JPH02288459A - Facsimile broadcast transmission/reception system - Google Patents

Abstract

PURPOSE:To receive a correct picture automatically by calculating a key after correction from correction information and a key set to a receiver when an error is detected so as to use the key thereby describing a facsimile signal. CONSTITUTION:The receiver side is provided with a descramble means 10 using a key set in advance to a receiver to a facsimile signal of a received prescribed program and a correction key calculation means 13 calculating a key after correction with a key set to a receiver and correction information obtained by a correction information read means 9 when an error is detected by an error detection means 6. Then a facsimile signal is descrambled based on a key after correction calculated by the correction key calculation means 13. Even when a recipient inputs a key before revision in error and receives a charged program, descrambling is applied automatically with a key after the revision at the receiver side in a range for a period of a degree from the period of revision. Thus, the key is automatically corrected to receive a correct picture.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a facsimile broadcast transmission/reception system suitable for use in pay-based facsimile broadcasting in which facsimile signals are multiplexed and broadcast on broadcast radio waves.

(b) Conventional Technology Currently, teletext services are being provided in order to diversify and improve the sophistication of television broadcasting services.

Furthermore, the Telecommunications Technology Council deliberated on the practical use of facsimile broadcasting, which multiplexes facsimile images onto broadcast radio waves, for the purpose of supplementary services for television and text broadcasting, as well as special services. A report was made.

The contents of this facsimile broadcasting service are diverse, such as program guides related to television broadcast programs, texts, stock market conditions, news, tourist information, and specialized information for occupations. This facsimile broadcasting transmission method uses a method in which subcarriers obtained by modulating facsimile signals are frequency-division multiplexed onto audio signals, which are FM-modulated onto audio carrier waves and then transmitted.

An outline of this method will be explained below. That is, the center frequency of the subcarrier is 4,5t11 (70,804kHz
z, r++=TV horizontal synchronization pulse frequency), on which the facsimile signal is modulated by a 4-phase DPSK (4-phase differential phase keying) system. As shown in FIG. 2, a facsimile signal is composed of a frame in which a 16-bit frame synchronization signal is added to the beginning of a group of 32 packets each consisting of 288 bits per packet. As shown in FIG. 3, each packet consists of a mode control (MC) section consisting of 16 bits and a data packet section consisting of 272 bits. Here, the MC section is a header that identifies whether the data packet section is facsimile broadcasting or another service.

Further, the data packet section has a format including a 14-bit prefix, a 176-bit data section, and 82 error correction bits added thereto. This prefix is a signal that identifies whether the contents of the data bucket section are an image signal or a control signal.

The image signal is obtained by converting the original image signal to MH (Modified H
uffman) and M R (Modified READ
) The signal is encoded using a redundancy reduction encoding method, and then a control code such as a line synchronization code is added.

Now, it is expected that this facsimile broadcasting will be considered and the service will be put into practical use in the future as well as paid facsimile broadcasting.

Paid broadcasting is a broadcasting system in which receivers can receive specific broadcasting services by entering into a remuneration contract with a broadcaster. In this method, the image signal part is scrambled with a predetermined key and transmitted with confidentiality, and only subscribers to the broadcasting service descramble using a decoder with the same key as the transmitter. , a scrambling method that can restore images is common, and this method is also used, for example, in paid satellite broadcasting.

This scrambling method consists of a shift register array as shown in FIG.
There is a method of adding the output signal of an N (pseudorandom) signal generation circuit to the digital signal string of the image signal (mod 2 addition). The key to this scrambling is the generator polynomial and P
It is composed of a combination of initial values of shift registers used in the N signal generation circuit, etc. On the receiver side, in order to receive the image correctly, it must be decoded by a descrambling circuit (a circuit similar to the scrambling circuit shown in Figure 4 can be used) that has the same scramble key as the transmitter side. You need to enter this key information into the machine. The method of inputting this information is to use a PIN code notified to the subscriber in advance by the pay TV operator, and enter the key information (included in the PIN code) using a key provided on the receiver. There are two methods: a method of inputting the key information, and a method of inputting the key information by inserting a card issued as a membership card (on which key information is stored in advance) into the receiver.

It is effective to update these keys at regular intervals in order to improve security capabilities (resistance to unauthorized use by non-contractors, etc.).

Now, in order for the recipient to receive the desired pay program, the following steps may be taken.

As an example, a case where a membership card is used will be explained.

