L6: WPAN-- Bluetooth

1. L6: WPAN-- Bluetooth • Characteristics • Piconet and Scatternet • MAC mechanism • Connection Management

2. Wireless PAN • WPAN • Wireless Personal Area Network • WPAN vs. WLAN • smaller coverage area (~10 m) • lower data rate (~1 Mbps) • ad hoc only topology • lower power consumption (~1mW)

3. Bluetooth • Short range (10 m) • Low power consumption • 2.4 GHz (Unlicensed ISM Band) • Advantage: worldwide availability • Disadvantage: interfere with IEEE 802.11b products • Voice and data transmission, totally 1 Mbps • Low cost • less than US$5 for a Bluetooth chip

4. Bluetooth • Universal radio interface for ad-hoc wireless connectivity • Voice and data transmission, approx. 1 Mbit/s gross data rate One of the first modules (Ericsson).

5. Application Scenarios Cable Replacement Ad Hoc Personal Network (e.g. connect multiple users in a conference room) Integrated Access Point: connect wireless devices to both voice and data backbone infrastructure.

6. History

7. Why is it called “Bluetooth”? • Harald Blaatand • translated in English means “Bluetooth” • A.D. 940-981 • a king of Denmark and Norway • Brought Christianity to Scandinavians to harmonize their beliefs with the rest of Europe. • symbolize the need for harmony among manufacturers of WPANs around the world.

8. History and hi-tech… 1999: Ericsson mobile communications.

9. …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…)

10. Characteristics • 2.4 GHz ISM (industry-scientific-medical) band, 79 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

11. Piconet • Before a connection is created, a device is in “standby” mode, periodically listen for messages every 1.28 sec. • Devices are connected in an ad hoc fashion, called piconet. • One unit acts as master and the others as slaves for the lifetime of the piconet. Each piconet has 1 master and up to 7 slaves. • Master determines hopping pattern, slaves have to synchronize. P S S M P SB S P SB M = Master S = Slave P = Parked SB = Standby

12. Piconet (con’t) • Each piconet has a unique hopping pattern • Participation in a piconet = synchronization to hopping sequence • Other devices within the piconet will be considered“parked”. • Parked devices, as well as the slaves, are synchronized to the master. P S S M P SB S P SB M = Master S = Slave P = Parked SB = Standby

13. 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) • Parked Member Address (PMA, 8 bit)    P  S SB  SB  S   SB   M P SB SB    SB  S   SB SB  P  SB SB SB

14. Scatternet • Linking of multiple co-located piconets through the sharing of common master or slave devices • A device can be slave in one piconet and master of another • No device can be master of two piconets Piconets (each with a capacity of < 1 Mbit/s) P S S S M M P P SB M=Master S=Slave P=Parked SB=Standby S P SB SB S

15. Bluetooth protocol stack audio apps. NW apps. vCal/vCard telephony apps. mgmnt. apps. AT modem commands TCP/UDP OBEX 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.

16. Bluetooth protocols • "Bluetooth is defined as a layer protocol architecture consisting of core protocols, cable replacement protocols, telephony control protocols, and adopted protocols”. • Mandatory protocols for all Bluetooth stacks are: LMP, L2CAP and SDP. Additionally, these protocols are almost universally supported: HCI and RFCOMM.

17. Core Protocols • Radio • Physical layer aspects, e.g. frequency hopping • Baseband • Link control at bit and packet level, e.g. coding, encryption • Provides two types of physical links, SCO and ACL, to be described later • Link Manager Protocol (LMP) • Link setup and ongoing link management. Used for control of the radio link between two devices. Implemented on the controller. • Logical Link Control and Adaptation Protocol (L2CAP – see next) • Provide services to upper layer protocols (e.g. packet segmentation and assembly). • Service Discovery Protocol (SDP) • Discover available services and connects two or more devices to support a service such as faxing, printing, etc.

