=
Sana'a Community College
HPE Division
TCET Department
Study of upgrading cellular system
from 2G to 3G
Don by
Abdullah Al-Marwani
Adnan Abdulaziz Al-sabri
Hesham Adel Alwan Al-madhagi
Mohammed Abdulwahab Al-Gahmi
Omair Yousef Al-Jaadi
Emad alhasani
Supervised by
Dr. Jamil sultan
Content
LIST OF ABBREVIATIONS ................................................................................................................................. II
LIST OF FIGURES ............................................................................................................................................... IV
LIST OF TABLES ..................................................................................................................................................V
CHAPTER ONE ........................................................................................................................................................... 1
INTRODUCTION ..................................................................................................................................................... 1
INTRODUCTION ........................................................................................................................................................... 1
PROBLEM STATEMENT ................................................................................................................................................ 2
OBJECTIVES OF THE STUDY......................................................................................................................................... 2
LIMITATION OF THE STUDY......................................................................................................................................... 2
CHAPTER 2 ................................................................................................................................................................. 3
LITERATURE REVIEW OF GPS ..................................................................................................................................... 3
Introduction ........................................................................................................................................................... 3
Communications Satellite ...................................................................................................................................... 4
Types of Satellite .................................................................................................................................................... 6
Satellite Orbits ....................................................................................................................................................... 7
Satellite Services ...................................................................................................................................................10
Satellite Communications Segments .....................................................................................................................11
Application of satellite ..........................................................................................................................................14
Global Navigation Satellite System (GNSS) .........................................................................................................15
CHAPTER 3 ................................................................................................................................................................28
CIRCUIT &APPLICATION OF GPS ...............................................................................................................................28
Introduction ..........................................................................................................................................................28
Circuit and working ..............................................................................................................................................29
Applications of GPS ..............................................................................................................................................30
CHAPTER 4 .........................................................................................................................................................33
FACILITIES & DIFFICULTIES ..............................................................................................................................33
Introduction ..........................................................................................................................................................33
Difficulties ............................................................................................................................................................33
Facilities ...............................................................................................................................................................33
Future Work Suggestions ......................................................................................................................................33
REFERENCE .......................................................................................................................................................34
I
1. List of abbreviations
global position System
GPS
Global Navigation Satellite Systems
GNSS
Department of Defense
DoD
Geosynchronous Orbit
GSO or GEO
Low Earth Orbit
LEO
Medium Earth Orbit
MEO
High Earth Orbit
HEO
Direct-to-Home
DTH
Mobile Satellite Service
MSS
aeronautical MSS
AMSS
land MSS
LMSS
maritime MSS
MMSS
Very Small Aperture Terminals
VSATs
Satellite News Gathering
SNG
Tracking, Telemetry, Command
TT&C
Tracking, Telemetry, Command and Monitoring
TTC&M
Mobile-User-Link
MUL
Gateway-Link
GWL
positioning, navigation, and timing
PNT
Global Navigation Satellite System
GLONASS
India’s Regional Navigation Satellite System
IRNSS
Quasi-Zenith Satellite System
QZSS
Wide-area Augmentation System
WAAS
European Geostationary Navigation Overlay Service
EGNOS
System of Differential Correction and Monitoring
SDCM
GPS Aided Geo Augmented Navigation
GAGAN
Multi-functional Transport Satellite
MTSAT
International Committee on Global
ICG
Master Control Station
MCS
II
Monitor Stations
MS
Differential Global Positioning System
DGPS
United States Coast Guard
USCG
Canadian Coast Guard
CCG
Nationwide DGPS
NDGPS
U.S. Department of Defense's Army Corps of Engineers
USACE
Wide-Area DGPS
WADGPS
Automatic Dependent Surveillance - Broadcast
ADS-B
unmanned aerial vehicles
UAVs
national aeronautics and space administration
NASA
Vessel Traffic Services
VTS
Automatic Identification System
AIS
Geographical Information System
GIS
chip scale atomic clocks
CSAC
III
2. List of figures
FIGURE 2.1. WAVE PROPAGATION MODES ............................................................................................ 5
FIGURE 2.2. ACTIVE SATELLITE ................................................................................................................ 6
FIGURE 2.3. PASSIVE SATELLITE ................................................................................................................. 6
FIGURE 2.4. SATELLITE ORBITS ................................................................................................................... 7
FIGURE 2.5. GEOSYNCHRONOUS ORBIT (GEO) ....................................................................................... 8
FIGURE 2.6. MEDIUM EARTH ORBIT (MEO) .............................................................................................. 9
FIGURE 2.7. LOW EARTH ORBIT (LEO) ....................................................................................................... 9
FIGURE 2.8. HIGH EARTH ORBIT (HEO) ....................................................................................................10
FIGURE 2.9. VERY SMALL APERTURE TERMINALS (VSATS). .............................................................12
FIGURE 2.10. SATELLITE NEWS GATHERING (SNG)TRUCKS ............................................................12
FIGURE 2.11. TRACKING, TELEMETRY, COMMAND AND MONITORING (TTC&M) STATION 13
FIGURE 2.12. STRUCTURE OF GPS ..............................................................................................................19
FIGURE 2.13.
FOUR SATELLITES ARE USED TO DETERMINE THE POSITION OF THE
RECEIVER ON THE EARTH ...........................................................................................................................20
FIGURE 2.14. THREE SATELLITE WITH THREE DISTANCE D1&D2&D3 .........................................21
FIGURE 2.15. FOUR SATELLITE WITH FOUR DISTANCE D1&D2&D3&D4 ......................................22
FIGURE 2.16. DISTANCE BETWEEN GPS SATELLITE AND RECEIVER ............................................23
FIGURE 2.17. DIFFERENTIAL GPS ..............................................................................................................25
FIGURE 2.18. GPS PROTOTYPE ....................................................................................................................28
FIGURE.2.19. CIRCUIT OF GPS NAVIGATOR ........................................................................................... 29
IV
3.
List of tables
TABLE 1. DIFFERENCE BETWEEN GPS AND DGPS.................................................................................26
V
Chapter one
INTRODUCTION
1.1.
