EE Optimization for Downlink NOMA-Based Multi-Tier CRANs

Non-orthogonal multiple access (NOMA) is increasingly becoming very attractive in cloud radio networks (CRANs) to further boost the overall spectral efficiency, connectivity and, capacity of such networks. This paper addresses optimizing energy efficiency (EE) for downlink a NOMA-based two tiers CRAN. The stochastic geometry represented by Poisson Point Process (PPP) distribution used decide number and locations base stations (BSs) each tier within coverage area. A numerical optimal solution obtained compared against proposed subgradient solution, as well another unoptimized based on false positioning method. For comparison purposes, other power allocation techniques are presented allocate different powers various BS categories; one allocates their relative distances cloud-based central station bisection scheme. Two simulation scenarios examine performance two-tier NOMA-CRANs with NOMA adopted both cases. first scenario considers heterogeneous CRAN (NOMA-HCRAN) case using categories tier, namely, macro-BSs RRHs. second homogeneous (NOMA-CRAN) RRHs but has frequency layer prevent cross interference. Simulation results show promising gain can be achieved existing approaches. More specifically, it was illustrated that offers better than CRAN, which turn techniques, particular, distance NOMA-CRAN.