Wireless communication device, wireless communication device method, and program

Abstract

The objective of the present disclosure is to provide a radio communication device, a method for a radio communication device, and a program with which it is possible to perform calibration of an antenna easily. A radio communication device (11) according to the present disclosure comprises: a calibration control unit (111) that performs DL control to transmit a calibration downlink (DL) signal from an antenna other than one of a plurality of antennas DA and to receive a calibration DL signal by the one antenna, and UL control to transmit a calibration uplink (UL) signal from the one antenna and to receive a calibration UL signal by the antenna other than the one antenna; a calibration coefficient calculating unit (112) that calculates a calibration coefficient on the basis of a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver that have been calculated on the basis of the calibration DL signal transmitted and the calibration DL signal received in the DL control and the calibration UL signal transmitted and the calibration UL signal received in the UL control; and a calibration applying unit (113) that adjusts the phase and amplitude of a radio DL signal on the basis of the calibration coefficient.

Description

[Technical field]

[0001] The present disclosure relates to a wireless communication device, a wireless communication device method, and a program, and more particularly to a wireless communication device, a wireless communication device method, and a program that can easily calibrate a distributed antenna. [Background technology]

[0002] In recent years, base stations have been trying to improve communication capacity by using the MIMO (Multiple Input Multiple Output) transmission method. A base station that supports the MIMO transmission method is equipped with multiple antennas and modems, each of which transmits and receives different radio signals. Using these multiple radio signals (transmitted and received signals), the radio signal (user signal) is spatially multiplexed to increase frequency utilization efficiency. A base station that supports the MIMO transmission method can use multiple antennas to increase antenna gain in a specific direction and suppress interference by forming nulls. This technology is called beamforming, and there are two main types. One is analog beamforming and the other is digital beamforming. Analog beamforming is a technology that distributes (distributes) one or more radio signals to multiple antennas and gives each a different phase using a phase shifter or the like to increase antenna gain in a specific direction. On the other hand, digital beamforming is a technology that adjusts the phase and amplitude of the transmitted and received signals of each antenna. A base station that supports digital beamforming is equipped with the same number of transceivers as the number of antennas, and digitally controls the transmitted and received signals from each antenna. This makes it possible to use spatial multiplexing techniques such as ZF (Zero Forcing) and MMSE (Minimum Mean Square Error). ZF and MMSE also control the null direction of the antenna gain, suppressing interference between multiple transmit and receive signals and enabling more efficient signal multiplexing.

[0003] In order to use spatial multiplexing technology, it is necessary to obtain a channel coefficient indicating the radio wave propagation environment. The base station estimates the channel coefficient from, for example, a reference signal included in a signal received by the base station (UL (Uplink) signal). The process of estimating the channel coefficient is called channel estimation. When the base station receives UL signals from multiple user terminals (UE: User Equipment), these UL signals will interfere with each other. Therefore, the base station can perform UL communication with each UE by separating the multiplexed UL signals using the channel coefficient obtained by channel estimation and the spatial multiplexing technology. On the other hand, in DL (Down Link) communication from the base station to the UE, multiplexed DL communication is performed by transmitting a DL signal to which spatial multiplexing technology has been applied in advance using the channel coefficient estimated from the UL signal. The process of generating a DL signal to which spatial multiplexing technology has been applied in advance using the channel coefficient is called precoding. By performing precoding, the base station can suppress interference between UEs in DL communication and can communicate with multiple UEs. As a result, the base station can communicate with multiple users in the same frequency band and in the same time zone, thereby improving frequency utilization efficiency.

[0004] In DL communications, a DL signal that has been pre-adapted for spatial multiplexing technology is transmitted using channel coefficients estimated from UL signals. This utilizes the reciprocity of the propagation channels in UL and DL communications, and is used in TDD (Time Division Duplex) communications. In order to use channel reciprocity in a MIMO transmission system, it is necessary to calibrate the transmit and receive signals transmitted from each antenna. If this calibration is imperfect, the channel coefficients obtained by channel estimation contain errors caused by the receiver, making it impossible to accurately spatially multiplex wireless signals. Transmitter errors also affect spatial multiplexing, degrading communication characteristics.

[0005] Therefore, in some cases, a base station is provided with a calibration transceiver circuit in addition to the transceiver circuit used for communication, and the calibration transceiver circuit is used to calibrate the transceiver circuit used for communication. In this way, calibration is possible even after the base station is installed at the operating location, so changes in transmission and reception characteristics due to temperature and aging can be corrected, and highly accurate spatial multiplexing technology can be used. On the other hand, the base station has to add a calibration transceiver circuit, which increases costs and power consumption. In addition, there are base stations that use a technology called hybrid beamforming, which combines analog beamforming and digital beamforming. Even in such base stations, calibration of the transceiver circuit is required.

[0006] A base station compatible with the MIMO transmission method is called a MIMO device or a MIMO base station. MIMO devices are divided into two types. One is a C-MIMO (Collocated - MIMO) device in which multiple antenna units are mounted in one housing, and the other is a distributed MIMO device in which multiple antenna units are mounted in separate housings. A distributed MIMO device is called a D-MIMO (Distributed - MIMO) device. Calibration of the antenna units is particularly important in D-MIMO devices. The multiple antenna units of a D-MIMO device are installed in different positions and connected to one RU (Radio Unit) unit by wire. The RU unit includes a DFE (Digital Front End) that performs digital baseband signal processing and a modulation / demodulation unit. Each of the multiple antenna units includes an antenna and an up / down converter unit that converts the DL signal from the RU to a high-frequency band. In a D-MIMO device, the RU and antenna unit are separated, so it is difficult to calibrate the amplitude and phase of the DL signal at each antenna end of the multiple antenna units in advance during manufacturing. For this reason, calibration of the D-MIMO device had to be performed using an external measuring device after the D-MIMO device was installed at the operation site. If calibration was performed using an external measuring device, it would be difficult to change the position of the antenna unit after the D-MIMO device was installed, and it would also be difficult to respond to changes in phase and amplitude due to temperature changes in the D-MIMO device, resulting in a decrease in communication quality.

