JP2001345781A - OFDM receiver using selection diversity - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an OFDM receiver capable of efficiently performing selective diversity reception. SOLUTION: A multi-channel correlation detecting section measures the correlation power of the complex digital signal and outputs a correlation detection signal. The power measurement control unit uses the signal control information, the correlation detection information, and the power comparison information to generate the power measurement control information and F
Set the FT window position information. The power measuring unit measures the power of the complex digital signal by sequentially switching the integration cycle and the integration timing according to the power measurement information. The power comparison unit compares the power measurement results, selects the one with the larger value, and outputs it as power comparison information.

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 receiver configured to be small in size by performing selective diversity reception by selectively using a received signal having the highest signal power among a plurality of received signals, and in particular, to an OFDM receiver having a small size. , An OFDM receiver for efficiently performing selective diversity reception.

[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.

A further object of the present invention is to provide an excellent OFDM receiving apparatus which is small-sized by performing selective diversity reception by selectively using a received signal having the highest signal power among a plurality of received signals. To provide.

It is a further object of the present invention to provide an excellent OFD capable of efficiently estimating a transmission path from an incoming wave distribution and efficiently performing selective diversity reception.
An M receiving device is provided.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is an OFDM selective diversity combining and receiving apparatus that selectively uses a plurality of OFDM (orthogonal frequency division multiplexing) received signals. Receiving unit, an RF unit for down-converting a signal received via the receiving antenna from an RF frequency band to a baseband signal, and A / D converting the down-converted baseband signal into a complex digital signal. A plurality of reception systems each including a digital conversion unit, and correlation peak power and FF are calculated by correlating the complex digital signal in each reception system.
A multi-channel correlation detection unit that measures the top position of the T window and outputs it as correlation detection information; and a selection unit that selects one of complex digital signals from the plurality of reception systems based on the correlation detection information in each reception system. Means and OFDM for the selected complex digital signal.
An FFT unit for performing a Fourier transform for one symbol period to obtain a complex digital signal for each OFDM subcarrier;
And a demodulation unit for demodulating a symbol of a complex digital signal for each OFDM subcarrier.

The selecting means includes: a power measurement control unit for setting power measurement control information and FFT window position information using signal control information such as FFT size and transmission quality information and / or correlation detection information; A power measuring unit provided for each receiving system, integrating a complex digital signal according to the measurement control information and dumping, a power comparing unit for comparing measurement results in each power measuring unit, and a power in the power comparing unit. And a selector for selecting one of the complex digital signals from the plurality of receiving systems based on the comparison information.

The power measuring section includes an integral dump section for performing an integral dump of an input complex digital signal, a power threshold comparing section for comparing an integral value in the integral dump section with a predetermined threshold, and an externally supplied power measuring section. Based on the measured power control information (signal control information and correlation detection information) and / or the comparison result in the power threshold comparing unit, the integration information (integration dump integration cycle and reset timing) used by the integration dump unit and And / or a power measurement timing control unit that determines threshold information used by the power threshold comparison unit.

[0016] The power measurement control unit may be configured to perform the following based on the correlation detection information supplied from the multi-channel correlation detection unit.
Channel estimation may be performed such that the incoming wave distribution is classified into direct wave only or flat fading, or multipath and selective fading. In such a case, a complex digital signal to be selected by a selector based on a power measurement result obtained by integrating and dumping the transmission path estimation result and the complex digital signal,
The FFT window position and the power integration cycle can be set.

In addition, the integral dump unit outputs integral data during integration in addition to the dump value, which is a power measurement result obtained for each integration cycle, and the power threshold comparator compares the signal control information and the correlation detection information. The set power threshold may be compared with the integrated data, and the result of the comparison may be output to the power measurement timing control unit and the power measurement control unit. Further, the power measurement control unit, when there is a comparison result indicating a value equal to or less than a power threshold value at which transmission quality can be guaranteed, a complex digital signal of a reception system corresponding to at least one of the largest comparison results. The power measurement and the correlation detection may be continued, and the power measurement and the correlation detection may be stopped as needed for the rest.

