emergency alert system using fm band hilmi mujahid `adli bin husin

EMERGENCY ALERT SYSTEM USING FM BAND
HILMI MUJAHID ‘ADLI BIN HUSIN
UNIVERSITI TEKNOLOGI MALAYSIA
EMERGENCY ALERT SYSTEM USING FM BAND
HILMI MUJAHID `ADLI BIN HUSIN
A report submitted in partial fulfillment of
requirements for the award of the degree of
Bachelor of Engineering (Electrical-Telecommunication)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
MAY 2011
iii
Dedicated to my beloved parents
iv
ACKNOWLEDGEMENTS
All praise be to Allah, the Almighty, the Benevolent for His blessing and
guidance for giving me inspiration and spirit to embrace on this journey and
inculcating patience in my heart complete my final year project successfully.
I would like to acknowledge my supervisor, Dr. Sharifah Kamilah Syed
Yusof for advice, giving the idea and knowledge in my final year project. Without
her help, maybe I cannot complete this project in timely fashion.
I would like to thank also to Arief Marwanto, Mohd Adib Sarjari and
Muhammad Haikal Satria for giving guidance and cooperation to complete my final
project.
I am particularly indebted to my friends for their supports and guidance. Last
but not least, I would like to thank others who I may left out for their help and
encouragement.
v
ABSTRACT
Conventional FM transmission system commonly utilizes a combination of
hardware and software structures. However, the system is lack of flexibility because
the design is focus on hardware-based development. The purpose of this project is to
design a FM transmission system with sole purpose to broadcast emergency message
signal to general population. The focus of this system is to implement Software
Defined Radio (SDR) in the design. The advantage of using SDR is because of the
flexibility, which is able to reconfigure back easily should the transmission scheme
change. SDR implementation comprises of hardware and software structure. The
software structure is highlighted on GNU Radio while the hardware structure is
Universal Software Radio Peripheral (USRP). In order to transmit and receive FM
wave signal, GNU Radio software is responsible to control all the process needed
such as modulation and demodulation of FM signal. USRP only act as a platform to
receive and transmit signal only. The performance of this system will be analyzed
using developed FM receiver and standard FM receiver such as FM radio. The total
expenditure will be minimised and reconfigurable emergency alert system will be
applicable for future applications
vi
ABSTRAK
Kebiasaannya, sistem perhubungan radio FM konvensional terdiri daripada
gabungan struktur perkakasan dan perisian. Walaubagaimanapun, sistem ini
kekurangan ciri-ciri fleksibel kerana rekabentuknya lebih kepada pembangunan
perkakasan. Tujuan projek ini adalah merekabentuk sistem perhubungan radio FM
dengan tujuan utamanya ialah untuk menyebarkan isyarat kecemasan kepada orang
ramai. Fokus utama dalam projek ini ialah mengiplementasikan Software Defined
Radio
(SDR)
didalam
rekabentuk.
Kelebihan
menggunakan
SDR
ialah
kefleksibelannya, dimana sesuatu sistem dapat diubah semula sekiranya corak
penghantaran isyarat berubah. Implementasi SDR merangkumi struktur perkakasan
dan perisian. Untuk struktur perisian, ia lebih fokus kepada penggunaan GNU Radio,
manakala untuk perkakasan ialah Universal Software Radio Peripheral (USRP).
Untuk menghantar dan menerima isyarat, GNU Radio akan melakukan segala proses
seperti modulasi dan demodulasi isyarat FM. USRP hanya bertindak sebagai pelantar
untik menghantar dan menerima isyarat radio sahaja. Prestasi sistem ini akan
dianalisa menggunakan penerima FM yang direka dan penerima FM biasa seperti
radio FM. Jumlah kos untuk sistem ini adalah rendah dan boleh digunapakai untuk
masa hadapan.
vii
TABLE OF CONTENTS
CHAPTER
1
2
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF ABBREVIATIONS
xiv
LIST OF SYMBOLS
xvi
INTRODUCTION
1
1.1
Overview
1
1.2
Problem Statement
3
1.3
Objective
4
1.4
Scope of Work
4
1.5
Thesis Outline
5
LITERATURE REVIEW
6
2.1
Introduction
6
2.2
Emergency Alert System
6
2.2.1 Introduction
6
2.2.2 History of Emergency Alert System
7
viii
2.3
2.4
2.2.3 Activation Procedure
8
FM Architecture
9
2.3.1 Introduction
9
2.3.2 FM Basic
10
2.3.3 Modulation Index
12
2.3.4 FM Broadcast
13
2.3.5 FM Stereo Transmitter
14
2.3.6 FM RDS
16
2.3.7 FM in Malaysia
17
Software Defined Radio (SDR)
18
2.4.1 Hardware
23
2.4.1.1 USRP
23
2.4.1.2 Daughterboard
24
2.4.1.3 Analog-Digital-Converter (ADC)
25
2.4.1.4 Digital-Analog-Converter (DAC)
25
2.4.1.5 Field Programmable Gate Array
26
2.4.1.6 Programmable Gain Amplifier
26
2.4.1.7 USB 2.0 Controller
26
2.4.2 Software
3
27
2.4.2.1 GNU Radio
27
2.4.2.2 GNU Radio Companion
28
2.4.2.3 Python
29
2.4.2.4 C++
30
METHODOLOGY
31
3.1
Methodology of the Project
31
3.2
System Architecture
32
3.2.1 Hardware Structure
32
3.2.2 Software Structure
33
3.2.2.1 GNU Radio Installation
3.3
34
System Design in Software Structure
35
3.3.1 Transmitter Design
36
3.3.1.1 Stereo Channel Transmitter
36
3.3.1.2 Multiple Channel Transmitter
42
ix
4
5
3.3.2 Receiver Design
41
3.4
System Setup
45
3.5
Activation of Proposed Emergency Alert System
47
RESULT AND ANALYSIS
48
4.1
Introduction
48
4.2
Performance Analysis of FM Emergency System
48
4.3
Performance Analysis on Stereo Transmission
50
4.4
Performance Analysis on Multiple Channel Tx
52
4.5
Overall Signal Transmission Performance
54
CONCLUSION
56
5.1
Conclusion
56
5.2
Recommendation and Future Work
56
REFERENCES
58
x
LIST OF TABLES
TABLE NO.
2.1
TITLE
Different Frequency Assigned for Different
PAGE
18
Radio Station at Different Location
2.2
USRP Daughterboards
24
xi
LIST OF FIGURES
FIGURE NO.
