Clock frequency synchronisation in OFDM system for power line communications

Orthogonal frequency division multiplexing (OFDM) divides the available spectrum into several narrowband subchannels. To obtain a high spectral efficiency, the frequency responses of the subchannels are overlapping and orthogonal. An OFDM system can suffer from two types of frequency errors-a carrier frequency offset and a master clock frequency offset. Both types of frequency error degrade the performance of the OFDM receiver by loosing orthogonality between the subcarriers and introducing interchannel interference. Since the power line communications are performed in the baseband, only the second type of frequency error can occur. This paper analyses the effect of master clock frequency offset and suggests a method for its estimation based on the pilot signal. Furthermore, a method for frequency error correction is presented.