KR19980023751A - How to Choose an Initial Repeater for a Digital DBS Receiver - Google Patents

Abstract

The present invention relates to a method for selecting an initial repeater for a digital DBS receiver, comprising: a repeater selecting step (S1) when the viewer applies power for the first time after purchasing a digital DBS receiver; Transport stream receiving step S2; Determining whether the received transport stream is a normal information stream or noise (S3); If the received transport stream is a normal information stream, a valid PID setting step (S4) after detecting a program related table and a program map table; Determining whether there is actually a service stream input to the set valid PID, and ending all initial repeater selection processes according to the determination result (S5); Determining whether the time required from the present time after determining whether there is actually a service stream input to the set valid PID exceeds the reference time (S6); And after the receiver selects another repeater from the detected program related table and the program map table, step S7 to the transport stream receiving step S2, according to the present invention. When power is applied for the first time after purchasing a receiver, there is an effect that a valid initial repeater that relays a valid service stream can be selected by the receiver itself.

Description

A method of choosing an initial transponder in a digital direct broadcasting service receiver

The present invention relates to a method for selecting an initial repeater for a digital direct satellite service (DBS) receiver. In particular, when a power is applied for the first time after purchasing a digital DBS receiver, the receiver relays actual service information. An initial repeater selection method of a digital DBS receiver to select a valid initial repeater.

In general, DBS refers to a broadcast method of retransmitting a broadcast signal through a satellite repeater for the purpose of receiving it directly in a general home. With recent developments, DBS can be directly received by installing a small antenna and a digital DBS receiver. have.

The DBS is not capable of local broadcasting, has the disadvantage of requiring a large investment due to high reliability requirements and the occurrence of radio wave menstruation problems, while enabling a uniform, high quality broadcasting in a large area with a small output compared to terrestrial broadcasting. Since there is an advantage of reducing reception disturbance and ghosting, Korea has begun to provide a pilot broadcast on July 1, 1996 using Mugunghwa satellite.

Meanwhile, FIG. 1 is a block diagram showing the overall configuration of a general digital DBS system. The general digital DBS system shown in FIG. 1 includes a service provider side 1, a satellite repeater 2 and a subscriber side 3; The service provider side 1 and the subscriber side 3 are connected through a public switched telephone network (PSTN).

The service provider side 1 converts, compresses, and multiplexes a television signal, which is composed of transport stream packets, and then channel-encoded and transmitted to a satellite at a frequency of 14 GHz. It consists of a resource and subscriber management system (hereinafter referred to as RSMS) that controls subscriber access to the network and collects usage information of the subscriber. The transmitter 11 includes a moving picture expert group-2 (MPEG-2) encoder 11-1, a forward error correction (FEC) encoder 11-2, and a quaternary phase shift keying (QPSK) modulator 11-3. And a transmit antenna 11-4.

The satellite repeater 2 receives the transport stream from the transmitter 11 and amplifies and retransmits it at the 12 GHz frequency.

The subscriber side 3 is composed of a receiving antenna 31, an LNB (Low Noise Block-Down Converter (hereinafter referred to as LNB) 32), a digital DBS receiver 33 (Integrated Receiver Decoder) and a television 34. The digital DBS receiver 33 is composed of a tuner 33-1, a QPSK demodulator 33-2, an FEC decoder 33-3, and an MPEG-2 decoder 33-4.

The operation of the digital DBS system configured as described above is as follows.

The MPEG-2 encoder 11-1 of the transmitter 11 converts video, audio, and data signals into digital signals according to the MPEG-2 standard, and configures them into a packet stream after compression. Create a stream The multiple digital television signal streams are then multiplexed into transport stream packets and sent to the FEC encoder 11-2. The FEC encoder 11-2 performs channel encoding to correct an error generated during transmission. The QPSK modulator 11-3 performs a modulation process to transmit the channel coded signal to a satellite. The modulated signal is converted to an ku-band (14 GHz) in an up-converter (not shown), and then sufficiently amplified in a high power amplifier (HPA) to transmit satellites through the transmit antenna 11-4. Is fired into.

