JPS62254529A - Data transmission system in satellite system - Google Patents

Abstract

PURPOSE:To allow a user station to receive a raw picture data acquired by a satellite together with a data subject to picture processing by a round station simply by allowing a satellite to reduce the data rate of a series of digitized picture data observed and acquired, to apply spread spectrum and send the result and allowing the ground station to add an error correction code to the picture data subject to picture processing and to send the result. CONSTITUTION:The system consists of a satellite A provided with an observation function and a signal relay function, a ground station B and a user station C receiving the distribution of a picture data through a satellite line. The ground station B is provided with a demodulation/reception means 17, a picture processing means 18, a correction code addition means 20 and a transmission means, and the satellite A is provided with a reduction means 1, a spread spectrum processing means 2, a synthesis means 6 and a transmission means. Thus, the raw picture data and the picture data after picture processing are sent simultaneously by frequency division. Then the reception gain of the user station C is improved by the coding gain to a picture data subject to primary picture processing at the ground station B and the reception antenna is miniaturized by the share.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a data transmission system in a satellite system such as a meteorological satellite system.

(Prior Art) As is well known, a meteorological satellite system consists of a satellite equipped with a weather observation function and a signal relay function, and a ground system that receives observation image data from the satellite, performs image processing on it, and transmits it to the satellite. It consists of a station and a satellite image user (user station) that receives the image-processed data via a satellite.

A conventional data transmission system in this type of satellite system is configured as shown in FIG. 3, for example.

In FIG. 3, A is a satellite, B is a ground station, C is a user station, 3 is a low noise amplifier, 4 is a down converter, 5 is a band pass filter, 7 is an up converter, 8 is a power amplifier, 9 is a guiplexer, 10 is an antenna, 11 is a ground station antenna, 12 is a guiplexer, 13 is a low noise amplifier,
14 is a down converter, 15 is a band pass filter, 1
7 is a demodulator, 18 is an image processing device, 19 is a storage device, 2
1 is an up converter, 22 is a power amplifier, 23 is a user station antenna, 24 is a low noise amplifier, 25 is a down converter, 26 is a band pass filter, 28 is a demodulator, 2
9 is an image processing device, 30 is a display device, 32, 33.34
35 is a transmission output reduction circuit, 36 is a PN code generator, 37 is a QPSK modulator, and 38 is a modulator.

In the above configuration, in the conventional data transmission method, satellite A first transmits raw image data observed and acquired to ground station B, and then ground station B transmits image-processed data to user station C via satellite A. It is set to send.

That is, first, on satellite A, a series of raw image data (data rate is, for example, 14 Mbps) acquired by a camera within a certain observation time and digitized is sent to P by the switch 33.
This is alternately switched with a random signal from an N code generator 36, which is quadrature phase modulated by a QPSK modulator 37, frequency converted to a carrier frequency by an up converter 7 via a switch 34, and then power amplified by a power amplifier 8. switch 3 that bypasses the transmission output reduction circuit 35
The signal is input to the guiplexer 9 via the direct connection route of the receiver 32, and is transmitted from the antenna 10.

As shown in Figure 4 (A), this transmitted radio wave consists of raw image data (a) and random signals (b) arranged alternately on the time axis, and the spectra of both signals at this time are as follows:
The frequency band is considerably wide centered around the frequency f1.

Next, at the ground station B, the received signal received by the antenna 11 is demodulated into image data by the demodulator 17 via the guiplexer 12, the low noise amplifier 13° down converter 14, and the band pass filter 15, and the image data is demodulated by the image processing device 18. All of the image data that has been subjected to image processing is temporarily stored in the storage device 19.