TITLE
PAGE
1.1
Universal Software Radio Peripheral (USRP)
3
2.1
Frequency Modulation
10
2.2
Block Diagram Shows the Steps to Generate
11
FM Signal
2.3
Quadrature Modulator
12
2.4
FM Spectrum Frequency
14
2.5
FM Stereo Transmitter Block Diagram
15
2.6
Stereo FM Signal Spectrum with RDS
16
2.7
Common Use of RDS in FM, In This Case
17
Showing Name of the Radio Station and Name
of the Song Being Broadcast
2.8
(a) Conventional Radio, (b) SDR
19
2.9
SDR Design Principle
20
2.10
Combination of USRP and GNU Radio
21
2.11
Universal Software Radio Peripheral (USRP)
22
2.12
Block Diagram of USRP
25
2.13
USRP Motherboard
25
2.14
GNU Radio Architecture
28
2.15
Dial-tone Example in GRC
29
2.16
Python Code of Dial-tone Example
30
3.1
Flow Chart of the Project Plan
31
3.2
GNU Radio and USRP Block Diagram
32
3.3
Software Structure
34
3.4
Block Diagram for Stereo FM Transmitter
37
xii
3.5
Design of Stereo Transmission for Emergency
38
Alert System
3.6
GRC Design of Stereo Transmission for
39
Emergency Alert System
3.7
Design of Multiple Channel Transmission for
40
Emergency Alert System
3.8
GRC Design of Multiple Channel Transmission
41
for Emergency Alert System
3.9
GRC Design of the FM Receiver
43
3.10
FM Spectral Analyzer
44
3.11
Portable Radio
45
3.12
The Suitable Distance of USRP Receiver to
46
Analyze Emergency Signal Transmission
3.13
Setup for Performance Analysis of the
46
Emergency Alert System
3.14
How Emergency Alert System Using FM Band
47
Works
4.1
Original IKIM.FM Spectrum
49
4.2
Original FM spectrum between 104.5 MHz to
50
107.8 MHz
4.3
Modulated Signal of the Emergency
51
Message for Stereo Transmission
4.4
Received FM spectrum shows the effect of
52
emergency signal overlap with original IKIM.FM
signal
4.5
Transmitted Emergency Signal at 105.7 Mhz,
53
106.2 Mhz, and 106.7 Mhz
4.6
FM Spectrum Shows the Radio Station Signals
54
for Muzik FM, IKIM.FM and Klasik Nasional
have been Distorted by the Emergency Signal
4.7
Unwanted Fluctuations
55
xiii
LIST OF ABBREVIAIONS
ADC
-
Analog-Digital-Converter
AM
-
Amplitude Modulation
DAC
-
Digital-Analog- Converter
DDC
-
Digital Down Converting
DSP
-
Digital Signal Processing
EAN
-
Emergency Alert Notification
EAS
-
Emergency Alert System
EBS
-
Emergency Broadcast System
FCC
-
Federal Communications Commission
FEMA
-
Federal Emergency Management Agency
FM
-
Frequency Modulation
FPGA
-
Field Programmable Gate Array
GRC
-
GNU Radio Companion
IF
-
Intermediate Frequency
NWS
-
National Weather Service
OS
-
Operating System
OSS
-
Open Source Software
PGA
-
Programmable Gain Amplifier
RBDS
-
Radio Broadcast Data System
RDS
-
Radio Data System
RF
-
Radio Frequency
RTM
-
Rancangan Televisyen Malaysia
RX
-
Receiver
SDR
-
Software Defined Radio
US
-
United States
USB
-
Universal Serial Bus
xiv
SWIG
-
Simplified Wrapper and Interface Generator
TX
-
Transmitter
TV
-
Television
UHF
-
Ultra High Frequency
VHF
-
Very High Frequency
WAV
-
Waveform Audio File Format
xv
LIST OF SYMBOLS
MHz
-
Megahertz
Hz
-
Hertz
MB
-
Megabits
bps
-
Bit per Second
kHz
-
Kilohertz
s
-
Second
dBm/dB
-
Decibel
1
CHAPTER 1
INTRODUCTION
1.1
Overview
On the 26th of December 2004, a megathrust earthquake of magnitude of 9.3
occurred at the seabed of the Indian Ocean. The resulting event had triggered a series
of devastating tsunamis along the coasts of several countries bordering the Indian
Ocean. Nearly 230,000 people in fourteen countries were killed because of this
natural disaster.
Even though this natural disaster was unavoidable, but the death toll could
have been reduced if the population in the affected area were alerted earlier. This is
due to a lag of up to several hours between the earthquake and the impact of tsunami.
Moreover, nearly all the tsunami victims were taken completely by surprise. During
that time, there were no tsunami warning systems in the Indian Ocean to detect
tsunamis or to alert and handle general population living nearby. This is because the
setting up of communication infrastructure to notify timely warnings is quite a
problem, especially in poor parts of the world.
2
Therefore, public awareness and preparedness is a key element in proper
handling of any type of emergency. In cases of public welfare threatening
emergencies, quick notification and guidance to public could reduce the human and
economic cost of the emergency significantly. In order to broadcast emergency
information promptly to civilians, the system must be capable of notifying them
using all sorts of available channel and medium of communication.
One of the reliable media to dissipate emergency message is through FM
spectrum. FM medium is considered as a popular mass medium even though TV has
more viewers than FM listeners. In Malaysia, there are total of 53 FM radio stations
nationwide, where 19 of them are private and others are government -owned.
Therefore, FM spectrum band can be a reliable mechanism to dissipate emergency
messages.
In Malaysia, the radio station frequency varies in different locations. In
addition, not all locations have the same radio broadcast reception. As an example, in
rural area, the people only get to hear government-owned or states-oriented FM radio
station. Contrary to more busy area, the people have more options of choosing radio
stations other than government-owned. Based on that fact, if the emergency alert
system is going to be developed, it must be flexible and nomadic due to different
frequency of radio station relative to demographic of Malaysia.
One way to achieve it is to develop a system based on software-controlled.
Software-controlled based system provides the user ability to configure back or
change the system setting should the transmission scheme changes. SDR or also
known as Software Defined Radio provides service providers to develop any RF
system based on software-controlled. The design principle behind SDR is to bring
software code nearly as possible to radio antenna. This is achieved by using
hardware that translates radio waves to a data stream, which a computer can handle.
The hardware too should be transparent from the view of software.
3
The popular implementation of SDR is a combination of Universal Software
Radio Peripheral (USRP) hardware element with the GNU Radio software toolkit.
USRP or also known as Universal Software Radio Peripheral is a RF hardware,
which functions to transmit and receive RF signal only. It also digitizes the analog
signal captured from RF world and conveys it in the for m of data stream to host
computer. GNU Radio is software installed in a host computer, which functions as a
DSP processor and controls the USRP.
Figure 1.1: Universal Software Radio Peripheral (USRP)
1.2
Problem Statement
Emergency alert message can be disseminated to the public society by
utilizing FM band. However, conventional FM transmission system is lack of
flexibility in terms of reconfigurable and ease of deployment. Thus, flexibility is a
main concern in the proper and effective system of emergency alert because one of
the purpose is to increase the convenience and deployable at any place, any time.
