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Bluetooth: 1.Applications, Technology

Bluetooth: 1.Applications, Technology. And Performance Dr. Mario Gerla UCLA gerla@cs.ucla.edu MWCN 2002. September 2002. http:// www.cs.ucla.edu/ NRL. Bluetooth. A cable replacement technology 1 Mb/s symbol rate Range 10+ meters Single chip radio + baseband

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Bluetooth: 1.Applications, Technology

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  1. Bluetooth: 1.Applications, Technology And Performance Dr. Mario Gerla UCLA gerla@cs.ucla.edu MWCN 2002 September 2002 http://www.cs.ucla.edu/NRL

  2. Bluetooth • A cable replacement technology • 1 Mb/s symbol rate • Range 10+ meters • Single chip radio + baseband • at low power & low price point ($5) Why not use Wireless LANs? - power - cost

  3. 802.11 • Replacement for Ethernet • Supported data rates • 11, 5.5, 2, 1 Mbps; and recently up to 20+Mbps @ 2.4 GHz • up to 54 Mbps in 5.7 GHz band (802.11 a) • Range • Indoor 20 - 25 meters • Outdoor: 50 – 100 meters • Transmit power up to 100 mW • Cost: • Chipsets $ 35 – 50 • AP $200 - $1000 • PCMCIA cards $100 - $150

  4. Emerging Landscape New developments are blurring the distinction • 802.11b for PDAs • Bluetooth for LAN access • Which option is technically superior ? • What market forces are at play ? • What can be said about the future ? Bluetooth 802.11 Cordless headset LAN AP

  5. Bluetooth working group history • February 1998: The Bluetooth SIG is formed • promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba • May 1998: Public announcement of the Bluetooth SIG • July 1999: 1.0A spec (>1,500 pages) is published • December 1999: ver. 1.0B is released • December 1999: The promoter group increases to 9 • 3Com, Lucent, Microsoft, Motorola • March 2001: ver. 1.1 is released • Aug 2001: There are 2,491+ adopter companies

  6. New Applications

  7. Synchronization User benefits • Automatic synchronization of calendars, address books, business cards • Push button synchronization • Proximity operation

  8. Cordless Headset User benefits • Multiple device access • Cordless phone benefits • Hands free operation Cordless headset

  9. Usage scenarios examples • Data Access Points • Synchronization • Headset • Conference Table • Cordless Computer • Business Card Exchange • Instant Postcard • Computer Speakerphone

  10. Bluetooth Specifications

  11. Bluetooth Specifications IP HCI Data Single chip with RS-232, USB, or PC card interface • A hardware/software/protocol description • An application framework Applications SDP RFCOMM Audio L2CAP Link Manager Baseband RF

  12. Interoperability & Profiles Applications Protocols Profiles • Represents default solution for a usage model • Vertical slice through the protocol stack • Basis for interoperability and logo requirements • Each Bluetooth device supports one or more profiles

  13. Bluetooth Profiles (in version 1.2 release) • Generic Access • Service Discovery • Cordless Telephone • Intercom • Serial Port • Headset • Dial-up Networking • Fax • LAN Access • Generic Object Exchange • Object Push • File Transfer • Synchronization

  14. Technical Overview

  15. Bluetooth Radio Specification Applications IP SDP RFCOMM Control Data Audio L2CAP Link Manager Baseband RF

  16. Unlicensed Radio Spectrum  12cm 5cm 33cm 26 Mhz 83.5 Mhz 125 Mhz 902 Mhz 2.4 Ghz 5.725 Ghz 2.4835 Ghz 5.785 Ghz 928 Mhz 802.11a HyperLan 802.11 Bluetooth Microwave oven cordless phones baby monitors Wireless LANs

  17. Bluetooth radio link • frequency hopping spread spectrum • 2.402 GHz + k MHz, k=0, …, 78 • 1,600 hops per second • GFSK modulation • 1 Mb/s symbol rate • transmit power • 0 dbm (up to 20dbm with power control) 1Mhz . . . 79 1 2 3 83.5 Mhz

  18. Review of basic concepts

  19. Baseband Applications IP IP SDP RFCOMM Control Control Data Data Audio L2CAP Link Manager Baseband RF Applications SDP RFCOMM Audio L2CAP Link Manager Baseband RF

  20. Bluetooth Physical link m s m s s • Piconet • Master can connect to 7 slaves • Each piconet has max capacity =1 Mbps • hopping pattern is determined by the master s • Point to point link • master - slave relationship • radios can function as masters or slaves

  21. Connection Setup • Inquiry - scan protocol • to learn about the clock offset and device address of other nodes in proximity

  22. Inquiry on time axis Inquiry hopping sequence f1 f2 Slave1 Master Slave2

  23. Piconet formation Master Active Slave Parked Slave Standby • Page - scan protocol • to establish links with nodes in proximity

  24. Addressing • Bluetooth device address (BD_ADDR) • 48 bit IEEE MAC address • Active Member address (AM_ADDR) • 3 bits active slave address • all zero broadcast address • Parked Member address (PM_ADDR) • 8 bit parked slave address

