JP2932839B2 - Satellite communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple access satellite communication system for performing communication between one station (master station) and many stations (slave stations) via a satellite through a common channel. The present invention relates to a satellite communication system with an improved access method to a master station.

[0002]

2. Description of the Related Art In a multiple access satellite communication system in which communication between a master station and a slave station via a satellite is performed on a common channel,
There are an Aloha system and a slot Aloha system as methods for accessing a master station from a slave station. These two systems are so-called random access systems. The Aloha method is not synchronized between slave stations, and when data to be transmitted occurs,
It is based on the basic procedure of immediately transmitting data to the line shared with other slave stations, colliding with other data, and resending data when some or all of the data is lost, Since the data collision rate is high, the slot ALOHA method shown in FIG. 5 is adopted as a random access method.

[0005] In FIG. 5, a symbol S is a time slot, and the time slot S is obtained by dividing a time axis of a communication channel into fixed time units corresponding to one packet length. In each of the slave stations, the stations 1, 2, and 3 receive data and synchronize so that a transmission packet enters this time slot before transmitting. However, since which time slot S is to be inserted depends on the timing of data generation of each station, the transmission packet A of the station 1 and the station 2
The packet may collide like the transmission packet B of FIG. When a collision occurs, each slave station knows that the data has been lost due to the collision because there is no reception response signal from the master station, and the station 1 retransmits the transmission packet A 'after an arbitrary time elapses. , Retransmit the transmission packet B 'at a time different from the time when the transmission packet A' is retransmitted.

[0004]

In the conventional slot ALOHA system, since the length of each slot is determined in advance, the packet length, that is, the data length included in one packet, is also defined. If you frequently send data with a shorter data length,
There is a problem that the channel throughput is greatly reduced.

An object of the present invention is to provide a satellite communication system capable of improving slot utilization efficiency and performing high-throughput communication.

[0006]

In order to achieve the above object, the present invention comprises a master station and a plurality of slave stations in a star configuration, and communication from the slave station to the master station is performed via a satellite. In a satellite communication system using a common random access channel and a broadcasting channel that allows the master station to communicate with all slave stations via satellites, an antenna that transmits the master station using satellites and radio waves A synchronization signal generation unit that generates a frame timing and a timing signal indicating a break between a long time slot and a short time slot in the frame;
A receiving unit that performs a process of receiving data from a slave station, a receiving data buffer that receives an output of the receiving unit and buffers the received data as received data, and a short slot and a long frame in a frame that receives an output from the receiving unit. Received data statistic part for calculating the throughput of the slot part, receiving the output, and changing the time division distribution ratio for each slot part so as to minimize the difference in throughput of each slot part, A frame distribution conversion circuit that transmits a timing signal indicating a break of a long time slot section to the synchronization signal generation section, and further notifies the control signal generation section that the time division distribution ratio is to be changed. A control signal generator for generating a notification to the slave station and receiving the output of the receiver to generate a reception response signal; and a transmission data buffer for buffering the transmission data. And a multiplexing unit that receives and multiplexes the outputs of the transmission data buffer, the synchronization signal generation unit, and the control signal generation unit, and a transmission unit that receives the output of the multiplexing unit and sends the output to the antenna. is there.

In order to achieve the above object, the present invention comprises a master station and a plurality of slave stations in a star configuration, and communication from the slave station to the master station is performed by a common random access via a satellite. Using a channel, the master station receives a signal transmitted synchronously from the master station with an antenna in a satellite communication system with a broadcast type channel that allows communication to all slave stations via satellite. And select the timing signal,
A frame synchronization unit that generates a frame timing signal common to each slave station and a timing signal indicating a break between a short time slot unit and a long time slot unit, and subdivides each slot unit based on the timing signal to provide a short time The timing of the slot and the long time slot is generated, and when a notification of the change of the time division distribution ratio for each slot from the receiving unit is received from the master station, the short slot timing and the long slot timing are generated accordingly. The transmission slot management unit determines short data and long data depending on whether the transmission data is above or below a certain threshold. If the data is short, the data is sent to the short data transmission control unit. If the data is long, the long data is transmitted. A data length determination circuit to be sent to the control unit, and buffering data sent from the data length determination circuit, And transmitted using the slot, also,
A short data transmission control unit and a long data transmission control unit that perform retransmission according to a signal from the delivery determination unit, a multiplexing unit that receives and multiplexes outputs from the short data transmission control unit and the long data transmission control unit, And a receiving unit for receiving data from the receiving unit and buffering data from the receiving unit.

