Access to a satellite communication system by measuring the quality of transmitted signals

摘要

A satellite communications system comprises satellites 9A-C, earth stations 7A-E, user terminals 11 and controlling gateways 3 in the form of mobile satellite switching centres 5A-E. Access to and from a user terminal 11 may be gained from and to a terrestrial telephone system 1 by earth stations 7A-E contacting the satellites 9A-C and by the satellites contacting the user terminals 11. The satellites 9A-C periodically broadcast messages indicative of the earth station 7A-E with which they are instantly in contact. The user terminal 11 listens to these broadcasts, assesses the quality of the received signal, and keeps a league table based on an accumulated score allocated to each earth station 7A-E which can be heard. When calling into the system, the user terminal pages earth stations in descending order of score in the league table. When in contact, the user terminal 11 sends the league table to the system. When subsequently trying to contact the user terminal 11, the system uses earth stations in descending order of score in the league table, last received from the user terminal.