JP2001345780A - Ofdm receiving device using maximum ratio synthesization diversity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an OFDM method receiving device for efficient maximum ratio synthesization diversity reception. SOLUTION: A multichannel correlation detection part acquires FFT window timing, subcarrier phase correction information, and weight factor correction information based on correlation peak detection position and correlation peak detection frequency corresponding to the number of reception antennas. A subcarrier phase control part sets complex symbol phase and timing correction amount for each OFDM subcarrier with the last FFT window timing as a reference, while a subcarrier phase correcting part outputs with phase and output timing according to the correction amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to OFDM (Orthogonal Frequency Divisio) in which the frequency of each carrier is set so that each carrier is orthogonal to each other within a symbol section.
The present invention relates to a receiver of the n multiplexing (orthogonal frequency division multiplexing) type, and more particularly to an OFDM receiver that performs diversity reception using signals received by a plurality of antennas arranged so that correlation between signals is reduced.

More specifically, the present invention relates to an OFDM receiving apparatus configured to provide a higher diversity gain than demodulating a plurality of received signals and taking the maximum ratio combination thereof. The present invention relates to an OFDM receiving apparatus that performs the operation.

[0003]

2. Description of the Related Art In recent years, the spread and demand of mobile communications such as mobile phones and vehicle-mounted phones have been remarkably developing. Now everyone is using mobile communication devices and is being recognized as a necessity in social life.

[0004] When wireless transmission is performed in a mobile propagation environment, deterioration of transmission quality due to fading is a particular problem.

As a technique for realizing high-speed and high-quality wireless transmission, "OFDM (Orthogonal Frequency Division)
Multiplexing: orthogonal frequency division multiplexing) is expected. The OFDM system is a type of multi-carrier (multi-carrier) transmission system, and the frequency of each carrier is set such that the carriers are orthogonal to each other within a symbol section. An example of information transmission is that information transmitted in serial is transmitted serially at every symbol period lower than the information transmission rate.
A plurality of data output by parallel conversion are assigned to each carrier and modulated for each carrier, and the inverse FFT is performed on the plurality of carriers, thereby maintaining the orthogonality of each carrier on the frequency axis and the signal on the time axis. Convert to and send. For example, each carrier is BPSK (Binary Phase S)
hift Keying) It is assumed that the information transmission rate is 256
When serial / parallel conversion is performed at a 1 / symbol period, the total number of carriers becomes 256, and inverse FFT is performed on 256 carriers. Demodulation is performed in the reverse operation, that is, FFT is performed to convert a signal on the time axis into a signal on the frequency axis. This is performed by reproducing the transmitted information. It has been experimentally confirmed that the OFDM transmission system has good transmission characteristics even with a delayed wave.

In the OFDM transmission, one symbol period is longer than that of a single carrier transmission system having the same transmission capacity. Therefore, the fading resistance against multipath fading or selective fading with a large delay time difference between incoming waves is strong. There are features. However, it is hard to say that the fading resistance characteristic against flat fading, in which the delay time difference between the arriving waves is relatively small, is strong.

As an effective countermeasure against flat fading, it is known that "diversity reception" using signals received by a plurality of antennas arranged so as to reduce the correlation between signals is effective. I have. Diversity reception includes "selective diversity", which selectively uses the received signal with the highest signal power among multiple received signals, and "maximum ratio combining," which demodulates each of the received signals and takes the maximum ratio combination. Diversity. "

[0008] Compared with the device scale, selective diversity can combine reception systems after selecting a reception signal into one, but maximum ratio combining diversity requires a reception system until demodulation for each reception signal. Therefore, it becomes large-scale. Further, when compared in terms of the diversity gain, the selective diversity is degraded by about 2 dB from the maximum ratio combining diversity. Therefore, when performing diversity reception, it is necessary to determine which method is appropriate in terms of both the size of the desired receiving apparatus and the diversity gain.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an OFDM (Orthogonal Frequency) in which the frequency of each carrier is set so that each carrier is orthogonal to each other within a symbol section.
An object of the present invention is to provide an excellent receiver of an ency division multiplexing (orthogonal frequency division multiplexing) system.

It is a further object of the present invention to provide an excellent OFDM for diversity reception using signals received at a plurality of antennas arranged such that the correlation between the signals is small.
A receiving device is provided.

It is a further object of the present invention to provide an excellent OFDM receiver having a higher diversity gain than demodulating a plurality of received signals and obtaining the maximum ratio combination.

A further object of the present invention is to provide an excellent OF which can efficiently perform maximum ratio combining diversity reception.
An object of the present invention is to provide a DM receiver.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has been made in consideration of the above-described problems.
A receiving device, a receiving antenna, an RF unit for down-converting a signal received via the receiving antenna from an RF frequency band to a baseband signal, and performing A / D conversion on the down-converted baseband signal A digital converter for converting to a complex digital signal, an FFT for obtaining a complex digital signal for each OFDM subcarrier by performing a Fourier transform for one period of the OFDM symbol according to the FFT window timing, and an OFDM based on the subcarrier phase correction amount A plurality of reception units each including a subcarrier phase correction unit that corrects the phase and output timing of a complex symbol for each subcarrier, and a transmission line estimation unit that detects an error amount of a received signal such as transmission line fluctuation, frequency offset, and noise. System and the complex digital signal Seki measures the correlation power taking, based on the number of detected correlation peak with a correlation peak detection position, FF
A multi-channel correlation detection unit for obtaining T window timing, OFDM subcarrier phase information, and weight coefficient correction information; and a subcarrier so that the subcarrier phase and output timing in each receiving system match based on the OFDM subcarrier phase information. Subcarrier phase control unit for setting the amount of phase correction, and OFDM in each reception system
A weighting factor calculating unit that calculates a weighting factor of a complex symbol for each subcarrier, a maximum ratio combining soft-decision demodulating unit that performs demodulation and maximum ratio combining of a complex digital signal for each of the Fourier-transformed OFDM subcarriers in each receiving system; And an OFDM receiver using maximum ratio combining diversity.

