Coverage and Capacity Optimization in STAR-RISs Assisted Networks: A Machine Learning Approach

Abstract

Coverage and capacity are the important metrics for performance evaluation in wireless networks, while the coverage and capacity have several conflicting relationships, e.g. high transmit power contributes to large coverage but high inter-cell interference reduces the capacity performance. Therefore, in order to strike a balance between the coverage and capacity, a novel model is proposed for the coverage and capacity optimization of simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) assisted networks. To solve the coverage and capacity optimization (CCO) problem, a machine learning-based multi-objective optimization algorithm, i.e., the multi-objective proximal policy optimization (MO-PPO) algorithm, is proposed. In this algorithm, a loss function-based update strategy is the core point, which is able to calculate weights for both loss functions of coverage and capacity by a min-norm solver at each update. The numerical results demonstrate that the investigated update strategy outperforms the fixed weight-based MO algorithms.

STAR-RIS Aided NOMA in Multicell Networks: A General Analytical Framework With Gamma Distributed Channel Modeling

“…Recently, the system performance of RIS aided multi-cell networks has been evaluated. In [18], the authors simultaneously optimized the coverage and capacity in a two-cell system. The authors in [19] considered a multi-cell multipleinput single-output network, where transmit and reflective beamforming vectors were jointly optimized to maximize the minimum weighted signal-to-interference-plus-noise ratio (SINR) at UEs.…”