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Professor Antti Räisänen

Inauguration speech as Doctor Honoris Causa of Professor Antti Räisänen

Antti Räisänen: Wireless world

Mr. Rector, my dear Colleagues and Friends, Ladies and Gentlemen,
I am deeply grateful for the honor you have bestowed upon me. I would like to express my deepest gratitude to you, Mr. Rector, and to all other academic authorities responsible for the decisions made towards this award. Of course, I would also like to convey my sincere thanks to my colleagues, professors and researchers at Universidad Carlos III de Madrid. Especially I would like to mention Profs Magdalena Salazar Palma, Daniel Segovia Vargas, and Luis Enrique Garcia Muñoz, and Dr Alejandro Rivera Lavado at the Department of Signal Theory and Communications, and Prof. Guillermo Carpintero del Barrio at the Department of Electronics Technology. Besides as good colleagues, I would call them also as good friends.
The academic activities with my colleagues and friends here at Universidad Carlos III de Madrid mean mainly our joint research efforts into better understanding and the mastery of short radio waves: microwaves, millimeter waves, and terahertz waves. For this reason, I have titled my speech as “Wireless world”, and now I would like to give you a brief history overview and then share my own experiences and thoughts on this topic with you.

The Scottish physicist James Clerk Maxwell predicted the existence of electro-magnetic waves for more than 150 years ago. He formulated a set of equations, which he published for the first time in 1864. The German physicist Heinrich Hertz was the first to prove experimentally the existence of radio waves, thus verifying Maxwell’s equations. He published the first results in 1888. The first one to use radio waves for communication was the Italian inventor Guglielmo Marconi. He made experiments in 1895 and submitted his patent application “Improvements in transmitting electrical impulses and signals and in apparatus therefor” in England in 1896. In 1901, Marconi using his wireless telegraph succeeded in sending a short radio signal across the Atlantic. First broadcasting radio stations started their operation in 1919. Regular TV transmissions started in Germany and in the U.S. in 1935. Communication was not the only application of radio waves. Karl Jansky while studying radio noise at Bell Laboratories in 1932 detected a weak signal, a steady hiss from our own galaxy, the Milky Way. This was the beginning of radio astronomy. Both radar and radio navigation were invented already soon after Marconi’s demonstrations, but became important applications later, during World War II. The invention of microwave tubes, klystron and magnetron, was essential for the development of microwave radar in 1940’s. The invention of the transistor started the semiconductor era in radio electronics at the end of 1940’s. In 1960’s, the earth orbiting satellites found applications both in communications and radio navigation, and soon after that also in microwave remote sensing.

This was the status of the wireless world in 1960’s, one hundred years after Maxwell’s equations. When I entered the academic studies at the end of 1960’s, I could already enjoy futuristic lectures on digital and mobile communications. However, nobody seemed to understand nor predict how much those will change the world during the next five decades - until today. Instead, the scientific applications of radio waves, especially radio astronomy was the reason why I decided to concentrate my studies on electromagnetics and radio engineering. Today, I am very happy for this choice. When I defended my PhD thesis in 1980, nation-wide cellular radio networks were under development in the Nordic countries. In 1981, we entered the so-called first generation (1G) of mobile communications, when the analog Nordic Mobile Telephone cellular networks allowing roaming from one country to another opened for public use in the Nordic countries. Ten years later we entered the second generation (2G), as the digital GSM networks opened. In 1992, I was responsible for organizing in Helsinki an international microwave conference, the European Microwave Conference that was attended also by my friend, Professor Salazar Palma. Mobile phones were already quite common in Finland and in other Nordic countries, but not so much elsewhere. Therefore, I remember that the conference attendees paid a lot of attention to the conference secretary and conference chair, myself, who carried and frequently used their still heavy and clumsy Nokia Cityman mobile phones at the conference site.

At the beginning of this century, we entered the third generation (3G) era in mobile communications. The 3G allows much higher information throughput and much more users of the network because the standard is based on code division multiple access instead of frequency division as in 1G or time division as in 2G. More recently, we have moved to the fourth generation (4G) era, and right now we are entering the fifth generation (5G). What is new in the 5G standards? A lot! 5G is using not only the traditional microwave frequencies at about 1-2 GHz, but also higher microwave frequencies and millimeter-wave frequency bands up to at least 100 GHz. Another important difference from the earlier generations is in antennas: in many parts of the system the antennas must be electronically beam steerable arrays. Millimeter-wave technologies with electronically steerable antennas, sensitive receivers, and compact transmitters, all of these earlier of interest only in scientific applications, are now objects of intensive research and development for wireless communications networks in 5G and beyond. This is exactly the area of our common interest between Carlos The Third University and my home university, Aalto University. This research and development give benefits not only for wireless communications, but also to many other wireless applications, such as radar, medical and security imaging and other sensing applications. Today, we definitely live in the wireless world.

Research collaboration is extremely important. In theoretical work, a lot of collaboration may happen through internet and with brief meetings at conferences etc. In experimental work, long research visits are of utmost importance, because many experimental facilities are too expensive to be owned by every research group, and therefore we must specialize our laboratories. I must congratulate Carlos III University for establishing with Banco Santander the Chair of Excellence system, which allows professors to visit Carlos III University for 6 or 12 months. I personally enjoyed the Chair of Excellence for a 6-month visit in 2013-14. Of course, at Aalto University we have also been able to provide good research environment for Carlos III University visitors.

This is a happy day to me. I enjoy for being here! I wish all the best for the whole Carlos III University academic community. Once again I would like to thank Mr. Rector for the award and my colleagues at the Department of Signal Theory and Communications for good collaboration. Finally, I would like to thank my lovely wife Hannele for supporting me in all ups and downs over more than four decades. 
Thank you very much for your attention!