(12) Patent Application Publication (10) Pub. No.: US 2015/ A1

Transcription

1 (19) United tate U A1 (12) Patent Application Publication (10) Pub. No.: U 2015/ A1 MOTOZUKA et al. (43) Pub. Date: Aug. 27, 2015 (54) RADIO COMMUNICATION APPARATU AND INTERFERENCE DETECTION METHOD (71) Applicant: Panaonic Corporation, Oaka (JP) (72) Inventor: HIROYUKI MOTOZUKA, Kanagawa (JP). NAGANORIHIRAKATA, Kanagawa (JP) (21) Appl. No.: 14/626,873 (22) Filed: Feb. 19, 2015 (30) Foreign Application Priority Data Feb. 26, 2014 (JP) OO Publication Claification (51) Int. Cl. H04B I5/00 ( ) HO47 (6/14 ( ) H0472.4/10 ( ) (52) U.. Cl. CPC... H04B 15/00 ( ); H04W 24/10 ( ); H04 W 16/14 ( ) (57) ABTRACT A radio communication apparatu include a dicrete Fourier tranformer that perform a frequency-domain tranform on each of a plurality of reception ignal received at a plurality of receiver chain and generate a plurality of frequency domain ignal, a covariance matrix calculator that calculate covariance of the plurality of frequency-domain ignal, a deviation calculator that calculate a cumulative value of covariance in a firt frequency range and a econd frequency range and calculate deviation of the covariance in the plu rality of frequency range, and an adjacent-channel interfer ence determiner that determine preence or abence of adja cent-channel interference uing the cumulative value of the covariance. ayarayaaaaaaaaaaa ' a wi R & R

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15 U 2015/ A1 Aug. 27, 2015 RADIO COMMUNICATION APPARATU AND INTERFERENCE DETECTION METHOD BACKGROUND Technical Field 0002 The preent dicloure relate to a radio communi cation apparatu with a function of detecting interference caued by an adjacent-channel ignal and to an interference detection method Decription of the Related Art In recent year, tandard for hort-ditance radio ytem that ue the 60 GHz band, uch a the IEEE802.11ad tandard, have been et and each country allocate frequen cie to a maximum of four channel FIG. 11 illutrate the allocation of radio channel ued in IEEE802.1 lad. A illutrated in FIG. 11, four radio channel (ch) are ued at the maximum in Japan. The repec tive pecified center frequencie of the channel are GHZ, GHZ, GHZ, and GHz, while the center frequencie of adjacent one of the channel are 2.16 GHz apart The ampling rate of a ingle-carrier modulated wave or a tranmiion ignal baed on the IEEE802.11ad tandard i 1.76 GHZ, and under ideal circumtance, no interference occur among adjacent channel and communi cation i poible uing a plurality of channel at the ame time. In an actual tranmitter, however, a factor typified by characteritic ditortion of a high-frequency circuit, uch a an amplifier, caue power leakage to an adjacent channel. The permiible amount of uch power leakage i pecified a a tranmiion mak in the IEEE802.11ad tandard The amount of power leakage from an adjacent channel i generally mall. However, when another radio communication apparatu uing the adjacent channel come cloer to a radio communication apparatu at a local tation, the amount of the power leakage received at the local tation from the adjacent channel become no more negligible and the quality of communication at the local tation i lowered. Thi i called adjacent-channel interference When a radio communication apparatu i affected by adjacent-channel interference, the adjacent-channel inter ference i controlled o a to be avoided or uppreed. For example, the radio channel that the local tation ha ued i changed to another channel, or another radio communication apparatu, which i an interfering tation cauing the inter ference, i requeted to reduce tranmiion power. In another example, when adjacent-channel interference i detected, the characteritic of a reception filter of a receiver at the local tation are changed To avoid or uppre uch interference effectively, it i neceary to detect that adjacent-channel interference i occurring, with high reliability. That i, it i neceary to ditinguih the interference from another kind of interfer ence. uch a co-channel interference. It i alo neceary to identify the radio channel that the interfering tation ue A technique for detecting interference caued by an adjacent-channel ignal ue meaurement of a pectrum of an undeired ignal a dicued in, for example, U.. Pat. No. 7,039,093. Another technique, which i for determining whether the adjacent-channel interference i from a high frequency channel or a low-frequency channel, ue a high pa filter to extract interference wave component a di cued in, for example, Japanee Unexamined Patent Application Publication (Tranlation of PCT Application) No UMMARY One non-limiting and exemplary embodiment pro vide a radio communication apparatu, which enable the preence or abence of adjacent-channel interference to be determined with high reliability In one general apect, the technique dicloed here feature a radio communication apparatu, which include a frequency-domain tranfer that perform a frequency-domain tranform on each of a plurality of reception ignal received at a plurality of receiver chain and generate a plurality of frequency-domain ignal, a covariance calculator that calcu late covariance of the plurality of frequency-domain ignal, a cumulative value calculator that calculate a cumulative value of the covariance, and a determiner that determine preence or abence of adjacent-channel interference uing the cumulative value of the covariance According to the preent dicloure, the preence or abence of adjacent-channel interference may be determined with high reliability It hould be noted that general or pecific embodi ment may be implemented a a ytem, a method, an inte grated circuit, a computer program, a torage medium, or any elective combination thereof Additional benefit and advantage of the dicloed embodiment will become apparent from the pecification and drawing. The benefit and/or advantage may be indi vidually obtained by the variou embodiment and feature of the pecification and drawing, which need not all be pro vided in order to obtain one or more of uch benefit and/or advantage. BRIEF DECRIPTION OF THE DRAWING 0016 FIG. 1 illutrate a configuration of a radio commu nication apparatu according to a firt embodiment of the preent dicloure; 0017 FIG. 2 illutrate a concept of block diviion of dicrete Fourier tranform (DFT) in the firt embodiment; 0018 FIG. 3 illutrate a calculation example of covari ance for detecting adjacent-channel interference in the firt embodiment; 0019 FIG. 4 illutrate a configuration example of an adjacent-channel interference (ACI) detection unit in the radio communication apparatu according to the firt embodi ment; 0020 FIG. 5 illutrate example of calculation reult of covariance deviation; 0021 FIG. 6 illutrate evaluation reult of detection rate of adjacent-channel interference in the firt embodi ment; 0022 FIG. 7 illutrate a configuration example of an ACI detection unit in a radio communication apparatu according to a econd embodiment; 0023 FIG. 8 illutrate a configuration of a radio commu nication apparatu according to a third embodiment of the preent dicloure; 0024 FIG. 9 illutrate a configuration of a radio commu nication apparatu according to a fourth embodiment of the preent dicloure;

