JP2008022339A - Radio communication device and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make high-precision phase corrections based upon a phase shift detected from a pilot subcarrier while taking tolerance of a phase noise into consideration. <P>SOLUTION: When tolerance of a random white noise is increased, a degree of equalization is increased to achieve convergence on a fixed phase shift value due to a residual frequency offset. When tolerance of a phase noise is increased, the degree of equalization is decreased to increase a weight of a detected value corresponding to an OFDM (Orthogonal Frequency Division Multiplexing) symbol. It is assumed that multi-level modulation is performed when a reception packet with high SNR is received, and phase correction of high precision can be made by more following up a low-frequency part of the white noise. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio communication apparatus and a radio communication method for receiving a radio signal modulated by OFDM (Orthogonal Frequency Division Multiplexing), and in particular, detected from a pilot subcarrier inserted in an OFDM symbol. The present invention relates to a wireless communication apparatus and a wireless communication method for correcting a residual frequency offset by correcting a phase shift from a data signal.

  More particularly, the present invention relates to a radio communication apparatus and radio communication method for correcting a phase error with high accuracy for an OFDM signal modulated with multi-level QAM (Quadrature Amplitude Modulation), and more particularly to resistance to phase noise. The present invention relates to a radio communication apparatus and a radio communication method that perform phase correction with high accuracy based on phase shift detected from pilot subcarriers.

  When a wireless network is constructed indoors, there is a problem in that a multipath environment is formed in which a receiving device receives a superposition of a direct wave and a plurality of reflected / delayed waves. Multipath causes delay distortion (or frequency selective fading), and causes an error in communication. Intersymbol interference resulting from delay distortion occurs. For this reason, IEEE 802.11, which is a typical standard for wireless LANs, employs an OFDM modulation scheme that is one of the multicarrier schemes.

  An OFDM transmitter assigns multiple data to be output by serial / parallel conversion of information sent serially for each symbol period slower than the information transmission rate, and modulates amplitude and phase for each subcarrier. And performing inverse FFT on the plurality of subcarriers to convert each subcarrier on the frequency axis into a signal on the time axis for transmission. The OFDM receiver performs the reverse operation, that is, performs FFT to convert the time-axis signal to the frequency-axis signal, demodulates each subcarrier in accordance with the modulation method, and performs parallel / serial conversion. The information sent with the original serial signal is reproduced. Here, the frequency of each carrier is set so that each subcarrier is orthogonal to each other within the symbol interval. That subcarriers are orthogonal to each other means that the peak point of the spectrum of an arbitrary subcarrier always coincides with the zero point of the spectrum of another subcarrier. Therefore, since transmission data is distributed and transmitted to a plurality of carriers having different frequencies, the bandwidth of each carrier is narrow, the frequency utilization efficiency is very high, and it is strong against frequency selective fading interference.

  Here, the OFDM communication device has problems of frequency offset and phase noise.

  The frequency offset is caused by a subtle error in the frequency of the oscillator mounted on each transceiver (for example, an oscillator having an accuracy of about 20 ppm is used in a wireless LAN), and the analog part of the transceiver is used. The oscillator error is observed as a phenomenon of phase rotation of the received signal in the digital part on the receiver side.

  The phase noise is phase noise generated between the IQ modulation unit and the demodulation unit of the analog unit of the transceiver. Looking at the data in the frequency domain of the FFT value at the receiver side, the low frequency component of the phase noise can be observed as a phenomenon that the phase of all subcarriers rotates by almost the same angle for each OFDM symbol. In different OFDM symbols, the rotation angle varies, but the angle for each subcarrier is observed to be the same.

  As a countermeasure against the frequency offset in the wireless LAN, a preamble, that is, a reference signal having a known pattern is added to the head of a transmission frame (or packet) from the transmitter side (that is, the preceding stage of user data). On the receiver side, the reference signal is used to acquire synchronization and observe the frequency offset with the transmitter, and the frequency offset is corrected by reversely rotating the data phase in response to the frequency shift.

  In addition, since the estimation of the frequency offset using the preamble actually includes an error, the frequency offset compensation for the payload cannot be performed completely. For this reason, the payload is received with the residual frequency offset remaining. For example, when an error occurs in the calculation of the frequency offset amount due to noise or other influences, the frequency offset remains.

