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CHAPTER 3

ZIGBEE, RFID, BLUETOOTH AND WI-FI

3.1 ZigBee (IEEE 802.15.4) technology

ZigBee standard is a popular low cost and low power mesh network standards for short

distance wireless networking worldwide with a defined rate of 250 kbps (well suited for

intermittent or periodic data). Most of the ZigBee nodes operate efficiently in sleep mode and

offer reduced average power consumption. Mesh networking provides high reliability and

more extensive range.The IEEE 802.15.4 standard is developed for personal area networks

and supports physical and data link layers for Low data Rate Wireless Personal Area

Network.The IEEE 802.15.4 standard is enhanced for the implementation of ZigBee by adding

network and an application framework as well as security layers.

3.1.1 Characteristics of ZigBee

a) 2.4 GHz upper frequency band is used.The lower band frequencies are 915 MHz in

America and 868 MHz in Europe. Free bands are also available as a pair of 4-2.4835

GHz, 868-870 megahertz and 902-928 megahertz.The number of channels assigned for

every band is considered as sixteen, one and ten respectively.

b) Low power usage.

c) Discovery and pairing techniques coexists in the application of IEEE 802.15.4

d) ZigBee uses various types of star topology and it is designed with inter-personal area

network (PAN) communication with a Centralized control of all ZigBee nodes under

coordinator.

e) The IEEE 802.15.4 uses various transmission techniques like broadcast, Security key

generation mechanism with AES-128.

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f) Reduced maintenance: The ZigBee network has its own function of self-configuring

and self-healing capabilities. These properties help Mesh networks to automatically

detect and troubleshoot problems that may occur in the connected nodes.

3.1.2 Devices and Topologies (ZigBee)

The IEEE 802.15.4 standard adopts two different types of device that are implemented in a

network namely; the FFD (Full-Function Devices) and the RFD (Reduced-Function Devices).

Figure 3.1 shows the different types of ZigBee topology.

ZigBee logical device types

There are mainly three different categories of nodes in a ZigBee topology. They are

classified as Coordinator, Router and End devices.

Coordinator (ZC)

This is the single main root of the network tree and as a bridge it connects to other

networks. This node is solely responsible for initiating as well as selecting the network

parameters like radio frequency channel, unique network identifier and setting other

operational parameters. This node can also store all the information about network and its

security levels.

Router (ZR)

Router function as intermediate nodes between coordinator and end device and it is

relaying data from other devices. Router can communicate with existing network and can able

to connect with other devices. It is retransmitting the information to the network. Any of the

networks can be extended with the use of ZigBee IEEE 802.15.4 standard routers.

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End Devices (ZED)

Always End Device can be designed with very low-power and battery-powered devices.

They can receive information from sensors and switches. End devices can communicate with

either the coordinator or a router and cannot retransmit data from any of the devices. Due to

this very less work schedule of end device, they can be designed with low power usage and it

is economical one. These end devices need not be active for the whole time while the

coordinator and router will work its entire time period. Due to this reason, the ZigBee end

node can remain asleep only up to the time its work needed by the particular network.

3.1.3 ZigBee physical device types

Full Function Devices can able to perform all available operations like coordination work,

routing and sensing the environment within the IEEE 802.15.4 standard. Always the FFD can

able to play either coordinator or router also the end devices. End device can be designed as

either FFD or RFD depends on its specific application. But Reduced Function Devices can

handle only a selected function of the IEEE 802.15.4 standard protocol. Table 3.1 shows

comparison between three types of ZigBee‟s topologies.

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Figure 3.1 ZigBee Topology

Start topology Cluster-Tree topology

PAN Coordinator (FFD) Router (FFD) End device (FFD)

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TABLE 3.1 Comparison of ZigBee’s three topologies

S.No

Star Topology

Tree Topology

Mesh Topology

1. Single coordinator is

connecting group of nodes or

devices.

Always a coordinator act as the

root of the tree.

Here all the

messages can be

transmitted through

multiple paths.

2 If the coordinator fails, the

entire network will stop its

work because all the data

communication was handled

by the coordinator only.

The messages are continuously

transmitted by any one level of

the source node and until it is

reached to the destination.

It will direct the

network to search for

an alternate path for

the message to be

transmitted.

3 The function is very simple. Very much reliable. Most flexible.

4 When the number of nodes

increases, the overall network

efficiency is reduced.

This topology can be applied

for any different levels of

nodes.

Can be implemented

in any of the

condition of the

particular network.

The IEEE 802.15.4 standard defines two different functions for the channel access.

a) Beacon enabled modes

This mode provides a power management technique based on duty cycle. This mode is

implemented with a super frame structure and is bounded by beacons.

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b) Non-beacon enabledmodes

In this type, there is no super frame technique and no power management implemented at

the MAC layer. In the non-beacon enabled mode, the CSMA/CA algorithm is used with the

unslotted version. ZigBee (IEEE 802.15.4) protocol stack diagram shows the specified layers

for application. It consists of the Application Layer, Application Framework, Network Layer,

MAC Layer and Physical Layer (Figure 3.2). The application layer consists of ZigBee Object

Device and Application Support (APS) Sub layer for particular application. The wireless

network of ZigBee is called ZigBee Object Device. It consists of the nodes end device, routing

and coordinator that participate in the network.

ZigBee alliance consists of an application framework and network layer. Network layer is

supporting its routing information, discovery of specific route and security. Frame counter is

managing all the messages it receives and detects it. The MAC and physical layer is located

after the IEEE 802.15.4. These layers provide secured communication between the entire

nodes of the specific network and improve efficiency after avoiding collisions between the

nodes. The main function of these layers is to decide as well as assemble routing the entire

data packets and frames.

ZigBee (IEEE 802.15.4) protocol stack diagram shows the specified layers for application.

It consists of the Application Layer, Application Framework, Network Layer, MAC Layer and

Physical Layer (Figure 3.2).The application layer consists of ZigBee Object Device and

Application Support (APS) Sub layer for particular application. The wireless network of

ZigBee is called ZigBee Object Device. It consists of the nodes end device, routing and

coordinator that participate in the network. ZigBee alliance consists of an application

framework and network layer. Network layer is supporting its routing information, discovery

of specific route and security. Frame counter is managing all the messages it receives and

detects it.

