Ergodic Capacity Analysis of Downlink NOMA Systems Over $\kappa-\mu$ Shadowed Fading Channels

In this research paper, we analyze the performance of two downlink NOMA systems with imperfect successive interference cancellation (SIC) over
$\kappa-\mu$
shadowed fading channels with the
$\kappa-\mu$
distribution. Our focus is on evaluating the ergodic capacity (EC) of a downlink NOMA system while taking into account imperfect SIC at the near user. First, we obtain the statistical characterization of the instantaneous signal-to-noise plus interference ratios (SINRs) for both users by applying the Gamma approximation and considering the imperfect SIC at the near user from the base station of the NOMA system over
$\kappa-\mu$
fading channels. Using the derived expressions of the distributions of these SINRs, we derive the exact closed-form expressions of the ECs of both users. We also obtain the ergodic sum capacity (ESC) of the NOMA system with imperfect SIC at the near user. We investigate the impact of different channel conditions of the
$\kappa- \mu$
fading channels on EC performance of the system. We also analyze the impact of imperfect SIC on the ergodic capacity performance of the system and observe that EC performance improves by decreasing the level of SIC error. Finally, we validate our analysis through numerical and simulation results.