KR20070030431A - Data structure and method for charged mobile-type broadcasting - Google Patents

Abstract

The present invention relates to a data structure and a service method for a pay mobile broadcast service. In particular, the present invention scrambles and transmits a phase reference symbol (PRS) of a synchronization channel in a signal for a pay mobile broadcast service. The mobile broadcast receiver capable of pay mobile broadcast service descrambles the scrambled PRS of the synchronization channel in the signal for the pay mobile broadcast service, and decodes the de-paid mobile broadcast service based on the descrambled PRS. Therefore, the present invention enables to provide high-quality services to the paid service subscribers even in the shaded area without disturbing the free service users.

Paid, Scrambled, PRS, Terrestrial DMB

Description

Data structure and method for charged mobile broadcasting service {Data structure and method for charged mobile-type broadcasting}

1 is a diagram showing the structure of a typical DMB transmission frame

2 illustrates a structure of a DMB transmission frame according to an embodiment of the present invention.

3 is a schematic structural block diagram of a transmitter for a paid DMB service according to an embodiment of the present invention

4 is a view showing a modification of the PRS according to the key value generation and key value according to the present invention

5 is a schematic diagram showing the relationship between a paid and free transmitter and receiver according to the present invention

6 is a flowchart illustrating operations for a paid DMB service according to an embodiment of the present invention.

Explanation of symbols for main parts of the drawings

301: source encoder 302: channel encoder

303: differential encoder 304: PRS generator

305: sync signal insertion unit 306: reverse frequency converter

307: NULL inserter 308: air wave signal generator

309: key generator 310: PRS processing unit

311: CAS signal processing unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile broadcast receiver, and more particularly, to a data structure, a method, and a mobile broadcast receiver using the same for a paid DMB service in a terrestrial digital multimedia broadcasting (DMB) receiver.

Digitalization of broadcasts has also affected existing analog radio broadcasts, which has led to the advent of digital radio broadcasts. In addition to the existing voice radio services, digital multimedia broadcasting (DMB) services including data transmission and multimedia services are now possible.

The terrestrial DMB service adopted in Korea is based on Eureka-147 Digital Radio Broadcasting (DAB), adopted as the European terrestrial radio standard. Added to improve multimedia broadcasting performance, RS codes (Reed-Solomon Code) and convolutional interleaver that are robust against burst errors that may occur on a transmission channel are added.

Therefore, the DMB service is robust against noise and distortion on a transmission channel, has a high transmission efficiency, and has various advantages of enabling various multimedia services.

In addition, the DMB transmission channel is a wireless mobile reception channel, and the amplitude of the received signal is not only time-varied, but also the Doppler Spreading of the spectrum of the received signal occurs due to the influence of the mobile receiver. . In consideration of the transmission and reception in such a channel environment, the DMB transmission scheme is based on Orthogonal Frequency Division Multiplexing (OFDM). Since the OFDM scheme uses a plurality of multicarriers, it is very resistant to ghosts generated by the multipath channel, and channel estimation based on a pilot signal is easy.

Although the Eureka-147 was created for digital audio broadcasting (DAB), the Eureka-147 is also used as a technology for terrestrial DMB that uses a narrow frequency bandwidth of 2 MHz to serve a video of a small screen size. In other words, the Eureka-147 system has a packet or stream mode that can be extended to transmit multimedia data. Therefore, the existing terrestrial DAB system can be used to transmit multimedia data with minimal changes.

In the Eureka-147 system, one broadcast service may be configured with a plurality of service components, and multiple broadcasts may be multiplexed and transmitted through about 2Mhz frequency band.

That is, the Eureka-147 system transmits data through repetitive transmission of a unit structure called a frame. The transmission frame is a synchronization channel (SYNC) for signal synchronization and actual service data, as shown in FIG. 1. A main service channel (MSC) and a fast information channel (FIC) through which configuration information of a data channel transmitted through the MSC is transmitted.