16 U 2015/ A1 Aug. 27, FIG. 10 illutrate a configuration of a radio com munication apparatu according to a fifth embodiment of the preent dicloure; 0026 FIG. 11 illutrate allocation of radio channel ued in IEEE ad; 0027 FIG. 12 illutrate a configuration of a radio com munication apparatu with a conventional function of detect ing interference caued by an adjacent-channel ignal; 0028 FIG. 13 illutrate an example of power pectral denity ditribution of a meaured undeired ignal; and 0029 FIG. 14 illutrate an example of power pectral denity ditribution of an undeired ignal in a cae where power of noie and power of an adjacent-channel interference wave are approximately the ame. DETAILED DECRIPTION Underlying Knowledge Forming Bai of Embodiment of the Preent Dicloure 0030 Prior to decribing embodiment of a radio commu nication apparatu and an interference detection method according to the preent dicloure, what i deired to be addreed in detecting adjacent-channel interference i decribed firt FIG. 12 illutrate a configuration of a radio com munication apparatu with a conventional function of detect ing interference caued by an adjacent-channel ignal, which i dicued in U.. Pat. No. 7,039,093 mentioned above In the radio communication apparatu in FIG. 12, a reception data erie etimation unit include a reception filter, a channel etimater, an equalizer, and a demodulator, and calculate an etimated value of a reception data erie. A deired-ignal waveform regeneration unit include a modu lator and a filter, and regenerate a reception waveform of a ignal tranmitted from a deired tation. A ubtractor (-) regenerate an undeired ignal including an interference wave and noie by ubtracting a ignal with the regenerated waveform, which ha been output by the deired-ignal wave form regeneration unit, from a reception ignal output by an analog-to-digital (AD) converter A dicrete Fourier tranform (DFT) unit perform a dicrete Fourier tranform on the regenerated undeired ig nal and calculate the pectrum of the undeired ignal. A correlator 1 calculate a value of correlation with an interfer ence pattern of adjacent-channel interference, which i tored in a receiver in advance a an interference pattern 1. A corr elator 2 calculate a value of correlation with an interference pattern of co-channel interference, which i tored in the receiver in advance a an interference pattern 2. A maximum value detection unit compare the magnitude of the two calculated correlation value and output the reultant a an interference detection reult With reference to the interference detection reult output from the maximum-value detection unit, the radio communication apparatu determine that adjacent-channel interference i preent when the output of the correlator 1 i large, or that co-channel interference i preent when the output of the correlator 1 i mall FIG. 13 illutrate an example of the power pectral denity ditribution of a meaured undeired ignal. In FIG. 13, the power pectral denity ditribution of an interference wave from a radio channel 1 i indicated, which i oberved in a radio channel 2. The power pectral waveform in FIG. 13 i obtained by performing imulation on an interference ignal while the channel ued by the interfering tation i referred to a the radio channel 1 and the deired-ignal receiving chan nel i referred to a the radio channel 2. ince the power pectrum i computed in a baeband region, the center of frequencie i 0 GHz. 0036) A illutrated in FIG. 13, power fall when the fre quency i equal to or larger than GHz. A for the frequencie equal to or lower than GHZ, large power i oberved approximately between GHz and GHz. An interference wave caued by an adjacent-channel ignal involve power pectral ditribution, where power fall at a certain frequency or more. The conventional radio commu nication apparatu illutrated in FIG. 12 obtain correlation with a known interference pattern and detect characteritic of power pectral ditribution to detect adjacent-channel interference According to the configuration of the conventional radio communication apparatu, when the power of an inter ference wave i maller than or a large a the power of noie, the power pectral waveform of an undeired ignal may be flat and a correlator may fail to obtain a correlation value that ha a peak, and a a reult, the detection error rate may increae FIG. 14 illutrate an example of the power pectral denity ditribution of an undeired ignal in a cae where the power of noie and the power of an adjacent-channel inter ference wave are approximately the ame. FIG. 14 indicate the power pectral denity ditribution of the um of an inter ference wave and noie from the radio channel 1, which are oberved in the radio channel In the power pectral waveform in FIG. 14, com pared to FIG. 13, the degree of the fall in power i le noticeable at a frequency of GHz or more. Accordingly, with the configuration of the conventional radio communica tion apparatu, it i difficult to detect the preence of adjacent channel interference for a power pectral waveform like the power pectral waveform depicted in FIG. 14, with high reliability In view of the repect decribed above, the preent dicloure provide a radio communication apparatu and an interference detection method, which enable adjacent-chan nel interference to be detected with high reliability even when noie i preent, and example of the radio communication apparatu and the interference detection method are decribed below. EMBODIMENT OF THE PREENT DICLOURE 0041 Embodiment of the preent dicloure are decribed in detail with reference to the drawing. Regarding the figure ued in the decription below, the ame reference numeral or ymbol are given to the ame contituent and the explanation on uch contituent i omitted. Firt Embodiment 0042 FIG. 1 illutrate a configuration of a radio commu nication apparatu according to a firt embodiment of the preent dicloure In FIG. 1, a radio communication apparatu 100 include antenna 101 and 102, reception radio-frequency (RF) circuit 103 and 104, AD converter 105 and 106, and DFT unit 107 and 108 in two reception chain. Further, the radio communication apparatu 100 include a frequency

17 U 2015/ A1 Aug. 27, 2015 domain equalization and combining unit 109, an invere di crete Fourier tranform (IDFT) unit 110, a demodulation unit 111, a forward error-correction code (FEC) decoding unit 112, a frame detection unit 113, witche 114 and 115, a covariance matrix calculation unit 121, a deviation calcula tion unit 122, and an adjacent-channel interference (ACI) determination unit 123. The covariance matrix calculation unit 121, the deviation calculation unit 122, and the ACI determination unit 123 function a an ACI detection unit ) The antenna 101, the reception RF circuit 103, and the AD converter 105 are contituent for obtaining a firt reception ignal. The antenna 102, the reception RF circuit 104, and the AD converter 106 are contituent for obtaining a econd reception ignal The frame detection unit 113 ha a function of a deired-ignal determination unit, and with reference to the firt and econd reception ignal, detect that a deired ig nal, which i a ignal with a deired wave from a deired tation, i received at a channel of a reception target. Example of the detection of a deired ignal in the frame detection unit 113 include meauring the trength of power and detecting the pattern of a preamble in a reception ignal. The frame detection unit may be alo referred to a, for example, a power detection unit, a preamble detection unit, a burt detection unit, or a packet detection unit The DFT unit 107 and 108 each have a function of a frequency-domain tranform unit, and perform a dicrete Fourier tranform on the firt reception ignal and the econd reception ignal, repectively, for converion into frequency domain ignal The computation of the frequency-domain tran form performed by the DFT unit 107 and 108 i expreed in mathematical equation 1. W i. ) Mathematical Equation In mathematical equation 1 m repreent a recep tion antenna number. The reception antenna number m indi cating 1 correpond to the DFT unit 107 and the reception antenna number m indicating 2 correpond to the DFT unit 108. When t repreent an integer equal to or more than 0. X(m.t) indicate the reception antenna m and the t-th ignal equence. That i, X(1..t) indicate an output ignal equence of the AD converter 105 and X(2,t) indicate an output ignal equence of