Multiple Access Communications for Age Minimization in UAV Aided Data Collection

Data collection with unmanned aerial vehicles (UAVs) is a novel technology with many practical applications. In this paper, UAV aided data collection in sensor networks for time-critical applications is considered. Maximum age of information (AoI) is used as the performance metric, where both communication time and flight time contribute to AoI. Given that sensors form groups of two, the UAV aims to visit each line segment formed by the two sensors in each group once and to return to the data center. To minimize the maximum AoI, two trajectory design algorithms are proposed. In both algorithms, the UAV communicates with the sensors in each group through a multiple access channel. In the first algorithm, the UAV hovers on the communication time optimal point on the line segment. In the second algorithm, it hovers on the path-length optimal point. The algorithms are compared with time sharing schemes, and also with the case when all sensors are visited individually. The results reveal that multiple access transmission is optimal, when sensors are not too far apart and packet lengths are long, whereas path-length optimal trajectory is better when packet lengths are short.