ACKNOWLEDGEMENTS

The Satisfaction and the euphoria that accompany the successful completion of any

task would be incomplete without the mention of the people who made it possible

and whose constant guidance and encouragement crowned our efforts with success.

We consider at our privilege to express our gratitude to the following people for

their help, encouragement and intellectual influence during the course of the

semester.

We are grateful to our institution Jawaharlal Nehru National College of

Engineering. With its very ideals and inspirations for having provided us with the

facilities, which has made our work a great success.

We would like to express our gratitude to Prof. Dr. Srinivasa Rao Kunte,

principal J.N.N.C.E for providing us a congenial environment and surrounding to

work in.

We sincerely regard our thanks to Mr H.K Harisha, Head of the Department,

Electronics and communication Engineering, J.N.N.C.E, whose support and

guidance was invaluable.

And finally our heartfelt gratitude to project coordinators Dr.S.V.

Sathyanarayana, Professor, Dept of Electronics and Communication

Engineering, J.N.N.C.E, for their support, advice and continuous encouragement

through out the period of our research.

1

CONTENTS

Abstract……………………………………………………4

1. Chapter 1-Introduction……...…………………………...5

1.1 Zigbee alliance………...………………………………………...6

2. Chapter 2-802.15.4/ZigBee……………………………...….8

2.1Phy and MAC layers……………………………………………9

2.2CSMA…………………………………………………………...9

3. Chapter 3- ZigBee……………………………………………10

3.1IEE 802.15.4 standard…………………………………………..11

3.2ZigBee standard…………………………………………………13

3.2.1Power consumption…………………………………………...13

3.2.2Applications profiles……………………………………….....14

3.3Suitable areas for ZigBee…………………………………….....14

4. Chapter 4-Technical Specifications………………….....17

4.1IEEE 802.15.4 Specification…………………………………....17

4.1.1PHY Layer..………………………………………………….17

4.1.2 MAC Layer………………………………………………......18

2

4.1.3 Network Topologies…………………………………………18

4.1.4IEE 802.15.4 Performance……………………………...........20

4.2ZigBee Specification……………………………………….......21

4.2.1Network Layer……………………………………………….21

4.2.2Application Layer……………………………………………22

5. Chapter 5-Applications of ZigBee………………………..24

6. Chapter 6-Zigbee vs. other wireless standards…….........29

6.1Zigbee vs. BlueeTooth……………………………………........29

7. Chapter 7- Advantages of Zigbee…………………….......30

8. Chapter 8-Conclusion………………………………….......31

9. References……………………………………………………32

3

ABSTRACT

ZigBee-Wireless Technology and its Applications

Preface ZigBee is one of the newest technologies enabling Wireless Personal Area Networks

(WPAN). See how the specification characterized by low data rates and very low power

consumption is revolutionizing networking of different environment.

ZigBee is an established set of specifications for wireless personal area networking (WPAN), i.e.

digital radio connections between computers and related devices.

WPAN Low Rate or ZigBee provides specifications for devices that have low data rates,

consume very low power and are thus characterized by long battery life. ZigBee makes possible

completely networked environment where all devices are able to communicate and be controlled

by a single unit.

ZigBee is one of the global standards of communication protocol formulated by the relevant task

force under the IEEE 802.15 working group. The fourth in the series, WPAN Low Rate/ZigBee

is the newest and provides specifications for devices that have low data rates, consume very low

power and are thus characterized by long battery life. Other standards like Bluetooth and IrDA

address high data rate applications such as voice, video and LAN communications.

The ZigBee Alliance has been set up as “an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard

4

Chapter 1: Introduction to ZigBee

Technologists have never had trouble coming up with potential applications for wireless sensors.

In a home security system, for example, wireless sensors would be much easier to install than

sensors that need wiring. The same is true in industrial environments, where wiring typically

accounts for 80% of the cost of sensor installations. And then there are applications for sensors

where wiring isn't practical or even possible.

