JP2001223626A - Digital satellite communications equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital satellite communications equipment that can avoid situations which leads to deterioration in channel quality and communication interrupt. SOLUTION: The equipment has N-systems (N>=2) or more of reception systems from one satellite, the one reception system is connected to other prescribed digital satellite communication equipment through a single hop path via the satellite, the remaining (N-1) sets of the reception systems are connected to the other prescribed digital satellite communication equipment via a path of double hop or more relayed by a relay station, and each digital satellite communication equipment is provided with an error correction decoder, that is placed to each reception system to correct an error of a received signal and to detect error rates, an error rate monitor that respectively monitors the detection output of a bit error in the received signal corrected by each error correction decoder, and a changeover switch that selects the received signal of one system among the received signals of the N-sets of the reception systems, on the basis of the monitor result by the error rate monitor section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital satellite communication device.

[0002]

2. Description of the Related Art Hitherto, a digital satellite communication system for communicating between earth stations using a satellite has been known. As a specific example of the digital satellite communication system, a TV conference system using a satellite (hereinafter referred to as a satellite TV)
Conference system). The satellite TV conference system is used for distance education, distance lectures, distance medical care, and the like.

FIG. 7 shows a configuration of a conventional satellite TV conference system.

This satellite TV conference system is a system in which X and Y stations provided in two areas in one satellite A's coverage area communicate via satellite A.

[0005] The X station and the Y station each have an antenna 1
01, 201, Satellite Earth Station (ES) 102, 20
2. Codecs (CODEC) 103, 203 for encoding or decoding images and sounds; echo cancellers 104, 204 for canceling echoes generated when sound output from a speaker is input to a microphone;
Camera 10 which is an input / output device for images and sounds of a TV conference
5, 205, monitors 106, 206, microphones 107,
07, speakers 108 and 208.

In the X station, the satellite communication earth station 102 and the codec 103 are connected by, for example, an RS449 interface. The interface signal includes image data, audio data, a clock, and other control signals.

[0007] A transmission video signal output from the camera 105 and a transmission audio signal output from the microphone 107 are input to the codec 103 and encoded. The encoded data obtained by the codec 103 is sent to the satellite earth station 102 as digital transmission data conforming to the RS449 interface.

[0008] The transmission data transmitted to the satellite communication earth station 102 is transmitted by the antenna 101 to the satellite with a predetermined satellite channel and a predetermined transmission power.
It is sent to the Y station which is the communication partner via the satellite.

On the other hand, a radio wave arriving at the X station from the Y station via the satellite is received by the antenna 101 of the X station and the satellite communication earth station 102. The received data (image data and audio data) received by the satellite earth station 102 is sent to the codec 103.

[0010] The received data sent to the codec 103 is decoded by the codec 103. The audio signal obtained by the codec 103 is sent to the speaker 108 via the echo canceller 104 and is output as audio. The video signal obtained by the codec 103 is sent to the monitor 106 and output as a video.

FIG. 8 shows the configuration of the satellite communication earth station 102.

The satellite communication earth station 102 includes an error correction encoder 401, a modulator 402, a transmitting section 403, a receiving section 404,
It comprises a demodulator 405 and an error correction decoder 406.

At the X station, when transmitting, the codec 103
The digital transmission signal input to the satellite communication earth station 102 is added with an error correction code such as a convolutional code by an error correction encoder 401, and
After modulation such as PSK is performed, the signal is transmitted from antenna 101 through transmitting section 403.

At the time of reception, a reception signal input from the antenna 101 to the satellite communication earth station 102 is input to the demodulator 405 through the reception unit 404, and the demodulator 405
Demodulation such as PSK is performed, and the error of the received signal is decoded by the error correction encoder 406 by Viterbi decoding or the like, and then sent to the codec 103.

The transmitting section 403 sets a transmission frequency (channel) and a transmission power (operation level) for emitting a radio wave from an antenna. The receiving unit 404 sets a receiving frequency (channel).

As shown in FIG. 7, assuming that the transmission channel of the X station is TX1, the reception channel of the X station is RX2, the transmission channel of the Y station is TX2, and the reception channel of the Y station is RX1, the transmission channel TX1 of the X station. Is received on the receiving channel RX1 of the Y station via the satellite,
When the transmission signal on the transmission channel TX2 of the station is received on the reception channel RX2 of the X station via the satellite,
Two-way communication is performed. Note that the configuration and operation of the Y station are the same as the configuration and operation of the X station, and a description thereof will be omitted.