Introduction
The global position System (GPS) has conveyed to the scientific and engineering community an
unprecedent source of data to be exploited in many research fields. It was conceived as a military tool to
provide the capability of absolute positioning and timing with the only help on ground of a dedicated
portable receive, during the years, however, the availability of a constellation of satellites constantly
sending precise time stamp encoding electromagnetic waves, has led to the use of these data not only for
coordinate determination but also as global coverage sounding signal. Thus, civilian use of the GPS ranges
from the millimeter accuracy level monitoring of crustal motion to real time atmospheric profiling,
including in this wide range roving receivers tracking, buoys, feet control, spacecrafts, orbit determination
and maintenance of both time and frequency standards.
The positioning system is based on the accurate determination of the delay experienced by the signal. Data
processing techniques have improvement together with receiver’s quality so that it is now possible to
discriminate effects on the order of millimeters over a whole measurement 20,000 Km (a ratio of 10-10).
With this assessment in mind, it is conceivable to use the GPS as a data source to infer the state of the
atmosphere since it introduces delays into the electromagnetic signals o the order of tens of meters in the
ionosphere and meters in the neutral atmosphere, and even to study the wave vapor contents of the
troposphere. Which causes delays in the centimeter level. This is of particular importance since the
monitoring of the ionosphere may have a positive impact in communications systems and the knowledge
of the patio-temporal distribution of water vapor can certainly help in the weather forecast systems.
Therefore, by pursuing in the use of GPS for atmosphere studies, we are in fact, contributing to many
different applications.
The GPS has been used for the ionospheric calibration of other systems such as interplanetary probes or
very long baseline interferometry. Later the imaging of the four-dimensional structure of the ionosphere
was stated. The application of tomography to the troposphere cane later because of the higher difficulty in
its implementation.
1
1.2.
Problem statement
Positioning from space, currently almost solely based on the Global Positioning System (GPS), has become
nearly omnipresent in an ever-growing variety of applications, both civilian and military. In this proposal,
we identify two major trends in terms of modernizing Global Navigation Satellite Systems (GNSS). Today,
two satellite systems besides GPS exist: the Russian (Glonass) and the Chinese (B0eidou). However, the
former is incomplete due to financial problems and the latter is a closed regional system. There is great
expectation with the new European Galileo system now under development. Our proposal focuses on the
modernization of GNSS with GPS II-M and GPS III and the Galileo system. Advantages coming from a
modernized GNSS include improved positioning and navigation performance by means of doubling the
availability of signals, impacting single point positioning accuracy, faster and more reliable positioning
techniques including those based on carrier phase ambiguity resolution.
These two systems (GPS and Galileo), whether used together or in parallel, will provide tremendous
commercial opportunities for Canadian enterprises.
1.3.
Objectives of the Study
The objectives of this study can be summarized as follows:
1- To get enough knowledge about GPS.
2- To get enough knowledge about how can we received signals from GPS.
3- To get enough knowledge about how works
1.4. Limitation of the Study
This project took place in the time period from 21/2/2021 to 10/3/2021. The project was
technically limited to Global positioning system (GPS).
2
4. CHAPTER 2
Literature review of GPS
2.1 Introduction
The Global Positioning System or GPS is a great technological success story. Developed in the 1970s
and 1980s by the U.S Department of Defense (DoD), the system was primarily intended for the U.S military.
It was successfully used in the U.S-Iraq War (1990-1991) and U.S interventions in Kosovo (1999) and
Afghanistan (2001-2002). Non-military use was a secondary objective, and throughout the 1990s civil users
were limited to a purposefully degraded subset of the signals broadcast by GPS. Despite these limitations,
civil applications of GPS grew at an astonishing rate. Applications unforeseen by the designers of the
system are now thriving, and many more are on the way. Through applications in land transportation, civil
aviation, maritime commerce, surveying and mapping, construction, mining, agriculture, earth
science, electric power systems, telecommunications, and outdoor recreational activities, GPS is well on its
way to becoming an essential part of the commercial and public infrastructure.
The baseline the GPS constellation comprises 24 satellites arranged in six orbital planes (lettered A-F).
Each plane is inclined at 55° from the equatorial plane. The orbital period is 12 hours.
The principle of satellite navigation is very simple: your position can be determined if you can measure
your distance from each of three objects whose positions (i.e., coordinates in a well-defined reference
frame) are known to you. In order to implement a global navigation system based on this principle, GPS
has fielded a constellation of 24 satellites in medium-earth orbits with a 12-hour orbital period. These
satellites are the objects at known locations from which a GPS receiver measures ranges. Actually, the
satellites are moving in space at a speed of about 4 kilometers (about 2.5 miles) per second, but the position
of each at any instant can be estimated from its broadcast message with an error no worse than a few meters.
The distance between the user and a satellite is measured in terms of the time it takes a radio signal to travel
from the satellite to the user. Precise measurement of transit time is accomplished by transmitting signals
with precision in accordance with nearly perfectly synchronized clocks carried aboard the satellites.
With GPS, you can determine your three-dimensional position instantaneously, continuously, and globally
with an accuracy of several meters. Thanks to precise and ultra-stable clocks carried aboard the satellites,
an inexpensive GPS receiver can also serve as a precise clock, keeping time with an accuracy of about 0.1
3
microsecond (that’s a tenth of one millionth of a second!). In fact, GPS has become a true global time
reference for commercial and scientific activities. GPS users the world over have become accustomed to
such accuracy in specifying position and time. The only requirement is for the receiver antenna to have a
halfway clear view of the sky to be able to “see” a minimum of four satellites.
The GPS signals are extraordinarily faint and may be so attenuated in propagation (that is, weakened)
through foliage that it becomes difficult for a hiker to navigate in the woods. Indoors, the signals are far too
weak to be tracked independently. But GPS will provide position and time indoors in the near future with
a little assistance from terrestrial radio signals transmitted specifically for this purpose.
2.2 Communications Satellite
A satellite is a smaller object that revolves around a larger object in space. For example, moon is a natural
satellite of earth.
We know that Communication refers to the exchange (sharing) of information between two or more entities,
through any medium or channel. In other words, it is nothing but sending, receiving and processing of
information.
If the communication takes place between any two earth stations through a satellite, then it is called as
satellite communication in this communication, electromagnetic waves are used as carrier signals. These
signals carry the information such as voice, audio, video or any other data between ground and space and
vice-versa.
A communications satellite is an artificial satellite that relays and amplifies radio telecommunication
signals via a transponder; it creates a communication channel between a source transmitter and
a receiver at different locations on Earth.