[0014] The subcarrier phase control unit is configured to provide an OFF in a receiving system having the latest FFT window timing.
A subcarrier phase correction amount is set based on the phase and timing of the complex symbol for each DM subcarrier, and the subcarrier phase correction unit converts the complex symbol for each OFDM subcarrier based on the subcarrier phase correction amount. You may make it output with a phase and output timing.

Further, the weighting coefficient calculation unit calculates the in-phase O
The weighting factor of the complex symbol for each OFDM subcarrier in each receiving system may be calculated from the received signal power of the complex symbol for each FDM subcarrier or the power ratio of the reference carrier and the weighting factor correction information.

The maximum ratio combining soft-decision demodulation unit demodulates a complex symbol for each OFDM subcarrier in each reception system, and after multiplying each of the weighting factors calculated by the weighting factor calculation unit, OFD
The sum of the demodulated symbols for each of the M subcarriers may be calculated.

Further, the multi-channel correlation detecting section uses the signal of the guard interval portion to take a correlation for each of complex digital signals for each of a plurality of OFDM subcarriers corresponding to the number of receiving antennas, and obtains a correlation power. The measurement is performed, the correlation peak position and the number of correlation peaks are detected, and for each complex digital signal, each FFT window is calculated from the largest peak position.
The timing is determined, and if the number of correlation peaks is more than one or the magnitude and width of the correlation peak position are larger than a preset threshold value indicating multipath detection, the presence or absence of multipath detection is determined. May be determined for each complex digital signal for each of a plurality of OFDM subcarriers in each reception system, in accordance with the presence or absence of the coefficient.

The multi-channel correlation detector monitors transmission signal format information, such as FFT size, guard interval, guard band, and modulation scheme, transmitted from the transmitting side as correlation detection control information. When the FFT size, guard interval, and guard band are changed, the correlation calculation cycle and threshold are changed according to the respective information, the complex digital signal is correlated, and the correlation power is measured. F for the receiving system based on the correlation peak detection position and the correlation peak detection number.
The FT window timing, the subcarrier phase correction information, and the weighting coefficient correction information are reset, and the correlation peak detection position and the correlation peak detection number are calculated for each reception system to obtain F.
The FT window timing, the subcarrier phase correction information, and the weight coefficient correction information may be updated. When the modulation scheme is changed, the error amount of the received signal when the pilot symbol is inserted is calculated by using an equalized signal for each subcarrier obtained from the reproduced carrier calculated based on the pilot symbol, When the equalization is performed, the error amount of the received signal is calculated based on the difference between the symbol of the complex digital signal of each OFDM subcarrier and the symbol at the previous time, and the error amount of the phase and amplitude is equalized signal for each subcarrier. The calculation of the weighting factor used as may be performed by switching each time it is changed.

The weighting factor calculation unit calculates the weighting factors of the complex symbols for each OFDM subcarrier for each receiving system, adds all the values, and divides each weighting factor by the addition result to normalize And if the addition result is equal to or smaller than a threshold value that can guarantee a predetermined line quality, the transmission quality information such as transmission quality deterioration is transmitted to the OFDM.
You may make it output by attaching to the complex symbol for every subcarrier.

[0020]

The OFDM maximum ratio combining receiver according to the present invention comprises:
A plurality of receiving antennas, that is, a plurality of receiving systems are provided. In each receiving system, the received signal of the receiving antenna is
The digital signal is converted into a complex digital signal by the digital signal converter and the digital converter, and is sent to the FFT unit and the multi-channel correlation detector.

The multi-channel correlation detector measures the correlation power by taking the correlation of the complex digital signal, and based on the correlation peak detection position corresponding to the number of receiving antennas and the correlation peak detection number, the FFT window timing,
OFDM subcarrier phase information and weight coefficient correction information are obtained, and these pieces of information are supplied to an FFT unit, a subcarrier phase control unit, and a weight coefficient calculation unit, respectively.

In the FFT section, a complex OFD corresponding to the number of reception antennas is performed according to the FFT window timing.
Performs Fourier transform for one period of M symbols, and obtains OFDM
Generate a complex symbol for each subcarrier.

[0023] The subcarrier phase control unit determines, for all OFDM subcarriers corresponding to the number of receiving antennas,
A correction amount is set when the phase and the timing are different from each other based on the phase and the timing of the complex symbol for each OFDM subcarrier having the latest FFT window timing. The subcarrier phase correction unit outputs complex symbols for each OFDM subcarrier corresponding to the number of receiving antennas at each phase and output timing based on the correction amount set by the subcarrier phase control unit.

The weighting factor calculators are configured to output OF signals having the same phase.
From the received signal power of the complex symbol for each DM subcarrier or the power ratio of the reference carrier and the weighting factor correction information, the weighting factor of the complex symbol for each of a plurality of OFDM subcarriers corresponding to the number of receiving antennas is calculated.

The maximum ratio combination soft decision demodulation unit performs maximum ratio combination. That is, a plurality of Os corresponding to the number of receiving antennas
By demodulating complex symbols for each FDM subcarrier,
After multiplying each received signal weighting factor calculated by the weighting factor calculation unit, the sum of demodulated symbols for each OFDM subcarrier is calculated.

According to the OFDM maximum ratio combining diversity receiving apparatus according to the present invention, in the blocks after the FFT section of each receiving system, a plurality of OFDM subcarriers all operate at the same phase and timing, so that the symbol for each subcarrier The calculation of the weight coefficient and the maximum ratio combination in units can be easily performed. Also, blocks subsequent to the FFT unit can operate with a single clock.

