JPS62178024A - Transmission power controller for satellite communication earth station - Google Patents

Abstract

PURPOSE:To attain the control with high accuracy by using the error rate of a digital data representing the line quality itself to apply the transmission power control of an earth station. CONSTITUTION:The digital modulation wave of a control line emitted from its own station to a satellite is received again by its own station, a demodulator 11 demodulates the wave as a coded symbol, which is delayed (21) by a time required for the error correction in a correction decoding circuit 12. The correlation 23 between its output and an output being the result of the re-cording of a data corrected and decoded in the state without any error at the transmission through the detection of an error by the circuit 12, is taken to count the number of dissidence per prescribed time. The long range means value is obtained by an integration circuit 24 to obtain the set error rate of the coded symbol and measure the error rate of the coded symbol having much errors due to the noise received from a satellite.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission power control device for automatically compensating for radio wave attenuation due to rain or the like in a satellite communication earth station.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional satellite communication earth station transmission power control system. In the figure, (1) is a transmission digital data input terminal, and (2) is a terminal for error correction encoding of this digital data, and a coded symbol. (3) is a digital modulator that performs digital conversion in the intermediate frequency band; (4) is a variable attenuator that changes the amount of attenuation of the digitally modulated wave according to the output of level converter 4 below. ,
(5) is a transmission frequency conversion device that converts a digitally modulated wave in an intermediate frequency band to an RF (radio frequency) band; (6)
is a high-power amplifier, (7) is a power feeding unit that separates transmitted radio waves, (8) is a transmitting/receiving antenna, and (9) is a low-noise amplifier that performs low-noise amplification of received digitally modulated waves and beacon waves. , αQ is a reception frequency converter that converts from a radio frequency band to an intermediate frequency band, (1]) is a demodulator that demodulates coded symbols from a digital modulated wave, and (6) is an error correction decoding circuit for transmission with the satellite. and a circuit that detects and corrects errors occurring in the reception route and decodes the original digital data. Examples of error correction methods include convolutional coding and Tavi decoding. (2) is the output terminal for decoded digital data, and αhiro is! A beacon receiver detects the level of the beacon wave from the star, (2) is an average level detector that averages the level of the detected beacon wave, and αQ is this average level and the reference input to the terminal (1'1) A comparator outputs an error signal after the comparison, and a level converter converts this error signal to an appropriate level and outputs it to the variable attenuator (4).

Next, the operation will be explained. Generally, there are various types of satellite communication systems, but the following systems are considered here. In other words, it consists of one or more central stations and multiple user stations, and uses a demand assignment method to allocate, connect, and disconnect communication lines between these user stations on demand. #i) This is a system controlled by a central office through #i).

A conceptual diagram of such a system is shown in FIG. It is assumed that the control line can be received by all stations (including the central station) participating in the system.

By the way, the transmission power control of satellite communications earth stations is such that when radio waves are attenuated mainly due to rain in the earth station's Acrylic link, the amount of attenuation of the Acrylic link is detected, the transmission power is increased by that amount, and the transmission power is increased. This control method is used to minimize quality deterioration due to rainfall.

The conventional typical transmission power control method shown in FIG. This is done using the amount of attenuation of the sine wave) signal. That is, in the figure, the beacon wave receiver α◆ detects the level of the -con wave received from the satellite, the output signal is averaged through an average level detector (to) with a long time constant, and then the comparator α・Compare with a preset reference V-bell signal input to terminal αη.

Next, the error signal after the comparison is passed through a level converter, which corrects the difference in rain attenuation due to the frequency difference between the amplifier link and downlink, and adds it to the variable attenuator (4), which adjusts the transmission power of the transmitted digital modulation wave. I am preparing the sea bream.

[Problem that the invention seeks to solve]

The conventional satellite communication earth station transmission power control system is configured as described above, so it is possible to control the fluctuation of the beacon wave oscillator output level in the satellite and the earth station receiving system (low noise amplifier, reception frequency converter, beacon reception The drawback was that the instability of the transmitter directly affected the transmission power. Additionally, there were other problems such as all the stations making up the system had to use beacon receivers that were not particularly necessary due to the system configuration.

This invention was made in order to solve the above-mentioned problems, and in a satellite communication system in which communication between a central station and user stations is controlled by the demant sign method, the satellite beacon wave itself is The present invention aims to provide a satellite communication earth station transmission power control system that is not affected by fluctuations in the earth station and the earth station reception system, and does not require a special receiving device such as a beacon receiver.

[Means for solving problems]

According to this invention, the central station first receives digital data on the control line issued by its own station, measures its error rate, and calculates the attenuation in the amplifier link of its own station based on this error rate. seek compensation. Next, all other user stations measure the error rate of the digital data on the control line transmitted from the central station, and use this error rate to calculate and compensate for their own uplink attenuation. do.

[Function] In this invention, the parameter to be measured for transmission power control is not the amount of attenuation of the beacon receiver from the satellite (it is because the error rate of digital data (i.e., line quality) itself is used). There is no influence of fluctuations in the output level of the peakon wave oscillator in the satellite and instability of the receiver at the earth station as described above.

Furthermore, in order to measure the error rate, an error correction circuit commonly used in digital satellite communication systems is used, as shown below, so a special circuit such as a beacon receiver is not required.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 11
FIG. 11 shows an embodiment of the present invention, which has the same configuration as the central user station.

