GSM GPS ARM7 Vehicle Tracking Project Report

A project report on
“TRACKING SYSTEM USING GSM, GPS & ARM7”
Submitted in partial fulfilment of the requirement for the award of the
Degree Of
Bachelor of Technology from
Guru Gobind Singh Indraprastha University
In
Electronic & Communication
Under the guidance of: Submitted by: ASHUTOSH UPADHAYAY
Mr. Jagrit : SAMIR BOTHRA
Asst. Prof., ECE Department : RASHMI SINGH
: SHIVANSHU GUPTA
HMR Institute of Technology & Management
Delhi-110036
2011-2015

CERTIFICATE
This is to certify that “ASHUTOSH UPADHAYAY, SAMIR BOTHRA,
RASHMI SINGH, SHIVANSHU GUPTA” have carried out the project
work presented in this report entitled “TRACKING SYSTEM USING
GSM, GPS & ARM7” for award of Bachelor of Technology (E.C.E) from
GGSIPU, Delhi under my guidance and supervision. The report embodies
the result of original work and studies are carried out by the students
themselves and the contents of the report do not form basis for award of any
other degree to the candidates or anybody else.
Prof. A. K. Shrivastva Asst. Prof. Jagrit
Head of Department Project Guide
ECE ECE

ACKNOWLEDGEMENT
With due respect and gratitude we would like to thank our supervisorAsst.
Prof. Jagrit for his constant support, able guidance and ever following stream
of encouragement throughout this work.
We would also like to thank Ms Yukti who helped us in our endeavour and
all the staff of the Department of Electronics and Communication
Engineering of HMRITM who made working on this project and completing
it an enjoyable job for us.
Date:
ASHUTOSH UPADHAYAY (08213302811)
SAMIR BOTHRA (06113302811)
RASHMI SINGH (09913302811)
SHIVANSHU GUPTA (05096504911)

TABLE OF CONTENTS
Certificate
Acknowledgement
Table of Contents
List of Figures
List of Tables
Abbreviations
Chapter 1: Introduction to VTS
1.1 Introduction
1.2 Vehicle Security using VTS
1.3 Active versus Passive Tracking
1.4 Types of GPS Vehicle Tracking
1.5 Typical Architecture
1.6 History of Vehicle Tracking
1.6.1 Early Technology
1.6.2 New development in technology
1.7 Vehicle Tracking System Features
1.7.1 Vehicle Tracking Benefits
1.8 Vehicle Tracing in India
Chapter 2: Block Diagram of VTS
2.1 Block Diagram of Vehicle Tracing Using GSM and GPS
Modem
2.2 Hardware Components
2.2.1 GPS
2.2.1.1 Working of GPS
2.2.1.2 Triangulation
2.2.1.3 Augmentation

2.2.2 GSM
2.2.3 RS232 Interface
2.2.3.1 The scope of the standard
2.2.3.2 History of RS 232
2.2.3.3 Limitation of Standard
2.2.3.4 Standard details
2.2.3.5 Connectors
2.2.3.6 Cables
2.2.3.7 Conventions
2.2.3.8 RTS/CTS handshaking
2.2.3.9 3-wire and 5-wire RS-232
2.2.3.10 Seldom used features
2.2.3.11 Timing Signals
2.2.3.12 Other Serial interfaces similar to RS-232
2.2.4 LCD
2.2.4.1 Advantages and Disadvantages
Chapter 3:Working of VTS
3.1 Schematic Diagram of VTS
3.2 Circuit Description
3.3 Circuit Operation
3.3.1 Power
3.3.2 Serial Ports
3.4 Operating procedure
Chapter 4:Microcontroller ARM7
4.1 Features
4.2 The Pin Configuration

4.2.1 Special Function Registers (SFR)
4.3 Memory Organization
4.4 Timers
Chapter 5:GSM Module
5.1 GSM History
5.2 Services Provided by GSM
5.3 Mobile Station
5.4 Base Station Subsystem
5.4.1 Base Station Controller
5.5 Architecture of the GSM Network
5.6 Radio Link Aspects
5.7 Multiple Access and Channel Structure
5.8 Frequency Hopping
5.9 Discontinuous Reception
5.10 Power Control
5.11 Network Aspects
5.12 Radio Resources Management
5.13 Handover
5.14 Mobility Management
5.15 Location Updating
5.16 Authentication and Security
5.17 Communication Management
5.18 Call Routing
Chapter 6:GPS Receiver
6.1 GPS History
6.1.1 Working and Operation
6.2 GPS Data Decoding

Chapter 7:KEIL Software
7.1 Introduction
7.2 KEIL uVision4
7.3 KEIL Software Programing Procedure
7.3.1 Procedure Steps
7.4 Applications of KEIL Software
Chapter 8:Applications
8.1 Applications
8.2 Limitations
Chapter 9:Result Analysis
Chapter 10:Conclusion and Future Scope
References

LIST OF FIGURES
Figure 1.1 Vehicle tracking system
Figure 2.1 Block diagram
Figure 2.2 A 25 pin connector as described in the RS-232 standard
Figure 2.3 Trace of voltage levels for uppercase ASCII "K" character
Figure 2.4 Upper Picture: RS232 signalling as seen when probed by an
actual oscilloscope
Figure 2.5 A general purpose alphanumeric LCD, with two lines of
characters.
Figure 3.1 Schematic diagram of vehicle tracing using GSM and GPS
Figure 5.1 Mobile station SIM port
Figure 5.2 Baste Station Subsystem.
Figure 5.3 Siemens BSC
Figure 5.4 Siemens’ TRAU
Figure 5.5 General architecture of a GSM network
Figure 5.6 Signalling protocol structure in GSM
Figure 5.7 Call routing for a mobile terminating call
Figure 6.1 G.P.S receivers communicating with the satellite
Figure 9.1 Picture of final VTS kit
Figure 9.2 Message received from the VTS kit

LIST OF TABLES
Table 2.1 Commonly used RS-232 signals and pin assignments
Table 2.2 Pin assignments
Table 2.3 RS-232 Voltage Levels
Table 2.4 TX and RX pin connection

ABBREVIATIONS
VTS Vehicle Tracking System
GSM Global System for Mobile Communication
GPS Global Positioning System
RI Ring Indicator
Tx Transmitter
Rx Receiver
SFR Special Function Register
LCD Liquid Crystal Display
RAM Random Access Memory
ROM Read Only Memory
RS-232 Recommended Standard
TTL Transistor Transistor Logic
CMOS Complementary Metal Oxide Semi-Conductor
UART Universal Asynchronous Receiver Transmitter
RST Reset
ALE Address Latch Enable
PSEN Program Store Enable

CHAPTER 1
INTRODUCTION TO VTS
1.1 Introduction
Vehicle Tracking System (VTS) is the technology used to determine the
location of a vehicle using different methods like GPS and other radio
navigation systems operating through satellites and ground based stations. By
following triangulation or trilateration methods the tracking system enables
to calculate easy and accurate location of the vehicle. Vehicle information
like location details, speed, distance travelled etc. can be viewed on a digital
mapping with the help of a software via Internet. Even data can be stored and
downloaded to a computer from the GPS unit at a base station and that can
later be used for analysis. This system is an important tool for tracking each
vehicle at a given period of time and now it is becoming increasingly popular
for people having expensive cars and hence as a theft prevention and
retrieval device.
1. The system consists of modern hardware and software components
enabling one to track their vehicle online or offline. Any vehicle tracking
system consists of mainly three parts mobile vehicle unit, fixed based station
and, database and software system.
2. Vehicle Unit: It is the hardware component attached to the vehicle having
either a GPS/GSM modem. The unit is configured around a primary
modem that functions with the tracking software by receiving signals from
GPS satellites or radio station points with the help of antenna. The controller
modem converts the data and sends the vehicle location data to the server.
3. Fixed Based Station: Consists of a wireless network to receive and
forward the data to the data centre. Base stations are equipped with tracking
software and geographic map useful for determining the vehicle location.
Maps of every city and landmarks are available in the based station that has
an in-built Web Server.
4. Database and Software: The position information or the coordinates of
each visiting points are stored in a database, which later can be viewed in a
display screen using digital maps. However, the users have to connect
themselves to the web server with the respective vehicle ID stored in the
database and only then s/he can view the location of vehicle travelled.

1.2 Vehicle Security using VTS
Vehicle Security is a primary concern for all vehicle owners. Owners as well
as researchers are always on the lookout for new and improved security
systems for their vehicles. One has to be thankful for the upcoming
technologies, like GPS systems, which enables the owner to closely monitor
and track his vehicle in real-time and also check the history of vehicles
movements. This new technology, popularly called Vehicle Tracking
Systems has done wonders in maintaining the security of the vehicle tracking
system is one of the biggest technological advancements to track the
activities of the vehicle. The security system uses Global Positioning System
GPS, to find the location of the monitored or tracked vehicle and then uses
satellite or radio systems to send to send the coordinates and the location data
to the monitoring centre. At monitoring centrevarious software’s are used to
plot the Vehicle on a map. In this way the Vehicle owners are able to track
their vehicle on a real-time basis. Due to real-time tracking facility, vehicle
tracking systems are becoming increasingly popular among owners of
expensive vehicles.
The vehicle tracking hardware is fitted on to the vehicle. It is fitted in such a
manner that it is not visible to anyone who is outside the vehicle. Thus it
operates as a covert unit which continuously sends the location data to the
monitoring unit.
When the vehicle is stolen, the location data sent by tracking unit can be used
to find the location and coordinates can be sent to police for further action.
Some Vehicle tracking System can even detect unauthorized movements of
the vehicle and then alert the owner. This gives an edge over other pieces of
technology for the same purpose
Monitoring centre Software helps the vehicle owner with a view of the
location at which the vehicle stands. Browsing is easy and the owners can
make use of any browser and connect to the monitoring centre software, to
find and track his vehicle. This in turn saves a lot of effort to find the
vehicle's position by replacing the manual call to the driver.
As we have seen the vehicle tracking system is an exciting piece of
technology for vehicle security. It enables the owner to virtually keep an eye
on his vehicle any time and from anywhere in the world.
A vehicle tracking system combines the installation of an electronic device in
a vehicle, or fleet of vehicles, with purpose-designed computer software at
least at one operational base to enable the owner or a third party to track the
vehicle's location, collecting data in the process from the field and deliver
itto the base of operation. Modern vehicle tracking systems commonly use

