1

Chapter 1

Introduction

1.1 Introduction

The innovation in technology today has made our lifestyle much easier and fun. This research

work proposes and implements a solution for enhancing public transportation management

services based on RFID and GSM. The system consists of three modules: In-BUS Module,

BUS Stop Module and BASE Station Module. The microcontroller based In-BUS Module

consisting mainly of a GSM modem and RFID Readers on the entry and exit gates. When

driver press the INIT button, IN-Bus module sends the bus number and license plate number

to BASE station and starts transmitting its location to BASE Station Module about a

particular bus location out of BUS stops. BASE Station Module equipped with a

microcontroller unit and GSM modems interfaced to PCs is designed to keep track record of

every bus, processes user request from Android mobile application about a particular bus

location out of BUS stops and updates buses location on bus stop’s LCD display. BUS Stop

Module is installed at every bus stop and consists of a GSM modem, RFID tags and LCD

display all interfaced to a microcontroller. This module receives bus location information

coming towards that stop from BASE Station module and displays the information on a LCD

display.

Keywords: RFID reader, GSM, RFID Tag, LCD.

Radio-frequency identification (RFID) is an automatic identification method, relying on

remotely retrieving data using devices called transponders or RFID tags. The technology

requires some extent of cooperation of an RFID reader and an RFID tag. An object called

RFID tag that can be applied to a product, person or animal for the purpose of identification

and tracking using radio waves. Some tags can be read from meters away and beyond the line

of sight of the reader.

The RFID has come up as emerging technology which started evolving in World War II. A

RFID system has several components which include tags, antennas and readers. This set up

can be used either in high frequency or ultra-high frequency. In 1946, Leon Theremin

invented a toll for the Soviet Union which retransmitted radio waves with some audio

information attached to it. Though it was not an identification device it can be considered a

predecessor to the RFID technology. The IFF transponder was used by United Kingdom in

2

1939 which was then used for identifying planes as an ally plane or enemy plane as early in

19th century in World War II. The transponder of this kind is still used in today’s aircrafts.

What is RFID?

The RFID system is consists of three components:

a) Coil or An antenna

b) RF tags or transponder.

c) A transceiver with decoder.

These components are electronically programmed with unique information. In the market

there are many different types of RFID systems. These systems are categorized according to

their frequency ranges.

Some of the RFID kits that are used commonly are as follows:

1) Low-frequency (30 KHz to 500 KHz)

2) Mid-Frequency (900 KHz to 1500MHz)

3) High Frequency (2.4GHz to 2.5GHz)

These frequency ranges tell the RF ranges of the tags from low frequency tag ranging from

3m to 5m, mid-frequency ranging from 5m to 17m and high frequency ranging from 5ft to

90ft. [3]

When designing this system, the following constraints have been considered:

software and hardware should be divided into small components or modules to ensure easy

scalability for further feature expansions. Modules must be independently produced from

each other, so that the crash of one module cannot affect the other ones or changes to module

will not affect other.

performance ratio so as to design a cost-effective solution.

impact on environment. To keep the system power very low, low power consumption devices

should be. Energy optimization should be involved in all the design’s steps.[3]

3

1.2 Literature Review Due to non-availability of prior information about the buses arrival schedule, people have to

wait for longer on bus stops especially in morning when they have to reach the offices in

time. When buses get overloaded it results in bus fault and people gets late further. [1]

The travel time of buses varies depending on several external parameters such as accidents,

traffic and snow. In fact, buses are stuck in traffic and are thus hampered by the passage of

junctions which makes the management of the bus schedule in the bus stations a difficult

task. Bus station follows fixed schedules and routines, and don’t make use of intelligent

systems for vehicle tracking and control. Many administrators are deployed at the station who

controls the exit of buses and the entrance of buses and he prepares the trip sheets containing

the schedules manually which are time consuming and inaccurate. Even transport

departments have no visibility over utilization of its fleet on real-time, which leads in

underutilization of resources. All these results in avoidable costly errors and mistakes, stress

and sub cost optimal fleet utilization and finally dissatisfaction and inconvenience to millions

of commuters. The provision of accurate and timely transit travel time information is so

importat . An automatic route guider display can be installed in buses to better update the

alternative route in case of serious road congestions. We can connect RFID reader wirelessly

to the host application. There are different advanced wireless technologies that can be used

such as Bluetooth (802.15.3) and ZigBee (802.15.4) to extend the range of an RFID reader.

Fare collecting system can also be automated by providing another mobile service to which

all the passengers using public transport are subscribed.

4

to automatic radio frequency identification systems were automatic object detection systems

With the help of new technology the administrator can monitor the buses traffic while

increasing the satisfaction of transit users and reducing cost through efficient operations asset

utilization.

Table 1: Study & comparison of existing systems

Well-known examples of identification technologies include Closed-Circuit Television

(CCTV) and Global Positioning System (GPS). CCTV can be deployed at each entrance gate

and image processing techniques can be utilized to identify the arrival of buses, where image

recognition was performed to detect the bus in the traffic. This testing has shown poor

performance in tracking based detection (~20% precision). During the past, GPS integrated to

Geographic Information Systems (GIS) was used to monitor buses traffic. GPS receiver

communicates with at least 4 satellites before giving the location of the bus. It gives a very

good forecasting. However, line of sight between the satellites and the receiver is required

otherwise the GPS signal is attenuated. The main limitation of this technology is especially

when it comes to monitor bus traffic inside an underground bus station.

Due to the limitation of these technologies, the RFID technology can be used to track buses.

RFID technology can be effectively applied for real-time tracking and identification. RFID

was developed in the 1940s by the US department of defence (DoD) which used transponders

to differentiate between friendly and enemy aircrafts. Since this time, RFID technology has

been evolving to change the way people live and work. Many research projects have explored

the possibility of integrating RFID in different areas, from toll collection, agriculture, access

control, supply chain, logistics, healthcare, and library. RFID technology can response to our

tracking needs that’s why we used RFID in our design to identify buses entering and leaving

the bus station.

