Optimal Power Allocation and Harvesting Duration for Cooperative NOMA in the Presence of Nakagami Fading Channels

Abstract

The paper derives the throughput, outage and packet error probabilities of cooperative non-orthogonal multiple access (NOMA) with energy harvesting. In the first time slot, relay node harvests energy using radio frequency (RF) signal received from the base station (BS). In the second time slot, BS transmits a combination of two symbols $$s_\mathrm{f}$$ and $$s_\mathrm{n}$$ dedicated for far and near users. This signal is received by the two users and a relay. In the third time slot, the relay node amplifies the received signal to the two users. Both users use the signal with the highest signal-to-interference plus noise ratio (SINR) among direct and relayed signals. The far user detects only its symbol. Near user first detects symbol $$s_\mathrm{f}$$ of far user. After removing the contribution of far user, near user detects its own symbol $$s_\mathrm{n}$$ . We propose the use of the gradient algorithm to optimize harvesting duration and the powers allocated to far and near users to maximize the total throughput.