JPS63219237A - Satellite communication system - Google Patents

Abstract

PURPOSE:To improve the transmission efficiency through quick recovery of reply of plural stations and avoidance of collision by using a time slot detected by each reception station based on a response control table so as to send a data. CONSTITUTION:When a transmission station 1 sends a message of a prescribed frame based on the time slot, each reception station 3 judges the message kind of the transmission frame and discriminates multiple address communication, then all the reception stations 3 stop data transmission. Then the reception station 3 references the reply control table to judges whether or not its own station is a multiple address communication object station depending on the multiple address and in case of the object station, the transmission time slot is referenced to calculate (transmission time slot number+correction time slot number) and retards the transmission time slot and sends the transmission frame where a reply flag is set. The correction slot number is decided fixedly to each reception station 3 to correct the difference from the arrival time of each transmission station 1 and reception station 3 from the satellite 2 and to correct the processing time by each station.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a satellite communication system in which a transmitting station and a plurality of receiving stations are connected via a satellite by random access time division multiple access, and in particular, the present invention relates to a satellite communication system in which a transmitting station and a plurality of receiving stations are connected via a satellite by multiple access using random access time division. The present invention relates to a satellite communication system that can reliably and smoothly receive response data.

[Conventional technology]

Conventional satellite communication systems of this type are shown in FIGS. 4 to 6. Figure 4 is a schematic diagram of a general satellite communication system, Figure 5 is an operation flowchart for transmission and reception, and Figure 6 is a transmission signal frame diagram for transmission and reception. A transmitting station serving as a base unit for transmitting, (2) a satellite that relays and transmits a broadcast message from the transmitting station (1), (3) receiving a broadcast message from the satellite (2), It is a receiving station that returns a response message.

The conventional satellite communication system is from the above transmitting station (1) to the satellite (2).
A transmission signal having a frame structure shown in FIG. 6 is sent to the receiving station (3) via the receiving station (3). The transmitting station (1) calculates time slots to be divided and allocated as small time slots to each receiving station (3) on the satellite (2) based on the reference burst in the frame structure of the transmitted signal, and then performs random access. send a message to satellite (2) (step 1).

The message sent to the above satellite (2) is sent to the receiving station (3)
(Step 2). This receiving station (3) determines whether the type of the received message is broadcast communication or individual communication (step 3).

If the receiving station (3) determines that it is a broadcast communication in this (step 3), the receiving station (3) generates a random number (step 4) and sets the transmission time slot based on this random number. A response message is transmitted to the transmitting station (1) by delayed response transmission. The generation of random numbers in the above (step 4) is performed so that the response transmissions of each receiving station (3) do not cause collisions.

On the other hand, if the above (step 3) determines that the communication is independent, the receiving station will immediately send a response (
Step 6).

[Problem that the invention seeks to solve]

The conventional satellite communication system is configured as described above.
It has the disadvantage that there is always a probability that more than one receiving station will transmit in the same time slot in order to collect a response. In order to reduce this probability, it is necessary to increase the number of time slots selected by random numbers, and even in this case, reducing the collision probability requires a long response confirmation time, which further causes a decrease in transmission efficiency due to collisions. There was a problem.

This invention was made in order to solve the above-mentioned problems, and provides a satellite communication system that can improve transmission efficiency by quickly collecting responses from multiple stations and avoiding collisions in broadcast communication. The purpose is to

[Means for solving problems]

In the satellite communication system according to the present invention, when a transmitting station and a plurality of receiving stations simultaneously perform broadcast communication to a plurality of receiving stations by random access time division multiple access, each of the receiving stations receives data. This configuration is such that transmission is stopped, each receiving station detects a transmission time slot based on a predetermined response control table, and performs data transmission in the detected transmission time slot.

[Effect]

The response control table in this invention allocates response transmission time slots to each ground station in a fixed manner and indicates the number of time slots in which the right to use the satellite line is occupied for response confirmation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is an operational flowchart in this embodiment, FIG. 2 is a configuration diagram of a response control table of each receiving station, and FIG. 3 is a transmission frame configuration diagram. In each of the above figures, the satellite communication system according to this embodiment has a transmitting station (1) and a plurality of receiving stations (1) and multiple receiving stations (1) through random access time division multiple access.
3), when performing broadcast communication to multiple receiving stations (3) at the same time, each of the receiving stations (3) above stops transmitting data, and each receiving station (3) The presence or absence of broadcast communication is determined based on the broadcast address of the transmission frame transmitted from the transmitting station (1) based on the response control table, and if the station is a broadcast target station, each receiving station (
The response data is added from each receiving station (3) to the transmitting station (1) by adding the number of correction slots to correct the difference in arrival time from the satellite for 3), and if the station is not a broadcast target station, the mode holding slot is added. In this configuration, data transmission is stopped by the number of transmission time slots obtained by adding the corrected number of slots to the number of corrected slots.

