Multiantenna relay beamforming design for QoS discrimination in two-way relay networks.
Xiong, Ke; Zhang, Yu; Li, Dandan; Chang, Chih-Yung; Zhong, Zhangdui
2013-01-01
This paper investigates the relay beamforming design for quality of service (QoS) discrimination in two-way relay networks. The purpose is to keep legitimate two-way relay users exchange their information via a helping multiantenna relay with QoS guarantee while avoiding the exchanged information overhearing by unauthorized receiver. To this end, we propose a physical layer method, where the relay beamforming is jointly designed with artificial noise (AN) which is used to interfere in the unauthorized user's reception. We formulate the joint beamforming and AN (BFA) design into an optimization problem such that the received signal-to-interference-ratio (SINR) at the two legitimate users is over a predefined QoS threshold while limiting the received SINR at the unauthorized user which is under a certain secure threshold. The objective of the optimization problem is to seek the optimal AN and beamforming vectors to minimize the total power consumed by the relay node. Since the optimization problem is nonconvex, we solve it by using semidefinite program (SDP) relaxation. For comparison, we also study the optimal relay beamforming without using AN (BFO) under the same QoS discrimination constraints. Simulation results show that both the proposed BFA and BFO can achieve the QoS discrimination of the two-way transmission. However, the proposed BFA yields significant power savings and lower infeasible rates compared with the BFO method.
Distributed cognitive two-way relay beamformer designs under perfect and imperfect CSI
Pandarakkottilil, Ubaidulla
2011-09-01
In this paper, we present distributed two-way relay beamformer designs for a cognitive radio network (CRN) in which a pair of cognitive (or secondary) transceiver nodes communicate with each other assisted by a set of cognitive two-way relay nodes. The secondary nodes share the spectrum with a licensed primary user (PU) node, and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. First, we consider relay beamformer designs assuming the availability of perfect channel state information (CSI). For this case, a mean-square error (MSE)-constrained beamformer that minimizes the total relay transmit power, and an MSE-balancing beamformer with a constraint on the total relay transmit power are proposed. Next, we consider relay beamformer designs assuming that the available CSI is imperfect. For this case too, we consider the same problems as those in the case of perfect CSI, and propose beamformer designs that are robust to the errors in the CSI. We show that the proposed designs can be reformulated as convex optimization problems that can be solved efficiently. Through numerical simulations, we illustrate the performance of the proposed designs. © 2011 IEEE.
Distributed beamforming designs to improve physical layer security in wireless relay networks
Qian, Mujun; Liu, Chen; Fu, Youhua
2014-12-01
This paper investigates security-oriented beamforming designs in a relay network composed of a source-destination pair, multiple relays, and a passive eavesdropper. Unlike most of the earlier works, we assume that only statistical information of the relay-eavesdropper channels is known to the relays. We propose beamforming solutions for amplify-and-forward (AF) and decode-and-forward (DF) relay networks to improve secrecy capacity. In an AF network, the beamforming design is obtained by approximating a product of two correlated Rayleigh quotients to a single Rayleigh quotient using the Taylor series expansion. Our study reveals that in an AF network, the secrecy capacity does not always grow as the eavesdropper moves away from the relays or as total relay transmit power increases. Moreover, if the destination is nearer to the relays than the eavesdropper is, a suboptimal power is derived in closed form through monotonicity analysis of secrecy capacity. While in a DF network, secrecy capacity is a single Rayleigh quotient problem which can be easily solved. We also found that if the relay-eavesdropper distances are about the same, it is unnecessary to consider the eavesdropper in a DF network. Numerical results show that for either AF or DF relaying protocol, the proposed beamforming scheme provides higher secrecy capacity than traditional approaches.
Robust distributed cognitive relay beamforming
Pandarakkottilil, Ubaidulla
2012-05-01
In this paper, we present a distributed relay beamformer design for a cognitive radio network in which a cognitive (or secondary) transmit node communicates with a secondary receive node assisted by a set of cognitive non-regenerative relays. The secondary nodes share the spectrum with a licensed primary user (PU) node, and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. The proposed robust cognitive relay beamformer design seeks to minimize the total relay transmit power while ensuring that the transceiver signal-to-interference- plus-noise ratio and PU interference constraints are satisfied. The proposed design takes into account a parameter of the error in the channel state information (CSI) to render the performance of the beamformer robust in the presence of imperfect CSI. Though the original problem is non-convex, we show that the proposed design can be reformulated as a tractable convex optimization problem that can be solved efficiently. Numerical results are provided and illustrate the performance of the proposed designs for different network operating conditions and parameters. © 2012 IEEE.
Beamforming Design for Coordinated Direct and Relay Systems
Sun, Fan; De Carvalho, Elisabeth; Thai, Chan
2012-01-01
Joint processing of multiple communication flows in wireless systems has given rise to a number of novel transmission techniques, notably the two-way relaying based on wireless network coding. Recently, a related set of techniques has emerged, termed coordinated direct and relay (CDR) transmissions......, where the constellation of traffic flows is more general than the two-way. Regardless of the actual traffic flows, in a CDR scheme the relay has a central role in managing the interference. In this paper we investigate the novel transmission modes, based on amplify-and-forward, that arise when the relay...
Weijia Lei
2016-07-01
Full Text Available The physical security strategy in the wireless network with a single-antenna eavesdropper is studied. The information transmits from a single-antenna source to a single-antenna destination, and an energy-limited multi-antenna relay is employed to forward information. The antennas of the relay are divided into two groups. One group receives and forwards information, and the other converts the received signal into energy. Beamforming is used by the relay to prevent the eavesdropper from intercepting confidential information. For the purpose of maximizing the secrecy rate, antenna grouping and beamforming vectors are designed. A low complexity scheme of antenna grouping is presented. The simulation results show that the secrecy rate can be significantly improved by arranging part of the antennas for energy harvesting, and part for forwarding and optimizing the beamforming vector at the relay. The antenna grouping scheme significantly reduces the computational complexity at the cost of acceptable performance loss.
Cognitive two-way relay beamforming: Design with resilience to channel state uncertainties
Ubaidulla, P.
2016-07-26
In this paper, we propose a robust distributed relay beamformer design for cognitive radio network operating under uncertainties in the available channel state information. The cognitive network consists of a pair of transceivers and a set of non-regenerative two-way relays that assist the communication between the transceiver pair. The secondary nodes share the spectrum with a licensed primary user node while ensuring that the interference to the primary receiver is maintained below a certain threshold. The proposed robust design maximizes the worst-case signal-to-interference-plus-noise ratio at the secondary transceivers while satisfying constraints on the interference to the primary user and on the total relay transmit power. Though the robust design problem is not a convex problem in its original form, we show that it can be reformulated as a convex optimization problem, which can be solved efficiently. Numerical results are provided and illustrate the merits of the proposed design for various operating conditions and parameters. © 2016 IEEE.
Cooperative Beamforming for Dual-Hop Amplify-and-Forward Multi-Antenna Relaying Cellular Networks
Xing, Chengwen; Ma, shaodan; Wu, Yik-Chung
2011-01-01
In this paper, linear beamforming design for amplify-and-forward relaying cellular networks is considered, in which base station, relay station and mobile terminals are all equipped with multiple antennas. The design is based on minimum mean-square-error criterion, and both uplink and downlink scenarios are considered. It is found that the downlink and uplink beamforming design problems are in the same form, and iterative algorithms with the same structure can be used to solve the design problems. For the specific cases of fully loaded or overloaded uplink systems, a novel algorithm is derived and its relationships with several existing beamforming design algorithms for conventional MIMO or multiuser systems are revealed. Simulation results are presented to demonstrate the performance advantage of the proposed design algorithms.
Cooperative beamforming for dual-hop amplify-and-forward multi-antenna relaying cellular networks
Xing, Chengwen
2012-11-01
In this paper, linear beamforming design for amplify-and-forward relaying cellular networks is considered, in which base station, relay station and mobile terminals are all equipped with multiple antennas. The design is based on minimum mean-square-error criterion, and both uplink and downlink scenarios are considered. It is found that the downlink and uplink beamforming design problems are in the same form, and iterative algorithms with the same structure can be used to solve the design problems. For the specific cases of fully loaded or overloaded uplink systems, a novel algorithm is derived and its relationships with several existing beamforming design algorithms for conventional MIMO or multiuser systems are revealed. Simulation results are presented to demonstrate the performance advantage of the proposed design algorithms. © 2012 Published by Elsevier B.V. All rights reserved.
Coordinated Direct and Relay Transmission with Linear Non-Regenerative Relay Beamforming
Sun, Fan; De Carvalho, Elisabeth; Popovski, Petar;
2012-01-01
Joint processing of multiple communication flows in wireless systems has given rise to a number of novel transmission techniques, notably the two-way relaying, but also more general traffic scenarios, such as coordinated direct and relay (CDR) transmissions. In a CDR scheme the relay has a central...... role in managing the interference and boosting the overall system performance. In this letter we consider the case in which an amplify-and-forward relay has multiple antennas and can use beamforming to support the coordinated transmissions. We focus on one representative traffic type with one uplink...... user and one downlink user. Two different criteria for relay beamforming are analyzed: maximal weighted sum-rate and maximization of the worst-case weighted SNR. We propose iterative optimal solutions, as well as low-complexity near-optimal solutions....
Beamforming Design of AF MIMO Two-Way Relay Channels Based on MSMSE%基于MSMSE的MIMO放大转发双向中继信道中波束成形设计
王梓斌; 向良军; 郑林华; 丁宏
2011-01-01
本文主要研究了基于最小化均方误差和准则的MIMO放大转发双向中继信道中的波束成形向量(矩阵)的设计.我们分别在集中式与分布式两种应用环境中提出了一套解决方案.在集中式方案中,多个中继之间完全协作,因此将多个单天线中继等效成一个多天线的中继节点,设计了基于所有中继天线的总功率控制的波束成形向量(矩阵).在分布式方案中,中继节点之间无协作,分别设计了基于所有中继总功率控制波束成形向量(矩阵)和基于单个中继功率控制的波束成形向量(矩阵).仿真表明,通过波束成形设计,可以显著提高通信节点平均误码率.由于中继节点之间的完全协作,集中式方案要优于分布式方案.但是,由于中继结构简单,分布式方案更易于在实践中应用.%In this paper, we design the beamforming in multiple-input multiple-output ( MIMO) two-way relay channels to minimize the sum mean squared errors (SMSE). Two source nodes communicate to each other with the help of multiple relays each with a single antenna. A scheme for a centralized model and another scheme for distributed model are proposed, respectively. In the first scheme, relays are assumed to be able to fully cooperate with each other and the multiple relay nodes can be equivalent to a single relay with multiple antennas. Relay beamforming under total power constraint of all relays is unitedly designed with the transmit beamforming and the receive beamforming. In the aecond scheme, there are no coopenration between relay nodes , and beamforming schemes under relay total power constraint and individual power constraint are designed, respectively. the simulation results show that beamforming at source and relay nodes significantly improve the average bit error rate (BER) performance. Furthermore, with cooperation across different relays, the performance of the centralized scheme is better than the distributed one, but the
Robust distributed two-way relay beamforming in cognitive radio networks
Pandarakkottilil, Ubaidulla
2012-04-01
In this paper, we present distributed beamformer designs for a cognitive radio network (CRN) consisting of a pair of cognitive (or secondary) transceiver nodes communicating with each other through a set of secondary non-regenerative two-way relays. The secondary network shares the spectrum with a licensed primary user (PU), and operates under a constraint on the maximum interference to the PU, in addition to its own resource and quality of service (QoS) constraints. We propose beamformer designs assuming that the available channel state information (CSI) is imperfect, which reflects realistic scenarios. The performance of proposed designs is robust to the CSI errors. Such robustness is critical in CRNs given the difficulty in acquiring perfect CSI due to loose cooperation between the PUs and the secondary users (SUs), and the need for strict enforcement of PU interference limit. We consider a mean-square error (MSE)-constrained beamformer that minimizes the total relay transmit power and an MSE-balancing beamformer with a constraint on the total relay transmit power. We show that the proposed designs can be reformulated as convex optimization problems that can be solved efficiently. Through numerical simulations, we illustrate the improved performance of the proposed robust designs compared to non-robust designs. © 2012 IEEE.
Distributed Beamforming in Wireless Multiuser Relay-Interference Networks with Quantized Feedback
Koyuncu, Erdem
2010-01-01
We study quantized beamforming in wireless amplify-and-forward relay-interference networks with any number of transmitters, relays, and receivers. We design the quantizer of the channel state information to minimize the probability that at least one receiver incorrectly decodes its desired symbol(s). Correspondingly, we introduce a generalized diversity measure that encapsulates the conventional one as the first-order diversity. Additionally, it incorporates the second-order diversity, which is concerned with the transmitter power dependent logarithmic terms that appear in the error rate expression. First, we show that, regardless of the quantizer and the amount of feedback that is used, the relay-interference network suffers a second-order diversity loss compared to interference-free networks. Then, two different quantization schemes are studied: First, using a global quantizer, we show that a simple relay selection scheme can achieve maximal diversity. Then, using the localization method, we construct both ...
Optimization of beamforming and path planning for UAV-assisted wireless relay networks
Ouyang Jian
2014-04-01
Full Text Available Recently, unmanned aerial vehicles (UAVs acting as relay platforms have attracted considerable attention due to the advantages of extending coverage and improving connectivity for long-range communications. Specifically, in the scenario where the access point (AP is mobile, a UAV needs to find an efficient path to guarantee the connectivity of the relay link. Motivated by this fact, this paper proposes an optimal design for beamforming (BF and UAV path planning. First of all, we study a dual-hop amplify-and-forward (AF wireless relay network, in which a UAV is used as relay between a mobile AP and a fixed base station (BS. In the network, both of the AP and the BS are equipped with multiple antennas, whereas the UAV has a single antenna. Then, we obtain the output signal-to-noise ratio (SNR of the dual-hop relay network. Based on the criterion of maximizing the output SNR, we develop an optimal design to obtain the solution of the optimal BF weight vector and the UAV heading angle. Next, we derive the closed-form outage probability (OP expression to investigate the performance of the dual-hop relay network conveniently. Finally, computer simulations show that the proposed approach can obtain nearly optimal flying path and OP performance, indicating the effectiveness of the proposed algorithm. Furthermore, we find that increasing the antenna number at the BS or the maximal heading angle can significantly improve the performance of the considered relay network.
Yang, Wei; Wu, Gang; Wang, Haifeng
2010-01-01
Relay selection enhances the performance of the cooperative networks by selecting the links with higher capacity. Meanwhile link adaptation improves the spectral efficiency of wireless data-centric networks through adapting the modulation and coding schemes (MCS) to the current link condition. In this paper, relay selection is combined with link adaptation for distributed beamforming in a two-hop regenerative cooperative system. A novel signaling mechanism and related optimal algorithms are proposed for joint relay selection and link adaptation. In the proposed scheme, there is no need to feedback the relay selection results to each relay. Instead, by broadcasting the link adaptation results from the destination, each relay will automatically understand whether it is selected or not. The lower and upper bounds of the throughput of the proposed scheme are derived. The analysis and simulation results indicate that the proposed scheme provides synergistic gains compared to the pure relay selection and link adapt...
Beamforming in Two-Way Fixed Gain Amplify-and-Forward Relay Systems with CCI
Duong, Trung Q; Zepernick, Hans-Jurgen; Yuen, Chau
2012-01-01
We analyze the outage performance of a two-way fixed gain amplify-and-forward (AF) relay system with beamforming, arbitrary antenna correlation, and co-channel interference (CCI). Assuming CCI at the relay, we derive the exact individual user outage probability in closed-form. Additionally, while neglecting CCI, we also investigate the system outage probability of the considered network, which is declared if any of the two users is in transmission outage. Our results indicate that in this system, the position of the relay plays an important role in determining the user as well as the system outage probability via such parameters as signal-to-noise imbalance, antenna configuration, spatial correlation, and CCI power. To render further insights into the effect of antenna correlation and CCI on the diversity and array gains, an asymptotic expression which tightly converges to exact results is also derived.
Optimal Beamforming and Performance Analysis of Wireless Relay Networks with Unmanned Aerial Vehicle
Ouyang, Jian; Lin, Min
2015-03-01
In this paper, we investigate a wireless communication system employing a multi-antenna unmanned aerial vehicle (UAV) as the relay to improve the connectivity between the base station (BS) and the receive node (RN), where the BS-UAV link undergoes the correlated Rician fading while the UAV-RN link follows the correlated Rayleigh fading with large scale path loss. By assuming that the amplify-and-forward (AF) protocol is adopted at UAV, we first propose an optimal beamforming (BF) scheme to maximize the mutual information of the UAV-assisted dual-hop relay network, by calculating the BF weight vectors and the power allocation coefficient. Then, we derive the analytical expressions for the outage probability (OP) and the ergodic capacity (EC) of the relay network to evaluate the system performance conveniently. Finally, computer simulation results are provided to demonstrate the validity and efficiency of the proposed scheme as well as the performance analysis.
Li, Min
2014-07-01
In this paper, the performance of beamforming (BF) for a dual-hop amplify-and-forward (AF) relay network, where the source and destination are each equipped with multiple antennas, is investigated. It is assumed that the source-relay and relay-destination channels experience mixed fading distributions, namely, correlated Nakagami-m/Rician and correlated Rician/Nakagami-m, respectively. By considering fixed-gain relaying, analytical expressions for outage probability (OP) and average symbol error rate (ASER) are derived in closed-form. Numerical results are presented to demonstrate the efficacy of our performance analysis, also illustrate the impact of channel correlation, fading severity, Rician factor and antenna configuration on the performance of the system. It is shown that the correlated Nakagami-m/Rician fading channel can achieve better performance than the correlated Rician/Nakagami-m fading channel with the increase of fading severity parameter, and the correlated Rician/Nakagami-m fading channel may outperform the correlated Nakagami-m/Rician fading channel by enlarging the Rician factor.
DESIGN THREE PHASE OVERCURRENT RELAYS
Mohammed Y Suliman,
2013-05-01
Full Text Available A new design of three phase overcurrent relay described in this paper. The performance of the new design shows the ability to obtain any shape of characteristic with high accuracy and distinguish between transient and steady state fault. This design used more precise and flexible model Sachdev linear model for get any characteristic, also fast measurement theory to measure load current for less than half cycle and good hardware system design controlled by Pentium version 4 processor.
Analysis of Wideband Beamformers Designed with Artificial Neural Networks
1990-12-01
TECHNICAL REPORT 0-90-1 ANALYSIS OF WIDEBAND BEAMFORMERS DESIGNED WITH ARTIFICIAL NEURAL NETWORKS by Cary Cox Instrumentation Services Division...included. A briel tutorial on beamformers and neural networks is also provided. 14. SUBJECT TERMS 15, NUMBER OF PAGES Artificial neural networks Fecdforwa:,l...Beamformers Designed with Artificial Neural Networks ". The study was conducted under the general supervision of Messrs. George P. Bonner, Chief
Robust Beamforming for Amplify-and-Forward MIMO Relay Systems Based on Quadratic Matrix Programming
Xing, Chengwen; Wu, Yik-Chung; Ng, Tung-Sang
2010-01-01
In this paper, robust transceiver design based on minimum-mean-square-error (MMSE) criterion for dual-hop amplify-and-forward MIMO relay systems is investigated. The channel estimation errors are modeled as Gaussian random variables, and then the effect are incorporated into the robust transceiver based on the Bayesian framework. An iterative algorithm is proposed to jointly design the precoder at the source, the forward matrix at the relay and the equalizer at the destination, and the joint design problem can be efficiently solved by quadratic matrix programming (QMP).
Design of Fuze Antenna Beamformer Based on DSP
FENG Qing-juan; HUANG Zhong-hua; LI Ping
2007-01-01
According to the algorithm of the fuze antenna beamforming and the requirement for the realtime performence,a fuze antenna beamformer based on digital signal processor (DSP) was designed.The program was written in C,and in order to reduce the operation time of DSP,the key part of the matrix operation was written in simple algorithm.The precise and speediness of DSP calculation results were analyzed through Matlab and the Profiling tools in Code Composer Studio (CCS).The results show that the precise and the speediness both can satisfy the requirement for the fuze antenna beamforming.
Energy efficient circuit design using nanoelectromechanical relays
Venkatasubramanian, Ramakrishnan
Nano-electromechanical (NEM) relays are a promising class of emerging devices that offer zero off-state leakage and behave like an ideal switch. Recent advances in planar fabrication technology have demonstrated that microelectromechanical (MEMS) scale miniature relays could be manufactured reliably and could be used to build fully functional, complex integrated circuits. The zero leakage operation of relays has renewed the interest in relay based low power logic design. This dissertation explores circuit architectures using NEM relays and NEMS-CMOS heterogeneous integration. Novel circuit topologies for sequential logic, memory, and power management circuits have been proposed taking into consideration the NEM relay device properties and optimizing for energy efficiency and area. In nanoscale electromechanical devices, dispersion forces like Van der Waals' force (vdW) affect the pull-in stability of the relay devices significantly. Verilog-A electromechanical model of the suspended gate relay operating at 1V with a nominal air gap of 5 - 10nm has been developed taking into account all the electrical, mechanical and dispersion effects. This dissertation explores different relay based latch and flip-flop topologies. It has been shown that as few as 4 relay cells could be used to build flip-flops. An integrated voltage doubler based flip flop that improves the performance by 2X by overdriving Vgb has been proposed. Three NEM relay based parallel readout memory bitcell architectures have been proposed that have faster access time, and remove the reliability issues associated with previously reported serial readout architectures. A paradigm shift in design of power switches using NEM relays is proposed. An interesting property of the relay device is that the ON state resistance (Ron) of the NEM relay switch is constant and is insensitive to the gate slew rate. This coupled with infinite OFF state resistance (Roff ) offers significant area and power advantages over CMOS
Digital transceiver design for two-way AF-MIMO relay systems with imperfect CSI
Hu, Chia-Chang; Chou, Yu-Fei; Chen, Kui-He
2013-09-01
In the paper, combined optimization of the terminal precoders/equalizers and single-relay precoder is proposed for an amplify-and-forward (AF) multiple-input multiple-output (MIMO) two-way single-relay system with correlated channel uncertainties. Both terminal transceivers and relay precoding matrix are designed based on the minimum mean square error (MMSE) criterion when terminals are unable to erase completely self-interference due to imperfect correlated channel state information (CSI). This robust joint optimization problem of beamforming and precoding matrices under power constraints belongs to neither concave nor convex so that a nonlinear matrix-form conjugate gradient (MCG) algorithm is applied to explore local optimal solutions. Simulation results show that the robust transceiver design is able to overcome effectively the loss of bit-error-rate (BER) due to inclusion of correlated channel uncertainties and residual self-interference.
A robust beamformer design for underlay cognitive radio networks using worst case optimization
Wijewardhana, Uditha Lakmal; Codreanu, Marian; Latva-aho, Matti; Ephremides, Anthony
2014-01-01
We propose a robust beamforming design for underlay cognitive radio networks where multiple secondary transmitters communicate with corresponding secondary receivers and coexist with a primary network...
A NEW RELAY DESIGN FOR REACTIVE POWER COMPENSATION AND ECONOMICAL COMPARISION WITH CLASSICAL RELAY
Mustafa ŞEKKELİ
2007-02-01
Full Text Available In most cases, reactive power compensation is otomatically achieved with reactive power control relay by switching on and off, stationary shunt capasitors to the electrical network. İn this study , a new relay has been designed and developed. İn this method, capasitors which is switched on and of are optimally choosen. İn classical relay , only one capasitor can be added or extructed to the network. But,in designing new relay, 1,2 or 3 capasitor banks which are nearest value for desired inductive reactive power can be optimally choosen. As a result , switching number of capacitor and contactor is reduced minimum value and line is loaded less inductive current , it means that less active power losses. New designed relay has been compared with classical one economically . This relay has been manufactured and approved experimantally.
Filter-and-Forward Transparent Relay Design for OFDM Systems
Kim, Donggun; Sung, Youngchul
2012-01-01
In this paper, the filter-and-forward (FF) relay design for orthogonal frequency-division multiplexing (OFDM) transmission systems is considered to improve the system performance over simple amplify-and-forward (AF) relaying. Unlike conventional OFDM relays performing OFDM demodulation and remodulating, to reduce processing complexity, the proposed FF relay directly filters the incoming signal with a finite impulse response (FIR) and forwards the filtered signal to the destination. Two design criteria are considered to optimize the relay filter for given source power allocation. One is to minimize the relay transmit power subject to per-subcarrier signal-to-noise ratio (SNR) constraints and the other is to maximize the worst subcarrier channel SNR subject to the total relay transmit power constraint. It is shown that the two problems reduce to semi-definite programming (SDP) problems. Furthermore, the problem of joint source power allocation and relay filter design is considered for the second criterion, and ...
Design of chirped fiber gratings for optical beamforming networks
YE Ying-bo; SHI Pei-ming; HUANG Shan-guo; ZHOU Jing
2011-01-01
The properties of the linear chirped fiber grating (CFG) which is used in the true time delay unit of the optical beamforming networks (OBFNs) are studied intensively through theoretical analyses and numerical calculations.It is concluded that the dispersion of the CFG is equal to 1/(3Gc),where G is the chirp coefficient of CFG and c is the light speed.Based on this relationship,a simplified designing process of a CFG which satisfies the requirements of the OB FN is given.The simulation results are coincident with the theoretical conclusions.
Design of Fixed Beamformers Based on Vector-Sensor Arrays
Matthew Hawes
2015-01-01
Full Text Available Vector-sensor arrays such as those composed of crossed dipole pairs are used as they can account for a signal’s polarisation in addition to the usual direction of arrival information, hence allowing expanded capacity of the system. The problem of designing fixed beamformers based on such an array, with a quaternionic signal model, is considered in this paper. Firstly, we consider the problem of designing the weight coefficients for a fixed set of vector-sensor locations. This can be achieved by minimising the sidelobe levels while keeping a unitary response for the main lobe. The second problem is then how to find a sparse set of sensor locations which can be efficiently used to implement a fixed beamformer. We propose solving this problem by converting the traditional l1 norm minimisation associated with compressive sensing into a modified l1 norm minimisation which simultaneously minimises all four parts of the quaternionic weight coefficients. Further improvements can be made in terms of sparsity by converting the problem into a series of iteratively solved reweighted minimisations, as well as being able to enforce a minimum spacing between active sensor locations. Design examples are provided to verify the effectiveness of the proposed design methods.
Design of broadband beamformers based on an expected response interpolation technique
GUO Qili; SUN Chao; YANG Yixin
2006-01-01
A method for designing broadband beamformers based on an expected response interpolation technique was proposed, with the aim of reducing the heavy optimization burden in the broadband beamformer design problem. In the method, some typical fr equencies in the designing frequency band are selected and the optimal array weights are designed on these typical frequencies, based on which a broadband expected response function is constructed.Then, FIR filters are designed to realize the broadband beamforming over the whole designing frequency band, via the interpolation technique which is utilized to the expected responses of the FIR filters. Broadband beamforming can be fulfilled by applying these filters to each of the sensors in the array. By using the proposed method, designers need not to divide the whole designing frequency band into narrow subbands so as to make the narrow band assumption valid, which not only reduces the heavy designing burden, but also releases the requirement for measurements at fine frequency grids in the robust beamformer design. Results of both computer simulations and watertank experiments verify the effectiveness of the proposed method.
Joint Source and Relay Precoding Designs for MIMO Two-Way Relaying Based on MSE Criterion
Wang, Rui
2011-01-01
Properly designed precoders can significantly improve the spectral efficiency of multiple-input multiple-output (MIMO) relay systems. In this paper, we investigate joint source and relay precoding design based on the mean-square-error (MSE) criterion in MIMO two-way relay systems, where two multi-antenna source nodes exchange information via a multi-antenna amplify-and-forward relay node. This problem is non-convex and its optimal solution remains unsolved. Aiming to find an efficient way to solve the problem, we first decouple the primal problem into three tractable sub-problems, and then propose an iterative precoding design algorithm based on alternating optimization. The solution to each sub-problem is optimal and unique, thus the convergence of the iterative algorithm is guaranteed. Secondly, we propose a structured precoding design to lower the computational complexity. The proposed precoding structure is able to parallelize the channels in the multiple access (MAC) phase and broadcast (BC) phase. It th...
Hu, Chia-Chang; Su, Hao-Hsian; Tang, Kang-Tsao
2014-09-01
This paper considers a two-way multiple-input multiple-output (MIMO) relaying system with multiple relays between two terminals nodes. The relay antenna selection scheme based on channel singular valued decomposition (SVD) is used to reduce energy consumption. To enhance the system performance, we apply a SVD-based algorithm with MSE criterion which calculates optimal linear transceivers precoding jointly at the source nodes and relay nodes for amplify-and-forward (AF) protocols. In computer simulations, we use an iteration method to compute the non-convex function of joint source and relays power allocation. The simulation results show the SVD-based precoding design with SVD-based relay and antenna selection scheme can achieve a superior system bit error rate (BER) performance and reduce the power consume of relay antennas.
Software-based high-level synthesis design of FPGA beamformers for synthetic aperture imaging.
Amaro, Joao; Yiu, Billy Y S; Falcao, Gabriel; Gomes, Marco A C; Yu, Alfred C H
2015-05-01
Field-programmable gate arrays (FPGAs) can potentially be configured as beamforming platforms for ultrasound imaging, but a long design time and skilled expertise in hardware programming are typically required. In this article, we present a novel approach to the efficient design of FPGA beamformers for synthetic aperture (SA) imaging via the use of software-based high-level synthesis techniques. Software kernels (coded in OpenCL) were first developed to stage-wise handle SA beamforming operations, and their corresponding FPGA logic circuitry was emulated through a high-level synthesis framework. After design space analysis, the fine-tuned OpenCL kernels were compiled into register transfer level descriptions to configure an FPGA as a beamformer module. The processing performance of this beamformer was assessed through a series of offline emulation experiments that sought to derive beamformed images from SA channel-domain raw data (40-MHz sampling rate, 12 bit resolution). With 128 channels, our FPGA-based SA beamformer can achieve 41 frames per second (fps) processing throughput (3.44 × 10(8) pixels per second for frame size of 256 × 256 pixels) at 31.5 W power consumption (1.30 fps/W power efficiency). It utilized 86.9% of the FPGA fabric and operated at a 196.5 MHz clock frequency (after optimization). Based on these findings, we anticipate that FPGA and high-level synthesis can together foster rapid prototyping of real-time ultrasound processor modules at low power consumption budgets.
无
2003-01-01
The design and analysis of special type beamformer, the Butler matrix, to achieve orthogonal beamforming networks is presented in this paper. A 4×4 microstrip planar array antenna is assumed to simulate a 4×4 Butler matrix to demonstrate orthogonal beamforming and beam steering. The dimensions of rectangular patches in the planar array are chosen according to the Dolph-Chebyshev current distribution in order to minimize the side-lobe level ratio for a given value of beamwidth. The simulations are carried out using an antenna design and analysis software PCAAD. It is shown that orthogonal beams can be formed to cover about 163° angle with a constant beam crossover level and high directivity.
Beamforming in Ad Hoc Networks: MAC Design and Performance Modeling
Khalil Fakih
2009-01-01
Full Text Available We examine in this paper the benefits of beamforming techniques in ad hoc networks. We first devise a novel MAC paradigm for ad hoc networks when using these techniques in multipath fading environment. In such networks, the use of conventional directional antennas does not necessarily improve the system performance. On the other hand, the exploitation of the potential benefits of smart antenna systems and especially beamforming techniques needs a prior knowledge of the physical channel. Our proposition performs jointly channel estimation and radio resource sharing. We validate the fruitfulness of the proposed MAC and we evaluate the effects of the channel estimation on the network performance. We then present an accurate analytical model for the performance of IEEE 802.11 MAC protocol. We extend the latter model, by introducing the fading probability, to derive the saturation throughput for our proposed MAC when the simplest beamforming strategy is used in real multipath fading ad hoc networks. Finally, numerical results validate our proposition.
On the Beamforming Design for Efficient Interference Alignment
Choi, Sang Won; Chung, Sae-Young
2009-01-01
An efficient interference alignment (IA) scheme is developed for $K$-user single-input single-output frequency selective fading interference channels. The main idea is to steer the transmit beamforming matrices such that at each receiver the subspace dimensions occupied by interference-free desired streams are asymptotically the same as those occupied by all interferences. Our proposed scheme achieves a higher multiplexing gain at any given number of channel realizations in comparison with the original IA scheme, which is known to achieve the optimal multiplexing gain asymptotically.
Robust Nearfield Wideband Beamforming Design Based on Adaptive-Weighted Convex Optimization
Guo Ye-Cai
2017-01-01
Full Text Available Nearfield wideband beamformers for microphone arrays have wide applications in multichannel speech enhancement. The nearfield wideband beamformer design based on convex optimization is one of the typical representatives of robust approaches. However, in this approach, the coefficient of convex optimization is a constant, which has not used all the freedom provided by the weighting coefficient efficiently. Therefore, it is still necessary to further improve the performance. To solve this problem, we developed a robust nearfield wideband beamformer design approach based on adaptive-weighted convex optimization. The proposed approach defines an adaptive-weighted function by the adaptive array signal processing theory and adjusts its value flexibly, which has improved the beamforming performance. During each process of the adaptive updating of the weighting function, the convex optimization problem can be formulated as a SOCP (Second-Order Cone Program problem, which could be solved efficiently using the well-established interior-point methods. This method is suitable for the case where the sound source is in the nearfield range, can work well in the presence of microphone mismatches, and is applicable to arbitrary array geometries. Several design examples are presented to verify the effectiveness of the proposed approach and the correctness of the theoretical analysis.
Xi, Songnan; Zoltowski, Michael D.
2008-04-01
Multiuser multiple-input multiple-output (MIMO) systems are considered in this paper. We continue our research on uplink transmit beamforming design for multiple users under the assumption that the full multiuser channel state information, which is the collection of the channel state information between each of the users and the base station, is known not only to the receiver but also to all the transmitters. We propose an algorithm for designing optimal beamforming weights in terms of maximizing the signal-to-interference-plus-noise ratio (SINR). Through statistical modeling, we decouple the original mathematically intractable optimization problem and achieved a closed-form solution. As in our previous work, the minimum mean-squared error (MMSE) receiver with successive interference cancellation (SIC) is adopted for multiuser detection. The proposed scheme is compared with an existing jointly optimized transceiver design, referred to as the joint transceiver in this paper, and our previously proposed eigen-beamforming algorithm. Simulation results demonstrate that our algorithm, with much less computational burden, accomplishes almost the same performance as the joint transceiver for spatially independent MIMO channel and even better performance for spatially correlated MIMO channels. And it always works better than our previously proposed eigen beamforming algorithm.
A SDP based design of relay precoding for the power minimization of MIMO AF-relay networks
Rao, Anlei
2015-09-11
Relay precoding for multiple-input and multiple-output (MIMO) relay networks has been approached by either optimizing the efficiency performance with given power consumption constraints or minimizing the power consumption with quality-of-service (QoS) requirements. For the later type design, previous works has worked on minimizing the approximated power consumption. In this paper, exact power consumption for all relays is derived into a quadratic form by diagonalizing the minimum-square error (MSE) matrix, and the relay precoding matrix is designed by optimizing this quadratic form with the help of semidefinite programming (SDP) relaxation. Our simulation results show that such a design can achieve a gain of around 3 dB against the previous design, which optimized the approximated power consumption. © 2015 IEEE.
Mems Electromagnetic Micro Relays Overview and Design Considerations
Zuraini Dahari, Thurai Vinay and Dinesh Sood
2012-10-01
Full Text Available Miniature electromagnetic relay matrices capable of switching currents up to one ampere range are widely used in commercial applications such as instrumentation and telecommunication. Traditionally these devices have been fabricated from a number of discrete components, however in recent years the emergence of Micro Electro Mechanical System (MEMS technology has opened up the possibility for batch fabrication of microrelays at much reduced unit cost. While several electromagnetic microrelay designs have been successfully developed and commercialized for use as individual units, development work on electromagnetic microrelay matrices where individual relays can be selectively switched on and off have been fewer and less successful. Due to inherent limitations of the micromachining processes, significant dimensional and material property variations occur among individual relays in a matrix. These variations severely limit the tolerance window and hence the reliability of operation of the device. After reviewing existing designs of electromagnetic microrelays, a set of desirable design features that would make the electromagnetic microrelay more robust are identified. A novel design incorporating these features is proposed and preliminary results of ANSYS1 simulation studies are presented.Keywords: MEMS, microrelay and electromagnetic
Park, Kihong
2013-02-01
In this paper, we study a two-hop relaying network consisting of one source, one destination, and three amplify-and-forward (AF) relays with multiple antennas. To compensate for the capacity prelog factor loss of 1/2$ due to the half-duplex relaying, alternate transmission is performed among three relays, and the inter-relay interference due to the alternate relaying is aligned to make additional degrees of freedom. In addition, suboptimal linear filter designs at the nodes are proposed to maximize the achievable sum rate for different fading scenarios when the destination utilizes a minimum mean-square error filter. © 1967-2012 IEEE.
Hong, Mingyi; Baligh, Hadi; Luo, Zhi-Quan
2012-01-01
We consider the interference management problem in a multicell MIMO heterogenous network. Within each cell there are a large number of distributed micro/pico base stations (BSs) that can be potentially coordinated for joint transmission. To reduce coordination overhead, we consider user-centric BS clustering so that each user is served by only a small number of (potentially overlapping) BSs. Thus, given the channel state information, our objective is to jointly design the BS clustering and the linear beamformers for all BSs in the network. In this paper, we formulate this problem from a {sparse optimization} perspective, and propose an efficient algorithm that is based on iteratively solving a sequence of group LASSO problems. A novel feature of the proposed algorithm is that it performs BS clustering and beamformer design jointly rather than separately as is done in the existing approaches for partial coordinated transmission. Moreover, the cluster size can be controlled by adjusting a single penalty paramet...
Fundamentals of differential beamforming
Benesty, Jacob; Pan, Chao
2016-01-01
This book provides a systematic study of the fundamental theory and methods of beamforming with differential microphone arrays (DMAs), or differential beamforming in short. It begins with a brief overview of differential beamforming and some popularly used DMA beampatterns such as the dipole, cardioid, hypercardioid, and supercardioid, before providing essential background knowledge on orthogonal functions and orthogonal polynomials, which form the basis of differential beamforming. From a physical perspective, a DMA of a given order is defined as an array that measures the differential acoustic pressure field of that order; such an array has a beampattern in the form of a polynomial whose degree is equal to the DMA order. Therefore, the fundamental and core problem of differential beamforming boils down to the design of beampatterns with orthogonal polynomials. But certain constraints also have to be considered so that the resulting beamformer does not seriously amplify the sensors’ self noise and the mism...
Relaying experiences for care home design
Raudaskoski, Pirkko Liisa
2014-01-01
stakeholders (researchers, family members, etc.) could put forward their ideas and wishes about the facilities of a soon-to-be-built care home for people with brain injury. In other words, the seminar was part of a wider diagnostic endeavor that was to be started in a specially designed building. The future......The paper discusses organizational planning and decision making as situated material-semiotic practices in which various local and non-local meaningful elements (e.g. texts and photos) are invocated and resemiotized. The discussion is based on an analysis of a seminar meeting where different...
Design and Implementation of O/C relay using Microprocessor
Dr.Abdul-Sattar H. Jasim
2012-03-01
Full Text Available This work presents the design and implementation of a versatile digital overcurrent (O/C relay using a single microprocessor. The relay is implemented by a combination of a look-up table and a counter. The software development and hardware testing are done using a microcomputer module based on a 8-bit microprocessor. The digital processing of measured currents enables a separate setting of operating values selection of all types of inverse or constant time characteristics overcurrent protection. This protection provides reasonably fast tripping, even at terminal close to the power source were the most serve faults can occur excluding the transient condition. So this method has an excellent compromise between accuracy hardware and speed
Science Hybrid Orbiter and Lunar Relay (SCHOLR) Architecture and Design
Trase, Kathryn K.; Barch, Rachel A.; Chaney, Ryan E.; Coulter, Rachel A.; Gao, Hui; Huynh, David P.; Iaconis, Nicholas A.; MacMillan, Todd S.; Pitner, Gregory M.; Schwab, Devin T.
2011-01-01
Considered both a stepping-stone to deep space and a key to unlocking the mysteries of planetary formation, the Moon offers a unique opportunity for scientific study. Robotic precursor missions are being developed to improve technology and enable new approaches to exploration. Robots, lunar landers, and satellites play significant roles in advancing science and technologies, offering close range and in-situ observations. Science and exploration data gathered from these nodes and a lunar science satellite is intended to support future human expeditions and facilitate future utilization of lunar resources. To attain a global view of lunar science, the nodes will be distributed over the lunar surface, including locations on the far side of the Moon. Given that nodes on the lunar far side do not have direct line-of-sight for Earth communications, the planned presence of such nodes creates the need for a lunar communications relay satellite. Since the communications relay capability would only be required for a small portion of the satellite s orbit, it may be possible to include communication relay components on a science spacecraft. Furthermore, an integrated satellite has the potential to reduce lunar surface mission costs. A SCience Hybrid Orbiter and Lunar Relay (SCHOLR) is proposed to accomplish scientific goals while also supporting the communications needs of landers on the far side of the Moon. User needs and design drivers for the system were derived from the anticipated needs of future robotic and lander missions. Based on these drivers and user requirements, accommodations for communications payload aboard a science spacecraft were developed. A team of interns identified and compared possible SCHOLR architectures. The final SCHOLR architecture was analyzed in terms of orbiter lifetime, lunar surface coverage, size, mass, power, and communications data rates. This paper presents the driving requirements, operational concept, and architecture views for SCHOLR
Non-Regenerative Multi-Antenna Multi-Group Multi-Way Relaying
Klein Anja
2011-01-01
Full Text Available Abstract We consider non-regenerative multi-group multi-way (MGMW relaying. A half-duplex non-regenerative multi-antenna relay station (RS assists multiple communication groups. In each group, multiple half-duplex nodes exchange messages. In our proposal, the required number of communication phases is equal to the maximum number of nodes among the groups. In the first phase, all nodes transmit simultaneously to the RS. Assuming perfect channel state information is available at the RS, in the following broadcast (BC phases the RS applies transceive beamforming to its received signal and transmits simultaneously to all nodes. We propose three BC strategies for the BC phases: unicasting, multicasting and hybrid uni/multicasting. For the multicasting strategy, network coding is applied to maintain the same number of communication phases as for the other strategies. We address transceive beamforming maximising the sum rate of non-regenerative MGMW relaying. Due to the high complexity of finding the optimum transceive beamforming maximising the sum rate, we design generalised low complexity transceive beamforming algorithms for all BC strategies: matched filter, zero forcing, minimisation of mean square error and BC-strategy-aware transceive beamforming. It is shown that the sum rate performance of non-regenerative MGMW relaying depends both on the chosen BC strategies and the applied transceive beamforming at the RS.
Duplex Schemes in Multiple Antenna Two-Hop Relaying
Anja Klein
2008-04-01
Full Text Available A novel scheme for two-hop relaying defined as space division duplex (SDD relaying is proposed. In SDD relaying, multiple antenna beamforming techniques are applied at the intermediate relay station (RS in order to separate downlink and uplink signals of a bi-directional two-hop communication between two nodes, namely, S1 and S2. For conventional amplify-and-forward two-hop relaying, there appears a loss in spectral efficiency due to the fact that the RS cannot receive and transmit simultaneously on the same channel resource. In SDD relaying, this loss in spectral efficiency is circumvented by giving up the strict separation of downlink and uplink signals by either time division duplex or frequency division duplex. Two novel concepts for the derivation of the linear beamforming filters at the RS are proposed; they can be designed either by a three-step or a one-step concept. In SDD relaying, receive signals at S1 are interfered by transmit signals of S1, and receive signals at S2 are interfered by transmit signals of S2. An efficient method in order to combat this kind of interference is proposed in this paper. Furthermore, it is shown how the overall spectral efficiency of SDD relaying can be improved if the channels from S1 and S2 to the RS have different qualities.
Design of a multimode beamforming network based on the scattering matrix analysis
CHENG YuJian; HONG Wei; WU Ke
2009-01-01
The investigation of the multimode beamforming network (BFN) has been developed from its scattering matrix (S-matrix) analysis. A substrate integrated waveguide (SIW) BFN is designed and fabricated on a single Rogers 5880 substrate. This device is not only marked by features of conventional BFN, such as Butler matrix, but also has additional benefits, e.g. more compact configuration and higher radiation efficiency. Measured and simulated results based on the proposed structure are in a good agreement, which indicates that this novel type of BFN has good characteristics and presents an excellent candidate in the development of intelligent microwave and millimeter-wave multibeam antenna systems.
Colocated MIMO Radar: Beamforming, Waveform design, and Target Parameter Estimation
Jardak, Seifallah
2014-04-01
Thanks to its improved capabilities, the Multiple Input Multiple Output (MIMO) radar is attracting the attention of researchers and practitioners alike. Because it transmits orthogonal or partially correlated waveforms, this emerging technology outperformed the phased array radar by providing better parametric identifiability, achieving higher spatial resolution, and designing complex beampatterns. To avoid jamming and enhance the signal to noise ratio, it is often interesting to maximize the transmitted power in a given region of interest and minimize it elsewhere. This problem is known as the transmit beampattern design and is usually tackled as a two-step process: a transmit covariance matrix is firstly designed by minimizing a convex optimization problem, which is then used to generate practical waveforms. In this work, we propose simple novel methods to generate correlated waveforms using finite alphabet constant and non-constant-envelope symbols. To generate finite alphabet waveforms, the proposed method maps easily generated Gaussian random variables onto the phase-shift-keying, pulse-amplitude, and quadrature-amplitude modulation schemes. For such mapping, the probability density function of Gaussian random variables is divided into M regions, where M is the number of alphabets in the corresponding modulation scheme. By exploiting the mapping function, the relationship between the cross-correlation of Gaussian and finite alphabet symbols is derived. The second part of this thesis covers the topic of target parameter estimation. To determine the reflection coefficient, spatial location, and Doppler shift of a target, maximum likelihood estimation yields the best performance. However, it requires a two dimensional search problem. Therefore, its computational complexity is prohibitively high. So, we proposed a reduced complexity and optimum performance algorithm which allows the two dimensional fast Fourier transform to jointly estimate the spatial location
Distributed Multicell Beamforming Design Approaching Pareto Boundary with Max-Min Fairness
Huang, Yongming; Bengtsson, Mats; Wong, Kai-Kit; Yang, Luxi; Ottersten, Bjorn
2012-01-01
This paper addresses coordinated downlink beamforming optimization in multicell time-division duplex (TDD) systems where a small number of parameters are exchanged between cells but with no data sharing. With the goal to reach the point on the Pareto boundary with max-min rate fairness, we first develop a two-step centralized optimization algorithm to design the joint beamforming vectors. This algorithm can achieve a further sum-rate improvement over the max-min optimal performance, and is shown to guarantee max-min Pareto optimality for scenarios with two base stations (BSs) each serving a single user. To realize a distributed solution with limited intercell communication, we then propose an iterative algorithm by exploiting an approximate uplink-downlink duality, in which only a small number of positive scalars are shared between cells in each iteration. Simulation results show that the proposed distributed solution achieves a fairness rate performance close to the centralized algorithm while it has a bette...
An Approach to Optimum Joint Beamforming Design in a MIMO-OFDM Multiuser System
Pascual-Iserte Antonio
2004-01-01
Full Text Available This paper describes a multiuser scenario with several terminals acceding simultaneously to the same frequency channel. The objective is to design an optimal multiuser system that may be used as a comparative framework when evaluating other suboptimal solutions and to contribute to the already published works on this topic. The present work assumes that a centralized manager knows perfectly all the channel responses between all the terminals. According to this, the transmitters and receivers, using antenna arrays and leading to the so-called multiple-input-multiple-output (MIMO channels, are designed in a joint beamforming approach, attempting to minimize the total transmit power subject to quality of service (QoS constraints. Since this optimization problem is not convex, the use of the simulated annealing (SA technique is proposed to find the optimum solution.
Kwon, JaeWoo
2012-10-01
In this paper, we investigate a relay enhanced cellular system, where a relay station is located in the overlap area served by two base stations. We propose cooperative joint precoding schemes for the downlink transmission of such relay enhanced cellular system to maximize the system capacity while minimizing the interference at both the relay station and the mobile stations. We formulate the optimization problems to maximize the system capacity and design the multiuser precoding vectors at each base station and the relay station. We quantify the ergodic rate performance of the proposed multiuser precoding schemes through statistical analysis. The extensively derived ergodic expressions will facilitate the accurate performance evaluation of the proposed transmission schemes. Numerical results show that the proposed schemes can effectively cancel the interference and improve the sum rate and the outage performance for cell edge users. © 2002-2012 IEEE.
Design of Asymmetrical Relay Resonators for Maximum Efficiency of Wireless Power Transfer
Bo-Hee Choi
2016-01-01
Full Text Available This paper presents a new design method of asymmetrical relay resonators for maximum wireless power transfer. A new design method for relay resonators is demanded because maximum power transfer efficiency (PTE is not obtained at the resonant frequency of unit resonator. The maximum PTE for relay resonators is obtained at the different resonances of unit resonator. The optimum design of asymmetrical relay is conducted by both the optimum placement and the optimum capacitance of resonators. The optimum placement is found by scanning the positions of the relays and optimum capacitance can be found by using genetic algorithm (GA. The PTEs are enhanced when capacitance is optimally designed by GA according to the position of relays, respectively, and then maximum efficiency is obtained at the optimum placement of relays. The capacitance of the second resonator to nth resonator and the load resistance should be determined for maximum efficiency while the capacitance of the first resonator and the source resistance are obtained for the impedance matching. The simulated and measured results are in good agreement.
A novel beamformer design method for medical ultrasound. Part I: Theory.
Ranganathan, Karthik; Walker, William F
2003-01-01
The design of transmit and receive aperture weightings is a critical step in the development of ultrasound imaging systems. Current design methods are generally iterative, and consequently time consuming and inexact. We describe a new and general ultrasound beamformer design method, the minimum sum squared error (MSSE) technique. The MSSE technique enables aperture design for arbitrary beam patterns (within fundamental limitations imposed by diffraction). It uses a linear algebra formulation to describe the system point spread function (psf) as a function of the aperture weightings. The sum squared error (SSE) between the system psf and the desired or goal psf is minimized, yielding the optimal aperture weightings. We present detailed analysis for continuous wave (CW) and broadband systems. We also discuss several possible applications of the technique, such as the design of aperture weightings that improve the system depth of field, generate limited diffraction transmit beams, and improve the correlation depth of field in translated aperture system geometries. Simulation results are presented in an accompanying paper.
Frequency invariant beamforming via optimal array pattern synthesis and FIR filters design
YAN Shefeng; MA Yuanliang
2005-01-01
An approach to designing time domain broadband frequency invariant beamformer via optimal array pattern synthesis and optimal FIR filters design is proposed. First, the working frequency band is decomposed into a number of narrow band frequency bins. The array weights at each frequency bin are designed via optimal array pattern synthesis methods to insure that the synthesized pattern approximates the desired one within the mainlobe area.Then, a bank of FIR filters corresponding to the input channels are designed to provide the frequency responses that approximate the array weights in the working frequency band for each sensor. Finally, each sensor feeds a FIR filter and the filter outputs are summed to produce the beam output time series. Both array pattern synthesis and FIR filters design problems are formulated as the second-order cone programming (SOCP), which can be easily solved using well-developed interior-point methods. Results of computer simulations and lake-experiment for a twelve-element semicircular array demonstrate satisfactory performance of the proposed approach.
