KR19990065544A - Decoder device of digital broadcast receiver - Google Patents

Abstract

A soft decision value generator for outputting a soft decision value and a puncher signal by inputting the demapper output of the DVB-T receiver and the channel state information value of the channel state information generator, and the soft decision value and the puncher signal. A deinterleaver soft decision value, an inner deinterleaver for generating a reverse interleaver puncher signal, and a bitter video decoder for outputting a decode bit by inputting the deinterleaver soft decision value and a puncher signal. For Viterbi decoding, the Viterbi decoder used in other conventional systems can be used as it is.In this case, the calculation of the reliability value in generating a new soft decision value suitable for the input of the Viterbi decoder is performed by dividing the reliability interval. By inserting a section that generates a puncher signal, Viterbi decoding can be performed with better performance. A.

Description

Decoder device of digital broadcast receiver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoder device for a digital broadcast receiver. In particular, the channel state information (CSI) of a DVB-T (Digital Video Broadcasting Terrestrial) receiver without modifying a Viterbi decoder used in other existing systems is disclosed. The present invention relates to a decoder of a digital broadcast receiver configured to perform Viterbi decoding.

The DVB_T system is a terrestrial digital TV transmission system in Europe, and is currently being tested by several countries in Europe.

The DVB-T system uses a coded orthogonal frequency division multiplexing (COFDM) modulation scheme that transmits information on multiple carriers as a transmission scheme. The 2B mode with 1705 carriers and the 8817 mode with 6817 carriers, depending on the number of carriers. Divided into.

The DVB-T system transmits multiple carriers simultaneously at a low data rate to increase the period of one OFDM symbol when viewed on the time axis, and to provide a guard interval for each symbol, which is caused by the inter symbol interface (ISI) and the ghost. It has the advantage of improving system performance degradation.

The COFDM system has a strong characteristic for multipath fading channels because it is based on the above-mentioned contents, but another great feature is Viterbi decoding using CSI.

1 illustrates Viterbi decoding using CSI, which is generally used. The operation is as follows.

First, the received signal is de-mapped by the QAM receiver 11 and input to the metric operator 14.

For example, in case of 16QAM, one symbol is composed of four bits, so the output of the QAM demapper 12 is four bits.

Since the current soft decision is used, four values are output and input to the metric operator 14. Details of this are shown in US Pat. No. 5134635, which is used to calculate the metric, as well as the demapping 12 output as well as the CSI.

The metric calculator 14 calculates a metric using the input demapper 12 output and CSI information, and is calculated as follows.

If the signal 0 without noise is -1 and 1 is 1 and K is the number of bits constituting the symbol, the output of the demapper 12 is b (k). It looks like the following equation.

With y = -1

With y = +1

Here, the CSI is a power of a value obtained by dividing the transmitted pilot signal by the original pilot signal known to the receiver. In the case of 16QAM, k = 1 to 4.

m (k, 0) is the value representing the likelihood that the kth bit of the demodulated symbol is zero. Likewise, m (k, 1) is the value representing the likelihood that the kth bit of the demapped symbol is 1; to be.

The calculated values are input to the Viterbi decoder 15 as two metric values m (k, 0) and m (k, 1) and used for decoding.

Since the conventional Viterbi decoder is configured to receive only a puncher signal and one de-mapped data, as shown in FIG. 2, there is a problem that the conventional Viterbi decoder cannot be used.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a decoder device of a DVB-T receiver that allows a conventional Viterbi decoder to be used as it is even when decoding using channel state information of a DVB-T receiver. .

1 is a block diagram schematically illustrating a diterbi decoding apparatus using conventional channel state information (CSI).

2 is a diagram schematically showing a conventional Viterbi decoder.

Figure 3 is a block diagram schematically showing the overall system of the present invention.

4 is a detailed block diagram of the soft decision value generator of FIG.

5 is a diagram illustrating a method of determining a confidence value.

6 is a table showing soft decision values of 3 bit resolution.

Explanation of symbols for main parts of the drawings

10,20 antenna 14 metric calculator

11: QAM receiver 15,15 ': Viterbi decoder

21 tuner 22 OFDM demodulator

23: channel evaluator 24: equalizer

25 demapper 26 soft decision generator

27: Innerdie interleaver 28: Viterbit decoder

29: CSI generator 30: 'O' metric calculation unit

31: '1' metric calculation unit 32: the adder

33: code discriminating unit 34: reliability value generator

A decoder device of a DVB-T receiver for achieving the object of the present invention is a soft decision value and a puncher by inputting the demapper output of the DVB-T receiver and the channel state information value of the channel state information generator of the channel state information generator. A soft decision value generator for outputting a signal; an inner deinterleaver for generating a reverse interleaver soft decision value and a reverse interleaver puncher signal by inputting the soft decision value and the puncher signal; And a Viterbi decoder for outputting decode bits by inputting the deinterleaved puncher signal.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail based on an accompanying drawing.

