Relay selection for maximizing the number of successive transmission in cooperative networks

Relay selection has an important effect on improving the performance of cooperative communication system. However, the frequent operation of relay selection can bring enormous control message overhead, and then decrease the performance of cooperative communication. To reduce the relay selection frequency, in this paper, we propose a relay selection scheme to choose the best relay considering successive packets transmission. In this scheme, through the parameters of data transmission rate, the length of data packet and the estimated channel state information, the best relay is selected to maximize the number of successive packets transmission while guaranteeing the given outage probability. It is proven by numerical results that the proposed relay selection scheme can support the successive packets transmission in cooperative wireless networks and the maximum number of successive packets transmission is affected by the different network parameters, i.e. packet length, data transmission rate, signal to noise ratio and Doppler frequency. Compared to previous relay selection schemes by simulation results, it is shown that the proposed relay selection scheme can improve the throughput performance efficiently.     

MIMO系统中的最优中继选择方案

研究多输入多输出中继系统中基于放大转发协议的最优中继选择方案,推导出中断概率和平均信道容量的闭式表达式,并对不同中继节点数时的中断概率和平均信道容量进行仿真。结果表明,该方案可以有效降低系统中断概率,且随着中继节点数的增多,系统平均信道容量优于直接传输方案。     

协作通信中基于AHP的灵活节能中继选择算法

目前无线协作通信系统中存在系统能量消耗大、网络生命周期短等问题,良好的中继选择方案是减小能耗的有效途径。因此,提出基于AHP的灵活节能中继选择算法。在信息传输阶段,由控制单元根据协作概率判断节点是否激活自身侦听广播信息包,为减小能耗对协作概率进行优化,并根据系统中断概率获得预计信息量的表达式。采用层次分析法综合考虑节点剩余能量比、链路信噪比、中断概率,从激活状态下的节点中灵活选择优化中继节点进行协作传输。仿真结果表明,该方案在预计即时信息量、中断概率、能耗均衡方面具有一定优势,能够有效减少协作通信网络中的能量消耗,提升网络整体性能。     

双向AF中继系统中继选择及功率分配策略

为了提高双向中继系统的系统可达总速率,提出一种Two-way AF中继系统的最大化瞬时信噪比乘积（MISP）的中继选择策略,该策略联合考虑了两条链路的链路质量,实现了最优中继选择。在此基础上,运用信噪比平衡技术进行瞬时功率分配（SNR-Balancing-IPA）,推导出了最优功率分配方案的表达式。理论分析和仿真结果都表明,建议的最大瞬时信噪比乘积中继选择及SNR-Balancing-IPA的策略有效提高了系统的可达总速率,降低了系统的中断概率,改善了系统的性能。     

Simplified relay antenna selection with source beamforming for MIMO two-way relaying networks

A simplified relay antenna selection with source beamforming (RAS-BF) scheme is advocated for multiple-input multiple-output (MIMO) two-way relaying networks (TWRNs) employing amplify-and-forward (AF) protocol, which does not require channel estimation at the relay node and the optimal relay antenna can be simply determined by comparing the minimum received pilot signaling powers pertaining to each antenna. The theoretical analysis of system outage probability and average symbol error rate (SER) shows that full diversity order can also be achieved by the simplified scheme. Simulation results are provided to verify our theoretical results and further illustrate that the simplified scheme outperforms the outage-optimal counterpart in the presence of channel state information (CSI) imperfections.     

中继选择协议下的认知无线电系统性能研究

在保证授权用户服务质量(QoS)和认知用户峰值功率限制的前提下,推导出高信噪比时放大转发中继选择(SAF)协议、解码转发中继选择(SDF)协议和混合中继选择协议(HPRS)下认知中继系统中断概率的近似表达式。Monte Carlo仿真验证了三种协议下中断概率近似表达式的合理性,理论和仿真结果表明,三种协议的中断概率与干扰限制条件和认知用户峰值功率密切相关,且HPRS中断性能要优于SAF和SDF。     

Outage-optimal relaying through opportunistic hybrid forward cooperation

In this paper, a new scheme based on relay selection and data forwarding in multi-relay cooperative networks is introduced. Unlike most existing solutions focused on amplify-and-forward (AF) or decode-and-forward (DF) protocol separately, the proposed hybrid forward (HF) scheme takes advantage of both AF and DF protocols in relay forwarding. Based on theoretical analysis, a closed-form expression for the tight lower bound of its outage probability is derived, and further performance analysis is also present...     

