An Adaptive Backoff Algorithm with Time Constraint for Airborne Ad hoc Networks

A multi-priority adaptive backoff algorithm with tolerable time constraint is proposed to solve the problems that the traditional medium access control (MAC) backoff algorithms cannot meet the demands of high reliability and low latency for high priority traffic in airborne Ad hoc networks and their performances are poor under heavy load. This algorithm introduces the time constraint mechanism and adaptive contention window for each service through considering different QoS requirements for different services. The mechanism guarantees the transmission of high priority service by confining the access of the low priority service when the network is in heavy load. Moreover, the 3-D Markov chain is adopted to model the algorithm. The backoff state transfer probability of different services with time constraint conditions is obtained in various network loads, and the mathematical expressions of average throughput and average MAC delay are derived. Simulation results show that the proposed algorithm effectively guarantees the low latency (<2 ms) and high reliability (>99%) QoS demand for high priority in heavy loads, and comparisons with enhanced distributed channel access and priority adaptive backoff algorithms show that the throughput is improved by 33% and 21.5% when the load is greater than 9 000 packets/s, respectively. © 2018, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.