JPH03217138A - Transmission/reception system for operation state information of earth station using superposition modulation - Google Patents

Abstract

PURPOSE:To easily add a function to an earth station equipment and to eliminate a need of the operation to insert the operation state information to the original information by superposing the operation state information of each earth station onto the original information without changing the transmission form of the original information and detecting the operation state information in a specific earth station. CONSTITUTION:A repeater earth station 2 has a function to monitor the operation states of all small earth stations 3 to 8 through a satellite 1. Each small earth station is provided with a multiphase MPSK (two-phase BPSK in this case) modulator 11 and a PSK modulator 14 and subjects multiphase PSK (MPSK) (two phases in this case) of a first modulator output 12 modulated with the original information to PSK superposition modulation by the operation state information of the reception signal quality or the like and transmits the superposition modulated wave to the repeating earth station, and the repeating earth station receives this superposition modulated wave and gets the carrier reproducing circuit output or the frequency error detecting circuit output from an MPSK demodulator used for reproducing and detects the operation state information of each small earth station by a secondary modulation detecting circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for transmitting and receiving operation status information of earth stations between earth stations in a satellite communication system.

(Conventional technology) In recent years, communication satellites have become larger, digital communication technology has developed,
With the development of communication elements, satellite communication is being actively introduced not only as a means of international communication but also as a means of regional and domestic communication. In particular, satellite communication systems consisting of a large number of small earth stations using small antennas are likely to be widely introduced in the future because communication lines can be quickly constructed. In such cases, the operational status of the small earth station should be centrally monitored by one or more system monitoring earth stations in order to operate the system efficiently and reliably and to make the system economical through unmanned operation. A method to do this has been studied and put into practical use. There is also a method in which a large earth station accurately controls the transmission power of an opposing small earth station by referring to information returned from the small earth station.

In transmitting and receiving operational status information between earth stations as described above, communication channels or control channels are used to transmit the information to the other earth station. For example, when the line is configured using TDMA, there is a method of inserting the bit error rate of the received signal or the received signal C/N into the preamble of the TDMA signal. On the other hand, in the case of a continuous signal, a method is used in which the transmitted signal is framed and received C/N information representative of the bit error rate or received signal quality is inserted at the beginning of the frame.

A patent application has been filed by the same applicant for the invention related to superimposed modulation of the present invention (Japanese Patent Application No. 1999-99936).
, H1.4.21).

(Problem to be solved by the invention) In the conventional method of transmitting and receiving operational status information of an earth station using a communication channel that originally transmits information, the transmission format of the information is changed and the transmitting side interpolates monitoring information. On the receiving side, extraction work is required, which complicates signal processing, and requires additional circuitry for this purpose, resulting in an expensive device.

The present invention superimposes operational status information such as received signal quality at each earth station on original information without changing the transmission format of the information,
The purpose of the present invention is to provide a method for transmitting information to a specific earth station such as a relay earth station or a system monitoring earth station, and detecting operational status information at the specific earth station.

(Means for Solving the Problems) According to the present invention, each earth station receives polyphase PSK (MPSK) of the output of the first modulator modulated with original information, and further receives operational status information such as received signal quality. performs PSK superimposed modulation and transmits it to a specific earth station, and the specific earth station receives the superimposed modulated wave and modulates the MPSK signal used for reproduction of the specific earth station.
A feature is that the output of the carrier wave regeneration circuit or the output of the frequency error detection circuit is obtained from the demodulator, and the operational state information of each earth station is detected by the secondary modulation detection circuit.

(Embodiment 1) FIG. 1 is a diagram for explaining a communication system including a relay earth station and multiple small earth stations, which is one embodiment of the present invention. By describing this embodiment, the structure and operation of the present invention will be explained together.

In FIG. 1, relay earth station 2 also has the function of monitoring the operational status of all small earth stations 3 to 8 via satellite 1. Note that the line from the earth station to the satellite 1 is called an uplink, and the line from the satellite 1 to the earth station is called a downlink. It is also assumed that communication between each small earth station is set using a frequency division method.

In this configuration, the relay earth station 2 receives a plurality of signals from each of the small earth stations 3 to 8 via the satellite 1, demodulates these signals independently, and then (1) hosts connected to the relay earth station The demodulated data is transmitted to a computer, database, etc., or (2) it is re-modulated and transmitted to the satellite 1. The relay earth station 2 not only communicates with each small earth station but also functions as a monitor station, and centrally manages the operational status of the earth station for the purpose of maintenance and operation of the small earth station. .

