Digital communications M - Z

Knowledge and understanding the most important elements regarding digital communications

Capture and understanding the basic elements to analyze digital transmission techniques, and the procedures for achieving the main parameters characterizing a digital and analog communication system.
Improving capabilities to analyze both vector spaces to represent signals, and techniques for analog-to-digital conversion.

Applying knowledge and understanding of the state-of-art technologies of digital communications systems, also targeted to the practical application in non-usual contexts

Skills development for analysis of reference systems of analog and digital communications systems, also aimed at the individuation of the main system parameters (signal-to-noise ratio, bit error rate, bandwidth, energy consumption, circuit complexity). The target is to allow the student to use this knowledge also for future systems, although different from the ones studied in this course.

Making judgements of the main topics of this course

Outgrowth of a sufficient level of making judgements in discovering the main peculiarities of analog and digital communications systems and of the available tools not only for the design of simple systems like the ones studied during the course, but also of more complex systems, like satellite communications, 5G e 6G, which require further maturation of what studied during the course.

Communication skills finalized to heterogeneous interlocutors

Outgrowth of an effective and high-level communications skill for topics regarding analog and digital transmission, modulation systems and transmission devices.

Learning skills of the evolutions of the topics studied during the course, independently

Outgrowth of skills for autonomous training regarding scientific evolution and specific digital communications technologies to deepen new transmission technologies for cables, fiber and wireless, also with reference to techniques applied to ADSL, LTE, 4G, 5G and 6G.

The course includes 58 hours of lessons (frontal teaching, exercises and laboratory).

In the case lectures will be partially or fully realized remotely by a video-communications platform, what declared above could undergo some changes, in order to achieve the objectives targeted in this Syllabus.

Fourier series expansion, Modulation theorem, Convolution, Fourier transform, LTI systems, Filters, Frequency analysis, Sampling, Statistical indices, Probability density function of a random variable, Autocorrelation, Power spectral density, Probability theory, Random variables and random processes.

The course is organized in the following six Elementary Teaching Units (ETU):

1. Introduction

Course organization, the history of TLC (*). Recall of signal theory. General description of a communication system, analog and digital sources, classification of signals and services, transducers. Performance parameters: bit-rate, SNR, MOS, BER, SER. Types of messages and audio frequencies. Hearing and pain threshold, hearing loss (*). Communication channels: ideal, perfect, linear and permanent, linear and non-permanent. Channel bandwidth. Equalization. Non-linear channels: harmonic distortion and intermodulation noise, effects and solutions. Noisy channels. AWGN noise and interference. The radio channel and electromagnetic waves. Attenuation in free space and Friis' formula. Effects of the medium and atmospheric phenomena on propagation (*). The multipath phenomenon. Noisy quadripoles: equivalent noise bandwidth, temperature and noise figure. Resistive quadrupoles (*). Friis formula for cascaded quadrupoles. Antenna and system temperature. Exercises.

2. Digital transmission of voice signals

Characteristics of the speech signal. A/D conversion: sampling, uniform and non-uniform quantization. Quantization SNR. PCM encoding, A-law and μ-law companding. DPCM linear prediction vocoder. ITU-T and ETSI standards for speech compression. Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM). Exercises.

3. Source coding and channel coding

Information theory: information measure and entropy. Examples of discrete sources. Source coding: code properties, code length, coding efficiency, block coding (*), Gray codes, Shannon–Fano coding, and Huffman coding. Exercises. Channel coding: block codes. Code rate. Encoding/decoding delay. Linear and systematic codes. Spectral efficiency. Repetition and parity codes. Interleaving (*). Semantic communications.

4. Baseband digital transmission

Binary and M-ary line coding. Power spectrum of a line code. Clock recovery. Binary and M-ary PAM systems. Intersymbol interference (ISI) and the Nyquist criterion. Eye diagram. Calculation of bit error probability and symbol error probability for binary and M-ary baseband receivers. Shannon–Hartley theorem on channel capacity. Transmission of PCM signals over noisy channels (*). Pulse-carrier modulations: PDM and PPM, and their comparison (*).

5. Introduction to passband modulations

Amplitude modulation and demodulation: DSB, SSB, AM, and VSB. Angle modulation: FM and PM (*). Phase and frequency offsets. Comparison of modulation techniques in terms of power, bandwidth, SNR, and complexity.

6. Digital modulations

Binary modulation schemes: ASK, PSK, and FSK. Performance comparison in terms of power, bandwidth, BER, and complexity. Multidimensional M-ary modulation schemes (*): M-PSK, QAM, and M-FSK. Hybrid modulation schemes: APSK and QAM. Multicarrier modulation: OFDM. Vector representation of digital signals: transmitted and received signals, decoding, and optimum decision rule for AWGN channels.

(*) Topic belonging only to the complete program

[1] Teacher's notes (available on Studium)
[2] K. Sam, Shanmugam “Digital and Analog Communication Systems”, John Wiley & Sons. (References to the individual sections are specified on Studium).
 

The student may choose one of the following assessment methods:

Assessment Type 1 (For those who choose the term paper):

- Midterm exam consisting of 2 exercises in 90 minutes on the first 3 parts of the syllabus – valid for 1 year

- Term paper (groups of 3–4 students, submission by May) – valid for 1 year

- Oral exam with 2 questions on a reduced syllabus – excluding topics marked with (*)

Assessment Type 2 (For those who choose the project):

- Midterm exam consisting of 1 exercise in 45 minutes on the first 2 parts of the syllabus – valid for 1 year

- Project (groups of 3–4 students, submission by May) – valid for 1 year

- Oral exam with 2 questions on a reduced syllabus – excluding topics marked with (*)

Assessment Type 3 (For those who do not pass or do not take the midterm exam):

- Written exam consisting of 1 exercise in 45 minutes on the first 3 parts of the syllabus – valid for one exam session

- Term paper or project (groups of 3–4 students, submission by May) – valid for 1 year

- Oral exam with 3 questions on the complete syllabus

The midterm exam is passed with at least 50% correct execution. Furthermore, a correct execution rate between 50% and 70% results in a deduction of up to 3 points from the overall grade (out of 30).