Wireless Communication using Zigbee.pdf

8/13/2019 Wireless Communication using Zigbee.pdf

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Wireless Communication usingZigbee

Presented by:Ashish Ranjan

200101244


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Topics

Wireless Communication Market Why Zigbee

Technology Application example


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Wireless Standards

GSM 3G

Wireless LANs Bluetooth


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Feature(s) IEEE 802.11b Bluetooth ZigBeePower Profile Hours Days YearsComplexity Very Complex Complex Simple

Nodes/Master 32 7 64000

Latency Enumeration upto 3 seconds Enumeration upto 10

secondsEnumeration 30ms

Range 100 m 10m 70m-300mExtendability Roaming possible No YES

Data Rate 11Mbps 1Mbps 250Kbps

Security Authentication Service SetID (SSID)

64 bit, 128 bit 128 bit AES and ApplicationLayer user defined

HVAC control in building automation

Comparison of key features ofcomplementary protocols


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Why ZigBee? Reliable

Supports large number of nodes Easy to deploy

Very long battery life Secure Low cost Can be used globally


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Even mains powered equipment needs to be conscious ofenergy. Consider a future home with 100 wirelesscontrol/sensor devices,

Case 1: 802.11 Rx power is 667 mW (always on)@ 100devices/home & 50,000 homes/city = 3.33 megawatts

Case 2: 802.15.4 Rx power is 30 mW (always on)@ 100devices/home & 50,000 homes/city = 150 kilowatts

Case 3: 802.15.4 power cycled at .1% (typical duty cycle)

= 150 watts.Zigbee devices will be more ecological than its predecessorssaving megawatts at it full deployment.


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Advantages of ZigBee over proprietarysolutions?

Product interoperability Vendor independence Increased product innovation as a result of industry

standardization A common platform is more cost effective than

creating a new proprietary solution from scratchevery time

Companies can focus their energies on finding andserving customers


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What You Should Know about the

Wireless that simply works


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Development of the Standard ZigBee Alliance

50+ companies: semiconductor mfrs,IP providers, OEMs, etc. Defining upper layers of protocol

stack: from network to application,including application profiles

First profiles published mid 2003 IEEE 802.15.4 Working Group

Defining lower layers of protocolstack: MAC and PHY scheduled forrelease in April

SILICON

ZIGBEE STACK

APPLICATION Customer

IEEE802.15.4

ZigBeeAlliance


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Frequencies and Data Rates

BAND COVERAGE DATA RATE # OF CHANNEL(S)

2.4 GHz ISM Worldwide 250 kbps 16

868 MHz Europe 20 kbps 1

915 MHz ISM Americas 40 kbps 10


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Stack Reference Model

IEEE 802.15.4 PHY

IEEE 802.15.4 MAC (CPS)

Zigbee NWK

MAC (SSCS)802.2 LLC

IP

API UDP

ZA1 ZA2 ZA n IA1 IA n

Transmission & reception on thephysical radio channel

Channel access, PAN maintenance,reliable data transport

Topology management, MACmanagement, routing, discovery

protocol, security management

Application interface designed usinggeneral profile

End developer applications,designed using application profiles


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Protocol Stack Features Microcontroller utilized

Full protocol stack


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IEEE 802.15.4 Standard


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IEEE 802.15.4 Basics

802.15.4 is a simple packet data protocol for lightweight wireless networks Channel Access is via Carrier Sense Multiple Access with collision

avoidance and optional time slotting Message acknowledgement and an optional beacon structure Multi-level security

Three bands, 27 channels specified 2.4 GHz: 16 channels, 250 kbps 868.3 MHz : 1 channel, 20 kbps 902-928 MHz: 10 channels, 40 kbps

Works well for Long battery life, selectable latency for controllers, sensors, remote

monitoring and portable electronics Configured for maximum battery life, has the potential to last as long

as the shelf life of most batteries


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Introduction to the IEEE802.15.4 Standard

IEEE 802.15.4 standard released May 2003 Semiconductor manufacturers

Sampling Transceiver ICs and platform hardware/software toAlpha Customers now

Users of the technology Defining application profiles for the first products, an effort

organized by the ZigBee Alliance


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IEEE 802.15.4 standard

Includes layers up to and including Link Layer Control LLC is standardized in 802.1 Supports multiple network topologies including Star, Cluster Tree and

Mesh

IEEE 802.15.4 MAC

IEEE 802.15.4 LLC IEEE 802.2LLC, Type I

IEEE 802.15.42400 MHz PHY

IEEE 802.15.4868/915 MHz PHY

Data Link Controller (DLC)