Counter-Measures for Relay Failures due to Dynamic Welding: A Robust Engineering Design
Schoepf, Thomas J.
In prior work, contact welding phenomena were observed in automotive relays during break of motor inrush current. The switching performance of the type of relay investigated could be correlated with the parameters: over-travel, coil suppression, and the break current. In the present work the author further explores the impact of both the contact material (silver tin oxide versus fine grain silver) and the contact surface topography (brand new and pre-aged contacts). He further assesses the robustness of the system “relay” with those parameters using the Taguchi methods for robust design. Furthermore, the robustness of two alternative automotive relay types will be discussed.
Distributed Beamforming with Feedback: Convergence Analysis
Lin, C; Meyn, S
2008-01-01
The focus of this work is on the analysis of transmit beamforming schemes with a low-rate feedback link in wireless sensor/relay networks, where nodes in the network need to implement beamforming in a distributed manner. Specifically, the problem of distributed phase alignment is considered, where neither the transmitters nor the receiver has perfect channel state information, but there is a low-rate feedback link from the receiver to the transmitters. In this setting, a framework for systematically analyzing the performance of a general set of distributed beamforming schemes is proposed. To illustrate the advantage of this framework, a simple adaptive distributed beamforming scheme that was recently proposed by Mudambai et al. is studied. Two important properties for the received signal magnitude function are derived. Using these properties and the systematic framework, it is shown that the adaptive distributed beamforming scheme converges both in probability and in mean. Furthermore, it is established that ...
Reference Beam Pattern Design for Frequency Invariant Beamforming Based on Fast Fourier Transform.
Zhang, Wang; Su, Tao
2016-09-22
In the field of fast Fourier transform (FFT)-based frequency invariant beamforming (FIB), there is still an unsolved problem. That is the selection of the reference beam to make the designed wideband pattern frequency invariant (FI) over a given frequency range. This problem is studied in this paper. The research shows that for a given array, the selection of the reference beam pattern is determined by the number of sensors and the ratio of the highest frequency to the lowest frequency of the signal (RHL). The length of the weight vector corresponding to a given reference beam pattern depends on the reference frequency. In addition, the upper bound of the weight length to ensure the FI property over the whole frequency band of interest is also given. When the constraints are added to the reference beam, it does not affect the FI property of the designed wideband beam as long as the symmetry of the reference beam is ensured. Based on this conclusion, a scheme for reference beam design is proposed.
Athanasopoulos, Georgios I; Carey, Stephen J; Hatfield, John V
2011-07-01
This paper describes the design of a programmable transmit beamformer application-specific integrated circuit (ASIC) with 8 channels for ultrasound imaging systems. The system uses a 20-MHz reference clock. A digital delay-locked loop (DLL) was designed with 50 variable delay elements, each of which provides a clock with different phase from a single reference. Two phase detectors compare the phase difference of the reference clock with the feedback clock, adjusting the delay of the delay elements to bring the feedback clock signal in phase with the reference clock signal. Two independent control voltages for the delay elements ensure that the mark space ratio of the pulses remain at 50%. By combining a 10- bit asynchronous counter with the delays from the DLL, each channel can be programmed to give a maximum time delay of 51 μs with 1 ns resolution. It can also give bursts of up to 64 pulses. Finally, for a single pulse, it can adjust the pulse width between 9 ns and 100 ns by controlling the current flowing through a capacitor in a one-shot circuit, for use with 40-MHz and 5-MHz transducers, respectively.
A Novel Design of Radio Frequency Energy Relays on Power Transmission Lines
Jin Tong
2016-06-01
Full Text Available In this paper, we investigate the energy problem of monitoring sensors on high-voltage power transmission lines and propose a wireless charging scheme for a Radio Frequency IDentification (RFID sensor tag to solve a commercial efficiency problem: the maintenance-caused power outage. Considering the environmental influences on power transmission lines, a self-powered wireless energy relay is designed to meet the energy requirement of the passive RFID sensor tag. The relay can obtain the electric field energy from the transmission lines and wirelessly power the RFID sensor tags around for longer operating distance. A prototype of the energy relay is built and tested on a 110 kv line. The measurement results show that the energy relay can provide stable energy even with the influences of wind, noise and power outage. To our knowledge, it is the first work to power the RFID sensor tags on power transmission lines.
Joint Linear Filter Design in Multiuser Cooperative Nonregenerative MIMO Relay Systems
Li Gen
2009-01-01
Full Text Available This paper addresses the filter design issues for multiuser cooperative nonregenerative MIMO relay systems in both downlink and uplink scenarios. Based on the formulated signal model, the filter matrix optimization is first performed for direct path and relay path respectively, aiming to minimize the mean squared error (MSE. To be more specific, for the relay path, we derive the local optimal filter scheme at the base station and the relay station jointly in the downlink scenario along with a more practical suboptimal scheme, and then a closed-form joint local optimal solution in the uplink scenario is exploited. Furthermore, the optimal filter for the direct path is also presented by using the exiting results of conventional MIMO link. After that, several schemes are proposed for cooperative scenario to combine the signals from both paths. Numerical results show that the proposed schemes can reduce the bit error rate (BER significantly.
GPU-Powered Coherent Beamforming
Magro, Alessio; Hickish, Jack
2014-01-01
GPU-based beamforming is a relatively unexplored area in radio astronomy, possibly due to the assumption that any such system will be severely limited by the PCIe bandwidth required to transfer data to the GPU. We have developed a CUDA-based GPU implementation of a coherent beamformer, specifically designed and optimised for deployment at the BEST-2 array which can generate an arbitrary number of synthesized beams for a wide range of parameters. It achieves $\\sim$1.3 TFLOPs on an NVIDIA Tesla K20, approximately 10x faster than an optimised, multithreaded CPU implementation. This kernel has been integrated into two real-time, GPU-based time-domain software pipelines deployed at the BEST-2 array in Medicina: a standalone beamforming pipeline and a transient detection pipeline. We present performance benchmarks for the beamforming kernel as well as the transient detection pipeline with beamforming capabilities as well as results of test observation.
Robust Transceiver Design for AF MIMO Relay Systems with Column Correlations
Xing, Chengwen; Wu, Yik-Chung; Ma, Shaodan; Kuang, Jingming
2012-01-01
In this paper, we investigate the robust transceiver design for dual-hop amplify-and-forward (AF) MIMO relay systems with Gaussian distributed channel estimation errors. Aiming at maximizing the mutual information under imperfect channel state information (CSI), source precoder at source and forwarding matrix at the relay are jointly optimized. Using some elegant attributes of matrix-monotone functions, the structures of the optimal solutions are derived first. Then based on the derived structure an iterative waterfilling solution is proposed. Several existing algorithms are shown to be special cases of the proposed solution. Finally, the effectiveness of the proposed robust design is demonstrated by simulation results.
Relay simulated moving bed chromatography: concept and design criteria.
Silva, Ricardo J S; Rodrigues, Rui C R; Mota, José P B
2012-10-19
We present a new class of multicolumn chromatographic processes that change the classical way of handling the product outlets of simulated moving-bed (SMB) chromatography to avoid the use of flow controllers or an extra pump-the objective is to have just two- or three-way valves at a column outlet-while maintaining the analogy with the SMB in terms of displaced volumes of fluid per switch interval. In this class of processes the flow through a zone (or column) is always in one of the three states: (i) frozen, (ii) completely directed to the next zone (or column), or (iii) entirely diverted to a product line. We use the term relayed stream to refer to this particular type of manipulation of the outflow from a column. For this class of processes we derive a SMB analog-the R-SMB process-and demonstrate, under the framework of the equilibrium theory, that this process has the same separation region as the classical SMB for linear adsorption systems. In addition, the results from the equilibrium theory show that the R-SMB process consists of two distinct cycles that differ only in their intermediate sub-step: one cycle for selectivities α smaller than (3+√5)/2 and another cycle for larger values of α; in the former case no product stream is collected during the intermediate sub-step, whereas in the latter case both product streams are collected. We also examine the R-SMB process under conditions of finite column efficiency and compare its performance against those of the classical open- and closed-loop SMBs. Our simulation results show that the R-SMB process requires less desorbent and is more productive than the standard SMB processes under conditions of finite column efficiency and that the comparison increasingly favors the R-SMB as the column efficiency decreases. Copyright © 2012 Elsevier B.V. All rights reserved.
Joint Robust Weighted LMMSE Transceiver Design for Dual-Hop AF Multiple-Antenna Relay Systems
Xing, Chengwen; Fei, Zesong; Wu, Yik-Chung; Kuang, Jingming
2012-01-01
In this paper, joint transceiver design for dual-hop amplify-and-forward (AF) MIMO relay systems with Gaussian distributed channel estimation errors in both two hops is investigated. Due to the fact that various linear transceiver designs can be transformed to a weighted linear minimum mean-square-error (LMMSE) transceiver design with specific weighting matrices, weighted mean square error (MSE) is chosen as the performance metric. Precoder matrix at source, forwarding matrix at relay and equalizer matrix at destination are jointly designed with channel estimation errors taken care of by Bayesian philosophy. Several existing algorithms are found to be special cases of the proposed solution. The performance advantage of the proposed robust design is demonstrated by the simulation results.
Xing, Chengwen; Wu, Yik-Chung; Ng, Tung-Sang
2010-01-01
In this paper, joint design of linear relay precoder and destination equalizer for dual-hop non-regenerative amplify-and-forward (AF) MIMO-OFDM systems under channel estimation errors is investigated. Second order moments of channel estimation errors in the two hops are first deduced. Then based on the Bayesian framework, joint design of linear robust precoder at the relay and equalizer at the destination is proposed to minimize the total mean-square-error (MSE) of the output signal at the destination. The optimal designs for both correlated and uncorrelated channel estimation errors are considered. The relationship with existing algorithms is also disclosed. Simulation results show that the proposed robust designs outperform the design based on estimated channel state information only.
Cross-Layer Design for Two-Way Relaying Networks with Multiple Antennas
zhuo wu
2015-10-01
Full Text Available In this paper, we developed a cross-layer design for two-way relaying (TWR networks with multiple antennas, where two single antenna source nodes exchange information with the aid of one multiple antenna relay node. The proposed cross-layer design considers adaptive modulation (AM and space-time block coding (STBC at the physical layer with an automatic repeat request (ARQ protocol at the data link layer, in order to maximize the spectral efficiency under specific delay and packet error ratio (PER constraints. An MMSE-interference cancellation (IC receiver is employed at the relay node, to remove the interference in the fist phase of the TWR transmission. The transmission mode is updated for each phase of the TWR transmission on a frame-by-frame basis, to match the time-varying channel conditions and exploit the system performance and throughput gain. Simulation results show that retransmission at the data link layer could alleviate rigorous error-control requirements at the physical layer, and thereby allows higher data transmission. As a result, cross-layer design helps to achieve considerable system spectral efficiency gain for TWR networks, compared to those without cross-layer design.
Broadband transceiver design of distributed amplify-and-forward MIMO relays in correlated channels
Hu, Chia-Chang; Tang, Kang-Tsao
2013-12-01
Combined optimization of the source precoder, relay weighting matrices, and destination decoder is proposed in dual-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) multiple-relay networks with the source-to-destination link in correlated channels. This broadband cooperative transceiver design is studied based on the minimum mean-squared error (MMSE) criterion under correlated fading channels. The optimization problem belongs neither concave nor convex so that an iterative nonlinear matrix conjugate gradient (MCG) search algorithm is applied to explore local optimal solutions. Simulation results show that the broadband cooperative transceiver joint architecture performs better the non-cooperative transceiver design in terms of the bit-error-rate (BER).
Malik, Muhammad Talha
2014-09-01
We propose a new bit-interleaved coded modulation (BICM)-based cooperative communication system where different BICM modules can be optimized jointly considering the average signal to noise ratios of the direct and the two-hop Rayleigh fading channels. As such, the full benefit of BICM can be exploited in the context of cooperative communication. Our design considers cooperative communication systems with so called max-min relay selection scheme that has no loss in performance in terms of diversity- multiplexing trade off in orthogonal cooperation. The presented numerical results for rate 1/2 convolutional code with 8-ary pulse amplitude modulation equivalently 64-ary quadrature amplitude modulation show that the proposed design can offer gains up to 1.4 dB over the traditional BICM design for a target bit error rate of 10-6. Moreover the results show that the amount of gain depends on the relays\\' positions and increases with the number of relays available for selection.
Preliminary Design Options for Meteor Burst Communications Systems Buoy Relays
1986-12-01
the lithium - thionyl chloride cell exhibit specific energies of the order of 500 watt hours per kilogram, more than 50 percent higher than previous...Supply Buoy Design Type 90 Day Storage Weight Type Energy Type Size (lb) Remote Lithium 2.2 kWh Deployable 8" x 8" x 4’ 200 Battery Pendulous Master...however, that there are various typcs of lithium batteries presently being developed that have energy densities equal to’fuel cell power systems. It is
Efficient Signal-Time Coding Design and its Application in Wireless Gaussian Relay Networks
Fan, Pingyi; Letaief, Khaled Ben
2009-01-01
Signal-time coding, which combines the traditional encoding/modulation mode in the signal domain with signal pulse phase modulation in the time domain, was proposed to improve the information flow rate in relay networks. In this paper, we mainly focus on the efficient signal-time coding design. We first derive an explicit iterative algorithm to estimate the maximum number of available codes given the code length of signal-time coding, and then present an iterative construction method of codebooks. It is shown that compared with conventional computer search, the proposed iterative construction method can reduce the complexity greatly. Numerical results will also indicate that the new constructed codebook is optimal in terms of coding rate. To minimize the buffer size needed to store the codebook while keeping a relatively high efficiency, we shall propose a combinatorial construction method. We will then consider applications in wireless Gaussian relay networks. It will be shown that in the three node network ...
Design and Implementation of Transport Relay Translator and its security Mitigations
P. Shanmugaraja
2013-08-01
Full Text Available The extensive growth of the Internet in the recent years has depleted all the IPv4 address space. It results in scarcity of the IPv4 addresses and leads to design of temporary techniques like NAT. IETF developed IPv6 to overcome this issue. IPv6 is more than 7.9×1028 times as many as IPv4. Again, it leads to a new issue of compatibility. IPv6 overcomes the problem of address scarcity but it is incompatible with IPv4 address. So machines configured with IPv4 and machines configured with IPv6 cannot communicate directly. This communication is mandatory because IPv6 cannot replace IPv4 rapidly. It takes time to convert completely from IPv4 infrastructure to IPv6 infrastructure. Until then, both should cooperate. Transition technologies developed to solve this incompatibility. One suchtechnology is Transport Relay Translator. It is based on RFC-3142. A translator located in the transport layer called as transport relay translator. The relay is located somewhere between the communicatinghosts and enables IPv6-only hosts to exchange traffic with IPv4-only hosts. A TRT, which runs on a dualstack node, can use one protocol when communicating with the client and another protocol when communicating with the application server. This paper discusses the implementation of TRT and methods to solve the security issues caused due to this translation.
A Bio-Inspired Robust Adaptive Random Search Algorithm for Distributed Beamforming
Tseng, Chia-Shiang; Lin, Che
2010-01-01
A bio-inspired robust adaptive random search algorithm (BioRARSA), designed for distributed beamforming for sensor and relay networks, is proposed in this work. It has been shown via a systematic framework that BioRARSA converges in probability and its convergence time scales linearly with the number of distributed transmitters. More importantly, extensive simulation results demonstrate that the proposed BioRARSA outperforms existing adaptive distributed beamforming schemes by as large as 29.8% on average. This increase in performance results from the fact that BioRARSA can adaptively adjust its sampling stepsize via the "swim" behavior inspired by the bacterial foraging mechanism. Hence, the convergence time of BioRARSA is insensitive to the initial sampling stepsize of the algorithm, which makes it robust against the dynamic nature of distributed wireless networks.
Transceiver Design for Dual-Hop Nonregenerative MIMO-OFDM Relay Systems Under Channel Uncertainties
Xing, Chengwen; Ma, Shaodan; Wu, Yik-Chung; Ng, Tung-Sang
2010-12-01
In this paper, linear transceiver design for dual-hop non-regenerative (amplify-and-forward (AF)) MIMO-OFDM systems under channel estimation errors is investigated. Second order moments of channel estimation errors in the two hops are first deduced. Then based on the Bayesian framework, joint design of linear forwarding matrix at the relay and equalizer at the destination under channel estimation errors is proposed to minimize the total mean-square-error (MSE) of the output signal at the destination. The optimal designs for both correlated and uncorrelated channel estimation errors are considered. The relationship with existing algorithms is also disclosed. Moreover, this design is extended to the joint design involving source precoder design. Simulation results show that the proposed design outperforms the design based on estimated channel state information only.
Ma, Hao
2012-06-01
In this thesis, we investigate two different system infrastructures in underlay cognitive radio network, in which two popular techniques, cross-layer design and cooperative communication, are considered, respectively. In particular, we introduce the Aggressive Adaptive Modulation and Coding (A-AMC) into the cross-layer design and achieve the optimal boundary points in closed form to choose the AMC and A-AMC transmission modes by taking into account the Channel State Information (CSI) from the secondary transmitter to both the primary receiver and the secondary receiver. What’s more, for the cooperative communication design, we consider three different relay selection schemes: Partial Relay Selection, Opportunistic Relay Selection and Threshold Relay Selection. The Probability Density Functions (PDFs) of the Signal-to- Noise Ratio (SNR) in each hop for different selection schemes are provided, and then the exact closed-form expressions for the end-to-end packet loss rate in the secondary link considering the cooperation of the Decode-and-Forward (DF) relay for different relay selection schemes are derived.
Ryu, Hyun-Seok; Park, Kyung-Mi; Lee, Hee-Soo; Kang, Chung-Gu
This letter proposes a type of mutually cooperative relaying (MCR) scheme based on a spatially coordinate-interleaved orthogonal design (SCID), in which two cooperative users are spatially multiplexed without bandwidth expansion. It provides not only diversity gain (with order of two) as in the existing MCR scheme, but also additional coding gain. Our simulation results demonstrate that the proposed SCID scheme is useful for improving the uplink performance as long as one user can find another active user as a close neighbor that is simultaneously communicating with the same destination, e.g., a base station in the cellular network.
Beamforming using compressive sensing.
Edelmann, Geoffrey F; Gaumond, Charles F
2011-10-01
Compressive sensing (CS) is compared with conventional beamforming using horizontal beamforming of at-sea, towed-array data. They are compared qualitatively using bearing time records and quantitatively using signal-to-interference ratio. Qualitatively, CS exhibits lower levels of background interference than conventional beamforming. Furthermore, bearing time records show increasing, but tolerable, levels of background interference when the number of elements is decreased. For the full array, CS generates signal-to-interference ratio of 12 dB, but conventional beamforming only 8 dB. The superiority of CS over conventional beamforming is much more pronounced with undersampling.
Ruigrok, Elmer; Gibbons, Steven; Wapenaar, Kees
2016-10-01
An areal distribution of sensors can be used for estimating the direction of incoming waves through beamforming. Beamforming may be implemented as a phase-shifting and stacking of data recorded on the different sensors (i.e., conventional beamforming). Alternatively, beamforming can be applied to cross-correlations between the waveforms on the different sensors. We derive a kernel for beamforming cross-correlated data and call it cross-correlation beamforming (CCBF). We point out that CCBF has slightly better resolution and aliasing characteristics than conventional beamforming. When auto-correlations are added to CCBF, the array response functions are the same as for conventional beamforming. We show numerically that CCBF is more resilient to non-coherent noise. Furthermore, we illustrate that with CCBF individual receiver-pairs can be removed to improve mapping to the slowness domain. An additional flexibility of CCBF is that cross-correlations can be time-windowed prior to beamforming, e.g., to remove the directionality of a scattered wavefield. The observations on synthetic data are confirmed with field data from the SPITS array (Svalbard). Both when beamforming an earthquake arrival and when beamforming ambient noise, CCBF focuses more of the energy to a central beam. Overall, the main advantage of CCBF is noise suppression and its flexibility to remove station pairs that deteriorate the signal-related beampower.
Robust Linear Transceiver Design for Multi-Hop Non-Regenerative MIMO Relaying Systems
Xing, Chengwen; Ma, Shaodan; Kuang, Jingming; Wu, Yik-Chung
2011-01-01
In this paper, optimal linear transceiver designs for multi-hop amplify-and-forward (AF) Multiple-input Multiple-out (MIMO) relaying systems with Gaussian distributed channel estimation errors are investigated. Some commonly used transceiver design criteria are unified into a single matrix-variate optimization problem. With novel applications of majorization theory and properties of matrix-variate function, the optimal structure of robust transceiver is first derived. Based on the optimal structure, the original transceiver design problems are reduced to much simpler problems with only scalar variables whose solutions are readily obtained by iterative water-filling algorithms. The performance advantages of the proposed robust designs are demonstrated by the simulation results.
Generic Multiuser Coordinated Beamforming for Underlay Spectrum Sharing
Denkovski, Daniel; Atanasovski, Vladimir; Gavrilovska, Liljana; Mähönen, Petri
2015-01-01
The beamforming techniques have been recently studied as possible enablers for underlay spectrum sharing. The existing beamforming techniques have several common limitations: they are usually system model specific, cannot operate with arbitrary number of transmit/receive antennas, and cannot serve arbitrary number of users. Moreover, the beamforming techniques for underlay spectrum sharing do not consider the interference originating from the incumbent primary system. This work extends the common underlay sharing model by incorporating the interference originating from the incumbent system into generic combined beamforming design that can be applied on interference, broadcast or multiple access channels. The paper proposes two novel multiuser beamforming algorithms for user fairness and sum rate maximization, utilizing newly derived convex optimization problems for transmit and receive beamformers calculation in a recursive optimization. Both beamforming algorithms provide efficient operation for the interfer...
Industrial Process Identification and Control Design Step-test and Relay-experiment-based Methods
Liu, Tao
2012-01-01
Industrial Process Identification and Control Design is devoted to advanced identification and control methods for the operation of continuous-time processes both with and without time delay, in industrial and chemical engineering practice. The simple and practical step- or relay-feedback test is employed when applying the proposed identification techniques, which are classified in terms of common industrial process type: open-loop stable; integrating; and unstable, respectively. Correspondingly, control system design and tuning models that follow are presented for single-input-single-output processes. Furthermore, new two-degree-of-freedom control strategies and cascade control system design methods are explored with reference to independently-improving, set-point tracking and load disturbance rejection. Decoupling, multi-loop, and decentralized control techniques for the operation of multiple-input-multiple-output processes are also detailed. Perfect tracking of a desire output trajectory is realiz...
Tomas Uricar
2010-01-01
Full Text Available The unavoidable parametrization of the wireless link represents a major problem of the network-coded modulation synthesis in a 2-way relay channel. Composite (hierarchical codeword received at the relay is generally parametrized by the channel gain, forcing any processing on the relay to be dependent on channel parameters. In this paper, we introduce the codebook design criteria, which ensure that all permissible hierarchical codewords have decision regions invariant to the channel parameters (as seen by the relay. We utilize the criterion for parameter-invariant constellation space boundary to obtain the codebooks with channel parameter-invariant decision regions at the relay. Since the requirements on such codebooks are relatively strict, the construction of higher-order codebooks will require a slightly simplified design criteria. We will show that the construction algorithm based on these relaxed criteria provides a feasible way to the design of codebooks with arbitrary cardinality. The promising performance benefits of the example codebooks (compared to a classical linear modulation alphabets will be exemplified on the minimum distance analysis.
Effective and versatile software beamformation toolbox
Kortbek, Jacob; Nikolov, Svetoslav; Jensen, Jørgen Arendt
2007-01-01
aperture to obtain a preferred constant F-number. An effective and versatile software toolbox for off-line beamformation designed to address all of these issues has been developed. It is capable of exploiting parallelization of computations on a Linux cluster and is written in C++ with a MATLAB (Math Works...... and stored in lookup-tables (LUT). Parametric beamforming can also be applied where calculations are done by demand, thus, reducing the storage demand dramatically. On a standard PC with a Pentium 4, 2.66 GHz processor running Linux the toolbox can beamform 100,000 points in lines of various directions in 20...
Microwave-powered airship system design for high-altitude power relay and other applications
Dickinson, R.M. [California Inst. of Tech., Pasadena, CA (United States). Guggenheim Jet Propulsion Center
1997-11-01
A concept for a next generation of stratospheric airship platforms was presented and examined. The design was based on a 1MW DC power output from beamed microwave power from the ground. The ground and airborne major subsystems were described. In the future, airborne near-stationary platforms could provide power beaming relay functions plus telecommunications and observation. The system will allow for near-continuous regional Earth sensing of soil moisture, crop condition, vehicular traffic on the ground or vessels at sea and craft in the air, environmental impacts, local weather, stream flow and floods, ice, migration patterns, land use, aerial photographs for mapping, surveillance, detection and tracking. A summary description of how the system might be applied and the currently available applicable technology was presented. System requirements and constraints were also described. A rough cost estimate of a point-design was provided. 22 refs., 1 fig.
Precoder Design and Power Allocation for MIMO Cognitive Radio Two-Way Relaying Systems
Sboui, Lokman
2016-08-11
In this paper, we study a multiple-antenna two-way relaying (TWR) cognitive radio (CR) system. A space alignment (SA) technique is adopted by the secondary users (SUs) to avoid interference with the primary users (PUs). We derive the optimal power allocation that maximizes the TWR achievable SU sum- rate while respecting the total power budget and the relay power constraints. We also analyze the case in which the relay is able to optimize its gain matrix structure to enhance the SU sum-rate. In the numerical results, we quantify the sum-rate gain of using the SA in the TWR CR and we show that the SU sum-rate is very limited when the relay power is low or the PU power and its resulting interference are high. In addition, we optimize the relay gain using an iterative algorithm and compare between different relay matrix structures.
Designing a Double-Pole Nanoscale Relay Based on a Carbon Nanotube: A Theoretical Study
Mu, Weihua; Ou-Yang, Zhong-can; Dresselhaus, Mildred S.
2017-08-01
We theoretically investigate a novel and powerful double-pole nanoscale relay based on a carbon nanotube, which is one of the nanoelectromechanical switches being able to work under the strong nuclear radiation, and analyze the physical mechanism of the operating stages in the operation, including "pull in," "connection," and "pull back," as well as the key factors influencing the efficiency of the devices. We explicitly provide the analytical expression of the two important operation voltages, Vpull in and Vpull back , therefore clearly showing the dependence of the material properties and geometry of the present devices by the analytical method from basic physics, avoiding complex numerical calculations. Our method is easy to use in preparing the design guide for fabricating the present device and other nanoelectromechanical devices.
Alternate MIMO relaying with three AF relays using interference alignment
Park, Kihong
2012-06-01
In this paper, we study a two-hop half-duplex relaying network with one source, one destination, and three amplify-and-forward (AF) relays equipped with M antennas each. We consider alternate transmission to compensate for the inherent loss of capacity pre-log factor 1/2 in half duplex mode, where source transmit message to two relays and the other relay alternately. The inter-relay interference caused by alternate transmission is aligned to make additional degrees of freedom (DOFs). It is shown that the proposed scheme enables us to exploit 3M/4 DOFs compared with the M/2 DOFs of conventional AF relaying. More specifically, suboptimal linear filter designs for a source and three relays are proposed to maximize the achievable sum-rate. We verify using some selected numerical results that the proposed filter designs give significant improvement of the sum-rate over a naive filter and conventional relaying schemes. © 2012 IEEE.
Rasmussen, Morten Fischer; Christiansen, Thomas Lehrmann; Thomsen, Erik Vilain
2015-01-01
-integrated apodization increased the apparent diameter of the vessel from 2.0 mm to 2.4 mm, corresponding to an increase from 67% to 80% of the true vessel diameter. The line element beamforming approach is shown to be essential for achieving correct time-of-flight calculations, and hence avoid geometrical distortions...
A Leakage-Based MMSE Beamforming Design for a MIMO Interference Channel
Sun, Fan; De Carvalho, Elisabeth
2012-01-01
We propose a low complexity design of the linear transmit filters for a MIMO interference channel. This design is based on a minimum mean squared error (MMSE) approach incorporating the signal and the interference leakage for each transmitter. Unlike the previous methods, it allows a closed...
Staff Association
2011-01-01
The CERN relay race will take place around the Meyrin site on Thursday 19th May starting at 12·15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on the course, and how to register your team for the relay race, can be found at: https://espace.cern.ch/Running-Club/CERN-Relay Some advice for all runners from the medical service can also be found here: https://espace.cern.ch/Running-Club/CERN-Relay/RelayPagePictures/MedicalServiceAnnoncement.pdf
Staff Association
2011-01-01
The CERN relay race will take place around the Meyrin site on Thursday 19th May starting at 12:15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on the course, and how to register your team for the relay race, can be found at: https://espace.cern.ch/Running-Club/CERN-Relay Some advice for all runners from the medical service can also be found here: https://espace.cern.ch/Running-Club/CERN-Relay/RelayPagePictures/MedicalServiceAnnoncement.pdf
Bhasin, Kul B.; Warner, Joseph D.; Oleson, Steven; Schier, James
2014-01-01
The main purpose of the Small Space-Based Geosynchronous Earth orbiting (GEO) satellite is to provide a space link to the user mission spacecraft for relaying data through ground networks to user Mission Control Centers. The Small Space Based Satellite (SSBS) will provide services comparable to those of a NASA Tracking Data Relay Satellite (TDRS) for the same type of links. The SSBS services will keep the user burden the same or lower than for TDRS and will support the same or higher data rates than those currently supported by TDRS. At present, TDRSS provides links and coverage below GEO; however, SSBS links and coverage capability to above GEO missions are being considered for the future, especially for Human Space Flight Missions (HSF). There is also a rising need for the capability to support high data rate links (exceeding 1 Gbps) for imaging applications. The communication payload on the SSBS will provide S/Ka-band single access links to the mission and a Ku-band link to the ground, with an optical communication payload as an option. To design the communication payload, various link budgets were analyzed and many possible operational scenarios examined. To reduce user burden, using a larger-sized antenna than is currently in use by TDRS was considered. Because of the SSBS design size, it was found that a SpaceX Falcon 9 rocket could deliver three SSBSs to GEO. This will greatly reduce the launch costs per satellite. Using electric propulsion was also evaluated versus using chemical propulsion; the power system size and time to orbit for various power systems were also considered. This paper will describe how the SSBS will meet future service requirements, concept of operations, and the design to meet NASA users' needs for below and above GEO missions. These users' needs not only address the observational mission requirements but also possible HSF missions to the year 2030. We will provide the trade-off analysis of the communication payload design in terms of
Weighted Sum-Rate Maximization Using Weighted MMSE for MIMO-BC Beamforming Design
Christensen, Søren; De Carvalho, Elisabeth; Agarwal, Rajiv
2009-01-01
This paper studies linear transmit filter design for weighted sum-rate (WSR) maximization in the multiple input multiple output broadcast channel (MIMO-BC). The problem of finding the optimal transmit filter is non-convex and intractable to solve using low complexity methods. Motivated by recent ...
Conceptual Design of a Communications Relay Satellite for a Lunar Sample Return Mission
Brunner, Christopher W.
2005-01-01
In 2003, NASA solicited proposals for a robotic exploration of the lunar surface. Submissions were requested for a lunar sample return mission from the South Pole-Aitken Basin. The basin is of interest because it is thought to contain some of the oldest accessible rocks on the lunar surface. A mission is under study that will land a spacecraft in the basin, collect a sample of rock fragments, and return the sample to Earth. Because the Aitken Basin is on the far side of the Moon, the lander will require a communications relay satellite (CRS) to maintain contact with the Earth during its surface operation. Design of the CRS's orbit is therefore critical. This paper describes a mission design which includes potential transfer and mission orbits, required changes in velocity, orbital parameters, and mission dates. Several different low lunar polar orbits are examined to compare their availability to the lander versus the distance over which they must communicate. In addition, polar orbits are compared to a halo orbit about the Earth-Moon L2 point, which would permit continuous communication at a cost of increased fuel requirements and longer transmission distances. This thesis also examines some general parameters of the spacecraft systems for the mission under study. Mission requirements for the lander dictate the eventual choice of mission orbit. This mission could be the first step in a period of renewed lunar exploration and eventual human landings.
Robustness Beamforming Algorithms
Sajad Dehghani
2014-04-01
Full Text Available Adaptive beamforming methods are known to degrade in the presence of steering vector and covariance matrix uncertinity. In this paper, a new approach is presented to robust adaptive minimum variance distortionless response beamforming make robust against both uncertainties in steering vector and covariance matrix. This method minimize a optimization problem that contains a quadratic objective function and a quadratic constraint. The optimization problem is nonconvex but is converted to a convex optimization problem in this paper. It is solved by the interior-point method and optimum weight vector to robust beamforming is achieved.
Robustness Beamforming Algorithms
Sajad Dehghani
2014-09-01
Full Text Available Adaptive beamforming methods are known to degrade in the presence of steering vector and covariance matrix uncertinity. In this paper, a new approach is presented to robust adaptive minimum variance distortionless response beamforming make robust against both uncertainties in steering vector and covariance matrix. This method minimize a optimization problem that contains a quadratic objective function and a quadratic constraint. The optimization problem is nonconvex but is converted to a convex optimization problem in this paper. It is solved by the interior-point method and optimum weight vector to robust beamforming is achieved.
Cross-layer design for cooperative MIMO systems with relay selection and imperfect CSI
YU XiangBin; ZHOU TingTing; RUI Yun; YIN Xin; CHEN Ming
2013-01-01
Based on imperfect channel state information （CSI） and relay selection, a cross-layer optimization scheme is developed for cooperative MIMO system, and the corresponding system performance is investigated in Rayleigh fading channel. By the theoretical analysis and mathematical manipulation, the average spectral efficiency （SE）, packet error rate （PER） and packet loss rate （PLR） are derived. As a result, closed-form expressions of the average SE, PER and PLR are obtained, respectively. According to these, a cross-layer design （CLD） scheme subject to the average PER constraints is proposed to avoid the SE performance loss caused by the conventional instantaneous PER constraints. The scheme optimizes the adaptive thresholds by maximizing the average SE of the system, and an iteration method joint the Lagrange multiplier and Newton methods is presented to solve the above optimization problem. Simulation results verify the validity of the theoretical analysis. The results show that the proposed CLD scheme can improve the SE while target PLR is maintained. The CLD scheme under average PER constraints has higher SE than the conventional CLD scheme under instantaneous PER constraints.
Cooperative Jamming for Secure Communications in MIMO Relay Networks
Huang, Jing
2011-01-01
Secure communications can be impeded by eavesdroppers in conventional relay systems. This paper proposes cooperative jamming strategies for two-hop relay networks where the eavesdropper can wiretap the relay channels in both hops. In these approaches, the normally inactive nodes in the relay network can be used as cooperative jamming sources to confuse the eavesdropper. Linear precoding schemes are investigated for two scenarios where single or multiple data streams are transmitted via a decode-and-forward (DF) relay, under the assumption that global channel state information (CSI) is available. For the case of single data stream transmission, we derive closed-form jamming beamformers and the corresponding optimal power allocation. Generalized singular value decomposition (GSVD)-based secure relaying schemes are proposed for the transmission of multiple data streams. The optimal power allocation is found for the GSVD relaying scheme via geometric programming. Based on this result, a GSVD-based cooperative jam...
Synthetic Aperture Sequential Beamforming and other Beamforming Techniques in Ultrasound Imaging
Kortbek, Jacob
This thesis consists of various subjects and applications within beamforming in general, and subjects within synthetic aperture focusing. An insight into the software architecture and beamformer design principles of a software beamformation toolbox is given. Some of the many considerations......, and up-sampling and FIR filtering. Directional beamforming for angle estimation of the velocity vector has been investigated using simulations and measurements. Using the measurements more than 96% valid estimates were produced for the flow angles q = {60±,75±,90±} and with a bias below 2± and a standard...... deviation below 5±. The two synthetic aperture imaging techniques described in this thesis are both candidates for a realistic implementation in a commercial scanner. In one technique synthetic aperture focusing (SAF) is applied to 2-dimensional imaging with a single rotating mechanically focused concave...
Protocol design and stability/delay analysis of half-duplex buffered cognitive relay systems
Chen, Yan; Zhang, Shunqing; Qiu, Peiliang
2010-01-01
In this paper, we quantify the benefits of employing relay station in large-coverage cognitive radio systems which opportunistically access the licensed spectrum of some small-coverage primary systems scattered inside. Through analytical study, we show that even a simple decode-and-forward (SDF) relay, which can hold only one packet, offers significant path-loss gain in terms of the spatial transmission opportunities and link reliability. However, such scheme fails to capture the spatial-temporal burstiness of the primary activities, that is, when either the source-relay (SR) link or relay-destination (RD) link is blocked by the primary activities, the cognitive spectrum access has to stop. To overcome this obstacle, we further propose buffered decode-and-forward (BDF) protocol. By exploiting the infinitely long buffer at the relay, the blockage time on either SR or RD link is saved for cognitive spectrum access. The buffer gain is shown analytically to improve the stability region and average end-to-end dela...
Energy efficient design for MIMO two-way AF multiple relay networks
Alsharoa, Ahmad M.
2014-04-01
This paper studies the energy efficient transmission and the power allocation problem for multiple two-way relay networks equipped with multi-input multi-output antennas where each relay employs an amplify-and-forward strategy. The goal is to minimize the total power consumption without degrading the quality of service of the terminals. In our analysis, we start by deriving closed-form expressions of the optimal powers allocated to terminals. We then employ a strong optimization tool based on the particle swarm optimization technique to find the optimal power allocated at each relay antenna. Our numerical results illustrate the performance of the proposed scheme and show that it achieves a sub-optimal solution very close to the optimal one.
Noncoherent Physical-Layer Network Coding with FSK Modulation: Relay Receiver Design Issues
2011-03-01
digital network coding ( DNC ) to distinguish it from ANC. Under 0090-6778/11$25.00 c⃝ 2011 IEEE Report Documentation Page Form ApprovedOMB No. 0704-0188...223 2596 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 59, NO. 9, SEPTEMBER 2011 many channel conditions, DNC offers enhanced performance over ANC. This...is because the decoding operation at the relay helps DNC to remove noise from the MAC phase, while the noise is amplied by the relay when ANC is used
Outage probability of distributed beamforming with co-channel interference
Yang, Liang
2012-03-01
In this letter, we consider a distributed beamforming scheme (DBF) in the presence of equal-power co-channel interferers for both amplify-and-forward and decode-and-forward relaying protocols over Rayleigh fading channels. We first derive outage probability expressions for the DBF systems. We then present a performance analysis for a scheme relying on source selection. Numerical results are finally presented to verify our analysis. © 2011 IEEE.
Design of network-coding based multi-edge type LDPC codes for multi-source relaying systems
Li, Jun; Malaney, Robert; Yuan, Jinhong
2009-01-01
In this paper we investigate a multi-source LDPC scheme for a Gaussian relay system, where M sources communicate with the destination under the help of a single relay (M-1-1 system). Since various distributed LDPC schemes in the cooperative single-source system, e.g. bilayer LDPC and bilayer multi-edge type LDPC (BMET-LDPC), have been designed to approach the Shannon limit, these schemes can be applied to the $M-1-1$ system by the relay serving each source in a round-robin fashion. However, such a direct application is not optimal due to the lack of potential joint processing gain. In this paper, we propose a network coded multi-edge type LDPC (NCMET-LDPC) scheme for the multi-source scenario. Through an EXIT analysis, we conclude that the NCMET-LDPC scheme achieves higher extrinsic mutual information, relative to a separate application of BMET-LDPC to each source. Our new NCMET-LDPC scheme thus achieves a higher threshold relative to existing schemes.
Beamforming Techniques for Large-N Aperture Arrays
Faulkner, A J; de Vaate, J G Bij; Kant, G W; Pickard, P
2010-01-01
Beamforming is central to the processing function of all phased arrays and becomes particularly challenging with a large number of antenna element (e.g. >100,000). The ability to beamform efficiently with reasonable power requirements is discussed in this paper. Whilst the most appropriate beamforming technology will change over time due to semiconductor and processing developments, we present a hierarchical structure which is technology agnostic and describe both Radio-Frequency (RF) and digital hierarchical beamforming approaches. We present implementations of both RF and digital beamforming systems on two antenna array demonstrators, namely the Electronic Multi Beam Radio Astronomy ConcEpt (EMBRACE) and the dualpolarisation all-digital array (2-PAD). This paper will compare and contrast both digital and analogue implementations without considering the deep system design of these arrays.
Beamformer for Cylindrical Conformal Array of Non-isotropic Antennas
ZOU, L.
2011-02-01
Full Text Available The principal objective of this investigation is to facilitate minimum variance distortionless response (MVDR beamforming technique for a cylindrical conformal array geometry. An array of directional radiating elements is postulated to cover a surface typical of the cylinder of an aircraft or missile. Borrowing the analysis of conformal array antennas, the authors first derive a deterministic expression that describes the beam pattern of arbitrary weighted cylindrical conformal array. Then, making use of the MVDR beamforming, we derive the beamformer for uniform linear array (ULA of directional antennas which are different from the traditional omnidirectional elements. Thus, the pattern of a directional element is synthesized by the antennas on the same ring array, and we design the MVDR beamformer, which uses MVDR beamforming for ULA of the synthesized pattern. To demonstrate the validity of the method, and cylinder arrays are constructed and experimental results agree well with theoretical expectations.
Torras Rosell, Antoni; Barrera Figueroa, Salvador; Jacobsen, Finn
2012-01-01
There is a great variety of beamforming techniques that can be used for localization of sound sources. The differences among them usually lie in the array layout or in the specific signal processing algorithm used to compute the beamforming output. Any beamforming system consists of a finite numb...
Beamforming with Reduced Complexity in MIMO Cooperative Cognitive Radio Networks
Mehdi Ghamari Adian
2014-01-01
Full Text Available An approach for beamforming with reduced complexity in MIMO cooperative cognitive radio networks (MIMO-CCRN is presented. Specifically, a suboptimal approach with reduced complexity is proposed to jointly determine the transmit beamforming (TB and cooperative beamforming (CB weight vectors along with antenna subset selection in MIMO-CCRN. Two multiantenna secondary users (SU constitute the desired link, one acting as transmitter (SU TX and the other as receiver (SU RX and they coexist with single-antenna primary and secondary users. Some of single antenna secondary users are recruited by desired link as cooperative relay. The maximization of the achievable rates in the desired link is the objective of this work, provided to interference constraints on the primary users are not violated. The objective is achieved by exploiting transmit beamforming at SU TX, cooperation of some secondary users, and cooperative beamforming. Meanwhile, the costs associated with RF chains at the radio front end at SU RX are reduced. Through simulations, it is shown that better performance in the desired link is attained, as a result of cooperation of SUs.
Hee-Nam Cho
2010-01-01
Full Text Available This paper considers coordinated transmission for interference mitigation and power allocation in a correlated two-user two-hop multi-input multioutput (MIMO relay system. The proposed transmission scheme utilizes statistical channel state information (CSI (e.g., transmit correlation to minimize the cochannel interference (CCI caused by the relay. To this end, it is shown that the CCI can be represented in terms of the eigenvalues and the angle difference between the eigenvectors of the transmit correlation matrix of the intended and CCI channel, and that the condition minimizing the CCI can be characterized by the correlation amplitude and the phase difference between the transmit correlation coefficients of these channels. Then, a coordinated user-scheduling strategy is designed with the use of eigen-beamforming to minimize the CCI in an average sense. The transmit power of the base station and relay is optimized under separate power constraint. Analytic and numerical results show that the proposed scheme can maximize the achievable sum rate when the principal eigenvectors of the transmit correlation matrix of the intended and the CCI channel are orthogonal to each other, yielding a sum rate performance comparable to that of the minimum mean-square error-based coordinated beamforming which uses instantaneous CSI.
Roberts, Lewis C., Jr.; Page, Norman A.; Burruss, Rick S.; Truong, Tuan N.; Dew, Sharon; Troy, Mitchell
2013-01-01
The Laser Communication Relay Demonstration will feature a geostationary satellite communicating via optical links to multiple ground stations. The first ground station (GS-1) is the 1m OCTL telescope at Table Mountain in California. The optical link will utilize pulse position modulation (PPM) and differential phase shift keying (DPSK) protocols. The DPSK link necessitates that adaptive optics (AO) be used to relay the incoming beam into the single mode fiber that is the input of the modem. The GS-1 AO system will have two MEMS Deformable mirrors to achieve the needed actuator density and stroke limit. The AO system will sense the aberrations with a Shack-Hartmann wavefront sensor using the light from the communication link's 1.55 microns laser to close the loop. The system will operate day and night. The system's software will be based on heritage software from the Palm 3000 AO system, reducing risk and cost. The AO system is being designed to work at r(sub 0) greater than 3.3 cm (measured at 500 nm and zenith) and at elevations greater than 20deg above the horizon. In our worst case operating conditions we expect to achieve Strehl ratios of over 70% (at 1.55 microns), which should couple 57% of the light into the single mode DPSK fiber. This paper describes the conceptual design of the AO system, predicted performance and discusses some of the trades that were conducted during the design process.
Multistage Relaying Using Interference Networks
Muthuramalingam, Bama; Thangaraj, Andrew
2010-01-01
Wireless networks with multiple nodes that relay information from a source to a destination are expected to be deployed in many applications. Therefore, understanding their design and performance under practical constraints is important. In this work, we propose and study three multihopping decode and forward (MDF) protocols for multistage half-duplex relay networks with no direct link between the source and destination nodes. In all three protocols, we assume no cooperation across relay nodes for encoding and decoding. Numerical evaluation in illustrative example networks and comparison with cheap relay cut-set bounds for half-duplex networks show that the proposed MDF protocols approach capacity in some ranges of channel gains. The main idea in the design of the protocols is the use of coding in interference networks that are created in different states or modes of a half-duplex network. Our results suggest that multistage half-duplex relaying with practical constraints on cooperation is comparable to point...
Constellation Precoded Multiple Beamforming
Park, Hong Ju; Ayanoglu, Ender
2009-01-01
Beamforming techniques that employ Singular Value Decomposition (SVD) are commonly used in Multi-Input Multi-Output (MIMO) wireless communication systems. In the absence of channel coding, when a single symbol is transmitted, these systems achieve the full diversity order provided by the channel; whereas when multiple symbols are simultaneously transmitted, this property is lost. When channel coding is employed, full diversity order can be achieved. For example, when Bit-Interleaved Coded Modulation (BICM) is combined with this technique, full diversity order of NM in an MxN MIMO channel transmitting S parallel streams is possible, provided a condition on S and the BICM convolutional code rate is satisfied. In this paper, we present constellation precoded multiple beamforming which can achieve the full diversity order both with BICM-coded and uncoded SVD systems. We provide an analytical proof of this property. To reduce the computational complexity of Maximum Likelihood (ML) decoding in this system, we emplo...
Joint Tilt Angle Adaptation and Beamforming in Multicell Multiuser Cellular Networks
Moghaddam, Soheil Khavari; Razavizadeh, S. Mohammad
2017-01-01
3D beamforming is a promising approach for interference coordination in cellular networks which brings significant improvements in comparison with conventional 2D beamforming techniques. This paper investigates the problem of joint beamforming design and tilt angle adaptation of the BS antenna array for maximizing energy efficiency (EE) in downlink of multi-cell multi-user coordinated cellular networks. An iterative algorithm based on fractional programming approach is introduced to solve the...
A General Robust Linear Transceiver Design for Multi-Hop Amplify-and-Forward MIMO Relaying Systems
Xing, Chengwen; Ma, Shaodan; Fei, Zesong; Wu, Yik-Chung; Poor, H. Vincent
2013-03-01
In this paper, linear transceiver design for multi-hop amplify-and-forward (AF) multiple-input multiple-out (MIMO) relaying systems with Gaussian distributed channel estimation errors is investigated. Commonly used transceiver design criteria including weighted mean-square-error (MSE) minimization, capacity maximization, worst-MSE/MAX-MSE minimization and weighted sum-rate maximization, are considered and unified into a single matrix-variate optimization problem. A general robust design algorithm is proposed to solve the unified problem. Specifically, by exploiting majorization theory and properties of matrix-variate functions, the optimal structure of the robust transceiver is derived when either the covariance matrix of channel estimation errors seen from the transmitter side or the corresponding covariance matrix seen from the receiver side is proportional to an identity matrix. Based on the optimal structure, the original transceiver design problems are reduced to much simpler problems with only scalar variables whose solutions are readily obtained by iterative water-filling algorithm. A number of existing transceiver design algorithms are found to be special cases of the proposed solution. The differences between our work and the existing related work are also discussed in detail. The performance advantages of the proposed robust designs are demonstrated by simulation results.
Adaptive broadband beamformer for nonuniform linear array based on second order cone programming
Chen Peng; Hou Chaohuan; Ma Xiaochuan; Cao Zhiqian; Liang Yicong; Yan Sheng
2009-01-01
Adaptive broadband beamforming is a key issue in array applications. The adaptive broadband beamformer with tapped delay line (TDL) structure for nonuniform linear array (NLA) is designed according to the rule of minimizing the beamformer's output power while keeping the distortionless response (DR) in the direction of desired signal and keeping the constant beamwidth (CB) with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming (SOCP). The computer simulations are presented which illustrate the effectiveness of our bearaformer.
Benkhelifa, Fatma
2017-03-02
In this paper, we investigate the simultaneous wireless information and power transfer (SWIPT) in a Multiple-Input Multiple-Output (MIMO) Amplify-and-Forward (AF) relay communication system where the relay is an energy harvesting (EH) node and harvests the energy the signals transmitted from the source. The harvested energy is partially used to forward signals from the source to the destination, and the remaining energy is stored for other usages. The SWIPT in relay-assisted communication is interesting as long as the relay stores energy from the source and the destination receives successfully the data from the source. In this context, we propose to investigate the source and relay precoders that characterize the relationship between the achievable stored energy at the relay and the achievable sourceto- destination rate, namely the rate-stored energy (R-E) tradeo region. First, we consider the ideal scheme where there is the simultaneous operation of the EH and ID receivers at the relay. Then, we consider practical schemes such as the power splitting (PS) and the time switching (TS) that separate the operation of EH and information decoding (ID) receivers over power domain or time domain, respectively. Moreover, we study the case of imperfect channel state information (CSI) at the relay and the destination and characterize its impact on the achievable R-E region. Through the simulation results, we show the eect of the position of the relay and the channel uncertainty on the achievable R-E regions of all the schemes when the used energy at the relay is constant or variable. We also show that, although it provides an outer bound on the achievable rate-energy region in one-hop MIMO systems, the ideal scheme provides only an upper bound on the maximum achievable end-to-end rate and not an outer bound on the R-E region.
Smart Antenna UKM Testbed for Digital Beamforming System
Islam, Mohammad Tariqul; Misran, Norbahiah; Yatim, Baharudin
2009-12-01
A new design of smart antenna testbed developed at UKM for digital beamforming purpose is proposed. The smart antenna UKM testbed developed based on modular design employing two novel designs of L-probe fed inverted hybrid E-H (LIEH) array antenna and software reconfigurable digital beamforming system (DBS). The antenna is developed based on using the novel LIEH microstrip patch element design arranged into [InlineEquation not available: see fulltext.] uniform linear array antenna. An interface board is designed to interface to the ADC board with the RF front-end receiver. The modular concept of the system provides the capability to test the antenna hardware, beamforming unit, and beamforming algorithm in an independent manner, thus allowing the smart antenna system to be developed and tested in parallel, hence reduces the design time. The DBS was developed using a high-performance [InlineEquation not available: see fulltext.] floating-point DSP board and a 4-channel RF front-end receiver developed in-house. An interface board is designed to interface to the ADC board with the RF front-end receiver. A four-element receiving array testbed at 1.88-2.22 GHz frequency is constructed, and digital beamforming on this testbed is successfully demonstrated.