The synchronization channel has a certain form defined to recognize that the DMB receiver is the beginning of the frame, and carries information for decoding in digital communication. That is, the synchronization channel is composed of a null symbol for transmitting no signal and a phase reference symbol (PRS) for ?? / 4-DQPSK modulation and demodulation.

The MSC is composed of one or more Common Interleaved Frames (CIFs), and is used for transmitting broadcast services (ie, video services, audio services, and data services) to be actually broadcast. Since data must be transmitted without error in this channel, error correction data other than the actual data is transmitted together. In other words, video services, audio services, and data services are transmitted to the MSC. In the FIC, the actual data is transmitted to which channel in the MSC and other necessary information.

In the FIC, error correction data other than the CRC is not transmitted because it is intended for fast information transfer. The FIC is composed of a plurality of FIBs, and is used for transmitting various information for receiving a broadcast service.

In this case, the synchronization channel, the FIC, and the MSC part are composed of a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols. For example, in transmission mode 1, the PRS of a synchronization channel is composed of one OFDM symbol, and the FIC and the MSC are each composed of three and 72 OFDM symbols. In this case, each OFDM symbol in one frame is differentially encoded based on the PRS.

That is, in the DMB transmitter, each service (audio, video, data service) is individually encoded for error prevention, interleaved in the time domain, and each service interleaved in the time domain is multiplexed and combined into an MSC, which is a data channel. . The multiplexed signal is interleaved in a frequency domain together with multiplexing configuration information (MCI) and service information (Service Informaton (SI)) transmitted to the control channel FIC. At this time, since information transmitted to the FIC does not allow time delay, time domain interleaving is not performed. The frequency interleaved bit stream is mapped to a differential quaternary phase shift keying (DQPSK) symbol and becomes an OFDM symbol through an inverse fast Fourier transform (IFFT). The OFDM symbol is modulated into an RF signal and transmitted.

In this case, since the terrestrial DMB service is required to provide multimedia services regardless of location, the installation of a gap filler for a shadow area of a city such as a building or a subway is very important for quality of service.

That is, the gap filler is installed in a shaded area where DMB service is difficult to receive by subways, dense buildings, and high-rise buildings, and the mobile broadcast receiver in the shaded area receives DMB service by receiving and retransmitting DMB service transmitted from a broadcasting station. It's a kind of relay device that makes it possible.

However, since terrestrial DMB service is basically a free service, the service provider has a lot of cost burden in securing a service area by installing a gap filler.

The present invention is to solve the above problems, an object of the present invention is to allow the user who wants to receive the DMB service in the service shadowed area, when receiving the retransmitted signal through the gap filler pay the fee and receive the DMB service data It is to provide a structure, a method, and a mobile broadcast receiver using the same.

In order to achieve the above object, a transmission frame of a signal for a pay mobile broadcast service in a data structure for a pay DMB service according to an embodiment of the present invention,

A synchronization channel consisting of a NULL symbol and a scrambled phase reference symbol;

A main service channel (MSC) through which actual service data is transmitted; And

The fast information channel (FIC) through which the configuration information of the data channel transmitted through the MSC is transmitted is configured between the synchronization channel and the MSC.

Method for a pay mobile broadcast service according to the present invention,

(a) scrambled and transmitting a phase reference symbol (PRS) of a synchronization channel in a transmission frame for a pay mobile broadcast service according to a key value;

(b) determining whether a pay mobile broadcast service is available if a mobile broadcast service is received;

(c) if it is determined in step (b) that the pay mobile broadcast service is possible, determining whether the received mobile broadcast frame is a frame for the pay mobile broadcast service; And

(d) If it is determined as a frame for pay mobile broadcast service in step (c), the scrambled PRS in the frame is descrambled according to the key value, and each OFDM of the FIC and MSC in the frame based on the descrambled PRS. And differentially decoding the symbols.

In step (a), the gap filler installed for the pay mobile broadcasting service retransmits a phase reference symbol PRS of the synchronization channel in the frame according to a key value.

In the step (a), a broadcast station providing a mobile broadcast service delays and transmits a phase reference symbol (PRS) of a synchronization channel in a frame according to a key value for a pay mobile broadcast service.