Communications satellites are used for television, telephone, radio, internet, and military applications. As
of 1 August 2020, there are 2,787 artificial satellites in Earth's orbit, with 1,364 of these being
communications satellites, used by both private and government organizations. Most communications
satellites are in geostationary orbit 22,236 miles (35,785 km) above the equator, so that the satellite appears
stationary at the same point in the sky; therefore, the satellite dish antennas of ground stations can be aimed
permanently at that spot and do not have to move to track the satellite.
4
The high frequency radio waves used for telecommunications links travel by line of sight and so are
obstructed by the curve of the Earth. The purpose of communications satellites is to relay the signal around
the
curve
of
the
Earth
allowing
communication
between
widely
separated
geographical
points. Communications satellites use a wide range of radio and microwave frequencies. To avoid signal
interference, international organizations have regulations for which frequency ranges or "bands" certain
organizations are allowed to use. This allocation of bands minimizes the risk of signal interference.
Need of Satellite Communication
Long distance communication beyond 30 MHz in three modes failed:
•
Ground wave due to conduction losses.
•
Space wave due to limited line of sight.
•
Sky wave due to penetration of the ionosphere by the higher frequencies beyond critical frequency
And thus, there came the need of satellite communications.
24. Figure 42.1. Wave Propagation Modes
5
2.3 Types of Satellite
ACTIVE SATELLITE
It is a functioning satellite that receives and transmits or retransmits radio communication signals
to or from the earth station.
They have a processing equipment called Transponder. These transponders serve dual purpose
i.e. provides amplification of the incoming and performs the frequency translation of the incoming
signal to avoid interference between the incoming and outgoing signals.
23. Figure 42.2. Active satellite
PASSIVE SATELLITE
Passive satellites are relay stations in space. It simply reflects light or radio waves transmitted from
one ground terminal to another without amplification or retransmission.
22. Figure 2.3. Passive satellite
6
2.4 Satellite Orbits
1- Geosynchronous Orbit (GSO or GEO).
2- Low Earth Orbit (LEO).
3- Medium Earth Orbit (MEO).
4- High Earth Orbit (HEO).
21. Figure 2.4. satellite orbits
2.4.1 Geosynchronous Orbit (GSO or GEO)
The GSO orbit is by far the most popular orbit used for communications satellites, it is located in a circular
orbit in the equatorial plane. A nominal distance of 36,000 km at a stable point. The satellite maintains its
position at a fixed location in the sky, the ground antenna does not need to track a moving satellite.
GEO satellites are synchronous with respect to earth. Looking from a fixed point from Earth, these satellites
appear to be stationary. These satellites are placed in the space in such a way that only three satellites are
sufficient to provide connection throughout the surface of the Earth (that is; their footprint is covering
almost 1/3rd of the Earth). The orbit of these satellites is circular. The inclination of satellite with respect
to earth must be 00. These satellites are used for TV and radio broadcast, weather forecast and also, these
satellites are operating as backbones for the telephone networks.
7
Disadvantages
The long delay time of ∼260 ms, which can affect network synchronization or impact voice
communications.
20. Figure 2.5. Geosynchronous Orbit (GEO)
2.4.2 Medium Earth Orbit (MEO)
The MEO is similar to the LEO, it is a circular orbit. However, the satellite is in a higher circular orbit
1600 to 4200 km. The delay is (∼100 ms). It is a popular orbit for navigation satellites
MEOs can be positioned somewhere between LEOs and GEOs, both in terms of their orbit and due to their
advantages and disadvantages. Using orbits around 10,000 km, the system only requires a dozen satellites
which is more than a GEO system, but much less than a LEO system. These satellites move more slowly
relative to the earth’s rotation allowing a simpler system design (satellite periods are about six hours).
Depending on the inclination, a MEO can cover larger populations, so requiring fewer handover.
Disadvantages
Again, due to the larger distance to the earth, delay increases to about 70–80 ms. the satellites need higher
transmit power and special antennas for smaller footprints.
8
19. Figure 2.6. Medium Earth Orbit (MEO)
2.4.3
Low Earth Orbit (LEO)
The most common orbit is the low earth orbit (LEO), it is a circular orbit. The altitude is from 160 to 640
km above the earth. The delay is low (∼10 ms). The satellite moves across the sky. The ground station must
actively track the satellite to maintain communications. LEO is used for military spy satellites to keep a
watchful eye on other countries.
18. Figure 2.7. Low Earth Orbit (LEO)
Disadvantages
The biggest problem of the LEO concept is the need for many satellites if global coverage is to be reached.
Several concepts involve 50–200 or even more satellites in orbit. The short time of visibility with a high
elevation requires additional mechanisms for connection handover between different satellites. The high
number of satellites combined with the fast movements resulting in a high complexity of the whole satellite
system. One general problem of LEOs is the short lifetime of about five to eight years due to atmospheric
drag and radiation from the inner Van Allen belt1. Assuming 48 satellites and a lifetime of eight years, a
9
new satellite would be needed every two months. The low latency via a single LEO is only half of the story.
Other factors are the need for routing of data packets from satellite to if a user wants to communicate around
the world. Due to the large footprint, a GEO typically does not need this type of routing, as senders and
receivers are most likely in the same footprint.
2.4.4
High Earth Orbit (HEO)
The HEO is the only non-circular orbit of the four types. It operates with an elliptical orbit. A maximum
altitude (apogee) similar to the GSO. A minimum altitude (perigee) similar to the LEO. The HEO is often
used for scientific applications where coverage of high latitude locations is required.
17. Figure 2.8. High Earth Orbit (HEO)
2.5 Satellite Services
2.5.1 Direct-to-Home (DTH) service
Direct to home technology refers to the satellite television broadcasting process which is actually
intended for home reception. This technology is originally referred to as direct broadcast satellite (DBS)
technology. The technology was developed for competing with the local cable TV distribution services by
providing higher quality satellite signals with a greater number of channels.
In short, DTH refers to the reception of satellite signals on a TV with a personal dish in an individual home.
The satellites that are used for this purpose is geostationary satellites. The satellites compress the signals
digitally, encrypt them and then are beamed from high powered geostationary satellites. They are received
by dishes that are given to the DTH consumers by DTH providers.