Smart Antenna UKM Testbed for Digital Beamforming System
2009-03-01
Full Text Available A new design of smart antenna testbed developed at UKM for digital beamforming purpose is proposed. The smart antenna UKM testbed developed based on modular design employing two novel designs of L-probe fed inverted hybrid E-H (LIEH array antenna and software reconfigurable digital beamforming system (DBS. The antenna is developed based on using the novel LIEH microstrip patch element design arranged into 4×1 uniform linear array antenna. An interface board is designed to interface to the ADC board with the RF front-end receiver. The modular concept of the system provides the capability to test the antenna hardware, beamforming unit, and beamforming algorithm in an independent manner, thus allowing the smart antenna system to be developed and tested in parallel, hence reduces the design time. The DBS was developed using a high-performance TMS320C6711TM floating-point DSP board and a 4-channel RF front-end receiver developed in-house. An interface board is designed to interface to the ADC board with the RF front-end receiver. A four-element receiving array testbed at 1.88–2.22 GHz frequency is constructed, and digital beamforming on this testbed is successfully demonstrated.
A Proposed Chaotic-Switched Turbo Coding Design and Its Application for Half-Duplex Relay Channel
Tamer H. M. Soliman
2015-01-01
Full Text Available Both reliability and security are two important subjects in modern digital communications, each with a variety of subdisciplines. In this paper we introduce a new proposed secure turbo coding system which combines chaotic dynamics and turbo coding reliability together. As we utilize the chaotic maps as a tool for hiding and securing the coding design in turbo coding system, this proposed system model can provide both data secrecy and data reliability in one process to combat problems in an insecure and unreliable data channel link. To support our research, we provide different schemes to design a chaotic secure reliable turbo coding system which we call chaotic-switched turbo coding schemes. In these schemes the design of turbo codes chaotically changed depending on one or more chaotic maps. Extensions of these chaotic-switched turbo coding schemes to half-duplex relay systems are also described. Results of simulations of these new secure turbo coding schemes are compared to classical turbo codes with the same coding parameters and the proposed system is able to achieve secured reasonable bit error rate performance when it is made to switch between different puncturing and design configuration parameters especially with low switching rates.
Golden Coded Multiple Beamforming
Li, Boyu
2010-01-01
The Golden Code is a full-rate full-diversity space-time code, which achieves maximum coding gain for Multiple-Input Multiple-Output (MIMO) systems with two transmit and two receive antennas. Since four information symbols taken from an M-QAM constellation are selected to construct one Golden Code codeword, a maximum likelihood decoder using sphere decoding has the worst-case complexity of O(M^4), when the Channel State Information (CSI) is available at the receiver. Previously, this worst-case complexity was reduced to O(M^(2.5)) without performance degradation. When the CSI is known by the transmitter as well as the receiver, beamforming techniques that employ singular value decomposition are commonly used in MIMO systems. In the absence of channel coding, when a single symbol is transmitted, these systems achieve the full diversity order provided by the channel. Whereas this property is lost when multiple symbols are simultaneously transmitted. However, uncoded multiple beamforming can achieve the full div...
Development of Learning Board for the Digital Relay Using DSP
Ahn, Yong Jin; Choi, Young Woo [Youho Elec. Ind. Co., LTD. (Korea)
2002-07-01
A relaying board is developed for the study of digital relay, which is based on digital Signal Processor(DSP). The present development is capable of understanding and application for digital relay hardware. To support the design of relaying hardware, first A/D convertor, MMI and serial port for communication are embedded, and next a booting cables of three types are supplied. More particularly the relaying board that is convenient to test digital relaying algorithm. This paper concludes by into a relaying board. The hardware test results show practically high performance. (author). 35 refs., 10 figs.
Implementation of broadband low-sidelobe beamforming in time domain
YANG Yixin; SUN Chao; MA Yuanliang
2003-01-01
In modern active and passive sonar systems, broadband beamforming for acoustic arrays is widely used to suppress unwanted interference and to detect target signals of interest. A broadband low sidelobe beamforming scheme in time domain is proposed in this paper. The first step of this scheme is to delay the outputs of each element in the acoustic array by a tapped-delay-line (TDL) to accomplish the integer part of the time delay need to form a beam. Then, finite impulse response (FIR) digital filters are used to implement the fractional part of the time delay. The weighting coefficients for all array elements at different frequencies to realize the low sidelobe beams are also implemented with the FIR digital filters. Finally, the outputs of the digital filters are summed up to yield the time domain beam output. The design of low sidelobe beam pattern and that of the FIR digital filters are two crucial technical issues in this beamforming procedure. The low sidelobe beams of each sub-band are designed using the optimized beam synthesis approach based on the principle of MVDR beamforming. An improved adaptive approach are used for the design of FIR digital filters, and the design requirements of these filters were specified by the weights of low sidelobe beams of each sub-band over the broad frequency band. Results of computer simulation for a twelve-element arc array show that the beamforming scheme is very effective in forming low sidelobe broadband beam.
An Optimal Beamforming Algorithm for Phased-Array Antennas Used in Multi-Beam Spaceborne Radiometers
Iupikov, O. A.; Ivashina, M. V.; Pontoppidan, K.;
2015-01-01
Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays...
Performance Analysis of Optimal Single Stream Beamforming in MIMO Dual-Hop AF Systems
Zhong, Caijun; Jin, Shi; Wong, Kai Kit
2012-01-01
This paper investigates the performance of optimal single stream beamforming schemes in multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) systems. Assuming channel state information is not available at the source and relay, the optimal transmit and receive beamforming vectors are computed at the destination, and the transmit beamforming vector is sent to the transmitter via a dedicated feedback link. Then, a set of new closed-form expressions for the statistical properties of the maximum eigenvalue of the resultant channel is derived, i.e., the cumulative density function (cdf), probability density function (pdf) and general moments, as well as the first order asymptotic expansion and asymptotic large dimension approximations. These analytical expressions are then applied to study three important performance metrics of the system, i.e., outage probability, average symbol error rate and ergodic capacity. In addition, more detailed treatments are provided for some important special cases, ...
Sun, Fan; De Carvalho, Elisabeth
2012-01-01
This paper proposes a low-complexity design for the linear weighted MMSE (WMMSE) transmit filters of a coordinated multi-cell system with multiple users per cell. This design is based on a modified WMMSE approach applied to each transmitting base station individually incorporating the signals sent...... the linear transmit filter maximizing the weighted sum-rate of the multicell system. This algorithm is based on WMMSE where the MSE weights are optimally adjusted so that the WMMSE optimum coincides with the WSR optimum....
Photonic Beamformer Model Based on Analog Fiber-Optic Links’ Components
Volkov, V. A.; Gordeev, D. A.; Ivanov, S. I.; Lavrov, A. P.; Saenko, I. I.
2016-08-01
The model of photonic beamformer for wideband microwave phased array antenna is investigated. The main features of the photonic beamformer model based on true-time-delay technique, DWDM technology and fiber chromatic dispersion are briefly analyzed. The performance characteristics of the key components of photonic beamformer for phased array antenna in the receive mode are examined. The beamformer model composed of the components available on the market of fiber-optic analog communication links is designed and tentatively investigated. Experimental demonstration of the designed model beamforming features includes actual measurement of 5-element microwave linear array antenna far-field patterns in 6-16 GHz frequency range for antenna pattern steering up to 40°. The results of experimental testing show good accordance with the calculation estimates.
Optimization of a two-way MIMO amplify-and-forward relay network
Zhang, Ying; Chen, Yinjiang; Pan, Chuanyi; Zhao, Huapeng; Kang, Ning
2014-12-01
In this paper, we consider optimization of a two-way multiple-input multiple-output (MIMO) amplify-and-forward relay network which consists of a pair of transceivers and several relay nodes. Multiple antennas are equipped on the transceivers and relays. Multiple access broadcast scheme which finishes communication in two time slots is considered. In the first time slot, signals received by the relays are scaled by several beamforming matrices. In the second time slot, the relays transmit the scaled signals to the two transceivers. Upon receiving these signals, a MIMO equalizer is implemented at each transceiver to recover the desired signal. In this paper, zero forcing equalizers are used. Joint optimization of the beamforming matrices and the equalizers are realized using the following criteria: 1) the total relay transmission power is minimized subject to the minimal output signal-to-noise ratio (SNR) constraint at each transceiver, 2) the minimal output SNR of the two transceivers is maximized subject to total relay transmission power constraint, and 3) the minimal output SNR of the two transceivers is maximized subject to individual relay transmission power constraint. It is shown that the proposed optimization problems can be formulated as the second-order cone programming problems which can be solved efficiently. The validity of the proposed algorithm is verified by computer simulations.
Staff Association
2012-01-01
The CERN Relay Race will take place around the Meyrin site on Thursday 24th May at 12:00. This annual event is for teams of six runners covering distances of 1000 m, 800 m, 800 m, 500 m, 500 m and 300 m respectively. Teams may be entered in the Seniors, Veterans, Ladies, Mixed or Open categories. There will also this year be a Nordic Walking event, as part of the Medical Service’s initiative “Move more, eat better!” The registration fee is 10 CHF per runner, and each runner will receive a souvenir prize. There will be a programme of entertainment from 12:00 on the arrival area (the lawn in front of Restaurant 1): 12:00 - 12:45 Music from the Old Bottom Street band 12:15 Start of the race 12:45 - 13h Demonstrations by the Fitness club and Dancing club 13:00 Results and prize giving (including a raffle to win an iPad2 3G offered by the Micro club) 13:20 à 14:00 Music from “What’s next” And many information st...
Smith, Amos B; Kim, Won-Suk; Tong, Rongbiao
2010-02-05
Union of type II Anion Relay Chemistry (ARC) with Pd-induced Cross Coupling Reactions (CCR) has been achieved, in conjunction with the design, synthesis, and evaluation of a new class of bifunctional linchpins, comprising a series of vinyl silanes bearing beta- or gamma-electrophilic sites. The synthetic tactic permits both alkylation and Pd-mediated CCR of the anions derived via 1,4-silyl C(sp(2))-->O Brook Rearrangements.
A Delta-Sigma beamformer with integrated apodization
Tomov, Borislav Gueorguiev; Stuart, Matthias Bo; Hemmsen, Martin Christian
2013-01-01
remains the same as in an unmodified one. The outputs of all receiving channels are delayed and summed, and the resulting multi-bit sample stream is filtered and decimated to become an image line. The simplicity of this beamformer allows the production of high-channel-count or very compact beamformers......This paper presents a new design of a discrete time Delta-Sigma (ΔΣ) oversampled ultrasound beamformer which integrates individual channel apodization by means of variable feedback voltage in the Delta-Sigma analog to digital (A/D) converters. The output bit-width of each oversampled A/D converter...... suitable for 2-D arrays or compact portable scanners. The new design is evaluated using measured data from the research scanner SARUS and a BK-8811 192 element linear array transducer (BK Medical, Herlev, Denmark), insonifying a water-filled wire phantom containing four wires orthogonal to the image plane...
Research on Microelectromagnetic Relays
LI De-sheng; LIU Ben-dong
2006-01-01
A new microelectromagnetic relay is presented and fabricated based on micromachining technology,aiming at the miniaturization and high manufacturing efficiency of electromagnetic relays.This microrelay is composed of a lower magnetic circuit,a planar exciting coil,and an upper magnetic armature.A complete magnetic circuit is composed.and the"ON"and"OFF"states are controlled by the current of the exciting coil.The dimension Ofthis microrelay i 5 mm×5 mm×0.4 mm.The fabrication process mainly includes lithography,sputtering,electroplating,etching,sacrifice-layer technology,etc.Electromagnetic force is calculated theoretically.The calculation results are used for the optimization design of the armature and the number of tums of the exciting coil.A microelectromagnetic relay is fabricated and the initial test results are given.The resistance of the exciting coil is about 300 Ω.The switch-on state resistance is about 1.7 Ω at an exciting current of about 50 mA.
Integrated 60GHz RF beamforming in CMOS
Yu, Yikun; van Roermund, Arthur H M
2011-01-01
""Integrated 60GHz RF Beamforming in CMOS"" describes new concepts and design techniques that can be used for 60GHz phased array systems. First, general trends and challenges in low-cost high data-rate 60GHz wireless system are studied, and the phased array technique is introduced to improve the system performance. Second, the system requirements of phase shifters are analyzed, and different phased array architectures are compared. Third, the design and implementation of 60GHz passive and active phase shifters in a CMOS technology are presented. Fourth, the integration of 60GHz phase shifters
Theoretical Design and Simulation of an Overcurrent Relay with Dynamic Setting
Conde-Enriquez A.
2011-04-01
Full Text Available : This article presents the design and implementation of a speed controller for a DC motor through a buck converter, which tracks a smooth reference trajectory designed by a Bezier polynomial interpolation. The system reduces voltage and current sudden peaks in the armature circuit of the motor during the start. The calculation of the speed control is obtained from an output F called flat output (calculated through the Kalman controllability matrix. This control is based on feedback from all states rewritten in terms of the flat output and its successive derivatives for tracking the trajectory. With the aid of the pole placement technique it is possible to properly tune the controller in closed loop. The effectiveness of the system is verified experimentally by means of a platform that consists of the DC motor-buck converter and a PWM modulator.
Imaging and suppression of Lamb modes using adaptive beamforming
Engholm, Marcus; Stepinski, Tadeusz; Olofsson, Tomas
2011-08-01
Lamb waves have proven to be very useful for plate inspection because large areas of a plate can be covered from a fixed position. This capability makes them suitable for both inspection and structural health monitoring (SHM) applications. During the last decade, research on the use of active arrays in combination with beamforming techniques has shown that a fixed array can be used to perform omni-directional monitoring of a plate structure. The dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on conventional, delay-and-sum (DAS) beamforming, while reducing the effects of multiple modes through frequency selectivity and transducer design. The paper describes an adaptive beamforming technique using a minimum variance distortionless response beamforming (MVBF) approach for spatial Lamb wave filtering with multiple-transmitter-multiple-receiver arrays. Dispersion is compensated for by using theoretically calculated dispersion curves. Simulations are used for evaluating the performance of the technique for suppression of interfering Lamb modes, both with and without the presence of mode conversion using different array configurations. A simple simulation model of the plate is used to compare the performance of different sizes of active arrays. An aluminum plate with artificial defects is used for the experimental evaluation. The results show that the MVBF approach performs a lot better in terms of resolution and suppression of interfering modes than the widely used standard beamformer.
Adaptive Beamforming for Medical Ultrasound Imaging
Holfort, Iben Kraglund
This dissertation investigates the application of adaptive beamforming for medical ultrasound imaging. The investigations have been concentrated primarily on the Minimum Variance (MV) beamformer. A broadband implementation of theMV beamformer is described, and simulated data have been used...... to demonstrate the performance. The MV beamformer has been applied to different sets of ultrasound imaging sequences; synthetic aperture ultrasound imaging and plane wave ultrasound imaging. And an approach for applying MV optimized apodization weights on both the transmitting and the receiving apertures...
Broadband Minimum Variance Beamforming for Ultrasound Imaging
Holfort, Iben Kraglund; Gran, Fredrik; Jensen, Jørgen Arendt
2009-01-01
to the ultrasound data. As the error increases, it is seen that the MV beamformer is not as robust compared with the DS beamformer with boxcar an Harming weights. Nevertheless, it is noted that the DS does not outperform the MV beamformer. For errors of 2% and 4% of the correct value, the FWHM are {0.81, 1.25, 0...
Experimental evaluation of earthquake induced relay chattering
Bandyopadhyay, K.; Hofmayer, C.; Shteyngart, S.
1990-01-01
An experimental evaluation of relay performance under vibratory environments is discussed in this paper. Single frequency excitation was used for most tests. Limited tests were performed with random multifrequency inputs. The capacity of each relay was established based on a two-millisecond chatter criterion. The experimental techniques are described and the effects of parameters in controlling the relay capacity levels are illustrated with test data. A wide variation of the capacity levels was observed due to the influence of parameters related to the design of the relay and nature of the input motion. 3 refs., 15 figs.
Bit-Interleaved Coded Multiple Beamforming with Imperfect CSIT
Ayanoglu, Ersin Sengul Ender
2007-01-01
This paper addresses the performance of bit-interleaved coded multiple beamforming (BICMB) with imperfect knowledge of beamforming vectors. Various wireless standards become equivalent to BICMB when they are operated in beamforming mode. In BICMB, the invariance of the precoding matrix under an arbitrary unitary transform widely studied in the literature is not applicable. On the other hand, the optimum precoder and detector are not unique because of invariance under a diagonal unitary transform. We propose an optimal Euclidean distortion measure and a new linear detector. In addition, a new codebook design is proposed via the generalized Lloyd algorithm based on the new distortion measure. We provide simulation results demonstrating the performance improvement achieved with the proposed distortion measure and the linear detector.
Performance analysis of distributed beamforming in a spectrum sharing system
Yang, Liang
2012-09-01
In this paper, we consider a distributed beamforming scheme (DBF) in a spectrum sharing system where multiple secondary users share the spectrum with the licensed primary users under an interference temperature constraint. We assume that DBF is applied at the secondary users. We first consider optimal beamforming and compare it with the user selection scheme in terms of the outage probability and bit-error rate performance. Since perfect feedback is difficult to obtain, we then investigate a limited feedback DBF scheme and develop an outage probability analysis for a random vector quantization (RVQ) design algorithm. Numerical results are provided to illustrate our mathematical formalism and verify our analysis. © 2012 IEEE.
Sequential Beamforming Synthetic Aperture Imaging
Kortbek, Jacob; Jensen, Jørgen Arendt; Gammelmark, Kim Løkke
2013-01-01
Synthetic aperture sequential beamforming (SASB) is a novel technique which allows to implement synthetic aperture beamforming on a system with a restricted complexity, and without storing RF-data. The objective is to improve lateral resolution and obtain a more depth independent resolution...... and a range independent lateral resolution is obtained. The SASB method has been investigated using simulations in Field II and by off-line processing of data acquired with a commercial scanner. The lateral resolution increases with a decreasing F#. Grating lobes appear if F# 6 2 for a linear array with k-pitch...
Efficient incremental relaying
Fareed, Muhammad Mehboob
2013-07-01
We propose a novel relaying scheme which improves the spectral efficiency of cooperative diversity systems by utilizing limited feedback from destination. Our scheme capitalizes on the fact that relaying is only required when direct transmission suffers deep fading. We calculate the packet error rate for the proposed efficient incremental relaying scheme with both amplify and forward and decode and forward relaying. Numerical results are also presented to verify their analytical counterparts. © 2013 IEEE.
2011-09-01
18 Grant Ehrlich, "Lithium-Ion Batteries ," In Handbook of Batteries (Third Edition), ed. D. Linden and T. Reddy, (New York: McGraw...Ehrlich, Grant. "Lithium-Ion Batteries ." In Handbook of Batteries (Third Edition), edited by D. Linden and T. Reddy, 35.1–35.94, New York...Concept of Operations for a Clandestine Data Relay UUV To Circumvent Jungle Canopy Effects on Satellite Communications 6. AUTHOR( S ) Michael G.Tyree
An Optimal Beamforming Algorithm for Phased-Array Antennas Used in Multi-Beam Spaceborne Radiometers
Iupikov, O. A.; Ivashina, M. V.; Pontoppidan, K.
2015-01-01
Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays...... (FPA) in push-broom radiometers. This algorithm is formulated as an optimization procedure that maximizes the beam efficiency, while minimizing the side-lobe and cross-polarization power in the area of Earth, subject to a constraint on the beamformer dynamic range. The proposed algorithm is applied...
Lin Wang
2010-01-01
Full Text Available Frequency-domain blind source separation (BSS performs poorly in high reverberation because the independence assumption collapses at each frequency bins when the number of bins increases. To improve the separation result, this paper proposes a method which combines two techniques by using beamforming as a preprocessor of blind source separation. With the sound source locations supposed to be known, the mixed signals are dereverberated and enhanced by beamforming; then the beamformed signals are further separated by blind source separation. To implement the proposed method, a superdirective fixed beamformer is designed for beamforming, and an interfrequency dependence-based permutation alignment scheme is presented for frequency-domain blind source separation. With beamforming shortening mixing filters and reducing noise before blind source separation, the combined method works better in reverberation. The performance of the proposed method is investigated by separating up to 4 sources in different environments with reverberation time from 100 ms to 700 ms. Simulation results verify the outperformance of the proposed method over using beamforming or blind source separation alone. Analysis demonstrates that the proposed method is computationally efficient and appropriate for real-time processing.
An Opportunistic Relaying Selection Scheme Based on Relay Fairness
Ting An
2013-07-01
Full Text Available Opportunistic relaying scheme is a single cooperative relay selection method based on Channel State Information. However, the failure probability of the best relay selection may become unacceptable when the number of relays increases. Although most of the existing solutions can reduce the failure probability of relay selection, they ignore the fairness of the relay selection. In order to improve the fairness of the relay selection without affecting the failure probability of the best relay selection, we propose a modified practical best relay selection scheme in this paper, and by introducing proportional fair algorithm, the relay timer will be given a smaller correlation coefficient. The proposed method makes the probability of selection be improved. In the light of defined fairness factor, the relay fairness is represented. Simulation results show that the new algorithm can improve the fairness of the relay selection on the basis of maintaining the original failure probability of relay selection.
CERN Running Club
2010-01-01
The CERN relay race will take place around the Meyrin site on Thursday 20 May, starting at 12.15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on the route, and how to register your team for the relay race, can be found at: https://espace.cern.ch/Running-Club/CERN-Relay
Design of Mass transit vehicles Tc car relay cabinet%城轨车辆Tc车继电器柜的设计
赵爽
2016-01-01
介绍了城轨车辆Tc车继电器柜的骨架、组装与布线及安装设计，旨在规范Tc车继电器柜的设计，降低设计时的不确定性和复杂性，压缩产品开发时间以及减少总体成本。%the article introduces the design of the skeleton、assemble、wiring and install of Mass transit vehicles Tc car relay cabi-net,Objective is to standardize the design,reduce uncertainty and complexity,compression product design time and reduce total cost.
Borovikov, Yu S.; Sulaymanov, A. O.; Andreev, M. V.
2015-10-01
Development, research and operation of smart grids (SG) with active-adaptive networks (AAS) are actual tasks for today. Planned integration of high-speed FACTS devices greatly complicates complex dynamic properties of power systems. As a result the operating conditions of equipment of power systems are significantly changing. Such situation creates the new actual problem of development and research of relay protection and automation (RPA) which will be able to adequately operate in the SGs and adapt to its regimes. Effectiveness of solution of the problem depends on using tools - different simulators of electric power systems. Analysis of the most famous and widely exploited simulators led to the conclusion about the impossibility of using them for solution of the mentioned problem. In Tomsk Polytechnic University developed the prototype of hybrid multiprocessor software and hardware system - Hybrid Real-Time Power System Simulator (HRTSim). Because of its unique features this simulator can be used for solution of mentioned tasks. This article introduces the concept of development and research of relay protection and automation with usage of HRTSim.
Sleva, Anthony F
2009-01-01
This title lets you improve failure detection and optimize protection. In the ever-evolving field of protective relay technology, an engineer's personal preference and professional judgment are as important to power system protection as the physical relays used to detect and isolate abnormal conditions. With invaluable insights from an experienced expert, ""Protective Relay Principles"" focuses on probable power system failure modes and the important characteristics of the protective relays used to detect these postulated failures.This book presents useful new concepts in a way that is easier
Multiple Beamforming with Perfect Coding
Li, Boyu
2011-01-01
In Singular Value Decomposition (SVD) beamforming, without channel coding, there is a trade-off between full diversity and full multiplexing. Adding channel coding, full diversity and full multiplexing can be both achieved, as long as the code rate Rc and the number of subchannels S satisfy RcS1. Recently discovered Perfect Space-Time Block Codes (PSTBCs) are full-rate full-diversity space-time codes, achieving maximum coding gain. In this paper, two novel techniques, Perfect Coded Multiple Beamforming (PCMB) and Bit-Interleaved Coded Multiple Beamforming with Perfect Coding (BICMB-PC), are proposed, employing PSTBCs. PCMB achieves full diversity, full multiplexing, and full rate simultaneously, and its performance is close to PSTBC and FPMB, while the decoding complexity is significantly less than PSTBC and much lower than FPMB of dimensions 2 and 4. On the other hand, BICMB-PC achieves both full diversity and full multiplexing, and its performance is similar to BICMB-FP, but provides much lower decoding com...
Lightweight Distance Bounding Protocol against Relay Attacks
Kim, Jin Seok; Cho, Kookrae; Yum, Dae Hyun; Hong, Sung Je; Lee, Pil Joong
Traditional authentication protocols are based on cryptographic techniques to achieve identity verification. Distance bounding protocols are an enhanced type of authentication protocol built upon both signal traversal time measurement and cryptographic techniques to accomplish distance verification as well as identity verification. A distance bounding protocol is usually designed to defend against the relay attack and the distance fraud attack. As there are applications to which the distance fraud attack is not a serious threat, we propose a streamlined distance bounding protocol that focuses on the relay attack. The proposed protocol is more efficient than previous protocols and has a low false acceptance rate under the relay attack.
A low power, area efficient fpga based beamforming technique for 1-D CMUT arrays.
Joseph, Bastin; Joseph, Jose; Vanjari, Siva Rama Krishna
2015-08-01
A low power area efficient digital beamformer targeting low frequency (2MHz) 1-D linear Capacitive Micromachined Ultrasonic Transducer (CMUT) array is developed. While designing the beamforming logic, the symmetry of the CMUT array is well exploited to reduce the area and power consumption. The proposed method is verified in Matlab by clocking an Arbitrary Waveform Generator(AWG). The architecture is successfully implemented in Xilinx Spartan 3E FPGA kit to check its functionality. The beamforming logic is implemented for 8, 16, 32, and 64 element CMUTs targeting Application Specific Integrated Circuit (ASIC) platform at Vdd 1.62V for UMC 90nm technology. It is observed that the proposed architecture consumes significantly lesser power and area (1.2895 mW power and 47134.4 μm(2) area for a 64 element digital beamforming circuit) compared to the conventional square root based algorithm.
Optimal Selective Feedback Policies for Opportunistic Beamforming
Samarasinghe, Tharaka; Evans, Jamie S
2011-01-01
This paper studies the structure of downlink sum-rate maximizing selective decentralized feedback policies for opportunistic beamforming under finite feedback constraints on the average number of mobile users feeding back. Firstly, it is shown that any sum-rate maximizing selective decentralized feedback policy must be a threshold feedback policy. This result holds for all fading channel models with continuous distribution functions. Secondly, the resulting optimum threshold selection problem is analyzed in detail. This is a non-convex optimization problem over finite dimensional Euclidean spaces. By utilizing the theory of majorization, an underlying Schur-concave structure in the sum-rate function is identified, and the sufficient conditions for the optimality of homogenous threshold feedback policies are obtained. Applications of these results are illustrated for well known fading channel models such as Rayleigh, Nakagami and Rician fading channels, along with various engineering and design insights. Rathe...
Synthetic Aperture Beamformation using the GPU
Hansen, Jens Munk; Schaa, Dana; Jensen, Jørgen Arendt
2011-01-01
A synthetic aperture ultrasound beamformer is implemented for a GPU using the OpenCL framework. The implementation supports beamformation of either RF signals or complex baseband signals. Transmit and receive apodization can be either parametric or dynamic using a fixed F-number, a reference, and...... workstation with 2 quad-core Xeon-processors....
An analog integrated circuit beamformer for high-frequency medical ultrasound imaging.
Gurun, Gokce; Zahorian, Jaime S; Sisman, Alper; Karaman, Mustafa; Hasler, Paul E; Degertekin, F Levent
2012-10-01
We designed and fabricated a dynamic receive beamformer integrated circuit (IC) in 0.35-μm CMOS technology. This beamformer IC is suitable for integration with an annular array transducer for high-frequency (30-50 MHz) intravascular ultrasound (IVUS) imaging. The beamformer IC consists of receive preamplifiers, an analog dynamic delay-and-sum beamformer, and buffers for 8 receive channels. To form an analog dynamic delay line we designed an analog delay cell based on the current-mode first-order all-pass filter topology, as the basic building block. To increase the bandwidth of the delay cell, we explored an enhancement technique on the current mirrors. This technique improved the overall bandwidth of the delay line by a factor of 6. Each delay cell consumes 2.1-mW of power and is capable of generating a tunable time delay between 1.75 ns to 2.5 ns. We successfully integrated the fabricated beamformer IC with an 8-element annular array. Experimental test results demonstrated the desired buffering, preamplification and delaying capabilities of the beamformer.
APES Beamforming Applied to Medical Ultrasound Imaging
Blomberg, Ann E. A.; Holfort, Iben Kraglund; Austeng, Andreas
2009-01-01
Recently, adaptive beamformers have been introduced to medical ultrasound imaging. The primary focus has been on the minimum variance (MV) (or Capon) beamformer. This work investigates an alternative but closely related beamformer, the Amplitude and Phase Estimation (APES) beamformer. APES offers...... added robustness at the expense of a slightly lower resolution. The purpose of this study was to evaluate the performance of the APES beamformer on medical imaging data, since correct amplitude estimation often is just as important as spatial resolution. In our simulations we have used a 3.5 MHz, 96...... element linear transducer array. When imaging two closely spaced point targets, APES displays nearly the same resolution as the MV, and at the same time improved amplitude control. When imaging cysts in speckle, APES offers speckle statistics similar to that of the DAS, without the need for temporal...
Zhang, Haichong K.; Bell, Muyinatu A. Lediju; Guo, Xiaoyu; Kang, Hyun Jae; Boctor, Emad M.
2016-01-01
Photoacoustic (PA) imaging has been developed for various clinical and pre-clinical applications, and acquiring pre-beamformed channel data is necessary to reconstruct these images. However, accessing these pre-beamformed channel data requires custom hardware to enable parallel beamforming, and is available for a limited number of research ultrasound platforms. To broaden the impact of clinical PA imaging, our goal is to devise a new PA reconstruction approach that uses ultrasound post-beamformed radio frequency (RF) data rather than raw channel data, because this type of data is readily available in both clinical and research ultrasound systems. In our proposed Synthetic-aperture based photoacoustic re-beamforming (SPARE) approach, post-beamformed RF data from a clinical ultrasound scanner are considered as input data for an adaptive synthetic aperture beamforming algorithm. When receive focusing is applied prior to obtaining these data, the focal point is considered as a virtual element, and synthetic aperture beamforming is implemented assuming that the photoacoustic signals are received at the virtual element. The resolution and SNR obtained with the proposed method were compared to that obtained with conventional delay-and-sum beamforming with 99.87% and 91.56% agreement, respectively. In addition, we experimentally demonstrated feasibility with a pulsed laser diode setup. Results indicate that the post-beamformed RF data from any commercially available ultrasound platform can potentially be used to create PA images. PMID:27570697
Cooperative Relaying with State Available Non-Causally at the Relay
Zaidi, Abdellatif; Laneman, J Nicholas; Vandendorpe, Luc
2009-01-01
We consider a three-terminal state-dependent relay channel with the channel state noncausally available at only the relay. Such a model may be useful for designing cooperative wireless networks with some terminals equipped with cognition capabilities, i.e., the relay in our setup. In the discrete memoryless (DM) case, we establish lower and upper bounds on channel capacity. The lower bound is obtained by a coding scheme at the relay that uses a combination of codeword splitting, Gel'fand-Pinsker binning, and decode-and-forward relaying. The upper bound improves upon that obtained by assuming that the channel state is available at the source, the relay, and the destination. For the Gaussian case, we also derive lower and upper bounds on the capacity. The lower bound is obtained by a coding scheme at the relay that uses a combination of codeword splitting, generalized dirty paper coding, and decode-and-forward relaying; the upper bound is also better than that obtained by assuming that the channel state is avai...
Multidimensional-DSP Beamformers Using the ROACH-2 FPGA Platform
Vishwa Seneviratne
2017-07-01
Full Text Available Antenna array-based multi-dimensional infinite-impulse response (IIR digital beamformers are employed in a multitude of radio frequency (RF applications ranging from electronically-scanned radar, radio telescopes, long-range detection and target tracking. A method to design 3D IIR beam filters using 2D IIR beam filters is described. A cascaded 2D IIR beam filter architecture is proposed based on systolic array architecture as an alternative for an existing radar application. Differential-form transfer function and polyphase structures are employed in the design to gain an increase in the speed of operation to gigahertz range. The feasibility of practical implementation of a 4-phase polyphase 2D IIR beam filter is explored. A digital hardware prototype is designed, implemented and tested using a ROACH-2 Field Programmable Gate Array (FPGA platform fitted with a Xilinx Virtex-6 SX475T FPGA chip and multi-input analog-to-digital converters (ADC boards set to a maximum sampling rate of 960 MHz. The article describes a method to build a 3D IIR beamformer using polyphase structures. A comparison of technical specifications of an existing radar application based on phased-array and the proposed 3D IIR beamformer is also explained to illustrate the proposed method to be a better alternative for such applications.
Horowitz, Stanley H; Niemira, James K
2013-01-01
The previous three editions of Power System Relaying offer comprehensive and accessible coverage of the theory and fundamentals of relaying and have been widely adopted on university and industry courses worldwide. With the third edition, the authors have added new and detailed descriptions of power system phenomena such as stability, system-wide protection concepts and discussion of historic outages. Power System Relaying, 4th Edition continues its role as an outstanding textbook on power system protection for senior and graduate students in the field of electric power engineering and a refer
2008-01-01
The CERN relay race will take place around the Meyrin site on Thursday 5 June starting at 12:15 p.m. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on how to register your team for the relay race are given on the Staff Association Bulletin web site. You can access the online registration form at: http://cern.ch/club-running-relay/form.html
2007-01-01
The CERN relay race will take place around the Meyrin site on Wednesday 23 May starting at 12:15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details on how to register your team for the relay race are given on the Staff Association Bulletin web site. You can access the online registration form at: http://cern.ch/club-running-relay/form.html
LTE-Advanced Relay Technology and Standardization
Yuan, Yifei
2013-01-01
LTE-Advanced Relay Technology and Standardization provides a timely reference work for relay technology with the finalizing of LTE Release 10 specifications. LTE-Advanced is quickly becoming the global standard for 4G cellular communications. The relay technology, as one of the key features in LTE-Advanced, helps not only to improve the system coverage and capacity, but also to save the costs of laying wireline backhaul. As a leading researcher in the field of LTE-Advanced standards, the author provides an in-depth description of LTE-A relay technology, and explains in detail the standard specification and design principles. Readers from both academic and industrial fields can find sections of interest to them: Sections 2 & 4 could benefit researchers in academia and those who are engaged in exploratory work, while Sections 3 & 4 are more useful to engineers. Dr. Yifei Yuan is the Technical Director at the Standards Department of ZTE Inc.
Improved beamforming performance using pulsed plane wave decomposition
Munk, Peter; Jensen, Jørgen Arendt
2000-01-01
A tool for calculating the beamformer setup associated with a specified pulsed acoustic field is presented. The method is named Pulsed Plane Wave Decomposition (PPWD) and is based on the decomposition of a pulsed acoustic field into a set of PPWs at a given depth. Each PPW can be propagated...... to the location of the elements of an array transducer by a time delay. The contribution of each propagated PPW is summed to form one time function for each array element (the BMF matrix). This approach gives the beamformer setup needed to obtain a close approximation to the desired bounded pulsed acoustic field...... without involving any optimization scheme. The approximation arises due to the limited size of the acoustic aperture and the spatial sampling property of the array transducer. Thus, the acoustical field can be designed according to the imaging needs. The method is demonstrated by examples in the 2D space...
Concentric artificial impedance surface for directional sound beamforming
Song, Kyungjun; Anzan-Uz-Zaman, Md.; Kwak, Jun-Hyuk; Jung, Joo-Yun; Kim, Jedo; Hur, Shin
2017-03-01
Utilizing acoustic metasurfaces consisting of subwavelength resonant textures, we design an artificial impedance surface by creating a new boundary condition. We demonstrate a circular artificial impedance surface with surface impedance modulation for directional sound beamforming in three-dimensional space. This artificial impedance surface is implemented by revolving two-dimensional Helmholtz resonators with varying internal coiled path. Physically, the textured surface has inductive surface impedance on its inner circular patterns and capacitive surface impedance on its outer circular patterns. Directional receive beamforming can be achieved using an omnidirectional microphone located at the focal point formed by the gradient-impeding surface. In addition, the uniaxial surface impedance patterning inside the circular aperture can be used for steering the direction of the main lobe of the radiation pattern.
A recurrent neural network for adaptive beamforming and array correction.
Che, Hangjun; Li, Chuandong; He, Xing; Huang, Tingwen
2016-08-01
In this paper, a recurrent neural network (RNN) is proposed for solving adaptive beamforming problem. In order to minimize sidelobe interference, the problem is described as a convex optimization problem based on linear array model. RNN is designed to optimize system's weight values in the feasible region which is derived from arrays' state and plane wave's information. The new algorithm is proven to be stable and converge to optimal solution in the sense of Lyapunov. So as to verify new algorithm's performance, we apply it to beamforming under array mismatch situation. Comparing with other optimization algorithms, simulations suggest that RNN has strong ability to search for exact solutions under the condition of large scale constraints.
Relay Precoder Optimization in MIMO-Relay Networks With Imperfect CSI
Ubaidulla, P.
2011-11-01
In this paper, we consider robust joint designs of relay precoder and destination receive filters in a nonregenerative multiple-input multiple-output (MIMO) relay network. The network consists of multiple source-destination node pairs assisted by a MIMO-relay node. The channel state information (CSI) available at the relay node is assumed to be imperfect. We consider robust designs for two models of CSI error. The first model is a stochastic error (SE) model, where the probability distribution of the CSI error is Gaussian. This model is applicable when the imperfect CSI is mainly due to errors in channel estimation. For this model, we propose robust minimum sum mean square error (SMSE), MSE-balancing, and relay transmit power minimizing precoder designs. The next model for the CSI error is a norm-bounded error (NBE) model, where the CSI error can be specified by an uncertainty set. This model is applicable when the CSI error is dominated by quantization errors. In this case, we adopt a worst-case design approach. For this model, we propose a robust precoder design that minimizes total relay transmit power under constraints on MSEs at the destination nodes. We show that the proposed robust design problems can be reformulated as convex optimization problems that can be solved efficiently using interior-point methods. We demonstrate the robust performance of the proposed design through simulations. © 2011 IEEE.
2008-01-01
Thursday 5 June. With another year comes another success for CERN’s Relay Race. With 76 teams taking part it was the second highest turnout in the race’s history. ‘The Shabbys’ won the relay race in 10 minutes 51 seconds.As popular as ever, this year the relay race took on the atmosphere of a mini carnival. Gathering on the lawn outside Restaurant 1, various stalls and attractions added to the party feeling of the event, with beer courtesy of ‘AGLUP’, the Belgian beer club, and a wandering jazz group entertaining spectators and competitors alike. Reflecting the greater involvement of other associations in the relay race, the president of the Staff Association Clubs Committee, James Purvis, was the guest of honour, launching the start of the race and presenting the prizes. As regular followers of the race could have probably predicted, The Shabbys were once again victorious and claimed first place. The team members th...
Cooperative Interference Management in Multi-Cell Downlink Beamforming
Zhang, Rui
2009-01-01
This paper studies the downlink beamforming for a multi-cell system, where multiple base stations (BSs) each with multiple antennas cooperatively design their respective transmit beamforming vectors. It is assumed that all mobile stations (MSs) are equipped with a single antenna each, and there is one active MS in each cell at one time. Accordingly, the system of interest can be modeled by a multiple-input single-output (MISO) Gaussian interference channel (IC), termed as MISO-IC, with interference treated as additive Gaussian noise. We are interested in designing a multi-cell cooperative downlink beamforming scheme to achieve different rate-tuples for active MSs on the Pareto boundary of the achievable rate region for the MISO-IC, which is in general a non-convex problem due to the coupled signal structure. By exploring the relationship between the MISO-IC and the cognitive radio (CR) MISO channel, we show that each Pareto-boundary rate-tuple of the MISO-IC can be achieved when each of the MSs attains its ow...
2009-01-01
The CERN relay race will take place around the Meyrin site on Thursday 14th May starting at 12:15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. More details on how to register your team for the relay race
Beamformer for simultaneous magnetoencephalography and electroencephalography analysis
Ko, Seokha; Jun, Sung Chan
2010-05-01
We proposed the beamformer for simultaneous magnetoencephalography (MEG)/electroencephalography (EEG) analysis which has the synergy effects such as high spatial resolution, low localization bias and robustness for orientation of brain sources. Through Monte Carlo simulation study, it was found that the localization performance of our proposed beamformer was far superior to those of MEG-only and EEG-only. For the given specific sensor geometry (160 MEG, 50 EEG sensors), we investigated comparative localization performance of our proposed beamformer over various weighting factors of MEG data, while weighting factor of EEG keeps fixed. Furthermore, we demonstrated its capability for simulated two dipole problem and empirical somatosensory median nerve stimulation data.
Sungjoon Park,
2011-11-01
In this paper we present opportunistic relay communication strategies of decode and forward relaying. The channel that we are considering includes pathloss, shadowing, and fast fading effects. We find a simple outage probability formula for opportunistic relaying in the channel, and validate the results by comparing it with the exact outage probability. Also, we suggest a new relay selection algorithm that incorporates shadowing. We consider a protocol of broadcasting the channel gain of the previously selected relay. This saves resources in slow fading channel by reducing collisions in relay selection. We further investigate the optimal relay selection period to maximize the throughput while avoiding selection overhead. © 2011 IEEE.
Relay selection from an effective capacity perspective
Yang, Yuli
2013-09-01
In this work, we consider a cooperative network where multiple relay nodes having different modulation capabilities assist the end-to-end communication between a source and its destination. Firstly, we evaluate the effective capacity (EC) performance of the network under study. According to the analysis, an EC-based relay selection criterion is proposed. Based on the proposed selection rule and half-duplex decode-and-forward protocol, the activated relays cooperatively help with the packet transmission from the source. At the destination, packet combining is taken into account to improve the quality of service. Compared to the popular scheme, opportunistic relay selection, numerical results are provided to prove the validity and advantages of our proposed scheme in certain scenarios. Moreover, the analysis presented herein offers a convenient tool to the relaying transmission design, specifically on which relay selection scheme should be used as well as how to choose the receiving strategy between with and without packet combining at the destination. © 2013 IEEE.
Worst-Case SINR Constrained Robust Coordinated Beamforming for Multicell Wireless Systems
Shen, Chao; Chang, Tsung-Hui; Qiu, Zhengding; Chi, Chong-Yung
2011-01-01
Multicell coordinated beamforming (MCBF) has been recognized as a promising approach to enhancing the system throughput and spectrum efficiency of wireless cellular systems. In contrast to the conventional single-cell beamforming (SBF) design, MCBF jointly optimizes the beamforming vectors of cooperative base stations (BSs) (via a central processing unit(CPU)) in order to mitigate the intercell interference. While most of the existing designs assume that the CPU has the perfect knowledge of the channel state information (CSI) of mobile stations (MSs), this paper takes into account the inevitable CSI errors at the CPU, and study the robust MCBF design problem. Specifically, we consider the worst-case robust design formulation that minimizes the weighted sum transmission power of BSs subject to worst-case signal-to-interference-plus-noise ratio (SINR) constraints on MSs. The associated optimization problem is challenging because it involves infinitely many nonconvex SINR constraints. In this paper, we show that...
Glaser, Peter E.
The availability and use of renewable energy sources compatible with reducing risks to the global environment are key to sustainable development. Large-scale, renewable energy resources at undeveloped or underutilized sites are potentially available on several continents. The Power Relay Satellite (PRS) concept has the potential to access these remote energy resources by coupling primary electricity generation from terrestrial transmission lines. A global PRS network can be envisioned to provide a high degree of flexibility for supplying energy demands worldwide with wireless power transmitted from sites on Earth to geosynchronous orbit and then reflected to receivers interfacing with terrestrial power transmision networks. Past developments in wireless power transmission (WPT) are reviewed and recent successful results are noted. The origins of the PRS concept, and a possible configuration are discussed, principles of WPT at microwave frequencies, functional requirements, and system design contraints are outlined, and space transportation concepts presented. PRS assessments including applicable technologies, economic projections, and societal issues are highlighted. It is concluded that the PRS provides a promising option to access renewable resources at great distances from major markets, and represents an important stage in the future development in the future of solar power satellites.
Compact beamforming in medical ultrasound scanners
Tomov, Borislav Gueorguiev
2003-01-01
This Ph.D. project was carried out at the Center for Fast Ultrasound Imaging, Technical University of Denmark, under the supervision of Prof. Jørgen Arendt Jensen, Assoc. Prof. Jens Sparsø and Prof. Erik Bruun. The goal was to investigate methods for efficient beamforming, which make it possible...... compact implementation of the beamformer compared to the case where conventional A/D conversion is used. The compact and economic beamforming is a key aspect in the progress of medical ultrasound imaging. Currently, 64 or 128 channels are widely used in scanners, top-of-the-range scanners have 256...... with an introduction into medical ultrasound, its basic principles, system evolution and its place among medical imaging techniques. Then, ultrasound acoustics is introduced, as a necessary base for understanding the concepts of acoustic focusing and beamforming, which follow. The necessary focusing information...
Parametric Beamformer for Synthetic Aperture Ultrasound Imaging
Nikolov, Svetoslav; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt
2006-01-01
. The beamformer consists of a number of identical beamforming blocks, each processing data from several channels and producing part of the image. A number of these blocks can be accommodated in a modern field-programmable gate array device (FPGA), and a whole synthetic aperture system can be implemented using......In this paper a parametric beamformer, which can handle all imaging modalities including synthetic aperture imaging, is presented. The image lines and apodization coefficients are specified parametrically, and the lines can have arbitrary orientation and starting point in 3D coordinates...... several FPGAs. For the current implementation, the input data is sampled at 4 times the center frequency of the excitation pulse and is match-filtered in the frequency domain. In-phase and quadrature data are beamformed with a sub-sample precision of the focusing delays of 1/16th of the sampling period...
A NOVEL SUPER-RESOLUTION BEAMFORMING ALGORITHM
Guo Li; Guo Yan; Li Ning
2007-01-01
A novel simply-structured hybrid smart antenna system suitable to be used in ad-hoc network terminals is proposed in this letter.The super-resolution beamforming algorithm is also presented based on the system using DOA estimation results.The algorithm can switch the beamforming to the direction of the expected signal and get the best transmitting performance after the pre-beamforming of the Butler matrix.The shifting value formulas are presented to obtain the best SNR when there is no interfering signal and to acquire the highest Signal to Interference Ratio(SIR)as there is one interfering signal.When there are more than one interfering signals,the pre-beamforming feature of the Butler matrix Can also suppress the interfering signals.Simulation results verified the algorithm.
Zhang, Chao; Ren, Pinyi; Peng, Jingbo; Wei, Guo; Du, Qinghe; Wang, Yichen
2011-01-01
In this paper, we propose an optimal relay power allocation of an Amplify-and-Forward relay networks with non-linear power amplifiers. Based on Bussgang Linearization Theory, we depict the non-linear amplifying process into a linear system, which lets analyzing system performance easier. To obtain spatial diversity, we design a complete practical framework of a non-linear distortion aware receiver. Consider a total relay power constraint, we propose an optimal power allocation scheme to maxim...
Burfeindt, Matthew J.; Zastrow, Earl; Hagness, Susan C.; Van Veen, Barry D.; Medow, Joshua E.
2011-05-01
We present a numerical study of an array-based microwave beamforming approach for non-invasive hyperthermia treatment of pediatric brain tumors. The transmit beamformer is designed to achieve localized heating—that is, to achieve constructive interference and selective absorption of the transmitted electromagnetic waves at the desired focus location in the brain while achieving destructive interference elsewhere. The design process takes into account patient-specific and target-specific propagation characteristics at 1 GHz. We evaluate the effectiveness of the beamforming approach using finite-difference time-domain simulations of two MRI-derived child head models from the Virtual Family (IT'IS Foundation). Microwave power deposition and the resulting steady-state thermal distribution are calculated for each of several randomly chosen focus locations. We also explore the robustness of the design to mismatch between the assumed and actual dielectric properties of the patient. Lastly, we demonstrate the ability of the beamformer to suppress hot spots caused by pockets of cerebrospinal fluid (CSF) in the brain. Our results show that microwave beamforming has the potential to create localized heating zones in the head models for focus locations that are not surrounded by large amounts of CSF. These promising results suggest that the technique warrants further investigation and development.
Burfeindt, Matthew J; Zastrow, Earl; Hagness, Susan C; Van Veen, Barry D [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, WI (United States); Medow, Joshua E, E-mail: bmatthew@wisc.edu, E-mail: earl.zastrow@ieee.org, E-mail: hagness@engr.wisc.edu, E-mail: vanveen@engr.wisc.edu, E-mail: medow@neurosurg.wisc.edu [Department of Neurological Surgery, University of Wisconsin-Madison, WI (United States)
2011-05-07
We present a numerical study of an array-based microwave beamforming approach for non-invasive hyperthermia treatment of pediatric brain tumors. The transmit beamformer is designed to achieve localized heating-that is, to achieve constructive interference and selective absorption of the transmitted electromagnetic waves at the desired focus location in the brain while achieving destructive interference elsewhere. The design process takes into account patient-specific and target-specific propagation characteristics at 1 GHz. We evaluate the effectiveness of the beamforming approach using finite-difference time-domain simulations of two MRI-derived child head models from the Virtual Family (IT'IS Foundation). Microwave power deposition and the resulting steady-state thermal distribution are calculated for each of several randomly chosen focus locations. We also explore the robustness of the design to mismatch between the assumed and actual dielectric properties of the patient. Lastly, we demonstrate the ability of the beamformer to suppress hot spots caused by pockets of cerebrospinal fluid (CSF) in the brain. Our results show that microwave beamforming has the potential to create localized heating zones in the head models for focus locations that are not surrounded by large amounts of CSF. These promising results suggest that the technique warrants further investigation and development.
Relay Assisted F/TDMA Ad Hoc Networks: Node Classification, Power Allocation and Relaying Strategies
Serbetli, Semih
2007-01-01
This paper considers the design of relay assisted F/TDMA ad hoc networks with multiple relay nodes each of which assists the transmission of a predefined subset of source nodes to their respective destinations. Considering the sum capacity as the performance metric, we solve the problem of optimally allocating the total power of each relay node between the transmissions it is assisting. We consider four different relay transmission strategies, namely regenerative decode-and-forward (RDF), nonregenerative decode-and-forward (NDF), amplify-and-forward (AF) and compress-and-forward (CF). We first obtain the optimum power allocation policies for the relay nodes that employ a uniform relaying strategy for all nodes. We show that the optimum power allocation for the RDF and NDF cases are modified water-filling solutions. We observe that for a given relay transmit power, NDF always outperforms RDF whereas CF always provides higher sum capacity than AF. When CF and NDF are compared, it is observed that either of CF o...
