JP2644651B2 - Satellite communication system and data distribution type transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data delivery type transmission method for transmitting transmission request data from a plurality of users to one or more destinations designated by each user by satellite communication. is there.

[0002]

2. Description of the Related Art Conventionally, a satellite communication system sharing a transmitting earth station, a communication satellite, and a carrier by a data distribution network using a communication satellite as a relay station is configured as shown in FIG. In FIG. 9, A is a transmitting earth station that transmits data to the communication satellite 1, and is sequentially connected to the antenna 2, the transmitting device 3, the transmitting frequency converting device 4,
It includes a modulator 5 and a buffer memory 6 for clock matching between the satellite line and the terrestrial line.

[0003] Reference numeral 7 denotes a terminal device of a first user, 8 denotes a terminal device of a second user, 9 denotes a transmission signal transmitted from the transmitting earth station A, 11 denotes a user-only receiving station and a data terminal device, and
2 is a reception-only station and data terminal device of another user, 13
Is a terrestrial line of the first user, 14 is a terrestrial line of the second user, and 20 is a switch for connecting the user terminal device and the transmitting earth station device A in a time zone designated by the user.

Next, the operation will be described. The terminal device 7 sends the requested data to the transmitting earth station A via the ground line 13 in response to a request from the user. In the transmitting earth station A, the transmitted data is stored in the buffer memory 6 via the switch 20 and is converted into a clock for the satellite line. Then, the data is transmitted from the antenna 2 via the modulating device 5, the transmitting frequency converting device 4 and the transmitting device 3. The signal is transmitted to the satellite 1 as a transmission signal 9.

[0005] The transmitted signal is retransmitted to the earth via the communication satellite 1 and received by all reception-only stations. The terminal device of the reception-only station detects the address addressed to the own station in the header of the received data, and sends the received data to the terminal device.
Since the other reception-only stations are not headers addressed to the own station, the reception data is discarded without being taken into the terminal device. The same is performed for the second user.

In the above series of operations, the first user and the second user independently transmit data, so that the data transmission timings overlap, and a collision may occur at the entrance of the transmitting earth station A. In order to avoid this problem, the transmission time zone of the user is allocated in advance, the predetermined time zone is allocated by the switch 20, and the user terminal devices 7, 8 and the transmission earth station A are connected. Station A
Can be shared.

FIG. 10 shows an example using the above satellite communication system.
The time sequence of a transmission signal 9 for transmitting data from the two terminal devices 7 and 8 from the transmitting earth station A is shown. Reference numerals 71 and 72 denote transmission signals for transmitting data transmitted from the terminal device 7 and 81 and 82, respectively. Indicates a transmission signal for transmitting data transmitted from the terminal device 8.

The above description relates to the case where the terminal device 7 or 8 independently broadcasts data and sends data addressed to a specific reception-only station. Via terminal device 7 or 8
The same operation is performed when a data transmission request is made.

In the above description, a satellite communication system in a data distribution type network has been described in the case of a station dedicated to receiving data via a single-transmission satellite line. No change.

[0010]

Since the conventional satellite communication system is configured as described above, in order to perform data transmission of a plurality of users, two or more data transmissions are performed based on the user's request.
In general, a time slot must be allocated, so that an idle time T is generated as shown in FIG. 10, and it is difficult to increase the utilization time rate of the satellite line. There is a problem in that the cost competitiveness is poor, which hinders the spread of satellite communications.

The invention described in claim 1 has been made in order to solve the above problems, and a plurality of users share a transmitting earth station facility, a communication satellite used as a relay station, and a carrier wave frequency. An object of the present invention is to obtain a satellite communication system capable of maximizing the utilization time rate of a satellite link.

According to a second aspect of the present invention, there is provided a data distribution method capable of overcoming a limitation in improving the efficiency of a communication line and further improving the utilization time rate of the communication line.
The aim is to obtain a transmission method .

[0013]

According to a first aspect of the present invention, there is provided a satellite communication system comprising first and second transmission lines.
In addition, the accumulated amount of the buffer memory does not exceed the predetermined value
In such a case, control is performed to transmit using the first transmission line,
If the accumulated amount of the buffer memory exceeds a predetermined value, the first
Transmission using the transmission line and the second transmission line.
Controlled.

