KR20080083858A - Method for transmitting/receiving a signal and apparatus for transmitting/receiving a signal - Google Patents

Abstract

A method and an apparatus for transmitting/receiving a signal are provided to prevent the data included in a sub-carrier from being lost by a frequency selective fading by previously spreading the data when the data is modulated to the sub-carrier. An apparatus for transmitting/receiving a signal includes a first signal arranging unit(110), a pre-coding unit(120), a signal transforming unit(130), a second signal arranging unit(140), a guard interval insertion unit(150), an up-conversion unit(160), and a transmission unit(170). The first signal arranging unit arranges data which are sequentially inputted, as many as sub-carriers in parallel. The pre-coding unit multiplies the arranged data by a vanderMonde matrix and outputs the multiplied result. The signal transforming unit transforms the output signal of the pre-coding unit to a time domain. The second signal arranging unit arranges and outputs sequentially signals which are outputted from the signal transforming unit. The guard interval insertion unit inserts a guard interval into the signals outputted from the second signal arranging unit. The up-conversion unit converts the signal having the guard interval into a radio frequency band. The transmission unit transmits the output signal of the up-conversion unit.

Description

Method for transmitting / receiving a signal and apparatus for transmitting / receiving a signal

1 is a view schematically showing an embodiment of a signal transmission apparatus according to the present invention

FIG. 2 is a diagram illustrating an example of a method in which the precoding unit of FIG. 1 may distribute input data. FIG.

3 is a view showing a specific embodiment of a signal transmission apparatus according to the present invention

4 is a view showing a specific embodiment of a signal receiving apparatus according to the present invention

5 illustrates an embodiment of a signal transmission and reception method according to the present invention.

<Description of the code of the main part of drawing>

110: first signal array unit 120: precoding unit

130: signal conversion unit 140: second signal array unit

150: protection section insertion section 160: upconvesion section

170: transmission unit 210: outer coder

220: outer interleaver 310: inner coder

320: inner interleaver 350: symbol mapper

400: frame forming unit 410: modulator

440: transmitter 510: receiver

520: synchronizer 530: demodulator

540: frame parsing unit 550: symbol demapping unit

560: inner deinterleaver 570: inner decoder

580: Outer Deinterleaver 590: Outer Decoder

The present invention relates to a signal transmission and reception method and a signal transmission and reception apparatus, and more particularly, to a signal transmission and reception method and a signal transmission and reception apparatus resistant to frequency selective fading.

Orthogonal frequency division multiplexing (OFDM) is a signal modulation technique that transmits multiple symbols simultaneously over multiple transmission bands having very narrow bandwidths. That is, the OFDM scheme is a multi-carrier transmission scheme with good spectral efficiency, and divides a wideband signal into narrow-band sub-carriers having mutual orthogonality, and transmits them by overlapping them.

When transmitting high-speed data with a short symbol period in a wireless communication channel in which multipath fading occurs, the complexity of the receiver is greatly increased because the inter-symbol interference becomes more severe when a single carrier method is used. However, in the multi-carrier scheme, since the symbol period in each subcarrier can be extended by the number of subcarriers while maintaining the data transmission rate, the relative signal dispersion in time caused by multipath delay spreading is reduced. Therefore, when the signal is modulated using the OFDM technique, the signal may have robust characteristics in time domain synchronization error or channel delay time.

The OFDM technique can remove intersymbol interference by inserting a guard interval longer than the delay spread of the channel between symbols. However, in a transmission channel having a long delay time, selective fading appears in the frequency domain, and the magnitude of the distortion is severe according to the delay spread of the channel. Accordingly, there is a problem in that a signal-to-noise ratio (SNR) for each transmission band is changed and a reception rate is decreased for a transmission channel having a low SNR.

An object of the present invention is to provide a signal transmission and reception method and a signal transmission and reception apparatus capable of transmitting and receiving a modulated signal to be robust to frequency selective fading.

The present invention is to solve the above problems, the present invention is to pre-distribute the data in the frequency domain so that the values of the data to be assigned to each sub-carrier, is allocated to at least two or more subcarriers Performing coding, converting the precoded data into a time domain, converting the data of the time domain into a signal in a radio frequency (RF) band, and transmitting the converted signal. Provided is a signal transmission method.

In another aspect, the present invention provides a method of converting signals in a received RF band into digital signals, and converting the converted RF signals into digital signals so that values of data allocated to each subcarrier are converted into at least two subcarriers. A method for receiving a signal, the method comprising: obtaining distributed data; and performing inverse calculation of the distributed data to obtain a data value assigned to each subcarrier.

