RU2155451C2 - Method for information distribution in mass terminal network and device which implements said method - Google Patents

Abstract

FIELD: information systems. SUBSTANCE: method may be used for designing distribution of text information to multiple receivers from multiple sources, when sources can form groups of users which may have access to transmitted information. Method for transmission of text and command messages from source to receiver involves generation of code sequence, which consists of synchronization , address, message type and message content fields. Source text is encoded (compressed) using preliminary produced thematic encoding tables. Information sources control content of decoding tables which are stored at each receiver as well as list of addresses which are allowed to receive information. Transmission of information from different sources is coordinated by central unit of system by means of time distribution of transmission in time. In addition, information from sources is gathered through public telephone line, while information is distributed to receivers through radio channel. EFFECT: increased protection of distributed information against unauthorized access, possibility of on-line control of transmitted information, reduced traffic through communication channel, decreased restrictions on location of information sources and receivers. 5 cl, 5 dwg

Description

 The inventive group of inventions relates to text information distribution systems for a large number of users, primarily to provide, on a commercial basis, specific users with information on topics of interest to them.

 A known method of disseminating textual information through computer networks, in which users' computers are connected to a source of information via a telephone network [1]. Using the existing telephone infrastructure allows you to organize a network with a simple connection of subscribers. However, the capabilities of such an information system are limited. This is due to the fact that the telephone network at any time allows you to establish a connection between the source of information and only one subscriber. Therefore, the transmission of even the same information to different users should be carried out sequentially. For simultaneous servicing of different subscribers, additional hardware is needed, the cost of which is growing rapidly with the number of subscribers.

 Orientation to sequential service predetermines the organization of communication between the source and consumer of information mainly at the initiative of the consumer. This leads to an additional delay, since information is transmitted not at the time of its occurrence, but at the request of a user who does not know this moment. In turn, when servicing on request, the central node (server) must contain an information storage device, since it is not known in advance when and by whom this information will be required. The disadvantage is that the quality of customer service is largely determined by the quality of telephone channels.

 A broadcast system of the teletext type is known in which the quenching pulse time in a television signal is used to transmit texts [2]. This system is capable of transmitting information for an unlimited number of users, the cost of transmission does not depend on the number of subscribers. As an addition to broadcasting, teletext successfully uses the existing broadcasting infrastructure, but this also has negative consequences.

 Teletext does not have independent use, so the number of information channels and their working hours depend on the number and time of television channels. Autonomous (without a TV program receiver) use of the teletext receiver is irrational, since it must contain nodes that are not related to the information system. The teletext system does not provide for the accumulation, processing and long-term storage of received information. In addition, the teletext system does not have a mechanism for restricting access to transmitted information. This indirectly reduces the quality of service, as it does not stimulate the transfer of information having a high cost of collection and processing, and part of a very limited resource is devoted to advertising. At the same time, with a large number of users, even low tariffs would sharply increase the profitability of the system and, as a result, the variety of information transmitted.

 An important characteristic of any information distribution system is the bandwidth of the communication channel. When transferring texts, throughput without high costs can be significantly increased due to data compression. Compression algorithms [3] are based on the fact that the source text searches for and replaces repeating sequences of characters with one character from a special set. The source text is restored using the dictionary (correspondence table of replacement characters for replaced sequences). Compression algorithms are oriented, as a rule, to work with texts of arbitrary content; therefore, it is impossible to determine in advance which tokens, i.e., which sequences of characters will be repeated most often. For this reason, the formation of the dictionary is performed separately for each text, which is a disadvantage of the method. The dictionary becomes an integral part of each compressed text, it must be stored and transmitted along with the compressed text. In addition, the preparation of the text each time requires time to compile the dictionary, and this happens during the operation of the system, that is, in real time, which is always limited. The time limit reduces the compression efficiency, which depends on the number of combinations of characters viewed.

 Closest to the technical nature of the claimed invention is a method of disseminating information [4] used in a multi-subscriber search radio call system for selective one-way transmission of signals containing digital or alphanumeric messages. The method is recommended by the International Advisory Committee on Radio Engineering (CCIR) [4]. It consists in the fact that the dissemination of information is carried out by transmitting a signal generated in the form of a code sequence consisting of a synchronizing code word entered in the signal synchronization field, an address code word entered in the address field and message code words or free code words entered in the field "message content". The signal thus formed through the communication channel, namely the radio channel, is sent to the subscriber receivers, on which the received signal is analyzed and, if the codes of its address field and the address codes assigned to this subscriber coincide, it is stored in the memory of the subscriber receiver.

 This method provides both the transmission of messages addressed to individual subscribers, and the transmission of messages immediately for a group of subscribers. Groups can be formed by assigning the same address to a certain number of subscriber receivers.

 The disadvantages of this method include the fact that the protection of distributed information from unauthorized access, which is especially relevant when creating systems that disseminate information on a commercial basis, is limited only by the specific addressing of the messages transmitted.

 In addition, in this method, the procedure for adjusting the established rules for transmitting messages in terms of changing the addresses assigned to the subscriber is rather laborious. The need for this arises when transmitting messages with a group address, when it is necessary to change the subscriber’s affiliation to one or another group or exclude individual subscribers from the number served by a specific source of information or the system as a whole. The difficulty lies in the fact that the assignment of addresses to a specific subscriber in this method is carried out during the manufacture of his individual receiver, and the message is transmitted with the address common to all receivers of the group. And if for some reason some subscribers should be excluded from the group, this can be done only on the initiative of the subscriber, while the source of information is primarily interested in this.

