Patent ID: 8243713

Claim:
A method comprising: transmitting cellular radiotelephony signals on a main symmetric two-directional channel comprising a main uplink and a main downlink, particularly transmitting signaling and control data and information at low or medium speed; transmitting, with a device, further cellular radiotelephony signals on at least one supplementary channel 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, said predefined entities being sub-frames or frames of the supplementary channel; transmitting 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 inserting, with the device, a position identifier into at least one symbol of each entity received via the supplementary channel, which identifies 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 the beginning of the next entity by predetermined sequence of position identifiers, thus obtaining synchronization of the supplementary channel at the level of the entity considered.