In another aspect, the present invention is a first signal array for arranging sequentially input data in parallel by the number of subcarriers, a precoding unit for multiplying each of the arranged data in a vanderMonde matrix, and outputs A signal conversion unit for converting the output signal to the time domain, a second signal array unit for sequentially arranging the signals output by the signal converter, and a protection interval for inserting a guard interval into the signals output from the second signal array unit An insertion unit, an upconversion unit for converting the signal inserted into the guard interval (upconversion) for providing a signal transmission apparatus including a transmission unit for transmitting the signal output by the upconversion unit.

In another aspect, a receiver for receiving a signal including a video signal, a synchronizer for acquiring a signal output by the receiver, and converting the signals output from the synchronizer into data in a frequency domain, A demodulator for outputting the transformed data by performing subdispersion operations on respective subcarriers, a frame parser for outputting data included in a data section among the data output by the demodulator, and bits for data output by the frame parser Provides a signal receiving apparatus including a symbol demapped unit for demapping and outputting a column, a deinterleaver for deinterleaving the bit string output by the symbol demapping unit, and a decoder for decoding the deinterleaved data do.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a view schematically showing an embodiment of a signal transmission apparatus according to the present invention. An embodiment of the apparatus for transmitting a signal of FIG. 1 may include a first signal array 110, a precoding unit 120, a signal converter 130, a second signal array 140, and a guard interval inserter 150. And an upconvesion unit 160 and a transmission unit 170.

The first signal array unit 110 arranges the data in order to process the data sequentially input in parallel in a predetermined unit. The precoding unit 120 codes the input data to be robust to frequency selective fading of the channel by distributing each of the input data to the transport carrier. The precoding unit 120 may distribute the input data values into a plurality of sub carriers. Therefore, even when fading occurs in a specific frequency band in the frequency selective fading channel, the subcarriers of the frequency band have values of distributed data, thereby reducing the effects of fading. A specific precoding scheme is described in detail in FIG.

The signal converter 130 converts the data output from the precoding unit 120 into a time domain. The signal converter 130 may convert the input data into the time domain according to an inverse fourier transform algorithm. The signal converter 130 may convert data according to an inverse fast fourier transform (IFFT) algorithm among inverse discrete fourier transnforms (IDFTs) in order to convert the input data into the time domain.

The second signal array unit 140 arranges and outputs data output from the signal converter 130 in a sequential order. The guard interval insertion unit 150 inserts and outputs the guard intervals of the signals modulated according to the described process. For example, the protection period may use a method of adding a partial period to the data output by the second signal array unit 140 again.

The upconvesion unit 160 up-converts the frequency band of the data output by the protection interval inserter 150 and outputs the RF band as a radio frequency (RF) signal, and the transmitter 170 transmits the RF signal. Only the real part of can be transmitted.

FIG. 2 illustrates an example of a method in which the precoding unit of FIG. 1 may distribute input data. The data values input to the precoding unit may be distributed to be transmitted to a plurality of subcarriers, and the probability of losing data values on a specific subcarrier may be reduced when the receiver restores a signal. That is, the precoding unit may distribute data values in the frequency domain such that data values to be allocated to each sub-carrier are allocated to at least two or more subcarriers. Therefore, overall data transmission efficiency can be improved. By adjusting the coding scheme of the precoding unit, the peak-to-average power ratio (PAPR) of the output signal of the signal converter may be lowered.

2 discloses an example of a precoding scheme that may be called a vanderMonde matrix. To be transmitted, the data may be arranged in parallel in the length (L) of the subcarriers. For example, θ can be expressed by the following equation and can be defined in other ways. The vanderMonde matrix can control the matrix component by Equation 1. Thus, adjusting the matrix component can disperse the inputted values into at least two or more values according to their characteristics.

In Equation 1, L represents the number of subcarriers. In FIG. 2, if the data group x input to the precoding unit is y, the data group coded and output by the precoding unit by the matrix illustrated in FIG. 2 is y.

3 shows a specific embodiment of a signal transmission apparatus according to the present invention. 3 illustrates an example of transmitting a signal using an OFDM modulation technique when transmitting video data such as a broadcast signal. For example, the signal transmission apparatus of FIG. 3 may be a broadcast signal transmission apparatus according to a digital video broadcasting (DVB) system. An embodiment of a signal transmission apparatus according to the present invention will be described with reference to FIG. 3.

