JP2010232938A - Wireless receiver, and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless receiver and the like capable of detecting interference of a reception signal and specifying NBI. <P>SOLUTION: A device 1 including a wireless receiver is configured to receive signals of frequencies over wide bands and includes an interference buffering unit 20 as a buffering means and a signal processing unit 30 as a detection means. The interference buffering unit 20 is provided for buffering influences of interference that is occurring in a reception signal. The signal processing unit 30 includes a function for detecting NBI. Further, the signal processing unit 30 includes a specification means for specifying a center frequency of NBI. The interference buffering unit 20 then uses information on the predetermined center frequency of NBI to buffer interference that is occurring in the reception signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless receiver, a wireless communication method, and the like, and more particularly, to a wireless receiver capable of receiving a signal having a wide frequency band, and a wireless communication method using such a wireless receiver.

  A UWB (ultra-wide band) system is known as a wireless communication system. The UWB system is a system that transfers a signal with a very small output (-41.3 dBm or less per 1 MHz) in a distributed manner so that the frequency becomes very wide. According to the FCC (Federal communications committee), the UWB system needs to be operated in a frequency band between 3.1 GHz and 10.6 GHz when used for service purposes.

  A typical example of a UWB system is a WLAN (wireless local area network) that operates at a frequency of 5 GHz. Actually, services using this WLAN are provided mainly in commercial centers and business centers.

  In the UWB system as described above, a radio receiver is used to receive a radio signal (UWB signal) having a wide frequency band. As such a receiver, a coherent receiver and an autocorrelation receiver (hereinafter also referred to as “AcR”) are known. Although a coherent receiver has many advantages, it has the disadvantage of complicating the device when mounted on the device. AcR is configured to be able to receive a UWB signal by TR (transmitted-reference) modulation, and has an advantage of low complexity and resistance to a multipath environment.

  By the way, due to the environment where the UWB system is installed, interference occurs in the received signal. As interference, narrowband interference (NBI) having a narrow frequency is known. If information on the degree of interference including such NBI can be acquired, it can be expected that the noise of the received signal is reduced based on the information. Therefore, in order to specify the degree of NBI, a first method and a second method described below have been proposed.

  In the first method, the received signal is sampled at the Nyquist sampling rate to directly estimate the degree of interference. The second method is to arrange a large number of filters and determine the degree of interference based on their outputs.

  However, in the above-mentioned AcR, the front part (receiving end part) is opened in order to receive an analog signal in a frequency band that can be passed by the filter. Therefore, AcR has a disadvantage that it is very sensitive to NBI (see Non-Patent Document 1, for example). Therefore, when AcR is used as a receiver in a UWB system, the degree of interference tends to increase (that is, noise tends to occur), and as a result, the performance (communication performance) of the UWB system tends to be remarkably lowered.

  In addition, a receiver such as the above-described AcR has an advantage of low complexity (for example, see Non-Patent Documents 2 and 3). For this reason, in an apparatus equipped with a receiver, the first method and the second method cannot be employed if the advantage of the receiver that the complexity is small is used. This is because the first method and the second method have a problem that the overall size of the device on which the receiver is mounted increases, and the power consumption of the device increases.

  Therefore, there is a need for a technique that can detect the interference of a received signal and mitigate the interference while enjoying the advantages of a receiver such as AcR. That is, there is a need for a wireless receiver or a wireless communication method that can reduce noise included in a received signal while suppressing the complexity of the device.

T.A. Q. S. Quek, M .; Z. Win, and D.D. Dardari, “Unified analysis of UWB transmitted-reference schemes in the presence of narrowband interference”, IEEE Trans. Wireless Commun. , Vol. June, June, 2007 T.A. Quek, and M.M. Win, “Analysis of UWB transmitted-reference communication systems in dense multipath channels”, IEEE J. et al. Select. Areas Commun. , Vol. 23, no. 9 September, 2005 K. Witrisal, G.M. Leus, M.M. Pausini, and C.I. Kall, "Equivalent system model and equalization of differential impulse radio UWB systems", IEEE J. et al. Select. Areas Commun. , Vol. 23, pp. 1851-1862, September, 2005

In view of the above, a main object of the present invention is to provide a wireless receiver capable of detecting interference of a received signal and specifying an NBI. If the detection of interference and the identification of the NBI can be realized, the NBI can be removed or filtered.
It is a second object of the present invention to provide a wireless receiver and a wireless communication method that can reduce noise included in a received signal while suppressing the complexity of the apparatus.