  25. Piconet channel FH/TDD f5 f1 f4 f3 f2 f6 m s1 s2 625 sec 1600 hops/sec

  26. Multi slot packets FH/TDD f1 f5 f4 f6 m s1 s2 625 µsec Data rate depends on type of packet

  27. Physical Link Types ACL ACL ACL ACL ACL ACL SCO SCO SCO SCO SCO SCO • Synchronous Connection Oriented (SCO) Link • slot reservation at fixed intervals • Asynchronous Connection-less (ACL) Link • Polling access method m s1 s2

  28. Packet Types Data/voice packets Control packets Voice data ID* Null Poll FHS DM1 HV1 HV2 HV3 DV DH1 DH3 DH5 DM1 DM3 DM5

  29. Packet Format 54 bits 72 bits 0 - 2744 bits Access code Header Payload header Data Voice CRC No CRC No retries ARQ FEC (optional) FEC (optional) 625 µs master slave

  30. Access Code Types • Channel Access Code (CAC) • Device Access Code (DAC) • Inquiry Access Code (IAC) • Synchronization • DC offset compensation • Identification • Signaling 72 bits Access code Payload Header Purpose X

  31. Packet Header m Max 7 active slaves s s s • Addressing (3) • Packet type (4) • Flow control (1) • 1-bit ARQ (1) • Sequencing (1) • HEC (8) 54 bits Access code Payload Header Purpose 16 packet types (some unused) Broadcast packets are not ACKed For filtering retransmitted packets Verify header integrity total 18 bits Encode with 1/3 FEC to get 54 bits

  32. Data Packet Types DM1 DH1 DM3 DH3 DM5 DH5 Asymmetric Symmetric 2/3 FEC Asymmetric Symmetric No FEC

  33. Inter piconet communication Cordless headset mouse Cell phone Cordless headset Cell phone Cell phone Cordless headset

  34. Scatternet

  35. Scatternet, scenario 2 How to schedule presence in two piconets? Forwarding delay ? Missed traffic?

  36. Baseband: Summary Device 1 Device 2 L2CAP L2CAP Data link LMP LMP Baseband Baseband Physical • TDD, frequency hopping physical layer • Device inquiry and paging • Two types of links: SCO and ACL links • Multiple packet types (multiple data rates with and without FEC)

  37. Link Manager Protocol Applications IP SDP RFCOMM Control Data Audio L2CAP LMP Link Manager Baseband RF Setup and management of Baseband connections • Piconet Management • Link Configuration • Security

  38. Piconet Management m s s s • Attach and detach slaves • Master-slave switch • Establishing SCO links • Handling of low power modes ( Sniff, Hold, Park) Paging req Master Slave response

  39. Low power mode (hold) Hold offset Slave Hold duration Master

  40. Low power mode (Sniff) Sniff offset Sniff duration Slave Sniff period Master • Traffic reduced to periodic sniff slots

  41. Low power mode (Park) Slave Beacon instant Master Beacon interval • Power saving + keep more than 7 slaves in a piconet • Give up active member address, yet maintain synchronization • Communication via broadcast LMP messages

  42. Connection establishment & Security • Goals • Authenticated access • Only accept connections from trusted devices • Privacy of communication • prevent eavesdropping Paging LMP_host_conn_req • Constraints • Processing and memory limitations • $10 headsets, joysticks • Cannot rely on PKI • Simple user experience LMP Accepted Security procedure Master Slave LMP_setup_complete LMP_setup_complete

  43. Authentication • Authentication is based on link key (128 bit shared secret between two devices) • How can link keys be distributed securely ? challenge response Claimant Verifier accepted Link key Link key

  44. Pairing (key distribution) • Pairing is a process of establishing a trusted secret channel between two devices (construction of initialization key Kinit) • Kinit is then used to distribute unit keys or combination keys PIN + Claimant address PIN + Claimant address Claimant Verifier Random number challenge Random number Random number response accepted Kinit Kinit

  45. Link Manager Protocol Summary Device 1 Device 2 L2CAP L2CAP Data link LMP LMP Baseband Baseband Physical • Piconet management • Link configuration • Low power modes • QoS • Packet type selection • Security: authentication and encryption

  46. L2CAP IP Logical Link Control and Adaptation Protocol Applications SDP RFCOMM Data L2CAP provides • Protocol multiplexing • Segmentation and Re-assembly • Quality of service negotiation Audio L2CAP Link Manager Baseband RF

  47. Why baseband isn’t sufficient IP RFCOMM IP RFCOMM Multiplexing demultiplexing MTU reliable*, flow controlled Baseband in-sequence, asynchronous link • Baseband packet size is very small (17min, 339 max) • No protocol-id field in the baseband header

  48. Need a multiprotocol encapsulation layer no integrity unreliable, IP RFCOMM IP RFCOMM reliable*, in-order, flow controlled, ACL link Desired features • Protocol multiplexing • Segmentation and re-assembly • Quality of service What about • Reliability? • Connection oriented or connectionless? • integrity checks?

  49. Segmentation and reassembly Payload Length Baseband packets CRC CRC CRC start of L2CAP continuation of L2CAP continuation of L2CAP • cannot cope with re-ordering or loss • mixing of multiple L2CAP fragments not allowed • If the start of L2CAP packet is not acked, the rest should be discarded min MTU = 48 672 default

  50. Serial Port Emulation using RFCOMM IP Applications SDP RFCOMM Data Serial Port emulation on top of a packet oriented link • Similar to HDLC • For supporting legacy apps Audio L2CAP Link Manager Baseband RF

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