KR20060101649A - Method of time-shift function in digital multimedia broadcasting a receiving set - Google Patents

Abstract

The present invention provides a method of providing a time shifting function in a digital multimedia broadcasting system. The present invention provides a method of providing a forward error correction encoding unit (FEC) that is error corrected and output to a final AV decoding stage when a request for using the time shifting function is received. A first step of feeding back and storing the output to a storage medium; A second step of checking whether a play request is received when the storage is started, and continuing to store the play request if it is not received, and determining whether storage space remains in a storage medium when the play request is received; And a third step of performing a cyclic read / write on the used area if the storage space remains, and a cyclic read / write on all the areas of the storage medium if the storage space remains. By providing a time shifting method in a digital multimedia broadcasting receiving apparatus, a time shifting function may be provided to a user by utilizing a free time and a free space that the bit deinterleaver does not handle the memory.

Digital multimedia broadcasting, time shift function, SDRAM

Description

Method of Time-Shift function in Digital Multimedia Broadcasting a receiving set}

1 is a conceptual block diagram of a digital multimedia broadcasting receiver including the present invention.

2 is a flowchart illustrating a process of performing a time transition function according to the present invention.

* Explanation of symbols for main parts of the drawings

19: bit reverse interleaver 25: RS decoder

26: A / V data decoder 28: memory

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital multimedia broadcasting receiver and, more particularly, to the bit deinterleaver when the bit deinterleaver does not access using a synchronous dynamic random access memory (SDRAM) allocated for the bit deinterleaver. The present invention relates to providing a time-shift function to a user by storing output data of an RS decoder in a memory area not used by a deinterleaver.

Digital multimedia broadcasting can be classified into terrestrial digital multimedia broadcasting and satellite digital multimedia broadcasting.

The terrestrial digital multimedia broadcasting provides audio and video services during movement based on an orthogonal frequency division multiplexing (OFDM) scheme.

The satellite digital multimedia broadcasting is based on the CDM (Code Division Multiplexing) method, which uses audio gaps and terrestrial gap fillers, which are used for resolving satellites and shadowed areas that do not receive radio waves directly from the satellites, to the audio and video. It is to enable the service.

Currently, the technical standard of satellite digital multimedia broadcasting adopted in Korea and Japan is the system defined by ITU and basically adopts CDM transmission method, and it provides CD (Compact Disk) quality and weather, traffic, video information using various channels. It provides new concept services of representative communication and broadcasting convergence.

The satellite digital multimedia broadcasting uses frequencies of the upper 13.824 to 18.883 GHz band and the lower 2.630 to 2.655 GHz and 12.21 to 12.23 GHz bands, and supports up to 64 channels. Korea and Japan use 32 channels each.

In addition, the satellite digital multimedia broadcasting has a wide coverage as a national broadcast, but the transmission channel is a wireless mobile reception channel, the size of the received signal is not only time-varying, but also the reception signal due to the influence of the mobile reception Doppler shift of the spectrum occurs.

In consideration of the transmission and reception under such a channel environment, the satellite digital multimedia broadcasting adopts the CDM method as a transmission method, and may correct an error occurring in a transmission channel by interleaving a time domain signal. It was made.

The CDM method multiplies the data to be transmitted by a pseudo noise signal having a transmission rate much faster than that of the data, thereby spreading and transmitting the frequency by narrow frequency signal interference (Narrow-). band interference), and it is possible to reduce the deterioration of reception performance due to the multipath through the receiver of the RAKE structure.

However, since the pilot channel, which is a control channel, contains information on interleaver size and convolutional coding rate, it must be demodulated.

In this case, in order to additionally provide a time transition function by using the above-mentioned digital multimedia broadcasting receiver, a method of providing the time transition function to a user by using the configuration of the conventional receiver as it is proposed.

An object of the present invention is to provide a method for providing a time transition function using an existing configuration without adding a new component in the digital multimedia broadcasting receiver.

In order to achieve the above object, the present invention provides a first step of feeding back and storing an output of a forward error correction coding unit (FEC) that is error corrected and output to a final AV decoding stage when a request for using a time transition function is received; ; A second step of checking whether a play request is received when the storage is started, and continuing to store the play request if it is not received, and determining whether storage space remains in a storage medium when the play request is received; And a third step of performing a cyclic read / write on the used area if the storage space remains, and a cyclic read / write on all the areas of the storage medium if the storage space remains. It provides a time transition method in the digital multimedia broadcasting receiving apparatus.

In this case, the determining whether the storage space remains in the second step is to find a position to start reading according to the reproduction request.

If the storage space remains in the third step, it is preferable to start reading from the beginning of the storage medium.

In addition, if there is no storage space remaining in the third step, it is preferable to start reading from the position where the oldest data among the stored data is stored.

In this case, the cyclic modulo read / write in the third step is characterized in that the storage medium is continuously read and written in order from the position where the reading is started.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

The same components as in the prior art are given the same names and the same reference numerals for convenience of description, and detailed description thereof will be omitted.

