20 Aug 2007

Bluetooth Networks

Bluetooth Networks
Once two or more Bluetooth devices start communication, they form a network which makes up the personal area network (PAN) or pico-net which varies in size depending on the type of connection. A maximum of eight devices can be supported in one PAN at a time, with one device acting as the central controller. Individual devices also may act as bridges, or connections, for other devices joining the network.

Structure of Bluetooth Networks
Bluetooth's complex structure utilizes signals and techniques that protect its integrity and enhances the effectiveness of the technology. A Bluetooth-enabled device uses 79 individual randomly chosen frequencies within designated ranges while changing from one frequency to another 1600 times a second. This allows more devices to be able to make use of the radio spectrum without any cross-interference occurring. Because the transmitters are hopping randomly between frequencies so often, any interference that does occur will only last a fraction of a second. This technique is called "spread spectrum frequency hopping".

Interference is also minimized by the relative signal strength of Bluetooth transmissions - it is the weakest of any wireless technology. This is beneficial, because the weak signals rarely interfere with each other, or any stronger transmissions. The wireless transmissions that create a personal area networks (PANs) typically generate signals of only a milliwatt (the most powerful cell phones, by comparison, transmit a signal of 3 watts). This low signal strength is what limits the range to 10 meters, but it's also the reason you'll never experience interference from your cell phone's network, the cordless phone's network, garage door's network or any other PAN existing in the area.