Gheorghe Asachi Technical University of Iași [611007]

„Gheorghe Asachi ” Technical University of Iași
FACULTY OF ELECTRONICS, TELECOMMUNICATIONS & INFORMATION
TEHNOLOGY

BATINCU PETRU -GABRIEL

DIPLOMA PROJECT

SUPERVISOR

PROF . DR. ENG. ION BOGDAN
2019

GPS NAVIGATION
SYSTEM

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Table of Contents
CHAPTER 1 ………………………….. ………………………….. ………………………….. ………………………… 5
GPS PRINCIPLES ………………………….. ………………………….. ………………………….. …………….. 5
1 Introduction ………………………….. ………………………….. ………………………….. ………………… 5
CHAPTER 2 ………………………….. ………………………….. ………………………….. ………………………… 7
GPS ARHITECTURE ………………………….. ………………………….. ………………………….. ………… 7
2 Introduction ………………………….. ………………………….. ………………………….. ………………… 7
2.1 The space segment ………………………….. ………………………….. ………………………….. …….. 7
2.2 The control segment ………………………….. ………………………….. ………………………….. ….. 9
2.3 The user segment ………………………….. ………………………….. ………………………….. …….. 10
CHAPTER 3 ………………………….. ………………………….. ………………………….. ………………………. 11
MODULATION TECHNIQUES ………………………….. ………………………….. ……………………. 11
3 Introduction ………………………….. ………………………….. ………………………….. ………………. 11
3.1 Multiple access techniques ………………………….. ………………………….. ……………………. 12
3.2 Frequency Division Multiple Access ………………………….. ………………………….. ……… 13
3.3 Time -division multiple access ………………………….. ………………………….. ……………….. 15
3.4 Code division multiple access ………………………….. ………………………….. ……………….. 16
CHAPTER 4 ………………………….. ………………………….. ………………………….. ………………………. 18
GPS SIGNAL S TRUCTURE ………………………….. ………………………….. …………………………. 18
4 Introducti on ………………………….. ………………………….. ………………………….. ………………. 18
4.1 Signal operation frequencies ………………………….. ………………………….. …………………. 18
4.2 Sig nal modulation ………………………….. ………………………….. ………………………….. ……. 20
4.3 Improved GPS signal ………………………….. ………………………….. ………………………….. .. 22
CHAPTER 5 ………………………….. ………………………….. ………………………….. ………………………. 26
MOBILE POSOTION ING TECHINIQUES ………………………….. ………………………….. ……. 26
5 Introduction ………………………….. ………………………….. ………………………….. ………………. 26
5.1 Techniques of cellular positioning ………………………….. ………………………….. …………. 26
5.3 Location of the terminal ………………………….. ………………………….. ……………………….. 27
5.4 Measured level of power received by mobile ………………………….. ……………………….. 27
5.5 The AoA method ………………………….. ………………………….. ………………………….. …….. 29
5.6 The ToA method ………………………….. ………………………….. ………………………….. ……… 30
5.7 Hybrid metho ds ………………………….. ………………………….. ………………………….. ………. 31
PRACTICAL PART ………………………….. ………………………….. ………………………….. ……………. 32

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GPS TRACKER ………………………….. ………………………….. ………………………….. ………………….. 32
MAIN FEATURES ………………………….. ………………………….. ………………………….. ………….. 32
Introduction ………………………….. ………………………….. ………………………….. …………………. 32
Short description of the system ………………………….. ………………………….. …………………… 32
Hardware components of the system ………………………….. ………………………….. ………………. 33
ARDUINO DEVELOPMENT BOARD ………………………….. ………………………….. ………. 33
FONA 808 BOARD ………………………….. ………………………….. ………………………….. ……… 36
SHIELD PCB ………………………….. ………………………….. ………………………….. ………………. 41
BATTERY ………………………….. ………………………….. ………………………….. …………………… 42
GSM ANTENNA ………………………….. ………………………….. ………………………….. …………. 44
GPS ANTENNA ………………………….. ………………………….. ………………………….. …………… 45
SHIELD BOX ………………………….. ………………………….. ………………………….. ………………. 47
Software components ………………………….. ………………………….. ………………………….. ……….. 49
Introduction ………………………….. ………………………….. ………………………….. …………………. 49
Implementation goal in the project ………………………….. ………………………….. ………………. 49
Header code <.h> ………………………….. ………………………….. ………………………….. ………….. 49
Description of the system ………………………….. ………………………….. ………………………….. ….. 50
Conclusi on ………………………….. ………………………….. ………………………….. …………………… 52
Annexes ………………………….. ………………………….. ………………………….. ………………………….. …. 53
Bibliography ………………………….. ………………………….. ………………………….. ………………………. 55

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CHAPTER 1
GPS PRINCIPLES

1 Introduction

In the 1960s, US Naval forces successfully tested the first satellite navigation system called
Transit and used by the US Nav y. Using a constellation of five satellites, this system could
provide to the user his position approximately once an hour. The similar Soviet system called
Tsikada, followed in 1976 . A limitation for both systems is given by the fact that the user
positio ning requir es 15 -20 minutes of processing from the receiver and an estimation of the
user location . Therefore , the systems are only suited for low -speed navigation ( for example on
water where you do not need so much speed ). Because the requirements were so mewhat larger,
they led to the US Global Positioning System (GPS), which was designed with the following
attributes:
Global coverage, continuous operation, high accuracy of localization, ability to serve users
traveling at high speeds (airplanes or cars ). The GPS dev elopment program was drafted by the
Ministry of Defense in 1969 as a common program between several US governmental
organizations . In 1995, the United States declared NAVSTAR GPS had reached its full
operational capability .

Figure 1 – Transit Satellite

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A GPS navigation is a device capable of receiving information from GPS satellites and then
calculating geographic position o f the device . By using the appropriate software, the device
can display the position on a map and provide guidanc e. The Global Positioning System is a
global satellite navigation system (GNSS) consisting of a network of at least 24, but currently
there are 30 satellites in orbit placed by the US Department of Defense .
Global navigation satellite systems are considere d the basis in many modern daily use
applications (free time, defense and civil protection, agriculture and transport, only to cite a
few) that are designed and carried by out several Independent GNSS .
The main players on this area are:
• The US GPS
• The Eur opean Galileo
• The Russian GLONASS
• The Chinese Compass (BeiDou 2)

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CHAPTER 2
GPS ARHITECTURE
2 Introduction
The GPS consists of three parts, illustrated in Figure 2, the space segment, the control segment
and the segment for users .

Figure 2-GPS Components

2.1 The space segment
The spatial segment is composed of GPS satellites . The GPS constellation is formed formally
from 24 satellites, deployed on six quasi -circular orbits, each with four satellites . At present
the constellation contains 3 0 satellites . The six orbits have an inclination of approximately 55
° (relative to the equator) and are separated by an angle of 60 ° from the ascending node (angle
in the plane of the equator from a reference point to the orbital intersection with the plane) . The
orbits are centered on the Earth and are arranged so that, from almost any place on the surface
of the Earth, at least six satellites are always in direct vi sibility . Each satellite performs two
complete orbits every day, flying at an altitude of approximately 20,200 km .
Five generations of satellites (called Block) have been launched so far: Block I (Initial
Concept Validation), II (Initial Production), IIA (Improved Production), IIR (Replacement),

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IIR M. Four generations are planned (IIF , IIIA, IIIB, IIIC) . Currently (May 201 9), there are
30 satellites currently transmitting GPS constellations, three obsolete satellites, withdrawn
from the active service a nd conserved as backup units and a satellite launched in March 2009 .
Additiona l satellites improve accuracy position calculated by the receiver by providing
redundant measurements . With the increase in the number of satellites, the constellation has
come t o an uneven arrangement .
The main functions of the space segment are:
• Receivi ng and storing data transmitted by the control segment;
• time measurement with high precision;
• transmitting navigation data to system users by multi -frequency radio emissions;
• control of altitude and position of satellites;
• activating a radio link between satellites;
As the basis for extremely stable generation of spreading codes and carrier freque ncies, very
precise atomic clocks are used . Each satellite contains several atomic clocks to meet the
required reliability standards and uses only one of them at a time .