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.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. At this time, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, by which the technical spirit of the present invention and its core configuration and operation is not limited.

The term used in the present invention was selected as a general term widely used as possible at present, but in some cases, the term is arbitrarily selected by the applicant, in which case the meaning is described in detail in the description of the invention, the name of a simple term The present invention is to be understood as the meaning of the term rather than the present invention.

First, the present invention defines a gap filler installed for paying DMB service for convenience of description, a paid gap filler, and a gap filler installed for existing free service, as a free gap filler. In addition, users of mobile broadcast receivers that can use retransmitted signals from paid gap fillers as well as free gap fillers and broadcasting stations are called paid DMB service users, and users of mobile broadcast receivers who cannot use retransmitted signals from paid gap fillers are users of free DMB service users. It is defined as

In this case, the user of the mobile broadcast receiver may register as a paid DMB service user in advance, or select whether to receive a retransmitted signal from the pay gap filler without additional registration (that is, subscription), and, if selected, according to a preset condition. You may be charged a fee. Here, the preset conditions may be various, for example, the viewing time of the DMB service retransmitted in the pay gap filler. In this case, when the user selects the reception of the retransmitted signal from the pay gap filler, the pay DMB service user becomes a user.

If the user is registered as a paid DMB service user in advance, the user may use the paid gap filler's DMB service for a fee or charge a fee only when using the paid gap filler's DMB service. In the latter case, it is preferable to allow the user to select whether to receive the retransmitted DMB signal in the pay gap filler through the mobile broadcasting receiver as in the method of using the paid DMB service of the non-subscriber. In this case, information such as fee information and whether or not to pay may be provided to the user through a corresponding mobile broadcast receiver in the form of text or sound. On the other hand, when manufacturing a mobile broadcast receiver can be produced by distinguishing between free and free. In this case, it is better to sell the receiver with a differential price.

In the present invention, a mobile broadcast receiver is subscribed to a paid DMB service according to an embodiment, and a fee is set as an embodiment.

In the paid gap filler installed to charge DMB service of the present invention, by changing the frame structure at the time of retransmission of the signal transmitted from the broadcasting station, the paid DMB service user has a high quality DMB service in a shadow area such as a building or subway. To receive.

That is, the free gap filler simply retransmits a signal transmitted from a broadcasting station without changing the frame structure, and the paid gap filler changes and retransmits the frame structure so that only the paying user can use it.

In particular, when the pay gap filler of the present invention retransmits the DMB service transmitted from the broadcast station, it is characterized in that the retransmission by changing the synchronization channel interval of the received DMB transmission frame.

Therefore, the user of the free DMB service can use only the DMB service transmitted from a broadcasting station or a free gap filler, so that the DMB service cannot be used in the shadow area or the low quality DMB service is provided.

On the other hand, users of the paid DMB service can use all of the DMB services transmitted from broadcasting stations, free gap fillers, and paid gap fillers, so that they always receive high-quality DMB services regardless of the shadow area. That is, the existing free DMB service user does not interfere with receiving a signal transmitted from a gap filler for a broadcasting station or a free DMB service, and the paid DMB service user can receive a high quality DMB service in a shadow area.

On the other hand, the mobile broadcast receiver finds the start of the frame by finding the NULL symbol of the synchronization channel in the transmission frame, and then locates the PRS. In addition, differential decoding of signals that are differentially encoded in a predetermined order based on the PRS is performed to recover necessary information. Therefore, since the PRS in each frame serves as a reference for differential decoding, it is very important to accurately locate the PRS. In addition, the PRS may be used to recover an integer multiple of the frequency error between the carrier frequency of the received signal and the carrier frequency in the receiver. In addition, the correlation between the received PRS and the reference PRS generated in the receiver can be obtained to determine the state of the transmission channel of the signal. Fast Fourier Transformation) region can be determined. Therefore, the contents of the PRS are promised in advance between the transmitter and the receiver. If the promise is not fulfilled, normal reception is impossible at the receiver.

