Course teached as: B029701 - COMUNICAZIONI DIGITALI Second Cycle Degree in TELECOMMUNICATION ENGINEERING Curriculum SISTEMI DI TELECOMUNICAZIONE
Teaching Language
Italian language
Course Content
Introduction to digital communications.
Communications through band limited channels.
Equalization techniques.
Optimum receiver for signal with random phase in AWGN channels.
Carrier and symbol synchronization.
Digital communication of waveforms with memory.
Propagation through time varying channels affected by multipath. Fading.
OFDM modulation.
Digital television: DVB-T standard
R. Steele: Mobile radio communications. Pentech Press, London, 1992.
D. Parsons: The mobile radio propagation channel. Pentech Press, London, 1992.
E. Damosso, R. Stola: Radiopropagazione. Sola superiore G. Reiss Romoli, 1992.
Learning Objectives
The aims are:
- describing the fundamental characteristics and operating principles of digital transmission systems;
- providing mathematical tools for the analysis and evaluation of their performance and for the design of various constituent subsystems;
- providing application examples in systems of general interest.
Skills acquired by the student:
- ability of evaluating the behavior of numerical communications systems in actual operating conditions;
- ability to design these systems.
Prerequisites
Topics of Analog and Digital Communications
Teaching Methods
Classroom lectures
Further information
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Type of Assessment
Oral examination consisting of four questions.
These questions concern:
- learning of the fundamental characteristics and principles of digital transmission schemes, with reference to those analysed in the course;
- knowledge of mathematical tools for the analysis and design of different subsystems constituting a digital transmission system;
- acquired ability of evaluating the behavior of numerical communications systems in actual operating conditions.
Course program
Introduction to Digital Communications - Model of a communication system; description of the main subsystems; definition of the performance parameters.
Transmission through band-limited channels - The problem of Inter-Symbol Interference. The eye diagram, the Nyquist criterion. Technical limitation of intersymbol interference. Main methodologies for channel equalization: Zero-Forcing equalization, MMSE equalization. Equalizers: T and T/2 equalizers, zero-forcing and MMSE adaptive equalizers, decision-feedback equalizer.
Synchronization recovery of carrier and symbol - Influence of synchronization errors on the performance of a digital communication system. MAP and ML parameter estimation for recovering carrier synchronization and timing. Some circuits for carrier synchronization and timing.
Waveform transmission through Gaussian channels with incoherent demodulation – Optimum demodulation criterion. Physical implementation of the optimum demodulator. Applications to digital modulation schemes: performance of incoherent demodulation of an M-ary FSK scheme.
Differential Techniques: DPSK and DQPSK, differential modulators, coherent and incoherent demodulators, performance.
Transmission of waveforms with memory - Main properties. The MLSE decision criterion; application of the Viterbi algorithm for the MLSE demodulation. Full and partial response CPM. Coded modulation for band-limited channels (TCM): trellis representation, set partitioning method and rules of Ungerboeck, demodulation using the Viterbi algorithm, performance.
Fundamentals of OFDM transmission; implementation of OFDM modulation and demodulation using DFT; implementation of OFDM modulation for transmissions in mobile radio channels: use of the guard and COFDM. Differential encoding.
Fundamentals of Digital Terrestrial Television (DVB-T). Comparison between standards DVB-T2 and DVB-T.
Applications: concept of link adaptation (Adaptive Coding and Modulation) and dynamic use of resources, application examples in OFDM systems; synchronization and equalization in OFDM systems, examples in next generation wireless systems.
The 6 CFU-"Digital Communications" Course does not include the following topics:
OFDM transmission; Analysis of effects of frequency and phase erors on system performance.
Characterization of the propagation on multi-paths, time-varying transmission channels. General characteristics of the mobile radio channels. Analysis of small-scale approximation for a finite number of paths. Dispersion in frequency and time. Bello’ functions of the channel. Statistical characterization: Rayleigh and Rice channels. Autocorrelation functions of the functions of Bello in the case of WSSUS channel; power delay profile and correlation function in frequency; Doppler spectrum and the correlation function in time; band and time of coherence; scattering function. Flat channel in frequency (non-selective); flat channel in time (slowly varying); flat channel in frequency and time.
Effects of multipath fading on digital modulations and countermeasures. Evaluation of the performance of binary PSK and FSK modulations in the presence of flat frequency and time fading. Diversity transmissions and performance evaluation of diversity techniques for binary modulations; Maximal Ratio Combiner.