AN IMPROVED EDUCATIONAL SOFTWARE FOR LEARNING SPREAD-SPECTRUM COMMUNICATIONS OVER A REAL ACOUSTIC CHANNEL USING AUDIO HARDWARE

Focusing on the subject “Signal processing for communications” taught in the Master of Telecommunication Engineering at University of Jaen (Spain), it is difficult to learn advanced digital communications because the student must have a deep mathematical background and to master the fundamentals of digital communications explained in previous subjects of Telecommunication Engineering Degree. This paper is an improved and extended version of a previous work titled “Enhancing the transference of knowledge of topics about advanced digital communications techniques using a multimedia interactive simulator” published in the 6th International Technology, Education and Development Conference (INTED) in 2012. Specifically, we propose an educational software for learning direct sequence spread-spectrum communications over a real acoustic channel (it ranges until 20Khz) using audio hardware such as speakers and microphone. The proposed software evaluates a multiuser transmission scenario in which a real transmission has been considered, in other words, each received signal from a user is not synchronized with the rest of the users. Each speaker is used to generate the transmission of each user while the unique receiver of the system is implemented using only one microphone. All stages of a direct sequence spread-spectrum communication system have been implemented and adapted to use the acoustic channel, such as spreading codes, modulation using an audible carrier, synchronization… In order to achieve a powerful and reliable tool of self-learning, each student can modify a set of parameters related to the spread-spectrum communication system (number of users, bitrate, length of the spreading codes, signal-to-noise ratio, length of the header…) evaluating different transmission scenarios. The advantage of the software is that each student can see all temporal-spectral transformations suffered by the input signal at each stage of the communication system from the transmitter to the receiver. Due to the use of an acoustic channel, each student can listen how each signal sounds before and after the spreading transformation. All these complementary information increases the efficiency of the transference of knowledge between lecturer-student.
New material associated to direct sequence spread-spectrum communications has been created. The student must study the content of the material and interacts with the educational software in order to complement the theoretical concepts explained in classroom. The material and the educational software will be available in the web-based platform ILIAS of the University of Jaen. In this way, the autonomous study of the student is reinforced personalizing different communications systems and multiuser scenarios using the web-based platform resources.