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Figure 3.2 ZigBee Protocol Stack

3.1.4 ZigBee Protocol Architecture

Physical Layer

The physical layer of the IEEE802.15.4 standard is the closest layer to the hardware,

which control and communicate with the radio transceiver directly. It handles all tasks

involving the access to the ZigBee hardware, including initialization of the hardware, channel

selection, link quality estimation, energy detection measurement and clear channel assessment

to assist the channel selection.

APPLICATION FRAMEWORK

NETWORK LAYER

APPLICATION PROFILE

MAC LAYER

PHYSICAL LAYER

ZigBee Alliance

IEEE 802.15.4

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Figure 3.3 IEEE 802.15.4 PHY Overview – Packet Structure

MAC Layer

This layer provides interface between physical layer and network layer. This provides two

services; MAC layer is responsible for generating beacons and synchronizing devices to the

beacon signal in a beacon enabled services. It is also performing association and dissociation

function. It defines four frame structures, are Beacon frame, Data frame, Acknowledge frame,

MAC command frame.

Network Layer

Network layer interfaces between application layer and MAC Layer. This Layer is

responsible for network formation and routing. Routing is the process of selection of path to

relay the messages to the destination node.

Application Layer

The application Layer is the highest protocol layer and it hosts the application objects.

ZigBee specification separates the APL layer into three different sub-layers: the Application

Support Sub layer, the ZigBee Device Objects, and Application Framework having

manufacturer defined Application Objects.

Preamble Start of Packet PHY PHY Service

Delimiter Header Date Unit (PSDU)

6 Octets 0-127 Octets

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The application objects (APO)

Control and manages the protocol layers in ZigBee device. It is a piece of software which

controls the hardware. A ZigBee application must conform to an existing application profile

which is accepted ZigBee Alliance. An application profile defines message formats and

protocols for interactions between application objects.

ZigBee Device Object

The key definition of ZigBee is the ZigBee device object, which addresses three main

operations; service discovery, security and binding. The role of discovery is to find nodes and

ask about MAC address of coordinator/router by using unicast messages. The security services

in this ZigBee device object have the role to authenticate and derive the necessary keys for

data encryption. The role of binding manager is to binding nodes to recourses and applications

also binding devices to channels.

Application support sub layer

The Application Support (APS) sub layer provides an interface between the network and

the application layers through a general set of services provided by APS data as well as

management entities.

Security service provider

ZigBee provides security mechanism for application support layers and network layer,

each of which is mainly responsible for securing their frames. Security services include

methods for key establishment, key transport, frame protection and device management.

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3.1.5 The Propagation Model

The main purpose of propagation model is to find the probability of satisfactory

performance of a wireless system that depends on radio wave propagation. H. T. Friis assumes

that the free space propagation model is an ideal propagation condition. The model has only

one clear line-of-sight path between the specified transmitter and receiver. The model is used

to estimate path loss initially. The relationship between the transmit power, antenna gains,

wavelength and distance between transmitter and receiver is given in eqn.3.1.

Pr (d) = PTGTGR(λ/4πd)2

------------ (3.1)

Where PT is the transmitted power; Pr (d) is the received power; GR is the receiver-

antenna gain; GT is the transmitter-antenna gain, d is the distance between the transmitter and

the receiver; and λ is the wavelength. When the antennas are assumed to have unity gain, the

path loss in dB (PL) can be defined as:

PL (dB) = 10 log pT ∕pR ------------ (3.2)

3.1.6 Need for ZigBee

There is more number of standards that address mid to high data rates for PC LANs, voice,

video, etc. However, there has not been a wireless standard that meets the needs of control

devices and sensors. Controls and Sensors don‟t need high bandwidth but they do need very

low energy consumption and low latency for long battery lives and for large device arrays.

1. There are many proprietary wireless systems manufactured nowadays to solve

problems that do not require high data rates but they require very low current drain and

low cost.

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2. These proprietary wireless systems were designed because there were no such

standards to meet their requirements. These systems are creating interoperability issues

with each other and with current technologies.

3.1.7 Form a ZigBee Network and Architecture

The Co-ordinator is mainly responsible for starting a ZigBee network. Network

initialization involves the following steps:

Search a Radio Channel-The Co-ordinator searches a suitable radio channel (generally

it has least activity). This search can also be limited to usable channels - for example,

wireless LAN operating frequencies are avoided.

PAN ID is assigned - PAN ID (Personal Area Network identifier) is assigned to the

network by the Co-ordinator. The PAN ID can be obtained or can be pre-determined

dynamically by checking other networks using the same frequency channel and

assigning a PAN ID that may not conflict with theirs. The Co-ordinator assigns a

network address also to itself. Generally, that address is 0x0000.

To Start the Network- The Co-ordinator is configuring and starts itself in Co-ordinator

mode. It will respond to queries from other devices those wants to join the network.

3.1.8 Forming a Security Architecture for ZigBee

A 128-bit key can be associated either to both the MAC sub layer and ZigBee layers or to

a link, acquired through agreement, pre-installation or transport. Secured network will find

special device which other devices trust for the security keys distribution: the trust center.

Typical applications without special security needs will use a network key provided by the

trust center (through the initially insecure channel) to communicate.

The trust center maintains the network key and point-to-point security is provided.

Devices can accept messages originating from a key provided by the trust center only, except

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for the particular initial master key. The architecture for security is distributed in the network

layers as follows:

The MAC sub layer can be capable of reliable single-hop communications. The

security level is specified by the upper layers.

The network layer manages processing received information, routing and broadcasting

requests. The adequate link key will be used by outgoing frames according to the

routing, if it may be available; or to protect the payload from external devices, the

network key will be used.

The application layer offers transport services and key establishment to both

applications and ZDO. Master, link and network keys are three kinds of Keys

available.

