JPH07212286A - Extractor of fit synchronizing signal in small-sized earth station system and its extraction method - Google Patents

Abstract

PURPOSE: To attain system synchronization with a central station at a user terminal equipment by storing clock components in fit information from the central ration in a RAM, and collating with a ROM which stores its own fit information in the RAM. CONSTITUTION: This device is constituted of; a clock frequency divider 1 to divide an inputted system clock; a RAM 2 which stores a frequency divided by the clock frequency-divider 1; a ROM 3 which reproduces the value of a preliminarily stored state by the output value of the RAM 2 and a received data; and a control logical part 4 operated by the reproduction of the ROM 3 which controls the extraction logic of a fit synchronizing signal. The clock of the inputted fit synchronizing signal is frequency-divided, and this frequency- divided value is stored in the RAM 2 and extracted. Then, the value of the state preliminarily stored in the ROM 3 is reproduced by the extracted value and the received data, and the extraction logic of the fit synchronizing signal is controlled by this reproduced value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small earth station system capable of transmitting information between a user terminal device and a large computer of a central station in a small earth station consisting of a large number of terminal stations by using a satellite. Especially, in order to synchronize the communication between the central station and the terminal station, three sub-channels created by the central station, Fit FIT: Frame indication (Framin
g) It is possible to achieve communication synchronization between the central station and the terminal station by directly extracting the identification signal and the timing signal from the user terminal device and using them for system synchronization. And a method for extracting the fit sync signal of the small earth station system.

[0002]

2. Description of the Related Art FIG. 3 is a schematic diagram showing a structure of a general small earth station system. In FIG. 3, the small earth station system includes a central station 10 that controls all networks using satellites; a number of terminal stations 20 that communicate through the central station 10; and between the terminal station 20 and the central station 10. A network management system 30 for controlling the communication of the computer; a large computer 40 for storing information to be provided through the network or the like.
And a user terminal device 50 of each terminal station 20; In the above system, the data from the central station 10 to each terminal station 20 is sent by one or a number of consecutive carrier waves, and this data is output as outb.
sound data). On the contrary, a large number of terminal stations 20 share one carrier wave and send data to the central station 10. This data is referred to as inbound data.

In this case, 1 for input to the central station 10.
In order for many terminal stations 20 to share one incoming carrier wave,
Various channel access protocols are used, which are procedures for accessing over channels, but the most common one is Random-Aloha.
And Slotted-Aloha. On the other hand, the bits in the series of outgoing data sent from the central station 10
Streams have two different types of information.

The first form of information is the data packets exchanged between the central office 10 and the terminal office 20. In this case, one outgoing carrier, which is a carrier wave to be output from the central station, has a large number of packets sent to a large number of terminal stations, and each packet has appropriate address information corresponding to the terminal stations. Since it is present, a specific terminal station 20 can accept the packet. The second form of information is terminal station 2
This is synchronization information for the communication device of 0. The signal of this synchronization information, which is composed of the fit synchronization signal as described above, is generated by the modulator of the central station 10 and extracted by the receiver of the communication device in the terminal station 20, which is the terminal station 2.
Used to synchronize communication with 0.

FIG. 6 is a block diagram for explaining the bit structure of the fit sync signal. In FIG. 6, the frame indication bit 9F bit in the fit sync signal is composed of a total of 9 bits of "011111111" in one slot,
It is used to distinguish the bit stream input to the terminal 20 into fit information and data packets.
On the other hand, the identifier bit 9I bit is composed of a total of 9 bits per slot, and is used to obtain only an outgoing carrier wave used by a specific terminal station 20 among a plurality of outgoing carrier waves. The 9T bit is a timing bit.

[0006]

However, it is possible to synchronize the communication between the central station and the terminal station in the satellite communication system by using the above-described conventional fit-sync signal extracting device for the small earth station system and the extracting method thereof. However, there were the following problems. In the communication satellite system, first, the terminal station 20 extracts the fit synchronization signal from the outgoing carrier wave, and then the user terminal device 50 of the terminal station 20 uses this fit synchronization signal. Since it is not possible to extract and use the fit synchronization signal with, there is a drawback that many restrictions are involved in the operation of the user terminal device 50. The present invention has been made in view of the above-mentioned problems, and an object thereof is to solve the above-mentioned drawbacks of the prior art, in which a terminal device of a terminal station directly extracts and uses a fit synchronization signal. It is an object of the present invention to provide a fit synchronization signal extracting device for a small earth station system and an extracting method thereof.

