Telephone Line Data Transmission, Using Locaitaik '

Telephone Line Data Transmission, Using LocaiTaik ' A Thesis Submitted to the College of Graduate Studies and Research in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Department of Electrical Engineering University of Saskatchewan Saskatoon By JunYe Spring, 1997 @ Copyright Jun Yeo 1997. All rights reserved. Permission to Use In presenting this thesis in partial fulfillment of the requirements for a Postgraduate degree from the University of Saskatchewan, I agree that the Libraries of this· university may make it freely available for inspection. I further agree that permission for copying of this thesis in any manner, in whole or i� part, for scholarly purposes may be granted by the or who thesis work or, in their absence, the professor professors supervised my by .. Head of the Department or the Dean of the College in which my thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for fmancial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be make of any material in my thesis. Requests for permission to copy or to make any other use of the material in this thesis in whole or in part should be addressed to: Head of the Department of Electrical Engineering University of Saskatchewan Saskatoon, Canada. S7N OWO i Telephone Line Data Transmission Using LocalTaik Candidate: Jun Ye Supervisor: David E. Dodds Master of Science Thesis Presented to the College of Graduate Studies and Research University of Saskatchewan July 1997 Abstract With the growth of the Internet, more and more people want their computers to be connected to the Internet and to get information from the Internet as fast as possible. Presently available remote network access methods are limited in speed and cannot support simultaneous voice transmission. They do not fully satisfy the Internet users' needs. This thesis presents a new high speed network access tecbnology. With this method, a residential telephone line can be used to connect home computers at 230 kbitsls to the Internet without loss of the voice service. In order to put this system in practical . use, some problems, such as the interference between the voice and data, the limited transmission distance and the effect of a bridged tap on the telephone line, must be solved. These problems and their solutions have been discussed in this thesis. ii Acknowledgments I wish to express my special thanks to my supervisor Professor David E. Dodds. I would like to thank him for his helpful guidance and wisdom during the course of this work. My work would not have been possible without the outstanding help from Greg Erker and Garth ·Wells, the research engineers in TRLabs Saskatoon. I would like to thank Cliff Klein, the director of TRLabs Saskatoon, for the financial assistance, the first class equipment and the excellent environment that TRLabs provided during this work. The help that Leon Lipoth, Denard Lynch, Jack Hanson and others at TRLabs gave me is greatly appreciated. I also would like to thank Trudy Gall. Finally, I want to thank my wife, Yanping, my parents and my sister for their consistent encouragement and support. iii Table of .Contents Permission to Use i Abstract n Acknowledgments ill Table of Contents iv List of Tables vn List of Figures List of Abbreviations xii Chapter 1 Introduction 1 1.1 Today's Network Access Methods 1 1.2 A New Network Access Method 4 1.3 Thesis Objectives 6 1.4 Thesis Overview 7 Chapter 2 The LocalTaIk Local Area Network 8 2.1 AppleTalk Protocol 8 2.2 LocalTalk Network Configurations 11 2.3 LocalTalk Physical Layer 13 2.3.1 LocalTalk Connection Module 14 2.3.2 Transmitter and Receiver 17 2.3.3 Serial Communication Controller (SCC) 20 2.3.4 Spectrum of the Apple LocalTalk signal 21 2.4 LocalTalk Link Access Protocol (LLAP) 23 2.4.1 Link Access Management 23 2.4.2 Data Framing 24 2.4.3 Frame Transmission/Reception 26 . 2.4.4 Node Addressing 29 2.5 Network Layer and Other Upper Layers 29 iv Chapter 3 Transmission Line. Theory 31 3.1 Transmission Line Model 31 3.2 Circuit Analysis of the Model 32 3.3 Tennination of the Transmission Line 37 3.4 Transmission Cables in Telephone Networks . 