JPS58141040A - Ss-tdma satellite communication synchronization system - Google Patents

Abstract

PURPOSE:To permit all earth stations to synchronize with superframes on a communication satellite, by using a synchronizing burst sent out of a reference station to all the earth stations, and to allocate satellite circuits flexibly against communication traffic variation, by providing the communication statellite with a terminator, a terminator connection/disconnection controlling function, and a superframe generating function. CONSTITUTION:To maintain a synchronizing wind, the terminator 13 is provided to the satellite in an example (a) and then connected to a matrix switch 7. In an example (b), the terminator 13 is connected to the output of a receiver 5 corresponding to a zone to which the reference station belongs through a changeover switch 14, which connects the output of the receiver 5 to the terminator or to the switch 7 under the control of a control circuit 8. In a figure, 10 is a telemeter/command antenna (or dedicated control circuit). For control accompanying a connection pattern change of the satellite by using superframes, the reference station sends a connection pattern switching command through a telemeter/command station, and then receives its answer and also sends a command for changing circuit allocation to all earth stations.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a superframe synchronization system for synchronizing an earth station with a superframe generated on a satellite in the 88-TDMA satellite communication system.

(Background technology) 88-TDMA is 5atellite Switch
ing-Time Division Multiple
It is an abbreviation for Access, and is a satellite communication system in which a matrix switch with a predetermined connection pattern is mounted on the satellite.

Figure 1 is a schematic diagram of the 88-TDMA satellite communication system.
It shows the structure of the repeater inside the satellite and the relationship between the corresponding earth station. In the figure, reference numeral 1 indicates a spot beam antenna mounted on a satellite; for example, it shows a case with four transmitting and receiving antennas. Each antenna generates a thin spot beam 2, and irradiate zone 3 (A, B, C and D). And conversely, each antenna has four earth stations located in zones A, B, C and D.
receive radio waves emitted from each.

In the figure, only one earth station 4 is shown in each zone, but in reality each zone can include a plurality of earth stations. Note that 9 is a telemeter/command earth station, 10 is a satellite-mounted telemeter/command antenna, and 11 is a telemeter/command transceiver.

Radio waves emitted from earth stations in zones A, B, C, and D are received by the corresponding antennas 1, R,
The power to be applied to the receivers 5, designated as A, R, B, RC, and RD, is supplied by the transmitters 6, designated as TA, TB, TC, and TD, respectively. A matrix switch 7 is provided to connect an uplink from an earth station in one zone to a satellite and a downlink to an earth station in another zone, and is controlled by a matrix switch control circuit 8. The function of a matrix switch is to periodically connect any uplink and downlink by switching according to a time schedule determined by a connection pattern that indicates the combination of which uplink and which downlink are connected. will be combined with

FIG. 2 shows an example of a connection pattern connecting an originating zone and a terminating zone. In this figure, the earth station that serves as the reference for synchronization control that synchronizes the operation timing of each earth station to the TDMA frame period on the satellite, that is, the reference station, is located in zone A, and from A located at the beginning of the TDMA frame, all zones are simultaneously It is common to perform this synchronization control by sending a synchronization burst through a synchronization window in which the signal can be transmitted.The data window for transmitting data can vary depending on the amount of traffic between zones. be divided. If the amount of traffic between zones is always constant, there is no problem with one type of connection pattern that divides the data window according to the amount of traffic, but in general, traffic is divided hourly, day and night, seasonally, and during disasters. In order to make effective use of the 88-TDMA satellite communication line, it is necessary to operate the connection pattern according to the traffic condition. To do this, control is required to change the connection pattern, for example from (al to (b) in Figure 2).The conventional connection pattern change procedure first changes the connection pattern by using a part of the satellite line. A reference station, one of the earth stations, notifies each other earth station using a common control channel or ground line.Each earth station stops transmitting all communication signals in response to this notification, and issues a command to start retransmission. Next, wait for telemeter/command (hereafter T/
(abbreviated as "for C") From earth station 9 to satellite-mounted T/C antenna 1
0. After confirming the change in the connection pattern for T/C, a retransmission start command is issued to each earth station, and each earth station resumes communication by allocating lines corresponding to the new connection pattern.

As described above, when changing the connection pattern of the conventional satellite-mounted matrix switch, it is necessary for all earth stations to temporarily stop communication, which causes traffic congestion and other inconveniences in operation.

(Problem to be solved by the invention) In order to change the connection pattern of matrix switches without stopping communication, the present invention configures a superframe that is an integral multiple of a TDMA frame on a satellite, and By intermittent synchronization windows, changes are made to the synchronization burst from the reference station, the changes are detected at each earth station, and the superframe of the earth station is synchronized with the superframe on the satellite, making it possible to control connection pattern changes. It is designed to be executed in synchronization with the frame, and the drawings will be explained in detail below.

(Structure and operation of the invention) FIG. 3 shows two embodiments of the present invention. In the example of (a), a terminator 13 is installed on the satellite, and the matrix switch 7 is connected to this in order to intermittent the synchronization window. Connect. (bl
In example O, the terminator 13 is connected to the output of the receiver 5 corresponding to the zone to which the reference station belongs via the changeover switch 14,
14 is controlled by 8 to send the output of 5 to 13 or 7
Connect to. Note that 10 indicates a telemeter/command antenna (or dedicated control line).