Below, using the configuration in Figure 1 as an example, the primary modulation is BPSK.
(Two-phase digital phase modulation), P with secondary modulation of ±θ°
The operation of the present invention will be explained in detail by taking superimposed modulation using SK as an example. Note that the present invention uses not only BPSK but also polyphase PSK (MPS
K) are all available.

Figure 2 shows the circuit configuration for generating superimposed modulated waves at a small earth station, where 10 is a primary modulated digital baseband signal such as voice, data, facsimile, etc., and 11 is a B
PSK modulator, l2 is its output, l3 is a secondary modulation digital baseband signal representing operational status information in the small earth station, l4 is PSK for generating a phase deviation of ±θ° according to the signal of 13 It is a modulator, 15 is its output, and 16 is an encoder for framing one or more pieces of operational state information to create a secondary modulation signal. 13
The secondary modulated digital baseband signal includes, for example, signal quality such as the received C/N (signal power to noise power ratio) and bit error rate of the small earth station, operational status information such as transmitted and received signal level, power supply voltage, and operating temperature. , and its transmission speed is 1
0 primary modulation digital baseband signal.

FIGS. 3(a) to 3(c) are phase diagrams of modulated waves. 3(a) shows the output 12 of the BPSK modulator 1 2 , (b) . (C) shows that the secondary modulation digital baseband signal 13 is "1". "P in case of ON
The output 15 of the SK modulator l4 is shown respectively. That is, in PSK modulator l4, (0', 1
When the low-speed secondary modulation digital baseband signal 13 is "1"(10',180'), the BPSK wave of
When the signal l3 is “0”, the BPSK wave is modulated again into the BPSK wave of 100°+θ″) and the BPSK wave of 100°+θ″).Then, the P
The SK wave l5 is transmitted from the small earth station to the relay earth station 2.

FIG. 4 shows an example of a configuration for demodulating the secondary modulation signal of the PSK wave 15 transmitted from the small earth station. 40 represents an input signal of a superimposed modulated wave, 41 is a bandpass filter for removing noise outside the band of the input signal, 42 is a carrier regeneration circuit for creating a reference carrier wave required for synchronous detection, and 43 is the regeneration circuit. Reference carrier obtained from the circuit, 4
4 is a frequency error detection circuit for detecting the carrier frequency offset amount of the input signal; 45 is the output of the frequency error detection circuit 44; 46 is a phase detection circuit for the primary modulation signal; 47 is a timing recovery circuit; 48 is a signal determination circuit; 49 is the output of the signal determination circuit 48, and 50 is the phase locked circuit (PL).
This is a phase discrimination circuit for a secondary modulation signal composed of L) and the like.

In FIG. 4, the superimposed modulated waves shown in FIGS. 3(b) and 3(c) become the input signal 40 in FIG. ”
Frequency errors △f (=θ/2πT) and −△f (=−θ/2
An output 45 proportional to πT) is output to the carrier regeneration circuit 42. Here T is the secondary modulation rate. The carrier wave regeneration circuit 42 is controlled by the output 45 of the frequency error detection circuit and outputs the reference carrier wave of the carrier frequency fO+Δf and fO−Δf to the phase detection circuit 46 as its output 43. In other words, when the carrier wave of the input signal 40 is offset by +△f with respect to the steady frequency fO, an error component proportional to the offset amount appears in 45, and the carrier wave regeneration circuit 42 generates a reference carrier wave of the carrier frequency fO+△f. is output to 43, and the output 43 is branched, one being a phase detection circuit 46 for primary modulation and the other being a phase discrimination circuit 5 for secondary modulation.
The input will be 0. The output 51 of the phase discrimination circuit 50 is proportional to the phase deviation due to secondary modulation, that is, small earth station operational status information which is a secondary modulated digital baseband signal.

FIG. 5 shows another configuration example for demodulating the secondary modulation signal shown in FIG. 3, and 40 to 49 are the same as those in FIG. 4. 52 indicates a polarity discrimination circuit. Since the output 45 of the frequency error detection circuit 44 has an output corresponding to ±Δf, the polarity discrimination circuit level detector 52 detects this polarity, thereby outputting the small earth station operation status information 5l.

An example of earth station monitoring in communication between a relay earth station and a small earth station has been described above, but it goes without saying that the same concept can be applied to communication between small earth stations via a relay earth station.

