JP2008306662A - Transmitting/receiving device and communication method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve efficient cognitive radio while avoiding interference to a Primary system, without providing new additional functions to the Primary system, at all. <P>SOLUTION: Signal detectors 15-1, 15-2 detect two receiving signals having frequency bands f1, f2. A power comparison section 15-3 compares the reception power of the two detected reception signals. A signal selection section 15-4 selects the reception signal having large reception power. A reception weight calculation section 15-5 creates the correlation matrix of the reception signal and minimizes power, based on the information of the selected reception signal, and calculates a weighting value for eliminating interference. A receiving signal weight multiplying section 17 multiplies a branched weight value by the reception signal and outputs the result as an output signal. A reception frequency determining section 19-1 determines the frequency of the receiving signal to be received by a receiver, in accordance with the reception signal having large reception power. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radio communication system that operates a plurality of systems at the same frequency. In a new system (secondary system), an interference cancellation technique that uses the characteristics of a conventional system (priority system, primary system) FDD (Frequency Division Duplex) system. The present invention relates to a transmission / reception apparatus and a communication method thereof that can significantly improve the surface frequency utilization efficiency when considering the entire system without lowering 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 undesirable 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. 8 is a conceptual diagram for explaining the outline of the cognitive radio technology. In FIG. 8, 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 (Time Division Duplex). 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.

  Also, for example, even if the receivers of the secondary systems 2-1 to 2-6 determine that a signal has not 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 (D. Cabric, SM Mishra, and RW Brodersen, “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, Reference 2 (Morikura, Kubota, “Revised 802.11 High-Speed Wireless LAN Textbook”, Impress, 2004). When the secondary systems 2-1 to 2-6 approach the receivers of the primary systems 1-1 and 1-2, the primary system 1 is received by receiving signals transmitted from the primary systems 1-1 and 1-2. -1, 1-2 are grasped, and the secondary systems 2-1 to 2-6 can perform the procedure 2 based on the magnitude of the signal power.

  However, when considering cognitive radio, if the primary systems 1-1 and 1-2 eventually generate intentional signals for notifying their existence, it is necessary to provide a mechanism other than normal communication. This leads to hardware complexity. Further, it is necessary to newly provide a frequency and time for transmitting this signal. This causes a problem that it becomes a factor of reducing the communication utilization efficiency of the primary systems 1-1 and 1-2.

  The present invention has been made in view of such circumstances, and its purpose is to provide efficient cognitive radio while avoiding interference with the primary system without providing any new additional function in the primary system. Is to provide a transmission / reception device and a communication method thereof.

  In order to solve the above-described problem, the present invention provides a plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, and a transmission connected to each of the plurality of transmission / reception branching means. Among the received signals obtained from at least two different frequency bands received by the receiving means, in an array antenna transmitting / receiving apparatus comprising: a receiving means connected to each of the plurality of transmitting / receiving branching means; A transmission / reception apparatus comprising weighting determination means for determining a weighting value for a transmission / reception signal at the time of transmission by the transmission means and reception by the reception means based on information of a received signal having high power.

  In order to solve the above-described problem, the present invention provides a plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, and a transmission connected to each of the plurality of transmission / reception branching means. And an array antenna transmitting / receiving apparatus comprising: a receiving means connected to each of the plurality of transmitting / receiving branching means; and a signal for detecting two received signals in at least two different frequency bands received by the receiving means Detection means, power comparison means for comparing the received power of the two received signals detected by the signal detection means, and signal selection for selecting a received signal having a large received power obtained as a result of comparison by the power comparison means And a correlation matrix of the received signal and the power minimization based on the information of the received signal selected by the signal selecting means, and the interference elimination. Receiving weight calculating means for calculating a weighting value for performing the receiving weight, receiving signal weight multiplying means for multiplying the weighting value calculated by the receiving weight calculating means and the received signal received by the receiving means, and the signal selection Receiving signal frequency determining means for determining the frequency of the received signal to be received by the receiving means based on information of the received signal selected by the means; and transmission signal weight multiplying means for multiplying the transmission signal by a predetermined weighting value; A transmission / reception apparatus comprising: a transmission signal frequency determination unit that determines a frequency of a transmission signal to be transmitted by the transmission unit based on information of a reception signal selected by the signal selection unit.

