JP2006279905A - Calibration method, wireless device and communications system employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for executing calibration for a plurality of antennae, even when a steering matrix is to be applied. <P>SOLUTION: A processing part 22 multiplies at least one series to be transmitted by a calibration coefficient, after multiplying it by a steering matrix Q(1), and then transmits the result. A terminal receives at least one series which is multiplied by a steering matrix Q(2). A control device 30 derives an H matrix and also receives an H matrix derived by the terminal. The control part 30 derives the calibration coefficient for the terminal, from the two H matrices and the steering matrix Q(1). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a calibration technique, and more particularly to a calibration method for correcting mismatches in a plurality of antennas, and a radio apparatus and a communication system using the same.

  An OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is a communication scheme that enables high-speed data transmission and is strong in a multipath environment. This OFDM modulation scheme is applied to IEEE802.11a, g and HIPERLAN / 2, which are standardized standards for wireless LAN (Local Area Network). Since burst signals in such a wireless LAN are generally affected by frequency selective fading, the receiving apparatus dynamically performs transmission path estimation.

In order for the receiving apparatus to perform transmission path estimation, two types of known signals are provided in the burst signal. One is a known signal provided for all carriers at the head of the burst signal, which is a so-called preamble or training signal. The other is a known signal provided for some of the carriers in the data section of the burst signal, which is a so-called pilot signal (see, for example, Non-Patent Document 1).
Sine Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai, “Channel Estimation Techniques Based on Pilot Arrangement in OFDM Systems”, IbnEnts. 48, no. 3, pp. 223-229, Sept. 2002.

  One technique for effectively using frequency resources in wireless communication is an adaptive array antenna technique. Adaptive array antenna technology controls the directivity pattern of an antenna by controlling the amplitude and phase of a signal corresponding to each of a plurality of antennas (hereinafter referred to as “adaptive pattern”). ). A technique for increasing the data rate by such an adaptive array antenna technique is a MIMO (Multiple Input Multiple Output) system. In the MIMO system, each of the transmission device and the reception device includes a plurality of antennas, and sets a channel corresponding to each antenna. Therefore, the MIMO system improves the data rate by setting channels up to the maximum number of antennas for communication between the transmission device and the reception device. Furthermore, if an OFDM modulation system is combined with such a MIMO system, the data rate is further increased.

  A combination of antenna directivity patterns in the transmission apparatus and the reception apparatus in the MIMO system is shown as follows, for example. One is a case where the antenna of the transmitting apparatus has an omni pattern and the antenna of the receiving apparatus has an adaptive pattern. Another is the case where both the antenna of the transmitting device and the antenna of the receiving device have adaptive patterns. The former can simplify the system, but the latter can control the antenna directivity pattern in more detail, thereby improving the characteristics. In the latter case, a known signal for transmission path estimation is provided in advance from the receiving apparatus so that the transmitting apparatus performs adaptive array signal processing for transmission. Further, in order to improve the accuracy of adaptive array antenna control, the transmission apparatus has transmission path characteristics corresponding to all combinations between a plurality of antennas included in the transmission apparatus and a plurality of antennas included in the reception apparatus. Should get. Therefore, the receiving apparatus transmits a known signal for transmission path estimation from all antennas. Hereinafter, a known signal for channel estimation transmitted from a plurality of antennas is referred to as a “training signal” regardless of the number of antennas to be used for data communication.

  When data is arranged after the training signal, if the number of antennas to which the training signal is transmitted differs from the number of antennas to which the data is transmitted, the signal strength for the training signal and the signal strength for the data on the receiving side. There will be a difference. If this difference increases, the signal strength for at least one of the training signal and the data cannot be properly controlled by the AGC. As a result, transmission path estimation by the training signal and data reception characteristics deteriorate. In order to suppress such deterioration, the transmission side of the training signal is directed to the data to be transmitted and the training signal (hereinafter, each of the training signals and data processed in parallel or a group is referred to as “series”). By multiplying the steering matrix, the training signal multiplied by the steering matrix and the data increased in number up to the number of training signals are generated.

  Under such circumstances, the present inventor has come to recognize the following problems. When a radio apparatus including a transmission apparatus performs adaptive array signal processing at the time of transmission, a mismatch between an analog circuit for transmission and an analog circuit for reception (hereinafter simply referred to as “mismatch”) is an antenna unit. If they are different from each other, the directivity pattern at the time of transmission is different from the desired one. That is, the wireless device calculates a weight for forming a directivity pattern at the time of transmission based on the received signal, but is not a directivity pattern to be realized by the weight due to a mismatch different for each antenna. Realize directivity pattern. Therefore, calibration for a plurality of antennas is required. Such calibration should be feasible even under conditions where the steering matrix as described above is applied.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a calibration technique for executing calibration for a plurality of antennas even when a steering matrix is applied.

  In order to solve the above-described problem, in a radio apparatus according to an aspect of the present invention, a first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and at least one to be transmitted Is multiplied by the first steering matrix and then multiplied by a calibration coefficient held in advance, and then transmitted to the communication target wireless device, and the communication target wireless device is multiplied by the second steering matrix. A communication unit that receives at least one sequence, an influence of a transmission function in the wireless device to be communicated, a second steering matrix, a wireless transmission path characteristic from the wireless device to be communicated, The first matrix reflecting the influence of the reception function of the receiver, the influence of the reception function in the wireless device to be communicated, the first steering matrix, the communication pair A first derivation unit that receives a second matrix reflecting a wireless transmission characteristic to the wireless device, an influence of a transmission function in the communication unit, and an influence of a calibration coefficient held in advance from the wireless device to be communicated, and a first derivation A first matrix derived by the unit, a second matrix received by the first derivation unit, and a second derivation unit for deriving a calibration coefficient for the wireless device to be communicated from the first steering matrix in the communication unit. .

  According to this aspect, the calibration coefficient for the wireless device to be communicated is derived by using the first matrix, the second matrix, and the first steering matrix, so that the second steering matrix in the wireless device to be communicated is recognized. Even if not, the calibration coefficient can be derived.

  The second deriving unit multiplies the inverse matrix of the first steering matrix by the second matrix, and multiplies the transposed matrix obtained by the multiplication and the inverse matrix of the first matrix, thereby providing a communication target wireless device. Means for deriving a calibration coefficient. In this case, since only the matrix operation is performed on the first matrix, the second matrix, and the first steering matrix, the calibration coefficient is derived even if the second steering matrix in the wireless device to be communicated is not recognized. it can.

The second derivation unit is configured to multiply the inverse matrix of the first steering matrix by the second matrix, and to satisfy the relationship that the product of the first matrix, the third matrix, and the first matrix becomes the first matrix. Means for deriving three matrices and means for deriving a calibration coefficient for the wireless device to be communicated by multiplying the transposed matrix obtained by multiplication and the third matrix may be included. The “third matrix” corresponds to “H ⁻ ” in the relationship of HH ⁻ H = H when the first matrix is indicated as H, and may be a generalized inverse matrix. In this case, since the third matrix is used, the calibration coefficient can be derived without recognizing the second steering matrix in the wireless device to be communicated regardless of the format of the first matrix.

  A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix, and a first derivation when the detection unit detects An instruction unit for instructing postponement of derivation of the calibration coefficient may be further provided to the unit and the second deriving unit. “Postponement” means that a calibration coefficient is derived after a predetermined period. For this reason, the calibration coefficient may be once derived, and the calibration coefficient may be derived again after a predetermined period. In this case, since the derivation of the calibration coefficient is postponed, if the number of ranks of the wireless transmission path increases during that time, the calibration coefficient can be accurately derived.

  A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix, and when detection is performed in the detection unit, Means for classifying a plurality of antennas provided in the radio apparatus into a plurality of groups, and means for instructing the first derivation unit and the second derivation unit to derive calibration coefficients in units of each of the plurality of groups; And an instruction unit including In this case, by classifying a plurality of antennas into a plurality of groups, it is possible to avoid that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix. Therefore, the calibration coefficient can be accurately derived.

  Means for classifying the plurality of antennas provided in the wireless device to be communicated into a plurality of groups when the number of antennas provided in the wireless device to be communicated is larger than the number of transmission antennas in the communication unit; And means for instructing the second derivation unit to derive the calibration coefficient in units of each of the plurality of groups. In this case, by classifying a plurality of antennas into a plurality of groups, it is possible to avoid that the number of antennas provided in the wireless device to be communicated is larger than the number of transmission antennas in the communication unit. The coefficient can be accurately derived.

  The number of antennas provided in the communication target wireless device is received from the communication target wireless device, and the number of antennas provided in the communication target wireless device is determined based on the number of received antennas. You may further provide the detection part which detects that it is larger than a number. In this case, since the number of ranks in the first matrix is detected based on the number of antennas provided in the wireless device to be communicated, the detection accuracy can be improved.

  The instructing unit may perform classification into a plurality of groups such that some of the plurality of antennas provided in the wireless device to be communicated are included in the plurality of groups. In this case, since some antennas are included in each of the plurality of groups, a calibration coefficient can be derived as a relative error with respect to some antennas.

  The first deriving unit classifies the plurality of antennas provided in the wireless device to be communicated into a plurality of temporary groups, and based on signals transmitted from the antennas included in each of the plurality of temporary groups, A first matrix corresponding to each of the temporary groups is derived, and the instruction unit performs classification into a plurality of groups based on the rank number of the first matrix corresponding to each of the plurality of temporary groups. Also good. In this case, since the classification into groups is executed so as to be combined with antennas that increase the rank number of the first matrix to some extent, it is possible to improve the accuracy of deriving calibration coefficients for the groups.

  The instructing unit may instruct the wireless device to be communicated to transmit a signal from an antenna included in each of the plurality of groups. In this case, since the signal is transmitted from the antenna included in each of the plurality of groups, the first matrix can be accurately derived.

  Another aspect of the present invention is also a wireless device. In this apparatus, a first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and communication is performed after multiplying at least one sequence to be transmitted by the first steering matrix. A communication unit that performs transmission to the target wireless device and receives at least one sequence multiplied by the second steering matrix in the communication target wireless device; Deriving the first matrix reflecting the influence of the transmission function, the second steering matrix, the wireless transmission path characteristics from the wireless device to be communicated, and the reception function in the communication unit, and the influence of the transmission function in the communication unit , Receiving the second matrix reflecting the first steering matrix, the wireless transmission characteristics to the wireless device to be communicated, and the reception function of the wireless device to be communicated from the wireless device to be communicated. Singular value decomposition is performed on the first matrix derived by the first derivation unit and the first matrix derived by the first derivation unit, and the second matrix received by the first derivation unit is multiplied by the inverse matrix of the first steering matrix. The second deriving unit, the first matrix subjected to singular value decomposition in the second deriving unit, and the second matrix subjected to singular value decomposition in the second deriving unit, the calibration coefficient for the wireless device to be communicated and the communication unit A third deriving unit for deriving a calibration coefficient.

  According to this aspect, the calibration coefficient for the communication unit and the calibration coefficient for the communication unit are derived by using the result of singular value decomposition of the first matrix and the second matrix, respectively. Even when the calibration coefficient is not derived in advance, the calibration coefficient for the wireless device to be communicated can be derived.

