KR20060064904A - Hub system in the bi-directional satellite communication system - Google Patents

Abstract

In a bidirectional satellite communication system, the present invention relates to a technique for solving a network synchronization problem caused by re-correction of PCR values generated by using a general commercial MPEG2-TS remultiplexer.

The present invention is a central station system of a two-way satellite communication system, which transmits broadcasting and communication data to a forward link according to DVB (Digital Video Broadcasting) -S standard, from a terminal station to a DVB-RCS (Return Channel Satellite) standard. And a central station receiver for data processing of the signal input to the reverse link. The central station transmitter performs multiplexing of the broadcast and communication data into one MPEG2 stream, and then uses the NCR to synchronize the clock and timing of the reverse link. Create and insert (Network CLock Reference).

The present invention provides an effect that the clock and timing synchronization for the reverse link is stable by transmitting the NCR value required for the reverse link network to the terminal station without being modified during transmission on the forward link.

DVB-RCS, PCR, NCR, Bidirectional Satellite Communication System, Network Synchronizer

Description

Hub System in the Bi-directional Satellite Communication System             

1 is a block diagram of a bidirectional satellite communication system to which the present invention is applied.

2 is a detailed block diagram of a central station system according to the present invention.

3 is a detailed block diagram of an NCR packet inserter according to the present invention.

The present invention conforms to the DVB (Digital Video Broadcasting) -S standard using TDM (Time Division Multiplexing) as a forward link method, and enables high-speed data communication and broadcast service using TDMA as a reverse link multiple access method. In a bidirectional satellite communication system that conforms to the DVB-RCS (Return Channel Satellite) standard, the present invention relates to a technique for solving a network problem caused by re-correction of PCR values generated by using a general commercial MPEG2-TS remultiplexer.

In the prior art, the satellite broadcasting system enables multiple broadcasting services by multiplexing multiple broadcasting service streams into one MPEG2 stream using a common commercial MPEG2-TS remultiplexer.

In addition, when the terrestrial network is used as a reverse link among two methods of providing a bidirectional communication service through a satellite, a general commercial MPEG2-TS remultiplexer converts multiple broadcast service streams and data in the form of MPEG2 streams for a communication service into one MPEG2. Multiplexing into streams enabled not only broadcasting but also communication services.

In such a satellite broadcasting and communication system, a PCR (Program Clock Reference) is periodically included in an MPEG2-TS packet having a specific PID (Program ID) in order to restore a clock of a receiver. PCR is a 42-bit timestamp value generated by the 27 MHz clock, which is the reference clock of the central station. The receiving side restores the 27 MHz clock, which is the reference clock of the central station, using the transmitted PCR value itself and the period of the received PCR, and uses it as the reference clock of the receiving side.

On the other hand, in the bidirectional satellite communication system conforming to the DVB-RCS standard for configuring the reverse link through satellites, the MPEG value of the PCR standard is transmitted with time stamp information indicating the reference time point of the central station required to maintain the clock and timing synchronization of the reverse link. Insert it into the field to send periodically. In order to maintain the clock and timing synchronization of the reverse link through the satellite as described above, a value inserted into the PCR field of the MPEG standard is called NCR (Network Clock Reference). The terminal station recovers the 27 MHz clock which is the reference clock of the central station by using the intervals of the periodically received NCR values, and maintains the absolute time synchronization with the central station by using the NCR value itself at the moment when the NCR value is received. do. In such a satellite bidirectional satellite communication system, in general, only MPEG2 streams for providing a communication service are transmitted through a forward link without considering a broadcast stream. Accordingly, in order to simultaneously provide not only a communication service but also a broadcast service in a satellite bidirectional communication system conforming to the DVB-RCS standard, an MPEG2 remultiplexer which multiplexes an MPEG2 stream for broadcasting and an MPEG2 stream for communication is required. . However, in this case, a problem arises due to the characteristics of the general MPEG2-TS remultiplexer.

A typical commercial MPEG2-TS remultiplexer performs a function of generating one MPEG2 stream by dividing and multiplexing a plurality of input MPEG2 streams on a time axis. For such multiplexing, each MPEG2 stream input is stored and output in the memory of the remultiplexer, and in this process, PCR values and NCR values included in each MPEG2 stream are generated inside the remultiplexer. In order to compensate for the temporal delay factors, the output is modified at the time output from the remultiplexer.

As described above, the modified PCR value in the MPEG2-TS remultiplexer provides two-way communication using a satellite broadcasting system and a land network that recovers the clock of the receiver by using a difference between the cycle of the received PCR value and the consecutive PCR values. It can satisfy the requirements of clock recovery performance and MPEG2 standard in the system.

However, the NCR value used in the bi-directional communication system via satellites conforming to the DVB-RCS standard is not only the difference between the periods of the NCR values periodically transmitted from the central station and the successive NCR values, but also the received NCR value itself is absolute with the central station. Used to keep time synchronized. Therefore, if the NCR value input from the remultiplexer is corrected and output in consideration of the delay factor generated inside the remultiplexer, it does not affect the recovery of the clock, but there is a problem in finding an accurate time for transmitting data on the reverse link. Occurs.

