ECGR-6185 Advanced Embedded SystemsIEEE 802.15 WPANSlide 3ZigBeeZIGBEE operates in ISMFeatures of ZigBeeIEEE 802.15.4 SpecificationsSpecificationsFrame StructureSlide 10Slide 11Frame StructurePhysical LayerMAC LayerZigBee Protocol StackZIGBEE NETWORK ARCHITECTURESlide 17Slide 18Traffic TypesSlide 20Slide 21Data Transfer ModelBeacon Mode FeaturesNon- Beacon ModeNon- Beacon ModeZigBee AllianceArchitecture of a ZigBee deviceSecurityApplication of ZigBee devicesSlide 30Wireless Standard ComparisonsSlide 32Slide 33ECGR-6185Advanced Embedded SystemsZIGBEE802.15.4University of North Carolina at CharlotteShikha TikkuIEEE 802.15 WPAN A WPAN is a wireless personal area network for interconnecting computer devices centered around an individual person's workspace A wireless PAN consists of a dynamic group of less than 255 devices that communicate within about a 33-feet rangeIEEE 802.15 WPAN IEEE 802.15 is the 15th working group of the IEEE 802 which specializes in Wireless PAN standards.It includes five task groups • Task group 1 (WPAN/Bluetooth) • Task group 2 (Coexistence)• Task group 3 (High Rate WPAN) • Task group 4 (Low Rate WPAN) • Task group 5 (Mesh Networking)ZigBee•Established set of specifications for wireless personal area networking (WPAN) •Builds on IEEE 802.15 Task group 4 (Low Rate WPAN) •First version of Zigbee specification was released on December 16, 2004•The name "ZigBee" is derived from the erratic zigging patterns many bees make between flowers when collecting pollenZIGBEE operates in ISM • Global use: ISM 2.4 GHz band with 16 channels and data rate of 250 kb/s• Europe: 868 MHz band with single channel and data rate of 20 kb/s• USA and Australia: 915 MHz band with 10 channels and data rate of 40 kb/sFeatures of ZigBee•Extremely low power consumption •Short-range operations •The ability to sleep for a long time •Message acknowledgement •CCA (Clear Channel Assessment) •Multiple levels of security•Simplicity •Low costIEEE 802.15.4 Specifications • Data rates of 250 kbps, 40 kbps, and 20 kbps • Two addressing modes; 16-bit short and 64-bit IEEE addressing• Support for critical latency devices, such as joysticks • CSMA-CA channel access• Automatic network establishment by the coordinator• Fully handshaked protocol for transfer reliability • Power management to ensure low power consumption• 16 channels in the 2.4GHz ISM band, 10 channels in the 915MHz and one channel in the 868MHz bandSpecificationsFrame StructureThere are four basic frame types defined in 802.15.4• Data• ACK• MAC Command• Beacon Data Frame •Payload of up to 104 bytes•Frame is numbered- tracking•Frame-check sequence – Error free reception•Improves reliability in difficult conditionsAcknowledgment (ACK) Frame•FeedbackMAC Command Frame• Mechanism for remote control• Configure client nodes Beacon Frame •Wakes up client devices, which listen for their address and go back to sleep if they don't receive it•Nodes synchronizationFrame StructurePhysical Layer•Contains the radio frequency transceiver•Controls the activation and deactivation •Channel selection•Channel assessment •Transmission and reception of data packets •Medium access using DSSS and O-QPSKMAC Layer Employs 64 bit IEEE & 16 bit short addresses Services•MAC data service and MAC management service Functions•Enabling the transmission and reception of MPDUs•Beacon management•Channel access•Frame validation•Acknowledged frame delivery •Security certificationZigBee Protocol StackZIGBEE NETWORK ARCHITECTURENetwork Coordinator Most sophisticated of the three types Maintains overall network knowledge Requires the most memory and computing powerFull Function Device (FFD) Can function in any topology Capable of being the network coordinator Can talk to any other device DEVICE TYPES AND NETWORK TOPOLOGIESReduced Function Device (RFD)Cannot become a network coordinator Talks only to a network coordinator Very simple implementationDEVICE TYPES AND NETWORK TOPOLOGIESTraffic Types ZigBee/IEEE 802.15.4 addresses three typical traffic types. IEEE 802.15.4 MAC can accommodate all the types Data is periodic•The application dictates the rate•Sensor activates•Checks for data•Deactivates•Example: Sensing TemperatureTraffic TypesData is inte rmittent•Application/stimulus determines the rate•Device is connected to the network only when communication is necessitated•Optimum saving on energy•Example: Smoke Detectors, Light SwitchTraffic Types Data is repetitive• Rate is fixed • Depending on allotted time slots, called GTS (guaranteed time slot), devices operate for fixed durations•Example: MouseData Transfer ModelBeacon mode•Coordinator runs on batteries •Offers maximum power savings •Device watches out for the coordinator's beacon •Locks on and looks for messages addressed to it •Coordinator dictates a schedule for next beaconBeacon Mode Features•All the devices in a mesh network know when to communicate with each other•Timing circuits have to be quite accurate, or wake up sooner to be sure not to miss the beacon•Increase in power consumption by the coordinator's receiver, entailing an optimal increase in costs.Non- Beacon Mode Non- Beacon Mode•Coordinator is mains-powered•Devices are ‘asleep' nearly alwaysNon- Beacon Mode• Devices wake up to confirm their continued presence in the network at random intervals• On detection of activity, transmit to the ever-waiting coordinator's receiver • If channel is busy, receiver would miss a callZigBee Alliance•Association of companies working together to enable reliable, cost effective, low power, wirelessly networked monitoring and control products based on an open global standard•Specify minimum firmware features for compatibility between devices form different manufacturers, and the compliance to the IEEE 802.15.4 standardArchitecture of a ZigBee deviceSecuritySecurity Model of the IEEE 802.15.4 MAC sublayerspecifies four security services•Access control •Data encryption •Frame integrity •Sequential freshness to reject data frames that have been replayedApplication of ZigBee devices• Wireless home security• Remote thermostats• Remote lighting• Drape controller• Personal healthcareApplication of ZigBee devices• Advanced tagging•Automated meter reading•Wireless smoke
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