Intelligent reflecting surface (IRS) is an emerging technology and serves as a key component of any smart radio environment. In this article, we consider an IRS that assists communication of a direct link between a single-antenna transmitter and a receiver. It is assumed that a direct link experiences composite fading/shadowing and is modeled by Generalized-K distribution. Moreover, IRS has line-of-sight (LoS) paths, therefore, Rician distribution is used to characterize the fading for these paths. We also consider phase errors that exist due to discrete number of phase shifts. We derive an approximation for the end-to-end signal-to-noise ratio (SNR) which shows that an amplitude of the direct link is increased by a positive offset because of the presence of IRS. Based on this SNR approximation, a new statistical framework that includes cumulative distribution function (CDF), probability density function (PDF), and moment generating function (MGF) is developed. Leveraging this statistical framework, we derive new and accurate closed-form approximations for the outage probability, average error probability, ergodic capacity and generalized moments. It is shown that the considered IRS-aided system (IAS) achieves much better performance even with a few numbers of phase shifts as compared to other baseline systems. Simulations are also provided which verify the tightness of our derived approximations.

中文翻译：

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具有复合衰落/阴影直接链路和离散相移的 IRS 辅助通信系统的性能分析

智能反射面 (IRS) 是一项新兴技术，是任何智能无线电环境的关键组成部分。在本文中，我们考虑一种 IRS，它有助于在单天线发射器和接收器之间进行直接链路的通信。假设直接链路经历复合衰落/阴影，并由 Generalized- K建模分配。此外，IRS 具有视距 (LoS) 路径，因此，使用 Rician 分布来表征这些路径的衰落。我们还考虑了由于离散数量的相移而存在的相位误差。我们推导出端到端信噪比 (SNR) 的近似值，它表明直接链路的幅度由于 IRS 的存在而增加了正偏移。基于这种 SNR 近似，开发了一个新的统计框架，包括累积分布函数 (CDF)、概率密度函数 (PDF) 和矩生成函数 (MGF)。利用这个统计框架，我们为中断概率、平均错误概率、遍历容量和广义矩推导出新的、准确的封闭形式近似值。结果表明，与其他基线系统相比，所考虑的 IRS 辅助系统 (IAS) 即使具有少量相移也能实现更好的性能。还提供了模拟，以验证我们导出的近似值的紧密性。