GPS or GLONASS technology for locating the vehicle, but other types of
automatic vehicle location technology can also be used. Vehicle information
can be viewed on electronic maps via the Internet or specialized software.
Urban public transit authorities are an increasingly common user of vehicle
tracking systems, particularly in large cities.
Vehicle tracking systems are commonly used by fleet operators for fleet
management functions such as fleet tracking, routing, dispatch, on-board
information and security. Along with commercial fleet operators, urban
transit agencies use the technology for a number of purposes, including
monitoring schedule adherence of buses in service, triggering changes of
buses' destination sign displays at the end of the line (or other set location
along a bus route), and triggering pre-recorded announcements for
passengers. The American Public Transportation Association estimated that,
at the beginning of 2009, around half of all transit buses in the United States
were already using a GPS-based vehicle tracking system to trigger automated
stop announcements. This can refer to external announcements (triggered by
the opening of the bus's door) at a bus stop, announcing the vehicle's route
number and destination, primarily for the benefit of visually impaired
customers, or to internal announcements (to passengers already on board)
identifying the next stop, as the bus (or tram) approaches a stop, or both.
Data collected as a transit vehicle follows its route is often continuously fed
into a computer program which compares the vehicle's actual location and
time with its schedule, and in turn produces a frequently updating display for
the driver, telling him/her how early or late he/she is at any given time,
potentially making it easier to adhere more closely to the published schedule.
Such programs are also used to provide customers with real-time
information as to the waiting time until arrival of the next bus or
tram/streetcar at a given stop, based on the nearest vehicles' actual progress
at the time, rather than merely giving information as to the scheduled time of
the next arrival. Transit systems providing this kind of information assign a
unique number to each stop, and waiting passengers can obtain information
by entering the stop number into an automated telephone system or an
application on the transit system's website. Some transit agencies provide a
virtual map on their website, with icons depicting the current locations of
buses in service on each route, for customers' information, while others
provide such information only to dispatchers or other employees.
Other applications include monitoring driving behaviour, such as an
employer of an employee, or a parent with a teen driver.
Vehicle tracking systems are also popular in consumer vehicles as a theft
prevention and retrieval device. Police can simply follow the signal
emittedby the tracking system and locate the stolen vehicle. When used as a

security system, a Vehicle Tracking System may serve as either an addition
to or replacement for a traditional car alarm. Some vehicle tracking systems
make it possible to control vehicle remotely, including block doors or engine
in case of emergency. The existence of vehicle tracking device then can be
used to reduce the insurance cost, because the loss-risk of the vehicle drops
significantly.
Vehicle tracking systems are an integrated part of the "layered approach" to
vehicle protection, recommended by the National Insurance Crime Bureau
(NICB) to prevent motor vehicle theft. This approach recommends four
layers of security based on the risk factors pertaining to a specific vehicle.
Vehicle Tracking Systems are one such layer, and are described by the NICB
as “very effective” in helping police recover stolen vehicles.
Some vehicle tracking systems integrate several security systems, for
example by sending an automatic alert to a phone or email if an alarm is
triggered or the vehicle is moved without authorization, or when it leaves or
enters a geofence.
1.3 Active versus Passive Tracking
Several types of vehicle tracking devices exist. Typically they are classified
as "passive" and "active". "Passive" devices store GPS location, speed,
heading and sometimes a trigger event such as key on/off, door open/closed.
Once the vehicle returns to a predetermined point, the device is removed and
the data downloaded to a computer for evaluation. Passive systems include
auto download type that transfer data via wireless download. "Active"
devices also collect the same information but usually transmit the data in
real-time via cellular or satellite networks to a computer or data centre for
evaluation.
Many modern vehicle tracking devices combine both active and passive
tracking abilities: when a cellular network is available and a tracking device
is connected it transmits data to a server; when a network is not available the
device stores data in internal memory and will transmit stored data to the
server later when the network becomes available again.
Historically vehicle tracking has been accomplished by installing a box into
the vehicle, either self-powered with a battery or wired into the vehicle's
power system. For detailed vehicle locating and tracking this is still the
predominant method; however, many companies are increasingly interested
in the emerging cell phone technologies that provide tracking of multiple
entities, such as both a salesperson and their vehicle. These systems also
offer tracking of calls, texts, and Web use and generally provide a wider
range of options.

1.4 Types of GPS Vehicle Tracking
There are three main types of GPS vehicle tracking, tracking based mobile,
wireless passive tracking and satellite in real-time GPS tracking. This article
discusses the advantages and disadvantages to all three types of GPS vehicle
tracking circumference.
1. Mobile phone based tracking
The initial cost for the construction of the system is slightly lower than
the other two options. With a mobile phone-based tracking average
price is about $ 500. A cell-based monitoring system sends
information about when a vehicle is every five minutes during a rural
network. The average monthly cost is about thirty-five dollars for
airtime.
2. Wireless Passive Tracking
A big advantage that this type of tracking system is that there is no
monthly fee, so that when the system was introduced, there will be
other costs associated with it. But setting the scheme is a bit
'expensive. The average is about $ 700 for hardware and $ 800 for
software and databases. With this type of system, most say that the
disadvantage is that information about where the vehicle is not only
can exist when the vehicle is returned to the base business. This is a
great disadvantage, particularly for companies that are looking for a
monitoring system that tells them where their vehicle will be in case of
theft or an accident. However, many systems are now introducing
wireless modems into theirdevices so that tracking information can be
without memory of the vehicle to be seen. With a wireless modem that
is wireless passive tracking systems are also able to gather information
on how fast the vehicle was traveling, stopping, and made other
detailed information. With this new addition, many companies believe
that this system is perfect, because there is no monthly bill.
3. Via satellite in real time
This type of system provides less detailed information, but work at the
national level, making it a good choice for shipping and trucking
companies. Spending on construction of the system on average about $

700. The monthly fees for this system vary from five dollars for a
hundred dollars, depending on how the implementation of a reporting
entity would be.
Technology
Over the next few years, GPS tracking will be able to provide businesses
with a number of other benefits. Some companies have already introduced a
way for a customer has signed the credit card and managed at local level
through the device. Others are creating ways for dispatcher to send the
information re-routing, the GPS device directly to a manager. Not a new
requirement for GPS systems is that they will have access to the Internet and
store information about the vehicle as a driver or mechanic GPS device to
see the diagrams used to assist with the vehicle you want to leave. Beyond
that all the information be saved and stored in its database.
1.5 Typical Architecture
Major constituents of the GPS based tracking are
1. GPS tracking device
The device fits into the vehicle and captures the GPS location
information apart from other vehicle information at regular intervals to
a central server. The other vehicle information can include fuel
amount, engine temperature, altitude, reverse geocoding, door
open/close, tire pressure, cut off fuel, turn off ignition, turn on
headlight, turn on taillight, battery status, GSM area code/cell code
decoded, number of GPS satellites in view, glass open/close, fuel
amount, emergency button status, cumulative idling, computed
odometer, engine RPM, throttle position, and a lot more. Capability of
these devices actually decides the final capability of the whole tracking
system.
2. GPS tracking server
The tracking server has three responsibilities: receiving data from the
GPS tracking unit, securely storing it, and serving this information on
demand to the user.
3. User interface
The UI determines how one will be able to access information, view
vehicle data, and elicit important details from it.

1.6 History of Vehicle Tracking
GPS or Global Positioning Systems were designed by the United States
Government and military, which the design was intended to be used as
surveillance. After several years went by the government signed a treaty to
allow civilians to buy GPS units also only the civilians would get precise
downgraded ratings.
Years after the Global Positioning Systems were developed the military
controlled the systems despite that civilians could still purchase them in
stores. In addition, despite that Europe has designed its own systems called
the Galileo the US military still has complete control.
GPS units are also called tracking devices that are quite costly still. As more
of these devices develop however the more affordable the GPS can be
purchased. Despite of the innovative technology and designs of the GPS
today the devices has seen some notable changes or reductions in pricing.
Companies now have more access to these devices and many of the
companies can find benefits.
These days you can pay-as-you go or lease a GPS system for your company.
This means you do not have to worry about spending upfront money, which
once stopped companies from installing the Global positioning systems at
one time.
Today’s GPS applications have vastly developed as well. It is possible to use
the Global Positioning Systems to design expense reports, create time sheets,
or reduce the costs of fuel consumption. You can also use the tracking
devices to increase efficiency of employee driving. The GPS unit allows you
to create Geo-Fences about a designated location, which gives you alerts
once your driver(s) passes through. This means you have added security
combined with more powerful customer support for your workers.
Today’s GPS units are great tracking devices that help fleet managers stay in
control of their business. The applications in today’s GPS units make it
possible to take full control of your company. It is clear that the tracking
devices offer many benefits to companies, since you can build automated
expense reports anytime.
GPS units do more than just allow companies to create reports. These
devices also help to put an end to thieves. According to recent reports, crime
is at a high, which means that car theft is increasing. If you have the right
GPS unit, you can put an end to car thefts because you can lock and unlock
your car anytime you choose.

GPS are small tracking devices that are installed in your car and it will
supply you with feedback data from tracking software that loads from a
satellite. This gives you more control over your vehicles.
The chief reason for companies to install tracking devices is to monitor their
mobile workforce. A preventive measure device allows companies to
monitor their employees’ activities. Company workers can no longer take
your vehicles to unassigned locations. They will not be able to get away with
unauthorized activities at any time because you can monitor their every
action on a digital screen.
The phantom pixel is another thing some webmasters do to get better
rankings. Unfortunately it will backfire on you since the search engines do
not want this to occur. You see, the phantom pixel is when you might have a
1 pixel image or an image so small it cannot be seen by the regular eye. They
use the pixel to stuff it with keywords. The search engine can view it in the
code, which is how they know it is there and can give you better rank for the
keywords in theory. Of course since the search engines don’t like this
phantom pixel you are instead not getting anything for the extra keywords
except sent to the bottomless pit.
1.6.1 Early Technology
In the initial period of tracking only two radios were used to exchange
the information. One radio was attached to the vehicle while another at
base station by which drivers were enabled to talk to their masters.
Fleet operator could identify the progress through their routes.
The technology was not without its limits. It was restricted by the
distance which became a hurdle in accuracy and better connectivity
between driver and fleet operators. Base station was dependent on the
driver for the information and a huge size fleet could not have been
managed depending on man-power only.
The scene of vehicle tracking underwent a change with the arrival of
GPS technology. This reduced the dependence on man-power. Most of
the work of tracking became electronic. Computers proved a great help
in managing a large fleet of vehicle. This also made the information
authentic. As this technology was available at affordable cost all
whether small or big fleet could take benefit of this technology
Because of the cheap accessibility of the device computer tracking
facilities has come to stay and associated with enhanced management.
Today eachvehicle carries tracking unit which is monitored from the
base station. Base station receives the data from the unit.

