Chapter 1

Introduction

ZigBee is a rather new wireless technology that looks to have applications in a variety of fields. ZigBee is a technological standard based on the IEEE 802.15.4 specification for low data rates technology allows for devices to communicate with one another with very low power consumption, allowing the devices to run on simple batteries for several years. ZigBee is targeting various forms of automation, as the low data rate communication is ideal for sensors, monitors, and the like. Home automation is one of the key market areas for ZigBee, with an example of a simple network .

ZigBee is designed for wireless controls and sensors. It could be built into just about anything you have around your home or office, including lights,switches, doors and appliances. These devices can then interact without wires, and you can control them all . . . from a remote control or even your mobile phone.Although ZigBee's underlying radio-communication technology isn't revolutionary, it goes well beyond single-purpose wireless devices, such as garage door openers and "The Clapper" that turns light on and off. It allows wireless two-way communications between lights and switches, thermostats and furnaces, hotel-room air-conditioners and the front desk, and central command posts. It travels across greater distances and handles many sensors that can be linked to perform different tasks.

ZigBee works well because it aims low. Controls and sensors don't need to send and receive much data. ZigBee has been designed to transmit slowly. It has a data rate of 250kbps (kilobits per second), pitiful compared with WiFi,which is hitting throughput of 20Mbps or more. But because ZigBee transmits slowly, it doesn't need much power, so batteries will last up to 10 years. Because ZigBee consumes very little power, a sensor and transmitter that reports whether a door is open or closed, for example, can run for up to five years on a single double-A battery.

Operators are much happier about adding ZigBee to their phones than faster technologies such as Wi-Fi; therefore, the phone will be able to act as a remote control for all the ZigBee devices it encounters.

ZigBee is an established set of specifications for low rate-wireless personal area networking (LR-WPAN), i.e. digital radio connections between computers and related devices.

Evolution of LR-WPAN Standarization

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♦ low rate

♦ low power

♦ short range

♦ very small size

The IEEE working group of the Institute of Electrical and Electronics Engineers is a professional association headquartered in New York city, USA.

The IEEE 802.15 working group is form to creat WPAN standard. The focus of WPAN is low-cost, low power, short range and very small size. This group has currently defined three classes of WPANs that are differentiated by data rate, battery drain and quality of service(QoS).

♦ High data rate rate WPANs (IEEE 802.15.3) is suitable for multi-media application that require very high QoS.

♦ Medium rate WPANs (IEEE 802.15.1/Bluetooth) will handle a variety of tasks ranging from cell phones to PDA communications and have QoS suitable for voice communication.

♦ The low rate WPANs (IEEE 802.15.4/LR-WPAN) is intended to serve a set of industrial, residential and medical applications with very low power consumption and cost requirement not considered by above WPANs and with relaxed needs for data rate and QoS. The low data rate enables the LR-WPAN to consume very little power.

ZigBee and IEEE 802.15.4

International standard IEEE 802.15.4

Devloped by ZigBee Alliance (http//www.zigbee.org)

Opration ISM radio bands ( Industrial, scientific and medical )

Physical range 10- 100 meters (approx)

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ZigBee technology is a low data rate, low power consumption, low cost, wireless networking protocol targeted towards automation and remote control applications. IEEE 802.15.4 committee started working on a low data rate standard a short while later. Then the ZigBee Alliance and the IEEE decided to join forces and ZigBee is the commercial name for this technology.

The relationship between IEEE 802.15.4 and ZigBee is similar to that between IEEE 802.11 and the Wi-Fi Alliance. For non-commercial purposes, the ZigBee specification is available free to the general public. An entry level membership in the ZigBee Alliance, called Adopter, costs US$ 3500 annually and provides access to the as-yet unpublished specifications and permission to create products for market using the specifications.

The low cost allows the technology to be widely deployed in wireless control and monitoring applications. Low power-usage allows longer life with smaller batteries. Mesh networking provides high reliability and more extensive range.

The ZigBee network layer natively supports both star and tree typical networks, and generic mesh networks. Every network must have one coordinator device, tasked with its creation, the control of its parameters and basic maintenance. Within star networks, the coordinator must be the central node. Both trees and meshes allows the use of ZigBee routers to extend communication at the network level.

ZigBee ISM radio band operation specification

ZigBee operates in the industrial, scientific and medical (ISM) radio bands; 868 MHz in Europe, 915 MHz in the USA and Australia and 2.4 GHz in most jurisdictions worldwide. Data transmission rates vary from 20 to 250 kilobits/second.