3.2 RF COMMUNICATION

Radio frequency (RF) is the EM (electromagnetic) wave frequencies that frequency range

lie around 3 kHz to 300 GHz and it may be included those frequencies used for radar signals

or general communications. RFID (Radio Frequency Identification) originated in the period of

World War – II. Recently, RFID based devices have been applied successfully to the areas of

supply chain, manufacturing, transportation, agriculture, healthcare and services etc. Research

in RFID has been growing at a fast pace. RF refers generally to electrical oscillations but not

mechanical oscillations. RFID concept has been applied to transportation systems. RFID-

based toll collection systems in highways are employed nowadays in many countries, like the

Autopass system in Norway or the Telepass system in Italy. Freely access control to car

parking or private areas or monitoring systems to avoid vehicle theft are the other applications

included. The Traffic Alert System is used to transmit traffic signals at required parts of the

road. The RF transmitter is fixed on roadsides and emits RF signals based on the sign boards.

RF receiver in the particular vehicle will receive this code and send it to the microcontroller.

Microcontroller decodes the received signals and indicates the traffic signal in the LCD

screen. The driver is warned by the Anti- Collision Circuit when the vehicle is close to other

objects dangerously.

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RFID technology has both the combination of tags and readers. The tags transmit and store

data using radio waves to readers. The readers receive data from the various tags and relay

them back to the server for further processing and analysis. The system serves the purposes of

monitoring, identification, alerting and authentication through this exchange of information

between the the reader and tag. The tag and the reader will not be in plain sight and also the

process is automatic.

RFID with barcodes can be compared. In barcodes technology, scanner and the barcode

are in direct line of sight to be scanned and the both items have to be moved against the

scanner physically for data collection. But, RFID tags transmit data to the reader automatically

even without a line of sight. RFID can be used to data capture automatically. RFID may be

compared to BAR CODES

Similarly - a support tool to improve operations management and automate processes.

Eliminates human errors and reduces labor.

Used to hold a wealth of data at your fingertips.

Different, in that:

No need for line-of-sight because tags can be embedded and hidden. They can be read

easily through plastic, wood, cardboard and any material except metal.

Tags can be reprogrammed whenever needed.

Applicable in harsh environments like moisture, high temperatures, chemicals and

outdoors.

3.2.1 RFID Principles

RFID has more number of types, but RFID devices can be divided into two classes: active

and passive. Active tags need a power source and may be connected to a powered

infrastructure or may use an integrated battery. But in the latter case, lifetime of a tag can be

limited by the stored energy; the device must undergo the number of read operations. One

general applications of an active tag is an aircraft attached with the transponder that identifies

its national origin. In passive RFID, the tags require no batteries or maintenance. The tags are

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very small practical one to fit into an adhesive label and have an indefinite operational life. A

passive tag has three parts: a semi- conductor chip, an antenna attached to the chip and

encapsulation. The tag reader is mainly responsible for communicating with a tag and

powering. The tag antenna transfers the tag‟s ID and captures energy. Magnetic induction and

electromagnetic (EM) wave capture are the two different RFID approaches exist for

transferring power to the tag from the reader. These two designs have an advantage of an RF

antenna associated with the EM properties; the near field and the far field. To sustain its

operation, both the fields may transfer enough power to a remote tag between 10 μW and 1

mW, depending on the particular tag type. When comparing Intel XScale processor and Intel

Pentium 4, an Intel XScale processor consumes is approximately 500 mW and an Intel

Pentium 4 consumes maximum up to 50 W. Applying different modulation techniques, near-

and far-field signals can transmit as well as receive data.

3.2.2 Near-field RFID

Near-field coupling between a reader and tag is the basis of Faraday‟s principle of

magnetic induction. A tag is placed that may incorporate a smaller coil (Figure 3.4) in this

field; an alternating voltage will develop across it. If this voltage is coupled and rectified to a

capacitor, a charge accumulates, which can be used to power the tag chip. Using load

modulation, Tags will use near-field coupling and send data back to the reader. Own small

magnetic field will rise when any current drawn from the tag coil which may oppose the

reader‟s field and the reader coil can detect and find this as minimum increase in current

flowing through it. Usually to ensure efficient power transfer, a transformer‟s primary as well

as secondary coil is wound closely together. When the magnetic field extends beyond the

given primary coil, a secondary coil may acquire energy at a distance, similar to a tag and a

reader. By monitoring any change in current through the reader coil, the reader can then easily

recover this signal. A more number of modulation encodings are possible based on the number

of ID bits needed, additional redundancy bits placed in the code to remove errors resulting

from noise in the communication channel and the data transfer rate.

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Near-field coupling is the main approach for implementing a passive RFID system. Near-

field communication has many limitations. When the operation frequency increases, the

distance of near-field coupling may operate decreases. Some other limitation is the energy

available for induction of the coil as a function of distance from the reader coil. So as all

applications require more number of ID bits and discrimination between multiple number of

tags in the same place for a fixed read time, each tag may require higher operating frequency

as well as a higher data rate. These kinds of design pressures have found a new passive RFID

based designs on far-field communication.

Figure 3.4 Near-field communications (for RFID tags operating at less than 100

MHz.)

Using induction for power coupling from

reader to tag & load modulation to transfer

data from tag to reader

RFID reader

RFID tag

Data changes

in the field

Alternating magnetic field in

the near-field region

Magnetic field affected by the

tag data

Glass or plastic encapsulation

Near field region Far field region

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3.2.3 Far-field RFID

Far-field emissions based on RFID tags capture electromagnetic waves propagating from

a dipole antenna which is attached to the reader. A dipole antenna in the tag can receive this

energy as potential difference that may appear across the arms of the dipole. A diode can

easily rectify this alternating potential and link it to a given capacitor, which may result in an

accumulation of energy in order to power its circuit. The technique used for commercial far-

field RFID tags is now back scattering (Figure 3.5). If an antenna is designed with precise

dimensions, it may be tuned to a specific frequency and absorb the maximum of energy that

can reach it at that frequency. If an impedance mismatch occurs at this particular frequency,

the antenna will definitely reflect back small amount of the energy (as tiny waves) toward the

reader, which can detect the energy using a radio receiver. By changing the antenna‟s

impedance, the tag can reflect back less or more of the incoming signal in a specific pattern

that encodes the tag‟s ID. In general practice, a tag‟s antenna can be detuned for this purpose

by placing a transistor across its dipole and then turning it on and off. Tags used for far field

principles operate at greater than 100 MHz in the UHF (ultra high-frequency) band (i.e 2.45

GHz) typically; below this range of frequency is the domain of RFID based on near-field

coupling.