10
Though DBS and DTH present the same services to the consumers, there are some differences in the
technical specifications. While DBS is used for transmitting signals from satellites at a particular frequency
band [the band differs in each country], DTH is used for transmitting signals over a wide range of
frequencies [normal frequencies including the KU and KA band]. The satellites used for the transmission
of the DTH signals are not part of any international planned frequency band. DBS has changed its plans
over the past few years so as to include new countries and also modify their mode of transmission from
analog to digital. But DTH is more famous for its services in both the analog and digital services which
includes both audio and video signals. The dishes used for this service is also very small in size. When it
comes to commercial use, DBS is known for its service providing a group of free channels that are allowed
for its targeted country. Now surround sound, home theaters, live concerts and daily television
programming are all delivered to your home with the same quality as any modern movie theater.
2.5.2
Mobile Satellite Service (MSS)
Refers to networks of communication satellites intended for use with mobile and portable wireless
telephones.
There are three major types:
-
AMSS (aeronautical MSS).
-
LMSS (land MSS).
-
MMSS (maritime MSS).
A telephone connection using MSS is similar to a cellular telephone link, except the repeaters are in orbit
around the earth, rather than on the surface. An MSS can link any two wireless telephone sets at any time,
no matter where in the world they are located. There are enough satellites in the system, and satellites are
properly spaced around the globe. MSS systems are interconnected with land-based cellular networks.
2.6
Satellite Communications Segments
2.6.1 Ground Segment
The ground segment of the communications satellite system consists of the earth surface areabased terminals that utilize the communications capabilities of the Space Segment. TTC&M
ground stations are not included in the ground segment. The ground segment terminals consist of
three basic types:
11
2.6.1.1 Fixed (in-place) terminals
They are designed to access the satellite while fixed in-place on the ground, they are not moving
while communicating with the satellite.
Examples:
-
Small terminals used in private networks [Very Small Aperture Terminals (VSATs)].
-
Terminals mounted on residence buildings
2.6.1.2
15. Figure 2.9. Very Small Aperture Terminals (VSATs).
Transportable terminals
16.
They are designed to be movable, but once on location remain fixed during transmissions to the satellite.
Examples: Satellite News Gathering (SNG) trucks, which move to locations, stop in place, and then deploy
an antenna to establish links to the satellite.
Figure 2.10. Satellite News Gathering (SNG)trucks
14.
12
2.6.1.3
Mobile terminals
They are designed to communicate with the satellite while in motion. They are further defined as land
mobile, aeronautical mobile, or maritime mobile, depending on their locations on or near the earth surface
2.6.2
Space Segment
The space segment includes:
- The satellite (or satellites) in orbit in the system
- The ground station that provides the operational control of the satellite(s) in orbit.
- The ground station is variously referred to the Tracking, Telemetry, Command (TT&C) or the
Tracking, Telemetry, Command and Monitoring (TTC&M) station. It provides essential
spacecraft management and control functions to keep the satellite operating safely in orbit. The
TTC&M links between the spacecraft and the ground are usually separate from the user
communications links.
12. Figure 2.11. Tracking, Telemetry, Command
and Monitoring (TTC&M) station
13.
Advantages and disadvantages of Satellite Communication.
Following are the advantages of using satellite communication:
-
Area of coverage is more than that of terrestrial systems
-
Each and every corner of the earth can be covered
-
Transmission cost is independent of coverage area
-
More bandwidth and broadcasting possibilities
13
Following are the disadvantages of using satellite communication:
2.7
-
Launching of satellites into orbits is a costly process.
-
Propagation delay of satellite systems is more than that of conventional terrestrial systems.
-
Difficult to provide repairing activities if any problem occurs in a satellite system.
-
Free space loss is more.
Application of satellite
Weather Forecasting
Certain satellites are specifically designed to monitor the climatic conditions of earth. They
continuously monitor the assigned areas of earth and predict the weather conditions of that region.
This is done by taking images of earth from the satellite. These images are transferred using
assigned radio frequency to the earth station. (Earth Station: it’s a radio station located on the earth
and used for relaying signals from satellites.) These satellites are exceptionally useful in predicting
disasters like hurricanes, and monitor the changes in the Earth's vegetation, sea state, ocean color,
and ice fields.
Radio and TV Broadcast
These dedicated satellites are responsible for making 100s of channels across the globe available
for everyone. They are also responsible for broadcasting live matches, news, world-wide radio
services. These satellites require a 30-40 cm sized dish to make these channels available globally.
Military Satellites
These satellites are often used for gathering intelligence, as a communications satellite used for
military purposes, or as a military weapon. A satellite by itself is neither military nor civil. It is the
kind of payload it carries that enables one to arrive at a decision regarding its military or civilian
character.
Global Telephone
One of the first applications of satellites for communication was the establishment of
international telephone backbones. Instead of using cables it was sometimes faster to launch a new
satellite. But fiber optic cables are still replacing satellite communication across long distance as in
fiber optic cable, light is used instead of radio frequency, hence making the communication much
14
faster (and of course, reducing the delay caused due to the amount of distance a signal needs to
travel before reaching the destination.). Using satellites, to typically reach a distance approximately
10,000 kms away, the signal needs to travel almost 72,000 kms, that is, sending data from ground
to satellite and (mostly) from satellite to another location on earth. This cause’s substantial amount
of delay and this delay becomes more prominent for users during voice calls.
Connecting Remote Areas
Due to their geographical location many places all over the world do not have direct wired
connection to the telephone network or the internet (e.g., researchers on Antarctica) or because of
the current state of the infrastructure of a country. Here the satellite provides a complete coverage
and (generally) there is one satellite always present across a horizon.
Global Mobile Communication
The basic purpose of satellites for mobile communication is to extend the area of coverage.
Cellular phone systems, such as AMPS and GSM (and their successors) do not cover all parts of a
country. Areas that are not covered usually have low population where it is too expensive to install
a base station. With the integration of satellite communication, however, the mobile phone can
switch to satellites offering world-wide connectivity to a customer. Satellites cover a certain area
on the earth. This area is termed as a „footprint‟ of that satellite. Within the footprint,
communication with that satellite is possible for mobile users. These users communicate using a
Mobile-User-Link (MUL). The base-stations communicate with satellites using a Gateway-Link
(GWL).
