JPH0295034A - Satellite communication system using request assignment multiple accessing system and permanent assignment multiple accessing system - Google Patents

Abstract

PURPOSE:To safely control the whole of a network with the use information of a PAMA line with a master station by providing a demodulator for PAMA and a synthesizer to be able to select the full frequency of a PAMA communication channel at a receiving part in a master station transmitter-receiver. CONSTITUTION:In a transmitter-receiver 10A of a master station 2A, a demodulator 32 for permanent assignment multiple access (PAMA) and a synthesizer 34 are provided and in a control device 9A, a synthesizer control part 39 is provided. The master station 2A selects and receives the full frequency of a PAMA line, judges the use condition of the PAMA line according to the presence of the carrier of the communication line, and when the carrier is prevent, the signal from the slave station 1A is received by the carrier and demodulation data 321 are outputted. Thus, even when the PAMA communication is executed at the section of the slave station 1A, the master station can safely control the whole of the network.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a request allocation multiple access (DAM) system that allocates communication lines between earth stations in response to line allocation requests from a plurality of earth stations.
A) method and the Fixed Allocation Multiple Access (PAMA) method, which assigns communication lines to multiple earth stations in a fixed manner in advance.If there are many collisions of line allocation request signals, the DAMA method is switched from the PAMA method. Regarding the satellite communication method to be switched.

[Conventional technology]

Conventionally, in order to send and receive information by satellite communication between a master station (central station) and multiple slave stations (earth stations), a common signaling channel was used.
A slotted random access signal is sent from the slave station to the master station, and a time division multiplexing method is used from the master station to the slave stations to mutually transmit and receive the communication line. Request allocation multiple access method (DAMA method)
A satellite communication system was being used.

A block diagram of the above-mentioned conventional DAMA satellite communication system is shown in FIG. In Figure 2, this DAMA
The satellite communication system consists of a slave station (usually plural) IB, a master station 2B, and a satellite 3. Also, slave station IB is DA
MA subscriber terminal 4A.

It is composed of a control device 5B and a transmitting/receiving device 6B, and the master station 2B is composed of DAMA subscriber terminals 7A to 7N, an exchange 8, a control device 9B, and a transmitting/receiving device 10B. Furthermore, the transmitting/receiving device 10B (6E) of the master station 2B (slave station IB) includes a modulator 26 (11), a BF transmitter 28 (15), a duplexer 2
9 (16), RF receiving section 30 (17), demodulator 31 (1
8), synthesizers 27.33 (13, 20), and the control device 9B of the master station 2B is a slave station line control section 35.
B, master station line control unit 36B, central processing unit (CPU37
), a communication control unit 38, and a control device 5 of the slave station IB.
B is the slave station line control section 22, CPU 23B, communication control section 2
It is composed of 4B.

Next, the operation of this DAMA satellite communication system will be explained.

First, a slotted random access signal requesting a call output from the duplexer 16 of the slave station IB is transmitted to the master station 2B via the satellite 3 through the common signal line (C10 line). In the master station 2B, the duplexer 29 receives the signal, and the RF receiver 3
0. Demodulator 31. The signal is input to the master station line control unit 36B via the slave station line control unit 35B. Here, the usage status of the communication line is checked, an empty communication line is specified, and the slave station line control unit 35
B.

CPU37. Communication control unit 38. Modulator 26. From the duplexer 29 via the RF transmitter 28 to the slave station I through the C8C line.
B by time division multiplexing. In the slave station IB, the signal is received by the duplexer 16 and inputted to the slave station line controller 22 via the RF receiver 17 and the demodulator 18. Here, a control signal is output to the CPU 23B to use the communication line instructed by the master station 2B, and the CPU 23B
A designated vacant communication line is selected via the modulator 11 and the RF transmitter 15, and the signal is transmitted from the duplexer 16 to another desired slave station or master station. Here, the slotted random access signal transmitted from each slave station on the C8C line is
Although transmission is performed with a certain probability of collision, in the event of a collision, it is retransmitted, resulting in a call loss rate that is hardly a problem under normal call conditions. However, as in the case of order wire lines of in-vehicle stations, a large number of calls occur simultaneously from one news source, and C
A problem arises in which 8C line collisions occur and a connection cannot be established forever. As a countermeasure to this problem, a means is used in which the slave station switches to a fixed allocation multiple access line (PAMA line) in the event of an abnormality.

