KR100466590B1 - System and method for terrestrial digital broadcasting service using single frequency band - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an apparatus and method for terrestrial digital broadcasting service using a single frequency network.

2. Technical problem to be solved by the invention

The present invention synchronizes the transmitter input signal by periodically inserting a transmission synchronization signal into the header of the TS, and by separately providing a switching unit in the trellis encoder to initialize the memory to solve the ambiguity of the trellis encoder without any additional device. It is intended to provide a system and method for enabling digital TV broadcasting using a single frequency network.

3. Summary of Solution to Invention

The present invention provides a terrestrial digital broadcasting system comprising a broadcasting station for transmitting a multiplexed video, audio, and additional signal to a transmitter, and a transmitter for receiving the TS and broadcasting the same to a receiver through a single frequency network. Transmission synchronous insertion means for inserting a field synchronous header into a TS for every predetermined data field period N, wherein the transmitter is configured to transmit transmission synchronization detecting means for synchronizing TS transmitted from the broadcasting station based on the field synchronous header and predetermined data And trellis encoding means for generating an initialization symbol having a predetermined interval length for each field period M and synchronizing the TS output to the receiver.

4. Important uses of the invention

The present invention is used for terrestrial digital broadcasting service system.

Description

Terrestrial digital broadcasting system using single frequency network and its method {System and method for terrestrial digital broadcasting service using single frequency band}

The present invention relates to a system and method for terrestrial digital broadcasting service using a single frequency network (SFN), and more particularly, a plurality of transmitters provide a broadcast service through a single frequency network when terrestrial digital broadcasting service is provided. The present invention relates to a system and a method for enabling the same.

In general, a digital broadcasting service uses a multi-frequency network in which a transmitter is arranged according to a surrounding terrain, a feature, or a broadcasting zone, and broadcast data is transmitted in a frequency band allocated to each transmitter.

1 is a schematic diagram of a terrestrial digital broadcasting system using a conventional multi-frequency network. Referring to the figure, the broadcasting station 100 multiplexes a video, audio, and additional data signal, and transmits the first transmitter 130 and the second transmitter into a transport stream (hereinafter, abbreviated as "TS") in a predetermined packet form. Transmit to 170. The first transmitter 130 and the second transmitter 170 transmit broadcast signals through respective transmission frequencies A and B, and provide broadcast services to the first broadcast zone 150 and the second broadcast zone 190, respectively. Conduct.

2 shows a detailed configuration of a conventional terrestrial digital TV broadcasting system. Referring to the figure, the broadcasting station 100 multiplexes a video signal 102 compressed by the MPEG-2 technique, an audio signal 104 compressed by the Dolby AC-3 technique, and a control signal 106 for controlling the transmitter. 108). The multiplexer 108 packetizes the input signal to generate a digital data sequence TS, which is transmitted to each transmitter through a studio to transmitter link (STL) 110.

Meanwhile, the first transmitter 130 transmits the signal transmitted through the STL 110 through the channel encoder 132, the VSB modulator 140, the frequency enhancer 142, the high power amplifier 144, and the antenna 146. Broadcast to the 1 broadcasting zone (150).

FIG. 3 is a functional diagram for explaining the channel encoder of FIG. 2. As shown, the channel encoder 132 is a randomizer 133 for randomizing the TS received from the STL 110. RS encoder (reed-solomon encoder) 134 for outer encoding the randomized data, interleaver 135 for distributing burst errors generated through the communication channel by interleaving the data and interleaved It is composed of a trellis encoder 136 for inner encoding the data. In addition, the trellis encoder 136 includes a trellis coded modulation (TCM) encoder 137 and a pre-coder 138 for signal processing on an input signal.

However, such a broadcast service according to the related art requires many frequency resources because the same broadcast data is broadcasted through multiple frequencies. This is very inefficient in terms of frequency utilization because the same frequency cannot be reused except in a remote area where there is no frequency interference effect. Therefore, it is preferable to use a single frequency network.

