This paper analyzes the performance of multiple reconfigurable intelligent surfaces (RISs)-aided networks. The paper also provides some optimization results on the number of reflecting elements on RISs and the optimal placement of RISs. We first derive accurate closed-form approximations for RIS channels' distributions assuming independent non-identically distributed (i.ni.d.) Nakagami-\emph{m} fading environment. Then, the approximate expressions for outage probability (OP) and average symbol error probability are derived in closed-form. Furthermore, to get more insights into the system performance, we derive the asymptotic OP at the high signal-to-noise ratio regime and provide closed-form expressions for the system diversity order and coding gain. Finally, the accuracy of our theoretical analysis is validated through Monte-Carlo simulations. The obtained results show that the considered RIS scenario can provide a diversity order of $\frac{a}{2}K$, where $a$ is a function of the Nakagami fading parameter $m$ and the number of meta-surface elements $N$, and $K$ is the number of RISs.
翻译:本文分析了多种可重新校准智能表面(RIS)辅助网络的性能。 本文还就RIS的反射元素数量和RIS的最佳位置提供了一些优化结果。 我们首先在假设独立分布( i. ni. d.) Nakagam-\emph{m} 衰减环境的情况下,为RIS频道的分布获得准确的闭式近似值。 然后, 闭式模型中得出了外差概率( OP) 和平均符号误差概率的大致表达法。 此外, 为了更深入了解系统性能,我们在高信号对噪音比率系统中得出无信号OP,并为系统多样性订单和编码收益提供闭式表达法。 最后,我们理论分析的准确性通过蒙特卡洛模拟得到验证。 所获得的结果表明, 所考虑的RIS情景可以提供多样性顺序为$\frac{ {a2}KK$, 其中美元是NACAGFAL 参数的函数, $- N$, 美元是元表层元素的数量。