[0007]

In order to achieve the above object, the present invention has the following means. (1) In a small earth station system consisting of a central station and a plurality of terminal stations, a fit synchronizing signal extracting device for a small earth station system that extracts a fit synchronizing signal for synchronizing communication synchronization between the central station and the terminal stations is input. A clock divider that divides the clock of the fit synchronization signal that has been generated; a storage unit that stores the value divided by the clock divider;
Non-volatile storage means for reproducing the value of the state stored in advance by the value retrieved from the storage means and the received data; and extraction logic of the fit synchronization signal by the value reproduced by the non-volatile storage means. And a control logic means for controlling, and a device for extracting a fit synchronization signal in a small earth station system.

(2) A method for extracting a fit synchronization signal in a small earth station system for extracting a fit synchronization signal for synchronizing communication synchronization between the center station and the terminal station in a small earth station system including a central station and a plurality of terminals In extracting a fit sync signal comprising framing bits, identifier bits, and timing bits, which are the three subchannels created in the central station; and determining an identifier bit from the extracted fit sync signal. A step of obtaining timing synchronization from the extracted fit synchronization signal; and a method of extracting a fit synchronization signal in a small earth station system.

[0009]

With the configuration of the above item (1), the clock of the input fit synchronizing signal is divided, the divided value is stored and extracted, and the extracted value and the received data are stored in advance. The value in the open state is reproduced, and the extracted value controls the extraction logic of the fit synchronization signal. In addition, a fit synchronization signal including a frame indication bit, an identifier bit, and a timing bit, which are three subchannels created in the central station, is extracted by the method of the above (2), and from the extracted fit synchronization signal, The identifier bit is determined, and the timing synchronization is determined from the extracted fit synchronization signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an apparatus and method for extracting a fit synchronization signal in a small earth station system according to the present invention in a communication satellite system will now be described in detail with reference to the drawings. First, an embodiment of the device of the present invention will be described. FIG. 1 is a schematic diagram showing the configuration of an embodiment of the device of the present invention. In FIG. 1, this device comprises a clock divider 1 for dividing an input system clock; a RAM 2 as a storage means for storing a value divided by the clock divider 1; A ROM 3 which is a non-volatile storage means for reproducing a value of a state stored in advance according to an output value and received data; and a control logic unit 4 which operates by reproduction of the ROM 3 and controls the extraction logic of the fit synchronization signal. Composed of;

The apparatus of the present invention thus constructed operates as follows. First, as shown in FIG. 5, the reception data (Rx-Data) received from the central station 10 to the terminal station 20 is 66.666 Kbps, which is 66.666 KHz extracted by the decoder of the terminal station 20. Of the clock (CLK) of the present invention, is input to the 75-divider 1A of the clock divider 1 according to the present invention and is divided, and the divided output becomes the input addresses A _{0 to} A ₇ of the RAM 2. This received data (Rx-Data)
Is a 64 Kbps communication data body and 2.6 as shown in FIG.
It is composed of a 66 Kbps fit sync signal and at this time, the 0th bit (F0) of the frame indication bit 9F bit.
Since 75 to 1st bit (F1) have a width of 75-bit data, the 75-frequency divider 1A is required to extract the frame indication bit 9F bit. This is the same for the extraction of the identifier bit 9I bit and the timing bit 9T bit.

FIG. 2 is a timing chart for explaining the timing of the fit sync signal in the apparatus of FIG. Figure 2
2, the output of the 25 frequency divider 1B is provided to the control logic unit 4, and the fit synchronization FIT-Sync as shown in (a) of FIG. 2 outputted from the control logic unit 4 and (b) of FIG. 2 is provided as fit data FIT-Data and fit clock FIT-CLK as shown in FIG. 2 (c).
It becomes a clock divided by 5. Here, the clock of each fit synchronization signal is 66.666 KHz ÷ 75 = 0.888 K.
, And the clock of the entire fit sync signal is 0.
It is 888 KHz × 3 = 2.666 KHz. The count value of clock divider 1 is incremented each time each data bit is received. The value of the frequency-divided 75 output from the clock frequency divider 1 and the restoring (res
The received data (Rx-Data) value tore) is stored together.

The ROM 3 stores each received data (Rx-Dat
In order to compare with the value of a), a value of certain fit information which is information of communication synchronization in a specific terminal station 20 is stored for each address. When the value of the fit information stored in the ROM 3 and the value of the fit information in the received data (Rx-Data) match, the terminal station 20 determines that the received data (Rx-Data).
Identifies (x-Data) as own and synchronizes carrier waves. ROM3 synchronizes the received data (Rx-Data),
Before the address counter is incremented due to the state of the next reception, the received data (Rx-Dat
The fit information in a) is further stored in the RAM 2, and the fit information in the stored received data (Rx-Data) becomes a new address of the ROM 3. Once the carrier wave is synchronized and the received data (Rx-Data) is identified as its own, the fit information of this received data (Rx-Data) is output to the control logic unit 4.

