June 24, 2007
June 24, 2007
June 27, 2007
Computers in Education
12.752.1 - 12.752.12
Fixed-Point DSP Implementation: Advanced Signal Processing Topics and Conceptual Learning
In this paper a description of a unique fixed point systems course, including a list of topics, a description of labs, and a discussion of the focus on a course project. The course has run four times using simulation environments to promote analysis and visualization. The content of the course has made it apparent that there are numerous linkages to advanced signal processing topics, and these are described. The course has also led to the initiation of an educational experiment using the Signals and Systems Concept Inventory (SSCI) to measure how two very different electives affect student understanding of basic concepts. The experiment compares the fixed point course which is very lab oriented, to a theoretical elective. Preliminary results are described. Work to develop a course text and lab materials is described as part of an effort to promote the adoption of fixed point material widely in electrical and computer engineering curricula.
Fixed-point implementation issues in digital signal processing (DSP) are not widely taught or deeply covered in most U.S. undergraduate (or graduate) curricula. There seems to be a perception among faculty that fixed-point implementation is difficult to tie to theory, and not important for advanced work in the field. However, the author’s experiences show that industrial practitioners rely heavily on fixed-point implementation skills, and that many opportunities exist to link a fixed-point implementation course to advanced signal processing topics. The author has taught a fixed-point system design course four times, and each time the need to draw on advanced topics has become more obvious.
The course is called DSP System Design, not Fixed-Point Algorithm Development, because the only way to give students adequate experience with the tradeoffs and performance issues involved is to build the course around a project. Learning to measure, specify, and adjust the system’s performance is a critical element of the course, and it drives the students to deepen their understanding of the fixed-point effects. Although many possible projects could serve well, the course has been based on an SSB communication system which takes input speech at an 8 kHz sample rate and then raises the sample rate to 96 kHz (12x) for SSB modulation at 40 kHz (actually four channels are implemented eventually). The receiver removes out of band interference, demodulates the signal, and then reduces the sample rate back to 8 kHz. The basic design is then extended to operate at four channel frequencies with minimal inter-channel interference, and subject to various (conflicting) performance criteria such as speech quality, SNR, and computational complexity.
In the past three offerings, all of the course project work has been done in MATLAB, primarily using the Fixed Point Toolbox functions. All of the fixed-point system development is done as
Padgett, W. (2007, June), Fixed Point Dsp Implementation: Advanced Signal Processing Topics And Conceptual Learning Paper presented at 2007 Annual Conference & Exposition, Honolulu, Hawaii. https://peer.asee.org/2545
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