Realization of Adaptive NEXT canceller for ADSL on DSP kit

Crosstalk canceller plays a key role in achieving high bit rates in wire line multicarrier Asymmetric Digital Subscriber Line (ADSL) systems. Adjacent systems within a cable binder that transmit or receive data in the same frequency range can create crosstalk interference. In an ongoing effort to study and improve the performance of ADSL Central office and CPE modems, the effect of Near-end crosstalk (NEXT) is examined. In this paper we introduce filter for NEXT mitigation to improve signal to noise ratio(SNR) at the input of the receiver which improves data rate. An Adaptive LMS filter to eliminate the effect of NEXT is designed. Adaptive LMS filter simulation was done in Matlab environment and also implemented on TMS 320C 6713 DSP. An analysis of the Receiver output with and without filter is presented for various lengths. Results presented shows an improvement in SNR with this filter. Efficient bit loading strategies can be adopted to provide a higher user data rate in the presence of NEXT.