Multiple unmanned aerial vehicles (UAVs) with inter-UAV communication capabilities can be used to extend the communication range with the ground control station (GCS). Researchers from the Mechanical and Electrical Engineering at the University of Ottawa have developed a new dirigible autonomous UAV with a flight duration of 24+ hrs, a limitied payload of 1 kg for electronics, and requiring a communication range of 1–10 kilometres. To support this requirement a new communication framework was introduced and implemented based on the ad hoc network concepts. With one radio module per dirigible the designed and developed wireless interface allows any UAV or the GCS to exchange flight control commands, telemetry data, and aerial photos. We made use of the advanced networking tools of the Digi's 9XTend™ radio modules to develop route tracing, traffic prioritization, and minimizing self-interference between simultaneous transmissions. Initial test results showed that without any data flow control in the network, packets can be received in the wrong order following different routes and cause errors in the transmission of photos or recorded video. This issue was resolved through acknowledgements to control the flow of packets. Using radios with half-wavelength dipole antennas we were able to achieve a one-hop range of up to 5 km with the radio-frequency line-of-sight.
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