Experimental Facsimile Communication System on Packet Switched Data Network

The use of the public data network for facsimile communication has remarkable advantages with regard to high speed and reliable transmission and, in addition, it is well applicable to provide value added facilities for future service extension. The Research and Development Laboratories of Kokusai Denshin Denwa (KDD) Company, Ltd. have developed an experimental facsimile communication system on the packet switched data network (PSDN). The system is composed of packet switching exchanges (PSE), high speed digital facsimile terminal equipment, a facsimile communication processor (FCP), and facsimile packet assembly/ disassembly equipment (FAX-PAD). The facsimile equipment in the system adopts a two-dimensional modified READ code and has the interface protocol to the PSDN. The FCP provides the store-and-forward facilities to provide such services as delayed delivery, multiaddress delivery, and mailbox service. The FAX-PAD realizes the interworking between facsimile equipments on the public switched telephone network (PSTN) and those on PSDN. After various experiments including international field tests, it was confirmed that the system is useful for future advanced facsimile service.     

Transmission quality of Group III facsimile on IDR satellite links with circuit multiplication equipment

The focus of this paper is on ways to improve the quality of Group III facsimile on intermediate data rate (IDR) satellite links. First, we present the results of an evaluation of the quality of Group III (G3) facsimile images transmitted on satellite links through circuit multiplication equipment (CME). Based on the results of this study, we propose a model to relate the facsimile image quality requirements to the bit error ratio (BER) on the link. A procedure is introduced to associate the long-term percentage of error-free pages in G3 facsimile transmission with various bit error probability (BEP) masks used for satellite link design. The intent of this procedure is to provide comparable end-to-end transmission quality for international telephone circuits, irrespective of whether the transmission medium is a satellite link or a fibre-optic cable. It is concluded that, unless the performance objectives of satellite systems significantly exceed those derived from CCITT/ITU-T Recommendation G.826, fibre-optic cables will become the preferred choice for international transmission.     

Error Sensitivity of CCITT Standard Facsimile Coding Techniques

The CCITT has defined Group 3 facsimile apparatus as that which digitally transmits an ISO A4 document over a switched telephone circuit in approximately one minute. Data compression is employed to achieve the reduced transmission time. Study Group XIV of the CCITT has drafted Recommendation T.4 to achieve compatibility between Group 3 facsimile devices. The standard data compression technique specified by T.4 is a one-dimensional coding scheme in which runlengths are encoded using a modified Huffman code (MHC). The recommendation also includes an optional twodimensional compression technique known as the modified READ code (MRC). It is recognized that the switched telephone network is prone to error when transmitting digital data at the standard T.4 data rate of 4800 bits/s. This paper evaluates the error sensitivity of the MHC and MRC when operating over a typical telephone circuit. The error sensitivity analysis is accomplished by means of computer simulation. The error performance of the two coding techniques is analyzed both quantitatively and qualitatively. The quantitative analysis is accomplished using the error sensitivity factor which represents the average number of incorrect pels in the output document caused by a transmission error. The qualitative analysis is based upon viewing actual error-contaminated images generated in the simulation process. Two separate analyses have been performed. First, error sensitivity data for both the MHC and MRC are developed under identical operational conditions, and their relative performance is discussed. In the second part four different techniques for processing the received facsimile signal (MRC), to minimize the subjective effect of transmission errors, are analyzed.     

Simulation of burst error models and an adaptive error controlscheme for high speed data transmission over analog cellularsystems

To realize high-speed data communication in a cellular system, the characteristics of mobile radio propagation paths (MRPP) and a robust error control scheme for poor circuit quality are studied. MRPP are analyzed by computer simulation, and an analysis method is described that uses a Markov model for burst errors generated by the simulation. By simulating the locus of moving vehicles, the relationship between the carrier-to-noise ratio (CNR), the fading frequency of a moving vehicle, and the three-states Markov model is obtained. An adaptive error control scheme (AECS) is developed as an effective high-speed data communication scheme in an analog cellular system. The effectiveness of the AECS is analyzed by simulating its application in a subcarrier transmission system with a 4800 b/s data transmission rate, using the three-states Markov model. The analysis method is verified and the characteristics of the AECS are evaluated using field data     

无线网络中的G3传真通信技术

无线通信技术已经广泛应用于社会各个方面,但是基于无线网络的传真应用却是刚刚起步。介绍了在CDMA、GSM等无线网络中的传真通信技术,研究设计了基于GSM的无线传真通信规程,并通过实验完成了无线传真终端与普通G3传真机的传真通信。     

