Time synchronization system and method for synchronizing locating units within a communication system using a known external signal

A controller for synchronizing locating units in a radio communication system, the controller comprising:

• a receiver configured to receive from two or more locating units respective measurements of a radio frequency (RF) signal and respective timestamps of said respective measurements, the RF signal being transmitted to the two or more locating units from a transmitter at a known geographical location, wherein each of said timestamps is recorded at substantially the same time of a respective local clock of said two or more locating units;
• and
• a processor operable to determine a measured time difference of arrival between said two or more locating units using said measurements and said respective timestamps, to compute a time synchronization error between said two or more locating units from a difference between said measured time difference of arrival and an expected time difference of arrival and to provide a respective time adjustment to each of said two or more locating units to offset said time synchronization error.