Joint Power and Time Allocation in NOMA-SWIPT Enabled Wireless Caching Networks

In this paper, the non-orthogonal multiple access (NOMA) and simultaneous wireless information and power transfer (SWIPT) are applied to wireless caching networks (WCN). Particularly, in the content pushing stage, base station sends the most popular contents to helpers with NOMA and the helpers harvest energy from the received signals. Then, the helpers send the requested files to the users with NOMA in the content delivery stage. In the content pushing stage, we minimize the maximum delay of the helpers by jointly optimizing the power allocation and time switching factors. Due to the non-convexity of the problem, the bisection method and two-layer iterative algorithm are devised to solve the problem. In the content delivery stage, the energy efficiency (EE) optimization problem is formulated under the quality-of-service, energy harvesting, and transmit power constraints. By using the nonlinear fractional programming theory and the Lagrange dual method, the original optimization problem is solved and the optimal power and time allocation coefficients are obtained. Simulation results show that the proposed algorithm reduces the delay of the helpers and improves the EE performance of helpers compared to the benchmark schemes.