Processing for mode s signals suffering multipath distortion

Abstract

A communication system for receiving aircraft reply squits (transmissions) normally used in a radar beacon system for surveilling aircraft in a given geographic area. The communication system includes a plurality of omnidirectional receivers, each receiver having a function of omnidirectionally receiving the aircraft squits and developing therefrom two types of information strings, namely a data string, indicative of a message in the aircraft squit, and a corresponding confidence string indicative of the reliability of the developed data string. A data communication link transmits the data and confidence strings between the plurality of omnidirectional receivers and the master data processor. The master data processor processes the data strings and corresponding confidence strings developed by each of the plurality of omnidirectional receivers by performing a bit-by-bit comparison of the received data strings and corresponding confidence strings, so as to develop by the comparison a corrected data string which minimizes the use of data bits from the data strings received over the data communication link that are indicated by the corresponding confidence strings as having a low reliability.