In addition, the terms used in the present invention was selected as a general term widely used as possible now, but in certain cases, the term is arbitrarily selected by the applicant, in which case the meaning is described in detail in the corresponding description of the invention, It is to be clear that the present invention is to be understood as the meaning of terms rather than names.

First, a preferred embodiment of a bit deinterleaver and a satellite digital multimedia broadcasting system using the same will be described with reference to the accompanying drawings. At this time, to avoid overlapping description, for convenience of explanation, the description will be made while comparing the conventional bit reverse interleaver with the bit reverse interleaver of the present invention.

The present invention feeds back and stores the output data of the RS decoder in the forward error correction coding part by using a free space not used by the bit deinterleaver during the spare time that the bit deinterleaver does not access the memory originally allocated for the bit deinterleaver. This is to provide a time transition function to the user.

1 is a conceptual block diagram of a digital multimedia broadcasting receiver including the present invention.

Looking at the reception process of the receiver, the received signal input to the antenna is converted into a baseband (tuner 10) in the tuner 10, the converted signal is maintained in a constant size of the signal to the A / D (12) For this purpose, the A / D 12 is converted into a digital signal through an automatic gain control unit 11 which measures the power of the received signal and multiplies the calculated gain value.

In this case, in order to demodulate a signal in the CDM transmission scheme, the acquisition of a pseudo-noise sequence used for signal spreading should be prioritized. This process involves two steps of acquisition and tracking of a signal. Is made of.

The division unit of the pseudonoise sequence is called a chip, and the signal acquisition is a process of securing signal synchronization within a half chip in a receiver, and is performed by a searcher 13. In addition, the signal tracking refers to fine synchronization of the found signal and is performed in the trackers 141 to 14n.

The synchronized signal is despread by multiplying the pseudo-noise sequence generated by the receiver through the despreaders 151 to 15n, and multiplying the symbol of the desired CDM channel by multiplying the WALSH code used to distinguish the CDM channels. Extract.

This process is performed in all the multiple paths found by the searcher 13, each of which is called a finger.

In this case, the frequency offset estimator 27 estimates the frequency offset for each finger, synthesizes it, and then feeds back the tuner to correct the frequency offset.

The symbols thus extracted are synthesized by the RAKE synthesizer 16. In this case, a method of improving reception performance may be improved by estimating and compensating a reception channel environment.

In this case, the RAKE synthesis in the RAKE synthesizer 16 is performed for all CDM channels to be demodulated, and then the pilot decoding consists of a pilot Viterbi decoder 18, a pilot deinterleaver 20, and a pilot RS decoder 22. The grandfather 30 extracts and decodes the pilot signal.

A forward error correction coder 40 composed of a bit deinterleaver 19, a Viterbi decoder 21, a byte deinterleaver 23, and an RS decoder 25 is passed through the data mode detector 24. To correct any errors in the data.

The error corrected data in the forward error correction encoder 40 is decoded through the A / V data decoder 26 and output.

In this case, satellite digital multimedia broadcasting is a CDMA-based system in which several data channels are received in parallel in time. Accordingly, the bit deinterleaver 19 is positioned at the front end of the forward error correction encoding unit 40 for error correction robust to burst errors of the wireless channel.

First, in the present invention, the SDRAM for the bit deinterleaver is used in the digital multimedia broadcasting receiver to provide the time shifting function, which is the additional function. In this regard, the SDAM will be described.

In the bit deinterleaver 19 used in the conventional satellite digital multimedia broadcasting system, a storage space of about 6.67 M bits per channel is required when the soft bit is 4 bits.

Therefore, when supporting 4 channels, about 26.67M bits are required. Currently commercially available memory (preferably SDRAM) usually has a memory capacity of at least 64M bits.

Therefore, in the case of having the memory capacity of 64M bits as an example, the free space of about 37.33M bits is in the memory 28 in this case.

In addition, the current bit deinterleaving method accesses the memory by bit deinterleaving only when the enable signal is high based on a symbol enable signal, and bit inverses when the enable signal is low. Since the interleaving is not performed, there is a spare time for accessing the memory 28 using this.

Therefore, it is possible to provide a time transition function to the user as an additional function by using the free space of the memory 28 and the free time without bit deinterleaving.

In the above-mentioned time-shift operation, a time-shift operation is performed so that a user may store content not visible for a predetermined time in a memory, then transition to the previous time and continue to miss content from that point in time. This is an additional function that can be added in addition to the digital multimedia broadcasting receiver.

For example, when a user requests a time transition function, the user receives the request and starts to feed back the data completed by RS decoding to the memory 28 and store it.

After the storage is started, the user waits for a playback request from the user and returns to the point where the time transition function is started for playback, that is, the operation time at which the storage is started, and outputs the stored data therefrom to provide a service to the user. By doing the above, the broadcast which has time shifted as a whole continues to be decoded and output by the AV decoding stage 26.

