KR100231779B1 - System clock generator in slave paging central system - Google Patents

Abstract

The present invention uses a clock of the reference clock generation unit as a system clock of the preliminary central station multiplexing unit in a radio call satellite transmission system, so that a radio call service can be made possible even if the clock of the public switched telephone network provided by the multiplexing line fails. A reference clock generation unit which divides and transmits a reference frequency to an interlink part of a preliminary central station multiplexer and provides a reference clock generator when a problem occurs in a central station that receives and transmits a radio call signal to a satellite. Using the clock generated by the unit as a system clock, it consists of a preliminary central station that receives the radio call signal and transmits it to the satellite to perform radio call service.

Description

Spare center station equipped with system clock generator in radio calling satellite transmission system

The present invention relates to a radio calling satellite transmission system, and more particularly, to improve the reliability of a radio calling satellite transmission system by implementing a system clock generator in a preliminary center multiplexer.

In general, a radio calling satellite transmission system (PagerSat) is a system that transmits radio calling data through a satellite, and a unidirectional data transmission system in which a path between base stations is replaced by a link using a satellite in a conventional leased line at a TDX-PS. to be.

As shown in FIG. 1, the general radio call satellite transmission system includes: a central station 10 for receiving a radio call signal, modulating it into a high frequency signal, and transmitting the signal to a satellite; A preliminary central station 20 which transfers the central station 10 to receive a radio call signal, modulates the radio call signal into a high frequency signal, and transmits the signal to a satellite when a problem occurs in the central station 10; It is composed of a plurality of base stations 30 for receiving and restoring a radio call signal transmitted to the satellite from the central station 10 or the preliminary central station 20.

In the above, the central station 10 of the radio calling satellite transmission system includes: a switch (11) for receiving a signal of a radio calling subscriber; A Paging Central Interface Block (PCIB) 12 for converting an analog paging signal into a digital signal by a frequency shift keying (hereinafter, abbreviated as "FSK") of the exchange 11; A channel card (QSP; Quad Synchronous Processor) 14 for synchronizing the clocks of the channel input / output data of the subscriber access unit 12 and compensating for the deviation between the system clock and the reception clock, and connected to the channel card 14. An interlink unit (ILC) 15 for processing data and voice between a channel and an intermachine link, and a network controller NCL for controlling the multiplexer 13; A multiplexer (MUX; Multiplexer) 13 having a Network Control Logic (16) to multiplex the signals of the digitally switched exchanges; Modulation and radio frequency transmission unit (MOD / RF; Modulation / Radio Frequency) for modulating the baseband signal input from the multiplexer 13 to output the signal of the intermediate frequency band and transmit the signal of the intermediate frequency band to the satellite as a high frequency signal 17; A high speed modem 18 is connected to the interlink unit 15 of the multiplexer 12 to allow the central station 10 to communicate with the preliminary center 20 via a dedicated line.

In the above, the preliminary center station 20 of the radio call satellite transmission system is connected to the central station 10 in a dedicated line so that the preliminary center station 20 can communicate with the center station 10. and; A channel service unit (CSU) 22 connected to the central station 10 by a dedicated line to enable the preliminary central station 20 to perform data service with the central station 10; It is connected to the high-speed modem 21 and the channel service unit 22 and comprises a plurality of four pairs and includes an interlink unit 24 for processing data and voice, and transmits data of up to four stations from the central station 10. A multiplexer 23 for receiving and multiplexing; A modulator (25) for generating an intermediate frequency by modulating the multiplexed data of the multiplexer (23); A coupling unit 26 for coupling an intermediate frequency output from the modulation unit 25; The high frequency transmitter 27 converts the intermediate frequency coupled by the combiner 26 into a high frequency signal and transmits the satellite signal to the satellite.