Country Frequency Speed Channels

Europe 868 MHz 20 kbps 1

USA & Australia 915 MHz 40 kbps 10

Worldwide 2.4 GHz 250 kbps 16

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History

ZigBee-style networks began to be conceived around 1998, when many installers realized that both Wi-Fi and Bluetooth were going to be unsuitable for many applications. In particular, many engineers saw a need for ZigBee self-organizing ad-hoc digital radio networks.

The IEEE 802.15.4-2003 standard was completed in May 2003 and has been superseded by the publication of IEEE 802.15.4-2006. In the summer of 2003, Philips Semiconductors, a major mesh network supporter, ceased the investment. Philips Lighting has, however, continued Philips' participation, and Philips remains a promoter member on the ZigBee Alliance Board of Directors.

The ZigBee Alliance announced in October 2004 that the membership had more than doubled in the preceding year and had grown to more than 100 member companies, in 22 countries. By April 2005 membership had grown to more than 150 companies, and by December 2005 membership had passed 200 companies.

The ZigBee specifications were ratified on 14 December 2004. The ZigBee Alliance announced availability of Specification 1.0 on 13 June 2005, known as ZigBee 2004 Specification. In September 2006, ZigBee 2006 Specification is announced.

In 2007, ZigBee PRO, the enhanced ZigBee specification wasfinalized.

♦ The first stack release is now called ZigBee 2004.

♦ The second stack release is called ZigBee 2006, and mainly replaces the MSG/KVP structure used in 2004 with a "cluster library". The 2004 stack is now more or less obsolete.

♦ ZigBee 2007, now the current stack release, contains two stack profiles, stack profile 1 (simply called ZigBee) for home and light commercial use, and stack profile 2 (called ZigBee PRO).

ZigBee PRO offers more features, such as multi-casting, many-to-one routing and high security with Symmetric-Key Key Exchange (SKKE), while ZigBee (stack profile 1) offers a smaller footprint in RAM and flash.

Both offer full mesh networking and work with all ZigBee application profiles.

ZigBee 2007 is fully backward compatible with ZigBee 2006 devices: A ZigBee 2007 device may join and operate on a ZigBee 2006 network and vice versa.

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Due to differences in routing options, ZigBee PRO devices must become non-routing ZigBee End-Devices (ZEDs) on a ZigBee 2006 network, the same as for ZigBee 2006 devices on a ZigBee 2007 network must become ZEDs on a ZigBee PRO network. The applications running on those devices work the same, regardless of the stack profile beneath them.

The ZigBee 1.0 specification was ratified on 14 December 2004 and is available to members of the ZigBee Alliance.

The first ZigBee Application Profile, Home Automation, was announced 2 November 2007.

ZigBee Alliance

Established in 2002, They are an open, non-profit association of members that has created a thriving global ecosystem. Anyone can join their membership comprised of businesses, universities and government agencies from around the globe. Their activities and direction are determined by members as they act to meet evolving needs in a fast-paced world.

Today, They have created a growing family of innovative, reliable and easy-to-use ZigBee standards.

Mission

ZigBee

♦ Provides green, low-power and open global wireless networking standards focused on monitoring, control and sensor applications.

♦ Allows products to run on harvested energy or batteries for years with its low-power wireless standards, making greener lifestyles possible.

♦ Uniquely connects dramatically different types of devices into a single network, giving you unprecedented control.

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♦ Offers a variety of intelligent features designed to ensure devices communicate in any environment, and around the world.

♦ Is simple to set up and can easily grow to meet your needs and deliver years of maintenance-free use.

ZigBee Charecteristics

The focus of network applications under the IEEE 802.15.4 / ZigBee standard include the features of low power consumption, needed for only two major modes (Tx/Rx or Sleep), high density of nodes per network, low costs and simple implementation.

These features are enabled by the following characteristics

• 2.4GHz and 868/915 MHz dual PHY modes. This represents three license-free bands: 2.4-2.4835 GHz, 868-870 MHz and 902-928 MHz. The number of channels allotted to each frequency band is fixed at sixteen (numbered 11-26), one (numbered 0) and ten (numbered 1-10) respectively. The higher frequency band is applicable worldwide, and the lower band in the areas of America, Australia and Europe.

