Hybrid RIS-assisted Interference Mitigation for Heterogeneous networks

Reconfigurable intelligent surfaces (RIS) have evolved as a low-cost and energy-efficient option to increase wireless communication capacity. In this research, we suggest using hybrid reconfigurable intelligent surfaces (H-RIS) to reduce interference in heterogeneous networks (HetNet). In contrast to traditional passive RIS, a hybrid RIS is suggested, which is fitted with a few active elements to not only reflect but also amplify incident signals for a significant performance increase. By jointly optimising the passive and active coefficients of the HRIS, we aim to maximise the rate of the small cell user (SUE). We presented an effective alternating optimisation-based phase shift matrix coefficients (AO-PMC) technique to tackle this problem by iteratively optimising these variables because the optimisation problem is not convex. The simulation results demonstrate that, in comparison to the passive RIS-assisted HetNet scheme and the scheme without RIS, the suggested scheme, with just a few active elements, can enable the HetNet to gain superior spectral efficiency (SE) and energy efficiency (EE). The outcomes also demonstrate that, in the majority of the cases taken into account, H-RIS can outperform the active RIS-assisted HetNet scheme.