JPS6362422A - Forced wave stopping system - Google Patents

Abstract

PURPOSE:To prevent the decrease in the frame utilizing efficiency by using a base band signal different in the constitution from a base band signal used to modulate a communication signal wave as a forced stop wave while unifying the reception system. CONSTITUTION:A base station 2 always monitors a communication channel and if the station 2 finds out that an undesired wave is sent from a small sized earth station into a communication channel not subject to channel designation, or in case of the necessity to stop communication urgently, the signal wave modulated by using a base band signal different in the constitution from a base band signal used to modulate the communication signal wave is sent through the communication channel through which the small sized earth station receives the wave. As a result, since the state whose error rate is deteriorated by a predetermined value continues in the said small sized earth station, the transmission in a base station 2 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a forced stop method in a satellite communication system, and more particularly to a forced stop method in a satellite communication system that communicates with each other using digital signal waves.

(Prior Art) In recent years, in the field of satellite communication, the introduction of satellite communication systems that perform communication using digital signal waves obtained by modulating carrier waves with digital signals has been actively promoted. In these systems, FDMA (Frequency Division Multiple Access) or TDMA (Time Division Multiple Access) is usually used as the multiple access method. Especially recently, FDM
S CP C (Si'ngle) is a form of A method.
A satellite communication system using a small earth station that performs communication using the Channel Per Carrier method is attracting attention because of its economic efficiency.

Forms of communication between small earth stations using small antennas include a method in which small earth stations communicate directly with each other via a satellite (hereinafter referred to as the sinkle pop method), a method in which a base station is used as an intermediary,
Receive signal waves from a small earth station via a base station or satellite,
A method of reproducing this, modulating it again, and transmitting it to the small earth station of phase f via a satellite (hereinafter referred to as the double hop method)
, and a mixed method in which a single-hop method and a double-hop method are mixed.

In such a small earth station inter-satellite communication system, the base station controls the small earth station, and at the same time monitors the No. 13 wave transmitted by the small earth station. If a small earth station is transmitting unnecessary waves or it is necessary to stop communication immediately, the base station will send a forced stop signal to the small earth station and stop the small earth station from transmitting. . The following methods are generally used for this forced stop.

First, in the single-hop method, each small earth station has a
A total of two demodulators are installed, one each to receive the channel and control channel, and even during communication, the control channel sent from the base station is always received, and a forced stop signal is sent to the own station. There is no method that can be used to stop the transmission if the In the double-hop method, in addition to the same method as the single-hop method, a forced stop signal is inserted in the header of the 5cpc signal wave transmitted from the base station toward the small earth station, and each small earth station A method is used in which transmission is stopped when forced stop signal No. 13 addressed to the station is sent. In the mixed method, a method similar to the single-hop method is generally used.

Also in the TDMA system, the base station controls each earth station and transmits a forced stop signal to earth stations that require forced stop. The forced stop signal is inserted into the reference burst sent from the base station to control each earth station.Each earth station always receives this reference burst and sends the forced stop signal to its own station. If a wave signal is transmitted, the transmission is stopped.

(Problems to be solved by the invention) A satellite communication system that performs communication using the FDMA method,
In particular, when the conventional forced stop method described above is used in a small earth station-to-earth station satellite communication system, the following problems arise. first,
In the single-hop forced stop method, two channels are received simultaneously, so two reception systems are required, and since small earth station satellite communication systems are originally characterized by low cost, this poses an economical problem. There is. Also, when using a header for the forced stop method in the double hop method,
There is a problem that frame usage efficiency decreases. The mixed method also has the same problems as the single-hop method.

In addition, in the TDMA system, each earth station always receives information such as forced stop signals inserted in the reference burst and transmitted, but if a particular earth station malfunctions and the information cannot be deciphered correctly, the The problem is that unless the earth station is forcibly shut down immediately, communication with other earth stations, and in the worst case scenario, with the entire system, will be impossible.

(Means for Solving the Problems) In view of the above-mentioned current state of the prior art, the present invention solves the problem that two receiving systems are required in a satellite communication system that communicates using the FDMA method, particularly in a small earth station inter-satellite communication system. At the same time, it is possible to realize a simple and economical forced stop method without reducing frame utilization efficiency, and to implement TDM.
The objective is to realize a highly reliable forced stop method in a satellite communication system that communicates using method A.

