JP4704375B2 - Transmission / reception device and communication method thereof - Google Patents

Description

  In a wireless communication system that operates a plurality of systems at the same frequency, the present invention uses, in a new system (Secondary system), interference cancellation technology that uses the characteristics of a TDD (Time Division Multiplexing) system in a priority system (Primary system). Thus, the present invention relates to a transmission / reception apparatus and a communication method thereof that significantly improve the surface frequency utilization efficiency when the entire system is considered without reducing the communication efficiency of the primary system.

  In recent years, with the widespread use of mobile phones, wireless LANs, and the like, techniques for performing transmission as fast as possible in a limited frequency band have been studied. In recent years, MIMO (Multiple Input Multiple Output) technology has attracted attention as means for realizing high-speed transmission in a limited band. MIMO uses array antennas for the transmitting side and the receiving side, respectively, and on the transmitting side, different data is transmitted for each antenna, and on the receiving side, different signals are restored by some interference cancellation / decoding technology. By doing so, it is a technique that remarkably improves the transmission speed at the same frequency as compared with transmission / reception between single antennas. Already introduced in wireless LAN systems and the like.

  However, in the MIMO technology, the number of transmission / reception antennas is a key for high-speed transmission. Therefore, in order to realize very high frequency utilization efficiency, a considerable number of antenna elements are required. When considering a small terminal, an increase in the number of antenna elements is not desirable because it increases the hardware scale.

  Cognitive radio technology has attracted attention as a means for effectively using frequencies by a method different from the MIMO technology (see, for example, Non-Patent Document 1). The cognitive radio technology is a technology in which a radio device recognizes a surrounding radio wave environment, selects an appropriate frequency band and uses it, thereby effectively utilizing an available frequency band. Since cognitive radio can effectively use frequencies and time that have not been attracting attention, the frequency per unit area can be greatly improved.

  FIG. 12 is a conceptual diagram for explaining the outline of the cognitive radio technology. In FIG. 12, 1-1 and 1-2 are two priority systems (Primary systems), and 2-1 to 2-6 are a plurality of cognitive systems (Secondary systems). Reference numeral 3 denotes a communicable area of the primary system. Reference numerals 4-1 and 4-2 denote antenna directivities of the primary systems 1-1 and 1-2, respectively.

In cognitive radio, the primary systems 1-1 and 1-2 that originally use a certain communication band and the frequencies and times that are not used by the primary systems 1-1 and 1-2 are monitored, and this information is obtained. There are secondary systems 2-1 to 2-6 that perform communication based on the above. Basically, the primary systems 1-1 and 1-2 can use a preferentially assigned communication band, and the secondary systems 2-1 to 2-6 can perform communication by themselves. By interfering with the primary systems 1-1 and 1-2, the efficiency of the primary systems 1-1 and 1-2 should not be reduced. In addition, the primary systems 1-1 and 1-2 cannot normally recognize the existence of the secondary systems 2-1 to 2-6.
S. Haykin, “Cognitive radio: Brain-empowered wireless communications”, vol.23, no.2, pp.201-220, Feb. 2005.

In cognitive radio, communication is usually performed by the following means.
(Procedure 1) The Secondary systems 2-1 to 2-6 detect times or frequencies that are not used by the Primary systems 1-1 and 1-2.
(Procedure 2) The Secondary systems 2-1 to 2-6 confirm whether or not to interfere with the receivers of the Primary systems 1-1 and 1-2 through communication performed by themselves.
(Procedure 3) If the Secondary systems 2-1 to 2-6 determine that there is no problem in the procedure 2, the communication is performed at the frequency or time detected in the procedure 1.

  The above is the communication procedure in cognitive radio. However, first, a problem occurs when the procedure 1 is performed. For example, consider TDD. In a TDD system, a station receives at a certain timing and does not transmit during that time. On the other hand, no signal is received during transmission. As hardware, a time division switch (TDD switch) is arranged between the transmission device and the reception device. Therefore, for example, even if interference from the primary system 1-1 is not detected at a certain time, if transmission is performed at that time, interference is given to the primary system 1-2.

  Further, even if the receivers of the secondary systems 2-1 to 2-6 determine that no signal has arrived at “a certain frequency” or “a certain time”, the state fluctuates with time. The signal may not be detected correctly due to the possibility or the presence of a hidden terminal. Therefore, in cognitive radio, signal detection with very high accuracy is required.

  As a means for improving this, a detection method using signal cyclostationary has been proposed. For example, Reference 1 (Cabric, D, et al., “Implementation issues in spectrum sensing for cognitive radios”, Conference Record of the Thirty-Eighth Asilomar Conference, vol.1, pp.772-776, 7-10. Nov. 2004.). In this method, signal detection is possible even at a very low CNR (Carrier to Noise Ratio) if the carrier frequencies of the primary systems 1-1 and 1-2, or the symbol rate and modulation scheme are known in advance. . However, this method requires a very large amount of time and the number of signal samples for detection, so that it is difficult to cope with a case where the propagation environment of the primary systems 1-1 and 1-2 changes. Occurs.

  Next, a problem also occurs in the above procedure 2. As described above, in principle, the primary systems 1-1 and 1-2 cannot recognize the secondary system. For example, even if the secondary systems 2-1 to 2-6 determine that the signal level from the transmitter of the primary system 1-1 is low at a certain frequency and determine that this frequency can be used, transmission is performed as is at that frequency. May cause interference to the primary system 1-2. Therefore, the interference given by the Secondary systems 2-1 to 2-6 is most surely determined by the receivers of the Primary systems 1-1 and 1-2.

  However, the primary systems 1-1 and 1-2 cannot recognize the existence of the secondary systems 2-1 to 2-6. Therefore, in order to realize this, the secondary systems 2-1 to 2-6 regularly observe a certain signal generated by the primary systems 1-1 and 1-2, and the primary systems 1-1 and 1-2 have A method of grasping the existence is considered.

  Even if this is not cognitive radio, it can be considered as the same principle as carrier sense in the conventional radio system. The carrier sense is disclosed in, for example, Document 2 (Morikura, Kubota, “Revised 802.11 High-Speed Wireless LAN Textbook, Chapter 4”, Impress, 2005). When the secondary systems 2-1 to 2-6 approach the receivers of the primary systems 1-1 and 1-2, by receiving signals from the primary systems 1-1 and 1-2, the primary system 1-1-2 is received. 1 and 1-2, the secondary systems 2-1 to 2-6 can perform the procedure 2 based on the magnitude of the signal power.

  However, when cognitive radio is considered, this accuracy is required to be very high. Therefore, it is effective to perform carrier sensing at all frequencies of the primary systems 1-1 and 1-2. However, if this is performed, it is extremely effective for interference detection (communication signal detection of the primary systems 1-1 and 1-2). This causes a problem that it takes a lot of time.