 The disadvantages of this method can also be attributed to the fact that it does not save airtime when transmitting large amounts of text messages, or this savings is very small. In this method, all texts of transmitted messages are divided into two types: alphanumeric and digital. The texts of the first type contain a complete set of characters that are represented when the transmitted signal is formed by a seven-digit code. Texts of the second type contain only numbers, spaces, hyphens and brackets, and only four bits are used to represent these characters. This saves some of the airtime, but only when transmitting digital messages.

 The inventive method solves the problem of the regulated dissemination of a variety of textual information in a multi-subscription information system with the ability to adjust the regulations during the operation of the system, with the effective (economical) use of the communication channel.

 The essence of the proposed method lies in the fact that in the method of disseminating information in a multi-subscriber system, including on the transmitting side generating a transmitted signal in the form of a code sequence consisting of a synchronization field, an address field and a message content field, the latter being intended for the information part of the transmitted messages, and transmission of the signal thus formed via the communication channel to subscriber receivers, as well as analysis of the contents of the address field received by the subscriber signal receivers, and if it contains an address that matches one of the addresses assigned to the subscriber, transmitting the signal for further processing, supplement the transmitted signal with the "message type" field, and if a text message is transmitted, then the information part is encoded when the transmitted signal is generated using one of the pre-formed thematic coding tables, the choice of which is determined by the subject of the text, while the code of the table is entered in the "message type" field, adjustments are made The addresses assigned to a particular subscriber are transmitted by transmitting a signal containing the corresponding command message, the code of which, when generating the transmitted signal, is entered in the "message type" field, and at the subscriber receiver, the text message received and skipped for further processing is decoded using the corresponding decoding table previously entered in his memory. Each thematic coding table stored on the transmitting side corresponds to its own decoding table stored on subscriber receivers.

 Moreover, thematic coding tables (hereinafter referred to as coding tables) are formed in the process of statistical processing of texts of the corresponding subject. Why do we find repeating fragments of texts and for each of them we calculate a parameter equal to the product of the length of the fragment by the probability of its occurrence in the text. And if this parameter exceeds the specified value due to the selected bit depth of this table, then the identified fragment is assigned the code with which it is entered into the table.

 In addition, the correction of the decoding tables previously entered into the memory of the subscriber receiver is carried out by transmitting the corresponding command message through the communication channel.

 The technical result of the method is an additional restriction of unauthorized access to the distributed information, an increase in the amount of transmitted information without increasing the throughput of the communication channel by using the additional encoding (compression) of the transmitted text information, as well as by providing remote control (from source to subscriber) of access to information that also allows you to freely adjust the rules for disseminating information, increasing t m the most commercial value of the information system.

 The technical result is achieved as follows. The transmission of information for a specific group of subscribers differs fundamentally from broadcast transmission ("to everyone who hears") by restricting access to the transmitted information.

 In the claimed method, access restriction is ensured not only by sending messages to specific addresses originally assigned to subscribers, but also by managing a list of these addresses during the operation of the information system, as well as encoding (encrypting) transmitted text messages using encoding tables, and this is the basis This encoding principle of text compression allows you to significantly increase the amount of transmitted information without increasing the bandwidth of the communication channel. In addition, access to the transmitted information is limited by controlling the content of the decoding tables during the operation of the information system.

 The essence of the encoding of transmitted text messages is as follows. In specialized texts (texts on a specific subject), the same vocabulary corresponding to specialization is most often used. This circumstance makes it possible to compile a table of the most frequently repeated sequences of characters common to all texts of the same subject (thematic coding table). Replacing such sequences (fragments) with one character can significantly reduce the overall length of the text. When compiling the table, it is necessary to take into account not only the probability of a fragment repeating, but also its length. For this, a coefficient equal to the product of the indicated parameters is calculated. The process of compiling the table is separate from the process of transmitting information, therefore, the time factor and the complexity of the algorithm when compiling the table is not significant. In addition to repeating fragments, individual characters that are not included in fragments are also converted, which increases the security of information from unauthorized access.

 The inventive method allows you to distribute information from each information source to its specific group of subscribers. Moreover, information sources can be divided physically (territorially) or thematically. At the same time, each territorially autonomous source can have a thematic division, and a group of territorially autonomous sources can work on the same topics. In this sense, for the subscriber, the sources are virtual, they differ in the assigned addresses and in the codes of the coding tables.

 Accordingly, each subscriber receiver can belong simultaneously to different groups organized according to different characteristics. If the assigned addresses are interpreted as the addresses of territorially autonomous sources of information, and the coding tables correspond to different thematic information sections, then groups are formed on the basis of receiving information from the same source, or on the basis of receiving information on the same topic. The ability to remotely (from the source of information) control the assignment of addresses in subscriber receivers allows the source to transmit information only to those subscribers who satisfy the conditions for the dissemination of information established by it, and the subscriber to receive only that information that interests him.

 In addition, the time spacing of the processes of creating tables and transmitting information allows for a more detailed analysis of the texts, and provides additional savings in airtime by transmitting a single table for multiple texts. The method used does not exclude, after encoding the transmitted text messages, the execution of other algorithms for additional compression of the transmitted information.

The essence of the proposed method is illustrated by the following graphic materials:
FIG. 1 is a structural diagram of a system that implements the inventive method;
FIG. 2 is a diagram of a subscriber receiver of the system;
FIG. 3 - encoding algorithm for a text message;
FIG. 4 - format of the transmitted signal;
FIG. 5 is a diagram of the inventive device.

 The inventive method can be implemented in the system shown in FIG. 1 and comprising an input unit 1, a memory unit 2, an encoding unit 3, a transmission unit 4, as well as a communication channel 5 and a group of subscriber receivers 6.

 Consider an example of a system that implements the inventive method, which does not provide for the physical (territorial) separation of information sources.

 The memory unit 2 contains a special area for storing pre-formed coding tables.

 The coding unit 3 is a programmable device, the operation algorithm of which is shown in FIG. 3.