A far-field range can be limited by the energy that can reach the tag from the reader and by

how sensitive the reader‟s radio receiver is to the reflected signal. The actual reflected signal is

small, because of two attenuations, each signal based on an inverse square law. The first

attenuation occurs when electromagnetic waves radiate from the reader to the tag, and the

second attenuation happens when reflected waves comes back from the tag to the reader. Now

the returning energy is 1/r4 (r is the separation of the tag and reader). The energy required to

power a tag at a particular frequency may continue to decrease (few microwatts) by the

shrinking feature size of semiconductor manufacturing based on Moore‟s law. We may design

tags that can be read at greater distances increasingly with modern semiconductors than were

not possible a few years ago. With improved sensitivity, economical radio receivers have been

developed and they can easily detect signals, with power levels of 100 dBm in the 2.4-GHz

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band. A typical far-field reader may interrogate successfully tags 3 m away, and very few of

the RFID companies claim their devices can be applied to read ranges of up to 6 m.

Figure 3.5 Far-field communications (for RFID tags operating at greater than 100

MHz).

3.2.4 RF Module

The Radio frequncy module operates at Radio Frequency Transmission through RF is

better than infrared (IR) because of more number of reasons. Initialy, signals through RF may

Antenna dipole

Power

Data (If tag

supports data write)

RFID tag

Data modulated on

signal reflected by tag

RFID reader

Using electromagnetic (EM) wave capture to transfer power from reader

electromagnetic (EM) wave capture to transfer power from reader to tag

c (EM) wave capture to transfer power from reader to tag and EM

capture to transfer power from reader to tag and EM backscatter to

transfer power from reader to tag and EM backscatter to transfer data

from reader to tag and EM backscatter to transfer data from tag to reader

tag and EM backscatter to transfer data from tag to reader

backscatter to transfer data from tag to reader

transfer data from tag to reader

from tag to reader

reader

electromagnetic waves

c waves (typically UHF)

(typically UHF)

UHF)

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travel through longer distances and suitable for long range communications. IR operates in

line-of-sight mode mostly. RF signals can pass even when there may be an obstruction

between transmitter and receiver. Next, when comparing IR transmission with RF

transmission, RF commnication is more strong and reliable. RF transmission uses a particular

frequency unlike IR signals which may be affected by other IR emitting sources.

RFID systems have three components in two combinations: antenna and a transceiver

(transmitter/receiver) are combined as an RFID reader as shown in Figure 3.6. Antenna and a

transponder (transmitter/responder) are combined to act as an RFID tag. When the reader

emits a RF signal that activates the transponder, an RFID tag is read which sends back data to

the transceiver. A basic RFID system must have the three components:

A transceiver with decoder

An antenna or coil

A transponder (RF tag) electronically programmed with unique information

There are two types of transponders that can be correlated to the two main types of RFID tags.

RFID tags and Passive transponders have no energy source of their own, for the power

to respond to rely on the energy given off by the reader. Passive RFID tags are cheaper

and likely to be used for general consumer goods.

Tag and an active transponder has power source internally and it uses to generate a

signal to a reader. Passive transponders are less expensive than active ones. They can

transmit signals over miles like general radiocommunications. They may be commonly

used in navigation systems for private and commercial aircraft.

Radio signals can be emitted by the antenna to activate the tag and to read as well as

write data to it.

The reader can emit radio waves in ranges of one inch to 100 feet or more, depending

upon the radio frequency used and its power output. RFID detects the reader's

activation signal, when an RFID tag passes through the electromagnetic zone.

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The reader can decode the data encoded in the tag's silicon chip (integrated circuit) and

the data is passed to the host computer for processing.

Figure 3.6 Working of RFID

3.2.5 Benefits of RFID

RFID may replace commonly used barcodes in the near future; the following advantages

apply RFID for added value of identification:

Tag detection will not require human intervention, so reduces employment costs in

order to eliminate human errors from data collection

Tag placement is very less constrained because of no line-of-sight is required,

RFID tags have a longer read range than barcodes

Tags may have memory capability of read/write, but barcodes do not have it.

An RFID tag can generally store maximum amounts of data to a unique identifier,

Unique item identification is one of the easier function to implement with RFID than

with barcodes,

It can easily identify items individually rather than generically.

RF

Module

Control

Module

Host

Computer

RS232/RS422

Reader Antenna Transponder

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Tags are very less sensitive to adverse conditions such as chemicals, dust, physical

damage etc.

Many number of tags can be read simultaneously,

RFID tags can be generally combined with sensors,

Automatic reading at many places reduces time lags and also inaccuracies in an

inventory,

Tags can store additional information locally; such type of distributed data storage can

increase fault tolerance of the given entire system,

Reduces provisioning costs and inventory control,

Tags reduce warranty claim processing costs.

