KR100226600B1 - The network synchronizing method in the satellite comunication system and its apparatus - Google Patents

Abstract

The present invention relates to a network synchronization method for a satellite communication system for synchronizing network synchronization between a current exchange network and a satellite communication network in a satellite communication system adapted to perform communication between remote sites using a satellite, will be.

In the method and apparatus for generating network synchronization according to the present invention, the central control station generates a synchronizing signal to be used by itself in synchronization with an EWSN signal input from a first exchange. Then, a predetermined synchronous bit is added to an initial predetermined period of data to be transmitted to the base station, and the synchronous signal is transmitted to each base station in synchronization with the network synchronous signal of the switching network. In the control station, a signal received from the central control station is transmitted Demodulates and detects a transmitted frequency signal, and generates a required frequency signal in the apparatus based on the detected frequency signal.

Therefore, both the switching network and the satellite communication system, and the base station between the central control station and the base station located at the remote locations in the satellite communication system are set to be the same.

Description

Network synchronization method and apparatus for satellite communication system

FIG. 1 is a system overview diagram illustrating an overview of a typical satellite communication system; FIG.

FIG. 2 is a block diagram showing a configuration of a central control station according to the present invention; FIG.

FIG. 3 is a block diagram showing a detailed configuration of a synchronization signal generating unit in FIG. 2; FIG.

FIG. 4 is a block diagram showing a configuration of the network control unit in FIG. 2; FIG.

FIG. 5 is a block diagram showing a configuration of a base station according to the present invention; FIG.

FIG. 6 is a block diagram showing a detailed configuration of a synchronizing signal generating unit in FIG. 5; FIG.

BRIEF DESCRIPTION OF THE DRAWINGS

1: satellite 2: central control station

3A and 3B: base stations 11A and 11B:

12A, 12B: telephones 13A, 13B: data terminals

14A, 14B: facsimile 21: antenna

22: orthogonal mode converter 23: low noise amplifier

24: frequency down converter 25: intermediate frequency combination /

26, 31: SCPC channel unit 27: trunk interface port

32: frequency up converter 33: high power amplifier

35: Sync signal generator 36: UPH

40: network control unit 41: processor

42: Service channel controller 43: Dual port RAM

44: Program storage unit 45: Data storage unit

50: network management system 60: telephone data card

61, 62: SCPC channel unit 63: Network control unit

64: Sync signal generator 351:

642, 645: frequency divider 353, 643: phase comparator

354, 644: integration circuit 351, 641: voltage controlled oscillator

The present invention relates to a satellite communication system adapted to perform communication between remote sites using a satellite, and more particularly, to a network synchronization method for a satellite communication system for matching a network synchronization of a satellite communication network to a current exchange network, .

2. Description of the Related Art In recent years, with the rapid development of communication technology, satellite communication that allows a subscriber located at a remote location to make a call through a satellite is gradually becoming common. Such satellite communication requires no separate signal line Therefore, it is mainly used as a long distance communication between countries or as a communication method of a mountainous country like Korea.

FIG. 1 is an overall system configuration diagram showing an outline of a satellite communication system currently being tried in Korea. In FIG. 1, reference numeral 1 is a satellite having a plurality of communication channels, 2 is a central control station for controlling the entire satellite communication system, 3 3A and 3B have an interface function with respect to terminals such as exchanges 11A and 11B and telephones 12A and 12B and data terminals 13A and 13B such as computers and facsimile machines 14A and 14B, And a base station for providing a call function between the various terminals through data transmission / reception with the central control station 2.

In FIG. 1, reference symbol S denotes a service channel for transmitting and receiving control data, and T denotes a traffic channel for transmitting and receiving data and voice.

That is, in the above configuration, the central control station 2 transmits the control message through the service channel in a normal state, and then, based on the response message transmitted from the corresponding base station 3, And performs a polling function for checking the communication capacity or the use state of the communication channel. At this time, the transmission of the message to the base station 3 is performed using a TDM channel (Time Division Multi-channel), and the message transmission to the central control station 2 at the base station 3 is performed by the S- (Sloted ALOHA).