In addition, in Figure 1, (1) relay earth station 2 and small earth station 3
, 4, 5, (2) Relay earth station 2 and small earth station 6, 7, 8
, and (3) small earth stations 3, 4, 5 and small earth station 6,
1 5 shows an example of communication between satellites 7 and 8, but it is also possible to communicate within each small earth station group via a relay earth station, and the relay earth station also has an antenna that can connect to two satellites. If the equipment is available, wide range communication between small earth stations can be realized via two satellites, and it goes without saying that the present invention can also be applied to these systems.

(Embodiment 2) FIG. 6 shows a small earth station 100. This is an embodiment of the present invention in which a communication line is configured between 101 and a large earth station 103. BPSK is used as the primary modulation method.

FIG. 7 shows a signal modulation section and a demodulation section in the large earth station 103 of FIG. The modulation section has BPs of 110 and 111.
108,1 for varying the SK modulator and transmission level
It consists of 09 variable attenuators. The demodulator includes 104 and 10
It consists of a BPSK demodulator 5 and a secondary modulation detection circuit 106 and 107 for detecting secondary modulation components. The outputs of the secondary modulation circuits 106 and 107 are input to the decoding circuit 112, where the operational status signals multiplexed according to the frame structure are separated, and the received C/N, BER, 16 equipment status signals, etc. are independently monitored. Output as a signal. Also, some signals are input to the control circuit 113,
The variable attenuators 108 and 109 are controlled by the control circuit output, and the transmission output is set. BPS in this example
κ demodulators 104 and 105 and secondary modulation detection circuit 106
, 107 is equivalent to the structure shown in FIGS. 4 and 5.

(Example 3) In the configuration shown in Fig. 1, the relay earth station extracts operational status information from the superimposed modulated carrier wave received from the small earth station, and uses the necessary information therein to determine the reception level of the small earth station. The configuration of a relay earth station in the case where the transmission output of the relay earth station for the small earth station is controlled so that the transmission output of the relay earth station is kept almost constant regardless of changes in the environment such as rainfall will be explained with reference to FIG.

FIG. 8 is a block diagram of a device related to transmission power control at a relay earth station. Here, in correspondence with FIG. 1, it is assumed that the relay earth station 2 relays between the small earth stations 3, 4, and 5 and the small earth stations 6, 7, and 8. here,
20-22. 20° to 22° are input signals of respective channels received from small earth stations 3 to 8, 23 to 25,
23° to 25° are secondary modulation detection circuits for detecting the secondary modulation signal of a small earth station, such as the phase detection circuit 50 or the level detection circuit 52 shown in FIGS. 4 and 5; 26 to 2
8, 26° to 28° is a BPSK demodulator for the primary modulation signal of the earth station, 29 to 31, 29° to 31° is a P
SK modulator, 32-34, 32゛-34゛ are variable attenuators, 35-37, 35゜-37゜ are the outputs of each channel, 38 is the control circuit of the variable attenuator, 56, 56゜ is the secondary This is a decoding circuit for restoring a modulated signal, and has the function of deframing one or more pieces of operational status information that was framed on the transmitting side and outputting it independently. Here, the structure consisting of BPSK demodulators 26-28, 26°-28° and secondary modulation detection circuits 23-25, 23°-25 is equivalent to the structure shown in FIGS. 4 and 5. Outputs 53-55, 53 of secondary modulation detection circuits 23-25, 23°-25
° ~ 55 ° is decoded by decoding circuits 56 and 56 °, extracts only information related to transmission power control, and sends it to the control circuit 3.
Enter 8. The control circuit 38 uses the difference between a preset signal quality reference value and the small earth station received signal quality information to reduce the amount of attenuation of the variable attenuators 32° to 34° and 32 to 34 by the difference. Control as follows.

In addition, the digital baseband signal of the primary modulation among the input signals 20 to 22, 20' to 22 degrees is sent to the BPSK demodulator 26.
~28, demodulated at 26°~28°, modulators 29~31
, 29° to 31', and variable attenuators 32 to 3
4, 32° to 34', a transmitter (not shown), and the satellite 1, and are transmitted to the small earth stations 3 to 8 in FIG.

By applying the relay earth station having the configuration shown in FIG. 8, a transmission power control system having the following configuration can be implemented.

