Ser performance analysis of decode-and-forward cooperative scheme in satellite mobile channel

In this paper, Symbol-Error-Rate (SER) performance analysis is provided for a Decode-and-Forward (DF) cooperative scheme in satellite mobile channel environment. We present a satellite mobile cooperative communication system model and derive two generalized error probability expressions with Cyclical Redundancy Check (CRC) or not. We also derive and simulate SER of the proposed system over different satellite mobile channels. The results show that the analytical results are in great accordance with the ones obtained by simulation. Also, it was shown that, whether or not adopt CRC depends on the channel link quality between the source node and the relay node.     

协作通信技术在卫星移动通信中的应用

卫星移动通信信道是典型的衰落信道,其存在的阴影效应、多径效应、多普勒效应给系统性能带来了较大影响,严重时会导致系统通信中断。协作通信技术利用不同节点间的相互协作,可以带来空间分集优势,能够有效对抗信道衰落,提高通信质量。针对协作通信技术在卫星移动通信中的应用,提出了典型的应用思路和方式,并进行了性能仿真与分析。仿真结果表明,将协作通信技术引入卫星移动通信系统,能够有效提升系统的传输性能。     

基于虚拟MIMO的协作通信节点选择算法

针对一种新的协作通信方式O-DSTC(Opportunistic Distributed Space-Time Coding),该文在保证误码率的前提下,基于效益函数和后悔函数,提出了均衡剩余能量的协作节点选择算法。在只能得到信道的统计特性并考虑距离信息的情况下,由于O-DSTC的平均误码率无法计算,所以该文提出并简化了协作中继的平均误码率逼近公式。根据该逼近公式选择满足误码率要求的协作节点集合,集合中的节点通过后悔函数分布式地设置延迟时间,并采用竞争方式成为协作节点。仿真结果验证了该文提出的误码率逼近公式的有效性和可靠性。实验结果也表明,协作节点选择算法可以保证误码率,提高最小剩余能量,同时减少竞争接入时间。     

一种最小误码率约束的动态地理协作路由算法

为了提高无线多跳通信的可靠性,提出一种联合物理层和网络层设计的动态地理协作路由(DGCR)算法,推导计算了单个协作单元协作中继节点的选择区域,在该区域内选择的协作中继节点可以满足误码率要求.最佳中继节点的位置会根据实际协作中继节点的位置和目的节点的位置动态选取.仿真计算表明,该算法相比非协作路由算法和传统地理协作路由算法具有更好的误码率性能,更适用于多径条件下的应用.     

时变信道下ADF协作车载通信误码率分析

智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性,为有效评估系统的误码性能,给出了符合车载时变信道的一阶自回归(AR1)模型,提出了一种基于AR1模型的自适应解码转发(ADF)协作误码率分析方法.该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发,提升了智能交通系统的可靠性.此外,利用矩生成函数(MGF)推导出ADF协作下多进制正交幅度调制(M-QAM)信号误码率封闭表达式,并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响.数值仿真结果表明,车载系统能通过增加CSI估计精度,有效地减少车载快速移动引起的误码平顶值.该方法相对于放大转发(AF)协作通信方式,平均误码性能提高约8.7 dB.     

Decode-to-cooperate: a sequential alamouti-coded cooperation strategy in dual-hop wireless relay networks

An optimal cooperation strategy, decode-to-cooperate, is proposed and investigated for performance improvements in dual-hop wireless relay networks. Based on decode-and-forward (DF) strategy with multiple relay selection, we design a novel scheme such that the source node keeps transmitting sequentially and the selected relays cooperate by transmitting the decoded signal using distributed Alamouti coding. We exploit the multipath propagation effect of the wireless channel to achieve lower probability of error and introduce optimum power allocation and relay positioning. We analyze the scenario when the source to destination direct link is not available and derive a closed form expression for symbol error rate (SER), its upper bound and an asymptotically tight approximation to exploit the performance gain by selecting the optimum relays in a multiple-relay cooperation scheme. Moreover, asymptotic optimum power allocation (based on the SER approximation) and optimal relay positioning are also considered to further improve the SER. The proposed relay selection scheme outperforms cooperative (DF) and non-cooperative schemes by more than 2 dB.     

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.      

Power allocations in minimum-energy SER-constrained cooperative networks

In this paper, we propose minimum power allocation strategies for repetition-based amplify-and-forward (AF) relaying, given a required symbol error rate (SER) at the destination. We consider the scenario where one source and multiple relays cooperate to transmit messages to the destination. We derive the optimal power allocation strategy for two-hop AF cooperative network that minimizes the total relay power subject to the SER requirement at the destination. Two outstanding features of the proposed schemes are that the power coefficients have a simple solution and are independent of knowledge of instantaneous channel state information (CSI). We further extend the SER constraint minimum power allocation to the case of multibranch, multihop network and derive the closed-form solution for the power control coefficients. For the case of power-limited relays, we propose two iterative algorithms to find the power coefficients for the SER constraint minimum-energy cooperative networks. However, this power minimization strategy does not necessarily maximize the lifetime of battery-limited systems. Thus, we propose two other AF cooperative schemes which consider the residual battery energy, as well as the statistical CSI, for the purpose of lifetime maximization. Simulations show that the proposed minimum power allocation strategies could considerably save the total transmitted power compared to the equal transmit power scheme.     