In addition, the base station 30 of the radio call satellite transmission system, the low-frequency amplification signal received from the satellite and then converted into an intermediate frequency signal, the high frequency reception and demodulator 31 to restore the intermediate frequency signal to the original signal )Wow; An interlink unit 33 connected to the demodulator 31 to demultiplex data and voice from a signal demodulated by the demodulator 31, and connected to the interlink unit 33 and connected between a system clock and a reception clock. A demultiplexer (DEMUX; DEMultiplexer) having a channel card 34 for compensating for misalignment and a network controller 35 for controlling the demultiplexer 32 to demultiplex a signal transmitted from a satellite into a digital signal. 32; A paging remote interface block (PRIB) 36 for restoring digital data of the demultiplexer 32 to an FSK analog paging signal; A transmitter 37 is connected to the subscriber access unit 36 and transmits a radio call signal restored by the subscriber.

Referring to the operation of the conventional radio calling satellite transmission system configured as described above, the central station 10 of the radio calling satellite transmission system transmits the FSK analog paging signal transmitted from the TDX (Time Division Multiplexing) -PS exchanger 11, which is a paging data exchange. The subscriber access unit 12 converts the digital signal to the multiplexer 13. Then, the multiplexer 13 synchronizes the clocks of the channel input / output data in the channel card 14, compensates for the deviation between the system clock and the reception clock, and then interlocks the channel module and the intermachine in the interlinker 15. Data and voice are processed between the links. The modulation and high frequency transmitter 17 then baseband signals (64Kbps / 128Kbps) input from the multiplexer 13 to the CCITT (International Telegraph and Telephone Consultative Committee) V.35 Scrambling, Discrete (Differential) coding, R = 1/2 k = 7 convolutional coding, and Binary Phase Shift Keying (BPSK) to modulate the intermediate frequency from 52 MHz to 88 MHz (70 ± 18 MHz) After converting to IF signal having a bandwidth of 250KHz / 500KHz in the band), the IF signal is inputted to the attenuator and adjusted by UPCU and Beacon receiver to perform redundancy control. In order to be transmitted to the outdoors by UPRC, the signal transmitted to the outdoors is distributed by the outdoor power distributor and transmitted to the transmitter. Then, the transmitter is amplified to a predetermined uplink frequency and power level, and the signal of the outdoor transmitter selected by the waveguide switch is connected to the feeder of the antenna to emit radio waves to the satellite.

On the other hand, if a problem occurs in the multiplexing unit 13 of the central station 10, the preliminary central station 20 may transfer the multiplexing unit 13 of the central station 10 in question to receive the radio call from the preliminary central station 20. Make sure Thus, the preliminary central station 20 receives the modulated multiplexed data of the central station 10 through the high speed modems 18 and 21, modulates and combines the multiplexed data, and transmits them to the satellite as a high frequency signal.

Accordingly, the plurality of base stations 30 of the radio calling satellite transmission system low-amplify the small signals of 12.25 ~ 12.75GHz received from the satellite in the high frequency reception and demodulator 31, and then converts them into IF signals of 950 ~ 1450MHz, Restore the original data with BPSK demodulation, descrambling, discrete decoding and R = 1/2 k = 7 Viterbi decoding. The recovered data is demultiplexed by the interlink unit 33 of the demultiplexer 32 and transferred to the channel card 34. The subscriber access unit 36 is then operated to restore the digital data of the channel card 34 to the FSK analog paging signal and transmit it through the transmitter 37 so that the user's wireless pager can receive the radio call signal.

Here, in the radio call data satellite transmission system using a geostationary satellite, the number of system clock fallback systems that can be set by the network controller 16 card in one multiplexer 13 is limited to three. That is, the system clock replacement system list of each central station 10 multiplexer 13 is set to "DLT 03, DLT 17, SKP", and the system clock replacement system list of the redundant central station 20 multiplexer 23 is "DLT 02, DLT 04, SKP" is set. Therefore, when site diversity transfer is performed, each central station 10 uses the interlink unit 15 of the 17th slot, and the preliminary central station 20 multiplexer 23 uses the interlink units 24 of the 02 and 04th slots. Public Switched Telephone Network (PSTN) is used as a system clock by receiving the network clock provided by a dedicated line.