  The first steering matrix defined in the communication unit may be a unitary matrix. The unitary matrix as the first steering matrix defined in the communication unit is defined in the frequency domain, and may be indicated by the product of an orthogonal matrix and a matrix representing a cyclic time shift. In this case, it is effective for the OFDM system.

  A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix, and a first derivation when the detection unit detects An instruction unit for instructing postponement of derivation of the calibration coefficient may be further provided to the unit, the second derivation unit, and the third derivation unit. In this case, since the derivation of the calibration coefficient is postponed, if the number of ranks of the wireless transmission path increases during that time, the calibration coefficient can be accurately derived.

  A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix, and when detection is performed in the detection unit, Means for classifying a plurality of antennas provided in a radio apparatus into a plurality of groups, and derivation of calibration coefficients in units of the plurality of groups with respect to the first derivation unit, the second derivation unit, and the third derivation unit And an instruction unit including an instruction unit. In this case, by classifying a plurality of antennas into a plurality of groups, it is possible to avoid that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix. Therefore, the calibration coefficient can be accurately derived.

  Means for classifying a plurality of antennas provided in a communication target wireless device into a plurality of groups when the number of antennas provided in the communication target wireless device is larger than the number of transmission antennas in the communication unit; And an instruction unit including means for instructing the second derivation unit and the third derivation unit to derive the calibration coefficient in units of each of the plurality of groups. In this case, by classifying a plurality of antennas into a plurality of groups, it is possible to avoid that the number of antennas provided in the wireless device to be communicated is larger than the number of transmission antennas in the communication unit. The coefficient can be accurately derived.

  Yet another embodiment of the present invention is a communication system. In this communication system, a first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and after multiplying at least one sequence to be transmitted by the first steering matrix, A first wireless device that transmits a signal generated by multiplying a calibration coefficient held in advance, and a second wireless device that transmits a signal generated by multiplying at least one sequence to be transmitted by a second steering matrix With. The second wireless device, based on the signal received from the first wireless device, the influence of the transmission function of the first wireless device, the first steering matrix, the wireless transmission characteristics from the first wireless device, the reception of the second wireless device After deriving the first matrix reflecting the influence of the function and the previously held calibration coefficient, the first matrix is transmitted to the first radio apparatus, and the first radio apparatus is transmitted from the second radio apparatus. Based on the received signal, the influence of the transmission function in the second wireless device, the second steering matrix, the characteristics of the wireless transmission path from the second wireless device, and the influence of the reception function in the first wireless device are reflected. Means for deriving two matrices, means for deriving a calibration coefficient for the second radio apparatus from the first matrix, the second matrix, and the first steering matrix.

  According to this aspect, since the calibration coefficient for the second radio apparatus is derived by using the first matrix, the second matrix, and the first steering matrix, the second steering matrix in the second radio apparatus is not recognized. However, the calibration coefficient can be derived.

  The first radio apparatus calibrates the second radio apparatus by multiplying the inverse matrix of the first steering matrix and the first matrix, and multiplying the transposed matrix obtained by the multiplication and the inverse matrix of the second matrix. And a means for deriving a distribution coefficient. When the second matrix is an irregular matrix or not a square matrix, the first wireless device includes means for multiplying the inverse matrix of the first steering matrix by the first matrix, the second matrix, the third matrix, and the second matrix. A calibration coefficient for the second radio apparatus is obtained by multiplying the third matrix by means for deriving a third matrix satisfying the relationship that the product of the matrix and the matrix becomes the second matrix, and the transposed matrix obtained by multiplication and the third matrix. And means for deriving. The first radio apparatus has a means for multiplying an inverse matrix of the first steering matrix by the first matrix, and satisfying a relationship that a product of the second matrix, the third matrix, and the second matrix is a second matrix. Means for deriving three matrices and means for deriving a calibration coefficient for the second radio apparatus by multiplying the transposed matrix obtained by multiplication and the third matrix may be included.

  The first radio apparatus is detected by means for detecting that the rank number of the second matrix is smaller than the smaller one of the number of rows and the number of columns in the second matrix and the means for detecting. In this case, it may further include means for determining postponement of the derivation of the calibration coefficient. The first radio apparatus is detected by means for detecting that the rank number of the second matrix is smaller than the smaller one of the number of rows and the number of columns in the second matrix and the means for detecting. In this case, it may include means for classifying a plurality of antennas provided in the second radio apparatus into a plurality of groups, and means for determining derivation of a calibration coefficient in units of each of the plurality of groups.

  A first wireless device configured to classify a plurality of antennas provided in the second wireless device into a plurality of groups when the number of antennas provided in the second wireless device is larger than the number of transmission antennas; And means for determining the derivation of the calibration coefficient in units of each of the above. The first wireless device receives the number of antennas provided in the second wireless device from the second wireless device, and based on the number of received antennas, the number of antennas provided in the second wireless device is equal to that of the transmission antenna. A means for detecting that the number is larger than the number may be further provided.

  In the first radio apparatus, classification into a plurality of groups may be performed such that some of the plurality of antennas provided in the second radio apparatus are included in the plurality of groups. The first radio apparatus classifies the plurality of antennas included in the second radio apparatus into a plurality of temporary groups, and based on signals transmitted from the antennas included in each of the plurality of temporary groups, Means for deriving a second matrix corresponding to each of the groups, and means for performing classification into a plurality of groups based on the rank number of the second matrix corresponding to each of the plurality of temporary groups. Good. The first radio apparatus may instruct the second radio apparatus to transmit a signal from an antenna included in each of the plurality of groups.

  Yet another aspect of the present invention is also a communication system. In this communication system, a first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and the first steering matrix is multiplied by at least one sequence to be transmitted. A first wireless device that transmits the generated signal; and a second wireless device that transmits the signal generated by multiplying at least one sequence to be transmitted by the second steering matrix. The second wireless device, based on the signal received from the first wireless device, the influence of the transmission function of the first wireless device, the first steering matrix, the wireless transmission characteristics from the first wireless device, the reception of the second wireless device After deriving the first matrix reflecting the influence of the function, the derived first matrix is transmitted to the first wireless device, and the first wireless device receives the first matrix based on the signal received from the second wireless device. Means for deriving a second matrix reflecting the influence of the transmission function in the two wireless devices, the second steering matrix, the characteristics of the wireless transmission path from the second wireless device, and the influence of the reception function in the first wireless device; Means for deriving a calibration coefficient for the first radio apparatus and a calibration coefficient for the second radio apparatus by performing singular value decomposition on the result of multiplying one matrix by the inverse matrix of the first steering matrix and the second matrix, respectively; including.

  According to this aspect, the calibration coefficient for the wireless device to be communicated and the calibration coefficient for the communication unit are derived by using the singular value decomposition results of the first matrix and the second matrix, respectively. Even if the calibration coefficient for is not derived in advance, the calibration coefficient for the second radio apparatus can be derived.

  The first steering matrix defined in the first radio apparatus may be a unitary matrix. The unitary matrix as the first steering matrix defined in the first radio apparatus is defined in the frequency domain, and may be indicated by the product of an orthogonal matrix and a matrix representing a cyclic time shift.

  Yet another embodiment of the present invention is a calibration method. In this method, a first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and after multiplying at least one sequence to be transmitted by the first steering matrix, A wireless device that performs transmission to the wireless device to be communicated after multiplying the held calibration coefficient and receives at least one sequence multiplied by the second steering matrix in the wireless device to be communicated. A calibration method for deriving a calibration coefficient for a wireless device in which the wireless device to be communicated affects the transmission function, the second steering matrix, the wireless transmission path characteristics from the wireless device to be communicated, Deriving the first matrix reflecting the influence of the reception function in the device, and the wireless device to be communicated The second matrix reflecting the influence of the reception function, the first steering matrix, the wireless transmission characteristics to the wireless device to be communicated, the influence of the transmission function in the wireless device, and the influence of the calibration coefficient held in advance The calibration coefficient for the wireless device to be communicated is derived from the first matrix, the second matrix, and the first steering matrix.

  A step of multiplying the inverse matrix of the first steering matrix by the second matrix, and multiplying the transposed matrix resulting from the multiplication and the inverse matrix of the first matrix to derive a calibration coefficient for the wireless device to be communicated Steps may be included. If the first matrix is an irregular matrix or not a square matrix, the step of multiplying the inverse matrix of the first steering matrix by the second matrix and the product of the first matrix, the third matrix, and the first matrix are Deriving a third matrix that satisfies the relationship of becoming one matrix, and deriving a calibration coefficient for the wireless device to be communicated by multiplying the transposed matrix obtained by multiplication and the third matrix. May be included. Multiplying the inverse of the first steering matrix by the second matrix, and deriving a third matrix that satisfies a relationship in which the product of the first matrix, the third matrix, and the first matrix becomes the first matrix. And a step of deriving a calibration coefficient for the wireless device to be communicated by multiplying the transposed matrix obtained by the multiplication and the third matrix.

  Detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix, and deferring the derivation of the calibration coefficient if detected. May be further included. A step of detecting that the rank number of the first matrix is smaller than the smaller one of the number of rows and the number of columns in the first matrix; The method may further comprise a step of classifying the plurality of antennas into a plurality of groups and a step of determining derivation of a calibration coefficient in units of each of the plurality of groups.

  When the number of antennas included in the communication target wireless device is larger than the number of transmission antennas, a step of classifying the plurality of antennas included in the communication target wireless device into a plurality of groups, and a unit of each of the plurality of groups And determining the derivation of the calibration coefficient. The number of antennas provided in the communication target wireless device is received from the communication target wireless device, and the number of antennas provided in the communication target wireless device is larger than the number of transmission antennas based on the number of received antennas. You may further comprise the step which detects that it is large.

  Classification into a plurality of groups may be performed such that some of the plurality of antennas provided in the wireless device to be communicated are included in the plurality of groups. The plurality of antennas provided in the wireless device to be communicated are classified into a plurality of temporary groups, and each of the plurality of temporary groups is determined based on signals transmitted from the antennas included in each of the plurality of temporary groups. A step of deriving a corresponding first matrix and a step of performing classification into a plurality of groups based on the rank number of the first matrix corresponding to each of the plurality of temporary groups may be further included. The wireless device to be communicated may be instructed to transmit a signal from an antenna included in each of the plurality of groups.

  Yet another embodiment of the present invention is also a calibration method. In this method, a first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and communication is performed after multiplying at least one sequence to be transmitted by the first steering matrix. In order to derive a calibration coefficient for the communication target wireless device in the wireless device that performs transmission to the target wireless device and receives at least one sequence multiplied by the second steering matrix in the communication target wireless device. In this calibration method, the influence of the transmission function in the wireless device to be communicated, the second steering matrix, the characteristics of the wireless transmission path from the wireless device to be communicated, and the influence of the reception function in this wireless device are reflected. The first matrix is derived, and the influence of the transmission function in the wireless device, the first steering matrix, the wireless device to be communicated The second matrix reflecting the wireless transmission characteristics and the reception function of the communication target wireless device is received from the communication target wireless device, and the result obtained by multiplying the second matrix by the inverse matrix of the first steering matrix and the first matrix Respectively, to derive a calibration coefficient for the wireless device to be communicated and a calibration coefficient for the communication device.