39 3.4.1 Open Wire Lines 39 3.4.2 Coaxial Cable 39 3.4.3 Paired Cables 41 Chapter 4 Data Transmission 46 4.1 Baseband Transmission 46 4.1.1 Coded Baseband Transmission 46 4.1.2 Baseband Pulse Transmission 50 4.2 Intersymbol Interference 51 4.3 Equalization and Predistortion 52 4.3.1 Frequency Domain Equalization 53 4.3.2 Time Domain Equalization 54 4.4 Eye Diagram 58 Chapter 5 Voice and Data Simultaneous Communication 61 5.1 Signals Transmitted on the Subscriber Line 61 5.2 The Interference Between Voice and Data Communication 64 5.3 Proposed Solutions for Voice and Data Simultaneous Transmission 68 5.4 The Circuit Design of the New LocalTalk Interface Module 70 Chapter 6 Extended Range Transmission 77 6.1 The Local Telephone Network 77 . 6.2 Design of the Equalizer 78 6.2.1 Equalizer Type 79 6.2.2 Equalizer Circuit 79 6.2.3 The Results of the New LocalTalk Interface with Equalizer 86 6.3 Presdistorter and Equalizer Design 97 6.3.1 Predistorter Design 98 6.3.2 Circuits of the Predistorter and Equalizer 100 v 6.3.3 Test Results 105 . 6.4 Solutions to the Bridged Tap 106 6.4.1 Solution 1: Pure Resistor Termination to the Bridged Tap J08 6.4.2 Solution 2: R-C Termination to the Bridged Tap 110 6.5 Summary 112 Chapter 7 Conclusion 114 References 117 Appendix 1 Macintosh Serial Port 120 Appendix 2 Circuits of the Pseudo-Random Data Generator and the Baseband Encoder 121 .. Appendix 3 Output Voltages of the Predistorter 122 vi List of Tables Table 2.1: The power distribution of the LocalTalk data. 22 Table 3.1: AWG wire size. 41 Table 5.1: Central office originated signals. 63 Table 6.1: The data communication quality at different cable lengths. 90 Table 6.2: Packet drop rate at different telephone signaling. 96 vii List of Figures Fig. 1.1: Network access by a voicband modem. 2 Fig. 1.2: The new network access method. 5 Fig. 2.1: AppleTalk protocol layers. 9 Fig. 2.2: Stand-alone LocalTalk network. 11 Fig. 2.3: The configuration of a local bridge. 11 Fig. 2.4: The configuration of a half.bridge. 12 Fig. 2.5: Diagram of LocalTalk hardware. 13 Fig. 2.6: Connection modules in a LocalTalk network. 14 Fig. 2.7: LocalTalk connection module. 15 Fig. 2.8: Common mode input signals. 16 Fig. 2.9: Star topology. 17 Fig. 2.10: LocalTalk line driver and balanced signals. 18 Fig. 2.11: The function of the LocalTalk receiver. 18 Fig. 2.12: Common mode noise rejection. 19 Fig. 2.13: Biphase space signal. 20 Fig. 2.14: Power spectraldensity. 21 Fig. 2.15: LLAPframe. 24 Fig. 2.16: Start of a LocalTalk RTS frame. 2S Fig. 2.17: Directed data transmission dialog. 28 Fig. 3.1: Transmission line model. 32 Fig. 3.2: Voltages at different paints on a line. 37 viii Fig. 3.3: Coaxial cable. 40 Fig. 3.4: Attenuation of different size cables vs. frequency. 42 Fig. 3.5: Delay of different sizecebles vs. frequency. 42 Fig. 3.6: Attenuation of AWG 26 cable at different temperature. 43 Fig. 3.7: Delay of AWG 26 cable at different temperature. 43 Fig. 3.8: Characteristic impedance of AWG 26 cable vs. frequency. 44. Fig. 3.9: Angle of the characteristic impedance vs. frequency. 44 Fig. 3.10: Dlustration of delay distortion. 45 Fig. 4.1: Coded baseband transmission model. 47 Fig. 4.2: Channel codes formats. 47 Fig. 4.3: Example of differential coding. 49 Fig. 4.4: Baseband pulse transmission system model. 50 Fig. 4.5: The application of the equalizer, 52 Fig.4.6a: Ideal equalization (Attenuation). 53 Fig.4.6b: Ideal equalization (phase). 53 Fig. 4.7: Waveform with zero ISL 55 Fig; 4.8: Transversal filter. 55 Fig. 4.9: System for laboratory eye diagram recording. 58 Fig. 4.10: Eye diagram of the undistorted data signal. 59 Fig. 4.11: Eye diagram of the distorted data signal. 60 Fig. 5.1: A simple test interface module between a Mac and a subscriber line 64 Fig. 5.2: C-message weighting curve. 65 Fig. 5.3: Bit patterns of the biphase data. 67 Fig. 5.4: New LocalTalk interface module for data and voice simultaneous communication 68 ix Fig. 5.5: New LocalTalk interface module. 71 Fig. 5.6: The response of the high pass filter when transmitting data. 72 Fig. 5.7: LocalTalk data before and after the high pass filter, 73 Fig. 5.8: The response of the low pass filter. 74 . Fig. 5.9: The total.attenuation of the data noise . 75 Fig. 5.10: The response of the high pass filter when receiving data. 75 Fig. 6.1: Loop plant of the telephone network. 78 Fig. 6.2: Frequency domain equalizer. 79 Fig. 6.3: Equalizer gain verse frequency. 80 Fig. 6.4: Obvious equalizer for LocalTalk data. 81 Fig. 6.5: The improved equalizer. 82 Fig. 6.6: Equalizer gain and cable attenuation verse frequency.

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