Full-duplex fast estimation of echo and channel responses in the presence of frequency offsets in both far echo and far signal

The problem of reducing the initialization time of the echo cancellers and the channel equalizers in modems is extremely important for high-speed full-duplex data transmission over two-wire lines. In a previous publication Chen et al. (see IEEE Trans. Information Theory, vol.41, no.5, 1995) proposed a full-duplex fast training procedure for simultaneously estimating the echo and channel responses. It reduces the tap-setting time to half of that required by the traditional half-duplex fast training schemes. However, its estimation accuracy may be degraded by the frequency offsets in both the far echo and far signal that are caused by the analog carrier network. We extend the previous work and develop a new algorithm that can compensate for the frequency offsets in both the far echo and far signal. The performance of the new method is analyzed in terms of the mean-square error. Simulation results are presented to confirm the analysis