Nakagami-m信道下全双工解码转发中继中断概率分析

研究存在残余自干扰（residual self-interference, RSI）条件下全双工解码转发中继的中断概率性能。在Nakagami-m信道下,推导了多跳解码转发（multi-hop decode-and-forward,MH-DF）策略和选择解码转发（selected decode-and-forward,SDF）策略的端到端中断概率闭合表达式和渐近表达式,分析了两种策略的可达分集度。结果显示,MH-DF策略的可达分集度为0,SDF策略的可达分集度由信道成型因子和中继功率伸缩方案决定。相比于MH-DF策略,SDF策略具有更优的中断概率性能和抗自干扰能力。      

解码转发方案下混合RF-UWOC传输系统的性能分析

本文研究了解码转发(Decode-and-Forward,DF)方案下的混合射频/水下无线光通信(Radio Frequency-Underwater Wireless Optical Communication,RF-UWOC)系统的性能,其中RF链路服从广义K(Generalized-K,GK)衰落,UWOC链路服...     

基于解码转发的协作频谱感知技术

频谱感知技术中的单点检测设计复杂度低,采用技术成熟,易于实现,但是由于自身的局限性,面临着隐藏终端,感知灵敏度底等问题,而协作分集技术可以克服这些问题。基于解码转发(DF,DecodeAnd Forward)的协作频谱感知技术,利用了分集增益原理,提高了认知用户的单点检测概率,从而改善了整个无线电系统的性能。在瑞利衰落环境下对该检测方案进行分析,并通过与非协作检测的性能比较,说明了协作检测的优势。     

协作通信中的解码转发中继策略优化

在单中继协作通信系统模型下,研究了直接传输、固定解码转发（ DF）中继、选择DF中继和增量中继协议。为了提高协作通信系统的频谱效率和中断性能,通过比较源-目的端和中继-目的端的瞬时信道增益来判定是否需要采用协同通信模式,提出一种改进的解码转发方式（ IDF）。通过将选择DF中继和增量中继的优点结合,提出了一种增量选择中继（ ISR）策略,并给出了2种改进协议任意信噪比的中断概率表达式。仿真结果表明,与传统的单中继解码转发协议相比, IDF和ISR均具有更低的中断概率, ISR具有最低的中断概率。     

基于全双工的中继选择协作通信网络性能分析

文章针对全双工的解码转发机会中继选择协作通信网络的性能展开分析研究。分别在假设服从独立同分布的Nakagami-m和Rayleigh衰落链路下,推导出所提方案的中断概率闭式表达式,并通过仿真证实了其有效性。仿真分析表明,中断概率受一些关键参数影响,如残存自干扰强度,中继节点个数和链路平均信噪比,此外,还受衰落深度参数影响。     

解码协作分集技术研究

协作分集技术是为了解决无线通信系统中MIMO技术在移动终端的多天线制约问题而提出来的,协作分集可以使得具有单天线的用户共享其它用户的天线,从而形成虚拟的多天线系统,从而为MIMO技术的实用化提供了一条可行的道路。文中先讲述了协作分集的概念和协作分集的种类,然后详细分析了解码协作模型的协作过程,给出了其在不同情况下的误码率,最后通过仿真并观察其误码率,证明其拥有很好的性能。     

放大转发认知中继协作系统中继增益分配方案和性能分析

由于在传统的放大转发认知中继协作方案中,中继增益因子的分配只考虑了部分主、从系统参数,使得系统的能量效率较低、系统资源未被充分利用。为此,基于主系统传输速率约束和从系统终端接收信号平均误符号率最小准则,文章提出了一个新颖的中继增益最优化分配方案,获得了中继增益最优化精确解以及相应的上、下限封闭解析解;并基于获得的最优化中继增益,分析了系统的平均误符号率。结果表明,文章所获得的中继增益因子分配方案由于不仅考虑了从信源功率和从信源-中继链路增益,而且还综合考虑了中继-从信宿链路和主系统参数,可以实现系统资源的最优化配置,系统性能得到改善。      

多中继放大转发协作通信中的功率分配和中继位置联合优化

文章研究了多中继放大转发协作分集系统中的功率分配和中继位置联合优化问题。利用信道的统计状态信息,在总功率一定的条件下,以最大化系统的信道容量为目标,推导了多中继和选择中继两种模型下基于高信噪比近似的联合优化算法的闭式解。理论分析和仿真验证表明,提出的算法大大提高了传统的等功率分配方案下系统的性能。     

基于解码重传的最佳协作中继选择策略

近年来提出的协作分集技术通过使网络中各单天线用户共享彼此天线以形成虚拟多天线阵列,从而可以显著提高网络容量,也使得其备受科研工作者的关注。提出了基于解码重传（DaF）下的被动式最佳协作中继选择准则,该准则是通过推导协作中继传输系统的误符号率而得出的。在总功率限制下,可以证明基于解码重传下的机会中继在中断性能上考虑是最佳的,更确切地说,它的中断性能和利用全部候选中继传输的最佳解码重传策略是一样的。     

Diversity order of decode-and-forward MIMO relaying with transmit antenna selection

This article analyzes the diversity order of several proposed schemes, where the transmit antenna selection (TAS) strategies are combined with low-complexity decode-and-forward (DF) protocols in the multiple-input multiple-output (MIMO) relaying scenario. Although antenna selection is a suboptimal form of beamforming, it enjoys the advantages of tractable optimization and low feedback overhead. Specifically, this article proposes schemes that combine TAS strategies with fixed decode-and-forward (FDF) and selection decode-and-forward (SDF) protocols. Following that, the asymptotic expressions of outage probabilities are derived and the diversity order of the proposed schemes analyzed. These kinds of combination of transmit antenna selection strategies and low-complexity decode-and-forward protocols can achieve partial diversity order in the MIMO relaying scenario. The numerical simulations verify the analysis.     

