KR20000047245A - Generating method of transmission timing synchronous signals in set top box of multimedia satellite communication system - Google Patents

Abstract

PURPOSE: A generating method of transmission timing synchronous signals in set top box of multimedia satellite communication system is provided to easily match the data transmission time between respective set top box. CONSTITUTION: A generating method of transmission timing synchronous signals in set top box of multimedia satellite communication system comprises: an offset calculation step calculating offsets on the basis of PCR/OPCR data received from a central station; an offset comparison step comparing the offsets calculated in the offset calculation step with a previous offset; an offset storing step updating the calculated offsets if a current offset and the previous offset are different; a transmission timing synchronous value generating step generating a transmission timing synchronous value on the basis of the offset updated in the offset storing step; and a transmission timing generating step generating a transmission timing on the basis of the value generated in the transmission timing synchronous value generating step.

Description

A method of generating transmission timing synchronous signals in a set top box of a multimedia satellite communication system.

The present invention relates to a multimedia satellite communication system, and more particularly, to a multimedia satellite communication system capable of providing a synchronizer between set-top boxes by generating a transmission timing synchronization signal from a set top box to a central station based on a PCR / OPCR value received from a central station. The present invention relates to a method for generating a transmission timing synchronous signal in a set-top box.

At present, as the wireless communication technology is rapidly developed, a wireless communication system that enables a subscriber to execute voice and data communication with a counterpart through a wireless network rather than a conventional wired network is rapidly spreading. Accordingly, mobile communication systems or personal communication systems that allow communication subscribers to carry out communication while moving are widely used. Also, communication devices of general households are connected to existing PSTN (Wireless Local Loop) or satellite communication systems. Public switched telephone network networks are also becoming more common.

In particular, in the case of a satellite communication system, there is an advantage in that it is possible to enable ultra-long distance communication such as communication between countries without providing a separate communication line. Therefore, a satellite broadcasting system that can directly receive satellite broadcasting in a home by using a set top box, etc. by utilizing the advantages of the satellite communication system has already been developed and spread, and mobile communication devices or personal communication There is also a rapid research on a system for executing satellite communication through a device.

On the other hand, with the recent establishment of a communication method based on TCP / IP (Transport control protocol / Internet protocol), a global Internet network has been established. In satellite communication systems, the Internet service can be provided to the subscribers. The research on the multimedia satellite communication system that has been made possible is in earnest.

Accordingly, the present applicant has developed and applied for a multimedia satellite communication system that allows a subscriber to access the Internet using satellite communication and also can receive a large amount of image data at high speed through such an Internet connection.

1 is a system configuration diagram showing a system configuration of a multimedia satellite communication system filed by the present applicant.

In FIG. 1, reference numeral 1 denotes a central station connected to the Internet, which provides various multimedia services to terminal stations, and performs overall network operation management and control functions. In addition, reference numeral 3 is a terminal station antenna, 4 is a set top box as a terminal station providing multimedia services to a general subscriber, 5 is a personal computer as a terminal for a user to perform multimedia communication, and 6 is a satellite. to be.

In the above system, in the case of a forward link transmitted from the central station 1 to the set-top box 4, a large amount of messages can be transmitted through the TDMA method, and the set-top box 4 to the central station 1 are transmitted. In the case of a return link to be transmitted, a synchronous code division multiple access (CDMA) scheme is used to accommodate a plurality of subscribers so that multimedia data can be transmitted to a large number of subscribers at high speed.

However, in the above-described multimedia satellite communication system, since the return link from the set top box 4 to the central station 1 is synchronous, in particular, the synchronization between the set top boxes 4 is very important. In this case, it is necessary to match the transmission time with other set-top boxes 4 in transmitting predetermined data to the central station 1.

Accordingly, an object of the present invention is to provide a transmission timing synchronous signal generation method in a set-top box of a multimedia satellite communication system that enables easy matching of data transmission time between set-top boxes. have.

1 is a system configuration diagram showing a system configuration of a general multimedia satellite communication system.

Fig. 2 is a block diagram showing the construction of the transmission data processing apparatus of the central station according to the embodiment of the present invention.

Figure 3 is a block diagram showing the configuration of a set-top box 4 according to an embodiment of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

41: RF device, 42: tuner,

43: demodulator, 44: demultiplexer,

45: network interface card (NIC), 46: transmission frame generation unit,

47: CDMA channel transmitter, 48: modulator,

49: IF generator, 50: transmission timing generator,

51: data memory, 52: offset storage,

53: processor.