When there is a call request from a specific base station, for example, the base station 3A, to the terminal of the base station 3B, the central control station 2 requests the base station 3B based on the information obtained in the polling process. The base stations 3A and 3B directly communicate with each other by allocating to the base stations 3A and 3B the available traffic channels T of the satellites in the communication enabled state .

When communication is completed between the base stations 3A and 3B and the communication end signal is applied from the base station 3A through which the communication request has been made via the service channel S, the central control station 2 transmits The communication end process is performed to release the traffic channel T that has been provided to both the base stations 3A and 3B.

In general, when data and messages are transmitted and received between communication systems, it is necessary to synchronize system synchronization, that is, the synchronization between the communication systems. In the above-described satellite communication system, the central control station 2, It is impossible to perform the network synchronization control through the wired line. Moreover, since the satellite communication system is also connected to the exchange network currently used through the exchange, there is a problem that the exchange network must be matched.

Accordingly, a network synchronization method and apparatus for synchronizing a satellite communication system as a whole in synchronization with a network synchronization signal of a switching network currently in use are needed.

Accordingly, it is an object of the present invention to provide a network synchronization method and apparatus that can be applied to a satellite communication system.

A network synchronization method for a satellite communication system according to a first aspect of the present invention for achieving the above object comprises a synchronization bit setting step of adding a predetermined synchronization bit to a start section of data to be transmitted to each base station, A reference clock signal generation step of generating a predetermined reference clock signal synchronized with the synchronization signal, a data output step of outputting the data to which the synchronization bit is added in synchronization with the reference clock signal, A receiving frequency signal demodulating step of demodulating the frequency signal transmitted from the central control station, and a demodulating step of demodulating the received frequency signal to generate a required clock frequency signal based on the frequency signal obtained in the receiving data demodulating step And a synchronization signal generation step of generating a synchronization signal.

The network synchronizing apparatus for a satellite communication system according to a second aspect of the present invention for realizing the above object generates data to be transmitted to a base station and also generates transmission data for adding a predetermined synchronization bit to a start section of the data A reference clock generating means for generating a predetermined reference clock signal in synchronization with a synchronizing signal of a switching network applied from an exchange; a reference clock generating means for generating transmission data for outputting data generated by the transmission data generating means in synchronization with the reference clock signal; A demodulation means for demodulating the frequency signal transmitted from the central control station, and a demodulation means for demodulating the frequency signal transmitted from the central control station, A synchronous signal generating unit for generating a clock signal of various frequencies in synchronization with the obtained frequency signal And it characterized by comprising a base station configured to include.

According to the present invention, the central control station generates a synchronous signal to be used by itself in synchronization with the network synchronous signal of the switching network input at the priority exchange. The base station adds a predetermined synchronization bit to an initial predetermined period of data to be transmitted to the base station, and transmits the synchronous bit in synchronization with the switching network synchronization signal. The base station demodulates the signal received from the central control station After the transmitted frequency signal is detected, a necessary frequency signal is generated in the device based on the detected frequency signal.

Therefore, both the switching network and the satellite communication system, and the base station between the central control station and the base station located at the remote locations in the satellite communication system are set to be the same.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

2 is a block diagram showing a configuration of a central control station in a satellite communication system according to the present invention. In FIG. 2, reference numeral 21 denotes an uplink signal and a downlink signal 22 denotes an orthogonal mode transducer (OMT) for separating and inputting signals transmitted and received through the antenna 22 using the polarization characteristics of the frequency, 23 denotes an orthogonal mode transducer 22 A Low Noise Amplifier (LNA) 24 for low-noise amplifying a downlink frequency signal of, for example, 12.25 to 12.75 GHz input through the low noise amplifier 23, and 24 a frequency signal applied through the low noise amplifier 23, (DC) down-converter (IF).