The image data from the storage device 19 is subjected to angular modulation by a modulator 38, then frequency-converted to a carrier frequency by an up-converter 21, and then transmitted from the antenna 11 via a power amplifier 22 and a guiplexer 12. As shown in FIG. 4(B), this transmitted radio wave consists of an FM-AM wave or an FM-FM wave, and its spectrum is centered around the frequency f2 near the frequency f1, and the band is IMH.
z or less. In other words, as is clear from Fig. 4 (A) and (B), the transmission frequency f of the raw image data (A)
, and the transmission frequency f2 of the image data after image processing are close to each other, so both cannot be transmitted from the satellite at the same timing, and ground station B processes the image after receiving all the raw image data (A). It is transmitting image data.

The transmission signal from ground station B is transmitted from antenna 10 on satellite A.
, the guiplexer 9, the low-noise amplifier 3, the down converter 4, the bandpass filter 5, the switch 32, the transmission output reduction circuit 35, the switch 32, the guiplexer 9, and the antenna 10, and are looped back and transmitted to the user station C.

Note that the transmission power reduction circuit 35 is for suppressing the transmission power flux density of the satellite A to a specified value or less.

At user station C, the received signal received by antenna 23 is demodulated by demodulator 28 via low-noise amplifier 24, down converter 25, and band-pass filter 26, subjected to image processing by image processing device 29, and displayed as an image by display device 30. Information will be available.

(Problem to be solved by the invention) However, in the conventional data transmission method described above, a series of image data acquired by a satellite camera is first transmitted to a ground station, the image is processed by the ground station, and then the ground station Since image data is distributed to user stations via satellites, there are various problems as follows.

First of all, if the image data acquired by the satellite camera is acquired 8 times a day, for example,
It takes about 4 hours a day for data transmission, and during this time users of image data cannot receive image-processed data distributed via satellite, that is, it lacks immediacy.

In addition, in order for a user to process the raw image data acquired by a satellite camera by themselves, it is necessary to receive the raw image data directly, but a series of raw image data acquired by a satellite camera is a high-speed data Since the data rate (for example, 14 Mbps) is wide, the bandwidth is wide, and a large antenna is required to receive the data. This imposes a large economic burden on the user and is difficult to implement.

Furthermore, although it is desirable for users to be able to distribute image data at low cost, the upper limit of transmission power from satellites is limited in order to satisfy the power flux density regulations of the Radio Law (therefore, (a transmission output reduction circuit is required), the user's antenna cannot be made smaller beyond a certain level, which places a heavy burden on the user.

Finally, in the case of image data users such as ships, antennas cannot be made smaller, and ships are subject to rocking, so an advanced tracking mechanism is required to obtain image data from satellites. .

The present invention was made in view of these conventional problems, and its purpose is to provide data transmission in a satellite system in which raw image data acquired by a satellite can be easily received at a user station along with data processed by a ground station. The goal is to provide a method.

(Means for Solving the Problems) In order to achieve the above object, the data transmission system in the satellite system of the present invention has the following configuration. That is, the data transmission method in a satellite system of the present invention is applicable to a satellite system comprising a satellite having an observation function and a signal relay function, a ground station, and a user station that receives image data via a satellite line. ; The ground station includes a receiving unit that receives and demodulates a spread spectrum signal of image data that the satellite continuously transmits; an image processing unit that performs image processing on the received and demodulated image data; and image-processed data. a correction code addition means for adding an error correction code to the image; and a transmission means for transmitting the output of the correction code addition means to the satellite; a data rate reduction means for reducing the data rate of;
Spread spectrum processing means for performing spread spectrum processing on image data with reduced data rate to form the spread spectrum signal; Combining means for combining the formed spread spectrum signal and the transmission signal from the ground station; A transmitting means for transmitting the output of the means to the ground station and the user station.

(Function) Next, the function of the data transmission method in the satellite system of the present invention having the above configuration will be explained.

First, in the satellite, the data rate reduction means reduces the data rate of a series of image data that has been observed and digitized, and the spread spectrum processing means performs spectrum spread processing on the image data whose data rate has been reduced to spread the spectrum. A signal is formed and the spread spectrum signal is transmitted continuously to the earth station and the user station by the transmitting means via the combining means.

