CPET 260 Bluetooth. What is Bluetooth? Not IEEE802.11 (Wi-Fi) or HomeRF Originally designed to...
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Transcript of CPET 260 Bluetooth. What is Bluetooth? Not IEEE802.11 (Wi-Fi) or HomeRF Originally designed to...
CPET 260
Bluetooth
What is Bluetooth?
Not IEEE802.11 (Wi-Fi) or HomeRFOriginally designed to replace wires
Short-range, lower-power wireless technologyA means to replace cables
Keyboard, mouse, printer, etc.
What is Bluetooth?
A method to allow data communications between diverse devices
I.e. computers, mobile phones, network appliances, handheld devices, digital cameras, etc.
Bluetooth Special Interest Group (SIG)
Originally developed by Swedish Company EricssonSee http://www.bluetooth.comA royalty free, open specification to create a wide range of products that can communicate without wires.
SIG
Based on a set of standardsCalled profilesEasy interconnectEnable exchange of voice, and data
Overview of Bluetooth
Versions 1.0, 1.1 and now 2.0Frequency Hopping Spread Spectrum (FHSS)
1,600 hops per second (HomeRF 50-100)79 frequencies separated by 1 MHz2.4 GHz bandAsynchronous @ 712 KbpsSynchronous @ 432.6 Kbps
Overview
Motorola’s PianoAllows formation of small ad hoc networks – Personal Area Networks (PANs)Up to 10 meters
Digital Enhanced Cordless Telecommunications (DECT)
Voice and telephony
Overview
Object Exchange Protocol (OBEX)Borrowed from IrDa (Infrared Data Association) Allows for data exchanges like synchronizing address books between Bluetooth enabled PDA and a PC
Overview
Each transmission lasts only 625 sSingle master and up to seven slavesAll devices on ‘piconet’ use the same frequency hopping pattern.
Piconets can be in range of one anotherWhen device joins a piconet, a Frequency Hop Synchronization packet is sent by master
Overview
Communications can take place in both directions
0-227 – 1 time slotsMaster starts on even numbered time slotSlave starts on odd numbered time slotsUp to 5 consecutive time slots can be used.
Piconets
Formed when to or more devices discover each other
Scatternets
Formed when a master of one piconet is a slave of a second piconet.
Modes
Hold – power saving mode for slaveNo longer actively exchanges data with other nodes.
Sniff – device in listen Park – low-power mode no longer has a MAC address
Listens for broadcast messagesResynchronizes clock w/ master
SCO and ACL links
SCO – a Synchronous Connection Oriented link
Established between Master and a particular slave in the networkSuitable for voice since time slots are reserved
SCO and ACL links
ACL – Asynchronous Connection-less link
Packet switched connections between master and one or more slavesCan use any time slots not reserved by SCO links.Only one ACL link can exist at any one time between master and a part. slave
Bluetooth Packets
Access Code – 68 or 72 bitsUsed for synchronizationThree different access codes used
CAC – Channel Access CodeIdentifies a particular piconet
DAC – Device Access CodeUsed during signaling – ie. paging
IAC – Inquiry Access CodeGIAC – General Inquiry Access CodeDIAC – Dedicated Inquiry Access Code
Bluetooth Packets
Header – fixed at 54 bitsAM_ADDR – active Member addressType – 4 bits = 16 packet typesFlow – 1 bit for flow controlARQN – 1 bit Acknowledge SEQN – 1 bit sequence toggleHEC – Header Error Check 8 bit
Bluetooth Packets
The type field varies, but 5 common types include
ID Packet Null PacketPoll PacketFHS packetDM1 packet
Bluetooth Packets
Payload 0-2,745 bitsContains the actual data portion of the packet
Bluetooth profiles
A set of specifications for how end-user functionality should be implementedThe Serial Port Profile Group
Used the RFCOMM for serial port emulation
The Generic Object Exchange Profile GroupThe OBEX protocol is used by all profiles in this group
The Telephony Control Protocol Specification Group
For profiles for telephone & intercom functions
General Access Profile
Protocols used to establish and maintain links
LC – Link ControllerLMP – Link Manager ProtocolL2CAP – Logical Link Control and Adaptation ProtocolTCST – Telephony Control ProtocolRFCOMMSDP – Service Discovery Protocol
Security
Security Mode 1 (non-secure)Cannot initiate any security mechanisms
Security Mode 2 (service level enforced security)
Initiates after channel-established
Security Mode 3 (link-level …)Initiates before LMP
Profiles
The Service Discovery Application ProfileThe Cordless Telephony ProfileThe Intercom ProfileThe Serial Port ProfileThe Headset ProfileThe Dial-up networking profile
Other Bluetooth profiles
FaxLAN AccessGeneric Object ExchangeObject PushFile TransferSynchronization