We propose a reconfigurable intelligent surface (RIS)-assisted underlay spectrum sharing system, in which a RIS-assisted secondary network shares the spectrum licensed for a primary network. The secondary network consists of a secondary source (SS), an RIS, and a secondary destination (SD), operating in a Rician fading environment. We study the performance of the secondary network while considering a peak power constraint at the SS and an interference power constraint at the primary receiver (PR). Initially, we characterize the statistics of the signal-to-noise ratio (SNR) of the RIS-assisted secondary network by deriving novel analytical expressions for the cumulative distribution function (CDF) and probability density function (PDF) in terms of the incomplete H-function. Building upon the SNR statistics, we analyze the outage probability, ergodic capacity, and average bit error rate, subsequently deriving novel exact expressions for these performance measures. Furthermore, we obtain novel asymptotic expressions for the performance measures of interest when the peak power of the SS is high. Finally, we conduct exhaustive Monte-Carlo simulations to confirm the correctness of our theoretical analysis.

翻译：本文提出了一种可重构智能表面（RIS）辅助的底层频谱共享系统，其中RIS辅助的次级网络与主网络授权频谱共享使用。该次级网络由次级源（SS）、RIS和次级目的地（SD）组成，在瑞利衰落环境下运行。我们在考虑SS峰值功率约束和主接收机（PR）干扰功率约束的条件下，研究了次级网络的性能。首先，通过以不完全H函数推导累积分布函数（CDF）和概率密度函数（PDF）的新型解析表达式，刻画了RIS辅助次级网络信噪比（SNR）的统计特性。基于SNR统计特性，我们分析了中断概率、遍历容量和平均误码率，并推导出这些性能指标的新型精确表达式。此外，在SS峰值功率较高时，我们获得了目标性能指标的新型渐近表达式。最后，通过全面的蒙特卡洛仿真验证了理论分析的准确性。