مطالعه و بررسي تطبيقي ساختارهاي جبران ساز براي سيستم هاي ADSL

COMPARATIVE ANALYSIS OF ADSL EQUALIZATION TECHNIQUES

This paper provides an overview of equalization techniques for Discrete MultiTone (DMT) modulation systems, which are used in ADSL modems. ADSL modems are used to provide broadband connectivity to home users using the existing telephone wirelines. Noting the distortions caused by the wireline channel by the wireline channel transfer function, ADSL receivers should use equalizers to compensate the channel effects. Several different techniques have been proposed for the design and implementation of an equalization block in DMT receivers. In this article, we provide an overview of some of the key techniques, report the results of their implementation on a sample standard loop and compare their respective performances. The analyzed and compared equalization methods are: Maximum Shortened SNR, the Divide and Conquer minimization technique, Maximum Geometric SNR and the Eigen ap- proach. Simulation results demonstrate that the eigen approach provides the best performance: This technique can also be implemented with lower complexity compared to MGSNR technique.