KR100747543B1 - Apparatus for demodulating broadcasting signal - Google Patents

Abstract

An apparatus for demodulating a broadcasting signal is provided to demodulate the signal to be capable of more accurately compensating a channel. A channel estimating unit(202) estimates and outputs channel characteristics of signals received through a multi-path. A training signal removing unit(201) receives the channel characteristics outputted from the channel estimating unit(202), and removes a training signal interval from the signals received through the multi-path. A signal reallocating unit(220) reallocates frame body signals of the respective multi-path signals to temporally synchronize frame body intervals of the multi-path signals outputted from the signal reallocating unit(220).

Description

Apparatus for demodulating broadcasting signal}

1 is a diagram showing the structure of a frame of a transmission signal having a guard interval of 1/9 of a TDS-OFDM transmission signal;

2 is a block diagram showing an embodiment of a TDS-OFDM transmission apparatus;

3 is a structural diagram showing an embodiment of a TDS-OFDM broadcast signal demodulation device

4A and 4B conceptually illustrate one method of a method in which a broadcast signal demodulation device periodically configures a data section according to the present invention.

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

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

10: channel encoder 20: modulator

30: reverse DFT section 40: PN generation section

50: multiplexer 60: filter unit

70: RF transmitter 110: tuner

120: automatic gain control unit 130: A / D converter

140: phase separator 145: multiplier

150: resampler 160: filter unit

170: signal synchronization unit 171: PN correlation unit

172: signal acquisition unit 174: signal tracking unit

177: automatic frequency control unit 180: DFT unit

190: equalizer 200: signal reconstruction unit

201: training signal removing unit 202: channel estimation

220: signal relocation unit 221: temporary storage unit

222: interval calculation unit 223: signal extraction unit

225: calculator

The present invention relates to a broadcast signal demodulation device, and more particularly, to a broadcast signal demodulation device capable of demodulating a signal to facilitate device implementation of a broadcast reception terminal.

Recently, Tsinghua University has proposed a new standard for terrestrial digital television (“Terrestrial DTV”) broadcasting to China. The proposal relates to a broadcast standard called Terrestrial Digital Multimedia / Television Broadcasting (DMB-T). In DMB-T, a new modulation scheme called Time Domain Synchronous OFDM (hereinafter referred to as TDS-OFDM) is used.

The data transmitted after being modulated at the transmitting end of the TDS-OFDM is applied with an Inverse Discrete Fourier Transform (IDFT) like the method used in the cyclic prefix OFDM (CP-OFDM) scheme.

However, a pseudonoise (PN) is inserted in the guard interval instead of CP and used as a training signal.

The above-described method can reduce overhead when transmitting a broadcast signal, improve channel usage efficiency, and improve performance of a synchronizer and a channel estimator of a broadcast signal receiver.

1 shows an example of a TDS-OFDM transmission signal and shows a structure of a frame of a transmission signal having a guard interval of 1/9. A transmission frame structure having a guard interval of 1/9 will be described with reference to FIG. 1.

The one frame includes frame sync and frame body.

The frame body is a place where data to be transmitted (hereinafter, referred to as a data interval) is a DFT block to which a Discrete Fourier Transform (DFT) is applied, and the DFT block generally includes 3780 stream data.

The frame sync consists of a PN sequence, and the PN sequence used for the frame sync may use a sequence having an order of 8 (m = 8). When m = 8, 255 different sequences can be generated. The sequences are extended to preambles and postambles for use in guard intervals.

The preamble and the postamble are repetition intervals of the PN sequence for cyclic extension of the PN sequence.

Of the 255 PN sequences of the frame sync, the first 115 PNs of the PN sequence are added as a postamble to the end of the 255 PN sequence, and the last 50 PNs of the PN sequence are added as preambles before the 255 PN sequence. To expand.

The polynomial of the PN sequence is P (x) = x ⁸ + x ⁶ + x ⁵ + x + 1, and the generated phase varies from 0 to 254 according to the initial state of the PN sequence.

When the guard interval is 1/9, the preamble and the postamble are added to the 255 PN sequences before and after the frame sync including 420 data. In other words, 420 data, which is 1/9 of 3780 data of the DFT block, are used for frame sync. One OFDM frame includes a frame sink of 420 data and a frame body of 3780 data.

The structure of the data frame may vary depending on the protection period, and the number of data distributed in each frame may also be distributed differently.

In addition, the protective section may be 1/4 or 1/9 of the frame body, in addition to the 1/6 length protective section may be used, other lengths are possible.

As described above, the signal transmitted by the TDS-OFDM scheme is different from the conventional OFDM (e.g., DVB-T, TDMB) broadcasting signal. Is to use PN sequences.