Design of Beam-forming of Broadband Steerable-Parametric Array%相控参量阵波束合成设计
张富东; 徐利梅; 陈敏
2013-01-01
The simulation and analysis of beam-forming about broadband parametric array with rectangle trans-duction array and loop transduction array have been completed in this paper. The results show that under the condition of the same array element numbers with N=9 and same array size with rm = 49 mm,the - 3 dB beam width of rectangle array is about 6. 3° (comparing to 7. 4° of loop array), and its side-lobe amplitude is inhibited completely (comparing to the value of 10% about loop array). It means that the rectangle array is more effective at beam directivity improving and side-lobe amplitude inhibition. The method of element signal time-delay is used to parametric array signals beam-steering implement. As a result of Beam-steering, the beam main-lobe turned to width more, its peak value of amplitude reduces obviously,and it doesn't point to the direction which is planned to. The reasons of these problems are discussed in this paper. It is verified that these problems could be corrected by increasing array elements and spreading array size.%针对矩形和圆环形换能器阵列,完成了宽带参量阵信号的波束合成仿真与结果比较分析.仿真结果表明,同等阵元个数N=9、相似阵列边界半径rm=49 mm条件下,矩形阵列差频波波束主瓣-3 dB指向角约为6.3°(圆环阵列约为7.4°),旁瓣几乎被完全抑制(圆环阵列约为主瓣峰值的10％),矩形阵列更利于提高主瓣指向性和抑制旁瓣幅度.针对矩形阵列,该文仿真分析了采用阵元信号延时方法实现参量阵信号波束偏转时的各波束特征,仿真结果显示,偏转后波束存在主瓣峰值点幅值削弱、主瓣峰值点未对准预定方向、主瓣宽度增大等问题.分析表明,以上问题可通过增加阵元数目及增大阵列尺寸进行修正.
邹卫霞; 崔志芳; 李斌; 赵心言
2012-01-01
提出了一种支持60 GHz毫米波通信波束赋形机制的码本设计方法.为满足低功耗需求,码本设计仅进行相位移动而未作幅度调整,其中码本矩阵采用相位间隔相同、幅度为1的N个复数权值构建.仿真结果证实,与IEEE802.15.3c码本设计相比,高阶相位码本可获得相似的波束主瓣形状,同时波束将具有更低的旁瓣电平和更高的主瓣增益.该码本方案可在多用户环境下显著抑制空间干扰,提高网络累计信道容量,且对相位误差产生的波束偏移同样具有稳健性.%A method for codebook design is proposed to support beamforming mechanism in a 60 GHz millimeter-wave wireless communication environment. The codebook is designed with only phase shifting but not any amplitude adjustment to meet the low power consumption requirement. N complex numbers of the same phase interval and amplitude of 1 are designed to generate a codebook matrix. Simulation shows that, compared with the codebook in IEEE802. 15. 3c, a similar mainlobe patterns can be obtained in the proposed high-order codebook, while the sidelobe level appears lower, and the antenna gain at the direction of main response axis is higher. Meanwhile the interference decreases obviously with an improved total channel capacity in the practice environment, and the codebook is also robust to the beam shifting deriving from phase errors.
Ultrasound beamforming using compressed data.
Li, Yen-Feng; Li, Pai-Chi
2012-05-01
The rapid advancements in electronics technologies have made software-based beamformers for ultrasound array imaging feasible, thus facilitating the rapid development of high-performance and potentially low-cost systems. However, one challenge to realizing a fully software-based system is transferring data from the analog front end to the software back end at rates of up to a few gigabits per second. This study investigated the use of data compression to reduce the data transfer requirements and optimize the associated trade-off with beamforming quality. JPEG and JPEG2000 compression techniques were adopted. The acoustic data of a line phantom were acquired with a 128-channel array transducer at a center frequency of 3.5 MHz, and the acoustic data of a cyst phantom were acquired with a 64-channel array transducer at a center frequency of 3.33 MHz. The receive-channel data associated with each transmit event are separated into 8 × 8 blocks and several tiles before JPEG and JPEG2000 data compression is applied, respectively. In one scheme, the compression was applied to raw RF data, while in another only the amplitude of baseband data was compressed. The maximum compression ratio of RF data compression to produce an average error of lower than 5 dB was 15 with JPEG compression and 20 with JPEG2000 compression. The image quality is higher with baseband amplitude data compression than with RF data compression; although the maximum overall compression ratio (compared with the original RF data size), which was limited by the data size of uncompressed phase data, was lower than 12, the average error in this case was lower than 1 dB when the compression ratio was lower than 8.
Securing Relay Networks with Artificial Noise: An Error Performance-Based Approach
Ying Liu; Liang Li; George C Alexandropoulos; Marius Pesavento
2017-01-01
... (AN) symbols to jam the relay reception. The objective of our considered AN design is to degrade the error probability performance at the untrusted relay, for different types of channel state information (CSI) at the destination...
Amplify-and-forward relaying in wireless communications
Rodriguez, Leonardo Jimenez; Le-Ngoc, Tho
2015-01-01
This SpringerBrief explores the advantage of relaying techniques in addressing the increasing demand for high data rates and reliable services over the air. It demonstrates how to design cost-effective relay systems that provide high spectral efficiency and fully exploit the diversity of the relay channel. The brief covers advances in achievable rates, power allocation schemes, and error performance for half-duplex (HD) and full-duplex (FD) amplify-and-forward (AF) single-relay systems. The authors discuss the capacity and respective optimal power allocation for a wide range of HD protocols ov
Li, Jiangyuan; Petropulu, Athina P.; Poor, H. Vincent
2011-03-01
Cooperative beamforming in relay networks is considered, in which a source transmits to its destination with the help of a set of cooperating nodes. The source first transmits locally. The cooperating nodes that receive the source signal retransmit a weighted version of it in an amplify-and-forward (AF) fashion. Assuming knowledge of the second-order statistics of the channel state information, beamforming weights are determined so that the signal-to-noise ratio (SNR) at the destination is maximized subject to two different power constraints, i.e., a total (source and relay) power constraint, and individual relay power constraints. For the former constraint, the original problem is transformed into a problem of one variable, which can be solved via Newton's method. For the latter constraint, the original problem is transformed into a homogeneous quadratically constrained quadratic programming (QCQP) problem. In this case, it is shown that when the number of relays does not exceed three the global solution can always be constructed via semidefinite programming (SDP) relaxation and the matrix rank-one decomposition technique. For the cases in which the SDP relaxation does not generate a rank one solution, two methods are proposed to solve the problem: the first one is based on the coordinate descent method, and the second one transforms the QCQP problem into an infinity norm maximization problem in which a smooth finite norm approximation can lead to the solution using the augmented Lagrangian method.
Andreas Buechner
Full Text Available OBJECTIVE: To investigate the performance of monaural and binaural beamforming technology with an additional noise reduction algorithm, in cochlear implant recipients. METHOD: This experimental study was conducted as a single subject repeated measures design within a large German cochlear implant centre. Twelve experienced users of an Advanced Bionics HiRes90K or CII implant with a Harmony speech processor were enrolled. The cochlear implant processor of each subject was connected to one of two bilaterally placed state-of-the-art hearing aids (Phonak Ambra providing three alternative directional processing options: an omnidirectional setting, an adaptive monaural beamformer, and a binaural beamformer. A further noise reduction algorithm (ClearVoice was applied to the signal on the cochlear implant processor itself. The speech signal was presented from 0° and speech shaped noise presented from loudspeakers placed at ±70°, ±135° and 180°. The Oldenburg sentence test was used to determine the signal-to-noise ratio at which subjects scored 50% correct. RESULTS: Both the adaptive and binaural beamformer were significantly better than the omnidirectional condition (5.3 dB±1.2 dB and 7.1 dB±1.6 dB (p<0.001 respectively. The best score was achieved with the binaural beamformer in combination with the ClearVoice noise reduction algorithm, with a significant improvement in SRT of 7.9 dB±2.4 dB (p<0.001 over the omnidirectional alone condition. CONCLUSIONS: The study showed that the binaural beamformer implemented in the Phonak Ambra hearing aid could be used in conjunction with a Harmony speech processor to produce substantial average improvements in SRT of 7.1 dB. The monaural, adaptive beamformer provided an averaged SRT improvement of 5.3 dB.
2011-01-01
The CERN relay race will take place around the Meyrin site on Thursday 19 May starting at 12-15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. Thank you for your cooperation. Details of the course and of how to register your team for the relay race can be found here. Some advice for all runners from the Medical Service can also be found here.
Zhou, Weimin; Stead, Michael; Weiss, Steven; Okusaga, Olukayode; Jiang, Lingjun; Anderson, Stephen; Rena Huang, Z
2017-01-20
We have designed a simplified true-time-delay beamforming architecture using integrated photonics for phased-array antennas. This architecture can independently control multiple RF beams simultaneously with only a single tuning parameter to steer the beam in each direction for each beam. We have made a proof-of-the-principle demonstration of an X-band, 30×4-elements, fiber-optics-based beamformer for one-dimensional steering in transmission mode. The goal is to develop a semiconductor-based integrated photonic circuit so that a 2D beamforming array for both transmit and receive operations can be made on a single chip. For that, we have designed a Si-based integrated waveguide circuit using two types of "slow-light" waveguide for tunable time delays for two-dimensional steering.
电力通信中继无人机的设计与实现%Design and Implementation of UAV in Communication Relay
段星辉; 王建伟; 赵彦平; 杨孟卓
2016-01-01
文中设计实现了一套无人机通信中继系统，以增加前端作业无人机的巡航距离以及前端作业飞机的安全系数。通过实地拉锯测试，验证了该无人机通信中继系统对于提高前端作业无人机的巡检距离有增倍甚至更高的提高效果，有效改善了前端作业无人机的通信环境，提高了无人机巡检工作的安全性。%This paper designs the UAV communications relay system to increase the cruising distance and safety factor of aircraft. The test shows that the system has more obvious effect for the cruising distance of UAV. It improves the communi-cation environment effectively and the security of inspection work of the UAV.
Multiuser Beamforming with Limited Feedback for FDD Massive MIMO Systems
Senyao Zheng
2016-01-01
Full Text Available This paper discusses the multiuser beamforming in FDD massive MIMO systems. It first introduces the feature of FDD massive MIMO systems to implement multiuser beamforming schemes. After that, considering the realistic implementation of multiuser beamforming scheme in FDD massive MIMO systems, it introduces the knowledge of channel quantization. In the main part of the paper, we introduce two traditional multiuser beamforming schemes and analyse their merits and demerits. Based on these, we propose a novel multiuser beamforming scheme to flexibly combine the merits of the traditional beamforming schemes. In the final part of the paper, we give some simulation results to compare the beamforming schemes mentioned in the paper. These simulation results show the superiority of the proposed beamforming scheme.
Xiong, Wenhao; Wang, Gang; Tian, Xin; Pham, Khanh; Blasch, Erik; Chen, Genshe
2016-05-01
In this work, we propose a novel beam-forming power allocation method for a satellite communication (SATCOM) multiple-input multiple-output (MIMO) system to mitigate the co-channel interference (CCI) as well as limiting the signal leakage to the adversary users. In SATCOM systems, the beam-forming technique is a conventional way of avoiding interference, controlling the antenna beams, and mitigating undesired signals. We propose to use an advanced beam-forming technique which considers the number of independent channels used and transmitting power deployed to reduce and mitigate the unintentional interference effect. With certain quality of service (QoS) for the SATCOM system, independent channels components will be selected. It is desired to use less and stronger channel components when possible. On the other hand, considering that SATCOM systems often face the problem that adversary receiver detects the signal, a proposed power allocation method can efficiently reduce the received power at the adversary receiver. To reduce the computational burden on the transponder in order to minimize the size, mass, power consumption and delay for the satellite, we apply a hybrid onboard and ground based beam-forming design to distribute the calculation between the transponder and ground terminals. Also the digital channelizer beam-forming (DCB) technique is employed to achieve dynamic spatial control.
Patrice Loiez
2005-01-01
The CERN Relay Race takes place each year in May and sees participants from all areas of the CERN staff. The winners in 2005 were The Shabbys with Los Latinos Volantes in second and Charmilles Technologies a close third. To add a touch of colour and levity, the CERN Jazz Club provided music at the finishing line.
2009-01-01
The CERN relay race, now in its 39th year, is already a well-known tradition, but this year the organizers say the event will have even more of a festival feeling. Just off the starting line of the CERN relay race.For the past few years, spectators and runners at the CERN relay race have been able to enjoy a beer while listening to music from the CERN music and jazz clubs. But this year the organizers are aiming for "even more of a festival atmosphere". As David Nisbet, President of the CERN running club and organizer of the relay race, says: "Work is not just about getting your head down and doing the theory, it’s also about enjoying the company of your colleagues." This year, on top of music from the Santa Luis Band and the Canettes Blues Band, there will be demonstrations from the Aikido and softball clubs, a stretching session by the Fitness club, as well as various stalls and of course, the well-earned beer from AGLUP, the B...
李新民; 邱玲
2015-01-01
Massive MIMO technique can effectively increase system capacity in the fifth Generation (5G) cellular network, where Base Station (BS) is equipped with a very large number of antennas. Considering the impact of channel estimation error on performance, the transmission power minimization problem is formulated subject to the non-outage probability constraints of each user’s signal to interference plus noise ratio. In respect that the non-convex probability constraints make the downlink beamforming difficult to solve, Uplink-Downlink Duality Algorithm (UDDA) is proposed to design Coordinated BeamForming (CBF) by using the property of trace of the matrix to scale the non-convex probability constraint. To reduce the signaling overhead in Massive MIMO system, a Distributed Algorithm based on Large System Analysis (DALSA) is proposed, which only needs the large-scale channel information. The simulation results show that DALSA, in the targeted SINR constraint, not only reduces instantaneous channel state information transmission overhead in Massive MIMO system, but also performs well in robustness compared with UDDA.%大规模多输入多输出(Massive MIMO)技术通过在基站端配置大规模天线能有效提升5G蜂窝系统容量。考虑信道估计误差对系统性能的影响，该文在多小区大规模MIMO系统中形成了用户信干噪比的非溢出概率约束下最小化系统功率的优化问题。针对非凸概率约束中下行波束难于求解的问题，该文根据矩阵迹的性质将优化问题中的非凸约束缩放，进而提出上下行对偶算法求解波束矢量。为进一步减少多小区系统中信令开销，基于大系统分析，提出了仅采用大尺度信息的分布式算法。仿真结果表明，所提的分布式算法与对偶算法相比，在保证用户信干噪比的概率约束时，降低了大规模MIMO系统中传输瞬时信道状态信息的开销，同时具有良好的鲁棒性。
Cognitive Relay Networks: A Comprehensive Survey
Ayesha Naeem
2015-07-01
Full Text Available Cognitive radio is an emerging technology to deal with the scarcity and requirement of radio spectrum by dynamically assigning spectrum to unlicensed user . This revolutionary technology shifts the paradigm in the wireless system design by all owing unlicensed user the ability to sense, adapt and share the dynamic spectrum. Cognitive radio technology have been applied to different networks and applications ranging from wireless to public saf ety, smart grid, medical, rela y and cellular applications to increase the throughput and spectrum efficiency of the network. Among these applications, cognitive relay networks is one of the application where cognitive radio technology has been applied. Cognitiv e rela y network increases the network throughput by reducing the complete pa th loss and also by ensuring cooper ation among secondary users and cooperation among primary and secondary users. In this paper , our aim is to provide a survey on cognitive relay network. We also provide a detailed review on existing schemes in cognitive relay networks on the basis of relaying protocol, relay cooperation and channel model.
Beamforming in noninvasive brain-computer interfaces.
Grosse-Wentrup, Moritz; Liefhold, Christian; Gramann, Klaus; Buss, Martin
2009-04-01
Spatial filtering (SF) constitutes an integral part of building EEG-based brain-computer interfaces (BCIs). Algorithms frequently used for SF, such as common spatial patterns (CSPs) and independent component analysis, require labeled training data for identifying filters that provide information on a subject's intention, which renders these algorithms susceptible to overfitting on artifactual EEG components. In this study, beamforming is employed to construct spatial filters that extract EEG sources originating within predefined regions of interest within the brain. In this way, neurophysiological knowledge on which brain regions are relevant for a certain experimental paradigm can be utilized to construct unsupervised spatial filters that are robust against artifactual EEG components. Beamforming is experimentally compared with CSP and Laplacian spatial filtering (LP) in a two-class motor-imagery paradigm. It is demonstrated that beamforming outperforms CSP and LP on noisy datasets, while CSP and beamforming perform almost equally well on datasets with few artifactual trials. It is concluded that beamforming constitutes an alternative method for SF that might be particularly useful for BCIs used in clinical settings, i.e., in an environment where artifact-free datasets are difficult to obtain.
A study into the design of steerable microphone arrays
Lai, Chiong Ching; Leung, Yee Hong
2017-01-01
The book covers the design formulations for broadband beamformer targeting nearfield and farfield sources. The book content includes background information on the acoustic environment, including propagation medium, the array geometries, signal models and basic beamformer designs. Subsequently it introduces design formulation for nearfield, farfield and mixed nearfield-farfield beamformers and extends the design formulation into electronically steerable beamformers. In addition, a robust formulation is introduced for all the designs mentioned.
A Multi-Interference-Channel Matrix Pair Beamformer for CDMA Systems
Wang, Jian; Yuan, Jian; Ge, Ning; Wei, Shuangqing
2010-01-01
Matrix pair beamformer (MPB) is a promising blind beamformer which exploits the temporal signature of the signal of interest (SOI) to acquire its spatial statistical information. It does not need any knowledge of directional information or training sequences. However, the major problem of the existing MPBs is that they have serious threshold effects and the thresholds will grow as the interference power increases or even approach infinity. In particular, this issue prevails in scenarios with structured interference, such as, periodically repeated white noise, tones, or MAIs in multipath channels. In this paper, we will first present the principles for designing the projection space of the MPB which are closely correlated with the ability of suppressing structured interference and system finite sample performance. Then a multiple-interference-channel based matrix pair beamformer (MIC-MPB) for CDMA systems is developed according to the principles. In order to adapt to dynamic channels, an adaptive algorithm for...
Khabbazibasmenj, Arash; Hassanien, Aboulnasr
2010-01-01
We develop a new approach to robust adaptive beamforming in the presence of signal steering vector errors. Since the signal steering vector is known imprecisely, its presumed (prior) value is used to find a more accurate estimate of the actual steering vector, which then is used for obtaining the optimal beamforming weight vector. The objective for finding such an estimate of the actual signal steering vector is the maximization of the beamformer output power, while the constraints are the normalization condition and the requirement that the estimate of the steering vector does not converge to an interference steering vector. Our objective and constraints are free of any design parameters of non-unique choice. The resulting optimization problem is a non-convex quadratically constrained quadratic program, which is NP hard in general. However, for our problem we show that an efficient solution can be found using the semi-definite relaxation technique. Moreover, the strong duality holds for the proposed problem ...
Utility of Beamforming Strategies for Secrecy in Multiuser MIMO Wiretap Channels
Mukherjee, Amitav
2009-01-01
This paper examines linear beamforming methods for secure communications in a multiuser wiretap channel with a single transmitter, multiple legitimate receivers, and a single eavesdropper, where all nodes are equipped with multiple antennas. No information regarding the eavesdropper is presumed at the transmitter, and we examine both the broadcast MIMO downlink with independent information, and the multicast MIMO downlink with common information for all legitimate receivers. In both cases the information signal is transmitted with just enough power to guarantee a certain SINR at the desired receivers, while the remainder of the power is used to broadcast artificial noise. The artificial interference selectively degrades the passive eavesdropper's signal while remaining orthogonal to the desired receivers. We analyze the confidentiality provided by zero-forcing and optimal minimum-power beamforming designs for the broadcast channel, and optimal minimum-MSE beamformers for the multicast channel. Numerical simul...
PSMG sets A and B protective relaying
Burnett, J.E.
1978-07-24
The ''TAN/LOFT 13.8 kV, 2.4 kV, and 480 V Relay and Circuit Breaker Coordination Study'' presented an analysis to determine overcurrent settings for the LOFT Power System protective relays including those for the drive motors of the PSMG sets. This LTR is written to form the basis of the relay settings entered in Specification ES-60238 Rev. B, for protection of the PSMG generator, primary coolant pump motor and interconnecting power cable. A momentary commercial power voltage dip occurred on January 10, 1978 which caused a trip of the PSMG field breakers. A corrective design to prevent reoccurrence is discussed and recommendations are presented.
Beamforming with a circular microphone array for localization of environmental sources of noise
Tiana Roig, Elisabet; Jacobsen, Finn; Fernandez Grande, Efren
2010-01-01
It is often enough to localize environmental sources of noise from different directions in a plane. This can be accomplished with a circular microphone array, which can be designed to have practically the same resolution over 360. The microphones can be suspended in free space or they can...... be mounted on a solid cylinder. This investigation examines and compares two techniques based on such arrays, the classical delay-and-sum beamforming and an alternative method called circular harmonics beamforming. The latter is based on decomposing the sound field into a series of circular harmonics...
Beamforming with a circular microphone array for localization of environmental noise sources
Tiana Roig, Elisabet; Jacobsen, Finn; Fernandez Grande, Efren
2010-01-01
It is often enough to localize environmental sources of noise from different directions in a plane. This can be accomplished with a circular microphone array, which can be designed to have practically the same resolution over 360. The microphones can be suspended in free space or they can...... be mounted on a solid cylinder. This investigation examines and compares two techniques based on such arrays, the classical delay-and-sum beamforming and an alternative method called circular harmonics beamforming. The latter is based on decomposing the sound field into a series of circular harmonics...
Development of NASA's Next Generation L-Band Digital Beamforming Synthetic Aperture Radar (DBSAR-2)
Rincon, Rafael; Fatoyinbo, Temilola; Osmanoglu, Batuhan; Lee, Seung-Kuk; Ranson, K. Jon; Marrero, Victor; Yeary, Mark
2014-01-01
NASA's Next generation Digital Beamforming SAR (DBSAR-2) is a state-of-the-art airborne L-band radar developed at the NASA Goddard Space Flight Center (GSFC). The instrument builds upon the advanced architectures in NASA's DBSAR-1 and EcoSAR instruments. The new instrument employs a 16-channel radar architecture characterized by multi-mode operation, software defined waveform generation, digital beamforming, and configurable radar parameters. The instrument has been design to support several disciplines in Earth and Planetary sciences. The instrument was recently completed, and tested and calibrated in a anechoic chamber.
MaROS Strategic Relay Planning and Coordination Interfaces
Allard, Daniel A.
2010-01-01
The Mars Relay Operations Service (MaROS) is designed to provide planning and analysis tools in support of ongoing Mars Network relay operations. Strategic relay planning requires coordination between lander and orbiter mission ground data system (GDS) teams to schedule and execute relay communications passes. MaROS centralizes this process, correlating all data relevant to relay coordination to provide a cohesive picture of the relay state. Service users interact with the system through thin-layer command line and web user interface client applications. Users provide and utilize data such as lander view periods of orbiters, Deep Space Network (DSN) antenna tracks, and reports of relay pass performance. Users upload and download relevant relay data via formally defined and documented file structures including some described in Extensible Markup Language (XML). Clients interface with the system via an http-based Representational State Transfer (ReST) pattern using Javascript Object Notation (JSON) formats. This paper will provide a general overview of the service architecture and detail the software interfaces and considerations for interface design.
MaROS Strategic Relay Planning and Coordination Interfaces
Allard, Daniel A.
2010-01-01
The Mars Relay Operations Service (MaROS) is designed to provide planning and analysis tools in support of ongoing Mars Network relay operations. Strategic relay planning requires coordination between lander and orbiter mission ground data system (GDS) teams to schedule and execute relay communications passes. MaROS centralizes this process, correlating all data relevant to relay coordination to provide a cohesive picture of the relay state. Service users interact with the system through thin-layer command line and web user interface client applications. Users provide and utilize data such as lander view periods of orbiters, Deep Space Network (DSN) antenna tracks, and reports of relay pass performance. Users upload and download relevant relay data via formally defined and documented file structures including some described in Extensible Markup Language (XML). Clients interface with the system via an http-based Representational State Transfer (ReST) pattern using Javascript Object Notation (JSON) formats. This paper will provide a general overview of the service architecture and detail the software interfaces and considerations for interface design.
Hybrid Beamforming for Massive MIMO Backhaul (Working Title)
Rajatheva, Namal; Sousa, Elvino
2016-01-01
The uplink where both the transmitter and receiver can use a large antenna array is considered. This is proposed as a method of antenna offloading and connecting small cell access points (SCAP) in a Two-Tier cellular network. Due to having a limited number of RF-chains, hybrid beamformers are designed where phase-only processing is done at the RF-band, followed by digital processing at the baseband. The proposed receiver is a row combiner that clusters sufficiently correlated antenna elements...
Sorenson, Danny S [Los Alamos National Laboratory; Pazuchanics, Peter D [Los Alamos National Laboratory; Malone, Robert M [NSTEC; Cox, Brian C [NSTEC; Frogget, Brent C [NSTEC; Kaufman, Morris I [NSTEC; Capelle, Gene A [NSTEC/SB; Grover, M [NSTEC/SB; Stevens, Gerald D [NSTEC/SB; Turley, William D [NSTEC/SB
2009-01-01
The design and assembly of a nine-element lens that achieves >2000 1p/mm resolution at a 355-nm wavelength (ultraviolet) has been completed. By adding a doublet to this lens system, operation at a 532-nm wavelength (green) with > 1100 1p/mm resolution is achieved. This lens is used with high-power laser light to record holograms of fast-moving ejecta particles from a shocked metal surface located inside a test package. Part of the lens and the entire test package are under vacuum with a 1-cm air gap separation. Holograms have been recorded with both doubled and tripled Nd:YAG laser light. The UV operation is very sensitive to the package window's tilt. If this window is tilted by more than 0.1 degrees, the green operation performs with better resolution than that of the UV operation. The setup and alignment are performed with green light, but the dynamic recording can be done with either UV light or green light. A resolution plate can be temporarily placed inside the test package so that a television microscope located beyond the hologram position can archive images of resolution patterns that prove that the calibration wires., interference filter, holographic plate, and relay lenses are in their correct positions. Part of this lens is under vacuum, at the point where the laser illumination passes through a focus. Alignment and tolerancing of this high-resolution lens are presented. Resolution variation across the 12-mm field of view and throughout the 5-mm depth of field is discussed for both wavelengths.
Robust adaptive beamforming for MIMO monopulse radar
Rowe, William; Ström, Marie; Li, Jian; Stoica, Petre
2013-05-01
Researchers have recently proposed a widely separated multiple-input multiple-output (MIMO) radar using monopulse angle estimation techniques for target tracking. The widely separated antennas provide improved tracking performance by mitigating complex target radar cross-section fades and angle scintillation. An adaptive array is necessary in this paradigm because the direct path from any transmitter could act as a jammer at a receiver. When the target-free covariance matrix is not available, it is critical to include robustness into the adaptive beamformer weights. This work explores methods of robust adaptive monopulse beamforming techniques for MIMO tracking radar.
Solar concentrator with a toroidal relay module.
Lin, Jhe-Syuan; Liang, Chao-Wen
2015-10-01
III-V multijunction solar cells require solar concentrators with a high concentration ratio to reduce per watt cost and to increase solar energy transforming efficiency. This paper discusses a novel solar concentrator design that features a high concentration ratio, high transfer efficiency, thin profile design, and a high solar acceptance angle. The optical design of the concentrator utilizes a toroidal relay module, which includes both the off-axis relay lens and field lens design in a single concentric toroidal lens shape. The optical design concept of the concentrator is discussed and the simulation results are shown. The given exemplary design has an aspect ratio of 0.24, a high averaged optical concentration ratio 1230×, a maximum efficiency of 76.8%, and the solar acceptance angle of ±0.9°.
Zheng, T. Y.; Cha, Seung-Tae; Crossley, P. A.;
2013-01-01
To avoid undesirable disconnection of healthy wind generators (WGs) or a wind power plant, a WG protection relay should discriminate among faults, so that it can operate instantaneously for WG, connected feeder or connection bus faults, it can operate after a delay for inter-tie or grid faults...
Efficient Resource Scheduling by Exploiting Relay Cache for Cellular Networks
Chun He
2015-01-01
Full Text Available In relay-enhanced cellular systems, throughput of User Equipment (UE is constrained by the bottleneck of the two-hop link, backhaul link (or the first hop link, and access link (the second hop link. To maximize the throughput, resource allocation should be coordinated between these two hops. A common resource scheduling algorithm, Adaptive Distributed Proportional Fair, only ensures that the throughput of the first hop is greater than or equal to that of the second hop. But it cannot guarantee a good balance of the throughput and fairness between the two hops. In this paper, we propose a Two-Hop Balanced Distributed Scheduling (TBS algorithm by exploiting relay cache for non-real-time data traffic. The evolved Node Basestation (eNB adaptively adjusts the number of Resource Blocks (RBs allocated to the backhaul link and direct links based on the cache information of relays. Each relay allocates RBs for relay UEs based on the size of the relay UE’s Transport Block. We also design a relay UE’s ACK feedback mechanism to update the data at relay cache. Simulation results show that the proposed TBS can effectively improve resource utilization and achieve a good trade-off between system throughput and fairness by balancing the throughput of backhaul and access link.
Bandwidth-Efficient Cooperative Relaying Schemes with Multiantenna Relay
Tho Le-Ngoc
2008-05-01
Full Text Available We propose coded cooperative relaying schemes in which all successfully decoded signals from multiple sources are forwarded simultaneously by a multiantenna relay to a common multiantenna destination to increase bandwidth efficiency. These schemes facilitate various retransmission strategies at relay and single-user and multiuser iterative decoding techniques at destination, suitable for trade-offs between performance, latency, and complexity. Simulation results show that the proposed schemes significantly outperform direct transmission under the same transmit power and bandwidth efficiency.
Analog gradient beamformer for a wireless ultrasound scanner
Di Ianni, Tommaso; Hemmsen, Martin Christian; Bagge, Jan; Jensen, Henrik; Vardi, Nitsan; Jensen, Jørgen Arendt
2016-04-01
This paper presents a novel beamformer architecture for a low-cost receiver front-end, and investigates if the image quality can be maintained. The system is oriented to the development of a hand-held wireless ultrasound probe based on Synthetic Aperture Sequential Beamforming, and has the advantage of effectively reducing circuit complexity and power dissipation. The array of transducers is divided into sub-apertures, in which the signals from the single channels are aligned through a network of cascaded gradient delays, and summed in the analog domain before A/D conversion. The delay values are quantized to simplify the shifting unit, and a single A/D converter is needed for each sub-aperture yielding a compact, low-power architecture that can be integrated in a single chip. A simulation study was performed using a 3:75MHz convex array, and the point spread function (PSF) for different configurations was evaluated in terms of lateral full-width-at-half-maximum (FWHM) and -20 dB cystic resolution (CR). Several setups were simulated varying the sub-aperture size N and the quantization step, and design constraints were obtained comparing the PSF to that of an ideal non-quantized system. The PSF is shown for N = 32 with a quantization step of 12 ns. For this configuration, the FWHM is degraded by 0.25% and the CR is 8.70% lower compared to the ideal situation. The results demonstrate that the gradient beamformer provides an adequate image quality, and open the way to a fully-integrated chip for a compact, low-cost, wireless ultrasound probe.
Opportunistic Relay Selection in Multicast Relay Networks using Compressive Sensing
Elkhalil, Khalil
2014-12-01
Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. However, for relay selection algorithms to make a selection decision, channel state information (CSI) from all cooperating relays is usually required at a central node. This requirement poses two important challenges. Firstly, CSI acquisition generates a great deal of feedback overhead (air-time) that could result in significant transmission delays. Secondly, the fed back channel information is usually corrupted by additive noise. This could lead to transmission outages if the central node selects the set of cooperating relays based on inaccurate feedback information. In this paper, we introduce a limited feedback relay selection algorithm for a multicast relay network. The proposed algorithm exploits the theory of compressive sensing to first obtain the identity of the “strong” relays with limited feedback. Following that, the CSI of the selected relays is estimated using linear minimum mean square error estimation. To minimize the effect of noise on the fed back CSI, we introduce a back-off strategy that optimally backs-off on the noisy estimated CSI. For a fixed group size, we provide closed form expressions for the scaling law of the maximum equivalent SNR for both Decode and Forward (DF) and Amplify and Forward (AF) cases. Numerical results show that the proposed algorithm drastically reduces the feedback air-time and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback channels.
2015-01-01
This paper investigates the relay transmission system in the presence of multiple collusion single-antenna eavesdroppers. A physical layer security scheme employing nullspace Artificial Noise (AN) and Amplify-and-Forward (AF) relay beamforming is designed. In the case that channel state information can not be accurately obtained, the weighted matrice of relay beamforming and the nullspace AN covariance are jointed optimized based on the Semi-Definite Programs (SDP), which can effectively reduce the amount of the information likely to be obtained by the multiple collusion eavesdroppers and significantly improve the security capacity of the system. It is an effective physical security transmission scheme with good robustness. Simulation results verify that the scheme has good performance.%该文研究存在多个相互勾结的单天线窃听者的多中继传输系统中，采用零空间人工噪声和放大转发的中继波束赋形的物理层安全传输方案。在中继—窃听端的信道状态信息不准确的情况下，基于半定规划理论，对中继的波束赋形加权矩阵和人工噪声协方差矩阵进行联合优化，有效减少相互勾结的多个窃听者所获得的信息量，显著提高系统保密容量，是一种具有良好鲁棒性的物理层安全传输方案。仿真结果显示方案具有良好的性能。
Adaptive and Distributed Beamforming for Cognitive Radio
Lian, X.
2013-01-01
Cognitive Radio (CR) is an energy efficient technique that is capable of optimizing the premium radio resources, such as power and spectrum. In this thesis, we focus on exploiting spatial diversity for CR. We have adopted two spatial signal processing techniques, i.e., Adaptive Beamforming (ABF) and
Fast Parametric Beamformer for Synthetic Aperture Imaging
Nikolov, Svetoslav; Jensen, Jørgen Arendt; Tomov, Borislav Gueorguiev
2008-01-01
. The implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed...
Loudness estimation of simultaneous sources using beamforming
Song, Woo-keun; Ellermeier, Wolfgang; Minnaar, Pauli
2006-01-01
An algorithm is proposed for estimating the loudness of several simultaneous sound sources by means of microphone-array beamforming. The algorithm is derived from two listening experiments in which the loudness of two simultaneous sounds (narrow-band noises with 1-kHz and 3.15-kHz center frequenc...
Stochastic Beamforming via Compact Antenna Arrays
Alrabadi, Osama; Pedersen, Gert Frølund
2012-01-01
The paper investigates the average beamforming (BF) gain of compact antenna arrays when statistical channel knowledge is available. The optimal excitation (precoding vector) and impedance termination that maximize the average BF gain are a compromise between the ones that maximize the array...
The typical behaviour of relays
Alamino, Roberto C.; Saad, David
2007-01-01
The typical behaviour of the relay-without-delay channel and its many-units generalisation, termed the relay array, under LDPC coding, is studied using methods of statistical mechanics. A demodulate-and-forward strategy is analytically solved using the replica symmetric ansatz which is exact in the studied system at the Nishimori's temperature. In particular, the typical level of improvement in communication performance by relaying messages is shown in the case of small and large number of re...
Diverging Wave Volumetric Imaging Using Subaperture Beamforming.
Santos, Pedro; Haugen, Geir Ultveit; Lovstakken, Lasse; Samset, Eigil; D'hooge, Jan
2016-12-01
Several clinical settings could benefit from 3-D high frame rate (HFR) imaging and, in particular, HFR 3-D tissue Doppler imaging (TDI). To date, the proposed methodologies are based mostly on experimental ultrasound platforms, making their translation to clinical systems nontrivial as these have additional hardware constraints. In particular, clinically used 2-D matrix array transducers rely on subaperture (SAP) beamforming to limit cabling between the ultrasound probe and the back-end console. Therefore, this paper is aimed at assessing the feasibility of HFR 3-D TDI using diverging waves (DWs) on a clinical transducer with SAP beamforming limitations. Simulation studies showed that the combination of a single DW transmission with SAP beamforming results in severe imaging artifacts due to grating lobes and reduced penetration. Interestingly, a promising tradeoff between image quality and frame rate was achieved for scan sequences with a moderate number of transmit beams. In particular, a sparse sequence with nine transmissions showed good imaging performance for an imaging sector of 70 (°)×70 (°) at volume rates of approximately 600 Hz. Subsequently, this sequence was implemented in a clinical system and TDI was recorded in vivo on healthy subjects. Velocity curves were extracted and compared against conventional TDI (i.e., with focused transmit beams). The results showed similar velocities between both beamforming approaches, with a cross-correlation of 0.90 ± 0.11 between the traces of each mode. Overall, this paper indicates that HFR 3-D TDI is feasible in systems with clinical 2-D matrix arrays, despite the limitations of SAP beamforming.
Laser Communications Relay Demonstration Project
National Aeronautics and Space Administration — The Laser Communications Relay Demonstration project will advance optical communications technology, expanding industry’s capability to produce competitive,...
Educational Software Tool for Protection System Engineers. Distance Relay
Trujillo-Guajardo L.A.
2012-04-01
Full Text Available In this article, a graphical software tool is presented; this tool is based on the education of protection system engineers. The theoretical fundaments used for the design of operation characteristics of distance relays and their algorithms are presented. The software allows the evaluation and analysis of real time events or simulated ones of every stage of design of the distance relay. Some example cases are presented to illustrate the activities that could be done with the graphical software tool developed.
On the capacity of multiple cognitive links through common relay under spectrum-sharing constraints
Yang, Yuli
2011-06-01
In this paper, we consider an underlay cognitive relaying network consisting of multiple secondary users and introduce a cooperative transmission protocol using a common relay to help with the communications between all secondary source-destination pairs for higher throughput and lower realization complexity. A whole relay-assisted transmission procedure is composed of multiple access phase and broadcast phase, where the relay is equipped with multiple antennas, and the secondary sources and destinations are single-antenna nodes. Considering the spectrum-sharing constraints on the secondary sources and the relay, we analyze the capacity behaviors of the underlay cognitive relaying network under study. The corresponding numerical results provide a convenient tool for the presented network design and substantiate a distinguishing feature of introduced design in that multiple secondary users\\' communications do not rely on multiple relays, hence allowing for a more efficient use of the radio resources. © 2011 IEEE.
Ohira, Toru
2016-01-01
We present here a system with collection of random walks relaying a signal in one dimension with a presence of a delay. We are interested in the time for a signal to travel from one end (start) to the other end (finish) of the lined group of random walkers. It is found that there is an optimal number of walkers for the signal to travel fastest if the delay is present. We discuss implications of this model and associated behaviors to physical and biological systems.
陈可; 胡晓光
2011-01-01
The design scheme of concentrator based on electric line broadband carrier and its automatic relay routing algorithm are proposed. The concentrator takes S3C2440 chip as its core, adopting the electric line broadband carrier technology to communicate with the collector and the GPRS technology to communicate with the management center. Its software is based on the embedded Linux operating system, adopting the multi-channel I/O multiplexing technology and the embedded database technology to realize the receiving, transmitting and storage of user data. For low-voltage electric line, the automatic relay routing algorithm with relay constrains is employed for meter reading. The operating experience indicates that,the concentrator based on electric line broadband carrier has fast transmission speed,high reliability, excellent real-time performance and low operating cost, and the automatic relay routing algorithm with relay constrains improves the meter reading efficiency.%针对国内目前低压电力线抄表系统中采用的窄带载波集中器及人工中继路由方式,提出了基于电力线宽带载波的集中器设计方案及自动中继路由算法.宽带载波集中器硬件是以S3C2440为核心,采用电力线宽带载波技术与采集器通信、通用分组无线服务(GPRS)技术与管理中心通信；软件是基于嵌入式Linux操作系统设计,采用多路I/0复用技术以及嵌入式数据库技术实现对用户电量的接收、转发及存储.同时依据低压电力线的特点,采用具有中继约束条件的自动中继路由算法实现用户电量的抄收.运行经验和实践表明:宽带载波集中器具有传输速率快、可靠性高、实时性强和运行费用低等优点；具有中继约束条件的自动中继路由算法能有效缩短自动中继的时间,提高抄表效率.
Performance analysis of distributed beamforming in a spectrum sharing system
Yang, Liang
2013-05-01
In this paper, we consider a distributed beamforming scheme (DBF) in a spectrum sharing system where multiple secondary users share the spectrum with some licensed primary users under an interference temperature constraint. We assume that the DBF is applied at the secondary users. We first consider optimal beamforming and compare it with the user selection scheme in terms of the outage probability and bit error rate performance metrics. Since perfect feedback is difficult to obtain, we then investigate a limited feedback DBF scheme and develop an analysis for a random vector quantization design algorithm. Specifically, the approximate statistics functions of the squared inner product between the optimal and quantized vectors are derived. With these statistics, we analyze the outage performance. Furthermore, the effects of channel estimation error and number of primary users on the system performance are investigated. Finally, optimal power adaptation and cochannel interference are considered and analyzed. Numerical and simulation results are provided to illustrate our mathematical formalism and verify our analysis. © 2012 IEEE.
Performance evaluation of the fixed relay in OFDMA systems
Gao Peng; Wu Xiaoyan; Meng Dexiang; Chen Yanming; Tu Guofang
2010-01-01
Performance of fixed relays in orthogonal frequency division multiple access (OFDMA) systems, especially the coverage and capacity performance at the cell edge, is evaluated in this paper.Two methods, theoretical analysis and calculation and Monte Carlo simulation, are used for the evaluations.By theoretical analysis and calculation, frequency efficiency equation of a relay is introduced and numerical results are calculated.Monte Carlo simulation results also verify that the calculation method is reasonable.The evaluation shows that a relay can increase system performance to a certain level if it is designed appropriately, otherwise it will be harmful for the system performance, even to reduce it.
Running Club
2010-01-01
This year’s CERN Relay Race will take place around the Meyrin site on Thursday 20th May at 12h00. This annual event is for teams of 6 runners covering distances of 1000m, 800m, 800m, 500m, 500m and 300m respectively. Teams may be entered in the Seniors, Veterans, Ladies, Mixed or Open categories. The registration fee is 10 CHF per runner, and each runner receives a souvenir prize. As usual, there will be a programme of entertainments from 12h in the arrival area, in front of the Restaurant no. 1. Drinks, food, CERN club information and music will be available for the pleasure of both runners and spectators. The race starts at 12h15, with results and prize giving at 13:15. For details of the race, and of how to sign up a team, please visit: https://espace.cern.ch/Running-Club/CERN-Relay The event is organised by the CERN Running Club with the support of the CERN Staff Association.
Staff Association
2017-01-01
On Thursday June 1st at 12.15, Fabiola Gianotti, our Director-General, will fire the starting shot for the 47th Relay Race. This Race is above all a festive CERN event, open for runners and walkers, as well as the people cheering them on throughout the race, and those who wish to participate in the various activities organised between 11.30 and 14.30 out on the lawn in front of Restaurant 1. In order to make this sports event accessible for everyone, our Director-General will allow for flexible lunch hours on the day, applicable for all the members of personnel. An alert for the closure of roads will be send out on the day of the event. The Staff Association and the CERN Running Club thank you in advance for your participation and your continued support throughout the years. This year the CERN Running Club has announced the participation of locally and internationally renowned runners, no less! A bit over a week from the Relay Race of 1st June, the number of teams is going up nicely (already almost 40). Am...
Scalable Intersample Interpolation Architecture for High-channel-count Beamformers
Tomov, Borislav Gueorguiev; Nikolov, Svetoslav I; Jensen, Jørgen Arendt
2011-01-01
Modern ultrasound scanners utilize digital beamformers that operate on sampled and quantized echo signals. Timing precision is of essence for achieving good focusing. The direct way to achieve it is through the use of high sampling rates, but that is not economical, so interpolation between echo...... samples is used. This paper presents a beamformer architecture that combines a band-pass filter-based interpolation algorithm with the dynamic delay-and-sum focusing of a digital beamformer. The reduction in the number of multiplications relative to a linear perchannel interpolation and band-pass per......-channel interpolation architecture is respectively 58 % and 75 % beamformer for a 256-channel beamformer using 4-tap filters. The approach allows building high channel count beamformers while maintaining high image quality due to the use of sophisticated intersample interpolation....
Opportunistic Collaborative Beamforming with One-Bit Feedback
Pun, Man-On; Poor, H Vincent
2008-01-01
An energy-efficient opportunistic collaborative beamformer with one-bit feedback is proposed for ad hoc sensor networks over Rayleigh fading channels. In contrast to conventional collaborative beamforming schemes in which each source node uses channel state information to correct its local carrier offset and channel phase, the proposed beamforming scheme opportunistically selects a subset of source nodes whose received signals combine in a quasi-coherent manner at the intended receiver. No local phase-precompensation is performed by the nodes in the opportunistic collaborative beamformer. As a result, each node requires only one-bit of feedback from the destination in order to determine if it should or shouldn't participate in the collaborative beamformer. Theoretical analysis shows that the received signal power obtained with the proposed beamforming scheme scales linearly with the number of available source nodes. Since the the optimal node selection rule requires an exhaustive search over all possible subs...
Investigation of Sound Speed Errors in Adaptive Beamforming
Holfort, Iben Kraglund; Gran, Fredrik; Jensen, Jørgen Arendt
2008-01-01
Previous studies have shown that adaptive beam-formers provide a significant increase of resolution and contrast, when the propagation speed is known precisely. This paper demonstrates the influence of sound speed errors on two adaptive beamformers; the minimum variance (MV) beamformer and the am......Previous studies have shown that adaptive beam-formers provide a significant increase of resolution and contrast, when the propagation speed is known precisely. This paper demonstrates the influence of sound speed errors on two adaptive beamformers; the minimum variance (MV) beamformer...... drop is proposed; diagonal loading (DL) and forward-backward (FB) averaging of the covariance matrix. The investigations show that DL provides a slightly decreased resolution and amplitude compared to FB. It is noted that APES provides more robust estimates than MV at the mere expense of a slight...
Implementing Ultrasound Beamforming on the GPU using CUDA
Grønvold, Lars
2008-01-01
This thesis discusses the implementation of ultrasound beamforming on the GPU using CUDA. Fractional delay filters and the need for it when implementing beamforming is discussed. An introduction to CUDA programming is given as well as a study of the workings of the NVIDIA Tesla GPU(or G80). A number of suggestions for implementing beamforming on a GPU is presented as well as an actual implementation and an evaluation of it's performance.
Two-hop Secure Communication Using an Untrusted Relay
He, Xiang
2009-01-01
We consider a source-destination pair that can only communicate through an untrusted intermediate relay node. The intermediate node is willing to employ a designated relaying scheme to facilitate reliable communication between the source and the destination. Yet, the information it relays needs to be kept secret from it. In this two-hop communication scenario, where the use of the untrusted relay node is essential, we find that a positive secrecy rate is achievable. The center piece of the achievability scheme is the help provided by either the destination node with transmission capability, or an external "good samaritan" node. In either case, the helper performs cooperative jamming that confuses the eavesdropping relay and disables it from being able to decipher what it is relaying. We next derive an upper bound on the secrecy rate for this system. We observe that the gap between the upper bound and the achievable rate vanishes as the power of the relay node goes to infinity. Overall, the paper presents a ca...
A study on Relay Effect via Magnetic Resonant Coupling for Wireless Power Transfer
Rashid N.A.
2016-01-01
Full Text Available Wireless power transfer (WPT transmits electrical energy from a power source to an electrical load wirelessly or without any conductors. The capability of WPT to transmit the energy is limited. Therefore, a relay was introduced to increase the distance of the WPT capabilities. The effect of the relay has been investigated to extend the energy transfer distance. The effect of relay was demonstrated by placing a relay coil between transmitter and receiver, relay biased to transmitter and placing two relay coils in the designed system. Experimental results are provided to prove the concept of the relay effect. The power transmission efficiency can be achieved up to 75% at 1 meter distance.
Cooperative HARQ protocol and diversity analysis of systems with multiple incremental relays
FAN Bin; WANG Wen-bo; LIN Yi-cheng; ZHENG Kan
2009-01-01
Wireless networks contain an inherent distributed spatial diversity that can be exploited by relays. Relay networks can take advantage of the broadcast-oriented nature of wireless transmission, but require more radio resource to transmit data for their multi-hop traits. Fortunately, incremental relaying technique, which can choose direct or multi-hop transmission adaptively, can efficiently utilize resource. In this article, the incremental transmission with amplify-and-forward (AF) relays is focused on. A practical hybrid-automatic retransmission request (HARQ) protocol is designed, and the related optimal relay selection strategy is proposed. To analyze the cooperative diversity of system with the proposed protocol, the capacity lower bound is deduced. Simulation and analytical results indicate that by adopting the optimal relay selection strategy, the system with the proposed HARQ protocol can achieve an order of cooperative diversity that equals the aggregated number of the relay and source nodes.
Minimum Variance Beamforming for High Frame-Rate Ultrasound Imaging
Holfort, Iben Kraglund; Gran, Fredrik; Jensen, Jørgen Arendt
2007-01-01
This paper investigates the application of adaptive beamforming in medical ultrasound imaging. A minimum variance (MV) approach for near-field beamforming of broadband data is proposed. The approach is implemented in the frequency domain, and it provides a set of adapted, complex apodization...... weights for each frequency sub-band. As opposed to the conventional, Delay and Sum (DS) beamformer, this approach is dependent on the specific data. The performance of the proposed MV beamformer is tested on simulated synthetic aperture (SA) ultrasound data, obtained using Field II. For the simulations...
AREA OPTIMIZED FPGA IMPLEMENTATION OF ADAPTIVE BEAMFORMER
Harpreet Kaur
2012-06-01
Full Text Available Quadratic Rotation decomposition (QRD based recursive least squares (RLS algorithm can be used in variety of communication applications and its low complexity implementation can be of interest. In this paper we have presented an application of QRD based RLS algorithm using Coordinate Rotation by Digital Computer (CORDIC operator for implementing an adaptive beamformer. FPGA resource estimates along with actual implementation results have been presented and are being compared with its existing implementation.
On the Performance of Selection Relaying
Adinoyi, Abdulkareem; Fan, Yijia; Yanikomeroglu, Halim; Poor, H. Vincent
2008-01-01
Interest in selection relaying is growing. The recent developments in this area have largely focused on information theoretic analyses such as outage performance. Some of these analyses are accurate only at high SNR regimes. In this paper error rate analyses that are sufficiently accurate over a wide range of SNR regimes are provided. The motivations for this work are that practical systems operate at far lower SNR values than those supported by the high SNR analysis. To enable designers to m...
2005-01-01
The CERN Relay Race will take place around the Meyrin site on Wednesday 18 May between 12.15 and 12.35. This year, weather permitting, there will be some new attractions in the start/finish area on the field behind the Main Building. You will be able to: listen to music played by the CERN Jazz Club; buy drinks at the bar organised by the CERN Running Club; buy lunch served directly on the terrace by the restaurant Novae. ATTENTION: concerning traffic, the recommendations are the same as always: If possible, please avoid driving on the site during this 20 minute period. If you do meet runners in your car, please STOP until they all have passed. Thank you for your understanding.
钱栋军; 张静; 顾夏珺
2013-01-01
In MIMO relay system, the scheme of designing the joint linear transmitters and the receiver considering the joint source, relay and destination based on perfect channel state information ( CSI) is derived. Based on this, the paper considering the channel estimate errors modeled as Gaussian random variables and under power constraint at both the source and the relay node, the transmitters and receiver could be realized through a joint iterative algorithm. Compared with the existing methods, the results show that the proposed scheme could effectively improve the BER performance and reduce the minimum mean square error of the system.%在MIMO中继系统中,基于完全信道状态信息的基站、中继节点和终端联合收发机设计方案能够改善系统的误比特率性能,在放大转发(AF)中继的基础上提出了一种基于不完全信道状态信息的联合收发机设计方案.新方案在基站和中继节点的功率都受限条件下,将信道估计误差建模为高斯随机变量,以最小均方误差(MMSE)为准则,采用迭代算法,得到了基站预编码矩阵、中继转发矩阵和终端解码矩阵.该方案与不考虑信道估计误差的方案相比,能够有效地改善系统的均方误差和误比特率性能.