The feature is that each earth station monitors the error status of the received signal, and stops transmission if the error rate deteriorates below a predetermined value and this condition continues for a predetermined period of time. An earth station that is equipped with a strong 1ttlJ function and transmits a wave for forced termination to an earth station that requires a strong 1ttlJ termination is
A wave modulated using a baseband signal with a different configuration from the baseband signal used for modulating the signal wave is transmitted to an earth station that requires forced stop, and the error rate of reception No. 13 at the earth station is calculated. If the condition deteriorates beyond the specified value and the condition continues for more than the specified time, as a result,
Transmission at the earth station will be stopped.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

First, as an example of the case where the present invention is applied to a satellite communication system that performs communication using the FDMA method, an embodiment of a small earth station inter-satellite communication system will be described. Figure 1 shows
FIG. 2 is a diagram for explaining a small earth station inter-satellite communication system that performs communication using a mixed method. In the figure, 1 is a satellite, 2 is a base station, 3 to 8 are small earth stations, and 9 is a satellite beam. All small earth stations 3 to 8 and base station 2 are placed within satellite beam 9, and communication between each small earth station is via 5
It is assumed that the process is performed using the cpc method. In this configuration, the base station 2 receives multiple signal waves from the small earth stations 3 to 8 via the satellite 1, independently demodulates them, re-modulates them, and transmits them to the satellite 1. double-hop method (indicated by solid lines in Figure 1), and single-hop method (indicated by broken lines in Figure 1) in which small earth stations communicate directly with each other only through satellite 1 without going through base station 2. Communication is performed using either of the following:

Even when the present invention is applied to a single-hop system and a double-hop system, the results are the same as the single-hop system and double-hop system in the mixed system, respectively, so the following explanation will proceed by taking the mixed system shown in FIG. 1 as an example.

In FIG. 1, each of the small earth stations 3 to 8 is designated with a communication channel for transmission and reception under the control of the base station 2, and performs communication. In other words, a small earth station that wants to communicate sends a request signal to a line request channel, and when base station 2 receives the request signal, it transmits and receives a communication channel to the small earth station through a control channel. Specify. Since only one receiving system is installed in the small earth station according to the present invention, the control channel is not received during communication, and only the communication channel is received. Base station 2 constantly monitors the communication channel.
If it is found that unnecessary waves are being transmitted from a small earth station to a communication channel that has not been specified, or if it is necessary to stop communication immediately, the small earth station will P N (
Pscnd.

No1se)! Send a wave modulated with a random signal like a train. The bandwidth of this wave can be the same as or smaller than the communication channel, but if there are several types of communication channel bandwidths, it is best to set it to the same as the communication channel with the smallest bandwidth to force a stop. 1 modulator is required for
This is advantageous because only a stand is required. In addition, there is no restriction in principle on the baseband signal for modulating waves, even if it is not a PN series, as long as the frame structure, etc. is completely different from the baseband signal used for communication.

FIG. 2 is a diagram showing the configuration of the transmitting side of the base station 2 according to the present invention, where 10 to 12 are modulators that modulate the baseband signal, and 13 to 15 are modulators that modulate the baseband signal, and 13 to 15 that set the transmission frequency according to the communication channel designation signal. 16 is a PN signal generator for forced stop, 17 is a modulator for modulating the PN signal generated by the PN signal generator I6, and 18 is a frequency converter for setting the transmission frequency according to the forced stop channel designation signal. This is a frequency converter. 7 frequency converter 1: ], 14, 15.1
8 is usually constructed using a synthesizer. The small earth station according to the present invention monitors the error state of the receiver I5, and if the error rate deteriorates below a predetermined value and the condition continues for more than a predetermined time, the Stop A∆+
It is equipped with a function to do L-. A simple method for monitoring error conditions is, for example, to configure the baseband signal into a frame, insert a known pattern into the frame, and then, on the receiving side, compare the pattern obtained by demodulating the received wave with the known pattern. There are methods to find the error rate using

When the small earth station receives a wave for forced stop from the base station, the error rate deteriorates below a predetermined value, and when the time exceeds the predetermined time, transmission f3 is stopped.

As a result, a forced outage was carried out.

In the above example, all small earth stations and base stations were arranged in one satellite beam, but next we will briefly describe an embodiment in which there are two satellite beams. Figure 3 is a diagram showing a satellite communication system between small earth stations when there are two satellite beams, 1 being a satellite, 2 being a base station, and 3 being a satellite beam.
-8 are small earth stations, I9 monitor stations, 20.21 are satellite beams, and 22-24 are transponders. Small earth stations 3 to 5 and monitor station 19 are arranged in satellite beam 20, and small earth stations 6 to 8 and base station 2 are arranged in satellite beam 21. Comparing Figures 1 and 3, we see that monitor station 19
You can see that it has been newly added. Monitor station I9 is
It monitors all receivable communication channels within the satellite beam 20 and transmits the monitoring results to the base station 2. Here, it is assumed that all communication channel control is performed by the base station 2. Therefore, in addition to the transponder 22 and 23 that connects the two beams, the transponder is a return transponder that is necessary for the small earth stations 6 to 8 in the satellite beam 21 to communicate with the base station 2 to set up a communication channel. A total of 3 pieces of 24 pieces are required. The method of forced stoppage is that the base station 2 determines whether forced stoppage is necessary according to the monitoring results at the base station 2 and the monitor information sent from the monitor station 19, and then
If a forced stop is necessary for a small earth station within the satellite base station 2, the base station 2 directly transmits a wave for forced stop,
If a forced stop is required for a small earth station within the station, the base station 2 gives a command to the monitor station 19, and the monitor station 19 transmits a wave for forced stop. Therefore, the monitor station 19 also includes the PN signal generator 16, modulator 17, and
A frequency converter 18 and a transmitter must be installed. The operation l of the small earth station that has received the forced stop wave is the same in this case as in the case where the number of satellite beams is one as described above. The implementation method of the present invention in the small earth station inter-satellite communication system has been explained above using two examples.
It goes without saying that the present invention can be easily implemented in other configurations of small earth station-to-earth station satellite communication systems, as well as other configurations of satellite communication systems that communicate using FDMA system 1.

