Low-overhead Multi-antenna-enabled Random Access for Machine-type Communications with Low Mobility

A pseudo-random beamforming (PRBF) based random access (RA) system is proposed to enable uplink (UL) machine-type communications (MTC) with ultra low signaling overheads. Specifically, a pseudo random (PR) sequence is used as public information to coordinate the beamforming vectors used at the base station (BS) and the devices. Within the coherence time window, each device distributively determines in advance the "good" time slots and receiving beams for transmission. This UL protocol reduces the overheads due to the feedback of channel state information and the control signals for centralized scheduling. This paper derives the throughput and user scaling of the proposed M-PRBF-CA protocol for achieving spatial multiplexing gain, under both an i.i.d. slow fading channel and a correlated slow fading channel. Our simulation results confirm the analysis in both fading channel models.