The feedback of the output of the RS decoder 25 is the least parity part in the forward error correction coding unit, which needs to be actually stored, and is the last end of the forward error correction coding unit to go to the AV decoding unit 26 which is the final output terminal. After the output data of the decoder 25 is stored in the memory 28 and a playback request is received by the user, the time shift function is directly transmitted from the memory 28 to the AV decoder 26 through a process to be described later. Implement

That is, as shown in FIG. 1, since the data is already forward error corrected, it is not necessary to transmit it to the AV decoding unit 26 again through the forward error correction coding unit when the reproduction request is made.

At this time, when storing the RS-decoded data in the memory 28, as described above, the bit deinterleaver 19 utilizes the spare time and the free space in which the memory 28 is not accessed.

Looking at the process of implementing the time transition function using the above-described conceptual building block of Figure 1, Figure 2 is a flow chart illustrating a process for providing a time transition function according to the present invention.

The time shifting function is an additional function, and in order to provide it, a user needs to use the time shifting function.

Therefore, it should be determined whether there is a request for using the time transition function by the user (step S10).

As a result of the determination, if there is no use request for the time transition function, the reception apparatus performs a general operation (S20).

However, as a result of the determination, when a request for using the time shifting function is received by the user, the receiving apparatus corrects the demodulated signal received through the antenna by the forward error correction coding unit and outputs the final AV terminal from the RS decoder 25 for display. Before this, the output of the RS decoder 25 is fed back to the bit deinterleaver memory 28 and stored in the memory (step S30).

While continuing to store in the memory 28, it continuously checks whether there is a play request of a broadcast whose time is requested by the user (step S40).

This is for determining whether to continue to store in the memory 28. If the playback request is not received, the storage is continuously stored in the memory 28.

Now when the check results a playback request is received, it compares the amount used in the memory 28 with how much space is available for storage in the memory 28, which is used to reproduce the time-shifted signal by the user. It is necessary to read the data stored at), in order to determine from which part to read from the beginning of the time transition (step S50).

As a result of the comparison, if the amount used in the memory 28 is larger than the space that can be stored in the memory 28, a cyclic modulo read / write is performed for the entire area of the memory 28 (S Step 60).

This is a case where the memory is continuously stored in excess of the capacity that can be stored in the memory 28. That is, the user requests the use of the time transition function to use the free time and free space of the memory 28 to perform the function. Although the storage is started, as described above, the capacity of the memory 28 is limited, and after the user requests the use of the time shift function, the user does not continue to play the playback request to watch the contents stored for the time shift function. In the case of writing only, the processing of the data which is continuously input even beyond the storage capacity is problematic.

In the present invention, in order to deal with this, the data continuously inputted after the capacity is overwritten is overwritten from the most recent data.

This is solved by increasing the capacity of the memory 28, but the time shifting function is an additional function. If the capacity of the memory 28 is additionally increased, the volume of the forward error correction coding unit is unnecessarily large and the chip size of the entire receiving system is increased. There is a problem that increases, the power consumption increases accordingly.

Therefore, in the present invention as described above, in order to implement the time shifting function, which is an additional function by using the free space of the memory 28, the free space of the memory 28 is used as much as possible. For this, it is inevitably handled by a cyclic modulo read / write method which overwrites the past data.

Therefore, when the read operation is performed, the most recent data is searched except for the portion to be overwritten, and the above described cyclic modulo read / write is performed to transmit to the AV decoder 26 for display and decoding.

This time, as a result of the comparison, if the amount used in the memory 28 is smaller than the space that can be stored, a cyclic modulo read / write is performed only for the area used in the memory 28 (step S70).

That is, the data stored in the memory 28 is read from the data stored in the past to the part where the data is read.

However, since data must be continuously input during the reading, the portion of the memory 28 read and output to the AV decoding unit 26 to be decoded is empty. The read broadcast data is read and written repeatedly.

At this time, since the data stored in the memory 28 does not need to go through the forward error correction encoder again when read by the user's reproduction request, it is immediately outputted to the AV decoder 26 for decoding.

When explaining the effect of the time transition method in the digital multimedia broadcasting system according to the present invention described above, the time transition function to the user by using the free time and the free space that the bit reverse interleaver does not access the memory in the digital multimedia broadcasting system By providing the efficient use of the memory and there is an effect that can provide a convenient service to the user.

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 (5)

A first step of feeding back and storing an output of a forward error correction coding unit (FEC) that is error corrected and output to a final AV decoding stage when a request for using a time shifting function is received; A second step of checking whether a play request is received when the storage is started, continuing to store the play request if it is not received, and determining whether storage space remains in a storage medium when the play request is received; And a third step of performing a cyclic read / write on the used area if the storage space remains, and a cyclic read / write on all the areas of the storage medium if the storage space remains. Method of providing a time transition function in the digital multimedia broadcasting receiver. The method of claim 1, And determining whether or not the storage space remains in the second step is to find a position to start reading in response to a playback request. The method of claim 1, And if the storage space remains in the third step, reading starts from the beginning of the storage medium. The method of claim 1, And if the storage space remains in the third step, reading starts from a location where the most recent data is stored among the stored data. The method of claim 1, In the third step, the cyclic modulo read / write is a method of providing a time shifting function in a digital media broadcasting receiver, in which the storage medium is continuously read / written in order from the position at which reading is started.

Images