The satellite consists of one or more satellite repeaters 2, which receive and amplify uplink signals of 14 GHz from the base station, convert them to 12 GHz and retransmit them back to the ground. The satellite repeater may be classified as follows according to the signal processing method and the frequency conversion frequency, respectively. The satellite repeater is a general repeater satellite repeater that simply converts a received signal into a downlink frequency and transmits the signal according to a signal processing method, and a reproduced satellite that detects the received signal, converts the signal into a baseband, processes it, and modulates it again. It is divided into a repeater. In addition, the satellite repeater is a single frequency conversion type satellite repeater that directly converts the received frequency to the downlink frequency according to the frequency conversion frequency, and converts the received frequency into an intermediate frequency and then amplifies and converts the downlink frequency It is divided into dual frequency conversion type satellite repeater.

The transport stream signal of the 12 GHz band relayed from the satellite repeater 2 is received by the reception antenna 31. The LNB 32 drops the received 12 GHz transport stream signal into an intermediate frequency signal of 1 GHz band, removes noise, and sends the noise to the tuner 33-1 through a cable. The signal selected by the tuner 33-1 is demodulated by the QPSK demodulator 33-2, and the demodulated signal is recovered by the FEC decoder 33-3. The signal from which the transmission error is restored is decoded into a video, audio and data signal by the MPEG-2 decoder 33-4. The decoded signal is displayed to the viewer via the television 34.

In this case, the digital DBS receiver synchronizes the carrier frequency of one repeater with the carrier frequency of the receiver in a manufacturing step, and has the previously tuned carrier frequency when the viewer applies power for the first time after purchasing the receiver. It receives the transport stream relayed from the repeater.

However, since not all repeaters relay valid transport streams including service information actually provided, it is concluded that not all repeaters are valid relays which relay valid transport streams.

As a result, when the repeater first selected by the digital DBS receiver is not a valid repeater, the digital DBS receiver itself must select a valid repeater to provide actual service information to the viewer.

Accordingly, the present invention has been made in view of the above-mentioned point, and when the power is applied for the first time after purchasing the digital DBS receiver, the receiver initially selects a valid initial repeater that relays actual service information. The purpose is to provide a repeater selection method.

In order to achieve the above object, in the initial repeater selection method of the digital DBS receiver according to the present invention, the carrier frequency of one repeater and the carrier frequency of the digital DBS receiver are synchronized at the manufacturing stage, and the viewer purchases the receiver. In the initial relay selection method in a digital DBS receiver receiving the transport stream relayed from the repeater having a pre-tuned carrier frequency when the power is applied for the first time after,

A first step of the digital DBS receiver selecting a repeater having a carrier frequency equal to a preset carrier frequency;

A second step of receiving a transport stream from the selected repeater;

Determining whether the received transport stream is a normal service information stream or noise;

As a result of the determination in the third step, when the received transport stream is a normal service information stream, a program related table and a program map table are detected among the received transport streams, and the detected program related table and program map table are detected. Setting a valid PID in the fourth step;

A fifth step of determining whether there is a service stream input in the set valid PID, and then, when there is a service stream input as a result of the determination, terminating all initial repeater selection processes;

Determining whether the required time from the fifth step to the present time exceeds the reference time, and if the required time does not exceed the reference time as a result of the determination, moving to the fifth step;

If the result of the determination in the third step is that the received transport stream is noise other than the normal service information stream, or as the result of the determination in the sixth step, the required time exceeds the reference time, the receiver After the other repeater is selected from the program related table and the program map table detected in the fourth step, it is characterized by consisting of a seventh step going to the second step.

According to the present invention as described above, when a viewer applies power for the first time after purchasing a digital DBS receiver, the receiver itself can select a valid initial repeater that relays a valid service stream.

