It is more than a century since Guglielmo Marconi pioneered wireless data transmission. Yet, if the current pace of innovation in the field is anything to go by, wireless technology is still in its infancy. The surge in popularity of mobile phones — their number will overtake that of fixed phones during 2002 — has prompted both established firms and start-ups to investigate ways to make phones more efficient and versatile. At the same time, the Internet is going wireless, driving a separate wave of innovation as the Internet’s legendary ability to disrupt traditional ways of doing things enters a new arena.
It is too early to see where all this might be leading, or even how these two waves of wireless enthusiasm will fit together. But the parlous state of the wireless-telecoms industry, and the difficulties surrounding the deployment of “third generation” (3G) networks in particular, could be taken as evidence that existing ways of doing things are reaching their limits, and that some radical new ideas are needed.
Here, then, are four emerging technologies that show much promise: smart antennas, mesh networks, ad hoc architectures, and ultra-wideband transmission. Smart antennas are already in use and mesh networks are starting to appear, while ad hoc architectures and ultra-wideband are still largely restricted to the laboratory. But each challenges existing ways of doing things; each, on its own, or in combination with others, could shake up the wireless world.
Wireless antennas, in their simplest form, are dumb. A base-station on a cellular telephony network, for example, typically communicates with nearby handsets by broadcasting in all directions, which is rather like shouting to ensure that everyone in a small room can hear you. Base-stations use only a fraction of the radio spectrum available, to avoid interference with adjacent cells, but the use of directional antennas enables radio frequencies to be reused more efficiently, thus boosting capacity. So instead of one omni-directional antenna, many base-stations now use three-directional antennas pointing in different directions, each of which covers a 120° sector.
Smart antenna systems go a step further, using multiple antennas to provide more accurate directional targeting and additional improvements in efficiency. “The base-station works out where you are from the relative signal strengths at multiple antennae,” explains Marc Goldburg of ArrayComm, a smart-antenna firm based in San Jose, California. “Then it can direct its transmission.” ArrayComm’s IntelliCell technology is now deployed in nearly 100,000 base-stations in Japan, China and Taiwan. Adding IntelliCell technology to a base-station typically boosts capacity by a factor of three to seven, says Mr Goldburg. Metawave, another smart-antenna firm that is based in Redmond, Washington, claims similar benefits for its SmartCell “cell sculpting” technology.
In theory, says François Chin, a researcher at the Institute for Communications Research in Singapore, the capacity enhancement is proportional to the number of antennas, but in practice it is only possible to achieve about three-quarters of this improvement. His systems, which are being tested in Tokyo by NTT DoCoMo, Japan’s leading wireless operator, typically achieve a five-fold capacity improvement with eight antennas. It is thus possible to support either more users, or the same number of users at a higher data rate, or to reduce the number of base-stations needed to provide a particular level of service.