多中继协作通信系统的中断概率分析

协作分集不仅能提升数据传输速率,还可以提高数据传输的稳定性。协作通信方法使用带有一根天线的移动台,在多用户环境中可以共享其他移动用户的天线,这样可产生多根虚拟发射天线,进而得到相应的分集增益,改善移动通信系统的性能。现在通过研究发现,在多中继协作通信中,非对称信道采用放大转发方式下的中继传输,在AF重复转发和机会转发2种方式下表现出了较小的链路中断概率,系统性能得到明显的提升。     

多中继与多用户选择的中继系统安全性能分析

为了考察使用多中继选择与多用户选择的放大转发（AF）中继系统的物理层安全性能,推导了其在瑞利衰落信道上和联合发送天线选择/接收最大比合并天线分集下的非零安全容量概率和安全中断概率的精确表达式以及在高信噪比下的渐近安全中断概率解析表达式。AF中继系统的非零安全容量概率和安全中断概率的数值计算和仿真结果相吻合,验证了以上理论分析的正确性;分析结果表明,其安全分集增益为源节点发射天线数、最优中继节点接收天线数、中继节点数的三者乘积与最优中继节点发射天线数、最优用户接收天线数、用户数三者乘积之间的最小值,且与窃听信道无关。     

基于网络编码的分布式天线系统性能分析

文章针对多输入多输出（MIMO）系统在移动终端实现上的限制,提出分布式天线系统（DAS）的解决方案来获得空间分集增益。采用DAS模型,通过使用一个具有网络编码解码运算能力的辅助天线增强用户与基站间的通信,探讨基于网络编码的天线分集增益。分析比较无辅助天线系统、简单DAS和基于网络编码的DAS中断概率性能后,理论分析和计算机仿真结果表明,相比简单DAS,基于网络编码的DAS节约硬件成本并提高了频谱利用率;系统中断概率平均降低0．0164,可获得更大的分集增益。     

相关MIMO信道下空间分集系统中多用户分集性能

多用户MIMO(Multi-input multi-output)系统中,研究空间相关对联合空间分集和多用户分集的性能影响.推导了接收天线之间存在相关的多用户MIMO STBC(Space-time block coding)和MIMO MRT/MRC(Maximum-ratio-transmis-sion/maximal-ratio-combining)系统的中断容量、平均容量表达式,并由此进行性能分析.计算机仿真验证了理论分析的有效性.结果表明,相对于闭环的多用户MI-MO MRT/MRC系统,空间相关下开环的多用户MIMO STBC系统具有较低的平均容量和较高的调度增益.     

固定增益的两跳OSTBC中断概率分析

研究信源和终端需要配置多根天线,而中继只有单根天线的两跳中继转发系统。为了获得空间分集,信源利用了正交空时分组编码（OSTBC）的发射策略,终端利用了选择合并方式。为了尽可能简化中继配置的复杂度,中继采用固定增益放大转发的协议。在信源和终端直接通信链路存在的情形下,首先导出总的接收信噪比的表达式,接着导出瑞利衰落条件下系统中断概率的封闭表达式,最后通过蒙特卡洛仿真和数值结果的比较,验证了理论导出表达式的精确性。     

蜂窝通信中的多用户协作分集

协作分集技术是一种新型的空间分集技术,它通过使多个具有单天线的终端共享彼此的天线,达到获得多天线分集增益的目的.协作分集技术能够提高系统的容量,降低系统的误码率.本文主要介绍了协作分集的概念分类,以及在多用户协作条件下的系统模型.     

MIMO多中继辅助通信中的优化调度

针对中继辅助通信系统,讨论了多中继并行传输下的优化设计问题,提出了一种简化的线性优化方案,并从多用户分集的角度,在等待服务用户中选择中继协作分集增益较大的用户对其进行服务.这种方案巧妙地减少了由于多中继并行传输所造成的用户间干扰,保持了多中继并行传输引入的空间分集所带来的性能优势,达到了提高系统总吞吐量的目的.     

