KR100734378B1 - Apparatus for demodulating broadcasting signal - Google Patents

Abstract

A broadcasting signal decoding apparatus is provided to include a noise removal part which filters only an interval where a channel impulse response exists and removes noise when a time interpolation part performs time interpolation. The first symbol timing restoring part(105) calculates a delay range of signals received through multiple paths. The second symbol timing restoring part(145) generates a time interpolation control signal and a noise removal control signal according to the delay range calculated by the time interpolation. A time interpolation part(150) performs time interpolation of pilot signals of the received signals according to the time interpolation control signal applied from the second symbol timing restoring part. A noise removal part(170) removes noise according to the noise removal control signal applied from the second symbol timing restoring part by referring to channel impulse responses of the received signals.

Description

Apparatus for demodulating broadcasting signal}

1 is a diagram illustrating a pattern of a transmission signal of a DVB-H including a distributed pilot.

2 is a diagram showing an embodiment of a broadcast signal demodulation device according to the present invention;

3 is a diagram illustrating a concept of determining a delay range of a signal by a multipath by a first symbol timing recovery unit according to the present invention;

4 is a diagram illustrating a concept of a noise removing unit for removing noise according to time interpolation in a broadcast signal demodulation device according to the present invention.

<Explanation of symbols in the main part of the drawing>

105: first symbol timing recovery unit

110: guard interval removal unit

120: Fourier transform unit 130: Guard band removal unit

145: second symbol timing recovery unit 150: time interpolation unit

160: temporary storage

170: noise canceling unit

The present invention relates to a broadcast signal demodulation device, and more particularly, to a broadcast signal demodulation device capable of performing channel estimation adaptively to an environment of a reception signal channel.

Digital video broadcasting-handheld (DVB-H) is a European digital mobile mobile terminal specification based on terrestrial digital multimedia broadcasting (terrestrial; DVB-T).

A terrestrial digital multimedia broadcasting (DVB-T) terminal receives a broadcast at a fixed location, moves while receiving it, and demodulates the received signal.

On the other hand, in the DVB-H system, the transmission terminal modulates the transmission signal to adapt to the fast mobile reception environment. Since the receiving terminal has a very small multipath range, such as an urban area, and receives a broadcast while moving fast, such as when driving in a car, it should be able to consider various channel environments.

1 is a diagram illustrating a pattern of a transmission signal of a DVB-H including a distributed pilot. The transmission signal pattern of the DVB-H will be described with reference to FIG. 1.

1 is a direction in which the frequency of subcarriers transmitted at the same time is increased (frequency axis), and a vertical direction is a direction in which time proceeds (time axis). Circles arranged in a horizontal line indicate the positions of subcarriers forming an OFDM symbol.

The distributed pilot is repeated at every 12 subcarrier positions in the OFDM symbol transmitted at the same time. In the OFDM symbol transmitted at the next time, the distributed pilot may be located at a position where the subcarrier frequency interval is separated by 3 from the subcarrier position of the distributed pilot in the OFDM symbol transmitted at the previous time. Thus, the same distributed pilot pattern may be repeated every four OFDM symbols consecutive in time.

In FIG. 1, Tu represents the number of usable subcarriers, Dt represents a distance between distributed pilots on the time axis, and Df represents a distance between distributed pilots on the frequency axis, respectively.

The distance Df between the distributed pilots in the frequency domain determines the delay range of the estimated ghost in the transmission channel.

Since the same pilot pattern appears every four input symbols, time interpolation can be performed at the same pilot position. That is, the first input symbol t = 1 represents the same symbol pattern as the symbol input at t = 5, and the time interpolation for the symbol input at t = 2, 3, 4 at the position of the distributed pilot of the symbols Can be performed.

The symbol input at t = 6 has the same distributed pilot pattern as the symbol input at t = 2, and t = 3,4,5 on the distributed pilot position of the symbol input at t = 6 and the symbol input at t = 2. Time interpolation may be performed on the symbols of.

Therefore, when a symbol is input at t = 7 and then time interpolated in the above manner, the symbols input at t = 4 are distributed pilots every four subcarrier positions. Thus, the spacing between the distributed pilots in the frequency domain of the input symbol at t = 4 is reduced to one quarter of the spacing between the original distributed pilots, and the input symbol at t = 4 has a distributed pilot at every four subcarrier positions. Has a pattern to be located.

When a receiving terminal receives a signal of the above type, an interpolation scheme may be used for four distributed pilot symbols. The interpolation technique improves channel estimation performance for multipaths with very high latency.

However, DVB-H is a broadcasting standard that considers the environment of receiving a broadcast when moving a vehicle mainly in an urban area with many high-rise buildings. Therefore, in the method of interpolating four OFDM symbols consecutive in the time axis direction as described above, channel estimation for a multipath delay channel is possible, but channel estimation performance is degraded when estimating a time-varying channel.

