Spatial Filtering Based Random Access for Machine-Type Communications in Massive MIMO Cellular Networks

Machine-type communication (MTC) is one of the most important enabling technologies for the emerging Internet of Things (IoT). However, the potential massive access will significantly degrade the access performance of MTC. To meet the massive access requirement of MTC, we propose a spatial filtering based random access (SFRA) scheme in massive MIMO cellular networks. Specifically, the angle of arrival (AOA) information provided by massive MIMO is utilized to distinguish collided MTC devices (MTDs). To improve the preamble utilization as possible, we further propose a novel preamble reuse scheme to eliminate the influence of multipath angular spread on preamble detection at the base station (BS). Theoretical analysis and simulation results both show that the proposed SFRA scheme can efficiently reuse preambles and considerably improve the access capacity. In typical urban environments, preambles can be perfectly reused for 9 times at most. Moreover, the average access delay of SFRA is only about one seventh of that of the conventional random access scheme when 10000 MTDs attempt to access the network simultaneously.