JPH0193220A - Videotex transmission system - Google Patents

Abstract

PURPOSE:To transmit a large amount of videotex information simultaneously at a low rate by transmitting the videotex information via a communication satellite. CONSTITUTION:A videotex terminal 3 is provided at a slave station 1, and a data retrieval request by a user is issued from the terminal, and a videotex retrieval signal to select an image, a graphic, and a character, etc., is generated. The videotex retrieval signal is supplied to a packet encoder and decoder 4, and is converted to synchronized packet data suitable for satellite communication. Transmission information of 14GHz emitted to the communication satellite from the slave station 1 is converted to a prescribed frequency, for example, a transmission frequency of 12GHz, by the communication satellite, and received by a parabolic antenna 14. Decoded data is supplied to a demultiplexer 20, and the data related to the videotex retrieval signal is supplied to a packet encoder and decoder 21, then, it is recovered to the videotex retrieval signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a videotex transmission system capable of transmitting videotex information via a communication satellite.

[Summary of the invention]

In a videotex transmission system having a master station and at least one slave station, the master station selects corresponding videotex data in response to a videotex search signal from the slave station, and transmits this videotex data through satellite communication. This packet data is converted into packet data that has been passed through , an error correction code is added to this packet data, it is PSK modulated and transmitted to the slave station via V&Hoshi, and the slave station demodulates the received signal in PSK and performs error correction. By doing so, and restoring the data to the original videotex data, it is possible to transmit a large amount of videotex information at once at a low cost.

[Conventional technology]

As a system for transmitting videotex data consisting of digital signals encoded with 9 images, 9 figures, 9 characters, etc.
In our country, we have a captain system.

The Napurpus system is known in North America, and the Sept system is known in Europe. In these systems, it is common to transmit videotex data using a wired line such as a telephone network or a dedicated line.

[Problem that the invention seeks to solve]

However, as described above, the method of transmitting videotex data using a wired line has the disadvantage that the fee is high because the fee is calculated based on the time.

In addition, when transmitting videotex data using a wired line, the amount of information is, for example, 4800 bits at most on a telephone network.
Less than ps, more t! ! It is difficult to transmit the amount of information at once.

The present invention has been made in view of the above, and provides a videotex transmission system that can transmit a large amount of information at once at low cost.

[Means to solve problems]

This invention comprises a master station (2) and at least one slave station (1).
In the videotex transmission system with
9) L, add error correction code to this packet data (2
4) L, PSK modulated 11 (25) and transmitted to the slave station via the satellite, PSK demodulates the received signal on the slave station side (30)
L. It is configured to perform error correction (31) and restore the data to the original videotex data (4).

[Effect]

In the master station (2), corresponding videotex data is selected at the videotex center (20) in response to the videotex search signal from the slave station (1). This selected videotex data is transferred to the packet encoder/decoder (19).
converts the asynchronous videotex data into synchronized packet data, adds an error correction code to it in the error correction code addition circuit (24), and uses the data to pass through the PSK modulator. In (25), the carrier wave is PSK modulated and transmitted to the slave station via the satellite. On the slave station side, the PSK demodulator (30) converts the received signal into PSK.
The data is demodulated and subjected to error correction by an error correction circuit (31), and then the packet encoder/decoder (4) restores the original videotex data, that is, asynchronous videotex data. This allows a large amount of information to be transmitted at once at low cost.

(Example) Hereinafter, an example of the present invention will be described in detail based on FIGS. 1 and 2.

FIG. 1 shows the circuit configuration of this embodiment, in which (1) is a slave station and (2) is a master station. There may be a plurality of slave stations (1).

First, the relationship between the slave station (11) and the master station (2) will be briefly explained.
When a videotex search request is made by a user at a slave station (11), the video search signal is transmitted to the master station (2) by amplification (slave station - master station), and the master station (2) transmits the videotex search signal to the videotex search signal. The corresponding videotex data is selected, and the selected videotex data as a search result is transferred to the slave station (1
), and the user can view the search result screen on the terminal of the slave station (1).

Next, the details will be explained with reference to FIG.

The slave station (1) is provided with a videotex terminal (3), where a data search request is made by the user and a videotex search signal for selecting nine characters of one image, etc. is generated. This videotex search signal is a digital signal and is asynchronous. This videotex search signal is supplied to a packet encoder/decoder (4), where it is converted into synchronized packet data suitable for satellite communication as shown in FIG. 2. In FIG. 2, the flag sequence is for bit or byte synchronization, the address is for station identification, the control field is for specifying the type of data, and the frame check sequence is for error detection.

Then, data related to the videotex search signal is inserted at the data location. The packet data is fed to a multiplexer (5).

(6) is a telephone set, and the audio signal from this telephone set (6) is transmitted through a telephone codec (Coder & Decod).
er) T? ) is A/D converted and sent to multiplexer (5
), multiplexed with packet data, and serialized.

Note that the audio signal from the telephone (6) is for communication between the slave station (1) and the master station (2), and is therefore generated as necessary. Further, the multiplexer (3) adds necessary control data such as a synchronization signal and an error correction code. The amount of information obtained at the output side of the multiplexer (5) is, for example, 64 bps, of which 32 Kbps is the telephone voice signal, 16 X bps is the packet data, and 8 X bps
are occupied by control data, and the remaining 8 bps are reserved.

