82069 - Electromagnetic Propagation for Wireless Systems M

Learning outcomes

Mastery in engineering electromagnetic topics related to wave propagation. Knowledge of the main properties of radio propagation in real environment, expertise on path-loss models, multipath propagation modeling and radio channel wideband characterization. General comprehension of MIMO systems, diversity and spatial multiplexing techniques. Awareness of the main coverage and planning strategies for cellular radio, broadcasting and wireless systems. Assessment of wireless systems efficiency.

Course contents

Part I – Fundamentals of Electromagnetic Theory (20 hours approx.)

Maxwell’s Equations

Complex representation of sinusoidal fields. Polarization of sinusoidal, vectorial fields. Maxwell’s equations in the time and frequency domain, boundary conditions.

Electromagnetic Waves

The wave concept and the electromagnetic radiation.

Electromagnetic field of a source in homogeneous medium: potential vectors, electromagnetic field generated by a point-source and by a volume-source. Far-field conditions and radiation field. Spherical waves. The reasons for attenuation of electromagnetic waves, propagation speed.

Plane waves: wave vector, uniform and evanescent plane waves.

Reflection of waves, standing waves.

Short hint to near-field communication.

Resonant electromagnetic fields.

Theorems

Poyinting and equivalence theorems, electromagnetic image principle.

Elettromagnetic Interactions

Reflection and refraction: reflection law and Fresnel coefficients for dielectric interfaces. Reflection and refraction in metals. Diffraction: Huygens principle and Kirhhoff’s theorem, Single knife-edge diffraction.

Geometrical Theory of Propagation

Historical survey, definition of optical ray. Wave equation for an inhomogeneous medium. Eikonal and Transport equations. Rays equations and rays trajectory. Examples: planar and spherical stratified medium. Ray tube and spreading factor. General expression of the electromagnetic field along a ray. Geometrical Optics: reflected and refracted rays. Geometrical Theory of Diffraction: Keller’s cone and diffraction coefficients.

Part II – Propagation in Wireless Systems (70 hours approx.)

Tropospheric/ionospheric propagation for long-range wireleless communications

Rays trajectory in the troposphere: refractivity, vertical gradient of refractivity and tropospheric ray curvature. Tropospheric index and sub-standard, standard and super-standard atmosphere. Radio horizon and equivalent earth radius.

Atmospheric losses on electromagnetic propagation

Atmosphere as a mixture of gases. Joule effects and electromagnetic absorption. Specific loss related to oxygen and water vapour, evaluation of total atmospheric loss for horizontal and slant wireless links. Rain loss and rain intensity. Statistical evaluation of the specific rain loss.

Wireless propagation in real environment

From ideal (Friis formula) to real propagation. Fading effects: radio link obstruction and multipath propagation. Dependence of a wireless digital system performance on the propagation conditions. Signal attenuation and distortion, flat and selective fading.

Introduction to the environmental effects: Impact of the terrain on the radio link (2-rays model).

Dispersive properties of the wireless channel: delay spread/coherence bandwidth, Doppler spread/coherence time, angle spread.

Radio channel modelling in time, space and frequency

Narrowband analyses of field distribution: path loss, shadowing and fast fading. Path Loss exponent and statistical distribution of fast/slow fluctuations. Narrowband propagation models (Okumura-Hata formula, Epstein-Peterson model,…). Fading margin and radio coverage.

Multipath effects and input-output functions of the (mobile) radio channel

WSSUS channel and characterization of the wideband propagation parameters (Delay Spread, Angle Spread, etc.) and wideband propagation models (rays models).

Multi-antenna systems

MIMO solutions and techniques for fading mitigation / channel capacity increase: spatial diversity, beamforming and spatial multiplexing

Readings/Bibliography

Course slides and notes.

D.A. McNamara. C.W.I Pistorius, J.A.G. Malherbe, Introduction to the uniform geometrical theory of diffraction, Artech House, 1990.

H. L. Bertoni, Radio Propagation for Modern Wireless Systems, Prentice Hall, 2000

S.J. Orfanidis, Electromagnetic Waves and Antennas, free download at: http://eceweb1.rutgers.edu/~orfanidi/ewa/

N. Costa, S. Haykin, Multiple-Input Multiple Output Channel Models – Theory and Practice, Wiley& Sons, 2010.

E. Björnson, J. Hoydis L. Sanguinetti, Massive MIMO Networks: Spectral, Energy, and Hardware Efficiency, free download at: https://massivemimobook.com/wp/free-pdf/

Teaching methods

The course includes lectures as well as guided exercises carried out both in class and at home. The in-class exercises mainly consist of the guided and reasoned solution of problems in preparation for the final examination.

Assessment methods

The exam consists of a written test followed by an oral discussion.

The written test consists of an exercise structured into multiple open-ended questions, to be completed in person in approximately one hour, and covering one or more topics addressed during the course. The written examination is intended to assess the student’s ability to solve a problem, as well as their ability to demonstrate the soundness and coherence of the reasoning that led to the final result.

During the written test, the use of books, notes, and calculators is permitted. The use of any artificial intelligence tool during the examination is strictly prohibited and will result in the annulment of the test. For this reason, the use of electronic devices (smartphones, tablets) to consult digital material is strictly forbidden, without exception. In other words, during the exam, students may consult any supporting material provided that it is in printed form.

A passing mark on the written test (i.e., at least 18/30 on the exercise) is required in order to be admitted to the oral examination. The grading of the written examination takes into account not only the correctness of the results obtained, but also the clarity of the reasoning and arguments supporting the final result.

The oral discussion (lasting approximately 15–20 minutes) is intended to assess the student’s understanding of the fundamental concepts presented during the course.

The written test and the corresponding oral discussion must be completed within the same examination session (summer – June/July, autumn – September, or winter – January/February), though not necessarily on the same examination date.

The final grade, expressed out of thirty, is based on the overall assessment of both the written and oral examinations.

Teaching tools

Blackboard, PC, projector.

Office hours

See the website of Franco Fuschini