Patent ID: 6122507
Filing Date: 2000-09-19
Classification: H04B

Abstract:
A method of handing over calls of predetermined users in a cellular telecommunications system using a constellation of non-geostationary satellites and satellite-fixed cells, said cells with which call channels are respectively associated, having predetermined respective contours and moving relative to the surface of the Earth in a predetermined direction, the speed of predetermined users relative to the surface of the Earth being negligible in comparison to the speed of travel of the cells, the predetermined users having locations known at the time of each call set-up request emitted by predetermined user's terminals,said method including, for a given user among said predetermined users, after a call set-up request emitted by the terminal of said given user and for each cell of a predetermined group of adjacent cells to which said given user may be successively allocated, said given user being in a first cell of the predetermined group at the time of the call set-up request:first steps wherein, if a first distance between said given user and a predetermined handover point into said each cell at the time of said call set-up request is greater than a predetermined distance equal to a maximal length of said each cell parallel to said predetermined direction, a reservation of a call channel associated with said each cell is requested for the terminal if said given user's terminal is substantially at said predetermined distance from said predetermined handover point, said first distance being zero if said each cell is said first cell of said predetermined group,second steps in which, if said first distance is less than said predetermined distance, (a) if there is a free communication channel associated with said each cell, said free communication channel is reserved for said given user's terminal, (b) if said each cell is not said first cell and if no channel associated with said each cell is free but if among the latter there is an unreserved channel occupied by the terminal of any user of said telecommunications system situated at a distance from the contour of said each cell in a direction opposite to said predetermined direction less than said first distance, then said occupied unreserved channel is reserved for said given user's terminal, (c) otherwise, said call set-up request is refused, andthird steps in which said call set-up request is refused if a number of predetermined users communicating and included in an area obtained by translation of said each cell in said predetermined direction by a distance between said first distance and a second distance is at least equal to a communication channel capacity of said each cell, said second distance at the time of the call set-up request extending between said given user and a predetermined transfer point of said given user into an allocation cell succeeding said each cell.