认知无线电选择中继放大转发协议性能分析

研究了基于完全信道信息和部分信道信息的最佳中继选择策略认知中继网络中断概率,详细推导了这两种策略中断概率的封闭表达式,然后分析了它们的平均误码率。仿真结果表明,基于完全信道信息的中断概率和平均误码率性能要优于部分信道信息,并且两种策略的性能随中继节点数目、干扰温度增加而提高。     

Nakagami衰落信道下合作分集的无线家庭网络性能分析

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.     

机会式网络编码的系统中断性能

该文在两用户通过一个中继节点的协作向基站传送数据的无线通信环境下,研究了基于网络编码的中继策略。与通常的用户到中继的信道是可靠的这一假设不同,该文假设所有的信道都存在衰落现象,比较了复制重传中继策略、确定性网络编码策略和机会式网络编码策略对系统中断概率的影响。仿真结果说明了机会式网络编码中继策略具有较好的性能。     

双向协作系统的中继选择和功率分配策略

针对瑞利衰落信道下双向多中继协作通信系统,为了降低中断概率,提出了一种基于最小化中断概率的中继选择策略和功率分配方案。首先联合考虑两条链路的中继节点处信噪比和信道增益实现双链路中继选择,然后推导出一种新的最优中继下双向放大转发协作中断概率的近似表达式上界,并利用凸优化求解得到使中断概率最小的最优功率分配解。仿真结果表明,与现有策略相比,提出的策略能够明显降低系统中断概率和误码率,显著提高系统性能。     

一种基于有限信息反馈的最佳中继选择协议研究

针对多用户的TDMA无线自组织协同通信网络,深入研究了基于有限信息反馈的最佳编码协作中继选择策略,在瑞利和莱斯信道条件下对该协议的中断概率和误码率性能进行了计算机仿真,并对协议做了进一步细化和优化。仿真和分析结果表明,该中继选择策略的中断概率和误比特率性能较传统策略有较大提升,且改进后的方案能明显减少协同交互信息开销。     

过时信道状态信息下的机会式中继选择系统的安全性能分析

在 Nakagami m衰落信道下,目的端和窃听者采用最大比合并策略,本文研究了在机会式自适应解码转发中继选择安全协作系统中的安全性能。由于实际信道中的反馈延迟,最优的合法中继选择基于合法信道反馈的过时信道状态信息。为了评价机会式中继选择在改善安全性能上的表现,分别推导了准确的正安全容量概率和准确的安全中断概率闭合表达式。此外,针对两种不同情况, 推导了形式简单的渐近表达式,并明确给出安全分集阶数和安全阵列增益。理论分析和数值仿真表明,增加中继个数和目的节点的天线数能够改善安全中断概率的性能表现,且在信道状态信息过时的条件下,系统的安全分集阶数与中继数无关。      

物理层网络编码机会中继及中断性能分析

该文研究了频率非选择性瑞利衰落信道中的物理层网络编码系统容量问题。基于放大转发机制提出了一种基于最大最小互信息准则的机会中继策略。在瑞利衰落信道环境下,从双向通信的角度,通过理论分析得出其中断概率解析式,同时推导了理想物理层网络编码和传统直接传输系统的中断概率解析式。通过理论分析,发现在某些节点发射功率条件下,系统中断概率将完全取决于单向链路。在此基础上完成了数值仿真实验,结果表明所提策略的中断性能与理想物理层网络编码和传统直接传输相比有了显著的提高。     

新型机会中继编码协作:源自适应传输校验信息

在多中继协作网络中,机会中继编码协作已然成为一种高效且被广泛研究的协作策略,然而现有工作存在着资源浪费或者系统复杂度高的问题。为此,针对如何在资源利用率与系统复杂度之间获得良好折中的问题,该文提出一种新型的机会中继编码协作策略,在不增加额外开销的情况下,使源节点能够自适应地向目的节点发送校验信息。并在Nakagami信道模型下,给出了系统中断概率的解析表达和误比特率上界的闭式表达。仿真结果表明,与已有机会中继编码协作策略相比,在获得性能提升的同时,所提策略对系统复杂度和资源利用率均有所改善。     