  The present invention basically relates to a radio receiver. The radio receiver according to the present invention is a radio receiver capable of receiving a signal having a wide frequency band. The wireless receiver has mitigation means and detection means. Here, the mitigation means is for mitigating the influence of interference occurring in the received signal, and the detection means is for detecting a narrowband interference signal having a narrow frequency band. Further, the detecting means includes a specifying means for specifying the center frequency of the narrowband interference signal. As a result, a wireless receiver capable of detecting the interference of the received signal and identifying the NBI is provided.

  The mitigation unit mitigates interference occurring in the reception signal using information on the center frequency of the narrowband interference signal identified by the identification unit. Thereby, the noise contained in a received signal can be reduced. Further, since the wireless receiver only needs to include the mitigation means and the specifying means, it is possible to suppress the complexity of the device (a wireless receiver or a device equipped with the wireless receiver).

  In another aspect of the present invention, the mitigation means is connected to the filter unit for attenuating a frequency component corresponding to a predetermined frequency region of the received signal, and input from the filter unit. And an averaging processing unit that performs an averaging process on the signal. The detection means includes a detector that is connected to the averaging processing unit and detects whether the signal output from the averaging processing unit is a narrowband interference signal. The wireless receiver further includes filter control means for controlling the filter unit. The filter control means controls the filter unit when the detector detects a narrowband interference signal. According to this aspect, the narrowband interference signal can be reliably attenuated by the filter unit.

  In another aspect of the present invention, the filter section includes a notch filter that does not pass a narrow frequency domain signal among the input signals. The notch filter is configured to be able to change a frequency region that does not pass a signal. The filter control means performs control to change the frequency region of the signal that does not pass through the notch filter to include the center frequency of the narrowband interference signal when the detector detects the narrowband interference signal. Thereby, it is possible to more reliably remove (or cancel) the narrowband interference signal.

  Furthermore, in another aspect of the present invention, the wireless receiver is configured to be able to perform parallel sampling. The averaging processing unit includes a plurality of correlators that perform autocorrelation processing on the input signal. The detector is connected in series with each of the plurality of correlators. Thereby, the detection of the narrowband interference signal is performed so that the group of the frequency domain of the signal that does not pass through the notch filter covers the entire wide band. As a result, even if a large number of narrowband interference signals are detected, they can be reliably removed.

  Still further, in another aspect of the present invention, the filter control means is further connected to an averaging processing unit and a detector, and information relating to a detection result obtained by the detector is input to a signal input from the averaging processing unit. An information adding unit for adding is included. When the detection result obtained by the detector indicates the detection of the narrowband interference signal, the filter unit is controlled. On the other hand, when the detection result obtained by the detector does not indicate the detection of the narrowband interference signal, the control of the filter unit is omitted, and the received signal is directly input to the averaging processing unit. The Thereby, the optimal operation can be realized.

  Another aspect of the present invention is a wireless communication method. This wireless communication method is a method for receiving a signal having a wide frequency band by a wireless receiver, and includes a detection step and a mitigation step. In the detection step, a narrowband interference signal having a narrow frequency is detected. In the mitigation step, received signal interference is mitigated. Further, in the detection step, the center frequency of the narrowband interference signal is specified (specification step). Thereby, detection of interference of received signals and identification of NBI can be realized by the wireless receiver.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless receiver which can implement | achieve detection of the interference of a received signal and specification of NBI is provided. Further, according to the present invention, it is possible to reduce noise included in a received signal while suppressing the complexity of the device (a wireless receiver or a device equipped with a wireless receiver).

FIGS. 1A and 1B are block diagrams showing the configuration of a device that functions as a wireless receiver of the present invention, and FIG. 1A is a diagram schematically showing the configuration of the device. FIG. 1B is a diagram illustrating an example of the basic configuration of the device in detail. FIG. 2 is a block diagram showing a specific example of the device 1 shown in FIG. FIG. 3 is a flowchart showing the flow of signal processing operations by the device 1 of the present invention. FIG. 4 is a flowchart showing in detail the process in step S12 of FIG. FIG. 5 is a flowchart showing in detail the process of step S18 of FIG. FIG. 6 is a graph for explaining the simulation result, and is a graph showing the relationship between the root mean square error of the estimated frequency and the SIR. FIG. 7 is a graph for explaining the simulation result, and is a graph showing the relationship between the root mean square error of the estimated frequency and the SNR.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the form described below is an example, and can be appropriately modified within a range obvious to those skilled in the art.

