Communication Characterization for a ZigBee Based Airborne Wireless Sensor Network

Abstract

This paper presents an experimental characterization of communications in a wireless sensor network of micro aerial vehicles. The experiment uses two ground stations and several 32 inch unmanned aerial vehicles. Each unmanned aerial vehicle is equipped with a IEEE 802.15.4 ZigBee radio operating in the 2.4 GHz band. Data packets contain information about the state of the unmanned aerial vehicle, including but not limited to, position and velocity information. The radios in the vehicles broadcast their data packets and listen for data transmitted by other vehicles. The ground stations simply receive data and do not transmit any data. The ground stations are positioned in such a way that when a vehicle goes out of range of one ground station, it gets within range of the other. Using two ground stations at opposite ends of the testing arena prevents blind spots in the collection of data from the unmanned aerial vehicles. The results from this experiment is used to build a wireless sensor network of unmanned aerial vehicles. I. Introduction Unmanned aerial vehicles (UAVs) have shown great promise in the field of mobile sensor networking. A team of UAVs can be quickly and easily deployed in areas that are relatively inaccessible from the ground. The potential applications include diverse operations ranging from atmospheric research to Reconnaissance Surveillance and Target Acquisition (RSTA). Based on the nature of their application, UAVs vary greatly in their weight and size. Large UAVs are capable of carrying very powerful computing, communication, and sensing resources on-board with them. However, they are heavy and pose a danger to life and property in case of a failure. Moreover, they are expensive and cost of failure is extremely high. Small bird-sized UAVs, on the other hand, are light-weight and expendable. Bird-sized UAVs are fast gaining popularity because of their low cost and ease of production. They pose little or no threat to people or property on the ground and may be reused for several different applications, including but not limited to remote sensing 1 , plume detection 2 , wind speed measurements 3 , surveillance and target detection 4 , communication relay and rural search operations. Owing to their low cost, several small sized UAVs may also be used to operate as a team to accomplish a given objective. A team of these vehicles can be programmed to perform various tasks based on cooperative control algorithms. In order to cooperate with each other, the vehicles need to have a reliable system of communication, with high performance air-to-air and air-to-ground links. The efficacy of the cooperative algorithms depend directly on the reliability of the communication system. It becomes important to characterize the communication for such a system of vehicles. In this paper, we use a team of five delta-wing UAVs and two ground stations to perform a series of experiments designed to determine the range and the performance for the air-to-air and air-to-ground communication. The small size of these vehicles and their low payload capacity, impose practical constraints on the available battery power