[0007] Patent Document 1 states that "First correction information determined from a first calibration of a base station is received from a system module. A signal from at least one antenna of the base station is received by a radio frequency module. Second correction information is determined based on the received signal and the first correction information." Patent Document 2 states that "In a communication base station performing adaptive array communication, a calibration process is performed during communication in which a CCH carrier transmitted from any one of N antenna elements equipped in the communication base station is received by the remaining (N-1) antenna elements, and calibration data for each antenna element is determined from the amplitude ratio and phase difference at the time of reception of each antenna element." Patent Document 2 does not state that "DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of a plurality of antennas and receiving the calibration DL signal from the one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal from the antenna other than the one antenna are performed for each of the plurality of antennas." [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2013-535124 [Patent Document 2] JP 2008-166866 A Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, in a MIMO device, calibration of multiple antenna units, that is, calibration of the transmission and reception error between antennas is required. In particular, in a C-MIMO device using spatial multiplexing technology, a feedback transceiver (transmitter / receiver circuit) for calibration may be added inside the device and used for calibration. When a feedback transceiver circuit is provided, signal wiring from each signal path to the feedback transceiver circuit is also required. This causes the C-MIMO device to become complicated and increases the cost and power consumption. In addition, in a D-MIMO device, the antenna unit and the modulation / demodulation unit are separated, making it difficult to calibrate the antenna unit during manufacturing. Therefore, after the D-MIMO device is installed at the operating location, it is necessary to calibrate the antenna unit using an external measuring device. Since it is difficult to frequently perform calibration using an external measuring device, it is difficult to change the installation position of the antenna unit. In addition, there is a problem that it is difficult to calibrate the antenna unit each time in order to deal with deterioration of communication characteristics due to temperature changes in the D-MIMO device.

[0010] An object of the present disclosure is to provide a wireless communication device, a method for the wireless communication device, and a program that solves any of the above-mentioned problems. [Means for solving the problem]

[0011] A wireless communication device according to the present disclosure includes: a calibration control unit that performs, for each of the plurality of antennas, DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of the plurality of antennas and receiving the calibration DL signal at the one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal at the antenna other than the one antenna; calculating a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver connected to each of the plurality of antennas based on the DL signals for calibration transmitted from the plurality of antennas and the DL signals for calibration received by the plurality of antennas in the DL control, and the UL signals for calibration transmitted from the plurality of antennas and the UL signals for calibration received by the plurality of antennas in the UL control; a calibration coefficient calculation unit that calculates a calibration coefficient for calibrating a wireless DL signal based on the DL channel coefficient and the UL channel coefficient; a calibration application unit that adjusts a phase and an amplitude of the wireless DL signal transmitted from each of the plurality of antennas based on the calibration coefficient; Equipped with.

[0012] A method for a wireless communication device according to the present disclosure includes: performing DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of the plurality of antennas and receiving the calibration DL signal at the one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal at the antenna other than the one antenna, for each of the plurality of antennas; calculating a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver connected to each of the antennas based on the DL signals for calibration transmitted from the antennas and the DL signals for calibration received by the antennas in the DL control, and the UL signals for calibration transmitted from the antennas and the UL signals for calibration received by the antennas in the UL control; calculating calibration coefficients for calibrating a wireless DL signal based on the DL channel coefficients and the UL channel coefficients; adjusting a phase and an amplitude of the wireless DL signal transmitted from each of the plurality of antennas based on the calibration coefficient; Equipped with.

[0013] The program according to the present disclosure is performing DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of the plurality of antennas and receiving the calibration DL signal at the one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal at the antenna other than the one antenna, for each of the plurality of antennas; calculating a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver connected to each of the antennas based on the DL signals for calibration transmitted from the antennas and the DL signals for calibration received by the antennas in the DL control, and the UL signals for calibration transmitted from the antennas and the UL signals for calibration received by the antennas in the UL control; calculating calibration coefficients for calibrating a wireless DL signal based on the DL channel coefficients and the UL channel coefficients; adjusting a phase and an amplitude of the wireless DL signal transmitted from each of the plurality of antennas based on the calibration coefficient; to be executed by the computer. Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a wireless communication device, a method for the wireless communication device, and a program that enable easy calibration of a distributed antenna. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram illustrating a wireless communication device according to a first embodiment. [Diagram 2] 1 is a schematic diagram illustrating installation of a distributed antenna according to a first embodiment. FIG. [Diagram 3] 1 is a schematic diagram illustrating installation of a distributed antenna according to a first embodiment. FIG. [Figure 4] 1 is a block diagram illustrating a configuration of a D-MIMO device according to a first embodiment. [Diagram 5]FIG. 2 is a block diagram illustrating a digital front-end DFE according to the first embodiment. [Figure 6] 4 is a flow chart illustrating the operation of the D-MIMO apparatus according to the first embodiment. [Figure 7] 4 is a schematic diagram illustrating a frequency allocation of a calibration DL signal according to the first embodiment. FIG. [Figure 8] 4 is a schematic diagram illustrating a frequency allocation of a calibration DL signal according to the first embodiment. FIG. [Figure 9] 4 is a schematic diagram illustrating a frequency allocation of a calibration DL signal according to the first embodiment. FIG. [Figure 10] 4 is a schematic diagram illustrating a frequency allocation of a calibration DL signal according to the first embodiment. FIG. [Figure 11] 4 is a schematic diagram illustrating a frequency arrangement of a calibration UL signal according to the first embodiment. FIG. [Figure 12] 11 is a schematic diagram illustrating the installation of a distributed antenna and an external antenna according to a second embodiment. FIG. [Figure 13] FIG. 11 is a block diagram illustrating a configuration of a D-MIMO device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or corresponding elements are given the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0017] [Embodiment 1] <Overview of the wireless communication device configuration> FIG. 1 is a block diagram illustrating a wireless communication device according to the first embodiment. FIG. 1 shows a minimum configuration of a wireless communication device according to the first embodiment. The wireless communication device is sometimes called a D-MIMO device. In the first embodiment, the description will be given taking distributed antennas of a D-MIMO device as an example of a plurality of antennas, but the present invention is not limited to this.