18. L2CAP • Multiplex multiple logical connections between two devices using different higher level protocols. Provides segmentation and reassembly of on-air packets. • Basic mode, • L2CAP provides payload up to 64kB, with 672 bytes as the default MTU, and 48 bytes as the minimum mandatory supported MTU. • Retransmission & Flow Control modes • L2CAP can be configured for reliable or isochronous data per channel by performing retransmissions and CRC checks. • Reliability in any of these modes is optionally

19. Service Discovery Protocol (SDP) • Service Discovery Protocol (SDP) allows a device to discover services supported by other devices, and their associated parameters. • E.g. when connecting a mobile phone to a Bluetooth headset, SDP will be used for determining which Bluetooth profiles are supported by the headset (Headset Profile, Hands Free Profile, Advanced Audio Distribution Profile (A2DP) etc.) and the protocol multiplexer settings needed to connect to each of them. Each service is identified by a Universally Unique Identifier (UUID), with official services (Bluetooth profiles) assigned a short form UUID (16 bits rather than the full 128)

20. Bluetooth – other protocols • HCI (Host/Controller Interface) • Standardised communication between the host stack (e.g., a PC or mobile phone OS) and the controller (the Bluetooth IC). This standard allows the host stack or controller IC to be swapped with minimal adaptation. • There are several HCI transport layer standards, each using a different hardware interface to transfer the same command, event and data packets. The most commonly used are USB (in PCs) and UART (in mobile phones and PDAs). • In Bluetooth devices with simple functionality (e.g., headsets) the host stack and controller can be implemented on the same microprocessor. In this case the HCI is optional, although often implemented as an internal software interface.

21. Bluetooth – other protocols • RFCOMM (Serial Port Emulation) for Radio frequency communications • Provides for binary data transport and emulates EIA-232 (formerly RS-232) control signals over the Bluetooth baseband layer. • Provides a simple reliable data stream to the user, similar to TCP. • Used directly by many telephony related profiles as a carrier for AT commands, as well as being a transport layer for OBEX (OBject Exchange) over Bluetooth. • Widespread support and publicly available API on most operating systems.

22. Bluetooth protocol -- HCI (Host/Controller Interface) • BNEP (Bluetooth Network Encapsulation Protocol) • BNEP is used for transferring another protocol stack's data via an L2CAP channel. Its main purpose is the transmission of IP packets in the Personal Area Networking Profile. BNEP performs a similar function to SNAP in Wireless LAN. • AVCTP (Audio/Video Control Transport Protocol) • Used by the remote control profile to transfer AV/C commands over an L2CAP channel. The music control buttons on a stereo headset use this protocol to control the music player. • AVDTP (Audio/Video Distribution Transport Protocol) • Used by the advanced audio distribution profile to stream music to stereo headsets over an L2CAP channel. Intended to be used by video distribution profile.

23. Other Bluetooth protocols -- Telephony control protocol • Telephony control protocol-binary (TCS BIN) is the bit-oriented protocol that defines the call control signaling for the establishment of voice and data calls between Bluetooth devices. Additionally, "TCS BIN defines mobility management procedures for handling groups of Bluetooth TCS devices." • TCS-BIN is only used by the cordless telephony profile, which failed to attract implementers. As such it is only of historical interest.

24. Other Bluetooth protocols : Adopted protocol • Adopted protocols are defined by other standards-making organizations and incorporated into Bluetooth’s protocol stack, allowing Bluetooth to create protocols only when necessary. The adopted protocols include: • Point-to-Point Protocol (PPP) • Internet standard protocol for transporting IP datagrams over a point-to-point link. • TCP/IP/UDP • Foundation Protocols for TCP/IP protocol suite • Object Exchange Protocol (OBEX) • Session-layer protocol for the exchange of objects, providing a model for object and operation representation • Wireless Application Environment/Wireless Application Protocol (WAE/WAP) • WAE specifies an application framework for wireless devices and WAP is an open standard to provide mobile users access to telephony and information services.

