KR20070111225A - Digital broadcast signal and apparatus and method of processing the signal - Google Patents

Abstract

A digital broadcast signal and an apparatus and a method for processing the signal are provided to select client caches widely, reduce response time of a client request significantly, and manage cache in a middleware effectively. A digital broadcast signal and method for processing the signal comprise the following steps of: parsing data and effective time information of data; storing parsed data and effective time information of the parsed data in a cache; deleting associated data from the cache, if an effective time information value of the associated data stored in the cache is smaller than a value of current time when a client requests data or detects effectiveness of data stored in the cache; and requesting retransmission of the deleted data and receiving the data.

Description

Digital broadcast signal and apparatus and method for processing the signal {Digital broadcast signal and apparatus and method of processing the signal}

1 is a schematic illustration of a digital video broadcasting system in connection with the present invention;

2 is a diagram illustrating "valid_time" descriptor information in relation to the present invention.

3 illustrates an example of a digital broadcast receiver configured to process a digital broadcast signal including a "valid_time" descriptor according to the present invention.

4 is a flowchart illustrating an example of a method of processing a digital broadcast signal including valid time information of data stored in a cache according to the present invention.

* Explanation of symbols for the main parts of the drawings

301: tuner part 302: demodulation part

303: demultiplexer 304: A / V decoder

305: display unit 306: application manager

307: channel manager 308: SI decoder

309: SI database 310: carousel decoder

311: Application Database 312: NVRAM

313: control unit 314: descrambling module

The present invention relates to a digital broadcast signal and an apparatus and method for processing the signal.

Digital video broadcast (DVB) uses a data transmission technique called carousel in consideration of a transmission environment of a television. That is, the digital video broadcasting (DVB) is a method of repeatedly transmitting data in order to effectively use a downlink channel having a relatively wide bandwidth compared to an uplink channel. Carousel).

In this regard, if future data broadcasts become more popular than the present time, broadcasters will need to be able to transmit more data than they do today. This means that users will continue to demand higher quality content, and broadcasters will have to increase the quality of the content they send according to their needs. Therefore, in order to improve the quality of the content as described above, the broadcaster will increase the amount of data required for the content. Therefore, it will be necessary to transmit the increasing data.

Therefore, the broadcaster transmits a larger amount of data in order to transmit high quality content, and the receiver must download the data through the carousel at the time required by the host user. .

However, when the amount of data transmitted by the broadcaster increases as described above, there is a problem that the receiver is a heavy load to download and process the data through the carousel.

Accordingly, in order to solve the above problems, an object of the present invention is to provide a digital broadcast signal and an apparatus and method for processing the signal.

Accordingly, in order to achieve the above object, an example of a digital broadcast signal according to the present invention is to transmit the broadcast signal through a data carousel, but the data carousel may include at least one or more groups. Having at least one control layer (s) including tables containing control information for explanation, said tables comprising descriptors pointing to the location of DownloadDataBlock (DDB) messages. a descriptor pointing to a DownloadInfoIndication (DII) message to describe modules in a data carousel using a mi (ModuleInforByte) field including a loop of a descriptor, wherein the DII (DownloadInfoIndication) is included. ) Message is valid time information (valid time information) for the transmitted data, characterized in that The.

In this case, the valid time information is preferably defined as a message descriptor in the DII message.

The valid time information is preferably defined in module units.

In addition, the valid time information is preferably defined using any one of a second, a global positioning system (GPS) time, or a time stamp.

The valid time information is preferably information indicating how long the corresponding data stored in the cache is valid.

An example of a method of processing a digital broadcast signal in accordance with the present invention comprises the steps of parsing data and valid time information for the data; Storing the parsed data and valid time information for the data in a cache; And when the client requests data or validates the data stored in the cache, if a valid time information value for the data stored in the cache is smaller than a value indicating a current time, the corresponding data is removed from the cache. Characterized in that it comprises a step.