多天线系统中的多用户分集方案的性能分析及比较

在多天线多用户无线通信系统中,可以利用用户之间彼此独立的随机衰落信道的特点,结合随机波束成型技术,或者空间分集技术,或者天线选择技术,获得多用户分集增益。然而不同多用户分集方案的系统性能不尽相同。该文分析了在多输入单输出(MISO)信道中目前几种典型的多用户分集方案的性能,给出系统吞吐率的定量表达式,并综合比较了不同用户数和不同天线数对各种多用户分集方案性能的影响,为实际多天线多用户系统设计提供了有益的参考。     

蜂窝通信中的多用户协作分集

协作分集技术是一种新型的空间分集技术,它通过使多个具有单天线的终端共享彼此的天线,达到获得多天线分集增益的目的。协作分集技术能够提高系统的容量,降低系统的误码率。本文主要介绍了协作分集的概念分类,以及在多用户协作条件下的系统模型。     

分布式环境中协作分集的移动中继动态选择和切换策略研究

在协作无线通信系统中,中继节点的移动会大大降低系统的性能,目前该方面的结果很少。本文探讨分布式环境中协作分集的移动中继选择算法,在放大转发（AF）协作通信模式下,给出了基于信道统计状态信息的功率分配和中继的动态选择策略。针对单中继情况提出了中继切换方案,针对多中继情况提出了动态剔除、补充中继的方案,并导出了分集增益及系统容量的计算公式。通过模拟仿真分析,该方案能有效的降低中断概率,提高系统分集增益,扩大系统容量,实现良好的整体性能。      

Performance Analysis of OSTBC Transmission in Amplify-and-Forward Cooperative Relay Networks

A performance analysis is presented for amplify-and-forward (AF) cooperative relay networks employing transmit antenna diversity with orthogonal space-time block codes (OSTBCs), where multiple antennas are equipped at the transmitter. We develop a symbol-error-rate (SER) and outage performance analysis for OSTBC transmissions with and without cooperative diversity over flat Rayleigh fading channels. We first derive exact probability density functions (pdf's) and cumulative distribution functions (cdf's) for the system SNR without direct transmission with an arbitrary number of transmit antennas and then present the exact closed-form SER and outage probability expressions. Next, we derive the moment-generating function (MGF) for the overall system SNR with direct transmission and present the exact SER and outage probability with joint transmit antenna diversity and cooperative diversity. The theoretical analysis is validated by simulations, which indicate an exact match between them. The results also show how the transmit antenna diversity and the cooperative diversity affect the overall system performance.      

Performance analysis of multiuser diversity in cooperative multi-relay networks under rayleigh-fading channels

In multiuser cooperative relay networks, cooperative diversity can be obtained with the help of relays, while multiuser diversity is an inherent diversity in multiuser systems. In this letter, the performance analysis of multiuser diversity in cooperative multi-relay networks is presented. Both the case of all relay participating and the case of relay selection are considered. We first derive asymptotic expressions of outage probability and symbol error probability for amplify-and-forward (AF) and decode-and-forward (DF) protocols with joint multiuser and cooperative diversity. Then, the theoretical analysis are validated by Monte Carlo simulations. Both the theoretical analysis and simulations show that a multiuser diversity order of K and a cooperative diversity order of M+ 1 can be achieved simultaneously for both AF and DF protocols (where K is the number of accessing users and M is the number of available relays). These demonstrate that the multiuser diversity can be readily combined with the cooperative diversity in multiuser cooperative relay networks.     

Performance analysis of dual-hop fixed-gain AF relaying systems with OSTBC over Nakagami-m fading channels

In this paper, we present outage probability and symbol error rate (SER) performance analyses of a dual-hop transmission using fixed-gain amplify-and-forward relaying in flat Nakagami-m fading channels. The system under consideration is equipped with multiple antennas at source and destination adopting orthogonal space-time block coding to provide transmit diversity and maximum ratio combining to provide receive diversity, respectively. For integer and half-integer m values, closed forms of exact outage probability and moment generating function (MGF) expressions are derived through cumulative distribution function (CDF) of the overall system signal-to-noise ratio. Closed-form exact SER expressions based on the overall CDF are obtained for binary phase shift keying, binary frequency shift keying and M-ary pulse amplitude modulation. Exact SER expressions based on the MGF method are also obtained for binary differential phase shift keying, M-ary phase shift keying and M-ary quadrature amplitude modulation. Moreover, the asymptotic diversity order analysis is performed through derivations of asymptotic outage probability and SER. Theoretical analyses are validated by Monte Carlo simulations showing perfect match between each other.     

