Performance of echo canceller during start-up for high-speed data transmission

Echo cancellers that use the spectral estimation approach for the fastest possible starting-up time need to know the approximate delay and duration of the echo, and require a cyclic input of a pseudo-noise (PN) sequence. This paper describes the effects of an inaccurate estimate of the echo duration by the initial sounding of the echo path. It also compares the performance of the well-known Barker sequences, the Relaxed-Barker sequences, and the arbitrarily constructed PN sequences when used for the starting up process. It offers an explanation and gives the necessary characteristics of the PN sequences that ensure the successful operation of the echo canceller. Finally the paper gives a guideline for the choice of a suitable PN sequence for the estimation of an unknown echo path of any but roughly-known duration.<>