Method and apparatus for symbol timing if OFDM systems

摘要

The invention synchronises the Symbol Timing in OFDM Systems using scattered pilots. Coarse symbol timing is achieved by autocorrelating 2 with a cyclic prefix and detecting a correlation peak 3. At the same time, a frequency offset can be estimated 4. Received samples are frequency offset compensated 5, and a symbol index is determined 6 which allows a pattern of transmitted pilots to be identified. These frequency domain pilot sub-carrier symbols are then transformed to the time domain via an IFFT (Inverse Fast Fourier Transform) 7. Given a search window around the coarse timing point, the frequency compensated samples are cross correlated with the time domain pilot sub-carriers waveform 8 to generate an estimate of the channel impulse response (CIR). Then the absolute value of the correlation is accumulated within a sliding window 9 and the position of the maximum 10 is regarded as the optimum timing point.