شبكه هاي عصبي، روشي نوين در حذف پژواك سيستم ADSL

Neural Networks, A New Method for Echo Cancellation in ADSL System

Multicarrier methods have long been identified for optimizing data transceivers on bandlimited channels. Discrete Multitone is a multicarrier transmission method which can be implemented using DSP techniques. Transmission rate in a simple DMT system can be increased by adding a full duplex echo canceller. So far, there have been several problems with the proposed echo cancellers regarding their high computational complexity and the relatively low stability. In this paper, a new high speed technique based on neural network with a good stability is represented. By using of this method, the echo of DMT modulation in ADSL system is cancelled. This technique optimizes the learning factor and consequently increases the echo cancellation rate in comparison with LMS method in about 2.3 7dB. In this method, only the operational phase of neural network is applied to DMT system. After training network, the weights are frozen and the computational cost is reduced to an acceptable level.