Further, at the time of initial synchronization, the power measurement section measures the power of the complex digital signal at a preset integration cycle and timing, and performs the power measurement at the time of performing the correlation detection by the multi-channel correlation detection section. The control unit may detect the FFT window position by weighting the correlation detection result in each reception system with the power measurement result and detect the window position.

After the initial synchronization is obtained, each power measuring unit measures the power of the complex digital signal in accordance with the integration cycle and timing set by the power measuring control unit, and the multi-channel correlation detecting unit performs the measurement. Correlation detection may be performed. In such a case, the power comparison unit compares power measurement results in each power measurement unit, selects a larger value, and outputs the selected value as power comparison information, Selectively outputs a corresponding complex digital signal to the FFT unit according to the power comparison information, and the FFT unit performs OFD processing according to the FFT window position information.
A complex digital signal for each OFDM subcarrier is obtained by performing Fourier transform for one cycle of M symbols, and the demodulation unit can perform symbol demodulation of the complex digital signal for each subcarrier.

[0020]

The OFDM selective diversity combining receiving apparatus according to the present invention has a plurality of receiving antennas, that is, a plurality of receiving systems. In each reception system, a reception signal of a reception antenna is converted into a complex digital signal by an RF unit and a digital conversion unit and sent to a buffer, a power measurement unit, and a multi-channel correlation detection unit.

The multi-channel correlation detector measures the correlation power of the complex digital signal and outputs it as correlation detection information. The power measurement control unit uses the signal control information (FFT size, transmission quality information, etc.), the correlation detection information, and the power comparison information to generate the power measurement control information and the FF.
T window position information is set. The power measurement unit performs power measurement of the complex digital signal by sequentially switching an integration cycle and an integration timing according to the power measurement information.
The power comparison unit compares the power measurement results in each reception system, selects the one with the larger value, and outputs it as power comparison information. The selector selectively extracts a complex digital signal from one of the complex digital signals stored in the buffer according to the power comparison information, and outputs the complex digital signal to the FFT unit.

The FFT unit performs a Fourier transform for one period of the OFDM symbol according to the FFT window position information, obtains a complex digital signal for each OFDM subcarrier, and outputs the result to the demodulation unit. The demodulation unit performs symbol demodulation of the complex digital signal for each subcarrier.

According to the present invention, by configuring the OFDM receiving apparatus as described above, ODM signals received by a plurality of antennas can be received.
Selection diversity of the FDM signal can be performed before the Fourier transform. In addition, the FFT unit, the demodulation unit, and the correlation detection unit can be integrated into one system without being arranged for each receiving antenna, so that the device configuration is simplified and the cost is reduced.

Further, the power measurement control unit is configured to determine whether the incoming wave distribution is a direct wave only or flat fading or a multipath and selective fading based on the correlation detection information supplied from the multi-channel correlation detecting unit. It is possible to perform a transmission path estimation that is classified as The complex digital signal to be selected by the selector, the FFT window position, and the power integration cycle can be set based on the transmission path estimation result and the power measurement result obtained by integrating and dumping the complex digital signal. That is, it is possible to configure so as to control the power measurement and set the FFT window position using the transmission path estimation information.

The power measuring section outputs integration data during integration other than the integration dump value, which is a power measurement result obtained for each integration cycle, and sets a power threshold set based on signal control information and correlation detection information. Can be configured to perform the comparison. By sending the comparison result to the power measurement timing control unit, and further supplying the comparison result to the power measurement control unit, if there is a comparison result indicating a value equal to or less than a power threshold value that can guarantee transmission quality, at least 1
The power measurement corresponding to the two largest comparison results and the correlation detection of the corresponding complex digital signal by the multi-channel correlation detection unit can be performed continuously, while the rest is stopped. In this case, there is no need to constantly perform power measurement and correlation detection, and power consumption can be reduced.

At the time of initial synchronization, the power of the complex digital signal is measured at a preset integration cycle and timing, and when the multi-channel correlation detection section performs correlation detection, the power measurement control section reduces the number of complex digital signals. The corresponding correlation detection result is weighted by the power measurement result and
The window position is detected by detecting the FT window position.