4
1.3
Objective
There are three main objectives of this project:
i.
To develop flexible emergency alert system using FM band via SDR using
GNU Radio and USRP
ii.
To study the interface between the hardware and software development for
emergency alert system using FM band
iii.
To analyse the performance of the emergency signal transmission system
using the SDR
1.4
Scope of Work
The focus of this project is to notify FM listener, therefore emergency alert
message will be broadcasted through FM spectrum. Moreover, the FM spectrum is
between 88 MHz to 108 MHz.
In this project, SDR implementation will be used to increase the flexibility
and mobility of the system. The design principle behind SDR is to bring the software
near to the radio antenna as near as possible. This means most of the signal
processing is software controlled.
GNU Radio and USRP are the most important elements in this softwarebased project.
and RF world. GNU Radio is a software toolkit used to drive and acquire data from
USRP. Before using the USRP, one must choose the correct daughterboard for the
USRP to works in suitable spectrum. Thus, WBX daughterboard will be used
because it covers FM spectrum.
5
1.5
Thesis Outline
This thesis is divided into five chapters. Each chapter will focus on different
issues related to the project.
Chapter 2 focuses on the literature review corresponding with the project. It
provides a better platform of understanding before proceeding to next chapters.
Specifically, the areas addressed will be emergency alert system, FM architecture
and SDR implementation. Chapter 3 shows the techniques to develop the system. It
consists of technique and method used to develop and setup the system. The result
and discussion will be discussed in Chapter 4. Last but not least is Chapter 5, which
discusses the conclusion and recommendations for future work of this project.
6
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
This chapter includes the study of emergency alert system, FM architecture,
and Software Defined Radio (SDR). It also briefly discusses on GNU Radio and
USRP hardware, which are the main part utilized in this project.
2.2
Emergency Alert System
2.2.1 Introduction
Nowadays, the emergency alert system is available on television, radio
media, and mobile communication to provide effective information spread all over
general population. Demographic studies in Malaysia have shown an increasing
pattern towards the coverage of FM radio reception. Moreover, this pattern is
associated with the increasing number of new radio channels. In this project, an
7
emergency alert system is developed and focused on the FM listeners. Although
there are many medium to dissipating the information to general population, this
project is a stepping-stone for more comprehensive emergency system.
Generally, this section is concern on Emergency Alert System utilized in
United States (US) because currently Malaysia still developing their own emergency
alert system. Emergency Alert System (EAS) has been used in US more than forty
decade. Many countries have implemented their own emergency alert system by
following US system model.
2.2.2 History of Emergency Alert System
The brief history of the emergency alert system is mainly focus on national
warning system in United States (US). In 1963, the Emergency Broadcast System
(EBS) was developed as a national warning system. The sole purpose of this system
is to provide the US president with a swift method of communicating with the people
of United States in the event of war, threat of war, or solemn national crisis. Even
though the system never activated for national emergency, it was used over 20,000
times from 1976 until 1996 to broadcast civil emergency messages and warning
about severe weather hazards.
The Emergency Alert System (EAS) was put into place in 1997 to replace
EBS. The function of EAS is still same as EBS. In addition to cover local
emergencies such as hurricanes, the official EAS is designed to let the US president
to talk to United States around 10 minutes. The EAS is controlled by Federal
Communications Commission (FCC) in joint with National Weather Service (NWS)
and Federal Emergency Management Agency (FEMA). EAS plan has been planted
in every state and several territories in America to increase its effectiveness and
8
coverage. It also covers AM, FM and Land Mobile Radio Service, as well as VHF,
UHF and cable television.
In Malaysia, the emergency alert system is still in development process.
Although Malaysia is said to be safe from hurricane and tornado, in 26 of December
2004 has been a wake-up call for this country to install the system. Hundreds of
people in west coast of Malaysia become tsunami victims because they w ere
unaware of incoming tsunami. The tsunami is reported coming from Sumatera due to
earthquake happening in seabed of Indian Ocean. Summing up all the victims in
other fourteen country, nearly 230,000 people killed by this nature cause. This
statistics maybe can be reduced if the countries equip an early emergency alert
system to warning people about an incoming natural disaster.
2.2.3 Activation Procedure
Activation of the EAS is originated from primary station that would transmit
the Attention Signal. The Attention Signal was a combination of 853 Hz and 960 Hz,
an interval suited to draw audience collective attention. Every relay station equipped
with a decoders which will sound an alarm, alerting the station operators to the
incoming messages. Each relay station would broadcast the alert tone and repeat the
emergency message from primary station.
For a whole country activation of EAS, the Emergency Action Notification
(EAN) will take place. While this event happens, every broadcast stations wer e not
allowed to ignore it. However to activate EAN, much stricter protocol must be follow
first to avoid abuse and mistakes. Some of the protocol is to enter the confirmation
password, which changed daily before activating the system.
9
2.3
FM Architecture
2.3.1 Introduction
Modulation is a process of deliver a message signal such as analog audio
signal inside another signal that can be physically transmitted. Common modulation
of analog signal is to transform a baseband signal message into passband signal, for
example low frequency audio from radio operator into a radio frequency signal (RF
signal). The purpose of the modulation is to increase the effectiveness of the signal
transmission system. It also can reduce the size of the antenna, reduce the noise
effect and allowing multiplexing process where several information signals can be
transmit in one channel simultaneously.
The common modulation methods are divided into three, which are analog
modulation, digital modulation and pulse modulation. In analog modulation, a sine
wave is used as carrier signal. Generally, the carrier signal can be mathematically
defined as:
Equation above represent
as carrier frequency,
carrier phase. In amplitude modulation (AM),
signal. However, in frequency modulation (FM),
as carrier amplitude and
as
vary linearly with information
vary linearly with information
signal
In analog modulation, the modulation is applied continuously in response to
the analog information. Common analog information methods are:
i.
Amplitude modulation (AM)
ii.
Frequency modulation (FM)
10
In this project, frequency modulation (FM) will be used rather than analog
modulation. This is because of the advantages offered by FM compared to AM. The
advantage are noise resilience, fidelity enhancement and to increase the effectiveness
of power usage. However, there also several drawbacks of FM such as bigger
bandwidth needed and the complexity of FM transmitter and FM receiver circuit.
2.3.2 FM Basics
Frequency Modulation (FM) is a type of modulation in which changes in the
carrier signal frequency correspond directly to changes in the baseband signal. FM is
considered an analog form of modulation because the baseband signal is typically an
analog waveform without discrete values.
Basic theory behind FM is the amplitude of an analog baseband signal can be
represented by a frequency different of the carrier. This can be represents by this
relationship in the graph in Figure 2.1.