 The transmission unit 4 contains a code sequence generator, as well as a software machine that controls the operation of the blocks providing the preparation and transmission of messages.

 The inventive method allows you to use as channel 5 any communication channel, the choice of which is determined by the specific operating conditions of the information system.

 Each subscriber receiver 6, as shown in FIG. 2, comprises a clock selector 7, a codeword allocation unit 8, an address selector 9, a message type selector 10, a text reception unit 11, a table memory unit 12, and a buffer memory unit 13.

 Block 8 selection of code words contains a shift register and a register with parallel recording and a control circuit by which the code sequence is converted to a parallel binary code of fixed length.

 The address selector 9 comprises a code comparison circuit and an address memory unit.

 A message type selector 10 comprises a comparison circuit and an encoder generating command codes.

 Block 11 receiving text is a software that controls the operation of blocks 12 and 13 of the memory.

 In block 12 of the memory is a list of codes of decoding tables, as well as these tables themselves.

 The formation of coding tables is as follows. On the topic of the information section for which the table is formed, a certain number of texts are selected, which are sequentially entered into the computer and processed according to the following algorithm. In these texts, repeating fragments are revealed, for each of which a parameter is calculated that is equal to the product of the fragment length and the probability of its repeating. Fragments with the highest parameter values are included in the table. Each fragment is assigned a code that replaces the fragment when transmitting texts of this subject. The number of fragments included in the table is determined by the given bit depth of the codes replacing the fragments. The formation of the table ends when the newly entered texts cease to substantially alter the already formed table. The generated table is assigned an individual code for its identification - "table code". The coding table and its corresponding decoding table have a common “table” code.

 Messaging is as follows. The input of the input unit 1 receives the command or text message intended for transmission and the address with which it should be transmitted. In this case, a text message is accompanied by an indication of the corresponding coding table. The input unit 1 assigns the corresponding codes (address code, table code or command code and message character codes) to the input data, which are recorded in the memory unit 2.

 Upon completion of data recording in the memory unit 2, the input unit 1 sends a command to the transmission unit 4, which starts the process of generating the transmitted signal by the unit 4.

 The signal generated by block 4 is a digital sequence divided into code words; its format is shown in FIG. 4. The transmitted signal contains a synchronization field, an address field, a message type field and a message content field. When generating the transmitted signal, these fields are filled with the corresponding code words. Each message ends with a special code word "end of message".

 The transmission unit 4, according to the data (table code, command code) entered into the memory unit 2, determines the type of message to be transmitted and, if a command message is transmitted, immediately proceeds to generate the transmitted signal, and if it is a text message, text encoding is performed before the signal is generated .

 The coding of the text is as follows. The transmitting unit 4 starts the unit 3 implementing the text encoding algorithm shown in FIG. 3 and consisting in the fact that in the source text such sequences of consecutive characters are searched that match the text fragments included in the coding table. If such a fragment is found, then the corresponding code from the table is entered in the memory area where the encoded text is stored. If the fragment is not found, then the code from the table corresponding to the first character of the sequence being checked is written to the memory, and then the search begins for the fragment starting with the next character of the sequence. In the algorithm depicted in FIG. 3, the following notation is used: S is the character of the source text, a + b is its serial number, a is the number of the first character of the sequence being checked, b is the serial number of the character in this sequence. The table for encoding is selected by the table code entered in the memory unit 2. As a result of the encoding algorithm, an array of characters (codewords) of the encoded text is formed in the memory unit 2. At the end of the coding, the coding unit 3 generates a signal, according to which the transmission unit 4 proceeds to the formation of the transmitted signal.

 The formation of the transmitted signal for any type of message consists in reading data to fill in the fields defined by the signal format (Fig. 4), and forwarding this data to the code sequence generator available in the transmission unit 4. In this case, the code words necessary to fill in the synchronization field and to indicate the end of the message, which have constant values, are stored directly in block 4, and data to fill in other fields is read from block 2.

 In accordance with the signal format (Fig. 4), the address code is entered in the address field, and the command code or table code is entered in the "message type" field. Field "message content" is intended for the information part of the transmitted message. For a text message, this field contains an array of code words obtained as a result of encoding the text, and for a command message, the data recorded in block 2 when entering the message is entered without conversion.

 The following types of command messages are provided in this system: "Write Address", "Delete Address", "Write Table" and "Delete Table". These commands manage lists of addresses assigned to subscriber receivers, as well as lists of table code stored in these receivers and the contents of the tables themselves.

 The information part of the “Write Address" and "Delete Address" command messages is the address code that needs to be recorded or deleted in the subscriber's address list. The information part of the “Write the table” command messages is the code of the table and its contents, and in the message “Delete the table” it is only the table code.

 The signal is transmitted through the communication channel 5 in sequence, as it is formed.

 The signal transmitted via the communication channel 5 is transmitted to the subscriber receivers 6. The detection and processing of this signal is as follows. In the initial state, the clock selector 7 of the subscriber receiver 6 continuously listens to the communication channel 5 and compares the digital sequences received at the input of the receiver 6 with a constant corresponding to the synchronization code word. Having found their coincidence, the selector 7 of the clock generates a pulse, which sets the initial block 8 of the selection of code words and starts the selector 9 addresses.

 Block 8 converts the digital sequence into codewords.

 The address selector 9 receives from the block 8 the address code word immediately following the sync signal (synchronization code word) and compares it with the address codes assigned to this subscriber receiver and stored in the memory of the address selector 9. If the received address is not found in the address list, the signal processing stops. If such an address is detected, then the address selector 9 generates a pulse triggering a message type selector 10.

 The selector 10 receives from the block 8 a code word contained in the "message type" field, and depending on its value generates a corresponding signal, which is supplied either to the address selector 9 or to the text receiving unit 11.