[0008]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an entire configuration of a satellite communication system for implementing the present invention. This satellite communication system uses the master station C
And a plurality of slave stations R in a star shape, and the plurality of slave stations R access the master station C via the satellite S via a common random access channel. In this satellite communication system, the random access channel is time-divided into a short slot having a plurality of short time slots and a long slot having a plurality of long time slots. The time slot and the long time slot are transmitted separately, and the master station can compare the throughput of the short slot portion and the long slot portion and change the time division distribution ratio for the short slot portion and the long slot portion.

The master station C is configured as shown in FIG. In FIG. 2, a master station C includes an antenna 1 that performs transmission using radio waves with a satellite S, and a synchronization signal generation unit 2 that generates a frame timing and a timing signal indicating a break between a long time slot and a short time slot in a frame.
A receiving unit 3 for receiving data from the slave station, a receiving data buffer 4 for receiving the output of the receiving unit 3 and buffering it as received data, and Receiving data statistic unit 5 for calculating the throughput of the short slot unit and the long slot unit, and changing the time division distribution ratio for each slot unit so as to minimize the difference in throughput of each slot unit in response to the output. And a frame distribution conversion circuit 6 for transmitting a timing signal indicating a break between the short time slot portion and the long time slot portion to the synchronization signal generation portion 2 and further transmitting to the control signal generation portion 7 that the time division distribution ratio is to be changed. A control signal generator 7 for generating a notification to each slave station about the change of the time division distribution ratio, receiving an output of the receiver 3 and generating a reception response signal, Submit carry out the grayed data buffer 8
And the transmission data buffer 8, the synchronization signal generation unit 2, and
Multiplexer 9 for receiving and multiplexing each output of control signal generator 7
And a transmitting unit 10 for receiving the output of the multiplexing unit 9 and transmitting the output to the antenna.

The slave station R is configured as shown in FIG. In FIG. 3, the slave station R receives a signal transmitted synchronously from the master station C with the antenna 11, selects a timing signal, and generates a frame timing signal and a short time slot portion common to each slave station R. A frame synchronization unit 12 for generating a timing signal indicating a break of a time slot unit
Based on the timing signal, each slot section is subdivided to generate timings for short time slots and long time slots, and a notification of a change in the time division distribution ratio for each slot section from the receiving section 13 is sent from the master station. If so, the transmission slot management unit 14 that generates the short slot timing and the long slot timing accordingly, and determines the short data and the long data based on whether the transmission data is equal to or greater than a certain threshold, Short data transmission control unit 1 for short data
6, and in the case of long data, a data length judgment circuit 15 to be sent to the long data transmission control unit 17 and data sent from the data length judgment circuit 15 are buffered, and a short slot or a long slot is used. The short data transmission control unit 16 and the long data transmission control unit 17 that transmit and retransmit in response to the signal from the transmission determination unit 18 and the outputs from the short data transmission control unit 16 and the long data transmission control unit 17 A multiplexing unit 19 for receiving and multiplexing the signals,
1 and a reception data buffer 21 for buffering data from the reception unit 13.

FIG. 4 shows an example in which an access channel common to each slave station R is time-divided into a short slot portion and a long slot portion, and shows that the division ratio is variable.

[0013]

As described above, the present invention is a system in which each slave station randomly accesses a master station, and a slot to be used is randomly accessed depending on whether transmission data is short data or long data. The short slot and the long slot are separately set in the channel by time division, and the time division distribution ratio to each slot section is made variable, so that the slot utilization efficiency can be increased and the effect that high throughput communication can be performed. Have.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a satellite communication system for implementing the present invention.

