JP4300204B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a radio communication apparatus having a plurality of antennas and a frame synchronization timing detection system, and more particularly to an OFDM communication system reception apparatus.

  Conventionally, as in Patent Document 1, for example, in an OFDM receiver having a plurality of reception systems, the reception power level of the reception signal is measured for each reception system, and the synchronization symbol of the reception signal having the largest reception power level is used. Therefore, the common frame synchronization timing was determined in all systems.

Also, as in Patent Document 2, frame synchronization timing for each system is determined using a synchronization symbol received by each system for each of a plurality of reception systems, or a signal obtained by synthesizing received signals of each system is used. Thus, there has been an OFDM receiver that determines a common frame synchronization timing for all systems.
JP 2003-143105 A JP 2004-180313 A

  As described above, in a conventional OFDM receiving apparatus having a plurality of receiving systems, for example, a received signal having a large received power is selected or all received signals are synthesized. As a result, a synchronization symbol with good reception quality can be obtained, and a frame synchronization timing common to all systems is detected using this synchronization symbol.

  However, in an actual propagation environment, the magnitude and number of delay waves and the arrival time differ for each reception system. Therefore, when the synchronization position (FFT window position) for performing the common FFT processing is determined based on the common frame synchronization timing, there is a problem that intersymbol interference occurs in some reception systems.

  Also, in the case of the above-described method of detecting the frame synchronization timing individually for each reception system using the synchronization symbol received for each reception system, the reception power of the synchronization symbol is affected by the influence of multipath fading depending on the reception system. There is a problem that the frame synchronization timing cannot be correctly detected due to deterioration. Hereinafter, this will be described in detail with reference to FIG. 9 and FIG.

  FIG. 9 and FIG. 10 show the frame synchronization timing distribution of the OFDM receiving apparatus that performs reception processing using a synchronization symbol of 16 sample periods. FIG. 9 and FIG. 10 show the results of the present inventors performing a computer simulation for obtaining frame synchronization timing 2000 times in a propagation path model in which a delayed wave arrives for a period of time comparable to the guard interval length of the OFDM signal. It is.

  Although 0 samples is an ideal synchronization timing, when the reception power of the synchronization symbol is small as shown in FIG. 9, a large frame synchronization error occurs in which the synchronization timing is shifted by the period of the synchronization symbol. On the other hand, when the received power is large as shown in FIG. 10, it can be seen that the synchronization timing is obtained around the ideal synchronization timing. If the frame synchronization timing is largely wrong, the FFT window position cannot be determined correctly, and the information frame following the synchronization symbol cannot be received correctly.

  The present invention has been made to solve the above-described problem. Even when the reception power of the synchronization symbol is reduced due to the influence of multipath fading, the frame synchronization timing is prevented from greatly deviating and received. An object of the present invention is to provide a radio receiving apparatus that prevents intersymbol interference caused by different propagation environments for each system.

  According to another aspect of the present invention, there is provided a radio reception device that correlates between a reception unit that receives a radio signal, a synchronization symbol pattern included in the radio signal received by the reception unit, and a symbol pattern designated in advance. A correlation processing unit that performs processing to calculate a correlation value; an FFT unit that performs FFT processing on a radio signal received by the receiving unit based on a specified FFT (Fast Fourier Transform) processing timing; and an FFT for the FFT unit A plurality of reception systems having an FFT processing timing detection unit for detecting processing timing, a correlation value synthesis unit for synthesizing correlation values calculated by each of the correlation processing units, and a correlation synthesized by the correlation value synthesis unit A frame synchronization timing detection unit for detecting a frame synchronization timing common to each of the reception systems based on the value; and each of the FFTs A demodulation unit that performs a demodulation process using a radio signal that has been subjected to an FFT process by a unit, and each of the FFT processing timing detection units corresponds to the corresponding reception unit from the correlation value calculated by the corresponding correlation processing unit If the first arrival wave can be detected, the FFT processing timing is detected from the correlation value corresponding to the first arrival wave. If the first arrival wave is not detectable, the FFT processing timing is detected from the frame synchronization timing. The detected FFT processing timing is designated to the FFT unit.

  According to another aspect of the present invention, there is provided a radio reception device that correlates between a reception unit that receives a radio signal, a synchronization symbol pattern included in the radio signal received by the reception unit, and a symbol pattern designated in advance. A correlation processing unit that performs processing to calculate a correlation value; an FFT unit that performs FFT processing on a radio signal received by the receiving unit based on a specified FFT (Fast Fourier Transform) processing timing; and an FFT for the FFT unit FFT processing timing detecting unit for detecting processing timing, a plurality of receiving systems, a correlation value calculating unit for each correlation processing unit, calculating the average value of the correlation values, and comparing the magnitudes of the average values, A correlation value selection unit for selecting a reception system having the largest value, and a frame synchronization timing common to each reception system from the correlation value of the selected reception system Frame synchronization timing detectors, and demodulation units that perform demodulation processing using radio signals that have been subjected to FFT processing by the FFT units. Each of the FFT processing timing detection units corresponds to the corresponding correlation processing unit. When the earliest arrival wave in the receiving unit corresponding to the correlation value calculated by the above can be detected, FFT processing timing is detected from the correlation value corresponding to the earliest arrival wave, and when the earliest arrival wave cannot be detected, The FFT processing timing is detected from frame synchronization timing, and the detected FFT processing timing is designated to the FFT unit.

