在多个IRS之间管理干扰和利用二次反射
Managing Interference and Leveraging Secondary Reflections Amongst Multiple IRSs
摘要：
智能反射表面（IRS）最近已经成为智能无线电环境的使能者，其中无源天线阵列可以用于主动地定制/控制无线电传播。随着多个IRS被发射以支持不同的用户组，关键是联合优化所有IRS的相移以减轻干扰以及利用IRS之间的二次反射。这项工作考虑了上行链路的多个用户分组，并支持多个IRS的多天线基站。每个具有多个可控相移元件的IRS旨在服务于附近的用户组。我们首先制定的最小可实现的速率最大化问题，通过联合优化相移的元素从所有IRS和接收波束形成器在MIMO基站。这个问题原来是非凸的。然后，我们推导出其解决方案，使用交替优化机制。我们的模拟表明，通过适当地管理干扰和利用IRS之间的二次反射，部署更多的IRS来支持不同的用户组以实现更高的每用户速率是非常有益的。相比之下，在不适当地管理二次反射的情况下，增加IRS的数量可能不利地影响网络吞吐量，特别是对于较高的发射功率。
英文摘要：
Intelligent reflecting surface (IRS) has recently been emerging as an enabler for smart radio environment in which passive antenna arrays can be used to actively tailor/control the radio propagation. With multiple IRSs being launched to support various group of users, it is critical to jointly optimize the phase-shifts of all IRSs to mitigate the interference as well as to leverage the secondary reflections amongst IRSs. This work considers the uplink of multiple users that are grouped and supported by multiple IRSs to a multi-antenna base station. Each IRS with multiple controllable phase-shift elements is intended to serve a group of near-by users. We first formulate the minimum achievable rate maximization problem by jointly optimizing phase-shifts of elements from all IRSs and the received beamformers at the MIMO base station. The problem turns out to be non-convex. We then derive its solution using the alternating optimization mechanism. Our simulations show that by properly managing interference and leveraging the secondary reflections amongst IRSs, there is a great benefit of deploying more IRSs to support different groups of users to achieve a higher rate per user. In contrast, without properly managing the secondary reflections, increasing the number of IRSs can adversely impact the network throughput, especially for higher transmit power.
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