graph, so named because it graphically represents function factorization, with which and its sum-product algorithm the iterative algorithm can be derived clearly. An iterative multiuser receiver based on factor graph for asynchronous coded CDMA system is proposed. In this paper, the a posteriori probability of users information bits conditioned on the noise-whitening filters output is represented by factor graphs, after numbers of iterations with the sum-product algorithm the information bits are estimated. The authors also propose a reduced complexity algorithm. Simulation results show that with this proposed receiver, near-single-user performance can be achieved, and small performance degradation for the reduced complexity algorithm with significant complexity reduction.

  5. A Particle Filter of Blind Equalization and Multiuser Detection in Asynchronous DS/CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jing; DONG Jian-ping; ZHANG Qian

    2008-01-01

    The particle filter (PF) is proposed to be the asynchronous direct-sequence eude-division multiple-access (DS/CDMA) multiuser detector without knowing the channel state information. The PF performs symbol detection according to the joint posterior density probability of simulated particles including relative delays, fading gains and symbols via sequential importance sample and resample. A simplified scheme is also proposed by separating the independent relative delays and fading with symbols. These parameters are modeled as the extended aggressive processes and estimated by the Kalman fdter, so as to provide their arbitrary importance distribution for symbol detection. Simulation results show that the bit error rate of the PF is less than convntional detectors.Moreover, the complexity of PF is moderate comaparable to other nonlinear suboptimal approaches.

  6. Asynchronous Free-Space Optical CDMA Communications System for Last-mile Access Network

    DEFF Research Database (Denmark)

    Jurado-Navas, Antonio; Raddo, Thiago R.; Sanches, Anderson L.;

    2016-01-01

    We propose a new hybrid asynchronous OCDMA-FSO communications system for access network solutions. New ABER expressions are derived under gamma-gamma scintillation channels, where all users can surprisingly achieve error-free transmissions when FEC is employed.......We propose a new hybrid asynchronous OCDMA-FSO communications system for access network solutions. New ABER expressions are derived under gamma-gamma scintillation channels, where all users can surprisingly achieve error-free transmissions when FEC is employed....

  7. Optimum Multiuser Detector for Multipath Slow Fading Asynchronous CDMA Channels

    Institute of Scientific and Technical Information of China (English)

    WangZhaocheng; YangZhixing; 等

    1995-01-01

    A structure of optimum multiuser detector for asynchronous CDMA in multipath slow fading channels is derived and the significant performance gain over the conventional RAKE receiv-er is shown by simulation.

  8. CDMA systems capacity engineering

    CERN Document Server

    Kim, Kiseon

    2004-01-01

    This new hands-on resource tackles capacity planning and engineering issues that are crucial to optimizing wireless communication systems performance. Going beyond the system physical level and investigating CDMA system capacity at the service level, this volume is the single-source for engineering and analyzing systems capacity and resources.

  9. A NOVEL ONE—SHOT DECORRELATOR IN CDMA SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    DuZheng; ZhuJinkang

    2002-01-01

    A novel one-shot decorrelator for asynchronous CDMA systems is developed.Com-pared with existing one-shot decorrelator, it can reduce complexity and has better performance while eliminating all MAI.This decorrelator is shown to be near-far resistant in both AWGN and fading channel.

  10. A NOVEL ONE-SHOT DECORRELATOR IN CDMA SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Du Zheng; Zhu Jinkang

    2002-01-01

    A novel one-shot decorrelator for asynchronous CDMA systems is developed. Compared with existing one-shot decorrelator, it can reduce complexity and has better performance while eliminating all MAI. This decorrelator is shown to be near-far resistant in both AWGN and fading channel.

  11. MACROSCOPIC DIVERSITY FOR CDMA MOBILE SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Pei Xiaoyan; Hu Jiandong

    2002-01-01

    A novel system of macroscopic diversity with voting rule in CDMA cellular system is suggested in order to raise the coverage and quality of service of CDMA mobile communication system. The estimation of the impact of macroscopic diversity on performance of CDMA cellular system is analyzed and investigated.

  12. Compositional asynchronous membrane systems

    Institute of Scientific and Technical Information of China (English)

    Cosmin Bonchis; Cornel Izbasa; Gabriel Ciobanu

    2007-01-01

    This paper presents an algorithmic way of building complex membrane systems by coupling elementary membranes. Its application seems particularly valuable in the case of asynchronous membrane systems, since the resulting membrane system remains asynchronous. The composition method is based on a handshake mechanism implemented by using antiport rules and promoters.

  13. OV-CDMA System: Concept and Implementation

    Directory of Open Access Journals (Sweden)

    Inaty Elie

    2008-01-01

    Full Text Available A new method is proposed to achieve a multirate overlapped code division multiple access system (OV-CDMA based on a novel code overlapping procedure. The signal-to-interference ratio (SIR performance has been investigated for such system. A channel model that allows multirate overlapped transmission is presented based on which a closed form solution for the SIR has been derived. In addition, a simple yet very efficient block diagram of the transmitter and the receiver architecture has been proposed for such a system. Based on the proposed block diagram, the encoder-decoder has been implemented using an FPGA. Numerical results show that the newly proposed OV-CDMA scheme outperforms the classical variable processing gain fast frequency hopping CDMA (VPG-FFH-CDMA for different system scenarios. Finally, real-time measurements have been successfully obtained using a hardware prototype utilizing the simple Xilinx Spartan IIE (XC2S200E FPGA.

  14. OV-CDMA System: Concept and Implementation

    Directory of Open Access Journals (Sweden)

    Rafic Ayoubi

    2008-04-01

    Full Text Available A new method is proposed to achieve a multirate overlapped code division multiple access system (OV-CDMA based on a novel code overlapping procedure. The signal-to-interference ratio (SIR performance has been investigated for such system. A channel model that allows multirate overlapped transmission is presented based on which a closed form solution for the SIR has been derived. In addition, a simple yet very efficient block diagram of the transmitter and the receiver architecture has been proposed for such a system. Based on the proposed block diagram, the encoder-decoder has been implemented using an FPGA. Numerical results show that the newly proposed OV-CDMA scheme outperforms the classical variable processing gain fast frequency hopping CDMA (VPG-FFH-CDMA for different system scenarios. Finally, real-time measurements have been successfully obtained using a hardware prototype utilizing the simple Xilinx Spartan IIE (XC2S200E FPGA.

  15. A MATCHED FILTER BANK BASED DOA ESTIMATION FOR ASYNCHRONOUS MULTIPATH CDMA CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Yang Wei; Chen Junshi; Tan Zhenhui; Takis Mathiopoulos

    2005-01-01

    In this paper, a Direction Of Arrival (DOA) estimation algorithm is proposed for multiuser signals through uplink asynchronous multipath Code Division Multiple Access (CDMA)channels. The algorithm is based directly on the correlation matrices of matched filter bank outputs of desired user's multipath signals and it does not require that the elements of base station antenna array outnumber the multipath signals, which is necessary for the conventional sub-space based direction-finding algorithm. Simulation results show that the proposed algorithm estimates the DOA of multipath signals effectively and acceptably. The proposed algorithm has the prominent advantages of low complexity, simpleness and practicality, which make it much more suitable for practical application.

  16. Comparison between MC-CDMA and CDMA-OFDM/OQAM systems in presence of MIMO channel

    Directory of Open Access Journals (Sweden)

    Radhia Gharsallah

    2012-07-01

    Full Text Available In this paper, we present a comparison between MC-CDMA and CDMA-OFDM/OQAM systems in the case of MIMO channel. The advanced Multi Carrier CDMA OFDM/OQAM modulation is a combination of CDMA and OFDM/OQAM. This combination takes advantages from multicarrier modulation and spread spectrum. Indeed, the use of OFDM has proved its ability to fight against frequency selective channels but the insertion of guard interval yields spectral efficiency loss and sensitivity to frequency dispersion due to the use of rectangular pulse shape. Thus, cyclic prefix OFDM is replaced by an advanced #64257;lterbank-based multicarrier system OFDM/OQAM that operates without guard interval. However, OFDM/OQAM provides orthogonality only on the real domain, so transmitted symbols must be real valued. In the other hand, the CDMA component has two advantages: multiple access interference cancellation and providing orthogonality in the complex domain. From the orthogonality property provided, the Alamouti ST code can be combined with MC-CDMA-OQAM system in order to exploit space and time diversity. Numerical results show the utility of this new wireless communication system MIMO-CDMA-OFDM/OQAM in comparison with MIMO-MC-CDMA system

  17. Redundant Asynchronous Microprocessor System

    Science.gov (United States)

    Meyer, G.; Johnston, J. O.; Dunn, W. R.

    1985-01-01

    Fault-tolerant computer structure called RAMPS (for redundant asynchronous microprocessor system) has simplicity of static redundancy but offers intermittent-fault handling ability of complex, dynamically redundant systems. New structure useful wherever several microprocessors are employed for control - in aircraft, industrial processes, robotics, and automatic machining, for example.

  18. Strategies for Dense Optical CDMA Communication Systems

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-bao; LIN Jin-tong

    2005-01-01

    In this paper,we have formulated a strategy that the limited available code sequences in pure Direct-Sequence(DS)or Frequency-Hopping(FH)system can be reused to realize dense optical CDMA:the strategy of novel hybrid DS/FH system.In which,the case that there are n users employing the same FH pattern but different DS code patterns is considered.On the condition that the impact of channel noises is neglected,the upper bound probability of error is evaluated based on the stationary random process theory.The results show that the hybrid system is suitable for Dense Optical CDMA(DOCDMA)communication.Moreover,the problems such as the link-impairment,dispersion of group velocity,etc.in the pure(DS or FH)system can be solved effectively.

  19. Diversity Analysis in CDMA Based Broadband Wireless System

    Directory of Open Access Journals (Sweden)

    M. Hemalatha

    2012-03-01

    Full Text Available This proposed study exploits transmit and receive diversity to mitigate multipath propagation and interference in CDMA system which is characterized by multipath interference. Code Division Multiple Access (CDMA is the vital technology for modern wireless communication systems to share the available finite amount of radio bandwidth expeditiously. The CDMA system has soft capacity which polishes off the problem of limitation on the number of users in a system. In this paper the simulated results of CDMA system deployed with transmit diversity using Alamouti code and receiver diversity with Maximum Ratio Combining (MRC technique are presented. The proposed system optimizes the effect of multipath propagation and concludes the way to improve BER.

  20. An Adaptive Multiuser Chip-Rate Equalizer for CDMA Underwater Communication System

    Institute of Scientific and Technical Information of China (English)

    HAN Jing; HUANG Jian-guo; SHEN Xiao-hong

    2008-01-01

    Direct-sequence code-division multiple access (CDMA) is considered for multiuser communication network in underwater acoustic channel, where extended multipath and rapid time-variability are encountered. To track and compensate the channel distortion, a decentralized hypothesis-feedback equalization (HFE) algorithm based on chip-rate update has been used[1]. But due to multiple access interference (MAI), its performance suffers degradation. For this reason, successive interference cancellation hypothesis-feedback equalization (SIC-HFE) algorithm is proposed, which combines the capabilities of HFE to track the time-varying channel and SIC implemented by cross-over feedback filters to cancel out the MAI effects between users. Simulation and experiment results show that the proposed algorithm can significantly improve the performance of asynchronous multiuser CDMA underwater communication system.

  1. An Iterative Multiuser Detector for Turbo-Coded DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Takawira Fambirai

    2005-01-01

    Full Text Available We propose an iterative multiuser detector for turbo-coded synchronous and asynchronous direct-sequence CDMA (DS-CDMA systems. The receiver is derived from the maximum a posteriori (MAP estimation of the single user's transmitted data, conditioned on information about the estimate of the multiple-access interference (MAI and the received signal from the channel. This multiple-access interference is reconstructed by making hard decisions on the users' detected bits at the preceding iteration. The complexity of the proposed receiver increases linearly with the number of users. The proposed detection scheme is compared with a previously developed one. The multiuser detector proposed in this paper has a better performance when the transmitted powers of all active users are equal in the additive white Gaussian noise (AWGN channel. Also, the detector is found to be resilient against the near-far effect.

  2. Analysis of MC-CDMA System in Mobile Communications

    Directory of Open Access Journals (Sweden)

    M. F. Ghanim

    2012-11-01

    Full Text Available Wireless communication plays an important role in our daily life. One of the most important techniques which is Candidate for the fourth generation is Multicarrier Code Division Multiple Access (MC-CDMA due to its high data rate. This research paper presents the MC-CDMA system using different modulation techniques. The variety of modulation types are depended in order to show the effects of modulation index and type on broadcasting data. The bit error rate of the system is plotted for a range of signal to noise ratio so that the effect of modulation on the MC-CDMA system will be evident. Actually, the simulation results show that QAM gives less bit error rate that makes MC-CDMA more flexible and suitable for mobile communication next generation technology. Also, the peak-to-average power (PAPR of MC-CDMA is analyzed to show that high PAPR is the main disadvantage of MC-CDMA system then the possible solutions for this problem are discussed in this research paper.

  3. Overloaded Minimum Total Squared Correlation Signatures Based Pilot Aided System for MC-CDMA and STBC MC-CDMA

    Science.gov (United States)

    Arifianto, M. S.; Chekima, A.; Hamid, M. Y.; Barukang, L.; Viswacheda, D. V.

    This paper proposes multiple-access schemes based on Overloaded Minimum Total Squared Correlation (TSC) signatures, namely Pilot Aided Multi-Carrier Code-Division Multiple-Access (MC-CDMA) and Pilot Aided Space Time Block Codes (STBC) MC-CDMA. Since overloaded minimum TSC signatures were used as the spreading codes, a number of sub-channels in the MC-CDMA and STBC MC-CDMA schemes were not utilized for data transmission. These empty sub-channels can be exploited for comb-type pilot signaling. To maintain low system complexity, for the pilot sub-channels Least Square (LS) estimation was employed and for interpolating the characteristics of the data sub-channels linear interpolator was applied. The validity of the schemes is confirmed by comparing them with the original MC-CDMA method using Walsh-Hadamard orthogonal codes and also with Walsh-Hadamard based STBC MC-CDMA with block-type pilot. All systems use Equal Gain Combining (EGC) or Maximum Ratio Combining (MRC) in the MC-CDMA block at the receiver. The simulation result shows that although the spreading codes of interest are not fully orthogonal codes, for a low number of users the systems under investigation performed better than their Walsh-Hadamard based counterpart. This will be valuable for Wireless Personal Area Network (PAN) where the number of users is typically low.

  4. On Analyzing LDPC Codes over Multiantenna MC-CDMA System

    Directory of Open Access Journals (Sweden)

    S. Suresh Kumar

    2014-01-01

    Full Text Available Multiantenna multicarrier code-division multiple access (MC-CDMA technique has been attracting much attention for designing future broadband wireless systems. In addition, low-density parity-check (LDPC code, a promising near-optimal error correction code, is also being widely considered in next generation communication systems. In this paper, we propose a simple method to construct a regular quasicyclic low-density parity-check (QC-LDPC code to improve the transmission performance over the precoded MC-CDMA system with limited feedback. Simulation results show that the coding gain of the proposed QC-LDPC codes is larger than that of the Reed-Solomon codes, and the performance of the multiantenna MC-CDMA system can be greatly improved by these QC-LDPC codes when the data rate is high.

  5. CAPACITY CALCULATION OF TD-CDMA HIGH ALTITUDE PLATFORM SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Wang Zhenyong; Liu Xiaowei; Li Zhuoshi

    2011-01-01

    A capacity calculation method of High Altitude Platform System (HAPS) is proposed in which TD-CDMA multiple access schemes are applied.With the influence of both power limit and bandwidth limit on capacity integrated,the paper derives the equations by which the capacity of TD-CDMA systems can be calculated,and performs calculation on a practical system.This calculation method is quite simple and effective with a comparatively small error,which is essential to the designing and research on HAPS.

  6. A modified multitarget adaptive array algorithm for wireless CDMA system

    Institute of Scientific and Technical Information of China (English)

    刘云辉; 杨宇航

    2004-01-01

    The paper presents a modified least squares despread respread multitarget constant modulus algorithm (LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate (MBER) criterion. The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate (BER) of code division multiple access (CDMA) mobile communication system. In order to achieve adaptive update of weight vectors, a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance, capacity and near-far effect resistance of a given CDMA communication system.

  7. Asynchronous control for networked systems

    CERN Document Server

    Rubio, Francisco; Bencomo, Sebastián

    2015-01-01

    This book sheds light on networked control systems; it describes different techniques for asynchronous control, moving away from the periodic actions of classical control, replacing them with state-based decisions and reducing the frequency with which communication between subsystems is required. The text focuses specially on event-based control. Split into two parts, Asynchronous Control for Networked Systems begins by addressing the problems of single-loop networked control systems, laying out various solutions which include two alternative model-based control schemes (anticipatory and predictive) and the use of H2/H∞ robust control to deal with network delays and packet losses. Results on self-triggering and send-on-delta sampling are presented to reduce the need for feedback in the loop. In Part II, the authors present solutions for distributed estimation and control. They deal first with reliable networks and then extend their results to scenarios in which delays and packet losses may occur. The novel ...

  8. Security Enhancement Using Mutual Authentication in Existing CDMA Systems

    Directory of Open Access Journals (Sweden)

    L. Krishna Bharathi

    2010-03-01

    Full Text Available Even though CDMA2000 wireless networks are being widely deployed as a cellular digital standard around the world, it has some hidden vulnerabilities concerned with security issues. The existing CDMA systems use authentication mechanism by CAVE (Cellular Authentication and Voice Encryption algorithm. This authentication method has several disadvantages. Only one way authentication is provided, that is, only a base station authenticates a subscriber. And, CAVE algorithm is prone to cryptographic attacks. This work proposes to implement authentication method using ESA (Enhanced Subscriber Authentication algorithm instead of CAVE algorithm in the existingCDMA systems. Authentication mechanism using ESA algorithm uses AKA (Authentication and Key Agreement to enhance security strength and to provide mutual authentication between a base station and a mobileterminal. AKA with 128-bit key adopts the SHA1 hash algorithm to generate authentication value and message encryption keys. Performance analysis of the proposed work is done by calculating the autocorrelation, crosscorrelation of the transmitted voice signal and also the BER (Bit Error Rate of the system. Thus the proposedwork enhances the security strength of the system with increased key strength and bilateral authentication. The proposed scheme can readily be applied to the existing CDMA systems because only the algorithm is replaced but the input parameters remain the same.

  9. Joint Transmitter-Receiver Optimization in the Downlink CDMA Systems

    Directory of Open Access Journals (Sweden)

    Mohammad Saquib

    2002-08-01

    Full Text Available To maximize the downlink code-division multiple access (CDMA system capacity, we propose to minimize the total transmitted power of the system subject to users′ signal-to-interference ratio (SIR requirements via designing optimum transmitter sequences and utilizing linear optimum receivers (minimum mean square error (MMSE receiver. In our work on joint transmitter-receiver design for the downlink CDMA systems with multiple antennas and multipath channels, we develop several optimization algorithms by considering various system constraints and prove their convergence. We empirically observed that under the optimization algorithm with no constraint on the system, the optimum receiver structure matches the received transmitter sequences. A simulation study is performed to see how the different practical system constraints penalize the system with respect to the optimum algorithm with no constraint on the system.

  10. A modified multitarget adaptive array algorithm for wireless CDMA system

    Institute of Scientific and Technical Information of China (English)

    刘云辉; 杨宇航

    2004-01-01

    The paper presents a modified least squares despread respread multitarget constant modulus algorithm(LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate(MBER)criterion.The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate(BER)of code division multiple access(CDMA)mobile communication system. In order to achieve adaptive update of weight vectors,a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance,capacity and near-far effect resistance of a given CDMA communication system.

  11. Adaptive Denoising and Equalization of Infrared Wireless CDMA System

    Directory of Open Access Journals (Sweden)

    Fernando Xavier N.

    2005-01-01

    Full Text Available Infrared has abundant, unregulated bandwidth enabling rapid deployment at low cost. However, safety limits on power emission levels (IEC825, large noise due to ambient lighting, and multipath dispersion remain as hurdles in diffused indoor environments. Especially, the high-frequency periodic interference produced by fluorescent lights is a major concern. Spread spectrum techniques enable low-power operation and noise rejection, at the expense of large processing gain. In this paper, we quantify the noise received and propose an adaptive FIR filter to jointly cancel the multipath dispersion and the fluorescent light noise in an infrared CDMA system. From analytical and simulation results, the adaptive filter significantly enhances the noise rejection capability of the CDMA system and tracks well the quasistationary indoor wireless channel. Our results show tenfold improvement in the BER for a given SNR and processing gain due to the adaptive filter. The filter also performs well in the multiuser environment.

  12. New multitarget constant modulus array for CDMA systems

    Institute of Scientific and Technical Information of China (English)

    Zhang Jidong; Zheng Baoyu

    2006-01-01

    A new multitarget constant modulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constant modulus algorithm (DDDLSCMA). In the new algorithm, the pre-despreading is first applied for multitarget arrays to remove some multiple access signals, then the despreaded signal is processed by the algorithm which united the constant modulus algorithm and decision directed method. Simulation results illustrate the good performance for the proposed algorithm.

  13. Fair channel-dependent scheduling in CDMA systems

    OpenAIRE

    Bruin, de, W.; Heijenk, Geert; El Zarki, Magda; Zan, Jasmine Lei

    2003-01-01

    In this study a scheduling algorithm for CDMA systems is presented which is a trade-off between two extreme ways of scheduling: C/I based and Round-Robin scheduling. The simulation results indeed display that the advantages of both these extremes have been combined in the new algorithm: a good fairness, comparable to that of the Round-Robin scheduling, together with almost the same power gain as reached in the C/I based scheduling.

  14. Adaptive Rate DS-CDMA Systems using Variable Spreading Factors

    OpenAIRE

    Yang, L-L.; Hanzo, L.

    2004-01-01

    Abstract—In this contribution, adaptive rate transmissions are investigated in the context of direct-sequence code-division multiple-access (DS-CDMA) systems using variable spreading factors (VSFs). In the context of the recently established family of adaptive rate-transmission schemes, the transmission rate is typically adapted in response to the channel’s fading-induced quality fluctuation. By contrast, in this contribution the transmission rate is adapted in response to the multiuser inter...

  15. An Acquisition Performance Analysis of DS-MC-CDMA System under Multiple Access Interference Conditions

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Multi-Access Interference's (MAI's) effect on parallel acquisition performance of DS-Multi-carrier CDMA system under the typical indoor radio channel is discussed in the paper. Moreover, a comparison of acquisition performance impairment produced by the MAI in DS-MC-CDMA and DS-Single-carrier CDMA is also made. Results are given in terms of average acquisition time obtained by means of simulations and theory analysis.

  16. Hybrid chaotic sequence for QS-CDMA system with RAKE receiver

    Institute of Scientific and Technical Information of China (English)

    饶妮妮; 许晓晶; 李少谦

    2004-01-01

    A class of the hybrid chaotic sequences is presented. The generator of the sequences is given and realized by the digital method. The hybrid chaotic sequences exhibit good random properties that are very important for the performance of QS-CDMA system with RAKE receiver. The performance of the system is analyzed when the hybrid chaotic sequences are used as spreading codes in a QS-CDMA system with RAKE receiver and compared with those obtained for m-sequences and logistic sequences. The results show that the hybrid chaotic sequences are a class of very promising spreading codes for QS-CDMA system.

  17. An Efficient Paging Algorithm for Multi-Carrier CDMA System

    Directory of Open Access Journals (Sweden)

    Sheikh Shanawaz Mostafa

    2011-05-01

    Full Text Available To cope with the increasing demand of wireless communication services multi-carrier systems are being used. Radio resources are very limited and efficient usages of these resources are inevitable to get optimum performance of the system. Paging channel is a low-bandwidth channel and one of the most important channels on which system performance depends significantly. Therefore it is vulnerable to even moderate overloads. In this paper, an efficient paging algorithm, Concurrent Search, is proposed for efficient use of paging channel in Multi- carrier CDMA system instead of existing sequential searching algorithm. It is shown by the simulation that the paging performance in proposed algorithm is far better than the existing system.

  18. Passive location using CDMA mobile communication system based on repeater equipment

    Institute of Scientific and Technical Information of China (English)

    TIAN Zeng-shan; ZHOU Fei; ZHANG Tian-qi

    2008-01-01

    To overcome the drawback of a short operation range and low-resolution of a passive location system using a civil communication signal, the new idea that utilizes code division multiple access (CDMA) signal and repeater is disposed off. First, the CDMA passive location model and observation function are given, and the error source and error range are analyzed. Subsequently, the CDMA passive location algorithm in a repeater environment is described and simulated. The simulation result shows that the algorithm can provide the location value with high accuracy.

  19. Performance of MC-CDMA Systems with Orthogonal Transmit Diversity over Rayleigh Fading Channel

    Institute of Scientific and Technical Information of China (English)

    樊凌涛; 李高志; 陈健

    2003-01-01

    Transmit diversity has been recently proposed to reduce the effects of fading channels in various wireless applications. Orthogonal transmit diersity (OTD) is one of the standardized techniques in 3G systems. In this paper, we apply orthogonal transmit diversity technique to multicarrier CDMA systems. Andlysis and simulation results show that performance benefits can be achieved compared with conventioal MC-CDMA systems in multipath fading channels.

  20. Duration of asynchronous operations in distributed systems

    OpenAIRE

    Makhaniok, Mikhail; Männer, Reinhard

    1995-01-01

    A distributed asynchronous system is investigated. Its processing elements execute common operations concurrently and distributively. They are implemented as combinatorial circuits and exchange data via open collector bus lines. A method is presented to identify and to minimize the duration of an operation and therefore to increase the performance of the system. No hardware modifications are required.

  1. Diversity reception for advanced multi-satellite networks: A CDMA approach

    Science.gov (United States)

    Colzi, E.; Degaudenzi, R.; Elia, C.; Giannetti, F.; Viola, R.

    Diversity reception for Synchronous CDMA (S-CDMA) is introduced and analyzed. A Gaussian co-channel synchronous and asynchronous interference approximation is derived to evaluate the effects on the system bit error rate. Numerical results are provided for a simple mobile communication system where the signals transmitted by two distinct satellites in visibility are coherently combined by a three fingers Rake receiver. A second example showing performance of an integrated ground/satellite single frequency network for digital audio broadcasting is presented. Results show the capacity advantage of utilizing S-CDMA in combination with diversity reception.

  2. CDMA Technology for Intelligent Transportation Systems

    OpenAIRE

    Bera, Rabindranath; Bera, Jitendranath; Sil, Sanjib; Mondal, Dipak; Dhar, Sourav; Kandar, Debdatta

    2007-01-01

    Scientists and Technologists involved in the development of radar and remote sensing systems all over the world are now trying to involve themselves in saving of manpower in the form of developing a new application of their ideas in Intelligent Transport system(ITS). The world statistics shows that by incorporating such wireless radar system in the car would decrease the world road accident by 8-10% yearly. The wireless technology has to be chosen properly which is capable of tackling the sev...

  3. Intelligent Paging Strategy for Multi-Carrier CDMA System

    Directory of Open Access Journals (Sweden)

    Sheikh Shanawaz Mostafa

    2011-11-01

    Full Text Available Subscriber satisfaction and maximum radio resource utilization are the pivotal criteria in communication system design. In multi-Carrier CDMA system, different paging algorithms are used for locating user within the shortest possible time and best possible utilization of radio resources. Different paging algorithms underscored different techniques based on the different purposes. However, low servicing time of sequential search and better utilization of radio resources of concurrent search can be utilized simultaneously by swapping of the algorithms. In this paper, intelligent mechanism has been developed for dynamic algorithm assignment basing on time-varying traffic demand, which is predicted by radial basis neural network; and its performance has been analyzed are based on prediction efficiency of different types of data. High prediction efficiency is observed with a good correlation coefficient (0.99 and subsequently better performance is achieved by dynamic paging algorithm assignment. This claim is substantiated by the result of proposed intelligent paging strategy.

  4. Performance of MC-MC CDMA Systems with Nonlinear Models of HPA

    CERN Document Server

    Gergis, Labib Francis

    2011-01-01

    A new wireless communication system denoted as Multi-Code Multi-Carrier CDMA (MC-MC CDMA), which is the combination of Multi-Code CDMA and Multi-Carrier CDMA, is analyzed in this paper. This system can satisfy multi-rate services using multi-code schemes and muti-carrier services used for high rate transmission. The system is evaluated using Traveling Wave Tube Amplifier (TWTA). This type of amplifiers continue to offer the best microwave high power amplifiers (HPA) performance in terms of power efficiency, size and cost, but lag behind Solid State Power Amplifiers (SSPA's) in linearity. This paper presents a technique for improving TWTA linearity. The use of predistorter (PD) linearization technique is described to provide TWTA performance comparable or superior to conventional SSPA's. The characteristics of the PD scheme is derived based on the extension of Saleh's model for HPA.

  5. CDMA Technology for Intelligent Transportation Systems

    CERN Document Server

    Bera, Rabindranath; Sil, Sanjib; Mondal, Dipak; Dhar, Sourav; Kandar, Debdatta

    2007-01-01

    Scientists and Technologists involved in the development of radar and remote sensing systems all over the world are now trying to involve themselves in saving of manpower in the form of developing a new application of their ideas in Intelligent Transport system(ITS). The world statistics shows that by incorporating such wireless radar system in the car would decrease the world road accident by 8-10% yearly. The wireless technology has to be chosen properly which is capable of tackling the severe interferences present in the open road. A combined digital technology like Spread spectrum along with diversity reception will help a lot in this regard. Accordingly, the choice is for FHSS based space diversity system which will utilize carrier frequency around 5.8 GHz ISM band with available bandwidth of 80 MHz and no license. For efficient design, the radio channel is characterized on which the design is based. Out of two available modes e.g. Communication and Radar modes, the radar mode is providing the conditiona...

  6. The non-anticipation of the asynchronous systems

    OpenAIRE

    Vlad, Serban E.

    2008-01-01

    The asynchronous systems are the models of the asynchronous circuits from the digital electrical engineering and non-anticipation is one of the most important properties in systems theory. Our present purpose is to introduce several concepts of non-anticipation of the asynchronous systems.

  7. PRERAKE JOINT WITH STTCM FOR TDD DS-CDMA SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Cheng Jian; Wu Gang; Cheng Shixin

    2001-01-01

    A novel synthetical transmit diversity, namely Prerake joint with Space-Time Trellis Coded Modulation (STTCM), for TDD DS-CDMA system is proposed in this paper. Space-Time Code (STC) is applied under the multipath fading circumstance. Prerake is used in stead of Rake to overcome multipath fading for the simplicity of the receiver configuration. Through computer simulation, the performance of our proposed scheme in multipath fading can be better than that of just STC is used, the taps of the Prerake should be chosen to be equal to the multipath number in the matter of minimum mean square error. A new constellation (8APK) is presented to construct a kind of STC that achieves better performance than that of 8PSK.

  8. A Novel Space-time Spreading Transmit Diversity Scheme for Wireless CDMA System

    Institute of Scientific and Technical Information of China (English)

    ZOU Yong-zhong; LI Dao-ben

    2004-01-01

    This paper presents a new two-branch space-time spreading transmit diversity scheme for wireless CDMA systems, which differs from Space-Time Spreading (STS) of CDMA-2000. Using two transmit and M receiving antennas, the new scheme provides diversity order of 2M. This new technique does not require any bandwidth expansion and any feed back from the receiver to the transmitter and its computation complexity is similar to the Maximal-Ratio Combining (MRC).

  9. Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System

    Directory of Open Access Journals (Sweden)

    Raulefs Ronald

    2004-01-01

    Full Text Available We investigate rotated Walsh-Hadamard spreading matrices for a broadband MC-CDMA system with robust channel estimation in the synchronous downlink. The similarities between rotated spreading and signal space diversity are outlined. In a multiuser MC-CDMA system, possible performance improvements are based on the chosen detector, the channel code, and its Hamming distance. By applying rotated spreading in comparison to a standard Walsh-Hadamard spreading code, a higher throughput can be achieved. As combining the channel code and the spreading code forms a concatenated code, the overall minimum Hamming distance of the concatenated code increases. This asymptotically results in an improvement of the bit error rate for high signal-to-noise ratio. Higher convolutional channel code rates are mostly generated by puncturing good low-rate channel codes. The overall Hamming distance decreases significantly for the punctured channel codes. Higher channel code rates are favorable for MC-CDMA, as MC-CDMA utilizes diversity more efficiently compared to pure OFDMA. The application of rotated spreading in an MC-CDMA system allows exploiting diversity even further. We demonstrate that the rotated spreading gain is still present for a robust pilot-aided channel estimator. In a well-designed system, rotated spreading extends the performance by using a maximum likelihood detector with robust channel estimation at the receiver by about 1 dB.

  10. Application of Zero Correlation Zone Sequences in Quasi-synchronous CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    LI Shu-feng; JIA Zhi-cheng; WANG Jing; LI Qi

    2007-01-01

    In a quasi-synchronous code division multiple access(QS-CDMA) system, the correlation functions around the origin influence the system performance and odd functions are as important as the even functions. Three kinds of zero correlation zone(ZCZ) sequences are used to analyze and compare the correlation functions. Binary phase shift keying(BPSK) simulations of QS-CDMA system with the three kinds of QS sequences as spreading codes on additive white Gaussian noise(AWGN) channel show that these sequences are quasi-orthogonal, so they are suitable for QS-CDMA system. The correlation between the system performance and the zero correlation zone of the sequence is also proved.

  11. The Applicative Investigation of Adaptive BP Networks for Multi-user Detection in Asynchronous DS-CDMA Mobile Communications

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Three-layer Adaptive Back-Propagation Neural Networks(TABPNN) are employed for the demodulation of spread spectrum signals in a multiple-access environment. A configuration employing three-layer adaptive Back-propagation neural networks is put forward for the demodulation of spread-spectrum signals in asynchronous Gaussian channels. The theoretical arguments and practical performance based on the neural networks are analyzed. The results show that whether the resistance to the multiple access interference or the robust to near-far effects, the proposed detector significantly outperforms not only the conventional detector but also the BP neural networks detector and is comparable to the optimum detector.

  12. New Parallel Interference Cancellation for Convolutionally Coded CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    Xu Guo-xiong; Gan Liang-cai; Huang Tian-xi

    2004-01-01

    Based on BCJR algorithm proposed by Bahl et al and linear soft decision feedback, a reduced-complexity parallel interference cancellation (simplified PIC) for convolutionally coded DS CDMA systems is proposed. By computer simulation, we compare the simplified PIC with the exact PIC. It shows that the simplified PIC can achieve the performance close to the exact PIC if the mean values of coded symbols are linearly computed in terms of the sum of initial a prior log-likelihood rate (LLR) and updated a prior LLR, while a significant performance loss will occur if the mean values of coded symbols are linearly computed in terms of the updated a prior LLR only. Meanwhile, we also compare the simplified PIC with MF receiver and conventional PICs. The simulation results show that the simplified PIC dominantly outperforms the MF receiver and conventional PICs, at signal-noise rate (SNR) of 7 dB, for example, the bit error rate is about 10-4 for the simplified PIC, which is far below that of matched-filter receiver and conventional PIC.

  13. Optical PPM-CDMA Communication System with Optical Hard-Limiter

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An optical PPM-CDMA communication system with an opticalhard-limiter in front of the correlator of a receiver is proposed in order to reduce multi-user interference. The performance of the system is evaluated when the effects of both multi-user interference and photo detector shot noise are considered. An upper bound on the bit error rate is derived. The comparison of the performance of the above receiver with that of the optical PPM-CDMA system without an optical hard-limiter is made. Simulation results show that the performance of the system with an optical hard-limiter is superior to that of the conventional one.

  14. Optimization of sequences in CDMA systems: a statistical-mechanics approach

    CERN Document Server

    Kitagawa, Koichiro

    2008-01-01

    Statistical mechanics approach is useful not only in analyzing macroscopic system performance of wireless communication systems, but also in discussing design problems of wireless communication systems. In this paper, we discuss a design problem of spreading sequences in code-division multiple-access (CDMA) systems, as an example demonstrating the usefulness of statistical mechanics approach. We analyze, via replica method, the average mutual information between inputs and outputs of a randomly-spread CDMA channel, and discuss the optimization problem with the average mutual information as a measure of optimization. It has been shown that the average mutual information is maximized by orthogonally-invariant random Welch bound equality (WBE) spreading sequences.

  15. On the Capacity Degradation Due to Coexistence of WCDMA and CDMA2000 Systems

    Institute of Scientific and Technical Information of China (English)

    WU Jiang; LIANG Shuang-chun; NIU Kai; WU Wei-ling

    2004-01-01

    In this paper, we investigate the capacity degradation due to the coexistence of WCDMA and CDMA2000 networks by system-level Monte Carlo simulation. Both systems are simulated according to the deployment of macro cells, and speech service is considered. The capacity losses under different carrier spacing and different geographical offset are evaluated. Simulation results show that considerable capacity loss is seen when WCDMA is the victim system, while the influence of WCDMA to CDMA2000 is slight. Increasing carrier-to-carrier spacing and decreasing geographical offset lead to less capacity loss and co-locating the base stations of both systems is a preferred solution.

  16. Performance of MC-MC CDMA Systems With Nonlinear Models of HPA

    Directory of Open Access Journals (Sweden)

    Labib Francis Gergis

    2011-02-01

    Full Text Available A new wireless communication system denoted as Multi-Code Multi-Carrier CDMA (MC-MCCDMA, which is the combination of Multi-Code CDMA and Multi-Carrier CDMA, is analyzed in thispaper. This system can satisfy multi-rate services using multi-code schemes and muti-carrier servicesused for high rate transmission. The system is evaluated using Traveling Wave Tube Amplifier (TWTA.This type of amplifiers continue to offer the best microwave high power amplifiers (HPA performance interms of power efficiency, size and cost, but lag behind Solid State Power Amplifiers (SSPA's in linearity.This paper presents a technique for improving TWTA linearity. The use of pre-distorter (PDlinearization technique is described to provide TWTA performance comparable or superior toconventional SSPA's. The characteristics of the PD scheme is derived based on the extension of Saleh'smodel for HPA

  17. Blind Identification and Equalization of MC-CDMA Systems Using Higher Order Cumulants

    Directory of Open Access Journals (Sweden)

    Mohammed Zidane

    2014-04-01

    Full Text Available In this work we propose an algorithm based on fourth order cumulants for identification of the linear system (Finite- Impulse Response (FIR with Non Minimum Phase (NMP excited by non-Gaussian sequences, independent identically distributed (i.i.d. In order to test its efficiency, we have compared with the Safi et al. algorithm, for that we considered three practical frequency-selective fading channel, called Broadband Radio Access Network (BRAN A, BRAN B, and BRAN D, normalized for  MC-CDMA systems. In the part of MC-CDMA, we use the zero forcing (ZF and the minimum mean square error (MMSE equalizers to perform our algorithms. The simulation results show that the bit error rate (BER performances of the downlink MC-CDMA systems, using proposed algorithm (AlgoZ is more accurate compared with the results obtained with the Safi et al. (Alg-CUM algorithm.

  18. Tides in asynchronous binary systems

    OpenAIRE

    Toledano, Oswaldo; Moreno, Edmundo; Koenigsberger, Gloria; Detmers, R.; Langer, Norbert

    2006-01-01

    Stellar oscillations are excited in non-synchronously rotating stars in binary systems due to the tidal forces. Tangential components of the tides can drive a shear flow which behaves as a differentially forced rotating structure in a stratified outer medium. In this paper we show that our single-layer approximation for the calculation of the forced oscillations yields results that are consistent with the predictions for the synchronization timescales in circular orbits. In addition, calibrat...

  19. A Two-Level Spreading-despreading CDMA System and Its Performance Evaluation

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new two-level spreading-despreading scheme is presented in this paper. By adopting the two-level scheme, the Generalized Orthogonal (GO) zone of GO codes can be utilized. In this paper, the forward link of a multi-cell CDMA system employing the two-level scheme is presented and analyzed. The BER performance obtained by Gaussian Approximation is compared with that of the conventional single-level spreading-despreading system. The results reveal that the two*$-level CDMA system introduced in this paper exhibits larger performance gain when time delay can be restricted within a given zone.

  20. Bit Error Rate Analysis for MC-CDMA Systems in Nakagami- Fading Channels

    Directory of Open Access Journals (Sweden)

    Li Zexian

    2004-01-01

    Full Text Available Multicarrier code division multiple access (MC-CDMA is a promising technique that combines orthogonal frequency division multiplexing (OFDM with CDMA. In this paper, based on an alternative expression for the -function, characteristic function and Gaussian approximation, we present a new practical technique for determining the bit error rate (BER of multiuser MC-CDMA systems in frequency-selective Nakagami- fading channels. The results are applicable to systems employing coherent demodulation with maximal ratio combining (MRC or equal gain combining (EGC. The analysis assumes that different subcarriers experience independent fading channels, which are not necessarily identically distributed. The final average BER is expressed in the form of a single finite range integral and an integrand composed of tabulated functions which can be easily computed numerically. The accuracy of the proposed approach is demonstrated with computer simulations.

  1. Multicarrier CDMA Systems with Transmit Diversity in Two—Ray Multipath Fading Channels

    Institute of Scientific and Technical Information of China (English)

    FANLingtao; CHENJian

    2003-01-01

    Transmit diversity is recently proposed to reduce the effects in fading channels in various wireless applications. In this paper, we apply a transmit diversity technique to downlink multicarrier CDMA (Code devision multiple access) systems, which utilize the cyclic shift ver-sions of the normal spread codes as the spread sequences in transmit diversity branches. A RAKE-like parallel receiver is employed in frequency domain to obtain diversity gains.Simulation results show that performance benefits can be achieved compared to conventional MC-CDMA systems in Z-ray multipath fading channels.

  2. COMPUTER SIMULATION OF RAYLEIGH FADING CHANNELS IN MC-CDMA SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    For Multi-Carrier-Code Division Multiple Access (MC-CDMA) systems, it is usually assumed that the fading of the subcarriers is frequency non-selective and independent of each other.This paper shows that the two assumptions are incompatible. In fact, the MC-CDMA signals at each subcarrier undergo fading that are highly correlated. Based on this observation, this paper develops a simulation algorithm for Rayleigh fading channels via frequency-domain correlation function, which incorporates the Doppler effect simultaneously. Numerical examples are presented to demonstrate the effectiveness of the new algorithm, with the conclusion that the independence assumption of subcarrier fading overrates the system performance.

  3. Interference Analysis of TD-SCDMA System and CDMA2000 System

    Directory of Open Access Journals (Sweden)

    Hao Chen

    2012-01-01

    Full Text Available  Abstract—In this paper, the feasibility of co-channel coexistence of Time Division- Synchronous Code Division Multiple Access(TD-SCDMA)and Code Division Multiple Access 2000(CDMA2000)systems operating in a macro cell environment is investigated. The deterministic analysis and simulation method are used to evaluate the performance compromising of both systems. Based on a more efficient calculation scheme, a novel deterministic equation is proposed and used to provide a better interpretation of the relationship between aggressor and victim in the interference system. The evaluation and simulation results show consistency with the corresponding experiment results. Furthermore, the interference characteristics of Omni-antenna and smart antenna in TD-SCDMA and CDMA2000 are compared, providing an important guideline to reduce the interference of two systems.

  4. Interference Analysis of TD-SCDMA System and CDMA2000 System

    OpenAIRE

    Hao Chen; Tong Yang; Jianfu Teng; Hong He

    2012-01-01

     Abstract—In this paper, the feasibility of co-channel coexistence of Time Division- Synchronous Code Division Multiple Access(TD-SCDMA)and Code Division Multiple Access 2000(CDMA2000)systems operating in a macro cell environment is investigated. The deterministic analysis and simulation method are used to evaluate the performance compromising of both systems. Based on a more efficient calculation scheme, a novel deterministic equation is proposed and used to provide a better inter...

  5. Equivalent Joint Space-Time Multiuser Detection for Uplink ISI-Corrupted Multicarrier CDMA Systems with Arbitrary Antenna Arrays

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The multicarrier code division multiple access (MC-CDMA) systems without cyclic prefix (CP) hold a finespectral efficiency though they are unavoidably corrupted by the intersymbol interference (ISI) over the finite impulseresponse (FIR) channel. We call MC-CDMA systems without CP the ISI-corrupted MC-CDMA systems in some sense.Considering the fact that combining antenna arrays with so-called ISI-corrupted MC-CDMA systems is advantageous insuppressing cochannel interference in cellular communication systems, this paper investigates ISI-corrupted MC-CDMAsystems with base station antenna arrays. Joint space-time multiuser detection (MUD) schemes for DS-CDMA systemswith antenna arrays have drawn much attention recently. Based upon them, we can derive the equivalent joint spatial-temporal MUD scheme for ISI-corrupted MC-CDMA systems with antenna arrays. In order to achieve this goal, anequivalent space-time estimation method of uplink vector channel is first derived for the ISI-corrupted MC-CDMA systemwith the arbitrary antenna array over frequency-selective fading channels. Then, based on the estimated equivalent space-time channel, an equivalent joint space-time multiuser detector is constructed. Computer simulations illustrate that ouralgorithm is more robust against noise and can well mitigate multiple access interference (MAI) in multiuser scenarios.

  6. Multi User Detection For Cdma-Ofdm/Oqam System Combined With Space Time Coding

    Directory of Open Access Journals (Sweden)

    Radhia GHARSALLAH

    2012-09-01

    Full Text Available In this paper, we propose the combination of Multi Carrier (MC OFDM/OQAM modulation and CDMAcalled MC-CDMA-OQAM system with Space Time (ST coding in a multi user context. This combination takes advantages from multicarrier modulation, spread spectrum and spatial time diversity. Indeed, theuse of OFDM has proved its ability to fight against frequency selective channels but the insertion of guard interval yields spectral efficiency loss and sensitivity to frequency dispersion due to the use of rectangular pulse shape. Thus, cyclic prefix OFDM is replaced by an advanced filterbank-based multicarrier system OFDM/OQAM that operates without guard interval. However, OFDM/OQAM provides orthogonality only on the real domain, so transmitted symbols must be real valued. In the other hand, the CDMA component has two advantages: multiple access interference cancellation and providing orthogonality in the complex domain. From the orthogonality property provided, the Alamouti ST code can be combined with MC-CDMA-OQAM system. The resulting MIMO-MC-CDMA-OQAM system improves the spectral efficiency of wireless system, combat channel fading and reduce narrowband interference. Numerical results show the utility of this new wireless communication system; a significant BER versus Signal to Noise Ratio (SNR was achieved thus Multiple access interference (MAI is suppressed and so supporting a large number of users.

  7. QUADRATIC PROGRAMMING NEURAL NETWORK BASED INTEGRATED SPACE-TIME INTERFERENCE SUPPRESSION IN CDMA SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Song Rongfang; Bi Guangguo

    2001-01-01

    Quadratic programming models for integrated space-time interference suppression in CDMA systems are proposed in this paper. The models integrate the advantages of smart antenna and RAKE receiver, mitigate multiuser access interference (MAI) and interchip interference (ICI),and combine multipath components. The zero-forcing conditions are derived. Neural network implementation of the models is also studied.

  8. On the High Altitude Platform (HAP W-CDMA System Capacity

    Directory of Open Access Journals (Sweden)

    L. de Haro-Ariet

    2004-06-01

    Full Text Available The performance of a downlink power control model, based on a n-thpower distance law, is evaluated for high altitude platform station(HAPS W-CDMA systems. The downlink capacity using this model iscompared with the uplink capacity. It is shown that the uplink capacityis higher than the downlink capacity.

  9. Differential Space-Time Block Code Modulation for DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Liu Jianhua

    2002-01-01

    Full Text Available A differential space-time block code (DSTBC modulation scheme is used to improve the performance of DS-CDMA systems in fast time-dispersive fading channels. The resulting scheme is referred to as the differential space-time block code modulation for DS-CDMA (DSTBC-CDMA systems. The new modulation and demodulation schemes are especially studied for the down-link transmission of DS-CDMA systems. We present three demodulation schemes, referred to as the differential space-time block code Rake (D-Rake receiver, differential space-time block code deterministic (D-Det receiver, and differential space-time block code deterministic de-prefix (D-Det-DP receiver, respectively. The D-Det receiver exploits the known information of the spreading sequences and their delayed paths deterministically besides the Rake type combination; consequently, it can outperform the D-Rake receiver, which employs the Rake type combination only. The D-Det-DP receiver avoids the effect of intersymbol interference and hence can offer better performance than the D-Det receiver.

  10. DOA Estimation in the Uplink of Multicarrier CDMA Systems

    OpenAIRE

    Antonio A. D'Amico; Michele Morelli; Luca Sanguinetti

    2008-01-01

    We consider the uplink of a multicarrier code-division multiple-access (MC-CDMA) network and assume that the base station is endowed with a uniform linear array. Transmission takes place over a multipath channel and the goal is the estimation of the directions of arrival (DOAs) of the signal from the active users. In a multiuser scenario, difficulties are primarily due to the large number of parameters involved in the estimation of the DOAs which makes this problem much more challenging than...

  11. MULTI USER PERFORMANCE ON MC CDMA SINGLE RELAY COOPERATIVE SYSTEM BY DISTRIBUTED STBC IN RAYLEIGH FADING CHANNEL

    Directory of Open Access Journals (Sweden)

    Gelar Budiman

    2015-01-01

    Full Text Available Increasing data rate and high performance is the target focus of wireless communication. The multi carrier on multi-hop communication system using relay's diversity technique which is supported by a reliable coding is a system that may give high performance. This research is developing a model of multi user and two scheme of multi carrier CDMA on multi hop communication system with diversity technique which is using Alamouti codes in Rayleigh fading channel. By Alamouti research, Space Time Block Code (STBC for MIMO system can perform high quality signal at the receiver in the Rayleigh fading channel and the noisy system. In this research, MIMO by STBC is applied to single antenna system (Distributed-STBC/DSTBC with multi carrier CDMA on multi hop wireless communication system (relay diversity which is able to improve the received signal performance. MC DS CDMA on multi hop wireless communication system with 2 hops is better performing than MC CDMA on multi user without Multi User Detector. To reach BER 10-3 multi hop system with MC CDMA needs more power 5 dB than MC DS CDMA at 5 users using Alamouti scheme for symbol transmission at the relay

  12. CUCKOO SEARCH-AIDED LMS ALGORITHM FOR CHANNEL ESTIMATION IN MC-CDMA SYSTEMS

    OpenAIRE

    Balaji, S.; N. Vasudevan

    2014-01-01

    In the progress of transmission systems that uses the diversity in various domains, the execution of competent baseband receivers categorized by affordable computational load is an essential thing. This would be an imperative point in the future expansion of 4G systems in which the space, time and frequency diversity will be merged together to enhance the system throughput. Here, we develop a channel estimation technique for MC-CDMA system for the minimization of BER and the maximization of t...

  13. WAVELET-BASED OFDM-CDMA HIGH SPEED POWER LINE COMMUNICATION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Zhou Lerong; Guo Jinghong; Wei Gang

    2004-01-01

    This letter derives the Equivalent M-band Discrete Wavelet(EMDW) transmission mode of Orthogonal Frequency Division Multiplexing(OFDM) transmission systems, and presents a new Quadrature M-band Discrete Wavelet(QMDW) based OFDM-CDMA(Code Division Multiple Access) communication systems for high speed Power Line Communication (PLC) channels.This system gives much better robustness to Inter-Channel Interference (ICI), Multi-User Interference (MUI) and noise interference, which is verified by simulation.

  14. Single Carrier Cyclic Prefix-Assisted CDMA System with Frequency Domain Equalization for High Data Rate Transmission

    Directory of Open Access Journals (Sweden)

    Madhukumar A. S.

    2004-01-01

    Full Text Available Multiple-access interference and interfinger interference limit the capacity of conventional single-carrier DS-CDMA systems. Even though multicarrier CDMA posses the advantages of conventional CDMA and OFDM, it suffers from two major implementation difficulties such as peak-to-average power ratio and high sensitivity to frequency offset and RF phase noise. A novel approach based on single-carrier cyclic prefix-assisted CDMA has been proposed to overcome the disadvantages of single-carrier CDMA and multicarrier modulation. The usefulness of the proposed approach for high-speed packet access with simplified channel estimation procedures are investigated in this paper. The paper also proposes a data-dependent pilot structure for the downlink transmission of the proposed system for enhancing pilot-assisted channel estimation in frequency domain. The performance of the proposed pilot structure is compared against the data-independent common pilot structure. The proposed system is extensively simulated for different channel parameters with different channel estimation and equalization methods and the results are compared against conventional multicarrier CDMA systems with identical system specifications.

  15. Solving SAT and Hamiltonian Cycle Problem Using Asynchronous P Systems

    Science.gov (United States)

    Tagawa, Hirofumi; Fujiwara, Akihiro

    In the present paper, we consider fully asynchronous parallelism in membrane computing, and propose two asynchronous P systems for the satisfiability (SAT) and Hamiltonian cycle problem. We first propose an asynchronous P system that solves SAT with n variables and m clauses, and show that the proposed P system computes SAT in O(mn2n) sequential steps or O(mn) parallel steps using O(mn) kinds of objects. We next propose an asynchronous P system that solves the Hamiltonian cycle problem with n nodes, and show that the proposed P system computes the problem in O(n!) sequential steps or O(n2) parallel steps using O(n2) kinds of objects.