Accordingly, in the pay gap filler of the present invention, as shown in FIG. 2, the PRS of the synchronization channel is scrambled differently according to a key value and retransmitted according to an embodiment.

In this case, the key value is transmitted to the paying DMB signal transmitter and receiver through a mobile network or a communication network such as the Internet.

That is, the PRS transmitted after the null symbol by the broadcasting station and the PRS scrambled by the pay gap filler are different information. Therefore, the mobile broadcast receiver cannot decode subsequent data symbols without decoding the scrambled PRS.

In this way, existing DMB service users are not interrupted in receiving signals transmitted from broadcast stations or gap fillers for free DMB services, and paid DMB service users can receive high-quality DMB services in shaded areas.

In the present invention, if the receiver is subscribed to the paid DMB service, the synchronization channel can decode both the DMB frame having the NULL symbol + PRS structure and the DMB frame having the NULL symbol + scrambled PRS structure, and the terminal is not subscribed to the paid DMB service. In this embodiment, the synchronization channel is controlled to enable decoding only for DMB frames having a NULL symbol + PRS structure.

3 is a block diagram illustrating an embodiment of a transmitter for transmitting a transmission frame for a paid DMB service according to the present invention, which may be a broadcasting station or a pay gap filler.

3 shows a broadcast station as an embodiment, in which case the source encoder 301, the channel encoder 302, the differential encoder 303, the PRS generator 304, the synchronization signal inserter 305, the inverse frequency converter 306 ), A NULL inserter 307, an over-the-air signal converter 308, a key generator 309, and a PRS processor 310.

The source encoder 301 compresses the DMB service signal to reduce the amount of information and outputs the information to the channel encoder 302. The compressed DMB service signal arrives at the receiver through a transmission channel, which is distorted due to interference of an adjacent signal while passing through the transmission channel. Accordingly, the channel encoder 302 performs channel encoding on the output signal of the source encoder 301 so that the receiver can compensate for such distortion.

The output of the channel encoder 302 is differentially coded by the differential encoder 303, where the reference signal is a PRS generated by the PRS generator 304. That is, each data symbol of FIC and MSC in one frame is differentially encoded based on the PRS.

The differentially encoded signal is output to the synchronization signal inserter 305. The synchronization signal inserter 305 inserts the scrambled PRS outputted from the PRS processor 310 into the front end of the differentially encoded signal and outputs the scrambled PRS to the inverse frequency converter 306.

The inverse frequency converter 306 converts a signal in the frequency domain into which the scrambled PRS is inserted, converts it into a time domain by performing an Inverse Fast Fourier Transform (IFFT), and then outputs it to the NULL symbol inserter 307. The NULL symbol inserter 307 inserts a NULL symbol after the PRS and outputs the null symbol to the over-the-air signal converter 308. The over-the-air signal converter 308 converts the DMB service signal including the NULL symbol into an RF signal and then transmits the RF signal through a transmit antenna.

Next, the operation of the PRS processor 310 will be described in more detail.

That is, the PRS processor 310 scrambles the PRS generated by the PRS generator 304 differently according to the key value generated by the key generator 309 and outputs it to the synchronization signal inserter 310.

The key generator 309 generates different key values according to the received Conditional Access System (CAS) information and outputs different key values to the PRS processor 310.

The CAS is a system for a broadcast (communication) service provider to manage a user who uses a paid DMB service and charge a user fee. The CAS controls a key value generation of the key generator 309.

4 illustrates an example of a PRS in which scrambles vary according to key values generated by the key generator 309.

That is, if the generated key value is key1, the PRS processor 310 outputs the PRS generated by the PRS generator 304 to the sync signal inserter 305 without modification.

However, if the key value is key2, the PRS is delayed by one sample and the key is delayed by two samples. That is, the PRS is delayed by the key value and output to the synchronization signal inserting unit 305. In this case, the free mobile broadcast receiver does not know the content of the modified PRS and thus cannot receive normal decoding on the received DMB service signal.