All these facilities require a heavy investment of capital for the
installation of the infrastructure of tracking system for monitoring and
dispatching.
1.6.2 New development in technology
New system costs less with increased efficiency. Presently it is small
tracking unit in the vehicle with web-based interface, connected
through a mobile phone. This device avoids unnecessary investment in
infrastructure with the facility of monitoring from anywhere for the
fleet managers. This provides more efficient route plan to fleet
operators of all sizes and compositions saving money and time.
Vehicle tracking system heralded a new era of convenience and affordability
in fleet management. Thus due to its easy availability it is going to stay for
long.
1.7 Vehicle Tracking System Features
Monitoring and managing the mobile assets are very important for any
company dealing with the services, delivery or transport vehicles.
Information technologies help in supporting these functionalities from
remote locations and update the managers with the latest information of their
mobile assets. Tracking the mobile assets locations data and analysing the
information is necessary for optimal utilization of the assets.
Vehicle Tracking System is a software & hardware system enabling the
vehicle owner to track the position of their vehicle. A vehicle tracking
system uses either GPS or radio technology to automatically track and record
a fleet's field activities. Activity is recorded by modules attached to each
vehicle. And then the data is transmitted to a central, internet-connected
computer where it is stored. Once the data is transmitted to the computer, it
can be analysed and reports can be downloaded in real-time to your computer
using either web browser based tools or customized software.
1.7.1 Vehicle Tracking Benefits
An enterprise-level vehicle tracking system should offer customizable
reporting tools, for example to provide a summary of the any day
activities. It should have the ability to produce and print detailed maps
and reports displaying actual stops, customer locations, mileage
travelled, and elapsed time at each location, and real-time access to
vehicle tracking data and reports. Vehicle tracking system can be
active, passive or both depending upon the application. Here are steps
involved in the vehicle tracking:

1. Data capture: Data capturing is the first step in tacking your
vehicle. Data in a vehicle tracking system is captured through a
unit called automated vehicle unit. The automated vehicle unit
uses the Global Positioning System (GPS) to determine the
location of the vehicle. This unit is installed in the vehicle and
contains interfaces to various data sources. This paper considers
the location data capture along with data from various sensors
like fuel, vehicle diagnostic sensors etc.
2. Data storage: Captured data is stored in the memory of the
automated vehicle unit.
3. Data transfer: Stored data are transferred to the computer
server using the mobile network or by connecting the vehicle
mount unit to the computer.
4. Data analysis: Data analysis is done through software
application. A GIS mapping component is also an integral part
of the vehicle tracking system and it is used to display the
correct location of the vehicle on the map.
1.8 Vehicle Tracing in India
Vehicle tracking system in India is mainly used in transport industry that
keeps a real-time track of all vehicles in the fleet. The tracking system
consists of GPS device that brings together GPS and GSM technology using
tracking software. The attached GPS unit in the vehicle sends periodic
updates of its location to the route station through the server of the cellular
network that can be displayed on a digital map. The location details are later
transferred to users via SMS, e-mail or other form of data transfers.
There are various GPS software and hardware developing companies in India
working for tracking solutions. However, its application is not that much of
popular as in other countries like USA, which regulates the whole GPS
network. In India it is mostly used in Indian transport and logistics industry
and not much personal vehicle tracking.
But with better awareness and promotion the market will increase. Let’s have
a look at its current application in India using vehicle tracking though in less
volume.
a) Freight forwarding
Logistic service providers are now increasingly adopting vehicle-tracking
system for better fleet management and timely service. The system can

continuously monitor shipment location and so can direct the drivers directly
in case of any change of plan. Fleet managers can keep an eye on all
activities of workers, vehicle over speed, route deviation etc. The driver in
turn can access emergency service in case of sickness, accident or vehicle
breakdown. All in turn supports money and time management, resulting
better customer service.
b) Call centres
In commercial vehicle segments the taxi operators of various call centres are
now using vehicle tracking system for better information access. However,
its application is in its infant stage in India and if adequate steps are taken in
bringing the cost of hardware and software low then it can be used for
tracking personal vehicle, farming (tractor), tourist buses, security and
emergency vehicle etc. Again Government needs to cut down the restriction
imposed upon the availability of digital maps for commercial use and this
will encourage software industry in developing cost-effective tracking
solutions. Though, sales of both commercial and passenger vehicles are
growing but price of tracking service is very high and this is the key issue in
Indian market. Hence, it’s important for market participants to reduce prices
of GPS chips and other products in order to attract more and more users.
As far as Indian vehicle tracking and navigation market is concerned the
recent association of India with Russian Global Navigation Satellite System
(GLONASS) will act as a catalyst in the improvement of vehicle tracking
system. This will give an advantage in managing traffic, roadways and ports
and also as an important tool for police and security agency to track stolen
vehicles. Hence, in near future there is large prospect for the utility of vehicle
tracking system in India, which can revolutionize the way we are
communicating.

CHAPTER 2
Block Diagram Of VTS
2.1 Block Diagram of Vehicle Tracing Using GSM and GPS Modem
2.2 Hardware Components
ARM7
GPS MODULE
GSM MODULE
RS232
LCD
In this project ARM7 microcontroller is used for interfacing to various
hardware peripherals. The current design is an embedded application, which
will continuously monitor a moving Vehicle and report the status of the
Vehicle on reset. For doing so an ARM7 microcontroller is interfaced
serially to a GSM Modem and GPS Receiver. A GSM modem is used to send
the position (Latitude and Longitude) of the vehicle from a remote place. The
GPS modem will continuously give the data i.e. the latitude and longitude
indicating the position of the vehicle. The GPS modem gives many
parameters as the output, but only the needed data coming out is read and
displayed on to the LCD. The same data is sent to the mobile at the other end
from where the position of the vehicle is demanded.

The hardware interfaces to microcontroller are LCD display, GSM modem
and GPS Receiver. The design uses RS-232 protocol for serial
communication between the modems and the microcontroller. When the
request by user is sent to the number at the modem, the system automatically
sends a return reply to that mobile indicating the position of the vehicle in
terms of latitude and longitude.
As the Micro Controller, GPS and GSM take a sight of in depth knowledge,
they are explained in the next chapters.
2.2.1 GPS
GPS, in full Global Positioning System, space-based radio-navigation
system that broadcasts highly accurate navigation pulses to users on or
near the Earth. In the United States’ Navstar GPS, 24 main satellites in
6 orbits circle the Earth every 12 hours. In addition, Russia maintains a
constellation called GLONASS (Global Navigation Satellite System).
2.2.1.1 Working of GPS
GPS receiver works on 9600 baud rate is used to receive the
data from space Segment (from Satellites), the GPS values of
different Satellites are sent to microcontroller AT89S52, where
these are processed and forwarded to GSM. At the time of
processing GPS receives only $GPRMC values only. From
these values microcontroller takes only latitude and longitude
values excluding time, altitude, name of the satellite,
authentication etc. E.g. LAT: 1728:2470 LOG: 7843.3089
GSM modem with a baud rate 57600.
A GPS receiver operated by a user on Earth measures the time it
takes radio signals to travel from four or more satellites to its
location, calculates the distance to each satellite, and from this
calculation determines the user’s longitude, latitude, and
altitude. The U.S. Department of Defence originally developed
the Navstar constellation for military use, but a less precise form
of the service is available free of charge to civilian users around
the globe. The basic civilian service will locate a receiver within
10 meters (33 feet) of its true location, though various
augmentation techniques can be used to pinpoint the location
within less than 1 cm (0.4 inch). With such accuracy and the
ubiquity of the service, GPS has evolved far beyond its original
military purpose and has created a revolution in personal and
commercial navigation. Battlefield missiles and artillery
projectiles use GPS signals to determine their positions and

velocities, but so do the U.S. space shuttle and the International
Space Station as well as commercial jetliners and private
airplanes. Ambulance fleets, family automobiles, and railroad
locomotives benefit from GPS positioning, which also serves
farm tractors, ocean liners, hikers, and even golfers. Many GPS
receivers are no larger than a pocket calculator and are powered
by disposable batteries, while GPS computer chips the size of a
baby’s fingernail have been installed in wristwatches, cellular
telephones, and personal digital assistants.
2.2.1.2 Triangulation
The principle behind the unprecedented navigational capabilities
of GPS is triangulation. To triangulate, a GPS receiver precisely
measures the time it takes for a satellite signal to make its brief
journey to Earth—less than a tenth of a second. Then it
multiplies that time by the speed of a radio wave—300,000 km
(186,000 miles) per second—to obtain the corresponding
distance between it and the satellite. This puts the receiver
somewhere on the surface of an imaginary sphere with a radius
equal to its distance from the satellite. When signals from three
other satellites are similarly processed, the receiver’s built-in
computer calculates the point at which all four spheres intersect,
effectively determining the user’s current longitude, latitude,
and altitude. (In theory, three satellites would normally provide
an unambiguous three-dimensional fix, but in practice at least
four are used to offset inaccuracy in the receiver’s clock.) In
addition, the receiver calculates current velocity (speed and
direction) by measuring the instantaneous Doppler Effect shifts
created by the combined motion of the same four satellites.
2.2.1.3 Augmentation
Although the travel time of a satellite signal to Earth is only a
fraction of a second, much can happen to it in that interval. For
example, electrically charged particles in the ionosphere and
density variations in the troposphere may act to slow and distort
satellite signals. These influences can translate into positional
errors for GPS users—a problem that can be compounded by
timing errors in GPS receiver clocks. Further errors may be
introduced by relativistic time dilations, a phenomenon in which
a satellite’s clock and a receiver’s clock, located in different
gravitational fields and traveling at different velocities, tick at
different rates. Finally, the single greatest source of error to
users of the Navstar system is the lower accuracy of the civilian

