JPS6313616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a satellite communication system, and particularly to a simple satellite communication system of request-assignment multiple access (DAMA) in which a plurality of earth stations share a frequency and allocate it to communication between requested earth stations. .

SCPC (Single Channel
There is a per carrier method. . This method consists of a fixed allocation method in which carrier frequencies used for calls between each earth station are fixedly allocated in advance, and a DAMA method in which the frequency used is not fixed and the control station allocates unused frequencies according to requests. There is. The former has simple terminal equipment for each earth station, but the operational efficiency of the satellite line is low, while the latter has good operational efficiency, but the terminal equipment, especially the control equipment, is complex, and the control for exchanging information for line assignment and connection is difficult. It requires a dedicated signal channel, and has drawbacks such as a failure in the control station affecting the switching function of the entire system. Intelsat's
The SPADE method is a distributed control DAMA method in which each earth station owns the control station function, and although it eliminates the last drawback mentioned above, it requires mutual exchange and storage of control information, which requires each earth station to have complex control. It has the disadvantage of requiring equipment.

The purpose of the present invention is to eliminate the drawbacks of the conventional method described above, and to provide a simple DAMA-connected satellite communication method that does not require a complicated control device at each earth station, does not require a channel dedicated to control signals, and has good line operation efficiency. It is to be.

The satellite communication system of the present invention is a satellite communication system in which a plurality of earth stations share at least one set of transmission and reception frequencies for transmission and response that form a pair with each other to configure a four-wire wireless line in the DAMA system. Transmitting/receiving means for each of the plurality of earth stations to selectively receive any of the receiving frequencies for transmission and response, and transmitting/receiving means for transmitting a corresponding transmission frequency for response or transmission; and control means for controlling the frequency of the transmitting/receiving means. The transmitting/receiving means waits in a state in which it receives the receiving frequency for transmitting, and when it detects a communication request addressed to its own station, it transmits the transmitting frequency for response to configure a line and communicate from its own station. In response to a request, the transmission frequency for transmission is transmitted, and the reception frequency for response is received to configure a line.

Next, the present invention will be explained in detail with reference to the drawings. Figure 1 shows an SCPC in one embodiment of the present invention.
In the carrier frequency map of the system, a shows the uplink from the earth station to the satellite, that is, the transmission frequency from the earth station, and b shows the downlink from the satellite to the earth station, that is, the reception frequency of the earth station.
In terms of uplink, there are n transmission frequencies _S1 , _S2 , _S3 , _respectively , arranged at equal intervals on both sides of the pilot signal p.
represents the transmission frequency, represented by _S ), and the response frequencies _R1 , _R2 , _R3 , ... _Ro (the first subscript R represents the response frequency, represented by _R ), and _S1 and _R1 , _S2 and _R2 , _S3 and _R3 , ... _So and
_Ro
(The second and subsequent subscript numbers represent the number of the pair of transmission and response frequencies, ₁ , ₂ , ₃ ,...
(represented by _o , etc.) are used in pairs to form a round-trip four-wire radio line.
The frequencies marked with a dash (') on the downlink each correspond to the same symbol on the uplink, and are the downlink frequencies that have undergone frequency conversion at the satellite repeater, that is, the reception frequency of the earth station.

FIG. 2 is a system configuration diagram of the first embodiment of the present invention in which four earth stations communicate by sharing the three sets of frequencies ₁ , ₂ , and ₃ shown in FIG. ，
4 and 5 are earth stations, respectively. Each earth station is equipped with three transmitting/receiving devices TR1, TR2, and TR3, and can receive any reception frequency for transmission or response, corresponding to ₁ , ₂ , or _3, respectively, and the corresponding reception frequency for response or transmission. It is now possible to transmit at the designated transmission frequency. In Figure 2, ₁ is not used between any earth stations and is "empty", and ₂
indicates that earth stations 2 and 3 are in use, and ₃ indicates that earth stations 2 and 4 are in use. TR1 transmitter/receiver for each earth station
Both are on standby in a state in which they receive the transmission reception frequency _S1 ' for transmission and transmit the transmission frequency _R1 for response (indicated by the broken line in the figure). ₂ indicates that the line is connected due to a request from earth station 3, and the TR of earth station 2
2 receives the transmission reception frequency _S2 ' transmitted from the earth station 3 and frequency-converted by the satellite, detects that the communication is directed to its own station, transmits the response transmission frequency _R2 , and establishes a communication with the earth station 3. A four-wire wireless line is constructed between them. At this time, earth stations 4 and 5 receive _S2 ' and determine that the communication is not directed to their own stations.
Transmission of this channel is prohibited until a call termination signal is sent and the radio waves are disconnected (indicated by an x in the diagram).
₃ is a case where the line is set up by a request from the earth station 2. When there is a request to set up a communication line, the earth station 2 selects the "empty" channel ₃ and waits in the receiving state of the transmission frequency _S3 ' until then. Change the transmitting and receiving frequency of TR3 that was previously used and transmit the transmitting frequency _S3 for outgoing transmission. Other earth stations waiting to receive the transmission reception frequency _S3 ' receive this, and then the earth station deciphers the sent destination identification signal and detects that the communication is directed to its own station. 4 transmits the response transmission frequency _R3 to configure a line, and earth stations 3 and 5, which have determined that it is not intended for their own station, prohibit the use of ₃ .

