Performance of wireless multihop communications systems with cooperative diversity over fading channels

We present closed‐form bounds for the performance of wireless multihop communications systems with cooperative diversity over Nakagami‐m fading channels. The end‐to‐end signal‐to‐noise ratio is formulated and upper bounded by using the inequality between harmonic and geometric means of positive random variables. Closed‐form expression is derived for the moment‐generating function and is used to obtain lower bounds for the average error probability. Numerical results are compared with computer simulations showing the tightness of the proposed bounds. Copyright © 2007 John Wiley & Sons, Ltd.     

System performance analysis of cooperative multihop relaying network applying approximation to dual‐hop relaying network

In this paper, the closed‐form expressions for outage probability, channel capacity, and average symbol error probability are derived for amplify‐and‐forward multihop relay network. Based on approximation of multihop relay by dual‐hop relay systems, the analytical expressions are obtained for the case when maximal ratio combining technique is employed at each relay while destination node uses selection combining technique. The impact of system and channel parameters on the system performances is investigated, and numerical results are graphically presented. The derived analytical expressions are verified by numerical simulation.     

Performance analysis of wireless communication system over nonidentical cascaded generalised gamma fading channels

Multiplicative fading statistics usually encountered in different radio propagation environments. In this context, we evaluate and analyse the performance of a wireless communication system over the nonidentical cascaded generalised Gamma Fading Channels, also known as generalised Bessel‐K fading channel. To this end, the closed‐form expressions for the amount of fading (AOF), the outage probability (OP), the average symbol error probability (SEP), and the channel capacity are derived. In addition approximate expressions for the average SEP with maximal ratio combining (MRC) diversity are also provided. The low‐ and high‐power solutions for the channel capacity are also provided. Furthermore, simplified asymptotic average SEP expressions for MRC and selection combining (SC) are presented to gain the system performance with diversity. The proposed methodologies provide more flexibility to accommodate different radio propagation scenarios. To examine the accuracy of the proposed solutions, numerical and simulation results are compared and shown to fit for variety of fading parameters.     

Performance analysis of coded cooperation diversity in wireless networks

Diversity is an effective technique in enhancing the link quality and increasing network capacity. When multiple antennas cannot be used in mobile units, user cooperation can be employed to provide transmit diversity. In this paper, we analyze the error performance of coded cooperation diversity with multiple cooperating users. We derive the end‐to‐end bit error probability of coded cooperation (averaged over all cooperation scenarios). We consider different fading distributions for the interuser channels. Furthermore, we consider the case of two cooperating users with correlated uplink channels. Results show that more cooperating users should be allowed under good interuser channel conditions, while it suffices to have two cooperating users in adverse interuser conditions. Furthermore, under bad interuser conditions, more cooperating users can be accommodated as the fading distribution becomes more random. Copyright © 2006 John Wiley & Sons, Ltd.     

Performance analysis of switch‐and‐examine diversity systems with interference and Rayleigh fading channels

This paper studies the behavior of the low‐complexity switch‐and‐examine diversity combining (SEC) and switch‐and‐examine diversity combining with post‐examine selection (SECps) antenna selection schemes with interference. In this paper, we first derive the cumulative distribution function (CDF) of the end‐to‐end (e2e) signal‐to‐interference plus noise ratio at the selection scheme combiner output. This CDF is then used to derive closed‐form expressions for the e2e outage and symbol error probabilities for the independent nonidentically distributed and independent identically distributed cases of diversity branches. In the analysis, the channels of the desired user and the interferers are assumed to follow Rayleigh distribution. Furthermore, to have more details about the system insights, the performance is evaluated at the high signal‐to‐noise ratio (SNR) values where the diversity order and coding gain are derived and analyzed. The derived analytical and asymptotic results are validated via a comparison with Monte‐Carlo simulations. Main findings show that with interference power does not scale with average SNR; the system can still achieve performance gain when more receive antennas are used. This happens at the values of switching threshold that are close to average SNR. Also, results illustrate that the interference is noticeably affecting the gain achieved in system performance when more antennas are used. Furthermore, findings show that the SECps selection scheme outperforms the conventional SEC scheme when more antennas are added with the switching threshold is much larger than the average SNR. Finally, findings show that the SEC and SECps antenna selection schemes are efficient for systems which operate at the range of low SNR values and this makes them attractive candidates to be implemented in the emerging mobile broadband communication systems. Copyright © 2015 John Wiley & Sons, Ltd.     