After the initial synchronization is obtained, each power measurement unit measures the power of the complex digital signal according to the integration cycle and timing set by the power measurement control unit, and performs the correlation detection by the multi-channel correlation detection unit. . Each power measurement result is compared by the power comparison unit, and the one with the larger value is selected and output as power comparison information. In the selector,
According to the power comparison information, one of the complex digital signals stored in each buffer is selectively extracted and output to the FFT unit. The FFT unit performs Fourier transform for one period of the OFDM symbol in accordance with the FFT window position information, obtains a complex digital signal for each OFDM subcarrier, and outputs the result to the demodulation unit. The demodulation unit performs symbol demodulation of the complex digital signal for each subcarrier.

Therefore, the position of the FFT window can be detected with high accuracy by using a plurality of received signals in the initial synchronization, and until the initial synchronization succeeds.
By not operating the FFT unit and the demodulation unit, it is possible to reduce the power consumption of the receiving device.

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.

[0030]

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.

As shown in FIG. 1, the OFDM transmitting apparatus 10
0 is the modulation unit 101 and the serial / parallel conversion unit 10
2, IFFT 103, guard interval insertion section 104,
It comprises an analog conversion section 105, a transmission RF section 106, a transmission antenna 107, and a transmission control section 108.

Modulation section 101 modulates input data according to the modulation information and timing supplied from transmission control section 108 and outputs the result to serial / parallel conversion section 102.

The serial / parallel converter 102 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 108, Output to the unit 103.

IFFT section 103 performs FFT according to the FFT size and timing supplied from transmission control section 108.
Inverse FFT for FT size is performed.

The guard section insertion section 104 includes the transmission control section 1
According to the guard interval size, guard band size, and timing supplied from 08, a guard signal such as a guard interval (a section in which part of a signal is repeatedly transmitted) or a guard band is inserted. The guard interval absorbs multipath (multiple reflected radio wave propagation) propagation of a guard interval size or less to prevent fatal deterioration of reception quality.

The digital transmission signal into which the guard signal has been inserted is subjected to quadrature modulation and D
/ A conversion is performed, up-converted in transmission RF section 106, and transmitted from transmission antenna 107 to the outside of apparatus 100.

The OFDM receiving apparatus according to this embodiment can receive an OFDM signal transmitted from the OFDM transmitting apparatus 100 shown in FIG. 1 by using selective diversity. In the following description, the OFDM receiving apparatus according to the present embodiment uses two receiving antennas to perform selective diversity reception. However, the number of receiving antennas is not limited to this, and three or more receiving antennas may be used. It should be understood that the effects of the present invention can be similarly obtained.

FIG. 2 shows a schematic configuration of an 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 reception 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. Each of the buffers 207 and 208 delays each complex digital signal according to the control signal supplied from the power measurement control unit 209 and outputs the signal at an appropriate timing.

The power measurement control unit 209 controls the power integration cycle according to the transmission quality information and the information from the multi-channel correlation detection unit 216. Each power measurement unit 210
And 211 integrate and dump each complex digital signal according to the control signal supplied from the power measurement control unit 209. The power integration cycle corresponds to a data unit of one cycle of the Fourier transform.

The power comparing section 212 is connected to each power measuring section 210
And 211 compare the dumped power measurement results.

The selector 213 selects one of the complex digital signals stored in each of the buffers 207 and 208 based on the comparison result output from the power comparing section 212.

The FFT section 214 performs a Fourier transform on a signal obtained by performing an inverse Fourier transform on the complex digital signal supplied from the selector 213 for one period of the OFDM symbol.

The demodulation section 215 demodulates the Fourier-transformed received signal for each subcarrier.

The multi-channel correlation detecting section 216 performs correlation power measurement by independently correlating the guard interval signal with respect to the complex digital signal output from each of the digital converting sections 205 and 206, and calculates an appropriate FFT window head position. And a phase and frequency error are selected and output.

