JPH10341213A - Satellite communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the satellite communication system for unidirectional data communication where a code error is reduced and channel quality is improved. SOLUTION: A time division multiplexer 3 uses two ways of data sent through two channels from a host computer 2 thrice respectively and applies time division multiplex to them as 6-channel data. Receiver side earth stations 7a-7k compare three ways of reception data relating to same transmission data and select reception data in which no code error is seemingly in existence to execute error correction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a satellite communication system for one-way data communication, and more particularly to a satellite communication system effective for reducing code errors.

[0002]

2. Description of the Related Art Due to its wide area and broadcast capability, a satellite communication system simultaneously transmits the same data (for example, futures transactions or gold prices) from a host computer at the head office in Tokyo to data terminal devices at branches in various parts of Japan. Etc.) for unidirectional data communication.
In such a satellite communication system, error control is performed in order to obtain a required line quality. As a method of this error control, emphasis is placed on avoiding a decrease in transmission efficiency or throughput. So-called FEC
(Forward Error Correction
n).

[0003]

As described above, in a satellite communication system for performing one-way data communication, FEC is generally employed as error control. However, there is a limit to the removal of code errors in this FEC. However, it is difficult to say that sufficient error control is possible. On the other hand, a current satellite communication system for one-way data communication will be described with reference to FIG. 1 for describing an embodiment of the present invention. Also, since the number of data transmission channels of the host computer 2 is generally two, four channels are not used and are empty. It can be considered that the data sent from a device other than the host computer 2 can be used effectively by using the empty channel, but data from the host computer 2 used for a specific purpose is not used. Since multiplexing with data from other devices by the time-division multiplexing device 3 is not preferable for the operation of the entire satellite communication system, the above-mentioned use is not adopted, and an empty channel is left. ing.

The present invention has been made in view of the above circumstances, and provides a satellite communication system for unidirectional data communication in which code errors can be further reduced by effectively utilizing the empty channel. With the goal.

[0005]

SUMMARY OF THE INVENTION A satellite communication system for one-way data communication is constructed as follows. That is, a host computer having a transmission line of N (here, N is an integer of 1 or more and the same applies hereinafter) channels for transmitting data at a predetermined data transmission rate, and Input the data of the N channels sent via the transmission line,
The data of each of the N channels is M
(Where M is an integer equal to or greater than 2 and the same applies to the following), data of M × N channels is obtained, and these are multiplexed in a time-division manner. The time-division multiplexing device transmits the signal to the transmitting-side digital service unit connected to the transmitting-side digital service unit and the time-division multiplexed signal from the receiving-side digital service unit connected to the receiving earth station antenna. M × N
Input the received data for the number of channels and decompose it,
For each of the N channels, M data are obtained and this M
And a receiving-side time-division multiplexing device that compares the individual data as much as possible, selects data that is most likely not to be affected by noise, and sends the selected data to the data terminal device as data of the channel. A configuration was provided.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to an embodiment of the present invention shown in the drawings. FIG.
Shows the configuration of the above-described embodiment, which includes the transmitting earth station 1, the communication satellite 6, a large number of receiving earth stations 7a, 7b,... 7k, and the receiving earth station 7a. Data terminals 11a, 11b,... 11m which receive data sent from these receiving earth stations 7a etc.
…….

The host computer 2 in the transmitting earth station 1 is an existing one generally used.
The transmission-side host computer has a function of transmitting transmission data through two channels having a data communication speed of 9600 bits / second or less. The time-division multiplexing device 3 has a configuration to be described later, and obtains transmission data for six channels by using transmission data transmitted from the host computer 2 on two channels three times each. This is a circuit section for performing multiplexing in a time-division manner (in multiplexing, multiplexing is performed by adding a demultiplexing bit) and transmitting.

The digital service unit 4 has a convolutional encoder having a data coding rate of 3/4, and passes the multiplexed transmission data sent from the time division multiplexer 3 through the convolutional encoder. And transmits the data to the communication satellite 6 via the earth station transmitting antenna 5. The digital service unit 4 is connected to the earth station transmitting antenna 5 by 192.
Data is transmitted and received at a rate of 64 kilobits / second with the time-division multiplexing device 3, respectively. The communication satellite 6 is a communication satellite that can use a digital service of 192 kilobits / second by a satellite communication carrier.

