Performance Analysis of User Pairing in Cooperative NOMA Networks

In this paper, we study the coverage probability and average data rate of user pairing in cooperative non-orthogonal multiple access (NOMA) networks. With fixed locations of the source and typical user, the candidate users for pairing follow homogeneous Poisson point process. Considering the geometric distance between nodes, close-to-user pairing (CUP) and close-to-source pairing (CSP) schemes are investigated with the near user acting as half-duplex relay or full-duplex (FD) relay. Lower bounds on the coverage probability and average data rate are approximately obtained using stochastic geometry and Gaussian-Chebyshev quadrature. Numerical and simulation results corroborate the accuracy of the analytical results and reveal that CUP-based cooperative NOMA outperforms CSP-based cooperative NOMA in terms of the data rate performance. With typical user close to the source, CUP-based FD NOMA is the best transmission scheme (among CUP-based and CSP-based cooperative NOMA, non-cooperative NOMA, and OMA schemes) that maximizes the sum data rate and the minimum user rate.