Performance Study of Cooperative Non-orthogonal Multiple Access with Energy Harvesting

Non-Orthogonal Multiple Access (NOMA) is a candidate channel access technique for the future generation wireless communication systems. It exploits the power domain to enable simultaneous access for multiple users. In this paper, a NOMA system with a base station (BS) and two users is studied. A novel scheme where the near user (UE 1) harvests energy from the signals sent from BS and relays the previously decoded message of the far user (UE 2) is proposed. It includes two common energy harvesting schemes, namely, power splitting and time switching, as special cases. The performance is evaluated by the achievable data rate of UE 2 under different requirements on the data rate of UE 1. Numerical simulations and analysis reveal that when the channel conditions between BS and UE 1, and between UE 1 and UE 2 are good, while that between BS and UE 2 is bad, the proposed scheme works the best and has a significant gain over the conventional NOMA scheme without cooperation. In addition, for the sake of simplicity, the power splitting scheme can be used to replace the generalized scheme for energy extraction without jeopardizing the performance gain much.