the AD converter Further, in mathematical equation 1, N, which i an integer equal to or more than 1, repreent the length of the DFT and b, which i an integer equal to or more than 0. repreent a block number FIG. 2 illutrate a concept of block diviion of the DFT in the preent embodiment. A illutrated in FIG. 2, the DFT unit 107 and 108 divide the ignal equence x(m.t) of received ample that ha been input into block, which each have the length N, and perform DFT computation. In the example of FIG. 2, the block length N i equal to Further, in mathematical equation 1, k repreent a frequency number and i an integer that i 0 or more and i le than N. Additionally, in mathematical equation 1, e repreent Napier' contant, at repreent the ratio of a circle' circum ference to it diameter, and i repreent a unit of an imaginary number The implementation of the computation of the fre quency-domain tranform performed by the DFT unit 107 and 108 i not limited to mathematical equation 1 decribed above and another method known a the DFT may be alo ued. For example, a method of dividing the right ide of mathematical equation 1 by N i known. A another example, a fat Fourier tranform (FFT), which i almot equivalent to the DFT, may be alo ued ome explanation about the frequency number k i added below. Although in a typical DFT computation, k i defined a an integer that i 0 or more and i le than N while N repreent the length of the DFT, in the decription below, k i defined a an integer that i -N/2 or more and i le than N/2 for convenience. When k indicate a negative value, the value of u(m.k.b) i equal to the value of u(m.k+n,b). Due to the above-decribed definition, the value of k equal to 0. which correpond to 0 Hz, i indicated at the center in a calculation example of covariance illutrated in FIG.3, which i decribed below, and the explanation i implified accord ingly The proceing for the frequency-domain ignal calculated by the DFT unit 107 and 108 differ, depending on whether or not a deired ignal i detected in the frame detection unit 113. In the radio communication apparatu 100 of the preent embodiment, the ignal proceing i changed, depending on the detection or no detection of the deired ignal. For example, a ignal proceing witching control ignal correponding to the deired-ignal detection reult of the frame detection unit 113 i upplied to the witche 114 and 115 and the witche 114 and 115 are turned on or off. Thu, depending on the detection or no detection of the deired ignal, the output of the DFT unit 107 and 108 are electively input to the frequency-domain equalization and combining unit 109 or the covariance matrix calculation unit 121. Operation Performed when the Deired ignal i Detected 0055 When the deired ignal i detected, the witche 114 and 115 are coupled to the frequency-domain equaliza tion and combining unit 109 and the frequency-domain ig nal calculated by the DFT unit 107 and 108 are input to the frequency-domain equalization and combining unit The frequency-domain equalization and combining unit 109 etimate a ignal with a deired wave, which i a reception data erie obtained by removing diturbance fac tor caued in a propagation path and a tranmiion and reception circuit, uch a noie, ditortion, or fading, from the frequency-domain ignal that have been input. Example of the etimation method that i uable include a minimum mean quared error (MME) method, a maximum likelihood detec tion (MLD) method, and an interference canceller method When the MME method i ued, the frequency domain equalization and combining unit 109 multiplie each of the frequency-domain ignal output from the DFT unit 107 and 108 through the two chain by a weighting factor, add the multiplication reult, and calculate the etimated value of the tranmiion ignal. The etimated ignal i input to the IDFT unit The IDFT unit 110 perform an IDFT on the eti mated ignal and convert the ignal into a time-domain ig nal. The demodulation unit 111 generate a ignal called likelihood information by performing a demodulation pro ceing on the output of the IDFT unit 110. The FEC decoding

18 U 2015/ A1 Aug. 27, 2015 unit 112 perform error-correction decoding on the likelihood information and calculate the etimated value of the tran mitted data. Operation Performed when the Deired ignal i not Detected When the deired ignal i not detected, the witche 114 and 115 are coupled to the covariance matrix calculation unit 121 and the frequency-domain ignal calculated by the DFT unit 107 and 108 are input to the covariance matrix calculation unit The covariance matrix calculation unit 121 ha a function of a covariance calculation unit and calculate a covariance matrix R(k) defined by mathematical equation 2 and 3. c(k, 1, 1) c(k, 1. Mathematical Equation 2 R(k) = 2, 1) c(k, 2, 2) c(k, m1, m2) = Eu(m, k, b)xu (m2., k, b) = Mathematical Equation 3. 1 El Xu m, k, b)xu (m), k, b) E= In the right ide on the firt line of mathematical equation 3, the operator EII denote the expectation and the upercript * repreent the complex conjugate. In an actual computation, a indicated on the econd line of mathematical equation3, in a cae where B DFT block are received while B repreent the number of DFT block and b=0,1,2,..., or B-1, covariance i calculated for each block and an average i calculated In the covariance matrix R(k) in mathematical equation 2, diagonal element indicate the repective power pectra of the reception ignal of the reception antenna while off-diagonal element indicate the correlation between the reception ignal of the two reception antenna In the firt embodiment, one of the off-diagonal element in the obtained covariance matrix, which i c with m1 and m2 that have different value. Here, c(k,1,2) i cal culated. In other word, the covariance of the output of the DFT unit 107 and 108 i calculated The deviation calculation unit 122 ha a function of a cumulative value calculation unit, calculate the cumulative value of the obtained covariance, and calculate the degree of the deviation of the covariance. Here, the deviation calcula tion unit 122 calculate the abolute value of the covariance c(k, 1.2) obtained uing mathematical equation 3 and further, for a predetermined range of the frequency k, calculate the total value of the calculated abolute value A firt frequency range for which the deviation cal culation unit 122 calculate a total value correpond to fre quencie, which are GHz or more and are le than GHz. A total value R of the firt frequency range i calculated uing mathematical equation 4. Kna-l Mathematical Equation In mathematical equation 4. Krepreent a value of k, which correpond to GHZ, and K. repreent a value of k, which correpond to GHz A econd frequency range for which the deviation calculation unit 122 calculate a total value correpond to frequencie, which are GHz or le and are GHz or more. A total value R, in the econd frequency range i calculated uing mathematical equation 5. KL Mathematical Equation 5 R = X c(k, 1, 2) Fi In mathematical equation5, K, repreent a value of k, which correpond to GHz, and K, repreent a value of k, which correpond to GHz A third frequency range for which the deviation calculation unit 122 calculate a total value correpond to frequencie, which are GHz or more and are le than GHz, that i, the whole of the band. A total value Rin the third frequency range may be calculated uing mathemati cal equation 6. Knax-l Mathematical Equation In an example, the DFT length N i et to 128, K i et to 16, K i et to -15, K i et to 63, and K i et to -64. (0071. In another example, the DFT length N i et to 128, K i et to 16, K i et to -15, K i et to 39, and K i et to -40. Thi correpond to that the firt frequency range i et for frequencie of GHz or more and le than GHZ, the econd frequency range i et for frequencie of GHz or le and GHz or more, and the