Protocol integrating videotex communication system

Abstract: A protocol integrating videotex communication system includes a group of data base centers (101, 102, 103) conforming to various presentation level protocol syntax (PLPS) of a videotex, a plurality of subscriber's terminals (112, 113, 116) conforming to PLPS corresponding to the group of data base centers, and a device for interconnecting the group of data base centers conforming to the various PLPS and the plurality of subscriber's terminals, which includes a gateway unit (104) connected to the plurality of data base centers, a videotex communication control apparatus (105, 106 - 109) connected to the gateway unit, and an interconnection unit having a single ISDN exchange apparatus (110, 111) for connecting the videotex communication control apparatus to the plurality of subscriber's terminals.

Description: BACKGROUND OF THE INVENTION The present invention relates to a protocol integrating videotex communication system according to the preamble of claim 1. As the international standards for the videotex PLPS, there have been recommended three systems including the CAPTAIN, CEPT, and NAPLPS; however, the complete interconversion and integration between the different PLPS subscriber's terminals and data base centers are remained to be discussed for a solution. As a method to solve the problem above, there has been known a method described in the JP-A-62-143586. In this configuration example, as a subscriber's terminal, there is installed a universal terminal including therein a function to convert a plurality of protocols corresponding to the various PLPS protocols so as to enable the videotex communication to be conducted between the single terminal and various kinds of PLPS data base centers. However, since this conventional example requires the conversion functions associated with the respective protocols to be installed in the subscriber's terminal, which leads to a problem with respect to the cost of the terminal and accommodation thereof. In addition, the JP-A-62-143586 describes a system of a configuration in which an identification (ID) transmit function is provided on a subscriber's terminal side such that on the data base center side, the protocol of the subscriber's terminal is determined depending on the ID so as to connect the terminal to a communication control unit conforming to the protocol. The system of this configuration is designed to be employed in an environment associated with a telephone network; furthermore, the protocols are limited to the CAPTAIN protocol. Moreover, the object is to access a direct-type information center (DF) for each protocol, which hence cannot enable the object of the videotex service integration to be achieved. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a protocol integrating videotex communication system as a method to solve a problem of a system integration in a videotex communication system in which image information retrieval is conducted between a plurality of subscriber's terminals conforming to the different PLPS protocols and the PLPS data base centers corresponding thereto wherein through a network conforming to a single PLPS protocol between the subscriber's terminals and the data base centers, the videotex communication can be conducted between the subscriber's terminals of the same types of PLPS protocols and the data base centers. The object above can be achieved by configuring a videotex communication controller constituting the network with a videotex exchange conforming to a single PLPS protocol and a protocol converter conforming to the various PLPS protocols in which service image information from an arbitrary PLPS data base center selected according to a call control procedure through a signal channel at a call initiation issued from a subscriber is once converted into a data format of the PLPS to which the videotex exchange conforms and is thereafter subjected to a protocol conversion according to a protocol associated with the call initiation terminal in the protocol converter disposed in the videotex communication controller in association with the various PLPS protocols, thereby transmitting the obtained data to the call initiation terminal via the ISDN user/network interface and an exchange. By using the ISDN user/network interface as the user/network interface, when necessary information including a terminal class and a service type is transmitted to a signal (D) channel at a call initiation from a subscriber, the videotex communication controller recognizes the information and establishes a connection via a gateway unit to a data base center desired by the subscriber; furthermore, effects a call termination to a protocol converter disposed in the videotex communication controller in associated with the terminal. In this fashion, after a user session is opened, in the gateway unit, image information which is sent from a data base center and which belongs to a desired videotex PLPS protocol is once converted into the telesoft information format (existing CAPTAIN-PLPS) or into a data format which can be transferred through the network in the transparent mode; thereafter, the information undergoes a protocol conversion associated with the terminal in the protocol converter so as to be sent to the call initiation terminal of the user. This enables the user easily utilize the retrieval service of image information belonging to a desired videotex PLPS. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings in which: FIG. 1 is a configuration diagram showing an embodiment of a communication system according to the present invention; FIG. 2 is a block diagram schematically showing a configuration example of a videotex exchange of FIG. 1; FIG. 3 is a block diagram showing a configuration example of a protocol converter of FIG. 1; FIG. 4 is a block diagram showing a configuration example of a gateway unit of FIG. 1; FIG. 5 is an interaction sequence diagram showing a call establish operation and the subsequent connect processing in the communication system; FIG. 6 is a schematic diagram showing a format example of retrieval information; FIG. 7 is a format diagram showing information transmitted from a data base center; and FIG. 8 is a format diagram showing transparent information sent from the data base center. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, description will be given of an embodiment according to the present invention. This invention is applicable to the various videotex PLPS protocols in any videotex communications to be effected between subscribers' terminals conforming to the same types of videotex PLPS protocol and data base centers. As an example, a concrete description will be given of the embodiment only in a case where image information conforming to the CEPT-PLPS is retrieved by means of a videotex exchange according to the CAPTAIN-PLPS. First, description will be given of a videotex communication system in accordance with the present invention. FIG. 1 shows an outline of the configuration of an example of the system. In this case, a videotex communication controller (VCP) centered on a videotex exchange (VEX) 105 can be connected to the center side including the data base centers (DBCs) 101 to 103 corresponding to the respective protocols via a gateway unit (VGW) 104. On the other hand, the connection is established to the subscribers' side including an ISDN user/network interface, for example, an ISDN primary group interface 110 via protocol converters 106 to 109 conforming to the various PLPS protocols and further to an ISDN exchange 111. The ISDN primary group interface 110 is linked to the ISDN exchange 111 by means of a signal channel 114 and information channels 115. In the ISDN exchange, there are housed CAPTAIN terminals 112 and other subscribers' terminals 113 and 116 corresponding to the various protocols. Description will now be given of an outline of the configuration with reference to the block configuration diagrams of FIGS. 2 to 4 showing the videotex exchange 105, the protocol converters 106 to 109, and the gateway unit 104 each constituting the primary section according to the present invention. FIG. 2 is a configuration diagram showing an outline of the videotex converter (VEX) 105, which is constituted in a duplicate system including two super minicomputers CPUs 0 and 1 and which includes a memory MEM for storing therein an online program; furthermore, an overlay portion of the online program is stored in a disk device DK. Call establish information is transferred as D channel information control from a line controller LC to the CPUs via an interface control adapter ICA. The interface between the gateway 104 and the protocol converters 106 to 109 is a channel interface, which is controlled by an I/O processor IOP and a multichannel controller MCC. In addition, the channel interface is also adopted as the interface for the I/O devices associated with other devices such as a magnetic tape MT, a floppy disk FD, a hard disk DK, and console CNS. FIG. 3 is a configuration diagram showing an outline of the protocol converters 106 to 109 in which a microprocessor is employed as the CPU thereof and a program is loaded in an initial program loading operation from a floppy disk FD into a memory MEM. This portion may also be implemented by use of a read-only memory ROM. Communications with the videotex exchange 105 is controlled by a channel adapter CHA such that the information is once stored in a communication memory CM. The protocol conversion is carried out thereon by a converter CNV according to conversion parameters stored in an ROM integrated therein. Input and output operations with respect to the communication line is effected through a duplicated communication by means of a line interface controller LIC according to the LAPB procedure. In addition, the input and output devices are controlled via an I/O controller IOC. Furthermore, in this configuration, only the contents of the memory MEM vary among the converters 106 to 109 conforming to the respective PLPS protocols. In the configuration of Fig. 4, the gateway 104 is constituted in a duplicated system by means of two super minicomputer 0 and 1 and is interfaced with the videotex exchange 105 and the respective data base centers 102 to 103 through a channel interface so as to be controlled by an I/O processor IOP and a multichannel controller MCC. This is also the case for the interface with respect to the other input/output devices. Assume here that a subscriber issues a call from a terminal associated with CEPT to a data base center 102 corresponding to CEPT so as to effect a retrieve operation of image information conforming to the CEPT-PLPS, then processing is conducted according to the procedure of FIG. 5. Call control information issued from the subscriber's terminal 113 at a call issuance from the