Abstract:

Though analog-to-digital (A/D) signal conversion is addressed to in almost all telecom textbooks, associated implementation issues networks are considered beyond the scope of most relevant textbooks and are referred to rather briefly if all. Yet, encountering actual digital transmission applications is necessary for students to enhance their conceptual understanding and comprehend how the relevant theory is applied in real telecom problems.

As in most relevant courses, the lectures described in this article (part of the “Telecommunication Systems” course offered at the Electrical & Electronic Engineering Dept, School of Pedagogical & Technological Education (ASPETE), Athens, Greece) focus on Pulse Code Modulation (PCM) which is the dominant analog-to-digital (A/D) conversion technique used in telecom networks. However, in addition to presenting the essential A/D processes (such as, sampling, quantization and coding), the teaching approach followed aims at the students encountering actual implementation issues mainly in the context of digital telephony. It has to be noted that, though nowadays telecom services (such as telephony, data or broadcasting) tend to be delivered in an integrated manner, digital telephony (by means of the conventional time-division-multiplexing or TDM hierarchy) forms a background necessary for the students to encounter state-of-the-art telecom applications.

Application oriented topics that are addressed to during the lectures include the following:
- Non-linear quantization (in its digital format) as a means to improve quantization noise in digital telephone networks.
- Line coding, as a means to improve transmission quality and keep the telecom link synchronized.
- The E1 digital signal (including the formation and the role of the synchronization/servicing and the signaling bytes) and the implementation of an E1 telephone link.
- Other applications such as the A/D conversion of audio and video signals (including a reference to the need for signal compression).
- Transmission of PCM signals through fiber-optic and satellite links.

To further support the teaching procedure and enhance students’ active participation, gaming tools such as Kahoot may be used, through which students will be called to answer to specific questions regarding the A/D process. In any case (and in order to encounter the overall digitization process) the students are given a simple analog signal that have to convert into a transmissible PCM signal.

A difficulty that several students encounter when dealing with the A/D conversion has to do with the relevant mathematical analysis, particularly regarding sampling theorem and quantization noise. To avoid distracting students’ attention from the core issues of A/D conversion, mathematics is kept rather brief and simplified, however, students are encouraged to use the additional material they are provided with, most of which refers to the mathematics of the PCM process.

Keywords:

Engineering Education, Electronic Engineering Education, Telecommunications.