IN THE beginning there were lots of computers on office desks. Some of them were connected to other computers in the same office. Each of these offices was, in turn, hooked up to the public-telephone network, but only for phone calls. Then an idea took hold: why not get all these computing islands somehow to connect to all the others, using variants on those same phone lines? So dawned the age of the Internet.

Today, users are at much the same point with mobile computing and communications. A typical technophile on a train will carry a cellular phone, a personal digital assistant (PDA), a notebook computer and possibly a pager. All around the commuter are radio waves of the wireless public-telephone networks. With sufficient will, dexterity and technical know-how, he can connect his PDA or notebook to his mobile phone via an infra-red connection or cable and then connect to the Internet over the cellular network. He may even be able to download a few e-mail messages or a web page, although it is more than likely that he will be disconnected by some failure in this makeshift chain of communications.

What the gadgeteer is waiting for is a technology that will do for his rag-bag of mobile devices what the Internet did for the PC and local-area networks (LANs)—link them seamlessly to the rest of the digital world.

The wait could be nearly over. New digital telephone networks designed for high-speed data that are on their way can turn a conventional telephone into an “always-on” broadband Internet device. The telephone would then become a true utility—just like the electricity and water supply—that is permanently connected to the user and available instantly on demand. Meanwhile, another technology called Bluetooth is about to do the same for the mini-constellation of devices that an individual carries around, connecting them all together wirelessly.

This tantalising prospect has launched thousands of breathless headlines since the two technologies were first promoted two years ago. And for good reason. The possibilities they raise are as broad and transforming as the Internet itself. The commuter would be able to surf the web and check e-mail on his palm-sized PDA which, by relying on a wireless connection for external storage and communications, would be both thin and cheap. The PDA's main communications link would be to his mobile phone. Meanwhile, the phone would be connected, at a speed as fast as the best of today's corporate Internet links, to the cellular beacons scattered around the passing city-scape.

It gets better. The commuter could listen to music through wireless headphones that play music albums from his notebook computer, which could store an entire collection of CDs in compressed MP3 files. Or he could play a quick bout of a shoot-'em-up video game on his PDA with a passenger across the aisle. When a call comes in on his mobile phone, it would automatically pause the music (or gunfire) on the headphones and, after a confirming press on a headphone button, switch to the incoming caller.

When the commuter arrives at the office or home, the network around him would reconfigure itself. Instead of relatively expensive public networks for his Internet connection, the devices would switch to a wireless LAN that connected to the outside world via cheaper high-speed landlines. The PDA would instantly sense the different devices around it. At home, it might be audio and video players or computer printers, MP3 music servers or Internet appliances that it can communicate with. At work, it might be secure corporate servers, other PDAs or software robots that schedule meetings. Meanwhile, his phone would switch to local mode, acting like a cordless phone with a local base-station rather than a mobile, saving both money and batteries. The notebook would also connect automatically to a wireless LAN that offered everything from video-conferencing to multi-player gaming.

Back to earth

Wishful thinking? Not entirely. Most of these things are possible today—albeit at incredible expense and with a level of complexity that would require an engineering degree. The whole point of the coming wireless technologies is to make them so easy and cheap that using them becomes as common as using a mobile phone itself. But for this, three things need to happen more or less simultaneously.

•First, the world's mobile networks must be replaced. Most of today's wireless digital networks are “circuit-switched”. When you make a call, you establish an exclusive circuit that is one of only a limited number that the network can handle at any one moment. When you finish the call, the connection is cut. This is fine for speech, which is what such networks were designed for. But it is a poor way to handle data.

The problems are all too familiar to those who use conventional landlines and dial-up modems to connect to the Internet. It takes a long time (ten seconds or more) to make a connection. The connection is slow and remains open with the meter ticking, even during pauses between data transfers. And it is the user who has to initiate it.

These networks need to be replaced by “packet-switched” networks which, being always on, can send and receive data (in Internet-like packets) whenever needed, with no pause to establish a link. Charges for today's “persistent” digital connections, such as a cable modem, DSL (digital subscriber line) or ISDN (integrated services digital network), are typically either flat monthly fees or by volume of data transferred. Being permanently connected, a charge based on a rate-per-minute would be meaningless.

A few packet-switched networks are already in operation, ranging from Japan's i-mode phones to the interactive paging networks used in North America by Research in Motion's popular hand-held devices. But widespread adoption is waiting for a new generation of wireless technologies that range from upgrades of existing digital networks to new 3G (third generation) networks that use different frequency bands (see article).

•The second requirement is to do the same at the individual level. By way of analogy, public mobile carriers are “wide-area networks” (WANs). Then there are LANs, private versions of which may range no farther than a building. The new technology will take the progression to the next level: personal-area networks (PANs). These will be wireless networks that connect the digital gadgets that a user carries around to each other, as well as to gadgets of other people nearby.

Today, the closest thing to a PAN is the tangle of wires and some unreliable infra-red connections that connect one computer to another. While it is possible to link computers, PDAs, mobile telephones, printers and the like together, each typically needs its own special connector, and each speaks a communications language unknown to the others. And, like the circuit-switched public wireless networks of today, each connection has to be established manually and tends to be designed for single use.