The recipient presses the pay program reservation key on the receiver and then inserts the membership card. The receiver reads the key information stored on the inserted card and stores it.

Next, the receiver inputs the number of the program, the TV channel number on which the program is multiplexed, and the time slot in which the program will be broadcast into the receiver using key operations, and then presses the reservation confirmation key to confirm the program. A reservation is made.

At the specified time, the receiver sets the tuner to the specified channel, receives the facsimile signal, extracts the program number contained in it, and checks whether it matches the predetermined reserved program number. compare. If the numbers match, a descrambling circuit is set to the stored key, the image signal of the received facsimile signal is descrambled, and further MH and MR decoding processing is performed to restore the image. .

Now, as mentioned above, in order to increase security, it is desirable to update the key at certain intervals, but in this case, the following points need to be considered.

On the recipient side, it may not be possible to input the updated key exactly in synchronization at the time of key update switching.

For example, if the recipient forgets that the key has been updated and enters the old PIN code, uses the old card to make a program reservation, or if the recipient forgets that the key has been updated, This can happen if the issued card for some reason does not reach the recipient by the time of renewal.

Therefore, due to the above-mentioned situation, the receiver cannot properly descramble the image because he or she cannot input the updated key, making it impossible to receive the image of the desired pay program.

(c) Problems to be Solved by the Invention In view of the above points, the present invention provides that, for a certain period of time after the key is updated, even if the old key is input, the receiver side automatically uses the updated key. The purpose of the present invention is to provide a system that can perform descrambling based on the above information and correctly receive paid broadcast images.

(d) Means for solving the problem In the present invention, the sending side scrambles the facsimile image signal and broadcasts it, and the receiving side descrambles it using the same scrambling key as the sending side, so that the image is restored. In a facsimile broadcasting transmission/reception system that can transmit and receive facsimile broadcasts, when the sending side updates the scrambling key and sends out a facsimile signal, the sending side uses correction information that allows the updated key to be calculated by a predetermined calculation from the pre-updated key information to the facsimile signal. The receiving side includes a means for adding correction information to be broadcast in addition to the received facsimile signal of a predetermined program, and a means for descrambling the received facsimile signal of a predetermined program using a key set in advance in the receiver, and a means for descrambling the image restored by the means. an error detection means for detecting an error; a correction information reading means for reading the correction information sent from the transmission side; and correction information obtained from the correction information reading means when an error is detected by the error detection means and the receiving unit. The present invention is characterized by comprising a correction key calculation means for calculating a corrected key based on a key set in the machine, and a means for descrambling a facsimile signal based on the corrected key calculated by the correction key calculation means. It is something to do.

(E) Effect According to the above means, even if the receiver enters the key before the update by mistake or for some reason and receives the paid program, within a certain period of time from the time of update, Descrambling can be performed automatically on the receiver side using the updated key.

(f) Example Examples of the present invention will be described below.

On the transmitting side, when transmitting a pay broadcast program as described above,
The apparatus includes a means for adding and transmitting correction information that can determine the updated key from the previous key.

For example, when using scrambling using a PN signal generation circuit composed of a shift register array as described above, the generator polynomial and initial setting value can be configured as key parameters, and the generator polynomial can be used as the key before updating. GO(X), the initial setting value is A6(X), and the next updated values are G+ (x) and A+ (x) respectively, then the correction information is ΔG (x)=G+ (x)■G, (x)ΔA (x)
=A+ (x)■A, (x) is transmitted only for a certain period of time from the time of update. This period varies depending on the operation of the broadcasting station and the guarantee of security for the key, but in practical terms, it is sufficient to send the message for several days.

As an example of the transmission method, there may be a method of transmitting the program selection signal using the blank part of the code assignment of the control signal.

Next, an embodiment on the receiving side will be described based on FIG.

(1) is a tuner which receives broadcast waves of a set channel, demodulates and outputs a composite signal with audio multiplexed with a facsimile signal. (2) is a demodulator that extracts the modulated signal of the facsimile signal from the composite signal, performs four-phase DPSK demodulation, and outputs a digital signal sequence.

(3) is a packet generation unit that performs frame synchronization and frame decomposition on the demodulated signal and generates a mode control (MC) part packet and a data packet, and the MC part packet is subjected to BCH correction in the MC identification part (4). After, M
The contents of C are identified, and if MC has a value corresponding to paid facsimile broadcasting, the data packet section corresponding to this MC is made valid and processing from the signal separation section (5) onward is performed.

