JPH0946287A - Satellite communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arrange a frequency in a most proper state even when a frequency band is different with difference in line velocity assigned at every slave station. SOLUTION: The communication line control part 13 of a master station controls a slave station status and information such as routing information, frequency information, etc., necessary for the slave station to communicate, processes the communication request of the slave station, which is received from a CSC frame processing part 12, execute routing and transmits information to which the frequency is assigned to a satellite through a CSC frame processing part 12 and a transmitting/receiving part 11. When communication end information of the slave station is received from the CSC frame processing part 12, information for changing the frequency so as to fill up the band is transmitted to the satellite in the same way. The slave station converts an information signal into the one with fixed time length obtained by time compression when communicating with another slave station, executes exchange by a burst frame and changes the communication frequency by utilizing a time interval in time compression transmission when there is a frequency change instruction from the master station under communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication system, and more particularly to a DAMA satellite communication system for controlling frequency allocation by a common control channel.

[0002]

2. Description of the Related Art As one of multiple access satellite communication systems for transmitting voice and data between earth stations via satellites, frequency multiple access (FDMA: FDMA: FDMA: F
There is a requency division multiple access) method. Among the FDMA systems, the SCPC (Single Channel Per Carrier) system is suitable for a satellite communication system including a large number of earth stations having a relatively small communication capacity. In this SCPC method, one carrier is assigned to one voice and data line, and therefore, the allocation is very flexible.

Further, when classified from frequency allocation,
Pre-assignment multiple access (PAMA: Pre Assignment Mul)
tiple Access) method and demand assign multiple access (DA
MA: Demand Assignment Multiple Access) method. In the PAMA system, since frequencies are fixedly allocated, the line is put on hold even during communication, the use efficiency of the line is poor, and the number of earth stations accommodated is limited. Therefore, the DAMA method is often adopted in which the frequency is assigned only when a communication request is generated.

A DAMA type satellite communication system is generally constructed as shown in FIG. DAMA
In the satellite communication system of the method, there is a configuration in which the satellite channel allocation control is performed only by the slave stations and there is no master station, but here, the master station performs centralized control. That is, as shown in the figure, this DAMA type satellite communication system includes a master station C that manages the allocation of satellite channels and the connection status of each slave station, slave stations R1 to Rn of a plurality of n stations, and a relay station. And satellite S as

A slave station that has made a communication request is a CSC (Comm
Connection control information is exchanged via a common control channel called "on Signaling Channel". Now, assuming that a communication request to another child station Rn is generated in a certain child station Rk, the child station Rk transmits the band required for transmission to the connected child station Rn via the satellite S by a common control channel. To notify the parent station C.

In response to this connection request, the master station C checks whether the slave station Rn at the connection destination is in a communicable state, and if possible, searches for a free request band from the managed frequency band,
A satellite channel allocation notification is sent to the requesting slave station Rk and the connection destination slave station Rn via the satellite S using the 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 SCPC using the frequency assigned through the satellite S. After that, the slave station which has completed the communication transmits a disconnection notice to the master station C. When the master station C receives this disconnection notification,
Release the assigned frequency.

[0007]

However, in the above-mentioned conventional DAMA satellite communication system, since the channel use time by the slave stations communicating between the slave stations is not constant, it is used between the allocated frequencies. However, the released bandwidth may be generated. If the information transmission rate in each communication is the same, the frequency bandwidth allocated to the slave station is also the same as shown in FIG. 6, so that the re-allocation of the released frequency band can be made flexible.

However, in a system accommodating groups of slave stations having different compression coding methods for voice and data, the transmission rate is often different for each group. In that case, FIG.
As shown in (1), since the width of the band required for transmission is different, even if the frequency band of f2 is released, it is not possible to allocate the band of Fn that requires a wider frequency band than this, and a communication request is sent. It is difficult to allocate a frequency band that is optimally arranged. That is, in the conventional satellite communication system, it is not possible to keep the frequency arrangement in an optimum state when the frequency band is different due to the difference in line speed assigned to each slave station.

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 that can efficiently use the satellite frequency band.

[0010]

To achieve the above object, according to the present invention, an arbitrary one of a plurality of slave stations makes a communication request for another slave station common to a master station via a satellite. Notification is sent using the control channel, the master station allocates the required band based on the communication request, and the common control channel is used to notify each of the communication request source slave station and the communication connection destination slave station via satellites. Thus, thereafter, in the satellite communication system that enables communication of voice and data via the satellite between the communication request source slave station and the communication connection destination slave station, the plurality of slave stations
When a period longer than the satellite delay time that is common to satellite communication systems is defined as a frame period, when communicating with other slave stations, the transmission signal consisting of voice and data input from each terminal is time-compressed to 1 frame period. A burst signal that does not transmit a single signal is inserted and generated and transmitted to the satellite.When a burst signal is received, the burst signal is expanded and output as a continuous signal to the terminal. When the communication end information is received from the existing slave station via the satellite, the frequency change information for changing the allocated frequency so as to fill the space between the allocated frequency bands is transmitted to other slave stations communicating through the satellite. Each of the slave stations, which has notified each other and is in communication, performs the frequency changing operation during the idle time between the burst signals when the frequency changing information is received.

