KR100824367B1 - Orthogonal Frequency Division Multiplexing transmitter and a method of processing ???? signal thereof - Google Patents

Abstract

N is an arbitrary positive integer, and under the condition that K '(= ^2N )> K (≠ ^2N ), signal processing K (≠ ^2N ) parallel data into one OMD symbol in the frequency domain The OMD transmitter has an insertion unit for inserting guard bands so that the parallel data of one OMD DM symbol is K '(= 2 ^N ), and the K' (= 2 ^N ) parallel data of the frequency domain in the time domain. of K K corresponding to the parallel data, the sample data K (≠ 2 ^N) of the '(= 2 ^N) of the sample sub-data inverse-Fourier-transforming the conversion, and K of the filtered time domain' (= 2 ^N) ( And a resampling section for resampling K '(= ^2N ) pieces of sample data so as to be equal to? ^2N pieces of sample data. Thus, it may be possible to simplify the hardware implementation and operation of the system and also be designed to be compatible with other devices, such as DVB-T, in which ^2N- IFFT is generally used.

Resampling, IFFT, 4096, IDFT, Sampling Rate, OFDM, Inverse Fourier Transform

Description

ODFM transmitter and signal processing method {Orthogonal Frequency Division Multiplexing transmitter and a method of processing

1 is a schematic block diagram of a conventional TDS-OFDM transmitter;

FIG. 2 is a view showing that OFMD symbols are switched from a frequency domain to a time domain by K (≠ ^2N ) -IDFT of FIG. 1;

3 is a schematic block diagram of a TDS-OFDM transmitter of the present invention;

FIG. 4 is a view illustrating conversion of an OFMD symbol from a frequency domain to a time domain by K ′ (= 2 ^N ) -IFFT of FIG. 3, and

FIG. 5 is a flowchart illustrating a signal processing method of the OMD transmitter of FIG. 3.

Explanation of symbols on the main parts of the drawings

100: FEC 200: serial / parallel converter

310: inserting portion 330: 2 ^N -IFFT

350: resampling part 400: parallel / serial conversion part

500: GI insertion part 600: PN part                 

700: filter portion 800: RF portion

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) transmitter, and more particularly, to an Inverse Fourier Transform (IFFT) for converting an OPM signal from a frequency domain to a time domain in an OFM transmitter. .

Orthogonal Frequency Division Multiple (OFDM) technology is commonly used in digital audio broadcasting (DAB), digital television, wireless local area networks (WLANs), and wireless asynchronous transmission. It is widely applied to digital transfer technologies such as wireless asynchronous transfer mode (WATM). The OFDM scheme is a multi-carrier technology in which data to be transmitted is divided into several pieces and modulated and then transmitted in parallel. The OFDM scheme is similar to the conventional FDM, but above all, it is possible to obtain optimal transmission efficiency in high-speed data transmission by maintaining orthogonality between subcarriers.

1 is a block diagram illustrating a function of a TDS-OFDM transmitter for transmitting a conventional OFDM signal. The input data bit stream is coded so that a receiver (not shown) can detect and correct an error by an error detection method set by the FEC 10. After that, the serial data inputted by the serial / parallel conversion unit 20 is converted into K (? ^2N ) parallel data and outputted. Thereafter, K (≠ ^2N ) -IDFT, that is, K (≠ ^2N ) point inverse discrete Fourier transform (hereinafter referred to as IDFT) 30, is transformed into sample data in the time domain. Here, K (≠ ^2N ) is a frequency domain index, and may indicate an index of a subcarrier. The K parallel data inputs of the IDFT 30 are defined as one OFDM symbol in the frequency domain. That is, the IDFT 30 modulates K (≠ 2 ^N ) parallel data in the frequency domain into K subcarriers in the time domain and outputs K (≠ 2 ^N ) sample data. That is, K (≠ 2 ^N ) parallel data is converted into one complex number corresponding to the phase and amplitude of each subcarrier, assigned to each subcarrier on the frequency spectrum, and then the complex data on the frequency spectrum is timed. By performing an inverse fast Fourier transform on a time spectrum, sample data modulated with K (≠ ^2N ) subcarriers is output. For example, the number of input points of the IDFT 30 may be 3780.

