Multi-user Secrecy SWIPT for 5G OFDMA Networks with Particle Swarm Optimizations

This paper maximizes the minimum downlink secrecy throughput of the multi-user orthogonal frequency division multiplexing access (OFDMA) network with simultaneous wireless information and power transfer (SWIPT), where the optimizers include subcarrier allocation and power splitting ratio. The network is composed of a base station, and several receiver nodes (users). Every user does not have its own power supply, and uses the power splitting scheme to harvest energy and to decode information simultaneously from the received signal. Every user can eavesdrop all other users' subcarriers, and more than one subcarriers can be allocated to a user. We aim to maximize the total instantaneous secrecy rate of the weakest user. All user nodes experience the same path loss and shadowing, but dissimilar fast fading. To jointly allocate subcarriers and find the power splitting ratios for all users, the full search is tedious. Therefore, we propose the algorithm, based on particle swarm optimizations. The obtained average total instantaneous secrecy rate of the weakest user indicate that the total transmit power should be high enough to overcome the minimum operating energy. Increasing the total transmit power beyond a threshold does not increase the average total instantaneous secrecy rate of the weakest user.