Energy and QoS-Aware Contention-Based Medium Access Control in Machine-Type Communications

Special characteristics of Machine-Type Communications (MTC) result in new challenges in 5G mobile networks including Medium Access Control (MAC) mechanisms. The traditional methods for contention-based MAC are unable to manage a massive number of simultaneous requests. On another side, recent methods for MTCs have not adequately attended to energy consumption of machines along with QoS. In this paper, a method for contention-based massive access protocol is presented based on p-persistent CSMA which considers both energy and delay requirement of machines, a multi-objective optimization problem is solved by BS at the beginning of each time frame in order to find the optimum value of transmission probability based on the number of machines and their distances from the BS. The optimization problem aims at achieving maximum energy efficiency and minimum access delay. To avoid the overhead of solving the optimization problem, the value of probability is temporarily updated by the machine at the end of each time slot, based on its delay requirement and the number of its recent access failures. The simulation results show a considerable increase in the number of successful transmissions, a decrease in access time and improvements in throughput and energy consumption.