  In an OFDM communication system, data after performing FFT on the receiving side is frequency domain data. The frequency offset is observed as a phenomenon in which all subcarriers rotate uniformly, that is, by the same angle for each OFDM symbol. FIG. 5 three-dimensionally represents the ratio between the subcarrier after channel correction and the modulation point on the phase space (constellation). The residual frequency offset causes intersubcarrier interference and causes a phase shift in the signal after being subjected to FFT.

  Due to the influence of the residual frequency offset, the phase of all subcarriers of the OFDM symbol rotates by the same angle, but the amount of rotation differs for each OFDM symbol. Therefore, using the known pilot subcarriers that the transmitter inserts into each OFDM symbol (for example, four pilot subcarriers are inserted into 52 subcarriers), the residual frequency offset is set on the receiver side. It is common to perform “Pilot Tone Tracking” to compensate. That is, the receiver side extracts pilot subcarriers attached to the OFDM symbol, estimates the amount of phase rotation for each OFDM symbol, and gives the data signal the reverse rotation of the estimated phase, whereby the residual frequency The phase shift caused by the offset can be corrected.

  For example, the reference phase / amplitude is reproduced at the beginning of the burst, the residual frequency offset is estimated from the pilot information included in the symbol to be detected and the immediately preceding reference phase information, and the reference phase used at the time of symbol detection from the estimated residual frequency offset By generating information, good demodulation is possible (see, for example, Patent Document 1).

  In addition, a frequency error primary correction unit that corrects a relative phase error in symbol units based on the frequency error in the preamble unit, and a residual phase error for each symbol with respect to a signal that has been expanded into frequency components after being multiplied by FFT. There has been proposed a receiving apparatus that includes a frequency error secondary correction means that corrects with a carrier and corrects the frequency error of an OFDM signal with a circuit configuration that reduces the amount of computation and the amount of memory (for example, see Patent Document 2). ).

  Here, there is a problem that random noise is mixed in pilot symbols. For this reason, when pilot tone tracking is performed, the detected value of the phase error for each pilot subcarrier is averaged (the detected value is averaged over a plurality of symbols in a certain section) and mixed random noise. Is to be suppressed as much as possible.

  With the recent demand for higher transmission rates, multilevel modulation schemes have been advanced. For example, in multi-level modulation such as 256QAM, it is desirable to remove phase noise generated by a local oscillator of a transceiver. However, in the conventional pilot tone tracking technology, the main focus is on suppressing the random white noise by averaging the detection results of the phase error in a certain section, in other words, resistance to phase noise. Is hardly considered.

JP 2001-69113 A, paragraphs 0014 and 0016. JP2003-333209A, paragraph 0037

  An object of the present invention is to provide an excellent radio communication apparatus and radio that can suitably correct a residual frequency offset by correcting a phase shift detected from a pilot subcarrier inserted in an OFDM symbol from a data signal. It is to provide a communication method.

  It is a further object of the present invention to provide an excellent wireless communication apparatus and wireless communication method capable of performing highly accurate phase error correction on multi-level QAM modulated OFDM signals.

  A further object of the present invention is to provide an excellent wireless communication apparatus and wireless communication capable of performing highly accurate phase correction based on a phase shift detected from a pilot subcarrier while also considering resistance to phase noise. It is to provide a method.

The present invention has been made in consideration of the above problems, and is a wireless communication apparatus for receiving and processing an OFDM signal,
Receiving means for receiving a packet comprising an OFDM signal;
Phase error detection means for detecting a phase error using pilot subcarriers included in the OFDM symbol;
Averaging processing means for averaging the detection result of the phase error by the phase error detection means over a predetermined period;
SNR information acquisition means for acquiring SNR information in the propagation path from which the OFDM signal arrives;
An averaging processing control means for determining an averaging processing method by the averaging processing means based on the acquired SNR information;
A phase shift removing unit for removing a phase shift included in the received signal based on the phase error output from the averaging processing unit;
A wireless communication device comprising:

  The present invention relates to a wireless communication apparatus that receives and processes an OFDM signal. The OFDM modulation method is resistant to intersymbol interference caused by delay distortion due to multipath, but has a problem of frequency offset and phase noise due to the frequency error that the local oscillator between the transmitter and receiver has delicately. .

  Regarding the frequency offset, a primary correction of the frequency offset is performed using a preamble added to the head of the transmission frame, and a plurality of pilot subcarriers inserted in the OFDM symbol also in the data signal (payload) portion Is generally used to perform second-order correction, that is, pilot tone tracking, which eliminates a phase shift caused by a residual frequency offset.

