JPH01168126A - Multiple access communication system - Google Patents

Abstract

PURPOSE:To remarkably improve the utilizing efficiency of a satellite line only by storing tentatively an input data into a buffer, and sending only a first data packet only by means of a contention system even to a data series generated intermittently, and transmitting the other data in a reservation system. CONSTITUTION:The data generated in slave stations 13, 14 are stored in a temporary buffer 2, the information representing the number of stores data is added to the head of a packet in compliance with a slot timing from a master station 12 and the number of packet reservations corresponding to the number of stores data is applied. Thus, the efficient transmission is realized independently of the data quantity. Then a QI signal generated by a buffer controller 3 of a slave station is transmitted to a master station in a data packet incorporatedly with an information section signal to eliminate the need for a special slot required to reserve the satellite line. Thus, it is not required to provide the slots for reservation of the number of the earth stations, and the utilizing efficiency of the satellite line is improved flexibly.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a system in which a plurality of ground stations utilize the same satellite line.
This invention relates to a multiple access communication method for efficiently communicating data.

(Prior Art) A conventional multiple access communication system will be explained using FIG. 5 and FIG. 6.

Reference numeral 19 indicates a transmission sequence from the slave station 14, slots 20 arranged in large numbers on the line 17 are time slots, and packet 10 indicates a data packet.

FIG. 5 shows a multiple access communication system using a contention system. When the slave station 13 generates data to be transmitted, it divides the data into data packets 10 according to the slots 20,
It is transmitted as transmission sequence 18. Similarly, the slave station 14 also transmits data as a transmission sequence 19. Among the data packets 10 of each slave station, Al and B1 are transmitted using different slots 20, so the transmission is successful, but
Since A2 and B2 are transmitted using the same slot 20, a collision of data packets 10 occurs and the transmission fails. When the slave stations 13 and 14 detect a collision of the data packets 10 transmitted by themselves, each slave station 13, 14 brand random is transmitted with A3. It is retransmitted as B3. What has been described above is one method.

Another method is the multiple access communication method shown in FIG. When the slave stations 13 and 14 generate data to be transmitted,
Before sending data packet 10, select appropriate slot 2.
0 to reserve slot 20 for your own station,
Data packet 1 by reserved slot 20 only
Transmit 0.

However, for one slot 20, one slave station 13
．． 14 can be reserved, and stations other than the reserved stations are prohibited from transmitting data in that slot 20. As representative examples, there are the two methods described above.

(Problems to be solved by the invention) As mentioned above, in the conventional multiple access communication system,
In this contention method, as the amount of data packets increases,
It takes time to make reservations, and packet collisions tend to be more common, reducing the efficiency of satellite line usage. In this method, the utilization efficiency of the satellite link is at most 0.36. On the other hand, the reservation method is superior in that the collision probability of data packets is zero, but it requires slots for reservations in addition to slots for transmitting data, which reduces the number of ground stations. As the number of slots increases, the number of slots for this reservation also increases, leading to problems such as a decline in the overall usage efficiency of the satellite line.

The present invention has been made in view of the above points, and an object of the present invention is to realize a flexible satellite communication system that can efficiently transmit data without depending on the amount of data or the number of stations.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a communication system in which a master station controls this communication when slave stations communicate via a satellite link. In this method, a slave station has a buffer that stores packet-like data to be transmitted, an information addition section that reads the data from the buffer after an arbitrary period of time has elapsed, and adds information in the buffer to the data. The master station is equipped with a transmitting section that transmits data with "information" added thereto, and a receiving section that receives information from the master station and data from other slave stations, and the master station receives the data transmitted from the slave station. a receiving section that receives data, a collision detecting section that detects a collision of the data, a slot management section that extracts information in the buffer and reserves the packet-like data, and information on this reservation and the collision detecting section. and a transmitting section that transmits the information to the slave station.

(Operation) The data generated in each slave station is stored in a temporary buffer, and information indicating the number of stored data is added to the beginning of the packet according to the slot timing from the master station. Packets are reserved for the number of pieces of data. This makes it possible to achieve efficient transmission regardless of the amount of data. In addition, the Ql signal generated by the buffer control device of the slave station is
By transmitting data packets combined with intelligence signals to the master station, there is no need to provide special slots required for reserving satellite lines, so there are as many reservation slots as there are ground stations. It is not necessary, is flexible, and can improve the usage efficiency of satellite lines.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Description will be made below using an example of the configuration of the satellite communication system shown in FIG.

In FIG. 1, 11 is a communication satellite and 12 is a master station.

13.14 is a slave station, 15 is a slave station 13, 14 to the master station 12
16 is an outbound channel from the master station 12 to the slave stations 13 and 14. The slave stations 13 and 14 send their respective data to inbound channel 1.
5, the data is transmitted to the master station 12 via the communication satellite 11. The master station 12 sends the received data outbound.
Channel 16 is used to relay communication satellite 11 to slave station 13.
14, and the slave stations 13 and 14 extract only the data addressed to their own stations. Note that the data of each channel is divided into slots and transmitted as data packets, and information regarding slot timing is constantly transmitted from the master station 12 to the slave stations 13 and 14 using the outbound ◆ channel 16.