In this case, the method may further include requesting and receiving a retransmission for the removed corresponding data.

In the removing step, if the valid time information value of the corresponding data stored in the cache is larger than the value indicating the current time, it is preferable to determine that the data is valid data and store the data as it is.

One example of a digital broadcast receiver according to the present invention includes: a tuner unit for tuning and receiving a digital broadcast signal; A demodulator for demodulating the received broadcast signal; A demultiplexer configured to filter the message descriptor including the demodulated data received and valid time information of the data; A parser for parsing the filtered and received message descriptor; A memory unit for storing the received data and the parsed message descriptor information; And a controller configured to determine validity of the data using the parsed message descriptor information to control the memory unit.

In this case, the controller may compare the parsed message descriptor information with a value indicating a current time in determining the validity of the data.

If the parsed message descriptor information is smaller than a value indicating a current time, the controller determines that the corresponding data is not valid and controls to remove the corresponding data from the memory unit.

In addition, the control unit, after the removal is preferably controlled to request retransmission for the removed data.

If the parsed message descriptor information is larger than a value indicating a current time, the controller determines that the data is valid and stores the data as it is, and stores the data as it is.

The controller may not request retransmission of the data when it is determined that the corresponding data is valid.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings. In addition, the terminology used in the present invention was selected as a general term widely used as possible now. However, in certain cases, the applicant arbitrarily selected a term, and in this case, the meaning is described in detail in the corresponding part. Therefore, the terms used in the present invention should be understood as meanings of the terms rather than simply names of the terms.

The digital broadcast signal and the apparatus and method for processing the signal according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

In the present specification, a digital video broadcast is used as a data broadcast format.

1 schematically illustrates a digital video broadcasting system in connection with the present invention.

As shown in FIG. 1, a digital video broadcasting system is largely composed of a broadcasting station transmitting a broadcast signal and a broadcast receiver receiving a signal transmitted from the broadcasting station and providing the signal to a user.

In this case, the broadcasting station includes a server therein, and the server may hold message descriptors such as descriptors indicating valid time information according to the present invention, which will be described later.

In addition, the digital video broadcasting system as shown in FIG. 1 basically provides a means for delivering a broadcast signal using an MPEG-2 transport stream. In the context of the present invention, data broadcasting is an important extension of MPEG-2 based on the digital video broadcasting transmission standard.

Examples for such data broadcasting include downloading of software via satellite, cable or terrestrial links, delivery of Internet services via IP tunneling and interactive TV. Etc. The four different application areas, the data broadcast profiles that make different demands for data transmission, include data piping, data streaming, multiprotocol encapsulation, and data caching. It can be defined as cells (data carousels) and object carousels (object carousels).

In connection with the present invention, data broadcasting through a data carousel may support data broadcasting services requiring periodic transmission of data modules through digital video broadcasting compliant broadcasting networks.

In connection with the present invention, in downloading data through the carousel, a cache technique may be utilized to reduce the heavy load of the receiver. That is, the receiver may provide fast response speed to the user by utilizing the cache according to the user's pattern instead of retransmitting the repeated carousel when necessary.

Accordingly, in the present invention, when transmitting broadcast data through a carousel, it is possible to determine the validity of the corresponding data using a time value for the transmitted data.

Therefore, according to the present invention, even if the transmitted data increases, the receiver can effectively solve the problem by managing the transmitted data using the existing apparatus.

In relation to the present invention, data transmitted through the carousel and a valid time value for determining whether the data is valid may be stored together in a cache. When it is time to determine the validity of the stored data or when the user requests to check the validity of the stored data, the valid time value for the corresponding data stored in the cache is compared with a value representing the current time and transmitted through the carousel. You can effectively manage the data in the cache.

The present invention is characterized in that the broadcast signal including the data to be transmitted as described above is transmitted including the valid time value for the data.

