"It's a research topic that goes beyond 2010." Adds Osten Makitalo, Telia Mobile's research director who developed mobile telephony in Scandinavia more than a decade ago: "4G is a system of systems that can take advantage of all kinds of different wireless technologies." Thank you. In a nutshell, 4G is an ultra-high-speed wireless network, an information superhighway without cables. The new network would enable wireless, three-dimensional virtual reality connections between phone users. Base stations - the now-costly transmitters that pass mobile-phone signals from one antenna to the other - would be as widespread as light bulbs. As envisioned, 4G would enable wireless data transmission at the dizzying speed of up to 100 megabits per second, exponentially faster than today's handsets, which transfer a mere 10 kilobits per second.

Moreover, researchers claim that some services like wireless real-time video links won't be as expensive with 4G as they will be with 3G, the system on which companies have just spent billions of dollars for licenses, but which isn't really up and running smoothly yet. For those who don't speak telecom fluently, a little more explanation may be useful: 2G is the current system, which allows the transfer of small text messages, while 1G is old-fashioned analog, with very limited data transfer ability.

Basically, 1G is meant for old-style wireless calls - not the ones made from snazzy lightweight phones, but instead calls made with the heavy bricks and their meter-long antennae that once were popular with business people and park rangers in the early 1990s. Talk about 4G comes amid a tidal wave of other new telecom technology developments - from wireless application protocol, or WAP, to general packet radio service, or GPRS, to 3G. WAP is an Internet browser for mobile devices. GPRS, or 2.5G, is a telecom network that allows data to be sent in packets of 50 kilobits per second, a slightly higher speed than today's 2G system.

Operators and telecom equipment manufacturers in Europe say new wireless technology one day soon will allow consumers to use their mobile phones to surf the Net, watch real-time video footage and download audio tunes. But right now, the latest wave of new telecom technology either isn't up and running or faces significant problems and delays. To investors' agony, few companies have shown how exactly they plan to pay back the billions of dollars of 3G license fees or how they will bill and make money from services that aren't developed yet. It is clear, however, that most glitzy wireless services will be too expensive for average consumers in the next few years.

For example, based on the expenses of setting up 3G, it looks like simple video conferencing will cost thousands of dollars. So gone is the feel-good factor of telecom operators' glitzy wireless Web ads. With 4G ill-defined and meaning different things to different people, and with the difficulties of 3G, development is tough. Along with some telecom equipment makers, some investors are unimpressed with 4G. "It's really too early to talk about 4G," says Mikka Paloranta, a telecom analyst with ArosMaisles in Helsinki. "It would be nice if first we'd get to see some working WAP services or know what GPRS or 3G is going to offer us." At Nokia Corporation, officials don't even want to use the expression 4G. "It can be a misleading and confusing term," says Tapio Hedman, a Nokia spokesman. "We don't think it's right to start talking about this future technology if 3G has not yet come into place." So what's driving telecom sages to discuss 4G anyway? Researchers at companies like Ericsson and NTT DoCoMo are mainlyfocusing on the technological aspect and applications of 4G. They see it as a new so-called air interface, a wireless way of transferring data from base stations to terminals like mobile phones, which will lead to unthinkable applications a decade from now. They are also thinking about new antennae, base stations and whatever else may be involved with the building of an advanced new network. Some characteristics: 4G would entail 20 megabits to 100 megabits per second data transfer - compared to less than 10 kilobits per second for the current GSM system - the kind of speed that makes techno nerds smile.

With 4G, the world would have base stations everywhere, ensuring phone users' connection to a high-speed network anywhere, anytime - just the way operators promised in their ads for 3G, only this time, it would be affordable and 10 years down the road instead of tomorrow.

Other nifty but yet-to-be-developed 4G tricks that would make Buck Rogers look medieval: video connections between phone users and homes, motion-controlled devices and eyeglasses with 3-D video projects. Thinking so far ahead is nothing new. Ericsson did the same with 3G nearly a decade ago, and today the company is the world leader in third generation telecom infrastructure, conquering more than half of all 3G network construction contracts with operators world-wide. "We're simply trying to imagine what the world would look like with such high bandwidth," says Mr. Eriksson. "Nothing is clear yet. But we have to start thinking about it." Others don't think of 4G as a new technology, but rather as a hodgepodge of existing or soon-to-be-developed systems like GPRS, wireless local area networks, GSM 3G and Edge.

Combing these technologies and others could allow consumers to toggle between high-speed data services and low-speed services when needed. "It's like traveling," says Mr Makitalo. "When you're in a hurry, you take an airplane. In other cases, when it's more practical, you take the car, or your bike." Telia hopes to start its 4G services even before 3G technology is set to arrive, with HomeRun, its wireless local area network service at the Stockholm airport. The idea is that later this year, HomeRun will let visiting business travelers log on to the Web by plugging a wireless local area network, or LAN, card into their laptops and connecting to a GPRS network. That means people can use the wireless LAN services to access the Web at high speed and use GPRS for accessing text files or e-mail messages, which don't require a very high bandwidth. "There is an irony here," says Mr Makitalo. "4G comes first, 3G comes second." But Mr Eriksson doesn't agree with the usage of "4G" for such a mixture of technologies."They're talking about the evolution of 3G," he says. "That's not really 4G." Again, others don't really know what the term means at all.

Bouygues Chief Executive Martin Bouygues said that a 4G network was one of the four options open to his Bouygues Telecom SA wireless affiliate after it bowed out of the running for a French 3G license last month. When pressed for more details, Mr. Bouygues conceded that his company didn't have much to say about 4G, but that it planned to get in touch with whoever else was working on 4G in the near future.

Write to Almar Latour at almar.latour@wsj.com