Millimeter waves (mmW) have seen a fast-growing interest in recent years, fueled by the development of 5G. Its “frequency range 2” (FR2), corresponding to the 24 250 - 52 600 GHz part of the spectrum, is intended for short-range, very high data rate communications.
Not many know that, in the nineties, Instituto de Telecomunicações was already working in mmW mobile communications. It was a pioneering effort to develop in Europe a cellular mobile broadband communication system, operating in the 40 GHz and 60 GHz bands.
That was in the framework of the European Commission-funded MBS project (1992-1995), and the SAMBA project (1996-1998). The two projects were led by Companhia Portuguesa Radio Marconi (CPRM) and involved about 19 European partners around Europe, including, among others, BBC, BT Labs, Deutsche Aerospace, VTT, Telnor, Thomson, U Aachen, Bosch, Phillips, further to IT, IST and UA, later joined by Mitsubishi.
The goal was ambitious, even by today’s standards: to offer 150 Mbit/s data rate per user, at user terminal speeds up to 150 km/h. That was the project’s vision for 4G, although no one could envision at that time, a killer application for such huge bandwidths. And, frankly, when the project started, IT had no mmW lab equipment whatsoever. It is noted, for context, that the first GSM commercial services ever launched, started just the year before, in 1991.
When designing the system, it was immediately apparent that the game was totally different from GSM and UMTS, requiring re-thinking every layer of the communication system, including the air interface. IT contributed to channel modeling, modulation and coding, shaped beam antennas, and mm-wave front-end electronics.
The concept was successfully demonstrated at the 1998 Lisbon World Expo. The mobile terminal was shrunk to a somewhat portable 60 Kg beast, consuming 60 W of DC power. But it demonstrated publicly, and for one hour, a flawless high-definition wireless high-definition video transmission inside the crowded Utopia Pavilion (now renamed). Gross bit rates exceeding 40 Mbit/s were reached in a remote transmission from an ambulance on-the-move scenario.
It was too much, too early!
Although GSM could only offer 9.6 kbit/s at the time, it still had long commercial life ahead, and successive overlays ramped up data rates, culminating in 3G. The 4G ended up not using mm-waves yet. That started in 5G, 30 years after the first dream of a mobile broadband mm-wave system, now in a totally different application context, with Youtube, streaming, augmented reality, autonomous vehicles, and Internet of Everything. Unthinkable in 1992!
But mm-waves remained one of the main topics of research for 30 years in IT, for instance in antennas for sensing, and lately for 5G and satellite communications, involving state-of-the-art metamaterial solutions.
Carlos Fernandes (IT Lisboa)
Image: mockup of the original photo - MBS/SAMBA user terminal, operating in the 40 GHz band in 1998