On the other hand, if the interpolation method is not used, a good channel estimation performance can be obtained for the time-varying channel, but the performance of the estimation of the multipath delay channel is poor.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a broadcast signal demodulation device capable of adaptively estimating a channel according to a channel environment of a received signal.

In order to achieve the above object, the present invention includes a first symbol timing recovery unit for calculating a delay range between the signals by the multi-path of the received signal; A second symbol timing recovery unit outputting a time interpolation control signal and a noise canceling control signal according to a delay range calculated by the first symbol timing recovery unit; A time interpolation unit capable of time interpolating pilot signals of the received signal according to a time interpolation control signal of the second symbol timing recovery unit; And a noise canceling unit configured to remove noise from the channel impulse response of the received signals according to the noise canceling control signal of the second symbol timing recovery unit.

The second symbol timing recovery unit may output a time interpolation control signal to time interpolate the pilot signal only when the delay range is larger than one-twelfth of the symbol length of the received signal.

When the time interpolator performs time interpolation, the noise remover may remove noise by filtering only a section in which the channel impulse response exists.

The noise canceller may remove noise by filtering a channel impulse response within one-twelfth of a symbol length when the time interpolator does not perform time interpolation.

The first symbol timing recovery unit may calculate a clock signal according to a guard period of a received signal and a data payload period.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of a broadcast signal demodulation device according to the present invention that can specifically realize the object of the present invention.

2 is a diagram illustrating an embodiment of a broadcast signal demodulation device according to the present invention. Referring to FIG. 2, an operation of an embodiment of a broadcast signal demodulation device according to the present invention will be described.

The broadcast signal demodulation device according to the present invention includes a guard interval remover 110, a Fourier transform unit 120, a guard band remover 130, a time interpolator 150, and a temporary storage unit. 160 and the noise removing unit 170 may be included.

In addition, the broadcast signal demodulation apparatus according to the present invention may include a first symbol timing recovery unit 105 for processing a time domain signal and a second symbol timing recovery unit 145 for processing a signal in a frequency domain.

The first symbol timing recovery unit 105 may detect a symbol start point so as to Fourier transform only valid data samples excluding a guard interval among the received data, and output a delay range on a signal received through a multipath. .

The guard interval removing unit 110 may remove and output a guard interval transmitted before each payload data interval among the received signals.

The Fourier transform unit 120 may receive the information on the start point of the symbol from the first symbol timing recovery unit 105 to convert the received signal into the frequency domain.

The guard band removing unit 130 may remove and output the padded guard band data in order to generate data of two powers in the payload section.

On the other hand, the offset for the transform section during the Fourier transform may generate inter-symbol interference and phase rotation of the subcarrier.

The second symbol timing recovery unit 145 may predict and output the position of the fine transform section generated due to the offset with respect to the transform section during the Fourier transform. The position of the fine transform section to be predicted may be transmitted to the guard interval removing unit 110 so that the Fourier transform is performed only in the data payload section.

Meanwhile, the second symbol timing recovery unit 145 may output a control signal for controlling whether to interpolate the received signal using a channel impulse response of the received signal.

To this end, the second symbol timing recovery unit 145 may include a distributed pilot extractor, an inverse Fourier transform unit, and a micro-conversion interval detector (not shown).

The distributed pilot extractor may output a channel transfer function by extracting the distributed pilot from the data from which the guard band is removed. The inverse Fourier transform unit may output a channel impulse response obtained by inversely transforming the extracted distributed pilot. The fine transform section detector may detect an offset with respect to the transform section when performing Fourier transform using the channel impulse response.

The time interpolator 150 may perform time interpolation on the distributed pilot signal of the received signal according to the control signal. The temporary storage unit 160 may temporarily store payload data of the received signal.

The noise removing unit 170 receives the first information on the time interpolation from the time interpolation unit 150 and the second information on the noise removing range from the second symbol timing recovery unit 145, and then temporarily stores the 160. ) Can be output by removing the noise for the signal stored in).

The concept that the noise canceller 170 operates according to time interpolation will be described in detail with reference to FIG. 4.

3 illustrates a concept in which the first symbol timing recovery unit determines a delay range of a signal by multipath according to the present invention. Referring to FIG. 3, an embodiment in which the first symbol timing recovery unit determines a multipath delay range of a received signal is as follows.

In FIG. 3, the second received signal represents a delay signal by multiple paths of the first received signal. In FIG. 3, Nu represents a payload section of data, and Ng represents a section serving as a guard section among some sections of the data payload.

