# Outage Performance for Cooperative NOMA Transmission with an AF Relay

## TL;DR

This paper analyzes the outage performance of cooperative NOMA networks with an AF relay, deriving closed-form outage probability approximations and revealing performance gains over orthogonal access.

## Contribution

It provides the first accurate closed-form approximation for outage probability in cooperative NOMA with an AF relay and compares its diversity and coding gains to orthogonal multiple access.

## Key findings

- Cooperative NOMA achieves the same diversity order as orthogonal access.
- It exhibits superior coding gain in outage performance.
- Relay transmit power and distance influence outage performance.

## Abstract

This letter studies the outage performance of cooperative non-orthogonal multiple access (NOMA) network with the help of an amplify-and-forward relay. An accurate closed-form approximation for the exact outage probability is derived. Based on this, the asymptotic outage probability is investigated, which shows that cooperative NOMA achieves the same diversity order and the superior coding gain compared to cooperative orthogonal multiple access. It is also revealed that when the transmit power of relay is smaller than that of the base station, the outage performance improves as the distance between the relay and indirect link user decreases.