  According to the present invention, in the above invention, the reception weight calculation means calculates a weighting value for performing interference removal by calculating a correlation matrix of a reception signal and a minimum eigenvector obtained by eigenvalue decomposition. Features.

  In order to solve the above-described problem, the present invention provides a plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, and a transmission connected to each of the plurality of transmission / reception branching means. And a reception means connected to each of the plurality of transmission / reception branching means, wherein the signal detection means detects two received signals in at least two different frequency bands received by the reception means Power comparing means for comparing the received power of the two received signals detected by the signal detecting means, and signal selecting means for selecting a received signal having a large received power obtained as a result of comparison by the power comparing means. Branching means for branching the received signal selected by the signal selecting means, and receiving signal based on the information of the received signal branched by the branching means. Generating a correlation matrix and minimizing power and calculating a weight value for performing interference removal, a weight value calculated by the reception weight calculation means, and a reception received by the reception means A received signal weight multiplying unit for multiplying a signal, a received signal frequency determining unit for determining a frequency of a received signal to be received by the receiving unit based on information of the received signal selected by the signal selecting unit, and Transmission signal weight multiplication means for multiplying a transmission signal by a predetermined weight value based on information on the reception signal branched by the branching means, and transmission means based on information on the reception signal selected by the signal selection means Transmission signal frequency determining means for determining the frequency of a transmission signal to be transmitted by the transmission / reception device It is.

  According to the present invention, in the above invention, the transmission signal weight multiplying means includes an estimation means for estimating in which direction directivity nulls can be generated when the reception weight is used as it is on the transmission side, and directivity Generates a virtual channel response vector determined from the phase response of each element determined from the element spacing determined from the element spacing corresponding to the transmission frequency and the array antenna arrangement based on the angle information of the direction in which the null is formed Response vector generation means, correlation matrix generation means for generating a correlation matrix from the virtual channel response vector, and weight acquisition means for acquiring the weight on the transmission side from the correlation matrix by power minimization. .

  Further, in order to solve the above-described problem, the present invention is connected to each of a plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, and each of the plurality of transmission / reception branching means. In the communication method by the transmission / reception apparatus comprising the transmission means and the reception means connected to each of the plurality of transmission / reception branching means, received signals obtained from at least two different frequency bands received by the reception means A step of comparing received power, and a step of determining a weighting value for a transmission signal by the transmission unit and a transmission / reception signal at the time of reception by the reception unit based on information of a reception signal having a large reception power from the comparison result. This is a communication method characterized by the above.

  Further, in order to solve the above-described problem, the present invention is connected to each of a plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, and each of the plurality of transmission / reception branching means. In the communication method by the transmission / reception apparatus comprising the transmission means and the reception means connected to each of the plurality of transmission / reception branching means, two received signals in at least two different frequency bands received by the reception means are received. A step of detecting, a step of comparing the received power of the two detected received signals, a step of selecting a received signal having a large received power obtained as a result of the previous comparison, and information on the selected received signal And generating a correlation matrix of the received signal and minimizing the power, calculating a weighting value for performing interference removal, and calculating the weighting Multiplying the value by the received signal received by the receiving means, determining the frequency of the received signal to be received by the receiving means based on the information of the selected received signal, and A communication method comprising: multiplying a predetermined weight value; and determining a frequency of a transmission signal to be transmitted based on information of the selected reception signal having a large reception power.

  Further, in order to solve the above-described problem, the present invention is connected to each of a plurality of antenna elements, a plurality of transmission / reception branching means connected to each of the plurality of antenna elements, and each of the plurality of transmission / reception branching means. In the communication method by the transmission / reception apparatus comprising the transmission means and the reception means connected to each of the plurality of transmission / reception branching means, two received signals in at least two different frequency bands received by the reception means are received. A step of detecting, a step of comparing the received power of the two detected received signals, a step of selecting a received signal having a large received power obtained from the comparison result, and information on the selected received signal And generating a correlation matrix of the received signal and minimizing the power to calculate a weighting value for performing interference removal, and receiving the weighting value and the receiving value. Multiplying the received signal to be received, determining the frequency of the received signal to be received by the receiving means based on the information of the selected received signal, and based on the information of the selected received signal And a step of multiplying the transmission signal by a predetermined weight value and determining a frequency of the transmission signal to be transmitted by the transmission means based on the information of the selected reception signal. Is the method.