The signal separation unit (5) separates the paid facsimile broadcast signal (
This is a circuit that separates and controls the image signal and control signal after error correction of the shortened difference set cyclic code for the data packet section).

(6) is a program number comparison unit which extracts a program number from the control signal extracted from the signal separation unit (5), and from this and a reservation table previously stored in the program reservation storage unit (7) as a program reservation. It is compared to see if it matches the designated paid program number, and if they match, a match flag is input to the control unit (8). Further, (9) is a correction information reading section, which is a circuit that reads the correction information of the scramble key from the control signal from the signal separation section.

In this example, the program reservation is the program number, channel number,
This can be done by manually entering a password including the time zone and key information, and this information is stored in the storage section (7).

Now, when the program number matching flag is input from the program number comparison section (6), the control section (8) refers to the program reservation storage section (7) and sets the descrambling circuit (10) to the key keyed in by the reservation. setting, the image signal (scrambled) output from the signal separation unit (5) is descrambled, and then the image reception processing unit (11) performs MH, M
R is decoded to obtain an image signal, which is sent to the printer (12)
and print the image.

Here, the image reception processing unit (11) counts the number of pixels of each line from the decoded image signal, and calculates the number of pixels of each line based on a predetermined value (for example, A
1728 pixels on 4 screens), and if they do not match, it is determined that there is a line error, and this flag is sent to the control unit (
8). Normally, if the entered key is incorrect, a line error will occur from the top of the screen. Therefore, the control unit (8) anticipates the possibility of a line error occurring due to noise intrusion into the receiver, and if there is an error in the first few lines of the screen, it determines that it is a key input error, and the correction key calculation unit (13 ) to perform descrambling based on the corrected key,
Image reception processing and print output operations are then performed.

The correction by the correction key calculation unit (13) may be obtained by the following calculation.

Let G' (x) and A' (x) be the corrected keys, then G
'(x)=G1. (x)■ΔG(x)A' (x)-
A1. (x)■ΔA (x) where G+-(x),
A+-(x) is the input key and the above G6(x), Ao
Equal to (X).

Further, ΔG(x) and ΔA(x) are the transmitted correction information.

Therefore, if the key information before the update has been input, the corrected key can be obtained as the key after the update.

With the above circuit, if there is an error in the first few lines of the image signal after Tescrumple on the receiver side, the key is automatically corrected and reception is performed using the corrected key. conduct.

Now, since the resolution of a facsimile broadcast screen is 7.7 lines/line, the screen with the error only needs to be about 1mm from the top until a line error is detected and received with the correct key, which is considered to be sufficient for practical purposes. .

It should be noted that the present invention is not limited to the above-described embodiment, and for example, the circuit elements shown in FIG. 1 may be realized by computer software. Furthermore, the scrambling method, key information, and key correction information can also be changed in various ways.

(g) Effects According to the present invention, even if the receiver mistakenly enters the old key after updating the key or for some reason, the receiver side automatically inputs the key for a certain period of time from the time of update. It is possible to correct the key and receive the correct image. Therefore, the present invention is suitable for a paid system of facsimile broadcasting.

[Brief explanation of drawings]

Fig. 1 is a diagram of the receiving side circuit configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the frame structure of a facsimile signal in facsimile broadcasting, Fig. 3 is an explanatory diagram of the packet structure of a facsimile J signal, and Fig. 4 is a scrambled FIG. 3 is a diagram showing the configuration of a circuit. (9)... Correction information reading unit, (10)... Scrambling unit, (13)... Correction key calculation unit, (11)
...Image reception processing section

Claims (1)

[Claims] (1) In a facsimile broadcast transmission/reception system in which the transmitting side scrambles and broadcasts the facsimile image signal, and the receiving side descrambles it using the same scrambling key as the transmitting side to restore the image, the transmitting side: When the scramble key is updated and the facsimile signal is sent, correction information adding means adds and broadcasts correction information that allows the updated key to be calculated by a predetermined calculation from the key information before the update to the facsimile signal. On the receiving side, descrambling means for the received facsimile signal of a predetermined program using a key set in advance in the receiver, error detecting means for detecting errors in the image restored by the means, and on the transmitting side. and a correction information reading means for reading the correction information sent from the receiver, and when an error is detected by the error detection means, the correction information obtained from the correction information reading means and a key set in the receiver are used to read the corrected information. A facsimile broadcast transmission/reception system comprising a correction key calculation means for calculating a key, and a means for descrambling a facsimile signal based on the corrected key calculated by the correction key calculation means.