 If the code command "Write address" is transmitted with this code word, then the corresponding signal is sent to the address selector 9, which, upon receiving the signal, receives the code word from the "message content" field (in this case, the code word will be the address code) and enter it to the list of addresses assigned to the subscriber receiver, stored in the address memory unit of the selector 9.

 With the "Erase Address" command, the address selector 9, having received the corresponding signal from the selector 10, receives a code word (address code) from the "message content" field, finds in the list of addresses assigned to this subscriber receiver an address that matches the received code word, and excludes it from the address list.

 When the command "Write table" the corresponding signal from the selector 10 is sent to the block 11 receiving text, which then writes the first code word of the field "message content" (table code) in the list of table codes stored in the memory block 12 tables, and all other code the words from the "message content" field are sent to block 12. Recoding of the decoding table continues until the reception unit detects the code word "end of message".

 With the command "Erase the table", the corresponding signal from the selector 10 is also sent to the receiving unit 11, which then receives the code word from the field "message content" (table code) and excludes this code from the list of table codes, and also frees the area of the memory unit 12, occupied by this table.

 If the value accepted by the codeword selector 10 is a table code, then a signal is received at the receiving unit 11 from the selector 10, which starts the process of receiving the text. The receiving unit 11 checks the presence of this code in the table code list stored in the memory unit 12, and if such a code is not in the list, the signal processing stops. If in block 12 of the memory there is such a code, then according to the corresponding decoding table, decoding (restoration) of the message is performed. For each codeword of the information part of the text message (except for the first codeword), the text receiving unit 11 finds the corresponding text fragment or single character in the indicated table and enters it into the buffer memory unit 13. The text receiving unit 11 receives all subsequent codewords of the information part of the message until it finds the code word "End of text". As a result, after receiving the code word "End of text" in block 13, the restored text is recorded.

 The inventive method can be used to build an information system in which many sources transmit information to many subscribers. Moreover, each source of the system independently forms groups of subscribers to whom the information transmitted to them is available.

 Information from autonomous, unrelated sources is transmitted at random times, including at the same time. To ensure that information is not lost, you must either provide simultaneous reception of information from different sources at each subscriber receiver, or organize the transfer of information from different sources at different times. The first option complicates the design and increases the cost of the most replicated element of the system - the subscriber unit, therefore, the preferred option is the transmission spaced in time.

 Sources of information (hereinafter referred to as sources) are usually randomly located in the space in which the information system operates. To coordinate the work of different sources, it is necessary to ensure the connection of sources among themselves, or the connection between sources and a center that performs the functions of an information system administrator.

 The closest in technical essence is the information system described in the patent of the Russian Federation N 2030113, which includes M modulators and generators, N subscriber nodes and K nodes for the preparation and transmission of information, each of which contains a control unit connected to the information input unit, a display unit, a memory unit, a matching unit with a group of telephone modems, as well as several modems. The information generated by the nodes of the preparation and transmission of information (UPPI) through the transmitting elements, which are generators and modulators, and the line of wire broadcasting (the first communication channel) is transmitted to the subscriber nodes. Subscriber units consist of a group of receiving units, which include a filter and a demodulator, and a group of nodes of receiving and displaying information, which include a memory unit and a control unit associated with it. All USPIs and subscriber units also have communication with each other through the telephone network (second communication channel) to correct errors that occur during reception. All active at a certain point USPI transmit at different carrier frequencies, which are separated by filters in the receiving units of the subscriber units. Thus, the main function of the UPPI is to prepare information for the end user and they could be called information preparation nodes. The output matching unit included in the UPPI can be considered an independent element that performs coordination between the information preparation nodes and the transmitting elements.

 The disadvantage of this system is that the transmission of information from different sources, carried out at different frequencies, is not coordinated in any way, while the subscriber unit is capable of receiving reception on only one frequency at a particular moment in time. Therefore, if several sources transmit simultaneously, then each subscriber will be able to receive information from only one of them, and all other information will be lost. Another disadvantage of the system is the inability to limit unauthorized access to the transmitted information.

 In the information system under consideration, the reliability of information reception is ensured by the transfer of lost blocks through an additional communication channel, which is used as a telephone network. Connecting a subscriber node simultaneously to two communication channels significantly degrades the characteristics of the information system, because, firstly, a subscriber node can only be installed where there is access to these two channels, and secondly, introducing a modem into a subscriber node complicates it design and increases cost. At the same time, high reliability of reception with a small level of failures can be obtained through retransmissions, and with large failures the use of the system in question is generally impractical, since the main information stream will go through the second (additional) communication channel.

 The inventive device solves the problem of creating with the least hardware cost a unidirectional information system in which many sources distribute information to many consumers, each consumer having the ability to receive information from a group of sources selected by him, and each source has the ability to establish reception conditions and transmit information only to those subscribers that satisfy these conditions.

 The essence of the invention lies in the fact that in an information system containing a group of information preparation nodes (UPI), the outputs of which are connected to the first communication channel and a group of subscriber nodes, the inputs of which are connected to the second communication channel, in which each UPI contains an input unit, the input of which is the input of the UPI, and the output is connected to the input of the control unit, which is also connected to the memory block and matching unit by the corresponding conclusions, the second output of which is the output of the UPI, and each subscriber unit contains the unit an input whose input is the input of the subscriber unit, the control unit and the associated memory block and matching unit, the second output of which is the output of the subscriber unit, an additional central unit is connected, connected by its output to the first communication channel and containing the matching unit in series, the output of which is the output of the central node, the transmission program forming unit, the transmission machine, the code sequence generator and the transmission unit, the output of which is sub is accessible to the second communication channel and is the output of the central node, as well as a memory block and an input block, the input of which is the input of the central node, and the output is connected to the second input of the transmission program forming block, also connected by the corresponding output to the first output of the memory block, the second output of which connected to the corresponding terminal of the automatic transmission, in addition, an encoding unit connected to the third terminal of the control unit is additionally introduced into each UPI, and an address selector, inform the control and control inputs of which are connected to the corresponding outputs of the receiving unit, and the output to the control unit, and a decoding unit connected respectively to the output of the control unit and to the third output of the matching unit.