Advances in FAX

One of the most important techniques introduced into the recent facsimile is redundancy-reduction coding. The CCITT already standardized the coding schemes to be employed in Group 3 and Group 4. There are, however, left for further study the optional non-information-preserving coding scheme for black-and-white pictures and the coding scheme for multilevel and color pictures. Much work has been carried out with respect to these kinds of coding, including pattern-matching coding for black-and-white pictures and various information-preserving and non-information-preserving coding for multilevel and color pictures. The Group 4 apparatus is a new generation facsimile apparatus, which is mainly operated on public switched data networks. This kind of facsimile apparatus features higher resolution and error-free reception, and has the teletex-facsimile mixed mode capability as an option. The most important technical problem in the standardization of the Group 4 facsimile is the communication protocol which has been developed based on the existing teletex protocol. Facsimile communication is carried out not only on general public switched telephone or data networks, but also on specialized networks dedicated to it. Some sorts of communication processing such as speed conversion, automatic appending function, repeated delivery attempt, etc., are incorporated into these networks. The development of facsimile equipment has also shown progress in these few years. For example, a very compact apparatus has been developed using a new contact type imager and a codec built by special-purpose LSIs. The press fax apparatus employing flat-bed scanner and multicolor facsimile apparatus have also been put into market. This paper describes the outline of recent advances in facsimile, including the above-mentioned items.     

Transmission of group 3 facsimile over inmarsat maritime digital satellite mobile channels

The importance of facsimile communication over public telephone networks is evidenced by the rapid growth in the number of Group 3 facsimile end-user terminals. In this paper the main characteristics of a real-time bit-rate reducing approach are described whereby facsimile signals are demodulated and their associated protocols converted by a facsimile interface unit (FIU) to a format suitable for transmission over Inmarsat-B maritime digital satellite channels. The FIU concept was developed to allow ‘off-the-shelf’ facsimile terminals to be interconnected via the PSTN through Inmarsat's satellite networks and to permit the provision of enhanced user services by converting Group 3 facsimile protocols to broadcast operation. In addition, the FIU concept is designed to compensate for the longer access and transport link delays encountered in mobile satellite systems, and to permit facsimile call recovery procedures to be successfully concatenated with satellite channel error detection mechanisms.     

Analysis of Group 4 Facsimile Throughput

The CCITT (Consultive Committee for International Telephone and Telegraph) is developing recommendations for a new generation of facsimile equipment which is designed as Group 4. This class of equipment will transmit an ISO A4-sized page overcommunications networks having error control. Most commercial packet switched and circuit data networks have been designed primarily for the communications of short bursty messages (typically 1000-2000 bits/message between computers and data terminals. The length of a G4 message is forecast to be very long-typically 500 000 bits. There is serious concern that data networks may not handle facsimile traffic very efficiently. This paper projects the near term characteristics of data networks and Group 4 facsimile systems, and estimates the efficiency with which Group 4 messages will be transmitted over three types of data networkspacket switching (PSDN), circuit switched (CSDN), and the public switched telephone network (PSTN). Throughput has been measured by the amount of time required to send a single facsimile page of 500 000 coded bits. In all cases the overhead, as a percentage of the basic facsimile transmission time, is in the range of 50-60 percent. For each network there is a different factor is the halts are forced is transmission as a result of the network window. For the CSDN, the process if converting from voice to data mode is the dominating factor. For the PSTN, packet retransmission due to transmission errors is the dominating factor. The paper includes the assumptions and some of the analytical details of the throughput analysis. Conclusions are drawn regarding the relative transmission efficints through the three types of networks.     

Protocol configuration and verification of an adaptive errorcontrol scheme over analog cellular networks

A high-speed and error-free voiceband data communication method using a hybrid automatic repeat request (ARQ) protocol over an analog cellular system is described. The present method adopts an adaptive error control scheme. This error control scheme automatically selects the optimal error correction code according to circuit bit error rate (BER), so as to match it to the frequently changing mobile radio propagation path conditions. This method adopts multiframe rejection as a retransmission scheme for a high throughput efficiency on the burst error circuit. Actual field evaluation was made by mounting this protocol on a CCITT V.22 bis modem with a data transmission speed of 2400 b/s and a modulation method using 16 carrier states over the Advanced Mobile Phone Service (AMPS) in Atlanta, GA, verifying that data communications can be achieved with an average throughput efficiency of 70% over a radio channel having a BER up to 10^-2     