  16. Detailed Mathematical Analysis and Performance Evaluation of MIMO-OFDM-CDMA System Using ZF Receiver

    Directory of Open Access Journals (Sweden)

    Ekta Charaya

    2013-07-01

    Full Text Available In this paper, we have presented the detailed mathematical analysis of the output signal to interference noise ratio (SINR for MIMO-OFDM-CDMA system using joint space-time frequency (STF spreading with ZF receiver. A 2x2 and 4x4 MIMO system is used for performance evaluation in terms of BER. The analysis shows that output SINR decreases, as the number of users increases. The average bit error probability of the system using ZF receiver is derived for different number of users. We also present exponential bound of the complementary error function (erfc for probability of error. Simulation results of MIMO-OFDM-CDMA system are in line with the results obtained through mathematical analysis

  17. Optimal Filtering Algorithm-Based Multiuser Detector for Fast Fading CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A multiuser detector was developed for fast fading code-division multiple-access systems by representing the channels as a system with the multiplicative noise (SMN) model and then using the known optimal filtering algorithm for the SMN for multiuser detection (MUD). This multiuser detector allows the channel response to be stochastic in one symbol duration, which can be regarded as an effective method of MUD for fast fading CDMA systems. Performance analyses show that the multiuser detector is theoretically valid for CDMA systems over fast fading channels. Simulations show that the multiuser detector performs better than the Kalman filter-based multiuser detector with a faster convergence rate and lower bit error rate.

  18. Impact of Different Spreading Codes Using FEC on DWT Based MC-CDMA System

    OpenAIRE

    Masum, Saleh; Kabir, M. Hasnat; Islam, Md. Matiqul; Shams, Rifat Ara; Ullah, Shaikh Enayet

    2012-01-01

    The effect of different spreading codes in DWT based MC-CDMA wireless communication system is investigated. In this paper, we present the Bit Error Rate (BER) performance of different spreading codes (Walsh-Hadamard code, Orthogonal gold code and Golay complementary sequences) using Forward Error Correction (FEC) of the proposed system. The data is analyzed and is compared among different spreading codes in both coded and uncoded cases. It is found via computer simulation that the performance...

  19. A novel adaptive joint power control algorithm with channel estimation in a CDMA cellular system

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Joint power control has advantages of multi-user detection and power control; and it can combat the multi-access interference and the near-far problem. A novel adaptive joint power control algorithm with channel estimation in a CDMA cellular system was designed. Simulation results show that the algorithm can control the power not only quickly but also precisely with a time change. The method is useful for increasing system capacity.

  20. DS-CDMA system outer loop power control and improvement for multi-service

    Institute of Scientific and Technical Information of China (English)

    Guan Mingxiang; Guo Qing; Li Xing

    2008-01-01

    When a new user accesses the CDMA system, the load will change drastically, and therefore, the advanced outer loop power control (OLPC) technology has to be adopted to enrich the target signal interference ratio (SIR) and improve the system performance. The existing problems about DS-CDMA outer loop power control for multi-service are introduced and the power control theoretical model is analyzed. System simulation is adopted on how to obtain the theoretical performance and parameter optimization of the power control algorithm. The OLPC algorithm is improved and the performance comparisons between the old algorithm and the improved algorithm are given. The results show good performance of the improved OLPC algorithm and prove the validity of the improved method for multi-service.

  1. A review on synchronous CDMA systems: optimum overloaded codes, channel capacity, and power control

    Directory of Open Access Journals (Sweden)

    Hosseini Seyed Amirhossein

    2011-01-01

    Full Text Available Abstract This paper is a tutorial review on important issues related to code-division multiple-access (CDMA systems such as channel capacity, power control, and optimum codes; specifically, we consider optimum overloaded codes that achieve errorless transmission in the absence of noise for the binary and nonbinary cases. A survey of lower and upper bounds for the sum channel capacity of such systems is given in the presence and absence of channel noise. The asymptotic results for the channel capacity are also investigated. The channel capacity, errorless transmission codes, and power estimation for near-far effects are also explored. The emphasis of this tutorial review is on the overloaded CDMA systems.

  2. On the Performance of Synchronous DS—CDMA Systems with Generalized Orthogonal Spreading Codes

    Institute of Scientific and Technical Information of China (English)

    HAOLi; FANPingzhi

    2003-01-01

    A new synchronous DS-CDMA system em-ploying generalized orthogonal (GO) spreading codes and maximum ratio combining (MRC) scheme is presented in this paper. In particular, the forward link of the system is discussed in detail. The GO codes are used to combat the interference caused by multipath components. The aver-age correlation properties of GO codes are evaluated andthe signal interference ratio (SIR) expressions based on the Rayleigh and Racian fading multipath channel models are derived respectively. The link performance in terms of bit error rate (BER) is obtained for GO codes with different orthogonal zones by Gaussian Approximation and Monte-Carlo simulation respectively. The results reveal that the GO codes appear better BER performance than traditional orthogonal codes in synchronous CDMA systems, and the GO code with larger orthogonal zone exhibits larger per-formance gain.

  3. Novel Asynchronous Wrapper and Its Application to GALS Systems

    Institute of Scientific and Technical Information of China (English)

    Zhuang Shengxian; Peng Anjin; Lars Wanhammar

    2006-01-01

    An asynchronous wrapper with novel handshake circuits for data communication in globally asynchronous locally synchronous (GALS) systems is proposed. The handshake circuits include two communication ports and a local clock generator. Two approaches for the implementation of communication ports are presented, one with pure standard cells and the others with Müller-C elements. The detailed design methodology for GALS systems is given and the circuits are validated with VHDL and circuits simulation in standard CMOS technology.

  4. Chain simulation of DS-CDMA communication systems

    OpenAIRE

    Armisén Morell, Albert

    2010-01-01

    Català: En aquest projecte s'ha analitzat e implementat un sistema basat amb DSSS-CDMA amb un receptor comú y diversos transmissors sobre una plataforma modular en Matlab, essent aquesta una eina de validació teòrica. S'ha primat aquesta per sobre d'una implementació en DSP principalment pel cost ecònomic de les plaques DSP. Així, s'ha decidit fer una implementació en Matlab amb les restriccions pròpies d'una placa DSP. El principal objectiu del projecte es la validació del sistema mitjançant...

  5. Performance of Turbo Interference Cancellation Receivers in Space-Time Block Coded DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Emmanuel Oluremi Bejide

    2008-07-01

    Full Text Available We investigate the performance of turbo interference cancellation receivers in the space time block coded (STBC direct-sequence code division multiple access (DS-CDMA system. Depending on the concatenation scheme used, we divide these receivers into the partitioned approach (PA and the iterative approach (IA receivers. The performance of both the PA and IA receivers is evaluated in Rayleigh fading channels for the uplink scenario. Numerical results show that the MMSE front-end turbo space-time iterative approach receiver (IA effectively combats the mixture of MAI and intersymbol interference (ISI. To further investigate the possible achievable data rates in the turbo interference cancellation receivers, we introduce the puncturing of the turbo code through the use of rate compatible punctured turbo codes (RCPTCs. Simulation results suggest that combining interference cancellation, turbo decoding, STBC, and RCPTC can significantly improve the achievable data rates for a synchronous DS-CDMA system for the uplink in Rayleigh flat fading channels.

  6. Bounds for the Sum Capacity of Binary CDMA Systems in Presence of Near-Far Effect

    CERN Document Server

    Pad, P; Mansouri, S M; Kabir, P; Marvasti, F

    2010-01-01

    In this paper we are going to estimate the sum capacity of a binary CDMA system in presence of the near-far effect. We model the near-far effect as a random variable that is multiplied by the users binary data before entering the noisy channel. We will find a lower bound and a conjectured upper bound for the sum capacity in this situation. All the derivations are in the asymptotic case. Simulations show that especially the lower bound is very tight for typical values Eb/N0 and near-far effect. Also, we exploit our idea in conjunction with the Tanaka's formula [6] which also estimates the sum capacity of binary CDMA systems with perfect power control.

  7. Coding Across Multicodes and Time in CDMA Systems Employing MMSE Multiuser Detector

    Directory of Open Access Journals (Sweden)

    Park Jeongsoon

    2004-01-01

    Full Text Available When combining a multicode CDMA system with convolutional coding, two methods have been considered in the literature. In one method, coding is across time in each multicode channel while in the other the coding is across both multicodes and time. In this paper, a performance/complexity analysis of decoding metrics and trellis structures for the two schemes is carried out. It is shown that the latter scheme can exploit the multicode diversity inherent in convolutionally coded direct sequence code division multiple access (DS-CDMA systems which employ minimum mean squared error (MMSE multiuser detectors. In particular, when the MMSE detector provides sufficiently different signal-to-interference ratios (SIRs for the multicode channels, coding across multicodes and time can obtain significant performance gain over coding across time, with nearly the same decoding complexity.

  8. A NEW DESIGN METHOD OF CDMA SPREADING CODES BASED ON MULTI-RATE UNITARY FILTER BANK

    Institute of Scientific and Technical Information of China (English)

    Bi Jianxin; Wang Yingmin; Yi Kechu

    2001-01-01

    It is well-known that the multi-valued CDMA spreading codes can be designed by means of a pair of mirror multi-rate filter banks based on some optimizing criterion. This paper indicates that there exists a theoretical bound in the performance of its circulating correlation property, which is given by an explicit expression. Based on this analysis, a criterion of maximizing entropy is proposed to design such codes. Computer simulation result suggests that the resulted codes outperform the conventional binary balanced Gold codes for an asynchronous CDMA system.

  9. Coherent Code Tracking for Spatial Transmit Diversity DS-CDMA Systems

    OpenAIRE

    Stewart, R. W.; Iain G. Stirling; Garrey W. Rice

    2005-01-01

    Spatial transmit diversity schemes are now well integrated into third-generation cellular mobile communication system specifications. When DS-CDMA-based technology is deployed in typical macro- and microcell environments, multipath diversity and spatial diversity may be exploited simultaneously by a 2D RAKE receiver. The work presented in this paper focuses on taking advantage of spatial transmit diversity in synchronising the 2D RAKE structure. We investigate the use of coherent and noncoher...

  10. Semi-hard interference cancellation for uncoded DS-CDMA systems

    OpenAIRE

    Kasparis, C; Piechocki, RJ; Nix, AR; Fletcher, PN

    2004-01-01

    A new iterative technique for suppressing multiuser interference in uncoded DS-CDMA systems is proposed. In the new approach semi-hard decisions are taken at the output of the linear MMSE detector. This involves taking hard decisions only for symbols which satisfy a reliability criterion, while the rest are left unaltered in their soft form. The semi-hard estimate is subsequently used for parallel interference cancellation, which is then followed by additional linear MMSE filtering. This proc...

  11. 基于CDMA的移动学系统%Mobile Learning System Over CDMA

    Institute of Scientific and Technical Information of China (English)

    郑明秀

    2003-01-01

    本文构建的以CDMA为承载基础的基于连接的移动学习系统MLSC(Mobile Learning System over CDMA),采取若干策略将现有的固定远程学习系统转换到移动环境中而形成移动学习系统.

  12. Two Schemes of Blind MMSE Multiuser Receiver for Space-Time Coded CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    LU Min; XU Chang-jiang; FENG Guang-zeng

    2004-01-01

    Minimum Mean Square Error (MMSE) multiuser detection yields the highest output SINR among all linear detectors. The blind MMSE linear detector can be implemented with batch processes or sequential processes. In this paper, according to the different implementations of blind detectors, the authors analyze two schemes of the blind MMSE multiuser receiver for space-time coded CDMA Systems and make a comparison between both schemes by the theoretical analysis and numerical simulations.

  13. Improved Space-Time Selective Interference Cancellation Scheme for CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    戎璐; 谢剑英; 支小莉

    2003-01-01

    Space-time selective parallel interference cancellation(ST-SPIC) is a computationally effective approach combining multiuser detection (MUD) with antenna array technology for CDMA systems. The exploitation of signal reliability is a key issue in ST-SPIC. In order to improve the reliability estimation, a pair of reliability thresholds are introduced. Then an improved selective interference cancellation algorithm is proposed to exploit the reliability accordingly. More practical space-time processing algorithms are also incorporated in the proposed ST-SPIC scheme to overcome the limitation caused by some idealised assumptions taken in the original ST-SPIC scheme. Numerical results show that the proposed ST-SPIC scheme outperforms its traditional counterpart in a CDMA microcell environment.

  14. JOINT SPACE-FREQUENCY MULTIUSER SYMBOL DETECTOR FOR MC-CDMA SYSTEM WITH UNIFORM LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    Wu Xiaojun; Yin Qinye; Feng Aigang; Zhao Zheng; Zhang Jianguo

    2002-01-01

    The MultiCarrier Code Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence (DS-) CDMA systems due to serious InterChip Interference (ICI) and MultiUser Interference (MUI) in high-data-rate wireless communication systems. In this paper, the Uniform Linear Array (ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment. A joint space-frequency multiuser symbol sequence detector is developed for all active users within one macrocell without space-frequency channel estimation. Simultaneously, Directions-Of-Arrivals (DOAs) of all active users can also be estimated. By dividing the ULA into two identical overlapping subarrays, a specific auxiliary matrix is constructed, which includes both symbol sequence and DOA information of all active users. Then, based on the subspace method, performing the eigen decomposition on such auxiliary matrix, the closed-form solution of symbol sequences and DOAs for all active users can be obtained. In comparison with schemes based on channel estimation, our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity. Extensive computer simulations demonstrate the overall performance of this novel scheme.

  15. JOINT SPACE-FREQUENCY MULTIUSER SYMBOL DETECTOR FOR MC-CDMA SYSTEM WITH UNIFORM LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The MultiCarrier COde Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence(DS-CDMA systems due to serious InterCip Interference(ICI) and MultiUser Interference(MUI)in high-data-rate wireless communication systems.In this paper the Uniform Linear Array(ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment.A joint space-frequency multiuser symblo sequence detector is developed for all active users within one macrocell without space-frequency channel estimation.Simultaneously,Directions-of -Arrivals (ODAs)of all active users can also be estimated.By dividing the ULA into two identical overlapping subarrays,a specific auxiliary matrix is constructed,which includes both symbol sequence and DOA information of all active users,Then,based on the subspace method,performing the eigen decomposition on such auxiliary matrix,the closed-form solution of symbol sequences and DOAs for all active users can be obtained.In comparison with schemes based on channel estimation,our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity,Extensive computer simulations demonstrate the overall performance of this novel scheme.

  16. Time Delay Tracking for Multiuser Synchronization in CDMA Networks

    Directory of Open Access Journals (Sweden)

    Zahid Ali

    2013-09-01

    Full Text Available Multipath propagation, multiple access interference and non-line of sight propagation, etc. have impeded the accuracy in mobile data measurements. Multiuser receivers in asynchronous Code Division Multiple Access (CDMA systems require the knowledge of several parameters such as timing delay between users. In this paper, the problem of time delay estimation for CDMA systems is examined by proposing an approach based on blind nonlinear least mean squares (LMS based early-late delay tracker. A system model is developed and a delay tracking algorithm is presented. The simulation results of the proposed delay tracker are compared with the classical delay-locked loop (DLL approach in a multipath scenario and these show that the proposed delay tracker provides very good performance in challenging cases of closely spaced multipath delays.

  17. Adaptive digital beamforming for a CDMA mobile communications payload

    Science.gov (United States)

    Munoz-Garcia, Samuel G.; Ruiz, Javier Benedicto

    1993-01-01

    In recent years, Spread-Spectrum Code Division Multiple Access (CDMA) has become a very popular access scheme for mobile communications due to a variety of reasons: excellent performance in multipath environments, high scope for frequency reuse, graceful degradation near saturation, etc. In this way, a CDMA system can support simultaneous digital communication among a large community of relatively uncoordinated users sharing a given frequency band. Nevertheless, there are also important problems associated with the use of CDMA. First, in a conventional CDMA scheme, the signature sequences of asynchronous users are not orthogonal and, as the number of active users increases, the self-noise generated by the mutual interference between users considerably degrades the performance, particularly in the return link. Furthermore, when there is a large disparity in received powers - due to differences in slant range or atmospheric attenuation - the non-zero cross-correlation between the signals gives rise to the so-called near-far problem. This leads to an inefficient utilization of the satellite resources and, consequently, to a drastic reduction in capacity. Several techniques were proposed to overcome this problem, such as Synchronized CDMA - in which the signature sequences of the different users are quasi-orthogonal - and power control. At the expense of increased network complexity and user coordination, these techniques enable the system capacity to be restored by equitably sharing the satellite resources among the users. An alternative solution is presented based upon the use of time-reference adaptive digital beamforming on board the satellite. This technique enables a high number of independently steered beams to be generated from a single phased array antenna, which automatically track the desired user signal and null the unwanted interference source. In order to use a time-reference adaptive antenna in a communications system, the main challenge is to obtain a

  18. HOT SPOT RELIEF WITH EMBEDDED BEAM FOR CDMA SYSTEMS IN HAPS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper proposes a novel micro/macro beam coverage scheme used in High Altitude Platform System (HAPS) Code Division Multiple Access (CDMA) systems. A relief of traffic burden in hot spot areas is achieved by embedding micro-beams into the macro-beams at the hot spot locations, together with appropriate power ratio control and user ratio control. The simulation results show that the hot spot problem can be relieved efficiently with the presented configuration, and a higher and more stable system capacity is expectable despite the variation of user distribution.

  19. RF and ELF Exposures from Cellular Phone Handsets: TDMA and CDMA Systems (invited paper)

    International Nuclear Information System (INIS)

    The future digital systems for personal communications have now been partially standardised, so it is possible to get a good idea of the exposure power levels and time variation of the power, which may be assumed to be the two biologically relevant parameters. Using GSM and the coming UMTS system the relevant details are discussed, where the main difference is between the highly periodic TDMA (Time Division Multiple Access) power variation and the more smooth, slowly varying CDMA signal (Code Division Multiple Access). Epidemiological and biological studies must reflect the intricate details of the various systems. (author)

  20. Forward-Link Performance Analysis in CDMA Distributed Antenna Systems with Imperfect Channel Estimation

    Institute of Scientific and Technical Information of China (English)

    CHEN Peng; WU Wei-ling

    2005-01-01

    The impact of imperfect channel estimation on the forward-link performance in CDMA distributed antenna systems in multi-path fading environment is investigated.A detailed analytical model based on a hybrid signal combining method is presented and exact outage probability expression is derived.The investigation shows that the effect of imperfect channel estimates varies with system load.Furthermore,if simulcasting is employed,macro-diversity can decrease the sensitivity of forward-link to channel estimation errors and increase the forward-link outage performance,which is contrary to the conclusion drawn based on the ideal channel estimation assumption.

  1. On the analysis of peak-to-average ratio (PAR) for IS95 and CDMA2000 systems

    OpenAIRE

    Lau, VKN

    2000-01-01

    Peak-to-average ratio (PAR) of a signal is an important parameter to a linear amplifier because it determines the backoff factor needed to be applied to the amplifier in order to avoid clipping and hence spectral regrowth. In this paper, we analyzed the PAR of the downlink direct code-division multiple-access (DS-CDMA) signal for the IS-95 (2G) and the CDMA2000 (3G) systems. Both the single-carrier (SC) and the multi-carrier (MC) situations are considered. For MC systems, an analytical model ...

  2. NEW LSCM BLIND MULTIUSER DETECTION ALGORITHM FOR ANTENNA ARRAY CDMA SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Two blind multiuser detection algorithms for antenna array in Code Division Multiple Access (CDMA) system which apply the linearly constrained condition to the Least Squares Constant Modulus Algorithm (LSCMA) are proposed in this paper. One is the Linearly Constrained LSCMA (LC-LSCMA), the other is the Preprocessing LC-LSCMA (PLC-LSCMA). The two algorithms are compared with the conventional LSCMA. The results show that the two algorithms proposed in this paper are superior to the conventional LSCMA and the best one is PLC-LSCMA.

  3. Improved DOA Estimation Algorithm with Sensor Array Perturbations for CDMA System

    Institute of Scientific and Technical Information of China (English)

    杨维; 程时昕

    2003-01-01

    An improved direction of arrival (DOA) estimation algorithm with sensor gain and phase uncertainties for synchronous code division multiple access(CDMA) system with decorrelator is presented. Through decorrelating processing DOAs of the desired users can be estimated independently and all other resolved signal interferences are eliminated. Emphasis is directed to applications in which sensor gain and phase are perturbed that often happen actually. It is shown that improved DOA estimation can be achieved for decoupled signals by gain and phase pre-estimation procedures.

  4. NEW BINARY USER CODES FOR DS CDMA COMMUNICATION

    Directory of Open Access Journals (Sweden)

    NEELAM SRIVASTAVA

    2011-12-01

    Full Text Available Spread spectrum (SS is a modulation technique in which the signal occupies a bandwidth much larger than the minimum necessary to send the information. A synchronized reception with the code at the receiver is used for despreading the information before data recovery. From a long period, Walsh codes and Gold codes have been used as spread spectrum codes in Code Division Multiple Access (CDMA communications because of their ease of generation than the efficiency of these codes. Walsh codes are perfectly orthogonal binary user codes that have many popular applications in synchronous multicarrier communications although they perform poorly for asynchronous multi-user communications. Therefore, the nearly orthogonal Gold codes with their superior performance are the preferred user codes in asynchronous CDMA communications with small number of simultaneous users in the system due to their good auto-correlation (intracode correlation and cross-correlation (inter-code properties. Major drawback of these codes is that they are limited in number and in their lengths. In this paper, we performed MATLAB (7.1version algorithm to obtain the new orthogonal sets of binary space for multiuser spread-spectrum communications. We compared their performance with existing codes like Gold and Walsh code families. Our comparisons include their time domain properties like auto and cross-correlations along with bit error rate (BER performances in additive white Gaussian noise (AWGN and Rayleigh channel for the synchronous and asynchronous DS-CDMA communications. It is shown that these codes outperform the Walsh codes significantly and they match in performance with the popular nearly orthogonal Gold codes closely for asynchronous multiuser communications in AWGN noise. It is also shown that all of the binary code families considered performed comparable for Rayleigh flat-fading channels. So these new codes can be used both for asynchronous and synchronous direct sequence

  5. Average of peak-to-average ratio (PAR) of IS95 and CDMA2000 systems-single carrier

    OpenAIRE

    Lau, VKN

    2001-01-01

    Peak-to-average ratio (PAR) of a signal is an important parameter. It determines the input backoff factor of the amplifier to avoid clipping and spectral regrowth. We analyze and compose the PAR of the downlink signal for IS95 and the CDMA2000 single-carrier systems. It is found that the PAR of the transmitted signal depends on the Walsh code assignment. Furthermore, we found that the PAR of CDMA2000 signal is always lower than the IS95 signal. Finally, PAR control by Walsh code selection is ...

  6. PV-solar / wind hybrid energy system for GSM/CDMA type mobile telephony base station

    Directory of Open Access Journals (Sweden)

    Pragya Nema, R.K. Nema, Saroj Rangnekar

    2010-03-01

    Full Text Available This paper gives the design idea of optimized PV-Solar and Wind Hybrid Energy System for GSM/CDMA type mobile base station over conventional diesel generator for a particular site in central India (Bhopal . For this hybrid system ,the meteorological data of Solar Insolation, hourly wind speed, are taken for Bhopal-Central India (Longitude 77o.23'and Latitude 23o.21' and the pattern of load consumption of mobile base station are studied and suitably modeled for optimization of the hybrid energy system using HOMER software. The simulation and optimization result gives the best optimized sizing of wind turbine and solar array with diesel generator for particular GSM/CDMA type mobile telephony base station. This system is more cost effective and environmental friendly over the conventional diesel generator. It should reduced approximate 70%-80% fuel cost over conventional diesel generator and also reduced the emission of CO2 and other harmful gasses in environments. It is expected that the newly developed and installed system will provide very good opportunities for telecom sector in near future.

  7. Asynchronous Cooperative e-Learning System and Its Evaluation

    Science.gov (United States)

    Eto, Kazuhiro; Miyoshi, Takumi

    Much attention has been attracted to collaborative learning on an e-learning system. However, it is difficult to implement the collaborative environment to an asynchronous e-learning system since collaboration would be realized only when learners join the system at the same time. On the other hand, cooperative learning has been proposed. In this method, learners can study on their own pace without making mutual agreement but with receiving cognitive information from others. In this paper, the authors have developed the asynchronous cooperative e-learning system that provides learners' attendance and studying progress as the cognitive information. The subjective evaluation experiments show that our system is slightly inferior to the synchronous collaborative e-learning system, but it can motivate the learners more than the conventional system.

  8. Theoretical analysis and simulation of a code division multiple access system (cdma for secure signal transmission in wideband channels

    Directory of Open Access Journals (Sweden)

    Stevan M. Berber

    2014-06-01

    Full Text Available Chaotic spreading sequences can increase secrecy and resistance to interception in signal transmission. Chaos-based CDMA systems have been well investigated in the case of flat fading and noise presence in the channel. However, these systems operating in wideband channels, characterized by the frequency selective fading and white Gaussian noise, have not been investigated to the level of understanding their practical applications. This paper presents a detailed mathematical model of a CDMA system based on chaotic spreading sequences. In a theoretical analysis, all signals are represented in the discrete time domain. Using the theory of discrete time stochastic processes, the probability of error expressions are derived in a closed form for a multi-user chaos based CDMA system. For the sake of comparison, the expressions for the probability of error are derived separately for narrowband and wideband channels. The application of the system interleaving technique is investigated in particular, which showed that this technique can substantially improve probability of error in the system.  The system is simulated and the findings of the simulation confirmed theoretically expected results. Possible improvements in the probability of bit error due to multipath channel nature, with and without interleavers, are quantified depending on the random delay and the number of users in the system. In the analyzed system, a simplified version of the wideband channel model, proposed for modern wideband wireless networks, is used. Introduction Over the past years, the demand for wireless communications has increased substantially due to advancements in mobile communication systems and networks. Following these increasing demands, modern communication systems require the ability to handle a large number of users to process and transmit wideband signals through complex frequency selective channels. One of the techniques for transmission of multi-user signals is the

  9. New theoretical framework for OFDM/CDMA systems with peak-limited nonlinearities

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new theoretical framework for the evaluation of the in-band nonlinear distortion effects on the performance of OFDM systems is presented. In contrast to previous works that approximate the nonlinear noise as a Gaussian additive random process, the new framework is based on the properties of the large deviations of a stationary Gaussian process and shot noise theories, which can evaluate the performance of the OFDM system with high accuracy, especially at realistic scenarios where the Gaussian approximation of the nonlinear noise is no longer valid. The approach can be used to evaluate many communication systems with peak-limited nonlinearities and high PAPR, such as the downlink performance analysis of large capacity DS-CDMA systems.

  10. Improved Iterative Parallel Interference Cancellation Receiver for Future Wireless DS-CDMA Systems

    Science.gov (United States)

    Morosi, Simone; Fantacci, Romano; Bernacchioni, Andrea

    2005-12-01

    We present a new turbo multiuser detector for turbo-coded direct sequence code division multiple access (DS-CDMA) systems. The proposed detector is based on the utilization of a parallel interference cancellation (PIC) and a bank of turbo decoders. The PIC is broken up in order to perform interference cancellation after each constituent decoder of the turbo decoding scheme. Moreover, in the paper we propose a new enhanced algorithm that provides a more accurate estimation of the signal-to-noise-plus-interference-ratio used in the tentative decision device and in the MAP decoding algorithm. The performance of the proposed receiver is evaluated by means of computer simulations for medium to very high system loads, in AWGN and multipath fading channel, and compared to recently proposed interference cancellation-based iterative MUD, by taking into account the number of iterations and the complexity involved. We will see that the proposed receiver outperforms the others especially for highly loaded systems.

  11. Study on Cell Error Rate of a Satellite ATM System Based on CDMA

    Institute of Scientific and Technical Information of China (English)

    赵彤宇; 张乃通

    2003-01-01

    In this paper, the cell error rate (CER) of a CDMA-based satellite ATM system is analyzed. Two fading models, i.e. the partial fading model and the total fading model are presented according to multi-path propagation fading and shadow effect. Based on the total shadow model, the relation of CER vs. the number of subscribers at various elevations under 2D-RAKE receiving and non-diversity receiving is got. The impact on cell error rate with pseudo noise (PN) code length is also considered. The result that the maximum likelihood combination of multi-path signal would not improve the system performance when multiple access interference (MAI) is small, on the contrary the performance may be even worse is abtained.

  12. Performance Analysis of CDMA WLL Systems with Imperfect Power Control and Imperfect Sectorization

    Directory of Open Access Journals (Sweden)

    Sami A. El-Dolil

    2008-01-01

    Full Text Available Wireless local loop (WLL provides reliable, flexible, and economical access to the local telephone service using radio technology in the place of traditional wireline. In this paper, an analytical model is derived to evaluate the effect of both imperfect power control and imperfect sectorization on the performance of code division multiple access (CDMA WLL systems. The results show that the capacity degradation, due to imperfect power control, is about 25.8% and 11.5% for single cell and multiple cell systems, respectively. Increasing the overlapping angle from 0∘ to 5∘ causes the capacity gain to decrease from 6 to 5.53, while the corresponding sectorization efficiency drops from 100% to 92.3%.

  13. A Unified Approach to Energy-Efficient Power Control in Large CDMA Systems

    CERN Document Server

    Meshkati, Farhad; Poor, H Vincent; Schwartz, Stuart C

    2007-01-01

    A unified approach to energy-efficient power control is proposed for code-division multiple access (CDMA) networks. The approach is applicable to a large family of multiuser receivers including the matched filter, the decorrelator, the linear minimum mean-square error (MMSE) receiver, and the (nonlinear) optimal detectors. It exploits the linear relationship that has been shown to exist between the transmit power and the output signal-to-interference-plus-noise ratio (SIR) in the large-system limit. It is shown that, for this family of receivers, when users seek to selfishly maximize their own energy efficiency, the Nash equilibrium is SIR-balanced. In addition, a unified power control (UPC) algorithm for reaching the Nash equilibrium is proposed. The algorithm adjusts the user's transmit powers by iteratively computing the large-system multiuser efficiency, which is independent of instantaneous spreading sequences. The convergence of the algorithm is proved for the matched filter, the decorrelator, and the M...

  14. NOVEL MULTIMEDIA TRAFFIC MODELING BASED CAC SCHEME FOR CDMA COMMUNICATION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Zhang Dandan; Fang Xuming; Zhu Longjie

    2007-01-01

    As the radio spectrum is a very scarce resource, the Call Admission Control (CAC) is one of the most important parts in radio resource management. The Code Division Multiple Access (CDMA)based next generation wireless communications systems will support the transmission of multimedia traffic, such as voice, video and data, thus the CAC, which can support the multimedia traffic and guarantee the Quality of Service (QoS) of different traffic, has gained broad attention. In this paper, a novel multimedia traffic modeling method and a corresponding dynamic QoS based CAC are proposed.The analysis and simulation results show that the proposed CAC scheme can guarantee the QoS to different traffic demand, and improve the system performance significantly.

  15. Cross-Layer Design and Analysis of Downlink Communications in Cellular CDMA Systems

    Directory of Open Access Journals (Sweden)

    Sun Jin Yuan

    2006-01-01

    Full Text Available A cellular CDMA network with voice and data communications is considered. Focusing on the downlink direction, we seek for the overall performance improvement which can be achieved by cross-layer analysis and design, taking physical layer, link layer, network layer, and transport layer into account. We are concerned with the role of each single layer as well as the interaction among layers, and propose algorithms/schemes accordingly to improve the system performance. These proposals include adaptive scheduling for link layer, priority-based handoff strategy for network admission control, and an algorithm for the avoidance of TCP spurious timeouts at the transport layer. Numerical results show the performance gain of each proposed scheme over independent performance of an individual layer in the wireless mobile network. We conclude that the system performance in terms of capacity, throughput, dropping probability, outage, power efficiency, delay, and fairness can be enhanced by jointly considering the interactions across layers.

  16. Blind Uplink Channel Estimator and Mean-Squared Error Analysis for Very High Data-Rate Modified MC-CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    WUXiaojun; YINQinye; ZENGMing; LIXing; WANGJilong

    2004-01-01

    In very high data-rate wireless application scenarios, Multicarrier code-division multiple access (MC-CDMA) systems including Serial-to-parallel (S/P) converting operation are more applicable. We name them as modified MC-CDMA systems. In this paper, we focus on the blind channel estimation problem of these modified MC-CDMA systems on uplink. Because we can regard each subcarrier in multicarrier communications as a channel, the modified MC-CDMA system accordingly can become a multichannel system. Upon this understanding, we model the multiuser modified MC-CDMA system as a Multiple-input multiple-output (MIMO) system. Successively, based on subspace decomposition technique, we derive a novel blind estimation scheme of uplink channels for multiuser modified MC-CDMA systems. Furthermore, based on perturbation techniques, we derive the analytical approximation of the Mean-squared error (MSE) of this blind channel estimation scheme. Extensive computer simulations illustrate the performance of the proposed algorithm, and simulation results also verify the tightness of the MSE approximation.

  17. Performance of Multicarrier CDMA Rake System over Rayleigh Fading Channel

    Institute of Scientific and Technical Information of China (English)

    SONG Li-xin; HUANG Tian-shu; DING Yao-ming

    2005-01-01

    Based on the theory of multicarrier (MC) technique and the Rake receiver, a multicarrier DSCDMA Rake system is proposed, where a data sequence multiplied by a spreading sequence modulates multiple carriers. The receiver provides a Rake for each subcarrier, and the outputs of the Rakes are combined by a maximal-ratio combiner. The average probability of error of the system is derived from an uncorrelated subcarrier and frequency-selective fading channel model. The system performances are evaluated over Rayleigh fading channel with an exponential multipath intensity profile(MIP) and with a rectangular MIP, respectively,when multipath interference is present. It is found that this kind of model has larger superiority in an exponential MIP than in a rectangular MIP.

  18. Paper on Maximizing the Throughput for MIMO OFDM-CDMA Systems by Evaluating Space Time Frequency Spreading

    Directory of Open Access Journals (Sweden)

    Dr. Sandip Nemade

    2013-09-01

    Full Text Available The main goal is to access the appropriateness of OFDM as a modulation technique for a fixed wireless phone system. Several of the main factors affecting the performance of a OFDM system, were measured including multipath delay spread, channel noise, distortion of the signal (clipping, and timing requirements. This paper focuses on how MIMO OFDM-CDMA systems are capable of achieving diversity gains significantly larger than that of the day to day system

  19. BER Performance for Downlink MC-CDMA Systems over Rician Fading Channels

    Directory of Open Access Journals (Sweden)

    Vimal K. Dubey

    2005-04-01

    Full Text Available We consider downlink multicarrier code-division multiple-access (MC-CDMA systems using binary phase-shift keying (BPSK modulation scheme and maximal ratio combining (MRC in frequency-selective Rician fading channels. A time-domain method to obtain bit error rate (BER by calculating moment generating function (MGF of the decision variable for a tapped-delay-line channel model is proposed. This method does not require any assumption regarding the statistical or spectral distribution of multiple access interference (MAI, and it is also not necessary to assume that the fading encountered by the subcarriers is independent of each other. The analytical formula is also verified by simulations.

  20. Multiuser detection for DS-CDMA systems in non-Gaussian channels

    Institute of Scientific and Technical Information of China (English)

    ZHAO Ying; ZHENG Jun-li

    2006-01-01

    An adaptive multi-user detector was developed for direct-sequence code division multiple access (DS-CDMA) systems corrupted by non-Gaussian channel noise,which can be quite detrimental to the performance of the multi-user detectors based on classical white Gaussian assumption.This receiver simultaneously combats multiple-access interference (MAI) and non-Gaussian impulsive noise.The channel parameters are estimated and transmitted signals are jointly detected by a simple recursive algorithm derived from the EM/SAGE algorithm.Analytical and simulation results show that the proposed technique is robust with wider applicability than conventional multi-user detectors in terms of near-far resistance and bit-error ratio (BER) when either MAI or non-Gaussian impulsive noise is dominant.

  1. Coherent Code Tracking for Spatial Transmit Diversity DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    R. W. Stewart

    2005-09-01

    Full Text Available Spatial transmit diversity schemes are now well integrated into third-generation cellular mobile communication system specifications. When DS-CDMA-based technology is deployed in typical macro- and microcell environments, multipath diversity and spatial diversity may be exploited simultaneously by a 2D RAKE receiver. The work presented in this paper focuses on taking advantage of spatial transmit diversity in synchronising the 2D RAKE structure. We investigate the use of coherent and noncoherent techniques for tracking the timing parameters of each multipath component. It is shown that both noncoherent and coherent techniques benefit from transmit diversity. Additionally the performance gap between these two techniques increases with the number of antennas.

  2. Joint Angle and Delay Estimation (JADE) in Antenna Array CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The estimate of signals parameters is very important in wireless communications. In this paper, we combine subspace-based blind channel estimation algorithm with the extension of the JADE-WSF algorithm to jointly estimate the Angles-of-Arrival (AOAs) and delays of multipath signals arriving at an antenna array in Code Division Multiple Access (CDMA) systems. Our approach uses a collection of estimates of a consistent chip-sample of space-time vector channel. The channel estimates are assumed to have constant path AOA and delay over a finite number of symbols. Unlike the traditional MUltiple SIgnal Classification (MUSIC) and Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) algorithms for the estimation of signals parameters, the proposed method can work when the number of paths exceeds the number of antennas. The Cramer-Rao Bound (CRB) and simulations are provided.

  3. A new method to estimate DOA in CDMA system in multi-path environment

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An algorithm for direction angle of arrival(DOA) estimation and array calibration of signals from multiple mobile users in the CDMA systems and multi-path environment was presented . The main idea is that the algorithm employs code-matched filter and model of the inter-symbol interference and multiple-access interference exactly. The correlation matrices of the received signals before and after code-matched filtering were employed to eliminate the effect of the additive white Gaussian noise, and a new mathematical problem was created, a new maximum likelihood method based on the strong law of large number was derived for DOA estimation and array calibration.Computer simulation results prove that the algorithm is effective.

  4. ADAPTIVE STEP-SIZE CONSTANT MODULUS ALGORITHM FOR BLIND MULTIUSER DETECTION IN DS-CDMA SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Sun Liping; Hu Guangrui

    2004-01-01

    Blind Adaptive Step-size Constant Modulus Algorithm (AS-CMA) for multiuser detection in DS-CDMA systems is presented. It combines the CMA and the concept of variable step-size, uses a second LMS algorithm for the step size. It adjusts the step-size according to the minimum output-energy principle within a specified range, thus overcomes the problems of bad effect of fixed step-size LMS algorithm. Compared with Adaptive Step-size LMS (AS-LMS) algorithm, through simulations, this algorithm can adapt the changes of the environment, suppress multiple access interference in the dynamic environment and the stability of Signal to Interference Ratio (SIR) is superior to that of AS-LMS.

  5. A Difference Method of the Gravity Center with Double Pilots for the MC-CDMA System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A carrier recovery method of the power spectrum center difference adapting to the mobile channel of the MC-CDMA system with serious Doppler shift using double pilots is presented. In the transmitter, two pilots of equal frequency distance to the carrier with one putting on the left position and the other on the right position of the carrier frequency are used. Even if a continuous sine wave is transmitted, the power spectrum is expanded to a Doppler band in the receiver owing to the multi-path transmission and the Doppler shift. The pilot spectrum is made to pass through two narrow band filters which are transformed to the base band with local carrier wave in the receiver. The frequency difference between the local carrier and the transmitter carrier is obtained when the difference of the gravity centers of the two pilot spectra is computed.

  6. Efficient Smart Antenna Systems (4G) For CDMA Wireless Communication

    OpenAIRE

    Singla, Brahm Mohinder; Kumar, Ashish

    2012-01-01

    Today, mobile communications play a central role in the voice/data network arena. With the deployment of mass scale 3G just around the corner, new directions are already being researched. In this paper we address about the 4TH G mobile communications.The Fourth Generation (4G) Mobile Communications should not focus only on the data-rate increase and new air interface.4G Mobile should instead con-verge the advanced wireless mobile communications and high-speed wireless access systems into an O...

  7. Arithmetic Operations and Factorization using Asynchronous P Systems

    Directory of Open Access Journals (Sweden)

    Takayuki Murakawa

    2012-07-01

    Full Text Available

    In the present paper, we consider the asynchronous parallelism in membrane computing, and propose asynchronous P systems that perform two basic arithmetic operations and factorization. Since there is no restrictive assumption for application of rules, sequential and maximal parallel executions are allowed on the asynchronous P system.

    We first propose a P system that computes addition of two binary numbers of m bits.  The P system works in O(m sequential and parallel steps using O(m types of objects. We next propose a P system for multiplication of the two binary numbers of m bits, and show that the P system works in O(m log m parallel steps or O(m3 sequential steps using O(m2 types of objects. Finally, we propose a P system for factorization of a positive integer of $m$ bits using the above P system as a sub-system. The P system computes the factorization in O(m log m parallel steps or O(4m 

  8. Experience with synchronous and asynchronous digital control systems

    Science.gov (United States)

    Regenie, V. A.; Chacon, C. V.; Lock, W. P.

    1986-01-01

    Flight control systems have undergone a revolution since the days of simple mechanical linkages; presently the most advanced systems are full-authority, full-time digital systems controlling unstable aircraft. With the use of advanced control systems, the aerodynamic design can incorporate features that allow greater performance and fuel savings, as can be seen on the new Airbus design and advanced tactical fighter concepts. These advanced aircraft will be and are relying on the flight control system to provide the stability and handling qualities required for safe flight and to allow the pilot to control the aircraft. Various design philosophies have been proposed and followed to investigate system architectures for these advanced flight control systems. One major area of discussion is whether a multichannel digital control system should be synchronous or asynchronous. This paper addressed the flight experience at the Dryden Flight Research Facility of NASA's Ames Research Center with both synchronous and asynchronous digital flight control systems. Four different flight control systems are evaluated against criteria such as software reliability, cost increases, and schedule delays.

  9. XZ And a semidetached asynchronous binary system

    Science.gov (United States)

    Manzoori, Davood

    2016-05-01

    In this work the light curves (LCs) solutions along with the radial velocity curve of the semidetached binary systemXZ And are presented using the PHOEBE program(ver 0.31a). Absolute parameters of the stellar components were then determined, enabling us to discuss structure and evolutionary status of the system. The analysis indicates that the primary is a non-synchronous (i.e., F1 = 3.50 ± 0.01) Main Sequence (MS) star and the secondary is a bit more evolved, and fills its Roche critical surface. In addition, times of minima data (" O - C curve") were analyzed. Apart from an almost parabolic variation in the general trend of O - C data, which was attributed to a mass transfer from the secondary with the rate ˙2 = (9.52 ± 0.41) × 10-10 M ⊙ yr-1; two cyclic variations with mean periods of 34.8 ± 2.4 and 23.3 ± 3.0 yr, modulating the orbital period, were found, which were attributed to a third body orbiting around the system, and magnetic activity cycle effect, respectively.

  10. THE STUDY OF AN M-ARY MC-CDMA SYSTEM BASED ON CYCLIC SPREADING CODES & PRE-EQUALIZATION

    Institute of Scientific and Technical Information of China (English)

    Chu Zhenyong; Ying Xiaofan; Yi Kechu; Tian Hongxin

    2005-01-01

    A novel fast despreading scheme for M-ary Multi-Carrier Code-Division Multiple Access (MC-CDMA) system is proposed based on cyclic spreading codes and pre-equalizer. In the transmitter, the M spreading codes of each user are generated by circularly shifting the prototype spreading code. A feedback pre-equalizer is employed to process the M-ary MCCDMA signal before transmitted. The received signal is multiplied by the Inverse Discrete Fourier Transform (IDFT) result of the mirror image code of the prototype spreading code, and then demodulated by Orthogonal Frequency-Division Multiplexing (OFDM) demodulator. Compared with the conventional M-ary MC-CDMA receiver, the proposed scheme increases bandwidth efficiency, meanwhile, it achieves M-ary despread spectrum and multi-carrier demodulation, which reduces computation complexity remarkably.

  11. Multi-channel blind deconvolution algorithm for multiple-input multiple-output DS/CDMA system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Direct sequence spread spectrum transmission can be realized at low SNR,and has low probability of detection.It is aly problem how to obtain the original users'signal in a non-cooperative context.In practicality,the DS/CDMA sources received are linear convolute mixing.A more complex multichannel blind deconvolution MBD algorithm is required to achieve better source separation.An improved MBD algorithm for separating linear convolved mixtures of signals in CDMA system is proposed.This algorithm is based on minimizing the average squared cross-output-channel-correlation.The mixture coefficients are totally unknown.while some knowledge about temporal model exists.Results show that the proposed algorithm Can bring about the exactness and low computational complexity.

  12. ANALYSIS OF A CUMULANT-BASED 2D-RAKE RECEIVER FOR CDMA SYSTEM OVER FREQUENCY-SELECTIVE FADING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    杨维; 程时昕

    2003-01-01

    The conventional 2D-Rake receivers for code-division multiple access (CDMA) system over frequency-selective fading channels are generally based on the second-order statistics while assuming perfect array conditions. However, the sensor response, location uncertainty, and the use of sample statistics can severely degrade the performance of second-order statistics processing. And in practical application, it is impossible to calibrate the array frequently. In this paper a cumulant-based 2D-Rake receiver for synchronous CDMA system with decorrelator is presented. Decorrelating is a multi-user detection approach that not only provides a fundamental solution to the mutual interference problem in CDMA communications but also makes it convenient for the decoupled signal to be processed spatially and temporally. High-order signal processing has some inherent advantages over that of second-order. Employing second-order statistics it is impossible to estimate source steering vector blindly, while employing higher than second-order cumulants, this purpose can be achieved. The performance analysis shows that employing cumulant-based signal processing technique the proposed 2D-Rake receiver is blind and demonstrates excellent performance.

  13. Asynchronous Multilateral Control for Simplified Walking Haptic System

    Science.gov (United States)

    Okura, Takeshi; Katsura, Seiichiro

    Recently, there has been extensive development in remote communication technologies such as telephone, radio, and television. Haptic information is studied as the third type of multimedia information. Real-world haptics is getting attention not only for the feedback of real-world haptic information in teleoperation but also as the key technology for future human support. Most of the objects of study in haptics are stationary. Therefore, the moving range of such haptic systems is limited. This paper proposes a novel haptic device that receives force feedback of walking motion from a remote environment and manipulates remote system. Thus, its moving range is unrestricted. To drive this haptic system, the paper also proposes asynchronous multilateral control. By using this control, an operator can operate the remote system without changing his/her position. The proposed haptic system is expected to act as an effective interface for virtual reality applications and teleoperation.

  14. CUCKOO SEARCH-AIDED LMS ALGORITHM FOR CHANNEL ESTIMATION IN MC-CDMA SYSTEMS

    Directory of Open Access Journals (Sweden)

    S. Balaji

    2014-01-01

    Full Text Available In the progress of transmission systems that uses the diversity in various domains, the execution of competent baseband receivers categorized by affordable computational load is an essential thing. This would be an imperative point in the future expansion of 4G systems in which the space, time and frequency diversity will be merged together to enhance the system throughput. Here, we develop a channel estimation technique for MC-CDMA system for the minimization of BER and the maximization of throughput. The maximization of throughput is an essential thing for the successful reception of signal. At the receiver side, the original data is obtained based on the channel estimation algorithm and the inverse process of the transmitter side is performed in the receiver side. The major contribution of our work is to estimate the channel information in an adaptive way. We estimate the channel using the cuckoo search algorithm based on the best solution we obtain from the cuckoo search algorithm. After estimating the channel, we calculate the Bit Error Rate (BER performance and throughput based on the acknowledgement send by the receiver. Experimental results show that our technique is better in terms of BER and throughput compared to the existing technique.

  15. H∞ Controller Design for Asynchronous Hybrid Systems with Multiple Delays

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Sun

    2016-01-01

    Full Text Available Solutions for the H∞ synthesis problems of asynchronous hybrid systems with input-output delays are proposed. The continuous-time lifting approach of sampled-data systems is extended to a hybrid system with multiple delays, and some feasible formulas to calculate the operators of the equivalent discrete-time (DT system are given. Different from the existing methods derived from symplectic pair theory or by state augmentation, a Lyapunov-Krasovskii functional to solve the synthesis problem is explicitly constructed. The delay-dependent stability conditions we obtained can be described in terms of nonstrict linear matrix inequalities (LMIs, which are much more convenient to be solved by LMI tools.

  16. Improved Iterative Parallel Interference Cancellation Receiver for Future Wireless DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Andrea Bernacchioni

    2005-04-01

    Full Text Available We present a new turbo multiuser detector for turbo-coded direct sequence code division multiple access (DS-CDMA systems. The proposed detector is based on the utilization of a parallel interference cancellation (PIC and a bank of turbo decoders. The PIC is broken up in order to perform interference cancellation after each constituent decoder of the turbo decoding scheme. Moreover, in the paper we propose a new enhanced algorithm that provides a more accurate estimation of the signal-to-noise-plus-interference-ratio used in the tentative decision device and in the MAP decoding algorithm. The performance of the proposed receiver is evaluated by means of computer simulations for medium to very high system loads, in AWGN and multipath fading channel, and compared to recently proposed interference cancellation-based iterative MUD, by taking into account the number of iterations and the complexity involved. We will see that the proposed receiver outperforms the others especially for highly loaded systems.

  17. Adaptive Wavelet Neural Networks for Signal Detection in DS-CDMA System

    Institute of Scientific and Technical Information of China (English)

    WANGLing; JIAOLichengt; TAOHaihong; LIUFang

    2004-01-01

    The Multiple access interference (MAI) is the major factor that limits the performance and capacity of a nonorthogonal Direct sequence Code division multiple access (DS-CDMA) system. By using the adaptability of highly parallel structure neural networks and the excellent approximation ability of wavelets, two kinds of Adaptive wavelets neural networks (AWNN) signal detectors are proposed in the paper, in which the inputs of detectors are the received signal vector corresponding to a single interesting user sampled at the chip rate, named by AWNN single-user detector, respectively, and to all or partial active users sampled at the bit rate after passing through a matched filter, named by AWNN multiuser detector and partial users AWNN multiuser detector. The complexity of the multiuser detectors only depends on that of wavelet networks. The performance analysis of the proposed detectors compared with the matched filters under single-user and multiuser systems and the multiuser detector based on multilayer perceptrons are carried out by Monte Carlo simulations. Results show that the adaptive wavelet neural networks multiuser detectors are superior to other detectors mentioned above.

  18. A Novel Multiuser Detection Using Group Classification with Smart Antennas for Multi—carrier CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    LIJunqiangI; K.B.Ltaief; CAOZhigang

    2003-01-01

    The capacity of MC-CDMA communica-tion systems can be significantly enhanced by employing multiuser detection (MUD) techniques. In this paper, a group oriented MUD based on the combination of smart antennas and multiuser detection is presented. The pro-posed method is featured as a novel technique for further improving the system capacity and performance. In this method, all the users are first divided into several groups according to their impinging Direction of arrivals (DOA).All users with similar DOAs are classified into the same group and then MUD is employed in each group in parallel.Because spatial filtering cannot suppress all the interfer-ence between the groups, interference cancellation among groups is used prior to MUD within the groups. It is shown that the proposed group oriented MUD algorithm can sig-nificantly reduce the computational complexity and pro-cessing time delay compared with the conventional MUDschemes. Furthermore, it is demonstrated that significant performance improvement can be achieved.

  19. Performance Evaluation of Hybrid ARQ with Code Combining in Packet-Oriented CDMA System

    Institute of Scientific and Technical Information of China (English)

    CHENQingchun; FANPingzhi

    2004-01-01

    In this paper, an extended SNR (signal to noise ratio) concept is proposed to explicate the contribution of code combining to the performance improvement of hybrid ARQ (Automatic repeat request) over the additive white Gaussian noise channel. By extending the Pursley's SNR analysis to hybrid ARQ with code combining in packet-oriented CDMA (Code division multiple access)system, the extended SNR formula is derived, which describes explicitly the SNR variation of the code symbol involved in code combining. It is revealed that the extended SNR formula includes Pursley's SNR formula as a specialcase. Moreover, it is shown that the effective SNR of the combined symbol is increased by a coefficient, which is proportional to the number of repeated replicas involved in the code combining. Based on the extended SNR formula and the resultant SNR variation, a quasi-analytical approximation method is proposed for the performance evaluation of hybrid ARQ with code combining. The residual error rates, average transmission number together with throughput performance are presented by means of numerical analysis and through simulations. It is validated that the extended SNR formula and the resultant quasi-analytical approximations offer a simplified routine to estimate the performance of hybrid ARQ with code combining, particularly for the applications whose reliability performance with respect to the FEC counterpart system could be numerically calculated or evaluated through simulations.

  20. Performance Modeling of the Fast and Reliable Two-Layer Retransmission for CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    LIU Fang; KONG Jian; WANG Wen-bo; LIU Yuan-an

    2005-01-01

    In this paper,an analytical model of two-layer retransmission scheme is proposed for CDMA systems in which selective repeat Automatic Repeat reQuest(ARQ)is used at the Radio Link Protocol(RLP)layer and n-channel Stop-and-Wait hybrid ARQ at the Medium Access control(MAC)layer.The retransmission mechanism in the RLP has considerable amount of delay associated with it,which might not be able to sustain real-time communications with strict delay requirements.Retransmissions done at a lower layer,such as the MAC,enhance the performance of the system.We show how the joint reliability varies with respect to the maximum retransmission number of RLP layer and MAC layer.We also consider that soft packet combining at the MAC layer of receiver is supported,which effectively lowers the Frame Error Rate(FER).Compared with the RLP Layer ARQ used in IS-99,the two-layer retransmission scheme shows shorter packet transmission delay and smaller packet error rate.The results show that it can offer the faster and more reliable communication than conventional scheme used in IS-99.

