JPH11355195A - Satellite communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide satellite communication equipment which does not require any special change procedure except the broadcasting of ordinary slot allocation information from a central station to respective peripheral stations. SOLUTION: This equipment is composed of a communication satellite 30, central station 31 and plural first to Nth peripheral stations 321 , 322 ...32N arranged on the ground and between the central station 31 and the respective peripheral stations 321 -32N identified by peculiar peripheral station addresses, bidirectional data communication is performed through the communication satellite 30. The slot allocation information describing the allocation information of a time slot, in which a satellite line is timewisely divided into fixed length, to the respective peripheral stations with the peripheral station address is broadcasted from the central station 31 to all the peripheral stations 321 -32N and while referring to this slot allocation information, communication is performed from the respective peripheral stations 321 -32N to the central station 31 by time division multiple access control accommodating the transmission information of a present station in the next transmission frame.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication apparatus, and more particularly, to a satellite communication network comprising a communication satellite, a central station, and a plurality of peripheral stations. The present invention relates to a satellite communication device that performs division multiple access control.

[0002]

2. Description of the Related Art Conventionally, a satellite communication device is composed of a communication satellite, a central station and a plurality of peripheral stations arranged on the ground, and a communication terminal and a central station connected to each peripheral station transmit data. When communication is performed, the communication satellite relays data communication. In such a satellite communication device, transmission information is transmitted only from the peripheral station to the central station via the communication satellite,
Broadcast communication is performed from the central station to all peripheral stations via communication satellites. Particularly, when communicating from the peripheral station to the central station, one frame time of the framed transmission information is divided, and communication is performed by time division multiple access control using this as a time slot. The following three methods are mainly known as methods in which each peripheral station accesses a time slot.

[0003] The first method is a "fixed allocation access method". In the “fixed assignment access method”, a dedicated time slot is fixedly assigned to each peripheral station in advance,
Each time a transmission request to the central station occurs, a packet is transmitted to the central station using the fixed time slot dedicated to the own station. In particular, the configurations of the central station and the peripheral stations can be most simplified. Also, when the peripheral station constantly issues a transmission request, the time slot utilization efficiency is high. However, if the peripheral station generates a transmission request irregularly, the efficiency of using the time slot deteriorates.

The second method is a "random access method".
(Or “slot Aloha method”). In the “random access method”, every time a peripheral station generates transmission data, the data is transmitted using an arbitrary time slot. Therefore, transmission data from a plurality of peripheral stations may be transmitted using the same time slot, and the central station uses the same time slot when receiving transmission data from a plurality of peripheral stations, resulting in data collision. Is transmitted to all peripheral stations as a negative acknowledgment signal. When receiving the negative acknowledgment signal, if the negative acknowledgment signal corresponds to the time slot used at the time of transmitting the own station, each peripheral station transmits again after a lapse of time determined using a random number or the like. . In particular, when a peripheral station transmits a packet at a low frequency or transmits packets at random, the retransmission frequency of the packet is reduced, thereby increasing the throughput. However, when the frequency of sending packets from peripheral stations increases, the frequency of collisions in the same time slot also increases,
Rather, retransmission packet collisions occur and the throughput is reduced.

[0005] The third method is a "reservation allocation access method".
It is. In the “reservation allocation access method”, each time a communication terminal connected to each peripheral station requests communication, the peripheral station transmits a reservation request for the number of slots to be used to the central station. The central station allocates a time slot that can be used only by the peripheral station that has transmitted the reservation request as a reservation time slot. Then, the reserved time slot is notified to all the peripheral stations as the reserved slot allocation information.
In particular, it is suitable when a peripheral station transfers a large amount of data requiring a plurality of slots to the central station. In addition, even if the transmission frequency of peripheral stations increases, the "random access method"
Does not cause packet collision. However, each peripheral station cannot transmit to the central station unless receiving the reserved slot allocation information from the central station. Therefore, compared to the fixed allocation access method and the random access method,
After the transmitting terminal connected to the peripheral station sends out data,
It takes time for the data to reach the receiving terminal.

As described above, the communication system using the time division multiplex access control has advantages and disadvantages. In view of this, there have been proposed several composite systems combining these systems so as to make use of the advantages of each system. For example, there is a “random access / reservation combined method” in which a “random access method” and a “reserved allocation access method” are combined. The "random access / reservation combined method" detects the data length of data to be transmitted from the peripheral station to the central station, and sets a "short data" having a data length equal to or less than a certain threshold value, for example, a data length that can be transmitted in one time slot, and a threshold value. It is divided into “long data” having the above data length. When the “long data” is supplied from the connected communication terminal, the peripheral station sends a reservation request for reserving the number of time slots required for transmitting the “long data” to the central station. When notified of the reserved slot allocation information from the central station, "long data" is transmitted to the central station using the designated time slot. In addition, "short data"
Is transmitted to the central station using a time slot that is not allocated to the reserved time slot of the own station or another peripheral station. When the occurrence of a collision is detected by receiving a negative acknowledgment signal from the central station, the “short data” that has not been transmitted when the negative acknowledgment signal is received is transmitted together with the “long data” by the reserved allocation access method. Then, the retransmission data is also retransmitted by the reservation allocation access method. When a data reception signal is returned from the central station for all "short data" transmitted by the reservation allocation access method,
The subsequent “short data” is transmitted by the random access method. In particular, even if the supply of “short data” to peripheral stations increases, retransmission of packets by the random access method is prohibited to reduce the frequency of data collisions. At the same time, delay due to data retransmission can be reduced. further,
This is suitable when the amount of data transmitted from the peripheral station varies greatly. However, this method is not suitable for transmitting data from a terminal that constantly generates data to a central station prior to data from another terminal.

[0007] In addition, there is another technology that combines a "random access / reservation combined system" and a "fixed allocation access system" to accommodate terminals having different data generation frequencies and data generation amounts per transmission. For example, Japanese Patent Laid-Open No. 3-8
No. 8434, entitled "Satellite Communication System".

[0008]

In such a conventional satellite communication apparatus, communication from each peripheral station to the central station is performed by time division multiple access control using time slots. That is, at the time of communication, at the transmission source peripheral station and the transmission destination central station, time slot allocation information for each peripheral station must be in a known state. However, there are the following problems when changing communication traffic, installing a new peripheral station, reorganizing the communication system by introducing a new communication satellite, or changing the time slot accompanying the introduction of a new access method. .

FIG. 12 shows an outline of a time slot changing procedure in a conventional fixed allocation method of time division multiple access control. It is assumed that communication between the first and second peripheral stations and the central station is performed via a communication satellite, and the line information transmitted and received between them is shown over time. From the central station, slot allocation information is broadcasted to the first and second peripheral stations at predetermined time intervals (11 _{1 to} 11 ₉ and 12 ₁ to _{1 in} FIG. 12).
₂₉ ). This slot assignment information is information indicating whether or not each slot is assigned to a peripheral station. Therefore, it is assumed that the slot allocation is changed at the timing A, and the period up to the timing A is a period T ₁ and the period thereafter is a period T ₂ .

FIG. 13A shows an outline of the configuration of slot allocation information notified to the first and second peripheral stations during the period T ₁ . Here, it is assumed that one frame is time-divided into five time slots and used. The slot allocation information 13 represents a frame 5 are time division time slots 14 ₁ to 14 _5, whether the time slot is allocated to one of the peripheral stations in binary. A time slot in which “1” is set indicates that the time slot is assigned to any of the peripheral stations,
The time slot in which “0” is set indicates that it is not assigned to any peripheral station. Slot allocation information 13 shows a state in which the time slot 14 _1, 14 ₃ are respectively assigned to the first or second peripheral stations.

Here, returning to FIG. 12, the description will be continued. Slot assignment information 11 ₁ from the central station to the first peripheral station
But the slot allocation information 12 ₁ is notified respectively second peripheral stations. First peripheral station, the notification of the slot allocation information 11 _1, the slot corresponding to the time slot 14 ₁ in FIG. 13 (a), transmitted as a fixed assignment data 15 ₁ carrying the transmission information of its own station. Second peripheral station, the notification of the slot allocation information 12 _1, 13
The slot corresponding to the time slot 14 ₃ (a),
Transmitting the fixed assignment data 15 ₂ put the transmission information of its own station. Now, the slot assignment is changed in the timing A as the new third peripheral station is set, the slot allocation information after the change by the slot allocation information 11 _4, 12 ₄ is notified.