The key value generated by the key generator 309 varies according to the CAS information, and the same key value should be used to descramble the scrambled PRS according to the key value in the receiver. Therefore, the CAS information is transmitted to another transmission channel via the CAS signal processor 311 and the antenna. Accordingly, the pay mobile broadcast receiver generates the same key value used by the transmitter from the CAS information to descramble the scrambled PRS. Therefore, normal decoding is performed on the received pay DMB service signal.

Here, the transmission channel through which the CAS information is transmitted may be a general wireless network or may be a communication network such as a mobile wireless network or the Internet.

If the transmitter that scrambles and transmits the PRS is a pay gap filler other than a broadcasting station, a key value may be generated from the CAS information, and the scrambled PRS in the transmission frame may be retransmitted. That is, the process of source coding, channel coding, differential coding, synchronization signal insertion, inverse frequency transformation, and NULL symbol insertion are omitted.

FIG. 5 is a conceptual diagram illustrating a relationship between a transmitter, a CAS center for transmitting CAS information, a gap filler, and a receiver. In the free transmitter 501, a free DMB service signal is transmitted by a free mobile broadcast receiver 502 and a pay mobile broadcast receiver 503. Can be sent directly. In this case, if the current location is not the area where the free DMB service signal output from the free transmitter 501 is transmitted, that is, the shaded area, the free / free mobile broadcast receiver normally decodes and displays the received free DMB service signal.

In addition, the free transmitter 501 may transmit the free DMB service signal to the pay transmitter, that is, the pay gap filler 504. The pay transmitter 504 receives CAS information from the CAS center 507, generates a key value, scrambles the PRS according to the key value, and retransmits the PRS to the free broadcast receiver 505 and the pay mobile broadcast receiver 506. The CAS information is also transmitted to the pay mobile broadcast receiver 506.

At this time, if the current location is an area where the free DMB service signal output from the free transmitter 501 is not transmitted, that is, the shadow area, the free mobile broadcast receiver 505 does not normally decode the free DMB service signal transmitted from the free transmitter 501. can not do it. In addition, the pay DMB service signal transmitted from the pay transmitter 504 does not know the key value of the scrambled PRS and thus cannot be decoded normally. Accordingly, users of free mobile broadcast receivers cannot use DMB service or receive low quality DMB service.

In contrast, the pay mobile broadcast receiver may generate a key value according to CAS information transmitted from the CAS center, and thus, the pay DMB service signal transmitted from the pay transmitter 504 is normally decoded and displayed.

Therefore, the user of the pay mobile broadcast receiver can use all of the DMB services transmitted from the broadcasting station, the free gap filler, and the paid gap filler, so that a high quality DMB service is always provided regardless of the shadow area. That is, the existing free DMB service user does not interfere with receiving a signal transmitted from a gap filler for a broadcasting station or a free DMB service, and the paid DMB service user can receive a high quality DMB service in a shadow area.

6 is an operation flowchart for a paid DMB service according to the present invention. When a DMB service signal is received (step 601), it is determined whether a mobile broadcast receiver capable of paying DMB service is provided (step 602).

According to an embodiment of the present invention, if the mobile broadcast receiver is subscribed to a paid DMB service and the fee is a flat rate, the mobile broadcast receiver determines that the paid DMB service is possible. In addition, even if the mobile broadcast receiver is subscribed to the paid DMB service, if a fee is charged according to whether or not the user is watching the subscription or viewing time, first, the user is notified of the paid DMB service by text or sound, and whether the paid DMB service is provided. After selecting, it is good to control the paid DMB service only when it is selected. This can be applied even to non-subscribers.

If the mobile broadcast receiver is not subscribed to the paid DMB service, or if the paid DMB service is not selected in the question asking whether to receive the paid DMB service, it is preferable to control the paid DMB service not to be possible.

If it is determined in step 602 that the paid DMB service is not possible, the position of the NULL symbol is detected, and the next OFDM symbol is differentially decoded based on the PRS following the detected NULL symbol (step 605).

If it is determined in step 602 that the paid DMB service is not possible and the transmission frame has the structure as shown in FIG. 2, the step 605 does not descramble the scrambled PRS and thus does not perform differential decoding on the OFDM symbol following the PRS. can not do it.