The problem, though, is that most wireless sensors use too much power, which means that their

batteries either have to be very large or get changed far too often. Add to that some skepticism

about the reliability of sensor data that's sent through the air, and wireless sensors simply haven't

looked very appealing.

A low-power wireless technology called ZigBee is rewriting the wireless sensor equation,

however. A secure network technology that rides on top of the recently ratified IEEE 802.15.4

radio standard (Figure 1), ZigBee promises to put wireless sensors in everything from factory

automation systems to home security systems to consumer electronics.

This means that the devices and the control unit would all need a common standard to enable

intelligible communication. ZigBee is such a standard for embedded application software and

has been ratified in late 2004 under IEEE 802.15.4 Wireless Networking Standards.

ZigBee is an established set of specifications for wireless personal area networking (WPAN),

i.e., digital radio connections between computers and related devices. This kind of network

eliminates use of physical data buses like USB and Ethernet cables. The devices could include

telephones, hand-held digital assistants, sensors and controls located within a few meters of each

other.

ZigBee is one of the global standards of communication protocol formulated by the relevant task

force under the IEEE 802.15 working group. The fourth in the seriesWPAN Low Rate/ZigBee is

the newest and provides specifications for devices that have low data rates, consume very low

5

power and are thus characterized by long battery life. Other standards like Bluetooth and IrDA

address high data rate applications such as voice, video and LAN communications.

The ZigBee Alliance has been set up as “an association of companies working together to

enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control

products based on an open global standard.”

Figure 1:  ZigBee adds network, security, and application-

services layers to the PHY and MAC layers of the IEEE

811.15.4 radio

Although no formal specification for ZigBee yet exists (approval by the ZigBee Alliance, a trade

group, should come late this year), the outlook for ZigBee appears bright. Technology research

firm In-Stat/MDR, in what it calls a "cautious aggressive" forecast, predicts that sales of

802.15.4 nodes and chipsets will increase from essentially some millions today to 165 million

units by 2010. Not all of these units will be coupled with ZigBee, but most probably will be.

Research firm ON World predicts shipments of 465 million wireless sensor RF modules by

2010, with 77% of them being ZigBee-related.

In a sense, ZigBee's bright future is largely due to its low data rates—20 kbps to 250 kbps,

depending on the frequency band used (Figure 2)—compared to a nominal 1 Mbps for Bluetooth

and 54 Mbps for Wi-Fi's 802.11g technology. But ZigBee won't be sending email and large

documents, as Wi-Fi does, or documents and audio, as Bluetooth does. For sending sensor

6

readings, which are typically a few tens of bytes, high bandwidth isn't necessary, and ZigBee's

low bandwidth helps it fulfill its goals of low power, low cost, and robustness.

Figure 2:  ZigBee's data rates range from 20 kbps to 250 kbps,

depending on the frequency used

Because of ZigBee applications' low bandwidth requirements, a ZigBee node can sleep most of

the time, thus saving battery power, and then wake up, send data quickly, and go back to sleep.

A big part of ZigBee's power savings come from the radio technology of 802.15.4, which itself

was designed for low power. 802.15.4 uses DSSS (direct-sequence spread spectrum) technology,

for example, because the alternative FHSS (frequency-hopping spread spectrum) would have

used too much power just in keeping its frequency hops synchronized.

ZigBee nodes, using 802.15.4, can communicate in any of several different ways, however, and

some ways use more power than others.

A ZigBee network node can consume extra power, for example, if it tries to keep its

transmissions from overlapping with other nodes' transmissions or with transmissions from other

radio sources. The 802.15.4 radio used by ZigBee implements CSMA/CA (carrier sense multiple

access collision avoidance) technology, and a ZigBee node that uses CSMA/CA is essentially

taking a listen-before-talk approach to see if any radio traffic is already underway.

Another ZigBee and 802.15.4 communications option is the beacon mode, in which normally

sleeping network slave nodes wake up periodically to receive a synchronizing "beacon" from the

network's control node. But listening for a beacon wastes power, too, particularly because timing

uncertainties force nodes to turn on early to avoid missing a beacon.

