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CMPE 257: Wireless and Mobile Networking

CMPE 257: Wireless and Mobile Networking. Spring 2005 Bluetooth. Announcements. Today. Bluetooth. Simulation Results. Experimental Setup. Qualnet simulator 802.11 MAC with 371m radio range. 50 nodes in a 1500x1500 area. Random node placement.

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CMPE 257: Wireless and Mobile Networking

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  1. CMPE 257: Wireless and Mobile Networking Spring 2005 Bluetooth CMPE 257 Spring 2003

  2. Announcements CMPE 257 Spring 2003

  3. Today • Bluetooth. CMPE 257 Spring 2003

  4. Simulation Results CMPE 257 Spring 2003

  5. Experimental Setup • Qualnet simulator • 802.11 MAC with 371m radio range. • 50 nodes in a 1500x1500 area. • Random node placement. • Two different underlying multicast routing protocols (MAODV and ODMRP). • Application data size 512 bytes. • 5 sources and 10 group members. CMPE 257 Spring 2003

  6. Reliable Delivery Ratio over MAODV CMPE 257 Spring 2003

  7. Reliable Delivery Ratio over ODMRP CMPE 257 Spring 2003

  8. Average Goodput - MAODV CMPE 257 Spring 2003

  9. Average Goodput - ODMRP CMPE 257 Spring 2003

  10. Bluetooth CMPE 257 Spring 2003

  11. Cable Replacement • 1 Mb/s. • Range ~10 meters. • PANs • Single chip radio. • Low power & low cost. Why not use Wireless LANs? - power - cost CMPE 257 Spring 2003

  12. Applications: Synchronization • Automatic synchronization of calendars, address books, business cards. CMPE 257 Spring 2003

  13. Applications: Cordless Headset • Multiple device access. • Hands-free operation. Cordless headset CMPE 257 Spring 2003

  14. More applications… • Conference table. • Cordless computer. • Instant photo transmission. • Cordless phone. CMPE 257 Spring 2003

  15. Company Features Applications Cost Toshiba, Motorola, Digianswer 20 dBm (~100 m) Point-to-multipoint No Scatternet File Transfer, Dial-Up Networking LAN access, Fax, … 169 $ --- 200 $ File Transfer, Dial-Up Networking LAN access, Fax, … 169 $ --- IBM, TDK 0 dBm (~10 m) Point-to-multipoint No Scatternet 10 m user-user; 100 m user-Base Station Point-to-multipoint SW- & FW-upgradeable 3COM File Transfer, Dial-Up Networking LAN access, Fax, E-mail Unconscious connection 149 $ 10 m user-user; Point-to-point Connectivity Battery for the cell phone Nokia File Transfer, Dial-Up Networking LAN access, Fax, E-mail Unconscious connection 149 $ 10 m user-user; Point-to-point; ARM processor; USB; RFCOMM ports Ericsson, Sigma Basic BT Radio stack Embedded or Host stack Programmable 500 $ 1500$ Bluetooth on the market: PC cards, Cell phones, Head sets, Chip sets,… CMPE 257 Spring 2003

  16. Bluetooth WG History • May 1998: Bluetooth SIG is formed. • Promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba. • Goal: develop license-free technology for universal wireless connectivity. • Target: handheld market. • Bluetooth spec: defines RF wireless communication interface and protocols. CMPE 257 Spring 2003

  17. Bluetooth WG History • May 1998: Public announcement of Bluetooth SIG. • July 1999: 1.0A spec (>1,500 pages) published. • December 1999: version 1.0B released. • December 1999: promoters increases to 9. • 3Com, Lucent, Microsoft, Motorola • February 2000: 1,800+ adopters. • February 2001: version 1.1 out. CMPE 257 Spring 2003

  18. More History… • Recently, IEEE 803.15.1 standard for Wireless PANs (WPANs) • Only MAC and PHY. CMPE 257 Spring 2003

  19. Goals • Low cost. • Power efficiency. • Single-chip implementation. (early implementations are double-chip) These goals defined: • Link speed. • Communication range. • Transmit power. CMPE 257 Spring 2003