Design of JGD24-5 Solid State Time-Limited Protection Relay%JGD24-5型固体式限时保护继电器的设计
刘凯; 赵辉
2013-01-01
The paper provides basic technical properties for the JGD 24-5 solid state time-limited protection relay.And design method is described for such relays .The focus is on design of input circuit , delay filter circuit, time-limited protection circuit, isolation circuit, driver circuit and series output circuit .Additionally, calculation methods are shown for some significant parameters .% 文章给出了JGD24-5型固体式限时保护继电器的主要技术指标，介绍了该类产品的设计方法，重点介绍了输入电路、延时滤波电路、限时保护电路、隔离电路、驱动电路和串联输出电路的设计，并给出了一些重要参数的计算方法。
Relay Mirror Experiment overview: a GBL pointing and tracking demonstration
Dierks, Jeffrey S.; Ross, Susan E.; Brodsky, Aaron; Kervin, Paul W.; Holm, Richard W.
1991-08-01
The Relay Mirror Experiment (RME) has successfully demonstrated long-range, low-jitter tracking and pointing capabilities appropriate for ground-based laser (GBL) propagation. The RME program includes (1) a passively maneuverable, free-flying low-orbit spacecraft with a laser diode beacon and spoiled retroreflectors as acquisition aids; (2) a payload experiment package (PEP) consisting of sensors, optics, steerable mirrors, and control electronics. This subsystem accomplishes GBL tracking and pointing and the associated positioning of a space-based relay mirror sufficiently to relay an infrared beam between two ground sites. Design considerations for the control system included base motion disturbance and calibration; (3) two GBL sites each a tracking and pointing exercise in itself, using a combination of sensors and acquisition and tracking capabilities. One site includes a beam relay scoring capability.
Coordinated Beamforming for Multiuser MISO Interference Channel under Rate Outage Constraints
Li, Wei-Chiang; Lin, Che; Chi, Chong-Yung
2011-01-01
This paper studies the coordinated beamforming design problem for the multiple-input single-output (MISO) interference channel, assuming only channel distribution information (CDI) at the transmitters. For a given requirement on the rate outage probability for receivers, we aim to maximize the system utility (e.g., the weighted sum rate, weighted proportional fairness rate, and the weighed harmonic mean rate) subject to the rate outage constraints and individual power constraints. The outage constraints, however, lead to a complicated, nonconvex structure for the considered beamforming design problem and make the optimization problem difficult to handle. While this nonconvex optimization problem can be solved in an exhaustive search manner, this brute-force approach is only feasible when the number of transmitter-receiver pairs is small. For a system with a large number of transmitter-receiver pairs, computationally efficient alternatives are necessary. The focus of this paper is hence on the design of such e...
吴昊; 梁晓雯
2016-01-01
In view of the joint transceiver design for users and relay in multiple user pairs two-way amplify-and-forward ( AF ) multiple input multiple output ( MIMO) relay systems,and for the purpose of power saving,an optimization problem is proposed to mini-mize the total power consumption of relay and users under the mean square error (MSE) constraint of each user.Due to the non-convex-ity,it is difficult to obtain the globally optimal solution of this problem. Therefore the original problem is decomposed into three easier sub-problems,which are solved respectively. Then an iterative algorithm based on alternating optimization is proposed to solve the original problem.Simulation results show that the proposed algorithm can save the total power of users and relay effectively as compared to other algorithms.%针对多用户对双向放大转发多输入多输出中继系统中用户和中继的收发器联合设计问题，基于节省功率的目的，提出了在满足每个用户均方误差约束的条件下最小化用户和中继总功率的优化问题。由于所形成的优化问题是非凸的，难以求得全局最优解，因此将原问题分解为3个便于处理的子问题，对这3个子问题分别进行求解，在此基础上提出了一种基于交替优化的迭代算法去求解原问题。仿真结果表明，所提算法相较于其他算法可以有效地节省用户和中继的总功率。
Beamforming and Rate Allocation in MISO Cognitive Radio Networks
Tajer, Ali; Wang, Xiaodong
2009-01-01
We consider decentralized multi-antenna cognitive radio networks where secondary (cognitive) users are granted simultaneous spectrum access along with license-holding (primary) users. We treat the problem of distributed beamforming and rate allocation for the secondary users such that the minimum weighted secondary rate is maximized. Such an optimization is subject to (1) a limited weighted sum-power budget for the secondary users and (2) guaranteed protection for the primary users in the sense that the interference level imposed on each primary receiver does not exceed a specified level. Based on the decoding method deployed by the secondary receivers, we consider three scenarios for solving this problem. In the first scenario each secondary receiver decodes only its designated transmitter while suppressing the rest as Gaussian interferers (single-user decoding). In the second case each secondary receiver employs the maximum likelihood decoder (MLD) to jointly decode all secondary transmissions, and in the t...
Diversity Analysis of Bit-Interleaved Coded Multiple Beamforming
Park, Hong Ju
2008-01-01
In this paper, diversity analysis of bit-interleaved coded multiple beamforming (BICMB) is extended to the case of general spatial interleavers, removing a condition on their previously known design criteria and quantifying the resulting diversity order. The diversity order is determined by a parameter Qmax which is inherited from the convolutional code and the spatial de-multiplexer used in BICMB. We introduce a method to find this parameter by employing a transfer function approach as in finding the weight spectrum of a convolutional code. By using this method, several Qmax's are shown and verified to be identical with the results from a computer searching program tracing paths on the trellis. The diversity analysis and the method to find the parameter are supported by simulation results.
Fourier beamformation of multistatic synthetic aperture ultrasound imaging
Moghimirad, Elahe; Villagómez Hoyos, Carlos Armando; Mahloojifar, Ali
2015-01-01
A new Fourier beamformation (FB) algorithm is presented for multistatic synthetic aperture ultrasound imaging. It can reduce the number of computations by a factor of 20 compared to conventional Delay-and-Sum (DAS) beamformers. The concept is based on the wavenumber algorithm from radar and sonar...
A Broadband Beamformer Using Controllable Constraints and Minimum Variance
Karimian-Azari, Sam; Benesty, Jacob; Jensen, Jesper Rindom
2014-01-01
The minimum variance distortionless response (MVDR) and the linearly constrained minimum variance (LCMV) beamformers are two optimal approaches in the sense of noise reduction. The LCMV beamformer can also reject interferers using linear constraints at the expense of reducing the degree of freedom...
A novel deconvolution beamforming algorithm for virtual phased arrays
Fernandez Comesana, Daniel; Fernandez Grande, Efren; Tiana Roig, Elisabet;
2013-01-01
traditionally obtained using large arrays can be emulated by applying beamforming algorithms to data acquired from only two sensors. This paper presents a novel beamforming algorithm which uses a deconvolution approach to strongly reduce the presence of side lobes. A series of synthetic noise sources...
颜雪松; 曾文聪; 王汉宁; 夏文; 李晖
2011-01-01
继电器产品的优化设计是在给定的负载条件或环境条件下,在对继电器产品的性态、几何尺寸关系或其他因素限制约束范围内,确定设计参数、目标函数、约束条件以形成优化设计模型,并选择恰当的优化方法以获得最佳设计方案的一系列工作.继电器的体积数学模型涉及到机、电、磁、热等方面,其目标函数和约束函数均是高度非线性的.传统演化算法求解问题时容易陷入局部极小值.在简单演化算法的基础上,结合正交实验法的基本思想,将其应用于演化算法的种群初始化、交叉算子,并引入自适应正交局部搜索来防止局部收敛,得到了一种新型的正交演化算法.通过一系列数值实验验证了该算法的高效性.%Optimal design of relay products determine the design parameters in the given load conditions or environmental conditions,the state of relay products,geometry or other factors within the scope of restrictions,and makes sure of the design parameters,object function,constraints in order to form an optimized design model,and selects the appropriate optimization method to obtain the best design of a series of works.Mathematical model of the relay volume involves in mechanical,electricai, magnetic, thermal, etc.,the objective function and constraints are highly nonlinear function.Traditional evolutionary algorithm is trapped into the local minimum easily.Therefore,based on a simple evolutionary algorithm and combining the base ideology of orthogonal test,applied it to the population initialization,crossover operator, as well as the introduction of adaptive orthogonal local search to prevent local convergence,a new orthogonal evolutionary algorithm is proposed.The series of numerical experiments have proved the efficiency of this algorithm.
赵彦平; 段星辉; 王建伟; 马阳轲
2016-01-01
针对目前无人机在电力巡检应用中所受到的通信能力制约问题，分析讨论了几种常见的无人机通信方式，在此基础上提出了利用另一架无人机搭载通信中继设备组成空中通信中继平台的技术方案，从高性能飞行平台研制、中继系统通信信号研究、系统应用3个方面，设计实现了应用于电力巡检的无人机通信中继系统，解决了电力巡检无人机在山区、森林等复杂区域巡检作业时的通信问题。%For the problems of communication ability of UAVs in electrical inspection, several communications modes of UAVs are analyzed and discussed in this paper. Based on this, it proposes technology solution of air communication relay platform, designs the UAV communications relay system from high-performance platform, communication signal and system application. It can solve the communication problems of UAV in the complex areas such as mountain, forest and so on.
A beamforming algorithm for bistatic SAR image formation.
Yocky, David Alan; Wahl, Daniel Eugene; Jakowatz, Charles V., Jr.
2010-03-01
Beamforming is a methodology for collection-mode-independent SAR image formation. It is essentially equivalent to backprojection. The authors have in previous papers developed this idea and discussed the advantages and disadvantages of the approach to monostatic SAR image formation vis--vis the more standard and time-tested polar formatting algorithm (PFA). In this paper we show that beamforming for bistatic SAR imaging leads again to a very simple image formation algorithm that requires a minimal number of lines of code and that allows the image to be directly formed onto a three-dimensional surface model, thus automatically creating an orthorectified image. The same disadvantage of beamforming applied to monostatic SAR imaging applies to the bistatic case, however, in that the execution time for the beamforming algorithm is quite long compared to that of PFA. Fast versions of beamforming do exist to help alleviate this issue. Results of image reconstructions from phase history data are presented.
A beamforming algorithm for bistatic SAR image formation
Jakowatz, Charles V., Jr.; Wahl, Daniel E.; Yocky, David A.
2010-04-01
Beamforming is a methodology for collection-mode-independent SAR image formation. It is essentially equivalent to backprojection. The authors have in previous papers developed this idea and discussed the advantages and disadvantages of the approach to monostatic SAR image formation vis-à-vis the more standard and time-tested polar formatting algorithm (PFA). In this paper we show that beamforming for bistatic SAR imaging leads again to a very simple image formation algorithm that requires a minimal number of lines of code and that allows the image to be directly formed onto a three-dimensional surface model, thus automatically creating an orthorectified image. The same disadvantage of beamforming applied to monostatic SAR imaging applies to the bistatic case, however, in that the execution time for the beamforming algorithm is quite long compared to that of PFA. Fast versions of beamforming do exist to help alleviate this issue. Results of image reconstructions from phase history data are presented.
Robust adaptive beamforming algorithm based on Bayesian approach
Xin SONG; Jinkuan WANG; Yinghua HAN; Han WANG
2008-01-01
The performance of adaptive array beamform-ing algorithms substantially degrades in practice because of a slight mismatch between actual and presumed array res-ponses to the desired signal. A novel robust adaptive beam-forming algorithm based on Bayesian approach is therefore proposed. The algorithm responds to the current envi-ronment by estimating the direction of arrival (DOA) of the actual signal from observations. Computational com-plexity of the proposed algorithm can thus be reduced com-pared with other algorithms since the recursive method is used to obtain inverse matrix. In addition, it has strong robustness to the uncertainty of actual signal DOA and makes the mean output array signal-to-interference-plus-noise ratio (SINR) consistently approach the optimum. Simulation results show that the proposed algorithm is bet-ter in performance than conventional adaptive beamform-ing algorithms.
Yongkai Zhou
2013-01-01
Full Text Available The paper considers the secure transmission in a wireless environment in which both the transmitter (Alice and the legitimate receiver (Bob send artificial noise (AN to interfere with the eavesdropper (Eve. Optimal design is analyzed in detail for this AN-by-both-side model to deal with Eve’s stochastic channel condition and random spatial distribution. Bipolar-beamforming is first proposed to jointly design Alice and Bob’s transmitting signals. By optimally assigning the transmitting antenna for Bob and allocating the power ratio between Alice’s information and the AN signal, maximum secrecy capacity can be achieved. Simulation is done to illustrate the process of bipolar-beamforming optimization. Results show that the AN-by-both-side model has good secrecy performance on both average and extreme conditions as Eve approaches Alice or Bob.
2009-01-01
The 2009 CERN Relay Race was as popular as ever, with a record number of 88 teams competing. var flash_video_player=get_video_player_path(); insert_player_for_external('Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-0753-kbps-480x360-25-fps-audio-64-kbps-44-kHz-stereo', 'mms://mediastream.cern.ch/MediaArchive/Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-Multirate-200-to-753-kbps-480x360.wmv', 'false', 288, 216, 'https://mediastream.cern.ch/MediaArchive/Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-posterframe-480x360-at-10-percent.jpg', '1178303', true, 'Video/Public/Movies/2009/CERN-MOVIE-2009-048/CERN-MOVIE-2009-048-0600-kbps-maxH-360-25-fps-audio-128-kbps-48-kHz-stereo.mp4'); Even the rain didn’t dampen the spirits, and it still managed to capture the ‘festival feeling’ with live music, beer and stalls from various CERN clubs set up outside Restaurant 1. The Powercuts on the podium after win...
A Circular Polarizer with Beamforming Feature Based on Frequency Selective Surfaces
Yin, Jia Yuan; Wan, Xiang; Ren, Jian; Cui, Tie Jun
2017-01-01
We propose a circular polarizer with beamforming features based on frequency selective surface (FSS), in which a modified anchor-shaped unit cell is used to reach the circular polarizer function. The beamforming characteristic is realized by a particular design of the unit-phase distribution, which is obtained by varying the scale of the unit cell. Instead of using plane waves, a horn antenna is designed to feed the phase-variant FSS. The proposed two-layer FSS is fabricated and measured to verify the design. The measured results show that the proposed structure can convert the linearly polarized waves to circularly polarized waves. Compared with the feeding horn antenna, the transmitted beam of the FSS-added horn is 14.43° broader in one direction, while 3.77° narrower in the orthogonal direction. To our best knowledge, this is the first time to realize circular polarizer with beamforming as the extra function based on FSS, which is promising in satellite and communication systems for potential applications due to its simple design and good performance.
A Circular Polarizer with Beamforming Feature Based on Frequency Selective Surfaces
Yin, Jia Yuan; Wan, Xiang; Ren, Jian; Cui, Tie Jun
2017-01-01
We propose a circular polarizer with beamforming features based on frequency selective surface (FSS), in which a modified anchor-shaped unit cell is used to reach the circular polarizer function. The beamforming characteristic is realized by a particular design of the unit-phase distribution, which is obtained by varying the scale of the unit cell. Instead of using plane waves, a horn antenna is designed to feed the phase-variant FSS. The proposed two-layer FSS is fabricated and measured to verify the design. The measured results show that the proposed structure can convert the linearly polarized waves to circularly polarized waves. Compared with the feeding horn antenna, the transmitted beam of the FSS-added horn is 14.43° broader in one direction, while 3.77° narrower in the orthogonal direction. To our best knowledge, this is the first time to realize circular polarizer with beamforming as the extra function based on FSS, which is promising in satellite and communication systems for potential applications due to its simple design and good performance. PMID:28128345
Design of Relay File Delivery Protocol in Deep Space Communication%深空通信中继文件传输协议设计
焦健; 杨志华; 周洁; 李红兵; 罗辉; 张钦宇
2011-01-01
深空通信极远的传输距离导致链路误码率高,使文件的可靠传输需要较多的重传次数,而其传播时延长的特点,进一步加大了文件传输时延.研究以CCSDS(空间数据系统咨询委员会)文件传输协议的存储—转发机制,提出一种R-CFDP(中继型CFDP协议),设计了3种中继“存储—转发”策略,并数学建模推导了R-CFDP协议的文件传输时延理论计算式.仿真证明R-CFDP协议相对于CFDP(CCSDS文件传输协议)协议在传输时延方面具有优势.%The extremely far distance in deep space communication results in high link error rate. Therefore, reliable file delivery calls for frequent retransmissions. The propagation delay further prolongs file delivery time. This paper proposes an R-CFDP (Relay-CSSDS File Delivery Protocol) mechanism based on the store-and-forward strategy of CCSDS file delivery protocol. Three relay transmission algorithms are introduced. Theoretical and numerical expressions of the file delivery time are derived. Simulation results show that the R-CFDP mechanism has better performance than CFDP in terms of file delivery time.
Reliable Remote Relay Protection in Smart Grid
Jiapeng Zhang; Yingfei Dong
2015-01-01
As the false trips of remote protection relays are among the main reasons behind cascading blackouts, it is critical to design reli⁃able relay protection. Even though common protection schemes on traditional power systems have been investigated for a few de⁃cades, cascading failures in recent years indicate more research needed in this area. Consequently, researchers have proposed agent⁃based methods on the Smart Grid (SG) to address this issue. However, these existing agent⁃based methods simply use TCP protocol without considering real⁃time communication requirements (such as bandwidth and delay). To deal with this issue, several methods for efficient network resource management are proposed. Furthermore, these existing methods do not consider the poten⁃tial issues in practical communication networks, which may result in delay violation and trigger relay false trips. We have dis⁃cussed simple backup solutions in the previous work. In this paper, in addition to network efficiency, we focus on improving the system reliability by exploring known power system information and minimizing the chances of false trips of important remote re⁃lays, e.g., defining power line priorities based on their importance. Moreover, to further improve the system reliability, we also in⁃vestigate the peer⁃to⁃peer protection approaches to address the single point of failure of centralized control center.
Distributed Space Time Coding for Wireless Two-way Relaying
Muralidharan, Vijayvaradharaj T
2012-01-01
We consider the wireless two-way relay channel, in which two-way data transfer takes place between the end nodes with the help of a relay. For the Denoise-And-Forward (DNF) protocol, it was shown by Koike-Akino et. al. that adaptively changing the network coding map used at the relay greatly reduces the impact of Multiple Access interference at the relay. The harmful effect of the deep channel fade conditions can be effectively mitigated by proper choice of these network coding maps at the relay. Alternatively, in this paper we propose a Distributed Space Time Coding (DSTC) scheme, which effectively removes most of the deep fade channel conditions at the transmitting nodes itself without any CSIT and without any need to adaptively change the network coding map used at the relay. It is shown that the deep fades occur when the channel fade coefficient vector falls in a finite number of vector subspaces of $\\mathbb{C}^2$, which are referred to as the singular fade subspaces. DSTC design criterion referred to as ...
张海洋; 黄永明; 杨绿溪
2015-01-01
针对无线携能通信系统中存在能量获取不均衡的问题，提出了一种基于能量获取比例公平的波束成形设计方案。该方案在满足信息接收者的信干噪比以及发送端的最大发送功率等约束条件的基础上，通过优化波束矢量实现能量获取的比例公平。此设计在数学上是一个很难直接求解的非凸优化问题。为此，本文首先利用半定松弛技术将其转换为半定规划问题，然后结合二分法提出了可以获得最优波束矢量的迭代算法。此外，在发送端仅知道部分信道状态信息且知道信道误差范围的情况下，采用最差性能最优的方法对原优化问题进行了鲁棒波束成形设计，并提出了相应的迭代算法。仿真结果表明所提算法均可实现能量获取的比例公平且性能达到全局最优。%In this paper, we propose a beamforming design based on energy harvesting proportional fairness to overcome the unbalance of energy harvesting in a simultaneous wireless information and power transfer system. We aim at achieving the energy harvesting proportional fairness while guaranteeing the signal to interference plus noise ratio constraints at the information receivers and total power constraint at the transmitter by optimizing the beamforming vectors. This optimization problem is of non-convex and hence diﬃcult to solve. In order to solve it, in this paper, we first use the semi-definite relaxation technique as a tool to transform it into a semi-definite program problem, and then propose an iterative algorithm based on bisection method to obtain the optimal beamforming vectors. Besides, we also extend our result to a robust case where the transmitter only knows a part of the channel state information and the bound of channel errors, and propose an iterative algorithm based on worst-case method to obtain the corresponding beamforming vectors. Finally, the simulation results show that the proposed
丁天然; 王乐
2009-01-01
介绍了一种运行在嵌入式Linux平台下的以Web模式远程控制系统的实现方式.对硬件系统架构进行了介绍.以uCLinux操作系统为软件平台,对Boa Web服务器进行配置,然后编写相应的CGI程序响应用户输入,操作底层硬件寄存器,从而达到远程控制的目的.%ion:This paper mainly aims at describing how to design a embedded system in the field of industry-control. It is introduce the architecture of the system. This device based on uClinux op-eration system, combining boa and CGI to handle the input from user and develop some methods to control the relays form remote.
Robust regularized least-squares beamforming approach to signal estimation
Suliman, Mohamed
2017-05-12
In this paper, we address the problem of robust adaptive beamforming of signals received by a linear array. The challenge associated with the beamforming problem is twofold. Firstly, the process requires the inversion of the usually ill-conditioned covariance matrix of the received signals. Secondly, the steering vector pertaining to the direction of arrival of the signal of interest is not known precisely. To tackle these two challenges, the standard capon beamformer is manipulated to a form where the beamformer output is obtained as a scaled version of the inner product of two vectors. The two vectors are linearly related to the steering vector and the received signal snapshot, respectively. The linear operator, in both cases, is the square root of the covariance matrix. A regularized least-squares (RLS) approach is proposed to estimate these two vectors and to provide robustness without exploiting prior information. Simulation results show that the RLS beamformer using the proposed regularization algorithm outperforms state-of-the-art beamforming algorithms, as well as another RLS beamformers using a standard regularization approaches.
Alabbasi, Abdulrahman
2014-06-01
In this paper we consider a cognitive radio multi-input multi-output environment in which we adapt our beamformer to maximize both energy efficiency and signal to interference plus noise ratio (SINR) metrics. Our design considers an underlaying communication using adaptive beamforming schemes combined with the sensing information to achieve an optimal energy efficient system. The proposed schemes maximize the energy efficiency and SINR metrics subject to cognitive radio and quality of service constraints. Since the optimization of energy efficiency problem is not a convex problem, we transform it into a standard semi-definite programming (SDP) form to guarantee a global optimal solution. Analytical solution is provided for one scheme, while the other scheme is left in a standard SDP form. Selected numerical results are used to quantify the impact of the sensing information on the proposed schemes compared to the benchmark ones.
Stochastic beamforming for cochlear implant coding
Morse, Robert P.; Holmes, Stephen D.; Shulgin, Boris; Nikitin, Alexander; Stocks, Nigel G.
2007-06-01
Cochlear implants are prosthetic devices used to provide hearing to people who would otherwise be profoundly deaf. The deliberate addition of noise to the electrode signals could increase the amount of information transmitted, but standard cochlear implants do not replicate the noise characteristic of normal hearing because if noise is added in an uncontrolled manner with a limited number of electrodes then it will almost certainly lead to worse performance. Only if partially independent stochastic activity can be achieved in each nerve fibre can mechanisms like suprathreshold stochastic resonance be effective. We are investigating the use of stochastic beamforming to achieve greater independence. The strategy involves presenting each electrode with a linear combination of independent Gaussian noise sources. Because the cochlea is filled with conductive salt solutions, the noise currents from the electrodes interact and the effective stimulus for each nerve fibre will therefore be a different weighted sum of the noise sources. To some extent therefore, the effective stimulus for a nerve fibre will be independent of the effective stimulus of neighbouring fibres. For a particular patient, the electrode position and the amount of current spread are fixed. The objective is therefore to find the linear combination of noise sources that leads to the greatest independence between nerve discharges. In this theoretical study we show that it is possible to get one independent point of excitation (one null) for each electrode and that stochastic beamforming can greatly decrease the correlation between the noise exciting different regions of the cochlea.
Micro-relay technology for energy-efficient integrated circuits
Kam, Hei
2015-01-01
This book describes the design of relay-based circuit systems from device fabrication to circuit micro-architectures. This book is ideal for both device engineers as well as circuit system designers and highlights the importance of co-design across design hierarchies when optimizing system performance (in this case, energy-efficiency). This book is ideal for researchers and engineers focused on semiconductors, integrated circuits, and energy efficient electronics. This book also: · Covers microsystem fabrication, MEMS device design, circuit design, circuit micro-architecture, and CAD · Describes work previously done in the field and also lays the groundwork and criteria for future energy-efficient device and system design · Maximizes reader insights into the design and modeling of micro-relay, micro-relay reliability, integrated circuit design with micro-relays, and more
Design of Data Relay Station for Wireless Heating Network Meter Reading System%一种无线热网抄表的数据中继站设计
秦飞; 赵建平; 张景顺
2013-01-01
设计了一种基于高性能 ARM11处理器 S3C6410和 GPRS 无线远程通信技术的无线热网抄表系统的数据中继站。无线热网抄表系统的数据中继站主要由无线收发单元,数据处理单元,GPRS 远程数据发送单元3个功能部分组成,着重讨论了中继站数据处理单元部分的设计。实验表明,整个系统实时性好,工作可靠,解决了传统无线抄表成本过高的问题,促进了无线热网抄表应用的推广,具有可观的应用前景。%The paper gives the design of data relay station based on S3C6410 — a high-performance ARM11 processor — and GPRS long-distance wireless communication technology for wireless heating network meter reading system. This data relay station mainly consists of three components including wireless transceiver unit, GPRS data transmission unit and data processing unit. This paper focuses on the design of data processing unit. The experment indicates that this base-station system, with fairly good real-time performance and reliability, could solve the problem of high cost for the traditional wireless meter reading, and thus promote the application and developmeent of the wireless heating network meter reading technology.
Research on beamforming design for multi-user full-duplex SWIPT systems%多用户全双工无线携能系统中的波束赋形研究
王旨; 陈东华; 贺玉成
2016-01-01
A joint optimization scheme based on the dual goals which are the minimization of the power consumption and the maximization of the energy harvest was proposed for the multi-user full-duplex (FD)cellular communication system.The proposed scheme used zero-forcing algorithm to eliminate multi-user interference in the uplinks,in order to achieve the effective transfer of information and energy,the full-duplex base station provided users with communication services via information beamforming and energy beamforming in the downlinks.The proposed scheme made a simulta-neous improvement in power efficiency and spectrum efficiency while guaranteeing the quality-of-service(Qos)of all users and power constraints.Because the problem of power is non-convex,the original problem was transformed to a convex one via semi-definite relaxation.Simulation results show that the proposed scheme provides substantial power savings over traditional scheme.Moreover,FD base station transfers energy to the downlink users through energy beam-forming,which improves power efficiency of the system effectively.%针对多用户全双工蜂窝通信系统，提出了一种基于功耗最小及能量收获最大双目标准则的联合优化方案。该方案采用迫零消除上行链路中多用户干扰，在下行链路，为了实现信息和能量的有效传递，全双工基站分别采用信息波束赋形及能量波束赋形为用户提供通信服务，在保证用户的服务质量及功率约束的同时，实现了功率效率和频谱效率的同步改善。由于功率问题为非凸问题，通过半定松弛将其转化为凸优化问题。仿真结果表明，所提方案相比传统方案能够节约大量的功率，此外全双工基站通过能量波束赋形向下行用户传递能量，有效提高了系统的功率效率。
Plane Wave Medical Ultrasound Imaging Using Adaptive Beamforming
Holfort, Iben Kraglund; Gran, Fredrik; Jensen, Jørgen Arendt
2008-01-01
In this paper, the adaptive, minimum variance (MV) beamformer is applied to medical ultrasound imaging. The Significant resolution and contrast gain provided by the adaptive, minimum variance (MV) beamformer, introduces the possibility of plane wave (PW) ultrasound imaging. Data is obtained using...... Field H and a 7 MHz, 128-elements, linear array transducer with lambda/2-spacing. MV is compared to the conventional delay-and-sum (DS) beamformer with Boxcar and Hanning weights. Furthermore, the PW images are compared to the a conventional ultrasound image, obtained from a linear scan sequence...
Fast Adaptive Beamforming with Smart Antenna for Radio Frequency Repeater
Wang Chaoqun
2016-01-01
Full Text Available We present a fast adaptive beamforming null algorithm with smart antenna for Radio Frequency Repeater (RFR. The smart antenna system is realized by a Direction Of Arrival (DOA Estimator, whose output is used by an adaptive beamforming algorithm to shape a suitable radiation pattern of the equivalent antenna; so that the co-channel interference due to retransmitting antenna can be reduced. The proposed adaptive beamforming algorithm, which has been proved by formulaic analysis and simulation, has a lower computation complexity yet better performance.
Model-Switched Beamformer with Large Dynamic Range
Zeng Hao
2014-01-01
Full Text Available The strong desired signal will be mitigated due to “self-nulling” for the adaptive beamformer, even if the array calibration is used. The proposed methodology switches the models between phased array and adaptive array. In general, the system utilizes Frost adaptive beamforming. However, it will be switched to phased array if the “self-nulling” appears. According to the estimation of the array pattern at the direction of desired signal, we can determine if the “self-nulling” happens. The new approach is much easier to implement compared with the various robust beamforming algorithms.
Performance limitations of relay neurons.
Rahul Agarwal
Full Text Available Relay cells are prevalent throughout sensory systems and receive two types of inputs: driving and modulating. The driving input contains receptive field properties that must be transmitted while the modulating input alters the specifics of transmission. For example, the visual thalamus contains relay neurons that receive driving inputs from the retina that encode a visual image, and modulating inputs from reticular activating system and layer 6 of visual cortex that control what aspects of the image will be relayed back to visual cortex for perception. What gets relayed depends on several factors such as attentional demands and a subject's goals. In this paper, we analyze a biophysical based model of a relay cell and use systems theoretic tools to construct analytic bounds on how well the cell transmits a driving input as a function of the neuron's electrophysiological properties, the modulating input, and the driving signal parameters. We assume that the modulating input belongs to a class of sinusoidal signals and that the driving input is an irregular train of pulses with inter-pulse intervals obeying an exponential distribution. Our analysis applies to any [Formula: see text] order model as long as the neuron does not spike without a driving input pulse and exhibits a refractory period. Our bounds on relay reliability contain performance obtained through simulation of a second and third order model, and suggest, for instance, that if the frequency of the modulating input increases or the DC offset decreases, then relay increases. Our analysis also shows, for the first time, how the biophysical properties of the neuron (e.g. ion channel dynamics define the oscillatory patterns needed in the modulating input for appropriately timed relay of sensory information. In our discussion, we describe how our bounds predict experimentally observed neural activity in the basal ganglia in (i health, (ii in Parkinson's disease (PD, and (iii in PD during
Airborne relay-based regional positioning system
Lee, Kyuman; Noh, Hongjun; Lim, Jaesung
2015-01-01
.... To address these pseudolite system limitations, we propose an airborne relay-based regional positioning system that consists of a master station, reference stations, airborne relays and a user...
Proportional fair scheduling with superposition coding in a cellular cooperative relay system
Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar
2013-01-01
Many works have tackled on the problem of throughput and fairness optimization in cellular cooperative relaying systems. Considering firstly a two-user relay broadcast channel, we design a scheme based on superposition coding (SC) which maximizes the achievable sum-rate under a proportional fairn...
Mobility-Based Mobile Relay Selection in MANETs
Kim, Gilnam; Lee, Hyoungjoo; Lee, Kwang Bok
The future wireless mobile communication networks are expected to provide seamless wireless access and data exchange to mobile users. In particular, it is expected that the demand for ubiquitous data exchange between mobile users will increase with the widespread use of various wireless applications of the intelligent transportation system (ITS) and intelligent vehicles. Mobile ad hoc networks (MANETs) are one of the representative research areas pursuing the technology needed to satisfy the increasing mobile communication requirements. However, most of the works on MANET systems do not take into account the continuous and dynamic changes of nodal mobility to accommodate system design and performance evaluation. The mobility of nodes limits the reliability of communication between the source and the destination node since a link between two continuously moving nodes is established only when one node enters the transmission range of the other. To alleviate this problem, mobile relay has been studied. In particular, it is shown that relay selection is an efficient way to support nodal mobility in MANET systems. In this paper, we propose a mobility-based relay selection algorithm for the MANET environment. Firstly, we define the lifetime as the maximum link duration for which the link between two nodes remains active. Therefore, the lifetime indicates the reliability of the relay link which measures its capability to successfully support relayed communication when requested by the source node. Furthermore, we consider a series of realistic scenarios according to the randomness of nodal mobility. Thus, the proposed algorithm can be easily applied in practical MANET systems by choosing the appropriate node mobility behavior. The numerical results show that the improved reliability of the proposed algorithm's relayed communication is achieved with a proper number of mobile relay nodes rather than with the conventional selection algorithm. Lastly, we show that random
A scalable-low cost architecture for high gain beamforming antennas
Bakr, Omar
2010-10-01
Many state-of-the-art wireless systems, such as long distance mesh networks and high bandwidth networks using mm-wave frequencies, require high gain antennas to overcome adverse channel conditions. These networks could be greatly aided by adaptive beamforming antenna arrays, which can significantly simplify the installation and maintenance costs (e.g., by enabling automatic beam alignment). However, building large, low cost beamforming arrays is very complicated. In this paper, we examine the main challenges presented by large arrays, starting from electromagnetic and antenna design and proceeding to the signal processing and algorithms domain. We propose 3-dimensional antenna structures and hybrid RF/digital radio architectures that can significantly reduce the complexity and improve the power efficiency of adaptive array systems. We also present signal processing techniques based on adaptive filtering methods that enhance the robustness of these architectures. Finally, we present computationally efficient vector quantization techniques that significantly improve the interference cancellation capabilities of analog beamforming architectures. © 2010 IEEE.
Venkateswaran, Vijay; Pivit, Florian; Guan, Lei
2016-07-01
Modern wireless communication networks, particularly cellular networks utilize multiple antennas to improve the capacity and signal coverage. In these systems, typically an active transceiver is connected to each antenna. However, this one-to-one mapping between transceivers and antennas will dramatically increase the cost and complexity of a large phased antenna array system. In this paper, firstly we propose a \\emph{partially adaptive} beamformer architecture where a reduced number of transceivers with a digital beamformer (DBF) is connected to an increased number of antennas through an RF beamforming network (RFBN). Then, based on the proposed architecture, we present a methodology to derive the minimum number of transceivers that are required for marco-cell and small-cell base stations, respectively. Subsequently, in order to achieve optimal beampatterns with given cellular standard requirements and RF operational constraints, we propose efficient algorithms to jointly design DBF and RFBN. Starting from the proposed algorithms, we specify generic microwave RFBNs for optimal marco-cell and small-cell networks. In order to verify the proposed approaches, we compare the performance of RFBN using simulations and anechoic chamber measurements. Experimental measurement results confirm the robustness and performance of the proposed hybrid DBF-RFBN concept eventually ensuring that theoretical multi-antenna capacity and coverage are achieved at a little incremental cost.
Adaptive beamforming for array imaging of plate structures using lamb waves.
Engholm, Marcus; Stepinski, Tadeusz
2010-12-01
Lamb waves are considered a promising tool for the monitoring of plate structures. Large areas of plate structures can be monitored using active arrays employing beamforming techniques. Dispersion and multiple propagating modes are issues that need to be addressed when working with Lamb waves. Previous work has mainly focused on standard delay-and-sum (DAS) beamforming while reducing the effects of multiple modes through frequency selectivity and transducer design. This paper presents a minimum variance distortionless response (MVDR) approach for Lamb waves using a uniform rectangular array (URA) and a single transmitter. Theoretically calculated dispersion curves are used to compensate for dispersion. The combination of the MVDR approach and the two-dimensional array improves the suppression of interfering Lamb modes. The proposed approach is evaluated on simulated and experimental data and compared with the standard DAS beamformer. It is shown that the MVDR algorithm performs better in terms of higher resolution and better side lobe and mode suppression capabilities. Known issues of the MVDR approach, such as signal cancellation in highly correlated environments and poor robustness, are addressed using methods that have proven effective for the purpose in other fields of active imaging.
Optimized Hyper Beamforming of Linear Antenna Arrays Using Collective Animal Behaviour
Gopi Ram
2013-01-01
Full Text Available A novel optimization technique which is developed on mimicking the collective animal behaviour (CAB is applied for the optimal design of hyper beamforming of linear antenna arrays. Hyper beamforming is based on sum and difference beam patterns of the array, each raised to the power of a hyperbeam exponent parameter. The optimized hyperbeam is achieved by optimization of current excitation weights and uniform interelement spacing. As compared to conventional hyper beamforming of linear antenna array, real coded genetic algorithm (RGA, particle swarm optimization (PSO, and differential evolution (DE applied to the hyper beam of the same array can achieve reduction in sidelobe level (SLL and same or less first null beam width (FNBW, keeping the same value of hyperbeam exponent. Again, further reductions of sidelobe level (SLL and first null beam width (FNBW have been achieved by the proposed collective animal behaviour (CAB algorithm. CAB finds near global optimal solution unlike RGA, PSO, and DE in the present problem. The above comparative optimization is illustrated through 10-, 14-, and 20-element linear antenna arrays to establish the optimization efficacy of CAB.
Optimized hyper beamforming of linear antenna arrays using collective animal behaviour.
Ram, Gopi; Mandal, Durbadal; Kar, Rajib; Ghoshal, Sakti Prasad
2013-01-01
A novel optimization technique which is developed on mimicking the collective animal behaviour (CAB) is applied for the optimal design of hyper beamforming of linear antenna arrays. Hyper beamforming is based on sum and difference beam patterns of the array, each raised to the power of a hyperbeam exponent parameter. The optimized hyperbeam is achieved by optimization of current excitation weights and uniform interelement spacing. As compared to conventional hyper beamforming of linear antenna array, real coded genetic algorithm (RGA), particle swarm optimization (PSO), and differential evolution (DE) applied to the hyper beam of the same array can achieve reduction in sidelobe level (SLL) and same or less first null beam width (FNBW), keeping the same value of hyperbeam exponent. Again, further reductions of sidelobe level (SLL) and first null beam width (FNBW) have been achieved by the proposed collective animal behaviour (CAB) algorithm. CAB finds near global optimal solution unlike RGA, PSO, and DE in the present problem. The above comparative optimization is illustrated through 10-, 14-, and 20-element linear antenna arrays to establish the optimization efficacy of CAB.
Xia, Minghua
2012-11-01
For cooperative amplify-and-forward (AF) relaying in spectrum-sharing wireless systems, secondary users share spectrum resources originally licensed to primary users to communicate with each other and, thus, the transmit power of secondary transmitters is strictly limited by the tolerable interference powers at primary receivers. Furthermore, the received signals at a relay and at a secondary receiver are inevitably interfered by the signals from primary transmitters. These co-channel interferences (CCIs) from concurrent primary transmission can significantly degrade the performance of secondary transmission. This paper studies the effect of CCIs on outage probability of the secondary link in a spectrum-sharing environment. In particular, in order to compensate the performance loss due to CCIs, the transmit powers of a secondary transmitter and its relaying node are respectively optimized with respect to both the tolerable interference powers at the primary receivers and the CCIs from the primary transmitters. Moreover, when multiple relays are available, the technique of opportunistic relay selection is exploited to further improve system performance with low implementation complexity. By analyzing lower and upper bounds on the outage probability of the secondary system, this study reveals that it is the tolerable interference powers at primary receivers that dominate the system performance, rather than the CCIs from primary transmitters. System designers will benefit from this result in planning and designing next-generation broadband spectrum-sharing systems.
Optimal beamforming in MIMO systems with HPA nonlinearity
Qi, Jian
2010-09-01
In this paper, multiple-input multiple-output (MIMO) transmit beamforming (TB) systems under the consideration of nonlinear high-power amplifiers (HPAs) are investigated. The optimal beamforming scheme, with the optimal beamforming weight vector and combining vector, is proposed for MIMO systems with HPA nonlinearity. The performance of the proposed MIMO beamforming scheme in the presence of HPA nonlinearity is evaluated in terms of average symbol error probability (SEP), outage probability and system capacity, considering transmission over uncorrelated quasi-static frequency-flat Rayleigh fading channels. Numerical results are provided and show the effects of several system parameters, namely, parameters of nonlinear HPA, numbers of transmit and receive antennas, and modulation order of phase-shift keying (PSK), on performance. ©2010 IEEE.
Joint Transmit Beamforming and Power Control for CDMA System
LI Ji-long; CHEN Yu; LI Chun-yuan; ZHANG Ping
2005-01-01
Downlink transmit beamforming is a promising technique to reduce interference,and power control is a technique to adjust transmission power to satisfy the link quality.Joint transmission power control and beamforming are proposed to minimize total transmission power.The joint optimization problem is solved by receiver beamforming and power control in virtual uplink.SIR based power control is performed to adjust the power allocation,and transmit beamforming weight vectors are determined by Minimum Variance Distortionless Response(MVDR)criterion.The multipath combining weight vectors are determined by maximum ratio combining criterion.Simulation results show the joint optimization scheme decreases the transmission power,and system performance is enhanced.
Collaborative Randomized Beamforming for Phased Array Radio Interferometers
Ocal, Orhan; Cherubini, Giovanni; Kazemi, Sanaz
2014-01-01
The Square Kilometre Array (SKA) will form the largest radio telescope ever built and such a huge instrument in the desert poses enormous engineering and logistic challenges. Algorithmic and architectural breakthroughs are needed. Data is collected and processed in groups of antennas before transport for central processing. This processing includes beamforming, primarily so as to reduce the amount of data sent. The principal existing technique points to a region of interest independently of the sky model and how the other stations beamform. We propose a new collaborative beamforming algorithm in order to maximize information captured at the stations (thus reducing the amount of data transported). The method increases the diversity in measurements through randomized beam- forming. We demonstrate through numerical simulation the effectiveness of the method. In particular, we show that randomized beamforming can achieve the same image quality while producing 40% less data when compared to the prevailing method m...
Adaptive beamforming and phase bias compensation for GNSS receiver
Hongwei Zhao; Baowang Lian; Juan Feng
2015-01-01
Adaptive antenna arrays have been used to mitigate the interference on global navigation satel ite system (GNSS) re-ceivers. The performance of interference mitigation depends on the beamforming algorithms adopted by the antenna array. However, the adaptive beamforming wil change the array pattern in real-time, which has the potential to introduce phase center biases into the antenna array. For precise applications, these phase biases must be mitigated or compensated because they wil bring errors in code phase and carrier phase measurements. A novel adaptive beamforming algorithm is proposed firstly, then the phase bias induced by the proposed algorithm is estimated, and final y a com-pensation strategy is addressed. Simulations demonstrate that the proposed beamforming algorithm suppresses effectively the strong interference and improves significantly the capturing performance of GNSS signals. Simultaneously, the bias compensation method avoids the loss of the carrier phase lock and reduces the phase measurement errors for GNSS receivers.
基于微处理器的大电流模拟继电器的设计%Design of High Current Analogue Relay Based on SCM
林森; 崔转玲
2014-01-01
Due to the limitation of the traditional switch devices, high current switching power supply has small power, low ef-ficiency .After analyzing the PWM soft switching technology , the adjustable frequency and duty ratio of PWM pulse outputs by using AT89C52 microcontroller interrupt, switch or off the large power GT40T101 are controlled, then the control of on-off of the circuit is realized by simulating a relay.By building the circuit,the superiority of PWM in the control of high power soft switching power supply is verified, which has a certain reference value for the practical application of electrical engineering .%由于受到传统开关器件的限制，大电流开关电源存在功率小、效率低等问题，在对PWM软开关技术进行分析后，利用AT89 C52单片机的中断方式输出频率和占空比可调的PWM脉冲，控制大功率开关管GT40 T101的通断，从而实现以模拟继电器的方式控制电路的通断。通过搭建电路验证了PWM软开关在控制大功率电源方面的优越性，对于实际的电气工程应用具有一定的参考价值。
Process bus function design based on backboard bus for relay protection%基于背板总线的继电保护装置过程总线功能设计
丁毅; 叶品勇; 郭晓; 徐頔飞; 尹军
2013-01-01
设计了一种基于背板总线的继电保护装置平台架构.该方案优化装置内部数据流和配置流程,提升装置面向过程总线的通信及数据处理能力.在分析继电保护装置的功能及性能要求的基础上,提出过程总线功能设计总体架构;根据应用数据类型设计背板总线数据流和配置流程,分析以太网扩展、采样值接收与同步、报文透明传输等问题;基于IEC61850模型导出背板总线配置信息并设计下载流程.该设计方案在110 kV智能变电站主变保护测控一体化装置中得到应用,满足装置面向过程总线的功能及性能要求,现场运行结果表明该设计方案的有效性和实用性.%A kind of relay protection platform based on backboard bus is designed,which,with the optimized internal data flow and configuration process,enhances the process-bus-oriented communication and the data processing ability.The requirements of relay protection in functions and performances are analyzed,and a general framework of process bus function design is put forward.The data flow and configuration process are designed according to the types of application data and several topics are discussed,such as Ethernet extension,sample receiving and synchronization,transparent message transmission,etc.The configuration information of backboard bus is deduced based on IEC61850 model and its download process is designed.The proposed design scheme is applied in the integrated measuring and control device of primary transformer protection for 110 kV smart substation and the requirements for process-bus-oriented functions and performances are satisfied.Site operation proves its effectiveness and practicability.
Handover Framework for Relay Enhanced LTE Networks
Teyeb, Oumer Mohammed; Van Phan, Vinh; Raaf, Bernhard
2009-01-01
Relaying is one of the proposed technologies for future releases of UTRAN Long Term Evolution (LTE) networks. Introducing relaying is expected to increase the coverage and capacity of LTE networks. In order to enable relaying, the architecture, protocol and radio resource management procedures of...
Instantaneous Relaying: Optimal Strategies and Interference Neutralization
Ho, Zuleita
2012-01-01
In a multi-user wireless network equipped with multiple relay nodes, some relays are more intelligent than other relay nodes. The intelligent relays are able to gather channel state information, perform linear processing and forward signals whereas the dumb relays is only able to serve as amplifiers. As the dumb relays are oblivious to the source and destination nodes, the wireless network can be modeled as a relay network with *smart instantaneous relay* only: the signals of source-destination arrive at the same time as source-relay-destination. Recently, instantaneous relaying is shown to improve the degrees-of-freedom of the network as compared to classical cut-set bound. In this paper, we study an achievable rate region and its boundary of the instantaneous interference relay channel in the scenario of (a) uninformed non-cooperative source-destination nodes (source and destination nodes are not aware of the existence of the relay and are non-cooperative) and (b) informed and cooperative source-destination...
Quantum cryptography with an ideal local relay
Spedalieri, Gaetana; Ottaviani, Carlo; Braunstein, Samuel L.
2015-01-01
We consider two remote parties connected to a relay by two quantum channels. To generate a secret key, they transmit coherent states to the relay, where the states are subject to a continuous-variable (CV) Bell detection. We study the ideal case where Alice's channel is lossless, i.e., the relay...
Yang, Wei; Sun, Wanlu
2010-01-01
Energy-efficient communication is an important requirement for mobile relay networks due to the limited battery power of user terminals. This paper considers energy-efficient relaying schemes through selection of mobile relays in cooperative cellular systems with asymmetric traffic. The total energy consumption per information bit of the battery-powered terminals, i.e., the mobile station (MS) and the relay, is derived in theory. In the Joint Uplink and Downlink Relay Selection (JUDRS) scheme we proposed, the relay which minimizes the total energy consumption is selected. Additionally, the energy-efficient cooperation regions are investigated, and the optimal relay location is found for cooperative cellular systems with asymmetric traffic. The results reveal that the MS-relay and the relay-base station (BS) channels have different influence over relay selection decisions for optimal energy-efficiency. Information theoretic analysis of the diversity-multiplexing tradeoff (DMT) demonstrates that the proposed sc...
Stochastic Analysis of an Iterative Semi Blind Adaptive Beamforming Algorithm
2009-06-24
beam- forming, demodulation, equalization, and decoding . In each stage, the initial beamformer weights computed by the TDMA training data are refined by...performance of the receiver for the Global System for Mobile commu- nications ( GSM ). In recent years, there has been work on techniques to mitigate the...Viterbi algorithm (SOVA) [5], and decoding . In this paper, we extend the iterative beamformer to in- corporate training-based as well as blind
Practical constraints on estimation of source extent with MEG beamformers
Hillebrand, Arjan; Barnes, Gareth R.
2011-01-01
We aimed to determine practical constraints on the estimation of the spatial extent of neuronal activation using MEG beamformers. Correct estimation of spatial extent is a pre-requisite for accurate models of electrical activity, allows one to estimate current density, and enables non-invasive monitoring of functional recovery following stroke. The output of an MEG beamformer is maximum when the correct source model is used, so that the spatial extent of a source can in principal be determine...
Digital Beamforming Synthetic Aperture Radar (DBSAR) Polarimetric Upgrade
Rincon, Rafael F.; Perrine, Martin; McLinden, Matthew; Valett, Susan
2011-01-01
The Digital Beamforming Synthetic Aperture Radar (DBSAR) is a state-of-the-art radar system developed at NASA/Goddard Space Flight Center for the development and implementation of digital beamforming radar techniques. DBSAR was recently upgraded to polarimetric operation in order to enhance its capability as a science instrument. Two polarimetric approaches were carried out which will be demonstrated in upcoming flight campaigns.
CMOS Bit-Stream Band-Pass Beamforming
2016-03-31
the Antenna Inputs,” IEEE Journal of Solid-State Circuits, Jun., 2014. 4. H. Aliakbarian, et al., “Analogue versus Digital for Baseband Beam...Arbor, Michigan, USA, 48109 Abstract: We introduce a unique bandpass ΣΔ based common module with reconfigurable, bit-stream based digital beam...forming (DBF). An array of bandpass ΣΔ modulators accurately and efficiently digitizes the IF signals. Beam-forming is implemented directly through
Coordinated adaptive beamformer over distributed antenna network
Liu Desheng; Lu Songtao; Sun Jinping; Wang Jun
2013-01-01
The spatial diversity of distributed network demands the individual filter to accommodate the topology of interference environment.In this paper,a type of distributed adaptive beamformer is proposed to mitigate interference over coordinated antenna arrays network.The proposed approach is formulated as generalized sidelobe canceller (GSC) structure to facilitate the convex combination of neighboring nodes' weights,and then it is solved by unconstrained least mean square (LMS) algorithm due to simplicity.Numerical results show that the robustness and convergence rate of antenna arrays network can be significantly improved in strong interference scenario.And they also clearly illustrate that mixing vector is optimized adaptively and adjusted according to the spatial diversity of the distributed nodes which are placed in different power of received signals to interference ratio (SIR) environments.
Signal Processing for Digital Beamforming FMCW SAR
Qin Xin
2014-01-01
Full Text Available According to the limitations of single channel Frequency Modulation Continuous Wave (FMCW Synthetic Aperture Radar (SAR, Digital Beamforming (DBF technology is introduced to improve system performance. Combined with multiple receive apertures, DBF FMCW SAR can obtain high resolution in low pulse repetition frequency, which can increase the processing gain and decrease the sampling frequency. The received signal model of DBF FMCW SAR is derived. The continuous antenna motion which is the main characteristic of FMCW SAR received signal is taken into account in the whole signal processing. The detailed imaging diagram of DBF FMCW SAR is given. A reference system is also demonstrated in the paper by comparing with a single channel FMCW SAR. The validity of the presented diagram is demonstrated with a point target simulation results.
