How Bluetooth Works - Signal Strength, Frequency, and Profiles

Bluetooth: Low Power and Low Cost!

Bluetooth wireless technology operates on an open frequency within the 2.4 gigahertz band, which is the same as WiFi, cordless phones and various other wireless devices. Bluetooth is able to share the same frequency band without experiencing any interference because it utilizes various key technologies.
One of the ways Bluetooth avoids interference is through the use of low power signals (around one milliwatt). Devices using the Bluetooth Core Specification Version 1.1 or later (To learn about the different Bluetooth versions, click: Bluetooth Core Specification Versions) are able to avoid interference with other wireless devices because their signal is so weak.
Take into consideration that powerful cell phones use a signal of around three watts. Even though the signal is weaker, Bluetooth still offers a range of up to 30 feet (Newer versions can have a range over 100 feet).
The signal is also capable of passing through the walls in your home, making it useful for controlling several devices in different rooms. Data can be transferred at a rate of up to one Megabyte per second (Mbps).
Also, because Bluetooth transmitters require minimal amounts of power, they are relatively inexpensive to manufacture. Simply put, Bluetooth uses low-power radio waves to reliably communicate in an inexpensive way.

“Hopping” = No Interference

Another way Bluetooth devices are able to avoid interference is through a technique known as spread-spectrum frequency hopping. By using the “hopping” method, a device will use one of 79 different, randomly chosen frequencies within an assigned range, and will frequently change frequencies from one to another.
Bluetooth enabled devices, which all use the “hopping” method, change frequencies 1,600 times per second. As a result, more devices can use a portion of the radio spectrum.
The risk of a device like a cell phone or baby monitor interfering with Bluetooth devices is minimized, since any interference on a specific frequency will last for only a fraction of a second.
Bluetooth version 2.0 + EDR, the very latest of the Bluetooth specification versions, uses an enhanced technology called: Adaptive Frequency Hopping (AFH).
AFH allows Bluetooth devices to measure the quality of the wireless signal and then determine if there are bad channels present on specific frequencies due to interference from other wireless devices.
If bad channels are present on a specific frequency, the Bluetooth device will adjust its hopping sequence to avoid them. As a result, the Bluetooth connection is stronger, faster, and more reliable.

Bluetooth Profiles: How Bluetooth is Used

Bluetooth enabled devices must use and understand certain Bluetooth "profiles" in order to use Bluetooth technology to connect to one another. These profiles define the possible applications that a Bluetooth enabled device can support.
In order for one Bluetooth device to connect to another, both devices must share at least one of the same Bluetooth profiles.
To learn more about profiles and why they are important to those using Bluetooth devices, click: Bluetooth Profiles