As described above, the mobile broadcast receiver which is not capable of the paid DMB service does not decode the DMB frame as shown in FIG. 2 and thus cannot use the paid DMB service.

On the other hand, if it is determined in step 602 that the paid DMB service is available, it is determined whether the demodulated DMB service signal is a signal transmitted from a broadcasting station or a free gap filler or a signal transmitted from a paid gap filler (step 603).

If the DMB frame received in step 603 is determined to be a signal transmitted from a broadcasting station or a free gap filler, the demodulated DMB frame is decoded in a conventional manner (step 605). In this case, the DMB frame structure is shown in FIG. 1, and since the PRS is not scrambled, differential decoding of OFDM symbols in FIC and MSC is normally performed based on the PRS.

If the demodulated DMB service signal is determined to be a signal transmitted from the pay gap filler, the mobile broadcast receiver knows the changed frame structure and key value and thus descrambles the scrambled PRS based on the key value (step 604). ). Then, the OFDM symbols in the FIC and the MSC are sequentially differentially decoded based on the descrambled PRS (step 605).

Therefore, in a region where a signal for a free service transmitted from a broadcasting station or a free gap filler and a signal for a paid service transmitted from a paid gap filler coexist, the conventional mobile broadcast receiver for free reception does not interfere with receiving a free DMB service. do.

The present invention is not limited to the above-described embodiments, and as can be seen in the appended claims, modifications can be made by those skilled in the art to which the invention pertains, and such modifications are within the scope of the present invention.

According to the data structure and the method for the paid DMB service according to the present invention described above, by changing the frame structure when transmitting the paid DMB service signal, and retransmitted, to the paid service subscribers without any interference to the free service user It enables to provide high quality service even in the shadow area.

In particular, when the paid gap filler retransmits the paid DMB service signal, the cost of installing the gap filler can be secured to some extent through the paid service, thus enabling the installation of the gap filler in the shadow area, resulting in the activation of the terrestrial DMB service. have.

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 (7)

The transmission frame of the signal for the pay mobile broadcasting service A synchronization channel consisting of a NULL symbol and a scrambled phase reference symbol; A main service channel (MSC) through which actual service data is transmitted; And And a high speed information channel (FIC) in which configuration information of a data channel transmitted through the MSC is transmitted is configured between a synchronization channel and an MSC. (a) scrambled and transmitting a phase reference symbol (PRS) of a synchronization channel in a transmission frame for a pay mobile broadcast service according to a key value; (b) determining whether a pay mobile broadcast service is available if a mobile broadcast service is received; (c) if it is determined in step (b) that the pay mobile broadcast service is possible, determining whether the received mobile broadcast frame is a frame for the pay mobile broadcast service; And (d) If it is determined as a frame for pay mobile broadcast service in step (c), the scrambled PRS in the frame is descrambled according to the key value, and each OFDM of the FIC and MSC in the frame based on the descrambled PRS. Method for a pay mobile broadcast service comprising the step of differential decoding the symbol. The method of claim 2, wherein step (a) A method for a pay mobile broadcast service comprising retransmitting a phase reference symbol (PRS) of a synchronization channel in a frame according to a key value in a gap filler installed for a pay mobile broadcast service. The method of claim 2, wherein step (a) And transmitting a delayed phase reference symbol (PRS) of a synchronization channel in a frame according to a key value in a broadcast station providing a mobile broadcast service according to a key value. The method of claim 2, A frame for a pay mobile broadcast service and a frame for a free mobile broadcast service are distinguished from each other by a synchronization channel. The method of claim 2, wherein step (b) The pay mobile broadcast service is characterized by determining whether the pay mobile broadcast service is possible by combining at least one of whether the mobile broadcast receiver is subscribed to the pay mobile broadcast service or the pay mobile broadcast service. Way. The method of claim 2, wherein step (d) And if it is determined that the frame is not for a pay mobile broadcast service, decoding the received mobile broadcast service without a PRS descrambling process.

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