Asymptotic throughput analysis of massive M2M access

5G systems are expected to be able to handle channel access from a massive number of low cost machine-type devices (MTDs), requiring intermittent connectivity to a network. Ideally, these devices should be able to transmit their short message either immediately without prior connection establishment (random access) or with a lightweight connection establishment (access reservation). In this paper, we analyze the capacity of a system where a large number of devices transmit simultaneously to a single receiver, capable of performing multiple packet reception (MPR) by means of advanced decoding techniques, such as successive interference cancellation (SIC). We derive a simplified mathematical model that allows us to determine the average number of signals that can be successfully decoded by the receiver as a function of the number of overlapping transmissions and the MPR capabilities of the system. We observe that, according to our analysis, a receiver capable of performing perfect SIC and MPR can theoretically decode an arbitrarily large number of simultaneous transmissions by proportionally reducing the per-user data rate, in such a way that the aggregate system capacity remains almost constant.