An OFDM receiver 200 as shown in FIG.
According to the configuration described above, the selection of the received signal in the selective diversity reception can be arranged before the FFT unit 214, and the circuit for Fourier transform can be integrated into one system. Since the FFT unit generally has a large circuit scale, the structure of the receiving device can be greatly simplified.

According to the configuration of the OFDM receiver 200 as shown in FIG. 2, since the received signal is selected after converting the received signal into a digital signal, the accuracy for power measurement and synchronization can be increased. Can be.

Next, a description will be given of a selective diversity receiving operation by the OFDM receiving apparatus 200.

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 in the respective buffers 207 and 20 as baseband complex digital signals.
8, input to the power measurement units 210 and 211 and the multi-channel correlation detection unit 216.

Each of power measuring sections 210 and 211 calculates the power of the received signal in accordance with the power control information supplied from power measuring control section 209 and outputs the result to power comparing section 212 as a power measurement result.

The power comparison section 212 compares the respective power measurement results, selects the one with the larger value, and outputs it to the selector 213 as power comparison information. The selector 213 is
According to the power comparison information, one of the buffers 207 and 208 is selected to extract a complex digital signal, and outputs the complex digital signal to the FFT section 214.

The multi-channel correlation detection section 216 performs a correlation detection signal on the baseband complex digital signals output from the digital conversion sections 205 and 206 based on the control information supplied from the power measurement control section 209, respectively. The peak number of the signal and the peak power are output to power measurement control section 209 as correlation detection information.

The power measurement control unit 209 determines the power control information based on the signal control information and the correlation detection information, and also determines the FFT window position based on the information and the power comparison information input from the power comparison unit 212. It is determined whether the integration cycle can be changed during power measurement.

FFT section 214 performs Fourier transform for one period of the OFDM symbol according to the FFT window position, obtains a complex symbol value for each OFDM subcarrier, and outputs the result to demodulation section 215. Demodulation unit 215
Performs symbol demodulation and outputs demodulated symbols.

In FIG. 2, power measuring sections 210 and 211 provided for each receiving system have the same configuration.
FIG. 3 shows a schematic configuration of the power measuring unit. The power measuring unit includes an integral dump unit 301 and a power threshold comparing unit 3
02 and a power measurement timing control unit 303.

The integral dump unit 301 performs an integral dump of an input signal according to integral information such as an integral dump integration cycle and a reset timing supplied from the power measurement timing control unit 303.

Power threshold comparing section 302 compares the threshold value supplied from power measurement timing control section 303 with the integrated value calculated by integration dump section 301, and outputs the result to power measurement timing control section 303. I do.

Power measurement timing control section 303 receives integration information (signal control information and correlation detection information) from outside the power measurement section, and, based on the comparison result output from power threshold comparison section 302, integrates information and threshold value. The information is determined and supplied to each of the integration dump unit 301 and the power threshold comparison unit 302.

Next, the operation of the power measuring section configured as shown in FIG. 3 will be described.

The received signal is input to integration dump section 301. The integration dump unit 301 integrates the received signal in accordance with the integration cycle and integration timing provided from the power measurement timing control unit 303, outputs the value of the integration progress to the power threshold comparison unit 302, and further dumps at the end of the integration. Print the dump value.

The power threshold comparing section 302 compares the integration progress output from the integration dump section 301 with the threshold according to the threshold given by the power measuring timing control section 303 and the comparison timing, and compares the comparison result with the power measurement timing control section. Output to

The power measurement timing control unit 303 controls signal control information (FFT size, data format, etc.)
Based on the correlation detection information and the comparison result output from the power threshold comparing unit 302, integration information and threshold information are determined and supplied to each of the integration dump unit 301 and the power threshold comparing unit 302.

FIG. 4 shows a multi-channel correlation detecting section 2
16 shows a schematic configuration of the sixteenth embodiment. Hereinafter, description will be made with reference to FIG.

Each of the delay units 401 and 402 delays the received signals 1 and 2 according to the timing signal supplied from the correlation detection control unit 410, and outputs the signals at appropriate timing.

