Outage Performance of Cooperative NOMA System in Log-Normal Fading Channels

This paper considers a cooperative non-orthogonal multiple access, i.e., C-NOMA system consisting of a base station (BS), and two downlink users, i.e., a near user and a far user. We derive analytical expression for the outage probabilities experienced by both the users and the system outage probability of the C-NOMA network in log-normal fading channels. We perform extensive analytical and simulation studies to determine the impact of various parameters on the outage performance. We determine numerical values for the power allocation coefficient at the BS that leads to equal outage probabilities for the users. Further, we determine numerical values for the power allocation coefficient at the BS that ensures system outage minimization and validate results using particle swam optimization method.