Friday, December 17, 2010

The Role of Radio Frequency in Bluetooth

Author: Jhonder | at : 9:31 PM | Category : , , , |
Bluetooth is a standard of radio frequency developed by Ericsson, the Swedish phone manufacturer as a method to allow electronic equipment such as a mobile phone or a computer to use short radio waves to connect to each other without the use of cables or wires. Therefore, Bluetooth works just like a radio but using short-range radio frequency to connect Bluetooth enabled devices within a specific area of coverage.

The RFCOMM Protocol

The protocol for Bluetooth Radio Frequency Communications or simply Bluetooth RFCOMM emulates the RS232 serial ports over another protocol known as L2CAP or the Logical Link Control and Adaptation Protocol. The Bluetooth Special Interest Group or SIG maintains the protocol specification for the Bluetooth Radio Frequency Communications.

The basis for the Bluetooth RFCOMM protocol is the TS 07.10, an ETSI standard. Only a TS 07.10 standard subset and specific RFCOMM extension is used. The Bluetooth Radio Frequency Communications protocol can support up to sixty connections all at the same time between Blue-tooth enabled devices. It depends on the specific implementation how many simultaneous connections can be used in a Bluetooth device. For Radio Frequency Communications, the channel of communication is complete if it has two applications operating on separate devices with a segment in between them.

The Bluetooth RFCOMM can accommodate two types of devices – those that act as end points for the communication channel such as a computer or a printer and then those that serve as just a portion of the communication such as a modem.

Bluetooth Radio Frequency Details

Bluetooth uses a 2.45 gigahertz frequency, which international bodies have agreed on for the use in what is known as the ISM band of devices. ISM refers to industrial, scientific and medical. This same radio frequency is used by many other devices such as garage-door openers, Baby monitors, and the latest wireless phones. For this reason, the design of the Bluetooth technology ensures that Bluetooth devices will not cause interferences with ISM devices.

To avoiding radio frequency interference, Bluetooth devices send out signals that are very weak, about a milliwatt versus a 3 watt signal transmitted by powerful mobile phones. With a low power, the range radio frequency of the Bluetooth device is limited to about 30 feet, reducing the chances of creating interferences between different devices.


Despite its low power, a Bluetooth signal can still go through the walls of a room so it is capable of controlling different Bluetooth devices in several rooms. Even with many Bluetooth devices activated in a single room, there still would not be any interference because these devices will not be on the same radio frequency simultaneously. This is because Bluetooth employs a technique known as “spread-spectrum frequency hopping” wherein one device will employ 79 unique and randomly selected radio frequencies within a given range, hopping from one radio frequency to another regularly so that each second the device performs more than a thousand frequency changes.

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