Intelligent reflecting surface (IRS) has emerged as a promising technique to enhance wireless communication performance cost-effectively. The existing literature has mainly considered IRS being deployed near user terminals to improve their performance. However, this approach may incur a high cost if IRSs need to be densely deployed in the network to cater to random user locations. To avoid such high deployment cost, in this paper we consider a new IRS aided wireless network architecture, where IRSs are deployed in the vicinity of each base station (BS) to assist in its communications with distributed users regardless of their locations. Besides significantly enhancing IRSs’ signal coverage, this scheme helps reduce the IRS-associated channel estimation overhead as compared to conventional user-side IRSs, by exploiting the nearly static BS-IRS channels over short distance. For this scheme, we propose a new two-stage transmission protocol to achieve IRS channel estimation and reflection optimization for uplink data transmission efficiently. In addition, we propose effective methods for solving the user-IRS association problem based on long-term/statistical channel knowledge and the selected user-IRS-BS cascaded channel estimation problem. Finally, all IRSs’ passive reflections are jointly optimized with the BS’s multi-antenna receive combining to maximize the minimum achievable rate among all users for data transmission. Numerical results show that the proposed co-site-IRS empowered BS scheme can achieve significant performance gains over the conventional BS without co-site IRS and existing schemes for IRS channel estimation and reflection optimization, thus enabling an appealing low-cost and high-performance BS design for future wireless networks.

中文翻译：

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利用共站智能反射面赋能基站：用户关联、信道估计和反射优化

智能反射面 (IRS) 已成为一种很有前途的技术，可以经济高效地提高无线通信性能。现有文献主要考虑将 IRS 部署在用户终端附近以提高其性能。但是，如果 IRS 需要在网络中密集部署以满足随机用户位置的需求，这种方法可能会产生高成本。为了避免如此高的部署成本，在本文中，我们考虑了一种新的 IRS 辅助无线网络架构，其中 IRS 部署在每个基站 (BS) 附近，以帮助其与分布式用户进行通信，而不管他们的位置如何。除了显着增强 IRS 的信号覆盖范围外，与传统的用户侧 IRS 相比，该方案有助于减少与 IRS 相关的信道估计开销，通过在短距离内利用几乎静态的 BS-IRS 信道。对于该方案，我们提出了一种新的两阶段传输协议，以有效地实现上行链路数据传输的 IRS 信道估计和反射优化。此外，我们提出了基于长期/统计信道知识和选定的用户-IRS-BS级联信道估计问题解决用户-IRS关联问题的有效方法。最后，所有 IRS 的无源反射与 BS 的多天线接收组合共同优化，以最大限度地提高所有用户数据传输的最小可实现速率。