DESIGN OF EFFICIENT IMPLEMENTATION OF Π/4 DQPSK …eprints.utm.my/id/eprint/5300/1/FakhrulRadzyHamdanMFKE2005.pdfteknik modulasi π/4 Differential Quadrature Phase Keying (π/4 DQPSK)

i

DESIGN OF EFFICIENT IMPLEMENTATION OF Π/4 DQPSK

MODULATION FOR MULTIPATH FADING CHANNELS

FAKHRUL RADZY BIN HAMDAN

A project report submitted in partially fulfillment

of the requirements for the degree of

Master of Engineering (Electrical-Electronics & Telecommunication)

Faculty of Engineering

Universiti Technologi Malaysia

NOVEMBER 2005

iii

ACKNOWLEDGEMENT

I would like to express my gratitude to the Most Gracious and Merciful ALLAH

S.W.T. Praiseworthy to Almighty Allah for giving me free will and strength to complete

my Final Year Project.

To my family especially to my parents, Hj. Hamdan Bin Ahmad and Hjh. Nurul

Huda Binti Saleh for their love and support and it is a great pleasure for me to express

my thanks and appreciation for both of you.

I would also like to express my deepest appreciation and gratitude to my

supervisor, PM Dr. Ahmad Zuri Bin Sha’ameri, for his guidance, support, and patience

during my graduate education especially for my Final Year Project. He has been an

invaluable source of technical knowledge and has certainly helped inspire many of the

ideas expressed in this thesis. I had the great benefits of the graduate level courses

MEL1042 (Advance Digital Signal Processing) and MEL1052 (Advance Digital

Communication) taught by him.

Special thanks to my course mates, Syed Mohd Fairuz and Azlin for the

pressuring environment having myself forced to survive among the flock, which they are

exceptionally the best among the best.

May Allah bless all of you……….

iv

ABSTRACT

This project will be base on the wireless communication using π/4 Differential

Quadrature Phase Keying (π/4 DQPSK) modulation technique in the transceiver system.

This modulation technique will be evaluated using the channel with the present of

Additive White Gaussian Noise (AWGN) and multipath Rayleigh fading. The design of

the system will be totally base on simulation. In this case the simulation tool MATLAB

will be used. In this project, normal receiver structure for π/4 DQPSK was redesign by

using multiplier-less method. The new receiver was designed to obtain simpler structure

in term of hardware implementation where it able to reduce number of Integrated Circuit

(IC) used in the design. Performance of the new receiver structure then will be evaluate

base on the error performance of the system. In this case, relation of Bit-Error-Rate

(BER) and Signal to Noise Ration (SNR) will be used to produce the result of error

performance. Normal and new receiver structures which were design in π/4 DQPSK

system will be study base on error performance and hardware complexity to obtain the

most efficient result for the communication system.

v

ABSTRAK

Projek ini melibatkan kajian mengenai transmisi tanpa wayar yang menggunakan

teknik modulasi π/4 Differential Quadrature Phase Keying (π/4 DQPSK). Teknik

modulasi ini akan dikaji menggunakan laluan yang mempunyai Pertambahan Bunyi

Hingar Putih Gaussian (AWGN) dan kelenturan pelbagai laluan Rayleigh (multipath

Rayleigh fading). Sistem ini akan dikaji dengan menggunakan simulasi computer

MATLAB. Didalam projek ini, penerima biasa akan diubah suai dan dicipta

menggunakan cara tanpa pendaraban. Penerima jenis ini dicipta untuk mendapatkan

struktur yang lebih mudah terutama apabila melibatkan penggunaan alatan dimana ia

akan menggurangkan penggunaan penyatuan rekabentuk (IC) didalam struktur.