基于SC分集的混合FSO/RF航空通信系统性能分析

研究了基于选择合并(SC)分集的混合激光/射频(FSO/RF)航空通信系统性能,该系统设计简单且在发射端无需信道状态信息(CSI)。激光链路服从平均孔径效应下的Exponentiated Weibull大气湍流分布模型,射频采用Nakagami-m衰落信道模型,推导求出混合FSO/RF航空通信系统接收端信噪比的累积分布函数,进一步利用Meijer′s G函数推导了混合FSO/RF通信系统中断概率以及平均误码率的闭合表达式,通过仿真对比分析了不同湍流强度、调制方式及分集通信方案对系统中断、误码性能的影响。仿真结果表明,混合FSO/RF航空通信系统有效地利用了FSO及RF链路在不同大气信道条件下的互补性质,具有更优的中断和误码性能;采用BPSK调制能有效降低大气湍流对混合FSO/RF航空通信系统的影响;信噪比高时,并行传输、分集接收的通信方案对系统误码性能的改善要优于低阶调制对误码性能的改善。     

多跳分集系统中一种新的基于无比率编码的跨层方案

研究了多跳分集系统中由于链路的不可靠传输直接应用实用网络编码存在差错的扩散和传播问题.提出了一种新的基于无比率编码的跨层方案,该方案利用无比率编码的纠错能力及实用网络编码码字随机特性,控制了输入链路的差错扩散和传播.结果表明,在满足每条链路误包率一定的情况下,该方案获得了较好的差错性能.进一步分析了为了使每条链路达到给定的误包率,无比率编码在不同信噪比下的冗余.     

Error probability and channel capacity analysis of wireless system over inverse gamma shadowed fading channel with selection diversity

In this paper, we present an analytical framework to analyse the error probability and the channel capacity of the inverse gamma (I‐Gamma) shadowed fading channel. First, the work discusses the utility of the I‐Gamma over log‐normal (LN) and gamma fading models where the closeness of I‐Gamma with other existing shadowing models is carried out. Utilising the probability density function (PDF) of the I‐Gamma shadowed fading channel, various metrics of the communication system, namely, the average symbol error probability (SEP), the channel capacity under optimal rate adaptation (ORA), channel inversion with fixed rate (CIFR), and truncated CIFR (TIFR) are derived. Further, the work is extended to derive a novel selection combining (SC) PDF, and the analytical results for the SEP and the channel capacity of SC diversity are presented. Furthermore, we also provide simpler asymptotic expressions for the average SEP. In addition, the simplified high and low signal‐to‐noise‐ratio (SNR) solutions to channel capacity are also provided. The derived mathematical formulations have been endorsed by comparing with Monte Carlo simulations.     

Performance analysis of cooperative diversity for two-way multi-relay system with channel estimation error

In this work, we consider an amplify-and-forward two-way multi-relay system for wireless communication and investigate the effect of channel estimation error on the error rate performance. With the derivation of effective signal-to-noise ratio at the transceiver and its probability density function, we can get approximate expression for average bit error rate. Simulation results are performed to verify the analytical results.     

非理想信道估计下的放大转发协同通信系统性能分析

针对两跳多中继放大转发协同通信系统,分析了信道估计误差对系统性能的影响。考虑机会中继和全参与中继两种中继策略,分别推导了系统误码率的闭式表达式,并分析了不同信道估计质量阶数下的系统分集增益。平均信噪比损失率分析表明机会中继较全参与中继对信道估计误差更为敏感。仿真结果验证了理论分析。     

MIMO系统空时特征波束性能分析

针对结合了发射与接收分集技术和空时编码技术的MIM0无线通信系统误比特率性能问题,提出了一种利用信道矩阵的最大奇异值平方的概率密度函数（pdf）,来推导相干接收条件下,基于M-PAM和M-QAM调制的MIM0系统最大比合并精确误比特率显式表达式的方法。以该误比特率表达式为依据,分析了天线数目为可配置资源条件下,发射天线和接收天线的不同配置方案对系统性能的影响。通过计算机的蒙特卡洛仿真验证了理论分析结论。     

协作发射分集系统及其误码性能分析

协作分集（cooperative diversity）技术通过使网络中各单天线用户共享彼此天线，形成虚拟的多天线阵列来实现发射或接收分集，并结合一定的编码方式，可以有效地提高系统性能。多载波码分多址（MC-CDMA，multi．carder code division multiple access）技术将数据调制到各个子载波上发送，可以有效地抵抗信道频率选择性衰落的影响。由此提出了无线网络中频率选择性衰落信道环境下的一种基于分布式空时分组码（DSTBC，distributed space tim eblock code）和MC-CDMA的协作发射分集方案，建立了协作用户间的误码表示模型，基于该模型推导了在协作条件下整个系统误码性能的理论表达式。分析了协作用户间的平均解码差错概率对系统误码性能的影响，并给出了仿真结果。结果表明，本系统相对于未编码的MC-CDMA系统获得了明显的性能增益，同时仿真也较好地验证了理论结果。     

Performance evaluation of generalized selection diversity systems over Nakagami‐m fading channels