  In the future, as multi-level modulation such as 256QAM progresses, more accurate phase correction is required. That is, it is not sufficient to remove the fixed phase shift caused by the residual frequency offset, and it is desirable to remove the phase shift noise generated by the local oscillator. However, in the conventional pilot tone tracking that averages the detection results of the phase error in a certain section, the main focus is on the suppression of random white noise, and the resistance to the phase noise is hardly considered.

  Therefore, in the wireless communication apparatus according to the present invention, based on the SNR of the transmission path with the transmission source of the OFDM signal, the phase shift removal operation with increased resistance to random white noise and the resistance to phase noise are considered. One of the phase shift removal operations is selectively performed. Specifically, depending on the SNR of the received packet, the phase error detected using pilot subcarriers is switched to adapt to either white noise or phase noise. Yes.

  Also in the radio communication apparatus according to the present invention, basically, phase errors detected using pilot subcarriers are averaged over a certain interval. Here, in order to increase the resistance against random white noise, the degree of averaging is increased to more accurately converge to a fixed phase shift value caused by the residual frequency offset. Enhancing averaging corresponds to, for example, averaging a plurality of phase errors detected within a certain interval by weighting them almost equally (and taking a longer averaging interval). When a packet having a low SNR is received, a correction error due to random white noise is one of the dominant factors that determine the reception performance. Therefore, it is appropriate to increase the degree of averaging.

  On the other hand, in order to increase the resistance to phase noise, the weight of the detection value in the OFDM symbol is increased by decreasing the degree of averaging. To reduce the degree of averaging, for example, averaging a plurality of phase errors detected within a certain interval while reducing the weight according to the elapsed time (and shortening the averaging interval) ). The detected value of the OFDM symbol includes a low-frequency portion of phase noise common to all subcarriers (that is, a low-frequency portion less than the signal bandwidth), which is received when a packet having a high SNR is received. Become dominant. In view of this, the degree of averaging is reduced and correction is performed mainly by applying reverse rotation of the phase error detected from the OFDM symbol, thereby removing components related to the low-frequency portion of the phase noise. As a result, the pilot tone tracking has a stronger function of following the low frequency portion of the phase noise.

  A conventional technique can be applied to the method for detecting and measuring SNR information. In addition, IEEE. In a communication system that adaptively selects a transmission rate according to the SNR, such as 802.11, the SNR information can be replaced with transmission rate information described in the header of the packet.

  For example, when receiving a received packet with a high SNR, it is assumed that multilevel modulation with a high transmission rate such as 256QAM is performed. According to the wireless communication apparatus of the present invention, the degree of averaging is reduced, and correction is performed by applying reverse rotation of the phase error detected mainly from the OFDM symbol, while taking into account resistance to phase noise. The residual frequency offset is corrected. As a result, the pilot tone tracking has a strong function of following the low frequency portion of the phase noise, and sufficiently accurate phase correction can be performed even in multilevel modulation.

  According to the present invention, there is provided an excellent radio communication apparatus and radio communication method that can appropriately correct a residual frequency offset by correcting a phase shift detected from a pilot subcarrier inserted in an OFDM symbol. Can be provided.

  Further, according to the present invention, it is possible to provide an excellent wireless communication apparatus and wireless communication method capable of performing a highly accurate phase error correction on a multi-level QAM modulated OFDM signal.

  In addition, according to the present invention, an excellent radio communication apparatus and radio that can perform highly accurate phase correction based on a phase shift detected from a pilot subcarrier while also considering resistance to phase noise. A communication method can be provided.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration mainly in a digital baseband processing portion of a wireless communication apparatus 10 according to an embodiment of the present invention.

  A digital baseband signal from a receiving antenna (not shown) is divided by the synchronization circuit (Timing Detector) 12 for each OFDM symbol in the buffer 11. At the same time, the frequency error correction unit 14 corrects the frequency offset for the digital baseband signal based on the frequency error estimation value from the frequency error estimation circuit (Frequency Estimator) 13. Thereafter, the signals are respectively sent to a Fourier transformer (FFT) 15.

  At this stage, most of the frequency error and timing error are removed. However, if an error occurs in the calculation of the frequency offset amount due to noise or other influences in the frequency error estimation circuit 13, the error remains. This residual frequency offset is sent to the FFT 15.