  1. On Intercell Interference and Its Cancellation in Cellular Multicarrier CDMA Systems

    Directory of Open Access Journals (Sweden)

    Plass Simon

    2008-01-01

    Full Text Available Abstract The handling of intercell interference at the cell border area is a strong demand in future communication systems to guarantee efficient use of the available bandwidth. Therefore, this paper focuses on the application of iterative intercell interference cancellation schemes in cellular multicarrier code division multiple access (MC-CDMA systems at the receiver side for the downlink. First, the influence of the interfering base stations to the total intercell interference is investigated. Then, different concepts for intercell interference cancellation are described and investigated for scenarios with several interfering cells. The first approach is based on the use of the hard decision of the demodulator to reconstruct the received signals. This does not require the higher amount of complexity compared to the second approach which is based on the use of the more reliable soft values from the decoding process. Furthermore, the extrinsic information as a reliability measure of this soft iterative cancellation process is investigated in more detail based on the geographical position of the mobile terminal. Both approaches show significant performance gains in the severe cell border area. With the soft intercell interference cancellation scheme, it is possible to reach the single-user bound. Therefore, the intercell interference can be almost eliminated.

  2. Space-Time Block Coding for Time Slotted CDMA Systems with Frequency-Selective Fading

    Institute of Scientific and Technical Information of China (English)

    WANGYingmin; YIKechu; NIUZhongxia; TIANHongxin

    2003-01-01

    The radio channel fading is one of the most important physical limitations for wireless mobile communications. Space-time coding is a coding technique that is designed for use with multiple transmit antennas and offers an effective transmit diversity technique to combat fading. However, most existing space-time coding schemes assume fiat fading that may not be valid for wideband wireless mobile communication channels. In this paper, a novel spacetime block coding scheme based on block processing is proposed for time slotted CDMA systems with frequencyselective fading. In order to get quasi-orthogonality, we encode the information based on the two data fields (blocks) of a burst, other than the symbols in a data field (block). As a consequence, it is convenient for block processing of joint detection which can be used with just some small modifications of the algorithms with no space-time coding. For decoding the new space time codes, block linear joint detection algorithms are developed. Then, we simplify these algorithms with an iterative procedure. With moderate iterative times, the computation complexity of the simplified algorithms is much less than that of the exact algorithms. Simulation results show that the performance of the simplified joint detection algorithms approximates to that of the exact ones.

  3. Energy-Efficient Power Control in Multipath CDMA Channels via Large System Analysis

    CERN Document Server

    Buzzi, Stefano; Poor, H Vincent

    2008-01-01

    This paper is focused on the design and analysis of power control procedures for the uplink of multipath code-division-multiple-access (CDMA) channels based on the large system analysis (LSA). Using the tools of LSA, a new decentralized power control algorithm aimed at energy efficiency maximization and requiring very little prior information on the interference background is proposed; moreover, it is also shown that LSA can be used to predict with good accuracy the performance and operational conditions of a large network operating at the equilibrium over a multipath channel, i.e. the power, signal-to-interference-plus-noise ratio (SINR) and utility profiles across users, wherein the utility is defined as the number of bits reliably delivered to the receiver for each energy-unit used for transmission. Additionally, an LSA-based performance comparison among linear receivers is carried out in terms of achieved energy efficiency at the equilibrium. Finally, the problem of the choice of the utility-maximizing tr...

  4. Algorithm of sky-ground-wave signal separation in CDMA system

    Institute of Scientific and Technical Information of China (English)

    Zhang Jingjuan; Chen Shiru

    2008-01-01

    To solve the problem of the sky-wave interference in radio positioning system operating in CDMA mode, an algorithm of sky-ground-wave separation is provided. Based on the MLE (maximum likelihood estimate),and by estimating the amplitude and the phase of the sky-wave signal, the provided algorithm for separating sky-ground-wave is implemented. The mathematics model used for signal processing is established, and the possible solutions are provided. The structure and signal processing flow implementing the presented algorithm in the receiver are presented. A multi-channels signal searching idea is adopted, some of which process the sky-wave signal, and some of which process the ground-wave signal. Numerical analysis and simulation show that the proposed algorithm has higher accuracy, more rapid processing speed, and simpler implementation for the estimation of the sky-wave signal parameter, and can separate the sky-wave signal and ground-wave signal from the arrival combination signal effectively.

  5. Performance analysis of CDMA power control system based on fuzzy prediction

    Institute of Scientific and Technical Information of China (English)

    杨涛; 谢剑英

    2004-01-01

    Power control is of paramount importance in combating the near-far problem and co-channel interference in a CDMA cellular system. Due to fast fading and ambient interference in a wireless channel, conventional fixed-step power control schemes have difficulty in compensating for the fast fading channel dynamically and in a timely manner. To acquire flexible power regulation in order to maintain required transmission capacity under the given transmission quality requirement, we propose a hybrid power control scheme which makes full use of the simple fuzzy inference rule refined by an operator in the fuzzy control and prediction property from related previous results in Generalized Prediction Control (GPC). In implementation of this strategy, we classify the fading zone into three levels according to the signal-to-noise-rate (SNR) requirement. In each level the power compensation amount varies with fading gradient and the compensation scheme varies as well. The digital results show that adoption of the fuzzy-GPC power regulation scheme has acquired a reasonable performance improvement when compared with fixed-step and fuzzy schemes. According to theoretic analysis and simulation results,we can conclude that under a variational transmission environment, a flexible power regulation scheme such as fuzzy-GPC is easy to adapt to the environment and thus overcomes the near-far effect and multi-access interference effectively.

  6. UNIVERSAL REGULAR AUTONOMOUS ASYNCHRONOUS SYSTEMS: ω-LIMIT SETS, INVARIANCE AND BASINS OF ATTRACTION

    Directory of Open Access Journals (Sweden)

    Serban Vlad

    2011-07-01

    Full Text Available The asynchronous systems are the non-deterministic real timebinarymodels of the asynchronous circuits from electrical engineering.Autonomy means that the circuits and their models have no input.Regularity means analogies with the dynamical systems, thus such systems may be considered to be real time dynamical systems with a’vector field’, Universality refers to the case when the state space of the system is the greatest possible in the sense of theinclusion. The purpose of this paper is that of defining, by analogy with the dynamical systems theory, the omega-limit sets, the invariance and the basins of attraction of the universal regular autonomous asynchronous systems.

  7. Bit Error Rate Performance of a MIMO-CDMA System Employing Parity-Bit-Selected Spreading in Frequency Nonselective Rayleigh Fading

    Directory of Open Access Journals (Sweden)

    Claude D'Amours

    2011-01-01

    Full Text Available We analytically derive the upper bound for the bit error rate (BER performance of a single user multiple input multiple output code division multiple access (MIMO-CDMA system employing parity-bit-selected spreading in slowly varying, flat Rayleigh fading. The analysis is done for spatially uncorrelated links. The analysis presented demonstrates that parity-bit-selected spreading provides an asymptotic gain of 10log(Nt dB over conventional MIMO-CDMA when the receiver has perfect channel estimates. This analytical result concurs with previous works where the (BER is determined by simulation methods and provides insight into why the different techniques provide improvement over conventional MIMO-CDMA systems.

  8. Binary De Bruijn sequences for DS-CDMA systems: analysis and results

    Directory of Open Access Journals (Sweden)

    Spinsante Susanna

    2011-01-01

    Full Text Available Abstract Code division multiple access (CDMA using direct sequence (DS spread spectrum modulation provides multiple access capability essentially thanks to the adoption of proper sequences as spreading codes. The ability of a DS-CDMA receiver to detect the desired signal relies to a great extent on the auto-correlation properties of the spreading code associated to each user; on the other hand, multi-user interference rejection depends on the cross-correlation properties of all the spreading codes in the considered set. As a consequence, the analysis of new families of spreading codes to be adopted in DS-CDMA is of great interest. This article provides results about the evaluation of specific full-length binary sequences, the De Bruijn ones, when applied as spreading codes in DS-CDMA schemes, and compares their performance to other families of spreading codes commonly used, such as m-sequences, Gold, OVSF, and Kasami sequences. While the latter sets of sequences have been specifically designed for application in multi-user communication contexts, De Bruijn sequences come from combinatorial mathematics, and have been applied in completely different scenarios. Considering the similarity of De Bruijn sequences to random sequences, we investigate the performance resulting by applying them as spreading codes. The results herein presented suggest that binary De Bruijn sequences, when properly selected, may compete with more consolidated options, and encourage further investigation activities, specifically focused on the generation of longer sequences, and the definition of correlation-based selection criteria.

  9. On the basins of attraction of the regular autonomous asynchronous systems

    OpenAIRE

    Vlad, Serban E.

    2012-01-01

    The Boolean autonomous dynamical systems, also called regular autonomous asynchronous systems are systems whose 'vector field' is a function {\\Phi}:{0,1}^{n}{\\to}{0,1}^{n} and time is discrete or continuous. While the synchronous systems have their coordinate functions {\\Phi}_{1},...,{\\Phi}_{n} computed at the same time: {\\Phi},{\\Phi}{\\circ}{\\Phi},{\\Phi}{\\circ}{\\Phi}{\\circ}{\\Phi},... the asynchronous systems have {\\Phi}_{1},...,{\\Phi}_{n} computed independently on each other. The purpose of t...

  10. A proof system for asynchronously communicating deterministic processes

    NARCIS (Netherlands)

    de Boer, F.S.; van Hulst, M.

    1994-01-01

    We introduce in this paper new communication and synchronization constructs which allow deterministic processes, communicating asynchronously via unbounded FIFO buffers, to cope with an indeterminate environment. We develop for the resulting parallel programming language, which subsumes deterministi

  11. Distributed Consensus of Stochastic Delayed Multi-agent Systems Under Asynchronous Switching.

    Science.gov (United States)

    Wu, Xiaotai; Tang, Yang; Cao, Jinde; Zhang, Wenbing

    2016-08-01

    In this paper, the distributed exponential consensus of stochastic delayed multi-agent systems with nonlinear dynamics is investigated under asynchronous switching. The asynchronous switching considered here is to account for the time of identifying the active modes of multi-agent systems. After receipt of confirmation of mode's switching, the matched controller can be applied, which means that the switching time of the matched controller in each node usually lags behind that of system switching. In order to handle the coexistence of switched signals and stochastic disturbances, a comparison principle of stochastic switched delayed systems is first proved. By means of this extended comparison principle, several easy to verified conditions for the existence of an asynchronously switched distributed controller are derived such that stochastic delayed multi-agent systems with asynchronous switching and nonlinear dynamics can achieve global exponential consensus. Two examples are given to illustrate the effectiveness of the proposed method.

  12. A Joint Optimization Criterion for Blind DS-CDMA Detection

    Directory of Open Access Journals (Sweden)

    Sergio A. Cruces-Alvarez

    2007-01-01

    Full Text Available This paper addresses the problem of the blind detection of a desired user in an asynchronous DS-CDMA communications system with multipath propagation channels. Starting from the inverse filter criterion introduced by Tugnait and Li in 2001, we propose to tackle the problem in the context of the blind signal extraction methods for ICA. In order to improve the performance of the detector, we present a criterion based on the joint optimization of several higher-order statistics of the outputs. An algorithm that optimizes the proposed criterion is described, and its improved performance and robustness with respect to the near-far problem are corroborated through simulations. Additionally, a simulation using measurements on a real software-radio platform at 5 GHz has also been performed.

  13. LAS-CDMA using Various Time Domain Chip-Waveforms

    OpenAIRE

    Wei, H.; Hanzo, L.

    2005-01-01

    LAS CDMA exhibits a significantly better performance than that of classic random code based DS-CDMA, when operating in a quasi-synchronous scenario. Classic frequency-domain raised cosine Nyquist filtering is known to show the best possible performance, but its complexity may be excessive in highchip-rate systems. Hence in these systems often low-complexity time-domain waveform shaping is considered. Motivated by this fact, the achievable performance of LAS-CDMA is investigated in conjunction...

  14. Blind Separation of DS-CDMA Signals with ICA Method

    OpenAIRE

    Miao Yu; Jianzhong Chen; Lei Shen; Shiju Li

    2011-01-01

    The estimation of pseudo noise sequence and information sequence is of great importance in the security of DS-CDMA system, which remains a hot research problem in reconnaissance and supervision of wireless communication. In DS-CDMA system, the pseudo noise sequences of different users are uncorrelated and the information sequences of different users are statistical independent, thus independent component analysis (ICA) could be introduced to separate the DS-CDMA signals with little prior know...

  15. CDMA Technique with Inter-process Communication

    Directory of Open Access Journals (Sweden)

    V. Ravichandran

    2014-02-01

    Full Text Available A novel implementation of Inter process communication in CDMA NOC is proposed. In this study, the orthogonality properties of a Walsh code are used to route data packets between the IP-Cores.The asynchronous circuit design with combinational logic (Gate level design is used for transmission and receiving circuits, along with ip-cores and reduces the processing time and resource utilization. The use of asynchronous pipelined core design process increases the operating frequency as well. The data transfers over IP-Core based interconnect is implemented on gate level. The latency and throughput values are obtained for variable payload size. The performance of asynchronous and synchronous communication are measured and analyzed.

  16. Quadrature amplitude modulation from basics to adaptive trellis-coded turbo-equalised and space-time coded OFDM CDMA and MC-CDMA systems

    CERN Document Server

    Hanzo, Lajos

    2004-01-01

    "Now fully revised and updated, with more than 300 pages of new material, this new edition presents the wide range of recent developments in the field and places particular emphasis on the family of coded modulation aided OFDM and CDMA schemes. In addition, it also includes a fully revised chapter on adaptive modulation and a new chapter characterizing the design trade-offs of adaptive modulation and space-time coding." "In summary, this volume amalgamates a comprehensive textbook with a deep research monograph on the topic of QAM, ensuring it has a wide-ranging appeal for both senior undergraduate and postgraduate students as well as practicing engineers and researchers."--Jacket.

  17. DS-CDMA Cellular Systems Performance with Base Station Assignment, Power Control Error and Beamforming over Multipath Fading

    Directory of Open Access Journals (Sweden)

    Mohamad Dosaranian Moghadam

    2011-01-01

    Full Text Available The interference reduction capability of antenna arrays, base station assignment and the power controlalgorithms have been considered separately as means to increase the capacity in wireless communicationnetworks. In this paper, we propose base station assignment method based on minimizing the transmitterpower (BSA-MTP technique in a direct sequence-code division multiple access (DS-CDMA receiver inthe presence of frequency-selective Rayleigh fading and power control error (PCE. This receiverconsists of constrained least mean squared (CLMS algorithm, matched filter (MF, and maximal ratiocombining (MRC in three stages. Also, we present switched-beam (SB technique in the first stage of theRAKE receiver for enhancing signal to interference plus noise ratio (SINR in DS-CDMA cellularsystems. The simulation results indicate that BSA-MTP technique can significantly improve the networkbit error rate (BER in comparison with the conventional case. Finally, we discuss on three parameters ofthe PCE, number of resolvable paths, and channel propagation conditions (path-loss exponent andshadowing and their effects on capacity of the system via some computer simulations.

  18. Channel Estimation And Multiuser Detection In Asynchronous Satellite Communications

    CERN Document Server

    Chaouech, Helmi; 10.5121/ijwmn.2010.2411

    2010-01-01

    In this paper, we propose a new method of channel estimation for asynchronous additive white Gaussian noise channels in satellite communications. This method is based on signals correlation and multiuser interference cancellation which adopts a successive structure. Propagation delays and signals amplitudes are jointly estimated in order to be used for data detection at the receiver. As, a multiuser detector, a single stage successive interference cancellation (SIC) architecture is analyzed and integrated to the channel estimation technique and the whole system is evaluated. The satellite access method adopted is the direct sequence code division multiple access (DS CDMA) one. To evaluate the channel estimation and the detection technique, we have simulated a satellite uplink with an asynchronous multiuser access.

  19. Low-power Implementation of an Encryption/Decryption System with Asynchronous Techniques

    Directory of Open Access Journals (Sweden)

    Nikos Sklavos

    2002-01-01

    Full Text Available An asynchronous VLSI implementation of the International Data Encryption Algorithm (IDEA is presented in this paper. In order to evaluate the asynchronous design a synchronous version of the algorithm was also designed. VHDL hardware description language was used in order to describe the algorithm. By using Synopsys commercial available tools the VHDL code was synthesized. After placing and routing both designs were fabricated with 0.6 μm CMOS technology. With a system clock of up to 8 MHz and a power supply of 5 V the two chips were tested and evaluated comparing with the software implementation of the IDEA algorithm. This new approach proves efficiently the lowest power consumption of the asynchronous implementation compared to the existing synchronous. Therefore, the asynchronous chip performs efficiently in Wireless Encryption Protocols and high speed networks.

  20. Minimum Mean-Squared Error Iterative Successive Parallel Arbitrated Decision Feedback Detectors for DS-CDMA Systems

    CERN Document Server

    de Lamare, Rodrigo C

    2012-01-01

    In this paper we propose minimum mean squared error (MMSE) iterative successive parallel arbitrated decision feedback (DF) receivers for direct sequence code division multiple access (DS-CDMA) systems. We describe the MMSE design criterion for DF multiuser detectors along with successive, parallel and iterative interference cancellation structures. A novel efficient DF structure that employs successive cancellation with parallel arbitrated branches and a near-optimal low complexity user ordering algorithm are presented. The proposed DF receiver structure and the ordering algorithm are then combined with iterative cascaded DF stages for mitigating the deleterious effects of error propagation for convolutionally encoded systems with both Viterbi and turbo decoding as well as for uncoded schemes. We mathematically study the relations between the MMSE achieved by the analyzed DF structures, including the novel scheme, with imperfect and perfect feedback. Simulation results for an uplink scenario assess the new it...

  1. CDMA Transmission with Complex OFDM/OQAM

    Directory of Open Access Journals (Sweden)

    Lélé Chrislin

    2008-01-01

    Full Text Available Abstract We propose an alternative to the well-known multicarrier code-division multiple access (MC-CDMA technique for downlink transmission by replacing the conventional cyclic-prefix orthogonal frequency division multiplexing (OFDM modulation by an advanced filterbank-based multicarrier system (OFDM/OQAM. Indeed, on one hand, MC-CDMA has already proved its ability to fight against frequency-selective channels thanks to the use of the OFDM modulation and its high flexibility in multiple access thanks to the CDMA component. On the other hand, OFDM/OQAM modulation confers a theoretically optimal spectral efficiency as it operates without guard interval. However, its orthogonality is limited to the real field. In this paper, we propose an orthogonally multiplex quadrature amplitude modulation (OQAM- CDMA combination that permits a perfect reconstruction of the complex symbols transmitted over a distortion-free channel. The validity and efficiency of our theoretical scheme are illustrated by means of a comparison, using realistic channel models, with conventional MC-CDMA and also with an OQAM-CDMA combination conveying real symbols.

  2. CDMA Transmission with Complex OFDM/OQAM

    Directory of Open Access Journals (Sweden)

    Chrislin Lélé

    2007-12-01

    Full Text Available We propose an alternative to the well-known multicarrier code-division multiple access (MC-CDMA technique for downlink transmission by replacing the conventional cyclic-prefix orthogonal frequency division multiplexing (OFDM modulation by an advanced filterbank-based multicarrier system (OFDM/OQAM. Indeed, on one hand, MC-CDMA has already proved its ability to fight against frequency-selective channels thanks to the use of the OFDM modulation and its high flexibility in multiple access thanks to the CDMA component. On the other hand, OFDM/OQAM modulation confers a theoretically optimal spectral efficiency as it operates without guard interval. However, its orthogonality is limited to the real field. In this paper, we propose an orthogonally multiplex quadrature amplitude modulation (OQAM- CDMA combination that permits a perfect reconstruction of the complex symbols transmitted over a distortion-free channel. The validity and efficiency of our theoretical scheme are illustrated by means of a comparison, using realistic channel models, with conventional MC-CDMA and also with an OQAM-CDMA combination conveying real symbols.

  3. Teleoperation system using Asynchronous transfer mode, ATM network

    International Nuclear Information System (INIS)

    This paper examines the application of Asynchronous Transfer Mode (ATM) in a distributed industrial environment such as in teleoperation, which performs real time control manipulation from a remote location. In our study, two models of teleoperation are proposed; the first model is a point to point connection and the second model is through an ATM network. The performance results are analysed as to determine whether the two models can support the teleoperation traffics via simulation using commercial software design tool. (Author)

  4. FPGA Implementation of Block Parallel DF-MPIC Detectors for DS-CDMA Systems in Frequency-Nonselective Channels

    Directory of Open Access Journals (Sweden)

    Adel Omar Dahmane

    2008-01-01

    Full Text Available Multistage parallel interference cancellation- (MPIC- based detectors allow to mitigate multiple-access interference in direct-sequence code-division multiple-access (DS-CDMA systems. They are considered serious candidates for practical implementation showing a good tradeoff between performance and complexity. Better performance is obtained when decision feedback (DF is employed. Although MPIC and DF-MPIC have the same arithmetic complexity, DF-MPIC needs much more FPGA resources when compared to MPIC without decision feedback. In this letter, FPGA implementation of block parallel DF-MPIC (BP-DF-MPIC is proposed allowing better tradeoff between performance and FPGA area occupancy. To reach an uncoded bit-error rate of 10−3, BP-DF-MPIC shows a 1.5 dB improvement over the MPIC without decision feedback with only 8% increase in FPGA resources compared to 69% for DF-MPIC.

  5. Finite-time quantised feedback asynchronously switched control of sampled-data switched linear systems

    Science.gov (United States)

    Wang, Ronghao; Xing, Jianchun; Li, Juelong; Xiang, Zhengrong

    2016-10-01

    This paper studies the problem of stabilising a sampled-data switched linear system by quantised feedback asynchronously switched controllers. The idea of a quantised feedback asynchronously switched control strategy originates in earlier work reflecting actual system characteristic of switching and quantising, respectively. A quantised scheme is designed depending on switching time using dynamic quantiser. When sampling time, system switching time and controller switching time are all not uniform, the proposed switching controllers guarantee the system to be finite-time stable by a piecewise Lyapunov function and the average dwell-time method. Simulation examples are provided to show the effectiveness of the developed results.

  6. Defining the Symmetry of the Universal Semi-Regular Autonomous Asynchronous Systems

    OpenAIRE

    Vlad, Serban E.

    2012-01-01

    The regular autonomous asynchronous systems are the non-deterministic Boolean dynamical systems and universality means the greatest in the sense of the inclusion. The paper gives four definitions of symmetry of these systems in a slightly more general framework, called semi-regularity, and also many examples.

  7. Defining the Symmetry of the Universal Semi-Regular Autonomous Asynchronous Systems

    Directory of Open Access Journals (Sweden)

    Serban E. Vlad

    2012-02-01

    Full Text Available The regular autonomous asynchronous systems are the non-deterministic Boolean dynamical systems and universality means the greatest in the sense of the inclusion. The paper gives four definitions of symmetry of these systems in a slightly more general framework, called semi-regularity, and also many examples.

  8. New DOA Algorithms for CDMA System%适用于CDMA系统的DOA算法

    Institute of Scientific and Technical Information of China (English)

    吕旌阳; 高振明; 吴伟陵

    2003-01-01

    提出了一个直扩码分多址(DS-CDMA)通信系统的接收信号模型,并在此模型的基础上推导出一种适用于DS-CDMA系统的DOA(Directions of Arrival)算法.算法利用期望用户的扩频序列与接收信号的信号子空间的关系,来估计信号的DOA.该算法突破了在传统的DOA算法中检测的DOA数要小于阵列的天线数的限制,其性能也远远好于一般的DOA算法.

  9. Modelling and Simulation of Asynchronous Real-Time Systems using Timed Rebeca

    CERN Document Server

    Aceto, Luca; Ingolfsdottir, Anna; Reynisson, Arni Hermann; Sigurdarson, Steinar Hugi; Sirjani, Marjan; 10.4204/EPTCS.58.1

    2011-01-01

    In this paper we propose an extension of the Rebeca language that can be used to model distributed and asynchronous systems with timing constraints. We provide the formal semantics of the language using Structural Operational Semantics, and show its expressiveness by means of examples. We developed a tool for automated translation from timed Rebeca to the Erlang language, which provides a first implementation of timed Rebeca. We can use the tool to set the parameters of timed Rebeca models, which represent the environment and component variables, and use McErlang to run multiple simulations for different settings. Timed Rebeca restricts the modeller to a pure asynchronous actor-based paradigm, where the structure of the model represents the service oriented architecture, while the computational model matches the network infrastructure. Simulation is shown to be an effective analysis support, specially where model checking faces almost immediate state explosion in an asynchronous setting.

  10. An Asynchronous Time-Division-Multiplexed Network-on-Chip for Real-Time Systems

    DEFF Research Database (Denmark)

    Kasapaki, Evangelia

    design that supports time-predictability, and asynchronous routers that form a time-elastic network. The NI design integrates the DMA functionality and the TDM schedule, and uses dual-ported local memories. The routers combine the router functionality and asynchronous elastic behavior. They also use......Multi-processor architectures using networks-on-chip (NOCs) for communication are becoming the standard approach in the development of embedded systems and general purpose platforms. Typically, multi-processor platforms follow a globally asynchronous locally synchronous (GALS) timing organization...... more flexible timing within its structure, to address signal distribution issues, using a network of synchronous routers. NOCs consist of a switching structure of routers connected by links, with network interfaces (NIs) that connect the processors to the switching structure. Argo uses a novel NI...

  11. Asynchronous data-driven classification of weapon systems

    International Nuclear Information System (INIS)

    This communication addresses real-time weapon classification by analysis of asynchronous acoustic data, collected from microphones on a sensor network. The weapon classification algorithm consists of two parts: (i) feature extraction from time-series data using symbolic dynamic filtering (SDF), and (ii) pattern classification based on the extracted features using the language measure (LM) and support vector machine (SVM). The proposed algorithm has been tested on field data, generated by firing of two types of rifles. The results of analysis demonstrate high accuracy and fast execution of the pattern classification algorithm with low memory requirements. Potential applications include simultaneous shooter localization and weapon classification with soldier-wearable networked sensors. (rapid communication)

  12. Trajectory exploration within asynchronous binary asteroid systems using refined Lagrangian coherent structures

    Science.gov (United States)

    Shang, Haibin; Wu, Xiaoyu; Cui, Pingyuan

    2016-09-01

    Ground observations have found that asynchronous systems constitute most of the population of the near-Earth binary asteroids. This paper concerns the trajectory of a particle in the asynchronous system which is systematically described using periodic ellipsoidal and spherical body models. Due to the non-autonomous characteristics of the asynchronous system, Lagrangian coherent structures (LCS) are employed to identify the various dynamical behaviors. To enhance the accuracy of LCS, a robust LCS finding algorithm is developed incorporating hierarchical grid refinement, one-dimensional search and variational theory verification. In this way, the intricate dynamical transport boundaries are detected efficiently. These boundaries indicate that a total of 15 types of trajectories exist near asynchronous binary asteroids. According to their Kepler energy variations, these trajectories can be grouped into four basic categories, i.e., transitory, escape, impact and flyby trajectories. Furthermore, the influence of the ellipsoid's spin period on the dynamical behavior is discussed in the context of the change of dynamical regions. We found that the transitory and impact motions occur easily in the synchronous-like binary systems, in which the rotation period of the ellipsoid is nearly equal to that of the mutual orbit. Meanwhile, the results confirm a positive correlation between the spinning rate of the ellipsoid and the probability of the escape and flyby trajectories. The LCS also reveal a marked increase in trajectory diversity after a larger initial energy is selected.

  13. Blind Reduced-Rank MMSE Detector for DS-CDMA Systems

    Directory of Open Access Journals (Sweden)

    Xiaodong Cai

    2003-01-01

    Full Text Available We first develop a reduced-rank minimum mean squared error (MMSE detector for direct-sequence (DS code division multiple access (CDMA by forcing the linear MMSE detector to lie in a signal subspace of a reduced dimension. While a reduced-rank MMSE detector has lower complexity, it cannot outperform the full-rank MMSE detector. We then concentrate on the blind reduced-rank MMSE detector which is obtained from an estimated covariance matrix. Our analysis and simulation results show that when the desired user′s signal is in a low-dimensional subspace, there exists an optimal subspace so that the blind reduced-rank MMSE detector lying in this subspace has the best performance. By properly choosing a subsspace, we guarantee that the optimal blind reduced-rank MMSE detector is obtained. An adaptive blind reduced-rank MMSE detector, based on a subspace tracking algorithm, is developed. The adaptive blind reduced-rank MMSE detector exhibits superior steady-state performance and fast convergence speed.

  14. Investigation of Closed Vector Control System for Asynchronous Motor Drive of Shipboard Tow Winch

    OpenAIRE

    Н. Mehdiyev; Е. Sultanov

    2014-01-01

    The paper considers a closed vector control system for induction motor rotation speed of a shipboard tow winch. Structural schemes and transfer functions of the system at control and disturbing influences are presented in the paper. The system with asynchronous motor drive parameters of a shipboard tow winch has been investigated in the paper. It has been revealed that transit process duration of the given system is insignificant. The fact is rather important to prevent accidents in case of v...

  15. A modular control architecture for real-time synchronous and asynchronous systems

    International Nuclear Information System (INIS)

    This paper describes a control architecture for real-time control of complex robotic systems. The Modular Integrated Control Architecture (MICA), which is actually two complementary control systems, recognizes and exploits the differences between asynchronous and synchronous control. The asynchronous control system simulates shared memory on a heterogeneous network. For control information, a portable event-scheme is used. This scheme provides consistent interprocess coordination among multiple tasks on a number of distributed systems. The machines in the network can vary with respect to their native operating systems and the intemal representation of numbers they use. The synchronous control system is needed for tight real-time control of complex electromechanical systems such as robot manipulators, and the system uses multiple processors at a specified rate. Both the synchronous and asynchronous portions of MICA have been developed to be extremely modular. MICA presents a simple programming model to code developers and also considers the needs of system integrators and maintainers. MICA has been used successfully in a complex robotics project involving a mobile 7-degree-of-freedom manipulator in a heterogeneous network with a body of software totaling over 100,000 lines of code. MICA has also been used in another robotics system, controlling a commercial long-reach manipulator

  16. Asynchronous data change notification between database server and accelerator controls system

    International Nuclear Information System (INIS)

    Database data change notification (DCN) is a commonly used feature. Not all database management systems (DBMS) provide an explicit DCN mechanism. Even for those DBMS's which support DCN (such as Oracle and MS SQL server), some server side and/or client side programming may be required to make the DCN system work. This makes the setup of DCN between database server and interested clients tedious and time consuming. In accelerator control systems, there are many well established software client/server architectures (such as CDEV, EPICS, and ADO) that can be used to implement data reflection servers that transfer data asynchronously to any client using the standard SET/GET API. This paper describes a method for using such a data reflection server to set up asynchronous DCN (ADCN) between a DBMS and clients. This method works well for all DBMS systems which provide database trigger functionality. Asynchronous data change notification (ADCN) between database server and clients can be realized by combining the use of a database trigger mechanism, which is supported by major DBMS systems, with server processes that use client/server software architectures that are familiar in the accelerator controls community (such as EPICS, CDEV or ADO). This approach makes the ADCN system easy to set up and integrate into an accelerator controls system. Several ADCN systems have been set up and used in the RHIC-AGS controls system.

  17. Extended ℋ∞ Estimation for Two-Dimensional Markov Jump Systems under Asynchronous Switching

    Directory of Open Access Journals (Sweden)

    Rui Zhang

    2013-01-01

    Full Text Available This paper is concerned with the problem of designing ℋ∞ filters for a class of two-dimensional (2D Markov jump systems under asynchronous switching. The problem under consideration is primarily motivated by a realistic situation that the switching of candidate filters may have a lag to the switching of system modes. Different from conventional techniques, by a suitable augmentation, the jumping process of the error system is represented by a two-component Markov chain. Then, the extended transition probabilities are provided for the error system. A stochastic Lyapunov function approach is proposed for the design of desired filters that ensure a prescribed ℋ∞ performance for admissible asynchronous switching. Finally, a numerical example is given to illustrate the effectiveness of the developed method.

  18. Asynchronous H∞ filtering for linear switched systems with average dwell time

    Science.gov (United States)

    Wang, Bo; Zhang, Hongbin; Wang, Gang; Dang, Chuangyin

    2016-09-01

    This paper is concerned with the H∞ filtering problem for a class of continuous-time linear switched systems with the asynchronous behaviours, where 'asynchronous' means that the switching of the filters to be designed has a lag to the switching of the system modes. By using the Lyapunov-like functions and the average dwell time technique, a sufficient condition is obtained to guarantee the asymptotic stability with a weighted H∞ performance index for the filtering error system. Moreover, the results are formulated in the form of linear matrix inequalities that are numerical feasible. As a result, the filter design problem is solved. Finally, an illustrative numerical example is presented to show the effectiveness of the results.

  19. Asynchronous update based networked predictive control system using a novel proactive compensation strategy.

    Science.gov (United States)

    Duan, Yingyao; Zuo, Xin; Liu, Jianwei

    2016-01-01

    Networked predictive control system (NPCS) has been proposed to address random delays and data dropouts in networked control systems (NCSs). A remaining challenge of this approach is that the controller has uncertain information about the actual control inputs, which leads to the predicted control input errors. The main contribution of this paper is to develop an explicit mechanism running in the distributed network nodes asynchronously, which enables the controller node to keep informed of the states of the actuator node without a priori knowledge about the network. Based on this mechanism, a novel proactive compensation strategy is proposed to develop asynchronous update based networked predictive control system (AUBNPCS). The stability criterion of AUBNPCS is derived analytically. A simulation experiment based on Truetime demonstrates the effectiveness of the scheme. PMID:26582090

  20. MC CDMA PAPR Reduction Techniques using Discrete Transforms and Companding

    CERN Document Server

    Sarala, B

    2011-01-01

    High Peak to Average Power Ratio (PAPR) of the transmitted signal is a serious problem in multicarrier modulation systems. In this paper a new technique for reduction in PAPR of the Multicarrier Code Division Multiple Access (MC CDMA) signals based on combining the Discrete Transform either Discrete Cosine Transform (DCT) or multi-resolution Discrete Wavelet Transform (DWT) with companding is proposed. It is analyzed and implemented using MATLAB. Simulation results of reduction in PAPR and power Spectral Density (PSD) of the MC CDMA with companding and without companding are compared with the MC CDMA with DCT and companding, DWT and companding systems. The new technique proposed is to make use of multi-resolution DWT in combination with companding in order to achieve a very substantial reduction in PAPR of the MC CDMA signal

  1. Analysis of a Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Multipath Rician Fading Channels

    Directory of Open Access Journals (Sweden)

    Kim Yong-Seok

    2005-01-01

    Full Text Available We present the BER analysis of antenna array (AA receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT in order to effectively make a better estimation of covariance matrices at a beamformer-RAKE receiver. In this work, we provide a comprehensive analysis of user capacity which reflects several important factors such as the ratio of the specular component power to the Rayleigh fading power, the shape of multipath intensity profile, and the number of antennas. Theoretical analysis demonstrates that for the case of a strong specular path's power or for a high decay factor, the employment of RLSTT along with AA has the potential of improving the achievable capacity by an order of magnitude.

  2. Reverse Link Performance of DS-CDMA Cellular Systems through Closed-Loop Power Control and Beamforming in 2D Urban Environment

    Directory of Open Access Journals (Sweden)

    Hamidreza Bakhshi

    2010-11-01

    Full Text Available The interference reduction capability of antenna arrays and the power control algorithms have beenconsidered separately as means to decrease the interference in wireless communication networks. In thispaper, we propose smart step closed-loop power control (SSPC algorithm in direct sequence-codedivision multiple access (DS-CDMA receivers in a 2D urban environment. This RAKE receiver consistsof conjugate gradient adaptive beamforming (CGBF and matched filter (MF in two stages and finally,the output signals from the MFs are combined and then are fed into the decision circuit for the desireduser. Also, we present switched-beam (SB technique for enhancing signal to interference plus noise ratio(SINR in network. Also, we study an analytical approach for the evaluation of the impact of powercontrol error (PCE on DS-CDMA systems in a 2D urban environment. The simulation results indicatethat the convergence speed of the SSPC algorithm is faster than other algorithms. Also, we observe thatsignificant saving in total transmit power (TTP are possible with our proposed algorithm. Finally, wediscuss two parameters of the PCE and path-loss exponent and their effects on capacity of the system viasome computer.

  3. Dynamic analysis methods for detecting anomalies in asynchronously interacting systems

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Akshat; Solis, John Hector; Matschke, Benjamin

    2014-01-01

    Detecting modifications to digital system designs, whether malicious or benign, is problematic due to the complexity of the systems being analyzed. Moreover, static analysis techniques and tools can only be used during the initial design and implementation phases to verify safety and liveness properties. It is computationally intractable to guarantee that any previously verified properties still hold after a system, or even a single component, has been produced by a third-party manufacturer. In this paper we explore new approaches for creating a robust system design by investigating highly-structured computational models that simplify verification and analysis. Our approach avoids the need to fully reconstruct the implemented system by incorporating a small verification component that dynamically detects for deviations from the design specification at run-time. The first approach encodes information extracted from the original system design algebraically into a verification component. During run-time this component randomly queries the implementation for trace information and verifies that no design-level properties have been violated. If any deviation is detected then a pre-specified fail-safe or notification behavior is triggered. Our second approach utilizes a partitioning methodology to view liveness and safety properties as a distributed decision task and the implementation as a proposed protocol that solves this task. Thus the problem of verifying safety and liveness properties is translated to that of verifying that the implementation solves the associated decision task. We develop upon results from distributed systems and algebraic topology to construct a learning mechanism for verifying safety and liveness properties from samples of run-time executions.

  4. Frequency control system based on power factor control of asynchronous motor

    Institute of Scientific and Technical Information of China (English)

    MENG Qing-chun; YANG Fei-xia; REN Zhi-ling

    2005-01-01

    Deduced the relationship between the power factor (PF) and the angular frequency according to the simplified equivalent circuit of asynchronous motor, forming a power factor auto-control system. An anti-interference circuit was also introduced in the middle voltage link of inverter to avoid the shift of the optimum PF point caused by the change of the load and the reliable run of the control system was assured. The experiment results show that it has a good self-adaptation in the whole scope of speed adjustment and an obvious economization on energy while it runs under load.

  5. Robust stabilisation and L2 -gain analysis for switched systems with actuator saturation under asynchronous switching

    Science.gov (United States)

    Wang, Juan; Zhao, Jun

    2016-09-01

    Robust stabilisation and L2-gain analysis for a class of switched systems with actuator saturation are studied in this paper. The switching signal of the controllers lags behind that of the system modes, which leads to the asynchronous switching between the candidate controllers and the subsystems. By combining the piecewise Lyapunov function method with the convex hull technique, sufficient conditions in terms of LMIs for the solvability of the robust stabilisation and weighted L2-gain problems are presented respectively under the dwell time scheme. Finally, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed results.

  6. A Transactional Asynchronous Replication Scheme for Mobile Database Systems

    Institute of Scientific and Technical Information of China (English)

    丁治明; 孟小峰; 王珊

    2002-01-01

    In mobile database systems, mobility of users has a significant impact on data replication. As a result, the various replica control protocols that exist today in traditional distributed and multidatabase environments are no longer suitable. To solve this problem, a new mobile database replication scheme, the Transaction-Level Result-Set Propagation (TLRSP)model, is put forward in this paper. The conflict detection and resolution strategy based on TLRSP is discussed in detail, and the implementation algorithm is proposed. In order to compare the performance of the TLRSP model with that of other mobile replication schemes, we have developed a detailed simulation model. Experimental results show that the TLRSP model provides an efficient support for replicated mobile database systems by reducing reprocessing overhead and maintaining database consistency.

  7. Asynchronous Message Transmission Technique for Latency Requirements in Time Critical Ship-borne System

    Directory of Open Access Journals (Sweden)

    N. P. Shrivastava

    2016-01-01

    Full Text Available A solution to data ageing requirements in time critical ship system like fire control system is presented. In an operational sea borne platform, navigation requirements for the onboard systems are fulfilled by ring laser gyro-based inertial navigation system. For critical systems like fire control system, navigational data must be delivered in real time without any delay. However due to delay occurring in processing of raw information and transmission of data on interface bus some latency is introduced. Algorithm for an asynchronous message transmission technique from inertial navigation system to user system to meet its latency requirements is discussed. Latency requirement is achieved by sending a separate message with the time stamp for the instance the first byte of 100 Hz attitude data is received at the processing computer of navigation system.Defence Science Journal, Vol. 66, No. 1, January 2016, pp. 26-29, DOI: http://dx.doi.org/10.14429/dsj.66.8502

  8. Asynchronous data change notification between database server and accelerator control systems

    International Nuclear Information System (INIS)

    Database data change notification (DCN) is a commonly used feature, it allows to be informed when the data has been changed on the server side by another client. Not all database management systems (DBMS) provide an explicit DCN mechanism. Even for those DBMS's which support DCN (such as Oracle and MS SQL server), some server side and/or client side programming may be required to make the DCN system work. This makes the setup of DCN between database server and interested clients tedious and time consuming. In accelerator control systems, there are many well established software client/server architectures (such as CDEV, EPICS, and ADO) that can be used to implement data reflection servers that transfer data asynchronously to any client using the standard SET/GET API. This paper describes a method for using such a data reflection server to set up asynchronous DCN (ADCN) between a DBMS and clients. This method works well for all DBMS systems which provide database trigger functionality. (authors)

  9. CDMA Closed-loop Power Control in the Presence of Narrowband Interference

    Institute of Scientific and Technical Information of China (English)

    YU Ai; WANG Jiangzhou

    2001-01-01

    Power control is an important issue in the DS-CDMA communication systems. This paper investigates the power control error of a closedloop power controlled CDMA system in the presence of narrowband interference. By use of a simplified loglinear power control model, the power control error,based on a strength-based power control algorithm, is studied in the overlay situation.

  10. Data-Aware Retrodiction for Asynchronous Harmonic Measurement in a Cyber-Physical Energy System.

    Science.gov (United States)

    Liu, Youda; Wang, Xue; Liu, Yanchi; Cui, Sujin

    2016-08-18

    Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, under the large-scale distributed metering architecture, harmonic measurement faces the out-of-sequence measurement (OOSM) problem, which is the result of latencies in sensing or the communication process and brings deviations in data fusion. This paper depicts a distributed measurement network for large-scale asynchronous harmonic analysis and exploits a nonlinear autoregressive model with exogenous inputs (NARX) network to reorder the out-of-sequence measuring data. The NARX network gets the characteristics of the electrical harmonics from practical data rather than the kinematic equations. Thus, the data-aware network approximates the behavior of the practical electrical parameter with real-time data and improves the retrodiction accuracy. Theoretical analysis demonstrates that the data-aware method maintains a reasonable consumption of computing resources. Experiments on a practical testbed of a cyber-physical system are implemented, and harmonic measurement and analysis accuracy are adopted to evaluate the measuring mechanism under a distributed metering network. Results demonstrate an improvement of the harmonics analysis precision and validate the asynchronous measuring method in cyber-physical energy systems.

  11. Data-Aware Retrodiction for Asynchronous Harmonic Measurement in a Cyber-Physical Energy System

    Directory of Open Access Journals (Sweden)

    Youda Liu

    2016-08-01

    Full Text Available Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, under the large-scale distributed metering architecture, harmonic measurement faces the out-of-sequence measurement (OOSM problem, which is the result of latencies in sensing or the communication process and brings deviations in data fusion. This paper depicts a distributed measurement network for large-scale asynchronous harmonic analysis and exploits a nonlinear autoregressive model with exogenous inputs (NARX network to reorder the out-of-sequence measuring data. The NARX network gets the characteristics of the electrical harmonics from practical data rather than the kinematic equations. Thus, the data-aware network approximates the behavior of the practical electrical parameter with real-time data and improves the retrodiction accuracy. Theoretical analysis demonstrates that the data-aware method maintains a reasonable consumption of computing resources. Experiments on a practical testbed of a cyber-physical system are implemented, and harmonic measurement and analysis accuracy are adopted to evaluate the measuring mechanism under a distributed metering network. Results demonstrate an improvement of the harmonics analysis precision and validate the asynchronous measuring method in cyber-physical energy systems.

  12. Data-Aware Retrodiction for Asynchronous Harmonic Measurement in a Cyber-Physical Energy System.

    Science.gov (United States)

    Liu, Youda; Wang, Xue; Liu, Yanchi; Cui, Sujin

    2016-01-01

    Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, under the large-scale distributed metering architecture, harmonic measurement faces the out-of-sequence measurement (OOSM) problem, which is the result of latencies in sensing or the communication process and brings deviations in data fusion. This paper depicts a distributed measurement network for large-scale asynchronous harmonic analysis and exploits a nonlinear autoregressive model with exogenous inputs (NARX) network to reorder the out-of-sequence measuring data. The NARX network gets the characteristics of the electrical harmonics from practical data rather than the kinematic equations. Thus, the data-aware network approximates the behavior of the practical electrical parameter with real-time data and improves the retrodiction accuracy. Theoretical analysis demonstrates that the data-aware method maintains a reasonable consumption of computing resources. Experiments on a practical testbed of a cyber-physical system are implemented, and harmonic measurement and analysis accuracy are adopted to evaluate the measuring mechanism under a distributed metering network. Results demonstrate an improvement of the harmonics analysis precision and validate the asynchronous measuring method in cyber-physical energy systems. PMID:27548171

  13. THE RESEARCH OF GRADATION FUSION ALGORITHM BASED ON MULTISENSOR ASYNCHRONOUS SAMPLING SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    This letter explores the distributed multisensor dynamic system, which has uniform sampling velocity and asynchronous sampling data for different sensors, and puts forward a new gradation fusion algorithm of multisensor dynamic system. As the total forecasted increment value between the two adjacent moments is the forecasted estimate value of the corresponding state increment in the fusion center, the new algorithm models the state and the forecasted estimate value of every moment. Kalman filter and all measurements arriving sequentially in the fusion period are employed to update the evaluation of target state step by step, on the condition that the system has obtained the target state evaluation that is based on the overall information in the previous fusion period. Accordingly, in the present period, the fusion evaluation of the target state at each sampling point on the basis of the overall information can be obtained. This letter elaborates the form of this new algorithm. Computer simulation demonstrates that this new algorithm owns greater precision in estimating target state than the present asynchronous fusion algorithm calibrated in time does.

  14. Data-Aware Retrodiction for Asynchronous Harmonic Measurement in a Cyber-Physical Energy System

    Science.gov (United States)

    Liu, Youda; Wang, Xue; Liu, Yanchi; Cui, Sujin

    2016-01-01

    Cyber-physical energy systems provide a networked solution for safety, reliability and efficiency problems in smart grids. On the demand side, the secure and trustworthy energy supply requires real-time supervising and online power quality assessing. Harmonics measurement is necessary in power quality evaluation. However, under the large-scale distributed metering architecture, harmonic measurement faces the out-of-sequence measurement (OOSM) problem, which is the result of latencies in sensing or the communication process and brings deviations in data fusion. This paper depicts a distributed measurement network for large-scale asynchronous harmonic analysis and exploits a nonlinear autoregressive model with exogenous inputs (NARX) network to reorder the out-of-sequence measuring data. The NARX network gets the characteristics of the electrical harmonics from practical data rather than the kinematic equations. Thus, the data-aware network approximates the behavior of the practical electrical parameter with real-time data and improves the retrodiction accuracy. Theoretical analysis demonstrates that the data-aware method maintains a reasonable consumption of computing resources. Experiments on a practical testbed of a cyber-physical system are implemented, and harmonic measurement and analysis accuracy are adopted to evaluate the measuring mechanism under a distributed metering network. Results demonstrate an improvement of the harmonics analysis precision and validate the asynchronous measuring method in cyber-physical energy systems. PMID:27548171

  15. INVESTIGATION OF UPLINK RADIO RESOURCE MANAGEMENT SCHEMES FOR MULTI-SERVICES IN TDD-CDMA SYSTEMS EMPLOYING SMART ANTENNAS

    Institute of Scientific and Technical Information of China (English)

    Peng Mugen; Wang Wenbo

    2006-01-01

    In this paper, a theoretical analysis of Time Division Duplex-Code Division Multiple Access (TDD-CDMA) uplink capacity constraint is presented when employing the smart antenna techniques. The evaluation formulations of capacity and load for multi-services are proposed. In order to maximize the throughput, the objective of optimization is proposed, and an advanced uplink resource management algorithm is developed. The proposed algorithm based on the least interference admission control scheme focuses on the maximum throughput for the circuit switched multi-services. The simulation results show that the proposed strategy has a significant improvement in throughput when the optimum admission control threshold is set.

  16. Performance Analysis of SAC Optical PPM-CDMA System-Based Interference Rejection Technique

    Science.gov (United States)

    Alsowaidi, N.; Eltaif, Tawfig; Mokhtar, M. R.

    2016-03-01

    In this paper, we aim to theoretically analyse optical code division multiple access (OCDMA) system that based on successive interference cancellation (SIC) using pulse position modulation (PPM), considering the interference between the users, imperfection cancellation occurred during the cancellation process and receiver noises. Spectral amplitude coding (SAC) scheme is used to suppress the overlapping between the users and reduce the receiver noises effect. The theoretical analysis of the multiple access interference (MAI)-limited performance of this approach indicates the influence of the size of M-ary PPM on OCDMA system. The OCDMA system performance improves with increasing M-ary PPM. Therefore, it was found that the SIC/SAC-OCDMA system using PPM technique along with modified prime (MPR) codes used as signature sequence code offers significant improvement over the one without cancellation and it can support up to 103 users at the benchmarking value of bit error rate (BER) = 10-9 with prime number p = 11 while the system without cancellation scheme can support only up to 52 users.

  17. Inter-Cell Interference Cancellation Algorithm for Reverse Link TDD-CDMA Systems

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper proposes a new inter-cell interference cancellation algorithm called subspace projection in order to eliminate the stronger inter-cell interference. This algorithm is designed for the reverse link of time division duplex-code division multiple access systems. The algorithm works by projecting desired users' signal vector onto the subspace orthogonal to the subspace that interfers the users' signal. Link-level simulation results show that the scheme eliminates the inter-cell interference efficiently, improves the receiver performance, and increases the system capacity.

  18. Performance Analysis of Channel-barrowing Hand-off Scheme in CDMA Cellular Systems

    Directory of Open Access Journals (Sweden)

    G. Kesavan

    2015-02-01

    Full Text Available For cellular communication systems, mobility and limited radio coverage of a cell require calls to be handed over from one Base Station System (BSS to another. Due to the limited band width available in various cells, there is a finite probability that an ongoing call, while being handed off, may get dropped. Minimizing the dropping of ongoing calls during hand off is an important design criterion. Some digital cellular systems, e.g., the Global System for Mobile Communications and the IS-136, use Mobile-Assisted Hand off (MAHO, in which a Mobile Terminal (MT assists, it’s BSS and a mobiles witching center in making hand off decisions. MAHO requires an MT to regularly report, back to its serving BSS, its current radio-link state (defined in terms of the Received Signal Strength Indicator (RSSI and the Bit Error Rate (BER of transmissions received from neighboring BSSs. In the proposed technique, the MT reports back not only the RSSI and the BER but the number of free channels that are available for the hand off traffic as well. This will ensure that a handed-off call has acceptable signal quality as well as a free available channel. The performance of this hand off technique is analyzed using an analytical model whose solution gives the desired performance measures in terms of blocking and dropping probabilities.

  19. An Efficient Algorithm to Solve the Problem of Dropped Call in CDMA Cellular Systems

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In the mobile environment, the dropped calls can be resulted from shadowing and rapid signal loss. As the cells shrink to accommodate an increasingly large demand for services, the dropped-call recovery procedure will become more important over the air interface. But in the current protocols, the recovery procedure is too simple to demonstrate the procedure. In this paper, we present a Transparent Reconnection Procedure (TRP) which is an efficient algorithm that can be adapted easily to the benefit of decreased dropped calls. In the simulation of a typical cellular system, it is shown that there are fewer dropped calls using TRP compared to the conventional procedure. This benefit comes at the expense of a slight increase (less than percent 1) in blocked call percentage. It depends on some relevant system parameters, the values of which are decided by the operators accordingly.

  20. PERFORMANCE ANALYSIS OF OPTICAL CDMA SYSTEM USING VC CODE FAMILY UNDER VARIOUS OPTICAL PARAMETERS

    Directory of Open Access Journals (Sweden)

    HASSAN YOUSIF AHMED

    2012-06-01

    Full Text Available The intent of this paper is to study the performance of spectral-amplitude coding optical code-division multiple-access (OCDMA systems using Vector Combinatorial (VC code under various optical parameters. This code can be constructed by an algebraic way based on Euclidian vectors for any positive integer number. One of the important properties of this code is that the maximum cross-correlation is always one which means that multi-user interference (MUI and phase induced intensity noise are reduced. Transmitter and receiver structures based on unchirped fiber Bragg grating (FBGs using VC code and taking into account effects of the intensity, shot and thermal noise sources is demonstrated. The impact of the fiber distance effects on bit error rate (BER is reported using a commercial optical systems simulator, virtual photonic instrument, VPITM. The VC code is compared mathematically with reported codes which use similar techniques. We analyzed and characterized the fiber link, received power, BER and channel spacing. The performance and optimization of VC code in SAC-OCDMA system is reported. By comparing the theoretical and simulation results taken from VPITM, we have demonstrated that, for a high number of users, even if data rate is higher, the effective power source is adequate when the VC is used. Also it is found that as the channel spacing width goes from very narrow to wider, the BER decreases, best performance occurs at a spacing bandwidth between 0.8 and 1 nm. We have shown that the SAC system utilizing VC code significantly improves the performance compared with the reported codes.

