KR100556388B1 - Method of discriminating transmission mode in DMB receiver - Google Patents

Abstract

The present invention relates to a method for determining a transmission mode in a DMB broadcast receiver. According to the present invention, in a DMB receiver for receiving a broadcast signal transmitted in any one of a plurality of transmission modes according to the DMB broadcast standard, Comparing a null symbol period obtained from the received signal with a null symbol period of each of the plurality of transmission modes according to the DMB broadcasting standard; and as a result of the comparison, among the null symbol periods of each of the plurality of transmission modes according to the standard. Determining a transmission mode corresponding to the null symbol period having the closest null symbol period, generating a mode lock signal by checking a reliability of the determined transmission mode, and determining the transmission mode according to the mode lock signal. By including the step of outputting the transmission mode, the user does not have to enter a separate mode information By itself determines the transmission mode in the group, this has the effect of transmission allows reliable information transmission mode required by the synchronization unit and the FEC (Foward Error Correction).

DMB, DAB, Euraka-147, Transmission Mode, Reliability Counter

Description

Method of discriminating transmission mode in DMB receiver {Method of discriminating transmission mode in DMB receiver}

1 is a block diagram showing the overall configuration of a DMB receiver including a transmission mode discriminator according to the present invention.

2 illustrates a method of obtaining a null symbol length in accordance with the present invention.

3 is a block diagram showing an internal configuration of a transmission mode discriminator according to the present invention.

-Explanation of symbols for the main parts of the drawing-

1: antenna 2: tuner

3: AGC 4: A / D converter

5: I / Q distributor 6: Transmission mode discriminator (detector)

7: signal synchronizer 8: OFDM demodulator

9: frequency reverse interleaver 10: channel divider 1

11: FIC decoder 12: FIC data decoder

13: time deinterleaver 14: convolutional decoder

15: energy descrambler 16: channel divider 2

       17 audio / data decoder 18 convolutional deinterleaver

       19: RS decoder 20: video decoder

The present invention relates to a DMB receiver, and more particularly, to a method of determining a transmission mode in a DMB receiver.

Digitization of broadcasts has also affected conventional analog radio broadcasts, speeding up the advent of digital radio broadcasts. In addition to the conventional voice radio service, digital multimedia broadcasting (DMB), which includes data transmission and multimedia services, is enabled. Digital multimedia broadcasting is resistant to noise and distortion on a transmission channel, has a high transmission efficiency, and has various advantages of enabling various multimedia services.

This digital multimedia broadcasting (DMB), adopted in Korea, is based on the Eureka-147 digital radio broadcasting (DAB), which has been adopted as the European terrestrial radio standard.

Added to the DAB to improve multimedia broadcasting performance, RS codes and convolutional interleavers that are robust to burst errors that may occur on a transmission channel are included.

The two additional blocks are applied to the DAB Ensemble input signal at the transmitter and provide an error rate low enough for video service even in a mobile receiving environment.

The transmission channel of the DMB broadcast is a wireless mobile reception channel, and the amplitude of the received signal is not only time-varying but also the Doppler Spreading of the received signal spectrum due to the influence of the mobile receiver. Occurs.

In addition, the DMB transmission signal is transmitted at a much smaller signal strength than the conventional analog radio broadcast signal, and the signal strength of the actual received signal is very small considering the mobile reception such as in a car in a severe fading channel environment such as downtown. .

In consideration of the transmission and reception in such a channel environment, the DMB transmission method is based on Orthogonal Frequency Division Multplexing, and corrects an error occurring in a transmission channel by interleaving a signal in a time domain and a frequency domain. Do it.

In addition, according to the DMB standard, a transmission mode in broadcast transmission is divided into transmission mode I, mode II, mode III, and mode IV so that the transmission mode can be properly responded to according to the purpose and environment. To lose.

Each transmission mode is different in the number of carriers, orthogonal signal multiplexing, null symbol length, symbol length and frame length.

That is, since the configuration of the signal varies depending on the transmission mode of the transmitted signal, the transmission mode must first identify the transmission mode in order to demodulate the signal. Only then, accurate frame synchronization and OFDM symbol synchronization signals can be obtained, so the confirmation of the transmission mode plays a very important role in the reception process of the DMB receiver.

Conventionally, in order to check the transmission mode, when a user selects a specific broadcast, the transmission mode corresponding to the broadcast is selected through an external input device, or the transmission mode corresponding to each broadcast is stored in the receiver internal memory. When the user selects a broadcast, a method of reading the corresponding transmission mode is used.

However, this method is troublesome to the user, and there is a problem that demodulation and decoding of the correct signal are not performed when the transmission mode is changed.

In addition, storing the transmission mode in advance in the memory does not adequately cope with broadcast conditions, and there is a problem due to the limitation of the capacity of the memory.

