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Synchronization method for a mobile radiotelephone
| Details |
Inventors: Bilitza, Herbert; Gartner, Biegfried; Neuner, Hermann;
Assignee: Robert Bosch GmbH (Stuttgart, DE)
Primary Examiner: Chin; Stephen
Assistant Examiner: Vo; Don
Attorney, Agent or Firm: Frishauf, Holtz, Goodman & Woodward
The high requirements of digital mobile radiotelephone communication under the GSM Standard with respect to synchronization of a mobile radiotelephone to a fixed radiotelephone station is performed by frequently (four times per so-called baseband frequency cycle) sampling contemporary in-phase and quadrature phase components of received GMSK digital signals and utilization of time slots respectively containing a frequency correction burst, a normal burst and an extended synchronization burst, respectively for initial synchronization, normal maintenance of synchronization during communication and a background procedure during normal operation. The decoding of the GMSK signal provides one-bit of information from each pair of in-phase and quadrature components sampled. The sampling of in-phase and quadrature components greatly simplifies the synchronizing procedure. Initial synchronization includes coarse frequency synchronization, coarse frame synchronization, fine frequency synchronization and fine frame synchronization. Normal maintenance of synchronization consists fine frame synchronization with fine frequency synchronization and a data signal preliminary processing. Extended synchronization consists of coarse frame synchronization and a fine frame synchronization with fine frequency synchronization. |
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DETAILED DESCRIPTION It is an object of the invention to provide a synchronization method that fulfills all the requirements of digital information transmission with the least possible technical complication and expense.
The synchronization method of the invention is based on the evaluation of a continuously running phase angle, which is calculated again and again from an in-phase component I and a quadrature component Q.
The type of modulation used in the D-Network is Gaussian minimum shift keying (GMSK), in which a linear filter having a pulse response of Gaussian shape continuously reproduces discontinuous transitions from one to the other of the frequency modulation waves and thereby provides a saving of transmission bandwidth by providing continuity in place of the discontinuities of the transitions.
The resulting transition wave form can be resolved into varying contents of I and Q components, relative, for example, to one of the two symbol (bit value) frequency waves.
Briefly, in order to take advantage of that more economical synchronization technique, there is performed for the mobile radiotelephone, first, an initial synchronization, then a normal synchronization and then, an extended synchronization as a background procedure during normal operation.
The initial synchronization is divided into following steps: (1.
1) coarse frequency synchronization, (1.
2) coarse frame synchronization, (1.
3) fine frequency synchronization, and (1.
4) fine frame synchronization.
The normal synchronization comprises the steps of: (2.
1) frame synchronization with fine frequency synchronization and (2.
2) a preliminary processing of a data signal.
The extended synchronization comprises of (3.
1) a coarse frame synchronization and (3.
2) a fine frame synchronization with fine frequency synchronization.
By this procedure it is possible to realize synchronization of higher precision with a relatively small complication and expense.
The method of the invention is based on evaluation of phase angle many times per bit interval
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Cell Phones 
