• Bluetooth Overview

    Bluetooth technology is a wireless means of exchanging information between a computer and various devices such as laptops, personal digital assistants, cell phones, printers, digital cameras, and even keyboards and mice.

    The name "Bluetooth" comes from Harold Bluetooth, king of Denmark toward the end of the first millennium. He was known for unifying Denmark with the previously warring countries of Norway and Sweden. Bluetooth technology likewise is used to make unifying various computerized devices easier. The logo for Bluetooth takes the Nordic runic characters for H and B and blends them together.

    The Piconet

    A Bluetooth "master" can be set up to communicate with up to 7 "slave" devices. The resulting network is called a piconet. The master device will switch from slave to slave, waiting for one of them to tell it that there is information to be transferred. When that happens, the master device will receive information from the slave. The two devices may switch roles with slave becoming master and master slave if information needs to flow in the opposite direction.

    The Scatternet

    Two or more piconets can be linked together to form a scatternet. A device that plays the role of slave in one piconet can be set up to be the master of another piconet. That device will then be scanned by its own master for information while it in turn scans all the slaves in the other piconet.

    Or two piconets can be set up separately, say in adjoining cubicles. One of the devices in one piconet can be set up to scan and receive information from a single device in the other piconet. Giving someone else access to one device in your own piconet (such as the address book on a cell phone) does not mean you have to give access to everything else in the piconet.

    Bluetooth uses radio frequency in the 2.4GHz range to communicate. This is an unlicensed radio banned that is also used by some baby monitors, garage door openers, and portable phones. Bluetooth has a range of about 10 meters (33 feet). So Bluetooth isn't meant to be a replacement for a Wi-Fi network which can cover an entire house or building. But it doesn't require as much hardware and time to set up, and it doesn't use as much power. If Wi-Fi is like a wireless ethernet network, then think of Bluetooth as a sort of wireless USB port. It's ideal for an office, cubicle, or other single room space.

    To be more specific about the frequency, Bluetooth uses the frequencies from 2402 to 2480 MHz divided up into 79 channels of 1 MHz each. It hops from channel to channel at a rate of 1600 hops per second. This helps to minimize interference and fading. Each piconet is assigned its own unique hopping sequence derived from an algorithm that uses the device address of the piconet's master device.

    Security

    Bluetooth connections can be specified to require one-way, two-way or no authentication. Two or more devices can be paired using a "passkey" that is determined by the user. This allows the devices to share encrypted information that can't be listened in on. Key lengths of 40 o4 64 bits are supported. Additional password protection is available at the software level.

    Bluetooth 1.0 and 1.0b were the earliest versions and were beset by problems. These problems were corrected in Bluetooth 1.1 and support was added for non-encrypted channels.

    Bluetooth 1.2 is backwards compatible with Bluetooth 1.1 and features several major improvements. Among other things, transmission speeds were improved and audio links were improved in voice quality by providing for the detection and retransmission of corrupted packets.

    Bluetooth 2.0 is the newest version and devices that use it are just being made available. Bluetooth 2.0 is backwards compatible with all previous versions. It's main benefit is a transmission speed that is 3 times faster than previous versions. It also has higher bandwidth availability, better error correction, and lower power consumption.

    Some Typical Uses

    One typical use of Bluetooth is to pair a laptop computer or personal digital assistant (PDA) with a mobile phone. If both these devices have Bluetooth capability, getting them together is a cinch. Just use the Bluetooth software to pair the two devices together. Now that they recognize each other, you can instruct the laptop or PDA to use your mobile phone as a default dial-up device. When you want to go on the web, your laptop or PDA will automatically search for your mobile phone, use it to dial out, and link to the web through it.

    Another good use is to get a Bluetooth headset to go with your mobile phone. Again, you can pair the two devices so they're able to "see" each other. When the mobile phone rings, the headset rings too. Put on the headset and push the button to answer the call. The mobile phone will see that the headset is on and send the sound up there rather than through its own speaker. And you've got yourself a headset without any wires to get in the way.

    Another great way to put Bluetooth to work is by synchronizing your PIM (Personal Information Manager) data. When you get a new phone number or address for someone, you often have to enter that information in two or even three different places. Your Outlook contacts folder on your PC needs to know. Your laptop needs the same information. And your mobile phone also needs to be updated. Set these three devices up in a piconet and use Bluetooth software to tell them to synchronize with one another. Now whenever you update one of them, the others update automatically as soon as the updated device is within range.