  1. A Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Frequency-Selective Fading Channels with Power Control Error

    Directory of Open Access Journals (Sweden)

    Yong-Seok Kim

    2004-08-01

    Full Text Available An improved antenna array (AA has been introduced, in which reverse-link synchronous transmission technique (RLSTT is incorporated to effectively make better an estimation of covariance matrices at a beamformer-RAKE receiver. While RLSTT is effective in the first finger at the RAKE receiver in order to reject multiple-access interference (MAI, the beamformer estimates the desired user's complex weights, enhancing its signal and reducing cochannel interference (CCI from the other directions. In this work, it is attempted to provide a comprehensive analysis of user capacity which reflects several important factors such as the shape of multipath intensity profile (MIP, the number of antennas, and power control error (PCE. Theoretical analysis, confirmed by the simulations, demonstrates that the orthogonality provided by employing RLSTT along with AA may make the DS-CDMA system insensitive to the PCE even with fewer numbers of antennas.

  2. A Geometrical-Based Model for Cochannel Interference Analysis and Capacity Estimation of CDMA Cellular Systems

    Directory of Open Access Journals (Sweden)

    Baltzis KonstantinosB

    2008-01-01

    Full Text Available Abstract A common assumption in cellular communications is the circular-cell approximation. In this paper, an alternative analysis based on the hexagonal shape of the cells is presented. A geometrical-based stochastic model is proposed to describe the angle of arrival of the interfering signals in the reverse link of a cellular system. Explicit closed form expressions are derived, and simulations performed exhibit the characteristics and validate the accuracy of the proposed model. Applications in the capacity estimation of WCDMA cellular networks are presented. Dependence of system capacity of the sectorization of the cells and the base station antenna radiation pattern is explored. Comparisons with data in literature validate the accuracy of the proposed model. The degree of error of the hexagonal and the circular-cell approaches has been investigated indicating the validity of the proposed model. Results have also shown that, in many cases, the two approaches give similar results when the radius of the circle equals to the hexagon inradius. A brief discussion on how the proposed technique may be applied to broadband access networks is finally made.

  3. A Geometrical-Based Model for Cochannel Interference Analysis and Capacity Estimation of CDMA Cellular Systems

    Directory of Open Access Journals (Sweden)

    Konstantinos B. Baltzis

    2008-10-01

    Full Text Available A common assumption in cellular communications is the circular-cell approximation. In this paper, an alternative analysis based on the hexagonal shape of the cells is presented. A geometrical-based stochastic model is proposed to describe the angle of arrival of the interfering signals in the reverse link of a cellular system. Explicit closed form expressions are derived, and simulations performed exhibit the characteristics and validate the accuracy of the proposed model. Applications in the capacity estimation of WCDMA cellular networks are presented. Dependence of system capacity of the sectorization of the cells and the base station antenna radiation pattern is explored. Comparisons with data in literature validate the accuracy of the proposed model. The degree of error of the hexagonal and the circular-cell approaches has been investigated indicating the validity of the proposed model. Results have also shown that, in many cases, the two approaches give similar results when the radius of the circle equals to the hexagon inradius. A brief discussion on how the proposed technique may be applied to broadband access networks is finally made.

  4. RESEARCH ON HLR MOBILITY DATABASE FAILURE RECOVERY AND PERFORMANCE ANALYSIS FOR CDMA2000 SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Liu Caixia; Yu Dingjiu; Cheng Dongnian; Tang Hongbo; Wu Jiangxing

    2004-01-01

    In this paper, a novel Home Location Register(HLR) mobility database recovery scheme is proposed. With database backing-up and signal sending as its key processes, the presented scheme is designed for the purpose of both decreasing system costs and reducing number of lost calls. In our scheme, an algorithm is developed for an HLR to identify such VLRs that there are new MSs roaming into them since the latest HLR database backing up. The identification of those VLRs is used by the HLR to send Unreliable Roaming Data Directive messages to each of them to get the correct location information of those new MSs. Additionally, two kinds of relationships, one between the number of lost calls and the database backing-up period and the other between the backing-up cost and the period, are well analyzed. Both analytical and numerical results indicate that there will be an optimal HLR database backing-up period if certain system parameters are given and the total cost can be consequently minimized.

  5. Wind-powered asynchronous AC/DC/AC converter system. [for electric power supply regulation

    Science.gov (United States)

    Reitan, D. K.

    1973-01-01

    Two asynchronous ac/dc/ac systems are modelled that utilize wind power to drive a variable or constant hertz alternator. The first system employs a high power 60-hertz inverter tie to the large backup supply of the power company to either supplement them from wind energy, storage, or from a combination of both at a preset desired current; rectifier and inverter are identical and operate in either mode depending on the silicon control rectifier firing angle. The second system employs the same rectification but from a 60-hertz alternator arrangement; it provides mainly dc output, some sinusoidal 60-hertz from the wind bus and some high harmonic content 60-hertz from an 800-watt inverter.

  6. Relay system for phasing rotating disk selector with drive from asynchronous electric motor

    International Nuclear Information System (INIS)

    Regulating system is described which ensures rotation of a massive disk selector synphaseally with a rotating reactivity modulator in a pulse reactor. Unlike the proportional regulating principle and using d.c. motor commonly utilized in solving similar problems, the given system involves an asynchronous short-circuited electric motor and a relay regulation principle. Thyristor control provides sufficiently simple realization of two selector acceleration modes (strong and weak acceleration) and two retardation modes (strong and weak braking). The mode switch-over moments are due to the regulated magnitude and its product. The given system is simple in maintenance, and has low sensitivity to oscillations in circuit voltage. In an 80-200 mc range of the selector period, the mean-square value of the displacement angle between the selector and reactor is at least +-1 deg

  7. Passive optical networks based on optical CDMA: Design and system analysis

    Institute of Scientific and Technical Information of China (English)

    ZHANG ChongFu; QIU Kun; XU Bo

    2007-01-01

    In this paper, a novel Passive Optical Network based on Optical Code Division Multiple Access (OCDMA-PON) is presented. The design of the Optical Line Terminator (OLT) and the Optical Network Unit (ONU) for the OCDMA-PON are studied in detail. The proposed OCDMA-PON combines the advantages of PON and OCDMA technology and it can be applied to an optical access network with full services on demand, such as internet protocol, video on demand, tele-presence and high quality audio. Compared to other multiple access technologies, the proposed OCDMA-PON provides more ONU and assembly flexibly for PON. We analyze in detail the scalability and system transmission performance of such a network. Simulation results indicate that the proposed scheme is feasible and that the novel design can improve the scalability and transmission performance of the optical access networks.

  8. A Novel Multiuser Detection Algorithm for CDMA-Based MIMO-OFDM System

    Institute of Scientific and Technical Information of China (English)

    LIU Jun-shi; TANG Bi-hua; WANG Ya-chen; LIU Yua-nan

    2006-01-01

    This paper investigates QR matrix decomposition based successive interference cancellation multiuser detection algorithms in synchronous uplink for code division multiple access based multiple input multiple output orthogonal frequency division multiplexing system. The Symbol Error Rate(SER) performance of the optimal order and the suboptimal order QR-SIC MUD algorithms are compared with conventional zero forcing and minimum mean square error multiuser detection algorithms by Monte Carlo simulations. Complexity analysis is presented at the end of the paper. Both our simulation results and complexity analysis show that SER performance of QR-Successive Interference Cancellation (QR-SIC) algorithms is superior to those of zero forcing(ZF) and minimum mean square error algorithms, and the suboptimal order QR-SIC algorithm has a good trade-off between SER performance and computation complexity.

  9. How Equalization Techniques Affect the TCP Performance of MC-CDMA Systems in Correlated Fading Channels

    Directory of Open Access Journals (Sweden)

    Giacomo Leonardi

    2007-12-01

    Full Text Available This paper investigates the impact of several equalization techniques for multicarrier code division multiple access systems on the performance at both lower and upper layers (i.e., physical and TCP layers. Classical techniques such as maximal ratio combining, equal gain combining, orthogonality restoring combining, minimum mean square error, as well as a partial equalization (PE are investigated in time- and frequency-correlated fading channels with various numbers of interferers. Their impact on the performance at upper level is then studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user, allowing an investigation of the real gain produced by signal processing techniques at TCP level.

  10. Experimental investigation on the high chip rate of 2D incoherent optical CDMA system

    Science.gov (United States)

    Su, Guorui; Wang, Rong; Pu, Tao; Fang, Tao; Zheng, Jilin; Zhu, Huatao; Wu, Weijiang

    2015-08-01

    An innovative approach to realise high chip rate in OCDMA transmission system is proposed and experimentally investigation, the high chip rate is achieved through a 2-D wavelength-hopping time-spreading en/decoder based on the supercontinuum light source. The source used in the experiment is generated by high nonlinear optical fiber (HNLF), Erbium-doped fiber amplifier (EDFA) which output power is 26 dBm, and distributed feed-back laser diode which works in the gain switch state. The span and the flatness of the light source are 20 nm and 3 dB, respectively, after equalization of wavelength selective switch (WSS). The wavelength-hopping time-spreading coder can be changed 20 nm in the wavelength and 400 ps in the time, is consist of WSS and delay lines. Therefore, the experimental results show that the chip rate can achieve 500 Gchip/s, in the case of 2.5 Gbit/s, while keeping a bit error rate below forward error correction limit after 40 km transmission.

  11. The concept of "stability" in asynchronous distributed decision-making systems.

    Science.gov (United States)

    Lee, T S; Ghosh, S

    2000-01-01

    Asynchronous distributed decision-making (ADDM) systems constitute a special class of distributed problems and are characterized as large, complex systems wherein the principal elements are the geographically dispersed entities that communicate among themselves, asynchronously, through message passing and are permitted autonomy in local decision making. Such systems generally offer significant advantages over the traditional, centralized algorithms in the form of concurrency, scalability, high throughput, efficiency, low vulnerability to catastrophic failures, and robustness. A fundamental property of ADDM systems is stability that refers to their behavior under representative perturbations to their operating environments, given that such systems are intended to be real, complex, and to some extent, mission-critical, and are subject to unexpected changes in their operating conditions. This paper introduces the concept of stability in ADDM systems and proposes an intuitive yet practical and usable definition that is inspired by those used in control systems and physics. An ADDM system is defined as a stable system if it returns to a steady state in finite time, following perturbation, provided that it is initiated in a steady state. Equilibrium or steady state is defined through placing bounds on the measured error in the system. Where the final steady state is equivalent to the initial one, a system is referred to as strongly stable. If the final steady state is potentially worse then the initial one, a system is deemed marginally stable. When a system fails to return to steady state following the perturbation, it is unstable. The perturbations are classified as either changes in the input pattern or changes in one or more environmental characteristics of the system, such as hardware failures. For a given ADDM system, the definitions are based on the performance indices that must be judiciously identified by the system architect and are likely to be unique. To

  12. VOLTAGE REGULATORS ASYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    Grigorash O. V.

    2015-06-01

    Full Text Available A promising is currently the use of asynchronous generators with capacitive excitation as a source of electricity in stand-alone power systems. Drive asynchronous generators may exercise as a thermal engine and wind wheel wind power plant or turbines of small hydropower plants. The article discusses the structural and schematics of voltage stabilizers and frequency of asynchronous generators with improved operational and technical specifications. Technical novelty of design solutions of the magnetic system and stabilizers asynchronous generator of electricity parameters confirmed by the patents for the invention of the Russian Federation. The proposed technical solution voltage stabilizer asynchronous generators, can reduce the weight of the block capacitors excitation and reactive power compensation, as well as to simplify the control system power circuit which has less power electronic devices. For wind power plants it is an important issue not only to stabilize the voltage of the generator, but also the frequency of the current. Recommend functionality stabilizer schemes parameters of electric power made for direct frequency converters with artificial and natural switching power electronic devices. It is also proposed as part of stabilization systems use single-phase voltage, three-phase transformers with rotating magnetic field, reduce the level of electromagnetic interference generated by power electronic devices for switching, enhance the efficiency and reliability of the stabilizer.

  13. Method for Allocating Walsh Codes by Complete Group Information Walsh Code in CDMA Cellular System%一种在CDMA网状系统中通过完整分组信息分配Walsh码的方法

    Institute of Scientific and Technical Information of China (English)

    Waleej Haider; Seema Ansari; Muhammad Nouman Durrani

    2009-01-01

    A method for allocating Walsh codes by group in a CDMA(Code Division Multiple Access)cellular system is disclosed.The proposed system provides a method for grouping,allocating,removing and detecting of the minimum traffic group to minimize tlle time for allocating a call or transmitted data to an idle Walsh code.thereby,improving the performance of the system and reducing the time required to set up the call.The new concept of CGIWC has been presented tO solve the calls or data allocating and remoral from the Walsh Code.Preferably,these steps are performed by a BCS(Base station Call control Processor)at a CDMA base station.Moreover,a comparison with the previous work has been shown for the support of our related work.At the end,the future direction in which the related work can be employed,are highlighted.

  14. Analysis Of Functional Stability Of The Triphased Asynchronous Generator Used In Conversion Systems Of A Eolian Energy Into Electric Energy

    Directory of Open Access Journals (Sweden)

    Ion VONCILA

    2003-12-01

    Full Text Available This paper presents a study of the influence of the main perturbation agent over the functional stability of the triphased asynchronous generator (for the two alternative: with coiled and short circuit rotor, used for the conversion systems from a eolian energy into electric energy.

  15. Traffic Modelling for Capacity Analysis of CDMA Networks using Gausian Approximation Method

    Directory of Open Access Journals (Sweden)

    B. O. Omijeh

    2014-05-01

    Full Text Available This paper presents, modelling telephone traffic in cellular networks operating with Code Division Multiple Access (CDMA for the purpose of capacity analysis of such systems. With the current use of CDMA as the preferred multiple access technique due to its capacity advantage, there is the need for tools that will assist in ensuring quality of service and proper network dimensioning. This work produces a model useful for capacity analysis. Focusing on the reverse link, this is achieved by modelling telephone traffic using Gaussian assumptions to generate a CDMA blocking probability that is adapted into Erlang B formula for capacity calculations. A program written in MATLAB is used to realise the blocking probability formula with graphical outputs that is a tool for dimensioning. Results show that variations in network parameters affect CDMA capacity and that CDMA has a huge capacity advantage over TDMA and FDMA

  16. Asynchronous P300 BCI

    DEFF Research Database (Denmark)

    Panicker, Rajesh; Puthusserypady, Sadasivan; Sun, Ying

    2010-01-01

    An asynchronous hybrid brain-computer interface (BCI) system combining the P300 and steady-state visually evoked potentials (SSVEP) paradigms is introduced. A P300 base system is used for information transfer, and is augmented to include SSVEP for control state detection. The proposed system has...

  17. Improved DSE-CMA Error Function for Blind Multiuser Interference Suppression in DS/CDMA Systems%DS/CDMA系统中盲干扰抑制的抖动符号误差恒模算法

    Institute of Scientific and Technical Information of China (English)

    赵海波; 胡光锐; 朱丽平

    2005-01-01

    This paper presents an improved error function of dithered signed-error constant modulus algorithm (IDSE-CMA) for blind multiuser interference suppression in DS/CDMA systems. It uses a different error function to replace the former one in sign operation of the DSE-CMA and compares their performance in multiple access interference (MAI) suppression ability. Simulations indicate that the new algorithm has better performance than the similar CMA in terms of convergence speed and steady-state performance .

  18. Model checking methodology for large systems, faults and asynchronous behaviour. SARANA 2011 work report

    Energy Technology Data Exchange (ETDEWEB)

    Lahtinen, J. [VTT Technical Research Centre of Finland, Espoo (Finland); Launiainen, T.; Heljanko, K.; Ropponen, J. [Aalto Univ., Espoo (Finland). Dept. of Information and Computer Science

    2012-07-01

    Digital instrumentation and control (I and C) systems are challenging to verify. They enable complicated control functions, and the state spaces of the models easily become too large for comprehensive verification through traditional methods. Model checking is a formal method that can be used for system verification. A number of efficient model checking systems are available that provide analysis tools to determine automatically whether a given state machine model satisfies the desired safety properties. This report reviews the work performed in the Safety Evaluation and Reliability Analysis of Nuclear Automation (SARANA) project in 2011 regarding model checking. We have developed new, more exact modelling methods that are able to capture the behaviour of a system more realistically. In particular, we have developed more detailed fault models depicting the hardware configuration of a system, and methodology to model function-block-based systems asynchronously. In order to improve the usability of our model checking methods, we have developed an algorithm for model checking large modular systems. The algorithm can be used to verify properties of a model that could otherwise not be verified in a straightforward manner. (orig.)

  19. Sustainable project of microgeneration systems based on asynchronous generator; Projeto sustentavel de sistemas de microgeracao baseados em gerador assincrono

    Energy Technology Data Exchange (ETDEWEB)

    Salazar Herrera, Victoria Alejandra; Romero, Jesus Franklin Andrade [Universidade Federal do ABC (CECS/UFABC), Santo Andre, SP (Brazil). Centro de Engenharia, Modelagem e Ciencias Sociais Aplicadas. Programa de Pos-Graduacao em Energia], emails: victoria.herrera@ufabc.edu.br, jesus.romero@ufabc.edu.br

    2010-07-01

    Recently, the interest in decentralized generation systems has increased considering a multidisciplinary and sustainable approach. In this sense, this work proposes the evaluation of isolated microgeneration systems, focusing the life cycle of the asynchronous generator, considering the technological, economic and environmental dimensions. By means of the generator efficiency, the unbalanced voltage percentage and the emissions factor, the work point out the relevance of health diagnosis of isolated microgeneration systems objectifying minimize the impacts caused by faulty operation of the generator. (author)

  20. Overview of MC CDMA PAPR Reduction Techniques

    CERN Document Server

    Sarala, B; Bhandari, B N

    2012-01-01

    High Peak to Average Power Ratio (PAPR) of the transmitted signal is a critical problem in multicarrier modulation systems (MCM) such as Orthogonal Frequency Division Multiplexing (OFDM), and Multi-Carrier Code Division Multiple Access (MC CDMA) systems, due to large number of subcarriers. High PAPR leads to reduced resolution, and battery life. It also deteriorates system performance. This paper focuses on review of different PAPR reduction techniques with attendant technical issues as well as criteria for selection of PAPR reduction technique. To reduce PAPR the constraints are low power consumption, and low Bit Error Rate (BER). Spectral bandwidth is improved by better spectral characteristics, and low complexity/cost.

  1. Asynchronized synchronous machines

    CERN Document Server

    Botvinnik, M M

    1964-01-01

    Asynchronized Synchronous Machines focuses on the theoretical research on asynchronized synchronous (AS) machines, which are "hybrids” of synchronous and induction machines that can operate with slip. Topics covered in this book include the initial equations; vector diagram of an AS machine; regulation in cases of deviation from the law of full compensation; parameters of the excitation system; and schematic diagram of an excitation regulator. The possible applications of AS machines and its calculations in certain cases are also discussed. This publication is beneficial for students and indiv

  2. The Coverage-Capacity Analysis of CDMA Wireless Network

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xufeng; LI Chengshu

    2001-01-01

    The coverage and capacity tradeoff is one of the important characters of CDMA cellular system. In this paper, we investigate the relationship of coverage and capacity of CDMA wireless network. By analyzing the outage probability under softhandoff and providing the soft-handoff probability, we extend the outage probability analysis to the multi-cell environment with soft-handoff. Furthermore, a spatial Poisson process is introduced and both uniform and non-uniform subscriber distribution cases are analyzed. Based on these we make a derivation of the relation between coverage and capacity in single and multi-cell environments.

  3. Direct synchronous-asynchronous conversion system for hybrid electrical vehicle applications. An energy-based modeling approach

    OpenAIRE

    Muñoz-Aguilar, Raúl S.; Dòria-Cerezo, Arnau; Puleston, Pablo Federico

    2013-01-01

    This paper presents a proposal for a series hybrid electric vehicle propulsion system. This new configuration is based on a wound-rotor synchronous generator (WRSM) and a doubly-fed induction machine (DFIM). The energy-based model of the whole system is obtained taking advantage of the capabilities of the port-based modeling techniques. From the dq port-controlled Hamiltonian description of the WRSM and DFIM, the Hamiltonian model of the proposed Direct Synchronous-Asynchronous Conversion Sys...

  4. MULTICARRIER DS-CDMA WITH ADAPTIVE MODULATION AND POWER ALLOCATION

    Institute of Scientific and Technical Information of China (English)

    Zhao Yahong; Zhang Zhongpei; Wu Weiling

    2003-01-01

    Adaptive modulation and power allocation is introduced into the multicarrier DS-CDMA system to improve the system performance and bandwidth efficiency. First, the systemdesign appropriate for adaptive modulation and power allocation is given, then the algorithmof adaptive modulation and power allocation is applied. Simulation results demonstrate greatperformance improvement compared with the fixed modulated one.

  5. Asynchronous anti-noise hyper chaotic secure communication system based on dynamic delay and state variables switching

    International Nuclear Information System (INIS)

    This Letter designs an asynchronous hyper chaotic secure communication system, which possesses high stability against noise, using dynamic delay and state variables switching to ensure the high security. The relationship between the bit error ratio (BER) and the signal-to-noise ratio (SNR) is analyzed by simulation tests, the results show that the BER can be ensured to reach zero by proportionally adjusting the amplitudes of the state variables and the noise figure. The modules of the transmitter and receiver are implemented, and numerical simulations demonstrate the effectiveness of the system. -- Highlights: → Asynchronous anti-noise hyper chaotic secure communication system. → Dynamic delay and state switching to ensure the high security. → BER can reach zero by adjusting the amplitudes of state variables and noise figure.

  6. Performance Analysis of Polarization Modulated DirectDetection Optical CDMA Systems over Turbulent FSO LinksModeled by the Gamma-Gamma Distribution

    Directory of Open Access Journals (Sweden)

    Fan Bai

    2015-01-01

    Full Text Available This paper proposes a theoretical study to characterize the transmission of optical code division multiple access (CDMA systems deploying polarization shift keying (PolSK over a free space optical (FSO link under the impact of atmospheric turbulence. In our analysis, a novel transceiver architecture for atmospheric OCDMA FSO systems based on polarization modulation with direct detection is proposed and discussed. A detailed analytical model for PolSK-OCDMA systems over a turbulent FSO link is provided. Further, we derive a closed-form bit error ratio (BER and outage probability expressions, taking into account the multiple-access interference (MAI, optical noise and the atmospheric turbulence effect on the FSO link modeled by the Gamma-Gamma distribution. Finally, the results of this study show the most significant parameters that degrade the transmission performance of the PolSK-OCDMA signal over FSO links and indicate that the proposed approach offers improved bit error ratio (BER performances compared to the on-off-keying (OOK modulation scheme in the presence of turbulence.

  7. Zero-Forcing and Minimum Mean-Square Error Multiuser Detection in Generalized Multicarrier DS-CDMA Systems for Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Lie-Liang Yang

    2008-01-01

    Full Text Available In wireless communications, multicarrier direct-sequence code-division multiple access (MC DS-CDMA constitutes one of the highly flexible multiple access schemes. MC DS-CDMA employs a high number of degrees-of-freedom, which are beneficial to design and reconfiguration for communications in dynamic communications environments, such as in the cognitive radios. In this contribution, we consider the multiuser detection (MUD in MC DS-CDMA, which motivates lowcomplexity, high flexibility, and robustness so that the MUD schemes are suitable for deployment in dynamic communications environments. Specifically, a range of low-complexity MUDs are derived based on the zero-forcing (ZF, minimum mean-square error (MMSE, and interference cancellation (IC principles. The bit-error rate (BER performance of the MC DS-CDMA aided by the proposed MUDs is investigated by simulation approaches. Our study shows that, in addition to the advantages provided by a general ZF, MMSE, or IC-assisted MUD, the proposed MUD schemes can be implemented using modular structures, where most modules are independent of each other. Due to the independent modular structure, in the proposed MUDs one module may be reconfigured without yielding impact on the others. Therefore, the MC DS-CDMA, in conjunction with the proposed MUDs, constitutes one of the promising multiple access schemes for communications in the dynamic communications environments such as in the cognitive radios.

  8. Zero-Forcing and Minimum Mean-Square Error Multiuser Detection in Generalized Multicarrier DS-CDMA Systems for Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Wang Li-Chun

    2008-01-01

    Full Text Available Abstract In wireless communications, multicarrier direct-sequence code-division multiple access (MC DS-CDMA constitutes one of the highly flexible multiple access schemes. MC DS-CDMA employs a high number of degrees-of-freedom, which are beneficial to design and reconfiguration for communications in dynamic communications environments, such as in the cognitive radios. In this contribution, we consider the multiuser detection (MUD in MC DS-CDMA, which motivates lowcomplexity, high flexibility, and robustness so that the MUD schemes are suitable for deployment in dynamic communications environments. Specifically, a range of low-complexity MUDs are derived based on the zero-forcing (ZF, minimum mean-square error (MMSE, and interference cancellation (IC principles. The bit-error rate (BER performance of the MC DS-CDMA aided by the proposed MUDs is investigated by simulation approaches. Our study shows that, in addition to the advantages provided by a general ZF, MMSE, or IC-assisted MUD, the proposed MUD schemes can be implemented using modular structures, where most modules are independent of each other. Due to the independent modular structure, in the proposed MUDs one module may be reconfigured without yielding impact on the others. Therefore, the MC DS-CDMA, in conjunction with the proposed MUDs, constitutes one of the promising multiple access schemes for communications in the dynamic communications environments such as in the cognitive radios.

  9. An asynchronous writing method for restart files in the gysela code in prevision of exascale systems*

    Directory of Open Access Journals (Sweden)

    Thomine O.

    2013-12-01

    Full Text Available The present work deals with an optimization procedure developed in the full-f global GYrokinetic SEmi-LAgrangian code (GYSELA. Optimizing the writing of the restart files is necessary to reduce the computing impact of crashes. These files require a very large memory space, and particularly so for very large mesh sizes. The limited bandwidth of the data pipe between the comput- ing nodes and the storage system induces a non-scalable part in the GYSELA code, which increases with the mesh size. Indeed the transfer time of RAM to data depends linearly on the files size. The necessity of non synchronized writing-in-file procedure is therefore crucial. A new GYSELA module has been developed. This asynchronous procedure allows the frequent writ- ing of the restart files, whilst preventing a severe slowing down due to the limited writing bandwidth. This method has been improved to generate a checksum control of the restart files, and automatically rerun the code in case of a crash for any cause.

  10. A Unified Approach to BER Analysis of Synchronous Downlink CDMA Systems with Random Signature Sequences in Fading Channels with Known Channel Phase

    Directory of Open Access Journals (Sweden)

    M. Deriche

    2008-02-01

    Full Text Available A detailed analysis of the multiple access interference (MAI for synchronous downlink CDMA systems is carried out for BPSK signals with random signature sequences in Nakagami-m fading environment with known channel phase. This analysis presents a unified approach as Nakagami-m fading is a general fading distribution that includes the Rayleigh, the one-sided Gaussian, the Nakagami-q, and the Rice distributions as special cases. Consequently, new explicit closed-form expressions for the probability density function (pdf of MAI and MAI plus noise are derived for Nakagami-m, Rayleigh, one-sided Gaussian, Nakagami-q, and Rician fading. Moreover, optimum coherent reception using maximum likelihood (ML criterion is investigated based on the derived statistics of MAI plus noise and expressions for probability of bit error are obtained for these fading environments. Furthermore, a standard Gaussian approximation (SGA is also developed for these fading environments to compare the performance of optimum receivers. Finally, extensive simulation work is carried out and shows that the theoretical predictions are very well substantiated.

  11. A bio-inspired asynchronous skin system for crack detection applications

    International Nuclear Information System (INIS)

    In many applications of structural health monitoring (SHM) it is imperative or advantageous to have large sensor arrays in order to properly sense the state of health of the structure. Typically these sensor networks are implemented by placing a large number of sensors over a structure and running individual cables from each sensor back to a central measurement station. Data is then collected from each sensor on the network at a constant sampling rate regardless of the current timescales at which events are acting on the structure. These conventional SHM sensor networks have a number of shortfalls. They tend to have a large number of cables that can represent a single point of failure for each sensor as well as add significant weight and installation costs. The constant sampling rate associated with each sensor very quickly leads to large amounts of data that must be analyzed, stored, and possibly transmitted to a remote user. This leads to increased demands on power consumption, bandwidth, and size. It also taxes our current techniques for managing large amounts of data. For the last decade the goal of the SHM community has been to endow structures with the functionality of a biological nervous system. Despite this goal the community has predominantly ignored the biological nervous system as inspiration for building structural nervous systems, choosing instead to focus on experimental mechanics and simulation techniques. In this work we explore the use of a novel, bio-inspired, SHM skin. This skin makes use of distributed computing and asynchronous communication techniques to alleviate the scale of the data management challenge as well as reduce power. The system also periodically sends a ‘heat beat’ signal to provide state-of-health updates. This conductive skin was implemented using conductive ink resistors as well as with graphene-oxide capacitors. (paper)

  12. BER Comparison between CDMA & COFDM Model

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar Nigam

    2014-05-01

    Full Text Available The work emphasizes the suitability of Coded orthogonal Frequency Division Multiplexing (COFDM which is a technique of modulation for 3G transceiver systems. The performance of a COFDM system may be affected due to the main factors which were measured comprising of channel noise, multipath delay spread, distortion of the signal (clipping {&} requirement of timing. Using MATLAB to access the performance of COFDM the computer simulations is performed [18]. In the 3rd generation mobile phone system CDMA modulation techniques is mainly proposed for Code Division Multiple Access (CDMA. For the comparison between the two techniques to be established Code Division Multiple Access was used. It was observed and found on examination that a very high tolerance to channel noise, peak power clipping, multipath delay spread as was provided by COFDM [12]. On observation total immunity to multipath delay spread was found in COFDM and provided less reflection time as compared to the guard interval used in COFDM signal. We are aware that multipath signal would provide strengthening to the received signal. Corresponding to multipath reflection of 30 km, delay spread up to 100μsec could be borne. Frequency selective fading strikes a problem due to the multipath and due to this the thing which comes into the picture is that the received signal is heavily attenuated as well as interference comes into existence

  13. MC-CDMA Scheme in Wi-Fi Environment

    Directory of Open Access Journals (Sweden)

    Nacera Larbi

    2012-01-01

    Full Text Available The combination of OFDM and Code Division Multiple Access (CDMA is seen as an attractive and practical solution to enhance the throughput and/or robustness for future high-speed indoor WLANs. The multi-path Rayleigh channel represents a hostile environment for WLANs communication. So, we have proposed the MC-CDMA system to overcome the impact of this kind of wireless channel. The focus of this article is to simulate a modified physical layer (PHY based on the IEEE 802.11a combined with a stage of spread spectrum. This modified layer particularly concentrates on IEEE 802.11a standard. Basically, the proposed schemes can be split in different types depending on the CDMA code used. We investigated the modified physical layer performance on the basis of Bit Error Rate (BER and Signal-to-Noise Ratio (SNR. The numerical results show that the MC-CDMA is a powerful multi-carrier multiple access technology.

  14. Space-Time Coded MC-CDMA: Blind Channel Estimation, Identifiability, and Receiver Design

    Directory of Open Access Journals (Sweden)

    Li Hongbin

    2002-01-01

    Full Text Available Integrating the strengths of multicarrier (MC modulation and code division multiple access (CDMA, MC-CDMA systems are of great interest for future broadband transmissions. This paper considers the problem of channel identification and signal combining/detection schemes for MC-CDMA systems equipped with multiple transmit antennas and space-time (ST coding. In particular, a subspace based blind channel identification algorithm is presented. Identifiability conditions are examined and specified which guarantee unique and perfect (up to a scalar channel estimation when knowledge of the noise subspace is available. Several popular single-user based signal combining schemes, namely the maximum ratio combining (MRC and the equal gain combining (EGC, which are often utilized in conventional single-transmit-antenna based MC-CDMA systems, are extended to the current ST-coded MC-CDMA (STC-MC-CDMA system to perform joint combining and decoding. In addition, a linear multiuser minimum mean-squared error (MMSE detection scheme is also presented, which is shown to outperform the MRC and EGC at some increased computational complexity. Numerical examples are presented to evaluate and compare the proposed channel identification and signal detection/combining techniques.

  15. A CDMA Based Scalable Hierarchical Architecture for Network-On-Chip

    Directory of Open Access Journals (Sweden)

    Mohamed A. Abd El Ghany

    2012-09-01

    Full Text Available A Scalable hierarchical architecture based Code-Division Multiple Access (CDMA is proposed for high performance Network-on-Chip (NoC. This hierarchical architecture provides the integration of a large number of IPs in a single on-chip system. The network encoding and decoding schemes for CDMA transmission are provided. The proposed CDMA NoC architecture is compared to the conventional architecture in terms of latency, area and power dissipation. The overall area required to implement the proposed CDMA NoC design is reduced by 24.2%. The design decreases the latency of the network by 40%. The total power consumption required to achieve the proposed design is also decreased by 25%.

  16. Distributed embedded controller development with petri nets application to globally-asynchronous locally-synchronous systems

    CERN Document Server

    Moutinho, Filipe de Carvalho

    2016-01-01

    This book describes a model-based development approach for globally-asynchronous locally-synchronous distributed embedded controllers.  This approach uses Petri nets as modeling formalism to create platform and network independent models supporting the use of design automation tools.  To support this development approach, the Petri nets class in use is extended with time-domains and asynchronous-channels. The authors’ approach uses models not only providing a better understanding of the distributed controller and improving the communication among the stakeholders, but also to be ready to support the entire lifecycle, including the simulation, the verification (using model-checking tools), the implementation (relying on automatic code generators), and the deployment of the distributed controller into specific platforms. Uses a graphical and intuitive modeling formalism supported by design automation tools; Enables verification, ensuring that the distributed controller was correctly specified; Provides flex...

  17. REANALYSIS OF BER FOR WAVELET BASED MC-CDMA COMMUNICATION

    Directory of Open Access Journals (Sweden)

    Anil Kumar Dubey

    2011-05-01

    Full Text Available As demand for higher data rates is continuously rising,there is always a need to develop more efficientwireless communication systems. The workdescribed in this paper is my effort in thisdirection. We developed and evaluated a waveletpacket based multicarrier CDMA wirelesscommunication system. In this system design a set ofwavelet packets are used as the modulation waveformsin a multicarrier CDMA system. The need for cyclic prefix is eliminated in the system design due to the good orthogonality and time-frequency localization properties of the wavelet packets.Wavelet Packets have good properties such as orthogonality and multirate flexibility, and have resulted in a number of works for its applications to code division multiple access communications.

  18. Simulation of Power Control and Diversity of Cellular CDMA

    Institute of Scientific and Technical Information of China (English)

    RomanPichna; QiangWang; 等

    1995-01-01

    This paper presents a software package developed by the authors for the simulation of a cellular code division multiple access(CDMA)system.In the simulated system,a number of fac-tors are taken into account including time-correlated fading and shadowing,delays in power control and diversity ,errors in power control commands,soft hand-off,base station diversity,and pilots and diversity transmissions,contributions to the interference.

  19. Improved Algorithm for Throughput Maximization in MC-CDMA

    Directory of Open Access Journals (Sweden)

    Hema Kale

    2012-09-01

    Full Text Available The Multi-Carrier Code Division Multiple Access (MC-CDMA is becoming a very significant downlink multiple access technique for high-rate data transmission in the fourth generation wireless communication systems. By means of efficient resource allocation higher data rate i.e. throughput can be achieved. This paper evaluates the performance of group (subchannel allocation criteria employed in downlink transmission, which results in throughput maximization. Proposed algorithm gives the modified technique of sub channel allocation in the downlink transmission of MC-CDMA systems. Simulation are carried out for all the three combining schemes, results shows that for the given power and BER proposed algorithmcomparatively gives far better results .

  20. Improved Algorithm for Throughput Maximization in MC-CDMA

    Directory of Open Access Journals (Sweden)

    Hema Kale

    2012-08-01

    Full Text Available The Multi-Carrier Code Division Multiple Access (MC-CDMA is becoming a very significant down link multiple access technique for high-rate data transmission in the fourth generation wireless communication systems. By means of efficient resource allocation higher data rate i.e. throughput can be achieved. This paper evaluates the performance of group (sub channel allocation criteria employed in down link transmission, which results in throughput maximization. Proposed algorithm gives the modified technique of sub channel allocation in the down link transmission of MC-CDMA systems. Simulation are carried out for all the three combining schemes, results shows that for the given power and BER proposed algorithm comparatively gives far better results .

  1. Space-Time Coded Beamforming for DS-CDMA Downlink

    Institute of Scientific and Technical Information of China (English)

    WANG Shi-lu; XU Chang-jiang; FENG Guang-zeng

    2005-01-01

    In this paper,we analyze the scheme of Space-Time Coded BeamForming(STC-BF)for the downlink of DS-CDMA system over frequency-selective fading channels and give the numerical simulations on the scheme.The blind multiuser detection is employed at receiver to suppress the Multi-Access Interference(MAI).The Space-Time Coding(STC)and BF are combined to mitigate the performance degradation due to multipath fading and various interferences.The numerical simulations show that the BF can compensate the performance loss of STC due to the channel correlation and then the STC-BF can greatly improve the performance of CDMA system.

  2. Frequency hopping CDMA for flexible third generation wireless networks

    OpenAIRE

    Fitton, MP; Nix, AR; Beach, MA

    1997-01-01

    Frequency hopping spread spectrum (FH-SS) has found a number of applications in cellular systems, wireless local loop, and wireless local area networks. The suitability of slow frequency hopping code division multiple access (SFH-CDMA) is characterised, for application in third generation wireless communications. An FH architecture displays inherent frequency diversity, and consequently is resilient to the effects of intersymbol interference arising from significant time dispersion in the cha...

  3. WCDMA and CDMA2000 Communication Industry Standards

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Since the Ministry of Information Industry promulgated the Third Generation (3G) mobile communication "China Standard" TD-SCDMA as the standard for China's communication industry, the ministry has also promulgated WCDMA and CDMA2000 as industrial standards.

  4. A Two-Stage State Recognition Method for Asynchronous SSVEP-Based Brain-Computer Interface System

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zimu; DENG Zhidong

    2013-01-01

    A two-stage state recognition method is proposed for asynchronous SSVEP (steady-state visual evoked potential) based brain-computer interface (SBCI) system.The two-stage method is composed of the idle state (IS) detection and control state (CS) discrimination modules.Based on blind source separation and continuous wavelet transform techniques,the proposed method integrates functions of multi-electrode spatial filtering and feature extraction.In IS detection module,a method using the ensemble IS feature is proposed.In CS discrimination module,the ensemble CS feature is designed as feature vector for control intent classification.Further,performance comparisons are investigated among our IS detection module and other existing ones.Also the experimental results validate the satisfactory performance of our CS discrimination module.

  5. Analysis and Simulation of CDMA QAM-16 for AWGN and RAYLEIGH Channel

    Directory of Open Access Journals (Sweden)

    Arun Kumar

    2014-07-01

    Full Text Available In a Code Division Multiple Access (CDMA system, a lot of users use concurrently the entire frequency band to transmit their data and users’ data is separated on the basis of their unique spreading code. The aim of Communication System i.e. Communication at anytime, anywhere and by anybody is still not fulfilled but the technology like CDMA can fulfill the aim of communication system if it is properly analyzed. For a downlink transmission Quadrature Amplitude Modulation (QAM, Quadrature Phase Shift Keying (QPSK and Binary Phase Shift Keying (BPSK modulation Techniques are considered in a Wideband Code Division Multiple Access System. The work design and evaluate CDMA Transmitter and Receiver for QAM-16 modulation Scheme and deal with BER performance of WCDMA, when the design is subjected to a number of users as well as noise and interference in the AWGN channel and Rayleigh Fading channel

  6. Crest Factor Reduction in MC-CDMA Employing Carrier Interferometry Codes

    Directory of Open Access Journals (Sweden)

    Natarajan Balasubramaniam

    2004-01-01

    Full Text Available This paper addresses signal compactness issues in MC-CDMA employing carrier interferometry codes using the measure of crest factor (CF. Carrier interferometry codes, applied to N -carrier MC-CDMA systems, enable 2N users to simultaneously share the system bandwidth with minimal degradation in performance (relative to the N -orthogonal-user case. First, for a fully loaded ( K=N and K=2N users MC-CDMA system with practical values of N , it is shown that the CF in downlink transmission demonstrates desirable properties of low mean and low variance. The downlink CF degrades when the number of users in the system decreases. Next, the high CF observed in the uplink is characterized and the poor CF in a partially loaded downlink as well as uplink is effectively combated using Schroeder's analytical CF reduction techniques.

  7. Direct sequence spread spectrum CDMA in shared spectrum applications

    Science.gov (United States)

    Schilling, Donald L.; Milstein, Laurence B.; Pickholtz, Raymond L.; Miller, Frank

    1991-01-01

    Personal Communication Network (PCN) is an entirely wireless communication system with the capability of assessing the wired telephone system to reach anyone processing only a wired telephone. It is expected to compete with the existing mobile cellular system which connects directly to the wired telephone system. While many PCN systems employ TDMA technology, the PCN system described here uses Broadband CDMA (BCDMA(sup SM)) which is capable of sharing the spectrum with other users and which is extremely resistant to fading caused by multipath.

  8. SocialRAD: an infrastructure for a secure, cooperative, asynchronous teleradiology system.

    Science.gov (United States)

    Figueiredo, João Filho Matos; Motta, Gustavo Henrique Matos Bezerra

    2013-01-01

    The popularity of teleradiology services has enabled a major advance in the provision of health services to areas with difficult geographical access. However, this potential has also brought with it a number of challenges: the large volume of data, characteristic of imaging tests, and security requirements designed to ensure confidentiality and integrity. Moreover, there is also a number of ethical questions involving the dominant model on the market, whereby this service is outsourced to private companies, and is not directly undertaken by professional radiologists. Therefore, the present paper proposes a cooperative model of teleradiology, where health professionals interact directly with the hospitals providing patient care. This has involved the integration of a wide range of technologies, such as the interconnection models Peer-to-Peer, Cloud Computing, Dynamic DNS, RESTful Web Services, as well as security and interoperability standards, with the aim of promoting a secure, collaborative asynchronous environment. The developed model is currently being used on an experimental basis, providing teleradiology support to cities in the north-eastern hinterland of Brazil, and is fulfilling all expectations.

  9. Optimal Power Distribution Control for Multicode MC-CDMA with Zero-Forcing Successive Interference Cancellation

    Directory of Open Access Journals (Sweden)

    Yeheskel Bar-Ness

    2005-04-01

    Full Text Available Multicarrier CDMA (MC-CDMA has become a promising candidate for future wireless multimedia communications for its robustness to frequency-selective fading and its flexibility for handling multiple data rates. Among different multirate access schemes, multicode MC-CDMA is attractive for its high performance, good flexibility in rate matching, and low complexity. However, its performance is limited by self-interference (SI and multiuser interference (MUI. In this paper a zero-forcing successive interference cancellation (ZF-SIC receiver is used to mitigate this problem for multicode MC-CDMA. Furthermore, optimal power distribution control (PDC, which minimizes each user's bit error rate (BER, is considered. Our results show that, in correlated Rayleigh fading channels, the ZF-SIC receiver integrated with the optimal PDC dramatically improves the performance of the multicode MC-CDMA system in comparison to other receivers proposed in the literature. Moreover, the optimal PDC significantly outperforms the PDC based on equal BER criterion, particularly under a short-term transmit power constraint.

  10. Design and Simulation of MC-CDMA Transceiver via Slantlet Transform

    Directory of Open Access Journals (Sweden)

    Kattoush A. H.

    2012-04-01

    Full Text Available Wireless communications is a rapidly growing piece of the communications manufacturing, with the potential to provide high-speed high-quality information exchange between the portable devices located anywhere in the world. Multi-Carrier Code Division Multiple Access (MC-CDMA has emerged recently as a promising candidate for the next generation broad-band mobile networks. Recently, it was found that Slantlet transform (SLT based Orthogonal Frequency Division Multiplexing (OFDM is capable to reduce the Inter Symbol Interference (ISI and the Inter Carrier Interference (ICI, which are caused by the loss of orthogonality between the sub-carriers. SLT-OFDM can support higher spectrum efficiency than Fast Fourier Transform-based OFDM (FFT-OFDM due to the elimination of the Cyclic Prefix (CP. In this paper, a novel SLT-MC-CDMA transceiver design is presented based on the SLT-OFDM that is used as a basic building block in the design of MC-CDMA transceiver to maintain the orthogonality against the multi-path frequency Selective Fading Channels (SFC. Simulation results are provided to demonstrate the significant gain in the performance of the proposed technique. The Bit Error Rate (BER of SLT-MC-CDMA scheme is compared with FFT-MC-CDMA and tested in Additive White Gaussian Noise (AWGN, Flat Fading and Selective Fading Channels (SFH. The simulation results confirmed that, the proposed system outperforms the reference one.

  11. Performance Analysis of MC-CDMA in the Presence of Carriers Phase Errors

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper presents the effect of carriers phase error on MC-CDMA performance in downlink mobile communications. Signal-to-Noise Ratio (SNR) and Bit-Error-Rate (BER) are analyzed taking into account the effect of carrier phase errors. It is shown that the MC-CDMA system is very sensitive to a carrier frequency offset, the system performance rapidly degrades and strongly depends on the number of carriers. For a maximal load, the degradation caused by carrier phase jitter is independent of the number of the carriers.

  12. A Capacity Improvement Method for CDMA based Mesh Networks in SUI Multipath Fading Channels

    CERN Document Server

    Zeeshan, Muhammad; Malik, Muhammad Yasir

    2011-01-01

    Code Division Multiple Access (CDMA) is the most promising candidate for wideband data access. This is due to the advantage of soft limit on the number of active mobile devices. Many wireless mesh systems impose an upper bound on the BER performance which restricts the increase in number of mobile users. Capacity is further reduced in Multipath Fading Environment (MFE). This paper presents an effective method of improving the capacity of a CDMA based mesh network by managing the transmitted powers of the mobile devices and using MMSE based Multiuser Detection (MUD). The proposed scheme improves the capacity two times as compared to the conventional CDMA based mesh network. Simulation results have been presented to demonstrate the effectiveness of the proposed scheme.

  13. Digital Component Separator for future W-CDMA-LINC Transmitters implemented on an FPGA

    Directory of Open Access Journals (Sweden)

    W. Gerhard

    2005-01-01

    Full Text Available This paper presents the implementation of a Digital-Component-Separator (DCS for a LINC-transmitter (linear amplification using nonlinear components on an FPGA (field programmable gate array. It investigates and estimates the bandwidth requirements for such a LINC system. The influence of bandwidth limitations on a digitally based LINC-transmitter for W-CDMA utilization is studied by simulations. Furthermore a LINC transmitter is proposed which employs a flexible image-reject- or a direct up-conversion-architecture for transmission of single or combined multi-carrier/channel W-CDMA signals using the phase-modulation approach. The sampling frequency can be chosen at a value up to 32 times (122.88MHz the symbol rate of the W-CDMA chip rate of 3.84Mbits/s. Measurement results for a LINC transmitter are presented and discussed.

  14. Asynchronous Power Flow Controller

    Directory of Open Access Journals (Sweden)

    Rahul Juneja

    2014-04-01

    Full Text Available In the present system demand of electrical power increases so fast and transfer of electrical power is need of today‟s scenario. . The electrical power is transfer at same frequency through AC transmission line. However, power generation may be at different frequencies such as wind generation, sources at islanding or power generation in different countries. The proposed Asynchronous Power Flow Controller (APFC system essentially consists of two back-to-back voltage source converters as “Shunt Converter” and “Series Converter” which is coupled via a common dc link provided by a dc storage capacitor This paper suggests the power transfer and control between the sources operating at different or same frequencies.

  15. The Implementation of Digital Trunking System Based on CDMA%基于CDMA技术的数字集群通信系统的实现

    Institute of Scientific and Technical Information of China (English)

    谭学治; 李鹏; 贾世楼

    2005-01-01

    针对数字集群系统与蜂窝系统的不同之处,对能否以CDMA(码分多址)方式实现数字集群系统的功能进行了详细的分析.本文首先讨论了在CDMA方式下数字集群系统的功能实现方案,然后采用WCDMA的典型链路参数对系统余量进行了理论分析,采用Okumura(奥村),Egli两种传播模型分别进行估算,并给出了系统余量曲线图.

  16. SUBSPACE METHOD FOR BLIND IDENTIFICATION OF CDMA TIME-VARYING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Liu Yulin; Peng Qicong

    2002-01-01

    A new blind method is proposed for identification of CDMA Time-Varying (TV)channels in this paper. By representing the TV channel's impulse responses in the delay-Doppler spread domain, the discrete-time canonical model of CDMA-TV systems is developed and a subspace method to identify blindly the Time-Invariant (TI) coordinates is proposed. Unlike existing basis expansion methods, this new algorithm does not require .estimation of the base frequencies, neither need the assumption of linearly varying delays across symbols. The algorithm offers definite explanation of the expansion coordinates. Simulation demonstrates the effectiveness of the algorithm.

  17. SUBSPACE METHOD FOR BLIND IDENTIFICATION OF CDMA TIME—VARYING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    LiuYulin; PengQicong

    2002-01-01

    A new blind method is proposed for identification of CDMA Time-Varyin(TV) channels in this paper.By representing the TV channel's impulse responses in the delay-Doppler spread domain, the discrete-time canonical model of CDMA-TV systems is developed and a subspace method to identify blindly the Time-Invariant(TI) coordingates is proposed.Unlike existing basis expansion methods, this new algorithm does not require estimation of the base frequencies, neither need the assumption of linearly varying delays across symbols.The algorithm offers definite explanation of the expansion coordinates.Simulation demonstrates the effectiveness of the algorithm.

  18. Asynchronous design of Networks-on-Chip

    DEFF Research Database (Denmark)

    Sparsø, Jens

    2007-01-01

    The Network-on-chip concept has evolved as a solution to a broad range of problems related to the design of complex systems-on-chip (SoC) with tenths or hundreds of (heterogeneous) IP-cores. The paper introduces the NoC concept, identifies a range of possible timing organizations (globally......-synchronous, mesochronous, globally-asynchronous locally-synchronous and fully asynchronous), discusses the circuitry needed to implement these timing methodologies, and provides some implementation details for a couple of asynchronous NoCs designed at the Technical University of Denmark (DTU). The paper is written...

  19. Blind Synchronization in Asynchronous UWB Networks Based on the Transmit-Reference Scheme

    Directory of Open Access Journals (Sweden)

    Leus Geert

    2006-01-01

    Full Text Available Ultra-wideband (UWB wireless communication systems are based on the transmission of extremely narrow pulses, with a duration inferior to a nanosecond. The application of transmit reference (TR to UWB systems allows to side-step channel estimation at the receiver, with a tradeoff of the effective transmission bandwidth, which is reduced by the usage of a reference pulse. Similar to CDMA systems, different users can share the same available bandwidth by means of different spreading codes. This allows the receiver to separate users, and to recover the timing information of the transmitted data packets. The nature of UWB transmissions—short, burst-like packets—requires a fast synchronization algorithm, that can accommodate several asynchronous users. Exploiting the fact that a shift in time corresponds to a phase rotation in the frequency domain, a blind and computationally effcient synchronization algorithm that takes advantage of the shift invariance structure in the frequency domain is proposed in this paper. Integer and fractional delay estimations are considered, along with a subsequent symbol estimation step. This results in a collision-avoiding multiuser algorithm, readily applicable to a fast acquisition procedure in a UWB ad hoc network.

  20. Interference subspace rejection in wideband CDMA:

    DEFF Research Database (Denmark)

    Hansen, Henrik; Affes, Sofiene; Mermelstein, Paul

    2001-01-01

    This paper extends our study on a multi-user receiver structure for base-station receivers with antenna arrays in multicellular systems. The receiver employs a beamforming structure with constraints that nulls the signal component in appropriate interference subspaces. Here we introduce a new mode...... result of subspace suppression, as well as allow asynchronous transmission. Performance differences arise between the modes due to different sensitivities to channel identification and data detection errors. For homogeneous high data-rate situations ISR-DX manifests the best performance. However, due to...... its reduced complexity, ISR-TRX appears to offer the best complexity-performance tradeoffs....

  1. Application of asynchronous subprograms function in Siemens 840D system%西门子840D系统异步子程序功能的应用

    Institute of Scientific and Technical Information of China (English)

    张宝生

    2012-01-01

    With asynchronous subprograms in Siemens 840D system to realize manual tool shift of CNC lathe. And simplify PLC program so as to easily access to manual tool shift.%利用西门子840D系统的异步子程序来实现数控车床的刀架手动换刀功能,简化PLC程序的编制,使手动换刀更为方便和准确.