  A radio reception apparatus as one aspect of the present invention includes a reception unit that receives a radio signal, a reception power measurement unit that measures reception power of the radio signal, a minimum reception sensitivity of the reception unit, and the measured reception An effective reception level measurement unit that measures an effective reception level from power, a correlation symbol pattern included in a radio signal received by the reception unit, and a correlation pattern that is specified in advance are correlated A correlation processing unit that calculates a value, an FFT unit that performs FFT processing on a radio signal received by the receiving unit based on a specified FFT (Fast Fourier Transform) processing timing, and detects an FFT processing timing for the FFT unit A plurality of reception systems having an FFT processing timing detection unit, and an effective reception level measured by each of the effective reception level measurement units. And a magnitude comparison unit that selects a reception system having the largest effective reception level, and among the correlation values calculated by each of the correlation processing units, of the reception system selected by the magnitude comparison unit A correlation value selection unit for selecting one, a frame synchronization timing detection unit for detecting a frame synchronization timing common to each of the receiving systems from the selected correlation value, and a radio signal FFT-processed by each of the FFT units And each of the FFT processing timing detection units can detect the first arrival wave in the corresponding receiving unit from the correlation value calculated by the corresponding correlation processing unit. The FFT processing timing is detected from the correlation value corresponding to the earliest arrival wave. If the earliest arrival wave cannot be detected, the frame synchronization timing is used. Serial detect FFT processing timing, specifies the FFT processing timing detected in the FFT section, and wherein the.

  According to the present invention, it is possible to prevent the frame synchronization timing from greatly deviating even when the reception power of the synchronization symbol is reduced due to the influence of multipath fading, and to prevent intersymbol interference caused by different propagation environments for each system. be able to.

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

  FIG. 1 shows the configuration of a wireless communication apparatus according to the first embodiment of the present invention. In the following description, only the reception system according to the present invention will be described, but the wireless communication apparatus also includes a transmission system configuration.

  The wireless communication apparatus includes n reception systems (n is at least 2 or more). Each reception system includes an antenna 10k, an RF unit 11k, an A / D conversion unit 12k, a correlation processing unit (matched filter) 13k, an FFT (Fast Fourier Transform) window position detection unit 14k, and an FFT unit 15k (however, k 1 to n). In addition, the wireless communication apparatus includes a correlation value synthesis unit 161, a frame synchronization timing detection unit 171, and a demodulation unit 181.

  Each of the antennas 101 to 10n receives a radio signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) scheme transmitted from a communication partner and outputs the radio signal to a corresponding RF unit 11k. Here, the antennas 101 to 10n receive radio signals subjected to different fading. For this reason, the reception timing of the radio signals received by the antennas 101 to 10n is not necessarily simultaneous.

  Each of the RF units 111 to 11n converts the radio signal input from the corresponding antenna 10k into a baseband signal and outputs the baseband signal to the corresponding A / D conversion unit 12k. At this time, the RF units 111 to 11n adjust the amplitude of the baseband signal so as to match the dynamic range of the corresponding A / D conversion unit 12k, further remove the interference components from different bands, and then perform the A / D The data is output to the conversion unit 12k.

  The A / D conversion units 121 to 12n perform A / D conversion on the baseband signal input from the corresponding RF unit 11k, and output to the corresponding correlation processing unit 13k and the FFT unit 15k that performs FFT conversion.

  Correlation processing units 131 to 13n each include a correlation value between a symbol pattern of a known symbol for synchronization that is included in a baseband signal (A / D conversion output) and is repeated for a predetermined period, and a known symbol pattern that the wireless communication apparatus holds in advance. Hereinafter, this correlation value is used as a cross-correlation value). Alternatively, the correlation processing units 131 to 13n obtain a correlation value between the synchronization known symbol included in the received signal and the synchronization known symbol delayed by one symbol period (hereinafter, this correlation value is referred to as an autocorrelation value). calculate. Also, depending on the device, both the cross-correlation value and the autocorrelation value are calculated. The correlation processing units 131 to 13n output the calculated correlation values to the corresponding FFT window position detection unit 14k and the correlation value synthesis unit 161.

  The correlation value synthesis unit 161 synthesizes (for example, sums) the correlation values calculated by the correlation processing units 131 to 13n, and outputs the synthesized correlation value to the frame synchronization timing detection unit 171. By combining the correlation values of each system, the SNR (Signal to Noise Ratio) of the correlation values used for the frame synchronization timing detection process can be increased.

  The frame synchronization timing detection unit 171 detects a frame synchronization timing common to each reception system based on the synthesized correlation value input from the correlation value synthesis unit 161. As a specific detection method, a method of detecting the timing for obtaining the maximum correlation value (peak) of the combined cross-correlation value, or a symbol synchronization timing is detected from a timing at which the combined autocorrelation value is equal to or less than a threshold value. A method or a combination of these methods is used. The frame synchronization timing detected by the frame synchronization timing detection unit 171 is output to the FFT window position detection units 141 to 14n.

  The FFT window position detection units 141 to 14n start the FFT process in the corresponding FFT unit 15k using the correlation value input from the corresponding correlation processing unit 13k and the frame synchronization timing input from the frame synchronization timing detection unit 171, respectively. FFT window positions, which are sample positions to be detected, are detected independently and output to the corresponding FFT section 15k.

