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研究表明,协作中继选择能提高无线中继网络的鲁棒性和能效。文中研究一个多接入中继信道,包含2个信源,N个中继和1个信宿。中继节点为半双工,对两个信源的信号采用非再生的网络编码。考虑直接链路,基于最佳最差信道、最佳信噪比和最佳调和平均选择,提出新的选择策略。仿真结果表明其在性能上优于原有策略。 相似文献
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It has been demonstrated that either Channel Allocation (CA) or Relay Selection (RS) can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi-cell uplink scenarios. In this paper, we investigate the issue which considers the CA and RS to optimize the system transmission rate in an uplink scenario, while maintaining the re-source distribution fairness among users. This is first formulated as an optimization problem for a linear cellular system, where the same frequency channels can be reused in different cells. Based on the link and co-channel inter-ference conditions, two low-complexity CA and RS schemes are then proposed with dif-ferent decomposition sequences. Finally, nu-merical results are conducted to verify the effectiveness of the proposed CA and RS methods. Simulations results show that the proposed methods can yield significant im-provements in system performance in terms of average sum rate. 相似文献
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N/A 《激光与光电子学进展》1973,10(11):36
今年1973年夏天美国空军将选择进一步为其研制空间激光通讯系统的承包者;洛克希德导弹与空间公司,或者是麦克唐奈·道格拉斯宇宙航行公司,取舍的依据是评比它们制造的实验系统。 相似文献
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本文针对双跳全双工多中继系统,研究了在中继节点能量受限情况下的中继选择方案。在该文中,中继工作方式为放大转发(Amplify-and-Forward, AF),且中继通过收集源节点提供的能量来对源节点信息进行转发。整个通信过程分为两阶段,能量收集阶段与信息传输阶段,即采用的是时域分割方案。为了获得较好的性能与复杂度折中,本文分别研究了三种不同的中继选择策略,即最佳中继选择方案和两种次优中继选择方案。针对所提的三种方案,推导分析了其系统中断概率的理论值和下边界,以及系统的有效吞吐量。最后,利用蒙特卡洛仿真验证了理论分析的正确性,且仿真结果表明最佳中继选择方案的性能优于两种次优的中继选择方案,但其实现的复杂度高。 相似文献
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In this paper, we first overview some traditional relaying technologies, and then pre-sent a Network Coding-Aware Cooperative Relaying (NC2R) scheme to improve the performance of downlink transmission for relay- aided cellular networks. Moreover, sys-tematic performance analysis and extensive simulations are performed for the proposed NC2R and traditional relaying and non-relaying schemes. The results show that NC2R outperforms conventional relaying and non-relaying schemes in terms of blocking probability and spectral efficiency, especially for cell-edge users. Additionally, the location selections for relays with NC2R are also dis-cussed. These results will provide some insights for incorporating network coding into next-generation broadband cellular relay mo-bile systems. 相似文献
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《Communications, IEEE Transactions on》2009,57(3):626-629
In this letter the performance of multiple relay channels is analyzed for the situation in which multiple antennas are deployed only at the relays. The simple repetition-coded decodeand- forward protocol with two different antenna processing techniques at the relays is investigated. The antenna combining techniques are maximum ratio combining (MRC) for reception and transmit beamforming (TB) for transmission. It is shown that these distributed antenna combining techniques can exploit the full spatial diversity of the relay channels regardless of the number of relays and antennas at each relay, and offer significant power gain over distributed space-time coding techniques. 相似文献
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In this paper, we consider a wireless communication scenario with multiple source-destination pairs communicating through several cooperative amplify-and-forward relay terminals. The relays are equipped with multiple antennas that receive the source signals and transmit them to the destination nodes. We develop two iterative relay beamforming algorithms that can be applied in real-time. In both algorithms, the relay beamforming matrices are jointly designed by minimizing the received power at all the destination nodes while preserving the desired signal at each destination. The first algorithm requires the existence of a local processing center that computes the beamforming coefficients of all the relays. In the second algorithm, each relay can compute its beamforming coefficients locally with the help of some common information that is broadcasted from the other relays. This is achieved at the expense of enforcing the desired signal preservation constraints non-cooperatively. We provide two extensions of the proposed algorithms that allow the relays to control their transmission power and to modify the quality of service provided to different sources. Simulation results are presented validating the ability of the proposed algorithms to perform their beamforming tasks efficiently and to track rapid changes in the operating environment. 相似文献
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提出了一种放大转发网络中的中继选择方案,假设目的节点配置多个天线,源节点和所有中继节点都配置单个天线,方案选择一组中继同时在相同的频带上放大转发接收到的源节点信息以最大化接收信噪比。与只择一个最优中继的方案相比,方案在保持满分集阶数的情况下获得了更高的中断容量和更优的误符号率性能。与只选择一个最优中继的方案相比,在0.000 01的误符号率水平上,少需要发射功率1.6 dB。 相似文献
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The optimal beamforming weight matrix for amplify and forward multiple-antenna multiple-relay network is investigated. It is assumed that the partial first and second hop channel state information (CSI) is available at relays. In order to minimize the mean square error (MSE) at destination, all relay weight matrices must be designed simultaneously under individual relay power constraints. Using the Lagrange dual variables, it is shown that this general vector optimization problem can be converted into a scalar optimization problem whose scalar Lagrange multipliers can be obtained numerically. This is the generalized version of the scheme suggested for complete CSI. The proposed scheme is evaluated through computer simulation with various numbers of relays and antennas to obtain MSE and bit error rate (BER) metrics. It is also shown that the resulting MSE and BER are less than those of the schemes available in the literature by a good margin depending upon the amount of the utilized relay and antennas as well as the estimation error. 相似文献
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Binyue Liu 《ETRI Journal》2014,36(4):625-634
This paper studies a dual‐hop multiple‐access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single‐antenna amplify‐and‐forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low‐complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches. 相似文献