An equalizer is an apparatus for compensating for a channel in an OFDM broadcast terminal and performs a process of calculating an inverse matrix for a channel response matrix to compensate for the channel.

In the process of demodulating the OFDM transmission signal received through the multipath, if the DFT process is performed on a channel response matrix of data including a cyclic prefix (CP) form, the channel response matrix is a diagonal matrix ( diagonal matrix).

Since the channel response matrix is a circular matrix in which each component is symmetric about the diagonal direction, the diagonal matrix may calculate an inverse matrix using only the diagonal components of the matrix.

The equalizer of the broadcast receiving terminal may compensate for the channel of the received signal by calculating an inverse matrix of the channel response matrix.

However, since the TDS-OFDM transmission signal includes the PN sequence in the protection interval, the transmission signal received through the multipath does not become a periodic signal in the data interval.

Therefore, even though the DFT operation is performed, since the channel response matrix is not a circular matrix, many hardware resources are required to calculate an inverse matrix.

The assumption that the DFT is Fourier transform is that the data is periodically distributed. If the Fourier transform is performed on data that is not periodically distributed, the subsequent channel equalization process is not performed correctly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a broadcast signal demodulation device capable of demodulating a signal to facilitate device implementation of a broadcast receiving terminal.

Another object of the present invention is to provide a broadcast signal demodulation device for signal demodulation to enable more accurate channel compensation.

In order to achieve the above object, the present invention provides a device for demodulating a broadcast signal including a training signal and a frame body signal which is broadcast data continuous to the training signal. Channel estimation for estimating and outputting characteristics; A training signal removing unit receiving the channel characteristic output by the channel estimating unit and removing a training signal section of the signals received in the multi-path; And a signal repositioning unit for rearranging the frame body signals of the multipath signals so as to temporally match the frame body sections of the multipath signals output by the training signal removing unit.

The signal relocator may include a frame body section of a signal received before the main signal among the multipath signals output by the channel estimator or a frame body of a signal received later than the main signal among the multipath signals. It may include a section calculation unit for calculating any one or more of the length of the section.

The signal relocator may include a signal extractor configured to extract signals belonging to a frame body section output by the interval calculator from the multipath signals output by the channel estimator.

The signal relocator may include a signal extractor configured to extract signals belonging to a frame body section output by the interval calculator from the multipath signals output by the channel estimator.

The signal repositioning unit comprises: a temporary storage unit for temporarily storing and outputting a signal output from the training signal removing unit; And a calculation unit for calculating a signal section output by the signal extracting unit to a signal section output by the temporary storage unit so that the frame body section of the main signal coincides with the frame body section of the multipath signal except the main signal in time. can do.

When the signal outputted by the temporary storage unit is a multipath signal received before the main signal, the operation unit may determine a frame body section of the multipath signal received before the frame body section of the main signal, and the frame of the signal received first. Can be added to the end of the body section.

When the signal output by the temporary storage unit is a multipath signal received later than a main signal, the operation unit may determine a frame body section of the multipath signal received after the frame body section of the main signal. It can be added before the frame body section of the signal.

Preferably, the training signal is a pseudonoise sequence.

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

Hereinafter, a TDS-OFDM signal receiving device will be described as an example. However, the present invention is not limited thereto, and the present invention can be applied to a device for receiving an OFDM signal.

First, an embodiment of a transmission apparatus of the DMB-T will be described in order to easily describe the present invention. 2 is a block diagram showing an embodiment of a DMB-T transmitting apparatus. Referring to Figure 2 describes the operation of the transmitter of the DMB-T as follows.

The channel encoder 10 outputs a bitstream encoded by the channel in order to detect an error at the receiving end.

The modulator 20 receives the encoded bit stream and modulates the bit stream by quadrature amplitude modulation (QAM), such as 4-, 16-, or 64-values.

The inverse DFT unit 30 modulates a signal modulated by the OFDM scheme in the frequency domain into an OFDM signal in the time domain. In general, the DMB-T method converts a frequency domain signal of 3780 points of transmission data into a time domain signal.

The PN generator 40 generates a PN sequence to be used as a training signal of a broadcast signal to be transmitted.

The multiplexer 50 distributes the generated PN sequence and the OFDM signal converted by the inverse DFT unit 30 in a time domain, and multiplexes the same.

The filter unit 60 outputs the bandwidth of the multiplexed DMB-T signal by limiting the bandwidth. Square Root Rasied Cosine filter may be used as the filter part, and the roll-off factor α used for the bandwidth limit is 0.05.

The RF transmitter 70 up-converts the output signal of which the bandwidth is limited to an RF (Radio Frequency) transmission band of frequency fc to transmit a broadcast signal.

