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ZIGBEE Technology

Zig-bee

Zig-bee is a specification for a suite of high level communication protocols using small, low-power

digital radios based on the IEEE 802.15.4,2006 standard for wireless personal area networks

(WPANs),such as wireless headphones connecting with cell phones via short-range radio. The

technology defined by the Zig-bee specification is intended to be simpler and less expensive than

other WPANs, such as Bluetooth. Zig-bee is targeted at radio-frequency (RF) applications that

require a low data rate, long battery life, and secure networking.

Zig-bee is a low data rate, two-way standard for home automation and data networks. The

standard specification for up to 254 nodes including one master, managed from a single remote

control. Real usage examples of Zig-bee includes home automation tasks such as turning lights on,

setting the homesecurity system, or starting the VCR. With Zig-bee all these tasks can be done

from anywhere in the home at the touch of a button. Zig-bee also allows for dial-in access via the

Internet for automation control.

Zig-bee protocol is optimized for very long battery life measured in months to years from

inexpensive, off-the-shelf non-rechargeable batteries, and can control lighting, air conditioning and

heating, smoke and fire alarms, and other security devices. The standard supports 2.4 GHz

(worldwide), 868 MHz (Europe) and 915 MHz (Americas) unlicensed radio bands with range up to

100 meters.

IEEE 802.15.4

IEEE 802.15.4 is a standard which specifies the physical layer and medium access control for low-

rate wireless personal area networks (LR-WPAN's).This standard was chartered to investigate a

low data rate solution with multi-month to multi-year battery life and very low complexity. It is

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operating in an unlicensed, international frequency band. Potential applications are sensors,

interactive toys, smart badges, remote controls, and home automation.

802.15.4 Is part of the 802.15 wireless personal-area network efforts at the IEEE? It is a simple

packet-based radio protocol aimed at very low-cost, battery-operated widgets and sensors (whose

batteries last years, not hours) that can intercommunicate and send low-bandwidth data to a

centralized device.

As of 2007, the current version of the standard is the 2006 revision. It is maintained by the IEEE

802.15 working group.

It is the basis for the Zig-bee specification, which further attempts to offer a complete networking

solution by developing the upper layers which are not covered by the standard.

802.15.4 Protocol

Data rates of 250 kbps with 10-100 meter range.

Two addressing modes; 16-bit short and 64-bit IEEE addressing.

CSMA-CA channel access.

Power management to ensure low power consumption.

16 channels in the 2.4GHz ISM band

Low duty cycle - Provides long battery life

Low latency

Support for multiple network topologies: Static, dynamic, star and mesh

Up to 65,000 nodes on a network

Comparison with other technologies

Zig-Bee enables broad-based deployment of wireless networks with low-cost, low-power

solutions. It provides the ability to run for years on inexpensive batteries for a host of monitoring

applications: Lighting controls, AMR (Automatic Meter Reading), smoke and CO detectors,

wireless telemetry, HVAC control, heating control, home security, Environmental controls and

shade controls, etc.

Zigbee Technology: Wireless Control that Simply Works Why is Zigbee needed?

There are a multitude of standards that address mid to high data rates for voice, PC LANs, video,

etc. However, up till now there hasnt been a wireless network standard that meets the unique

needs of sensors and control devices. Sensors and controls dont need high bandwidth but they

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do need low latency and very low energy consumption for long battery lives and for large

device arrays.

There are a multitude of proprietary wireless systems manufactured today to solve a multitude of

problems that also dont require high data rates but do require low cost and very low current

drain.

These proprietary systems were designed because there were no standards that met their

requirements. These legacy systems are creating significant interoperability problems with each

other and with newer technologies.

Zigbee/IEEE 802.15.4 - General Characteristics

Dual PHY (2.4GHz and 868/915 MHz)

Data rates of 250 kbps (@2.4 GHz), 40 kbps (@ 915 MHz), and 20 kbps (@868 MHz)

Optimized for low duty-cycle applications (

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Three devices in network

1. zigbee PAN coordinator (MASTER)

2. zigbee router (full function device)

3. zigbee end device(reduced function device)

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ZIGBEE PROTOCOL STACK

ZigBee Stack System

PHYSICAL LAYER

The physical layer was designed to accommodate the need for a low cost yet allowing for high

levels of integration. The use of direct sequence allows the analog circuitry to be very simple

and

The PHY provides two services: the PHY data service and PHY management service

interfacing to the physical layer management entity (PLME). The PHY data service enables the

transmission and reception of PHY protocol data units (PPDU) across the physical radio channel.

