Intelligent reflecting surface (IRS) has emerged as a promising technique to extend the wireless signal coverage of access point (AP) and improve the communication performance cost-effectively. In order to reduce the path-loss of the cascaded user-IRS-AP channels, the IRS-integrated AP architecture has been proposed to deploy the IRSs and the antenna array of the AP within the same antenna radome. To reduce the pilot overhead for estimating all IRS-involved channels, in this paper, we propose a novel codebook-based IRS reflection design for the IRS-integrated AP to enhance the coverage performance in a given area. In particular, the codebook consisting of a small number of codewords is designed offline by employing an efficient sector division strategy based on the azimuth angle. To ensure the performance of each sector, we optimize its corresponding codeword for IRS reflection pattern to maximize the sector-min-average-effective-channel-power (SMAECP) by applying the alternating optimization (AO) and semidefinite relaxation (SDR) methods. With the designed codebook, the AP performs the IRS reflection training by sequentially applying all codewords and selects the one achieving the best communication performance for data transmission. Numerical results show that our proposed codebook design can enhance the average channel power of the whole coverage area, as compared to the system without IRS. Moreover, our proposed codebook-based IRS reflection design is shown to achieve significant performance gain over other benchmark schemes in both single-user and multi-user transmissions.

翻译：智能反射面（IRS）已成为一种有前景的技术，能以经济高效的方式扩展接入点（AP）的无线信号覆盖范围并提升通信性能。为降低级联用户-IRS-AP链路的路径损耗，业界提出了IRS集成接入点架构，将IRS与AP天线阵列部署于同一天线罩内。为减少估计所有IRS相关链路的导频开销，本文针对IRS集成接入点提出一种基于码本的IRS反射设计，以增强指定区域的覆盖性能。具体而言，采用基于方位角的高效扇区划分策略，离线设计包含少量码字的码本。为确保每个扇区的性能，我们通过交替优化（AO）和半定松弛（SDR）方法优化其对应的IRS反射模式码字，以最大化扇区平均最小有效信道功率（SMAECP）。基于所设计的码本，AP依次应用所有码字进行IRS反射训练，并选择实现最佳通信性能的码字用于数据传输。数值结果表明，与无IRS的系统相比，所提码本设计能增强整个覆盖区域的平均信道功率。此外，在单用户和多用户传输场景下，所提基于码本的IRS反射设计相较于其他基准方案均能获得显著的性能增益。