Venkatraman Atti

Interactive online undergraduate laboratories using J-DSP

An interactive Web-based simulation tool called Java-DSP (J-DSP) for use in digital signal processing (DSP)-related electrical engineering courses is described. J-DSP is an object-oriented simulation environment that enables students and distance learners to perform online signal processing simulations, visualize Web-based interactive demos, and perform computer laboratories from remote locations. J-DSP is accompanied by a series of hands-on laboratory exercises that complement classroom and textbook content. The laboratories cover several fundamental concepts, including z transforms, digital filter design, spectral analysis, multirate signal processing, and statistical signal processing. Online assessment instruments for the evaluation of the J-DSP software and the associated laboratory exercises have been developed. Pre/postassessment data have been collected and analyzed for each laboratory in an effort to assess the impact of the tool on student learning.

On-line laboratories for speech and image processing and for communication systems using J-DSP

J-DSP is a Java-based object-oriented programming environment that was developed at Arizona State University for use in the undergraduate DSP class [A. Sapnias et al., June 2000]. In this paper, we describe innovative software extensions on J-DSP to accommodate on-line laboratories for speech processing, image processing, and communications systems. Significant modifications in the object-oriented GUI of J-DSP that enable simulation of feedback systems are also presented. The speech processing functions enable on-line simulations of speech coding algorithms and include PCM and ADPCM quantization as well as more elaborate algorithms such as the LPC and the CELP. Image processing functionalities include development of 2-D signal processing capabilities including 2-D-FFT, 2-D-filter design, and 2-D graphics and picture processing. Communications functionality covers several aspects of analog and digital modulation and demodulation. On-line laboratory exercises have been developed in the aforementioned areas and posted on a web site (http://jdsp.asu.edu). This site also includes on-line evaluation forms for the exercises. Statistical and qualitative evaluations that assess the learning experiences of the students that use J-DSP are presented.

Experiments With Sensor Motes and Java-DSP

Distributed wireless sensor networks (WSNs) are being proposed for various applications including defense, security, and smart stages. The introduction of hardware wireless sensors in a signal processing education setting can serve as a paradigm for data acquisition, collaborative signal processing, or simply as a platform for obtaining, processing, and analyzing real-life real-time data. In this paper, a software interface that enables the Java-digital signal processing (J-DSP) visual programming environment to communicate in a two-way manner with a wireless sensor network is presented. This interface was developed by writing nesC (an extension to the C programming language for sensors) code that enables J-DSP to issue commands to multiple wireless sensor motes, activate specific transducers, and analyze data using any of the existing J-DSP signal processing functions in real time. A series of exercises were developed and disseminated to provide hardware experiences to signals and systems and signal processing undergraduate students. The hardware with the J-DSP software has been used for two semesters in the senior level digital signal processing (DSP) course at Arizona State University. The interface, the exercises, and their assessment (instruments and results) are described in the paper.

On-line signal processing using J-DSP

The Java-DSP (J-DSP) on-line laboratory software has been developed from the ground up at Arizona State University to support the computer lab portion of the senior-level DSP course. J-DSP provides capabilities for web-based DSP simulations that can be run using a PC with a Java-enabled browser. J-DSP is accompanied by exercises that actively engage students in several concepts including Z-transforms, filter design, spectral analysis, and random signal processing. Tools and on-line instruments for assessment of the J-DSP software and the associated lab exercises have been developed and described in this letter. Statistical analysis of the pre/post assessment data revealed that the effect of student involvement and the student learning has been enhanced by using J-DSP.

Rate determination based on perceptual loudness

We describe a perceptually-motivated rate determination algorithm (RDA) for variable bit rate speech coding. Unlike existing rate selection strategies that are based on a voice activity detector and energy thresholds, the proposed method employs a perceptual loudness (PL) measure. The TIA IS-127 enhanced variable rate codec (EVRC) has been chosen as the test-bed for evaluating the performance of the PL-based rate selection strategy relative to three existing methods. In particular, the comparative study includes the following rate determination algorithms: voice activity detection; speech frame energy-thresholding; phonetic segmentation. Experimental results demonstrate that the proposed PL-based RDA compares well against other rate selection techniques in terms of average bitrate and speech quality.

