Modulation Division based User Grouping Communication for Massive SIMO in IIoT

In this paper, a modulation division based user grouping communication scheme is proposed for massive single- input multiple-output (SIMO) in industrial Internet of Things (IIoT), in which the base station (BS) is equipped with a large number of antennas, and a number of single-antenna users use the same time-frequency source to transmit signals to the BS. Considering the limited pilot sequences, the users are divided into several groups, and orthogonal pilot sequences are arranged to different groups, while users in the same group reuse the same pilot sequence. Meanwhile, a sum-constellation is uniquely divided into a group of sub-constellations for the users in the same group, which constitute an additive uniquely decomposable constellation group design (AUDCG). At the BS, the sum signal is firstly detected for the whole group and then the signal of each user is determined using the AUDCG design. Subject to power constraints, the user grouping algorithm is investigated to improve the average signal detection performance of all the groups. Computer simulation results show that the proposed communication system and user grouping algorithm achieve good performance.