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
4.4.3 Simulation in Phase 2: Baseband Differential
Detector In Channel With Noise (AWGN)
42
4.4.4 Simulation in Phase 3: Baseband Differential
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
4.5.1 Model 2: Important Parameters and
Assumption
47
4.5.2 Simulation in Phase 1: Multiplier-less (1st
sector) Receiver In Channel Without Noise and
Fading
50
4.5.3 Simulation in Phase 2: Multiplier-less (1st
sector) Receiver In Channel With Noise
(AWGN)
52
4.5.4 Simulation in Phase 3: Multiplier-less (1st
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
4.6.1 Model 3: Important Parameters and
Assumption
57
4.6.2 Simulation in Phase 1: Multiplier-less (1st and
2nd sector) Receiver In Channel Without Noise
and Fading
60
4.6.3 Simulation in Phase 2: Multiplier-less (1st and
2nd sector) Receiver In Channel With Noise
(AWGN)
62
4.6.4 Simulation in Phase 3: Multiplier-less (1st and
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
4.10.2 Error Performance Phase 3: Channel With
AWGN and Rayleigh Fading
70
4.10.3 Hardware Performance 71
4.11 Performance Analysis of Model 2: π/4 DQPSK
Modulation System Using Multiplier-less (1st Sector)
Receiver
72
4.11.1 Error Performance Phase 2: Channel With
AWGN
72
4.11.2 Error Performance Phase 3: Channel With
AWGN and Rayleigh Fading
73
4.11.3 Hardware Performance 74
x
4.12 Performance Analysis of Model 2: π/4 DQPSK
Modulation System Using Multiplier-less (1st and 2nd
Sector) Receiver
75
4.12.1 Error Performance Phase 2: Channel With
AWGN
75
4.12.2 Error Performance Phase 3: Channel With
AWGN and Rayleigh Fading
76
4.12.3 Hardware Performance 77
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
4.2 Parameters used in model 2. 47
4.3 Parameters used in model 3. 57
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
4.8 π/4 DQPSK modulation using multiplier-less (1st
sector) receiver in channel with noise (AWGN).
53
4.9 π/4 DQPSK modulation using multiplier-less (1st
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
4.12 π/4 DQPSK modulation using multiplier-less (1st and
2nd sector) receiver in channel with noise (AWGN).
63
4.13 π/4 DQPSK modulation using multiplier-less (1st and
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
4.15 Error performance (BER vs SNR) for π/4 DQPSK
modulation system using baseband differential
detector as receiver in channel with AWGN and
Rayleigh Fading.
70
4.16 Baseband differential detector receiver structure. 71
4.17 Error performance (BER vs SNR) for π/4 DQPSK
modulation system using multiplier-less (1st sector) as
receiver in channel with AWGN.
72
xiv
4.18 Error performance (BER vs SNR) for π/4 DQPSK
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
4.20 Error performance (BER vs SNR) for π/4 DQPSK
modulation system using multiplier-less (1st and 2nd
sector) as receiver in channel with AWGN.
75
4.21 Error performance (BER vs SNR) for π/4 DQPSK
modulation system using multiplier-less (1st and 2nd
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
1.2 Matlab Source Code for Model 2: π/4 DQPSK
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
1.2.3 Receiver source code for model 2 105
1.3 Matlab Source Code for Model 3: π/4 DQPSK
modulation system using multiplier-less (1st and 2nd
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
1.3.3 Receiver source code for model 3 117
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.
3
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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