3.3 BLUETOOTH

Bluetooth is a most popular networking technology aimed at short range and low-powered

applications. Initially, it was developed by Ericsson. It is governed as an open specification by

the Bluetooth Special Interest Group. Recently Bluetooth is a standard for short range and low

power wireless communication. Initially, it is assigned simply as a wire replacement

technology. Its generally described application is that „cordless computer‟ consisting of many

devices including a p ossibly a laptop, personal computer, mouse, joystick, keyboard,

printer,scanner, etc., each one added with a Bluetooth card. There are no wired connections

between these devices, and the function of Bluetooth is to enable seamless communication

between all the devices, replacing what is today achieved with a combination of parallel cables

and serial cables essentially, and infrared links. However, Bluetooth has the potential for being

much more than a wire replacement technology, and the Bluetooth standard was indeed

drafted with such a more ambitious goal inmind. Bluetooth will become the technology for

adhoc networks of the future. Because it‟s low cost and low power consumption make it an

attractive solution for the mobile devices used in adhoc networks. Bluetooth is a common

specification for Wireless Personal Area. It is a novel way to connect as well as exchange data

and information between laptops, mobile phones, video games and digital cameras. The

transmition is wireless and has the range of up to 10 meters. Bluetooth may be used to transfer

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photos, files and songs from the mobile to other mobile/device. The Bluetooth consists with a

wireless headset and in free with the computer or mobile phone, the wireless headset may be

useful for people while driving the car because they are hands free.

3.3.1 Bluetooth operation

Connection establishment

Concept of an ad-hoc piconet

The basic operation of a Bluetooth network is indicated. All nodes are organized in small

groups called as piconets. Each piconet has a main leading node called „master‟ and other

nodes in a piconet may be referred to as „slaves‟. A node can belong to many or multiple

piconets, and it can be refered to as a „bridge‟. A piconet can have maximum of 7 members.

Each and every communication in a piconet may involve the master, so that slaves can not

directly communicate with each other but instead they rely on the master as a transit node.

Bluetooth communication is a half-duplex communication channel. Communication between

nodes in different types of piconets must involve the bridge nodes. Also a bridge node cannot

be simultaneously active in different types of piconets. It is generally active in one piconet and

„parked‟ in others types. Bluetooth allows various activity states for the nodes: idle, active,

sniffing and parked. Data transfer takes place between any two nodes only when both are in

active state. Periodically activity states of nodes may change.

Two devices are connected via Bluetooth requires phases:

Inquiry: This process consists of sender transmitting/broadcasting inquiry packets,

which will not contain the identity of the sender or any other information.

_ Inquiry Scan: In this condition, receiver devices listen for inquiry packets, and upon

detection of any such type of packet, the device broadcasts an inquiry response packet.

This message has the identity of the device and its native clock.

Page: When paging, a sender device form a connection with a node/device whose

identity and clock are known. Page packets are sent, for synchronization which

contains the sender‟s node address and clock.

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_ Page Scan: In this condition/state a receiver device/node listens for page packets.

Receipt is now acknowledged and synchronization between the devices/nodes is

established

3.3.2 Protocol Stacks of Bluetooth

A protocol stack is a combination of hardware/ software implementation of the actual

protocols specified in the given standard. The Bluetooth protocol stack is shown in Figure 3.7.

Every component of the Bluetooth stack is explained below.

Bluetooth Radio: specifics details of the air interface, modulation scheme, including

frequency, frequency hopping and transmission power.

Baseband: connection establishment within a piconet, packet format, addressing,

power control and timing.

Link manager protocol (LMP): It establishes the link setup between Bluetooth

devices/nodes and manages ongoing links, control and negotiation of baseband packet

size and including security aspects (e.g. authentication and encryption).

Logical link control and adaptation protocol (L2CAP): adapts to the baseband layer

with upper layer protocols. Provides both connection-oriented services and

connectionless.

Service discovery protocol (SDP): handles services, device information and queries

for service information between two or more Bluetooth devices.

Host Controller Interface (HCI): for accessing the Bluetooth hardware capabilities,

it provides an interface method.

TCS BIN (Telephony Control Service): bit-oriented protocol will define the call

control signaling for the establishment of data and voice calls between Bluetooth

devices.

OBEX (OBjectEXchange) : It is the session-layer protocol for the exchange of

objects, providing a model for operation and object representation.

RFCOMM: a most reliable transport protocol, which may provide emulation of

RS232 serial ports over the L2CAP protocol.

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WAE/WAP: Bluetooth incorporates the wireless environment for varioys applications

and the wireless application protocol into its architecture.

Figure 3.7 Bluetooth Protocol Stack

3.3.3 Piconets and Scatternets

The main basic unit of Bluetooth networking is a piconet. A general description of each of

the two terminologies is given below:

Piconet - It is one of the Bluetooth network that may have up to eight stations, one of

which is called as master and the others are called as slaves as shown in Figure 3.8.

Scatternet - It is computer network that has two or more piconets as shown in Figure

3.9. A scatternet has the main advantage of communication between more than eight

devices.

Host Controller Interface

(HCI) Baseband

Bluetooth Radio

UDP TCP

IP

PPP

RFCOMM

L2CAP

LMP

Audio

vCard/vCal

OBEX

WAE

WAP

wa

wwa

AT-

Commands

TCS BIN SDP

54

Figure 3.8 Piconet

Figure 3.9 Scatternet

3.3.4 Power management in Bluetooth

Two important states are defined for Bluetooth devices:

1. Standby: In this condition, no data are exchanged and only the clock is running.

2. Connection: Every device is connected with the master of the piconet. Here, Four sub-

states are possible:

Active mode: the device is always active in the piconet.

Piconet no.1

Piconet no.2

LAPTOP

Mobile

Phone

PDA

55

Sniff mode: this is considered as a low-power-consumption state as the

listening activity is working only during the sniff slots.

Hold mode: the ACL traffic of a device is stopped for a certain specific period.

Park mode: the device will be no longer a member of the piconet, but it may

remain synchronized with the particular master of the piconet; this is the

minimum power-consuming state.

3.4 IEEE 802.11 (Wi-Fi)

The IEEE 802.11 standard is used to provide wireless connectivity to devices that may

require a quick installation, such as PDAs, portable computers, or generally mobile devices

inside a Wireless Local Area Network (WLAN). It may use the MAC procedures for

accessing the physical medium, which can be either infrared or radio frequency. Mobility is

handled generally at the MAC layer, so handoff between adjacent cells is more transparent to

layers built on top of an IEEE 802.11 device.

