1 / 45

Wireless LANs (cont)

Wireless LANs (cont). Bluetooth. Landline. Cable Replacement. Data/Voice Access Points. Personal Ad-hoc Networks. What Is Bluetooth ?. Example. Some Bluetooth Facts…. 2.4 GHz ISM Open band Globally free available frequency, 89 MHz of spectrum available

nam
Download Presentation

Wireless LANs (cont)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. WirelessLANs (cont) Bluetooth

  2. Landline Cable Replacement Data/Voice Access Points Personal Ad-hoc Networks What Is Bluetooth?

  3. Example...

  4. Some Bluetooth Facts…. • 2.4 GHz ISM Open band • Globally free available frequency, 89 MHz of spectrum available • FHSS radio (1600 hops/s and 79 frequencies) • 10 -100 m range • 8 active devices per piconet (share datarate) • Up to 10 piconets in bubble (full datarate) • 1 Mbps gross rate • Simultaneous voice/data capable • 432 Kbps (full duplex), 721/56 Kbps (asymmetric) or • 3 simultaneous full duplex voice channels per piconet or • a combination of data and voice

  5. Network Topology – Piconet • Piconets created ad-hoc • Master-Slave concept • Piconet defined by itsfrequency hopping sequence slave 3 slave1 master slave 2

  6. UnconnectedStandby ConnectingStates ActiveStates Low PowerModes master connecting slaves active slave parked slave standby Piconet establishment • Ad-hoc setup • Connection oriented • Power save modes

  7. or The piconet D • All devices in a piconet hop together • To form a piconet: master gives slaves its clock and device ID • Hopping pattern determined by device ID(48-bit) • Phase in hopping pattern determined by Clock • Non-piconet devices are in standby • Piconet Addressing • Active Member Address (AMA, 3-bits) • Parked Member Address (PMA, 8-bits) A E B C

  8. FH/TDD Channel f(k) f(k+1) f(k+2) master t slave t One slot: 625 ms One frame: 1250 ms

  9. 0-2745 72 54 access code packet header payload Packet Format

  10. Packet Types Access code Header Payload 72 bits 54bits 0-2475 bits Bluetooth Packet • Bluetooth Protocol supports 16 packet types, 15 types defined 4 Control packets common to both links POLL,NULL,FHS and ID 4 SCO packets used to carry voice with different payload lengths. HV1,HV2,HV3 and DV, where DV carries both voice and data 7 ACL packets with different payload lengths DM1,DM3,DM5,DH1,DH3,DH5 and AUX1 Carries data only

  11. 625 s f(k) f(k+1) f(k+2) f(k+3) f(k+4) f(k+5) f(k) f(k+3) f(k+4) f(k+5) f(k) f(k+5) Multi-slot Packets

  12. Error handling 72bits 0-2745bits 54bits • Forward-error correction (FEC) • headers are protected with 1/3 rate FEC and 8 bit CRC (HEC) • payloads may be FEC protected • 1/3 rate: simple bit repetition (SCO packets only) • 2/3 rate: (10,15) shortened Hamming code • 3/3 rate: no FEC • ARQ (ACL packets only) • 16-bit CRC (CRC-CCITT) & 1-bit ACK/NACK • 1-bit sequence number payload access code header

  13. Physical Link Definition • Synchronous Connection-Oriented (SCO) Link • circuit switching • symmetric, synchronous services • slot reservation at fixed intervals • Asynchronous Connection-Less (ACL) Link • packet switching • (a)symmetric, asynchronous services • polling access scheme

  14. SCO ACL SCO ACL ACL SCO SCO ACL Mixed Link Example MASTER SLAVE 1 SLAVE 2 SLAVE 3

  15. TYPE symmetric asymmetric DM1 108.8 108.8 108.8 DH1 172.8 172.8 172.8 DM3 256.0 384.0 54.4 DH3 384.0 576.0 86.4 DM5 286.7 477.8 36.3 DH5 432.6 721.0 57.6 Data Rates (kb/s)

  16. LAN access point access point mobile phone mobile phone headset headset printer printer laptop laptop master laptop laptop slave mouse mouse master/slave Multiple Piconets: A Scatternet

  17. Multiple Piconets: A Scatternet master slave master/slave

  18. Ad-hoc IP networking on Bluetooth (MANET) IP Hosts Bluetooth Link and Baseband Layer slave 3 slave 1 slave 5 slave 4 master master slave 2

  19. Some issues…. • Scatternet - A device present in more than one piconet • How to jump efficiently between piconets? • Delay sensitive applications? • Things happening in “sleeping” piconets? LAN access point

  20. Scatternet Forming/Reforming • “Optimal” scatternet configuration depends on • Connectivity and Node density • Traffic Distribution (Traffic matrix) • Mobility&Traffic dynamics - steady state ever reached? • Integration of connection establishment and (ad-hoc) routing? At t... At t+D t.

