Wireless Personal Area Networks (WPAN) Part-2: IEEE Bluetooth IT351: Mobile & Wireless Computing Objectives: – To introduce Ad Hoc networking and discuss its application domain. –To provide a detailed study of the Bluetooth Wireless Technology including its architecture and protocol.

Outline Motivation History Application and usage scenarios Network architecture –Piconets –Scatternets Protocol stack –Core protocols –Cable replacement and telephony control protocols –Profiles Future developments Wi-Fi vs. Bluetooth

Bluetooth - Motivation A technology that aims at ad-hoc piconets -- LAN with very limited coverage without the need for infrastructure To connect small devices in close proximity (about 10 m) The envisaged gross data rate is 1 Mbits/s Both asynchronous (data) and synchronous (voice) services Transceiver should be very cheap Low power consumption chip Replace IrDA and solve its main problems: –limited range – 2m for built-in interfaces – line of sight –usually limited to two users, only point-to-point connections are supported –no internet working functions –has no MAC –Big advantage: COST

Bluetooth History –1994: Ericsson (Mattison/Haartsen) initiated “MC-link” (multi communicator link) project –Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen [son of Gorm], King of Denmark in the 10 th century –1998: foundation of Bluetooth SIG, –1999: erection of a rune stone at Ercisson/Lund ;-) –2001: first consumer products for mass market, spec. version 1.1 released –2005: 5 million chips/week Special Interest Group –Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba –Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola –> members –Common specification and certification of products Same time, an IEEE study group for a WPAN specifications started IEEE – Requirements fulfilled by Bluetooth (was: )

History and hi-tech… 1999: Ericsson mobile communications AB reste denna sten till minne av Harald Blåtand, som fick ge sitt namn åt en ny teknologi för trådlös, mobil kommunikation.

…and the real rune stone Located in Jelling, Denmark, erected by King Harald “Blåtand” in memory of his parents. The stone has three sides – one side showing a picture of Christ. This could be the “original” colors of the stone. Inscription: “auk tani karthi kristna” (and made the Danes Christians) Inscription: "Harald king executes these sepulchral monuments after Gorm, his father and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity." Btw: Blåtand means “of dark complexion” (not having a blue tooth…)

Bluetooth Was Originally a Cable- Replacement Technology

You arrive at the office … In the Office … While in a meeting, … When inspecting equipment, …

On the road … You arrive at the airport … You enter the airport waiting lounge, … You get on the rent-a- car bus, …

Bluetooth - overview Consortium: Ericsson, Intel, IBM, Nokia, Toshiba… Scenarios: –connection of peripheral devices loudspeaker, joystick, headset –support of ad-hoc networking small devices, low-cost –bridging of networks e.g., GSM via mobile phone - Bluetooth - laptop Simple, cheap, replacement of IrDA, low range, lower data rates, low-power –Worldwide operation: 2.4 GHz – Available globally for unlicensed users –Resistance to jamming and selective frequency fading: FHSS over 79 channels (of 1MHz each), 1600hops/s –Coexistence of multiple piconets: like CDMA –Links: synchronous connections and asynchronous connectionless –Interoperability: protocol stack supporting TCP/IP, OBEX, SDP –Range: 10 meters, can be extended to 100 meters Documentation: over 1000 pages specification:

Bluetooth Universal radio interface for ad-hoc wireless connectivity Interconnecting computer and peripherals, handheld devices, PDAs, cell phones – replacement of IrDA Embedded in other devices, goal: 5€/device (already < 1€) Short range (10 m), low power consumption, license-free 2.45 GHz ISM Voice and data transmission, approx. 1 Mbit/s gross data rate Supports open-ended list of applications –Data, audio, graphics, videos One of the first modules (Ericsson).

Characteristics 2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing –Channel 0: 2402 MHz … channel 78: 2480 MHz –G-FSK modulation, mW transmit power FHSS and TDD –Frequency hopping with 1600 hops/s –Hopping sequence in a pseudo random fashion, determined by a master –Time division duplex for send/receive separation Voice link – SCO (Synchronous Connection Oriented) –FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched Data link – ACL (Asynchronous ConnectionLess) –Asynchronous, fast acknowledge, point-to-multipoint, up to kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched Topology –Overlapping piconets (stars) forming a scatternet

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 Developed in late 90s –V1.2 → 1Mbps –V2.0 → 3Mbps –V3.0 → 24Mbps

Bluetooth Architecture Piconets and Scatternets –Piconet is the basic unit of networking –One master device and seven slaves –Slave can only communicate with its Master –Slave can be master of another piconet This is called a scatternet Piconet 1 Master Piconet 2 Scatternet Slave

Piconets and Scatternets Piconet –Basic unit of Bluetooth networking –Master and one to seven slave devices –Master determines channel and phase Scatternet –Device in one piconet may exist as master or slave in another piconet –Allows many devices to share same area –Makes efficient use of bandwidth

Piconet Collection of Bluetooth devices connected in an ad hoc fashion and synchronizes to a master node One unit acts as master and the others as slaves for the lifetime of the piconet All devices have the same network capabilities The node establishing the piconet automatically becomes the master Master determines hopping pattern, slaves have to synchronize Each piconet has a unique hopping pattern Participation in a piconet = synchronization to hopping sequence Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked) –Parked device is an inactive device (can be reactivated in milliseconds) –Standby device do not participate in piconet If a parked device wants to communicate and there are 7 active slaves, then one of the slaves has to switch to park mode M=Master S=Slave P=Parked SB=Standby M S P SB S S P P