Accordingly, an object of the present invention is to solve the problems of the prior art, and to automatically determine the transmission mode of the received DMB signal by using the null symbol period of the transmitted frame synchronization signal. To provide a way to improve.

The transmission mode determination method in the DMB receiver according to the present invention for achieving the above object, the transmission mode in the DMB receiver for receiving a broadcast signal transmitted in any one of a plurality of transmission modes according to the DMB broadcast standard In order to determine, comparing a null symbol period obtained from the received signal with a null symbol period of each of the plurality of transmission modes according to the DMB broadcasting standard, and as a result of the comparison, each of the plurality of transmission modes according to the standard Determining a transmission mode corresponding to the null symbol period having the closest null symbol period among the null symbol periods of the signal generator; and generating a mode lock signal by checking the determined transmission mode with reliability, and generating the mode lock signal. And outputting the determined transmission mode according to the signal.

The reliability checking step may include comparing a value corresponding to the determined transmission mode with a value according to a previously stored transmission mode, increasing the reliability value if the two values are the same as the result of the comparison; And generating a mode lock signal when the reliability value is greater than or equal to a predetermined value.

Hereinafter, a configuration and an operation according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram showing the overall configuration of a DMB receiving system including a transmission mode discriminator according to the present invention.

As shown in FIG. 1, the DMB receiver includes an antenna 1 for receiving a transmitted broadcast signal, and a pass-band signal of an intermediate frequency for which a received signal input to the antenna 1 is desired. AGC that multiplies the tuner 2 for conversion to and the gain value calculated according to the reference signal size in order to keep the size of the signal input to the A / D converter 4 to be subsequently input to the tuned signal. (Automatic Gain Control) unit 3, an A / D converter 4 for sampling and converting the predetermined size signal into a digital signal, and a complex signal of the converted digital signal (Complex Signal) I / Q divider 5 for restoring the real part of the receiver to a complex signal, a transmission mode discriminator (detector) 6 according to the present invention for detecting the transmission mode of the received signal, and unnecessary protection After removing the Guard Interval, the FFT (Fast Fourier Transform) An OFDM demodulator 8 for converting a signal in the inter-domain into a frequency domain, and a signal synchronizer for extracting information necessary for synchronization in a time / frequency domain of the signal using the input and output signals of the OFDM demodulator 8 ( 7), a frequency inverse interleaver (9) for restoring the positions of sub-carrier signals interleaved at the transmitting end, and a channel divider (1) separating the FIC channel as the control channel and the MSC channel as the data channel. 10, a FIC decoder 11 for receiving the separated FIC channel and separating information necessary for decoding an MSC channel, and 16 logical frames interleaved in a transmitter by receiving the MSC channel. A time deinterleaver 13 for restoring the data back to the original frame order, and a path for correcting a random error occurring in a transmission channel among the time deinterleaved MSC channels. A convolutional decoder 14, an energy descrambler 15 for restoring original data through the corrected data, and whether the transmitted data channel is an audio / data signal for a DAB service or not. A channel divider 2 (16) for discriminating whether the video signal is a video signal, an audio / data decoder (17) for decoding the audio / data signal for the separated DAB service, and a signal for the DMB service; A convolutional de-interleaver 18 for arranging additional interleaved data in the original order, an RS decoder 19 for restoring RS-encoded data at the transmitting end, and a DMB service; It consists of a video decoder 20 for reconstructing a video signal for an FIC data decoder 12 for decoding the separate data transmitted through the FIC channel.

The structure and operation of the transmission mode discriminator 6 according to the present invention for obtaining accurate frame synchronization and OFDM symbol synchronization signal among the configuration of the DMB receiver will be described below.

First, in order to determine a transmission mode of a received signal, different characteristics of each mode should be used. According to the present invention, a transmission mode is determined through a null symbol period, which is information that can be obtained without a synchronization signal of a signal.

This will be described with reference to the accompanying drawings.

2 is a diagram illustrating a method for obtaining a null symbol period according to the present invention.

As shown in FIG. 2, a window is taken for two consecutive sections to obtain a ratio W1 / W2 of the average value of the two windows.

In this case, the ratio of the two window average values has a maximum value at the beginning of the null symbol and a minimum value at the end of the null symbol.

That is, since the data of the null symbol section is 0, the data of the data symbols is divided by 0 at the beginning of the null symbol, so that the value represents the maximum value near infinity, and conversely, 0 is the data symbol at the end of the null symbol. This is divided by the same value, so the minimum value close to zero is the same.

Therefore, since the interval between the maximum and minimum values of the two window ratios becomes the null symbol interval, the length of the null symbol interval is known when this interval is obtained.

According to the present invention, the expected transmission mode is determined using the obtained null symbol period value, and the correct transmission mode found through the reliability check is found.

3 is a detailed block diagram illustrating a transmission mode discriminator in a DMB receiver according to the present invention.