  More specifically, if the FFT window position detectors 141 to 14n can detect the earliest arrival wave at the corresponding antenna 10k, the end of the GI frame in the earliest arrival wave or slightly before this (interference from different bands) The FFT window position is defined as the degree to which interference between adjacent symbols due to filtering for removing the component is not received. On the other hand, the FFT window position detectors 141 to 14n determine the FFT window position based on the frame synchronization timing detected by the frame synchronization timing detector 171 when the earliest arrival wave cannot be detected.

  Whether or not the earliest arrival wave can be detected is determined by the reception SNR of each reception system. The reception SNR is estimated from the correlation values obtained in the correlation value processing units 131 to 13n corresponding to the FFT window position detection units 141 to 14n. For example, when the variance of the peak value obtained when receiving the synchronization known symbol of the autocorrelation value obtained by the delayed autocorrelator is calculated and the variance is large, it is estimated that the SNR is small, and conversely when the variance is small Estimates that the SNR is large. In addition, there is also a method of estimating that the SNR is small when the difference value of the cross-correlation values of successive known symbols for synchronization is large, and conversely when the difference value is small. Further, the threshold value is set to an SNR at which the FFT window position can be appropriately detected with respect to the SNR that can be estimated in this way.

  Hereinafter, the FFT window position detection units 141 to 14n will be described in more detail.

  FIG. 4 is a diagram illustrating an example of detecting the FFT window position from the earliest arrival wave.

  FIG. 4 shows a frame (first arrival wave, delayed wave) received in a certain reception system. The height (vertical length) of the frame of the earliest arrival wave and the delay wave represents the magnitude of the received power.

  If the earliest arrival wave can be detected, the FFT window position detectors 141 to 14n use the data frame head of the earliest arrival wave as the FFT window position. However, if the head of the data frame of the earliest arrival is completely set to the FFT window position, if the FFT window position is shifted backward due to a slight error in the synchronization detection position, intersymbol interference occurs and the characteristics deteriorate. there is a possibility. Therefore, the end of the GI frame of the earliest wave or slightly before this (predetermined length) is set as the FFT window position. As a result, it is possible to perform FFT processing in which intersymbol interference is effectively suppressed.

  On the other hand, for example, when a frame synchronization timing common to each reception system is detected and the FFT window position is determined based on the frame synchronization timing, intersymbol interference may occur. For example, it is assumed that the reception power of the earliest arrival wave is the largest among all the reception waves among the incoming waves of the respective reception systems, and a common frame synchronization timing is detected from the reception timing of the earliest arrival wave. In general, in the case of OFDM communication, a position half the length of a guard interval frame (hereinafter referred to as GI frame), which is a multipath countermeasure frame, from the detected common frame synchronization timing (here, the center of the GI frame of the earliest arrival shown in the figure) ) Is often the FFT window position. However, in this case, intersymbol interference I occurs from the adjacent symbols of the delayed wave in the propagation path where the incoming wave having a particularly long delay time arrives, as shown in the figure. For this reason, in the receiving system capable of detecting the earliest arrival wave, the FFT window position is set at the end of the GI frame of the earliest arrival wave or slightly before this as in the present embodiment. In order to set the FFT window position at the end of the GI frame of the earliest wave or slightly before this, the earliest wave must be detected.

  FIG. 6 is a diagram for explaining a method of detecting the earliest arrival wave.

  The FFT window position detection units 141 to 14n detect the earliest arrival wave using the correlation value input from the corresponding correlation processing unit 13k. For example, the first arrival wave is detected using a difference value of cross-correlation values between adjacent samples. FIG. 6 shows a cross-correlation value (upper stage) calculated by the correlation processing unit 13i (where i is any one of 1 to n) and a difference value (lower stage) between adjacent samples of the cross-correlation value. The sample time interval corresponds to the sampling interval of A / D conversion. Among the frame synchronization timing detection in the conventional radio reception apparatus, there is one that detects T5 which is the peak timing of the correlation value and uses this as the frame synchronization timing. In this case, the frame synchronization timing does not necessarily coincide with the arrival time T3 of the earliest arrival wave. Therefore, in this embodiment, a difference value between adjacent samples of the cross correlation value is used. The difference value of the time Tm in the lower part of FIG. 6 is Tm−T (m−1) (where m is 2 to 12). When the frame synchronization symbol arrives, the cross-correlation value increases rapidly, and the difference value increases in the positive direction. Therefore, the arrival time (reception timing) of the earliest arrival wave can be detected by determining the threshold value of the positive difference value. That is, the earliest arrival wave can be easily inferred from the difference value between successive correlation values. In addition to this, as shown in FIG. 11, the method of detecting the earliest arrival wave includes the peak value of the correlation value in several samples before and after the frame synchronization timing (for example, the number of samples in one cycle of the known symbol for synchronization). The threshold value is set based on the difference between the minimum correlation values ahead of the peak value, the cross-correlation value ahead of the peak value is determined as a threshold value, and the arrival time of the earliest arrival is detected, or the cross-correlation value itself is determined as the threshold value Some exist. In addition, these methods may use an average cross-correlation value obtained by averaging adjacent cross-correlation values instead of the cross-correlation value itself. In FIG. 6, the arrival time of the earliest arrival wave is ahead of the frame synchronization timing (T3 <T5), but depending on the receiving system, the arrival time is the earliest behind the frame synchronization timing acquired by the composite signal (T5 <). A wave may arrive.

