Some of the latest Bluetooth-equipped printers can print photos transmitted directly from a nearby Bluetooth-compatible cellphone. (Damian Dovarganes/AP)

The author is a Toronto-based freelance writer

Bluetooth — it's designed to make wireless connections between electronic gadgets super-simple, but behind the odd name there's a whole lot of complex technology at work.

Bluetooth is a radio-frequency technology that is designed to use little power and link devices that are a few metres from each other — creating what's sometimes called a "personal area network." And it’s a standard mainly used for devices that are considered, well, personal.

Typically, Bluetooth-enabled devices tend to be things like headsets, cordless phones, cellphones, printers, laptops, digital cameras, keyboards, mice and PCs. With the use of Bluetooth adapters, other devices like MP3 players and video game consoles can be linked up, too.

The technology is named after a 10th-century Danish king, Harald Blatand (or Bluetooth). The name was chosen because the king unified parts of Scandinavia, and the technology was likewise envisioned as unifying a standard that would help bring telecommunications and computer technology together through things like headsets and peripherals that could work with computers and phones.

Bluetooth technology was first developed in Sweden, where Ericsson adopted it and formed a consortium with Nokia, IBM and Intel to promote it in 1999. Soon thereafter, Microsoft, Motorola and Lucent Technologies joined them.

Bluetooth had big backers, but was slow to take off due to some early technical and compatibility issues. But those problems have been ironed out over the past few years, and Bluetooth has been gaining steady acceptance as a standard way to connect wireless gear over short distances.

How it works

Pants designed by Wearable Technology are equipped with a bluetooth connection and remote control buttons down one leg for controlling the playback of an MP3 player. (Uwe Lein/AP)

Bluetooth operates on a radio frequency at 2.45 GHz, which is an internationally open band meant for industrial, scientific and medical devices. The band is better known as "ISM," and it’s likely that you already own something that uses it — newer cordless phones, microwaves, baby monitors and even wireless internet home networks make use of the frequency.

It’s fairly common for these devices to interfere with each other when operating at the same time. Bluetooth devices tend to cause little interference because they transmit a very low-powered signal of one milliwatt. Other devices like cellphones and microwaves generate signals much stronger than that.

But the low power also means that Bluetooth devices have limited range — usually a radius of about 10 metres (walls usually don’t impede the connection). While the range is short, a big benefit of Bluetooth is that up to eight devices can be "paired" within a small area to swap data with each other — without interference degrading the signal between them.

For example, you can connect your PC or Mac (assuming they have built-in or external Bluetooth adapters) to a set of Bluetooth headphones to listen to music. You can also pair a cellphone to that same headset at the same time, and if the phone rings, you can override the music and answer the phone call.

Moreover, if there’s a photo you want to print from your phone, you can do so by pairing it with a nearby Bluetooth-enabled printer and transferring files while you're listening to the headset, without any of the wireless connections between the devices causing interference with each other.

This multiple-connection capability is possible because each Bluetooth device uses 79 randomly chosen frequencies and constantly changes them in a "hopping" technique 1,600 times per second, thereby making it almost impossible for two devices to interfere with each other. And even if they do, any period of interference would be so brief you likely wouldn’t notice it anyway. This also means Bluetooth gadgets won’t interfere with your baby monitor or any other device on the 2.45GHz band.

Making connections

Frequency hopping and the lack of interference are big benefits of Bluetooth, but one of the main reasons it has gained popularity is the ease of making connections. When two Bluetooth-enabled devices are in range, they are designed to automatically "talk" to each other and determine how the connection will work.

In any Bluetooth pairing, there has to be a master and a slave — one device controls the connection and the other follows along. A good example of this is a PC and headset or a cellphone and printer, respectively. However, the roles can change as new things are paired up — like for instance, when a headset is connected to a laptop and then a connection to a cellphone is added. The laptop was the master initially, but the second pairing with the cellphone changed that role to the headset because it is the headset that will "decide" whether it transmits and receives signals with the laptop or the phone.

The wireless connection is authenticated through a digital "key," which is usually a four-number code automatically exchanged by two devices. Once the connection is secured, they form a personal-area network, or "piconet" for short, and the paired devices will frequency-hop in tandem.