  The radio receiver of the present invention is used as a receiver for receiving a radio signal in, for example, a UWB system. Here, the UWB system is configured to be operable in a frequency band between 3.1 GHz and 10.6 GHz, and operates, for example, in a 5 GHz wireless local area network (WLAN). For this reason, the UWB system has a wide range of uses such as commerce and business. A UWB signal in the UWB system is transmitted at -41.3 dBm or less. Here, the center frequency when the WLAN operates is set in the range of 5.15 GHz to 5.875 GHz, for example, when it is in the center of the spectrum of the UWB signal. Therefore, the output of the WLAN is much larger than the output of the UWB signal.

  The radio receiver of the present invention is a transmission interference (TR) type radio receiver (for example, AcR), not a coherent type radio receiver (that is, a non-coherent type radio receiver). Since a radio receiver such as AcR is provided at the receiving end of an analog signal, interference (particularly NBI) is likely to occur in the signal. However, in the present invention, the radio receiver detects the interference of the received signal and specifies the NBI. Therefore, even if interference occurs in the received signal, the influence (noise) can be reduced. Therefore, the UWB system including the wireless receiver of the present invention is suitable for wireless communication at a low data rate or a medium data rate, and can be used for, for example, a localized network or a wireless sensor network. In addition, the wireless receiver of the present invention is suitable for UWB systems used in an indoor environment because it has robustness against multipath fading, has low complexity, and is small in size.

  FIGS. 1A and 1B are block diagrams showing the configuration of a device that functions as a wireless receiver of the present invention, and FIG. 1A is a diagram schematically showing the configuration of the device. FIG. 1B is a diagram illustrating an example of the basic configuration of the device in detail.

  As shown in FIG. 1A, the device 1 is configured to receive a radio signal, and includes a radio reception unit 10, an interference mitigation unit 20, a signal processing unit 30, and a mitigation control unit 40. . The device 1 may be configured not only to receive a radio signal but also to transmit a radio signal.

  The wireless reception unit 10 includes an antenna 12, a band pass filter (BPF) 14, and a delay processing unit 16. The antenna 12 is for receiving a radio signal from the outside of the device 1 and is a receiving end provided on the front surface of the device 1. The radio signal received by the antenna 12 is input to the band pass filter 14. The band pass filter 14 is for passing a signal of a predetermined frequency band among the input radio signals. The signal that has passed through the bandpass filter 14 is distributed over multiple channels and input to the delay processing unit 16 and the interference mitigation unit 20 in the radio reception unit 10. The delay processing unit 16 includes a plurality of delay units 16 a connected in parallel to the band pass filter 14. Each delay unit 16a is for performing delay processing on the input signal. By providing the plurality of delay units 16a in this way, a signal group different from the signal group (data) directly input to the interference mitigation unit 20 can be acquired as a reference pulse.

  The interference mitigation unit 20 includes at least a correlation processing unit 22. The correlation processing unit 22 includes a correlator 22a connected in series to each delay unit 16a of the delay processing unit 16. That is, the correlation processing unit 22 includes a plurality of correlators 22a. Each correlator 22 a is for performing autocorrelation processing on the signal input from the delay unit 16 a and is connected to the signal processing unit 30. Each correlator 22a is assigned a chip number for specifying the correlator 22a (described later) for processing by the signal processing unit 30.

  The signal processing unit 30 performs a predetermined process on the signal input from each correlator 22a of the interference mitigation unit 20, and outputs the signal received in a distributed manner as one signal. In this embodiment, the digital signal processor (DSP) 32 is used. The signal processing unit 30 is configured to be able to detect the NBI and specify the center frequency of the NBI, as will be described in detail later with a specific example. Here, information indicating that NBI has been detected and information regarding the center frequency of NBI are used to control each correlator 22a. Therefore, in the example shown in FIG. 1B, the signal processing unit 30 is connected to the mitigation control unit 40, and transmits the acquired information to the interference mitigation unit 20 as a control command signal.

  The mitigation control unit 40 is connected to each correlator 22a of the interference mitigation unit 20, and performs control of each correlator 22a in parallel. Control of the correlator 22 a by the relaxation control unit 40 is performed based on a control command signal from the signal processing unit 30. The mitigation control unit 40 inputs a clock signal to each correlator 22a of the interference mitigation unit 20 in order to process the control of each correlator 22a in parallel.

  FIG. 2 is a block diagram showing a specific example of the device 1 shown in FIG. In addition, about the component demonstrated in FIG. 1 (a), (b), in order to avoid duplicate description, it abbreviate | omits.

  In FIG. 2, the device 1 includes a bypass line 25 and a notch filter 27. The bypass line 25 and the notch filter 27 are provided separately from the correlation processing unit 22 in the interference mitigation unit 20, and both are arranged between the radio reception unit 10 and the correlation processing unit 22. Has been. The notch filter 27 is for blocking the passage of signals in a predetermined frequency region. In this embodiment, the notch filter 27 is configured to be able to adjust the frequency region.