On the other hand, at the ground station, the receiving means receives and demodulates the spread spectrum signal of the image data continuously transmitted by the satellite, and the image processing means performs image processing on the received and demodulated image data, and adds a correction code. The means adds an error correction code to the image-processed data, and the transmitting means transmits the image data with the error-correction code after the image processing to the satellite.

The image data transmitted from the ground station is combined with the continuously transmitted spread spectrum signal by a combining means in the satellite, and then transmitted back.

In other words, the satellite simultaneously transmits raw image data obtained through observation and image data after image processing, and the user station receives both at the same time.

Here, since the image data after image processing has an error correction code added, when this signal is received at the user station, if the carrier frequency of the spread spectrum raw image data signal is different from the carrier frequency of the raw image data signal by several MH2llll, the image data will be processed. Image data after processing (-next image processing) can be separated and received at a predetermined bit error rate.

Therefore, according to the data transmission method of the present invention, raw image data and image data after image processing can be transmitted simultaneously by frequency division. In the user station, the reception gain is improved by the encoding gain of the image data that has been subjected to the primary image processing at the ground station, and the reception antenna can be made smaller accordingly.

Furthermore, since the raw image data has a reduced data rate, it is possible to receive the raw image data with a small antenna without increasing the size of the antenna, making it easier to use the image data.

Next, since the image-processed data is distributed together with the raw image data, the time required for distributing the image-processed data increases by at least 4 hours per day compared to the conventional method. Furthermore, for users of image data such as ships, the antenna can be made smaller (about half of the conventional size), so the tracking mechanism can be simplified. In addition, since spread-spectrum image data is emitted from the satellite, the power flux density radiated from the satellite to the earth's surface can sufficiently meet the specified values of the Radio Law, and a transmission output reduction circuit is installed inside the satellite. This eliminates the need for satellites, making the satellite smaller, lighter, and more reliable.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1st
The figure is a configuration block diagram of a data transmission system according to an embodiment of the present invention. Note that the same components as those shown in FIG. 3 are denoted by the same reference numerals, and their explanations will be omitted.

In FIG. 1, first, on satellite A, a data rate reduction device 1 is provided in place of the conventional PN code generator 36 and switch 33, and a spread spectrum transmitter 2 is provided in place of the conventional QPSK modulator 37. Furthermore, a composition device 6 is provided in place of the conventional switch 34, and the conventional switch 32, switch 32, and transmission output reduction circuit 35 are omitted.

The input form of digitized raw image data input to the data rate reduction device 1 is the same as the conventional one. That is,
For example, in a meteorological satellite, the rotation period is, for example, 600 m5, and the meteorological observation time is, for example, 30 m5, and raw image data obtained by observation and digitized during this period is input to the data rate reduction device 1 for each rotation period. The data rate reduction device 1 outputs the image data acquired within this period of 30 m5 to the spread spectrum transmitting device 2 over a period of, for example, 600 m5. That is, the data rate reduction device F1
So, in the above example, the data rate of the input data is reduced to 1/20, so if the data rate of the input data is 14 Mbps, the output data is 0.7 Mbps.
becomes. The following can be understood from the functions of this data rate reduction device 1.

In other words, in a conventional satellite, within the rotation period of 600 m5, 3
The problem of power flux density was solved by transmitting image data for a period of 0 m5 and transmitting a random signal related to the PN code for the remaining period of 570 m5 (see Fig. 3). The satellite of the present invention continuously transmits image data over the entire rotation period of 600 m5. At this time, it was decided that the transmission signal would be subjected to spectrum spread processing by the spread spectrum transmitter 2 to deal with the problem of power flux density.

The composite bag 'I16 is the output of the spread spectrum transmitter 2 (
(spread spectrum signal) and the transmission signal from ground station B. Furthermore, at the ground station B, a spread spectrum receiving device 16 is provided between the bandpass filter 15 and the demodulator 17, an error correction encoder 20 is provided in place of the modulator 38, and an error correction code is transmitted from the image processing device 18. The image-processed data is directly output to the device 20.