Figure 2.1: Frequency Modulation
The graph from Figure 2.1 depicts the relation of various amplitudes of baseband
signal (white) to specific frequencies of the carrier signal (red). Mathematically, it
11
can be represents by describing the equations which characterize FM. Basically,
message or baseband signal is represented by simple designation,
. Then, the
sinusoidal carrier is defined by this equation:
The required process of modulating a baseband signal,
, onto the carrier
requires a two steps. First, the message signal must be integrated with respect to time
to yield an
modulation process because phase modulation is directly straightforward with typical
I/Q modulator circuitry. A block diagram description of an FM transmitter shows in
Figure 2.2.
Vm(t)
Figure 2.2: Block Diagram Shows the Steps to Generate FM Signal
The block diagram above illustrates the integration of a message signal,
which results in an equation for phase with respect to time. The equation is defined
by the following equation:
12
where
is the frequency sensitivity. The resulting modulation that must occur is
phase modulation, which involves changing the phase of the carrier over time. This
process is directly straightforward and requires a quadrature modulator, shown in
Figure 2.3 below.
Figure 2.3: Quadrature Modulator
As a result of phase modulation, the resulting is FM signal,
defined as:
Simply the equation can be defined as:
2.3.3 Modulation Index
. This equation is
13
The important aspect of FM is the modulation index. Modulation index is
defined as the factor that determines the exact proportions of carrier deviates from its
center frequency. Mathematically, the integrated baseband signal is defined as
follow:
The equation can be simplified as:
in the equation above is the frequency deviation, which represents the maximum
frequency difference between the instantaneous frequency and the carrier frequency.
In fact, the ratio of
to the carrier frequency is the modulation index ( ).
As a result, after corresponding substitution of the equation, the final modulated FM
signal defined as follow:
The modulation index is important because it affects modulated signal. The greater
modulation index, the greater instantaneous frequency can be from carrier.
2.3.4 FM Broadcast
14
FM broadcast technology was found by Edwin Howard Armstrong, who used
frequency modulation (FM) to provide high fidelity sound over broadcast radio. The
broadcast band for FM broadcast lie within VHF part of radio spectrum. Commonly
88 to 108 MHz is utilized.
Figure 2.4 shows frequency spectrum for commercial FM broadcast. The
frequency range is from 88 MHz until 108 MHz and can allocate a hundred radio
channels. Every channel is separated with guard band (25 kHz) at every edge of the
channel bandwidth. Maximum bandwidth allocated for a channel is around 200 kHz.
In addition, if the radio channel has bigger bandwidth than allowed, the adjacent
radio channel will distorted.
CH 1 CH 2 CH 3
108 MHz
CH
100
88.1MHz
Figure 2.4: FM Spectrum Frequency
2.3.5 FM Stereo Transmitter
FM system is capable to deliver high quality or high fidelity sound due to low
effect on noise. This manner can be achieved by using stereo FM transmitting
technique. However, stereo FM requires slightly bigger bandwidth and quite
complex circuit for transmitter and receiver.
15
In a stereo system, two sources of sound or voice, which is right (R) and left
(L) will be transmitted simultaneously. This kind of sound delivering technique is
intended to produce a high quality sound. Figure 2.5 shows the technique use to
generate stereo FM.
TX
Figure 2.5: FM Stereo Transmitter Block Diagram
Output from sound source such as microphone or WAV file source, which are
L and R were combined to produce L+R and L-R signal. Each signal is bandwidthlimited to 15 kHz. A carrier pilot signal of 19 kHz is produced, and doubled its value
into 38 kHz to serve as subcarrier. A modulated signal of subcarrier and L-R signal
will be added together with L+R signal and carrier pilot signal before it transmitted
via FM modulation. The resulting of stereo FM is shown in signal spectrum in the
Figure 2.6.
16
Figure 2.6: Stereo FM Signal Spectrum with RDS
2.3.6 FM RDS
Radio Data System or RDS is a standard of communication protocol for
embedding small amounts of digital information in conventional FM radio broadcast.
Commonly RDS includes several types of information transmitted such as time,
station identification and program information. Thus, the FM receiver needs to
decode the RDS data before display it in the radio display. Commonly car radio and
built in mobile phone radio capable to decode RDS data and display it on the radio
display. In US, the RDS is officially named as RBDS or Radio Broadcast Data
System.
Basically, the RDS carry 1,187.5 bits per second data on a 57 kHz subcarrier.
The subcarrier for RDS is set to the third harmonic of the FM pilot tone (19 kHz) to
reduce the interference and intermodulation between the stereo pilot (38 kHz). Figure
2.6 shows the spectrum of FM radio station with RDS on the rightmost of the
spectrum.
17
The following Figure 2.7 illustrates the common use of RDS in FM radio
station. The other use of RDS in FM is to display information, news, weather
forecast and emergency alert.
Figure 2.7: Common Use of RDS in FM, In This Case Showing Name of the Radio
Station and Name of the Song Being Broadcast
2.3.7 FM in Malaysia
There are total of 53 radio stations spreading over Malaysia where 19 of them
are private-owned and others are government-owned. Radio Televisyen Malaysia
(RTM) group is responsible on operating and managing government radio station.
Commonly RTM group divides and manage their radio stations based on different
states of Malaysia. However, the private-owned radio station such as Media Prima
has several radio stations under their operation, and it reception is spread all over
Malaysia. In Malaysia, there are several FM radio operators also use RDS protocol to
transmit RDS data in their FM spectrum.
Most of radio stations in Malaysia have different reception frequency. As an
example, in Skudai, Johor, the frequency for IKIM.FM is assigned at 106.2 MHz,
while at Dungun, Terengganu, the frequency for same radio station is at 87.8 MHz.
This is because the transmission towers use different frequency to broadcast radio
18
signal. The numbers of FM radio station reception also different relatively with
location. Table 2.1 shows the different radio frequency in different location.
Table 2.1 Different Frequency Assigned for Different Radio Station at Different
Location
In Malaysia, the most popular radio station currently is owned by private
network such as Media Prima and AMP Radio. Government-owned radio station
usually popular in rural area rather than in city or suburb. This is because of limited
reception of private radio station in rural area.
2.4
Software Define Radio
Conventional RF hardware indicates that all signal processing such as
modulation, demodulation, filtering, and other function are implemented in hardware
19
and thus cannot be changed without alter the original design. Even though this
approach is proven to be practical for various applications, there are cases in which
the ability to alter the radio processing at runtime is highly desirable. There are few
examples of desirable reconfigurable system such as interoperability wit h the
existing applications, capable to operate with region-specific communication
standards and readiness for future communications protocols. Figure 2.8 depicts the
difference between conventional radio and SDR.
