Cross-Tier Interference Mitigation for RIS-Assisted Heterogeneous Networks

With the development of next generation mobile networks, new research challenges have emerged, and technologies been proposed to address them. On other hand, reconfigurable intelligent surface (RIS) technology is being investigated for partially controlling wireless channels. RIS a promising improving signal quality by scattering electromagnetic waves in nearly passive manner. Heterogeneous networks (HetNets) are another that designed meet capacity requirements network. can be used improve system performance context HetNets. This study investigates applications surfaces (RISs) heterogeneous downlink (HetNets). Due network densification, small cell base station (SBS) interferes with macrocell users (MUEs). In this paper, we utilise mitigate cross-tier interference HetNet via directional beamforming adjusting phase shift RIS. We consider RIS-assisted consisting multiple SBS nodes MUEs both direct paths reflected paths. Therefore, aim maximise sum rate all jointly optimising transmit (MBS) An efficient reflecting coefficient-based optimisation (RCO) based on successive convex approximation approach. Simulation results provided show effectiveness scheme terms its comparison without but random shifts.