The data according to the second aspect of the present invention.
The delivery type transmission method is based on the urgency of the transmitted data.
Priority is given to sending data with high urgency from the buffer memory
Fetching at the time and fetching transmission data with low urgency
The urgent transmission data is stored in the buffer memory
In such a case, remove the transmission data with low urgency.
Stop and retrieve the urgent transmission data
It was done.

[0015]

The satellite communication system according to the first aspect of the present invention.
The system has first and second transmission lines, and a buffer.
If the storage amount of the memory does not exceed a predetermined value, the first transmission
Controls transmission using the line, and stores data in the buffer memory.
If the load exceeds a predetermined value, the first transmission line and the
Control by using the transmission line 2
Up to the point where some overflow is allowed,
It is possible to improve the average utilization time rate of the original line.
And respond to sudden fluctuations in traffic,
Ensure that urgent transmission data with high urgency is transmitted more reliably
And be able to.

Further, the data according to the second aspect of the present invention.
Data transmission method, the transmission data corresponds to the urgency,
Priority transmission data with high urgency from buffer memory
Retrieve transmission data at any time and with low urgency
During transmission, urgent transmission data is stored in the buffer memory.
In the event of a
To retrieve the urgent transmission data
To prevent collision of transmitted data.
Transmission of transmission data with high urgency can be given priority
Become like

[0017]

[Embodiment 1] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 10 is a block diagram showing one embodiment of the invention described in claim 1, and the same or corresponding parts as those in the conventional satellite communication system shown in FIG. 9 are denoted by the same reference numerals and description thereof is omitted. In FIG. 1, 6a is a buffer memory for storing emergency transmission data, and 6b is a buffer memory for storing non-emergency transmission data. Here, the emergency transmission data is
It is data that is expected to be sent within the normal transmission time, and non-emergency transmission data is considered to be sufficient for file transfer data that should be sent during the day, or that it should be obtained within tens of minutes or hours. Search material. These emergency, non-emergency distinction is of some users is given by the user prior to transmitting the data.

Reference numeral 17 denotes the buffer memories 6a, 6
b, a buffer memory read interface for interfacing the read of data stored in the buffer memory 18; a read address controller 18 for giving a read address to the buffer memory read interface 17; 19, an interface for writing data to the buffer memories 6a and 6b. A write address control unit for giving a write address to the buffer memory write interface unit 19; and a buffer memory processor 22 for controlling the read address control unit 18 and the write address control unit 21. is there. B is the buffer memory 6
a, 6b, buffer memory read interface 1
7, read address control unit 18, buffer memory write interface unit 19, write address control unit 2
1. Data transmission processing means including the buffer memory processor 22.

Here, in the transmission of the satellite communication system, signals having various bands or speeds are usually multiplexed and transmitted in order to sufficiently use the frequency band of the communication satellite 1 which is a repeater. There are two methods of frequency division multiplexing (FDM) and time division multiplexing (TDM), and the effectiveness of the present invention is not changed by using either of them. Here, frequency multiplexing, particularly pre-assignment, single assignment・ Channel per carrier (Single Cha)
nper Per Carrier (hereinafter referred to as SCPC). SCPC means that one carrier is used for signal transmission of one channel. As shown in FIG. 2, multiplexing is performed by arranging n waves of carriers having a frequency bandwidth corresponding to the transmission speed of a transmission signal at predetermined intervals. Perform In this case the channel 1 is a pre-assignment method to leave assigned the frequency of the carrier wave from the beginning so that use a carrier wave of f _1. In the case where a large number of receiving stations are used in a data distribution network as in the application example of the present invention, this system is taken as an example because fixing the frequency makes the receiving stations simpler and cheaper and simplifies the system configuration. FIG. 1 shows one channel, and when the entire satellite repeater is used, n unit configurations in FIG. 1 may be arranged in parallel.