Interactive Java modules for the MPEG-1 psychoacoustic model [audio coding teaching applications]

This paper presents a collection of interactive Java modules for the purpose of introducing undergraduate DSP students to perceptual audio coding principles. This effort is part of a combined research and curriculum program funded by NSF that aims towards exposing undergraduate students to advanced concepts and research in signal processing. A computer laboratory with several supporting exercises and Java functions has been developed for use in our undergraduate DSP course. This exercise along with the accompanying Java software was assigned and assessed in the Summer of 2004 and will be reassessed in the Fall of 2004. Results of this assessment along with student comments are presented at the end of the paper.

On the use of J-DSP for on-line laboratories in linear systems courses

This paper describes the utility of the Java-DSP (J-DSP) technology and the associated on-line laboratories in linear systems courses. J-DSP originally was developed for use in a DSP undergraduate course. Recently the functionality of J-DSP has been extended to support communications, image processing and controls courses. In addition, several new functions have been developed to support advanced DSP applications, such as, speech coding, voice recognition, and spectral estimation. Some of these extensions have also been used to demonstrate the use of DSP in emerging research areas such as Genomics. The first part of the paper discusses these functionality extensions and planned functionality and the second part focuses on the on-line J-DSP laboratories and assessment of J-DSP labs.

On-line simulation modules for teaching speech and audio compression techniques

In this paper, we present a collection of software educational tools for introducing speech and audio compression (or coding) techniques to undergraduate and graduate students. These speech processing tools enable online simulations of speech compression algorithms that are being used in digital cellular phones, Internet streaming applications, teleconferencing, and voice over Internet protocol (VoIP) applications. This simulation software is accompanied by a series of computer experiments and exercises that can be used to provide hands-on training to class participants. With this on-line simulation tool and a set of well-complemented laboratory exercises, students can easily comprehend the basic techniques involved in speech and audio coding algorithms. Specific functions t hat have been developed include the typical modules that are usually embedded in CD-players, MP3-players, and mobile phones. Details on the software, exercises, and assessment data will be provided at the conference.

A simulation tool for introducing algebraic celp (ACELP) coding concepts in a DSP course

This paper presents an educational tool 1 for introducing Code Excited Linear Prediction (CELP) coding concepts in senior undergraduate and graduate DSP-related courses. The tool consists of a user-friendly graphical interface along with a complete MATLAB 2 realization of all aspects of the Algebraic CELP G.729 algorithm [2]. This simulation software is accompanied by a series of computer experiments and exercises that can be used to provide hands-on training to class participants. The exercises designed based on the simulation tool may be used by instructors in a class setting to demonstrate key signal processing concepts associated with the processing of telephone-based speech. The MATLAB ACELP tool is being used in Arizona State University undergraduate DSP courses as well as in a graduate course on speech coding and in a continuing education short course. Evaluation of the tool and the exercises is being performed by an educational software assessment specialist. In the last ten years we have witnessed a series of breakthroughs in speech coding followed by several standardization efforts [1]. Most of the standardized algorithms are based on CELP coders. Although speech coding researchers and practitioners are well aware of the fundamental ideas used in CELP, students do not get much of an opportunity in courses to study these algorithms. A software simulation tool, implementing the ACELP algorithm has been developed for the purpose of introducing speech coding and the associated signal processing concepts to both undergraduate and graduate students. We choose an Algebraic Code Excited Linear Prediction (ACELP) algorithm as a basis for this educational tool because of the wide proliferation of algebraic codebooks in cellular standards. The algorithm was coded in a modular manner and in its entirety using MATLAB. The tool is based on a user-friendly graphical user interface (GUI) that allows the student to study and verify through graphics the various aspects of the algorithm such as: the LP analysis, the open-loop pitch search, the adaptive codebook search (pitch search), the fixed codebook search, and the bit allocation patterns. We choose MATLAB as the implementation platform because it allows the user to easily understand the complex parts of the algorithm whose function is not

Web-based experiments for introducing speech recognition basics in a DSP course

In this paper, we describe Web-based educational software tools tailored to expose students in an undergraduate DSP course to the basics of hidden Markov model (HMM)-based speech recognition. In particular, we developed Java software that enables on-line computer laboratories on the essential preprocessing, HMM, and Viterbi algorithms as used in a basic speech recognition task. The software is complemented by streaming lectures, a set of on-line demonstrations with animation, and exercises that take the student through HMM training and recognition. The software is being made available to students in the Fall of 2003 and we expect to present assessment results at the conference.