[0018] As shown in FIG. 1, wireless communication apparatus 11 according to the first embodiment includes calibration control section 111, calibration coefficient calculation section 112, and calibration application section 113.

[0019] The calibration control unit 111 performs DL control to transmit a calibration DL (Down Link) signal from an antenna other than one of the multiple distributed antennas DA and receive the calibration DL signal at one antenna. That is, one antenna of the multiple distributed antennas DA is used as a calibration antenna. The one antenna is, for example, a distributed antenna DA1. The calibration control unit 111 performs UL control to transmit a calibration UL (Up Link) signal from one antenna and receive the calibration UL signal at an antenna other than the one. The calibration control unit 111 performs DL control and UL control for each of the multiple distributed antennas DA.

[0020] Calibration coefficient calculation unit 112 calculates DL channel coefficients of the transmitter and UL channel coefficients of the receiver connected to a distributed antenna for each of the multiple distributed antennas based on the calibration DL signals transmitted from the multiple distributed antennas DA and the calibration DL signals received by the multiple distributed antennas DA in DL control, and the calibration UL signals transmitted from the multiple distributed antennas DA and the calibration UL signals received by the multiple distributed antennas in UL control. Calibration coefficient calculation unit 112 calculates calibration coefficients for calibrating wireless DL signals based on the DL channel coefficients and UL channel coefficients.

[0021] The calibration coefficient calculation unit 112 may calculate a transmission / reception gain ratio for each of the multiple distributed antennas DA based on the DL channel coefficient and the UL channel coefficient, assuming that the DL propagation channel included in the DL channel coefficient is equal to the UL propagation channel included in the UL channel coefficient, and use the calculated ratio as a calibration coefficient for calibrating the wireless DL signal.

[0022] The calibration application unit 113 adjusts the phase and amplitude of the wireless DL signal transmitted from each of the multiple distributed antennas based on the calibration coefficient. The wireless DL signal may also be referred to as a DL signal.

[0023] The wireless communication device 11 according to the first embodiment performs calibration measurement by using one of the multiple distributed antennas DA as a calibration antenna. The calibration measurement is performed multiple times while changing the one distributed antenna DA used as the calibration antenna to any one of the multiple distributed antennas DA. As a result, according to the first embodiment, it is possible to calibrate the distributed antenna DA without an external measuring device, a dedicated calibration antenna, or a dedicated calibration circuit. As a result, it is possible to provide a wireless communication device, a wireless communication device method, and a program that can easily calibrate a distributed antenna.

[0024] Calibration coefficient calculation unit 112 calculates, for each of the multiple distributed antennas DA, multiple DL channel coefficients that correspond to the antennas other than one, which are DL channel coefficients including the DL radio wave propagation characteristics (propagation channel) and the transmission characteristics of the distributed antennas DA, based on the calibration DL signal at the time of transmission transmitted from the antennas other than one and the calibration DL signal at the time of reception received by one antenna. The calculation of the DL channel coefficients is also performed for multiple calibration measurements performed by changing the calibration antenna.

[0025] Calibration coefficient calculation unit 112 calculates, for each of the multiple distributed antennas DA, multiple UL channel coefficients that correspond to the antennas other than one, which are UL channel coefficients including the UL radio wave propagation characteristics (propagation channel) and the reception characteristics of the distributed antennas DA, based on the calibration UL signal at the time of transmission transmitted from one antenna and the calibration UL signal at the time of reception received by the antenna other than one. The calculation of the above UL channel coefficients is also performed for multiple calibration measurements performed by changing the calibration antenna.

[0026] Calibration coefficient calculation unit 112 calculates a ratio of the DL channel coefficient to the UL channel coefficient (UL / DL channel coefficient ratio) for each of the multiple calibration measurements and for each of the multiple distributed antennas DA, based on the multiple DL channel coefficients and the multiple UL channel coefficients for each of the multiple calibration measurements and for each of the multiple distributed antennas DA. Calibration coefficient calculation unit 112 calculates a calibration coefficient for calibrating the wireless DL signal based on the DL channel coefficient and the UL channel coefficient. The DL channel coefficient and the UL channel coefficient also include the transmission and reception characteristics of the distributed antenna DA. However, it is assumed that the propagation channel included in the DL channel coefficient is equal to the propagation channel included in the UL channel coefficient. In other words, since DL and UL are the same propagation path, it is assumed that the propagation channels are equal.