  The present invention has been made in consideration of such circumstances, and an object thereof is a transmission / reception apparatus capable of performing efficient cognitive radio with a simple configuration and avoiding interference with a primary system. And providing a communication method thereof.

In order to solve the above-described problem, the present invention provides a transmission / reception apparatus that constitutes the second radio communication system when the first radio communication system and the second radio communication system share the same frequency band. A plurality of antenna elements; a plurality of transmission / reception branching means connected to each of the plurality of antenna elements; a transmission means connected to each of the plurality of transmission / reception branching means; in the transceiver apparatus and a receiving means connected to each of the received signals received from said first radio communication system by the receiving unit in each two different time intervals is periodically repeated, the received power larger received signal to extract the, upon reception by the transmitting signal and said receiving means upon transmission by the transmission means to direct a null in the direction of the received signal Comprising interference cancellation means for determining a weighting value for the received signal, the transmission unit, of the received power from the first wireless communications system that were received before the weighting of the received signal by the weighting value is The transmission / reception apparatus performs transmission of the transmission signal weighted using the weighting value in the period of the time interval when the reception signal with small reception power is received .

In order to solve the above-described problem, the present invention provides a transmission / reception apparatus that constitutes the second radio communication system when the first radio communication system and the second radio communication system share the same frequency band. A plurality of antenna elements; a plurality of transmission / reception branching means connected to each of the plurality of antenna elements; a transmission means connected to each of the plurality of transmission / reception branching means; in the transceiver apparatus and a receiving means connected to each of which detects the two reception signals received from said first radio communication system by the receiving unit in each two different time intervals repeated periodically A signal detection means, a power comparison means for comparing the received power of the two received signals detected by the signal detection means, and a comparison result by the power comparison means. Obtained in the signal selecting means for selecting the greater received signal of the reception power, the reception signal selected by the signal selecting means, row computation power minimization method using the correlation matrix of the received signal Ukoto Accordingly, the reception weight calculating means for calculating a weighting value for performing interference cancellation, and branching means for branching the weighting value calculated by the reception weight calculation unit, branch weighting value and said receiving means by said branching means Multiplying the received signal weight multiplying means for multiplying the received signal received by the transmission means, the weighting value branched by the branching means, and the transmission signal transmitted by the transmitting means branched in the same number as the plurality of antenna elements. And a transmission signal weight multiplication means for transmitting and receiving.

  The present invention is characterized in that, in the above-mentioned invention, the reception weight calculation means calculates a minimum eigenvector obtained on the basis of creation of a correlation matrix of a received signal and eigenvalue decomposition.

  According to the present invention, in the above invention, orthogonal frequency division multiplexing means for performing orthogonal frequency division multiplexing, weighting branching means for branching the weighting value calculated by the reception weight calculation means to the same number as the number of subcarriers, and the reception Fourier transform means for performing Fourier transform for each subcarrier of the received signal received by the means, wherein the reception weight multiplier means for the received signal for each subcarrier Fourier transformed by the Fourier transform means, The weighting branching unit multiplies the common weighting value branched by the same number as the number of subcarriers.

  According to the present invention, in the above invention, the number of the signal detection means is the same as the number of the plurality of antenna elements, the guard interval removal means for removing the guard interval from the received signal, and the number of the plurality of antenna elements. A Fourier transform calculating means for performing Fourier transform on the received signal from which the guard interval has been removed by the guard interval removing means, and K (F ≧ F) from the F subcarriers transformed by the Fourier transform calculating means. K) subcarrier extracting means for extracting subcarriers, and subcarrier averaging processing means for creating and averaging a correlation matrix from the K subcarriers extracted by the subcarrier extracting means. Features.

In order to solve the above-described problem, the present invention provides a transmission / reception apparatus that constitutes the second radio communication system when the first radio communication system and the second radio communication system share the same frequency band. A plurality of antenna elements; a plurality of transmission / reception branching means connected to each of the plurality of antenna elements; a transmission means connected to each of the plurality of transmission / reception branching means; a communication method according to the transmitting and receiving apparatus comprising a receiving means connected to each of the received signals respectively received from said first radio communication system by the receiving unit in each two different time intervals repeated periodically a comparing step to compare, obtained in comparison, extracts a large reception signal received power, the to direct a null transmission in the direction of the received signal A determination step of determining a weighting value to the received signal at the time of reception by the transmitting signal and said receiving means during transmission by means of the first wireless communications that were received before the weighting is to the receiving signal by the weighting value A transmission step of transmitting the transmission signal weighted using the weighting value in the period of the time interval in which a reception signal with a small reception power is received out of the reception power from the system. It is a communication method.

In order to solve the above-described problem, the present invention provides a transmission / reception apparatus that constitutes the second radio communication system when the first radio communication system and the second radio communication system share the same frequency band. A plurality of antenna elements; a plurality of transmission / reception branching means connected to each of the plurality of antenna elements; a transmission means connected to each of the plurality of transmission / reception branching means; a communication method according to the transmitting and receiving apparatus comprising a receiving means connected to each periodically two received signals received from said first radio communication system by the receiving unit in each two different time intervals to be repeated A detection step for detecting the received power, a comparison step for comparing the received power of the two received signals detected, and the received power obtained by the comparison result A selection step of selecting a hearing received signal for the selected received signal, the row Ukoto the operation of the power minimization method using the correlation matrix of the received signals, calculates the weighting value for performing interference cancellation A calculation step; a branching step for branching the calculated weighting value; a first multiplication step for multiplying the branched weighting value by a reception signal received by the receiving means; and the branching weighting value. If, branched into the same number as the plurality of antenna elements, is a communication method characterized by comprising a second multiplication step of multiplying a transmission signal to be transmitted by said transmitting means.

  The present invention is characterized in that, in the above invention, the calculating step calculates a minimum eigenvector obtained on the basis of creation of a correlation matrix of a received signal and eigenvalue decomposition.

  According to the present invention, in the above invention, an orthogonal frequency division multiplexing step for performing orthogonal frequency division multiplexing, a weight value branching step for branching the weighting value calculated in the calculation step to the same number as the number of subcarriers, A Fourier transform step for performing a Fourier transform for each subcarrier, wherein the first multiplication step is a common weighting branched to the same number as the number of subcarriers for the received signal for each subcarrier subjected to the Fourier transform. It is characterized by multiplying values.

  According to the present invention, in the above invention, the signal detecting step includes a guard interval removing step for removing a guard interval from a received signal branched in the same number as the plurality of antenna elements, and a guard interval removing means by the guard interval removing means. A Fourier transform calculation step for performing Fourier transform on the same number of received signals as the plurality of antenna elements from which F has been removed, and K (F ≧ K) subcarriers from the F subcarriers subjected to the Fourier transform And a subcarrier averaging process step of creating a correlation matrix from the extracted K subcarriers and averaging it.

  In the present invention according to the above invention, the subcarrier extraction step extracts F subcarriers before communication, and extracts M subcarriers (F> M) determined in advance after communication. It is characterized by that.

