Coverage Analysis of Cooperative NOMA in Millimeter Wave Networks

Abstract

This letter analyzes the coverage probability of a cooperative non-orthogonal multiple access (NOMA) millimeter wave (mmWave) network consisting of source ( $S$ ) and destination ( $D$ ) pair without a direct link. A cooperative relay ( $R$ ), which is selected from a set of active users, helps $D$ to receive its data. The transmission from $S$ to $R$ is based on NOMA, by which $R$ can receive its own data and $D$ ’s data simultaneously. Two relay selection schemes are developed. For each scheme, the favorable users that meet a rate threshold are selected to be in the decoding set. Then from the decoding set, a relay is selected that is nearest to $S$ (in the 1st selection scheme), or nearest to $D$ (in the 2nd selection scheme). For both schemes, we characterize the spatial density (location dependent) of decoding sets and derive the coverage probability. Both schemes outperform orthogonal multiple access. We also derive the coverage of randomly picking a relay (i.e., no selection) to quantify the benefits of relay selection in mmWave NOMA.