Reference numeral 25 denotes a frequency division multiplexer for separating and outputting an intermediate frequency signal IF applied from the frequency down converter 24 to a plurality of intermediate frequency signals and for outputting a single channel per- (IF C / D: IF Combiner / Distributor) 26 for combining and outputting the intermediate frequency signals applied from the mixer / divider (SCU) 31. 26 (261 to 264) The SCPC channel unit 26 demodulates, decodes, and outputs an intermediate frequency signal applied from the base station 2, 25, and 25, wherein the SCPC channel user 26 is for receiving a message transmitted from each base station 3 in FIG. 1 .

Reference numeral 27 denotes a trunk interface port for connecting the central control station 2 with another exchange or the like. This is a synchronous signal generator 35 ).

2, reference numeral 31 denotes an SCPC channel slot for encoding and modulating a message of a TDM (Time Division Multiplex) stream output from the network control unit 40 to be described later, A frequency up-converter (UC) 33 for converting an IF signal of 70 MHz applied from the combination / distribution unit 25 to a microwave of 14.0 to 14.5 GHz to generate an uplink frequency signal, 33 a frequency up converter (HPA) that amplifies the uplink frequency signal output from the high power amplifier (HPA).

A synchronous signal generator 35 for generating a predetermined synchronous signal includes synchronous signal generator 35 for synchronizing with a clock signal of, for example, 2048 KHz input from the trunk interface port 27, Generates a clock signal of 32 KHz necessary for data transmission, and generates a reference clock of 2048 KHz and a frame start signal (SOF: Start Of Frame) of 8 KHz for communication between boards of the central control station itself.

FIG. 3 is a block diagram showing the detailed configuration of the synchronization signal generation main 35.

3, reference numeral 351 denotes a voltage-controlled oscillator for generating a frequency signal corresponding to an applied voltage level, reference numeral 353 denotes a frequency signal applied from the trunk interface port 27, and reference numeral 353 denotes a frequency- A phase comparator 354 for comparing the phase of the output frequency signal and outputting a clock signal corresponding to the phase difference; and 354 for integrating the clock signal output from the phase comparator 353 and outputting the corresponding clock signal, that is, And generates a level signal corresponding to the phase difference between the frequency signal of the trunk interface port 27 and the frequency signal applied to the trunk interface port 27. [

Reference numeral 355 denotes a frequency divider for outputting a frequency signal output from the voltage-controlled oscillator 351, a 256 frequency-divided signal and a 64 frequency-divided signal of the frequency signal.

That is, in the above configuration, the phase comparator 353 compares the frequency signal applied from the trunk interface port 27, that is, the network synchronization signal of the switching network, and the frequency signal output from the voltage controlled oscillator 351, And is applied to the voltage controlled oscillator 351 as a voltage signal through the integrating circuit 354. [

Thus, the frequency-controlled oscillator 351 outputs a frequency signal of 2048 KHz synchronized with the network synchronization signal of the switching network by the above-described operation.

The frequency signal output from the voltage controlled oscillator 351 is used as a reference clock for data transmission between the base stations and is also used as a frame start signal SOF of 8 kHz divided by 256 by the frequency divider 355 Particularly, the 32 KHz frequency signal output from the frequency divider 355 in the frequency divider 355 is applied to the network controller 40 and used as a clock signal for data transmission.

2, reference numeral 40 denotes a network controller for performing a control operation for the whole satellite communication network by transmitting and receiving a control message to each base station 3 through the SCPC channel unit 26, Units 26 and 31 and the trunk interface port 27 through a UPH 36 (Utility PCM Bus). The network control unit 40 transmits a synchronization bit to each base station 3 based on a clock signal applied from the above-described synchronization signal generating unit 35, that is, a clock signal synchronized with the synchronization signal of the switching network And controls the network of the entire network.

Reference numeral 50 denotes a network management system for the system manager to manage the overall network of the satellite communication system by managing the network control unit 40.