Next, the operation will be described. The terminal device 7 of the first user sends the requested data to the data transmission processing means B via the ground line 13. In the data transmission processing means B, when the transmitted data is received by the buffer memory write interface unit 19, an incoming interruption instruction is given to the write address control unit 21 and, at the same time, the buffer memory The data received by the write interface unit 19 is written to the buffer memory 6a or 6b. In this case, the data transmitted from the terminal device 7 of the first user is classified into emergency transmission data and non-emergency transmission data,
Since the identification code is assigned to each, the emergency transmission data is stored in the buffer memory 6a, and the non-emergency transmission data is stored in the buffer memory 6b, under the control of the write address control unit 21 in accordance with the instruction of the buffer memory processor 22, respectively. Classified and written in the order of arrival.

The emergency transmission data stored in the buffer memory 6a is read out via the buffer memory readout interface 17 according to an instruction from the readout address controller 18. At this time, the user identification signal generated by the buffer memory processor 22, the destination, and the data sequence number
The number is added to the header of the data. On the other hand, the data classified as the non-emergency transmission data is stored in the buffer memory 6b by the write address control unit 2 instructed by the processor 22.
The data is written in the order of arrival by the control of 1. The stored non-emergency transmission data is read when the buffer memory 6a storing the emergency transmission data becomes empty.
The packet is divided into packets of an appropriate length according to the instruction of 8, and is read via the buffer memory read interface unit 17. At this time, the user identification signal , the destination, and the sequence number of the data generated by the buffer memory processor 22 are added to the header of the data as in the case of the emergency transmission data. The non-emergency transmission data is read out and the modulation device 5
When the data for emergency transmission is written to the buffer memory 6a during the transmission to the buffer memory 6a, the buffer memory processor 22 instructs the read address control unit 18 to stop reading the non-emergency data, and
The read address control unit 18 is instructed to read the emergency transmission data written in a with priority.

The user identification signal 1 is read from the buffer memory 6a or 6b , and the destination number and data sequence number are read.
The data with the signal added to the header portion is transmitted to the communication satellite 1 as a transmission signal 9 via the modulation device 5, the transmission frequency conversion device 4, the transmission device 3, and the antenna 2. When receiving the transmission signal 9, the communication satellite 1 retransmits the signal toward the earth, and this signal is received by all the reception-only stations.
The receiving-only station detects the user identification signal in the header part of the received data and the address addressed to the own station, and takes it into the terminal device. Other reception-only stations discard the received data unless an address signal addressed to the own station is detected. The station receiving the non-emergency data stores the data in the memory of the terminal device in the order of arrival, and receives the data until all the data are collected. The second user performs the same operation as the first user. Further, the number of users may be increased.

FIG. 3 is a diagram showing a temporal arrangement of user data transmitted as the transmission signal 9. FIG. 3A shows a case of a conventional satellite communication system in which there is no distinction between emergency transmission data and non-emergency transmission data, and a vacant time occurs in the temporal arrangement of transmission signals. (B) is an example of the satellite communication system according to the first embodiment, in which non-emergency transmission data is inserted and transmitted using the idle time of emergency transmission data transmission.
This indicates that efficient transmission with almost no idle time is possible. In the first embodiment, the user terminal device 7,
8 shows the case of the broadcast distribution of the data independently transmitted from the receiver 8 and the data distribution to the specific reception-only station, but from the reception-only station 11 or 12 to the terminal device 7 or 8 via, for example, a ground line, The same applies to the case where a data distribution request is made.

Embodiment 2 FIG. Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing an embodiment according to the second aspect of the present invention. The same parts as those in FIG. In FIG. 4, reference numerals 6b and 6c separately store non-emergency transmission S data (first non-emergency transmission data) and non-emergency transmission L data (second non-emergency transmission data) described later. Buffer memories 23 and 24 connect the user's terminal devices 7 and 8 and the buffer memory writing interface unit 19, and in particular, the non-emergency transmission L
A terrestrial line used for data transmission.

Here, in the distribution system according to the second embodiment, a still image such as a facsimile,
All kinds of data to be delivered in one direction from one place to another desired place, such as data distribution of data, floppy disk or laser disk data, and file transfer, are handled. In this embodiment, the data is as follows. It is classified into three types according to the degree of urgency.

