Synchronization method for a mobile radiotelephone

A method of synchronizing a mobile radiotelephone in a cellular digital mobile radiotelephone network comprising a plurality of fixed radiotelephone stations and a plurality of mobile radio stations operating in accordance with a GSM standard or its equivalent, in which each communication frequency assignment is subdivided into interleaved time slots, a plurality of said time slots together comprising a frame, comprising the following steps which are carried out in the mobile radiotelephone:

• (1) conducting an initial synchronization by means of a frequency correction burst substantially fully occupying a time slot with an unmodulated wave corresponding to repetition of bits of the same binary logic value;
• (2) maintaining normal synchronization during communication by means of interspersed normal synchronization bursts, each normal synchronization burst containing a training sequence occupying less than a third of a time slot, and
• (3) performing extended synchronization during communication as a background procedure by means of interspersed frequency synchronization bursts, each frequency synchronization burst containing an extended training sequence occupying less than an entire time slot and more than a third of a time slot, and wherein:
• said step of conducting said initial synchronization comprises the substeps of:
• (1.1) conducting a coarse frequency synchronization,
• (1.2) conducting a coarse frame synchronization over a plurality of said time slots which comprise a frame,
• (1.3) conducting a fine frequency synchronization, and
• (1.4) conducting a fine frame synchronization over said plurality of time slots which comprise a frame;
• said step of maintaining said normal synchronization comprises the substeps of:
• (2.1) conducting a frame synchronization with fine frequency synchronization, and
• (2.2) carrying out preliminary data signal processing;
• and
• said step of performing said extended synchronization comprises the substeps of:
• (3.1) conducting a coarse frame synchronization, and
• (3.2) conducting a fine frame synchronization with fine frequency synchronization.