Low-Complexity Design of Unitary Constellations in Non-Coherent SIMO Systems for 5G NR URLLC Applications

In this paper, we propose a novel multi-symbol unitary constellation structure for non-coherent single-input multiple-output (SIMO) communications over block Rayleigh fading channels. To facilitate the design of large unitary constellations at reduced complexity, the proposed constellations are constructed as the Cartesian product of independent amplitude and phase-shift-keying (PSK) vectors. We exploit this structure to formulate an optimization problem to maximize the minimum distance, which has low complexity compared to optimal unitary constellations. Simulation results show that our proposed multi-symbol unitary constellation has higher minimum distance and better error performance than other low-complexity unitary constellations when using maximum likelihood (ML) detector.