Figure 2.8: (a) Conventional Radio, (b) SDR [8]
Current development of digital signal processing techniques and increasing in
available powerful computing mechanism have made it possible to replace rigid
analog signal processing with fast digital signal processing which is programmable
and fast enough to satisfy the needs of high rate signal processing in modern
communication system. These developments have led to reconfigurable RF hardware
whose functionality can be configured in real-time by altering the software installed
in the system. SDR is characterized as a software code brought to the radio antenna
as near as possible. This is achieved by using hardware that translates radio waves to
a data stream a computer can handle. This hardware should be invisible from the
view of the software.
20
Figure 2.9: SDR Design Principle [7]
In this project, USRP and GNU Radio are the combined elements utilized in
the SDR implementation. Notice in the Figure 2.9 the design principle of the SDR is
to minimize the hardware modification and increase the software operation.
Although the transmitter and receiver still in form of hardware, this project is try to
impose little modification on hardware and increase the flexibility by using
controllable software. Therefore, this project utilized USRP as a hardware and GNU
Radio as programmable software that substantially do all the digital signal
processing. The USRP operates as platform just to receive and transmit radio wave.
On the other hand, GNU Radio will do all signal processing such as the modulation,
demodulation or other RF operation depend on the users desire. Therefore, this
combination of USRP and GNU Radio follow the principle of SDR. Figure 2.10
shows a simple explanation on GNU Radio and USRP operation.
21
USRP
GNU Radio
Figure 2.10: Combination of USRP and GNU Radio [7]
2.4.1 Hardware
2.4.1.1 USRP
The USRP is the hardware structure that will be used in this emergency alert
system. It will be the platform for radio wave receiver and transmitter. However, it
still needs to be connected to host computer, which equipped with GNU Radio
software in order to perform the operation of transmitting the emergency signal.
USRP is one of the most cheap hardware device used to build a SDR system.
It also the most famous hardware device use as a testbed for telecommunication
related projects. Figure 2.11 illustrates the USRP hardware.
22
Figure 2.11: Universal Software Radio Peripheral (USRP)
USRP is designed to be flexible where developers were allowed to make their
own configuration for specific needs concerning on connectors, different frequency
bands, daughterboard and others. It works perfectly with host computer as long as the
computer equipped with GNU Radio and connected via USB port. The host
computer acts as a baseband processor by using a USRP as RF-frontend to interface
the RF medium. It takes the input of the antenna, which receives radio waves and
digitizes those. The USRP provides a number functions such as digitizing the input
signal, digital tuning the Intermediate Frequency (IF) band and sample rate
decimation before sending the digitized baseband data to host computer via USB
cable.
Figure 2.12 shows the internal block diagram of USRP. Notice that it consists
of Field Programmable Gate Array (FPGA), four Daughterboard, four ADC, four
DAC and USB controller.
23
Figure 2.12: Block Diagram of USRP [8]
Daughterboard
Figure 2.13 USRP Motherboard
24
2.4.1.2 Daughterboard
Figure 2.13 shows slots for daughterboards. Daughterboard makes it possible
to use a USRP in different spectrum of frequency because each daughterboard are
used to hold the RF receiver interface or tuner and the RF transmitter at different
spectrum of frequency. Without daughterboard, USRP motherboard alone cannot
function. On the motherboard, there are four slots for daughterboard, wher e it
supports up to two RX basic daughterboards and two TX basic daughterboards or
RFX boards. There are slots for two TX daughterboards, labeled TXA and TXB, and
two RX daughterboards, labeled RXA and RXB. The USRP is capable to transmit
and receive simultaneously because it is possible to connect multiple daughterboards.
Table 2.2 shows the available daughterboard with their corresponding frequency and
transmission power.
Table 2.2: USRP Daughterboards [7]
Daughterboard
Description
Basic RX and Basic TX
Receiving and transmitting from 1 MHz to 250 MHz
LFRX and LFTX
Receiving and transmitting up to 30 MHz with 100mW
transmitting power
DBSRX
Receiving in the range from 800 MHz up to 2.4 GHz
with 100mW transmitting power
TVRX
Complete receiver system from 50
860 MHz based
on TV tuner module.
WBX
Receiving and transmitting from 50 MHz up to 2.2
GHz with 100mW transmitting power
RFX 400
Receiving and transmitting from 400 MHz up to 500
MHz with 100mW transmitting power
RFX 900
Receiving and transmitting from 800 MHz up to 1000
MHz with 200mW transmitting power
RFX 1200
Receiving and transmitting from 1150 MHz up to 1450
MHz with 200mW transmitting power
RFX 1800
Receiving and transmitting from 1.5 GHz up to 2.1
25
GHz with 100mW transmitting power
RFX 2400
Receiving and transmitting from 2.3 GHz up to 2.9
GHz with 20mW transmitting power
In this project, WBX will be used as daughterboard because it can transmit and
receive radio signal in FM band.
2.4.1.3 Analog-Digital-Converter (ADC)
The function of ADC is to digitize analog signal and it is used on the USRP
to receive radio signal. On the USRP motherboard, there are four high speed 12 -bit
AD converters. The maximum sampling rate is 64M samples per second.
Theoretically, it could sample a bandwidth of 32 MHz. Therefore, 32 MHz is a
limitation for signal bandwidth and it is impossible to receive signal without any loss
in a bigger bandwidth then 32 MHz.
2.4.1.4 Digital-Analog-Converter (DAC)
The purpose of DAC is to converts a digital signal into analog signal. This is
used in the USRP while transmitting a signal. On the USRP motherboard, there are
four high-speed 14-bit DAC converters. The DAC clock frequency is 128M samples
per second, thus Nyquist frequency is 64 MHz. However, it is better to stay below it
to make filtering easier. Thus, an optimum bandwidth for transmitting signal without
loss is about 44 MHz.
26
2.4.1.5 Field Programmable Gate Array (FPGA)
The heart of the USRP is FPGA. The Cyclone EP1C12Q240C8 from
ALTERA manufacture is the FPGA used currently in the USRP. All ADC and DAC
are connected to the FPGA. The purpose of FPGA is to perform high bandwidth
math in Digital Down Converting (DDC). Firstly, it down converts the signal from
the IF band to baseband and then it decimated the signal so that the data stream rate
can be adapted by the USB cable.
2.4.1.6 Programmable Gain Amplifier
In the receive path, there is a PGA before the ADC. The purpose of PGA is to
amplify the input signal in case of the input signal is weak. The PGA can amplify up
to 20 dB.
2.4.1.7 USB 2.0 Controller
USB is used to connect the host computer with USRP. The USRP only can be
connected to the host by USB 2.0 only, but not with outdated USB 1.1 interface. The
maximum data throughput via USB is 32 MB/sec, which has serious impact on the
performance.
