Comparison of One-Shot and Handshaking Systems for MTC in 5G

Recently, machine type communications (MTC) has attracted attention to support massive connectivity for devices within a cellular system. Most existing schemes for MTC are based on a handshaking procedure that may cause a high access delay although the size of data packets is small. Thus, we can consider a one-shot or grant-free system of low signaling overhead for MTC. In the one-shot system, data and control signals can be transmitted without handshaking, and compressive sensing based multiuser detection (CS-MUD) is used at a receiver in order to recover multiple signals that are simultaneously transmitted from (unknown) devices. In this paper, we study the throughput and delay of a one-shot system as well as a handshaking system. We derive closed-form expressions for the throughput and delay when fast retrial is used for the retransmissions of collided packets (which can effectively shorten the access delay) under a high signal-to-noise ratio (SNR) environment. From the analysis and simulation results, we can see that the one-shot system performs better than the handshaking system for devices of short packets.