[0012] FIG. 13 (b), shows the outline of the configuration of the slot allocation information is notified to the first and second peripheral stations in the period T _2. As described above, the slot allocation information 16
A first peripheral station in the time slot 17 _2, second peripheral station in the time slot 17 ₅ represents a state where the third peripheral stations began to be allocated to the time slot 17 _1.

Returning to FIG. 12, the description will be continued. Such slot allocation information, slot allocation information 11 _4,
12 even if they are notified to the first and second peripheral station respectively as _4, but in each peripheral station which slot can be recognized whether empty slot is used exclusively by the own station is allocated to which slot You cannot recognize until you can do it. Thus, the central station is the first and second peripheral stations, and although not shown, the third peripheral station is provided with ordinary slot allocation information 11 _{1 to} 11 ₉ , 12
A procedure for notifying a new slot assignment by the assignment change information 18 ₁ and 18 ₂ is required separately from _{1 to} 12 ₉ . Notification of this allocation change information 18 _1, in a first peripheral station and transmits to the central station as a fixed assignment data 19 ₁ carrying the transmission information of its own station to the slot corresponding to the time slot 17 _2. In the second peripheral station, the notification by the allocation change information 18 _2, and transmits to the central station as a fixed assignment data 19 ₂ put the transmission information of its own station to the slot corresponding to the time slot 17 _5.

As described above, when a slot allocation change occurs, a procedure for notifying each peripheral station of a new slot allocation based on allocation change information different from normal slot allocation information is required. This not only complicates the procedure control of the central station and each peripheral station, but also causes a problem that the transmission and reception of data is temporarily stopped due to the notification procedure of the assignment change information. 12 and 13
In the above, the fixed allocation access method has been described, but it goes without saying that the same problem occurs even in the random access method or the reserved allocation access method.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a satellite communication apparatus which does not require a special change procedure besides normal slot allocation information broadcast from a central station to each peripheral station when a fixed allocation slot is changed. It is in.

[0016]

According to the first aspect of the present invention, (a) a unique peripheral station address is written in correspondence with each slot obtained by dividing a frame of a fixed time length into a predetermined number, so that the peripheral station can write the frame. Slot allocation information holding means for holding slot allocation information indicating peripheral stations assigned to each slot of the received frame, first transmission information generating means for generating first transmission information to each peripheral station, Multiplexing means for multiplexing the first transmission information generated by the first transmission information generation means and the slot allocation information held by the slot allocation information holding means; and a transmission signal multiplexed by the multiplexing means A central station comprising: first transmitting means for transmitting a signal to the communication satellite; first receiving means for receiving a reception signal addressed to the own station from the communication satellite; The second transmission signal transmitted from the stage to the central station from the peripheral station with broadcasts to all neighboring stations
(C) a second receiving means for receiving a transmission signal transmitted from the first transmitting means via the communication satellite, and a signal received by the second receiving means. Slot allocation information extracting means for extracting slot allocation information multiplexed in a received signal, second transmission information generating means for generating second transmission information from the own station to the central station, and slot allocation information extracting means The second transmission information generated by the second transmission information generating means is generated using the slot of the transmission frame corresponding to the slot in which the peripheral station address of the own station is written based on the slot allocation information extracted by Second transmitting means for transmitting to the communication satellite, and the satellite communication device is provided with a plurality of peripheral stations each identified by a unique peripheral station address.

That is, according to the first aspect of the present invention, the central station is provided with slot allocation information holding means, and a unique peripheral station address is written in correspondence with each slot obtained by dividing a frame of a fixed time length into a predetermined number. The slot allocation information indicating the peripheral station assigned to each slot of the frame received from the peripheral station is held. And
The slot assignment information and the transmission information are multiplexed and broadcasted to all the peripheral stations via the communication satellites for notification. Each peripheral station can be identified by a unique peripheral station address, extracts slot assignment information from the received signal, and uses the transmission frame slot corresponding to the slot in which the own station's peripheral station address is written to generate a peripheral frame. Stations transmit to the central station via communication satellites.

According to the second aspect of the present invention, (a) a unique peripheral station address is written in correspondence with each slot obtained by dividing a frame of a fixed time length into a predetermined number, so that each slot of a frame received from the peripheral station is written. , Slot assignment information holding means for holding slot assignment information indicating peripheral stations assigned as fixed assignment slots, first receiving means for receiving a reception signal addressed to the own station from a communication satellite, and the first reception means. Means for detecting whether or not the received signal received by the means is normally received, and generating delivery information indicating whether or not the received signal is normally received for each slot; and receiving information received by the first receiving means. A reserved slot request extracting means for extracting a reserved slot request for requesting a new slot allocation to a transmission request source peripheral station from a received signal; Referring to the slot assignment information held by the slot assignment information holding means based on the reservation slot request extracted by the lot request extraction means, the free slot not assigned to any of the peripheral stations is assigned to an empty slot that is not assigned to any peripheral station. Reservation slot allocating means for generating second slot allocation information in which a station is newly allocated as a reservation allocation slot; first transmission information generating means for generating first transmission information to each peripheral station; Multiplexing means for multiplexing the first transmission information generated by the transmission information generating means, the second slot allocation information generated by the reserved slot allocating means, and the delivery information generated by the delivery information generating means, A central station having first transmitting means for transmitting a transmission signal multiplexed by the multiplexing means to a communication satellite; A communication satellite that broadcasts a transmission signal transmitted from the transmitting means to all peripheral stations and relays second transmission information from each peripheral station to the central station; and (c) transmits transmission data from the local station to the central station. Packetizing means for generating second transmission data by packetizing, a reservation slot request outputting means for outputting a reservation slot request when the packetization means cannot accommodate one slot, and a random access method for transmission to the central station; Random access setting means for setting whether or not to perform, second receiving means for receiving a transmission signal transmitted from the first transmitting means via the communication satellite, and reception by the second receiving means Slot allocation information extracting means for extracting second slot allocation information multiplexed on the received signal; and multiplexing the received signal received by the second receiving means. Delivery information extracting means for extracting delivery information stored in the storage device;
Based on the delivery information extracted by the delivery information extracting means, the holding means for holding the second transmission data of the own station which is not normally received by the central station as the holding data, and the transmission to the central station by the random access setting means. When it is set to be performed by the random access method, second transmission data or reserved data is inserted into an empty slot based on the second slot allocation information extracted by the slot allocation information extracting means, and output by the reserved slot request output means. When the random access setting unit sets the transmission to the central station not to be performed by the random access scheme, the random access setting unit adds the reserved slot request to the base station based on the second slot allocation information extracted by the slot allocation information extracting unit. Corresponding to the slot in which the peripheral station address of the station is written. A second transmission information generating means for generating second transmission information by inserting the second transmission data into the fixed allocation slot or the reservation allocation slot; and a second transmission information generating means for generating the second transmission information. Second transmission means for transmitting transmission information to a communication satellite,
The satellite communication device is provided with a plurality of peripheral stations each identified by a unique peripheral station address.

That is, according to the second aspect of the present invention, the central station is provided with slot allocation information holding means, and a unique peripheral station address is written in correspondence with each slot obtained by dividing a frame of a fixed time length into a predetermined number. The slot allocation information indicating the peripheral station assigned to each slot of the frame received from the peripheral station is held. Further, the delivery information generating means detects whether or not the received reception signal has been normally received, and generates delivery information indicating whether or not the normal reception is possible for each slot. further,
The reserved slot requesting means extracts a reserved slot request for requesting a new slot allocation to the transmission requesting peripheral station from the received signal and, based on this, refers to the slot allocation information and assigns it to any peripheral station. Second slot allocation information is generated in which a peripheral station that has requested a reserved slot is newly allocated as a reserved allocation slot to an empty slot that has not been reserved. Then, the first transmission information, the delivery information, and the second slot allocation information to the peripheral stations are multiplexed and broadcasted to all the peripheral stations via communication satellites for notification. Each peripheral station can be identified by a unique peripheral station address, and it can be set whether or not to perform transmission to the central station by a random access method.
Data to be transmitted to the central station is packetized, and if it cannot be accommodated in one slot, a reservation slot request for requesting a reservation allocation slot to the central station is output. Also, the second slot allocation information and the delivery information are extracted from the received signal from the central station. When such a peripheral station transmits to the central station by the random access method, retransmission is performed by the second transmission data packetized in an empty slot based on the second slot allocation information or by the random access method. Necessary reservation data is inserted, and the reservation slot request output by the reservation slot request output means is added to transmit the reservation data to the central station via the communication satellite. On the other hand, when the peripheral station does not transmit to the central station by the random access method, the fixed allocation slot or the reserved allocation slot corresponding to the slot in which the peripheral station address of the local station is written based on the second slot allocation information. The packetized second transmission data is inserted into the slot and transmitted to the central station via a communication satellite.

