Improper Gaussian Signaling for Two-User MISO-NOMA Systems Considering Hardware Impairments and Imperfect SIC

In this paper, we study the advantages of improper Gaussian signaling (IGS) with existence hardware impairments (HWI) and imperfect successive interference cancellation (SIC) in downlink two-user power-domain non-orthogonal multiple access (PD-NOMA) systems. We first provide input-output relationships for MIMO system HWIs then derive rate expressions each user. The signals are assumed to be generated by widely linear precoding (WLP) transmitted under PD-NOMA scheme context SIC. To exhibit supremacy IGS, formulate two kinds optimization problems concerned max-min maximizing achievable sum (ASR) between users quality service (QoS) total power constraints (TPC). deal non-convex log-determinant objective functions, adopt concave quadratic programming (SCQP) obtain suboptimal results iterations. Simulation demonstrate that IGS cases outperform ZF precoders conventional proper (PGS) counterparts both ASR, particularly high I/Q imbalance (IQI) less efficient SIC scenarios. Besides, difference performance degradation is compared. Finally, briefly classify conditions where could preferable signal transmission.