Adaptive FRESH filter with vicarious reference for interference rejection: An application to signal detection in NOMA system

Abstract

AbstractAdaptive frequency shift (FRESH) filter is one of the most suggested methods for interference rejection. This filter extracts the desired cyclostationary signal by exploiting its spectral correlation through the adaptive periodically time‐varying filters. The reference signal in this filter has an essential role in the quality of the desired signal estimation. In this article, a vicarious signal is generated as a reference of an adaptive FRESH structure. Using the cyclostationary characteristics of the desired signal (eg, modulation, cyclic frequencies, etc.), the generated signal exhibits all feasible cyclostationary behaviors of the desired signal. The overall system significantly improves the performance of the FRESH filter. The advantage of using the vicarious signal is demonstrated with theoretical analysis. Furthermore, a multistage form of the proposed method is designed for severe noise and interference conditions. The method is used for signal detection in non‐orthogonal multiple access (NOMA) system. Simulation results validate its efficiency in this case and in different interference scenarios which include pulse chirp radar signal, orthogonal frequency division multiplexing (OFDM), and quadrature amplitude modulation (QAM).