Futuristic Network Technologies Begin to Emerge
January 14, 2003 (TOKYO) -- Research into leading-edge network technologies is well underway at a number of institutions, including universities, research institutes, and private companies. Specific mention can be made of five technologies that envision the shape of networks in the decades to come: Microwave power transmission, which transmits electricity to a distant location using radio waves; ultra wideband (UWB), which enables high-speed data transmission with minimal power consumption; augmented reality (AR), which overlays information via a head-mounted display onto the user's view of a scene; multi-modal communication, which can transmit the feel, taste, or smell of an object; and quantum information processing, which enables information to be sent and received at speeds of one million petabits per second.
Among these technologies, this week we will focus on microwave power transmission and UWB, and explore how close they are to realization.
Fundamentals Already in Place
The sense of trepidation as the batteries run down on one's laptop computer or mobile phone is familiar to most of us. But if microwave power transmission becomes a reality, such fears could be a thing of the past.
At the vanguard of this emerging technology is an idea that sounds almost like science fiction: Solar power satellites (SPS), consisting of panels of solar cells stretching many square kilometers in space, convert the electricity generated from light into radio waves and beam them wirelessly to the earth. The concept was first devised in 1968 by Dr. Peter Glaser of the United States. If the largest conceivable space power station were built and operated 24 hours a day all year round, it could produce the equivalent output of ten 1 million kilowatt-class nuclear power stations.
It has already been demonstrated that microwave power transmission is not a fantasy. In 1983, a Japanese team succeeded in a first-ever experiment to transmit microwave energy through the ionosphere using two rockets. They subsequently conducted further successful experiments that more closely approximated reality (see photo). In 1995, a team led by Prof. Nobuyuki Kaya of Kobe University managed to transmit electricity from the ground to an airship in the sky.
If microwaves carrying electric power can be beamed uniformly over the earth, they could be used as a power supply for mobile devices such as cell phones and PDAs. Of course, the power of the microwaves would have to be weaker than the regulatory standard to prevent any physical harm to people from the electromagnetic rays. The mobile phones now in use require up to approximately 800 milliwatts of power. To receive microwave energy, they would need an antenna about 25-30cm square. As it would not be feasible for a mobile handset to itself serve as the antenna, the options would be to reduce the power consumption or devise a large antenna.
Rocket Technology Holds the Key to Realization
The problem with microwave power transmission is the exorbitant cost of constructing an SPS -- around 2.4 trillion yen in total as a rough estimate. About 30 percent of this total is the transportation costs involved in shifting 50,000 tons of materials from earth into space to construct the satellite. Whether such a space power station could actually be realized will no doubt depend on progress in rocket technology.
Based on developments to date, Prof. Hiroshi Matsumoto of Radio Science Center for Space and Atmosphere, Kyoto University says that his team hopes to build a small experimental space power station, in the 10,000 kilowatt class, in the next 10 to 20 years. A government project, supported mainly by the Ministry of Public Management, Home Affairs, Post and Telecommunications and the Ministry of Education, Culture, Sports, Science and Technology, is also looking at building an SPS. If all goes well henceforth, a space power station with output equivalent to one nuclear power station could be completed around 2040.
UWB Technology Led by the U.S.
UWB, if it can be commercially utilized, could also significantly change the way we live. In addition to its obvious application in linking PCs on a wireless LAN, UWB might be used in cordless phones and for remote control of household appliances. It could eventually be incorporated in a variety of personal devices and accessories such as train tickets, bags, and watches. UWB research of this nature has already come a long way, and commercial application may soon be possible.
UWB transmits signals by chopping radio waves into tiny, momentary pulses, without using the carrier waves of conventional wireless transmission technologies. It saves power because no radio waves are transmitted except during impulse emission. UWB can also be speeded up easily, just by reducing the interval between impulses. The technology gets its name because the frequency component embodied in a single impulse results in a radio wave that spans a very wide spectrum.
Research into UWB was initiated in the United States for prospective military purposes. More recently, U.S. companies have begun UWB research with a view to eventual application in the private sector. Following these moves, in February 2002 the Federal Communications Commission (FCC), which governs radio spectrum in the United States, approved commercial usage of UWB, instantly sparking development efforts. For example, Intel Corp is working on incorporating UWB capability in its PC chipsets, and has presented several demos at developer conferences and other such venues (see photo). A number of US venture companies are also aggressively pursuing UWB research.
In Japan, basic research was initiated by Prof. Ryuji Kohno and others in 2000. Their program calls for validation experiments to begin in April 2003. The development project is broad-based, covering everything from UWB devices to systems. Assisting in the project are the Communications Research Laboratory (CRL), an independent administrative institution under the Ministry of Public Management, Home Affairs, Posts and Telecommunications, and private enterprises in Japan, including communications equipment vendors. "Our goal for commercialization is four years from now. We can complete the basic technology in two years," Prof. Kohno said.
Output Restrictions Inevitable in the Short Term
UWB is not without its difficulties, however. The greatest problem is the adverse effects on other radio waves, due to the very wide spectrum used.
Intel's demo system uses a massive 4GHz of bandwidth in the range 2GHz to 6GHz. These frequency bands are already in use for various purposes, and UWB in the same bands would cause interference. For this reason, UWB will likely be restricted to indoor usage where it will not disrupt other systems. Alternatively, output could be capped, although the range would therefore be shorter.
UWB could be used at full power without any fear of interference if it operates in frequency bands not used by any existing services. At present, there is unused spectrum only at very high frequencies above 30GHz. No technologies that make effective use of these frequencies have yet been established. However, Prof. Kohno believes that bandwidth above 30GHz will be utilized "in the next decade or so." |