  The FFT 15 converts the received signal on the time axis into a signal on the frequency axis and decomposes the received signal into subcarrier signals.

  The subcarrier signal is sent to the equalization and phase tracking unit 16, and after removal of the phase shift caused by the residual frequency offset and the phase error, the demodulator (Demapper) 17 modulates the modulation point on the phase space (constellation). To the original value.

  As described above, the frequency error correction unit 13 corrects the frequency of each signal based on the frequency error estimation value from the frequency error estimation circuit 14, but the frequency offset amount due to noise and other influences in the frequency error estimation circuit 14. If an error occurs in the calculation of the error, the error remains. This residual frequency offset is included in the subcarrier signal in the FFT 15 together with the data signal.

  The residual frequency offset appears as a uniform phase rotation across all subcarriers per OFDM symbol (see FIG. 5). In a data OFDM symbol, a phase error can be obtained using pilot subcarriers whose modulation is known.

  FIG. 2 shows the internal configuration of the equalization and phase tracking unit 16 in detail. The residual frequency offset and phase noise correction will be described with reference to FIG.

  Pilot subcarriers are extracted from the data signal that has been OFDM demodulated by the FFT 15, and complex-multiplied by the known pilot subcarriers stored in the reference signal memory 22 in the complex multiplier 21.

  The vector → angle conversion unit 23 converts the vector in the IQ space obtained by the complex multiplication into angle information and outputs the angle information.

  In the delay unit 27 composed of the D flip-flop, the phase shift amount is accumulated over the packet.

  The sign inversion unit 28 inverts the phase shift amount output from the delay unit 27 and adds it to the output of the vector → angle conversion unit 23 in the addition unit 24 to obtain the phase error of the OFDM symbol.

  The averaging processing unit 25 averages the phase error of the OFDM symbol over a predetermined period. In the present embodiment, an averaging process is performed according to the SNR of the received packet. That is, when receiving a packet with a low SNR, select an averaging process that increases resistance to random white noise, and when receiving a packet with a high SNR, select an averaging process that considers resistance to phase noise. However, details will be given later.

  The adding unit 26 adds the newly added phase shift amount output from the averaging processing unit 25 to the phase shift amount over the packet from the delay unit 27.

  The sign inverting unit 29 inverts the phase of the averaged phase shift amount to obtain the phase correction amount. Next, the angle → vector conversion unit 30 converts the phase correction amount into a vector on the IQ space.

  Then, the complex multiplication unit 31 as the phase shift removal unit corrects the phase shift by complex multiplication of the output of the angle → vector conversion unit 30 with respect to the data signal, and the residual frequency offset and the phase from all the data signals. Remove noise.

  The averaging processing unit 25 performs an averaging process on the phase error of the OFDM symbol over a predetermined period according to the SNR of the received packet. This will be described in detail below.

  Also in the radio communication apparatus 10 according to the present embodiment, basically, phase errors detected using pilot subcarriers are averaged over a certain interval.

  Here, in order to increase the resistance against random white noise, the degree of averaging can be increased to more accurately converge to a fixed phase shift value caused by the residual frequency offset. When a packet having a low SNR is received, a correction error due to random white noise is one of the dominant factors that determine the reception performance. Therefore, it is appropriate to increase the degree of averaging.

  On the other hand, in order to increase the resistance to phase noise, the weight of the detection value in the OFDM symbol is increased by decreasing the degree of averaging. The detected value of the OFDM symbol includes a low-frequency portion of phase noise common to all subcarriers (that is, a low-frequency portion less than the signal bandwidth), which is received when a packet having a high SNR is received. Become dominant. Therefore, by reducing the degree of averaging, correction is performed mainly by applying a reverse rotation of the phase error detected from the OFDM symbol, thereby removing components related to the low-frequency portion of the phase noise. As a result, the pilot tone tracking has a stronger function of following the low frequency portion of the phase noise.

  A conventional technique can be applied to the method for detecting and measuring SNR information. In addition, IEEE. In a communication system that adaptively selects a transmission rate according to the SNR, such as 802.11, the SNR information can be replaced with transmission rate information described in the header of the packet.

  Enhancing averaging corresponds to, for example, averaging a plurality of phase errors detected within a certain interval by weighting them almost equally (and taking a longer averaging interval). Also, reducing the degree of averaging means, for example, averaging each of a plurality of phase errors detected within a certain interval while reducing the weight according to the elapsed time (and shortening the averaged interval). Is equivalent to

  FIG. 3 shows an internal configuration example of the averaging processing unit 25.

When the phase error detection value Δd _k for the OFDM symbol is input, the amplification unit 25A weights it with the forgetting factor μ _k . Here, k represents the serial number (symbol counter) of the input signal.

In addition, the past phase correction coefficient C _k-1 is input to the amplifying unit 25D via the delay unit 25C made up of D flip-flops and is weighted by the forgetting factor 1-μ _k .

The adder 25B outputs the phase error detection value Δd _k weighted by the forgetting factor μ _k from the amplifying unit 25A and the past phase correction coefficient C _k weighted by the forgetting factor 1-μ _k from the amplifying unit 25D. ₋₁ is added and this is output as the current phase correction coefficient C _k .

According to such a circuit configuration, the degree of averaging can be adjusted by selecting an appropriate forgetting factor μ _k . When μ _k is reduced, the detected value of each phase error is weighted almost evenly, so that the degree of averaging increases. Conversely, by increasing μ _k , it is possible to reduce the degree of averaging by reducing the weight according to the elapsed time.

  When receiving a packet with a low SNR (or a low transmission rate), a lower forgetting factor value can be employed to increase the degree of averaging. Conversely, when receiving a packet with a high SNR (or a high transmission rate), the degree of averaging can be reduced by using a higher forgetting factor.

In the averaging processing unit 25, μ _k may be calculated from the SNR information by a predetermined calculation process. Alternatively, a table storing μ _k in advance may be prepared, and an appropriate one of the tables may be applied to the averaging processing unit 25 based on the SNR information.

Table 1 below shows specific examples of the forgetting factor value μ _k . In the set number (1) in the table, the forgetting factor value is lowered every time the symbol advances, and is finally fixed at a low value of 1/8, and the degree of averaging is strengthened. On the other hand, in the set number (2), since all symbols are fixed at a high value of 3/4, the degree of averaging is weakened.

  FIG. 4 shows an example of a simulation result when a specific example using FIG. 3 and Table 1 is adopted. Here, in a MMSE2 × 2 MIMO receiver compliant with the IEEE 802.11a / g specification (subcarrier bandwidth: 312.5 KHz, number of subcarriers: 52 OFDM transmission scheme), BPSK (Bi Phase Shift Keying) When performing three types of modulation schemes (coding rate: 1/2), 64QAM (coding rate: 1/2), and 256 QAM (coding rate: 3/4), the forgetting coefficient set (1 ) And (2) respectively show PER (Packet Error Rate) characteristics. However, the packet length is 1000 bytes, and the channel model used for the simulation is channel D defined by IEEE802.11n.

  For example, data communication in which two BPSK-modulated streams with a low transmission rate are spatially multiplexed is practically used in a communication environment where the SNR is around 10 dB. In such a low SNR region, a correction error due to random white noise is one of the dominant factors determining reception performance. Therefore, better PER characteristics can be obtained by using the forgetting coefficient set (1) to increase the degree of averaging of the detected values of the phase error.

  On the other hand, a modulation system having a high transmission rate such as 256QAM or 64QAM is practically used in a communication environment where the SNR is 30 dB or more. In such a high SNR region, the low frequency portion of the phase noise common to all subcarriers included in the detected value of the OFDM symbol (that is, the low frequency portion less than the signal bandwidth) determines the reception performance. Become the dominant factor. For this reason, it is necessary to increase resistance to phase noise rather than random white noise. Therefore, the PER characteristic is improved by using the forgetting coefficient set (2) to reduce the degree of averaging of the detected value of the phase error. In the example shown in FIG. 4, when the PER characteristics when the forgetting factors (1) and (2) are used at 256QAM (coding rate: 3/4) are compared, the latter shows much better characteristics. You can see that

  As described above, the “optimal forgetting factor” and, therefore, the “average degree of phase error detection value averaging” differ depending on the transmission rate or SNR. According to the wireless communication apparatus of the present invention, an OFDM signal is received while maintaining good characteristics by changing the “forgetting factor”, that is, “the degree of averaging of the phase error detection value” in accordance with the transmission rate or SNR. can do.

