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SYMMETRICAL HIGH-SPEED DIGITAL SUBSCRIBER LINE (SHDSL)
CHANNEL MODELLING
ROHISHAM BIN RAMLAN
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
i
SYMMETRICAL HIGH-SPEED DIGITAL SUBSCRIBER LINE (SHDSL) CHANNEL MODELLING
ROHISHAM BIN RAMLAN
This Report Is Submitted in Partial Fulfillment of Requirements for The Bachelor
Degree of Electronic Engineering (Wireless Electronic)
Fakulti Kejuteraan Elektronik dan Kejuteraan Komputer
Universiti Teknikal Malaysia Melaka
JUNE 2016
ii
BORANG PENGESAHAN STATUS LAPORAN
UNIVERSTI TEKNIKAL MALAYSIA MELAKA
FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER
BORANG PENGESAHAN STATUS LAPORAN
PROJEK SARJANA MUDA II
Tajuk Projek : ……………………………………………………………………………
……………………………………………………………………………
Sesi Pengajian
:
Saya ………………………………………………………………………………………………….. (HURUF BESAR) mengaku membenarkan Laporan Projek Sarjana Muda ini disimpan di Perpustakaan dengan syarat-syarat kegunaan seperti berikut:
1. Laporan adalah hakmilik Universiti Teknikal Malaysia Melaka.
2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja.
3. Perpustakaan dibenarkan membuat salinan laporan ini sebagai bahan pertukaran antara institusi
pengajian tinggi.
4. Sila tandakan ( √ ) :
SULIT*
*(Mengandungi maklumat yang berdarjah keselamatan atau
kepentingan Malaysia seperti yang termaktub di dalam AKTA
RAHSIA RASMI 1972)
TERHAD**
**(Mengandungi maklumat terhad yang telah ditentukan oleh
organisasi/badan di mana penyelidikan dijalankan)
TIDAK TERHAD
Disahkan oleh:
__ ________________________ ___________________________________
(TANDATANGAN PENULIS) (COP DAN TANDATANGAN PENYELIA)
iii
“I hereby declare that the work in this project is my own except for summaries and quotations which have been duly acknowledge.”
Signature : ....................................................... Author : ....................................................... Date : .......................................................
iv
“I acknowledge that I have read this report and in my opinion this report is sufficient in term of scope and quality for the award of Bachelor of Electronic
Engineering (Wireless Communication) with Honours.”
Signature : ....................................................... Supervisor’s Name : ....................................................... Date : .......................................................
vi
ACKNOWLEDGEMENT
First of all, praise to Allah SWT, Most Merciful for His guidance and blessing.
Lots of thanks to my beloved parents Dr. Ramlan Bin Mohamed A.M.N and Rosimah
Binti Sukur, who’s given constant support and love I have relied throughout my time
at university. Their unflinching courage and conviction will always inspire me. I hope
that I can continue in my own way the noble mission to which they gave their lives. I
dedicate this work to my family.
I would like to express my deep and sincere gratitude to my supervisor Dr.
Mohd Azlishah Bin Othman and my co-supervisor Profesor Madya Dr. Mohamad
Zoinol Abidin Bin Abd Aziz. His wide knowledge and his logical way of thinking
have been of great help for me. Furthermore, he always helps and guides me in
fulfilling and understands the task to be done. I also would like to express gratitude to
Team TM R&D, En. Mohd Shahril Izuan Bin Mohd Zin and Profesor Madya
Muhammad Syahrir Bin Johal for helping me to complete this study.
Finally, I would like express appreciation to my adoptive mother and my
special friend who always encourage and keep pushing me to my limit for completing
this study. Special thanks also to all my friends for their cooperation and support.
Thank you very much from bottom of my heart.
vii
ABSTRACT
Symmetrical high-speed digital subscriber line (SHDSL) is a data
communication technology for equal transmits and receive data rate over the copper
telephone lines. Difference from other DSL technologies, SHDSL uses multi-level
pulse-amplitude modulation (PAM) together with trellis coding. It is much faster than
a conventional voiceband modem that can provide nowadays. In this study the speed
of the SHDSL system was evaluated and estimated by observing the Bit Error Rate
(BER) during simulation process. Simulation of SHDSL single line base band and
transceiver was conducted by given the information to the system including a
transmitter, a receiver and a channel model. This simulation, perform a certain state of
trellis code and using a certain rate convolution with corresponding of Viterbi
algorithm at the receiver part. In the channel part, the calculation of signal-to-ratio
(SNR) was performed and this includes the insertion loss in the channel, Far-end
crosstalk (FEXT) and Near-end crosstalk (NEXT), and Power Spectral Density (PSD).
