Towards optical wireless communications between micro unmanned aerial and ground systems

A group of unmanned vehicles can provide essential support to human task forces in a variety of missions, like in search and rescue operations. A crucial factor for task coordination is to maintain a reliable connectivity among the autonomous platforms. Radio-frequency is the common technology adopted for unmanned systems to operate wirelessly. However, this technology has some limitations that can be mitigated by complementing it with optical wireless communications. In this paper, we propose the implementation of an optical wireless link between micro-scale unmanned systems: an aerial vehicle and a ground mobile robot. We describe a line-of-sight directed optical link between these platforms where the flying vehicle carries an optical transmitter while the mobile ground robot is equipped with an optical receiver. This light-based communication link requires to keep an adequate relative transmitter-receiver position to enhance the transmission rate. Therefore, we define a connectivity cone on top of the receiver such that if the transmitter stays inside of this cone a minimum bit rate can be guaranteed. Also, we propose a control algorithm for the aerial transmitter to get and stay within the connectivity cone. The performance of the control algorithm is demonstrated through numerical simulations.