  2. 异步讨论系统的设计与实现%The Design and Realization of Asynchronous Discussion System Based on Moodle

    Institute of Scientific and Technical Information of China (English)

    毛汉领; 吴振勇

    2008-01-01

    Peer learning and monitoring the procedure axe an important key to improve effectiveness and to increase the success rate of the learner in the distance education. The requirement of peer learning and monitoring the procedure were analyzed and outlined first in this paper, the asynchronous discussion system based on Moodle was designed and realized, the peer learning and monitoring the procedure were described in detail finally.

  3. A Low-Complexity Joint Synchronization and Detection Algorithm for Single-Band DS-CDMA UWB Communications

    DEFF Research Database (Denmark)

    Christensen, Lars P.B.

    2005-01-01

    The problem of asynchronous direct-sequence code division multiple access (DS-CDMA) detection over the ultra-wideband (UWB) multipath channel is considered. A joint synchronization, channel-estimation and multi-user detection scheme based on the adaptive linear minimum mean-square error (LMMSE......) receiver is presented and evaluated. The receiver is based on [3] extended with a synchronization method from [6]. Further, a novel non-recursive least-squares algorithm capable of reducing the complexity of the adaptation in the receiver while preserving the advantages of the recursive least-squares (RLS...

  4. Asynchronous Data Fusion With Parallel Filtering Frame

    OpenAIRE

    Na Li; Junhui Liu

    2011-01-01

    This paper studies the design of data fusion algorithm for asynchronous system with integer times sampling. Firstly, the multisensor asynchronous samplings is mapped to the basic axis, accordingly a sampling sequence of single sensor can be taken. Secondly, aiming at the sensor with the densest sampling points, the modified parallel filtering is given. Afterwards, the sequential filtering fusion method is introduced to deal with the case that there are multiple mapped measurements at some sam...

  5. Performance Analysis of Asynchronous Multicarrier Wireless Networks

    OpenAIRE

    Lin, Xingqin; Jiang, Libin; Andrews, Jeffrey G.

    2014-01-01

    This paper develops a novel analytical framework for asynchronous wireless networks deploying multicarrier transmission. Nodes in the network have different notions of timing, so from the viewpoint of a typical receiver, the received signals from different transmitters are asynchronous, leading to a loss of orthogonality between subcarriers. We first develop a detailed link-level analysis based on OFDM, based on which we propose a tractable system-level signal-to-interference-plus-noise ratio...

  6. Modeling radio link performance in UMTS W-CDMA network simulations

    DEFF Research Database (Denmark)

    Klingenbrunn, Thomas; Mogensen, Preben Elgaard

    2000-01-01

    This article presents a method to model the W-CDMA radio receiver performance, which is usable in network simulation tools for third generation mobile cellular systems. The method represents a technique to combine link level simulations with network level simulations. The method is derived from [...

  7. R-MOM: A Component-Based Framework for Interoperable and Adaptive Asynchronous Middleware Systems

    OpenAIRE

    Labéjof, Jonathan; Léger, Antoine; Merle, Philippe; Seinturier, Lionel; Vincent, Hugues

    2012-01-01

    International audience Systems of systems (SoS) are composed of subsystems such as Distributed, Information Technology, Real-Time and Embedded systems. Among distributed systems, Message- Oriented Middleware (MOM) is used by SoS in order to share status information from system elements (component, service, etc.). Often several different MOM technologies are used in one SoS, then interoperability between these MOM is a requirement. In this paper, we present R-MOM, a component-based framewor...

  8. Asynchronous MPI for the Masses

    OpenAIRE

    Wittmann, Markus; Hager, Georg; Zeiser, Thomas; Wellein, Gerhard

    2013-01-01

    We present a simple library which equips MPI implementations with truly asynchronous non-blocking point-to-point operations, and which is independent of the underlying communication infrastructure. It utilizes the MPI profiling interface (PMPI) and the MPI_THREAD_MULTIPLE thread compatibility level, and works with current versions of Intel MPI, Open MPI, MPICH2, MVAPICH2, Cray MPI, and IBM MPI. We show performance comparisons on a commodity InfiniBand cluster and two tier-1 systems in Germany...

  9. MC-CD MA 系统中的多进制联合稀疏图设计%Construction of non-binary united low density graph in MC-CDMA systems

    Institute of Scientific and Technical Information of China (English)

    文磊; 雷菁; 魏急波; 王建新

    2016-01-01

    为解决移动通信系统过载传输,在稀疏图多址接入基础上,将低密度扩频技术拓展至多载波传输系统,设计了基于多载波码分多址(MC‐CDMA)的多进制联合稀疏图。该多进制联合稀疏图通过变量节点和置换节点,将低密度扩频矩阵和多进制低密度奇偶校验码(LDPC)校验矩阵结合起来,使得系统的接收端能够在整幅稀疏图上同时完成多用户检测和信道译码。多进制联合稀疏图融合了扩频、多载波调制和信道编码等技术,包含多维信号的综合协作处理。计算机仿真表明,多进制联合稀疏图MC‐CDMA在系统严重过载情况下,仍然能达到理想的通信性能。%Idea of the low density spreading to multicarrier transmission systems was extended ,and nonbinary united low density graph for MC‐CDMA (multi‐carrier code division multiple access) was designed .Such graph linked low density spreading matrix and low density parity check(LDPC) matrix through variable nodes and transform nodes .On the receiver ,united detection and decoding could be implemented .Spreading ,multiuser access and channel coding were combined and processed jointly . Computer simulations show that compared with similar systems ,the nonbinary united low density graph MC‐CDMA can achieve better performance even when user′s number severely surpasses the sys‐tem capacity .

  10. Instructor-Aided Asynchronous Question Answering System for Online Education and Distance Learning

    Science.gov (United States)

    Wen, Dunwei; Cuzzola, John; Brown, Lorna; Kinshuk

    2012-01-01

    Question answering systems have frequently been explored for educational use. However, their value was somewhat limited due to the quality of the answers returned to the student. Recent question answering (QA) research has started to incorporate deep natural language processing (NLP) in order to improve these answers. However, current NLP…

  11. Asynchronous design pattern for many-core and cloud operating systems

    OpenAIRE

    Santos, Bruno; Barraca, João Paulo; Aguiar, Rui L.

    2012-01-01

    One of the key aspects for many-core and cloud operating systems is message passing communication. The networking aspect of this mechanism requires a high degree of concurrency to handle communicating with thousands of cores simultaneously in an efficient and scalable manner. Non-blocking interfaces allows us to efficiently use a core and gives us concurrency without multiple threads, this also minimizes context switch.

  12. 空间色噪声CDMA系统的一种基于累积量DOA估计算法%A Cumulant-Based DOA Estimation Algorithm for CDMA System in Spatial Colored Noise

    Institute of Scientific and Technical Information of China (English)

    杨维; 程时昕

    2003-01-01

    传统的DOA估计一般是假设噪声为白高斯的二阶谱估计算法.针对更接近于实际情况的空间色噪声,提出了一种基于累积量MUSIC算法的同步CDMA系统解相干DOA估计算法.该算法不仅能消除多径干扰并且与二阶MUSIC算法相比能更有效抑制空间色噪声,提高估计的准确性.%The conventional direction of arrival (DOA) detection algorithm is generally based on the second-orderspectrum estimation while assuming that the noise is additive white Gaussian noise (AWGN). Concentrating on spatial colored noise of unknown spectrum quality, which is more realistic in any scenario, a novel high-order cumulantMUSIC DOA estimation algorithm for synchronous CDMA system with decorrelator has been proposed. The proposed algorithm not only has the advantages that the DOA of multipath signals can be estimated independently byeliminating all the other resolvable multipath signal interference but while on spatial colored noise case the proposedalgorithm estimates DOAs of the decoupled multipath signal more effectively and accurately than the conventionalsecond-order MUSIC algorithm.

  13. Communication and Agreement Abstractions for Fault-Tolerant Asynchronous Distributed Systems

    CERN Document Server

    Raynal, Michel

    2010-01-01

    Understanding distributed computing is not an easy task. This is due to the many facets of uncertainty one has to cope with and master in order to produce correct distributed software. Considering the uncertainty created by asynchrony and process crash failures in the context of message-passing systems, the book focuses on the main abstractions that one has to understand and master in order to be able to produce software with guaranteed properties. These fundamental abstractions are communication abstractions that allow the processes to communicate consistently (namely the register abstraction

  14. Pulse Interval Modulation for Ultra-High Speed IR-UWB Communications Systems

    Directory of Open Access Journals (Sweden)

    Herceg Marijan

    2010-01-01

    Full Text Available This paper analyzes performances of the Pulse Interval Modulation (PIM scheme for impulse radio ultra-wideband (IR-UWB communication systems. Due to the PIM anisochronous nature, a tap delay line (TDL coded division multiple access (CDMA scheme based on strict optical orthogonal codes (SOOC is proposed. This scheme is suitable for multiuser high-speed data asynchronous transmission applications because the average symbol length is shorter than in Pulse Position Modulation (PPM schemes and it needs only chip synchronization. The error probability over the additive white Gaussian noise (AWGN channel is derived in the single- and multi-user environment and compared with other modulation schemes.

  15. Asynchronous Multiparty Computation

    DEFF Research Database (Denmark)

    Damgård, Ivan Bjerre; Geisler, Martin; Krøigaard, Mikkel;

    2009-01-01

    less than n/3 players. We also present a software framework for implementation of asynchronous protocols called VIFF (Virtual Ideal Functionality Framework), which allows automatic parallelization of primitive operations such as secure multiplications, without having to resort to complicated...

  16. Performance analysis of unslotted fiber-optic code-division multiple-access (CDMA) packet networks

    OpenAIRE

    Hsu, CS; Li, VOK

    1997-01-01

    This paper examines code-division multiple-access (CDMA) techniques used in unslotted fiber-optic packet networks. Since the inherent properties and signal processing of the conventional communication channels are different from those of the fiber-optic channels, new code sequences must be constructed for fiber-optic applications. In unslotted systems, the exact solution is very difficult to obtain. Therefore, two approximation methods are presented to analyze the performance of such systems....

  17. Super-Orthogonal Space-Time Turbo Transmit Diversity for CDMA

    Directory of Open Access Journals (Sweden)

    Pieter G. W. van Rooyen

    2005-05-01

    Full Text Available Studies have shown that transmit and receive diversity employing a combination of multiple transmit-receive antennas (given ideal channel state information (CSI and independent fading between antenna pairs will potentially yield maximum achievable system capacity. In this paper, the concept of a layered super-orthogonal turbo transmit diversity (SOTTD for downlink direct-sequence code-division multiple-access (CDMA systems is explored. This open-loop transmit diversity technique improves the downlink performance by using a small number of antenna elements at the base station and a single antenna at the handset. In the proposed technique, low-rate super-orthogonal code-spread CDMA is married with code-division transmit diversity (CDTD. At the mobile receiver, space-time (ST RAKE CDTD processing is combined with iterative turbo code-spread decoding to yield large ST gains. The performance of the SOTTD system is compared with single- and multiantenna turbo-coded (TC CDTD systems evaluated over a frequency-selective Rayleigh fading channel. The evaluation is done both by means of analysis and computer simulations. The performance results illustrate the superior performance of SOTTD compared to TC CDTD systems over practically the complete useful capacity range of CDMA. It is shown that the performance degradation characteristic of TC CDTD at low system loads (due to the inherent TC error floor is alleviated by the SOTTD system.

  18. User satisfaction with asynchronous telemedicine: a study of users of Santa Catarina's system of telemedicine and telehealth.

    Science.gov (United States)

    von Wangenheim, Aldo; de Souza Nobre, Luiz Felipe; Tognoli, Heitor; Nassar, Silvia Modesto; Ho, Kendall

    2012-06-01

    User satisfaction analyses in synchronous telemedicine and teleconsultation environments have been widely performed and generally show satisfied users. In the field of asynchronous telemedicine, however, satisfaction studies were performed only in one single location or with a restricted set of users. With the aim of offering an exemplar evaluation of the impact of the statewide use of a large-scale asynchronous telemedicine network on the satisfaction of the involved users, this study presents the results obtained from a survey of the perceived quality of the service by both patients and healthcare staff. For this purpose, a survey with satisfaction questionnaires was performed with 564 patients from seven upstate municipalities and 56 healthcare professionals from 46 municipalities, using a methodology from the process improvement field. The collected data were quantified and underwent statistical analysis, which showed a clear perception of the improvement in the quality of service by both patients and healthcare professionals. The present findings also showed that both patients and healthcare professionals felt that introducing these new technologies was a positive step, even in upstate areas and when they involved great changes in the usual processes of primary care. PMID:22703378

  19. Comparative Study of CDMA and OFDM in WI-FI

    Directory of Open Access Journals (Sweden)

    N. Larbi

    2012-03-01

    Full Text Available There have been extensive research efforts on simulating Wireless Local Area Networks. Many papers have studied the performance of IEEE 802.11 WLANs by using simulation under different channels and for different modulations. In this paper we first simulate a simplified IEEE 802.11a standard based on Orthogonal Frequency Division Multiplexing (OFDM with the cyclic prefix and IEEE 802.11b standard based on Direct-Sequence Code Division Multiple Accesses (DS-CDMA. Then a comparative study will be performed to evaluate them in Additive White Gaussian Noise (AWGN channel with Rayleigh fading to resemble the real world scenario. We investigated their physical layer performances on the basis of Bit Error Rate (BER and Signal-to-Noise Ratio (SNR. These parameters are discussed and compared in the two models. It has been demonstrated that OFDM system provides better performance in noisy conditions.

  20. Performance Evaluation of a Novel CDMA Detection Technique: The Two-State Approach

    Directory of Open Access Journals (Sweden)

    Luca Simone Ronga

    2005-04-01

    Full Text Available The use of code division multiple access (CDMA makes third-generation wireless systems interference limited rather than noise limited. The research for new methods to reduce interference and increase efficiency lead us to formulate a signaling method where fast impulsive silence states are mapped on zero-energy symbols. The theoretical formulation of the optimum receiver is reported and the asymptotic multiuser efficiency (AME as well as an upper bound of the probability of error have been derived and applied to the conventional receiver and the decorrelating detector. Moreover, computer simulations have been performed to show the advantages of the proposed two-state scheme over the traditional single-state receiver in a multiuser CDMA system operating in a multipath fading channel.

  1. Asynchronous Variational Integrators

    OpenAIRE

    Lew, A.; Marsden, J. E.; Ortiz, M.; West, M

    2003-01-01

    We describe a new class of asynchronous variational integrators (AVI) for nonlinear elastodynamics. The AVIs are distinguished by the following attributes: (i) The algorithms permit the selection of independent time steps in each element, and the local time steps need not bear an integral relation to each other; (ii) the algorithms derive from a spacetime form of a discrete version of Hamilton’s variational principle. As a consequence of this variational structure, the algorith...

  2. Text Mining: (Asynchronous Sequences

    Directory of Open Access Journals (Sweden)

    Sheema Khan

    2014-12-01

    Full Text Available In this paper we tried to correlate text sequences those provides common topics for semantic clues. We propose a two step method for asynchronous text mining. Step one check for the common topics in the sequences and isolates these with their timestamps. Step two takes the topic and tries to give the timestamp of the text document. After multiple repetitions of step two, we could give optimum result.

  3. Ping-pong effects study in PIC turbo joint detection for TDD CDMA

    Institute of Scientific and Technical Information of China (English)

    Song Changjian; Zhong Zifa; Zhang Shuo

    2009-01-01

    A kind of turbo joint detection scheme based on parallel interference cancellation (PIC) is studied; then, the eigenvalues of iteration matrix is deeply analyzed for studying the ping-pong effects in PIC JD and the corresponding compensation approach is introduced. Finally, the proposed algorithm is validated through computer simulation in TDD CDMA uplink transmission. The result shows that the ping-pong effects are almost avoided completely in the presence of the compensation scheme, and system performance is greatly improved.

  4. A Semi-blind Adaptive Beamforming Algorithm for Wideband Coherent CDMA

    Institute of Scientific and Technical Information of China (English)

    戎璐; 谢剑英

    2003-01-01

    This paper presented a novel semi-blind adaptive beamforming algorithm specially designed for widebandcoherent CDMA mobile communication systems with multiplexd control and data channels. The presented algo-rithm uses a parallel structure to exploit not only the desired user's pseudo noise sequence but also the informationfrom multiplexed pilot and data symbols, thus help achieve faster convergence and lower bit error rate. MonteCarlo simulation results verified the performance improvement in terms of BER.

  5. A novel chromatic dispersion monitoring method for 400 Gbit/s 256 QAM fiber-optic system based on asynchronous amplitude sampling

    Science.gov (United States)

    Wu, Hui-jun; Zhu, Bo; Liu, Guo-qing; Shen, Jia-wei; Hu, Fang-ren

    2015-11-01

    A novel chromatic dispersion (CD) monitoring technique based on asynchronous amplitude sampling (AAS) is proposed for a higher modulation format and higher rate system. The dispersion and other impairment factors can be separated with the definition of monitoring parameter M. A 400 Gbit/s 256 quadrature amplitude modulation (QAM) system is built using Optisystem13.0 beta software. Simulations of CD monitoring technique for different bandwidths of sampling Gaussian filter, optical signal to noise ratios ( OSNRs) and duty cycles are investigated, and the tolerance is also discussed. Simulation results show that the method can be less affected by noise, and a higher accuracy of 600 ps/(nm·km) can be achieved. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.

  6. Study on forward power allocation for CDMA 2000-1X

    Institute of Scientific and Technical Information of China (English)

    柴远波; 罗兴国; 葛宝忠; 王月清; 宋国文

    2004-01-01

    A new method for allocating the transmitting power on the CDMA(code division multiple access)2000-1x forward link channel under the conditions of multi-path and different rate is proposed. That is, based on the dependency that exists between the respective signal qualities of the pilot channel and traffic channels to allocate the forward link channels reasonably. The CDMA 2000-1 x forward link exploits coherent demodulation with continuously transmitting pilot signals. Therefore the stronger the pilot channel, the less traffic power is required while the same transmission quality is maintained. On the basis of the laboratory test, the diagrams of the dependency are given in the paper, and then an optimal pilot signal quality, which minimizes the total transmitting power is found. This result can be used to maximize the capacity of CDMA 2000-1x system or improve the service quality at cell edge. It has significant meaning for the R&D of the practical system project.

  7. Improvement of SNR with Chaotic Spreading Sequences for CDMA

    CERN Document Server

    Umeno, K; Umeno, Ken; Kitayama, Ken-ichi

    1999-01-01

    We show that chaotic spreading sequences generated by ergodic mappings of Chebyshev orthogonal polynomials have better correlation properties for CDMA(code division multiple access) than the optimal binary sequences (Gold sequences) in the sense of ensemble average.

  8. The Alamouti Scheme with CDMA-OFDM/OQAM

    Directory of Open Access Journals (Sweden)

    Pierre Siohan

    2010-01-01

    Full Text Available This paper deals with the combination of OFDM/OQAM with the Alamouti scheme. After a brief presentation of the OFDM/OQAM modulation scheme, we introduce the fact that the well-known Alamouti decoding scheme cannot be simply applied to this modulation. Indeed, the Alamouti coding scheme requires a complex orthogonality property; whereas OFDM/OQAM only provides real orthogonality. However, as we have recently shown, under some conditions, a transmission scheme combining CDMA and OFDM/OQAM can satisfy the complex orthogonality condition. Adding a CDMA component can thus be seen as a solution to apply the Alamouti scheme in combination with OFDM/OQAM. However, our analysis shows that the CDMA-OFDM/OQAM combination has to be built taking into account particular features of the transmission channel. Our simulation results illustrate the 2×1 Alamouti coding scheme for which CDMA-OFDM/OQAM and CP-OFDM are compared in two different scenarios: (i CDMA is performed in the frequency domain, (ii CDMA is performed in time domain.

  9. The Alamouti Scheme with CDMA-OFDM/OQAM

    Directory of Open Access Journals (Sweden)

    Siohan Pierre

    2010-01-01

    Full Text Available This paper deals with the combination of OFDM/OQAM with the Alamouti scheme. After a brief presentation of the OFDM/OQAM modulation scheme, we introduce the fact that the well-known Alamouti decoding scheme cannot be simply applied to this modulation. Indeed, the Alamouti coding scheme requires a complex orthogonality property; whereas OFDM/OQAM only provides real orthogonality. However, as we have recently shown, under some conditions, a transmission scheme combining CDMA and OFDM/OQAM can satisfy the complex orthogonality condition. Adding a CDMA component can thus be seen as a solution to apply the Alamouti scheme in combination with OFDM/OQAM. However, our analysis shows that the CDMA-OFDM/OQAM combination has to be built taking into account particular features of the transmission channel. Our simulation results illustrate the Alamouti coding scheme for which CDMA-OFDM/OQAM and CP-OFDM are compared in two different scenarios: (i CDMA is performed in the frequency domain, (ii CDMA is performed in time domain.

  10. Multi User Detector in CDMA Using Elliptic Curve Cryptography

    Directory of Open Access Journals (Sweden)

    M. Ranga Rao

    2012-03-01

    Full Text Available Code division multiple access (CDMA is used in various radio communication techniques due to its advantages. In CDMA one of the most important processes is multi user detection (MUD. There are numerous methods for MUD in CDMA, but in most of the methods, they identify the exact user but the interference signal is high. One of the methods used for MUD in CDM A is elliptic curve cryptography (ECC. Normally, the multi user detector in CDMA using elliptic curve cryptography is performed by using one prime field. In ECC method the exact user is identified and also interference signal reduces comparing with other techniques. To reduce the interference signal to very low, here propose a new technique forMUD in CDMA using ECC. The proposed technique uses multiple prime numbers for key generation. By generating key using different prime numbers using ECC, the bit error rate was very low. The results shows the performance of the proposed for reduce in bit error rate for MUD in CDMA.

  11. Multi User Detector in CDMA Using Elliptic Curve Cryptography

    Directory of Open Access Journals (Sweden)

    M. Ranga Rao

    2012-02-01

    Full Text Available Code division multiple access (CDMA is used in various radio communication techniques due to its advantages. In CDMA one of the most important processes is multi user detection (MUD. There are numerous methods for MUD in CDMA, but in most of the methods, they identify the exact user but the interference signal is high. One of the methods used for MUD in CDM A is elliptic curve cryptography (ECC. Normally, the multi user detector in CDMA using elliptic curve cryptography is performed by using one prime field. In ECC method the exact user is identified and also interference signal reduces comparing with other techniques. To reduce the interference signal to very low, here propose a new technique for MUD in CDMA using ECC. The proposed technique uses multiple prime numbers for key generation. By generating key using different prime numbers using ECC, the bit error rate was very low. The results shows the performance of the proposed for reduce in bit error rate for MUD in CDMA.

  12. Stand-Alone and Hybrid Positioning Using Asynchronous Pseudolites

    Directory of Open Access Journals (Sweden)

    Ciro Gioia

    2014-12-01

    Full Text Available global navigation satellite system (GNSS receivers are usually unable to achieve satisfactory performance in difficult environments, such as open-pit mines, urban canyons and indoors. Pseudolites have the potential to extend GNSS usage and significantly improve receiver performance in such environments by providing additional navigation signals. This also applies to asynchronous pseudolite systems, where different pseudolites operate in an independent way. Asynchronous pseudolite systems require, however, dedicated strategies in order to properly integrate GNSS and pseudolite measurements. In this paper, several asynchronous pseudolite/GNSS integration strategies are considered: loosely- and tightly-coupled approaches are developed and combined with pseudolite proximity and receiver signal strength (RSS-based positioning. The performance of the approaches proposed has been tested in different scenarios, including static and kinematic conditions. The tests performed demonstrate that the methods developed are effective techniques for integrating heterogeneous measurements from different sources, such as asynchronous pseudolites and GNSS.

  13. MODIFIED MICROPIPLINE ARCHITECTURE FOR SYNTHESIZABLE ASYNCHRONOUS FIR FILTER DESIGN

    Directory of Open Access Journals (Sweden)

    Basel Halak

    2016-02-01

    Full Text Available The use of asynchronous design approaches to construct digital signal processing (DSP systems is a rapidly growing research area driven by a wide range of emerging energy constrained applications such as wireless sensor network, portable medical devices and brain implants. The asynchronous design techniques allow the construction of systems which are samples driven, which means they only dissipate dynamic energy when there processing data and idle otherwise. This inherent advantage of asynchronous design over conventional synchronous circuits allows them to be energy efficient. However the implementation flow of asynchronous systems is still difficult due to its lack of compatibility with industrystandard synchronous design tools and modelling languages. This paper devises a novel asynchronous design for a finite impulse response (FIR filter, an essential building block of DSP systems, which is synthesizable and suitable for implementation using conventional synchronous systems design flow and tools. The proposed design is based on a modified version of the micropipline architecture and it is constructed using four phase bundled data protocol. A hardware prototype of the proposed filter has been developed on an FPGA, and systematically verified. The results prove correct functionality of the novel design and a superior performance compared to a synchronous FIR implementation. The findings of this work will allow a wider adoption of asynchronous circuits by DSP designers to harness their energy and performance benefits.

  14. TCDQ-TCT retraction and losses during asynchronous beam dump

    CERN Document Server

    Bracco, Chiara; Quaranta, Elena; CERN. Geneva. ATS Department

    2016-01-01

    The protection provided by the TCDQs in case of asynchronous beam dump depends strongly on their correct setup. They have to respect the strict hierarchy of the full collimation system and shield the tertiary collimators in the experimental regions. This MD aimed at performing asynchronous beam dump tests with different configurations, in order to assess the minimum allowed retraction between TCTs and TCDQs and, as a consequence, on the The protection provided by the TCDQs in case of asynchronous beam dump depends strongly on their correct setup. They have to respect the strict hierarchy of the full collimation system and shield the tertiary collimators in the experimental regions. This MD aimed at performing asynchronous beam dump tests with different configurations, in order to assess the minimum allowed retraction between TCTs and TCDQs and, as a consequence, on the β* reach.

  15. Pro asynchronous programming with .NET

    CERN Document Server

    Blewett, Richard; Ltd, Rock Solid Knowledge

    2014-01-01

    Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming

  16. Optimization design of independent photovoltaic supply system for CDMA repeaters%CDMA直放站独立光伏供电系统的优化设计

    Institute of Scientific and Technical Information of China (English)

    陈正武; 苏成仁; 胡芳林; 梁盛德

    2011-01-01

    Solar photovoltaic was adopted to provide electricity to repeaters away from urban, which could not only save energy and protect environment, but also avoid the inconvenience to set electric wires from dozens of miles away and reduce the cost. With solar energy as an independent power supply system, the principle problem was to optimize the design of the system: the best installation angle of the solar panel, the appropriate power of the solar panel to fit a certain power appliance, the capacity of the battery according to the system design requirements, choosing the relevant charge-discharge controller, and etc.. In order to avoid configuration waste and guarantee the system work correctly according to the design requirements, a concise algorithm was introduced, which could reach the optimization design.%用太阳能光伏给远离市区的直放站提供电能,不但节约能源、清洁,而且便捷,不需要从数十里远的地方架设电线,有利于保护环境,减少投资.用太阳能光伏作为独立供电系统,首先要解决的是系统的最优设计问题:太阳电池板安装的最佳倾角;对-定功率的用电器配多大功率的太阳电池板;按照系统设计的工作要求如何配套电瓶的容量;选择相应的充电放电控制器等.既要使系统避免配置浪费,又要使系统能按设计要求保证工作.用简捷的运算方法达到了优化设计的结果.

  17. Polymeric Optical Code-Division Multiple-Access (CDMA Encoder and Decoder Modules

    Directory of Open Access Journals (Sweden)

    Ray T. Chen

    2011-09-01

    Full Text Available We propose a low cost polymeric optical waveguides-based optical CDMA encoder and decoder modules. The structures of the optical CDMA encoder and decoder modules are presented. The performance of the optical CDMA encoder and decoder modules is simulated using 10-chip binary phase-shift keying (BPSK coding schemes. The optical CDMA encoder and decoder modules can effectively transmit and recover optical CDMA data streams. The SNR of the received signal is analyzed and determined to be primarily from the cross correlation with other channels.

  18. Multiuser Detection in Asynchronous Multibeam Communications

    CERN Document Server

    Chaouech, Helmi; 10.5121/ijwmn.2012.4102

    2012-01-01

    This paper deals with multi-user detection techniques in asynchronous multibeam satellite communications. The proposed solutions are based on successive interference cancellation architecture (SIC) and channel decoding algorithms. The aim of these detection methods is to reduce the effect of cochannel interference due to co-frequency access, and consequently, improves the capacity of the mulitbeam communications systems, by improving frequency reuse. Channel estimation allows the determination of interference coefficients, which helps their effects compensation. The developed multiuser detections techniques are iterative. Therefore, detection quality is improved from a stage to another. Moreover, a signals combining method, which is integrated into these detection solutions, enhances their capability. The proposed solutions are evaluated through computer simulations, where an asynchronous multibeam satellite link is considered over an AWGN channel. The obtained simulation results showed the robustness of thes...

  19. Pilot power based rate control in CDMA 2000 1x EV-DO Rev-A

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-feng; GU Jian; YANG Hong-wen

    2008-01-01

    This article proposes a new algorithm to improvethe rate control efficiency of enhanced reverse link mediumaccess control (RLMAC) in the code division multiple access(CDMA) lx EV-DO release A(Rev. A) system. The newalgorithm brings reverse access terminal (AT) pilot power tothe RLMAC rate control procedure and makes it easier for alow pilot power user to increase its data rate when the systemis slightly loaded and harder to decrease its date rate when thesystem is heavily loaded. Numerical results of system levelsimulations show that the new algorithm can bring highersystem throughput, lower AT transmission power, and lowersystem load.

  20. Two-Stage Maximum Likelihood Estimation (TSMLE for MT-CDMA Signals in the Indoor Environment

    Directory of Open Access Journals (Sweden)

    Sesay Abu B

    2004-01-01

    Full Text Available This paper proposes a two-stage maximum likelihood estimation (TSMLE technique suited for multitone code division multiple access (MT-CDMA system. Here, an analytical framework is presented in the indoor environment for determining the average bit error rate (BER of the system, over Rayleigh and Ricean fading channels. The analytical model is derived for quadrature phase shift keying (QPSK modulation technique by taking into account the number of tones, signal bandwidth (BW, bit rate, and transmission power. Numerical results are presented to validate the analysis, and to justify the approximations made therein. Moreover, these results are shown to agree completely with those obtained by simulation.

  1. Congestion Avoidance in IP Based CDMA Radio Access Network

    Directory of Open Access Journals (Sweden)

    Syed Shakeel Hashmi

    2011-02-01

    Full Text Available CDMA is an important air interface technologies for cellular wireless networks. As CDMAbasedcellular networks mature, the current point-to-point links will evolve to an IP-based Radio AccessNetwork (RAN. mechanisms must be designed to control the IP Radio Access Network congestion.This Paper implements a congestion control mechanism using Router control and channelcontrol method for IP-RAN on CDMA cellular network. The Router control mechanism uses the featuresof CDMA networks using active Queue Management technique to reduce delay and to minimize thecorrelated losses. The Random Early Detection Active Queue Management scheme (REDAQM is to berealized for the router control for data transmission over the radio network using routers as the channel.The channel control mechanism control the congestion by bifurcating the access channel into multiplelayer namely RACH, BCCH and DCH for data accessing. The proposed paper work is realized usingMatlab platform.

  2. Ternary Tree Asynchronous Interconnect Network for GALS' SOC

    Directory of Open Access Journals (Sweden)

    Vivek E. Khetade

    2013-03-01

    Full Text Available Interconnect fabric requires easy integration of computational block operating with unrelated clocks.Thispaper presents asynchronous interconnect with ternary tree asynchronous network for GloballyAsynchronous Locally Synchronous (GALS system-on-chip (SOC. Here architecture is proposed forinterconnection with ternary tree asynchronous network where ratio of number NOC design unit andnumber of router is 4:1,6:2, 8:3,10:4 etc .It is scalable for any number of NOC design unit. It offersaneasy integration of different clock domain with lowcommunication overhead .NOC design unit for GALS‘SOC is formulated by wrapping synchronous module with input port along with input port controller,output port along with output port controller and local clock generator. It creates the interface betweensynchronous to asynchronous and asynchronous to synchronous. For this purpose four port asynchronousrouters is designed with routing element and outputarbitration and buffering with micro-pipeline. Thisinterconnect fabric minimizes silicon area, minimize Latency and maximize throughput. Here functionalmodel is made for TTAN and application MPEG4 is mapped on the Network .Desired traffic pattern isgenerated and performance of the network is evaluated. Significant improvement in the networkperformance parameter has been observed.

  3. Secure Communications in High Speed Fiber Optical Networks Using Code Division Multiple Access (CDMA) Transmission

    Energy Technology Data Exchange (ETDEWEB)

    Han, I; Bond, S; Welty, R; Du, Y; Yoo, S; Reinhardt, C; Behymer, E; Sperry, V; Kobayashi, N

    2004-02-12

    This project is focused on the development of advanced components and system technologies for secure data transmission on high-speed fiber optic data systems. This work capitalizes on (1) a strong relationship with outstanding faculty at the University of California-Davis who are experts in high speed fiber-optic networks, (2) the realization that code division multiple access (CDMA) is emerging as a bandwidth enhancing technique for fiber optic networks, (3) the realization that CDMA of sufficient complexity forms the basis for almost unbreakable one-time key transmissions, (4) our concepts for superior components for implementing CDMA, (5) our expertise in semiconductor device processing and (6) our Center for Nano and Microtechnology, which is where the majority of the experimental work was done. Here we present a novel device concept, which will push the limits of current technology, and will simultaneously solve system implementation issues by investigating new state-of-the-art fiber technologies. This will enable the development of secure communication systems for the transmission and reception of messages on deployed commercial fiber optic networks, through the CDMA phase encoding of broad bandwidth pulses. CDMA technology has been developed as a multiplexing technology, much like wavelength division multiplexing (WDM) or time division multiplexing (TDM), to increase the potential number of users on a given communication link. A novel application of the techniques created for CDMA is to generate secure communication through physical layer encoding. Physical layer encoding devices are developed which utilize semiconductor waveguides with fast carrier response times to phase encode spectral components of a secure signal. Current commercial technology, most commonly a spatial light modulator, allows phase codes to be changed at rates of only 10's of Hertz ({approx}25ms response). The use of fast (picosecond to nanosecond) carrier dynamics of semiconductors

  4. BACKGROUNDS OF EXPERIMENTAL INVESTIGATION OF ELECTROMAGNETIC COMPATIBILITY OF TRACTION ASYNCHRONOUS ELECTRIC DRIVES IN THE STRUCTURE OF DC TRACTION POWER SUPPLY SYSTEM

    Directory of Open Access Journals (Sweden)

    YU. S. Bondarenko

    2014-04-01

    Full Text Available Purpose. Application of physical modeling as a tool for research of any events or systems is becoming more widespread, including the field of railway transport. At the same time the adequacy of results that can be obtained, depends largely on the similarity degree of the physical model to real system. From the standpoint of the traction asynchronous electric drive (TAED research together with the traction power supply system research, the similarity can not be determined by the direct proportion of the parameters, because the processes nature accompanying the operation of these systems is non-linear. These features should be taken into account in the experimental setup, the basis for constructing of which is establishing of the system similarity that defines the purpose of this paper. Methodology. At the heart of the experimental setup creation laid reproduction of processes of energy transformation in the system of the DC traction power supply. Determination of the similarity degree of the proposed facility to the real system was carried out using the basic theorems of the similarity theory, their additional provisions on the complexity and nonlinear systems, as well as elements of mathematical analysis. Findings. According to the results of work: 1 The block diagram, the energy conversion mechanism of which is similar to the real system was received. This scheme is the basis of experimental setup, built in the future for the study of electromagnetic compatibility of TAED in the structure of DC traction electric power supply system. 2 Similarity of obtained structural scheme with the real system with the mechanism definition of calculating the scaling relations was established. Originality. In the process of establishing the similarity a simplified method for determining the scaling relations for nonlinear systems was suggested. They are identical in their structure components, but have different capacities. Practical value. Experimental

  5. OFDM and MC-CDMA for broadband multi-user communications WLANs and broadcasting

    CERN Document Server

    2003-01-01

    "OFDM systems have experienced increased attention in recent years and have found applications in a number of diverse areas including telephone-line based ADSL links, digital audio and video broadcasting systems, and wireless local area networks. OFDM is being considered for the next-generation of wireless systems both with and without direct sequence spreading and the resultant spreading-based multi-carrier CDMA systems have numerous attractive properties. This volume provides the reader with a broad overview of the research on OFDM systems during their 40-year history. Part I commences with an easy to read conceptual, rather than mathematical, treatment of the basic design issues of OFDM systems. The discussions gradually deepen to include adaptive single and multi-user OFDM systems invoking adaptive turbo coding. Part II introduces the taxonomy of multi-carrier CDMA systems and deals with the design of their spreading codes and the objective of minimising their crest factors. This part also compares the be...

  6. Improving Multi Access Interference Suppression in Optical CDMA by using all-Optical Signal Processing

    Directory of Open Access Journals (Sweden)

    T. B. Osadola

    2013-06-01

    Full Text Available This paper presents the study of a novel all-optical method for processing optical CDMA signals towards improving suppression of multi access interference. The main focus is on incoherent OCDMA systems using multiwavelength 2D-WH/TS codes generated using FBG based encoders and decoders. The MAI suppression capabilities based on its ability to eliminate selective wavelength pulse processing have been shown. A novel transmitter architecture that achieves up to 3dB power saving was also presented. As a result of hardware savings, processing cost will be significantly reduced and power budget improvement resulted in improved performance.

  7. VLSI Structure for an All Digital Receiver for CDMA PABX Handset

    Institute of Scientific and Technical Information of China (English)

    ZhouShidong; BiGuangguo

    1995-01-01

    In this paper,a VLSI architecture of a CDMA receiver is put forward for wirelesss PABX handset.To meet the critically low cost and power consumption requirement with neglectable per-formance degradation,some new techniques are employed to reduce hardware complexity,including base band processing,chip-rate sampling,low ADC resolution,absolute value detector,double branch acquisition ,and modified carrier phase compensation.Performance of experimental system fits well with theoretical predition ,and the practical SNR lose compared with ideal reception is about 2-3dB.

  8. ASYNCHRONOUS ELECTRONIC DISCUSSION GROUP:

    Directory of Open Access Journals (Sweden)

    Tina Lim Swee KIM

    2007-01-01

    Full Text Available This paper examines the practice of online discussion in a course specially tailored for in-service teachers who are pursuing their basic degree qualification at a teacher training institute. Analyses of postings to the asynchronous electronic discussion group were made according to the type of postings as proposed by Poole (2000. Four focus areas were looked into, that is, content, technical, procedural, or non-academic. Analyses were done for each quarter of the 12 weeks of interaction. At the end of the learners’ participation in the EDG and before their end-of-course examination, the participants were then given a paper-based questionnaire asking their perceptions on the use of EDG as part of their coursework on the whole. Six aspects of EDG were examined, these are;Ø technical aspects, Ø motivation to use the EDG, Ø quality of interaction, Ø tutor’s response, Ø perceived learning, and Ø attitude towards EDG. Analyses on postings for the EDG showed that the bulk of the postings were made in the last quarter of the online discussions. Further, 97.8% of the postings were on content and the types of content posting registered were predominantly questions (41.19% and those that sought clarification/elaboration (37.48%. Findings from this study suggest that overall the participants were satisfied with the six aspects of EDG examined. The aspect that recorded the highest mean was ‘motivation to read tutor’s responses’ whilst the lowest mean (and the only one with negative perception was for ‘worthiness of time spent on online discussions’.

  9. Asynchronous API Pattern and its Application%异步接口模式及其应用

    Institute of Scientific and Technical Information of China (English)

    何华海; 丁柯

    2002-01-01

    In distributed systems,high efficiency can be achieved using asynchronous API between client and server.This paper provides an architectural pattern that implements asynchronous API generally. Asynchronous methods donot execute operations directly,however,they delegate the sending and receiving process to individual threads via aqueue ,the client deals with results by means of callback ,wait or check. Synchronous API is implemented on the baseof asynchronous API. Presently the asynchronous API pattern has been employed in the implementation of messagequeue middleware ISMQ.

  10. Effects of simultaneous combined exposure to CDMA and WCDMA electromagnetic fields on serum hormone levels in rats

    International Nuclear Information System (INIS)

    Despite more than a decade of research on the endocrine system, there have been no published studies about the effects of concurrent exposure of radiofrequency electromagnetic fields (RF-EMF) on this system. The present study investigated the several parameters of the endocrine system including melatonin, thyroid stimulating hormone, stress hormone and sex hormone after code division multiple access (CDMA, 849 MHz) and wideband code division multiple access (WCDMA, 1.95 GHz) signals for simultaneous exposure in rats. Sprague-Dawley rats were exposed to RF-EMF signals for 45 min/day, 5 days/week for up to 8 weeks. The whole-body average specific absorption rate (SAR) of CDMA or WCDMA was 2.0 W/kg (total 4.0 W/kg). At 4 and 8 weeks after the experiment began, each experimental group's 40 rats (male 20, female 20) were autopsied. Exposure for 8 weeks to simultaneous CDMA and WCDMA RF did not affect serum levels in rats of melatonin, thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxin (T4), adrenocorticotropic hormone (ACTH) and sex hormones (testosterone and estrogen) as assessed by the ELISA method

  11. ASCERTAINMENT OF THE EQUIVALENT CIRCUIT PARAMETERS OF THE ASYNCHRONOUS MACHINE

    Directory of Open Access Journals (Sweden)

    V. S. Safaryan

    2015-01-01

    Full Text Available The article considers experimental and analytical determination of the asynchronous machine equivalent-circuit parameters with application of the reference data. Transient processes investigation of the asynchronous machines necessitates the equivalent circuit parameters (resistance impedance, inductances and coefficient of the stator-rotor contours mutual inductance that help form the transitory-process mathematical simulation model. The reference books do not provide those parameters; they instead give the rated ones (active power, voltage, slide, coefficient of performance and capacity coefficient as well as the ratio of starting and nominal currents and torques. The noted studies on the asynchronous machine equivalent-circuits parametrization fail to solve the problems ad finem or solve them with admissions. The paper presents experimental and analytical determinations of the asynchronous machine equivalent-circuit parameters: the experimental one based on the results of two measurements and the analytical one where the problem boils down to solving a system of nonlineal algebraic equations. The authors investigate the equivalent asynchronous machine input-resistance properties and adduce the dependence curvatures of the input-resistances on the slide. They present a symbolic model for analytical parameterization of the asynchronous machine equivalent-circuit that represents a system of nonlineal equations and requires one of the rotor-parameters arbitrary assignment. The article demonstrates that for the asynchronous machine equivalent-circuit experimental parameterization the measures are to be conducted of the stator-circuit voltage, current and active power with two different slides and arbitrary assignment of one of the rotor parameters. The paper substantiates the fact that additional measurement does not discard the rotor-parameter choice arbitrariness. The authors establish that in motoring mode there is a critical slide by which the

  12. A beamformer for CDMA with enhanced near-far resistance

    DEFF Research Database (Denmark)

    Hansen, Henrik; Affes, S.; Mermelstein, P.

    1999-01-01

    The spatio-temporal array-receiver (STAR) achieves good performance in CDMA with multiple receiving antennas where the interference can be characterized as AWGN uncorrelated with the signal. To enhance its near-far resistance in correlated noise environments, we introduce optimal combining of the...

  13. Analysis of Optical CDMA Signal Transmission: Capacity Limits and Simulation Results

    Directory of Open Access Journals (Sweden)

    Lawrence R. Chen

    2005-06-01

    Full Text Available We present performance limits of the optical code-division multiple-access (OCDMA networks. In particular, we evaluate the information-theoretical capacity of the OCDMA transmission when single-user detection (SUD is used by the receiver. First, we model the OCDMA transmission as a discrete memoryless channel, evaluate its capacity when binary modulation is used in the interference-limited (noiseless case, and extend this analysis to the case when additive white Gaussian noise (AWGN is corrupting the received signals. Next, we analyze the benefits of using nonbinary signaling for increasing the throughput of optical CDMA transmission. It turns out that up to a fourfold increase in the network throughput can be achieved with practical numbers of modulation levels in comparison to the traditionally considered binary case. Finally, we present BER simulation results for channel coded binary and M-ary OCDMA transmission systems. In particular, we apply turbo codes concatenated with Reed-Solomon codes so that up to several hundred concurrent optical CDMA users can be supported at low target bit error rates. We observe that unlike conventional OCDMA systems, turbo-empowered OCDMA can allow overloading (more active users than is the length of the spreading sequences with good bit error rate system performance.

  14. Behavioral synthesis of asynchronous circuits

    DEFF Research Database (Denmark)

    Nielsen, Sune Fallgaard

    2005-01-01

    domain by introducing a computation model, which resembles the synchronous datapath and control architecture, but which is completely asynchronous. The model contains the possibility for isolating some or all of the functional units by locking their respective inputs and outputs while the functional unit...

  15. Performance of a Two-Level Call Admission Control Scheme for DS-CDMA Wireless Networks

    Directory of Open Access Journals (Sweden)

    Abraham O. Fapojuwo

    2007-11-01

    Full Text Available We propose a two-level call admission control (CAC scheme for direct sequence code division multiple access (DS-CDMA wireless networks supporting multimedia traffic and evaluate its performance. The first-level admission control assigns higher priority to real-time calls (also referred to as class 0 calls in gaining access to the system resources. The second level admits nonreal-time calls (or class 1 calls based on the resources remaining after meeting the resource needs for real-time calls. However, to ensure some minimum level of performance for nonreal-time calls, the scheme reserves some resources for such calls. The proposed two-level CAC scheme utilizes the delay-tolerant characteristic of non-real-time calls by incorporating a queue to temporarily store those that cannot be assigned resources at the time of initial access. We analyze and evaluate the call blocking, outage probability, throughput, and average queuing delay performance of the proposed two-level CAC scheme using Markov chain theory. The analytic results are validated by simulation results. The numerical results show that the proposed two-level CAC scheme provides better performance than the single-level CAC scheme. Based on these results, it is concluded that the proposed two-level CAC scheme serves as a good solution for supporting multimedia applications in DS-CDMA wireless communication systems.

  16. Performance of a Two-Level Call Admission Control Scheme for DS-CDMA Wireless Networks

    Directory of Open Access Journals (Sweden)

    Fapojuwo Abraham O

    2007-01-01

    Full Text Available We propose a two-level call admission control (CAC scheme for direct sequence code division multiple access (DS-CDMA wireless networks supporting multimedia traffic and evaluate its performance. The first-level admission control assigns higher priority to real-time calls (also referred to as class 0 calls in gaining access to the system resources. The second level admits nonreal-time calls (or class 1 calls based on the resources remaining after meeting the resource needs for real-time calls. However, to ensure some minimum level of performance for nonreal-time calls, the scheme reserves some resources for such calls. The proposed two-level CAC scheme utilizes the delay-tolerant characteristic of non-real-time calls by incorporating a queue to temporarily store those that cannot be assigned resources at the time of initial access. We analyze and evaluate the call blocking, outage probability, throughput, and average queuing delay performance of the proposed two-level CAC scheme using Markov chain theory. The analytic results are validated by simulation results. The numerical results show that the proposed two-level CAC scheme provides better performance than the single-level CAC scheme. Based on these results, it is concluded that the proposed two-level CAC scheme serves as a good solution for supporting multimedia applications in DS-CDMA wireless communication systems.

  17. ZTE Becomes Global Leader in CDMA Base Station Market with 33% Share

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    ZTE Corporation announced on November 3, 2011 that it has become the global leader in the CDMA base station market, with a 32.6 percent share in first half 2011. According to a recent IDC analytical report on the global CDMA market, ZTE has increased its shipments of CDMA base stations steadily in recent years. As of the end of first half of 2011, the company's shipment of base-stations had exceeded 320 thousand units, pushing it to the top spot in the global CDMA base station market.

  18. Downlink Power Control for CDMA Satellite Cognitive Radio

    Directory of Open Access Journals (Sweden)

    Peng Chen

    2013-03-01

    Full Text Available In this paper, we consider power control for a code-division-multiple-access (CDMA-based satellite cogni-tive radio network where the satellite acts as the common transmitter of primary users and secondary users. Specially, we assume that primary users are willing to share resource with secondary users by means of leasing spectrum, while secondary users have to pay for the shared spectrum. In addition, secondary users are allowed to transmit on any sub-channel provided that the resulting interference to any primary users is below a critical threshold. We focus on the downlink. The objective is to maximize the throughput in the licensed frequency band of the satellite network. We formulate the problem as a game theoretic problem with all users as the players. We propose a tow-phase control scheme that can be accepted willingly by both types of users and can maximize the throughput of the satellite network. In the first phase, the Nash Equilibrium point is calculated with an iterative method, the existence of the Nash Equilibrium point is also proved. In the second phase, Payoff Dominance Selection is used to choose the optimal power allocation under the constraints including quality of service protections of all users and maximum transmission power of the onboard power amplifier. Simulation is performed to study the parameters of the system and of each user. By simulation, we find that the throughput is greatly increased by the proposed scheme compared with traditional satellite networks where fixed power is allocated to only primary users. Onboard complexity is also analyzed.

  19. RELAXED ASYNCHRONOUS ITERATIONS FOR THE LINEAR COMPLEMENTARITY PROBLEM

    Institute of Scientific and Technical Information of China (English)

    Zhong-zhi Bai; Yu-guang Huang

    2002-01-01

    We present a class of relaxed asynchronous parallel multisplitting iterative methods forsolving the linear complementarity problem on multiprocessor systems, and set up theirconvergence theories when the system matrix of the linear complementarity problem is anH-matrix with positive diagonal elements.

  20. Simulation research of matrix converter and asynchronous motor control system%矩阵变换器-异步电机矢量控制系统仿真研究

    Institute of Scientific and Technical Information of China (English)

    姜香菊; 刘二林

    2012-01-01

    Space vector pulse width modulation of matrix converter and rotor field oriented vector control of asynchronous motor are combined, and the paper researchs combination strategy for vector control of the matrix converter and rotor field oriented vector control of asynchronous motor. Input voltage and current of matrix converter are simulated by MATLAB, at the same time, no-load starting torque and speed waveform and the electrical load torque waveform of motor are simulated. The simulation results show that the combined control strategy for matrix converter-asynchronous vector control system has good speed performance, and has the advantage of a AC-DC-AC voltage type PWM variable frequency speed regulation system.%研究了将矩阵变换器的空间矢量脉宽调制与异步电机转子磁场定向矢量控制相结合的组合控制策略,并采用MATLAB对矩阵变换器的输入电压波形、输入电流波形、电机空载启动转矩波形、电机空载启动转速波形以及在电机突加负载时的转矩波形等进行仿真.仿真结果表明了采用组合控制策略的矩阵变换器-异步电机矢量控制系统具备良好的调速性能,并且较交-直-交电压型PWM变频调速系统而言具有更多的优势.

  1. Asynchronous machines. Direct torque control; Machines asynchrones. Commande par controle direct de couple

    Energy Technology Data Exchange (ETDEWEB)

    Fornel, B. de [Institut National Polytechnique, 31 - Toulouse (France)

    2006-05-15

    The asynchronous machine, with its low cost and robustness, is today the most widely used motor to make speed variators. However, its main drawback is that the same current generates both the magnetic flux and the torque, and thus any torque variation creates a flux variation. Such a coupling gives to the asynchronous machine a nonlinear behaviour which makes its control much more complex. The direct self control (DSC) method has been developed to improve the low efficiency of the scalar control method and for the specific railway drive application. The direct torque control (DTC) method is derived from the DSC method but corresponds to other type of applications. The DSC and DTC algorithms for asynchronous motors are presented in this article: 1 - direct control of the stator flux (DSC): principle, flux control, torque control, switching frequency of the inverter, speed estimation; 2 - direct torque control (DTC): principle, electromagnetic torque derivative, signals shape and switching frequency, some results, DTC speed variator without speed sensor, DTC application to multi-machine multi-converter systems; 3 - conclusion. (J.S.)

  2. DESIGN METHODOLOGY OF SELF-EXCITED ASYNCHRONOUS GENERATOR

    Directory of Open Access Journals (Sweden)

    Berzan V.

    2012-04-01

    Full Text Available The paper sets out the methodology of designing an asynchronous generator with capacitive self-excitation. It is known that its design is possible on the basis of serial synchronous motor with squirrel cage rotor. With this approach, the design reworked only the stator winding of electrical machines, making it cost-effectively implement the creation of the generator. Therefore, the methodology for the design, optimization calculations, the development scheme and the stator winding excitation system gain, not only of practical interest, and may also be useful for specialists in the field of electrical machines in the design of asynchronous generators.

  3. Progresses in the Analysis of Stochastic 2D Cellular Automata: a Study of Asynchronous 2D Minority

    CERN Document Server

    Regnault, Damien; Thierry, Éric

    2007-01-01

    Cellular automata are often used to model systems in physics, social sciences, biology that are inherently asynchronous. Over the past 20 years, studies have demonstrated that the behavior of cellular automata drastically changed under asynchronous updates. Still, the few mathematical analyses of asynchronism focus on one-dimensional probabilistic cellular automata, either on single examples or on specific classes. As for other classic dynamical systems in physics, extending known methods from one- to two-dimensional systems is a long lasting challenging problem. In this paper, we address the problem of analysing an apparently simple 2D asynchronous cellular automaton: 2D Minority where each cell, when fired, updates to the minority state of its neighborhood. Our experiments reveal that in spite of its simplicity, the minority rule exhibits a quite complex response to asynchronism. By focusing on the fully asynchronous regime, we are however able to describe completely the asymptotic behavior of this dynamics...

