Degarbling Technique for Low Cost ADS-B Receivers

One of the most important parts of the present and future Air Traffic Control system is the Automatic Dependent Surveillance-Broadcast (ADS-B) system [1] [2]; in this system aircraft transmit (with a given periodicity) their position, velocity and identity to equipped aircraft or ground station for surveillance purposes [3]. The on-board navigation system, mainly based on the GPS unit, is used to calculate these information and the Secondary Surveillance Radar transponder is used to broadcast messages containing these information on the common RF channel. Receiving these messages the ATC centres are able to have a traffic awareness. An important limitation of this protocol is that the throughput is limited by a particular interfering problem: the garbling effect (that is the reception of superimposed signals coming from different aircraft). A method to reduce this effect is proposed in this work. The method exploits a multichannel receiver and the Principal Component Analysis and is suitable for implementation in low cost Software Defined Radio. It is also evaluated using real signals varying the Hardware parameters (such as Band, ADC characteristics and Oscillator stability) to identify which Hardware can be adopted for its implementation.