C/A-code pulse. However, various augmentation methods exist
for improving the accuracy of both the military and the civilian
systems.When positional information is required with pinpoint
precision, users can take advantage of differential GPS
techniques. Differential navigation employs a stationary “base
station” that sits at a known position on the ground and
continuously monitors the signals being broadcast by GPS
satellites in its view. It then computes and broadcasts real-time
navigation corrections to nearby roving receivers. Each roving
receiver, in effect, subtracts its position solution from the base
station’s solution, thus eliminating any statistical errors common
to the two. The U.S. Coast Guard maintains a network of such
base stations and transmits corrections over radio beacons
covering most of the United States. Other differential
corrections are encoded within the normal broadcasts of
commercial radio stations. Farmers receiving these broadcasts
have been able to direct their field equipment with great
accuracy, making precision farming a common term in
agriculture.
Another GPS augmentation technique uses the carrier waves
that convey the satellites’ navigation pulses to Earth. Because
the length of the carrier wave is more than 1,000 times shorter
than the basic navigation pulses, this “carrier-aided” approach,
under the right circumstances, can reduce navigation errors to
less than 1 cm (0.4 inch). The dramatically improved accuracy
stems primarily from the shorter length and much greater
numbers of carrier waves impinging on the receiver’s antenna
each second.
Yet another augmentation technique is known as
geosynchronous overlays. Geosynchronous overlays employ
GPS payloads “piggybacked” aboard commercial
communication satellites that are placed in geostationary orbit
some 35,000 km (22,000 miles) above the Earth. These
relatively small payloads broadcast civilian C/A-code pulse
trains to ground-based users. The U.S. government is enlarging
the Navstar constellation with geosynchronous overlays to
achieve improved coverage, accuracy, and survivability. Both
the European Union and Japan are installing their own
geosynchronous overlays.
2.2.2 GSM

GSM (or Global System for Mobile Communications) was developed
in 1990. The first GSM operator has subscribers in 1991, the
beginning of 1994 the network based on the standard, already had 1.3
million subscribers, and the end of 1995 their number had increased to
10 million!
There were first generation mobile phones in the 70's, there are 2nd
generation mobile phones in the 80's and 90's, and now there are 3rd
gen phones which are about to enter the Indian market. GSM is called
a 2nd generation, or 2G communications technology.
In this project it acts as a SMS Receiver and SMS sender. The GSM
technical specifications define the different entities that form the GSM
network by defining their functions and interface requirements.
2.2.3 RS232 Interface
In telecommunications, RS-232 is the traditional name for a series of
standards for serial binary single-ended data and control signals
connecting between a DTE (Data Terminal Equipment) and a DCE
(Data Circuit-terminating Equipment). It is commonly used in
computer serial ports. The standard defines the electrical
characteristics and timing of signals, the meaning of signals, and the
physical size and pin out of connectors. The current version of the
standard is TIA-232-F Interface between Data Terminal Equipment
and Data Circuit-Terminating Equipment Employing Serial Binary
Data Interchange, issued in 1997.
An RS-232 port was once a standard feature of a personal computer
for connections to modems, printers, mice, data storage, un-interruptible
power supplies, and other peripheral devices. However,
the limited transmission speed, relatively large voltage swing, and
large standard connectors motivated development of the universal
serial bus which has displaced RS-232 from most of its peripheral
interface roles. Many modern personal computers have no RS-232
ports and must use an external converter to connect to older
peripherals. Some RS-232 devices are still found especially in
industrial machines or scientific instruments.
2.2.3.1 The scope of the standard
The Electronic Industries Association (EIA) standard RS-232-C
as of 1969 defines:

1. Electrical signal characteristics such as voltage levels,
signalling rate, timing and slew-rate of signals voltage
withstand level, short-circuit behaviour, and maximum load
capacitance.
2. Interface mechanical characteristics, pluggable connectors
and pin identification.
3. Functions of each circuit in the interface connector.
4. Standard subsets of interface circuits for selected telecom
applications.
The standard does not define such elements as the character
encoding or the framing of characters, or error detection
protocols. The standard does not define bit rates for
transmission, except that it says it is intended for bit rates lower
than 20,000 bits per second. Many modern devices support
speeds of 115,200 bit/s and above. RS 232 makes no provision
for power to peripheral devices.
Details of character format and transmission bit rate are
controlled by the serial port hardware, often a single integrated
circuit called a UART that converts data from parallel to
asynchronous start-stop serial form. Details of voltage levels,
slew rate, and short-circuit behaviour are typically controlled by
a line driver that converts from the UART's logic levels to RS-
232 compatible signal levels, and a receiver that converts from
RS-232 compatible signal levels to the UART's logic levels.
2.2.3.2 History of RS 232
RS-232 was first introduced in 1962. The original DTEs were
electromechanical teletypewriters, and the original DCEs were
(usually) modems. When electronic terminals (smart and dumb)
began to be used, they were often designed to be
interchangeable with teletypewriters, and so supported RS-232.
The C revision of the standard was issued in 1969 in part to
accommodate the electrical characteristics of these devices.
Since application to devices such as computers, printers, test
instruments, and so on was not considered by the standard,
designers implementing an RS-232 compatible interface on their
equipment often interpreted the requirements idiosyncratically.
Common problems were non-standard pin assignment of circuits
on connectors, and incorrect or missing control signals. The lack

of adherence to the standards produced a thriving industry of
breakout boxes, patch boxes, test equipment, books, and other
aids for the connection of disparate equipment. A common
deviation from the standard was to drive the signals at a reduced
voltage. Some manufacturers therefore built transmitters that
supplied +5V and -5V and labelled them as "RS-232
compatible".
Later personal computers (and other devices) started to make
use of the standard so that they could connect to existing
equipment. For many years, an RS-232-compatible port was a
standard feature for serial communications, such as modem
connections, on many computers. It remained in widespread use
into the late 1990s. In personal computer peripherals, it has
largely been supplanted by other interface standards, such as
USB. RS-232 is still used to connect older designs of
peripherals, industrial equipment (such as PLCs), console
ports, and special purpose equipment, such as a cash drawer for
a cash register.
The standard has been renamed several times during its history
as the sponsoring organization changed its name, and has been
variously known as EIA RS-232, EIA 232, and most recently as
TIA 232. The standard continued to be revised and updated by
the Electronic Industries Alliance and since 1988 by the
Telecommunications Industry Association (TIA) .[3] Revision C
was issued in a document dated August 1969. Revision D was
issued in 1986. The current revision is TIA-232-F Interface
between Data Terminal Equipment and Data Circuit-
Terminating Equipment Employing Serial Binary Data
Interchange, issued in 1997. Changes since Revision C have
been in timing and details intended to improve harmonization
with the CCITT standard V.24, but equipment built to the
current standard will interoperate with older versions.
Related ITU-T standards include V.24 (circuit identification)
and V.28 (signal voltage and timing characteristics).
2.2.3.3 Limitation of Standard
Because the application of RS-232 has extended far beyond the
original purpose of interconnecting a terminal with a modem,
successor standards have been developed to address the
limitations.

Issues with the RS-232 standard include:
1. The large voltage swings and requirement for positive and
negative supplies increases power consumption of the interface
and complicates power supply design. The voltage swing
requirement also limits the upper speed of a compatible
interface.
2. Single-ended signalling referred to a common signal ground
limits the noise immunity and transmission distance.
3. Multi-drop connection among more than two devices is not
defined. While multi-drop "work-around" has been devised,
they have limitations in speed and compatibility.
4. Asymmetrical definitions of the two ends of the link make the
assignment of the role of a newly developed device problematic;
the designer must decide on either a DTE-like or DCE-like
interface and which connector pin assignments to use.
5. The handshaking and control lines of the interface are
intended for the setup and takedown of a dial-up
communication circuit; in particular, the use of handshake lines
for flow control is not reliably implemented in many devices.
6. No method is specified for sending power to a device. While
a small amount of current can be extracted from the DTR and
RTS lines, this is only suitable for low power devices such as
mice.
7. The 25-way connector recommended in the standard is large
compared to current practice.
2.2.3.4 Standard details
In RS-232, user data is sent as a time-series of bits. Both
synchronous and asynchronous transmissions are supported by
the standard. In addition to the data circuits, the standard defines
a number of control circuits used to manage the connection
between the DTE and DCE. Each data or control circuit only
operates in one direction that is, signalling from a DTE to the
attached DCE or the reverse. Since transmit data and receive
data are separate circuits, the interface can operate in a full
duplex manner, supporting concurrent data flow in both
directions. The standard does not define character framing
within the data stream, or character encoding.