[0017]

As is well known, a satellite link is not limited to the capacity of a satellite communication earth station, the capacity of a satellite at a transmitting / receiving point, the interference of the earth station and intermodulation, as well as natural environmental conditions such as rainfall. Due to the external factors described above, the line status changes every moment both spatially and temporally.

In particular, a radio wave on a satellite line is, for example, 14 GHz as an uplink frequency from a satellite communication earth station to a satellite.
A 12 GHz band frequency is used as a downlink frequency from the satellite to the satellite communication earth station in the z band. In such a frequency band, propagation loss of the transmission line increases due to atmospheric gas, rainfall, and the like.

As a result, in a satellite TV conference system, a communication error of video or audio may occur, or in the worst case, the communication may be interrupted. Therefore, the line design of the satellite communication is performed in advance according to the requirements of the line quality and the annual non-operation rate (= time when the user is disconnected (failure) due to rainfall / yearly time × 100 (%)) required by the user. Therefore, the specifications and configuration of the satellite communication system are determined.

In order to increase the line margin sufficiently, improve the reliability of communication, and reduce the error rate of the transmission signal, for example, on the satellite communication earth station side, increase the antenna diameter.
Automatically replaces high-power amplifiers with high transmission power, reduces reception noise characteristics of receivers including low-noise amplifiers, applies strong error correction codes, and automatically compensates for propagation loss due to rainfall It is common to add a transmission power control (TPC) function to increase the transmission power.

However, these are not only limited, but the satellite communication earth station is usually expensive, large, complicated and uneconomical by using these methods.

However, even when an economical and simple digital satellite communication system is used, the X station and the Y station can be used.
Even if a torrential rainfall happens to occur in one or both of the area where the station X is located and the area where the station Y is located, as in the case of relaying important events and conferences by satellite TV conference with the station, In some cases, it is troublesome to have an unexpected situation such as a communication error or a disconnection.

An object of the present invention is to provide a digital satellite communication apparatus capable of avoiding a situation where line quality is deteriorated or communication is interrupted even when an economical and simple digital satellite communication system is used. .

[0024]

A first digital satellite communication apparatus according to the present invention comprises N systems (N ≧ N) from the same satellite.
2) It has the above-mentioned receiving systems, one receiving system is connected to another predetermined digital satellite communication device via a single-hop route via a satellite, and the remaining (N-1) receiving systems are relay stations. It is connected to the other predetermined digital satellite communication device by a route of more than double hops relayed by,
An error correction decoder that is provided for each reception system and corrects an error in a received signal and detects an error rate, and an error that monitors a bit error detection output of the received signal corrected by each error correction decoder. It is characterized by comprising a changeover switch for selecting one reception signal from reception signals of N reception systems based on a monitoring result by the rate monitoring unit and the error rate monitoring unit.

The second digital satellite communication apparatus according to the present invention has N or more (N ≧ 2) receiving systems, and one receiving system is connected to another predetermined digital system via a first hop route via the first satellite. Connected to a satellite communication device,
The remaining (N-1) reception systems are connected to the other predetermined digital satellite communication device through a double hop or more route relayed by a relay station via another satellite different from the first satellite. An error correction decoder that is provided for each reception system and corrects an error in a received signal, and detects an error rate;
An error rate monitoring unit that monitors the detection output of the bit error of the received signal corrected by each error correction decoder, one system based on the monitoring result by the error rate monitoring unit, and from the reception signals of the N reception systems And a changeover switch for selecting the received signal.

The third digital satellite communication apparatus according to the present invention has N or more receiving systems (N ≧ 2), and one receiving system is connected to another predetermined digital system via a first hop route via the first satellite. Connected to a satellite communication device,
The remaining (N-1) reception systems are connected to the other predetermined digital satellite communication device by a single hop route via another satellite different from the first satellite, and each reception system An error correction decoder that is provided and corrects an error of a received signal, detects an error rate, an error rate monitoring unit that monitors a bit error detection output of the received signal corrected by each error correction decoder, and It is characterized by comprising a changeover switch for selecting one received signal from N received signals based on the monitoring result by the error rate monitoring unit.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

[1] Description of First Embodiment FIG. 1 shows a configuration of a satellite TV conference system which is one form of a digital satellite communication system.

In FIG. 1, communication is performed between an X station (digital satellite communication device) and a Y station (digital satellite communication device). The Z station is a relay station described later.

