KR20090056274A - Method for transmitting and receiving of digital multimedia broadcasting system - Google Patents

Abstract

A transmission method and a reception method for a DMB(Digital Multimedia Broadcasting) system are provided to maximally guarantee inverse compatibility of a real service signal in a receiver by transmitting hierarchical modulation information without changing a transmission format of the service signal. A first hierarchical signal and a second layer signal corresponding to data added to the first hierarchical data are modulated by using each modulation mode(S240). The modulated first and second hierarchical signal is hierarchically modulated(S250). A hierarchically modulated signal is transmitted through a data channel of a transmission frame. The transmission frame transmits information related to hierarchical modulation is transmitted through a sync channel for transferring decoding information(S260).

Description

Transmission method and reception method of digital multimedia broadcasting system {METHOD FOR TRANSMITTING AND RECEIVING OF DIGITAL MULTIMEDIA BROADCASTING SYSTEM}

The present invention relates to a transmission apparatus and method in a digital multimedia broadcasting system, a reception apparatus and a method, and more particularly, to a transmission apparatus and method for transmitting hierarchical modulation information in a digital multimedia broadcasting system using a hierarchical modulation scheme, and to a hierarchical modulation information. Receiving apparatus and method for receiving.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunication Research and Development. [Task Management No .: 2006-S-017-02, Title: Development of Advanced Terrestrial DMB Transmission Technology] .

Digital Multimedia Broadcasting (DMB) is a next-generation digital broadcasting service that digitally modulates various multimedia signals such as voice, video, and data to listen to broadcasts on the go.

The terrestrial DMB system is based on the Eureka-147 Digital Audio Broadcasting (DAB) system in Europe, providing various multimedia services such as video, audio, and data in a mobile environment. However, a method of applying a hierarchical modulation scheme to a terrestrial DMB system has been proposed due to the limitation of channel capacity due to limited bandwidth.

Hierarchical modulation enables more effective data rates, higher quality video services, and more broadcast service channels at the same time by inserting additional data streams into existing data streams.

Such hierarchical modulation means to modulate the service stream of the base layer and the stream of the enhancement layer in each manner, and generate the symbols of the modulated base layer and the enhancement layer into one transport stream. Using this hierarchical modulation technique, it is possible to generate different data streams in one channel and receive them in different receiving devices.

On the other hand, while maintaining backward compatibility with the existing terrestrial DMB that does not use the hierarchical modulation technique in the receiving device, it is necessary to distinguish whether or not the received signal is terrestrial DMB broadcasting using the hierarchical modulation scheme to operate according to the modulation scheme. The device should transmit the hierarchical modulation information by utilizing the maximum without changing the format of the transmission signal. In addition, in the terrestrial DMB system using the hierarchical modulation scheme, the value of the hierarchical modulation information may vary according to a channel environment and a broadcast environment.

Accordingly, there is a need for a method for efficiently transmitting hierarchical modulation information to all receiving apparatuses (eg, terminals) existing in the broadcasting network.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method and a method for transmitting a hierarchical modulated signal capable of efficiently transmitting hierarchical modulation information.

According to an embodiment of the present invention, a transmission method of a digital multimedia broadcasting system is provided. The transmission method includes modulating a first layer signal and a second layer signal corresponding to data added to the first layer signal with respective modulation schemes, and performing hierarchically modulation on the modulated first and second layer signals. And transmitting the hierarchical modulated signal through a data channel of a transmission frame, and transmitting the information according to the hierarchical modulation through a synchronization channel carrying information for decoding in the transmission frame.

According to another embodiment of the present invention, a transmission method of a digital multimedia broadcasting system is provided. The transmission method includes hierarchically modulating a first layer signal and a second layer signal corresponding to data added to the first layer signal, and transmitting the layer modulated signal through a transmission frame. In this case, the transmission frame includes a null symbol used by the receiving device to locate the transmission frame, includes a synchronization channel for transmitting information for decoding, and a data channel for transmitting the layer modulated signal. The null symbol includes information according to the hierarchical modulation.

According to another embodiment of the present invention, a method for receiving a hierarchically modulated signal through a transmission frame is provided. The receiving method comprises the steps of: extracting a first layer signal from a received signal; detecting a transmitter identification signal including an identifier of a transmitting device that has transmitted the layer modulated signal as the received signal; Extracting information according to hierarchical modulation, and extracting a second layer signal from the received signal using the information according to the hierarchical modulation.

According to an embodiment of the present invention, since the transmitting apparatus can transmit the hierarchical modulation information to the receiving apparatus without changing the transmission format of the actual service signal, the receiving apparatus can ensure the backward compatibility of the actual service signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification and claims, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, “block”, and the like described in the specification mean a unit that processes at least one function or operation, which is hardware or software or a combination of hardware and software. It can be implemented as.

Now, a transmission method and a reception method of a terrestrial DMB system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram schematically showing an apparatus for transmitting a terrestrial DMB system according to an exemplary embodiment of the present invention, and FIG. 2 is a flowchart illustrating a method for transmitting a terrestrial DMB system according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the transmitter 100 includes an encoder 110, a base layer processor 120, an enhancement layer processor 130, a layer modulator 140, and a signal transmitter 150.