A relay earth station that relays the communication is interposed in the satellite communication between small earth stations, and the relay earth station receives the signal from the small earth station via the satellite, performs signal reproduction processing, and then transmits the signal to the satellite. In a transmission power control method applied to a satellite communication system that transmits data to a partner small earth station via a Using the received signal quality information created from the measurement results, the carrier wave, which was originally modulated by 1 9 into an information signal, is further superimposed and modulated by the PSK modulator using the MPSK modulator, and the small earth station receives the superimposed modulated wave. The relay earth station receives the superimposed modulated wave, obtains the carrier wave regeneration circuit output or the frequency error detection circuit output of the MPSK demodulator used for regenerative relay of the relay earth station, and performs secondary modulation detection. A circuit detects received signal quality information of the small earth station, and according to the signal quality information, controls the transmission output to the small earth station within a preset value range so that the signal quality reaches a preset reference value. do.

(Effects of the Invention) The present invention makes it extremely easy to add functions to earth station equipment, and eliminates the need for operations to insert operational status information into original information compared to conventional systems. For example, if an existing small earth station requires transmission power control to prevent rain attenuation from a large earth station, the signal format of the original information from the small earth station will not need to be changed and the current equipment will not need to be modified. By adding the superimposition modulation circuit of the present invention for adding the status information of the present invention to the intermediate frequency stage of the modulator output, operational status information can be easily transmitted to large earth stations, and equipment maintenance, operation, and Monitoring is also extremely easy.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a satellite communication system including a relay earth station and a small earth station. Figure 2 is a BPSK-PSK superimposed modulation wave generation circuit.
The figure is a phase vector diagram, Figure 4 is a block diagram of a secondary modulation signal demodulation circuit using a phase detection circuit, Figure 5 is a block diagram of a secondary modulation signal demodulation circuit using a level detector, and Figure 6 Figure 7 is a block diagram of the modulator and demodulator in the large earth station. Figure 8 is a block diagram of the transmission power control circuit in the relay earth station. It is. 1...Satellite, 2...Relay earth station, 3-8
...Small earth station, 10...Primary modulation digital baseband signal, 11
...BPSK modulator, l2...Output of BPSK modulator, 13...Secondary modulation digital baseband signal, 14...PSK modulator, 15...PSK
Output of the modulator, l6...encoder, 20-22 and 20°-22°...input signal at the relay earth station, 23-25 and 23°-25°...secondary for the secondary modulation signal Modulation detection circuit, 26 to 28 degrees and 26 degrees to 28 degrees... BPSK demodulator for primary modulation signals, 29 to 31 and 29 degrees to 31' --- PSK modulator,
32-34 and 32°-34'...variable attenuator, 3
5 to 37 and 35° to 37°... Output of variable attenuator, 38... Control circuit, 40... Input signal of superimposed modulated wave, 41... Bandpass filter, 42... Carrier wave regeneration circuit , 43...Reference carrier wave which is the output of the carrier wave regeneration circuit, 44
...Frequency error detection circuit, 45...Frequency error detection circuit output, 46...Phase detection circuit, 47...Timing regeneration circuit, 48...Signal judgment circuit, 49...Signal judgment circuit Output, 50... Phase discrimination circuit, 5l... Output of 50, 52
...Polarity determination circuit, 56, 56°...Decoding circuit, 100, 101...Small earth station, 103...Large earth station, 104, 105...B
PSK demodulator, 106, 107... Secondary modulation detection circuit, 108, 109... Variable attenuator, 110, 111... BPSK modulator, 112...
decoding circuit, 113... control circuit;

Claims (11)

