GPS synchronized wide area multilateration system

This paper discusses a Global Position System (GPS) synchronized wide area multilateration (WAM) system for air traffic management. The system takes advantage of Secondary surveillance radar (SSR) downlink mode S/A/C signals on 1090MHz channel, determines the position of airplane passively by TDOA (Time Differential of Arrival) hyperbolic position method. Also this system has ADS-B (Auto-Dependent Surveillance-Broadcast) capability to position those airplanes with onboard ADS-B transponders, and the experimental results of WAM and ADS-B are discussed.