Low/medium Earth orbit satellite constellations are expected to play a key role in any future global mobile communications system. Mobility management is examined for these constellations. When an advanced terrestrial type of approach is taken in examining user mobility, a location instability (or flip-flop) is found to occur. It is seen to result in a large signalling overhead. Two new approaches, both based on a similar idea, are proposed which significantly reduce the signalling overhead for such constellations. Rather than associating a mobile terminal with an exact location, the new approach is to associate it, through a single Earth station, which may or may not have an associated team of Earth stations, with what may loosely be described as a location area. Through this association the network can contact the terminal if required to do so. A slight average increase in call set-up time is the cost of the reduction in system signalling. The use of this new protocol for network mobility management results in an important increase in network efficiency for certain constellation types.
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