  The present invention is characterized in that, in the above invention, the subcarrier extraction step extracts F subcarriers before communication, and extracts first and Fth subcarriers after communication. .

  According to the present invention, in the above invention, the detection step extracts time interval extraction for extracting one of the time intervals T1 and T2 during communication when two different time intervals are T1 and T2. A transmission signal is not transmitted by the transmission means in the extracted one time interval.

  According to the present invention, a weighting value for a transmission / reception signal at the time of transmission and reception is determined based on information of a reception signal having a large reception power among reception signals obtained from at least two different time intervals. Therefore, by performing interference removal with an array antenna using the characteristics of TDD in the secondary system, it is possible to perform efficient cognitive radio while having a simple interference detection function and avoiding interference with the primary system. The advantage that it can be obtained.

  According to the present invention, two received signals obtained from at least two different time intervals are detected, the received powers of the two received signals are compared, and the received power obtained by the comparison result is large. Select a received signal, create a correlation matrix of the received signal and minimize the power based on information of the selected received signal, calculate a weight value for performing interference removal, and calculate the calculated weight The value is branched, the branched weight value is multiplied by the received signal, and the weight value is multiplied by the transmission signal. Therefore, there is an advantage that interference detection from the Primary system can be easily realized without reducing the efficiency of the Primary system at all. In addition, there is an advantage that communication of the Secondary system can be started without causing interference to the Primary system.

  According to the present invention, the minimum eigenvector obtained based on the creation of the correlation matrix of the received signal and the eigenvalue decomposition is calculated. Therefore, there is an advantage that interference detection from the Primary system can be easily realized without reducing the efficiency of the Primary system at all. In addition, there is an advantage that communication of the Secondary system can be started without causing interference to the Primary system.

  According to the present invention, when performing orthogonal frequency division multiplexing, the calculated weight value is branched to the same number as the number of subcarriers, Fourier transform is performed for each subcarrier of the received signal, and each Fourier-transformed subcarrier is determined. The received signal is multiplied by a common weighting value branched as many as the number of subcarriers. Therefore, even in the OFDM system, there is an advantage that cognitive radio can be realized without greatly increasing the computation amount of the Secondary system.

  According to the present invention, the same number of antenna elements as the number of antenna elements are provided, the guard interval is removed from the received signal, the received signal from which the guard interval is removed is Fourier transformed, and the Fourier transformed F K subcarriers (F ≧ K) are extracted from the subcarriers, and a correlation matrix is created from the extracted K subcarriers and averaged. Therefore, even in the OFDM system, there is an advantage that cognitive radio can be realized without greatly increasing the computation amount of the Secondary system.

  According to this invention, F subcarriers are extracted before communication, and M (F> M) subcarriers determined in advance are extracted after communication. Therefore, even in the OFDM system, there is an advantage that cognitive radio can be realized without greatly increasing the computation amount of the Secondary system.

  According to the present invention, F subcarriers are extracted before communication, and the first and Fth subcarriers are extracted after communication. Therefore, even in an OFDM system in which the propagation environment of the Primary system changes from moment to moment, there is an advantage that cognitive radio can be realized without greatly increasing the amount of computation of the Secondary system.

  According to the present invention, when two different time intervals are T1 and T2, one of the time intervals T1 and T2 is extracted during communication, and the transmission signal is extracted in one extracted time interval. Do not send. Therefore, there is an advantage that the communication of the Secondary system can be started without causing interference to the Primary system.

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

A. First Embodiment FIG. 1 is a block diagram showing a configuration of an array antenna transmission / reception apparatus according to a first embodiment of the present invention. In FIG. 1, an array antenna transmission / reception apparatus 9 has, as a basic configuration, N antennas 10-1 to 10-N and transmission / reception separating means (switches) 11- connected to the antennas 10-1 to 10-N. 1 to 11-N, transmitters 12-1 to 12-N, and receivers 13-1 to 13-N. This corresponds to a basic array antenna apparatus. In the first embodiment, since digital signal processing is basically assumed, the memory 14 is arranged after the receiving devices 13-1 to 13-N. However, according to the principle of the present invention to be described later, control is possible regardless of analog or digital, and the present invention is not limited to digital signal processing. The function shown in FIG. 1 is desirably provided on the base station side (access point AP) side of the Secondary system in consideration of reducing the control burden on the terminal side.

  As shown in FIG. 1, the secondary system according to the first embodiment is characterized by having a primary system interference removal unit 15. The primary system interference canceling unit 15 has a mechanism for detecting signals of a time interval T1 and a time interval T2 transmitted by the primary system. In the first embodiment, as shown in FIG. 1, it can be realized by the signal detection devices 15-1 and 15-2. Moreover, in this 1st Embodiment, it has the power comparison part 15-3 which compares these signal powers, and the signal selection part 15-4 which selects the signal with higher electric power. This is because control is performed on a signal having a high reception power among signals at the time interval T1 or T2.

  The reception weight calculation unit 15-5 uses the signal selected by the signal selection unit 15-4 in FIG. 1 to determine a weight (weight value) for weighting the array antenna. Details of the operation of the reception weight calculation unit 15-5 will be described with reference to the flowchart of FIG. The weight information obtained by the reception weight calculation unit 15-5 is supplied by the branching unit 16 to the reception signal weight multiplication unit 17 and the transmission signal weight multiplication unit 18.

FIG. 2 is a block diagram showing a configuration of the reception weight calculation unit 17 according to the first embodiment. As shown in FIG. 2, the reception weight calculation unit 17 multiplies the received signals y _{1 to} y _N and the weights w ₁ ^{* to} w _N ^* obtained by the reception weight calculation unit 15-5 of the reception signal by a multiplier 17-1. Multiply by −1 to 17-1-N, and combine by adder 17-2. Here, the received signals y _{1 to} y _N mean a signal in which an interference wave from the Primary system and a communication signal of the Secondary system are superimposed after the Secondary system starts communication.

FIG. 3 is a block diagram showing a configuration of the transmission weight calculation unit 18 according to the first embodiment. Also on the transmission side, transmission is performed using the weights w ₁ ^{* to} w _N ^* obtained by the reception weight calculation unit 15-5. The transmission signal S is first branched into N signals equal to the number of antennas by the branching means 18-1. With respect to the N branched signals S, S,..., S, the multipliers 18-2-1 to 18-2-N use the first to Nth weights w ₁ ^{* to} w _N ^* . Multiply The transmission weight calculation unit 18 does not perform synthesis. This is because the antenna directivity is synthesized in space because the antennas 10-1 to 10-N can perform spatial power synthesis.

  FIG. 4 is a conceptual diagram showing the configuration of the communication system in the first embodiment. As shown in FIG. 4, assuming a situation where there is a pair of primary system 100-1 and primary system 100-2, primary system 100-1 and primary system 100-2 use different time intervals. Communicate. Further, an environment is assumed in which the Secondary system 101 exists between the Primary system 100-1 and the Primary system 100-2.

