Performance Optimization for Reconfigurable Intelligent Surface Aided Cellular Networks with D2D Communication.

Reconfigurable intelligent surface (RIS) is recognized as a promising technology to enhance the performance of wireless communication systems. In this paper, a RIS-aided cellular network with device-to-device communication is considered. We aim to maximize the energy efficiency (EE) by jointly optimizing the transmit power of the users and passive beamforming of RIS. To solve this non-convex problem, we decouple it into two sub-problems to optimize alternately, namely beamforming and power control. Specifically, we first transform the sub-problem of passive beamforming optimization into a quadratically constrained quadratic programming problem and use semidefinite relaxation algorithm to solve. Then we optimize the power by using the techniques of fractional programming, Dinkelbach's method, and immune algorithm. Finally simulation results show that the proposed joint optimization algorithm enhances the system EE compared to other benchmarks.