UT Austin ADSL2 Simulator

This freely distributable toolkit provides a graphical user interface and functions in LabVIEW to simulate a discretized multicarrier wired communication system. The structure and default parameters of the transmitter, channel model, and receiver follow the ADSL2 ITU-T G.992.3 standard, which provides asymmetric two-way high-speed wired data communication. The downstream direction indicates the higher data rate direction, and the upstream indicates the lower data rate direction. The simulation is in National Instruments LabVIEW software. A standalone executable of the simulation that runs on a PC without needing a LabVIEW license is also available in the releases.

Slides describing the simulator entitled "Design and Simulation of ADSL2 Transceivers Using LabVIEW" (August 9, 2006) are available in PowerPoint format. Also, please see the following report "High-Speed Wireline Communication Systems" (May 31, 2005) that provides a brief overview of the ADSL2 and ADSL2+ standards.

Download

• ADSL2 Simulator 1.1, May 24, 2006. This release simulates a standard-compliant physical layer discrete-time ADSL2 system, including training. The release contains a bi-directional simulator, ADSL2Bidirectional, and a uni-directional simulator, ADSL2Unidirectional. The simulators do not include models of the analog front ends for an ADSL2 modem. A user's manual and a developer's manual are now available.

  This release can be run without LabVIEW. To run it in LabVIEW, you will need

  • LabVIEW 7.1 or higher
  • LabVIEW Modulation Toolkit 3.0 or higher
  Please see Directions to Run the Simulations below.

  Caveats about version 1.1:

  • For upstream transmission, we have implemented the "oversampled IDFT with zero fill" option, as described in Section 8.8.2., page 91, in the G.992.3 (ADSL2) standard. The downstream case is the "non-oversampled IDFT" case.
  • The initialization sequence, which is a subset of the ADSL2 standard, provides enough information to synchronize the two transceivers and determine the bit allocation tables.
  • Upstream and downstream channel estimation is performed separately (rather than concurrently). This does not have any impact since we are not modeling nonlinear effects of the analog frontends.
  • In order for changes in parameter values to take effect, you will need to stop the simulation, change the parameter values, and rerun the simulation.
  • The channel model is a channel (FIR) impulse response plus additive white Gaussian noise. All eight carrier serving area channel impulse responses are available for the user to select.
  • In the bit error rate (BER) display, the instantaneous BER will show NaN (not a number) for the synchronization frame. A synchronization frame is sent every 69th frame during SHOWTIME.
  • The Reed-Solomon codec has been removed.
  On a 3.4 GHz PC, the ADSL2 simulator 1.1 runs at about 200 frames/s in uni-directional mode and about 100 frames/s in bi-directional mode, with Trellis coding disabled and with simulation delay set to 0 sec. In a simulation involving 4.2 x 10⁹ transmitted bits, the bit error rate was 1.2 x 10^-7 with Trellis coding turned off.

• ADSL2 Simulator 1.0, February 13, 2006. This release contains a standard-compliant discrete-time ADSL2 data transmission subsystem for transmission in one direction. The various training phases have not yet been implemented. The simulation does not include models of the analog front ends for an ADSL2 modem. In addition, the channel is also discretized in time.

  This release can be run without LabVIEW. To run it in LabVIEW, you will need

  • LabVIEW 7.1 or higher
  • LabVIEW Modulation Toolkit 3.0 or higher
  Please see Directions to Run the Simulations below.

  Caveats about version 1.0:

  • The default settings provide 1.344 Mbps downstream (336 bits/symbol) and 0.208 Mbps upstream (52 bits/symbol). The user can change the bit allocation table to achieve higher or lower data rates (see next bullet). The default bit allocation table has not been chosen with a particular channel in mind, and hence, is far from optimal for a given channel.
  • In order for changes in parameter values to take effect, you will need to stop the simulation, change the parameter values, and rerun the simulation.
  • The channel model is a channel (FIR) impulse response plus additive white Gaussian noise. All eight carrier serving area channel impulse responses are available for the user to select. The time-domain equalizer has been pre-computed using exact channel knowledge by using the Minimum ISI method.
  • The configuration of the Reed-Solomon codec is fixed. We will allow the user to configure it or disable it in a future release.

Directions to Run the Simulator

• To run the simulation within LabVIEW, you will need to have version 7.1 (or higher) of LabVIEW and version 3.0 (or higher) of the LabVIEW Modulation Toolkit. After you download and unzip the above release, start LabVIEW. Then,
  • For version 1.1, open either ADSL2Bidirectional.vi or ADSL2Unidirectional.vi in the LabVIEW sub-directory of the release.
  • For version 1.0, open ADSL2Sim.vi (which is uni-directional transmission) in the LabVIEW sub-directory of the release.
  Finally, run the virtual instrument (VI) by choosing Operate...Run, hitting Ctrl-R, or hitting the right arrow icon in the upper left part of the demo window.
• To run the simulation without LabVIEW, you'll need to download and install the freely distributable LabVIEW Run-time Engine Version 7.1 for Windows 2000/NT/XP. Then,
  • For version 1.1, open either ADSL2Bidirectional.exe or ADSL2Unidirectional.exe in the bin sub-directory of the release.
  • For version 1.0, open ADSL2Sim.exe (which is uni-directional transmission) in the bin sub-directory of the release.

According to the G.992.3 standard's support for trellis coding, there must be even number of "one bit" subchannels and odd number of "zero bit" subchannels in the Bit Allocation Table.

To obtain help about any parameter setting (control) or display (indicator), move the mouse over its text/icon, and the help information should appear in the context help window. The context help window can be opened by hitting Ctrl-H.

References

1. Albert Azzam and Niel Ranson, Broadband Access Technologies, McGraw-Hill, 1999.
2. John A. C. Bingham, ADSL, VDSL, and Multicarrier Modulation, Wiley, 2000, ISBN 0-471-29099-8.
3. Walter Y. Chen, DSL: Simulation Techniques and Standards Development for Digital Subscriber Line Systems, Macmillan Technical Publishing, 1998, ISBN 1-57870-017-5.
4. Ian Wong, Daifeng Wang, and Brian L. Evans, "High-Speed Wireline Communication Systems", May 31, 2005.
5. Thomas Starr, John M. Cioffi, and Peter J. Silverman, Understanding Digital Subscriber Line Technology (CD-ROM included), Prentice Hall PTR, 1999, ISBN 0-13-780545-4.

Mail comments about this page to bevans@ece.utexas.edu.