3 is a block diagram showing a DVB-T receiver incorporating a decoder of the present invention, in which a tuner 21, an orthogonal frequency division multiplexing demodulator 22, a channel evaluator 23, and an equalizer 24 are shown. In the DVB-T receiver having the demapper 25 and the channel state information generator 29, the output b (k) of the demapper 25 and the output of the channel state information generator 29 are input. A soft decision value generator 26 for outputting a soft decision value and a puncher signal using the CSI value as a control input, and an inner interleaver 27 for generating a reverse interleaver puncher signal using the soft decision value and the puncher signal as inputs. And a Viterbi decoder 28 that outputs the decode bits by inputting the deinterleaved soft decision value and the deinterleaved predecessor signal.

As illustrated in FIG. 4, the soft decision value generator 26 receives the output b (k) of the demapper 25 as an input and uses the CSI value as a control input, respectively, m (k, 0). ) '0' metric calculation unit 30 and '1' metric calculation unit 31 generating output and m (k, 1) output, and the 0 output m (k, 0) and m (k, 1) An adder 32 that adds negative values of and outputs m (k, 0)-m (k, 1); and outputs m (k, 0)-m (k, 1) of the adder 32. ) Is determined by inputting the code discriminating unit 33 which determines which of 0 and 1 is closest to generate a code bit, and the outputs m (k, 0)-m (k, 1) of the adder 32 as inputs. It is composed of a reliability value generator 34 for generating a 2-bit reliability value and a puncher signal bit by determining where it belongs.

Two bits which are one of the outputs of the reliability value generator 34 and the sign bits which are the outputs of the code discriminating unit 33 form a soft decision value.

The operation of the decoder device of the present invention configured as described above is as follows.

The signal received through the antenna 20 is detected only through the tuner 21 the desired channel signal, which is demodulated via an orthogonal frequency division multiplexing (OFDN) demodulator 22. At this time, the data transmitted on the frequency are output.

The channel estimator 23 finds a pilot carrier from these data and divides it by a pilot value known to the receiver to obtain channel information of the transmission channel. The equalizer 24 is received with the channel information thus obtained. The demodulated data is divided to correct the information distorted by the channel correctly.

The data passed through the equalizer 24 is input to the demapper 25 and converted into bit information b (k) corresponding to each symbol. If transmitted in I6QAM, one symbol consists of 4 bits of information.

The channel information obtained by the channel estimator 23 is used not only in the equalizer 24 but also in the Viterbi decoder 28. The channel information data is calculated by the CSI generator 29.

The CSI generator 29 may simply use the power of a channel impulse response on a frequency, but in the case of a multicarrier system, it is preferable to use a signal to noise ratio (SNR) because each carrier has a different noise picture. . That is, the ratio of channel impulse response power and noise power is used.

A large CSI value means that the information is less influenced by noise, and thus the information is highly reliable. On the contrary, a small CSI value means that the information is affected by noise, and thus the reliability is low. Can be.

4 is a block diagram showing the inside of the soft decision value generator 26 in detail, and its operation is as follows.

The signal b (k) input by the demapper 25 is a value corresponding to k-th bit information of one symbol and has a value ranging from -1 to 1. That is, the bit '0' without noise corresponds to -1 and the case of '1' without noise corresponds to 1.

If noise is added, it will be in between.

Based on this value and the channel information CSI value obtained by the CSI generator 29, two metrics can be calculated by the 0 metric calculator 30 and the 1 metric calculator 31. The input value b (k) is' A value m (k, 0) representing a probability of 0 'and a value m (k, 1) representing a probability of' 1 'may be calculated. m (k, 0) and m (k, 1) are calculated as in Equation 1.

As shown in Equation 1 above, when b (k) approaches -1, m (k, 0) becomes small and m (k, 1) becomes large. Similarly, when b (k) approaches 1, m (k, 1) becomes smaller and m (k, 0) becomes larger.

By comparing the magnitudes of m (k, 0) and m (k, 1) by this relationship, it is possible to know whether the current input signal is close to '0' or '1'.