A method for generating a transmission timing synchronization signal in a set top box of a multimedia satellite communication system according to the present invention for realizing the above object is a multimedia satellite communication system adapted to synchronize data transmission between set top boxes based on PCR / OPCR data received from a central station. An offset value calculating step of calculating an offset value based on PCR / OPCR data received from a central station, and an offset comparison step of comparing whether the offset value calculated in the offset value calculation step is equal to a previous offset value. As a result of the comparison in the offset comparison step, if it is determined that the current offset value and the previous offset value are different, the transmission timing synchronization value is based on the offset storage step of updating and storing the calculated offset value and the offset value updated in the offset storage step. Generating a transmission timing synchronization step of generating a transmission timing synchronization And a transmission timing generation step of controlling transmission timing to be generated based on the transmission timing synchronization generation value generated in the step.

That is, according to the above, when the PCR / OPCR value is present in the TS packet received from the central station, the offset value of the PCR / OPCR is calculated, and the transmission timing is only when the current calculated offset value is different from the previous offset value. By performing the correction operation, it is possible not only to reduce the load caused by the operation operation performed when the transmission timing correction is unnecessary, but also to reduce the time required for the set-top box synchronizer.

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

2 is a block diagram showing the configuration of the transmission data processing apparatus of the central station according to the embodiment of the present invention.

In the drawing, reference numeral 11 denotes an Ethernet interface for generating and outputting an IP packet based on an Ethernet frame input from an IP switch (not shown), and 12 denotes sequentially an IP packet data output through the Ethernet interface 11. The input buffer 13 to be stored determines the type of input data based on the header of the IP packet data stored in the input buffer 12, and the PS packet generation unit 15 to be described later based on the determined result. And an IP packet controller which controls the packet generation of the TS packet generation unit 16 and controls the transmission data processing apparatus based on the control data applied from the Ethernet interface 11.

In the drawing, reference numeral 14 denotes a subscriber information storage unit for storing PIDs allocated to each set top box 4, which maps the control PID and the traffic PID corresponding to the IP address of each set top box 4. To save it.

In the drawing, reference numeral 15 is a PS packet generation unit for generating a PS packet (Private Section Packet) based on data input from the IP packet controller 13, and 16 is input from this PS packet generation unit 15. MPEG-2 TS packet is generated based on PS packet data and PID (control PID, traffic PID or information service PID) applied from the IP packet controller 16 and the traffic data stored in the input buffer 12. TS packet generation unit for outputting In addition, the TS packet generation unit 16 counts the number of TS packets transmitted to the set-top box 4, and when the count value reaches a predetermined value, for example, 100, the PCR applied from the PCR generator 18 to be described later. The program clock reference value is read and sent to the set top box 4. When the PCR value is transmitted, the TS packet is transmitted through the information service PID so that all set top boxes 4 can receive the PCR value.

In the drawing, reference numeral 17 denotes a frequency generator for generating a frequency signal of 27 MHz, for example, and 18 denotes a PCR generator for counting the frequency signal output from the frequency generator 17 and outputting the count value data.

That is, in the above-described configuration, the TS packet generation unit 16 generates TS packets continuously based on the PS packets input from the PS packet generation unit 15, and continuously outputs the TS packets. In this case, the PCR data applied from the PCR generator 18 is added to the predetermined field of the TS packet as PCR data and OPCR data for transmission.

Subsequently, when the TS packet is output from the TS packet generator 16 and input to the multiplexer 20, the multiplexer 20 transmits the TS packet input from the TS packet generator 16 to the broadcast signal. The delay time is counted to correct the PCR value based on the count value. That is, when the delay time of the TS packet output from the TS packet generation unit 16 due to the insertion of the broadcast signal is "X", the PCR value of the TS packet including the PCR and OPCR data is "PCR value + X." Will be registered and printed.

Therefore, at this time, each set-top box 4 receives a TS packet including the corrected PCR value.

On the other hand, Figure 3 is a block diagram showing the configuration of a set-top box 4 according to an embodiment of the present invention.

In the drawing, reference numeral 41 denotes a frequency down-conversion and low-noise amplification of the high frequency signal transmitted from the central station 1, and a frequency up-conversion of the intermediate frequency signal output from the intermediate frequency generator 49, which will be described later. 42 is a tuner for frequency converting a high frequency signal output from the RF device 41 to output an intermediate frequency, and 43 is a QPSK for an intermediate frequency signal output from the tuner 42, that is, a central station 1. A demodulator demodulates a modulated signal.