  Here, when the received power is small as a whole (for example, when the average value of the correlation values is small), the correlation value may be buried due to noise, and the first arrival wave may not be detected correctly. Therefore, in the receiving system that cannot correctly detect the first arrival wave, the FFT window position detection is not performed by detecting the first arrival wave, and the FFT window position is determined based on the frame synchronization timing detected by the frame synchronization timing detection unit 171. Suitable reception characteristics can be obtained. In this case, although intersymbol interference may occur, a better reception characteristic can be obtained than in the case where the FFT window position is determined by erroneously detecting the earliest arrival wave by the conventional method of determining the frame synchronization timing for each reception system. .

  FIG. 5 is a diagram for explaining an example of detecting the FFT window position from the frame synchronization timing.

  This figure shows a case where the received power is small as a whole, and the earliest arrival wave cannot be detected by the above-described reference of FIG. In this case, the FFT window position is determined based on the frame synchronization timing detected by the frame synchronization timing detection unit 171. For example, a position half the GI frame length before the detected common frame synchronization timing is set as the FFT window position. Here, the frame synchronization timing detection unit 171 detects the head of the data frame of the delayed wave shown in the figure as the frame synchronization timing, and the center of the GI frame (half the length of the GI frame from the frame synchronization timing) is set as the FFT window position. . The FFT window position is commonly applied to all reception systems in which the earliest arrival wave cannot be detected. As can be seen from the figure, intersymbol interference can occur, but since the reception power of the earliest arrival wave is small, the degree of interference received from the earliest arrival wave is small, and favorable reception characteristics can be obtained.

  Returning to FIG. 1, the FFT units 151 to 15 n each receive the FFT window position input from the corresponding FFT window position detection unit 14 k with respect to the baseband signal input from the corresponding A / D conversion unit 12 k. To perform FFT processing. Each baseband signal after the FFT processing is output to demodulation section 181.

  The demodulator 181 performs synthesis processing and demodulation processing on each baseband signal input from the FFT units 151 to 15n in a single-input multi-output (SIMO) system, and multi-input multi-output (MIMO). The system performs MIMO signal processing and demodulation processing, and outputs the result to a signal processing unit (not shown) at the subsequent stage.

  Next, the operation of the reception apparatus having the above configuration will be described. In the following description, in order to simplify the description, a case of a receiving apparatus configuration in which the number of receiving systems is 2, that is, n = 2 will be described as an example.

  Radio signals modulated by the OFDM method transmitted from the communication partner are received by the antennas 101 and 102, respectively.

  Next, RF processing such as interference removal from different bands, frequency conversion to a baseband signal, and amplitude adjustment is performed in the corresponding RF units 111 and 112.

  Baseband signals output from the RF units 111 and 112 are A / D converted by the A / D conversion units 121 and 122 and output to the corresponding correlation processing units 131 and 132 and FFT units 151 and 152.

  In correlation processing sections 131 and 132, correlation processing is performed on the frame synchronization symbols, and the correlation value of each baseband signal is obtained. Each correlation value is output to the corresponding FFT window position detection units 141 and 142 and the correlation value synthesis unit 161.

  The correlation value synthesis unit 161 synthesizes each correlation value. Then, the frame synchronization timing detection unit 171 detects the frame synchronization timing common to each reception system from the combined correlation value.

  Thereafter, the FFT window position detectors 141 and 142 detect the FFT window position independently of each reception system using the frame synchronization timing and the correlation value input to each. FIGS. 7 and 8 show how the FFT window position is detected independently for each receiving system.

  In FIG. 7, the earliest arrival wave is detected in each receiving system, and a little before the end of the GI frame of the earliest arrival wave (no interference between adjacent symbols due to filtering to remove interference components from different bands) Degree) is detected as the FFT window position.

  In FIG. 8, the earliest arrival wave is detected in the receiving system of the antenna 102, and a position slightly before the end of the GI frame of the earliest arrival wave is detected as the FFT window position. On the other hand, in the reception system of the antenna 101, since the earliest arrival wave cannot be detected, the FFT window position is detected from the common frame synchronization timing. Specifically, the head of the data frame in the second incoming wave of the received signal of the antenna 102 is detected as the frame synchronization timing, and the center of this GI frame is detected as the FFT window position with respect to the antenna 101.

  Using the FFT window positions detected in this way, the FFT units 151 and 152 perform FFT conversion on the baseband signals input from the A / D conversion units 121 and 122. Thereafter, the demodulator 181 performs synthesis processing and demodulation processing in a SIMO (Single-Input Multi-Output) system, and performs MIMO signal processing and demodulation processing in a MIMO (Multi-Input Multi Output) system, and outputs them to a signal processing unit in the subsequent stage. To do.

  As described above, according to the present embodiment, the correlation values calculated in at least two or more receiving systems are combined, and the common frame synchronization timing is detected based on the combined correlation values. Then, the FFT window position is detected independently for each reception system from the correlation value of each reception system and the common frame synchronization timing. Thereby, the FFT window position can be detected in consideration of the propagation path for each reception system, interference between symbols can be prevented, and good demodulation performance can be exhibited.

  For example, the present invention is particularly effective when the receiving device is mounted on an object that moves at high speed, and the antenna interval installed in the receiving device is set large to reduce the correlation between the antennas. That is, in this case, the state of the transmission path varies greatly from reception system to reception system, and the reception power can be very small depending on the reception system. However, according to the present embodiment, the FFT is taken into account for each reception system. Since the window position can be detected, good demodulation performance can be exhibited. More specifically, in the receiving system capable of detecting the earliest arrival wave, the FFT window position is set at the end of the GI frame of the earliest arrival wave or slightly before this, and in the receiving system where the earliest arrival wave cannot be detected, the position based on the common frame synchronization timing By making the FFT window position a suitable demodulation performance can be obtained.