Each of the receiving earth stations 7a, 7b,..., 7k is an earth station having the same configuration and the same function, and receives data unilaterally transmitted from the transmitting earth station 1.
Data terminals 11a, 11b,..., 11m,.
At a data communication speed of 9600 bits / second or less. As described above, receiving earth stations 7a, 7b,..., 7k
Have the same configuration, so the receiving earth station 7
a will be described, and the other description will be omitted. Digital service unit 9 in receiving earth station 7a
Takes in the data transmitted from the communication satellite 6 via the earth station receiving antenna 8 and executes the tentative error correction by the built-in Viterbi decoder upon encoding in the digital service unit 4 Further, the circuit section transmits the time-division multiplexed data for six channels obtained by executing the error correction processing described later according to the present invention to the time-division multiplexing device 10. The time-division multiplexing device 10 has a configuration to be described later, and the time-division multiplexed data for each of the six channels sent from the digital service unit 9 (as described above, three channels if no code error has occurred, Each minute has the same data.
The two types of data that have been captured and transmitted are compared, and for each of the two types of transmitted data, three data are compared, and the one that is most likely to contain no code error is selected. This is a circuit unit that obtains data for two channels sent from the computer 2, passes the data through a built-in modem, and sends the data to the data terminal device 11a or the like via an analog line.

FIG. 2 shows the configuration of the time division multiplexer 3 in detail. The interface 15 is an interface for receiving transmission data transmitted from the host computer 2 on one channel, and the interface 16 is an interface for receiving transmission data transmitted from the host computer 2 on another channel. The connection circuit 17 for channel 1, the connection circuit 18 for channel 2, and the connection circuit 19 for channel 3 all receive the same data sent from the host computer 2 on one of the above channels via the interface 15. Are transmitted to the multiplexing circuit 23 as data for one independent channel. The connection circuit 20 for channel 4, the connection circuit 21 for channel 5, and the connection circuit 22 for channel 6 all receive the same data sent from the host computer 2 via the interface 16 via the other channel. Are transmitted to the multiplexing circuit 23 as data for one independent channel. The multiplexing circuit 23 receives the two types of transmission data of six channels sent from the channel 1 connection circuit 17 from the channel 6 connection circuit 22 and multiplexes them in a time-division manner. In this multiplexing, two bits are added as a demultiplexing bit at the time of this multiplexing), and this is a circuit unit for sending this to the digital service unit 4 described above.

FIG. 3 shows the structure of the time division multiplexing device 10 in detail. The decomposition circuit 30 receives the time division multiplexed data for 6 channels sent from the digital service unit 9, This is a circuit section which decomposes the data into data of each channel and transmits the data in parallel. Channel 1
Data transmission circuit 31, channel 2 data transmission circuit 3
The data transmission circuit 33 for channel 2 and channel 3 fetches data of three independent channels related to the same data (data transmitted by the one channel of the host computer 2), and transmits the data to the comparison and selection circuit 37. It is a circuit part. Further, the data transmission circuit 34 for channel 4
The data transmission circuit 35 for channel 5 and the data transmission circuit 36 for channel 6 respectively take in data of three independent channels related to the same data (data transmitted by the other channels of the host computer 2) and fetch the data. This is a circuit section for sending out to the comparison and selection circuit 38.

The comparison / selection circuit 37 receives three data (originally, the data transmitted from the channel 1 data transmission circuit 31).
This is a circuit unit for comparing data which is the same if there is no code error), selecting data having the lowest possibility of including a code error, and sending it to the modem 39. The comparison selection circuit 38 has the same configuration as the comparison selection circuit 37,
This is a circuit unit having a function, and compares three data (which are also the same data if there is no code error) sent from the channel 4 data transmission circuit 34 and the like, and contains the most code error. This is a circuit unit that selects data having a low possibility and sends it to the modem 40. The modem 39 is a circuit section for transmitting digital signal data transmitted from the comparison and selection circuit 37 through an analog line. Similarly, the modem 40 converts the digital signal data transmitted from the comparison and selection circuit 38 into analog data. This is a circuit unit for transmitting data via a line. Amplifying circuits 41 and 42 are circuit units for amplifying data signals transmitted from modems 39 and 40 and transmitting the amplified signals to the data terminal device 11a and the like.