According to a third aspect of the present invention, in the satellite communication apparatus according to the first or second aspect, the central station includes setting means for setting slot assignment information held by the slot assignment information holding means. It is characterized by having.

That is, in the invention according to the third aspect, since the setting means for setting the slot allocation information is provided in the central station, the optimal slot allocation change accompanying the traffic fluctuation or the configuration change by the communication network is provided. Can be easily performed.

According to a fourth aspect of the present invention, in the satellite communication apparatus according to the second aspect, the second slot allocation information is written with a non-existent peripheral station address which is predetermined as an empty slot. I have.

In other words, according to the present invention, when a predetermined non-existent peripheral station address is written in the second slot assignment information, the slot of the transmission frame corresponding to the slot of each peripheral station is set. An empty slot is used.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows an outline of a configuration of a satellite communication apparatus according to an embodiment of the present invention. This satellite communication device includes a communication satellite 30, a central station 31 arranged on the ground, and a plurality of first to N-th peripheral stations 32 ₁ , 32 ₂ ,
.., 32 _N. Bidirectional data communication is performed between the central station 31 and the peripheral stations 32 _{1 to} 32 _N via the communication satellite 30 to form a star communication network. From central station 31 to peripheral stations 32 _{1 to} 32 _N
, Broadcast-type communication is performed, and communication is performed from each of the peripheral stations 32 _{1 to} 32 _N to the central station 31 by time division multiple access control in which a satellite line is time-divided into time slots of a fixed length. . The central station 31 broadcasts the time slot assignment of each of the peripheral stations 32 _{1 to} 32 _N in the next frame to each assigned peripheral station as time slot assignment information.

In the following, signals transmitted and received between the central station 31 and the peripheral stations 32 _{1 to} 32 _{N of} the satellite communication apparatus shown in FIG. 1 will be described, and then the main parts of the configuration of the satellite communication apparatus will be described. I do.

FIG. 2 shows a central station 31 via a communication satellite 30.
3 shows the outline of the configuration of the signal format of the transmission signal transmitted to each of the peripheral stations 32 _{1 to} 32 _N. A transmission signal from the central station 31 to each of the peripheral stations 32 _{1 to} 32 _N is divided for each frame having a fixed time length. Each frame is defined as one frame, and each frame includes a control signal section and a data signal section. Control signal unit includes a frame synchronization pattern 33 ₁ to indicate the start of a frame, the slot allocation information 33 ₂ indicating which peripheral stations are assigned for each time slot, the transmission data center station from the peripheral station in and a acknowledgment information 33 ₃ for indicating whether or not successfully received. In the data signal portion, data packets 34 _{1 to} 34 _N transmitted from the central station 31 to the peripheral stations 32 _{1 to} 32 _N are time-division multiplexed and inserted. As described above, all transmission signals from the central station 31 to each of the peripheral stations 32 _{1 to} 32 _N are transmitted in a broadcast type.

The slot allocation information 33 ₂ to be transmitted to each peripheral station 32 ₁ to 32 _N from the central station 31, the peripheral station immediately after the slot allocation information is received by each peripheral station 32 ₁ to 32 _N 9 shows a slot allocation state in a transmission frame. Now, each of the peripheral stations 32 _{1 to} 32 _N can be identified by a peripheral station address uniquely assigned in advance, and the peripheral station address is represented by 16 bits. Also, "FFF
A peripheral station having a peripheral station address of “F” does not actually exist, and a slot in which “FFFF” is written as the peripheral station address to which the peripheral station is assigned is defined as an empty slot because it is not allocated to any peripheral station. be able to.
Slot assignment information _332, the peripheral station address of the number of time slots contained in one frame, it is arranged to write in accordance with the slot number order. In FIG. 2 the first address ₃₅₁ is a first peripheral station address of the peripheral stations 32 ₁ "0001", a peripheral station address nonexistent second address 35 ₂ "FFFF" is a third Address 3
5 to ₃ which is a second peripheral station address of the peripheral stations 32 ₂ "00
02 "and the peripheral station address" FFFF "which does not actually exist at the M-th address 35 _M. Therefore, the first peripheral station 32 ₁ is stored in the first slot.
The third slot assigned second peripheral stations 32 _2, respectively, indicating that it is otherwise empty slot.

[0030] The delivery confirmation information 33 ₃ In addition, each peripheral station 32 ₁
To 32 around station 31 to transmit data from the _N is information indicating whether received normally, the receiving frame immediately before the control signal section is transmitted, reception center station 31 corresponding to the received data This is acknowledgment information. Delivery confirmation information 33 ₃
Is a sequence in which reception acknowledgment information for each slot in such a reception frame is written and arranged in the order of slots. When the central station 31 normally receives the transmission data from the peripheral station as the reception confirmation response information, it writes the peripheral station address of the peripheral station of the transmission source in the slot position where the transmission data is received. On the other hand, when the central station 31 does not normally receive the transmission data, "FFFF" which does not correspond to any peripheral station address is written. In acknowledgment information 33 ₃ in FIG. 2, first the peripheral stations 32 ₁ near station address "0001", the third peripheral stations 32 ₃ near station address 36 _M of the M in the first address 36 ₁ Address "00
03 "is the peripheral station address nonexistent in the other address" FFFF "is written, respectively. Thus, the central station 31, the first peripheral station 32 ₁ in the first slot in the received frames with , And the data from the _third peripheral station 323 in the M-th slot, respectively, and indicate that the data was not normally received in the other second and third slots. I have.

FIG. 3 is a block diagram showing each peripheral station 3 via the communication satellite 30.
It represents the configuration of the signal format of the transmission signal to be transmitted to the central station 31 from 2 ₁ to 32 _N. Each peripheral station 3
Transmitting signals from 2 ₁ to 32 _N with respect to the center station 31 is divided into each frame of a fixed time length. The divided frames are transmitted from the central station 31 to the peripheral stations 32 _{1 to} 32 _N shown in FIG.
Has the same time length as the frame in the transmission signal for Then, this frame is further time-divided into _{M first} time slots 371 to M-th time slots 37M. A transmission signal from the peripheral station to the central station is transmitted as a data packet accommodated in one time slot.
This packet contains the address of the peripheral station of the transmission source. When the slot reservation allocation access method is used, a slot reservation request from the peripheral station is included.

Next, the configuration of the central station 31 and the peripheral stations 32 _{1 to} 32 _N for processing the transmission signal having the format configuration shown in FIGS. 2 and 3 will be described.

First, the essential parts of the configuration of the central station 31 will be described with reference to FIG. 4 and the outline of the operation of the central station 31 will be described with reference to FIG.

FIG. 4 shows a main part of the configuration of the central station 31 shown in FIG. This central station has a transmission / reception unit 31 for transmitting / receiving a radio wave 40 to / from the communication satellite 30. The transmission / reception unit 41 performs frequency conversion of a received signal in a high frequency band to an intermediate frequency band when receiving a radio wave from a peripheral station, and transmits the signal to the reception unit 42. On the other hand, when transmitting a radio wave to a peripheral station, the transmission signal from the transmission unit 43 is frequency-converted to a high frequency band and transmitted to the communication satellite 30. The transmission / reception signal transmitted or received via the transmission / reception unit 41 in this manner is transmitted to the timing signal generation unit 44.
The processing is performed based on various timings generated by. The timing signal generator 44 generates a transmission frame timing at the time of transmission and a transmission frame synchronization pattern signal in the transmission frame based on the reference clock 45 of the central station 31, and synchronizes the reception frame timing and the reception slot timing at the time of reception. Generate.

First, the configuration of the receiving side of the central station 31 will be described.

