Performance analysis of non-ortoganal multiple access systems in fading communication channels

In this thesis, examines the performance analysis of downlink non-orthogonal multiple access (NOMA) systems on cascaded Nakagami-m fading channels. The user signals are transmitted through superposition coding by the source. As on the receiver side, the user signals are detected through maximum likelihood (ML) and successive interference cancellation (SIC) techniques. In the system model discussed, the model is presupposed to be having a cascading channel due to its pertinence to practice. In addition, the imperfect SIC has been studied on the receiver side. To to the extent of our knowledge, the mathematical inferences acquired appears in the literature for the first time. The bit error rate performances of the users are analysed with Monte Carlo simulations by considering the power sharing coefficient, the degree of cascading, and the fading parameter. In the simulation results, it is found out that the system performance deteriorates with the increase in the degree of cascading. When the SNR value is taken as 25 dB, a = 0.2, m = 3 and N = 1, 2, 3, 5, the BHO values for the FU are acquired as 0.0003, 0.0053, 0.0252, 0.1206 respectively. When power sharing coefficient and the degree of cascading are kept stable, it is observed that bit error rate performance increases with the rising of the m fading parameter. When the SNR value is taken as 20 dB, a = 0.2, N = 3 and m = 1, 2, 3, 5, the BHO values for the NU are respectively obtained as 0.0987, 0.0346, 0.0164, 0.005. In the last place, due to its role in determining the amount of power allocated to the user signals in the source, the power sharing coefficient has an important impact on the total bit error rate of the system. When the SNR value is taken as 30 dB, m = 3, N = 2 and a = 0.15, 0.3, 0.8, BHO values for the NU are acquired as 0.000267, 0.000053, 0.000014, 0.000057, respectively.