Penerima baru ini akan dinilai melalui kadar kesilapan bit didalam sistem. Kaitan antara

kadar kesilapan bit dan kadar Signal dan hangar akan digunakan di dalam penilaian ini

untuk mendapatkan keputusan kadar kesilapan sistem. Penerima biasa dan penerima

yang baru yang dicipta dengan menggunakan modulasi π/4 DQPSK akan dikaji

berdasarkan kadar kesilapan dan kesenaggan hardware untuk mendapatkan keputusan

yang terbaik bagi digunakan didalam sistem komunikasi.

vi

TABLE OF CONTENTS

CHAPTER

TITLE

PAGE

ACKNOWLEDGEMENT iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENT vi

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF ABBREVIATION xv

LIST OF APPENDIX xvi

1 INTRODUCTION 1

1.1 Background 1

vii

1.1.1 Modulation 2

1.2 Problem Statements 3

1.3 Project Objective 4

1.4 Scope of Work 5

2 LITERATURE REVIEW 7

2.1 Previous Researches 7

2.2 Finding and Result 9

3 THEORITICAL FOUNDATION 10

3.1 Modulation Scheme in Wireless Communication System 10

3.2 π/4 Differential Quadrature Phase Keying (π/4 DQPSK)

Modulation Technique

11

3.3 Modulation Technique 12

3.3.1 Complex Envelope Representation 13

3.3.2 π/4 DQPSK Signal Description 14

3.3.3 Receiver Structure of π/4-DQPSK 17

3.3.3.1 Baseband Differential Detector 18

3.3.3.2 IF Differential Detector 20

3.3.3.3 FM Discriminator 21

3.3.3.4 Multiplier-less Receiver Structure 22

3.4 Transmission Channel 22

2.4.1 Additive White Gaussian Noise (AWGN) 23

2.4.2 Multipath Rayleigh Fading 24

3.5 Noise Measurement 27

3.5.1 Signal-to-Noise Ratio (SNR) 27

3.5.2 Bit Error Rate (BER) 28

3.6 MATLAB Simulation 29

viii

4 METHODOLOGY, RESULTS AND PERFORMANCE

ANALYSIS

31

4.1 Simulation Methodology 32

4.2 Transmitter of π/4 DQPSK Modulation System 33

4.3 Channel Configuration 36

4.4 π/4 DQPSK Modulation System Using Baseband

Differential Detector as Receiver Structure

36

4.4.1 Model 1: Important Parameters and

Assumption

37

4.4.2 Simulation in Phase 1: Baseband Differential

Detector In Channel Without Noise and Fading

40


Detector In Channel With Noise (AWGN)

42


Detector In Channel With Noise (AWGN) and

Fading (Rayleigh fading)

44

4.5 π/4 DQPSK Modulation System Using Multiplier-less

(1st sector) Receiver Structure

46


Assumption

47

4.5.2 Simulation in Phase 1: Multiplier-less (1st

sector) Receiver In Channel Without Noise and

Fading

50


sector) Receiver In Channel With Noise

(AWGN)

52


sector) Receiver In Channel With Noise

(AWGN) and Fading (Rayleigh fading)

54

4.6 π/4 DQPSK Modulation System Using Multiplier-less d

ix

(1st and 2nd sector) Receiver Structure 56


Assumption

57

4.6.2 Simulation in Phase 1: Multiplier-less (1st and

2nd sector) Receiver In Channel Without Noise

and Fading

60


2nd sector) Receiver In Channel With Noise

(AWGN)

62


2nd sector) Receiver In Channel With Noise

(AWGN) and Fading (Rayleigh fading)

64

4.7 Performance Analysis 66

4.8 Constrain and Limitation 67

4.9 Simulation Result Organization 67

4.10 Performance Analysis of Model 1: π/4 DQPSK

Modulation System Using Baseband Differential

Detector

69

4.10.1 Error Performance Phase 2: Channel With

AWGN

69


AWGN and Rayleigh Fading

70

4.10.3 Hardware Performance 71


Modulation System Using Multiplier-less (1st Sector)

Receiver

72


AWGN

72



73


x


Modulation System Using Multiplier-less (1st and 2nd

Sector) Receiver

75


AWGN

75



76


4.13 Performance Comparison for all Models 78

4.13.1 Error Performance for Channel With AWG 78

4.13.2 Error performance for Channel With AWGN

and Rayleigh Fading

79

4.13.3 Hardware Performance for all Models 80

5 CONCLUSION AND FUTURE WORK 81

5.1 Conclusion 81

5.2 Future Work 83

REFERENCES 85

APPENDIXES 88

xi

LIST OF TABLES

TABLE NO. TITLE PAGE NO.

3.1 Carrier Phase Shifts for π/4-DQPSK Correspondence

to Various Input Bit Pairs.

16

4.1 Parameters used in model 1. 37



xii

LIST OF FIGURES

FIGURE NO. TITLE PAGE NO.