The constant shifts in frequency ensure that you won’t tap into another person’s piconet and people can't eavesdrop on yours. This is why two people can wear Bluetooth headsets and talk on their respective cellphones while standing beside each other.

Connecting two or more piconets to form a "scatternet" is actually possible, though the devices capable of doing it have only trickled onto the market this year, and are thus few and far between.

"There is still a ways to go on all this," says Eddie Chan, a research analyst who watches the mobile device market for IDC Canada. "People are getting to know Bluetooth better, but that’s mainly from a handset/headset perspective. When you really look at it closely, there are a lot of devices that have the functionality inside, or can be made to via a Bluetooth adapter."

Though the principles behind Bluetooth seems similar to those of Wi-Fi and infrared, there are notable differences. Wi-Fi uses the same radio frequencies, but with more expensive hardware that uses more power to transmit signals over a much wider area. Infrared is also a low-power option like Bluetooth, but it uses beams of light and thus requires line of sight, much like a remote control (which is one of the most common infrared devices) when it is being pointed at a television.

Wibree

Nokia has developed a newer wireless system called Wibree. It's based on the Bluetooth standard, but it is meant to be more compact and use less power.

This Sony Ericsson wristwatch communicates wirelessly with a user's cellphone. It vibrates when the cellphone is ringing, and the face lights up with incoming caller ID phone number so that the owner doesn't have to scramble to get the phone from a pocket or briefcase to see whether the call is one they want to answer. (Mark Lennihan/AP)

Bluetooth wristwatches are available that can display things like caller ID information from a cellphone ringing in your briefcase or backpack, for instance, but they’re bulky because of the size and power demands of Bluetooth. Wibree is meant to be a complement to Bluetooth, providing a compact and energy-efficient personal-area-network link for very small devices. And because of its low power consumption, engineers say it could be possible to have some Wibree-enabled devices that need only one recharge over the course of an entire year.

Wibree got a boost in June when the Bluetooth Special Interest Group (SIG) — an 8,000-company strong trade association of companies that includes the founding consortium — agreed to include Wibree as an ultra low-power offshoot of the Bluetooth standard.

"The Bluetooth SIG and the Wibree Forum have merged, so Wibree on its own no longer exists and will be part of the Bluetooth specification moving forward, providing the basis of the ultra low-power Bluetooth version expected out next year," said a Bluetooth SIG spokesperson. "This version of the technology will be ideal for fitness and health sensors, watches, remote displays and other scenarios where extended battery life is required."

Bluetooth outlook

The adoption rate for Bluetooth has been slow over the years, though it seems to finally be catching on with consumers. Since mid-2005, there’s been a global increase of 200 per cent in sales of Bluetooth headsets for cellphones, for example.

An NPD Group report estimated that at least 50 per cent of all cellphones sold in the fourth-quarter of 2006 had Bluetooth functionality. A separate report from research firm IMS indicated that cellphones/smartphones and headsets will account for 75 per cent of all Bluetooth-enabled devices shipped by the end of this decade.

Some predict the next big market for Bluetooth will be as a wireless connection between headsets and iPods or other MP3 players. While a few models are currently available, they haven’t caught on as must-have items yet.

Part of that could be because of a lack of awareness. For example, many consumers know that pairing a headset with a cellphone or iPod is possible, but fewer might know that connections with gadgets like a car stereo are possible too — handy for back-seat DVD players, for example.

The technology is also expected to evolve to the point where a high rate of data transfer will be possible. It’s already possible to quickly exchange small files such as electronic business cards between handheld computers or cellphones using Bluetooth, but perhaps exchanging large files will be in the cards soon as well.

Overall, shipments of Bluetooth-enabled gear increased about 30 per cent this year. A report from research firm In-Stat suggests that Bluetooth adoption will continue to grow into 2008, but is then expected to slow as time goes on because of competing services like Wi-Fi, FM and GPS that are being built into mobile devices.

Cellphone vendors are ultimately working towards a radio-silicon standard that could incorporate all, or most, of these services together on a single low-cost chip.