Figure 2.1-Space Segment

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2.2 The control segment
The segment control is re spons ible for monitoring, commanding and the contro lling the
constellation .
Main features of this segment are:
• monitoring the navigation signals emit ted in L -BAND
• updates t he navigation signals
• resolves malfunctions in satellite operation
The segment also monit ors the proper operation of each satellite and manages tasks associated
with keeping each satellite in the correct orbit and recharging its batteries .
The control seg ment is composed by:
• monitoring stations located all over the globe (Hawaii, Kwajalein, Ascension Island,
Diego Garcia, Colorado Springs – Schriver Base, National Geoscience Information
Agency);
• land-space transmission stations (Ascension Island, Diego Ga rcia, Kwajalein,Colorado
Springs – Schriver Base, Cape Canaveral);
• central c ontrol stations (Colorado Springs, Gaithersburg ). figure 2.2, illustrates the
global positioning of the control segment elements;

Figure 2 .2-Geographic distribution of segment control

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2.3 The user segment

The block diagram of a GPS receiver is shown in Figure 2 .3. It consists of:
• antenna; receiver;
• processor;
• Input / output device, such as a display unit;
• power unit . Current receivers have multiple channels (example 12), th us being able to
track multiple satellites simultaneously .

Figure 2 .3- Main components of a GPS Receiver

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CHAPTER 3
MODULATION TECHNIQUES
3 Introduct ion

In this ch apter we will discuss about the main modulation techniques, used in mobile
communicatio n, the focus will be on direct sequence spread spectrum systems that are used in
global GNSS satellite navigation systems .
In electronics and telecommunications, modulation is the process of varying one or more
properties of a periodic waveform, called bea con signal, with a modulation signal typically
containin g information to be transmitted . Most radio systems in the 20th century have used
frequency modulation (FM) or amplitude modulation (AM) for radio broadcasting . A
modulator is a device that performs t he modulation . A demodulator (sometimes a detector) is
a device that performs demodulation, the inverse of the modulation . And the modem (from
modulator -demodulator) can perform both operations .
There are presented the multiple access techniques used in mo bile communications, along with
their features and perfo rmance . The most important ways to achieve duplex transmissions and
the main ways of achieving Multiple Access:
• Frequency Division Multiple Access ;
• Time Division Multiple Access ;
• Code Division Multi ple Access are described .
Spread spectrum modulation me thods produce a signal whose spectrum is much wider than the
data signal itself, the occupied frequency band being independent of the data signal band .
In recent decades, however, they have also witne ssed a spectacular development in the civilian
field, pa rticularly in mobile communications (IS95, UMTS, CDMA2000, etc .), high -speed
wireless networks (LAN, WAN, etc .)

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3.1 Multiple access techniques

In any communications system one of the fundamental i ssues is how many users can access a
common communications channel to transmit or receive information without interfering with
each other . Depending on the number of transmitters, the number of receivers and the meaning
of the connection we can classify th e communication systems as follows:
• a transm itter and several receivers, as in the case of satellite navigation systems or
broadcasting of radio and television stations;
• multiple transmitters and a single receiver, as in the case of communication between
several base stations and a communications s atellite;
• more users that communicate with one another or bidirectionally, as in the case of
mobile telephony;
In the case of the communications systems of the last category, namely bidirectional multi –
user, they communicate via a base station that receive s the information transmitted by the users
and sends them to the recipients . The station also has the role of controlling and organizing the
way this information is transmitted so that the system works properly . For a user to be able to
transmit informatio n to the base station even when receiving information from it, a duplex
transmission is required . It is composed of the link between the base station and the mobile
station, called the downlink and the link betwe en the mobile station and the base station, called
the uplink . Duplex transmission can be performed in Frequency Division Duplexing (FDD) or
Time Division Duplexing (TDD) .In the case of single -transmitter and multi -receiver systems
used in satellite naviga tion systems, only downlink from satellite to users is used for
positioning . If the duplex transmission takes place with frequency division, it requires two
different bands for each user, the first for the uplink and the second for the downlink .
In the cas e of a split -time duplex transmis sion, the same carrier frequency and frequency band
are used for both uplink and downlink . Another difference is that the data is arranged in packets
and different time slots are used for the two links . In many radio commun ication systems, there
is a need for multiple users to be able to simultaneously receive signals from one or more base
stations or satellites . The solution is given by three commonly used multiple access modes:
• Frequency Division Multiple Access (FDMA) acc ess technique;
• Time Division Mul tiple Access TDMA (Time Division Multiple Access TDMA)
• Code Division Multiple Access CDMA technique .
A criterion according to which the radio communication systems can be classified is the ratio
of the user band used by th e user and the bandwidth of the t ransmission channel . The
consistency band results from the range of frequencies within which the amplitudes of two
sinusoidal components at different frequencies are correlated with each other . Thus, we can
distinguish narr owband or broadband communication systems . In narrowband systems, the
band used by a channel is less than or equal to the bandwidth of the radio channel .
Consequently, the frequency spectrum allocated to the system is divided into as many
narrowband channe ls as possible, each user benefit ing from one of them . In these systems,
multiple access FDMA or TDMA access methods may be used .
In narrowband FDMA systems, each user receives a frequency band (centered on a carrier
frequency), which he uses individually for the duration of the communica tion. Duplex
communication is done using frequency division . The drawbacks of the narrow band FDMA
technique are: the need for a judicious allocation of occupied frequency bands and bandwidth
power dissipated by each user m ust be provided with guard gaps between adjacent users to
minimize interference between channels .
In TDMA narrowband systems, all users use a single radio channel, each of which has a cyclical
time slot . TDMA systems can operate from both the TDMA / FDD an d the split over time

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(TDMA / TDD ). Frequency division TDMA systems use two different frequencies, one for the
uplink, the other for the downlink . Time Division TDMA systems use the same carrier
frequency and the same frequency band for both links, the tra nsmission being in one direction
or the other at different time points . For this reason, the TDD type is quasi -simultaneous,
because when transmission of data in a certain direction involves the inhibition of the
transmission in the opposite direction . If the transmission rate is high eno ugh, the time that one
of the directions is inhibited is negligible, almost imperceptible during a voice communication .
By comparing the two TDMA systems described above, the following conclusions can be
drawn:
• the band oc cupied by the two systems is the same: thus, while the FDD system uses
two frequency bands separated from each other, the TDD system uses a single double –
band;
• because the band used for TDD systems is double to that used in FDD systems, the
radiofrequency filters of the transmitter and receiver are broader bandwidth, thus easier
to implement
• in the case of the TDD system, the duplexer is provided with a simple radio frequency
switch, which connects the transmitter or receiver antenna according to the direc tion of
the data stream . This structure is much less complicated than with FDD transmission
In broadband communications, the band used by a channel (user) is much broader than the
bandwidth of the communication channel . Thus, selective frequenc y attenuatio n will only
affect some of the spectral components of the transmitted signal, and the effect of fading may
be reduced . In broadband systems, several users share the same communications channel at the
same time, the separation between them being done throug h an individual code assigned to
each user in a set of orthogonal codes . Hence their code division multiple access cod e (CDMA) .
Depending on how the scrambling code acts on the transmitted data, there are three types of
scattered spectrum systems:
• Direct S equence (DS -CDMA) spread spectrum systems, in which spreading is done by
multiplying the data with the code directly; this technique is most often used in third –
generation mobile communication systems, especially due to its technological
simplicity .
• Frequ ency Hopping Spectrum (FH -CDMA) systems, in which the carrier frequency
varies according to the code sequence; this te chnique is mainly used in military
communications or requiring a high level of security because the equipment to be used
is generally cost ly.
• Time Hopping TH CDMA systems, which use carrier pulses much shorter than the time
allocated for its transmission, the position of this impulse within the interval being
dictated by the pseudo -random code . This technique, coupled with pulse modulation
in place, has led to the development of an ultra -wide band communication technique
that is now being developed in the experimental phase for several radars , positioning,
or even low -bandwidth communication networks for indoor applications .
3.2 Frequency D ivision Multiple Access
In the frequency division multiple access technique, each user is assigned a channel (composed
of a carrier frequency and a frequency band) upon request . Throughout the call, this channel is
used only by the user who has been assign ed to it . In a time -frequency -code coordinate system,

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allocation of channels in an FDMA system can be represented as i n Figure 3.2.1.

