JPS6342448B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a satellite communication system, particularly a satellite communication system that operates narrowband satellite communication represented by single channel communication system (SCPC system) using centrally controlled demand assignment multiple access (DAMA). Regarding.

In recent years, with the development of satellite communication technology and the expansion of its application fields, the diversification of communication methods and the use of high frequencies such as sub-millimeter waves are attracting attention. 1 phone call with 1 carrier wave
The SCPC method, which performs communication equivalent to a channel, is an effective method for configuring a communication network by connecting a large number of points with relatively low communication volume. The DAMA method, which allocates frequencies accordingly, is an excellent method from the standpoint of effective use of satellite power and frequency. There are two types of DAMA systems: a distributed control system where each earth station has the control function, as used in Intelsat's spade system, and a centralized control system where only a specific control station has the control function. This is advantageous in terms of easy and economical system construction since the equipment for each earth station other than the station is simple. On the other hand, when using high frequencies such as the sub-millimeter wave band, the attenuation due to rain is large, so countermeasures such as transmission power control and site diversity are being considered in order to effectively utilize satellite power and system economics. There is. Centralized control DAMA method using high frequency bands such as quasi-millimeter waves
When configuring an SCPC line network, in order to ensure system reliability, it is desirable to adopt site diversity as a rain attenuation measure at least for the control station that performs DAMA control. According to the conventional concept of site diversity, a diversity earth station (called an SD station) is set up at a certain distance or more from a target control station (called a master station), and terrestrial communication is established between the two stations. A possible method would be to connect the main station with a line and switch all functions, including communication and control, to the SD station if the main station becomes attenuated due to heavy rain. The distance between the main station and the SD station must be at least a certain value, taking into account the frequency and the size of the rain area, so that there is no correlation in rain attenuation. However, this method has the disadvantage of requiring antennas for the SD stations, radio equipment, and terrestrial communication lines connecting the stations, making it difficult to use economical SCPC.
This poses a major obstacle to the configuration of the line network.

The aim of the invention is to eliminate the above-mentioned drawbacks and to provide a dedicated
The purpose of the present invention is to provide an economical satellite communication system that does not require an SD station and has a site diversity effect in the centralized control function of DAMA to ensure the reliability of the line network.

The satellite communication system of the present invention is a centrally controlled DAMA.
In a satellite communication system in which a large number of earth stations perform narrowband communication via a satellite, at least two control stations separated by a certain distance or more among the earth stations each transmit control signals of the DAMA to perform centralized control. a pilot transmitting means for transmitting a pilot signal serving as a reference for the narrowband communication; and a memory included in the centralized control means for transferring and updating stored information necessary for the centralized control via the satellite. updating means; and switching determining means for simultaneously receiving signals sent by each of the control stations, comparing and determining the reception status, and controlling transmission/stop of at least the control signal, wherein any one of the control stations is configured to execute centralized control of the DAMA.

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

FIG. 1 is a system configuration diagram showing the configuration of an embodiment of the present invention, and shows frequencies other than those used for communication transmitted and received by each earth station that communicates via the satellite 1 in accordance with the SCPC method. Earth stations 2 to 9 are sufficiently far apart and transmit the pilot signal _p in time division.
It consists of control stations 2 and 3 equipped with a DAMA centralized control device and capable of transmitting control signals _c , and earth stations 4 to 9 that do not have a centralized control function. Control stations 2 and 3 receive pilot signals returned by the satellite.
Compare and judge each time-divided reception level of _p ′,
The control station with the higher level sends out the control signal _c .
DAMA is centrally controlled, and stations with lower levels are configured to stop transmitting control signals. FIG. 1 shows a state in which the control station 2 is sending out the control signal _c , and the broken line shows that the transmission is stopped. Earth station 4 without centralized control function
9 receive the pilot signal _p ' and control signal _c ' for AFC/AGC, and transmit the call/response signal _r for call origination and response. When control stations 2 and 3 are not transmitting control signals, they are under the control of other control stations that are transmitting control signals, similar to earth stations 4 to 9. The control station also receives call/response signals from each earth station.
The central control unit receives _r ′ and performs the necessary processing in response to it. In addition, even when the control station is not transmitting control signals, it always receives the control signal _c ′ and the call/response signal _r ′, updates the necessary storage information included in the central control device, and updates the necessary information stored in the central control device. The memory information is configured to match. If one control station becomes unable to receive data due to large rainfall attenuation, the information stored in that control station cannot be updated. Therefore, as soon as the reception status is restored, the information is transferred from the other control station via the control line or communication line and updated. is configured to do so. With the above configuration, if a control station experiences rain attenuation, it can be operated by switching to a control station with less attenuation, and with regard to the DAMA centralized control function, it can achieve the same effect as the site diversity of the switching method. be able to.