RFID (Radio Frequency Identification): Principles and Applications Stephen A. Weis MIT

CSAIL Outline 1Introduction 1.1RFID Origins 1.2Auto-Identification and RFID

2Applications 3Principles 3.1System Essentials 3.1.1 Tags 3.1.2Readers 3.1.3 Databases

3.2Power Sources 3.3Operating Frequencies 3.3.1Low Frequency (LF) 3.3.2 High Frequency

(HF) 3.3.3 Ultra-High Frequency (UHF) 3.3.4 Microwave 3.3.5 Ultra-Wideband (UWB)

3.4Functionality 3.4.1Electronic Article Surveillance (EAS) 3.4.2Read-only EPC 3.4.3EPC

3.4.4 Sensor Tags 3.4.5 Motes 3.5Standards 4Challenges 4.1Technical 4.2Economic

4.3Security and Privacy 4.3.1Eavesdropping 4.3.2 Forgery 4.3.3 Denial of Service 4.3.4

Viruses 5Emerging Technologies Key Words: RFID, radio frequency identification,

5

electronic article surveillance, sensor networks Abstract Deployment of radio frequency

identification (RFID) systems is rapidly growing and has the potential to affect many

different industries and applications. We present a brief history of RFID technology and

automatic identification systems. We summarize major RFID applications, and present a

primer on RFID fundamental principles. Finally, we discuss several challenges and obstacles

to RFID adoption, as well as emerging technologies relevant to RFID. 1Introduction Radio

frequency identification (RFID) is a rapidly growing technology that has the potential to

make great economic impacts on many industries. While RFID is a relatively old technology,

more recent advancements in chip manufacturing technology are making RFID practical for

new applications and settings, particularly consumer item level tagging. These advancements

have the potential to revolutionize supply-chain management, inventory control, and

logistics. At its most basic, RFID systems consist of small transponders, or tags, attached to

physical objects. RFID tags may soon become the most pervasive microchip in history. When

wirelessly interrogated by RFID transceivers, or readers, tags respond with some identifying

information that may be associated with arbitrary data records. Thus, RFID systems are one

type of automatic identification system, similar to optical bar codes. There are many kinds of

RFID systems used in different applications and settings. These systems have different power

sources, operating frequencies, and functionalities. The properties and regulatory restrictions

of a particular RFID system will determine its manufacturing costs, physical specifications,

and performance. Some of the most familiar RFID applications are item-level tagging with

electronic product codes, proximity cards for physical access control, and contact-less

payment systems. Many more applications will become economical in the coming years.

While RFID adoption yields many efficiency benefits, it still faces several hurdles. Besides

the typical implementation challenges faced in any information technology system and

economic barriers, there are major concerns over security and privacy in RFID systems.

Without proper protection, RFID systems could create new threats to both corporate security

and personal privacy. In this section, we present a brief history of RFID and automatic

identification systems. We summarize several major applications of RFID in Section 2. In

Section 3, we present a primer on basic RFID principles and discuss the taxonomy of various

RFID systems. Section 4 addresses the technical, economic, security, and privacy challenges

facing RFID adoption. Finally, Section 5 briefly discusses emerging technologies relevant to

RFID. 1.1RFID Origins The origins of RFID technology lie in the 19th century when

luminaries of that era made great scientific advances in electromagnetism. Of particular

6

relevance to RFID are Michael Faraday’s discovery of electronic inductance, James Clerk

Maxwell’s formulation of equations describing electromagnetism, and Heinrich Rudolf

Hertz’s experiments validating Faraday and Maxwell’s predictions. Their discoveries laid the

foundation for modern radio communications.

Features RFID GPS And

GPRS

RFID, GIS,

And GPS

GPS, GPRS,

And GIS

RFID, GSM

and

Android(Prop

osed System) Data

Transmission Slow within range

Moderate; delay due to

satellites blocking

Moderate Faster Faster

Data

Information Only RFID Only

coordinates RFID data and coordinates

Position, picture and vehicle

information

RFID data, Position, Vehicle

Information Control center No No No Yes Yes

Hardware

Cost Low Moderate High High Low

Hardware

Implementatio

n

Simple Simple Complex Complex Moderate

Reliability Less Less Moderate Moderate High Application Specific Specific Limited Limited Wide GUI No No No Yes Yes

7

Chapter 2

Design Methodology

The proposed system architecture for the bus monitoring and management system is shown in

Figure 2. A black box containing RFID reader, GSM modem is equipped in the moving bus.

As the bus approaches a bus station with an RFID tag, the distance between the reader and

the tag decreases so that they can interact with each other. This communication also produces

data and the data gained is sent to the BASE station via GSM.

The data circulation of the RFID and integrated communication technologies in the

constructed system are shown in Figure 3. The system is automatically turned on once the bus

is ignited. When the bus nears a tagged bus stop, RFID devices interact with each other. The

reader then reads and retrieves the information saved inside the tag once it recognizes the tag.

If the communication is successful, the information of the bus and the respective bus stop is

saved in the database; with the condition that GSM is ON. The data retrieved are then sent to

the BASE station via GSM, and this action initializes the data utilization. These data are

stored in the database. Filtered, clean information is sent to the BUS stop module, which

shows the data received from BASE station i.e. bus positions on the LCD display

In-BUS Module is installed inside every bus and consists of a RFID reader, a GSM modem

and an emergency button; all interfaced to AT89S52 microcontroller. After sending the

initialization signal to BASE Station Module, this module starts transmitting bus location to

the BASE Station. At each stop, RFID reader reads the RFID tag on bus stop and sends data

to BASE station. In case of an emergency situation (e.g., when fault occurs in bus), driver can

press the emergency button toinform BASE Station units about the location of bus. The BUS

station operator can then adjust the schedule accordingly and send an additional bus for

facilitating the passengers.

BUS Stop module is installed at every bus stop to let the passenger know about the location

of buses coming towards that stop. It comprises of a GSM modem, LCD display; all

interfaced to AT89S52 microcontroller. Microcontroller after retrieving the stored

information displays it on LCD display. The location of next incoming bus is displayed in

case of an emergency situation.

BASE Station module is the central part of the network. Through respective GSM, it accepts

location information of buses.

8

2.1 Block Diagram

Figure : Architecture of Intelligent Bus Monitoring and Management System

9

2.2 Flow Chart

Figure: flowchart of design methodology

10

Chapter 3

Modules

3.1 In-BUS Module

In-BUS Module is installed inside every bus and consists of a RFID reader, a GSM modem

and an emergency button; all interfaced to AT89S52 microcontroller. After sending the

initialization signal to BASE Station Module, this module starts transmitting bus location to

the BASE Station. At each stop, RFID reader reads the RFID tag on bus stop and sends data

to BASE station. In case of an emergency situation (e.g., when fault occurs in bus), driver can

press the emergency button to inform BASE Station units about the location of bus. The BUS

station operator can then adjust the schedule accordingly and send an additional bus for

facilitating the passengers.

Figure: Block Diagram of In-BUS Module

11

3.2 BUS Stop Module

BUS Stop module is installed at every bus stop to let the passenger know about the location

of buses coming towards that stop. It comprises of a GSM modem, LCD display; all

interfaced to AT89S52 microcontroller. Microcontroller after retrieving the stored

information displays it on LCD display. The location of next incoming bus is displayed in

case of an emergency situation.

Figure: BUS Stop Module

12

3.3 BASE Station module

BASE Station module is the central part of the network. Through respective GSM, it accepts

location information of buses. The PC after processing the data sends desired location

information in form of bus stop name to microcontroller at BUS Stop module. BASE station

also monitors the emergency situations transmitted from In-BUS Module.

