Introduction to Wireless Sensor NetworksOrganizationalWhat is ZigBee?Why ZigBee?ApplicationsIEEE 802.15.4 & ZigBee In ContextWhy IEEE 802.15.4?802.15.4 General Characteristics802.15.4 Frequency BandsChannel DivisionModulation & SpreadingMedia Access ControlPacket StructureTransceiver CharacteristicsPHY Layer PrimitivesBasic Network CharacteristicsTopology Models (cont)Topology ModelsDevice ClassesComparison of complimentary protocols802.15.4/ZigBee vs BluetoothDevice AddressingGeneral Data Packet StructureOptional Frame StructureTraffic TypesDevelopment BoardsDevelopment Boards (cont.)Slide 28Slide 29Low Data Rate Wireless EvolutionReferences1The University of Iowa. Copyright© 2005A. KrugerIntroduction to Wireless Sensor Networks ZigBee Overview24 February 20052The University of Iowa. Copyright© 2005A. KrugerOrganizationalMonday 4:30-5:20 Room 4511 SCThursday 12:30-1:20 Room 3220 SCPlease note that the room numbers are different for Mondays and Thursdays.Class Websitewww.engineering.uiowa.edu/~ece195/2005/Class TimeMidterm ExamTime: March 10, 20053The University of Iowa. Copyright© 2005A. KrugerWhat is ZigBee?•“Internet Everything”–Your toaster gets an IP address•Wireless standard formed by an alliance of industry leaders•Motorola, Phillips, Samsung, Cisco… over 100 companies!!4The University of Iowa. Copyright© 2005A. KrugerWhy ZigBee?•Reliable and self healing•Supports large number of nodes•Easy to deploy•Very long battery life•Secure•Low cost•Can be used globally5The University of Iowa. Copyright© 2005A. KrugerApplicationsZigBeeWireless Control that Simply WorksRESIDENTIAL/LIGHT COMMERCIAL CONTROLCONSUMER ELECTRONICSTVVCRDVD/CDremotesecurityHVAClighting controlaccess controllawn & garden irrigationPC & PERIPHERALSINDUSTRIALCONTROLasset mgtprocess controlenvironmentalenergy mgtPERSONAL HEALTH CAREBUILDING AUTOMATIONsecurityHVACAMRlighting controlaccess controlmousekeyboardjoystickpatient monitoringfitness monitoring6The University of Iowa. Copyright© 2005A. Kruger–“the software” –Network, Security & Application layers–Brand managementIEEE 802.15.4–“the hardware” –Physical & Media Access Control layersPHY868MHz / 915MHz / 2.4GHzMACNetworkStar / Mesh / Cluster-TreeSecurity32- / 64- / 128-bit encryptionApplicationAPIZigBeeAllianceIEEE 802.15.4CustomerSiliconStackAppIEEE 802.15.4 & ZigBee In Context7The University of Iowa. Copyright© 2005A. KrugerWhy IEEE 802.15.4?•Ultra Low complexity•Ultra Low cost•Ultra Low power consumption•Data reliability•Low data rate8The University of Iowa. Copyright© 2005A. Kruger802.15.4 General Characteristics•Data rates of 20 kbps and up to 250 kbps•Star or Peer-to-Peer network topologies•Support for Low Latency Devices•CDMA-CA Channel Access•Handshaking•Low Power Usage consumption•3 Frequencies bands with 27 channels•Extremely low duty-cycle (<0.1%)9The University of Iowa. Copyright© 2005A. Kruger802.15.4 Frequency Bands BAND COVERAGE DATA RATE CHANNELS2.4 GHz ISM Worldwide 250 kbps 16915 MHz ISM Americas 40 kbps 10868 MHz Europe 20 kbps 110The University of Iowa. Copyright© 2005A. KrugerChannel Division868MHz/915MHz PHY2.4 GHz868.3 MHzChannel 0Channels 1-10Channels 11-262.4835 GHz928 MHz902 MHz5 MHz2 MHz2.4 GHz PHY11The University of Iowa. Copyright© 2005A. KrugerModulation & Spreading•Direct Sequence Spread Spectrum (DSSS)–Chipping Sequences•2.4 GHz–32-chip PN codes–Chip modulation is MSK at 2.0 Mchips/s•868/915 MHz–15-chip m-sequence–Chip modulation is BPSK at 0.3 Mchips/s12The University of Iowa. Copyright© 2005A. KrugerMedia Access Control•Code Division Media Access w/ Collision Avoidance (CDMA-CA)•Bi-Directional Communications (Duplex)•Dynamic Device Addressing•Fully Handshaked Protocol•Optional Guaranteed Time Slots•2.4 GHz - 16-ary orthogonal•868/915 MHz - differential encoding13The University of Iowa. Copyright© 2005A. KrugerPacket Structure•Packet Fields–Preamble (32 bits) - synchronization–Start of Packet Delimiter (8 bits) - specifies one of 3 packet types–PHY Header (8 bits) - Sync Burst flag, PSDU length–PSDU (0 to 127 bytes) - DataPreambleStart ofPacketDelimiterPHYHeaderPHY ServiceData Unit (PSDU)6 Bytes 0-127 Bytes14The University of Iowa. Copyright© 2005A. KrugerTransceiver Characteristics•Transmit Power–Capable of at least 1 mW–Power reductions capability required if > 16 dBm (reduce to < 4dBm in a single step)•Receiver Sensitivity –-85 dBm (1 % Packet Error Rate)•RSSI measurements–Packet Strength indication–Clear channel assessment–Dynamic channel selection15The University of Iowa. Copyright© 2005A. KrugerPHY Layer Primitives•PHY Data Service–PD-DATA - exchange data packets between MAC and PHY•PHY Management Service–PLME-CCA - clear channel assessment–PLME-GET - retrieve PHY parameters–PLME-RX-ENABLE - enable/disable receiver–PLME-SET - set PHY parameters16The University of Iowa. Copyright© 2005A. KrugerBasic Network Characteristics•65,536 network (client) nodes•Optimized for timing-critical applications–Network join time: 30 ms (typ)–Sleeping slave changing to active: 15 ms (typ)–Active slave channel access time: 15 ms (typ)Network coordinatorFull Function nodeReduced Function nodeCommunications flowVirtual links17The University of Iowa. Copyright© 2005A. KrugerTopology Models (cont)•Star Networks (Personal Area Network)–Home automation–PC Peripherals–Personal Health Care•Peer-to-Peer (ad hoc, self organizing & healing)–Industrial control and monitoring–Wireless Sensor Networks–Intelligent Agriculture18The University of Iowa. Copyright© 2005A. KrugerTopology ModelsPAN coordinatorFull Function DeviceReduced Function DeviceStarMeshCluster Tree19The University of Iowa. Copyright© 2005A. KrugerDevice Classes•Full function device (FFD)–Any topology–Network coordinator capable–Talks to any other device•Reduced function device (RFD)–Limited to star topology–Cannot become a network coordinator–Talks only to a network coordinator–Very simple implementation20The University of Iowa. Copyright© 2005A. KrugerComparison of complimentary protocolsFeature(s) IEEE 802.11b Bluetooth ZigBeePower Profile Hours Days YearsComplexity Very Complex Complex