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SPREAD SPECTRUM TRAWING AND DEVELOPMENT
Marietta Rachel Lukie
TK
5103.45 M334
2004
Bachelor of Engineering with Honours
(Electronics and Telecommunication Engineering)
2004
UNIVERSITI MALAYSIA SARAWAK
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BORANG PENYERAHAN TESIS
Judul: SPREAD SPECTRUM TRAINING AND DEVELOPMENT
SESI PENGAJIAN: 2003 - 2004
Saya MARIETTA RACHEL LUKIE
(HURUF BESAR)
mengaku membenarkan tesis ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dengan syarat-syarat kegunaan seperti berikut:
I. Hakmilik kertas projek adalah di bawah nama penulis melainkan penulisan sebagai projek bersama dan dibiayai oleh UNIMAS, hakmiliknya adalah kepunyaan UNIMAS.
2. Naskhah salinan di dalam bentuk kertas atau mikro hanya boleh dibuat dengan kebenaran bertulis daripada penulis.
3. Pusat Khidmat Maklumat Akademik, UNIMAS dibenarkan membuat salinan untuk pengajian mereka.
4. Kertas projek hanya boleh diterbitkan dengan kebenaran penulis. Bayaran royalti adalah mengikut kadar yang dipersetujui kelak.
5. * Saya membenarkan/tidak membenarkan Perpustakaan membuat salinan kertas projek ini sebagai bahan pertukaran di antara institusi pengajian tinggi.
6. ** Sila tandakan (/)
II II
I / I
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972).
(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/
badan di mana penyelidikan dijalankan).
Disahkan oleh
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(TANDATANGAN PENULIS) (TANDAT
Alamat tetap: CIO LOZEING PETRUS
PETI SURAT 11201 88813 KOTA KINABALU, SABAH
0 AN PENYELIA)
NG LIANG YEW ( Nama Penyelia )
Tarikh: I MAC 2004 Tarikh:
CATATAN "
f"
Potong yang tidak berkenaan.
Jika Kertas Projek ini SULIT stau TERHAD, sila lampirkan surat daripada pihak berkuasa/
organisasi berkenaan dengan menyertakan sekali tempoh kertas projek. Ini perlu dikelaskan sebagai SULIT stau TERHAD.
Laporan Projek Tahun Akhir berikut:
Tajuk : Spread Spectrum Training and Development Nama penulis : Marietta Rachel Lukie
Matrik : 5514
telah dibaca dan disahkan oleh:
En. Ng Pghg Yew Tankh ý,.. ý
Penyeliä
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Pusat Khidmat Makiumat LUVERSITI Akademfk MALAYSIA SARAWAK 943(1(1 Kota Samarahan
P. KHIDMAT MAKLUMATAKADEMK UNIMAS
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1000125781I III
SPREAD SPECTRUM TRAINING AND DEVELOPMENT
MARIETTA RACHEL LUKIE
This project is submitted in partial fulfillment of
the requirements for the degree of Bachelor of Engineering with Honours (Electronics & Telecommunications)
Faculty of Engineering
UNIVERSITI MALAYSIA SARAWAK 2004
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To my family
ACKNOWLEDGEMENT
The author would like to take this opportunity to thank the supervisor, Mr. Ng Liang
Yew for his valuable advice and guidance throughout the project.
Thank you also to the author's family for being so. Strong moral support from the
family helped the author to endure all the difficulties while doing the project.
The author would also like to express her appreciation and gratitude to all the lecturers and fellow course mates especially Amy R Porle, Dzatul Ithri Amran, and Azudin Mohd Arif
for their helps and ideas in making the project a success. A very big thank you also to Faiezah Abdullah and Imelda Vivian Paul for their strong moral support.