  FIG. 2 shows a configuration of a wireless communication apparatus according to the second embodiment of the present invention. In the following description, only the reception system according to the present invention will be described, but the wireless communication apparatus also includes a transmission system configuration.

  The wireless communication apparatus includes n reception systems (n is at least 2 or more). Each reception system includes an antenna 20k, an RF unit 21k, an A / D conversion unit 22k, a correlation processing unit 23k, an FFT (Fast Fourier Transform) window position detection unit 24k, and an FFT unit 25k (where k is 1 to n). ). In addition, the wireless communication apparatus includes a magnitude comparison unit 261, a correlation value selection unit 271, a frame synchronization timing detection unit 281, and a demodulation unit 291.

  Each of the antennas 201 to 20n receives a radio signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) scheme transmitted from a communication partner and outputs the radio signal to a corresponding RF unit 21k. Here, the antennas 201 to 20n receive radio signals subjected to different fading. For this reason, the reception timing of the radio signals received by the antennas 201 to 20n is not necessarily simultaneous.

  The RF units 211 to 21n frequency-convert radio signals input from the corresponding antennas 20k into baseband signals and output the baseband signals to the corresponding A / D conversion units 22k. At this time, the RF units 211 to 21n adjust the amplitude of the baseband signal so as to match the dynamic range of the corresponding A / D conversion unit 22k, further remove the interference components from different bands, and then perform the A / D The data is output to the conversion unit 22k.

  The A / D conversion units 221 to 22n perform A / D conversion on the baseband signal output from the corresponding RF unit 21k, and output to the corresponding correlation processing unit 23k and the FFT unit 25k that performs FFT conversion.

  The correlation processing units 231 to 23n include a correlation value between a symbol pattern of a known symbol for synchronization that is included in a baseband signal (A / D conversion output) and is repeated for a certain period, and a known symbol pattern that the wireless communication apparatus holds in advance. (Correlation value) is calculated. Alternatively, the correlation processing units 231 to 23n calculate a correlation value (autocorrelation value) between the synchronization known symbol included in the received signal and the synchronization known symbol delayed by one symbol period. Also, depending on the device, both the cross-correlation value and the autocorrelation value are calculated. The correlation processing units 231 to 23n output the calculated correlation values to the corresponding FFT window position detection unit 24k, the magnitude comparison unit 261, and the correlation value selection unit 271.

  The magnitude comparison unit 261 obtains the average value of the correlation values calculated by the correlation processing units 231 to 23n for each correlation processing unit, compares the average values, and determines the reception system having the maximum average value. Then, the determination result is output to the correlation value selection unit 271.

  The correlation value selection unit 271 selects the reception system determined by the size comparison unit 261 from the correlation values calculated by the correlation processing units 231 to 23n, and outputs the selected one to the frame synchronization timing detection unit 281. Thus, by selecting the correlation value having the maximum average value, the SNR (Signal to Noise Ratio) of the correlation value used in the frame synchronization timing detection process is compensated.

  The frame synchronization timing detection unit 281 detects a frame synchronization timing common to each reception system based on the correlation value of the known symbol for synchronization input from the correlation value selection unit 271. Specific detection methods include a method of detecting the timing for obtaining the maximum correlation value (peak) of the cross-correlation value, a method of detecting the symbol synchronization timing from the timing when the autocorrelation value is equal to or less than a threshold value, or these methods. A method combining the above is used. The frame synchronization timing detected by the frame synchronization timing detection unit 281 is output to the FFT window position detection units 241 to 24n.

  The FFT window position detectors 241 to 24n perform the FFT processing in the corresponding FFT unit 25k using the correlation value input from the corresponding correlation processing unit 23k and the frame synchronization timing input from the frame synchronization timing detection unit 281. The FFT window position, which is the starting sample position, is detected independently and output to the corresponding FFT unit 25k. Specific processing contents performed by the FFT window position detection units 241 to 24n are the same as those in the first embodiment.

  The FFT units 251 to 25n perform FFT processing on each baseband signal input from the corresponding A / D conversion unit 22k from the FFT window position input from the corresponding FFT window position detection unit 24k. . Each baseband signal after the FFT processing is output to demodulation section 291.

  In the demodulator 291, the baseband signals input from the FFT units 251 to 25 n are combined and demodulated in a SIMO (Single-Input Multi-Output) system, and in the MIMO (Multi-Input Multi Output) system. MIMO signal processing and demodulation processing are performed and output to a subsequent signal processing unit (not shown).

  Next, the operation of the reception apparatus having the above configuration will be described. In the following description, in order to simplify the description, a case of a receiving apparatus configuration in which the number of receiving systems is 2, that is, n = 2 will be described as an example.

  Radio signals modulated by the OFDM scheme transmitted from the communication partner are received by the antennas 201 and 202, respectively.

  Next, RF processing such as interference removal from different bands, frequency conversion to a baseband signal, and amplitude adjustment is performed in the corresponding RF units 211 and 212.

  The baseband signals output from the RF units 211 and 212 are A / D converted by the A / D conversion units 221 and 222 and output to the corresponding correlation processing units 231 and 232 and FFT units 251 and 252.

