Sampling frequency offset tracking method and OFDM system using the same

An orthogonal frequency division multiplexing (OFDM) system comprising:

• an oscillator which generates a carrier frequency and a sampling frequency;
• a converter which samples a received signal with the generated sampling frequency;
• a frequency offset estimator which estimates a carrier frequency offset using at least one pilot subcarrier of the received signal;
• a fast Fourier transformer (FFT) which transforms the sampled received signal into a frequency domain;
• and
• an offset tracker which tracks a sampling frequency offset by calculating correlations between at least one of a reference pilot subcarrier predefined according to a resolution of maximum likelihood estimation (MLE) and the at least one pilot subcarrier of the received signal,
• wherein the calculating of the correlations is performed in a search direction of the MLE determined according to a sign of the estimated carrier frequency offset.

A sampling frequency offset tracking method in an orthogonal frequency division multiplexing (OFDM) system, the sampling frequency offset tracking method comprising:

• determining a search direction of maximum likelihood estimation (MLE) using a carrier frequency offset which is estimated using at least one pilot subcarrier of a received signal;
• calculating a size of an MLE search region using a maximum sampling frequency offset of the OFDM system and a resolution of the MLE;
• calculating a range of the MLE search region for each OFDM symbol based on the calculated size of the MLE search region;
• and
• tracking a sampling frequency offset by calculating a maximum correlation between the at least one pilot subcarrier of the received signal and at least one predefined reference pilot subcarrier within the MLE search region calculated for each OFDM symbol.