  In the time interval T1 transmitted by the primary system 100-1, the primary system 100-2 performs reception. On the other hand, in the time interval T2 that the primary system 100-1 receives, the primary system 100-2 performs transmission. This is one of the common communication forms and is called TDD. The transmission / reception operation is normally repeated continuously at regular intervals. Therefore, the time interval at which the primary system 100-1 receives and the primary system 100-2 transmits is defined as “T1,” and the time interval at which the primary system 100-1 transmits and the primary system 100-2 receives is defined as “T2.” There is no problem.

  Next, FIG. 5 is a flowchart for explaining the operation of the array antenna transmission / reception apparatus 9 according to the first embodiment. First, in the first embodiment, signal powers P (T1) and P (T2) arriving at time intervals T1 and T2 are measured using the signal detection devices 15-1 and 15-2 (step S1). At this point in time, the secondary system 101 has not yet started communication, so the only incoming signals are the interference waves of the primary systems 100-1 and 100-2.

  In addition, the values of the time intervals T1 and T2 are generally disclosed since they are basic parameters of the wireless system, and it is easy for the Secondary system 101 to know these values in advance. is there. The value of one section of the TDD system is, for example, 625 μsec in the PHS system. This fact is disclosed in Reference 3 (Personal Handy phones system ARIB standard (RCR STD-28), ver. 2 Association of Radio Industries and Businesses, Tokyo, Dec. 1995).

  Next, the power comparison unit 15-3 determines whether or not the signal power P (T1) is greater than the signal power P (T2) (step S2). The magnitude relationship between the signal powers P (T1) and P (T2) is determined by the positional relationship of the Secondary system 101. For example, in the example illustrated in FIG. 4, the Secondary system 101 exists in the vicinity of the Primary system 100-2, and thus there is a high possibility that the power that arrives at the time interval T <b> 2 will be high.

  This is because the received power is basically inversely proportional to the propagation loss, and the propagation loss is known to be proportional to the distance between transmission and reception. Therefore, as in the first embodiment, if signals transmitted from the primary systems 100-1 and 100-2 at the time intervals T1 and T2 are received, the received power of either one increases and the presence of an interference wave exists. Can be estimated with relatively high accuracy.

  In this way, in this first embodiment, it is possible to detect the arrival of communication signals of the primary systems 100-1 and 100-2 by using a very simple method. That is, this operation solves the problem with respect to (Procedure 1) described above. In addition, when the received power is equal to or lower than a predetermined threshold value at both time intervals, the radio waves from the primary system 100-1 and the primary system 100-2 are considerably small. Then, unless the Secondary system 101 transmits with higher power than the Primary systems 100-1 and 100-2, the interference from the Secondary system 101 to the Primary systems 100-1 and 100-2 hardly causes a problem.

  Then, according to the magnitude relationship between the signal powers P (T1) and P (T2), the signal having the larger signal power is extracted using the signal selection unit 15-4 (steps S3 and S4). That is, when the signal power P (T1) is larger, the signals X (i) and (i = 1 to M) that arrive at the signal power P (T1) are extracted (step S3). On the other hand, when the signal power P (T2) is larger, the signals X (i) and (i = 1 to M) arriving at the signal power P (T2) are extracted (step S4).

  In the example shown in FIG. 4, a signal having a time interval T <b> 2, that is, a signal coming from the primary system 100-2 is extracted. Here, X (i) is given by the following equation (1).

Here, i represents a sample on the i-th time axis, and x _k (i) represents a received signal of the k-th antenna at time i. T represents transposition. Here, it is assumed that the number of acquired data per antenna is M. Therefore, the signal to be extracted is N antenna data × M sample data, that is, NM data.

  Next, with respect to the signal extracted using the signal selection unit 15-4, the reception weight calculation unit 15-5 calculates a correlation matrix from the reception signal X using the following equation (2) (step S5).

  Here, H represents a complex conjugate transpose. This correlation matrix includes only interference components from the Primary system 100-1 or 1002 because the Secondary system 101 has not yet started communication. Therefore, if a weight for removing such a signal can be formed, the interference signal can be completely removed. Specifically, a power minimization method is known. This fact is disclosed in Reference 4 (Kikuma, Adaptive Signal Processing by Array Antenna, Science and Technology Publishers, 1998). In the power minimization method, the weight is calculated according to the following equation (3) (step S6).

  As can be seen from the above equation (3), in the power minimization method, information of only the correlation matrix of the primary systems 100-1 and 100-2 is used. Actually, in addition to the calculation using Equation (3), as a method for further reducing the amount of calculation, the weight may be calculated sequentially by a method such as RLS (Recursive Least Square) or LMS (Least Mean Square). Is possible.

In addition to the power minimization method, there is a method based on eigenvalue decomposition in Equation (2) as a method for obtaining the weight of interference removal. If the equation (2) is decomposed into the eigenvalues shown in the following equation (4), the eigenvector e _i (i = 1 to K) corresponding to the signal power and the eigenvector e _i (i = K + 1 to N) corresponding to the noise power can be obtained. . The correlation matrix, eigenvalues, and eigenvectors have the following relationship (4).

Here, the signal subspace is orthogonal to the noise subspace. If the incoming signal is a K wave, the eigenvector corresponding to the eigenvalues from K + 1 to N becomes the eigenvector corresponding to the noise subspace. Therefore, the directivity of the eigenvector corresponding to the minimum eigenvalue which is _{one of} λ _{K + 1} ,..., Λ _N forms a null in the signal direction.

Therefore, it is also possible to use eigenvector e _N for the minimum eigenvalue obtained by eigenvalue decomposition as weight (vector) w. In addition, as a method for obtaining the eigenvector corresponding to the minimum eigenvalue, eigenvalue decomposition can be directly performed, but it is also possible to obtain a sequential update method such as a power method for the inverse matrix of the correlation matrix. be able to.

  Next, the secondary system 101 starts communication using the weight information. The branch means 16 in FIG. 1 branches the weight w and supplies it to the reception weight multiplication unit 17 and the transmission weight multiplication unit 18.

  The reception weight multiplication unit 17 calculates reception weight multiplication in one of the time intervals T1 and T2 based on the magnitude relationship between the signal power P (T1) and the signal power P (T2). That is, the reception weight multiplication unit 17 determines whether or not the signal power P (T1) is larger than the signal power P (T2) (step S7), and if P (T1)> P (T2) The time interval T1 is selected (step S8), and if P (T1) <P (T2), the time interval T2 is selected (step S9), and the received signal (signal transmitted from the terminal of the Secondary system + Primary) 2 is multiplied by the weight previously used in the reception weight calculation unit 15-5 using the following equation (5) to calculate the output signal Z (step S10). ).