• Low power consumption, with battery life ranging from months to years. Considering the number of devices with remotes in use at present, it is easy to see that more numbers of batteries need to be provisioned every so often, entailing regular (as well as timely), recurring expenditure. In the ZigBee standard, longer battery life is achievable by either of two means: continuous network connection and slow but sure battery drain, or intermittent connection and even slower battery drain.

• Maximum data rates allowed for each of these frequency bands are fixed as 250 kbps @2.4 GHz, 40 kbps @ 915 MHz, and 20 kbps @868 MHz.

• High throughput and low latency for low dutycycle applications (<0.1%)

• Channel access using Carrier Sense Multiple Access with Collision Avoidance (CSMA - CA)

• Addressing space of up to 64 bit IEEE address devices, 65,535 networks.

• 100 meter typical range.

• Fully reliable “hand-shaked” data transfer protocol.

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• Different topologies as illustrated below: star, mesh, cluster tree.

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Star

Mesh

Cluster Tree

PAN coordinator

Full Function Device

Reduced Function Device

Chapter 2

System description

ZigBee Architecture

Zigbee architecture is based on the following blocks.

The upper layer is application layer with nodes to attach the end device and lower is the data / link layer make bridge in between both upper and lower layers there is network layer to carry out the function.  This whole model is known as stack as all the layers form a stack.

The ZigBee stack architecture is based on three major components; Zigbee Physical data/link layer, Zigbee network layers and Zigbee Application support layer.

ZigBee data / link level is comprises of two layers. One is physical layer (PHY) and the other is Media Access Control (MAC) sub layer. Physical layer is responsible for sending and receiving the data from resource. Media Access is responsible for networking and acts as a sensor try not to collide hence initiate the command.

ZigBee network layers adhere to function by enabling the correct use of MAC and act like a bridge by making networks based on topology by using between application layer and zigbee data / link level. These Zigbee network layers are responsible for networking and security matters. It enables a network and manage end joining or leaving. It is able to find another route in case of not availability of the immediate route and switch to the nearby route.

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Application support sub-layer is responsible for input and output though from end device.  It fulfills the data and management services. As the name implies that it supports applications and performs services for endpoints and ZigBee device objects.

Application Objects are the devices for which the whole ZigBee architecture is designed. These application objects are called endpoints. These application objects are placed at the top position in Zigbee stack architecture.

Application objects are managed and monitored by Zigbee device object (ZDO). ZigBee device object initiates the process of Data / Link layer by adopting the specific network topology and decides its function like coordinator, router or end device.

The ZigBee stack architecture supplies security measurements. It distributes its services into different layers MAC, APS and NWK securing the data loss hence provides multi level security.

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Detailed Architecture

Physical/Data Link Level

The Physical/Data Link level is concerned with low-level network operation such as addressing and message transmission/reception. It is based on the IEEE 802.15.4 standard and comprises the following two layers:

MAC (Media Access Control) sub-layer PHY (Physical) layer

IEEE 802.15.4 Physical Layer

IEEE 802.15.4 PHY (Physical) is the layer concerned with the interface to the physical transmission medium (radio, in the case). It exchange data bits with its medium as well as

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exchanging data bits wih the layer above(MAC sub layer)

• PHY functionalities:

– Activation and deactivation of the radio transceiver

– Energy detection within the current channel

– Link quality indication for received packets

– Clear channel assessment for CSMA-CA

– Channel frequency selection

– Data transmission and reception

Zigbee uses three frequency bands for transmission- 868 MHz band with a single channel has a raw data rate of 20 kb/s. The 915MHz band with 10 channels has each channel’s central frequency separated from the adjacent band by 2 MHz and data rate of 40 kb/s. BPSK modulated symbols are transmitted at 1 bit per symbol using Direct Sequence Spread Spectrum (DSSS) technique with 15 bit chips. The 2.4 GHz ISM band with 16 channels, 5 MHz wide offers 250 kb/s data rate. It employs O-QPSK modulation with 4 bits/symbol transmitted using DSSS with 32 Bit chips. To reduce the transmitted power, the Zigbee transmitters use Energy Detection (ED) and Link Quality Indication (LQI). It is the responsibility of the physical layer to perform channel assessment.