1 is a block diagram schematically illustrating a general digital DBS system;

2 is a block diagram showing a digital DBS receiver to be applied to the present invention;

3 is a diagram illustrating a structure of a channel received at a digital DBS receiver;

4 shows the structure of a program map table on a transport stream;

5 is a flowchart illustrating a method of selecting an initial repeater of a digital DBS receiver according to the present invention.

Explanation of symbols on the main parts of the drawings

20: Digital DBS Receiver 21: Tuner

22: A / D Converter 23: QPSK Demodulator

24: Channel Decoder 25: Transport Stream Demultiplexer

26: decryption unit 27: audio / video decoder

28: video memory 29: video encoder

30: D / A Converter 31: RF Modulator

32: remote control 33: microcomputer

34: modem 35: smart card

36: memory 40: resource and subscriber management system

60: public network

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the overall configuration of the digital DBS receiver applied to the present invention will be described as follows to help understanding of the present invention.

FIG. 2 is a block diagram illustrating a digital DBS receiver according to the present invention. The digital DBS receiver illustrated in FIG. 2 includes a tuner 21, an A / D converter 22, a QPSK demodulator 23, and a channel decoder ( 24, transport stream demultiplexer 25, decryptor 26, audio / video decoder 27, video memory 28, video encoder 29, D / A converter 30, radio frequency (Radio) frequency: hereinafter referred to as RF) modulator 31, remote control 32, microcomputer 33, modem 34, smart card 35, memory 36, RSMS (40) through the public network (60) )

The tuner 21 tunes a transport stream of a channel desired by the viewer from a satellite repeater (not shown) received at a receiving antenna (not shown).

The A / D converter 22 converts the tuned analog signal into a digital signal.

The QPSK demodulator 23 receives the A / D converted QPSK modulated signal and performs QPSK demodulation.

The channel decoder 24 receives the QPSK demodulated channel coded signal and performs channel decoding.

The transport stream demultiplexer 25 receives the channel decoded multiplexed stream and demultiplexes the audio / video data of a channel desired by the viewer.

The decryption unit 26 decrypts the data so that the subscriber can view the encrypted signal.

The audio / video decoder 27 receives the extracted audio / video data and performs decoding.

The video memory 28 is a data storage space required for the video decoding process.

The video encoder 29 encodes the decoded video data into an analog signal to receive and display the decoded video data.

There are two methods of encoding and outputting a video signal by the video encoder 29 as follows. One is outputting the encoded video signal to a display device (not shown) in the form of a base band video signal, and the other is outputting to the RF modulator 30.

The D / A converter 30 receives the decoded audio data, which is a digital signal, converts the decoded audio data into an analog signal and outputs the same in two ways. One is output to the display device in the form of an audio-right / left stereo, and the other is output to the high frequency modulator 31.

The RF modulator 31 modulates the audio / video signal and outputs an RF signal.

The microcomputer 33 controls the entire system according to the received signal from the remote controller 32, and the modem 34 is for communication with the RSMS 40 and the de-mula DBS receiver 20.

The smart card 35 grants the right to decrypt the encrypted data so that only the subscriber with the right to receive the data can receive the data, and stores and provides the information on the paid viewing.

The memory 36 stores the program of the microcomputer 33. The RSMS 40 controls subscriber access to the program and collects usage information of the subscriber. The public network 60 between the RSMS and the receiver It is used for exchanging information about paid viewing.

On the other hand, the digital DBS receiver receives a plurality of channels multiplexed from the satellite repeater, wherein one channel is composed of several transport streams, and the one transport stream is a program service reference stream (ES). (Hereinafter referred to as a stream), a data service stream and an RSMS data stream. Here, according to the specification of the Mugunghwa satellite (SPEC), the program service stream and the data service stream cannot coexist in the same channel. In addition, the RSMS data stream is always present in all channels because the RSMS data stream contains the information necessary for selecting an initial valid relay. Meanwhile, the program service stream is composed of a video signal and an audio signal including subtitle data.