3 illustrates an outer coder 210, an outer interleaver 220, an inner coder 310, an inner interleaver 320, and a symbol mapper. and a mapper 350, a frame forming unit 400, a modulator 410, and a transmitter 440.

The outer coder 210 and the outer interleaver 220 may encode and interleave the multiplexed data to improve transmission performance for the multiplexed signal. For example, a Reed-Solomon coded method may be used as an outer coding method, and a convolution interleaving method may be performed as an interleaving method.

The inner coder 310 and the inner interleaver 320 perform interleaving by recoding a signal to be transmitted in preparation for an error in the transmission signal. The inner coder 310 may encode a transmission signal according to a punctured convolution code. The inner-interleaving 320 scheme of the inner interleaver 320 is either Nate or In depending on the memory operation of the transmission modes of 2k, 4k and 8k for DVB-T, for example. An in-depth interleaving scheme may be used.

The symbol mapper 350 may map a transmission signal to a symbol according to 16QAM, 64QAM, QPSK, etc. in consideration of a pilot signal and a transmission parameter signal according to a transmission mode. The frame forming unit 400 modulates the mapped signal by an orthogonal frequency division multiplex (OFDM) scheme, and forms a frame in which a guard interval is inserted in a data section including the modulated signal.

For example, in the case of DVB-T, each frame includes 68 OFDM symbols. Each symbol includes 6817 carriers in 8k mode and 1705 carriers in 2k mode. The OFDM frame includes a distributed training signal, a continuous training signal and a transmission parameter signal (TPS) carrier, respectively.

The modulator 410 may code and output OFDM data output by the frame generator 400 as illustrated in FIG. 1. The modulator 410 includes the signal array unit 110, the precoding unit 120, the signal conversion unit 130, the second signal array unit 140, and the guard interval insertion unit 150 illustrated in FIG. 1. can do. In the case of DVB-T, the guard interval to be inserted is a cyclic continuation in which data of the data interval is copied, and the length of the guard interval varies according to the transmission mode.

The transmitter 440 may convert a digital format broadcast signal having a guard interval and a data interval into an analog signal, and transmit the converted analog signal by upconverting the RF signal.

4 is a diagram illustrating an embodiment of a signal receiving apparatus according to the present invention. An embodiment of a signal receiving apparatus according to the present invention will be described with reference to FIG. 4 as follows. 4 illustrates an apparatus capable of receiving the broadcast signal transmitted by FIG. 3. 4 may be included in the DVB receiving apparatus.

An embodiment of the signal receiving apparatus according to the present invention of FIG. 4 includes a receiver 510, a synchronizer 520, a demodulator 530, a frame parser 540, a symbol demapped 550, and an inner deinterleaver. a deinterleaver 560, an inner decoder 570, an outer deinterleaver 580, and an outer decoder 590.

The receiver 510 down-converts the frequency band of the RF signal and converts the frequency band into a digital signal. The synchronizer 520 acquires and outputs synchronization of a frequency domain and a time domain of the received signal. The synchronizer 520 may use the offset result of the frequency domain of the data output by the demodulator 530 to acquire the synchronization of the frequency domain signal.

The demodulator 530 demodulates the received data by performing a reverse process of the modulator 410 disclosed in FIG. 3. The demodulator 530 converts the received data into the frequency domain, and demodulates the data values distributed in the subcarriers to values assigned to each subcarrier. That is, the data distributed over two or more subcarriers are de-distributed to values that have been allocated to each subcarrier. To this end, the demodulator 530 may calculate and output the data converted into the frequency domain into an inverse matrix of the matrix illustrated in FIG. 2.

The frame parsing unit 540 may output data of the data section excluding the protection section according to the frame structure of the received signal. The symbol demapping unit 550 may restore data transmitted through each subcarrier into a bit string.

The inner deinterleaver 560 performs an inverse process of interleaving on the interleaved data strings, so that the inner decoder 570 may decode the deinterleaved data to correct an error included in the data. . The outer deinterleaver 580 and the outer decoder 590 again perform deinterleaving and error correction decoding.

The demodulator 530 of the example of FIG. 4 performs OFDM demodulation and predecoding processes on pre-coded and OFDM-modulated signals, so that all information carried on some subcarriers by a frequency selective fading channel during communication is lost. Can be prevented.

5 is a diagram illustrating an embodiment of a signal transmission and reception method according to the present invention. Hereinafter, an embodiment of a signal transmission and reception method according to the present invention will be described with reference to FIG. 5.