FIG. 3 shows a block diagram of a satellite communication system using the DAMA system and the PAMA system.

In the satellite communication system using the DAMA system and the PAMA system shown in FIG. 3, the slave station IB of the satellite communication system using the DAMA system shown in FIG.
A PAMA modulator 12, a PAMA demodulator 19, synthesizers 14 and 21, and a counter 25 are newly provided. P.A.M.
The subscriber terminal 4B for A is connected to the communication control section 24A, and
The power side of the AMA conversion gain adjuster 12 is connected to the communication control unit 24A,
The output side is connected to the RF transmitting section 15, the input side of the PAMA demodulator 19 is connected to the RF receiving section 17, and the output side is connected to the slave station line control section 22. Also, synthesizer 1
4 and 21 are connected to the PAMA modulator 12 and the PAMA demodulator 19, respectively, and the counter 25 is connected to the CPU 23A.

Furthermore, signals 241, 242, 243, and 244 for controlling the modulator 11, the PAMA modulator 12, the demodulator 18, and the PAMA demodulator 19 are outputted from the communication control section 24, respectively. Other equipment and connections are the same as in FIG.

In this satellite communication system, the counter 25 in the control device 5A of the slave station IA that is about to make a call connects the C8C line to switch from DAMA mode to PAMA mode. That is, the communication control unit 24A outputs a control signal to the modulator 11, the PAMA modulator 12, the demodulator 18, and the PAMA demodulator 19, moves to the already assigned PAMA communication line, and communicates with that line in PAMA mode. Connected to a slave station that can communicate.

[Problem to be solved by the invention]

In the conventional satellite communication system using the DAMA system and PAMA system described above, when the number of retransmissions of the slotted random access signal transmitted on the C8C line increases, the line is automatically switched to the PAMA line, so the PAMA line is not transmitted between slave stations.
Even if communication is occurring, the master station cannot determine. As a result, the master station could mistakenly sign a line during PAMA communication, and the billing process, in which the master station manages line usage fees, had the disadvantage of being impossible when operating PAMA between slave stations. .

An object of the present invention is to provide a DAMA system and PAMA system that can be managed by a master station even when PAMA communication is performed between slave stations.
The objective is to provide a satellite communication system using the above system.

[Means to solve the problem]

In order to solve the above problems, the satellite communication system using the request allocation multiple access system and the fixed allocation multiple access system of the present invention allows one master station and a plurality of slave stations to communicate through a common signal line and communicate via a satellite. When the master station receives a line allocation request signal from the calling slave station via the common line signal line when the arbitrary slave stations are connected by a line, the master station selects an empty communication line and sends the calling slave station to the calling slave station. Fixed assignment multiple access has a request assignment multiple access method in which instructions and communication are performed via a common line signal line, and when the number of collisions of the line assignment request signals increases, the slave stations are connected via a preset communication line. In the satellite communication system, the master station selectively receives all frequencies of the fixed allocation multiple access line, determines the usage status of the fixed allocation multiple access line based on the presence or absence of a carrier wave of the communication line, and, if a carrier wave is present, determines the usage status of the fixed allocation multiple access line. It includes means for receiving a signal from the slave station using a carrier wave and outputting demodulated data.

〔Example〕

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

FIG. 1 is a block diagram of one embodiment of the present invention.

In the satellite communication system shown in FIG.
2 and a synthesizer 34, and a synthesizer control section 39 is newly provided in the control device 9A. The IIAMA demodulator 32 is connected to the output side of the RF receiver 30, and its output is connected to the synthesizer 34, and the output of the synthesizer 34 is connected to the P
Each is connected to an AMA demodulator 32. Other equipment and connections are the same as in FIG.

Next, the operation of this satellite communication system will be explained.