However, there are various problems to perform single frequency network digital TV broadcasting using a conventional digital TV transmission system.

First, since each transmitter has a different distance and communication environment from the broadcasting station 100, TS data input to each transmitter may cause different signals to be input based on the same time. That is, since the first transmitter 130 and the second transmitter 170 are not synchronized with respect to time, the channel modulation start positions are different from each other, so that the output signals do not coincide with each other. It is difficult to distinguish between output signals. That is, if signals transmitted from multiple transmitters using the same frequency band are not identical to each other, the signals of each other appear in the same frequency band as noise, and these noise signals are difficult to distinguish from the receiver.

Secondly, even though the initial state of the memory of the TCM encoder 137 and the precoder 138 of each transmitter is not constant, a different output signal is transmitted for each transmitter even when the same signal is simultaneously input to each transmitter. This phenomenon is generally referred to as the ambiguity of trellis encoders.

In order to solve the above problem, there is a "Transmitter Synchronization For Terrestrial Broadcasting" method proposed by Merrill Weiss Group as ATSC standard on April 20, 2002.

The Advanced Television System Committee (ATSC) is a committee set up to consider the advanced television system (ATV), the next generation terrestrial television system in the United States.

According to the proposal, the broadcasting station periodically transmits a CS (Cadence Signal) to match the period of input signals of each transmitter, and separately transmits a TCSP (Trellis Code State Packet) signal, which is information about the memory of the trellis encoder. It solves the ambiguity of trellis encoder.

However, according to the above method, a broadcasting station requires various complicated additional devices such as a data renderer, an RS encoder, a data interleaver, a trellis encoder, a CS inserter, and a TCSP inserter to transmit a TCSP signal. There is another problem that the STL load is increased because the weight of the control signal becomes larger.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and periodically inserts a transmission synchronization signal into the header of the TS to synchronize the transmitter input signal, and has a separate trellis encoder switching unit to initialize the memory to trellis. It is an object of the present invention to provide a system and method for enabling digital TV broadcasting using a single frequency network without additional equipment by solving the ambiguity of an encoder.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. In addition, the objects and advantages of the present invention can be realized by means and combinations indicated in the claims.

1 is a schematic diagram of a terrestrial digital broadcasting service system according to the prior art;

FIG. 2 is a functional diagram illustrating a broadcast station and a transmitter of FIG. 1;

FIG. 3 is a functional diagram for explaining the channel encoder of FIG. 2;

4 is a schematic diagram of a single frequency network terrestrial digital broadcasting service system according to an embodiment of the present invention;

FIG. 5 is a functional diagram illustrating a broadcast station and a transmitter of FIG. 4; FIG.

6 is a transport stream data structure diagram in which a field synchronization signal is inserted according to a preferred embodiment of the present invention;

7 is a functional diagram illustrating the channel encoder of FIG. 5;

8 is an internal configuration diagram of the trellis encoder of FIG.

9 is a transport stream data structure diagram in which an initialization symbol is inserted according to a preferred embodiment of the present invention.

<Description of main reference numerals in the drawings>

400: broadcast station 410: STL

430: first transmitter 470: second transmitter

431: transmission synchronous detector 432: channel encoder

433: randomizer 434: RS encoder

435 interleaver 436 trellis encoder

440 VSB modulator 442 frequency booster

444: high power amplifier 810: TCM encoder

820: precoder 850: switching unit

In order to achieve the above object, the present invention provides a terrestrial digital broadcasting system including a broadcasting station for transmitting a multiplexed video, audio, and additional signal to a transmitter, and a transmitter for receiving the TS and broadcasting it to a receiver through a single frequency network. The transmission station of claim 1, wherein the broadcasting station includes transmission synchronization inserting means for inserting a field synchronization header into the TS every predetermined data field period N, and the transmitter is configured to synchronize a TS transmitted from the broadcasting station based on the field synchronization header. And a trellis encoding means for generating an initialization symbol having a predetermined interval length for each predetermined data field period M and synchronizing the TS output to the receiver.