@Figure 1 (Here, the circuit is a delay circuit that delays the encoded symbols demodulated by the demodulator (b) for a certain period of time, and the circuit is an error correction decoding circuit that re-encodes the decoded digital data. The circuit, a, is a correlation circuit that takes the correlation between the output of the delay circuit and the output of the encoder circuit, and a is the correlation circuit.
This is an integrator circuit that integrates the output for a certain period of time.

First, the operation of the central office will be explained using FIG.

In the conventional transmission power control method, in order to estimate the amount of attenuation of radio waves in the uplink from the earth station to both vehicles, the amount of attenuation of the beacore waves in the downlink from the satellite to the earth station is estimated. The reduction in IT in the amplifier link was estimated and compensated for by measuring the frequency difference between the amplifier link and the downlink. In the present invention, the transmission power control of the central station is performed as follows. That is, first, the digital modulated wave of the control line emitted from the local station to the satellite is received again by the local station, demodulated as a coded symbol by the demodulator (b), and then used for error correction in the error correction decoding circuit @. The output of the delay circuit ■ (delayed by the required time) and the error correction decoding circuit @ detect errors and re-encode the corrected and decoded data to a state without errors at the time of transmission. The correlation with the output is taken by the correlator, and the number of discrepancies between the two is counted over a certain period of time.

Next, the cent error rate of the encoded symbol is determined by averaging this over a long period of time using an example integrating circuit.

This means that the error rate of a coded symbol with many errors due to noise received from the satellite is measured using a coded symbol with few errors obtained by re-encoding data after error correction decoding.

If the correction ability of error correction decoding is high, highly accurate error rate measurement is possible using the above method.

This measured error rate can be considered to represent the channel quality of the central office amplifier link and the downlink itself, and therefore the central office transmission success control can be performed using this error rate. That is, an error signal between the measured error rate and the reference value αη is detected by the comparator αQ. Since this error signal includes information on both the central station amplifier link attenuation and the downlink attenuation, the level converter afElζ uses the correlation between the two to calculate only the uplink attenuation. The variable attenuator (
4) and controls the transmission power of the central station.

Next, the operation of each user station will be explained using the same diagram @1.

Each user station receives and demodulates digital data transmitted from the central station on the control line, but in order to control the transmission power of each user station, the digital data that goes from the central station to the satellite network to each user station must be The error rate of the coded symbol of the modulated wave is used. The method for measuring the error rate of encoded symbols is exactly the same as in the case of the central station described above. Central station here →
Attenuation caused by the central station amplifier link caused by internal forces on the satellite is compensated for by the central station transmit power control described above.

Therefore, the error rate calculated as described above for each user station is
It is thought that it indicates the amount of attenuation of the downlink from the satellite to each user station. Therefore, by Novel Converter 4,
The error signal corresponding to the attenuation of the user station downlink is
The correlation between the frequency difference l between the amplifier link attenuation and the downlink attenuation is corrected according to the frequency, and the error signal is converted into an error signal corresponding to the uplink attenuation of the user station. ), and performs power control for each user station. Note that user station transmission power control is not only performed on the user station amplifier link on the control line, but also on the user station amplifier link on the communication line. The same process is performed for the above-mentioned amplifier link using an error signal corresponding to the attenuation amount of the amplifier link.

In the above embodiment, the method of measuring the error rate of encoded symbols by instructing the central station is to correlate the received encoded symbols with the encoded symbols obtained by re-encoding the data after error correction decoding. However, in the case of the central office,
Since the data sent by the own station is received by the own station,
After the transmitted encoded symbols are stored in the bathophore memory for a certain period of time, the error rate may be determined by correlating them with the received encoded symbols. The configuration of the central office in such a case is
As shown in the figure. In FIG. 1, numeral 311 is a panzer memory for delaying the transmitted encoded symbol by more than the round trip propagation time.

〔Effect of the invention〕

As described above, according to the present invention, since the transmission power control of the earth station is performed using the error rate of digital data indicating the line quality itself, highly accurate control can be performed. In addition, transmission power control can be done by simply adding a simple digital circuit to the equipment specific to this system, without using a beacon receiver, which is not necessarily necessary for this communication system, making it inexpensive and highly reliable. There is an effect that can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a transmission power control device for a central station and a user station according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a transmission power control device for a central station according to another embodiment of the invention. 3 is a block diagram showing a conventional transmission power control device for a central station and user stations, and FIG. 9J4 is a conceptual diagram of a satellite communication line composed of a central station and user stations. In the figure, (2) is an encoding circuit, (3) is a digital modulator, (4) is a variable attenuator, (8) is an antenna, αη
is a demodulator, (6) is an error correction decoding circuit, α is a comparator,
αη is the reference value input terminal,
is a delay circuit, ■ is an encoding circuit, is a correlation circuit, (241
is an integration circuit, and 3B is a delay circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) Consists of one or more central stations that perform error correction encoding/decoding of digital data and digital modulation/demodulation of carrier waves, and multiple user stations, with the central station controlling the communication lines between each user station. In the satellite communication device, each station includes a delay means for delaying the coded symbols received and demodulated from the digital modulated wave received via the satellite using the control line for a certain period of time, and a delay unit for delaying the coded symbols by an error. an encoding means for error-correcting and re-encoding the decoded output that has been corrected and decoded; a correlation means for correlating the output of the encoding means with the output of the delay means; and an integral for integrating the output of the correlation means over a certain period of time. a comparing means for comparing the output of the integrating means with a reference value and outputting an error therebetween; and an attenuation amount of the transmitted digital modulated wave of the control line in accordance with the output error signal output of the comparing means. A satellite communication earth station transmission power control device, comprising: variable attenuation means for changing the transmission power of a satellite communication earth station.