Subject fundamentals

The goal of the course is to provide detailed knowledge about specific features, potential performance and design trade-offs of practical digital communication systems based on wireless and fiber-optic transmission. 
Wireless communications encompass mobile communications through single and multiple antenna devices (mobile phones, smartphones, tablets, etc), point-to-point radio links, and satellite communications (including direct-to-home TV broadcasting). Optical communications represent the worldwide ubiquitous cabled infrastructure of all of the global Internet, from data-centers and server farms, through cities, countries and continents, all the way to the end users’ homes or working places.

Expected learning outcomes

The student will acquire the knowledge of: 
• the wireless and optical systems main features, performance potential and impairments 
• the related transmitter and receiver technologies and algorithms needed to achieve reliable communication over the considered transmission medium, which is free space for wireless systems and the optical fiber for the optical systems 

The expected outcome of the course is the ability for the student to: 
• understand the design and optimization process of practical wireless transmitter and receiver systems 
• understand the design and optimization process of practical optical transmitter and receiver systems, as well as of the fiber plant connecting them 
• apply such design techniques and optimization processes autonomously to practical transmission system examples.

Prerequisites / Assumed knowledge

This course has the following mandatory prerequisites 
• a thorough understanding of the mathematical topics presented in the Bachelor (or "Laurea") degree, including calculus and linear algebra. 
• a sound and well-established prior knowledge of the fundamentals of signal theory (including probability and stochastic processes) and of basic digital communications (digital modulations and their performance on the AWGN channel).

Contents

Wireless Systems (6 credits) 

• Review of basic concepts for digital communications: analytic signal representation, signal spaces, linear modulations for the AWGN channel, error probability, achievable rate (Shannon formula) 
• Characteristics of the wireless fading channel (Rayleigh/Rician fading models) 
• Multiple-Input Multiple-Output (MIMO) communications 
• Channel estimation and equalization techniques for MIMO and SISO systems 
• Synchronization techniques. Frame, carrier and symbol timing recovery. 
• Effect of channel nonlinearities and countermeasures. 
• Advanced digital iterative receivers. 

Optical Systems (6 credits) 

• Introduction to optical communication systems – a historical perspective 
• Systems without optical amplifiers 
o the ideal on-off optical transmission systems, fundamental quantum limits 
o practical non-amplified systems: typical structure, PIN and APD photodetection, modeling and performance calculation 
o design of systems using non-amplified systems: short and medium-haul systems, access and last-mile systems 
o a short introduction to quantum-key-distribution (QKD) optical systems 
• Systems with optical amplifiers 
o the system-level modeling of the optical amplifier, quantum amplification noise (or ASE noise) 
o the performance of the single-optical-amplifier on-off keying system 
o the performance of the multi-span chained-amplifier on-off keying system 
o systems with coherent detection 
o generalities and description, block diagrams 
o ideal performance characterization 
o receiver DSP block diagrams and algorithms 
• Linear and non-linear propagation effects in the optical fiber 
o chromatic dispersion (linear effect) 
o the Kerr effect (non-linear effect) 
o modeling of the interaction of linear and non-linear effects 
o compensation of chromatic dispersion based on DSP 
o countermeasures against non-linear effects 
o modeling and evaluation of the impact on realistic systems of the fiber propagation effects 
• Optical Systems utilization scenarios and related design optimization: 
o multi-thousand km submarine systems 
o optically-routed national and international backbone networks 
o data-center networks 
o access networks (fiber-to-the-home, or FTTH)

Delivery modes

Lectures will encompass both theory and practical design problems. The latter will be solved in class.

Texts, readings, handouts and other learning resources

Both wireless and optical system topics are fully covered by the material (handouts) provided by the teachers, both for the lectures and the design problems. All such material will be available on the website prior to classes. No specific extra material is needed. 
For personal further reading: 
• Sergio Benedetto and Ezio Biglieri, Principles of Digital Transmission: With Wireless Applications, (1999). 
• Luise, Mengali, Morelli (2003), Synchronization in Digital Communication Systems, Encyclopedia of Telecommunications. 
• Optical Fiber Telecommunications Volume VIA and VIB: Systems and Networks (Optics and Photonics) by Kaminow, Ivan, Li, Tingye and Willner, Alan E., Academic Press; 6 edition (May 11, 2013). ASIN: B00CZANHGW 
• Xiang Zhou and Chongjin Xie, Enabling Technologies for High Spectral-efficiency Coherent Optical Communication Networks, John Wiley and Sons, Inc., 2015. 
• D. Tse and P. Viswanath, Fundamentals of Wireless Communication. Cambridge University Press, 2005 
• J.Proakis and M.Salehi, Digital Communications (5th ed). McGraw-Hill, 2008.

Assessment and grading criteria

The assessment of the student’s proficiency consists of a final written test. 

The written test consists of both theoretical questions and analysis/design problems that may require calculations. 
The written test grading criteria are as follows: 
1) the ability to clearly describe the procedure used to solve the test problems 
2) the ability to appropriately use technical language in the answers 
3) the correctness of the answers provided 

The written exam proposes practical numerical exercises that allows to judge if the student knows the topic of the course and is able to apply this knowledge to solve some simplified design examples on modern wireless and optical transmission systems. The open questions allows to judge if the student has acquired the most relevant theoretical topics of the course. 

The written exam is three hours long and it is scored on a full scale up to 30. During the written exam, the students will be allowed to carry with them a pocket calculator, paper and pen and four (single-sided) pages of formulas written by themselves. No other material will be allowed (such as laptops, handouts, etc).