However, if an error occurs in the dedicated line of the public switched telephone network connected to the 02 and 04 interlink units 24 of the preliminary central station 20, the multiplexing system cannot perform site diversity switching. That is, when a problem occurs in the public switched telephone network dedicated line connected to the interlink part 24 of the 02th and 04th slots, the multiplexer is not provided with the system clock through the dedicated line so that the system clock replacement system changes to the internal clock. do. In this case, the multiplexing generates a "PLL or Clock Source Error" alarm, and site diversity switching between all the central stations and the reserve central stations cannot be performed. Also, in case of implementing 4: 1 site diversity, if there is a problem with a dedicated line of the public switched telephone network that provides the system clock to the multiplexer, the redundant centralized station multiplexer will not operate, thus causing a problem with the dedicated line of the public switched telephone network. The problem arises that the site diversity transfer of the central station, which operates not only in one region but also in the other regions, is not performed.

Therefore, in the prior art, since the preliminary central station multiplexer receives and operates the system clock from the public switched telephone network, the EBI central station may be subject to some public switched telephone leased lines, resulting in 4: 1 site diver. There was a problem with the city implementation.

Therefore, the present invention has been proposed to solve the above-mentioned conventional problems, and an object of the present invention is to provide a multiplexing line by using a clock of a reference clock generation unit as a system clock of a preliminary center multiplexer in a radio calling satellite transmission system. The present invention provides a preliminary central station apparatus equipped with a system clock generation unit in a radio calling satellite transmission system capable of enabling a radio calling service even when a clock of a public switched telephone network occurs.

In order to achieve the above object, in the radio call satellite transmission system according to the present invention, a preliminary central station apparatus equipped with a system clock generator is provided.

A high speed modem connected to a plurality of central stations by a dedicated line to enable the reserve central station to communicate with the central station; A channel service unit connected to the central station through a dedicated line and allowing the preliminary central station to perform data service with the central station; A multiplexing unit connected to the high speed modem and the channel service unit and having a plurality of four pairs and having an interlink unit for processing data and voice and receiving and multiplexing data of up to four locations from the central station; And a reference clock generation unit for dividing and transmitting a reference frequency to the interlink unit of the multiplexer, and using a divided clock of the reference clock generator as a system clock to modulate the multiplexed data of the multiplexer and generate an intermediate frequency. Wow; A coupling unit coupling the intermediate frequency output from the modulation unit; It is characterized in that the technical configuration consists of a high frequency transmission unit for converting the intermediate frequency coupled by the coupling unit to a high frequency signal to transmit to the satellite.

1 is a block diagram showing a list of alternative systems of a site diversity block and a system clock of a conventional radio call satellite transmission system;

2 is a block diagram showing a list of alternative systems of a 4: 1 site diversity block and a system clock of a radio calling satellite transmission system according to the present invention;

Figure 3 is a detailed block diagram of the preliminary central station reference clock generation in Figure 2;

<Description of the code | symbol about the principal part of drawing>

110: central station 111: exchanger

112: subscriber connection 113, 123: multiplexing unit

114: channel card 115.124: interlink section

116: network control unit 117: modulation and high frequency transmission unit

118, 121: high speed modem 119, 122: channel service unit

120: reserve central station 125: modulation unit

126: reference clock generating unit 127: coupling unit

128: high frequency transmitter

Hereinafter, an embodiment according to the technical concept of a preliminary central station apparatus equipped with a system clock generation unit in the wireless call satellite transmission system configured as described above will be described in detail.

FIG. 2 is a block diagram illustrating a list of alternate systems of a 4: 1 site diversity block and a system clock of a radio calling satellite transmission system according to the present invention.

As shown therein, the central station 110 receives the radio call signal, modulates it into a high frequency signal, and transmits the signal to a satellite; When a problem occurs in the central station 110, the central station 110 is switched to receive a radio call signal, and is configured as a preliminary central station 120 for modulating the received radio call signal into a high frequency signal and transmitting it to the satellite.