7

Chapter 2: 802.15.4/ZigBee

Although Bluetooth's power requirements are much lower than that of 802.11b, it is still assumed

that Bluetooth-enabled devices will be recharged every few days. The IEEE 802.15.4 standard

defines the PHY and MAC for very low-power, low-duty network links [IEEE802.15.4]. This

standard is intended for deployment on long-lived systems with low data rate requirements,

where devices must be able to operate autonomously for months or even years without

recharging the battery.

2.1 802.15.4 PHY and MAC Layers

802.15.4 offers uses twenty-seven channels spread across three different areas of license-exempt

spectrum. One channel is available at 868 MHz. Ten channels are available from 902 MHz to

928 MHz,with a separation of 2 MHz between channels. Sixteen channels are available from 2.4

GHz to 2.4835GHz, with a channel separation of 5 MHz. Like Bluetooth, these channels are

used to avoid interference with neighboring PANs: each PAN uses a single unique channel.

However, unlike Bluetooth, devices do not hop across frequencies during the network's lifetime.

802.15.4 radios are required to transmit at aminimum of 1 mW, and must maintain a BER of less

than 1%. Depending on the power output,802.15.4 offers a range of approximately 1m to 100m,

which is comparable to Bluetooth.

Direct-sequence spread spectrum modulation is used to minimize data loss due to noise and

interference, though the exact parameters differ from spectrum to spectrum. The channels in the

2.4 GHz spectrum use a combination of 32-chip codes and QPSK modulation; these channels

have a signal rate of 2.0Mchips/s and a data rate of 250 kbps. The other channels use BPSK

modulation with 15-chip codes. The868 MHz channel has a signal rate of 300 kchips/sec and a

data rate of 20 kbps, whereas the 900 MHz channels have a signal rate of 600 kchips/s and a data

rate of 40 kbps.

802.15.4 devices can be divided into two categories, which determine the topology and media

access used by the network. Full-function devices (FFDs) can communicate directly with any

other devices in the network. In contrast, reduced-function devices (RFDs) can only

communicate with FFDs. The802.15.4 standard allows networks to form either a one-hop star

8

topology, or a multi-hop peer-to-peer topology; the former is most appropriate in networks with

few FFDs, whereas the latter is more resilient to node failure when many FFDs are available.

Though 802.15.4 defines the allowed topologies, it does not define the layers that actually

support them: routing within these topologies is the responsibility of layers above those defined

by IEEE.

One FFD can optionally act as a coordinator node, which regulates media access. This node

periodically sends beacons that identify the PAN it is coordinating. The interval between these

beacons is constant but user-selectable: any multiple of 15.38 ms may separate these beacons, up

to 252s. Two beacons forma superframe that is partitioned into 16 equally-sized timeslots, as

shown in Figure 2. Members of the PAN may request guaranteed time slots (GTSs) in the

contention free period at the end of the superframe. All other slots form the contention access

period, which is accessed using a CSMA-CA

scheme. Since the coordinator node must be relatively powerful, it may not be practical to deploy

one inall networks; in this case, all media access is regulated using a CSMA/CA scheme, and the

media isalways subject to contention.

Figure 2: Example 802.15.4 Superframe

2.2 : Carrier Sense Multiple Access

CSMA/CA is a modification of pure Carrier Sense Multiple Access (CSMA). Collision

avoidance is used to improve the performance of CSMA by attempting to be "less greedy" on the

channel. If the channel is sensed busy before transmission then the transmission is deferred for a

"random" interval. This reduces the probability of collisions on the channel.

CSMA/CA is used where CSMA/CD cannot be implemented due to the nature of the channel.

CSMA/CA is used in 802.11 based wireless LANs. One of the problems of wireless LANs is

that it is not possible to listen while sending, therefore collision detection is not possible.

9

Chapter 3 : ZigBee

ZigBee is aimed at applications where low power consumption is desired and low

data rates are acceptable. The standard is primarily focused on self organizing mesh networks.

ZigBee intends to be a complement to existing wireless standards and not a competitor.