A person with a Bluetooth PDA could walk through Grand Central Station and unknowingly join and quit dozens of personal—area networks between street and platform.

Bluetooth aims to replace this collection of cables, docking cradles and incompatible standards with a tiny chip and antenna in each device. These will provide wireless connections all around. Using a mere trickle of power (thanks to its short range) and offering data rates of around one megabit per second (ten times as fast as the serial cables or infra-red connections on the back of today's computers), Bluetooth will also provide a common language that all devices—from phones to computer printers—can speak, at least at a basic level.

•The last piece of the puzzle is to ensure that, once these devices can talk to one another, they have something to say. Hence the data protocols and conventions that will run on top of the underlying Bluetooth communications software. These are the instructions that will let a button on your headphones pause your MP3 player and switch to a phone call, or automatically switch your phone to quiet mode when entering a restaurant or theatre.

Unfortunately, this part of the jigsaw exists mostly on paper. Without it, Bluetooth could fall by the wayside—as did previous attempts to let couch potatoes communicate with audio and video equipment in their living rooms using a single, universal, remote control. What killed such efforts in the past was a failure by manufacturers to agree on standards. Each maker adopted its own communications protocol, in the hope of locking customers into its products. If that happens this time—with, say, Ericsson headsets working only with Ericsson phones and PDAs—then consumers can say goodbye to many of Bluetooth's benefits.

Viking invasion

There is little competition to Bluetooth as a replacement for wires at the personal level. From the start, the technology has been embraced as a consumer product. Its roots lie in a proposal made in the mid-1990s for wirelessly linking home audio and video systems, thus breaking the incompatibility log-jam that had ensnarled the consumer-electronics industry. But as the mobile phone took off, manufacturers, led by Ericsson, quickly spotted the technology as the best way to bring their growing constellation of personal gadgets together and link them to wireless data networks. Recognising that marketing was as important as technology when consumers were involved, the industry group dispensed with the usual string of incomprehensible letters and numbers and named the technology after Harald Blatand (Bluetooth), a tenth-century Danish king who conquered much of Scandinavia.

As a communications technology, Bluetooth is not that revolutionary. It is derived from wireless standards that are already found in many commercial products—from digital cordless phones to wireless LANs. Like them, it uses a “spread-spectrum” technique that maps out all the unused frequencies within its assigned frequency band, and then spreads its signal over these scattered clear spots—automatically hopping from frequency to frequency more than a thousand times a second. It constantly adjusts to changing noise and interference conditions, making the best use of the available frequencies wherever it finds itself.

Like digital mobile phones, Bluetooth increases or decreases the strength of its transmission signal according to how far away the receiver is, thus saving power. Again, like a digital mobile phone, it encrypts its signal and its frequency-hopping map so that its transmission cannot easily be intercepted or understood. And, like a range of consumer wireless devices from baby monitors to cordless phones, it operates in the 2.4-gigahertz frequency range that is unlicensed in most countries.

What makes Bluetooth special is the way it scans its surrounding area, which is normally a sphere with a radius of about ten metres, looking for devices that are in range and then checking their identification and access privileges. When it finds compatible devices, it establishes an ad-hoc network called a “piconet”—hooking up all the devices on a user's person, for instance. Several piconets can communicate with each other simultaneously, creating a “scatternet” that links, say, all the people around a conference table. Bluetooth devices can connect either like a simple wire, called “point-to-point”, or as what amounts to the server in a computer network, known as “point-to-multipoint” mode.

Admittedly, most of these things could already be done by existing wireless LANs using a standard known as 802.11b, which offers greater range, higher bandwidth (11 megabits a second compared with Bluetooth's one megabit a second) and greater compatibility with wired LANs. But plug-in circuit cards using this technology are aimed mainly at the corporate market because they are physically large, expensive and consume more power than most hand-held devices can tolerate. What is special about Bluetooth is that it is designed explicitly for the consumer market, in three important ways. If all three of these things are achieved, Bluetooth will be a spectacular success. If it fails on any one of them, Bluetooth could go the way of the Betamax video standard.

The lonely crowd

The first of the advantages that Bluetooth offers is that it has been designed, from the ground up, to be cheap. Ideally, it should use a single chip with built-in radio-transmission circuitry, selling for no more than $5. Bluetooth chips can have all, or just a few, of the range of possible functions, depending on the cost target. They can use their host's memory or have their own. They can support full point-to-multipoint connections, or just the cheaper point-to-point.

For now, cost remains a hurdle. Chip sets still sell for $25-50 apiece, and they may not reach the expected consumer sweet-spot of $5 until 2003 or 2004. The first Bluetooth products—the odd earpiece, phone and PC accessory—are only now reaching the market. Next year should see the beginning of a proper consumer push, with products ranging from Bluetooth-enabled laptop computers to digital cameras, printers and PDAs. If, however, the cost does not come down quickly, Bluetooth may take many years to become as ubiquitous as its boosters hope.