Figure: BASE Station module

13

Chapter 4

RFID Technology and Its Applications

4.1 Introduction

RFID is abbreviation of Radio Frequency Identification. RFID signifies to tiny electronic

gadgets that comprise of a small chip and an antenna. This small chip is competent of

accumulating approx 2000 bytes of data or information. RFID devices is used as a substitute

of bar code or a magnetic strip which is noticed at the back of an ATM card or credit card, it

gives a unique identification code to each item. And similar to the magnetic strip or bar code,

RFID devices too have to be scanned to get the details (identifying information)

An RFID reader is a network connected device (fixed or mobile) with an antenna that sends

power as well as data and commands to the tags. The RFID reader acts like an access point

for RFID tagged items so that the tags' data In a basic RFID system, tags are attached to all

items that are to be tracked. These tags are made from a tiny tag-chip, sometimes called an

integrated circuit (IC), that is connected to an antenna that can be built into many different

kinds of tags including apparel hang tags, labels, and security tags, as well as a wide variety

of industrial asset tags. The tag chip contains memory which stores the product's electronic

product code (EPC) and other variable information so that it can be read and tracked by RFID

readers anywherecan be made available to business applications.

Readers

RFID systems can be classified by the type of tag and reader. A Passive Reader Active

Tag (PRAT) system has a passive reader which only receives radio signals from active tags

(battery operated, transmit only). The reception range of a PRAT system reader can be

adjusted from 1–2,000 feet ( allowing flexibility in applications such as asset protection and

supervision.

An Active Reader Passive Tag (ARPT) system has an active reader, which transmits

interrogator signals and also receives authentication replies from passive tags.

An Active Reader Active Tag (ARAT) system uses active tags awoken with an interrogator

signal from the active reader. A variation of this system could also use a Battery-Assisted

Passive (BAP) tag which acts like a passive tag but has a small battery to power the tag's

return reporting signal.

14

Fixed readers are set up to create a specific interrogation zone which can be tightly

controlled. This allows a highly defined reading area for when tags go in and out of the

interrogation zone. Mobile readers may be hand-held or mounted on carts or vehicles.

Frequencies Radio-frequency identification (RFID) is the wireless use of electromagnetic

fields to transfer data, for the purposes of automatically identifying and tracking tags attached

to objects. The tags contain electronically stored information. Some tags are powered by

electromagnetic induction from magnetic fields produced near the reader. Some types collect

energy from the interrogating radio waves and act as a passive transponder. Other types have

a local power source such as a battery and may operate at hundreds of meters from the reader.

Unlike a barcode, the tag does not necessarily need to be within line of sight of the reader,

and may be embedded in the tracked object. Radio frequency identification (RFID) is one

method for Automatic Identification and Data Capture (AIDC).

RFID tags are used in many industries. An RFID tag attached to an automobile during

production can be used to track its progress through the assembly line. Pharmaceuticals can

be tracked through warehouses. Livestock and pets may have tags injected, allowing positive

identification of the animal.

Since RFID tags can be attached to cash, clothing, possessions, or even implanted within

people, the possibility of reading personally-linked information without consent has raised

serious privacy concerns.

Tags

A radio-frequency identification system uses tags, or labels attached to the objects to be

identified. Two-way radio transmitter-receivers called interrogators or readers send a signal

to the tag and read its response.

RFID tags can be either passive, active or battery-assisted passive. An active tag has an on-

board battery and periodically transmits its ID signal. A battery-assisted passive (BAP) has a

small battery on board and is activated when in the presence of an RFID reader. A passive tag

is cheaper and smaller because it has no battery; instead, the tag uses the radio energy

transmitted by the reader. However, to operate a passive tag, it must be illuminated with a

power level roughly a thousand times stronger than for signal transmission. That makes a

difference in interference and in exposure to radiation.

Tags may either be read-only, having a factory-assigned serial number that is used as a key

into a database, or may be read/write, where object-specific data can be written into the tag

15

by the system user. Field programmable tags may be write-once, read-multiple; "blank" tags

may be written with an electronic product code by the user.

RFID tags contain at least two parts: an integrated circuit for storing and processing

information, modulating and demodulating a radio-frequency (RF) signal, collecting DC

power from the incident reader signal, and other specialized functions; and an antenna for

receiving and transmitting the signal. The tag information is stored in a non-volatile memory.

The RFID tag includes either fixed or programmable logic for processing the transmission

and sensor data, respectively.

An RFID reader transmits an encoded radio signal to interrogate the tag. The RFID tag

receives the message and then responds with its identification and other information. This

may be only a unique tag serial number, or may be product-related information such as a

stock number, lot or batch number, production date, or other specific information. Since tags

have individual serial numbers, the RFID system design can discriminate among several tags

that might be within the range of the RFID reader and read them sim

RFID frequency bands

Band Regulations Range Data

speed Remarks

Approximate

tag cost

in volume

(2006) US $

120–150 kHz (LF)

Unregulated 10 cm Low Animal identification, factory data collection

$1

13.56 MHz (HF)

ISM bandworldwide

10 cm - 1 m

Low to moderate

Smart cards (ISO/IEC

15693, ISO/IEC 14443 A,B). Non fully

ISO compatible memory cards (Mifare Classic, iCLASS,

Legic, Felica ...). Micro processor ISO

compatible cards (Desfire EV1, Seos)

$0.50 to $5

16

433 MHz

(UHF)

Short Range

Devices

1–100

m Moderate

Defense applications,

with active tags $5

865-868 MHz

(Europe) 902-928 MHz

(North America)

UHF

ISM band 1–12 m

Moderate to high

EAN, various standards

$0.15 (passive tags)

2450-5800 MHz (microwave)

ISM band 1–2 m High 802.11 WLAN, Bluetooth standards

$25 (active tags)

3.1–10 GHz

(microwave)

Ultra wide

band

to 200

m High

requires semi-active or

active tags $5 projected

Signaling

Signaling between the reader and the tag is done in several different incompatible ways,

depending on the frequency band used by the tag. Tags operating on LF and HF bands are, in

terms of radio wavelength, very close to the reader antenna because they are only a small

percentage of a wavelength away. In this near field region, the tag is closely coupled

electrically with the transmitter in the reader. The tag can modulate the field produced by the

reader by changing the electrical loading the tag represents. By switching between lower and

higher relative loads, the tag produces a change that the reader can detect. At UHF and higher

frequencies, the tag is more than one radio wavelength away from the reader, requiring a

different approach. The tag can backscatter a signal. Active tags may contain functionally

separated transmitters and receivers, and the tag need not respond on a frequency related to

the reader's interrogation signal.[12]

An Electronic Product Code (EPC) is one common type of data stored in a tag. When written

into the tag by an RFID printer, the tag contains a 96-bit string of data. The first eight bits are

a header which identifies the version of the protocol. The next 28 bits identify the

organization that manages the data for this tag; the organization number is assigned by the

17

EPC Global consortium. The next 24 bits are an object class, identifying the kind of product;

the last 36 bits are a unique serial number for a particular tag. These last two fields are set by

the organization that issued the tag. Rather like a URL, the total electronic product code

number can be used as a key into a global database to uniquely identify a particular product.