Each of the correlation calculators 403 and 404 calculates the correlation power of the received signal output from each of the delay units 401 and 402 according to the correlation timing supplied from the correlation detection controller 410.

The threshold comparing sections 405 and 406 compare the correlation calculation results of the correlation calculating sections 403 and 404 with the threshold supplied from the correlation detection control section 410.

Each of the correlation judgment sections 407 and 408 is based on the threshold comparison results input from the threshold comparison sections 405 and 406 and the threshold comparison results stored so far in accordance with the timing signal supplied from the correlation detection control section 410. Then, the phase error and the frequency error are calculated from the success / failure determination of the FFT window position and the phase difference for each OFDM signal cycle,
It outputs FFT window position information and phase and frequency errors.

[0068] Correlation detection information output section 409 selectively outputs an appropriate correlation detection result according to the selection information supplied from correlation detection control section 410.

The correlation detection control unit 410 generates a timing control signal for each block in each process after the initial synchronization and the acquisition of the synchronization.

Next, the operation of the multi-channel correlation detection section 216 configured as shown in FIG. 4 will be described with reference to the correlation detection timing examples shown in FIGS. 5 and 6, respectively.

In this 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). , ...).

FIG. 5 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 401 and 402 delays by a known symbol period Ts.

Each of the correlation calculators 403 and 404 calculates the correlation between each delayed received signal and the current time received signal according to the respective correlation integration times and correlation calculation timing supplied from the correlation detection controller 410. Calculate the correlation data of

The threshold comparing units 405 and 406 compare the correlation data output from the correlation calculating units 403 and 404 with thresholds set in advance according to the correlation detection control information.

Each of the correlation judgment sections 407 and 408 outputs correlation judgment information based on the threshold comparison results stored so far in accordance with the timing signal supplied from the correlation detection control section 410.

[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.

[A-3] shows the integration dump timing of the power measuring units 210 and 211 when the power is measured in one cycle of OFDM. Synchronization acquisition information at the time of initial synchronization, and deviation information of a correlation peak position due to a change in noise, a propagation environment, or the like are correlation determination information.

FIG. 6 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].

[B-6] shows the integration dump timing of the power measuring units 210 and 211 when measuring the power in one cycle of the OFDM signal when D / U = 3 dB. Since the head of the OFDM signal cycle is set based on the larger of the correlation detection signal of the D wave and the U wave, the head of the integration dump timing is also made to match this timing.

Hereinafter, the power measurement operation in OFDM selection diversity combining / receiving apparatus 200 shown in FIG. 2 will be described with reference to the power measurement timing charts shown in FIGS.

FIG. 7 shows the power measurement timing at the time of initial synchronization. At the time of initial synchronization, since a correct FFT window has not yet been detected, the integration cycle and integration timing are measured and compared using a predetermined initial value as shown in s1 to s2, and two receptions are performed. The selector 213 outputs the received signal having the larger power measurement result among the signals.

If the synchronization has been successfully acquired, the multi-channel correlation detection section 216 transmits the synchronization acquisition information to the power measurement control section 2.
09 is output. As a result, the power measurement timing becomes s
It is changed to match the FFT window as shown in 3 to s5. The subsequent power measurement is performed from the beginning of the FFT window. The integration cycle timing of the integration dump unit 301 in this process is represented by c1 to c in FIG.
It looks like 5.

FIG. 8 shows the power measurement timing when the FFT size is changed. In this example, it is assumed that the FFT size switching timing is known.

In the example shown in the figure, the signal transmitted at the OFDM signal period 1 in s1 and s2 is initially a double FF.
This indicates that switching to the OFDM signal period 2 having a T size has been performed, and s3 and s4 correspond to the switched signal.

The FFT size switching timing is determined by the FF
The T size change information is input as signal control information to the power measurement control unit 209 in a section s2 immediately before switching. Then, the integration cycle specified from the beginning of the next OFDM signal cycle, that is, from the beginning of section s3, is set by power measurement control section 209, and the subsequent power measurement is performed in the switched integration cycle. The integration cycle timing of the integration dump unit 301 in this process is as shown by c1 to c4 in FIG.