  According to the present invention, based on information of a received signal having a large received power among received signals obtained from at least two different frequency bands, weight values for transmission and reception signals at the time of transmission and reception are determined. Therefore, by performing interference removal by the array antenna using the characteristics of the FDD method in the secondary system, it is possible to efficiently prevent cognitive while avoiding interference with the primary system without providing any new additional function in the primary system. The advantage that radio can be realized is obtained.

  Further, according to the present invention, at least two received signals in two different frequency bands are detected, the received powers of the two detected 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 the information of the selected received signal, calculate a weight value for performing interference removal, and calculate the weight value and the received signal. Multiply the signal, determine the frequency of the received signal to be received based on the information of the selected received signal, multiply the transmission signal by a predetermined weight value, and based on the information of the selected received signal, The frequency of the transmission signal to be transmitted is determined. Therefore, by performing interference removal by the array antenna using the characteristics of the FDD method in the secondary system, it is possible to efficiently prevent cognitive while avoiding interference with the primary system without providing any new additional function in the primary system. The advantage that radio can be realized is obtained.

  Further, according to the present invention, the weighting value for performing interference removal is calculated by calculating the correlation matrix of the signal and the minimum eigenvector obtained by eigenvalue decomposition. 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.

  In addition, according to the present invention, two received signals in at least two different frequency bands are detected, the received power of the two received signals detected is compared, and the received power of the received power obtained from the comparison result is compared. Selects a large received signal, branches the selected received signal, creates a correlation matrix of the received signal and minimizes power based on the branched received signal information, and weights to remove interference Is calculated and multiplied by the received signal, the frequency of the received signal to be received is determined based on the information of the selected received signal, and a predetermined weight is assigned to the transmitted signal based on the information of the branched received signal While multiplying the value, the frequency of the transmission signal to be transmitted is determined. Therefore, by performing interference removal by the array antenna using the characteristics of the FDD method in the secondary system, it is possible to efficiently prevent cognitive while avoiding interference with the primary system without providing any new additional function in the primary system. The advantage that radio can be realized is obtained.

  Further, according to the present invention, when the reception weight is used as it is on the transmission side, it is estimated in which direction the directional null can be generated, and based on the angle information of the direction in which the directional null is formed, A virtual channel response vector is generated, a correlation matrix is generated from the virtual channel response vector, and a transmission-side weight is obtained from the correlation matrix by power minimization. Therefore, in the secondary system, directivity that does not interfere with the primary system can be formed on the transmission side based on a strong signal, so that the primary system can be operated without problems even when using the secondary system. In addition, there is an advantage that no interference from the primary system 100 is received.

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

A. 1 First Embodiment FIG. 1 is a block diagram showing a configuration of a communication apparatus (access point) according to a first embodiment of the present invention. In FIG. 1, an array antenna transmission / reception device 9 has, as a basic configuration, N antennas 10-1 to 10-N and transmission / reception separating means (switches or circulators) connected to the antennas 10-1 to 10-N. 11-1 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.

  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 frequency f1 and frequency f2 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 with high reception power among the signals of frequency f1 and frequency f2.

  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 to the reception signal weight multiplication unit 17. The reception signal weight multiplication unit 17 multiplies the reception signal by the weight and outputs it as an output signal. The reception frequency determination unit 19-1 uses the reception device 13-1 to use the frequency of the reception signal with a large power for reception based on the comparison result by the power comparison unit 15-3 in the communication using the reception weight from which interference is removed. ~ 13-N is adjusted.

  Next, FIG. 2 is a block diagram showing a configuration of the reception weight multiplication unit 17. The reception weight multiplication unit 17 multiplies the reception signals y1 to yN and the weights w1 * to wN * obtained by the reception weight calculation unit 15-5 of the reception signals by multipliers 17-1-1-1 to 17-1-N. And the adder 17-2. Here, the received signals y1 to yN 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.

  1 and 2 are provided on both the base station side (access point: AP) side and the terminal side in the Secondary system. However, the number of antenna elements of the access point AP and the terminal is not necessarily the same.