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

Further, according to the present invention, a transmitter / receiver 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 transmitter / receiver. Information from the master station received from the CSC frame processing unit and the CSC frame processing unit for performing the frame processing of
The line control unit that transmits to the satellite via the frame processing unit and the transmission / reception unit, and the transmission signal from the terminal are time-compressed to generate a burst signal in which a vacant time in which the signal is not transmitted once is inserted in the frame cycle, and the burst signal is input. The received signal is expanded in time and output to the terminal as a continuous signal, and the burst signal input from the transmission rate control unit is framed and output to the transmitter / receiver, and the frame received by the transmitter / receiver is the information. A frame processing unit that extracts a signal and outputs it to the transmission rate control unit, and changes the communication frequency in the transmission / reception unit using the idle time of the burst signal based on the frequency change instruction or the frequency allocation instruction extracted by the line control unit. It is configured to have.

According to the present invention, the inter-slave station communication is carried out by using the time-compressed burst signal, and when the master station receives the communication end information from the slave station during communication through the satellite, the allocation between the allocated frequency bands is performed. The frequency change information that changes the allocated frequency to fill the space is notified to each of the other slave stations in communication via the satellite, and the other slave stations in communication receive the space between burst signals when receiving the frequency change information. Since the frequency changing operation is performed at the time, other slave stations in communication can change the communication frequency to the instructed frequency without disconnecting the communication line based on the frequency changing information from the master station. . Further, since the above frequency change instruction is performed so as to fill the vacant frequency in the allocatable satellite frequency band, it is possible to always secure the maximum vacant frequency band that can be allocated.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. In this embodiment, a slave station requests a line connection using a common control (CSC) channel, a master station allocates a line (frequency) to the slave station, and the slave stations communicate 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 allocated as the communication line between certain slave stations has been released, the frequency allocated to the communication between the slave stations. Is arranged, and when an extra band occurs between the assigned frequencies, a means for sequentially instructing the change of the frequency band assigned to each slave station through the CSC channel so as to fill the extra band is provided, and each slave station When communicating with other slave stations, it is equipped with means for converting the information signal into a fixed time length that is time-compressed and exchanging in burst frames, and when there is a frequency change instruction from the master station during communication, Comprises means for changing the communication frequency by using the time interval for transmitting time-compressed.

When changing to the frequency instructed by the master station C, it is necessary to match the change timing between the slave stations which communicate using the frequency. This is because the transmitting side slave station changes the frame. At the time of transmission, it suffices to be able to add information to the control field of the frame that the frame will be changed after transmission of the next frame.

FIG. 1 shows a block diagram of an embodiment of the master station C. In the figure, the master station C is a transmitter / receiver 11, a CSC
It includes a frame processing unit 12 and a communication line control unit 13.
The transmission / reception unit 11 transmits / receives a CSC signal to / from the satellite S using radio waves. The CSC frame processing unit 12 performs modulation / demodulation of signals and performs frame processing for transmission / 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 the slave station status, and processes the slave station communication request received from the CSC frame processor 12. And do the routing,
While the information for allocating the frequency is transmitted to the satellite S through the CSC frame processing unit 12 and the transmission / reception 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. Information is similarly transmitted to satellite S.

The slave stations R1 to Rn have the same structure, and have the structure 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 transmission / reception unit 21 uses the satellite S and radio waves to transmit C
Sends and receives SC signals and communication signals with other slave stations. C
The SC frame processing unit 22 modulates / demodulates the CSC signal and processes the CSC frame. CSC line controller 2
3 extracts information such as frequency allocation or allocation rejection from the master station C received from the CSC frame processing unit 22, and in the case of frequency allocation notification or change notification, the communication frequency (transmission, reception) to the frame processing unit 24. Instruct.

The frame processing unit 24 performs modulation / demodulation of signals transmitted / received to / from other slave stations, converts the transmission signal to the satellite S into a frame and sends it 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 when there is a frequency allocation instruction or a frequency change instruction from the CSC line control unit 23, the transmission / reception unit 21 is notified at the transmission interval at which the information signal is transmitted from the transmission rate control unit 25.