FIG. 3 is a block diagram showing an embodiment of the earth station shown in FIG.
21 is a low noise amplifier (LNA), 22 is a down converter (D/
C), 23 is an intermediate frequency amplifier (IFA) with AGC that amplifies the output of the D/C, 24 is a distributor (DIV) that branches the output of IFA, and 25 is a receiver that receives the pilot signal _p ' and outputs the AFC signal and AGC signal. D/C22, IFA
The pilot receivers (PIL REC) 26, 27, and 28 respectively supply one of the transmission receiving frequencies _S1 ', _S2 ', _S3 ' and the response receiving frequencies _R1 ', _R2 ', _R3 '. Reception channel unit (RX CHU) that selectively receives and demodulates telephone output (TP OUT), 29, 30, 31
is a transmission channel unit (TX CHU) that transmits an intermediate frequency carrier wave corresponding to either response transmission frequencies _R1 , _R2 , _R3 or transmission transmission frequencies _S1 , _S2 , _S3 for transmission modulated by telephone input (TP IN), respectively. ), 32 is a combiner (COMB) that combines the outputs of each TX CHU, 33 is an up converter (U/C) that converts the output into a transmission frequency, 3
4 is a transmission power amplifier (HPA) that amplifies the output of the U/C, and the above-mentioned 20 to 34 constitute a transmitting/receiving means. 35 is the control device (CONT)
And from each RX CHU26, 27, 28,
It receives supervisory signals 101, 102, 103 that convey the presence or absence of signals at transmission receiving frequencies _S1 ', _S2 ', _S3 ' and the result of identifying the destination of the signals, and if the signals are directed to the own station, the TX CHUs 29, 30 respectively. ，
31 and sends response command signals 111, 112, 113 to transmit response transmission frequencies _R1 , _R2 , _R3 , and also sends a connection signal 104 to the exchange to which the input/output of each channel unit is connected. Connect the line. Upon receiving the line connection request signal 105 from the exchange, the supervisory signal 101,1
02, 103 to select an empty frequency, send transmission command signals 121, 122, 123 to change the frequency of the transmitting/receiving channel unit, _S1 , _S2 ,
It is configured to transmit _S3 , receive _R1 ′ _R2 ′, _R3 ′, and connect the telephone line using a connection signal 104 .

As explained above, according to this embodiment, each earth station is only equipped with a relatively simple control device and can perform distributed control without exchanging control information with other stations.
A DAMA satellite link can be configured.

In the first embodiment described above, the case where each earth station has three transmitting/receiving devices for three sets of shared frequencies has been described, but a similar DAMA can also be used when the number of transmitting/receiving devices is less than the number of frequency sets. It is possible to configure the method. FIG. 4 is a system configuration diagram of the second embodiment configured as described above, in which the three sets of frequencies shown in FIG.
₄ , ₅ , _{and 6} each have one transmitter/receiver, where 1a is the satellite, 2 is the
9a are earth stations, 2b, 3b, . . . are transmitting/receiving devices (TR), and 2c, 3c, . . . are control devices (CE). Each transmitting/receiving device receives each receiving frequency _S4 ′, _R4 ′, _R5 ′, _R5 ′,
_S6 ′,
_R6 ′ can be received and the corresponding transmit frequency
For example, it is configured with a synthesizer local oscillator so that it can transmit _R4 , _S4 , _R5 , _S5 , _R6 , _S6 ,
If no communication is being performed, the receiving frequency for sending
Control is such that _S4 ', _S5 ', and _S6 ' are sequentially switched and received in circulation. The figure shows a state in which a line with a frequency of ₆ is configured between the earth station 9a and the earth station 9a in response to a request from the earth station 3a, and the transmitting/receiving devices 3b and 9b of the earth stations 3a and 9a are fixed to the frequency ₆ , and _{S6 and S6} , respectively, are shown. Sending _R6 and receiving _R6 ′, _S6 ′. The transmitting/receiving devices of the other earth stations are moving their frequencies cyclically, and there is no receiving output for _S4 ' and _S5 ', but the receiving output for _S6 ' continues to be detected, and ₄ and ₅ are "empty channels". It is determined that ₆ is in use. Now at earth station 5a
When a communication request to 2a occurs, the control device 5c
selects the vacant channel closest to that point, for example, ₄ (if the receiving frequency at the time of request generation is ₆ or ₄ , select ₄ , if it is ₅ , select ₅ ), invert the transmitting/receiving frequency of the transmitting/receiving device 5b, and select _S4. send
Waits in the receiving state of _R4 ′. When the other earth stations receive this radio wave on _S4 ', which had no output during the previous circulation, they temporarily stop frequency shifting and decipher the destination identification signal that is continuously sent for a certain period of time. Station 2a, which has detected the identification signal addressed to itself, fixes the frequency to ₄ and transmits response frequency _R4 . When the earth station 5a receives this signal, it stops transmitting the destination identification signal and completes the line connection. If the response frequency _R4 ' is not received even after a certain period of time has elapsed, transmission is stopped as the other station is busy. Earth stations other than 2a, e.g. 8
Since no destination identification signal is detected in case a, frequency movement starts again after one fixed period of time. Next time when ₄ is received, the detection output is still obtained during the previous circulation, so it is determined that it is in use like ₆ and the frequency continues to be shifted. In this way, each earth station can configure a communication line using one of the shared frequencies as required, and a DAMA satellite communication line can be configured without exchanging control information between each earth station. be done. In the above explanation, the earth station has one transmitting/receiving device, but the same configuration can be made even if the earth station has two transmitting/receiving devices, and the time for signal acquisition can be shortened by shifting the timing of reception frequency circulation. Also, the number of transmitting and receiving devices does not need to be the same for each earth station.

