zigbee technology

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A SEMINAR REPORT ON THE ZIGBEE TECHNOLOGY

BYkarthik nch

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Why ZigBee?

• Standard in a fragmented market– Many proprietary solutions,

interoperability issues• Low Power consumption

– Users expect battery to last months to years!

• Low Cost• High density of nodes per network• Simple protocol, global implementation

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Low Data Rate Radio Devices

TV VCR DVD CD Remote

Mouse Keyboard Joystick Gamepad

Security HVAC Lighting Closures

PETs Gameboys Educational

Monitors Diagnostics Sensors

Industrial & Commercial

Consumer Electronics

Personal Healthcare

Monitors Sensors Automation Control

Toys &

Games

Home Automation

PC Peripherals

ZigBee -Target Markets

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ZigBee - General Characteristics• Data rates of 250 kbps and 20 kbps• Star topology, peer to peer possible • 255 devices per network• CSMA-CA channel access• Optional Guaranteed Time Slot• Fully handshaked protocol for transfer reliability• Low power (battery life multi-month to years)• Dual PHY (2.4GHz and 868/915 MHz)• Range: 10m nominal (1-100m based on

settings)• Location Aware: Yes, but optional

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FREQUENCY BANDS AND DATA RATES

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Silicon

PHY Layer

MAC Layer

Network Layer

ZigBeeStack

Application

Application Support (sub layer)

Application Layer

Cu

stom

er

Zig

Bee A

llian

ce

IEE

E

ZigBee Alliance - IEEE - Customer Relationship

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Virtual links

Network Topology

Network coordinator(FFD)

Network node (FFD)

Communications flow

IEEE node (RFD)

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Full function device

Reduced function device

Communications flow

Master/slave

PANCoordinator

IEEE 802.15.4 MAC OverviewStar Topology

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Full function device Communications flow

Point to point Cluster tree

IEEE 802.15.4 MAC OverviewPeer-Peer Topology

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NETWORK MODEL

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The Network Coordinator

• Transmits network beacons

• Sets up a network

• Manages network nodes

• Stores network node information

• Routes messages between paired nodes

• Receives constantly

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The Network Node

• Is generally battery powered

• 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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Supported Traffic Types

• Periodic data– Application defined rate(e.g: sensors)

• Intermittent– Basic communication(e.g: Light switch)

• Repetitive low latency data– Allocation of guaranteed time slots

(e.g: mouse)

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FRAME STRUCTURE

4 to 20 bytes are used for address information, which can include both source anddestination information. This leaves a maximum of 104 bytes of actual data.

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SUPER FRAME STRUCTURE

DIVIDED INTO 16 EQUAL SIZED SLOTS WITH BECON REQUESTS

MAY ALLOCATE UPTO 7 SLOTS FOR GTS (Guaranteed time slots) APPLICATION

Super frame structure allows GTS operation, its is initiated by coordinator

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NETWORK COMMUNICATIONS

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THE ZIGBEE ALLIANCE

CompXs

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ZigBee vs Bluetooth

Competition or Complementary?

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Bluetooth is BestFor :

• Ad-hoc networks between capable devices

• Handsfree audio• Screen graphics,

pictures…• File transfer

But ZigBee is Better

IF :

• The Network is static• Lots of devices• Infrequently used• Small Data Packets

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Air Interface:ZigBeeDSSS11 chips/ symbol62.5 K symbols/s4 Bits/ symbol

Peak Information Rate~128 Kbit/second

BluetoothFHSS1 M Symbol / second

Peak Information Rate ~720 Kbit/second

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Silicon

RF

Baseband

Link Controller

Vo

ice

Link Manager

Host Control Interface

L2CAP

TelephonyControlProtocol

Inte

rco

m

Hea

dse

t

Co

rdle

ss

Gro

up

Cal

l

RFCOMM(Serial Port)

OBEX

HOST

MODULE

BluetoothStack

Applications

vCar

d

vCal

vNo

te

vMes

sag

e

Dia

l-u

pN

etw

ork

ing

Fax ServiceDiscoveryProtocol

User Interface

Bluetooth Protocol Stack Size/Complexity

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Bluetooth:• New slave enumeration = >3s• Sleeping slave changing to active = 3s typically• Active slave channel access time = 2ms typically

ZigBee:• New slave enumeration = 30ms typically • Sleeping slave changing to active = 15ms typically• Active slave channel access time = 15ms typically

Timing Considerations

ZigBee protocol is optimized for timing critical applications

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Power Considerations

ZigBee

• 2+ years from ‘normal’ batteries

• Designed to optimize slave power requirements

Bluetooth

• Power model as a mobile phone (regular charging)

• Designed to maximize ad-hoc functionality

Application example of a lightswitch with respect to latency and power consumption …...

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ZigBee - Bluetooth - PLC ComparisonZigBee Bluetooth PLCCost (BOM) $5 $10 $15-$40

Power years hours N/A

Data Rate 250Kbps 720Kbps 3/10 Mbps

Complexity Low Medium High

Density 255 + 7 20-250

Interop Yes Yes No

Ease of Use Simple Moderate Restrictive

Latency 15ms >3s <15ms

Interference Low High High

Security High High Low

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Conclusion• ZigBee and Bluetooth are two solutions for two

application areas

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