FIG. 2 is a diagram showing a configuration of a master station used in a satellite communication system embodying the present invention.

FIG. 3 is a diagram showing a configuration of a slave station used in a satellite communication system for implementing the present invention.

FIG. 4 is a diagram showing a frame configuration of a slave station used in a satellite communication system for implementing the present invention.

FIG. 5 is a time chart showing data collision and retransmission of the conventional slot Aloha method.

[Description of Signs] 1,11 Antenna 2 Synchronization Signal Generator 3,13 Receiver 4,21 Receive Data Buffer 5 Receive Data Statistical Unit 6 Frame Distribution Converter 7 Control Signal Generator 8 Transmit Data Buffer 9,19 Multiplexer 10 , 20 transmission unit 12 frame synchronization unit 14 transmission slot management unit 15 data length determination circuit 16 short data transmission control unit 17 long data transmission control unit 18 delivery determination unit

Claims (1)

(57) [Claims] 1. A master station and a plurality of slave stations are configured in a star configuration, and communication from the slave station to the master station uses a common random access channel via a satellite. In a satellite communication system having a broadcast-type channel capable of communicating with all of the slave stations through, an antenna that performs transmission and reception using radio waves with the satellite,
A synchronization signal generating unit that generates a frame timing and a timing signal indicating a break of a long time slot and a short time slot in a frame by an instruction, and a receiving unit that performs a process of receiving data from the slave station via the antenna. A reception data buffer that acquires the output of the reception unit and performs buffering as reception data, and a reception data statistics unit that acquires the output from the reception unit and calculates the throughput of the short slot portion and the long slot portion in the frame. Changing the time division distribution ratio for the short slot and the long slot so as to obtain the output of the received data statistical unit and minimize the difference in the throughput between the short slot and the long slot. And transmitting a timing signal indicating a break between the short slot portion and the long slot portion to the synchronization signal generation portion. Convey, further, a frame distribution conversion circuit for outputting the effect of changing the time division distribution ratio, and acquiring the effect of changing the time division distribution ratio, generating a notification to each slave station, A control signal generation unit that receives the output to generate a reception response signal; a transmission data buffer that buffers transmission data; and receives outputs of the transmission data buffer, the synchronization signal generation unit, and the control signal generation unit. A master unit having a multiplexing unit that multiplexes the signals and a transmitting unit that receives an output of the multiplexing unit and sends the output to the antenna; a signal synchronously transmitted from the master station received by the antenna; And a frame synchronization unit for generating a frame timing signal common to the slave stations and a timing signal indicating a separation between a short slot portion and a long slot portion; A receiving unit that transmits and receives radio waves to and from the master unit via the satellite, and based on the generated timing signal, divides the short slot portion and the long slot portion into short slot and long slot timings. Is generated, and if a notification of the change of the time division distribution ratio for the short slot portion and the long slot portion is received from the master station from the receiving portion, the timing of the short slot and the long slot is changed accordingly. A transmission slot management unit to generate, buffering the short data related to the short slot in the transmission data to be transmitted to the master station, transmitting using the short slot, and further performing a retransmission according to an instruction, and a short data transmission control unit. Buffering the long data for the long slot in the transmission data to be transmitted to the master station, transmitting using the long slot, and further instructing A long data transmission control unit that performs retransmission, a delivery determination unit that outputs a retransmission instruction to the short data transmission control unit and the long data transmission control unit based on information from the reception unit, and the transmission data. The short data or the long data is determined depending on whether it is equal to or greater than a threshold value, and the short data is sent to the short data transmission control unit, and the long data is sent to the long data transmission control unit in the case of long data. A length determination circuit, a multiplexing unit that receives and multiplexes an output from the short data transmission control unit and the long data transmission control unit, a transmission unit that receives data from the multiplexing unit and transmits the data to the antenna, A slave station having a reception data buffer for buffering data from a reception unit.