Further, the multi-channel correlation detecting section measures the correlation power by using the signals in the guard interval portion to obtain a correlation for each complex digital signal for each of a plurality of OFDM subcarriers corresponding to the number of receiving antennas. Is performed to detect the correlation peak position and the number of correlation peaks, so that the FFT window timing of each complex digital signal can be determined from the largest peak position. Further, when the number of correlation peaks is plural or when the magnitude and width of the correlation peak position are larger than a preset threshold value indicating multipath detection, it is possible to determine the presence or absence of multipath detection. Depending on the presence or absence of multipath detection, a correction coefficient for correcting the weight coefficient of the weight coefficient calculation unit is obtained for each complex digital signal for each of a plurality of OFDM subcarriers corresponding to the number of reception antennas. Transmission path conditions such as FFT window timing and presence / absence of multipath in each reception system can be obtained independently.

The multi-channel correlation detection unit monitors transmission signal format information such as FFT size, guard interval, guard band, and modulation scheme sent from the transmission side as correlation detection control information.
When the FFT size, the guard interval, and the guard band are changed, the correlation calculation cycle and the threshold are changed according to the respective information, and the correlation of the complex digital signal is taken to measure the correlation power. Further, based on the correlation peak detection position and the correlation peak detection number corresponding to the number of reception antennas, FFT window timing, subcarrier phase correction information, and weight coefficient correction information are reset,
A correlation peak detection position corresponding to the number of reception antennas and a correlation peak detection number are calculated, and FFT window timing, subcarrier phase correction information, and weight coefficient correction information are calculated.

When the modulation scheme is changed, the error amount of the received signal when the pilot symbol is inserted is calculated by using the equalized signal for each subcarrier obtained from the reproduced carrier calculated based on the pilot symbol, When coding is performed, the error amount of the received signal is calculated by taking the difference between the symbol of the complex digital signal of each OFDM subcarrier and the symbol at the previous time, and the error amount of the phase and amplitude is equalized for each subcarrier. The calculation of the weight coefficient used as a signal is switched every time the change is made. Thus, maximum ratio combining diversity can be performed according to the transmission signal format.

The weighting factor calculation unit calculates the weighting factors of the complex symbols for each OFDM subcarrier corresponding to the number of receiving antennas, adds all the values, and divides each weighting factor by the addition result. To perform normalization. If the addition result is equal to or less than a predetermined threshold that can guarantee line quality, transmission quality information such as transmission quality deterioration
The output is added to the complex symbol for each FDM subcarrier. By this means, it is possible to make a determination when all the signals received in a plurality of reception systems have fallen into a dip in multipath or frequency selective fading, and furthermore, the line quality degradation information is obtained for each complex symbol for each OFDM subcarrier. Can be output.

Still other objects, features and advantages of the present invention are:
It will become apparent from the following more detailed description based on the embodiments of the present invention and the accompanying drawings.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an OFDM receiving apparatus using selection diversity according to this embodiment, OFD receiving apparatus will be described.
A schematic configuration of an OFDM transmitting apparatus 100 that transmits an M signal will be described with reference to FIG.

[0033] As shown in FIG.
0 is a modulation unit 101 and a pilot symbol insertion unit 1
02, the serial / parallel converter 103, and the IFFT
104, guard interval insertion section 105, analog conversion section 106, transmission RF section 107, transmission antenna 108
And a transmission control unit 109.

The modulation section 101 modulates input data according to the modulation information and timing supplied from the transmission control section 109, and serially outputs modulation symbols.

Pilot symbol insertion section 102 inserts a known data sequence into a modulation symbol sequence as a pilot symbol according to the pilot symbol insertion pattern and timing supplied from transmission control section 109.

The serial / parallel converter 103 converts the input serial data into parallel data by the FFT size according to the FFT (fast Fourier transform) size and timing supplied from the transmission controller 109, Output to the unit 104.

[0037] IFFT section 104 performs FFT according to the FFT size and timing supplied from transmission control section 109.
Inverse FFT for FT size is performed.

The guard section insertion section 105 is provided with the transmission control section 1
According to the guard interval size, guard band size, and timing supplied from 09, guard signals such as guard intervals and guard bands are inserted. The guard interval (section where a part of the signal is repeatedly transmitted) absorbs multipath (multiple reflected radio wave propagation) propagation that is smaller than the guard interval size,
Prevent fatal degradation of reception quality.

The digital transmission signal with the guard signal inserted is subjected to quadrature modulation and D
/ A conversion is performed, up-converted in transmission RF section 107, and transmitted from transmission antenna 108 to the outside of transmission apparatus 100.

The OFDM receiving apparatus according to this embodiment can receive the OFDM signal transmitted from the OFDM transmitting apparatus 100 shown in FIG. 1 by using the maximum ratio combining diversity. In the following description, the OFDM according to the present embodiment is described.
The receiving apparatus performs demodulation by synchronous detection when a pilot symbol is inserted. In addition, two receiving antennas are used to perform maximum ratio combining diversity reception, but the number of receiving antennas is not limited to this, and it is understood that the same effect can be obtained even when three or more antennas are used. I want to be.

FIG. 2 shows a schematic configuration of a maximum ratio combining diversity OFDM receiver 200 according to this embodiment. Hereinafter, description will be made with reference to FIG.

Each of the RF units 203 and 204 converts the signals received by the receiving antennas 201 and 202 into R
Down-convert from the F frequency band to a baseband signal. Each of the digital converters 205 and 206 further converts the baseband signal into a complex digital signal by A / D conversion.