  In the correlation processing units 231 and 232, correlation processing is performed on the frame synchronization symbols, and the correlation value of each baseband signal is obtained. Each correlation value is output to the corresponding FFT window position detection unit 241, 242, magnitude comparison unit 261, and correlation value selection unit 271.

  The magnitude comparison unit 261 compares the average values of the correlation values, and determines the reception system having the maximum correlation value average value. Based on the determination result, the correlation value selection unit 271 selects the correlation value having the maximum average value.

  Then, the frame synchronization timing detection unit 281 detects the frame synchronization timing common to each reception system using the selected correlation value.

  Thereafter, the FFT window position detectors 241 and 242 detect the FFT window position independently for each reception system using the frame synchronization timing and the correlation value input to each.

  Using the detected FFT window positions, the FFT units 251 and 252 perform FFT conversion on the baseband signals input from the A / D conversion units 221 and 222.

  After that, the demodulator 291 performs synthesis processing and demodulation processing in a SIMO (Single-Input Multi-Output) system, and performs MIMO signal processing and demodulation processing in a MIMO (Multi-Input Multi Output) system, and outputs to the signal processing unit in the subsequent stage. To do.

  As described above, according to the present embodiment, the influence of noise is detected by detecting the frame synchronization timing using the correlation value having the maximum average value among the correlation values obtained by at least two reception systems. Thus, it is possible to prevent the frame synchronization timing from being greatly mistaken.

  FIG. 3 shows the configuration of a wireless communication apparatus according to the third embodiment of the present invention. In the following description, only the reception system according to the present invention will be described, but the wireless communication apparatus also includes a transmission system configuration.

  The wireless communication apparatus includes n reception systems (n is at least 2 or more). Each reception system includes an antenna 30k, an RF unit 31k, an A / D conversion unit 32k, a correlation processing unit 33k, an FFT (Fast Fourier Transform) window position detection unit 34k, an FFT unit 35k, and an effective reception level measurement unit 36k (see FIG. However, k is 1 to n). In addition, the wireless communication apparatus includes a magnitude comparison unit 371, a correlation value selection unit 381, a frame synchronization timing detection unit 391, and a demodulation unit 392.

  Each of the antennas 301 to 30n receives a radio signal modulated by an OFDM (Orthogonal Frequency Division Multiplexing) scheme transmitted from a communication partner and outputs the radio signal to a corresponding RF unit 31k. Here, the antennas 301 to 30n receive radio signals subjected to different fading. For this reason, the reception timing of the radio signals received by the antennas 301 to 30n is not necessarily simultaneous.

  The RF units 311 to 31n frequency-convert radio signals input from the corresponding antennas 30k into baseband signals and output the baseband signals to the corresponding A / D conversion units 32k. At this time, the RF units 311 to 31n adjust the amplitude of the baseband signal so as to match the dynamic range of the corresponding A / D conversion unit 32k, further remove the interference components from different bands, and then perform the A / D The data is output to the conversion unit 32k. In addition, the RF units 311 to 31n measure the power of the signal received by the corresponding antenna 30k and output it to the corresponding effective reception level measurement unit 36k.

  The A / D conversion units 321 to 32n perform A / D conversion on the baseband signal input from the corresponding RF unit 31k, and output it to the corresponding correlation processing unit 33k and the FFT unit 35k that performs FFT conversion.

  Correlation processing units 331 to 33n each have a correlation value (a symbol value of a known symbol for synchronization included in a baseband signal (A / D conversion output) and repeated for a certain period of time and a known symbol pattern held in advance by the wireless communication apparatus ( Hereinafter, this correlation value is used as a cross-correlation value). Alternatively, a correlation value (hereinafter, this correlation value is referred to as an autocorrelation value) between the synchronization known symbol included in the received signal and the synchronization known symbol delayed by one symbol period is calculated. Also, depending on the device, both the cross-correlation value and the autocorrelation value are calculated. The correlation processing units 331 to 33n output the calculated correlation value to the corresponding FFT window position detection unit 34k and the correlation value selection unit 381.

  The effective reception level measurement units 361 to 36n measure the effective reception level from the lowest reception level of the corresponding RF unit 31k and the received power input from the corresponding RF unit 31k, and output the measured reception level to the magnitude comparison unit 371. The effective reception level is the difference between the reception power and the minimum reception level of the reception system. Even if the signal power received by each reception system is the same, the signal received by the reception system having the lowest minimum reception level, that is, the reception signal having the maximum effective reception level has the highest quality.

  The size comparison unit 371 compares the effective reception levels calculated by the effective reception level measurement units 361 to 36n, and determines a reception system having the maximum effective reception level. Then, the determination result is output to the correlation value selection unit 381.

  Correlation value selection section 381 selects the one of the reception system determined by size comparison section 371 from the correlation values calculated by correlation processing sections 331 to 33n, and outputs the selected correlation value to frame synchronization timing detection section 391. By selecting the correlation value of the receiving system having the maximum effective reception level, the SNR (Signal to Noise Ratio) of the correlation value used in the frame synchronization timing detection process is compensated.

  The frame synchronization timing detection unit 391 detects the frame synchronization timing common to each reception system based on the correlation value of the synchronization known symbol input from the correlation value selection unit 381.

Specific detection methods include a method of detecting the timing for obtaining the maximum correlation value (peak) of the cross-correlation value, a method of detecting the symbol synchronization timing from the timing when the autocorrelation value is equal to or less than a threshold value, or these methods. A method combining the above is used.