Often more than one tag will respond to a tag reader, for example, many individual products

with tags may be shipped in a common box or on a common pallet. Collision detection is

important to allow reading of data. Two different types of protocols are used to "singulate" a

particular tag, allowing its data to be read in the midst of many similar tags. In a slotted

Aloha system, the reader broadcasts an initialization command and a parameter that the tags

individually use to pseudo-randomly delay their responses. When using an "adaptive binary

tree" protocol, the reader sends an initialization symbol and then transmits one bit of ID data

at a time; only tags with matching bits respond, and eventually only one tag matches the

complete ID string.[14]

Figure :Binary tree method

An example of a binary tree method of identifying an RFID tag

Both methods have drawbacks when used with many tags or with multiple overlapping

readers. Bulk reading is a strategy for interrogating multiple tags at the same time, but lacks

sufficient precision for inventory control.

Miniaturization

RFIDs are easy to conceal or incorporate in other items. For example, in 2009 researchers

at Bristol University successfully glued RFID micro-transponders to live ants in order to

study their behavior.[15] This trend towards increasingly miniaturized RFIDs is likely to

continue as technology advances.

Hitachi holds the record for the smallest RFID chip, at 0.05mm × 0.05mm. This is 1/64th the

size of the previous record holder, the mu-chip.[16] Manufacture is enabled by using

the silicon-on-insulator (SOI) process. These dust-sized chips can store 38-digit numbers

using 128-bit Read Only Memory (ROM).[17] A major challenge is the attachment of

antennas, thus limiting read range to only millimeters.

18

The RFID tag can be affixed to an object and used to track and manage inventory, assets,

people, etc. For example, it can be affixed to cars, computer equipment, books, mobile

phones, etc.

RFID offers advantages over manual systems or use of bar codes. The tag can be read if

passed near a reader, even if it is covered by the object or not visible. The tag can be read

inside a case, carton, box or other container, and unlike barcodes, RFID tags can be read

hundreds at a time. Bar codes can only be read one at a time using current devices.

In 2011, the cost of passive tags started at US$0.09 each; special tags, meant to be mounted

on metal or withstand gamma sterilization, can go up to US$5. Active tags for tracking

containers, medical assets, or monitoring environmental conditions in data centers start at

US$50 and can go up over US$100 each. Battery-Assisted Passive (BAP) tags are in the

US$3–10 range and also have sensor capability like temperature and humidity.

RFID stands for Radio-Frequency Identification. The acronym refers to small electronic

devices that consist of a small chip and an antenna. The chip typically is capable of carrying

2,000 bytes of data or less.

The RFID device serves the same purpose as a bar code or a magnetic strip on the back of a

credit card or ATM card; it provides a unique identifier for that object. And, just as a bar code

or magnetic strip must be scanned to get the information, the RFID device must be scanned to

retrieve the identifying information.

RFID Works Better Than Barcodes

A significant advantage of RFID devices over the others mentioned above is that the RFID

device does not need to be positioned precisely relative to the scanner. We're all familiar with

the difficulty that store checkout clerks sometimes have in making sure that a barcode can be

read. And obviously, credit cards and ATM cards must be swiped through a special reader.

In contrast, RFID devices will work within a few feet (up to 20 feet for high-frequency

devices) of the scanner. For example, you could just put all of your groceries or purchases in

a bag, and set the bag on the scanner. It would be able to query all of the RFID devices and

total your purchase immediately. (Read a more detailed article on RFID compared to

barcodes.)

RFID technology has been available for more than fifty years. It has only been recently that

the ability to manufacture the RFID devices has fallen to the point where they can be used as

a "throwaway" inventory or control device. Alien Technologies recently sold 500 million

RFID tags to Gillette at a cost of about ten cents per tag.

19

One reason that it has taken so long for RFID to come into common use is the lack of

standards in the industry. Most companies invested in RFID technology only use the tags to

track items within their control; many of the benefits of RFID come when items are tracked

from company to company or from country to country.

Common Problems with RFID

Some common problems with RFID are reader collision and tag collision. Reader collision

occurs when the signals from two or more readers overlap. The tag is unable to respond to

simultaneous queries. Systems must be carefully set up to avoid this problem. Tag collision

occurs when many tags are present in a small area; but since the read time is very fast, it is

easier for vendors to develop systems that ensure that tags respond one at a time.

20

Chapter 5

Global System for Mobile Communications (GSM)

5.1 Introduction

GSM is a digital, mobile; radio standard developed for mobile, wireless, voice

communications. GSM uses a combination of both the time division multiple access (TDMA)

and frequency division multiple access (FDMA). With this combination, more channels of

communications are available, and all channels are digital.

The GSM service is available in following frequency bands:

• 900-MHz & 900 E

• 1800-MHz

• 1900-MHz

GSM Network Elements

A GSM network consists of the following network components:

• Mobile station (MS)

• Base transceiver station (BTS)

• Base station controller (BSC)

• Mobile switching center (MSC)

• Authentication center (AuC)

• Home location registers (HLR)

• Visitor location registers (VLR)

Mobile Station;

The mobile station (MS) is the starting point of a mobile wireless network. The MS can

contain the following components:

• Mobile terminal (MT)—GSM cellular handset

• Terminal equipment (TE)—PC or personal digital assistant (PDA)

The MS can be two interconnected physical devices (MT and TE) with a point-to-point

interface or a single device with both functions integrated

Base Transceiver Station;

When a subscriber uses the MS to make a call in the network, the MS transmits the call

request to the base transceiver station (BTS). The BTS includes all the radio necessary for

radio transmission within a geographical area called a cell. The BTS is responsible for

21

establishing the link to the MS and for modulating and demodulating radio signals between

the MS and the BTS.

Base Station Controller;

The base station controller (BSC) is the controlling component of the radio network, and it

manages the BTSs. The BSC reserves radio frequencies for communications and handles the

handoff between BTSs when an MS roams from one cell to another. The BSC is responsible

for paging the MS for incoming calls.

Mobile Switching Center;

The mobile switching center (MSC) is a digital ISDN switch that sets up connections to other

MSCs and to the BSCs. The MSCs form the wired (fixed) backbone of a GSM network and

can switch calls to the public switched telecommunications network (PSTN). An MSC can

connect to a large number of BSCs.

What is a GSM Modem? (or GPRS Modem? or 3G Modem?)

A GSM modem is a specialized type of modem which accepts a SIM card, and operates over

a subscription to a mobile operator, just like a mobile phone. From the mobile operator

perspective, a GSM modem looks just like a mobile phone.

When a GSM modem is connected to a computer, this allows the computer to use the GSM

modem to communicate over the mobile network. While these GSM modems are most

frequently used to provide mobile internet connectivity, many of them can also be used for

sending and receiving SMS and MMS messages.

