Cognitive radio (CR) is an effective solution to improve the spectral efficiency (SE) of wireless communications by allowing the secondary users (SUs) to share spectrum with primary users (PUs). Meanwhile, intelligent reflecting surface (IRS), also known as reconfigurable intelligent surface (RIS), has been recently proposed as a promising approach to enhance energy efficiency (EE) of wireless communication systems through intelligently reconfiguring the channel environment. To improve both SE and EE, in this paper, we introduce multiple IRSs to a downlink multiple-input single-output (MISO) CR system, in which a single SU coexists with a primary network with multiple PU receivers (PU-RXs). Our design objective is to maximize the achievable rate of SU subject to a total transmit power constraint on the SU transmitter (SU-TX) and interference temperature constraints on the PU-RXs, by jointly optimizing the beamforming at SU-TX and the reflecting coefficients at each IRS. Both perfect and imperfect channel state information (CSI) cases are considered in the optimization. Numerical results demonstrate that IRS can significantly improve the achievable rate of SU under both perfect and imperfect CSI cases.

中文翻译：

---

智能反射面辅助认知无线电系统

认知无线电 (CR) 是通过允许次要用户 (SU) 与主要用户 (PU) 共享频谱来提高无线通信频谱效率 (SE) 的有效解决方案。同时，智能反射面（IRS），也称为可重构智能面（RIS），最近被提出作为通过智能重构信道环境来提高无线通信系统能源效率（EE）的一种有前途的方法。为了改善 SE 和 EE，在本文中，我们将多个 IRS 引入下行链路多输入单输出 (MISO) CR 系统，其中单个 SU 与具有多个 PU 接收器 (PU-RX) 的主网络共存。我们的设计目标是通过联合优化 SU-TX 的波束成形和反射系数，在 SU 发射机 (SU-TX) 上的总发射功率约束和 PU-RX 上的干扰温度约束下，最大化 SU 的可实现速率在每个 IRS。在优化中考虑了完美和不完美的信道状态信息 (CSI) 情况。数值结果表明，在完美和不完美的 CSI 情况下，IRS 可以显着提高 SU 的可实现率。