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Design and Simulation of ADSL2 Transceivers Using LabVIEW

Design and Simulation of ADSL2 Transceivers Using LabVIEW. Ian C. Wong and Prof. Brian L. Evans In collaboration with Alex Olson and Daifeng Wang Embedded Signal Processing Laboratory The University of Texas at Austin. Outline. Background Discrete Multitone (DMT) Modulation

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Design and Simulation of ADSL2 Transceivers Using LabVIEW

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  1. Design and Simulation of ADSL2 Transceivers Using LabVIEW Ian C. Wong and Prof. Brian L. Evans In collaboration with Alex Olson and Daifeng Wang Embedded Signal Processing Laboratory The University of Texas at Austin

  2. Outline • Background • Discrete Multitone (DMT) Modulation • ADSL/ADSL-2 • ADSL-2 Simulation in LabVIEW • Main features • Top-level architecture • Main front panel • Conclusion • Demonstration

  3. channel carrier magnitude subchannel(QAM signal) frequency Subchannels are 4.3 kHz wide in ADSL and VDSL Discrete Multitone (DMT) Modulation • Standardized for ADSL and VDSL • Divide broadband channel into narrowband subchannels • Based on the Fast Fourier Transform

  4. Internet Downstream (DS): High data rate DSLAM Central Office DSL modem DSL modem Upstream (US): Low data rate VoiceSwitch LPF LPF Customer Premises Telephone Network DSLAM - Digital Subscriber Line Access Multiplexer LPF – Low Pass Filter (passes voiceband frequencies) Digital Subscriber Line (DSL) Broadband Access

  5. ADSL2 and ADSL2+ - the new standards • ADSL2 (G.992.3 or G.dmt.bis, and G.992.4 or G.lite.bis) • Completed Jan. 2005 • Minimum of 8 Mbps downstream and 800 kbps upstream • Improvements on: • Data rate vs. reach performance • Spectrum and power control • Robustness against loop impairments • ADSL2+ (G.992.5) • Doubles the bandwidth used for downstream data (~20Mbps at 5000 ft)

  6. ADSL2 Simulation in LabVIEW • *Ver. 1.1 Released May 2006 • Freely distributable • GUI and functions in LabVIEW • Executable version available • Motivation • Provide a convenient framework for developers to design their algorithms • Provide a common environment for testing and performance comparison *http://www.ece.utexas.edu/~bevans/projects/adsl/simulator/index.html

  7. Main Features • Supports both uni-directional and bi-directional communication • Includes wire-line channel models • Carrier Servicing Area (CSA) loops 1-8 (based on measurements) • User customizable channel impulse response • Implements standard DMT transceiver functions, including • Transceiver training • Frame synchronization • Time- and frequency-domain equalization • Peak-to-average power reduction • Optimal bit- and power loading • Trellis-coded modulation

  8. Top-level Architecture Four independent while loops communicating via queues SS Loop: SS MAC, TX, and RX Different states CO Loop: CO MAC, TX, and RX

  9. Top-level Architecture (cont’d) • CO and SS loops • Transmit and receive a single DMT symbol/frame on each iteration • Communication done through LabVIEW queues • Models full-duplex transmission • Channel simulation loops • Sample-by-sample operation • FIR filter corresponding to the impulse response of the wire line channel plus AWGN • Standard carrier servicing area (CSA) loops 1-8 • Ideal impulse response (Kronecker delta) with and without delay

  10. Front Panel • Simulation controls • Simulation state indicator • Description window • Simulation parameters • Performance indicators

  11. 1. Simulation controls • The simulation may either be “Paused” or “Running” • Simulation parameters may be changed only when “Paused” • “Simulation Delay”control sets how long the simulation delays between ADSL symbols/frames • The “Quit Simulation" button will stop the simulation and terminate the program.

  12. 2. Simulation state indicator • Shows the states of the CO and SS loops • Roughly correspond to those in the ADSL2 standards • Counter for the number of symbols processed so far • “Symbols/Sec” indicator shows the wall-clock rate at which the simulation is progressing (in symbols per second)

  13. 3. Description window • Gives a user-friendly description of the current simulation state

  14. 4. Simulation parameters • DMT Parameters • Key DMT transceiver parameters (one for each direction) • Channel Parameters • Choose channel model and SNR level • Peak-to-average ratio reduction parameters • Error control coding parameters

  15. 5. Performance indicators Time-domain waveform PAR reduction Channel estimates/equalizers

  16. 5. Performance indicators (cont’d) Bits and gains results Frame synchronization performance BER and data rate performance

  17. Conclusion • ADSL2 Simulator in LabVIEW • User-friendly GUI • Modular and block-diagram based • Relatively easy for developers to modify/add features • Bidirectional communication • Models non-ideal conditions • Wireline channel, frame synchronization, training, estimation, and bits/gains setting • Future releases • MIMO-DMT • Dynamic spectrum management

  18. Demonstration

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