Synopsis
Bluetooth takes small-area networking to the next level by removing the need for user
intervention and keeping transmission power extremely low to save battery power.
The big draws of Bluetooth are that it is wireless, inexpensive and automatic. One of
the ways Bluetooth devices avoid interfering with other systems is by sending out very
weak signals of about 1 milliwatt. The low power limits the range of a Bluetooth
device to about 10 meters. Bluetooth can connect up to eight devices simultaneously
(including the master device). With all of those devices in the same 10-meter radius,
you might think they'd interfere with one another, but it's unlikely. Bluetooth uses a
technique called spread-spectrum frequency hopping that makes it rare for more
than one device to be transmitting on the same frequency at the same time. In this
technique, a device will use 79 individual, randomly chosen frequencies within a
designated range, changing from one to another on a regular basis. When Bluetooth-
capable devices come within range of one another, an electronic conversation takes
place to determine whether they have data to share or whether one needs to control
the other. Bluetooth systems create a personal-area network (PAN), or piconet, that
may fill a room or may encompass no more distance than 10 m. Once a piconet is
established, the members randomly hop frequencies in unison so they stay in touch
with one another and avoid other piconets that may be operating in the same room.
docsity.com