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Wireless Technologies

Internet Architecture - The 802.11 Standard - Bluetooth

Origins of the Name

Bluetooth is named after King Blaatand from Denmark. Blaatand roughly translates into Bluetooth. He got this name supposedly because his teeth were a shade of blue from his fondness of bluberries. He united Denmark and Norway. Bluetooth was created in Scandinavia and, therefore, international and the company thought it should be named after a king who united countries.

Specifications for Bluetooth

Bluetooth has an open specification, which means that it is publicly available and royalty free. It is a short-range wireless, which allows for low power consumption. It can transmit both voice and data, which makes it suitable for devices using both. It can be used anywhere in the world because it uses a frequency spectrum that is unlicensed.

The range for Bluetooth is very short at about 10 meters, but can get up to 100 meters. It is ideal for portable personal devices that run on batteries. Bluetooth has a capacity of transmitting 1 Mbps.

Bluetooth is good with devices such as a cordless computer, a headset for phones, a 3-in-1 phone, a file transfer during a conference, or an instant postcard.

Conservation of Power

Bluetooth uses master and slave roles in order to keep lower power. A piconet consists of one master, seven active slaves, and up to 255 parked slaves. The master governs synchronization of communications between the devices and determines the frequency hopping pattern. The slaves can be in four different modes: active, sniff, hold, and parked.

1. Active slaves:

Active slaves are always listening for the mater to transmit packets and consumes the most amount of power.

2. Sniff:

Sniff means that the slave is active periodically. An interval is chosen between the slave and the master. The slave turns on at the beginning of the interval and if it receives a packet from the master, then it stays awake to continue receiving packets. Otherwise, it will sleep again until the next interval.

3. Hold:

Hold is when the slave is put “on hold” for a given amount of time. While it is not active, it either sleeps or establishes links to other devices. The amount of power consumed for hold is determined by what it does while it is not active. Sniff and hold consume less power than the active slaves because they are not always on.

4. Parked slaves:

Parked slaves maintain synchronization with the master, but aren't active.

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