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By Author: fed pats
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A Bluetooth system comprises a radio unit, a link controller, link manager, and software. The Bluetooth radio interface is based on a nominal antenna power of 0 dBm. The air interface complies with the FCC rules for the ISM band at power levels up to 0 dBm. Spectrum spreading facilitates optional operation at power levels up to 100 mW worldwide. It is accomplished by frequency hopping in 79 hops displaced by 1 MHz, starting at 2.402 GHz and stopping at 2.480 Hz. The bandwidth is controlled by an internal software switch. The maximum frequency hopping rate is 1,600 hops/sec. The baseband describes the specifications of the digital signal processing part of the hardware the Bluetooth link controller, which carries out the baseband protocols and other low-level link routines. A piconet is a group of two to eight devices connected via Bluetooth technology. Before any connections in a piconet are created, all devices are in standby mode. In this mode, an unconnected unit periodically listens for messages every 1.28 seconds. Each time a device wakes up, it listens on a set of 32 hop frequencies defined for that unit. The number of ...
... hop frequencies is 32 for most countries, except Japan, Spain, and France. Any of the devices becomes the master by initiating the connection procedure. If the address is already known, connection is made by a page message. And if the address is unknown, connection is made by an inquiry message followed by a subsequent page message. In the initial page state, the master unit will send a train of identical page messages on 16 different hop frequencies defined for the device to be paged (slave unit). If there is no response, the master transmits a train of messages on the remaining 16 hop frequencies in the wake-up sequence. The maximum delay before the master reaches the slave is twice the wake-up period (2.56 seconds) while the average delay is half the wake-up period (0.64 second). The inquirymessage is used for finding Bluetooth devices, including public printers, fax machines, and similar devices with an unknown address. This message is very similar to the page message, but may require one additional train period to collect all the responses. A power-saving mode can be used for connected units in a piconet if no data needs to be transmitted. The master unit can put slave units into hold mode, where only an internal timer is running. Slave units can also demand to be put into hold mode. Data transfer restarts instantly when units transition out of hold mode. The hold mode is used when connecting several piconets or managing a low-power device such as a temperature sensor. Two more low-power modes are available, the sniff mode and the park mode. In the sniff mode, a slave device listens to the piconet at reduced rate, thus reducing its duty cycle. The sniff interval is programmable and depends on the application. In the park mode, a device is still synchronised to the piconet but does not participate in the traffic.The Bluetooth baseband technology supports two types of link, synchronous connection oriented (SCO) and asynchronous connectionless (ACL). The SCO link is used primarily for voice, and the ACL for packet data…

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