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ZigBee

ZigBee. Alex Wegznek Chris Griffis EEL 4514 Communications System. Overview. ZigBee Overview Purpose of ZigBee History of ZigBee How ZigBee works Pros & Cons Regulations & Standards Stack & Protocol Comparisons. ZigBee Overview.

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ZigBee

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  1. ZigBee Alex Wegznek Chris Griffis EEL 4514 Communications System

  2. Overview • ZigBee Overview • Purpose of ZigBee • History of ZigBee • How ZigBee works • Pros & Cons • Regulations & Standards • Stack & Protocol • Comparisons

  3. ZigBee Overview • Specification for communication protocols based upon IEEE 802.15.4 standard • Wireless sensor monitoring and control • Designed to be: • Highly reliable • Cost-effective • Low-power • Highly secure • Low-data rate http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAA&url=http%3A%2F%2Fwww.science.smith.edu%2F~jcardell%2FCourses%2FEGR390%2FReadings%2FZigBee-Tutorial.ppt&ei=S45vUL2MIpOY9QS164GADQ&usg=AFQjCNFTM-NOUd01KZbHOteELxu737imrQ

  4. Purpose • Provide reliable and cost effective solution for WPANs • Designed specifically for sensor networking and automation • Intended to fit on 8-bit microcontrollers with 16 and 32-bit solutions available • Low power leads to extended battery life

  5. History • Conceived around 1998 • Grew out of the realization that Wi-Fi and Bluetooth were unsuitable for many applications • The first IEEE 802.15.4 standard was finished in 2003 • ZigBee PRO (new standard) was finished in 2007 • ZigBee PRO has extra features: multi-casting, many-to-one routing, and more

  6. ZigBee Alliance • Formed in 1997 with 8 original promoter companies and now has over 200 members • Maintains and publishes the ZigBee standard

  7. Markets • Home Control • Automation, smart lighting, security, temperature control • Commercial Building Automation • Wireless Sensor Networks • Industrial Control • Embedded Sensing http://www.ti.com/lsds/ti/analog/zigbee.page?DCMP=hpa_rf_general&HQS=NotApplicable+OT+zigbee

  8. How does it work? • Mesh networking • Ad-hoc network • Nodes can forward data to other nodes which is called hopping • Multi-hopping can give the network extended range as well as avoid barriers • Tree and star routing also available

  9. How does it work? (Cont.) Low Power Low-Data Rate • Devices have low duty cycle • No constant contact • Allows devices to operate for the entire shelf life of the battery • Leads to low data rates • Ideal for sensor networks • Due to low cost/power • 250 kbps maximum • Actual throughput comes out closer to 25 kbps • Transceivers are half duplex • Can only receive or transmit at one time http://www.digikey.com/us/en/techzone/energy-harvesting/resources/articles/Ultra-Low-Power-MCUs.html

  10. How does it work? (Cont.) High Level of Security High Reliability • National Institute of Standards and Technology (NIST) Advanced Encryption Standard (AES) • AES-128 bit block cipher algorithm • ZigBee both encrypts and authenticates packets • Carrier sense multiple access with collision avoidance (CSMA-CA) • 16 bit cyclic redundancy check (CRC); parity bit • Mesh network finds route and acknowledges each hop • End-to-end data arrival acknowledgements

  11. How does it work? (Cont.) Direct-sequence spread spectrum (DSSS) Offset Quadrature Phase-Shift Keying (OQPSK) Binary Phase-Shift Keying (BPSK) • 868 and 915 MHz band • Simplest form of phase shift keying, also the most robust • Takes the highest level of noise/distortion to cause an incorrect decision by the demodulator • Only able to modulate at 1 bit/symbol (slow data rate) • 2.4 GHz band • Uses 4 different values of the phase to transmit • Offset reduces any unwanted amplitude fluctuation • Transmits twice the data rate in a given bandwidth as compared to BPSK