  The bypass line 25 is a line for bypassing the notch filter 27. Specifically, the bypass line 25 is connected in parallel with the notch filter 27 between the wireless reception unit 10 and the correlation processing unit 22. The wireless receiver 10 is connected to be switched between the notch filter 27 and the bypass line 25. As a result, when the wireless reception unit 10 and the bypass line 25 are connected to each other, the signal from the wireless reception unit 10 is directly input to the correlation processing unit 22 without passing through the notch filter 27. It has become. On the other hand, when the radio receiving unit 10 and the notch filter 27 are connected to each other, a signal from the radio receiving unit 10 is input to the correlation processing unit 22 via the notch filter 27.

  As shown in FIG. 2, the mitigation control unit 40 of the device 1 includes an NBI detection unit 45. Further, the signal processing unit 30 of the device 1 includes an NBI specifying unit 35. In the example illustrated in FIG. 1B, the interference control unit 40 controls each correlator 22 a based on the control command signal from the signal processing unit 30. In contrast, in the example shown in FIG. 2, the NBI specifying unit 35 in the signal processing unit 30 and the NBI detection 45 in the mitigation control unit 40 cooperate to control the interference mitigation unit 20. Therefore, the NBI specifying unit 35 may be regarded as a part of the relaxation control unit 40.

  The NBI detection unit 45 monitors in parallel each of the signals input to the signal processing unit 30 from the plurality of correlators 22a, and detects whether each monitored signal has NBI using a threshold value. The detection result is input to the NBI specifying unit 35.

  In addition, the relaxation control unit 40 generates a switching signal. The switching signal is a signal for switching whether the reception signal from the wireless reception unit 10 is input to the bypass line 25 or the notch filter 27. When the NBI detection unit 45 detects NBI, the mitigation control unit 40 generates a signal for inputting the reception signal to the notch filter 27 as a switching signal, so that the radio reception unit 10 and the notch filter 27 Are connected to each other. On the other hand, when the NBI detection unit 45 does not detect NBI, a signal for inputting the reception signal to the bypass line 25 is generated as a switching signal, so that the radio reception unit 10 and the bypass line 25 are connected. Connect to each other.

  The NBI specifying unit 35 (filter control means) is for generating an adjustment signal as a control signal for controlling the notch filter 27. The adjustment signal is for adjusting a frequency range through which the notch filter 27 does not pass. The generation of the adjustment signal by the NBI specifying unit 35 is started according to the information related to the detection result input from the NBI detector 45. Further, the NBI specifying unit 35 inputs the generated adjustment signal to the notch filter 27. The notch filter 27 changes the frequency range through which the notch filter 27 does not pass according to the adjustment signal. As a result, the center of the NBI is within the frequency range through which the notch filter 27 does not pass (preferably near the center frequency). The frequency is included.

  According to the example illustrated in FIG. 2, the NBI specifying unit 35 and the NBI detecting unit 45 cooperate to control the interference mitigating unit 20. Specifically, when NBI detection unit 45 detects NBI, control is performed so that a reception signal from radio reception unit 10 is input to notch filter 27, and information indicating NBI detection is transmitted to NBI specification unit 35. To enter. An input of information indicating NBI detection is a trigger for generating an adjustment signal by the NBI specifying unit 35. The notch filter 27 is controlled by the adjustment signal. By doing so, it is possible to shorten the time during which the received signal including NBI enters the correlation processing unit 22 via the bypass line 25. As a result, it is possible to increase the possibility that the NBI included in the received signal is removed by the notch filter 27.

  Next, an operation when the device 1 configured as shown in FIGS. 1A and 1B and FIG. 2 processes a received signal will be described. In the general flow of signal processing, sampling is first performed to determine whether NBI is detected. If NBI is not detected in a certain frequency range as a result of the sampling, the signal in that frequency range is utilized. On the other hand, when NBI is detected, the center frequency of NBI is further specified, and relaxation processing is performed on the signal in the frequency range using information on the specified center frequency. Thereby, the noise contained in the received signal is reduced. This will be described in detail below.

  3 to 5 are flowcharts showing a flow of signal processing operations by the device 1 of the present invention. 4 and 5 are flowcharts showing in detail the processing of steps S12 and S18 of FIG. 3, respectively.

  In FIG. 3, first, in step S10, the device 1 samples a received signal. In this aspect, a burst of UWB signal is received using multi-channel AcR. Specifically, AcR performs sampling by dividing a received signal (UWB signal) having a wide frequency band into signals of a plurality of frequency ranges and receiving signals in each frequency range in parallel (simultaneously) (parallel). sampling). This corresponds to the signal processing unit 30 receiving the signals input from the correlators 22a in parallel.

Here, a unique symbol (1, 2,..., K,... N) is assigned to a signal in each frequency range (that is, corresponding to each correlator 22a). Each symbol may include a plurality of frames. For example, when two frames are included in one symbol, one frame is shifted from the other frame by time T _f seconds. Here, when T _rms is an average channel delay spread, T _f is selected to be larger than T _rms (that is, T _f > T _rms ). This avoids internal frame interference.

Each frame further includes a 2-byte pulse, one of which is a reference (received data) and the other pulse is modulated data (delay processing). Pulse generated by the delay processing by the unit 16). In other words, one frame is composed of pulses of 2 bytes. A delay time between such a reference and the j-th data pulse is represented by D _j . Then, on the wireless receiver side, the delay time D _k of the k-th correlator 22a is matched with the delay time D _j .

  In the subsequent step S12, an eigen ratio is calculated for each sampled signal. This processing is performed by the signal processing unit 30. Details of the specific ratio calculation processing will be described with reference to FIG.

In FIG. 4, first, in step S122, a data matrix (hereinafter referred to as matrix Y) shown in the following equation (1) is formed for each symbol. The matrix Y is obtained by parallel sampling for all the correlators 22a of the device 1 shown in FIG. In the following formula (1), N _d is the number of symbols.

In the above equation (1), y [i], which is an example of y [i],..., Y [N _d ], is a linear data model of an AcR output signal for a certain frame j in parallel sampling, for example. , Expressed as the above formula (1a). In this equation (1a), h represents the output of the UWB signal, d represents the polarity of the data, g represents the bias due to internal frame interference, c is the NBI sign constant, φ Is related to the interference output, and v represents noise.

  Here, in the above formula (1a), the third item on the right side of y [i] corresponds to information on the NBI component (specifically, the instantaneous output of the NBI component), and the above formula (1b) It is approximated as follows.

Also, information regarding the elements of the NBI code constant vector is expressed by the following equation (2). However, in the following equation (2), the NBI autocorrelation function R _ββ (τ) is defined as the following equation (2a).

In the above equation (2), T _I is a time indicating an integration interval, P is a signal output, t _ij is a time constant for the j th chip of the i th symbol, and D _k is The delay time between the data pulse and the reference pulse, _fβ is the carrier frequency, and _Wβ is the block spectrum bandwidth. The block spectrum is a model of an orthogonal wave frequency division multiplexed signal (OFDM signal) in a frequency band of 5 GHz used in a WLAN system.

  In the subsequent step S124, the data in the first column (row corresponding to the first frame) of the matrix Y of each symbol is extracted for all symbols, thereby forming the matrix Y2. As a result, information on the received signal sampled at the same timing is obtained.

Subsequently, for a single NBI, a covariance matrix R _yy is estimated from the last two columns of the matrix Y2 (step S126). Note that the number (dimensions) of the last column of the matrix Y2 used here is preferably at least the number of expected NBIs plus one. That is, the number of columns at the end of the matrix Y2 to be used is not limited to two, but may be two or more. The smaller the number of columns at the end of the matrix Y2 used, the smaller the complexity of the detector. Furthermore, the influence of leakage of UWB energy caused by the mismatch of the correlator 22a can be reduced. On the other hand, in order to specify the NBI, the dimension of the matrix Y2 is preferably higher. For example, the matrix Y2 can be formed only by removing the first column of the matrix Y.

Then, a plurality of eigenvalues of R _yy of the covariance matrix estimated in step S126 are calculated by singular value decomposition (SVD) (step S128). Of the eigenvalues obtained by this singular value decomposition, a ratio value (hereinafter also referred to as “eigen ratio”) is calculated between two eigenvalues (step S130). The two eigenvalues are the first eigenvalue at the beginning obtained by singular value decomposition and the first eigenvalue at the end. Here, the first eigenvalue at the beginning represents NBI, and the first eigenvalue at the end represents noise.

As described above, the specific ratio is calculated. Here, when NBI is present in the received signal, it is known that the eigenvalue of the estimated covariance matrix R _yy (in particular, the first eigenvalue depending on the energy of NBI) takes a large value.

