On the Performance of NOMA with Hybrid ARQ

TL;DR

This paper analyzes the outage performance of NOMA systems enhanced with HARQ-CC, deriving analytical expressions and demonstrating improved reliability and power efficiency through simulations.

Contribution

It provides a closed-form outage probability expression for NOMA with HARQ-CC and explores the power-retransmission tradeoff, highlighting performance gains with limited channel information.

Findings

Analytical outage probability and diversity gain derived.

HARQ-CC improves performance of low-power NOMA users.

Significant performance benefits with limited channel info.

Abstract

In this paper, we investigate the outage performance of hybrid automatic repeat request with chase combining (HARQ-CC) assisted downlink non-orthogonal multiple access (NOMA) systems. A closed-form expression of the individual outage probability and the diversity gain are obtained firstly. Based on the developed analytical outage probability, a tradeoff between the minimum number of retransmissions and the transmit power allocation coefficient is then provided for a given target rate. The provided simulation results demonstrate the accuracy of the developed analytical results. Moreover, it is shown that NOMA combined with the HARQ-CC can achieve a significant advantage when only average channel state information is known at the transmitter. Particularly, the performance of the user with less transmit power in NOMA systems can be efficiently improved by utilizing HARQ-CC.