PHY frame structure

• PHY packet fields

– Preamble (32 bits) – synchronization

– Start of packet delimiter (8 bits) – shall be formatted as “11100101”

– PHY header (8 bits) –PSDU length

– PSDU (0 to 127 bytes) – data field

Operatin frequency bands

• The standard specifies two PHYs :

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− 868 MHz/915 MHz direct sequence spread spectrum (DSSS) PHY (11 channels)

• 1 channel (20Kb/s) in European 868MHz band • 10 channels (40Kb/s) in 915 (902-928)MHz ISM band

– 2450 MHz direct sequence spread spectrum (DSSS) PHY (16 channels)• 16 channels (250Kb/s) in 2.4GHz band

IEEE 802.15.4 MAC Layer

IEEE 802.15.4 MAC (Media Access Control) is the data link layer responsible for addressing:

• for outgoing data −it determines where the data is going.

• for incoming data

− It determines where the data come from.

− It also responsible for assembling data packets or frame to be transmitted and for decomposing received frams.

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868MHz/915MHz PHY

868.3 MHz

Channel 0 Channels 1-10

928 MHz902 MHz

2 MHz

2.4 GHz

Channels 11-26

2.4835 GHz

5 MHz2.4 GHz PHY

Channel access is primarily through Carrier Sense Multiple Access- Collision Avoidance (CSMA-CA). On a node hop to hop basis, the MAC layer can take care of transmitting data. Depending on the mode of transmission, i.e. Beacon or Non-Beacon mode, the MAC layer decides whether to use slotted or unslotted CSMA-CA. The MAC layer takes care of scanning the channel, starting PANs, detecting and resolving PAN ID conflicts, sending beacons, performing device discovery, association and disassociation, synchronizing network device and realigning orphaned devices on the network. Along with this, the MAC layer also provides some standard security features like access control, encryption of data, duplicate rejection and frame integrity. Like in the case of the standard OSI MAC Layer, MAC layer in Zigbee also cannot take care of the situation when the nodes have intermediate nodes between them. This functionality of routing the packets to their destinations is provided in the network layer.

• Traffic Type– Periodic data

• e.g. sensors

– Intermittent data• e.g. light switch

– Repetitive low latency data• e.g. mouse

• Device Classes

– Full function device (FFD)• Can function in any topology • Capable of being Network coordinator • Can talk to any other device (FFD/RFD)

– Reduced function device (RFD)• Limited to star topology• Cannot become network coordinator • Talks only to FFDs

• Address

– All devices must have 64 bit IEEE addresses– Short (16 bit) addresses can be allocated to reduce packet size

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• Frame Types

– Data Frame• used for all transfers of data.

– Beacon Frame• used by a coordinator to transmit beacons.

– Acknowledgment Frame• used for confirming successful frame reception.

– MAC Command Frame• used for handling all MAC peer entity control transfers.

• Transmission Mode

– Slotted (Beacon enable mode )• Periodic data and Repetitive low latency data using.

– Un-slotted (Non-Beacon enable mode)• Intermittent data using.

Network (NWK) Layer

The NWK layer handles network addressing and routing by invoking action in the MAC layer. Its task includes :

• starting the network (co-ordinator).

• assigning network addresses.

• adding devices to and removing them from the network.

• routing messages to their intended destinations.

• applying security to outgoing messages.

• implementing in route discovery in Mesh topologies and storing routing table information.

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ZigBee Networks

ZigBee provide the most modern technology infrastructure for wireless devices and other electronic instruments with extra benefits of cost-effectiveness and low-power usage. ZigBee networks are widely used in huge industrial plants to formulate one monitoring and controlling unit. ZigBee are spreading rapidly in home environment by replacing the manual controlling of a device with one remote control.

How ZigBee Network works

Zigbee networks uses Coordinator, router (optional) and End Devices to communicate. ZigBee technology based network devices like coordinators, routers and end devices are used to form a zigbee wireless network. In a ZigBee network coordinators work as a primary device. It is a source to commence a networking process. Coordinator sends information to the router. These routers are secondary medium which acts as a bridge between coordinator and end device. An important point to remember is end device only works as a receiver within crucial time span less than 15msec.

ZigBee Network Topologies

ZigBee uses the IEEE 802.15.4 2003 specification for its physical layer and MAC layer. IEEE 802.15.4 offers star, tree, cluster tree, and mesh topologies; however, ZigBee supports only star, tree, and mesh topologies.

It uses an association hierarchy; a device joining the network can either be a router or an end device, and routers can accept more devices.

