Representation of ICI as AWGN in PD-NOMA System Model

Power Domain Non-Orthogonal Multiple Access (PD-NOMA) is recognized as one of the most promising technologies for next-generation multiple access in future wireless networks. Such multiplexing leads to the controlled inter-channel interference (ICI) cancelled at the receiver. In reality, ICI is represented as quadrature amplitude modulated (QAM) symbols (or other modulation). However, the vast majority of research papers use signal models in which ICI is represented as the additive white Gaussian noise (AWGN) with the equivalent power. Yet, such a replacement is not fully equivalent, because it reduces the accuracy of signal decoding. This is a significant simplification of the system model, which results in an additional inaccuracy in obtaining a number of system characteristics. This paper presents an approach that allows solving this problem and representing ICI as AWGN by means of a coefficient without increasing the decoding error. It also describes an expression for calculating the coefficient obtained and its performance confirmed by simulation results.