3 is a structural diagram illustrating an embodiment of a TDS-OFDM broadcast signal demodulation device. The operation of the TDS-OFDM broadcast signal demodulation apparatus will now be described with reference to FIG. 3.

The tuner 110 of the TDS-OFDM residual signal receiving apparatus converts a signal of an RF transmission band into a base band signal and outputs it.

The automatic gain controller (AGC) 120 normalizes and outputs the power of the output signal.

The analog to digital converter 130 converts the output signal into an analog signal and outputs the digital signal.

The phase splitter 140 may have an inphase component signal (hereinafter, I signal) and a quadrature component signal (hereinafter, Q signal) from the signal output from the A / D converter 130. To print out.

The automatic frequency control (FCC) unit 177 compensates for the estimated frequency error of the separated I and Q signals, and the SRRC unit 160 controls the bandwidth of the received signal as in the transmitter. Perform a filter role to limit

The signal synchronizer 170 may be largely divided into three parts.

First, the AFC unit 177 calculates the frequency error of the received signal as described above, and calculates the product of the received signal and the signal whose frequency error is calculated by the multiplier 145 to compensate for the frequency error of the received signal. have.

Second, the acquisition unit 172 synchronizes the PN sequence sent by the transmitter.

Finally, the signal tracking unit 174 compensates for the symbol error using the captured PN sequence.

All of the received signal synchronizers use the results of the PN correlator 171.

The data estimated by the signal synchronization unit reconstructs and outputs the signals such that the frame body sections in the plurality of signals received by the signal relocator 200 in the multiple paths have a periodic relationship with each other before being performed by the DFT unit 180. .

The DFT unit 180 performs a Fourier transform on the data section output by the signal reconstructing unit 200, preferably, performs a Four Fourier Transform (FFT), and converts the data section to a frequency domain for output.

The signal output from the DFT unit 180 is output to the channel decoder (not shown) after the channel is compensated through the equalizer 190.

4A and 4B conceptually illustrate one method of a method in which the signal reconstruction unit 200 of the broadcast signal demodulation device according to the present invention periodically configures a data section. Referring to FIGS. 4A to 4B, the signal reconstruction unit 200 describes a process of reconstructing data as follows.

4A and 4B show an example of a frame structure of a signal received through a multipath channel. The signal of FIGS. 4A and 4B may be a signal in which a frequency error and a symbol timing error are compensated for.

Among the signals (a), (b), and (c) of FIG. 4A, the signal (b) is a main path signal and represents a signal from which frame sync is removed. The main path signal (b) preferably uses a signal having the greatest power among the multipath received signals as the main path signal.

And, (a) and (c) respectively indicate a signal ((c) signal received first or (a) signal later through multipath for (b). Hereinafter, for convenience, signals (a) are referred to as first path signals, (b) signals as second path signals, and (c) signals as third path signals, respectively.

The first path signal is a signal received earlier by the time Lpre for the second path signal, and the third path signal is a signal received delayed by the time Lpost for the second path signal.

If the Fourier transform is performed on the frame body period of the second path signal, which is a signal for the main path, an incorrect conversion result may be obtained due to the influence of the signals of the frame sync period of the first path signal and the third path signal.

Therefore, it is preferable to remove the signal frame sync section of the first path and the frame sync section of the signal of the third path.

Further, when Fourier transform is performed on the frame body section of the second path signal, the Fourier path frame sync period and the frame sync section of the third path signal respectively overlap the frame body section of the second path signal. This can affect the result of the conversion.

As a result, when channel compensating a signal converted into the frequency domain, the channel response matrix does not become a diagonal matrix.

In order for the channel response matrix to be a diagonal matrix, the frame body section of the second path signal and the section in which the first path signal and the third path signal overlap during the Fourier transform of the received signal are signals having a periodic relationship in the frequency domain. Do.

4B is a diagram conceptually illustrating a method for reconstructing a received multipath signal into a periodic signal of a main path signal as shown in FIG. 4A.

The broadcast signal demodulation device according to the present invention calculates a section in which the first path signal is received earlier than the second path signal and a section in which the third path signal is received later than the second path signal to easily perform channel compensation. do.

The first path signal and the third path signal may be reconstructed so that the calculated periods correspond to frame body sections of the second path signal, respectively.

The first path signal received before the main path may add the previously received section to the end of the frame body section of the first path signal.

The third path signal received later than the main path may add the later received section to the front of the frame body section of the third signal.

The frame body section of the second path signal, which is the main path signal, is converted into the frequency domain. For the converted signal, a channel response matrix, which is a diagonal matrix at the time of channel equalization, may be obtained, and channel compensation may be easily implemented.