2.8
Global Navigation Satellite System (GNSS)
The system allows for precise localization world-wide, and with some additional techniques, the
precision is in the range of some meters. Ships and aircraft rely on GPS as an addition to traditional
navigation systems. Many vehicles come with installed GPS receivers. This system is also used,
e.g., for fleet management of trucks or for vehicle localization in case of theft.
15
2.8.1 GNSS Overview
Global navigation satellite system (GNSS) is a general term describing any satellite constellation that
provides positioning, navigation, and timing (PNT) services on a global or regional basis. While GPS is the
most prevalent GNSS, other nations are fielding, or have fielded, their own systems to provide
complementary, independent PNT capability.
At present GNSS include two fully operational global systems, the United States’ Global Positioning
System (GPS) and the Russian Federation’s Global Navigation Satellite System (GLONASS), as well as
the developing global and regional systems, namely Europe’s European Satellite Navigation System
(GALILEO) and China’s COMPASS/BeiDou, India’s Regional Navigation Satellite System (IRNSS) and
Japan’s Quasi-Zenith Satellite System (QZSS). Once all these global and regional systems become fully
operational, the user will have access to positioning, navigation and timing signals from more than 100
satellites.
In addition to these, there are satellite-based augmentation systems, such as the United States’ Wide-area
Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), the
Russian System of Differential Correction and Monitoring (SDCM), the Indian GPS Aided Geo Augmented
Navigation (GAGAN) and Japanese Multi-functional Transport Satellite (MTSAT). Combining them with
proven terrestrial technologies such as inertial navigation, will open the door to new applications for socioeconomic benefits. The latter are applications that require not just accuracy, but in particular reliability or
integrity. Safety-critical transportation applications, such as the landing of civilian aircraft, have stringent
accuracy and integrity requirements.
For developing countries, GNSS applications offer a cost-effective way of pursuing sustainable economic
growth while protecting the environment. Satellite navigation and positioning data are now used in a wide
range of areas that include mapping and surveying, monitoring of the environment, precision agriculture
and natural resources management, disaster warning and emergency response, aviation, maritime and land
transportation and research areas such as climate change and ionospheric studies. The successful
completion of the work of the International Committee on Global Navigation Systems (ICG), particularly
in establishing interoperability among the global systems, will allow a GNSS user to utilize one instrument
to receive signals from multiple systems of satellites. This will provide additional data, particularly in urban
16
and mountainous regions, and greater accuracy in timing or position measurements. To benefit from these
achievements, GNSS users need to stay abreast of the latest developments in GNSS-related areas and build
the capacity to use the GNSS signal.
2.8.2 GNSSs components
The GNSS consist of three main satellite technologies: GPS, Glonass and Galileo. Each of them consists
mainly of three segments: (a) space segment, (b) control segment and (c) user segment. These segments are
almost similar in the three satellite technologies, which are all together make up the GNSS. As of today,
the complete satellite technology is the GPS technology and most of the existing worldwide applications
related to the GPS technology. The GNSS technology will become clearer after the operation of Galileo
and the reconstruction of Glonass in the next few years.
1. Space segment: The space segment includes the satellites of a GNSS. Usually, GNSS satellites are in a
so-called Medium Earth Orbit (MEO) at altitudes of about 20 000 km.
2. Control segment: The control segment or ground segment is located on Earth to monitor and control the
space segment and generates navigation data which is broadcast along with the ranging signal by the space
segment.
3. User segment: The user segment includes any user receiving and processing the GNSS signals. For this
task, an interface control document defines in detail how a GNSS receiver is to use the signals broadcast in
order to obtain a position solution.
All components have to be designed carefully in order to achieve a high level of performance. In addition
to an interface control document, most GNSS systems also provide a performance specification document
detailing the performance which users can expect under nominal conditions.
2.8.3 GPS
2.8.3.1 Introduction
Over the years, people have used a variety of techniques to navigate across the globe. Traditionally,
people relied on stars and landmarks to travel between various locations, while maps and compasses helped
to prevent people from getting lost. The advent of the Global Positioning System, or ‘GPS’ for short, means
17
people no longer have to rely on these traditional (and often complex) positioning techniques to find their
way around.
The GPS project first began in 1973 and became fully operational in 1994. The system is run by the United
States Department of Defense and was originally intended for military applications only, but was made
available for public use on completion.
The GPS system consists of a network of 24 active satellites (and 8 spares) located nearly 20,000 km above
the earth’s surface - that’s the same as driving from Melbourne to Perth six times! Each satellite broadcasts
different signals which can be tracked by a GPS receiver on earth, which are then analyzed by the GPS
receiver to determine its precise location.
GPS receivers come in all different shapes and sizes, are widespread and are affordable. Today, GPS
receivers can be found in watches, phones, tablets, computers, cars and a wide variety of other devices.
2.8.3.2 Parameters GPS
-
24 active satellites (and 8 spares)
-
6 orbits with 4 satellites each, inclination 55°
-
Orbit height ~ 20.000 km, time of circulation ~ 12h
-
Life expectancy of satellites 10 years
-
(current average 12 years, maximum 15 years)
-
Satellite mass 2.03t, power supply min. 1.14kW
-
Solar generators with 13.4m2
2.8.4 Structure of GPS
2.8.4.1.1 The Space segments
The space segment consists of 24 satellites circling the earth at 12,000 miles in altitude. This high altitude
allows the signals to cover a greater area. The satellites are arranged in their orbits so a GPS receiver on
earth can always receive a signal from at least four satellites at any given time. Each satellite transmits low
radio signals with a unique code on different frequencies, allowing the GPS receiver to identify the signals.
The main purpose of these coded signals is to allow for calculating travel time from the satellite to the GPS
receiver. The travel times multiplied by the speed of light equals the distance from the satellite to the GPS
18
receiver. Since these are low power signals and won’t travel through solid objects, it is important to have a
clear view of the sky.
2.8.4.1.2
The Control segments
The control segment tracks the satellites and then provides them with corrected orbital and time
information. The control segment consists of four unmanned control stations and one master control station.
The four unmanned stations receive data from the satellites and then send that information to the master
control station where it is corrected and sent back to the GPS satellites.
2.8.4.1.3
The User segments
The user segment consists of the users and their GPS receivers. The number of simultaneous users
is limitless.