The receiving section 42 includes a timing signal generating section 44
The demodulation, error correction, and transmission error detection of the reception signal frequency-converted to the intermediate frequency band by the transmission / reception unit 41 are performed at the reception frame timing and the reception slot timing generated in step (1). Then, only the normal received data packet 46 having no transmission error is sent to the separating unit 47, and the receiving slot timing normally received by the receiving unit 42 and the source peripheral station address 48 extracted from the received data are generated by the control signal generation. Notify section 49. The separating unit 47 includes the receiving unit 4
In addition to detecting whether or not the received packet data 46 received from the source 2 includes a slot reservation request from the source peripheral station, the received data packet 46 from the receiver 42 is transmitted to the received data buffer 51 as a received data packet 50. . When the received data packet 46 includes a slot reservation request of the source peripheral station, the source signal of the source peripheral station and the requested slot number 52 are stored in the control signal generator 49.
Notify. The reception data buffer 51 buffers the reception data packet 50 and outputs it as reception data 53 to a host computer connected to the central station 31 or a terrestrial communication network.

Next, the configuration of the transmitting side of the central station 31 will be described.

The central station 31 is connected to the input terminal device 54, and each of the peripheral stations 32 ₁ to 32 3 belonging to the central station 31.
An interface for designating a fixed slot allocation pattern to 2 _N is provided. The fixed slot assignment pattern input from the input terminal device 54 is sent to the slot assignment storage unit 56 as a fixed slot assignment designation pattern 55. The slot assignment storage unit 56 stores the fixed slot assignment information 55 in the form of a table in which peripheral station addresses of peripheral stations assigned to each slot are written and arranged for each frame with a plurality of frames as holding units. Hold. At this time, an imaginary peripheral station address “FFFF” that does not exist actually is written in the area of the table corresponding to the slot that is not fixedly assigned to any peripheral station to clearly indicate that the slot is an empty slot. Keep it.

Input data 57 from a host computer or a terrestrial communication network connected to the central station 31 is buffered in a transmission data buffer 58 and
This is packetized and transmitted to the multiplexing unit 60 as transmission packet data 59.

The control signal generation unit 49 uses the transmission frame timing generated by the timing signal generation unit 44 to transmit the control signal portion of the transmission signal shown in FIG. The fixed slot allocation information 61 held by 56 is read for each frame. Then, from the read fixed slot allocation information 61, slot allocation information is generated by writing the allocation destination peripheral station addresses of each slot in the slot order. Fixed slot allocation information 6 for one frame read out
1, when there is an empty slot not allocated to any peripheral station, and a slot reservation request of the peripheral station is notified from the above-described separating unit 47, the empty slot is separated simultaneously with the slot reservation request. The allocation of reserved slots is performed by writing the peripheral station address of the reservation request source notified from the unit 47, and slot allocation information is generated. Further, the control signal generation unit 49 includes the reception unit 4
From the reception slot timing of normal reception notified by No. 2, acknowledgment information indicating whether or not data has been normally received in each slot in the immediately preceding reception frame is also generated. The control signal generator 49 multiplexes the slot allocation information and the acknowledgment information 62 thus generated
Output to

The multiplexing section 60 includes a timing signal generating section 44
A frame synchronization pattern signal 63 generated by
Slot allocation information and acknowledgment information 62 generated by the control signal generation unit 49;
The transmission packet data 59 packetized by the time division multiplexing is time-division multiplexed, and this is output to the transmission unit 43 as a multiplexed signal 64. The transmitting unit 43 adds redundant bits for error detection, performs encoding and modulation, and sends the result to the transmitting / receiving unit 41.

The central station 31 enabling such control
Is a central processing unit (Central Processing Uni
t: CPU) and various programs based on a program stored in an external storage device such as a magnetic disk or a predetermined storage device such as a read only memory (ROM) provided separately therefrom. Control can be performed.

FIG. 5 shows an outline of a control procedure of the central station 31. The central station 31 performs a transmission operation and a reception operation based on the transmission frame timing and the reception frame timing generated by the timing signal generation unit 44 with reference to the reference timing 45. When the transmission frame timing generated by the timing signal generation unit 44 is supplied to the control signal generation unit 49 (step S65: Y), the fixed slot allocation information 61 held in the slot allocation storage unit 56 is stored in one frame. The slot allocation information is read in units. At this time, when the slot reservation request of the peripheral station is notified from the separation unit 47, the reservation request is written by writing the peripheral station address of the reservation request source notified from the separation unit 47 simultaneously with the slot reservation request to the empty slot. Allocate slots. Then, the packet data 59 packetized by the transmission data buffer 58 is read (step S66). Further, the above-mentioned slot allocation information, acknowledgment information generated from the reception slot timing normally received from the receiving unit 48, the frame synchronization pattern signal generated by the timing signal generating unit 44, and the packet data 59 Are multiplexed by the multiplexing unit 60 (step S67). The multiplexing unit 60 outputs the multiplexed multiplexed signal 6
4 is transmitted to the transmitting unit 43, and the transmitting unit 43 adds redundant bits for error detection, and performs encoding and modulation (Step S).
68). The transmission signal transmitted from the transmission unit 43 is frequency-converted to a high frequency band by the transmission / reception unit 41 (step S6).
9), this is transmitted as a transmission radio wave to the communication satellite 30 (step S70). Thereafter, the operation based on the various timings generated by the timing signal generation unit 44 is repeated again (return).

In step S65, when the reception frame timing generated by the timing signal generation section 44 is supplied to the reception section 42 (step S65: N, step S71: Y), the transmission / reception section 41 receives the received frame. The signal is frequency-converted from the high frequency band to the intermediate frequency band (step S72), and transmitted to the receiving unit 42. Receiver 42
Then, demodulation and error correction of the received signal and detection of a transmission error are performed (step S73), and based on the received frame timing generated by the timing signal generating unit 42, the data is transmitted to the separating unit 47 as a received data packet 46. Further, it notifies the control signal generator 49 of a reception slot timing indicating a slot in which data has been normally received. In the separation unit 47,
It detects whether or not the received data packet transmitted from the receiving section 42 includes a slot reservation request of the peripheral station of the transmission source. At this time, if the slot reservation request is included, the source peripheral station address and the number of requested slots are extracted and separated (step S74), and then the control signal generator 49.
To the receiving data buffer 5
1 (step S75). If the received data packet does not include a slot reservation request, the received data packet is directly buffered in the received data buffer 51. The reception data buffer 51 outputs the reception data 53 to a host computer connected to the central station 31 or a ground communication network (step S76). After that, similarly to the case where the reception timing is not the reception timing in step S71 (step S71: N), the operation based on the various timings generated by the timing signal generation unit 44 is repeated again (return).

As described above, the central station 31 performs a transmission / reception operation at various timings generated by the timing signal generation section 44 with reference to the reference timing 45. At the time of transmission, transmission packet data, a frame synchronization pattern signal, slot assignment information in which the peripheral station address of the peripheral station assigned to each slot is written, and whether or not a reception signal from each peripheral station has been normally received. Is multiplexed and transmitted. On the other hand, at the time of reception, by notifying a reception slot timing indicating a slot normally received at the time of demodulation and error correction, acknowledgment information required at the time of transmission is generated. When the received signal includes a reserved slot request from the source peripheral station, the source peripheral station address and the number of requested slots are extracted, and a new reserved slot is assigned based on this and the reception slot timing. The allocation information of each slot thus allocated is notified to each peripheral station as slot allocation information.

Next, the essential parts of the configuration of the peripheral station will be described with reference to FIG. 6, and the outline of the operation of the peripheral station will be described with reference to FIG. Here, the first peripheral station 32 ₁ will be described, but the configuration of the other second to N-th peripheral stations 32 _{2 to} 32 _N is the same as the configuration of the first peripheral station 32 ₁ .

FIG. 6 shows the first peripheral station 32 ₁ shown in FIG.
The main part of the configuration of FIG. First peripheral station 32
₁ has a transmission / reception unit 81 for transmitting / receiving a radio wave 80 to / from the communication satellite 30. The transmission / reception unit 81 performs frequency conversion of a received signal in a high frequency band to an intermediate frequency band when receiving a radio wave from the central station, and transmits the signal to the receiving unit 82. on the other hand,
When transmitting a radio wave to the central station, the transmission signal from the transmission unit 83 is frequency-converted to a high frequency band and transmitted to the communication satellite 30.

First, the configuration of the receiving side of the first peripheral station 32 ₁ will be described.

