IT351: Mobile & Wireless Computing Wireless Personal Area Networks (WPAN) Part-2: IEEE802.15 Bluetooth 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 • Packet structure • 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
(was: ) 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 10th century • 1998: foundation of Bluetooth SIG, www.bluetooth.org • 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 • > 10000 members • Common specification and certification of products • Same time, an IEEE study group for a WPAN specifications started IEEE802.15 – Requirements fulfilled by Bluetooth
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. 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." This could be the “original” colors of the stone. Inscription: “auk tani karthi kristna” (and made the Danes Christians) Btw: Blåtand means “of dark complexion” (not having a blue tooth…)
In the Office … You arrive at 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: www.bluetooth.com
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, 1-100 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 433.9 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 Piconet 2 Slave Master Master Scatternet
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 P • 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 S S M P SB S P SB P=Parked SB=Standby M=Master S=Slave
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 P S SB SB S M P SB SB SB SB S SB P SB SB SB SB
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 Piconets (each with a capacity of 720 kbit/s) P S S S P P M M SB S M=Master S=Slave P=Parked SB=Standby P SB SB S
Piconets & Scatternets M S S S S S S S M/S S S S S S S S S
Bluetooth Standards • Details of various layers of Bluetooth protocol architecture • Bluetooth v1.1 ratified in 2002 as IEEE 802.15.1 • 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 – 2007. • Bluetooth v3.0 adopted April 2009. 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 • OBEX • WAP
Bluetooth protocol stack audio apps. NW apps. vCal/vCard telephony apps. mgmnt. apps. TCP/UDP OBEX AT modem commands TCS BIN SDP Control IP BNEP PPP Audio RFCOMM (serial line interface) Logical Link Control and Adaptation Protocol (L2CAP) Host Controller Interface Link Manager Baseband Radio 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.
Protocol stack (core protocols) • Bluetooth Radio • 2.4 GHZ frequency band • Defines modulation (FSK), frequency, power • Baseband • FHSS with 1600 hops/s, 79 channels, FSK • FHSS provides resistance to interference and multipath effects • CDMA between different piconets (hopping sequence from the node MAC address) • Access in piconet: polling-based FH-TDD
Protocol stack (core protocols) • Two different kinds of physical links: • Synchronous Connection oriented (SCO) – for audio • Asynchronous ConnectionLess (ACL) – transmission of data • Audio: interfaces directly with the baseband. Each voice connection is over a 64Kbps SCO link.
Protocol stack (core protocols) • Link Manager • Responsible for link set-up between BT devices • Set-up security functions like authentication and encryption • Synchronization between device clocks • Control and negotiate the baseband packet size • Control the power mode and duty cycle of BT radio and the connection states of BT nodes in a piconet • Mode management: • switch master/slave role • change hold, sniff, park modes (low power mode)
Protocol stack (core protocols) L2CAP: Logical Link Control and Adaptation Protocol • Adapts to upper layer protocols • Protocol multiplexing • RFCOMM, SDP, telephony control • Segmentation and reassembly • QoS flow specification • Group abstraction • Create/close group, add/remove member • Provides two alternative services to upper-layer protocols • Connectionless service • Connection-oriented service: A QoS flow specification is assigned in each direction • Exchange of signaling messages to establish and configure connection parameters • Service Discovery Protocol • locates the characteristics/profile of devices in the local area
Application TCP/UDP OBEX AT Commands PPP RFCOMM TCS SDP L2CAP HCI Audio Link Manager (LMP) Baseband Bluetooth Radio Protocol Stack • Telephony Control Specification (TCS) • defines the call control signaling for the establishment of speech and data calls between Bluetooth devices • RFCOMM (cable replacement) • provides emulation of serial links
Bluetooth Adopted Protocols & Profiles • Adopted Protocols • Standards from other bodies that are supported • PPP (Point to Point Protocol) • TCP/UDP/IP • OBEX (OBject EXchange), e.g. vCard • WAP (Wireless Application Protocol) • Usage models and profiles define how these are integrated
Bluetooth Adopted Protocols & Profiles 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 Two main types • Wireless Audio • Cable replacement
Bluetooth Profiles File Transfer OBEX SDP RFCOMM L2CAP
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: to 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
Slave Connection State Modes • Active – participates in piconet • Listens, transmits and receives packets • the device is uniquely identified by a 3bits AM_ADDR and is fully participating • Sniff – only listens on specified slots • Hold – does not support ACL packets • Reduced power status • May still participate in SCO exchanges • Park – does not participate on piconet • Still retained as part of piconet • Release AM_ADDR, but have PM_ADDR • Low Power • Park (PM_Address): still a member of piconet, loses AM_Address • Hold (AM_Address): not active but wants to keep AMA • Sniff (AM_Address): listens to parts of the signals for activity
Example (without security) • A Person in a hotel wants to access her email over a BT enabled PDA. The device will automatically carry out the following steps • 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 • Paging • The device will invoke paging procedure • It synchronizes with the access point in terms of clock, phase and frequency hop • Link establishment • The LMP will establish a link with the master • ACL link will be used (email)
Example (cont.) • Service discovery • The LMP will use SDP to discover what services are available at the master (email access to the host possible?) • Assume the service is available, else it would stop • Other available services will be presented to the user • L2CAP channel • With information obtained from SDP, an L2CAP channel will be created to the master • RFCOMM channel • An RFCOMM channel will be created over The L2CAP channel. This emulates serial port so applications can run without modifications • Network Protocols • The network protocols like TCP/IP can now send and receive data over the link
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) Wi-Fi v Bluetooth
Bluetooth versions • Bluetooth 1.1 • also IEEE Standard 802.15.1-2002 • initial stable commercial standard • Bluetooth 1.2 • also IEEE Standard 802.15.1-2005 • eSCO (extended SCO): higher, variable bitrates, retransmission for SCO • AFH (adaptive frequency hopping) to avoid interference • Bluetooth 2.0 + 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 2.1 + EDR (2007) • better pairing support, e.g. using NFC • improved security • Bluetooth 3.0 + HS (2009) • Bluetooth 2.1 + EDR + IEEE 802.11a/g = 54 Mbit/s