1090 MHz channel capacity improvement in the Air traffic control context

This paper is focused on the 1090 MHz SSR channel capacity increase by innovative transmission and decoding techniques. A lot of Air traffic control systems use the 1090 MHz channel: SSR downlink (on-board transponders), ADS-B messages, TIS-B, FIS-B. We focus the attention on the MLAT (multilateration) system, useful to localize and identify transponder-equipped targets (aircraft and vehicles). Today multilateration receiver stations have omni-directional antennae, so considering the aircrafts traffic and including the extension of surveillance to cooperating vehicles, the reception of super-imposed signals is more and more probable especially in high traffic density airports. In this paper we show the problem mitigation introducing a technique proposed in the international patent , and the decoding techniques proposed in and. We analyze the channel capacity improvement, then exploit the detection and the TOA estimation of the frequency-shifted and separated signals, and finally the EUROCAE requirements compliance.