The multi-channel correlation detection section 207 performs correlation detection on the complex digital signals output from each of the digital conversion sections 205 and 206 in accordance with the correlation detection control signal, and performs appropriate FFT window timing,
Subcarrier phase correction information and weight coefficient correction information are detected.

Each of the FFT units 208 and 209 performs a Fourier transform on the complex digital signal output from each of the digital transform units 205 and 206, for the signal obtained by performing the inverse Fourier transform for one period of the OFDM symbol.

The subcarrier phase control section 210 uses the FFT window timing information supplied from the multi-channel correlation detection section 207, and when the FFT window timing of each of the FFT sections 208 and 209 is different, the two To match the timing,
A correction value is calculated so that the phase difference between the OFDM subcarriers becomes zero.

Subcarrier phase correction units 211 and 212
According to the phase information supplied from the subcarrier phase control section 210, the phase difference of the complex symbol sequence for each OFDM subcarrier outputted from each of the FFT sections 208 and 209 is made zero and outputted.

Each of the data storage units 213 and 214 stores the complex symbol for each OFDM subcarrier output from each of the subcarrier phase correction units 211 and 212 and outputs the complex symbol to the soft decision demodulation unit 218 at an appropriate timing. .

Each of the transmission path estimation units 215 and 216 reproduces a symbol error for each OFDM subcarrier from a pilot symbol.

The weight coefficient calculating section 217 compares the equalized signals for each OFDM subcarrier output from each of the transmission path estimating sections 215 and 216, and corrects the weight coefficient supplied from the multi-channel correlation detecting section 207. The weighting factor and the transmission quality are determined according to the information, and the soft decision demodulation unit 21
The weight coefficient is output to 8. In addition, transmission quality such as transmission quality degradation is output for a complex symbol for each OFDM subcarrier determined to have poor transmission quality.

The maximum ratio combining soft-decision demodulation section 218 outputs a symbol error amount for each OFDM subcarrier output from each of the transmission path estimating sections 215 and 216 of the two receiving systems shown in FIG. Using the weight coefficient of each received signal, demodulation by synchronous detection is performed on the complex symbol for each OFDM subcarrier stored in each of the data storage units 213 and 214. Then, a maximum ratio combining process of each soft decision demodulated symbol is performed, and demodulated data is output.

Next, the maximum ratio combining diversity O
The maximum ratio combining diversity reception operation by the FDM receiver 200 will be described.

The signals received by the receiving antennas 201 and 202 are input to RF units 203 and 204, respectively, and are converted into baseband signals. These baseband signals are supplied to the digital conversion units 205 and 206, respectively.
Are subjected to A / D conversion and orthogonal conversion, and input to the multi-channel correlation detection section 207 and the FFT sections 208 and 209 as a baseband complex digital signal.

The multi-channel correlation detection section 207 uses each FFT window / timing position obtained by performing correlation detection on each baseband complex digital signal output from each of the digital conversion sections 205 and 206 as FFT window information. FFT section 208
And 209. Further, the multi-channel correlation detection unit 207 detects the number of peaks of the correlation signal, the peak power thereof, and the subcarrier phase correction information from the window detection information, and outputs the information to the subcarrier phase control unit 210.
Further, a weight correction coefficient is detected and output to the weight coefficient calculation unit 217.

Each of the FFT units 208 and 209 has its own FFT supplied from the multi-channel correlation control unit 207.
According to the FT window information, Fourier transform for one period of the OFDM symbol is performed to obtain a complex symbol for each OFDM subcarrier, and the complex symbol is output to the transmission path estimation units 215 and 216 and the data storage units 213 and 214, respectively.

Each of the transmission path estimators 215 and 216 extracts a pilot symbol from a complex symbol for each OFDM subcarrier, reproduces a reference carrier, and performs amplitude and phase between transmission and reception for each OFDM subcarrier. Is detected.

The weighting factor calculation section 217 obtains power from the equalized signal for each OFDM subcarrier of each of the two receiving systems, corrects the power based on the weighting factor correction information, and adds the respective powers. By dividing each power by the result, a received signal weight coefficient for each subcarrier corresponding to each received sequence is obtained. Further, the addition result is compared with a predetermined threshold value that can guarantee the line quality, and the complex symbol for each OFDM subcarrier determined to have poor transmission quality outputs transmission quality information such as transmission quality deterioration.

The maximum ratio combining soft-decision demodulation section 218 performs a symbol error for each OFDM subcarrier for each OFDM subcarrier stored in the data storage sections 213 and 214 of each of the two reception systems. After dividing by the amount to remove the error component of the received signal, multiplying by the received signal weighting coefficient for each OFDM subcarrier, and then performing maximum ratio combining such as adding for each OFDM subcarrier, and further performing soft decision demodulation processing Then, maximum ratio combining soft decision demodulation data for each OFDM subcarrier is output.

FIG. 3 shows a multi-channel correlation detecting section 2
07 shows a schematic configuration. Hereinafter, description will be made with reference to FIG.

Each of the delay units 301 and 302 delays the complex digital signals 1 and 2 according to the timing signal supplied from the correlation detection control unit 310, and outputs the signals at appropriate timing.

Each of the correlation calculators 303 and 304 calculates the correlation power of the received signals output from each of the delay units 301 and 302 according to the correlation timing supplied from the correlation detection controller 310.

The threshold comparing sections 305 and 306 compare the correlation calculation results of the correlation calculating sections 303 and 304 with the threshold value supplied from the correlation detection control section 310.

Each of the correlation judging sections 307 and 308, based on the timing signal supplied from the correlation detection control section 310, based on the threshold comparison results input from the threshold comparing sections 305 and 306, respectively, and the threshold comparison results stored so far. Then, the FFT window timing is detected, and each FFT window detection success / failure, each window timing information 1 and 2 and a correlation detection result are output.