  4. Router Designs for an Asynchronous Time-Division-Multiplexed Network-on-Chip

    DEFF Research Database (Denmark)

    Kasapaki, Evangelia; Sparsø, Jens; Sørensen, Rasmus Bo;

    2013-01-01

    In this paper we explore the design of an asynchronous router for a time-division-multiplexed (TDM) network-on-chip (NOC) that is being developed for a multi-processor platform for hard real-time systems. TDM inherently requires a common time reference, and existing TDM-based NOC designs are either....... This adds hardware complexity and increases area and power consumption. We propose to use asynchronous routers in order to achieve a simpler, more robust and globally-asynchronous NOC, and this represents an unexplored point in the design space. The paper presents a range of alternative router designs. All...... routers have been synthesized for a 65nm CMOS technology, and the paper reports post-layout figures for area, speed and energy and compares the asynchronous designs with an existing mesochronous clocked router. The results show that an asynchronous router is 2 times smaller, marginally slower...

  5. Performance Evaluation of CDMA Router for Network-On-Chip

    Directory of Open Access Journals (Sweden)

    Anant W. Hinganikar

    2012-07-01

    Full Text Available This paper presents the performance evaluation of router based on code division multiple access technique (CDMA for Network-on-Chip (NoC. The design is synthesized using Xilinx Virtex4 XC4VLX200 device. The functional behavior is verified using Modelsim XE III 6.2 C. The delay and throughput values are obtained for variable payload sizes. Throughput-Power and Delay-Power characteristics are also verified for NoC.

  6. Performance Evaluation of CDMA Router for Network-On-Chip

    OpenAIRE

    Anant W. Hinganikar; Mahendra A. Gaikwad; Patrikar, Rajendra M.

    2012-01-01

    This paper presents the performance evaluation of router based on code division multiple access technique (CDMA) for Network-on-Chip (NoC). The design is synthesized using Xilinx Virtex4 XC4VLX200 device. The functional behavior is verified using Modelsim XE III 6.2 C. The delay and throughput values are obtained for variable payload sizes. Throughput-Power and Delay-Power characteristics are also verified for NoC.

  7. Performance Evaluation of CDMA Router for Network-On-Chip

    Directory of Open Access Journals (Sweden)

    Anant W. Hinganikar

    2012-06-01

    Full Text Available This paper presents the performance evaluation of router based on code division multiple access technique (CDMA for Network-on-Chip (NoC. The design is synthesized using Xilinx Virtex4 XC4VLX200 device. The functional behavior is verified using Modelsim XE III 6.2 C. The delay and throughput values are obtained for variable payload sizes. Throughput-Power and Delay-Power characteristics are also verified for NoC.

  8. CDMA PN规划实现与评估

    Institute of Scientific and Technical Information of China (English)

    朱义财

    2014-01-01

    本文探讨CDMA PN规划的实现并利用地理信息技术实现规划后的评估,可大幅度避免网优工程师经常碰到ONE-WAY、TWO-WAY、PN混淆等由于PN分配不合理造成的掉话、呼叫失败等影响网络性能的问题。

  9. Asynchronous Linking in a Service –Oriented Architecture.

    OpenAIRE

    Vivek, Sanjay; Tso, Kenneth; Thompson, Mark; De Roure, David

    2002-01-01

    In this paper, we identify research issues in the development of system infrastructure support for asynchronous linkservices in a service-oriented architecture. We explore the suitability and applicability of using MQSeries Everyplace to provide a messaging backbone for linkservices that increases reliability, fault tolerance, and scalability. We identify and discuss some important problems and research issues related to this approach.

  10. Analysis of the Relevance of Posts in Asynchronous Discussions

    Science.gov (United States)

    Azevedo, Breno T.; Reategui, Eliseo; Behar, Patrícia A.

    2014-01-01

    This paper presents ForumMiner, a tool for the automatic analysis of students' posts in asynchronous discussions. ForumMiner uses a text mining system to extract graphs from texts that are given to students as a basis for their discussion. These graphs contain the most relevant terms found in the texts, as well as the relationships between them.…

  11. Selective particle capture by asynchronously beating cilia

    Science.gov (United States)

    Ding, Yang; Kanso, Eva

    2015-12-01

    Selective particle filtration is fundamental in many engineering and biological systems. For example, many aquatic microorganisms use filter feeding to capture food particles from the surrounding fluid, using motile cilia. One of the capture strategies is to use the same cilia to generate feeding currents and to intercept particles when the particles are on the downstream side of the cilia. Here, we develop a 3D computational model of ciliary bands interacting with flow suspended particles and calculate particle trajectories for a range of particle sizes. Consistent with experimental observations, we find optimal particle sizes that maximize capture rate. The optimal size depends nonlinearly on cilia spacing and cilia coordination, synchronous vs. asynchronous. These parameters affect the cilia-generated flow field, which in turn affects particle trajectories. The low capture rate of smaller particles is due to the particles' inability to cross the flow streamlines of neighboring cilia. Meanwhile, large particles have difficulty entering the sub-ciliary region once advected downstream, also resulting in low capture rates. The optimal range of particle sizes is enhanced when cilia beat asynchronously. These findings have potentially important implications on the design and use of biomimetic cilia in processes such as particle sorting in microfluidic devices.

  12. Carrier Sense Random Packet CDMA Protocol in Dual-Channel Networks

    Directory of Open Access Journals (Sweden)

    C. Du

    2015-06-01

    Full Text Available Code resource wastage is caused by the reason that many hopping frequency (FH sequences are unused, which occurs under the condition that the number of the actual subnets needed for the tactical network is far smaller than the networking capacity of code division net¬working. Dual-channel network (DCN, consisting of one single control channel and multiple data channels, can solve the code resource wastage effectively. To improve the anti-jamming capability of the control channel of DCN, code division multiple access (CDMA technology was introduced, and a carrier sense random packet (CSRP CDMA protocol based on random packet CDMA (RP-CDMA was proposed. In CSRP-CDMA, we provide a carrier sensing random packet mechanism and a packet-segment acknowledgement policy. Furthermore, an analytical model was developed to evaluate the performance of CSRP-CDMA networks. In this model, the impacts of multi-access interference from both inter-clusters and intra-clusters were analyzed, and the mathematical expressions of packet transmission success probability, normalized network throughput and signal interference to noise ratio, were also derived. Analytical and simulation results demonstrate that the normalized network throughput of CSRP-CDMA outperforms traditional RP-CDMA by 10%, which can guarantee the resource utilization efficiency of the control channel in DCNs.

  13. Analysis of CDMA EV DO capacity%CDMA EV DO容量的分析研究

    Institute of Scientific and Technical Information of China (English)

    王俊

    2011-01-01

    With the development of CDMA EV DO technique, more and more subscribers are not satisfied with data link rate. This paper analyzes factors of forward link and reverse link capacity of EV DO network to guide network planning and optimization. The research in this field is to meet requirement of high speed data access and maximum throughput of data subscribers.%分析影响EV DO网络前、反向容量的因素,为CDMA EV DO数据业务网规网优提供方法论的指导,达到数据用户吞吐量的最大化,满足日益增长的多用户高速数据接入的需求.

  14. Asynchronous Methods for Deep Reinforcement Learning

    OpenAIRE

    Mnih, Volodymyr; Badia, Adrià Puigdomènech; Mirza, Mehdi; Graves, Alex; Lillicrap, Timothy P.; Harley, Tim; Silver, David; Kavukcuoglu, Koray

    2016-01-01

    We propose a conceptually simple and lightweight framework for deep reinforcement learning that uses asynchronous gradient descent for optimization of deep neural network controllers. We present asynchronous variants of four standard reinforcement learning algorithms and show that parallel actor-learners have a stabilizing effect on training allowing all four methods to successfully train neural network controllers. The best performing method, an asynchronous variant of actor-critic, surpasse...

  15. Forward Link Power Control Strategy and its Optimum Issue in CDMA Cellular Networks

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, we propose a theoretical method in order to estimate the forward link outage probability and user capacity of a cellular system which are based on IS-95 CDMA standard, especialy impact of power control strategy and voice activity monitoring in the system under long-term fading effects, in which the light and heavy fadings are considered. According to the numerical results obtained in this paper, the power control strategy leads to approximately the threefold user capacity in contrast to the situation without power control strategy. The reults are compared with Interference-to-Signal Ratio (ISR) driven power control scheme[6][9] which can be used only for simulation of the system. The power control strategy not only improves the desired signal to the interference ratio in the reference user's receiver, but also offers uniform service to the user wherever it is located in the cell.

  16. Asynchronous rotation scan for synthetic aperture interferometric radiometer

    Institute of Scientific and Technical Information of China (English)

    WU Ji; ZHANG Cheng; LIU Hao; SUN WeiYing

    2009-01-01

    Synthetic aperture interferometric technique has wide applications in optics, radio astronomy and mi-crowave remote sensing areas. With the increasing demands of high resolution imaging observation, a new time-sharing sampling scheme of asynchronous rotation scan is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application. This configuration is basically composed by two asynchronously and concentrically ro-tating antenna groups, whose revolving radii and speeds are different. The synthetic aperture system with asynchronous rotation scanning scheme can effectively solve the trade-off problem of system complexity, and greatly simplify the system hardware at the cost of sacrificing a certain time resolution. The basic rules and design methods of asynchronous rotation scan are investigated The Gridding method is introduced to inverse the spiral sampling data for image reconstruction. The potential ap-plications of geostationary orbit (GEO) earth observation and solar polar orbit (SPO) plasma cloud observation are explored with numerical simulations to validate the significance and feasibility of this new imaging configuration.

  17. Asynchronous rotation scan for synthetic aperture interferometric radiometer

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Synthetic aperture interferometric technique has wide applications in optics,radio astronomy and mi-crowave remote sensing areas.With the increasing demands of high resolution imaging observation,a new time-sharing sampling scheme of asynchronous rotation scan is proposed to meet the technical challenge of achieving a large equivalent aperture and overcome the operating barriers of space borne application.This configuration is basically composed by two asynchronously and concentrically ro-tating antenna groups,whose revolving radii and speeds are different.The synthetic aperture system with asynchronous rotation scanning scheme can effectively solve the trade-off problem of system complexity,and greatly simplify the system hardware at the cost of sacrificing a certain time resolution.The basic rules and design methods of asynchronous rotation scan are investigated The Gridding method is introduced to inverse the spiral sampling data for image reconstruction.The potential ap-plications of geostationary orbit(GEO)earth observation and solar polar orbit(SPO)plasma cloud observation are explored with numerical simulations to validate the significance and feasibility of this new imaging configuration.

  18. Asynchronous τ-leaping

    Science.gov (United States)

    JÈ©drzejewski-Szmek, Zbigniew; Blackwell, Kim T.

    2016-03-01

    Stochastic simulation of cell signaling pathways and genetic regulatory networks has contributed to the understanding of cell function; however, investigation of larger, more complicated systems requires computationally efficient algorithms. τ-leaping methods, which improve efficiency when some molecules have high copy numbers, either use a fixed leap size, which does not adapt to changing state, or recalculate leap size at a heavy computational cost. We present a hybrid simulation method for reaction-diffusion systems which combines exact stochastic simulation and τ-leaping in a dynamic way. Putative times of events are stored in a priority queue, which reduces the cost of each step of the simulation. For every reaction and diffusion channel at each step of the simulation the more efficient of an exact stochastic event or a τ-leap is chosen. This new approach removes the inherent trade-off between speed and accuracy in stiff systems which was present in all τ-leaping methods by allowing each reaction channel to proceed at its own pace. Both directions of reversible reactions and diffusion are combined in a single event, allowing bigger leaps to be taken. This improves efficiency for systems near equilibrium where forward and backward events are approximately equally frequent. Comparison with existing algorithms and behaviour for five test cases of varying complexity shows that the new method is almost as accurate as exact stochastic simulation, scales well for large systems, and for various problems can be significantly faster than τ-leaping.

  19. Space-division multiple access for CDMA multiuser underwater acoustic communications

    Institute of Scientific and Technical Information of China (English)

    Jingwei Yin; Pengyu Du; Guang Yang; Huanling Zhou

    2015-01-01

    Time reversal mirror (TRM) can use the physical cha-racteristics of the underwater acoustic (UWA) channel to focus on the desired user in multi-user UWA communication. The active average sound intensity (AASI) detector can estimate al azimuths of users with the same frequency band at the same time in or-der to achieve directional communication by vector combination. Space-division multiple access (SDMA) based on TRM combined with the AASI detector is proposed in this paper, which can make the capacity of the code division multiple access (CDMA) UWA system significantly increase. The simulation and lake test results show that the 7-user UWA multi-user system can achieve low bit error communication.

  20. A New Decoding Scheme for Errorless Codes for Overloaded CDMA with Active User Detection

    CERN Document Server

    Mousavi, Ali; Marvasti, Farokh

    2010-01-01

    Recently, a new class of binary codes for overloaded CDMA systems are proposed that not only has the ability of errorless communication but also suitable for detecting active users. These codes are called COWDA [1]. In [1], a Maximum Likelihood (ML) decoder is proposed for this class of codes. Although the proposed scheme of coding/decoding show impressive performance, the decoder can be improved. In this paper by assuming more practical conditions for the traffic in the system, we suggest an algorithm that increases the performance of the decoder several orders of magnitude (the Bit-Error-Rate (BER) is divided by a factor of 400 in some Eb/N0's The algorithm supposes the Poison distribution for the time of activation/deactivation of the users.

  1. Equalization of Multiuser Wireless CDMA Downlink Considering Transmitter Nonlinearity Using Walsh Codes

    Directory of Open Access Journals (Sweden)

    Pinter Stephen Z

    2007-01-01

    Full Text Available Transmitter nonlinearity has been a major issue in many scenarios: cellular wireless systems have high power RF amplifier (HPA nonlinearity at the base station; satellite downlinks have nonlinear TWT amplifiers in the satellite transponder and multipath conditions in the ground station; and radio-over-fiber (ROF systems consist of a nonlinear optical link followed by a wireless channel. In many cases, the nonlinearity is simply ignored if there is no out-of-band emission. This results in poor BER performance. In this paper we propose a new technique to estimate the linear part of the wireless downlink in the presence of a nonlinearity using Walsh codes; Walsh codes are commonly used in CDMA downlinks. Furthermore, we show that equalizer performance is significantly improved by taking into account the presence of the nonlinearity during channel estimation. This is shown by using a regular decision feedback equalizer (DFE with both wireless and RF amplifier noise. We perform estimation in a multiuser CDMA communication system where all users transmit their signal simultaneously. Correlation analysis is applied to identify the channel impulse response (CIR and the derivation of key correlation relationships is shown. A difficulty with using Walsh codes in terms of their correlations (compared to PN sequences is then presented, as well as a discussion on how to overcome it. Numerical evaluations show a good estimation of the linear system with 54 users in the downlink and a signal-to-noise ratio (SNR of 25 dB. Bit error rate (BER simulations of the proposed identification and equalization algorithms show a BER of achieved at an SNR of dB.

  2. Equalization of Multiuser Wireless CDMA Downlink Considering Transmitter Nonlinearity Using Walsh Codes

    Directory of Open Access Journals (Sweden)

    Stephen Z. Pinter

    2007-02-01

    Full Text Available Transmitter nonlinearity has been a major issue in many scenarios: cellular wireless systems have high power RF amplifier (HPA nonlinearity at the base station; satellite downlinks have nonlinear TWT amplifiers in the satellite transponder and multipath conditions in the ground station; and radio-over-fiber (ROF systems consist of a nonlinear optical link followed by a wireless channel. In many cases, the nonlinearity is simply ignored if there is no out-of-band emission. This results in poor BER performance. In this paper we propose a new technique to estimate the linear part of the wireless downlink in the presence of a nonlinearity using Walsh codes; Walsh codes are commonly used in CDMA downlinks. Furthermore, we show that equalizer performance is significantly improved by taking into account the presence of the nonlinearity during channel estimation. This is shown by using a regular decision feedback equalizer (DFE with both wireless and RF amplifier noise. We perform estimation in a multiuser CDMA communication system where all users transmit their signal simultaneously. Correlation analysis is applied to identify the channel impulse response (CIR and the derivation of key correlation relationships is shown. A difficulty with using Walsh codes in terms of their correlations (compared to PN sequences is then presented, as well as a discussion on how to overcome it. Numerical evaluations show a good estimation of the linear system with 54 users in the downlink and a signal-to-noise ratio (SNR of 25 dB. Bit error rate (BER simulations of the proposed identification and equalization algorithms show a BER of 10−6 achieved at an SNR of ∼25 dB.

  3. Abstracting Asynchronous Multi-Valued Networks: An Initial Investigation

    CERN Document Server

    Steggles, L Jason

    2011-01-01

    Multi-valued networks provide a simple yet expressive qualitative state based modelling approach for biological systems. In this paper we develop an abstraction theory for asynchronous multi-valued network models that allows the state space of a model to be reduced while preserving key properties of the model. The abstraction theory therefore provides a mechanism for coping with the state space explosion problem and supports the analysis and comparison of multi-valued networks. We take as our starting point the abstraction theory for synchronous multi-valued networks which is based on the finite set of traces that represent the behaviour of such a model. The problem with extending this approach to the asynchronous case is that we can now have an infinite set of traces associated with a model making a simple trace inclusion test infeasible. To address this we develop a decision procedure for checking asynchronous abstractions based on using the finite state graph of an asynchronous multi-valued network to reas...

  4. Secure DS-CDMA spreading codes using fully digital multidimensional multiscroll chaos

    KAUST Repository

    Mansingka, Abhinav S.

    2014-06-18

    This paper introduces a generalized fully digital hardware implementation of 1-D, 2-D and 3-D multiscroll chaos through sawtooth nonlinearities in a 3rd order ODE with the Euler approximation, wherein low-significance bits pass all NIST SP. 800-22 tests. The low-significance bits show good performance as spreading code for multiple-access DS-CDMA in AWGN and multipath environments, equivalent to Gold codes. This system capitalizes on complex nonlinear dynamics afforded by multiscroll chaos to provide higher security than conventional codes with the same BER performance demonstrated experimentally on a Xilinx Virtex 4 FPGA with logic utilization less than 1.25% and throughput up to 10.92 Gbits/s.

  5. A PO-CI/MC-CDMA scheme for high modulation styles

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Through analyzing the theoretical spreading principle,it has been proved in this paper that the benefit of pseudo-orthogonal carrier interferometry(PO-CI)spreading code is not supported when complex signal modulation(e.g.,quadrature phase-shift keying(QPSK)and quadrature amplitude modulation(QAM))types are employed.On this basis,a novel and feasible structure for this problem is brought forward.Within the structure mentioned,instead of complex modulation patterns,pulse amplitude modulation(PAM)combined with PO-CI spreading code is utilized.This allows us to maintain the throughput increase of a multi-carrier code division multiple access(MC-CDMA)system with minimal loss in performance and no bandwidth expansion.

  6. A MUSIC-Based Algorithm for Blind User Identification in Multiuser DS-CDMA

    Directory of Open Access Journals (Sweden)

    M. Reza Soleymani

    2005-04-01

    Full Text Available A blind scheme based on multiple-signal classification (MUSIC algorithm for user identification in a synchronous multiuser code-division multiple-access (CDMA system is suggested. The scheme is blind in the sense that it does not require prior knowledge of the spreading codes. Spreading codes and users' power are acquired by the scheme. Eigenvalue decomposition (EVD is performed on the received signal, and then all the valid possible signature sequences are projected onto the subspaces. However, as a result of this process, some false solutions are also produced and the ambiguity seems unresolvable. Our approach is to apply a transformation derived from the results of the subspace decomposition on the received signal and then to inspect their statistics. It is shown that the second-order statistics of the transformed signal provides a reliable means for removing the false solutions.

  7. Design of embedded software used on i.MX6 based asynchronous LED display control system%基于i.MX6的LED异步控制系统软件设计

    Institute of Scientific and Technical Information of China (English)

    杨博; 李可生; 何书专; 李伟; 李丽; 潘红兵

    2016-01-01

    为满足户外 LED屏幕对异步控制的需求,利用面向对象的设计方法,设计实现一款基于 i.MX6处理器的 LED全彩异步控制系统嵌入式软件。提出基于多线程的事件队列和基于插件的 GStreamer 流媒体播放系统等技术方案;利用嵌入式Linux环境下可移植库的特性,实现对上位机发送的数据进行灵活的动态化处理,以及对多种格式的多媒体节目播放的异步控制;在性能上优化开机时间和播放策略。测试结果表明,该方案拥有较好用户体验,满足了设计需求。%Aiming at asynchronous control requirement of outdoor LED screen,the design and implementation of embedded soft-ware was put forward,which could be used on the i.MX6 processor based asynchronous LED display control system.An event queue method based on multithreading in the announced embedded software was adopted,accompanied with the utilization of the GStreamer based streaming media player system.Using the characteristics of portable library in embedded Linux environment, the data from the upper computer were processed dynamically and asynchronous control of multimedia programs in multiple for-mats was realized.Considering the functionality of the system,boot time and playing strategy were optimized for the perfor-mance.Results of several tests show that the proposed methods have better user experiences and satisfying results.

  8. Synaptotagmin-7 Is an Asynchronous Calcium Sensor for Synaptic Transmission in Neurons Expressing SNAP-23

    DEFF Research Database (Denmark)

    Weber, Jens P; Toft-Bertelsen, Trine L; Mohrmann, Ralf;

    2014-01-01

    Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetiti...

  9. Asynchronous Sensor fuSion for Improved Safety of air Traffic (ASSIST) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — SSCI proposes to develop, implement and test a collision detection system for unmanned aerial vehicles (UAV), referred to as the Asynchronous Sensor fuSion for...

  10. Asynchronous Parallelization of a CFD Solver

    Directory of Open Access Journals (Sweden)

    Daniel S. Abdi

    2015-01-01

    Full Text Available A Navier-Stokes equations solver is parallelized to run on a cluster of computers using the domain decomposition method. Two approaches of communication and computation are investigated, namely, synchronous and asynchronous methods. Asynchronous communication between subdomains is not commonly used in CFD codes; however, it has a potential to alleviate scaling bottlenecks incurred due to processors having to wait for each other at designated synchronization points. A common way to avoid this idle time is to overlap asynchronous communication with computation. For this to work, however, there must be something useful and independent a processor can do while waiting for messages to arrive. We investigate an alternative approach of computation, namely, conducting asynchronous iterations to improve local subdomain solution while communication is in progress. An in-house CFD code is parallelized using message passing interface (MPI, and scalability tests are conducted that suggest asynchronous iterations are a viable way of parallelizing CFD code.

  11. THE SCHEME STUDY OF THE APPLICATION OF W-CDMA SPREAD SPECTRUM COMMUNICATION IN MINE MOBILE COMMUNICATION

    Institute of Scientific and Technical Information of China (English)

    杨维; 程时昕; 孙继平

    2000-01-01

    For the purpose of making the best use of the mine frequency resource and realizing the instruction idea “to exchange bandwidth for distance" a W-CDMA mine spread spectrum mobile communication scheme based on spread spectrum communication technique and the propagation characteristic of electromagnetic wave along laneways is proposed.The structure and make up of the system are studied and the working frequency and channels are assigned.Analysis indicates the scheme is a simple one that can fulfill the mine saying requirement.

  12. Reduced-Rank Chip-Level MMSE Equalization for the 3G CDMA Forward Link with Code-Multiplexed Pilot

    Directory of Open Access Journals (Sweden)

    Goldstein J Scott

    2002-01-01

    Full Text Available This paper deals with synchronous direct-sequence code-division multiple access (CDMA transmission using orthogonal channel codes in frequency selective multipath, motivated by the forward link in 3G CDMA systems. The chip-level minimum mean square error (MMSE estimate of the (multiuser synchronous sum signal transmitted by the base, followed by a correlate and sum, has been shown to perform very well in saturated systems compared to a Rake receiver. In this paper, we present the reduced-rank, chip-level MMSE estimation based on the multistage nested Wiener filter (MSNWF. We show that, for the case of a known channel, only a small number of stages of the MSNWF is needed to achieve near full-rank MSE performance over a practical single-to-noise ratio (SNR range. This holds true even for an edge-of-cell scenario, where two base stations are contributing near equal-power signals, as well as for the single base station case. We then utilize the code-multiplexed pilot channel to train the MSNWF coefficients and show that adaptive MSNWF operating in a very low rank subspace performs slightly better than full-rank recursive least square (RLS and significantly better than least mean square (LMS. An important advantage of the MSNWF is that it can be implemented in a lattice structure, which involves significantly less computation than RLS. We also present structured MMSE equalizers that exploit the estimate of the multipath arrival times and the underlying channel structure to project the data vector onto a much lower dimensional subspace. Specifically, due to the sparseness of high-speed CDMA multipath channels, the channel vector lies in the subspace spanned by a small number of columns of the pulse shaping filter convolution matrix. We demonstrate that the performance of these structured low-rank equalizers is much superior to unstructured equalizers in terms of convergence speed and error rates.

  13. 基于互联网的异步 LED 显示屏集群管理系统的设计与实现%Design and implementation of asynchronous LED display centralized management system based on internet

    Institute of Scientific and Technical Information of China (English)

    刘飞; 王瑞光; 陈伟

    2014-01-01

    For the current domestic market,most of multiple asynchronous LED display management system based on LAN or 485 bus technology have many problems such as screen limited distribution geographical scope,costly cabling,localized user operations,single project managed and so on.To solve these problems,an open multiple-project multiple-users multiple-screen cluster management system based on Internet technology is designed and implemented in this paper.In the system,a data relay server and a media are designed as a bridge of communication between user and asynchronous LED display on Internet,a relational database is built to maintain the information of client companies, users,LED screens and associated relationships between them on data relay server,and a set of scalable layered communication protocol is designed.This system provides a highly optimized implementation method for data relay server.Otherwise,a reusable architecture of client software and asynchronous terminal software are designed.After testing,system can operate stably and efficiently, achieve the ability that multiple-user can control the remote multiple-asynchronous LED display in real-time at any location that can access the Internet.%针对目前国内市场上基于局域网或者485总线的多异步 LED 显示屏管理系统存在的屏幕分布地理范围受限、布线成本高昂、用户只能本地操作、一个系统只能管理一种业务等问题,设计并实现了一种基于互联网技术的开放式多业务多用户多屏幕集群管理系统。系统基于 Internet 网络设计了一个数据中转服务器和一个媒体服务器作为用户和异步LED 显示屏之间通信的桥梁,并在数据中转服务器上对客户公司、用户、屏幕及其关联关系的信息维护搭建了关系数据库,同时设计了一套可扩展的分层通信协议,并给出了一种高性能的中转服务器实现方法,还设计了客户端和异步终端软件的可复用架

  14. Multi-Service Coverage Analysis for CDMA Planning

    Institute of Scientific and Technical Information of China (English)

    SUN Peng; LIU Zhi-ping; QIU Hong; YANG Da-cheng

    2004-01-01

    In CDMA network planning, it's important to understand the characteristics of multi-services. A novel method for analyzing the coverage of mixed voice and packet data traffics is presented in this paper. Based upon GIS and Monte-Carlo simulation method, this method can provide more precise but less time-consuming analysis result than before.A practical analysis case using real geographic information and network parameters is applied to verify its performance and find some useful solutions. Simulation results show that this coverage analysis method can provide helpful solution for the radio networks planning.

  15. Inference of asynchronous Boolean network from biological pathways.

    Science.gov (United States)

    Das, Haimabati; Layek, Ritwik Kumar

    2015-01-01

    Gene regulation is a complex process with multiple levels of interactions. In order to describe this complex dynamical system with tractable parameterization, the choice of the dynamical system model is of paramount importance. The right abstraction of the modeling scheme can reduce the complexity in the inference and intervention design, both computationally and experimentally. This article proposes an asynchronous Boolean network framework to capture the transcriptional regulation as well as the protein-protein interactions in a genetic regulatory system. The inference of asynchronous Boolean network from biological pathways information and experimental evidence are explained using an algorithm. The suitability of this paradigm for the variability of several reaction rates is also discussed. This methodology and model selection open up new research challenges in understanding gene-protein interactive system in a coherent way and can be beneficial for designing effective therapeutic intervention strategy.

  16. Application of asynchronous interrupt function in machine tool break for 840D system%840D系统的异步中断功能在机床断刀后的应用

    Institute of Scientific and Technical Information of China (English)

    罗建全; 吴春平; 王恒; 康晓兰

    2013-01-01

      利用840D系统的异步中断功能,可以实现机床在断刀后暂停当前的加工程序,转而执行中断程序,使机床移动到安全地方后执行手动换刀功能,当刀具更换完毕后继续执行断电程序自动返回断点继续加工。%To pause the current program after the machine tool break can be realized by using asynchronous interrupt function of 840D system. Then the interrupt program can be implemented for the machine moving to safe place to carry on manual tool changing function. The power-off procedure can be completed continually to return the breakpoint automatically for processing after the tool is changed.

  17. Hypersensitivity to RF fields emitted from CDMA cellular phones: a provocation study.

    Science.gov (United States)

    Nam, Ki Chang; Lee, Ju Hyung; Noh, Hyung Wook; Cha, Eun Jong; Kim, Nam Hyun; Kim, Deok Won

    2009-12-01

    With the number of cellular phone users rapidly increasing, there is a considerable amount of public concern regarding the effects that electromagnetic fields (EMFs) from cellular phones have on health. People with self-attributed electromagnetic hypersensitivity (EHS) complain of subjective symptoms such as headaches, insomnia, and memory loss, and attribute these symptoms to radio frequency (RF) radiation from cellular phones and/or base stations. However, EHS is difficult to diagnose because it relies on a person's subjective judgment. Various provocation studies have been conducted on EHS caused by Global System for Mobile Communications (GSM) phones in which heart rate and blood pressure or subjective symptoms were investigated. However, there have been few sham-controlled provocation studies on EHS with Code Division Multiple Access (CDMA) phones where physiological parameters, subjective symptoms, and perception of RF radiation for EHS and non-EHS groups were simultaneously investigated. In this study, two volunteer groups of 18 self-reported EHS and 19 non-EHS persons were tested for both sham and real RF exposure from CDMA cellular phones with a 300 mW maximum exposure that lasted half an hour. We investigated not only the physiological parameters such as heart rate, respiration rate, and heart rate variability (HRV), but also various subjective symptoms and the perception of EMF. In conclusion, RF exposure did not have any effects on physiological parameters or subjective symptoms in either group. As for EMF perception, there was no evidence that the EHS group better perceived EMF than the non-EHS group.

  18. Abstractions for asynchronous distributed computing with malicious players

    OpenAIRE

    Vukolic, Marko; Guerraoui, Rachid

    2009-01-01

    In modern distributed systems, failures are the norm rather than the exception. In many cases, these failures are not benign. Settings such as the Internet might incur malicious (also called Byzantine or arbitrary) behavior and asynchrony. As a result, and perhaps not surprisingly, research on asynchronous Byzantine fault-tolerant (BFT) distributed systems is flourishing. Tolerating arbitrary behavior and asynchrony calls for very sophisticated algorithms. This is in particular the case with ...

  19. An asynchronous controller for a daisychainable vme bus interrupter

    OpenAIRE

    Wollowski, Ralf; Beister, Jochen; Kuhn, Matthias

    1999-01-01

    An interrupter for use in a daisy-chained VME bus interrupt system has beendesigned and implemented as an asynchronous sequential circuit. The concur-rency of the processes posed a design problem that was solved by means of asystematic design procedure that uses Petri nets for specifying system and in-terrupter behaviour, and for deriving a primitive flow table. Classical designand additional measures to cope with non-fundamental mode operation yieldeda coded state-machine representation. Thi...

  20. Enhancing Discussions in the Asynchronous Online Classroom: The Lack of Face-to-Face Interaction Does Not Lessen the Lesson

    Science.gov (United States)

    Comer, Debra R.; Lenaghan, Janet A.

    2013-01-01

    This article addresses educators' concerns about using asynchronous online discussions in lieu of face-to-face discussions. Drawing from research on asynchronous online education and Bloom's taxonomy, the authors introduce the system of "original examples" and "value-added comments" that they have developed to promote engaging and meaningful…

  1. Carrying Synchronous Voice Data On Asynchronous Networks

    Science.gov (United States)

    Bergman, Larry A.

    1990-01-01

    Buffers restore synchronism for internal use and permit asynchronism in external transmission. Proposed asynchronous local-area digital communication network (LAN) carries synchronous voice, data, or video signals, or non-real-time asynchronous data signals. Network uses double buffering scheme that reestablishes phase and frequency references at each node in network. Concept demonstrated in token-ring network operating at 80 Mb/s, pending development of equipment operating at planned data rate of 200 Mb/s. Technique generic and used with any LAN as long as protocol offers deterministic (or bonded) access delays and sufficient capacity.

  2. Burst-Mode Asynchronous Controllers on FPGA

    Directory of Open Access Journals (Sweden)

    Duarte L. Oliveira

    2008-01-01

    Full Text Available FPGAs have been mainly used to design synchronous circuits. Asynchronous design on FPGAs is difficult because the resulting circuit may suffer from hazard problems. We propose a method that implements a popular class of asynchronous circuits, known as burst mode, on FPGAs based on look-up table architectures. We present two conditions that, if satisfied, guarantee essential hazard-free implementation on any LUT-based FPGA. By doing that, besides all the intrinsic advantages of asynchronous over synchronous circuits, they also take advantage of the shorter design time and lower cost associated with FPGA designs.

  3. Document Flow Model: A Formal Notation for Modelling Asynchronous Web Services Composition

    OpenAIRE

    Yang, Jingtao; Cirstea, Corina; Henderson, Peter

    2005-01-01

    This paper presents a formal notation for modelling asynchronous web services composition, using context and coordination mechanisms. Our notation specifies the messages that can be handled by different web services, and describes a system of inter-related web services as the flow of documents between them. The notation allows the typical web services composition pattern, asynchronous messaging, and has the capability to deal with long-running service-to-service interactions and dynamic confi...

  4. Violation of the equivalence principle for stressed bodies in asynchronous relativity

    Energy Technology Data Exchange (ETDEWEB)

    Andrade Martins, R. de (Centro de Logica, Epistemologia e Historia da Ciencia, Campinas (Brazil))

    1983-12-11

    In the recently developed asynchronous formulation of the relativistic theory of extended bodies, the inertial mass of a body does not explicitly depend on its pressure or stress. The detailed analysis of the weight of a box filled with a gas and placed in a weak gravitational field shows that this feature of asynchronous relativity implies a breakdown of the equivalence between inertial and passive gravitational mass for stressed systems.

  5. Data Collection for Mobile Group Consumption: An Asynchronous Distributed Approach.

    Science.gov (United States)

    Zhu, Weiping; Chen, Weiran; Hu, Zhejie; Li, Zuoyou; Liang, Yue; Chen, Jiaojiao

    2016-01-01

    Mobile group consumption refers to consumption by a group of people, such as a couple, a family, colleagues and friends, based on mobile communications. It differs from consumption only involving individuals, because of the complex relations among group members. Existing data collection systems for mobile group consumption are centralized, which has the disadvantages of being a performance bottleneck, having single-point failure and increasing business and security risks. Moreover, these data collection systems are based on a synchronized clock, which is often unrealistic because of hardware constraints, privacy concerns or synchronization cost. In this paper, we propose the first asynchronous distributed approach to collecting data generated by mobile group consumption. We formally built a system model thereof based on asynchronous distributed communication. We then designed a simulation system for the model for which we propose a three-layer solution framework. After that, we describe how to detect the causality relation of two/three gathering events that happened in the system based on the collected data. Various definitions of causality relations based on asynchronous distributed communication are supported. Extensive simulation results show that the proposed approach is effective for data collection relating to mobile group consumption. PMID:27058544

  6. Performance analysis of slotted fiber-optic code-division multiple-access (CDMA) packet networks

    OpenAIRE

    Hsu, CS; Li, VOK

    1997-01-01

    This paper examines code-division multiple-access (CDMA) techniques used in slotted fiber-optic packet networks. Since the inherent properties and signal processing of the conventional communication channels are different from those of the fiber-optic channels, new code sequences must be constructed for fiber-optic applications. The goal of our research is to analyze the performance of fiber-optic CDMA packet networks using code sequences with given orthogonality properties. © 1997 IEEE.

  7. Broadband MC DS-CDMA Using Space-Time and Frequency-Domain Spreading

    OpenAIRE

    Yang, L-L.; Hanzo, L.

    2002-01-01

    In this contribution multicarrier direct-sequence codedivision multiple-access (MC DS-CDMA) using space-time spreading (STS) assisted transmit diversity and frequency-domain (F-domain) spreading is investigated in the context of broadband communications over frequency-selective Rayleigh fading channels. We consider the attainable capacity extension of broadband MC DS-CDMA with the advent of using Time-Frequency-domain (TF-domain) spreading. The BER performance of STS assisted broadband MC DS-...

  8. Implementing LOTOS as asynchronously Communicating Processes

    OpenAIRE

    Sjödin, Peter

    1990-01-01

    A technique is presented for translating LOTOS specifications into implementations executing as asynchronously communicating processes. This generation of implementations is described as transformations of LOTOS expressions. A protocol for implementing LOTOS synchronisation is described.

  9. REACTIVE POWER COMPENSATION IN ASYNCHRONOUS ELECTRIC DRIVES

    Directory of Open Access Journals (Sweden)

    V.S. Malyar

    2013-10-01

    Full Text Available A problem of calculating capacity of cosine capacitors for individual compensation of reactive power in asynchronous electric drives in stationary and transient operation modes is considered. The algorithm introduced employs a high-adequacy mathematical model of asynchronous motor developed on the theory of representing vectors which takes into account both the magnetic core saturation and the current displacement in the rotor bars.

  10. Asynchronous communication in real space process algebra

    OpenAIRE

    Baeten, JCM Jos; Bergstra, JA Jan

    1992-01-01

    A version of classical real space process algebra is given in which messages travel with constant speed through a three-dimensional medium. It follows that communication is asynchronous and has a broadcasting character. A state operator is used to describe asynchronous message transfer and a priority mechanism allows to express the broadcasting mechanism. As an application, a protocol is specified in which the receiver moves with respect to the sender.

  11. Non-detection of nova shells around asynchronous polars

    Science.gov (United States)

    Pagnotta, Ashley; Zurek, David

    2016-05-01

    Asynchronous polars (APs) are accreting white dwarfs (WDs) that have different WD and orbital angular velocities, unlike the rest of the known polars, which rotate synchronously (i.e. their WD and orbital angular velocities are the same). Past nova eruptions are the predicted cause of the asynchronicity, in part due to the fact that one of the APs, V1500 Cyg, was observed to undergo a nova eruption in 1975. We used the Southern African Large Telescope 10 m class telescope and the MDM 2.4 m Hiltner telescope to search for nova shells around three of the remaining four APs (V1432 Aql, BY Cam, and CD Ind) as well as one Intermediate Polar with a high asynchronicity (EX Hya). We found no evidence of nova shells in any of our images. We therefore cannot say that any of the systems besides V1500 Cyg had nova eruptions, but because not all post-nova systems have detectable shells, we also cannot exclude the possibility of a nova eruption occurring in any of these systems and knocking the rotation out of sync.

  12. Non-Detection of Nova Shells Around Asynchronous Polars

    CERN Document Server

    Pagnotta, Ashley

    2016-01-01

    Asynchronous polars (APs) are accreting white dwarfs (WDs) that have different WD and orbital angular velocities, unlike the rest of the known polars, which rotate synchronously (i.e., their WD and orbital angular velocities are the same). Past nova eruptions are the predicted cause of the asynchronicity, in part due to the fact that one of the APs, V1500 Cyg, was observed to undergo a nova eruption in 1975. We used the Southern African Large Telescope 10m class telescope and the MDM 2.4m Hiltner telescope to search for nova shells around three of the remaining four APs (V1432 Aql, BY Cam, and CD Ind) as well as one Intermediate Polar with a high asynchronicity (EX Hya). We found no evidence of nova shells in any of our images. We therefore cannot say that any of the systems besides V1500 Cyg had nova eruptions, but because not all post-nova systems have detectable shells, we also cannot exclude the possibility of a nova eruption occurring in any of these systems and knocking the rotation out of sync.

  13. Performance analysis of MC-2D-CDMA with orthogonal restore combination(ORC) over frequency selective channel

    Institute of Scientific and Technical Information of China (English)

    强蔚; 张中兆; 沙学军

    2002-01-01

    a method is proposed to improve the performance of MC-2D-CDMA in frequency selective fading channel. Each chip of spreading spectrum sequence is contained in two sub-carriers, so when fading is deep in one sub-carrier, the other will compensate and the performance of this model is improved in frequency selective channel. Orthogonal restore combination (ORC) is used to explain the method. Computer simulation is used to exam the relation of signal noise ratio (SNR) and probability of bit error (BER), and the number of subscribers and BER. Then performance is compared among MC-2D-CDMA, MC-DS-CDMA and MC-CDMA.

  14. Voltage and frequency stability control for micro wind asynchronous generator with energy storage system%带储能系统的小型风力异步发电机稳压稳频控制

    Institute of Scientific and Technical Information of China (English)

    胡立坤; 胡东; 卢子广; 朱绯

    2014-01-01

    针对小型风力异步发电机机端特性的不稳定,提出了带储能系统的异步发电机稳压稳频控制方法。在直流侧并联铅酸蓄电池系统进行储能,通过控制整流器实现直流侧有功和无功的双向流动。该控制方法包括电压外环和频率内环两个控制环,电压和频率控制器都采用的是PI控制器,用改进的锁相环法实时检测系统的频率变化。为了验证控制方法的有效性,进行了MATLAB/Simulink控制系统仿真和实验。结果表明:采用带储能系统的稳压稳频控制可以提高异步发电机的机端特性,改善独立供电系统的电能质量。%This paper deals with the voltage and frequency controllers of a micro wind asynchronous generator with an energy storage system. The system,along with an energy storage equipment,charges or discharges at its direct current link. The proposed controllers have bidirectionally active and reactive powers flow capability by which it controls the system voltage and frequency with different consumer loads. The control method includes voltage and frequency loops. The voltage and frequency controllers are both PI controllers. The real-time detection system of the frequency variation adopts a PLL improved method. A set of new VF controllers are designed and their performance is simulated in the MATLAB/Simulink and experimented to verify the correctness of the control method. The result shows the control strategy can improve the asynchronous generator port characteristics and the power quality of the system.

  15. Adaptive Lattice Filters for CDMA Overlay

    OpenAIRE

    Prahatheesan, V; Wang, J.

    2000-01-01

    This paper presents the behavior of reflection coefficients of a stochastic gradient lattice (SGL) filter applied to a code-division multiple-access overlay system. Analytic expressions for coefficients for a two-stage filter are derived in a Rayleigh fading channel with the presence of narrow-band interference and additive white Gaussian noise. It is shown that the coefficients of the lattice filter exhibit separate tracking and convergent properties,and that compared to an LMS filter, the l...

  16. Design of Asynchronous LED Display Control System Based on Cortex-M3%基于Cortex-M3的异步LED显示控制系统设计

    Institute of Scientific and Technical Information of China (English)

    刘斌; 刘伟彦

    2012-01-01

    This paper designs a new asynchronous LED display control system based on ARM and CPLD, the core of the system is Cortex-M3, CPLD is the scan control unit, the communication with the PC is accomplished by the Ethernet. It can storage and play automatically, the contents of the host computer can be stored in Flash, the contents can be displayed on the LED screen. The system provides crystal clear and stable picture, and can be maintained conveniently.%以Cortex-M3为核心,CPLD芯片为扫描控制单元,设计完成异步LED显示屏系统.该系统通过以太网实现与上位机的通信,具有存储及自动播放的能力,能够将上位机发送的内容保存在存储芯片内,并将存储的内容显示在LED屏上,实现具有功能强大、维护方便、画质稳定清晰的异步LED显示屏.

  17. Asynchronous Rate Chaos in Spiking Neuronal Circuits

    Science.gov (United States)

    Harish, Omri; Hansel, David

    2015-01-01

    The brain exhibits temporally complex patterns of activity with features similar to those of chaotic systems. Theoretical studies over the last twenty years have described various computational advantages for such regimes in neuronal systems. Nevertheless, it still remains unclear whether chaos requires specific cellular properties or network architectures, or whether it is a generic property of neuronal circuits. We investigate the dynamics of networks of excitatory-inhibitory (EI) spiking neurons with random sparse connectivity operating in the regime of balance of excitation and inhibition. Combining Dynamical Mean-Field Theory with numerical simulations, we show that chaotic, asynchronous firing rate fluctuations emerge generically for sufficiently strong synapses. Two different mechanisms can lead to these chaotic fluctuations. One mechanism relies on slow I-I inhibition which gives rise to slow subthreshold voltage and rate fluctuations. The decorrelation time of these fluctuations is proportional to the time constant of the inhibition. The second mechanism relies on the recurrent E-I-E feedback loop. It requires slow excitation but the inhibition can be fast. In the corresponding dynamical regime all neurons exhibit rate fluctuations on the time scale of the excitation. Another feature of this regime is that the population-averaged firing rate is substantially smaller in the excitatory population than in the inhibitory population. This is not necessarily the case in the I-I mechanism. Finally, we discuss the neurophysiological and computational significance of our results. PMID:26230679

  18. Asynchronous Complex Pipeline Design Based on ARM Instruction Set

    Institute of Scientific and Technical Information of China (English)

    WANG Bing; WANG Qin; PENG Rui-hua; FU Yu-zhuo

    2008-01-01

    This paper proposes an asynchronous complex pipeline based on ARM-V3 instruction set. Muller pipeline structure is used as prototype, and the factors which may affect pipeline performance are analyzed. To balance the difficulty of asynchronous design and performance analysis, both complete asynchronous and partial asynchronous structures aere designed and compared. Results of comparison with the well-Rnown industrial product ARM922T verify that about 30% and 40% performance improvement of the partial and complete asynchronous complex pipelines can be obtained respectively. The design methodologies can also be used in the design of other asynchronous pipelines.

  19. ON THE ISSUE OF VECTOR CONTROL OF THE ASYNCHRONOUS MOTORS

    Directory of Open Access Journals (Sweden)

    B. I. Firago

    2015-10-01

    Full Text Available The paper considers the issue of one of the widespread types of vector control realization for the asynchronous motors with a short-circuited rotor. Of all more than 20 vector control types known presently, the following are applied most frequently: direct vector control with velocity pickup (VP, direct vector control without VP, indirect vector control with VP and indirect vector control without VP. Despite the fact that the asynchronous-motor indirect vector control without VP is the easiest and most spread, the absence of VP does not allow controlling the motor electromagnetic torque at zero velocity. This is the reason why for electric motor drives of such requirements they utilize the vector control with a velocity transducer. The systems of widest dissemination became the direct and indirect vector control systems with X-axis alignment of the synchronously rotating x–y-coordinate frame along the rotor flux-linkage vector inasmuch as this provides the simplest correlations for controlling variables. Although these two types of vector control are well presented in literature, a number of issues concerning their realization and practical application require further elaboration. These include: the block schemes adequate representation as consisted with the modern realization of vector control and clarification of the analytical expressions for evaluating the regulator parameters.The authors present a technique for evaluating the dynamics of an asynchronous electric motor drive with direct vector control and x-axis alignment along the vector of rotor flux linkage. The article offers a generalized structure of this vector control type with detailed description of its principal blocks: controlling system, frequency converter, and the asynchronous motor.The paper presents a direct vector control simulating model developed in the MatLab environment on the grounds of this structure. The authors illustrate the described technique with the results

  20. Wind Generator Stabilization with Doubly-Fed Asynchronous Machine

    Institute of Scientific and Technical Information of China (English)

    WU Li; WANG Zhi-xin

    2007-01-01

    This paper investigates the function of doubly-fed asynchronous machine(DASM) with emphasis placed on its ability to the stabilization of the power system including wind generators. P(active power) and Q(reactive power) compensation from DASM can be regulated independently through secondary-excitation controlling. Simulation results by power system computer aided design(PSCAD) show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures. Comparison studies have also been performed between wind turbine pitch control and proposed method.

  1. A Hybrid Path-Oriented Code Assignment CDMA-Based MAC Protocol for Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Huifang Chen

    2013-11-01

    Full Text Available Due to the characteristics of underwater acoustic channel, media access control (MAC protocols designed for underwater acoustic sensor networks (UWASNs are quite different from those for terrestrial wireless sensor networks. Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. An improved CDMA-based MAC protocol, named path-oriented code assignment (POCA CDMA MAC (POCA-CDMA-MAC, is proposed for UWASNs in this paper. In the proposed MAC protocol, both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Since the number of paths for information gathering is much less than that of nodes, the length of the spreading code used in the POCA-CDMA-MAC protocol is shorter greatly than that used in the CDMA-based protocols with transmitter-oriented code assignment (TOCA or receiver-oriented code assignment (ROCA. Simulation results show that the proposed POCA-CDMA-MAC protocol achieves a higher network throughput and a lower end-to-end delay compared to other CDMA-based MAC protocols.

  2. A hybrid path-oriented code assignment CDMA-based MAC protocol for underwater acoustic sensor networks.

    Science.gov (United States)

    Chen, Huifang; Fan, Guangyu; Xie, Lei; Cui, Jun-Hong

    2013-01-01

    Due to the characteristics of underwater acoustic channel, media access control (MAC) protocols designed for underwater acoustic sensor networks (UWASNs) are quite different from those for terrestrial wireless sensor networks. Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. An improved CDMA-based MAC protocol, named path-oriented code assignment (POCA) CDMA MAC (POCA-CDMA-MAC), is proposed for UWASNs in this paper. In the proposed MAC protocol, both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Since the number of paths for information gathering is much less than that of nodes, the length of the spreading code used in the POCA-CDMA-MAC protocol is shorter greatly than that used in the CDMA-based protocols with transmitter-oriented code assignment (TOCA) or receiver-oriented code assignment (ROCA). Simulation results show that the proposed POCA-CDMA-MAC protocol achieves a higher network throughput and a lower end-to-end delay compared to other CDMA-based MAC protocols.

  3. Asynchronous decentralized method for interconnected electricity markets

    International Nuclear Information System (INIS)

    This paper presents an asynchronous decentralized method to solve the optimization problem of interconnected electricity markets. The proposed method decomposes the optimization problem of combined electricity markets into individual optimization problems. The impact of neighboring markets' information is included in the objective function of the individual market optimization problem by the standard Lagrangian relaxation method. Most decentralized optimization methods use synchronous models of communication to exchange updated market information among markets during the iterative process. In this paper, however, the solutions of the individual optimization problems are coordinated through an asynchronous communication model until they converge to the global optimal solution of combined markets. Numerical examples are presented to demonstrate the advantages of the proposed asynchronous method over the existing synchronous methods. (author)

  4. 一种异步日志记录的入侵防御系统的设计与实现%Design and Implementation of an Asynchronous Logging Intrusion Prevention System

    Institute of Scientific and Technical Information of China (English)

    艾磊; 陈文

    2014-01-01

    传统的入侵防御系统对于告警日志的记录采取同步的方式,即在整个数据包获取、数据包预处理、数据包检测、数据包处理以及日志记录的过程中,数据包获取会以同步阻塞的方式等待日志记录完成后才会再次循环进行,因此在整个系统运行过程中产生了大量的I/O操作,在高速复杂的网络环境下成为入侵防御系统的主要性能瓶颈.针对以上问题,设计并实现了一种异步记录告警日志的入侵防御系统(an Asynchronous Logging Intrusion Prevention System,ALIPS),并应用多核技术进行并行处理,通过测试,相比传统入侵防御系统,本系统在吞吐量上有着3倍多的提高.

  5. SIMULASI TEKNIK POWER CONTROL DAN MULTI USER DETECTION PADA SISTEM KOMUNIKASI DS-CDMA

    Directory of Open Access Journals (Sweden)

    Yuli Christyono

    2012-02-01

    Full Text Available CDMA is interference limited multiple access system. Because all users transmit on the same frequency,internal interference generated by the system is the most significant factor in determining system capacity andcall quality. The transmit power for each user must be reduced to limit interference, however, the power shouldbe enough to maintain the required Eb/No (signal to noise ratio for a satisfactory call quality. Maximumcapacity is achieved when Eb/No of every user is at the minimum level needed for the acceptable channelperformance. As the MS moves around, the RF environment continuously changes due to fast and slow fading,external interference, shadowing , and other factors. The aim of the dynamic power control is to limittransmitted power on both the links while maintaining link quality under all conditions. Additional advantagesare longer mobile battery life and longer life span of BTS power amplifiers.In this research will be made a sumulation of power control and multi user detection to avoid the interferencebetween MS.Observations show that the increasing number of users will decrease the value of Signal to Interfrence Ratio(SIR / SIR below the target. To cope the growing number of users increases can be done by iteration / updatingpower transmit so the convergence computation can be reached and target value SIR can be achieved. Inaddition, to reduce interference can also be done by extending the number of chips.

