Some new results from TEQ design for maximum bit rate ADSL modem

The paper presents examples of the successful application of a new mathematical SNR model to bit rate evaluation of asymmetric digital subscriber line (ADSL) modem. Contrary to other methods, the present design of a time domain equalizer (TEQ) additionally takes into account nonideal frequency response of demodulation filters. Also strong demodulation filters influence on achievable modem bit rate is shown. Different types of disturbances (such as AWGN, NEXT, narrow band interference) are considered. The verified model can be very useful during design and optimization of the TEQ filters for general multicarrier DMT/OFDM transceivers. As an example presented in the paper clearly shows, application of the new model in a cost function during TEQ filter optimization leads to an increase in the ADSL modem bit rate. It is also demonstrated that this improvement is not directly SSNR (SNR of the shortened impulse response of the channel) dependent.