The RSMS data stream is composed of service information (SI) and an RSMS message. The service information (SI) is used to assist in tuning a selected carrier with program specific information (PSI) used for demultiplexing the received multiplexed transport stream and additional information for program guidance (Program Guide Messages). It is also called). The RSMS data stream consists of an Entitlement Management Message (EMM), an Entitlement Control Message (ECM), and a Receiver Command Message (RCM).

The program designation information (PSI) is composed of a Program Association Table (PAT), a Conditional Access Table (CAT), and a Program Map Table (PMT).

The additional information includes a network information table (NIT), a service description table (SDT), an event information table (EIT), and a time date table (TDT). do.

The following Table 1 shows the configuration of the channel input to the digital DBS receiver as described above.

Channel composition Channel 1 Transport stream Program Service Stream RSMS data stream Video signal containing closed caption data Audio signal SI RSMS message PSI Additional Information PAT CAT PMT NIT SDT EIT TDT ECM EMM RCM Channel 2 Transport stream Data service stream RSMS data stream - SI RSMS message PSI Additional Information PAT CAT PMT NIT SDT EIT TDT ECM EMM RCM

Here, the program related table PAT provides packet identifier values of program map table sections having a program definition for a service stream (a program service stream or a data service stream). And PID values of a transport packet carrying program guide message and receiver command message (RCM) components of the RSMS data stream. Table 2 below shows a program related table (PAT) according to the specification of the Mugunghwa satellite (SPEC).

Program Related Tables (PAT) program 0 PIN (PMM) Transport packet carrying PMM member of RSMS data stream program 1 PID (RCM) Transport packet carrying RCM member of RSMS data stream ? / CEL> ? / CEL> program i PID (PMT) Transport packet carrying PMT member of RSMS data stream ? / CEL> ? / CEL>

The conditional access table (CAT) provides the PID of the transport packet to carry the entitlement management message (EMM) of the RSMS data stream.

Table 3 below shows a condition access table (CAT) according to the specification of the Rose of Sharon.

Conditional Access Table (CAT) CA system 1section 0x00 System Description CA system id PID (EMM) Transport packet carrying PMM member of RSMS data stream ? / CEL> CA system nsection 0x00

The program map table PMT defines a program by mapping a program number to streams. That is, the program map table (PMT) includes a number of program numbers. The number of stream PIDs per program can be two or more, and the PID for a given program number is a program related table (PAT) associated with the corresponding program number. Can be extracted from Here, the program number means a unique number of each broadcasting station program. For example, when the program number is 1000, it means that the program is provided by KBS-1. When the program number is 1001, it is provided by KBS-2. If the program number is 1002, it means that the program is provided by MBC.

Table 4 shows a program map table (PMT) according to the specification of the Rose of Sharon.

Program Map Table (PMT) INDEX PG # (program number) VPID (Video PID) APID (Aideo PID) 0 0 × × One One × × 2 1000 101 102 3 1001 × × 4 × × × 5 1002 501 502 6 a - - :::: N-1 i - -

FIG. 3 is a diagram illustrating the structure of a channel received by the digital DBS receiver. One channel shown in FIG. 3 is composed of several transport streams, and one transport stream packet is 4 bytes. It consists of a header (100), an adaptation field (200), and a payload (300) of 184 bytes.

The header 100 is composed of an 8-bit sync signal (sync byte 110: the synchronization signal of the green light satellite is defined as 0010 1111), a 1-bit transport error indicator (120), and a 1-bit pay signal. Payload unit start indicator (130: payload unit start indicator), 1 bit transmission priority (140: transport priority), 13 bits PID (150), 2 bits of transport scrambling control (160: transport scrambling control), 2 bits Is an adaptation field control (170) and a 4-bit continuity counter (180).