The correlation detection information generation section 309 determines the number of peaks of the correlation signal, the comparison result of the respective correlation peak powers, and the window detection information from the correlation detection results in the respective receiving systems, and outputs them as correlation detection information. .

The correlation detection control unit 310 generates a timing control signal for each block in the initial synchronization and after the synchronization is obtained.

Next, the operation of the multi-channel correlation detection section 207 configured as shown in FIG. 3 will be described with reference to the correlation detection timing examples shown in FIGS. 4 and 5, respectively.

In the present embodiment, the OFDM signal is
It is composed of a symbol Dn and a guard interval Gn obtained by copying the latter part of the OFDM symbol for a length assigned as a guard interval, and is transmitted in the order of Gn and Dn (where n = 1, 2). , ...). It is also assumed that there is no clock error or frequency offset between transmission and reception.

FIG. 4 shows an example of correlation detection when the incoming wave is a direct wave only or flat fading. As shown in the figure, when receiving only a direct wave, each of the delay units 301 and 302 delays by a known symbol period Ts.

Each of the correlation calculators 303 and 304 calculates the correlation between each of the delayed complex digital signals and the current complex digital signal in accordance with the respective correlation integration times and correlation calculation timing supplied from the correlation detection controller 310. , And calculate the respective correlation data.

The threshold comparing units 305 and 306 compare the correlation data output from the correlation calculating units 303 and 304 with thresholds set in advance according to the correlation detection control information.

Each of the correlation determination units 307 and 308 performs FFT based on the threshold comparison results stored so far in accordance with the timing signal supplied from the correlation detection control unit 310.
By detecting the window timing, each F
FT window detection success / failure, each window timing information 1 and 2 and a correlation detection result are output.

The correlation detection information generating section 309 calculates the correlation signal peak number, the correlation peak power comparison result, the correlation detection information such as FFT window information, and the weight coefficient correction information from the correlation detection result in each receiving system. To detect.

The correlation detection information is supplied to a subcarrier phase control section 210, and the weight coefficient correction information is supplied to a weight coefficient calculation section 217. Further, the FFT window information is supplied to each of the FFT units 208 and 209. Correlation detection information generating section 309 integrates the respective pieces of correlation detection information and outputs the result to subcarrier phase control section 210 as correlation detection information.

[A-2] shows the timing of the correlation detection signal when the reception signal is synchronized when the time corresponding to the number of correlation integrations is set to Tg. Once the correlation data peak is detected, one cycle of the OFDM signal, unless the number of correlation integrations and the correlation calculation timing are changed.
That is, this indicates that the correlation peak is detected in the cycle of Tg + Ts.

FIG. 5 shows an example of correlation detection timing in the case of multipath or selective fading. However, the received signal is a direct wave (D wave) and a delayed wave (U wave)
Is a two-wave model.

In this case, according to the above-described correlation detection timing example, the correlation detection result indicates that the component corresponding to the D wave as shown in [b-2] and the U wave as shown in [b-4] As a result, a correlation detection signal in the form of adding these components is output as shown in [b-5].

FIG. 6 shows a schematic configuration of the weighting factor calculator 217. Hereinafter, description will be made with reference to FIG.

Each of the power calculation sections 401 and 402 outputs the O output from each of the transmission path estimation sections 215 and 216 according to the timing supplied from the weight coefficient calculation control section 408.
For a complex digital signal for each FDM subcarrier,
Power calculation is performed for each OFDM subcarrier.

Each of the weight correction units 403 and 404 has its own power calculation unit 401 and 402 according to the correction coefficient set by the weight coefficient calculation control unit 408 based on the weight coefficient correction information supplied from the multi-channel correlation detection unit 207. Corrects the calculated values.

The addition section 405 is provided with a weight coefficient calculation control section 40
In accordance with the timing supplied from No. 8, each power calculation result is added for each OFDM subcarrier.

The weighting factor calculators 406 and 407 determine whether the adding unit 405 is to operate based on the power calculation results input from the power calculators 401 and 402 and the weighting factor correction information supplied from the weighting factor calculation controller 408. The division is performed by the output addition result, and the weight coefficient corresponding to the complex digital signal for each OFDM subcarrier is calculated based on the result and information from the weight coefficient calculation control unit 408.

The weight coefficient calculation control unit 408 is
5 is compared with a predetermined threshold value that can guarantee the line quality, and the complex symbol for each OFDM subcarrier determined to have poor transmission quality outputs transmission quality information such as transmission quality deterioration and weights. Generate a timing control signal required for coefficient calculation.

FIG. 7 shows a maximum ratio combining soft decision demodulation section 218.
2 shows a schematic configuration of the first embodiment. The maximum ratio combining soft decision demodulation section 218 includes division sections 501 and 502, multiplication sections 503 and 504, an addition section 505, a soft decision demodulation section 506,
A maximum ratio combining soft decision demodulation control section 507 is provided. Hereinafter, description will be made with reference to FIG.

Each of the division units 501 and 502 has a transmission path estimating unit 215 and 216 for the complex digital signal for each OFDM subcarrier in accordance with the timing supplied from the maximum ratio combining soft decision demodulation control unit 507.
Is divided for each subcarrier by the symbol error amount for each OFDM subcarrier output from.

Each of the multipliers 503 and 504 receives the result of the multiplication by the respective multiplier 501 and 502 and the received signal output from the weight coefficient calculator 217 in accordance with the timing supplied from the maximum ratio combining soft decision demodulator controller 507. Multiplication by a weight coefficient is performed for each subcarrier.