[0026]

[Table 1]

In particular, L data for non-emergency transmission is a large amount of data such as CAD data, high-definition still images, and computer file updates, and the time from data collection to transmission at the transmitting station is allowed to be, for example, half a day or one day. The feature is that the data is wide and can be expected to be distributed periodically by reservation. Since the reservation-based data generally has a large data amount, the data for emergency transmission and the S for non-emergency transmission are used.
As compared with the case of data, a higher speed is required as a communication line, and there is a possibility that the line will be blocked for a long time. In such a case, it is necessary to input through another ground line 23, 24. As another method, it is conceivable that the data is called from the transmitting station when the user has the data.

Next, the operation will be described. Transmission request data from the user is sent from the terminal devices 7 and 8 to the data transmission processing means B via the ground lines 13 and 14 or 23 and 24 according to the respective protocols. In the data transmission processing means B, the data is sent to the write address control unit 21 via the buffer memory write interface unit 19, and at the same time, the buffer memory 6a,
6b and 6c. In this case, the data sent from the user's terminal devices 7 and 8 are classified into emergency transmission data, non-emergency transmission S data, and non-emergency transmission L data, each of which is provided with an identification code. The data is classified into the buffer memory 6a, the non-emergency transmission S data is stored in the buffer memory 6b, and the non-emergency transmission L data is stored in the buffer memory 6c under the control of the write address control unit 21 in accordance with the instruction of the buffer memory processor 22, respectively. And written in the order of arrival.

The emergency transmission data stored in the buffer memory 6a is read out via the buffer memory read interface 17 according to an instruction from the read address controller 18. At this time, the user identification signal generated by the buffer memory processor 22 , the destination , and the data sequence number
The number is added to the header of the data. On the other hand, the non-emergency transmission S data stored in the buffer memory 6b passes through the buffer memory read interface unit 17 according to the instruction of the read address control unit 18 when the buffer memory 6a storing the emergency transmission data becomes empty. Read out. At this time, the user identification signal generated by the buffer memory processor 22 as in the case of the emergency transmission data ,
The destination and the sequence number of the data are added to the header of the data. When the emergency transmission data is written to the buffer memory 6a while the non-emergency transmission S data is being read and sent to the modulation device 5, the buffer memory processor 2
Numeral 2 instructs the read address control unit 18 to stop reading the non-emergency transmission S data, and instructs the read address control unit 18 to preferentially read the written emergency transmission data. When the buffer memory 6a becomes empty again, the start of reading of the non-emergency transmission S data is instructed by the above procedure, and the above procedure is repeated until a series of non-emergency transmission S data is read.

The non-emergency transmission L data stored in the buffer memory 6c is determined when the buffer memory 6a storing the emergency transmission data and the buffer memory 6b storing the non-emergency transmission S data are simultaneously emptied. The data is read via the buffer memory read interface 17 according to an instruction from the read address control unit 18. At this time, the user identification signal, destination , and data sequence number generated by the buffer memory processor 22 are added to the data header. While the L data for non-emergency transmission is being read and sent to the modulator 5, the buffer memory 6a or 6b
, The buffer memory processor 22 issues a read stop instruction to the non-emergency transmission L data to the read address control unit 18 and preferentially reads the written data. When the buffer memories 6a and 6b become empty at the same time, an instruction to start reading the non-emergency transmission data L is issued, and the above procedure is repeated until a series of non-emergency transmission L data ends.

Read out from the buffer memory 6a, 6b or 6c and read the user identification signal, the destination , and the sequence number of the data.
The data with the signal added to the header portion passes through a modulator 5, a transmission frequency converter 4, a transmitter 3 and an antenna 2, and is transmitted as a transmission signal 9 to a communication satellite 1 through a satellite line which is a dedicated line. Sent out. The communication satellite 1 retransmits the received signal toward the earth, and this signal is received by all reception-only stations. The corresponding receiving-only station detects the user identification number of the received data and the destination addressed to the own station and takes in the data. The other reception-only stations do not detect the destination signal addressed to themselves, so the received data is discarded. Also it station that requested the S data or non-urgent transmission L data for non-emergency transmission, stores data in the order of arrival if the data is divided into the memory of the receive-only station, the gathered set of data The data
The reception is determined to have been completed at the time of confirmation by the sequence number . The data fetched by the receiving-only station is sent to the receiving terminal under required interface conditions according to the protocol of the terminal used.