ZigBee is primarily intended to be used for home automation, security systems, heating and

ventilation control, remote sensing and data collection. In many of these applications the price of

each device is a very important concern. By using a simple communications protocol, ZigBee

devices can use inexpensive transceivers and microcontrollers. The low power consumption

allows battery powered devices to run for a year or more on a regular alkaline battery.

ZigBee aims to be used in segments where most existing wireless standards are not suitable. Cost

and battery consumption is problem for WLAN while Bluetooth’s main drawback is the small

network size. ZigBee’s technological weakness is the low data rate. However the typical ZigBee

application only require simple status messages and control commands. Table 3.1 gives a brief

introduction to ZigBee by comparing it to other wireless technologies.

ZigBee is aimed at applications where low power consumption is desired and low data rates are

acceptable. The standard is primarily focused on self organizing mesh networks. ZigBee intends

to be a complement to existing wireless standards and not a competitor.

ZigBee is primarily intended to be used for home automation, security systems, heating and

ventilation control, remote sensing and data collection. In many of these applications the price of

each device is a very important concern. By using a simple communications protocol, ZigBee

devices can use inexpensive transceivers and microcontrollers. The low power consumption

allows battery powered devices to run for a year or more on a regular alkaline battery. ZigBee

aims to be used in segments where most existing wireless standards are not suitable. Cost and

battery consumption is a problem for WLAN while Bluetooth’s main drawback is the small

network size. ZigBee’s technological weakness is the low data rate.

10

However the typical ZigBee application only require simple status messages and control

commands. Table 3.1 gives a brief introduction to ZigBee

by comparing it to other wireless technologies.

3.1 The IEEE 802.15.4 standardThe ZigBee standard only defines high level network behavior. The lower layers

are defined by the IEEE 802.15.4[5] standard, as illustrated in Figure 3.1. IEEE

802.15.4 is an open communication standard suitable for low data rate, wireless

personal area networks (LR-WPAN). Devices that operate in such networks are

often battery powered and have the following properties:

• Low power consumption

• Low data rate

• Low hardware costs

• Low sensitivity of interference

• Short to medium range communications

The 802.15.4 standard defines the Physical (PHY) and Medium Access Control

(MAC) network layers. The MAC layer is part of the Open Standards Interconnect

(OSI)1 link layer. Part of the link layer is also the service specific convergence sublayer (SSCS)

which provides a common interface between the logical link layer (LLC) and the lower layers.

11

The PHY layer supports the frequencies and1The OSI model has 7 layers: physical, data link,

network, transport, session, presentation and application. The interface between each layer is

predefined, as long as this does not change, each layer can be improved individually without

affecting the others.

12

3.2 The ZigBee standard

The ZigBee portion of the standard defines the Network (NWK) and Application(APL) layers[6]

[7]. The most important function in the NWK layer is routing. Routing means that ZigBee

devices can communicate indirectly, this is one thing that makes it possible to create very large

networks. By allowing other set up than star topology, ZigBee permits the network to spread

beyond the range of the coordinator. The supported topologies: star, cluster tree and mesh are

illustrated in Figure 3.2.

3.2.1 Power consumption

Although ZigBee supports several network topologies, non-beaconed mesh networks

are expected to be the most common in larger installations. In the mesh topology there are many

possible routes for end to end communication, making the network less vulnerable to effects of

individual nodes failing. In this configuration, coordinator and routers have their transceivers

constantly on. Since there are no beacons to listen for, end devices can set their own duty cycle,

waking up from power down mode only when they transmit or request data.

The advantage of this configuration is very low power consumption for end devices, but this

comes at the expense of higher power consumption for routers and coordinators. Realistically

non-beaconed mesh networks need mains powered routers and coordinators to function

properly.The Application layer contains support subsystems that simplifies application

13

development.The Application Framework (AF) provides an interface for generating standardized

application level messages. The ZigBee Device Object (ZDO) is a built in helper application that

reduces the need to deal with the details of device and service discovery. The Application layer

defines the data and message types used to create a ZigBee profile.

