JP2874602B2 - Satellite communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a satellite communication system, and more particularly, to a DAMA satellite communication system that performs frequency allocation control using a common control channel.

[0002]

2. Description of the Related Art As one of multiple access satellite communication systems for communicating voice and data between earth stations via satellites, frequency multiple access (FDMA: FDMA) that allocates a frequency to each communication line.
There is a method called "requency division multiple access". Among the FDMA systems, the SCPC (Single Channel Per Carrier) system is suitable for a satellite communication system composed of a large number of earth stations having a relatively small communication capacity. In the SCPC system, one carrier is allocated to one voice and data line, and thus the allocation is very flexible.

[0003] Also, when classifying based on frequency allocation,
Pre-Assignment Multiple Access (PAMA)
tiple Access) and demand assignment multiple access (DA)
MA: Demand Assignment Multiple Access) method. In the PAMA system, since the frequency is fixedly allocated, the line is put on hold even during communication, and the line use efficiency is poor, and the number of earth stations accommodated is limited. For this reason, the DAMA system in which a frequency is assigned only when a communication request occurs is often adopted.

A DAMA satellite communication system is generally configured as shown in FIG. In addition, DAMA
In a satellite communication system of the system, there is a configuration in which satellite channel allocation control is performed only by a slave station and there is no master station. Here, a configuration in which central control is performed by the master station is shown. That is, as shown in FIG. 1, the DAMA satellite communication system includes a master station C for managing the assignment of satellite channels and the connection status of each slave station, a plurality of n slave stations R1 to Rn, and a relay station. And a satellite S.

[0005] A slave station that has issued a communication request is a CSC (Comm.
The connection control information is exchanged by a common control channel called “on Signaling Channel”. Now, assuming that a communication request to another slave station Rn occurs at a certain slave station Rk, the slave station Rk allocates a band required for transmission with the slave station Rn to which the slave station Rn is connected via the satellite S by a common control channel. To the master station C.

In response to the connection request, the master station C checks whether the connected slave station Rn is in a communicable state and, if possible, searches a vacant request band from the frequency bands to be managed, if possible.
The found band is notified to the requesting slave station Rk and the connected slave station Rn via the satellite S using a downlink common control channel. As a result, the slave station Rk that has made the connection request and the slave station Rn that is the connection destination perform communication by the SCPC using the frequency allocated via the satellite S. Thereafter, the slave station that has completed the communication transmits a disconnection notification to the master station C. When the master station C receives this disconnection notification,
Release the allocated frequency.

[0007]

However, in the above-mentioned conventional DAMA satellite communication system, the use time of the channel by the slave stations communicating between the slave stations is not constant, so that the use time between the allocated frequencies is not fixed. End, and a released band may occur. If the information transmission speed in each communication is the same, the frequency bandwidth allocated to the slave station is the same as shown in FIG. 6, so that the reassignment of the released frequency band can be flexibly performed.

However, in a system accommodating groups of slave stations having different voice and data compression / encoding methods, the transmission speed often differs for each group. In this case, FIG.
As shown in (2), since the width of the band required for transmission is different, even if the frequency band of f2 is released, a band of Fn that requires a wider frequency band cannot be allocated, and It is difficult to allocate a frequency band that results in an optimal arrangement. That is, in the conventional satellite communication system, if the frequency bands are different due to the difference in the line speed assigned to each slave station, the frequency arrangement cannot be kept in the optimum state.

The present invention has been made in view of the above points,
An object of the present invention is to provide a satellite communication system capable of efficiently using a satellite frequency band.

[0010]