The control logic unit 4 functions as a synchronization block in each sub-channel of the fit sync signal, and the 25 frequency divider 1B of the clock frequency divider 1 extracts the fit sync signal. When the 8th bit (F8) in the frame designating bit 9F bit pattern is generated in the fit sync signal of the reception data (Rx-Data), the ROM 3 reproduces the data D _{0 to} D _7, and the data is read through the control logic unit 4. 2 (a)
Output the fit synchronization (FIT-Sync) as shown in. On the other hand, in the fit synchronization signal of the received data (Rx-Data), the fit data (FIT-Data) is 25 by the 25 frequency divider 1B in the clock frequency divider 1 as shown in (b) of FIG. Reloading is performed for each data bit, and the identifier bit 9I bit and the timing bit 9T bit are extracted. On the other hand, the fit clock (FIT-CLK) of the control logic unit 4 is used for individual extraction in the fit sync signal by dividing the received clock (CLK) by 25, as shown in FIG. 2 (c). . Next, another embodiment according to the method of the present invention will be described in detail with reference to the drawings. The method according to this embodiment is configured to execute an identifier bit search program for obtaining an identifier bit and a timing synchronization processing program for obtaining timing synchronization. First, the algorithm of the identifier bit search program will be described.

FIG. 3 is a flow chart for explaining an identifier bit search program which is an embodiment of the method of the present invention. In FIG. 3, this identifier bit searching program includes a step A1 of reading a self-registered identifier number registered in advance by a dip switch of the terminal station 20; when any terminal station 20 is turned on, the central station 10 Step A2 of determining whether or not there is a sync signal in the output form signal indicating the output form of FIG. 1 and determining whether or not there is any output form signal in order to end the operation when this output form signal is not present. And;

Following the step A2 of determining whether or not there is this arbitrary output form signal, if this output form signal is present, after determining the output form signal, the fit synchronization signal in the output form signal is calculated. Step A3 of obtaining; if there is no fit synchronization signal, further output form signal is obtained, and if there is a fit synchronization signal, step A4 of obtaining an identifier bit in the fit synchronization signal; Step A5 of judging whether or not the identifier bits of the identifier numbers registered in advance in the terminal station 20 are the same; and if the identifier bits are different from each other, further output form signals are obtained, and the identifier bits are mutually different. If the two are the same, step A6 of tracking the required identifier bit and synchronizing
And;

Next, the algorithm of the timing synchronization processing program will be described. At that time, the timing bit 9T bit is composed of a total of 9 bits per slot, and is used for synchronizing the slots with all the terminal stations 20 of the network corresponding to the slot Aloha protocol. The number of slots is 100 slots, which are sequentially increased from 00 to 99, that is, one superframe is repeated. Also, in the case of the protocol based on slot Aloha, each terminal station 20 assigns a specific slot number that can be accessed from the network management system 30 of the central station 10 during the initialization process.

FIG. 4 is a flow chart for explaining a timing synchronization processing program according to the method of the present invention, in which a specific terminal station 20 in the earth station system is assigned a single slot or a plurality of slots by the network management system 30. In the assumed state, the timing synchronization processing program for this terminal station 20 is shown. In FIG. 4, the timing synchronization processing program includes a step B1 in which the terminal station 20 is assigned a specific slot number from the network management system 30; and 0 after the slot number is assigned.
Repeating with a period of 100 slots sequentially increasing from 0 to 99, setting a timing bit having a specific slot number allocated, B2; storing the timing bit, which is 9 bits per slot. B3; and after storing the timing bits, to allocate more timing bits when there is no transmission data, perform step B4 of judging whether there is transmission data from the central station 10.

Following the step B4 of judging whether or not there is transmission data, if there is transmission data, the terminal station 20
At step B5 of comparing the slot numbers assigned by the network management system 30 with the slot numbers of the timing bits to determine if they match; if these slot numbers do not match, then further timing bits are added. If the allocation and mutual slot numbers match, step B6 of processing the transmission data from the beginning of the next frame information in the synchronization information in the fit synchronization signal; and determining whether the processing of the transmission data has ended, When the processing of the transmission data is completed, the slot number, which is a new timing bit increased for the next transmission data, is stored in the ROM 3
Perform steps B7 and; After all, since all the terminal stations 20 belonging to one output form have the same specific slot number at the same time, it is possible to synchronize the slots.