Hereinafter, a method for establishing synchronization of superframes according to the present invention will be explained using FIG. 4. Matrix switch circuit 8
In this example, a superframe period consisting of an integral multiple of the TDMA frame period is generated, and the fourth superframe period is
For the IVIA frame (the first TI indicated by diagonal lines in Figure 1), during the synchronization window shown in Figure 4 (C1), the matrix switch control circuit of 8 controls the matrix switches of 7 (Figure 3 (a). ) or 14
The switch (example shown in FIG. 3(b)) is controlled to connect the 13 terminators by Δt for a certain period of time. The global station is transmitted from the reference station via the synchronization window in Figure 4(d).
synchronization burst is received for each TDMA frame,
By detecting that the length of the CW (unmodulated carrier portion) of the reception synchronization burst shown in FIG. 4(e) changes due to connection of a terminator, a superframe occurring on the satellite can be identified. In FIG. 4 (el), CW is an unmodulated carrier, BTR is a pit-same M signal, U'W is a unique word, P is various information, and METRIC &! synchronization control signal.

Note that the CW portion is sufficiently long so that even if the length changes due to instantaneous interruption for superframe synchronization, it will not cause any inconvenience to the synchronization maintenance control at the earth station. In order to synchronize the superframe more completely, the first TD of the superframe
A terminator is connected in the synchronization window of an MA frame and a certain number of subsequent TDMA frames to change the CW length during these multiple reception synchronization bursts, and from these, a method such as correlation detection is used to identify a superframe. It is also possible.

Now, in order to execute the control associated with changing the connection pattern of the satellite using the super frame described above, first, the reference station issues a connection pattern switching command to the satellite via the telemeter/command station 9, and the response is sent to the satellite. At the same time, it instructs all earth stations to change the line allocation using P (each type of information) in the synchronous burst shown in FIGS. 4(d) and 4(e). After both the satellite and the global station receive a change command, communication continues for a predetermined number of superframes using the previous connection pattern and the corresponding line assignment, and then the communication continues at the beginning of the next superframe. The satellite then switches to a new connection pattern, and each earth station synchronizes with this and continues communication using the new line assignment.

As is clear from the above explanation, communication is performed according to the previous line allocation until just before the superframe in which the connection pattern change is implemented, and from the first TDMA frame of the change implementation superframe, the satellite switches the matrix switch according to the new connection pattern. Since all earth stations can perform communication according to the new line allocation in synchronization with this switching, it is possible to eliminate communication interruptions due to changes in connection patterns.

In the above explanation, the line assignment change command from the reference station to the global station is transmitted using P in the synchronous burst, but the same control described above can be performed even if the command is transmitted using the terrestrial line. It is possible to do so.

(Effects of the Invention) As explained above, if a communication satellite is only equipped with a terminator, a terminator liquid/disconnection control function, and a superframe generation function, the reference station can transmit all The earth station can synchronize with the superframe on the satellite, and using this superframe, the satellite and all earth stations can synchronize at the same time and change the connection pattern without performing complex control between the satellite and the earth station. It is possible to control changes. Therefore, it is possible to change the connection pattern without interrupting the satellite line communication, and the satellite line can be allocated flexibly in response to communication traffic fluctuations, allowing efficient use.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the conventional 88-TDMA satellite communication system.
Figure 2 (al and (bl) is an example of the configuration of a matrix switch connection pattern in the case of a 4-spot beam, Figure 3 (al and (b) is an example of the configuration of a specific satellite of the present invention,
FIG. 4 shows an embodiment of the present invention. 1... Spot beam antenna 2...
・・・・・・・・・Spot beam 3・・・・・・・・・
Spot area 4...Earth station 5...Receiver 6...Transmitter 7...Matrix Switch 9...
...Telemeter/command earth station 10...
...Telemeter/command antenna 11...
...Telemeter/command transceiver 13...
...Terminator 14 ...... Changeover switch Patent applicant Nippon Telegraph and Telephone Public Corporation Patent application agent Patent attorney Megumi Yamamoto - Breast/Concave No. 2, Figure 2

Claims (1)

[Claims] A matrix switch installed on the satellite between the up link and the down link, which includes multiple spot frames on one or both of the up link from the earth station to the satellite and the down link from the satellite to the earth station. In the 88-TDMA satellite communication system, communication is performed by time division multiple access using a communication satellite that has the function of sequentially switching a connection pattern determined in advance according to the TDMA frame period and repeating this periodically in units of TDMA frame periods. - A circuit consisting of a combination of a switch and a terminator or a changeover switch and a terminator is installed, and the control circuit of the matrix switch is also equipped with a superframe generation function in units of integral multiples of TDMA frames. By controlling the matrix switch or changeover switch from the control circuit, the reference station in the earth station can superimpose the synchronization window provided for each TDMA frame for synchronization burst signal transmission to give synchronization information to other general earth stations. By giving a momentary interruption in the synchronization window of the TDMA frame at the beginning of the frame, the length of the unmodulated carrier part of the synchronization signal is changed, and this change synchronizes all earth stations with the superframe generated on the satellite. , an 88-TDMA satellite communication synchronization system characterized in that various controls associated with changes in connection patterns are performed in synchronization with the superframe.