Application of the chirp-z transform to fractional interpolation in DMT modems

Sampling clock synchronization in multi carrier systems, such as discrete multitone (DMT) digital subscriber line modems, can be done with a phase locked loop. This requires expensive voltage-controlled oscillators (VCO). Alternatively, clock-offset compensation can be done completely in the digital domain, replacing the VCO with a cheaper free-running oscillator. This solution requires the signal of interest to be fractionally interpolated in the digital domain. In DMT, the digital interpolator can be combined with the modulating DFT into one single fractional operator: the chirp-z transform. In this paper, we explore interpolation algorithms based on the Chirp-z transform and tailor them at clock-offset recovery for DMT modems.