Next, the operation of the first embodiment will be described.
FIG. 3 is a flowchart for explaining the operation of the first embodiment. FIG. 4 is a conceptual diagram for supplementing the explanation of the operation principle of the first embodiment. As shown in FIG. 4, assuming a pair of the primary system 100-1 and the primary system 100-2, the primary system 100-1 and the primary system 100-2 perform communication using different frequencies, respectively. . Assume an environment in which the secondary system 101 exists in the service area of this primary system. The primary system 100-2 is receiving at the frequency f1 transmitted by the primary system 100-1. On the other hand, the primary system 100-2 is transmitting at the frequency f2 received by the primary system 100-1. This is one of the common communication forms, and is generally called FDD.

  In the first embodiment, the receiver of the secondary system 101 shown in FIG. 1 can receive the signals of the frequency f1 and the frequency f2, but only one frequency is actually used for communication. The transmission / reception is performed by using one frequency band in a time division manner (TDD method).

  First, in the first embodiment, as shown in FIG. 2, signals arriving at frequencies f1 and f2 using the signal detection device 15-1 having the frequency f1 and the signal detection device 15-2 having the frequency f2 in FIG. The electric powers P (f1) and P (f2) are measured (step Sa1). Here, since the secondary system 101 has not yet started communication, the incoming signals are only the interference amounts of the primary systems 100-1 and 100-2. In addition, since the frequency difference between the frequencies f1 and f2 is a basic parameter of the wireless system, it is generally disclosed, and it is easy for the Secondary system 101 to recognize this value in advance. is there.

  Further, the magnitude relationship between the signal powers P (f1) and P (f2) is determined by the positional relationship of the Secondary system 101. For example, in the example shown in FIG. 4, since the Secondary system 101 is close to the Primary system 100-2, there is a high possibility that the received power at the frequency f2 will be high. This is because these received powers are basically inversely proportional to the propagation loss, and it is known that the propagation loss is proportional to the distance between transmission and reception. Therefore, as in the first embodiment, if signals transmitted at the frequencies f1 and f2 are received from the primary systems 100-1 and 100-2, one of the received power is increased, and a signal having a higher received power is Can be estimated with relatively high accuracy.

  In this way, in the first embodiment, it is possible to detect the arrival of signals from the primary systems 100-1 and 100-2 by a very simple method. That is, according to the first embodiment, the above-described problem with respect to (Procedure 1) is solved. In addition, when the received power is lower than a predetermined threshold value at both frequencies f1 and f2, the radio waves from the primary systems 100-1 and 100-2 are considerably small. In the area, interference from the Secondary system 100 to the Primary systems 100-1 and 100-2 is hardly a problem unless the Secondary system 100 transmits at a higher power than the Primary systems 100-1 and 100-2.

  Next, the magnitude comparison between the signal powers P (f1) and P (f2) is compared by the power comparison unit 15-3 in FIG. 1, and the signal with higher power is extracted using the signal selection unit 15-4. (Steps Sa3 and Sa4). That is, when the signal power P (f1) is larger, the signals X (i) and (i = 1 to M) that arrive at the signal power P (f1) are extracted (step Sa3). On the other hand, when the signal power P (f2) is larger, the signals X (i) and (i = 1 to M) arriving at the signal power P (f2) are extracted (step Sa4). In the example shown in FIG. 4, a signal having a frequency f2, that is, a signal coming from the Primary system 100-2 is extracted. Here, X (i) shown in FIG. 2 can be given by the following equation (1).

  Here, i represents a sample on the i-th time axis, and xk (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 Sa5).

  Here, H represents a complex conjugate transpose. This correlation matrix includes only interference components from the primary systems 100-1 and 100-2 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. The power minimization method is described, for example, in Reference 3 (Compton, RT, Jr., “The power-inversion adaptive array-Concept and performance”, IEEE Transactions on Aerospace and Electronic Systems, vol. AES-15, Nov. 1979. , p.803-814.). In the power minimization method, the weight is calculated according to the following equation (3) (step Sa6).

  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 calculation amount, the weight is sequentially calculated by a method such as RLS (Recursive Least Square) or LMS (Least Mean Square). Is also 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. When the equation (2) is decomposed into the eigenvalues shown in the following equation (4), the eigenvector ei (i = 1 to K) corresponding to the signal power and the eigenvector ei (i = K + 1 to N) corresponding to the noise power are obtained. The correlation matrix, eigenvalues, and eigenvectors have the relationship of the following equation (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 λK + 1,..., ΛN forms a null in the signal direction.

