ZigBeeAlex Wegznek

Chris GriffisEEL 4514 Communications System

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

Overview

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

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

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

ZigBee Alliance Formed in 1997 with 8 original promoter

companies and now has over 200 members Maintains and publishes the ZigBee standard

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

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?

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

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

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

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

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

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

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

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

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

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

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/

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.)

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

Comparisons

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

Questions?

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