 Moreover, the first communication channel may be a telephone network, and the second communication channel may be a radio channel.

 An additional central unit, introduced into the system, coordinates the transmission of information from various sources (UPI) by transmitting the transmissions over time. The transmission is carried out on the same carrier frequency, which eliminates the imposition of different packages, however, with a constant bandwidth of the communication channel, this reduces the maximum density of information flow that the information system can provide. To improve this characteristic, the proposed system uses compression (encoding) of the transmitted information, which is performed using the encoding unit entered in the UPI, and the decoding unit is entered into the subscriber units. Encoding information by compression also provides protection of the transmitted information from unauthorized access, which allows sources (UPI) to introduce restrictions on the reception of information by subscriber nodes.

 Access restriction is also achieved by the fact that the source (UPI) can remotely control the list of addresses stored in the address selector of each subscriber unit, according to which information can be received and that the source can control the content of decoding tables stored in the decoding unit.

 The technical result is to reduce information loss due to the temporary separation of the communication channel and the organization of centralized communication between multiple sources and multiple consumers of information. At the same time, an increase in the total load of the communication channel is ensured by compression of the transmitted data, which further limits access to the transmitted information. In addition, the organization of the collection of information through the telephone network and its distribution via the radio channel reduces restrictions on the spatial arrangement of sources and receivers of information.

The essence of the claimed device is illustrated by the following graphic figures: FIG. 5 - diagram of the inventive device
The information system (Fig. 5) contains information preparation nodes (UPI) 14 connected through the first communication channel 15 to the output of the central node 16, which through the second communication channel 17 is connected to the subscriber nodes 18.

 Each UPI 14 contains a control unit 19, the input of which is connected to the output of the input unit 20, and the output with the display unit 21. In addition, each UPI 14 contains a memory unit 22, a matching unit 23, and an encoding unit 24, the terminals of which are connected to the corresponding terminals of the control unit 19. The input of the input unit 20 is the input of the UPI 14, and the second output of the matching unit 23 is the output of the UPI.

 The Central node 16 contains sequentially connected block 25 matching, block 26 forming a program guide, automatic transmission 27, the generator 28 code sequence and block 29 transmission. Moreover, the output of the matching unit 25 is the output connecting the central node 16 with the first communication channel 15, and the output of the transmission unit 29 is the output connecting the central node 16 with the second communication channel 17. In addition, the central node 16 includes an input unit 30 and a memory unit 31, the first terminal of which is connected to the corresponding terminal of block 26, and the second terminal with the corresponding terminal of automatic transmission 27. The input of input block 30 is the input of the central node, and the output is connected to the second input of block 26.

 Each subscriber unit 18 contains a receiving unit 32, the input of which is the input of the subscriber unit, and the control and information outputs are connected to an address selector 33 connected to the control unit 34, the other outputs of which are connected to the memory unit 35, the decoding unit 36 and the matching unit 37, the second output of which is connected to the output of the decoding unit 36, and the third output is the output of the subscriber unit.

 The functions of the input units 20, 19 of the control, 21 of the display and 22 of the memory of the information preparation unit 14 are performed by an IBM computer using the appropriate program.

 The coding unit 24 is a programmable device with a memory in which coding tables are stored.

 The telephone network is used as the first communication channel 15 in this example. Accordingly, the blocks 23 and 25 coordination are telephone modems.

 As the second communication channel 17, a radio channel is used. Accordingly, the transmission unit 29 contains elements for generating, modulating, amplifying and transmitting a radio signal.

 Block 26 forming the program guide, block 30 input and block 31 of the memory of the Central node 16 are the nodes and program blocks of a computer type IBM. Automatic transmission 27 - programmable device. Code sequence generator 28 is a shift register.

 The address selector 33 consists of a software machine, an address memory, and a comparison circuit.

 Block 32 receiving subscriber node 18 contains a receiver that provides reception, amplification and demodulation of the radio signal. In addition, the reception unit 32 includes a clock selector and a codeword allocation circuit.

 The control unit 34 of the subscriber unit 18 is implemented on a microprocessor type MCS-51. Decoding unit 36 is a programmable device with memory. Block 37 matching contains elements that ensure the operation of a standard serial interface.

 The information system operates as follows.

 Each node 14 information preparation (UPI), together with groups of related subscriber nodes 18 form an autonomous information channel through which information is regularly broadcast on the topic declared when the channel is turned on. The information system brings information from the source (UPI) to the output of the subscriber unit 18, to which an external device, namely a display, registration, storage device, or a local network server can be connected. The unit of information passing through the information channel is an array of characters (text), which is fed to the input UPI 14.

 In addition to texts intended for output to a terminal device, commands that change parameters inside subscriber nodes are also transmitted via the second communication channel (radio channel) 17.

 The formation of a new information channel in the system is carried out by the initialization procedure. Each subscriber unit 18 can be connected to any existing information channels. Permission for such a connection is transmitted by commands from the corresponding UPI 14.

 The central node 16 controls the formation of information channels, checks the authority of the information sources (UPI) for transmission, regulates the data flows from various UPI 14 for transmission to the subscriber nodes 18 and ensures the transmission of information over the air over the air channel 17.