2.8.5 GPS Work
10. Figure 2.12. Structure of GPS
11.
Step1: Triangulating from Satellites
The working/operation of the Global positioning system is based on the ‘trilateration’ mathematical
principle. The position is determined from the distance measurements to satellites. From the figure, the four
satellites are used to determine the position of the receiver on the earth. The target location is confirmed by
19
the 4th satellite. And three satellites are used to trace the location place. A fourth satellite is used to confirm
the target location of each of those space vehicles. The global positioning system consists of satellite,
control station and monitor station and receiver. The GPS receiver takes the information from the satellite
and uses the method of triangulation to determine a user’s exact position.
8. Figure 2.13. Four satellites are used to determine the position of
the receiver on the earth
9. Earth, crisscrossing the sky in a latticework of preGPS relies on a constellation of satellites orbiting
determined paths. At regular intervals, the 24 satellites that comprise this network simultaneously broadcast
information about their position and the current time.
Smartphones with GPS chips, car navigation systems and other GPS-enabled devices are on the receiving
end of this regular broadcast. Picking up a satellite’s signal is a bit like a ship searching for a lighthouse
beacon while out at sea you have to be within seeing distance to spot it. Based on the way the satellites
orbit, your device can potentially see between five and eight satellites at any given time and place.
Once a signal is received in the form of radio waves, your device can calculate how far it is from a satellite
using two pieces of information: the time the message was relayed and how long it took to get to where you
are. Your device then needs to repeat the process and collect information from at least two other satellites
to calculate your coordinates. GPS technology is now so advanced that it can predict your location within
a 10 to 50 feet accuracy.
Determine the 2D position (longitude and latitude)
This process of honing in on your location is based on a mathematical principle called trilateration,
which uses overlapping regions to find a common, intersecting area. To picture this, imagine you have a
20
blank sheet of paper. Draw a circle this represents all the possible places you could be knowing that you’re,
say, 12,000 miles away from Satellite A. Now draw another circle to represent your distance from Satellite
B and you’ll see that based on how the circles overlap, there are two possible points you could be. A third
circle shows the single point where all three figures intersect and allows you to determine your location
6. Figure 2.14. three satellite with three distance D1&D2&D3
7.
In the real world, all this happens in three-dimensional space, so think in spheres rather than flat circles.
With information from three satellites, you’re able to get longitude and latitude data. Add a fourth satellite
and you’ll be able to know what altitude you’re at as well.
Determine the 3D position (with the addition of altitude)
In real time situations, having the ambiguity of GPS Receiver located at one out of the two positions is
not viable. This can be resolved by introducing a fourth satellite (Satellite 4) with a distance D4 from the
receiver.
The fourth satellite will be able to pin point the location of the GPS Receiver from the possible two locations
which were determined earlier with only three satellites. Hence, in real time, a minimum of 4 satellites are
required to determine the exact location of the object. Practically, the GPS System works such that at least
6 satellites are always visible to an object (GPS Receiver) located anywhere on Earth.
21
Figure 2.15. four satellite with four distance D1&D2&D3&D4
5.
Step-2: Measuring distance from a Satellite
Normally distances are calculated on GPS is based on signals of a Satellite ranging.
The easy formula to calculate the distance is:
Distance (d) = Speed of satellite ranging (3 x 108 m/second) x time
Time (Δ t) = t2 – t1
where, t1 = sending time
t2 = receiving time
How do you measure distance?
speed = distance / time
distance = speed x time
satellite signals contain 'time stamps' radio waves travel time = tsent – treceived
Radio waves travel at light speed "c"
22
– 300,000km in 1 second
– 300km in 1ms (1/1000th)
– 300m in 1μs (1/millionth)
– 300mm in 1ns
4. Figure 2.16. Distance between GPS satellite
and receiver
Step 3. Determine the Location of the Satellites
In order to determine the location of the satellites, the GPS Receivers makes use of two types of data
transmitted by the GPS Satellites: The Almanac Data and the Ephemeris Data. The GPS Satellites
continuously transmit its approximate position. This data is called the Almanac data, which is periodically
updated as the satellite moves in the orbit. This data is received by the GPS Receiver and stored in its
memory. With the help of Almanac data, the GPS Receiver can be able to determine the orbits of the
satellites and also where the satellites are supposed to be.
The conditions in the space cannot be predicted and there is a huge chance that the satellites might deviate
from their actual path. The Master Control Station (MCS) along with the dedicated Monitor Stations (MS)
track the path of the satellites along with other information like altitude, speed, orbit and location.
If there is any error in any of the parameters, the corrected data is sent to the satellites so that they stay in
exact position. This orbital data sent by the MCS to satellite is called Ephemeris Data. The satellite, upon
receiving this data, corrects its position and also sends this data to the GPS Receiver. With the help of both
the data i.e. Almanac and Ephemeris, the GPS Receiver can be able to know the exact position of the
satellites, all the time.
23
Step 4: Getting Perfect Timing
The GPS receiver gets a signal from each GPS satellite. The satellites transmit the exact time the signals
are sent. By subtracting the time, the signal was transmitted from the time it was received, the GPS can tell
how far it is from each satellite. The GPS receiver also knows the exact position in the sky of the satellites,
at the moment they sent their signals. So, given the travel time of the GPS signals from three satellites and
their exact position in the sky, the GPS receiver can determine your position in three dimensions - east,
north and altitude.
There is a complication. To calculate the time the GPS signals took to arrive, the GPS receiver needs to
know the time very accurately. The GPS satellites have atomic clocks that keep very precise time, but it's
not feasible to equip a GPS receiver with an atomic clock. However, if the GPS receiver uses the signal
from a fourth satellite it can solve an equation that lets it determine the exact time, without needing an
atomic clock.
If the GPS receiver is only able to get signals from 3 satellites, you can still get your position, but it will be
less accurate. As we noted above, the GPS receiver needs 4 satellites to work out your position in 3dimensions. If only 3 satellites are available, the GPS receiver can get an approximate position by making
the assumption that you are at mean sea level. If you really are at mean sea level, the position will be
reasonably accurate. However, if you are in the mountains, the 2-D fix could be hundreds of meters off.
A modern GPS receiver will typically track all of the available satellites simultaneously, but only a selection
of them will be used to calculate your position.
