Scalable hybrid MAC protocol for M2M communications

Machine-to-machine (M2M) communications is one of the enabling technologies for connecting massive number of devices to the Internet of Things (IoT). M2M communications have different characteristics than human-to-human (H2H) communications. In this work, we propose a scalable, hybrid MAC protocol that will satisfy quality-of-service (QoS) requirements of the users. The proposed MAC protocol organizes transmissions into frames. Each machine is assumed to generate probabilistically one or zero packet per frame. The model allows machines with different packet generation probabilities. This random packet generation enables modeling of both periodic and nonperiodic traffic. The generated traffic has been classified into different classes according to their packet loss tolerances. Each frame has been divided into a number of subframes each serving a class of traffic. Further, each subframe is divided into two subperiods one serving contention and the other reserved traffic of that class. We derived packet loss probability for each class of traffic. Then, we formulated a nonlinear optimization problem (NLP) that minimizes frame length subject to packet loss requirements of different classes. We compare the performance of the proposed protocol with other protocols proposed for M2M communications, which shows that it achieves better performance for small packet sizes.