JPH04162836A - Ss-tdma satellite communication system - Google Patents

Abstract

PURPOSE:To eliminate the need for installation of a synchronization maintenance equipment on the ground by providing 1st-3rd means to the system so as to control the changeover operation of a switch matrix with a switching sequence read based on a switching operation clock. CONSTITUTION:A multi-beam satellite is provided with antennas 11A-11D forming beams A-D, a selector 12 to select a reception output of the antenna 11A, a demodulator 13 demodulating a burst from each earth station, a unique burst detection circuit 14 to detect a unique word of a reference burst sent from a reference station 2, a switch frame counter 15 generating a switch frame timing on the satellite 1 based on the detected unique burst position, a microwave switch matrix 17 to switch the connection between beams synchronously with the switch frame timing, a switch memory 16, a clock oscillator 18 driving the switch frame counter 15 and a phase comparator 19 controlling the oscillating frequency of a clock oscillator 18 based on the period of the unique word. Thus, it is not required to install a synchronization maintenance equipment to a reference station.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an SS-TDMA satellite communication system.

[Conventional technology]

In a typical TDMA satellite communication system, this TDMA frame is time-divided and allocated to each earth station, considering the periodic division of time on the satellite, and each earth station transmits its own burst over its allocated time. Send it out so that it fits within the range.

In this TDMA satellite communication system, in the case of a multi-beam satellite with multiple beams, a burst sent by a certain earth station is transmitted between certain fixed beams via a repeater on the satellite. Therefore, communication between earth stations without inter-beam connection was impossible, and there was also the problem that repeaters were not always used efficiently due to changes in transmission capacity between connected beams. .

On the other hand, SS (sate l 1 ite-switch
-TDMA satellite communication system is equipped with a clock source on the satellite and a switch matrix that establishes a frame period based on the clock generated by this clock source and switches the transmission path between beams. It is possible to connect the bursts sent from the earth station to any beam at any time, and has the feature that repeaters on the satellite can be used efficiently.

In this SS-TDMA satellite communication system, it is necessary to synchronize the switch frame timing on the satellite and the TDMA frame timing on the earth station side, and many studies have been conducted on this synchronization method. That is, this synchronization technology is one of the important technologies in SS-TDMA satellite communication.

The conventional SS-TDMA satellite communication system employs a system in which a synchronization maintenance device is installed at a reference station on the ground side, and the TDMA frame on the earth station side is synchronized with the switch frame on the satellite.

FIG. 4 is a diagram showing an example of the conventional SS-TDMA system, and FIGS. 5 and 6 are block diagrams showing the configurations of the communication system and reference station 4 of the multi-beam satellite 3 in FIG. 4, respectively.

The conventional example shown in FIG. 4 includes a multi-beam satellite 3 having four beams A to D, a reference station 4 installed in beam A of beams A to D covered by the multi-beam satellite 3,
A plurality of slave stations (not shown) that are controlled by the reference station 4 and communicate with each other, and a TT &
It is equipped with station C and others.

The multi-beam satellite 5 drives the switch frame counter 15 with the clock from the clock oscillator 18, reads out a predetermined switching pattern stored in the switch memory 16 at the cycle of the switch frame timing generated, and uses this switching pattern to control the switch matrix. 17 to switch connections between beams in a time-division manner. This switch frame timing and the TDMA frame timing on the ground side are synchronized by a synchronization maintenance device 4 provided in the reference station 4.
3 is doing it.

In the switching sequence stored in the switch memory 16 on the satellite 3, a connection is set in advance so that the beam A loops back at the same time once every frame.
The synchronization maintenance device 43 transmits a synchronization burst called a metric burst 72 in the synchronization window 41 (see FIG. 7), which is this time slot, and transmits a synchronization burst called a metric burst 72.
The metric pattern 75, which is a specific bit pattern in the second half of the second half of the synchronization window 71, is controlled to be cut off at the trailing edge of the synchronization window 71, and the set metric pattern 75 and the metric pattern 75 received through the satellite 3 are compared. By determining the transmission position error of the metric burst 72 and controlling the transmission timing, synchronization with respect to the switch frame is maintained.

Also - within the membrane, a clock oscillator 18 on board the satellite 3
is inferior in long-term stability to the high stability clock source 42 provided in the reference station 4 on the ground side. Therefore, the synchronization maintenance device 43 calculates the drift value of the oscillation frequency of the clock generator 18 mounted on the satellite 3 based on the high stability clock source 42 of its own station, and calculates the drift value of the oscillation frequency of the clock generator 18 mounted on the satellite 3, The oscillation frequency of the clock oscillator 18 is controlled by sending commands to the satellite 3 via the .