2.8.6 A Differential Global Positioning System (DGPS)
It is an enhancement to the Global Positioning System (GPS) which provides improved location
accuracy, in the range of operations of each system, from the 15meter nominal GPS accuracy to about 1-3
cm in case of the best implementations.
The United States Coast Guard (USCG) and the Canadian Coast Guard (CCG) each run DGPSs in the
United States and Canada on long wave radio frequencies between 285 kHz and 325 kHz near major
waterways and harbors. The USCG's DGPS was named NDGPS (Nationwide DGPS) and was jointly
administered by the Coast Guard and the U.S. Department of Defense's Army Corps of Engineers
24
(USACE). It consisted of broadcast sites located throughout the inland and coastal portions of the United
States including Alaska, Hawaii and Puerto Rico. Other countries have their own DGPS.
A similar system which transmits corrections from orbiting satellites instead of ground-based transmitters
is called a Wide-Area DGPS (WADGPS) or Satellite Based Augmentation System.
Differential Global Positioning Systems (DGPS) are GPS systems that use fixed reference locations on
Earth to calculate positioning errors transmitted
by the satellites in view. Since the location of
these reference points in already knows, they can
easily calculate any positioning errors that are
being transmitted by the GPS constellation. This
error information is then transmitted out to GPS
devices, which use this information to calculate
their accurate position.
Difference between GPS and DGPS
GPS known as Global Positioning System is
a collection of number of satellites in the space
sending the precise location details in the space back to Earth.
Figure 2.17. differential GPS
Signals are obtained by the GPS instrument which uses to calculate its location, speed, and time at the
location, height of the location and other info. It is very popular in the military world and was first developed
by the USA military during the Cold war period. After early 1980 GPS technology is available to the public.
Before the military use, 1960 was the year when GPS was first used for ship navigation by USA navy.
DGPS: Differential Global Positioning System (DGPS) is an enhancement to the GPS (Global Position
System). GPS system based on the satellite technology can have the nominal accuracy of 15 meter whereas
DPGS can bring accuracy around 10 cm. DGPS uses the fixed ground-based reference stations to broadcast
the difference between the coordinates from the GPS and from the fixed position from the base station. The
digital correction signal is transmitted to all ground-based transmitters called rovers. DGPS rely on two
stations one is base station and next is rover.
In GPS world, handheld device receive signal from the satellite for the position where as in DGPS world
hand held device (rover) receives calibrated signal from the ground-based transmitter.
25
3. Table 1. Difference between GPS and DGPS
Basis for Comparison
GPS
DGPS
Number of receivers used
Only one, i.e., Stand-alone
GPS receiver
Two, Rover and stationary
receivers
Accuracy
15-10 m
10 cm
Range of the instruments
Global
Local (within 100 km)
Cost
Affordable as compared to
DGPS
Expensive
Frequency range
1.1 - 1.5 GHz
Varies according to agency
Factors affecting the
Accuracy
Selective availability, satellite
timing, atmospheric conditions,
ionosphere, troposphere and
multipath.
Distance between the transmitter
and rover, ionosphere, troposphere
and multipath.
Time coordinate system
used
WGS84
Local coordinate system
Range
GPS’s instruments range is
global.
While DGPS’s instruments range is
local.
2.8.6.1 Applications of DGPS
-
Air Navigation: One of its more popular applications is in air navigation. By using it a pilot can
receive constant information about where the plane is in 3 dimensions.
-
Farming: It is also becoming a hot topic in precision farming. Farmers can use DGPS to map out
their crops, map crop yields, and control chemical applications and seeding.
-
Hydrographic Survey: It is also proving to be useful in ground and hydrographic surveying.
-
Weather forecast: Another application is in weather forecasting, where atmospheric information
can be gained from its effects on the satellite signals.
-
Coastal Monitoring: There has also been at least one experiment where it was used for beach
morphology and monitoring.
-
Transport: DGPS can also be used for train control for such things as avoiding collisions and routing.
-
City Administrative: There is even been research into using it to help the visually impaired in getting
around in cities.
-
Car Navigation: There is also at least one project that is working on using DGPS for car navigation.
26
-
Sports field: In the sports world it is finding a place in balloon and boat racing. It will eventually
become an integral part of much of our technology.
27
CHAPTER 3
Circuit &Application of GPS
3.1 Introduction
A GPS navigational device is any device that receives GPS signals and processes them to
extract information for determining its exact location. Presented here is such a GPS device with a
tracking record system. It shows the path traversed by you from the initial position, so you are
never lost at unknown locations and can always come back to the initial point.
2. Figure 2.18. GPS prototype
28
1. Figure.2.19. Circuit of GPS Navigator
3.2 Circuit and working
Figure. 2 shows circuit of the GPS navigator. The circuit is built around microcontroller ATmega16
(IC1), 5V voltage regulator 7805 (IC2), GPS module (connected at CON1), graphical LCD
(GLCD1) and a few other components.
The circuit is powered by a 9V/12V adaptor. Regulator IC2 provides 5V regulated supply for the
circuit to operate. LED1 indicates presence of power in the circuit.
Microcontroller IC1 running at a clock frequency of 16 MHz communicates with the GPS receiver
modem via serial protocol. Tx pin of the GPS receiver is connected to Rx (PD0) pin of
microcontroller IC1. The GPS receiver continuously transmits data at 1Hz update rate.
A 128×64-pixel, KS0108-controller-based GLCD is used to display the navigation data. Port pins
PB0 through PB7 of IC1 are connected to data pins D0 through D7 of GLCD1. Port pins PD2
29
through PD6 are used to provide control signals RS, R/W, EN, CS1 and CS2 to GLCD1,
respectively. Switch S1 is used to reset the navigator.
Working of the navigator is simple. Once powered on, the microcontroller stores the initial
longitude and latitude data. Then it continuously plots the changing latitude and longitude as you
move around (Figure 18). One division change on the screen is equivalent to approximately 30
meters travelled. With the new latitude and longitude position plotted on the screen, you get a clear
idea of the direction and path traveled by you. The display also shows various other information
such as current latitude, longitude, speed, altitude, date, time and number of satellites the GPS
modem can capture.
3.3 Applications of GPS
The free global availability and accuracy of GPS signals for positioning and timing, combined
with the low cost of receiver chipsets, has made GPS the preferred solution for a very wide and
growing range of civilian applications.