In order to achieve the above-mentioned object, the present invention provides a communication system in which any one of a plurality of slave stations transmits a communication request to another slave station to a master station via a satellite. A notification is made using a control channel, the master station allocates a necessary band based on a communication request, and notifies each of the communication requesting slave station and the communication connection destination slave station via a satellite using a common control channel. Thereby, thereafter, in a satellite communication system that enables voice and data communication via a satellite between a communication requesting slave station and a communication connection destination slave station, a plurality of slave stations include:
When a period longer than the satellite delay time common to the satellite communication system is defined as a frame period, when communicating with another slave station, a transmission signal composed of voice and data input from a terminal is time-compressed to be 1 frame period. It generates a burst signal insertion of the idle time that does not transmit the rotational signal, the other slave stations
Signal generation means for generating communication end information at the end of communication with
And the burst signal from the signal generation means
Communication end information in the frequency band assigned to
Transmission means for transmitting to the satellite on the control channel ;
A receiver that receives signals notified from satellite stations via satellites
And a decompression means for decompressing the received burst signal and outputting it to the terminal as a continuous signal, and receiving the frequency change information
Frequency change operation during the idle time between burst signals.
A structure having a Cormorant frequency changing means, the master station, and a satellite
Transmission that transmits and receives signals on a common control channel using radio waves
A receiving unit, transmission from the slave station was communicating among a plurality of slave stations
When receiving communication end information via the receiving unit , frequency change information generation for generating frequency change information for changing an allocated frequency so as to fill a space between allocated frequency bands.
Means, and the frequency generated by the frequency change information generating means.
Common control of number change information to other slave stations communicating via satellite
Having notification means for sequentially notifying using a channel
It is obtained by the.

Further, the present invention provides a master station comprising: a transmitting / receiving section for transmitting / receiving a signal on a common control channel using radio waves with a satellite; a frame processing section for performing frame processing for transmission / reception; When a communication request from the station is received, routing is performed, the allocated frequency information is transmitted to the satellite via the frame processing unit and the transmission / reception unit, and when the communication end information of the slave station is received from the frame processing unit, the frequency management information is transmitted. And a communication line control unit for transmitting frequency change information for changing the allocated frequency so as to fill the space between the allocated frequency bands to the satellite via the frame processing unit and the transmission / reception unit.

Further, the present invention provides a transmitting / receiving section for transmitting / receiving each of a plurality of slave stations to / from a master station or another slave station via a satellite, and a signal transmitted / received on the common control channel by the transmitting / receiving section. A CSC frame processing unit that performs frame processing of the above, and extracts information from the master station received from the CSC frame processing unit.
A line control unit for transmitting to a satellite via a frame processing unit and a transmission / reception unit, and a transmission signal from a terminal are time-compressed to generate a burst signal into which an idle time in which a signal is not transmitted once in a frame period is inserted and input. A transmission rate control unit that time-expands the received signal and outputs it to the terminal as a continuous signal, and a burst signal input from the transmission rate control unit is framed and output to the transmission / reception unit. A frame processing unit that extracts a signal and outputs the signal to a transmission rate control unit, and that changes a communication frequency in a transmission / reception unit based on an idle time of a burst signal based on a frequency change instruction or a frequency allocation instruction extracted by a line control unit; It has the structure which has.

In the present invention, communication between slave stations is performed using a time-compressed burst signal, and when the master station receives communication end information from the slave station with which it was communicating via a satellite, the communication between the assigned frequency bands is performed. The frequency change information for changing the allocated frequency so as to fill the vacancy is notified to each of the other slave stations in communication via the satellite, and the other slave stations in communication receive the vacancy between burst signals when receiving the frequency change information. Since the frequency change operation is performed at the time, the other slave stations in communication based on the frequency change information from the master station can change the communication frequency to the specified frequency without disconnecting the communication line. . In addition, since the above-mentioned frequency change instruction is performed so as to fill the vacant frequencies in the allocable satellite frequency band, it is possible to ensure the maximum vacant frequency band that can always be allocated.

[0014]

Next, an embodiment of the present invention will be described. In this embodiment, a slave station requests a line connection using a common control (CSC) channel, and a master station allocates a line (frequency) to the slave stations for communication with each other. In the DAMA satellite communication system as shown in the figure, when the master station C is notified by the CSC channel that the frequency assigned as the communication line between certain slave stations has been released, the master station C assigns the frequency assigned to the communication between slave stations. A means for sequentially instructing, via a CSC channel, a change in the frequency band assigned to each slave station so as to fill the excess band when an extra band occurs between the assigned frequencies. Is equipped with a means to convert the information signal into a fixed time length that is time-compressed when communicating with other slave stations, and to exchange it in burst frames.If there is an instruction to change the frequency from the master station during communication, Comprises means for changing the communication frequency by using the time interval for transmitting time-compressed.

When the frequency is changed to the frequency designated by the master station C, it is necessary to match the timing of the change between the slave stations communicating with each other using this frequency. At the time of transmission, information that changes after the next frame transmission may be added to the control field of the frame.