Measurement of data compression in advanced group 4 facsimile systems

The CCITT (Consultative Committee for International Telephone and Telegraph) has defined Group 4 facsimile apparatus as that which transmits an ISO A4 (210 × 297 mm) document over public data networks including Packet Switched Data Networks (PSDN) and Circuit Switched Data Networks (CSDN). Data compression is employed in Group 4 systems to minimize the number of bits required for transmission of a message. CCITT Recommendation T.6 defines the basic Group 4 coding scheme to be a variation of the modified READ code (MRC II) which is the Group 3 coding option. This paper measures the compression of the MRC II algorithm for three different documents at resolutions of 200, 240, 300, 400, and 480 picture elements per inch. The compression measurement was accomplished by means of computer simulation. It was determined that the bits per page measure increases linearly with resolution. Results are presented and conclusions drawn. The Group 4 CCITT Recommendations include a mode of operation known as Mixed Mode where a page is divided into two parts: character-coded information and facsimile-coded information. This paper describes four alternative mixed-mode algorithms and measures the compression of each coding technique for CCITT document number 1. The compression measurements were performed by means of computer simulation. Conclusions are drawn regarding the relative advantages of the four algorithms.     

ITU-T standardization of audiovisual communication systems in ATMand LAN environments

This paper presents the ITU-T Study Group 15 development of H-series Recommendations that allow interworking between different audiovisual communication terminals manufactured by different equipment providers. The paper focuses on H.310 and H.321 systems for broad-band ATM environments and H.322 and H.323 systems for LAN environments where the quality of service may or may not be guaranteed. The paper first lists the Recommendations developed by the ITU-T for audiovisual communication systems and the network environments in which they may be used. It then describes the design philosophy, the network specific characteristics, and hardware trials for each system. Then it describes the communication control protocol defined in H.245 which is used commonly by different audiovisual communication systems. Finally, the paper discusses interworking scenarios for communication between the different types of terminal on different networks     

Detection and correction of transmission errors in facsimile images

Today, facsimile is recognized as the primary communication tool for both printed and written materials. Most facsimile machines operating on public switched telephone networks use the Group 3 (G3) facsimile compression standards, in which images are entropy-coded. Although the synchronization codeword end of line (EOL) is employed, a transmission error in a codeword may cause the current codeword, the subsequent codewords in the current line, even the codewords in the subsequent lines to be misinterpreted, resulting in a great degradation of the received image. The objective of the proposed error detection and correction approaches is to completely or partially eliminate transmission errors in G3 facsimile images, requiring no extra transmission bit rate and without changing the transmitter and the receiver. The proposed approaches are based on the error checking conditions derived from the relationship between the current line and the previous line as well as the constraints on compressed image data. A corrupted line is detected if any of the error checking conditions is satisfied. When a corrupted line is detected, a sequence of bit inversions and redecoding operations are performed on the current corrupted line and/or its previous lines so that at least one possible (feasible) redecoding solution can be found. Then, the best solution is selected by using some selection criterion. Based on simulation results, the proposed approaches can recover the original or high-quality facsimile images from their corresponding corrupted facsimile images. This shows the feasibility of the proposed approaches     

Facsimile today

Over the past few years, facsimile has become the most popular form of business text communication. The paper gives a brief outline of the way in which a facsimile terminal operates and explains the various scanning and printing technologies in use today. The use of facsimile on the integrated services digital network (ISDN) is also considered     

Transmission performance of 64 kbps switched digital internationalISDN connections

An international 64 kbps switched digital ISDN service has been commercially in place since October 1989 between Japan and the United States. Service providers had to know about transmission quality to facilitate service planning. Other performance information was necessary for designing terminal equipment for both network users and telecommunication providers. Transmission performance was therefore characterized under real operating conditions. This paper evaluates overall transmission quality in terms of errored seconds (ES) and severely errored seconds (SES), and it shows there is very little difference between the performance of international end-to-end connections via fiber and satellite. The daily variation of ES and SES reveals that these connections exhibit behavior typical of digital circuits. This study also characterizes the distributions of bit errors per errored second, error event inter-arrival time distributions, and the distributions of error event lengths and intensities. The time between freeze-frame events are estimated for 64 kbps compressed video and the retransmission rate is estimated for Group IV facsimile     

International digital facsimile coding standards

Recently Study Group XIV of CCITT has drafted a new Recommendation (T.4) with the aim of achieving compatibility between digital facsimile apparatus connected to general switched telephone networks. A one-dimensional coding scheme is used in which run lengths are encoded using a modified Huffman code. This allows typical A4 size documents in the form of black and white images scanned at normal resolution (3.85 lines/mm, 1728 pels/line) to be transmitted in an average time of about a minute at a rate of 4800 bit/s. The Recommendation also includes a two-dimensional code, known as the modified relative element address designate (READ) code, which is in the form of an optional extension to the one-dimensional code. This extension allows typical documents scanned at high (twice normal) resolution (with every fourth line one dimensionally coded) to be transmitted in an average time of about 75 s at 4800 bit/s. This paper describes the coding schemes in detail and discusses the factors which led to their choice. In addition, this paper assesses the performance of the codes, particularly in relation to their compression efficiency and vulnerability to transmission errors, making use of 8 CCITT reference documents.     