 The logical connection UPI 14 information channel and subscriber nodes 18 is through the addressing system. To do this, each message is transmitted with a destination address of one of three types: individual, multicast, and broadcast. The address indicated in the message received by the subscriber unit 18 is compared with the list of allowed addresses stored in the memory of the address selector 33 of the given subscriber unit. Depending on the result of the comparison, the address selector 33 allows or prohibits further processing of the received message. Initially, in the list of allowed addresses of each subscriber node, there are only two addresses: individual and broadcast. During the operation of the information system, these lists are dynamically changed as information channels are turned on and off.

 Each UPI 14 of the information system is assigned its own address with which it can transmit its information over the air. This address can be used as a group address. In addition, UPI 14 can transmit information to the individual addresses of subscribers and to the broadcast address, while the message must indicate its own address UPI. Transmissions to other addresses for a specific UPI are prohibited by the regulations. Own addresses UPI 14 are assigned by the Central node 16 during the initialization of the information channel.

 The central node 16 maintains a register that contains information about the parameters of the existing information channels, as well as a list of free addresses. The registry is located in the allocated memory area of block 31.

 The preparation of data for transmission is performed by the UPI 14 information channels. The source data is fed to the input of the UPI input unit 20. The input process is controlled by the display unit 21. The control unit 19 reads the input data, places it in the memory unit 22, and then breaks the input data into information blocks, the maximum length of which is a system variable. All information blocks formed in UPI 14 are numbered. The bit depth of the number is selected so that overflow would occur no more often than once in a given period of time. Numbering allows you to detect the fact of the loss of blocks at the receiving end (subscriber node 18). To increase the reliability of information reception, retransmissions are carried out at different times of the day. The number of retransmissions, as well as the time of transmission, is indicated when entering the data array in UPI 14 and is determined based on the required reliability of information distribution taking into account traffic and tariffs for radio channel rental. The transmission of individual blocks can also be repeated at the request of subscribers received via other communication channels that are not part of the information system. Each information block also contains the following data: number and time of transmissions, block number.

 If the text is transmitted, then before the formation of the information blocks, the source text is encoded. For this, the UPI control unit 19 loads the source text into the memory of the encoding unit 24. The software device of block 24 converts the source text into an array of encoded text characters. The conversion is carried out using the text of the codebook corresponding to the topic stored in the memory of block 24. The encoding algorithm is shown in FIG. 3. The encoded text is returned to the UPI memory block 22.

 In each information block with encoded text, in addition to its serial number, the numbers of the first and last blocks of the group constituting the full text are recorded. Each code block also contains the table code.

 For each information block, a checksum is calculated that covers all data except data on the number and time of transmissions.

 Information blocks prepared for transmission are sent from the UPI 14 through the first communication channel 15 (telephone network) to the central node 16. For this, the UPI 14 control unit 19 sends a command to the coordination unit 23 (telephone modem) to establish communication with the central node 16. Through the telephone network, the block 23 matching UPI 14 information channel is connected with the block 25 matching (telephone modem) of the Central node 16, after which the block 19 control UPI 14 transmits to the block 23 matching the prepared information block. Through the communication channel 15, the information goes to the coordination unit 25 of the central node 16. The transmission program generation unit 26 reads the incoming information, checks the authorization of this information source (UPI 14) for transmission, and, if the result is positive, sends this information to the memory unit 31. If the result of the authorization check is negative, the reception is terminated and a refusal to distribute information is sent to UPI 14. Verification of authority UPI 14 is as follows. It is checked whether the own address of this UPI is stored in the register stored in the memory block 31 and whether the corresponding transmission restrictions are observed. Transmission restrictions for each UPI are established during initialization of the corresponding information channel of the system and are recorded in the same registry. An example of a restriction is a ban on transmissions to a broadcast address.

 After reception and recording by the central node 16 of all information blocks transmitted by a specific UPI, the communication session is completed and the block for generating the program guide 26 starts preparing messages and including them in the program guide on radio channel 17. In this case, one message is formed from one information block.

 Via radio channel 17, messages are transmitted in the form of signals whose formats are shown in FIG. 4. Each message is accompanied by the following data: destination address, message type, message number, checksum, sign of the end of the message. In addition, for text messages, the numbers of the first and last messages of the group constituting the full text are transmitted. All these data are taken from the corresponding information block received from the UPI 14. The messages prepared for transmission are stored in a buffer organized in the memory unit 31 of the central node 16.

 Block 26 generates a program guide, in accordance with which it is established which message of which information channel at what time should be transmitted. The program of programs is formed taking into account the actual load of the radio channel, taking into account the information channels received from the UPI information about the transmission time and the number of retries, as well as taking into account the parameters of the information channels recorded during their initialization - such as channel priority and coordinated traffic. The program guide is located in block 31 and is a sequence of records, each of which indicates in explicit or relative form the time of transmission of a particular message, its length and the starting address of the memory area of block 31 in which it is stored.

 Messaging through radio channel 17 to the subscriber nodes 18 is as follows.

 Automatic transmission 27 reads from the block 31 of the memory the next record of the program guide, and if the transmission time indicated in it coincides with the current time or if there is no explicit indication of the time, it proceeds to transmit the message. For this, the transmission machine 27 in accordance with the CCIR protocol [4] generates synchronization bytes, reads the message data byte from the memory unit 31, and sends this data to the code sequence generator 28, which converts the incoming bytes into digital (code), from the memory unit 31 sequence. The code sequence generated in this way is fed to the transmission unit 29, which provides the necessary physical characteristics of the signal for its distribution through the radio channel 17. For the radio channel, the transmission unit 29 modulates the radio frequency with a code sequence, amplifies the radio signal, and transmits it through the antenna over the air.