FIG. 9 shows the power measurement timing for guard interval elimination. When a long guard interval such as a quarter of the OFDM signal period is set, or when there is a large fluctuation in transmission quality, it is more efficient to remove the power of the guard interval section outside the FFT window from the integration range. Accurate power measurement can be performed. The example shown in FIG. 9 illustrates a state in which the integration dump cycle is switched from a cycle including the guard interval to a cycle in which the guard interval is removed.

In the received signal shown in the figure, in the OFDM signal period of s1 and s2, integration is performed including the guard interval, and s3 to s5 correspond to the signal integrated and dumped except for the guard interval.

The switching timing is determined by the power measurement controller 2
09 is determined based on guard interval change information and transmission quality information supplied as signal control information. If switching is necessary, the power measurement control unit 209 sets the integration cycle specified from the beginning of the OFDM signal cycle to be switched, that is, from the beginning of s3, and the subsequent power measurement is performed at the switched integration cycle. .

In the example shown in FIG. 9, a reset signal is set in a portion corresponding to the guard interval. The integration cycle timing of the integration dump unit 301 in this process is as shown by c1 to c4 in FIG.

FIG. 10 shows an example of power measurement timing using transmission quality information in a flat fading environment. The illustrated power measurement shows a process of switching the integration dump cycle at an arbitrary timing, and is particularly effective in a flat fading environment without frequency distortion.

In the received signal shown in the figure, in the OFDM signal cycle of s1 and s2, the integrated dump is performed in one OFDM signal cycle, and s3 to s5 correspond to the signal integrated and dumped in a half cycle of the OFDM signal cycle. . This corresponds to, for example, a change from a small Doppler frequency to a large Doppler frequency in flat fading, and the transmission quality information or power measurement unit 21 which is signal control information input from the outside.
It can be estimated from the comparison result of the power threshold value comparison unit 302 in 0,211.

Power measurement control section 209 determines whether or not to switch the integration cycle based on the transmission quality information and the comparison result of power threshold value comparison section 302. If you need to switch,
It outputs integration cycle switching information to power measurement sections 210 and 211. After that, the integration dump unit 301
It is performed in a newly set integration cycle from the beginning of the FDM signal cycle. The integral dump unit 301 in this process
Are as shown in c1 to c9 in FIG.

FIG. 11 shows an example of power measurement timing using transmission quality information in an environment where the propagation environment changes from dynamic characteristics to static characteristics.

In the received signal shown in the figure, in the OFDM signal period of s1 and s2, the signal is integrated and dumped in a half cycle of the OFDM signal cycle, and s3 and s4 correspond to the signal integrated and dumped in one cycle of the OFDM signal cycle. I do. Switching of the integration dump cycle in this case can be realized by the same operation as in the case shown in FIG. The integration cycle timing of the integration dump unit 301 in this process is represented by c in FIG.
1 to c8.

FIG. 12 is a flowchart showing an example of a power measurement timing control procedure based on correlation detection information and a power measurement result. In this example, each of the correlation detection information detected by the multi-channel correlation detection unit 216 for the reception signals 1 and 2 and each of the power measurement units 21
The transmission quality is estimated based on the power threshold comparison results measured at 0 and 211 and the power comparison result determined at the power comparison unit 212, and the optimum transmission timing is selected from among the power measurement timings shown in FIGS. Procedures are set. Hereinafter, description will be made according to this flowchart.

After acquiring the initial synchronization, first, the multi-channel correlation detecting section 216 performs OFDM on each received signal.
Correlation detection information is obtained at the signal period, and this information is
Output to 10 and 211 (step S1).

Next, each of the power measuring units 210 and 211 measures a power threshold comparison result. As a result, the correlation detection information and the power threshold comparison result are obtained (step S2).

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

If none of the received signals has the number of correlation detection positions, one of the received signals having the higher measured power is selected and the FF is added to the correlation detection position of the selected received signal.
Adjust the T window. Further, the integration cycle is not changed (step S5).