third frequency range i et for frequencie of GHz or more and le than GHz The ACI determination unit 123 ha a function of a determination unit and determine the preence or abence of adjacent-channel interference, depending on whether or not condition 1 and 2 decribed below are atified for each of the covariance deviation R. R., and R calculated by the deviation calculation unit Condition 1: The ratio between R and R (R/R) i maller than a predetermined threhold value and the ratio between R, and R (R/R) i larger than a predetermined threhold value Th Condition 2: The ratio between R and R (R/R) i larger than the predetermined threhold value and the ratio between R, and R (R/R) i maller than the predetermined threhold value Th The ACI determination unit 123 determine that adjacent-channel interference on the low-frequency ide i preent when condition 1 i atified. When condition 2 i atified, the ACI determination unit 123 determine that adjacent-channel interference on the high-frequency ide i preent. When neither condition 1 nor condition 2 i atified, the ACI determination unit 123 determine that no adjacent channel interference i preent FIG. 4 illutrate a configuration example of the ACI detection unit in the radio communication apparatu accord ing to the firt embodiment. In FIG. 4, pecific example of the covariance matrix calculation unit 121, the deviation cal

19 U 2015/ A1 Aug. 27, 2015 culation unit 122, and the ACI determination unit 123 are depicted a the configuration example of the ACI detection unit 120 in FIG Referring to FIG. 4, the configuration and operation of the ACI detection unit 120 are decribed below in more detail The covariance matrix calculation unit 121 include a complex conjugate calculation unit (conj) 1211 and a com plex multiplier (x) 1212, and calculate c(k, 1.2) uing math ematical equation 3. The covariance matrix calculation unit 121 perform a complex multiplication on the output of the DFT unit 107 and the complex conjugate of the output of the DFT unit 108, and calculate the covariance matrix c(k, 1.2). The number of the complex conjugate calculation unit 1211 and the complex multiplier 1212 may each be plural for parallel proceing. FIG. 4 illutrate a configuration for eight parallel procee. That i, computation i performed on eight k concurrently at one timing The deviation calculation unit 122 include an amplitude calculation unit (ab) 1221, and a cumulative addi tion unit (X) The amplitude calculation unit 1221 cal culate the abolute value of c(k, 1.2). A an approximate value of the abolute value, the reultant value after adding the abolute value of a real part and an imaginary part may be alo ued. Intead of the abolute value, a quare value may be alo ued The cumulative addition unit 1222 perform cumu lative addition of the amplitude or the abolute value of c(k, 1.2) of the firt, econd, and third frequency range uing mathematical equation 4, 5, and 6, repectively, and calcu late the repective covariance deviation R. R., and R of the firt, econd, and third frequency range With reference to the repective covariance devia tion R. RL, and R of the firt, econd, and third frequency range, which have been calculated in the deviation calcula tion unit 122, the ACI determination unit 123 determine whether or not above-decribed condition 1 and 2 are ati fied. Here, the ACI determination unit 123 include a multi plier (x) 1231, a comparator 1232, and a determination unit 1233, and determine whether or not condition 1 and 2 are atified, with reference to R. R., and R and the predeter mined threhold value Th In the determination of condition 1 and 2, intead of uing a divider to compare R/R with Th, a multiplier may be ued to compare R with RxTh. In the configuration example illutrated in FIG. 4, the multiplier 1231 i ued. imilarly, intead of uing a divider to compare R/R with Th, a multi plier may be ued to compare R with RxTh. In the configu ration example illutrated in FIG. 4, the multiplier 1231 i ued According to the above-decribed computation, the ACI determination unit 123 determine whether or not condition 1 and 2 are atified, and output the determination reult regarding the preence or abence of adjacent-channel interference Advantage of the configuration according to the firt embodiment are now decribed by taking the determina tion of adjacent-channel interference, which i baed on the above-decribed mathematical equation and condition, a an example In thi example, the radio channel 2 i the reception channel of the deired ignal and a combination of an inter ference ignal and noie from the radio channel 1 i received. In other word, in thi example, adjacent-channel interfer ence on the low-frequency ide i preent and beide noie i preent. The condition in the preent example are the ame a the condition of FIG. 14. I0086 FIG. 3 illutrate a calculation example of covari ance for detecting adjacent-channel interference in the firt embodiment. FIG. 3 i an example of a graph, where the abolute value of c(k, 1.2) calculated uing mathematical equation 3 are plotted. In FIG. 3, the horizontal axi indicate a frequency intead of indicating the value of k. For example, it correpond to 0.00 GHz that k=0, it correpond to GHz that k=16, and it correpond to GHz, that k=-15. I0087 FIG. 5 illutrate example of the calculation reult of the covariance deviation R. R., and R. The calculation reult of the covariance deviation R. R. R. R/R, and R/Rare indicated in the chart of FIG. 5. The threhold value Thi I0088 At thi time, ince the ratio between R and R i maller than the threhold value Thand the ratio between R. and R i larger than the threhold value Th, condition 1 i atified. Accordingly, the ACI determination unit 123 may correctly determine that adjacent-channel interference on the low-frequency ide i preent A illutrated in FIG. 14, with a conventional con figuration, the preence of noie inhibit correct determina tion of the preence of adjacent-channel interference. In con trat, according to the preent embodiment, the preence of adjacent-channel interference may be determined correctly without depending on the preence of noie. When the cova riance i calculated a decribed in the preent embodiment, the correlation between the reception ignal of the two chain may be obtained from the covariance, and the obtained correlation enable interference component to be extracted. In addition, ince noie component have no correlation, the covariance enable the noie component to be removed When the correlation between the reception ignal of the two chain i mall, equalization enable interference component to be cancelled. Thu, according to the preent embodiment, the interference component that are unable to be cancelled through the equalization may be detected uing the covariance FIG. 6 illutrate the evaluation reult of the detec tion rate of adjacent-channel interference in the firt embodi ment. FIG. 6 indicate the reult obtained when the imula tion evaluation of the detection rate of adjacent-channel interference i performed When the interference-to-noie power ratio i -10 db, the detection rate in a conventional mode uing a power pectrum, which i indicated with a broken line, i 79% while the detection rate in a mode uing covariance according to the preent embodiment, which i indicated with a olid line, i 99%. A decribed above, even when the power of noie i large, compared to the interference power, the preence of adjacent-channel interference may be detected with few detection error and high reliability by uing the configura tion according to the preent embodiment A decribed above, in the firt embodiment, the abolute value of the covariance of the output of the DFT unit 107 and 108 are obtained and the obtained value are ummed on a frequency-range bai to determine the total value of the firt, econd, and third frequency range a the firt total value R, the econd total value R, and the third total value R, repectively, and then the covariance deviation R. R., and R are calculated. After that, the preence of adjacent-channel interference i determined uing the ratio