1.1 The overall system of wireless communications. 2

3.1 Unfiltered π/4-DQPSK Signal Constellation 17

3.2 Block diagram of a baseband differential detector

receiver structure.

18

3.3 Block diagram of an IF differential detector receiver

structure.

21

3.4 Block diagram for FM discriminator detector receiver

structure.

21

3.5 Relationship among the channel correlation function

and power density function.

25

4.1 Transmitter of π/4 DQPSK modulation technique. 35

4.2 Flow chart of the first model (baseband differential

detector as receiver).

39

4.3 π/4 DQPSK modulation using baseband differential

detector in channel without noise and fading.

41

4.4 π/4 DQPSK modulation using baseband differential

detector in channel with noise (AWGN).

43

4.5 π/4 DQPSK using baseband differential detector in

channel with noise (AWGN) and fading (Rayleigh).

45

xiii

4.6 Flow chart of the second model (multiplier-less 1st

sector as receiver).

49

4.7 π/4 DQPSK modulation using multiplier-less (1st

sector) receiver in channel without noise and fading.

51


sector) receiver in channel with noise (AWGN).

53


sector) receiver in channel with noise (AWGN) and

fading (Rayleigh).

55

4.10 Flow chart of the second model (multiplier-less 1st and

2nd sector as receiver).

59

4.11 π/4 DQPSK modulation using multiplier-less (1st and

2nd sector) receiver in channel without noise and

fading.

61


2nd sector) receiver in channel with noise (AWGN).

63


2nd sector) receiver in channel with noise (AWGN)

and fading (Rayleigh)

65

4.14 Error performance (BER vs SNR) for π/4 DQPSK

modulation system using baseband differential

detector as receiver channel with AWGN.

69


modulation system using baseband differential

detector as receiver in channel with AWGN and

Rayleigh Fading.

70

4.16 Baseband differential detector receiver structure. 71


modulation system using multiplier-less (1st sector) as

receiver in channel with AWGN.

72

xiv


modulation system using multiplier-less (1st sector) as

receiver in channel with AWGN and Rayleigh Fading.

73

4.19 Multipler-less (1st sector) receiver structure. 74


modulation system using multiplier-less (1st and 2nd

sector) as receiver in channel with AWGN.

75



sector) as receiver in channel with AWGN and

Rayleigh Fading.

76

4.22 Multipler-less (1st and 2nd sector) receiver structure. 77

4.23 Comparison of error performance (BER vs SNR)

for π/4 DQPSK modulation system using all type of

receivers in channel with AWGN.

78

4.24 Comparison of error performance (BER vs SNR)

for π/4 DQPSK modulation system using all type of

receivers in channel with AWGN and Rayleigh

Fading.

79

5.1 Relationship of error performance and hardware

implementation.

83

xv

LIST OF ABBREVIATIONS

π/4 DQPSK π/4 Differential Quadrature Phase Shift Keying

AWGN Additive White Gaussian Noise

IC Integrated Circuit

BER Bit Error Rate

SNR Signal to Noise Ration

MTSO Mobile Telephone Switching Office

PSTN Public Switched Telephone Network

DSP Digital Signal Processing

N-LOS Non-Line of Sight

CPFSK Continuous Phase Frequency Shift Keying

BPSK Binary Phase Shift Keying

QPSK Quadrature Phase Shift Keying

OKQPSK Offset Keyed Quadrature Phase Shift Keying

RF Radio Frequency

xvi

LIST OF APPENDIX

APPENDIX

NO.

TITLE PAGE NO

1.1 Matlab Source Code for Model 1: π/4 DQPSK

modulation system using baseband differential detector

as a receiver structure.

88

1.1.1 Main File: Simulation testing on transmitter, receiver

and channel.

88

1.1.2 Transmitter source code for model 1. 109

1.1.3 Receiver source code for model 1 95


modulation system using multiplier-less (1st sector) as a

receiver structure

98

1.2.1 Main File: Simulation testing on transmitter, receiver

and channel

99

1.2.2 Transmitter source code for model 2 101




sector) as a receiver structure

110

1.3.1 Main File: Simulation testing on transmitter, receiver 110

xvii

and channel

1.3.2 Transmitter source code for model 3 113


1.4 Other function used in project simulation 122

1.4.1 Source code to generate random binary data 122

1.4.2 Source code to generate sinusoidal wave 123

1.4.3 Source code to convert sinusoidal wave to square wave 123

1

CHAPTER 1

INTRODUCTION

1.1 Background.

Historically all telephone communications were accomplished by a wired line

network. All telephones were connected to the network with a pair of wires. Recently, a

wireless network has emerged where the link between the network and telephone is

wireless. This wireless technology has been employed and recognized as a step forward.