  6. TRAFFIC CHANNEL SIR ESTIMATION BASED ON REVERSE PILOT CHANNEL IN cdma2000

    Institute of Scientific and Technical Information of China (English)

    Zhou Hua Yang Dacheng

    2004-01-01

    Signal-to-Interference Ratio(SIR) is a very important metric of communication link quality. For wireless cellular systems, several control mechanisms, such as power control mechanisms, rate control mechanisms, and allocation of radio resource, are based on SIR estimation.In previous researches, most of researchers concentrated on WCDMA systems, in which pilot symbol is time-multiplexed with data symbol; the method developed in this case is not feasible for cdma2000 systems where pilot symbol is code-multiplexed with data symbol. This paper first develops the SIR estimators based on the reverse pilot channel and then derives the approximate analytic expression for its Mean Squared Error (MSE) function, the accuracy of which is validated through simulation. It is shown that the MSE of the new SIR estimator is significantly smaller than that of other widely used SIR estimators, especially in low SIR case. Finally, the estimate quality of the proposed method is further improved by long-termly averaging the sample interference.

  7. Synchronization of Asynchronous Switched Boolean Network.

    Science.gov (United States)

    Zhang, Hao; Wang, Xingyuan; Lin, Xiaohui

    2015-01-01

    In this paper, the complete synchronizations for asynchronous switched Boolean network with free Boolean sequence controllers and close-loop controllers are studied. First, the basic asynchronous switched Boolean network model is provided. With the method of semi-tensor product, the Boolean dynamics is translated into linear representation. Second, necessary and sufficient conditions for ASBN synchronization with free Boolean sequence control and close-loop control are derived, respectively. Third, some illustrative examples are provided to show the efficiency of the proposed methods.

  8. Handbook of asynchronous machines with variable speed

    CERN Document Server

    Razik, Hubert

    2013-01-01

    This handbook deals with the asynchronous machine in its close environment. It was born from a reflection on this electromagnetic converter whose integration in industrial environments takes a wide part. Previously this type of motor operated at fixed speed, from now on it has been integrated more and more in processes at variable speed. For this reason it seemed useful, or necessary, to write a handbook on the various aspects from the motor in itself, via the control and while finishing by the diagnosis aspect. Indeed, an asynchronous motor is used nowadays in industry where variation speed a

  9. Acceptability of an Asynchronous Learning Forum on Mobile Devices

    Science.gov (United States)

    Chang, Chih-Kai

    2010-01-01

    Mobile learning has recently become noteworthy because mobile devices have become popular. To construct an asynchronous learning forum on mobile devices is important because an asynchronous learning forum is always an essential part of networked asynchronous distance learning. However, the input interface in handheld learning devices, which is…

  10. 基于MATLAB/Simulink的异步电机控制系统建模与仿真%Modeling and simulation of asynchronous motor control system based on MATLAB/Simulink

    Institute of Scientific and Technical Information of China (English)

    孟朝霞; 任一峰

    2012-01-01

    In this paper, based on the means of asynchronous motor' s rotor flux-oriented vector control,and the shortcomings that rotor flux is influenced by motor parameters in magnetic linkage closed loop, this article adopts vector control scheme of magnetic flux opended loop.By modular thought,the functional modules of the opening magnetic flux loop of vector control system is modeled in MATLAB/Simulink. Through the organic integration of each functional modules, a simulation model of vector control system is modeled. The results show that the system has a good dynamic performance and the anti-interference ability,so the feasibility and effectiveness of the modeling method is validated. The results also provides a theoretical foundation for design and debug of actual motor control system.%本文在基于转子磁链定向的异步电机矢量控制理论基础上,针对磁链闭环的矢量控制系统中转子磁链易受电机参数影响的不足,提出了转子磁链开环的矢量控制方案。利用模块化思想,在MATLAB/Simulink建立磁链开环的矢量控制系统的各个功能模块,然后对各个功能模块进行有机的整合,构成矢量控制系统的仿真模型;仿真结果表明该系统具有良好的动态性能和抗干扰能力,进而验证了该控制系统设计的可行性和有效性,为实际电机控制系统的设计和调试奠定了理论基础。

  11. Simulating the operation action of an asynchronized turbogenerator under loss of excitation

    Institute of Scientific and Technical Information of China (English)

    SANGARE Adama Fanhiri; YANG Shunchang; LIU Ren

    2004-01-01

    The control strategy tor asynchronized turbogenerators (ASTGs) was studied by using two-axis equations. Simulation of the process of an asynchronized turbogenerator with faults of d or q axis or d and q axes in the excitation system was carried out with the simulating models including the model of the reverse thyristors in the excitation system established by Saber software. The simulation results show that at the loss of excitation at both windings or one winding of the rotor, the ASTGs can be automatically driven into an asynchronous or single axis excitation operation mode without a power unit tripping, and the characteristics for ASTGs with faults in the excitation system appear in good order.

  12. 多速率DS/CDMA信号扩频序列并行盲估计方法%Parallel Blind Estimation of Spreading Sequences in Multi-rate DS/CDMA Signals

    Institute of Scientific and Technical Information of China (English)

    吴旺军; 张天骐; 石穗; 张亚娟

    2015-01-01

    针对可变扩频长度多速率直接序列码分多址(direct sequence/code division multi-ple access,DS/CDMA)信号扩频序列盲估计问题,提出了一种基于盲源分离的并行估计方法,该方法首先利用二次功率谱的方法估计出信号不同速率的扩频码周期,然后利用多速率DS/CDMA信号周期特性将信号依据周期并行地建模为主用户和干扰用户(即将同一周期下的用户视为主用户,其余的用户和噪声一律视为独立的单个干扰用户)的模型,最后针对同步和异步两种情况,分别以单倍周期和两倍周期长度对数据进行分割,生成数据矩阵,并结合稳健的矩阵联合近似对角化(JADE)算法对扩频序列进行并行的盲估计。计算机仿真结果表明方法在较低信噪比下有效。%To solve the problem of blind estimation of spreading sequences for the variable spreading length multi-rate DS/CDMA signals,a new parallel blind estimation algorithm,based on blind source separation,is pro-posed.Firstly,the method uses the reprocessing of the power spectrum algorithm to estimate the periods users employ different rates of spreading sequences.Secondly,based on period characteristics,the signals are mod-eled with primary users and interference users,treating users with the same period as primary users and others as interference users.Finally,for synchronous and asynchronous systems,the signals are divided into single or double times of spreading period length,respectively,forming a data matrix.The robust JADE algorithm is used for the blind estimation of the spreading sequences.The computer simulation results show that this meth-od performs well at lower signal-to-noise ratios.

  13. An Efficient Hybrid Power Control Algorithm for Capacity Improvement of CDMA-based Fixed Wireless Applications

    CERN Document Server

    Zeeshan, Muhammad; Malik, Muhammad Yasir

    2011-01-01

    In Fixed Wireless Applications (FWA), the Code Division Multiple Access (CDMA) is the most promising candidate for wideband data access. The reason is the soft limit on the number of active mobile devices. Many Fixed Wireless Applications impose an upper bound on the BER performance which restricts the increase in number of mobile users. The number of active mobile users or Capacity is further reduced in Multipath Fading Environment (MFE). This paper presents an effective method of improving the capacity of CDMA based Fixed Wireless Networks by using a hybrid power control algorithm. The proposed scheme improves the capacity two times as compared to the conventional CDMA based networks. Simulation results have been presented to demonstrate the effectiveness of the proposed scheme.

  14. The Study of MSADQ/CDMA Protocol in Voice/Data Integration Packet Networks

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new packet medium access protocol, namely, minislot signalingaccess based on distributed queues(MSADQ/CDMA), is proposed in voice and data intergration CDMA networks. The MSADQ protocol is based on distributed queues and collision resolution algorithm. Through proper management of the PN codes, the number of random competition collision reduces greatly, the multiple access interference (MAI) decreases. It has several special access signaling channels to carry the voice and data access request. Each slot is devided into several control minislots (CMSs), in which the Data Terminals (DT) or Voice Terminals (VT) transmit their request. According to the voice and data traffic character, the signaling access structure is proposed. The code assign rules and queue managing rules are also proposed to ensure the QoS requirement of each traffic. Comparisions with other three protocol are developed by simulation, which shows that MSADQ/CDMA protocol occupies less PN codes, but still has very good performance.

  15. Hierarchical Decoupling Principle of a MIMO-CDMA Channel in Asymptotic Limits

    CERN Document Server

    Takeuchi, Keigo

    2007-01-01

    We analyze an uplink of a fast flat fading MIMO-CDMA channel in the case where the data symbol vector for each user follows an arbitrary distribution. The spectral efficiency of the channel with CSI at the receiver is evaluated analytically with the replica method. The main result is that the hierarchical decoupling principle holds in the MIMO-CDMA channel, i.e., the MIMO-CDMA channel is decoupled into a bank of single-user MIMO channels in the many-user limit, and each single-user MIMO channel is further decoupled into a bank of scalar Gaussian channels in the many-antenna limit for a fading model with a limited number of scatterers.

  16. Increasing Student Engagement Using Asynchronous Learning

    Science.gov (United States)

    Northey, Gavin; Bucic, Tania; Chylinski, Mathew; Govind, Rahul

    2015-01-01

    Student engagement is an ongoing concern for educators because of its positive association with deep learning and educational outcomes. This article tests the use of a social networking site (Facebook) as a tool to facilitate asynchronous learning opportunities that complement face-to-face interactions and thereby enable a stronger learning…

  17. Asynchronous Rumor Spreading on Random Graphs

    CERN Document Server

    Panagiotou, Konstantinos

    2016-01-01

    We perform a thorough study of various characteristics of the asynchronous push-pull protocol for spreading a rumor on Erd\\H{o}s-R\\'enyi random graphs $G_{n,p}$, for any $p>c\\ln(n)/n$ with $c>1$. In particular, we provide a simple strategy for analyzing the asynchronous push-pull protocol on arbitrary graph topologies and apply this strategy to $G_{n,p}$. We prove tight bounds of logarithmic order for the total time that is needed until the information has spread to all nodes. Surprisingly, the time required by the asynchronous push-pull protocol is asymptotically almost unaffected by the average degree of the graph. Similarly tight bounds for Erd\\H{o}s-R\\'enyi random graphs have previously only been obtained for the synchronous push protocol, where it has been observed that the total running time increases significantly for sparse random graphs. Finally, we quantify the robustness of the protocol with respect to transmission and node failures. Our analysis suggests that the asynchronous protocols are particu...

  18. Dynamic Resource Management in MC-CDMA Based Cellular Wireless Networks

    Directory of Open Access Journals (Sweden)

    Bala Jeevitha Vani

    2009-10-01

    Full Text Available Most of the multimedia and Internet services today are asymmetric in nature, and require high data rate support. Allocating equal band width in both uplink and downlink is not prudent solution, as most of the time user requirement is more either in uplink or downlink. The Multi Carrier Code Division Multiple Access (MC-CDMA system with time division duplex mode can easily met this requirement by dynamically declaring traffic direction in TDD slot, and adaptively allocating the sub channels. In this paper, we propose a adaptive slot and sub carrier allocation algorithm, that can be independently implemented in each cell of mobile communication network. Our analytical model is generalization of two cell concept to represent a multi cell model. Based on two cell concept four cases of interference pattern has been considered and simulated separately in presence of Additive White Gaussian Noise (AWGN and Rayleigh Channel. The simulated result suggests the requirement of approximately 9dB of Signal to Noise Ratio (SNR to maintain Bit Error Rate below 10-3. We also analyze the average delay incurred by the proposed algorithm in allocating resources.

  19. Adaptive Multi User Detection for FD-MC-CDMA in Presence of CFO

    Directory of Open Access Journals (Sweden)

    Guntu. Nooka Raju

    2014-11-01

    Full Text Available The main targets of multi-carrier direct sequence code division multiple access (MC-DS-CDMA mobile communication systems are to overcome the multi-path fading influences as well as the near-far effect and to increase its capacity. Different types of optimal and suboptimal multi-user detection schemes have been proposed and analyzed in literature. Unfortunately, most of them share the drawback of requiring an efficient practical solution. Genetic algorithm provides a more robust and efficient approach for solving complex real world problem such as multi user detection, but genetic algorithms are not computationally efficient. Computational complexity and performance of the genetic algorithms depends on number of generations and/or the population size, schemes involving genetic algorithms would compromise in computational complexity or performance. In this paper we propose adaptive population sizing genetic algorithm based multi user detection algorithm and compare its performance with existing multi user detection algorithms in various channels. Simulation results confirmed that the proposed adaptive genetic algorithm assisted multi user detection algorithm performs better compared to the existing multi user detection algorithms.

  20. Gigabit Ethernet signal transmission using asynchronous optical code division multiple access.

    Science.gov (United States)

    Ma, Philip Y; Fok, Mable P; Shastri, Bhavin J; Wu, Ben; Prucnal, Paul R

    2015-12-15

    We propose and experimentally demonstrate a novel architecture for interfacing and transmitting a Gigabit Ethernet (GbE) signal using asynchronous incoherent optical code division multiple access (OCDMA). This is the first such asynchronous incoherent OCDMA system carrying GbE data being demonstrated to be working among multi-users where each user is operating with an independent clock/data rate and is granted random access to the network. Three major components, the GbE interface, the OCDMA transmitter, and the OCDMA receiver are discussed in detail. The performance of the system is studied and characterized through measuring eye diagrams, bit-error rate and packet loss rate in real-time file transfer. Our Letter also addresses the near-far problem and realizes asynchronous transmission and detection of signal.

  1. AN OPTIMIZED SCHEME FOR FAST HANDOFF IN IP-BASED CDMA WIRELESS COMMUNICATION NETWORKS

    Institute of Scientific and Technical Information of China (English)

    段世平; 徐友云; 宋文涛; 罗汉文

    2002-01-01

    This paper proposed an optimized fast handoff scheme for real-time applications in next generation IPbased CDMA wireless networks. The idea is to utilize optimized IP multicasting handoff (based on PIM-SM),which is triggered by CDMA layer-2 functionality. An IP-based cellular network model with WCDMA FDD air interface and IP-based packet traffic is adopted. No special network entities and signaling for handoff are added in our network model. The simulation results show that low delay and low packet-lost-rate can be obtained.

  2. Performance of MC-2D-CDMA over Frequency Selective Channel

    Institute of Scientific and Technical Information of China (English)

    赵刚

    2002-01-01

    The de-spreading algorithm of MC-2D-CDMA (Multi-Carrier 2-Dimension Code Division Multiple Access) uses a simple correlator and complex spread spectrum sequences. Each chip of spreading spectrum sequence is in two sub-carriers. With one sub-carrier in deep fading, the chip in the other sub-carrier would compensate to improve performance. Orthogonal restore correlation (ORC) explained the algorithm. The performance was examined analytically and by computer simulations. The performance is better than that of regular MC-2D-CDMA model.

  3. TDOA技术在GSM和CDMA网络中的应用分析%TDOA technology application analysis in GSM and CDMA network

    Institute of Scientific and Technical Information of China (English)

    王鑫; 张朝柱

    2010-01-01

    介绍TDOA(Time Difference of Arrival)技术的数学模型,以及TDOA技术在GSM(Global System for Mobile Communication)和CDMA(Code Division Multiple Access)网络的实际应用.最后通过仿真分析,对GSM和CDMA网络进行了性能比较,深入分析了两种网络的特点,对于在实际应用中如何选择定位网络有很好的指导作用,具有很高的实际应用价值.

  4. N-CANDA data integration: anatomy of an asynchronous infrastructure for multi-site, multi-instrument longitudinal data capture

    OpenAIRE

    Rohlfing, Torsten; Cummins, Kevin; Henthorn, Trevor; Chu, WeiWei; Nichols, B Nolan

    2013-01-01

    The infrastructure for data collection implemented by the National Consortium on Alcohol and NeuroDevelopment in Adolescence (N-CANDA) for data collection comprises several innovative features: (a) secure, asynchronous transfer and persistent storage of collected data via a revision control system; (b) two-stage import into a longitudinal database; and (c) use of a script-controlled web browser for data retrieval from a third-party, web-based neuropsychological test battery. The asynchronous ...

  5. Research on DSP-based Asynchronous Motor Control Technology

    Directory of Open Access Journals (Sweden)

    Jun Yao

    2013-05-01

    Full Text Available The Motor in a variety of electrical transmission and position servo system occupies an extremely important position. After the DSP technology being applied to the motor control, the unification of the hardware and the flexibility of the software can be combined. Take the brushless DC motor for example, studied the mathematical model and the structure of the motor control system, also obtained the design scheme of the DSP-based asynchronous motor control system. With TI's 32 bit fixed point DSPTMS320F2812 as the core design of the hardware system, we wrote the system software, debug the motor control system and the results show that the system achieves the expected effect. The results of the research can be applied to brushless DC motor and other motor control, it will have a wide application prospects.

  6. EXPERIMENTAL STUDY OF THE ASYNCHRONOUS MULTISPLITTING RELAXATION METHODS FOR THE LINEAR COMPLEMENTARITY PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Zhong-zhi Bai

    2002-01-01

    We study the numerical behaviours of the relaxed asynchronous multisplitting methods for the linear complementarity problems by solving some typical problems from practical applications on a real multiprocessor system. Numerical results show that the parallel multisplitting relaxation methods always perform much better than the corresponding sequential alternatives, and that the asynchronous multisplitting relaxation methods often outperform their corresponding synchronous counterparts. Moreover, the two-sweep relaxed multisplitting methods have better convergence properties than their corresponding one-sweep relaxed ones in the sense that they have larger convergence domains and faster convergence speeds. Hence, the asynchronous multisplitting unsymmetric relaxation iterations should be the methods of choice for solving the large sparse linear complementarity problems in the parallel computing environments.

  7. THE ROLE OF OFFLINE METALANGUAGE TALK IN ASYNCHRONOUS COMPUTER-MEDIATED COMMUNICATION

    Directory of Open Access Journals (Sweden)

    Keiko Kitade

    2008-02-01

    Full Text Available In order to demonstrate how learners utilize the text-based asynchronous attributes of the Bulletin Board System, this study explored Japanese-as-a-second-language learners' metalanguage episodes (Swain & Lapkin, 1995, 1998 in offline verbal peer speech and online asynchronous discussions with their Japanese key pals. The findings suggest the crucial role of offline collaborative dialogue, the interactional modes in which the episodes occur, and the unique discourse structure of metalanguage episodes concerning online and offline interactions. A high score on the posttest also suggests the high retention of linguistic knowledge constructed through offline peer dialogue. In the offline mode, the learners were able to collaboratively construct knowledge with peers in the stipulated time, while simultaneously focusing on task content in the online interaction. The retrospective interviews and questionnaires reveal the factors that could affect the benefits of the asynchronous computer-mediated communication medium for language learning.

  8. 基于DSP的异步电机伺服控制系统%Based on DSP (digital signal processor) asynchronous motor servo control system

    Institute of Scientific and Technical Information of China (English)

    舒强

    2012-01-01

    This paper describes fully digital AC servo system based on DSP, pointing out that the use of vector control technology and cunent loop, position loop, velocity loop, three closed-loop combination of methods. The paper also describes the hardware system architecture and software system architecture, there is some guidance on building AC servo system.%介绍了基于DSP的全数字交流伺服系统,指出了采用矢量控制技术与电流环、位置环、速度环三闭环相结合的整体控制方法.并介绍了相应的硬件系统结构与软件系统结构,对交流异步伺服系统的构建有一定指导意义.

  9. Formation of the wide asynchronous binary asteroid population

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Seth A. [Department of Astrophysical and Planetary Science, UCB 391, University of Colorado, Boulder, CO 80309 (United States); Scheeres, Daniel J.; McMahon, Jay [Department of Aerospace Engineering Sciences, UCB 429, University of Colorado, Boulder, CO 80309 (United States)

    2014-01-01

    We propose and analyze a new mechanism for the formation of the wide asynchronous binary population. These binary asteroids have wide semimajor axes relative to most near-Earth and main belt asteroid systems. Confirmed members have rapidly rotating primaries and satellites that are not tidally locked. Previously suggested formation mechanisms from impact ejecta, from planetary flybys, and directly from rotational fission events cannot satisfy all of the observations. The newly hypothesized mechanism works as follows: (1) these systems are formed from rotational fission, (2) their satellites are tidally locked, (3) their orbits are expanded by the binary Yarkovsky-O'Keefe-Radzievskii-Paddack (BYORP) effect, (4) their satellites desynchronize as a result of the adiabatic invariance between the libration of the secondary and the mutual orbit, and (5) the secondary avoids resynchronization because of the YORP effect. This seemingly complex chain of events is a natural pathway for binaries with satellites that have particular shapes, which define the BYORP effect torque that acts on the system. After detailing the theory, we analyze each of the wide asynchronous binary members and candidates to assess their most likely formation mechanism. Finally, we suggest possible future observations to check and constrain our hypothesis.

  10. 应答式ALOHA-CDMA信道的吞吐量及稳定性分析%Analysis of throughput and stability for ACK-ALOHA-CDMA channel

    Institute of Scientific and Technical Information of China (English)

    邵建华; 殷奎喜; 赵华

    2009-01-01

    A new acknowledgment-type slotted-ALOHA code division multiple access(ACK-ALOHA-CDMA) channel which can be used in the inbound channels of very small aperture terminal(VSAT) networks is proposed in order to simplify the synchronization equipment of networks in the slotted-ALOHA-CDMA systems. By dividing all VSAT stations into M subsystems and sending out periodic inquiry signals from the Hub station to the VSAT station, the channel model is established. By the means of deriving multi-access interference(MAI) and packet detecting probability, steady-state throughput is calculated. By applying diffusion process theory to the analysis of the stability of the ACK-ALOHA-CDMA channel, the drift parameter a(r), the diffusion parameter b (r) and the steady transition probability density p (r) are investigated. Simulation results indicate that significant performance improvement and high-bandwidth efficiency can be gained and one or two steady equilibrium points can be obtained by using this channel. Consequently, the ACK-ALOHA-CDMA channel is very suitable for cutting down on the expense of satellite VSAT systems and distributed packet radio networks.%为了简化时隙ALOHA-CDMA系统的时间同步设备,提出了一种可用于卫星VSAT网络内向信道的应答式时隙ALOHA-CDMA信道模型.将端站分为M个子系统,利用主站发出周期性询问信号,建立了信道模型;通过扩频多址干扰(MAI)和分组检测概率的推导,计算出该信道的稳态吞吐量;并将扩散过程理论用于该信道的稳定性分析,得到扩散系数a(r)、漂移系数b(r)和信道平稳分布P(r).仿真结果表明,该系统可以显著提高信道吞吐性能和信道利用率,且存在1~2个稳定平衡点.应答式时隙ALOHA-CDMA信道可以降低卫星VSAT系统及分组无线网络系统的组网成本.

  11. Efficiency droop effects of GaN-based light-emitting diodes on the performance of code division multiple access visible-light communication system

    Science.gov (United States)

    Lu, Huimin; Yan, Chaowen; Gao, Wei; Yu, Tongjun; Wang, Jianping

    2016-02-01

    The physical mechanism in efficiency droop of GaN-based light-emitting diodes (LEDs) was investigated using a modified rate equation model considering inhomogeneous carrier distribution and was compared with the measured result. On this basis, the efficiency droop effect on the performance of a code division multiple access (CDMA) visible-light communication (VLC) system using GaN-based LEDs was also analyzed. The results reveal that the obvious transmitted signal error under the effect of LED efficiency droop leads to performance deterioration of multiuser CDMA VLC systems. Also, the performance of CDMA VLC systems is reduced with the user number increase due to LED efficiency droop. The bit error rate of a CDMA VLC system was further calculated for different branch signal levels and bias currents. It is demonstrated that the efficiency droop effect on the performance of CDMA VLC systems can be alleviated by adjusting the branch signal level and the bias current.

  12. Algebraic Number Precoded OFDM Transmission for Asynchronous Cooperative Multirelay Networks

    Directory of Open Access Journals (Sweden)

    Hua Jiang

    2014-01-01

    Full Text Available This paper proposes a space-time block coding (STBC transmission scheme for asynchronous cooperative systems. By combination of rotated complex constellations and Hadamard transform, these constructed codes are capable of achieving full cooperative diversity with the analysis of the pairwise error probability (PEP. Due to the asynchronous characteristic of cooperative systems, orthogonal frequency division multiplexing (OFDM technique with cyclic prefix (CP is adopted for combating timing delays from relay nodes. The total transmit power across the entire network is fixed and appropriate power allocation can be implemented to optimize the network performance. The relay nodes do not require decoding and demodulation operation, resulting in a low complexity. Besides, there is no delay for forwarding the OFDM symbols to the destination node. At the destination node the received signals have the corresponding STBC structure on each subcarrier. In order to reduce the decoding complexity, the sphere decoder is implemented for fast data decoding. Bit error rate (BER performance demonstrates the effectiveness of the proposed scheme.

  13. Asynchronous replica exchange software for grid and heterogeneous computing

    Science.gov (United States)

    Gallicchio, Emilio; Xia, Junchao; Flynn, William F.; Zhang, Baofeng; Samlalsingh, Sade; Mentes, Ahmet; Levy, Ronald M.

    2015-11-01

    Parallel replica exchange sampling is an extended ensemble technique often used to accelerate the exploration of the conformational ensemble of atomistic molecular simulations of chemical systems. Inter-process communication and coordination requirements have historically discouraged the deployment of replica exchange on distributed and heterogeneous resources. Here we describe the architecture of a software (named ASyncRE) for performing asynchronous replica exchange molecular simulations on volunteered computing grids and heterogeneous high performance clusters. The asynchronous replica exchange algorithm on which the software is based avoids centralized synchronization steps and the need for direct communication between remote processes. It allows molecular dynamics threads to progress at different rates and enables parameter exchanges among arbitrary sets of replicas independently from other replicas. ASyncRE is written in Python following a modular design conducive to extensions to various replica exchange schemes and molecular dynamics engines. Applications of the software for the modeling of association equilibria of supramolecular and macromolecular complexes on BOINC campus computational grids and on the CPU/MIC heterogeneous hardware of the XSEDE Stampede supercomputer are illustrated. They show the ability of ASyncRE to utilize large grids of desktop computers running the Windows, MacOS, and/or Linux operating systems as well as collections of high performance heterogeneous hardware devices.

  14. Asynchronous Task-Based Polar Decomposition on Manycore Architectures

    KAUST Repository

    Sukkari, Dalal

    2016-10-25

    This paper introduces the first asynchronous, task-based implementation of the polar decomposition on manycore architectures. Based on a new formulation of the iterative QR dynamically-weighted Halley algorithm (QDWH) for the calculation of the polar decomposition, the proposed implementation replaces the original and hostile LU factorization for the condition number estimator by the more adequate QR factorization to enable software portability across various architectures. Relying on fine-grained computations, the novel task-based implementation is also capable of taking advantage of the identity structure of the matrix involved during the QDWH iterations, which decreases the overall algorithmic complexity. Furthermore, the artifactual synchronization points have been severely weakened compared to previous implementations, unveiling look-ahead opportunities for better hardware occupancy. The overall QDWH-based polar decomposition can then be represented as a directed acyclic graph (DAG), where nodes represent computational tasks and edges define the inter-task data dependencies. The StarPU dynamic runtime system is employed to traverse the DAG, to track the various data dependencies and to asynchronously schedule the computational tasks on the underlying hardware resources, resulting in an out-of-order task scheduling. Benchmarking experiments show significant improvements against existing state-of-the-art high performance implementations (i.e., Intel MKL and Elemental) for the polar decomposition on latest shared-memory vendors\\' systems (i.e., Intel Haswell/Broadwell/Knights Landing, NVIDIA K80/P100 GPUs and IBM Power8), while maintaining high numerical accuracy.

  15. Inhibition Controls Asynchronous States of Neuronal Networks

    Science.gov (United States)

    Treviño, Mario

    2016-01-01

    Computations in cortical circuits require action potentials from excitatory and inhibitory neurons. In this mini-review, I first provide a quick overview of findings that indicate that GABAergic neurons play a fundamental role in coordinating spikes and generating synchronized network activity. Next, I argue that these observations helped popularize the notion that network oscillations require a high degree of spike correlations among interneurons which, in turn, produce synchronous inhibition of the local microcircuit. The aim of this text is to discuss some recent experimental and computational findings that support a complementary view: one in which interneurons participate actively in producing asynchronous states in cortical networks. This requires a proper mixture of shared excitation and inhibition leading to asynchronous activity between neighboring cells. Such contribution from interneurons would be extremely important because it would tend to reduce the spike correlation between neighboring pyramidal cells, a drop in redundancy that could enhance the information-processing capacity of neural networks. PMID:27274721

  16. Low Latency High Throughout Circular Asynchronous FIFO

    Institute of Scientific and Technical Information of China (English)

    XIAO Yong; ZHOU Runde

    2008-01-01

    This paper describes a circular first in first out (FIFO) and its protocols which have a very low la-tency while still maintaining high throughput. Unlike the existing serial FIFOs based on asynchronous micro-pipelines, this FIFO's cells communicate directly with the input and output ports through a common bus, which effectively eliminates the data movement from the input port to the output port, thereby reducing the latency and the power consumption. Furthermore, the latency does not increase with the number of FIFO stages. Single-track asynchronous protocols are used to simplify the FIFO controller design, with only three C-gates needed in each cell controller, which substantially reduces the area. Simulations with the TSMC 0.25 Ijm CMOS logic process show that the latency of the 4-stage FIFO is less than 581 ps and the throughput is higher than 2.2 GHz.

  17. Existence test for asynchronous interval iterations

    DEFF Research Database (Denmark)

    Madsen, Kaj; Caprani, O.; Stauning, Ole

    1997-01-01

    In the search for regions that contain fixed points ofa real function of several variables, tests based on interval calculationscan be used to establish existence ornon-existence of fixed points in regions that are examined in the course ofthe search. The search can e.g. be performed as a...... synchronous (sequential) interval iteration:In each iteration step all components of the iterate are calculatedbased on the previous iterate. In this case it is straight forward to base simple interval existence and non-existencetests on the calculations done in each step of the iteration. The search can also...... be performed as an asynchronous (parallel) iteration: Only a few components are changed in each stepand this calculation is in general based on components from differentprevious iterates. For the asynchronous iteration it turns out thatsimple tests of existence and non-existence can be based on...

  18. Inhibition Controls Asynchronous States of Neuronal Networks.

    Science.gov (United States)

    Treviño, Mario

    2016-01-01

    Computations in cortical circuits require action potentials from excitatory and inhibitory neurons. In this mini-review, I first provide a quick overview of findings that indicate that GABAergic neurons play a fundamental role in coordinating spikes and generating synchronized network activity. Next, I argue that these observations helped popularize the notion that network oscillations require a high degree of spike correlations among interneurons which, in turn, produce synchronous inhibition of the local microcircuit. The aim of this text is to discuss some recent experimental and computational findings that support a complementary view: one in which interneurons participate actively in producing asynchronous states in cortical networks. This requires a proper mixture of shared excitation and inhibition leading to asynchronous activity between neighboring cells. Such contribution from interneurons would be extremely important because it would tend to reduce the spike correlation between neighboring pyramidal cells, a drop in redundancy that could enhance the information-processing capacity of neural networks.

  19. Multirate IP traffic transmission in flexible access networks based on optical FFH-CDMA

    DEFF Research Database (Denmark)

    Raddo, Thiago R.; Sanches, Anderson L.; Tafur Monroy, Idelfonso;

    2016-01-01

    In this paper, we propose a new IP transmission architecture over optical fast frequency hopping code-division multiple-access (OFFH-CDMA) network capable of supporting multirate transmissions for applications in flexible optical access networks. The proposed network architecture is independent...

  20. Throughput performance analysis of multirate, multiclass S-ALOHA OFFH-CDMA packet networks

    DEFF Research Database (Denmark)

    Raddo, Thiago R.; Sanches, Anderson L.; Borges, Ben Hur V;

    2015-01-01

    In this paper, we propose a new throughput expression for multirate, multiclass slotted-ALOHA optical fast frequency hopping code-division multiple-access (OFFH-CDMA) packet networks considering a Poisson distribution for packet composite arrivals. We analyze the packet throughput performance of ...

  1. Low Complexity Iterative Joint Channel Estimation and Multiuser Detection for DS-CDMA

    DEFF Research Database (Denmark)

    Christensen, Søren Skovgård; Kocian, Alexander; Fleury, Bernard Henri

    2004-01-01

    Previously the SAGE algorithm was applied to sub-optimal yet efficient Joint data Detection and channel Estimation (JDE) for DS-CDMA of moderate time complexity. Modifying the expectation and maximization steps of the SAGE-JDE scheme, it is possible to obtain an efficient receiver architecture...

  2. Asynchronous Nano-Electronics: Preliminary Investigation

    OpenAIRE

    Martin, Alain J.; Prakash, Piyush

    2008-01-01

    This paper is a preliminary investigation in implementing asynchronous QDI logic in molecular nano-electronics, taking into account the restricted geometry, the lack of control on transistor strengths, the high timing variations. We show that the main building blocks of QDI logic can be successfully implemented; we illustrate the approach with the layout of an adder stage. The proposed techniques to improve the reliability of QDI apply to nano-CMOS as well.

  3. Asynchronous exponential growth of a bacterial population

    Directory of Open Access Journals (Sweden)

    Mohamed Boulanouar

    2014-01-01

    Full Text Available In this work, we complete a study started earlier in [1,2] wherein a model of growing bacterial population has been the matter of a mathematical analysis. We show that the full model is governed by a strongly continuous semigroup. Beside the positivity and the irreducibility of the generated semigroup, we describe its asymptotic behavior in the uniform topology which leads to the asynchronous exponential growth of the bacterial population.

  4. Accurate estimator of correlations between asynchronous signals

    OpenAIRE

    Toth, Bence; Kertesz, Janos

    2008-01-01

    The estimation of the correlation between time series is often hampered by the asynchronicity of the signals. Cumulating data within a time window suppresses this source of noise but weakens the statistics. We present a method to estimate correlations without applying long time windows. We decompose the correlations of data cumulated over a long window using decay of lagged correlations as calculated from short window data. This increases the accuracy of the estimated correlation significantl...

  5. Blending Online Asynchronous and Synchronous Learning

    Directory of Open Access Journals (Sweden)

    Lisa C. Yamagata-Lynch

    2014-04-01

    Full Text Available In this article I will share a qualitative self-study about a 15-week blended 100% online graduate level course facilitated through synchronous meetings on Blackboard Collaborate and asynchronous discussions on Blackboard. I taught the course at the University of Tennessee (UT during the spring 2012 semester and the course topic was online learning environments. The primary research question of this study was: How can the designer/instructor optimize learning experiences for students who are studying about online learning environments in a blended online course relying on both synchronous and asynchronous technologies? I relied on student reflections of course activities during the beginning, middle, and the end of the semester as the primary data source to obtain their insights regarding course experiences. Through the experiences involved in designing and teaching the course and engaging in this study I found that there is room in the instructional technology research community to address strategies for facilitating online synchronous learning that complement asynchronous learning. Synchronous online whole class meetings and well-structured small group meetings can help students feel a stronger sense of connection to their peers and instructor and stay engaged with course activities. In order to provide meaningful learning spaces in synchronous learning environments, the instructor/designer needs to balance the tension between embracing the flexibility that the online space affords to users and designing deliberate structures that will help them take advantage of the flexible space.

  6. Ant Colony Optimization Algorithm For PAPR Reduction In Multicarrier Code Division Multiple Access System

    Directory of Open Access Journals (Sweden)

    Kanchan Singla

    2014-06-01

    Full Text Available MC CDMA is a rising candidate for future generation broadband wireless communication and gained great attention from researchers. It provides benefits of both OFDM and CDMA. Main challenging problem of MC CDMA is high PAPR. It occurs in HPA and reduces system efficiency. There are many PAPR reduction techniques for MC CDMA. In this paper we proposed Ant colony optimization algorithm to reduce PAPR with different number of user using BPSK and QPSK modulation. ACO is a metaheuristic technique and based on the foraging behavior of real ants. It provides solution to many complex problems. Simulation result proves that ACO using BPSK modulation is effective for reducing PAPR in MC CDMA.

  7. 基于FPGA的异步电动机变频调速系统%Variable frequency driver system of asynchronous motor based on FPGA

    Institute of Scientific and Technical Information of China (English)

    吴俊; 邱建琪; 史涔溦; 王莉

    2012-01-01

    Aiming at the slow speed and poor stability of control system designed by traditional micro control unit(MCU)or digital signal processor (DSP) in the way of software, a hardware designed scheme of space vector pulse width modulation (SVPWM) based on field programmable gate array (FPCA) was presented, which based on the background of full digital motor-controller. Combining complished EDA design methodology and Verilog HDL, it was verified and implemented on one-chip FPGA. The "top-down" theme was used to develop core by dividing system according to it's function in the design. It was realized that, at first, design and simulation on single module, secondly, on the whole system, at last verification using FPCA. The algorithm was proved feasible through the simulation and experiment. On the basis of the platform, V/F open loop speed regulation system experiment was completed. The results indicate that the system has excellent stablity characteristic,reasonable chip utility,good reusability,superiority that the MCU and DSP do not have in real time,flexibility etc., and lays the foundation for the design of a special motor-controlling chip.%针对传统的单片机(MCU)或数字信号处理器(DSP)以软件方式实现的控制系统普遍存在速度慢、稳定性差等问题,以实现全数字电机控制器的集成化为背景,提出了一种基于现场可编程门阵列( FPGA)的空间电压矢量脉宽调制(SVPWM)硬件设计方案,并结合EDA模块化的设计方法和Verilog HDL硬件描述语言,在一片FPGA芯片中得到了验证和实现;采用“top-down”设计思想,对系统按功能划分模块进行了设计;首先对各功能模块进行了设计、仿真、验证,然后将整个系统组合起来进行了仿真、验证,最后利用FPGA进行了硬件验证;在此基础上,完成了异步电机SVPWM调制方式的V/F开环变频调速系统的实验.研究结果表明,该系统稳定性高、占用资源少、复用性高,在实

  8. 面向异步视频的嵌入式图像处理系统设计%Design of embeded images processing system oriented for asynchronous video

    Institute of Scientific and Technical Information of China (English)

    郑鑫

    2012-01-01

    An oriented asynchronous video embedded image processing system based on DSP and FPGA is designed in this paper. The flexible architecture of the system avoids the requirement of dual-port RAM display memory for which the inter-frame synchronization method is desired. This architecture can ensure the quality of output images and is convenient to improve the performance index of image processing. Taking FPGA as kernel, the system connects DSP and 4-chip frame memory, and incorporates buffer and display memory by frame memory cycle reusing, which saves the process of data transmission. When frame frequencies of input video are less than those of output video, status transformation rules of frame memory are analyzed in term of overall systemi as frame frequencies of output video are less than those of input video, status transformation rules of frame memory are analyzed in term of single frame memory, and finally source codes is provided. This scheme has already applied to some products. The higher technology specifications can be met by upgrading.%在此设计出一种基于DSP+FPGA技术的面向异步视频的嵌入式图像处理系统,以一种灵活的架构避免了帧间不同步方法对双口RAM显存的需求,既能够保证图像输出质量,又有利于提升图像处理的性能指标.系统以FPGA为核心,连接DSP和4片帧存,通过帧存的循环复用将缓存和显存融合起来,省略了数据搬运的环节.当输入帧频小于输出帧频时,从系统总体的角度分析帧存的状态转换规律;当输入帧频大于输出帧频时,从单个帧存的角度分析帧存的状态转换规律,并给出了可编程逻辑设计的源程序.该方案已在产品中应用,通过升级能够满足更高的技术要求.

  9. Multilevel LDPC Codes Design for Multimedia Communication CDMA System

    Directory of Open Access Journals (Sweden)

    Hou Jia

    2004-01-01

    Full Text Available We design multilevel coding (MLC with a semi-bit interleaved coded modulation (BICM scheme based on low density parity check (LDPC codes. Different from the traditional designs, we joined the MLC and BICM together by using the Gray mapping, which is suitable to transmit the data over several equivalent channels with different code rates. To perform well at signal-to-noise ratio (SNR to be very close to the capacity of the additive white Gaussian noise (AWGN channel, random regular LDPC code and a simple semialgebra LDPC (SA-LDPC code are discussed in MLC with parallel independent decoding (PID. The numerical results demonstrate that the proposed scheme could achieve both power and bandwidth efficiency.

  10. An Asynchronous P300 BCI With SSVEP-Based Control State Detection

    DEFF Research Database (Denmark)

    Panicker, Rajesh C.; Puthusserypady, Sadasivan; Sun, Ying

    2011-01-01

    In this paper, an asynchronous brain–computer interface (BCI) system combining the P300 and steady-state visually evoked potentials (SSVEPs) paradigms is proposed. The information transfer is accomplished using P300 event-related potential paradigm and the control state (CS) detection is achieved...

  11. An Approach for Asynchronous Awareness Support in Collaborative Non-Linear Storytelling

    NARCIS (Netherlands)

    Schumann, J.; Buttler, T.; Lukosch, S.

    2012-01-01

    Workspace awareness support is mandatory for group support systems. It allows users not only to follow actions of others, but to understand and respond to any changes others make to the workspace. In this paper, we present a novel approach for asynchronous awareness support by offering different fil

  12. Cooperative Learning in Graduate Student Projects: Comparing Synchronous versus Asynchronous Collaboration

    Science.gov (United States)

    Strang, Kenneth

    2013-01-01

    Cooperative learning was applied in a graduate project management course to compare the effectiveness of asynchronous versus synchronous online team meetings. An experiment was constructed to allocate students to project teams while ensuring there was a balance of requisite skills, namely systems analysis and design along with HTML/Javascript…

  13. Credit Hours with No Set Time: A Study of Credit Policies in Asynchronous Online Education

    Science.gov (United States)

    Prasuhn, Frederick Carl

    2014-01-01

    U.S. public university system policies were examined to learn how credit hours were determined for asynchronous online education. Findings indicated that (a) credit hour meaning and use are not consistent, (b) primary responsibility for credit hour decisions was at the local level, and (c) no policies exist to guide credit hour application for…

  14. Asynchronous Code-Division Random Access Using Convex Optimization

    CERN Document Server

    Applebaum, Lorne; Duarte, Marco F; Calderbank, Robert

    2011-01-01

    Many applications in cellular systems and sensor networks involve a random subset of a large number of users asynchronously reporting activity to a base station. This paper examines the problem of multiuser detection (MUD) in random access channels for such applications. Traditional orthogonal signaling ignores the random nature of user activity in this problem and limits the total number of users to be on the order of the number of signal space dimensions. Contention-based schemes, on the other hand, suffer from delays caused by colliding transmissions and the hidden node problem. In contrast, this paper presents a novel asynchronous (non-orthogonal) code-division random access scheme along with a convex optimization-based MUD algorithm that overcomes the issues associated with orthogonal signaling and contention-based methods. Two key distinguishing features of the proposed algorithm are that it does not require knowledge of the delay or channel state information of every user and it has polynomial-time com...

  15. A Unified Comparison of CDMA EVDO Key Performance Parameters in Multi-vendor Environment

    Directory of Open Access Journals (Sweden)

    Rabnawaz Anwar

    2012-08-01

    Full Text Available With the standardization of CDMA2000-1x, EVDO, and its subsequent release/revisions (0, A, B, and C each telecom vendor continues to develop their equipment as well as network management software for supporting EVDO services and defines EVDO performance parameters separately. This leads to sort of redundancy and perplexity in multivendor network environments in which network optimization engineer has to deal with all these performance parameters to optimize the system performance. There is need tounify these different EVDO performance parameters defined by different vendors to overcome this redundancy and confusion. To complete this objective we first has identified different EVDO key performance indicators defined by different vendors through their software i.e. element management systems (EMS. After identification of these KPIs we then take one most important KPI i.e., the Session Setup Success Rate (SSSR and analyses its constituent counters and find out differences through dailystatistic reports, standard definitions formula and message flow diagrams defined by each vendor. Thenwe proposed a new KPI, HSN Ratio (Harmonic mean of session setup success and session negotiation success Ratios to get a complete picture of end-to-end session setup success rate. Finally we have collected 15 days hourly statistic report of SSSR and session negotiation success rate defined by eachvendor through their EMS’s and applied minimum mean square error method to unify the proposed HSN ratio. As a result of this process we have figure out differences between multivendor KPIs and minimizes these differences to unify them. Similarly this whole process could be repeated to unify other EVDO KPIs.

  16. Dynamic quality of service differentiation using fixed code weight in optical CDMA networks

    Science.gov (United States)

    Kakaee, Majid H.; Essa, Shawnim I.; Abd, Thanaa H.; Seyedzadeh, Saleh

    2015-11-01

    The emergence of network-driven applications, such as internet, video conferencing, and online gaming, brings in the need for a network the environments with capability of providing diverse Quality of Services (QoS). In this paper, a new code family of novel spreading sequences, called a Multi-Service (MS) code, has been constructed to support multiple services in Optical- Code Division Multiple Access (CDMA) system. The proposed method uses fixed weight for all services, however reducing the interfering codewords for the users requiring higher QoS. The performance of the proposed code is demonstrated using mathematical analysis. It shown that the total number of served users with satisfactory BER of 10-9 using NB=2 is 82, while they are only 36 and 10 when NB=3 and 4 respectively. The developed MS code is compared with variable-weight codes such as Variable Weight-Khazani Syed (VW-KS) and Multi-Weight-Random Diagonal (MW-RD). Different numbers of basic users (NB) are used to support triple-play services (audio, data and video) with different QoS requirements. Furthermore, reference to the BER of 10-12, 10-9, and 10-3 for video, data and audio, respectively, the system can support up to 45 total users. Hence, results show that the technique can clearly provide a relative QoS differentiation with lower value of basic users can support larger number of subscribers as well as better performance in terms of acceptable BER of 10-9 at fixed code weight.

  17. EPOS for Coordination of Asynchronous Sensor Webs Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop, integrate, and deploy software-based tools to coordinate asynchronous, distributed missions and optimize observation planning spanning simultaneous...

  18. Designing Asynchronous Circuits for Low Power: An IFIR Filter

    DEFF Research Database (Denmark)

    Nielsen, Lars Skovby; Sparsø, Jens

    1999-01-01

    This paper addresses the design of asynchronous circuits for low power through an example: a filter bank for a digital hearing aid. The asynchronous design re-implements an existing synchronous circuit which is used in a commercial product. For comparison, both designs have been fabricated...... by numerically small samples). Apart from the improved RAM design, these measures are only viable in an asynchronous design. The principles and techniques explained in this paper are of a general nature, and they apply to the design of asynchronous low-power digital signal-processing circuits in a broader...

  19. 基于局部加权k近邻的多机器人系统异步互增强学习%Asynchronous interaction reinforcement learning for multi-robot systems based on local weighted kNN-TD

    Institute of Scientific and Technical Information of China (English)

    杨月全; 韩飞; 金露; 倪春波; 曹志强; 张天平

    2012-01-01

    To accelerate the learning speed of robots for multi-robot systems and make full use of experience and results of other robots in the communication domain, two kinds of multi-robot learning strategies based on the local weighted k-nearest neighbor temporal difference (kNN-TD) algorithm are proposed. Without consideration of time delays during the communications of robots, based on the method of local weighted kNN-TD state selection by using environment sense information and task destination information, the optimal iteration of Q value table of a robot is updated by the employment of comparison and analysis of Q value tables of itself and other communicating robots. After that, asynchronous interaction reinforcement learning schemes are presented in the case of global communication and local communication in the working environment, respectively. Finally, the simulations verify the effectiveness and efficiency of the proposed strategy.%针对多机器人系统的增强学习问题,为提高机器人的学习速度和充分利用通信范围内其他机器人的增强学习的经验和结果,给出了2类基于局部加权k近邻时间差分的多机器人系统的交互式学习策略.对于机器人之间通信无时滞情形,基于环境感测和任务信息状态描述的局部加权k近邻状态选择方法,机器人通过对自身和通信范围内其他机器人Q值表的比较和分析,对其自身的Q值表进行优化迭代更新.在此基础上,分别给出了基于全局通信条件下和局部通信条件下多机器人系统的异步的互增强学习方案.最后,通过仿真实验进一步验证了所提方案的可行性和有效性.

  20. Asynchronous Control System for the LED Screen Based on the ARM Cortex-M3 Processor%基于ARMCortex-M3的LED显示屏异步控制卡

    Institute of Scientific and Technical Information of China (English)

    朱迁虎; 姜文斌; 葛燕; 汪萍

    2014-01-01

    随着LED显示技术的飞速发展,LED显示屏作为一种新的传播媒介,应用领域不断扩大。与之相对应的控制器应运而生。为了解决本公司原有产品带载范围小、分立元件多、器件昂贵、开发难度等问题,本文提出了一种新型的LED显示方案,该方案采用ARMCortex-M3内核,运用嵌入式开发技术,开发了低成本、高显示效果、多功能的显示屏异步控制卡。包括核心的硬件电路图及DMA控制器工作原理,部分系统软件流程图,RS485与RS232自适应通信电路及自动波特率的实现。%With the rapid development of LED display technology, LED screen as a new media has been applied to many more and more fields. Correspondingly, the stronger controller is made. However, the load range of traditional controller is small, with massive multiple discrete components. Besides, it costs money and is difficult to develop. Here, we present a new LED display method. In this method embedded development technology is applied and an ARMCortex-M3 core is equipped. Which is low-cost with an enjoying display effect. Moreover a multi-function asynchronous control center is created. In addition, circuit of hardware, working machanism of the DMA controller, part of the progress chart of the system software are detailed described. And this paper introduces how RS485 and RS232 communication circuit and how the automatic baud rate realized.

  1. Asynchronous P300 classification in a reactive brain-computer interface during an outlier detection task

    Science.gov (United States)

    Krumpe, Tanja; Walter, Carina; Rosenstiel, Wolfgang; Spüler, Martin

    2016-08-01

    Objective. In this study, the feasibility of detecting a P300 via an asynchronous classification mode in a reactive EEG-based brain-computer interface (BCI) was evaluated. The P300 is one of the most popular BCI control signals and therefore used in many applications, mostly for active communication purposes (e.g. P300 speller). As the majority of all systems work with a stimulus-locked mode of classification (synchronous), the field of applications is limited. A new approach needs to be applied in a setting in which a stimulus-locked classification cannot be used due to the fact that the presented stimuli cannot be controlled or predicted by the system. Approach. A continuous observation task requiring the detection of outliers was implemented to test such an approach. The study was divided into an offline and an online part. Main results. Both parts of the study revealed that an asynchronous detection of the P300 can successfully be used to detect single events with high specificity. It also revealed that no significant difference in performance was found between the synchronous and the asynchronous approach. Significance. The results encourage the use of an asynchronous classification approach in suitable applications without a potential loss in performance.

  2. An Asynchronous Cellular Automata-Based Adaptive Illumination Facility

    Science.gov (United States)

    Bandini, Stefania; Bonomi, Andrea; Vizzari, Giuseppe; Acconci, Vito

    The term Ambient Intelligence refers to electronic environments that are sensitive and responsive to the presence of people; in the described scenario the environment itself is endowed with a set of sensors (to perceive humans or other physical entities such as dogs, bicycles, etc.), interacting with a set of actuators (lights) that choose their actions (i.e. state of illumination) in an attempt improve the overall experience of these users. The model for the interaction and action of sensors and actuators is an asynchronous Cellular Automata (CA) with memory, supporting a self-organization of the system as a response to the presence and movements of people inside it. The paper will introduce the model, as well as an ad hoc user interface for the specification of the relevant parameters of the CA transition rule that determines the overall system behaviour.

  3. The Formation of the Wide Asynchronous Binary Asteroid Population

    CERN Document Server

    Jacobson, Seth A; McMahon, Jay

    2013-01-01

    We propose and analyze a new mechanism for the formation of the wide asynchronous binary population. These binary asteroids have wide semi-major axes relative to most near-Earth and Main Belt asteroid systems. Confirmed members have rapidly rotating primaries and satellites that are not tidally locked. Previously suggested formation mechanisms from impact ejecta, planetary flybys and directly from rotational fission events cannot satisfy all of the observations. The newly hypothesized mechanism works as follows: (i) these systems are formed from rotational fission, (ii) their satellites are tidally locked, (iii) their orbits are expanded by the BYORP effect, (iv) their satellites de-synchronize due to the adiabatic invariance between the libration of the secondary and the mutual orbit, and (v) the secondary avoids resynchronization due to the the YORP effect. This seemingly complex chain of events is a natural pathway for binaries with satellites that have particular shapes, which define the BYORP effect torq...

  4. Asynchronous P300-based brain-computer interface to control a virtual environment: initial tests on end users.

    Science.gov (United States)

    Aloise, Fabio; Schettini, Francesca; Aricò, Pietro; Salinari, Serenella; Guger, Christoph; Rinsma, Johanna; Aiello, Marco; Mattia, Donatella; Cincotti, Febo

    2011-10-01

    Motor disability and/or ageing can prevent individuals from fully enjoying home facilities, thus worsening their quality of life. Advances in the field of accessible user interfaces for domotic appliances can represent a valuable way to improve the independence of these persons. An asynchronous P300-based Brain-Computer Interface (BCI) system was recently validated with the participation of healthy young volunteers for environmental control. In this study, the asynchronous P300-based BCI for the interaction with a virtual home environment was tested with the participation of potential end-users (clients of a Frisian home care organization) with limited autonomy due to ageing and/or motor disabilities. System testing revealed that the minimum number of stimulation sequences needed to achieve correct classification had a higher intra-subject variability in potential end-users with respect to what was previously observed in young controls. Here we show that the asynchronous modality performed significantly better as compared to the synchronous mode in continuously adapting its speed to the users' state. Furthermore, the asynchronous system modality confirmed its reliability in avoiding misclassifications and false positives, as previously shown in young healthy subjects. The asynchronous modality may contribute to filling the usability gap between BCI systems and traditional input devices, representing an important step towards their use in the activities of daily living.

