A unified approach to evaluate the precise outage probability of NOMA over various fading scenarios.

Non-orthogonal multiple access (NOMA) is an emerging multiple access technique for future generation wireless networks. Owing to the wide applicability of NOMA, precise expressions for the outage performance under various fading conditions are very much needed. The literature on the outage analysis of NOMA systems is extensive. However, a unified approach is required to test the outage performance of NOMA under various impairments as well as fading scenarios. Hence, in this paper we provide a unique procedure to evaluate the outage probability of downlink-NOMA and preciseness in the derived expressions is achieved by including error in channel state information and successive interference cancellation (SIC), intra- and inter-cell interference. The outage probability is derived over (i) homogeneous fading channels: Rayleigh and Nakagami-m faded distributions with and without log-normal shadowing, Rician fading, and (ii) non-homogeneous fading channels: α - μ , η - μ , α - η - μ , κ - μ and α - κ - μ shadowed distributions. The numerical results are evaluated by varying different fading parameters, error in channel estimation and SIC, and number of interferers. The impact of shadowing on the outage performance of NOMA is also analyzed. The obtained analytical results are validated with simulated results. [ABSTRACT FROM AUTHOR]