  Thus, when P (T1)> P (T2), reception is performed at the time interval T1, while when P (T1) <P (T2), reception is performed at the time interval T2. That is, the reception of the Secondary system 101 is performed using a time interval in which the reception power increases. In the example of FIG. 4, since P (T2)> P (T1), the base station in the Secondary system 101 receives at the time interval T2 and transmits at the time interval T1. On the other hand, the terminal side transmits at time interval T2 and receives at time interval T1.

  On the other hand, the transmission weight multiplication unit 18 calculates transmission weight multiplication in one of the time intervals T1 and T2 based on the magnitude relationship between the signal power P (T1) and the signal power P (T2). That is, the transmission weight multiplication unit 18 determines whether or not the signal power P (T1) is larger than the signal power P (T2) (step S11), and if P (T1)> P (T2) The time interval T2 is selected (step S12). If P (T1) <P (T2), the time interval T1 is selected (step S13), and the reception weight calculation unit for the N-branched transmission signal is selected. The weight obtained in 15-5 is multiplied using the following equation (6) (step S14).

  Thus, when P (T1)> P (T2), transmission is performed at the time interval T2, while when P (T1) <P (T2), transmission is performed at the time interval T1. That is, the transmission of the Secondary system 101 is performed using a time interval in which the reception power is small. Note that the transmission weight multiplication unit 18 does not require a synthesis process as described above.

  Next, phenomena and effects in the Secondary system 101 according to the first embodiment will be described with reference to FIG. First, in the time interval T1, transmission is performed on the base station side of the secondary system 101, and reception is performed on the terminal side. On the base station side, if the non-directional transmission is performed from the base station at the time interval T1, as in the prior art, interference is given to the primary system 100-2.

  However, in the first embodiment, since transmission can be performed using a weight that forms a directional null in the direction of the Primary system 100-2, no interference is given to the Primary system 100-2. Moreover, since the Primary system 100-1 is transmitting and does not receive a signal, the interference with the Primary system 100-1 does not need to be considered here.

  That is, interference from the secondary system 101 to the primary system 100-2 due to the start of communication of the secondary system 101 can be avoided, so that the problem in (procedure 2) described above can be solved. On the other hand, since the signal is received at the time interval T1 with a small amount of interference on the terminal side, the amount of interference to the terminal side of the secondary system 101 is automatically set without any control on the terminal side. It becomes possible to reduce. Since miniaturization and simplification are desirable in the terminal, this is a very important advantage that the amount of interference can be reduced without performing any control.

  Next, in the time interval T2, reception is performed on the base station side of the secondary system 101, and transmission is performed on the terminal side. Since the access point (base station) 101-1 holds a weight capable of canceling interference in advance, if the received signal is multiplied by the received signal, the interference wave can be completely removed and good communication can be performed. Quality can be kept.

  In the example illustrated in FIG. 4, it is assumed that the service areas of the primary systems 100-1 and 100-2 are larger than the service area of the secondary system 101. Therefore, since the signal of the terminal of the Secondary system 101 is weaker than the signal of the Primary system 100-2, the amount of interference with the Primary system 100-1 is small, and the Primary system 100-2 is transmitting. , Interference with the Primary 100-2 may not be considered.

  According to the first embodiment described above, it is possible to easily realize interference detection from the Primary system without reducing the efficiency of the Primary system at all. In addition, the communication of the Secondary system can be started without causing interference to the Primary system. That is, the problem in the conventional cognitive radio can be solved.

B. Second Embodiment Next, a second embodiment of the present invention will be described. In the second embodiment, an OFDM (Orthogonal Frequency Division Multiplexing) system is used in the secondary system, which is different from the first embodiment.

  FIG. 6 is a block diagram showing a configuration of an array antenna transmitting / receiving apparatus according to the second embodiment of the present invention. In the figure, parts corresponding to those in FIG. In FIG. 6, GI (Guard Interval) removing units 20-1 to 20-F and FFT (Fast Fourier Transform) calculating units 21-1 to 21-F are provided on the receiving side after the memory. On the other hand, on the transmitting side, an S / P (serial / parallel) conversion unit 22 that divides the number of transmission signals into the number of OFDM subcarriers, an IFFT (Inverse Fast Fourier Transform) calculation unit 23, a GI addition unit 24, Is provided.

  An OFDM system having a reception function and a transmission function described here has recently been adopted in a wireless LAN system or the like, and is an indispensable technique indispensable for broadband transmission. This fact is described in, for example, Document 4 (supervised by Morikura and Kubota, 802.11 high-speed wireless LAN textbook, Impress). Therefore, it is very important that the second embodiment can be applied to the OFDM system.

  In the ODFM, in the case of performing the above-described interference cancellation, generally, a method is employed in which a weighting value is calculated and combined for each subcarrier signal after FFT on the receiving side. In order to realize this by the method described in the first embodiment, GI removal and IFFT are performed on the received signal from the primary system, and the signal of the primary system is divided into subcarrier units. It is necessary to obtain the above-described interference removal weight for each carrier.

  However, the Primary system does not always use OFDM, and even if the Primary system is an OFDM system, the number of subcarriers and the subcarrier band are not necessarily the same as those of the Secondary system. Further, when the number of subcarriers is F, in order to obtain the weight by the primary system interference removal unit 15 for each subcarrier, calculation of F times as described in FIG. 1 is required. In an actual system, the number of F is from several tens to several hundreds, so a huge amount of calculation is required for the process of calculating the weight for each subcarrier. In the second embodiment, in order to solve this problem, the primary system interference canceling unit 15 is exactly the same as the configuration of FIG. 1, and the reception weight multiplying unit 17a is different from the configuration of FIG.

FIG. 7 is a block diagram showing a configuration of the reception weight multiplication unit 17a according to the second embodiment. In FIG. 7, first, the weights w ₁ ^{* to} w _N ^* obtained by the primary system interference canceling unit 15 are simply set to the number of subcarriers F by branching means 17 a-1-1 to 17 a-1 -N. Divide into Thereafter, the divided weights are multiplied for each subcarrier by multipliers 17a-2-1 to 17a-2-1-N,..., 17a-2-F-1 to 17a-2-F-N. . That is, the same weight is multiplied between subcarriers. The outputs of the multipliers 17a-2-1 to 17a-2-1-N,..., 17a-2-F-1 to 17a-2-F-N are respectively added to the corresponding adders 17a-3. -1 to 17a-3-F are added and supplied to the parallel / serial converter 17a-4. The parallel / serial conversion unit 17a-4 converts the addition result (parallel) from the adders 17a-3-1 to 17a-3-F into serial data, and outputs it as an output signal.

  In the primary system, when assuming a base station such as FWA (Fixed wireless Access) or a mobile phone, the base station or the receiving station is installed on the rooftop of the building. It is known that the spread is quite small (within a few degrees). On the other hand, when the Secondary system is applied to a situation where the antenna is arranged in a low place and the system is a narrow area such as a wireless LAN, the spread of the angular distribution of the propagation path is considerably large (several tens of times). It is known that the degree is more than 360 degrees. A propagation environment with a narrow angular spread is equivalent to a radio wave coming from a certain direction. In this case, even if the weight of interference removal is obtained by averaging the entire subcarriers, or if the weight of interference removal is obtained for each subcarrier, there is no significant difference. Using this property, the second embodiment multiplies the same weight between subcarriers.

