A Robust OFDM IM-QAM NOMA Scheme for URLLC and eMBB Downlink Service Coexistence
preprintposted on 2022-05-17, 18:28 authored by Athanasios IossifidesAthanasios Iossifides, Athanasios LioumpasAthanasios Lioumpas, Traianos Yioultsis
This work introduces a non-orthogonal multiple access (NOMA) downlink scheme, reinforced by a simple multiplexing technique of index modulation (IM) and quadrature amplitude modulation (QAM) signals, tailored to minimize their mutual interference. Integrated with orthogonal frequency division multiplexing (OFDM), this scheme achieves low bit error probability for the IM signal, at the cost of lower information rate, while practically affecting the performance of the QAM signal only due to power sharing. These characteristics, along with the provided wide range of power allocation possibilities, facilitate favorable user pairing strategies, which can be efficiently applied to multiplexing low-rate ultra-reliable low-latency communication (URLLC) and enhanced mobile broadband (eMBB) services, conveyed by the IM, and QAM signals, respectively. Aiming at providing a proof of concept of the proposed scheme, the bit error probability of both signals, the rate reduction of the eMBB service under a power constraint, and the excess power required for the URLLC service, on top of the eMBB service, are quantified and analyzed, over diversity Rayleigh fading channels, with conventional, low complexity detection. Overall, the results show that the proposed scheme provides a robust solution for URLLC and eMBB downlink service coexistence for 5G communications and beyond.