subject: How Bluetooth Really Works [print this page] Bluetooth units will usually operate at 2.four GHZ in the license free, globally obtainable ISM radio band. The benefit to this band includes worldwide availability and compatibility. An obstacle to this however, is that the gadgets should share this band with other RF emitters. This includes car security systems, other wi-fi gadgets, and other noise sources, corresponding to microwaves.
To overcome this problem, Bluetooth employs a fast frequency hopping scheme and therefore uses shorter packets than different requirements within the ISM band. This scheme helps to make Bluetooth communication more strong and extra secure.
Frequency hopping
Frequency hopping is basically leaping from frequency to frequency throughout the ISM radio band. After a bluetooth device sends or receives a packet, it and the device (or gadgets) it's speaking with hop to a different frequency earlier than the following packet issent. This scheme presents three advantages:
1. Allows Bluetooth gadgets to make use of the entire lot of the obtainable ISM band, while by no means transmitting from a fixed frequency for more than a short period of time. This helps insure that Bluetooth conforms to the ISM restrictions on the transmission amount per frequency.
2. Ensures that any interference will not last long. Any packet that does not arrive safely to its destination can be resent to the following frequency.
3. Offers a base stage of safety as it is very laborious for an eavesdropping machine to predict which frequency the Bluetooth devices will use next.
The related gadgets nevertheless, must agree upon the frequency they may 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 makes use of system particular info when calculating the frequency hop sequences.
A Bluetooth system that operates in grasp mode can talk with as a lot as seven units which might be set in slave mode. To each of the slaves, the grasp Bluetooth device will send its own distinctive deal with and the value of its own internal clock. The information despatched is then used to calculate the frequency hop sequences.
As a end result of the master machine and each of the slave units use the identical algorithm with the identical preliminary enter, the linked gadgets will always arrive together at the next frequency that they've agreed upon.
As a substitute for cable technology, it's no wonder that Bluetooth gadgets are normally battery powered, corresponding to wireless mice and battery powered cell phones. To preserve the power, most units function in low power. This helps to offer Bluetooth gadgets a range of around 5 - 10 meters.
This vary is much enough for wireless communication however shut enough to keep away from drawing too much power from the power source of the device.
