Back in 960AD, Harald Bluetooth, a traditional Viking, was christened and began converting the rest of the Danes to Christianity. As far as I can tell, he has nothing to do with the new Bluetooth technology, despite the fact that the Bluetooth special interest group (SIG) claims it was named after him.

For things to work with other things, they have to, at some point, have some interaction. With early computers, even up to recent years, that was facilitated by the use of cables. Then, within recent years, enterprising companies worked on infrared communications. These allowed for peripherals to interface, as long as they had line of sight with the infrared transmitter/receiver. The logical next step would be to eliminate line of sight requirements. This is where Bluetooth comes in.

Mmm…Radio Ain’t Just your Grandpa’s Toy
Bluetooth utilizes not infrared, but radio waves. This means that as long as the items are within any maximum distance, there are full communications capabilities possible. The RF band used by the Bluetooth technology is an unlicensed global 2.4GHz band ranging from 2.402 to 2.480GHz. This range allows for multiple devices to be present, communicating independently, without interfering with other devices on nearby frequencies. The actual bandwidth available for use by the Bluetooth specification is 1MBps per connection, with two possible connection types (those being SCO and ACL). Asynchronous connectionless type (ACL) is the standard packet oriented connection. Communications can be either asynchronous or synchronous, and the bandwidth available is variable, depending upon the setup. The synchronous connection oriented (SCO) connection can be added on top of the ACL as well. This allows devices to send data, unrequested, to other devices. The only present use for this would be voice communication over the Bluetooth connection, much like a walkie-talkie.

Topograpopaphy (sic)

Bluetooth was designed primarily for a few specific networking setups. One of the most evident setups would be the data/voice access connection. This is the key setup, one of the highlights of the Bluetooth specifications. In this setup, a single Bluetooth enabled device has a secure link with a single other Bluetooth enabled device. An example of this would be a Bluetooth enabled laptop connecting with a Bluetooth enabled cellular phone. By this method, you could leave your cell phone in your briefcase and connect to the internet with your laptop, which connects through the wireless connection to your cell phone. Another example would be a PDA getting email when coming into a designated access area, which would be within range of an internet connection of some kind, thus allowing the PDA to connect, download, and terminate the connection, all relatively quickly.

Another usage Bluetooth is designed for is that of peripheral connectivity. Everybody loved wireless keyboards, but they were tough to use because they always had to be pointed somewhat at the receiver. If the keyboard is using an RF band, suddenly you can use your keyboard behind a brick wall, and it will still work just fine. This is intended for all kinds of peripherals, including keyboards, joysticks, and on a more interesting level, things like headphones. Imagine using your headset to listen to music, until the phone rings, at which point your headset is suddenly the earpiece of the phone, with the boom mic being the mouthpiece, all without touching the phone, and no wires attached.

Arguably the most difficult to manage, as well as the most interesting, usage is that of the personal area network. With a personal area network, as devices come and go in and out of range, the possibility exists to have a network intelligently assembled and disassembled as per basic instructions. With each device having an active member address (AMA) of 3 bits, a master can support up to seven slaves for a network of a maximum of 8 active users. If another user comes into range, any device which is not active may give up its AMA for an 8 bit passive member address (PMA), allowing for just over 256 members connected to the personal area network (PAN). In a PAN, a single device acts as the master, which controls the frequency all the data is transmitted on, as well as the data offset. All of this information is set during a paging state where new devices are requested to join the network as slaves. Members who are not active slaves are parked, and listen at intervals for data addressed to them. The maximum range for devices is currently approximately 10 meters (with a power output of 1mW), although the specification supports power outputs much greater, and could get up to 100 meters (100mW) while still complying with regulations.

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