The receiving section 82 demodulates the received signal frequency-converted from the high frequency band to the intermediate frequency band by the transmitting / receiving section 81,
Error correction is performed, and the resultant signal is output to the separation unit 85 as a reception demodulation signal 84. Separating section 85 separates received demodulated signal 84 into a control signal section and a data signal section shown in FIG. The control signal section is further separated into a frame synchronization pattern, slot allocation information, and acknowledgment information.

The data signal section separated by the separation section 85 is
Further, transmission error detection is performed in the separation unit 85. afterwards,
The data packet is transmitted to the reception data buffer 87 as a data packet 86 having no transmission error. The reception data buffer 87 buffers the data packet 86 and transmits the data packet 86 to a communication terminal or a terrestrial communication network connected to a peripheral station.
8 is output.

The frame synchronization pattern 89 of the control signal section separated by the separation section 85 is
Sent to 0. Similarly, the slot allocation information 91 of the separated control signal section is sent to the slot type management section 92. The acknowledgment information 93 of the control signal section separated in the same manner is sent to the acknowledgment management section 94.

The frame / slot synchronizing section 90 transmits a transmission frame and transmission slot timing 95 synchronized with the frame timing of the central station 31 based on the frame synchronization pattern 89 extracted from the received signal from the central station 31.
Is generated and transmitted to the transmission management unit 96. The slot type management unit 92 identifies the slot in which the address of the peripheral station of the own station is described from the slot allocation information 91 similarly extracted from the received signal, and assigns a slot number that can be exclusively used by the own station in the next transmission frame. The slot number is stored as the transmission slot number 97, and an empty slot not allocated to any peripheral station is identified from the slot allocation information 91, and the slot number is also stored. When the random access scheme is used, the delivery confirmation management unit 94, based on the transmission slot timing information 98 indicating whether or not data has been transmitted at each transmission slot timing notified from the transmission management unit 96,
The transmission history indicating which transmission slot timing the own station transmitted data is held. Based on the transmission history, it is possible to confirm from the acknowledgment information notified from the central station 31 whether the data transmitted by the own station has been normally received by the central station 31. And the delivery confirmation 99
, The transmission data buffered in the hold buffer 100 is retransmitted or discarded.

Next, the transmission configuration of the _first peripheral station 32 ₁ will be described.

A communication terminal (not shown) is connected to the first peripheral station 32 ₁ , and input data 101 from this communication terminal or a terrestrial communication network is input to the packetizing section 102. The packetizing unit 102 receives the input data 1
01 is converted into a data packet that can be accommodated in one time slot on the satellite line. If the input data 101 cannot be accommodated in one time slot on the satellite line, the data is divided into data packets that can be accommodated in a plurality of time slots. When the data packet is divided in this way, necessary information for restoring the original data message from the data packet divided by the reception data buffer 51 of the central station 31 is added to the transmission mode selection unit 103. Output.

[0055] In the transmission mode selection unit 103, as an access method by division multiple access control when the time for transmitting data to the first peripheral station 32 ₁ center station 31, whether or not to perform communication in a random access method Can be selected. This transmission mode selection unit 103
The output destination is Demand Assign as a memory for buffering depending on the access method.
ign: hereinafter abbreviated as DA. ) A data buffer 104;
A random access (hereinafter, abbreviated as RA) data buffer 105 is connected. Further, a suspension buffer 100 is connected to the RA data buffer 105 so that output data from the RA data buffer 105 is input to the suspension buffer 100 and output data of the suspension buffer 100 is input to the RA data buffer 105. Has become. This RA data buffer 1
Input and output of data between the buffer 05 and the hold buffer 100 are performed based on the delivery confirmation 99.

When the transmission mode selection unit 103 is selected not to use the random access method, the transmission mode selection unit 103 outputs all data packets input from the packetization unit 102 to the DA data buffer 104 as they are. That is,
The DA data buffer 104 buffers transmission data packets that use the fixed allocation slot and the reserved allocation slot allocated in response to the reservation request to the central station 31. On the other hand, when the transmission mode selection unit 103 is selected to use the random access method, the transmission mode selection unit 103 converts the data packet that has not been divided by the packetizing unit 102 and the packet data at the head of the packet if the packet division is performed. Output to the data buffer 105.
Data packets other than the head portion of the packet-divided data packets are output to the DA data buffer 104.

If the input data 101 cannot be accommodated in one time slot on the satellite line, the peripheral station makes a reservation request for an empty slot, so that only the first data packet is stored in the RA data buffer 105 and divided. Subsequent data packets are transmitted by the reservation allocation access method, and are stored in the DA data buffer 104. Therefore, RA data buffer 105
Means that data packets to be transmitted by random access are buffered using empty slots not allocated to any peripheral station.

The hold buffer 100 connected to the RA data buffer 105 is a buffer for temporarily holding the data packet 106 read from the RA data buffer 105 and transmitted by the random access method. As described above, in the random access method, since each of the peripheral stations 32 _{1 to} 32 _N transmits data at any time when transmission data is generated to the central station 31, a plurality of peripheral stations transmit data in the same time slot. May be
In this case, transmission data is lost due to collision between data. When such a collision occurs, the central station 31
Assuming that the data could not be received normally, the peripheral station reads out the retransmission data packet 107 from the holding buffer 100 and retransmits it. That is, the pending buffer 100 performs retransmission due to data collision,
The transmission data packet by the random access method is held until the delivery confirmation from 1 is obtained.

The transmission management unit 96 includes a slot type management unit 9
2 based on the transmission slot number 97 stored in the DA data buffer 10 at the transmission slot timing fixedly allocated or reserved exclusively for the own station in the next frame.
4 is read from the transmission data packet, and at an empty slot timing not assigned to any peripheral station, R
A transmission data packet is read from the A data buffer 105. Further, the transmission management unit 96, for example,
A reservation request for using an empty slot that cannot be accommodated in a time slot exclusively for the own station can be added to transmission data. Further, the transmission management section 96 generates transmission slot timing information 98 indicating whether or not data has been transmitted at each slot timing, and notifies the delivery confirmation management section 94 of the transmission slot timing information 98.

As described above, when the random access method is used, the delivery confirmation management unit 94 uses the transmission slot timing information 98 indicating whether or not data has been transmitted at each transmission slot timing notified from the transmission management unit 96. Thus, the transmission history of which transmission slot timing the own station transmitted data is held. This transmission history
It is held as a fixed value from the time when each peripheral station transmits a transmission data packet in a transmission frame to the time when acknowledgment information corresponding to the frame arrives from the central station 31 to the source peripheral station. Thereby, based on the held transmission history, it is possible to confirm whether the data transmitted by the own station has been normally received by the central station based on the acknowledgment information notified from the central station, and as a result of the confirmation. The transmission confirmation 99 can retransmit or discard the transmission data buffered in the hold buffer 100. The transmission data whose delivery is confirmed by the central station is deleted from the holding buffer 100, and the transmission data whose delivery is not confirmed is read out again from the holding buffer 100,
The data is retransmitted from the data buffer 105.

As described above, the transmission management section 96 sends the data packets read from each of the data buffers 104 and 105 to the transmission section 83. The transmission unit 83 includes the transmission management unit 9
6 is added to the transmission data packet from No. 6, redundant bits for error detection, encoded and modulated, and output to the transmission / reception unit 81. The transmission / reception unit 81 converts the frequency into a high frequency band, and transmits a radio wave 80 as transmission data.

The first peripheral station 32 ₁ capable of performing such control has a CPU (not shown), and has a predetermined storage such as an external storage device such as a magnetic disk or a ROM provided separately therefrom. Various controls can be executed based on a program stored in the device.

FIG. 7 shows an outline of a control procedure of the _first peripheral station 32 ₁ . The first peripheral station 32 ₁
When data to be transmitted is generated from the connected communication terminal or the terrestrial communication network, the data that has been packetized by the packetizer 102 in advance is transmitted to the transmission mode selector 10.
According to the access method selected in step 3, the data is buffered in the DA data buffer 104 or the RA data buffer 105 as described above. That is, when the transmission mode selection unit 103 is selected not to use the random access scheme, the packetization unit 102
Are buffered in the DA data buffer 104. On the other hand, when it is selected to use the random access scheme, the data packets that have not been packet-divided by the In this case, the packet data of the head portion is buffered in the RA data buffer 105, and the data packets other than the head portion of the packet-divided data packets are buffered in the DA data buffer 104.