In the following description of the present invention, (1) a digital broadcast signal including a valid time value for transmitted data, (2) a digital broadcast receiver for processing the broadcast signal, and (3) a method for processing the broadcast signal Look at them separately.

(1) Digital broadcast signal including valid time value for data to be transmitted

In connection with the present invention, in the digital video broadcast, a download information indication (DII) may be used to utilize a cache in transmitting a carousel. In the following description, the technical idea of the present invention will be described.

According to the present invention, in transmitting a data carousel, a message descriptor indicating valid time information on data stored in a cache is included in DownloadInfoIndication (DII) of a data carousel. .

That is, in transmitting a digital carousel according to the present invention, the DownloadInfoIndication (DII) may include a descriptor defining valid time information according to the present invention.

The DownloadInfoIndication (DII) is defined in a data carousel of a digital video broadcast using a descriptor for smooth reception and management of data.

Before describing the valid time information descriptor according to the present invention, transmission of a data carousel is described as follows.

A data carousel transmits data to receivers periodically. Data transmitted in the data carousel can be organized into modules divided into blocks. have. All blocks of all modules in the data carousel may have the same size except for the last block of each module, which may be of smaller size.

The modules are a delineation of logically separated groups of data in a data carousel, and can be clustered into a group of modules if required by services. Likewise groups can be clustered into supergroups.

In addition, the data carousel may include the following control message for effective management of the downlink channel. At this time, the control message may use a DownloadServerInitiate (DSI) message, a DownloadInfoIndication (DII) message, a DownloadDataBlock (DDB) message and a DownloadCancel (DC) message.

Data in the data carousel is carried in the DDB message, while control over modules may be provided by the DSI message, DII message and DC message.

And while the DSI message describes groups in one super group, the DII message can describe modules in the one group.

Based on the control messages, the receivers may obtain one sub-set of modules from the network.

The DSI message can be used to create a super group. The DDB message may include blocks of fragmented modules. The DC message can be used to indicate a receiver.

The DC message may be sent at the group or super group level. The DC message may be sent in the payload of MPEG-2 transport stream packets.

In connection with the present invention, the DII message may include descriptions of the general parameters of the data carousel or the module in the group having the same block size as the download ID.

Each module can be described by the number of attributes. For example, attributes such as module ID, module size and module version may be defined in the DII message field. Module attributes other than the above attributes may be transmitted to descriptors.

Therefore, it may be desirable to include valid time information for the data stored in the cache according to the present invention as a descriptor.

In connection with the present invention, a brief look at the above cache scheme, it is possible to basically manage the cache in the version of the module. That is, the cached information may be provided or returned based on whether the version of the stored module is higher or lower than that of the currently broadcasted module. At this time, the version information of the stored information can be known by checking the information transmitted to the DII.

Therefore, several cache management levels may be determined according to the verification method of the DII. Hereinafter, referring to the attached table for the cache management level.

value description 0 reserved One transparent caching 2 semi-transparent caching 3 static caching 4 to 255 reserved for future use

As shown in Table 1, the level value '1' represents a scheme of displaying information stored in the cache after checking the DII, and the level value '2' assumes that the information of the DII is valid for some time. Techniques can be represented. Therefore, the technique according to the level value '2' may consider and provide the data correctly if the DII is checked within a certain time instead of checking and transmitting the version of the stored data each time to check the validity of the cache. .

On the other hand, the level value '3' may verify and provide data validity only once in the entire cycle of the application. That is, the technique according to the level value '3' assumes that the data does not change well.

The level of management of the cache is provided by the information provider, and can be relied on by a person who is familiar with the nature of the data.

Hereinafter, descriptors used to indicate a current carousel within a range of digital video broadcasting (DVB) data carousels will be described with reference to Table 2 below. The descriptors may have their own private "descriptor_tag" space, meaning that they are not used outside the digital video broadcast data carousel scope.