[0027] Calibration coefficient calculation unit 112 calculates a UL / DL channel coefficient ratio between a calibration antenna in a calibration measurement that is used as a reference among a plurality of calibration measurements and a distributed antenna that is used as a reference, The UL / DL channel coefficient ratio between the calibration antenna in non-reference calibration measurements and the reference distributed antenna, Calculate the ratio. This ratio is called the correction factor for the calibration measurement. A correction coefficient between the multiple calibration measurements is used to correct the ratio of the DL channel coefficient to the UL channel coefficient for the multiple calibration measurements. The reference distributed antennas may be a plurality of antennas, and the correction coefficients calculated for the plurality of reference distributed antennas may be averaged to obtain a new correction coefficient.

[0028] Calibration coefficient calculation unit 112 performs calibration measurements multiple times, and when multiple DL channel coefficients and UL channel coefficients are obtained for one distributed antenna DA (when multiple valid measurements are obtained), it calculates a weighting coefficient based on the received power of the calibration DL signal or the calibration UL signal. Calibration coefficient calculation section 112 calculates a UL / DL channel coefficient ratio for each calibration measurement from the DL channel coefficient and the UL channel coefficient. Calibration coefficient calculation section 112 performs correction between the calibration measurements on the UL / DL channel coefficient ratio for each of the calibration measurements using the correction coefficient. The calibration coefficient calculation unit 112 calculates a weighted average UL / DL channel coefficient ratio for each of the multiple distributed antennas DA by weighting and averaging the corrected UL / DL channel coefficient ratios for each of the multiple calibration measurements based on the weighting coefficients. The weighted average UL / DL channel coefficient ratio is called the calibration coefficient.

[0029] Calibration coefficient calculation unit 112 selects a DL channel coefficient corresponding to a calibration DL signal having a reception power equal to or greater than a predetermined power from among the multiple measured DL channel coefficients. Calibration coefficient calculation unit 112 selects a DL channel coefficient corresponding to a calibration UL signal having a reception power equal to or greater than a predetermined power from among the multiple measured UL channel coefficients. Calibration coefficient calculation unit 112 may calculate a calibration coefficient for each of multiple distributed antennas DA using the selected DL channel coefficient and the selected UL channel coefficient.

[0030] The calibration control unit 111 may perform measurements for calibration by adding a calibration DL signal or a calibration UL signal to a wireless DL signal transmitted from each of the multiple distributed antennas.

[0031] <Overview of wireless communication device operation> In the following, a D-MIMO device will be described as an example of a wireless communication device. The D-MIMO device 11 will be described as being compatible with MIMO transmission and using the TDD method.

[0032] FIG. 2 is a schematic diagram illustrating the installation of the distributed antenna according to the first embodiment. FIG. 3 is a schematic diagram illustrating the installation of the distributed antenna according to the first embodiment. 2 and 3 are diagrams showing distributed antennas of the D-MIMO apparatus according to the first embodiment as viewed from above when installed in an operation location, for example, indoors.

[0033] Fig. 2 shows the communication state during calibration. Fig. 3 shows the communication state during operation. In the first embodiment, the number of distributed antennas DA is four, and they are installed at the four corners of a room. As shown in Fig. 2, the radio waves transmitted from distributed antenna DA1 are blocked by a pillar and do not reach distributed antenna DA3, and vice versa. The dotted lines in Fig. 2 indicate that multiple distributed antennas DA can communicate with each other.

[0034] It is assumed that all of the distributed antennas DA1 to DA4 are to be calibrated. Calibration is performed by transmitting and receiving a calibration signal, which is a known signal for calibration, by these distributed antennas DA. In the first embodiment, calibration can also be performed by using an external measuring device or UE (User Equipment), but it is assumed that calibration is performed only by the distributed antenna DA.

[0035] The method of performing calibration with the distributed antenna DA according to the first embodiment is not to switch between transmission and reception for all distributed antennas DA at the same timing as in normal operation. In the first embodiment, one of the distributed antennas DA is operated in such a way that transmission and reception are reversed from those of the other distributed antennas DA. That is, one distributed antenna DA is used like an external measuring instrument. This one distributed antenna DA is called a calibration antenna. This makes it possible to perform calibration using only the D-MIMO device 11.

[0036] The distributed antennas DA of the D-MIMO device 11 according to the first embodiment are installed in various locations depending on the operation location. Therefore, there are cases where signals do not reach each other, such as the case of the distributed antennas DA1 and DA4 shown in FIG. 2. Therefore, calibration (measurement) using the calibration signal of the D-MIMO device 11 is performed multiple times by changing the distributed antenna DA used as the calibration antenna. The D-MIMO device 11 uses the results of the multiple measurements to obtain a calibration coefficient for calibrating the transmission part of the D-MIMO device 11. After that, the D-MIMO device 11 performs calibration by adding the obtained calibration coefficient to the DL signal transmitted from each distributed antenna DA.

[0037] <Details of the wireless communication device configuration> FIG. 4 is a block diagram illustrating a configuration of a D-MIMO apparatus according to the first embodiment. FIG. 5 is a block diagram illustrating a digital front-end DFE according to the first embodiment.

