ANALYSIS PERFORMANCE OF 256 AND 1024 QAM BY USING … · Laporan Akhir Penyelidikan bertajuk “Analysis Performance Of 256 and 1024 QAM By Using Reed Solomon Codes apply in Digital

ANALYSIS PERFORMANCE OF 256 AND 1024 QAM BY USING REED

SOLOMON CODES APPLY IN DIGITAL VIDEO BROADCASTING

THROUGH ADDITIVE WHITE GHAUSSIAN NOISE CHANNEL

INSTITUT PENGURUSAN PENYELIDIKAN

UNIVERSITI TEKNOLOGI MARA

40450 SHAH ALAM, SELANGOR

MALAYSIA

DISEDIAKAN OLEH :

SUZI SEROJA SARNIN

NORFISHAH AB WAHAB

NOOR HAFIZAH ABDUL AZIZ

NOVEMBER 2009

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Tarikh : 1 November 2009

No. Fail Projek : 600-RMI/ST/DANA 5/3/Dst (124/2008)

Penolong Naib Canselor (Penyelidikan)

Institut Pengurusan Penyelidikan

Universiti Teknologi MARA

40450 Shah Alam

Ybhg. Prof.,

LAPORAN AKHIR PENYELIDIKAN “ANALYSIS PERFORMANCE OF

256 AND 1024 QAM BY USING REED SOLOMON CODES APPLY IN

DIGITAL VIDEO BROADCASTING THROUGH ADDITIVE WHITE

GHAUSSIAN NOISE CHANNEL”

Merujuk kepada perkara di atas, bersama-sama ini disertakan 2 (dua) naskah

Laporan Akhir Penyelidikan bertajuk “Analysis Performance Of 256 and 1024

QAM By Using Reed Solomon Codes apply in Digital Video Broadcasting

through Additive White Ghaussian Noise Channels”.

Sekian, terima kasih.

Yang benar,

SUZI SEROJA SARNIN

Ketua

Projek Penyelidikan

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PROJECT TEAM MEMBERS

SUZI SEROJA SARNIN

Project Leader

………………………………………………………………

NORFISHAH AB WAHAB

Project Member

……………………………………………………..

NOOR HAFIZAH ABDUL AZIZ

Project Member

……………………………………………………..

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DECLARATION

I hereby pledge this thesis is my original writing except the quotations and summaries

that I had clearly quoted the sources.

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ACKNOWLEDGEMENT

First and foremost, I praised God the Almighty for the blessings endowed upon

me. My deep sense of gratitude to the group members, madam Norfishah Ab Wahab

and miss Noor Hafizah Abdul Aziz for their support and commitment throughout this

research.

I would also like to thank all of the persons who have directly or indirectly

involved and contributed for the success of the project.

Finally, my special gratitude is dedicated to my husband, children and family

members for their endless support that make this research possible.

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TABLE OF CONTENTS

CHAPTER PAGE

DECLARATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

LIST OF ABREVIATIONS

1. INTRODUCTION

Background

Objective

Scope of project

Thesis Organization

2. LITERATURE RIVIEW

Quadrature Phase Shift Keying (QPSK)

QPSK Modulator

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QPSK Bandwidth

QPSK Demodulator

Minimum Shift Keying (MSK) modulation

Cyclic Codes

Coding Process (Cyclic Codes)