20 U 2015/ A1 Aug. 27, 2015 between the firt total value R and the third total value R, and the ratio between the econd total value R, and the third total value R. A a reult, the preence of adjacent-channel inter ference may be determined with high reliability while reduc ing the influence of noie and enhancing the determination reliability of adjacent-channel interference Although in the ACI determination unit 123 accord ing to the firt embodiment, the ratio between R and Rand the ratio between R, and Rare ued to determine the preence of adjacent-channel interference, other value that are ub tantially equivalent may be alo ued. For example, the ratio between R and (R-R) and the ratio between the R and (R-R) may be alo ued. ince (R-R) indicate the um total of the part that doe not include R, the computation proceing in thi example may be performed more eaily than the computation proceing uing R. A another example, the preence or abence of adjacent-channel inter ference may be determined by comparing R and R and detecting the deviation of the cumulative value of the cova riance in the radio channel The repective frequency range of R. R., and R are not limited to the above-decribed example and only when the deviation of the covariance at high frequencie or low frequencie in the radio channel may be calculated, other variation are conceivable Intead ofuing ratio, for example, it may be deter mined whether or not R and R exceed a predetermined threhold value. Thi correpond to that R i regarded a a contant. The method that ue a contant intead of R i decribed below in a econd embodiment. Further, the um total of the cumulative value of the covariance in the radio channel enable adjacent-channel interference to be deter mined uing R for example Although the firt embodiment decribe the method where computation i performed on reception ignal of two chain while two AD converter are arranged, imilar configuration i applicable when the number of chain i three O. O When there are three chain or more for reception ignal, the number of line and the number of column in the covariance matrix defined by mathematical equation 2 increae. For example, when the number of chain i three, both the number of line and the number of column are three in the matrix a indicated in mathematical equation 7. c(k, 1, 1) c(k, 1, 2) c(k, 1, 3) R(k) = c(k, 2, 1) c(k, 2, 2) c(k, 2, 3) c(k, 3, 1) c(k, 3, 2) c(k, 3, 3) Mathematical Equation The computation that the deviation calculation unit 122 perform when the number of chain i three employ any one of the method decribed below Method 1: The computation baed on mathematical equation 4 to 6 i performed by electing an arbitrary ele ment from the off-diagonal element in the covariance matrix. For example, c(k, 1.2) i elected fixedly. A another example, an element different from the element elected previouly may be elected each time the determination of adjacent channel interference i performed. A another example, ran dom election i performed. A another example, when adja cent-channel interference i detected in the preceding determination, the ame element a the element of the pre ceding determination may be ued and when no adjacent channel interference i detected in the preceding determina tion, another element may be ued Method 2: One of the off-diagonal element in the covariance matrix, which ha a large abolute value, i elected and the computation baed on mathematical equa tion 4 to 6 i performed Method 3: The computation baed on mathematical equation 4 to 6 i performed on the um or the average of the off-diagonal element in the covariance matrix Method 4: The computation of R i performed for each of the off-diagonal element in the covariance matrix uing mathematical equation 6, and the computation baed on mathematical equation 4 and 5 i performed uing the ele ment that ha the larget value Method 5: The computation baed on mathematical equation 4 to 6 i performed for each of the off-diagonal element in the covariance matrix and the determination of adjacent-channel interference i performed for each of the reultant value for total determination. In the total determi nation, for example, adjacent-channel interference i regarded a being preent when adjacent-channel interfer ence i detected in a half or more of the off-diagonal element in accordance with a majority rule, or when adjacent-channel interference i detected for at leat one time. econd Embodiment 0105 FIG. 7 illutrate a configuration example of an ACI detection unit in a radio communication apparatu according to the econd embodiment of the preent dicloure The econd embodiment provide another configu ration example of the ACI detection unit and employ a con figuration with a different covariance matrix calculation unit, a different deviation calculation unit, and a different ACI determination unit in comparion with the firt embodiment. Below decribed are part different from the configuration according to the firt embodiment and the explanation on the other part i omitted A another configuration example of the ACI detec tion unit, FIG. 7 illutrate pecific example of a covariance matrix calculation unit 221, a deviation calculation unit 222, and an ACI determination unit The covariance matrix calculation unit 221 include complex conjugate calculation unit (conj) 2211 and 2213, and complex multiplier (x) 2212 and 2214, and calculate c(k,1,1) and c(k, 1.2) uing mathematical equation 3. That i, the econd embodiment i different from the firt embodi ment in that c(k,1,1) i alo calculated in addition to c(k, 1.2). Here, c(k,1,1) i referred to a a power pectrum The covariance matrix calculation unit 221 per form a complex multiplication on the output of a DFT unit 107 and the complex conjugate of the output of a DFT unit 108, and calculate the covariance matrix c(k, 1.2). Further, the covariance matrix calculation unit 221 perform a com plex multiplication on the output of the DFT unit 107 and the complex conjugate of the output of the DFT unit 107, and calculate the covariance matrix c(k,1,1). The number of the complex conjugate calculation unit 2211 and 2213 and the complex multiplier 2212 and 2214 may each be plural for parallel proceing. FIG. 7 illutrate a configuration foreight parallel procee. That i, computation i performed on eight k concurrently at one timing The deviation calculation unit 222 include an amplitude calculation unit (ab) 2221, and cumulative addi

