procedure and device for the synchronization of digital transmission systems of the type ofdm

摘要

PCT No. PCT/SE94/00560 Sec. 371 Date Jan. 22, 1996 Sec. 102(e) Date Jan. 22, 1996 PCT Filed Jun. 9, 1994 PCT Pub. No. WO95/03656 PCT Pub. Date Feb. 2, 1995The invention relates to a method and apparatus for synchronization of transmitters and receivers in digital transmission systems of the OFDM type. The system uses FFT technique to carry out the modulation and demodulation procedures. According to the invention, the transmitter sends synchronization frames with known frequencies and phase positions and with known time intervals in certain time slots. The receiver carries out a series of time-shifted FFT operations over the time position where the synchronization frame is calculated to be. For each operation, a cross-correlation is carried out in the frequency plane of the output signal with the known frequency function of the synchronization frame. The correlation maximum is detected, and this determines the time slot which contains the synchronization frame, whereupon this is used as time base for the following data frames.