 Through the channel 17, the radio signal enters the input of the receiving unit 32 of the subscriber unit 18. The receiver of the unit 32 amplifies and demodulates the received radio signal and supplies the code sequence thus obtained to the codeword allocation circuit and to the clock signal selector of the same unit. The latter, having detected synchronization bits in this code sequence, generates a pulse that sets the codeword allocation block of block 32 to the initial state and starts the address selector 33. The codeword allocation circuit of block 32 converts the code sequence into a sequence of parallel binary codes (codeword sequence). Having received an impulse from block 32, the selector 33 software selects from the sequence of code words from block 32 the address code word and remembers it. Then, the software of block 33 sequentially reads data from the address memory of the same block. If one of the addresses stored in this memory coincides with the received address, the software of block 33 sends a signal to the control block 34 to allow the message to be received. Further, the address selector 33 passes all the codewords coming from the reception block 32 to the input of the control block 34. Reception continues until the program machine detects block 33 of the code word "end of message". If a copy of the received address in the address memory of block 33 is not found, the address selector 33 takes no action until the next message is received.

 The control unit 34 places the received message in the receive buffer located in the memory unit 35. Messages are posted at the addresses assigned by the record pointer stored in block 35. The newly received message is placed immediately after the previous one.

The control unit 34 keeps track of the received messages, for which an area for the directory is allocated in the memory unit 35. Each entry in the directory contains the following information:
- date and time of admission,
- own address of the source of information (UPI),
- message number,
- message length
- address of the receive buffer in which the message is placed,
- sign of reception failure,
- sign of the output of the message to the output of the subscriber unit (for text) or sign of the command.

 After the end of reception, the control unit 34 at its own address UPI and the message number determines whether the catalog contains a copy of this message, received without fail. If such a copy is available, the value that was in it before it is returned to the record pointer, and work with the message is terminated.

 If there is no copy of the message in the directory, the control unit 34 calculates the checksum of the message and makes an entry in the directory with the value of the failure flag equal to zero or one, depending on whether the checksum matches or does not match.

 If the directory contains a copy of the message with a failure symptom equal to one, the control unit 34 calculates the checksum of the newly received message, and if it is correct, then the copy of the message with the failure flag is erased from the directory, and instead the entry with the parameters of the newly received message is made in the directory .

 If both the copy and the new message are received with a malfunction, the control unit 34 sequentially compares the same fragments, calculates checksums for them, and replaces the damaged areas. The CCIR protocol provides checksums for each twenty-bit fragment. After fixing the errors, the total checksum of the message is calculated, and if it is correct, only one fixed copy is stored in the directory. Block 34 scans the entire directory and destroys all copies of the corrected message. In the saved copy, the failure flag is reset to zero.

 If the message cannot be completely restored, the control unit 34 searches the catalog for other copies of the received message. In the absence of other copies, the newly received message is entered into the directory with a failure symptom equal to one.

 If in the receive buffer of block 35 in the catalog several copies are found that were received with a failure, the control unit 34, by sequentially comparing the fragments, tries to restore their original form by calculating the checksums and replacing the mismatched bits according to the majority principle. If recovery succeeds, all copies in the directory are erased, instead of them there is only one record of the corrected message with the failure sign "0".

 After receiving the message without failures or its full recovery, the control unit 21 determines the type of message. To determine the type of message, the code word located in the corresponding field of the received signal is read. If a command is received, the control unit 21 performs the actions prescribed by the command. Work with text messages continues only if the external device is connected to the subscriber unit and is ready to receive texts.

 On the radio channel 17 for the subscriber node 18, a command of one of four types can be sent: “Write address” or “Delete address” and “Write table” or “Delete table”.

 To execute the "Write Address" command, the control unit 34 finds the address indicated in the "message content" field of the received signal (see Fig. 4) and writes it to the address memory available in the address selector 33.

 For the "Erase address" command, the control unit 34 deletes the address specified in the "message content" field from the address memory of the selector 33.

 For the "Write table" command, the control unit 34 finds the table code indicated in the first code word of the "message content" field, places it in the table code list stored in the memory of the decoding unit 36, and assigns a memory segment to place the table. The data contained in the remainder of the "message content" field, block 34 writes to the designated segment of the table memory of block 36 decoding.

 Similarly, for the "Erase table" command, the control unit 34 erases the table code from the corresponding list and frees up the memory area of the decoding unit 36 occupied by the table.

 The output of the text begins if the external device sets the signal of readiness for receiving text at the output of the subscriber unit 18. The ready signal through the matching unit 37 is supplied to the control unit 34, which then sequentially scans the directory in the memory unit 35 and, having found in it a text message record with the error sign “0”, proceeds to decoding (restoration) of the text.

The received text in encoded form is stored in the receive buffer of block 35. Each character of the received text should be replaced with the corresponding character or sequence of characters from the table stored in the table memory of the decoding unit 36. The decoding table contains lines containing the following information:
- code character encoded text,
- sign "0" if the character code of the encoded text corresponds to a single character of the restored text,
or sign "1" if the character code of the encoded text matches the character sequence of the restored text,
- character code of the restored text, if the sign is "0",
or the address of the memory region of the decoding table, where the sequence of characters of the restored text is stored, if the sign is "1".

 The sequence of characters of the recovered text is stored in a table in the form of a record that begins with an indication of its length, and the following are the codes of the characters in the order in which they should be played.

 The restoration of the received text and the output of the restored text is performed by block 36 according to the following algorithm.

 1. Using the adopted code of the table, determine the address of the memory segment of block 36, in which the corresponding decoding table is stored.

 2. Read the code of the first character of the received text.

3. Find in the decoding table a line with the code of the current character of the received text;
if the sign recorded in this line is "0", then read and output to the output of block 36 the corresponding character code of the restored text;
if the sign is "1", read the number of characters in the sequence at the address indicated on the line, then read and send all the characters in the sequence in the order of the addresses.