The transmission rate control unit 25 transmits the transmission signal to the other slave station received from the connection interface unit 26, as schematically shown in FIGS. 3A and 3B, in order to provide a transmission time interval. The frame processing unit 2 increases the rate and performs time compression to form a burst signal 32 having a predetermined time length.
On the other hand, the burst signal for the ground received from the frame processing unit 24 is time-expanded into a continuous signal at the transmission speed of the ground line. The connection interface unit 26 transmits / receives encoded voice and data to / from the ground line.

Next, the operation of the embodiment shown in FIGS. 1 and 2 will be described. In the slave station shown in FIG. 2, a connection interface unit 26 sends a communication line connection request from a terminal (not shown).
And the frame processing unit 24 via the transmission rate control unit 25.
To a CSC signal having a predetermined format, and then converted into a CSC signal having information indicating the own station requesting connection of the communication line and the connection destination by the CSC line control unit 23, and further the CSC frame processing unit 22. After being modulated by, the signal is transmitted from the transmitting / receiving unit 21 to the master station C via the satellite.

The master station C uses the transmitter / receiver 11 shown in FIG.
The SC signal is received, supplied to the CSC frame processing unit 12, demodulated, and subjected to frame processing. According to 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 free frequency among the satellite frequencies and sets the assigned frequency to CS.
The C frame processing unit 12 converts the CSC signal into a CSC signal, and further, through the transmitting / receiving unit 11, transmits a frequency allocation notification on the CSC channel to each of the slave station that has requested the connection and the slave station of the connection destination via the satellite S.

When the transmitting / receiving section 21 of FIG. 2 receives the CSC channel frequency allocation notification, the slave station which has requested the connection and the slave station of the connection destination supply it 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.

After that, when voice and data for the slave station to communicate with the partner 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 section 25 is a transmission that does not transfer data at a rate of once per frame, as schematically shown in FIG. 3B, for signals such as voice and data that are temporally continuous and schematically shown in FIG. Time interval (blank time)
The burst signal 32 is converted into a time-compressed burst signal 32, and the burst signal 32 is supplied to the frame processing unit 24, where the burst signal is framed and the transmission / reception unit 21
To the satellite S for conversion to the assigned frequency band.
To be sent as a transmission signal to.

When the transmitter / receiver 21 receives a transmission signal from the partner side via the satellite S, the slave station sends the received signal to the frame processor 24, where the frames obtained by demodulation are converted into voice and data. And the like is extracted and sent to the transmission rate control unit 25, where it is time-expanded to the transmission rate of the terrestrial line. The output signal of the transmission rate control unit 25 is output to a terminal (not shown) as voice and data encoded with the terrestrial line via the connection interface unit 26.

When the above communication between the slave stations is completed, a disconnection notification signal (communication completion 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 transmitter / receiver 11 of the master station C in FIG. 1, demodulated by the CSC frame processor 12, and supplied to the communication line controller 13. Then, the communication line control unit 1
3 knows that the frequency assigned as a communication line between certain slave stations has been released, and as a result, the arrangement of the frequencies assigned to the communication between the remaining slave stations is checked, and an extra band is allocated between the assigned frequencies. When the error occurs, change the frequency band assigned to each slave station by C
The data is sequentially transmitted from the transmission / reception unit 11 through the SC channel.

As a result, the other slave stations performing inter-slave station communication are transmitted / received by the transmitter / receiver 21 and the CSC frame processor 2 of FIG.
2 and the frequency change instruction via the CSC line controller 23, and instructs the frame processor 24 to change the communication frequency (transmission, reception). The frame processing unit 24 transmits the information signal from the transmission rate control unit 25 in response to the frequency change instruction from the CSC line control unit 23.
1 is used to notify the transceiver 21 of the frequency change.

Therefore, for example, as shown in FIG. 4 (A), the center frequencies are F1, F2 and F3 in the group of slave stations whose compression coding method of voice and data is the first method.
At the same time, communication is performed by allocating frequencies each having a frequency band of B, and at the same time, in a group of another slave station whose compression encoding method of voice or data is the second method, In the DAMA satellite communication system in which the frequencies f1 and f2 and the frequency bands b (where b <B) are assigned and communicating, the inter-slave station communication that communicates at the frequency f1 ends. Assuming that the frequency f1
The band b having the center frequency of is released and becomes an empty frequency band.

Conventionally, in this case, when a new communication request is generated in the next group of slave stations of the first method, even if the master station tries to allocate a new frequency band to this communication request, The released frequency band b cannot be allocated because it is narrower than the newly allocated frequency band B, and cannot be allocated when there is no margin in the allocatable frequency band.