Next, the operation of the present embodiment configured as described above will be described. For example, now, "1", "A", "A" are transmitted from one of two channels for transmitting data from the host computer 2 to the time division multiplexer 3 in FIG.
Are sequentially transmitted in this order.
It is assumed that 1-bit data indicated by "2", "B", and "A" are sequentially transmitted from the other channel in synchronization with "1", "A", and "A", respectively. The time-division multiplexing device 3 fetches each of the six pieces of 1-bit data as burst data of each channel, and performs time-division multiplexing to make one frame 8 bits (including the above-mentioned 2 bits for demultiplexing), It is assumed that this time division multiplexed signal is transmitted to the digital service unit 4. The time division multiplexed signal is transmitted to the digital service unit 4 as described above.
Is transmitted as a convolution signal having a coding rate of 3/4, and is given to a digital service unit 9 via an earth station transmitting antenna 5, a communication satellite 6, and an earth station receiving antenna 8,
In the digital service unit 9, the above-mentioned encoding is deciphered. That is, when transmitting to a satellite line, encoding is performed for every three bits, so that the eight bits constituting one frame are included in separate codes.
FIG. 4 shows this state in detail. That is, 1-bit data “1” transmitted through one channel of the host computer 2 and 1-bit data “2” transmitted through another channel of the host computer 2 are used three times each. One frame consisting of 8 bits (6 bits in the figure), which is data for 6 channels (ie, 6 bits), and 2 bits are added to these as bits for demultiplexing (indicated by the characters “appended” in the figure). The leftmost frame) is 2 for multiple decomposition.
A set of three bits (indicated by a character F1 in the figure) of one bit and one bit of one-bit data “1” is encoded as a set, and the three bits of one-bit data “1” and “2” following this are encoded.
Bits (indicated by the character F2 in the figure) are encoded as a set, and thereafter, as in the above, three bits are encoded as a set. That is, in a satellite link (in which a random error is captured by this link), data is transmitted in units of 3 bits as described above. For this reason, if the same data happens to be included in two sets, the following processing becomes possible. When the digital service unit 9 cannot be subjected to the error correction by the Viterbi decoder (1 as described above). If three bits, which are two codes, are lost), the above processing according to the present application is executed.
That is, even when the code corresponding to the 3 bits indicated by the character F5 is lost due to a random error in the satellite link, the same data remains in the set indicated by the character F4 and the set indicated by the character F6. Therefore, reproduction is performed by using the remaining data. Then, the time-division multiplexing apparatus 10 selects one of the three types of received data of the transmitted data which has the lowest possibility of containing a code error and transmits it to the data terminal device 11a or the like.

With the above-described operation, in the present embodiment, it is possible to perform a process of reducing a code error to some extent while avoiding a decrease in transmission efficiency or throughput.

[0015]

As described above in detail, according to the present invention, a satellite communication system for one-way data communication in which a code error can be further reduced by utilizing an empty channel generated in time division multiplexing. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing the configuration of the time division multiplexing device 3 in FIG. 1 in detail.

FIG. 3 is a diagram showing the configuration of the time division multiplexing device 10 in FIG. 1 in detail.

FIG. 4 is a diagram for explaining the operation of the embodiment.

[Explanation of symbols]

 1 transmitting earth station 2 host computer 3 time division multiplexing device 4 digital service unit 5 earth station transmitting antenna 6 communication satellite 7a receiving earth station 8 earth station receiving antenna 9 digital service unit

Claims (1)

[Claims] 1. A satellite communication system for performing one-way data communication, wherein each of the data communication systems transmits data at a predetermined data transmission rate.
(Where N is an integer of 1 or more, and the same applies to the following). A host computer having transmission channels for the channels, and the N channels transmitted from the host computer via the transmission lines. Enter the data of
By using the data of each channel of the M channels M times (where M is an integer of 2 or more, and the same applies to the following), data of M × N channels is obtained,
A transmitting-side time-division multiplexing device that multiplexes them in a time-division manner and sends them to the transmitting-side digital service unit connected to the transmitting earth station antenna, and a receiving-side digital service unit connected to the receiving earth station antenna The received data for the M × N channels transmitted in a time-division multiplexed state is input and decomposed, and M data is obtained for each of the N channels. A receiving-side time-division multiplexing device that compares the M data as much as possible, selects data most likely to be least affected by noise, and sends the selected data to the data terminal device as data for the channel; A satellite communication system comprising: