Efficient and Robust Data Link for Wireless Aeronautical Communications

The work

Where it appeared

Abstract

According to recent studies, there will be a heavily increasing number of Unmanned Aerial Vehicles (UAVs) in the near future, whereby the majority of all unmanned aircraft is expected to be of medium and small sizes. In order to allow a safe and secure operation of these UAVs, possibly in non-segregated airspace, a strong demand and an essential prerequisite is to find a suitable Control and Non-Payload Communication (CNPC) solution. Hence, the goal of this thesis is the development and the prototype presentation of an innovative data link concept with an unprecedented combination of requirements, targeting the operation of such size-, weightand power-restricted platforms. On the one hand, link robustness and reliability were driving factors. On the other hand, for several efficiency reasons, serious efforts were made to simplify the algorithms and their implementation as much as possible without adversely affecting demodulation and synchronization performances. To achieve these objectives, a holistic approach was chosen, starting with a channel analysis in C-band using self-built sounding equipment. For this purpose, one ground and one flight measurement campaign were performed at and around the airport of Ingolstadt/Manching to characterize UAV-typical scenarios with respect to their radio propagation properties. Then, MIMO enhancements are discussed for non- and lowscattering aircraft-to-aircraft and aircraft-to-ground conditions. After motivating the selection of the most suitable binary single carrier waveform Shaped Offset QPSK and the presentation of its novel non-binary extension with improved spectral efficiency, the focus of the remaining part of the thesis is on the design of highly efficient frame, frequency, phase and timing synchronization algorithms and their low-complexity Software Defined Radio (SDR) implementations with the target to boost hardware and energy efficiencies while maintaining close-to-optimum performance. As a proof-of-concept, a fully functional communication system demonstrator, based on flight-proven hardware, is presented. The FPGA implementation of its baseband signal processing part reveals superior hardware efficiencies and improved functionality compared with literature results. Despite their computational simplicity, the implementations of the newly derived synchronization mechanisms have shown competitive correction performances, even for the harsh conditions of aircraft-to-ground communication. With the presented demonstrator evaluations, a verification of its robustness (in terms of resilience to real UAV operation related channel conditions) and its efficiency (spectrum, energy and hardware efficiency) is given.