  21. s s s s s s s m s m s s m s s m ”Work” your Bluetooth Network • Bluetooth handles overlaid Piconets well • Overall capacity gained by setting up new piconets

  22. S-M 10 % of traffic S-M 55 % of traffic S-S 45 % of traffic S-S 90 % of traffic s s s s m s s s m s s s s s Smart Scatternet... • Move out large slave to slave traffic • Still part of old piconet - a scatternet P2 s s P1 P1 m s s s

  23. IP L2(Broadcast segment) Ad-hoc networking slave 3 slave 1 slave 5 slave 4 master master Bluetooth slave 2

  24. 2 2 1 1 3 3 2 2 1 1 3 3 Piconet scheduling slave 3 slave1 • Intra-piconet scheduling • Master controlled polling algorithm • Round Robin? • Inter-piconet scheduling • One transceiver • Different FHS master slave 2 master slave 3 slave 4 4 4

  25. A P2 s P1 s s s m2 s m1 s s s s s Inter-piconet Timing • Interpiconet communication may be “costly” • An interpiconet unit active in only one piconet at a time • SNIFF Mode - Periodic presence in each piconet INQUIRY Scan/PAGE Scan P1 P2

  26. SNIFF Mode • SNIFF Parameters • Tsniff • max(Nsniffattempt, Nsnifftimeout) = Wsniff • Approximately one frame lost per “Piconet switch” • Trade off: Delay vs. Throughput • Delay: Tsniff • Throughput: WsniffP2 TsniffP1 P1 P2 WsniffP2 TsniffP2

  27. Bluetooth Experiments Gerla, M et al,Tyrrenia Conf, sept 2000 • Experiment #!:TCP throughput in a single piconet. Throughput versus the no. of TCP connections. Each TCP connection starts from a different slave on the common piconet, and goes through the access point (BT master). • Experiment #2: TCP throughput when multiple piconets are used in parallel. Each piconet here supports a separate TCP connection. • Experiment #3: TCP and IP Telephony in a multiple piconet configuration. IP Telephony uses ACL channel. Question: can TCP and Telephony coexist?

  28. IP backbone IP backbone IP backbone IP router IP router IP router LAN LAN LAN M M S M 1 1 1 1 S M M M M M S M 3 3 2 3 2 2 2 3 S S (a) (b) (c) Fig. 4.

  29. Exp # 1:TCP throughput in Bluetooth (single piconet)

  30. Exp #2:TCP Throughput in WaveLAN vs BT (multiple piconets)

  31. Exp #2 (cont): Throughput of TCP flows

  32. TCP and IP Telephony • Voice carried on the ACL channel • Four piconets • In each piconet: 1 TCP and 6 Voice connections • TCP connections “always on” (file transfers) • Voice: ON-OFF model; 8Kbps coding rate • Voice packets: 20ms packetization -> 20 bytes • With header overhead: voice pkt = 30 bytes

  33. Exp #3: Bluetooth; TCP + VoIP

  34. Exp #3: Bluetooth; TCP + VoIP

  35. Exp #3: WaveLan 802.11: TCP + VoIP

  36. Exp #3: WaveLan 802.11: TCP + VoIP With 750 ms playout buffer, 5% packets lost

  37. Simulation: what have we learned? • Bluetooth performance predictable, dependable • Fairsharing across TCP connections (IEEE 802.11 is unfair, “capture”- prone) • BT aggregate throughput exceeds IEEE 802.11 • BT supports voice well even in heavy TCP load (IEEE 802.11 cannot deliver voice with TCP load) • BT not overly sensitive to microwave ovens Future work • BT load sensitive polling schedule • BT in low latency applications (sensors on walls) • BT scatternets (formation, schedules, routing etc) • BT vs UMTS comparison

  38. Bluetooth SIG2 - PAN WG • Personal Area Network • Ad-hoc Bluetooth work groups • QoS support (audio/video) • Possibly: “associated” members • opens up for academia • research oriented work

  39. Bluetooth Program Update • Final Specification published Monday 7/26/99 • Result of work from ~200 engineers • Updated Specification 1.0 B published 12/1/99 • SIG Membership Exceeds 1,700 Companies! • Becoming the choice for wireless connectivity • Membership list at www.bluetooth.com • Program on Track for Products in 2000 • Products announced • Next step is Qualification Program • Specification is basis for the proposed IEEE 802.15.1 standard

  40. PAN Impact on Internet Access for Mobile Devices • PAN allows sharing of “gateway” device • E.g., Only one cellular “modem” needed • E.g., Only one ADSL connection needed • PAN allows sharing of access “tariff” • All personal devices share same account • Allows multiple combinations of wireless and wired technology for Internet access with one or two communication interfaces

  41. PAN to Cellular Data Network • Available today using cables or IR • 2nd generation cellular better than analog • Cost and speed are still issues • RF value add is wireless connectivity without “line of sight” limitations • Also allows “unconscious” data reception PAN to WWAN

  42. PSTN, ISDN,HomePNA, xDSL PAN to Wired Infrastructure • Wireless “last hop” to the Internet • Public kiosks provide alternative to wireless wide-area networks PAN to LAN/WAN

  43. Summary • Bluetooth is a radio system (not a radio) • Building block for personal area networks • More information available at: http://www.bluetooth.com • PAN will improve the cost and convenience of achieving mobile Internet access

More Related