The adder 505 adds the multiplication results output from the multipliers 503 and 504 for each subcarrier according to the timing supplied from the maximum ratio combining soft-decision demodulation controller 507, and generates the maximum ratio combining complex digital signal. Output as a signal.

[0086] Soft decision demodulation section 506 performs soft decision demodulation of the maximum ratio combined complex digital signal for each OFDM subcarrier, and outputs the result as demodulated data.

The maximum ratio combining soft decision demodulation control section 507 generates a timing control signal required for maximum ratio combining and soft decision demodulation.

FIGS. 8 and 9 show examples of the FFT window timing of the OFDM maximum ratio combining diversity receiver 200 shown in FIG. Hereinafter, the timing control of the OFDM maximum ratio combining diversity receiver 200 will be described with reference to these drawings.

FIG. 8 shows an FFT section 208 of the first receiving system received by the first receiving antenna 201 and an FFT section 20 of the second receiving system received by the second receiving antenna 202.
9 shows a timing chart when the respective window timings are equal.

The window timings of the baseband complex digital signals input to the first and second FFT units are equal, as shown in [a-1].

[A-2] indicates the window timing detected by the multi-channel correlation detection section 207. Each FFT unit performs FFT on the baseband complex digital signal for the time Ts corresponding to the FFT size from the head timing of each window c1, c2,. [A-3] indicates the output of the FFT unit, and the next F
Output FFT transformed symbol from FT window timing

In the example shown in FIG. 8, since the phase difference between the FFT units is zero, there is no phase difference between the FFT converted symbols output from the FFT units. This FFT transformed symbol is represented by [a
-4], output as a complex symbol for each OFDM subcarrier.

FIG. 9 shows the first receiving antenna 20.
1 and the FFT unit 208 of the second reception system received by the second reception antenna 202.
10 shows a timing chart when the window timing of each of the units 209 is different. However, here, it is assumed that the correlation detection power of each of the receiving antennas 201 and 202 is equal.

The baseband complex digital signal, FFT1 window timing, and FFT unit 1 output relating to the first FFT unit (208) are represented by [b-1] and [b-
2] and [b-3]. Further, the second FFT unit (20
9) baseband complex digital signal, FFT
The two window timings and the output of the FFT unit 2 are shown in [b-4], [b-5], and [b-6], respectively. Each of these timings is as described above with reference to FIG.

As can be seen by comparing [b-3] and [b-6], OFD at the output of each of the FFT units 208 and 209
The output timings of the complex symbols for each of the M subcarriers do not match.

In the subcarrier phase control section 210, [b
-2] and FFT sections 208 and 2 shown in [b-5]
09 monitor the window timing.
If the two timings are different, the OFD of the two is based on the later of the FFT window timing.
The phase correction amount is calculated so that the carrier numbers of the M subcarriers become equal, and the correction amount is output to each of the subcarrier phase correction units 211 and 212.

Each sub-carrier phase correction section 211 and 21
2 outputs a complex symbol for each OFDM subcarrier corresponding to each of the FFT units 208 and 209 according to the phase correction amount.

In the example shown in FIG. 9, the second FFT unit 209
Has the FFT window timing delayed by X. Therefore, the phase correction amount X calculated by the subcarrier phase control unit 210 is output to the subcarrier phase correction unit 211, and the other subcarrier phase correction unit 212 is output with zero phase correction amount. As a result, the complex symbols 1 and 2 for each OFDM subcarrier, which are the outputs of the FFT units 208 and 209, respectively, are [b-7] and [b
-8].

Such a phase correction is performed by using an FFT window
By performing it each time the timing is changed, the complex symbol for each OFDM subcarrier of each reception system is always output with the same carrier number and timing. Therefore,
In the subsequent functional blocks, signals of each reception system can be processed at the same timing.

FIG. 10 is a flowchart showing a processing procedure for setting the correlation detection information and the weight coefficient correction information. Here, subcarrier phase correction information and weight coefficient correction information are generated based on information such as the number of correlation detections and the correlation detection position detected by the multi-channel correlation detection unit 207 for each of the received signals from the two reception systems. Are output to the subcarrier phase control unit 210 and the weight coefficient calculation unit 217. Hereinafter, description will be made according to this flowchart.

After obtaining the initial synchronization, the multi-channel correlation detection section 207 performs correlation detection on the received signal from each receiving system (step S1).

Next, for each received signal, it is checked whether or not there is a change in the correlation detection position and the number of positions (step S2).

If there is no change in the correlation position and the number of positions in each received signal, the process returns to step S1 and waits until there is a change. On the other hand, if there is a change in the correlation detection position or the number of positions, it is further checked whether the number of correlation detection positions of the received signal 1 in one receiving system is equal to 1 (step S3).

If the number of correlation detection positions of the received signal 1 is equal to 1, it is further checked whether or not the number of correlation detection positions of the received signal 2 in the other reception system is equal to 1 (step S4).

If any of the correlation detection positions of the reception signals 1 and 2 is equal to 1, it is further checked whether or not the correlation detection positions of the respective reception signals are equal (step S5).

If the number of correlation detection positions of each received signal is 1 and the correlation detection positions are equal, OFD
The M subcarrier phase reference is the FFT window timing of one received signal 1, and does not output a phase correction amount.
Also, the weight coefficient correction information is not output (step S
6).

When the number of correlation detection positions of each received signal is 1, but the correlation detection positions do not match,
The OFDM subcarrier phase reference detects and outputs the amount of phase correction based on the later of the detection positions in the FFT window timing of each received signal. Also, no weight coefficient correction information is output (step S7).

If the result of the determination in step S4 is negative, that is, if the number of correlation detection positions of received signal 1 is 1 but the number of correlation detection positions of received signal 2 is not 1, the OFDM subcarrier phase reference Is the FF of each received signal
The phase correction amount is detected and output based on the later of the detection positions in the T window timing. Also, for the received signal 2, weight coefficient correction information corresponding to multipath detection is output (step S8).