  The first steering matrix may be a unitary matrix. The unitary matrix as the first steering matrix is defined in the frequency domain, and may be indicated by the product of an orthogonal matrix and a matrix representing a cyclic time shift.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, calibration for a plurality of antennas can be executed even when a steering matrix is applied.

  Before describing the present invention in detail, an outline will be described. An embodiment of the present invention relates to a MIMO system including a base station device and a terminal device. Here, the base station apparatus performs beamforming transmission, but the terminal apparatus performs multiplication of the steering matrix without performing beamforming transmission. The base station apparatus performs calibration for each terminal apparatus before performing beamforming. When executing the calibration, the base station apparatus performs multiplication of the steering matrix without executing beamforming transmission. As described above, the training signal and data included in at least one sequence to be transmitted are multiplied by the steering matrix, thereby reducing the power difference between the training signal and the data receiving side. The base station apparatus performs beamforming transmission using the transmission path characteristics estimated from the training signal multiplied by such a steering matrix. The base station apparatus and the terminal apparatus execute calibration for the purpose of reducing mismatches different for each antenna. For this reason, calibration is required that can cope with a case where a steering matrix is applied to a training signal exchanged during calibration. Further, in order to facilitate the device configuration of the terminal device, it is desirable that calibration for the terminal device is performed in the base station device. Therefore, in this embodiment, calibration is performed as follows.

  As a premise, it is assumed that the calibration for the base station apparatus has already been completed. In order to cause the terminal device to estimate the transmission path characteristics, the base station device transmits a training signal. The terminal apparatus estimates transmission path characteristics corresponding to combinations of a plurality of antennas of the base station apparatus and a plurality of antennas of the terminal apparatus (hereinafter, the transmission path characteristics corresponding to each combination are combined into a matrix format, etc. Is called "H matrix"). Also, the H matrix estimated in the terminal device corresponds to the transmission path characteristics of the downlink. Further, the terminal device transmits a training signal in order to cause the base station device to estimate the transmission path characteristics. At that time, the terminal device transmits the downlink H matrix as data. The terminal device may transmit the transposition of the H matrix as data. In that case, if the base station apparatus recognizes the transposition of the H matrix, it can perform the same operation as the operation described below. The base station apparatus estimates the transmission path characteristics corresponding to the combinations of the plurality of antennas of the base station apparatus and the plurality of antennas of the terminal apparatus as an H matrix. The H matrix corresponds to an uplink transmission path characteristic.

  Here, the transmission path characteristics included in the H matrix include the effects of mismatch between the steering matrix and the analog circuit of the transmission / reception system, in addition to the transmission path characteristics as the wireless transmission path. Hereinafter, such comprehensive transmission path characteristics are also simply referred to as transmission path characteristics. The base station apparatus performs calibration for the terminal apparatus using the uplink H matrix, the downlink H matrix, and the steering matrix in the base station apparatus, and derives a calibration coefficient. The calibration coefficient is used at the time of beamforming transmission to be executed later. Through the processing as described above, the base station apparatus can execute calibration for the terminal apparatus without recognizing the steering matrix applied in the terminal apparatus.

  FIG. 1 shows a spectrum of a multicarrier signal according to an embodiment of the present invention. In particular, FIG. 1 shows the spectrum of a signal in the OFDM modulation scheme. One of a plurality of carriers in the OFDM modulation system is generally called a subcarrier, but here, one subcarrier is designated by a “subcarrier number”. Here, as in the IEEE802.11a standard, 53 subcarriers from subcarrier numbers “−26” to “26” are defined. The subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal. Each subcarrier is modulated by a variably set modulation scheme.

  As a modulation method, any one of BPSK (Binary Phase Shift Keying), QSPK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM is used. Also, convolutional coding is applied to these signals as an error correction method. The coding rate of convolutional coding is set to 1/2, 3/4, and the like. Furthermore, the number of antennas used in the MIMO system is variably set. As a result, the data rate is also variably set by variably setting the modulation scheme, coding rate, and number of antennas.

  FIG. 2 shows a configuration of a communication system according to an embodiment of the present invention. The communication system 100 includes a base station device 10 and a terminal device 90. The base station apparatus 10 includes a first antenna 12a, a second antenna 12b, a third antenna 12c, and a fourth antenna 12d that are collectively referred to as an antenna 12, and the terminal apparatus 90 is a first antenna that is collectively referred to as an antenna 14. 14a, the second antenna 14b, the third antenna 14c, and the fourth antenna 14d. In the downlink, the base station apparatus 10 corresponds to a transmission apparatus, and corresponds to a reception apparatus of the terminal apparatus 90. The uplink is the opposite of the downlink.

  Before describing the configuration of the communication system 100, an outline of a MIMO system will be described. It is assumed that the downlink is an object of explanation and data is transmitted from the base station apparatus 10 to the terminal apparatus 90. The base station apparatus 10 transmits different data from each of the first antenna 12a to the fourth antenna 12d. As a result, the data rate is increased. The terminal device 90 receives data from the first antenna 14a to the fourth antenna 14d. Further, the terminal device 90 independently demodulates the data transmitted from each of the first antenna 12a to the fourth antenna 12d by adaptive array signal processing.

  Here, since the number of antennas 12 is “4” and the number of antennas 14 is also “4”, the combination of transmission paths between the antennas 12 and 14 is “16”. A transmission path characteristic between the i-th antenna 12i and the j-th antenna 14j is denoted by hij. In the figure, the transmission path characteristic between the first antenna 12a and the first antenna 14a is h11, the transmission path characteristic between the first antenna 12a and the second antenna 14b is h12, the second antenna 12b and the first antenna. 14a, the transmission path characteristic between the second antenna 12b and the second antenna 14b is h22, and the transmission path characteristic between the fourth antenna 12d and the fourth antenna 14d is h44. Has been. Note that transmission lines other than these are omitted for clarity of illustration.

  The terminal device 90 operates such that data transmitted from the first antenna 12a to the second antenna 12b can be independently demodulated by adaptive array signal processing. Further, the base station apparatus 10 performs adaptive array signal processing from the first antenna 12a to the fourth antenna 12d during transmission. As described above, the base station apparatus 10 on the transmission side also executes adaptive array signal processing, thereby ensuring space division in the MIMO system. As a result, since interference between signals transmitted from the plurality of antennas 12 is reduced, this embodiment can improve communication quality. Note that the operations of the base station device 10 and the terminal device 90 may be reversed.

Although details will be described later, in the configuration of the communication system 100 as described above, the calibration is executed as follows. The base station apparatus 10 defines a steering matrix Q (1). The base station device 10 multiplies at least one sequence to be transmitted by Q (1), thereby generating training signals multiplied by the steering matrix and data whose number is increased to the number of training signals. Furthermore, the base station apparatus 10 transmits a signal generated by multiplying the calibration coefficient C _AUTO (1) held in advance. The terminal device 90 transmits a signal generated by multiplying the training signal and data by the steering matrix Q (2).

Further, the terminal device 90 derives an H matrix based on the training signal received from the base station device 10. The H matrix includes the influence of the transmission function of the base station apparatus 10, the steering matrix Q (1), the wireless transmission characteristics from the base station apparatus 10, the influence of the reception function of the terminal apparatus 90, and the calibration coefficient C _AUTO (1). The effect of is reflected. Further, the terminal device 90 transmits the derived H matrix to the base station device 10. The base station apparatus 10 derives an H matrix based on the training signal received from the terminal apparatus 90. This H matrix reflects the influence of the transmission function at the terminal device 90, the steering matrix Q (2), the wireless transmission path characteristics from the terminal device 90, and the influence of the reception function at the base station device 10. Further, the base station apparatus 10 derives a calibration coefficient for the terminal apparatus 90 from the two H matrices and the steering matrix Q (1).

  FIG. 3 shows the configuration of the base station apparatus 10. The base station apparatus 10 includes a first radio unit 20a, a second radio unit 20b, a fourth radio unit 20d, a processing unit 22, a modem unit 24, an IF unit 26, and a control unit 30, which are collectively referred to as a radio unit 20. Further, as signals, a first time domain signal 200a, a second time domain signal 200b, a fourth time domain signal 200d, which are collectively referred to as a time domain signal 200, a first frequency domain signal 202a, which is collectively referred to as a frequency domain signal 202, and a second time domain signal 200b. Includes a frequency domain signal 202b. Here, in order to clarify the explanation, the number “2” of data included in the sequence to be transmitted and the received sequence and the number “4” of training signals are fixed. However, these numbers may be adjusted adaptively. In the following description, the transmission operation corresponds to downlink communication, and the reception operation corresponds to uplink communication.

  As a reception operation, the radio unit 20 performs frequency conversion on a radio frequency signal received by the antenna 12 and derives a baseband signal. The radio unit 20 outputs the baseband signal as the time domain signal 200 to the processing unit 22. In general, baseband signals are formed by in-phase and quadrature components, so they should be transmitted by two signal lines. Here, for clarity of illustration, only one signal line is used. Shall be shown. An AGC (Automatic Gain Control) and an A / D conversion unit are also included. As a transmission operation, the radio unit 20 performs frequency conversion on the baseband signal from the processing unit 22 and derives a radio frequency signal. Here, a baseband signal from the processing unit 22 is also shown as a time domain signal 200. The radio unit 20 outputs a radio frequency signal to the antenna 12. Further, a PA (Power Amplifier) and a D / A converter are also included. The time domain signal 200 is a multicarrier signal converted into the time domain, and is a digital signal. Further, the signal processed in the radio unit 20 forms a burst signal. In the burst format, a training signal is arranged in the preceding stage and data is arranged in the succeeding stage.

  As a receiving operation, the processing unit 22 converts each of the plurality of time domain signals 200 into the frequency domain, and performs adaptive array signal processing on the frequency domain signal. The processing unit 22 outputs the result of adaptive array signal processing as the frequency domain signal 202. One frequency domain signal 202 corresponds to data included in one sequence transmitted from a terminal device 90 (not shown). As a transmission operation, the processing unit 22 receives the frequency domain signal 202 as a frequency domain signal from the modem unit 24 and performs adaptive array signal processing. That is, beam forming is executed. Further, the processing unit 22 uses a calibration coefficient for the terminal device 90 at the time of beamforming. Furthermore, the processing unit 22 corrects the signal obtained by performing the adaptive array signal processing using the calibration coefficient for the base station apparatus 10. When executing calibration, the processing unit 22 performs multiplication of the steering matrix without executing beamforming.

  The processing unit 22 converts the frequency domain signal into the time domain and outputs the time domain signal 200. It is assumed that the number of antennas 12 to be used in the transmission process is specified by the control unit 30. Here, the frequency domain signal 202, which is a frequency domain signal, includes a plurality of subcarrier components as shown in FIG. For the sake of clarity, it is assumed that the signals in the frequency domain are arranged in the order of subcarrier numbers to form a serial signal. Further, the calibration coefficient for the terminal device 90 and the calibration coefficient for the base station apparatus 10 have different values for each antenna 12 unit. These coefficients are derived by the control unit 30.