♦ Star topology:

The star topology consists of a coordinator and several end devices (nodes). In this topology, the end device communicates only with the coordinator. Any packet exchange between end devices must go through the coordinator. The disadvantage of this topology is the operation of the network depends on the coordinator of the network, and because all packets between devices must go through coordinator, the coordinator may become bottlenecked. Also, there is no alternative path from the source to the destination. The advantage of star topology is that it is simple and packets go through at most two hops to reach their destination.

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• Advantages of Star Topology

− As compared to Bus topology it gives far much better performance, signals don’t necessarily get transmitted to all the workstations. A sent signal reaches the intended destination after passing through no more than 3-4 devices and 2-3 links. Performance of the network is dependent on the capacity of central hub.

− Easy to connect new nodes or devices. In star topology new nodes can be added easily without affecting rest of the network. Similarly components can also be removed easily.

− Centralized management. It helps in monitoring the network.

− Failure of one node or link doesn’t affect the rest of network. At the same time its easy to detect the failure and troubleshoot it.

• Disadvantages of Star Topology

− Too much dependency on central device has its own drawbacks. If it fails whole network goes down.

− The use of hub, a router or a switch as central device increases the overall cost of the network.

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− Performance and as well number of nodes which can be added in such topology is depended on capacity of central device.

♦ Tree topology:

In this topology, the network consists of a central node (root tree), which is a coordinator, several routers, and end devices. The function of the router is to extend the network coverage. The end nodes that are connected to the coordinator or the routers are called children. Only routers and the coordinator can have children. Each end device is only able to communicate with its parent (router or coordinator). The coordinator and routers can have children and, therefore, are the only devices that can be parents. An end device cannot have children and, therefore, may not be a parent. A special case of tree topology is called a cluster tree topology.

• Advantages of Tree Topology

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− It is an extension of Star and bus Topologies, so in networks where these topologies can't be implemented individually for reasons related to scalability, tree topology is the best alternative.

− Expansion of Network is possible and easy.

− Here, we divide the whole network into segments (star networks), which can be easily managed and maintained.

− Error detection and correction is easy.

− Each segment is provided with dedicated point-to-point wiring to the central hub.

− If one segment is damaged, other segments are not affected.

• Disadvantages of Tree Topology

− Because of its basic structure, tree topology, relies heavily on the main bus cable, if it breaks whole network is crippled.

− As more and more nodes and segments are added, the maintenance becomes difficult.

− Scalability of the network depends on the type of cable used.

− If one of the parents becomes disabled, the children of the disable parent cannot communicate with other devices in the network.

− Even if two nodes are geographically close to each other, they cannot communicate directly.

♦ Cluster tree topology:

A cluster tree topology is a special case of tree topology in which a parent with its children is called a cluster. Each cluster is identified by a cluster ID. ZigBee does not support cluster tree topology, but IEEE 802.15.4 does support it.

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♦ Mesh topology:

Mesh topology, also referred to as a peer-to-peer network, consists of one coordinator, several routers, and end devices. The following are the characteristics of a mesh topology:

A mesh topology is a multihop network; packets pass through multiple hops to reach their destination.

The range of a network can be increased by adding more devices to the network.

It can eliminate dead zones.

A mesh topology is self-healing, meaning during transmission, if a path fails, the node will find an alternate path to the destination.

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Devices can be close to each other so that they use less power.

Adding or removing a device is easy.

Any source device can communicate with any destination device in the network.

Compared with star topology, mesh topology requires greater overhead.

Mesh routing uses a more complex routing protocol than a star topology.

• Advantages of Mesh topology

− Data can be transmitted from different devices simultaneously. This topology can withstand high traffic.− Even if one of the components fails there is always an alternative present. So data transfer doesn’t get affected.

− Expansion and modification in topology can be done without disrupting other nodes.

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• Disadvantages of Mesh topology

− There are high chances of redundancy in many of the network connections.

− Overall cost of this network is way too high as compared to other network topologies.

− Set-up and maintenance of this topology is very difficult. Even administration of the network is tough.

ZigBee Network Capacity

ZigBee network has a capacity of connecting more than 65,000 devices through different networking topologies. The data travel through this range from 20Kbps up to 250 Kbps.

Application Support Sub-layer (APS)

The APS layer is responsible for:

Communicating with the relevant application- for example, when a message arrives to illuminate an LED, the APS layer relays this instruction to the responsible application using the end point information the message. The message is passed through the Service Access Point which exist between the APS layer and each application (end point).