[0038] As shown in Fig. 4, the D-MIMO device 11 according to the first embodiment includes a distributed antenna unit DA1, a distributed antenna unit DA2, a distributed antenna unit DA3, a distributed antenna unit DA4, and a radio unit RU. Each distributed antenna unit DA mainly includes an antenna and an RF up-down converter unit. The distributed antenna unit DA1, the distributed antenna unit DA2, the distributed antenna unit DA3, and the distributed antenna unit DA4 are collectively referred to as the distributed antenna unit DA.

[0039] Digital front-end DFE shown in Fig. 4 includes calibration control unit 111, calibration coefficient calculation unit 112, and calibration application unit 113 shown in Fig. 1. The RF up-down converter unit of distributed antenna unit DA shown in Fig. 4 is included in transceiver 114 shown in Fig. 1.

[0040] In DL (Down Link) communication, the radio unit RU converts a digital signal, which is a transmission signal, into an analog signal, and in UL (Up Link) communication, it converts an analog signal, which is a reception signal, into a digital signal. The radio unit RU and each of the four distributed antenna units DA (distributed antenna unit DA1 to distributed antenna unit DA4) are connected by cables. The distributed antenna units DA can be installed freely within the reach of the cables. In the first embodiment, the number of distributed antenna units DA is four, but this is not limited to this. The number of distributed antenna units DA may be three or more.

[0041] The radio unit RU includes a digital front end DFE (Digital Front End) that performs digital signal processing, and a modulator / demodulator MODEM that converts between digital signals and analog modulated signals. The radio unit RU has four modulator / demodulator MODEMs, the same number as the number of distributed antenna units DA, and performs digital beamforming. The radio unit RU and the four distributed antenna units DA are connected by coaxial cables, which are used to transmit analog modulated signals.

[0042] The distributed antenna unit DA up-converts the analog modulated signal transmitted from the radio unit RU to an RF signal in its RF up-down converter unit, and then transmits this from the antenna.The distributed antenna unit DA also down-converts the signal received by the antenna to an analog modulated signal in its RF up-down converter unit, and then transmits this to the radio unit RU.

[0043] The DL signal processing of the digital front end (DFE) is shown below. As shown in FIG. 5, in the processing of DL signals, the digital front-end DFE divides a transmission signal into layers in a layer mapper unit 1151 and outputs a layer signal X. In this example, the number of layers is, for example, two. A precoding unit 1152 generates four DL signals WX by weighting each layer signal X according to a precoding weight coefficient W and adding them together. A calibration application unit 113 multiplies the DL signal WX after precoding by a coefficient C for calibrating the error of the transmitter and receiver, and outputs a DL signal CWX. An OFDM signal generation unit 1153 performs OFDM modulation on the DL signal CWX that has been subjected to precoding and calibration, and generates a digital baseband signal. The digital baseband signal is sent to a modem MODEM and converted into an analog modulated signal.

[0044] The UL signal processing of the digital front end DFE is shown below. The OFDM signal demodulation unit 1154 demodulates the received baseband signal (OFDM signal) input from the modem MODEM, and outputs a signal U. As a result, the received baseband signal is converted from a time domain signal to a frequency domain signal. In other words, it is converted into a signal for each subcarrier. The OFDM demodulated signal U is a signal whose phase and amplitude change due to interference between multiple communications with multiple UEs, the propagation environment, and the like.

[0045] The channel estimation unit 1155 uses a known reference signal included in the OFDM signal or a distributed antenna unit DA calibration signal to estimate the channel coefficient H u , H d The channel coefficient obtained by channel estimation from the UL signal or the UL signal for DA calibration of the distributed antenna unit is expressed as H u The channel coefficient obtained by channel estimation from the DL signal for calibration of the distributed antenna unit DA is H d The D-MIMO device 11 uses the channel coefficient H u Using spatial multiplexing technology, signal interference is eliminated and changes in phase and amplitude are corrected to obtain UL signals for each layer.

[0046] The precoding weight calculation unit 1156 uses spatial multiplexing technology to estimate the channel coefficient H u The weight coefficient W for DL ​​precoding is calculated from the channel coefficient H u , H d Calibration application section 113 uses calibration coefficient C to calculate calibration coefficient C. Calibration application section 113 uses calibration coefficient C to calibrate the DL signal.

[0047] <Details of the operation of the wireless communication device> FIG. 6 is a flow chart illustrating the operation of the D-MIMO apparatus according to the first embodiment. FIG. 6 shows an operation during calibration of the D-MIMO apparatus according to the first embodiment. FIG. 7 is a schematic diagram illustrating a frequency allocation of the calibration DL signal according to the first embodiment. FIG. 7 shows a frequency arrangement of the calibration DL signal transmitted from the distributed antenna DA1. FIG. 8 is a schematic diagram illustrating a frequency allocation of the calibration DL signal according to the first embodiment. FIG. 8 shows a frequency arrangement of the calibration DL signal transmitted from the distributed antenna DA2. FIG. 9 is a schematic diagram illustrating a frequency allocation of the calibration DL signal according to the first embodiment. FIG. 9 shows a frequency arrangement of the calibration DL signal transmitted from the distributed antenna DA3. FIG. 10 is a schematic diagram illustrating a frequency allocation of the calibration DL signal according to the first embodiment. FIG. 10 shows a frequency arrangement of the calibration DL signal transmitted from the distributed antenna DA4. FIG. 11 is a schematic diagram illustrating a frequency arrangement of the calibration UL signal according to the first embodiment.