  FIG. 4 shows the configuration of a signal in the frequency domain. Here, one combination of subcarrier numbers “−26” to “26” shown in FIG. 1 is referred to as an “OFDM symbol”. In the “i” th OFDM symbol, subcarrier components are arranged in the order of subcarrier numbers “1” to “26” and subcarrier numbers “−26” to “−1”. Also, the “i−1” th OFDM symbol is placed before the “i” th OFDM symbol, and the “i + 1” th OFDM symbol is placed after the “i” th OFDM symbol. And

  Returning to FIG. The modem unit 24 performs demodulation and decoding on the frequency domain signal 202 from the processing unit 22 as reception processing. Note that demodulation and decoding are performed in units of subcarriers. The modem unit 24 outputs the decoded signal to the IF unit 26. Further, the modem unit 24 performs encoding and modulation as transmission processing. The modem unit 24 outputs the modulated signal to the processing unit 22 as the frequency domain signal 202. It is assumed that the modulation scheme and coding rate are specified by the control unit 30 during the transmission process.

  The IF unit 26 combines signals from the plurality of modulation / demodulation units 24 as a reception process to form one data stream. The IF unit 26 outputs a data stream. In addition, the IF unit 26 inputs one data stream as transmission processing and separates it. Further, the separated data is output to a plurality of modems 24.

  The control unit 30 controls the timing of the base station apparatus 10 and the like. Further, the control unit 30 derives a calibration coefficient for the terminal device 90 and a calibration coefficient for the base station device 10. Assuming that the calibration coefficient for the base station apparatus 10 has already been derived, the procedure for deriving the calibration coefficient for the terminal apparatus 90 will be briefly described. The calibration procedure described below is performed before beamforming transmission is executed on the transmission side. Details will be described later. As described above, the processing unit 22 or the like performs transmission after multiplying the training signal and data by the steering matrix Q (1) and then by multiplying the calibration coefficient for the base station apparatus 10. Further, the processing unit 22 or the like receives at least one sequence multiplied by the steering matrix Q (2) in the terminal device 90 (not shown). The control unit 30 derives the H matrix via the processing unit 22 and the like. Further, the control unit 30 receives the H matrix derived by the terminal device 90 (not shown). The control unit 30 derives a calibration coefficient for the terminal device 90 from these H matrix and steering matrix Q (1).

  Here, it is assumed that the variation amount of the calibration coefficient for the base station apparatus 10 is small. Therefore, once the calibration coefficient for the base station apparatus 10 is derived, it is used for several days, for example. Therefore, it can be said that it is a quasi-static value. On the other hand, the calibration coefficient for the terminal device 90 is different for each terminal device 90. Therefore, the base station apparatus 10 uses the calibration coefficient for the terminal apparatus 90 while switching according to the terminal apparatus 90 with which it is communicating. The control unit 30 may store calibration coefficients for a plurality of terminal devices 90 and use calibration coefficients corresponding to the terminal devices 90 that are communicating.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 5 shows the configuration of the processing unit 22. The processing unit 22 includes an FFT (Fast Fourier Transform) unit 50, a first synthesis unit 54a, a second synthesis unit 54b, a fourth synthesis unit 54d, a spatial dispersion unit 56, a transmission side correction unit 62, An IFFT unit 64 is included.

  The FFT unit 50 receives a plurality of time domain signals 200 and performs a Fourier transform on each of them to derive a frequency domain signal. As described above, signals corresponding to subcarriers are serially arranged in the order of subcarrier numbers as one frequency domain signal.

  The synthesizer 54 performs adaptive array signal processing on the frequency domain signal from the FFT unit 50. That is, array synthesis is executed. Here, it is assumed that the steering matrix is also applied to the signal transmitted from the terminal apparatus 90, and the number of data before the steering matrix is applied in the terminal apparatus 90 is “2”. Corresponding to this, out of the synthesizer 54, the first synthesizer 54a and the second synthesizer 54b output data. Further, the remaining combining unit 54 calculates transmission line characteristics in order to generate the above-described H vector.

  The synthesizer 54 includes a plurality of multipliers (not shown), and each of the plurality of multipliers weights the frequency domain signal with a reception weight vector. An adder (not shown) is also provided, and the adder adds the outputs of a plurality of multipliers. Here, since the signals in the frequency domain are arranged in the order of the subcarrier numbers, the multiplication of the reception weight vector in the multiplier corresponds to that. Further, the addition unit adds the multiplication results in units of subcarriers. As a result, the added signals are also serially arranged in the order of subcarrier numbers as shown in FIG. The added signal is the frequency domain signal 202 described above.

  Also in the following description, when the signal to be processed corresponds to the frequency domain, the processing is basically executed in units of subcarriers. Here, in order to simplify the description, the processing in one subcarrier will be described. Therefore, processing for a plurality of subcarriers can be handled by executing processing on one subcarrier in parallel or serially.

  The synthesizing unit 54 derives a reception weight vector based on the frequency domain signal, the frequency domain signal 202, and the reference signal from the FFT unit 50. Here, the synthesizer 54 stores a training signal as a reference signal. In the data period, the frequency domain signal 202 is determined based on a predetermined threshold value, and the result is used as a reference signal. The determination may be a soft determination instead of a hard determination. The method for deriving the reception weight vector may be any method, one of which is the derivation by the LMS (Least Mean Square) algorithm. Further, the synthesizer 54 derives a reception response vector that is a transmission path characteristic by correlation processing. Since this is a known technique, a description thereof will be omitted. The derived reception response vectors are combined into a matrix format together with the reception response vectors derived in the other synthesis unit 54 for use in calibration. This corresponds to the aforementioned H matrix. It is assumed that such a function for deriving the H matrix is also provided in the terminal device 90.

  The space dispersion unit 56 performs beam forming during communication. On the other hand, at the time of calibration, the spatial dispersion unit 56 multiplies the training signal and the data by a steering matrix. As a result, a training signal multiplied by the steering matrix and data increased in number up to the number of training signals are generated. Here, the spatial distribution unit 56 extends the order of the input data to the number of training signals before performing multiplication. The number of input data is “2”, which is represented by “Nin” here. Therefore, the input data is indicated by a vector “Nin × 1”. Further, the number of training signals is “4”, and is represented by “Nout” here. The spatial distribution unit 56 extends the order of the input data from Nin to Nout. That is, the vector “Nin × 1” is expanded to the vector “Nout × 1”. At that time, “0” is inserted into the components from the Nin + 1 line to the Nout line.

ステアリング行列は、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。また、Ｗは、直交行列であり、「Ｎｏｕｔ×Ｎｏｕｔ」の行列である。直交行列の一例は、ウォルシュ行列やフーリエ行列である。ここで、ｌは、サブキャリア番号を示しており、ステアリング行列による乗算は、サブキャリアを単位にして実行される。さらに、Ｃは、以下のように示され、ＣＤＤ（Ｃｙｃｌｉｃ Ｄｅｌａｙ Ｄｉｖｅｒｓｉｔｙ）のために使用される。

The steering matrix S is shown as follows.

The steering matrix is a “Nout × Nout” matrix. W is an orthogonal matrix, which is a “Nout × Nout” matrix. An example of the orthogonal matrix is a Walsh matrix or a Fourier matrix. Here, l indicates a subcarrier number, and multiplication by the steering matrix is executed in units of subcarriers. Further, C is shown as follows and is used for CDD (Cyclic Delay Diversity).

  Here, δ represents the shift amount. From the above description, it can be said that the steering matrix has been subjected to a cyclic time shift with a row of the orthogonal matrix as one unit. Further, the steering matrix defined in the spatial dispersion unit 56 is the above-described Q (1), and the steering matrix defined in the terminal device 90 (not shown) is the above-described Q (2). Note that the base station apparatus 10 generally does not recognize the steering matrix Q (2).

  At the time of communication, the space dispersion unit 56 performs beam forming. The spatial dispersion unit 56 estimates a transmission weight vector necessary for beamforming from the reception weight vector. The method for estimating the transmission weight vector is arbitrary, but as the simplest method, the reception weight vector may be used as it is. Alternatively, the reception weight vector may be corrected by a conventional technique in consideration of the Doppler frequency fluctuation of the propagation environment caused by the time difference between the reception process and the transmission process. Alternatively, transmission beam forming using singular value decomposition may be performed. This can be said to be eigenmode transmission. Here, the received transmission response vector derived by the combining unit 54 is multiplied by a calibration coefficient for the terminal device 90 to obtain a corrected transmission path characteristic, and a transmission weight vector is derived from the corrected transmission path characteristic. Note that the calibration coefficient for the terminal device 90 is acquired from the control unit 30 (not shown). In addition, the calibration coefficient for the terminal device 90 has different values in units of antennas, and further has different values in units of subcarriers.

  The spatial dispersion unit 56 weights the signal with the transmission weight vector. The transmission side correction unit 62 multiplies the signal from the spatial dispersion unit 56 by a calibration coefficient in the base station apparatus 10. At that time, the transmission side correction unit 62 acquires a calibration coefficient for the base station apparatus 10 from the control unit 30 (not shown). The IFFT unit 64 performs inverse Fourier transform on the signal from the transmission side correction unit 62 to convert it into a time domain signal. In FIG. 5, the first time domain signal 200a and the like are shown in two places. These are signals in one direction, and these correspond to the first time domain signal 200a and the like which are bidirectional signals in FIG.

  FIGS. 6A to 6B show signal formats in the communication system 100. FIG. FIG. 6A shows the format in the sequence input to the spatial distribution unit 56. The top level of the figure shows the first series, and the second series, the third series, and the fourth series are shown as the stage moves down. Here, “4” “Long Training Sequences” are added to each of “4” sequences, which are a plurality of sequences. On the other hand, data of “2” series, which is at least one of a plurality of series, is added as “first data” and “second data”. Here, “LTS” is a signal used for estimation of transmission path characteristics. “LTS” corresponds to a training signal. In addition, other signals other than these, for example, “STS (Short Training Sequence)” to be used for timing synchronization or the like are also arranged, but are omitted here.

  FIG. 6B shows a plurality of sequences output from the spatial dispersion unit 56 when calibration is executed. The LTS in FIG. 6A is “LTS ′” as a result of the multiplication of the steering matrix. In FIG. 6B, this is indicated as “first LTS ′” to “fourth LTS ′”. The “first data” and “second data” in FIG. 6A are four series of data as a result of multiplication of the steering matrix. In FIG. 6B, this is shown as “first data” to “fourth data”.

  The calibration operation with the above configuration will be described. Here, the response on the transmitting side of the base station device 10 is indicated as A (1), the response on the receiving side of the base station device 10 is indicated as B (1), and the response on the transmitting side of the terminal device 90 is indicated by A ( 2), and the response on the receiving side of the terminal device 90 is indicated as B (2). A and B are diagonal matrices. In addition, the H matrix derived in the terminal device 90 is denoted as H (1 → 2) ′, and the H matrix derived in the base station device 10 is denoted as H (2 → 1) ′. On the other hand, the H matrix reflecting only the radio transmission characteristics is represented as H (1 → 2) and H (2 → 1) corresponding to the above.