3.2.2 Application profiles

To support device and service discovery, ZigBee has standardized a way of describing

Device capabilities. A capability in this context is the ability to perform a certain task or provide

a specific type of information. E.g. controlling an air conditioning unit or reading the

temperature are both examples of capabilities. Capabilities are described by Clusters of

Attributes. Attributes are basically variables, e.g. the current temperature, or states, e.g. if the air

conditioner is on or off. Attributes can be read or written by remote devices using key value pair

(KVP) packets. A cluster usually contains a group of similar attributes.

To allow interoperability between devices produced by different manufacturers, the ZigBee

Alliances intends to define several application profiles. Each profile covers a specific class of

devices, such as the Home Control Lighting profile, which define basic behavior and capabilities

of dimmers, light switches, occupancy sensors etc. Profiles define: clusters, attributes, data types,

valid ranges and a set of numeric constants. There are currently plans for, at least according to

rumors, profiles in security systems and sensor networks.

3.3 Suitable areas for ZigBee

The ZigBee alliance predicts several areas as suitable for ZigBee. Some possible

future applications in these areas are described in below and Table 3.3 summaries

14

their requirements. The objective is to show that a certain ZigBee application is possible to

develop by implementing its requirements in the demonstrator. The ZigBee alliance projects the

following application areas for ZigBee:

• Home control

• Building automation

• Personal health care

• Industrial control and monitoring

• Consumers electronics

• PC peripherals

3.3.1 Home control

The simplest home control application is to remotely control the lights. Controlling

other electrical devices in a similar manner is also possible, e.g. turning on the coffee machine

from the bedroom or heating the basement sauna from the living room. There are also the

potential of integrating systems, like ZigBee compliant smoke detectors that could communicate

with the lights, instantly lighting up the entire home in case of a fire. Wireless temperature

sensors would allow intelligent heating and ventilation systems, creating an even temperature in

the entire house. The nodes in the light fixtures could be mains powered allowing them to work

15

indefinitely as coordinators or routers. The light switches could be battery powered and thus

movable, allowing for flexible interior decoration.

3.3.2 Consumer electronics

Consumer electronics refers to devices like DVD-players and televisions. All of these could be

controlled by a single ZigBee remote. A possible extension to this is to place a ZigBee

transceiver in a mobile phone or a PDA. For consumer electronics a star network is sufficient

since ranges are short.

3.3.3 Security system

Security system with ZigBee means a network of sensors that communicate with a security

terminal. The terminal could be connected to a PC or a GPRS2 terminal so it can send an alarm

when an intrusion is detected. Other systems like fire alarm system could be integrated and use

this functionality as well. Using wireless technology to connect the security system would

significantly lower installation costs since wiring is very costly and cumbersome. Another

advantage is very simple extension of an existing system, just add more sensors and they will be

used automatically. For such large networks, a mesh topology is required.

3.3.4 Industrial control and monitoring

Consider the case where corrosion due to humidity causes problem in a factory. Wireless sensors

can be placed throughout the factory, communicating with a control center via routers placed at

strategic locations, forming a mesh network over the entire factory. If the humidity at some

sensor reaches unacceptable levels the needed counter measurements can be activated. The

system that lowers humidity could possibly also be controlled with ZigBee, sharing the same

wireless infrastructure. The control center could log humidity values in a database, possibly

transmitting it for analysis via the Internet or GPRS. The large number of nodes means that the

cost of each node is an important parameter.

16

Chapter 4 : Technical specifications

4.1 The IEEE 802.15.4 specification

The IEEE 802.15.4 standard defines the following communication layers:• Physical (PHY)• Medium access control (MAC)

4.1.1 Physical layer

The physical (PHY) layer handles the low level data communication, controlling the transceiver

itself. It defines the channels available and physical modulation used to transmit data over the

IEEE 802.15.4 air interface. It also provides for clear channel assessment, making sure the

channel can be used, and link quality indication. The standard defines two PHY layers suitable

for three different frequency bands, 868 MHz (Europe), 915 MHz (USA) and 2.4 GHz

(Worldwide1). Neither of these bands require broadcasting licenses, but can be subject to output

power restrictions. The 868 and 915 MHz band uses the same PHY, making it possible for

transceivers to support both bands.

