| 摘要 |
A method and apparatus reduces the complexity of initial synchronization in mobile terminals operating in TDMA communications systems. A TDMA transmission comprises multiple repeating time slots marked by synchronization words. Initial synchronization requires locating at least one time slot in the received signal. Information in a slot is received as a sequence of symbols at a defined symbol rate. The mobile terminal receives the TDMA transmission for a period longer than one time slot and samples a baseband version of the received signal at M times the symbol rate. This oversampling produces M symbol-rate sample sets, with each sample set corresponding to one of M sampling phases. The mobile terminal performs a FFT on each one of the plurality of the M sample sets after raising it to the n<th >power, where n is based on the number of modulation phases used to transmit the symbols. Results from the FFT permit the mobile terminal to identify possible frequency offsets in the local oscillator and to select the preferred sample set for sync word correlation. The mobile terminal correlates a known sync pattern with the preferred sample set compensated using the possible frequency offsets to determine the sync word location.
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