The synchronization maintenance device 43 transmits frame timing synchronized with the switch frame timing on the satellite side to the reference station TDMA device 41. The reference station TDMA device 41 synchronizes the TDMA frame timing with the frame timing input from the synchronization maintenance device 43, and sends out a reference burst. Each slave station located within beams A to D uses this reference burst to transmit its own burst in synchronization with the TDMA frame timing.

[Problem to be solved by the invention]

The conventional SS-TDMA satellite communication method described above uses a method in which each station on the ground side synchronizes the timing with the switch frame timing on the satellite side, so it was necessary to install a synchronization maintenance device as a reference station equipment. .

In addition, in an intra-film TDMA satellite communication system, a plurality of reference stations are provided as a redundant system to improve system reliability. - Since multiple reference stations are installed in the membrane even in the SS-TDMA satellite communication system, having a synchronization maintenance device in the reference station will make system control procedures such as synchronization in the reference station equipment and network control procedures increasingly complicated. There was a problem.

Also, as mentioned above, the deviation in the oscillation frequency of the clock source on the satellite is measured on the ground side, and the correction of this oscillation frequency deviation is sent to the satellite via the TT&C station, so the TT&C station equipment such as data links were required.

The object of the present invention can be achieved without installing a synchronization maintenance device in the TDMA reference station, that is, without changing the equipment of each reference station and each slave station used in the conventional TDMA satellite communication system. The objective is to provide an SS-TDMA satellite communication system.

[Means to solve the problem]

The SS-TDMA satellite communication system of the present invention includes at least one antenna that creates beams corresponding to each of a plurality of different regions on the earth's surface, and at least one antenna for relaying communications within each of the regions or between the regions. one repeater, and
a multi-beam satellite comprising a switch matrix for switching the connection between said repeaters and each of said beams produced by said antenna; and at least one transmitting control burst located in one of said areas and comprising a reference burst providing frame timing. one reference station and at least one base station located in each of the areas, controlled by the control burst sent from the reference station via the multi-beam satellite, and communicating with each other in burst form via the multi-beam satellite; In the SS-TDMA satellite communication system, the multi-beam satellite is provided with a first means for demodulating a received signal from the beam corresponding to the area in which the reference station is located; second means for detecting the reference burst from the demodulated output outputted by the means and outputting the frame timing; and generating a switching operation clock for the switch matrix in synchronization with the frame timing outputted by the second means. and a third means for storing the switching sequence of the switch matrix within one frame and reading out the switching sequence based on the frame timing outputted by the second means and the switching operation clock outputted by the third means. and fourth means for controlling switching operations of the switch matrix in a sequence.

Further, the SS-TDMA satellite communication system of the present invention includes the fourth
The control station sends out the switching sequence to be stored in the control burst by the control station, and the switching sequence is included in the control burst and sent to the multi-beam satellite from the demodulated output outputted by the first means. It may be configured to include fifth means for detecting the switching sequence and storing it in the fourth means.

〔Example〕

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

FIG. 2 is a diagram illustrating the overall configuration of an embodiment of the present invention.

The embodiment shown in FIG. 2 is a multi-beam satellite 1 equipped with a frame synchronization function and a clock source oscillation frequency control function.
And the four beams A~ covered by multibeam satellite 1
Of D, reference station 2 installed in beam A and reference station 2
Multiple slave stations (not shown) that communicate with each other under the control of
It is equipped with.

The multi-beam satellite 1 periodically switches connections between beams in a time-division manner using a switch matrix in which a predetermined switching pattern is set.

This switching period is called a switch frame, and this period occurs within the satellite 1 based on the position of the reference burst transmitted by the reference station 2.

Furthermore, the difference in frequency of the clock source mounted on the satellite 1 is determined from the period of the reference burst received by the satellite 1, and oscillation frequency control is performed.

FIG. 1 is a block diagram showing the configuration of the communication system of the multi-beam satellite 1 in FIG. 2. As shown in FIG.

As shown in Figure 1, the multi-beam satellite has beam A
, B, C, and D. Antenna 11A.

11B, IIC, IID, and antenna I of beam A where reference station 2 is located among the received outputs of these antennas.
Selector 12 for selecting the reception output of IA, and selector 1
2, i.e., a demodulator 13 that demodulates the bursts sent out by each earth station in beam A, and a unique word output of the reference burst sent out by the reference station 2 from among the demodulated bursts sent out by each station. The burst detection circuit 14 and the satellite 1 from the detected unique burst position
A switch frame counter 15 that generates the above switch frame timing, and a connection between beams, that is, an antenna IA, in synchronization with this switch frame timing.
A microwave switch matrix 17 that switches the connection from the reception output end of the ~ID to the transmission input end of the antenna IA~ID via a repeater (not shown) as determined, and the switching pattern of the switch matrix 17 is written. a clock oscillator 18 that drives the switch frame counter 15; and a phase comparator 19 that forms a PLL loop that controls the oscillation frequency of the clock oscillator 18 from the period of the unique word output by the unique word detection circuit 4. It is equipped with.