27
2.4.2 Software
2.4.2.1 GNU Radio
GNU Radio is an open source software (OSS) founded in 1998 by Eric
blossom. The software is run on host computer and used to drive and acquire data
from the USRP. The software package comprises of a collection of components, one
of it is the firmware that is uploaded to the USRP upon initialization at runtime. The
firmware that comes with GNU Radio is designed to allow efficient communication
with the USRP and its daughterboards via USB, and to perform time-compression or
expansion of incoming or outgoing signals. Major components of DSP, which are
applied to a baseband signal, are running by GNU Radio in a host computer.
Inside GNU Radio are two-tier structures that an application programmer
sees. Low-level, performance-critical DSP blocks code are written in C++. Here also
the developer implements code to demodulate or modulate radio signal, restructure
the information into packets or perform frequency-domain signal filtering. Highlevel code is written in Python. Main purpose of high-level code is to connecting and
gluing signal blocks together. Due to Python is an interpreted language, it does not
require additional compilation time during development or testing, and this is
advantage because application deploy faster. Figure 2.14 illustrates more about this
two-tier structure and the software architecture.
In GNU Radio, DSP blocks can be considered as being in one of three
categories: sources, sinks and filters. Sources are blocks having outgoing signal and
no inputs. Sinks are blocks that allow one or more inputs but no output. Filters are
intermediate blocks that allow for one or more incoming signal and outgoing signals.
28
Figure 2.14: GNU Radio Architecture [8]
2.4.2.2 GNU Radio Companion
GNU Radio Companion (GRC) is graphical user interface, which allows
GNU Radio components or DSP blocks to be put together graphically. Figure 2.15
shows an example for GRC, which is a dial-tone example. GRC are created from the
XML flow graph, and it translated to Python code. This mean GRC file can be
convert to Python code. However, a Python code of the radio software design cannot
be translated to GRC file.
In this project, all the design will be implemented in GRC rather than Python
code.
29
Figure 2.15: Dial-tone Example in GRC [7]
2.4.2.3 Python
Python code is the script language used to connect the signal processing
blocks together. In Python, the necessary signal processing blocks such as signal
sources and sinks are selected and configured with the correct parameter. Thus the
main purpose of the Python is to select sources, sinks and signal processing blocks,
set parameter for each blocks and connect the signal processing blocks of C++.
Figure 2.16 shows an example of dial tone in form of Python code.
30
Figure2.16: Python Code of Dial-tone Example [7]
2.4.2.4 C++
In a processing block, there are one or more of data stream flow from input
port or to output port. The data stream is process by the processing block, which is
written in C++. In order to use C++ code in Python, SWIG is used. SWIG is a
wrapper for the C++ modules and it function is to generate the corresponding Python
code and library so that these classes and function can be called from Python.
However in GNU Radio, usually all the default signal processing blocks are a lready
created in GNU Radio project. Therefore, the C++ only comes in play when the
developers try to create their own special signal processing blocks.
31
CHAPTER 3
METHODOLOGY
3.1
Methodology of the Project
Details on the methodology used in this project will be given in this chapter.
Basically, the progress on this project is focused on the development of GNU Radio
software rather than hardware. The flow of this project will be divided into few parts
and the project will be executed stage by stage. Figure 3.1 is the flow chart of the
project:
START
Gain the related information on emergency alert system
Literature review about FM architectures
Understanding the SDR technique
Hardware/software development
Performance evaluation
Figure 3.1: Flow Chart of the Project Plan
32
3.2
System Architecture
The architecture of the system is comprised of transmitters and receiver part.
All parts are developed using SDR implementation, which is GNU Radio
development and USRP as a front-end hardware. Basically, the main concern is
software development because the success of this project is determined by it.
3.2.1 Hardware Structure
The hardware structure comprise of one USRP and one computer only. USRP
and computer will be connected together by USB cable. USRP only acts as a
platform to receive and transmit signal generated from the software in the computer.
Figure 3.2 illustrates more about the structure of GNU Radio and USRP. Moreover,
the software which controls the signal processing and USRP is called GNU Radio
which will be discussed later in software structure section.
Figure 3.2: GNU Radio and USRP Block Diagram [6]
33
Linux Operating System (OS) is used rather than popular OS such as
Windows because it provides more stable platform for GNU Radio to work. In this
project, the computer is equipped with Ubuntu 10.10 OS at first before GNU Radio
being installed in the fresh Linux environment. The steps taken for GNU Radio
installation will be discussed in next section.
For the USRP part, the daughterboard that will be used is WBX board. The
WBX board provides a frequency range of from 50 Hz to 2.2 GHz operation, which
is suitable for the project that uses FM band from 87 MHz to 108 MHz.
3.2.2 Software Structure
GNU Radio software provides many numerical techniques in its library to
perform important radio operations such as modulation and demodulation. In order to
use the software, one must be installed first. GNU Radio works perfectly in Linux
environment contrary to Windows environment because it was actually developed in
Linux environment in earlier days. Moreover, there are many online communities
over the internet ready to help new users. In this project, GNU Radio version 3.3 and
GNU Radio Companion have been installed in a laptop with Ubuntu 10.10 Operating
System. Figure 3.2 illustrate the component of software structure of the project.
34
Figure 3.3: Software Structure
3.2.2.1 GNU Radio Installation
There are many versions for GNU Radio such as GNU Radio 3.1.3, GNU
Radio 3.2.2 and GNU Radio 3.3. However, in this project latest GNU Radio 3.3 will
be installed. In Ubuntu 10.10, software installation begins by inserting command line
on the Terminal application in Ubuntu 10.10. This first command will install the prerequisites:
sudo apt-get -y install libfontconfig1-dev libxrender-dev libpulse-dev swig
g++ automake autoconf libtool python-dev libfftw3-dev libcppunit-dev
libboost-all-dev libusb-dev fort77 sdcc sdcc-librarieslibsdl1.2-dev pythonwxgtk2.8 git-core guile-1.8-dev libqt4-dev python-numpy ccache pythonopengl libgsl0-dev python-cheetah python-lxml doxygen qt4-dev-tools
libqwt5-qt4-dev libqwtplot3d-qt4-dev pyqt4-dev-tools python-qwt5-qt4
After installing the pre-requisites, it is time to install GNU Radio. This
command is to download, bootstrap, configure, compile and install GNU Radio
package:
35
# Install GNU Radio from git
git clone http://gnuradio.org/git/gnuradio.git
cd gnuradio
./bootstrap
./configure
make
sudo make install
Next part is to configure USRP support. The following script will sets up
groups to handle USRP via USB:
sudo addgroup usrp
sudo usermod -G usrp -a <YOUR_USERNAME>
echo 'ACTION=="add", BUS=="usb", SYSFS{idVendor}=="fffe",
SYSFS{idProduct}=="0002", GROUP:="usrp", MODE:="0660"' >
tmpfile
sudo chown root.root tmpfile
sudo mv tmpfile /etc/udev/rules.d/10-usrp.rules
sudo udevadm control --reload-rules
After the installation has been completed, it is advised to verify that the GNU
Radio works with USRP by trying out to execute any examples that come with GNU
Radio. Even though GNU Radio has been installed, GNU Radio Companion also
needs to be installed. An easier step to install it is just typing GNU Radio Companion
in Terminal and then an instruction will appear asking permission to install it.
