Modeling and evaluation of enhanced reception techniques for ADS-B signals in high interference environments

The RTCA (Radio Technical Commission for Aeronautics) DO-260B document has stimulated in latest years the adoption of novel algorithms to improve the ability of receivers to detect and decode ADS-B (Automatic Dependent Surveillance-Broadcast) signals, with particular emphasis on preamble detection, declaration of bit state and confidence level, detection and correction of errors. Motivated by an industry-driven research project, this paper reports on performance analysis of a set of enhanced techniques that we have implemented for detection and decoding of ADS-B signals transmitted at 1090 MHz carrier frequency also in high interference conditions. An extensive set of results has been derived through a specifically developed simulation environment, able to closely model a wide range of operational scenarios by generating ADS-B frames and Mode A/C interfering signals. The simulation environment also includes an implementation of two RF (Radio Frequency) receiver chains that refer to a linear amplifier and a logarithmic amplifier, respectively. The investigations are mainly focused on evaluating the impact of the interference generated by Mode A/C replies on preamble detection and data decoding for ADS-B signals. In this regard, the ability of enhanced reception techniques to improve detection performance is assessed. Numerical results obtained from extensive simulation runs are reported and commented. They actually demonstrate that enhanced techniques are essential to guarantee adequate detection performance in the harsh environments envisaged by increased intensity of air traffic and the extensive use of ADS-B for traffic control.