A novel hybrid medium access control protocol for inter-M2M communications

A scalable medium access control (MAC) protocol is crucial for machine-type devices to access the channel simultaneously in a machine-to-machine (M2M) network. There can be two types of scenarios in an M2M network. First, where the M2M devices communicate with the base station one-by-one, and second, where the M2M devices directly communicate with each other within a group or cluster without any human intervention (Inter-M2M communication). Considering the second type of scenario, the devices can use basic contention or reservation-based MAC protocols. But with such a large number of M2M devices, adaptability, and scalability become bottlenecks. Therefore, in this paper, we propose a novel scalable hybrid-MAC protocol, which combines the benefits of both contention-based and reservation-based medium access schemes. We assume that the contention and reservation portion of M2M devices is a frame structure, which mainly has two parts: contention interval (CI) and data transmission interval (DTI). The devices contend for the channel access during CI. After contention, the successful devices win time-slots and transmit data packets during DTI. In our proposed hybrid-MAC scheme, each M2M device is IEEE 802.11 DCF enabled, and within each time slot during DTI, the devices share data with each other. The analytical and simulation results show that the proposed hybrid-MAC protocol performs better than slotted-ALOHA, p-persistent CSMA, and TDMA in terms of aggregate throughput, average transmission delay, channel utility, and energy consumption.