System and method for managing multiple transmission resources of a spatial multi-cell radio-communication system

Abstract

A satellite cellular radio-communication system using beam formation is provided. The satellite cellular radio-communication system includes a satellite, at least one satellite access station, terminals, at least one control unit of a virtual cell. A terminal is configured to transmit and receive on a transmission channel having at least two frequency and spatial transmission resources of a same virtual cell that are different by their frequency band, a frequency and spatial transmission resource being a sub-band of a frequency band used in a beam, the frequency band being taken from among a predetermined number of frequency bands and having been allocated to said beam according to a reuse function. A method for changing transmission resources within a same virtual cell during a communication of a terminal and a method for changing transmission resources with switching from a first virtual cell to a second virtual cell during switching of a terminal in a satellite cellular radio-communications are also provided.

What is claimed is: 
     
         1 . A method for changing transmission resources within a same virtual cell during a communication of a terminal in a satellite cellular radio-communications system comprising a transparent communication satellite, serving as a relay, placed in a geostationary orbit or a highly inclined elliptical orbit, at least one satellite access station, transmitting and receiving, configured to transmit and receive service and signal messages to and from the satellite on a first bidirectional wireless way, a set of user terminals configured to receive and transmit the service and signal messages from and to the satellite on a second bidirectional wireless way, the second bidirectional wireless way being made up of a second outbound downlink and a second inbound uplink and at least one control unit of a virtual cell connected to one or more satellite access stations, a virtual cell being a set of frequency and spatial transmission resources, the method comprising the steps of:
 performing a wide band measurement of the transmission quality of each sub-band of the virtual cell, the terminal previously attached to a virtual cell having a first list of frequency sub-bands used in the virtual cell;   sending, from the terminal to the control unit of the virtual cell, through a first channel using one or more sub-bands of the virtual cell, a first message containing information representative of the quality of each sub-band administered by the control unit of the virtual cell;   using the control unit to determine, from the quality information of the sub-bands of the current virtual cell and a second list of free channels of the virtual cell, the transmission parameters of a second channel comprising one or more sub-bands that corresponds to wireless reception conditions that are more favorable than those of the first channel, when such a second channel exists;   when a second channel exists, using the control unit to reserve the one or more sub-bands of the second channel, and to prepare and send a second message to the terminal containing identification information of the one or more new sub-bands of the second transmission channel, and an order to switch from the first channel to the second channel; and   after receiving and decoding the second message, using the terminal to execute the order to switch from the first channel to the second channel and to send the satellite any new message using the one or more reserved sub-bands used by the second channel.   
     
     
         2 . A method for changing transmission resources with switching from a first virtual cell to a second virtual cell during switching of a terminal in a satellite cellular radio-communications system comprising a transparent communication satellite, serving as a relay, placed in a geostationary orbit or a highly inclined elliptical orbit, at least one satellite access station, transmitting and receiving, configured to transmit and receive service and signal messages to and from the satellite on a first bidirectional wireless way, a set of user terminals configured to receive and transmit the service and signal messages from and to the satellite on a second bidirectional wireless way, the second bidirectional wireless way being made up of a second outbound downlink and a second inbound uplink, at least one control unit of a virtual cell connected to one or more satellite access stations, a virtual cell being a set of frequency and spatial transmission resources, the method comprising the steps of:
 performing a wide band measurement of the transmission quality of each sub-band of the first virtual cell the terminal previously attached to the first virtual cell, the terminal having a first list of frequency sub-bands used in the first virtual cell;   sending, from the terminal to a first control unit of the first virtual cell, a first message containing information representative of the quality of each sub-band administered by the first control unit of the first virtual cell currently in force, through a first transmission channel currently using one or more frequency sub-bands of the first virtual cell;   then, using the first control unit to determine, from quality information of the sub-bands of the current first virtual cell and a set of second lists of sub-bands of adjacent virtual cells in terms of beams, whether a second adjacent virtual cell exists in terms of beams capable of providing, for a long period, more favorable wireless reception conditions than those of any channel of the first virtual cell;   when such a second virtual cell exists, preparing, with a mobile switching center and a second control unit associated with the second virtual cell, a new high throughput connection on the high throughput network side and sending, using the first control unit, the terminal a second message comprising an order to prepare a switch to a second transmission channel, identification information for the second virtual cell to which to switch, and a third list of sub-bands to scan of the second virtual cell to perform a wide band measurement of the set of channels offered by the second virtual cell,   after receiving the second message, sending, using the terminal, the second control unit, through a second transmission channel, a third message containing information representative of the quality of each sub-band administered by the second control unit of the second virtual cell;   determining, using the second control unit, from quality information of the sub-bands of the second virtual cell architecture, determined and supplied by the terminal and a fourth list of free transmission channels of the second virtual cell, a third channel formed from one or more sub-bands comprised in the fourth list of free channels of the second virtual cell that corresponds to more favorable wireless reception conditions than those of the first channel;   using the second control unit to reserve the one or more sub-bands of the third channel, and to prepare and send, on the second signal channel, a fourth message to the terminal containing identification information of the third channel and the one or more sub-bands allocated to the third channel;   using the terminal to receive and decode the fourth message, to store the information on the one or more new sub-bands assigned by the second control unit, and then to send the first control unit a fifth announcement message that it is ready to switch to the third channel of the second virtual cell;   after the first control unit receives the fifth message, using the first control unit to send an order to the mobile switching center to activate a second connection between the second control unit and the high throughput network, and to prepare and send the terminal a sixth message containing an order to switch to the second control unit of the second virtual cell and to use the third transmission channel; and   after the terminal receives and decodes the sixth message, using the terminal to execute the switching order from the first channel to the third channel and sends any new message on the second control unit.