基地局装置１０は、以上のＨ行列を次のように変形させる。

なお、α、β、ｈは、Ａ、Ｂ、Ｈに含まれる成分である。また、基地局装置１０によって導出されるＨ行列は、次のように示される。

First, an operation for the base station apparatus 10 to derive the calibration coefficient C _AUTO (1) for the base station apparatus 10 will be described. At that time, the base station apparatus 10 transmits a training signal to the terminal apparatus 90, but the terminal apparatus 90 transmits a signal from one antenna 14 to the base station apparatus 10. The H matrix derived by the terminal device 90 is shown as follows.

The base station apparatus 10 transforms the above H matrix as follows.

Α, β, and h are components included in A, B, and H. Further, the H matrix derived by the base station apparatus 10 is shown as follows.

このようなキャリブレーション係数Ｃ_ＡＵＴＯ（１）によれば、γ（１）をスカラー量として次のような関係が成立する。

From these, the calibration coefficient C _AUTO (1) is expressed as follows.

According to such a calibration coefficient C _AUTO (1), the following relationship is established with γ (1) as a scalar quantity.

また、基地局装置１０によって導出されるＨ行列は、次のように示される。

Next, an operation for the base station apparatus 10 to derive the calibration coefficient C _Cross (2) for the terminal apparatus 90 will be described. At that time, the base station device 10 and the terminal device 90 transmit training signals to each other. Further, it is assumed that the calibration coefficient C _AUTO (1) has already been derived. The H matrix derived by the terminal device 90 is shown as follows.

Further, the H matrix derived by the base station apparatus 10 is shown as follows.

ＡやＢは、対角化行列であるので、基地局装置１０は、Ｈ行列を以下のように変形する。

Here, assuming TDD (Time Division Duplex) and assuming that the uplink and downlink are targets, the following is shown.

Since A and B are diagonal matrices, the base station apparatus 10 modifies the H matrix as follows.

これを利用すると以下の関係が成立するので、Ｃ_{Ｃｒｏｓｓ}（２）はキャリブレーション係数の機能を有する。

すなわち、制御部３０は、ステアリング行列Ｑ（１）の逆行列とＨ（１→２）’とを乗算し、乗算した結果の転置行列とＨ（２→１）’の逆行列とを乗算することによって、Ｃ_{Ｃｒｏｓｓ}（２）を導出する。ただし、このとき端末装置９０から予め転置されたＨ行列を受け取ってもよい。この場合、基地局装置１０側においてＨ行列の転置を補正することによって、同様にキャリブレーション係数が導出される。このとき、端末装置９０では、基地局装置１０がビームフォーミング送信を開始または更新する際に送信するトレーニング信号にも、同一のステアリング行列Ｑ（２）を使用すると仮定している。したがって、基地局装置１０においてＣ_{Ｃｒｏｓｓ}（２）をキャリブレーション補正値として使用することによって、ビームフォーミング送信が可能になる。 From these, the calibration coefficient C _Cross (2) is expressed as follows.

When this is utilized, the following relationship is established, so C _Cross (2) has a function of a calibration coefficient.

That is, the control unit 30 multiplies the inverse matrix of the steering matrix Q (1) and H (1 → 2) ′, and multiplies the transposed matrix obtained by the multiplication and the inverse matrix of H (2 → 1) ′. Thus, C _Cross (2) is derived. However, an H matrix transposed in advance may be received from the terminal device 90 at this time. In this case, the calibration coefficient is similarly derived by correcting the transposition of the H matrix on the base station apparatus 10 side. At this time, it is assumed that the terminal device 90 uses the same steering matrix Q (2) for the training signal transmitted when the base station apparatus 10 starts or updates the beamforming transmission. Therefore, by using C _Cross (2) as the calibration correction value in the base station apparatus 10, beam forming transmission can be performed.

Here, a modified example related to calibration will be described. The first modification relates to the derivation of the calibration coefficient C _Cross (2) when the inverse matrix of the H matrix cannot be derived, that is, when the H matrix is not a regular matrix. This corresponds to the case where the H matrix is not a square matrix or the rank of the H matrix is low. The former is a case where the number of antennas 12 and the number of antennas 14 are different, and the latter is a case where the correlation of space is high. The second modification is a case where the base station apparatus 10 does not derive the calibration coefficient C _AUTO (1) in advance.

制御部３０は、基地局装置１０と端末装置９０に対して、特異値分解を実行すると、次の関係が成立する。

これらより、キャリブレーション係数Ｃ_{Ｃｒｏｓｓ}（２）は、次のように示される。

これを利用すると以下の関係が成立するので、Ｃ_{Ｃｒｏｓｓ}（２）はキャリブレーション係数の機能を有する。

すなわち、制御部３０は、ステアリング行列Ｑ（１）の逆行列とＨ（１→２）’とを乗算し、乗算した結果の転置行列とＨ（２→１）’の一般化逆行列とを乗算することによって、Ｃ_{Ｃｒｏｓｓ}（２）を導出する。 For the first variation, a generalized inverse matrix shown as follows is introduced.

When the control unit 30 performs singular value decomposition on the base station device 10 and the terminal device 90, the following relationship is established.

From these, the calibration coefficient C _Cross (2) is expressed as follows.

When this is utilized, the following relationship is established, so C _Cross (2) has a function of a calibration coefficient.

That is, the control unit 30 multiplies the inverse matrix of the steering matrix Q (1) and H (1 → 2) ′, and obtains the transposed matrix resulting from the multiplication and the generalized inverse matrix of H (2 → 1) ′. By multiplying, C _Cross (2) is derived.

  A second modification will be described. A communication system 100 for the second modification is shown in the same manner as in FIG. The base station apparatus 10 defines a steering matrix Q (1). The base station apparatus 10 generates a plurality of sequences in which the number of training signals is equal to the number of antennas including data by multiplying at least one sequence to be transmitted by Q (1). Furthermore, the base station apparatus 10 transmits the generated signal.

Further, the terminal device 90 derives an H matrix based on the training signal received from the base station device 10. This H matrix reflects the influence of the transmission function of the base station apparatus 10, the steering matrix Q (1), the radio transmission characteristics from the base station apparatus 10, and the reception function of the terminal apparatus 90. Further, the terminal device 90 transmits the derived H matrix to the base station device 10. The base station apparatus 10 derives an H matrix based on the training signal received from the terminal apparatus 90. This H matrix reflects the influence of the transmission function at the terminal device 90, the steering matrix Q (2), the wireless transmission path characteristics from the terminal device 90, and the influence of the reception function at the base station device 10. Further, the control unit 30 of the base station apparatus 10 performs singular value decomposition on the two H matrices, thereby calibrating the calibration coefficient C _Cross (1) for the base station apparatus 10 and the calibration coefficient C _Cross (2 for the terminal apparatus 90). ) Is derived.

また、基地局装置１０によって導出されるＨ行列は、次のように示される。

制御部３０によって特異値分解されたＨ行列は、次のように示される。

The H matrix derived by the terminal device 90 is shown as follows.

Further, the H matrix derived by the base station apparatus 10 is shown as follows.

The H matrix subjected to singular value decomposition by the control unit 30 is expressed as follows.

これは、次のようにも示される。

Here, the calibration coefficient _{C Cross} (2) is against the calibration coefficient _{C Cross} (1) and the terminal device 90 to the base station apparatus 10, it should be derived as to satisfy the following relation.

This is also shown as follows.

あるいは、次のように導出されてもよい。

ここで、次の関係が成立しているものとする。

The number of antennas 12 of the base station apparatus 10, if the number or more antennas 14 of the terminal apparatus 90, the calibration coefficient _{C Cross} for calibration coefficient _{C Cross} (1) and the terminal device 90 to the base station apparatus 10 (2) Is derived as follows.

Alternatively, it may be derived as follows.

Here, it is assumed that the following relationship is established.

The number of antennas 12 of the base station apparatus 10 is smaller than the number of antennas 14 of the terminal apparatus 90, the calibration coefficient _{C Cross} for calibration coefficient _{C Cross} (1) and the terminal device 90 to the base station apparatus 10 (2) Is derived as follows.

Here, a specific example is shown. If the number of antennas 12 of the base station apparatus 10 is “4” and the number of antennas 14 of the terminal apparatus 90 is “2”, the calibration coefficient C _Cross (1) for the base station apparatus 10 and the terminal apparatus 90 The calibration coefficient C _Cross (2) is derived as follows.

Here, C _Cross (1) is a 4 × 4 matrix, and C _Cross (2) is a 2 × 2 matrix. On the other hand, if the number of antennas 12 of the base station apparatus 10 is “2” and the number of antennas 14 of the terminal apparatus 90 is “4”, the calibration coefficient C _Cross (1) for the base station apparatus 10 and the terminal apparatus The calibration coefficient C _Cross (2) for 90 is derived as follows.

  The operation of the communication system 100 configured as above will be described. FIG. 7 is a sequence diagram illustrating a calibration procedure in the communication system 100. The base station apparatus 10 transmits a training signal (S10). The terminal device 90 derives an H matrix based on the training signal (S12). The terminal device 90 transmits a training signal and transmits the derived H matrix as data (S14). The base station apparatus 10 derives an H matrix based on the training signal (S16). The base station apparatus 10 performs calibration while using the H matrix (S18). The base station apparatus 10 stores the calibration result (S20). Moreover, the base station apparatus 10 uses the result of calibration for communication.

  The third and fourth modified examples of calibration will be described. The third and fourth modification examples are applicable to the embodiment and the first and second modification examples. Here, description will be made assuming that the present invention is applied to the embodiment. In the embodiment, the base station device 10 derives a calibration coefficient for the terminal device 90. At that time, the number of antennas 12 in the base station apparatus 10 is equal to or greater than the number of antennas 14 in the terminal apparatus 90, and the rank number of channels, that is, the rank number of the H matrix is the number of antennas 14 in the terminal apparatus 90. It was equal to the number. In the third and fourth modifications, the base station device 10 derives the calibration coefficient for the terminal device 90 as in the embodiment. However, this corresponds to the case where the number of antennas 12 in the base station apparatus 10 is smaller than the number of antennas 14 in the terminal apparatus 90 or the number of ranks of the H matrix is smaller than the number of antennas 14 in the terminal apparatus 90.

そのため、次の関係が成立する。

また、Ｂ（１）は対角行列なので、次の関係が成立する。

Although overlapping with the description so far, the calibration coefficient C _Cross (2) for the terminal device 90 is expressed as follows.

Therefore, the following relationship is established.

Since B (1) is a diagonal matrix, the following relationship is established.

また、前述のごとく、Ｃ_{Ｃｒｏｓｓ}（２）は、キャリブレーション係数として使用される。以上の関係は、実施例の他、ひとつ目とふたつ目の変形例においても成立する。 The following relationship always holds between the calibration coefficient C _Cross (2) for the terminal device 90 and A (2), B (2), and Q (2).

As described above, C _Cross (2) is used as a calibration coefficient. The above relationship is also established in the first and second modified examples in addition to the embodiment.

  In the third and fourth modifications, a case will be described in which the number of rows of the H matrix is smaller than the number of columns of the H matrix, or the rank number of the H matrix is smaller than the number of columns of the H matrix. Here, the case where the number of rows of the H matrix is smaller than the number of columns of the H matrix corresponds to the case where the number of antennas 12 in the base station apparatus 10 is smaller than the number of antennas 14 in the terminal apparatus 90. Further, the case where the rank number of the H matrix is smaller than the number of columns of the H matrix corresponds to the case where the rank number of the channel is smaller than the number of antennas 14 in the terminal device 90. In this case, in the method according to the above description, Expression 32 does not always hold.

