Who or What Is Bluetooth?

One of the most often talked about wireless standards, besides Wi-Fi, is Bluetooth. The Bluetooth wireless technology, named for the tenth-century Danish King Harald Blatand “Bluetooth,” was invented by the L.M. Ericsson company of Sweden in 1994. King Harald helped unite his part of the world during a conflict around 960 AD. Ericsson intended for Bluetooth technology to unite the mobile world. In 1998, Ericsson, IBM, Intel, Nokia, and Toshiba founded the Bluetooth Special Interest Group (SIG), Inc. to develop an open specification for always-on, short-range wireless connectivity based on Ericsson’s Bluetooth technology. Their specification was publicly released on July 26, 1999. The Bluetooth SIG now includes 3Com, Agere, Ericsson, IBM, Intel, Microsoft, Motorola, Nokia, Toshiba, and nearly 2,000 other companies. Dozens of Bluetooth-enabled products are already on the market, with many more on the way.

Sometimes a network of devices communicating via Bluetooth is described as a personal area network (PAN) to distinguish it from a network of computers often called a local area network (LAN). In March 2002, the Institute for Electrical and Electronics Engineers (IEEE) approved IEEE 802.15.1, a standard for wireless PANs (WPANs), which was adapted from portions of the Bluetooth wireless specification. IEEE 802.15.1 is fully compliant with the Bluetooth v1.1 specification. As IEEE worked toward the 802.15 standard, the Bluetooth SIG simultaneously has been working on Bluetooth Version 3.0. Any new Bluetooth standard will likely also become an updated IEEE 802.15 standard. (Read more at the Bluetooth Web site at www.bluetooth.com.)

The following is a small sampling of existing Bluetooth products:

Microsoft Wireless IntelliMouse Explorer for Bluetooth (a wireless mouse)

Microsoft Wireless Optical Desktop for Bluetooth (wireless multimedia center keyboard and mouse)

Sony digital video camera recorder

HP Deskjet 995c printer

HP iPAQ H5450 Pocket PC with Bluetooth (and Wi-Fi) onboard

Ericsson Bluetooth Phone Adapter

Motorola Bluetooth Handsfree Car Kit

Belkin Bluetooth Universal Serial Bus (USB) Adapter

The easiest way to distinguish Wi-Fi from Bluetooth is to focus on what each replaces:

Wi-Fi is wireless Ethernet. Wi-Fi is a wireless version of the Ethernet communication protocol and is intended to replace networking cable that would otherwise be run through walls and ceilings to connect computers in multiple rooms or even multiple floors of a building.

Bluetooth replaces peripheral cables. Bluetooth wireless technology operates at short distances — usually about 10 meters — most often replaces cables that connect peripheral devices, such as a printer, keyboard, mouse, or personal digital assistant (PDA) to your computer.

Bluetooth replaces IrDA. Bluetooth can also be used to replace another wireless technology — Infrared Data Association (IrDA) wireless technology — that’s already found in most laptop computers, PDAs, and even many printers. Although IR signals are very secure and aren’t bothered with radio frequency (RF) interference, IrDA’s usefulness is hindered by infrared’s requirement for line-of-sight proximity of devices. Just like how your TV’s remote control must be pointed directly at your TV to work, the infrared ports on two PDAs must be lined up to trade data, and your laptop has to be “pointing” at the printer to print over the infrared connection. Because Bluetooth uses radio waves rather than light waves, line-of-sight proximity is not required.

Like Wi-Fi, Bluetooth offers wireless access to LANs, including Internet access. Bluetooth devices can potentially access the Public Switched Telephone Network (PSTN: you know, the phone system) and mobile telephone networks. Bluetooth should be able to thrive alongside Wi-Fi by making possible such innovative solutions as a hands-free mobile phone headset, print-to-fax, and automatic PDA, laptop, and cell phone/address book synchronization.

Piconets, Masters, and Slaves

Communication between Bluetooth devices is similar in concept to the ad hoc mode of Wi-Fi wireless networks (which we describe in Chapter 2). A Bluetooth device automatically and spontaneously forms informal WPANs, called piconets, with from one to seven other Bluetooth devices that have the same Bluetooth profile. Piconets get their name from merging the prefix pico (probably from the Italian word piccolo [small]) and network. A capability called unconscious connectivity enables these devices to connect and disconnect almost without any user intervention.

Figure 3-2:

A Bluetooth scatternet

comprises Master

several

piconets. Slave

In order to maintain the security of the data that you send over a Bluetooth link, the Bluetooth standard includes several layers of security. First, the two Bluetooth devices that are connecting use a process called authentication to identify each other. After the authentication process is done (sometimes called pairing in the Bluetooth world), the devices can begin sharing information. The data being sent across the radio link is encrypted (scrambled) so that only other authenticated devices have the key that can decrypt (unscramble) the data.

Both Wi-Fi (the IEEE 802.11b and g versions) and Bluetooth use the 2.4 GHz frequency radio band, but note the significant differences in how these technologies use the band. Bluetooth radios transmit a signal strength that complies with transmission regulations in most countries and is designed to connect at distances from 10 centimeters to 10 meters through walls and other obstacles — although like any radio wave, Bluetooth transmissions can be weakened by certain kinds of construction material, such as steel or heavy concrete. Although Bluetooth devices can employ a transmission power that produces a range in excess of 100 meters, you can assume that most Bluetooth devices are designed for use within 10 meters of other compatible devices, which is fine for the applications for which Bluetooth is intended, such as replacing short run cables.