Cooperative Relaying Based Non-Orthogonal Multiple Access (NOMA) With Relay Selection

In this paper, we propose a two-phase non-orthogonal multiple access (NOMA) scheme with cooperative relaying. In the first phase, an access point (AP) linearly combines the signals of near-user Ui and far-user U2 and then broadcasts the superimposed signal to Ur and multiple relays. U1 tries to decode its desired data by treating the signal of U2 as interference. In a cooperative zone between AP and U2, multiple relays try to decode the signal of U2 by decoding and canceling the signal of U1. In the second phase, a decodable relay is selected to forward the far-user's signal and, meanwhile, if Ul fails to decode its desired signal in the first phase, it will try to decode and cancel the far-user's signal to further decode its desired signal again. We analyze the system throughput and investigate the impacts of various parameters. Numerical results show that our proposed scheme can greatly outperform the time division multiple access and the non-cooperative NOMA schemes in terms of throughput for most system settings.