JPH0436635B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a communication method for a CATV system that uses a telephone line for communication from a receiving terminal device to a center.

[Conventional technology]

In this type of CATV system, viewing information data is sent from the receiving terminal device to the center using a telephone line in response to a transmission command from the center, and then the viewing information of the receiving terminal device is sent to the center using a telephone line. It is known what clears the . FIGS. 1 and 2 show the configuration of such a CATV system. What is shown in Fig. 1 is the configuration of the center side of the CATV system, in which a plurality of TV transmitters 1 are prepared for the number of transmission channels, and the TV signal is transmitted to the CATV system.
Sent to the main line. Further, the downlink data signal from the center to the receiving terminal device outputted from the computer 3 is also modulated by the FSK modulator 2 and sent to the CATV main line. On the other hand, uplink data signals, which are viewing information from each receiving terminal device, are sent to the computer 3 via the modem 4. What is shown in Fig. 2 is the configuration of the receiving side terminal device 12.
A TV signal branched from the CATV cable is input to the receiving terminal device 12 together with a downlink data signal. The input TV signal is tuned by a converter 5, reproduced into a regular video by a descrambler 6, and then input to a TV set 13.
The control signals for controlling the converter 5 and the descrambler 6 are obtained by writing the downlink data signal sent from the microcomputer 8, modulated by the FSK modulator, and demodulated by the FSK demodulator 7, and the tuning signal from the keyboard 11 into the ROM 10. It is given by processing according to the given program. Then, paid viewing information such as billing obtained from the paid program fee, viewing time, and number of viewed programs written in the RAM of the computer 8 is transmitted as a telephone protocol start request command from the center side to the receiving terminal device 12. The command is transmitted by telephone modem 9 onto the telephone line. In the CATV system having such a configuration, the TV transmitter 1 sends a TV signal to the CATV main line. In the receiving side terminal device 12, by operating the keyboard 11 and inputting a desired channel, the computer 8 determines whether or not the inputted desired channel is a channel permitted for viewing.
If it is a viewing-permitted channel, a control signal is output to the converter 5 and descrambler 6 to tune to the desired channel and descramble it. At this time, if the channel is a paid program, the fact that the channel was viewed is recorded in the RAM backed up by the power supply in the computer 8. On the other hand, the computer 3 at the center repeatedly and periodically outputs a transmission command to each receiving terminal device. Specifically, first, the receiving terminal device 12 from which paid viewing information is to be collected is called using the address of the subscriber terminal from which to collect paid viewing information. Then, the computer 8 of the receiving terminal device 12
Using the telephone number of the CATV center written in the ROM 10, the paid viewing information in the RAM is sent out as upstream data using the telephone line. Next, when a paid information clear command is sent from the center, the paid viewing information stored in the RAM in the receiving terminal device 12 is erased. In this system, if the content of communication between the modems 4 and 9 is analyzed, there is a possibility that erroneous data will be sent as viewing information, which will make normal fee collection difficult. That is, since modems are easily available, unauthorized viewing can be performed by connecting a commercially available personal computer to generate pseudo data and sending it to the center.

[Problem to be solved by the invention]

The present invention was made based on the above circumstances, and it transmits the uplink data signal from the telephone directly from the center to the receiving terminal device, and in the receiving terminal device, the sent back data and the data stored in the RAM are combined. By comparing the data and clearing the viewing information data, which is a part of the data, only when the two data match, and not clearing the viewing information data if they do not match, made it possible to prevent
It provides a communication method for CATV systems.

[Means to solve the problem]

In order to achieve the above object, the present invention has the following features:
"The viewing information data of the CATV signal is stored in the receiving terminal device, and the viewing information data is sent to the center via the telephone line in response to a transmission command repeatedly sent from the center via the CATV line.
In this communication method of the CATV system, in addition to the viewing information data, the receiving terminal device also stores data on the number of tuning times and cumulative number of tuning times of paid viewing channels between two transmission commands. When the side terminal device receives the transmission command, it transmits the viewing information data, the number of channel selections, and the cumulative number of channel selections to the center via the telephone line, and the center receives the data reception confirmation signal together with the data reception confirmation signal via the CATV line. Transmits the tuning frequency data and cumulative tuning frequency data to the receiving terminal device, and transmits the tuning frequency data and cumulative tuning frequency data received by the receiving terminal device and the stored tuning frequency data and cumulative tuning frequency. To provide an invention of a communication method for a CATV system, which is characterized in that viewing information and tuning number data are cleared only when both data match.