  The multipliers 17a-2-1 to 17a-2-N,..., 17a-F-1 to 17a-FN have functions added to the configuration of FIG. Compared with the increase in the calculation amount in the interference removal unit 15, the influence is considerably small.

  According to the second embodiment described above, even in the OFDM system, cognitive radio can be realized without greatly increasing the amount of computation of the secondary system.

C. Third Embodiment Next, a third embodiment of the present invention will be described. The third embodiment is characterized in that the Primary system also uses the OFDM system. However, the number of subcarriers and the bandwidth of the Secondary system do not necessarily need to match those of the Primary system. In the first or second embodiment described above, it is not assumed that the propagation environment of the Primary system changes every moment.

  However, for example, in FIG. 4, when it is assumed that the primary system 100-2 is a mobile station, the propagation environment between the primary systems changes with time. Here, when communication is started, the interference between the primary system and the desired signal of the secondary system is actually mixed, so that there is not much difference between the interference power and the desired power, or the desired power is less than the interference power. If this value is too large, simple interference removal according to the first or second embodiment described above becomes difficult. Therefore, in the third embodiment, even when the propagation environment of the primary system changes due to time fluctuation, stable interference detection of the primary system is realized.

  FIG. 8 is a block diagram showing a configuration of an array antenna transmitting / receiving apparatus according to the third embodiment of the present invention. In the figure, parts corresponding to those in FIG. As shown in FIG. 8, in the interference detection method according to the third embodiment, the operation in the signal detectors 15-1a and 15-2a arriving at the time interval T1 or T2 before and after the communication of the Secondary system is started. Different.

  Here, FIG. 9 is a block diagram showing a configuration of the signal detection device 15-1a shown in FIG. Since the configuration of the signal detection device 15-2a is the same as that of the signal detection device 15-1a, the description thereof is omitted. In FIG. 9, the signal detectors 15-1a and 15-2a arriving at the time interval T1 or T2 perform GI removal by the GI removal units 15-1a-1-1-1 to 15-1a-1-N before starting communication. An FFT calculation is performed by the FFT calculation units 15-1a-2-1 to 15-1a-2-N. This is the same as the normal OFDM demodulation, but actually uses regular arithmetic processing as in the Secondary system, so it is written in a different place in the block diagram, but GI removal and FFT in the Secondary system. You may divert a calculation part. Therefore, even if the FFT calculation is repeated, the hardware scale does not increase.

  The subcarrier extraction unit 15-1a-3 extracts all incoming subcarriers. Next, the subcarrier average processing unit 15-1a-4 averages the signal for each subcarrier. That is, all subcarriers are detected, the signal for each subcarrier is used as a correlation matrix, and these signals are averaged. This signal is equivalent to averaging in the frequency direction, and can be said to be almost equivalent to the correlation matrix averaged with the time axis information described in FIG. That is, the same interference removal as in FIG. That is, calculations other than the correlation matrix averaged in the frequency direction are the same as those in FIG. In other words, signal selection and reception weight calculation itself are the same as in FIG.

  Next, processing after the start of communication will be described. Even after the start of communication, in the signal detectors 15-1a and 15-2a arriving at the time interval T1 or T2, the GI removal unit 15-1a-1-1-1 to 15-1a-1-N performs the GI removal and FFT calculation unit. The FFT calculation by 15-1a-2-1 to 15-1a-2-N is performed in the same manner as the processing described above. However, after the communication starts, the signal of the Secondary system is superimposed here, so that the above-described interference cancellation may not operate properly. Therefore, in the third embodiment, interference can be easily and effectively removed even in such an environment by appropriately using the subcarrier information extracted by the subcarrier extraction unit 15-1a-3. Is proposing.

  FIG. 10 shows the relationship between the actual subcarrier arrangement (band βHz), the actual communication band (band αHz), and the guard band band (band γHz) in the OFDM system when the characteristics of the primary system and the secondary system are the same. It is a conceptual diagram shown in a different case (FIG. 10B) from (FIG. 10A). First, in the case of FIG. 10A, the spectrums of the signals in the Secondary system and the Primary system appear to be exactly the same.

  However, in the relationship between the actual communication band (band αHz) and the actual subcarrier arrangement (band βHz), the relationship between the FFT point number L and the subcarrier F is always designed to satisfy L> F. That is, α> β. Ideally, L-point subcarriers can be arranged, but the information of subcarriers at both ends is set to 0 in order to avoid interference with adjacent channels. This band is called a guard band, and in FIGS. 10A and 10B, the band is γ Hz.

  Considering the features described above, it means that an environment for extracting only interference waves can be created even during communication. Originally, the antenna pattern for interference cancellation can be formed, and it is sufficient that the fluctuation can be derived. First, subcarrier information in the vicinity of the guard band described above can be used. In the secondary system, if the subcarrier (1) and the information of (F) are transmitted without being transmitted, the signal from the secondary system is not received by this subcarrier. In this case, if attention is paid to subcarriers (1) and (F), comparison of interference levels between time intervals T1 and T2 and calculation of interference removal can be performed based on information of received signals of the subcarriers. Since these are accurately performed in advance for the start of communication, it is only necessary to check the fluctuations in the interference detection and the interference removal after the start of communication. Therefore, the initial accuracy is not necessary.

  In the third embodiment, when the status of the primary system changes due to environmental changes such as movement, it is necessary to recheck the interference amount of the primary system. Usually, in a TDD system, a guard interval (non-communication section) is provided in order to avoid a time collision between users. By providing this section in the Secondary system and checking the signal strength of the Primary system that arrives in this section, it is possible to check the interference amount of the Primary system. The check may be performed every time reception is performed, but may be performed at a frequency of about once when receiving the secondary system several times to several tens of times.

  Therefore, in the signal detection devices 15-1a and 15-2a in the primary system interference removal unit 15, the subcarrier extraction units 15-1a-3 and 15-2a-3 receive subcarriers (1) and ( F) Pick up only. Thereafter, the correlation matrix of the two subcarriers is averaged. The subsequent processing is the same as the processing before starting communication. In the case of FIG. 10B, since the subcarrier arrangement band and the guard band band are different, in the secondary system, for example, transmission is not performed with 0 as subcarriers (1) and (F). However, only the interference wave arrives at the carrier at the end of the communication band β2 in FIG.