21 U 2015/ A1 Aug. 27, 2015 tion unit (X) 2222 and The amplitude calculation unit 2221 calculate the abolute value of c(k, 1.2). A an approxi mate value of the abolute value, the reultant value after adding the abolute value of a real part and an imaginary part may be alo ued. Intead of the abolute value, a quare value may be ued The cumulative addition unit 2222 perform cumu lative addition of the amplitude (the abolute value) of c(k, 1.2) of the firt and econd frequency range uing math ematical equation 4 and 5, repectively, and calculate repective covariance deviation R and R of the firt and econd frequency range. Further, the cumulative addition unit 2223 calculate R' defined by mathematical equation 8. That i, the cumulative addition unit 2223 perform a cumu lative addition of c(k,1,1) and calculate R'. Knaa-l Mathematical Equation 8 R = X. c(k, 1, 1) With reference to the repective covariance devia tion R. R., and R' of the frequency range, which have been calculated in the deviation calculation unit 222, the ACI deter mination unit 223 determine whether or not condition 1 a and 2a decribed below are atified. Here, the ACI determi nation unit 223 include a multiplier (x) 2231, a comparator 2232, and a determination unit 2233, and determine whether or not condition 1a and 2a are atified, with reference to R. R, and R' and a predetermined threhold value Th Condition 1a: The ratio between R and R' (R/R') i maller than a predetermined threhold value and the ratio between R, and R' (R/R') i larger than the predetermined threhold value Th Condition 2a: The ratio between R and R' (R/R') i larger than the predetermined threhold value and the ratio between R, and R' (R/R') i maller than the predetermined threhold value Th The ACI determination unit 223 determine that adjacent-channel interference on the low-frequency ide i preent when condition 1a i atified. When condition 2a i atified, the ACI determination unit 223 determine that adjacent-channel interference on the high-frequency ide i preent. When neither condition 1a nor condition 2a i ati fied, the ACI determination unit 223 determine that no adja cent-channel interference i preent In the econd embodiment, the deviation calculation unit 222 calculate R' defined by mathematical equation 8 intead ofr defined by mathematical equation 6, and the ACI determination unit 223 perform the determination of condi tion 1a and 2a uing R' intead of R to etimate the preence of adjacent-channel interference In the econd embodiment, imilar to the firt embodiment, the preence of adjacent-channel interference may be determined with few detection error and high reli ability while uppreing the influence of noie by perform ing the determination of adjacent-channel interference uing the value of R and R Further, in the econd embodiment, R i ued intead of R in the determination of adjacent-channel inter ference. ince the change in magnitude of R', which i affected by the interference power, i mall, compared to R, the preence of adjacent-channel interference may be deter mined with few detection error and high reliability when the interference power i relatively mall Intead of uing the configuration in FIG. 7 for the computation of R', a predetermined contant may be ued a a ubtitute value of R". Further, although R" i computed uing the output value of the DFT unit 107, power calculated from the output of an AD converter may be ued a a ubti tute of R". In addition, temporary R' i calculated according to each of the output of the DFT unit 107 and 108 and the average value may be ued a R. Third Embodiment I0120 FIG. 8 illutrate a configuration of a radio commu nication apparatu according to a third embodiment of the preent dicloure. In FIG. 8, the ame reference numeral or ymbol are given to the contituent the ame a the contitu ent in the firt embodiment illutrated in FIG. 1 and the explanation on uch contituent i omitted. I0121. In addition to the configuration in FIG. 1, a radio communication apparatu 300 include a known-ignal gen eration unit 301, a waveform generation unit 302, and ub tractor (-) 303 and 304. The known-ignal generation unit 301, the waveform generation unit 302, and the ubtractor 303 and 304 implement a function of a replica-ignal ubtrac tion unit. The radio communication apparatu 300 doe not include witche 114 and 115. I0122. In the radio communication apparatu 300, a frame detection unit 113 determine that a known ignal i received and determine the type of the known ignal. For example, among radio ignal baed on the IEEE802.11ad tandard, a preamble and a guard interval are known a the known ig nal. I0123. The known-ignal generation unit 301 generate a ignal the ame a the known ignal that i currently received The waveform generation unit 302 perform wave form converion baed on propagation-path characteritic on the ignal generated by the known-ignal generation unit 301, and output the reultant ignal a a replica ignal of a deired ignal. The replica ignal i a frequency-domain ignal. ince the propagation-path characteritic include value different for each reception antenna, the waveform generation unit 302 generate two different equence of the replica ignal for the two receiver chain. ( The ubtractor 303 and 304 ubtract the replica ignal from the reception ignal. A a reult of the ubtrac tion, ignal mainly containing interference wave and noie are obtained. When the obtained ignal are input to a cova riance calculation unit 121 and covariance i calculated, imi lar to the firt embodiment, the preence or abence of adja cent-channel interference may be determined. I0126. In the third embodiment, ince the ignal obtained by ubtracting the replica ignal from the reception ignal, which are ignal mainly containing interference wave and noie, are ued to calculate the covariance, the preence of adjacent-channel interference may be determined even while receiving a deired wave. I0127. A decribed above, the ignal obtained by ubtract ing the replica ignal from the reception ignal, which i a ignal mainly containing an interference wave and noie, may occaionally contain an error caued in the ubtraction, depending on the accuracy of the replica ignal. The error i oberved in the covariance calculation unit 121 a equivalent to noie. A decribed in the firt embodiment, ince the influence of noie i reduced becaue of the covariance cal

22 U 2015/ A1 Aug. 27, 2015 culation unit 121, a deviation calculation unit 122, and an ACI determination unit 123, the preence of adjacent-channel interference may be determined even when an error i caued by the replica ignal The other advantage are imilar to the advantage of the firt embodiment, and the preence of adjacent-channel interference may be determined with few detection error and high reliability while uppreing the influence of noie. Fourth Embodiment 0129 FIG. 9 illutrate a configuration of a radio commu nication apparatu according to a fourth embodiment of the preent dicloure. In FIG.9, the ame reference numeral or ymbol are given to the contituent the ame a the contitu ent in the third embodiment illutrated in FIG. 8 and the explanation on uch contituent i omitted A radio communication apparatu 400 include a known-ignal generation unit 401, a waveform generation unit 402, and DFT unit 403 and 404. The known-ignal generation unit 401, the waveform generation unit 402, and ubtractor (-)303 and 304 implement a function of a replica ignal ubtraction unit The known-ignal generation unit 401 generate a ignal the ame a a known ignal that i currently received. The generated known ignal i a time-domain ignal. 0132) The waveform generation unit 402 perform wave form converion baed on propagation-path characteritic on the ignal generated by the known-ignal generation unit 401, and output the reultant ignal a a replica ignal of a deired ignal. The replica ignal i a time-domain ignal The ubtractor 303 and 304 ubtract the replica ignal from the reception ignal. The fourth embodiment i different from the third embodiment in that the generation and ubtraction of the replica ignal are performed uing a time domain ignal Each of the DFT unit 403 and 404 perform a dicrete Fourier tranform on the reultant ignal after the ubtraction of the replica ignal and obtain a frequency-do main ignal. imilar to the firt to third embodiment, the determination of adjacent-channel interference i performed in an ACI detection unit according to the obtained ignal The DFT unit 403 and 404 may employ a DFTize different from the DFT ize of the DFT unit 107 and 108 for reception ignal. For example, the DFTize of the DFT unit 403 and 404 i 64 and the DFT ize of the DFT unit 107 and 108 i In the fourth embodiment, the amount of power conumption needed for the determination of adjacent-chan nel interference may be reduced by decreaing the DFT ize of the DFT unit 403 and The other advantage are imilar to the advantage of the third embodiment, and the preence of adjacent-chan nel interference may be determined even while receiving