Networking App Layer (NWK)

ZigBee Application Framework Features of the MAC:Association/dissociation, ACK,frame delivery, channel accessmechanism, frame validation,guaranteed time slot management,

beacon management, channel scan Low complexity: 26 primitives

versus 131 primitives for802.15.1 (Bluetooth)


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IEEE 802.15.4 MAC Overview Employs 64-bit IEEE & 16-bit short addresses

Ultimate network size can reach 2 64 nodes (more than well probably need) Using local addressing, simple networks of more than 65,000 (2^16) nodes can be configured,

with reduced address overhead

Three devices specified Network Coordinator Full Function Device (FFD) Reduced Function Device (RFD)

Simple frame structure Reliable delivery of data Association/disassociation AES-128 security CSMA-CA channel access Optional superframe structure with beacons GTS mechanism


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IEEE 802.15.4 Device Types

Three device types Network Coordinator

Maintains overall network knowledge; most sophisticated of the three types; mostmemory and computing power

Full Function Device Carries full 802.15.4 functionality and all features specified by the standard

Additional memory, computing power make it ideal for a network router function Could also be used in network edge devices (where the network touches the real world)

Reduced Function Device Carriers limited (as specified by the standard) functionality to control cost and complexity General usage will be in network edge devices

All of these devices can be no more complicated than the transceiver, a simple8-bit MCU and a pair of AAA batteries!


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Data Frame format

One of two most basic and important structures in 15.4

Provides up to 104 byte data payload capacity Data sequence numbering to ensure that all packets are tracked Robust frame structure improves reception in difficult conditions Frame Check Sequence (FCS) ensures that packets received are without error


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Acknowledgement Frame Format

The other most important structure for 15.4

Provides active feedback from receiver to sender that packet wasreceived without error


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MAC Command Frame format

Mechanism for remote control/configuration of clientnodes

Allows a centralized network manager to configureindividual clients no matter how large the network


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Beacon Frame format

Beacons add a new level of functionality to a network

Client devices can wake up only when a beacon is to be broadcast, listen for theiraddress, and if not heard, return to sleep

Beacons are important for mesh and cluster tree networks to keep all of the nodessynchronized without requiring nodes to consume precious battery energy listening forlong periods of time


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MAC Options Two channel access mechanisms

Non-beacon network Standard ALOHA CSMA-CA communications Positive acknowledgement for successfully received packets

Beacon-enabled network Superframe structure

For dedicated bandwidth and low latency Set up by network coordinator to transmit beacons at predetermined intervals

15ms to 252sec (15.38ms*2n where 0 n 14) 16 equal-width time slots between beacons Channel access in each time slot is contention free

Three security levels specified

None Access control lists Symmetric key employing AES-128


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ISM Band Interference and Coexistence

Potential for interference exists in every ISM band, not just 2.4GHz

IEEE 802.11 and 802.15.2 committees are addressing coexistenceissues

ZigBee/802.15.4 Protocol is very robust Clear channel checking before transmission

Backoff and retry if no acknowledgement received Duty cycle of a ZigBee-compliant device is usually extremely low Its the cockroach that survives the nuclear war

Waits for an opening in otherwise busy RF spectrum

Waits for acknowledgements to verify packet reception at other end


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PHY Performance

802.15.4 has excellentperformance in lowSNR environments


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Reliability: Mesh Networking

ZigBee End Device (RFD or FFD)

ZigBee Router (FFD)

ZigBee Coordinator (FFD)

Mesh Link

Star Link


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Topology Models

PAN coordinator Full Function Device

Reduced Function Device

Star

Mesh

Cluster Tree


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The Zigbee Network Coordinator

Sets up a network Transmits network beacons Manages network nodes Stores network node information Routes messages between paired nodes

Typically operates in the receive state


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The Zigbee Network Node

Designed for battery powered or high energysavings Searches for available networks Transfers data from its application as necessary Determines whether data is pending

Requests data from the network coordinator Can sleep for extended periods


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Network Layer

Starting a network: Joining and leaving a network . Configuring a new device

Addressing Synchronization within a network Security: applying security to outgoing frames

and removing security to terminating frames Routing: routing frames to their intendeddestinations.


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Application Layer

The Zigbee application layer consists of theAPS sub-layer and ZDO.