This is typical for start-stop communications, but the standard
does not dictate a character format or bit order.
The RS-232 standard defines the voltage levels that correspond
to logical one and logical zero levels for the data transmission
and the control signal lines. Valid signals are plus or minus 3 to
15 volts; the ±3 V range near zero volts is not a valid RS-232
level.
The standard specifies a maximum open-circuit voltage of 25
volts: signal levels of ±5 V, ±10 V, ±12 V, and ±15 V are all
commonly seen depending on the power supplies available
within a device. RS-232 drivers and receivers must be able to
withstand indefinite short circuit to ground or to any voltage
level up to ±25 volts. The slew rate, or how fast the signal
changes between levels, is also controlled.
For data transmission lines (TxD, RxD and their secondary
channel equivalents) logic one is defined as a negative voltage,
the signal condition is called marking, and has the functional
significance. Logic zero is positive and the signal condition is
termed spacing. Control signals are logically inverted with
respect to what one sees on the data transmission lines. When
one of these signals is active, the voltage on the line will be
between +3 to +15 volts. The inactive state for these signals is
the opposite voltage condition, between −3 and −15 volts.
Examples of control lines include request to send (RTS), clear to
send (CTS), data terminal ready (DTR), and data set ready
(DSR).
Because the voltage levels are higher than logic levels typically
used by integrated circuits, special intervening driver circuits are
required to translate logic levels. These also protect the device's
internal circuitry from short circuits or transients that may
appear on the RS-232 interface, and provide sufficient current to
comply with the slew rate requirements for data transmission.
Because both ends of the RS-232 circuit depend on the ground
pin being zero volts, problems will occur when connecting
machinery and computers where the voltage between the ground
pin on one end and the ground pin on the other is not zero. This
may also cause a hazardous ground loop. Use of a common
ground limits RS-232 to applications with relatively short
cables. If the two devices are far enough apart or on separate
power systems, the local ground connections at either end of the

cable will have differing voltages; this difference will reduce the
noise margin of the signals. Balanced, differential, serial
connections such as USB, RS-422 and RS-485 can tolerate
larger ground voltage differences because of the differential
signalling.
Unused interface signals terminated to ground will have an
undefined logic state. Where it is necessary to permanently set a
control signal to a defined state, it must be connected to a
voltage source that asserts the logic 1 or logic 0 level. Some
devices provide test voltages on their interface connectors for
this purpose.
2.2.3.5 Connectors
RS-232 devices may be classified as Data Terminal Equipment
(DTE) or Data Communication Equipment (DCE); this defines
at each device which wires will be sending and receiving each
signal. The standard recommended but did not make mandatory
the D-subminiature 25 pin connector. In general and according
to the standard, terminals and computers have male connectors
with DTE pin functions, and modems have female connectors
with DCE pin functions. Other devices may have any
combination of connector gender and pin definitions. Many
terminals were manufactured with female terminals but were
sold with a cable with male connectors at each end; the terminal
with its cable satisfied the recommendations in the standard.
Presence of a 25 pin D-sub connector does not necessarily
indicate an RS-232-C compliant interface. For example, on the
original IBM PC, a male D-sub was an RS-232-C DTE port
(with a non-standard current loop interface on reserved pins),
but the female D-sub connector was used for a parallel
Centroids printer port. Some personal computers put non-standard
voltages or signals on some pins of their serial ports.
The standard specifies 20 different signal connections. Since
most devices use only a few signals, smaller connectors can
often be used.
The signals are named from the standpoint of the DTE. The
ground signal is a common return for the other connections. The
DB-25 connector includes a second "protective ground" on pin
1.Data can be sent over a secondary channel (when
implemented by the DTE and DCE devices), which is

equivalent to the primary channel. Pin assignments are
described in shown in Table 2.2:
Table 2.1. Commonly used RS-232 signals and pin assignments
Signal Origin
DB-25 pin
Name Typical purpose Abbreviation DTE DCE
Data Indicates presence of
DTR ●
20
Terminal Ready DTE to DCE.
Data DCE is connected to the
DCD
● 8
Carrier Detect telephone line.
Data Set Ready
DCE is ready to receive
DSR
● 6
commands or data.
DCE has detected an
Ring Indicator incoming ring signal on RI ● 22
the telephone line.
Request To DTE requests the DCE
RTS ●
4
Send prepare to receive data.
Clear To Send
Indicates DCE is ready to
CTS
● 5
accept data.
Transmitted Carries data from DTE to
TxD ●
2
Data DCE.
Received Data
Carries data from DCE to
RxD
● 3
DTE.
Common
GND common 7
Ground
Protective
PG common 1
Ground

Table 2.2 Pin assignments
Signal Pin
Common Ground 7 (same as primary)
Secondary Transmitted Data (STD) 14
Secondary Received Data (SRD) 16
Secondary Request To Send (SRTS) 19
Secondary Clear To Send (SCTS) 13
Secondary Carrier Detect (SDCD) 12
Ring Indicator' (RI), is a signal sent from the modem to the
terminal device. It indicates to the terminal device that the
phone line is ringing. In many computer serial ports, a hardware
interrupt is generated when the RI signal changes state. Having
support for this hardware interrupt means that a program or
operating system can be informed of a change in state of the RI
pin, without requiring the software to constantly "poll" the state
of the pin. RI is a one-way signal from the modem to the
terminal (or more generally, the DCE to the DTE) that does not
correspond to another signal that carries similar information the
opposite way.
On an external modem the status of the Ring Indicator pin is
often coupled to the "AA" (auto answer) light, which flashes if
the RI signal has detected a ring. The asserted RI signal follows
the ringing pattern closely,which can permit software to detect
distinctive ring patterns.
The Ring Indicator signal is used by some older uninterruptible
power supplies (UPS's) to signal a power failure state to the
computer.
Certain personal computers can be configured for wake-on-ring,
allowing a computer that is suspended to answer a phone call.

2.2.3.6 Cables
The standard does not define a maximum cable length but
instead defines the maximum capacitance that a compliant drive
circuit must tolerate. A widely used rule of thumb indicates that
cables more than 50 feet (15 m) long will have too much
capacitance, unless special cables are used. By using low-capacitance
cables, full speed communication can be maintained
over larger distances up to about 1,000 feet (300 m) .[8] For
longer distances, other signal standards are better suited to
maintain high speed.
Since the standard definitions are not always correctly applied,
it is often necessary to consult documentation, test connections
with a breakout box, or use trial and error to find a cable that
works when interconnecting two devices. Connecting a fully
standard-compliant DCE device and DTE device would use a
cable that connects identical pin numbers in each connector (a
so-called "straight cable"). "Gender changers" are available to
solve gender mismatches between cables and connectors.
Connecting devices with different types of connectors requires a
cable that connects the corresponding pins according to the table
above. Cables with 9 pins on one end and 25 on the other are
common. Manufacturers of equipment with 8P8C connectors
usually provide a cable with either a DB-25 or DE-9 connector
(or sometimes interchangeable connectors so they can work
with multiple devices). Poor-quality cables can cause false
signals by crosstalk between data and control lines (such as
Ring Indicator). If a given cable will not allow a data
connection, especially if a Gender changer is in use, a Null
modem may be necessary.
2.2.3.7 Conventions
For functional communication through a serial port interface,
conventions of bit rate, character framing, communications
protocol, character encoding, data compression, and error
detection, not defined in RS 232, must be agreed to by both
sending and receiving equipment. For example, consider the
serial ports of the original IBM PC. This implementation used
an 8250 UART using asynchronous start-stop character
formatting with 7 or 8 data bits per frame, usually ASCII
character coding, and data rates programmable between 75 bits
per second and 115,200 bits per second. Data rates above 20,000
bits per second are out of the scope of the standard, although

higher data rates are sometimes used by commercially
manufactured equipment. Since most RS-232 devices do not
have automatic baud rate detection, users must manually set the
baud rate (and all other parameters) at both ends of the RS-232
connection.
In the particular case of the IBM PC, as with most UART chips
including the 8250 UART used by the IBM PC, baud rates
were programmable with arbitrary values. This allowed a PC to
be connected to devices not using the rates typically used with
modems. Not all baud rates can be programmed, due to the
clock frequency of the 8250 UART in the PC, and the
granularity of the baud rate setting. This includes the baud rate
of MIDI, 31,250 bits per second, which is generally not
achievable by a standard IBM PC serial port. MIDI-to-RS-232
interfaces designed for the IBM PC include baud rate translation
hardware to adjust the baud rate of the MIDI data to something
that the IBM PC can support, for example 19,200 or 38,400 bits
per second.
2.2.3.8 RTS/CTS handshaking
In older versions of the specification, RS-232's use of the RTS
and CTS lines is asymmetric: The DTE asserts RTS to indicate a
desire to transmit to the DCE, and the DCE asserts CTS in
response to grant permission. This allows for half-duplex
modems that disable their transmitters when not required, and
must transmit a synchronization preamble to the receiver when
they are re-enabled. This scheme is also employed on present-day
RS-232 to RS-485 converters, where the RS-232's RTS
signal is used to ask the converter to take control of the RS-485
bus - a concept that does not otherwise exist in RS-232. There is
no way for the DTE to indicate that it is unable to accept data
from the DCE.
A non-standard symmetric alternative, commonly called
"RTS/CTS handshaking," was developed by various equipment
manufacturers. In this scheme, CTS is no longer a response to
RTS; instead, CTS indicates permission from the DCE for the
DTE to send data to the DCE, and RTS indicates permission
from the DTE for the DCE to send data to the DTE. RTS and
CTS are controlled by the DTE and DCE respectively, each
independent of the other. This was eventually codified in

version RS-232-E (actually TIA-232-E by that time) by defining
a new signal, "RTR (Ready to Receive)," which is CCITT V.24
circuit 133. TIA-232-E and the corresponding international
standards were updated to show that circuit 133, when
implemented, shares the same pin as RTS (Request to Send),
and that when 133 is in use, RTS is assumed by the DCE to be
ON at all times.
Thus, with this alternative usage, one can think of RTS asserted
(positive voltage, logic 0) meaning that the DTE is indicating it
is "ready to receive" from the DCE, rather than requesting
permission from the DCE to send characters to the DCE.
Note that equipment using this protocol must be prepared to
buffer some extra data, since a transmission may have begun
just before the control line state change.
RTS/CTS handshaking is an example of hardware flow control.
However, "hardware flow control" in the description of the
options available on an RS-232-equipped device does not
always mean RTS/CTS handshaking.
2.2.3.9 3-wire and 5-wire RS-232
Minimal “3-wire” RS-232 connections’ consisting only of
transmit data, receive data, and ground, is commonly used when
the full facilities of RS-232 are not required. Even a two-wire
connection (data and ground) can be used if the data flow is one
way (for example, a digital postal scale that periodically sends a
weight reading, or a GPS receiver that periodically sends
position, if no configuration via RS-232 is necessary). When
only hardware flow control is required in addition to two-way
data, the RTS and CTS lines are added in a 5-wire version.
2.2.3.10 Seldom used features
The EIA-232 standard specifies connections for several features
that are not used in most implementations. Their use requires the
25-pin connectors and cables, and of course both the DTE and
DCE must support them.
a) Signal rate selection
The DTE or DCE can specify use of a "high" or "low" signalling
rate. The rates as well as which device will select the rate must
be configured in both the DTE and DCE. The prearranged
device selects the high rate by setting pin 23 to ON.

