Capacity Analysis and Rate Maximization Design in RIS-Aided Uplink
Multi-User MIMO
Abstract
Reconfigurable intelligent surface (RIS) has recently drawn intensive
attention due to its potential of simultaneously realizing high spectral
and energy efficiency in a sustainable way. This paper focuses on the
design of efficient transmission methods to maximize the uplink sum
throughput in a RIS-aided multi-user multi-input multi-output (MU-MIMO)
system. To provide an insightful basis, the channel capacity of
RIS-aided MU-MIMO is theoretically analyzed. Then, the conventional
transmission schemes based on orthogonal multiple access are presented
as the baseline. From the information-theoretic perspective, we propose
two novel schemes, i.e., \textit{joint transmission}
based on the semidefinite relaxation of quadratic optimization problems
and \textit{opportunistic transmission} relying on the
best user selection. The superiority of the proposed schemes over the
conventional ones in terms of achievable rates is justified through
simulation results.