In the drawing, reference numeral 44 denotes a demultiplexer for extracting a TS packet corresponding to the set-top box from the TS packet data output from the demodulator 44, which includes a register for storing PID information therein. The PID applied from the processor 53 to be described later is stored in the register. The TS packet including the PID stored in the register is extracted from the TS packets applied from the demodulator 43 and applied to the processor 53.

In the drawing, reference numeral 45 denotes a network interface card (NIC) that executes an interface with the personal computer 5, which converts Ethernet packets applied from the processor 53 into IP packets to convert the personal computer 5 into an IP packet. In addition to the above), the IP packet applied by the personal computer 5 is converted into an Ethernet packet and applied to the processor 53.

In the drawing, reference numeral 46 denotes a serial transmission data frame based on the transmission data applied in parallel from the processor 53, and the transmission timing applied by the transmission timing generation unit 50 to be described later. A transmission frame generation unit sequentially outputs the transmission data frame in accordance with a signal. 47 is a CDMA modulation by mixing a CDMA code applied from the processor 53 with respect to transmission data output from the transmission frame generation unit 46. A CDMA channel transmitter for executing the data, 48 a modulator for modulating and outputting the data output from the CDMA channel transmitter 47, for example, QPSK, and 49 a modulator 48 based on frequency data applied from the processor 53. Is an intermediate frequency generating unit for converting the modulated signal output from the predetermined frequency signal into a predetermined intermediate frequency signal.

In the drawing, reference numeral 50 denotes a transmission timing generator for generating a transmission timing signal for the transmission frame generator 46 under the control of the processor 50, and 51 denotes various data, in particular, from the central station 1. It is a data memory that stores the control PID, the traffic PID and the service information PID for receiving the service information (Service Information).

In addition, reference numeral 52 is an offset storage unit for storing the offset value calculated by arithmetic processing, that is, PCR-OPCR received from the central station, 53 is a processor for controlling the overall operation of the set-top box (4), This converts the TS packet for the personal computer 5 received from the demultiplexer 44 into an IP packet and outputs it to the network interface card 45, and from the personal computer 5 input from the network interface card 45. This data is outputted to the transmission frame generator 46 and transmitted to the central station 1.

In particular, the processor 53 determines whether PCR and OPCR are added to the TS packet currently received by reading the header of the TS packet transmitted from the central station 1, wherein the PCR and the OPCR are added. If it is determined, the synchronous timing signal is generated and controlled by performing a predetermined calculation process based on the PCR and OPCR values.

That is, the processor 53 reads the PCR value and the OPCR value from the TS packet, performs a computation process of the PCR-OPCR, calculates the offset value, and stores the currently calculated offset value in the offset storage unit 52. If it is the same as the previous offset value, the transmission timing signal is controlled to be the same as the previous timing signal. If the current offset value and the previous offset value are different, the offset value of the offset storage unit 52 is currently calculated. In addition, the number of TS packets of the inserted broadcast signal is calculated by converting and storing the current offset value by the time corresponding to the period of one TS packet. Then, based on the result, the transmission timing generation unit 50 is controlled to set the data transmission timing transmitted to the central station 1.

Therefore, when the PCR / OPCR value exists in the TS packet received from the central station, the offset value of the PCR / OPCR is calculated to perform the transmission timing correction operation only when the currently calculated offset value is different from the previous offset value. As a result, not only the load caused by the operation operation performed when the transmission timing correction is unnecessary, but also the time required for this can be reduced.

On the other hand, the present invention is not limited to the above embodiments and can be modified in various ways without departing from the technical spirit of the present invention.

As described above, according to the present invention, when the PCR / OPCR value is present in the TS packet received from the central station, the offset value of the PCR / OPCR is calculated, and only when the currently calculated offset value is different from the previous offset value. By performing the transmission timing correction operation, it is possible not only to reduce the load caused by the operation operation performed when the transmission timing correction is unnecessary, but also to reduce the time required, thereby performing the synchronization between the set-top boxes.

Claims (1)

In a multimedia satellite communication system adapted to synchronize data transmission between set-top boxes based on PCR / OPCR data received from a central station, An offset value calculation step of calculating an offset value based on PCR / OPCR data received from a central station; An offset comparison step of comparing whether the offset value calculated in the offset value calculation step is equal to the previous offset value, If the comparison result in the offset comparison step, it is determined that the current offset value and the previous offset value is different, the offset storage step of updating and storing the calculated offset value, A transmission timing synchronization generating step of generating a transmission timing synchronization value based on the offset value updated in the offset storing step; And a transmission timing generation step of controlling the transmission timing to be generated based on the transmission timing synchronization generation value generated in the transmission timing synchronization generation step.