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PERFORMANCE EVALUATION OF OFDM AND MC-CDMA BASED COGNITIVE RADIO SYSTEM SALEM MOHAMMED SALEM BINDHAIQ UNIVERSITI TEKNOLOGI MALAYSIA

PERFORMANCE EVALUATION OF OFDM AND MC-CDMA …eprints.utm.my/id/eprint/32406/1/SalemMohamedMFKE2012.pdfMultiplexing (OFDM) and Multi-carrier Code Division Multiple Access (MC-CDMA)

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PERFORMANCE EVALUATION OF OFDM AND MC-CDMA BASED COGNITIVE

RADIO SYSTEM

SALEM MOHAMMED SALEM BINDHAIQ

UNIVERSITI TEKNOLOGI MALAYSIA

PERFORMANCE EVALUATION OF OFDM AND MC-CDMA BASED COGNITIVE

RADIO SYSTEM

SALEM MOHAMMED SALEM BINDHAIQ

This project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Engineering (Electrical- Electronics and Telecommunications)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

JUNE 2012

iii

To

To my beloved mother and father,

To

To my brothers and sisters.

iv

ACKNOWLEDGEMENT

In The Name Of ALLAH, The Most Beneficent, The Most Merciful

All praise is due only to ALLAH, the lord of the worlds. Ultimately, Only

ALLAH has given us the strength and courage to proceed with our entire life.

His works are truly splendid and wholesome, and his knowledge is truly complete

with due perfection.

I am particularly appreciative of my supervisor, Assoc. Prof. Dr. Sharifah

Kamilah Bt Syed Yusof for her invaluable supervision, guidance and assistance.

She has provided me with some precious ideas and suggestions throughout this

dissertation.

Besides that, my highly appreciation extended to my parents for their

supporting, patience, love, prayer and sacrifice are unbounded during my study.

I am also grateful to Al-Sheikh Eng. Abdullah Ahmad Bogshan for his financial

support.

I am grateful for the help of my best friends. Among these are Dr. Hassan

M. Bawazier and Mr. Redwan Shadad.

v

ABSTRACT

The present development of high data rate wireless applications has lead

to extra bandwidth demand. However, finding a new spectrum bandwidth

to accommodate these applications and services is a challenging task due to

lack of spectrum resources. In fact, recent studies have shown that the

spectrum are utilized inefficiently especially for conventional spectrum allocation.

Therefore, in order to enhance spectrum efficiency, Federal Communications

Commission (FCC) has proposed dynamic spectrum access (DSA) mechanism,

where unlicensed users can opportunistically borrow unused spectrum from

licensed owners. The radio that enables this concept is called Cognitive Radio

(CR). Nevertheless, it is difficult for single transmission to get a large contiguous

frequency spectrum block in DSA and this have significant impact on broadband

and multi-carrier transmission systems such as Orthogonal Frequency Division

Multiplexing (OFDM) and Multi-carrier Code Division Multiple Access (MC-

CDMA). This thesis investigates on non-contiguous OFDM (NC-OFDM) and

non-contiguous MC-CDMA (NC-MC-CDMA) system. The implementation of

NC-OFDM and NC-MC-CDMA systems provide high data rate via large number

of non-contiguous sub-carriers without interfering to the existing transmissions by

turning off the sub-carriers corresponding to these spectrum bands. This thesis

evaluates Bit Error Rate (BER) performance of NC-OFDM and NC-MC-CDMA

on mobile scenario where each propagation path will experience an apparent shift

in frequency due to the relative motion between the transmitter and receiver while

the number null sub-carriers is constant for all.

vi

ABSTRAK

Pembangunan aplikasi tanpa wayar untuk data berkelajuan tinggi

telah membawa kepada permintaan kepada tambahan jalur lebar. Walau

bagaimanapun, untuk mendapat jalur spektrum bagi untuk menampung aplikasi

dan perkhidmatan ini adalah satu tugas yang mencabar kerana kekurangan

sumber spektrum. Malah, kajian terkini telah menunjukkan penggunaan

spektrum yang tidak cekap terutama pada peruntukan spektrum konvensional.

Oleh itu, untuk meningkatkan kecekapan penggunaan spektrum, FCC telah

mencadangkan satu mekanisma untuk mengakses spektrum secara dinamik

(DSA), di mana pengguna yang tidak berlesen boleh meminjam spektrum yang

tidak digunakan oleh pemilik spektrum berlesen tersebut secara oportunistik.