工业5G的D2D多跳中继辅助传输方法及中断性能分析

面向工业5G网络的超可靠强实时传输要求,研究基于设备到设备通信（device-to-device,D2D）的多跳多中继辅助传输方法。基于随机几何理论,采用泊松点过程对工业现场设备进行建模,并划分中继选择区域。多跳中继过程中,每一跳中继选择信干噪比最大的节点进行解码转发,充分考虑层叠部署的多条D2D传输路径上的节点干扰以及随机噪声,推导出端到端中断概率的闭式表达式。仿真分析了中继节点部署密度、发射功率、路径距离等因素对端到端中断概率的影响。结果表明,采用多跳多中继辅助的D2D传输可以大幅降低工业5G网络的端到端中断概率,提高传输可靠性。     

A simple amplify-and-forward opportunistic relaying based on outdated channel state information

Opportunistic relay selection(ORS)is a promising approach for cooperative communications owing to its low complexity by activating only the best relay.However,in mobile scenarios,the channel state information(CSI)estimated in relay selection may be different from the actual CSI employed in data transmission due to relatively fast varying channels,i.e.,CSI is outdated,which may lead to incorrect relay selection,and hence system performance deteriorates.To address the problem,this paper designs a relay selection strategy with instaneous and statistical CSIs in amplify-and-forward(AF)cooperative networks whose instantaneous CSIs of two hops employed in relay selection are both outdated.Based on high signal-to-noise ratio(SNR)analysis,we propose a distinctive relay selection strategy which can be described as selecting the relay with the asymptotic optimum average symbol error probability(SEP)and outage probability at high SNR.The corresponding asymptotic outage probability and SEP performance analysis are also provided.Finally,simulation results not only validate our theoretical analysis,but also show that in asymmetrical outdated CSI scenarios,the proposed strategy achieves better performance than existing relay selection strategies at medium and high SNR values.     

Physical layer security via maximal ratio combining and relay selection over Rayleigh fading channels

In this paper, the impact of both maximal ratio combining (MRC) and relay selection on the physical layer security in wireless communication systems is investigated by analyzing critical issues such as the probability characteristics of the legitimate receiver (Bob) and malicious eavesdropper (Eve)’s end-to-end signal-to-noise ratio (SNR), the secrecy outage probability and the average secrecy channel capacity over Rayleigh fading Channel, etc. Unlike the conventional physical layer security schemes, we assume that Bob receives its data from both the relay and the source via cooperative relay, provided that MRC is employed at the receiver. Particularly, compared to the conventional MRC methods, the proposed method is capable of achieving a higher spatial diversity order by performing relay selection, as validated by performing the theoretical analysis as well as numerical simulation. Furthermore, the closed-form expressions in terms of secrecy outage probability and average secrecy capacity are all consistent with the numerical results. Finally, the proposed scheme may be substantially affected by a number of parameters such as the number of relays, the SNR of links and the ratio of main-to-eavesdropper ratio (MER) λ_ME.     

Joint relay selection and power control for robust cooperative multicast in mmWave WPANs

We propose an optimization algorithm for joint relay selection and source and relay power allocation under mixed line-of-sight (LoS) and non-LoS path scenarios for both power saving and robustness enhancement of cooperative multicast in millimeter-wave wireless personal area networks. Our aims are to reduce power consumption and enhance the robustness of cooperative multicasts in millimeter-wave wireless personal area networks. First, we describe a novel beam training protocol that is capable of overhearing and information feedback to filter relay candidates with non-LoS links and avoid selecting relays for transceivers with LoS paths. Second, the joint relay selection and power allocation issue is formulated as an optimization problem with the objective of minimizing the maximum combined power consumption of the source and relay under maximum tolerable outage probabilities and transmit powers. By introducing relaxation and Lagrange multiplier methods, a closed-form expression for the joint relay selection and power allocation is obtained. Finally, simulation results indicate significant improvements in terms of both outage probability and power consumption over the conventional combined transmit power minimization algorithm.     

协作通信的中继选择策略性能研究

在解码转发协议的基础上,研究了全选中继策略和机会中继选择策略的中断概率性能,推导了瑞利衰落下的两种策略的中断概率精确闭式结果,给出了高信噪比时的中断概率近似表达式.通过理论分析和数值仿真结果得出:在信噪比足够高或在中继-目的信道性能优于源-中继的信道性能的情况下,这两种策略具有相同的中断概率性能;源-中继的信道性能比中继-目的节点的信道性能越好,全选中继策略的性能越优于机会中继选择策略的中断概率性能.     