If the result of the determination in step S3 is negative, that is, if the correlation detection position of the received signal is not 1, it is further checked whether the number of correlation detection positions of the received signal is 1 (step S3). S9).

If the number of correlation detection positions of the received signal 1 is not 1, but the number of correlation detection positions of the received signal 2 is 1, the OF
The DM subcarrier phase reference detects and outputs a phase correction amount with reference to the later detection position of the FFT window timing of each received signal. Also, for the reception signal 1, weight coefficient correction information corresponding to multipath detection is output (step S10).

If the number of correlation detection positions is not 1 for any of the received signals, the OFDM subcarrier phase reference detects the amount of phase correction based on the later detection position among the FFT window timings of each received signal. And output. In addition, for each received signal, weight coefficient correction information corresponding to multipath detection is output (step S11).

[Supplement] The present invention has been described in detail with reference to the specific embodiments. However, it is obvious that those skilled in the art can modify or substitute the embodiment without departing from the spirit of the present invention.

In this specification, an OFDM maximum ratio combining diversity combining receiver using two receiving antennas has been described as an example. However, even when three or more receiving antennas are used, two combining antennas are used. The power measurement timing by the receiving antenna can be extended and realized. That is,
The receiving antenna, the RF unit, the digital conversion unit shown in FIG.
Each of the sub-carrier phase correction unit, the data storage unit, the transmission channel estimation unit and the multi-channel correlation detection block is increased by the number corresponding to the number of reception antennas, and the sub-carrier phase control unit detects OFDM sub-carrier phase correction for the number of reception antennas. Information may be generated, the weighting factor calculation unit may calculate weighting factors for the number of receiving antennas, and the maximum ratio combining soft-decision demodulation unit may perform control at the above-described timing so that synthesis for the number of receiving antennas can be performed.

Further, the pilot and the pilot described in this embodiment
Even when not only synchronous detection using symbols but also differential detection using differential coding is used, the error amount of the received signal is the same as that of the symbol at the previous time for the complex digital signal for each OFDM subcarrier. By using the error amount of the phase and the amplitude obtained by taking the difference between as the equalized signal for each subcarrier, the effect of the present invention can be similarly exerted.

In short, the present invention has been disclosed by way of example, and should not be construed as limiting.
In order to determine the gist of the present invention, the claims described at the beginning should be considered.

[0116]

As described above in detail, according to the present invention,
OFDM (Orthogonal FDM) in which the frequency of each carrier is set such that each carrier is orthogonal to each other within a symbol section.
It is possible to provide an excellent receiving apparatus of a requency division multiplexing (orthogonal frequency division multiplexing) method.

Further, according to the present invention, an excellent OFDM for performing diversity reception using signals received by a plurality of antennas arranged so that the correlation between the signals is small.
A receiving device can be provided.

Further, according to the present invention, it is possible to provide an excellent OFDM receiver having a higher diversity gain than demodulating a plurality of received signals and obtaining the maximum ratio combination.

Further, according to the present invention, an excellent OF can be efficiently performed for maximum ratio combining diversity reception.
A DM receiver can be provided.

[Brief description of the drawings]

FIG. 1 is an OFDM transmission apparatus 10 that transmits an OFDM signal.
FIG. 3 is a diagram showing a schematic configuration of a zero.

FIG. 2 is a diagram illustrating a schematic configuration of an OFDM receiving apparatus 200 according to the embodiment.

FIG. 3 is a diagram illustrating a schematic configuration of a multi-channel correlation detection unit 207.

FIG. 4 is an example of correlation detection timing showing the operation of the multi-channel correlation detection unit 207 configured as shown in FIG. 3, and more specifically, the correlation detection timing in the case of only a direct wave or flat fading. FIG.

5 is an example of a correlation detection timing showing an operation of the multi-channel correlation detection unit 207 configured as shown in FIG. 3, and more specifically, a multipath (two-wave model D / U =
FIG. 9 is a diagram illustrating correlation detection timing in the case of 3 dB).

FIG. 6 is a diagram showing a schematic configuration of a weighting factor calculation unit 217.

FIG. 7 is a diagram showing a schematic configuration of a maximum ratio combination soft decision demodulation section 218.

8 is a chart illustrating an example of an FFT window timing of the OFDM maximum ratio combining diversity receiving apparatus 200 illustrated in FIG. 2, and more specifically, a first receiving system of a first receiving system that receives signals by a first receiving antenna 201. FFT section 208
FIG. 9 is a timing chart in a case where window timings of the FFT unit 209 of the second reception system received by the second reception antenna 202 and the window timing of the second reception system are equal.

9 is a chart showing an example of an FFT window timing of the OFDM maximum ratio combining diversity receiving apparatus 200 shown in FIG. 2, and more specifically, a first receiving system of the first receiving antenna 201 receiving the signal. FFT section 208
7 is a timing chart in a case where window timings of FFT units 209 of a second reception system received by the second reception antenna 202 differ from window timings of the second reception system.

FIG. 10 is a flowchart illustrating a processing procedure for setting correlation detection information and weight coefficient correction information.