FIG. 2 shows an example of the configuration of the slave station 13, and 1 indicates the slave station 13.
2 is a buffer for temporarily storing input data 1, 3 is a buffer control device for monitoring the status of buffer 2, 4 is a timer, and Ql generation/adding section 5 is a buffer control device. A device that generates, for example, a Ql signal representing the number of stored data in response to a signal from the device 3, and adds this to the information portion from the buffer 2;
6 is a transmitting section, 7 is a receiving section, 8 is an information section of the data packet 10, and 9 is a Ql signal section.

FIG. 3 shows an example of the configuration of the master station 12, where 21 is a collision detection unit for detecting whether a packet collision has occurred in each slot, and 22 is a Ql from a successfully transmitted data packet 10. 23 is a QI extraction unit that extracts QI
9, a slot management unit that makes slot reservations according to 2;
Reference numeral 4 designates a control signal generation unit that generates information to notify the slave station of transmission success/failure and whether or not a slot is reserved. Reference numeral 25 represents a timing generation unit that indicates slot separation.

FIG. 4 shows the state of the time slot according to the present invention as time passes.

Input data 1 that is generated intermittently is inputted to the buffer 2 and is stored therein from time to time. The buffer control device 3 monitors the buffer 2, and when the data 1 stored in the buffer 2 reaches a predetermined amount, it sequentially divides the data 1 inputted first into bursts of a fixed length, and At the same time as outputting to the generation/adding section 5, the queue status in the buffer 2 is outputted to the buffer control device 3. On the other hand, the timer 4 monitors the three hours during which each input data is stored in the buffer 2, and when the amount of data 1 in the buffer 2 does not reach a certain value even after a certain period of time, the timer 4 outputs the data from here. The data 1 that is not generated is forcibly divided into bursts of a certain length and output to the Ql generation/addition section 5. Here, the fixed amount of the buffer control device 3 and the fixed time of the timer 4 necessary for outputting the data 1 from the buffer 2 are set in advance so that the data transmission can be performed within the allowable delay time of the satellite communication system user. has been done. QI generation addition unit 5
generates QI9 according to the queue status at the time when burst data 1 received from buffer 2 is output from buffer 2 (this information is given from buffer control device 3), and A data packet 10 is generated using the state data as the information part 8. For example, QI
is composed of 3 bits, as shown in FIG. 4, at the time when data packet A1 is output from buffer 2 in slave station 13, three data packets remain in buffer 2. If so, 3 expressed in binary r
o 111 becomes QI9 of data packet A1. QI
The data packet generated by the generation/addition unit 5 of the master station 1
slot timing information generated by the timing generation unit 25 of the master station 2 and given to the slave station via the outbound channel 16; and the control signal generation unit 2 of the master station 12.
Inbound channel 1 using unreserved slots according to the slot reservation information generated by
Sent at 5. At this time, as shown in FIG. 4, if data packet A1 of slave station 13 and data packet B1 of slave station 14 are transmitted in the same slot, a collision occurs.

After this collision is detected by the collision detection unit 21 of the master station 12, a signal representing a transmission failure generated by the control signal generation unit 24 is notified to all slave stations via the outbound channel 16. Packet AI that caused the collision.

After B1 is delayed by slave stations 13 and 14,
Data packet A2. They are each retransmitted as B2. Then, the successfully transmitted data packet, for example A2, is
In the master station 12, from the collision detection section 21 to the Ql extraction section 22
is output to. In the Ql extraction section 22, the data packet A2
From part 01 of , the slave station 13 detects that three data packets remain unsent in the buffer 2 , and outputs this information to the slot management section 23 . The slot management section 23 reserves three unreserved slots among the subsequent slots for the slave station 13, and the control signal generation section 24 generates reservation information and notifies all the slave stations. Then, the slave station 13 uses the reserved slot according to this reservation information from the master station 12 to send the remaining three data packets A3 . A4. Send A5. This is the method explained above.

[Effects of the Invention] As described in detail above, according to the present invention, input data is temporarily stored in a buffer, so that only the first data packet can be used for contention even for data series that occur intermittently. transmission method, and others can be transmitted using a reservation method.
Compared to conventional multiple access communication systems, the efficiency of satellite link usage can be greatly improved.

In addition, the procedure for a slave station to reserve a slot is transmitted in a shared manner in the same packet as the information part as Ql, so there is no need for a slot just for reservation, and it is possible to accommodate changes in the number of ground stations. We can respond flexibly.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram showing an embodiment of the present invention, and Fig. 2 is a block diagram showing an embodiment of the present invention.
FIG. 3 is a configuration diagram of the slave station of the present invention, FIG. 4 is a diagram showing the operation of the present invention, and FIGS. 5 and 6 are diagrams showing the operation of the conventional system. FIG. 11...Master station 12,13.14...Slave station 2...
Buffer 3...Buffer control device 4...Timer
5...QI generation and addition unit 6...Transmission unit 7...Reception unit 21...Collision detection unit 22...Ql extraction unit 2
3... Slot management section 24... Control signal generation section

Claims (1)

[Claims] In a communication system in which a master station controls communication between slave stations via a satellite link, the slave station has a buffer that stores packet-like data to be transmitted, and a buffer that stores the data from the buffer after an arbitrary period of time has elapsed. an information adding section that adds information in the buffer to the read data; a transmitting section that transmits the data with this information added; and a receiving section that receives information from the master station and data from other slave stations. and
The master station includes a receiving unit that receives the data transmitted from the slave station, and a collision detection unit that detects a collision of the data.
A slot management unit that extracts information in the buffer and reserves the packet-like data, and a transmission unit that transmits this reservation information and information from the collision detection unit to the slave station. A multiple access communication method.