Sistem radio yang memperkenalkan konsep ini dikenali sebagai Radio Kognitif

(CR). Walau bagaimanapun, ia adalah sukar untuk sistem penghantaran tunggal

untuk mendapatkan blok spektrum frekuensi yang besar melalui DSA dan ini

mempunyai kesan yang ketara ke atas sistem jalur lebar serta penghantaran

berbilang pembawa seperti pemultipleksan pembahagian frekuensi ortogon

(OFDM) dan berbilang pembawa pembahagian kod pelbagai masukan (MC-

CDMA). Tesis ini mengkaji OFDM tidak rapat (NC-OFDM) dan MC-CDMA

tidak rapat (NC-MC-CDMA). Pelaksanaan NC-OFDM dan sistem NC-MC-

CDMA menyediakan kadar data yang tinggi melalui sebilangan besar sub-

pembawa tidak rapat tanpa mengganggu kepada penghantaran sedia ada dengan

mematikan sub-pembawa yang sama dengan jalur spektrum ini. Tesis ini menilai

prestasi kadar bit ralat (BER) NC-OFDM dan NC-MC-CDMA dalam senario

bergerak bebas di mana setiap laluan perambatan mengalami perubahan ketara

dalam frekuensi disebabkan oleh gerakan relatif antara penghantar dan penerima,

serta jumlah subpembawa batal adalah malar.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF FIGURES x