[0048] The D-MIMO device 11 may start a calibration operation, that is, an operation of adjusting the phase and amplitude of a DL signal, when any of the following operations is triggered. When the D-MIMO device 11 starts up (when power is turned on). When the difference between the temperature of any of multiple distributed antennas DA and the temperature at the time of the last calibration is equal to or greater than a specified temperature, or when the difference between the average temperature of all distributed antennas DA and the temperature at the time of the last calibration is equal to or greater than a specified temperature. If a certain amount of time has passed since the last calibration, - When the communication quality of the DL signal is lower than a specified quality for a specified period of time or longer.

[0049] Taking this as a trigger, a variable k is set to 1 (step S101) as shown in Fig. 6. Note that the variable k is an integer.

[0050] Since the variable k=1, the distributed antenna DAk becomes the distributed antenna DA1. The distributed antenna DA1 is set as the calibration antenna, and the calibration measurement is performed using the distributed antenna DA1 (step S102). However, the k-th distributed antenna DA is set as the distributed antenna DAk.

[0051] A known calibration DL signal is transmitted from all distributed antennas DA other than the distributed antenna DAk, and is received by the distributed antenna DAk (step S103). In order to avoid interference between the distributed antennas DA, the calibration DL signal uses an OFDM signal that is allocated to a different frequency (subcarrier) for each of the multiple distributed antennas DA.

[0052] As shown in Fig. 7 to Fig. 10, a calibration DL signal arranged on a different subcarrier is assigned to each of the multiple distributed antennas DA. For the calibration DL signal, one subcarrier is arranged for every four subcarriers. The calibration DL signal is not transmitted from the distributed antenna DAk used as the calibration antenna. The calibration DL signal (data) transmitted from a distributed antenna DA other than the distributed antenna DAk used as the calibration antenna and received and measured by the distributed antenna DAk is demodulated and channel-estimated in the same manner as when receiving a normal OFDM signal, and then stored in a storage unit (not shown). In this example, an example of distributed antennas DA1 to DA4 is shown, but the present invention is not limited to this.

[0053] After step S103, a known calibration UL signal is transmitted from the distributed antenna DAk and received by the distributed antennas DA other than the distributed antenna DAk (step S104).

[0054] As shown in Fig. 11, unlike the calibration DL signal, the calibration UL signal does not change the subcarriers allocated to each distributed antenna DA. Unlike the calibration DL signal, the subcarrier mapping (frequency allocation) of the calibration UL signal is allocated to all subcarriers. The calibration UL signal (data) received by each distributed antenna DA is demodulated and channel estimated in the same way as when receiving a normal OFDM signal, and then stored in a memory unit.

[0055] After step S104, the variable k is incremented by 1 (step S105).

[0056] If the variable k is 4 or less (step S106: No), the process returns to step S102. If the variable k is greater than 4 (step S106: Yes), the process proceeds to step S107. In the first embodiment, the distributed antennas are set as calibration antennas in order starting from distributed antenna DA1, and measurements are performed such that all distributed antennas DA are set as calibration antennas at least once.

[0057] After step S106 is Yes, a calibration coefficient is calculated based on the calibration DL signal or calibration UL signal (data) measured by repeating steps S103 and S104, and applied to calibration application unit 113 (step S107).

[0058] After step S107, the measurement for calculating the calibration coefficient is completed, and the operation returns to normal (step S108).

[0059] <Calculation method of calibration coefficient> Here, a method for calculating the calibration coefficients in step S107 shown in FIG. 6 will be described. As shown in Figures 7 to 10, the calibration DL signals output from the distributed antennas DA are allocated to different subcarriers for each distributed antenna DA. For example, the calibration DL signals transmitted from distributed antennas DA2 to DA4 are received by distributed antenna DA1, which serves as a calibration antenna. The calibration DL signals are OFDM demodulated and divided by subcarrier, allowing them to be received without interference between the multiple distributed antennas DA.

[0060] Here, the subcarrier used for communication with the i-th distributed antenna DAi is s i The calibration DL signal and the calibration UL signal are sometimes collectively referred to as calibration signals. In the first embodiment, the variable i is an integer from 1 to 4. As shown in Figs. 7 to 10, the subcarrier s1 is, for example, the 1st, 5th, 9th, ..., subcarrier. The subcarrier s2 is, for example, the 2nd, 6th, 10th, ..., subcarrier. The s obtained by demodulating the OFDM signal received by the kth calibration antenna is i The data of the th subcarrier isk、i (s i ) for k=i, d k、i (s i )=0.

[0061] In the measurement of the calibration UL signal, the s of the calibration UL signal transmitted from the kth distributed antenna DAk and received by the ith distributed antenna DAi is i The signal of the th subcarrier is k、i (s i ) for k=i, u k、i (s i ) = 0. The calibration UL signal is allocated to all subcarriers as shown in Fig. 11, and the calibration coefficients are calculated using the subcarriers used for the calibration DL signal of each distributed antenna DA.

[0062] In the first embodiment, the calibration antenna is changed and the calibration DL signal and the calibration UL signal are measured four times. Since the calibration antenna is changed, the transmission and reception characteristics are different between the calibration antennas. The transmission complex gain of the k-th calibration antenna is ε k、t and the complex receiving gain is ε k、r Here, the gain is a value expressed by a complex number, and has amplitude and phase information. Therefore, it is called a transmission complex gain and a reception complex gain, but in the following description, the word "complex" may be omitted and it may be called a transmission gain and a reception gain.

