共查询到20条相似文献,搜索用时 640 毫秒
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彭小平 《太赫兹科学与电子信息学报》2007,5(4):267-270
基于Jing-Hassibi的合作分集协议和Rajan等人的普通非正交放大传送(GNAF)协议,提出了具有完全分集和最大似然译码复杂度低的分布空时编码(DSTC)。这些编码是四次群最大似然可译分布空时编码,并且功率在中继之间随时间均匀分布。仿真结果显示这种编码具有较好的性能。 相似文献
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讨论了分布空时编码的性能。介绍了分集方案,提出了分布式网络中分散的空时编码协议,重点讨论了随机空时编码的设计,通过仿真给出了分布式合作通信中的随机空时编码平均错误概率的性能。 相似文献
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提出了一种基于OFDM达到最大可达分集增益的空频码设计方案。该编码利用正交频分复用把频率选择性衰落信道变换成平衰落信道的特性,同时引入了基于多天线的空间分集和基于时延扩展的频率分集,比空时编码具有更高的分集增益。 相似文献
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本文研究多带正交频分复用瑞利衰落信道中,空时网格编码发射天线间空间相关性的分集性能.空时网格编码将单个输出的编码符号转换成多个编码符号,并通过多个发射天线传输,在接收端,Viterbi优化软判决算法用于译码.我们分析了MB-OFDM系统在quasi-static和interleaved两种信道中相关空间衰落对误码率的影响.在空间相关性较小时,分集阶数能得到保持;而在空间相关性较大时,interleaved信道能保持分集阶数,quasi-static信道的分集阶数将减小.空时编码总体上对空间相关性表现出鲁棒性. 相似文献
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Yu Guanding Zhang Zhaoyang Qiu Peiliang 《电子科学学刊(英文版)》2006,23(4):594-597
A novel Automatic repeat ReQuest (ARQ) protocol called cooperative ARQ is presented in this letter, where a relay terminal is requested to retransmit an erroneously received packet, instead of the source terminal. The data link layer Packet Error Rate (PER) performance of cooperative ARQ is derived in correlated wireless channel. The results show that even though the relay-destination channel is worse than the sourcedestination channel, the new protocol outperforms the traditional one as long as the average SNR of the relaydestination channel is better than a certain threshold. It is also demonstrated that a second order diversity gain can be achieved with the cooperative ARQ protocol. 相似文献
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基于相位旋转的多跳Alamouti放大转发协作方案 总被引:1,自引:0,他引:1
多跳Alamouti放大转发(AAF-MH)协作方案中,信号的传输没有考虑信道状态信息(CSI)。针对此问题,该文提出了基于相位旋转的多跳Alamouti放大转发(AAF-MH-PR)协作方案,通过部分中继节点发送的信号旋转适当的角度,改变了系统的等效信道矩阵。理论分析表明AAF-MH-PR的可靠性显著优于AAF-MH,仿真结果验证了理论分析的正确性,误符号率(SER)为10-5时,AAF-MH-PR只需1 bit的反馈量就获得了5 dB的增益。 相似文献
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提出在未来无线家庭网中采用合作分集的思想,通信时利用处于空闲状态的终端用户对所发送信息进行中继发送,保证整个网络误码率性能、中断概率以及发送功率达到最佳折衷.在Nakagami平衰落信道条件下研究了再生中继和非再生中继两种合作方式下的中断概率和误码率性能,给出误码率和中断概率的解析表达式,并用matlaab进行仿真,仿真结果表明,在低信噪比条件下再生中继大大优于非再生中继方式,但高信噪比条件下两者性能接近. 相似文献
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该文针对频率选择性衰落下的多中继分布式空频编码协同通信系统,提出了基于导频转发新时序的频域信道估计算法,包括最小二乘(LS)估计算法和低阶近似的线性最小均方误差(Lr-LMMSE)估计算法。互相协同的各中继节点在收到源节点广播发送的频域导频符号向量后,通过互不相同的时隙将其转发给目的节点,从而避免了各中继节点转发的导频符号在目的节点上的混叠干扰。理论分析和仿真结果表明,该算法成功地分辨了多中继协同通信系统的所有频域信道系数,其估计精度高,算法复杂度低,具有较高的实用价值。 相似文献
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Cooperative Communication Protocols in Wireless Networks: Performance Analysis and Optimum Power Allocation 总被引:5,自引:3,他引:2
In this paper, symbol-error-rate (SER) performance analysis and optimum power allocation are provided for uncoded cooperative
communications in wireless networks with either decode-and-forward (DF) or amplify-and-forward (AF) cooperation protocol,
in which source and relay send information to destination through orthogonal channels. In case of the DF cooperation systems,
closed-form SER formulation is provided for uncoded cooperation systems with PSK and QAM signals. Moreover, an SER upper bound
as well as an approximation are established to show the asymptotic performance of the DF cooperation systems, where the SER
approximation is asymptotically tight at high signal-to-noise ratio (SNR). Based on the asymptotically tight SER approximation,
an optimum power allocation is determined for the DF cooperation systems. In case of the AF cooperation systems, we obtain
at first a simple closed-form moment generating function (MGF) expression for the harmonic mean to avoid the hypergeometric