Descriptor Tag value Type 0x01 Name 0x02 Info 0x03 module_link 0x04 CRC_32 0x05 Location 0x06 est_download_time 0x07 compressed_module 0x08 Valid_Time 0x0A

The "Type" descriptor has a tag value of '0x01' and may include a type of a module or a group according to the order of characters.

The descriptor "Name" has a tag value of '0x02' and may include names of modules and groups.

The "Info" descriptor has a tag value of '0x03' and may include a description in plain text.

The "module_link" descriptor has '0x04' as a tag value and may include information about modules linked to obtain a complete piece of data other than a data carousel. The "module_link" descriptor also informs the decoder of the order of linked modules.

The " CRC32 " descriptor has a tag value of '0x05' and can indicate the calculation of CRC32 for a complete module.

The "Location" descriptor has a tag value of '0x06' and may include a location of a PID (Packet IDentifier) of blocks, modules or groups found in data included in a carousel.

The descriptor "est_download_time" has a tag value of '0x07' and may include an integer for estimating a download time for a module or a group.

The "compressed_module" descriptor has a tag value of '0x09' and may indicate data in modules having a "zlib" structure.

In the present invention, a descriptor that defines valid time information for data to be transmitted is called a "valid_time" descriptor. Hereinafter, the "valid_time" descriptor will be described with reference to the accompanying drawings. 2 is a diagram illustrating a "valid_time" descriptor in relation to the present invention.

The "valid_time" descriptor has a tag value of '0x0A' and may indicate valid time information on the transmitted data. In this case, the valid time information is time information about how long the transmitted data stored in the cache is valid.

It is assumed that data stored in the current client cache is Data 1 to Data N in a module unit. At this time, the "valid_time" descriptor according to the present invention may be stored together with the data (Data 1 to Data N) of the module unit.

Therefore, when the validity of the cache is determined using the "valid_time" descriptor, a value representing the current time and a "valid_time" descriptor including valid time information for each data may be compared. That is, the value representing the current time and the value representing the valid time stored in the "valid_time" descriptor for each data can be compared.

Therefore, according to the comparison result, the validity of each data may be determined at the time desired by the user or when the validity of the data stored in the cache is determined.

That is, if the validity time information value in the "valid_time" descriptor stored for each data is greater than the value representing the current time as a result of the comparison, each stored data is regarded as valid data and left as it is.

However, if the validity time information value in the "valid_time" descriptor stored for each data is smaller than the value representing the current time as a result of the comparison, each stored data may be regarded as invalid data and removed from the cache.

That is, in FIG. 2, it is assumed that a user requests data or validates data in a cache at a current time (CTime). At this time, before the current time based on the current time (CTime), that is, the upper part of the current time of FIG. The state of the cache before the operation, and after the current time, that is, the lower part of the current time of FIG. 2, validates the data in the cache using the valid time information value in the "valid_time" descriptor according to the present invention. The state of the cache after).

In this case, the checking may refer to comparing a valid time information value in the "valid_time" descriptor with a current time value. In addition, in FIG. 2, the checking is performed at the present time.

Referring to FIG. 2, prior to the checking, data and valid time information values in a "valid_time" descriptor, which are time information indicating how long the data is valid, are stored in a cache. After the current time, the validity of each data is determined.

As a result of the checking, it is determined that the "valid_time" descriptor values of Data 2 and Data N are smaller than the current time value, and thus the invalid data is processed. Therefore, the data corresponding to the position can be removed. The retransmission may be waited for the removed data.

However, if the current time (CTime) is smaller than the valid time of the stored data, that is, if the current time exceeds the valid time of the data, the data is invalidated.

As described above, by defining and providing a "valid_time" descriptor according to the present invention, the load on the host can be reduced. That is, from a user or receiver's point of view, using a cache according to a user's pattern, rather than retransmitting a carousel repeatedly transmitted when necessary, can provide a fast response speed to the user.