Figure 3 .2.1 – Channel allocation in FDMA systems

In satellite locating systems using the FDMA technique, each satellite is allocated a bandwidth
to emit the useful signal to the ground receivers .
Main characteristics of FDMA systems are:
• each FDMA channel is used at once only by one user;
• after a given channel is allocated to a user, both the base station and the mobile s tation
can transmit messages simultaneously and continuously;
• if the transmission rate is relatively low, the symbol period is greater than the
propagation delays due to the channel this causes the inter -symbol interference level to
be reduced without the need for a sophisticated equalization system;
• the complexity of FDMA systems is generally lower than TDMA systems from the
point of view of the need to process the trans mitted signal;
• since the FDMA technique supports a continuous transmission, it is not necessary to
transmit so many bits for system signals (e .g., timing or shuffling) as in TDMA;
• the costs required to implement FDMA systems are higher than those of the T DMA
type because the use of a channel by a single user at one time does not lead to a judicious
use of resources; In addition, it is necessary to use complicated and expensive band pass
filters to reduce the radiated power outside the band;
• FDMA -type syste ms require the use of ultra -steep slope pass filters for reception to
eliminate inter -channel interference;
• both base and mobile stations must use duplex circuits, since both the transmitter and
receiver operate at the same time . It also leads to an incre ase in the cost of equipment .
The number of channels that can be used simultaneously in an FDMA system is:

N=𝐵𝑡−2𝐵𝑔
𝐵𝑐 Equation 1

Bt=the frequency band assigned to the system .
Bg=the guard band required at the ends of the assigned frequ ency range .
Bc=the band of an individual channel .

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3.3 Time -division multiple access
In time division multip le access systems, all users use the same frequency band, each of which
has allocated a time slot in which it can transmit or receive messages, a slot that is allocated to
it in a cyclical manner . In the time -frequency -code coordinate system, TDMA channel
allocation can be represented as in Figure 3 .3 To transmit data from a specific user, they are
stored in a buffer and then transmitted at a rate of N times or more during the slot allocated to
that user . This way the transmission is discontinuous . Data sen t from different users is
intertwine into a frame structure . In the case of TDMA / TDD, half of the slots are used for the
uplink and the other half for the downlink . In the case of TDMA / FDD, identical frame
structures are used for both uplink and downli nk and the frequencies to which data is
transmitted in this case are different .

Figure 3 .3 – Channel allocation in TDMA systems

The main features of TDMA systems are:
• TDMA systems use a single carrier frequency and a single frequency band, each user
being allocated a time slot . The number of slots per frame depends on the technology,
the type o f modulation used, the allocated frequency band;
• the data transmission in TDMA systems is not continuous but in pack ets, this leads to
reduced battery consumpti on of the mobile station, since a given user only transmits
data over the allocated slot;
• because the data transmission is discontinuous, the handove r of the call from a base
station to another is made easier since, when the mobile station is inactive, it can
perform the necessary measurements to determine the most appropriate base station

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TDMA a lso allows signal strength and reception error probability to be monitored on
each frame;
• because a user uses different time slots for transmission and receptio n, there is no need
to use duplexers in TDD mode, and in FDD mode a simple switch between transmitter
and receiver can be used;
• as the data transmission rate in TDMA is generally hig h, it is necessary to use an
adaptive reception equalization system to counteract the effects of the communication
channel;
• in the TDMA, it is necessary to transmit a relatively high number of synchronization
bits because the data transmission is in pac kets, so the receiver must synchronize upon
the arrival of each data pa cket, additionally it is necessary to insert a number of guard
bits to avoid overlapping slots from different users, therefore, the additional
information to be transmitted with useful information is much higher for TDMA than
for FDMA ;
• in the TDMA, a di fferent number of slots can be assigned to the users, so the
transmission rate can be changed according to user requirements; so the TDMA allows
the use of wide range of transmission ra tes, generally multiples of the multiplex rate
(the rate at which switc hing from one user to another), so a wide range of coding
techniques can be used different bits and different qualities, in this way the price can
be chosen by the user according to th e qualities imposed by the application;
• TDMA systems can be fully inte grated into digital technology through large -scale
integration without the use of narrow band radio frequency filters, which leads to a
substantial decrease in cost .
A relatively import ant parameter of a TDMA system is the number of channels provided
by a TDMA system:
N=𝑀(𝐵𝑡𝑜𝑡 −2𝐵𝐺)
𝐵𝑐 Equation 2

m=maxim number of users on each TDMA channel
Btot= the total band allocated to the system .
BG= the two guard bands at the ends of the busy frequency range .
Bc= is the band of a TDMA channel .
The Global Sys tem for Mobile Communications (GSM) uses a combination of FDMA and
TDMA access techniques .
3.4 Code division multiple access
In code division multiple access systems, the average power spectral density of the narrowband
information signal is widened by mea ns of a spreading code (pseudo -random code) that has a
chip period of several orders of magnitude less than the data period . All users use the same
carrier frequency and the same bandwidth simultaneously, independently of each other, being
individualized b y the allocated spreading code . In the time -frequency -code coordinate system,
the allocation of CDMA channels can be represe nted as in Figure 3.4. On reception, the data
transmitted to a given user is returned to the band by correlation with the assigned code, while
the rest of the signals to other users, remain broadband, being treated as a noise in terms of
demodulated data.

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Figure 3 .4 – Channel allocation in TDMA systems

To be able to detect the transmitted message, the handset must know the code and be perfectly
synchronized with it . In the case of satellite positioning systems (GPS and Galileo) using the
CDMA technique, each satellite is allocated a distinct code . By correlating the received signal
with the allocated code, the ground receiver can se parate the useful signal emitted by a visible
satellite . This access technology is also used by third -generation cellular mobile
communications .
Among the features of CDMA systems, the most important are:
• all users of a CDMA system use the same carrier fre quency and bandwidth
simultaneously , for duplexing, both FDD and TDD can be used;
• unlike TDMA and FDMA, CDMA systems have a soft capacity limit . Increasing the
number of users will increase the value of the reception noise level, which makes the
system pe rformance degrade for all users as their number increases;
• the effect of the phenomenon of fading due to multiple path propagation is substanti ally
reduced due to spectral s preading . If the signal bus is larger than the channel correlation
band, there i s a default frequency diversity that will combat the effect of selective
fading in frequency;
• the channel data rate is very high in CDMA systems, so the scattered data is very low,
much less than the temporal spread of the channel .
To increase performance , a RAKE receiver can be used that combines several delayed
signals from the received signal .
• one of the problems that may arise in CDMA systems is that of its own noise since the
spreading sequences used are not perfectly orthogonal to each other , for thi s reason,
certain contributions due to other users will also occur when decoding a signal ;
• another problem that may arise is that of capturing the receiver by another signal if its
power is much greater than that of the desired signal .
The number o f users of CDMA systems is given by the number of orthogonal codes used for
spreading . If pseudo -random (PN) codes are generated using length registers n, the number of
users is:
N=2𝑛-1 Equation 3

So, the length of the shift registers and implicitly of the scatter code is higher as the number of
users is higher . On the other hand, a high value of n means a higher rate of code and a greater
bandwidth .

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CHAPTER 4
GPS SIGNAL STRUCTURE

4 Introduction

The signals transmitted by the GPS satellites consist of the following components: carrier,
navigation data and sequence . On trans mission, the RF wave undergoes a circular right -hand
polarization (RHCP) .

4.1 Signal operation frequencies
Several carrier frequencies a re currently used:
• L1 (1575 .42 MHz): Navigation and spreading data (Coarse -acquisition (C / A) signal
and encrypted P (Y) signal for accurate location) and L1C signal and M – code, which
will be tran smitted starting with Block III satellites;
• L2 (1227 .60 M Hz): used for the P (Y) signal, for the new L2C signal and for the M –
code transmitted from the Block IIR -M satellites;
• L3 (1381 .05 MHz): used by nuclear detector detection units and other energy -emitting
events in the infrared spectrum . Used to enforce cl auses of nuclear test ban;
• L4 (1379 .913 MHz): used for studying additional ionospheric correction;
• L5 (1176 .45 MHz): proposed for use a civilian safety -of-life (SoL) signal;
Navigation data contains information about satellite orbits and has a bit rate of 50 bps . These
data are mostly composed of ephemeris (accurate orbit and clock corrections, corresponding to
the transmitting satellites) and almanac (approximate orbit parameters for each satellite in the
entire constellation) . The basic format for navigat ion data is a 1500 -bit long frame, containing
5 subframes, each 300 bits in length . A subframe contains 10 words, each word having 30 bits
in length . As shown in Figure 4.1 sub -frames 1, 2, and 3 ar e repeated in each frame . The last
two subclasses, 4 and 5 , have 25 versions (with the same structure but different dates), hereafter
referred to as pages 1 to 25 .
All satellites broadcast at the same frequencies, encoding signals using unique code division
multiple access (CDMA) so receivers can distinguish individual satellites from each other . The
system uses two distinct CDMA encoding types: th e coarse/acquisition (C/A) code, which is
accessible by the public , and the precise (P(Y)) code, which is encrypted so that only the U .S.
military and other NATO na tions who have been given access to the encryption code can access
it.
The ephemeris is upda ted every 2 hours and is generally valid for 4 hours, with provisions for
updates every 6 hours or longer in non -nominal conditions . The almanac is updated typicall y
every 24 hours . Additionally, data for a few weeks following is uploaded in case of
transm ission updates that delay data upload .

