- developed by Ericsson, IBM, Nokia, Intel, and Toshiba in a SIG(Special Interest Group)
- bluetooth utilizes pairing to securely transfer data between mobile devices
Bluetooth Architecture
- piconet a master node with up to seven slave nodes
- multiple piconets can be connected into a scatternet
- up to 255 parked nodes in a set, master set these devices into a low power state to reduce drain on batteries
- at its heart is a TDM system
Bluetooth Applications
- most network protocols provide channels
- Bluetooth provides applications called profiles
- 6 are for audio and video
- human interface profile such as keyboards and mice
- profiles for networking
- personal area network profile, ad hoc network or remote access to another network through an AP
- profiles for higher level info exchange
The Bluetooth Protocol Stack
- loose group into layers does not follow OSI or TCP/IP or the 802 model
- layer description here
- bottom layer is the physical radio layer
- link control is baseband layer similar to MAC sublayer with some physical layer
- two protocols to use link control
- link manager
- establishment channels, pairing and encryption, QoS
- below the line implemented on the chip
- L2CAP(Logical Link Control Adaptation Protocol)
- frames variable length messages and provides reliability as needed
- many protocols use this
- Top layer is where applications are located
- profiles are vertical boxes because they define a slice of the protocol stack
The Bluetooth Radio Layer
- radio layer moves bis from master to slave, operating range 10 meters
- uses adaptive frequency hopping
- 3 forms of modulation used to send bits
- frequency shift keying to send a 1 bit symbol every microsecond
- 2 or 3 bit enhanced rates introduced in 2.0 used for only data portion of frame
The Bluetooth Link Layers
- link control or baseband layer close to MAC
- turns the raw bit stream into frames and defines formats
- piconet defines 625 microsecond time slots
- frames 1, 3, 5 slots long
- overhead of 126 bits for access code and header, settling time of 250-260 microseconds per hop to allow for stability
- 5 slot frame much more efficient than 1 slot frame
- link manager sets up channels called links using pairing procedure, configured with same PIN(Personal Identification Number)
- SCO (Synchronous Connection Oriented)
- used for real time data
- fixed slot in each direction
- ACL (Asynchronous Connectionless Link)
- used for packet switched data
- sent over L2CAP layer
- accepts packets of up to 64KB from upper layers breaks them into frames
- handles multiplexing/demultiplexing of multiple packet sources
- handles error control and retransmission
The Bluetooth Frame Structure
- defines several formats, two types of frames
- Header field
- Adress identifies which of the 8 active devices we can go for
- type identifies ACL, SCO, poll, or null
- Flow assert by slave when buffer is full
- ack is for acknowledgements
- Sequence is to number the frames for transmission, since its stop and wait protocol only need one bit
- 8 bit checksum
- entire header repeated 3 times for error correction, if all 3 same received, if not majority option is accepted
- data field has its own formatting
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