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Networking over Bluetooth: overview and issues

Networking over Bluetooth: overview and issues. m. s. s. s. Pravin Bhagwat Mobile Networking Group IBM T. J. Watson Research. http://www.research.ibm.com/people/p/pravin pravinb@us.ibm.com. IAB Wireless Workshop Feb 29 - March 2, 2000 Sunnyvale, CA. Bluetooth.

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Networking over Bluetooth: overview and issues

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  1. Networking over Bluetooth:overview and issues m s s s Pravin Bhagwat Mobile Networking Group IBM T. J. Watson Research http://www.research.ibm.com/people/p/pravin pravinb@us.ibm.com IAB Wireless Workshop Feb 29 - March 2, 2000 Sunnyvale, CA

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

  3. Value proposition of Bluetooth Cordless headset mouse Cell phone Data access point Internet access Cable replacement Ad hoc networking P. Bhagwat (IBM Research)

  4. Bluetooth working group history • February 1998: The Bluetooth SIG is formed • promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba • May 1998: The Bluetooth SIG goes “public” • 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 • February 2000: There are 1,500+ adopters • adopters "enjoy" royalty free use of the Bluetooth technology • products must pass Bluetooth certification P. Bhagwat (IBM Research)

  5. New Applications P. Bhagwat (IBM Research)

  6. Synchronization User benefits • Automatic synchronization of calendars, address books, business cards • Push button synchronization • Proximity operation P. Bhagwat (IBM Research)

  7. Cordless Headset User benefits • Multiple device access • Cordless phone benefits • Hand’s free operation Cordless headset P. Bhagwat (IBM Research)

  8. Usage scenarios examples • Data Access Points • Synchronization • Headset • Conference Table • Cordless Computer • Business Card Exchange • Instant Postcard • Computer Speakerphone P. Bhagwat (IBM Research)

  9. Bluetooth Specifications P. Bhagwat (IBM Research)

  10. Bluetooth Stack IP Control 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 P. Bhagwat (IBM Research)

  11. Interoperability & Profiles • A profile represents a 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 P. Bhagwat (IBM Research)

  12. Technical Overview P. Bhagwat (IBM Research)

  13. Bluetooth Radio Specification IP Control Data Applications SDP RFCOMM Audio L2CAP Link Manager Baseband RF P. Bhagwat (IBM Research)

  14. Radio • Low Cost • Single chip radio (minimize external components) • Today’s technology • Time divison duplex • Low Power • Standby modes Sniff, Hold, Park • Low voltage RF • Robust Operation • Fast frequency hopping 1600 hops/sec • Strong interference protection • Fast ARQ • Robust access code • Forward header correction P. Bhagwat (IBM Research)

  15. Radio • Allow low cost low IF • Trade sensitivity for integration • One chip radio is possible Tx power 0 dBm Rx power @ 10 cm -20 Rx power @ 10m -70 C/I = 21 dB -91 Noise floor P. Bhagwat (IBM Research)

  16. Baseband IP Control Data Applications SDP RFCOMM Audio L2CAP Link Manager Baseband RF P. Bhagwat (IBM Research)

  17. Connection Setup • Inquiry - scan protocol • to lean about the clock offset and device address of other nodes in proximity P. Bhagwat (IBM Research)

  18. Piconet formation Master Active Slave Parked Slave Standby • Page - scan protocol • to establish links with nodes in proximity P. Bhagwat (IBM Research)

  19. 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 P. Bhagwat (IBM Research)

  20. Piconet channel FH/TDD f5 f1 f4 f3 f2 f6 m s1 s2 625 sec 1600 hops/sec P. Bhagwat (IBM Research)

  21. Multi slot packets FH/TDD f1 f5 f4 f6 m s1 s2 625 sec Data rate depends on type of packet P. Bhagwat (IBM Research)

  22. Packet Format 54 bits 72 bits 0 - 2745 bits Access code Header Payload Error correction 1/3 rate FEC 2/3 rate FEC ARQ scheme for the data Synchronization identification Filtering Address Packet Type Flow control ARQ SEQN HEC Smaller than an ATM cell ! Notice that there is no protocol type field P. Bhagwat (IBM Research)

  23. Physical Link Types • Synchronous Connection Oriented (SCO) Link • slot reservation at fixed intervals • No ARQ, No CRC • FEC (optional) • 64 Kbps • Asynchronous Connection-less (ACL) Link • Polling access method • ARQ, CRC • FEC (optional) • Symmetric data rate 108 - 433 Kbps • Asymmetric data rate up to 723 Kbps P. Bhagwat (IBM Research)

  24. Mixed Link Example ACL ACL ACL ACL ACL ACL SCO SCO SCO m s1 s2 P. Bhagwat (IBM Research)

  25. Inter piconet communication Cordless headset mouse Cell phone Cordless headset Cell phone Cell phone Cordless headset P. Bhagwat (IBM Research)

  26. Scatternet P. Bhagwat (IBM Research)

  27. Scatternet, scenario 2 How to schedule presence in two piconets? Forwarding delay ? Missed traffic? P. Bhagwat (IBM Research)

  28. Link Manager Protocol IP Control Data LMP • Setup and Management • of Baseband connections • Piconet Management • Link Configuration • Security Applications SDP RFCOMM Audio L2CAP Link Manager Baseband RF P. Bhagwat (IBM Research)

  29. Link Manager Protocol • Piconet Management • Attach and detach slaves • Master-slave switch • Establishing SCO and ACL links • Handling of low power modes ( Sniff, Hold, Park) • Link Configuration • packet type negotiation • power control • Security functions • Authentication • Encryption P. Bhagwat (IBM Research)

