Hybrid MAC Protocol for UAV-Assisted Data Gathering in a Wireless Sensor Network

Abstract

A wireless sensor network (WSN) that deploys an unmanned aerial vehicle (UAV) for the data gathering process differs from the common WSN system. In a UAV-WSN, the sensor nodes have a limited time to communicate with the UAV. Thus, the sensor nodes have to contend with each other to transmit their data to the UAV within a short amount of time. The fairness among the contended nodes is degraded, which affects the network performance in terms of throughput and packet delivery ratio (PDR). To overcome this issue, an effective protocol that can maintain or increase fairness among nodes is needed. This paper proposes a novel protocol named HP-MAC which is a hybrid medium access control (MAC) protocol for data gathering in a UAV-WSN. This proposed scheme works by setting the UAV to periodically send a beacon frame to sensor nodes in order to inform its presence, then each sensor node that receives the beacon frame contends to send a registration frame to the UAV. A second beacon frame then transmitted by the UAV to the registered nodes regarding their transmission schedule. HP-MAC uses CSMA/CA during the registration process of the sensor nodes and allocates the registered sensor nodes time slots in the data gathering process. The time-slot scheme is used to determine the transmission schedule of each sensor based on their priority during the registration process. The results show that the proposed MAC protocol achieved fairness while enhancing network performance in terms of PDR and throughput.