A GSM modem can be a dedicated modem device with a serial, USB or Bluetooth

connection, or it can be a mobile phone that provides GSM modem capabilities.

For the purpose of this document, the term GSM modem is used as a generic term to refer to

any modem that supports one or more of the protocols in the GSM evolutionary family,

including the 2.5G technologies GPRS and EDGE, as well as the 3G technologies WCDMA,

UMTS, HSDPA and HSUPA.

A GSM modem exposes an interface that allows applications such as NowSMS to send and

receive messages over the modem interface. The mobile operator charges for this message

sending and receiving as if it was performed directly on a mobile phone. To perform these

tasks, a GSM modem must support an “extended AT command set” for sending/receiving

SMS messages, as defined in the ETSI GSM 07.05 and and 3GPP TS 27.005 specifications.

GSM modems can be a quick and efficient way to get started with SMS, because a special

subscription to an SMS service provider is not required. In most parts of the world, GSM

22

modems are a cost effective solution for receiving SMS messages, because the sender is

paying for the message delivery.

A GSM modem can be a dedicated modem device with a serial, USB or Bluetooth

connection, such as the Falcom Samba 75. (Other manufacturers of dedicated GSM modem

devices include Wavecom, Multitech and iTegno. We’ve also reviewed a number of modems

on our technical support blog.) To begin, insert a GSM SIM card into the modem and connect

it to an available USB port on your computer.

A GSM modem could also be a standard GSM mobile phone with the appropriate cable and

software driver to connect to a serial port or USB port on your computer. Any phone that

supports the “extended AT command set” for sending/receiving SMS messages, as defined

in ETSI GSM 07.05 and/or 3GPP TS 27.005, can be supported by the Now SMS & MMS

Gateway. Note that not all mobile phones support this modem interface.

Due to some compatibility issues that can exist with mobile phones, using a dedicated GSM

modem is usually preferable to a GSM mobile phone. This is more of an issue with MMS

messaging, where if you wish to be able to receive inbound MMS messages with the

gateway, the modem interface on most GSM phones will only allow you to send MMS

messages. This is because the mobile phone automatically processes received MMS message

notifications without forwarding them via the modem interface.

It should also be noted that not all phones support the modem interface for sending and

receiving SMS messages. In particular, most smart phones, including Blackberries, iPhone,

and Windows Mobile devices, do not support this GSM modem interface for sending and

receiving SMS messages at all at all. Additionally, Nokia phones that use the S60 (Series 60)

interface, which is Symbian based, only support sending SMS messages via the modem

interface, and do not support receiving SMS via the modem interface.

23

Chapter 6

Liquid-crystal Display

6.1 Introduction

A liquid-crystal display (LCD) is a flat panel display, electronic visual display, or video

display that uses the light modulating properties of liquid crystals. Liquid crystals do not emit

light directly.

LCDs are available to display arbitrary images (as in a general-purpose computer display) or

fixed images which can be displayed or hidden, such as preset words, digits, and 7-

segment displays as in a digital clock. They use the same basic technology, except that

arbitrary images are made up of a large number of small pixels, while other displays have

larger elements.

LCDs are used in a wide range of applications including computer monitors,

televisions, instrument panels, aircraft cockpit displays, and signage. They are common in

consumer devices such as DVD players, gaming devices, clocks, watches, calculators, and

telephones, and have replaced cathode ray tube (CRT) displays in most applications. They are

available in a wider range of screen sizes than CRT and plasma displays, and since they do

not use phosphors, they do not suffer image burn-in. LCDs are, however, susceptible

to image persistence.

The LCD screen is more energy efficient and can be disposed of more safely than a CRT. Its

low electrical power consumption enables it to be used in battery-

powered electronic equipment. It is an electronically modulated optical device made up of

any number of segments filled with liquid crystals and arrayed in front of a light

source (backlight) or reflector to produce images in color or monochrome. Liquid crystals

were first discovered in 1888. By 2008, annual sales of televisions with LCD screens

exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes.

Liquid crystal between the polarizing filters, light passing through the first filter would be

blocked by the second (crossed) polarizer.

Before an electric field is applied, the orientation of the liquid-crystal molecules is

determined by the alignment at the surfaces of electrodes. In a twisted nematic device (still

the most common liquid-crystal device), the surface alignment directions at the two

electrodes are perpendicular to each other, and so the molecules arrange themselves in

a helical structure, or twist. This induces the rotation of the polarization of the incident light,

24

and the device appears gray. If the applied voltage is large enough, the liquid crystal

molecules in the center of the layer are almost completely untwisted and the polarization of

the incident light is not rotated as it passes through the liquid crystal layer. This light will

then be mainly polarized perpendicular to the second filter, and thus be blocked and

the pixel will appear black. By controlling the voltage applied across the liquid crystal layer

in each pixel, light can be allowed to pass through in varying amounts thus constituting

different levels of gray.

LCD with top polarizer removed from device and placed on top, such that the top and bottom

polarizers are parallel.

The optical effect of a twisted nematic device in the voltage-on state is far less dependent on

variations in the device thickness than that in the voltage-off state. Because of this, these

devices are usually operated between crossed polarizers such that they appear bright with no

voltage (the eye is much more sensitive to variations in the dark state than the bright state).

These devices can also be operated between parallel polarizers, in which case the bright and

dark states are reversed. The voltage-off dark state in this configuration appears blotchy,

however, because of small variations of thickness across the device.

Both the liquid crystal material and the alignment layer material contain ionic compounds. If

an electric field of one particular polarity is applied for a long period of time, this ionic

material is attracted to the surfaces and degrades the device performance. This is avoided

either by applying an alternating current or by reversing the polarity of the electric field as the

device is addressed (the response of the liquid crystal layer is identical, regardless of the

polarity of the applied field).

Displays for a small number of individual digits and/or fixed symbols (as in digital

watches and pocket calculators) can be implemented with independent electrodes for each

segment. In contrast full alphanumeric and/or variable graphics displays are usually

implemented with pixels arranged as a matrix consisting of electrically connected rows on

one side of the LC layer and columns on the other side, which makes it possible to address

each pixel at the intersections. The general method of matrix addressing consists of

sequentially addressing one side of the matrix, for example by selecting the rows one-by-one

and applying the picture information on the other side at the columns row-by-row. For details

on the various matrix addressing schemes see Passive-matrix and active-matrix addressed

LCDs.

25

Since LCD panels produce no light of their own, they require external light to produce a

visible image. In a "transmissive" type of LCD, this light is provided at the back of the glass

"stack" and is called the backlight. While passive-matrix displays are usually not backlit (e.g.

calculators, wristwatches), active-matrix displays almost always are.