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Zigbee Device Object

Defines the role of the device within the network (e.g., ZigBeecoordinator or end device)

Initiates and/or responds to binding requests

Establishes a secure relationship between network devices selecting oneof Zigbee security methods such as public key, symmetric key, etc.

Application Support Layer

Discovery: The ability to determine which other devices are operatingin the personal operating space of a device.

Binding: The ability to match two or more devices together based ontheir services and their needs and forwarding messages between bounddevices


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ZigBee and Bluetooth

Competitive or Complementary?


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ZigBee and Bluetooth ZigBee

Smaller packets overlarge network

Mostly Static networks

with many, infrequentlyused devices

Home automation, toys,remote controls, etc.

Bluetooth

Larger packets over smallnetwork

Ad-hoc networks File transfer

Screen graphics, pictures, hands-free audio, Mobile phones,headsets, PDAs, etc.

O p t i m i z e d f o r d i f f e r e n t a p p l i c a t i o n s


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Bluetooth is a cablereplacement for itemslike Phones, Laptop

Computers, Headsets Bluetooth expects

regular charging

Target is to use


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ZigBee is better for devicesWhere the battery is rarelyreplaced Targets are :

Tiny fraction of host power New opportunities where wireless

not yet used

ZigBee and Bluetooth d d r e s s D i f f e r e n t N e e d s


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Air interface

ZigBee DSSS- 11 chips/ symbol 62.5 K symbols/s 4 Bits/ symbol Peak Information Rate

~128 Kbit/second

Bluetooth FHSS 1 M Symbol / second

Peak Information Rate~720 Kbit / second



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Silicon

PHY Layer

MAC Layer MAC Layer

Data Link Layer

Network Layer

ZigBeeStack Appl ication

Application Interface

Application

Protocol Stack Comparison

Silicon

RFBaseband

Link Controller

V o

i c e

Link Manager Host Control Interface

L2CAP

TelephonyControl

Protocol

I n t e r c o m

H e a

d s e

t

C o r d

l e s s

G r o

u p

C a

l l

RFCOMM(Serial Port )

OBEX

BluetoothStack

Applications

v C

a r d

v C a

l

v N

o t e

v M e s s a g e

D i a l - u p

N e

t w o r k

i n g

Fax ServiceDiscoveryProtocol

User Interface

Zigbee Bluetooth



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Bluetooth: Network join time = >3s Sleeping slave changing to active = 3s typically Active slave channel access time = 2ms typically

ZigBee: Network join time = 30ms typically Sleeping slave changing to active = 15ms typically Active slave channel access time = 15ms typically

T i m i n g C o n s i d e r a t i o n s

ZigBee protocol is optimized fortiming critical applications



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Initial EnumerationCoordinator Coordinator

ZigBee Bluetooth


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ZigBee and BluetoothBluetooth ZigBee

AIR INTERFACE FHSS DSSS

PROTOCOL STACK 250 kb 28 kb

BATTERY rechargeable non-rechargeable

DEVICES/NETWORK 8 65000

LINK RATE 1 Mbps 250 kbps

RANGE ~10 meters (w/o pa) ~30 meters

C o m p a r i s o n O v e r v i e w


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An Application Example

Wireless Light switch Easy for Builders to Install A Bluetooth Implementation

would either : keep a counter running so that

it could predict which hopfrequency the light would have

reached or use the inquiry procedure to

find the light each time theswitch was operated.

Battery Life & Latency in a Light Switch


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Light switch using Bluetooth Option 1: use counter to predict hop frequency reached

by light

The two devices must stay within 60 us (~1/10 of a hop) With 30ppm crystals, devices need to communicate once a

second to track each other's clocks. Assume this could be improved by a factor of 100 then devices

would need to communicate once every 100 seconds tomaintain synchronization. => 900 communications / day with no information transfer +

perhaps 4 communications on demand

99.5% Battery Power wasted


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Light switch using Bluetooth Option 2: Inquiry procedure to locate light

each time switch is operated Bluetooth 1.1 = up to 10 seconds typical Bluetooth 1.2 = several seconds even if

optimized

Unacceptable latency


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Conclusion

ZigBee targets applications not addressable byBluetooth or any other wireless standard

ZigBee and Bluetooth complement for a broadersolution



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References

http://www.zigbee.org/imwp/idms/popups/pop_download.asp?contentID=812

http://www.embedded.com/showArticle.jhtml?articleID=18902431

http://www.zigbee.org/imwp/idms/popups/pop_download.asp?contentID=805


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Thank you

Wireless Communication using Zigbee.pdf

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