Interactive DSP education using Java

In this paper, we argue that Java is a natural language to develop interactive teaching material that can be shared and distributed widely. Unlike any other programming language or platform we know, Java development is justified because of its almost universal acceptance. We develop a Block Diagram (BD) based approach that allows to develop interactive and downloadable signal processing laboratories. As an example, we show how specific experiments for a DSP class, as well as for an advanced course on wavelets have been developed. The article first explains why the Java language has been chosen, and then describes what has been realized today. Finally, we show how the BD representation can be efficiently used for the development of a wavelet theory course. It is shown that only a few simple blocks are sufficient for creating many didactic programs. This can be seen as an a posteriori justification of the BD model. 1. Platform and programming language for Web-based teaching 1.1 State-of-the-art In the context of Computer Based Education (CBE), the Web has been mostly used as a method of disseminating static information or as a support medium to traditional books. This is due mainly to the lack of a Web programming standard for designing truly interactive courses. The arrival of the Java language has allowed to design programs (applets) that can be executed on the student’s computer. Many Java applets have been developed that demonstrate standard DSP algorithms [4]. In these applets, the interaction with the user is based on previously existing Matlab (or other packages) demos [6][8] (the student is using sliders to modify parameters and buttons to perform some actions), and therefore represents mostly converting code to Java. Although this interaction mode is easy to use and represents what a researcher needs, it has several drawbacks. From the educational standpoint, the student does not know in detail how the algorithm works since he is seeing only input and output data. In this case, the algorithm is like a black box, whose behavior can be determined by monitoring input and output data. From the programming standpoint, there is an obvious advantage in writing code in Java directly; most algorithms can be decomposed in several phases; some may be reusable, like for instance all the I/O part and the graphical output that is similar for many algorithms. Moreover, these tasks are usually the most time-consuming and the least interesting to develop. 1.2 The Block Diagram model In this article, we propose a model based on a Block Diagram (BD) representation. In this model, the algorithm is described as ’ = Bell Labs, Lucent Technologies, Murray Hill, NJ a set of blocks joined together, where basically the output of a block is linked to the input of the next. The system allows to describe a BD-based algorithm that represents the flow of data through operators. An algorithm is decomposed into basic blocks (e.g. lirst get the data, then take an Fm and finally display the spectrum). The applet is created by building its BD model. When run, each block is highlighted as the data flows through it, so that the student knows what is taking place at every moment. The student can interactively place probes on the block diagram to monitor any signal coming out of any block. A typical algorithm is depicted in Figure 1. Input data is fetched or generated, then the algorithm is run (processing). Many iterations can be necessary to reach the correct result and the user may change input data for computing a new result. Input data Processing r____-----------______________