3.3
System Design in Software Structure
36
In this section, system design for the emergency alert system will be
described. The design is divided into transmitter and receiver parts. The design of the
transmitter is main part of the project. The receiver only acts as platform to analyze
the performance of the transmitter.
In addition, this project is using GNU Radio Companion rather than GNU
Radio. GNU Radio Companion is same as GNU Radio. The difference is GNU
Radio Companion provide graphical interface contrary to GNU Radio which is focus
on Python coding. However, GNU Radio Companion comes together with GNU
Radio installation. Every design for transmitter and receiver developed using GNU
Radio Companion can be converted to Python code which is can be run in GNU
Radio software.
3.3.1 Transmitter Design
There are two transmitter designs in this project, which is for stereo channel
transmission and multiple channel signal transmission. Basically, stereo channel
transmission is capable of transmitting emergency signal in stereo. For multiple
channel transmission, the transmitter is capable of transmitting emergency signal to
multiple channels at once.
3.3.1.1 Stereo Channel Transmitter
37
For the stereo channel transmitter system, the design follows the conventional
block diagram for Stereo FM Transmitter. Figure 3.4 below depicts the Stereo FM
Transmitter block diagram.
Figure 3.4: Block Diagram for Stereo FM Transmitter
The design stereo transmission for emergency alert system is shown in Figure
3.5. The input source or the emergency message is in form of simple WAV tone,
which has a bit rate around 44 kHz. The input source is divided into two parts to
represent as left and right input channel. Both inputs need to be resampled before it
passes throug
subcarrier before it passes through band pass filter. After the mono part has passed
the low pass filter, it needs to be added together with the stereo part and pilot carrier.
Lastly, the resulting from adder is frequency modulated and passed through USRP
for transmission.
38
Figure 3.5: Design of Stereo Transmission for Emergency Alert System
Figure 3.6 shows the design of stereo transmission for emergency alert
system in GRC. Notice that the input source is fed with simple WAV tone as an
emergency alert message.
40
3.3.1.2 Multiple Channel Transmitter
Emergency alert system with multiple channel transmission is a different
design from the stereo channel transmission. The design is much simpler because all
the modulation processes such as filter, mixer and adder are combined together in
one blockset. Figure 3.7 shows design of multiple channel transmission for
emergency alert system. Notice that the input source is still in form of WAV file
because it transmits simple WAV tone as an emergency message. The input source is
passed through FM modulation blockset where all process required for frequency
modulation is done in this blockset. Output of this blockset is directly transmitted at
the designated frequency. However, the output of this blockset is also multiplied by
additional carrier. The additional carriers multiply the output signal and transmit it to
new frequency. The new frequency is a sum of designated frequency and additional
carrier frequency. As an example, the designated frequency is at 106.2 MHz and the
additional carrier frequency is 500 kHz. Therefore, the emergency message is
transmitted to 106.2 MHz and 106.7 MHz simultaneously.
Figure 3.7: Design of Multiple Channel Transmission for Emergency Alert System
42
Figure 3.8 depicts the design for multiple channel transmission for emergency alert
system. Notice there are two additional signal sources multiplied with the output.
Therefore, this design is capable to transmit three outputs signals simultaneously.
Figure 3.8 also shows the FFT Sink blocksets connected to design flow chart. The
purpose of the FFT Sink blockset is to display the output of signal processed at the
current location of the flow chart.
3.3.2 Receiver Design
The receiver is designed to capture back the signal being fed at the
transmitter. It also acts like typical radio because it also captures local radio channel
signal, process it and turn it into sound. However, the main purpose of the receiver in
this project is to see the effect of transmitted emergency signal to the original radio
signal transmitted from radio base station. Figure 3.9 show the design for the FM
receiver.
FM spectral analyzer is used to analyze the effects of FM spectrum due to
multiple transmission of emergency signal. Figure 3.10 is the design of FM spectral
analyzer. FM spectral analyzer also can be used to find frequency of radio station
over the FM spectrum.
45
3.4
System Setup
Before initiating the system, it is better to take note that the input of this
emergency alert system is WAV tone. The WAV tone is fed into this system and
broadcasted at the designated frequency. Therefore, the FM receiver tuned at the
designated frequency will receive and produce the transmitted WAV tone at the
audio sink. Another point to highlight, only the receiver in the reception coverage
able to produce the emergency WAV tone,
In order to determine the reception coverage or maximum distance of signal
reception, a portable FM radio is used. Maximum distance of the emergency signal
reception is determined by the maximum radius of the portable radio located when
the emergency signal start to deteriorate or barely audible. Figure 3. 11 shows the
portable radio used to determine the maximum distance of emergency alert system
transmission.
Figure 3.11: Portable Radio
Performance analysis of the system is initiated by placing the receiver within
the maximum radius. In this project, the receiver is also developed using GNU
46
Radio. Thus, it needs another USRP to act as receiver to receive the transmitted
emergency signal from transmitter. Figure 3.12 and 3.13 illustrate the summary of
the setup for performance analysis of emergency alert system.
Figure 3.12: The Suitable Distance of USRP Receiver to Analyze Emergency Signal
Transmission
Figure 3.13: Setup for Performance Analysis of the Emergency Alert System
47
3.5
Activation of Proposed Emergency Alert System
Figure 3.14: How Emergency Alert System Using FM Band Works
Figure 3.12 shows the icons represent the steps involved to activate the
proposed emergency alert system using FM band. Firstly, when the emergency
management officials receive a report about an emergency, they will distinguish the
appropriate type of emergency happen and the specific tone to transmit. Noted that a
different type of emergency have unique tone. After that, they will transmit the
emergency tone to the affected location by using FM band. The message also relayed
to the transmission towers. The FM towers will broadcast the emergency tone to the
intended receivers. However, the general population must be aware of type of
emergency tone broadcasted. Thus, the general population must be educated and
informed first about the type of tone used specifically.
48
CHAPTER 4
RESULT AND ANALYSIS
4.1
Introduction
This chapter discusses the results achieved in emergency alert system using
FM band. The experiment was conducted at UTM Skudai campus. The performance
analysis of the project is comprised of the result collected at the end receiver for both
type of transmission, stereo and multiple channel transmission
4.2
Performance Analysis of FM Emergency System
This subsection emphasizes on original FM channel spectrum transmitted
from local radio operator. The received spectrum is captured using FM spectral
analyzer and FM receiver. Detailed description of the structures can be referred in
Chapter 3. Figure 4.1 shows the original spectrum of IKIM.FM radio station.