FIG. 2 is a block diagram of an embodiment of the control station 2 or 3 shown in FIG.
4, distributor 15, pilot reception processing section 16, comparison/judgment section 17, control signal reception demodulation board 18,
DAMA control device 19, control signal modulation transmission board 20,
Control signal switching board 21, pilot transmitter 22, combiner 23, up converter 24, power amplifier 2
It consists of 5. Pilot reception processing section 1
6 receives the time-division pilot signal _p ' and performs the AFC
While generating a signal 101 and an AGC signal 102,
A control signal 103 is transmitted that reproduces the clock signal and corrects the transmission timing and frequency of the pilot signal transmitted from the own station, so that the oscillation frequency and transmission timing of the pilot transmitter 22 are correctly time-divisionally transmitted at the same frequency. control like this. The comparison/judgment section compares the pilot signal reception levels of both control stations, and if the reception level of the pilot sent out from the own station is below a certain value or the level of the pilot sent out from the own station is lower than the level sent out from another control station by a certain value or more, the DAMA is Switching signal 1 to stop sending control signals
04 is generated. The control signal switching board 21 stops sending out the control signal _c in response to the switching signal 104, and the control signal reception demodulation board 18 detects that the received power of the control signal _c ' is no longer available and sends out the switching signal 105.
In response to this, it starts sending out the control signal _c . DAMA
The control device 19 has a memory that stores frequency allocation status, etc., and its contents are always updated via the satellite line regardless of whether or not a control signal is sent. The output of the distributor 15 is sent to the receiving channel unit (RX
CHU), and the input of the combiner 23 is connected to a transmit channel unit (TX CHU), respectively. According to this configuration, if the control signal of one control station is disconnected, the other control station transmits the control signal, and in order to prevent rain attenuation, the comparison of the pilot signals is a comparison of the uplink attenuation of each control station. Because it means
A certain dead zone is provided for switching, and the control station with the least attenuation always sends a control signal to perform DAMA control. In the explanation of FIG. 2, the pilot transmitter 22 adjusts the frequency and transmission timing, but the other control station that transmits the pilot signal in a time-division manner does not require frequency and timing adjustment.

FIG. 3 is a block diagram of an embodiment of earth stations 4 to 9 that do not have a centralized control function as shown in FIG. Therefore, no special configuration is required. In FIG. 3, antenna 11'
and low noise amplifier 12', down converter 13',
The receiving system consisting of an intermediate frequency amplifier 14' and a divider 15' and the transmitting system consisting of a combiner 23', an up converter 24' and a power amplifier 25' are the same as shown in FIG. With a normal pilot receiver that detects only AFC signals, when the reception levels of the pilot signals from two control stations 2 and 3 sent out in a time-sharing manner are different, the AGC signal is detected based on the higher level pilot signal. is output. The local DAMA device 27 uses the control signal for its own station demodulated by the control signal reception demodulation board 18' to transmit and receive channel unit TX.
CHU, RX The CHU frequency is set, and a calling signal is sent in response to a communication call from the own station, and a response signal is sent in response to a command from the control station via the calling/response signal modulation transmitter board 28. Send.

