Time and relay shared full/half duplex cooperative NOMA with paired cell edge users

Abstract

In this work, a novel time and relay shared (TRS) based full/half duplex (FD/HD) cooperative non-orthogonal multiple access (C-NOMA) scheme namely TRS FD/HD C-NOMA is proposed to efficiently exploit the spectrum of unpaired users in the wireless communication system. More specifically, a scenario has been investigated where cell edge users (CEUs) are more than the cell centre users (CCUs) and the base station has no direct connection with the CEUs. A CCU is employed as a shared relay to form clusters with the CEUs in a time-sharing fashion. To characterize the performance of the proposed scheme, four performance metrics ergodic capacity, outage probabilities, system throughput and system efficiency are discussed. More particularly, ergodic sum capacities are analytically derived and an exact closed-form expression of the outage probabilities is derived for three users in the system. Numerical results show that the TRS FD/HD C-NOMA scheme outperforms the conventional benchmarks. The ergodic capacities and outage performance of TRS FD C-NOMA enhanced in low SNR regime whereas due to the inclusion of loop interference in FD, TRS HD C-NOMA performs better in high SNR regime. Additionally, the system throughput and efficiency are also improved.