FIG. 5 is an explanatory diagram showing a temporal arrangement of user data sent to the satellite line, that is, a time distribution of transmission request data assuming a use state of the line.
FIG. 5A shows a case where only emergency transmission data is used, FIG. 5B shows a case where emergency transmission data is distinguished from non-emergency transmission S data, and FIG. 5C shows a case where non-emergency transmission L data is further added. . As described above, the second embodiment shows a case in which the pre-assignment SCPC is used, which is transmitted in parallel and randomly from a limited number of n users as shown in FIG. Means that the transmitted data is transmitted through an output line having a constant line capacity (transmission speed).

Here, when urgency is required for data transmission, it is necessary to make the capacity (transmission speed) of the output line larger than the capacity (transmission speed) of the input line corresponding to the peak of traffic. . Actually, since the line capacity cannot be arbitrarily selected, the output line capacity (for example, 64 kb / sec.
The number of users is determined in consideration of traffic according to c). FIG. 5A shows "time distribution of transmission request data" and "line use state" in such a state. As for the time distribution of the transmission request data, assuming that the user is mainly a business, traffic concentration is observed from 9:00 to 10:00 in the morning, at the beginning of the afternoon and around the end of business hours, as in a normal communication service, and thereafter becomes sparse. Is considered an average pattern. Although the actual traffic distribution is more complicated, it is normalized in this figure by the line capacity for simplicity. Since the time delay is small in the emergency transmission, the use state of the line is almost equal to the time distribution.

Next, FIG. 5B shows a case where non-emergency transmission S data for which a slight delay is recognized is added. In this case, transmission delay of non-emergency transmission S data is allowed,
Non-emergency transmission S data may be input over the capacity of the output line, and the line usage state can be transmitted with less idle time and more time efficient than when only emergency transmission data is used as shown in the figure. It is. However, as long as only data to be transmitted when a transmission request occurs, such as emergency transmission data or non-emergency transmission S data, traffic concentration in a specific time zone cannot be avoided, and when the output line capacity is adjusted to this, The vacant time in the intermediate time zone still remains considerably as shown in FIG. In addition , when the fluctuation of traffic due to the transmission date is anticipated, the free time ratio becomes even larger.

FIG. 5C shows a case where, in addition to the emergency transmission data and the non-emergency transmission S data, non-emergency transmission L data that can be expected to be regularly distributed by reservation as described above is newly added. It is. This non-emergency L data has a large amount of data. In this case, the line for the emergency transmission data and the non-emergency transmission S data may block the line for a long time. Input to the buffer memory separately from the emergency transmission data and the non-emergency transmission S data. As another method, it is conceivable that the data is called from the transmission side when the data is prepared on the user side. FIG. 5C shows the storage state of the non-emergency transmission L data separately captured from the emergency transmission data and the non-emergency transmission S data. By newly adding this non-emergency transmission L data, the idle time of the line is remarkably filled, and the line utilization time rate can be sufficiently increased. The efficiency gain depends on the daily traffic volatility. In the second embodiment, the data urgency is set to three levels as the most general one. However, the non-emergency S data level may be omitted according to the user's request, or the request may be responded to a more detailed request. Therefore, even if the number of stages of the non-emergency S data is increased, the concept is the same.

In Examples 1 and 2,
Transmission by the connection procedure according to the protocol determined by the terminal device used is performed between the transmitting terminal ← → data transmission processing means and the receiving-only station ← → receiving terminal, and is exclusively performed by the satellite line between the transmitting earth station → the receiving-only station. The line section is data transmission by one-way transmission. The fact that the dedicated line is unidirectional as described above means that the efficiency of data transmission is substantially improved because the procedure for setting and releasing the communication path every time communication is not required, and at the same time, the above-described data transmission processing means is used. hand,
It is suitable for directly transmitting a data signal sequence sent with almost no gap. In this system, when it is necessary to return a signal such as a delivery confirmation or a retransmission request from the receiving side to the transmitting side, a separate terrestrial line is used.

