Performance Evaluation of NOMA-Based Cooperative Communications over Cascaded Rician Fading Channels

The necessity of the retransmissions of the source signal from the relay terminals restricts the spectral efficiency of the wireless cooperative communications systems. It has been shown that cooperative communications systems using non-orthogonal multiple access (NOMA) technique can prevent these capacity decreases and constitutes an ideal physical layer solution for inter-vehicular communication systems which is an important future 5G applications. In this study, the performance of NOMA based cooperative communications is investigated over the cascaded Rician fading channels since theoretical and experimental studies have shown that cascaded channel structure supplies more realistic statistical model for mobile network models such as inter-vehicular communication systems. The achievable average rate provided by cooperative communication systems using NOMA is found by computer simulations. The obtained results for cascaded Rician fading channels have shown that the capacity is decreased as the cascading degree increases.