A new digital timing correction scheme for DMT systems combining temporal and frequential signal properties

In discrete multi-tone (DMT) systems, demodulation of the QAM modulated sinusoids is achieved by a fast Fourier transform (FFT) on blocks of samples generated from the received continuous-time signal. A clock difference between transmitter and receiver, annihilates the orthogonality of the carriers. Therefore, a receiver using asynchronous sampling must perform timing correction in the discrete-time domain. A new digital timing synchronization method is presented which is based on temporal and frequency domain digital signal processing. Correction of the sample clock offset is done in the time domain whereas DMT symbol timing alignment is done in the frequency domain. The method alleviates the need for accurate free running Xtals generating the sample clocks and can be used for high rate DMT systems like for instance the emerging very high rate digital subscriber loop (VDSL) transceivers.