Application Objects

Upto 240 application objects are supported on a single ZigBee node. Each application object is an endpoint and is numbered between 1 to 240 (note that end point 0 is reserved for the ZigBee device objects of the node).

ZDO (ZigBee Device Object)

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The ZDO (ZigBee Device Object) represents the ZigBee node type of the device (Co-ordinator, Router or End device), and has a number of initialization and communication roles. The ZDO is the endpoint numbered 0.

ZDO Management Plane

This plane spans the APS & NWK layer, and allow the ZDO to communicate with these layers when performing its internal tasks. It also allow the ZDO to deal with requests from application for network access and security function using ZDP (ZigBee Device Profile) messages.

Application Framework

The Application Framework (AF) contains the application objects and facilitates interaction between the applications and the APS layer. An application object interacts with the APS layer through an interface known as a Service Access Point (SAP).

Service Access Points

A Service Access Point (SAP) implements a set of operations to pass information and commands between layers. There are usually four types of operation implemented by a SAP:

Request: Typically, a layer using the services of another layer generates a Request to the lower layer.

Confirm: In general, the lower layer responds with a Confirm, which indicates whether it has accepted or rejected the request. A rejection could occur if the Request is invalid or the layer does not implement the operation concerned (the operation could be defined as optional).

Response: Normally, Requests result in some sort of Response from the lower layer. This may be a simple status message indicating that the Request has been performed, or may contain further information that the Request has asked for. Responses can be immediate or delayed:

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Synchronous Response: Responses may be generated immediately after the Request has been issued - for example, if the information or command is available on the local node.

Asynchronous Response: A Request may require messages to be sent over the network to a remote node, in which case there will be a delay between issuing the Request and the arrival of the Response.

The SAP mechanism allows both types of Response to be handled and delivered to the higher layer.

Indication: An Indication is generated when the lower layer has unsolicited information or commands to be delivered to the higher layer, possibly as a result of a Request from a remote node for local information.

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Chapter 3

Applications, Advantages, Limitations, Future possibilities

Applications of ZigBee

There are many application of ZigBee

ZigBee-based Home Automation System through Mobile

Home automatic system will not only enable the residents to integrate or distribute controlled-homely interior equipments via Web or telephone, but also realize remote monitoring of home security systems, including anti-theft, anti-gas leak, fire and other functions, which is the future direction of intelligent home. ZigBee based home automation design is so good that we can expand and upgrade it. We can achieve the home automation

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control, and the sharing of resources can be done to meet the needs of different users at present and in the future. ZigBee technology is a very reliable wireless data transmission network, from the standard communication distance of 75 meters to the infinite expansion, it is a network platform made by 65,000 to the wireless data transmission network modules, as each ZigBee

technology used Netcom letter in self-organizing way, every data transmit between ZigBee network can be communicated by each other, so people in any room can control the other room’s device and display it. In data communications, ZigBee Network Self-organization approach has each ZigBee module terminal. As long as each other in the network communication module is present, they find each other automatically, quickly, they can develop into a interoperability of ZigBee networks, if the relative position of the network module terminal has changed, modules can search through the re-targeted communications to determine the contact of each other, then refresh the existing network. As the ZigBee technology is a combination of self-organizing dynamic routing mesh topology, even if the path is interrupted, or too busy to make timely delivery, it can solve this problem very well, thus ensuring reliable data transmission, and therefore it is very suitable for the development and utilization of home.

A. Structure design of general circuit network topology

The general circuit network with low cost, data access flexible for the end users, site or failure of each end user does not affect other sites or end users at an advantage of, more importantly, wiring is simple, easy to expand, for household equipment, selected bus network topology is most suitable for solving the general circuit conflict, the use of master-slave structure. Transmission medium is the actual transmission of information communications carrier, a reasonable choice transmission medium helps improve both the quality and cost-effective communication, so we use ZigBee wireless technology. The general circuit network system structure is as shown in Fig. 1.

Host and the whole system of power as a module, responsible for receiving data from the slave machine, and distributing to the other machine. They have different the machine's address code, a machine corresponding to a group of switches. When a slave machine need to turn on the switch that is under the control of another machine, it only need to send the address code corresponding to another machine, after the host received this address code immediately send it to all the slave machine, the slave machine can receive the signal, but only the very slave machine switch in accordance with the address code can make the corresponding operations (startup or shutdown). Of course, the slave machines can also control their own switch, and has the same operation process as above mentioned.