Abstrak
Sistem Komunikasi Penyebaran Spektrum telah berkembang dengan pesatnya sejak dikomersialkan oleh FCC (Federal Communication Commission). Salah satu daripada teknik penyebaran spektrum ialah Direct Sequence Spread Spectrum (DSSS), yang digunakan dengan meluasnya dalam sistem Code Division Multiple Access (CDMA). Dalam DSSS, pembawa isyarat (carrier signal) digabungkan dengan kod rawak sebelum dihantar melalui ruang penghantaran. Kelebihan menggunakan kod rawak ialah sistem ini lebih kukuh, susah dikesan, menggunakan kuasa yang rendah, dan boleh digunakan oleh beberapa pengguna dalam suatu masa, serta susah untuk di hentikan. Projek ini mengkaji dan menyelidik prinsip- prinsip asas sistem komunikasi penyebaran spektrum melalui eksperimen. Eksperimen ini termasuk latihan manual, eksperimen makmal, keputusan eksperimen, dan perbincangan berkaitan dengan sistem ini.
Abstract
Spread Spectrum communication system has been evolving rapidly since it was first commercialized by FCC (Federal Communication Commission). One of the techniques, which is Direct Sequence Spread Spectrum (DSSS), is widely used in CDMA system. In DSSS, a carrier signal is multiplied with pseudorandom codes before being transmitted through a channel. The advantage of using pseudorandom codes in DSSS is that it is robust, hard to detect, use low signal power, allow multiple access and antijam. This project is to study and understand the basic principle of spread spectrum communication through the utilization of some training experiments. The experiment include the spread spectrum communication training, training manual, laboratory experiments, results and discussion on the system.
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Table of Content
Abstrak Abstract
Table of Content
List of Figures List of Tables
List of Abbreviations
Chapter 1 Introduction of Spread Spectrum Communication System 1.0 History of Spread Spectrum Communication
1.1 The Basic Concept 1.2 Project Objectives 1.3 Report Structure
Chapter 2 Basic Spread Spectrum System 2.0 Definition
2.1 Basic Spread Spectrum Component 2.1.1 Transmitted Reference System
2.1.2 Stored Reference System
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11
iii
vii ix
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1
2 3
4
6
6 8
9
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2.1.3 Matched Filter Reference System 10
2.2 Characteristics of Spread Spectrum 11
2.2.1 Wide bandwidth/less interference and multiple access 11 2.2.2 Hard to detect/intercept and demodulate 11
2.2.3 Antijam 12
2.2.4 Ranging and radar 13
2.3 Types of Modulation 13
2.3.1 Binary Phase Shift Keying (BPSK) 14 2.3.2 Quaternary Phase Shift Keying (QPSK) 15 2.3.3 Differential Phase Shift Keying (DPSK) 17 2.3.3.1 Differential Binary Phase Shift Keying (DBPSK) 17 2.3.3.2 Differential Quaternary Phase Shift Keying (DQPSK) 18
2.3.4 Frequency Shift Keying (FSK) 19
2.4 Pseudorandom Codes 21
2.4.1 Walsh-Hadamard Codes 23
2.4.2 M-sequence Codes 24
2.4.3 Gold Codes 26
2.4.4 Kasami Codes 27
2.5 Processing Gain 27
2.6 Synchronization 27
2.6.1 Acquisition Time 2.6.2 Tracking
28 29
- iv
-
Chapter 3 Types of Spread Spectrum System 3.0 Types of Spread Spectrum System
3.1 Direct Sequence Spread Spectrum (DSSS)
3.2 Frequency Hopping Spread Spectrum (FHSS) 3.3 Hybrid of DSSS and FHSS
3.4 Time Hopping Spread Spectrum 3.5 Chirp System
Chapter 4 Training on DSSS 4.1 Transmitter
4.2 Receiver
Chapter 5 Analysis of DSSS using M-Sequence 5.0 Introduction
5.1 Flow of Information in the Transmitter
32 32 35
39 40 41
42 49
55 55
5.2 Flow of Information in the Receiver 57
5.2.1 Synchronization 58
5.2.1.1 Time Uncertainty 58
5.3 Comparison of Performance for Different Types of PN Codes 61 5.4 Autocorrelation of Four Different Codes and the Power Spectral 63
Density of all the Modulating Signals
-V-
Chapter 6 Conclusion and Recommendation
6.0 Conclusions 65
6.1 Recommendations 66
References 68
Appendix A Results ( Barker Code) 70
Appendix B Results (M-sequence) 74
Appendix C Results (Gold Code) 77
Appendix D Results (Kasami Code) 82
Appendix E Comparison of Power Spectral Density of M-sequence, 86 Barker Code and Kasami Modulation Signals
Appendix F Comparison of Autocorrelation Between Barker Code, 88 M-sequence, Kasami and Gold Code Signal
Appendix G Comparison of Correlation and Power Spectrum of 89 M-sequence, Barker Code, Kasami Code and Gold Code.
