1. Wireless LANs (cont) Bluetooth

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

3. Example...

5. 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

7. Network Topology – Piconet master slave 1 slave 2 slave 3 Piconets created ad-hoc Master-Slave concept Piconet defined by its frequency hopping sequence

8. Unconnected Standby Connecting States Active States Low Power Modes Piconet establishment Ad-hoc setup Connection oriented Power save modes active slave master parked slave standby connecting slaves

9. The piconet or A D C B E 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)

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

11. access codepacket headerpayload 7254 0-2745 Packet Format

12. Packet Types 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 Access code Header Payload

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

14. Error handling 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 access codeheader payload 72bits 54bits 0-2745bits

15. 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

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

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

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

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

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

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

22. 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+  t.

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

24. Smart Scatternet... Move out large slave to slave traffic Still part of old piconet - a scatternet s s s s m s s s s s m s s s m s s s S-M 10 % of traffic S-S 90 % of traffic P1P1 P1P1 P2P2 S-M 55 % of traffic S-S 45 % of traffic s s

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

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

27. 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 s s s m1m1 s s P1P1 s s s s s P2P2 A m2m2 P2P2 P1P1 INQUIRY Scan/PAGE Scan

28. SNIFF Mode SNIFF Parameters –T sniff –max(N sniffattempt, N snifftimeout ) = W sniff Approximately one frame lost per “Piconet switch” Trade off: Delay vs. Throughput –Delay: T sniff –Throughput: T sniffP1 T sniffP2 W sniffP2 P2P2 P1P1

29. 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?

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

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

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

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

34. 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

35. Exp #3: Bluetooth; TCP + VoIP

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

38. With 750 ms playout buffer, 5% packets lost

39. Simulation: what have we learned? Bluetooth performance predictable, dependable Fair sharing 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

40. 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

41. 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.comwww.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

42. 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

43. PAN to Cellular Data Network Available today using cables or IR 2 nd 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

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

45. 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