Next, an embodiment of the present invention in a satellite communication system that performs communication using the TDMA method will be described. Here, we will consider a system in which frame synchronization is achieved by each earth station transmitting a synchronization burst 2, receiving its own synchronization burst by satellite return, and comparing the position within the frame with a reference burst. FIG. 4 shows an example of burst arrangement within a TDMA frame. In the same figure, 25
．． 26 is the main reference burst and sub-reference burst transmitted from the main reference station and the sub-reference station, 27 to 29 are synchronization bursts transmitted by each earth station, and 30 to 32 are transmitted by each earth station for communication. It's a traffic burst. In principle, only one reference burst is sufficient, but even if the main reference station fails, it will affect the system! The main reference station and the sub-base station send a reference burst 25 and a sub-reference burst 26, respectively, so that the reference burst 25 and the sub-reference burst 26 are avoided. For example, the earth station that transmitted the synchronization burst 27 receives the main reference burst 25 and the synchronization burst 27 by satellite loopback, and maintains frame synchronization by adjusting the transmission timing so that the difference in reception timing becomes a specified value. do. Various information such as a forced stop signal is inserted into the reference burst, and the reference burst is transmitted to each earth station. If the reference station transmits a forced stop signal to a certain earth station, but the forced stop signal is not correctly decoded by the earth station and the forced stop is not executed, the reference station will be able to transmit the forced stop signal to a certain earth station. P is superimposed on the synchronous burst
A burst wave modulated using N(; It is equipped with a function to stop sending Δ if the rate has deteriorated below a predetermined value and reception is not possible.

As a result, when a reference station superimposes a burst modulated with a PN signal on a synchronized burst transmitted by a certain earth station,
The earth station will no longer be able to receive the synchronization burst from its own station because the error rate will be worse than the predetermined value.
If this state continues for a predetermined period of time, transmission will be stopped. The method of implementing the present invention in a TDMA satellite communication system has been described above by giving an example, but it goes without saying that the method can be easily implemented in a TDMA satellite communication system with other configurations.

(Effects of the Invention) As explained above, according to the present invention, two receiving systems are not required in a satellite communication system that communicates using the FDMA method, especially in a satellite communication system between small earth stations.
Moreover, at the same time, a simple and economical forced stop method and a highly reliable forced stop method in a satellite communication system that communicates using the TDMA method can be realized without reducing frame utilization efficiency.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a satellite communication system between small earth stations using a mixed method, Figure 2 is a diagram showing the configuration of the transmitting side of a base station according to the present invention, and Figure 3 is a diagram showing a satellite communication system between small earth stations using two beams. FIG. 4 is a diagram showing a satellite communication system, and is a diagram showing a burst arrangement within a TDMA frame. 1...Satellite, 2...-Base station, 3-8...Small earth station, 9...Satellite beam, 10-I 2-...Modulator,
13~] 5--Frequency converter, 16-PN signal generator, 17--Modulator, 18--Frequency converter, 19-
...Monitor station, 20-21...Satellite beam, 22-2
4...Transponder, 25...Main reference burst, 26-...Sub reference burst, 27-29-...Synchronization burst, 30-32-...Traffic burst.

Claims (1)

[Claims] In a satellite communication system consisting of a plurality of earth stations and communication satellites that communicate with each other using digital signal waves, each earth station monitors the error state of the received signal and the error rate is determined. It is equipped with a function to stop transmission at the relevant earth station if the condition deteriorates beyond the specified value and continues for a specified period of time, and is attached to the earth station that requires forced stop. A base station that transmits waves uses a baseband signal with a different configuration from the baseband signal used to modulate communication signal waves, and transmits the modulated waves to the earth station that requires forced stoppage. The error rate of the received signal at the earth station deteriorates below a predetermined value, and this condition continues for more than a predetermined time, and as a result, transmission from the earth station is stopped. Forced stop method.