When the transmission frame and transmission slot timing 95 generated by the frame / slot synchronization section 90 based on the frame synchronization pattern 89 extracted from the received signal are transmitted (step S110: Y), the transmission management section 96 Detects the transmission slot fixedly allocated or reserved exclusively for the own station based on the transmission slot number 97 notified by the slot type management unit 92 (step S111).

If the transmission slot is detected as fixed or reserved in step S111 (step S111: Y), it is read from the DA data buffer 104 and inserted into the corresponding slot (step S11).
2). On the other hand, if no fixed or reserved transmission slot is detected in step S111 (step S111: N), it is determined that transmission is to be performed by the random access method, and the transmission slot notified by the slot type management unit 92 is determined. An empty slot is detected based on the number 97 (step S113). When an empty slot is detected (step S113: Y), the packet read from the RA data buffer 105 is inserted into the corresponding slot (step S114). If no empty slot is detected (step S113: N), the transmission timing is checked again.

The transmission management section 96 generates transmission slot timing information 98 indicating whether or not data has been transmitted at each slot timing, and transmits this to the delivery confirmation management section 94.
, It is possible to perform retransmission when the random access method is selected. For the transmission data packet or the retransmission data packet read from the DA data buffer 104 or the RA data buffer 105, the transmission unit 83 performs addition of redundant bits for error detection, encoding and modulation (step S115). Thereafter, the transmission / reception unit 81 performs frequency conversion to a high frequency band (step S116) and transmits the signal to the communication satellite 30 (step S117).

On the other hand, when reception data is received from the communication satellite 30 (step S110: N, step S118:
In Y), the transmission / reception unit 81 performs frequency conversion of the received radio wave into the intermediate frequency band (step S119). The reception signal subjected to frequency conversion by the transmission / reception unit 81 is demodulated and error-corrected by the reception unit 82 (step S120). The error-corrected and error-free received data is separated into a frame synchronization pattern, slot allocation information, acknowledgment information, and a received data packet by the separating unit 85 (step S12).
1).

As described above, the frame synchronization pattern is used by the frame / slot synchronization section 90 to generate a transmission frame and transmission slot timing synchronized with the frame timing of the central station. In the slot allocation information, the slot in which the address of the own station is written is identified by the slot type management unit 92, and a slot number that can be used exclusively by the own station and a slot number of an empty slot are stored in the next transmission frame. Used for time slot allocation. The acknowledgment information indicates whether or not transmission data has been normally received at the central station when transmission is being performed from the peripheral station to the central station by a random access method. It is used for retransmitting necessary transmission data based on the transmission slot timing 98 notified from 96. The received data packet is
The received data 88 is buffered in the reception data buffer 87 (step S122), and the reception data 88 is output to the communication terminal or the terrestrial communication network connected to the _first peripheral station 32 ₁ (step S123). Thereafter, the transmission timing is checked and the same operation is repeated (return).

As described above, at the time of transmission, the first peripheral station 32 ₁ generates a transmission timing synchronized with the frame timing of the central station based on the frame synchronization pattern included in the received signal. The input data input to the peripheral station is packetized and buffered in the DA data buffer 104 or the RA data buffer 105 according to the access method selected by the transmission mode selection unit 103. That is, DA data buffer 104 buffers transmission data packets using the fixed allocation slot and the reservation allocation slot allocated in response to the reservation request to central station 31. RA data buffer 10
5 buffers a data packet to be transmitted by random access using an empty slot not allocated to any peripheral station. In the transmission management unit 96,
Based on the transmission timing generated by the frame / slot synchronization section 90, the packet data is read from the DA data buffer 104 or the RA data buffer 105 from the transmission slot number notified by the slot type management section 92, and transmitted via the transmission section 83. To the communication satellite 30.

On the other hand, upon reception, the received signal is separated into a frame synchronization pattern, slot allocation information, delivery confirmation information, and a received data packet. The frame synchronization pattern is used by the frame / slot synchronization section 90 to generate a transmission frame and transmission slot timing synchronized with the frame timing of the central station. As the slot assignment information, the slot in which the address of the own station is written is extracted by the slot type management unit 92, and the slot number that can be exclusively used by the own station and the slot number of the vacant slot are stored in the next transmission frame. Used for time slot allocation. The acknowledgment information indicates whether or not transmission data has been normally received at the central station when transmission is being performed from the peripheral station to the central station by a random access method. It is used for retransmitting necessary transmission data based on the transmission slot timing 98 notified from 96.

Next, a procedure for changing a time slot in the satellite communication apparatus described above will be described.

FIG. 8 shows an outline of a first time slot change procedure of the satellite communication apparatus in the present embodiment. Here, the first and second peripheral stations 32 ₁ , 32 ₂
Communication between the central station 31 and the central station 31 is performed via the communication satellite 30, and the line information transmitted and received between them is shown with the passage of time. Also, it is assumed that a random access method is not used as a method for transmitting data from each of the first and second peripheral stations 32 ₁ and 32 ₂ to the central station 31. The central station 31 broadcasts slot assignment information to the first and second peripheral stations 32 ₁ and 32 ₂ at predetermined time intervals (see 130 ₁ to 130 _{1 in} FIG. 8).
130 ₉ , 131 _{1 to} 131 ₉ ). At timing B, it is assumed that there is a change in slot assignment due to the new slot assignment of the _third peripheral station 323, and the period up to timing B is defined as period T ₁ , and the period thereafter is defined as period T ₂ .

FIG. 9A shows an outline of the configuration of the slot allocation information notified to the first and second peripheral stations during the period T ₁ in FIG. Here, it is assumed that one frame is time-divided into five time slots and used.
The slot assignment information 132 is stored as fixed slot assignment information in frame units in the slot assignment storage unit 56 of the central station 31, and one frame is divided into _five time slots 133 _{1 to} 133 ₅ and divided into each time slot. Indicates the peripheral station address of the peripheral station assigned to the slot. That is, the first slot 133 ₁ of each frame to a first peripheral station 32 ₁ surrounding terminal address is "0001", the second peripheral third slot 133 ₃ surrounding terminal address is "0002" Station 32
₂ is a state in which each is fixedly assigned. Remaining second slot 133 ₂ , fourth slot 1
Since the non-existent peripheral station address “FFFF” is written in 33 ₄ and the fifth slot 133 ₅ , respectively.
It can be an empty slot.

Here, returning to FIG. 8, the description will be continued. FIG.
Slot assignment information 130 _{1 to} 13 as shown in FIG.
0 ₆ and 131 _{1 to} 13 ₁₆ are broadcast from the central station 31 to the first and second peripheral stations 32 ₁ and 32 ₂ . Therefore, from the first peripheral station 32 ₁ , the first peripheral station 32 1
Data read from the DA data buffer is sent to the slot (134 _{1 to 134 6} in FIG. 8). Also, the second
The data read from the DA data buffer is also transmitted to the third slot of each transmission frame from the peripheral station 32 ₂ (135 ₁ and 135 _{2 in} FIG. 8). Since the other peripheral stations do not access the first and third slots that do not match the peripheral station addresses of the own station with reference to the slot assignment information transmitted from the central station 31, the first and second peripheral stations do not. The transmission data of the peripheral stations 32 ₁ and 32 ₂ are received by the central station 31 without occurrence of data collision.

Now, the central station 31 sends the slot allocation information 1
When 30 ₃ and 131 ₃ are broadcast, the second peripheral station 32
_It is assumed that the second peripheral station 32 ₂ has requested the central station 31 to reserve and allocate an empty slot because more transmission data than usual has occurred in 2. This reservation request is added to the data transmitted using the third slot allocated to the _second peripheral station 32 ₂ (136 in FIG. 8).

[0076] central station 31 receives this reservation request with the transmission data 136, it is assumed that newly allocated the second slot to the second peripheral station 32 ₂ of the empty slots in each frame. Then, the second slot assignment information 130 _5, 131 ₅ near station address of the peripheral station 32 ₂ is written is broadcasted to each peripheral station to the newly second slot. In the second peripheral station 32 ₂ , the slot assignment information 1
31 ₅ After receiving the, DA using the third slot already assigned in a fixed manner (135 _5, 135 ₆ 8), the second slot is newly reserved for allocation slots
The data read from the data buffer is transmitted (137 in FIG. 8). However, the slot assignment information 13
Until ₁₅ is received, the fixedly assigned third
Is performed using the slot of FIG.
5 _4).