The data serialized by the multiplexer (5) is supplied to the convolutional encoder (8), where it is convolutionally encoded for error correction. It shall be determined based on the balance between The convolutionally encoded data is P
The data is supplied to an SK modulator (9), and a carrier wave of a predetermined frequency, for example, 140/2, is PSK-modulated using the data. The output signal of the PSK modulator (9) is supplied to an upconverter (1O), and is upconverted to match the frequency of a repeater of a communication satellite (not shown) used here, for example, 14 GHz.

The upconverted signal is passed through a high power amplifier (High
The power is supplied to a power amplifier (11), amplified, and passed through a branching filter (12) to a parabolic antenna with a small diameter, for example, about 1.2 to 168 m.
) from which it is transmitted to a communications satellite.

(14) is a medium diameter installed in the master station (for example, about 3 to 5
As mentioned above, the 14 GHz transmission information emitted from the slave station (1) toward the communication satellite is converted to a predetermined frequency, for example, 12 GHz, by the communication satellite, and then sent to the parabolic antenna (14). received by. Information from the parabolic antenna (12) is sent to the low-91 tone intensifier (S.-Noise) via the duplexer (15).
Amplifier ) (16) for amplification. Low noise tank @! The output signal of (16) is supplied to a down converter (17), where it is set to a predetermined frequency, for example, 1
Down converted to 40M1lz. The output signal from the down converter (17) is PSK converter eI4'a (1
8), where it is modulated by psK11 and the data is demodulated.

The PSK demodulated data is supplied to the Viterbi decoder 8 (19), and error correction is performed by Viterbi decoding.

In other words, the convolutional code is trained and decoded using Torito's algorithm. The decoded data is fed to a demultiplexer (20) where the data associated with the videotex search signal and the telephone voice signal are separated. Data related to the videotex search signal is fed to a packet encoder-decoder (21) where it is restored to an asynchronous videotex search signal. This restored videotex search signal is supplied to the videotex center (22), and the videotex center (2o) selects and retrieves videotex data such as the corresponding image 1 figure 2 characters from the database according to the videotex search signal. .

Further, the telephone audio signal from the demultiplexer (20) is D/A converted by the telephone codec (23), and is supplied as an analog signal to the terminal (24). The message is transmitted to the master station (2).

The asynchronous videotex data taken out from the videotex center (22) is supplied to the packet encoder/decoder (21), where it is converted into synchronized packet data as shown in Fig. 1182, which is passed through satellite communication. . In this case, videotex data is inserted in place of the data in the packet data format shown in FIG. The packet data is fed to a multiplexer (25).

Further, if necessary, the audio signal from the telephone (24) is A/D converted by the telephone codec (23) and supplied to the multiplexer (25), where it is multiplexed with packet data and serialized.

The serialized data is supplied to an error correction code adding circuit (26), where an error correction code is added. On the output side of this error correction code adding circuit (26), an amount of information corresponding to the number of slave stations, for example, 24 Kbps is obtained. Of course, the amount of information for one slave station is 64 Kbps. The data to which the error correction code has been added in this way is PSK changed tl [
(27), and the data is supplied to a predetermined frequency, for example, 1
A 40 MHz carrier wave is psK modulated. PSK modulator (
The output signal of 27) is supplied to an upconverter (28), where it is upconverted to match the frequency of a repeater of a communication satellite (not shown) used here, for example, 14 GHz. The upconverted signal is passed through a high power amplifier (29
), where it is amplified, supplied to a parabolic amplifier (14) via a duplexer (15), and transmitted from there to a communication satellite.

When the videotex data etc. transmitted as described above are received by the parabolic antenna (13) of the slave station via the communication satellite, the information such as the videotex data is transmitted through the duplexer (12). The output signal of the low noise amplifier (30) is supplied to a down converter (31), where it is supplied to a low noise amplifier (30) and amplified.
The signal is down-converted to a predetermined frequency, for example, 140 Ml1z, in accordance with the center frequency of the demodulator (32). The output signal from the down converter (31) is sent to the PSK converter (32).
), where it is subjected to PSK'tji modulation and the data is demodulated. The PSK demodulated data is sent to an error correction circuit (
33), and performs error correction based on the error correction code.

The error-corrected videotex data is divided by the demultiplexer (34) and supplied to the packet encoder/decoder (4), where it is restored to the original asynchronous videotex data and supplied to the videotex terminal (3). and is displayed on its display (not shown), thereby allowing the user to view a screen related to videotex data corresponding to the designated videotex search signal.

In addition, the audio tri signal from the demultiplexer (34) is D/A converted by the telephone codec (7) and then
), thereby transmitting the communication from the master station (2) to the slave station (1).

As described above, in this embodiment, by using a communication satellite, it is possible to greatly increase the amount of information transmitted at one time to, for example, 64 Kbps. This is particularly advantageous for large users, as they will be purchasing one of the multiple relay stations in their network on an annual contract.

〔Effect of the invention〕

As described above, according to the present invention, since the videotex information is transmitted via a communication satellite, a large amount of videotex information can be transmitted at once at a low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a packet data format used in the present invention. (11 is a slave station, (2) is a master station, (3) is a Videotex terminal, (41, (21) is a packet encoder,
decoder, (26) is an error correction code circuit, (27) is p
sK modulator, (14) and (13) are parabolic antennas, (32) is a PSK demodulator, and (33) is an error correction circuit.

Claims (1)

[Claims] In a videotex transmission system having a master station and at least one slave station, the master station selects corresponding videotex data in response to a videotex search signal from the slave station, The data is converted into packet data suitable for satellite communication, an error correction code is added to the packet data, PSK modulated, and transmitted to the above slave station via the satellite.The slave station demodulates the received signal in PSK. , a videotex transmission system characterized by performing error correction and restoring the data to the original videotex data.