  Therefore, the eigenvector eN for the minimum eigenvalue obtained by eigenvalue decomposition can be used as the 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. Therefore, the eigenvector eN for the minimum eigenvalue obtained by eigenvalue decomposition can be used as the weight w. Moreover, as a method for obtaining the eigenvector corresponding to the minimum eigenvalue, direct eigenvalue decomposition can be performed, but it can be obtained by obtaining a sequential update method such as a power method for the inverse matrix of the correlation matrix. it can.

  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 multiplier 17. The reception weight multiplication unit 17 calculates reception weight multiplication at either the frequency f1 or the frequency f2 based on the magnitude relationship between the signal power P (f1) and the signal power P (f2). That is, the reception weight multiplying unit 17 determines whether or not the signal power P (f1) is larger than the signal power P (f2) (step Sa7), and in the case of P (f1)> P (f2) The frequency f1 is selected (step Sa8), and if P (f1) <P (f2), the frequency f2 is selected (step Sa9) and reception is performed.

  That is, reception is performed using a frequency at which received power is increased. The reception frequency is adjusted by the reception frequency determination unit 19-1 in FIG. In the example shown in FIG. 4, since P (f2)> P (f1), the base station 101-1 (access point AP) in the secondary system 101 receives at the frequency f2. In the reception weight calculation unit 15-5, the weight previously used in the reception weight calculation unit 15-5 with respect to the reception signal (desired signal from the communication partner of the Secondary system 101 + interference signal from the Primary system) is expressed by the following equation (5 ) To calculate the output signal Z (step Sa10). The output signal Z is given by the following equation.

Next, a control flow at the time of transmission will be described.
During transmission, transmission is performed at the same frequency as the reception frequency. 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 (f1) is larger than the signal power P (f2) (step Sa12), and if P (f1)> P (f2) The frequency f2 is selected (step Sa13), and if P (f1) <P (f2), the frequency f1 is selected (step Sa14).

  For example, in the example illustrated in FIG. 4, the primary system 100-2 receives the signal of the frequency f2, and thus the signal transmitted at the frequency f1 does not cause any interference to the primary system 100-2. In addition, since the primary system 100-1 is far away, there is little interference on the system. Therefore, the problem in the (procedure 2) described above can be solved by the first embodiment. At the time of transmission, first, the signal is branched by the number of antenna elements by the branching means 16 shown in FIG. Thereafter, the transmission signal weight multiplier 18 multiplies the signal by the weight. The weight used for the transmission signal weight multiplication is not a weight obtained at the time of reception, but a fixed value is given in advance. For example, when it is desired to transmit non-directionally, the weight for a certain antenna element is set to 1, and the others are set to 0.

  According to the first embodiment described above, the problems of the prior art can be solved. In other words, the primary systems 100-1 and 100-2 are not interfered, and the signals of the primary systems 100-1 and 100-2 are efficiently detected at the time of reception, and communication is performed while removing these signals. it can.

B. Second Embodiment Next, a second embodiment of the present invention will be described.
In the first embodiment described above, at the time of transmission, in order not to easily cause interference from the secondary system 101 to the primary systems 100-1 and 100-2, a signal having a frequency at which reception power becomes high for the secondary system 101. The Secondary system 101 was used (only the frequency f2 in FIG. 4). However, the Secondary system 101 does not use a low frequency signal (frequency f1 in FIG. 4). That is, the fact that both the frequency f1 and the frequency f2 are not used cannot be said to be sufficiently effective in view of the frequency utilization efficiency. In the second embodiment, on the access point AP side, null transmission to the primary systems 100-1 and 100-2 is realized even at the time of transmission, so that the secondary system 101 also uses the frequency f1 and the frequency f2. It becomes possible to operate a communication system based on the FDD method.

  FIG. 5 is a block diagram showing a configuration of a communication apparatus (access point) according to the second embodiment. FIG. 5 shows the configuration on the access point AP side, but the terminal TS side has the same configuration except that it is not necessary to use an array antenna. It should be noted that portions corresponding to those in FIG.

  In the second embodiment, the signal selected by the signal selection unit 15-4 is supplied to the branching unit 15-6. The branching unit 15-6 supplies the selected signal to the reception signal weight calculation unit 20 and also supplies it to the transmission signal weight calculation unit 21. The reception weight calculation unit 20 calculates the reception weight in the same manner as the reception weight calculation unit 15-5 of the first embodiment described above. The transmission signal weight calculation unit 21 calculates the transmission weight in the same manner as the reception weight calculation unit 20.

