Digital communications A - L

Objectives

The course aims to provide students with the basic knowledge and methodological tools required for the analysis and design of digital communication systems, with particular reference to the main baseband and passband transmission schemes. The fundamental principles of digital transmission will be addressed, with particular attention to signal representation, the characteristics of noisy channels, and performance in terms of error probability, energy, power, bandwidth, and spectral efficiency.

In particular, the fundamentals of digital coding and modulation will be introduced through the study of vector signal representation, orthogonal and orthonormal bases, and the main decision rules, such as MAP and ML. PAM systems, intersymbol interference, and Nyquist criteria will also be analyzed, together with the main passband digital modulation techniques, including OOK, BPSK, FSK, PSK, and QAM. The principles of analog modulation techniques, including AM, DSB-SC, SSB, VSB, PM, and FM, as well as multicarrier transmission techniques such as DMT and OFDM, will also be presented.

The course will also cover the principles of analog-to-digital conversion and PCM, with particular reference to sampling, uniform and non-uniform quantization, signal encoding and reconstruction, and companding techniques. The fundamentals of information theory and source coding will also be introduced, with reference to Shannon-Fano and Huffman coding, together with channel coding techniques for error detection and correction.

Practical exercises will be carried out during the course to provide students with operational skills in the analysis and design of digital communication systems. The activities will include exercises on vector signal representation, decision regions and error probability, Nyquist filter design, performance evaluation of modulation techniques, and PCM and coding systems. Software tools, particularly MATLAB/bertool, will also be used to compare the performance of different modulation techniques.

Students will also develop the ability to critically compare different design solutions according to bandwidth, power, reliability, and spectral efficiency requirements, and to discuss the results obtained, developing problem-solving skills and transferable competences useful in technical-scientific and professional activities.

Knowledge and understanding

Acquire and understand the fundamental principles of digital transmission, with particular reference to vector signal representation, decision rules, digital modulation techniques, and baseband and passband transmission systems. Understand the issues related to noise, intersymbol interference, error probability, bandwidth, and spectral efficiency.

Develop the ability to analyze analog-to-digital conversion processes, source and channel coding techniques, and the main analog and digital modulation techniques.

Applying knowledge and understanding

Develop the skills required to analyze a digital communication system and determine its main performance parameters, such as symbol and bit error probability, energy per bit, power, bandwidth, and spectral efficiency. Students will also be able to compare different modulation and coding techniques and assess their suitability for use in real communication systems.

Making judgements

Develop an appropriate degree of independent judgement in identifying the characteristics of digital transmission systems and in selecting the most appropriate techniques according to performance, bandwidth, power, and complexity requirements. These skills may also be applied to more complex communication systems, such as those based on mobile networks, satellite systems, and 5G and 6G architectures.

Communication skills

Develop the ability to communicate effectively, using appropriate technical language, concepts and issues related to digital transmission, coding, modulation techniques, and transmission equipment.

Learning skills

Develop the ability to independently investigate scientific and technological developments in the field of digital communications, with particular reference to transmission, modulation, and coding techniques employed in modern wireless systems and high-capacity networks.

The course is composed of a part of theory (28 hours), and a part of practice (30 hours).

Learning assessment may also be carried out on-line, should the conditions require it. To ensure equal opportunities and in compliance with current laws, interested students may request a personal interview in order to plan any compensatory and/or dispensatory measures based on educational objectives and specific needs. Students can also contact the CInAP (Centro per l’integrazione Attiva e Partecipata — Servizi per le Disabilità e/o i DSA) referring teacher within their department (https://www.cinap.unict.it/content/referenti).

Essential knowledge:

• Bandwidth of a baseband and passband signal
• Periodic signals
• Probability theory, random variables, and random processes
• Random processes, with particular emphasis on white noise and Gaussian processes
• Linear time-invariant (LTI) systems, filters, and distortion

Important knowledge:

• Convolution
• Power spectral density and autocorrelation function
• Probability density function of a random variable
• Gaussian random process
• Signal sampling and sequence interpolation

Useful knowledge:

• TCP/IP communication architecture
• Encoding of a speech signal
• Propagation of electromagnetic waves in free space

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

Reference material

[T1] Leon W. Couch, Fondamenti di Telecomunicazioni, Prentice Hall

[T2] Alessandro Falaschi, Trasmissione dei Segnali e Sistemi di Telecomunicazione, Web edition, Versione 2.0, 2023.

[T3] K. Sam, Shanmugam “Digital and Analog Communication Systems”, John Wiley & Sons.

[T4] Appunti del docente.

Contribution of the course to the objectives of the 2030 Agenda for Sustainable Development

The topics covered in the course and the knowledge acquired are directly or indirectly instrumental to the development of sustainable technological solutions, while also contributing to quality education, in accordance with Goals 3, 4, 7, 9, 11, 12, 13, 14, and 15 of the 2030 Agenda for Sustainable Development.

[T1] Leon W. Couch, Fondamenti di Telecomunicazioni, Prentice Hall

[T2] Alessandro Falaschi, Trasmissione dei Segnali e Sistemi di Telecomunicazione, Web edition, Versione 2.0, 2023.

[T3] K. Sam, Shanmugam “Digital and Analog Communication Systems”, John Wiley & Sons.

[T4] Appunti del docente

The examination consists of an in-course assessment (optional) and an oral examination.

The in-course assessment, lasting 3 hours, is evaluated according to the following three levels:

• Level A: the student may take the examination by answering only 2 questions on a reduced syllabus.
• Level B: the student has two options:

1) take an oral examination consisting of only 2 questions on a reduced syllabus; however, the final grade cannot exceed 27/30

2) take an oral examination consisting of 2 questions on the complete syllabus if they wish to obtain a final grade without the limitation specified above

• Level C: the student must take an oral examination consisting of 3 questions on the complete syllabus.

Students who do not pass the in-course assessment or do not take it must take a complete examination, which also includes a numerical exercise.

If a demonstration session with stands showcasing telecommunications projects is held during the academic year, students may bring to the examination a brief description of two projects of their choice. In this case, it will be possible to:

• take the examination in Level A even if the student passed the in-course assessment at Level B
• take the examination in Level B even if the student did not pass the in-course assessment.

The in-course assessment is valid until September 30 of the same year in which the course was delivered. After this date, all students must take a complete examination, which also includes a numerical exercise.