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Figure 4.1 – Structure of a GPS navigation data message .

With a bit rate of 50 bps, transmission of a subframe lasts 6 seconds, a frame lasts 30 seconds,
and a full navigation message (containing 25 frames) lasts 12.5 minutes . Thus, if the user's
receiver is on and has no prior information about his current position or visible satellites, the
receiver needs a maxim um of 12 .5 minutes to identify the positions of the visible satellites
(time required to receive the complete almanac) and to calculate the position of the user . This
time is called the time to first fix . Each satellite has several unique sequences or cod es. One is
the C / A scatter code, the other is the encrypted scrambling code P (Y) . The C / A code i s a
sequence of 1023 chips . A chip corresponds to a bit and does not transmit any user information .
The C / A code is repeated every millisecond, offering a 1.023 MHz chip rate . P code is a
longer code (≈ 2 .35 • 104 chips) with a 10 .23 MHz chip rate . This code is repeated every week,
starting at the beginning of the GPS week, considered to be at midnight between Saturday and
Sunday . The C / A code is modulat ed only on carrier L1, while code P (Y) is modulated on
both L1 and L2 carrier s.

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4.2 Signal modulation
On the L1 level which is the main frequency and L2 is the secondary frequency the carriers on
these two frequencies are modulated by DSSS using codes c ontaining pseudo -alarm s, unique
to each satellite, and common information signals for the entire constellation . All satellites
transmit using the CDMA technique on the same carrier frequency . To track the signal emitted
by a satellite through the CDMA tech nique, while other GPS satellites are in direct visibility
with the receiver, the receiver must locally generate the pseudo -alert sequence for the desired
satellite and the local carrier variant affected by the Doppler effect .
To understand how a GPS signal is generated, Figure 4.2, which is the block diagram of a
generator, should be followed .

Figure 4.2 – Diagram block of a GPS signal generator
From the left, the main clock signal is sent to the other blocks . The clock frequency is 10 .23
MHz to prevent the unwanted effects o f relativistic theory affecting a clock operating on a
satellite in a medium -altitude orbit around the Earth, the exact frequency is 10 .22999999543
MHz, resulting in a 10 .23 MHz on earth . By multiplying this frequency with the factors 154
and 120 the carri er frequencies L1 and L2 are obtained .
In the lower left corner of the schematic is the 'Limiter' block, which is used to stabilize the
clock signal before it reaches the P (Y) and C / A co de generators . At the bottom of the
schematic, the navigation data generator is located . The code generator and the data generator
are synchronized by the X1 signal produced by the code generator P (Y) .
After generating the code sequences, they are combine d with navigation data by modulo 2
adders using the DS -SS scattered spectrum modulation technique .

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The two modulators working on the carrier frequency L1 receive input signals obtained from
the sum of the C / A
data and the sum of the given P (Y)
code .
Here the signals are modulated on the carrier using the Binary Phase Shift Keying technique .
The t wo signals are phase and quadrature modulated to each other on the L1 carrier, so there
is a phase difference of 90 ° between the two . After P (Y) is attenua ted by 3 dB, these two
signals are added to obtain the L1 signal . The standard positioning service is based on C / A
and is intended for public use . The L2 carrier is only modulated by the signal obtained from
the sum of the given P (Y)
code and is inten ded for military use only . Since the C / A signal
is the most used civil signal, we will continue to focus on it .
The signal 𝑠𝑘 is issued by th e satellite no . k can be expressed as follows in equation 1 :
Equation 4

Where PC, PPL1, and PPL2 represent the powers of the signals encoded with the sequences C/A
or P, 𝐶𝐾 is the C / A sequence of the satellite k, 𝑃𝐾 is P(Y) corresponding t o the satellite k, 𝐷𝐾,
is the data sequence and fL1 and fL2 are carrier frequencies L1 and L2 .
In Figure 4.3 are illustrated the three waveforms that make up the C / A signal on the L1
frequency . The C / A code repeats every millisecond, and a data bi t of the navigation data lasts
20ms . Thus, each data bit overlaps over 20 repetitions of the C / A code .

Figure 4.3 – lC/A signal structure on L1 frequency

The figure 4.4 shows the code C, the navigation data D, the sum modulo 2 C
D and the
carrier . The final signal is obtained by the Binary Phase Shift Keying modulation, through
which the carrier phase is changed by 180 ° for each chip shift . When a data bit transition
occurs (for example in the right half of the figure), the phase of the modulated signal also
changes by 180 ° .

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Figure 4.4 – Modulation DS -SS and BPSK on L1 frequency

The first -generation GPS signal spectrum is drawn in Figure 4.5.
In conclusion:
• For GPS, the spread code length is 1023 chips, with a duration of 1ms . The navigation
data rate is 50 Hz, and so 20 code periods are required over a data bit . Approximately
90% of the signal strength is found in a 2 MHz band centered around the L1 frequency .
Figure 4.5 Spectrum of signals L1 and L2
4.3 Improved GPS signal
The GPS system has reached its operational capabilities in 1995, fulfilling its design
requirements . However, emerging technologies and new requirements on the existing system
have led to a project to upgrade the GPS . In 2000, the US Congress authorized this project,
called GPS III . This includes the deployment of new base stations, the launch of new sat ellites,

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the use of additional navigation signals for both civilian and military users and aims to improve
the accuracy and availability of the system for all users, in 2013 the operation was complet ed.
Four new signals were introduced: L2C, L5, M and L1C .
To allow interoperability between the GPS and Galileo systems, the US. UU and the European
Union (EU) started and recently completed negotiations on the compatibility of Gali leo L1
signals with both military and civilian GPS signals . As part of these nego tiations, the US UU
The State Department proposed that the United States would implement a new signal in L1
with a binary compensation carrier modulation (BOC) if Europe would do the same in Galileo .
In the next section, we review the Galileo European GNSS formats, including the new
modulation formats .
Among the first innovations to the GPS is the addition of a new civil signal that will be
transmitted at a frequency other than the L1 frequency used by the existing C / A signal . This
new signal is called L2 C because it is issued on L2 and is transmitted by all satellites starting
with Block IIR -M since 2005 . The L2C signal is to improve navigation accuracy by providing
an easy -to-follow signal, and to represent a redundant signal that can be used as an alter native
to local interference .
The presence of civil ian signals from the same satellite immediately gives the advantage of
being able to directly measure and eliminate the err or caused by the ionospheric delay . In the
absence of this measurement, the GPS r eceiver uses a generic correction model or can receive
ionospheric corrections from another source .
The L2C signal contains two distinct pseudorandom (PRN) sequences:
• the CM s equence (abbreviated to the Civil Code of Moderate Length) is 10,230 bits
long an d repeats every 20ms;
• the CL sequence (the Civil L ong abbreviation) is 767,250 bits long and repeats every
1500ms
Each signal is transmitted at a rate of 511,500 bps, but bot h are multiplexed over time to form
a signal at a rate of 1,023,000 bps . The CM s equence is modulated with a 25bps navigation
message (rate is low to facilitate reception in poor reception environments), using the error
correction before, while the CL sequ ence is not modulated with a data signal, being a pilot
signal and allowing robus t signal tracking by the receiver . The L2C signal is formed by BPSK
modulation of the carrier .
Another new signal is the Safety of Life SOL, issued on L5 frequency and implem ented since
the first GPS launch of the GPS IIF . The signal is in the airborne radio navigation band and is
made available to civil aviation .
QPSK modulation is used to combine the phase component of the signal (I5) with the
quadrature component (Q5) . This signal improves the signal structure to optimize performance
using a wider band and a transmitting power greater than the L1 or L2C signals .
To improve anti -jamming performance and to enhance the security of access to military GPS
signals, a new military signal called the M code has been introduced, which is an importa nt
component of the modernization process . The M code is transmitted on the same frequencies
L1 and L2 already used by the code P (Y) . The new signal is chosen so that most of the energy
is placed at the ends of the band, thus avoiding overlapping on P (Y) and C / A carriers . The M
code is designed to be emitted by an antenna with a wide range of directivity, also used to
transmit all other signals, as well as a high gain directional antenna . The directional antenna
can be directed to a certain region of se veral hundred kilometers in diameter, locally increasing
the signal level by 20dB .
The most recently introduced signal is the L1C civil signal to be issued on the same L1
frequency (1575 .42 M Hz) as the C / A signal . The L1C signal was introduced from the first
Block III generation satellite in 2013 . Signal implementation will ensure compatibility with
the C / A signal . It is also planned to issue a (unmodulated) pilot carrier that will improve

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tracking performance of the GPS receiver . Also, the L1C signal is designed to ensure better
interoperability with the Galileo L1 civil signal . Figure 4.6 illustrates the spectr um of the
upgraded GPS signal .