b) Loopback testing
Many DCE devices have a loopback capability used for testing.
When enabled, signals are echoed back to the sender rather than
being sent on to the receiver. If supported, the DTE can signal
the local DCE (the one it is connected to) to enter loopback
mode by setting pin 18 to ON, or the remote DCE (the one the
local DCE is connected to) to enter loopback mode by setting
pin 21 to ON. The latter tests the communications link as well as
both DCE's. When the DCE is in test mode it signals the DTE
by setting pin 25 to ON.
A commonly used version of loopback testing does not involve
any special capability of either end. A hardware loopback is
simply a wire connecting complementary pins together in the
same connector
Loopback testing is often performed with a specialized DTE
called a bit error rate tester (or BERT).
2.2.3.11 Timing Signals
Some synchronous devices provide a clock signal to
synchronize data transmission, especially at higher data rates.
Two timing signals are provided by the DCE on pins 15 and 17.
Pin 15 is the transmitter clock, or send timing (ST); the DTE
puts the next bit on the data line (pin 2) when this clock
transitions from OFF to ON (so it is stable during the ON to
OFF transition when the DCE registers the bit). Pin 17 is the
receiver clock, or receive timing (RT); the DTE reads the next
bit from the data line (pin 3) when this clock transitions from
ON to OFF.
Alternatively, the DTE can provide a clock signal, called
transmitter timing (TT), on pin 24 for transmitted data. Data is
changed when the clock transitions from OFF to ON and read
during the ON to OFF transition. TT can be used to overcome
the issue where ST must traverse a cable of unknown length and
delay, clock a bit out of the DTE after another unknown delay,
and return it to the DCE over the same unknown cable delay.
Since the relation between the transmitted bit and TT can be
fixed in the DTE design, and since both signals traverse the
same cable length, using TT eliminates the issue. TT may be
generated by looping ST back with an appropriate phase change
to align it with the transmitted data. ST loop back to TT lets the

DTE use the DCE as the frequency reference, and correct the
clock to data timing.
2.2.3.12 Other Serial interfaces similar to RS-232
1. RS-422 (a high-speed system similar to RS-232 but with
differentialsignalling)
2. RS-423 (a high-speed system similar to RS-422 but with
unbalancedsignalling)
3. RS-449 (a functional and mechanical interface that used RS-
422 and RS-423 signals - it never caught on like RS-232 and
was withdrawn by the EIA)
4. RS-485 (a descendant of RS-422 that can be used as a bus in
multidrop configurations)
5. MIL-STD-188 (a system like RS-232 but with better
impedance and rise time control)
6. EIA-530 (a high-speed system using RS-422 or RS-423
electrical properties in an EIA-232 pinout configuration, thus
combining the best of both; supersedes RS-449)
7. EIA/TIA-561 8 Position Non-Synchronous Interface between
Data Terminal Equipment and Data Circuit Terminating
Equipment Employing Serial Binary Data Interchange
8. EIA/TIA-562 Electrical Characteristics for an Unbalanced
Digital Interface (low-voltage version of EIA/TIA-232)
9. TIA-574 (standardizes the 9-pin D-subminiature connector
pinout for use with EIA-232 electrical signalling, as originated
on the IBM PC/AT)
10.SpaceWire (high-speed serial system designed for use on
board spacecraft).
2.2.6 LCD
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 (LCs). LCs does not emit light directly.
LCDs are used in a wide range of applications, including computer
monitors,television, instrument panels, aircraft cockpit displays,
signage, etc. They are common in consumer devices such as video

players, gaming devices, clocks, watches, calculators, andtelephones.
LCDs 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
cannot suffer image burn-in. LCDs are, however, susceptible to image
persistence.
LCDs are more energy efficient and offer safer disposal than CRTs. 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 colour or monochrome.
The mostflexible ones use an array of small pixels. The earliest
discovery leading to the development of LCD technology, the
discovery of liquid crystals, dates from 1888. By 2008, worldwide
sales of televisions with LCD screens had surpassed the sale of CRT
units. Following figure is a 16x2 LCD.
Monochrome passive-matrix LCDs were standard in most early
laptops (although a few used plasma displays) and the original
Nintendo GameBoy until the mid-1990s, when colour 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, portable devices with
less information content to be displayed, where lowest power
consumption (no backlight), low cost and/or readability in direct
sunlight are needed, use this type of display.
2.2.6.1 Advantages and Disadvantages
In spite of LCDs being a well proven and still viable
technology, as display devices LCDs are not perfect for all
applications.
Advantages
1. Very compact and light.
2. Low power consumption.
3. No geometric distortion.

4. Little or no flicker depending on backlight technology.
5. Not affected by screen burn-in.
6. Can be made in almost any size or shape.
7. No theoretical resolution limit.
Disadvantages
1. Limited viewing angle, causing colour, saturation, contrast
and brightness to vary, even within the intended viewing angle,
by variations in posture.
2. Bleeding and uneven backlighting in some monitors, causing
brightness distortion, especially toward the edges.
3. Smearing and ghosting artefacts caused by slow response
times (>8 ms) and "sample and hold" operation.
4. Fixed bit depth, many cheaper LCDs are only able to display
262,000 colours. 8-bit S-IPS panels can display 16 million
colours and have significantly better black level, but are
expensive and have slower response time.
5. Low bit depth results in images with unnatural or excessive
contrast.
6. Input lag
7. Dead or stuck pixels may occur during manufacturing or
through use.

CHAPTER 3
WORKING OF VTS
3.1 Schematic Diagram of VTS
3.2 Circuit Description
The hardware interfaces to microcontroller are LCD display, GSM modem
and GPS receiver. The design uses RS-232 protocol for serial
communication between the modems and the microcontroller. A serial driver
IC is used for converting TTL voltage levels to RS-232 voltage levels.
When the reset is sent by the number at the modem, the system automatically
sends a return reply to that mobile indicating the position of the vehicle in
terms of latitude and longitude.
3.3 Circuit Operation
The project is vehicle positioning and navigation system we can locate the
vehicle around the globe with ARM7microcontroller, GPS receiver, GSM
modem, Power supply. Microcontroller used is ARM7. The code is written in

the internal memory of Microcontroller i.e. ROM. With help of instruction
set it processes the instructions and it acts as interface between GSM and
GPS with help of serial communication of ARM7. GPS always transmits the
data and GSM transmits and receive the data. GPS pin TX is connected to
microcontroller via serial ports. GSM pins TX and RX are connected to
microcontroller.
3.3.1 Power
The power is supplied to components like GSM, GPS and Micro
control circuitry using a 12V/3.2A battery .GSM requires 12v,GPS and
microcontroller requires 5v .with the help of regulators we regulate the
power between three components.
3.3.2 Serial ports
Microcontroller communicates with the help of serial communication.
First it takes the data from the GPS receiver and then sends the
information to the owner in the form of SMS with help of GSM
modem.

CHAPTER 4
MICROCONTROLLER ARM7
Why we use ARM7?
The ARM processor is a 32-bit RISC processor, meaning it is built using the
reduced instruction set computer (RISC) instruction set architecture (ISA).
ARM processors are microprocessors and are widely used in many of the
mobile phones sold each year, as many as 98% of mobile phones. They are
also used in personal digital assistants (PDA), digital media and music
layers, hand-held gaming systems, calculators, and even computer hard
drives.
The first ARM processor-based computer was the Acorn Archimedes,
released in 1987. Apple Computer became involved with helping to improve
the ARM technology in the late 1980s, with their work resulting in the
ARM6 technology in 1992. Later, Acorn used the ARM6-based ARM 610
processor in their Risc PC computers in 1994. Today, the ARM architecture
is licensed for use by many companies, including Apple, Cirrus Logic, Intel,
LG, Microsoft, NEC, Nintendo, Nvidia, Sony, Samsung, Sharp, Texas
Instruments, Yamaha, and many more. The latest developed ARM processor
families include ARM11 and Cortex. ARM processors capable of 64-bit
processing are currently in development.
4.1 Features
The main features of the microcontroller are:
• 16/32-bit ARM7 microcontroller.
• 8 to 40kB of on-chip static RAM and 32 to 512kB of on-chip flash
program memory. 128 bit wide interface/accelerator enables high speed 60
MHz operation.
• In-System/In-Application Programming (ISP/IAP) via on-chip boot-loader
software. Single flash sector or full chip erase in 400 ms and programming of
256bytes in 1ms.
• Embedded ICE RT and Embedded Trace interfaces offer real-time
debugging with the on-chip Real Monitor software and high speed tracing of
instruction execution.
• USB 2.0 Full Speed compliant Device Controller with 2kB of endpoint
RAM. In addition, the LPC2148 provides 8kB of on-chip RAM accessible to
USB by DMA.

• One or two (LPC2141/2 vs. LPC2148) 10-bit A/D converters provide a
total of 6/14 analog inputs, with conversion times as low as 2.44 s per
channel.
• Single 10-bit D/A converter provide variable analog output.
• Two 32-bit timers/external event counters (with four capture and four
compare channels each), PWM unit (six outputs) and watchdog.
• Low power real-time clock with independent power and dedicated 32 kHz
clock input.
• Multiple serial interfaces including two UARTs (16C550), two Fast I2C-bus
(400kbit/s), SPI and SSP with buffering and variable data length
capabilities.
• Vectored interrupt controller with configurable priorities and vector
addresses.
• Up to nine edge or level sensitive external interrupt pins available.
• On-chip integrated oscillator operates with an external crystal in range from
1 MHz to 30 MHz and with an external oscillator up to 50MHz.
• Individual enable/disable of peripheral functions as well as peripheral clock
scaling for additional power optimization.
• Processor wake-up from Power-down mode via external interrupt, USB,
Brown-Out Detect (BOD) or Real-Time Clock (RTC).
• Single power supply chip with Power-On Reset (POR) and BOD circuits: –
CPU operating voltage range of 3.0 V to 3.6 V (3.3 V 10 %) with 5 V
tolerant I/O pads.
4.2The Pin Configuration
4.2.1 Special Function Registers (SFR)
4.3 Memory Organization
On-chip flash memory system: The LPC2141/2/4/6/8 incorporate a
32kB, 64kB, 128kB, 256kB, and 512kB Flash memory system, respectively.
This memory may be used for both code and data storage. Programming of
the Flash memory may be accomplished in several ways: over the serial
built-in JTAG interface, using In System Programming (ISP) and UART0, or
by means of In Application Programming (IAP) capabilities. The application
program, using the IAP functions, may also erase and/or program the Flash
while the application is running, allowing a great degree of flexibility for
data storage field firmware upgrades, etc. When the LPC2141/2/4/6/8 on-chip
bootloader is used, 32kB, 64kB, 128kB, 256kB, and 500kB of Flash
memory is available for user code. The LPC2141/2/4/6/8 Flash memory
provides minimum of 100,000 erase/write cycles and 20 years of data-retention.