The X, Y, and Z stations each have an antenna 1
01, 201, 301, Satellite Communication Earth Station (ES) 10
2, 202, 302; codecs (CODEC) 103, 203 for encoding or decoding images and sounds; echo cancellers 104, 204 for canceling echoes generated when sound output from a speaker is input to a microphone. , Cameras 105 and 205, monitors 106 and 206, microphones 107 and 207, and speakers 108 and 208, which are input / output devices for images and audio of a TV conference. In FIG. 1, for station Z, antenna 30
1 and only the satellite earth station (ES) 302 are shown, and other devices are not shown.

The satellite TV conference system shown in FIG. 1 differs from the conventional example shown in FIG. 7 in that a Z station serving as a relay station is included.
Is different. The configurations of the satellite communication earth stations 202 and 302 of the Y and Z stations are the same as the configuration of the satellite communication earth station 102 shown in FIG.

In satellite communication, a satellite communication earth station is deployed in each region to construct a satellite communication network, and a satellite TV conference and the like are held. Therefore, the Z station and the like are arranged in the same configuration as the X station and the Y station, and both are within the coverage area of the satellite A.

In FIG. 1, radio waves arriving at the X station from the Y station via the satellite A at the TX2 frequency (channel) as the RX2 frequency (channel) are transmitted to the Z station at the same time.
It arrives as X2 frequency (channel).

At the Z station, the signal from the Y station is received and demodulated at the satellite communication earth station 302, and then the received signal of the RS449 interface output and the reception clock are received by the satellite communication earth station 3.
02 is input to the transmission signal input terminal and the transmission clock input terminal. After this, after error correction coding and modulation are performed,
Radio waves are emitted from the antenna 301 with the transmission channel set to TX3.

At the X station, the transmission signal of the Z station is transmitted to the R station via a satellite.
Receive as X3 channel. That is, the signal from the station Y is relayed to the station X by a double hop through the station Z.

FIG. 2 shows the configuration of the X station satellite communication earth station 102.

In FIG. 2, the X station satellite communication earth station 10
2 receives the received signal from the Y station by the receiving unit 404, demodulates the received signal by the demodulator 405, corrects the error of the received signal by the error correction decoder 406, and outputs the received signal to the changeover switch 412. . The error correction decoder 406 measures the error rate of the received signal, and inputs the error rate Ey at that time to the error rate monitoring unit 410.

Similarly, the X station satellite communication earth station 102
A reception signal from the Z station is received by the reception unit 407 and the demodulator 4
The demodulated signal is demodulated at 08, the error of the received signal is corrected at the error correction decoder 409, and the received signal is output to the changeover switch 412. The error correction decoder 409 measures the error rate of the received signal, and determines the error rate Ez at that time by the error rate monitoring unit 410.
To enter.

The error rate monitoring unit 410 calculates both error rates Ey, E
z is compared, and the result of the determination is output to the control unit 411. The control unit 411, based on the determination result of the error rate monitoring unit 410, selects one of the two received signals input to the changeover switch 412 with the smaller error rate from the changeover switch 4
The changeover switch 412 is controlled so as to be output from the switch 12. The switching timing of the changeover switch 412 is determined by the control unit 411. The received signal output from the changeover switch 412 is sent to the codec 103.

The transmission path is different between the Y station → X station path and the Y station → Z station → X station path. The X-station, the Y-station, and the Z-station may have different specifications (such as an antenna diameter and transmission power) of the digital satellite communication system. Further, even if each station has exactly the same specifications, the reception signal frequency of the Y station at the X station is different from the reception signal frequency of the Z station at the X station. Further, the performance (EIRP, G / T, etc.) of the satellite itself in the area where the X, Y, and Z stations exist differs. Due to such various factors, the receiving line margin received by the X station also differs depending on the receiving system.

Therefore, for example, when the quality and reliability of the transmission signal on the route from the Y station to the X station are reduced,
If the quality and reliability of the transmission signal in the route from the Z station to the X station are good, the receiving route is changed from the Y station to the X station to the Y station.
If the path is switched from the station Z to the station X and used, it is possible to prevent a decrease in the quality and reliability of the transmission signal. In the opposite case,
The same can be said.

Therefore, if the error rate of the received signal is monitored and the one having the least error is switched between the two reception systems, the reception line margin can be maintained and the deterioration of the quality can be prevented.

If no error occurs in both systems or the error rates are the same, it is often desirable to select the received signal of the Y station with a small transmission delay by the changeover switch 412 in many cases.

FIG. 3 shows a control processing procedure of the changeover switch 412 performed by the satellite communication earth station 102 of the X station.