To minimize the effects of interference, 802.15.4 uses Direct Sequence Spread Spectrum

(DSSS), a spread spectrum technique that is simple to implement in 1The 2.4 GHz band is not

truly worldwide, since the actual width of the band varies and is quite small in some countries

integrated circuits. Unlike Frequency Hopping Spread Spectrum (FHSS), used in

for example Bluetooth, the carrier frequency does not change with DSSS, instead

the signal energy is constantly spread over a wider band.

17

4.1.2 Medium Access Control layer

The medium access control layer handles how a node get access to the network

and how the network is set up, including topology and beacons.

4.1.3 Network topologies

18

In 802.15.4 there are two device types: the Full Function Device (FFD) and the Reduced

Function Device (RFD). A FFD implements the entire protocol stack and can act as a network

coordinator or router while a RFD implements only a subset of the protocol and can only act as

an end device. The memory, processor and power requirements are lower for reduced function

devices. The MAC layer supports two different network topologies: the star topology and the

peer to peer topology, which are both illustrated in Figure A.1. In the star topology all

communication is routed through the central node called the PAN coordinator. In peer-to-peer

topology any FFD node within range can communicate, this allows for routing and more

complex topologies like mesh and cluster tree. The behavior of a mesh topology are not part of

the 802.15.4 standard itself, however it is part of the ZigBee Network (NWK) layer, see Section

A.2.1. All 802.15.4 compliant devices have a unique 64-bit address, assigned in a manner

defined by the IEEE Registration Authority[17]. This address type is often referred to as the

extended address of the device. A 16-bit short address is assigned by the PAN coordinator when

a device joins a network. This allows networks with over 64k (216) devices. The extended

address is used for single hop communication.

The short address is used for end to end communication, the coordinator is responsible for

translating between short and extended during routing. The MAC sub layer defines multiple

frame types: beacon frame, data frame, command frame and acknowledgment frame. The beacon

frame is used to synchronize node duty cycles, because it is essential that nodes spend most of

their time in power down mode to conserve power.

If the network uses peer-to-peer. e.g. non-star, topology, the PAN coordinators beacon might not

reach all nodes. Allowing multiple nodes to transmit beacons introduces difficult synchronization

19

problems. The solution is to run such networks in non-beaconed mode. Since there is no way to

signal inactive periods without the use of beacons, the coordinator must be active constantly.

This increases its power usage significantly and makes it impractical to use battery powered

coordinators or routers in non-beaconed networks. Without beacons, nodes are allowed to

transmit at any time, using unslotted CSMA-CA, collision will cause a random back off period

since there are no time slots.

Data transfer is done using the data frame, which can be seen in Figure A.2. The data frame can

contain a maximum payload of 102 bytes. Instead of transmitting data directly between nodes,

802.15.4 uses a polling mechanism, which is illustrated in Figure A.3. Data is first sent to the

PAN coordinator, where it is stored until the destination node sends a command frame of data

request type. This allows nodes to control their own duty cycles by lowering the frequency of

data requests. The MAC layer supports single hop acknowledgment through the use

of special acknowledgment frames. The transmitter activates its receiver a short while after

transmitting and will automatically resend each frame 3 times if no acknowledgment frame is

received. This is only a single hop acknowledgment. Indicating only that the packet has reached

the nearest router or coordinator, not the addressed device. End to end acknowledgment is

handled at the application level.

4.1.4 IEEE 802.15.4 performance

The IEEE 802.15.4 air interface is primarily designed to be: resistant to interference, require low

transmitter power and have low hardware complexity. Unlicensed frequency bands can contain

20

large numbers of transmitters, making resistance to interference the most important design goal.