Further, the examples shown in FIGS. 1 and 4 are for the case where the receiving terminal is connected to a public line and a dedicated line in a receiving-only station or in the same premises. Sometimes, of course, they are connected by a public line. FIG. 4 illustrates the case where a satellite line is used as the dedicated line. However, even if a terrestrial dedicated line limited to one-way transmission is used, the same operation as a distribution system is performed. Similar effects can be obtained.

Embodiment 3 FIG. The second embodiment described with reference to FIG. 4 is a case where the pre-assignment SCPC is used in order to reduce the price of the reception-only station placed on the user side as much as possible, so that it is widely used by small users. For this reason, it is necessary to pack traffic with fluctuations from a large number of users into one line, and there is naturally a limit in improving the average utilization time rate of the line. In order to further increase the average utilization time rate of this line, if the required traffic increases rapidly and it is determined that one line cannot send data within a prescribed time, the second line that sends out the surplus data Must be provided.

FIG. 7 is a block diagram of a system according to such an embodiment. Most of the components are the same as those in FIG. 4, and the description of the same components will not be repeated. In the figure, 4a, 5a and 4
Reference numerals b and 5b denote frequency converters and modulators that respectively generate carrier waves of different frequencies, and reference numeral 25 denotes a transmission route selection processor that monitors the transmission status of two transmission routes and selects a transmission route. Reference numerals 9 and 10 are transmission signals transmitted from the transmitting earth station A via the frequency converter and the modulators 4a and 5a and 4b and 5b. FIG. 8 is an explanatory diagram showing the frequency spectrum of the repeater of the communication satellite 1. In the figure, reference numeral 41 denotes the bandwidth of the repeater (the communication satellite 1), and reference numerals 42 and 43 denote modulations with the frequency converters 4a and 4b, respectively. 2 shows the carrier spectrum of the transmission signals 9, 10 transmitted from the transmitting earth station A via the devices 5a and 5b.

Next, the operation will be described. Data that is classified in advance into one of emergency transmission data, non-emergency transmission S data, and non-emergency transmission L data according to the degree of urgency, and sent from the user terminal device to the data transmission processing means via the ground line. Are buffer memories 6a, 6b, 6c
, And thereafter transmitted to the transmitting earth station A in accordance with the order of urgency in accordance with the prescribed procedure. This procedure is as already described based on the second embodiment shown in FIG.

In this process, the traffic requested by some users increases, and one of the data amounts stored in the buffer memories 6a, 6b, and 6c exceeds a predetermined amount individually set within a predetermined time. When the data cannot be delivered to the buffer memory processor 22, the buffer memory processor 22 receives an instruction of an empty route from the transmission route selection processor 25, and designates the data of the buffer memory on a first-come, first-served basis on a user-by-user basis via the buffer memory read interface 17 each time. Data is sent to the route. When the amount of data stored in the buffer memory becomes smaller than a certain amount, transmission from another route is stopped, and transmission returns to the original one route only. If the amount of remaining data in the buffer memory exceeds a certain amount due to a sudden increase in traffic in two or more buffer memories at the same time, the data in the buffer memory containing the data of high urgency is transmitted first. I do.

The fixed amount for determining the start of the two-wave transmission can be determined in various ways, but the simplest example is shown below. Considering the urgency specified in the buffer memory, the remaining time allowed for the transmission of stored data is α hours, the transmission speed of the line for sending data is 64 kb / s, and the higher urgency is input within α hours. If the assumed data amount is D, the constant amount K is as follows.

K = α × 3600 × 64 kb-D

The signal sent back to the ground via the communication satellite 1 is received by all receiving-only stations. The reception-only station incorporated in this system has a function of receiving two carriers simultaneously, monitors the identification signal in the header section for the own station, and executes the terminal device only when data addressed to the own station is detected. And data not addressed to the own station is discarded. In this way, one extra carrier is provided, another route is provided, and two waves are used at the same time when necessary, so that the average utilization time rate of the original line can be reduced to a point where a certain amount of overflow is allowed even for traffic with fluctuations. It can be improved.

In the above description, an example of two-wave transmission in which another normal carrier is added with another spare carrier for a sudden increase in traffic has been described. However, the degree of traffic overflow is too frequent. Otherwise, it is also possible to set up one common spare carrier for N regular carriers.

