Cellular radiotelephone signal which enables synchronisation at an entity of a supplementary channel by means of symbol numbering, and corresponding method, terminal and base station

A method for synchronization, by a terminal, of a supplementary channel associated with a symmetric two-directional main channel,

• said symmetric two-directional main channel comprising a main uplink and a main downlink, particularly for transmission of signaling and control data and information at low or medium speed,
• said supplementary channel being assigned to the down direction only, particularly for transmission of high speed data using a multi-carrier technique for distribution of data in the time / frequency space, and with a structure in predefined entities each including a predetermined number of symbols, wherein said predefined entities are sub-frames or frames of the supplementary channel,
• receiving from the main channel a notification inviting said terminal to do said synchronization of the supplementary channel at a level of the entity considered, for a changeover of the terminal from the main channel to the supplementary channel,
• wherein the terminal performs synchronizing of the supplementary channel at the level of the entity considered, wherein synchronizing comprises:
• detecting and reading a position identifier comprised within a current symbol received via the supplementary channel, said position identifier being used to identify, among the predetermined number of symbols, the position of said current symbol in the entity to which it belongs;
• and
• deducing, by a predetermined sequence of position identifiers, the beginning of the next entity as a function of the position identifier of the current symbol.

A terminal in a cellular radiotelephony system, comprising:

• a transmitter, which transmits a main uplink, a receiver, which receives a main downlink and a receiver, which receives at least one supplementary channel, said main uplink and said main downlink forming a symmetric two-directional main channel, particularly for low or medium speed transmission of signaling and control data and information, said supplementary channel being assigned to the down direction only, particularly for transmission of high speed data, using a multi-carrier technique for distribution of data in the time / frequency space, and with a structure in predefined entities each including a predetermined number of symbols, wherein said predefined entities are sub-frames of the supplementary channel;
• a synchronizer, which receives from the main channel a notification inviting said terminal to synchronize the supplementary channel at a level of the entity considered, for a changeover of the terminal from the main channel to the supplementary channel, wherein the synchronizer comprises:
• elements that detect and read a position identifier comprised within a current symbol received via the supplementary channel, said position identifier being used to identify, among the predetermined number of symbols, the position of said symbol in the entity to which it belongs;
• and
• elements that deduce, by a predetermined sequence of position identifiers, the beginning of the next entity as a function of the position identifier of the current symbol.

A base station in a cellular radiotelephony system, the base station comprising:

• a receiver, which receives a main uplink, a transmitter, which transmits a main downlink, and a transmitter, which transmits at least one supplementary channel, said main uplink and said main downlink forming a symmetric two-directional main channel particularly for low or medium speed transmission of signaling and control data and information, said supplementary channel being assigned to the down direction only, particularly for high speed data transmission, using a multi-carrier technique for distribution of data in the time / frequency space, and with a structure in predefined entities each including a predetermined number of symbols, wherein said predefined entities are sub-frames or frames of the supplementary channel,
• wherein the base station is configured to transmit on the main channel a notification inviting a terminal to synchronize the supplementary channel at a level of the entity considered, for a changeover of the terminal from the main channel to the supplementary channel, and is configured to insert a position identifier in at least one symbol of each entity received via the supplementary channel, said position identifier being used to identify, among the predetermined number of symbols, the position of said symbol in said entity, such that the terminal can read the position identifier of said symbol and use it to deduce, by a predetermined sequence of position identifiers, the beginning of the next entity, thus obtaining synchronization of the supplementary channel at the level of the entity considered.