Compound imaging using Synthetic Aperture Sequential Beamformation
Jensen, Casper Bo; Jensen, Jonas; Hemmsen, Martin Christian
2011-01-01
Synthetic Aperture Sequential Beamforming (SASB) is a technique with low complexity and the ability to yield a more uniform lateral resolution with range. However, the presence of speckle artifacts in ultrasound images degrades the contrast. In conventional imaging speckle is reduced by using...... spatial compounding at the cost of a reduced frame rate. The objective is to apply spatial compounding to SASB and evaluate if the images have a reduced speckle appearance and thereby an improved image quality in terms of contrast compared to ordinary SASB. Using the simulation software Field II, RF data...... detection the five second stage images are added to form the compounded image. Using a ProFocus scanner and the 8804 linear array transducer (BK Medical, Herlev, Denmark) measurements of a phantom containing water filled cysts are obtained to validate the simulation results. The setup is the same...
苏为; 黄晓燕; 程恩; 袁飞; 孙海信
2011-01-01
A novel wideband beam-forming structure with constant beam width based on complex coefficients （FIR） digital filters used in underwater acoustic communication is proposed. First, the received signals are compensated with integer sampling period by using delay line. Then their complex envelopes are calculated by using frequency shift method. Finally, the envelopes are weighted by using complex coefficients FIR digital filters whose coefficients are optimized. Simulation re- sults show that, in the communication band, the maximum difference between the designed beam and desired beam is less than 0.3 dB when the ratio of communication band to carrier frequency is 0. 85.
Wang, Rui; Huang, Kaibin
2009-01-01
In this paper, utilizing the relay buffers, we propose an opportunistic decode-wait-and-forward relay scheme for a point-to-point communication system with a half-duplexing relay network to better exploit the time diversity and relay mobility. For instance, we analyze the asymptotic throughput-delay tradeoffs in a dense relay network for two scenarios: (1) fixed relays with \\textit{microscopic fading} channels (multipath channels), and (2) mobile relays with \\textit{macroscopic fading} channels (path loss). In the first scenario, the proposed scheme can better exploit the \\textit{multi-relay diversity} in the sense that with $K$ fixed relays and a cost of $\\mathcal{O}(K)$ average end-to-end packet delay, it could achieve the same optimal asymptotic average throughput as the existing designs (such as regular decode-and-forward relay schemes) with $K^2$ fixed relays. In the second scenario, the proposed scheme achieves the maximum throughput of $\\Theta(\\log K)$ at a cost of $\\mathcal{O}(K/q)$ average end-to-end...
Cyclic Communication and the Inseparability of MIMO Multi-way Relay Channels
Chaaban, Anas
2015-10-27
The K-user MIMO multi-way relay channel (Ychannel) consisting of K users with M antennas each and a common relay node with N antennas is studied in this paper. Each user wants to exchange messages with all the other users via the relay. A transmission strategy is proposed for this channel. The proposed strategy is based on two steps: channel diagonalization and cyclic communication. The channel diagonalization is applied by using zero-forcing beam-forming. After channel diagonalization, the channel is decomposed into parallel sub-channels. Cyclic communication is then applied, where signal-space alignment for network-coding is used over each sub-channel. The proposed strategy achieves the optimal DoF region of the channel if N M. To prove this, a new degrees-of-freedom outer bound is derived. As a by-product, we conclude that the MIMO Y-channel is not separable, i.e., independent coding on separate sub-channels is not enough, and one has to code jointly over several sub-channels.
Exact performance analysis of decode-and-forward opportunistic relaying
Tourki, Kamel
2010-06-01
In this paper, we investigate a dual-hop decode-and-forward opportunistic relaying scheme where the source may or may not be able to communicate directly with the destination. In our study, we consider a regenerative relaying scheme in which the decision to cooperate takes into account the effect of the possible erroneously detected and transmitted data at the best relay. We derive an exact closed-form expression for the end-to-end bit-error rate (BER) of binary phase-shift keying (BPSK) modulation based on the exact statistics of each hop. Unlike existing works where the analysis focused on high signal-to-noise ratio (SNR) regime, such results are important to enable the designers to take decisions regarding practical systems that operate at low SNR regime. We show that performance simulation results coincide with our analytical results.
ARQ strategies for relay cooperative systems
无
2007-01-01
We propose two novel automatic repeat request (ARQ) strategies for relay cooperative systems over Rayleigh fading channel: one uses relay ARQ and the other destination ARQ. The BER performance of these two strategies is derived in fast block fading. Numerical analysis and simulation show the systems can get more performance gain when the inter-channel (the source to the relay) quality is bad in the relay ARQ strategy. In the destination ARQ strategy, when the uplink qualities of the source and relay to the destination are poor, the average received SNR of the destination is much low, the systems performance can be improved efficiently.
Sensitivity improvement of time overcurrent relays
Enriquez, Arturo Conde; Martinez, Ernesto Vazquez [Universidad Autonoma de Nuevo Leon, Facultad de Ingenieria Mecanica y Electrica, Apdo. Postal 114-F, Ciudad Universitaria, CP 66450, San Nicolas de los Garza, Nuevo Leon (Mexico)
2007-02-15
In this paper, we recommend a new adaptive function for time overcurrent relays. The purpose of the adaptation process is to improve the sensitivity of time overcurrent relays, which then operate with a dynamic pickup setting such as a load current. The results obtained from time overcurrent adaptive relays are collated, and the results from analysis of negative sequence relays and conventional time overcurrent relays are also presented. In this article, we describe the control logic structure of an adaptive pickup current and its performance under different operating states. (author)
Relay Selection with Limited and Noisy Feedback
Eltayeb, Mohammed E.
2016-01-28
Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. Nonetheless, relay selection algorithms generally require error-free channel state information (CSI) from all cooperating relays. Practically, CSI acquisition generates a great deal of feedback overhead that could result in significant transmission delays. In addition to this, the fed back channel information is usually corrupted by additive noise. This could lead to transmission outages if the central node selects the set of cooperating relays based on inaccurate feedback information. In this paper, we propose a relay selection algorithm that tackles the above challenges. Instead of allocating each relay a dedicated channel for feedback, all relays share a pool of feedback channels. Following that, each relay feeds back its identity only if its effective channel (source-relay-destination) exceeds a threshold. After deriving closed-form expressions for the feedback load and the achievable rate, we show that the proposed algorithm drastically reduces the feedback overhead and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback from all relays. © 2015 IEEE.
胡晓静; 李志勇; 杨慧霞; 蒋冠前; 杨静
2015-01-01
Perfect station auxiliary power system main diagram and efficient standby power supply automatic switching-on logic should be designed in converter station of HVDC system for the safe and stable operation. According to the electric diagram and operation requirement of Pu'er converter station, five operation conditions are considered and charge/discharge logic and thirteen automatic switching-on/off logic are designed for 10 kV standby power supply automatic switching-on relay, two automatic switching-on/off logics are designed for 400 V standby power supply automatic switching-on relay. Meanwhile, the setting principle and coordination are discussed and the recommended settings are given. The standby power supply automatic switching-on/off logic has been applied in Pu'er converter station, experimental results and operation conditions show that standby power supply automatic switching-on relay will trip the circuit breaker of fault line and switch to standby power supply rapidly while one or two station auxiliary power supply fault without reducing HVDC transmission power, the reliability and stability of HVDC system are greatly improved.%为了保证直流输电工程换流站站用电设备安全稳定运行，必须合理设计站用电系统及备用电源自动投入装置的动作逻辑。以糯扎渡直流输电工程普洱换流站为例，根据主接线形式、运行要求和具体运行工况，对10 kV备自投的五种运行工况分别设计了备自投充放电逻辑和十三种动作投切逻辑，对400 V备自投单母分段运行方式设计了两种动作投切逻辑。同时，对备自投装置的定值整定原则及定值配合相关问题进行了研究，给出了推荐定值。所提出的备自投方案经现场实际运行证明：通过10 kV和400 V两级备自投装置的配合，在各种运行工况下某路或某两路站用电源失电时备自投装置都能快速动作投切至备用电源，无需降低直流输送功率或
Alternate transmission with half-duplex relaying in MIMO interference relay networks
Park, Seongho
2013-12-01
In this paper, we consider an alternate transmission scheme for a multiple-input multiple-output interference relay channel where multiple sources transmit their own signals to their corresponding destinations via one of two relaying groups alternately every time phase. Each of the relaying groups has arbitrary number of relays, and each relay operates in half-duplex amplify-and-forward mode. In our scheme, the received signals at the relay nodes consist of desired signals and two different interference signals such as the inter-source interferences and the inter-group interferences which are caused by the phase incoherence of relaying. As such, we propose an iterative interference alignment algorithm to mitigate the interferences. We show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying system in the interference relay channels. © 2013 IEEE.
Joint design of network-channel coding on relay node%一种中继节点上的网络-信道编码联合设计方案
纪鹏宇; 谢红; 赵蕴龙
2012-01-01
Network coding become the research focus of widespread concerning. Because of it can improve the network throughput, has better robustness, and effectively improve the efficiency of forwarding by relay nodes. Therefore, in the relay node, a joint design of network-channel coding can further improve BER performance of the system BER performance. Based on the research of Razaghi, who designed the two kinds of Bilayer-LDPC codes (divided into Expurgated and Lengthened type), proposes a kind of network-channel coding called NBL-LDPC code (Network Bilayer Lengthened LDPC, referred to as the NBL-LDPC). Meanwhile, This paper shows the process of encoding and decoding, and for this code, the Gaussian density evolution algorithm has to be improved, so the BER performance can be calculated and simulated. Simulation results show that the proposed coding scheme performs better than the NBE-LDPC code(Network Bilayer Expurgated LDPC, referred to as NBE-LDPC).%网络编码技术由于其能提高网络吞吐量、具有较好的鲁棒性、能有效提高中继节点转发效率等优点成为目前广泛关注的研究热点.在中继节点上,采用网络-信道编码联合设计方案能进一步提高系统的误码性能.基于Razaghi等人研究的两种双层LDPC码(Bilayer LDPC,分为删余型和延长型),设计了一种在中继节点上联合设计的网络双层LDPC延长码(Network Bilayer Lengthened LDPC,NBL-LDPC).给出了此码的编译码过程,并针对此码,对高斯密度进化算法进行改进,计算误码率并完成误码性能仿真.仿真结果表明,所提出的编码方案性能要优于利用双层LDPC删余码设计的网络双层LDPC删余码(Network Bilayer Expurgated LDPC,NBE-LDPC).
Opportunistic Scheduling and Beamforming for MIMO-OFDMA Downlink Systems with Reduced Feedback
Pun, Man-On; Poor, H Vincent
2008-01-01
Opportunistic scheduling and beamforming schemes with reduced feedback are proposed for MIMO-OFDMA downlink systems. Unlike the conventional beamforming schemes in which beamforming is implemented solely by the base station (BS) in a per-subcarrier fashion, the proposed schemes take advantages of a novel channel decomposition technique to perform beamforming jointly by the BS and the mobile terminal (MT). The resulting beamforming schemes allow the BS to employ only {\\em one} beamforming matrix (BFM) to form beams for {\\em all} subcarriers while each MT completes the beamforming task for each subcarrier locally. Consequently, for a MIMO-OFDMA system with $Q$ subcarriers, the proposed opportunistic scheduling and beamforming schemes require only one BFM index and $Q$ supportable throughputs to be returned from each MT to the BS, in contrast to $Q$ BFM indices and $Q$ supportable throughputs required by the conventional schemes. The advantage of the proposed schemes becomes more evident when a further feedback ...
Telemetry data via communications relay
Strock, O. J.; Witchey, Michael
This paper responds to a test range engineer's need to relay one or more channels of various types of telemetry data from a remotely-located receiving station to the central telemetry station at range headquarters for real-time processing and display. Several types of data are identified, and specific equipment and technology for multiplexing, transmission, and demultiplexing up to eight streams from a variety of sources is discussed. The widely-used T3 communications link, also known as DS-3, can relay data via satellite, microwave link, or other high-speed path at 44.736 megabits per second, of which about 95 percent can be actual telemetry data; other standard links operate at lower aggregate rates. Several links and rates are discussed, with emphasis in the high-rate T3 link.
Achievable Rates for a Two-Relay Network with Relays-Transmitter Feedbacks
Tebbi, Mohammad Ali; Attari, Mahmoud Ahmadian; Aref, Mohammad Reza
2011-01-01
We consider a relay network with two relays and two feedback links from the relays to the sender. To obtain the achievability results, we use the compress-and-forward and the decode-and-forward strategies to superimpose facility and cooperation analogue to what proposed by Cover and El Gamal for a relay channel. In addition to random binning, we use deterministic binning to perform restricted decoding. We show how to use the feedback links for cooperation between the sender and the relays to transmit the information which is compressed in the sender and the relays.
Simple Low-Rate Non-Binary LDPC Coding for Relay Channels
Suthisopapan, Puripong; Meesomboon, Anupap; Imtawil, Virasit; Sakaniwa, Kohichi
2011-01-01
Binary LDPC coded relay systems have been well studied previously with the assumption of infinite codeword length. In this paper, we deal with non-binary LDPC codes which can outperform their binary counterpart especially for practical codeword length. We utilize non-binary LDPC codes and recently invented non-binary coding techniques known as multiplicative repetition to design the low-rate coding strategy for the decode-and-forward half-duplex relay channel. We claim that the proposed strategy is simple since the destination and the relay can decode with almost the same computational complexity by sharing the same structure of decoder. Numerical experiments are carried out to show that the performances obtained by non-binary LDPC coded relay systems surpass the capacity of direct transmission and also approach within less than 1.5 dB from the achievable rate of the relay channels.
Achieving the capacity of half-duplex degraded relay channels using polar coding
Duo Bin; Wang Zhenyong; Gu Xuemai; Guo Qing
2014-01-01
In this paper, a novel transmission protocol based on polar coding is proposed for the half-duplex degraded relay channel. In the proposed protocol, referred to as the partial message relaying, the relay only needs to forward a part of the decoded source message that the destination needs according to the exquisite nested structure of polar codes. Theoretically, it is proved that the scheme can achieve the capacity of the half-duplex relay channel under the decode-and-forward (DF) cooperation strategy while enjoying low encoding/decoding complexity. Practically, in order to minimize the global transmission power, the optimization of the power allocation is performed between the source and the relay by using information theoretic tools. Furthermore, a joint iterative soft parallel interference cancellation receiver structure is developed to suit to the proposed scheme. Simulation results show that the proposed scheme outperforms the conventional scheme designed by low-density parity-check (LDPC) codes.
Fahui Wu
2016-01-01
Full Text Available This paper considers a simultaneous wireless information and power transfer (SWIPT mechanism in an interference alignment (IA relay system, in which source nodes send wireless information and energy simultaneously to relay nodes, and relay nodes forward the received signal to destination nodes powered by harvested energy. To manage interference and utilize interference as energy source, two-SWIPT receiver is designed, namely, power splitting (PS, and antennas switching (AS has been considered for relay system. The performance of AS- and PS-based IA relay systems is considered, as is a new energy cooperation (ECop scheme that is proposed to improve system performance. Numerical results are provided to evaluate the performance of all schemes and it is shown from the simulations that the performance of proposed ECop outperformed both AS and PS.
Opportunistic Relay Selection With Limited Feedback
Eltayeb, Mohammed E.
2015-08-01
Relay selection is a simple technique that achieves spatial diversity in cooperative relay networks. Generally, relay selection algorithms require channel state information (CSI) feedback from all cooperating relays to make a selection decision. This requirement poses two important challenges, which are often neglected in the literature. Firstly, the fed back channel information is usually corrupted by additive noise. Secondly, CSI feedback generates a great deal of feedback overhead (air-time) that could result in significant performance hits. In this paper, we propose a compressive sensing (CS) based relay selection algorithm that reduces the feedback overhead of relay networks under the assumption of noisy feedback channels. The proposed algorithm exploits CS to first obtain the identity of a set of relays with favorable channel conditions. Following that, the CSI of the identified relays is estimated using least squares estimation without any additional feedback. Both single and multiple relay selection cases are considered. After deriving closed-form expressions for the asymptotic end-to-end SNR at the destination and the feedback load for different relaying protocols, we show that CS-based selection drastically reduces the feedback load and achieves a rate close to that obtained by selection algorithms with dedicated error-free feedback. © 1972-2012 IEEE.
Two Birds and One Stone: Gaussian Interference Channel with a Shared Out-of-Band Relay
Razaghi, Peyman; Zhou, Lei; Yu, Wei; Caire, Giuseppe
2011-01-01
The two-user Gaussian interference channel with a shared out-of-band relay is considered. The relay observes a linear combination of the source signals and broadcasts a common message to the two destinations, through a perfect link of fixed rate R_0 bits per channel use. The out-of-band nature of the relay is reflected by the fact that the common relay message does not interfere with the received signal at the two destinations. We are interested in designing "oblivious" relay strategies that incrementally improve upon the communication strategy in place, i.e., the source encoding strategy (apart from rate allocation) is independent of the relay presence. An ideal relay strategy would have a two-for-one gain, i.e., for every common bit relayed, the rate of each user is increased by one bit. We show that this ideal upper bound cannot be always achieved. Still, for a range of weak interference regimes and for R_0 below a certain threshold depending on signal-to-noise and interference-to-noise ratios (SNR and INR...
On the Performance of Selection Relaying
Adinoyi, Abdulkareem; Yanikomeroglu, Halim; Poor, H Vincent
2008-01-01
Interest in selection relaying is growing. The recent developments in this area have largely focused on information theoretic analyses such as outage performance. Some of these analyses are accurate only at high SNR regimes. In this paper error rate analyses that are sufficiently accurate over a wide range of SNR regimes are provided. The motivations for this work are that practical systems operate at far lower SNR values than those supported by the high SNR analysis. To enable designers to make informed decisions regarding network design and deployment, it is imperative that system performance is evaluated with a reasonable degree of accuracy over practical SNR regimes. Simulations have been used to corroborate the analytical results, as close agreement between the two is observed.
李全忠; 黄济宇; 罗丽平; 秦家银
2012-01-01
This paper considers linear transceiver design for amplify-and-forward multiple-input multiple-output (MMO) multiple-relay systems,aiming to minimize the mean squared error (MSE) under the total relay transmit power constraint.We first introduce the singular value decomposition (SVD) of matrix product and simplify the original optimization problem to one which takes a singular value vector and a unitary matrix as optimization variables.By employing variable substitution and penalty term, the simplified problem only has one unitary matrix constraint.Then we develop a new Riemann Euclidean steepest descent algorithm to deal with the unitary matrix constraint.Finally,simulation results demonstrate that the performance of the proposed scheme is better than traditional schemes and closes to the lower bound of MSE.%本文以放大转发MIMO多中继系统为研究对象,研究其联合线性收发机的优化设计问题,其基本思想是在中继的总发射功率约束下,最小化系统的均方误差(MSE).为降低系统复杂度,本文首先引入了乘积矩阵的奇异值分解,把收发机的设计简化为以奇异值向量和酉矩阵为优化变量的优化问题;接着利用变量替换并引入罚项,将简化后的问题转化成只有酉矩阵约束的优化问题.在此基础上,通过引入替换变量的欧氏梯度,设计了新的黎曼欧氏最陡下降算法,从而有效地处理酉矩阵约束.仿真结果表明,与传统的设计方法相比,本文提出的方案性能最优,最接近MSE下界.
刘洋; 李京娥; 李颖
2014-01-01
The bilayer density evolution algorithm is always used to design bilayer lengthened LDPC codes for the decode-and-forward relay system.The general approach is to fix the lower variable degree distribution and then find an upper variable degree distribution,which has higher complexity.To solve this problem,the Gaussian approximation algorithm is proposed to implement the overall optimization for the lower and upper variable degree distributions.The proposed algorithm aims at maximizing the rates of the source-to-relay and the source-to-destination link simultaneously,which has lower complexity.Simulation results show that the gap between the convergence threshold and the theoretical limit of the proposed LDPC codes is smaller and that BER performance is almost the same as that of the ensembles obtained by bilayer density evolution.%译码转发中继系统中双层延长低密度奇偶校验(LDPC)码设计，一般采用双层密度进化算法，固定下层变量节点度分布来搜索上层变量节点度分布，复杂度很高。针对这一问题，提出了高斯近似算法对上下层变量节点度分布进行整体优化，以达到信源到目的和信源到中继两条链路上的传输速率同时最大的目的，复杂度较低。仿真结果表明，文中设计的双层延长 LDPC码的译码阈值与理论限的间隔较小，误码性能与利用双层密度进化算法搜索到的最优码集接近。
Diamantis, Konstantinos; Greenaway, Alan H.; Anderson, Tom
2017-01-01
Recent progress in adaptive beamforming techniques for medical ultrasound has shown that current resolution limits can be surpassed. One method of obtaining improved lateral resolution is the Minimum Variance (MV) beamformer. The frequency domain implementation of this method effectively divides ...... the MVS beamformer is not suitable for imaging continuous targets, and significant resolution gains were obtained only for isolated targets....
Guided wave phased array beamforming and imaging in composite plates.
Yu, Lingyu; Tian, Zhenhua
2016-05-01
This paper describes phased array beamforming using guided waves in anisotropic composite plates. A generic phased array algorithm is presented, in which direction dependent guided wave parameters and the energy skew effect are considered. This beamforming at an angular direction is achieved based on the classic delay-and-sum principle by applying phase delays to signals received at array elements and adding up the delayed signals. The phase delays are determined with the goal to maximize the array output at the desired direction and minimize it otherwise. For array characterization, the beam pattern of rectangular grid arrays in composite plates is derived. In addition to the beam pattern, the beamforming factor in terms of wavenumber distribution is defined to provide intrinsic explanations for phased array beamforming. The beamforming and damage detection in a composite plate are demonstrated using rectangular grid arrays made by a non-contact scanning laser Doppler vibrometer. Detection images of the composite plate with multiple surface defects at various directions are obtained. The results show that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.
Localization of coherent sources by simultaneous MEG and EEG beamformer.
Hong, Jun Hee; Ahn, Minkyu; Kim, Kiwoong; Jun, Sung Chan
2013-10-01
Simultaneous magnetoencephalography (MEG) and electroencephalography (EEG) analysis is known generally to yield better localization performance than a single modality only. For simultaneous analysis, MEG and EEG data should be combined to maximize synergistic effects. Recently, beamformer for simultaneous MEG/EEG analysis was proposed to localize both radial and tangential components well, while single modality analyses could not detect them, or had relatively higher location bias. In practice, most interesting brain sources are likely to be activated coherently; however, conventional beamformer may not work properly for such coherent sources. To overcome this difficulty, a linearly constrained minimum variance (LCMV) beamformer may be used with a source suppression strategy. In this work, simultaneous MEG/EEG LCMV beamformer using source suppression was formulated firstly to investigate its capability over various suppression strategies. The localization performance of our proposed approach was examined mainly for coherent sources and compared thoroughly with the conventional simultaneous and single modality approaches, over various suppression strategies. For this purpose, we used numerous simulated data, as well as empirical auditory stimulation data. In addition, some strategic issues of simultaneous MEG/EEG analysis were discussed. Overall, we found that our simultaneous MEG/EEG LCMV beamformer using a source suppression strategy is greatly beneficial in localizing coherent sources.
Novel Adaptive Beamforming Algorithm Based on Wavelet Packet Transform
Zhang Xiaofei; Xu Dazhuan
2005-01-01
An analysis of the received signal of array antennas shows that the received signal has multi-resolution characteristics, and hence the wavelet packet theory can be used to detect the signal. By emplying wavelet packet theory to adaptive beamforming, a wavelet packet transform-based adaptive beamforming algorithm (WP-ABF) is proposed . This WP-ABF algorithm uses wavelet packet transform as the preprocessing, and the wavelet packet transformed signal uses least mean square algorithm to implement the adaptive beamforming. White noise can be wiped off under wavelet packet transform according to the different characteristics of signal and white under the wavelet packet transform. Theoretical analysis and simulations demonstrate that the proposed WP-ABF algorithm converges faster than the conventional adaptive beamforming algorithm and the wavelet transform-based beamforming algorithm. Simulation results also reveal that the convergence of the algorithm relates closely to the wavelet base and series; that is, the algorithm convergence gets better with the increasing of series, and for the same series of wavelet base the convergence gets better with the increasing of regularity.
Joint Transceiver Design Scheme for MU-MIMO Relay System%多用户中继系统中联合收发机的设计方案
戎平; 李莉; 罗汉文; 张静
2013-01-01
A joint transceiver design scheme where the direct link is considered based on the minimum mean squared error (MMSE) criterion is proposed in this paper.An iterative algorithm is employed which can alternately optimize the relay precoder and user decoder.Numerical results show that,the proposed scheme outperforms the existing schemes,such as MMSE without direct link and LMMSE schemes in terms of MSE and BER.%在多用户中继系统中,根据最小均方误差(MMSE)准则,提出了一种考虑直接路径的联合收发机设计方案.给出了迭代算法,对中继发射机和用户接收机进行了联合优化,其中用户接收机是用来接收合并源端发送信号和中继发送信号.数据仿真结果表明,提出的方案与不考虑直接路径的收发机方案以及其他已知的LMMSE方案相比,在均方误差(MSE)和误码率(BER)性能方面,有较大的提高.
刘振安; 杨鸣; 徐菁
2001-01-01
This paper is concerned with the hardware design of the long-distance digital speech communication system without relay. This system use AMBE1000(tm) codec chip combined with LSP1027 PCM processor for digital voice processing, FX909A and FX429A chip as modem, and AT89C52 single chip controller as central unit for data interface and communication.%本文主要讨论了远距离无中继有线通讯系统的硬件设计思想。本通讯系统采用AMBE1000TM CODEC结合LSP1027语音PCM信号处理芯片进行语音信号的处理；同时，采用FX909A和FX429A传输数字化后的语音信号；在整体上，采用AT89C52单片处理器负责接口、各环节之间的数据通讯和必要的数据处理。
Pingping Huang
2015-01-01
Full Text Available For future spaceborne synthetic aperture radar (SAR missions, digital beamforming (DBF on receive in elevation to form a sharp high receive beam will be adopted to improve the signal to noise ratio (SNR level and suppress range ambiguities. However, in some special cases, range ambiguities may be received by grating lobes with the high receive beam gain, and range ambiguities would not be well suppressed and even may be increased. In this paper, a new receiving approach based on analog beamforming (ABF and DBF is proposed. According to the spaceborne SAR imaging geometry and the selected pulse repetition frequency (PRF, the antenna patterns of all subapertures of the whole receive antenna in elevation are adjusted by ABF at first. Afterwards, signals from all subapertures in elevation are combined by a real time DBF processor onboard. Since grating lobes could be suppressed by the antenna pattern of the subapertures via ABF, range ambiguities would be well suppressed even if ambiguities are received by grating lobes. Simulation results validate the proposed approach.
Performance analysis of opportunistic nonregenerative relaying
Tourki, Kamel
2013-01-01
Opportunistic relaying in cooperative communication depends on careful relay selection. However, the traditional centralized method used for opportunistic amplify-and-forward protocols requires precise measurements of channel state information at the destination. In this paper, we adopt the max-min criterion as a relay selection framework for opportunistic amplify-and-forward cooperative communications, which was exhaustively used for the decode-and-forward protocol, and offer an accurate performance analysis based on exact statistics of the local signal-to-noise ratios of the best relay. Furthermore, we evaluate the asymptotical performance and deduce the diversity order of our proposed scheme. Finally, we validate our analysis by showing that performance simulation results coincide with our analytical results over Rayleigh fading channels, and we compare the max-min relay selection with their centralized channel state information-based and partial relay selection counterparts.
On information flow in relay networks
El Gamal, A.
Preliminary investigations conducted by El Gamal and Cover (1980) have shown that a max-flow min-cut interpretation for the capacity expressions of the classes of degraded and semideterministic relay channels can be found. In this paper it is shown that such an interpretation can also be found for fairly general classes of discrete memoryless relay networks. Cover and El Gamal (1979) have obtained general lower and upper bounds to capacity. However, the capacity of the general relay channel is not known. Past results are here extended to establish the capacity of deterministic relay networks with no interference and degraded relay networks. A general upper bound is given to the capacity of any relay network with this upper bound being a natural generalization of Theorem 4 in the study conducted by Cover and El Gamal (1979).
Alternate transmission relaying based on interference alignment in 3-relay half-duplex MIMO systems
Park, Seongho
2012-09-01
In a half-duplex relaying, the capacity pre-log factor 1/2 is a major drawback in spectral efficiency. This paper proposes a linear precoding/decoding scheme and an alternate relaying protocol in a dual-hop half-duplex system where three relays help the communication between the source and the destination. In our proposed scheme, we consider a phase incoherent method in relays in which the source alternately transmits message signals to the different relays. In addition, we propose a linear interference alignment scheme which can suppress the inter-relay interference resulting from the phase incoherence of relaying. Based on our analysis of degrees of freedom and our simulation results, we show that our proposed scheme achieves additional degrees of freedom compared to the conventional half-duplex relaying. © 2012 IEEE.
Motion compensated beamforming in synthetic aperture vector flow imaging
Oddershede, Niels; Jensen, Jørgen Arendt
2006-01-01
. Here the SNR is -10 dB compared to the stationary scatterer. A 2D motion compensation method for synthetic aperture vector flow imaging is proposed, where the former vector velocity estimate is used for compensating the beamforming of new data. This method is tested on data from an experimental flow......In synthetic aperture imaging the beamformed data from a number of emissions are summed to create dynamic focusing in transmit. This makes the method susceptible to motion, which is especially the case for the synthetic aperture flow estimation method, where large movements are expected......) of the beamformed response from the scatterer at all velocities is compared to that of a stationary scatterer. For lateral movement, the SNR drops almost linearly with velocity to -4 dB at I m/s, while for axial movement the SNR drop is largest, when the scatterer moves a quarter of a wavelength between emissions...
Square Kilometre Array station configuration using two-stage beamforming
Jiwani, Aziz; Razavi-Ghods, Nima; Hall, Peter J; Padhi, Shantanu; de Vaate, Jan Geralt bij
2012-01-01
The lowest frequency band (70 - 450 MHz) of the Square Kilometre Array will consist of sparse aperture arrays grouped into geographically-localised patches, or stations. Signals from thousands of antennas in each station will be beamformed to produce station beams which form the inputs for the central correlator. Two-stage beamforming within stations can reduce SKA-low signal processing load and costs, but has not been previously explored for the irregular station layouts now favoured in radio astronomy arrays. This paper illustrates the effects of two-stage beamforming on sidelobes and effective area, for two representative station layouts (regular and irregular gridded tile on an irregular station). The performance is compared with a single-stage, irregular station. The inner sidelobe levels do not change significantly between layouts, but the more distant sidelobes are affected by the tile layouts; regular tile creates diffuse, but regular, grating lobes. With very sparse arrays, the station effective area...
Robust Beamforming in Interference Channels with Imperfect Transmitter Channel Information
Mochaourab, Rami
2011-01-01
We consider $K$ links operating concurrently in the same spectral band. Each transmitter has multiple antennas, while each receiver uses a single antenna. This setting corresponds to the multiple-input single-output interference channel. We assume perfect channel state information at the receivers whereas the transmitters only have estimates of the true channels. The channel estimation errors are assumed to be bounded in elliptical regions whose geometry is known at the transmitters. Robust beamforming optimizes worst-case received power gains, and a Pareto optimal point is a worst-case achievable rate tuple from which it is impossible to increase a link's performance without degrading the performance of another. We characterize the robust beamforming vectors necessary to operate at any Pareto optimal point. Moreover, these beamforming vectors are parameterized by $K(K-1)$ real-valued parameters. We analyze the system's spectral efficiency at high and low signal-to-noise ratio (SNR). Zero forcing transmission...
Composite multiobjective optimization beamforming based on genetic algorithms
Shi Jing; Meng Weixiao; Zhang Naitong; Wang Zheng
2006-01-01
All thc parameters of beamforming are usually optimized simultaneously in implementing the optimization of antenna array pattern with multiple objectives and parameters by genetic algorithms (GAs).Firstly, this paper analyzes the performance of fitness functions of previous algorithms. It shows that original algorithms make the fitness functions too complex leading to large amount of calculation, and also the selection of the weight of parameters very sensitive due to many parameters optimized simultaneously. This paper proposes a kind of algorithm of composite beamforming, which detaches the antenna array into two parts corresponding to optimization of different objective parameters respectively. New algorithm substitutes the previous complex fitness function with two simpler functions. Both theoretical analysis and simulation results show that this method simplifies the selection of weighting parameters and reduces the complexity of calculation. Furthermore, the algorithm has better performance in lowering side lobe and interferences in comparison with conventional algorithms of beamforming in the case of slightly widening the main lobe.
Introduction to the SKA low correlator and beamformer system
Hampson, Grant A.; Bunton, John D.; Gunst, Andre W.; Baillie, Peter; bij de Vaate, Jan-Geralt
2016-07-01
The Square Kilometre Array (SKA) organisation is building a low frequency (50-350 MHz) aperture array to be located in remote Western Australia. The array consists of 512-stations, each consisting of 256-dual polarisation log-periodic antennas. The stations are distributed over a distance of 80km, with the greatest density of stations located in the central core. The input bandwidth is processed in a two stage polyphase filterbank, with the first stage channeliser producing 384 x 781 kHz narrow-band channels. Each station beamforms the antennas together to form a single dual polarisation beam with a bandwidth of 300 MHz (additional beams can also be traded for bandwidth). The second stage polyphase filterbank is located in a system called the Correlator and BeamFormer (CBF) which is the topic of this paper. In the CBF the station signals are first aligned in time. Thereafter the signals are simultaneously correlated and beamformed.
Beam-Forming Concentrating Solar Thermal Array Power Systems
Cwik, Thomas A. (Inventor); Dimotakis, Paul E. (Inventor); Hoppe, Daniel J. (Inventor)
2016-01-01
The present invention relates to concentrating solar-power systems and, more particularly, beam-forming concentrating solar thermal array power systems. A solar thermal array power system is provided, including a plurality of solar concentrators arranged in pods. Each solar concentrator includes a solar collector, one or more beam-forming elements, and one or more beam-steering elements. The solar collector is dimensioned to collect and divert incoming rays of sunlight. The beam-forming elements intercept the diverted rays of sunlight, and are shaped to concentrate the rays of sunlight into a beam. The steering elements are shaped, dimensioned, positioned, and/or oriented to deflect the beam toward a beam output path. The beams from the concentrators are converted to heat at a receiver, and the heat may be temporarily stored or directly used to generate electricity.
The Laser Communications Relay and the Path to the Next Generation Near Earth Relay
Israel, David J.
2015-01-01
NASA Goddard Space Flight Center is currently developing the Laser Communications Relay Demonstration (LCRD) as a Path to the Next Generation Near Earth Space Communication Network. The current NASA Space Network or Tracking and Data Relay Satellite System is comprised of a constellation of Tracking and Data Relay Satellites (TDRS) in geosynchronous orbit and associated ground stations and operation centers. NASA is currently targeting a next generation of relay capability on orbit in the 2025 timeframe.
Uplink Capacity of 802.16j Mobile Multihop Relay Networks with Transparent Relays
Wang, Hua; Andrews, Jeffrey G.; Iversen, Villy Bæk
2009-01-01
-input multi-output (MIMO) transmission is applied in the relay link. We derived the cell coverage and average spectral efficiency, as well as the system Erlang capacity supporting both voice and data traffic. The numerical results show that MIMO transmission in the relay link can significantly improve the end...... in the relay link, significant capacity gains can be achieved with a two-hop 802.16J relay system compared to the conventional single-hop 802.16e system....
Relay self interference minimisation using tapped filter
Jazzar, Saleh
2013-05-01
In this paper we introduce a self interference (SI) estimation and minimisation technique for amplify and forward relays. Relays are used to help forward signals between a transmitter and a receiver. This helps increase the signal coverage and reduce the required transmitted signal power. One problem that faces relays communications is the leaked signal from the relay\\'s output to its input. This will cause an SI problem where the new received signal at the relay\\'s input will be added with the unwanted leaked signal from the relay\\'s output. A Solution is proposed in this paper to estimate and minimise this SI which is based upon using a tapped filter at the destination. To get the optimum weights for this tapped filter, some channel parameters must be estimated first. This is performed blindly at the destination without the need of any training. This channel parameter estimation method is named the blind-self-interference-channel-estimation (BSICE) method. The next step in the proposed solution is to estimate the tapped filter\\'s weights. This is performed by minimising the mean squared error (MSE) at the destination. This proposed method is named the MSE-Optimum Weight (MSE-OW) method. Simulation results are provided in this paper to verify the performance of BSICE and MSE-OW methods. © 2013 IEEE.
An improved minimum variance beamforming applied to plane-wave imaging in medical ultrasound
Deylami, Ali Mohades; Asl, Babak Mohammadzadeh; Jensen, Jørgen Arendt
2016-01-01
Minimum variance beamformer (MVB) is an adaptive beamformer which provides images with higher resolution and contrast in comparison with non-adaptive beamformers like delay and sum (DAS). It finds weight vector of beamformer by minimizing output power while keeping the desired signal unchanged. We...... used the eigen-based MVB and generalized coherence factor (GCF) to further improve the quality of MVB beamformed images. The eigen-based MVB projects the weight vector with a transformation matrix constructed from eigen-decomposing of the array covariance matrix that increases resolution and contrast...
Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems
Sheng Chen; Wang Yao; Lajos Hanzo
2010-01-01
A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna array's elements, are first utilised to provide a rough initial least squares estimate of the beamformer's weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.
A weighting orthogonal method for constant beamwidth beamforming matrices
DU Jinxiang; YAN Shenggang; LI Zhishun
2007-01-01
A weighting orthogonal method for constant beamwidth beamforming matrices is proposed. This method multiplies weighting factors to each orthogonal beamforming matrix corresponding to different frequency bins. The method proposed doesn't cause waveform aberration, and doesn't cause additional loss of array signal-to-noise ratio when the sources have uniform spectrum. The waveform aberration and additional loss of array signal-to-noise ratio can not be avoided simultaneously by ordinary orthogonal method. So we can get good detection and estimation performances at the same time by the weighting method. Simulation results and water tank experiments are presented to confirm the conclusion above.
Bit-Interleaved Coded Multiple Beamforming with Constellation Precoding
Park, Hong Ju
2009-01-01
In this paper, we present the diversity order analysis of bit-interleaved coded multiple beamforming (BICMB) combined with the constellation precoding scheme. Multiple beamforming is realized by singular value decomposition of the channel matrix which is assumed to be perfectly known to the transmitter as well as the receiver. Previously, BICMB is known to have a diversity order bound related with the product of the code rate and the number of parallel subchannels, losing the full diversity order in some cases. In this paper, we show that BICMB combined with the constellation precoder and maximum likelihood detection achieves the full diversity order. We also provide simulation results that match the analysis.
Systems, Apparatuses and Methods for Beamforming RFID Tags
Fink, Patrick W. (Inventor); Lin, Gregory Y. (Inventor); Ngo, Phong H. (Inventor); Kennedy, Timothy F. (Inventor)
2017-01-01
A radio frequency identification (RFID) system includes an RFID interrogator and an RFID tag having a plurality of information sources and a beamforming network. The tag receives electromagnetic radiation from the interrogator. The beamforming network directs the received electromagnetic radiation to a subset of the plurality of information sources. The RFID tag transmits a response to the received electromagnetic radiation, based on the subset of the plurality of information sources to which the received electromagnetic radiation was directed. Method and other embodiments are also disclosed.
Protective relaying theory and applications
Elmore, Walter A
2003-01-01
Targeting the latest microprocessor technologies for more sophisticated applications in the field of power system short circuit detection, this revised and updated source imparts fundamental concepts and breakthrough science for the isolation of faulty equipment and minimization of damage in power system apparatus. The Second Edition clearly describes key procedures, devices, and elements crucial to the protection and control of power system function and stability. It includes chapters and expertise from the most knowledgeable experts in the field of protective relaying, and describes micropro
Liu, Huaping; Sun, Fan; De Carvalho, Elisabeth;
2013-01-01
Two-way relaying in wireless systems has initiated a large research effort during the past few years. Nevertheless, it represents only a specific traffic pattern and it is of interest to investigate other traffic patterns where such a simultaneous processing of information flows can bring...... in such a way that one RS and the terminals associated with it do not interfere with the other RS, and vice versa. We introduce and analyze a two-phase transmission scheme to serve the four-way traffic pattern defined in this scenario. Each phase consists of combined broadcast and multiple access. We analyze...
Ultrasound Beamforming Methods for Large Coherent Apertures
Bottenus, Nick
improved with growing aperture size up to the extent of the simulated array. Contrast was increased by up to 8.4 dB and CNR by 15.5% for the full aperture compared to a 1.92 cm length array in addition to the significantly improved resolution. While the magnitude of aberration was estimated to be 25.4 ns in the simulation, reverberation clutter seemed to be the dominant source of image degradation in these studies. Selected nonlinear beamforming methods were applied to both data sets to produce images with reduced acoustic clutter. Spatial compounding was applied to the large aperture to improve contrast by 13.4 dB and CNR by 54.4%, greatly increasing the visibility of the anechoic lesion target. It is hypothesized that the variation in the acoustic properties of the abdominal wall across the extent of the large aperture led to variations in the observed clutter that were favorable for spatial compounding. Short-lag spatial coherence (SLSC) imaging applied to the synthetic aperture images also improved image quality, but had a smaller impact for the large array data than has been previously described in the literature. Strongly suppressed spatial coherence was observed across the large array and may have limited the ability of SLSC to reduce the impact of clutter in the images. In summary, by combining advanced beamforming methods with a large aperture extent, high quality images were produced in challenging imaging environments. This work suggests that development of a large coherent ultrasound system would benefit patients whose needs cannot be met with current technologies due to insufficient resolution at depth.
Beamforming effects on generalized Nakagami imaging
Yu, Xue; Guo, Yuexin; Huang, Sheng-Min; Li, Meng-Lin; Lee, Wei-Ning
2015-10-01
Ultrasound tissue characterization is crucial for the detection of tissue abnormalities. Since the statistics of the backscattered ultrasound signals strongly depend on density and spatial arrangement of local scatterers, appropriate modeling of the backscattered signals may be capable of providing unique physiological information on local tissue properties. Among various techniques, the Nakagami imaging, realized in a window-based estimation scheme, has a good performance in assessing different scatterer statistics in tissues. However, inconsistent m values have been reported in literature and obtained only from a local tissue region, abating the reliability of Nakagami imaging in tissue characterization. The discrepancies in m values in relevant literature may stem from the nonuniformity of the ultrasound image resolution, which is often neglected. We therefore hypothesized that window-based Nakagami m estimation was highly associated with the regional spatial resolution of ultrasound imaging. To test this hypothesis, our study investigated the effect of beamforming methods, including synthetic aperture (SA), coherent plane wave compounding (CPWC), multi-focusing (MF), and single-focusing (SF), on window-based m parameter estimation from the perspective of the resolution cell. The statistics of m parameter distribution as a function of imaging depth were characterized by their mean, variance, and skewness. The phantom with a low scatterer density (16 scatterers mm-3) had significantly lower m values compared to the ones with high scatterer densities (32 and 64 scatterers mm-3). Results from the homogeneous phantom with 64 scatterers mm-3 showed that SA, MF, and CPWC had relatively uniform lateral resolutions compared to SF and thus relatively constant m estimates at different imaging depths. Our findings suggest that an ultrasound imaging regime exhibiting invariant spatial resolution throughout the entire imaging field of view would be the most appropriate for
Relay Selection and Resource Allocation in One-Way and Two-Way Cognitive Relay Networks
Alsharoa, Ahmad M.
2013-05-08
In this work, the problem of relay selection and resource power allocation in one- way and two-way cognitive relay networks using half duplex channels with different relaying protocols is investigated. Optimization problems for both single and multiple relay selection that maximize the sum rate of the secondary network without degrading the quality of service of the primary network by respecting a tolerated interference threshold were formulated. Single relay selection and optimal power allocation for two-way relaying cognitive radio networks using decode-and-forward and amplify-and-forward protocols were studied. Dual decomposition and subgradient methods were used to find the optimal power allocation. The transmission process to exchange two different messages between two transceivers for two-way relaying technique takes place in two time slots. In the first slot, the transceivers transmit their signals simultaneously to the relay. Then, during the second slot the relay broadcasts its signal to the terminals. Moreover, improvement of both spectral and energy efficiency can be achieved compared with the one-way relaying technique. As an extension, a multiple relay selection for both one-way and two-way relaying under cognitive radio scenario using amplify-and-forward were discussed. A strong optimization tool based on genetic and iterative algorithms was employed to solve the formulated optimization problems for both single and multiple relay selection, where discrete relay power levels were considered. Simulation results show that the practical and low-complexity heuristic approaches achieve almost the same performance of the optimal relay selection schemes either with discrete or continuous power distributions while providing a considerable saving in terms of computational complexity.
Innovation Relay: Empowering School Nurses to Find New Solutions for Old Problems.
Maughan, Erin D; Galemore, Cynthia; Mattey, Beth
2016-09-01
NASN's 48th Annual School Nurse Conference-Learning, Linking, Leading-included the first ever innovation relay contest. The relay was based on a design developed by the Institute of Healthcare Improvement's Innovation Relay. Participation included 43 contestants from 16 states and one foreign country. Teams were given 24 hours to develop a solution. This article describes the process utilized, the problem introduced, and a brief synopsis of each team's solution. The ongoing purpose of the exercise is to encourage innovation by school nurses as they experience student health-related barriers in the academic setting.
Design on Injection Mould for Small Relay Promoting Block%小型继电器推动块注塑模具设计
郭新玲; 潘晓析
2013-01-01
针对尺寸小、批量大的推动块制品在生产过程中出现其不能自动落下这一问题,从型腔、浇注系统和推出机构设计等方面进行了分析和改进,通过采用潜伏式浇口和增设气动吹出装置,解决了小型制品脱模困难这一问题.该模具结构合理,动作可靠,成型制品质量好,效率高,生产成本低.%Aiming at the problem of small size and large quantities of promoting block products which can't demould automatically during the production process, the cavity design, gating system and the introduction of institutional design were analyzed and improved; through the use of the submarine gate and additional pneumatic blowing institutions, the demolding problem of small products was solved. The mould is reasonable in structure and reliable in operation; the quality of molding products are good, the molding efficiency is high, and the production cost is low.
Cognitive relaying and power allocation under channel state uncertainties
Pandarakkottilil, Ubaidulla
2013-04-01
In this paper, we present robust joint relay precoder designs and transceiver power allocations for a cognitive radio network under imperfect channel state information (CSI). The secondary (or cognitive) network consists of a pair of single-antenna transceiver nodes and a non-regenerative two-way relay with multiple antennas which aids the communication process between the transceiver pair. The secondary nodes share the spectrum with a licensed primary user (PU) while guaranteeing that the interference to the PU receiver is maintained below a specified threshold. We consider two robust designs: the first is based on the minimization of the total transmit power of the secondary relay node required to provide the minimum quality of service, measured in terms of mean-square error (MSE) of the transceiver nodes, and the second is based on the minimization of the sum-MSE of the transceiver nodes. The robust designs are based on worst-case optimization and take into account known parameters of the error in the CSI to render the performance immune to the presence of errors in the CSI. Though the original problem is non-convex, we show that the proposed designs can be reformulated as tractable convex optimization problems that can be solved efficiently. We illustrate the performance of the proposed designs through some selected numerical simulations. © 2013 IEEE.
Lossless data compression for improving the performance of a GPU-based beamformer.
Lok, U-Wai; Fan, Gang-Wei; Li, Pai-Chi
2015-04-01
The powerful parallel computation ability of a graphics processing unit (GPU) makes it feasible to perform dynamic receive beamforming However, a real time GPU-based beamformer requires high data rate to transfer radio-frequency (RF) data from hardware to software memory, as well as from central processing unit (CPU) to GPU memory. There are data compression methods (e.g. Joint Photographic Experts Group (JPEG)) available for the hardware front end to reduce data size, alleviating the data transfer requirement of the hardware interface. Nevertheless, the required decoding time may even be larger than the transmission time of its original data, in turn degrading the overall performance of the GPU-based beamformer. This article proposes and implements a lossless compression-decompression algorithm, which enables in parallel compression and decompression of data. By this means, the data transfer requirement of hardware interface and the transmission time of CPU to GPU data transfers are reduced, without sacrificing image quality. In simulation results, the compression ratio reached around 1.7. The encoder design of our lossless compression approach requires low hardware resources and reasonable latency in a field programmable gate array. In addition, the transmission time of transferring data from CPU to GPU with the parallel decoding process improved by threefold, as compared with transferring original uncompressed data. These results show that our proposed lossless compression plus parallel decoder approach not only mitigate the transmission bandwidth requirement to transfer data from hardware front end to software system but also reduce the transmission time for CPU to GPU data transfer. © The Author(s) 2014.
2010-10-01
... Cab Signal Systems Inspection and Tests; Locomotive § 236.589 Relays. (a) Each relay shall be removed from service, subjected to thorough test, necessary repairs and adjustments made, and shall not be... spring tension to return contacts to deenergized position in noncoded continuous inductive...
Demonstration Model of Self Inductance Using Relay
2016-05-01
Using an electrical component like a relay, the phenomenonof self inductance caneasily be demonstrated to undergraduatestudents. By wiring simple electrical components like relay,neon bulb and a DC power supply, intermittent backelectromotive force (emf) can be generated in the range from60 to 100 volt. The glowing of neon bulb provides visualevidence for the generation of large back emf due to selfinductance.
Sort-based relay selection algorithm for decode-and-forward relay system
XIE Gang; LIU YuanAn; GAO JinChun; LI XingZheng
2013-01-01
In this paper, a sort-based relay selection algorithm is proposed for decode-and-forward wireless relay systems. The proposed algorithm can reduce computational complexity and system overhead in the relay selection for practical decode-and-forward wireless relay systems with multiple sources and multiple relays. This would be a very important improvement. Firstly, the sufficient and necessary conditions for a relay to be feasible to a source are derived. By adopting relay transmission via its feasible relay, the source can improve channel capacity compared to direct transmission. Then, a sort-based relay selection algorithm is proposed based on the sufficient and necessary conditions. In the proposed algorithm, each relay makes decision on its feasibility individually, but the final source-relay paring decision is made in a centralized manner. Simulation results show that the proposed algorithm can provide considerable system performance improvement over the existing algorithm. Especially at low signal-to-noise （SNR） region, the performance of the proposed algorithm almost reaches the optimal one.
On the achievable degrees of freedom of alternate MIMO relaying with multiple AF relays
Park, Kihong
2012-03-01
In this paper, we consider a two-hop relaying network where one source, one destination, and multiple amplify-and-forward (AF) relays equipped with M antennas operate in a half-duplex mode. In order to compensate for the inherent loss of capacity pre-log factor of 1/2 due to half-duplex relaying, we propose a new transmission protocol which combines alternate relaying and inter-relay interference alignment. We prove that the proposed scheme can (i) exploits M degrees of freedom (DOFs) and (ii) perfectly recover the pre-log factor loss if the number of relays is at least six. From our selected numerical results, we show that our proposed scheme gives significant improvement over conventional AF relaying which offers only M/2 DOFs. © 2012 IEEE.