FIG. 2 is a diagram for explaining an example where the input point of the IDFT 30 is 3780, that is, the 3780-IDFT 30. As shown in FIG. 2, 3780 parallel data in the frequency domain are input to the 3780-IDFT 30 to be inverse Fourier transformed to obtain 3780 sample data and a sampling rate of 3780 × 27.56 MHz (carrier spacing) = 7.56 MHz. shows an example of processing in the time domain. That is, 3780 parallel data are allocated to each subcarrier in the frequency domain, and then the inverse fast Fourier transform is performed in the time domain to output sample data modulated with K (≠ 2 ^N ) subcarriers. The sampling rate is 7.56 MHz.

The K (≠ ^2N ) sample data output in parallel are converted into serial data by the parallel / serial conversion unit 40, and are output. The GI (Guard interval) inserting unit 50 outputs the serial data output by K ( A guard interval (GI) is inserted and output in ≠ 2 ^N ) sample data units, that is, one OFDM symbol unit. The guard interval is data obtained by copying some sample data of the end of the OFDM symbol composed of K (? ^2N ) sample data and is inserted at the front of the OFDM symbol.

The PN unit 60 inserts a timing synchronization signal and a PN sequence for channel prediction before the guard period GI.

The filter unit 70 transmits K (≠ 2 ^N ) sample data and an OFDM symbol covered with PN to a predetermined waveform by a predetermined waveform, and transmits the result to a wireless channel through the RF unit 80.

As described above, a technique of converting an OFDM symbol from a frequency domain to a time domain using an IDFT 30 having a K (≠ 2 ^N ) has been used. However, the structure of such an IDFT is described in references Zhi-Xing Yang, Yu-Peng Hu, Chang-Yong Pan, and Lin Yang, "Design of a 3780-Point IFFT Processor for TDS-OFDM," IEEE TRANSACTIONS ON BROADCASTING, VOL. , 48, NO, 1, MARCH 2002, Page 57-61 and the like, it can be seen that the implementation complexity and calculation inefficiency is large, as shown in the following Table 1 shown.

3780-point IDFT (≠ 2 ^N ) 4096-point IFFT (= 2 ^N ) Real additions 140184 123792 Real Multiplications 50712 48248 Latency Prouduced by buffer 8064 sample clocks 4095 sample clocks Buffer Requirement 141612 bits 106470 bit

In other words, as shown in the results of Table 1, when using K (≠ 2 ^N : 3780) -IFFT rather than K '(= 2 ^N : 4096) -IFFT, the amount of computation, the required buffer, and the latency by the buffer are significantly higher. It can be seen that a lot is consumed.

Therefore, the OFDM transmitter o K (≠ 2 ^N) -IDFT in K '(= 2 ^N), if using a -IFFT to the inverse Fourier transformation, to improve the complexity of a simpler implementation and calculation OFDM You will get a transmitter.

The present invention has been made to solve the above problems, and a first object of the present invention is to simplify the system implementation of the OSF transmitter using K '(= ^2N ) -IFFT.

A second object of the present invention is to provide an FM transmitter which can be designed to be compatible with other devices.

In the OMD transmitter according to the present invention for achieving the above object, in the frequency domain under the condition that N is any positive integer, K '(= 2 ^N )> K (≠ 2 ^N ), K ( In the OMD transmitter which processes ≠ 2 ^N ) parallel data into one OFM die symbol, an insertion for inserting guard bands so that the parallel data of one OFM die symbol becomes K '(= 2 ^N ) unit, and a frequency domain of K '(= 2 ^N) of the parallel data time domain K' (= 2 ^N) of the inverse Fourier transformer, and the converted time domain to convert sample data K '(= 2 ^N ), the sample data K (≠ 2 ^N) of K corresponding to the parallel data (≠ 2 ^N) of samples to be the same as the data K '(= 2 ^N) having parts of re-sampling to re-sampling the sample data, the re-sampling portion K of '(= 2 ^N) of samples corresponding to the data K' K samples corresponding to the sampling rate for K (≠ 2 ^N) samples data The re-sampling so as to be equal to the byte.

Preferably, the inserting unit inserts {K '(= ^2N ) -K (≠ ^2N )} invalid data in both bands of K (≠ ^2N ) parallel data, and the invalid data is'Zero' data. .

