IEEE Workshop on Signal Processing Advances in Wireless Communications, June 15-18, 2003, Rome, Italy.

Infinite Length Results for Channel Shortening Equalizers

Rick K. Martin (1), C. Rick Johnson, Jr. (1), Ming Ding (2), and Brian L. Evans (2)

(1) Department of Electrical and Computer Engineering, Rhodes Hall, Cornell University, Ithaca, NY 14853 USA
frodo@ece.cornell.edu - johnson@ece.cornell.edu

(2) Department of Electrical and Computer Engineering, Engineering Science Building, The University of Texas at Austin, Austin, TX 78712-1084 USA
ming@ece.utexas.edu - bevans@ece.utexas.edu

Paper - Poster

ADSL Research at Cornell - ADSL Research at UT Austin

Abstract

Time-domain equalization is crucial in reducing state dimension in maximum likelihood sequence estimation, and inter-carrier and inter-symbol interference in 802.11a and ADSL multicarrier systems. A time-domain equalizer, or TEQ, which is a finite impulse response (FIR) filter, placed in cascade with the channel produces an effective impulse response of v+1 samples that is shorter than the channel impulse response. This paper analyzes the two families of TEQ design methods amenable to cost-effective real-time implementation: minimum mean squared error (MMSE) and maximum shortening SNR (MSSNR) methods. For infinite length TEQs, we prove that MMSE target impulse responses are symmetric and have all v zeros on the unit circle, and MSSNR TEQs have v of their zeros un the unit circle. Consequently, finite-length MMSE and MSSNR TEQs will eventually yield increasing bit error rates (for broadcast systems) or decreasing bit rates (for point-to-point systems that allow bit allocation) with increasing filter length.

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Last Updated 03/10/06.