基于卫星移动MIMO系统的天线相关性性能分析

研究了卫星移动MIMO系统中,上、下行信道存在阴影衰落和空间相关条件下的系统性能,利用围线积分、留数定理及特殊函数积分等方法推导了系统中断概率(OP),平均符号错误概率(SER)的闭合表达式。利用Monte-Carlo仿真分析了系统在不同相关系数、天线数目及调制方式下的性能表现。仿真结果表明,尽管阴影衰落和空间相关性降低了系统性能,但与单天线系统相比,卫星移动MIMO系统的OP及SER改善明显。     

Performance of Decode-and-Forward Cooperative Communications with Multiple Dual-Hop Relays over Nakagami-m Fading Channels

In this letter, we examine the symbol-error-rate (SER) performance of decode-and-forward (DF) cooperative communications. Our focus is on the scenario in which multiple dual-hop relays are employed and the channel environment is described by Nakagami-m fading. Cooperative diversity is observed from the derived error-rate expressions, and some insight into how channel conditions in the relay nodes affect the SER performance is obtained. In addition, with the knowledge of the partial channel state information (CSI) at the transmitting sides, we derive an optimal power allocation scheme to further enhance the SER performance. Simulation results are finally presented to demonstrate the correctness of our analysis and perception for the considered DF protocol.     

协作通信技术在卫星系统中的应用

针对卫星移动通信信道具有复杂时变衰落的特点,提出了将协作通信技术引入卫星系统,从而达到抗衰落、获取分集增益的目的。具体给出了卫星与用户之间彼此协作的模型,且仿真了卫星相互协作时系统的误码率曲线。仿真结果表明,协作通信会降低系统误码率,并带来显著的性能增益。     

PERFORMANCE STUDY OF AN INTEGRATED SATELLITE/TERRESTRIAL MOBILE COMMUNICATION SYSTEM

Terrestrial cellular networks and mobile satellite systems are expected to converge towards a future integrated satellite/terrestrial mobile communication network. Besides a system globalization, the integration of terrestrial and satellite mobile systems will lead to the unloading of the fixed part of the mobile network. This paper proposes an integrated satellite/terrestrial mobile communication system and evaluates its performance in terms of the blocking probability for new call attempts, the call dropping probability and the probability of unsuccessful call. This communication system was simulated and its performence compared with that of a stand-alone terrestrial mobile system. In the terrestrial part of the system we have considered fixed channel allocation (FCA) and dynamic channel allocation (DCA) techniques. Satellite channels can have equal or lower priority compared to terrestrial channels. The improvement of the system performance by means of satellite-to-terrestrial handovers was also estimated.     

Performance analysis of repetition-based cooperative networks with partial statistical CSI at relays

This letter analyzes the performance of repetitionbased cooperative diversity wireless networks using amplifyand forward relaying, in which each relay has only statistical knowledge of the source-relay link. The network channels are modeled as independent, non-identical, Rayleigh distributed coefficients. The exact symbol error rate is derived using the moment generating function (MGF). We derive the probability density function and MGF of the total SNR. Then, the MGF is used to determine the symbol error rate (SER). The diversity order of the amplify-and-forward cooperation with partial statistical channel state information is also found via the asymptotic behavior of the average SER, and it is shown that the cooperative network achieves full diversity. Our analytical results are confirmed by simulations.     

一种超宽带模拟合并转发协作通信系统

针对频率选择性衰弱信道下协作通信系统信道估计复杂的问题,提出了一种模拟合并放大转发超宽带(UWB)协作通信方案.该方案在源节点处对发送符号进行实数分布式空时编码并附加传输参考,在中继节点处利用传输参考对多径分量进行模拟合并,从而构建了一种改进型非正交放大转发协作通信系统.仿真结果证明,相对于无协作通信系统,模拟合并转发...     

协作通信系统中基于频谱效率优化的跨层设计

为改善协作分集系统的频谱效率,提出一种改进的跨层设计方案,对协作通信系统物理层的自适应调制编码（AMC）技术和链路层的混合自动重传(HARQ)协议进行联合优化设计。该方案利用少量比特的反馈,使得仅当目的节点通过直接信道不能正确译码分组时或者当直接信道处于深度衰落时触发中继节点转发协作伙伴数据。给出了所提方案基于瑞利衰落信道、解码转发（DF）条件下频谱效率的表达式,然后搜索在任意信噪比条件下使频谱效率最大化的调制与编码方案。通过计算机仿真对理论分析进行了验证。理论分析和仿真表明该跨层设计在中低信噪比(SNR)可进一步提升协作通信系统的频谱效率。      