More preferably, the re-sampling portion K '(= 2 ^N) of samples corresponding to the data K' sampling rate, the K (≠ 2 ^N) wherein in the time domain so as to be equal to the K sampling rate corresponding to the sample data Increase the time interval between K '(= 2 ^N ) sampling data.

On the other hand, in the frequency domain according to the present invention, a signal processing method of an OPM transmitter which processes K (≠ ^2N ) parallel data into one OMD symbol, includes the parallel data of one OMD symbol. Inserting guard bands such that there are K '(= 2 ^N ) pieces; Inverse Fourier transforming the K '(= ^2N ) parallel data in the frequency domain into K' (= ^2N ) sample data in the time domain; And the converted time-domain K '(= 2 ^N) of the to be the same as K (≠ 2 ^N) samples data corresponding to the sample data to the K (≠ 2 ^N) parallel data K' of (= 2 ^N) comprising the step of resampling the sampled data, re-sampling stage, as in K K sampling rate corresponding to the sampling rate to sample data ^{K (≠ 2 N) '(} = 2 N) samples K corresponding to the data " Resampling as possible.

Preferably, in the inserting step, {K '(= 2 ^N ) -K ((≠ 2 ^N )} pieces of invalid data are inserted into both bands of the K (≠ 2 ^N ) parallel data, and the invalid data is'Zero'. Data.

In addition, the re-sampling step, K sampling rate '(= 2 ^N) samples K corresponding to the data' K (≠ 2 ^N) in the time domain so as to be equal to the K sampling rate corresponding to the sample data K '( It is characterized in that to increase the time interval between = 2 ^N ) sampling data.

Thus, the old developing complex, computationally inefficient K (≠ 2 ^N) -IDFT instead of K (= 2 ^N) - By using the IFFT, to simplify the hardware implementation and operation of the system, and also, generally 2 ^N - It may be possible to design for compatibility with other devices such as DVB-T, where IFFT is used.

Hereinafter, with reference to the drawings will be described in detail an embodiment according to the present invention.

Figure 3 is an embodiment according to the present invention, a prior art K (≠ 2 ^N) -IDFT of Figure 1 K '(= 2 ^N) T for the case by use -IFFT DS - OFDM (TDS-OFDM) A schematic block diagram of the transmitter. Here, N is an arbitrary positive number, and it is a condition of K '(= ^2N )> K (≠ ^2N ), and below, it demonstrates that K is 3780 and K' is 4096 as an example.

The TDS-OFDM transmitter includes a forward error corrector (FEC) 100, a serial / parallel conversion unit 200, an insertion unit 310, and K '(= 2 ^N ) -IFFT (Inverse Fast). Fourier Transform (330), Resampling (350), Parallel / Serial Transformation (400), Guard Interavl (GI) Insertion Unit 500, PN Unit 600, Filter Unit 700, RF Unit (800) and so on.

The FEC 100 codes the input data bit stream so that the receiver can detect and correct an error by an error detection method set for an OFDM symbol.

The serial / parallel conversion unit 200 converts the error coded serial data into predetermined parallel data and outputs the converted parallel data. That is, as in the conventional transmitter of FIG. 1, K (? 2 ^N ) parallel data are output.

The inserter 310 inserts a guard band to the OFDM symbol in the frequency domain converted into K (≠ 2 ^N ) parallel data by the serial / parallel converter 200. That is, as shown in FIG. 4, by filling 'Zero' data by {K '(= 2 ^N ) -K (≠ 2 ^N )} in the outer band of K (≠ 2 ^N ) parallel data in the frequency domain, K '(= 2 ^N ) parallel data are prepared. Where N is any positive integer and K '(= 2 ^N ) > K (≠ 2 ^N ), K '(= 2 ^N ) is the frequency domain index (index), and may represent the index of the subcarrier. Accordingly, K '(= 2 ^N ) parallel data are defined as one OFDM symbol in the frequency domain.

In this way, 'Zero' data is inserted into both bands of the K (≠ 2 ^N ) parallel data by {K '(= 2 ^N ) -K (≠ 2 ^N )}, so that K' (= 2 ^N ) parallel data. Providing the is for use as parallel data of the K '(= 2 ^N ) -IFFT unit 330 of the next stage. Hereinafter, a case where K (≠ 2 ^N ) is 3780 and K '(= 2 ^N ) is 4096 will be described as an example.