functions as commonly used in the literature. By taking advantage of the simple MGF expression, we obtain a closed-form SER
performance analysis for the AF cooperation systems with PSK and QAM signals. Moreover, an SER approximation is also established
which is asymptotically tight at high SNR. Based on the asymptotically tight SER approximation, an optimum power allocation
is determined for the AF cooperation systems. In both the DF and AF cooperation systems, it turns out that an equal power
strategy is good, but in general not optimum in cooperative communications. The optimum power allocation depends on the channel
link quality. An interesting result is that in case that all channel links are available, the optimum power allocation does
not depend on the direct link between source and destination, it depends only on the channel links related to the relay. Finally,
we compare the performance of the cooperation systems with either DF or AF protocol. It is shown that the performance of a
systems with the DF cooperation protocol is better than that with the AF protocol. However, the performance gain varies with
different modulation types and channel conditions, and the gain is limited. For example, in case of BPSK modulation, the performance
gain cannot be larger than 2.4 dB; and for QPSK modulation, it cannot be larger than 1.2 dB. Extensive simulation results
are provided to validate the theoretical analysis. 相似文献
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This paper investigates a time-switching energy-harvesting system in which a source communicates with a destination via energy-constrained amplify-and-forward relays. To exploit the benefit of using multiple relays, we propose a relay scheduling called consecutive relay selection (CRS), which allows all relays to assist the source-to-destination communication, to improve the transmission efficiency of the time-switching policy. The partial relay selection (PRS) is examined for performance comparison. The selected relay in the PRS protocol is considered in two cases: in one, it is selected based on the first-hop channel gains (PRS-1 protocol), and in the other, it is selected based on the second-hop channel gains (PRS-2 protocol). For performance evaluation, the analytical expressions of the outage probability and throughput for Nakagami-m fading channel are derived. Our results show that the CRS protocol outperforms the PRS protocol in terms of throughput, the PRS-1 protocol achieves better performance than the PRS-2 protocol. Moreover, we discuss the effects of various key system parameters on system performance, such as the energy-harvesting ratio, source transmission rate, and locations of relays, to provide insights into the various design choices. 相似文献
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The deployment of an incremental hybrid decode-amplify and forward relaying scheme is a promising and superior solution for cellular networks to meet ever-growing network traffic demands. However, the selection of a suitable relaying protocol based on the signal-to-noise ratio threshold is important in realizing an improved quality of service. In this paper, an incremental hybrid relaying protocol is proposed using polar codes. The proposed protocol achieves a better performance than existing turbo codes in terms of capacity. Simulation results show that the polar codes through an incremental hybrid decode-amplify-and-forward relay can provide a 38% gain when γth(1) and γth(2) are optimal. Further, the channel capacity is improved to 17.5 b/s/Hz and 23 b/s/Hz for 2 × 2 MIMO and 4 × 4 MIMO systems, respectively. Monte Carlo simulations are carried out to achieve the optimal solution. 相似文献