The first symbol timing recovery unit may generate a clock signal according to a peak value cross-correlated with the received signal. Accordingly, the first clock signal a is a signal having a small size in the guard interval of the first received signal, and the second clock signal b is a shape having a small size in the guard interval portion of the second received signal. Signal.

The first symbol timing recovery unit may calculate a length of a section in which the magnitude of each clock signal is low (indicated by L1 in (a) and L2 in (b)).

When the first clock signal and the second clock signal are added together, a signal section L3 having the lowest magnitude of the summed signal may be calculated. When the section L3 is subtracted from the section L1 calculated above. An interval in which the second received signal is delayed than the first received signal may be calculated. That is, the first symbol timing recovery unit may calculate a delay range due to a multipath by calculating a position difference between a clock signal having a large signal and a clock signal having a small signal.

The above-described embodiment is just one example, and the delay range may be calculated using a rising signal section of a clock signal.

4 is a diagram illustrating a concept of a noise removing unit for removing noise according to time interpolation in the broadcast signal demodulation apparatus according to the present invention. The operation of the noise canceller will be described with reference to FIG. 4.

If time interpolation is performed between the received symbols, the delay range due to the multipath of the signal can be detected up to Tu (symbol length) / 3 (since the distributed pilot is located every four data after time interpolation), and if time interpolation is not performed Delay range detection for Tu (symbol length) / 12 is possible.

The difference in the peak value of the channel impulse response of the signals received in the multipath may indicate a delay range between the signals.

The second symbol timing recovery unit may output a control signal to the time interpolation unit so as not to perform time interpolation on the received signal when the delay range for the channel impulse response on which time interpolation has been performed is within Tu / 12.

That is, when the delay range is within Tu / 12, the second symbol timing recovery unit may output a control signal to the noise canceller so as to perform noise cancellation according to a proportional delay range of Tu.

As an example, a method of filtering to remove noise is illustrated in FIG. 4.

(a) shows an example in which the noise canceling unit removes noise when the delay range of the signal due to the multipath is larger than Tu / 12. First, the second symbol timing recovery unit performs time interpolation to the time interpolation unit. The noise removing unit may filter out the remaining sections except for the section including the channel impulse response of the signal.

In this case, the noise removing unit divides a section in which a significant channel impulse response appears (Tu / 3 in FIG. 4) into a plurality of sections in order to remove a section in which the channel impulse response does not exist, and the channel impulse response is divided among the divided sections. It is preferable to pass only the existing section.

(b) shows an example in which the noise canceling unit removes noise when the delay range of the signal due to the multipath is smaller than Tu / 12 steps. The second symbol timing recovery unit may output a control signal to the time interpolator so as not to perform time interpolation when the delay range is smaller than Tu / 12. If the delay range is smaller than Tu / 12, the channel impulse response is repeated in the same pattern, but the noise canceller can pass only the channel impulse response of which the delay range of the signal is less than Tu / 12 of the channel impulse response.

(A) and (b) of FIG. 4 divide a section in which a channel impulse response exists into 0, 1, 2, and 3 sections, respectively, where a section in which a channel impulse response exists is 0, 1, 2, or 3 sections. It is a method of determining the filtering interval according to the recognition. Therefore, as shown in (a) of FIG. 4, when there is a channel impulse response within 0 section, only the section of 0 is passed, and values of 1, 2, and 3 sections can be filtered out.

It is easy for a person skilled in the art to change or modify the present invention from the present specification. Therefore, although an embodiment of the present invention has been described above clearly, various modifications thereof should be made without departing from the spirit and the scope of the present invention.

 The effects of the broadcast signal demodulation device according to the present invention described above are as follows. According to the broadcast signal demodulation device according to the present invention, it is possible to adaptively estimate a channel according to a channel environment of a received signal, thereby improving signal reception performance.

Claims (5)

A first symbol timing recovery unit for calculating a delay range between signals by multiple paths of a received signal; A second symbol timing recovery unit outputting a time interpolation control signal and a noise canceling control signal according to a delay range calculated by the first symbol timing recovery unit; A time interpolation unit capable of time interpolating pilot signals of the received signal according to a time interpolation control signal of the second symbol timing recovery unit; And And a noise canceling unit configured to remove noise from the channel impulse response of the received signals according to the noise canceling control signal of the second symbol timing recovery unit. The method of claim 1, And the second symbol timing recovery unit outputs a time interpolation control signal for time interpolating the pilot signal only when the delay range is larger than one-twelfth of the symbol length of the received signal. The method of claim 1, And removing the noise by filtering only a section in which the channel impulse response exists when the time interpolator performs time interpolation. The method of claim 1, And removing the noise by filtering the channel impulse response within a twelfth section of the symbol length when the time interpolator does not perform time interpolation. The method of claim 1, And the first symbol timing recovery unit calculates a clock signal according to a guard period of a received signal and a data payload period.

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