In addition, in order to achieve the above object, the present invention provides a terrestrial digital broadcasting service using a single frequency network, wherein a broadcasting station inserts a field synchronization header at predetermined data field periods N into TSs transmitted to a plurality of transmitters. In the first step, the transmitter detects the field synchronization header to match the processing start point of the TS input to each transmitter, and generates an initialization symbol having a predetermined interval length for each data field period M for the input signal. A third step of synchronizing the TS output to the receiver and a fourth step of broadcasting the synchronized TS to the receiver.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

4 is a schematic diagram of a terrestrial digital broadcasting system using a single frequency network according to a preferred embodiment of the present invention. Referring to the figure, the broadcasting station 400 multiplexes a video, audio, and additional data signal and transmits the same to the first transmitter 430 and the second transmitter 470 by TS, and the first transmitter 430 and the second transmitter ( The signal 470 processes the transmitted TS and broadcasts the first TS to the first broadcast zone 450 and the second broadcast zone 490 at the same frequency A, respectively.

US terrestrial digital broadcasting system using such a single frequency network is shown in more detail in FIG.

FIG. 5 is a functional diagram for distinguishing between a broadcasting station and a transmitter according to the present invention. Referring to the drawings, the broadcasting station 400 includes a video signal 402 compressed by the MPEG-2 technique and a voice compressed by the Dolby AC-3 technique. A signal 404 and a control signal 406 for controlling the transmitter are input to the multiplexer 408 to generate a digital data sequence TS.

Meanwhile, the transmission synchronous inserter 420 periodically inserts a predetermined transmission synchronous signal described below into a specific header of the generated TS. In general, according to the ATSC A.53 standard, 47 ₁₆ (47, which is a hexadecimal value) is input into the header of a TS as header information. However, according to the present invention, the transmission synchronization inserter 420 is separately provided, and the B8 ₁₆ value in which 47 ₁₆ values are periodically inverted in units of bits for each of the N data fields is input as the field synchronization header. The data field period N is a natural number and can be flexibly adjusted according to a communication environment. That is, if the communication channel environment is excellent, the N value can be increased, and if the environment is poor, the N value is decreased to frequently transmit the field synchronization signal. It will be apparent to those skilled in the art that the N value may vary depending on the communication environment of the terrestrial digital broadcasting system. Therefore, it should be understood that the present invention is not limited to specific N values.

6 illustrates a TS structure in which a field sync header is inserted. Referring to the figure, B8 ₁₆ is included in the first header 610 of the N period data field as a field synchronization header. In this embodiment, since N value is assumed to be 1, a field sync header is inserted for each data field composed of 312 segments. If N is not 1, the field sync header is inserted for every N data fields according to the N value.

In the remaining segment header 620, 47 ₁₆ values are stored as header information as before. The number of remaining segment headers is defined as an X value (a natural number greater than one). In the present embodiment, since the N value is 1, the X value is 311.

The field sync header allows multiple transmitters to synchronize input signals. That is, in the present embodiment, since the first transmitter 430 and the second transmitter 470 are different in physical distance and communication environment from the broadcasting station 400, when the first transmitter 430 and the second transmitter 470 are determined based on the same time, The signals input to the two transmitters 470 are different. However, in order for the first transmitter 430 and the second transmitter 470 to transmit the same output signal, the data positions at which signal processing starts as a precondition must be the same. For this reason, the transmit synchronous inserter 420 inserts a field synchronous header, so that each transmitter can match the data position at which signal processing starts.

The TS into which the field synchronization signal is inserted is transmitted to each transmitter through an STL (studio to transmitter) 410.

Meanwhile, the first transmitter 430 receives the TS and transmits the TS to the transmission synchronous detector 431. The transmission synchronous detector 431 recognizes that a valid TS is received when the field synchronization header B8 ₁₆ and the X data segment header 47 ₁₆ are detected, and starts the channel encoding process from the data segment in which the field synchronization header B8 ₁₆ exists. The signal processing procedure is then performed.