FIG. 1 is a block diagram showing an embodiment of the master station C. In the figure, a master station C is a transmitting / receiving section 11, a CSC
It comprises a frame processing unit 12 and a communication line control unit 13.
The transmission / reception unit 11 transmits and receives a CSC signal to and from the satellite S using radio waves. The CSC frame processing unit 12 performs modulation and demodulation of a signal and performs frame processing for transmission and reception. The cycle of this frame is set to a cycle longer than the satellite delay time common to all systems.

The communication line controller 13 manages information necessary for the slave station to communicate, such as routing information and frequency information, and slave station status, and processes a slave station communication request received from the CSC frame processor 12. And do routing,
While the information for allocating the frequency is transmitted to the satellite S through the CSC frame processing unit 12 and the transmitting / receiving unit 11, when the communication end information of the slave station is received from the CSC frame processing unit 12, the frequency is changed so as to fill the band. The information is transmitted to the satellite S in the same manner.

Each of the slave stations R1 to Rn has the same configuration as shown in the block diagram of FIG. Slave stations R1 to R
Each of n includes a transmission / reception unit 21, a CSC frame processing unit 22, a CSC line control unit 23, a frame processing unit 24, a transmission rate control unit 25, and a connection interface unit 26.

The transmitting / receiving unit 21 uses the satellite S and radio waves to transmit
It transmits and receives SC signals and communication signals with other slave stations. C
The SC frame processing unit 22 modulates and demodulates the CSC signal and processes the CSC frame. CSC line control unit 2
3 extracts information such as frequency allocation and allocation rejection from the master station C received from the CSC frame processing unit 22, and sends a communication frequency (transmission, reception) to the frame processing unit 24 in the case of frequency allocation notification or change notification. Instruct.

The frame processing unit 24 modulates and demodulates a signal transmitted / received to / from another slave station, converts the signal transmitted to the satellite S into a frame, sends the frame to the transmission / reception unit 21, and extracts an information signal from the frame received from the satellite S. Transmission rate control unit 2
5 and, further, when a frequency assignment instruction or a frequency change instruction is received from the CSC line control unit 23, the transmission / reception unit 21 is notified at a transmission interval at which an information signal is transmitted from the transmission rate control unit 25.

The transmission rate control section 25 transmits the transmission signal to the other slave station received from the connection interface section 26 as shown schematically in FIGS. 3A and 3B to provide transmission time intervals. The rate is increased and time-compressed to form a burst signal 32 having a predetermined time length.
4, while time-expanding the terrestrial burst signal received from the frame processing unit 24 to a continuous signal at the transmission rate of the terrestrial line. The connection interface unit 26 transmits and receives encoded voice and data to and from the terrestrial line.

Next, the operation of the embodiment shown in FIGS. 1 and 2 will be described. In the slave station of FIG. 2, a communication line connection request from a terminal (not shown)
And a frame processing unit 24 via a transmission rate control unit 25
Is converted into a CSC signal having information indicating the local station requesting the connection of the communication line and the connection destination by the CSC line control unit 23, and further converted into the CSC frame processing unit 22. , And transmitted from the transmitting / receiving unit 21 to the master station C via the satellite.

The master station C is controlled by the transmitting / receiving unit 11 shown in FIG.
The SC signal is received, supplied to the CSC frame processing unit 12, demodulated, and subjected to frame processing. In accordance with the communication request from the slave station extracted from the frame processing unit 12, the communication line control unit 13 performs routing of a necessary vacant frequency among the satellite frequencies, and sets the allocated frequency to CS.
The C frame signal is converted into a CSC signal by the C frame processing unit 12, and a frequency assignment notification is transmitted on the CSC channel to each of the slave station requesting connection via the satellite S and the slave station to be connected via the transmission / reception unit 11.

When the slave station that has made the connection request and the slave station to which the connection has been made receive this frequency assignment notification of the CSC channel at the transmission / reception section 21 in FIG. 2, the slave station supplies the notice to the CSC frame processing section 22 to demodulate the CSC signal. , CSC frame processing. The CSC line control unit 23 extracts the frequency allocation notification from the master station C received from the CSC frame processing unit 22, and instructs the frame processing unit 24 on the allocated frequency.

Thereafter, when voice and data for the slave station to communicate with the other slave station are supplied from the terminal (not shown) to the transmission rate control unit 25 via the connection interface unit 26, the transmission rate control is performed. The unit 25 transmits a signal such as voice or data that is temporally continuous as schematically shown in FIG. 3A without transferring data once per frame as schematically shown in FIG. 3B. Time interval (blank time)
The burst signal 32 is converted into a time-compressed burst signal 32 having the signal 31 and the burst signal 32 is supplied to a frame processing unit 24.
To the assigned frequency band,
Is transmitted as a transmission signal.