Decode and Zero-Forcing Forward Relaying with Relay Selection in Cognitive Radio Systems
Park, Kihong
2014-05-01
In this paper, we investigate a cognitive radio (CR) relay network with multiple relay nodes that help forwarding the signal of CR users. Best relay selection is considered to take advantage of its low complexity of implementation. When the primary user (PU) is located close to the relay nodes, the performance of the secondary network is severely degraded due to the interference power constraint during the transmission in the second hop. We propose a decode and zero-forcing forward scheme to suppress the interference power at the relay nodes and analyze the statistics of the end-to-end signal-to-noise ratio when the relay nodes are located arbitrarily and experience therefore non-identical Rayleigh fading channels. Numerical results validate our theoretical results and show that our proposed scheme improves the performance of the CR network when the PU is close to the relay nodes. © 2014 IEEE.
On Alternate Relaying with Improper Gaussian Signaling
Gaafar, Mohamed
2016-06-06
In this letter, we investigate the potential benefits of adopting improper Gaussian signaling (IGS) in a two-hop alternate relaying (AR) system. Given the known benefits of using IGS in interference-limited networks, we propose to use IGS to relieve the inter-relay interference (IRI) impact on the AR system assuming no channel state information is available at the source. In this regard, we assume that the two relays use IGS and the source uses proper Gaussian signaling (PGS). Then, we optimize the degree of impropriety of the relays signal, measured by the circularity coefficient, to maximize the total achievable rate. Simulation results show that using IGS yields a significant performance improvement over PGS, especially when the first hop is a bottleneck due to weak source-relay channel gains and/or strong IRI.
G. Marconi: A Data Relay Satellite for Mars Communications
Dionisio, C.; Marcozzi, M.; Landriani, C.
2002-01-01
Mars has always been a source of intrigue and fascination. Recent scientific discoveries have stimulated this longstanding interest, leading to a renaissance in Mars exploration. Future missions to Mars will be capable of long-distance surface mobility, hyperspectral imaging, subsurface exploration, and even life-detection. Manned missions and, eventually, colonies may follow. No mission to the Red Planet stands alone. New scientific and technological knowledge is passed on from one mission to the next, not only improving the journey into space, but also providing benefits here on Earth. The Mars Relay Network, an international constellation of Mars orbiters with relay radios, directly supports other Mars missions by relaying communications between robotic vehicles at Mars and ground stations on Earth. The ability of robotic visitors from Earth to explore Mars will take a gigantic leap forward in 2007 with the launch of the Guglielmo Marconi Orbiter (GMO), the first spacecraft primarily dedicated to providing communication relay, navigation and timing services at Mars. GMO will be the preeminent node of the Mars Relay Network. GMO will relay communications between Earth and robotic vehicles near Mars. GMO will also provide navigation services to spacecraft approaching Mars. GMO will receive transmissions from ground stations on Earth at X-band and will transmit to ground stations on Earth at X- and Ka-bands. GMO will transmit to robotic vehicles at Mars at UHF and receive from these vehicles at UHF and X-band. GMO's baseline 4450 km circular orbit provides complete coverage of the planet for telecommunication and navigation support. GMO will arrive at Mars in mid-2008, just before the NetLander and Mars Scout missions that will be its first users. GMO is designed for a nominal operating lifetime of 10 years and will support nominal commanding and data acquisition, as well as mission critical events such as Mars Orbit Insertion, Entry, Descent and Landing, and Mars
Opportunistic Relaying for Space-Time Coded Cooperation with Multiple Antenna Terminals
Maham, Behrouz
2011-01-01
We consider a wireless relay network with multiple antenna terminals over Rayleigh fading channels, and apply distributed space-time coding (DSTC) in amplify-and-forward (A&F) mode. The A&F scheme is used in a way that each relay transmits a scaled version of the linear combination of the received symbols. It turns out that, combined with power allocation in the relays, A&F DSTC results in an opportunistic relaying scheme, in which only the best relay is selected to retransmit the source's space-time coded signal. Furthermore, assuming the knowledge of source-relay CSI at the source node, we design an efficient power allocation which outperforms uniform power allocation across the source antennas. Next, assuming M-PSK or M-QAM modulations, we analyze the performance of the proposed cooperative diversity transmission schemes in a wireless relay networks with the multiple-antenna source and destination. We derive the probability density function (PDF) of the received SNR at the destination. Then, th...
Precise-Orientation-Beamforming Scheme for Wireless Communications between Buoys
Zhihui Wu
2016-01-01
Full Text Available Utilizing wireless sensor network (WSN to monitor the marine environment is one of the major techniques in oceanographic monitoring, and how to increase the limited communication distance between the buoys in WSN has become a hot research issue. In this paper, a new technique called precise-orientation-beamforming (POB which uses the beamforming algorithm to increase the communication distance between buoys is presented. As was widely applied in the radar and sonar, the beamforming method was not used to extend the communication distance between buoys so far. The POB method overcomes the unstable position of buoys caused by waves by implementing the orientation filter. The whole process includes two steps: First, the real-time attitude of the antenna array is calculated by the orientation filter. With the known relative direction of the destination node to the antenna array, the second step is to control phased array antenna beamforming parameters, directing the beam at the destination node. The POB scheme has been simulated under the condition of regular waves. The results reveal that POB provides significant power gains and improves the distance between two communicating nodes effectively.
Robust Adaptive LCMV Beamformer Based On An Iterative Suboptimal Solution
Xiansheng Guo
2015-06-01
Full Text Available The main drawback of closed-form solution of linearly constrained minimum variance (CF-LCMV beamformer is the dilemma of acquiring long observation time for stable covariance matrix estimates and short observation time to track dynamic behavior of targets, leading to poor performance including low signal-noise-ratio (SNR, low jammer-to-noise ratios (JNRs and small number of snapshots. Additionally, CF-LCMV suffers from heavy computational burden which mainly comes from two matrix inverse operations for computing the optimal weight vector. In this paper, we derive a low-complexity Robust Adaptive LCMV beamformer based on an Iterative Suboptimal solution (RAIS-LCMV using conjugate gradient (CG optimization method. The merit of our proposed method is threefold. Firstly, RAIS-LCMV beamformer can reduce the complexity of CF-LCMV remarkably. Secondly, RAIS-LCMV beamformer can adjust output adaptively based on measurement and its convergence speed is comparable. Finally, RAIS-LCMV algorithm has robust performance against low SNR, JNRs, and small number of snapshots. Simulation results demonstrate the superiority of our proposed algorithms.
Transverse flow imaging using synthetic aperture directional beamforming
Jensen, Jørgen Arendt; Nikolov, Svetoslav
2002-01-01
during emission. The RF data were subsequently beamformed off-line and stationary echo canceling was performed. The 60 degrees flow was determined using 16 groups of 8 emissions and the relative standard deviation was 0.36 % (0.65 mm/s). Using the same setup for the purely transverse flow gave a std...
Beamforming and Power Control in Sensor Arrays Using Reinforcement Learning
Almeida, Náthalee C.; Fernandes, Marcelo A.C.; Neto, Adrião D.D.
2015-01-01
The use of beamforming and power control, combined or separately, has advantages and disadvantages, depending on the application. The combined use of beamforming and power control has been shown to be highly effective in applications involving the suppression of interference signals from different sources. However, it is necessary to identify efficient methodologies for the combined operation of these two techniques. The most appropriate technique may be obtained by means of the implementation of an intelligent agent capable of making the best selection between beamforming and power control. The present paper proposes an algorithm using reinforcement learning (RL) to determine the optimal combination of beamforming and power control in sensor arrays. The RL algorithm used was Q-learning, employing an ε-greedy policy, and training was performed using the offline method. The simulations showed that RL was effective for implementation of a switching policy involving the different techniques, taking advantage of the positive characteristics of each technique in terms of signal reception. PMID:25808769
Beamforming and Power Control in Sensor Arrays Using Reinforcement Learning
Náthalee C. Almeida
2015-03-01
Full Text Available The use of beamforming and power control, combined or separately, has advantages and disadvantages, depending on the application. The combined use of beamforming and power control has been shown to be highly effective in applications involving the suppression of interference signals from different sources. However, it is necessary to identify efficient methodologies for the combined operation of these two techniques. The most appropriate technique may be obtained by means of the implementation of an intelligent agent capable of making the best selection between beamforming and power control. The present paper proposes an algorithm using reinforcement learning (RL to determine the optimal combination of beamforming and power control in sensor arrays. The RL algorithm used was Q-learning, employing an ε-greedy policy, and training was performed using the offline method. The simulations showed that RL was effective for implementation of a switching policy involving the different techniques, taking advantage of the positive characteristics of each technique in terms of signal reception.
Bit-Interleaved Coded Multiple Beamforming with Perfect Coding
Li, Boyu
2010-01-01
When the channel state information is known by the transmitter as well as the receiver, beamforming techniques that employ Singular Value Decomposition (SVD) are commonly used in Multiple-Input Multiple-Output (MIMO) systems. Without channel coding, when a single symbol is transmitted, these systems achieve the full diversity order. Whereas, this property is lost when multiple symbols are simultaneously transmitted. Full diversity can be restored when channel coding is added, as long as the code rate Rc and the number of employed subchannels S satisfy the condition RcS =< 1. Moreover, by adding a proper constellation precoder, full diversity can be achieved for both uncoded and coded SVD systems, e.g., Fully Precoded Multiple Beamforming (FPMB) and Bit-Interleaved Coded Multiple Beamforming with Full Precoding (BICMB-FP). Perfect Space-Time Block Code (PSTBC) is a full-rate full-diversity space-time code, which achieves maximum coding gain for MIMO systems. Previously, Perfect Coded Multiple Beamforming (P...
Digitally assisted analog beamforming for millimeter-wave communication
Kokkeler, A.B.J.; Smit, G.J.M.
2015-01-01
The paper addresses the research question on how digital beamsteering algorithms can be combined with analog beamforming in the context of millimeter-wave communication for next generation (5G) cellular systems. Key is the use of coarse quantisation of the individual antenna signals next to the anal
Aliasing-free wideband beamforming using sparse signal representation
Tang, Z.; Blacquière, G.; Leus, G.
2011-01-01
Sparse signal representation (SSR) is considered to be an appealing alternative to classical beamforming for direction-of-arrival (DOA) estimation. For wideband signals, the SSR-based approach constructs steering matrices, referred to as dictionaries in this paper, corresponding to different frequen
Photonic Integrated Circuits for Phased-Array Beamforming
Vliet, F.E. van; Stulemeijer, J.; Benoist, K.W.; Maat, D.H.P.; Smit, M.K.; Dijk, R. van
1999-01-01
Photonic integration is very promising to bring down volume and weight of phased-array beamforming networks. In addition, photonics allows for increased functionality for wide bandwidth systems. In this paper we demonstrate the feasibiÌity of phase and amplitude control of a 16-elernent phased-array
On the power amplifier nonlinearity in MIMO transmit beamforming systems
Qi, Jian
2012-03-01
In this paper, single-carrier multiple-input multiple-output (MIMO) transmit beamforming (TB) systems in the presence of high-power amplifier (HPA) nonlinearity are investigated. Specifically, due to the suboptimality of the conventional maximal ratio transmission/maximal ratio combining (MRT/MRC) under HPA nonlinearity, we propose the optimal TB scheme with the optimal beamforming weight vector and combining vector, for MIMO systems with nonlinear HPAs. Moreover, an alternative suboptimal but much simpler TB scheme, namely, quantized equal gain transmission (QEGT), is proposed. The latter profits from the property that the elements of the beamforming weight vector have the same constant modulus. The performance of the proposed optimal TB scheme and QEGT/MRC technique in the presence of the HPA nonlinearity is evaluated in terms of the average symbol error probability and mutual information with the Gaussian input, considering the transmission over uncorrelated quasi-static frequency-flat Rayleigh fading channels. Numerical results are provided and show the effects on the performance of several system parameters, namely, the HPA parameters, numbers of antennas, quadrature amplitude modulation modulation order, number of pilot symbols, and cardinality of the beamforming weight vector codebook for QEGT. © 2012 IEEE.
Fast Optical Beamforming Architectures for Satellite-Based Applications
B. Vidal
2012-01-01
Full Text Available Photonic technology offers an alternative implementation for the control of phased array antennas providing large time bandwidth products and low weight, flexible feeding networks. Measurements of an optical beamforming network for phased array antennas with fast beam steering operation for space scenarios are presented. Experimental results demonstrate fast beam steering between 4 and 8 GHz without beam squint.
Shape and Doppler corrected beamforming for low frequency active sonars
Groen, J.; Beerens, S.P.; Doisy, Y.
2004-01-01
ASW operations have shifted toward shallow water environments, where water space is limited and manoeuvring an essential part of operations. The problem that is tackled in this article is the performance loss due to the shape and motion of a manoeuvring sonar. Standard beamforming in towed sonar arr
Beamforming Arrays with Faulty Sensors in Dynamic Environments
2004-01-01
slightly outperforms MMSE at all SNR’s. • ALPINEX ( Swinger and Walker) degrades significantly in correlated multipath. • Single snapshot ROC for...MMSE at all SNR’s. • ALPINEX ( Swinger and Walker) degrades significantly in correlated multipath. 14 Simulated BTR for ACC vs. Clairvoyant Beamformer
A comparison between temporal and subband minimum variance adaptive beamforming
Diamantis, Konstantinos; Voxen, Iben Holfort; Greenaway, Alan H.
2014-01-01
This paper compares the performance between temporal and subband Minimum Variance (MV) beamformers for medical ultrasound imaging. Both adaptive methods provide an optimized set of apodization weights but are implemented in the time and frequency domains respectively. Their performance is evaluated...
Synthetic aperture ultrasound Fourier beamformation using virtual sources
Moghimirad, Elahe; Villagómez Hoyos, Carlos Armando; Mahloojifar, Ali
2016-01-01
An efficient Fourier beamformation algorithm is presented for multistatic synthetic aperture ultrasound imaging using virtual sources (FBV). The concept is based on the frequency domain wavenumber algorithm from radar and sonar and is extended to a multi-element transmit/receive configuration using...
Proportional fair scheduling with superposition coding in a cellular cooperative relay system
Kaneko, Megumi; Hayashi, Kazunori; Popovski, Petar
2013-01-01
Many works have tackled on the problem of throughput and fairness optimization in cellular cooperative relaying systems. Considering firstly a two-user relay broadcast channel, we design a scheme based on superposition coding (SC) which maximizes the achievable sum-rate under a proportional...... fairness constraint. Unlike most relaying schemes where users are allocated orthogonally, our scheme serves the two users simultaneously on the same time-frequency resource unit by superposing their messages into three SC layers. The optimal power allocation parameters of each SC layer are derived...... by analysis. Next, we consider the general multi-user case in a cellular relay system, for which we design resource allocation algorithms based on proportional fair scheduling exploiting the proposed SC-based scheme. Numerical results show that the proposed algorithms allowing simultaneous user allocation...
Zone 3 Relay Blocking Scheme to Prevent Cascaded Events
LIM Seong-Il
2008-01-01
Defense systems are needed to prevent catastrophic failures of a power grid due to cas- caded events. Cascaded events can be attributed to improper operations of protective relays. The most challenging problem for the design and implementation of a defense system is the perform- ance in accuracy and speed in a real time environment. Protective devices are normally designed to operate fast in order to isolate the fault(s). This paper proposes a new methodology to distin- guish line overloads from actual faults for distance relays. In order to distinguish between line flow transfers from a line outage and an actual fault, the line outage distribution factor (LODF) and gen-eration shift factor (GSF) based power flow estimation method, and a secure peer to peer (P2P) communication structure are adopted. Computer simulations of cascaded events for a 6-bus sys- tem and the Korean power grid have been performed to establish the feasibility of the proposed scheme.
Unmanned Aerial Vehicle as Communication Relay for Autonomous Underwater Vehicle - Field Tests
Johansen, Tor Arne; Zolich, Artur Piotr; Hansen, Torkel; Sørensen, Asgeir Johan
2014-01-01
This paper describes field experiments with an X8 Unmanned Aerial Vehicle (UAV) operating as a wireless communication relay while loitering over a REMUS 100 Autonomous Underwater Vehicle (AUV) being at the ocean surface. The paper describes the design of the communication relay payload, network configuration, optimal flight conditions and UAV antenna mounting, and experimental results. Experiments were conducted under less than ideal conditions with rain and turbulent winds leading to unfavor...
A qualification test for relay contacts as isolation devices in nuclear power plants
Beck, C.E.; Behera, A.K. [Kiran Consultants, Inc., Downers Grove, IL (United States); Polanco, S.; Terry, B. [ComEd Materials Engineering Group, Bolingbrook, IL (United States). Central Receiving, Inspection, and Test Facility
1995-10-01
A methodology is introduced for testing the integrity of relay contacts as isolation devices in Class IE circuits. A design activity that installed a new relay established the need for a new type of qualification test. This paper descries the process of establishing the test methodology, the development of the test plan, and the results of testing. It also describes the limitations of applying the results of any specific test to actual field installations, and offers other potential uses of the methodology.
Ultrasound phase rotation beamforming on multi-core DSP.
Ma, Jieming; Karadayi, Kerem; Ali, Murtaza; Kim, Yongmin
2014-01-01
Phase rotation beamforming (PRBF) is a commonly-used digital receive beamforming technique. However, due to its high computational requirement, it has traditionally been supported by hardwired architectures, e.g., application-specific integrated circuits (ASICs) or more recently field-programmable gate arrays (FPGAs). In this study, we investigated the feasibility of supporting software-based PRBF on a multi-core DSP. To alleviate the high computing requirement, the analog front-end (AFE) chips integrating quadrature demodulation in addition to analog-to-digital conversion were defined and used. With these new AFE chips, only delay alignment and phase rotation need to be performed by DSP, substantially reducing the computational load. We implemented the delay alignment and phase rotation modules on a Texas Instruments C6678 DSP with 8 cores. We found it takes 200 μs to beamform 2048 samples from 64 channels using 2 cores. With 4 cores, 20 million samples can be beamformed in one second. Therefore, ADC frequencies up to 40 MHz with 2:1 decimation in AFE chips or up to 20 MHz with no decimation can be supported as long as the ADC-to-DSP I/O requirement can be met. The remaining 4 cores can work on back-end processing tasks and applications, e.g., color Doppler or ultrasound elastography. One DSP being able to handle both beamforming and back-end processing could lead to low-power and low-cost ultrasound machines, benefiting ultrasound imaging in general, particularly portable ultrasound machines.
Cell-Edge Multi-User Relaying with Overhearing
Sun, Fan; Kim, Tae Min; Paulraj, Arogyaswami
2013-01-01
Carefully designed protocols can turn overheard interference into useful side information to allow simultaneous transmission of multiple communication flows and increase the spectral efficiency in interference-limited regime. In this letter, we propose a novel scheme in a typical cell-edge scenario....... By exploiting the overhearing link through proper relay precoding and adaptive receiver processing, rate performance can be significantly improved compared to the conventional transmission which does not utilize overhearing....
Degrees of Freedom of Asymmetrical Multi-Way Relay Networks
Sun, Fan; De Carvalho, Elisabeth
2011-01-01
In this paper, we introduce an asymmetrical multi-way relay channel where a base station conveys independent symbols to K different users while receiving independent symbols from the users. In this network, user i Shas Mi antennas (i ∈ [1, ..., K]), the base station has Σi=1K Mi antennas and the ...... with a proposed joint multiple access and broadcast precoding design using the signal space alignment concept....
崔杨; 杨帆; 肖白; 刘晓军
2016-01-01
To design the power grid structure independently,update the equipment and transmission line parameters timely,and perform calculations automatically,this paper develops a setting calculation visualization system for the course design of protective relaying based on Matlab/GUI. By calling modules including PSAT and Simulink,the devel⁃oped system integrates functions such as graphics,computation,analysis and output visualization. Generator,trans⁃former and line parameters can be added at any time,and visual analysis and application can be implemented by exter⁃nalized result with graphs,tables,reports,etc. Teaching practice proved that this system can achieve power grid draw⁃ing,and perform the calculations of power flow,short circuit and setting automatically.%为实现电网网架结构自主设计、设备及线路参数及时更新、相应计算自动执行等功能，该文设计和开发了一套继电保护课程设计可视化整定计算系统。该系统基于Matlab/GUI环境，通过调用PSAT、Simulink等模块，设计集成了绘图、运算、分析、可视化输出等功能。可随时增添数据与保存常用发电机与变压器、线路型号等参数，并以图形、表格、报表等方式外化运算结果，便于可视化分析与应用。教学实践证明该系统具备绘制电力网络及自动完成电力系统潮流计算、短路计算和整定计算的功能。
Energy Efficiency and SINR Maximization Beamformers for Spectrum Sharing With Sensing Information
Alabbasi, Abdulrahman
2014-09-01
In this paper, we consider a cognitive radio multi-input-multi-output environment, in which we adapt our beamformer to maximize both energy efficiency (EE) and signal-to-interference-plus-noise ratio (SINR) metrics. Our design considers an underlaying communication using adaptive beamforming schemes combined with sensing information to achieve optimal energy-efficient systems. The proposed schemes maximize EE and SINR metrics subject to cognitive radio and quality-of-service constraints. The analysis of the proposed schemes is classified into two categories based on knowledge of the secondary-transmitter-to-primary-receiver channel. Since the optimizations of EE and SINR problems are not convex problems, we transform them into a standard semidefinite programming (SDP) form to guarantee that the optimal solutions are global. An analytical solution is provided for one scheme, while the second scheme is left in a standard SDP form. Selected numerical results are used to quantify the impact of the sensing information on the proposed schemes compared to the benchmark ones.
Study on reliability technology of contactor relay
LIU Guo-jin; ZHAO Jing-ying; WANG Hai-tao; YANG Chen-guang; SUN Shun-li
2007-01-01
In this paper, the reliability of contactor relay is studied. There are three main parts about reliability test and analysis. First, in order to analyze reliability level of contact relay, the failure ratio ranks are established as index base on the product level. Second, the reliability test method is put forward. The sample plan of reliability compliance test is gained from reliability sample theory. The failure criterion is ensured according to the failure modes of contactor relay. Third, after reliability test experiment, the analysis of failure physics is made and the failure reason is found.
Packet scheduling for OFDMA based relay networks
无
2008-01-01
The combination of relay networks with orthogonal frequency division multiple access (OFDMA) has been proposed as a promising solution for the next generation wireless system. Considering different traffic classes and user quality of service (QoS), three efficient scheduling algorithms are introduced in such networks. The round-robin (RR) algorithm in relay networks serves as a performance benchmark. Numerical results show that the proposed algorithms achieve significant improvement on system throughput and decrease system packet loss rate, compared with the RR and absence of relaying system (traditional network). Furthermore, comparisons have been carried out among the three proposed algorithms.
An all-optical time-delay relay based n a bacteriorhodopsin film
Chen Gui-Ying; Xu Xu-Xu; Zhang Chun-Ping; Qi Shen-Wen; Song Qi-Wang
2008-01-01
Using a special property of dynamic complementary-suppression-modulated transmission (DCSMT) in the bacteriorhodopsin (bR) film,we have demonstrated an all-optical time-delay relay.To extend our work,the relationship between the delay time of the all-optical time-delay relay and parameters of a bR film is numerically studied.We show how the delay time changes with the product of concentration and thickness (PCT) of a bR film.Furthermore,the shortest and longest delay times are given for the relay of 'switch off'.The saturable delay time and maximum delaytime of 'switch on' are also given.How the wavelengths (632.8,568,533 and 412 nm) and intensities of the illuminating light influence the delay time is also discussed.The simulation results are useful for optimizing the design of all-optical time-delay relays.
Distributed Space Time Codes with Low Decoding Complexity for Asynchronous Relay Networks
Rajan, G Susinder
2007-01-01
Recently Li and Xia have proposed a transmission scheme for wireless relay networks based on the Alamouti space time code and orthogonal frequency division multiplexing to combat the effect of timing errors at the relay nodes. This transmission scheme is amazingly simple and achieves a diversity order of two for any number of relays. Motivated by its simplicity, this scheme is extended to a more general transmission scheme that can achieve full cooperative diversity for any number of relays. The conditions on the distributed space time code (DSTC) structure that admit its application in the proposed transmission scheme are identified and it is pointed out that the recently proposed full diversity four group decodable DSTCs from precoded co-ordinate interleaved orthogonal designs and extended Clifford algebras satisfy these conditions. It is then shown how differential encoding at the source can be combined with the proposed transmission scheme to arrive at a new transmission scheme that can achieve full coope...
49 CFR 236.52 - Relayed cut-section.
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Relayed cut-section. 236.52 Section 236.52...: All Systems Track Circuits § 236.52 Relayed cut-section. Where relayed cut-section is used in... shall be open and the track circuit shunted when the track relay at such cut-section is in deenergized...
Impact of Beamforming on the Path Connectivity in Cognitive Radio Ad Hoc Networks
Le The Dung
2017-03-01
Full Text Available This paper investigates the impact of using directional antennas and beamforming schemes on the connectivity of cognitive radio ad hoc networks (CRAHNs. Specifically, considering that secondary users use two kinds of directional antennas, i.e., uniform linear array (ULA and uniform circular array (UCA antennas, and two different beamforming schemes, i.e., randomized beamforming and center-directed to communicate with each other, we study the connectivity of all combination pairs of directional antennas and beamforming schemes and compare their performances to those of omnidirectional antennas. The results obtained in this paper show that, compared with omnidirectional transmission, beamforming transmission only benefits the connectivity when the density of secondary user is moderate. Moreover, the combination of UCA and randomized beamforming scheme gives the highest path connectivity in all evaluating scenarios. Finally, the number of antenna elements and degree of path loss greatly affect path connectivity in CRAHNs.
Simulation Study of Real Time 3-D Synthetic Aperture Sequential Beamforming for Ultrasound Imaging
Hemmsen, Martin Christian; Rasmussen, Morten Fischer; Stuart, Matthias Bo;
2014-01-01
This paper presents a new beamforming method for real-time three-dimensional (3-D) ultrasound imaging using a 2-D matrix transducer. To obtain images with sufficient resolution and contrast, several thousand elements are needed. The proposed method reduces the required channel count from...... the transducer to the main imaging system, by including electronics in the transducer handle. The reduction of element channel count is achieved using a sequential beamforming scheme. The beamforming scheme is a combination of a fixed focus beamformer in the transducer and a second dynamic focus beamformer...... in the main system. The real-time imaging capability is achieved using a synthetic aperture beamforming technique, utilizing the transmit events to generate a set of virtual elements that in combination can generate an image. The two core capabilities in combination is named Synthetic Aperture Sequential...
Self-oscillations in dynamic systems a new methodology via two-relay controllers
Aguilar, Luis T; Fridman, Leonid; Iriarte, Rafael
2015-01-01
This monograph presents a simple and efficient two-relay control algorithm for generation of self-excited oscillations of a desired amplitude and frequency in dynamic systems. Developed by the authors, the two-relay controller consists of two relays switched by the feedback received from a linear or nonlinear system, and represents a new approach to the self-generation of periodic motions in underactuated mechanical systems. The first part of the book explains the design procedures for two-relay control using three different methodologies – the describing-function method, Poincaré maps, and the locus-of-a perturbed-relay-system method – and concludes with stability analysis of designed periodic oscillations. Two methods to ensure the robustness of two-relay control algorithms are explored in the second part, one based on the combination of the high-order sliding mode controller and backstepping, and the other on higher-order sliding-modes-based reconstruction of uncertainties and their compensation where...
Time of arrival based location estimation for cooperative relay networks
Çelebi, Hasari Burak
2010-09-01
In this paper, we investigate the performance of a cooperative relay network performing location estimation through time of arrival (TOA). We derive Cramer-Rao lower bound (CRLB) for the location estimates using the relay network. The analysis is extended to obtain average CRLB considering the signal fluctuations in both relay and direct links. The effects of the channel fading of both relay and direct links and amplification factor and location of the relay node on average CRLB are investigated. Simulation results show that the channel fading of both relay and direct links and amplification factor and location of relay node affect the accuracy of TOA based location estimation. ©2010 IEEE.
Application of a proposed overcurrent relay in radial distribution networks
Conde, A.; Vazquez, E. [Universidad Autonoma de Nuevo Leon, Facultad de Ingenieria Mecanica y Electrica, A.P. 36-F, CU, CP 66450, San Nicolas de los Garza, Nuevo Leon (Mexico)
2011-02-15
This paper contains the application criteria and coordination process for a proposed overcurrent relay in a radial power system with feed from one or multiple sources. This relay uses independent functions to detect faults and to calculate the operation time. Also this relay uses a time element function that allows it to reduce the time relay operation, enhancing the backup protection. Some of the proposed approaches improve the sensitivity of the relay. The selection of the best approach in the proposed relay is defined by the needs of the application. The proposed protection can be considered as an additional function protection to conventional overcurrent relays. (author)
Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity
Aitor del Coso
2007-11-01
Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of N wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, Ã°ÂÂ’Âž=logÃ¢ÂÂ¡2(W0(N. Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.
Distributed Antenna Channels with Regenerative Relaying: Relay Selection and Asymptotic Capacity
del Coso Aitor
2007-01-01
Full Text Available Multiple-input-multiple-output (MIMO techniques have been widely proposed as a means to improve capacity and reliability of wireless channels, and have become the most promising technology for next generation networks. However, their practical deployment in current wireless devices is severely affected by antenna correlation, which reduces their impact on performance. One approach to solve this limitation is relaying diversity. In relay channels, a set of wireless nodes aids a source-destination communication by relaying the source data, thus creating a distributed antenna array with uncorrelated path gains. In this paper, we study this multiple relay channel (MRC following a decode-and-forward (D&F strategy (i.e., regenerative forwarding, and derive its achievable rate under AWGN. A half-duplex constraint on relays is assumed, as well as distributed channel knowledge at both transmitter and receiver sides of the communication. For this channel, we obtain the optimum relay selection algorithm and the optimum power allocation within the network so that the transmission rate is maximized. Likewise, we bound the ergodic performance of the achievable rate and derive its asymptotic behavior in the number of relays. Results show that the achievable rate of regenerative MRC grows as the logarithm of the Lambert W function of the total number of relays, that is, . Therefore, D&F relaying, cannot achieve the capacity of actual MISO channels.
Partial relay selection in underlay cognitive networks with fixed gain relays
Hussain, Syed Imtiaz
2012-05-01
In a communication system with multiple cooperative relays, selecting the best relay utilizes the available spectrum more efficiently. However, selective relaying poses a different problem in underlay cognitive networks compared to the traditional cooperative networks due to interference thresholds to the primary users. In most cases, a best relay is the one which provides the maximum end-to-end signal to noise ratio (SNR). This approach needs plenty of instantaneous channel state information (CSI). The CSI burden could be reduced by partial relay selection. In this paper, a partial relay selection scheme is presented and analyzed for an underlay cognitive network with fixed gain relays operating in the vicinity of a primary user. The system model is adopted in a way that each node needs minimal CSI to perform its task. The best relay is chosen on the basis of maximum source to relay link SNR which then forwards the message to the destination. We derive closed form expressions for the received SNR distributions, system outage, probability of bit error and average channel capacity of the system. The derived results are confirmed through simulations. © 2012 IEEE.
Developing a Domain Model for Relay Circuits
Haxthausen, Anne Elisabeth
2009-01-01
the statics as well as the dynamics of relay circuits, i.e. how a relay circuit can be composed legally from electrical components as well as how the components may change state over time. Finally the circuit model is transformed into an executable model, and we show how a concrete circuit can be defined......In this paper we stepwise develop a domain model for relay circuits as used in railway control systems. First we provide an abstract, property-oriented model of networks consisting of components that can be glued together with connectors. This model is strongly inspired by a network model...... for railways madeby Bjørner et.al., however our model is more general: the components can be of any kind and can later be refined to e.g. railway components or circuit components. Then we show how the abstract network model can be refined into an explicit model for relay circuits. The circuit model describes...
Transmission Techniques for Relay-Interference Networks
Mohajer, Soheil; Fragouli, Christina; Tse, David N C
2008-01-01
In this paper we study the relay-interference wireless network, in which relay (helper) nodes are to facilitate competing information flows over a wireless network. We examine this in the context of a deterministic wireless interaction model, which eliminates the channel noise and focuses on the signal interactions. Using this model, we show that almost all the known schemes such as interference suppression, interference alignment and interference separation are necessary for relay-interference networks. In addition, we discover a new interference management technique, which we call interference neutralization, which allows for over-the-air interference removal, without the transmitters having complete access the interfering signals. We show that interference separation, suppression, and neutralization arise in a fundamental manner, since we show complete characterizations for special configurations of the relay-interference network.
Torch Relay:Love Is Passing on
无
2008-01-01
@@ May is not an ordinary month for the whole China, as the 8.0-magnitude earthquake hit sonthwest of China and shocked thc whole nation. And now, the torch relay in China is endowed with more responsibility and significance: to pass on the passion, also the compassion. No matter the torch relay is paused or going on, Olym-pic spirit is passing on. So is the love.
Approximate Capacity of Gaussian Relay Networks
Avestimehr, Amir Salman; Tse, David N C
2008-01-01
We present an achievable rate for general Gaussian relay networks. We show that the achievable rate is within a constant number of bits from the information-theoretic cut-set upper bound on the capacity of these networks. This constant depends on the topology of the network, but not the values of the channel gains. Therefore, we uniformly characterize the capacity of Gaussian relay networks within a constant number of bits, for all channel parameters.
Harmonic imaging with fresnel beamforming in the presence of phase aberration.
Nguyen, Man Minh; Shin, Junseob; Yen, Jesse
2014-10-01
Fresnel beamforming is a beamforming method with a delay profile similar in shape to a physical Fresnel lens. The advantage of Fresnel beamforming is the reduced channel count, which consists of four to eight transmit and two analog-to-digital receive channels. Fresnel beamforming was found to perform comparably to conventional delay-and-sum beamforming. However, the performance of Fresnel beamforming is highly dependent on focal errors. These focal errors result in high side-lobe levels and further reduce the performance of Fresnel beamforming in the presence of phase aberration. With the advantages of lower side-lobe levels and suppression of aberration effects, harmonic imaging offers an effective solution to the limitations of Fresnel beamforming. We describe the implementation of tissue harmonic imaging and pulse inversion harmonic imaging in Fresnel beamforming, followed by dual apodization with cross-correlation, to improve image quality. Compared with conventional delay-and-sum beamforming, experimental results indicated contrast-to-noise ratio improvements of 10%, 49% and 264% for Fresnel beamforming using tissue harmonic imaging in the cases of no aberrator, 5-mm pork aberrator and 12-mm pork aberrator, respectively. These improvements were 22%, 57% and 352% for Fresnel beamforming using pulse inversion harmonic imaging. Moreover, dual apodization with cross-correlation was found to further improve the contrast-to-noise ratios in all cases. Harmonic imaging was also found to narrow the lateral beamwidth and shorten the axial pulse length by at least 25% and 21%, respectively, for Fresnel beamforming at different aberration levels. These results suggest the effectiveness of harmonic imaging in improving image quality for Fresnel beamforming, especially in the presence of phase aberration. Even though this combination of Fresnel beamforming and harmonic imaging does not outperform delay-and-sum beamforming combined with harmonic imaging, it provides the
Low complexity symbol-wise beamforming for MIMO-OFDM systems
Lee, Hyun Ho
2011-12-01
In this paper, we consider a low complexity symbol-wise beamforming for MIMO-OFDM systems. We propose a non-iterative algorithm for the symbol-wise beamforming, which can provide the performance approaching that of the conventional symbol-wise beamforming based on the iterative algorithm. We demonstrate that our proposed scheme can reduce the computational complexity significantly. From our simulation results, it is evident that our proposed scheme leads to a negligible performance loss compared to the conventional symbol-wise beamforming regardless of spatial correlation or presence of co-channel interference. © 2011 IEEE.
Low complexity non-iterative coordinated beamforming in 2-user broadcast channels
Park, Kihong
2010-10-01
We propose a new non-iterative coordinated beamforming scheme to obtain full multiplexing gain in 2-user MIMO systems. In order to find the beamforming and combining matrices, we solve a generalized eigenvector problem and describe how to find generalized eigenvectors according to the Gaussian broadcast channels. Selected simulation results show that the proposed method yields the same sum-rate performance as the iterative coordinated beamforming method, while maintaining lower complexity by non-iterative computation of the beamforming and combining matrices. We also show that the proposed method can easily exploit selective gain by choosing the best combination of generalized eigenvectors. © 2006 IEEE.
A MISO UCA Beamforming Dimmable LED System for Indoor Positioning
Attaphongse Taparugssanagorn
2014-01-01
Full Text Available The use of a multiple input single output (MISO transmit beamforming system using dimmable light emitting arrays (LEAs in the form of a uniform circular array (UCA of transmitters is proposed in this paper. With this technique, visible light communications between a transmitter and a receiver (LED reader can be achieved with excellent performance and the receiver’s position can be estimated. A hexagonal lattice alignment of LED transmitters is deployed to reduce the coverage holes and the areas of overlapping radiation. As a result, the accuracy of the position estimation is better than when using a typical rectangular grid alignment. The dimming control is done with pulse width modulation (PWM to obtain an optimal closed loop beamforming and minimum energy consumption with acceptable lighting.
Synthetic Aperture Flow Imaging Using a Dual Beamformer Approach
Li, Ye
Color flow mapping systems have become widely used in clinical applications. It provides an opportunity to visualize the velocity profile over a large region in the vessel, which makes it possible to diagnose, e.g., occlusion of veins, heart valve deficiencies, and other hemodynamic problems....... However, while the conventional ultrasound imaging of making color flow mapping provides useful information in many circumstances, the spatial velocity resolution and frame rate are limited. The entire velocity distribution consists of image lines from different directions, and each image line...... the capability of acquiring color flow mapping with a high frame rate. Secondly, the new method is extended to the vector velocity estimation using directional beamforming, which beamforms data in the flow direction. The magnitude of the flow can be obtained and results of simulations and phantom measurements...
A beamformer post-filter for cochlear implant noise reduction.
Hersbach, Adam A; Grayden, David B; Fallon, James B; McDermott, Hugh J
2013-04-01
Cochlear implant users have limited ability to understand speech in noisy conditions. Signal processing methods to address this issue that use multiple microphones typically use beamforming to perform noise reduction. However, the effectiveness of the beamformer is diminished as the number of interfering noises increases and the acoustic environment becomes more diffuse. A multi-microphone noise reduction algorithm that aims to address this issue is presented in this study. The algorithm uses spatial filtering to estimate the signal-to-noise ratio (SNR) and attenuates time-frequency elements that have poor SNR. The algorithm was evaluated by measuring intelligibility of speech embedded in 4-talker babble where the interfering talkers were spatially separated and changed location during the test. Twelve cochlear implant users took part in the evaluation, which demonstrated a significant mean improvement of 4.6 dB (standard error 0.4, P noise is spatially separated from the target speech.
Rate-Constrained Beamforming in Binaural Hearing Aids
Srinivasan, Sriram; den Brinker, Albertus C.
2009-12-01
Recently, hearing aid systems where the left and right ear devices collaborate with one another have received much attention. Apart from supporting natural binaural hearing, such systems hold great potential for improving the intelligibility of speech in the presence of noise through beamforming algorithms. Binaural beamforming for hearing aids requires an exchange of microphone signals between the two devices over a wireless link. This paper studies two problems: which signal to transmit from one ear to the other, and at what bit-rate. The first problem is relevant as modern hearing aids usually contain multiple microphones, and the optimal choice for the signal to be transmitted is not obvious. The second problem is relevant as the capacity of the wireless link is limited by stringent power consumption constraints imposed by the limited battery life of hearing aids.
Rate-Constrained Beamforming in Binaural Hearing Aids
Sriram Srinivasan
2009-01-01
Full Text Available Recently, hearing aid systems where the left and right ear devices collaborate with one another have received much attention. Apart from supporting natural binaural hearing, such systems hold great potential for improving the intelligibility of speech in the presence of noise through beamforming algorithms. Binaural beamforming for hearing aids requires an exchange of microphone signals between the two devices over a wireless link. This paper studies two problems: which signal to transmit from one ear to the other, and at what bit-rate. The first problem is relevant as modern hearing aids usually contain multiple microphones, and the optimal choice for the signal to be transmitted is not obvious. The second problem is relevant as the capacity of the wireless link is limited by stringent power consumption constraints imposed by the limited battery life of hearing aids.
2004-01-01
Athletes sizzled around CERN on Wednesday 19 May at the 34th annual relay race. On one of the warmest days of the year so far, sunkissed competitors ran for the finish line and then straight for the drinks table. The Shabbys were on fire again, hurtling across the line first in a time of 10 min. 42.6 sec. and making an even stronger claim to being hailed as the traditional winners of the race with their fourth triumph in a row. Also on form were the Lynx Runners who won the Veteran's trophy, continuing their winning ways since 2002 and placing 29th overall. Ildefons Magrans of the ALICE Quarks on the Loose team ran the fastest 1000m in a time of 2 min. 47 sec. Second-placed Charmilles Technologies won the Open category in a time of 11 min. 03 sec., taking the prize for teams whose members work in different departments or who come from outside CERN. The OPALadies won the women's trophy and placed 48th. With 9 trophies up for grabs, more than 300 people in 55 teams ran the fun run, covering distances of 1000m ...
Physical Layer Security Using Two-Path Successive Relaying.
Liau, Qian Yu; Leow, Chee Yen; Ding, Zhiguo
2016-06-09
Relaying is one of the useful techniques to enhance wireless physical-layer security. Existing literature shows that employing full-duplex relay instead of conventional half-duplex relay improves secrecy capacity and secrecy outage probability, but this is at the price of sophisticated implementation. As an alternative, two-path successive relaying has been proposed to emulate operation of full-duplex relay by scheduling a pair of half-duplex relays to assist the source transmission alternately. However, the performance of two-path successive relaying in secrecy communication remains unexplored. This paper proposes a secrecy two-path successive relaying protocol for a scenario with one source, one destination and two half-duplex relays. The relays operate alternately in a time division mode to forward messages continuously from source to destination in the presence of an eavesdropper. Analytical results reveal that the use of two half-duplex relays in the proposed scheme contributes towards a quadratically lower probability of interception compared to full-duplex relaying. Numerical simulations show that the proposed protocol achieves the ergodic achievable secrecy rate of full-duplex relaying while delivering the lowest probability of interception and secrecy outage probability compared to the existing half duplex relaying, full duplex relaying and full duplex jamming schemes.
Physical Layer Security Using Two-Path Successive Relaying
Qian Yu Liau
2016-06-01
Full Text Available Relaying is one of the useful techniques to enhance wireless physical-layer security. Existing literature shows that employing full-duplex relay instead of conventional half-duplex relay improves secrecy capacity and secrecy outage probability, but this is at the price of sophisticated implementation. As an alternative, two-path successive relaying has been proposed to emulate operation of full-duplex relay by scheduling a pair of half-duplex relays to assist the source transmission alternately. However, the performance of two-path successive relaying in secrecy communication remains unexplored. This paper proposes a secrecy two-path successive relaying protocol for a scenario with one source, one destination and two half-duplex relays. The relays operate alternately in a time division mode to forward messages continuously from source to destination in the presence of an eavesdropper. Analytical results reveal that the use of two half-duplex relays in the proposed scheme contributes towards a quadratically lower probability of interception compared to full-duplex relaying. Numerical simulations show that the proposed protocol achieves the ergodic achievable secrecy rate of full-duplex relaying while delivering the lowest probability of interception and secrecy outage probability compared to the existing half duplex relaying, full duplex relaying and full duplex jamming schemes.
A Study of Filled and Sparse Line Array Beamformers.
1980-09-01
RESOLUTION TESI CHART NAIII NAt RItRI Al SI 1TANT ART 1161 A - LEVEL($ 0met 0o 1 A STUDY OF FILLED AND SPARSE LINE ARRAY BEAMFORMERS y! C- I L1 0___...8217 deviennent importantes . L’auteur d~montre que le PSB posse~de des avantages par rapport au CB pour produire le diagraune de directiviteA. Toutefois
An Overview of Algorithms for Downlink Transmit Beamforming
2007-11-02
Swindlehurst Electrical & Computer Engineering Brigham Young University Vector Modulo Pre-coding Use a perturbation of the form SP =,Cc =t(a+ jb) where -c...constellation "spacing" A. Lee Swindlehurst Electrical & Computer Engineering Brigham Young University Vector Modulo Pre-coding (cont.) * Choose c to solve...An Overview of Algorithms for Downlink Transmit Beamforming A. Lee Swindlehurst and Chris Peel Brigham Young University phone: 801-422-4343 email
Lee, Jong-Ho; Sohn, Illsoo; Kim, Yong-Hwa
2016-10-17
In this paper, we consider a transmit power allocation problem for secure transmission in multi-hop decode-and-forward (DF) full-duplex relay (FDR) networks, where multiple FDRs are located at each hop and perform cooperative beamforming to null out the signal at multiple eavesdroppers. For a perfect self-interference cancellation (PSIC) case, where the self-interference signal at each FDR is completely canceled, we derive an optimal power allocation (OPA) strategy using the Karush-Kuhn-Tucker (KKT) conditions to maximize the achievable secrecy rate under an overall transmit power constraint. In the case where residual self-interferences exist owing to imperfect self-interference cancellation (ISIC), we also propose a transmit power allocation scheme using the geometric programming (GP) method. Numerical results are presented to verify the secrecy rate performance of the proposed power allocation schemes.
Jong-Ho Lee
2016-10-01
Full Text Available In this paper, we consider a transmit power allocation problem for secure transmission in multi-hop decode-and-forward (DF full-duplex relay (FDR networks, where multiple FDRs are located at each hop and perform cooperative beamforming to null out the signal at multiple eavesdroppers. For a perfect self-interference cancellation (PSIC case, where the self-interference signal at each FDR is completely canceled, we derive an optimal power allocation (OPA strategy using the Karush-Kuhn-Tucker (KKT conditions to maximize the achievable secrecy rate under an overall transmit power constraint. In the case where residual self-interferences exist owing to imperfect self-interference cancellation (ISIC, we also propose a transmit power allocation scheme using the geometric programming (GP method. Numerical results are presented to verify the secrecy rate performance of the proposed power allocation schemes.
A Multiple Beamforming Network for Unequally Spaced Linear Array Based on CORPS
Armando Arce
2015-01-01
Full Text Available This paper proposes an alternative and innovative way to design a simpler beamforming network (BFN based on balancing alternated power combiners and dividers, to feed a nonuniformly spaced linear array with Gaussian amplitude and coherent (in-phase signals. Thus, a two-beam design configuration of the feeding network for a nonuniform array with beam steering capability is proposed and analyzed. The nonuniform aperture and the complex inputs of the feeding network are optimized by means of a differential evolution algorithm. In addition, a comparative analysis between a uniform and nonuniform linear array with the proposed feeding network is performed. Simulation results show the advantages and effectiveness of the proposed feeding network exploiting the nonuniformity of the antenna elements, in terms of side lobe level and directivity. Furthermore, research results show an inherent reduction in hardware complexity of the network.
Hierarchical beamformer and cross-talk reduction in electroneurography
Calvetti, Daniela; Wodlinger, Brian; Durand, Dominique M.; Somersalo, Erkki
2011-10-01
Electroneurography (ENG) is a method of recording neural activity within nerves. Using nerve electrodes with multiple contacts the activation patterns of individual neuronal fascicles can be estimated by measuring the surface voltages induced by the intraneural activity. The information about neuronal activation can be used for functional electric stimulation (FES) of patients suffering from spinal chord injury, or to control a robotic prosthetic limb of an amputee. However, the ENG signal estimation is a severely ill-posed inverse problem due to uncertainties in the model, low resolution due to limitations of the data, geometric constraints and the difficulty in separating the signal from biological and exogenous noise. In this paper, a reduced computational model for the forward problem is proposed, and the ENG problem is addressed by using beamformer techniques. Furthermore, we show that using a hierarchical statistical model, it is possible to develop an adaptive beamformer algorithm that estimates directly the source variances rather than the voltage source itself. The advantage of this new algorithm, e.g., over a traditional adaptive beamformer algorithm, is that it allows a very stable noise reduction by averaging over a time window. In addition, a new projection technique for separating sources and reducing cross-talk between different fascicle signals is proposed. The algorithms are tested on a computer model of realistic nerve geometry and time series signals.
Nonfeedback Distributed Beamforming Using Spatial-Temporal Extraction
Pongnarin Sriploy
2016-01-01
Full Text Available So far, major phase synchronization techniques for distributed beamforming suffer from the problem related to the feedback procedure as a base station has to send the feedback reference signal back to the transmitting nodes. This requires stability of communication channel or a number of retransmissions, introducing a complicated system to both transmitter and receiver. Therefore, this paper proposes an alternative technique, so-called nonfeedback beamforming, employing an operation in both space and time domains. The proposed technique is to extract a combined signal at the base station. The concept of extraction is based on solving a simultaneous linear equation without the requirement of feedback or reference signals from base station. Also, the number of retransmissions is less compared with the ones available in literatures. As a result, the transmitting nodes are of low complexity and also low power consumption. The simulation and experimental results reveal that the proposed technique provides the optimum beamforming gain. Furthermore, it can reduce Bit Error Rate to the systems.
Minimax robust relay selection based on uncertain long-term CSI
Nisar, Muhammad Danish
2014-02-01
Cooperative communications via multiple relay nodes is known to provide the benefits of increase diversity and coverage. Simultaneous transmission via multiple relays, however, requires strong coordination between nodes either in terms of slot-based transmission or distributed space-time (ST) code implementation. Dynamically selecting a single best relay out of multiple relays and then using it alone for cooperative transmission alleviates the need for this strong coordination while still reaping the benefits of increased diversity and coverage. In this paper, we consider the design of relay selection (RS) under an imperfect knowledge of long-term channel state information (CSI) at the relay nodes, and we pursue minimax optimization to arrive at a robust RS approach that promises the best guarantee on the worst-case end-to-end signal-to-noise ratio (SNR). We provide some intuitive examples and extensive simulation results, not only in terms of worst-case SNR performance but also in terms of average bit-error-rate (BER) performance, to demonstrate the benefits of the proposed minimax robust RS scheme. © 2013 IEEE.
Reactive relay selection in underlay cognitive networks with fixed gain relays
Hussain, Syed Imtiaz
2012-06-01
Best relay selection is a bandwidth efficient technique for multiple relay environments without compromising the system performance. The problem of relay selection is more challenging in underlay cognitive networks due to strict interference constraints to the primary users. Generally, relay selection is done on the basis of maximum end-to-end signal to noise ratio (SNR). However, it requires large amounts of channel state information (CSI) at different network nodes. In this paper, we present and analyze a reactive relay selection scheme in underlay cognitive networks where the relays are operating with fixed gains near a primary user. The system model minimizes the amount of CSI required at different nodes and the destination selects the best relay on the basis of maximum relay to destination SNR. We derive close form expressions for the received SNR statistics, outage probability, bit error probability and average channel capacity of the system. Simulation results are also presented to confirm the validity of the derived expressions. © 2012 IEEE.
Incremental Relaying for the Gaussian Interference Channel with a Degraded Broadcasting Relay
Zhou, Lei
2011-01-01
This paper studies a two-user Gaussian interference channel with an in-band-reception and out-of-band-transmission relay, where the link between the relay and the two receivers is modeled as a degraded broadcast channel. It is shown that %by using the Han-Kobayashi coding a generalized hash-and-forward (GHF) relaying strategy can achieve the capacity region of this channel to within a constant number of bits in a certain weak relay regime, where the transmitter-to-relay link gains are not unboundedly stronger than the interference links between the transmitters and the receivers. In such a regime, the GHF relaying strategy can be performed in an incremental fashion, where the relay message to one receiver is a degraded version of the message to the other receiver. A generalized-degree-of-freedom analysis reveals that in the symmetric channel setting, each common relay bit can improve the sum rate roughly by about one bit or two bits asymptotically, and the rate gain can be thought as coming solely from the im...
