A study is made of the performance of a class of adaptive data-driven echo cancellers (DDECs). The authors first investigate the interrelationship in a unified framework among the system equations of various data-driven echo cancellers. As a result, they obtain a new DDEC algorithm that consists of only one real-valued adaptive structure. The authors analyze and compare the convergence behavior of DDECs. They analyze their complexities when the least-mean-square (LMS) algorithm and the frequency-domain block LMS algorithm are used for adjusting the canceller weights. The results show that the echo canceller structure realized in the frequency domain has advantages in convergence rate and in implementation complexity as compared to existing DDEC structures.>

In this letter, we propose a reduced structure for realization of a passband fractionally spaced equalizer (FSE) using the block LMS (BLMS) algorithm. Since this structure consists of one real transversal filter, its complexity is considerably simpler than existing equalizer structures. The passband FSE using the real passband input converges to the same steady-state value as that of the FSE with the complex analytic input, but its convergence time takes twice as long.

In this paper the realization and performance of a twodimensional finite impulse response (FIR) digital filter using adaptive delta modulation (ADM) have been studied. The analytical results have been verified by computer simulation. Also, it has been shown that onedimensional DM is adequate in the realization of a two-dimensional FIR ADM digital filter. Since the ADM digital filter requires no multiplication, it offers many advantages over conventional PCM filters in cost reduction, hardware simplicity, and reduced size.