As described above, the present invention can effectively manage the transmitted data by defining a "valid_time" descriptor as a message descriptor in a downloadinfoindication (DII) to utilize a cache in transmission of a current carousel.

In connection with the present invention, a time stamp may be defined and used together with the "valid_time" descriptor value in a manner similar to the "valid_time" descriptor, without being limited to the above-described method.

Therefore, according to the present invention, by comparing the value representing the current time and the value of valid time information in the "valid_time" descriptor, it is possible to remove invalid data among cached data. And by removing the invalid data from the cache, the client cache can always fill the cache of data with valid values.

In addition, the data that is found to be invalid data as a result of the comparison is removed from the cache to wait for retransmission through the data carousel.

Therefore, according to the present invention, it is possible to provide a fast response speed to a user by utilizing a cache according to a user's pattern instead of retransmitting a carousel repeatedly transmitted when necessary.

As described above, if data is managed according to the present invention, it is possible to effectively manage data whose effectiveness of information varies with time due to the characteristics of a medium called television. That is, data transmitted through the carousel may invalidate data stored in the cache as time passes. Therefore, according to the present invention, by including the descriptor including the valid time information in the broadcast signal and transmitting, it is possible to effectively manage the characteristics of the data.

(2) an apparatus for processing a digital broadcast signal including valid time information

A digital broadcast receiver for processing a digital broadcast signal including a "valid_time" descriptor defining valid time information for data transmitted according to the present invention will be described below.

3 is a diagram illustrating an example of a digital broadcast receiver configured to process a digital broadcast signal including valid time information of data transmitted according to the present invention.

The configured digital broadcast receiver includes a tuner unit 301, a demodulator 302, a demultiplexer 303, an A / udi decoder V, and a display part. 305), application manager 306, channel manager 307, SI decoder 308, SI database 309, carousel decoder 310 ), An application database 311, an NVRAM 312, a controller 313, and the like, and may be externally connected to a descrambling module 314. .

The digital broadcast receiver may be, for example, a digital television receiver. In this case, the digital television receiver may receive and process audio / video data and a descriptor defining valid time information of the data transmitted according to the present invention.

The tuner 301 may receive an airwave or cable digital television signal through an antenna, and transmit the received signal to the demodulator 302. In this case, the tuner 301 may be controlled by the channel manager 307 and report the result and strength of the signal received by the control to the channel manager 307.

The demodulator 302 may demodulate the broadcast signal tuned and received by the tuner 301 and transmit the demodulated signal to the demultiplexer 303. In this case, the demodulator 302 may perform 64 or 256 VSB (vestigial side band) demodulation when the signal received from the tuner 301 is an over-the-air broadcast signal. In the case of a signal, 64 or 256 quadrature amplitude modulation (QAM) demodulation may be performed.

The demultiplexer 303 may demultiplex the broadcast signal demodulated by the demodulator 302. That is, the demultiplexer 303 may filter data related to audio, video, and data broadcasting from input transport stream packets. In this case, the demultiplexer 303 may also filter a descriptor defining valid time information of the transmitted data in accordance with the present invention.

That is, the demultiplexer 303 may demultiplex the received broadcast signal under the control of the SI decoder 308 and / or the carousel decoder 310. For example, the demultiplexer 303 may demultiplex tables including audio, video and data broadcast related data from transport stream packets as described above. In this case, the demultiplexing unit 303 may perform the demultiplexing by inspecting a header part common to each received table.

That is, the demultiplexer 303 may create a section of a table for A / V broadcasting service and transmit it to the SI decoder 308, and transmits carousel data for data broadcasting service according to the present invention. A table section may be generated by filtering and transmitted to the carousel decoder 310.

The demultiplexer 303 may demultiplex an A / V transport stream packet under the control of the channel manager 307. Accordingly, when the A / V PID (Packet IDentifier) of the corresponding virtual channel is set, the demultiplexer 303 demultiplexes the elementary stream of the A / V to A / V. Each may be transmitted to the decoder 304.

