Embedded Signal Processing Laboratory

Department of Electrical and Computer Engineering

The University of Texas at Austin, Austin, TX 78712-1084

11/27/05

This freely distributable toolbox provides a graphical user interface and functions in Matlab to design four different multicarrier equalizer structures: conventional, dual-path, per tone, and filter bank. A total of 18 design methods to compute the equalizer coefficients have implemented: 13 for conventional, two for dual-path, two for per tone, and one for filter bank equalizers. Default parameters are from the G.DMT ADSL standard for downstream transmission. This toolbox was initially released in Fall 2000.

- MATLAB Multicarrier Equalizer Design
Toolbox 3.1 Release,
May 10, 2003
To run the graphical user interface, type

`teqdemov3`

. The user will then be asked to choose one of four equalizer architectures to design. New features of version 3.1 vs. version 3.0 include- Conventional equalizer methods
- New symmetric maximum shortening SNR method for time-domain equalizer design (from Cornell-UT Austin papers)
- The target impulse response is displayed only for those methods that define one (minimum mean-squared error training methods) when the shortened impulse response is displayed.

- Per-tone equalizer equalizer design methods
- Trained with 511 symbols (from KU Leuven recommendation)
- New minimum mean squared error method per tone (from KU Leuven paper)

- New time-domain filter bank equalizer (from UT Austin paper)
- Toolbox-wide improvements
- Improved spectral estimation (sliding FFT with a Hamming window and 50% overlap of samples in consecutive blocks)
- Information window gives references for all training methods
- New button to save equalizer designs as Matlab text files

- The MMSE per-tone and time-domain filter bank equalizer training methods do not by default search for the optimal transmission delay, due to the amount of execution time required, and use a heuristic to determine the transmisson delay parameter instead. As a result, their bit rates are 10-20% below optimal. There is an option that can be enabled to search for the optimal transmission delay.
- In Matlab 6.0 under Redhat Linux, the initial popup window
from running
`teqdemov3`

does not display the logo for the UT Austin Embedded Signal Processing Laboratory nor provide scroll bars for the text in the right-hand window.

- Conventional equalizer methods
- MATLAB DMTTEQ Toolbox 3.0 Release,
September 9, 2002
This version adds design methods for two new DMT equalizer architectures, dual-path TEQ [8] and frequency-domain per-tone equalizer [9], to the existing support for a conventional single-TEQ architecture [1-6]. To run the graphical user interface, type

`teqdemov3`

. The user will then be asked to choose one of the three equalizer architectures. The bit rate calculations for per tone equalizer are based on the estimation of mean square error between input-output data for each subband, whereas the bit rate calculations of the other two architectures are based on a matched filter bound for a single TEQ. - MATLAB DMTTEQ Toolbox 2.0,
July 9, 2001
This version chooses default simulation parameters to be consistent with the G.DMT ADSL standard, fixes several bugs including one in the bit rate calculation, and works in Matlab 6. To run the graphical user interface, type

`teqdemo`

. - MATLAB DMTTEQ Toolbox User's Manual,
October 15, 2000
This is the user's manual for versions 1.0 and 2.0. It covers most of the features of version 3.0.

- Minimum mean squared error -- unit energy constraint [1]
- Minimum mean squared error -- unit tap constraint [1]
- Maximum shortening signal to noise ratio (SSNR) method [2]
- Maximum geometric SNR method [3]
- Divide and conquer -- cancellation [4]
- Divide and conquer -- minimization [4]
- Maximum bit rate method [5]
- Minimum intersymbol interference method [5]
- Matrix pencil design method [4]
- Modified matrix pencil design method [4]
- Eigen approach [6]
- Autoregressive Moving Average
- Symmetric maximum shortening SNR [10]

- Shortened impulse response (SIR) length. This is the desired length of the channel after equalization. For example, it should be set to 33 (one plus the cyclic prefix length) for the ANSI and G.DMT ADSL standards.
- Time domain equalizer (TEQ) length. Defines the number of taps of the TEQ.
- Fast Fourier transform (FFT) size. Sets the FFT size used in DMT modulation. It is twice the number of subchannels.
- Coding gain (dB). Defines a coding gain in dB which is used during capacity calculations [7]
- Margin (dB). Sets the desired system margin in dB. This is also used in capacity calculations [7]
- Dmin and Dmax. The interval of Delta [Dmin Dmax] in which to search for the optimal delay value.
- Input power (dBm). Defines the input signal power in dBm.
- AWGN power (dBm/Hz). Sets the amount of additive white Gaussian noise in dBm/Hz. AWGN is added to the near-end crosstalk noise.
- CSA loop #(1-8). Selects the desired ADSL channel on which to run the simulation. Currently the eight standard CSA loops are supported.