Figure 4.6 – Modernized GPS signal spectrums

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This section focuses on C / A sequences (which are used to get the civil signal L1) as they are
housed in GPS receivers on the market .
Signal Central
Frequency
(MHz) Modulation Data
rate(bps) Bandwidth Code length PRN
L1 C/A 1575 .42 BPSK -R (1) 50 2.046 1023
L1 P(Y) 1575 .42 BPSK -R
(10) 50 20.46 P:6187104000000
Y: encrypted
L2 P(Y) 1227 .6 BPSK -R
(10) 50 2.046 P:6187104000000
Y: encrypted
L2C 1227 .6 BPSK -R (1) 25 20.46 CM: 10230
CL: 767250
(2 sequences PRN
are multiplexed
chip by chip)
L5 1176 .45 BPSK -R
(10) 50 20.46 I5: 10230
Q5: 10230
L1 M 1575 .42 BOC (10,5) undetermined 30.69 encrypted
L2 M 1227 .6 BOC (10,5) undetermined 30.69 encrypted
L1C 1575 .42 Time
Multiplexed
BOC undetermined 4.092 undetermined

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CHAPTER 5
MOBILE POSOTIONING TECHINIQUES
5 Introduction
Standards for mobile cellular communications have not been developed with the objective of
determining the position of the terminals with the precision required by the E911 .The most
accurate information about the location of a mobile terminal is that of its cell, the BSIC (Base
Station Identification Code) being transmitted as general information on the Cell Broadcast
Control Channel (CBCCH) . The network keeps track of the location of the terminals in the two
main databases: in the HLR – as the a ddress of the VLR register on which the mobile terminal
is located, and in the VLR – as the location area address (LAC) the mobile terminal . It is obvious
that software and / or hardware changes in the cellular network and / or mobile terminals must
be ach ieved to achieve greater accuracy in the location of mobile terminals .
There are a lot of vital applications based on mobile user location concerning both civilian and
military services . Positioning accuracy plays an important role in achieving such applic ations .
In literature many methods of mobile user positioning in UMTS network have been introduced,
each has its fundamentals, requirements and levels of accuracy .
5.1 Techniques of cellular positioning
First, an additional network entity must b e introduce d to manage the location of all mobile
terminals, which in the simplest case is a periodically updated database containing positions
with the desired precision of mobile terminals . However, this localization center may be
equipped with the neces sary featur es to calculate these positions and trigger mechanisms to
periodically update them . Depending on the technique used to determine the positions of the
mobile terminals, other software equipment or modules may be included in the network .
Depending on the loc ation and function of the equipment or algorithm for calculating the
position of the furniture with the desired accuracy, the localization techniques are divided into
two main categories:
• Techniques implemented at the communications network leve l. They use equipment
and algorithms usually included in BTS or BSC units . They present the advantages of
a modest cost price increase (BTS units, BSCs are already expensive enough), the
possibility of using powerful computing algorithms due to the large c omputing po wer
(processor and memory) existing in these entities and applicability to existing mobile
terminals in the network because there is no need to change them . However, they have
the disadvantage that they can make the position calculation only whe n the mobil e
terminal is in communication because it is necessary to exchange information between
the terminal and the network; location cannot be accomplished during the period when
the mobile terminal is not engaged in a communication .
• Techniques impleme nted at the mobile terminal level . These techniques require
hardware and software modifications of mobile terminals that allow them to calculate
their position with the desired accuracy and transmit this information to the network .
Their implementation lea ds to highe r mobile cost and cannot use high performance
computing algorithms due to the limited computing power available at the mobile
terminal level . In addition, existing mobile terminals in the network cannot benefit from
the new localization techniqu e. But it h as the major advantage that location can be done
regardless of whether the mobile terminal is engaged or not in a communication .
Position information can be obtained using a Global Positioning System (GPS) receiver

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embedded in the mobile termina l or can be calculated with a dedicated algorithm
through specific message exchanges with fixed network entities . In the latter case, the
role of the mobile terminal can be reduced only to the collection of primary location
information, the computing effor t being tra nsferred to fixed network entities (the
mobile terminal assists the network in determining its position) . Whatever the situation,
information on the position of the mobile terminal must be transmitted by specific
messages to the cellular network location . When the mobile terminal assists the cellular
network in determining the position, there are the disadvantages of increased control
traffic and a longer delay, especially if location information is also required at the
mobile level .
Although loc ating a mob ile terminal with a GPS receiver is done with a very good accuracy,
there are still reservations about the widespread implementation of this solution . The reasons
would be the increased cost of the mobile terminal and the overall dependence on a military
application system which is open to public applications without guaranteeing the availability
of the system at any time . Other drawbacks such as the system's unavailability in densely built
and indoor environments, or the high location error in t he absence of additional equipment have
diminished their importance lately . Given that efforts are currently being made to integrate into
a unique system location of the three global satellite positioning systems: GPS (US), Galileo
(Europe) and Glonass (Russia), it i s estimated that the location of mobile terminals over the
long term using this integrated system can be an effective solution for accuracy, cost and
availability .
5.3 Location of the terminal
The cell identity information (BSIC) that the mobile terminal o btains from the Cell Broadcast
Commo Control Channel (CBCCH) con trol channel if transmitted to the network allows it to
locate cell -level mobile terminal . Unfortunately, this localization is less accurate in rural areas
where the cells are very large . The positioning error can be reduced by special techniques, for
example, by using additional information on the cell sector where the cell is located (if the cell
is sectorized) .
5.4 Measured level of power received by mobile
According to the standard, a mobi le engaged in a communication periodically makes
measurements of the received signal level on the pilot channel of the cell on which it is located
and on the pilot channels of the neighboring cells . The results of these measurements are
transmitted to the network . If we admit that base station antennas are omnidirectio nal, that the
cell area is flat, and that the propagation of the radio waves is identical in all directions in space,
then the constant received power levels curves around a base station are c ircles and the
intersection of the corresponding circles at thre e stations base for power levels reported by
mobile provides mobile position . Unfortunately, the propagation of radio waves in a real
environment is far from complying with the above assumptio ns, so that the steady -state curves
of the power received are ex tremely complicated and difficult to estimate . Moreover, the
reception power level is variable over time (fading) and changes to wide ranges (20 – 40 dB)
over a tenth of wavelength . Long -time mediation of mobiles reported by the mobile can
eliminate errors introduced by fast fading, but those introduced by slow fading (due to
shadowing effect, for example) are hard to estimate and eliminate .

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The received signal The signal after Kalman filtering
Figure 5.4 – Kalman filter

Precisely locating mobile terminals using the results of their power measurements can be
achieved by using more sophisticated data processing methods such as Kalman filtering, for
example. Localization error can be significantly reduced by introducing a Ka lman filter on
mobile positions directly based on the measured power level received. Figure 5.4 shows the
estimated trajectory of a mobile based on the received power reported by the mobile. It is
noticeable that by filtering the initial localization resul ts, the estimated trajectory of the mobile
is very close to the real one (represented by a line bold in the figure).There are also proposals
to store in a very large database the results of the power m easurements reported by the mobile
for long periods of time depending on their calculated location and thus to build the constant
level curves of the received power, appears in a form much closer to the real one. In addition
to the high cost of the solutio n, other disadvantages arise from the large amount of c ontrol
information to be conveyed in the system and the high delay in determining the position of the
mobile terminal due to the long search time in a given database of such dimensions. In addition,
the use of long -term average values to eliminate fading can lead to large localization errors
when the propagation medium changes substantially (intense precipitation, construction
emergence / disappearance, vegetation change, etc.). An interesting applicat ion of the above –
described principle consists in descri bing the distribution of power received by the mobile to
the cell area not by constant curves, but by suitably chosen lengths of trajectories. When
describing discrete points to the power variation rec eived along the segment, other parameters
(synchronizat ion feed, cell identity, location area code, etc.) can be added to individualize the
segment relative to other segments. The set of these parameters forms the footprint of that
segment. The network loc alization center compares the data string containing th e parameters
measured by the monitored mobile with the fingerprints of all the trajectory segments stored in
the database. It is assumed that the position of the mobile is on that segment for which the
difference in measured data from its fingerprint is mi nimal. Since the movement of the mobile
is made on a continuous trajectory, the localization process can be optimized by minimizing
the difference from the fingerprints of a sequence of segments. The m obile trajectory setting is
like that used by the Viter bi detector (maximum like lihood ) to determine the optimal sequence
of states of a signal.
Figure 5.4.1 shows a possible segmentation of mobile trajectories on the area of an urban cell.
The cell area i s divided into circular synchronous feed areas constant ly around the base station.
A mobile moving successively on the 1 -2-3-4-5-6-7-8-9-0-ABCDEF segments can be located
with good precision, following the (maximum) similarity of the data string to be measu red with
the fingerprints of the segments trajectory st ored in the database. The amount of data explored
during the search is greatly reduced by the inclusion of a cell's identity and the timing advance

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in the segment fingerprint. The localization algorith m can easily correct any errors by
observing seamless s equences of segments. In the example of the figure, if the resultant
sequence from the calculation is 1 -2-3-4-5-b-7-8-9-0-e-BC-DEF, it can be easily detected that
the 5 -b-7 and 0 – eB are physical impos sible and therefore can be corrected.