一种新的编码协作中继选择策略性能仿真

针对多用户的编码协作通信网络,给出了增量中继和机会中继结合起来的增量最佳编码协作中继选择策略并对其进行了计算机仿真。结果表明,与其它编码协作节点选择方法相比,该策略在取得机会中继中断概率性能的基础上,进一步节省了信道资源,提高了系统有效信息速率。     

联合协作与网络编码的性能分析

无线通信通过信道传输的过程难免会有干扰和衰落,从而导致接收信息出错。通过理论分析与MATLAB仿真的方法对协作网络编码方案进行分析研究,仿真结果表明:在信噪比为14d B时,协作通信比直接传输降低了大约的误码率;另外,在各信道误码率均为0.3时,协作网络编码通信方案比直接传输方案的中断概率降低了大约0.25。从而得出结论:协作、网络编码这两种技术的联合可以降低系统总的误码率;在系统总功率不变的情况下,也能降低系统发生中断的概率,增加系统的可靠性;在相同的误码率下,通过协作通信可以降低系统总的发送功率。     

User-relay Assignment based Antenna Selection Scheme in Multi-user Multi-relay AF Cooperative Communication Network

In this paper, the user-relay assignment based antenna selection scheme for multi-user cooperative network is proposed to improve the transmission bit rate and system performance. The low complexity suboptimal user-relay assignment algorithm is first proposed to simultaneously improve both the system performance and individual user’ performance in the multi-user amplify-and-forward (AF) cooperative user-relay network, where each user can fairly select its best relay according to the instantaneous channel state information (CSI). Based on the user-relay assignment scheme and space shift keying (SSK), we further present the antenna selection scheme to further enhance the system performance for the multi-user AF cooperative user-relay network. In order to minimize the system bit error rate (BER), three antenna selection criteria based on the maximum likelihood (ML) detection have been proposed. Numerical results and theoretical analysis show that the proposed schemes can effectively improve the average system sum rate, the outage probability of the worst user, and the system BER performance, compared with the other schemes.     

Exact Outage Probability of Two-Way Decode-and-Forward Scheme with Opportunistic Relay Selection Under Physical Layer Security

The combination of cooperative communication and physical layer security is an effective approach to overcome the disadvantages of the fading environment as well as to increase the security capacity of the wireless network. In this paper, we propose a two-way decode-and-forward scheme with a relay selection method. In the proposed protocol, two source nodes communicate with each other with the help of intermediate relays under the eavesdropping of another wireless node, called the eavesdropper node. The best relay, which is chosen by the max–min strategy, uses digital network coding to enhance secure communication and spectrum use efficiency. The system performance is analyzed and evaluated in terms of the exact closed-form outage probability over Rayleigh fading channels. The Monte-Carlo simulation results are presented to verify the theoretical analysis. Finally, the proposed protocol is compared with the two-way protocol, which does not use digital network coding.     

一种协作网络编码方案的功率优化分配方法

该文针对传统双路无线中继系统中的源和中继采用等功率发送,导致系统资源利用率低的问题,提出一种译码转发-空时协作网络编码方案的功率优化分配方法。该方法以最小化两源用户中断概率中的较大者为目标,并利用中断概率的高阶近似解,通过迭代计算获得最优功率分配因子。所提功率优化分配方法计算复杂度低且仅需信道的平均增益信息。仿真结果表明,与平均功率分配方法相比,所提功率优化分配方法使系统的中断概率和误码率性能均得到有效提升。     

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.     

On the study of network coded AF transmission protocol for wireless multiple access channels

In this correspondence, the performance of the network coded amplify-forward cooperative protocol is studied. The use of network coding can suppress the bandwidth resource consumed by relay transmission, and hence increase the spectral efficiency of cooperative diversity. A distributed strategy of relay selection is applied to the cooperative scheme, which can reduce system overhead and also facilitate the development of the explicit expressions of information metrics, such as outage probability and ergodic capacity. Both analytical and numerical results demonstrate that the proposed protocol can achieve large ergodic capacity and full diversity gain simultaneously.     

On the Performance of Cellular Two-Way Relay Systems with Analog Network Coding and Multiuser Diversity

We consider a cellular two-way relaying system in which a multi-antenna base station (BS) communicates bidirectionally with one of several single-antenna mobile stations (MSs) via a single-antenna relay using analog network coding. We employ MS selection coupled with beamforming at the BS so as to maximize the end-to-end signal-to-noise ratios. In the considered system, the target rates at the sources can generally be different owing to the asymmetric traffic flow in opposite directions. With such a general setup, we perform an overall system outage probability analysis over Rayleigh fading channels. For more insights, we derive a closed-form asymptotic expression for overall outage probability and an upper bound expression for ergodic sum-rate of the system. Based on these expressions, we show that the system achieves a performance gain, and a diversity order of minimum of the number of BS antennas and the number of MSs. Moreover, we address the problem of optimization of relay location in order to minimize the overall system outage under asymmetric traffic conditions. Finally, we provide numerical and simulation results to corroborate the theoretical analysis and the advantages offered by the proposed scheme.     

基于双向中继和网络编码的NOMA网络性能分析

针对实际场景中存在的具有上下行双向传输任务的通信系统,本文提出了一种双向中继协作非正交多址接入(NOMA, non-orthogonal multiple access)传输方案,基于解码转发(DF, Decode and Forward)协议研究信号的上行和下行双向传输技术,与现有NOMA方案不同,本方案为近端用户分配较大的功率,利用网络编码(NC, network coding)原理在两个时隙内实现基站和用户之间的双向信息交换。进一步考虑不完美信道状态信息(CSI, Channel State Information)条件,分析系统的传输性能并推导了系统中断概率以及遍历和速率闭合表达式。仿真结果表明,在完美CSI和不完美CSI条件下,相比于现有文献所提方案、单向中继(OWR,One-Way Relay)和正交多址(OMA, Orthogonal Multiple Access)网络,本文所提方案有效降低了系统的传输中断概率,提高了系统的遍历和速率以及系统吞吐量。      

Performance Analysis of Two-Way Hybrid Decode-and-Amplify Relaying Scheme with Relay Selection for Secondary Spectrum Access

In this paper, we propose and analyze the outage probability of a two-way hybrid decode-and-amplify relaying scheme with relay selection for secondary spectrum access. In this scheme, a secondary network is co-located and uses the same spectrum as the primary network. The primary network is comprised of two primary terminals that attempt to transmit signals to one another; the secondary network is comprised of M secondary transmitter-receiver pairs (ST-SR). One of the secondary transmitters chosen to cooperate with the primary network uses a hybrid decode-and-amplify forward technique in order to relay primary and secondary signals. We derive expressions for the outage probability of the primary network as well as the secondary network over a Rayleigh fading channel. Simulation results are presented to verify theoretical analyses and to compare the performance of the proposed protocol to that of a two-way direct transmission protocol.     

双向中继信道的模拟网络编码最优功率分配

在双向信息非对称条件下,研究了基于模拟网络编码的双向中继信道中的最优功率分配问题。分别给出了中断概率最小化、和速率最大化意义下的最优功率分配闭式数学表达式,并证明了两种约束下最优功率分配问题的统一性。分析表明:现有的基于模拟网络编码的双向中继信道中的最优功率分配方法是本文提出方法在某些条件下的特例。计算机仿真分析证明了提出的最优功率分配方法在中断概率和和速率性能方面均优于平均功率分配方法。      

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.