Communications apparatus and method

Abstract

A mobile satellite communications system having at least one mobile terminal (2), at least one ground station (6), at least one relay satellite (4) interconnecting said user terminal (2) and said ground station (6), and a management store (48) associated with said ground station (6), in which the user terminal (2) is configured to initiate registration signalling with said store (48). The user terminal (2) initiates registration signalling when reception conditions relating to a downlink channel relayed via said satellite (4) become unsatisfactory over a given time greater than a predetermined minimum value and then return to a satisfactory condition. Specifically, signals received in a given channel are monitored in relation to predetermined criteria, and the duration of periods when the monitored signals do not meet the criteria are timed. Signals for updating the location of the user terminal registered in the management store, are transmitted when said monitored signals in said channel again meet said criteria, only if the timed duration for which the monitored signals do not meet the criteria, is not less than a predetermined time (T2).

Dependencies are inferred from the claim text.