The plurality of central stations (110) of the radio calling satellite transmission system includes: a switch (111) for receiving a signal of a radio calling subscriber; A subscriber connection unit (112) for converting an analog paging signal by the FSK of the exchange unit (111) into digital; A channel card 114 for synchronizing the clock of the channel input / output data of the subscriber access unit 112 and compensating for the deviation between the system clock and the reception clock; and a link connected to the channel card 114 to the channel A multiplexer 113 for multiplexing a signal of a digitally switched exchanger with an interlinker 115 for processing data and voice therebetween, and a network controller 116 for controlling the multiplexer 113; A modulation and high frequency transmitter 117 for modulating the baseband signal input from the multiplexer 113 to output a signal of an intermediate frequency band and transmitting the signal of the intermediate frequency band to a satellite as a high frequency signal; A high speed modem (118) connected to the interlinking unit (115) of the multiplexing unit (112) to allow the central station (110) to communicate with the reserve central station (120) via a dedicated line; It is composed of a channel service unit 119 connected to the preliminary center station 120 through a dedicated line and communicating so that data of the center station 110 can be serviced.

In addition, the preliminary center station 120 of the radio call satellite transmission system is connected to the central station 110 in a dedicated line so that the preliminary center station 120 may communicate with the center station 110. and; A channel service unit 122 connected to the central station 110 through a dedicated line to allow the preliminary central station 120 to perform data services with the central station 110; It is connected to the high-speed modem 121 and the channel service unit 122 and comprises a plurality of four pairs interlink unit 124 for processing data and voice to transmit data of up to four stations from the central station 110 A multiplexer 123 for receiving and multiplexing; And a reference clock generator 126 for dividing and transmitting a reference frequency to the interlink unit 124 of the multiplexer 123, and using the divided clock of the reference clock generator 126 as a system clock. A modulator 125 for modulating the multiplexed data of the multiplexer 123 and generating an intermediate frequency; A combiner 127 for coupling the intermediate frequency output from the modulator 125; The high frequency transmitter 128 converts the intermediate frequency coupled by the combiner 127 into a high frequency signal to transmit to the satellite.

In addition, the reference clock generation unit 126 of the preliminary central station 120, as shown in Figure 3, the comparison unit for receiving a sine wave of the reference oscillator and outputting a square wave; A BCD counter 142 for counting square waves output from the comparator by a binary coded decimal (BCD); A hexadecimal counter 143 for hexadecimal counting the clock output from the BCD counter 142; A first divider unit 144 for dividing the clock counted by the hexadecimal counter 143 at 1/25; A phase synchronous loop unit 145 for outputting a synchronous clock by synchronizing a clock divided by the first divider 144; A deflip-flop (146) for delaying and outputting a clock divided by the first divider (144); A second dividing unit 147 which receives and outputs the output signals of the phase locked loop unit 145 and the flip-flop 146 to output three reference clocks; The switch 148 selects one of the three reference clocks output from the second divider 147 and outputs the same to the multiplexer 123.

Referring to the accompanying drawings, the operation of the preliminary central station apparatus equipped with the system clock generation unit in the radio call satellite transmission system according to the present invention configured as described above is as follows.

First, the central station 110 of the radio calling satellite transmission system converts the FSK analog paging signal transmitted from the TDX-PS switch 111, which is a paging data exchanger, into a digital signal in the subscriber access unit 111 and inputs it to the multiplexer 113. . Then, the channel card 114 composed of four redundancies of the multiplexer 113 synchronizes the clocks of the channel input / output data and compensates for the deviation between the system clock and the reception clock. The interlinker 115 then processes data and voice between the channel module and the intermachine link. That is, it multiplexes data and voice, assembles frames, maintains interlink link synchronization, and allows asynchronous and single operations to be performed. As such, the baseband signal (64 Kbps / 128 Kbps) input from the multiplexer 113 is modulated by CCITT V.35 scrambling, discrete coding, R = 1/2 k = 7 convolutional coding, and BPSK in the modulation and high frequency transmitter 117. It has a bandwidth of 250KHz / 500KHz in the middle frequency band of 52MHz to 88MHz (70 ± 18MHz), which is input to the attenuator, controlled by UPCU and beacon receiver, and transmitted to the outdoors by UPRC which performs redundancy control. It is then distributed by the outdoor power divider and forwarded to the transmitter. Then, the transmitter amplifies to a predetermined uplink frequency and power level, and then the signal of the outdoor transmitter selected by the waveguide switch is connected to the feeding part of the antenna by the object modeling technique (OMT) to emit radio waves to the satellite.

