Well I've watched my colleagues on lordpercy.com getting very excited about Bluetooth apart from being just a little strange I do worry that it is banded around as a wireless utopia and therefore wanted to guide you through what Bluetooth is and explain what makes it tick?

Bluetooth was conceived as a low speed, short range wireless protocol that could be adopted by many "things" allowing them to communicate primarily in a domestic environment, in short its pitched at you and me to connect the gadgets in our homes. The chips that power Bluetooth and small lower power devices that have found their way into a wide variety of mobile phones and PDA's allowing "enabled" devices to communicate and exchange data.

Bluetooth was brought to us by the white coated boffins at Ericsson in Sweden, no doubt after a late night session of ABBA inspired boffinating they came up with the protocol to allow devices communicating on the 2.4 gigahertz band to overcome the limitations of other wireless communication methods like Infrared (IR). Of course using this frequency that is internationally available brought problems with interference everything from baby monitors to garage door openers use this range and getting round this was a high priority for the Ericsson boys.

The first and simplest way of avoiding interference is to use low power, indeed Bluetooth can use only 1 milliwatt compared to a mobile phone at 3 watts, secondly Bluetooth uses spread-spectrum frequency hopping which allows devices to change frequency to one of 79 within a pre defined range a bit like selecting the radio channel to be used on a remote control toy but here the changes occur 1600 time a second.

So once a device is within the 10 meter range how does it know who is there and if they want to communicate?  Devices join a piconet or personal area network, each "enabled" device uses a defined range of Mac addresses, these tell other devices whether its a DVD player or Fridge freezer. The devices then announce their presence and if they have been "paired" (a process where the user allows 2 devices to automatically communicate) the connection is made and the data can be transferred, the claimed 1 mbit (about 720kbits) speed allows for full duplex voice conversations or data transfer. The master devices (the one that initiates the connection) can have up to 7 slaves of varying types of device, of course the bandwidth is shared so each new device reduces the available bandwidth to the entire piconet.

Security is provided within the protocol with a challenge and accept model with the keys managed by the software layer the standard supports key lengths of 40 or 64 bits and further encryption is provided in software by many Bluetooth equipment manufacturers.

So what use is this anyway?  It is possible to network any enabled device, so your laptop can reach a printer without wires, a PDA can send a virtual business card to another PDA across a room, your fridge can tell your PC to mail you and let you know its defrosting! The protocol is there to be used and if you decide to open your curtains with it then so be it, of course it can stream audio and low resolution video but this really is a standard for mobile interaction which is why phones and MP3 players are popping up with the chip inside.

Great so why Bluetooth?  Well this is down to the Swedes, they looked to a 10th century king of Denmark named Harold Blåtand for inspiration. Blåtand is, Danish for Bluetooth. He was called this either because of his dark hair or perhaps his liking for blueberries which stained his teeth. Either way, Harold united Denmark and Norway which I guess is why the Ericsson boffins thought that naming a wireless standard which unites enabled devices seemed like a good idea.

The jury is still out on full adoption of the protocol into the majority of devices this depends on the manufacturers, signs are good as the initial group of 5 has now expanded into a special interest group (SIG) with over 1000 members, as with most new standards its success is a measure of the applications that use it!

Further info - Bluetooth Explained

Device Power Class	Max Output Power (mW)	Max Output Power (dBm)	Expected Range
Class 1	100mW	20dBm	100m
Class 2	2.5mW	4dBm	10m
Class 3	1mW	0dBm	10cm

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