  Other than the method described above, there is a method in which only the interference wave is received by the primary system interference removal unit 15 during communication. In the OFDM system, a signal called a pilot subcarrier is constantly transmitted to ensure carrier synchronization. For example, in IEEE 802.11a, 4 carriers out of 52 subcarriers are used for this carrier. Since the position of this subcarrier is known in advance by standardization or the like, it can be considered that it is recognized also in the Secondary system. If this subcarrier is not transmitted in the secondary system, the primary system interference canceling unit 15 selects and focuses only this carrier during communication, and only the interference component is obtained in the same manner as described above. Is obtained.

  It is also possible to focus on data in the time axis direction without focusing on the subcarrier. In a normal communication system, first, a base station and a terminal send a known preamble signal to each other. Thereafter, normal data is transmitted. Therefore, in the secondary system, it is possible not to transmit in the preamble section of this primary system. In this case, the signal arrives from the primary system only in the preamble section of the primary system, and the signal of the section of the secondary system arrives in the subsequent section. Also in this case, after detecting the signal in the preamble section, it is possible to obtain a weight for obtaining interference cancellation by the same procedure as that before the start of communication.

Next, effects of the first to third embodiments described above will be described.
The calculation was performed in an environment assuming the configuration shown in FIG. The calculation assumes an environment in which each of the primary systems 100-1 and 100-2 has one transmission / reception antenna. The primary systems 100-1 and 100-2 are operated in a TDD system. The Secondary system 101 calculates the communication quality when moving within the service areas of the Primary systems 100-1 and 100-2 assuming a wireless LAN environment. The calculation parameters are shown in Table 1.

  The secondary system assumes a communication range that takes into account the 54 Mbps transmission of IEEE802.11a to be about 23 m. Therefore, it is assumed that the terminal moves within this range. The SNR of the Secondary system is set to 20 dB at the zone end. Table 2 shows the propagation loss equation.

  Propagation loss is given in the literature “Shitsubogai,“ Examination of 2GHz band urban propagation loss estimation from the road to the outdoor height ”, IEICE Technical Report, AP96-15, (1996-15) 1996.” The path loss model is used. In this path model, a path loss for an arbitrary antenna height of 30 m or less can be given. The antenna height of the primary system base station is 30 m, and the height of the primary system mobile station is 2 m. In addition, the antenna height of the Secondary system was 20 m and the frequency was 5 GHz. The configuration of the second embodiment is used for the base station of the Secondary system. The number of antenna elements of the base station of the secondary system is set to 2, which is the minimum number of elements. Interference cancellation is not performed on the terminal side of the Secondary system. The number of antenna elements is one.

  FIG. 11 is a conceptual diagram showing communication quality (SINR: Signal to Noise) of the Secondary system 101 according to the present invention. FIG. 11 shows communication quality (worst case) L1 when not carrying out the present invention, communication quality L2 at the terminal side, communication quality L3 at the base station side, and communication quality L4 when there is no interference. As is apparent from FIG. 11, the communication quality L1 of the Secondary system 101 is greatly degraded unless interference cancellation is performed. On the other hand, when the present invention is used, the communication quality L3 on the base station side gradually approaches the communication quality L4 when there is almost no interference. For example, when the cumulative probability is 10%, an improvement in SINR of about 20 dB is obtained, and it can be seen that the effect of the present invention is remarkable.

  In addition, although the terminal does not perform any interference removal or control, the communication quality L2 can be greatly improved as compared with the case where the interference removal is not performed. With a probability of 85% or more, the SINR becomes 20 dB or more, and the Secondary system 101 can be operated in a considerable area. According to the method of the present invention, on the base station side, the two interferences of the time intervals T1 and T2 coming from the primary systems 100-1 and 100-2 are always in a time with high interference power. This is because the terminal side can automatically perform reception at a time when the interference power is low.

  Thus, in the present invention, focusing on the timing of the TDD system, the secondary system 101 achieves good quality without performing any control on the terminal side by performing a simple interference removal function on the base station side. Communication can be performed while maintaining. That is, the surface frequency utilization efficiency can be improved in the entire system.

It is a block diagram which shows the structure of the array antenna transmission / reception apparatus by 1st Embodiment of this invention. It is a block diagram which shows the structure of the reception weight calculation part 17 by this 1st Embodiment. It is a block diagram which shows the structure of the transmission weight calculation part 18 by this 1st Embodiment. It is a conceptual diagram which shows the structure of the communication system in this 1st Embodiment. It is a flowchart for demonstrating operation | movement of the array antenna transmission / reception apparatus 9 by this 1st Embodiment. It is a block diagram which shows the structure of the array antenna transmission / reception apparatus by 2nd Embodiment of this invention. It is a block diagram which shows the structure of the reception weight multiplication part 17a by this 2nd Embodiment. It is a block diagram which shows the structure of the array antenna transmission / reception apparatus by 3rd Embodiment of this invention. It is a block diagram which shows the structure of the signal detection apparatus 15-1a. It is a conceptual diagram which shows the relationship between actual subcarrier arrangement | positioning (band | zone (beta) Hz), an actual communication band (band | zone (alpha) Hz), and a guard band band (band | zone (gamma) Hz) in an OFDM system. It is a conceptual diagram which shows the communication quality (SINR: Signal to Noise) of the Secondary system 101 by this invention. It is a conceptual diagram for demonstrating the outline | summary of a cognitive radio | wireless technique.

Explanation of symbols

10-1 to 10-N antenna (multiple antenna elements)
11-1 to 11-N transmission / reception separating means (multiple transmitting / receiving branching means)
12-1 to 12-N transmitter (transmitter)
13-1 to 13-N Receiver (Receiver)
14 Memory 15 Primary System Interference Rejection Unit 15-1, 15-2 Signal Detection Device (Signal Detection Unit)
15-3 Power comparison unit (power comparison means)
15-4 Signal selection unit (signal selection means)
15-5 Reception weight calculation unit (weighting determination means, reception weight calculation means)
16 Branch means (branch means)
17 Received signal weight multiplier (Received signal weight multiplier)
18 Transmission signal weight multiplication section (transmission signal weight multiplication means)
17-1-1-1 to 17-1-N multiplier 17-2 adder 18-1 branching means 18-2-1 to 18-2-N multiplier 100-1, 100-2 Primary system 101 Secondary system 17a reception Signal weight multiplier (received signal weight multiplier)
20-1 to 20-F GI removal unit 21-1 to 21-F FFT calculation unit (Fourier transform means)
22 S / P converter 23 IFFT calculator 24 GI adder 17a-1-1 to 17a-1-N Branch means (weighted branch means)
17a-2-1-1 to 17a-2-F-N multiplier 17a-3-1 to 17a-3-F adder 17a-4 parallel / serial conversion unit 15-1a, 15-2a signal detection device 22- 1-22-F subcarrier extraction unit 15-1a-1-1-1 to 15-1a-1-N GI removal unit (guard interval removal means)
15-1a-2-1 to 15-1a-2-N FFT calculation unit (Fourier transform calculation means)
15-1a-3 Subcarrier extraction unit (subcarrier extraction means)
15-1a-4 Subcarrier averaging processing unit (subcarrier averaging processing means)

