Digital Facsimile Information Distribution System;
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f;~:; 7 /9 I The Implementation of a Personal Computer-Based ~ Digital Facsimile Information Distribution System; A Thesis Presented to The Faculty of the College of Engineering and Technology Ohio University In Partial Fulfillment of the Requirements for the Degree Master of Science by f'it Edward C. Chung; J November, 1991 iii ACKNOWLEDGEMENTS I would like to take this opportunity to express my sincere gratitude to those people who provided me with encouragement and guidance during the completion of this education endeavor. Special thanks is given to my thesis advisor, Dr. Mehmet Celenk, for his patience, understanding and support throughout the project. His dedication to work and attention to detail have always been my inspiration. I am also grateful to my other committee members; to Dr. Hari Shankar, Dr. Jeffery Dill and Dr. H. Klock for their time and valuable suggestions. lowe much thanks to Mrs. Lolly Chan and Mr. Issidore Chan ofEDISSI Systems Technology, Inc., Beverly Hills, C.A., for their invaluable support. Mr. Issidore Chan is an exceptional friend whose suggestions are often inspirational and challenging. Partial funding ofthis project by EDISSI Systems Technology, Inc., is gratefully acknowledged. Also deserving acknowledgement are the following individuals for their kind assistance. Mr. Timothy Bambeck who provided me with numerous ideas, insights and moral support. And most important of all, his willingness to listen to my problems when things got tough. Mrs. Denise Ragan who gave her time to assist me with things that I could not have lived without. Mr. Bryan Jordan for doing the layout of the printed circuit board used in this project. Mr. Jordan's expertise in printed circuit boards is very much admired. Ms. Lisa Lung for her spiritual and emotional support. She also reminded me of those things which are really essential in my life that I sometimes overlooked. Lastly, my heartfelt gratitude goes to my family. My grandfather, Mr. Men-han Cheng, for his love and his confidence in my ability. My sister, Ms. Vivian Chung, for iv her emotional support. My parents, Dora and Eric Chung, for their encouragement, support, love and friendship which I cherish now and will treasure forever. v TABLE OF CONTENTS ACKNOWLEDGEMENTS iii 1. INTRODUCTION ................................... .. 1 2. INFORMATION TRANSMISSION OVER BAND-LIMITED CHANNELS .. 6 2.1 Information Handling Capacity of a Channel 6 2.2 Intersymbol Interference. ......................... .. 7 3. THE FAX INFORMATION DISTRIBUTION SYSTEM HARDWARE .... 13 4. SOURCE CODING FAX DOCUMENTS ..................... .. 30 4.1 The Source ............................ .. 32 4.2 Modified Huffman Coding and Recommendation T.4 32 4.3 Optional Coding Schemes Supported by Recommendation T.4 ... .. 38 4.3.1 2-D Modified READ Coding 38 4.3.2 The Three Coding Modes in 2-D Modified READ Coding ..................................... 40 4.3.3 Two-dimensional Coding Procedure 46 5. SYNCHRONIZATION AND SIGNALLING PROCEDURES 52 vi 5.1 Binary Coded Signal Functions and Formats . .. 52 5.2 Facsimile Call Placement 60 5.3 Description of Facsimile Call Phases 61 5.4 Optional and Non-standard Facilities Call. ............... .. 73 5.5 Fax Broadcasting 74 5.6 Polling Called Party . .. 76 6. ERROR CORRECTION SCHEMES IN GROUP 3 FAX TRANSMISSION .. 80 6.1 Error Concealment Techniques . .. 80 6.2 Error Limiting Mode . .. 82 6.3 Error Correction Mode and HDLC Framing . .. 87 7. FAX DOCUMENT CONVERSION FROM OTHER ELECTRONIC DOCUMENT FORMATS 123 7.1 Converting ASCII Text Files 124 7.2 Decoding PCX Graphics Format Files 128 8. LAN FAX-SERVER 140 8.1 LAN User Initiated Fax Transmission 141 8.2 LAN User Initiated Fax Reception 144 8.3 PSTN User Initiated Fax Services 145 vii 9. CONCLUSION 149 REFERENCES 152 CHAPTER 1 INTRODUCTION Facsimile, or fax for short, is the method by which written documents or photographic materials are converted into electrical signals, transmitted over telephone lines to reproduce as duplicates at the receiving end. A fax system consists of the mechanisms to transform the graphical materials to electrical signals suitable for transmission over telephone lines, a modem that transmits the signals to the receiving station, and the mechanisms to record and replicate the original documents. One can think of the fax system as a "remote copier machine" or an "instant mail facility." Although the basic principle of fax communication was known as early as 1843 [1], its real use for business communication did not begin until 1970 [2]. This was the direct result from the lack of any form of standard protocols for fax equipment. The Consultative Committee on International Telegraph and Telephone (CCITI) realized the need for such standards and developed the Group 1 Fax Recommendation in 1968. Even though Group 1 units generally worked better than the earlier fax systems, they were slow (requiring four to six minutes of transmission time for an A4 size document) and the copies produced were ofpoor quality. Few manufacturers adopted