Towards A Data Link For Unmanned Aviation: DLR Flight Measurement Campaign for C2 Data Link Development

Unmanned Aircraft (UA) are expected to play a more and more important role in global aviation during the next years. Besides the "smart" onboard control equipment leading to a certain amount of autonomy of the vehicle, a reliable data link ("Command and Control", C2-link) is a key enabler to control UA in civil airspace. This C2 link is used to exchange information between the UA and the remote pilot, for example positioning information, telemetry data or flight trajectories, respectively. None of the currently available aeronautical communication standards can fulfil the requirements for such a multi-user, multi-point datalink in terms of reliability, flexibility, data integrity, robustness and latency. The German Aerospace Center (DLR) initiated the "C-Band Digital Aeronautical Communication System" (CDACS) project to develop a C-band data link for this purpose. Part of this project is a flight measurement campaign to evaluate initial CDACS waveform designs, besides performing radio channel measurements of the terrestrial ground-air channel in C-band. Detailed knowledge on the behavior of the physical communication channel is crucial for an optimal design of a new communication system. Therefore, it is necessary to perform C-band channel measurements (aka "channel sounding") and use the collected information to develop a channel model. In turn, this channel model can be used to optimize and evaluate the CDACS waveform design in simulations. The bandwidth used for the C-band channel measurements of this campaign was ~50MHz whereas the CDACS waveforms tested spanned a bandwidth of ~1.5MHz. Multiple flight routes and maneuvers are chosen to collect information on different flight scenarios, e.g. take-off and landing, hard banking and en-route.