First, the error rates Ey and Ez are measured by the error correction encoders 206 and 209 (step 1).

It is checked whether or not the received signal received from the Y station has an error based on the error rate Ey (step 2). If the received signal received from the Y station has no error (YES in step 2). ), Since the line quality is good even in the route from the Y station to the X station, the received signal output from the satellite communication earth station 102 to the codec 103 controls the switch 412 so that the received signal from the Y station is output. (Step 3).

If an error has occurred in the received signal received from the Y station (NO in step 2), it is checked whether or not the received signal received from the Z station has an error based on the error rate Ez. (Step 4). If there is no error in the received signal received from the Z station (YES in step 4), it is determined that the received signal from the Z station has better line quality than the received signal from the Y station, and the received signal from the Z station is received. The changeover switch 412 is controlled so as to select a signal (step 6).

If an error has occurred in both the received signal received from the Y station and the received signal received from the Z station (NO in step 4), the error rates Ey and Ez are compared (step 5). ). If the error rate Ey is larger than Ez, the changeover switch 412 is controlled so as to select the reception signal of the Z station (step 6). If the error rate Ez is larger than Ey, the changeover switch 412 is controlled so as to select the reception signal of the Y station (step 3).

When the receiving path is selected by controlling the changeover switch 412 by the processing of step 3 or step 6, communication is performed via the selected receiving path (step 7). If the communication is continued (NO in step 8), the process waits for an appropriate time that can follow the fluctuation speed of the line quality (step 9), and returns to step 1 to perform the same processing. .
Thus, the changeover switch 412 is provided at predetermined time intervals.
Is performed and the communication is completed (step 8).
YES), the current switch control process ends.

[2] Description of Second Embodiment

FIG. 4 shows a digital satellite communication system.
1 shows a configuration of a satellite TV conference system as an embodiment.
FIG. 5 shows the configuration of the X satellite earth stations 102 and 112 of FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 5, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

In this system, the X, Y and Z stations are:
It exists in the coverage area of two satellites A and B. X
The stations and the Y station include, in addition to the antennas 101 and 201 for the satellite A and the satellite earth stations 102 and 202 corresponding to the antennas 101 and 201, an antenna 112 for the satellite B,
Satellite communication earth stations 112 and 212 corresponding to 211 and antennas 111 and 211 are provided.

Further, the Y station includes a satellite communication earth station 212.
213 and echo canceller 2 corresponding to
14 are provided. Codec 213 has camera 2
The output signal of the microphone 207 is supplied to the echo canceller 214.

At the Z station, an antenna 301 for the satellite B and a satellite communication earth station 302 are provided. Although not shown, the Z station is provided with an echo canceller, a camera, a monitor, a microphone, a speaker, and the like.

A transmission signal from the Y station is input to the satellite communication earth station 112 of the X station via the Z station. As shown in FIG. 5, the satellite communication earth station 112 of the X station receives the
1, a demodulator 502 and an error correction decoder 503. The error rate Ez measured by the error correction decoder 503 is equal to the error rate monitor 410 in the satellite communication earth station 102.
Is input to Further, a received signal from the Z station is input to the changeover switch 412.

That is, in the second embodiment, the transmission signal from the Y station is input to the satellite communication earth station 102 of the X station via the satellite A, and the transmission signal from the Y station is transmitted to the satellite B, Satellite station earth station 11 of station X via station B and satellite B
2 is input.

The control unit 4 in the satellite communication earth station 102 of the X station
11 is an error rate E of a signal received from the Y station via the satellite A.
The changeover switch 412 is controlled based on y and the error rate Ez of the received signal from the Z station via the satellite B. Since the control method of the changeover switch 412 is the same as that of the first embodiment, the description is omitted.

Here, FIG. 5 shows that the error rate monitoring unit 410, the control unit 411, and the changeover switch 412 are configured inside the satellite communication earth station 102.
These may be used as external devices while keeping the connection.

[3] Description of Third Embodiment

FIG. 6 shows a digital satellite communication system.
1 shows a configuration of a satellite TV conference system as an embodiment.
6, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. In addition, the X station satellite communication earth station 10
The configuration of 2, 112 is the same as that of the satellite communication earth stations 102, 112 shown in FIG.

In the satellite TV conference system shown in FIG. 6, unlike the satellite TV conference system shown in FIG.
The Y station and the X station are directly connected by a single hop by using the line.

