CPET 260 Bluetooth

What is Bluetooth? Not IEEE (Wi-Fi) or HomeRF Originally designed to replace wires Short-range, lower-power wireless technology A 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 Ericsson See A royalty free, open specification to create a wide range of products that can communicate without wires.

SIG Based on a set of standards Called profiles Easy interconnect Enable exchange of voice, and data

Overview of Bluetooth Versions 1.0, 1.1 and now 2.0 Frequency Hopping Spread Spectrum (FHSS) 1,600 hops per second (HomeRF ) 79 frequencies separated by 1 MHz 2.4 GHz band 712 Kbps Kbps

Overview Motorola’s Piano Allows 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  s Single master and up to seven slaves All devices on ‘piconet’ use the same frequency hopping pattern. Piconets can be in range of one another When device joins a piconet, a Frequency Hop Synchronization packet is sent by master

Overview Communications can take place in both directions – 1 time slots Master starts on even numbered time slot Slave starts on odd numbered time slots Up 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 slave No longer actively exchanges data with other nodes. Sniff – device in listen Park – low-power mode no longer has a MAC address Listens for broadcast messages Resynchronizes clock w/ master

SCO and ACL links SCO – a Synchronous Connection Oriented link Established between Master and a particular slave in the network Suitable 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 slaves Can 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 bits Used for synchronization Three different access codes used CAC – Channel Access Code Identifies a particular piconet DAC – Device Access Code Used during signaling – ie. paging IAC – Inquiry Access Code GIAC – General Inquiry Access Code DIAC – Dedicated Inquiry Access Code

Bluetooth Packets Header – fixed at 54 bits AM_ADDR – active Member address Type – 4 bits = 16 packet types Flow – 1 bit for flow control ARQN – 1 bit Acknowledge SEQN – 1 bit sequence toggle HEC – Header Error Check 8 bit

Bluetooth Packets The type field varies, but 5 common types include ID Packet Null Packet Poll Packet FHS packet DM1 packet

Bluetooth Packets Payload 0-2,745 bits Contains the actual data portion of the packet

Bluetooth profiles A set of specifications for how end-user functionality should be implemented The Serial Port Profile Group Used the RFCOMM for serial port emulation The Generic Object Exchange Profile Group The 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 Controller LMP – Link Manager Protocol L2CAP – Logical Link Control and Adaptation Protocol TCST – Telephony Control Protocol RFCOMM SDP – 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 Profile The Cordless Telephony Profile The Intercom Profile The Serial Port Profile The Headset Profile The Dial-up networking profile

Other Bluetooth profiles Fax LAN Access Generic Object Exchange Object Push File Transfer Synchronization