Intelligent reflecting surface (IRS) is a new and revolutionary technology capable of reconfiguring the wireless propagation environment by controlling its massive low-cost passive reflecting elements. Different from prior works that focus on optimizing IRS reflection coefficients or single-IRS placement, we aim to maximize the minimum throughput of a single-cell multiuser system aided by multiple IRSs, by joint multi-IRS placement and power control at the access point (AP), which is a mixed-integer non-convex problem with drastically increased complexity with the number of IRSs/users. To tackle this challenge, a ring-based IRS placement scheme is proposed along with a power control policy that equalizes the users' non-outage probability. An efficient searching algorithm is further proposed to obtain a close-to-optimal solution for arbitrary number of IRSs/rings. Numerical results validate our analysis and show that our proposed scheme significantly outperforms the benchmark schemes without IRS and/or with other power control policies. Moreover, it is shown that the IRSs are preferably deployed near AP for coverage range extension, while with more IRSs, they tend to spread out over the cell to cover more and get closer to target users.
翻译:智能反射表面(IRS)是一种能够通过控制其大规模低成本被动反射元素来重新配置无线传播环境的新技术和革命性技术,能够通过控制其大规模低成本被动反射元素来重新配置无线传播环境。不同于以往侧重于优化IRS反射系数或单一IRS定位的工作,我们的目标是通过在多个IRS的帮助下,通过在入口点联合采用多IRS配置和动力控制,最大限度地实现单细胞多用户系统的最低吞吐量,这是混合的内向型非阴道问题,与IRS/用户的数量相比,其复杂性急剧增加。为了应对这一挑战,我们提出了一个环基IRS安置计划,同时提出了一种权力控制政策,使用户的不外向概率相等。我们还进一步提议了一个高效的搜索算法,以便为任意数量的IRS/环获取近至最佳解决办法。数字结果证实了我们的分析,并表明我们拟议的计划大大超出了基准计划,而没有IRS和/或与其他电力控制政策相形形形形形形色。此外,它表明IRS系统最好是在靠近AP部署,以便更接近目标的用户扩大范围,同时,同时更倾向于使用IRS。