  In the third modification, the derivation of the calibration coefficient is postponed if the rank number of the channel is low. Here, the number of ranks of the channel depends on the characteristics of the wireless transmission path. For this reason, the characteristics of the wireless transmission path vary with the passage of time, so that the number of channel ranks also varies with the passage of time. In the third modification, even if the number of ranks of the current channel is low, the derivation of the calibration coefficient is postponed until the number of ranks increases.

  The control unit 30 in FIG. 3 derives the H matrix as described above. Further, the control unit 30 derives the rank number of the H matrix. At that time, in order to derive the rank number of the H matrix, the control unit 30 may perform singular value decomposition. Further, the control unit 30 may derive the rank number of the H matrix by a known technique. The control unit 30 sets the smaller one of the number of rows and the number of columns in the H matrix as the threshold value. Furthermore, if the rank number of the H matrix is smaller than the threshold value, the control unit 30 detects this. The control unit 30 calculates the value of the determinant for the H matrix, and if the calculated matrix value is close to “0”, the control unit 30 considers that the rank number of the H matrix is smaller than the threshold value. May be. In order to detect that the calculated matrix value is close to “0”, the control unit 30 may compare another threshold value with the value of the determinant.

  Further, when the detection is made in the control unit 30, the control unit 30 instructs the inside of the control unit 30 and the processing unit 22 to postpone the derivation of the calibration coefficient. In addition, the control unit 30 includes a timer (not shown), and causes the processing unit 22 to derive transmission path characteristics after a predetermined period. At that time, it is assumed that the base station apparatus 10 has received a training signal from the terminal apparatus 90. Furthermore, the control unit 30 derives the H matrix from the transmission path characteristics, and derives the rank number of the H matrix. The above processing is executed until the rank number of the H matrix becomes equal to or greater than the threshold value.

  FIG. 8 is a sequence diagram showing a calibration procedure in the communication system 100 according to the third modification of the present invention. The base station apparatus 10 transmits a training signal (S30). The terminal device 90 derives an H matrix based on the training signal (S32). The terminal device 90 transmits a training signal and transmits the derived H matrix as data (S34). The base station apparatus 10 derives an H matrix based on the training signal (S36). The base station device 10 detects that the rank number of the H matrix is low (S38), and determines the postponement of calibration (S40). The base station apparatus 10 transmits a training signal after a predetermined period has elapsed (S42). The terminal device 90 derives an H matrix based on the training signal (S44). The terminal device 90 transmits a training signal and transmits the derived H matrix as data (S46). The base station apparatus 10 derives an H matrix based on the training signal (S48). The base station apparatus 10 confirms that the rank number of the H matrix is not low, and executes calibration while using the H matrix (S50). The base station apparatus 10 stores the calibration result (S52). Moreover, the base station apparatus 10 uses the result of calibration for communication.

  FIG. 9 is a flowchart showing a calibration procedure in the base station apparatus 10. The processing unit 22, the radio unit 20, and the like transmit a training signal (S60). The radio unit 20, the processing unit 22, etc. receive the training signal (S62). The processing unit 22 derives transmission path characteristics based on the received training signal, and the control unit 30 derives an H matrix (S64). In addition, the processing unit 22 sets the number of columns of the H matrix, that is, the number of antennas 14 of the terminal device 90 as a threshold (S66). At this time, the number of antennas 14 of the terminal device 90 may be defined in advance. Or the base station apparatus 10 may acquire the number of the antennas 14 of the terminal device 90 with a predetermined control signal. If the rank number of the H matrix is smaller than the threshold value (Y in S68), the control unit 30 determines to repeatedly execute the processing from step 60 after the lapse of a predetermined period. If the rank number of the H matrix is not smaller than the threshold value (N in S68), the control unit 30 derives a calibration coefficient (S70).

  In the fourth modification, if the number of antennas 14 of the terminal device 90 is larger than the number of antennas 12 of the base station device 10, the plurality of antennas 14 are classified into a plurality of groups, and each of the plurality of groups is classified. Perform calibration in units. Further, the calibration for all the antennas 14 is executed by repeating the calibration. As described above, calibration for the terminal device 90 corresponds to deriving a relative error between the antennas 14. Therefore, classification into a plurality of groups is performed so that the predetermined antenna 14 is included in all groups. For example, the first group is formed by the first antenna 14a and the second antenna 14b, the second group is formed by the first antenna 14a and the third antenna 14c, and the third group is the first antenna 14a and the fourth antenna. 14d. In this case, the calibration process is repeated three times. Note that the number of antennas 14 included in one group is determined according to the number of antennas 12 in the base station apparatus 10. That is, the number of antennas 14 included in one group is determined so as to be smaller than the number of antennas 12 in the base station apparatus 10.

  The control unit 30 in FIG. 3 derives the H matrix as described above. Further, the control unit 30 derives the rank number of the H matrix. Furthermore, if the rank number of the H matrix is smaller than the threshold value, the control unit 30 detects this. Since the above operation is the same as that of the third modification, a description thereof will be omitted. Furthermore, when the detection is made in the control unit 30, the control unit 30 classifies the plurality of antennas 14 provided in the terminal device 90 into a plurality of groups. At that time, the control unit 30 performs classification into a plurality of groups such that some of the plurality of antennas 14 included in the terminal device 90 are included in the plurality of groups. The classification into a plurality of groups is as described above.

  In addition, the control unit 30 instructs the inside of the control unit 30 and the processing unit 22 to derive calibration coefficients in units of a plurality of groups. For example, when the above-described first group is to be processed, calibration coefficients corresponding to the first antenna 14a and the second antenna 14b are derived. In order to execute such processing, the control unit 30 instructs the terminal device 90 to transmit a signal from the antenna 14 included in each of the plurality of groups. For example, when executing the process for the first group, the control unit 30 instructs the terminal device 90 to transmit the training signal only from the first antenna 14a and the second antenna 14b. The processing unit 22 derives the transmission path characteristics based on the training signals transmitted from only the first antenna 14a and the second antenna 14b. The control unit 30 derives the H matrix from the transmission path characteristics. Since the process of deriving the calibration coefficient from the H matrix is as described above, the description is omitted. The control unit 30 executes the above processing for all groups, and finally derives calibration coefficients for the terminal device 90, that is, calibration coefficients for all the antennas 14.

  FIG. 10 is a sequence diagram showing a calibration procedure in the communication system according to the fourth modification of the present invention. The base station apparatus 10 transmits a training signal (S80). The terminal device 90 derives an H matrix based on the training signal (S82). The terminal device 90 transmits a training signal and transmits the derived H matrix as data (S84). The base station apparatus 10 derives an H matrix based on the training signal (S86). The base station apparatus 10 detects that the rank number of the H matrix is low (S88), and classifies the plurality of antennas 14 into three groups (S90). For simplification of explanation, it is assumed that the above-described classification from the first group to the third group is performed.

  The base station apparatus 10 transmits a training signal, and notifies the instruction about the antenna 14 to be used when the terminal apparatus 90 transmits the training signal (S92). The terminal device 90 derives an H matrix based on the training signal (S94). In accordance with the instruction, the terminal device 90 transmits a training signal from the first antenna 14a and the second antenna 14b, and transmits the derived H matrix as data (S96). The base station apparatus 10 derives an H matrix based on the training signal (S98). The base station apparatus 10 performs calibration for the first group (S100).

  The base station apparatus 10 notifies the instruction about the antenna 14 to be used when the terminal apparatus 90 transmits a training signal (S102). The terminal device 90 transmits a training signal from the first antenna 14a and the third antenna 14c according to the instruction (S104). The base station apparatus 10 derives an H matrix based on the training signal (S106). The base station apparatus 10 executes calibration for the second group (S108). The base station apparatus 10 notifies the instruction about the antenna 14 to be used when the terminal apparatus 90 transmits a training signal (S110). The terminal device 90 transmits a training signal from the first antenna 14a and the fourth antenna 14d according to the instruction (S112). The base station apparatus 10 derives an H matrix based on the training signal (S114). The base station apparatus 10 executes calibration for the third group (S116). The base station apparatus 10 stores the calibration result (S118). Moreover, the base station apparatus 10 uses the result of calibration for communication.

  FIG. 11 is a flowchart showing a calibration procedure in the base station apparatus 10. The processing unit 22, the radio unit 20, and the like transmit a training signal (S130). The radio unit 20, the processing unit 22 and the like receive the training signal (S132). The processing unit 22 derives a transmission path characteristic based on the received training signal, and the control unit 30 derives an H matrix (S134). In addition, the processing unit 22 sets the number of columns of the H matrix, that is, the number of antennas 14 of the terminal device 90 as a threshold value (S136). At this time, the number of antennas 14 of the terminal device 90 may be defined in advance. Or the base station apparatus 10 may acquire the number of the antennas 14 of the terminal device 90 with a predetermined control signal. If the rank number of the H matrix is smaller than the threshold value (Y in S138), the control unit 30 classifies the plurality of antennas 14 into a plurality of groups (S142).

  The processing unit 22 and the like transmit a training signal (S144), and the control unit 30 transmits an instruction regarding the antenna 14 to be used when the terminal device 90 transmits the training signal (S146). Further, the processing unit 22 derives transmission path characteristics based on the received training signal, and the control unit 30 derives an H matrix (S148). The control unit 30 derives a calibration coefficient (S150). If the processing for all the groups has not been completed (N in S152), the processing from step 146 is repeated. On the other hand, if the processing for all the groups is finished (Y in S152), the control unit 30 finishes the processing. If the rank number of the H matrix is not smaller than the threshold value (N in S138), the control unit 30 derives a calibration coefficient (S140).

  In the fourth modification, when the plurality of antennas 14 are classified into a plurality of groups, the groups are formed such that the predetermined antennas 14 are included in the plurality of groups. A modification of the formation of such a group will be described. The control unit 30 defines a plurality of temporary groups and classifies the plurality of antennas 14 into a plurality of temporary groups. Classification into a temporary group may be performed by an arbitrary method, and may be performed in the same manner as the classification into a group in the fourth modification. The control unit 30 derives an H matrix for each of the plurality of temporary groups, and derives a rank number for each of the H matrices. The details of the above processing are the same as in the fourth modification example, and thus the description thereof is omitted.

  The control unit 30 defines a threshold value, and compares the number of ranks for each of the H matrices with the threshold value. If the number of ranks for each of the H matrices is greater than the threshold value, the temporary group is taken as a group. On the other hand, if there is a rank number equal to or less than the threshold value among the rank numbers for each of the H matrices, the control unit 30 performs classification into the temporary group again while changing the combination of the antennas 14. Further, the above processing is repeatedly executed until the rank number for each of the H matrices becomes larger than the threshold value. For example, after the first antenna 14a is classified so as to be included in all temporary groups, if there is a rank number equal to or less than the threshold value among the rank numbers for each of the H matrices, the control unit 30 may Classification is performed so that the antenna 14b is included in all temporary groups.