That is, in the third embodiment, a transmission signal is input from the Y station to the satellite communication earth station 102 of the X station via the satellite A, and a transmission signal is transmitted from the Y station to the satellite B. The signal is input to the satellite communication earth station 112 of the X station via the communication terminal.

The control unit 4 in the satellite communication earth station 102 of the X station
Reference numeral 11 (see FIG. 5) controls the changeover switch 412 based on the error rate Ey of the received signal from the Y station via the satellite A and the error rate Ez of the received signal from the Y station via the satellite B. . Since the control method of the changeover switch 412 is the same as that of the first embodiment, the description is omitted.

In the first and second embodiments, only the Z station has been described as a spare route. However, the present invention can be applied to the case where the number of passing stations is further increased. In that case, the reception system of the X station increases by the number of the stations.

In the Z station serving as the relay station, the reception signal and the reception clock output from the satellite communication earth station 302 through the RS449 interface are input to the transmission signal and the transmission clock. If possible, video and audio may be reproduced once by a codec and an echo canceller (not shown), and then transmitted again from the satellite communication earth station 302 and the antenna 301 via the codec and the echo canceller.

In the above embodiments, the present invention is applied to the receiving system of the X station, but the present invention can also be applied to the receiving system of the Y station.

[0067]

According to the present invention, even when an economical and simple digital satellite communication system is used, it is possible to avoid a situation where the line quality is deteriorated or the communication is disconnected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a satellite TV conference system according to a first embodiment.

FIG. 2 is a block diagram showing a configuration of a satellite communication earth station 102 in the X station of FIG.

FIG. 3 is a flowchart illustrating a control processing procedure of a changeover switch 412 performed by a satellite communication earth station 102 of the X station in FIG. 1;

FIG. 4 is a block diagram illustrating a configuration of a satellite TV conference system according to a second embodiment;

5 is a satellite earth station 102, 112 in the X station of FIG. 4;
FIG. 3 is a block diagram showing the configuration of FIG.

FIG. 6 is a block diagram illustrating a configuration of a satellite TV conference system according to a third embodiment.

FIG. 7 is a block diagram showing a configuration of a conventional satellite TV conference system.

8 is a block diagram illustrating a configuration of a satellite communication earth station 102 in the X station in FIG. 7;

[Explanation of symbols]

102, 112, 202, 212, 302 Satellite communication earth station 103, 203, 213 Codec 104, 204 214 Echo canceller 105, 205 Camera 106, 206 Monitor 107, 207 Microphone 108, 208 Speaker 404, 407, 501 Receiver 405, 408, 502 Demodulator 406, 409, 503 Error correction decoder 410 Error rate monitoring unit 411 Control unit 412 Switch

Claims (3)

[Claims] The system has N or more (N ≧ 2) receiving systems from the same satellite, and one receiving system is connected to another predetermined digital satellite communication device via a single hop route via a satellite. The remaining (N-1) reception systems are connected to the other predetermined digital satellite communication device through a path of at least double hops relayed by a relay station, and are provided for each reception system and receive. An error correction decoder that corrects a signal error and detects an error rate, an error rate monitoring unit that monitors each bit error detection output of a received signal corrected by each error correction decoder, and monitoring by an error rate monitoring unit A digital satellite communication device, comprising: a changeover switch for selecting one system reception signal from N reception systems based on the result. 2. The system has N or more reception systems (N ≧ 2), one of which is connected to another predetermined digital satellite communication device via a first satellite via a single hop route, and Of the (N-1) receiving systems are connected to the other predetermined digital satellite communication device through a double hop or more route relayed by a relay station via another satellite different from the first satellite. An error correction decoder that is provided for each reception system and corrects an error in a received signal, detects an error rate, and monitors a bit error detection output of the received signal corrected by each error correction decoder. A digital satellite communication apparatus comprising: an error rate monitoring unit; and a changeover switch for selecting one reception signal based on the monitoring result of the error rate monitoring unit and from reception signals of N reception systems. . 3. There are N or more reception systems (N ≧ 2), and one reception system is connected to another predetermined digital satellite communication device via a first satellite via a single hop route, and The (N-1) receiving systems are connected to the other predetermined digital satellite communication device by a single hop route via another satellite different from the first satellite, and are provided for each receiving system. An error correction decoder that corrects an error in a received signal and detects an error rate, an error rate monitoring unit that monitors a bit error detection output of the received signal corrected by each error correction decoder, and an error A digital satellite communication device, comprising: a changeover switch for selecting one of the received signals of the N receiving systems based on the result of monitoring by the rate monitoring unit.