Outage analysis of opportunistic multi-antenna relay selection in decode-and-forward relay networks

This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward(DF)relay networks over Rayleigh fading channels,assuming that multiple antennas are available at the relay node.According to whether instantaneous signal-to-noise ratio(SNR)or average SNR can be utilized for relay selection,two opportunistic relay schemes,opportunistic multi-antenna relay selection(OMRS)and average best relay selection(ABRS)are proposed.The performances of both two schemes are evaluated by means of theoretical analysis and simulation.It is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming(BF)scheme known as theoretical outage-optimal.Compared with previous single-antenna opportunistic relaying(OR)scheme,OMRS brings remarkable performance improvement,which is obtained from maximum ratio combining(MRC)and beamforming techniques.It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.     

Performance of new relay selection scheme for buffer-assisted multihop decode-and-forward networks

In this paper, a new relay selection scheme is proposed to reduce the end-to-end packet delivery delay for buffer-assisted multihop decode-and-forward cooperative networks. The proposed method selects a relay node having more packets in the associated buffer and relay's proximity to the destination node. Mathematical expressions for the outage probability and average packet delay in Rician fading are obtained by modeling the system as a Markov chain. The proposed relay selection scheme has less packet delay as compared to the max-link relay selection scheme with marginally higher outage probability. Thus, the proposed relay selection scheme is a good alternative to low latency wireless applications.     

Performance analysis of spectrally efficient amplify‐and‐forward opportunistic relaying scheme for adaptive cooperative wireless systems

In this paper, we propose an adaptive amplify‐and‐forward (AF) relaying scheme that selects the best relay among the available relay nodes opportunistically to cooperate with a source node for improvement of the spectral efficiency. This improvement can be achieved by introducing a policy that gives the useful cooperative regions and defines a switching threshold signal‐to‐noise ratio that guarantees the bit error rate (BER) of cooperative transmission is below the target. We model all links as independent non‐identically distributed Rayleigh fading channels. We then derive closed‐form expressions for the average spectral efficiency, average BER, and outage probability when an upper bound for the signal‐to‐noise ratio of the end‐to‐end relay path is applied and adaptive discrete rate is considered. Numerical and simulation results show that the proposed scheme, compared with the outage‐based AF incremental relaying, AF fixed relaying, and the conventional direct transmission, can achieve the maximum average spectral efficiency while maintaining the average BER and outage probability. Copyright © 2013 John Wiley & Sons, Ltd.     

编码协作分集研究与展望

用户协作方案是协作分集研究的一个重要方面。在慢衰落和快衰落信道条件下,均能带来传输性能改善的编码协作分集方案,是目前协作分集方案中备受关注的一种。尤其在将空时编码的思想引入该方案后,更带来了编码协作分集在快衰落信道条件下的良好性能。用户要想从协作中受益,协作伙伴/中继节点的选取是编码协作分集中一个重点。     

Cooperative HARQ protocol and diversity analysis of systems with multiple incremental relays

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.     

基于接收信噪比和网络寿命的最优中继选择

为了增大网络寿命,降低误符号率,优化无直传链路协作通信系统的性能,本文提出基于接收信噪比和网络寿命的最优中继选择算法。由于网络寿命的问题无法直接求解,将其转化为中继节点剩余能量与目的节点达到接收信噪比门限时发射功率的比值。首先计算各个中继在目的节点的接收信噪比,将大于信噪比门限加入候选中继,然后依次计算候选中继的联合优化函数值并排序,值最大者即为最优中继。理论推导了系统误符号率的上下界,仿真表明理论值与仿真值较为吻合,验证了系统在保证较低误符号率的基础上延长了网络寿命。     

Performance analysis of selective cooperation in amplify‐and‐forward relay networks over identical Nakagami‐m channels

In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple‐relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify‐and‐forward mode over identical Nakagami‐m channels using an exact source–relay–destination signal‐to‐noise ratio (SNR).We derived accurate closed‐form expressions for various system parameters including the probability density function of end‐to‐end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

基于定向天线的多中继DF协作通信系统性能分析

为提高多中继协作通信系统可靠性,将定向天线和多中继协作通信系统相结合,提出基于定向天线的解码转发最佳中继选择协作策略.首先理论推导出定向发送一定向接收模式下通信系统中断概率闭合表达式,并推导出定向发送一全向接收、全向发送一全向接收模式下的系统中断概率计算式.然后对3种模式下,协作通信系统中断概率和信噪比、中继节点数、天线增益、信道衰落系数以及信道容量之间的关系进行了数值仿真分析.理论分析和仿真结果表明,采用定向天线的协作通信系统可以有效降低协作通信系统中断概率,提高频谱利用率,并且存在最佳中继节点和最优功率分配系数使得中断概率进一步下降.     

移动中继通信技术综述

随着无线通信的发展,以中继为代表的协作通信技术被认为是未来无线通信系统中的关键技术之一。利用中继可以以较小的代价扩展小区覆盖范围和增加系统容量。目前,固定中继的研究已日趋成熟,移动中继正成为一个新的研究热点。由于移动中继本身的特性,它在带来诸多好处的同时也面临一些挑战。文中阐述了移动中继的研究现状,介绍了移动中继的应用场景,对其关键技术进行了综述与展望。