CMPE 257 Spring CMPE 257: Wireless and Mobile Networking Spring 2005 Bluetooth

CMPE 257 Spring Announcements

CMPE 257 Spring Today Bluetooth.

CMPE 257 Spring Simulation Results

CMPE 257 Spring Experimental Setup Qualnet simulator 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 Reliable Delivery Ratio over MAODV

CMPE 257 Spring Reliable Delivery Ratio over ODMRP

CMPE 257 Spring Average Goodput - MAODV

CMPE 257 Spring Average Goodput - ODMRP

CMPE 257 Spring Bluetooth

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

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

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

CMPE 257 Spring Features Cost 20 dBm (~100 m) Point-to-multipoint No Scatternet Applications File Transfer, Dial-Up Networking LAN access, Fax, … 169 $ $ 0 dBm (~10 m) Point-to-multipoint No Scatternet File Transfer, Dial-Up Networking LAN access, Fax, … 169 $ --- Company Toshiba, Motorola, Digianswer IBM, TDK 3COM 10 m user-user; 100 m user-Base Station Point-to-multipoint SW- & FW-upgradeable File Transfer, Dial-Up Networking LAN access, Fax, Unconscious connection 149 $ Nokia 10 m user-user; Point-to-point Connectivity Battery for the cell phone File Transfer, Dial-Up Networking LAN access, Fax, Unconscious connection 149 $ Ericsson, Sigma 10 m user-user; Point-to-point; ARM processor; USB; RFCOMM ports 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 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 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 More History… Recently, IEEE standard for Wireless PANs (WPANs) Only MAC and PHY.

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

CMPE 257 Spring 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 Unlicensed Radio Spectrum 902 Mhz 928 Mhz 26 Mhz 83.5 Mhz 125 Mhz 2.4 Ghz Ghz Ghz Ghz cordless phones baby monitors Wireless LANs Bluetooth Microwave oven unused 33cm 12cm 5cm

CMPE 257 Spring Bluetooth Radio Link MA scheme: Frequency hopping spread spectrum 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.... 1Mhz Mhz

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

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

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

CMPE 257 Spring Paging Master Active Slave Parked Slave Standby 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 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 Bluetooth Link Formation Point-to-point link: Master-slave relationship. ms s s m 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.

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

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

CMPE 257 Spring Packet Header Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8) Access code Header Payload 54 bits Purpose Broadcast packets are not ACKed For filtering retransmitted packets 18 bitstotal s s m s 16 packet types (some unused) Max 7 active slaves Verify header integrity

CMPE 257 Spring 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 Scatternets Interconnection of multiple piconets. Master Slave

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

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

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

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

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

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