  The frame synchronization timing detected by the frame synchronization timing detection unit 391 is output to the FFT window position detection units 341 to 34n.

  The FFT window position detection units 341 to 34n perform the FFT processing in the corresponding FFT unit 35k using the correlation value input from the corresponding correlation processing unit 33k and the frame synchronization timing input from the frame synchronization timing detection unit 391. The FFT window position, which is the starting sample position, is detected and output to the corresponding FFT unit 35k. Specific processing contents performed by the FFT window position detection units 341 to 34n are the same as those in the first embodiment.

  The FFT units 351 to 35n perform FFT processing on each baseband signal input from the corresponding A / D conversion unit 32k based on the FFT window position input from the corresponding FFT window position detection unit 34k. To do. Each baseband signal after the FFT processing is output to demodulation section 392.

  The demodulator 392 combines and demodulates the baseband signals input from the FFT units 351 to 35n in the SIMO (Single-Input Multi-Output) system, and the MIMO (Multi-Input Multi Output) system. MIMO signal processing and demodulation processing are performed and output to a subsequent signal processing unit (not shown).

  Next, the operation of the reception apparatus having the above configuration will be described. In the following description, in order to simplify the description, a case of a receiving apparatus configuration in which the number of receiving systems is 2, that is, n = 2 will be described as an example.

  Radio signals modulated from the communication partner and modulated by the OFDM method are received by antennas 301 and 302, respectively.

  Next, RF processing such as interference removal from different bands, frequency conversion to baseband signals, and amplitude adjustment is performed in the corresponding RF units 311 and 312, and output to the A / D conversion units 321 and 322. In addition, the RF units 311 and 312 measure the power of the respective received signals, and the measured received power is output to the effective reception level measuring units 361 and 362.

  The baseband signals output from the RF units 311 and 312 are A / D converted by the A / D conversion units 321 and 322 and output to the corresponding correlation processing units 331 and 332 and the FFT units 351 and 352.

  In correlation processing sections 331 and 332, correlation processing is performed on the frame synchronization symbols, and the correlation value of each baseband signal is obtained. The respective correlation values are output to the corresponding FFT window position detection units 341 and 342 and the correlation value selection unit 381.

  The effective reception level measurement units 361 and 362 measure the effective reception level based on the reception power input from the corresponding RF units 311 and 312 and output the measurement result to the magnitude comparison unit 371.

  The magnitude comparison unit 371 compares the respective effective reception levels, and determines a reception system having the maximum effective reception level. From the determination result, the correlation value selection unit 381 selects the correlation value of the reception system having the maximum effective reception level.

  The frame synchronization timing detection unit 391 detects a frame synchronization timing common to each reception system using the correlation value of the selected reception system.

  Thereafter, FFT window position detection units 341 and 342 detect the FFT window position independently for each reception system using the frame synchronization timing and the respective correlation values.

  Using the FFT window positions thus detected, the FFT units 351 and 352 perform FFT conversion on the baseband signals input from the A / D conversion units 321 and 322.

  Thereafter, the demodulator 392 performs synthesis processing and demodulation processing in a single-input multi-output (SIMO) system, and performs MIMO signal processing and demodulation processing in a multi-input multi-output (MIMO) system. Output to.

  As described above, in the receiving apparatus configured as described above, by detecting the frame synchronization timing using the correlation value of the received signal having the maximum effective reception level among the correlation values obtained by at least two or more receiving systems, It is possible to prevent the frame synchronization timing from being greatly erroneous due to the influence of the reception system noise.

  In the first to third embodiments described above, the OFDM wireless communication apparatus having a plurality of antennas has been mainly described. However, the present invention uses not only OFDM but also a single carrier wireless communication apparatus having a plurality of antennas, particularly FFT. It is also effective for a wireless communication system that performs FDE (Frequency Domain Equalizing). Furthermore, the application target of the present invention is not limited to a wireless communication device, and the present invention can be applied to a communication device having a GI frame in a transmission frame and having a plurality of reception systems and using FFT for reception processing. It is.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a circuit block diagram showing a configuration of a first embodiment of a wireless communication apparatus according to the present invention. A circuit block diagram showing a configuration of a second embodiment of a wireless communication apparatus according to the present invention. A circuit block diagram showing a configuration of a third embodiment of a wireless communication apparatus according to the present invention. The figure explaining the example which detects a FFT window position from the correlation value of the earliest arrival wave The figure explaining the example which detects a FFT window position from frame synchronous timing The figure for explaining the detection method of the first arrival wave The figure showing a mode that a FFT window position was detected independently in each system | strain in 1st Embodiment. The figure showing the mode of FFT window position detection when the received power of the antenna is small in the first embodiment Diagram showing frame synchronization error distribution when received power is low Diagram showing frame synchronization error distribution when received power is large The figure for demonstrating the method of detecting the first arrival wave from the peak value and minimum value of a cross-correlation value

Explanation of symbols

101 to 10n, 201 to 20n, 301 to 30n: antennas 111 to 11n, 211 to 21n, 311 to 31n: RF units 121 to 12n, 221 to 22n, 321 to 32n: A / D conversion units 131 to 13n, 231 to 23n, 331 to 33n: correlation processing units 141 to 14n, 241 to 24n, 341 to 34n: FFT window position detection units 151 to 15n, 251 to 25n, 351 to 35n: FFT unit 161: correlation value combining units 171, 281, 391: Frame synchronization timing detection units 181, 291 and 392: Demodulation units 261 and 371: Size comparison units 271 and 381: Correlation value selection units 361 to 36n: Execution reception level measurement units