The encoding unit 110 encodes and outputs a plurality of service signals of the base layer and the enhancement layer, respectively (S210). The plurality of service signals may include a video signal, an audio and a data signal, etc., and only the video signal and the audio signal will be described below. To this end, the encoding unit 110 includes first and second video encoders 112 and 116 and first and second audio decoders 114 and 118. The first and second video decoders 112 and 116 encode the video signal of the base layer and the video signal of the enhancement layer, respectively, and output the video bit string of the base layer and the video bit string of the enhancement layer. The first and second audio encoders 114 and 118 encode audio signals of the base layer and audio signals of the enhancement layer, respectively, and output the video bit stream of the base layer and the video bit stream of the enhancement layer.

The base layer processor 120 generates a base layer signal by multiplexing signals output from the first video encoder 112 and the first audio encoder 114, respectively (S220). Here, the base layer signal means an existing data stream.

The enhancement layer processor 130 generates an enhancement layer signal by multiplexing signals output from the second video encoder 114 and the second audio encoder 118, respectively (S230). Here, the enhancement layer signal means an additional data stream added to an existing data stream.

The hierarchical modulator 140 modulates the base layer signal and the enhancement layer signal according to each modulation scheme (S240), and generates a hierarchical modulation signal by adding the base layer symbol sequence and the modulated enhancement layer symbol sequence according to the modulation ( S250). In this case, the hierarchical modulation signal may be generated by mapping signals of the enhancement layer according to the position of the constellation according to the modulation method of the base layer signal.

The signal transmitter 150 transmits the hierarchical modulation signal and the information according to the hierarchical modulation (hereinafter referred to as "hierarchical modulation information") to the receiving apparatus through the transmission frame (S260).

3 is a diagram illustrating a structure of a transmission frame according to an embodiment of the present invention, and FIG. 4 is a diagram illustrating a constellation of a hierarchical modulation signal according to an embodiment of the present invention.

As shown in FIG. 3, the transmission frame includes a synchronization channel (hereinafter referred to as "SC"), a fast information channel (hereinafter referred to as "FIC"), and a main service channel (hereinafter referred to as "FIC"). "MSC").

SC is a channel for transmitting information for decoding and is composed of a null symbol and a phase reference symbol (PRS). The null symbol is the first symbol of the SC and is used to locate a transmission frame at a receiving device. In addition, the phase reference symbol is a symbol that is a reference for modulation and demodulation. At this time, transmitter identification information (hereinafter referred to as "TII") is imposed on a null symbol. That is, the null symbol may be composed of an orthogonal frequency division multiplexing symbol (OFDM symbol) in the guard period and the frequency domain, and the OFDM symbol may have a predetermined number (eg, 1536) of subcarriers. have. The TII is generally composed of a predetermined number of adjacent subcarrier pairs among OFDM symbols, and the ID of the transmitting apparatus can be identified according to the pattern of subcarriers in which the TII exists.

The FIC is a channel for transmitting actual information on the MSC through which channel in the MSC is transmitted and information necessary for reception of the transmitted signal.

The MSC is a channel through which actual data such as an audio service, a video service, and a data service is transmitted, and includes a hierarchical modulated signal. That is, FIC and MSC correspond to data channels.

)를 포함한다.In an embodiment of the present invention, hierarchical modulation information is included in addition to a null symbol, and the signal transmitter 150 transmits hierarchical modulation information by using TII. That is, the signal transmitter 150 allocates a specific code value of the hierarchical modulation information to a subcarrier not allocated to TII among a predetermined number of subcarriers of the OFDM symbol in a TII pattern as shown in Table 1. In this case, the hierarchical modulation information includes a hierarchical modulation index (i) according to the hierarchical modulation signal prefix and the hierarchical modulation field.

).

)는 도 4에 도시한 바와 같이 기본 계층 신호와 강화 계층 신호를 분리하는 데 사용하는 값이다. 도 4에서, a와 b는 계층 변조 후 인접한 심볼간의 길이를 나타낸다. 이때,

는 수학식 1과 같이 정의된다. Here, the hierarchical modulation signal prefix is a bit string to be allocated to indicate that the hierarchical modulation signal among the code values of the TII.

) Is a value used to separate the base layer signal and the enhancement layer signal as shown in FIG. 4. In FIG. 4, a and b represent lengths between adjacent symbols after hierarchical modulation. At this time,

Is defined as in Equation 1.

의 값이 작을수록 심볼간의 간격이 짧아짐을 의미한다.In other words,

The smaller the value of, the shorter the interval between symbols.

As described above, when the hierarchical modulation information is transmitted using TII, the channel decoder or the FIC decoder is not required at the receiving device, compared to using the field of the channel to which the actual data value of the FIC or MSC is applied. Or more efficient in terms of data access. In addition, when the hierarchical modulation information is transmitted using the TII, the data carried in the FIC and / or the MSC which are actually related to the service is not modified, and thus the reception apparatus can guarantee maximum backward compatibility.