First, a slotted random access signal requesting a call sent from the duplexer 16 of the slave station IA is transmitted to the master station 2A via the satellite 3 through the C8C line. In the master station 2A, it is received by the duplexer 29, amplified and frequency converted by the RF receiving section 30, and demodulated by the output frequency from the synthesizer 33 by the demodulator 31a.
The signal is input via the slave station line control unit 35A to the master station line control unit 36A, which manages the entire network. Here, the usage status of the communication line is checked, and a signal instructing a free communication line is modulated by the modulator 26 via the slave station line control unit 35A, CPU 37, and communication control unit 38, and the frequency is converted and amplified by the RF transmitter 28. The data is transmitted from the duplexer 29 to the slave station IA via the satellite 3 via the C8C line in a time division multiplexing manner. In the slave station IA, the signal is received by the duplexer 16, amplified and frequency-converted by the RF receiver 17, demodulated by the demodulator 18, and input to the slave station line controller 22. Here, a control signal is output to the CPU 23 to use the communication line specified by the master station 2, and the CPU
The signal 23A is modulated by the communication control number, frequency-converted and amplified by the RF transmitter 15, and then transmitted from the duplexer 16.

The control device 5 controls the number of retransmissions of the slotted random access signal requesting a call transmitted from the slave station IA on the C8C line.
When the counter 25 in A counts and reaches a predetermined number of times,
The line is switched to the PAMA line via the CPU 23A and the communication control unit 24A. That is, the communication control unit 24A sends control signals 241, 242, 24 to the modulator 11, PAMA modulator 12, demodulator 18, and PAMA demodulator 19, respectively.
3°244 is output, switched from DAMA mode to PAMA mode, modulated by the predetermined number for the station to be connected, frequency converted and amplified by the RF transmitter 15, and then transmitted from the duplexer 16 via the satellite 3. You will be connected to the desired station.

In the master station 2A, the PAMA line sent from the slave station IA is received by the duplexer 29, amplified and frequency converted by the RF receiver 30, and a demodulation frequency is selected from the output frequency from the synthesizer 34 by the PAMA demodulator 32. demodulated data 321
get. Here, the presence or absence of a carrier wave is determined during demodulation to obtain an output signal 322. This output signal 322 is input to the sensor control section 39 via the slave station line control section 35A, and causes the sensor 34 to sweep at high speed when there is no carrier wave, and to use the carrier wave when there is a carrier wave. Control is performed to obtain demodulated data 321 of the received signal. The demodulated data 321 is input to the master station line control unit 36A via the slave station line control unit 35A, so that the base station 2 can also determine the usage status of the PAMA line.

〔Effect of the invention〕

As explained above, the present invention includes a PAMA demodulator and a scissor that can select all frequencies of the PAMA communication channel in the receiving section of the master station transmitting/receiving device.
Since the master station has the PAMA line usage information, it has the advantage of being able to safely manage the network.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a satellite communication system having an allocation request multiple access system and a fixed allocation multiple access system according to the present invention, and FIG. 2 is a block diagram of a conventional satellite communication system using an allocation request multiple access system. , FIG. 3 is a block diagram of a satellite communication system having a conventional allocation request multiple access system and a fixed allocation multiple access system 7A to 7N... DAMA subscriber terminals,
4B・・・PAMA subscriber terminal, 5A, 9A・
...Control device, 6A, IOA... Transmitter/receiver, 11.26...Modulator, 12...
・PAMA modulator, 15.28...RF transmitter, 16.29...duplexer, 17.30...
...RF receiving section, 18.31 ... Demodulator, 1
9... PAMA demodulator, 13, 14, 20,
21゜27.33...Shiso Sesa Scissor-22,3
5A...Slave station line control section, 23A, 37...
...CPU, control unit, exchanger. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] One master station and a plurality of slave stations are connected via a satellite with a common line signal line and a communication line, and when any of the slave stations is connected, a line allocation request is received from the calling slave station via the common line signal line. When the master station receives a signal, it selects an idle communication line and instructs the calling slave station to communicate via the common signal line, and the system employs an allocation request multiple access method, and there are many collisions of the line allocation request signals. In a satellite communication system that switches to a fixed allocation multiple access system in which the slave stations are connected via a preset communication channel, the master station selectively receives all frequencies of the fixed allocation multiple access line and transmits the carrier wave of the communication line. The request allocation multiple access line is characterized by comprising means for determining the usage status of the fixed allocation multiple access line based on the presence or absence of a carrier wave, receiving a signal from the slave station using the carrier wave, and outputting demodulated data if there is a carrier wave. A satellite communication method using a connection method and a fixed assignment multiple access method.