[Explanation of symbols]

200: OFDM maximum ratio combining diversity combining receiving apparatus 201, 202 ... Receiving antennas 203, 204 ... RF sections 205, 206 ... Digital converting section 207 ... Multi-channel correlation detecting section 208, 209 ... FFT section 210 ... Subcarrier phase control section 211 , 212 ... subcarrier phase correction units 213, 214 ... data storage units 215, 216 ... channel estimation units 217 ... weighting factor calculation units 218 ... maximum ratio combining soft decision demodulation units 301, 302 ... delay units 303, 304 ... correlation calculations Units 305, 306 Threshold comparison unit 307, 308 Correlation determination unit 309 Correlation detection information generation unit 310 Correlation detection control unit 401, 402 Power calculation units 403, 404 Weight correction unit 405 Addition units 406, 407 Weight coefficient calculation unit 408 ... Weight coefficient calculation control unit 501, 50 ... divider 503, 504 ... multiplying unit 505 ... adding unit 506 ... soft decision demodulator 507 ... maximum ratio combining soft decision demodulation controller

Claims (7)

[Claims] An OFDM receiver using maximum ratio combining of a plurality of OFDM (Orthogonal Frequency Division Multiplexing) received signals, comprising: a receiving antenna; and a signal received via the receiving antenna being converted from an RF frequency band to a baseband signal. An RF unit for down-converting to a signal, a digital conversion unit for A / D converting the down-converted baseband signal into a complex digital signal, and performing a Fourier transform for one period of the OFDM symbol according to the FFT window timing. An FFT unit for obtaining a complex digital signal for each OFDM subcarrier, and an OFF based on the subcarrier phase correction amount.
A plurality of sub-carrier phase correction units for correcting the phase and output timing of the complex symbol for each DM sub-carrier, and a plurality of transmission line estimation units each including an error amount of a received signal such as fluctuation of a transmission line, frequency offset and noise. For the receiving system, for each receiving system, the correlation power of the complex digital signal is measured and the correlation power is measured, and the FFT window timing,
A multi-channel correlation detector for obtaining OFDM sub-carrier phase information and weight coefficient correction information; and setting a sub-carrier phase correction amount based on the OFDM sub-carrier phase information so that the sub-carrier phase and output timing in each receiving system match. Subcarrier phase control unit, a weighting factor calculating unit that calculates a weighting factor of a complex symbol for each OFDM subcarrier in each receiving system, demodulating and performing a Fourier-transformed complex digital signal for each OFDM subcarrier in each receiving system. An OFDM receiver using maximum ratio combining diversity, comprising: a maximum ratio combining soft-decision demodulation unit that performs maximum ratio combining. 2. The subcarrier phase control section according to claim 1, wherein said subcarrier phase control section controls an OFF in a reception system having the latest FFT window timing.
A subcarrier phase correction amount is set based on the phase and timing of the complex symbol for each DM subcarrier, and the subcarrier phase correction unit converts the complex symbol for each OFDM subcarrier based on the subcarrier phase correction amount. The OFDM receiving apparatus using maximum ratio combining diversity according to claim 1, wherein the OFDM receiving apparatus outputs the signal at a phase and an output timing. 3. The in-phase OFDM unit according to claim 1, wherein
The weighting factor of the complex symbol for each OFDM subcarrier in each receiving system is calculated from the received signal power of the complex symbol for each subcarrier or the power ratio of the reference carrier and the weighting factor correction information. An OFDM receiver using the maximum ratio combining diversity described. 4. The maximum ratio combining soft-decision demodulation unit demodulates a complex symbol for each OFDM subcarrier in each reception system, and multiplies each of the weighting factors calculated by the weighting factor calculation unit. The OFDM receiver using maximum ratio combining diversity according to claim 1, wherein the sum of demodulated symbols for each OFDM subcarrier is calculated. 5. The multi-channel correlation detecting section, using a signal of a guard interval portion, calculates a correlation for each complex digital signal for each of a plurality of OFDM subcarriers corresponding to the number of reception antennas, and calculates a correlation power. The measurement is performed, the correlation peak position and the correlation peak number are detected, and the FFT window timing is determined from the largest peak position for each complex digital signal. And if the width is larger than a preset threshold value indicating multipath detection, the presence or absence of multipath detection is determined, and according to the presence or absence of multipath detection, the weight coefficient of the weight coefficient calculation unit is corrected. Complex coefficient for each of a plurality of OFDM subcarriers in each receiving system Determined for signals, respectively, using a maximum ratio combining diversity of claim 1, wherein the OF
DM receiver. 6. The multi-channel correlation detection section monitors transmission signal format information such as an FFT size, a guard interval, a guard band, and a modulation scheme sent from a transmission side as correlation detection control information,
When the FFT size, guard interval, and guard band are changed, the correlation calculation cycle and threshold are changed according to the respective information, the complex digital signal is correlated, and the correlation power is measured. FFT for the receiving system based on the correlation peak detection position and the correlation peak detection number
Window timing and subcarrier phase correction information,
The weight coefficient correction information is reset, the correlation peak detection position and the correlation peak detection number are calculated for each reception system, and the FFT is performed.
Window timing, subcarrier phase correction information,
When the weighting factor correction information is updated and the modulation scheme is changed, the error amount of the received signal when the pilot symbol is inserted is equalized signal for each subcarrier obtained from the reproduced carrier calculated based on the pilot symbol. The error amount of the received signal when differential encoding is performed is calculated by subtracting the error amount of the phase and amplitude obtained by taking the difference between the symbol at the previous time and the symbol of the complex digital signal for each OFDM subcarrier. 2. The OFDM receiving apparatus using maximum ratio combining diversity according to claim 1, wherein the calculation of the weighting factor used as the equalized signal for each carrier is switched every time it is changed. 7. The weighting factor calculation unit calculates a weighting factor of a complex symbol for each OFDM subcarrier for each receiving system, adds all the values, and divides each weighting factor by a result of addition to normalize. And if the addition result is equal to or less than a predetermined threshold value that can guarantee the line quality,
The OFDM receiving apparatus using maximum ratio combining diversity according to claim 1, wherein transmission quality information such as transmission quality deterioration is added to a complex symbol for each OFDM subcarrier and output.