49
Figure 4.1: Original IKIM.FM Spectrum
Figure 4.2 shows the FM spectrum range between 104.5 and 107.8 MHz.
Notice that there are three radio channels in that range, which are at frequencies
105.7 MHz (Muzik FM), 106.2 MHz (IKIM FM), and 106.7 MHz (Klasik Nasional).
Do take note that power received of received radio signal is around of 50 dBm while
the transmitted power from USRP for emergency signal transmission is around of
20dBm.
50
IKIM.FM
Muzik FM
Klasik Nasional
Figure 4.2: Original FM spectrum between 104.5 MHz to 107.8 MHz
4.3
Performance Analysis on Stereo Transmission
Figure 4.3 shows the spectrum of modulated emergency signal at stereo FM
transmitter. On the leftmost of the spectrum shows the audio-band signal for mono.
On 19 kHz, depicts the pilot tone for stereo signal. From around 22 kHz and 53 kHz,
shows the stereo part, which is the differences in the signal between the left and right
(L-R) channel.
51
L+R
mono
L-R
stereo
Pilot carrier
Figure 4.3: Modulated Signal of the Emergency Message for Stereo Transmission
FM receiver shows spectrum of received signal at frequency 106.2 MHz.
Notice that there is a difference exists between original spectrum in Figure 4.1 and in
Figure 4.4. Figure 4.4 shows the original signal altered after the original signal
overlaps with the emergency signal tuned at that frequency. Notice in that figure,
shows a several harmonic signal resulted from transmitted emergency signal in the
form of WAV tone. The amplitude of the resultant signal also increased from 50
dBm to 80 dBm.
52
Figure 4.4: Received FM spectrum shows the effect of emergency signal overlap
with original IKIM.FM signal
4.4
Performance Analysis on Multiple Channel Transmitter
Multiple channel transmission means the emergency signal will be
transmitted at multiple radio frequencies at the same time. In this project, emergency
signal can be transmitted up to three radio frequencies at one time. Thus, the FM
listeners at three designated frequency will hear the same signal from one source at
the same time. Figure 4.5 illustrates the three emergency signals being transmitted at
105.7 MHz, 106.2 MHz, and 106.7 MHz.
53
Figure 4.5: Transmitted Emergency Signal at 105.7 Mhz, 106.2 Mhz, and 106.7
Mhz
Comparing the original spectrum in Figure 4.2 with that in Figure 4.6, the
original spectrum of Muzik FM, IKIM FM, and Klasik Nasional have been distorted
with the overlapping emergency signal. The FM listeners at these three frequencies
will hear the WAV tone transmitted at the same time. The original power received
from the transmitted signal from radio base station is around 50 dBm. However, after
the emergency signal being transmitted, the power received was increased from 50
dBm to 90 dBm.
54
Muzik FM
IKIM.FM
Klasik Nasional
Figure 4.6: FM Spectrum Shows the Radio Station Signals for Muzik FM, IKIM.FM
and Klasik Nasional Have Been Distorted By the Emergency Signal
4.5
Overall Signal Transmission Performance
The maximum signal reception covered from the USRP is around of 30 meter
radius. Further from that, the receiver will start to hear back the original signal
transmitted from radio base station. However, if the receiver is too close with USRP
source, the transmission of the emergency signal at designated frequency will also
deteriorate the adjacent radio frequency. As an example, the transmission of
emergency signal is focused on to alert the IKIM FM listener only. But, the adjacent
radio channels which are Muzik FM and Klasik Nasional also being slightly
deteriorated by the emergency signal. This means Muzik FM and Klasik Nasional
listeners will slightly hear the emergency signal. However, it is not a problem if the
adjacent radio stations were disturbed by the emergency signal because the sole
purpose of the emergency alert system is to notify as many people as possible.
55
Unwanted fluctuations
Figure 4.7: Unwanted Fluctuations
Notice at both receptions of FM spectrum indicates several signal fluctuations
of the signal. Figure 4.7 shows several unwanted fluctuations in the receiver
spectrum. This happens maybe due to incorrect sampling or modulation of WAV
tone at the transmitter before it being transmitted.
56
CHAPTER 5
CONCLUSION
5.1
Conclusion
Emergency alert system using FM band have been developed under SDR
implementation with a combination of GNU Radio and USRP. Actually, the system
is developed using GNU Radio Companion, which is available in GNU Radio
software toolkit. GNU Radio Companion provides graphical interface to guide the
user to develop the RF system. In this system, users are able to configure the input
source and select different radio channel frequency for the emergency signal
transmission. This reconfiguration capability allows the system to be flexible and
nomadic, especially when the system is deployed at different location where radio
channel frequencies are assigned differently.
5.2
Recommendation and Future Work
57
The recommendation for the future work is to extend the maximum distance
for signal reception. This improvement can be achieved by installing an additional
transmitter amplifier and antenna. In this project, the input being transmitted is in
form of WAV source. Another recommendation is to add a variety of input source
such as voice from microphone where the user can directly inform the listener. Last
recommendation is to utilize RDS system. Actually, RDS system has been applied in
Malaysia for several years now, so there are quite a large number of FM receivers,
which are able to demodulate and decode RDS data.
58
REFERENCES
1.
Ferrel G. Stremler, Introduction to Telecommunication Systems, University of
Wisconsin, Madison: Addison-Wesley Publishing Company.
2.
A. Michell Noll, Introduction to Telecommunication Electronics, 2 nd Edition,
University of Southern California: Artech House.
3.
Martin S. Roden, Analog and Digital Communication Systems, 4th Edition,
California State University, LA: Prentice Hall.
4.
Warren Hioki, Telecommunications, 4th Edition, Community College of
Southern Nevada, Prentice Hall.
5.
Wesley J. Chun. Core Python Programming, USA: Prentice Hall. 2001
6.
Naveen Manicka. GNU Radio Testbed. Master Thesis. University of
Delaware: 2007
7.
Alex Verduin, GNU Radio: Wireless protocols analysis approach. Master
Thesis. Universiteit Van Amsterdam: 2008
8.
Verma, P. and Verma, D.C. 2005. Internet emergency alert system. Military
Communications Conference, 2005. MILCOM 2005. IEEE, Vol. 5, pp 2936 2942.
9.
LeBow, G.M. 1993. RBDS As An Emergency Broadcasting And Alert System.
Consumer Electronics, 1993. Digest of Technical Papers. ICCE., IEEE 1993
International Conference, pp 198 199.
59
10.
Hall, M.; Betts, A.; Cox, D.; Pointer, D.; Kindratenko, V. 2005. The visible
radio: process visualization of a software-defined radio. Visualization, 2005.
VIS 05. IEEE, pp. 159-165.
11.
Matt Ettus.