  MIMO (Multi-Input Multi-Output) communication is a communication method in which a plurality of transmission streams are spatially multiplexed and transmitted between a transceiver having a plurality of antennas. The MIMO receiver can spatially separate the spatially multiplexed signal based on channel characteristics and decode the original stream without crosstalk. MMSE (Minimum Mean Square Error) is one method for calculating a reception weight matrix for spatial separation. Since MIMO communication itself is not directly related to the subject matter of the present invention, it will not be described further here.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  Although the present specification has been described mainly with respect to embodiments relating to the wireless LAN, the gist of the present invention is not limited to this. For example, the present invention can be similarly applied to various types of wireless communication devices that receive multi-level modulated OFDM signals, such as tuners that receive digital broadcast waves such as televisions and radios, and mobile phones. it can.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram illustrating a configuration of a digital baseband processing portion of a wireless communication device 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing the internal configuration of the equalization and phase tracking unit 16 in detail. FIG. 3 is a diagram illustrating an internal configuration example of the averaging processing unit 25. FIG. 4 is a diagram showing an example of a simulation result when a specific example using FIG. 3 and Table 1 is adopted. FIG. 5 is a diagram three-dimensionally representing the ratio between the subcarrier and the modulation point after channel correction on the phase space (constellation).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Wireless communication apparatus 11 ... Buffer 12 ... Synchronous circuit 13 ... Frequency error estimation part 14 ... Frequency error correction part 15 ... Fast Fourier-transform part (FFT)
DESCRIPTION OF SYMBOLS 16 ... Equalization and phase tracking part 17 ... Demodulator 21 ... Complex multiplication part 22 ... Reference signal memory 23 ... Vector-to-angle conversion part 24 ... Addition part 25 ... Averaging process part 26 ... Addition part 27 ... Delay part 28 ... Code Inversion unit 29 ... sign inversion unit 30 ... angle → vector conversion unit 31 ... complex multiplication unit (phase shift removal unit)

Claims (8)

A wireless communication device for receiving and processing an OFDM signal,
Receiving means for receiving a packet comprising an OFDM signal;
Phase error detection means for detecting a phase error using pilot subcarriers included in the OFDM symbol;
Averaging processing means for averaging the detection result of the phase error by the phase error detection means over a predetermined period;
SNR information acquisition means for acquiring SNR information in the propagation path from which the OFDM signal arrives;
An averaging processing control means for determining an averaging processing method by the averaging processing means based on the acquired SNR information;
A phase shift removing unit for removing a phase shift included in the received signal based on the phase error output from the averaging processing unit;
A wireless communication apparatus comprising: The averaging process control means selects, based on the acquired SNR information, an averaging process that enhances resistance against random white noise, or an averaging process that considers resistance against phase noise.
The wireless communication apparatus according to claim 1. The averaging process control means selects an averaging process with increased resistance against random white noise when receiving a packet having a low SNR in the propagation path, and receives a packet having a high SNR in the propagation path. Select an averaging process that takes into account immunity to phase noise,
The wireless communication apparatus according to claim 1. The averaging process control means selects an averaging process with a high degree of averaging when receiving a packet with a low SNR in the propagation path, and receives a packet with a high SNR in the propagation path. Select an averaging process that reduces the degree of averaging.
The wireless communication apparatus according to claim 1. The averaging processing control means weights the plurality of phase errors detected within the predetermined interval almost equally to increase the degree of averaging, or each of the plurality of phase errors detected within the interval. Reduce the weighting according to the elapsed time to reduce the degree of averaging,
The wireless communication apparatus according to claim 4. The SNR information acquisition means acquires SNR information based on a transmission rate of a received packet;
The wireless communication apparatus according to claim 1. A wireless communication method for receiving and processing an OFDM signal,
A receiving step of receiving a packet comprising an OFDM signal;
A phase error detection step of detecting a phase error using pilot subcarriers included in the OFDM symbol over a predetermined period;
An SNR information acquisition step of acquiring SNR information in a propagation path on which the OFDM signal arrives;
An averaging process control step for determining an averaging process method for a plurality of phase errors based on the acquired SNR information;
Averaging processing step of averaging a plurality of phase error detection results in the phase error detection step according to the determined averaging processing method;
A phase shift removal step for removing a phase shift included in the received signal based on the phase error output from the averaging processing means;
A wireless communication method comprising: In the averaging process control step, when a packet having a low SNR in the propagation path is received, an averaging process with a high degree of averaging is selected, and when a packet having a high SNR in the propagation path is received. Select an averaging process that reduces the degree of averaging.
The wireless communication method according to claim 7.