Figure 5.4.1 – Locate the mobile terminal with the trace segment fingerprints
Also , in UMTS networks, it is possible to use the measured power at the reception to locate
mobile terminals because each cell transmits w ith a constant power of 33 dBm on its own pilot
channel (CPICH -Common Pilot Channel). Due to the wider bandwidth of the channel, it is
more efficient to eliminate fading by averaging the measurements, but there may be areas
where mobile terminals do not r eceive enough base stations to perform localization cal culations
(due to much bigger path losses ).
5.5 The AoA method
If the base stations are equipped with antenna arrays , they can determine the direction from
which the wave trans mitted by the mobile ter minal arrives. In a p lane environment, only two
base st ations are enough to locate a mobile terminal, and this is the main advantage of the
method.
The locating error depends on the measurement error of the radio wave arrival direction and
increases as the distance to the base station increases (Figure 5.5). In addition, the method
assumes that only direct wave is received and is therefore not used in densely built urban
environments where direct wave is not received on an important fraction of the cell are a and is
accompanied by many reflected multiplexed waves. In rural areas, direct wave is received on
an important fraction of the cell area, and the small number of base stations required to perform
localization calculations can be an essential asset for s uch environments.

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Figure 5.5 – Locating mobile terminals based on the
the angle of arrival of the radio wave

Finally, the method is more useful i n UMTS networks than in GSM for two reasons: direct
wave is much more present on a UMTS cell than a GSM cell and there are few implementations
of GSM base stations with antenna strings , while the presence of a range of antennas at base
station level is a rule in UMTS networks.
5.6 The ToA method
If the mobile terminals and the base stations in the network are synchronized (have the same
time reference) and if the transmitter inserts a time marker in the trans mitted signal indicating
to the receiver the ti me of the trans mission, then it can calculate the time needed for the radio
wave to travel the trans mitter -to-receiver and hence the value of this distance. The calculation
can be made at the level of the mobile terminal (direct way) or the base station (t he reverse
path); the disadvantage in the first case is that modifications are required in the mobile termin al
structure, and in the second case – that the location is only possible during a mobile terminal
communication. It always counts on direct wave re ception. The distance curves around the
receiver are circles, so there is a need for three base stations to locate unambiguously the mobile
terminal.
If the mobile terminals are not synchronized, only the differences in the time of arrival (TDoA
– Time Dif ference of Arrival) of radio waves at (or from) two base stations (they must have the
same time reference, u sually provided, by a built -in GPS receiver). The constant -distance
curves are hyperboles, so measurements are needed relative to four base stations for
unambiguous location of the mobile terminal. This method is recommended in a differential
form by the G SM standard. The calculations are performed at base station level and the mobile
terminal is forced to request the transfer of the communication to a few base stations to measure
the necessary arrival time differences. For this purpose, the must transmit a ccess bursts to these
base stations, marked accordingly with the time of the broadcast.
At about 3.69 μs period of the bit of information in GSM networks, if one measurement is made
over a bit, there is an error estimating the emitter -receiver distance of about 554 meters. In
UMTS networks, the length of a chip is about 0.26 μs, resulting in an error estimating the
distance of about 78 meters. With four measurements being made per bit (over -sampling) or
chip count, the measurement error decreases to about 2 77 meters in GSM and 19.5 meters in
UMTS respectively. Standard UMTS networks have implemented the mobile positioning
facility at the level
RNC serving nodes, calculation based on the arrival time differences in the UTRAN TDD
(RNC nodes being synchronized ) and based on the observed arrival time differences in the
UTRAN FDD (the RNC nodes not being synchronized). The operator can also allow locatio n
localization calculations on the mobile if they have this built -in feature. Eventual

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synchronization of RNC n odes in UTRAN FDD should be done with great accuracy because a
10 nanoseconds synchronization error results in locating errors of about 3 meters.
Because of the transmission power control (mandatory to c ancel the near -far effect) in UMTS
networks, mobile t erminals that are very close to a base station are no longer able to receive
pilot signals from other base stations, making positioning impossibl e due to of the small
number of base stations in relation to which measurements can be made. To avoid these
situations, the UMTS standard defines a special mode of operation of base stations in which
one of the time windows slots within a 10 millisecond , frame does not trans mit its own base
station (IPDL – Idle Period Down Link) and, as a result, mobile from that cell are able to receive
pilot signals from neighboring base stations and measure arrival time differences. IPDL (Idle
Period Down Link) slots can be organized and grouped, but not in every frame. Also, IPDL
slots can be defined to appear simultaneously in all cells (TAIPDL -Time -Aligned IPDL).
5.7 Hybrid methods
Simultaneous use of two parameters to locate mobile terminals can be a solution for increasing
localization accuracy or avoiding situations where localization is not possible. For example, in
UMTS in rural areas, it is very likely that most of the cell's area cannot be received by more
than one of the neighboring base stations becaus e of the large distances separating them and
none of the localization techniques can provide a solution. But if in addit ion to the OTDoA
algorithm that is implemented in a standard way, the AoA algorithm is also used to locate
mobiles. Note that the use of this hybrid method does not involve changes to the base station
equipment, which is standardly equipped with an array o f antennas that allow for AoA
measurement based on a specialized software package.
Also, in the same rural areas, the location of the mo bile terminals becomes possible even if
only the base station is received if the AoA information adds the base station b ase station –
mobile – base station (RTT – Round Trip propagation Time) as direct wave is received across
the cell area.
Finally, for th e cells deployed along a motorway, the position of the mobile provided by the
AoA algorithm is affected by very high err ors due to the in -line layout of the base stations.
Simultaneous use of the OTDoA algorithm can significantly reduce localization error.
The same combination of algorithms allows to reduce localization error and in areas where
direct wave is less or presen t.
Implementing hybrid methods involves higher localization costs, but the localization error
becomes smaller.

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PRACTICAL PART
GPS TRAC KER
MAIN FEATURES
Introduction
For the practical part of my diploma project , I will set up a tracking system based on GP S
combined with a GSM mobile network.
Short description of the system
The system is designed to send a Short Service Message contain ing the GPS coordinates using
the GSM Network , whenever the system is powered up.
The work contains a hardware part which i s composed by:
❖ Arduino development board
❖ FONA 808 board
❖ PCB
❖ Battery
❖ GSM antenna
❖ GPS antenna
❖ USB cable
❖ SHIELD BO X
The work also contains a software part which is composed by:
❖ Header code <.h>
❖ Source code <.c>
❖ Arduino IDE software

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Hardware components of t he system
ARDUINO DEVELOPMENT BOARD
Arduino is an open -source electronics platform based on easy -to-use hardware and software.
Arduino boards can read inputs – light on a sensor, a finger on a button, or a Twitter message –
and turn it into an output – activating a motor, turning on an LED, publishing something online.
You ca n tell your board what to do by sending a set of instructions to the microcontroller on
the board. To do so you use the Arduino programming language (based on Wiring ), and the
Arduino Software (IDE) , based on Processing .
I choose to use Arduino development board because it is simple and acces sible user experience,
it has been used in thousands of different projects and applications.
Teachers and students use it to buil d low cost scientific instruments, to prove chemistry and
physics principles, or to get start with programming and robotics. De signers and architects
build interactive prototypes.
The main characteristics are:
❖ Inexpensive
❖ Cross platform
❖ Simple, programmi ng environment
❖ Open source for extensible software
❖ Open source for extensible hardware
For my project I choose ARDUINO UNO R3 (ATmega328p).