The A / V decoder 304 may receive the A / V elementary stream packets from the demultiplexer 303 and decode them in a manner such as MPEG-2 or AC3. The A / V decoder 304 may transmit and decode the decoded A / V data to the display unit 305 in synchronization with a video display processor (VDP).

The display unit 305 may output A / V data decoded and received from the A / V decoder 304 through a screen in the case of an audio signal through a screen in the case of a video signal. . In this case, when the data decoded and received from the decoder 304 is a video signal and is output through a screen, the display unit 305 may be controlled by OSD (On Screen Display) graphic data.

The application manager 306 may receive a viewer's or user's settings and respond to viewer requests with a Graphical User Interface (GUI) on the display.

That is, the application manager 306 may receive the decoding state from the A / V decoder 304 and control the display unit 305 with the OSD. In this case, the application manager 306 may manage an application status and a database, and manage and control an OSD related to data broadcasting.

In addition, the application manager 306 may control the channel manager 307 to perform channel related operations (channel map management and SI decoder operation). In addition, GUI control, user demands, and television system state of the entire television can be stored and restored in NVRAM (or flash memory) 312.

The channel manager 307 may manage a channel map and control the tuner 301 and the SI decoder 308 to respond to the channel request of the viewer. The channel manager 307 receives a parsing request and a result of a channel related table of a channel to be tuned to the SI decoder 308, and updates the channel map based on the received result. The A / V PID may be set in the demultiplexer 303 to request a decoding.

The SI decoder 308 is an SI control module that parses a table section included in a broadcast signal and may perform a slave operation under the control of the channel manager 307.

That is, the SI decoder 308 may control the demultiplexer 303 to parse a table section included in the broadcast signal. That is, the SI decoder 308 may set the PID for the table in the demultiplexer 303 to create the table section.

The SI decoder 308 may receive and parse a PSI section made by the demultiplexer 303 for an MPEG-2 system or a PSIP section made by the demultiplexer 303 for an ATSC. The SI decoder 308 may store the parsed information in the SI database 309.

In this case, the SI decoder 308 may parse the data of the actual section data that is not filtered or not by the demultiplexer 303, that is, read all of them, and record the data in the SI database 309. have.

The carousel decoder 310 may receive and parse data broadcast related data transmitted from the demultiplexer 303, for example, descriptors of valid time information of the transmitted data according to the present invention.

The carousel decoder 310 may store the parsed data in the application database 311 and may monitor whether the carousel decoder 310 is updated. Therefore, when an update situation occurs, the carousel decoder 310 may play a role of always keeping the information stored in the application database 311 up to date through reinterpretation of the corresponding part.

The carousel decoder 310 may perform a slave operation like the SI decoder 308 under the control of the channel manager 307.

In addition, the digital television receiver may comprise a descrambling module 314. In this case, the descrambling module 314 may be involved in demodulation of the digital broadcast signal received through the tuner unit 301. That is, when the descrambling module 314 transmits data related to the demodulation to the digital television receiver, the control unit 313 in the digital television receiver receives the data and receives a signal capable of controlling the received digital broadcast signal. It may be generated and transmitted to the demodulator 302. The demodulator 302 may demodulate the signal according to the control signal and decode the same through the above-described process.

In this case, the descrambling module 314 may be, for example, a cable card in connection with cable broadcasting, and may be a smart card in connection with satellite broadcasting.

As described above, according to the present invention, a digital broadcast signal including valid time information of data transmitted may be received and processed.

(3) a method of processing a digital broadcast signal including valid time information

Hereinafter, a process of processing a digital broadcast signal including valid time information of data stored in a cache according to the present invention will be described.

4 is a flowchart illustrating an example of a method of processing a digital broadcast signal including valid time information of data stored in a cache according to the present invention.

First, according to the present invention, a digital broadcast signal including data and valid time information of the data stored in the cache is received (S401).

