Abstract
This letter exploits reconfigurable intelligent surface (RIS) in the heterogeneous networks (HetNets) with wireless backhaul to improve the task computing energy efficiency. To minimize the overall energy consumption of all users, we formulate the problem as a combinatorial optimization problem by jointly optimizing the transmit power of users and small cell base stations, computational capacity of users and base stations, task offloading rate of users, and passive beamforming matrix at RIS. The problem is NP-hard and difficult to solve directly. We decompose the problem into two sub-problems of energy consumption optimization at users and base stations, respectively, taking into account of wireless backhaul capacity. The two sub-problems are solved iteratively to find the final solution. Simulation results demonstrate that the proposed scheme can greatly reduce the energy consumption compared with the baselines.