Bluetooth is a wireless networking protocol (like WIFI) designed to quickly and automatically connect devices like printers, PDAs, Cameras etc to computers and to each other without wires.
Common Bluetooth applications are:
- Connecting mobile phones to each other to exchange pictures,ring tones, music etc
- Connecting computer peripherals like mice, keyboards, printers etc to a computer.
- Connecting headsets to mobile phones for hands free operation (Bluetooth car kits)
Bluetooth uses low power, low cost transmitters and receivers with a
range of 10-100 meters making it ideal for mobile use.
Bluetooth devices automatically detect and contact each other making communication between devices very easy.
Bluetooth Versus Wi-Fi
Because both technologies are associated with computers and mobile phones there is considerable confusion as to which one to use or which one should be used.
WIFI is the wireless equivalent of Ethernet making fast data transfer
possible between computers.
It is the choice for connecting computers together in a Home/Office environment.
Bluetooth can connect computers together, but the data transfer rate between the computers is too slow to be off practical use.
It is more commonly associated with connecting PDAs to computers for synchronization, and for connecting other (low speed) peripheral devices like mice and keyboards.
Bluetooth Class and Standards
Bluetooth devices come in three classes 1-3. The device class determines the effective operating range/distance of the the device.
Class 1 devices have a range up to 100m, class 2 devices up to 30 meters and a class 3 device up to 10 meters.
Bluetooth is still being actively developed and the standard has already been through a number of versions.
Each version is backwards compatible with the last making it possible to inter-operate devices with different version numbers.
The current Bluetooth standard is at version 4.0, Bluetooth 4 has 2 flavours
- Classic Bluetooth and
- Bluetooth Low energy
Classic Bluetooth is backwards compatible with the previous Bluetooth versions but Bluetooth Low energy isn’t backward compatible.
Devices like smart phones PC etc. will support both modes (dual mode) but devices like sensors will likely support a single mode (Low energy).
Bluetooth Low energy will be very a very important technology for connecting everyday devices to the Internet (internet of things).
|Technical Specification||Classic Bluetooth||Low Power Bluetooth|
|Distance||10-100 meters||10-100 meters|
|Power consumption||1 as the reference||0.01 to 0.5 (depending on use case)|
|Primary Uses||Mobile phones, gaming, headsets, stereo audio streaming, smart homes, wearables, automotive, PCs, security, proximity, healthcare, sports & fitness, etc.||Mobile phones, gaming, PCs, watches, sports and fitness, healthcare, security & proximity, automotive, home electronics, automation, Industrial, etc.|
Wikipedia has more technical details on the different standards and the differences.
There are two pairing mechanisms
Legacy pairing which was only method available in v2.0 and previous versions,and Secure Simple Pairing (SSP) which is available in v2.1 and above.
v2.1 devices can use legacy pairing to connect to v2.0 and earlier devices.
Bluetooth devices can automatically discover other Bluetooth devices that are within range if discovery is enabled.
However the discovery process takes time and the device connection must be approved.
This is obviously not satisfactory for devices that must always be in contact with each other like a bluetooth keyboard and mouse or an in car hands free kit and the mobile phone.
Device pairing make an effective permanent connection between the two devices so that they always connect without following the normal discovery process.
In legacy pairing the connection is made by assigning the devices a shared passkey (PIN) which they use to authenticate each other.
The process will vary slightly depending on the device but the
general process for pairing two devices (Device A and B) is.
- Switch on both devices
- Device A should detect device B
- Select Pairing on device A and enter the PIN (passkey)
- Device B will ask the user for the PIN. Enter the same PIN
- You should get confirmation that the devices are paired.
For devices that don’t allow you to enter a PIN (e.g headsets) the PIN is fixed and is usually 0000 or 1234.
Other devices may be restricted in character sets i.e. they may only allow numbers, and you must take this in consideration when assigning a PIN.
Secure Simple Pairing (SSP) uses a variety of pairing mechanisms and is able to detect the capabilities of the connecting devices.
However the main mechanism also uses a PIN called a passkey which is 6 digit numeric code.
Here is a useful video that shows how to transfer a picture from a mobile phone to a PC using bluetooth that illustrates the pairing process.
Bluetooth is a point to point protocol and is ideal for connecting peripherals like headphones to a computer/tablet/smart phone.
It uses a hub and spoke networking topology. This type of topology isn’t suitable for connecting 100s of devices to each other as will be the case as the Internet of things grows.
The next release of Bluetooth (in 2016)will incorporate mesh networking.
Related articles and resources:
- Official bluetooth website
- Difference between Bluetooth 3,4,4.1,4.2 and 5