On-chip Static RAM (SRAM): On-chip Static RAM (SRAM) may be used
for code and/or data storage. The on-chip SRAM may be accessed as 8-bits,
16-bits, and 32-bits. The LPC2141/2/4/6/8 provides 8/16/32kB of static
RAM, respectively.
4.4 SYSTEM CONTROL BLOCK
The System Control Block includes several system features and control
registers for a number of functions that are not related to specific peripheral
devices. These include:
• Crystal Oscillator
• External Interrupt Inputs
• Miscellaneous System Controls and Status
• Memory Mapping Control
• PLL
• Power Control
• Reset
• APB Divider
• Wakeup Timer
Each type of function has its own register(s) if any are required and
unneeded bits are defined as reserved in order to allow future expansion.
Unrelated functions never share the same register addresses

CHAPTER 5
GSM MODULE
5.1 GSM History
The acronym for GSM is Global System for Mobile Communications.
During the early 1980s, analog cellular telephone systems were experiencing
rapid growth in Europe, particularly in Scandinavia and the United Kingdom,
but also in France and Germany. Each country developed its own system,
which was incompatible with everyone else's in equipment and operation.
This was an undesirable situation, because not only was the mobile
equipment limited to operation within national boundaries, which in a unified
Europe were increasingly unimportant, but there was also a very limited
market for each type of equipment, so economies of scale and the subsequent
savings could not be realized.
The Europeans realized this early on, and in 1982 the Conference of
European Posts and Telegraphs (CEPT) formed a study group called the
Groupe Special Mobile (GSM) to study and develop a pan-European public
land mobile system. The proposed system had to meet certain criteria:
1. Good subjective speech quality
2. Low terminal and service cost
3. Low terminal and service cost
4. Ability to support handheld terminals
5. Support for range of new services and facilities
6. Spectral efficiency
7. ISDN compatibility
8. Pan-European means European-wide. ISDN throughput at 64Kbs was
never envisioned, indeed, the highest rate a normal GSM network can
achieve is 9.6kbs.
Europe saw cellular service introduced in 1981, when the Nordic Mobile
Telephone System or NMT450 began operating in Denmark, Sweden,
Finland, and Norway in the 450 MHz range. It was the first multinational
cellular system. In 1985 Great Britain started using the Total Access
Communications System or TACS at 900MHz. Later, the West German C-Netz,
the French Radio COM 2000, and the Italian RTMI/RTMS helped
make up Europe's nine analog incompatible radio telephone systems. Plans
were afoot during the early 1980s, however, to create a single European wide

digital mobile service with advanced features and easy roaming. While North
American groups concentrated on building out their robust but increasingly
fraud plagued and featureless analog network, Europe planned for a digital
future.
In 1989, GSM responsibility was transferred to the European
Telecommunication Standards Institute (ETSI), and phase I of the GSM
specifications were published in 1990. Commercial service was started in
mid-1991, and by 1993 there were 36 GSM networks in 22 countries.
Although standardized in Europe, GSM is not only a European standard.
Over 200 GSM networks (including DCS1800 and PCS1900) are operational
in 110 countries around the world. In the beginning of 1994, there were 1.3
million subscribers worldwide, which had grown to more than 55 million by
October 1997. With North America making a delayed entry into the GSM
field with a derivative of GSM called PCS1900, GSM systems exist on every
continent, and the acronym GSM now aptly stands for Global System for
Mobile communications.
The developers of GSM chose an unproven (at the time) digital system, as
opposed to the then-standard analog cellular systems like AMPS in the
United States and TACS in the United Kingdom. They had faith that
advancements in compression algorithms and digital signal processors would
allow the fulfilment of the original criteria and the continual improvement of
the system in terms of quality and cost. The over 8000 pages of GSM
recommendations try to allow flexibility and competitive innovation among
suppliers, but provide enough standardization to guarantee proper
networking between the components of the system. This is done by providing
functional and interface descriptions for each of the functional entities
defined in the system.
5.2 Services Provided by GSM
From the beginning, the planners of GSM wanted ISDN compatibility in
terms of the services offered and the control signalling used. However, radio
transmission limitations, in terms of bandwidth and cost, do not allow the
standard ISDN B-channel bit rate of 64 kbps to be practically achieved.
Telecommunication services can be divided into bearer services, teleservices,
and supplementary services. The most basic teleservice supported by GSM is
telephony. As with all other communications, speech is digitally encoded and
transmitted through the GSM network as a digital stream. There is also an
emergency service, where the nearest emergency-service provider is notified
by dealing three digits.

a) Bearer services: Typically data transmission instead of voice. Fax and
SMS are examples.
b) Teleservices: Voice oriented traffic.
c) Supplementary services: Call forwarding, caller ID, call waiting and the
like.
A variety of data services is offered. GSM users can send and receive data, at
rates up to 9600 bps, to users on POTS (Plain Old Telephone Service),
ISDN, Packet Switched Public Data Networks, and Circuit Switched Public
Data Networks using a variety of access methods and protocols, such as X.25
or X.32. Since GSM is a digital network, a modem is not required between
the user and GSM network, although an audio modem is required inside the
GSM network to interwork with POTS.
Other data services include Group 3 facsimile, as described in ITU-T
recommendation T.30, which is supported by use of an appropriate fax
adaptor. A unique feature of GSM, not found in older analog systems, is the
Short Message Service (SMS). SMS is a bidirectional service for short
alphanumeric (up to 160 bytes) messages. Messages are transported in a
store-and-forward fashion. For point-to-point SMS, a message can be sent to
another subscriber to the service, and an acknowledgement of receipt is
provided to the sender. SMS can also be used in a cell-broadcast mode, for
sending messages such as traffic updates or news updates. Messages can also
be stored in the SIM card for later retrieval.
Supplementary services are provided on top of teleservices or bearer
services. In the current (Phase I) specifications, they include several forms of
call forward (such as call forwarding when the mobile subscriber is
unreachable by the network), and call barring of outgoing or incoming calls,
for example when roaming in another country. Many additional
supplementary services will be provided in the Phase 2 specifications, such
as caller identification, call waiting, multi-party conversations.
5.3 Mobile Station
The mobile station (MS) consists of the mobile equipment (the terminal) and
a smart card called the Subscriber Identity Module (SIM). The SIM provides
personal mobility, so that the user can have access to subscribed services
irrespective of a specific terminal. By inserting the SIM card into another
GSM terminal, the user is able to receive calls at that terminal, make calls
from that terminal, and receive other subscribed services.

The mobile equipment is uniquely identified by the International Mobile
Equipment Identity (IMEI). The SIM card contains the International Mobile
Subscriber Identity (IMSI) used to identify the subscriber to the system, a
secret key for authentication, and other information. The IMEI and the IMSI
are independent, thereby allowing personal mobility. The SIM card may be
protected against unauthorized use by a password or personal identity
number.
GSM phones use SIM cards, or Subscriber information or identity modules.
They're the biggest difference a user sees between a GSM phone or handset
and a conventional cellular telephone. With the SIM card and its memory the
GSM handset is a smart phone, doing many things a conventional cellular
telephone cannot. Like keeping a built in phone book or allowing different
ring tones to be downloaded and then stored. Conventional cellular
telephones either lack the features GSM phones have built in, or they must
rely on resources from the cellular system itself to provide them. Let me
make another, important point.
With a SIM card your account can be shared from mobile to mobile, at least
in theory. Want to try out your neighbour’s brand new mobile? You should
be able to put your SIM card into that GSM handset and have it work. The
GSM network cares only that a valid account exists, not that you are using a
different device. You get billed, not the neighbour who loaned you the
phone.
This flexibility is completely different than AMPS technology, which
enables one device per account. No switching around. Conventional cellular
telephones have their electronic serial number burned into a chipset which is
permanently attached to the phone. No way to change out that chipset or
trade with another phone. SIM card technology, by comparison, is meant to
make sharing phones and other GSM devices quick and easy.
5.4 Base Station Subsystem:
The Base Station Subsystem is composed of two parts, the Base Transceiver
Station (BTS) and the Base Station Controller (BSC). These communicate
across the standardized Abis interface, allowing (as in the rest of the system)
operation between components made by different suppliers.
The Base Transceiver Station houses the radio transceivers that define a cell
and handles the radio-link protocols with the Mobile Station. In a large urban
area, there will potentially be a large number of BTSs deployed, thus the
requirements for a BTS are ruggedness, reliability, portability, and minimum
cost.

The BTS or Base Transceiver Station is also called an RBS or Remote Base
station. Whatever the name, this is the radio gear that passes all calls coming
in and going out of a cell site. The base station is under direction of a base
station controller so traffic gets sent there first. The base station controller,
described below, gathers the calls from many base stations and passes them
on to a mobile telephone switch. From that switch come and go the calls
from the regular telephone network. Some base stations are quite small; the
one pictured here is a large outdoor unit. The large number of base stations
and their attendant controllers are a big difference between GSM and IS-136.
5.4.1 Base Station Controller
The Base Station Controller manages the radio resources for one or
more BTSs. It handles radio-channel setup, frequency hopping, and
handovers, as described below. The BSC is the connection between the
mobile station and the Mobile service Switching Centre (MSC).
Another difference between conventional cellular and GSM is the base
station controller. It's an intermediate step between the base station
transceiver and the mobile switch. GSM designers thought this a better
approach for high density cellular networks. As one anonymous writer
penned, "If every base station talked directly to the MSC, traffic would
become too congested. To ensure quality communications via traffic
management, the wireless infrastructure network uses Base Station
Controllers as a way to segment the network and control congestion.
The result is that MSCs route their circuits to BSCs which in turn are
responsible for connectivity and routing of calls for 50 to 100 wireless
base stations."
Many GSM descriptions picture equipment called a TRAU, which
stands for Transcoding Rate and Adaptation Unit. Of course also
known as a Trans-Coding Unit or TCU, the TRAU is a compressor
and converter. It first compresses traffic coming from the mobiles
through the base station controllers. That's quite an achievement
because voice and data have already been compressed by the voice
coders in the handset. Anyway, it crunches that data down even
further. It then puts the traffic into a format the
Mobile Switch can understand. This is the Trans-Coding part of its
name, where code in one format is converted to another. The TRAU is
not required but apparently it saves quite a bit of money to install one.
Here's how Nortel Networks sells their unit: “Reduce transmission
resources and realize up to 75% transmission cost savings with the
TCU."

