Intelligent Reflecting Surface (IRS) is a promising technology for next generation wireless networks. Despite substantial research in IRS-aided communications, the assumed antenna and channel models are typically simplified without considering site-specific characteristics, which in turn critically affect the IRS deployment and performance in a given environment. In this paper, we first investigate the link-level performance of active or passive IRS taking into account the IRS element radiation pattern (ERP) as well as the antenna radiation pattern of the access point (AP). Then the network-level coverage performance is evaluated/optimized in site-specific multi-building scenarios, by properly deploying multiple IRSs on candidate building facets to serve a given set of users or Points of Interests (PoIs). The problem is reduced to an integer linear programming (ILP) based on given link-level metrics, which is then solved efficiently under moderate network sizes. Numerical results confirm the impact of AP antenna/IRS element pattern on the link-level performance. In addition, it is found that active IRSs, though associated with higher hardware complexity and cost, significantly improve the site-specific network coverage performance in terms of average ergodic rate and fairness among the PoIs as well as the range of serving area, compared with passive IRSs that have a much larger number of elements.

翻译：智能反射面（IRS）是下一代无线网络的一项有前景的技术。尽管在IRS辅助通信领域已有大量研究，但所假设的天线与信道模型通常经过简化处理，未考虑场地特定特性，这进而会严重影响IRS在特定环境中的部署与性能。本文首先在考虑IRS单元辐射方向图（ERP）及接入点（AP）天线辐射方向图的前提下，研究有源或无源IRS的链路级性能。随后，通过在候选建筑面上合理部署多个IRS以服务给定用户集或兴趣点（PoI），在多建筑场地特定场景中评估/优化网络级覆盖性能。基于给定的链路级指标，该问题被简化为整数线性规划（ILP），并在中等网络规模下得以高效求解。数值结果证实了AP天线/IRS单元方向图对链路级性能的影响。此外，研究发现，与具有更多单元的无源IRS相比，尽管有源IRS硬件复杂度与成本更高，但在平均遍历速率、PoI间公平性以及服务区域范围方面，其能显著提升场地特定的网络覆盖性能。