OFDM Based Data Link for the DLR Research Aircraft ATRA

Kurzfassung

Currently, the ATRA (Advanced Technology Research Aircraft) is going into service as new flight test platform of the German Aerospace Center (DLR) based on an Airbus A320. One important requirement is to allow real time measurement data analysis at the ground. Thus, in 2008 the Institute of Communication and Navigation started the development of a new robust, high bandwidth data link, named Broadband Datalink Radio (B-DLR), used for the exchange of information between the flying aircraft and the base station. Due to the experience gathered in the development of a future L-band Digital Aeronautical System candidate (L-DACS1) [1], the new B-DLR data link is developed as a simplified version of L-DACS1. It also employs orthogonal frequency division multiplexing (OFDM), separating the reverse and forward link using frequency division duplex (FDD). Also channel coding and interleaving parameters are equivalent. Unlike L-DACS1, B-DLR has not to be designed as a multi-user system, since only transmissions between the aircraft and the base station have to be handled. Therefore, major simplifications in both the higher layers and the frame formats are possible. The development and employment of B-DLR serves two purposes: Firstly, it allows the exchange of measurement data between the ground station and the aircraft. Secondly, it serves as demonstrator for a (simplified) L-DACS1 system and demonstrates the advantages of OFDM in a real aeronautical environment. Both the generation and reception of the B-DLR signal is currently being implemented in FPGA technology. Only few higher layer procedures like the handling of retransmissions are performed in software. Within the final paper an overview over the B-DLR system is given. This will be followed by a detailed description of the hardware necessary for operation of the entire communication system. Within this section a special focus is laid upon issues regarding the implementation of the algorithms in FPGA technology as well as challenges concerning the RF frontend.