  FIG. 6 is a block diagram showing a configuration of the transmission weight calculation unit 18 according to the second embodiment. Also on the transmission side, transmission is performed using the weights w1 * to wN * obtained by the transmission weight calculation unit 21. The transmission signal S is first branched into N signals equal to the number of antennas by the branching means 18-1. The N branched signals S, S,..., S are multiplied by the values of the first to Nth weights w1 * to wN * by multipliers 18-2-1 to 18-2-N. To do. 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.

  In the second embodiment, as described above, in the same way as in the first embodiment, reception weight calculation and weighting by the reception weight are performed, and transmission weight calculation and weighting by the transmission weight are newly performed. Is a feature. First, when the power comparison unit 15-3 illustrated in FIG. 5 determines that the signal power P (f1) at the frequency f1 is larger than the signal power P (f2) at the frequency f2, the signal of the signal at the frequency f1. Is selected by the signal selection unit 15-4.

  On the other hand, when it is determined that the signal power P (f1) of the frequency f1 is smaller than the signal power P (f2) of the frequency f2, the signal selection unit 15-4 selects the signal of the signal of the frequency f1. That is, the reception weight and the transmission weight are calculated using a signal having a frequency determined to be large by the power comparison unit 15-3. Further, in the second embodiment, reception is performed at a frequency determined to increase power, and transmission is performed at a frequency determined to decrease power. Regarding this determination, frequency information is supplied to the transmission frequency determination unit 19-2 and the reception frequency determination unit 19-1 in FIG. 5 through the power comparison unit 15-3.

  Through the above operation, the transmission weight calculation unit 21 and the reception weight calculation unit 20 calculate weights for removing interference waves. The method described in the first embodiment can be directly applied to the method for obtaining the reception weight itself.

  Next, a method for obtaining the transmission weight will be described. In the configuration of the second embodiment, since the reception frequency and the transmission frequency are different, the weight for reducing the interference wave, such as the reception weight, cannot be used as it is at the time of transmission. Therefore, the transmission weight is obtained using the following method.

  FIG. 7 is a flowchart showing how to determine the transmission weight according to the second embodiment. First, the weight obtained by the reception weight calculation unit 20 is directly acquired by the transmission weight calculation unit 21 (step Sb1). As in the first embodiment, for example, when the same frequency is used for transmission and reception as in a TDD communication system, this reception weight can be used as it is on the transmission side. However, in the second embodiment, since it is assumed that different frequencies are used for the transmission frequency and the reception frequency (FDD method), it is necessary to separately generate a weight on the transmission side.

  Therefore, in the second embodiment, first, it is estimated in which direction directivity null is possible when the reception weight is used as it is on the transmission side (step Sb2). Here, the antenna response FTx (θ) in each direction is measured using the following equation (6) (θ = 0 to 360 degrees).

  In the above equation (6), dTx / λ is different between transmission and reception when the transmission and reception frequencies are different due to the element spacing of the transmission antenna. N is the number of antenna elements. Here, a certain threshold value is provided, and an angle θ that satisfies the threshold value is picked up. Here, Equation (6) assumes the case of a linear array antenna, but there is no problem with other antenna shapes. In the case of other antenna shapes, the inside of (·) of Exp (·) in Equation (6) changes. This fact is described in, for example, Document 4 (Kikuma, “Adaptive signal processing by array antenna”, 1998, Science and Technology Publishers).

  Next, based on the estimated angle information, a transmission weight is formed again. In general, an N-element array antenna can reduce only N−1 interference waves, and therefore N−1 angle information is extracted ( Step Sb3). The standard to be extracted is the angle information obtained in step Sb2, and the values are selected in order from the smallest FTx (θ).

  Next, a virtual channel response vector is generated again based on the angle information obtained in step Sb3 (step Sb4). Here, the amplitude value is taken into account when determining the channel response. Since FTx (θ) obtained in step Sb1 is a value calculated using the weight obtained by the power minimization method, the larger the interference his power is, the smaller the value is. Therefore, if a virtual channel response vector is generated and multiplied by a value that is the reciprocal thereof, the influence can be given later when transmission weights are considered.