When the transmission / reception unit 21 receives a transmission signal from the other side via the satellite S by the transmission / reception unit 21, the slave station sends the reception signal to the frame processing unit 24, and demodulates the voice and data from the frame obtained by demodulation. And the like, and sends the information signal to the transmission rate control unit 25, where it is time-expanded to the transmission speed of the terrestrial line. The output signal of the transmission rate control unit 25 is output to a terminal (not shown) as voice or data encoded with the terrestrial line via the connection interface unit 26.

When the communication between the slave stations is completed, a disconnection notification signal (communication end information of the slave station) is transmitted from one of the slave stations to the master station C via the satellite S on the CSC channel. The communication end information of the slave station is received by the transmission / reception section 11 of the master station C in FIG. 1 and then demodulated by the CSC frame processing section 12 and supplied to the communication line control section 13. Then, the communication line control unit 1
3 knows that the frequency allocated as a communication line between certain child stations has been released, and thereby examines the arrangement of frequencies allocated to the communication between the remaining child stations, and finds an extra band between the allocated frequencies. When the occurrence of the error occurs, the change of the frequency band assigned to each slave station is changed so as to fill the extra band.
The data is sequentially transmitted from the transmission / reception unit 11 through the SC channel.

As a result, the other slave stations performing communication between the slave stations are connected to the transmission / reception section 21 and the CSC frame processing section 2 shown in FIG.
2 and a frequency change instruction via the CSC line control unit 23, and instructs the frame processing unit 24 to change the communication frequency (transmission and reception). The frame processing unit 24 transmits a transmission time interval 3 at which an information signal is transmitted from the transmission rate control unit 25 in response to a frequency change instruction from the CSC line control unit 23.
1 to notify the transmission / reception unit 21 of the frequency change.

Therefore, for example, as shown in FIG. 4 (A), in the group of slave stations in which the voice and data compression coding method is the first method, the center frequencies are F1, F2 and F3.
Are assigned to frequencies having frequency bands of B, respectively, and at the same time, within the group of another slave station in which the voice and data compression coding method is the second method, In a DAMA satellite communication system in which frequencies f1 and f2 and frequency bands each of which is b (where b <B) are allocated and communication is performed, communication between slave stations performing communication at frequency f1 ends. As shown in FIG. 4B, the frequency f1
Is released, and becomes a free frequency band.

Conventionally, in this case, when a new communication request is generated next in the group of the slave stations of the first scheme, even if the master station attempts to assign a new frequency band to the communication request, released frequency band b can not be assigned to narrower than the frequency band B that newly allocated, assignable said have a Ki de be assigned when separately there is no margin in the frequency band.

On the other hand, in the embodiment of the present invention,
Check the allocation of frequencies that the master station has assigned to the communication between the remaining slave stations, and fill in the extra bands when there is an extra band between the assigned frequencies.In this case, FIG. 4 shows a frequency band assigned to each of the slave stations currently communicating at the frequencies F3 and f2 so as to fill the band b communicating at the frequency f1.
As shown in (C), an instruction is sequentially given through the CSC channel to move in the direction of the frequency F2.

As a result, the frequencies F3 and f2
Each of the slave stations communicating with each other has a communication frequency of F3 'and f2' as shown in FIG.
And the empty frequency is filled. Therefore, when a new communication request is generated within the group of the slave stations of the first scheme thereafter, the master station can allocate a new frequency band B to the communication request.

As described above, in this embodiment, even if the transmission speed differs for each group, as in a system accommodating groups of slave stations having different voice and data compression coding schemes, there is always no waste. Communication can be performed between slave stations in a frequency arrangement.

[0034]

As described above, according to the present invention,
If there is an extra band in the arrangement state of the frequencies used by the slave stations, it can always be allocated by instructing each slave station to sequentially change the frequency so that the master station fills the band. Because the maximum available frequency band is ensured, there is always no waste even if the transmission speed differs for each group, such as a system that accommodates groups of slave stations with different voice and data compression coding methods. Communication can be performed between slave stations in a frequency arrangement.

