A Priority-Based CSMA/CA Protocol and Performance Analysis for AAV-Assisted WSNs

In unmanned aerial vehicle assisted wireless sensor networks (UAV-assisted WSNs), due to the mobility of UAV and the heterogeneity of ground nodes’ locations, the communication windows in which the ground nodes can communicate with UAV varies greatly. Unlike the existing carrier sense multiple access with collision avoidance (CSMA/CA) protocols, which often set a random or fixed back off value when channel access collisions occur, this paper takes communication requirements of the ground nodes at different locations into account, factors comprehensively the amount of data to be uploaded by ground nodes, UAV’s velocity, the communication window and the transmission rate between UAV and ground nodes, proposes a priority-based CSMA/CA protocol to allocate channel access and analyzes network performance. Firstly, a binary exponential back off rule based on priority in CSMA/CA protocol is designed for the contention stage. The communication window of the ground nodes in UAV’s transmission coverage is calculated. According to the communication window and the amount of data to be uploaded, the priority of ground nodes in the coverage is computed, then it is processed with previous samples as the normal distribution function and its cumulative distribution function is used to determine the initial back off value. Secondly, a two-dimensional Markov chain model is built to analyze the access process. A quitting probability is defined and one-step stationary transition probability is calculated. Then the saturation throughput of the network is derived. Simulation results verify that our proposal outperforms the compared schemes.