Adaptive digital filtering for data transmission systems

Abstract

The main objectives of this dissertation are to develop efficient structures for echo canceller and equalizer, analyze their performances, and compare with other existing systems. First, a passband complex data-driven echo canceller (DDEC) that has the same convergence property as the baseband DDEC but has less computational complexity has been proposed. Also, a reduced passband DDEC which has about the same convergence speed as the passband real structure and consists of only one real transversal filter has been obtained. Performance analysis of those four cancellers has been done. As a result, it has been shown that the convergence speed of the canceller which uses complex analytic error for tap adjustment is twice faster than that of the canceller using real passband error. We have realized efficiently the four cancellers based on the frequency domain block least-mean-square (FBLMS) algorithm, and then analyzed their computational complexities. For a performance comparison of various DDEC``s realized using the FBLMS algorithm, analysis and computer simulation have been done. Second, we have studied four equalizer structures and their performances. Interrelationships among system equations of the baseband equalizer, the passband complex equalizer, the passband real equalizer and the reduced passband equalizer have been investigated in the same MSE performance criterion. Also, a computational complexity analysis of the four equalizers realized based on the FBLMS algorithm has been done. We have done comparative analytical study of the performance of the four equalizers. As a result, it has been shown that the convergence time of the passband equalizer using real passband input is twice longes than that of the passband equalizer having complex analytic input. In realization of the reduced passband equalizer based on the FBLMS algorithm, we have investigated by computer simulation the effects of frequency domain approximation of the discrete Hilbert transform (D...