Cooperative Beam Routing for Multi-IRS Aided Communication

Abstract

Intelligent reflecting surface (IRS) is envisioned to play a significant role in future wireless communication systems thanks to its powerful capability of enabling smart and reconfigurable radio environment. In this paper, we study the multi-IRS aided downlink communication in a massive multipleinput multiple-output (MIMO) system, where a multi-antenna BS simultaneously serves multiple remote single-antenna users with orthogonal beams reflected by multiple IRSs. By exploiting the line-of-sight (LoS) link between each pair of selected IRSs, a multihop cascaded LoS link can be established between the BS and each user via their cooperative beam routing. Under this setup, we optimize the selected IRSs and their beam routing path for each user, along with the BS/IRS active/passive beamforming such that the minimum received signal power among all users is maximized, subject to a new multi-beam routing path separation constraint for avoiding the inter-user/route interference. To tackle this problem, we first derive the optimal BS/IRS active/passive beamforming in closed-form for any given beam routes and show the beam routing optimization is NP-complete by recasting it as an equivalent graphoptimization problem. To solve this challenging problem, we then propose an efficient recursive algorithm to partially enumerate the feasible solutions, which effectively balances the performancecomplexity trade-off by tuning its design parameter. Numerical results demonstrate that the proposed algorithm can achieve nearoptimal performance with low enumeration complexity and also outperform other benchmark schemes.

Performance of Cooperative Communication System With Multiple Reconfigurable Intelligent Surfaces Over Nakagami-m Fading Channels

“…Notice that the ideal phase shift assumption was widely used in the RIS-assisted wireless communication systems and it is inline with realistic implementations [4], [5], [13], [24]. In addition, this assumption has been extensively used for single-RIS-assisted wireless communication systems [3], [5], [7] and multi-RIS-assisted wireless communication systems [13], [17], [25]. It is also noted that in practice, the RIS-assisted wireless communication systems are generally implemented with discrete phase shifts.…”

Double Intelligent Reflecting Surface-Assisted Multi-User MIMO Mmwave Systems With Hybrid Precoding

“…To be specific, the cascaded passive BF design in a double-IRS-assisted network was investigated in [34]. While a routing technique in a multi-hop IRS-enabled network was proposed in [35]. Then in [36], the authors proposed a phase shifter method in a double-IRS-enhanced uplink MIMO network.…”

Weighted Sum Secrecy Rate Maximization Using Intelligent Reflecting Surface

“…While in [26], the authors studied the cooperative May 24, 2021 DRAFT passive BF design in a double-IRS-assisted MIMO uplink network. Recently in [25], the authors studied the multi-hop signal reflection in a multi-IRS-aided network.…”