Compressive Sensing-Based Random Access with Multiple-Sequence Spreading for MTC

In this paper, we present a new structure for compressive sensing(CS)-based random access (RA) scheme for machine-type communications (MTC). In the proposed scheme, we consider a one-shot transmission in which users transmit their packets right away by spreading them with multiple spreading sequences (MS) over a frame without waiting for scheduling grant from the base station. The scheme is designed for delayconstrained & sporadic traffic where a massive number of users have a very low activity factor, small packet sizes and limited power. It has been shown that by employing the proposed scheme the channel access success rate can be increased without incurring additional detection complexity. In different regions of users´ activity factor, two sources of random access failure have been identified. In the design of the MS scheme, the tradeoff between these two factors can be considered to optimize the system. For strictly delay-intolerant applications where retransmission is not allowed, it is shown that about 10 times more users can be supported by employing MS in comparison with a type of random access in long term evolution (LTE) network.