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 and 5G, 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

The course is composed of a part of theory (35 hours), and a part of practice (15 hours). 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

Convolution

Bandwidth of a base-band and passband signal

Power spectrum and autocorrelation function

Periodical signals

Probability theory, random variables and random processes

Time-invariant linear systems and distortions

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

1. [COU] Leon W. Couch, Digital & Analog Communication Systems (8th Edition), Pearson Education Limited, 2013.
2. [COV] Thomas M. Cover, Joy A. Thomas, Elements of Information Theory, John Wiley & Sons, 28 nov 2012.
3.  [PRO] J. G. Proakis, M. Salehi, Communication System Engineering, Prentice Hall

The exam consists of an optional in-itinere test and an oral exam.

The in-itinere test, lasting 3 hours, is evaluated with a score that will be taken into account during the oral examination.

In particular:

• who pass the test with a “A” score will be able to participate to the exam with a reduced program, in which there will not be any numerical exercise. He will also have to answer only two questions, while the third will be considered passed with a correct answer.
• who pass the test with a “B” score will be able to take the exam with a reduced program, in which there will be only some supplementary exercises to cover the gaps shown in the in-itinere test. He will also have to answer only two questions, while the third will be considered passed with a correct answer.
• who do not pass the in-itinere test will have to take an exam with the full program, as well as those who have not participated in the in-itinere test.

Who pass the in-itinere test with a “B” score will be able to take the exam as “A” score, but obtaining a final score that cannot exceed 27/30.

The oral exam consists of 3 questions. Two of them will concern theory and the description or the implementation of a GNURadio project among those previously provided by the lecturer. The third question will concern the resolution of a numerical exercise.

• Multidimensional digital coding. Main multidimensional modulation techniques. Multidimensional transmission scheme (sequence of bits to be transmitted - transmitter - channel - receiver - received sequence). Multidimensional digital transmitter. Example of transmission of a sequence of bits (11001011) with multidimensional modulation. Modulator and demodulator. Probability of error on the symbol and on the bit. Use of Gray encoding.
• Inter-symbol interference (definition and motivations). First Nyquist criterion; Nyquist filters; ISI cancellation with adapted filter. General expression of the BER for 2-PAM modulations (via the total probability theorem).
• Signal-to-noise ratio (SNR) for uniform quantization for uniformly distributed signal; 6 dB rule; load factor for a uniformly distributed signal. p* threshold of -3dB. Noise power in a given amplitude range, and SNR for generically distributed signal (statement only).
• Introduction to modulation: motivation, definition of: passband signals, modulating signal, modulated signal, carrier signal, complex envelope; spectrum and power spectral density of a modulated signal; average power and peak power of the modulated signals. GNU RADIO G project.