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