The range of a Bluetooth radio is dependent on the class. The following chart shows the range of a Bluetooth radio by the class:
|
Class |
Power (mW) |
Power (dBm) |
Range in meters |
|
1 |
100 |
20 |
~100 |
|
2 |
2.5 |
4 |
~10 |
|
3 |
1 |
0 |
~1 |
As with any radio technology the area surrounding the radio has a substantial effect on the range of the radio. The range listed in the previous chart is the theoretical maximum range with ideal conditions. The typical range is usually less than this theoretical maximum range.
Where the Bluetooth LE radio operates from 2,402 MHz to 2,480 MHz with each channel being 2 MHz apart, the Bluetooth Classic radio uses 79 channels from 2,402 MHz to 2,480 MHz with each channel being 1 MHz apart. As with Bluetooth LE, the Bluetooth Classic radio uses frequency hopping, where the radio changes channels 1,600 times a second, to reduce interference.
With Bluetooth LE, the radio continuously turns itself off to reduce power, Bluetooth Classic does not do this. This makes the Bluetooth LE radio technology better at short bursts of data with low power while the Bluetooth Classic radio is better at transmitting large amounts of data or data streaming because the radio is continuously on.
All Bluetooth devices have a unique 48-bit address that is assigned to the Bluetooth radio by the manufacturer. The upper half of the address (the most significant 24 bits) is known as the Organizationally Unique Identifier and consists of two parts. These parts are the Non-Significant Address (NAP) and the Upper Address Part (UAP).
The NAP is the first 16 bits of the address and is used in frequency hopping synchronization. The UAP is the next 8 bits and is assigned to the radio manufacturer by the IEEE organization.
The last 24-bits of the address is known as the Lower Address Part (LAP). The LAP is assigned by the manufacturer to identify the radio uniquely. The following diagram shows how the Bluetooth address is made up:
Now let's look that the network topology for Bluetooth Classic.