25. Three Classes of Transmitters • Class 1 • Output power: 1 mW – 100 mW • Range: up to 100 m • Power control is mandatory • Class 2 • Output power: 0.25 mW – 2.4 mW • Range: 10 m • Power control is optional • Class 3 • Output power: 1 mW • Range: 0.1 – 10 m

26. MAC mechanism • FH-CDMA/TDD • Frequency Hopping CDMA • Time Division Duplex • Polling • Master polls the slaves for transmission • No collision/interference within a piconet

27. Frequency Hopping • Totally, 79 frequencies for hopping • Each of bandwidth 1 MHz • 2402 + k MHz, k = 0, 1, ..., 78 • ALL devices on a piconet follow the SAME frequency hopping sequence. • 1600 hops per second • Therefore, each frequency is occupied for a duration of 625 sec., called a slot.

28. Hopping Sequence • Every Bluetooth device has • a unique device ID (48 bits Bluetooth address) • a clock • Master gives its device ID and clock to its slaves • Hopping pattern: determined by device ID • Timing in hopping pattern: determined by clock • All slaves synchronizes to the master

29. Polling for Transmission The MASTER polls the SLAVES according to certain rules - e.g. round robin P S S M P • Time Division Duplex (TDD) • When a master is transmitting, the slave is receiving and cannot transmit. SB S P SB

30. Baseband link types • Polling-based TDD packet transmission • 625µs slots, master polls slaves • SCO (Synchronous Connection Oriented) – Voice • Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point • ACL (Asynchronous Connectionless) – Data • Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint

31. Alternate Transmission • Master transmits on even numbered slots • Slave transmits on odd numbered slots • A slave can transmit only if the master has just transmitted to this slave f(k): the frequency used in slot k according to the hopping sequence.

32. Frequency selection during data transmission 625µs fk fk+1 fk+2 fk+3 fk+4 fk+5 fk+6 M S M S M S M t fk fk+3 fk+4 fk+5 fk+6 M S M S M t fk fk+1 fk+6 M S M t

33. Baseband Packet Format Synchronization, paging and inquiry Identify packet type and carry control information Carry information bits The header field has 18 bits that are repeated 3 times for error correction. 72 54 0-2745 bits access code packet header payload 4 64 4 3 4 1 1 1 8 bits preamble sync. (trailer) AM address type flow ARQN SEQN HEC Active Member Address: Up to 7 active slaves; 000 reserved for broadcast Parity Check for the header Packet Types Status Reports

34. Baseband data rates/rules Payload User Symmetric Asymmetric Max. Rate Header Payload max. Rate [kbit/s] Type [byte] [byte] FEC CRC [kbit/s] Forward Reverse DM1 1 0-17 2/3 yes 108.8 108.8 108.8 DH1 1 0-27 no yes 172.8 172.8 172.8 DM3 2 0-121 2/3 yes 258.1 387.2 54.4 DH3 2 0-183 no yes 390.4 585.6 86.4 DM5 2 0-224 2/3 yes 286.7 477.8 36.3 DH5 2 0-339 no yes 433.9 723.2 57.6 AUX1 1 0-29 no no 185.6 185.6 185.6 HV1 na 10 1/3 no 64.0 HV2 na 20 2/3 no 64.0 HV3 na 30 no no 64.0 DV1 D 10+(0-9) D 2/3 D yes D 64.0+57.6 D ACL 1 slot 3 slot 5 slot SCO Data Medium/High rate, High-quality Voice, Data and Voice

35. Physical Links • Two types of links can be established between a master and a slave. • Synchronous Connection Oriented (SCO) • For delay-sensitive traffic, e.g. voice • Slots are reserved at regular intervals • Basic unit of reservation is two consecutive slots (one in each direction). • Asynchronous ConnectionLess (ACL) • For best-effort traffic, e.g. data • Use variable packet size (1,3,5 slots) to support asymmetric bandwidth

36. Packet Types • Control packets • Four different types • SCO • Three different types • 64 kbps voice with different error protection • ACL • Six different types • Different error protection and different data rates • Integrated • Carries both voice and data