LIST OF ABBREVIATIONS xii

LIST OF APPENDICES xiv

1 INTRODUCTION

1.1 Introduction 1

1.2 Statement of Problem 2

1.3 Objectives of the Study 2

1.4 Scope of the Study 3

1.5 Thesis Organization 3

2 LITERATURE REVIEW

2.1 Introduction 5

2.2 Multi-Carrier Transmission 7

2.2.1 Principles of OFDM 8

viii

2.2.2 Principles of MC-CDMA 12

2.3 Dynamic Spectrum Access Techniques 14

2.3.1 Underlay and Overlay Spectrum

Sharing Approaches 15

2.4 Brief on Non-Contiguous Transmission 16

2.5 Channel Models 18

2.5.1 Additive White Gaussian Noise Channel 18

2.5.2 Rayleigh Fading Channel 19

2.5.3 Doppler Shift 21

2.6 Chapter Summary 21

3 METHODOLOGY

3.1 Introduction 23

3.2 OFDM Implementation with Cognitive Radio 24

3.3 MC-CDMA Implementation with Cognitive Radio 26

3.4 Performance Analysis 27

3.5 Chapter Summary 28

4 RESULT AND DISCUSSION

4.1 Introduction 29

4.2 BER Performance Analysis 32

4.2.1 NC-OFDM BER Calculation for

100 Hz Doppler Shift 33

4.2.2 NC-MC-CDMA BER Calculation

for 100 Hz Doppler Shift 33

4.2.3 NC-OFDM BER Calculation for

80 Hz Doppler Shift 34

4.2.4 NC-MC-CDMA BER Calculation

for 80 Hz Doppler Shift 34

4.2.5 NC-OFDM BER Calculation for

60 Hz Doppler Shift 36

4.2.6 NC-MC-CDMA BER Calculation

ix

for 60 Hz Doppler Shift 36

4.3 Chapter Summary 39

5 CONCLUSIONS AND FUTURE WORK

5.1 Conclusion 40

5.2 Future Work 41

REFERENCES 43

Appendix A 46

Appendix B 50

x

LIST OF FIGUERS

FIGURE NO. TITLE PAGE

2.1 Spectrum holes 6

2.2 The impulse response of the channel

for single carrier and multi-carrier 9

2.3 Block diagram of an OFDM transceiver 10

2.4 Block diagram of MC-CDMA transceiver 14

2.5 Spectrum sharing approaches 16

2.6 Non-contiguous OFDM sub-carriers 17

2.7 AWGN channel 18

2.8 Time variant channel impulse response and channel transfer

function with frequency selective fading 20

3.1 Block diagram of an NC-OFDM transceiver 25

3.2 Block diagram of NC-MC-CDMA transceiver 28

4.1 BER calculation for NC-OFDM 32

4.2 BER calculation for NC-MC-CDMA 33

4.3 BER calculation for NC-OFDM

at 100 Hz doppler shift 34

4.4 BER calculation for NC-MC-CDMA

at 100 Hz doppler shift 35

4.5 BER calculation for NC-OFDM

at 80 Hz doppler shift 35

4.6 BER calculation for NC-MC-CDMA

at 80 Hz doppler shift 36

4.7 BER calculation for NC-OFDM

at 60 Hz doppler shift 37

4.8 BER calculation for NC-MC-CDMA

xi

at 60 Hz doppler shift 37

xii

LIST OF ABBREVIATIONS

AWGN - Additive White Gaussian Noise

BER - Bit Error Rate

CDMA - Code Division Multiple Access

CP - Cyclic Prefix

CR - Cognitive Radio

D/A - Digital-to-Analog

DSA - Dynamic Spectrum Access

DFT - Discrete Fourier Transform

FCC - Federal Communications Commission

FFT - Fast Fourier Transform

HPA - High Power Amplifier

ICI - Inter-Carrier Interference

IDFT - Inverse Discrete Fourier Transform

IFFT - Inverse Fast Fourier Transform

ISI - Inter-Symbol Interference

MC-CDMA - Multi-Carrier Code Division Multiplexing

MCM - Multi-Carrier Modulation

NC-MC-CDMA- Non-Contiguous Multi-Carrier Code Division Multiplexing

NC-OFDM - Non-Contiguous Orthogonal Frequency Division Multiplexing

OFDM - Orthogonal Frequency Division Multiplexing

P/S - Parallel-to-Serial

PA - Power Amplifier

PAPR - Peak-to-Average Power Ratio

PSK - Phase Shift Keying

QAM - Quadrature Amplitude Modulation

xiii

QPSK - Quadrature Phase Shift Keying

RCC - Radio Control Channel

RF - Radio Frequency

S/P - Serial-to-Parallel

SDR - Software Defined Radio

SNR - Signal-to-Noise Ratio

UWB - Ultra Wide Band

xiv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A NC-OFDM Simulation Program 46

B NC-MC-CDMA Simulation Program 50

CHAPTER 1

INTRODUCTION

1.1 Introduction

Due to the advancement of new wireless applications, as well as

development of existing wireless services, demand for extra bandwidth has been

on rise [1,10]. As a result, the possibility of spectrum scarcity becomes more

of a reality. In other words, emerging technologies and with the ever increasing

number of wireless devices,the radio spectrum scarcity is increased every day [19].

There is a spectrum allocation called Command-and-Control came to

prevent unlicensed access to access the spectrum, it is defined by government

regulatory agencies. Measurements studies indicated that big part of the

spectrum is in a rare use while some parts are in a heavy use most of the time

and frequency [2,3].

Federal Communications Commission (FCC) is working on the unlicensed

users to borrow spectrum from incumbent license users, this can be done by

concept knows as Dynamic Spectrum Access (DSA). Wireless communication

should be agile to perform dynamic spectrum access such that spectrum

efficiency can be improved while no interference occurred with neighbored user

2

transmissions. To exploit frequency and time gaps which are not occupied by

license holders, such a communication technique called Cognitive Radio. It can

be defined as a smart wireless system that is aware of its surrounding environment

through sensing and measurements [4, 5].

The common digital communication techniques of multi-carrier

transmission such as Orthogonal Frequency Division Multiplexing (OFDM)

and Code Division Multiplexing Access (MC-CDMA) are the most widely used

technologies in current wireless communications systems. Theses techniques

have the potential of fulfilling the requirements of cognitive radios inherently

or with minor changes [15]. They provided an interest over other transmission

technologies such as good spectrum efficiency, fading channel robustness,

prevention of impulse interference, dealing with fading paths and frequency

selective fading without channel equalization [20]. In addition, they have ability

to turn off the sub-carriers which probably are close to the spectrum occupied

by the incumbent users as to not allow any interference to current transmissions,

enhance the spectrum efficiency by enabling second usage of the unused parts of

the spectrum and addressing the issues of spectrum scarcity as well [19].

1.2 Statement of Problem

The problem behind this work is spectrum bandwidth shortage to send

high data rate communication. It is very difficult to gain access to a large

continuous block of frequency spectrum that is the limitation for high data rate

transmission in mobile radio environment.

1.3 Objectives of the Study

The objectives of this study are:

3

1. To improve the spectrum efficiency in wireless communication.

2. To develop non-contiguous OFDM system and non-contiguous MC-CDMA

system for supporting high data rate communication.

3. To evaluate the performance of NC-OFDM and NC-MC-CDMA in mobile

radio environment.

1.4 Scope of the Study

The scope of the study in this project are:

• Conceptual Study

Understand the concept of cognitive radio, OFDM and MC-CDMA. DSA

model is shared using Overlay Spectrum sharing Approach with non-

contiguous.

• Development and Analysis

Develop OFDM and MC-CDMA based cognitive radio on dynamic

spectrum access. Performance analysis of this project will consider

performance evaluation such as Signal-Noise Ratio (SNR) and (BER) with

doppler shift.

• Simulation

The simulation tool used is Matlab.

1.5 Thesis Organization

This thesis is organized as follows:

4

In Chapter 2, a brief introduction to cognitive radio concept and basic

principles of OFDM and MC-CDMA are presented. This chapter also overview

of DSA techniques such as underlay and overlay approach to improve spectrum

utilization efficiency and scarcity issue. Moreover, basic introduction to the non-

contiguous transmission and channel models are also included.

In Chapter 3, methodology of OFDM and MC-CDMA implementation

based on cognitive radio are discussed.

In Chapter 4, BER performance of NC-OFDM and NC-MC-CDMA is

evaluated and viability of NC-OFDM and NC-MC-CDMA techniques for DSA

with doppler shift.

In Chapter 5, the project final conclusions are outlined and future work

directions are presented.

43

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45

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