In this paper, we investigate the performance of mixed millimeter‐wave (mmWave)/multiple input multiple output (MIMO)‐free space optics (FSO) cooperative relaying system. The mmWave link is assumed to undergo multipath fading and shadowing which has been modeled as generalized‐K distributed fading, whereas the diversity aided FSO link is considered to experience Gamma–Gamma turbulence. We consider amplify‐and‐forward (AF) relaying strategy and multiple signals arriving at the receiver are combined using equal gain combining (EGC) scheme. Analytical closed form expressions for performance metrics such as outage probability, bit error rate (BER), and the ergodic channel capacity are derived in terms of bivariate Fox's H‐function for the considered mixed mmWave/MIMO‐FSO relaying system. In order to further simplify the obtained results, we analyze the system performance for the case of high signal‐to‐noise ratio (SNR) to present the asymptotic expressions for the outage probability and BER in terms of elementary functions. To this end, we have formulated an optimum power allocation scheme which minimizes the probability of outage experienced by the end user by allocating the optimum power on the FSO link. We also analyze the proposed system for the impact of pointing errors in a separate section by deriving closed‐form expressions for the outage probability and BER. Finally, numerical results have been demonstrated the findings of the research work which have supplemented by Monte Carlo simulations.

中文翻译：

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分集辅助的毫米波/自由空间光合作中继系统

在本文中，我们研究了混合毫米波（mmWave）/无多输入多输出（MIMO）的空间光学（FSO）协作中继系统的性能。假设mmWave链路经历了多路径衰落和阴影化，其建模为通用K分布式衰落，而分集辅助的FSO链路被认为会经历伽玛–伽玛湍流。我们考虑了放大转发（AF）中继策略，并使用等增益合并（EGC）方案对到达接收器的多个信号进行合并。对于混合毫米波/ MIMO-FSO中继系统，使用双变量Fox H函数，得出了性能指标（如断电概率，误码率（BER）和遍历信道容量）的解析式封闭形式表达式。为了进一步简化获得的结果，我们分析了高信噪比（SNR）情况下的系统性能，以基本功能的形式给出了中断概率和BER的渐近表达式。为此，我们制定了一种最佳功率分配方案，该方案通过在FSO链路上分配最佳功率来最大程度地降低最终用户遭受停电的可能性。通过导出中断概率和BER的闭式表达式，我们还分析了建议系统在单独部分中对指向错误的影响。最后，数值结果证明了研究工作的发现，并通过蒙特卡洛模拟进行了补充。