Wireless LAN equipment revenue rose 80% worldwide in 2000, according to market researcher IDC. They go on to predict a market approaching $3.2 billion by the end of 2005. The news at the most "local" of these wireless local-area networks has been Bluetooth - almost a household name - for a wireless technology that fits best, perhaps, within a house. It replaces cable over distances of 30 feet or less.

Though it's received a lot of publicity, Bluetooth is only first beginning to bring real products to market. Does Bluetooth have teeth?

Named for the 10th century Viking King Harald Bluetooth, who united the Nordic nations under Christianity, Bluetooth was originally conceived by Swedish company Ericsson in 1994, then studying the feasibility of using low-power radio links to replace cables between mobile phones and accessories. In 1998, a Special Interest Group (SIG) was formed by Ericsson, Nokia, IBM, Toshiba, and Intel for the purpose of developing and promoting this new wireless solution. Since then, they've been joined by over 2,000 other companies, including heavyweights such as Lucent, Microsoft, and Motorola.

Bluetooth Basics

The concept is a simple one. Bluetooth uses a 2.4 GHz radio link to communicate from point to point, or from a single point to several connections. Current specifications allow for distances of up to 100 meters. However, most devices will be low power, only capable of up to 10 meters.

Because the technology can be contained within a single CMOS chip, it is ideal for inclusion in small mobile devices. For example, you can use a headset that is connected via Bluetooth to your mobile phone without having to physically connect the two - or even without having to take your phone out of your briefcase, since the two do not have to "see" each other in order to connect (as with infrared connections). Other applications include automatically synchronizing your PDA with your PC when they get within range, or using your mobile phone to send credit information to a Bluetooth-equipped sales system.

The types of products best suited to Bluetooth are contained in a list of profiles which, together with the basic protocols, make up the guidelines for developers. These profiles currently cover such acpplications as file transfer, cordless telephones, headsets, and LAN access. By certifying only products that adhere to these profiles, Bluetooth proponents hope to ensure interoperability between products.

David McCall is senior applications engineer with Cambridge Silicon Radio (CSR), (Richardson, TX - 972-238-2300) which manufacturers single-chip Bluetooth solutions. "Bluetooth was originally conceived as a cable replacement technology, and all the usage profiles in (current version) 1.1 are fairly simple. They replace a cable between a mobile phone and a laptop so that you can use the phone as a modem, between a PDA and a PC so that you can synchronize the two, or between a headset and a mobile phone. These are the sorts of things companies are working on right now."

The Bluetooth specifications don't limit the connections to two devices, of course. In these ad hoc personal-area networks (PANs), up to eight devices can be linked into what is being called a "piconet." To regulate traffic on the channel, one of the participating devices becomes a "master" of the piconet, while all other units become "slaves." With the current Bluetooth specification, up to seven slaves can actively communicate with one master.

In order to extend the reach of these networks, several piconets can then be linked together in what are called scatternets. Theoretically, the owner of a Bluetooth-equipped device can then hook up anywhere within that network and connect to another Bluetooth device.

LAN-Ready, Or Not?

But it doesn't quite work ... yet. Current Bluetooth products don't completely support the scatternets spec sketched out in the first revision of the standard. So they don't provide true roaming, or this kind of any-to-any connectivity across conjoined piconets. There are vendors working on this problem - for example, a company called Commil Technology (Petah Tikva, Israel - 972-3-9217770) has designed a system to allow for uninterrupted data and voice communication. However, this still makes Bluetooth less useful for wireless LAN implementations than other technologies.

This doesn't bother McCall. "At the moment, none of the existing profiles rely on a scatternet operation," he says. "Scatternet was in the first version of the specification, but there are still a lot of holes. If anyone tells you they can do it, they're making assumptions. It's getting there, but it still needs work."

In fact, McCall feels that the limited number of devices that form a Bluetooth connection is one of its advantages. "You don't have to have a huge amount of devices out there before the customer has a reason to buy these products," he points out.

And there already are technologies in use that can better handle large-scale wireless networks. A widely considered competitor is the 802.11b wireless LAN, currently favored as a business solution to replace a wired LAN throughout a building. The 802.11b protocol has a high transmission capacity and can handle a large number of simultaneous users. However, it is more expensive than Bluetooth technology, with a higher level of power consumption. It also requires more space, making it less suitable for small mobile devices operating outside of a building.

The two technologies are often seen in opposition because they both operate in the 2.4GHz band. As a result, many are worried that the two systems can clash when used in proximity. What happens when an employee with a Bluetooth-equipped mobile phone and headset walks into a business equipped with 802.11b?

It is a problem that has not escaped either developers or the IEEE. "They do both operate in the same frequency spectrum," says Brent Miller, senior software engineer for IBM's (Armonk, NY - 914-499-1900) Pervasive Computing division. "It's an attractive spectrum, because it's unlicensed. However, the Bluetooth SIG is working with IEEE's 802.15 Coexistence Task Group, and they are considering a proposal as to how these two technologies can coexist."

In addition, the IEEE recently accepted a proposal from two companies, Mobilian Corporation (Hillsboro, OR - 888-314-3606) and Symbol Technologies (Holtsville, NY - 631-738-2400) for techniques that prevent interference by using what they described as an intelligent "traffic cop'' to optimize throughput when the two systems are located in the same device.