Presentation on theme: "Introduction to Zigbee"— Presentation transcript:
1 Introduction to Zigbee Wireless Sensor NetworksMEET SHAH IT 5TH SEM
2 Sensor Network Challenges Low computational powerLess than 10 MIPSLow memory budget: 4-10 KBLimited energy budgetAA batteries provide ~2850 mAhLiIon and NiMH batteries provide mAhSolar cells: around 5 mA/cm2 in direct sunlightCommunication?
3 Wireless Communication Wireless communication standards:IEEE a/b/gBluetoothGSMWhat makes them unattractive for WSN:Power hungry (need big batteries)Complexity (need lots of clock cycles and memory)New protocol for WSN:and Zigbee (ratified in Dec 14, 2004)
4 Outline Why not 802.11 ? How about Bluetooth? X-10? What is ZigBee? ZigBee Protocol: PHY and aboveHardware: CC2420Example and discussion
5 Technology Space 802.11a 802.11b 802.11g Bluetooth 802.15.4 Zigbee 11Mbps54MbpsBluetoothZigbee720 kbps“Mica2”/cc1000250 kbpsData rate38.4 kbps
7 Why NOT 802.11 ? The Cost of Throughput High data ratesup to 11Mbps for b andup to 54Mbps for g and a)Distance up to 300 feet, or more with special antennasHigh power consumptionSources about 1800mA when transceiver is operational.
8 IEEE b exampleConsider running a mote with b on two AA batteries.Consumes 1800mA when transmittingAssume NiMH battery capacity 2400mA/hAssume transmitting 1/3 of the timeHow long will the batteries last?Is the given information sufficient for the question asked?
9 How About Bluetooth ? The Cost of Universalism Designed for communicationsbetween portable andperipheral devices720 kbps, 10m rangeOne master and 7 slave devices in each “Piconet”Time Division Multiple Access (TDMA)Frequency hopping to avoid collisions between PiconetsHop between channels 1600 times a second79 channels (1MHz each) to avoid collisions
10 Protocol tailored to many different data types: Audio, Text, Raw data Makes the protocol rather complex to accommodate for all data typesNeeds more memory and clock cycles than we are willing to afford on the MotesZigbee needs only about 10-50% of the software in comparison with Bluetooth and WiFi
11 WHY ZIGBEE Supports large number of nodes. Ultra low power consumption SecureReliableLow costEasy to deploy.World wide usabilityVery small protocol stackStandard based wireless technology
12 What is Zigbee Affordable Simplicity ZigBee is a published specification set of high level communication protocols for:Low data rate, low power, low cost wireless systems operating in unlicensed RF domainFormely known asPURLnet, RF-Lite, Firefly, and HomeRF LiteBased on IEEE
16 ZigBee Applications Wireless home security Remote thermostats for air conditionerRemote lighting, drape controllerCall button for elderly and disabledUniversal remote controller to TV and radioWireless keyboard, mouse and game padsWireless smoke, CO detectorsIndustrial and building automation and control (lighting, etc.)
17 Zigbee General Low power Multiple topologies Addressing space: 64 bits battery life multi-month to yearsMultiple topologiesstar, peer-to-peer, meshAddressing space: 64 bitsQuestion: how many nodes?Fully hand-shake protocol (reliability)Range: 50m typical5-500m based on environment
18 Zigbee Intended Traffic Periodic dataIntermittent dataApplication defined rate (e.g., sensors)External stimulus defined rate (e.g., light switch)Low latency data (Q: Any examples?)
24 ZigBee Upper Layers Messaging Configurations that can be used Security:Key setup and maintenance: Commercial, ResidentialDefines key types: Master, Link, NetworkCCM (unified, simple mode of operation)More: Key freshness checks, message integrity, authentication (network and device level)Network layer (NWK) supports three topologies:StarMeshCluster-Tree ( = Star + Mesh)
25 How A ZigBee Network Forms Devices are pre-programmed for their network functionCoordinator scans to find an unused channel to start a networkRouter scans to find an active channel to join, then permits other devices to joinEnd Device will always try to join an existing networkDevices discover other devices in the network providing complementary servicesService Discovery can be initiated from any device within the networkDevices can be bound to other devices offering complementary servicesBinding provides a command and control feature for specially identified sets of devices
26 ZigBee Routing Routing table entry: Route request command frame: Destination Address (2 bytes)Route status (3 bits)Next Hop (2 bytes)Route request command frame:FrameID, Options, RequestID, Destination Address, Path costRoute reply command frame:FrameID, Options, Req.ID, Originator Addr, Responder Addr, Path costA device wishing to discover or repair a route issues a route request command frame which is broadcast throughout the networkWhen the intended destination receives the route request command frame it responds with at least one route reply command framePotential routes are evaluated with respect to a routing cost metric at both source and destination
27 ZigBee NWK Parameters nwkMaxDepth and nwkMaxChildren nwkMaxRouters Size of the routing tableSize of neighbor tableSize of route discovery tableNumber of reserved routing table entriesHow many packets to buffer pending route discoveryHow many packets to buffer on behalf of end devicesRouting cost calculationnwkSymLinknwkUseTreeRouting
28 Hardware: CC2420 How Stuff Works Chipcon/Ember CC2420: Single-chip radio transceiver compliant with IEEELow power:1.8V supplyLess than 20mA operation currentPHY and encryption in hardwareOpen source software availableO-QPSK modulationMinimizes interference with WiFi and BluetoothLow cost (about $5)
31 Advantages Product interoperability Vendor independence Increased product innovation as a result of industry standardizationA common platform making it cost effectiveSo companies can focus their energies on finding and serving customers
32 Conclusion The choice of protocol depends on the application: An array of wireless video cameras –802.11b or g is probably betterAn array of low data rate sensor nodes – is probably betterMust consider several factors, such asProtocol overhead and payload data size, wake-up overhead, ……in terms of power, computation, and time.
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