In the present invention, the reliability of the input signal b (k) was determined in the same manner as in Equation (2). In other words, the reliability is determined based on the difference between m (k, 0) and m (k, 1).

Using this method, the proportional relationship between CSI and reliability is established, so that an accurate soft decision value can be obtained.

As can be seen in Equation 2, the reliability value, rv, can be represented by the magnitude of the two metric differences. As described above, when the rv value increases, the reliability increases, and when the rv value decreases, the reliability decreases. Therefore, in Equation 2, it can be seen that rv and CSI are in a proportional relationship.

In FIG. 4, the sign discriminator 33 determines whether the currently input signal b (k) is closer to '0' and '1'. If m (k, 0)-m (k, 1) 0, If '1', m (k, 0)-m (k, 1) 0, '0' is output.

If the soft decision value is a 3-bit resolution, the sign bit obtained above constitutes the most significant bit.

Since one bit is used as a sign bit among the three bits representing the soft decision value, reliability must be represented by the remaining two bits. To do this, the reliability value rv calculated above should be assigned to four interval ranges.

In the present invention, the above section is inserted into one section together with four sections. That is, the whole is divided into five sections. In addition, in the present invention, rather than dividing the rv value by equal intervals according to the size, a value in a specific range divides the size of the interval.

5 shows a method of dividing the interval, and the method of dividing is as follows.

First, when the rv value is above a certain value Th4, the data is determined to have a very high reliability, and the highest reliability value is assigned. This corresponds to Region 5 in FIG. 5 and the confidence value is 3. On the contrary, if the value of rv is almost 0, that is, the value is smaller than Th1, it is determined that the data is almost unreliable and outputs the puncher signal.

In this case, the reliability value has no meaning, and the Viterbi decoder 28 recognizes the metric value as 0 without performing the same operation as that of the puncher code generally used, that is, distance calculation.

In other words, this has the same effect as erasing, thereby improving the performance of the Viterbi decoder 28. This interval becomes Region 1.

The section between the two sections mentioned above is divided into three parts at equal intervals and divided by Regions 2, 3 and 4. Then assign 0, 1, and 2 reliability values, respectively.

As described above, the 3-bit soft decision value is newly configured using the reliability value calculated in Equation 2. This newly configured soft decision value has channel information inside and can be used as it is for a Viterbi decoder which can make soft decision that was previously used in other systems.

Therefore, Viterbi can be decoded by using CSI information without designing a new Viterbi decoder, and puncturing effect is provided for data with little reliability, which is a criterion for judgment in Viterbi decoder. You can get better performance by preventing it.

6 shows a 3-bit soft decision value and a puncher signal.

The soft decision value and the puncher signal thus output are deinterleaved together in the inner deinterleaver 27 and then input to the Viterbi decoder. In this case, when the puncher signal is low, the metric is generally calculated to find the path with the smallest sum of the metrics. Used as a metric value.

This approach allows Viterbi decoding without modifying the Viterbi decoder, taking into account channel conditions most appropriately.

As described above, the decoder device of the DVB-T receiver according to the present invention may use the Viterbi decoder used in other conventional systems as it is to perform Viterbi decoding in consideration of channel state information (CSI) in a multipath fading channel. At this time, in generating a new soft decision value suitable for the input of the Viterbi decoder, the calculation of the reliability value divides the reliability interval and inserts the interval generating the puncher signal to perform the Viterbi decoding with better performance. have.

Claims (3)

A soft decision value generator for outputting a soft decision value and a puncher signal by inputting the demapper output of the digital broadcast receiver and the channel state information value of the channel state information generator; An inner deinterleaver for inputting the soft decision value and the puncher signal to generate a deinterleaved soft decision value and a reverse interleaver puncher signal; And a Viterbi decoder for outputting decode bits by inputting the deinterleaved soft decision value and a puncher signal. The method of claim 1, The soft decision value generator includes a zero metric calculation unit configured to generate an m (k, 0) output using the output of the channel state information generator as a control input and the demapper output as an input, and the channel state information generator. A '1' metric calculation unit for generating an m (k, 1) output using the demapper output as an input and a m (k, 0) data and the m (k, 1) output as a control input. An adder generating an output of m (k, 0)-m (k, 1) by adding a negative value of data, and generating a sign bit by determining which of 0 and 1 the output of the adder is close to. And a code value discrimination unit configured to generate a reliability value and a puncher signal by determining which of the reliability intervals is input by using the output of the adder as an input. The method of claim 2, And the reliability value generator is configured to form different reliability intervals, and to output a reliability value represented by the bits and a puncher signal bit having zero reliability.