- Target & shortened channel. Displays the shortened channel impulse response and the target channel impulse response for the minimum mean-squared error (MMSE) and geometric SNR methods. For all other methods, the location of the target window is displayed instead of a target impulse response.
- TEQ impulse response. Shows the impulse response of the TEQ.
- TEQ frequency response. Shows the frequency response of the TEQ.
- SNR & MFB. The SNR and matched filter bound (MFB) to the SNR is displayed as a function of frequency (subchannels).
- Original & shortened channel. Displays the channel impulse response before and after equalization.
- Noise power spectrum. Shows the power spectrum of the noise which consists of NEXT noise plus AWGN.
- Delay plot. Displays the performance measure (i.e., MSE, SSNR, and channel capacity) of the method with respect to the delay.
- Equalized channel frequency response. Displays the frequency response of the channel after equalization.

- Info. Displays information on how to use the GUI.
- Calculate. Starts the calculation and performance evaluation of the TEQ.

- Rate. Gives the achievable bit rate with the given channel and TEQ settings.
- SNR. Shows the SNR at the output of the equalizer in dB.
- SSNR. Shows the shortening SNR in dB. This is defined as the ration of the energy of the shortened channel impulse response in the target window the the energy outside the target window.
- MSE. Gives the MSE for the MMSE and geometric SNR methods.
- Delay. Shows the optimal delay for the system.
- Max Rate. Shows the absolute maximum achievable bit rate given the channel and equalizer settings. It is calculated from the MFB.

The simulator then calls the desired TEQ design function to calculate the equalizer taps, target impulse response (if it exists for that method), and optimal delay. All of the results are then passed to a performance evaluation function which returns the six performance measures. The selected graph is plotted and the results are written in the table. For different graphs the simulations does not need to be run again, all results are saved.

[1] N. Al-Dhahir and J. M. Cioffi, "Efficiently computed reduced-parameter
input-aided MMSE equalizers for ML detection: A unified approach,"
*IEEE Trans. on Info. Theory,* vol. 42, pp. 903-915, May 1996.

[2] P. J. W. Melsa, R. C. Younce, and C. E. Rhors, "Impulse response
shortening for discrete multitone transceivers," * IEEE Trans. on
Communications,* vol. 44, pp. 1662-1672, Dec. 1996.

[3] N. Al-Dhahir and J. M. Cioffi, "Optimum finite-length equalization for
multicarrier transceivers," *IEEE Trans. on Communications,* vol. 44,
pp. 56-63, Jan. 1996.

[4] G. Arslan,
B. Lu,
L. D. Clark, and
B. L. Evans,
"Iterative Refinement Methods for Time Domain Equalizer Design",
*EURASIP Journal on Applied
Signal Processing*,
accepted for publication.

[5] G. Arslan ,
B. L. Evans,
and S. Kiaei,
"Equalization for Discrete Multitone Receivers To Maximize Bit Rate,"
*IEEE Trans. on Signal Processing,*
vol. 49, no. 12, pp. 3123-3135, Dec. 2001.

[6] B. Farhang-Boroujeny and
Ming Ding,
"Design Methods for Time Domain Equalizer in DMT Transceivers",
*IEEE Trans. on Communications*, vol. 49, pp. 554-562, March 2001.

[7] J. M. Cioffi, *A Multicarrier Primer.* Amati Communication
Corporation and Stanford University, T1E1.4/97-157, Nov. 1991.

[8] M. Ding,
A. J. Redfern, and B. L. Evans,
"A
Dual-path TEQ Structure For DMT-ADSL Systems",
*Proc.* *IEEE Int. Conf.
on Acoustics, Speech, and Signal Proc.*,
May 13-17, 2002, Orlando, FL, accepted for publication.

[9] K. V. Acker, G. Leus, M. Moonen, O. van de Wiel, and T. Pollet,
"Per tone equalization for DMT-based systems,"
*IEEE Trans. on Communications*,
vol. 49, no. 1, pp. 109-119, Jan 2001.

[10] R. K. Martin, C. R. Johnson, Jr., M. Ding, and B. L. Evans,
"Exploiting Symmetry in Channel Shortening Equalizers",
*Proc. IEEE Int. Conf. on Acoustics, Speech, and Signal Proc.*,
April 6-10, 2003, Hong Kong, China.