Since the same operation is performed in the second transmitter 470, the synchronization may be maintained to match the starting point of the signal processing even though the signal input to the first transmitter 430 is slightly different in time.

On the other hand, the channel encoding process according to the present invention is performed in the channel encoder 432, the configuration is as shown in FIG. 7 is a functional diagram of a channel encoder, referring to the drawing, a channel encoder 432 includes a randomizer 433 which randomizes a TS, an RS encoder 434 that outer-codes randomized data, An interleaver 435 distributes burst errors generated through a communication path, and a trellis encoder 436 inner encodes the interleaved data.

The trellis encoder 436 according to the present invention equally matches the output signal of each transmitter unlike the prior art.

8 shows a detailed configuration of the trellis encoder 436. Referring to the drawing, the trellis encoder 436 includes a trellis coded modulation (TCM) encoder, a pre-coder 820, a memory 830 and a switching unit 850 of the TCM encoder and the precoder. Include.

The TCM encoder 810 and the precoder 820 signal-process the input x ₁ and x ₂ signals in the same manner as in the prior art to generate a symbol. However, the initialization of the memory 830 is performed for each M (natural number) data field to be input, which is performed by the switching unit 850 as shown by the broken line shown in the drawing. That is, when switching is performed as shown by a broken line in the drawing, an exclusive OR is performed with a signal of the memory 830 itself instead of the input x ₁ and x ₂ signals, and each memory 830 is initialized to a '0' state (null state). do. When the memory 830 of the trellis encoder 436 of each transmitter is initialized, subsequent data fields are generated with the same symbol in each transmitter.

The data field period M (natural number) is a value that can be flexibly adjusted according to the communication channel environment between the transmitter and each receiver. If the communication channel environment is excellent, the M value can be increased. can do. It is apparent to those skilled in the art that the M value may be variously changed according to the communication environment of the terrestrial digital broadcasting system. Therefore, it should be understood that the present invention is not limited to specific M values.

The memory 830 is periodically initialized by the switching operation of the switching unit 850, and the initial state of the trellis encoder 436 is set to the same period if the M values of all transmitters are the same. As a result, since the signals input to each transmitter are the same as described with reference to FIGS. 5 and 6, and the signals output from each transmitter are the same as described with reference to FIGS. 7 and 8, terrestrial broadcasting using a single frequency network is performed. It becomes possible.

On the other hand, the operation of the switching unit 850 is inserted into the initialization symbol in place of the data symbol for each predetermined period (data field period M). That is, a signal stored in the memory 830 is introduced into the input terminal instead of the input x ₁ and x ₂ signals to generate an initialization symbol. In the process of initializing the memory 830, two initialization symbols are generated for one trellis encoder 436. On the other hand, ATSC A.53 uses twelve trellis encoders in the channel encoding process, and as a result, a total of 24 initialization symbols are generated, and 24 initialization symbols are inserted every M cycle.

9 illustrates a data structure in which an initialization symbol is inserted into broadcast data transmitted to a receiver. Referring to the figure, 24 initialization symbols are inserted into broadcast data every M cycle.

On the other hand, an error of information occurs in the 24 initialization symbol intervals, but such an error can be corrected at an error correction stage of the receiver, and the error becomes insignificant as the period M in which the initialization symbol is inserted is increased.

When the channel encoding is completed by the channel encoder 432, the broadcast data is transmitted to each broadcasting zone through the antenna 446 through the VBS modulator 440, the frequency uplinker 442, the high power amplifier 444, and the like. Since the above processes are the same as the prior art, a detailed description thereof will be omitted.