3.4.1 Protocol overview

A Wi-Fi Wireless LAN (WLAN) is based on a concept of cellular architecture; each and

every cell is called a Basic Service Set (BSS). A BSS is a set of fixed or mobile Wi-Fi

stations. Access to the communication medium is controlled by a set of rules called a

coordination function. Wi-Fi defines a Point Coordination Function (PCF) and Distributed

Coordination Function (DCF). The simplest wireless network configuration is the IBSS

(Independent BSS), which may implement an ad hoc network comprising minimum two

stations: no standard structure exists. So to create a multihop network, it requires higher-level

protocols. A BSS infrastructure may be part of a wider network and then it is called as

extended service set (ESS). An ESS is a set of more than one infrastructure BSSes connected

via a Distribution System, whose system nature is not specified by the standard: it may be a

cabled network, or other type of wireless network; 802.11f will indicate the Inter-AP Protocol.

The stations connected to the Distribution System may be called as Access Points (AP).

56

Services offered by the particular stations fall into two classes: distribution system services

and station services. The first one is offered by the APs, and allows transfer of datas between

stations belonging to different BSSes. The standard may also define the Portal functions,

which is a bridge for interconnecting a Wi-Fi WirelessLAN with an IEEE 802.x LAN. Figure

3.10 illustrates all the components of a Wi-Fi network.

The available bandwidth may be divided into 14 overlapping channels partially, each 22

MHz wide. Only 13 of these channels are available in the Europe, 11 in US, and 1 in Japan.

All the devices in the same BSS (it may be either infrastructured or ad hoc) use the same

channel. One of the particular three techniques is used for multiplexing: a) the DSSS (Direct

Sequence Spread Spectrum), which may use a Barker sequence, can be adopted for the 1 and 2

Mb/s signal rates; b) the CCK (Complementary Code Keying), defined in 802.11b, can be

used for the 5.5 and 11 Mb/s signal rates; and c) the OFDM (Orthogonal Frequency Division

Multiplexing), defined in 802.11a and may be also used in 802.11g, which is used for 6, 9, 12,

18, 24, 36, 48 and 54 Mb/s.

DSSS uses Barker sequence of 11-bit, so each sequence of 11 chips may codify a single

information bit. The modulation rate is 1 Msymbol/s using either Binary Phase Shift Keying

(BPSK) or Quadrature Phase Shift Keying (QPSK), for data transmission rates of 1 or 2 Mb/s,

respectively. With CCK, a 16-bit sequence can be transmitted on the channel codifies either 4

or 8 information bits. The modulation is QPSK at 1.375 Msymbol/s, for signal rates of either

5.5 or 11 Mb/s. Note that in both CCK and DSSS cases the chip rate is 11 Mchip/s, which

mean that the radio section‟s lowest layer is the same; the difference lies in the multiplexing

and modulation. OFDM uses 52 sub-carriers (48 for data) with a spacing of 0.3125 MHz and

symbol duration of 4 ms, for a maximum total of 12 Msymbol/s. Each symbol may be

protected with a convolutional code of either 3/4, 2/3 or 1/2 rate, using M-ary Quadrature

Amplitude Modulation (MQAM) with M being 2, 4, 16 or 64. The resulting set of

combinations provides signal rates of 6, 9, 12, 18, 24, 36, 48 and 54 Mb/s.

57

Figure 3.10 Typical components of a Wi-Fi network

The basic Wi-Fi MAC protocol, which must be implemented by every station, is called

DCF (Distributed Coordination Function). DCF is nothing but a CSMA/CA (Carrier Sense

Multiple Access / Collision Avoidance) channel access method, used in both infrastructured

and ad hoc networks. If the station senses that no other station has transmitted for a short time,

called IFS (Inter Frame Space), it transmits a frame. In the case of unicast transmissions, the

ESS (extended service)

set)

BSS 2

AP

DS

Distribution system

BSS 1

AP

Ethernet

Desktop Disk Server

58

receiving station replies with an ack; if the transmitter did not receive the ack, it will

continuously retransmit the frame up to a maximum number of times before giving up: this is

a general standard ARQ mechanism. When a particular station must send a new frame just

after having sent one, it will wait for IFS, after that it initializes a backoff interval counter in

random and starts decrementing it at a given fixed rate while listening to the specific channel.

If it will detect that another station is transmitting, it will stop decrementing the counter value,

waits until the end of the present transmission, waits for IFS time period, and starts

decrementing the value of the counter from where it had left the work: this is called a backoff

procedure. When the backoff counter reaches zero, a backoff procedure ends, at which point a

frame may be sent. A station now enters a backoff procedure even when it may want to

transmit a frame, but detects that the channel is busy.

In the basic DCF access method, stations may use an RTS/CTS (request to send/clear to

send) mechanism optionally, which may be useful for decreasing the number of collisions

where hidden terminals are present. Let‟s suppose assume that stations A and C are both in

view of station B, but they can not see each other, either they may be too far apart, or because

there is an obstacle between them. When both A and C transmit data to B, they will often

collide, because neither will sense the transmission of the other, and neither will back off. To

reduce the collision, the transmitting station (say A) first sends an RTS, a short frame used to

get permission to transmit, and the particular receiving station (say B) responds with a CTS,

that means it is ready to listen. Station C does not receive the RTS, but it hears the CTS, and it

defers transmission. Since an RTS is very shorter than a given data frame, chances of a

collision are minimized.

Wi-Fi defines an optional medium access protocol called PCF (Point Coordination

Function), which can be applied for an infrastructured topology. Figure 3.11 shows the roles

of DCF and PCF in the Wi-Fi MAC, together with the new HCCA and EDCA coordination

functions described below.

The Point Coordinator (PC), a function generally performed by the AP, implementing a

round-robin policy to poll each and every station for data to be transmitted. PCF can also be

59

used to implement a CF (contention-free) access mechanism, in the meaning that the PC can

control the easy access of the stations, thus it will be avoiding any contention. The Wi-Fi

standard states that the two types called DCF and PCF may coexist: when in a BSS a PC is

present, PCF as well as DCF alternate, thus it is creating a contention-free period (CFP)

followed by a contention period (CP). Here it is not important for an AP to act as a PC, and it

is optional for a given station to implement the chance of replying to the PC‟s requests for the

CFP. The stations can implement this facility and are referred to as CF pollable stations.