According to the present invention, when an MPEG2-TS remultiplexer is used to multiplex multiple input streams for broadcasting and two-way communication service through satellite, and simultaneously provides broadcasting and two-way communication service, MPEG2 including an NCR value for maintaining a network synchronizer is provided. -TS packets are not input to the MPEG2-TS remultiplexer, and a separate component that generates and inserts an MPEG2-TS packet containing an NCR value at the output of the remultiplexer does not add any modifications to the NCR value. Clock and timing synchronization for the reverse link can be made stable.

The present invention is a central station system of a two-way satellite communication system, which transmits broadcasting and communication data to a forward link according to DVB (Digital Video Broadcasting) -S standard, from a terminal station to a DVB-RCS (Return Channel Satellite) standard. And a central station receiver for data processing of the signal input to the reverse link. The central station transmitter performs multiplexing of the broadcast and communication data into one MPEG2 stream, and then uses the NCR to synchronize the clock and timing of the reverse link. Create and insert (Network CLock Reference).

In particular, the central station transmitting unit includes an MPEG-2 converter for converting the communication data in the IP form input from the external Internet into an MPEG-2 stream, an MPEG-2 encoder for converting the broadcast data into an MPEG-2 stream, and the reverse link. MPEG2-TS for outputting the output of the PSI / SI table generator for generating a PSI / SI (Program Specific Information / System Information) table for communication, the MPEG-2 converter and the MPEG-2 encoder as a single MPEG-2 stream A remultiplexer, an NCR packet inserter for generating an MPEG2-TS packet including the NCR and inserting it into an output of the MPEG2-TS remultiplexer, a modulator for RF modulating the output of the NCR packet inserter, and an output of the modulator It consists of an RF transmitter to transmit to.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention;

1 is a system configuration diagram having a broadcasting and bidirectional communication service function to which the present invention is applied. The bidirectional satellite communication system follows the DVB-S standard using TDM as the forward link method, and the DVB-RCS standard enabling high-speed data communication and broadcasting service using TDMA as the reverse link multiple access method. The central station is connected to the Internet to provide two-way communication service. In addition, the central station receives a plurality of broadcast streams, provides multiplexing streams, transmits them on the forward link, and demodulates and restores the signals transmitted from the terminal stations. The terminal station receives broadcast and bidirectional communication services transmitted from the central station.

2 is a detailed block diagram of a central station according to the present invention. The central station is a central station transmitter 200 for transmitting data for broadcasting and bidirectional communication over a DVB-S based forward link and a central station receiver 100 for receiving and demodulating a signal input through a TDMA based reverse link from a terminal station. It is divided up.

The central station transmitter 200 includes an MPEG2 converter 210, an MPEG2 encoder 220, a PSI / SI table generator 230, an MPEG2-TS remultiplexer 240, an NCR packet inserter 250, a modulator 260, and an RF. A transmitter 270. The MPEG2 converter 210 converts IP data provided from the Internet into an MPEG2-TS stream for transmission over a DVB-S based forward link. The MPEG2 encoder 220 converts the input broadcast stream into an MPEG2-TS stream.

The PSI / SI (Program Specific Information / Service Information) Table Generator 230 generates a PSI / SI table for the reverse link. The MPEG2-TS remultiplexer 240 multiplexes multiple MPEG2 streams input from the MPEG2 converter 210 and the MPEG2 encoder 220 into one MPEG2 stream. The NCR packet inserter 250 generates and inserts an MPEG2-TS packet including an NCR value for the synchronizer at the output of the MPEG2-TS remultiplexer 240. The modulator 260 modulates the output of the NCR packet inserter 250 into an RF signal, and the RF transmitter 270 outputs the modulated RF signal to the antenna.

The central station receiver 100 includes an RF receiver 110, a reception data demodulator 120, a reception timing generator 130, and a reception data processor 140. The RF receiver 110 receives a signal from the antenna, and the received data demodulator 120 demodulates the output signal of the RF receiver 110. The reception timing generator 130 generates reference timing required for the operation of the reception data demodulator 120, and the reception data processor 140 converts the demodulated data into original IP data and outputs the original IP data to the Internet network.

NCR packet inserter 250 is a configuration that was not used in a central station for a conventional satellite broadcasting service or a satellite bidirectional communication service, and receives a stable 27 MHz clock from the reference clock generator 300 to operate its own counter. To generate an NCR value of 42 bits, which is then generated as an MPEG2-TS packet according to the MPEG2 standard. The MPEG2-TS packet including the NCR is inserted into the MPEG2-TS stream output from the MPEG2-TS remultiplexer 240. In addition, the NCR packet inserter 250 provides the reference timing of the reverse link to the reception timing generator 130 of the central station receiver 100 to ensure stable demodulation.

