Joint echo canceller/equalizer and timing recovery for high speed full duplex baseband transmission systems

The interaction between echo cancellation/equalization and timing recovery is analyzed, a complete simulation of a high-speed full-duplex digital subscriber loop system is reported, and issues related to the support of multirate sampling and feedback are discussed. The simulation results suggest that the number of equalizer (EQ) training symbols must be reduced, rather than the number of echo canceler (EC) training symbols, to save total EC/EQ training time, regardless of the length of the bridged taps. The pole-zero EC performs much better than the all-zero EC. In the all-zero EC, the system needs more EQ training symbols. Fractionally spaced EC/EQ performs better than symbol rate EC/EQ when the number of EC/EQ training symbols is large. The symbol rate EC/EQ has better or equivalent performance for small number of EC/EQ training symbols, relatively large noise, and long bridged taps. The symbol rate EC/EQ reaches a performance limit however, unlike the fractionally spaced EC/EQ system, for large SNR or large training sequences