  The virtual channel response vector can be given by the following equation (7).

  Here, hi is a virtual channel response in the i-th antenna element, Am is an amplitude weighting, and H is a vectorization of h.

  Next, as described in the first embodiment, a correlation matrix is obtained (step Sb5), and the weight is obtained by power minimization (step Sb6), just like the processing obtained by the reception weight calculator 10. However, a weight different from the reception weight is obtained by the processing in steps Sb2 to Sb3 described above, and this can be used as a weight for interference removal on the transmission side.

  In the TDD system, since the transmission frequency and the reception frequency are the same, the directivity obtained on the reception side can be matched with the directivity obtained on the transmission side. That is, the weight for interference removal obtained by reception can be used for transmission as it is. However, in the case of FDD, since the transmission and reception frequencies are different, the weight obtained by reception cannot be used for transmission. Therefore, in the present invention, as shown in FIG. 6, the arrival direction of the interference signal is obtained using the reception weight (step Sb2), and the channel assumed on the new transmission side is estimated based on the direction. (Step Sb6).

  Here, in general, the phase incident on the element of the i-th array antenna can be given by exp (j × 2π × d / λ × (i−1) × sin (θ)) in the case of a linear array. . Here, d / λ is the element spacing normalized by the wavelength, and θ is the signal arrival direction. If multiple signals arrive, assuming that the signal arriving at the kth antenna has a constant amplitude, Σexp (j × 2π × d / λ × (k−1) × sin ( θm)). Here, θm is the mth signal. Thus, if the arrival direction of the signal can be estimated, the response of the signal in the i-th element can be estimated. In the above description, this response value is referred to as a virtual channel response. Specifically, the signal hi is given by step Sb of FIG. 6, which is a virtual channel response in the i-th element.

  According to the second embodiment described above, first, the access point AP can form directivity that does not interfere with the primary system 100 on the transmission side based on a signal with strong power, so the secondary system 101-1, Even when 101-2 is used, the primary system 100 can be operated without any problem. Further, since the access point AP performs interference removal at the time of reception, the access point AP does not receive any interference from the primary system 100 at all.

  On the other hand, on the terminal side, since signals are received at a frequency with a small amount of interference, the terminals of the secondary systems 101-1 and 101-2 are automatically set on the terminal TS side without any control. It is possible to reduce the amount of interference on the TS side. Since the terminal TS is desirably downsized and simplified, it is a very important advantage that the amount of interference can be reduced without performing any control.

  According to the first or second embodiment described above, the secondary system 101-1 and 101-2 do not perform any special control on the terminal TS side, and when there are a plurality of systems, the secondary system 101- 1, 101-2 can communicate while maintaining good quality. 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 communication apparatus (access point) by 1st Embodiment of this invention. It is a block diagram which shows the structure of the reception weight multiplication part 17 by this 1st Embodiment. It is a flowchart for demonstrating the operation | movement of this 1st Embodiment. It is a conceptual diagram for supplementing description of the operation principle of the first embodiment. It is a block diagram which shows the structure of the communication apparatus (access point) by this 2nd Embodiment. It is a block diagram which shows the structure of the transmission weight multiplication part 18 by this 2nd Embodiment. It is a flowchart which shows the calculation method of the transmission weight by this 2nd Embodiment. 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)
15-6 Branching Unit 16 Branching Unit 17 Received Signal Weight Multiplying Unit 17-1-1-1 to 17-1-N Multiplier 17-2 Adder 19-1 Reception Frequency Determining Unit (Receiving Signal Frequency Determining Unit)
19-2 Transmission signal frequency determination unit (transmission signal frequency determination means)
20 Receive weight calculation unit (Receive signal weight multiplication means)
21 Transmission weight calculation unit (transmission signal weight multiplication means)
18 Transmission signal weight multiplication section (transmission signal weight multiplication means)
18-1 Branching Unit 18-2-1 to 18-2-N Multiplier 100-1, 100-2 Primary System 101 Secondary System

Claims (8)

