Outage analysis for user selection based downlink cooperative NOMA network over generalized fading channels

Downlink cooperative non-orthogonal multiple access scheme (C-NOMA) with user selection. • A user selection scheme is adopted at BS for downlink C-NOMA system for reducing system complexity. • The analytical expression of OP are derived for C-NOMA over κ − μ and η − μ fading channel. • Further, the analytical and simulation results are compared with the conventional schemes. • The outage performance of C-NOMA system is investigated by considering the I-SIC, I-CSI value. • The OP of various fading channels are analysed as a special case of η − μ and κ − μ fading distribution. Recently, non-orthogonal multiple access (NOMA) scheme is integrated with cooperative communication (C-NOMA) to increase the connectivity and coverage area. In this paper, we analyzed the outage performance of downlink C-NOMA system with the imperfect successive interference cancellation (I-SIC) and imperfect channel state information (I-CSI) aiding multiple users over κ − μ and η − μ independent and identically distributed fading environments. Further, a user selection scheme is adopted for downlink C-NOMA scheme for enhancing the performance of the system. To be precise, the system model considers multiple users at the destination, out of which two users are selected to serve with NOMA standards. The analytical expressions of outage probability (OP) are derived, analyzed, and compared with cooperative-orthogonal multiple access (C-OMA) scheme over generalized fading environments. Moreover, the accuracy of analytical results is validated through Monte Carlo simulation. In addition, the analytical expression of OP for the paired user is also derived, analyzed, and correlated with the C-OMA scheme. Furthermore, through κ − μ and η − μ fading distribution, the outage performance of Rayleigh, Nakagami- m , Rice, Hoyt, and one-sided Gaussian fading environment is also investigated. From the obtained results, it is evident that when compared to C-OMA scheme, the C-NOMA scheme achieves 4.4 and 6.6 percentage gain in terms of SNR for a near user and a far user, respectively at κ = 1 , μ = 1.0 to attain outage of 10 − 1 . On the other hand, for the same outage, C-NOMA achieves 4.6 and 6.7 percentage gain in terms of SNR for a near user and a far user, respectively at η = 1.0 , μ = 1.5 .