  The control unit 30 in FIG. 3 classifies the plurality of antennas 14 provided in the terminal device 90 into a plurality of temporary groups, and based on training signals transmitted from the antennas 14 included in each of the plurality of temporary groups. The H matrix corresponding to each of the plurality of temporary groups is derived. The control unit 30 compares the rank number of the H matrix corresponding to each of the plurality of temporary groups with a threshold value. If the rank number of the H matrix corresponding to each of the plurality of temporary groups is larger than the threshold value, the temporary group is set as a group. On the other hand, if there is a rank number equal to or less than the threshold value, the processing unit 22 changes the combination of the antennas 14 included in the temporary group. The processing unit 22 and the control unit 30 repeat similar processing. If the above processing is repeated a predetermined number of times and the classification into groups is not performed, the classification according to the fourth modification may be executed.

  FIG. 12 is a flowchart showing a group classification procedure in the base station apparatus 10. FIG. 12 corresponds to step 142 in FIG. The control unit 30 classifies the plurality of antennas 14 into a temporary group (S160). The control unit 30 derives an H matrix for each temporary group (S162). If the rank number of the H matrix is lower than the threshold value (Y in S164), and if another temporary group can be set (Y in S168), the processing from step 160 is repeated. If another provisional group cannot be set (N in S168), the control unit 30 classifies the antennas 14 into predetermined groups (S170). On the other hand, if there is no rank in the H matrix lower than the threshold (N in S164), the control unit 30 determines a temporary group as a group (S166).

  The third modification and the fourth modification have been described while being applied to the embodiment. However, the third modification and the fourth modification are also applicable to the first modification and the second modification. In the first modification, the control unit 30 performs singular value decomposition on the H matrix, and therefore can obtain the rank number of the H matrix from the result of singular value decomposition. If the rank number of the H matrix is lower than the threshold value, the control unit 30 postpones calibration for a predetermined period in the third modification. Further, if the rank number of the H matrix is lower than the threshold value, the control unit 30 classifies the plurality of antennas 14 into a plurality of groups in the fourth modification. The control unit 30 derives an H matrix for each of the plurality of groups, and derives a calibration coefficient while applying a generalized inverse matrix to the H matrix. The fourth modification is different from the first modification in that the H matrix is derived for each of a plurality of groups, but the process for deriving the calibration coefficient from the derived H matrix is as follows. This is the same as the first modification.

  In the second modification, the control unit 30 performs singular value decomposition on the H matrix, and thus can obtain the rank number of the H matrix from the result of singular value decomposition. If the rank number of the H matrix is lower than the threshold value, the control unit 30 postpones calibration for a predetermined period in the third modification. That is, the control unit 30 instructs the processing unit 22 in the control unit 30 to postpone derivation of the H matrix, singular value decomposition for the H matrix, and derivation of the calibration coefficient. Further, if the rank number of the H matrix is lower than the threshold value, the control unit 30 classifies the plurality of antennas 14 into a plurality of groups in the fourth modification. The control unit 30 derives an H matrix for each of the plurality of groups, and derives a calibration coefficient while performing singular value decomposition on the H matrix. That is, the control unit 30 instructs the inside of the control unit 30 and the processing unit 22 to execute derivation of the H matrix, singular value decomposition for the H matrix, and derivation of the calibration coefficient for each of the plurality of groups. The fourth modification differs from the second modification in that the H matrix is derived for each of a plurality of groups, but the process of deriving the calibration coefficient from the derived H matrix is as follows. This is the same as the second modification.

  According to the embodiment of the present invention, since the calibration coefficient for the terminal apparatus is derived from the two H matrices and the steering matrix Q (1), the calibration coefficient is derived even if the steering matrix in the terminal apparatus is not recognized. it can. In addition, since only matrix calculation is performed on the two H matrices and the steering matrix Q (1), the calibration coefficient can be derived without recognizing the steering matrix Q (2) in the terminal device. In addition, since the calibration coefficient is derived, it is possible to suppress deterioration in communication quality by performing calibration. Further, since the calibration coefficient can be derived without obtaining the steering matrix in the terminal device, the notification of the steering matrix can be made unnecessary. In addition, since the notification of the steering matrix can be made unnecessary, the frequency utilization efficiency can be improved. Further, since calibration coefficients for a plurality of terminal devices are derived and used while switching, deterioration in communication quality can be suppressed even when communicating with a plurality of terminal devices. Moreover, since the terminal device does not derive the calibration coefficient, the processing of the terminal device can be simplified.

  Further, since the generalized inverse matrix of the H matrix derived by the base station apparatus is used, the second steering matrix in the terminal apparatus can be recognized even when the H matrix derived by the base station apparatus is not a regular matrix. Without deriving calibration coefficients. Further, calibration can be executed even when the number of antennas of the base station apparatus and the terminal apparatus is different. Further, calibration can be performed even when the spatial correlation is high. In addition, since the calibration coefficient for the terminal device and the calibration coefficient for the base station device are derived using the results of singular value decomposition of the two H matrices, the calibration coefficient for the base station device is not derived in advance. Even so, the calibration coefficient for the terminal device can be derived.

  In addition, since the derivation of the calibration coefficient is postponed if the rank number of the H matrix is low, the calibration coefficient can be accurately derived if the rank number of the wireless transmission path increases during that time. Further, when the terminal device moves, the calibration coefficient can be accurately derived. In addition, when the rank number of the H matrix is low, by classifying the plurality of antennas into a plurality of groups, the rank number of the H matrix is smaller than the smaller of the number of rows and the number of columns in the H matrix. Therefore, the calibration coefficient can be accurately derived. Even if the number of antennas of the terminal device is larger than the number of antennas of the base station device, the calibration coefficient for the terminal device can be derived.

  In addition, since the classification into a plurality of groups is executed so that some of the antennas are included in each of the plurality of groups, a calibration coefficient can be derived as a relative error with respect to some of the antennas. In addition, since the calibration coefficient is derived as a relative error with respect to some antennas, it is possible to easily perform development from the calibration coefficient for each of a plurality of groups to the calibration coefficients for all the antennas. Further, since the classification into groups is executed so that the antennas are combined with antennas whose rank number of the H matrix is increased to some extent, the accuracy of deriving calibration coefficients for the groups can be improved. Further, since signals are transmitted from the antennas included in each of the plurality of groups, the H matrix corresponding to the group can be accurately derived.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the communication system 100 has been described as using the OFDM modulation scheme. However, the present invention is not limited to this, and the communication system 100 may use a single carrier method. According to this modification, the present invention can be applied to various communication systems. That is, any communication system that performs beam forming using a plurality of antennas may be used.

  In the embodiment of the present invention, the base station device 10 derives a calibration coefficient for the terminal device 90. However, the present invention is not limited to this. For example, the terminal device 90 may derive a calibration coefficient for the base station device 10. In that case, the operation of the base station device 10 described in the embodiment is performed by the terminal device 90. According to this modification, the configuration of the base station device 10 can be simplified.

  In the embodiment of the present invention, the control unit 30 detects that the rank number of the H matrix is smaller than the threshold value by singular value decomposition or the like of the H matrix. However, the present invention is not limited to this. For example, the control unit 30 receives the number of antennas 14 provided in the terminal device 90 from the terminal device 90, and based on the number of antennas 14 received, the number of rows and columns in the H matrix. It may be detected that the rank number of the H matrix is smaller than the smaller of the numbers. That is, detection is performed when the number of antennas 14 is larger than the number of antennas 12. According to the present modification, since the number of ranks of the H matrix is detected based on the number of antennas 14 provided in the terminal device 90, the detection accuracy can be improved. That is, it is only necessary to detect a case where a calibration coefficient for the terminal device cannot be derived by inverse matrix, singular value decomposition, or the like.

  In the embodiment of the present invention, the control unit 30 performs the classification into a plurality of groups so that the predetermined antenna 14 is included in all the groups. However, the present invention is not limited to this. For example, classification into a plurality of groups may be performed such that any of the antennas 14 included in each group is included in another group. For example, the first group includes a first antenna 14a and a second antenna 14b, the second group includes a second antenna 14b and a third antenna 14c, and the third group includes a third antenna 14c and a fourth antenna 14d. It may be included. According to this modification, the degree of freedom of the antennas 14 included in the group can be increased. That is, it is sufficient that the calibration coefficient can be derived as a relative error between the antennas 14.

In the embodiment of the present invention, “A ⁻ ” that satisfies the relationship “AA ⁻ A = A” is used as the generalized inverse matrix. Further, by performing singular value decomposition on “A ⁻ ”, the generalized inverse matrix is expressed by a matrix “V”, a matrix “Σ ⁺ ”, and a matrix “U ^H ”. Here, the matrix “V” is defined by M rows and M columns, the matrix “Σ ⁺ ” is defined by M rows and N columns, and the matrix “U ^H ” is defined by N rows and N columns. However, the matrix “V” is defined by M rows and K columns, the matrix “Σ ⁺ ” is defined by K rows and K columns, and the matrix “U ^H ” is defined by K rows and N columns. Also good. That is, the matrix “Σ ⁺ ” may be defined by a square matrix. Although both expressions are different, they are substantially equivalent. In addition, the expression of the modified example can be found in the literature (Haruo Yanai, “Multivariate Data Analysis Method: Theory and Application”, pp.198, Asakura Shoten, 1994) and the literature (JDCarroll, PEGreen (with contributions by A. Chaturvedi ), "Mathematical tools for applied multivariate analysis, revised edition.", Pp. 376, Academic Press, 1997.).

It is a figure which shows the spectrum of the multicarrier signal which concerns on the Example of this invention. It is a figure which shows the structure of the communication system which concerns on the Example of this invention. It is a figure which shows the structure of the base station apparatus of FIG. It is a figure which shows the structure of the signal of the frequency domain in FIG. It is a figure which shows the structure of the process part of FIG. FIGS. 6A to 6B are diagrams showing signal formats in the communication system of FIG. It is a sequence diagram which shows the procedure of the calibration in the communication system of FIG. It is a sequence diagram which shows the procedure of the calibration in the communication system which concerns on the 3rd modification of this invention. It is a flowchart which shows the procedure of the calibration in the base station apparatus of FIG. It is a sequence diagram which shows the procedure of the calibration in the communication system which concerns on the 4th modification of this invention. It is a flowchart which shows the procedure of the calibration in the base station apparatus of FIG. 12 is a flowchart showing a group classification procedure in the base station apparatus of FIG.

Explanation of symbols

  10 base station apparatus, 12 antenna, 14 antenna, 20 radio section, 22 processing section, 24 modulation / demodulation section, 26 IF section, 30 control section, 50 FFT section, 54 combining section, 56 spatial dispersion section, 62 transmission side correction section, 64 IFFT unit, 90 terminal device, 100 communication system.