Parsing the received digital broadcast signal. That is, a "valid_time" descriptor including data included in the digital broadcast signal and valid time information of the data is parsed.

The parsed data and valid time information of the data in the "valid_time" descriptor are stored in a cache (S402).

After the storage, it is determined whether the client requests data or when it is time to check the validity of the data stored in the cache (S403).

If the determination result is that there is no data request from the client and it is not the time to check the validity of the data stored in the cache, the check is continued to check whether the request is present or the check time is reached.

However, if the determination result is a request for a data from the client or when it is time to validate the data stored in the cache, according to the present invention, a value indicating valid time information and a current time in the "valid_time" descriptor for each stored data and Comparison is made (S404).

As a result of the comparison, when the valid time information in the "valid_time" descriptor, that is, the value indicating how long the data is valid is greater than the value indicating the current time, the corresponding data stored in the cache is still valid data, and the client may determine the data again. The request is stored until it is time to determine whether it is time to validate the data.

However, as a result of the comparison, when the valid time information in the "valid_time" descriptor, that is, the value indicating how long the corresponding data is valid is smaller than the value indicating the current time, the corresponding data stored in the cache may be determined to be invalid data. . Therefore, the cache may remove the data from the cache (S405). And it can wait for retransmission for the removed data.

According to the digital broadcast signal and the method and apparatus for processing the signal according to the present invention as described above,

First, there are much more choices for the client cache.

Second, there is an effect that can significantly reduce the response time (response time) for the client request.

Third, there is an effect that can effectively manage the cache in the middleware.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (14)

In a digital broadcast signal, The broadcast signal is transmitted through a data carousel, The data carousel has at least one control layer (s) including tables including control information to describe at least one group, The tables are modules in a data carousel using a mi (ModuleInforByte) field containing a loop of descriptors containing pointers pointing to locations of DownloadDataBlock (DDB) messages. Include a descriptor that points to a DownloadInfoIndication (DII) message to The DII (DownloadInfoIndication) message includes a valid time information (valid time information) for the transmitted data. The method of claim 1, The valid time information is defined by a message descriptor in the DII message. The method of claim 1, The valid time information is defined in module units. The method of claim 1, The valid time information is defined by using any one of a second, a global positioning system (GPS) time, or a time stamp. The method of claim 1, The valid time information is information indicating how long the corresponding data stored in the cache is valid. In the method for processing a digital broadcast signal, Parsing data and valid time information for the data; Storing the parsed data and valid time information for the data in a cache; And When the client requests data or validates the data stored in the cache, if the valid time information value for the data stored in the cache is smaller than the value indicating the current time, the data is removed from the cache. A method comprising the steps of. The method of claim 6, And requesting and receiving a retransmission for the removed corresponding data. The method of claim 6, In the removing step, if the valid time information value of the data stored in the cache is larger than the value indicating the current time, the data is determined to be valid data and stored as it is. In a digital broadcast receiver, A tuner unit for tuning and receiving a digital broadcast signal; A demodulator for demodulating the received broadcast signal; A demultiplexer configured to filter a message descriptor including the demodulated data received and valid time information of the data; A parser for parsing the filtered and received message descriptor; A memory unit for storing the received data and the parsed message descriptor information; And And a controller configured to control the memory unit by determining validity of data using the parsed message descriptor information. The method of claim 9, The control unit compares the parsed message descriptor information with a value representing a current time in determining the validity of the data. The method of claim 10, The controller may determine that the corresponding data is invalid when the parsed message descriptor information is smaller than a value indicating a current time, and control to remove the corresponding data from the memory unit. The method of claim 11, And the controller controls to request retransmission of the removed data after the removal. The method of claim 10, The control unit determines that the parsed message descriptor information is larger than a value indicating a current time when the comparison result indicates that the data is valid and controls to store the data as it is. The method of claim 13, The controller, if it is determined that the data is valid, characterized in that the device does not request retransmission of the data.

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