a deired wave. Further, the preence of adjacent-channel inter ference may be determined with few detection error and high reliability while uppreing the influence of noie. Fifth Embodiment 0138 FIG. 10 illutrate a configuration of a radio com munication apparatu according to a fifth embodiment of the preent dicloure. In FIG.10, the ame reference numeral or ymbol are given to the contituent the ame a the contitu ent in the fourth embodiment illutrated in FIG. 9 and the explanation on uch contituent i omitted A radio communication apparatu 500 include a recoding modulation unit 501, a waveform generation unit 502, and a delay circuit 503. The recoding modulation unit 501, the waveform generation unit 502, the delay circuit 503, and ubtractor (-) 303 and 304 implement a function of a replica-ignal ubtraction unit The recoding modulation unit 501 perform error correction coding again and then perform modulation on the data that ha undergone the error-correction decoding of an FEC decoding unit 112, and reproduce a tranmiion ignal Intead of performing the error-correction coding again, ytematic bit of the decoded data may be extracted to perform the modulation. The ytematic bit are bit part with value that remain unchanged both before and after perform ing the error-correction coding again The waveform generation unit 502 ue the recoded data and generate a replica ignal of a deired ignal accord ing to the data and propagation-path characteritic According to the fifth embodiment, the determina tion of adjacent-channel interference may be performed not only in receiving a known pattern but may be alo performed at a deired timing in receiving data When an error i included in the FEC decoding reult in receiving data, an error occur in the replica ignal. Although the error of the replica ignal i oberved a equiva lent to noie, imilar to the error decribed in the third embodiment, the influence of noie may be reduced in an ACI detection unit and the preence of adjacent-channel interfer ence may be determined even when the replica ignal con tain an error The other advantage are imilar to the advantage of the fourth embodiment, and the preence of adjacent channel interference may be determined with few detection error and high reliability A decribed above, the radio communication appa ratu according to the preent embodiment enable adjacent channel interference to be detected with high reliability when noie i preent Variou apect of the embodiment according to the preent dicloure include what i decribed below A radio communication apparatu of the preent dicloure include a frequency-domain tranformer that per form a frequency-domain tranform on each of a plurality of reception ignal received at a plurality of receiver chain and generate a plurality of frequency-domain ignal, a covari ance calculator that calculate covariance of the plurality of frequency-domain ignal, a cumulative value calculator that calculate a cumulative value of the covariance, and a deter miner that determine preence or abence of adjacent-chan nel interference uing the cumulative value of the covariance The radio communication apparatu of the preent dicloure i the above-decribed radio communication appa ratu, where the cumulative value calculator calculate a firt cumulative value obtained by cumulating covariance in a firt frequency range of a radio channel of the plurality of recep tion ignal and calculate a econd cumulative value obtained by cumulating covariance in a econd frequency range of the radio channel of the plurality of reception ignal, the econd frequency range being different from the firt frequency range, and the determiner determine preence or abence of adjacent-channel interference according to devia

23 U 2015/ A1 Aug. 27, 2015 tion of the covariance in the radio channel of the reception ignal uing the firt cumulative value and the econd cumu lative value The radio communication apparatu of the preent dicloure i the above-decribed radio communication appa ratu, where the determiner calculate each of ratio of the firt cumulative value and the econd cumulative value to a cumulative value of covariance throughout the radio channel of the plurality of reception ignal, and determine preence or abence of adjacent-channel interference The radio communication apparatu of the preent dicloure i the above-decribed radio communication appa ratu, where the determiner calculate each of ratio of the firt cumulative value and the econd cumulative value to a cumulative value of a power pectrum throughout the radio channel of the plurality of reception ignal, and determine preence or abence of adjacent-channel interference The radio communication apparatu of the preent dicloure i the above-decribed radio communication appa ratu, where in the radio channel of the plurality of reception ignal, the firt frequency range i a partial frequency range including a frequency lower than a channel center frequency, and the econd frequency range i a partial frequency range including a frequency higher than the channel center fre quency, the determiner determine that adjacent-channel interference on a lower-frequency ide i preent when the firt cumulative value or a value calculated baed on the firt cumulative value i larger than a predetermined threhold value, and the determiner determine that adjacent-channel interference on a higher-frequency ide i preent when the econd cumulative value or a value calculated baed on the econd cumulative value i larger than the predetermined threhold value The radio communication apparatu of the preent dicloure i the above-decribed radio communication appa ratu further including a deired-ignal determiner that deter mine whether or not a deired ignal i preent in the plural ity of reception ignal, where when the deired ignal i not received, the covariance calculator calculate the covariance, the cumulative value calculator calculate the cumulative value of the covariance, and the determiner determine pre ence or abence of adjacent-channel interference uing the cumulative value of the covariance The radio communication apparatu of the preent dicloure i the above-decribed radio communication appa ratu further including a replica-ignal ubtracter that ub tract a plurality of replica ignal of a plurality of deired ignal from the plurality of reception ignal or the plurality of frequency-domain ignal repectively, where the covari ance calculator calculate covariance baed on the plurality of frequency-domain ignal from which the plurality of replica ignal are ubtracted, and the determiner determine pre ence or abence of adjacent-channel interference uing a cumulative value of the covariance calculated by removing the plurality of replica ignal An interference detection method of the preent di cloure include performing a frequency-domain tranform on each of a plurality of reception ignal received at a plu rality of receiver chain and generating a plurality of fre quency-domain ignal, calculating covariance of the plural ity of frequency-domain ignal, calculating a cumulative value of the covariance, and determining preence or abence of adjacent-channel interference uing the cumulative value of the covariance The interference detection method of the preent dicloure i the above-decribed interference detection method, which further include calculating a firt cumulative value obtained by cumulating covariance in a firt frequency range of a radio channel of the plurality of reception ignal and calculating a econd cumulative value obtained by cumu lating covariance in a econd frequency range of the radio channel of the plurality of reception ignal, the econd fre quency range being different from the firt frequency range, and determining preence or abence of adjacent-channel interference according to deviation of the covariance in the radio channel