Figure 3.11 indicates how the DCF and PCF methods may alternate: B shows the reference

beacon sent by the PC, at the start of every CFP, for the purposes of synchronization, which

can contain important information relevant to the CFP; NAV (network allocation vector) is set

by the particular station to compute the expected end of the current transmission.

Figure 3.11 How PCF and DCF alternate

3.4.2 Wi-Fi power management

A Wi-Fi device can be in either of the two states that is Awake or Doze states. In the Doze

state the station may not either transmit or receive, which reduces the energy consumption.

There are two modes of Power management: Active mode (AM), and Power save mode (PS).

PCF PCF

Busy

Medium

B B

DCF DCF

Contention

period

CF period Contention

period Contention free period

CFP repetition interval Foreshortened

Delay (due to a busy medium)

60

The handling of the specific stations in PS mode differs according to the topology of the Wi-Fi

network as follows (Refer Figure 3.12).

Figure 3.12 Power handling states in an infrastructured Wi-Fi device

Infrastructured network: a particular station in AM which wants to pass in PS must signal

the AP (access point) by implementing the power management bit in the header of its packets.

The AP stores all the traffic addressed to stations that are now in PS mode; when transmitting

the given periodic beacon, the AP sends the list of the available stations in PS mode and

whether it has traffic queued for them. At configurable and regular time intervals, the stations

in PS switch to AM in order to receive the beacon. If there is traffic addressed to them, the

specific stations can receive it and then return to PS.

Ad hoc network: stations can use the PS mode, but the function of storing the traffic

addressed to them is distributed to all of the the active stations, since no AP exists. All stations

in PS mode switch to awake state in a temporal window (ATIM window) during which the

stations that may have traffic stored for others send special frames (ATIM frames). If a station

Doze

Awake

AP

Stored data

Active

mode

Power save mode

Beacon received

at regular time

intervals

61

receives an ATIM frame, it remains or maintains in awake state in order to receive its traffic;

if not the station returns in PS mode until the next ATIM window is started. Note that:

b) Absence of a reference station such as the AP, the instantaneous state of a station (awake or

doze) can be estimated by all the other stations of the ad hoc network, for example according

to the history of the previous transmissions. In this topology, the standard will not specify any

methodology for estimating the power state of the stations.

c) The transmission and reception of the ATIM frames during the ATIM window occur

according to the specific DCF rules, i.e. according to the given CSMA/CA access method. It

means that a station should receive an ATIM frame addressed to itself, wait for the data

received, and yet not receive them because of congestion of the datas on the shared channel. In

conclusion, the Wi-Fi standard specifies one low-power state only, i.e. the Doze state.

3.4.3 Comparison between Bluetooth and Wi-Fi / Zigbee and RFID

Various parameters are analyzed between the nodes of Bluetooth and Wi-Fi as well as

Zigbee and RFID and tabulated as shown below (Table 3.2 and 3.3) respectively.

62

Table 3.2 Comparison between Bluetooth and Wi-Fi

Bluetooth Wi-Fi

IEEE

Standards

Initially under IEEE

802.15.1standard but now under by a

Special Interest Group (SIG).

It is defined under the IEEE standards

802.11.x (x=a, b, c,…….)

Versions Bluetooth 2.0, Bluetooth 2.1,

Bluetooth 3.0 and now the latest is

Bluetooth 4.0

Wi-Fi versions are defined as 02.11.a,

802.11b and so on.

Frequency 2.4 GHz frequency.

Wi-Fi based networks work at 2.4

GHz, 3.6 GHz and 5 GHz.

Data

Transfer

Rates

Latest Bluetooth type (Bluetooth 4.0)

has data transfer rates to be upto

25mbps

Latest version of Wi-Fi direct can

reach upto maximum of 250mbps of

data transferring rate.

Range Maximum communication range for

Bluetooth based wireless connections

is 30m

Maximum communication range for

Wi-Fi can extend well upto 100m.

Security Earlier versions of Bluetooth has

encryption process and but even now

Bluetooth security is limited to key

matching.

Wireless Equivalent Privacy (WEP)

and Wi-Fi Protected Access (WPA)

are two most used security accesses in

Wi-Fi widely.

Power

Consumption

It is less power consuming protocol. But it can able to works at longer

distances and always loaded with high

quality security protocols makes Wi-

Fi a more power consuming protocol.

Application Bluetooth is generally used to

connect peripherals to the computer.

Wi-Fi technology is generally used in

connecting computers to routers or

internet gateways.

63

Table 3.3 Comparison between Zigbee and RFID

Zigbee RFID

ZigBee is used for high-level communication

protocol. It comes under IEEE 802.15.4

standard and is also generally related to many

other wireless protocols.

RFID is considered as a part of Automatic

Identification and Data Capture (AIDC).

Zigbee network creates PANs (Personal Area

Networks) and these are built from small and

low-powered radio waves.

RFID is a wireless system in which data is

transmitted with the help of radio waves.

ZigBee always requires line-of-sight. RFID does not require line-of-sight.

ZigBee nodes are used for low-rate data

applications and it requires a long battery life.

Its data transmission range is limited to 10-

100 meters.

RFID has generally covers greater distance

for data transmission when compared to

ZigBee.

It is the ideal choice for devices that requires

low-rate wireless data transfer.

It is used for tracking any objects in the

assembly line. RFID has been credited for

revolutionizing the object tracking systems.

Zigbee nodes slightly more cost ($25?) than

RFID

RFID tags generally cost less ($5?)

Zigbee does not inherently give any specified

location information.

But with RFID to locate anything,we must

scan it from a few inches away.

Zigbee is a Personal Area Network (the nodes

all have batteries) range is many yards.

RFID usually refers passive tags, very low

cost and no battery needed but maximum

range only a few inches.

64

3.5 IoT: Applications in various fields

The IoT may offer wide range of applications in almost every aspect of our daily life, of

which only a few parts is currently available to us.