[0020]

As described above in detail, the present invention has the following effects. According to the apparatus of the preceding paragraph (1), the user terminal device of the terminal station has a RAM for temporarily storing the clock component in the fit information from the central station and a ROM for storing its own fit information for identifying itself. Since it has this RAM, it buffers the system clock with the central station over time, and the ROM verifies the fit information from the central station with its own, and synchronizes the system with the central station with this user terminal device. be able to.

According to the method of the above item (2), in the communication satellite system, the user terminal device can directly extract the fit synchronization signal and use it as the system synchronization signal with the central station. In addition, it is possible to interconnect many user terminal devices and the central station,
By enabling accurate information transmission, communication performance can be improved, and thus the reliability of the communication satellite system can be increased. Therefore, it is possible to provide a fit synchronization signal extraction device for a small earth station system and an extraction method thereof so that a fit synchronization signal can be directly extracted and used in a terminal device of a terminal in a small earth station system. Is now possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing a configuration of an embodiment of an apparatus of the present invention.

FIG. 2 is a timing diagram illustrating the timing of a fit sync signal in the device of FIG.

FIG. 3 is a flow chart illustrating an identifier bit search program according to the method of the present invention.

FIG. 4 is a flowchart illustrating a timing synchronization processing program according to the method of the present invention.

FIG. 5 is a configuration diagram schematically showing a configuration of a general small earth station system.

6 is a configuration diagram illustrating a bit configuration of a fit synchronization signal in FIG.

[Explanation of symbols]

1: Clock frequency divider 2: RAM as storage means 3: ROM as nonvolatile storage means 4: Control logic unit 10: Central station 20: Terminal station 30: Network management system 40: User terminal device

Claims (4)

[Claims] 1. A compact earth station system comprising a central station and a plurality of terminal stations, wherein a fit synchronizing signal extracting device for a small earth station system extracts a fit synchronizing signal for synchronizing communication synchronization between the central station and the terminal stations. A clock divider for dividing the clock of the input fit synchronizing signal; a storage means for storing the value divided by the clock divider; and a value retrieved from the storage means and received data A nonvolatile storage means for reproducing the value of the state stored in advance; a control logic means for controlling the extraction logic of the fit synchronization signal according to the value reproduced by the nonvolatile storage means; A device for extracting the fit synchronization signal in a characteristic small earth station system. 2. A method of extracting a fit synchronization signal in a small earth station system for extracting a fit synchronization signal for synchronizing communication synchronization between a center station and a terminal station in a small earth station system comprising a center station and a plurality of terminals. Extracting a fit sync signal including framing bits, identifier bits, and timing bits, which are three sub-channels made by the central station; and determining an identifier bit from the extracted fit sync signal. A step of obtaining timing synchronization from the extracted fit synchronization signal; and a method of extracting a fit synchronization signal in a small earth station system, the method comprising: 3. The step of obtaining the identifier bit includes the step of reading a self-identifier number registered in advance by a DIP switch of the terminal station; the output from the central station when any terminal station is turned on. Determining whether or not there is an output form signal in order to determine the presence or absence of a sync signal in the output form signal indicating the form; When there is a morphological signal, after obtaining the output morphological signal, obtaining a fit synchronization signal in the output morphological signal; The step of obtaining an identifier bit in the fit synchronization signal; the step of determining whether the obtained identifier bit is the same as the identifier bit of the self-identifier number registered in advance in the terminal station; Further determining an output form signal if the identifier bits are different from each other, and tracking the obtained identifier bits to synchronize if the identifier bits are the same. Item 2. A method for extracting a fit synchronization signal in the small earth station system according to Item 2. 4. The step of obtaining the timing synchronization comprises the steps of assigning a specific slot number when the terminal station is assigned a slot from the central station and the timing of the terminal station and the timing of the terminal station are matched; Setting a timing bit having a particular slot number assigned, which is repeated with a period of 100 slots sequentially increasing from 00 to 99 after being assigned a number;
Storing the set timing bit in 9 bits corresponding to one slot; determining whether or not there is transmission data from the central station after storing the timing bit; Is assigned more timing bits, and if there is transmission data,
Comparing the specific slot number assigned by the central station and the slot number of the timing bit to each other to determine whether they match; if these slot numbers do not match, assign more timing bits When the slot numbers match each other, a step of processing the transmission data from the beginning of the next frame information in the synchronization information in the fit synchronization signal; and a step of determining whether the processing of the transmission data is completed and transmitting 3. The small earth station system according to claim 2, further comprising the step of storing a slot number, which is a new timing bit increased for the next transmission data, when the data processing is completed. Extraction method of fit synchronization signal.