The above two embodiments have been explained in detail,
It goes without saying that the method and number of shared paired frequencies, the number of earth stations, and the number and configuration of transmitting and receiving equipment for each earth station are not limited to those in the example, and may be used as part of the frequency array of SCPC. By using this method to organize multiple DAMA line groups based on this method and allocating the rest fixedly between earth stations with a large amount of communication, it is possible to create an efficient simple DAMA line configuration. Figure 5 shows such a simple DAMA
This is a line configuration diagram of one embodiment of the system, and includes central stations A and A', which are the core, and peripheral stations B, which are closely connected to the central stations A and A'.
The line configuration connecting C, D, E, F, G, and B', C', D', E', and F' is shown. According to the present invention, a SCPC frequency is fixedly assigned to each station connected by a solid line with a large amount of communication, and the system consists of several stations that are closely related.
By organizing a simple PAMA block using the DAMA method and assigning several sets of frequencies to each, and further allocating an appropriate number of frequencies to each station as one block (), there is no need for a specific control station or dedicated control channel, resulting in efficient operation. SCPC lines can be constructed economically. If the above-mentioned method of the first embodiment is adopted for the block, all the assigned frequencies can be used to strengthen the communication path between one peripheral station and the central station within the block, and the second If the system of the embodiment is adopted, the number of transmitting/receiving devices at each earth station can be reduced, and the necessary direct lines between each station can be configured as desired.

Although the SCPC method has been explained so far, the satellite communication method of the present invention is not limited to the SCPC method, but can also be applied to carrier waves of FM or PSK modulation that transmit multiplex telephones, high-speed data, etc. It can also be used as a backup in sections where failures occur, if necessary. Further, although an example has been described in which all four-wire lines are configured, it is also possible to configure not only four-wire lines but also one-way communication lines such as broadcast communication.

As explained in detail above, the satellite communication system of the present invention does not require a channel dedicated to control signals, and only requires a simple control device at each earth station, allowing for simple DAMA-based satellite communication with distributed control. This has the effect that the line can be constructed economically.

[Brief explanation of the drawing]

FIG. 1 is a carrier frequency allocation diagram according to an embodiment of the present invention, FIG. 2 is a system configuration diagram of the first embodiment of the present invention, and FIG. 3 is a block diagram of an embodiment of the earth station shown in FIG. , FIG. 4 is a system configuration diagram of a second embodiment of the present invention, and FIG. 5 is a line configuration diagram of an embodiment of the simple DAMA system. 1, 1a...satellite, 2, 3, 4, 5, 2a, 3
a to 9a...Earth station, 2b to 9b...Transmission/reception device, 2c to 9c, 35...Control device, 20...Antenna, 21...Low noise amplifier, 22...Down converter, 23...Intermediate frequency amplifier , 24...
Distributor, 25...Pilot receiver, 26,2
7, 28...Reception channel unit, 29, 3
0, 31... Transmission channel unit, 32...
Combiner, 33... Up converter, 34... Transmission power amplifier, A, A'... Center station, B to G,
B′～F′……peripheral stations.

Claims (1)

[Claims] 1. In a satellite communication system in which a plurality of earth stations share at least one set of transmitting and receiving frequencies for transmission and response that form a pair with each other to configure a four-wire radio line using a demand allocation multiple access method, the plurality of earth stations each comprises a transmitting/receiving means that can selectively receive any of the receiving frequencies for the transmission and for the response, and transmits a corresponding transmission frequency for the response or the transmission, and a control means for controlling the frequency of the transmitting/receiving means, The transmitter/receiver waits while receiving the transmitting frequency, and when it detects a communication request directed to its own station, it transmits the response transmitting frequency to configure a line, and responds to the communication request from its own station. A satellite communication system characterized in that the satellite communication system is controlled to transmit the transmission frequency for the transmission and receive the reception frequency for the response to configure a line.