37. SCO payload types payload (30) HV1 audio (10) FEC (20) HV2 audio (20) FEC (10) HV3 audio (30) DV audio (10) header (1) payload (0-9) 2/3 FEC CRC (2) (bytes)

38. SCO Packet Frame Formats No. of bits High-quality Voice Three different types Forward Error Correction

39. Example SCO ACL SCO ACL SCO ACL SCO ACL MASTER f14 f0 f6 f12 f18 f8 f4 f20 SLAVE 1 f1 f7 f13 f19 f9 SLAVE 2 f17 f5 f21 A multislot packet is transmitted using the same frequency until the entire packet has been sent. In the next slot after the multislot packet, the frequency is chosen according to the original hopping sequence. Therefore, two or four hop frequencies have been skipped.

40. Robustness • Slow frequency hopping with hopping patterns determined by a master • Protection from interference on certain frequencies • Separation from other piconets (FH-CDMA) • Retransmission • ACL only, very fast • Forward Error Correction • SCO and ACL Error in payload (not transmitted!) NAK ACK A C C F H MASTER SLAVE 1 B D E SLAVE 2 G G

41. ACL Packet Frame Formats (in bit) Data Medium Data High Six different types

42. ACL Payload types (in byte) payload (0-343) header (1/2) payload (0-339) CRC (2) DM1 header (1) payload (0-17) 2/3 FEC CRC (2) DH1 header (1) payload (0-27) CRC (2) (bytes) DM3 header (2) payload (0-121) 2/3 FEC CRC (2) DH3 header (2) payload (0-183) CRC (2) DM5 header (2) payload (0-224) 2/3 FEC CRC (2) DH5 header (2) payload (0-339) CRC (2) AUX1 header (1) payload (0-29)

43. Data Rate • DH1 – data high rate – 1 slot/pkt + 1 byte header • DM1 – data medium rate – 1 slot/pkt + 1 byte header • DH3 – data high rate – 3 slot/pkt + 2 byte header • DM3 – data medium rate – 3 slot/pkt + 2 byte header • DH5 – data high rate – 5 slot/pkt+ 2 byte header • DM5 – data medium rate – 5 slot/pkt + 2 byte header

44. Example: Data Rate of DH1 • Suppose that there is 1 master and 1 slave. What is the data rate of DH1 packets in each direction? • Solution: • 216 bits per slot • 800 slots per second (every other slot) in each direction • Data rate = 216 (bits/slot) × 800 (slots/sec) = 172.8 Kbps

45. ACL Packet Types and Associated Data Rates

46. How to calculate the rate? • DM3 – 3 slot/pkt + 2 byte header; Symmetric – Each direction use 3 slot, thus, 800/3(slots/s)*968 bits = 258133 bits/s • DH5 – Symmetric – Each direction use 5 slot, thus, 800/5(slots/s)*2712 bits = 433920 bits/s • DM3 – Asymmetric – One direction use 3 slot and another direction uses 1 slot (ack), thus, 1600/4(slots/s)*968 bits = 387200 bits/s

47. Connection Management

48. States of a Bluetooth device standby Unconnected inquiry page Connecting transmit AMA connected AMA Active park PMA hold AMA sniff AMA Power saving Standby: do nothing Inquire: search for other devices Page: connect to a specific device Connected: participate in a piconet Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACLs, SCO still possible, possibly participate in another piconet

49. Establishing a Connection • Standby • Devices not connected in a piconet are in standby mode • Inquiry • A device sends an inquiry message to locate other devices within communication range. • That device becomes Master • Timing and ID of other devices are sent to the Master • Those devices become Slaves • Page • The Master sends its timing and ID to the slaves using a page message. • A piconet is established and communication session takes place

50. Power Saving Modes • Hold • No data is transmitted • The device may connect to another piconet • Sniff • The device listens to the piconet at reduced intervals • Park • The device gives up its Active Member address but remains synchronized to the piconet • It does not participate in the traffic but check on broadcast messages.