Bluetooth is a wireless communication technology that allows electronic devices
to communicate over small distances and, just as Wi-Fi, operates on the 2.4
GHz ISM frequency band. Despite operating on an open band, the Bluetooth
technology is regulated by the “Bluetooth Special Interest Group” (SIG) and
was standardized by IEEE as IEEE 802.15.1, even though it no longer maintains
the standard. Common examples of Bluetooth devices are Bluetooth
speaker,Bluetooth headsets, game controllers, wireless keyboards and mice
and Bluetooth beacon.
Bluetooth uses 79 channels to transmit data, starting with the first channel at a
frequency of 2402 MHz and continuing up to the last one at a frequency of 2480
MHz in 1 MHz increments.In order to avoid interference from other RF signals,a
technique known as frequency hopping where data is transmitted over one of
the available channels for a small period of time and resent over another
channel in case of interference, is used in order to transmit data, Bluetooth
devices must first stablish a connection. One single device is capable of
connecting to up to 7 devices and communicating with each one of them
simultaneously.This is done by using a connection model known
as“master-slave”, in which the device that initiates the connection takes the
role of master over the other devices. Whenever a master and a slave
establish a connection, a bond is created, enabling them to transmit and
receive data.
Designed as a low-power technology, Bluetooth is meant to function on battery
power devices over relatively short distances. Just as with Wi-Fi, the maximum
distance over which a Bluetooth device can stablish a connection depends on
its output power, as well as other factors such as signal reflection caused by
obstacles.Three different classes are used to classify Bluetooth devices
according to their maximum output power and their corresponding maximum
range. These can be seen in Table as below:
Class | Maximum Output Power | Range |
1 | 20 db | Up to 100m |
2 | 4 db | Up to 10m |
3 | 0 db | 0-10m |