Procedure of Obtaining the Transmitted Polynomial

Systematic Encoding of a Cyclic Code

Error Correction

Additive white Gaussian Noise (AWGN) channel

3. METHODOLOGY

4. RESULTS AND DISCUSSION

Flowchart of the simulation

Result and analysis from the simulation

Input message

Encoding process

Modulation process

Transmission medium

Demodulation process

Decoding process

BER error performance

5. CONCLUSION

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6. REFERENCES

7. APPENDIX

LIST OF FIGURES

FIGURE TITLE PAGE

2.1 QPSK modulator block diagram 7

2.2 QPSK scatter diagram 8

2.3 MSK signal 10

2.4 QPSK demodulator block diagram 13

2.5 MSK encoding signal 14

2.6 Encoding circuit 21

2.7 Example of syndrome calculation with an (n-k)-stage shift

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24

3.1 Cyclic code encoder 27

4.1 Flow chart of simulation 31

4.2(a) QPSK input message 33

4.2(b) MSK input message 33

4.3(a) QPSK encoded signal 35

4.3(b) Output signal QPSK 36

4.4(a) QPSK modulated signal 37

4.4(b) MSK modulated signal 37

4.5(a) QPSK modulated signal added with noise 38

4.5(b) MSK modulated signal added with noise 38

4.6(a) Demodulated signal 39

4.6(b) Demodulated signal 39

4.7 MSK output signal

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41

4.8(a) QPSK Bit error rate performance 42

4.8(b) MSK Bit error rate performance 43

4.9 Performance of QPSK and MSK Modulation 44

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LIST OF ABBREVIATIONS

AWGN - Additive White Gaussian Noise

CRC - Cyclic Redundancy Check

ECC - Error Control Coding

Ex-OR - Exclusive OR

FCS - Frame Check Sequence

FEC - Forward Error Correction

FSK - Frequency Shift Keying

MSK - Minimum Shift Keying

QPSK - Quadrature Phase Shift Keying

MOD-2 - Modulo-2

PISO - Parallel in Serial Out

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PSK - Phase Shift Keying

S/N - Signal to Noise

SISO - Serial In Serial Out

Tb - Bit Period

Ts - Time Symbol

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ABSTRACT

This project is highlight about the performance of 256-Quadrature Amplitude

Modulation (QAM) and 1024-QAM applying in Digital Video Broadcasting (DVB)

through Additive White Gaussian Noise (AWGN) channel. Besides, this project using

Reed-Solomon (R-S) code as the decode/encode technique in order to act as a forward

error correcting code. Furthermore, this project is basically deal with one transmit

antenna and one receive antenna at the transmission part and receiving part respectively.

There are some comparison will be made between the 256-QAM and 1024-QAM

purposefully to get the best performance when applying in DVB through AWGN

channel in which both of them is using the same forward error correcting code (Reed-

Solomon code) technique. Basically, the best performance is determined in term of Bit

Error Rate (BER) and Signal Energy to Noise Power Density Ratio (Eb/No). It is

observed that as the constellation order of QAM increase the performance will be

degraded. Thus, 256-QAM will give the best performances either in term of Eb/No or

BER. In the mean time, both of the QAM (256-QAM and 1024-QAM) also being

compared in term of the symbol-error correcting capability that is known as t in which it

is observed that the performance is graded in response to the increasing of the value of t.

During this project, all the simulation process that presented the performances of both of

the QAM is done by using software that is known as MATLAB version 7.6.0.

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ANALYSIS PERFORMANCE OF 256 AND 1024 QAM BY USING REED

SOLOMON CODES APPLY IN DIGITAL VIDEO BROADCASTING

THROUGH ADDITIVE WHITE GHAUSSIAN NOISE CHANNEL

DISEDIAKAN OLEH :

SUZI SEROJA SARNIN

NORFISHAH AB WAHAB

NOOR HAFIZAH ABDUL AZIZ

NOVEMBER 2009

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CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

It is well known that the QAM has been widely used as a modulation technique for

digital communication system due to its simple detection [1] and the ability to achieve

high rate transmission without increasing the bandwidth [2]. In response to this fact,

QAM become a suitable modulation technique in order to fulfill the requirement that

needs high speed transmission in DVB. However, there is a need for efficient process or

techniques of implementation of QAM to make sure that QAM can operate in maximum

or optimize performance. This is because by moving to a higher-order constellation, it is

possible to transmit more bits per symbol but on the other hands, if the mean energy of

the constellation is remain the same thus more susceptible to noise and other corruption

[3]. The fact that increasing the order of the QAM constellation will degrade the QAM

performance will be study in this project.