Next, the operation of the system of this embodiment based on the above configuration will be explained. First, the transmitting station (1) transmits the message of the transmission frame shown in FIG. 3 above based on the time slot (
Step 1). This transmitted message is received by the receiving station (3
) is received (Step 2), and the message type is determined based on the message type of the transmission frame that constitutes the message (Step 3). This determination is made by determining whether or not there is broadcast communication, and if it is broadcast communication, whether any one of the plurality of receiving stations (3) is the target station for broadcast communication.

If it is determined in the above (step 3) that the communication is broadcast communication, all of the plurality of receiving stations (3) (including receiving stations that are not target stations for broadcast communication) stop data transmission. That is, in the case of broadcast communication, the satellite line is occupied for transmitting data for response confirmation from the receiving station (3).

Next, in the case of broadcast communication, the receiving station (3)
Referring to the response control table shown in the figure, it is determined whether the station is a target station for broadcast communication based on the broadcast address, and if the station is not a target station for broadcast communication,
In step 4), the transmission of user data is stopped based on this calculated value.

On the other hand, if it is a broadcast communication and the station is a broadcast communication target station, calculate (number of transmission time slots + number of correction time slots) with reference to the transmission time slots (step 6).
, delay the transmission time slot from this calculated value, set a response flag on the transmission frame, and transmit it (step 7).
.

In this case, even if a message from the transmitting station (1) cannot be received due to an error in the satellite line, the response message sent by another receiving station (3) will be received and the user will know that the line is occupied and the user data will be sent. The transmission of the message is canceled based on the response control table for determining whether or not the station corresponds to the broadcast target station shown in FIG.

The above correction slot number is fixed for each receiving station (3) in order to correct the difference in arrival time from the satellite (2) of each transmitting station (1) and receiving station (3) and to correct the processing time of each station. It shall be a fixed value.

As a result, the transmitting station (1) in FIG. 3 knows the time slot in which the response is returned, so it can know which station the response has not reached. Next, retransmission is performed after the time slot in which transmission was stopped.

Furthermore, if the communication is not a broadcast communication, the response transmission is from the receiving station (
3), the signal is immediately transmitted to the transmitting station (1) via the satellite (2).

In the above embodiment, each receiving station (3) has a response control table, but when sending from one station to the next station, no table is provided and the transmission time is determined from the address of each station. It is also possible to use a method of calculating and transmitting slots.

[Effects of the Invention] As described above, according to the present invention, since the time slot in which an acknowledgment is returned is set in advance in the transmitting station, it is immediately possible to know which station the broadcast message has not reached.
Since retransmission can be performed immediately and the line is occupied for response confirmation, the response can be confirmed in a short time.

[Brief explanation of the drawing]

Fig. 1 is an operation flowchart of an embodiment of the present invention, Fig. 2 is a configuration diagram of a response control table of each receiving station, Fig. 3 is a transmission frame configuration diagram, and Fig. 4 is a schematic configuration of a general satellite communication system. 5 is an operational flowchart of conventional transmission and reception, and FIG. 6 is a diagram showing the structure of a transmission signal frame for transmission and reception. (1): Transmitting station (2): Satellite, (3): Receiving station. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a satellite communication system that transmits and receives data between a transmitting station and multiple receiving stations using random access time-division multiple access, when performing broadcast communication to multiple receiving stations at the same time, each of the above A satellite characterized in that a receiving station stops data transmission, each receiving station detects a transmission time slot based on a predetermined response control table, and performs data transmission in the detected transmission time slot. Communication method. (2) The above response control table is provided in each receiving station, and determines the presence or absence of broadcast communication based on the broadcast address of the transmission frame sent from the transmitting station, and if the station is a broadcast target station, the transmission time is The response data is sent from each receiving station to the transmitting station by adding the correction slot number to correct the difference in arrival time from the satellite to each receiving station to the number of slots, and if the station is not a broadcast target station, the number of mode holding slots is added. 2. The satellite communication system according to claim 1, wherein data transmission is stopped by the number of transmission time slots obtained by adding the corrected number of slots.