In the embodiment shown in FIG. 2, the comparative judgment unit judges the pilot signal level of the control station as a relative value, and the control station with the higher level sends out the control signal. have a relationship,
It is also possible to use a determination circuit in which the leading station performs control as long as the leading station exceeds a certain standard, and the dependent station performs control only when the leading station falls below this standard. There is also a method in which there is no master-slave relationship, and the control station switches to the other only when it falls below a certain standard. Note that the comparison/determination section may compare carrier-to-noise ratios (C/N) instead of reception levels. Furthermore, in the above embodiment, each control station is configured to transmit the pilot signal in a time-division manner, but only the station executing control transmits the pilot signal, and the other control stations transmit the pilot signal on a different frequency. It is also possible to transmit a monitor signal and to switch the control execution station based on the reception level or C/N comparison between the pilot signal and the monitor signal. Furthermore, a method in which each control station constantly sends out a monitor signal of a different frequency and receives this monitor signal to switch the control execution station, or a method in which each control station sends out a monitor signal in a time-sharing manner is also conceivable. All of the above explanations have been made with two control stations sharing the control function, but the number is not necessarily limited to two, and three or more stations may be used.Also, although the explanation was given using an SCPC line, one carrier wave can handle 2 to 3 telephone calls. Transmit communication equivalent to a channel
There is no problem with the MCPC method.

As explained in detail above, according to the satellite communication system of the present invention, in narrowband satellite communication operated by the centrally controlled DAMA system, a dedicated SD station is not provided.
Earth stations separated by such a distance that there is no correlation are equipped with a centralized control function to receive and receive satellite return signals.
By comparing, determine the degree of rainfall attenuation,
Since the control execution station can be switched, a site diversity effect can be obtained in the control function, and an economical line can be constructed in a high frequency band such as sub-millimeter waves.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.
FIG. 2 is a block diagram of an embodiment of a DAMA centralized control station, and FIG. 3 is a block diagram of an embodiment of an earth station without a centralized control function. 1... Satellite, 2, 3... Control station, 4 to 9... Earth station, 11, 11'... Antenna, 12, 12'...
...Low noise amplifier, 13,13'...Down converter, 14,14'...Intermediate frequency amplifier, 15,
15'...Distributor, 16...Pilot reception processing section, 17...Comparison/judgment section, 18, 18'...Control signal reception demodulation board, 19...DAMA control device, 2
0... Control signal modulation transmitting board, 21... Control signal switching board, 22... Pilot transmitting section, 23, 23'
...Composition section, 24, 24'... Up converter,
25, 25'...Power amplifier, 26...Pilot receiver, 27...Local DAMA device, 28
...Call/response signal modulation transmission board.

Claims (1)

[Scope of Claims] 1. In a satellite communication system in which a large number of earth stations perform narrowband communication via satellites by a centralized control request allocation multiple access system, at least two of the earth stations are separated by a certain distance or more. a centralized control means for each control station to perform centralized control by transmitting a control signal for the request allocation multiple access; a pilot transmitting means for transmitting a pilot signal serving as a reference for the narrowband communication; A memory update means for transferring and updating memory information necessary for control via the satellite; and a memory updating means that simultaneously receives signals sent from each of the control stations, compares and judges the reception status, and transmits/stops at least the control signal. switching determination means for controlling said satellite communication system, wherein any one of said control stations is configured to execute centralized control of said request allocation multiple access. 2. Satellite communication according to claim 1, wherein each of the control stations transmits the pilot signal in a time-division manner, and the switching determining means receives the pilot signal and compares and determines the pilot signal. method. 3. When each of the control stations does not send out the pilot signal, it sends out a monitor signal for monitoring propagation loss, and the switching determining means receives and compares the pilot signal and the monitor signal to determine the control signal. The first aspect of the present invention is characterized in that sending and stopping of the pilot signal and the pilot signal are controlled.
Satellite communication method described in section. 4. Each of the control stations constantly transmits a monitor signal for monitoring propagation loss on a time-division basis or at different frequencies, and the switching determination means receives and receives the monitor signal.
2. The satellite communication system according to claim 1, wherein transmission and stop of the control signal and the pilot signal are controlled by comparison.