In digital communication, one of the most important technical issues that might be

occurred which are synchronization problem and the forward error correction used in

this project which is R-S code has a unique advantage that suited to modify this

problem. This is because this R-S code has the ability to recover the synchronization

problem since this code is self-synchronizable [4]. Owing to this reasons, the R-S code

has been choose in order to study the performance of QAM apply in DVB. Nevertheless,

the R-S code is affected with its Symbol-Error Correcting Capability (t) in which the R-

S code will perform better in higher value of t. This fact also will be discuss during this

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project in order to study the performance of both 256-QAM and 1024-QAM apply in

DVB through AWGN channel for various value of t.

Since, this project is study the performance of QAM in DVB, it is necessary to find the

most suitable channel that use to propagate the signal. Basically, channel is fall into

three types which are fading channels, channels in which the noise stems from the others

and AWGN channel. As the author compared all the three type of channels, the best

suite channel for DVB is AWGN channel. This is because in the practical world is that

AWGN never infinite in bandwidth. Thus, the destruction process is successfully safe

since the receiver or measuring instrument has finite bandwidth [5].

1.2 OBJECTIVE

This project has several objectives such as to analysis and simulates the performance

between 256-QAM and 1024-QAM using Reed-Solomon code applying in DVB

through AWGN channel. Besides, this project also purposefully to compare both

constellation order of QAM (256-QAM and 1024-QAM) in order to yield the best

performances when applying in DVB in term of BER as well as Eb/No. Furthermore, the

performance of Reed-Solomon code also being highlight in term of symbol-error

correcting capability (t) for both of the constellation order of QAM. Lastly, this project

also guides me to have the ability in using the MATLAB 7.6.0.

1.3 SCOPE OF PROJECT

This project focusing on the analysis performance of 256 QAM as well as 1024 QAM

when applying in DVB. AWGN channel and Reed –Solomon code have been choose in

this project in which the Reed-Solomon code is act as the decode/encode technique or

also can be describe as forward error correction and on the other hands, AWGN is act as

the medium for signal propagation. Basically, this project makes a comparison between

both of the constellation order of QAM (256-QAM and 1024-QAM) in order to find

which one of them can yield the best performance in DVB through AWGN channel.

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Besides, the performance comparison for both constellation order of QAM also being

done in term of symbol-error correcting capability (t) as the value of t will determined

the capability of Reed-Solomon code to correct error. All the comparison during this

project is represented using the graph of BER versus Eb/No as the performance for both

order of QAM applying in DVB is analyze in term of BER and Eb/No using MATLAB

version 7.6.0.

1.4 PROBLEM STATEMENT

Modulation and demodulation process is the important process that involved in this

project in which modulation process is modulated the information signal with carrier

signal in order to make the signal compatible to the transmission channel. On the other

hands, demodulation process is the reverse process of the modulation process since it is

responsible to convert the modulated signal back to the original information signal

(remove the carrier signal from the information signal). Thus, it is important to

determine what type of modulation that is suitable applying in DVB. Since QAM has

ability due to its simple detection and the ability to achieve high rate transmission

without increasing the bandwidth, QAM become a suitable modulation technique in

order to fulfill the requirement that needs high speed transmission in DVB. This is

because QAM allowing two digital carrier signals to get transmitted on the same

bandwidth that will give QAM an advantage of conservation of bandwidth. Furthermore,

with QAM, amplitude and phase shift keying are combined so that can optimized the

distance between the point in the constellation diagrams and will reduced the probability

of one point to misinterpreted with neighbour point as compared to other digital

modulation technique. All of these facts lead to make the QAM being chosen as the

modulation technique for this project.

The synchronization problem which is one of the most important technical issues in

digital communication required the best coding/decoding technique in order to make the

information or signal successfully received at the receiving part. Since the Reed-

Solomon code have an ability to provide self-synchronization, this type of code being

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selected to act as the code/decode technique or also can be known as the forward error

correcting code. In the mean time, the Reed-Solomon is a powerful class of code and

extremely flexible in use since Reed-Solomon code is a good choice for a variety of

channel condition as has low redundancy overhead. Besides, with Reed-Solomon code,

one code can be use both to detect and correct errors in which depends to the redundant

message being added.