[0077] FIG. 9 (b), shows the outline of the configuration of the slot allocation information is notified to the first and second peripheral stations in the period T ₂ of the FIG. Timing B in FIG.
In, the third peripheral stations 32 ₃ near station address "0003" is newly added from the input terminal 54 connected to the central station 31, with respect to the first through third peripheral station 321 _to 323 It is assumed that a new slot is allocated. That is, as indicated by the slot allocation information 138 in FIG. 9 (b), the first slot 139 _1, third peripheral stations 32 ₃ peripheral station address is "0003" of each frame, the second
Slot 139 ₂ of the first peripheral station 32 ₁ having a peripheral station address of “0001”, and fifth slot 139 ₅ of the second peripheral station 32 ₂ having a peripheral station address of “0002”.
, Respectively. The remaining third slot 139 ₃ and fourth slot 139 ₄ are vacant slots because the non-existent peripheral station address “FFFF” is written in each of them.

Returning to FIG. 8, the description will be continued. FIG.
The lot allocation information as shown in FIG.
Thereafter, the slot allocation information 130 _{7 to} 130 ₉ , 131 ₇ to
131 ₉ is broadcast. First peripheral station 3 receiving this
2 ₁ changes the fixed assignment slot to the second slot, and transmits the read data from the DA data buffer (140 _{7-140 8} in FIG. 8). Similarly, the second peripheral stations 32 _2, by changing the fixed assignment slots to the fifth slot, and transmits the read data from the DA data buffer (141 _{7-141 8} in FIG. 8).

As described above, when the fixed slot assignment is changed, no special change procedure other than the normal slot assignment information is required, and no special notification means is used.
Further, since each peripheral station can recognize the change of the fixed allocation slot of the own station at the same time, no data collision occurs.

Next, a case where the peripheral station uses the random access method will be described.

FIG. 10 shows an outline of a second time slot changing procedure of the satellite communication apparatus in the present embodiment. Here, the first and fourth peripheral stations 32 ₁ , 3
It shall be made via the communication communications satellite 30 between the 2 ₄ and the central station 31, which represents the line information transmitted and received between these over time. Also, the first transmitting station 32
₁ as the data transmission method to the central station 31, although not using the random access method, the fourth transmitting station 32 ₄ shall use the random access method as a data transmission method to the central station 31. From the center station 31, slot assignment information is broadcast to the first and fourth peripheral stations 32 _1, 32 ₄ for each predetermined time interval (150 in FIG. 10
_{1-150 9,} 151 _{1-151 9).} At timing C, it is assumed that there is a change in slot assignment due to the _third peripheral station 323 being assigned to a new slot,
The period up to the timing C is referred to as a period T ₁ , and the period thereafter is referred to as a period T ₂ .

FIG. 11A shows an outline of the configuration of the slot allocation information notified to the first and fourth peripheral stations during the period T ₁ in FIG. Here, it is assumed that one frame is time-divided into five time slots and used. The slot allocation information 152 to the slot assignment storage unit 56 of the center station 31 are stored as fixed slot assignment information in units of frames, one frame is divided in five time slots 153 _{1 to 153 5,} to each time slot Indicates the peripheral station address of the peripheral station assigned to the slot. That is, the first slot 153 ₁ of each frame the peripheral station address "0001"
, The fourth slot 153 ₄ corresponds to the second peripheral station 32 ₁ whose peripheral station address is “0002”.
₂ is a state in which each is fixedly assigned. Remaining second slot 153 ₂ , third slot 1
53 _3, the fifth slot 153 near station address nonexistent respectively the ₅ "FFFF" is written,
It becomes an empty slot. In the period T _1, the fourth peripheral stations 32 ₄
Has no fixed slot assignment.

Here, returning to FIG. 10, the description will be continued. Slot allocation information 150 ₁ to ₁ as shown in FIG.
50 _6, 151 _{1 to 151 6} is being broadcast from the central station 31 to each peripheral station. Therefore, the data read from the DA data buffer is transmitted from the first peripheral station 32 ₁ to the first slot of each transmission frame (15 in FIG. 10).
4 _{1-154 6).} Further, the fourth peripheral station 32 ₄ recognizes that the second slot, the third slot, and the fifth slot of each frame are empty slots based on the notified slot allocation information, The read data is inserted into, for example, the second slot and transmitted by the random access method (155 in FIG. 10).

Now, the central station 31 sends the slot allocation information 1
When 50 ₃ and 151 ₃ are broadcast, the fourth peripheral station 32
₄ fourth peripheral station 32 ₄ for a number of transmitted data than usual occurs assume that a request to the center station 31 the reservation allocation of empty slots. The reservation request, fourth peripheral station 32 ₄ is one of idle slots to be used in a random access scheme, it is added to the data to be transmitted using, for example, the second slot (156 in FIG. 10).

[0085] central station 31 receives this reservation request with the transmission data 156, the second and third slots of the empty slots in each frame, newly assigned to the fourth peripheral stations 32 _4. Then, slot assignment information 150 ₅ and 151 _{5 in} which the peripheral station address of the _fourth peripheral station 324 is written in the second and third slots is broadcast to each peripheral station. When the fourth peripheral station 32 ₄ receives the slot allocation information 151 ₅ , it transmits the data of the DA data buffer to the two slots, the second and third slots, which are the reserved allocation slots, in the next frame (FIG. 10 157, 158).

[0086] FIG. 11 (b), shows the outline of the configuration of the slot allocation information is notified to the first and fourth peripheral stations in the period T ₂ of the FIG. 10. The input terminal device 5 connected to the central station 31 at timing C in FIG.
4 to the third peripheral station 32 of the peripheral station address “0003”
₃ is newly added, and the first to third peripheral stations 32 _{1 to} 32 ₃
, A new slot is allocated.
That is, as indicated by the slot allocation information 159 in FIG. 11B, the first slot 160 ₁ of each frame is assigned to the third peripheral station 32 whose peripheral station address is “0003”.
_3, the fourth slot 160 ₄ of the peripheral station address "00
A first peripheral station 32 ₁ is 01 ", the fifth slot 1
60 ₅ peripheral station address is "0002" which is the second peripheral stations 32 _2, newly allocated respectively. In the remaining second slot 160 ₂ and third slot 160 ₃ , the non-existent peripheral station address “FFFF” has been written, so that they become empty slots.

Returning to FIG. 10, the description will be continued. FIG.
The lot allocation information as shown in FIG.
Thereafter, slot allocation information 150 _{7 to} 150 ₉ , 151 ₇ to
151 ₉ is broadcast. First peripheral station 3 receiving this
2 ₁ changes the fixed assignment slot to the fourth slot, and transmits the read data from the DA data buffer (161 _{7-161 8} in FIG. 10). In addition, the fourth peripheral station 3
2 ₄ from the slot allocation information 151 _{7-151 9,} recognizes that the empty slot is changed to the second and third slots, to transmit a random access scheme, for example, using the third slot of the idle slot (16 in FIG. 10)
2).

As described above, even when peripheral stations performing transmission by the random access method are mixed, a special change procedure other than ordinary slot allocation information can be made unnecessary when changing fixed slot allocation.

As described above, the satellite communication apparatus according to the present embodiment holds the time slot allocation information in which the peripheral station address unique to the peripheral station is written in the central station, and broadcasts the information to each peripheral station as the slot allocation information. By changing the allocation of time slots in response to fluctuations in communication traffic and addition or deletion of peripheral stations, a special change procedure other than broadcasting of normal slot allocation information can be made unnecessary. Become.

In this embodiment, whether or not a random access method is used as a line access method in which each peripheral station transmits data to the central station is performed in units of peripheral stations. However, the present invention is not limited to this. Not something. For example, if selection is made for each communication terminal connected to a peripheral station or for each logical call, more flexible satellite communication can be performed.

Further, in the present embodiment, the opportunity for the peripheral station to request the reservation of an empty slot is when transmission data having a length of one time slot or more is generated, but the present invention is not limited to this. For example, a DA data buffer and R
It may be triggered by the accumulation of a predetermined number or more of data in the A data buffer.

[0092]

As described above, according to the first aspect of the present invention, the central station broadcasts the latest slot allocation information to each peripheral station in frame units at a time, and each peripheral station broadcasts the broadcast slot information. Based on the allocation information, the next transmission frame is transmitted using an allocation slot dedicated to the own station.
This makes it possible to easily change the optimal slot assignment in response to traffic fluctuations and changes in the configuration of the communication network, and to perform special slot assignment information between the central station and each peripheral station other than broadcasting of normal slot assignment information. The change procedure can be made unnecessary.