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Fig.1 Home Network System Design

B. Intelligent home interior design of ZigBee network topology

Each ZigBee network nodes not only can serve as a monitoring object, can be connected directly to the sensor for data collection and monitoring, can also automatically transfer from other network nodes data. In addition, each ZigBee network nodes can also signal coverage in their scope and number of network information does not undertake the task of isolating transit sub-node wireless connectivity. And routing in the network, since the underlying ZigBee uses DSSS (Direct-Sequence Spread Spectrum) technology, if the use of non-standard mode of information, the network can be expanded even wider, because without synchronization, and node join the network and the process of re-join the network soon, the general can be done within 1s. In the routing aspects of it can support the high reliability of network routing, so it can be arranged a wide range of networks, and supports multicast and broadcast properties, it’s able to bring a wealth of application support.

Intelligent home control system software design

Single-chip Control System software is the most important,

the functions achievement and reliability of a single-chip microcomputer control system determine to a large extent on the software. The system software has two major parts: one is

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the host procedures; the other is the slave machine terminal process.

1. Mainframe program flowIn fact the host is as the network server, is mainly responsible for the coordination of the

entire system, setting up the whole network, allocating the addresses, adding and deleting nodes, maintaining the node equipment data and data transfer tables, not to cause confusion communications. In this system the specific function of program on the ZigBee server host is to receive data form slave machine and transmit data to each slave machine. The host sets up the network firstly and then communicates with the slave machines located in various rooms via ZigBee modules. The inquire commands are sent by host to awake all network terminal machine. As the ZigBee is a self-organizing network technology, when some or other slave terminal node request for connecting to the network or don’t work properly, the server host can discover this change, and modify the address table to update the network.

2. Machine program flowThe slave machine has the following functions: display the information, input control commands and complete some specific task automatically. When slave machine power up, firstly it finishes the server initiation, then the machine searches the network and requests for connecting to the network, after that the server host will transmit the answer signal, only when the slave machine receives the answer signal , it can add to the network.

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Flowchart for Program flow

Program Flowchart for Slave Machine

The slave machine’s (control switch) main function is to receive the data from the host, scan the input command and complete the corresponding operation (such as control the switch, monitoring and data collection), and send data to the server host. Fig. 4, shows the program flow chart slave machine.

3. Widely applicability of close distance and a short time delayZigBee transmission range is normally between 10-100m, after an increase in RF

transmits power, the increase can also increase to 1-3 km. If the routing and inter-node from

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the sleep state into the work of just 15ms, the network connection between nodes only 30ms, further saving energy. In comparison, the Bluetooth need 3-10.

4. Scalability goodZigBee may Stellate, Flake and mesh network structure, by a master node take

management of a number of sub- nodes, a node can manage up to 254 sub-nodes. At the same time, the main node also from one Network Node Manager, which can be expanded composition of 65,000 node network.

PC And Peripherals Desktop

PCs and Home Entertainment Systems (Home Theatre TV) Computer peripherals; HID devices Video conference equipment Remote control Video gaming equipment Multi-player PC & video games Remote controls for audio and video equipment.

Human Input Devices (HID)

Keyboard Mouse / Pointing Device Remote Controls (controls for audio & video equipment) Gaming device Double Joystick.

PATIENT MONITORING

May allow more patient freedom Monitors vital statistics and sends via internet Patient can remain in their own home Lowers cost and improves comfort Can be used in hospice care. Patients are allowed greater movement Reduced staff to patient ratio Light way to bathroom when they get out of bed Reduces patient confusion.

LIGHTING CONTROL

Wireless Lighting Control Dimmable ballasts Light switches anywhere Customizable lighting schemes Energy Saving on bright days.

ZIGBEE VS BLUETOOTH ZigBee Smaller packets over large network Mostly Static networks with many, infrequently used devices Home automation, toys, remote controls, etc.Bluetooth Larger packets over small network Ad-hoc networks File transfer Screen

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

ZigBee and othrer wireless technologies

ZigBee operates in the industrial, scientific and medical (ISM) radio bands; 868 MHz in Europe, 915 MHz in the USA and Australia, and 2.4 GHz in most jurisdictions worldwide. The technology is intended to be simpler and less expensive than other WPANs such as Bluetooth.