When 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, or the number of correlation detection positions of the received signal 2 is not 1, but the correlation of the received signal 1 is not equal. If the number of detected positions is 1, the larger of the measured power is selected from the received signals (step S6), and it is checked whether the correlation detection positions of the received signals are equal (step S7).

If the correlation detection positions of both received signals are not equal, the FFT window is adjusted to the correlation detection position of the selected received signal in step S6. In this case, the integration cycle can be changed (step S8).

If the correlation detection positions of both received signals are equal, the FFT window is adjusted to the one having the largest peak at the common correlation detection position. In this case, the integration cycle can be changed (step S9).

If the correlation detection position of each of the received signals is 1 (step S10), one of the received signals having the higher measured power is selected, and the correlation detection of the selected received signal is performed. Adjust the FFT window to the position. In this case, the integration cycle can be changed (step S1).
1).

[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 selective diversity combining receiver using two receiving antennas has been described as an example. However, even when three or more receiving antennas are used, two receiving antennas are used. The power measurement timing by the antenna can be extended and realized. That is, the reception antenna, the RF unit, the digital conversion unit, the power measurement unit, and the correlation detection block of the multi-channel correlation detection unit shown in FIG. The power measurement control unit may control the power measurement timing such that the received signal of the large receiving antenna is determined and the selector selectively outputs the received signal.

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.

[0109]

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 that performs diversity reception using signals received by a plurality of antennas arranged so that the correlation between signals is small.
A receiving device can be provided.

According to the present invention, there is provided an excellent OFDM receiving apparatus which has a small size by performing selective diversity reception by selectively using a received signal having the highest signal power among a plurality of received signals. Can be provided.

Further, according to the present invention, an excellent OFD capable of efficiently performing a selective diversity reception by enabling a transmission path to be efficiently estimated from an incoming wave distribution.
M receiving devices 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 power measuring unit.

FIG. 4 is a diagram illustrating a schematic configuration of a multi-channel correlation detection unit 207.

FIG. 5 is an example of correlation detection timing showing an operation of the multi-channel correlation detection unit 216 configured as shown in FIG. 4, and more specifically, the correlation detection timing in the case of only a direct wave or flat fading. FIG.

FIG. 6 is an example of correlation detection timing showing the operation of the multi-channel correlation detection unit 216 configured as shown in FIG. 4, 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. 7 is an OFDM selection diversity combining receiver 20;
5 is a timing chart showing the power measurement operation at 0 (however, at the time of initial synchronization).

FIG. 8 shows an OFDM selection diversity combining receiver 20.
5 is a timing chart showing the power measurement operation at 0 (when the FFT size is changed).

FIG. 9 shows an OFDM selection diversity combining / receiving apparatus 20;
6 is a timing chart showing a power measurement operation at 0 (when a guard interval is removed).

FIG. 10 shows OFDM selection diversity combining / receiving apparatus 2
This is a timing chart showing the power measurement operation at 00 (however, when the line quality information is used (flat fading)).

FIG. 11 shows OFDM selection diversity combining / receiving apparatus 2
This is a timing chart showing the power measurement operation at 00 (however, when the line quality information is used (multipath detection)).

FIG. 12 is a flowchart illustrating an example of a processing procedure of power measurement timing control based on correlation detection information and a power measurement result.

[Description of Signs] 200 OFDM selection diversity combining receiving apparatus 201, 202 receiving antennas 203, 204 RF units 205, 206 digital conversion units 207, 208 buffer 209 power measurement control unit 210, 211 power measurement unit 212 power comparing section 213 selector 214 FFT section 215 demodulating section 216 multi-channel correlation detecting section 301 integral dumping section 302 power threshold comparing section 303 power measuring timing control sections 401, 402 delay sections 403, 404 ··· Correlation calculation units 405 and 406 ··· Threshold comparison units 407 and 408 ··· Correlation determination units 409 ··· Correlation detection information output units

Claims (7)