The common implementations of LCD backlight technology are:

Figure: 18 parallel CCFLs as backlight for a 42-inch LCD TV

CCFL: The LCD panel is lit either by two cold cathode fluorescent lamps placed at opposite

edges of the display or an array of parallel CCFLs behind larger displays. A diffuser then

spreads the light out evenly across the whole display. For many years, this technology had

been used almost exclusively. Unlike white LEDs, most CCFLs have an even-white spectral

output resulting in better color gamut for the display. However, CCFLs are less energy

efficient than LEDs and require a somewhat costly inverter to convert whatever DC voltage

the device uses (usually 5 or 12 V) to ~1000 V needed to light a CCFL. The thickness of the

inverter transformers also limit how thin the display can be made.

EL-WLED: The LCD panel is lit by a row of white LEDs placed at one or more edges of the

screen. A light diffuser is then used to spread the light evenly across the whole display. As of

2012, this design is the most popular one in desktop computer monitors. It allows for the

thinnest displays. Some LCD monitors using this technology have a feature called "Dynamic

Contrast" where the backlight is dimmed to the brightest color that appears on the screen,

allowing the 1000:1 contrast ratio of the LCD panel to be scaled to different light intensities,

resulting in the "30000:1" contrast ratios seen in the advertising on some of these monitors.

Since computer screen images usually have full white somewhere in the image, the backlight

will usually be at full intensity, making this "feature" mostly a marketing gimmick.

WLED array: The LCD panel is lit by a full array of white LEDs placed behind a diffuser

behind the panel. LCD displays that use this implementation will usually have the ability to

dim the LEDs in the dark areas of the image being displayed, effectively increasing the

contrast ratio of the display. As of 2012, this design gets most of its use from upscale, larger-

screen LCD televisions.

26

RGB-LED: Similar to the WLED array, except the panel is lit by a full array of RGB LEDs.

While displays lit with white LEDs usually have a poorer color gamut than CCFL lit displays,

panels lit with RGB LEDs have very wide color gamuts. This implementation is most popular

on professional graphics editing LCD displays. As of 2012, LCD displays in this category

usually cost more than $1000.

Today, most LCD screens are being designed with an LED backlight instead of the traditional

CCFL backlight.

Connection to other circuits

Figure: A pink elastomeric connector mating an LCD panel to circuit board

A pink elastomeric connector mating an LCD panel to circuit board traces, shown next to a

centimeter-scale ruler. (The conductive and insulating layers in the black stripe are very

small, click on the image for more detail.)

LCD panels typically use thinly-coated metallic conductive pathways on a glass substrate to

form the cell circuitry to operate the panel. It is usually not possible to use soldering

techniques to directly connect the panel to a separate copper-etched circuit board.

Instead, interfacing is accomplished using either adhesive plastic ribbon with conductive

traces glued to the edges of the LCD panel, or with an elastomeric connector, which is a strip

of rubber or silicone with alternating layers of conductive and insulating pathways, pressed

between contact pads on the LCD and mating contact pads on a circuit board.

Figure: Prototype of a passive-matrix STN-LCD

27

Prototype of a passive-matrix STN-LCD with 540x270 pixels, Brown Boveri Research,

Switzerland, 1984

Monochrome passive-matrix LCDs were standard in most early laptops (although a few used

plasma displays[and the original Nintendo Game Boy until the mid-1990s, when color active-

matrix became standard on all laptops. The commercially unsuccessful Macintosh

Portable (released in 1989) was one of the first to use an active-matrix display (though still

monochrome).

Passive-matrix LCDs are still used today for applications less demanding than laptops and

TVs. In particular, these are used on portable devices where less information content needs to

be displayed, lowest power consumption (no backlight) and low cost are desired, and/or

readability in direct sunlight is needed.

Displays having a passive-matrix structure are employing super-twisted nematic STN

(invented by Brown Boveri Research Center, Baden, Switzerland, in 1983; scientific details

were published) or double-layer STN (DSTN) technology (the latter of which addresses a

color-shifting problem with the former), and color-STN (CSTN) in which color is added by

using an internal filter.

STN LCDs have been optimized for passive-matrix addressing. They exhibit a sharper

threshold of the contrast-vs-voltage characteristic than the original TN LCDs. This is

important, because pixels are subjected to partial voltages even while not

selected. Crosstalk between activated and non-activated pixels has to be handled properly by

keeping the RMS voltage of non-activated pixels below the threshold voltage,[34] while

activated pixels are subjected to voltages above threshold. STN LCDs have to be

continuously refreshed by alternating pulsed voltages of one polarity during one frame and

pulses of opposite polarity during the next frame. Individual pixels are addressed by the

corresponding row and column circuits. This type of display is called passive-matrix

addressed, because the pixel must retain its state between refreshes without the benefit of a

steady electrical charge. As the number of pixels (and, correspondingly, columns and rows)

increases, this type of display becomes less feasible. Slow response times and

poorcontrast are typical of passive-matrix addressed LCDs with too many pixels.

28

Figure: An active-matrix structure

How an LCD works using an active-matrix structure

New zero-power (bistable) LCDs do not require continuous refreshing. Rewriting is only

required for picture information changes. Potentially, passive-matrix addressing can be used

with these new devices, if their write/erase characteristics are suitable.

High-resolution color displays, such as modern LCD computer monitors and televisions, use

an active-matrix structure. A matrix of thin-film transistors (TFTs) is added to the electrodes

in contact with the LC layer. Each pixel has its own dedicated transistor, allowing each

column line to access one pixel. When a row line is selected, all of the column lines are

connected to a row of pixels and voltages corresponding to the picture information are driven

onto all of the column lines. The row line is then deactivated and the next row line is selected.

All of the row lines are selected in sequence during a refresh operation. Active-matrix

addressed displays look brighter and sharper than passive-matrix addressed displays of the

same size, and generally have quicker response times, producing much better images.

Figure: A Casio 1.8 in color TFT LCD

A Casio 1.8 in color TFT LCD, used in the Sony Cyber-shot DSC-P93Adigital compact

cameras

Main articles: Thin-film-transistor liquid-crystal display and Active-matrix liquid-crystal

display

Twisted nematic displays contain liquid crystals that twist and untwist at varying degrees to

allow light to pass through. When no voltage is applied to a TN liquid crystal cell, polarized

29

light passes through the 90-degrees twisted LC layer. In proportion to the voltage applied, the

liquid crystals untwist changing the polarization and blocking the light's path. By properly

adjusting the level of the voltage almost any gray level or transmission can be achieved.

In-plane switching is an LCD technology that aligns the liquid crystals in a plane parallel to

the glass substrates. In this method, the electrical field is applied through opposite electrodes

on the same glass substrate, so that the liquid crystals can be reoriented (switched) essentially

in the same plane, although fringe fields inhibit a homogeneous reorientation. This requires

two transistors for each pixel instead of the single transistor needed for a standard thin-film

transistor (TFT) display. Before LG Enhanced IPS was introduced in 2009, the additional

transistors resulted in blocking more transmission area, thus requiring a brighter backlight

and consuming more power, making this type of display less desirable for notebook

computers. Currently Panasonic is using an enhanced version eIPS for their large size LCD-

TV products as well as Hewlett-Packard in its WebOS based TouchPad tablet and their

Chromebook 11.