of the reception ignal uing the firt cumula tive value and the econd cumulative value Although variou embodiment are decribed above with reference to the drawing, it i needle to mention that the preent dicloure i not limited to thee example. A peron killed in the art may obviouly arrive at variation or modification within the cope recited in the claim, and the variation or modification hould be undertood a belong ing to the technical cope of the preent dicloure a a matter of coure. Alo, the contituent of the above-decribed embodiment may be combined a deired within the cope not departing from the pirit of the dicloure Although in each of the embodiment above, the preent dicloure i decribed by taking the configuration uing hardware a example, the preent dicloure may be alo implemented uing oftware in conjunction with hard Wa Each of the functional block ued in the decription of the embodiment above i typically implemented a large cale integration (LI), which i an integrated circuit. The individual functional block may be made a one chip, or may be made a one chip o a to include part or all of each of the functional block. Depending on the degree of the integration, the LI ued here may be alo referred to a an integrated circuit (IC), ytem LI, uper LI, or ultra LI In addition, the circuit-integrating technique i not limited to the LI, a peronal circuit or a general-purpoe proceor may be ued for the implementation. After manu facturing the LI, a field-programmable gate array (FPGA), which i programmable, or a reconfigurable proceor, which i capable of reconfiguring the connection and etting of circuit cell inide LI, may be utilized Moreover, when a circuit-integrating technique that replace the LI i brought by the advance of a emiconductor technique or another derivative technique, of coure, the inte gration of the functional block may be performed by another technique. Application of biotechnology and the like are po ible The preent dicloure may be repreented a an interference detection method performed in a radio commu nication apparatu. Further, the preent dicloure may be alo repreented a an interference detection apparatu, which ha a function to perform an interference detection method, or a program for cauing a computer to operate the interference detection method or the interference detection apparatu. That i, the preent dicloure may be repreented in any category of apparatue, method, and program The preent dicloure ha advantage, which enable the preence or abence of adjacent-channel interfer ence to be determined with high reliability and i ueful a, for example, a radio communication apparatu that perform

24 U 2015/ A1 10 Aug. 27, 2015 hort-ditance radio communication, an interference detec tion method ued for the radio communication apparatu, and the like. What i claimed i: 1. A radio communication apparatu compriing: a frequency-domain tranformer that perform a fre quency-domain tranform on each of a plurality of reception ignal received at a plurality of receiver chain and generate a plurality of frequency-domain ignal: a covariance calculator that calculate covariance of the plurality of frequency-domain ignal; a cumulative value calculator that calculate a cumulative value of the covariance; and a determiner that determine preence or abence of adja cent-channel interference uing the cumulative value of the covariance. 2. The radio communication apparatu according to claim 1, wherein the cumulative value calculator calculate a firt cumula tive value obtained by cumulating covariance in a firt frequency range of a radio channel of the plurality of reception ignal and calculate a econd cumulative value obtained by cumulating covariance in a econd frequency range of the radio channel of the plurality of reception ignal, the econd frequency range being dif ferent from the firt frequency range, and the determiner determine preence or abence of adjacent channel interference according to deviation of the cova riance in the radio channel of the reception ignal uing the firt cumulative value and the econd cumulative value. 3. The radio communication apparatu according to claim 2, wherein the determiner calculate each of ratio of the firt cumu lative value and the econd cumulative value to a cumu lative value of covariance throughout the radio channel of the plurality of reception ignal, and determine preence or abence of adjacent-channel interference. 4. The radio communication apparatu according to claim 2, wherein the determiner calculate each of ratio of the firt cumu lative value and the econd cumulative value to a cumu lative value of a power pectrum throughout the radio channel of the plurality of reception ignal, and deter mine preence or abence of adjacent-channel interfer CCC. 5. The radio communication apparatu according to claim 2, wherein in the radio channel of the plurality of reception ignal, the firt frequency range i a partial frequency range including a frequency lower than a channel center fre quency, and the econd frequency range i a partial frequency range including a frequency higher than the channel center frequency, the determiner determine that adjacent-channel interfer ence on a lower-frequency ide i preent when the firt cumulative value or a value calculated baed on the firt cumulative value i larger than a predetermined threh old value, and the determiner determine that adjacent-channel interfer ence on a higher-frequency ide i preent when the econd cumulative value or a value calculated baed on the econd cumulative value i larger than the predeter mined threhold value. 6. The radio communication apparatu according to claim 1, further compriing: a deired-ignal determiner that determine whether or not a deired ignal i preent in the plurality of reception ignal, wherein when the deired ignal i not received, the covariance calculator calculate the covariance, the cumulative value calculator calculate the cumulative value of the covariance, and the determiner determine preence or abence of adjacent channel interference uing the cumulative value of the covariance. 7. The radio communication apparatu according to claim 1, further compriing: a replica-ignal ubtracter that ubtract a plurality of rep lica ignal of a plurality of deired ignal from the plurality of reception ignal or the plurality of fre quency-domain ignal repectively, wherein the covariance calculator calculate covariance baed on the plurality of frequency-domain ignal from which the plurality of replica ignal are ubtracted, and the determiner determine preence or abence of adjacent channel interference uing a cumulative value of the covariance calculated by removing the plurality of rep lica ignal. 8. An interference detection method compriing: performing a frequency-domain tranform on each of a plurality of reception ignal received at a plurality of receiver chain and generating a plurality of frequency domain ignal; calculating covariance of the plurality of frequency-do main ignal; calculating a cumulative value of the covariance; and determining preence or abence of adjacent-channel inter ference uing the cumulative value of the covariance. 9. The interference detection method according to claim 8. further compriing: calculating a firt cumulative value obtained by cumulating covariance in a firt frequency range of a radio channel of the plurality of reception ignal and calculating a econd cumulative value obtained by cumulating cova riance in a econd frequency range of the radio channel of the plurality of reception ignal, the econd fre quency range being different from the firt frequency range; and determining preence or abence of adjacent-channel inter ference according to deviation of the covariance in the radio channel of the reception ignal uing the firt cumulative value and the econd cumulative value. k k k k k