Natural disasters such as Prediction and monitoring

Industry based applications

Smart home environments

Medical and Healthcare

Intelligent transport system

Security and surveillance applications

Challenges

The IoT may change the shape of the Internet and can offer enormous economic benefits

but it also faces many key challenges.

Management of Identity and Naming System

Standardization

Information Privacy

Networking issue and network

3.6 Cloud computing

IoT connects billions of sensors and devices to create novel and innovative applications. In

order to support these types of applications, elastic, a reliable and agile platform is essential.

Cloud computing is one of the fast enabling platforms to support IoT. Iot is the devices which

can be connected to the internet to perform service related requirement that support our basics

65

need, our health and our environment. Hence cloud computing will act front end to access

Internet of Things. The cloud computing are tightly coupled in the Internet of thing.

3.6.1 Characteristics

On-Demand Self Service: Cloud computing based resources are web-based service that can

be access by the user without any helping or permission from other people but need the

communication within internet because internet is everything in the world.

Broad Network Access: Cloud computing resources may be access through a device that can

access network or have internet connection such as mobile devices, tablets and laptops.

Resource Pooling: Resource pooling will make that people are know the address can access

anytime and anywhere as they want.

Rapid Elasticity: This characteristic will empower IoT by providing elastic computing power,

storage and networking.

Measured Service: This cloud computing will measure your usage about their service such as

storage, bandwidth, and processing and active user accounts inside your cloud computing.

Service models

o Infrastructure-as-a-Service (IaaS)

o Platform-as-a-Service (PaaS)

o Software-as-a-Service (SaaS).

Infrastructure-as-a-Service (IaaS)

In IaaS, the use of hardware such as sensors and actuators can be made available to

consumers as cloud resources. Consumers can set up arbitrary services and manage the

hardware via cloud resource access control.

66

Platform as a Service (PaaS)

Platform as a service is a cloud model in which providers deliver apps over the Internet

and host users' software and hardware on their infrastructure. Platform as a service (PaaS) is a

cloud computing model that delivers applications over the Internet. Most Paas platforms are

geared toward software development and they offer developers several advantages. For

example, PaaS allows developers to frequently change or upgrade operating system features. It

also helps development teams collaborate on projects.

Software as a Service (SaaS)

Software as a Service (SaaS) is a software distribution model in which every application

are hosted by a vendor or service provider and made available to customers over a network

typically the Internet. Software as a Service (SaaS) is a software distribution model in which

applications are hosted by a vendor or service provider and made available to customers over a

network, typically the Internet. SaaS is closely related to the ASP (application service

provider) and on demand computing software delivery models.

3.6.2 Security and Privacy

Recently various authentication and encryption technologies such as message

authentication code (MAC) and Rivest Shamir Adleman (RSA) protect the authenticity and

confidentiality of transaction data as it transits between networks. Encryptions like full disk

encryption (FDE) are also performed for user specific data at rest to prevent unauthorized

access and data tampering. Other IP-based security solutions such as Internet Key Exchange

(IKEv2) and Host Identity Protocol (HIP) can also be used to perform authenticated key

exchanges over IPSec protocol for secure payload delivery. For data privacy, technical

implementations and policy approaches exist to ensure that sensitive data is removed or

replaced with realistic data (not real data).

67

This cloud computing is free to use anywhere and anytime as long as the computer is

connected with the Internet based on the service models which is Infrastructure-as-a-Service

(IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). The cloud is the only

technology suitable for filtering, analyzing, storing and accessing the information in useful

ways. The deployment models are based on the group, purpose and community.

3.6.3 Cloud IoT paradigm

Figure 3.13 shows the various applications of IoT and Cloud in day to day life. Cloud

IoT finds applications in every field. Cloud IoT products may be classified broadly into

various categories such as smart home, smart logistics, smart environment, smart city, smart

Energy and smart grid, Healthcare, Automotive and smart mobility and video surveillance etc.

Cloud IoT systems may be in charge of collecting data ranging from natural ecosystems to

buildings and factories, so finding applications in broad fields of environmental sensing and

urban planning. On the other hand, IoT based systems could also be responsible for not just

sensing things. Intelligent shopping systems, for example, could monitor particular users'

purchasing habits in a mall or store by tracking their personal mobile phones. Clients could be

provided with special offers about their favorite products, or find location of things that they

need, which their refrigerator has automatically conveyed to the clients smart phone.

Nowadays everything connected with the help of Cloud IoT.

Migrating IoT application into Cloud environment offers convenience, such as cost

minimized and complexity related to hardware management. The complex structure of Cloud

IoT includes many different aspects related to various heterogeneous topics, each type

imposing challenges when particular capabilities to be satisfied. For example, the following

capabilities such as privacy, security, availability, reliability, portability, and semantic

interoperability are required to guarantee trusted and efficient services. When the most critical

IoT applications move towards the Cloud, new concerns may arise due to the lack of essential

properties such as knowledge about service level agreements (SLAs), trust in the service

provider and information about the physical location of the data storage.

68

Figure 3.13 Application scenarios driven by the Cloud IoT paradigm

3.7 Chapter Conclusion

In this chapter, ZigBee (IEEE 802.15.4) technology is studied including its

characteristics, types, topologies and Architecture of ZigBee protocol stack. RFID Principles

and its operation such as Near field coupling and Far field coupling between a reader and tag

are discussed with the neat sketch. The basic operation of a Bluetooth network and every

component of the Bluetooth stack are explained. For the devices that may require a quick

installation and quality of the signal, The IEEE 802.11 standard is used to provide wireless

connectivity. Integrating Cloud environments and IoT devices may be classified broadly into

various categories such as smart home, smart logistics, smart environment, smart city, smart

Energy and smart grid, Healthcare, Automotive and smart mobility and video surveillance etc.

and these applications comes under CloudIoT paradigm.

Cloud IoT

Video

surveillance Smart energy

and smart

grid

Environmental

Monitoring

Smart city

Automotive and

smart mobility

Smart Logistics

Healthcare

Smart home and

smart metering