LG claimed the smartphone LG Optimus Black (IPS LCD (LCD NOVA)) has the brightness

up to 700 nits, while the competitor has only IPS LCD with 518 nits and double anactive-

matrix OLED (AMOLED) display with 305 nits. LG also claimed the NOVA display to be

50 percent more efficient than regular LCDs and to consume only 50 percent of the power of

AMOLED displays when producing white on screen. When it comes to contrast ratio,

AMOLED display still performs best due to its underlying technology, where the black levels

are displayed as pitch black and not as dark gray. On August 24, 2011, Nokia announced the

Nokia 701 and also made the claim of the world's brightest display at 1000 nits. The screen

also had Nokia's Clearblack layer, improving the contrast ratio and bringing it closer to that

of the AMOLED screens.

Super-IPS was later introduced after in-plane switching with even better response times and

color reproduction.

Figure: Pixel-layout

30

This pixel-layout is found in S-IPS LCDs. A chevron-shape is used to widen the viewing-

cone (range of viewing directions with good contrast and low color shift)

Known as fringe field switching (FFS) until 2003, advanced fringe field switching is similar

to IPS or S-IPS offering superior performance and color gamut with high luminosity. AFFS

was developed by Hydis Technologies Co., Ltd, Korea (formally Hyundai Electronics, LCD

Task Force).

AFFS-applied notebook applications minimize color distortion while maintaining a wider

viewing angle for a professional display. Color shift and deviation caused by light leakage is

corrected by optimizing the white gamut which also enhances white/gray reproduction.

In 2004, Hydis Technologies Co., Ltd licensed AFFS to Japan's Hitachi Displays. Hitachi is

using AFFS to manufacture high-end panels. In 2006, HYDIS licensed AFFS to Sanyo Epson

Imaging Devices Corporation.

Shortly thereafter, Hydis introduced a high-transmittance evolution of the AFFS display,

called HFFS (FFS+).

Hydis introduced AFFS+ with improved outdoor readability in 2007. AFFS panels are mostly

utilized in the cockpits of latest commercial aircraft displays.

]

Vertical-alignment displays are a form of LCDs in which the liquid crystals naturally align

vertically to the glass substrates. When no voltage is applied, the liquid crystals remain

perpendicular to the substrate, creating a black display between crossed polarizers. When

voltage is applied, the liquid crystals shift to a tilted position, allowing light to pass through

and create a gray-scale display depending on the amount of tilt generated by the electric field.

It has a deeper-black background, a higher contrast ratio, a wider viewing angle, and better

image quality at extreme temperatures over traditional twisted-nematic displays.[40]

Blue phase mode LCDs have been shown as engineering samples early in 2008, but they are

not in mass-production yet. The physics of blue phase mode LCDs suggest that very short

switching times (~1 ms) can be achieved, so time sequential color control can possibly be

realized and expensive color filters would be obsolete. Some LCD panels have

defective transistors, causing permanently lit or unlit pixels which are commonly referred to

as stuck pixels or dead pixels respectively. Unlike integrated circuits (ICs), LCD panels with

a few defective transistors are usually still usable. Manufacturers' policies for the acceptable

number of defective pixels vary greatly. At one point, Samsung held a zero-tolerance policy

31

for LCD monitors sold in Korea. As of 2005, though, Samsung adheres to the less

restrictive ISO 13406-2 standard. Other companies have been known to tolerate as many as

11 dead pixels in their policies. Dead pixel policies are often hotly debated between

manufacturers and customers. To regulate the acceptability of defects and to protect the end

user, ISO released the ISO 13406-2 standard. However, not every LCD manufacturer

conforms to the ISO standard and the ISO standard is quite often interpreted in different

ways.

LCD panels are more likely to have defects than most ICs due to their larger size. For

example, a 300 mm SVGA LCD has 8 defects and a 150 mm wafer has only 3 defects.

However, 134 of the 137 dies on the wafer will be acceptable, whereas rejection of the whole

LCD panel would be a 0% yield. In recent years, quality control has been improved. An

SVGA LCD panel with 4 defective pixels is usually considered defective and customers can

request an exchange for a new one. Some manufacturers, notably in South Korea where some

of the largest LCD panel manufacturers, such as LG, are located, now have "zero defective

pixel guarantee", which is an extra screening process which can then determine "A" and "B"

grade panels. Many manufacturers would replace a product even with one defective pixel.

Even where such guarantees do not exist, the location of defective pixels is important. A

display with only a few defective pixels may be unacceptable if the defective pixels are near

each other.

LCD panels also have defects known as clouding (or less commonly mura), which describes

the uneven patches of changes in luminance. It is most visible in dark or black areas of

displayed scenes.

The zenithal bistable device (ZBD), developed by QinetiQ (formerly DERA), can retain an

image without power. The crystals may exist in one of two stable orientations ("Black" and

"White") and power is only required to change the image. ZBD Displays is a spin-off

company from QinetiQ who manufacture both grayscale and color ZBD devices.

Kent Displays has also developed a "no power" display that uses polymer

stabilized cholesteric liquid crystal (ChLCD). In 2009 Kent demonstrated the use of a

ChLCD to cover the entire surface of a mobile phone, allowing it to change colors, and keep

that color even when power is cut off.

In 2004 researchers at the University of Oxford demonstrated two new types of zero-power

bistable LCDs based on Zenithal bistable techniques.

32

Several bistable technologies, like the 360° BTN and the bistable cholesteric, depend inly on

the bulk properties of the liquid crystal (LC) and use standard strong anchoring, with

alignment films and LC mixtures similar to the traditional monostable materials. Other

bistable technologies, e.g. BiNem technology, are based mainly on the surface properties and

need specific weak anchoring materials.

Resolution versus range: Fundamentally resolution is the granularity (or number of levels)

with which a performance feature of the display is divided. Resolution is often confused with

range or the total end-to-end output of the display. Each of the major features of a display has

both a resolution and a range that are tied to each other but very different. Frequently the

range is an inherent limitation of the display while the resolution is a function of the

electronics that make the display work.

Spatial performance: LCDs come in only one size for a variety of applications and a variety

of resolutions within each of those applications. LCD spatial performance is also sometimes

described in terms of a "dot pitch". The size (or spatial range) of an LCD is always described

in terms of the diagonal distance from one corner to its opposite. This is an historical remnant

from the early days of CRT television when CRT screens were manufactured on the bottoms

of glass bottles, a direct extension of cathode ray tubes used in oscilloscopes. The diameter of

the bottle determined the size of the screen. Later, when televisions went to a more square

format, the square screens were measured diagonally to compare with the older round

screens.