3 is a detailed block diagram of an NCR packet inserter. The NCR packet inserter 250 includes an input data storage block 251, a PCR correction block 252, an NCR correction block 253, an MPEG2-TS start signal generation block 254, and an NCR insertion MPEG2-TS generation block 255. ), A remultiplexing block 256 and a timing signal generating block 257. The input data storage block 251 stores the MPEG2 stream output from the MPEG2-TS remultiplexer 240, and the PCR correction block 252 filters the MPEG2-TS packet in which the PCR value is inserted in the MPEG2 stream to insert the NCR packet. The PCR value is corrected by reflecting the delay factor generated inside the instrument 250.

The NCR counter block 253 generates an NCR value based on the 27 MHz clock input from the reference clock generator 300. The MPEG2-TS start signal generation block 254 generates a start time of the MPEG2-TS packet, notifies the extraction time of the NCR value, and transmits a reference time to the operation of the remultiplexing block 256. The NCR embedded MPEG2-TS generation block 255 generates an MPEG2-TS packet based on the NCR value transferred from the NCR counter block 253. The remultiplexing block 256 inserts the MPEG2-TS packet including the NCR into the MPEG2 stream whose PCR value is corrected through the PCR correction block 252. The timing signal generation block 257 generates and transmits a reference timing to the reception timing generator 130 of the central station receiver 100.

As described above, the NCR packet inserter 250 corrects and transmits an internal delay element in accordance with the requirements of the MPEG2 standard for the PCR value of the input MPEG2 stream. In addition, the NCR packet inserter 250 directly generates or outputs an NCR value required for the reverse link synchronizer and outputs it to the RF transceiver, thereby correcting or correcting the NCR value while the NCR value is transmitted through the forward link. To the terminal station without Therefore, the terminal station can perform stable and accurate clock and timing synchronization using the received NCR value.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described. In particular, those skilled in the art will appreciate that the linear gain control technique according to the present invention can be applied as it is to the linear power control technique.

The present invention provides an effect that the clock and timing synchronization for the reverse link is stable by transmitting the NCR value required for the reverse link network to the terminal station without being modified during transmission on the forward link.

Claims (6)

In the central station system of the two-way satellite communication system, A central station transmitter for transmitting broadcast and communication data through a forward link according to Digital Video Broadcasting (DVB) -S standard; And Including a central station receiving unit for data processing signal input from the terminal station to the reverse link in accordance with DVB-RCS (Return Channel Satellite) standard, The central station transmitter unit multiplexes the broadcast and communication data into one MPEG2 stream, and then generates and inserts an NCR (Network CLock Reference) used for timing synchronization with a clock of the reverse link. Central station system. The method of claim 1, The central station transmitting unit An MPEG-2 converter for converting the communication data in an IP form input from an external Internet into an MPEG-2 stream; An MPEG-2 encoder for converting the broadcast data into an MPEG-2 stream; A PSI / SI table generator for generating a PSI / SI (Program Specific Information / System Information) table for communication on the reverse link; An MPEG2-TS remultiplexer for outputting the output of the MPEG-2 converter and the MPEG-2 encoder into one MPEG-2 stream; An NCR packet inserter for generating an MPEG2-TS packet including the NCR and inserting the MPEG2-TS packet into an output of the MPEG2-TS remultiplexer; A modulator for RF modulating the output of the NCR packet inserter; And An RF transmitter for transmitting an output of the modulator to an antenna Central station system. The method of claim 1, A reference clock generator for providing a 27 MHz clock for generating the NCR to the central station transmitter; Central station system. The method of claim 1, The NCR is 42 bits Central station system. The method of claim 2, The central station receiving unit An RF receiver for receiving a signal output from the terminal station; A received data demodulator for demodulating the output signal of the RF receiver; A reception timing generator for generating a reference timing required for the operation of the received data demodulator; And A received data processor for converting the demodulated data by the received data demodulator into IP data and outputting the converted data to the Internet network Central station system. The method of claim 5, The NCR packet inserter An input data storage block for temporarily storing an MPEG2 stream output from the MPEG2-TS remultiplexer; A PCR correction block for filtering the MPEG2-TS packet into which the PCR value is inserted in the temporarily stored MPEG2 stream and correcting the PCR value by reflecting a delay factor generated in the NCR packet inserter; An NCR counter block for generating an NCR value based on a 27 MHz clock input from a reference clock generator; An MPEG2-TS start signal generation block for generating a start time of an MPEG2-TS packet to indicate an extraction time point of the NCR value; An MPEG2-TS generation block configured to generate an MPEG2-TS packet based on the NCR value delivered from the NCR counter block; A remultiplexing block for inserting an MPEG2-TS packet generated by the MPEG2-TS generation block into an MPEG2 stream whose PCR value is corrected through the PCR correction block; And A timing signal generation block configured to generate and transmit a reference timing to the reception timing generator, The MPEG2-TS start signal generation block transmits a reference time to the operation of the remultiplexing block. Central station system.

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