Optimization of Spectrum Use by Mode S Surveillance Systems Through Coordinated DAP Extraction

The cooperative surveillance systems used for air traffic management rely completely on air–ground transactions carried out in the 1030/1090 MHz frequency bands to fulfill their surveillance mission. However, these spectrum bands are currently subject to an excessive number of transactions that make difficult the access to the channels and often exceed the reply capabilities of aircraft transponders, which may impact air traffic capacity or even create safety risks. Several mitigation strategies have been studied in recent years to decrease the occupancy of the 1030/1090 MHz bands. Nevertheless, none of the proposed strategies have yet addressed the possibility of decreasing transactions related to downlinked aircraft parameters (DAP) extracted from transponder registers of aircraft. This work proposes and tests a methodology to coordinate the DAP extractions performed by several Mode S systems in order to avoid a high number of unnecessary transactions in the spectrum channels, while keeping the same level of information available at the endpoint of the surveillance chain.