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The features of the PHY are activation and deactivation of the radio transceiver, energy

detection(ED), link quality indication (LQI), channel selection, clear channel assessment (CCA)

and transmitting as well as receiving packets across the physical medium.

The standard offers two PHY options based on the frequency band. Both are based on direct

sequence spread spectrum (DSSS). The data rate is 250kbps at 2.4GHz, 40kbps at 915MHz and

20kbps at 868MHz. The higher data rate at 2.4GHz is attributed to a higher-order modulation

scheme. Lower frequency provide longer range due to lower propagation losses. Low rate can be

translated into better sensitivity and larger coverage area. Higher rate means higher throughput,

Lower latency or lower duty cycle.

There is a single channel between 868 and 868.6MHz, 10 channels between 902.0 and

928.0MHz, and 16 channels between 2.4 and 2.4835GHz.

MAC LAYER

The media access control (MAC) layer was designed to allow multiple topologies without

complexity. The power management operation doesnt require multiple modes of operation.

The MAC allows a reduced functionality device (RFD) that neednt have flash nor large

amounts of ROM or RAM. The MAC was designed to handle large numbers of devices

without requiring them to be parked.

MAC Primitives:

MAC Data ServiceMCPS-DATA exchange data packets between MAC and PHYMCPS-PURGE purge an MSDU from the transaction queue

MAC Management ServiceMLME-ASSOCIATE/DISASSOCIATE network associationMLME-SYNC / SYNC-LOSS - device synchronization

MLME-SCAN - scan radio channelsMLME- COMM-STATUS communication status

MLME-GET / -SET retrieve/set MAC PIB parameters

MLME-START / BEACON-NOTIFY beacon managementMLME-POLL - beaconless synchronization

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MLME-GTS - GTS management

MLME-RESET request for MLME to perform reset

MLME-ORPHAN - orphan device managementMLME-RX-ENABLE - enabling/disabling of radio system

BEACON ENABLED NETWORK

Network Layer

The responsibilities of the Zigbee NWK layer include:

Starting a network: The ability to successfully establish a new network.

Joining and leaving a network: The ability to gain membership (join) or relinquish membership

(leave) a network.

Configuring a new device: The ability to sufficiently configure the stack for operation as

required.

Addressing: The ability of a Zigbee coordinator to assign addresses to devices joining the

network.

Synchronization within a network: The ability for a device to achieve synchronization with

another device either through tracking beacons or by polling.

Security: applying security to outgoing frames and removing security to terminating frames

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Routing: routing frames to their intended destinations.

Network Routing Overview

Perhaps the most straightforward way to think of the Zigbee routing algorithm is as a hierarchical

routing strategy with table-driven optimizations applied where possible.

NWK uses an algorithm that allows stack implementers and application developers to balance unit

cost, battery drain, and complexity in producing Zigbee solutions to meet the specific cost-

performance profile of their application.

Started with the well-studied public-domain algorithm AODV and Motorolas Cluster-Tree

algorithm and folding in ideas from Ember Corporations GRAd.

Network Summary

The network layer builds upon the IEEE 802.15.4 MACs features to allow extensibility of

coverage. Additional clusters can be added; networks can be consolidated or split up.

Application layer

The Zigbee application layer consists of the APS sub-layer, the ZDO and the manufacturer-

defined application objects. The responsibilities of the APS sub-layer include maintaining tables

for binding, which is the ability to match two devices together based on their services and their

needs, and forwarding messages between bound devices. Another responsibility of the APS sub-

layer is discovery, which is the ability to determine which other devices are operating in the

personal operating space of a device. The responsibilities of the ZDO include defining the role of

the device within the network (e.g., Zigbee coordinator or end device), initiating and/or responding

to binding requests and establishing a secure relationship between network devices. The

manufacturer-defined application objects implement the actual applications according to the

Zigbee-defined application descriptions

Zigbee Device Object

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

Initiates and/or responds to binding requests

Establishes a secure relationship between network devices selecting one of ZigBees security

methods such as public key, symmetric key, etc.

Application Support Layer:

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This layer provides the following services:

Discovery: The ability to determine which other devices are operating in the personal

operating space of a device.

