Rate Maximization and Mode Selection for RDARS-Assisted Uplink MIMO Communications

Reconfigurable distributed antennas and reflecting surface (RDARS) has been recently proposed as a promising technology. This architecture enables each element to operate either in the reflection mode, like the conventional passive reconfigurable intelligent surface (RIS), or in the connection mode, akin to the distributed antenna system (DAS). This dual capability allows RDARS to harness both reflection gain and distribution gain. In this paper, to further unleash the potential of the RDARSaided multiple-input multiple-output (MIMO) communication system in terms of additional selection gain, we formulate an achievable rate maximization problem by jointly designing the mode selection matrix, the power allocation matrix and the reflection coefficient matrix. Due to the mode selection design of RDARS, this problem is more challenging than those of the conventional RIS-aided systems with fixed elements locations. To tackle it, by investigating the beneficial properties of the objective function, we propose a greedy-based alternating optimization (AO) algorithm with low-complexity. Numerical results clearly illustrate the reflection gain, distribution gain and selection gain of RDARS and show that RDARS-assisted system can achieve superior performance than the passive-RIS assisted system and DAS.