An enhanced technique for online discrete cosine transform-based time-varying delay estimation

Time-delay estimation is developed in the transform domain where discrete c osine transform (DCT) coefficients of time-varying delay signals are estima ted. The DCT is very efficient in compacting the signal energy in a small n umber of coefficients. Hence, the estimation of time-varying delay is obtai ned through the calculation of a small number of the DCT coefficients. An o nline maximum likelihood estimator of time-varying delay is developed. The coefficients of the transformed delay signal are obtained by maximizing the likelihood function. When dealing with noisy signals, it is observed that increasing the number of estimated DCT coefficients beyond a certain level does not produce better estimates of the delay signal. This happens because the extra DCT coefficients accommodate the noise present in the received s ignals.