Optimal transmit spectra for communication in the presence of crosstalk and imperfect echo cancellation

Nadeem Ahmed, Richard G. Baraniuk, Donald P. Shaver

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In many communication systems, including Digital Subscriber Lines, performance is severely limited by crosstalk interference. Previous work has presented a general framework for designing optimal transmit spectra for crosstalk avoidance. The technique uses the channel, noise, and interference characteristics to setup and solve an optimization problem which maximizes the capacity of neighboring lines, while maintaining spectral compatibility with other services. This joint signaling and optimal power distribution technique yields significant performance gains over conventional fixed spectra in terms of bit-rates and performance margins. In general, the spectra that result from this scheme have both an echo cancelled and frequency division multiplexed region. To ease the analysis, this technique assumed that the echo canceller has perfect echo rejection capability, which in practice is not true. In this paper, we propose an extension to these techniques, in which we factor the performance of practical echo cancellers into the optimization procedure. When echo rejection is not perfect, as is generally the case, our technique shows significant performance gains over previous techniques. As the performance of the echo canceller increases, our technique converges to the same solution.

Original languageEnglish
Title of host publicationConference Record / IEEE Global Telecommunications Conference
Number of pages5
StatePublished - Dec 1 2001
EventIEEE Global Telecommunicatins Conference GLOBECOM'01 - San Antonio, TX, United States
Duration: Nov 25 2001Nov 29 2001


OtherIEEE Global Telecommunicatins Conference GLOBECOM'01
Country/TerritoryUnited States
CitySan Antonio, TX


  • Capacity
  • Crosstalk
  • Digital Subscriber Line (DSL)
  • Echo canceller
  • Power distribution
  • Transmit spectra
  • Waterfilling

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Global and Planetary Change


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