Claims (27)

A first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and the calibration held in advance after multiplying at least one sequence to be transmitted by the first steering matrix A communication unit that performs transmission to a wireless device to be communicated after multiplying by a coefficient, and receives at least one sequence multiplied by a second steering matrix in the wireless device to be communicated;
Through the communication unit, the influence of the transmission function in the communication target wireless device, the second steering matrix, the wireless transmission path characteristic from the communication target wireless device, the influence of the reception function in the communication unit are reflected. The first matrix is derived and the influence of the reception function in the communication target wireless device, the first steering matrix, the wireless transmission characteristic to the communication target wireless device, the influence of the transmission function in the communication unit, A first derivation unit that receives a second matrix reflecting the effect of the held calibration coefficient from the wireless device to be communicated;
The first matrix derived from the first deriving unit, the second matrix received from the first deriving unit, and the first steering matrix from the communication unit are used to derive a calibration coefficient for the wireless device to be communicated. Two derivation units;
A wireless device comprising:   The second deriving unit multiplies the inverse matrix of the first steering matrix and the second matrix, and multiplies the transposed matrix obtained by the multiplication and the inverse matrix of the first matrix to thereby obtain the wireless communication target Means for deriving a calibration factor for the apparatus.   The second deriving unit, when the first matrix derived in the first deriving unit is an irregular matrix or not a square matrix, means for multiplying an inverse matrix of the first steering matrix and a second matrix; Means for deriving a third matrix such that the product of the first matrix, the third matrix and the first matrix satisfies the relationship of becoming the first matrix, and by multiplying the transposed matrix and the third matrix obtained by multiplication, The wireless device according to claim 2, further comprising means for deriving a calibration coefficient for the wireless device to be communicated.   The second derivation unit satisfies a relationship in which the product of the inverse matrix of the first steering matrix and the second matrix and the product of the first matrix, the third matrix, and the first matrix become the first matrix. The means for deriving a third matrix, and means for deriving a calibration coefficient for the wireless device to be communicated by multiplying the transposed matrix obtained by the multiplication and the third matrix, The wireless device according to 1.   The radio apparatus according to claim 1, wherein the first steering matrix defined in the communication unit is a unitary matrix.   The unitary matrix as the first steering matrix defined in the communication unit is defined in the frequency domain, and is indicated by a product of an orthogonal matrix and a matrix representing a cyclic time shift. Item 6. The wireless device according to Item 5. A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix;
2. The apparatus according to claim 1, further comprising: an instruction unit that instructs the first derivation unit and the second derivation unit to postpone derivation of a calibration coefficient when detection is performed by the detection unit. The wireless device according to any one of 6. A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix;
Means for classifying a plurality of antennas provided in the communication target wireless device into a plurality of groups, and a plurality of groups with respect to the first derivation unit and the second derivation unit when the detection unit performs detection; The wireless device according to claim 1, further comprising: an instruction unit including means for instructing derivation of a calibration coefficient in units of each of the above.   Means for classifying a plurality of antennas provided in the communication target wireless device into a plurality of groups when the number of antennas provided in the communication target wireless device is larger than the number of transmission antennas in the communication unit; An instruction unit further comprising means for instructing the first deriving unit and the second deriving unit to derive a calibration coefficient in units of each of a plurality of groups. The wireless device according to any one of 6.   The number of antennas provided in the communication target wireless device is received from the communication target wireless device, and the number of antennas provided in the communication target wireless device is determined based on the number of received antennas. The wireless device according to claim 9, further comprising a detection unit that detects that the number is larger than the number of transmission antennas.   The instructing unit executes classification into a plurality of groups such that some of the plurality of antennas provided in the wireless device to be communicated are included in the plurality of groups, respectively. Item 11. The wireless device according to any one of Items 8 to 10. The first derivation unit classifies a plurality of antennas provided in the communication target wireless device into a plurality of temporary groups, and based on signals transmitted from the antennas included in each of the plurality of temporary groups, Deriving a first matrix corresponding to each of the plurality of temporary groups,
The said instruction | indication part performs the classification to a some group based on the rank number of the 1st matrix corresponding to each of a some temporary group, The Claim 11 characterized by the above-mentioned. Wireless devices.   The radio apparatus according to claim 8, wherein the instruction unit instructs the radio apparatus to be communicated to transmit a signal from an antenna included in each of a plurality of groups. A first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and at least one sequence to be transmitted is multiplied by the first steering matrix and then a wireless device to be communicated A communication unit that performs transmission to and receives at least one sequence multiplied by a second steering matrix in the communication target wireless device;
Through the communication unit, the influence of the transmission function in the communication target wireless device, the second steering matrix, the wireless transmission path characteristic from the communication target wireless device, the influence of the reception function in the communication unit are reflected. The first matrix was derived and the influence of the transmission function in the communication unit, the first steering matrix, the wireless transmission characteristics to the wireless device to be communicated, and the reception function in the wireless device to be communicated were reflected. A first derivation unit for receiving a second matrix from the wireless device to be communicated;
A second derivation unit that performs singular value decomposition on the result of multiplying the second matrix received by the first derivation unit by the inverse matrix of the first steering matrix, and singular value decomposition of the first matrix derived by the first derivation unit When,
From the first matrix subjected to singular value decomposition in the second derivation unit and the second matrix subjected to singular value decomposition in the second derivation unit, the calibration coefficient for the communication target wireless device and the calibration coefficient for the communication unit A third derivation unit for deriving
A wireless device comprising:   The radio apparatus according to claim 14, wherein the first steering matrix defined in the communication unit is a unitary matrix.   The unitary matrix as the first steering matrix defined in the communication unit is defined in the frequency domain, and is indicated by a product of an orthogonal matrix and a matrix representing a cyclic time shift. Item 16. The wireless device according to Item 15. A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix;
And an instruction unit that instructs the first deriving unit, the second deriving unit, and the third deriving unit to postpone derivation of a calibration coefficient when detection is performed by the detection unit. The wireless device according to any one of claims 14 to 16. A detection unit for detecting that the rank number of the first matrix is smaller than the smaller of the number of rows and the number of columns in the first matrix;
A means for classifying a plurality of antennas provided in the wireless device to be communicated into a plurality of groups, a first deriving unit, a second deriving unit, and a third deriving unit, The wireless device according to claim 14, further comprising: an instruction unit including means for instructing derivation of a calibration coefficient in units of each of the plurality of groups.   Means for classifying the plurality of antennas provided in the communication target wireless device into a plurality of groups when the number of antennas provided in the communication target wireless device is larger than the number of transmission antennas in the communication unit; And an instruction unit including means for instructing the first derivation unit, the second derivation unit, and the third derivation unit to derive a calibration coefficient in units of each of the plurality of groups. The wireless device according to any one of claims 14 to 16.   The number of antennas provided in the communication target wireless device is received from the communication target wireless device, and the number of antennas provided in the communication target wireless device is determined based on the number of received antennas. The wireless device according to claim 19, further comprising a detection unit that detects that the number of transmission antennas is larger than the number of transmission antennas.   The instructing unit executes classification into a plurality of groups so that some of the plurality of antennas provided in the wireless device to be communicated are included in the plurality of groups, respectively. Item 21. The wireless device according to any one of Items 18 to 20. The first derivation unit classifies a plurality of antennas provided in the communication target wireless device into a plurality of temporary groups, and based on signals transmitted from the antennas included in each of the plurality of temporary groups, Deriving a first matrix corresponding to each of the plurality of temporary groups,
The said instruction | indication part performs the classification to a some group based on the rank number of the 1st matrix corresponding to each of a some temporary group, The any one of Claim 18 to 21 characterized by the above-mentioned. Wireless devices.   The wireless device according to any one of claims 18 to 22, wherein the instruction unit instructs the wireless device to be communicated to transmit a signal from an antenna included in each of a plurality of groups. A first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and at least one sequence to be transmitted is multiplied by at least one sequence and then held in advance A first wireless device that transmits a signal generated by multiplying by a coefficient;
A second wireless device for transmitting a signal generated by multiplying at least one sequence to be transmitted by a second steering matrix;
The second wireless device is based on the signal received from the first wireless device, the influence of the transmission function of the first wireless device, the first steering matrix, the wireless transmission characteristics from the first wireless device, and the second wireless device. Derivation of the first matrix reflecting the influence of the reception function and the calibration coefficient held in advance, and then transmitting the derived first matrix to the first wireless device,
The first wireless device is based on the signal received from the second wireless device, the influence of the transmission function in the second wireless device, the second steering matrix, the wireless transmission path characteristics from the second wireless device, the first Means for deriving a second matrix reflecting the influence of the reception function in the wireless device, means for deriving a calibration coefficient for the second wireless device from the first matrix, the second matrix, and the first steering matrix A communication system comprising: A first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and a signal generated by multiplying the first steering matrix by at least one sequence to be transmitted is transmitted. A first wireless device that
A second wireless device for transmitting a signal generated by multiplying at least one sequence to be transmitted by a second steering matrix;
The second wireless device is based on the signal received from the first wireless device, the influence of the transmission function of the first wireless device, the first steering matrix, the wireless transmission characteristics from the first wireless device, and the second wireless device. Deriving the first matrix reflecting the influence of the receiving function, and transmitting the derived first matrix to the first wireless device;
The first wireless device is based on the signal received from the second wireless device, the influence of the transmission function in the second wireless device, the second steering matrix, the wireless transmission path characteristics from the second wireless device, the first Means for deriving a second matrix reflecting the influence of the reception function in the wireless device, and by multiplying the result obtained by multiplying the first matrix by the inverse matrix of the first steering matrix and the second matrix, respectively, A communication system comprising: a calibration coefficient for the first wireless device; and means for deriving a calibration coefficient for the second wireless device. A first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and the calibration held in advance after multiplying at least one sequence to be transmitted by the first steering matrix A wireless device that performs transmission to a wireless device to be communicated after multiplying a coefficient and receives at least one sequence multiplied by a second steering matrix in the wireless device to be communicated; A calibration method for deriving a calibration coefficient for an apparatus,
Deriving the first matrix reflecting the influence of the transmission function in the wireless device to be communicated, the second steering matrix, the characteristics of the wireless transmission path from the wireless device to be communicated, and the influence of the reception function in the wireless device And the influence of the reception function in the wireless device to be communicated, the first steering matrix, the wireless transmission characteristics to the wireless device to be communicated, the influence of the transmission function in the wireless device, the influence of the calibration coefficient held in advance Is received from the communication target wireless device, and a calibration coefficient for the communication target wireless device is derived from the first matrix, the second matrix, and the first steering matrix. Method. A first steering matrix for distributing at least one sequence to be transmitted to a plurality of transmission antennas is defined, and at least one sequence to be transmitted is multiplied by the first steering matrix and then a wireless device to be communicated Calibration for deriving a calibration coefficient for the communication target wireless device in the wireless device that performs transmission to the communication target and receives at least one sequence multiplied by a second steering matrix in the communication target wireless device The method of
Deriving the first matrix reflecting the influence of the transmission function in the wireless device to be communicated, the second steering matrix, the characteristics of the wireless transmission path from the wireless device to be communicated, and the influence of the reception function in the wireless device And the second matrix reflecting the influence of the transmission function in the wireless device, the first steering matrix, the wireless transmission characteristics to the wireless device to be communicated, and the receiving function in the wireless device to be communicated. And the first matrix obtained by multiplying the second matrix by the inverse matrix of the first steering matrix and the singular value decomposition, respectively, and the calibration coefficient for the communication target wireless device and the communication device A calibration method characterized by deriving a calibration coefficient for.

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