Performance Analysis of OSTBC-NOMA System in the Presence of Practical Impairments

This paper investigates the performance of a power-domain downlink non-orthogonal multiple access (NOMA) system in the presence of practical impairments such as channel estimation error (CEE), feedback delay (FBD) and imperfect successive interference cancellation (SIC), where the base station communicates with multiple users by applying orthogonal space-time block coding (OSTBC) technique in order to exploit the benefits of transmit diversity. Outage probability (OP), ergodic capacity and fairness index analyses are conducted in case channels are subjected to Nakagami-m fading in order to illustrate the level of system performance, and closed-form mathematical expressions are obtained. Furthermore, to demonstrate the impact of CEE and FBD, asymptotic OP is also maintained. The analytical results validated by Monte Carlo simulations demonstrate that all performance metrics reach a non-zero fixed value in high signal-to-noise region due to the CEE and FBD while imperfect SIC worsens the performance of user with the lowest power allocation to the full outage. In addition, NOMA outperforms its counterpart orthogonal multiple access in terms of OP and ergodic capacity generally. Also, G
₂
-OSTBC code has higher fairness index than G
₃
-OSTBC code.