The second great advantage of Bluetooth is that it is, at heart, a passive technology. It is meant to work invisibly and automatically. Unlike cables and infra-red links, which require the user to make a manual connection, Bluetooth devices sense each others' presence and connect and communicate spontaneously whenever they need to. This creates the potential for all sorts of gadgets—from wristwatches to smart cards—to become connected, network-aware devices. There are already hints of this in the smart cards that you can wave over subway gates or office doors, or in wireless PDAs used to take orders in restaurants. Bluetooth would make a wireless connection as universal in hand-held devices as an Internet connection has become in a desktop one.

Fundamental to this is Bluetooth's embrace of “ad-hoc networking”, or the ability to form networks on the fly without having a single server device attending to many clients. A person with a Bluetooth-equipped PDA could walk through Grand Central Station and unknowingly join and quit dozens of ad hoc networks between street and platform. Some might be piconets around other commuters with Bluetooth devices. Others could be part of the station itself, from vending machines to information kiosks. In some cases (buying a ticket, for instance), the person might take advantage of the connection. Most of the time, however, the connection would be as fleeting and insignificant as eyes that accidentally meet in a crowded street.

Lastly, if Bluetooth is to come near to its much-hyped potential, it has to work better than other wireless devices. Anyone who has used anything from a baby monitor to a mobile phone knows that wireless often means trouble. Interference, lost connections and limited range plague wireless devices today—especially those in the unlicensed band that Bluetooth will share. For a technology designed primarily to replace wires, this sort of unreliability would be disastrous; nobody wants to have to orient their printer at a particular angle to the computer just to get a article out, or to place their speakers next to their stereo to avoid hiss.

With this in mind, Bluetooth has been designed to be the most fault-tolerant wireless technology that consumers have ever been offered. It gets some of this through its spread-spectrum approach and its use of digital packets, which can tolerate drop-outs and resends without the user sensing a loss of quality. It also benefits from being limited to a ten-metre range, which avoids all the dead-spot or network-congestion problems of mobile-phone networks. Bluetooth also hops around its frequencies faster than any other consumer wireless technology, which should allow it to adapt to changing radio conditions quicker than a cordless phone.

Yes, but...

For all Bluetooth's advantages, it is not without limitations. The most serious is that it will probably run into trouble when pushed much beyond its original role as a semi-smart replacement for a cable. Today, the main role for local-area wireless technology is to connect mobile devices to corporate LANs—a job that the existing 802.11b wireless standard was designed to do. Laptops with 802.11b cards plugged into them can connect via local wireless “access points” (small boxes on the walls of conference rooms or in other open spaces) at high speed, and use all the network as if they were physically connected via a standard Ethernet cable.

Bluetooth does not do this well. For a start, a piconet is restricted to eight devices. This in effect limits the number of users that a Bluetooth access point can support at any one time.

Bandwidth is another issue. With just one megabit per second to share between all users, a Bluetooth wireless LAN will be drearily slow. And to extend its working range to that of 802.11b (about 100 metres), the individual Bluetooth transmitters would have to boost their power output 100-fold, draining their batteries rapidly.

There is also concern that Bluetooth devices will conflict with those using 802.11b, since the two technologies share the same frequency band. Studies suggest that operating the two side-by-side can cut Bluetooth's already meagre bandwidth by as much as a third. And because Bluetooth is a simpler protocol without the identification and encryption built into 802.11b, it will take special software on both LAN and device sides to accomplish what 802.11b does automatically.

Indeed, the most important component of Bluetooth has yet to be built. As it stands, Bluetooth is just a dumb communications link. All the smart interactions between Bluetooth devices—from the way one such device controls another to the automatic synchronisation that is needed when two or more devices share the same data—will require a sophisticated “applications layer” running on top of the Bluetooth link. As yet, almost no universal applications standards have been set for Bluetooth.

For this, blame the makers. Although they gave in on a common standard for Bluetooth itself, manufacturers are still looking for ways to bend the technology to their own advantage. Microsoft, for instance, wants its semi-proprietary “universal plug-and-play” standard to be included. Tough as it was to get the biggest companies from different industries to agree on a basic Bluetooth specification, it is going to be even harder to do the same for each application-specific standard—from simple tasks such as controlling music players to complex hand-over rules needed between public-wireless networks and local cordless connections for phone calls.

This does not mean that Bluetooth will be a failure. It just means that it will take longer to reach its potential than today's pre-launch claims suggest. Even with its more limited ambitions, it has taken 802.11 in all its versions (the “b” variant, which increased the bandwidth, has been around only since 1997) the best part of a decade to become sufficiently cheap and functional to achieve its present modest level of market penetration. Laptop computers with 802.11b built into them are only now beginning to hit the streets.

Bluetooth may be cheaper, but it faces many of the same chicken-and-egg problems: why pay extra for a Bluetooth-enabled printer if you do not have a Bluetooth-enabled laptop, and vice versa? Initially, Bluetooth devices may be sold in tandem—say, a headset with a phone—which risks Balkanising the standard with proprietary extensions. The fact is that until the 3G wireless networks become a reality the potential of connected hand-held devices will remain untapped, restricting demand for Bluetooth. The wireless revolution is coming, but not as fast as the revolutionaries would like.