"The Trans-Coding Unit (TCU), inserted between the BSC and MSC,
enables speech compression and data rate adaptation within the radio
cellular network. The TCU is designed to reduce transmission costs by
minimizing transmission resources between the BSC and MSC. This is
achieved by reducing the number of PCM links going to the BSC,
since four traffic channels (data or speech) can be handled by one
PCM time slot. Additionally, the modular architecture of the TCU
supports all three GSM vocoders (Full Rate, Enhanced Full Rate, and
Half Rate) in the same cabinet, providing you with a complete range of
deployment options."
Voice coders or vocoders are built into the handsets a cellular carrier
distributes. They're the circuitry that turns speech into digital. The
carrier specifies which rate they want traffic compressed, either a great
deal or just a little. The cellular system is designed this way, with
handset vocoders working in league with the equipment of the base
station subsystem.
5.5 Architecture of the GSM Network
A GSM network is composed of several functional entities, whose functions
and interfaces are specified. Figure 1 shows the layout of a generic GSM
network. The GSM network can be divided into three broad parts. The
Mobile Station is carried by the subscriber. The Base Station Subsystem
controls the radio link with the Mobile Station. The Network Subsystem, the
main part of which is the Mobile services Switching Centre (MSC), performs
the switching of calls between the mobile users, and between mobile and
fixed network users. The MSC also handles the mobility management
operations. Not shown is the Operations and Maintenance Centre, which
oversees the proper operation and setup of the network. The Mobile Station
and the Base Station Subsystem communicate across the Um interface, also
known as the air interface or radio link. The Base Station Subsystem
communicates with the Mobile services Switching Centre across the A
interface.
As John states, he presents a generic GSM architecture. Lucent, Ericsson,
Nokia, and others feature their own vision in their own diagrams.
Lucent GSM architecture/Ericsson GSM architecture/Nokia GSM
architecture/Siemens’s GSM architecture.
5.6 Radio Link Aspects

The International Telecommunication Union (ITU), which manages the
international allocation of radio spectrum (among many other functions),
allocated the bands 890-915 MHz for the uplink (mobile station to base
station) and 935-960 MHz for the downlink (base station to mobile station)
for mobile networks in Europe. Since this range was already being used in
the early 1980s by the analog systems of the day, the CEPT had the foresight
to reserve the top 10 MHz of each band for the GSM network that was still
being developed. Eventually, GSM will be allocated the entire 2x25 MHz
bandwidth.
5.7 Multiple Access and Channel Structure:
Since radio spectrum is a limited resource shared by all users, a method must
be devised to divide up the bandwidth among as many users as possible. The
method chosen by GSM is a combination of Time- and Frequency-Division
Multiple Access (TDMA/FDMA). The FDMA part involves the division by
frequency of the (maximum) 25 MHz bandwidth into 124 carrier frequencies
spaced 200 kHz apart. One or more carrier frequencies are assigned to each
base station. Each of these carrier frequencies is then divided in time, using a
TDMA scheme. The fundamental unit of time in this TDMA scheme is
called a burst period and it lasts 15/26 ms (or approx. 0.577 ms). Eight burst
periods are grouped into a TDMA frame (120/26 ms, or approx. 4.615 ms),
which forms the basic unit for the definition of logical channels. One
physical channel is one burst period per TDMA frame.
i) Traffic channels
A traffic channel (TCH) is used to carry speech and data traffic. Traffic
channels are defined using a 26-frame multi-frame, or group of 26 TDMA
frames. The length of a 26-frame multi-frame is 120 ms, which is how the
length of a burst period is defined (120 ms divided by 26 frames divided by 8
burst periods per frame). Out of the 26 frames, 24 are used for traffic, 1 is
used for the Slow Associated Control Channel (SACCH) and 1 is currently
unused (see Figure 2). TCHs for the uplink and downlink are separated in
time by 3 burst periods, so that the mobile station does not have to transmit
and receive simultaneously, thus simplifying the electronics.
ii) Control channels
Common channels can be accessed both by idle mode and dedicated mode
mobiles. The common channels are used by idle mode mobiles to exchange
the signalling information required to change to dedicated mode. Mobiles
already in dedicated mode monitor the surrounding base stations for
handover and other information. Dedicated mode means a mobile is in use.

5.8 Frequency Hopping
The mobile station already has to be frequency agile, meaning it can move
between a transmit/ receive, and monitor time slot within one TDMA frame,
which normally are on different frequencies. GSM makes use of this inherent
frequency agility to implement slow frequency hopping, where the mobile
and BTS transmit each TDMA frame on a different carrier frequency. The
frequency hopping algorithm is broadcast on the Broadcast Control Channel.
Since multipath fading is dependent on carrier frequency, slow frequency
hopping helps alleviate the problem. In addition, co-channel interference is in
effect randomized.
Here's a huge difference between conventional cellular (IS-136) and GSM:
frequency hopping. When enabled, slots within frames can leapfrog from one
frequency to another. In IS-136, by comparison, once assigned a channel
your call stays on that pair of radio frequencies until the call is over or you
have moved to another cell.
5.9 Discontinuous Reception
Another method used to conserve power at the mobile station is
discontinuous reception. The paging channel, used by the base station to
signal an incoming call, is structured into sub-channels. Each mobile station
needs to listen only to its own sub-channel. In the time between successive
paging sub-channels, the mobile can go into sleep mode, when almost no
power is used.
5.10 Power Control
There are five classes of mobile stations defined, according to their peak
transmitter power, rated at 20, 8, 5, 2, and 0.8 watts. To minimize co-channel
interference and to conserve power, both the mobiles and the Base
Transceiver Stations operate at the lowest power level that will maintain an
acceptable signal quality. Power levels can be stepped up or down in steps of
2 dB from the peak power for the class down to a minimum of 13 dBm (20
mill watts).
We need only enough power to make a connection. Any more is superfluous.
If you can't make a connection using one watt then two watts won't help at
these near microwave frequencies. Using less power means less interference
or congestion among all the mobiles in a cell.

The mobile station measures the signal strength or signal quality (based on
the Bit Error Ratio), and passes the information to the Base Station
Controller, which ultimately decides if and when the power level should be
changed. Power control should be handled carefully, since there is the
possibility of instability. This arises from having mobiles in co-channel cells
alternating increase their power in response to increased co-channel
interference caused by the other mobile increasing its power. This in unlikely
to occur in practice but it is (or was as of 1991) under study.
Two points: The first is that the base station can reach out to the mobile and
turn down the transmitting power the handset is using, Very cool. The second
point is that a digital signal will drop a call much more quickly than an
analog signal. With an analog radio you can hear through static and fading.
But with a digital radio the connection will be dropped, just like your
landline modem, when too many 0s and 1s go missing. You need more base
stations, consequently, to provide the same coverage as analog.
5.11 Network Aspects
Ensuring the transmission of voice or data of a given quality over the radio
link is only part of the function of a cellular mobile network. A GSM mobile
can seamlessly roam nationally and internationally, which requires that
registration, authentication, call routing and location updating functions exist
and are standardized in GSM networks. In addition, the fact that the
geographical area covered by the network is divided into cells necessitates
the implementation of a handover mechanism. These functions are performed
by the Network Subsystem, mainly using the Mobile Application Part (MAP)
built on top of the Signalling.
The signalling protocol in GSM is structured into three general layers
depending on the interface, as shown in Figure 3. Layer 1 is the physical
layer, which uses the channel structures discussed above over the air
interface. Layer 2 is the data link layer. Across the Um interface, the data
link layer is a modified version of the LAPD protocol used in ISDN (external
link), called LAPDm. Across the A interface, the Message Transfer Part
layer 2 of Signalling System Number 7 is used. Layer 3 of the GSM
signalling protocol is itself divided into 3 sub layers.
1. Radio Resources Management
2. Controls the setup, maintenance, and termination of radio and fixed
channels,
3. Including handovers.

4. Mobility Management
5. Manages the location updating and registration procedures, as well as
security and authentication.
6. Connection Management
7. Handles general call control, similar to CCITT Recommendation Q.931,
and manage Supplementary Services and the Short Message Service.
5.12 Radio Resources Management
The radio resources management (RR) layer oversees the establishment of a
link, both radio and fixed, between the mobile station and the MSC. The
main functional components involved are the mobile station, and the Base
Station Subsystem, as well as the MSC. The RR layer is concerned with the
management of an RR-session [16], which is the time that a mobile is in
dedicated mode, as well as the configuration of radio channels including the
allocation of dedicated channels.
An RR-session is always initiated by a mobile station through the access
procedure, either for an outgoing call, or in response to a paging message.
The details of the access and paging procedures, such as when a dedicated
channel is actually assigned to the mobile, and the paging sub-channel
structure, are handled in the RR layer. In addition, it handles the management
of radio features such as power control, discontinuous transmission and
reception, and timing advance.
5.13 Handover
In a cellular network, the radio and fixed links required are not permanently
allocated for the duration of a call. Handover, or handoff as it is called in
North America, is the switching of an on-going call to a different channel or
cell. The execution and measurements required for handover form one of
basic functions of the RR layer.
There are four different types of handover in the GSM system, which involve
transferring a call between:
1. Channels (time slots) in the same cell
2. Cells (Base Transceiver Stations) under the control of the same Base
Station Controller (BSC),

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