[Claims] An OFDM selective diversity combining receiver for selectively using a plurality of OFDM (Orthogonal Frequency Division Multiplexing) received signals, comprising: a receiving antenna and a base station for receiving a signal received via the receiving antenna from an RF frequency band. A plurality of reception systems each including an RF unit for down-converting to a band signal, a digital conversion unit for A / D converting the down-converted baseband signal to convert to a complex digital signal, A multi-channel correlation detection unit that measures correlation peak power and the FFT window head position and outputs the result as correlation detection information; and a complex digital signal from the plurality of reception systems based on the correlation detection information in each reception system. Selecting means for selecting one of the above, and the selected complex digital An FFT unit for performing a Fourier transform for one period of the OFDM symbol on the signal to obtain a complex digital signal for each OFDM subcarrier; and a demodulation unit for performing symbol demodulation of the complex digital signal for each OFDM subcarrier. An OFDM receiver using diversity. 2. The information processing apparatus according to claim 1, wherein the selecting means uses signal control information such as FFT size and transmission quality information, and / or power measurement control information by using correlation detection information.
A power measurement control unit for setting T window position information; a power measurement unit provided for each reception system for integrating and dumping a complex digital signal according to the power measurement control information; and a measurement in each power measurement unit. A power comparison unit for comparing results, and a selector for selecting one of complex digital signals from the plurality of reception systems based on power comparison information in the power comparison unit. Item 2. An OFDM receiver using the selection diversity according to item 1. 3. The power measuring section includes: an integral dump section for performing an integral dump of an input complex digital signal; a power threshold comparing section for comparing an integral value in the integral dump section with a predetermined threshold; Based on the measured power control information (signal control information and correlation detection information) and / or the comparison result in the power threshold comparing unit, the integral information (integrated dump integration cycle and reset timing) used by the integral dump unit and /
Or a power measurement timing control unit that determines threshold information used by the power threshold comparison unit. 3. The OFDM using selection diversity according to claim 2, wherein
Receiver. 4. The power measurement control section, based on correlation detection information supplied from a multi-channel correlation detection section, when the incoming wave distribution is a direct wave only or flat fading, or multipath and selective fading. Based on the transmission path estimation result and the power measurement result obtained by integrating and dumping the complex digital signal, the complex digital signal to be selected by the selector, the FFT window position, the power 3. The OFDM receiver using selection diversity according to claim 2, wherein an integration period is set. 5. The integration dump unit outputs integration data during integration in addition to a dump value, which is a power measurement result obtained for each integration cycle, and the power threshold comparison unit outputs based on signal control information and correlation detection information. Performs comparison between the set power threshold value and the integrated data and outputs the comparison result to the power measurement timing control unit and the power measurement control unit, wherein the power measurement control unit guarantees transmission quality among the comparison results. If there is something that shows a value below the possible power threshold,
The power measurement and the correlation detection can be continued for the complex digital signal of the receiving system corresponding to at least one of the largest comparison results, and the power measurement and the correlation detection can be stopped as necessary for the rest. An OFDM receiving apparatus using the selection diversity according to claim 3. 6. At the time of initial synchronization, the power measuring section measures the power of the complex digital signal at a preset integration cycle and timing, and performs the power measurement when the multi-channel correlation detecting section performs correlation detection. 2. The selection diversity according to claim 1, wherein the control unit weights the correlation detection result in each reception system with the power measurement result, detects the FFT window position, and detects the window position. OFDM receiver. 7. After acquiring the initial synchronization, each power measuring unit measures the power of the complex digital signal in accordance with the integration cycle and timing set by the power measuring control unit.
The multi-channel correlation detection unit performs correlation detection, and the power comparison unit compares power measurement results in each power measurement unit, selects a larger value, and outputs the selected value as power comparison information. Selectively outputting a corresponding complex digital signal to the FFT unit according to the power comparison information;
Performs Fourier transform for one period of DM symbol and performs OFDM
The OFDM receiving apparatus using selective diversity according to claim 1, wherein a complex digital signal for each subcarrier is obtained, and the demodulation unit performs symbol demodulation of the complex digital signal for each subcarrier.