Bluetooth Protocols
Bluetooth is a radio technology that uses
frequency-hopping spread spectrum. This splits up the data being
transmits sections of it on number of different frequencies, in
fact there 79 frequencies that can be used. The frequency band
used is the 2.4 GHz short-range radio band. Early Bluetooth
protocols could achieve data transfer rates at up to 1 Mbit/s
but that was improved considerably by more recent protocols, for
instance Bluetooth 2.0 can transfer data at 3 Mbit/s.
The range of a Bluetooth device is dependent on the
amount of energy that it uses. Most Bluetooth devices are either
Class 1 which has a range of around 100 meters or Class 2 which
has a range of approximately 10 metres. The power consumption of
these Classes is 100 mW and 2.5 mW respectively.
The original Bluetooth specification dates back to 1994
and was published in 1998 by the Bluetooth Special Interest
Group. The original specification was Bluetooth 1.0 though this
had a number of bugs and was soon replaced by Bluetooth 1.1.
Over the intervening years a number of different specification
were developed and the latest one of these is Bluetooth 4.0, or
Bluetooth Low Energy. Next we will see how these different
versions compare.
Overview of Bluetooth
Specifications
Bluetooth 1.0
Bluetooth 1.0 was the original specification but there were a
number of fundamental problems. These were that a Bluetooth
device from one manufacturer frequently would not communicate
with a Bluetooth device from a different manufacturer. There
were also security concerns in connecting different devices.
Bluetooth 1.1
Bluetooth 1.1 followed quickly on the heels of Bluetooth 1.0.
This new specification fixed many of the flaws in the previous
specification though in practical terms there remained
incompatibilities between manufacturers, for instance some early
Bluetooth headsets would work only with specific Bluetooth
phones.
Bluetooth 2 + EDR
Bluetooth 2 + EDR was backward compatible with Bluetooth 1.2 but
provided considerable enhancements over the earlier protocol.
Extended Data Rate increased the data transfer speed of 1 1 Mbit/s
to 3 Mbit/s. This improvement was achieved by modifying the
radio transmission methodology to make use of Phase Shift
Keying.
Power consumption was reduced by subrating the sniff mode, that
is when the device is waiting to be contacted. This made a huge
difference to devices such as the Bluetooth mouse improving the
battery life by many times.
Data encryption was improved as was the security of device
pairing. New ways of pairing were also enabled which, once
permitted by the user, would allow devices to pair when in close
proximity.
Bluetooth 3 + HS
This specification was released in 2009. It increases the data
transmittion speed by almost an order of magnitude to 24 Mbit/s.
Essentially it is a hybrid of Bluetooth technology, which is
used for making connections between devices, and WiFi which is
used for high speed data transmission.
An additional feature is reduced power consumption during the
period when data is not being transferred. It is only recently
that this technology has been incorporated into computers.
Bluetooth 4.0
Bluetooth 4.0 is
Bluetooth Low
Energy. This is an exciting
technology that will increase vastly the number of Bluetooth
applications. Such low power demands are made by Bluetooth low
energy devices that items such as a Bluetooth Sportswatch can be
powered for up to a year on a single button cell. We have
written a detailed explanation of Bluetooth Low Energy and you
can read it
here.
Final Words
Bluetooth protocols have gone through considerable enhancements
since the introduction of Bluetooth 1 in 1998. Initially these
were bug fixes and general improvements, but with Bluetooth 3.0
+ HS and Bluetooth 4.0 the technology his diverged into new
areas. These two protocols have not yet been fully implemented
in the market place but as they come of age in the coming months
and years we will see some very new and exciting Bluetooth
applications.
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