旋转编码协作方案中的功率优化分配研究

针对等功率分配(EPA)导致系统资源利用率低的问题,提出了一种旋转编码协作方案中的功率优化分配(OPA)方法。该方法首先利用Chernoff界推导了端到端系统误符号率(SER)的上界,然后在总功率一定的条件下,以最小化SER上界为目标,根据平均信道增益来计算源和中继间的功率分配因子。最后将功率分配信息通过反馈信道发送给协作用户,从而实现了功率的自适应分配,提高了系统的资源利用率。仿真结果验证了所提OPA方法的有效性。     

Performance Analysis and Optimal Power Allocation for Space–Time and Amplify-and-Forward Cooperative System

In this paper, we consider a space?Ctime and amplify-and-forward (ST-AF) cooperative system which consists of two-antenna source, single-antenna relay and destination. Source transmits Alamouti space?Ctime coding symbols to destination with cooperation of relay which adopts AF strategy. Closed-form symbol error rate (SER) is derived for the ST-AF system with PSK signals. Moreover, a SER approximation is developed to show the asymptotic performance of the ST-AF cooperative system in medium and high SNR regimes. For comparison, the SER approximation of another cooperative space?Ctime coding (C-STC) scheme is also derived. Theoretical analysis shows that the ST-AF can obtain more diversity gain and achieve higher diversity order than C-STC. Statistical optimal power allocation (OPA) algorithm for the ST-AF cooperative system is presented based on the SER performance. It turns out the OPA only depends on the channel links related to the relay, not depend on the direct link between source and destination. Finally, numerical simulations validate the theoretical analysis.     

Symbol error rate analysis and power allocation for hybrid cooperation in Rayleigh fading environment

In this paper, we investigate the symbol error rate (SER) performance and power allocation for hybrid cooperation (HC) system in a Rayleigh fading environment. Specifically, we derive closed‐form and approximate SER expressions for the HC system by using the moment generating function (MGF)‐based approach. However, the resultant SER expressions contain an MGF of the harmonic mean of two independent random variables, which is not tractable in SER analysis. Then, we present simple and tight bounds on the SER to show the asymptotic behavior of the HC system. It is shown that the HC system achieves full diversity order. On the basis of the tight SER bound, the power allocation is investigated. It is found that the optimal power allocation (OPA) of the HC system does not depend on the fading parameter of the source‐to‐destination channel and it only depends on the channel links related to the relay. With the increase of the ratio of mean channel power gains (i.e., the ratio of the relay‐to‐destination channel gain to the source‐to‐relay channel gain), more performance gain can be acquired by using the OPA scheme. Finally, the analytical results are validated through computer simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimal power allocation to minimize SER for multinode amplify-and-forward cooperative communication systems

An optimal power allocation （OPA） method with mean channel gains is proposed for a multinode amplify-and-forward cooperative communication system. By making use of M-PSK modulation, a closed-form symbol-error-rate （SER） formulation and corresponding upper bound are first derived. Subsequently the OPA method is utilized to minimize the SER. Comparison of the SER of the proposed OPA method with that of the equal power allocation （EPA） method, shows that the SER of both methods, which is approximately optimal performance, is almost the same when relays are near the source. OPA outperforms the EPA when the relays are near the middle between the source and destination or near the destination. The proposed OPA method depends only on the ratio of mean channel gains of the source-to-relay to those of the relay-to-destination. Extensive simulations are performed to validate the theoretical results.     

Optimal reliable relay selection in multiuser cooperative relaying networks

In this paper, we investigate the problem of optimal reliable relay selection in multiuser cooperative wireless networks in the presence of malicious relay nodes. A general discrete time queueing model for such networks is introduced which takes into account the dynamic variations of the channel state, the dynamic malicious behaviour of relay nodes as well as stochastic arrival of data packets into the system. The model consists of a set of mobile users, one destination node and a set of relay nodes which may be either mobile or fixed. The system uses the benefit of cooperative diversity by relaying in the decode and forward mode. We assume that each user either transmits its packets directly to the destination (direct mode) or transmits them with the cooperation of a selected relay node (cooperative mode). It is assumed that a centralized network controller manages the relay selection process in the system. At each time slot, a malicious relay node in the system may behave spitefully and refuse to cooperate with a user deliberately when it is selected to cooperate with that user. A malicious relay node usually acts stochastically to hide its malicious behaviour for longer time. In such a system, at each time slot the network controller should decide whether a user has to cooperate with any relay node or not and if so, which relay node must be selected for cooperation. First, we show that the malicious behaviour of relay nodes makes the stable throughput region shrink. Then, we propose a throughput optimal secure relay selection policy that can stabilize the system for all the arrival rate vectors strictly inside the network stability region. We show that the optimal policy is equivalent to finding the maximum weighted matching in a weighted bipartite graph at each time slot. Finally, we use simulations to compare the performance of the proposed policy with that of four other sub-optimal policies in terms of average queue occupancy (or queueing delay).