Bit loading algorithm to maximize datarate with energy constraint for ADSL in the presence of NEXT & FEXT

摘要

In this paper bit loading algorithm for ADSL is developed to achieve maximum data rate with energy constraint. The effect of near end and far end cross talk on the twisted pair copper line supporting Asymmetric Digital Subscriber Line (ADSL) standards is analyzed. The Signal to Noise Ratio (SNR) profile with frequency dependent channel attenuation and in the presence of cross talk impairments is obtained for various loop lengths. Water filling algorithm is used to compute the bits per tone over the ADSL frequency band from 30KHz to 1.1 MHz, with Discrete Multitone (DMT) Modulation. The data rates are tabulated for different gauges and lengths of twisted pair. ADSL transmitter, channel and noise are modeled and simulated in MATLAB. The bit loading pattern is plotted for 26AWG, 24 AWG and 22 AWG copper lines. The simulation is easily extended to other types of multiple interferers and other flavors of DSL.