The spread spectrum receiver 16 receives the spread spectrum signal of the image data continuously transmitted by the satellite A, reproduces a signal with a reduced data rate, and outputs it to the demodulator 17. The image data will be demodulated. Therefore, the spread spectrum receiving device 16 and the demodulator 17 collectively constitute a receiving means.

The error correction encoder 20 encodes the image-processed data using, for example, a convolutional code with a constraint length of 7 and a coding rate of 1/2. In other words, since the conventional modulator 38 uses an analog modulation method, the power flux density of the transmitted signal becomes large, so the transmission output reduction circuit 35 is required in the satellite. However, in the present invention, an error correction code is added to the transmitted signal, and the data rate thereof is 0.7 Mbps or more due to the data rate reduction bag M1 of satellite A, so the power flux density is reduced due to the spread spectrum effect.

Therefore, a transmission output reduction circuit is not required in satellite A.

The primary image data processed by ground station B is directly input to the error correction encoder 20 via the storage device 19, and the image data to which the error correction code has been added is input to the synthesizer 36 of satellite A. The raw image data is synthesized,
Transmitted from satellite A. This transmitted radio wave is shown in Figure 2 (A).
As shown in Figure 2 (B), the raw image data and the image data with the error correction code added after image processing become a continuous signal contained in one modulated wave, and its spectrum is as shown in Figure 2 (B). The carrier wave frequency of the image data and the carrier wave frequency of the image data with error correction code are arranged at appropriate intervals.

Here, since the secondary processed image data is temporarily stored in the storage device 19, the temporarily stored primary processed image data can be transmitted from the ground station B to the storage device 19 periodically, for example.

This is done, for example, by switching the inputs in the error correction encoder 20.

In the user station C that receives such transmitted radio waves, a switch 39 interlocked between the bandpass filter 26 and the demodulator 28;
Spectrum receiving device 27 and decoder 31 via same 39
are installed in parallel, and switch 39 is a spread spectrum receiving bag! When switching to the decoder 31 side, raw image data can be obtained, and when switching to the decoder 31 side, image data with error correction codes can be obtained.

Here, since the user station receives the image data after image processing using an error correction encoder, the reception gain for the image data is improved by the encoding gain, and the reception antenna can be made smaller accordingly. Furthermore, since the raw image data has a reduced data rate, it can be received with a small antenna without increasing the size of the antenna.

Here, the reason why raw image data transmitted from satellite A and image data after image processing can be transmitted simultaneously without mutual interference will be explained using a specific example.

First, when the above two signals are transmitted from the satellite at the same time,
Assume that each transmit power is the same. At this time, the interference margin M of both becomes OdB.

Therefore, for raw image data, the bit error rate is 10-5.
Assuming that the required S/N required to achieve is 10 dB,
The processing gain G required for spread spectrum is expressed by the formula G,=M,
+ [L,..., 10 required S/N]. Here, if we assume that the system loss is 1 dB, then the processing gain G
, requires 11 dB, and the radio frequency bandwidth ByλF after spectrum spreading of the raw image data is 10 MHz.
z, the maximum data rate R of raw image data is expressed by the formula R=111-G, and transmission up to approximately 0.79 Mbps is possible.

Therefore, the data rate reduction device 1 reduces the input data rate to 1/20 to obtain output data of 0.7 Mbps.

On the other hand, if image data after image processing is encoded using, for example, a convolutional code, the required S required to achieve a bit error rate of 10-5 for this image data is
/N is approximately 5 dB.

Therefore, when user station C receives this signal, the carrier frequency of the image data after image processing is at the first null point (a point several MH2 apart from the carrier frequency) of the spectrum of the raw image data signal that has been spread spectrum. If there is, the required S/N of 5 dB or more, which is sufficient to achieve a bit error rate of 10-5 for image data after image processing, can be achieved, and the second
As shown in the figure, frequency division enables simultaneous transmission of image data.