FIG. 3 is a block diagram showing the configuration of the reference station 2. As shown in FIG.

The reference station TDMA device 21 of the reference station 2 controls the switch frame timing within the multibeam satellite 1 as described above by generating and transmitting a control burst including a reference burst synchronized with the clock from the high stability clock oscillator 22. In addition, the burst sending timing of each slave station is controlled so that the transmitting side slave station transmits a burst at the timing when the beam of the transmitting side slave station and the beam of its partner slave station are connected in the multi-beam satellite 1.

As a result, the burst sent by the transmitting side slave station is received by the antenna corresponding to the beam where the slave station is placed, and transmitted to the beam where the other side slave station is placed via the repeater and microwave switch matrix 17. It is transmitted from the corresponding antenna and received by the slave station on the other side.

Note that if the multi-beam satellite 1 uses a detection repeater type repeater, a baseband switch matrix is used instead of the microwave switch matrix 17.

Further, when a reference station is provided in beams B to D in addition to the reference station 2, it is necessary to switch the selector 12 in accordance with the replacement of the current reference station. Even if there are a plurality of reference stations, the selector 12 is not necessary if they are all arranged within the same beam.

Furthermore, the reference station 2 transmits the control burst including the switching sequence of the microwave switch 17, and the multi-beam satellite 1 detects this switching sequence from the demodulated output of the demodulator 13 and stores the contents of the switch memory 16. By adding rewriting means, the switching sequence can be changed in response to changes in transmission capacity requirements between beams.

〔Effect of the invention〕

As explained above, in the present invention, the satellite side realizes synchronization between the TDMA frame timing on the earth station side and the switch frame timing on the satellite side, so there is no need to install a synchronization maintenance device on the ground side, and complicated initial connection is required. In addition, there is an advantage that the procedure in the conventional TDMA device can be used as is without executing the synchronization maintenance procedure.

Furthermore, since the frequency deviation of the clock on the satellite side is also corrected on the satellite side, there is no need to provide a data link between the reference station and the TT&C station for this correction.

The most advantageous feature of the present invention is that a conventionally used TDMA satellite communication device can be used as is on the ground side to form an SS-TDMA satellite communication system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a communication system of a multi-beam satellite provided in an embodiment of the present invention, and FIG.
3 is a block diagram showing the configuration of the reference station 2 in FIG. 2, and FIG.
- A diagram for explaining the overall configuration of an example of the TDMA satellite communication system, FIG. 5 is a block diagram showing the configuration of the communication system of the multi-beam satellite 3 in FIG. 4, and FIG. 6 also shows the configuration of the reference station 4. The block diagram in FIG. 7 is a diagram for explaining the synchronization operation performed by the synchronization maintenance device 43 in FIG. 6. 1...Multi-beam satellite, 2...Reference station, 11A~
11D...Antenna, 12...Selector, 13...
- Demodulator, 14... Unique word detection circuit, 15.
... Switch frame counter, 16... Switch memory, 17... Microwave switch matrix, 18
... Clock oscillator, 19... Phase comparator, A to D
···beam.

Claims (1)

[Claims] 1. An antenna that creates a beam corresponding to each of a plurality of different regions on the earth's surface, and at least one repeater for relaying communications within each of the regions or between the regions. , and a multi-beam satellite having a switch matrix for switching the connection between these repeaters and each of the beams produced by the antenna, and transmitting a control burst including a reference burst located in any of the areas and providing frame timing. at least one reference station located in each of the regions, the control bursts being controlled by the control bursts sent from the reference station via the multi-beam satellite, and communicating with each other in a burst pattern via the multi-beam satellite; SS-T equipped with a slave station that communicates with
In the DMA satellite communication system, the multi-beam satellite includes a first means for demodulating a received signal from the beam corresponding to the area where the reference station is located, and a demodulated output output from the first means. second means for detecting the reference burst and outputting the frame timing;
a third means for generating a switching operation clock for the switch matrix in synchronization with the frame timing outputted by the second means; and a third means for storing a switching sequence of the switch matrix within one frame; and fourth means for controlling the switching operation of the switch matrix based on the switching sequence read based on the frame timing outputted by the SS- and the switching operation clock outputted by the third means. TDM
A satellite communication method. 2. The control station transmits the switching sequence to be stored by the fourth means in the control burst, and includes the switching sequence in the control burst from the demodulated output outputted by the first means to the multi-beam satellite. a fifth means for detecting the switching sequence sent by the user and storing it in the fourth means;
The SS-T according to claim 1, characterized in that the SS-T comprises the means of
DMA satellite communication method.