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Wireless networks - Lecture 39: Bluetooth/Wireless personal area networks (WPAN). The main topics covered in this chapter include: bluetooth introduction; technical features; access technique; bluetooth topology/scenario; specifications; architecture; core protocols; packet format; link connections;...
Wireless Networks Lecture 39 Bluetooth/Wireless Personal Area Networks (WPAN) Dr Ghalib A Shah Outlines Bluetooth introduction Technical features Access technique Bluetooth topology/scenario Specifications Architecture Core Protocols Packet format Link connections Last Lecture Security primitives in TinySec Encryption Schemes Keying mechanism WMSN ► ► ► ► ► Architecture Applications Advantages Design Considerations Protocols WSAN ► ► ► ► Motivation WSN vs WSAN Architecture Issues What is Bluetooth? “Bluetooth wireless technology is ► ► ► ► an open specification for a low-cost, low-power, short-range radio technology for ad-hoc wireless communication of voice and data anywhere in the world.” Ultimate Headset Cordless Computer Bluetooth Application Areas Data and voice access points ► Real-time voice and data transmissions Cable replacement ► Eliminates need for numerous cable attachments for connection Ad hoc networking ► Device with Bluetooth radio can establish connection with another when in range Overview of Bluetooth History What is Bluetooth? ► Bluetooth is a short-range wireless communications technology Why this name? ► It was taken from the 10th century Danish King Harald Blatand who unified Denmark and Norway When does it appear? ► 1994 – Ericsson study on a wireless technology to link mobile phones & accessories ► companies joined to form the Bluetooth Special Interest Group (SIG) in 1998 ► First specification released in J uly 1999 Technical features Conne ction Type Spread Spectrum (Frequency Hopping) & Time Division Duplex (1600 hops/sec) S pe ctrum 2.4 GHz ISM Open Band (79 MHz of spectrum =79 channels) Modulation Gaussian Frequency Shift Keying Trans m is s ion Powe r mw – 100 mw Data R ate Mbps R ange 30 ft S upporte d S tations devices Data S e curity –Authe ntication Ke y 128 bit key Data S e curity –Encryption Ke y 8-128 bits (configurable) Module s iz e x mm Time-Division Duplex Scheme Channel is divided into consecutive slots (each 625 s) One packet can be transmitted per slot Subsequent slots are alternatively used for transmitting and receiving ► Strict alternation of slots between the master and the slaves ► Master can send packets to a slave only in EVEN slots ► Slave can send packets to the master only in the ODD slots 10 Bluetooth protocols RFCOMM (based on GSM TS07.10) ► emulates a serial-port to support a large base of legacy (serialport-based) applications ► allows multiple “ports” over a single physical channel between two devices Telephony Control Protocol Spec (TCS) ► call control (setup & release) ► group management for gateway serving multiple devices Legacy protocol reuse ► reuse existing protocols, e.g., IrDA’s OBEX, or WAP for interacting with applications on phones 20 Baseband Addressing ► Blue to o th de vic e addre s s (BD_ADDR) – 48 bit IEEE MAC address ► Ac tive Me mbe r addre s s (AM_ADDR) – bits active slave address – all zero broadcast address ► Parke d Me mbe r addre s s (PM_ADDR) – bit parked slave address This MAC address is split into three parts ► The No ns ig nific ant Addre s s Part (NAP) – Used for encryption seed ► The Uppe r Addre s s part (UAP) – Used for error correction seed initialization & FH sequence generation ► The Lo we r Addre s s Part (LAP) – Used for FH sequence generation 21 Packet Structure 72 bits Access Code 54 bits Header Voice No CRC FEC (optional) - 2744 bits Payload header Data CRC ARQ FEC (optional) 22 Types of Access Codes Channel access code (CAC) – identifies a piconet Device access code (DAC) – used for paging and subsequent responses Inquiry access code (IAC) – used for inquiry purposes 23 Inquiry Procedure Potential master identifies devices in range that wish to participate ► Transmits ID packet with inquiry access code (IAC) ► Occurs in Inquiry state Device receives inquiry ► Enter Inquiry Response state ► Returns FHS packet with address and timing information ► Moves to page scan state 24 Page Procedure Master uses devices address to calculate a page frequencyhopping sequence Master pages with ID packet and device access code (DAC) of specific slave Slave responds with DAC ID packet Master responds with its FHS packet Slave confirms receipt with DAC ID Slaves moves to Connection state 25 Channel Establishment Seven substates ► Inquiry ► Inquiry s c an ► Inquiry re s po ns e ► Pag e ► Pag e s c an ► Mas te r re s po ns e ► S lave re26 s po ns e Link Manager Protocol 27 Link Manager Protocol The Link Manager carries out link setup, authentication & link configuration Channel Control ► All the wo rk re late d to the c hanne l c o ntro l is manag e d by the mas te r • The master uses polling process for this ► The mas te r is the firs t de vic e whic h s tarts the c o nne c tio n • This roles can change (master-slave role switch) 28 Connection State Ac tive Mo de ► Device participates actively on the transmission channel The master regularly sends a packet to the slaves (polling) to enable the slaves to be able to send a packet to the master and re-synchronise themselves S niff Mo de ► This is a low consumption mode A Bluetooth module in the Sniff mode stays synchronised in the piconet It listens to the piconet at regular intervals (Tsniff) for a short instant on specified slots for its message Ho ld Mo de ► The module remains synchronised This is lower consumption mode than the Sniff mode Only the counter on the Bluetooth chip in hold mode is active At the end of the Hold period, the Bluetooth module returns to the active mode Park Mo de ► A Bluetooth module in this mode is no longer an active member of the piconet However, it remains synchronised with 29 the master and can listen to a broadcast channel (Beacon L2CAP Service provided to the higher layer: ► L2CAP provides connection-oriented and connectionless data services to upper layer protocols ► Protocol multiplexing and demultiplexing capabilities ► Segmentation & reassembly of large packets ► L2CAP permits higher level protocols and applications to transmit and receive L2CAP data packets up to 64 kilobytes in length 30 Links between Master and Slave Synchronous connection oriented (SCO) ► Allocates fixed bandwidth between point-to-point connection of master and slave ► Master maintains link using reserved slots ► Master can support three simultaneous links ► Bandwidth reservation/QoS ► No retransmissions required or done in this mode Asynchronous connectionless (ACL) ► Point-to-multipoint link between master and all slaves ► Only single ACL link can exist ► 1, or slot packets are defined 31 32 Flow Specification Parameters QoS parameter in L2CAP defines traffic flow specification indicating the performance level that the sender will attempt to achieve ► ► ► ► ► ► Service type Token rate (bytes/second) Token bucket size (bytes) Peak bandwidth (bytes/second) Latency (microseconds) Delay variation (microseconds) 33 Summary Bluetooth introduction Technical features Access technique Bluetooth topology/scenario Specifications Architecture Core Protocols Packet format Link connections Next Lecture ► High Speed WPAN 34 ... Issues What is Bluetooth? “Bluetooth wireless technology is ► ► ► ► an open specification for a low-cost, low-power, short-range radio technology for ad-hoc wireless communication of voice and... Scenario Bluetooth will support wireless point-to-point and point-to-multipoint (broadcast) between devices in a piconet Point to Point Link m ► Master - slave relationship ► Bluetooth devices... TDMA FH-TDD-TDMA 13 Ad-hoc Network – the Scatternet Inter-piconet communication Up to 10 piconets in a scatternet Multiple piconets can operate within same physical space This is an ad-hoc,