  12. Pros and Cons Pros Cons • High reliability • Low cost • Ultra Low power • Highly secure • Open global standard • Remote operation • Easy to implement • Self healing networks • Low data rate • Relatively small transmission range if hopping is not used (10-75 m)

  13. Regulations & Standards • IEEE 802.15.4 low rate WPAN standard • Uses the ISM bands • OQPSK - 2.4GHz band • BPSK – lower bands • 250 kbps, 40 kbps, and 20 kbps http://evolt-ektor.com/zigbee-as-a-wireless-network

  14. Regulations • 16 channels: 5 MHz of BW each • All 16 channels because low BW protocol • Interference tolerant • Fc = (2350 + (5*ch))MHz where ch = 11,12,…26 http://www.intechopen.com/books/factory-automation/wireless-sensor-networks-for-networked-manufacturing-systems

  15. Standards • Lower protocol specifications • IEEE 802.15.4 defines how to: • Discover networks • Form & join networks • Change channels • Detect interference • Single hop, broadcast and data-packet delivery method bwrc.eecs.berkeley.edu/people/grad_students/.../zigbee%20master.ppt

  16. Stack • Simple Stack – easy for user • Physical layer - direct sequence, cheap, high integration • MAC layer – several topologies, works with many devices • Network layer – control, communication, and monitoring the nodes http://www.tutorial-reports.com/wireless/zigbee/zigbee-architecture.php

  17. Stack (Cont.) • MAC and PHY layers are under IEEE control • The physical layer is the circuitry • The MAC layer allows networks to form and for data transfer • ZigBee assures security, multi-hops, and interoperability • ZigBee’s security differs from IEEE 802.15.4 • The APS layer has tables to keep track of which nodes it can accept data from • User only worries about task ZigBee Wireless Networking, Drew Gislason

  18. Topologies • Star, Peer-to-Peer, & Mesh • ZigBee network layer has 3 device types: coordinator, router, and end device • Network layer deals with network discovery, formation, address allocation, message routing, network wide security • The APS layer uses the address tables to act as a filter http://www.tutorial-reports.com/wireless/zigbee/zigbee-characterstics.php

  19. Protocol • Coordinator • Forms network • Monitor/establish/maintains network • Chooses channel • Acts as the trust center • Can act as a router • Router • Finds and joins networks • Pushes broadcasts along • Maintains routes • Stores data for sleeping end devices http://www.zigbee.org/

  20. Protocol (Cont.) • End devices • Most often sleeping • Periodically wake to check if their parent nodes have anything for them • They perfom their tasks • Send data if necessary • Back to sleep • Orphaned nodes will find new parents

  21. Protocol (Cont.) • Fully reliable hand-shake data transfer protocol • Error detection and retransmission • ZigBee communicates similar to us • Collision avoidance • Cannot listen and talk at same time • Designed to minimize time the radio is on • Beaconing (asleep) • Non-beaconing (always on) https://docs.zigbee.org/zigbee-docs/dcn/06/docs-06-4513-00-00mg-zigbee-network-layer-technical-overview.pdf

  22. Comparisons

  23. When to choose ZigBee • Infrequent, small data packets • Many nodes • Timing is critical • 30 ms to add a new slave • 15 ms to wake up • Lots of devices http://www.wirelessdesignmag.com/ShowPR.aspx?PUBCODE=055&ACCT=0000100&ISSUE=1209&RELTYPE=blog&PRODCODE=000000&PRODLETT=ES&CommonCount=0

  24. Questions?

  25. Additional References • http://www.tutorial-reports.com/wireless/zigbee/zigbee-architecture.php • http://www.newcircuits.com/article.php?id=tut004 • http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAA&url=http%3A%2F%2Fwww.science.smith.edu%2F~jcardell%2FCourses%2FEGR390%2FReadings%2FZigBee-Tutorial.ppt&ei=S45vUL2MIpOY9QS164GADQ&usg=AFQjCNFTM-NOUd01KZbHOteELxu737imrQ • Zigbee.org • bwrc.eecs.berkeley.edu/people/grad_students/.../zigbee%20master.ppt

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