Figure 6 – Arduino board overview

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TECHNICAL SPECS OF THE BOARD
Operating Voltage 5V
Input Voltage (recommen ded) 7-12V
Input Voltage (limit) 6-20V
Digital I/O Pins 14
PWM Digital I/O Pins 6
Analog Input Pins 6
DC Current per I/O Pin 20mA
DC Current for 3.3V Pin 50mA
Flash Memory 32 KB 0.5 KB use by bootloader
SRAM 2 KB
EEPROM 1 KB
Clock Speed 16 MHz
LED_BUILTIN 12
Length 68.6 mm
Width 53.4 mm
Weight 25 g

Layout of the board:

Figure 6.1 – Arduino board schematic

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Pin Mapping is shown in figure 6.2.

Figure 6.2 – Arduino pinout

For my tracker I used the following pins:
❖ 5V Pin
❖ GND
❖ RX
❖ TX
❖ RST
5V-this pin outputs a regulated 5V from the regulator on the board. The board can be
supplied with power either from the DC power jack (7 – 12V), the USB connector
(5V), or the VIN pin of the board (7 -12V).
GND -Short for ‘Ground’. There are several GND p ins on the Arduino, any of which can be
used to ground your circuit.
RX-This pin is used to receive data from the board
TX-this pin is used to transmit data to the board
RST-comes from “reset” it is a pin used to transmit a software reset.

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FONA 808 BO ARD
Fona is a development board with many integrated features like GSM, GPS ,HTTP.
Is a very stable and reliable board for a project.
I choose this board because can transmit data, without being connected to a pc, fulfill my
requirements for the project , to work independent ly.

Figure 6.3 – FONA board overview
Main characteristics of the board:
❖ Mid cost product
❖ High precision (in terms of GPS and GSM carrier)
❖ Supports open source software and hardware
❖ Small dimensions it can be integrated anywhere, to implement a project

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TECHNICAL SPECS OF THE BOARD

Operating Voltage 5V
Length 69 mm
Width 54 mm
Thickness 4 mm
Weight 25 g

➢ Quad -band 850/900/1800/1900MHz – connect onto any global GSM network with
any 2G SIM;
➢ Fully -integrated GPS ( MT3336 chipset with -165 dBm tracking sensitivity) that
can be controlled and query over the same serial port;
➢ Make and receive voice calls using a headset or an external 32Ω speaker + electret
microphone;
➢ Send and receive SMS messages;
➢ Send and receive GPRS data (TCP/IP, HTTP, etc.);
➢ PWM/Buzzer vibrational motor control;
➢ AT command interface with "auto baud" detection;
GPS specifications:
➢ 22 tracking /66 acquisition channels;
➢ GPS L1 C/A code
➢ Sensit ivity
Tracking: -165 dBm
Cold starts: -147 dBm
➢ Time -To-First-Fix: Cold starts: 30s
• Hot starts: 1s (typ.)
• Warm starts: 28s (typ.)
➢ Accuracy: approximative 2.5 meters

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Pin mapping is shown in Figure 6.4.

Figure 6.4 – Fona pinout

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For my project I used th e following pins:
➢ Vio – This is the pin that is connected with an external voltage from 3V -5V to set the
logic level converter. The converter also buffers the indicator LEDs, so nothing will
appear to work unless this pin is powered! The level voltage is usually set as
microcontroller uses for logic. A 5V micro ( like Arduino) should have it be 5V, a 3V
logic micro should set it to 3V.
➢ Key – This is also a super important pin (but not as important as Vio). This is the power
on/off indicator. It’s also tied t o the button in the top left. Tie this pin to ground for 2
seconds to turn the module on or off. It's not a level signal so it isn't like "low is off,
high is on" – instead you must pulse it for 2 seconds to turn off/on. The module comes
by default off. Ti e this permanently to ground if you never want your micro to turn off
the FONA for power saving
➢ 5V – this is the USB 5V from the microUSB connector when it’s in and powered. Good
if you need to know when the microUSB is plugged in and/or want to recharge t he
battery from an external plug.
➢ PS – this is the Power Status pin. It is low when the module is off and high when the
module has power. If you're using the Key button or pin, you can monitor this pad to
see when the module's booted up. This is tied to th e Pwr LED too.
➢ NS – this is the Network Status pin. It pul ses to signal the status of the module. This is
also tied to the Net LED so for more detail see the LEDs section below.
➢ Reset – this is module hard reset pin. By default, it has a high pull -up (modu le not in
reset). If you absolutely got the module in a ba d space, toggle this pin low for 100ms
to perform a hard reset.
➢ RX & TX – OK now that I made you read all that you can use the UART pins. The
module uses UART to send and receive commands and data. These pins are auto -baud
so whatever baud rate you send "A T" after reset or boot is the baud rate is used. RX is
into the module, TX is out of the module.
➢ RTS – this is the hardware flow control pin. If you turn on flow control on the SIM808
you can use th is pin to stop and start data transfer from the SIM808 to your
microcontroller
➢ RI – this is the Ring Indicator. It is basically the 'interrupt' out pin from the module. It
is by default high and will pulse low for 120ms when a call is received. It can also be
configured to pulse when an SMS is rece ived.
➢ SPK+ and -: This is for connecting an external 32-ohm speaker. This is shared with the
headphone jack. The two pins are differential, so they don't have output DC blocking
capacitors. You cannot connect this to a stereo, powered speakers or other non –
differential amplifier without adding a 100uF+ blocking cap in series to the + pin and
then not using the – pin. Instead, your amp should use GND for the – reference
➢ MIC + and -: this is for connecting an externa l electret microphone, it will bias the mic
with 2V. Most electrets will work just fine. No extra circuitry is required for the mic
such as a biased or amplifier, just wire it up directly!

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Board functionality:
➢ PWR – Blue! Lit when the module is booted a nd running
➢ NET – Red! You can use this for checking the current state without sending an AT
command:
a) 64ms on, 800ms off – the module is running but hasn't made connection to the
cellular network yet .
b) 64ms on, 3 seconds off – the module has contacted the c ellular networ k band can
send/receive voice and SMS .
c) 64ms on, 300ms off – the GPRS data connection you requested is active
By watching the blinks you can get a visual feedback on what’s going on.
➢ Charging – Orange! This is next to the microUSB jack. Indica tes the onboar d lipo
charger is charging
➢ Done – Green! This is next to the JST jack. Indicates that the battery charging is
done, and the battery is full

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SHIELD PCB
This is the board which I used to put together the 2 boards.

Figure 6.5 – PCB Shield

I used this board to connect the two boards more easily, and to have a more compact
design.

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BATTERY
To be a project that works even when it does not have a continuous power supply, I chose to
attach a battery to the project. In case of running on batte ry it can last for 1week.In this time
will maintain a constant supply of the GPS TRACKER.
TECHNICAL SPECS

VOLTAGE 3.7V
CAPACITY 1200mAH
MATERIAL Li-ion
SELF -DISCHARGE RATE 0.35% to 2.5% per month

Li-ion operating principle
In the batteries lithium ions move from the negative electrode to the positive electr ode during
discharge and back when charging. Li -ion batteries use an intercalated lithium compound as
one electrode material, compared to the metallic lithium used in a non-rechargeable lithium
battery . The batteries have a high energy density , no memory effect and low self-discharge .
I choose li -ion for my project because:
➢ They're generally much lighter than other types of recharge able batteries of the
same size.
➢ A lead-acid battery can store only 25 watt -hours per kilogram. Using lead -acid
technology, it takes 6 kilograms to store the same amount of energy that a 1kilogram
lithium -ion battery can handle.
➢ They have no memory effect , which means that you do not have to completely
discharge them before recharging, as with some other battery chemist ries.
➢ Lithium -ion batteries can handle hundreds of charge/d ischarge cycles.
➢ They hold their charge. A lithium -ion battery pack loses only about 5 percent of its
charge per month, compared to a 20 percent loss per month for NiMH batteries.
➢ Lithium is also a highly reactive element, meaning a lot of energy can be st ored in
its atomic bonds.

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I used a battery from an old notebook ,it is shown in Figure 6.6.