Appendix H Parameters Used In The System 91
- Vl
List of Figures
Figure Page
2.0 Basic component of spread 7
spectrum system
2.1 Effect of spread spectrum process 7
2.2(a) Transmitted reference system 8
2.2(b) Stored reference system 9
2.2(c) Matched filter reference system 10
2.3 Timing diagram at the transmitter 17
2.4 Timing diagram at the receiver 18
2.5 Timing diagram of the transmitter 19
of DQPSK
2.6 FSK Transmitter waveform 20
2.7 PLL demodulator 21
2.8 4-stage LFSR 22
2.9 3 stage register for m-sequence 25
2.10 M-sequence autocorrelation 25
properties
2.11 Generation of Gold code length 31 26
2.12 DLL for PN code tracking 30
3.0 Simplified model of a DSSS system [1] 33
- vii -
3.1 Direct sequence coding 34
3.2 Frequency hopping concept 35
3.3 Simplified model of FHSS [1] 36
3.5 Frequency hopping using 8-ary FSK modulation 38
3.6 Hybrid DS/FS 39
3.7 Time hopping spread spectrum 40
4.0 Transmitter of DSSS 42
4.1 DBPSK encoding 44
4.2 DQPSK encoding 46
4.3 Receiver of DSSS 49
5.0 Transmitter dialog box 55
5.1 Input data 56
5.2 Block diagram of receiver 57
List of Tables
Table Page
2.1 DQPSK encoding 18
4.1 AN in accordance with data bit of DBPSK 43
4.2 Encoding method of DBPSK 44
4.3 iOk in accordance with a data bit of DQPSK 45
4.4 Encoding method of DQPSK 46
4.5 Differential demodulator rotation control 50
4.6 AFC viewport loop filter control 51
List of Abbreviations
AM Amplitude Modulation
ASIC Application Specific Integrated Circuit ATM Asynchronous Transfer Mode
BPSK Binary Phase Shift Keying
CDMA Code Division Multiple Access CRC Cyclic Redundancy Code
DBPSK Differential Binary Phase Shift Keying DLL Delay Locked Loop
DQPSK Differential Quaternary Phase shift Keying DSP Digital Signal Processing
DSSS Direct Sequence Spread Spectrum
FHSS Frequency Hopping Spread Spectrum FM Frequency Modulation
LAN Local Area Network
LSFR Linear Shift Feedback Register MAN Metropolitan Area Network
PDA Personal Digital Assistant PM Pulse Modulation
POS Point of Sales
QPSK Quaternary Phase Shift Keying
-X-
SDLC Synchronous Data Link Control VCC Voltage Control Clock
VLSI Very Large Scale Integrated
X1
CHAPTER I
Introduction to Spread Spectrum
Communication System
1.0 History of Spread Spectrum Communication
The idea of spread spectrum came way back to the World War II. An actress, Hedwig Maria Eva Kiesler, today known as Hedy Lamarr, brought the idea to George Antheil, a piano player [4]. Hedy Lamarr was married to Fritz Mandl, Europe's armament manufacturer.
Mandl was doing a research in weapon's control system. The problem with weapons at that time was the inefficiency of wire cable to ensure the communication between the commander and the torpedo would not break. Mandl was doing research of replacing the wire cable by radio waves. Mandl successfully connect the commander and the torpedoes using radio waves but it had a problem, which is it can be easily detected and jammed.
Hedy was exposed to technology ideas. She left Mandl and told Antheil about her idea on secret communication system that would guide torpedoes to their target without being detected, using radio waves, but by sending the signals over multiple radio frequencies in a random pattern. However, this idea also has a problem with the synchronization. Antheil who was an expert in music synchronization solved the problem by using paper rolls perforated with a pseudo random pattern that would delineate the frequency path. Two paper rolls with
I
the same pattern, one at the transmitter and one at the receiver are installed. Both rolls are
started at the same time.