On the other hand, in the embodiment of the present invention,
Check the arrangement of frequencies that the master station has allocated for communication between the remaining slave stations, and fill the extra band when an extra band occurs between the allocated frequencies, that is, in this case, until then As shown in FIG. 4, the frequency bands assigned to the respective slave stations currently communicating at the frequencies F3 and f2 are filled so as to fill the band b that was communicating at the frequency f1.
As shown in (C), the CSC channels are sequentially instructed to move in the frequency F2 side direction.

As a result, the frequencies F3 and f2 are maintained until then.
The slave stations communicating with each other have communication frequencies of frequencies F3 'and f2' as shown in FIG. 4 (D).
Is changed to fill the empty frequency. Therefore, when a new communication request is subsequently generated within the group of the slave stations of the first method, the master station can allocate a new frequency band B to this communication request.

As described above, in this embodiment, even if the transmission rate is different for each group like a system accommodating a group of slave stations having different compression coding methods for voice and data, there is always no waste. The slave stations can communicate with each other in the frequency arrangement.

[0034]

As described above, according to the present invention,
When there is a surplus band in the frequency allocation state used for the slave station, it can be always assigned by the master station instructing each slave station to sequentially change the frequency so as to fill the band. Since the maximum free frequency band is secured, there is always no waste even if the transmission rate differs from group to group, such as in a system that accommodates groups of slave stations with different voice and data compression encoding methods. The slave stations can communicate with each other in the frequency arrangement.

Further, according to the present invention, since the slave station in communication executes the frequency change by utilizing the time interval of time compression transmission, the communication is performed based on the frequency change information from the master station. The other slave stations can change the communication frequency to the instructed frequency without disconnecting the communication line.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a master station of a 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 the transmission rate control unit of the slave station of the system of the present invention.

FIG. 4 is an explanatory diagram of a frequency allocation 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 frequency allocation of the DAMA satellite communication system.

FIG. 7 is a diagram showing an example of frequency arrangement when frequency bandwidths assigned to slave stations are different.

[Explanation of symbols]

 11 transmitter / receiver 12 CSC frame processor 13 communication line controller 21 transmitter / receiver 22 CSC frame processor 23 CSC line controller 24 frame processor 25 transmission rate controller 26 connection interface 31 transmission time interval (blank time) 32 burst signal

Claims (3)

[Claims] 1. An arbitrary one of a plurality of slave stations notifies a master station of a communication request to another slave station via a satellite to a master station using a common control channel, and the master station is based on the communication request. By allocating a necessary band and using the common control channel to notify each of the slave station of the communication request source and the slave station of the communication connection destination via the satellite. In a satellite communication system that enables voice and data communication via a satellite between a station and a slave station of a communication connection destination, 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,
At the time of communication with other slave stations, a transmission signal composed of voice and data respectively input from the terminal is time-compressed to generate a burst signal into which a vacant time in which no signal is transmitted once in the frame period is inserted to generate a burst signal to the satellite. When the burst signal is received, the burst signal is decompressed and output as a continuous signal to the terminal, and the master station terminates communication from the slave station that was in communication among the plurality of slave stations via the satellite. When you receive the information,
Frequency change information for changing the assigned frequency to fill the space between the assigned frequency bands is notified to each of the other slave stations in communication via the satellite, and the other slave stations in communication are the frequency change information. A satellite communication system characterized by performing a frequency changing operation during the idle time between the burst signals during reception. 2. The transmitting / receiving unit, wherein the master station transmits / receives signals to / from the common control channel by using radio waves with the satellite,
A frame processing unit that performs frame processing for transmission and reception,
When the communication request of the slave station is received from the frame processing unit, routing is performed, and the allocated frequency information is transmitted to the satellite via the frame processing unit and the transmission / reception unit, and the frame processing unit transmits the frequency information of the slave station. When the communication end information is received, the frequency management information is investigated, and frequency change information for changing the assigned frequency so as to fill the space between the assigned 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 controller. 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 transmits and receives on the common control channel by the transceiver. A CSC frame processing unit for performing signal frame processing, and information from the master station received from the CSC frame processing unit is extracted, and at the end of the call, call end information is generated and the CSC frame processing unit and the transceiver unit are connected. The line control unit for transmitting to the satellite via the satellite and the transmission signal from the terminal are time-compressed to generate a burst signal in which a vacant time in which the signal is not transmitted once is inserted in the frame period, and the input reception signal is A transmission rate control unit that time-expands and outputs 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, and then transmitted. The frame received by the receiving unit extracts an information signal and outputs the information signal to the transmission rate control unit. Based on the frequency change instruction or the frequency allocation instruction extracted by the line control unit, the communication frequency in the transmitting / receiving unit is the burst signal. 3. The satellite communication system according to claim 1, further comprising: a frame processing unit that changes the free time of the frame processing unit.