8-QAM Division for Uplink Massive SIMO Systems

In this letter, we consider an ultra-reliable low-latency communication (URLLC) scheme for one uplink massive single-input multiple-output (SIMO) system with three users. In our design, to enable all the users to update status information to the base station (BS) concurrently with an extremely low latency, we specifically decompose a cross 8-QAM constellation into one additive uniquely decomposable constellation group (AUDCG), and then devise a new multiuser space-time modulation scheme at the transmitters accordingly. For the receiver side, to assure that the BS can detect all the transmitted signals of different users simultaneously with a high reliability and a low latency, we investigate a noncoherent maximum likelihood (ML) receiver in comparison to a minimum Riemannian distance (MRD) estimator and a minimum Euclidean distance (MED) detector when the antenna array size is scaled up. Finally, extensive computer simulations are carried out to validate the effectiveness of our proposed design when the antenna array size is large.