Down-Link NOMA Networks in the Presence of IQI and Imperfect SIC: Receiver Design and Performance Analysis

This article addresses the practical aspects that may affect the performance of down-link non-orthogonal multiple access (NOMA) systems. The system performance of two down-link NOMA users, where both users suffer from the effects of in-phase/quadrature-phase imbalance (IQI), while the first user also experiences imperfect successive interference cancellation (SIC) is examined. In order to mitigate the effects of IQI, an optimal maximum likelihood (ML) receiver is designed and analyzed, and the performance of the proposed receiver is compared with the traditional ML one. Moreover, closed-form mathematical expressions of the conditional pairwise error probability (PEP) for each user are derived. The simulation results validate the analysis and demonstrate that the proposed receiver outperforms the traditional one, with the ability to reduce the effects of IQI for both users.