Intelligent reflecting surfaces (IRSs) were introduced in the literature in order to enhance the performance of the wireless systems. However, from a cellular service provider's point of view, a concern with the use of an IRS is its effect on out-of-band (OOB) quality of service. Specifically, if there are two operators, say X and Y, providing services in a given geographical area using non-overlapping frequency bands, and if operator X uses an IRS to optimally enhance the throughput of it's users, does the IRS degrade the performance of operator Y? We study this scenario by analyzing the ergodic sum-rates achieved by both the operators under round-robin scheduling. We also derive the complementary cumulative distribution function of the change in the effective channel gain at an OOB user with and without the IRS, which provides deeper insights into the effect of the IRS on the overall channel quality. Surprisingly, we find that even though the IRS is randomly configured from operator Y's point of view, the OOB operator still benefits from the presence of the IRS, witnessing a performance enhancement for free. This happens because the IRS introduces additional paths between the transmitter and receiver, increasing the overall signal power arriving at the receiver and providing diversity benefits. We verify our findings via numerical simulations, and conclude that an IRS is always beneficial to every operator, even when the IRS is deployed to optimally serve only one operator in the system.

翻译：智能反射面（IRS）被引入文献中以提升无线系统的性能。然而，从蜂窝服务提供商的角度来看，使用IRS的一个担忧是其对带外（OOB）服务质量的影响。具体而言，若存在两个运营商（例如X和Y）在同一地理区域使用非重叠频段提供服务，且运营商X利用IRS来最优地提升其用户的吞吐量，那么IRS是否会降低运营商Y的性能？我们通过分析轮询调度下两个运营商所实现的和遍历速率来研究这一场景。我们还推导了IRS存在与否时OOB用户有效信道增益变化的互补累积分布函数，从而深入理解IRS对整体信道质量的影响。令人惊讶的是，尽管从运营商Y的角度看IRS是随机配置的，但OOB运营商仍能受益于IRS的存在，无偿获得性能提升。这是因为IRS在发射机和接收机之间引入了额外路径，增加了到达接收机的总信号功率，并提供了分集增益。我们通过数值仿真验证了研究结果，并得出结论：即使IRS仅被部署以最优服务于系统中的某一个运营商，它对所有运营商总是有益的。