Figure 1.1 shows an overall wireless communications systems. Communications

today is on the move. In cars, office buildings, manufacturing plants, shopping malls and

wherever people go, wireless telephones and other communications systems go with

them. Base stations are at the heart of wireless communications systems. All base station

cell sites connect to the Mobile Telephone Switching Office (MTSO). The MTSO in

turn interfaces to the Public Switched Telephone Network (PSTN) by connecting to a

Central Office. Control of all cell sites, all subscriber records, statistics, and billing is

maintained at the MTSO. In the future, smaller "Microstations" will bring wireless

2

services into offices, factories, schools, shopping malls and wherever there is a need for

mobile communications.

Figure 1.1: The overall system of wireless communications.

Driving this new mobility in communications is high-speed digital technology,

and in the forefront of this technology is Digital Signal Processing (DSP). DSP is a

prime enabler for digital communications and is confronting the specific needs of

wireless systems for higher levels of integration and greater performance with low

power consumption. DSP technology will also continue to be the key baseband

technology on which digital wireless systems are built. DSP solutions will grow in

importance as the partition between the radio and the baseband subsystem gradually

moves to drive more and more functionality into the signal processor.

1.1.1 Modulation.

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Modulation plays a key role in any communication system. The type of

modulation used depends on the type of the communication channel. The choice for

modulation technique has a direct impact on the capacity of a digital communication

system. It determines the bandwidth efficiency of a single physical channel is terms of

the number of bits per second per hertz (bit/s/Hz) and it is therefore important that this

choice is discussed in detail.

In selection a suitable modulation scheme for a digital communication system,

consideration must be given to achieving the following:

1. High bandwidth efficiency

2. High power efficiency.

3. Low carrier-to-co channel interference power ration (CCI)

4. Low out-of-band radiation

5. Low sensitivity to multipath fading

6. Constant or near constant envelope

7. Low cost and ease of implementation

To optimize all these features at the same time is not possible as each has its

practical limitation and also is related to the others. For example, to achieve high

bandwidth efficiency one may choose to use high-level modulation. However, if this is

done two consequent disadvantages are introduced. Hence, a trade-off among all the

above features must be adopted.

1.2 Problem Statements

Nowadays wireless has been very important and choice of communication for

world wide user. However, there are two important criteria need to be consider in every

4

type of communication which are efficiency in term of error performance and hardware

design.

The implementation of modulation technique in communication that has efficient

error performance and hardware design is very difficult to achieve in practical

environment. With the additional circuitries, good error performance for communication

system is very easy to achieve but not for hardware design.

Basically most of modulation techniques used a lot of multiplier in its design.

The multiplier is difficult to design in term of hardware especially if the multiplication

operation involves floating point. Base on the difficulties involve, the communication

system will be expensive especially for the application required simpler and cheaper

system.

1.3 Project Objective

The objectives and aims of this project are to investigate and evaluate the error

performance of π/4 Differential Quadrature Phase Keying (π/4 DQPSK) modulation

technique with the new implementation of hardware design subject to the channel with

Additive White Gaussian Noise (AWGN) and Rayleigh fading. The performance study

will be carried out base on the relationship of Bit Error rate (BER) and Signal to Noise

Ratio (SNR). The relationship will be compare for the variable of receiver structures.

The receiver structures will be design to have batter implementation in term of hardware

design.

There will be three different type of π/4 DQPSK system models will be use d in

this project. Those models are:

5

1. π/4 DQPSK modulation system using baseband differential detector as

a receiver structure.

2. π/4 DQPSK modulation system using multiplier-less (1st sector)

receiver structure.

3. π/4 DQPSK modulation system using multiplier-less (1st and 2nd

sector) receiver structure.