  5. Asynchronous Pipeline Micro—Control—Unit (MCU) Chip Design

    Institute of Scientific and Technical Information of China (English)

    ZHOUQian; XUKe; MINHao

    2003-01-01

    The work of this paper includes a researchon asynch ronous design methodology, and a design and implementation of an asynchronous 8-Bit micro-control-unit (MCU). This paper introduces a new application of New-Instruction-Fetching method to detect new instruc-tion which makes this chip fit for demand changeable sys-tem. The instruction set of this asynchronous MCU is compatible with PIC16C6X (Sicrochip Technology Inc).This paper also introduces a new architecture of pipeline,which increases the average speed of chip operation. The asynchronous low power MCU has been fabricated with CSMC (central semiconductor manufacturing corporation)0.6μm CMOS process in Aug 2001. The chip size is about 1.60mm*2.00mm (without taking account of PAD size).Now the test work has been accomplished and the test-ing result of this chip is also presented. The testing result shows that the asynchronous architecture could fulfill all the expected functions, additionally with higher processs peed and lower power consumption than its synchronous counterpart under the same supply voltage.

  6. Integrating Asynchronous Digital Design Into the Computer Engineering Curriculum

    Science.gov (United States)

    Smith, S. C.; Al-Assadi, W. K.; Di, J.

    2010-01-01

    As demand increases for circuits with higher performance, higher complexity, and decreased feature size, asynchronous (clockless) paradigms will become more widely used in the semiconductor industry, as evidenced by the International Technology Roadmap for Semiconductors' (ITRS) prediction of a likely shift from synchronous to asynchronous design…

  7. Asynchronous Learning Sources in a High-Tech Organization

    Science.gov (United States)

    Bouhnik, Dan; Giat, Yahel; Sanderovitch, Yafit

    2009-01-01

    Purpose: The purpose of this study is to characterize learning from asynchronous sources among research and development (R&D) personnel. It aims to examine four aspects of asynchronous source learning: employee preferences regarding self-learning; extent of source usage; employee satisfaction with these sources and the effect of the sources on the…

  8. Asynchronicity of facial blood perfusion in migraine.

    Directory of Open Access Journals (Sweden)

    Nina Zaproudina

    Full Text Available Asymmetrical changes in blood perfusion and asynchronous blood supply to head tissues likely contribute to migraine pathophysiology. Imaging was widely used in order to understand hemodynamic variations in migraine. However, mapping of blood pulsations in the face of migraineurs has not been performed so far. We used the Blood Pulsation Imaging (BPI technique, which was recently developed in our group, to establish whether 2D-imaging of blood pulsations parameters can reveal new biomarkers of migraine. BPI characteristics were measured in migraineurs during the attack-free interval and compared to healthy subjects with and without a family history of migraine. We found a novel phenomenon of transverse waves of facial blood perfusion in migraineurs in contrast to healthy subjects who showed synchronous blood delivery to both sides of the face. Moreover, the amplitude of blood pulsations was symmetrically distributed over the face of healthy subjects, but asymmetrically in migraineurs and subjects with a family history of migraine. In the migraine patients we found a remarkable correlation between the side of unilateral headache and the direction of the blood perfusion wave. Our data suggest that migraine is associated with lateralization of blood perfusion and asynchronous blood pulsations in the facial area, which could be due to essential dysfunction of the autonomic vascular control in the face. These findings may further enhance our understanding of migraine pathophysiology and suggest new easily available biomarkers of this pathology.

  9. Zero Dynamics Analysis for Inverse Decoupling Control of Asynchronous Traction Motor

    Directory of Open Access Journals (Sweden)

    Haiying Dong

    2013-07-01

    Full Text Available Considering the problem for inverse system method in EMU AC induction traction motor linear decoupling, the zero dynamics subsystem will be separated from the original dynamic system through coordinate transformation. Firstly, a getting method for zero dynamics of the multiple input multiple output nonlinear system is discussed when γ<n. Second, the zero dynamics analysis for five order nonlinear model of asynchronous traction motor which base on the stationary coordinate system is given by using inverse decoupling method. The analysis results show that if the stability of the zero dynamics can be ensured, then the entire linearization of original nonlinear system is not necessary, need only partial linearization which effect on the external dynamic portion. The inverse decoupling process of asynchronous traction motor can be simplified by this conclusion.

  10. Analysis and Algorithm Simulation of Forward-link CDMA Signal Spectral Regrowth

    Institute of Scientific and Technical Information of China (English)

    LIN Mao-liu; XU Qing-hua

    2006-01-01

    Closed-form expressions for the spectral regrowth of CDMA signal passing through a nonlinear amplifier with a digitally modulated carrier are derived using the power series and statistical methods of high-order cumulant. The technique yields an analytical expression for the autocorrelation function of the output signal as a function of the statistics of the input signal transformed by a behavioral model of the amplifier. The third-order nonlinearity is expressed in terms of to include the memory effects of the circuit in-band and out-of-band reactance. The analysis is based on a time-domain model of the signal and the model is used to derive the power spectrum density and other statistical properties of the CDMA signal. Such analytical results are useful in finding optimal operating conditions of the power Amplifier.

  11. Blind Multiuser Receivers for ISI CDMA Channels Using the ε-Approximation Algorithms

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The problem of the blind demodulation of multiuser information symbols in a high-rate Code Division Multiple Access (CDMA) network in the presence of InterSymbol Interference (ISI) is of considerable interest. The dispersive CDMA channel is first cast into a Multiple-Input Multiple-Out (MIMO) signal model framework. Then, the problem of the blind channel equalization and multiuser detection is considered. In this paper, we formulate the problem of blind channel estimation and signal detection into a quadratic programming with binary constraints. Then, the efficient ε-approximation algorithms are presented and applied to find the solution to the quadratic programming. The proposed approach does not estimate the channel directly or rely on any statistics. Simulation results support our theoretical analysis.

  12. Energy Optimization Mechanism for Mobile Terminals using Vertical Handoff between WLAN and CDMA2000 Networks

    Directory of Open Access Journals (Sweden)

    Elizabeth N. ONWUKA

    2009-12-01

    Full Text Available This paper presents energy optimization mechanism for mobile terminals (MTs using vertical handoff between Wireless LAN (WLAN and CDMA2000 networks. Several techniques for optimizing the power consumption of MTs have been considered in literature. Some of these techniques could be used separately or in tandem. Considering the importance of efficient energy management for MTs, the research in this area could be taken a step further. The technique considered in this paper allows a multimode terminal to take advantage of two integrated networks to efficiently manage its energy consumption. Two integrated networks considered are WLAN and CDMA2000. This paper develops an algorithm that allows the MT to always get connected to the most cost-effective network. The results obtained showed that the MTs power is more efficiently managed when the MT is using the integrated networks than when it is using each of the networks independently.

  13. Vector control structure of an asynchronous motor at maximum torque

    Science.gov (United States)

    Chioncel, C. P.; Tirian, G. O.; Gillich, N.; Raduca, E.

    2016-02-01

    Vector control methods offer the possibility to gain high performance, being widely used. Certain applications require an optimum control in limit operating conditions, as, at maximum torque, that is not always satisfied. The paper presents how the voltage and the frequency for an asynchronous machine (ASM) operating at variable speed are determinate, with an accent on the method that keeps the rotor flux constant. The simulation analyses consider three load types: variable torque and speed, variable torque and constant speed, constant torque and variable speed. The final values of frequency and voltage are obtained through the proposed control schemes with one controller using the simulation language based on the Maple module. The dynamic analysis of the system is done for the case with P and PI controller and allows conclusions on the proposed method, which can have different applications, as the ASM in wind turbines.

  14. Realization of station for testing asynchronous three-phase motors

    Science.gov (United States)

    Wróbel, A.; Surma, W.

    2016-08-01

    Nowadays, you cannot imagine the construction and operation of machines without the use of electric motors [13-15]. The proposed position is designed to allow testing of asynchronous three-phase motors. The position consists of a tested engine and the engine running as a load, both engines combined with a mechanical clutch [2]. The value of the load is recorded by measuring shaft created with Strain Gauge Bridge. This concept will allow to study the basic parameters of the engines, visualization motor parameters both vector and scalar controlled, during varying load drive system. In addition, registration during the variable physical parameters of the working electric motor, controlled by a frequency converter or controlled by a contactor will be possible. Position is designed as a teaching and research position to characterize the engines. It will be also possible selection of inverter parameters.

  15. Normalized and Asynchronous Mirror Alignment for Cherenkov Telescopes

    CERN Document Server

    Ahnen, M L; Balbo, M; Bergmann, M; Biland, A; Blank, M; Bretz, T; Bruegge, K A; Buss, J; Domke, M; Dorner, D; Einecke, S; Hempfling, C; Hildebrand, D; Hughes, G; Lustermann, W; Mannheim, K; Mueller, S A; Neise, D; Neronov, A; Noethe, M; Overkemping, A -K; Paravac, A; Pauss, F; Rhode, W; Shukla, A; Temme, F; Thaele, J; Toscano, S; Vogler, P; Walter, R; Wilbert, A

    2016-01-01

    Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and as they are composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment is a challenge. Here we present a computer vision based star tracking alignment method, which also works for limited or changing star light visibility. Our method normalizes the mirror facet reflection intensities to become independent of the reference star's intensity or the cloud coverage. Using two CCD cameras, our method records the mirror facet orientations asynchronously of the telescope drive system, and thus makes the method easy to integrate into existing telescopes. It can be combined with remote facet actuation, but does not require one to work. Furthermore, it ca...

  16. LOAD CONTROL OF A 3-Ø SELF- EXCITED ASYNCHRONOUS GENERATOR

    Directory of Open Access Journals (Sweden)

    SUBRAMANIAN KULANDHAIVELU

    2011-02-01

    Full Text Available This paper describes the simulation based performance study of a 3-Ø self-excited asynchronous generator (SEASG in constant power operation. A feed back voltage based controller by using a load control technique to control and retain the generator terminal voltage constant. This technique mostly used in uncontrolled hydroturbine driven induction generators in a stand-alone power generator. The results has been validate by the steady state equivalent circuit analysis of a 2.2kW, 415Volts, 4.7A, Star connected, 1440-rpm induction generator. The proposed study system has been simulated using Mat lab/Simulink version-7.0.The simulated results arepresented.

  17. Indoor Positioning for Smartphones Using Asynchronous Ultrasound Trilateration

    Directory of Open Access Journals (Sweden)

    James D. Carswell

    2013-06-01

    Full Text Available Modern smartphones are a great platform for Location Based Services (LBS. While outdoor LBS for smartphones has proven to be very successful, indoor LBS for smartphones has not yet fully developed due to the lack of an accurate positioning technology. In this paper we present an accurate indoor positioning approach for commercial off-the-shelf (COTS smartphones that uses the innate ability of mobile phones to produce ultrasound, combined with Time-Difference-of-Arrival (TDOA asynchronous trilateration. We evaluate our indoor positioning approach by describing its strengths and weaknesses, and determine its absolute accuracy. This is accomplished through a range of experiments that involve variables such as position of control point microphones, position of phone within the room, direction speaker is facing and presence of user in the signal path. Test results show that our Lok8 (locate mobile positioning system can achieve accuracies better than 10 cm in a real-world environment.

  18. Minor Planet 1016 Anitra: A Likely Asynchronous Binary

    Science.gov (United States)

    Pilcher, Frederick; Benishek, Vladimir; Jacobsen, Jens; Kristensen, Leif Hugo; Lang, Kim; Larsen, Frank R.; Odden, Caroline; Pravec, Petr

    2016-07-01

    Analysis of photometry data for 1016 Anitra using a single period analysis shows a lightcurve with a period of 5.9296 hours and amplitude of 0.30 mag, with short period fluctuations. A simultaneous two-period analysis of the data found two smooth bimodal lightcurves with periods and amplitudes of P1 = 5.92951 h, A1 = 0.30 mag and P2 = 2.609143 h, A2 = 0.10 mag. These results are interpreted as the rotation of the two components of an asynchronous binary system. Four additional attenuations were observed that may have been caused by satellite mutual events, but those data were insufficient to yield an orbital period.

  19. ANALISIS PERILAKU KONSUMEN DALAM MEMILIH JASA LAYANAN OPERATOR MOBILE PHONE YANG BERBASIS CDMA DAN GSM

    OpenAIRE

    Demitri Marvin Kadhaffi; Solimun - -; Armanu - Thoyib

    2012-01-01

    ABSTRAKS Tujuan penelitian ini adalah (1) menganalisis faktor-faktor yang dipertimbangkan konsumen dalam memilih suatu jasa layanan operator mobile phone (baik CDMA maupun GSM), (2) menganalsis variabel dominan yang mempengaruhi perilaku konsumen dalam memilih jasa layanan operator Jenis penelitian ini adalah applied research dengan metode penelitian studi kausal. Penelitian ini ditujukan pada segmen pelajar dan mahasiswa di Kota Malang yang termasuk kelompok Net Generations (yang lahir antar...

  20. Electromagnetic Interference Assessment of CDMA and GSM Wireless Phones to Aircraft Navigation Radios

    Science.gov (United States)

    Ely, Jay J.; Nguyen, Truong X.; Koppen, Sandra V.; Salud, M. Theresa

    2002-01-01

    To address the concern for cellular phone electromagnetic interference (EMI) to aircraft radios, a radiated emission measurement process for CDMA (IS-95) and GSM (ETSI GSM 11.22) wireless handsets was developed. Spurious radiated emissions were efficiently characterized from devices tested in either a semi-anechoic or reverberation chamber, in terms of effective isotropic radiated power. Eight representative handsets (4 GSM, 4 CDMA) were commanded to operate while varying their radio transmitter parameters (power, modulation, etc.). This report provides a detailed description of the measurement process and resulting data, which may subsequently be used by others as a basis of consistent evaluation for cellular/PCS phones, Bluetooth, IEEE802.11b, IEEE802.11a, FRS/GMRS radios, and other portable transmitters. Aircraft interference path loss (IPL) and navigation radio interference threshold data from numerous reference documents, standards, and NASA partnerships were compiled. Using this data, a preliminary risk assessment is provided for CDMA and GSM wireless phone interference to aircraft localizer, Glideslope, VOR, and GPS radio receivers on typical transport airplanes. The report identifies where existing data for device emissions, IPL, and navigation radio interference thresholds needs to be extended for an accurate risk assessment for wireless transmitters in aircraft.

  1. A New Parallel Algorithm in Power Flow Calculation: Dynamic Asynchronous Parallel Algorithm

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the general methods in power flow calculation of power system and onconceptions and classifications of parallel algorithm, a new approach named DynamicAsynchronous Parallel Algorithm that applies to the online analysis and real-time dispatching and controlling of large-scale power network was put forward in this paper. Its performances of high speed and dynamic following have been verified on IEEE-14 bus system.

  2. A Leader Election Protocol for Fault Recovery in Asynchronous Fully-Connected Networks

    OpenAIRE

    Franceschetti, Massimo; Bruck, Jehoshua

    1998-01-01

    We introduce a new algorithm for consistent failure detection in asynchronous systems. Informally, consistent failure detection requires processes in a distributed system to distinguish between two different populations: a fault free population and a faulty one. The major contribution of this paper is in combining ideas from group membership and leader election, in order to have an election protocol for a fault manager whose convergence is delayed until a new consistent view ...

  3. CDMA2000中信号交织器的设计与仿真%Design and Simulation of Signal Interleaver in CDMA2000

    Institute of Scientific and Technical Information of China (English)

    华钰; 孙运强; 姚爱琴

    2013-01-01

    为了提高低信噪比情况下系统的纠错能力,Turbo码作为通信传输系统中的一种新兴的信道纠错编码技术,逐渐成为了信息编码界的研究热点。交织器是Turbo码编、译码器的重要组成部件。本设计对CDMA2000中的Turbo交织器进行了介绍,设计了交织器模块,并通过MATLAB进一步对交织器的应用进行了仿真。%To improve the error -correcting capabilities under the condition of low SNR , the Turbo codes has become the research hotspot in the field of channel encoding .The interleaver is the most important part of Turbo coding machine .The Turbo interleaver of CDMA2000 is introduced in the design .The paper designs the interleaver module , and then makes a further simulation about the appli-cation of interleaver by MATLAB .

  4. Asynchronous Parallel Evolutionary Algorithms for Constrained Optimizations

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Recently Guo Tao proposed a stochastic search algorithm in his PhD thesis for solving function op-timization problems. He combined the subspace search method (a general multi-parent recombination strategy) with the population hill-climbing method. The former keeps a global search for overall situation,and the latter keeps the convergence of the algorithm. Guo's algorithm has many advantages ,such as the sim-plicity of its structure ,the higher accuracy of its results, the wide range of its applications ,and the robustness of its use. In this paper a preliminary theoretical analysis of the algorithm is given and some numerical experiments has been done by using Guo's algorithm for demonstrating the theoretical results. Three asynchronous paral-lel evolutionary algorithms with different granularities for MIMD machines are designed by parallelizing Guo's Algorithm.

  5. Kalai-Smorodinsky bargaining solution for optimal resource allocation over wireless DS-CDMA visual sensor networks

    Science.gov (United States)

    Pandremmenou, Katerina; Kondi, Lisimachos P.; Parsopoulos, Konstantinos E.

    2012-01-01

    Surveillance applications usually require high levels of video quality, resulting in high power consumption. The existence of a well-behaved scheme to balance video quality and power consumption is crucial for the system's performance. In the present work, we adopt the game-theoretic approach of Kalai-Smorodinsky Bargaining Solution (KSBS) to deal with the problem of optimal resource allocation in a multi-node wireless visual sensor network (VSN). In our setting, the Direct Sequence Code Division Multiple Access (DS-CDMA) method is used for channel access, while a cross-layer optimization design, which employs a central processing server, accounts for the overall system efficacy through all network layers. The task assigned to the central server is the communication with the nodes and the joint determination of their transmission parameters. The KSBS is applied to non-convex utility spaces, efficiently distributing the source coding rate, channel coding rate and transmission powers among the nodes. In the underlying model, the transmission powers assume continuous values, whereas the source and channel coding rates can take only discrete values. Experimental results are reported and discussed to demonstrate the merits of KSBS over competing policies.

  6. Asynchronous Magnetic Bead Rotation (AMBR Microviscometer for Label-Free DNA Analysis

    Directory of Open Access Journals (Sweden)

    Yunzi Li

    2014-03-01

    Full Text Available We have developed a label-free viscosity-based DNA detection system, using paramagnetic beads as an asynchronous magnetic bead rotation (AMBR microviscometer. We have demonstrated experimentally that the bead rotation period is linearly proportional to the viscosity of a DNA solution surrounding the paramagnetic bead, as expected theoretically. Simple optical measurement of asynchronous microbead motion determines solution viscosity precisely in microscale volumes, thus allowing an estimate of DNA concentration or average fragment length. The response of the AMBR microviscometer yields reproducible measurement of DNA solutions, enzymatic digestion reactions, and PCR systems at template concentrations across a 5000-fold range. The results demonstrate the feasibility of viscosity-based DNA detection using AMBR in microscale aqueous volumes.

  7. Current Trends in High-Level Synthesis of Asynchronous Circuits

    DEFF Research Database (Denmark)

    Sparsø, Jens

    2009-01-01

    This paper is a survey paper presenting what the author sees as two major and promising trends in the current research in CAD-tools and design-methods for asynchronous circuits. One branch of research builds on top of existing asynchronous CAD-tools that perform syntax directed translation, e.......g. the Haste/TiDE tool from Handshake Solutions or the Balsa tool from the University of Manchester. The aims are to add highlevel synthesis capabilities to these tools and to extend the tools such that a wider range of (higher speed) micro-architectures can be generated. Another branch of research takes...... a conventional synchronous circuit as the starting point, and then adds some form of handshake-based flow-control. One approach keeps the global clock and implements discrete-time asynchronous operation. Another approach substitutes the clocked registers by asynchronous handshake-registers, thus creating truly...

  8. Asynchronous FSK wireless data traffic interface circuit design

    International Nuclear Information System (INIS)

    This article gives a practical interface circuit, which is able to conduct asynchronous wireless data communication through data transfer broadcasting station. And the circuit's design as well as its applications are introduced. (authors)

  9. A New Watermarking Approach Based on Combination of Reversible Watermarking and CDMA in Spatial and DWT Domain

    Directory of Open Access Journals (Sweden)

    S.Bekkouche & A.Chouarfia

    2011-04-01

    Full Text Available Image watermarking can be defined as a technique that allows insertion of imperceptible andindelible digital data into an image. In addition to its initial application which is the copyright,watermarking can be used in other fields, particularly in the medical field in order to contribute tosecure images shared on the network for telemedicine applications. In this report we study somewatermarking methods and the comparison result of their combination, the first one is based onthe CDMA (Code Division Multiple Access in DWT(Discrete Wavelet Transform domain, notedCDMA-DWT and CDMA in spatial domain, noted CDMA-SD and their aim are to verify theimage authenticity whereas the second one is the reversible watermarking (the least significantbits LSB and cryptography tools , the reversible carte mapping RCM their objective are to checkthe integrity of the image and to keep the Confidentiality of the patient data. A new scheme ofwatermarking is the combination of the reversible watermarking method and the method ofCDMA-DWT and the second is the combination of the reversible watermarking and the methodof CDMA-sp to verify the three security properties Integrity, Authenticity and Confidentiality ofmedical data and patient information. In the end, we made a comparison between these methodswithin the parameters of quality of medical images Initially, an in-depth study on thecharacteristics of medical images would contribute to improve these methods to measurementshave been done on the watermarked image to verify that this technique does not lead to a wrongdiagnostic. The robustness of the watermarked images against attacks has been verified on theparameters of PSNR (Peak Signal to Noise Ratio, MSE (Mean Square Error, MAE (MeanAbsolute Error and SNR (Signal to Noise Ratio which show that the resulting quality ofcombination watermarking method is good in DWT than other techniques.

  10. Reasoning on Robot Knowledge from Discrete and Asynchronous Observations

    OpenAIRE

    Ziafati, Pouyan; Elrakaiby, Yehia; Torre, Leon van der; Voos, Holger; dastani, mehdi; Meyer, John-Jules; Van Zee, Marc

    2014-01-01

    Robot knowledge of the world is created from discrete and asynchronous events received from its perception components. Proper representation and maintenance of robot knowledge is crucial to enable the use of robot knowledge for planning, user-interaction, etc. This paper identifies some of the main issues related to the representation, maintenance and querying of robot knowledge based on discrete asynchronous events such as event-history management and synchronization, and introduces a langua...

  11. CLOSED-FORM SPACE-TIME CHANNEL BLIND ESTIMATION FOR SPACE-TIME CODED MC-CDMA SYTEMS WITH UNIFORM LINEAR ARRAY

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper proposes a closed-form joint space-time channel and Direction Of Arrival (DOA) blind estimation algorithm for space-time coded Multi-Carrier Code Division Multiple Access (MC-CDMA) systems equipped with a Uniform Linear Array (ULA) at the base station in frequency-selective fading environments. The algorithm uses an ESPRIT-like method to separate multiple co-channel users with different impinging DOAs. As a result, the DOAs for multiple users are obtained. In particular, a set of signal subspaces,every one of which is spanned by the space-time vector channels of an individual user, are also obtained. From these signal subspaces, the space-time channels of multiple users are estimated using the subspace method.Computer simulations illustrate both the validity and the overall performance of the proposed scheme.

  12. Building asynchronous geospatial processing workflows with web services

    Science.gov (United States)

    Zhao, Peisheng; Di, Liping; Yu, Genong

    2012-02-01

    Geoscience research and applications often involve a geospatial processing workflow. This workflow includes a sequence of operations that use a variety of tools to collect, translate, and analyze distributed heterogeneous geospatial data. Asynchronous mechanisms, by which clients initiate a request and then resume their processing without waiting for a response, are very useful for complicated workflows that take a long time to run. Geospatial contents and capabilities are increasingly becoming available online as interoperable Web services. This online availability significantly enhances the ability to use Web service chains to build distributed geospatial processing workflows. This paper focuses on how to orchestrate Web services for implementing asynchronous geospatial processing workflows. The theoretical bases for asynchronous Web services and workflows, including asynchrony patterns and message transmission, are examined to explore different asynchronous approaches to and architecture of workflow code for the support of asynchronous behavior. A sample geospatial processing workflow, issued by the Open Geospatial Consortium (OGC) Web Service, Phase 6 (OWS-6), is provided to illustrate the implementation of asynchronous geospatial processing workflows and the challenges in using Web Services Business Process Execution Language (WS-BPEL) to develop them.

  13. A 0.6-V 8.3-ENOB asynchronous SAR ADC for biomedical applications

    Science.gov (United States)

    Yan, Song; Zhongming, Xue; Pengcheng, Yan; Jueying, Zhang; Li, Geng

    2014-08-01

    A microwatt asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) is presented. The supply voltage of the SAR ADC is decreased to 0.6 V to fit the low voltage and low power requirements of biomedical systems. The tail capacitor of the DAC array is reused for least significant bit conversion to decrease the total DAC capacitance thus reducing the power. Asynchronous control logic avoids the high frequency clock generator and further reduces the power consumption. The prototype ADC is fabricated with a standard 0.18 μm CMOS technology. Experimental results show that it achieves an ENOB of 8.3 bit at a 300-kS/s sampling rate. Very low power consumption of 3.04 μW is achieved, resulting in a figure of merit of 32 fJ/conv.-step.

  14. A 0.6-V 8.3-ENOB asynchronous SAR ADC for biomedical applications

    International Nuclear Information System (INIS)

    A microwatt asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) is presented. The supply voltage of the SAR ADC is decreased to 0.6 V to fit the low voltage and low power requirements of biomedical systems. The tail capacitor of the DAC array is reused for least significant bit conversion to decrease the total DAC capacitance thus reducing the power. Asynchronous control logic avoids the high frequency clock generator and further reduces the power consumption. The prototype ADC is fabricated with a standard 0.18 μm CMOS technology. Experimental results show that it achieves an ENOB of 8.3 bit at a 300-kS/s sampling rate. Very low power consumption of 3.04 μW is achieved, resulting in a figure of merit of 32 fJ/conv.-step. (semiconductor integrated circuits)

  15. Application of Artificial Intelligence Techniques for the Control of the Asynchronous Machine

    Directory of Open Access Journals (Sweden)

    F. Khammar

    2016-01-01

    Full Text Available The induction machine is experiencing a growing success for two decades by gradually replacing the DC machines and synchronous in many industrial applications. This paper is devoted to the study of advanced methods applied to the command of the asynchronous machine in order to obtain a system of control of high performance. While the criteria for response time, overtaking, and static error can be assured by the techniques of conventional control, the criterion of robustness remains a challenge for researchers. This criterion can be satisfied only by applying advanced techniques of command. After mathematical modeling of the asynchronous machine, it defines the control strategies based on the orientation of the rotor flux. The results of the different simulation tests highlight the properties of robustness of algorithms proposed and suggested to compare the different control strategies.

  16. ANALISIS PERILAKU KONSUMEN DALAM MEMILIH JASA LAYANAN OPERATOR MOBILE PHONE YANG BERBASIS CDMA DAN GSM

    Directory of Open Access Journals (Sweden)

    Demitri Marvin Kadhaffi

    2012-05-01

    Full Text Available ABSTRAKS Tujuan penelitian ini adalah (1 menganalisis faktor-faktor yang dipertimbangkan konsumen dalam memilih suatu jasa layanan operator mobile phone (baik CDMA maupun GSM, (2 menganalsis variabel dominan yang mempengaruhi perilaku konsumen dalam memilih jasa layanan operator Jenis penelitian ini adalah applied research dengan metode penelitian studi kausal. Penelitian ini ditujukan pada segmen pelajar dan mahasiswa di Kota Malang yang termasuk kelompok Net Generations (yang lahir antara tahun 1977-1997 dengan batas minimal umur untuk responden adalah 17 tahun.  Kerangka Sampel untuk penelitian ini adalah pengguna kartu CDMA dan GSM sebanyak 175 responden. Tehnik Sampling yang digunakan adalah desain sampel non probability dengan metode purposive sample yang kedua yaitu quota sampling. Metode analisa data yang digunakan adalah analisa faktor dan analisa diskriminan Hasil analisa faktor terhadap 34 variabel diperoleh  7 faktor baru, yang diberi label sebagai berikut : (1 faktor citra produk (2 faktor pelayanan, (3 faktor pengaruh lingkungan, (4 faktor promosi,(5 faktor individual, (6 faktor harga, dan (7 faktor proses. Dari analisa diskriminan diperoleh hasil yang bertentangan dengan hipotesis yaitu ternyata variabel harga bukan merupakan variabel yang dominan dalam membedakan perilaku pelanggan operator CDMA dengan GSM. Mereka lebih sensitif terhadap proses produk. Hal ini mengarahkan pelanggan untuk kalangan pelajar dan mahasiswa sebagai kelompok smart. Hasil penelitian menyimpulkan bahwa untuk membangun keunggulan bersaing operator harus meraih keunggulan posisional melalui diferensiasi “content” jasa yang dihasilkan yaitu berupa proses, sebagai hasil dari aplikasi  positioning produk.   Kata kunci: perilaku konsumen, jasa layanan, mobile phone   ABSTRACT Objective of this research are (1 to identify factors that customer consider in choosing mobile phone operator service (whether CDMA and GSM, (2 to identify dominant variable that

  17. An FDES-Based Shared Control Method for Asynchronous Brain-Actuated Robot.

    Science.gov (United States)

    Liu, Rong; Wang, Yong-Xuan; Zhang, Lin

    2016-06-01

    The asynchronous brain-computer interface (BCI) offers more natural human-machine interaction. However, it is still considered insufficient to control rapid and complex sequences of movements for a robot without any advanced control method. This paper proposes a new shared controller based on the supervisory theory of fuzzy discrete event system (FDES) for brain-actuated robot control. The developed supervisory theory allows the more reliable control mode to play a dominant role in the robot control which is beneficial to reduce misoperation and improve the robustness of the system. The experimental procedures consist of real-time direct manual control and BCI control tests from ten volunteers. Both tests have shown that the proposed method significantly improves the performance and robustness of the robotic control. In an online BCI experiment, eight of the participants successfully controlled the robot to circumnavigate obstacles and reached the target with a three mental states asynchronous BCI while the other two participants failed in all the BCI control sessions. Furthermore, the FDES-based shared control method also helps to reduce the workload. It can be stated that the asynchronous BCI, in combination with FDES-based shared controller, is feasible for the real-time and robust control of robotics.

  18. Low Power Analysis of Network-Level On-chip communication using Asynchronous AMBA protocol

    Directory of Open Access Journals (Sweden)

    E. Sakthivel

    2012-07-01

    Full Text Available Network on-chip (NoC is a novel structuraldesign template, which can be defied for complicatedsystem level on-chip design. NoC has a potential tolimit and present the bus-based communication. In thispaper, the crisis to discuss is Low power consumptionin an Asynchronous Network on-chip (NoC levelcommunication. NoC is implemented using FPGAwhich has less fabrication cost and reduces thecomplexity. An Asynchronous NoC has beenimplemented in Spartan kit using Xilinx FPGA ISEtools and its network interface is AdvancedMicrocontroller Bus Architecture (AMBA whichfeatures numerous bus masters and a sole clock edgeevolution and so on. Here the AMBA highperformance 32-bit AHB bus is employed in which ithas a high clock frequency system and it is the heart ofour bus system. To accomplish low power consumptionby interfacing SoC with AMBA- AHB protocol. TheAHB model and an Asynchronous NoC are employedand executed using VHDL programming module

  19. An Asynchronous Multi-Sensor Micro Control Unit for Wireless Body Sensor Networks (WBSNs

    Directory of Open Access Journals (Sweden)

    Ching-Hsing Luo

    2011-07-01

    Full Text Available In this work, an asynchronous multi-sensor micro control unit (MCU core is proposed for wireless body sensor networks (WBSNs. It consists of asynchronous interfaces, a power management unit, a multi-sensor controller, a data encoder (DE, and an error correct coder (ECC. To improve the system performance and expansion abilities, the asynchronous interface is created for handshaking different clock domains between ADC and RF with MCU. To increase the use time of the WBSN system, a power management technique is developed for reducing power consumption. In addition, the multi-sensor controller is designed for detecting various biomedical signals. To prevent loss error from wireless transmission, use of an error correct coding technique is important in biomedical applications. The data encoder is added for lossless compression of various biomedical signals with a compression ratio of almost three. This design is successfully tested on a FPGA board. The VLSI architecture of this work contains 2.68-K gate counts and consumes power 496-μW at 133-MHz processing rate by using TSMC 0.13-μm CMOS process. Compared with the previous techniques, this work offers higher performance, more functions, and lower hardware cost than other micro controller designs.

  20. Designing a WISHBONE Protocol Network Adapter for an Asynchronous Network-on-Chip

    Directory of Open Access Journals (Sweden)

    Ahmed H M Soliman

    2011-07-01

    Full Text Available The Scaling of microchip technologies, from micron to submicron and now to deep sub-micron (DSM range, has enabled large scale systems-on-chip (SoC. In future deep submicron (DSM designs, the interconnect effect will definitely dominate performance. Network-on-Chip (NoC has become a promising solution to bus-based communication infrastructure limitations. NoC designs usually targets Application Specific Integrated Circuits (ASICs, however, the fabrication process costs a lot. Implementing a NoC on an FPGA does not only reduce the cost but also decreases programming and verification cycles. In this paper, an Asynchronous NoC has been implemented on a SPARTAN-3Eandamp;reg; device. The NoC supports basic transactions of both widely used on-chip interconnection standards, the Open Core Protocol (OCP and the WISHBONE Protocol. Although, FPGA devices are synchronous in nature, it has been shown that they can be used to prototype a Global Asynchronous Local Synchronous (GALS systems, comprising an Asynchronous NoC connecting IP cores operating in different clock domains.

  1. Managing Asynchronous Data in ATLAS's Concurrent Framework

    CERN Document Server

    Leggett, Charles; The ATLAS collaboration

    2016-01-01

    In order to be able to make effective use of emerging hardware, where the amount of memory available to any CPU is rapidly decreasing as the core count continues to rise, ATLAS has begun a migration to a concurrent, multi-threaded software framework, known as AthenaMT. Significant progress has been made in implementing AthenaMT - we can currently run realistic Geant4 simulations on massively concurrent machines. the migration of realistic prototypes of reconstruction workflows is more difficult, given the large amounts of legacy code and the complexity and challenges of reconstruction software. These types of workflows, however, are the types that will most benefit from the memory reduction features of a multi-threaded framework. One of the challenges that we will report on in this paper is the re-design and implementation of several key asynchronous technologies whose behaviour is radically different in a concurrent environment than in a serial one, namely the management of Conditions data and the Detector D...

  2. Rapid, generalized adaptation to asynchronous audiovisual speech.

    Science.gov (United States)

    Van der Burg, Erik; Goodbourn, Patrick T

    2015-04-01

    The brain is adaptive. The speed of propagation through air, and of low-level sensory processing, differs markedly between auditory and visual stimuli; yet the brain can adapt to compensate for the resulting cross-modal delays. Studies investigating temporal recalibration to audiovisual speech have used prolonged adaptation procedures, suggesting that adaptation is sluggish. Here, we show that adaptation to asynchronous audiovisual speech occurs rapidly. Participants viewed a brief clip of an actor pronouncing a single syllable. The voice was either advanced or delayed relative to the corresponding lip movements, and participants were asked to make a synchrony judgement. Although we did not use an explicit adaptation procedure, we demonstrate rapid recalibration based on a single audiovisual event. We find that the point of subjective simultaneity on each trial is highly contingent upon the modality order of the preceding trial. We find compelling evidence that rapid recalibration generalizes across different stimuli, and different actors. Finally, we demonstrate that rapid recalibration occurs even when auditory and visual events clearly belong to different actors. These results suggest that rapid temporal recalibration to audiovisual speech is primarily mediated by basic temporal factors, rather than higher-order factors such as perceived simultaneity and source identity.

  3. A DUAL RESERVATION CDMA-BASED MAC PROTOCOL WITH POWER CONTROL FOR AD HOC NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Jia Min; Chen Huimin; Yuan Yuhua

    2007-01-01

    This paper proposes a new multi-channel Medium Access Control (MAC) protocol named as Dual Reservation Code Division Multiple Access (CDMA) based MAC protocol with Power Control (DRCPC). The code channel is divided into common channel, broadcast channel and several data channels. And dynamic power control mechanism is implemented to reduce near-far interference. Compared with IEEE 802.11 Distributed Coordination Function (DCF) protocol, the results show that the proposed mechanism improves the average throughput and limits the transmission delay efficiently.

  4. The LSCM_SUB algorithm for blind multiuser detection in multipath CDMA channels

    Institute of Scientific and Technical Information of China (English)

    LIU Sheng-mei; FENG Guang-zeng; ZHU Qi

    2006-01-01

    In this article, the least square constant modulus algorithm (LSCMA) is combined with the subspace approach and a LSCM_SUB (Subspace) blind adaptive multiuser detection in multipath code division multiple access (CDMA)channels is presented. The poor performance of LSCMA in the low signal to noise ratio (SNR) is improved by the LSCM_SUB algorithm. The performance of the proposed LSCM_SUB algorithm is compared with that of LSCMA.Simulation results show that the LSCM_SUB algorithm is superior to the LSCMA, especially in the low SNR.

  5. Operational aspects of asynchronous filtering for improved flood forecasting

    Science.gov (United States)

    Rakovec, Oldrich; Weerts, Albrecht; Sumihar, Julius; Uijlenhoet, Remko

    2014-05-01

    and assimilation and is suitable to be connected to any kind of environmental model. This setup is embedded in the Delft Flood Early Warning System (Delft-FEWS, Werner et al., 2013) for making all simulations and forecast runs and handling of all hydrological and meteorological data. References: Evensen, G. (2009), Data Assimilation: The Ensemble Kalman Filter, Springer, doi:10.1007/978-3-642-03711-5. OpenDA (2013), The OpenDA data-assimilation toolbox, www.openda.org, (last access: 1 November 2013). OpenStreams (2013), OpenStreams, www.openstreams.nl, (last access: 1 November 2013). Sakov, P., G. Evensen, and L. Bertino (2010), Asynchronous data assimilation with the EnKF, Tellus, Series A: Dynamic Meteorology and Oceanography, 62(1), 24-29, doi:10.1111/j.1600-0870.2009.00417.x. Werner, M., J. Schellekens, P. Gijsbers, M. van Dijk, O. van den Akker, and K. Heynert (2013), The Delft-FEWS flow forecasting system, Environ. Mod. & Soft., 40(0), 65-77, doi: http://dx.doi.org/10.1016/j.envsoft.2012.07.010.

  6. Synaptotagmin-7 is an asynchronous calcium sensor for synaptic transmission in neurons expressing SNAP-23.

    Directory of Open Access Journals (Sweden)

    Jens P Weber

    Full Text Available Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetitive stimulation, and can even play a dominant role in some synapses. Here, we show that substitution of SNAP-23 for SNAP-25 in mouse autaptic glutamatergic hippocampal neurons results in asynchronous release and a higher frequency of spontaneous release events (mEPSCs. Use of neurons from double-knock-out (SNAP-25, synaptotagmin-7 mice in combination with viral transduction showed that SNAP-23-driven release is triggered by endogenous synaptotagmin-7. In the absence of synaptotagmin-7 release became even more asynchronous, and the spontaneous release rate increased even more, indicating that synaptotagmin-7 acts to synchronize release and suppress spontaneous release. However, compared to synaptotagmin-1, synaptotagmin-7 is a both leaky and asynchronous calcium sensor. In the presence of SNAP-25, consequences of the elimination of synaptotagmin-7 were small or absent, indicating that the protein pairs SNAP-25/synaptotagmin-1 and SNAP-23/synaptotagmin-7 might act as mutually exclusive calcium sensors. Expression of fusion proteins between pHluorin (pH-sensitive GFP and synaptotagmin-1 or -7 showed that vesicles that fuse using the SNAP-23/synaptotagmin-7 combination contained synaptotagmin-1, while synaptotagmin-7 barely displayed activity-dependent trafficking between vesicle and plasma membrane, implying that it acts as a plasma membrane calcium sensor. Overall, these findings support the idea of alternative syt∶SNARE combinations driving release with different kinetics and fidelity.

  7. Effect of asynchronous updating on the stability of cellular automata

    International Nuclear Information System (INIS)

    Highlights: ► An upper bound on the Lyapunov exponent of asynchronously updated CA is established. ► The employed update method has repercussions on the stability of CAs. ► A decision on the employed update method should be taken with care. ► Substantial discrepancies arise between synchronously and asynchronously updated CA. ► Discrepancies between different asynchronous update schemes are less pronounced. - Abstract: Although cellular automata (CAs) were conceptualized as utter discrete mathematical models in which the states of all their spatial entities are updated simultaneously at every consecutive time step, i.e. synchronously, various CA-based models that rely on so-called asynchronous update methods have been constructed in order to overcome the limitations that are tied up with the classical way of evolving CAs. So far, only a few researchers have addressed the consequences of this way of updating on the evolved spatio-temporal patterns, and the reachable stationary states. In this paper, we exploit Lyapunov exponents to determine to what extent the stability of the rules within a family of totalistic CAs is affected by the underlying update method. For that purpose, we derive an upper bound on the maximum Lyapunov exponent of asynchronously iterated CAs, and show its validity, after which we present a comparative study between the Lyapunov exponents obtained for five different update methods, namely one synchronous method and four well-established asynchronous methods. It is found that the stability of CAs is seriously affected if one of the latter methods is employed, whereas the discrepancies arising between the different asynchronous methods are far less pronounced and, finally, we discuss the repercussions of our findings on the development of CA-based models.

  8. Two-Particle Asynchronous Quantum Correlation: Wavefunction Collapse Acting as a Beamsplitter

    Science.gov (United States)

    Kowalski, F. V.; Browne, R. S.

    2016-03-01

    A two-body quantum correlation is calculated for a particle reflecting from a moving mirror. Correlated interference results when the incident and reflected particle substates and their associated mirror substates overlap. Using the Copenhagen interpretation of measurement, an asynchronous joint probability density (PDF), which is a function both of the different positions and different times at which the particle and mirror are measured, is derived assuming that no interaction occurs between each measurement. Measurement of the particle first, in the correlated interference region, results in a splitting of the mirror substate into ones which have and have not reflected the particle. An analog of the interference from the Doppler effect for only measurements of the particle (a marginal PDF), in this two-body system, is shown to be a consequence of the asynchronous measurement. The simplification obtained for a microscopic particle reflecting from a mesoscopic or macroscopic mirror is used to illustrate asynchronous correlation interferometry. In this case, the small displacement between these mirror states can yield negligible environmental decoherence times. In addition, interference of these mirror states does not vanish in the limit of large mirror mass due to the small momentum exchange in reflecting a microscopic particle.

  9. Space-Time Chip Equalization for Maximum Diversity Space-Time Block Coded DS-CDMA Downlink Transmission

    NARCIS (Netherlands)

    Leus, G.; Petré, F.; Moonen, M.

    2004-01-01

    In the downlink of DS-CDMA, frequency-selectivity destroys the orthogonality of the user signals and introduces multiuser interference (MUI). Space-time chip equalization is an efficient tool to restore the orthogonality of the user signals and suppress the MUI. Furthermore, multiple-input multiple-

  10. IHadoop: Asynchronous iterations for MapReduce

    KAUST Repository

    Elnikety, Eslam Mohamed Ibrahim

    2011-11-01

    MapReduce is a distributed programming frame-work designed to ease the development of scalable data-intensive applications for large clusters of commodity machines. Most machine learning and data mining applications involve iterative computations over large datasets, such as the Web hyperlink structures and social network graphs. Yet, the MapReduce model does not efficiently support this important class of applications. The architecture of MapReduce, most critically its dataflow techniques and task scheduling, is completely unaware of the nature of iterative applications; tasks are scheduled according to a policy that optimizes the execution for a single iteration which wastes bandwidth, I/O, and CPU cycles when compared with an optimal execution for a consecutive set of iterations. This work presents iHadoop, a modified MapReduce model, and an associated implementation, optimized for iterative computations. The iHadoop model schedules iterations asynchronously. It connects the output of one iteration to the next, allowing both to process their data concurrently. iHadoop\\'s task scheduler exploits inter-iteration data locality by scheduling tasks that exhibit a producer/consumer relation on the same physical machine allowing a fast local data transfer. For those iterative applications that require satisfying certain criteria before termination, iHadoop runs the check concurrently during the execution of the subsequent iteration to further reduce the application\\'s latency. This paper also describes our implementation of the iHadoop model, and evaluates its performance against Hadoop, the widely used open source implementation of MapReduce. Experiments using different data analysis applications over real-world and synthetic datasets show that iHadoop performs better than Hadoop for iterative algorithms, reducing execution time of iterative applications by 25% on average. Furthermore, integrating iHadoop with HaLoop, a variant Hadoop implementation that caches

  11. Efficiency asynchronous application programming language Python

    OpenAIRE

    Толстікова, О. В.; Національний авіаційний університет; Мирошниченко, І. С.; Національний авіаційний університет; Коцюр, А. Б.; Національний авіаційний університет

    2016-01-01

    Consider tools that implement asynchronous programming in Python and allow more efficient use ofasynchronous programming applications. The efficiency of the module asyncio (PEP 3156) incomparison with classical spivprohramamy Рассмотрены инструменты, которые реализуют асинхронное программирование в языкеPython и позволяют повысить эффективность использования программирования асинхронныхприложений. Показана эффективность работы модуля asyncio (PEP 3156) по сравнению с классическими сопрогра...

  12. Asynchronous reference frame agreement in a quantum network

    Science.gov (United States)

    Islam, Tanvirul; Wehner, Stephanie

    2016-03-01

    An efficient implementation of many multiparty protocols for quantum networks requires that all the nodes in the network share a common reference frame. Establishing such a reference frame from scratch is especially challenging in an asynchronous network where network links might have arbitrary delays and the nodes do not share synchronised clocks. In this work, we study the problem of establishing a common reference frame in an asynchronous network of n nodes of which at most t are affected by arbitrary unknown error, and the identities of the faulty nodes are not known. We present a protocol that allows all the correctly functioning nodes to agree on a common reference frame as long as the network graph is complete and not more than t\\lt n/4 nodes are faulty. As the protocol is asynchronous, it can be used with some assumptions to synchronise clocks over a network. Also, the protocol has the appealing property that it allows any existing two-node asynchronous protocol for reference frame agreement to be lifted to a robust protocol for an asynchronous quantum network.

  13. A Case Study on Ip Based Cdma Ran by Controlling Router

    Directory of Open Access Journals (Sweden)

    K Sravan Abhilash

    2014-08-01

    Full Text Available As communication plays an important role in day to day life, the effective and efficient data transmission is to be maintained. This paper mainly deals with implements a congestion control mechanism using Router control method for IP-RAN on CDMA cellular network. The Router control mechanism uses the features of CDMA networks using active Queue Management technique to reduce delay and to minimize the correlated losses. When utilizing these new personal tools and services to enrich our lives, while being mobile, we are using Mobile Multimedia applications. As new handsets, new technologies and new business models are introduced on the marketplace, new attractive multimedia services can and will be launched, fulfilling the demands. Because the number of multimedia services and even more so, the context in which the services are used is numerous, the following model is introduced in order to simplify and clarify how different services will evolve, enrich our lives and fulfill our desires.The proposed paper work is to be realized using Matlab platform.

  14. Normalized and asynchronous mirror alignment for Cherenkov telescopes

    Science.gov (United States)

    Ahnen, M. L.; Baack, D.; Balbo, M.; Bergmann, M.; Biland, A.; Blank, M.; Bretz, T.; Bruegge, K. A.; Buss, J.; Domke, M.; Dorner, D.; Einecke, S.; Hempfling, C.; Hildebrand, D.; Hughes, G.; Lustermann, W.; Mannheim, K.; Mueller, S. A.; Neise, D.; Neronov, A.; Noethe, M.; Overkemping, A.-K.; Paravac, A.; Pauss, F.; Rhode, W.; Shukla, A.; Temme, F.; Thaele, J.; Toscano, S.; Vogler, P.; Walter, R.; Wilbert, A.

    2016-09-01

    Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and as they are composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment is a challenge. Here we present a computer vision based star tracking alignment method, which also works for limited or changing star light visibility. Our method normalizes the mirror facet reflection intensities to become independent of the reference star's intensity or the cloud coverage. Using two CCD cameras, our method records the mirror facet orientations asynchronously of the telescope drive system, and thus makes the method easy to integrate into existing telescopes. It can be combined with remote facet actuation, but does not require one to work. Furthermore, it can reconstruct all individual mirror facet point spread functions without moving any mirror. We present alignment results on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT).

  15. Renewal Approach to the Analysis of the Asynchronous State for Coupled Noisy Oscillators

    CERN Document Server

    Farkhooi, Farzad

    2015-01-01

    We develop a framework in which the activity of nonlinear pulse-coupled oscillators is posed within the renewal theory. In this approach, the evolution of inter-event density allows for a self-consistent calculation that determines the asynchronous state and its stability. This framework, can readily be extended to the analysis of systems with more state variables. To exhibit this, we study a nonlinear pulse-coupled system, where couplings are dynamic and activity dependent. We investigate stability of this system and we show it undergoes a super-critical Hopf bifurcation to collective synchronization.

  16. Asynchronous event-based corner detection and matching.

    Science.gov (United States)

    Clady, Xavier; Ieng, Sio-Hoi; Benosman, Ryad

    2015-06-01

    This paper introduces an event-based luminance-free method to detect and match corner events from the output of asynchronous event-based neuromorphic retinas. The method relies on the use of space-time properties of moving edges. Asynchronous event-based neuromorphic retinas are composed of autonomous pixels, each of them asynchronously generating "spiking" events that encode relative changes in pixels' illumination at high temporal resolutions. Corner events are defined as the spatiotemporal locations where the aperture problem can be solved using the intersection of several geometric constraints in events' spatiotemporal spaces. A regularization process provides the required constraints, i.e. the motion attributes of the edges with respect to their spatiotemporal locations using local geometric properties of visual events. Experimental results are presented on several real scenes showing the stability and robustness of the detection and matching. PMID:25828960

  17. A Loosely Synchronizing Asynchronous Router for TDM-Scheduled NOCs

    DEFF Research Database (Denmark)

    Kotleas, Ioannis; Humphreys, Dean; Sørensen, Rasmus Bo;

    2014-01-01

    This paper presents an asynchronous router design for use in time-division-multiplexed (TDM) networks-on-chip. Unlike existing synchronous, mesochronous and asynchronous router designs with similar functionality, the router is able to silently skip over cycles/TDM-slots where no traffic is...... scheduled and hence avoid all switching activity in the idle links and router ports. In this way switching activity is reduced to the minimum possible amount. The fact that this relaxed synchronization is sufficient to implement TDM scheduling represents a contribution at the conceptual level. The idea can...... only be implemented using asynchronous circuit techniques. To this end, the paper explores the use of “click-element” templates. Click-element templates use only flipflops and conventional gates, and this greatly simplifies the design process when using conventional EDA tools and standard cell...

  18. Molecular mechanisms for synchronous, asynchronous, and spontaneous neurotransmitter release.

    Science.gov (United States)

    Kaeser, Pascal S; Regehr, Wade G

    2014-01-01

    Most neuronal communication relies upon the synchronous release of neurotransmitters, which occurs through synaptic vesicle exocytosis triggered by action potential invasion of a presynaptic bouton. However, neurotransmitters are also released asynchronously with a longer, variable delay following an action potential or spontaneously in the absence of action potentials. A compelling body of research has identified roles and mechanisms for synchronous release, but asynchronous release and spontaneous release are less well understood. In this review, we analyze how the mechanisms of the three release modes overlap and what molecular pathways underlie asynchronous and spontaneous release. We conclude that the modes of release have key fusion processes in common but may differ in the source of and necessity for Ca(2+) to trigger release and in the identity of the Ca(2+) sensor for release. PMID:24274737

  19. Analisis Faktor-Faktor Yang Mempengaruhi Perilaku Konsumen Terhadap Keputusan Menggunakan Dua Ponsel (GSM dan CDMA) Pada Mahasiswa Departemen Manajemen Fakultas Ekonomi USU.

    OpenAIRE

    Hutagalung, Raja Bongsu; Aisha, Novi

    2010-01-01

    The purpose of this research is to find out and to analysis culture factor, social factor, personal factor, and psychology factor have influence on the decision of using two handphone (GSM and CDMA). The result of research indicate that the factors of influence consumer behaviour which is consist of culture factor, social factor, personal factor, and psychology factor are together have significant effect toward decision of using two handphone (GSM and CDMA). The result also indicates that cul...

  20. Asynchronous updating of threshold-coupled chaotic neurons

    Indian Academy of Sciences (India)

    Manish Dev Shirmali; Sudeshna Sinha; Kazuyuki Aihara

    2008-06-01

    We study a network of chaotic model neurons incorporating threshold activated coupling. We obtain a wide range of spatiotemporal patterns under varying degrees of asynchronicity in the evolution of the neuronal components. For instance, we find that sequential updating of threshold-coupled chaotic neurons can yield dynamical switching of the individual neurons between two states. So varying the asynchronicity in the updating scheme can serve as a control mechanism to extract different responses, and this can have possible applications in computation and information processing.