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Bluetooth devices will normally run at 2.4 GHZ
in the license free, globally available ISM radio
band. The advantage to this band includes wide-ranging
availability and compatibility. A disadvantage to
this nonetheless, is that the devices must share this
band with different RF emitters. This includes
automobile protection systems, different wireless devices,
and other noise sources, such as microwaves.

To overcome this challenge, Bluetooth employs a
fast frequency hopping scheme and consequently uses
shorter packets than other standards within the
ISM band. This scheme helps to set up Bluetooth
communication more robust and more protected.

Frequency hopping
Frequency hopping is generally jumping from frequency
to frequency within the ISM radio band. After a
bluetooth device sends or receives a packet, it
and the device (or devices) it’s communicating by
hop to another frequency once the next packet is
sent. This scheme offers three advantages:
1. Allows Bluetooth devices to use the
entirety of the available ISM band, while never
transferring from a set frequency for more than a
small span of time. This helps insure that
Bluetooth conforms to the ISM restrictions on the
transfer amount per frequency.
2. Ensures that any interference won’t
last long. Any packet that doesn’t come safely
to its destination can be sent back to the next
frequency.
3. Provides a base level of protection as
it’s extremely hard for an inquisitive device to foretell
which frequency the Bluetooth devices will likely use
next.

The connected devices regardless, must approve of upon the
frequency they will desire to use next. The specification
in Bluetooth ensures this in two ways. First, it
defines a master and slave type relationship between
bluetooth devices. Next, it specifies an algorithm
that uses device specific information when
calculating the frequency hop sequences.

A Bluetooth device that operates in master mode can
communicate with up to seven devices that are set in
slave mode. To each of the slaves, the master
Bluetooth mechanism will send its own unique address
and the value of its own internal features. The
information sent is formerly used to add up the
frequency hop sequences.

Because the master device and each of the slave
devices use the exact algorithm with the identical original
input, the connected devices will often turn up
together at the next frequency that they will have agreed
upon.

As a replacement for cable technology, it’s no
sight that Bluetooth devices are normally battery
powered, such as wireless mice and battery powered
cell phones. To conserve the power, most devices
operate in low capacity. This helps to give Bluetooth
devices a range of around 5 - 10 meters.

This range is far more sufficient for wireless communication
but similar enough to refrain from using too much power
from the power source of the device.