1.4 Scope of Work

This project is an entirely simulation project using scientific computer simulation

software, MATLAB 7.0. All models which been explained in previous sub chapter will

be design by using m files in MATLAB 7.0. There will be no hardware design and

application field test involve in this project.

As describe in sub chapter 1.3, there will be only three receivers structure will be

investigate and evaluate which are baseband differential detector, multiplier-less (1st

sector) and multiplier-less (1st and 2nd sector). All of those receiver will be evaluate

using the same transmitter.

There are two extreme cases of channel noise and fading that will be subjected to

the π/4 DQPSK system models. The model will be simulated with different receiver

structure under thermal noise, represented by Additive White Noise Gaussian (AWGN).

Then, the channel is simulated with various different parameters using Non-Line of

Sight (N-LOS) multiple reflected rays represented as multipath Rayleigh fading. In other

word, the channel simulation will be focus on AWGN and Rayleigh fading only.

6

Since there are involvement of noise and fading in the channel, error will

produce during data transmission across the channel. In this case additional circuitries

(error correction) can be used to reduce the error. But for this project, the evaluation and

investigation will be base on transmitter and receiver without error correction scheme.

85

REFERENCES

[1] Sandeep Chennakeshu and Gary J. Saulnier (1993), “Differential Detection of π/4-

Shifted- DQPSK for Digital Cellular Radio”, IEEE Trans. Veh. Technol., Vol. 42,

No. 1, Feb. 1993, pp.46-57.

[2] Fitri Dewi Bt Jaswar (2003). FPGA Implementation of CPFSK Modulation

Techniques for HF Data Communication. University Technology Malaysia: Master

thesis.

[3] Bernard Sklar, "Digital Communications: Fundamentals and Applications", Prentice-

Hall, 2nd Edition, pp. 30-33.

[4] Bernard Sklar, "Rayleigh Fading Channel in Mobile Digital Communication System

Part 1: Characterization", IEEE Communication Magazine, pp. 90-100, July 1997.

[5] Theodore S. Rappaport, "Wireless Communication: Principle and Practice", Pearson

Educational International, 2nd edition. 2002.

[6] WARREN HIOKI (1995), “Telecommunications”, Second Edition. Prentice Hall.

501p.

[7] Bernard Sklar, "Rayleigh Fading Channel in Mobile Digital Communication System

Part 2: Mitigation", IEEE Communication Magazine, pp. 90-100, July 1997.

86

[87] Ahmad Zuri Bin (2003). Bit Error Rate Performance Analysis of Spectrum Based

Detector for FSK Digital Modulation. University Technology Malaysia: PhD thesis.

[9] Kamilo Feher, "Advance Digital Communication System and Signal Processing

Technique", Prentice-Hall. 1987.

[10] Rodger E.Ziemer, "Introduction to Digital Communication ", Prentice-Hall, 2nd

edition. 2001.

[11] Boaz Porat, "A Course in Digital Signal Processing ", John Wiley & Sons, Inc.

1997.

[12] Glover.Ian , "Digital Communication ", Prentice-Hall. 1998.

[13] A. H. Aghvami, (June 1993), “Digital Modulation Techniques for Mobile and

Personal Communication System” Electronics & Communication Engineering

Journal.

[14] PEE, SEE TAT (1999). “Simulation of Bit Error Rate and Signal-to-Noise Ratio

under Different Radio Channels.” Universiti Teknologi Malaysia: Thesis B. Eng.

[15] WENTAO LI (1999). “A DSP-Based π/4 DQPSK Modem.” University of

Saskatchewan, Saskatoon: Thesis B. Eng.

[16] CHUN SUM NG (1993). “On the Error Rate of Differential Detected Narrowband

π/4 DQPSK in Rayleigh Fading and Gaussia Noise”, IEEE Communication

Magazine, Vol. 42 No. 3, August 1993.

[17] GERARD J.M SMITH (2001). “BER Estimation for Wireless Links Using

BPSK/QPSK Modulation” Department of Electrical Engineering, Mathematics &

Computer Science, University of Twenty, Enschede Netherlands.

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DESIGN OF EFFICIENT IMPLEMENTATION OF Π/4 DQPSK …eprints.utm.my/id/eprint/5300/1/FakhrulRadzyHamdanMFKE2005.pdfteknik modulasi π/4 Differential Quadrature Phase Keying (π/4 DQPSK)