All this is referred to the standard ITU-T G.991.2. For the result of this study, the BER
achieve is 10-6 with transmitted bits of 106 bits. The BER achieved is based on the
calculated SNR and the value of SNR to get BER 10-6 is around 37dB. It is assuming
that the BER can be achieve 10-7 by transmit 109 of bits. By performing this simulation
with the result stated, the SHDSL can be estimate its speed.
viii
ABSTRAK
Simetri kelajuan tinggi talian pelanggan digital (SHDSL) adalah teknologi
komunikasi data untuk memancar sama dan menerima kadar data melalui talian telefon
tembaga. Perbezaan daripada teknologi DSL lain, SHDSL menggunakan pelbagai
peringkat modulasi nadi amplitud (PAM) bersama-sama dengan trellis pengkodan. Ia
adalah lebih cepat daripada modem jalur suara konvensional yang boleh memberikan
masa kini. Dalam kajian ini kelajuan sistem SHDSL itu dinilai dan dianggarkan
dengan memerhatikan Kadar Bit Error (BER) semasa proses simulasi. Simulasi band
asas SHDSL baris dan transceiver dikendalikan diberikan maklumat untuk sistem
termasuk sebuah pemancar, penerima dan model saluran. Simulasi ini, melaksanakan
keadaan tertentu kod jari-jari dan menggunakan kekusutan kadar tertentu dengan
sepadan algoritma Viterbi di bahagian penerima. Dalam bahagian saluran, pengiraan
isyarat kepada nisbah (SNR) telah dilaksanakan dan ini termasuk kehilangan sisipan
dalam saluran, Far-end crosstalk (FEXT) dan Near-end crosstalk (NEXT), dan kuasa
spektral Ketumpatan (PSD). Semua ini disebut standard ITU-T G.991.2 itu. Untuk
hasil daripada kajian ini, BER mencapai adalah 10-6 dengan bit dihantar 106 bit. The
BER dicapai adalah berdasarkan SNR dikira dan nilai SNR untuk mendapatkan BER
10-6 adalah sekitar 37dB. Ia menganggap bahawa BER boleh mencapai 10-7 oleh
penghantar 109 bit. Dengan melakukan simulasi ini dengan keputusan yang
dinyatakan, SHDSL boleh menjadi menganggarkan kelajuannya.
ix
TABLE OF CONTENT
TITLE PAGE
PROJECT TITLE i
DECLARATION REPORT ii
DECLARATION iii
SUPERVISOR DECLARATION iv
DEDICATION v
ACKNOWLEDGEMENT vi
ABSTRACT vii
ABSTRAK viii
TABLE OF CONTENT ix
LIST OF TABLE xii
LIST OF FIGURE xiii
ABBREVIATIONS xv
INTRODUCTION 1
1.1 Project Overview 1
1.2 Problem Statement 3
1.3 Objectives 3
1.4 Scope of work 3
1.5 Project Significance 4
LITERRATURE REVIEW 5
2.1 Digital Subscriber Line (DSL) 5
x
2.2 Overview on Asymmetric Digital Subscriber Line (ADSL) Technology 6
2.3 Overview of SHDSL System Performance 7
2.4 SHDSL Transceiver 8 2.4.1 Scrambler 8 2.4.2 TCM Encoder 9 2.4.3 Mapper 13 2.4.4 Tomlinson-Harashima Precoder 13 2.4.5 Decision Feedback Equalizer 14 2.4.6 Demapper 15 2.4.7 Viterbi 15 2.4.8 Descrambler 16
2.5 Design of G.SHDSL Signal Reconfigurable System Based on FPGA 16
2.6 Data Error in ADSL and SHDSL Systems due to Impulse Noise 17
METHODOLOGY 19
3.1 Introduction 19
3.2 Software implementation 22
3.3 SHDSL System Development 22
3.4 Transmitter 22 3.4.1. Bit Generator 22 3.4.2. Scrambler 23 3.4.3. Trellis @ Convolution Encoder 24 3.4.4. Mapper 25 3.4.5. Tomlinson-Harashima Precoder (THP) 26
3.5 Spectral Shaper 27
3.6 Receiver 30 3.6.1 Decision Feedback Equalizer (DFE) 30 3.6.2 Demapper 30 3.6.3 Viterbi 30 3.6.4 Descrambler 31
3.7 Compare BER 31
3.8 Parameters of the simulation 32
RESULTS AND DISCUSSION 33
4.1 Output On Each Block Diagram of SHDSL system 33
4.2 FEXT 36
4.3 NEXT 37
4.4 PSD 38
4.5 Probability of Error 39
xi
CONCLUSION AND SUGGESTION 42
5.1 Conclusion 42
5.2 Suggestion 43
REFERENCES 44
APPENDIX A 46
APPENDIX B 48
APPENDIX C 49
APPENDIX D 50
APPENDIX E 51
APPENDIX F 53
APPENDIX G 54
APPENDIX H 55
xii
LIST OF TABLE
1.1 DSL Technology version since 1999 to 2005 2
2.1 List of Convolution encoder Polynomial 12
3.1 Mapping 32-PAM 24
3.2 PSD Parameter 26
4.1 Simulation result of SHDSL system SNR 37
4.2 Simulation result of SHDSL system BER 38
xiii
LIST OF FIGURE
Title Page
2.1 Typical Realization of an SHDSL System 7
2.2
Block diagram of an SHDSL transceiver. TX data (transmit
data); RX data (receive data); AFE (analog front end); DFE
(Decision Feedback Equalizer); FFE (Feed Forward Equalizer)
8
2.3 Transmitter operations in data mode 10
2.4 Block diagram of TCM encoder 11
2.5 Block Diagram of Convolution Encoder 12
2.6 4-PAM Mapping. Im (imaginary); Re (real) 14
2.7 Structure of decision feedback equalizer (DFE) system 15
2.8
G.SHDSL link model. PMD (Physical Medium Dependent);
SRU (SHDSL Regenerator Unit); STU-R (SHDSL Transceiver
Unit Remote-End); STU-C (SHDSL Transceiver Unit Central
Office)
16
3.1 Flow Chart of Project 19
3.2 SHDSL Block Diagram. TCM (Trellis-Coded Modulation); AFE
(Analog Front End); DFE (Decision Feedback Equalizer) 20
3.3 Transmitter of SHDSL. TCM (Trellis-Coded Modulation) 21
3.4 Scrambler Circuit 22
3.5 Convolution Encoder (rate 1/2, K=5) 23
3.6 Receiver of SHDSL System. DFE (Decision Feedback
Equalizer) 28
4.1 (a) The Generated Data; (b) The Scrambled Data 30
4.2 (a) Data Arrange in Series Form; (b) Data Arrange in Parallel
Form 31
xiv
4.3 (a) 4 row of bits; (b) 5 row of bits 32
4.4 (a) Parallel bits; (b) Data in symbol in 32-PAM 32
4.5 Tomlinson Harashima Precoder Output 33
4.6 FEXT interference of SHDSL. Each line representation of the
length of cables of copper wires (1, 2, 3, 4, 5, 6, 7 and 8km). 34
4.7
Near-End Crosstalk (NEXT) of SHDSL. The line represents of
the number of users in the SHDSL system. (2, 10, 20, 30, 50 and
100 users).
35
4.8 PSD of SHDSL. The line represents the payload of the SHDSL
system. (192, 256, 512, 768, 1024, 1536, 2048 and 2304 kbit/s) 36
4.9
Probability of Error simulation vs Theory. The first line (above)
represent the theory part and the second line represent simulation
part (below).
36
xv
ABBREVIATIONS
ADSL Asymmetric Digital Subscriber Line
AFE Analog Front End
BER Bit Error Rate
DFE Decision Feedback Equalizer
DMT Discrete Multitoned Transmission
DSL Digital Subscriber Line
DSP Digital Signal Processor
FEXT Far-end Crosstalk
FFE Feed Forward Equalizer
FFT Fast Fourier Transform
FIR Finite Impulse Response
FPGA Field Programmable Gate Array
HDSL High-Bit-Rate Digital Subscriber Line
IL Insertion Loss
ISDN Integrated Services Digital Network
ITU-T International Telecommunication Union Standardization
LMS Least Mean Squares
xvi
MIMO Multi Input Multi Output
MIPS Million Instruction Per Second
NEXT Near-end Crosstalk
PAM Pulse Amplitude Modulation
PBO Power Backoff
PDR Payload Data Rate
PMD Physical Medium Dependent
POTS Plain Old Service
QAM Quadrature Amplitude Modulation
RX Receive
SDSL Symmetric Digital Subscriber Line
SHDSL Symmetric High-Speed Digital Subscriber Line
SNR Signal-to-Noise Ratio
STU SHDSL Transceiver Unit
STU-C STU at the Central Office
STU-R STU at the Remote End
SRU SHDSL Regenerator Unit
TCM Trellis Coded Modulation
TCPAM Trellis Coded Pulse Amplitude Modulation
THP Tomlinson-Harashima Precoder
TM Telecom Malaysia
TM R&D Telecom Malaysia Research and Development
TX Transmit
VDSL Very-High-Bit-Rate Digital Subscriber Line
CHAPTER 1
INTRODUCTION
1.1 Project Overview
Digital Subscriber Line (DSL) is a broadband high-speed internet technology
that brings high-bandwidth information to homes and offices over ordinary copper
telephones lines analog form and back to digital form. Digital data is transmitted
directly to the computer, as is, exploiting the maximum bandwidth and the wide range
of unused frequencies available in the existing copper wire of telephone networks for
high-speed broadband communication. Moreover, the signal can also be separated if
one chooses, so that some of the bandwidth is used to transmit an analog signal for
simultaneously using the telephone line for voice.
DSL can achieve higher data-transfer-rates than dail-up modems by utilizing
more of the available bandwidth in a local loop. The old telephone service only makes
use very limited amount of the lower frequencies. But the bandwidth of the old
telephone service is enough for transmitting reasonable-quality analog voice.
Although the service is enough for transmitting reasonable-quality of data but it is
unable to transmit high-speed data. Most DSL technology sent their digital signals
2
over twisted-copper telephone lines (local loop) using amplitude-modulated analog
tones. This technique is referred to as discrete multitoned transmission (DMT). Today,
there are many type of DSL technology as shown in Table 1.
Table 1.1: DSL Technology version since 1999 to 2005
Family ITU Name Ratified Maximum Speed Capability
ADSL G.992.1 G.dmt 1999 7 Mbps down, 800 kbps up
ADSL2 G.992.3 G.dmt.bis 2002 8 Mbps down, 1 Mbps up
ADSL2plus G.992.5 ADSLplus 2003 24 Mbps down, 1 Mbps up
ADSL2-RE G.992.3 Reach Extended
2003 8 Mbps down, 1 Mbps up
SHDSL (update 2003)
G.991.2 G.SHDSL 2003 5.6 Mbps up/down
VDSL G.993.1 Very-high-data-rate DSL
2004 55 Mbps down, 15 Mbps up
VDSL2 – 12 MHz long reach
G.993.2 Very-high-data-rate DSL 2
2005 55 Mbps down 30 Mbps up
VDSL2 – 30 MHz short reach
G.993.2 Very-high-data-rate DSL 2
2005 100 Mbps up/down
SHDSL is the first standardized multi-bit-rate symmetric DSL for data rates
between 192kbit/s up to 2312kbit/s. A state-level trellis coded PAM line code is used
for this technology. At present, SHDSL system uses PAM modulation and trellis coded
modulation and is hence more spectral efficient than HDSL. It uses two-way baseband
transmission and will cause NEXT and FEXT interference to other system. The
specification is given in ITU-T Recommendation G.991.2 [1].
When compared to other symmetric transport technologies such as SDSL and
HDSL, SHDSL boasts approximately 30 percent greater reach. A good example is that
the highest bit rate defined in the standard (2.3 Mbps) is supported at loop length up
to 2.3 kilometers.
3
1.2 Problem Statement
In SHDSL, FEXT and NEXT is the interference happen when the signal travel
in both directions. The impact of the special correlation characteristic of these noises
impacts the performance of SHDSL when a cable or binder is used in a MIMO
configuration. MIMO configurations involve the combined or joint processing of more
than one, single, twisted pair loop. Even though SHDSL can support at high data rate,
there is still possibility that the BER of the system is high.
1.3 Objectives
To complete this project, there are several objectives need to achieve. The
objectives of this study are:
I. To design and develop channel model for SHDSL in MATLAB for MIMO
system based on TCPAM.
II. To propose and develop a noise cancellation technique for FEXT and NEXT.
III. To introduced modelling and performance study of SHDSL using TM copper
cable data (insertion loss, FEXT and NEXT).
1.4 Scope of work
The scope of the study is designing a channeling model for SHDSL system. The
design of SHDSL system will be use MATLAB software. From the simulation result
the data generated (data transmit) will be compare with the receive data and the BER
will be monitor. If the result did not get as mentioned, the MATLAB coding need to
4
be troubleshoot and identify the bug in the coding thus insert the new coding. The flow
for work are as follows:
1. Develop and design channel model in MATLAB programming for MIMO
system based on Trellis Coded Modulation (TCM) and Pulse Amplitude
Modulation (PAM) to predict achievable bit rate performance. The design of
the system is followed on the block diagram and the specification is followed
ITU-T G.991.2 standard.
2. Development of workable noise cancellation technique FEXT and NEXT
model for the SHDSL. The specification is followed ITU-T G.991.2 standard.