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This paper presents a scheme for dual-hop amplify-and-forward multi-antenna, multi-relay selection over Nakagami-m fading channels. A source-selected best relay performs maximal ratio combining on received data, applies variable gain, and then uses beamforming to transmit to a destination device. Such a configuration is beneficial for end-to-end communication using single antenna mobile terminals with a multi-antenna relay infrastructure. Closed form expressions for performance metrics are derived that cater for arbitrary number of relays, arbitrary number of receive and transmit antennas and different fading parameters. Results are verified through simulation. Furthermore, the influence of multiple antennas, the effects of fading, power imbalance between hops, and the beneficial impact of additional relays are explored. 相似文献
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Abdul Sattar Saand Varun Jeoti Mohamad Naufal Mohamad Saad 《Wireless Personal Communications》2016,88(3):645-655
Relay beamforming is a key signal processing technique to mitigate interference in single and multiuser multiple input and multiple output (MIMO) wireless communication networks. In MIMO relay networks interference cancellation is an essential task of the study to get optimal network capacity. In this paper, the problem of interference resulted from leakage signal from desired signal for intended antenna, which causing interference to other antennas of the same user with multiple antennas is tackled. The criterion of signal to leakage plus noise ratio (SLNR) maximization is considered to design a vector by vector relay downlink precoding based on Fukunaga Koontz transform. This can control the interference among multiple antennas and maximize SLNR. However, matched filter beamforming is utilized at the relay receiving side that can increase output signal to noise ratio at the relay node. The channel state information of both the channel between source to relay and relay to destination is assumed at the relay node. The effectiveness of the proposed technique is studied and compared with conventional relay precoding techniques. Simulation is carried out in MATLAB environment using ideal channel conditions. This study demonstrates that, the proposed scheme for relay assisted MIMO networks can improve overall system performance in terms of ergodic capacity. 相似文献
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Cooperative Strategies and Capacity Theorems for Relay Networks 总被引:11,自引:0,他引:11
《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(9):3037-3063
Coding strategies that exploit node cooperation are developed for relay networks. Two basic schemes are studied: the relays decode-and-forward the source message to the destination, or they compress-and-forward their channel outputs to the destination. The decode-and-forward scheme is a variant of multihopping, but in addition to having the relays successively decode the message, the transmitters cooperate and each receiver uses several or all of its past channel output blocks to decode. For the compress-and-forward scheme, the relays take advantage of the statistical dependence between their channel outputs and the destination's channel output. The strategies are applied to wireless channels, and it is shown that decode-and-forward achieves the ergodic capacity with phase fading if phase information is available only locally, and if the relays are near the source node. The ergodic capacity coincides with the rate of a distributed antenna array with full cooperation even though the transmitting antennas are not colocated. The capacity results generalize broadly, including to multiantenna transmission with Rayleigh fading, single-bounce fading, certain quasi-static fading problems, cases where partial channel knowledge is available at the transmitters, and cases where local user cooperation is permitted. The results further extend to multisource and multidestination networks such as multiaccess and broadcast relay channels. 相似文献
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Weikun Hou Ming Jiang Suili Feng 《Wireless Communications and Mobile Computing》2016,16(15):2274-2286
To effectively reduce the inter‐relay interference (IRI) in two‐path successive relaying, two beamforming schemes are proposed in this paper, utilizing multiple‐antenna relay nodes. Specifically, the two cooperation nodes perform receive combining of the source signal and transmit beamforming of the relayed signal alternately in the successive relaying process. As a result, the IRI between them can be effectively suppressed, thanks to the additional degree of freedom provided by the multiple‐input multiple‐output inter‐relay channel. In the first beamforming scheme, the source‐to‐destination signal‐to‐interference‐plus‐noise ratios (SINR) of separate paths are maximized with approximation, leading to a minimum variance distortionless response beamformer under the high SINR condition. To further improve the system performance, noting that the received SINRs of the two paths have impact on each other due to the mutual coupling of the beamformers, the sum of mean squared errors from these two transmission paths is minimized in the second scheme. Based on this performance criterion, a suboptimal beamformer design is developed numerically through cyclic minimization of the sum of mean squared error cost function. Simulation results demonstrate the superiority of both proposed beamforming schemes in terms of symbol error rate and the achievable system rate, in particular, at high IRI levels. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Liang Yang 《Wireless Communications and Mobile Computing》2012,12(4):345-351
In this paper, we investigate the performance of a multiuser wireless relay network with each of its nodes equipped with N antennas and transmit beamforming at its source and relay, where multiuser diversity (MD) is exploited to further improve the system performance. In the first part of this paper, by deriving the approximate error performance expression for a single‐relay MD system without the direct link, we obtain the maximum diversity order achievable by the CSI‐assisted amplify‐and‐forward (CAF) protocol. Then, by taking the direct link into consideration, we propose a sub‐optimal transmit beamforming scheme and show the performance loss is very small. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献