JPH056839B2 - - Google Patents

Description

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

The present invention relates to a two-way communication method for a CATV system that realizes upstream data transmission from a terminal to a center using a telephone line.

[Conventional technology]

As this type of bidirectional communication system, the configuration shown in FIGS. 1 and 2 has been used. 1st
The figure shows the configuration of the CATV center side, where a number of TV transmitters 1 corresponding to the number of transmission channels are prepared, and their outputs are combined by a combiner,
It is sent to the CATV main line. At this time, the downlink data signal is combined with the TV signal and transmitted from the FSK transmitter 2. Further, the uplink data signal is received by the center telephone modem 4 via the telephone line and analyzed by the center computer 3. This computer 3
specifies the address of each terminal and passes a downlink data signal for polling to the FSK transmitter 2. Figure 2 shows the configuration of the CATV terminal side.
The TV signal branched from the main line is sent to the terminal 12, tuned by the converter 5 within the terminal 12, and the scrambled video signal is returned to a normal video signal by the descrambler 6 and sent to the TV set 13. be done. On the other hand, the downlink data signal combined with the TV signal is demodulated by the FSK receiver 7 and input to the microcomputer 8. The microcomputer 8 gives a control signal to the converter 5 and the descrambler 6 based on the program data written in the ROM 10. At this time, the judgment of channel permission/prohibition is made by operating the channel selection key 11. This is done by comparing the signal with the one given. Also, when polled by the downlink data signal, the computer 8
The viewing information stored on the RAM is read out as an uplink data signal and sent to the telephone line via the telephone modem 9. Once the data transmission is complete, the RAM is cleared by a command signal from the center.

[Technical issues]

The problem with this method is that when the output signal from the computer 8 to the telephone modem 9 is decoded on the terminal side, the data may be modified during this time, and data collection for normal toll collection may no longer be possible. It is a certain thing.

[Purpose of the invention]

The present invention was made based on the above-mentioned circumstances, and it performs calculations on upstream data signals sent from a terminal via a telephone modem and encrypts them, prevents data analysis, and thereby ensures normal billing. The purpose of this project is to provide a two-way communication method for CATV systems.

[Structure of the invention]

For this purpose, the present invention provides a two-way communication method for a CATV system that uses downlink data transmission from a center side to a terminal and uplink data transmission from the terminal to the center side, the method comprising polling by the downlink data transmission. When sending an upstream data signal from the terminal to the center side by the upstream data transmission,
One of the downlink data signals resulting from the downlink data transmission includes an operation code and is sent to the terminal, and the uplink data signal is sent from the terminal to the center side as a data signal calculated using the operation code. It is something.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to FIGS. 3 and 4. Here, since the configuration in FIG. 1 and the main configuration in FIG. 2 are the same, the same parts are given the same reference numerals and the explanation will be omitted. In the present invention shown in FIG. 3, an arithmetic circuit 14 is connected to a computer 8. However, after selecting a pay program or the like and selecting a channel by operating the key 11, pay viewing information is stored in the RAM, which is exactly the same as in the conventional system. And with polling from the center side,
When an uplink data request command and an operation code (for example, "0101") are sent from the center as a downlink data signal to the address of the terminal, the computer 8 analyzes this, reads out the information from the RAM, and uses it as a downlink data signal. The provided operation code is operated through the operation circuit 14, and the upstream data signal is scrambled. For example, as shown in Figure 4, if the charge is $23, it is recorded in RAM at $0.5*, so it becomes 46 units, which is binarized and expressed as "00101110". However, for example, add a fixed code "0111" using the last four digits of the address code assigned to each terminal in advance to make "001011100111", and then repeat the operation code "1010" three times. as “101010101010”,
An EXOR logical operation is performed with the above "001011100111" to obtain data "100001001101" as a result. However, the CATV center remembers the arithmetic code sent to the terminal at this time, and uses this to rewrite "100001001101" with "101010101010", which is three times the arithmetic code "1010".
Take the EXOR and make it "001011100111", analyze the lower 4 bits of this to see that it is the fixed code "0111", confirm that it is the correct data from the terminal, and then extract "46" from the upper 8 bits. Read the unit and the charge for that terminal will be “$23”
This is what we read. Since this operation code changes each time polling is performed, falsification of upstream data is easily discovered when the center analyzes the upstream data, making it virtually impossible. In this embodiment, simple logical operations such as EXOR are performed, but other complex scrambling operations may be applied to the upstream data signal.

【Effect of the invention】

Since the present invention is as detailed above,
Put the operation code in the FSK data and send it to the terminal,
Since the upstream data signal is scrambled using this, it becomes difficult to tamper with the upstream data at the terminal, and the effect is that the regular billing system can be maintained.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the center side of the conventional system.
FIG. 2 is a block diagram of the terminal side, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing logical operations on data. 1...TV transmitter, 2...FSK transmitter, 3...
Computer, 4...Telephone modem, 5...Converter, 6...Descrambler, 7...FSK receiver, 8...Microcomputer, 9...Telephone modem, 10...ROM, 11...Key, 12... …
CATV terminal, 13...TV set, 14...arithmetic circuit.

Claims (1)

[Claims] 1. Downlink data transmission from the center side to the terminal,
A two-way communication method for a CATV system that uses uplink data transmission from the terminal to the center side, wherein the uplink data signal is transmitted from the terminal to the center side by the uplink data transmission in response to polling by the downlink data transmission. When sending to
One of the downlink data signals resulting from the downlink data transmission includes an operation code and is sent to the terminal, and the uplink data signal is sent from the terminal to the center side as a data signal calculated using the operation code. Two-way communication method for CATV systems.