This is achieved with Direct Sequence Spread Spectrum (DSSS). DSSS spreads the signal over a

wider band by multiplying the outgoing signal

with a pseudo noise (PN) sequence. Each pulse in a PN sequence is called a chip and can be

either +1 or -1. The number of chips per second is higher than the symbol rate, causing the signal

energy to spread into a wider band. At the receiver, the same PN sequence is used to despread

the signal, retrieving the original information. The advantage of this technique is that

despreading the signal, spreads out the interference, suppressing narrow band interference. This

interference rejection capability is referred to as the processing gain and is illustrated in Figure

A.4. The processing gain (PG) is defined as

PG =Ts/Tc

Where Ts is symbol duration, and Tc the chip duration. The processing gain for the

.Higher processing gain means better ability to suppress interference. The downside is that the

bandwidth (in Hz) is increased significantly. By using a 32 chip PN sequence, which can be

considered long, the 802.15.4 design favors interference suppression over high data rate.

4.2 The ZigBee specification

The ZigBee standard defines the following communication layers:

• Network (NWK)

• Application (APL)

Additionally it defines the Security Service Provider (SSP) that handles encryption

and access control lists (ACL) to ensure secure communication.

4.2.1 Network layer

The network (NWK) layer lies directly above the IEEE 802.15.4 MAC layer (see

Figure A.5). The NWK layer automatically manage MAC layer functions like network creation,

beacons, association and disassociation requests. Additionally it provides for packet routing,

route discovery and message reflection. It also defines three device types:

21

• Coordinator

• Router

• End device

Coordinators and routers must be Full Function Devices (FFD), while end devices

typically are Reduced Function Devices (RFD). Coordinators are responsible for

creating and maintaining the network. Router nodes provide a subset of coordinator functionality

and are primarily responsible for routing packets. There can only be one active coordinator per

network, so additional coordinators will be passive and assume the role of routers. If the active

coordinator becomes disconnected, a passive coordinator should automatically take its place in

the network. The use of dedicated coordinators or routers can be useful in certain circumstances

but all three devices types are are meant to run applications.

4.2.2 Application layer

The application layer (APL) is the highest layer in ZigBee standard and exist to

simplify application development. It consists of three components:

• Application support layer (APS)

• Application framework (AF)

• ZigBee Device Object (ZDO)

22

4.2.2.1 Application support layer

The application support layer (APS) provides the following functionality to the

higher layers:

• Creation of application protocol data units (APDU)

• Discovery

• Binding

Application protocol data units (APDU) are regular MAC data frames with a formated

payload. The APDUs header contains: destination endpoint, cluster id and profile id. An

endpoint is an internal address, analogous to the TCP/IP concept of ports. This makes it easy to

run multiple applications on a single device, since they can be uniquely addressed by their

endpoints. A device that both supports reading of temperature and light level would contain two

application objects with separate endpoints.

4.2.2.2 Application Framework

The application framework (AF) aims to simplify data exchange between Zig-Bee devices. The

payload to a APDU can contain the following AF defined data formats:

• Key value pair (KVP)

• Message (MSG)

A KVP formatted packet contains:

• Command type

• Attribute id

• Attribute data

• Data type

• Data length

• Error code (only in responses)

Data exchange is most commonly done using the key value pair data format, containing

a key, referred to as the attribute id and the value, called attribute data. KVP supports data types

such as: signed/unsigned integers, floats and a special time stamp type. KVP packets can be used

to both trigger remote events, read and write data, using the event, get and set command types

respectively.

23

Chapter 5: Application of ZigBee

The ZigBee Alliance targets applications "across consumer, commercial, industrial and

government markets worldwide".

Unwired applications are highly sought after in many networks that are characterized by

numerous nodes consuming minimum power and enjoying long battery lives.

ZigBee technology is designed to best suit these applications, for the reason that it enables

reduced costs of development, very fast market adoption, and rapid ROI.

Airbee Wireless Inc has tied up with Radiocrafts AS to deliver "out-of-the-box" ZigBee-ready

solutions; the former supplying the software and the latter making the module platforms. With

even light controls and thermostat producers joining the ZigBeeAlliance, the list is growing

healthily and includes big OEM names like HP, Philips, Motorola and Intel.

