alex wegznek chris griffis eel 4514 communications system
TRANSCRIPT
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ZigBeeAlex Wegznek
Chris GriffisEEL 4514 Communications System
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ZigBee Overview Purpose of ZigBee History of ZigBee How ZigBee works Pros & Cons Regulations & Standards Stack & Protocol Comparisons
Overview
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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
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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
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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
History
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ZigBee Alliance Formed in 1997 with 8 original promoter
companies and now has over 200 members Maintains and publishes the ZigBee standard
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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
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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
How does it work?
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How does it work? (Cont.)Low Power Low-Data Rate
• 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
• 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
http://www.digikey.com/us/en/techzone/energy-harvesting/resources/articles/Ultra-Low-Power-MCUs.html
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How does it work? (Cont.)
• National Institute of Standards and Technology (NIST) Advanced Encryption Standard (AES)
• AES-128 bit block cipher algorithm
• ZigBee both encrypts and authenticates packets
High Level of Security High Reliability
• 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
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How does it work? (Cont.)Direct-sequence spread spectrum (DSSS)
Binary Phase-Shift Keying (BPSK)
Offset Quadrature Phase-Shift Keying (OQPSK)
• 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
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Pros and 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)
Pros Cons
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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
Regulations & Standards
http://evolt-ektor.com/zigbee-as-a-wireless-network
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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
Regulations
http://www.intechopen.com/books/factory-automation/wireless-sensor-networks-for-networked-manufacturing-systems
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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
Standards
bwrc.eecs.berkeley.edu/people/grad_students/.../zigbee%20master.ppt
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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
Stack
http://www.tutorial-reports.com/wireless/zigbee/zigbee-architecture.php
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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
Stack (Cont.)
ZigBee Wireless Networking, Drew Gislason
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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
Topologies
http://www.tutorial-reports.com/wireless/zigbee/zigbee-characterstics.php
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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
Protocol
http://www.zigbee.org/
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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
Protocol (Cont.)
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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)
Protocol (Cont.)
https://docs.zigbee.org/zigbee-docs/dcn/06/docs-06-4513-00-00mg-zigbee-network-layer-technical-overview.pdf
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Comparisons
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Infrequent, small data packets Many nodes Timing is critical
◦ 30 ms to add a new slave◦ 15 ms to wake up
Lots of devices
When to choose ZigBee
http://www.wirelessdesignmag.com/ShowPR.aspx?PUBCODE=055&ACCT=0000100&ISSUE=1209&RELTYPE=blog&PRODCODE=000000&PRODLETT=ES&CommonCount=0
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Questions?
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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
Additional References