Low complexity successive interference cancellation receiver for DCT-NOMA-OFDM system with CFO

Abstract

The integration of orthogonal frequency division multiplexing (OFDM) with non-orthogonal multiple access (NOMA) for multiplexing of multiple users has been previously studied for the 5G and beyond networks. It has been used to fulfill the demand for high spectral and energy efficiency, massive connectivity, and ultra-low latency with user fairness. However, with higher mobility, the residual interference power remaining after the Successive interference cancellation (SIC) and equalization process significantly deteriorates the system’s symbol error rate (SER) performance. This paper considers a downlink discrete cosine transform (DCT) based NOMA-OFDM system with equalization and interference-compensation jointly in the fractional Fourier domain (FFD). The traditional full matrix compensation strategy attracts a lot of complexity. So, the proposed system architecture considers a low complexity banded joint equalization and interference-compensation (JEIC) method for each user equipment (UE). With the help of the proposed architecture, an SNR gain of 3 dB in the case of UE-2 and 8 dB in the case of UE-1 has been achieved over the conventional system in the presence of normalized carrier frequency offset (ϵ) = 0.05 at BER =10−3. Further, in the presence of ϵ= 0.1, the UE-2 with the proposed architecture gains 5 dB over the conventional system at 1×10−3 SNR range. The proposed architecture brings the performance of the system similar to the interference-free system with reduced complexity in O(N) compared to the full matrix compensation scheme having O(N3) complexity.