Infrared serial connections have been around for a long time. The first mass use of IR serial connections was for the remote control of the television set. IR connections are good for this specific type of operation where there is a line of sight between the two devices and the data transfer speed is low. For connections at higher speed—for example to transfer high quality audio—or for situations where there is no direct line of sight like with portable headsets, IR is not the best technical solution. With infrared light there is also the problem that the communication can easily be intercepted by other devices, or even tampered with. One game children like to do is standing outside of the house with a second remote control and zapping through the available channels on television while mom and dad are sitting in the house not knowing what is happening to their TV. This kind of interception and hostile takeover should not be possible with low-power datatransmission for computers. This is why two developers of Ericsson Mobile Platforms came up with a low-power solution using radio transmission called Bluetooth.
Bluetooth was developed with many different uses in mind, ranging from phone book transfer from mobile phones, audio from headsets and position data from GPS receivers. Because of this the internal protocol running on Bluetooth systems is very versatile. Because of the many small, advanced and relatively cheap devices targetted by Bluetooth, you could easily call it the gadget interface.
Bluetooth has been developed for low power, low costs situations where data transfers are necessary. The low power requirement has two good reasons. First of all battery powered devices will work longer on their batteries if less power is consumed by the data transfer technology. Low power also means less radius of the radio signal. If the radius of the signal is smaller, more devices can operate in the same frequency bands with higher bandwidth available for each devices, and the chance that the signal is intercepted by third parties is lower. For some situations longer reach may however be necessary. For this reason three power classes for Bluetooth devices have been defined.
|1||100 mW||100 m|
|2||2.5 mW||15 m|
|3||1 mW||8 m|
High power devices can communicate with low power devices, but in general the low power device will define the maximum allowed distance between the two peers.
|2.0 + EDR||2004||3 Mbit/s|
|3.0 + HS||2009||24 MBit/s|
Despite these early startup problems, Bluetooth is now available on a large number of devices including: