Symmetrical High-Speed Digital Subscriber Line (SHDSL) Channel Modelling.

SYMMETRICAL HIGH-SPEED DIGITAL SUBSCRIBER LINE (SHDSL) CHANNEL MODELLING

ROHISHAM BIN RAMLAN

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

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:

__ ________________________ ___________________________________

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 : ...

v

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 10}6 _{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 10}9 _{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 10}6 _{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

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

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

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

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

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).

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

CHAPTER 1

INTRODUCTION

1.1Project 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.

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.

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.

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.