The 4096-IFFT unit 330 inserts 'Zero' data by the insertion unit 310 to inverse Fourier transform the 4096 parallel data in the frequency domain to have 4096 sample data and 8.192 MHz sampling rate in the time domain. .                     

More specifically, the 4096-IFFT 330 modulates 4096 parallel data in the frequency domain into 4096 subcarriers in the time domain and outputs 4096 sample data. That is, as shown in FIG. 4, 4096 parallel data into which 'Zero' data is inserted are converted into one complex number corresponding to the phase and amplitude of each subcarrier and assigned to each subcarrier in the frequency domain. Then, by performing inverse fast Fourier transform on the complex data of this frequency domain in the time domain, sample data modulated with 4096 subcarriers is output. In addition, the sampling rate for 4096 sample data in the time domain is 4096 x 2KHz (carrier spacing) = 8.192 MHz.

Therefore, resampling is required to equalize 3780 sample data and sampling rate in the time domain.

That is, the resampling unit 350 reduces the 4096 sample data in the time domain to 3780 by 4096-IFFT, and also reduces the sampling rate of 8.192 MHz to 7.56 MHz, which is shown in the conventional 3780-IDFT (Fig. 1). In 30), inverse Fourier transform is performed to adjust the sample data and the sampling rate to be the same.

The 30780 sample data resampled is converted into serial data by the parallel / serial converter 400 and output. The GI (Guard interval) inserting unit 500 converts the output serial data into 3780 sample data units, that is, 1 A guard interval (GI) is inserted and output in units of OFDM symbols. The guard period (GI) is a copy of some sample data at the end of the OFDM symbol composed of 3780 sample data and is inserted at the front of the OFDM symbol.

In addition, the PN unit 600 inserts a timing synchronization signal and a PN sequence for channel prediction before the guard period GI.

The filter 700 filters 3780 pieces of sample data and an OFDM symbol covered with a PN in a predetermined waveform by a predetermined waveform and is transmitted to the wireless channel through the RF unit 800.

That is, the 3780 sample data and the sampling rate (7.56 MHz) processed by the resampling unit 350 are processed in the same way as the sample data and the sampling rate converted by inverse Fourier by the conventional 3780-IDFT 30, The signal processing is performed in the same manner as the conventional method shown in FIG.

Therefore, the implementation of the OSF transmitter using ^2N- IFFT enables a simpler implementation and operation in hardware than when using an IFFT that does not become ^2N . It is also possible to design to be compatible with other devices, such as DVB-T, in which ^2N- IFFT is generally used.

Referring to Figure 5 will be described in detail the OPM signal processing method of the OMD transmitter according to the present invention.

An error is detected in the data bit stream input by the FEC 100 by the error detection method set for the OFDM symbol, and the detected error is corrected (S10).

A guard band is inserted into an OFDM symbol of a frequency domain of predetermined parallel data (3780 pieces) output by the serial / parallel converter 200 (S20). That is, as shown in FIG. 4, 4096 parallel data are prepared by filling 'Zero' data in the outer band of 3780 parallel data in the frequency domain.                     

'Zero' data is inserted by the inserting unit 310 to convert 4096 parallel data into the inverse Fourier in the 4096-IFFT 330 in the frequency domain (S30). Therefore, the OFDM symbol in the time domain has 4096 sample data and a sampling rate of 8.192 MHz.

Thereafter, the sample data and sampling rate of the OFDM symbol in the time domain are resampled to adjust to 3780 and 7.56 MHz (S40). That is, the 4096-IFFT 330 reduces the 4096 sample data in the time domain to 3780, and also reduces the sampling rate of 8.192 MHz to 7.56 MHz, which is inverse to the conventional 3780-IDFT 30 shown in FIG. The sample data to be processed by Fourier transform and the sampling rate are adjusted in the same way.

Thereafter, the 3780 sample data processed as serial data by the parallel / serial conversion unit 400 are protected by the guard interval (GI) insertion unit 500 in 3780 sample data units, that is, 1 OFDM symbol unit. The section GI is inserted and output (S50).

The PN unit 600 covers the PN on an OFDM symbol composed of GI (Guard Interavl) and 3780 sample data, and the OFDM symbol is filtered by a predetermined waveform by the filter unit 700, and then the RF unit 800 is applied. The RF signal is processed and transmitted over a wireless channel (S60).