Precoding is performed to distribute data into the frequency domain so that values of data to be allocated to each subcarrier in the frequency domain are allocated to two or more subcarriers (S120).

In operation S130, the precoded data is converted into a time domain.

Then, the data in the time domain is converted into a signal of the RF band and transmitted (S140).

When the modulated signals are received as described above, the received RF band signals are converted into digital signals (S150). The signals in the time domain are converted into data in the frequency domain (S160). When converting to the frequency domain, the signal is converted to the frequency domain in consideration of synchronization of signals in the time domain.

The data for each subcarrier in the frequency domain is data whose values assigned to each subcarrier are distributed over two or more subcarriers. That is, data for any one subcarrier is data distributed according to the precoding operation of step S120 in the frequency domain. Therefore, inverse operation of the precoding of step S120 is performed to obtain data of the original frequency domain (S170).

Therefore, even when some data in the frequency domain is lost due to frequency selective fading in the transmission channel, since each subcarrier data in the frequency domain is originally distributed data of the frequency domain, if the reverse process of the dispersion process is performed, Data with less influence of selective fading can be obtained.

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.

Referring to the signal transmission and reception method and signal transmission and reception apparatus according to the present invention described above are as follows. According to the method for transmitting and receiving a signal and the apparatus for transmitting and receiving a signal according to the present invention, a signal can be modulated and transmitted to be robust to frequency selective fading, and a signal modulated to be robust to frequency selective fading can be received.

Claims (13)

Performing precoding to distribute data in the frequency domain such that values of data to be assigned to each sub-carrier are assigned to at least two or more subcarriers; Converting the precoded data into a time domain; And And converting the data of the time domain into a signal of a radio frequency (RF) band, and transmitting the converted signal. The method of claim 1, The precoding is a signal transmission method for multiplying the vanderMonde matrix data of the frequency domain. The method of claim 1, The vanderMonde matrix Θ has a natural number L of subcarriers and a component θ of the matrix with respect to the natural number k.

If, the signal transmission method according to the following formula.

Converting the received RF band signals into digital signals; Converting to the transformed frequency domain to obtain data in which values of data allocated to each subcarrier are distributed to at least two or more subcarriers; And Performing an inverse operation of variance on the distributed data to obtain a data value assigned to each subcarrier. The method of claim 4, wherein The precoding is a signal receiving method for multiplying the vanderMonde inverse matrix data of the time domain. The method of claim 4, wherein In the vanderMonde inverse matrix, the number of subcarriers is a natural number L, and the component θ of the matrix is a natural number k.

If, the signal receiving method is an inverse matrix of the matrix Θ of the following equation.

A first signal array unit for arranging sequentially input data in parallel by the number of subcarriers; A precoding unit which multiplies each of the arranged data by a vanderMonde matrix and outputs the data; A signal converter converting the output signal into a time domain; A second signal array configured to sequentially arrange and output signals output from the signal converter; A guard interval inserting unit inserting a guard interval into the signals output by the second signal array; An upconversion unit for converting the signal with the protection interval inserted into an RF band; And And a transmitter for transmitting a signal output by the upconversion unit. The method of claim 7, wherein The vanderMonde matrix Θ has a natural number L of subcarriers and a component θ of the matrix with respect to the natural number k.

In the case, the signal transmission apparatus according to the following formula.

The method of claim 7, wherein The signal transmission device is a signal transmission device capable of transmitting a broadcast signal according to the digital video broadcasting (DVB) system. A receiver configured to receive a signal including a video signal; A synchronization unit for acquiring synchronization of the signal output from the reception unit; A demodulator for converting the signals outputted by the synchronizer into data of a frequency domain, and performing a reverse dispersion operation on the data converted in at least two subcarriers to each subcarrier; A frame parser configured to output data included in a data section among data output by the demodulator; A symbol demapping unit which demaps and outputs data output by the frame parsing unit into a bit string; A deinterleaver for deinterleaving the bit string output by the symbol demapping unit; And And a decoder which decodes the deinterleaved data. The method of claim 10, The inverse dispersion operation of the demodulator is performed by an inverse matrix of the vanderMonde matrix. The method of claim 11, In the inverse matrix, the number of subcarriers is a natural number L, and the component θ of the matrix is a natural number k.

Is a signal receiving device which is an inverse matrix of the matrix Θ of the following equation.

The method of claim 10, The signal receiving device is a signal receiving device capable of receiving a broadcast signal according to the digital video broadcasting (DVB) system.

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