Exploiting Intentional Frequency Offset in NOMA-OFDM Systems: From Basic to Practical

This paper investigates an asynchronous non-orthogonal multiple access (NOMA) scheme that intentionally generates a frequency offset between users in the orthogonal frequency division multiplexing (OFDM) system. We begin by proposing frequency asynchronous NOMA (FA-NOMA) as a basic system. The characteristics and challenges of FA-NOMA are then described. However, the challenges hinder the utilization of FA-NOMA in a practical environment. To further improve and utilize FA-NOMA in practice, we propose a novel sub-band filtered FA-NOMA (SBFA-NOMA) system. We also provide a new transceiver to implement SBFA-NOMA. Simulation results show that the proposed system can achieve performance improvement via gains in received power and degrees of freedom (DoF) compared to the power-domain NOMA (P-NOMA) system.