The adaptation field 200 includes an adaptation field length 210 of 8 bits, a discontinuity indicator of 1 bit (220), a random access indicator of 1 bit (230), and a bit of 1 bit. It consists of an elementary stream priority (240), a 5 bits flag (250 flags), optional fields (260) and stuffing bytes (270).

FIG. 4 is a diagram illustrating a program map table PMT on a transport stream according to the structure of the transport stream packet shown in FIG. 3 and with reference to the program map table PMT of Table 4. FIG.

On the other hand, when the viewer applies power for the first time after purchasing the digital DBS receiver, the first thing the digital DBS receiver needs to do is to select a valid initial satellite repeater. Selecting a valid initial repeater means selecting a repeater that relays a transport stream containing a service information stream to be provided to an actual viewer.

FIG. 5 is a flowchart illustrating a method for selecting an initial repeater for a digital DBS receiver according to the present invention. The initial repeater selection method illustrated in FIG. 5 is as follows.

First, the digital DBS receiver synchronizes the carrier frequency of one repeater with the carrier frequency of the receiver in a manufacturing step, and has the previously tuned carrier frequency when the viewer applies power for the first time after purchasing the receiver. It receives the transport stream relayed from the repeater. For example, in the case of Mugunghwa satellite, since one satellite has six satellite repeaters, the carrier frequency of one of the six repeaters is synchronized with the carrier frequency of the receiver. In a first step S1, the digital DBS receiver selects a repeater having a carrier frequency equal to a preset carrier frequency.

In a second step S2, a transport stream from the selected repeater is received.

In a third step S3, it is determined whether the received transport stream is a normal service information stream or noise.

That is, in step 3-1 (S3-1), since the received transport stream is a QPSK modulated signal at the transmitter, it is determined whether there is a QPSK carrier that can demodulate it.

In step 3-2 (S3-2), if the QPSK carrier exists as a result of the determination in step 3-1 (S3-1), the bit error rate of the received transport stream is checked. Here, the bit error rate indicates the error rate in the transmission path in units of bits, and is expressed as the ratio of the number of error bits in the total number of received reproduction bits.

In step 3-3, it is determined whether the checked bit error rate exceeds the reference bit error rate. When the checked bit error rate exceeds the reference bit error rate, it means that the transport stream relayed from the selected repeater is noise, not an actual service information stream. After all, since the selection of the repeater is wrong, it is necessary to start searching for another repeater without having to determine whether the selected repeater inputs a service stream.

In step 3-4 (S3-4), if the checked bit error rate does not exceed the reference bit error rate as a result of the determination in step 3-3 (S3-3), synchronization of the received transport stream It is determined whether the signal (sync byte) is a prescribed synchronization signal (synchronization signal according to the standard of Mugunghwa satellite). When the sync signal is a prescribed sync signal, it means that the actual service information stream can be received in accordance with the received sync.

When the synchronization signal of the received transport stream is 0010 1111 in the fourth step S4 as a result of the determination in the third to fourth steps S3-4, a program related table (PAT) of the received transport streams is used. ) And a program map table (PMT), and set a valid PID in the detected program related table (PAT) and program map table (PMT). Here, the valid PID may be a PID even if a program number exists, as shown in Table 4 above. If a program number exists and a PID within the program number exists, the PID is referred to as a valid PID. (E.g. VPID = 501 at INDEX = 5, PG # = 1002, APID = 502)

That is, an RSMS data stream is detected in the received transport stream in step 4-1 (S4-1).

In step 4-2, the program related table PAT and the program map table PMT are detected in the detected RSMS data stream. The reason for detecting the program related table (PAT) and the program map table (PMT) when selecting an initial channel is basically that the same program related table (PAT) and program map table (PMT) are repeatedly loaded on a normal satellite repeater. This is because it is basic information used for moving to another satellite repeater and other channels.

A valid PID is set in the detected program related table PAT and program map table PMT in step S4-3.