Thus, by complex phenomena and it obtains, using computationally inefficient K (≠ 2 ^N) -IDFT instead of K (= 2 ^N) -IFFT, to simplify the hardware implementation and operation of the system, and also, generally 2 ^N - It may be possible to design for compatibility with other devices such as DVB-T, where IFFT is used.

According to the present invention, in an OFM transmitter which signals K (≠ ^2N ) parallel data in a frequency domain with one OMD symbol, K '(= 2 ^N instead of K (≠ 2 ^N ) -IDFT By inverse Fourier transform using) -IFFT, the hardware implementation and operation of the system can be simplified. It may also be possible to design to be compatible with other devices, such as DVB-T, in which ^2N- IFFT is generally used.

In the above described and illustrated with respect to the preferred embodiment of the present invention, the present invention is not limited to the specific preferred embodiment described above, without departing from the gist of the invention claimed in the claims in the art Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

Claims (12)

N is any positive integer and K '(= 2 ^N ) According> K under the condition (2 ≠ ^N), the K ^(N ≠ 2) parallel data in the frequency domain in the OFDM transmitter for processing signals in one OFDM symbol, An insertion unit for inserting guard bands so that the K (≠ ^2N ) parallel data of one OMD DM symbol becomes K '(= ^2N ) pieces; An inverse Fourier transform unit converting the K '(= 2 ^N ) parallel data in the frequency domain into K' (= 2 ^N ) sample data in the time domain; And It converted the in the time domain K '(= 2 ^N) of the to be the same as K (≠ 2 ^N) samples data corresponding to the sample data to the K (≠ 2 ^N) parallel data K' (= 2 ^N ) a resampling unit for resampling sample data; The re-sampling portion o F. characterized in that the re-sampling to be the same as K sampling rate that the K corresponds to the sampling rate "(= 2 ^N) K corresponding to the sample data, the K (≠ 2 ^N) samples data DM transmitter. The method of claim 1, The insertion unit, And {K '(= ^2N ) -K (≠ ^2N )} invalid data are inserted into both bands of the K (≠ ^2N ) parallel data. The method of claim 2, And the invalid data is zero data. The method of claim 1, The resampling unit, The K 'in the time domain such that the K' sampling rate corresponding to the K '(= 2 ^N ) sample data is equal to the K sample rate corresponding to the K (≠ 2 ^N ) sample data. = 2 ^N ) OFM transmitter, characterized in that to extend the time interval between each sampling data. The method of claim 1, The K (≠ 2 ^N ) is 3780 transmitter, characterized in that the. The method of claim 1, The K '(= 2 ^N ) is 4096, characterized in that the FM transmitter. In the signal processing method of the OEM transmitter of the K (≠ 2 ^N ) parallel data in the frequency domain signal processing as one OFM symbol, Inserting guard bands so that the parallel data of one OMD symbol is equal to K '(= 2 ^N ); Inverse Fourier transforming the K '(= 2 ^N ) parallel data in the frequency domain into K' (= 2 ^N ) sample data in the time domain; And It converted the in the time domain K '(= 2 ^N) of the to be the same as K (≠ 2 ^N) samples data corresponding to the sample data to the K (≠ 2 ^N) parallel data K' (= 2 ^And resampling ^N ) sample data. In the re-sampling step, the K to the sample rate '(= 2 ^N) samples K corresponding to the data, characterized in that the re-sampling to be the same as K sampling rate corresponding to the K (≠ 2 ^N) samples data Signal Processing Method of UF DM Transmitter. The method of claim 7, wherein In the insertion step, And {K '(= ^2N ) -K ((≠ ^2N )} invalid data are inserted into both bands of the K (≠ ^2N ) parallel data. The method of claim 8, And the invalid data is zero data. The method of claim 7, wherein The resampling step, The K 'in the time domain such that the K' sampling rate corresponding to the K '(= 2 ^N ) sample data is equal to the K sample rate corresponding to the K (≠ 2 ^N ) sample data. = 2 ^N ) A signal processing method of the OMD transmitter, characterized by increasing the time interval between each sampling data. The method of claim 7, wherein And the K (≠ ^2N ) number is 3780. The method of claim 7, wherein The K '(= 2 ^N ) is 4096 signal processing method of the FM transmitter.

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