Distributed mechanism design for multi‐cell communications aided by multiple reconfigurable intelligent surfaces

Abstract

Reconfigurable intelligent surface (RIS) has drawn great attention as a promising technique that triggers a revolution in multi-antenna systems. It can intelligently reconstruct the propagation environments passively without extra hardware or power consumption. In this paper, the multi-RIS aided downlink multi-cell communication systems are considered. Adjacent base stations (BSs) are allowed to share and jointly control the same RISs to mitigate the influence brought by the inter-cell interference. For the sum-rate maximisation, a distributed negotiation mechanism is designed where each BS only communicates with its neighbours to reach a consensus on the RIS-based analogue beamforming. Meanwhile, given the incomplete knowledge of other cells, each BS independently optimises its digital beamformer based on its iteratively updated estimates over the other cells without revealing any location and channel information of its own serving users. Simulation results show that the proposed scheme achieves a close performance compared to the centralised scheme, and much better than the traditional no-RIS system. The influence of the discrete phase shifts and the RIS size on the system performance are also evaluated.