4 is a block diagram schematically showing the configuration of the network control unit 40. Reference numeral 41 in the figure controls the entire system, and in particular, controls the entire base station 3 to have a predetermined number of bits, for example, 10 bits And generates and outputs a synchronous bit. Reference numeral 42 denotes a processor for extracting packet information from a message applied by the SCPC channel unit 26 to generate an S-ALOHA (Sloted ALOHA) packet, Is a service channel controller (SCC) for generating and outputting a message of a TDM stream to the SCPC channel unit 31 in synchronization with a clock signal of 32 KHz applied from the signal generating unit 35.

Also, reference numeral 43 is a dual port RAM, which is provided for data transmission / reception between the processor 41 and the service channel controller 42.

Reference numeral 44 denotes a program storage unit in which an operation program of the processor 44 is stored. Reference numeral 45 denotes a base station information storage unit in which status information of each base station obtained by the polling operation of the network control unit 40 is stored.

That is, in the above-described configuration, the processor 44 performs a polling operation by transmitting / receiving a predetermined message to / from each base station 3 through the seamless channel controller 41.

That is, when the processor 41 writes data for inquiring the state of each base station 3 in the dual port RAM 43, the service channel controller 42 causes the synchronous signal generator 35 to generate synchronous signals Port RAM 43 to generate a message of a TDM stream and transmit it to each base station 3 through the SCPC channel unit 31 in FIG. 2 . When a response message to the inquiry message is received through the SCPC channel unit 26, the service channel controller 42 extracts predetermined packet information from the received message and writes the packet information to the dual port RAM 43, The processor 41 stores the applied packet information in the data storage unit 45 to correspond to a communication request from a specific base station 3 to be generated later.

In performing the above-described polling operation, the processor 41 writes synchronous data, for example, 1010 ... to the lowest 10 bits of the dual port RAM 43, for example, at the time of sending out the inquiry message. The service channel controller 42 reads the synchronous bit in synchronization with the clock frequency signal applied by the synchronizing signal generator 35, that is, 32 KHz, as described above, and sends it to the SCPC channel unit 31 . Therefore, the frame data output from the central control station 2 to each base station 3 is output with a 32 KHz synchronous signal synchronized with the synchronization signal of the switching network during the initial period.

FIG. 5 is a configuration diagram showing a configuration of the base station 3. FIG. In FIG. 5, substantially the same parts as in FIG. 2 are denoted by the same reference numerals, and a detailed description thereof will be omitted.

5, reference numeral 60 denotes a telephone data card for connecting terminals such as the telephone 12, the data terminal 13, and the facsimile 14 as shown in FIG. 1, and 61 (61 1 To 61n demodulate and decode the frequency signal from the other base station output from the intermediate frequency combining / distributing unit 25 described above and transmit the transmission signal from the switching center input through the trunk interface port 27 or the telephone signal And a SCPC channel unit for encoding and modulating the transmission signal from the terminal 60 and outputting the transmission signal.

Reference numeral 621 denotes an SCPC channel unit for encoding and modulating a message output from the network control unit 63 to be described later, that is, a message transmitted from the base station 3 to the central control station 2 And 622 is an SCPC channel unit for decoding and demodulating the message of the TDM stream transmitted from the central control station 2 and outputting it.

Here, the SCPC channel unit 622 performs decoding and demodulation based on the synchronization frequency signal added to the initial data interval of the message transmitted from the central control station 2 as described in FIGS. 2 and 4, And outputs the corresponding frequency signal, that is, the frequency signal of 32 KHz, to the synchronization signal generating unit 64 to be described later.

Reference numeral 63 denotes a control channel for controlling the SCPC channel unit 61, the trunk interface port 27 and the telephone data card 60 to provide a predetermined communication channel to the subscriber, 64 denotes a reference clock of 2048 KHz required for the entire apparatus based on the frequency signal of 32 KHz applied from the SCPC channel unit 62 2 and a reference clock of 8 KHz (SOF), i.e., a synchronizing signal generating unit for generating a frame starting signal SOF of the video signal.

