Secondary surveillance radar does not depend on tracked aircraft knowing their own position, though. ADS-B is an augmentation of that, which makes receivers si

Secondary surveillance radar does not depend on tracked aircraft knowing their own position, though. ADS-B is an augmentation of that, which makes receivers simpler, but ATC generally does not rely on it exclusively (except in some very remote regions), nor on any type of active/cooperative signal or response – if everything else fails (maliciously or accidentally), there's usually primary radar as well.