[0046]

As described above, according to the first aspect of the present invention, the first and second transmission lines are provided and the buffer is provided.
If the storage amount of the memory does not exceed the predetermined value, the first transmission
Control to transmit using the communication line, and
If the accumulated amount exceeds a predetermined value, the first transmission line and
Since the transmission is controlled using the second transmission line,
To the point where the overflow
If we can improve the average utilization time rate of the line
Both respond to sudden changes in traffic,
High-speed emergency transmission data can be transmitted more reliably.
There is a clear effect.

According to the second aspect of the present invention, the transmission
The transmission data corresponds to the urgency, and the urgent transmission data
Priority from buffer memory at any time, and urgent
While retrieving inferior transmission data, send urgent transmission data.
If the data is stored in the buffer memory,
Stop fetching transmission data of low urgency and
Since it is configured to extract high transmission data,
Transmission data with high urgency while preventing data collision.
There is an effect that data transmission can be preferentially performed.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing frequency assignment in SCPC.

FIG. 3 is an explanatory diagram showing a temporal arrangement of transmission signals in the embodiment.

FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a temporal arrangement of transmission signals in the embodiment.

FIG. 6 is an explanatory diagram schematically showing a relationship between an input line and an output line of a buffer memory.

FIG. 7 is a configuration diagram showing a third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a frequency spectrum of the repeater in the embodiment.

FIG. 9 is a configuration diagram showing a satellite communication system in a conventional data distribution network.

FIG. 10 is a configuration diagram showing a satellite communication system in a distribution network of a conventional system.

[Explanation of symbols]

 1 Communication Satellite 6a Buffer Memory 6b Buffer Memory 6c Buffer Memory A Transmission Earth Station B Data Transmission Processing Means

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-132325 (JP, A) JP-A-61-128634 (JP, A) JP-A-57-37939 (JP, A) JP-A-61-37939 202541 (JP, A) JP-A 1-261032 (JP, A)

Claims (2)

(57) [Claims] 1. A satellite communication system based on a data distribution network for collecting transmission data from a plurality of users and transferring the collected data to a plurality of receiving earth stations using a transmitting earth station and a communication satellite as a relay station. Baffame storing distinguishes transmit data from the user to the urgent transmission data and non-urgent transmission data
Memory and the emergency transmission data and the non-emergency transmission data.
When taking out from the buffer memory, the emergency transmission data
Data for the non-emergency transmission data
And a transmission control unit for transmitting transmission data extracted from the buffer memory.
A first transmission line, which is provided separately from the first transmission line.
Second transmission for transmitting transmission data extracted from the memory
The line and the buffer memo according to the storage amount of the buffer memory
The transmission data taken out of the first transmission line and the
And / or transmit using the second transmission line.
Transmission line control means for controlling the transmission line control means, wherein the transmission line control means
If the value does not exceed the predetermined value, the first transmission line is used.
And transmit the emergency transmission data.
If the amount of data stored in the buffer memory exceeds
The transmission is performed using the first transmission line and the second transmission line.
A satellite communication system characterized by controlling the communication. 2. Data transmitted from a plurality of users is transmitted to a satellite.
Day to be forwarded to a destination designated by the respective users by the communication
In the data distribution type transmission method , the user side transmits transmission data when a transmission request occurs ,
The urgency of the data is lower than the data, and a transmission request is issued.
First non-emergency transmission data transmitted at birth,
1 is urgent data lower than the non-emergency transmission data
And the second non-consolidated distribution
It is divided into data for sudden transmission,
And transmit the transmitted data independently according to the identification code.
Transmission data, the first non-emergency transmission data, and
The buffer memo is divided into the second non-emergency transmission data.
The transmission data is stored in the
Data is preferentially retrieved from the buffer memory as needed
And the urgency during retrieval of transmission data of low urgency
High transmission data is stored in the buffer memory
Stops extracting the transmission data of low urgency
The transmission data with high urgency is taken out and the buffer
A data delivery type transmission method, wherein transmission data taken out of a memory is delivered to a destination by satellite communication via a dedicated line having a limited transmission direction.