  20. Single chip with RS-232, USB, or PC card interface Bluetooth Protocol Stack Applications Radio+part of baseband= Physical layer RFCOMM/SDP L2CAP Host Controller Interface Link Manager Link Controller Baseband RF CMPE 257 Spring 2003

  21. Radio Band • Public, i.e., no need for licenses. • Available worldwide. • Industrial, Scientific, Medical (ISM) band. • Unlicensed, globally available. • Centered around 2.4 GHz. • Frequency hopping. • Range: 10cm to 10m. CMPE 257 Spring 2003

  22. 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 unused 802.11 Bluetooth Microwave oven cordless phones baby monitors Wireless LANs CMPE 257 Spring 2003

  23. Bluetooth Radio Link 1Mhz • MA scheme: Frequency hopping spread spectrum. • 2.402 GHz + k MHz, k=0, …, 78 • 1,600 hops per second. • 1 Mb/s data rate. • Number of hopping sequences defined. • Master node defines sequence to be used. • Slave units use master id to pick sequence. . . . 79 1 2 3 83.5 Mhz CMPE 257 Spring 2003

  24. BT Radio Link (Cont’d) • Time-division duplex (TDD) • Separation of Xmission and reception in time: one-chip implementation. • Units alternately transmits and receives. • Gaussian Frequency Shift Keying (G-FSK) modulation. • ‘1’s as positive frequency deviations from carrier frequency; ‘0’s as negative deviations. CMPE 257 Spring 2003

  25. Multiple Access • BT targets large number of independent communications active in the same area at the same time. • Single FH channel: 1 Mb/s. • Each 1Mb/s channel shared by limited number of participants. • In target user scenarios, it’s unlikely that all units in-range will share data among all of them. • 1 MB/s is reasonable. (is it?) • Theoretically, total bandwidth is 79 Mb/s. • In practice, < 79 Mb/s since codes are non-orthogonal. CMPE 257 Spring 2003

  26. Baseband Control end of baseband +link controller= Data link layer Applications RFCOMM/SDP L2CAP Host Controller Interface Link Manager Carries out MAC functions. Link Controller Baseband RF CMPE 257 Spring 2003

  27. Piconets • BT communication takes place over piconets. • Piconet formation initiated by master. • All other participants are slaves. • Number of participants limited to 8 (1 master and 7 slaves). • Channel capacity and addressing overhead. • Each slave assigned a locally unique ID. • Master/slave role last for the duration of the piconet. CMPE 257 Spring 2003

  28. Piconets: considerations • Most target applications involve local communication among small group of devices. • Piconets with up to 8 nods match well. • If many groups of devices active simultaneously, each group as separate piconet. • Overlapping piconets can coexist. CMPE 257 Spring 2003

  29. Contention-Free MA • Master and slaves. • Master performs medium access control. • Schedules traffic through polling. • Time slots alternate between master and slave transmission. • Master-slave: master includes slave address. • Slave-master: only slave chosen by master in previous master-slave slot allowed to transmit. • If master has data to send to a slave, slave polled implicitly; otherwise, explicit poll. CMPE 257 Spring 2003

  30. BT States Standby . Initially, all nodes in standby. . Node (master) can begin inquiry to find nearby devices. . Piconet is then formed. . Devices join by paging. Unconnected Inquiry Page Connecting Transmit Connected Active Sniff Park Hold Low power CMPE 257 Spring 2003

  31. Inquiry • Device discovery • Listeners respond with their address. CMPE 257 Spring 2003

  32. Master Active Slave Parked Slave Standby Paging • Device enters paging to invite others to join its piconet. • Establishes links with nodes in proximity. • Paging message unicast to selected receiver. • Receiver sends ACK. • Sender becomes master, receiver slave. CMPE 257 Spring 2003

  33. Piconet New Node Admission • Master can actively try to discover new nodes or wait (in scan/listen mode) to be discovered. • Communication in the current piconet suspended. • Admission latency versus piconet capacity tradeoff. CMPE 257 Spring 2003