  30. L2CAP Applications IP SDP RFCOMM Data Audio L2CAP Link Manager Baseband RF Logical Link Control and Adaptation Protocol • L2CAP provides • Protocol multiplexing • Segmentation and Re-assembly • Quality of service negotiation • Group abstraction P. Bhagwat (IBM Research)

  31. L2CAP Packet Format (CO) 16 bits 15 bits 0 - 64K bytes Payload DCID Length Minimum MTU is 48 bytes ! default is 672 bytes ! Baseband packets P. Bhagwat (IBM Research)

  32. L2CAP Packet Format (CL) 16 bits 15 bits 0 - 64K bytes Payload DCID PSM Length Baseband packets P. Bhagwat (IBM Research)

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

  34. Bluetooth Service Discovery Protocol IP Data Applications SDP RFCOMM Audio L2CAP Link Manager Baseband RF P. Bhagwat (IBM Research)

  35. Example usage of SDP • Establish L2CAP connection to remote device • Query for services • search for specific class of service, or • browse for services • Retrieve attributes that detail how to connect to the service • Establish a separate (non-SDP) connection to user the service P. Bhagwat (IBM Research)

  36. IP over Bluetooth V 1.0 IP Data • Internet access using cell phones • Connect PDA devices & laptop computers to the Internet via LAN access points Applications SDP RFCOMM GOALS Audio L2CAP Link Manager Baseband RF P. Bhagwat (IBM Research)

  37. LAN access point profile Why use PPP? • Security • Authentication • Access control • Efficiency • header and data compression • Auto-configuration • Lower barrier for deployment IP Access Point PPP RFCOMM L2CAP LMP Baseband P. Bhagwat (IBM Research)

  38. Inefficiency of layering • Emulation of RS-232 over the Bluetooth radio link could be eliminated Palmtop LAN access point IP IP packet oriented PPP PPP rfc 1662 rfc 1662 byte oriented RFCOMM RFCOMM packet oriented Bluetooth Bluetooth P. Bhagwat (IBM Research)

  39. Terminate PPP at LAN access point • PPP server function at each access point • management of user name/password is an issue • roaming is not seamless Palmtop Access Point IP IP PPP ethernet PPP RFCOMM RFCOMM Bluetooth Bluetooth P. Bhagwat (IBM Research)

  40. L2TP style tunneling UDP UDP IP IP ethernet ethernet • Tunneling PPP traffic from access points to the PPP server • 1) centralized management of user name/password • 2) reduction of processing and state maintenance at each access point • 3) seamless roaming Palmtop Access Point PPP server IP IP PPP PPP RFCOMM RFCOMM radio link radio link P. Bhagwat (IBM Research)

  41. IP over Bluetooth Next steps Internet connectivity for non-PC devices IP based network connectivity peer-to-peer connectivity IP over wireless media Investigation of the right design point for running IP over toasters, light switches, & fire alarms Decentralized techniques for link formulation, naming, addressing, and routing P. Bhagwat (IBM Research)

  42. Research challenges m s s s s m s s keyboard mouse keyboard mouse m m cable modem cable modem s s s s head set head set PC PC s s Cordless base Cordless base cell phone cell phone Palmpilot Palmpilot Internet Plug-n-play applications Resource Discovery Routing over scatternets Techniques for link formation Will the current solutions for each layer work in this environment? P. Bhagwat (IBM Research)

  43. What is different in this scenario ? m s s s s m s s keyboard mouse m m cable modem s s s s head set PC s s cordless base cell phone Palmpilot Connection oriented, low-power link technology Small, multi-hop networks Simple devices Isolated network Dynamic network Applications ---> services ----> routing ----> link creation P. Bhagwat (IBM Research)

  44. Link Formation  Proximity Link x5 x1 y1 y2 x2 x4 x6 x8 x3 x7 The problem does not exist in most wired/wireless networks Low power modes require careful use of broadcast Maintaining connectivity in absence of application traffic seems wasteful Hints from higher layer are needed P. Bhagwat (IBM Research)

  45. Routing over Scatternets Nodes must co-operate to forward packets (MANET style protocols) x5 x1 y1 y2 Forwarding at Layer 2 or Layer 3? Bridging or routing ? x2 x4 x6 x8 x3 x7 What interface should be exported to the above layer? Better coupling with the service discovery layer is needed P. Bhagwat (IBM Research)

  46. Service discovery m s s s s m s s keyboard mouse m m cable modem s s s s head set PC s s cordless base cell phone Palmpilot Need solutions for address allocation, name resolution, service discovery Existing solutions in the Internet depend on infrastructure Judicious use of Multicast/broadcast is needed These goals are similar to what Zero-conf WG is already working on P. Bhagwat (IBM Research)

  47. Point to ponder Zero-conf m s s s s m s s MANET r r r r s r r r Scatternet formation Will Zero-conf on top of MANET on top of scatternet construction algorithm solve our problem? Layered and simple, but potential inefficiencies Cross-layer optimizations are worth considering P. Bhagwat (IBM Research)

  48. Final Remarks • Zero-conf and Bluetooth can benefit from each other • Similarly, MANET and Bluetooth can also benefit from each other • A new working group in IETF for IP over Bluetooth ? • Multi-hop wireless networks will force us to re-evaluate our assumptions about network layering. Should IRTF start looking into those issues? http://www.research.ibm.com/people/p/pravin P. Bhagwat (IBM Research)

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