(Effects of the Invention) As detailed above, according to the data transmission method in the satellite system of the present invention, a series of image data (raw image data) obtained by observation and digitized can be transmitted on the satellite at a reduced data rate. Since the signal is transmitted as a spread spectrum signal, and the ground station transmits the processed image data with an error correction code added, when the user station receives this signal, it uses the spread spectrum raw image data. If the frequency is several MHz apart from the carrier frequency of the data signal, image data after image processing (-next image processing) can be separated and received at a predetermined bit error rate.

Therefore, according to the data transmission method of the present invention, raw image data and image data after image processing can be transmitted simultaneously by frequency division. In the user station, the reception gain is improved by the encoding gain of the image data that has been subjected to the primary image processing at the ground station, and the reception antenna can be made smaller accordingly.

Furthermore, since the raw image data has a reduced data rate, it is possible to receive the raw image data with a small antenna without increasing the size of the antenna, making it easier to use the image data.

Next, since the image-processed data is distributed together with the raw image data, the time required for distributing the image-processed data increases by at least 4 hours per day compared to the conventional method. Furthermore, image data users such as ships can use smaller antennas.

Tracking IS can be simplified laterally. In addition, since spread-spectrum image data is emitted from the satellite, the power flux density radiated from the satellite to the earth's surface can sufficiently meet the specified values of the Radio Law, and a transmission output reduction circuit is installed inside the satellite. This eliminates the need for satellites, making satellites smaller, lighter, and more reliable. Furthermore, since the ground station receives raw image data that has been spread spectrum, the antenna needs to be less than 1/3 of the size of conventional antennas, which can contribute to reducing equipment costs. You can get the same effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of a data transmission system according to an embodiment of the present invention, FIG. 2 is a diagram showing a modulated wave and spectrum according to the invention, and FIG. 3 is a block diagram of the configuration of a conventional data transmission system. FIG. 4 is a diagram showing a modulated wave and spectrum of a conventional method. 1... Data rate reduction device, 2...
・Spread spectrum transmitter, 3...Low noise amplifier, 4...Down converter, 5...
...Band pass filter, 6...Synthesizing device,
7... Up converter, 8...
power amplifier, 9...guiplexer, 10.
...Antenna, 11...Antenna, 1
2... Guiplexer, 13... Low noise amplifier, 14... Down converter, 15
... Bandpass filter, 16 ... Spread spectrum receiver, 17 ... Demodulator, 1
8... Image processing device, 19... Storage device, 20... Error correction encoder, 21...
... Up converter, 22 ... Power amplifier, 23 ... Antenna, 24 ... Low noise amplifier, 25 ... Down converter,
26...Band pass filter, 27...
- Spread spectrum receiving device, 28... demodulator, 29... image processing device, 30...
...Display device, 31...Decoder, 39...
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) Moto Ryo Nyoru Henma Supuri Ryo and Sukori To V Part 2 Diagram tl Zukori Toru (zu) -° Obtained in Mamoru 1! lI image signal m〕--
・Rang A signal master's fifth clause arc) The master's position is the skin and the τ act λ A) Zgoktonon satellite f#+- 61 elephants are fiercely harvested [Shoulder ε Anti and Scuttonon (B) e-9/) Mugikunj and Scuttle≠ 4 Figure October 20, 1985

Claims (1)

[Claims] A satellite having an observation function and a signal relay function, a ground station,
In a satellite system comprising a user station that receives image data distributed via a satellite line; and; an image processing means for performing image processing on received and demodulated image data; a correction code addition means for adding an error correction code to the image-processed data; and a transmission for transmitting the output of the correction code addition means to the satellite. and a data rate reduction means for reducing the data rate of a series of image data obtained by observation and digitized; and performing spectrum spread processing on the image data whose data rate has been reduced, and a spread spectrum processing means for forming a spread spectrum signal; a combining means for combining the formed spread spectrum signal and a transmission signal from the ground station; and a transmitting means for transmitting the output of the combining means towards the ground station and the user station. A data transmission method in a satellite system characterized by comprising: and;