- operates in the unlicensed ISM band at 2.4 GHz
- employs a frequency hopping transceiver to combat interference and fading and provides many FHSS carriers.
- uses a shaped, binary frequency modulation to minimize transceiver complexity.
- Basic Rate: supporting 1 Mb/s bit rate.
- Enhanced Data Rate: supporting a gross air bit rate of 2 or 3Mb/s.
- physical radio channel is shared by a group of devices.
- those devices are synchronized by a common clock and frequency hopping pattern.
- the device provide the synchronization reference is called as master, others are called as slaves.
- a group of devices formed a piconet.
Frequency Hopping Pattern
## Physical Channel
* The physical channel is sub-divided into time units known as slots.
* Data in the packets are transmitted in those slots.
* Using TDD, bluetooth technology allow the effect of full duplex transmission.
- a specific frequency hopping pattern is algorithmically determined by certain fields in the Bluetooth address and the clock of the master.
- The basic hopping pattern is a pseudo-random ordering of the 79 frequencies, separated by 1 MHz, in the ISM band.
- The Hopping pattern can be adapted on per-salve device basis to exclude some frequencies.
Hierachy of Channels and Links
- above the physical channel are the layering of links , channels and associated control protocols.
- From physical channel upward are:
- physical channel
- physical link
- logical transport
- logical link
- L2CAP channel
- Typically, a physical link is formed between a master device and slave devices.
- Inquiry scan & Page scan don't need an associated physical link.
- Physical link is generally bi-directional transmition except in the case of a Connectionless Slave Broadcast physical link.
## Physical Link
* used as a transport for one or more logical links.
* Logical links support unicast synchronous, asynchronous and isochronous traffic, and broadcast traffic.
* Traffic on logical links is multiplexed onto the physical link by ocuppying slots.
- There is a physical link between each slave and master.
- NO direct physical links are formed between slaves.
Link Manager Protocol(LMP)
## Link Manager
* The Link Manager function uses LMP to control the operation of devices in the piconet.
* provide services to manage the lower architectural layers(radio layer and baseband layer).
- carried over logical links.
- ACL logical transport are the default asynchronous connection-oriented logical transport used to transport LMP protocol signaling.
- whenever a device joins a piconet, a primary ACL logical transport is created.
- Connectionless Slave Broadcast devices are exceptional, they are purely listening to Connectionless Slave Broadcast packets. a Connectionless Slave Broadcast logical transport is created.
- For all devices, additional logical transports may be created to transport synchronous data streams when required.
- provides a channel-based abstraction to applications and services.
- applicaiton segmentation and reassembly of application data.
- multiplexing and de-multiplexing of multiple channels over a shared logical link.
- has a protocol control channel carried over the default ACL logical transport.
- any logical link supporting L2CAP protocol can carry L2CAP encapsulated data.