【Example】

Hereinafter, embodiments of the present invention will be specifically described with reference to FIGS. 3 to 5. In the figures described below, parts common to FIGS. 2 and 3 are designated by the same reference numerals, and redundant explanations will be omitted. This embodiment differs from the conventional example shown in FIG. 2 in that a counter 14 consisting of three counters is configured on the computer 8, and its contents are stored in RAM. be. The first counter (the pay channel viewing counter in Figure 4) configured on the computer 8 counts the number of times a pay channel is selected during the telephone protocol start request command issued from the center at every predetermined period. The RAM memory is cleared when a confirmation signal is received. Second
The second counter (cumulative counter in Figure 4) accumulates the counting results of the first counter, and when it overflows beyond a predetermined number of digits, it returns to 0 and starts accumulating again. There is. The third counter (cycle counter in Figure 4) counts the number of times a telephone protocol start request is received from the center, and like the second counter, it returns to 0 if it overflows beyond a predetermined number of digits. It has returned to normal and continues to accumulate again. In such a configuration, the receiving terminal device 12
When a pay program is selected in , the process until pay viewing information such as the code number of the pay program is written into RAM in the computer 8 is the same as in the conventional example. As shown in the timing chart of FIG. 4, when a telephone call command (PCC) of a telephone protocol start request command is sent from the center to the receiving terminal device 12 via the CATV line, the receiving terminal device 12 performs dialing to the center side via the telephone line. The center sends an ENQ when it receives it on the telephone line.
(Enquire) Signal receiving terminal device 1
2, and when the receiving terminal device 12 receives the ENQ signal, it sends the contents of each counter (first to third counter) in addition to the address of the receiving terminal device and paid viewing information to the center. . When the center receives this information, it issues an ACK1 signal (acknowledgment) and terminates communication over the telephone line. Thereafter, the center sends the previously received pay channel viewing counter and cumulative counter data (first counter and second counter) back to the receiving terminal device as an ACK2 signal on the CATV line. The receiving terminal device receives the count values of the first and second two counters sent through the telephone line and CATV.
If the contents of the ACK2 signals received via the line match, the paid viewing information on the RAM of the computer 8 is cleared and the first counter is also cleared. However, when receiving a NAK1 (Nagative Acknowlege) signal or a NAK2 signal, such as when the information data cannot be decoded, the paid viewing information will not be cleared. Further, the third counter is incremented by 1 every time a PCC signal is received. The contents of these 3-digit counters are composed of 1 byte each and are placed in RAM, which is backed up by the power supply. FIG. 5 shows the format of each instruction (command) on the telephone line. 2-stage SYN (synchronization) signal as ENQ signal
ENQ data is sent from the center to the receiving terminal device, and the receiving terminal device sends the SYN signal, STX (Start Text) signal, data length signal, terminal address signal, paid viewing information, cycle counter, and other data signals. A paid viewing counter, cumulative counter, and EXT (End Text) signal are sent to the center. Next, the second stage is sent as the ACK1 signal from the center.
A two-stage SYN signal and NAK signal are sent as the SYN signal and ACK data or NAK1 signal to the receiving terminal device, and then sent from the center via the CATV line.
Sends an ACK2 signal or NAK2 signal to the receiving terminal device. Here, the BCC (Binary Check Code) signal indicates a check value based on the exclusive logical value of each data, and is used to confirm whether each data is correct or incorrect. As is clear from the above explanation, even if the personal computer and modem send paid viewing information that is less than the paid viewing information actually viewed to the center, the center side will calculate the previous value of the second cumulative counter. Since the counter value and the current counter value are compared and judged whether they are the same or not, it is possible to easily determine whether there is fraud such as modification of the modem. In addition, even if the modem is modified to tamper with data using a personal computer and modem in the receiving terminal device, the counter values will not match when the counter values are compared after receiving the ACK2 signal. Viewing information is never cleared. In general, data communication protocols and formats by modems using telephone lines are standardized and have low frequencies, making it easy to commit fraudulent acts by tampering with data.
The format of the FSK signal is system specific;
Its data communication protocol and format are not publicly available, and the frequency is high, so
Modifications such as clearing paid viewing information to NAK2 signals are technically difficult. Even if the telephone line is disconnected, upstream data cannot be received for PCC signals, so the center can detect any abnormalities. Also, when you check the terminal, how many times does it appear?
Whether the terminal was actually receiving the PCC signal or whether it was in a state where it could not be returned as uplink data can be monitored from the third counter, the cycle counter.

【Effect of the invention】

As explained above, according to the communication method of the CATV system of the present invention, if the telephone line is modified, clearing of viewing information is substantially avoided, so it is possible to prevent eavesdropping. can.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the transmission/reception configuration of a conventional center, and Figure 2 is a block diagram showing the transmission/reception configuration of a conventional receiving terminal.
FIG. 3 is a block diagram showing the transmitting/receiving structure of a receiving terminal device according to an embodiment of the present invention, FIG. 4 is a time chart thereof, and FIG. 5 is a diagram showing its protocol and format. FIG. 1...Transmitter, 2...FSK modulator, 3, 8...
...Computer, 4, 9...Modem, 5...Converter, 6...Descrambler, 7...FSK demodulator, 8...Computer, 10...ROM, 1
1...Keyboard, 12...Receiving side terminal device, 1
3...TV set.

Claims (1)

[Scope of Claims] 1 CATV in which viewing information data of a CATV signal is stored in a receiving terminal device, and the viewing information data is transmitted to a center via a telephone line in response to a transmission command repeatedly sent from the center via a CATV line. In the communication method of the system, in addition to the viewing information data, the receiving terminal device further stores tuning frequency data and cumulative tuning frequency data of paid viewing channels between the two transmission commands. , when the receiving terminal device receives the transmission command, it transmits the viewing information data as well as the tuning number data and the accumulated tuning number data to the center via the telephone line, and the center transmits the data via the CATV line. Transmit the tuning frequency data and the cumulative tuning frequency data received together with the reception confirmation signal to the receiving terminal device, and transmit the tuning frequency data and the cumulative tuning frequency data received at the receiving terminal device and the stored selection data. A communication method for a CATV system, characterized in that the data on the number of stations selected and the accumulated data on the number of stations selected are compared, and the viewing information and the number of stations selected data are cleared only when both data match.