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 an array antenna transmitting / receiving apparatus comprising:
Based on the information of the received signal having a large received power among the received signals obtained from at least two different frequency bands received by the receiving means, to the transmission / reception signal at the time of transmission by the transmitting means and reception by the receiving means A transmission / reception apparatus comprising weighting determination means for determining a weighting value of 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 an array antenna transmitting / receiving apparatus comprising:
Signal detecting means for detecting two received signals in at least two different frequency bands received by the receiving means;
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;
Based on the information of the received signal selected by the signal selecting means, a reception weight calculating means for creating a correlation matrix of the received signal and minimizing power and calculating a weight value for performing interference removal;
Received signal weight multiplying means for multiplying the weighted value calculated by the received weight calculating means by the received signal received by the receiving means;
Received signal frequency determining means for determining the frequency of the received signal to be received by the receiving means based on the information of the received signal selected by the signal selecting means;
Transmission signal weight multiplication means for multiplying the transmission signal by a predetermined weight value;
A transmission / reception apparatus comprising: a transmission signal frequency determination unit that determines a frequency of a transmission signal to be transmitted by the transmission unit based on information of a reception signal selected by the signal selection unit.   3. The transmission / reception unit according to claim 2, wherein the reception weight calculation unit calculates a weighting value for performing interference removal by calculating a correlation matrix of the reception signal and a minimum eigenvector obtained by eigenvalue decomposition. apparatus. 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 transmission / reception apparatus comprising:
Signal detecting means for detecting two received signals in at least two different frequency bands received by the receiving means;
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;
Branching means for branching the received signal selected by the signal selecting means;
Based on the information of the reception signal branched by the branching means, the reception weight calculation means for generating a correlation matrix of the reception signal and minimizing the power and calculating a weight value for performing interference removal;
Received signal weight multiplying means for multiplying the weighted value calculated by the received weight calculating means by the received signal received by the receiving means;
Received signal frequency determining means for determining the frequency of the received signal to be received by the receiving means based on the information of the received signal selected by the signal selecting means;
Transmission signal weight multiplication means for multiplying a transmission signal by a predetermined weight value based on information of the reception signal branched by the branching means;
A transmission / reception apparatus comprising: a transmission signal frequency determination unit that determines a frequency of a transmission signal to be transmitted by the transmission unit based on information of a reception signal selected by the signal selection unit. The transmission signal weight multiplication means includes:
When the reception weight is used as it is on the transmission side, estimation means for estimating in which direction directivity null is possible;
Virtual channel response determined from the phase response for each element determined from the element spacing determined from the element spacing corresponding to the transmission frequency and the array antenna arrangement based on the angle information in the direction in which the directional null is formed Response vector generating means for generating a vector;
Correlation matrix generating means for generating a correlation matrix from a virtual channel response vector;
The transmission / reception apparatus according to claim 4, further comprising: a weight acquisition unit configured to acquire a transmission-side weight from the correlation matrix by power minimization. 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 a communication method by a transmission / reception device comprising a receiving means,
Comparing received power of received signals obtained from at least two different frequency bands received by the receiving means;
And determining a weighting value for transmission / reception signals at the time of transmission by the transmission unit and reception by the reception unit based on information of a reception signal having large reception power from the comparison result. 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 a communication method by a transmission / reception device comprising a receiving means,
Detecting two received signals of at least two different frequency bands received by the receiving means;
Comparing the received power of the two detected received signals;
A step of selecting a received signal having a large received power obtained from the previous comparison result;
Based on the information of the selected received signal, creating a correlation matrix of the received signal and minimizing power, and calculating a weighting value for performing interference removal;
Multiplying the calculated weighting value by the received signal received by the receiving means;
Determining the frequency of the received signal to be received by the receiving means based on the information of the selected received signal;
Multiplying the transmission signal by a predetermined weighting value;
Determining a frequency of a transmission signal to be transmitted based on information of the selected reception signal having a large reception power. 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 a communication method by a transmission / reception device comprising a receiving means,
Detecting two received signals of at least two different frequency bands received by the receiving means;
Comparing the received power of the two detected received signals;
Selecting a received signal having a large received power obtained by the comparison result;
Based on the information of the selected received signal, creating a correlation matrix of the received signal and minimizing power, and calculating a weighting value for performing interference removal;
Multiplying the weighted value by the received signal received;
Determining the frequency of the received signal to be received by the receiving means based on the information of the selected received signal;
Multiplying a transmission signal by a predetermined weighting value based on the information of the selected reception signal;
Determining a frequency of a transmission signal to be transmitted by the transmission means based on information of the selected reception signal.

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