Figure 6.6 – Li-ion Battery

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GSM ANTENNA
To send a fast -short message service, without any delays, and with 100 % availability of the
carrier, I decided to use an antenna attached to the FONA board.
TECHNICAL SPECS

GAIN 3dBi
Bandwidth 850/900/1800/1900/2100 MHz
Length 75 mm
Thickness 3 mm
Weight 0.5g
Connector fuel

Figure 6.7 – GSM Antenna

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GPS ANTENNA
Antennas are a critical part of any GPS receiver design and their importance cannot be stated
highly enough. Even the best receiver cannot bring back what has been lost due to a poor ant
enna, in-band jamming, or a bad RF board design.
GPS signals are extremely weak and present unique demands on the antenna. The choice and
implementation of the antenna can ultimately play a significant role in GPS performance.
TECHNICAL SPECS
Frequencies 1575.42 MHz
Max Gain 14.5 dB
Noise figure 1.5 dB
Polarization RHCP
Voltage supply 1.5 V – 3.6 V
Curren t 4 mA
Power 14.4 mW
Operating temperature -40°C to +85°C
Length 18.5 mm
Width 18.5 mm
Thickness 4.7 mm
Cable length: 10 cm

A GPS receiver needs to receive signals from as many satellites as possible. Optimal
performance will not be available in narrow streets and underground parking lots or if objects
cover the antenna. Poor visibility may result in position drift or a prolong ed Time -To-First-Fix
(TTFF). Good sky visibility is therefore an important advantage. A GPS receiver will only
achieve the specified performance if the average carrier to noise power density ratio (C/N0) of
the strongest satellites reaches at least 44 dBHz . In a well -designed system, the average of the
C/N0 ratio of high elevation satellites should be in the range between 44 dBHz and about 50
dBHz. With a standard off -the-shelf active antenna, 47 dBHz should easily be achieved.

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I choose this antenna for my tracker because of his features, like precision, and low level of
noise it is shown in the figure 6.8.

Figure 6 .8 GPS Antenna

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SHIELD BOX
This is the final version that I successfully implemented on the car.

Shield box without cover

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Software components
Introduction
Computer software , or simply software , is a collection of data or computer instructions that tell
the computer how to work. This is in contrast to physical hardware , from which the system is
built and performs the work. In computer science and software en gineering , computer software
is all information processed by comp uter systems , programs and data. Computer software
includes computer programs , libraries and related non -executable data, such as online
documentation or digital media . Computer hardware and software require each other, and
neither can be realistically used on its own.
Implementation goal in the project
Since I wanted my project to be special on the GSM network side, I first encountered a few
issues regarding how I can send a message, I took some time to configure the code.
That`s why I choose to use Ardu ino ide ,the programming language is C.
C programs range from those that are quite simple to those that are very co mplex. In the
embedded world, many programs will tend toward the simple side of the spectrum, and the
basic programming elements described below provide a good foundation for further study of
C-language firmware development.

Header code <.h>

A header fil e is a file with extension .h which contains C function declarations and macro
definitions to be shared between several source files. There are two types of header files: the
files that the programmer writes and the files that comes with your compiler.
You request to use a header file in your program by including it with the C preprocessing
directive #includ e, like you have seen inclusion of stdio.h header file, which comes along
with your compiler.
Including a header file is equal to copying the content of the header file but we do not do it
because it will be error – prone and it is not a good idea to copy t he content of a header file in
the source files, especially if we have multiple source files in a program.
A simple practice in C or C++ programs is that we keep all the constants, macros, system wide
global variables, and function prototypes in the header files and include that header file
wherever it is required.
The #include directive works by directing the C preprocessor to scan the specified file as
input before continuing with the rest of the current source file. The output from the
preprocessor conta ins the output already generated, followed by the output resulting from the
included file, followed by the output that comes from the text after the #include directive .

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Description of the system

For the system to be better understand, a simple sketch of the system was drawn.
Car ignition
turned on
•It produces a 5V
signal,coresponding
to 1 logic level
•Arduino board starts
FONA board starts up
•GPS starts to fix
•The coordinates are
gathered
GSM network module
starts
•The autentification on
carrier is made

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PART 1

Initialization of all system is done when the car ignition is turned on, only then the power outlet
which stands in in trunk of the car is getting power. This made the entire system much more
reliable, because it only sends data when the car is started, a real situation, when someone bad
indentation to steal the car.
On the other part, the battery last for long only if the tracker is working if the car is started.
The power outlet maintains a voltage of 12V,in order to get a 5V signal a voltage stabilizer is
used.
After t he Arduino detects 5V signal, it starts the initializing process, consisting of starting the
CPU,RX and TX pins are initialized, that means the serial communication is started.

PART 2

FONA board is starting after it gets a signal from Arduino board.
If it is a cold start it could take up to 1 -2 minutes for the board to start, after that the GPS
module is starting to get the location, this take some time if it is a cold start.
To get the coordinates, it requ ires fourth satellite, because the four spheres of possible position
around the satellites intersect at only one point (the effective location of the device).
After few minutes the coordinates are gathered and are ready to be transmitted.

PART 3

On this part cellular network is needed, the system doe s not depend on a fixed connection like,
WI-FI, Bluetooth or LAN, because the system will be always on move. That`s the purpose of
implementing GSM network on the system.
GSM network module is initializing it is a fast one, it takes about 1 minute for the sim card to
be initialized on the network.
For the user to be registered on the network it needs an APN and a password.
After the part of authentication is done, a message containing the coordinates in this format:
➢ Latitude in degrees , minutes and seconds
➢ Longitude in degrees , minutes and seconds
A message is sent when all starts, and after messages are sent within a specified delay, it can
start from 5minutes, to 1h. Not so often because can became annoying when the car is used
daily. But in an emergency situation the delay should be as small as possible.

PART 4

After the car ignition is turned off, the system automatically shuts down, and stop transmitting
information .

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Overview at the message received
The message received from the GPS Tra cker is shown in figure bellow.

Conclusion

To show the GPS features I used this practical part.
In the feature this kit will be upgraded by making a waterproof shield, more than that it will be
connected, directly, to the ECU.
So, it can send more that GPS coordinates. Temperature inside the car, temperature of coolant
fluid, speed, rpm.
More than that these parameters, also will be displayed on an android application.

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Annexes
1. Header code
Adafruit_FONA.h is the board standard header file; all the functionalities of the board are
placed in that file.
SoftwareSerial.h is one of Arduino standard header, contains information about serial
communication.

#include "Adafruit_FONA.h"
#define FONA_RX 2
#define FON A_TX 3
#define FONA_RST 4
#include <SoftwareSerial.h>
2.Source code
The code I wrote is a simple one because all the functions are stored in the .h file.
This part of the code is responsible for the startup of the system, the initialization of the
communication. Set a system refresh rate.

void setup() {
while (! Serial);
Serial.begin(115200);
fonaSerial ->begin(4800);
if (! fona.begin(*fonaSerial)) {
while(1);
}
}
3.
This part is the main function, in the first par t initialize the variables, the second part is
responsible for reading writing variables on the boards.
Last part is for transmitting the message via GSM Network.

void loop() {

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float latitude, longitude;
boolean gps_success = fona.getGPS(&latitude, &longitude);
{;
if (fona.getNetworkStatus() == 1) {
boolean gsmloc_success = fona.getGSMLoc(&latitude, &longitude);
if (gsmloc_success) {
Serial.print("GPSLoc lat:");
Serial.println(latitude, 6);
Serial.print("GPSLoc long:");
Serial.print ln(longitude, 6);
fonaSS.print("AT+CMGF=1 \r");
fonaSS.print("AT+CMGS= \"0743458604 \"\r");
fonaSS.println("Your car GPS coordinates: ");
fonaSS.print("Latitude: ");
fonaSS.println(latitude, 6);
fonaSS.prin t("Longitude: ");
fonaSS.println(longitude, 6);
fonaSS.print(" \r");
delay(10000);
fonaSS.println((char)26);
fonaSS.println();
} else {
Serial.println(F("Enabling GPS"));
if (!fona.enableGPRS(true)) {
Serial.println(F("Failed to turn GPRS on"));
}
}
}
}
}

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Bibliography
1.Ion Bogdan – Course Notes Mobile Communications
2.Ion Bogdan – Global navigation satellite systems
3.M.Abo -Zahhad, Sabah M. Ah med, M. Mourad -Hybrid Uplink -Time Difference of
Arrival and Assisted – GPS Positioning Technique
4.Ciprian Comsa – Course Notes Digital Communication
5. https://www.Wikipedia.org/
6. https://www.blil ey.com/company -history/ Figure 1
7. http://what -when -how.com/gps/introduction -to-gps/ Figure 2
8. http://uregina.ca/~sauchyn/g eog411/orbits.gif/ Figure 2. 1
9. http://what -when -how.com/a -software -defined -gps-and-galileo -receive r/ Figure 2.2
10. http://wallsviews.co/tdma -frame -structure/ Figure 3.2.1
11. https://www.researchgate.net/ figure/TDMA -Frame -structure_fig14_324694254/ Figure
3.3
12. https://www.ques10.com/p/14050/explain -in-detail -tdma -cdma -and-fdma -1/ Figure 3.4
13. https://www.e -education.ps u.edu/geog862/node/1867/ Figure 4.6