Furthermore, the other problem that causes the author to study in this project is about the

most suite channel for yield the good performance of DVB. This is because it is difficult

to eliminate of all the noise of the received signal at the receiver part in order to get the

original input signal. As a result, the author is decided to study about the best channel in

DVB. Basically, channel is fall into three types which are fading channels, channels in

which the noise stems from the others and AWGN channel. As the author compared all

the three type of channels, the best suite channel for DVB is AWGN channel. This is

because in the practical world is that AWGN never infinite in bandwidth. Thus, the

destruction process is successfully safe since the receiver or measuring instrument has

finite bandwidth.

1.5 THESIS ORGANIZATION

This thesis has been divided into five chapters. Chapter 1 covers the introduction of this

thesis, the objective of this project, the scope of work and the thesis organization. In

Chapter 2, the basic theory has been discussed and this basic theory included Quadrature

Amplitude Modulation (QAM), Reed-Solomon (R-S) code, Additive White Gaussian

Noise (AWGN) channel and Digital Video Broadcasting (DVB). Chapter 3 presents the

methodology of this project and also contains the explanation about the simulation steps

that being used during this project using MATLAB version 7.6.0. Then, Chapter 4 is

focusing on the result obtained and all of the result has been discussed in this chapter.

Finally, Chapter 5 is provide the conclusion for the whole project and also provide the

idea for future development in order to improve the project in future

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CHAPTER 2

LITERATURE REVIEW

2.1 MODULATION AND DEMODULATION

Modulation and demodulation process are the important processes that involved in this

project and both of them play a specific utility applying at different part in this project’s

process in which modulation is takes place at transmission part and the demodulation is

requires at the receiving part. In order to propagate the information signal over standard

transmission media, it is necessary to modulate the information signal onto higher

frequency analog signal called a carrier. Thus, the modulation process can be define as a

process of impressing low frequency information signals onto a high frequency carrier

signal due to make the signal compatible to the transmission channel [6] .

On the other hands, the demodulation process is the reverse process of the modulation

process since it is responsible to convert the modulated carrier signal back to the original

signal (remove the information signal from the carrier signal). Furthermore, in digital

communication, there are several types of modulation process might be involves. For

instance:

Amplitude Shift Keying (ASK) – amplitude of the carrier is modulated.

Frequency Shift Keying (FSK) – frequency of the carrier is modulated.

Phase Shift Keying (PSK) – phase of the carrier is modulated.

Quadrature Amplitude Modulation (QAM) – amplitude and phase are

modulated.

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All of these types of digital communication as their own pros and contras and QAM

have been chosen as the modulation technique for this project as it has the ability that

fulfilled the DVB requirement. In respond to this, the theoritical part of QAM has been

further discussed later.

2.2 QUADRATURE AMPLITUDE MODULATION (QAM)

As a modulation technique in this project, QAM modulated the information signal due to

make it compatible to the channel then lead to successfully being transmitted to the

receiver. QAM is a modulation scheme which conveys data by changing or modulating

the amplitude and the phase of two carrier waves as QAM process involves two input

signal that is classified as in phase component, I-channel and quadrature component Q-

channel [2]. The process of QAM can best be described using QAM block diagram [6]:

Figure 2.1: (a) QAM Modulator; (b) QAM Demodulator

According to the QAM block diagram, the input signal is divided into two channels (I-

channel and Q-channel) as being state before in which both of them will added together

at linear summer in order to produce the QAM output. Basically, the balance modulator

is act as a multiplier that multiplied one channel by sine wave (I-channel) and the other

channel is multiplied by a cosine wave (Q-channel). Actually, the sine and cosine wave

is the carrier signal that being produced by carrier oscillator but one of them undergoes

90o phase shifter that make them differ by 90

o out of phase. Owing to this reason that

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cause both of the channel (I-channel and Q-channel) also 90o out of phases and lead to

bandwidth conservation (higher data rate without require increasing of bandwidth) as

one of the advantage for QAM. Then, when the signal is captured at the receiver, the

filter at the QAM demodulator will removes the high frequency terms leaving only the

independently modulated signal (independently of the quadrature component for I-

channel and independently of the in phase component for Q-channel) [7].

