We consider a multi-user multiple input single output (MU-MISO) system assisted by a reconfigurable intelligent surface (RIS). For such a system, we aim to optimally select the RIS phase shifts and precoding vectors for maximizing the effective rank of the weighted channel covariance matrix which in turn improves the channel capacity. For a low-complex transmitter design, we employ maximum ratio transmission (MRT) and minimum-mean square error (MMSE) precoding schemes along with water-filling algorithm-based power allocation. Further, we show that MRT and MMSE exhibit equivalent performance and become optimal when the channel effective rank is maximized by optimally configuring the RIS consisting of a large number of elements.
@article{arxiv.2404.08909,
title = {Capacity Maximization for RIS-assisted Multi-user MISO Communication Systems},
author = {M. S. S. Manasa and Kali Krishna Kota and Praful D. Mankar and Harpreet S. Dhillon},
journal= {arXiv preprint arXiv:2404.08909},
year = {2024}
}