A Minimum Distance Criterion Based Constellation Design for Uplink NOMA

Motivated by the future scenarios of ultra- reliability and low latency communications (URLLC) and integrated access and backhaul (IAB) that are currently discussed in 3GPP, we propose a novel parallelogram-structured constellation design based on minimum distance (MD) criterion for powerdomain uplink NOMA system. In comparison with previous work, which maximizes MD of the superimposition of the usual constellations, such as QPSK and 16 QAM, by inter-constellation rotation, the incorporation of parallelogram- structure into the NOMA constellation design can achieve a much better MD. Since the proposed constellations can be parameterized as a function of the power ratio î±, the signaling overhead for a base station to designate the constellations to be used by each user equipment is minimized. Simulation results show that our proposed constellation design can further improve the symbol error rate, as well as the achievable rate, of the inter-constellation-rotated superposition of usual square constellations.