ZigBee chip vendors typically sell integrated radios and microcontrollers with between 60K and 256K flash memory, such as the JennicJN5148, the Freescale MC13213, the Ember EM250, the Texas Instruments CC2530 and CC2520, the Samsung Electro-Mechanics ZBS240 and the Atmel ATmega128RFA1. Radios are also available as stand-alone components to be used with any processor or microcontroller. Generally, the chip vendors also offer the ZigBee software stack, although independent ones are also available. Because ZigBee can activate (go from sleep to active mode) in 15 msec or less, the latency can be very low and devices can be very responsive — particularly compared to Bluetooth wake-up delays, which are typically around three seconds. Because ZigBees can sleep most of the time, average power consumption can be very low, resulting in long battery life.

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Advantages Of ZigBee

Though development of Zibee standards is still under progress, there are lot many applications for ZigBee due to their some good advantages. Zigbee is mostly used in Home automation system and control.

Here's some advantages of ZigBee

1. Chip-vendor independence2. Rapid innovation3. Extremely Low cost4. Open standards enable markets5. Easy to deploy6. Excellent performance in environments with low signal-to-noise ratio7. Appropriate range of operation (30 - 100 meters)8. Appropriate and reliable data transfer, bit rate : 250kbps at 2.4 GHz9. Very low power consumption10. Secure data transfer11. Zigbee protocol needs less than 64 kb of ROM and 2-32 kb of RAM12. Zigbee can be implemented with any type of microcontroller

Limitation

The main disadvantages of ZigBee include short range, low complexity, and low data speed. Due to their high cost, GSM and GPRS are normally used in concentrators to transmit data to the main station, or in high end multi-function meters. ZigBee is used mainly in the concentrators, data collectors, repeaters, and meters installed in the urban distribution AMR systems and prepayment systems. Because of the good real time capability of RF, meters are often equipped with a remote control function.

Future

ZigBee – the future is wireless? ZigBee has emerged as the ‘next big thing’ in wireless technology. Between Bluetooth and RFID in terms of capability, ZigBee can network the micro-controllers found in so many of the products we buy – with around seven billion embedded in 2005 alone. It should enable a much wider range of wireless products – from sensor networks to ventilation controls, coffee makers to light switches.ZigBee, named after the honeybee’s communication technique, is a networking protocol that sits on top of globally standardised radio devices. For the semiconductor industry, this will

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lead to a huge new market for the chips required to produce such cheap networking hardware. For the product developer, ZigBee will transform current product design and reveal unexplored opportunities.

CONLUSION

It is likely that ZigBee will increasingly play an important role in the future of computer and communication technology. In terms of protocol stack size, ZigBee's 32 KB is about one-third of the stack size necessary in other wireless technologies (for limited capability end devices, the stack size is as low as 4 KB). The IEEE 802.15.4–based ZigBee is designed for remote controls and sensors, which are very many in number, but need only small data packets and, mainly, extremely low power consumption for (long) life. Therefore they are naturally different intheir approach to their respective application arenas. 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 and very fast market adoption.

REFERENCES

[1] ZigBee Alliance,ZigBee Specification.Version 1.0 ZigBee Document 053474r06, December 14th, 2004.

[2] P. Kinney, ZigBee Technology: Wireless Control that Simply Works, White Paper dated 2 October 2003.

[3] Behrouz A. Frouzan, “Data Communication”, Third Edition, Tata McGraw-Hill Publishing company Limited, 2004, Pp 19-110.

[4] Andrew S. Tenenbaum, “Computer Networks”, Fourth Edition Pearson Publication Limited, 2003, Pp 21-89.

[5] William Stalling, “Wireless Communication and Networks”, Fourth Edition, Pearson Publication Limited, 2004, Pp 39-118.

[6] 802.15.4, Part 15.4: Wireless Medium Access Control(MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (LRWPANs).

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[7] Sheng-Fu Su, The Design and Implementation of the ZigBee Protocol Driver in Linux, White Paper dated 26 July 2005.

[8] Jacob Munk-Stander,Implementing a ZigBee Protocol Stack and Light Sensor in TinyOS,White Paper dated October 2005.

[9] Freescale Semiconductor,ZigBee Implementer’s Guide ;Document Number:F8W-2004-0007,May 23, 2005

[10] Weiser, M. (1991). The Computer for the 21st Century. Scientific America, September 1991. 94-104.

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