Digital signal is being represented using constellation diagram. Similarly with QAM that

also represented using constellation diagram that purposefully to graphically represent

the quality of the signal as well as the distortion of the digital signal. There are many

types of constellation diagram which is depending on the constellation order of QAM,

. For instance, Square constellation is created when the order of QAM is a power of 4.

Besides, the Cross constellation diagram can be constructed when the order of QAM is

not equal to the power of 4. This statement can be summarized as [8]:

Square Constellation

M = 4n

(2.1)

Where n =1, 2, 3, …

Figure 2.2: Square Constellation Diagram

Cross Constellation

M ≠ 4n (2.2)

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Where n =1, 2, 3, …

Figure 2.3: Cross Constellation Diagram

However, it also can be other type of QAM constellation diagram:

Figure 2.4: Constellation Diagram Of 8-QAM

In digital telecommunication, the data is usually binary and the number of points in the

grid is usually a power of two (2, 4, 8, …). Thus, the Square Quadrature Amplitude

Modulation is produce and widely used as a modulation technique that has the number

of bits per symbol is even. This modulation technique is suitable for this project since

involves 256-QAM and 1024-QAM that have the number of bit is equal to eight and ten

respectively (even). On the other hands, for the odd number of bits per symbol, the most

suitable modulation technique is Cross Quadrature Amplitude Modulation [7].

Furthermore, the QAM technique is being development in order to improve its

performance. As a result, the new technique of QAM is yield such as Triangular

Quadrature Amplitude Modulation [1] and Rectangular Quadrature Amplitude

Modulation [2]. During this project, there are two constellation orders of QAM that has

been studied which are 256-QAM and also 1024-QAM.

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In mathematically, QAM represented as [9]:

;

; (2.3)

Where ε is represent the signal energy, is equal to the signal amplitude for the

information conveyed by the cosine of the carrier and the signal amplitude for the

information conveyed by the sine of the carrier is denoted as

2.2.1 256-QAM

256-QAM is one type of QAM that constructed with 256 as the constellation order

(M=256). Beside, the bit rate of input data of 256-QAM is denoted as . This

statement can best be described using the 256-QAM block diagram below:

Figure 2.5: 256-QAM Block Diagram at Transmission Part

Referring to the 256-QAM block diagram at the transmission part, it is shows that he

input data is divided into two channels which are I-channel and Q-channel and both of

them consists of bit rate that is equal to the original input data divided by eight. Then,

both of the channel is undergoes 2-to-16 level converter in order to produce 16 level

PAM signal. Next, I-channel is multiplied with the carrier signal that is denoted as sin

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wct. On the other hands, Q-channel also multiplied with carrier signal but the carrier

signal is undergoes 90o phase shifter first that make the carrier signal is in cosine

function (cos wct) and lead both channel are 90o out of phase. Lastly, the linear summer

will add both of them in order to yield the QAM output.

256-QAM has a capability to transmit only smaller data rate as the 256-QAM

constructed with number of bits is equal to eight. By mathematically:

(2.4)

Where is represent the constellation order of QAM and is equal to the number of

bits.

In respond to this, 256-QAM has less susceptible to noise. This is because the error

performance of QAM depends primarily on the minimum distance among points in its

constellation [5] and this distance is determined by the constellation order of QAM as

higher order will yield minimum distance of points in the constellation diagram. Its can

be proved using formula [5]:

(2.5)

Where represent the nearest-neighbour distance in the constellation, is the

number of distinct pairs at the distance and is represent the number of points in the

constellation.

Thus, the probability of error is decline as the point distance in the constellation is

increase since the probability for one point to misinterpret to the neighbour point is

reduced. Oppositely for large value of M, it causes in decreasing value of point distance

in the constellation, hence the probability for one point to misinterpret to others is

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