this standard. The CCITI Group 2 Recommendation came eight years later, in 1976, to improve the performance of Group 1 machines. Although Group 1 and Group 2 fax standards had triggered the worldwide acceptance of fax communication, their analog transmission techniques were inherently slow and produced low-resolution copies. It was until 1980 when the CCITI developed the Group 3 Recommendation for digital facsimile, that marked the new era of fax 2 communication. In fact, the first digital facsimile system made its debut' eleven years before the Group 3 standard was recommended. During this time, different coding techniques were developed to improve the performance of digital facsimile. Among the many coding schemes, some of them are one-dimensional (I-D) run-length codes; e.g., Bl-code [3], Truncated Huffman code [4] and Modified Huffman code [5], which utilize the statistical dependency of adjacent pictures within individual scan lines. Other more complex schemes; e.g., Kalle-Infotec code [6], Dacom code [7], Kokusai Denshin Denwa code [8] and TUH-code [9], which also exploit the line-to- line dependencies in a picture are denoted as two-dimensional (2-D) coding [10]. The standardization of Group 3 digital facsimile apparatus resulted in universally compatible fax systems that are reliable, efficient and produce high quality copies. Consequently, the fax growth rate was doubled in 1987 and in 1988, making a worldwide population of over fourteen million Group 3 digital fax apparatus by the end of 1989. It was predicted that this number would be doubled by the year 1991 [11]. As the demand for fax communication increases, the cost of stand-alone fax units drops substantially. However low-end fax units still lack the useful features such as regular (instead of thermal) paper output, fax broadcasting to a group of recipients, automatic resending upon error, etc.. Even high-end fax units may not be suitable for use as networking fax-stations or electronic document storage devices. The solution is to employ computer-based facsimile systems. Similar systems were used in the design of 1 The first digital facsimile made its debut in 1969. This was the DACOM's Rapidfax 100 utilizing the single-line adaptive ron-length coding algorithm patented by Donald Weber. 3 document delivery systems such as the ARTEMIS [12] and the request for quote (RFQ) system utilized by the Houston Lighting and Power Company with proven success. A PC-based fax adapter employs the programming power and the mass storage facilities of the personal computer (PC). This allows the PC to emulate the advanced features of a Group 3 fax system. With features that expedite the document delivery process, the popularity of PC-based facsimile adapters is growing rapidly. Nevertheless, none of the existing units can be considered as an integral part of the information distribution system [13]. Interfacing the existing systems to commercially available wordprocessors, graphics editors and desktop publishers are limited and none deals with interfacing to image databases. Error correction mode and LAN fax server implementations are rare and expensive. Furthermore, some of these adapters are either command-line-driven or carry awkward user interfaces making them very hard to use. This thesis describes an information distribution system that merges the personal computer and facsimile technologies to enhance and expand the capabilities of existing stand-alone Group 3 facsimile machines (see Figure 1). The goal is to identify and develop mechanisms to: 1. dispatch or receive a page of text or graphical material to or from any place on the globe within one minute, 2. maintain an accurate reproduction of the original documents, 3. provide universal compatibility that allows message exchanging with all Group 3 fax terminals regardless of their make or model, 4 4. automate sending and receiving processes in a user-friendly, menu-driven PC based environment to minimize human intervention, 5. integrate information dispatching with existing PC wordprocessors, graphics editors, desktop publishers and image databases, 6. maintain reliable transmissions via noisy telephone lines by incorporating an error correction scheme, 7. facilitate the implementation of a Local Area Network (LAN) fax sever, and 8. provide a cost effective solution for information exchange that rivals existing document delivery systems. The remaining part of this thesis is organized as follows. Chapter 2 addresses problems involved with information transmissions over band-limited channels. The implementation of the PC-based fax adapter is described in Chapter 3. Chapter 4 presents the source coding techniques that deal with the task of forming efficient descriptions of source information used in fax transmissions. Chapter 5 is devoted to the synchronization and signal procedures described by the T.30 recommendations for Group 3 fax units. Chapter 6 deals with High-level Data Link Control (HDLC) framing and error correction schemes. Chapter 7 treats fax document conversion from different text and graphical materials and discusses the integration with an image database.