According to the second aspect of the present invention, the fixed allocation access system, the reserved slot allocation access system, and the random access system based on the time division multiplex access control which have been used in the communication from the peripheral station to the communication station have been described. Even when used together, it is possible to easily change the optimal slot assignment in response to traffic fluctuations and changes in the communication network configuration without changing the protocol. This eliminates the need for a special change procedure other than the broadcast of the slot allocation information.

Further, according to the third aspect of the present invention, appropriate slot allocation can be easily performed in response to traffic fluctuations and changes in the communication network configuration, and a flexible satellite communication network can be configured.

Further, according to the fourth aspect of the invention, a special additional device is not required, an empty slot can be identified, and the satellite communication device can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an outline of a configuration of a satellite communication device according to an embodiment of the present invention.

FIG. 2 shows a central station 31 to peripheral stations 32 in the embodiment.
Is a format diagram showing an outline of a configuration of a signal format of the transmission signal to the ₁ to 32 _N.

FIG. 3 is a format configuration diagram illustrating an outline of a configuration of a signal format of a transmission signal from each of the peripheral stations 32 _{1 to} 32 _N to the central station 31 in the embodiment.

FIG. 4 is a block diagram illustrating an outline of a main part of a configuration of a central station 31 according to the embodiment.

FIG. 5 is a flowchart showing an outline of a control procedure of the central station 31 in the embodiment.

FIG. 6 is a block diagram illustrating an outline of a main part of a configuration of a _first peripheral station 321 according to the embodiment.

7 is a flowchart showing an overview of a first peripheral station 32 ₁ of the control procedure in this embodiment.

FIG. 8 is a sequence diagram illustrating an outline of a first time slot change procedure in the embodiment.

FIG. 9A is a signal configuration diagram illustrating a configuration of slot allocation information notified to first and second peripheral stations during a period T1 of a _first time slot change procedure in the embodiment. (B) it is a signal configuration diagram showing a configuration of the first and second slot assignment information notified to the peripheral station in the period T ₂ of the first time slot changing procedure in this embodiment.

FIG. 10 is a sequence diagram showing an outline of a second time slot change procedure in the embodiment.

11 (a) is a signal configuration diagram showing the configuration of the first and fourth slot allocation information notified to the peripheral station in the period T ₁ of the second time slot change procedure in the present embodiment. (B) A signal configuration diagram showing a configuration of slot allocation information notified to the first and fourth peripheral stations during a period T2 of a _second time slot change procedure in the embodiment.

FIG. 12 is a sequence diagram showing an outline of a time slot changing procedure in the conventional time division multiplex access control.

It is a 13 (a) signal configuration diagram showing the configuration of the slot allocation information for a period T ₁ in the conventional time slot change procedure shown in FIG. 12. (B) it is a signal configuration diagram showing the configuration of the slot allocation information for a period T ₂ in the conventional time slot change procedure shown in FIG. 12.

[Explanation of symbols]

30 Communication Satellite 31 Central Station 32 _{1 to} 32 _N Peripheral Station 33 ₁ Frame Synchronization Pattern 33 ₂ Slot Assignment Information 33 ₃ Delivery Confirmation Information 40, 80 Radio Wave 41, 81 Transmitter / Receiver 42, 82 Receiver 43, 83 Transmitter 44 Timing Signal Generation unit 45 Reference clock 47, 85 Separation unit 49 Control signal generation unit 51, 87 Receive data buffer 54 Input terminal device 56 Slot allocation storage unit 58 Transmission data buffer 60 Multiplex unit 90 Slot / frame synchronization unit 92 Slot type management unit 94 Delivery Confirmation management unit 96 Transmission management unit 100 Reserved buffer 102 Packetization unit 103 Transmission mode selection unit 104 DA data buffer 105 RA data buffer

Claims (4)

[Claims] 1. A peripheral station assigned to each slot of a frame received from a peripheral station by writing a unique peripheral station address corresponding to each slot obtained by dividing a frame of a fixed time length into a predetermined number. Slot allocation information holding means for holding slot allocation information; first transmission information generation means for generating first transmission information to each peripheral station; and first transmission information generation means generated by the first transmission information generation means. Multiplexing means for multiplexing transmission information and slot allocation information held by the slot allocation information holding means; first transmitting means for transmitting a transmission signal multiplexed by the multiplexing means to a communication satellite; A central station having first receiving means for receiving a reception signal addressed to the own station from a communication satellite; and transmitting the transmission signal transmitted from the first transmission means to all peripheral stations. A communication satellite that transmits and relays second transmission information from each peripheral station to the central station; and a second reception unit that receives a transmission signal transmitted from the first transmission unit via the communication satellite. A slot allocation information extracting unit for extracting the slot allocation information multiplexed on the received signal received by the second receiving unit, and a second generating unit for generating second transmission information from the own station to the central station. The second transmission information generating means uses the slot of the transmission frame corresponding to the slot in which the peripheral station address of the own station is written based on the slot allocation information extracted by the slot allocation information extracting means.
Transmitting means for transmitting the second transmission information generated by the transmission information generating means to the communication satellite, and a plurality of peripheral stations each identified by a unique peripheral station address. Characteristic satellite communication device. 2. A fixed assigned slot is assigned to each slot of a frame received from a peripheral station by writing a unique peripheral station address corresponding to each slot obtained by dividing a frame of a fixed time length into a predetermined number. Slot assignment information holding means for holding slot assignment information indicating a peripheral station; first receiving means for receiving a reception signal addressed to the own station from a communication satellite; and normal reception signals received by the first reception means. To detect whether it has been received,
Delivery information generating means for generating delivery information indicating whether or not normal reception is possible for each slot; and requesting a new slot assignment to a transmission requesting peripheral station from a received signal received by the first receiving means. A reserved slot request extracting means for extracting a reserved slot request to be made, and referring to the slot allocation information held by the slot allocation information holding means based on the reserved slot request extracted by the reserved slot request extracting means, Reserved slot allocating means for generating second slot allocation information in which the peripheral station requesting the reserved slot is newly allocated as a reserved allocated slot to an empty slot not allocated to the peripheral station; First transmission information generating means for generating the transmission information of Multiplexing means for multiplexing the transmission information, the second slot allocation information generated by the reserved slot allocation means, and the delivery information generated by the delivery information generation means, and the transmission signal multiplexed by the multiplexing means. And a first transmitting means for transmitting the transmission signal to a communication satellite; and transmitting a transmission signal transmitted from the first transmitting means to all the peripheral stations and a second transmission from each peripheral station to the central station. A communication satellite for relaying information; packetization means for packetizing transmission data from the own station to the central station to generate second transmission data; and a reservation slot request when the packetization means cannot accommodate one slot. Reserved slot request output means for outputting, and random access setting means for setting whether to perform transmission to the central station by a random access method, A second receiving means for receiving a transmission signal transmitted from the first transmitting means via the communication satellite; and a second multiplexing means for multiplexing the received signal received by the second receiving means. Slot allocation information extracting means for extracting slot allocation information, delivery information extracting means for extracting the delivery information multiplexed on the received signal received by the second receiving means, and extraction by the delivery information extracting means Holding means for holding the second transmission data of its own station, which is not normally received by the central station based on the received delivery information, as holding data; and a random access method for transmitting to the central station by the random access setting means. When the setting is made to perform in the above, the empty slot is set to an empty slot based on the second slot allocation information extracted by the slot allocation information extracting means. 2 and the reserved data inserted by the reserved slot request output means, and the transmission to the central station is not performed by the random access setting means by the random access method. When set, the fixed allocation slot or the reserved allocation slot corresponding to the slot in which the peripheral station address of the own station is written based on the second slot allocation information extracted by the slot allocation information extracting means. Second transmission information generating means for generating second transmission information by inserting the second transmission data, and transmitting the second transmission information generated by the second transmission information generating means to the communication satellite. Second
And a plurality of peripheral stations each identified by a unique peripheral station address. 3. The central station further comprises setting means for setting slot assignment information held by the slot assignment information holding means.
Or the satellite communication device according to claim 2. 4. The satellite communication apparatus according to claim 2, wherein said second slot allocation information is written with a non-existent peripheral station address which is predetermined as an empty slot.