  Returning to FIG. 3, in step S14, the calculated specific ratio is compared with a threshold value stored in advance, and it is determined whether the specific ratio is equal to or greater than the threshold value as a result of the comparison (threshold detection). . Here, the threshold value needs to be measured while NBI is not present, and needs to be stored in advance in the storage means of the wireless receiver. Therefore, in this aspect, it is assumed that the threshold measurement and storage have already been performed during the initialization of the wireless communication operation. The determination result in step S14 is represented by binary data (flag) of “1” or “0” (steps S16 and S30). That is, the signal processing unit 30 acquires information that NBI is detected in this way.

  As a result of the comparison in step S14, when the calculated specific ratio is equal to or greater than the threshold (YES in step S14), the flag “1” is set (step S16). In this case, NBI is detected. And this flag is a trigger for performing the specific process (step S18) demonstrated below. In the example shown in FIG. 2, this flag is also used as a switching signal for inputting the received signal to the notch filter 27. This specifying process (S18) is for specifying the center frequency of the detected NBI, and details thereof will be described with reference to FIG.

In FIG. 5, first, in step S182, the NBI code constant vector is estimated. The estimation of the code constant vector is obtained by averaging the matrix Y shown in the above equation (1) over all symbols (N _d ) as shown in the following equation (3).

  In the above equation (3), when both the term e regarding the noise component and the term g regarding the bias are regarded as “0”, the above equation (3a) is obtained. This equation (3a) is merely a modification of the NBI code constant vector scale given by equation (7). Therefore, the expression (3a) is treated as a vector serving as a template for specifying the NBI.

  On the other hand, the vector function shown in the following equation (4) is obtained by using the right side (representation after approximation) of the NBI code constant given by the equation (2). As shown in the following equation (4), the vector function is represented by a cosine signal.

  In the following step S184, the cost function is evaluated using the evaluation formula shown in the following formula (5). Specifically, the frequency at which the cost function takes the maximum value is obtained. Here, the cost function is related to the frequency, and is the part for which the maximum value is obtained in the evaluation formula of Formula (5), and is the inner product of Formula (3a) and Formula (4). Defined in This cost function is recorded in the memory in advance. The frequency obtained in this way is the center frequency of NBI.

  In step S184, instead of evaluating the cost function, DFT (discrete Fourier transform) processing may be performed on the above equation (3a) over the NBI code constant vector.

  Further, the same processing as in step S184 is performed for the frequency range that is not targeted in step S184 (step S186). Note that a large number of peaks may be detected as a result of the processing in steps S184 and S186. These peaks are not only due to multiple NBIs, but also due to false signals (aliasing). In this aspect, the peak caused by the false signal is also considered to be caused by NBI, and is subject to filtering in step S20 described later. This can make the false signal ambiguous. In addition, you may exclude the peak resulting from a false signal by a well-known method. As described above, the signal processing unit 30 acquires information on the NBI center frequency so as to cover the entire frequency range.

  Subsequently, the signal processing unit 30 generates control signals such as a control command signal, an adjustment signal, and a switching signal (step S188). In the case of the example shown in FIG. 1B, the signal processing unit 30 generates a control command signal and transmits it to the mitigation control unit 40. Specifically, the control command signal includes information on the detection of NBI and information on the center frequency of NBI. In the case of the example shown in FIG. 2, the NBI detection unit 35 of the signal processing unit 30 generates an adjustment signal for adjusting the frequency of the notch filter 27, and the NBI detection unit 45 of the mitigation control unit 40 is a signal reception unit. The switching signal is generated so that the reception signal from 10 is input to the notch filter 27. Specifically, the adjustment signal is a signal for adjusting the frequency range of the signal that does not pass through the notch filter so as to include the center frequency of the NBI. And the interference mitigation part 20 will be controlled according to control signals, such as a control command signal, an adjustment signal, and a switching signal.

  Returning to the processing of FIG. 3, in step S20, filtering or the like is performed based on the control signal. Here, the filter used for filtering is the notch filter 27 in the example shown in FIG. By this filtering, the frequency component corresponding to the symbol (frequency range) in which the NBI is detected is removed (cancelled) from the received signal. Thereby, the detected NBI is relaxed. However, filtering is not performed in the example shown in FIG. Thereafter, the correlation processing unit 22 performs an averaging process. In this averaging process, the autocorrelation process by the correlator 22a corresponding to the symbol (frequency range) in which the NBI is detected is performed, the frequency components are averaged, and the degree of NBI is reduced. This also alleviates NBI. The filtering is preferably performed before the averaging process, but may be performed after the averaging process.

  The above-described processing from step S10 to step S20 is repeatedly executed until the flag becomes “0” (that is, until the specific ratio becomes less than the threshold). Note that the present invention is effective in that at least the degree of NBI interference can be reduced without repeated execution.

  On the other hand, when the specific ratio becomes less than the threshold value and the flag becomes “0”, the signal processing unit 30 ends the signal processing related to NBI and performs normal signal processing. The switching signal at this time is a signal for switching so that the received signal is directly input to the correlator or the signal processing unit 30 without passing through the notch filter. Note that sampling may be performed periodically even when the flag becomes “0”.

  According to the above-described aspect, the function (identification means) for identifying the center frequency of NBI and the NBI are relaxed in the wireless receiver capable of receiving signals having a wide frequency range such as AcR or the device 1 equipped with the wireless receiver. By providing a function (relaxation means) that performs both NBI detection and NBI center frequency identification, it is possible to further reduce NBI (that is, noise reduction) using information on the identified NBI center frequency. Reduction) can also be performed. Therefore, noise contained in the received signal can be reduced.

  Therefore, the device 1 according to this aspect can be used in a UWB system applied to an environment (commercial or business indoor environment) in which various interferences (particularly NBI) exist. Here, the UWB system can operate at several hundred Mbits / second and has a very large transmission capacity. Therefore, by applying the device 1 equipped with the wireless receiver according to the present embodiment to a device that has been difficult to be wireless until now, between such devices (for example, a high-definition television and a hard disk player or a DVD) Wireless communication between the player and between the PC and the display will be possible. Similarly, by applying the device 1 equipped with the wireless receiver according to the present embodiment to a device that has already been wireless (for example, a device that uses Bluetooth (registered trademark)), transmission is performed more than before. The capacity can be dramatically increased.

  Further, according to this aspect, the wireless receiver or the device 1 equipped with the wireless receiver only needs to be provided with a function for specifying the center frequency of NBI (specifying means) and a function for relaxing NBI (relaxing means). . Therefore, it is not necessary to significantly change the configuration of the wireless receiver or the device 1. As a result, it is possible to suppress the device 1 from becoming complicated as compared with the case where a coherent radio receiver is employed.

  Furthermore, according to this aspect, by adopting AcR as a wireless receiver, it is possible to reduce noise by performing autocorrelation processing on the received signal. The process for reducing the noise of the received signal is not limited to the autocorrelation process, and any process may be used as long as it is an averaging process.

  Further, according to this aspect, as shown in FIG. 2, by providing the device 1 with the notch filter 27, it is possible to remove (attenuate) a received signal in a predetermined frequency region from the received signal. Note that a filter for attenuating a received signal (frequency component) in a predetermined frequency region is not limited to a notch filter, and any filter may be used. Further, in this aspect, the device 1 is provided with an NBI detection unit 45 and an NBI specifying unit 35, so that when the NBI exists in the received signal, the received signal is input to the notch filter 27. And control of the notch filter 27 is realized. With this configuration, NBI can be selectively relaxed.

  In particular, the NBI specifying unit 35 generates an adjustment signal in accordance with the center frequency of the NBI, and changes the frequency region of the signal that the notch filter 27 does not pass, so that the NBI can be mitigated more reliably. Further, the NBI specifying unit 35 can easily determine whether or not the control of the notch filter 27 is necessary by using the NBI detection result input from the NBI detection unit 45. If the control of the notch filter 27 is not necessary, the received signal is input to the bypass line 25 instead of the notch filter 27. Thereby, unnecessary processing can be omitted, and the processing load is reduced. As a result, optimal operation is realized.

  Further, according to this aspect, since the wireless receiver is configured to be able to execute parallel sampling, it is possible to detect the NBI by dividing the received signal into frequency components. By performing NBI detection in this way, the NBI detection accuracy can be increased.

  In the above-described aspect, the information about the NBI center frequency is used to control the notch filter 27. Further, control is performed so that the signal from the signal processing unit 30 (or the signal transmission unit) is not output to the outside. It may be used to In this case, a switch provided on the output side of the signal processing unit 30 is controlled. By doing in this way, it can also prevent that the received signal containing an interference signal is output outside.

  In the above-described aspect, the relaxation control unit 40 and the signal processing unit 30 are configured as separate units. However, the relaxation control unit 40 and the signal processing unit 30 may be configured as a single unit. It is done. In the above-described aspect, the bypass line 25 and the notch filter 27 are provided in the interference mitigation unit 20, but may be provided in the radio reception unit 10.

  In the above-described aspect, it is preferable that the number of correlators 22a constituting the correlation processing unit 22 is large because NBI can be detected with high accuracy. On the other hand, an increase in the number of correlators 22a is not preferable because the complexity of the device 1 increases. Therefore, the number of correlators 22a is preferably 4 to 8.