Claims (9)

A receiver for receiving a radio signal;
A correlation processing unit that performs correlation processing between a symbol pattern for synchronization included in the wireless signal received by the receiving unit and a symbol pattern designated in advance to calculate a correlation value;
An FFT unit that performs FFT processing on a radio signal received by the receiving unit based on designated FFT (Fast Fourier Transform) processing timing;
A plurality of receiving systems having an FFT processing timing detection unit for detecting an FFT processing timing for the FFT unit;
A correlation value synthesis unit for synthesizing the correlation values calculated by each of the correlation processing units;
A frame synchronization timing detection unit for detecting a frame synchronization timing common to each of the reception systems based on the correlation value synthesized by the correlation value synthesis unit;
A demodulation unit that performs a demodulation process using a radio signal FFT-processed by each of the FFT units,
Each FFT processing timing detection unit performs FFT processing from the correlation value corresponding to the earliest arrival when the earliest arrival at the corresponding reception unit can be detected from the correlation values calculated by the corresponding correlation processing units. When the timing is detected and the earliest arrival wave is not detectable, the FFT processing timing is detected from the frame synchronization timing, and the detected FFT processing timing is designated to the FFT unit.
A wireless communication apparatus. A receiver for receiving a radio signal;
A correlation processing unit that performs correlation processing between a symbol pattern for synchronization included in the wireless signal received by the receiving unit and a symbol pattern designated in advance to calculate a correlation value;
An FFT unit that performs FFT processing on a radio signal received by the receiving unit based on designated FFT (Fast Fourier Transform) processing timing;
A plurality of receiving systems having an FFT processing timing detection unit for detecting an FFT processing timing for the FFT unit;
An average value of correlation values is calculated for each correlation processing unit, and a magnitude comparison unit that compares the magnitudes of the average values;
A correlation value selection unit for selecting a receiving system having the largest average value;
A frame synchronization timing detection unit for detecting a frame synchronization timing common to each of the reception systems from the correlation value of the selected reception system;
A demodulation unit that performs a demodulation process using a radio signal FFT-processed by each FFT unit,
Each FFT processing timing detection unit performs FFT processing from the correlation value corresponding to the earliest arrival when the earliest arrival at the corresponding reception unit can be detected from the correlation values calculated by the corresponding correlation processing units. When the timing is detected and the earliest arrival wave is not detectable, the FFT processing timing is detected from the frame synchronization timing, and the detected FFT processing timing is designated to the FFT unit.
A wireless communication apparatus. A receiver for receiving a radio signal;
A received power measuring unit for measuring the received power of the radio signal;
An effective reception level measurement unit that measures an effective reception level from the minimum reception sensitivity of the reception unit and the measured received power;
A correlation processing unit that performs correlation processing between a symbol pattern for synchronization included in the wireless signal received by the receiving unit and a symbol pattern designated in advance to calculate a correlation value;
An FFT unit that performs FFT processing on a radio signal received by the receiving unit based on designated FFT (Fast Fourier Transform) processing timing;
A plurality of receiving systems having an FFT processing timing detection unit for detecting an FFT processing timing for the FFT unit;
A magnitude comparison unit that compares the magnitudes of the effective reception levels measured by each of the effective reception level measurement units and selects a reception system having the largest effective reception level;
Among the correlation values calculated by each of the correlation processing units, a correlation value selection unit that selects a reception system selected by the magnitude comparison unit;
A frame synchronization timing detection unit for detecting a frame synchronization timing common to each of the reception systems from the selected correlation value;
A demodulation unit that performs a demodulation process using a radio signal FFT-processed by each of the FFT units,
Each FFT processing timing detection unit performs FFT processing from the correlation value corresponding to the earliest arrival when the earliest arrival at the corresponding reception unit can be detected from the correlation values calculated by the corresponding correlation processing units. When the timing is detected and the earliest arrival wave is not detectable, the FFT processing timing is detected from the frame synchronization timing, and the detected FFT processing timing is designated to the FFT unit.
A wireless communication apparatus.   Each of the reception systems includes an A / D conversion unit, and each of the correlation processing unit and each of the FFT units handles a radio signal that has been A / D converted by the corresponding A / D conversion unit. The wireless communication apparatus according to claim 1.   5. Each of the correlation processing units uses a known symbol pattern given in advance or another symbol pattern for synchronization included in the radio signal as the symbol pattern designated in advance. The wireless communication device according to any one of the above.   Each FFT processing timing detection unit calculates a difference between correlation values continuously calculated from the corresponding correlation processing unit, and when the difference exceeds a predetermined threshold value, a correlation value later in time is calculated. 6. The wireless communication apparatus according to claim 1, wherein a correlation value corresponding to the earliest arrival wave is used.   The correlation value synthesizing unit detects the frame synchronization timing from a timing at which the synthesized correlation value becomes maximum or a timing at which the synthesized correlation value becomes a predetermined threshold value or less. The wireless communication apparatus according to any one of 1 to 6.   The demodulator performs a MIMO signal process or a synthesis process using each of the FFT-processed radio signals, and demodulates the signal after the MIMO signal process or the signal after the synthesis process. The wireless communication apparatus according to any one of 1 to 7.   9. The radio communication apparatus according to claim 1, wherein the radio signal is an OFDM-modulated radio signal.

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