Binding: The ability to match two or more devices together based on their services and their

needs and forwarding messages between bound devices

APPLICATIONS OF ZIGBEE TECHNOLOGY

Typical application areas include

Home Entertainment and Control Smart lighting, advanced temperature control, safetyand security, movies and music

Home Awareness Water sensors, power sensors, energy monitoring, smoke and fire

detectors, smart appliances and access sensors

Mobile Services m-payment, m-monitoring and control, m-security and access control,

m-healthcare and tele-assist

Commercial Building Energy monitoring, HVAC, lighting, access control

Industrial Plant Process control, asset management, environmental management,

energy management, industrial device control, machine-to-machine (M2M) communication

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Zigbee vs. Bluetooth

Zigbee looks rather like Bluetooth but is simpler, has a lower data rate and spends most of its time

snoozing. This characteristic means that a node on a Zigbee network should be able to run for six

months to two years on just two AA batteries. The operational range of Zigbee is 10-75mcompared to 10m for Bluetooth (without a power amplifier).

ZigBee sits below Bluetooth in terms of data rate. The data rate of Zigbee is 250kbps at 2.4GHz,

40kbps at 915MHz and 20kbps at 868MHz whereas that of Bluetooth is 1Mbps.

ZigBee uses a basic master-slave configuration suited to static star networks of many infrequently

used devices that talk via small data packets. It allows up to 254 nodes.

Bluetooths protocol is more complex since it is geared towards handling voice, images and file

transfers in ad hoc networks. Bluetooth devices can support scatter nets of multiple smaller non-

synchronized networks (piconets). It only allows up to 8 slave nodes in a basic master-slave

piconet set-up.

When ZigBee node is powered down, it can wake up and get a packet in around 15 msec whereas

Bluetooth device would take around 3sec to wake up and respond.

ZIGBEE MODULE:

Comparison with other technologies

StandardZigBee

802.15.4

Wi-Fi

802.11b

Bluetooth

802.15.1

Transmission Range (meters) 1 100* 1 100 1 10

Battery Life (days) 100 1,000 0.5 5.0 1 - 7

Network Size (# of nodes) > 64,000 32 7

Application Monitoring & Control Web, Email, Video Cable Replacement

Stack Size (KB) 4 32 1,000 250

Throughput kb/s) 20 250 11,000 720

Zigbee-compliant products operate in unlicensed bands worldwide, including 2.4GHz (global), 902

to 928MHz (Americas), and 868MHz (Europe). Raw data throughput rates of 250Kbps can be

achieved at 2.4GHz (16 channels), 40Kbps at 915MHz (10 channels), and 20Kbps at 868MHz (1

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channel). The transmission distance is expected to range from 10 to 100m, depending on power

output and environmental characteristics. Like Wi-Fi, Zigbee uses direct-sequence spread spectrum

in the 2.4GHz band, with offset-quadrature phase-shift keying modulation. Channel width is 2MHz

with 5MHz channel spacing. The 868 and 900MHz bands also use direct-sequence spread

spectrum but with binary-phase-shift keying modulation.

ZIGBEE MODULE SPECIFICATION:

Performance: XBee

Power output:: 1mW (+0 dBm) North American & International version

Indoor/Urban range: Up to 100 ft (30 m)

Outdoor/RF line-of-sight range: Up to 300 ft (90 m)

RF data rate: 250 Kbps

Interface data rate: Up to 115.2 Kbps

Operating frequency: 2.4 GHz

Receiver sensitivity: -92 dBm

Performance: XBee-PRO

Power output:

63 mW (+18 dBm) North American version

10 mW (+10 dBm) International version2 Indoor/Urban range: Up to 300 ft (90 m)

3 Outdoor/RF line-of-sight range: Up to 1 mile (1.6 km) RF LOS

4 RF data rate: 250 Kbps

5 Interface data rate: Up to 115.2 Kbps

6 Operating frequency: 2.4 GHz

7 Receiver sensitivity: -100 dBm (all variants)

Networking

Spread Spectrum type: DSSS (Direct Sequence Spread Spectrum)

Networking topology: Point-to-point, point-to-multipoint, & peer-to-peer

Error handling: Retries & acknowledgements Filtration options: PAN ID, Channel, and 64-bit addresses

Channel capacity:

XBee: 16 Channels

XBee-PRO: 12 Channels

2 Addressing: 65,000 network addresses available for each channel

Power

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Supply voltage:

XBee: 2.8 - 3.4 VDC

XBee-PRO: 2.8 - 3.4 VDC

XBee Footprint Recommendation: 3.0 - 3.4 VDC

2 Transmit current:

XBee: 45 mA (@ 3.3 V) boost mode 35 mA (@ 3.3 V) normal mode

XBee-PRO: 215 mA (@ 3.3 V)

3 Receive current:

XBee: 50 mA (@ 3.3 V)

XBee-PRO: 55 mA (@ 3.3 V)

4 Power-down sleep current:

XBee: