Abstract: There is provided systems and methods for mitigating interference from an interference signal. In one implementation the system comprises cancellation circuitry configured to: receive a first signal from a first antenna, the first signal comprising an interference component deriving from the interference signal and a desired component deriving from a desired signal; and receive a second signal comprising an interference component deriving from the interference signal and received at one or more of a different antenna or a different frequency to the first signal. The interference component in the second signal is stronger than that the interference component in the first signal. The cancellation circuitry is further configured to derive a cancellation signal from the second signal; generate an output signal by subtracting the cancellation signal from the input signal to substantially remove the interference component from the first signal; and output the output signal.

Abstract: There is provided systems and methods for mitigating interference from an interference signal. In one implementation the system comprises cancellation circuitry configured to: receive a first signal from a first antenna, the first signal comprising an interference component deriving from the interference signal and a desired component deriving from a desired signal; and receive a second signal comprising an interference component deriving from the interference signal and received at one or more of a different antenna or a different frequency to the first signal. The interference component in the second signal is stronger than that the interference component in the first signal. The cancellation circuitry is further configured to derive a cancellation signal from the second signal; generate an output signal by subtracting the cancellation signal from the input signal to substantially remove the interference component from the first signal; and output the output signal.

Abstract: Doppler-shift correction information broadcast in a satellite mobile telephone system is produced on the assumption that mobile stations (4a, 4b) are stationary or moving slowly. Consequently, a mobile station (4a, 4b) moving at high-speed cannot correct properly for Doppler shift. In order to solve this problem, provision is made for the mobile station (4a, 4b) to know its own position and velocity, as well as that of a satellite (3a, 3b), so that it can tune its transmitter to mimic, from the perspective of the satellite (3a, 3b), a stationary or slowly moving mobile station (4a, 4b).

Abstract: A multi user communications terminal apparatus providing simultaneous access for a plurality of users to a communications network in which the geographical locations of each user are registered and periodically updated, the terminal apparatus comprising a plurality of user terminals (320) each including electroacoustic transducers (34,36); and a common RF unit (304) comprising a shared RF amplifier (342) for coupling to a shared antenna system (302), in which the terminal apparatus comprises means (348) for transmitting common location updating signals, and is arranged not to transmit separate location update signals for every one of said users.

Abstract: In a satellite communication system where user terminals 11 communicate via satellites 9A-E with earth stations 7A-E to join with a terrestrial telephone network 1, a controller 18 at a master earth station 7A monitors all earth stations 7A-E for a request for service received from a user terminal 11, then calculates which earth station 7A-E is best placed to service the request and instructs the best placed earth station 7B to service the request. In servicing the request, the best placed earth station 7B uses that earth station 5C whereat the user terminal 11 is registered as a visitor as the gateway into the terrestrial system 1 by routing all voice grade messages thereto and therefrom via a voice link 21. If the user terminal 11 is not registered at any earth station 7A-E, the best placed earth station becomes the earth station of registration and acts as a gateway.

Abstract: In a satellite communication system, a user terminal (11) seeks response from a selected earth station (7A-E) for a request for service based analysing the signal quality of broadcasts from earth stations (7A-E). Whichever earth station (7A-E) responds calculates which earth station (7A-E) can best meet the request for service. If it is another earth station (7A-E), the user terminal (11) is intructed to redirect the request for service thereto and, once in contact, the user terminal (11) addresses all new requests directly thereto, until the best earth station (7A-E) calculates that there is a better earth station (7A-E), and instructs the user terminal (11) to address all future requests for service thereto.

Abstract: 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 centers 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.