Here, the SCPC channel units 61 and 62 and the trunk interface port 27, the telephone card 60, and the network control unit 63 are coupled through the UPH 65.

FIG. 6 is a block diagram showing a configuration of the synchronization signal generating unit 64. FIG.

6, reference numeral 641 denotes a voltage controlled oscillator for generating a frequency signal corresponding to the applied voltage level, and reference numeral 642 denotes a frequency divider for dividing the frequency signal output from the voltage controlled oscillator 641 by 64.

Reference numeral 643 denotes a phase comparator for comparing phases of a frequency signal applied from the SCPC channel unit 622 with a frequency signal applied from the frequency divider 642 and outputting a clock signal corresponding to the phase difference, And integrates the clock signal output from the phase comparator 643 to generate a level signal corresponding to the phase difference between the clock signal, that is, the frequency signal from the frequency divider 642 and the frequency signal applied from the SCPC channel unit 622 It is an integrating circuit.

Reference numeral 645 denotes a frequency divider that outputs a frequency signal output from the voltage controlled oscillator 641 and a 256 frequency division signal of the frequency signal.

That is, in the above configuration, the 64 frequency-divided signals of the frequency signal applied from the SCPC channel unit 622 and the frequency signal outputted from the voltage-controlled oscillator 641 are compared in the phase comparator 643, 644 to the voltage controlled oscillator 641 as a voltage signal.

Accordingly, the frequency signal from the SCPC channel unit 622, that is, the frequency signal of 2048 KHz corresponding to 64 times of 32 KHz is output from the voltage-controlled oscillator 641 by the above operation.

The frequency signal output from the voltage controlled oscillator 641 is used as a reference clock for data transmission between the base stations and is also used as a frame start signal SOF of 8 kHz divided by 256 by a frequency divider 645 .

That is, in the network synchronizing method and apparatus according to the present invention, the central control station generates a synchronous signal to be used by itself in synchronization with the switching network synchronizing signal input from the switching center. Then, a predetermined synchronization bit is added to an initial predetermined period of data to be transmitted to the base station, and then the synchronous signal is transmitted to each base station in synchronization with the network synchronization signal of the switching network. The control station transmits a signal received from the central control station Demodulates and detects a transmitted frequency signal, and generates a required frequency signal in the apparatus based on the detected frequency signal.

Therefore, both the switching network and the satellite communication system, and the base station between the central control station and the base station located at the remote locations in the satellite communication system are set to be the same.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the technical scope of the present invention.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a network synchronization method applicable to a satellite communication system and its apparatus can be realized.

Claims (3)

Generating a reference clock signal and a frame start signal for communication between boards of the central control station itself, in synchronization with a network synchronization signal of a switching network applied from an exchange; A synchronous bit generating step of adding a synchronous signal of a switching network applied from an exchange to a start period of data to be transmitted to the base station, a data outputting synchronous data to the synchronous bit synchronous signal generating step A demodulating step of demodulating the frequency signal transmitted from the central control station, a demodulating step of demodulating the frequency signal outputted from the demodulating step, To generate a clock frequency signal required by the device Network synchronization method of a satellite communication system, characterized in that configured to include a signal generation step. A reference synchronizing signal generating means for generating a clock signal according to data transmission in a central station in synchronization with a network synchronizing signal of a switching network applied from an exchange and a reference clock and a frame starting signal for communication between the boards of the central control station itself, A transmission data generating means for generating a data to be transmitted to the switching network and adding a synchronization signal of a switching network applied from an exchange to a start section of the data and generating data generated by the transmission data generating means in synchronization with the reference clock signal And a data transmission means for modulating and outputting the transmission data output from the transmission data output means, and a demodulation means for demodulating the frequency signal transmitted from the central control station, And a demodulating means for demodulating the frequency signals, Network synchronization apparatus of a satellite communication system that generates a clock signal. 3. The apparatus of claim 2, wherein the synchronization bits are added to the periodic polling data for the base station.