subscriber includes a terminal class, a service type, a call termination number (a telephone number of the data base center 102 corresponding to CEPT in this case), a protocol identifier, and a call number and is transmitted as control data through the signal channel 114 to the videotex exchange 105 (a). The videotex exchange 105 then recognizes and decodes the received call control information so as to request the gateway unit 104 to establish a connection to the data base center 102 associated with CEPT (b) and to cause the call including the obtained information to be terminated to the protocol converter 107 corresponding to CEPT (c). In this fashion, after there is established an in-channel information path indicated by a bold line in FIG. 5, retrieval information which has, for example, a format of FIG. 6 and which is inputted from the terminal associated with CEPT is transmitted as data through the information channel 115 up to the data base center 102 (d). In this operation, the retrieval information is converted by the protocol converter 107 according to the CAPTAIN-PLPS code system of the ascending direction to the center 102. In the data base center 102, based on the retrieval information, image information desired by the user is obtained and is then sent to the videotex communication controller VCP (e). Referring next to Fig. 7, description will be given of the conversion and transfer procedures of the image information in the videotex network. The image information is communicated between the gateway unit 104 and the protocol converter 107 according to the data format conforming to CAPTAIN-PLPS-telesoft information including a protocol header in network 204 as the leading item thereof as shown in FIG. 7. Incidentally, the fields of the transfer data formats of FIGS. 7 and 8 respectively have the following functions. Protocol header in network: Indicates a route number, a text ID, a line number, and the like to be communicated through the videotex communication controller VCP. A screen information: Specifies an image number, an image density, a display mode, a charge information, and the like for image information. C screen information: Designates necessary information items for a screen retrieval associated with image information. E screen information: Sepcifies service items such as a communication work and an order entry. Screen control information: Designates attributes of a screen such as a clear screen, a header raster color, and a screen raster color. Header information: Specifies display contents of the screen header portion. DI(T): Data indicator indicating that the subsequent information is transparent data. LI: Indicates the length of subsequent data belonging to DI(T). OP: Operation code identifying the data attribute of the subsequent data. ℓ: Indicates the length of data belonging the associated operation code. Telesoft header: Indicates that telesoft data follows. Telesoft data: Data in the format conforming to the CAPTAIN-PLPS. With respect to the attribute, this data belongs to the transparent data and is transferred through the network to a terminal in the transparent mode. Interpretation and work of this data are achieved by the terminal. Transparent transfer data: Data of an arbitrary format in which items such as A screen information is not included. This data is transferred through the network to a terminal in the transparent mode. As described above, the gateway unit 104 transmits to the protocol converter the information containing the protocol header in network 204, the A screen information 205, the screen control information 208, the header information 209, the data identifier 210, the length indicator 211, the PDU operation code 212 indicating telesoft data, the OP length 213, and the image information as a body 215 preceded by the telesoft header 214 so as to conform to the CPT-PLPS. On recognizing the image information above, the protocol converter 107 decodes the information based on the A screen information 205 into data in a terminal transmission data format defined by the CAPTAIN-PLPS, decodes the image information conforming to the CEPT-PLPS inserted as telesoft data into data in a CEPT-PLPS terminal output format, and then delivers the results as information channel data to the terminal corresponding to the CEPT. In addition, the other transfer data format is available, namely, as shown in FIG. 8, image information conforming to the CEPT-PLPS is inserted in the format of the transparent transfer data 216 so as to transfer the information through the videotex communication network in the transparent mode. As described above, by use of a single user/network interface, it is possible to integrally achieve retrieval service operations of image information items belonging to the different videotex PLPS protocols. In consequence, the retrieval service is available for a particular PLPS, for example, for an image information not conforming to the CAPTAIN-PLPS; furthermore, through a single user/network interface, the connection can be easily established to a desired data base center. Moreover, the user can integrally enjoy the retrieval service of image information items belonging to any videotex PLPS including the CAPTAIN-PLPS. For an implementation of the present invention, there is not required any particular modification of the CAPTAIN-PLPS and subscriber's terminals associated with the respective protocols are also easily accommodated.

