QAM Division Based Space-Time Modulation for Two-User Uplink Massive MIMO Systems

A two-user uplink massive MIMO system is considered in this paper, where each user has a single antenna and the base station (BS) is equipped with a large number of antennas. It is assumed that the small scale channel fading is Rayleigh fading and the channel fading coefficients keep quasi-static in two consecutive slots, and then, change to other values independently in the next two slots. For such a massive MIMO uplink system, a QAM division based space-time modulation scheme is proposed to execute the simultaneous communication of the two users with the same frequency, and four detectors are given to adapt to different conditions. In addition, the channel coefficients can also be figured out after the signals are correctly detected. Computer simulations demonstrate that the proposed scheme performs well and need less than 100 BS antennas to make the average BER below 10(-3).