[Claims] (1) In a satellite communication system in which multiple earth stations and one or more of the earth stations function as specified earth stations, each earth station other than the specified earth station is originally The phase PSK (MPSK) is further subjected to superimposition modulation using PSK using operation status information such as received signal quality, and transmitted to a specific earth station, and the specific earth station receives the superimposed modulated wave, and Obtain the carrier wave regeneration circuit output or frequency error detection circuit output of the MPSK demodulator, which is originally used for information reproduction,
A system for transmitting and receiving operation status information of an earth station using superimposed modulation, characterized in that the operation status information of the earth station is detected by a secondary modulation detection circuit. (2) A transmission power control system, wherein the secondary modulation detection circuit according to claim 1 comprises a phase discrimination circuit. (3) A transmission power control system, wherein the secondary modulation detection circuit according to claim 1 comprises a polarity discrimination circuit. (4) A relay earth station that relays the communication is interposed in the satellite communication between small earth stations, and after the relay earth station receives the signal from the small earth station via the satellite and performs signal reproduction processing, In a transmission power control method applied to a satellite communication system that transmits a signal to a partner small earth station via a satellite, each of the small earth stations uses a downlink signal from the satellite to improve the signal quality of the signal. The small earth station transmits the superimposed modulated wave by using the received signal quality information created from the measurement results to superimpose the carrier wave originally modulated by the information signal using the MPSK modulator. , the relay earth station receives the superimposed modulated wave, obtains the carrier wave regeneration circuit output or the frequency error detection circuit output of the MPSK demodulator used for regenerative relay of the relay earth station, and detects the superimposed modulation wave using the secondary modulation detection circuit. Detecting received signal quality information of a small earth station, and controlling the transmission output to the small earth station within a preset value range so that the signal quality reaches a preset reference value according to the signal quality information. Characteristic transmission power control method. (5) A transmission power control system, wherein the secondary modulation detection circuit according to claim 4 comprises a phase discrimination circuit. (6) A transmission power control system, wherein the secondary modulation detection circuit according to claim 4 comprises a polarity discrimination circuit. (7) MPSK that obtains a superimposed modulated received signal and demodulates the primary modulated digital baseband signal of the received signal
a demodulator; a phase discrimination circuit that obtains a carrier wave regeneration circuit output from the MPSK demodulator and outputs a secondary modulation digital baseband signal; and a phase discrimination circuit that obtains the secondary modulation digital baseband signal from the phase discrimination circuit and performs secondary modulation. a decoding circuit for restoring small earth station received signal quality information contained in a digital baseband signal; a control circuit that generates control information using the difference; a PSK modulator that re-modulates the signal demodulated by the MPSK demodulator; and an output signal of the modulator that is obtained and attenuated in accordance with the control information from the control circuit. A relay earth station comprising at least a variable attenuator and a transmitter for obtaining an output signal of the variable attenuator and transmitting the output signal. (8) MPSK that obtains a superimposed modulated received signal and demodulates the primary modulated digital baseband signal of the received signal
a demodulator; a polarity discrimination circuit that obtains a carrier wave regeneration circuit output from the MPSK demodulator and outputs a secondary modulation digital baseband signal; and a polarity discrimination circuit that obtains the secondary modulation digital baseband signal from the polarity discrimination circuit and performs secondary modulation. A decoding circuit that restores the small earth station received signal quality information contained in the digital baseband signal, and the small earth station received signal quality information obtained from the decoder, and the difference between the information and a preset signal quality reference value. a PSK modulator that re-modulates the signal demodulated by the MPSK demodulator; and a PSK modulator that obtains the output signal of the modulator and attenuates it in accordance with the control information from the control circuit. A relay earth station comprising at least a variable attenuator and a transmitter for obtaining an output signal of the variable attenuator and transmitting the output signal. (9) A polyphase PSK modulator that performs multilayer PSK modulation using a primary modulated digital baseband signal such as voice, data, facsimile, etc. as input, and a code that frames one or more operational status information and creates a secondary modulated signal. and a PSK modulator that receives an output from the multiphase modulator and generates a phase shift of ±θ° according to the secondary modulation signal. (10) A bandpass filter that inputs the superimposed modulated wave signal and removes noise outside the band of the input signal, and a carrier regeneration that obtains the output of the bandpass filter and creates a reference carrier wave required for synchronous detection. a frequency error detection circuit that obtains the output of the carrier wave regeneration circuit, detects a carrier wave frequency offset amount, and outputs it to the carrier wave regeneration circuit; a first phase detection circuit that performs phase detection; a timing recovery circuit that obtains the output of the bandpass filter and obtains timing; and a signal that obtains the output of the phase detection circuit and performs signal determination according to the output of the timing recovery circuit. A superposition modulation demodulation circuit comprising at least a determination circuit and a phase determination circuit that obtains the output of the carrier wave regeneration circuit and outputs a secondary modulation signal. (11) A bandpass filter that inputs the superimposed modulated wave signal and removes noise outside the band of the input signal, and a carrier regeneration that obtains the output of the bandpass filter and creates a reference carrier wave required for synchronous detection. a frequency error detection circuit that obtains the output of the carrier wave regeneration circuit, detects a carrier wave frequency offset amount, and outputs it to the carrier wave regeneration circuit; A phase detection circuit that performs phase detection, a timing recovery circuit that obtains the output of the bandpass filter and obtains timing, and a signal judgment circuit that obtains the output of the phase detection circuit and makes a signal judgment according to the output of the timing recovery circuit. , and a polarity discrimination circuit that obtains the output of the frequency error detection circuit and outputs a secondary modulation signal.