The course treats the design and analysis of some advanced techniques for the digital transmission systems, which are commonly found nowadays in most of the wireless communication standards (UMTS/3GPP, LTE, DVB, 802.11ac, WiMAX). In particular the course will focus on two very important advanced technologies, namely multi-terminal or MIMO techniques and iterative digital receiver techniques.

Multiterminal and MIMO techniques
With “multi terminal” physical layer technologies, multiple transmitter and receivers, or transmitters and receivers equipped with multiple antennas (MIMO) jointly use the same resources of the wireless channel. This possibility considerably increases the capacity of the wireless medium and define a whole new set of scenarios. The adoption of multi terminal scenarios requires a new set of techniques for the analysis of the system and for the design of efficient transmitter and receiver schemes allowing to obtain the results promised by theory.

Iterative receiver techniques
The classical coding and modulation systems and corresponding digital receivers introduced in the basic digital communication courses has been often superseded in modern standards by more advanced coding and modulation system. These modern coding systems, based on concatenation of multiple elementary channel codes and, at the receiver, the correspondent iterative decoder systems, will be the main focus of the second part of the course. The course will give to the student the necessary mathematical tools and methodologies for the analysis, the design and implementation of such concatenated decoding systems.
Some extensions of the concept of the iterative receiver, involving other blocks of the digital receiver will also be considered (turbo-synchronization, turbo equalization, turbo multi-user/multi-antenna detection).

MIMO and multiterminal technologies (3 credits)

1. Knowledge of MIMO communication systems and of their applications to modern communication standards
2. Knowledge of the capacity of MIMO systems with and without channel knowledge at the transmitter and at the receiver
3. Knowledge of coding techniques for MIMO systems
4. Knowledge of multiuser communication systems in multiple access (uplink) and broadcast (downlink) channels
5. Knowledge of relay channels
6. Ability to calculate the capacity of a MIMO system with known channel matrix at the transmitter
7. Ability to calculate the capacity of an independent Rayleigh MIMO system with known channel matrix only at the receiver
8. Ability to design space-time codes for the independent Rayleigh MIMO channel
9. Ability to design linear receivers for multiuser channels

Iterative techniques in digital receivers (3 credits)

1. Knowledge of concatenated coding systems (PCCC, SCCC, LDPC) and their generalizations
2. Knowledge of the methodologies for the design and analysis of concatenated coding systems
3. Knowledge of the methodologies for the design, analysis and implementation of iterative decoders
4. Knowledge of the methodologies for the design and implementation of iterative receivers
5. Ability to apply the acquired knowledge to design advanced channel encoding systems
6. Ability to apply the acquired knowledge to design iterative channel decoders
7. Ability to apply the acquired knowledge to design iterative receivers
8. Ability to compute theoretical limits to the performance of communication systems under some constraints on channel and signaling system

The ability to apply the gained knowledge will be verified also during the oral examination. The oral examination and the final report will also help students in improving their communication skills.

Here follows a list of prerequisites for this course.

• Probability (in particular: discrete and continuous distributions, averages, Central Limit Theorems, Gaussian distribution).
• Signal theory (convolution, correlation functions, signal spectra, Fourier series and transform).
• Random process theory (stationary random process, cyclo-stationarity, autocorrelation and power spectrum, colored and white Gaussian random process).
• Digital communications (Hilbert spaces, optimum decision rules, basic modulations, band-limited channels, Nyquist criterion, time-domain equalization).
• Wireless communications (multipath fading characterization, Rayleigh and Rician fading, receive diversity).
• Channel Coding: Linear block coding (BCH, Reed Solomon, Hamming), and convolutional codes. Puncturers and interleavers. Viterbi algorithm.
• Classical linear modulations (PSK and QAM), OFDM and CDMA. Trellis coded modulation (TCM), Continuous Phase Modulation (CPM).
• Channel models: AWGN channel, binary symmetric channel (BSC), binary erasure channel (BEC), frequency and time selective fading channel.
• Digital receivers: basic synchronization techniques (phase, frequency, and clock). Basic equalization and detection techniques. Minimum Mean Square Errror (MMSE) equalizer, zero forcing equalizer, data aided equalizer, maximum likelihood sequence estimation. Basic channel decoding techniques for block and convolutional codes. Viterbi algorithm, algebraic decoders.

Furthermore, for the laboratory classes, it is assumed that the students has programming skills in either C or C++ languages.

Multiterminal and multiantenna communications (3 credits)

• Multi-input multi-output (MIMO) channels
  • Multivariate Gaussian distribution
  • Capacity of known MIMO channels
  • Capacity of Rayleigh fading MIMO channels
  • Monte-Carlo approximations
• Coding techniques for MIMO channels
  • Basic schemes, beamforming, BLAST
  • Space-time codes
  • Orthogonal space-time codes, Alamouti codes
• Multiuser receivers
  • Optimum ML receiver
  • Sphere decoder
  • Linear receivers

Advanced coding techniques (3 credits)

• From classical coding schemes to concatenated codes
• Turbo codes (PCCC)
• Serially concatenated Codes (SCCC)
• Low Density parity check codes (LDPC)
• Generalizations
  • Code networks
  • Tanner graphs
• Iterative decoding techniques
  • Soft Input Soft output blocks
  • Decoding networks
  • Factor graphs and belief propagation
• Analysis of iterative decoding networks through EXIT chart and density evolution techniques
• Design of PCCC, LDPC e SCCC codes
• Adaptive coding and modulations systems for high spectral efficiency systems, pragmatic approach
• Generalizations of the turbo principle
  • Turbo equalization
  • Turbo synchronization
  • Turbo receivers for multi-antenna systems

The course will mainly consist of lectures delivered by the teachers in class.
Design problems will be proposed and solved in class as well.

For the all the course topics, lecture notes (handouts) will be available to the students at the beginning of the course through the web portal.
Additional reference books are the following.

• Bessai - MIMO signals and systems (2005)
• Cover,Thomas - Elements of information theory (2nd ed., 2005)
• Larsson,Stoica - Space-time block coding for wireless communications (2003)
• Oestges,Clerckx - MIMO Wireless Communications (2010)
• Paulraj, Nabar,Gore - Introduction to Space-Time Wireless Communications (2003)
• Tse,Viswanath - Fundamentals of wireless communication (2004)
• Verdù - Multiuser detection (1998)
• Vucetic,Yuan – Space-time coding (2003)
• J. Richardson, A. Urbanke, Modern Coding Theory, Cambridge University Press

The exam includes an oral examination and a final report. The final report will describe the activities performed during the practical classes for the software implementation and testing of a communication system.
The final mark is a weighted sum of the two parts. The weights are 0.6 for the oral exam and 0.4 for the final report.