Claims: A protocol integrating videotex communication system comprising: a group of data base centers (101, 102, 103) conforming to various presentation level protocol syntax (PLPS) of a videotex, a gateway unit (104) connected to said plurality of data base centers; characterized by a plurality of subscriber's terminals (112, 113, 116) conforming to PLPS corresponding to said group of data base centers; means for interconnecting said group of data base centers conforming to the various PLPS and said plurality of subscriber's terminals including: a videotex communication control apparatus (105, 106-109) connected to said gateway unit; and means including a single ISDN exchange apparatus (110, 111) for connecting said videotex communication control apparatus to said plurality of subscriber's terminals. A protocol integrating videotex communication system according to Claim 1 wherein based on call establish information from the subscriber's terminal, said videotex communication control apparatus establishes a connection via said ISDN exchange apparatus, said videotex communication control apparatus, and said gateway unit to a data base center selected from said plurality of data base center, said data base center being associated with a service request, and service image information from the data base center based on retrieval information from the subscriber's terminal in the connection state is once converted into data of a predetermined data formed by said gateway unit so as to be thereafter converted into data conforming to a protocol associated with the subscriber's terminal by said videotex communication control apparatus, thereby transmitting obtained information to the subscriber's terminal effecting the call initiation. A protocol integrating videotex communication system according to Claim 1 wherein said videotex communication control apparatus includes a videotex exchange (105) connected to a side of said gateway unit according to either one of said plurality of PLPS and a plurality of protocol converter (106 - 109) for protocols conforming to all said PLPS establishing connections in a parallel fashion between said videotex exchange apparatus and said ISDN exchange apparatus, and a protocol conversion corresponding to the subscriber's terminal in said videotex communication control apparatus is effected in one of said plurality of protocol converters. A protocol integrating videotex communication system according to Claim 1 wherein said single ISDN exchange apparatus includes an ISDN exchange (111) connected to a side of the subscriber's terminal and an ISDN primary rate group interface (110) establishing connections between said ISDN exchange and said videotex communication control apparatus. A protocol integrating videotex communication system according to Claim 2 wherein call establish information from the subscriber's terminal to said videotex exchange apparatus is achieved by use of a signal (D) channel (114) via said ISDN exchange apparatus. A protocol integrating videotex communication system according to Claim 2 wherein data supplied from said videotex communication control apparatus to the subscriber's terminal is transmitted by use of an information (B) channel (115) via said ISDN exchange apparatus. A protocol integrating videotex communication system according to Claim 1 wherein a connection between said group including said plurality of data base centers and said plurality of subscriber's terminals is effected between a particular data base center and a particular subscriber's terminal, said center and said terminal each conforming to the same PLPS. A protocol integrating videotex communication system according to Claim 1 wherein said various PLPS include at least either one of CAPTAIN, CEPT, and NAPLPS. A protocol integrating videotex communication system according to Claim 1 wherein the predetermined data format employed in the conversion by said gateway unit is a telesoft information format conforming to CAPTAIN-PLPS. A protocol integrating videotex communication system according to Claim 1 wherein the predetermined data format employed in the conversion by said gateway unit is a data format for which a transparent transfer is possible in the network.

Inventors: GOTO HIROSHI, SHIBATA YOJI, GOTO, HIROSHI, SHIBATA, YOJI
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1989
Main classification: H04M11
IPC codes: H04M11, H04N7