  34. m s m s s • Piconet: • 8 units: channel capacity. • Master (establishes piconet) can connect to up to 7 slaves. • Master/slave relationship lasts while link/piconet lasts. • No slave-to-slave communication. s Bluetooth Link Formation • Point-to-point link: • Master-slave relationship. CMPE 257 Spring 2003

  35. Link Types • 2 types of links: • Synchronous (SCO) links: • Point-to-point between master and slave. • Link established by reserving slots in either direction periodically. • Used to carry real-time traffic (voice). • Asynchronous (ACL) links: • Point-to-multipoint between master and slaves. • Use remaining slots on channel. • Traffic scheduled by master. CMPE 257 Spring 2003

  36. Error Control • Supports both FEC and retransmission. • FEC for SCO packets. • ARQ for ACL traffic. • If no ACKs, retransmit. • Stop-and-wait ARQ. • Fast-ARQ: ACK included in RX slot immediately following the TX slot in which packet was sent. • CRC to check for errors. CMPE 257 Spring 2003

  37. Packet Format 54 bits 72 bits 0 - 2744 bits Access code Header Payload No CRC No retries header Data Voice CRC FEC (optional) ARQ FEC (optional) 625 µs master slave CMPE 257 Spring 2003

  38. Access Code 72 bits • Address of piconet master. Access code Payload Header CMPE 257 Spring 2003

  39. 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 CMPE 257 Spring 2003

  40. Multiple Piconets • Piconets may overlap in space and time. • They can work independently. • Each with its own hopping sequence. • Packets with different access codes. • Or they can overlap, i.e., nodes can participate in more than 1 piconet. • “Time sharing”. CMPE 257 Spring 2003

  41. Scatternets • Interconnection of multiple piconets. Slave Master CMPE 257 Spring 2003

  42. Scatternets (cont’d…) • Interconnection by bridge nodes. • Bridge nodes are members of piconets they interconnect. • Bridge node “stay” in a piconet for some time, then switch to another piconet by changing hop sequence. • Do this for all member piconets. • Send and receive in each piconet. • Forward from one piconet to another. CMPE 257 Spring 2003

  43. Link Manager Protocol Applications . Main functions: power management and security. RFCOMM/SDP L2CAP Host Controller Interface Link Manager Link Controller Baseband RF CMPE 257 Spring 2003

  44. Power Management • Low-power modes: prolong battery life. • Devices can be turned-off when idle. • Devices wake up periodically to send/receive data. CMPE 257 Spring 2003

  45. Low-Power Operation • 3 modes: • Hold: node sleeps for specified interval. • Master can put slaves in hold while searching for new members, attending another piconet, etc. • No ACL packets. • Sniff: slave low-duty cycle mode. • Slave wakes up periodically to talk to master. • Fixed “sniff” intervals. • Park: • Very low power state. • Used to admit more than 7 slaves in piconet. • Slave gives up its active member address. • Receives “parked” member address. CMPE 257 Spring 2003

  46. Security • Authentication and encryption.. • Authentication using challenge-response mechanism based on shared secret key CMPE 257 Spring 2003

  47. Host Controller Interface Optional interface layer between higher and lower layers of the BT stack. Applications RFCOMM/SDP L2CAP Host Controller Interface Link Manager Link Controller Baseband RF CMPE 257 Spring 2003

  48. L2CAP Applications RFCOMM/SDP Logical Link Control and Adaptation Protocol= Session Layer. L2CAP Host Controller Interface Link Manager Link Controller • L2CAP provides • Protocol multiplexing • Quality of service negotiation Baseband RF CMPE 257 Spring 2003

  49. RFCOMM/SDP Applications RFCOMM/SDP L2CAP Service discovery, interoperability with IR applications, serial port interface. Host Controller Interface Link Manager Link Controller Baseband RF CMPE 257 Spring 2003

  50. References: • Bluetooth papers in reading list. • Johansson and Gerla’s Bluetooth Tutorial at Mobicom 2001. • Bluetooth 1.1: Connect Without Cables, Bray and Sturman. CMPE 257 Spring 2003

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