A genetic algorithm for multiple relay selection in two-way relaying cognitive radio networks
Alsharoa, Ahmad M.
2013-09-01
In this paper, we investigate a multiple relay selection scheme for two-way relaying cognitive radio networks where primary users and secondary users operate on the same frequency band. More specifically, cooperative relays using Amplifyand- Forward (AF) protocol are optimally selected to maximize the sum rate of the secondary users without degrading the Quality of Service (QoS) of the primary users by respecting a tolerated interference threshold. A strong optimization tool based on genetic algorithm is employed to solve our formulated optimization problem where discrete relay power levels are considered. Our simulation results show that the practical heuristic approach achieves almost the same performance of the optimal multiple relay selection scheme either with discrete or continuous power distributions. Copyright © 2013 by the Institute of Electrical and Electronic Engineers, Inc.
Chen, Yifan
2010-01-01
A novel channel representation for a two-hop decentralized wireless relay network (DWRN) is proposed, where the relays operate in a completely distributive fashion. The modeling paradigm applies an analogous approach to the description method for a double-directional multipath propagation channel, and takes into account the finite system spatial resolution and the extended relay listening/transmitting time. Specifically, the double-directional information azimuth spectrum (IAS) is formulated to provide a compact representation of information flows in a DWRN. The proposed channel representation is then analyzed from a geometrically-based statistical modeling perspective. Finally, we look into the problem of relay network tomography (RNT), which solves an inverse problem to infer the internal structure of a DWRN by using the instantaneous doubledirectional IAS recorded at multiple measuring nodes exterior to the relay region.
Wendy C. Wong
2010-01-01
Full Text Available We propose a transmit scheme for WiMAX systems, where multiple base stations (BSs employ downlink transmit beamforming and nulling for interference mitigation, with minimal coordination amongst BSs. This scheme improves system throughput and robustness, by increasing cell edge and overall cell throughputs by 68% and 19%, respectively, and by delivering improvement for mobile speed up to 60 km/h. First, cell edge users suffering from severe interferences are identified. Next, the RRM unit allocates resource to serving cell edge users only. BSs will schedule to serve their cell edge users independently using the allocated resources by the RRM. A special uplink sounding region is designed for BSs to learn the interference environment and form proper beams and nulls. The nulls formed towards users served by other BSs reduced interference from a BS towards these users and is the basic building block of our algorithm.
Han, Zhu
2007-01-01
Extending network lifetime of battery-operated devices is a key design issue that allows uninterrupted information exchange among distributive nodes in wireless sensor networks. Collaborative beamforming (CB) and cooperative transmission (CT) have recently emerged as new communication techniques that enable and leverage effective resource sharing among collaborative/cooperative nodes. In this paper, we seek to maximize the lifetime of sensor networks by using the new idea that closely located nodes can use CB/CT to reduce the load or even avoid packet forwarding requests to nodes that have critical battery life. First, we study the effectiveness of CB/CT to improve the signal strength at a faraway destination using energy in nearby nodes. Then, a 2D disk case is analyzed to assess the resulting performance improvement. For general networks, if information-generation rates are fixed, the new routing problem is formulated as a linear programming problem; otherwise, the cost for routing is dynamically adjusted a...
The Segmented Beamformer for Electromagnetic Waves of the Terahertz Free Electron Laser
Bogomolov, G D; Letunov, A A; Zavyalov, V V
2015-01-01
The quasi-optical segmented mirror for a formation of the target irradiation field was manufactured and investigated. It was designed for the high power THz beam of the free electron laser (FEL) using as a target a dust particle cloud, simulating cosmic dust. Numerical calculation of the beam shape and its low power laboratory measurements was made in the spectral region 1 - 3 THz of the first phase of the Novosibirsk FEL construction. The theoretical calculations of the diffraction effects reveal a speckle structure of a target spot, which was confirmed by the laboratory experiment. The beamformer technology was adapted for manufacturing and such device could be widely used for a concentration of powerful terahertz radiation.
Feng Zhao
2015-01-01
Full Text Available Multi-input multioutput (MIMO technique provides a promising solution to enhance the performance of wireless communication systems. In this paper, we consider antenna correlation at the transmitter in practical cognitive MIMO systems. What is more, a game-theoretic framework is conducted to analyze the optimum beamforming and power allocation such that each user maximizes its own rate selfishly under the transmitting power constraint and the primary user (PU interference constraint. The design of the cognitive MIMO system is formulated as a noncooperative game, where the secondary users (SUs compete with each other over the resources made available by the PUs. Interestingly, as the correlation parameter grows, the utility degrades. Nash equilibrium is considered as the solution of this game. Simulation results show that the proposed algorithm can converge quickly and clearly outperforms the strategy without game.
Beamforming transmission in IEEE 802.11ac under time-varying channels.
Yu, Heejung; Kim, Taejoon
2014-01-01
The IEEE 802.11ac wireless local area network (WLAN) standard has adopted beamforming (BF) schemes to improve spectral efficiency and throughput with multiple antennas. To design the transmit beam, a channel sounding process to feedback channel state information (CSI) is required. Due to sounding overhead, throughput increases with the amount of transmit data under static channels. Under practical channel conditions with mobility, however, the mismatch between the transmit beam and the channel at transmission time causes performance loss when transmission duration after channel sounding is too long. When the fading rate, payload size, and operating signal-to-noise ratio are given, the optimal transmission duration (i.e., packet length) can be determined to maximize throughput. The relationship between packet length and throughput is also investigated for single-user and multiuser BF modes.
Spherical Linear Interpolation for Transmit Beamforming in MIMO-OFDM Systems with Limited Feedback
2007-11-02
University of Texas at Austin Department of Electrical and Computer Engineering Wireless Networking and Communications Group 1 University Station...and Engineering Foundation (KOSEF). [10]. This approach, however, requires the knowledge about the transmit beamforming vectors at the transmitter. In...additional parameters for phase rotation, which consider the nonuniqueness of the optimal beamforming vector. Our interpolator can be used to reduce the
Li, Ye; Jensen, Jørgen Arendt
2011-01-01
A dual stage beamformer method for synthetic aperture flow imaging has been developed. The motivation is to increase the frame rate and still maintain a beamforming quality sufficient for flow estimation that is possible to implement in a commercial scanner. With the new method high resolution im...
Efficient radio transmission with adaptive and distributed beamforming for intelligent WiMAX
Lian, X.; Nikookar, H.; Ligthart, L.P.
2011-01-01
In this paper, we introduce Adaptive Beamforming (AB) and Distributed Beamforming (DB) as two efficient techniques for IntelligentWiMAX (I-WiMAX). I-WiMAX is a new maritime communication system, consisting of Smart Radio (SR) principles and mobile WiMAX based on the IEEE 802.16e standard. Adopting A
Robust Adaptive Beamforming Based on Worst-Case and Norm Constraint
Hongtao Li
2015-01-01
Full Text Available A novel robust adaptive beamforming based on worst-case and norm constraint (RAB-WC-NC is presented. The proposed beamforming possesses superior robustness against array steering vector (ASV error with finite snapshots by using the norm constraint and worst-case performance optimization (WCPO techniques. Simulation results demonstrate the validity and superiority of the proposed algorithm.
Outage-Constrained Beamforming for Two-Tier Massive MIMO Downlink with Pilot Reuse
Guozhen Xu
2015-01-01
efficient algorithm to combine these subproblems and solve them iteratively for generating the beamforming vectors. Monte Carlo simulations show that the average power consumption of the proposed pilot reuse scheme and its associated beamforming algorithm is close to that of the perfect CSI case.
The LDA beamformer: Optimal estimation of ERP source time series using linear discriminant analysis.
Treder, Matthias S; Porbadnigk, Anne K; Shahbazi Avarvand, Forooz; Müller, Klaus-Robert; Blankertz, Benjamin
2016-04-01
We introduce a novel beamforming approach for estimating event-related potential (ERP) source time series based on regularized linear discriminant analysis (LDA). The optimization problems in LDA and linearly-constrained minimum-variance (LCMV) beamformers are formally equivalent. The approaches differ in that, in LCMV beamformers, the spatial patterns are derived from a source model, whereas in an LDA beamformer the spatial patterns are derived directly from the data (i.e., the ERP peak). Using a formal proof and MEG simulations, we show that the LDA beamformer is robust to correlated sources and offers a higher signal-to-noise ratio than the LCMV beamformer and PCA. As an application, we use EEG data from an oddball experiment to show how the LDA beamformer can be harnessed to detect single-trial ERP latencies and estimate connectivity between ERP sources. Concluding, the LDA beamformer optimally reconstructs ERP sources by maximizing the ERP signal-to-noise ratio. Hence, it is a highly suited tool for analyzing ERP source time series, particularly in EEG/MEG studies wherein a source model is not available.
An optimized ultrasound digital beamformer with dynamic focusing implemented on FPGA.
Almekkawy, Mohamed; Xu, Jingwei; Chirala, Mohan
2014-01-01
We present a resource-optimized dynamic digital beamformer for an ultrasound system based on a field-programmable gate array (FPGA). A comprehensive 64-channel receive beamformer with full dynamic focusing is embedded in the Altera Arria V FPGA chip. To improve spatial and contrast resolution, full dynamic beamforming is implemented by a novel method with resource optimization. This was conceived using the implementation of the delay summation through a bulk (coarse) delay and fractional (fine) delay. The sampling frequency is 40 MHz and the beamformer includes a 240 MHz polyphase filter that enhances the temporal resolution of the system while relaxing the Analog-to-Digital converter (ADC) bandwidth requirement. The results indicate that our 64-channel dynamic beamformer architecture is amenable for a low power FPGA-based implementation in a portable ultrasound system.
WU Wentao; PU Jie; LU Yi
2012-01-01
In medical ultrasound imaging field, in order to obtain high resolution and correct the phase errors induced by the velocity in-homogeneity of the tissue, a high-resolution medical ultrasound imaging method combining minimum variance beamforming and general coherence factor was presented. First, the data from the elements is delayed for focusing; then the multi-channel data is used for minimum variance beamforming; at the same time, the data is transformed from array space to beam space to calculate the general coherence factor; in the end, the general coherence factor is used to weight the results of minimum variance beamforming. The medical images are gotten by the imaging system. Experiments based on point object and anechoic cyst object are used to verify the proposed method. The results show the proposed method in the aspects of resolution, contrast and robustness is better than minimum variance beamforming and conventional beamforming.
Diversity-Multiplexing Trade-off for Coordinated Relayed Uplink and Direct Downlink Transmissions
Thai, Chan; Popovski, Petar; Sun, Fan
2013-01-01
Abstract—There are two basic principles used in wireless network coding to design throughput-efficient schemes: (1) aggregation of communication flows and (2) interference is embraced and subsequently cancelled or mitigated. These principles inspire design of Coordinated Direct/Relay (CDR) scheme...
Non-Markovian Reactivation of Quantum Relays
Pirandola, Stefano; Jacobsen, Christian S; Spedalieri, Gaetana; Braunstein, Samuel L; Gehring, Tobias; Andersen, Ulrik L
2015-01-01
We consider a quantum relay which is used by two parties to perform several continuous-variable protocols: Entanglement swapping, distillation, quantum teleportation, and quantum key distribution. The theory of these protocols is extended to a non-Markovian model of decoherence characterized by correlated Gaussian noise. Even if bipartite entanglement is completely lost at the relay, we show that the various protocols can progressively be reactivated by the separable noise-correlations of the environment. In fact, above a critical amount, these correlations are able to restore the distribution of quadripartite entanglement, which can be localized into an exploitable bipartite form by the action of the relay. Our findings are confirmed by a proof-of-principle experiment and show the potential advantages of non-Markovian effects in a quantum network architecture.
B. Prasad
2016-06-01
Full Text Available In this paper outage performance of a secondary user (SU is evaluated under amplify and forward (AF relay selection scheme with an imperfect channel state information (CSIwhile sharing spectrum in an underlay cognitive radio network (CRN. In underlay, the SU coexists with primary user (PU in the same band provided the interference produced by SU at the PU receiver is below the interference threshold of PU which limits the transmission power of SU and coverage area. Relays help to improve the performance of SU in underlay. However relays are also constrained in transmit power due to interference constraint imposed by PU. Closed form expression of the outage probability of SU with maximum transmit power constraint of relay under imperfect CSI is derived. A scaling factor based power control is used for the SU transmitter and the relay in order to maintain the interference constraint at PU receiver due to imperfect CSI. The impact of different parameters viz. correlation coefficient, channel estimation error, tolerable interference threshold, number of relays and the maximum transmit power constraint of relay on SU performance is investigated. A MATLAB based test bed has also been developed to carry out simulation in order to validate the theoretical result.
Beamforming in Ad Hoc Networks: MAC Design and Performance Modeling
Fakih, Khalil; Diouris, Jean-Francois; Andrieux, Guillaume
2009-01-01
.... Our proposition performs jointly channel estimation and radio resource sharing. We validate the fruitfulness of the proposed MAC and we evaluate the effects of the channel estimation on the network performance...
CERN Relay Race: information for drivers
2012-01-01
The CERN relay race will take place around the Meyrin site on Thursday, 24 May starting at 12.15. If possible, please avoid driving on the site during this 20-minute period. If you do meet runners while driving your car, please STOP until they have all passed. In addition, there will be a Nordic Walking event which will finish around 12.50. This should not block the roads, but please drive carefully during this time. Thank you for your cooperation. Details on how to register your team for the relay race can be found here.
Secrecy in Cooperative Relay Broadcast Channels
Ekrem, E
2008-01-01
We investigate the effects of user cooperation on the secrecy of broadcast channels by considering a cooperative relay broadcast channel. We show that user cooperation can increase the achievable secrecy region. We propose an achievable scheme that combines Marton's coding scheme for broadcast channels and Cover and El Gamal's compress-and-forward scheme for relay channels. We derive outer bounds for the rate-equivocation region using auxiliary random variables for single-letterization. Finally, we consider a Gaussian channel and show that both users can have positive secrecy rates, which is not possible for scalar Gaussian broadcast channels without cooperation.
Advanced Strategic and Tactical Relay Request Management for the Mars Relay Operations Service
Allard, Daniel A.; Wallick, Michael N.; Gladden, Roy E.; Wang, Paul; Hy, Franklin H.
2013-01-01
This software provides a new set of capabilities for the Mars Relay Operations Service (MaROS) in support of Strategic and Tactical relay, including a highly interactive relay request Web user interface, mission control over relay planning time periods, and mission management of allowed strategic vs. tactical request parameters. Together, these new capabilities expand the scope of the system to include all elements critical for Tactical relay operations. Planning of replay activities spans a time period that is split into two distinct phases. The first phase is called Strategic, which begins at the time that relay opportunities are identified, and concludes at the point that the orbiter generates the flight sequences for on board execution. Any relay request changes from this point on are called Tactical. Tactical requests, otherwise called Orbit - er Relay State Changes (ORSC), are highly restricted in terms of what types of changes can be made, and the types of parameters that can be changed may differ from one orbiter to the next. For example, one orbiter may be able to delay the start of a relay request, while another may not. The legacy approach to ORSC management involves exchanges of e-mail with "requests for change" and "acknowledgement of approval," with no other tracking of changes outside of e-mail folders. MaROS Phases 1 and 2 provided the infrastructure for strategic relay for all supported missions. This new version, 3.0, introduces several capabilities that fully expand the scope of the system to include tactical relay. One new feature allows orbiter users to manage and "lock" Planning Periods, which allows the orbiter team to formalize the changeover from Strategic to Tactical operations. Another major feature allows users to interactively submit tactical request changes via a Web user interface. A third new feature allows orbiter missions to specify allowed tactical updates, which are automatically incorporated into the tactical change process
Outage performance of two-way DF relaying systems with a new relay selection metric
Hyadi, Amal
2012-04-01
This paper investigates a new constrained relay selection scheme for two-way relaying systems where two end terminals communicate simultaneously via a relay. The introduced technique is based on the maximization of the weighted sum rate of both users. To evaluate the performance of the proposed system, the outage probability is derived in a general case (where an arbitrary channel is considered), and then over independently but not necessarily identically distributed (i.n.i.d.) Rayleigh fading channels. The analytical results are verified through simulations. © 2012 IEEE.
Practical constraints on estimation of source extent with MEG beamformers.
Hillebrand, Arjan; Barnes, Gareth R
2011-02-14
We aimed to determine practical constraints on the estimation of the spatial extent of neuronal activation using MEG beamformers. Correct estimation of spatial extent is a pre-requisite for accurate models of electrical activity, allows one to estimate current density, and enables non-invasive monitoring of functional recovery following stroke. The output of an MEG beamformer is maximum when the correct source model is used, so that the spatial extent of a source can in principal be determined through evaluation of different source models with the beamformer. Here, we simulated 275-channel MEG data using sources of varying spatial extents that followed the cortical geometry. These data were subsequently used to estimate the spatial extent of generic disc elements without knowledge of the underlying surface, and we compared these results to estimates based on cortical surface geometry (with and without error in surface location). We found that disc-shaped source models are too simplistic, particularly for areas with high curvature. For areas with low curvature spatial extent was underestimated, although on average there was a linear relationship between the true and estimated extent. In contrast, cortical surface models gave accurate predictions of spatial extent. However, adding small errors (>2 mm) to the estimated location of the cortical surface abolished this relationship between true and estimated extent, implying that accurate co-registration is needed with such models. Our results show that models exploiting surface information are necessary in order to model spatial extent and in turn current density, but in order to render such models applicable in practical situations, the accuracy of the cortical surface model itself needs to improve.
Protocols for Relay-Assisted Free-Space Optical Systems
Chatzidiamantis, Nestor D; Kriezis, Emmanouil E; Karagiannidis, George K; Schober, Robert
2011-01-01
We investigate transmission protocols for relay-assisted free-space optical (FSO) systems, when multiple parallel relays are employed and there is no direct link between the source and the destination. As alternatives to all-active FSO relaying, where all the available relays transmit concurrently, we propose schemes that select only a single relay to participate in the communication between the source and the destination in each transmission slot. This selection is based on the channel state information (CSI) obtained either from all or from some of the FSO links. Thus, the need for synchronizing the relays' transmissions is avoided and the slowly varying nature of the atmospheric channel is exploited. For both relay selection and all-active relaying, novel closed-form expressions for their outage performance are derived, assuming the versatile Gamma-Gamma channel model. Furthermore, based on the derived analytical results, the problem of allocating the optical power resources to the FSO links is addressed, ...
76 FR 72124 - Internet-Based Telecommunications Relay Service Numbering
2011-11-22
...] Internet-Based Telecommunications Relay Service Numbering AGENCY: Federal Communications Commission. ACTION... collection associated with the Commission's Internet- Based Telecommunications Relay Service Numbering... notice as an announcement of the effective date of the rules. See Internet-Based Telecommunications...
Capacity gains of buffer-aided moving relays
Zafar, Ammar
2017-03-14
This work investigates the gain due to reduction in path loss by deploying buffer-aided moving relaying. In particular, the increase in gain due to moving relays is studied for dual-hop broadcast channels and the bidirectional relay channel. It is shown that the exploited gains in these channels due to buffer-aided relaying can be enhanced by utilizing the fact that a moving relay can communicate with the terminal closest to it and store the data in the buffer and then forward the data to the intended destination when it comes in close proximity with the destination. Numerical results show that for both the considered channels the achievable rates are increased as compared to the case of stationary relays. Numerical results also show that more significant increase in performance is seen when the relay moves to-and-fro between the source and the relay.
Dynamic Relaying in 3GPP LTE-Advanced Networks
Van Phan Vinh
2009-01-01
Full Text Available Relaying is one of the proposed technologies for LTE-Advanced networks. In order to enable a flexible and reliable relaying support, the currently adopted architectural structure of LTE networks has to be modified. In this paper, we extend the LTE architecture to enable dynamic relaying, while maintaining backward compatibility with LTE Release 8 user equipments, and without limiting the flexibility and reliability expected from relaying. With dynamic relaying, relays can be associated with base stations on a need basis rather than in a fixed manner which is based only on initial radio planning. Proposals are also given on how to further improve a relay enhanced LTE network by enabling multiple interfaces between the relay nodes and their controlling base stations, which can possibly be based on technologies different from LTE, so that load balancing can be realized. This load balancing can be either between different base stations or even between different networks.
EFFECTS OF THE NUMBER OF RELAY ANTENNAS AND RELAY-POWER ON MIMO PRECODED TWO-WAY RELAYING
S.S. Rajeshwari
2011-06-01
Full Text Available In this treatise a two-way Amplify and Forward (AF relay-aided system is considered, which employs the so-called Arithmetic Sum of Average Bit Error Rate (ASABER based MIMO precoding technique. The two-way AF relay system is comprised of the pair of transceiver nodes S1 and S2, and the Relay Node (RN R, where each node is equipped with N1, N2 and Nr antennas, respectively. We study the effects of varying Nr for fixed values of N1 and N2, and as well as the effects of having a fixed transmission power at the RN on the achievable ASABER performance. Based on our intensive simulation campaign, we infer that the attainable diversity order is increased approximately by Nr − min (N1, N2, whenever Nr assumes a value higher than min (N1, N2 for fixed N1, N2 values. However, this is observation is only valid for relay power pr ≥ (p1, p2, where p1 and p2 are the transmit power constraints imposed on the sources S1 and S2, respectively. We also observe that the ASABER MIMO precoder’s BER curve exhibits an error floor for pr ≤ (p1, p2.
Simplified 3D Fading Channels Adopted in MIMO Beamforming Schemes
Joy Iong-Zong Chen; Bo Huei Lee
2015-01-01
A simplified three-dimension (3D) fading channel model deployed in a multi-input multi-output (MIMO) beamforming system is explored in this article. Both angle of arrival (AoA) and angle of departure (AoD) which impact the overall system performance are examined. The numerical results are given for validating the accuracy of the theoretical derived formulas. Furthermore, the performances of the model with different number of transmitters and receivers are studied and compared. The increment in AoA parameters definitely generates the impact of the system performance when the consideration of simplified 3D channels.
Vector Modulator for Phase Shifting in Passive Beamforming Wireless Systems
P.Sampath,
2010-05-01
Full Text Available This paper proposes vector modulator for changing the phase of a signal in passive beamforming system. Vector modulator is used to perform a phase shift function with added benefit of amplitude control. It is used to improve the directivity of RF waves in Wireless systems. Vector modulator is implemented for a center frequency of 902.5 MHz. The simulation is performed for individual blocks of the vector modulator and for vector modulator with JFET and MOSFET as controlling device in the variable attenuator of the vector modulator.
Synthetic Aperture Sequential Beamformation applied to medical imaging
Hemmsen, Martin Christian; Hansen, Jens Munk; Jensen, Jørgen Arendt
2012-01-01
Synthetic Aperture Sequential Beamforming (SASB) is applied to medical ultrasound imaging using a multi element convex array transducer. The main motivation for SASB is to apply synthetic aperture techniques without the need for storing RF-data for a number of elements and hereby devise a system...... with a reduced system complexity. Using a 192 element, 3.5 MHz, λ-pitch transducer, it is demonstrated using tissue-phantom and wire-phantom measurements, how the speckle size and the detail resolution is improved compared to conventional imaging....
An object-oriented multi-threaded software beamformation toolbox
Hansen, Jens Munk; Hemmsen, Martin Christian; Jensen, Jørgen Arendt
2011-01-01
Focusing and apodization are an essential part of signal processing in ultrasound imaging. Although the fun- damental principles are simple, the dramatic increase in computational power of CPUs, GPUs, and FPGAs motivates the development of software based beamformers, which further improves image...... quality (and the accu- racy of velocity estimation). For developing new imaging methods, it is important to establish proof-of-concept before using resources on real-time implementations. With this in mind, an eective and versatile Matlab toolbox written in C++ has been developed to assist in developing...
Automatic Analog Beamforming Transceiver for 60 GHz Radios
Gupta, Shalabh
2009-01-01
We propose a transceiver architecture for automatic beamforming and instantaneous setup of a multigigabit-per-second wireless link between two millimeter wave radios. The retro-directive architecture eliminates necessity of slow and complex digital algorithms required for searching and tracking the directions of opposite end radios. Simulations predict <5 micro-seconds setup time for a 2-Gbps bidirectional 60-GHz communication link between two 10-meters apart radios. The radios have 4-element arrayed antennas, and use QPSK modulation with 1.5 GHz analog bandwidth.
Synthetic Aperture Sequential Beamforming implemented on multi-core platforms
Kjeldsen, Thomas; Lassen, Lee; Hemmsen, Martin Christian
2014-01-01
This paper compares several computational ap- proaches to Synthetic Aperture Sequential Beamforming (SASB) targeting consumer level parallel processors such as multi-core CPUs and GPUs. The proposed implementations demonstrate that ultrasound imaging using SASB can be executed in real- time...... with a significant headroom for post-processing. The CPU implementations are optimized using Single Instruction Multiple Data (SIMD) instruction extensions and multithreading, and the GPU computations are performed using the APIs, OpenCL and OpenGL. The implementations include refocusing (dynamic focusing) of a set...
Cyber and electromagnetic threats in modern relay protection
Gurevich, Vladimir
2014-01-01
PrefaceAbstractAuthorTechnological Advance in Relay Protection: Dangerous TendenciesIssues of Philosophy in Relay ProtectionExtrusion into the Historical DomainAbout Technological AdvanceSmart Grid: One More Dangerous Vector of the ""Technological Advantages"" in Power IndustrySmart Grid Russian StyleSmart Grid: Western StyleDangerous Tendencies in the Development of the Relay ProtectionWhat to Do?ReferencesNatural Electromagnetic Effects on Digital Protective RelaysElectro
Studies in Beamforming Tracking Neural Networks Mathematics
1991-01-01
designs. Therefore, as p is varied it isUP -- o 2)helpful to maintain a fixed beamwidth; specifically, we always where 4! , is the largest zero of the...fondamental de la theorie des jeux, C. R. Acad. Sci. Paris 234:2418-2420 (1952). 11 E. G. Gol’stein, Theory of Convex Programming, Translations of Mathematical
Dynamic Relaying in 3GPP LTE-Advanced Networks
Teyeb, Oumer Mohammed; Van Phan, Vinh; Redana, Simone
2009-01-01
Relaying is one of the proposed technologies for LTE-Advanced networks. In order to enable a flexible and reliable relaying support, the currently adopted architectural structure of LTE networks has to be modified. In this paper, we extend the LTE architecture to enable dynamic relaying, while ma...
76 FR 58412 - Relay Services for Deaf-Blind Individuals
2011-09-21
... COMMISSION 47 CFR Part 64 Relay Services for Deaf-Blind Individuals AGENCY: Federal Communications Commission... Communications and Video Accessibility Act of 2010, Section 105, Relay Services for Deaf-Blind Individuals...-First Century Communications and Video Accessibility Act of 2010, Section 105, Relay Services for...
Asymmetric Modulation Gains in Network Coded Relay Networks
Roetter, Daniel Enrique Lucani; Fitzek, Frank
2015-01-01
Wireless relays have usually been considered in two ways. On the one hand, a physical layer approach focused on per-packet reliability and involving the relay on each packet transmission. On the other, recent approaches have relied on the judicious activation of the relay at the network level to ...
76 FR 18490 - Contributions to the Telecommunications Relay Service Fund
2011-04-04
... COMMISSION 47 CFR Parts 1 and 64 Contributions to the Telecommunications Relay Service Fund AGENCY: Federal...- interconnected VoIP service to participate in and contribute to the Telecommunications Relay Services (TRS) Fund... summary of the Commission's Contributions to the Telecommunications Relay Service Fund, Notice of...
76 FR 65965 - Contributions to the Telecommunications Relay Services Fund
2011-10-25
... COMMISSION 47 CFR Parts 1 and 64 Contributions to the Telecommunications Relay Services Fund AGENCY: Federal... contributing to the interstate Telecommunications Relay Services (TRS) Fund in a manner prescribed by... to the Telecommunications Relay Service Fund, Report and Order (Order), document FCC 11-150,...
A low complexity algorithm for multiple relay selection in two-way relaying Cognitive Radio networks
Alsharoa, Ahmad M.
2013-06-01
In this paper, a multiple relay selection scheme for two-way relaying cognitive radio network is investigated. We consider a cooperative Cognitive Radio (CR) system with spectrum sharing scenario using Amplify-and-Forward (AF) protocol, where licensed users and unlicensed users operate on the same frequency band. The main objective is to maximize the sum rate of the unlicensed users allowed to share the spectrum with the licensed users by respecting a tolerated interference threshold. A practical low complexity heuristic approach is proposed to solve our formulated optimization problem. Selected numerical results show that the proposed algorithm reaches a performance close to the performance of the optimal multiple relay selection scheme either with discrete or continuous power distributions while providing a considerable saving in terms of computational complexity. In addition, these results show that our proposed scheme significantly outperforms the single relay selection scheme. © 2013 IEEE.
Optimal relay selection and power allocation for cognitive two-way relaying networks
Pandarakkottilil, Ubaidulla
2012-06-01
In this paper, we present an optimal scheme for power allocation and relay selection in a cognitive radio network where a pair of cognitive (or secondary) transceiver nodes communicate with each other assisted by a set of cognitive two-way relays. The secondary nodes share the spectrum with a licensed primary user (PU), and each node is assumed to be equipped with a single transmit/receive antenna. The interference to the PU resulting from the transmission from the cognitive nodes is kept below a specified limit. We propose joint relay selection and optimal power allocation among the secondary user (SU) nodes achieving maximum throughput under transmit power and PU interference constraints. A closed-form solution for optimal allocation of transmit power among the SU transceivers and the SU relay is presented. Furthermore, numerical simulations and comparisons are presented to illustrate the performance of the proposed scheme. © 2012 IEEE.
SWIPT in Multiuser MIMO Decode-and-Forward Relay Broadcasting Channel with Energy Harvesting Relays
Benkhelifa, Fatma
2017-02-09
In this paper, we consider a multiuser multiple- input multiple-output (MIMO) decode-and-forward (DF) relay broadcasting channel (BC) with single source, multiple energy harvesting relays and multiple destinations. Since the end-to-end sum rate maximization problem is intractable, we tackle a simplified problem where we maximize the sum of the harvested energy at the relays, we employ the block diagonalization (BD) procedure at the source, and we mitigate the interference between the relay- destination channels. The interference mitigation at the destinations is managed in two ways: either to fix the interference covariance matrices at the destination and update them at each iteration until convergence, or to cancel the interference using an algorithm similar to the BD method. We provide numerical results to show the relevance of our proposed solution.
First Things First: Internet Relay Chat Openings.
Rintel, E. Sean; Mulholland, Joan; Pittam, Jeffery
2001-01-01
Argues that Internet Relay Chat (IRC) research needs to systematically address links between interaction structures, technological mediation and the instantiation and development of interpersonal relationships. Finds that openings that occur directly following user's entries into public IRC channels are often ambiguous, can disrupt relationship…
Cable Television Service; Cable Television Relay Service.
Federal Register, 1972
1972-01-01
The rules and regulations of the Federal Communications Commission (FCC) concerning cable television service and cable relay service are presented along with the comments of the National Cable Television Association, the National Association of Broadcasters, the Association of Maximum Service Telecasters, and a major group of program suppliers.…
First Things First: Internet Relay Chat Openings.
Rintel, E. Sean; Mulholland, Joan; Pittam, Jeffery
2001-01-01
Argues that Internet Relay Chat (IRC) research needs to systematically address links between interaction structures, technological mediation and the instantiation and development of interpersonal relationships. Finds that openings that occur directly following user's entries into public IRC channels are often ambiguous, can disrupt relationship…
Diversity of MIMO Multihop Relay Channels
Yang, Sheng
2007-01-01
We consider slow fading relay channels with a single multi-antenna source-destination terminal pair. The source signal arrives at the destination via N hops through N-1 layers of relays. We analyze the diversity of such channels with fixed network size at high SNR. In the clustered case where the relays within the same layer can have full cooperation, the cooperative decode-and-forward (DF) scheme is shown to be optimal in terms of the diversity-multiplexing tradeoff (DMT). The upper bound on the DMT, the cut-set bound, is attained. In the non-clustered case, we show that the naive amplify-and-forward (AF) scheme has the maximum multiplexing gain of the channel but is suboptimal in diversity, as compared to the cut-set bound. To improve the diversity, space-time relay processing is introduced through the parallel partition of the multihop channel. The idea is to let the source signal go through K different "AF paths" in the multihop channel. This parallel AF scheme creates a parallel channel in the time domai...
Relay Feedback Analysis for Double Integral Plants
Zhen Ye
2011-01-01
Full Text Available Double integral plants under relay feedback are studied. Complete results on the uniqueness of solutions, existence, and stability of the limit cycles are established using the point transformation method. Analytical expressions are also given for determining the amplitude and period of a limit cycle from the plant parameters.
Du, Guanyao; Yu, Jianjun
2016-01-01
This paper investigates the system achievable rate for the multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system with an energy harvesting (EH) relay. Firstly we propose two protocols, time switching-based decode-and-forward relaying (TSDFR) and a flexible power splitting-based DF relaying (PSDFR) protocol by considering two practical receiver architectures, to enable the simultaneous information processing and energy harvesting at the relay. In PSDFR protocol, we introduce a temporal parameter to describe the time division pattern between the two phases which makes the protocol more flexible and general. In order to explore the system performance limit, we discuss the system achievable rate theoretically and formulate two optimization problems for the proposed protocols to maximize the system achievable rate. Since the problems are non-convex and difficult to solve, we first analyze them theoretically and get some explicit results, then design an augmented Lagrangian penalty function (ALPF) based algorithm for them. Numerical results are provided to validate the accuracy of our analytical results and the effectiveness of the proposed ALPF algorithm. It is shown that, PSDFR outperforms TSDFR to achieve higher achievable rate in such a MIMO-OFDM relaying system. Besides, we also investigate the impacts of the relay location, the number of antennas and the number of subcarriers on the system performance. Specifically, it is shown that, the relay position greatly affects the system performance of both protocols, and relatively worse achievable rate is achieved when the relay is placed in the middle of the source and the destination. This is different from the MIMO-OFDM DF relaying system without EH. Moreover, the optimal factor which indicates the time division pattern between the two phases in the PSDFR protocol is always above 0.8, which means that, the common division of the total transmission time into two equal phases in
Quasi-multistatic MIST beamforming for the early detection of breast cancer.
O'Halloran, Martin; Jones, Edward; Glavin, Martin
2010-04-01
Microwave imaging via space-time (MIST) beamforming has been shown to be one of the most promising imaging modalities for detecting small malignant breast tumors. This paper outlines two modifications to the MIST system developed by Hagness for the early detection of breast cancer, resulting in a quasi-multistatic MIST beamformer (multi-MIST). Multistatic MIST beamforming involves illuminating the breast with an ultrawideband (UWB) signal from one antenna while collecting the reflections at an array of antennas, as opposed to traditional monostatic MIST beamforming where only the transmitting antenna records the reflections from the breast. In order to process the multistatic data, traditional data-adaptive artifact removal algorithms have to be modified to accommodate signals from all antennas. Also, the MIST beamforming algorithm, which spatially focuses the signal and compensates for frequency-dependent propagation effects, has to be modified. The algorithms are tested on a 2-D anatomically accurate finite-difference time-domain model of the breast. The multi-MIST beamformer described here is shown to offer an improved signal to clutter ratio when compared to the traditional monostatic MIST beamformer.
Fully Quaternion-Valued Adaptive Beamforming Based on Crossed-Dipole Arrays
Xiang Lan
2017-04-01
Full Text Available Based on crossed-dipole antenna arrays, quaternion-valued data models have been developed for both direction of arrival estimation and beamforming in the past. However, for almost all the models, and especially for adaptive beamforming, the desired signal is still complex-valued as in the quaternion-valued Capon beamformer. Since the complex-valued desired signal only has two components, while there are four components in a quaternion, only two components of the quaternion-valued beamformer output are used and the remaining two are simply discarded, leading to significant redundancy in its implementation. In this work, we consider a quaternion-valued desired signal and develop a fully quaternion-valued Capon beamformer which has a better performance and a much lower complexity. Furthermore, based on this full quaternion model, the robust beamforming problem is also studied in the presence of steering vector errors and a worst-case-based robust beamformer is developed. The performance of the proposed methods is verified by computer simulations.
Cross-Layer Optimization of Two-Way Relaying for Statistical QoS Guarantees
lin, Cen; Tao, Meixia
2012-01-01
Two-way relaying promises considerable improvements on spectral efficiency in wireless relay networks. While most existing works focus on physical layer approaches to exploit its capacity gain, the benefits of two-way relaying on upper layers are much less investigated. In this paper, we study the cross-layer design and optimization for delay quality-of-service (QoS) provisioning in two-way relay systems. Our goal is to find the optimal transmission policy to maximize the weighted sum throughput of the two users in the physical layer while guaranteeing the individual statistical delay-QoS requirement for each user in the datalink layer. This statistical delay-QoS requirement is characterized by the QoS exponent. By integrating the concept of effective capacity, the cross-layer optimization problem is equivalent to a weighted sum effective capacity maximization problem. We derive the jointly optimal power and rate adaptation policies for both three-phase and two-phase two-way relay protocols. Numerical results...
Diversity of MIMO Multihop Relay Channels - Part I: Amplify-and-Forward
Yang Sheng
2007-01-01
In this two-part paper, we consider the multiantenna multihop relay channels in which the source signal arrives at the destination through N independent relaying hops in series. The main concern of this work is to design relaying strategies that utilize efficiently the relays in such a way that the diversity is maximized. In part I, we focus on the amplify-and-forward (AF) strategy with which the relays simply scale the received signal and retransmit it. More specifically, we characterize the diversity-multiplexing tradeoff (DMT) of the AF scheme in a general multihop channel with arbitrary number of antennas and arbitrary number of hops. The DMT is in closed-form expression as a function of the number of antennas at each node. First, we provide some basic results on the DMT of the general Rayleigh product channels. It turns out that these results have very simple and intuitive interpretation. Then, the results are applied to the AF multihop channels which is shown to be equivalent to the Rayleigh product cha...
Coding and Decoding for the Dynamic Decode and Forward Relay Protocol
Kumar, K Raj
2008-01-01
We study the Dynamic Decode and Forward (DDF) protocol for a single half-duplex relay, single-antenna channel with quasi-static fading. The DDF protocol is well-known and has been analyzed in terms of the Diversity-Multiplexing Tradeoff (DMT) in the infinite block length limit. We characterize the finite block length DMT and give new explicit code constructions. The finite block length analysis illuminates a few key aspects that have been neglected in the previous literature: 1) we show that one dominating cause of degradation with respect to the infinite block length regime is the event of decoding error at the relay; 2) we explicitly take into account the fact that the destination does not generally know a priori the relay decision time at which the relay switches from listening to transmit mode. Both the above problems can be tackled by a careful design of the decoding algorithm. In particular, we introduce a decision rejection criterion at the relay based on Forney's decision rule (a variant of the Neyman...
Asymptotic Analysis of Large Cooperative Relay Networks Using Random Matrix Theory
H. Poor
2008-04-01
Full Text Available Cooperative transmission is an emerging communication technology that takes advantage of the broadcast nature of wireless channels. In cooperative transmission, the use of relays can create a virtual antenna array so that multiple-input/multiple-output (MIMO techniques can be employed. Most existing work in this area has focused on the situation in which there are a small number of sources and relays and a destination. In this paper, cooperative relay networks with large numbers of nodes are analyzed, and in particular the asymptotic performance improvement of cooperative transmission over direction transmission and relay transmission is analyzed using random matrix theory. The key idea is to investigate the eigenvalue distributions related to channel capacity and to analyze the moments of this distribution in large wireless networks. A performance upper bound is derived, the performance in the low signal-to-noise-ratio regime is analyzed, and two approximations are obtained for high and low relay-to-destination link qualities, respectively. Finally, simulations are provided to validate the accuracy of the analytical results. The analysis in this paper provides important tools for the understanding and the design of large cooperative wireless networks.
A dynamic focusing technique for delta-sigma-based beamformers.
Li, P C; Huang, J J; Liu, H L; O'Donnell, M
2000-10-01
Beamformation using oversampling delta-sigma (deltasigma) modulators has been proposed for diagnostic ultrasound. Such a beamformer can reduce the size, complexity and cost of an imaging system while providing adequate signal-to-quantization noise ratio (SQNR). High quality images can also be generated if dynamic receive delays are applied correctly. Several dynamic focusing techniques were previously proposed. Generally, an additional bit or extra compensation circuit is required to preserve the power and frequency distribution of the signal. Without preserving the power and frequency distribution, the image background noise is increased. In this paper, an alternative technique is presented. The new technique exploits the symmetry of focusing delays relative to the center of a transducer array. By properly synchronizing the delays and selecting the inserted values, no noise is added to the beam sum signal and the image background level is not increased. Using real ultrasound data, it is shown that the proposed technique provides the same imaging performance as the previous approaches with reduced system complexity by using only a single bit to encode the output of the deltasigma modulator.
Beamforming Based Full-Duplex for Millimeter-Wave Communication.
Liu, Xiao; Xiao, Zhenyu; Bai, Lin; Choi, Jinho; Xia, Pengfei; Xia, Xiang-Gen
2016-07-21
In this paper, we study beamforming based full-duplex (FD) systems in millimeter-wave (mmWave) communications. A joint transmission and reception (Tx/Rx) beamforming problem is formulated to maximize the achievable rate by mitigating self-interference (SI). Since the optimal solution is difficult to find due to the non-convexity of the objective function, suboptimal schemes are proposed in this paper. A low-complexity algorithm, which iteratively maximizes signal power while suppressing SI, is proposed and its convergence is proven. Moreover, two closed-form solutions, which do not require iterations, are also derived under minimum-mean-square-error (MMSE), zero-forcing (ZF), and maximum-ratio transmission (MRT) criteria. Performance evaluations show that the proposed iterative scheme converges fast (within only two iterations on average) and approaches an upper-bound performance, while the two closed-form solutions also achieve appealing performances, although there are noticeable differences from the upper bound depending on channel conditions. Interestingly, these three schemes show different robustness against the geometry of Tx/Rx antenna arrays and channel estimation errors.
Beamforming Based Full-Duplex for Millimeter-Wave Communication
Xiao Liu
2016-07-01
Full Text Available In this paper, we study beamforming based full-duplex (FD systems in millimeter-wave (mmWave communications. A joint transmission and reception (Tx/Rx beamforming problem is formulated to maximize the achievable rate by mitigating self-interference (SI. Since the optimal solution is difficult to find due to the non-convexity of the objective function, suboptimal schemes are proposed in this paper. A low-complexity algorithm, which iteratively maximizes signal power while suppressing SI, is proposed and its convergence is proven. Moreover, two closed-form solutions, which do not require iterations, are also derived under minimum-mean-square-error (MMSE, zero-forcing (ZF, and maximum-ratio transmission (MRT criteria. Performance evaluations show that the proposed iterative scheme converges fast (within only two iterations on average and approaches an upper-bound performance, while the two closed-form solutions also achieve appealing performances, although there are noticeable differences from the upper bound depending on channel conditions. Interestingly, these three schemes show different robustness against the geometry of Tx/Rx antenna arrays and channel estimation errors.
Clustering and Beamforming for Efficient Communication in Wireless Sensor Networks
Francisco Porcel-Rodríguez
2016-08-01
Full Text Available Energy efficiency is a critical issue for wireless sensor networks (WSNs as sensor nodes have limited power availability. In order to address this issue, this paper tries to maximize the power efficiency in WSNs by means of the evaluation of WSN node networks and their performance when both clustering and antenna beamforming techniques are applied. In this work, four different scenarios are defined, each one considering different numbers of sensors: 50, 20, 10, five, and two nodes per scenario, and each scenario is randomly generated thirty times in order to statistically validate the results. For each experiment, two different target directions for transmission are taken into consideration in the optimization process (φ = 0° and θ = 45°; φ = 45°, and θ = 45°. Each scenario is evaluated for two different types of antennas, an ideal isotropic antenna and a conventional dipole one. In this set of experiments two types of WSN are evaluated: in the first one, all of the sensors have the same amount of power for communications purposes; in the second one, each sensor has a different amount of power for its communications purposes. The analyzed cases in this document are focused on 2D surface and 3D space for the node location. To the authors’ knowledge, this is the first time that beamforming and clustering are simultaneously applied to increase the network lifetime in WSNs.
Clustering and Beamforming for Efficient Communication in Wireless Sensor Networks.
Porcel-Rodríguez, Francisco; Valenzuela-Valdés, Juan; Padilla, Pablo; Luna-Valero, Francisco; Luque-Baena, Rafael; López-Gordo, Miguel Ángel
2016-08-20
Energy efficiency is a critical issue for wireless sensor networks (WSNs) as sensor nodes have limited power availability. In order to address this issue, this paper tries to maximize the power efficiency in WSNs by means of the evaluation of WSN node networks and their performance when both clustering and antenna beamforming techniques are applied. In this work, four different scenarios are defined, each one considering different numbers of sensors: 50, 20, 10, five, and two nodes per scenario, and each scenario is randomly generated thirty times in order to statistically validate the results. For each experiment, two different target directions for transmission are taken into consideration in the optimization process (φ = 0° and θ = 45°; φ = 45°, and θ = 45°). Each scenario is evaluated for two different types of antennas, an ideal isotropic antenna and a conventional dipole one. In this set of experiments two types of WSN are evaluated: in the first one, all of the sensors have the same amount of power for communications purposes; in the second one, each sensor has a different amount of power for its communications purposes. The analyzed cases in this document are focused on 2D surface and 3D space for the node location. To the authors' knowledge, this is the first time that beamforming and clustering are simultaneously applied to increase the network lifetime in WSNs.
Power and time slot allocation in cognitive relay networks using particle swarm optimization.
Derakhshan-Barjoei, Pouya; Dadashzadeh, Gholamreza; Razzazi, Farbod; Razavizadeh, S Mohammad
2013-01-01
The two main problems in cognitive radio networks are power and time slot allocation problems which require a precise analysis and guarantee the quality of service in both the primary and secondary users. In this paper, these two problems are considered and a method is proposed to solve the resulting optimization problem. Our proposed method provides an improved performance in solving the constrained nonlinear multiobject optimization for the power control and beamforming in order to reach the maximum capacity and proper adaption of time slots, and as a result a new scheme for joint power and time slot allocation in cognitive relay networks is proposed. We adopt space diversity access as the secondary users access scheme and divide the time between multiple secondary users according to their contribution to primary user's transmission. Helping primary users provides more opportunities for secondary users to access the channel since the primary users can release the channel sooner. In contrast, primary network leases portion of channel access time to the secondary users for their transmission using particle swarm optimization (PSO). Numerical studies show good performance of the proposed scheme with a dynamic cost function in a nonstationary environment.
Ren, Wanbin; He, Yuan; Jin, Jianbing; Man, Sida
2016-06-01
Dynamic welding, being the principal mechanism of sticking failure, correlates closely with the contact bounce of electromechanical relay. The typical waveforms of dynamic contact force and contact voltage at making and breaking process are obtained with the use of a new designed test rig. The variations in bounce time, bounce numbers, last bounce duration, and relevant welding force are investigated in the electrical endurance test. It is determined that the welding strength and the welding probability are increased with the reduced stationary force. The degradation physical mechanism is present to better understand the relationship between dynamic welding and operation characteristics of electromechanical relay.
Zhai, Guofu; Wang, Qiya; Ren, Wanbin
The cooperative characteristics of electromagnetic relay's attraction torque and reaction torque are the key property to ensure its reliability, and it is important to attain better cooperative characteristics by analyzing and optimizing relay's electromagnetic system and mechanical system. From the standpoint of changing reaction torque of mechanical system, in this paper, adjusted parameters (armature's maximum angular displacement αarm_max, initial return spring's force Finiti_return_spring, normally closed (NC) contacts' force FNC_contacts, contacts' gap δgap, and normally opened (NO) contacts' over travel δNO_contacts) were adopted as design variables, and objective function was provided for with the purpose of increasing breaking velocities of both NC contacts and NO contacts. Finally, genetic algorithm (GA) was used to attain optimization of the objective function. Accuracy of calculation for the relay's dynamic characteristics was verified by experiment.
High Excitation Transfer Efficiency from Energy Relay Dyes in Dye-Sensitized Solar Cells
Hardin, Brian E.
2010-08-11
The energy relay dye, 4-(Dicyanomethylene)-2-methyl-6-(4- dimethylaminostyryl)-4H-pyran (DCM), was used with a near-infrared sensitizing dye, TT1, to increase the overall power conversion efficiency of a dye-sensitized solar cell (DSC) from 3.5% to 4.5%. The unattached DCM dyes exhibit an average excitation transfer efficiency (EÌ?TE) of 96% inside TT1-covered, mesostructured TiO2 films. Further performance increases were limited by the solubility of DCM in an acetonitrile based electrolyte. This demonstration shows that energy relay dyes can be efficiently implemented in optimized dye-sensitized solar cells, but also highlights the need to design highly soluble energy relay dyes with high molar extinction coefficients. © 2010 American Chemical Society.
CHANNEL ESTIMATION TECHNIQUE IN MULTI-ANTENNA AF RELAY COMMUNICATION SYSTEMS
Chen Mingxue; Xu Chengqi
2011-01-01
The channel estimation technique is investigated in OFDM communication systems with multi-antenna Amplify-and-Forward (AF) relay.The Space-Time Block Code (STBC) is applied at the transmitter of the relay to obtain diversity gain.According to the transmission characteristics of OFDM symbols on multiple antennas,a pilot-aided Linear Minimum Mean-Square-Error (LMMSE) channel estimation algorithm with low complexity is designed.Simulation results show that,the proposed LMMSE estimator outperforms least-square estimator and approaches the optimal estimator without error in the performance of Symbol Error Ratio (SER) under several modulation modes,and has a good estimation effect in the realistic relay communication scenario.
Diversity-Multiplexing Tradeoffs in MIMO Relay Channels
Gunduz, Deniz; Poor, H Vincent
2008-01-01
A multi-hop relay channel with multiple antenna terminals in a quasi-static slow fading environment is considered. For both full-duplex and half-duplex relays the fundamental diversity-multiplexing tradeoff (DMT) is analyzed. It is shown that, while decode-and-forward (DF) relaying achieves the optimal DMT in the full-duplex relay scenario, the dynamic decode-and-forward (DDF) protocol is needed to achieve the optimal DMT if the relay is constrained to half-duplex operation. For the latter case, static protocols are considered as well, and the corresponding achievable DMT performance is characterized.
Uplink Power Saving Potential of Cellular System with Fixed Relays
SHI Hong-kui; RONG Meng-tian; LIU Tao; YU Dan
2007-01-01
This paper presented a scheme of relayed cellular mobile telecommunication network, which only employs fixed digital relays and not more than two-hop relay routes. Power saving potential of the network is deeply studied under the assumption of not occupying additional frequency bands (i. e. relays share the same frequency bands as used by the base stations). Theoretical analysis and simulation results have both shown that, with the same radio coverage requirement, the necessary effective transmission powers in such a relayed network have greatly decreased compared to conventional cellular network.
Using a micromachined magnetostatic relay in commutating a DC motor
Tai, Yu-Chong (Inventor); Wright, John A. (Inventor); Lilienthal, Gerald (Inventor)
2004-01-01
A DC motor is commutated by rotating a magnetic rotor to induce a magnetic field in at least one magnetostatic relay in the motor. Each relay is activated in response to the magnetic field to deliver power to at least one corresponding winding connected to the relay. In some cases, each relay delivers power first through a corresponding primary winding and then through a corresponding secondary winding to a common node. Specific examples include a four-pole, three-phase motor in which each relay is activated four times during one rotation of the magnetic rotor.