On the other hand, if a problem occurs in the multiplexing unit 113 of the central station 110, the preliminary central station 120 can switch the multiplexing unit 113 of the central station 110 in question to receive the radio call from the preliminary central station 120. Make sure Therefore, the preliminary central station 120 receives the modulated multiplexed data of the central station 110 through the high speed modems 118 and 121, modulates and combines the multiplexed data, and transmits them to the satellite as high frequency signals.

Here, the reference clock generator 126 mounted on the preliminary central station 120 modulator 125 receives a stable clock (10 MHz) from the reference oscillator, converts the sine wave into a square wave, and then receives a clock of 2 MHz from the BCD counter 142. After extraction, the result is divided into 1/25 at hexadecimal counter 143 at 133.3 KHz. Thus, the second division unit 147 divides the clock delayed by the 256 kHz synchronization clock and deflip-flop 146 through the phase synchronization loop unit 145 into 256 kHz, 128 kHz, and 64 kHz. Use it as a clock.

As such, the clock provided by the reference clock generator 126 is provided through the interlink unit 124 of the 18th slot of the multiplexer 123 of the preliminary central station 120, and the clock is used as the multiplexing system clock. At this time, the system clock replacement system of the multiplexer 123 may be set to "DLT 18, DLT 02, DLT 04".

Therefore, since the system clock is not a network clock provided by a dedicated line but an independent clock provided by the reference clock generator 126, an error occurs in the dedicated line connected to the interlink unit 124 of the 02th and 04th slots. Even if the central station connected to the leased line is not capable of site diversity, the central station of the other area where the remaining leased line is living will be able to switch between die diversity.

As described above, the preliminary central station apparatus equipped with the radio calling system clock generation unit according to the present invention uses an independent clock generated by the system clock generation unit as a system clock of the preliminary central station multiplexer and is provided in a multiplexing line. Even if a clock fails, site diversity is enabled to perform a radio call service, thereby improving reliability and performance of the radio call satellite transmission system.

Claims (2)

A high speed modem connected to a plurality of central stations by a dedicated line to enable the reserve central station to communicate with the central station; A channel service unit connected to the central station through a dedicated line and allowing the preliminary central station to perform data service with the central station; A multiplexing unit connected to the high speed modem and the channel service unit and having a plurality of four pairs and having an interlink unit for processing data and voice and receiving and multiplexing data of up to four locations from the central station; And a reference clock generation unit for dividing and transmitting a reference frequency to the interlink unit of the multiplexer, and using a divided clock of the reference clock generator as a system clock to modulate the multiplexed data of the multiplexer and generate an intermediate frequency. Wow; A coupling unit coupling the intermediate frequency output from the modulation unit; A preliminary central station apparatus equipped with a system clock generator in a radio calling satellite transmission system, characterized in that the high frequency signal transmitting unit converts the intermediate frequency coupled by the coupling unit into a high frequency signal. The method of claim 1, wherein the reference clock generation unit, A comparator configured to receive a sine wave of the reference oscillator and output the square wave; A BCD counter for counting square waves output from the comparator with a binary coded decimal (BCD); A hexadecimal counter for hexadecimal counting the clock output from the BCD counter; A first divider for dividing the clock counted in the hexadecimal counter by 1/25; A phase synchronizing loop unit configured to output a synchronizing clock by synchronizing a clock divided by the first division unit; A deflip-flop for delaying and outputting a clock divided by the first divider; A second divider unit which receives the phase synchronization loop unit and the output signals of the deflip-flop and divides them to output three reference clocks; And a switch configured to select one of the three reference clocks output from the second divider and output the multiplier to the multiplexing unit.

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