Proc. IEEE Int. Conf. on Acoustics, Speech, and Signal Processing, April 6-10, 2003, vol. V, pp. 97-100, Hong Kong, China.

Exploiting Symmetry in Channel Shortening Equalizers

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

(1) Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14850 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 inter-carrier and inter-symbol interference in multicarrier systems. A channel shortening time-domain equalizer (TEQ), which is a finite impulse response (FIR) filter, placed in cascade with the channel produces an effective impulse response that is shorter than the channel impulse response. We show that finite length minimum mean squared error (MMSE) and maximum shortening SNR (MSSNR) TEQs are approximately symmetric, and infinite length MSSNR TEQs with a unit norm TEQ (UNT) constraint are exactly symmetric. A symmetric TEQ halves FIR implementation complexity, enables the frequency-domain equalizer and TEQ to be trained in parallel, and exhibits only a small loss in bit rate over non-symmetric TEQs. In addition, a symmetric MSSNR-UNT TEQ reduces training computational complexity by a factor of 4 and doubles the length of the TEQ that can be designed.

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Last Updated 03/10/06.