This paper presents an analysis of a multiple dual-hop relaying system, which is composed of km-class radio frequency (RF)-free-space optical (FSO) links. Partial relay selection based on outdated channel state information (CSI) is employed in order to select active relay for further transmission. Amplify-and-forward relaying protocol is utilized. The RF links are assumed to be subject to Rayleigh fading, and the FSO links are influenced by both Gamma-Gamma atmospheric turbulence and pointing errors. On the basis of our previously derived expression for cumulative distribution function of the equivalent signal-to-noise ratio of the whole system, we derive novel analytical expressions for the average bit-error rate (BER) and ergodic capacity that are presented in terms of the Meijer's G-function and extended generalized bivariate Meijer's G-function, respectively. The numerical results are confirmed by Monte Carlo simulations. Considering the effect of time-correlation between outdated CSI and actual CSI related to the RF channel at the time of transmission, the average BER and the ergodic capacity dependence on various system and channel parameters are observed and discussed. The results illustrate that the temporal correlation between outdated and actual CSI has strong effect on system performance, particularly on BER values, when FSO hop is influenced by favorable conditions. Keywords: Bit error rate, ergodic capacity, free-space optical systems, partial relay selection, radio frequency systems.
翻译:本文分析了多重双速中继系统,该系统由公里级无线电频率(RF)无空间光学(FSO)链接组成。根据过时的频道状态信息(CSI)选择部分继电器,以选择主动中继器进行进一步传输。使用放大和前向转发协议。RF链接假定受雷利退缩的影响,FSO链接受伽马-伽马大气动荡和指针错误的影响。根据我们以前衍生的全系统等同信号-音频比累积分配功能的表达,我们根据已过时的频道状态信息(CSI)选择部分中继器选择部分中继器,以选择主动中继器,选择部分中继器(CSI)选择部分中继器,分别使用Meijer的G功能和扩展通用双向转发程序。数字结果由Monte Carlo模拟证实。考虑到过时的 CSI与实际CSI在传输时与RF频道相关时间-时间-频率比对等频率分配功能分配功能的影响,平均BER和平均BERO比率对平均比差率率(BER值)进行分析,讨论时对各系统的实际磁度影响。