Performance Analysis of NOMA With Fixed Gain Relaying Over Nakagami- $m$ Fading Channels

Abstract

This paper studies the application of cooperative techniques for\nnon-orthogonal multiple access (NOMA). More particularly, the fixed gain\namplify-and-forward (AF) relaying with NOMA is investigated over Nakagami-$m$\nfading channels. Two scenarios are considered insightfully. 1) The first\nscenario is that the base station (BS) intends to communicate with multiple\nusers through the assistance of AF relaying, where the direct links are\nexistent between the BS and users; and 2) The second scenario is that the AF\nrelaying is inexistent between the BS and users. To characterize the\nperformance of the considered scenarios, new closed-form expressions for both\nexact and asymptomatic outage probabilities are derived. Based on the\nanalytical results, the diversity orders achieved by the users are obtained.\nFor the first and second scenarios, the diversity order for the $n$-th user are\n$\\mu(n+1)$ and $\\mu n$, respectively. Simulation results unveil that NOMA is\ncapable of outperforming orthogonal multiple access (OMA) in terms of outage\nprobability and system throughput. It is also worth noting that NOMA can\nprovide better fairness compared to conventional OMA. By comparing the two\nscenarios, cooperative NOMA scenario can provide better outage performance\nrelative to the second scenario.\n