-
Road Transport
Based on the number of GPS receivers sold globally, road transport applications are the majority users of
GPS positioning for commercial fleet management and freight tracking, taxi services, public transport
monitoring and passenger information, and emergency vehicle location, dispatch and navigation. Private
car owners have also widely adopted in-car GPS navigation systems and most automobile manufacturers
now release new vehicles with optional factory-fitted GPS.
-
Aviation
In commercial aviation, most aircraft now use GPS for en-route navigation and GPS is increasingly being
used for initial approach and non-precision approach to specified airfields. Automatic Dependent
Surveillance - Broadcast (ADS-B) is being developed globally as the preferred future technology for
commercial air traffic control; this involves aircraft calculating their position using GPS and broadcasting
it to other aircraft. GPS is also widely used for navigation of unmanned aerial vehicles (UAVs) for
30
professional applications such as resource mapping and aerial surveying – imaging tasks previously
performed by satellites such as NASA’s Landsat.
-
Shipping & Rail Transport
Maritime applications include ocean and inshore navigation, dredging, port approaches, harbour entrance
and docking, Vessel Traffic Services (VTS), Automatic Identification System (AIS), hydrography, and
cargo handling. Railway applications include the management of rolling stock, passenger information,
preventing doors opening until the carriage is alongside the platform, cargo tracking signalling, train
integrity and level crossing approach.
-
Science
Scientific applications of GPS are widespread and include environmental and atmospheric monitoring,
animal behavior studies, botanical specimen location, meteorology and climate research. GPS is used in
agriculture and fisheries for land area mapping, yield monitoring, precision planting of crops, spraying and
harvesting, autonomous vehicle control and to monitor fishing limits.
-
Security
Security applications include tracking of vehicles, containers, other valuable cargoes and covert tracking of
suspects.
-
Heavy Vehicle Guidance
GPS is being used increasingly to guide and track heavy vehicles in engineering applications such as mining
and construction. For example, in highway construction, surveyors and marker pegs have been replaced
with in-cabin vehicle guidance and control systems for excavators, graders, bulldozers and road paving
machines that allow drivers to follow a surveyor’s pre-programmed site plans and achieve close tolerances
for position, level and gradient.
In open-cut mines, GPS is integrated into applications developed by companies such as Leica Geosystems,
Topcon Positioning Systems and Trimble/Caterpillar for vehicle guidance and tracking, and mine asset
management systems.
In these professional applications, GPS information is captured by sophisticated IT systems and meshed
with other engineering applications to provide multifunction guidance and control.
31
-
Surveying, Mapping and Geophysics
Professional, survey-grade GPS receivers, capable of utilizing signals from both L1 and L2 GPS
frequencies, can be used to position survey markers, buildings, bridges and other large infrastructure. GPS
is widely used in mapping, including aerial mapping, and other Geographical Information System (GIS)
applications. In geophysics, GPS is used to time stamp seismic activity and to monitor position changes in
sensitive physical formations such as volcanoes and earthquake fault lines.
-
Telecommunications
GPS timing is important for telecommunications applications, particularly for mobile telephone networks.
Synchronous technologies are much more efficient than asynchronous technologies but require a time
source with appropriate accuracy, stability and reliability to operate effectively or at all, and GPS satellites
can provide this. While ground-based clocks are accurate enough for this purpose (especially with the
availability of chip scale atomic clocks (CSAC)), the synchronization of many such clocks is problematic.
GPS allows the derivation of synchronized time through resolving the signals from a number of atomic
clock sources at known locations.
-
Financial Services
Global financial systems increasingly need precise timing systems to schedule and priorities local and
international money transfers, settlements and trades and to provide an audit trail for financial
transactions. For example, the time signal provided by the atomic clocks on board the GPS satellites is
used by financial institutions worldwide for providing date and time stamps for Electronic Funds
Transfers. In some developed countries up to 80% of retail transactions involve either credit or debit
cards. With millions of these transactions occurring every minute, a very high level of timing accuracy has
become a critical component of financial trading networks.
-
Social Activities
Widely available, low-cost hand-held GPS receivers have enabled a numerous variety of social
activities. The most ubiquitous application is in-car navigation, but there are dozens of other applications
GPS-based social networking, geotagging photographs, cross country cycling, hiking, skiing, paragliding,
skydiving, geocaching, geocaching and other gaming activities.
32
Chapter 4
FACILITIES & DIFFICULTIES
4.1 Introduction
This chapter contains the difficulties and facilities that are faced during the study. It includes
the Academic difficulties and facilities. Also, field difficulties and facilities.
4.2 Difficulties
Difficulties that faced during the study are:
4.2.1
Academic Difficulties
The academic difficulties that faced study are:
1. Current situation in Yemen.
3. No electricity and no internet.
4.3 Facilities
Facilities that help during study are:
4.3.1
Academic Facilities Academic facilities that facilitate the study which are
1. Getting helping in choosing the topic of the study by D/ Jamel sultan.
2. There are many websites talking in GPS.
3. Correcting the information of the document.
4. Easley contact with the supervisor.
4.4 Future Work Suggestions
We have come up with the following suggestions for future studies:
-
Our country should develop the GPS to be use in the whole country.
-
Improve our telecommunication system to work with GPS.
33
Reference
http://www.locata.com/applications-of-gps/civilian-applications/
https://d1.amobbs.com/bbs_upload782111/files_33/ourdev_584835O21W59.pdf
https://www.epa.gov/sites/production/files/2015-10/documents/global_positioning_system110_af.r4.pdf
https://www.google.com/search?q=gps+constellation&ei=NpBXYP_NI4nUsAfZyICoCA&oq=gps+cons
&gs_lcp=Cgdnd3Mtd2l6EAMYADIFCAAQkQIyAggAMgIIADIICC4QxwEQrwEyAggAMgIIADICCA
AyAggAMgIIADICCAA6BwgAEEcQsAM6BwgAELEDEEM6BAgAEEM6CAgAELEDEIMBOgUIA
BCxAzoLCC4QsQMQxwEQrwE6CAgAELEDEJECUKTAX1iSyl9g1NZfaAFwAngAgAH2AYgBwgiS
AQUwLjIuM5gBAKABAaoBB2d3cy13aXrIAQi4AQLAAQE&sclient=gws-wiz
34