After determining whether there is a service stream input in the set valid PID in the fifth step (S5), if there is a service stream input as a result of the determination, all initial repeater selection processes are terminated. That is, the repeater selected by the receiver in the first step S1 is selected as a valid initial repeater.

After determining whether the required time from the fifth step S5 to the present time exceeds the reference time in the sixth step S6, if the required time does not exceed the reference time as a result of the determination, Go to step 5.

As a result of the determination in the third step (S3-1) in the seventh step (S7), when the QPSK carrier does not exist, and as a result of the determination in the third step (S3-3), If the checked bit error rate exceeds the reference bit error rate, and also as a result of the determination in step 3-4 (S3-4), the synchronization signal of the received transport stream is not a specified synchronization signal, that is, not 0010 1111. In the case where the determination time in the sixth step S6 indicates that the required time exceeds the reference time, the digital DBS receiver detects the program related table PAT in the fourth step S4-2. After selecting the other repeater from the program map table (PMT), and goes to the second step (S20).

That is, all the repeaters in the program map table PMT are searched until the digital DBS receiver selects a valid repeater.

Once this initial repeater selection is made, the repeater at the time the viewer is powered off is stored in the non-volatile memory of the digital DBS receiver and there is no need to repeat the initial repeater selection process again.

When a viewer applies power for the first time after purchasing a digital DBS receiver, there is an effect that the receiver itself can select a valid initial relay to relay a valid service stream.

Claims (3)

In the manufacturing step, the carrier frequency of one repeater is synchronized with the carrier frequency of the receiver, and when the viewer applies power for the first time after purchasing the receiver, the transport stream relayed from the repeater having the previously tuned carrier frequency In the initial repeater selection method in the digital DBS receiver receiving a, A first step (S1) in which the digital DBS receiver selects a repeater having a carrier frequency equal to a preset carrier frequency; A second step (S2) of receiving a transport stream from the selected repeater; A third step (S3) of determining whether the received transport stream is a normal service information stream or noise; As a result of the determination in the third step S3, when the received transport stream is a normal service information stream, a program map table and a program related table are detected from the received transport stream, and the detected program related table is detected. A fourth step S4 of setting a valid PID in the program map table; A fifth step (S5) of determining whether there is a service stream input in the set valid PID, and when the service stream is input as a result of the determination, all initial repeater selection processes; After determining whether the required time from the fifth step (S5) to the present time exceeds the reference time, and as a result of the determination, if the required time does not exceed the reference time, the process goes to the fifth step (S5). Sixth step (S6); As a result of the determination in the third step S3, when the received transport stream is noise other than the normal service information stream, or as a result of the determination in the sixth step S6, the required time exceeds the reference time. In one case, after the receiver selects another repeater from the program-related table and the program map table detected in the fourth step (S4), it consists of a seventh step (S7) to go to the second step (S2) Initial repeater selection method of a digital DBS receiver. The method of claim 1, wherein the third step (S3) Step 3-1 (S3-1) of determining whether a QPSK carrier exists in the received transport stream; A third step (S3-2) of checking a bit error rate of the received transport stream when a QPSK carrier exists as a result of the determination in the third step (S3-1); Step 3-3 (S3-3) determining whether the checked bit error rate exceeds a reference bit error rate; And As a result of the determination in step 3-3 (S3-3), when the checked bit error rate does not exceed a reference bit error rate, a third step of determining whether the synchronization signal of the received transport stream is a prescribed synchronization signal. Initial repeater selection method of the digital DBS receiver, characterized in that consisting of -4 steps (S3-4). The method of claim 1, wherein the fourth step (S4) Step 4-1 (S4-1) of detecting an RSMS data stream in the received transport stream; Step 4-2 (S4-2) of detecting a program related table and a program map table in the detected RSMS data stream; And And a fourth step (S4-3) of setting valid PIDs in the detected program related table and the program map table.