As described above, field synchronization signals are inserted into the TS input to the transmitter for every predetermined period (N data fields) to synchronize a plurality of transmitter input signals, and the trellis encoder of the transmitter for each predetermined period (M data fields). The output signal of the transmitter is synchronized by initializing the memory of the transmitter. Therefore, the input signals of the transmitters are identically recognized for all transmitters, and the output signals of all transmitters are also the same, so that all transmitters can broadcast terrestrial digital broadcasting at the same single frequency.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this, The person of ordinary skill in the art to which this invention belongs, Of course, various modifications and variations are possible within the scope of equivalent claims.

According to the terrestrial digital broadcasting service system and method using a single frequency network of the present invention, since all transmitters are synchronized to output the same output signal, it is possible to provide a digital TV broadcasting service using a single frequency network. Therefore, the frequency reuse effect is obtained even in the near area, so that not only the frequency utilization efficiency is increased, but also the diversity gain using multiple transmitters can be obtained.

Claims (10)

A terrestrial digital broadcasting system comprising a broadcasting station transmitting a multiplexed video, audio, and additional signal to a transmitter and a transmitter receiving the TS and broadcasting the same to a receiver through a single frequency network, The broadcast station Transmission synchronous insertion means for inserting a field synchronous header into the TS every predetermined data field period N. Including, The transmitter is Transmission synchronization detecting means for synchronizing a TS transmitted from the broadcasting station based on the field synchronization header; And A trellis encoding means for generating an initialization symbol having a predetermined interval length for each data field period M and synchronizing the TS output to the receiver. Terrestrial digital broadcasting system comprising a. The method of claim 1, The trellis encoding means A first switching unit for initializing the output value of the TCM encoder and the memory by switching to input a value stored in the memory of the TCM encoder in place of the input signal of the TCM encoder for each period M; And A second switching unit for initializing the output value of the precoder unit and the memory by switching to input a value stored in the memory of the precoder unit instead of the input signal of the precoder unit at each period M; Terrestrial digital broadcasting system comprising a. The method according to claim 1 or 2, The field synchronization header is a terrestrial digital broadcasting system, characterized in that the first segment header of the N period data field is inverted bit by bit. The method of claim 3, wherein The transmission synchronization detecting means recognizes that a valid TS is received when a B8 ₁₆ value field sync header is detected in the first segment header of the N period data field and 47 ₁₆ value is detected in the header of the remaining data segments. Terrestrial digital broadcasting system, characterized in that. The method according to claim 1 or 2, The N value is adjusted in consideration of the communication channel environment between the broadcast station and the transmitter, The M value is a terrestrial digital broadcasting system, characterized in that adjusted in consideration of the communication channel environment between the transmitter and the receiver. In the method for providing a terrestrial digital broadcasting service using a single frequency network, The broadcast station includes a first step of inserting a field synchronization header at every data field period N into TSs transmitted to a plurality of transmitters; The transmitter detecting the field sync header to match a processing start point of the TS input to each transmitter; A third step of synchronizing the TS output to the receiver by generating an initialization symbol having a predetermined section length for each input data field period M with respect to the input signal; And A fourth step of broadcasting the synchronized TS to a receiver; Terrestrial digital broadcasting method comprising a. The method of claim 6, The third step is Generating an initialization symbol by switching to input a value stored in a memory of a TCM coder and a precoder in place of the input signal; Terrestrial digital broadcasting method characterized in that. The method according to claim 6 or 7, The field synchronization header inverts the first segment header of the N period data field bit by bit. Terrestrial digital broadcasting method characterized in that. The method of claim 8, The second stage If the field sync header of the B8 ₁₆ value is detected in the first segment header of the N period data field, and the value 47 ₁₆ is detected in the header of the remaining data segments, it is recognized that a valid TS is being received, and the field sync header is detected. A terrestrial digital broadcasting method characterized by matching a processing starting point by processing a signal from a field. The method according to claim 6 or 7, The N value is adjusted in consideration of the communication channel environment between the broadcast station and the transmitter, The M value is a terrestrial digital broadcasting method, characterized in that adjusted in consideration of the communication channel environment between the transmitter and the receiver.