3. Performance study and modeling of SHDSL based on TM copper cable (IL,
FEXT and NEXT), thus calculate the SNR. The SNR specification is followed
ITU-T G.991.2 standard.
4. Run the simulation and display the result BER and SNR.
5. Report writing and result dissemination.
1.5 Project Significance
At the end of this project I will be able to understand the basic knowledge and
information on whole process of research methodology by completing the SHDSL
project. The understanding about principle and how the system works including the
components and materials involve can be achieved in the progress during this project.
CHAPTER 2
LITERRATURE REVIEW
2.1 Digital Subscriber Line (DSL)
There are many advances in symmetric DSL technology since its first develop
and introduce in the early 90’s. The technology opened a new dimension of
communication technology that recognizing bandwidth on the local copper loops are
not limited by the application, voice or Plain Old Service (POTS). The combination of
new line code and Digital Signal Processor (DSP) techniques can provide greater
bandwidth. Line codes, when combined with other techniques will reduce power,
achieve longer reach, improve performance and encode more data within the spectrum
of frequency. This new line codes technology was called as Trellis Coded PAM
(TCPAM). The amount of usable bandwidth available over a loop is dependent on a
number of factors, including loop length, impedance, signal power, frequency and line
coding techniques. The higher the frequency, the greater the attenuation, and the
smaller the signal becomes when it is received at the far end. The strength of the
received signal decreasing as the frequency increases.
6
There are two general categories of DSL which are symmetric and asymmetric.
Symmetric DSL provides the same service bit-rate in both upstream and downstream
directions. While asymmetric DSL (ADSL) provides more downstream bit-rate (from
the network to the user) than upstream bit-rate. To date, SHDSL represents the best of
several symmetric DSL technologies employs trellis-coded pulse-amplitude
modulation (TCPAM) providing greater reach, spectral compatibility, low power and
application flexibility.
2.2 Overview on Asymmetric Digital Subscriber Line (ADSL) Technology Asymmetric digital subscriber line (ADSL) uses existing twisted pair
telephone lines to create access paths for high-speed data communications and
transmits at speeds up to 8.1 Mbps to a subscriber. This exciting technology is in the
process of overcoming the technology limits of the public telephone network by
enabling the delivery of high-speed Internet access to the vast majority of subscribers’
homes at a very affordable cost.
Delivery of ADSL services requires a single copper pair configuration of a
standard voice circuit with an ADSL modem at each end of the line, creating three
information channels – a high speed downstream channel, a medium speed upstream
channel, and a plain old telephone service (POTS) channel for voice. Data rates depend
on several factors including the length of the copper wire, the wire gauge, presence of
bridged taps, and cross-coupled interference. The line performance increases as the
line length is reduced, wire gauge increases, bridge taps are eliminated and cross-
coupled interference is reduced. The modem located at the subscriber’s premises is
called an ADSL transceiver unit-remote (ATU-R), and the modem at the central office
is called an ADSL transceiver unit-central office (ATU-C). The ATU-Cs take the form
of circuit cards mounted in the digital subscriber line access multiplexer (DSLAM). A
residential or business subscriber connects their PC and modem to a RJ-11 telephone
outlet on the wall. The existing house wiring usually carries the ADSL signal to the
NID located on the customer’s premises.
7
2.3 Overview of SHDSL System Performance
SHDSL is a flexible multi-bit-rate system, which support symmetric user data
rates from 192 kbit/s to 2312 kbit/s. SHDSL is a guaranteed service, in which that
the system technology must deliver a certain data rate in order to achieve 10-7 bit
error at certain distance under worse case noise condition. The line code use for
SHDSL is 16-level trellis coded baseband PAM, which also use for HDSL2. The use
of convolution encoders is to increase loop performance give a major impact from
earlier technology that use the same baseband PAM such as ISDN or HDSL, which
use uncoded 4-level PAM. For the convolution rate, rate-1/2 code rate is used. Three
information bits are mapped onto a 16-level PAM symbol and since the latency
requirements do not allow use outer feed-forward encoders, trellis coders with large
numbers of states are used to provide the necessary coding gain. For example, trellis
code with 128 states provides 4.6 dB effective coding gain; 256 states provide 4.9
dB, and 512 states provide 5.1 dB coding gain [2].
In this study, show a general structure of SHDSL or HDSL transceiver. The
main difference of SHDSL and HDSL is the additional of trellis encoder and decoder
and the use of Tomlinson precoding. Figure 1 shows the block diagram of typical
realization of an SHDSL system.
Figure 2.1: Typical Realization of an SHDSL System
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