同步协作中继系统的波束形成通信方案的设计*

从多输入多输出（multiple-input and multiple-output,MIMO）系统所设计的Alamouti码中得到启发,针对在无线协同信道之上的同步协作中继系统提出了一种新的通信方案。为了在大中断率和低成对误码率(PEP)的情况下能有效地传送信号,源天线采用功率分配波束形成技术,中继节点采用放大转发(amplify and forward,AF)技术。研究和仿真表明,对给定效率R,所提出的模型与以前的通信方案尤其是广播通信模型相比,在中断率和成对误码率上都有明显的改善。这一发现可能会对未     

Two-way中继系统中基于最小化中断概率的功率分配策略*

为了降低Two-Way中继系统中断概率,本文提出了一种Two-Way 中继系统中基于最小化中断概率的功率分配策略。首先推导了Two-way中继系统中断概率的闭合表达式,然后在总功率受限的条件下,提出了一种最小化中断概率的最优功率分配策略（OPA）。通过拉格朗日乘数法对该优化模型进行了求解。仿真结果证明了该策略能够有效的降低系统的中断概率,提高系统性能。     

基于非规则LDPC码的协作MIMO系统性能分析

该文提出了一种基于非规则LDPC码设计的用户协作分集方案,并且给出了准静态的瑞利衰落信道下单用户单中继环境下的三种中继协议的性能比较和中断概率理论推导,比较分析了采用编码协作策略的双用户多中继环境下的系统的误比特性能和中断概率的仿真图。结果表明通过将非规则LDPC码引入到协作MIMO中,系统误比特率大大降低,同时中断概率也明显降低,性能得到显著改善。     

ICRN功率分配与中继选择联合优化

针对工业认知无线电网络中出现的无线干扰和冲突严重,特别是工业现场的金属环境和移动特性造成多径与阴影衰落,从而使得传输可靠性难以保证的问题,引入感知信道概率及信道可用度概念,提出一种联合优化中继选择与功率分配的算法。该算法给出3种认知中继选择方案,分别是信道增益最大准则、最近准则及调和平均准则,并在源节点和所选中继节点之间进行最优功率分配,以最小化网络中断概率。仿真结果表明,与平均功率分配算法相比,所提算法能更好地降低系统中断概率,提高传输可靠性。     

基于非理想CSI的全双工双向中继系统保密中断概率性能研究

研究基于译码转发的全双工中继系统的物理层安全问题。假设系统模型中窃听者与合法用户以及中继之间存在直接链路,考虑在合法用户和中继之间的信道状态信息（channel state information,CSI）是非理想的情况下,通过分析信道估计误差、窃听信道的平均信噪比和残余自干扰对中继系统物理层安全的影响,推导出每个节点端到端瞬时信干噪比和非理想CSI下的保密中断概率表达式。仿真结果表明,信道估计误差、窃听信道的平均信噪比和残余自干扰越小,系统保密中断概率越小,系统安全性能越高;在高信噪比时,残余自干扰对保密中断概率的影响可以忽略不计;同时,全双工中继方案优于传统的半双工中继方案。     

Optimal algorithm for Multi-hop relay selection based on cognitive radio

Relay selection, also called opportunistic relay, is capable of fast narrowing the search scope, finding the optimal relays and achieving a better cooperative transmission. With the continuous expansion of network capacity, the coverage area and the participating relays, it is unwise to traverse all the nodes to select the best relay. An optimal scheme based on cognitive wireless multi-hop relay selection has been proposed in this study, in which a threshold value is set for the signal-to-interference-plus-noise ratio (SINR). Only when the SINR exceeds the threshold can the node be selected as the relay node. Because of the random distribution and geographical universality of the relay, the candidate relays would better be limited within a particular area. Then a model based on stochastic geometry is established to rapidly find the relay which meets the demand near optimally, without needing of the global channel state information of the network in advance. The simulation results show that the optimized scheme can reduce the searching time and improve the performance of the secondary transmission. In addition, theoretical formula of the outage probability and channel data transmission rate has also been derived and verified its effectiveness through simulation.

     

多天线认知协作通信系统的性能分析

在多个主用户同时存在的情境下,提出了一种新的两跳认知协作通信系统,并对该系统进行了性能分析。该系统的信源和中继均只具有单个天线,而在信宿处配置了多根接收天线并使用了最大比合并技术来进行信号的接收。此外,对该认知协作通信系统在瑞利衰落信道下的中断概率性能进行了研究,推导得到了中断概率的准确闭合表达式,以及在高信噪比时的渐进表达式。通过利用计算机仿真验证了理论分析的正确性。     

双向中继系统中断概率下界优化及分集增益

主要研究了瑞利衰落信道下基于放大转发策略的双向中继系统的中断性能及分集性能。首先利用信源节点信噪比间的关系和调和不等式对信噪比的范围进行优化,得到新的中断概率下界,仿真结果表明Monte Carlo仿真得到的中断概率接近新得到的中断概率下界;同时证明了多中继存在时,基于最大最小互信息准则的双向中继系统仍然取得全分集增益且能够优化中断概率下界。