UT Austin Multicarrier Equalizer Design Toolbox for Matlab

Guner Arslan, Ming Ding, Biao Lu, Milos Milosevic, Zukang Shen, and Brian L. Evans
Embedded Signal Processing Laboratory
Department of Electrical and Computer Engineering
The University of Texas at Austin, Austin, TX 78712-1084


ADSL Transceiver Design at UT Austin

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.



The MATLAB DMTTEQ Toolbox is a collection of MATLAB functions to design and test time domain equalizer (TEQ) design methods. For the conventional equalizer architecture of a single FIR TEQ, the toolbox implements the following TEQ design methods:
  1. Minimum mean squared error -- unit energy constraint [1]
  2. Minimum mean squared error -- unit tap constraint [1]
  3. Maximum shortening signal to noise ratio (SSNR) method [2]
  4. Maximum geometric SNR method [3]
  5. Divide and conquer -- cancellation [4]
  6. Divide and conquer -- minimization [4]
  7. Maximum bit rate method [5]
  8. Minimum intersymbol interference method [5]
  9. Matrix pencil design method [4]
  10. Modified matrix pencil design method [4]
  11. Eigen approach [6]
  12. Autoregressive Moving Average
  13. Symmetric maximum shortening SNR [10]
The toolbox has a graphical user interface (GUI) which enables the design of a TEQ by one of the methods above and the testing of its performance. A snapshot of the GUI for designing single FIR TEQs is shown below.



In the upper right of the control window is a pulldown menu from which a design method can be chosen. Below this pulldown menu are the following editable text windows which are used to set the design and simulation parameters: Below the editable text windows is another pull-down menu which is used to select the desired graph to be displayed. The following graphics can be selected: The two remaining buttons in the control frame are The following performance measures are calculated and listed in the table: Once all of the design and simulation parameters are set to the desired values and the design method is chosen, the user hits the ``Calculate'' button to start the calculations. The simulator first loads the channel information and generates the channel noise according to the parameter values. Then, it will generate a transmit sequence and pass it through the channel to obtain a received signal. In the next step, the simulator estimates the power spectra of the transmitted signal and channel noise. It also estimates the magnitude square of the channel frequency response. Based on these estimates, the SNR in each subchannel is estimated.

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.