 4. Read the code for the next character of the received text.

 5. Repeat steps 3 and 4 until the sign of the end of the text appears.

 The characters of the restored text are fed to the output of the subscriber unit 18 through the matching unit 37, which provides synchronization of the output with an external device.

 After the output of the next text message or after the command has been executed, the sign of the message output is set in the corresponding directory entry. After the output of all correctly received text messages, the reception buffer of block 35 is reorganized, which consists in erasing all messages that are finished with work and in rewriting the remaining ones. In the catalog, entries about messages received and erased from the buffer memory remain with the established sign of output until the end of the storage period. This is necessary to exclude the repeated reception of their copies. After the reception buffer has been reorganized, the control unit 34 scans the catalog in order to detect and erase records that have expired.

 The initialization of the information channel is as follows. The parameters of the initialized channel (name, traffic, priority, transmission restrictions, tariffs, UPI own address) are fed to the input of the input unit 30 of the central node 16. The transmission program generating unit 26 reads the parameters from the input unit 30 and places them in the register line of the information channels with idle address. The registry is located in the allocated area of the memory block 31 of the central node 16. After that, the information channel is open for transmitting information received with its own address entered in the register of the UPI. After connecting to the information channel, the information source (UPI) sends out a command to the subscriber nodes that allows receiving information from this channel. The method of distribution depends on the established restrictions on access to the transmitted information. For free channels with unlimited access, newsletters are sent to a common (broadcast) address. If there are any restrictions, the command is sent to the individual addresses of the subscribers when the conditions of the restriction are satisfied. Access restrictions are set by each source of information independently.

 To establish permission to connect the subscriber unit 18 to the information channel, the UPI 14 generates a command information block in which the address of the subscriber node, the type of the "Write Address" command, and the own address of the UPI are indicated.

 The information block is transmitted to the central node 16, which generates the corresponding command message. A message via radio channel 17 arrives at the subscriber unit 18, and the UPI address contained in its information part is recorded in the address memory of the address selector 33. After that, all messages transmitted with this address will be received and processed by the subscriber unit 18.

 If necessary, disconnect the subscriber unit from the information channel, the UPI forms a command information unit with the type of the command "Delete address". By this command, the address contained in the information part of the message is deleted from the address memory of the selector 33 in the subscriber unit. If a separate subscriber is disconnected from the information channel, the command is transmitted to an individual address. If the channel closes, the command is sent to the multicast address.

Literature
1. Local area networks. Ed. S.V. Nazarova. M .: "Finance and Statistics", 1994.

 2. Martin D. Video text and public information services. M .: Radio and communications, 1987.p. 27 - 31.

 3. Matthew Harris Disk Compression. M .: "Binom", 1995, p. 33 - 35.

 4. Recommendations of the International Radio Engineering Advisory Committee. Rec. 584.1, 1991, p. 11 - 15.

Claims (5)

 1. The method of disseminating information in a multi-subscriber system, which consists in forming on the transmitting side a transmitted signal in the form of a code sequence consisting of a synchronization field, an address field and a message content field, the information part of the transmitted message being entered in the latter, and transmitting the thus formed signal through a communication channel to subscriber receivers, where the contents of the address field of the received signal are analyzed and if it contains an address that matches one of the assignments addresses to the subscriber, they transmit a signal for further processing, characterized in that the transmitted signal is supplemented with the "message type" field and, if a text message is transmitted, then when generating the transmitted signal, its information part is encoded using one of the pre-formed thematic coding tables, the choice of which is determined by the subject of the text, while in the "message type" field the code of this table is entered, the addresses assigned to a particular subscriber are adjusted by sending signals ala with the appropriate command message, the formation of which in the field "message type" command code are entered, and at the subscriber receiver, the received and transmitted for further processing the signal with the text message is decoded using the appropriate decoding table previously entered in its memory.  2. The method according to claim 1, characterized in that for the formation of thematic coding tables by statistical processing of texts of the corresponding subject, duplicate text fragments are detected and for each of them a parameter is calculated that is equal to the product of the fragment length by the probability of its occurrence in the text, and if this the parameter exceeds the specified value due to the selected bit depth of the table, then the identified fragment is assigned a code with which it is entered into the encoding table.  3. The method according to p. 1, characterized in that the correction of thematic coding tables previously entered into the memory of the subscriber receiver is carried out by transmitting the corresponding command message through the communication channel.  4. An information system containing a group of information preparation nodes (UPI), the outputs of which are connected to the first communication channel, and a group of subscriber nodes, the inputs of which are connected to the second communication channel, in which each UPI contains an input block, the input of which is the input of the UPI, and the output is connected to the input of the control unit, which is also connected to the memory block and matching unit by the corresponding conclusions, the second output of which is the UPI output, and each subscriber unit contains a receiving unit, the input of which is the subscriber input of a node, a control unit and a memory unit and a matching unit associated with it with corresponding outputs, the second output of which is a terminal of a subscriber unit, characterized in that a central unit is additionally inserted into it, connected by its output to the first communication channel and containing a matching unit in series, the output of which is the output of the central node, the transmission program forming unit, the transmission machine, the code sequence generator and the transmission unit, the output of which is connected to the second the communication channel and is the output of the central node, as well as a memory block and an input block, the input of which is the input of the central node, and the output is connected to the second input of the transmission program forming unit, also connected to the first output of the memory block by the corresponding output, the second output of which is connected to the corresponding the output of the automatic transmission, in addition, an encoding unit connected to the third output of the control unit is additionally introduced into each UPI, and an address selector, information and control unit are entered into each subscriber unit -governing inputs connected with respective outputs of the reception block and the output from the control unit and the decoding unit, connected respectively to the output control unit and a third terminal block matching.  5. The system according to claim 4, characterized in that the telephone network is used as the first communication channel, and the radio channel as the second.

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