The spatial resolution of an LCD is expressed by the number of columns and rows of pixels

(e.g., 1024×768). Each pixel is usually composed 3 sub-pixels, a red, a green, and a blue one.

This had been one of the few features of LCD performance that was easily understood and

not subject to interpretation. However there are newer schemes that sharesub-pixels among

pixels and to add additional colors of sub-pixels. So going forward, spatial resolution may

now be more subject to interpretation.

One external factor to consider in evaluating display resolution is the resolution of the

viewer's eyes. Assuming 20/20 vision, the resolution of the eyes is about one minute of arc.

In practical terms that means for an older standard definition TV set the ideal viewing

distance was about 8 times the height (not diagonal) of the screen away. At that distance the

individual rows of pixels merge into a solid. If the viewer were closer to the screen than that,

they would be able to see the individual rows of pixels. When observed from farther away,

the image of the rows of pixels still merge, but the total image becomes smaller as the

33

distance increases. For an HDTV set with slightly more than twice the number of rows of

pixels, the ideal viewing distance is about half what it is for a standard definition set. The

higher the resolution, the closer the viewer can sit or the larger the set can usefully be sitting

at the same distance as an older standard definition display.

For a computer monitor or some other LCD that is being viewed from a very close distance,

resolution is often expressed in terms of dot pitch or pixels per inch. This is consistent with

the printing industry (another form of a display). Magazines, and other premium printed

media are often at 300 dots per inch. As with the distance discussion above, this provides a

very solid looking and detailed image. LCDs, particularly on mobile devices, are frequently

much less than this as the higher the dot pitch, the more optically inefficient the display and

the more power it burns. Running the LCD is frequently half, or more, of the power

consumed by a mobile device.

An additional consideration in spatial performance are viewing cone and aspect ratio.

The Aspect ratio is the ratio of the width to the height (for example, 4:3, 5:4, 16:9 or 16:10).

Older, standard definition TVs were 4:3. Newer High Definition televisions (HDTV) are

16:9, as are most new notebook computers. Movies are often filmed in much different (wider)

aspect ratios, which is why there will frequently still be black bars at the top and bottom of an

HDTV screen.

The Viewing Angle of an LCD may be important depending on its use or location. The

viewing angle is usually measured as the angle where the contrast of the LCD falls below

10:1. At this point, the colors usually start to change and can even invert, red becoming green

and so forth. Viewing angles for LCDs used to be very restrictive however, improved optical

films have been developed that give almost 180 degree viewing angles from left to right. Top

to bottom viewing angles may still be restrictive, by design, as looking at an LCD from an

extreme up or down angle is not a common usage model and these photons are wasted.

Manufacturers commonly focus the light in a left to right plane to obtain a brighter image

here.

Temporal/timing performance: Contrary to spatial performance, temporal performance is a

feature where smaller is better. Specifically, the range is the pixel response time of an LCD,

or how quickly a sub-pixel's brightness changes from one level to another. For LCD

monitors, this is measured in btb (black to black) or gtg (gray to gray). These different types

of measurements make comparison difficult. Further, this number is almost never published

in sales advertising.

34

Refresh rate or the temporal resolution of an LCD is the number of times per second in which

the display draws the data it is being given. Since activated LCD pixels do not flash on/off

between frames, LCD monitors exhibit no refresh-induced flicker, no matter how low the

refresh rate. High-end LCD televisions now feature up to 240 Hz refresh rate, which requires

advanced digital processing to insert additional interpolated frames between the real images

to smooth the image motion. However, such high refresh rates may not be actually supported

by pixel response times and the result can be visual artifacts that distort the image in

unpleasant ways.

Temporal performance can be further taxed if it is a 3D display. 3D displays work by

showing a different series of images to each eye, alternating from eye to eye. Thus a 3D

display must display twice as many images in the same period of time as a conventional

display, and consequently the response time of the LCD is more important. 3D LCDs with

marginal response times will exhibit image smearing.

These artifacts are most noticeable in a person's black and white vision (rod cells) than in

color vision (cone cells). Thus they will be more likely to see flicker or any sort of temporal

distortion in a display image by not looking directly at the display, because their eyes' rod

cells are mostly grouped at the periphery of their vision.

35

Conclusion

Thus we proposed the design and development of a low cost transportation management

system based on integration of RFID and GSM. The system consists of different modules

which are wirelessly linked with GSM modems. SMS service of GSM network is cost

effective which is used for the transfer of data between different modules. To facilitate the

people, a new service is introduced to make use of public transport for traveling, is

introduced inside the city. User is provided with the service, which gives them the current

location information of desired buses based on which the user can adjust his schedule

accordingly. The service therefore vanishes the need of waiting at the bus stop and hence it

saves lot of time. For the passengers not utilizing the service, to let them know the buses

location coming towards that stop, displays are installed at every Bus stop. The system is also

efficient and beneficial in handling an error and the emergency situations e.g., in case some

kind of technical fault occurred in bus, the operator at bus terminal is informed and the

departure time between the buses is reduced so that it will save time of the passengers.

It is believed that by the implementation of this system, problems such as underutilization of

buses fleet and long waiting time at the bus station will be reduced. So, both passenger and

bus station administrators will benefit from the system as real time information is provided.

36

Future Work

An automatic route guider display can be installed in buses to better update the alternative

route in case of serious road congestions. We can connect RFID reader wirelessly to the host

application. There are different advanced wireless technologies that can be used such as

Bluetooth (802.15.3) and ZigBee (802.15.4) to extend the range of an RFID reader. Fare

collecting system can also be automated by providing another mobile service to which all the

passengers using public transport are subscribed.

37

References

1. MAHAMMAD ABDUL HANNAN, AISHAH MUSTAPHA,ABDULLA AL MAMUN,

AINI HUSSAIN, HASSAN BASRI, “RFID and’communication technologies for an

intelligent bus monitoring and management system”

2. Ben Ammar Hatem, Hamam Habib, “Bus Management System Using RFID in WSN”,

European and Mediterranean Conference on Information Systems 2010

3. Akshay Bal, “RFID BASED IDENTIFICATION SYSTEM”, April 2009

4. LV ZHIAN HU HAN, “A Bus Management System Based on ZigBee and GSM/GPRS”,

201O International Conforence on Computer Application and System Modeling (ICCASM

2010)

5. Umar Farooq, Tanveer ul Haq, Senior Member IEEE, Muhammad Amar, Muhammad

Usman Asad, Asim Iqbal, “GPS-GSM Integration for Enhancing Public Transportation

Management Services”, 2010 Second International Conference on Computer Engineering and

Applications

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transportation using EPCGlobal-based WebServices”, 2013 27th International Conference on

Advanced Information Networking and Applications Workshops

7. Teki. Naga. Padmaja, Tejavath. Renuka, Anantha. Sushmitha. Srilakshmi, “Design of

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38