Bluetooth devices will normally operate at 2.4 GHz in the license is free, globally accessible ISM radio band. The advantage of this band includes worldwide availability and compatibility. This loss is that the device should be shared with another band RF transmitter. This includes automobiles security systems, wireless devices, and other audio sources, like a microwave.
To overcome this challenge Bluetooth uses fast frequency hopping scheme and therefore uses shorter packets than other standards in the ISM band. This scheme will help to make Bluetooth communication more powerful and more secure.
Frequency hopping
Frequency hopping is basically jumping from frequency to radio frequency in the ISM band. After the Bluetooth device to send or receive a packet, and the device (or devices) is communicating with the hops to another frequency for the next packet. This system offers three advantages:
1. Bluetooth allows devices to use the entire available ISM band, while never transmitting from the fixed frequency for more than a short period of time. This helps ensure that the Bluetooth ISM in accordance with the restrictions on the number of transmission per frequency.
2. Make sure that any disruption will not last long. All packets that do not arrive safely at its destination can be sent to the next frequency.
3. Provide a basic level of security because it is very difficult for an eavesdropping device to the frequency of Bluetooth devices will predict subsequent use.
The device is connected, but must agree on a schedule that will be used next. Specification in Bluetooth ensures this in two ways. First he defines a kind of master and slave relationship between Bluetooth devices. Moreover, it established an algorithm that a specific device information to calculate the frequency hop sequence of these applications.
A Bluetooth device that works in master mode can communicate with up to seven devices arranged in a fashion slave. For each slave, the master Bluetooth device transmits a unique address and the value of their own internal clock. The information is then sent to the frequency hop sequence used in this calculation.
Since the master device and each slave device using the same algorithm with the same initial input, the device connected will always meet at the next frequency that they had agreed.
As a substitute for cable technology, it is no wonder that Bluetooth devices are usually powered by batteries, such as wireless mice and battery-powered mobile phone. To conserve power, most devices operate at low power. This allows Bluetooth devices a range of about 50-10 meters. This range is far enough for wireless communication, but close enough to avoid drawing too much power from the electrical outlet device.
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