The government was not interested in the secret communication system. Yet, in 1950's, engineers from Sylvania Electronic System Division experimented with the secret communication patent using digital components and developed an electronic spread spectrum system.
In 1960s, spread spectrum began to evolve and recognized in the use of mobile communication in 1978. Federal Communication Commission allowed unlicensed use of
spread spectrum radios in 1985.
1.1 The Basic Concepts
Spread spectrum is a way of communicating using radio waves that enables users to share a frequency without interfering each other.
In the spread spectrum techniques, signals are spread over a bandwidth in excess of the minimum bandwidth required to transmit the signal. There are a few characteristics of spread spectrum that makes it a unique, and useful technique. Spread spectrum is:
i. Hard to detect
ii. Hard to intercept or demodulate
2
iii. Antijam
iv. Noise-like signal
v. Uses wide bandwidth
With these characteristics, this technique, which is once used in military, has evolved and commercialized. At present, spread spectrum is widely used in wireless LANs and MANs, wireless POS (Point-of-Sales) for example cash registers and barcodes readers, cordless telephones, PCMCIA cards modem for laptops and PDAs (Personal Digital Assistant) etc.
Other than that, spread spectrum communications are used in the advancement of mobile and wireless communication for example Global Positioning System (GPS), satellite, cellular mobile radio, Asynchronous Transfer Mode (ATM) combined with CDMA etc.
1.2 Project Objectives
The objectives of this thesis are to introduce the basic ideas of spread spectrum techniques and to identify the unique characteristics of spread spectrum that makes it useful in modern telecommunication. The goal of the project is to produce a training development program that gives a better understanding of spread spectrum technologies. CDMA training kit, ED-2930 is being used for this training.
3
1.3 Report Structure
Chapter 1 of this paper introduces spread spectrum communication. The history of its invention is investigated. Other than that, the basic concepts and the characteristics of spread spectrum will be discussed.
Chapter 2 discusses detailed concepts of spread spectrum. This chapter discussed the important elements of spread spectrum, such as the processing gain, modulation types, power density, codes that are being used, and the synchronization as well as how the spread spectrum techniques is being implemented.
Chapter 3 investigates five types of spread spectrum techniques, which is Frequency Hopping, Direct Sequence, Hybrid of Frequency Hopping and Direct Sequence, Chirp and Time Hopping.
Chapter 4 discusses the Direct Sequence Spread Spectrum System in detail. In this chapter, a simple manual of the spread spectrum technique will be presented. Parameters used in the training will be discussed and evaluated.
The process involved in both the transmitter and the receiver are being discussed in detail in Chapter 5. In this chapter, the performance of Kasami codes, Barker codes, M- sequence and Gold codes is being compared.
4
Conclusion of the project is presented in Chapter 6. Also included in this chapter, are
the recommendations that being proposed for future development in spread spectrum system.
5
CHAPTER 2
Basic Spread Spectrum System
2.0 Definition
De Nayer Institute of Belgium define spread spectrum as a transmission technique where a pseudo noise code, independent of the information data, is employed as a modulation waveform to spread the signal over a bandwidth larger than the signal information bandwidth.
Despreading is done at the receiver using a synchronized replica of the spreading signal. The following characteristics assist in defining spread spectrum system:
i. The signal occupies a bandwidth much in excess of the minimum bandwidth necessary to send the information.
ii. Spreading is accomplished by means of a spreading signal, often called code signal, which is independent of data.
iii. Despreading is accomplished by the correlation of the received spread signal with a synchronized replica of the spreading signal used to spread the information.
2.1 Basic Spread Spectrum Component
A basic spread spectrum component is as shown in the Figure 2.0.
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Figure 2.0: Basic component of spread spectrum system
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The first process involved in spread spectrum system is signal encoding. The encoded signal is then modulated and combined with a PN code. This process spreads the information signals and as a result, the information bandwidth becomes larger, which is the same as the bandwidth of the PN code used. The effect of spread spectrum process is shown in Figure 2.1.
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(d) Information signal, noise and jam after despreading at the receiver
Figure 2.1 : Effect of spread spectrum process
7