Further, according to the present invention, the communicating slave station executes the frequency change by using the time interval of time-compressed and transmitted, so that the communicating slave station performs the communication based on the frequency change information from the master station. Can change the communication frequency to the designated frequency without disconnecting the communication line.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a master station of the system of the present invention.

FIG. 2 is a block diagram of an embodiment of a slave station of the system of the present invention.

FIG. 3 is a schematic diagram for explaining the operation of a transmission rate control unit of a slave station in the system of the present invention.

FIG. 4 is an explanatory diagram of a frequency arrangement change control operation of the system of the present invention.

FIG. 5 is an overall configuration diagram of a satellite communication system to which the present invention is applied.

FIG. 6 is an example of a frequency arrangement of a DAMA satellite communication system.

FIG. 7 is a diagram illustrating an example of a frequency arrangement when frequency bands allocated to slave stations are different.

[Explanation of symbols]

 Reference Signs List 11 transmission / reception unit 12 CSC frame processing unit 13 communication line control unit 21 transmission / reception unit 22 CSC frame processing unit 23 CSC line control unit 24 frame processing unit 25 transmission rate control unit 26 connection interface unit 31 transmission time interval (blank time) 32 burst signal

Claims (3)

(57) [Claims] An arbitrary one of a plurality of slave stations notifies a communication request to another slave station to a master station via a satellite using a common control channel via a satellite, and the master station is notified based on the communication request. Allocating the required band and notifying each of the communication requesting slave station and the communication connection destination slave station via the satellite using the common control channel, thereafter, the communication requesting child station is notified. In a satellite communication system enabling communication of voice and data between a station and a slave station of a communication connection destination via the satellite, the plurality of slave stations are longer than a satellite delay time common to the satellite communication system. When the period is defined as the frame period,
Each when communicating with other slave station generates a burst signal of the transmission signal and an input speech or data by compressing time by inserting the idle time that does not transmit one signal to the frame period from a terminal, other child Communication ends when communication with the station ends
Signal generating means for generating information; and
The burst signal is assigned to the own station by the master station.
Communication end information in the common control channel
Transmitting means for transmitting to the satellite in a channel, the master station or other
Receiving a signal notified from the slave station via the satellite
Receiving means, expanding means for expanding the received burst signal and outputting it to the terminal as a continuous signal ,
When the signal is received, the frequency is
Frequency changing means for performing a wave number changing operation, wherein the master station uses the common control channel by using radio waves with the satellite.
A transceiver for transmitting and receiving a signal channel, before through the transceiver from the slave station was in communication among the plurality of slave stations
When receiving the serial communication termination information, the frequency change information generation means for generating the <br/> frequency change information for changing an allocated frequency to fill the vacant between allocated frequency bands,
The frequency generated by the frequency change information generating means
The co-change information to other slave stations in the communication via the satellite
Having a notification means for sequentially notified with passing control channel
Satellite communication system characterized in that that. 2. A transmitting and receiving unit for transmitting and receiving signals on the common control channel using radio waves with the satellite,
A frame processing unit that performs frame processing for transmission and reception;
When receiving a communication request of the slave station from the frame processing unit, performs routing, transmits the assigned frequency information to the satellite via the frame processing unit and the transmitting and receiving unit, from the frame processing unit of the slave station Upon receiving the communication end information, the frequency management information is checked, and frequency change information for changing the allocated frequency so as to fill the space between the allocated frequency bands is transmitted to the satellite via the frame processing unit and the transmitting / receiving unit. The satellite communication system according to claim 1, further comprising a communication line control unit. 3. Each of the plurality of slave stations transmits and receives to and from the master station or another slave station via the satellite, and is transmitted and received on the common control channel by the transceiver. A CSC frame processing unit that performs signal frame processing; and extracts information from the master station received from the CSC frame processing unit. A line control unit for transmitting to the satellite via the terminal, and a transmission signal from the terminal is time-compressed to generate a burst signal into which an idle time in which no signal is transmitted once in the frame period is inserted. A transmission rate control unit that extends the time and outputs the signal as a continuous signal to the terminal; and a burst signal input from the transmission rate control unit is framed and output to the transmission / reception unit. The frame received by the receiving unit extracts an information signal and outputs the information signal to the transmission rate control unit, and based on the frequency change instruction or the frequency allocation instruction extracted by the line control unit, sets the communication frequency in the transmitting / receiving unit to the burst signal. 3. The satellite communication system according to claim 1, further comprising: a frame processing unit that changes the available time.