基于发射分集的多点中继合作通信系统性能研究

为了降低合作通信系统中的误码率和中断概率,本文研究了多点中继合作通信系统.采用矩母函数(Moment Generating Function)分析方法,通过引入超几何函数,详尽推导出Rayleigh衰落信道下的平均符号错误率和中断率的精确表达式.通过蒙特卡洛仿真,验证了表达式的正确性,其性能优于单点中继合作通信系统.     

Beamforming in Dual-Hop AF Relaying with Imperfect CSI and Co-channel Interference

This letter studies the joint effects of imperfect channel state information (CSI) and co-channel interference (CCI) on a dual-hop variable gain amplify-and-forward (AF) relay network with beamforming. The source and destination are both equipped with multiple antenna, while the relay has a single antenna. Specifically, the analytical expressions for the outage probability and average symbol error rate of the considered AF relaying are derived. Moreover, the asymptotic analysis at high SNR is also presented to reveal the diversity order and array gain of the relay system. Finally, computer simulations are given to confirm the validity of the proposed theoretical analysis and quantify the combined influence of imperfect CSI and CCI on the system performance.     

基于机会中继和最大比合并下的协作通信系统

分析了机会中继和最大比合并下的协作通信系统性能.首次给出了Nakagami衰落信道下的符号错误率和中断概率的精确闭式结果.通过对中断概率的近似结果分析发现对于任意一条源节点-中继-目的节点链路,分集增益均由源节点-中继链路和中继-目的节点链路中的深衰落链路决定.     

Performance Analysis of Maximum SNR Scheduling with an Infrastructure Relay Link

We consider infrastructure-based amplify-and-forward (AF) relaying for extending downlink and uplink coverage areas of a cellular base station. The base station serves multiple mobile users via a multi-hop backhaul relay link by sharing out access link channel resources with maximum signal-to-noise ratio (SNR) scheduling. We analyze the performance of the system by deriving closed-form expressions for outage probability, outage capacity, ergodic capacity, average end-to-end SNR and amount of fading (AoF). These measures show that maximum SNR scheduling of multiple users in a cellular relay link offers significant diversity, capacity and SNR improvement over single-user transmission and round robin scheduling. We also relate performance of the relay link to that of a distributed antenna system (DAS), and show that the noisy wireless backhaul relay link induces tolerable performance deterioration compared to deploying a cable-connected distributed antenna.     

Diversity achieving full-duplex DF relaying with joint relay-antenna selection under Nakagami-m fading environment

One of the main imperfections degrading the performance of full-duplex (FD) relaying systems is the outage floor. In this work, a power scaling method is proposed, which overcomes this effect even when there does not exist a direct channel between source and destination nodes. The system is composed of $K$ decode-and-forward (DF) FD relays over the Nakagami-m fading environment. To promote system performance, joint antenna and relay selection methods are employed in the FD relaying systems. Each FD relay is equipped with multiple antennas for receiving and the other for transmitting the information. The transmitting and receiving antennas are chosen based on the instantaneous channel variations, and one relay is selected to improve the signal-to-interference and noise ratio (SINR) of the FD relaying system. The performance of the proposed design is investigated. Moreover, the closed-form equations of the ergodic capacity and outage probability are attained. The analytical results are confirmed by different simulations. Results indicate that the proposed design achieves an additional spatial diversity gain because of using the antenna selection at the relay nodes. Moreover, by power scaling (PS) method, the system performance is effectively improved compared to the conventional FD relaying structures.     

MIMO multichannel beamforming: SER and outage using new eigenvalue distributions of complex noncentral Wishart matrices

This paper analyzes MIMO systems with multichannel beamforming in Ricean fading. Our results apply to a wide class of multichannel systems which transmit on the eigenmodes of the MIMO channel. We first present new closed-form expressions for the marginal ordered eigenvalue distributions of complex noncentral Wishart matrices. These are used to characterize the statistics of the signal to noise ratio (SNR) on each eigenmode. Based on this, we present exact symbol error rate (SER) expressions. We also derive closed-form expressions for the diversity order, array gain, and outage probability. We show that the global SER performance is dominated by the subchannel corresponding to the minimum channel singular value. We also show that, at low outage levels, the outage probability varies inversely with the Ricean A*-factor for cases where transmission is only on the most dominant subchannel (i.e. a singlechannel beamforming system). Numerical results are presented to validate the theoretical analysis.