Synchronisation in multicarrier receivers

摘要

A preamble for synchronization, or a reference timing for operation of an OFDM packet communication receiver system is detected finely even under environment of large waveform distortion due to thermal noise and/or multi-path propagation, and/or large carrier frequency offset between a transmit side and a receiver side. A correlator (1) detects a pattern of a short preamble (t1 - t10) in a preamble for synchronization. An output of the correlator (1) is applied to a complex filter (7) which separates a short preamble having a predetermined repetition period from uniformly distributed noise. A scalar filter (9) integrates some period of short preambles which have distributed-delay by multi-path propagation as if a single short preamble with no delay were received for determining a reference timing. When a correlator output exceeds a predetermined threshold level a plurality of times for every repetition periods (T) of a short preamble, and an output of the correlator after time (T) from the last short preamble is decreased a predetermined ratio as compared with that of the last short preamble, it is determined that a preamble for synchronization is detected. Carrier frequency offset compensation is carried out either for each short preamble during reception of a short preamble, or based upon the last received short preamble during reception of an OFDM symbol after the last short preamble. As a preamble for synchronization is detected accurately, a guard interval of each OFDM symbol is removed accurately, or an FFT window is defined accurately, so that a demodulation is possible in spite of noise and/or interference.