The generalized selection combining (GSC) scheme that adaptively combines a subset of M strongest paths out of L available diversity paths finds applications in several wideband receivers and broadband wireless communications. In this paper, exact closed‐form expressions for the moment generating function (MGF), the probability density function (PDF) and the cumulative density function (CDF) of the GSC(M, L) output signal‐to‐noise ratio (SNR) in independent and identically distributed (i.i.d) Nakagami‐m fading channels are derived while the fading index is a positive integer. These expressions hold for any M and L and provide a comprehensive framework for performance analysis including the derivation of closed‐form formulas for the average symbol error probability (ASEP) of a broad class of binary and M‐ary modulations, mean combined SNR and the outage probability of GSC(M, L) receiver structures. When the Nakagami‐m fading index is not an integer, the MGF of GSC(M, L) output SNR is derived as an (M − 1)‐fold infinite series. With this MGF, analytical expressions for both the outage probability and error rates can be readily obtained. An easily programmable recursive solution of the MGF of GSC(M, L) output SNR is also outlined for both the positive integer and noninteger fading severity index cases. Copyright © 2002 John Wiley & Sons, Ltd.     

非选择性Rician衰落信道中MC-DS-CDMA系统的性能分析

MC—DS—CDMA系统是基于时域扩展的多载波CDMA系统，它通常使用少量的子载波来解决ISI和ICI问题。对同步MC—DS—CDNA系统在频率非选择性Riciall衰落信道中的抗噪声性能进行了分析。仿真结果表明，非选择性Rician衰落参数D对系统的误比特率影响很大，在信噪比相同时，误比特率随D增加而增大。     

基于随机相位误差Tikhonov分布的MC-DS-CDMA系统性能分析

本文针对工作于慢变频率选择性Rayleigh衰落信道中的部分相干的MC-DS-CDMA系统，基于随机相位误差的Tikhonov密度分布提出了误码率上边界的一种分析方法。仿真结果表明，随着环路信噪比的增加，相位误差损耗所产生的系统误码率性能损失变得越来越小，当环路信噪比高于系统信噪比(Eb/N0)20dB时，系统误码率性能损失小于0．2dB。在MC-DS-CDMA系统中，由于能用频率分集取代路径分集，因而接收机结构更易实现。     

空时分组码多音调制CDMA系统性能分析

提出了一种空时分组码（STBC,space-time block-code）多音调制CDMA（MT-CDMA）系统结构。对系统上行链路误码率（BER）性能进行了理论分析,推导出了在多径衰落信道下采用最大比合并时系统的BER表达式,并通过计算机仿真进行了验证。数值结果表明由于联合的空时与多径分集增益,使系统的BER性能、差错地板和容量都得到了显著地改善。     

双发射天线选择正交空时码分集系统性能分析

针对任意Nakagami衰落信道,分析了多输入多输出(MIMO)系统中采用双发射天线选择正交空时码的平均误码率(ASER)性能。利用矩生成函数方法,推导出采用相干检测的二进制相移键控/二进制频移键控(BPSK/BFSK)、多进制相移键控(MPSK)和多进制正交幅度调制(MQAM)的精确ASER闭合解析式,对不同条件下的系统性能做了数值仿真,验证了分析结果的正确性。     

MC-CDMA调制在散射通信信道下的性能分析

为提高对流层散射通信系统容量和抗干扰能力,对散射信道下的多载波扩频方案进行研究.基于所建立的Rayleigh 分布对流层散射信道模型,分析了频域扩频多载波技术MC-CDMA的系统性能,对典型散射信道下的系统误码率进行了分析与仿真.结果表明:MC-CDMA可有效提升散射通信系统容量,单用户时系统误码率性能较好,随着用户数和散射信道多普勒频移的增大,系统误码率随之增大,需采用多址干扰控制和子载波干扰消除技术来改善系统误码率性能.     

Rayleigh衰落信道下多载波DS-CDMA系统性能分析

本文基于多载波传输技术，提出了一种多载波码分多址模型。并在Rayleigh衰落信道下对其误码性能进行了分析。分析及仿真结果表明，系统具有降低多址干扰的能力，同传统的单载波直接序列码分多址系统相比，能支持更大的用户容量。本系统能满足第三代移动通信系统对高速数据传输的要求。     

信道预测联合收发分集的正交信号误码性能

为解决采用最小均方误差(MMSE)信道预测的发射天线选择(TASP)/接收天线最大比合并(MRC)的无线通信系统设计问题,利用抛物柱面函数以及高斯Q函数的近似表达式和矩生成函数(MGF)法,分别推导了瑞利块衰落信道上采用TASP/MRC天线分集的相干检测M进制正交和双正交信号的平均误符号率(ASER)精确表达式以及正交信号ASER的近似表达式.数值计算和仿真结果验证了采用TASP/MRC和相干检测的正交/双正交ASER精确表达式的正确性以及正交信号ASER近似表达式的准确性.上述M进制正交/双正交信号ASER精确或近似表达式,可用于设计采用相干检测M进制正交和双正交信号的TASP/MRC天线分集系统,并能够快速地确定收发天线数和信道预测器级数等参数,避免耗时的计算机仿真.