Throughput optimization of cooperative non orthogonal multiple access

This paper derives the outage and packet error probabilities of Non Orthogonal Multiple Access (NOMA) systems. In the first time slot, the Base Station transmits a combination of two symbols s_w and s_s dedicated for weak and strong users. This signal is received by the two users and a relay. In the second time slot, the relay amplifies the received signal to the two users. Both users use the signal with the highest Signal to Interference plus Noise Ratio among direct and relayed signals. The weak user detects only its signal. Strong user first detects symbol s_w of weak user. After removing the contribution of weak user, strong user detects its own symbol s_s. In this article, expressions for outage probability, Packet Error Probability and the throughput of cooperative NOMA are derived. We also optimize the power allocated to weak and strong users to maximize the system throughput.