Alcatel Espace

Thomson-csf

Yannick Tanguy

Denis Rouffet

Frederic Berthault

Michel Mazzella

Jose Robineau

In a method of handing off traffic in a low orbit satellite communication system serving terminals, a terminal being connected to a terrestrial communication network by means of a connection station, handing off of the satellite-terminal and satellite-connection station links is possible only within a particular area. The decision to hand off the traffic is based on deterioration of the quality of service and of the radio environment for a group of terminals of said area. The system for implementing this method includes transmit/receive terminals and terrestrial connection stations.

Method of handing off traffic in a low orbit satellite communication

The present invention relates to a communications system between low-orbit satellites and terminals, in which the beams (12) of each service area (14) are illuminated according to a beam-hopping spatial scanning. For each satellite and for each terminal transmission and reception are separated in time and synchronized. Time-division duplex is used. Applicable especially to the field of space telecommunications.

Low-orbit satellite communications system for terminals

The disclosed method consists in sampling the phase of the detected modulated signal, inside each symbol T period, with a comb of sampling pulses obtained from N clock pulses evenly spaced out by a time interval equal to T/N; computing the differential phase angle d.phi. between symbols for each phase sample of the detected current symbol, encoding each differential phase angle d.phi. in assigning it an encoding cost, computing the sums of the encoding costs for the samples of the same order belonging to a determined number L of consecutive symbols; memorizing, among the N sums obtained, that sum which gives the greatest result, taking, as a symbols synchronizing clock, that clock which, in the comb of pulses, has the same order as the order of the sample which have lead to the greatest sum and decoding the differential phase angle having the same order as the memorized sample.

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Paris, France

Yannick Tanguy