5 is a block diagram showing an embodiment of a broadcast signal demodulation device according to the present invention. The broadcast signal demodulation device according to the present invention may include a signal synchronizer 170 and a signal reconstruction unit 200. The signal reconstruction unit 200 may include a training signal removing unit 201, a channel estimator 202, and a signal repositioning unit 220. Referring to FIG. 5, an operation of an embodiment of a broadcast signal demodulation device according to the present invention will be described.

The signal synchronizer 170 may compensate for frequency and symbol timing errors, and may synchronize the received signal using power of the received signal.

The channel estimator 202 may estimate and output the characteristics of the channels of the synchronized received signal.

The training signal removing unit 201 may receive a training signal included in a protection section of the synchronized reception signal. In addition, the training signal removing unit 201 may remove the PN sequence by receiving the channel characteristic from the channel estimation unit 202.

Therefore, the multipath signals output by the training signal remover 201 have only a frame body section, and the guard section may be padded with zero.

The signal repositioning unit 220 may include a temporary storage unit 221, a section calculation unit 222, a signal extraction unit 223, and an operation unit 225.

The temporary storage unit 221 stores the signal output from the training signal removing unit 201 and outputs the delayed signal. The temporary storage unit 221 may operate as a first-in first-out (FIFO) to delay an input signal and output the same.

In this case, it is more preferable that the temporary storage unit 221 outputs the frame body section with a time delay.

The interval calculation unit 222 receives a signal output from the channel estimator 202, and receives a delayed or delayed signal before the main signal among the signals received through the multipath (Lpre interval or Lpost interval). The length of can be calculated.

The signal extractor 223 may extract signals of a frame body section which does not coincide with the frame body section of the main signal in time from among the signals output by the section calculator 222.

The calculating unit 225 may combine the signal extracted by the signal extracting unit 223 with the signal output by being delayed from the temporary storage unit 221 and output the result.

For the signal received before the main signal, the calculator 225 may add the frame body section of the multipath signal received before the frame body section of the main signal to the end of the frame body section of the signal received first.

For the signal received later than the main signal, the calculator 225 may add the frame body section of the multipath signal received after the frame body section of the main signal before the frame body section of the signal received thereafter.

In addition, the DFT unit 180 may change and output the data of the frame body section output by the calculation unit in the frequency domain.

In addition, when the equalizer performs channel compensation on the signal output from the DFT unit 180, the channel impulse matrix becomes a diagonal matrix so that an inverse matrix can be easily implemented.

It is easy for a person skilled in the art to change the present invention from the present specification to change or modify it. 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, when the channel demodulated in the equalizer by the signal demodulated by the demodulation device, it is possible to simply and easily implement the configuration of the equalizer.

Claims (7)

An apparatus for demodulating a broadcast signal including a training signal and a frame body signal which is broadcast data continuous to the training signal. A channel estimator for estimating and outputting channel characteristics of signals received in a multipath; A training signal removing unit receiving the channel characteristic output by the channel estimating unit and removing a training signal section of the signals received in the multi-path; And And a signal repositioning unit for rearranging the frame body signals of the multipath signals so as to temporally match the frame body sections of the multipath signals output by the training signal removing unit. The method of claim 1, The signal relocator may include a frame body section of a signal received earlier than a main signal among the multipath signals output by the channel estimator or a frame body of a signal received later than the main signal among the multipath signals. And a section calculating unit capable of calculating any one or more of the lengths of the sections. The method of claim 2, And the signal relocator comprises a signal extractor configured to extract signals belonging to a frame body section outputted by the interval calculator from multipath signals output by the channel estimator. The method of claim 3, wherein The signal repositioning unit comprises: a temporary storage unit for temporarily storing and outputting a signal output from the training signal removing unit; And And a calculation unit configured to calculate a signal section output by the signal extracting unit to a signal section output by the temporary storage unit so that the frame body section of the main signal matches the frame body section of the multipath signal except the main signal in time. Broadcast signal demodulation device, characterized in that. The method of claim 4, wherein When the signal outputted by the temporary storage unit is a multipath signal received before the main signal, the operation unit may determine a frame body section of the multipath signal received before the frame body section of the main signal, and the frame of the signal received first. And a broadcast signal demodulation device added to the end of the body section. The method of claim 4, wherein When the signal output by the temporary storage unit is a multipath signal received after the main signal, the operation unit may determine a frame body section of the multipath signal received after the frame body section of the main signal. A broadcast signal demodulation device, which is added before a frame body section of a signal. The method of claim 1, The training signal is a broadcast signal demodulation device, characterized in that the PN sequence (pseudonoise sequence).

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