Forward error correction for radiobeacon broadcast of differentialGPS data

Marine radiobeacon networks are being used to broadcast differential Global Positioning System (DGPS) corrections to marine users. The correction data digitally modulate signals from some of the existing marine radiobeacons, which operate in the 285 to 325 kHz band, creating DGPS/radiobeacons. The corrections improve the accuracy of the GPS fix from 100 m to 5-10 m, and provide position fixing service for many marine applications which are too demanding for the normal GPS service. Forward error correction can be used to improve the reliability or range of the DGPS/radiobeacon signal. The improvements made possible by channel coding are analyzed, and a code for DGPS/radiobeacons is recommended