Forming a piconet All devices in a piconet hop together –Master gives slaves its clock and device ID Hopping pattern: determined by device ID (48 bit, unique worldwide) Phase in hopping pattern determined by clock Addressing –Active Member Address (AMA, 3 bit, 8 nodes) for all active nodes –Parked Member Address (PMA, 8 bit, 256) for parked nodes –SB devices do not need address SB M S P S S P P                  

Scatternet Linking of multiple co-located piconets through the sharing of common master or slave devices –Devices can be slave in one piconet and master of another –Master-slave can switch roles Communication between piconets –Devices jumping back and forth between the piconets Overlapping piconets experience collisions. How? Hopping with same frequency at one time slot M=Master S=Slave P=Parked SB=Standby M S P SB S S P P M S S P Piconets (each with a capacity of 720 kbit/s)

Bluetooth Network Architecture

Piconets & Scatternets M SSSSSSSM/S SSSSSSSS

Bluetooth Standards Details of various layers of Bluetooth protocol architecture Bluetooth v1.1 ratified in 2002 as IEEE Bluetooth v2.0 goes to up to 3Mbps – 2004 Bluetooth v2.1 adopted July 2007 Wibree, an ultra low power Bluetooth technology adopted as part of the Bluetooth specification – Bluetooth v3.0 adopted April up to 24Mbps

Protocol Architecture Bluetooth is a layered protocol architecture –Core protocols –Cable replacement and telephony control protocols –Adopted protocols (using profiles) Core protocols –Radio –Baseband –Link manager protocol (LMP) –Logical link control and adaptation protocol (L2CAP) –Service discovery protocol (SDP)

Protocol Architecture Cable replacement protocol –RFCOMM Telephony control protocol –Telephony control specification – binary (TCS BIN) Adopted protocols –PPP –TCP/UDP/IP –WAP Profiles Specifications of how to support applications Specify which parts of the total specification are mandatory, optional, or not applicable No point having all functionality in all chips Helps interoperability between vendors

Bluetooth protocol stack Radio Baseband Link Manager Control Host Controller Interface Logical Link Control and Adaptation Protocol (L2CAP) Audio TCS BINSDP OBEX vCal/vCard IP NW apps. TCP/UDP BNEP RFCOMM (serial line interface) AT modem commands telephony apps.audio apps.mgmnt. apps. AT: attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification – binary BNEP: Bluetooth network encapsulation protocol SDP: service discovery protocol RFCOMM: radio frequency comm. PPP

Establishing a connection: BT – States Standby: unconnected but awake Inquiry: listening or wanting to connect Page: setting up connections Active: Connected or Transmitting

Inquiry Procedure Goal: aims at discovering other neighboring devices –Potential master or inquiring node identifies devices in range that wish to participate –Transmits ID packet with inquiry access code –Sends an inquiry message (packet with only the access code). This message is sent over a subset of all possible frequencies. –Listen for inquiry response –Occurs in Inquiry state Device receives inquiry: t o be discovered node: –Enters an inquiry_scan mode –When hearing the inquiry_message enter an inquiry_response mode: send a Frequency Hop Sync (FHS) packet with address and timing information –Moves to page scan state After discovering the neighbors and collecting information on their address and clock, the inquiring node can start a page routine to setup a piconet

Page Procedure Goal: e.g., setup a piconet after an inquiry Paging node (master): –uses devices address to calculate a page frequency- hopping sequence –Sends a page message (i.e., packet with only Device Access Code (DAC) of paged node) –Repeated until a response is received –When a response is received send a FHS message to allow the paged node to synchronize Paged node (slave): –Listens on its hopping sequence –When receiving a page message, send a page_response and wait for the FHS of the pager –When receiving, slave moves to connection state

Example (without security) A Person in a hotel wants to access her over a BT enabled PDA. The device will automatically carry out the following steps 1.Inquiry The device initiate an inquiry to find out access points (Masters) within its range All nearby access points respond with their addresses The device picks one out of the responding devices 2.Paging The device will invoke paging procedure It synchronizes with the access point in terms of clock, phase and frequency hop 3.Link establishment The LMP will establish a link with the master ACL link will be used ( )

Example (cont.) 4.Service discovery The LMP will use SDP to discover what services are available at the master ( access to the host possible?) Assume the service is available, else it would stop Other available services will be presented to the user 5.L2CAP channel With information obtained from SDP, an L2CAP channel will be created to the master 6.RFCOMM channel An RFCOMM channel will be created over The L2CAP channel. This emulates serial port so applications can run without modifications 7. Network Protocols The network protocols like TCP/IP can now send and receive data over the link

Wi-Fi v Bluetooth Wi-Fi – LAN (local area) – Medium range – 54Mbps (a/g) – Infrastructure LAN extension – Simple connection – Secure authentication via WPA2 (considered safe) – Layer 1+2 only Bluetooth – PAN (personal area) – Short range – 1-3Mbs (v1+2) – Ad Hoc Cable replacement – Complex connection – Secure authentication via SSP (known problems) – Integrates (profiles)

Bluetooth versions Bluetooth 1.1 –also IEEE Standard –initial stable commercial standard Bluetooth 1.2 –also IEEE Standard –eSCO (extended SCO): higher, variable bitrates, retransmission for SCO –AFH (adaptive frequency hopping) to avoid interference Bluetooth EDR (2004, no more IEEE) –EDR (enhanced date rate) of 3.0 Mbit/s for ACL and eSCO –lower power consumption due to shorter duty cycle Bluetooth EDR (2007) –better pairing support, e.g. using NFC –improved security Bluetooth HS (2009) –Bluetooth EDR + IEEE a/g = 54 Mbit/s