Next, examples of the present invention will be described. In this embodiment, a part of the simulation result for the above-described embodiment will be described with reference to FIGS. In the simulation, the symbol period T _sym is 50 (ns), the polarity of the data is +1, −1, the number of symbols N _d is 128, the period TI representing the integration interval is 20 (ns), and the delay time D _k Were set to 1.3, 1.5,.

  6 and 7 are graphs for explaining the simulation results. FIG. 6 shows the relationship between the estimated root mean square error and SIR, and FIG. 7 shows the relationship between the estimated mean square root error and SNR. SIR refers to the signal-to-interference (disturbance) ratio, and SNR refers to the signal-to-noise ratio.

  As shown in FIG. 6, when the SNR value is simulated as 5 dB and there are four correlators 22a (solid line connecting circular marks), the SIR is -5 dB and the error floor is 0.13 GHz. It was. When there were six correlators 22a (solid line connecting square marks), the SIR was -10 dB and the error floor was 0.056 GHz. When there were eight correlators 22a (solid line connecting the diamond marks), the SIR was -10 dB and the error floor was 0.0133 GHz. In addition, when the SNR value was simulated at −15 dB (broken line), no significant shift of the plot was observed compared to the above case.

  Therefore, FIG. 6 indicates that the error floor value tends to decrease as the number of correlators 22a increases.

  FIG. 7 shows a case where the simulation is performed with the SIR value fixed. Also in this case, as in the case of FIG. 6, it was found that the error floor value tends to decrease as the number of correlators 22a increases.

  Therefore, FIG. 6 indicates that the error floor value tends to decrease as the number of correlators 22a increases.

  The present invention can be suitably used in fields such as wireless communication.

1 Device 10 Wireless Receiver 12 Antenna 14 Band Pass Filter (BPF)
16 delay processing unit 16a delay unit 20 interference mitigation unit 22 correlation processing unit 22a correlator 25 bypass line 27 notch filter 30 signal processing unit 32 digital signal processor (DSP)
35 NBI identification unit 40 Mitigation control unit 45 NBI detection unit

Claims (6)

A wireless receiver capable of receiving signals over a wide frequency range,
Mitigation means for mitigating the effects of interference on the received signal;
Detecting means for detecting a narrowband interference signal having a narrowband frequency,
The detection means includes
Identifying means for identifying a center frequency of the narrowband interference signal;
The mitigation means is:
Mitigating interference occurring in the received signal using information on the center frequency of the narrowband interference signal identified by the identifying means;
Wireless receiver. The mitigation means is:
A filter unit for attenuating a frequency component corresponding to a predetermined frequency region of the received signal;
An averaging processing unit that is connected to the filter unit and performs an averaging process on the signal input from the filter unit;
Including
The detection means includes
A detector connected to the averaging processor and detecting whether a signal output from the averaging processor is the narrowband interference signal;
The wireless receiver further includes:
Including filter control means for controlling the filter unit;
The filter control means includes
Controlling the filter when the detector detects the narrowband interference signal;
The wireless receiver according to claim 1. The filter part is
Includes a notch filter that does not pass signals in a narrow frequency region among the input signals,
The notch filter is
It is configured to be able to change the frequency domain that does not pass signals,
The filter control means includes
When the detector detects the narrowband interference signal, control is performed to change the frequency region of the signal that the notch filter does not pass to include the center frequency of the narrowband interference signal.
The wireless receiver according to claim 2. The radio receiver
Configured to allow parallel sampling,
The averaging processing unit
It includes multiple correlators that perform autocorrelation processing on the input signal,
The detector is
Connected in series with each of the plurality of correlators;
Thus, the narrowband interference signal is detected so that a group of signal frequency regions that the notch filter does not pass covers the entire wideband region.
The wireless receiver according to claim 3. The filter control means further includes:
An information adding unit that is connected to the averaging processing unit and the detector and adds information on a detection result obtained by the detector to a signal input from the averaging processing unit;
If the detection result obtained by the detector indicates the detection of the narrowband interference signal, the filter unit is controlled,
When the detection result obtained by the detector does not indicate the detection of the narrowband interference signal, the control of the filter unit is omitted and the received signal is input to the averaging processing unit. Do,
The radio receiver according to claim 3 or 4. A wireless communication method for receiving a signal having a wide frequency band by a wireless receiver,
A detection step for detecting a narrowband interference signal having a narrow frequency;
A mitigation step for mitigating interference of the received signal,
The detection step includes:
Including a specifying step of specifying a center frequency of the narrowband interference signal;
Wireless communication method.

Images