PHS roaming signaling protocol architecture toward global mobilitynetwork

The network for supporting the global personal communication is called the global mobility network (GLOMONET), where global mobility is guaranteed by coordination between intelligent networks (INs). This paper describes the implementation of a roaming signaling protocol for the personal handy-phone system (PHS) GLOMONET, clarifying the concepts of the PHS architecture regarding the GLOMONET. The PHS is a more economical personal communication system than existing cellular systems, by introducing the concept that the PHS service is provided by the most effective use of the existing ISDN and IN functions, where the majority of network functions to provide ISDN services are commonly used for functions for PHS service provision. The PHS mobility function realized by the IN guarantees flexible and effective roaming service provision for the globalization of future personal communication. The proposed PHS signaling protocol architecture is based on the intelligent network capability set 2 (IN CS2) defined by the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Study Group 11 and a visitor location register (VLR) database scheme with efficient signal transfer in the GLOMONET. The PHS specific roaming signaling protocol is defined by the service-independent IN application protocol (INAP). The proposed PHS concepts and roaming signaling protocol were reflected to the national telecommunications standards in the Telecommunication Technical Committee (TTC) and standards in the PHS-memorandum of understanding (MoU)     

One-Way Multiaddress Satellite Data Communication System

An experimental one-way multiaddress data communication system accommodating many small receive-only terminals is described. In this system, a digital facsimile is used as the output equipment. A simple one-way transmission protocol adopting the flag synchronization method has been developed so that facsimile equipment of different speeds can be used. The receive-only terminal comprises an antenna, an RF receiver, a demodulator, and a channel selector. The antenna is an offset parabolic type with an effective diameter of 60 cm and uses a printed spiral type primary radiator. Dimensions of the terminal are 70 cm wide, 88 cm deep, and 126 cm high. The satellite channel bit rate is 64 kbits/s in order to transmit multiple facsimile data simultaneously. Experiments using the Japanese "CS" satellite have been carried out to verify the system feasibility. The normal bit error rate was less than 10^-6and line errors occurred less than once in three facsimile transmissions.     

Interface LSIs for data terminals and facsimile

Describes three high-performance interface LSIs, namely, the facsimile modem, universal receiver transmitter, and code converter LSIs, for facsimile, for communication control equipment, and for a digital service unit to connect the terminal equipment and the network. It is explained that optimization in block partitioning and common use of building block cells has been chosen as the LSI design method. These LSIs operate at from 1.4 (facsimile modem) to 6.1 MHz (universal transmitter receiver) clock frequencies with an adequate operating frequency margin. The power dissipation is 450-500 mW at 5 V the power supply voltage. The chip size for these LSIs is from 39 to 44 mm/SUP 2/. The LSIs consist of about 20000 transistors each. The output level is TTL compatible.     

2010年通信技术和业务概貌预测──AT＆T贝尔研究院John Mayo院长演讲笔记

本文是贝尔研究院ＪｏｈｎＭａｙｏ院长１９９４年７月１１日在上海所作学术报告的听讲笔记。报告预测２０１０年通信技术和业务十大方面的概貌：（１）微电子集成芯片；（２）光子逻辑控制；（３）光纤传输容量；（４）语音信号处理；（５）传真和可视通信；（６）通信网结构进化，（７）个人无线通信；（８）计算机处理能力；（９）通信软件生产率；（１０）多媒体信息终端。     

Access network architectural issues for future telecommunicationnetworks

This article discusses the evolution of access networks to support future multimedia services, with emphasis on the role of Working Party 3 of ITU-T Study Group 13. An overview of the access network is given, and the interfaces between the access network and other portions of the telecommunications network such as the user-network interface (UNI), service node interface (SNI), and telecommunication management (Q3) interface are described. The major functions of the access network are summarized, and various examples of multimedia access architectures are discussed. Fundamental principles for the broadband service node interface (VB5) standard are reviewed