I thought I would set myself the challenge of blogging about Bluetooth between now and Twelfth Night. I’m going to look at 12 topics covering the technology, the various services and capabilities as well as, of course, referencing how 32feet can help you use the technology.
What’s in a Name?
We probably all know the origin of the Bluetooth name – It comes from the nickname of a Norwegian king with severe dental problems. However, the actual technology was the result of collaboration between Nokia, Ericsson and Intel in the late 1990s to create a short-range radio technology for connecting devices. The Bluetooth name was only intended as a codename, but it stuck thankfully, rather than a number of bland product names suggested. Even the logo was created from Nordic runes representing King Harald’s initials.
On the Air
Bluetooth uses the unlicenced 2.4Ghz band. It uses Frequency-Hopping which helps to avoid interference and make it more difficult to jam or intercept the signal. A lot of how Bluetooth works at the radio level follows on from a technique developed by Hollywood actress Hedy Lamarr and composer George Antheil in the 1940s. They had designed a technique for sending secret messages to radio-guided torpedoes. The US Navy rejected the technology but seized it as “alien property” as Hedy Lamarr was an Austrian citizen at the time. It then got “lost” and not rediscovered again until the 1960s.
The Bluetooth 1.0 specification was published in 1999. Primarily supporting serial port connections wirelessly and with a throughput of just 721 kbps and a range of 10 metres (32 feet) it nevertheless provided a first step on the long journey to today’s capabilities. It would go on to replace the almost ubiquitous IrDA ports found on phones at the time which could be used to exchange contacts and other files, and support ever higher audio quality.
Once Again with Less Energy
In 2013 with Bluetooth 4.0 a new Low Energy mode to provide a much more efficient way of working with intermittently active devices. A whole separate set of service specifications exist for Bluetooth LE and each has one or more characteristic which represents a logical value. These can provide read, write and notify functionality. The latter of which allows devices to re-establish a connection to notify when a value changes, rather than the old approach of using a constantly open data stream.
Bluetooth and .NET
32feet is a .NET library for working with Bluetooth and related personal area networking technologies. When I created it in 2003 it originally contained Bluetooth serial support for Windows CE and desktop Windows along with IrDA and OBEX (Object Exchange). More recently the library has been modernised and Bluetooth LE added, along with support for more platforms. If you would like to get involved there are plenty of opportunities to contribute to the code or documentation as the project expands to new device platforms and functionality.
Next time we will look at how Bluetooth devices are discovered and identified.