Claims (13)

When the first radio communication system and the second radio communication system share the same frequency band, a transmission / reception apparatus constituting the second radio communication system,
A plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, a transmission means connected to each of the plurality of transmission / reception branching means, and connected to each of the plurality of transmission / reception branching means in the transceiver apparatus and a receiving means which is,
Of the received signals received from the first wireless communication system by the receiving means at two different time intervals that are periodically repeated, a received signal having a large received power is extracted and null in the direction of the received signal. comprising interference cancellation means for determining a weighting value to the received signal at the time of reception by the transmitting signal and said receiving means upon transmission by the transmission means to direct,
In the period of the time interval in which the transmission means receives a reception signal with a small reception power among the reception power from the first wireless communication system received before the reception signal is weighted by the weighting value. A transmission / reception apparatus that transmits the transmission signal weighted using the weighting value . When the first radio communication system and the second radio communication system share the same frequency band, a transmission / reception apparatus constituting the second radio communication system,
A plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, a transmission means connected to each of the plurality of transmission / reception branching means, and connected to each of the plurality of transmission / reception branching means in the transceiver apparatus and a receiving means which is,
Signal detecting means for detecting two received signals received from the first wireless communication system by the receiving means at two different time intervals that are periodically repeated ;
Power comparing means for comparing received power of two received signals detected by the signal detecting means;
Signal selection means for selecting a received signal having a large received power obtained by the comparison result by the power comparing means;
The received signal selected by said signal selection means, a reception weight calculation means for calculating an operation of the power minimization method using the correlation matrix of the received signal by a row Ukoto, the weighting value for performing interference cancellation,
Branching means for branching the weighting value calculated by the reception weight calculating means;
Received signal weight multiplying means for multiplying the weighting value branched by the branching means by the received signal received by the receiving means;
A transmission / reception apparatus comprising: a weighting value branched by the branching unit; and a transmission signal weight multiplication unit that multiplies the transmission signal transmitted by the transmission unit and branched by the same number as the plurality of antenna elements. .   The transmission / reception apparatus according to claim 2, wherein the reception weight calculation means calculates a minimum eigenvector obtained on the basis of creation of a correlation matrix of a reception signal and eigenvalue decomposition. Orthogonal frequency division multiplexing means for performing orthogonal frequency division multiplexing;
Weighting branching means for branching the weighting value calculated by the reception weight calculating means to the same number as the number of subcarriers;
Fourier transform means for performing Fourier transform for each subcarrier of the received signal received by the receiving means,
The reception weight multiplying unit multiplies the reception signal for each subcarrier Fourier-transformed by the Fourier transform unit by a common weighting value branched to the same number as the number of subcarriers by the weighting branching unit. The transmission / reception apparatus according to claim 2. The signal detection means includes
Guard interval removing means provided as many as the number of the plurality of antenna elements, and removing the guard interval from the received signal;
Fourier transform calculation means for performing Fourier transform on the received signal provided in the same number as the plurality of antenna elements, and guard intervals removed by the guard interval removal means;
Subcarrier extraction means for extracting K (F ≧ K) subcarriers from the F subcarriers transformed by the Fourier transform calculation means;
5. The transmission / reception apparatus according to claim 4, further comprising subcarrier averaging processing means for creating a correlation matrix from K subcarriers extracted by the subcarrier extraction means and averaging the correlation matrix. When the first radio communication system and the second radio communication system share the same frequency band, a transmission / reception apparatus constituting the second radio communication system,
A plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, a transmission means connected to each of the plurality of transmission / reception branching means, and connected to each of the plurality of transmission / reception branching means a communication method according to the transmitting and receiving apparatus comprising a receiving means which is,
A comparison step of comparing received signals received from the first wireless communication system by the receiving means at two different time intervals that are periodically repeated ;
A reception signal with a large reception power obtained from the comparison result is extracted, and a transmission signal at the time of transmission by the transmission means and a reception signal at the time of reception by the reception means are directed so as to direct null toward the reception signal . A determining step for determining a weighting value ;
Of the received power from the first wireless communication system received before the weighting of the received signal by the weighted value, the weighted value is set in the period of the time interval when the received signal with the smaller received power is received. A transmission step of transmitting the transmission signal weighted by using,
A communication method comprising: When the first radio communication system and the second radio communication system share the same frequency band, a transmission / reception apparatus constituting the second radio communication system,
A plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, a transmission means connected to each of the plurality of transmission / reception branching means, and connected to each of the plurality of transmission / reception branching means a communication method according to the transmitting and receiving apparatus comprising a receiving means which is,
A detecting step of detecting two received signals received from the first wireless communication system by the receiving means in two different time intervals that are periodically repeated ;
A comparison step of comparing the received power of the two detected received signals;
A selection step of selecting a received signal having a large received power obtained from the comparison result;
For the selected received signal, and calculating step of calculating an operation of the power minimization method using the correlation matrix of the received signal by a row Ukoto, the weighting value for performing interference cancellation,
A branching step for branching the calculated weight value;
A first multiplying step of multiplying the branched weight value by a received signal received by the receiving means;
A communication method, comprising: a second multiplication step of multiplying the branched weight value by a transmission signal transmitted by the transmission means and branched in the same number as the plurality of antenna elements.   8. The communication method according to claim 7, wherein the calculation step calculates a minimum eigenvector obtained based on creation of a correlation matrix of a received signal and eigenvalue decomposition. An orthogonal frequency division multiplexing step for performing orthogonal frequency division multiplexing;
A weighting value branching step for branching the weighting value calculated in the calculation step to the same number as the number of subcarriers;
A Fourier transform step for performing a Fourier transform for each subcarrier of the received signal,
8. The communication according to claim 7, wherein the first multiplying step multiplies the received signal for each subcarrier subjected to the Fourier transform by a common weighting value branched in the same number as the number of subcarriers. Method. The signal detection step includes
A guard interval removing step for removing a guard interval from a reception signal branched in the same number as the number of the plurality of antenna elements;
Fourier transform calculation step for performing Fourier transform on the same number of received signals as the plurality of antenna elements from which guard intervals have been removed by the guard interval removing means;
A subcarrier extraction step of extracting K (F ≧ K) subcarriers from the Fourier transformed F subcarriers;
The communication method according to claim 7, further comprising: a subcarrier averaging process step of creating and averaging a correlation matrix from the extracted K subcarriers.   11. The subcarrier extraction step extracts F subcarriers before communication and extracts a predetermined M (F> M) subcarriers after communication. Communication method.   The communication method according to claim 10, wherein the subcarrier extraction step extracts F subcarriers before communication, and extracts first and Fth subcarriers after communication. The detection step includes a time interval extraction step of extracting any one of the time intervals T1 and T2 during communication when two different time intervals are T1 and T2.
8. The communication method according to claim 7, wherein a transmission signal is not transmitted by the transmission means in the extracted one time interval.

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