5 is a block diagram schematically illustrating an apparatus for receiving a terrestrial DMB system according to an exemplary embodiment of the present invention, and FIG. 6 is a diagram illustrating a method for receiving a terrestrial DMB system according to an exemplary embodiment of the present invention.

As shown in FIG. 5, the reception apparatus 200 includes a signal receiver 210, a hierarchical demodulator 220, a transmitter identification information detector 230, a transmitter identification information decoder 240, a base layer processor 250, An enhancement layer processor 260 and a decoder 270 are included.

Referring to FIG. 6, the signal receiver 210 receives a signal that is hierarchically modulated and transmitted (S610). The following defines this as a received signal.

The signal demodulator 220 first demodulates the received signal according to a demodulation scheme corresponding to a modulation scheme of the base layer signal to first extract the base layer signal (S620).

Then, the signal demodulator 220 demodulates the received signal according to a demodulation scheme corresponding to the modulation scheme of the enhancement layer signal to extract the enhancement layer signal (S630).

The transmitter identification information detector 230 detects TII from the received signal, and the transmitter identification information decoder 240 extracts hierarchical modulation information from the detected TII. In this case, the extracted hierarchical modulation information is used by the signal demodulator 220 to extract the enhancement layer signal.

The base layer processor 250 extracts the video bit stream and the audio bit stream from the base layer signal, respectively (S640).

The enhancement layer processor 260 extracts the video bit stream and the audio bit stream from the enhancement layer signal, respectively (S650).

The decoder 270 decodes the video bit stream and the audio bit stream separated from the base layer processor 250 and the enhancement layer processor 260, respectively (S660). To this end, the decoding unit 270 includes first and second video decoders 272 and 276 and first and second audio decoders 274 and 278. The first and second video decoders 272 and 276 decode the video bitstream of the base layer and the video bitstream of the enhancement layer, respectively, and output the video signal of the base layer and the video signal of the enhancement layer. The first and second audio decoders 274 and 278 decode the audio bit string of the base layer and the audio bit string of the enhancement layer, respectively, and output the video signal of the base layer and the video signal of the enhancement layer.

An embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Such an implementation can be easily implemented by those skilled in the art to which the present invention pertains based on the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a diagram schematically showing an apparatus for transmitting a DMB system according to an embodiment of the present invention;

2 is a flowchart illustrating a transmission method of a DMB system according to an embodiment of the present invention;

3 is a view showing the structure of a transmission frame according to an embodiment of the present invention,

4 is a diagram illustrating a constellation of a hierarchical modulated signal according to an embodiment of the present invention;

5 is a block diagram schematically illustrating a receiving device of a DMB system according to an embodiment of the present invention;

6 is a diagram illustrating a receiving method of a DMB system according to an exemplary embodiment of the present invention.

Claims (11)

Modulating a second layer signal corresponding to a first layer signal and data added to the first layer signal with respective modulation schemes, Hierarchically modulating the modulated first and second layer signals; Transmitting the hierarchically modulated signal over a data channel of a transmission frame, and Transmitting the information according to the hierarchical modulation through a synchronization channel that carries information for decoding in the transmission frame Transmission method comprising a. The method of claim 1, The information according to the hierarchical modulation is included in a null symbol of the synchronization channel. The method of claim 2, The null symbol further includes transmitter identification information. The information according to the hierarchical modulation has the same pattern as the transmitter identification information. The method according to any one of claims 1 to 3, The hierarchical modulation includes mapping the second hierarchical signal according to the position of the constellation according to the modulation scheme of the first hierarchical signal. The method according to any one of claims 1 to 3, Generating a first layer signal by multiplexing a plurality of service signals of a first layer, and Multiplexing a plurality of service signals of a second layer to generate the second layer signal Transmission method further comprising. In the transmission method of the digital multimedia broadcasting system, Hierarchically modulating a second layer signal corresponding to a first layer signal and data added to the first layer signal, and Transmitting the hierarchical modulated signal through a transmission frame Including; The transmission frame, A synchronization channel including a null symbol used by a receiving device to locate the transmission frame, and carrying information for decoding, and A data channel for conveying said hierarchically modulated signal, The null symbol includes information according to the hierarchical modulation. The method of claim 6, The null symbol includes identification information of the transmitting device, The information according to the hierarchical modulation is included in the identification information of the transmitting device. The method according to claim 6 or 7, And the information according to the hierarchical modulation is used by the receiving device to demodulate the hierarchically modulated signal. A method of receiving a hierarchically modulated signal over a transmission frame, Extracting a first layer signal from the received signal; Detecting a transmitter identification signal including an identifier of a transmitting device that has transmitted the hierarchically modulated signal as the received signal; Extracting information according to the hierarchical modulation from the transmitter identification signal, and Extracting a second layer signal from the received signal using the information according to the layer modulation; Receiving method comprising a. The method of claim 9, And the transmitter identification signal is assigned to a null symbol of a synchronization channel in the transmission frame, and the information according to the hierarchical modulation is assigned to the null symbol in a pattern of the transmitter identification signal. The method of claim 9 or 10, Multiplexing the first and second layer signals and separating each into at least one service stream; Receiving method further comprising.

Images