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Ad Hoc Nets - MAC layer

Ad Hoc Nets - MAC layer. Part II – TDMA and Polling - Bluetooth. Bluetooth. Bluetooth Piconet : a polling/TDMA scheme Bluetooth working group history February 1998 : The Bluetooth SIG is formed promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba

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Ad Hoc Nets - MAC layer

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  1. Ad Hoc Nets - MAC layer Part II – TDMA and Polling - Bluetooth

  2. Bluetooth • Bluetooth Piconet: a polling/TDMA scheme • Bluetooth working group history • February 1998: The Bluetooth SIG is formed • promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba • + 3Com, Lucent, Microsoft, Motorola • Where does the name come from? • To honor a 10th century king Bluetooth in Denmark who united that country and established Christianity

  3. Landline Data/Voice Access Points …and combinations! Personal Ad-hoc Networks What does Bluetooth do for you? Cable Replacement - Synchronization - Cordless Headset

  4. Example...

  5. m s m s s s Bluetooth Physical link • Point to point link • master - slave relationship • radios can function as masters or slaves • Piconet • Master can connect to 7 slaves • Each piconet has max capacity =1 Mbps ~ 10 - 100 Meter • hopping pattern is determined by the master

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

  7. Master Active Slave • Parked Slave • Connected • Not in Pico Standby Piconet formation • Page - scan protocol • to establish links with nodes in proximity

  8. 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 • ParkedMember address (PM_ADDR) • 8 bit parked slave address

  9. Piconet MAC protocol : Polling FH/TDD f5 f1 f4 f3 f2 f6 m s1 s2 625 µsec 1600 hops/sec

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

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

  12. Packet Types Data/voice packets Control packets Voice data ID* Null Poll FHS DM1 HV1 HV2 HV3 DV DH1 DH3 DH5 DM1 DM3 DM5 FHS – Frequency Hop Synchronization DM – Data Medium rate HV – High quality Voice DV – Data Voice DH – Data High rate

  13. 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

  14. m Max 7 active slaves s s s Packet Header 54 bits • Addressing (3) • Packet type (4) • Flow control (1) • 1-bit ARQ (1) • Sequencing (1) • HEC (8) 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

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

  16. Scatternet- Gateway node participates in more than one piconet on a time-division basis

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

  18. Device 1 Device 2 L2CAP L2CAP Data link LMP LMP Baseband Baseband Physical Baseband: Summary • 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)

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

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

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

  22. IP RFCOMM (Radio Frequency Communication)-- Serial Port Emulation using RFCOMM Applications SDP Serial Port RFCOMM Data • Serial Port emulation on top of a packet oriented link • Similar to HDLC (High level • Data Link Control protocol) • RS232 • For supporting legacy apps Audio L2CAP Link Manager Baseband RF

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

  24. Palmtop LAN access point IP IP packet oriented PPP PPP rfc 1662 rfc 1662 byte oriented RFCOMM RFCOMM packet oriented L2CAP L2CAP Inefficiency of layering • Emulation of RS-232 over the Bluetooth radio link could be eliminated

  25. Bluetooth Networking: A Layer 2 Support IP Ethernet-like broadcast segment slave 3 slave 1 slave 5 slave 4 master master Bluetooth slave 2

  26. Applications TCP / UDP IP BNEP Where is BNEP in the Bluetooth Stack? Applications TCP / UDP IP Bluetooth Network Encapsulation Protocol Host Controller Interface PPP SDP RFCOMM L2CAP LMP Baseband Bluetooth Radio

  27. The Bluetooth Network Encapsulation Protocol (BNEP) Purpose? Create a Ethernet-like broadcast environment for IP in a Bluetooth Scatternet, hiding Bluetooth specifics (e.g. notion of piconet/scatternet forming and maintenance) from IP and above Features: • Clear division between Bluetooth spec and IP • IP and IP networking applications will work as usual (DHCP, ARP) • Easy to apply zeroconf protocols • across scatternets • Ad-hoc L2 routing, handle loop-free broadcast

  28. BNEP Overhead • Type: 7 bit Bluetooth value identifies the type of BNEP header contained in this packet • 1 bit extension flag that indicates if one or more extension headers follow the BNEP Header before the data payload. • 1M of Data transfer • Additional ~0.2% Overhead • Additional Bluetooth Transmission time: 11 mSec

  29. Bluetooth Personal Area Networks- Ad Hoc and extend to Mesh • PANs extend the Internet to the user personal domain • 3G (2.5G) networks will give Internet access to PANs • PANs will generate more traffic than a single device • Utilize an aggregate of access networks (WLAN, 3G, DSL)

  30. IP Bluetooth Networking - Conclusions Bluetooth IP networking opens up new possibilities ---- Mesh networks • Enables spontaneous Ad Hocnetworking • Between people, • Between machines, • Mainly small, short range ad-hoc networks • Solves your “personal problems”... • Limited complexity and security risks • The enabler for PANs! • Gives a natural extension of Internet into the PAN via 3G • Enables stepwise upgrading of devices -- not tied to one multimedia terminal! • Makes use of the 3G bandwidth immediately • QoS ~ Bluetooth ?

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