Texas Instruments Develeoper's Conference, Feb. 18-20, 2004, Houston, Texas.

Modem Design, Implementation, and Testing Using NI's LabVIEW

Brian L. Evans

with key contributions by Ahmet Toker, Vishal Monga Zukang Shen, and Ian Wong

Department of Electrical and Computer Engineering, 1 University Station C0803, The University of Texas at Austin, Austin, TX 78712 USA

bevans@ece.utexas.edu - shen@ece.utexas.edu - toker@ece.utexas.edu - Vishal.Monga@xeroxlabs.com - iwong@ece.utexas.edu

Draft of the Slides

Abstract

The TI TMS320C6000 DSP family is a key enabling technology for ADSL, mobile wireless basestation, and wireless LAN transceivers. These transceivers share many communication subsystems in common. For example, they include sinusoidal generation, finite impulse and infinite impulse response filters, adaptive subsystems (equalization, timing recovery, and clock recovery), and either pulse or quadrature amplitude modulation and demodulation. Interestingly, a V.22bit voiceband transceiver includes all of these subsystems. Essentially, modern high-speed transceivers use the same subsystems in a V.22bit modem but at a much higher sampling rate.

In the real-time DSP laboratory course at Austin, which is a junior elective, students design, implement, and test a V.22bit voiceband modem [1]. In the laboratory component, students implement transceiver subsystems on a C6701 evaluation module board by programming in C and assembly languages; develop and debug the software using TI's Code Composer; and test the real-time implementation using standard test equipment. The lecture and recitation components cover the background needed to complete the labs. The lecture also shows how the modem subsystems are used in modern signal processing and communication systems. More than 100 students take this course each year.

In the class, students often get caught up in the modem subsystem of the week and lose the perspective of the system in which it fits. To help the students maintain the larger picture, we are integrating LabVIEW, which is a graphical dataflow modeling and simulation tool from National Instruments, into the course. In particular, the students will use the

  1. LabVIEW v.22bis demo for desktop simulation to visualize the modem, starting in Fall 2003, and
  2. LabVIEW DSP Integration Toolkit to test the modem design, starting in Spring 2004.
Students are already familiar with LabVIEW from at least one of the pre-requisite courses.

Visualization has two components. First, the graphical block diagram for the transmitter and receiver shows the relationship between the subsystems. Second, the simulation will have a variety of active controls. Students can probe the values of wires, and alter parameters (e.g channel noise power) during simulation to see the effect on communication. The desktop simulation will be provided to the students to use where and when they see fit.

The LabVIEW DSP Integration Toolkit interacts directly with Code Composer. The Toolkit will enable the student to migrate subsystems from the desktop simulation of the modem to the C6700 DSP board. The student can use the same PC on which the DSP board resides to validate the design. Alternately, the desktop simulation can be run on a separate PC to serve as either the transmitter or the receiver that is connected to the modem the student is designing.

Reference:

  1. S. Tretter, Communication system design using DSP algorithms: with laboratory experiments for the TMS320C6700, Kluwer, ISBN 0-306-47429-8, March 2003.

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Last Updated 01/16/06.