As shown in FIG. 3, the transmission mode discriminator according to the present invention includes a plurality of comparators 61, a Mux 62, a reliability counter 63, and an OR gate 64.

The operation process of the transmission mode discriminator configured as described above is as follows.

The mode of the estimated null symbol period obtained by the method as shown in FIG. 2 is determined through the comparators 61.

In this process, the null symbol duration according to each transmission mode has 2656T (T = 1/2048000 sec) in Mode I, Mode 664T, Mode III 345T, and Mode IV 1328T according to the specification.

At this time, a mode decision is made so that the difference between the estimated null symbol period value and the mode value according to the standard is smaller. The boundary value for distinguishing each mode is the middle of the null symbol period of two modes adjacent to each other. Value.

That is, the null symbol periods are arranged in descending order of modes I, IV, II, and III, and the modes are determined according to the region to which the estimated null symbol period values belong using four boundary values, and the null symbol period values are transferred. You can also make judgments about when things are not.

The boundary values are as follows.

Threshold 1 (Thr1) = (2656 + 1328) T / 2 = 1992T

Threshold 2 (Thr2) = (1328 + 664) T / 2 = 996T

Threshold 3 (Thr3) = (664 + 345) T / 2 = 504T

Threshold 4 (Thr4) = (0 + 345T) / 2 = 172T

If the estimated null symbol period is greater than or equal to 1992T, then mode I, 996T or more, and less than 1992T, mode IV;

When the mode is determined in this way, the bit according to the corresponding mode has a value of 1 and the rest has a value of 0.

That is, if it is determined that the mode I, the 'mode 1' bit of Figure 3 has a value of 1, the 'mode 2', 'mode 3', 'mode 4' bit has a value of zero. If any one of 'mode 1', 'mode 2', 'mode 3', and 'mode 4' has a value of 1, the 'Mode En' bit is set to 1.

The values according to each mode are input to the mux 62, and in the mux 62, corresponding transmissions are performed according to a value having one of 'mode 1', 'mode 2', 'mode 3', and 'mode 4'. Export the mode value to the output.

That is, if 'mode 1' has a value of 1, 00 is the mode value, 01 is 'mode 2' has a value of 1, 10 is 'mode 3', and 11 is 'mode 4'. Will be exported.

When the mode value is determined to be reliable through the reliability checker 63, the mode value is transferred to the next block of the DMB receiver. The operation of the reliability checker 63 is as follows.

The mode value output through the mux 62 and the mode value stored before the delay 63a are compared through the comparator 63b. As a result of the comparison, if the value is the same, the counter 63c is increased, and if it is different, it is decreased.

When the value of the counter 63c reaches a certain value, the mode at this time is considered to be reliable, and the mode lock signal indicating that the mode is locked is changed from 0 to 1.

The delayer 63b and the counter 63c operate only when the Mode En value through the OR gate 64 to which the respective mode value is input is 1, in particular, the delayer 63b only when the value of the counter is 0. It works to accept new values.

This means that when the confidence in the current reference mode value falls, the new mode value will be used as the reference.

Through this process, when the transmission mode is determined and the mode lock signal is 1, the transmission mode discriminator no longer operates.

This is a method for reducing the power consumption of the DMB receiver, noting that the transmission mode is constant unless the broadcast channel is changed in the DMB receiver.

If the broadcast channel is changed, the entire DMB receiver is reset, and thus a new transmission mode may be found in the above manner.

As described above, the apparatus and method for determining a transmission mode in a DMB receiver according to the present invention has the following effects.

First, since the receiver can determine the transmission mode by the user without inputting additional mode information, it can reliably transmit the transmission mode, which is information required by the synchronizer and FEC (Foward Error Correction), without the user's hassle. It works.

Second, after the transmission mode determination is completed, the operation of the transmission mode determination block is stopped to reduce the power consumption of the DMB receiver.

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 examples, but should be defined by the claims.

Claims (4)

delete delete A plurality of comparators for comparing the estimated null symbol periods with a predetermined boundary value range and outputting the comparison result; A mux for outputting a bit signal for each transmission mode according to output signals of the plurality of comparators; An or gate receiving a signal output from the plurality of comparators and outputting a predetermined bit signal according to an output signal from one of the comparators; When receiving the predetermined bit signal from the or gate, the reliability checker for checking the reliability of the mode determination bit signal of the mux, and outputs a bit signal indicating that a certain mode is maintained according to the reliability. Apparatus for determining a transmission mode of a DMB receiver, characterized in that it comprises a. The method of claim 3, wherein The reliability checker includes: a delayer for delaying and outputting a bit signal of the mux; A second comparator for comparing the bit signal of the delayer with the bit signal of the mux; A counter for increasing a count when the comparison result of the second comparator is the same and outputting a signal indicating that a certain mode is maintained when the count value is equal to or greater than a predetermined value. Device.

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