With ZigBee designed to enable two-way communications, not only will the consumer be able to

monitor and keep track of domestic utilities usage, but also feed it to a computer system for data

analysis.

Futurists are sure to hold ZigBee up and say, "See, I told you so". The ZigBee Alliance is nearly

200 strong and growing, with more OEM's signing up. This means that more and more products

and even later, all devices and their controls will be based on this standard. Since Wireless

personal Area Networking applies not only to household devices, but also to individualised

office automation applications, ZigBee is here to stay. It is more than likely the basis of future

home-networking solutions.

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5.1.1: Some of the Application of ZigBee

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5.1.2 Home Awareness

5.1.3 In Home Patient Monitoring

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5.1.4 Commercial Lighting Control

5.1.5 HVAC Energy Management

5.1.6 Mobile Handset As Zigbee Gateway

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Chapter 6: Comparison of ZigBee with other Wireless Standards

6.1 Comparison to Blue Tooth

ZigBee was developed to serve very different applications than Bluetooth and leads to

tremendous optimizations in power consumption. Some of the key differentiators are:

o ZigBee: Very low duty cycle, very long primary battery life,

Static and dynamic star and mesh networks, >65,000 nodes, with low

latency available,

Ability to remain quiescent for long periods without communications,

Direct Sequence Spread Spectrum allows devices to sleep without the

requirement for close synchronization.

o Bluetooth: Moderate duty cycle, secondary battery lasts same as master,

Very high QoS and very low, guaranteed latency,

Quasi-static star network up to seven clients with ability to participate in

more than one network,

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Frequency Hopping Spread Spectrum is extremely difficult to create

extended networks without large synchronization cost.

Chapter 7: Advantages of ZigBee

The main advantages include product interoperability, vendor independence, and accessibility to

broader markets. Customers can expect increased product innovation as a result of the industry

standardization of the physical radio and logical networking layers. Instead of having to invest

resources to create a new proprietary solution from scratch every time, companies will now be

able to leverage these industry standards to instead focus their energies on finding and serving

customers. the United States.

This specification maintains the same usage and architecture as wired USB devices with a high-

speed host-to-device connection and connects to a maximum of 127 devices.  WUSB is based on

a hub and spoke topology.  

ZigBee Alliance member companies can enjoy accelerated development cycles and enhanced

product and industry competitiveness. ZigBee members are defining and creating new markets

for interoperable wireless networks. By actively participating in the ZigBee Alliance, members

have access to, and are able to influence, the emerging ZigBee specification. Members gain early

access to ZigBee design information, development details, interoperability specifications and

other companies with complementary skills and capabilities. In addition to helping define the

specification, members enjoy networking with other market leading companies committed to

providing interoperable wireless products and networks

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Chapter 8: CONCLUSION

The main conclusion of this Master’s thesis project is that, yes, ZigBee is a suitable

base for embedded wireless development. The main reason is that development is easy and fast.

ZigBee also meets the promised technical requirements. The areas that ZigBee is likely to be

used in is building automation and industrial networks. The chances seem highest in the industry

since ZigBee is currently the only option for such standardized wireless networks. Even though

there are some competition, due to better performance, price and compliance, ZigBee is likely to

dominate the home automation market as well. PC peripherals and consumers electronics are two

areas that ZigBee is very unlikely to be used in, because it offers very little over the competition.

The Master’s thesis project has shown that developing an application with a beta version of the

network stack is possible, but it the disadvantage that it longer development time and there will

be limitations. In such a cases, access to the source code should be demanded is possible since

the documentation can not be expected to be complete.

“Just as the personal computer was a symbol of the '80s, and the symbol of the '90s is the World

Wide Web, the next nonlinear shift, is going to be the advent of cheap sensors.”

-Paul Saffo

Institute for the Future

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Chapter 9: REFERENCES

ZigBee Alliance.http://www.zigbee.orgTeleca.http://www.teleca.se

Some of the websites referred by us:

www.google.comwww.tutorial-reports.comwww.wikipedia.com

We also consulted some IEEE papers for reference works.

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