[0063] Similarly, there is an error in each distributed antenna DA. Let the transmit complex gain of the i-th distributed antenna DAi be e i、t The complex receiving gain is e i、r The first embodiment aims to correct the effect of this gain on the DL signal during operation. In the first embodiment, one of the distributed antennas DA is used as a calibration antenna, so that when k=i, the transmission gain ε k、t and the transmission gain e i、t , or the receiving gain ε k、r and the receiving gain e i、r However, since there may be cases where the gains are different between the second and third embodiments described later, they are treated as different gains.

[0064] The kth measured calibration DL signal d k、i (s i ) can be expressed as follows: TIFF0007666522000001.tif7127h k、i is the channel coefficient of the propagation path from distributed antenna DAi to distributed antenna DAk, and x i is a known calibration DL signal transmitted from the distributed antenna DAi. i ) varies depending on the frequency (subcarrier), but for simplicity, this will be omitted below. Also, the calibration DL signal d k、i (s i ) contains noise because it was measured over the air (OTA), but this will be omitted in this example.

[0065] Similarly, for the kth measured calibration UL signal, the signal u received by the i-th distributed antenna DAi is k、i (s i ) can be expressed as follows: TIFF0007666522000002.tif7138y k is a known calibration UL signal transmitted from the calibration antenna CAk. i ) varies depending on the frequency (subcarrier), but for simplicity, this will be omitted below. Also, the calibration UL signal u k、i (s i ) is measured by OTA and therefore contains noise, which is omitted in this example.

[0066] Measured DL signal for calibration d k、i and the measured calibration UL signal u k、i The channel coefficients h included in k、i are assumed to be equal, assuming that the calibration signal propagates along the same propagation path. Channel estimation is performed using equations (1) and (2), respectively. Calibration DL signal d k、i The channel coefficients estimated from h d、k、i Let us assume that. TIFF0007666522000003.tif16116 Known calibration DL signal x i x i x i * = 1. (*) represents the conjugate complex number.

[0067] Similarly, the channel coefficients h u、k、i is calculated as shown in equation (5) or equation (6). TIFF0007666522000004.tif14125 Known calibration UL signal y k is y k y k * =1.

[0068] The channel coefficient h calculated using equations (3) and (5) d、k、i and the channel coefficient h u、k、i From the kth calibration antenna transmission gain ε k、t and the receiving gain ε k、r The correction coefficient γ k The correction coefficient γ k is obtained based on any measurement where k=1 to 4. In the following, the calibration signal (data) obtained by communicating with the i0th distributed antenna DAi0 among the k0th measurement is used as the reference. TIFF0007666522000005.tif28143k, k0, and i0 are all different numbers.

[0069] In equations (7) and (8), the correction coefficient γ k The correction coefficient γ k The correction coefficient γ k is calculated for all k (1 to 4 in this example). However, the number i0 of the distributed antenna DAi0 may be changed every time the value of k changes. The k0th correction coefficient γ k0 is set to 1.

[0070] Depending on the arrangement of the k-th calibration antenna and the k0-th calibration antenna used as the reference, radio waves may not reach the k-th calibration antenna, making it impossible to obtain the calibration signal (data). The number of the distributed antenna DA that is not reached by radio waves from the reference calibration antenna is newly set as k'. In this case, the k'th correction coefficient ε k’ is calculated using the k1-th measurement for which the correction coefficient has already been calculated, as shown in equations (9) and (10). TIFF0007666522000006.tif28142

[0071] As shown in equations (7) and (9), the correction coefficient γ k In order to calculate γ, two propagation paths are required. If there is one propagation path or less, k is set to zero. It may also be determined that there is no propagation path whose received power is equal to or less than the predetermined threshold. If the received power is equal to or less than the predetermined threshold, the measurement result d k、i Tou k、i Set both to zero.

[0072] Correction coefficient γ k is frequency dependent and varies from subcarrier to subcarrier. The correction factor γ k In addition, when the amplitude gain is small, the correction coefficient γ k The amplitude component of is ignored, and the correction coefficient γ k Alternatively, only the phase component of

[0073] The transmission gain e of the distributed antenna DA in the transmission section of the D-MIMO device 11 i、t and the receiving gain e i、r Calibration coefficient c to calibrate i is expressed as equation (11). TIFF0007666522000007.tif42148However, the number of calibration measurements performed by changing the calibration antenna is N m In the case of the first embodiment, N m = 4. The number of distributed antennas DA is N. The correction coefficient γ k If =0, (γk ) -1 = 0. Equation (11) can be expanded as in equation (12). According to equation (12), the calibration coefficient c i is (e i、r / e i、t ), (|ε k、r | 2 |h k、r | 2 ) is weighted and averaged. k、r | 2 |h k、r | 2 ) is proportional to the received power of the calibration signal.

[0074] When actually measuring the calibration signal, the received power varies greatly depending on the placement of the distributed antennas DA. Normally, the higher the received power, the smaller the effect of noise, and the more accurate the calibration signal can be obtained. Therefore, (|ε k、r | 2 |h k、r | 2 ) and averaging the results, the effect of high-precision measurements is increased and the effect of low-precision measurements is reduced, resulting in a highly accurate calibration coefficient c i can be obtained.

[0075] In fact, the calibration factor c i When applying to the D-MIMO device 11, the calibration coefficient c i In addition, (ε k0、t / ε k0、r ) is the correction coefficient γ k This is the ratio of the transmit and receive gains of the calibration antennas used as the reference. Since this is constant for all distributed antennas DA, it does not affect the accuracy of the DL signal. Therefore, in conjunction with standardization, (ε k0、t / ε k0、r ) can be omitted, and equation (12) can be approximately expressed as equation (13). TIFF0007666522000008.tif9141 Therefore, the transmission part of the D-MIMO device 11 is calibrated by using the ratio of the transmission and reception gains of the distributed antennas DA.

[0076] Calibration coefficient c i is the subcarrier s used for calibration i The calibration coefficient c of the subcarriers not used for calibration, such as the subcarriers used for the calibration of other distributed antennas DA, is calculated for each i is the subcarrier s i The calibration coefficients are obtained by interpolation or extrapolation from the calibration coefficients of . The calibration coefficients may also be obtained by averaging over a certain range of subcarriers. This allows calibration to be performed taking into account the frequency characteristics of the error between the distributed antennas DA.

[0077] In the first embodiment, calibration signals are allocated to all subcarriers, but calibration is also possible using only some of the subcarriers. Subcarriers for which calibration signals cannot be allocated are calibrated by interpolating / extrapolating from the calibration results of nearby subcarriers. Therefore, calibration can be performed using subcarriers and timing such as reference signals even during operation.

[0078] <Effects> The effects of the first embodiment will be described. Here, the effects will be described in a normal operation state (see FIG. 3) in which communication is performed with two UEs using spatial multiplexing. In the following description, the number of UEs is assumed to be M=2. The number of UEs is generally equal to or less than the number of antennas of the D-MIMO apparatus 11, and when the number of distributed antennas DA is N, M can be any integer from 1 to N.

[0079] The UL signal transmitted from each UE and received (measured) by the distributed antenna DA is denoted as U. The UL signal U is a matrix with N rows and 1 column (hereinafter, abbreviated as Nx1) and can be expressed as in equation (14). TIFF0007666522000009.tif695H is the channel coefficient of the propagation path, expressed as an NxM matrix, and Y is the UL signal transmitted from the UE, expressed as an Mx1 matrix. E r represents the receiving gain of the distributed antenna DA, and e i、r Using It is expressed as TIFF0007666522000010.tif21145, which is an NxN diagonal matrix.

[0080] The channel coefficient H obtained by channel estimation from the received UL signal U u is expressed as equation (16). TIFF0007666522000011.tif7126 Channel coefficient H u The receiving gain E r It is clear that this includes:

[0081] The precoding weight coefficient W is calculated using the ZF (Zero-Forcing) algorithm, which is one of the spatial multiplexing techniques, as shown in equation (17). TIFF0007666522000012.tif7130The superscript T in the precoding weight coefficient W indicates the transposed matrix, and the superscript + indicates the pseudo-inverse matrix. In addition to the ZF algorithm, there are several other spatial multiplexing techniques, such as the MMSE algorithm, which can achieve the same calibration effect as the ZF algorithm.

[0082] The precoding weight coefficient W and the calibration coefficient c shown in Equation (11) i The DL signal multiplied by is transmitted from each distributed antenna DA. Then, the DL signal D received by each UE is expressed as follows: TIFF0007666522000013.tif8123X is an Mx1 matrix, which is the original signal to be transmitted to each UE. In the first embodiment, a signal is transmitted in one layer per UE. C is the calibration coefficient c obtained by the method of the first embodiment. i It is an N x N diagonal matrix as shown in equation (19). TIFF0007666522000014.tif22149E t represents the transmission gain of the distributed antenna DA and is an NxN diagonal matrix as shown in equation (20). TIFF0007666522000015.tif21124The calibration coefficient matrix C is expressed as equation (21) using equations (13), (15), and (20). TIFF0007666522000016.tif7106

[0083] By substituting equations (17) and (21) into equation (18), we obtain equations (22) and (23). TIFF0007666522000017.tif14125 As a result, by using the calibration coefficient C obtained in the first embodiment, it is possible to correct the transmission gain and reception gain of D-MIMO apparatus 11 and transmit a DL signal with high accuracy.

[0084] In the first embodiment, the present invention is described by taking an example of application to a D-MIMO device, but is not limited thereto. The first embodiment can also be applied to a C-MIMO device. The C-MIMO device is a MIMO device in which multiple antennas are mounted in one housing. When the first embodiment is applied to a C-MIMO device, one of the multiple antennas mounted in one housing is operated as a calibration antenna, and calibration is performed in the same manner as in the D-MIMO device. The calibration antenna and an antenna other than the calibration antenna in the C-MIMO device transmit and receive a calibration DL signal and a calibration UL signal by radio wave leakage. This eliminates the need to mount a feedback circuit for calibration, etc.

[0085] [Embodiment 2] FIG. 12 is a schematic diagram illustrating the installation of the distributed antenna and the external antenna according to the second embodiment.

[0086] In the first embodiment, the calibration is performed using an antenna included in the D-MIMO device or the C-MIMO device. On the other hand, in the second embodiment, an external antenna for calibration is used. In this example, the number of external antennas is described as three. The antennas other than one of the multiple antennas are antennas that constitute MIMO. Also, one antenna of the multiple antennas is an external antenna that is not an antenna that constitutes MIMO.

[0087] As shown in Fig. 12, an external antenna EA is installed indoors. Depending on the installation location of the distributed antennas DA, it may be difficult to communicate with all the distributed antennas DA using only one external antenna (for example, external antenna EA1). Therefore, calibration measurements are performed using multiple external antennas EA. Alternatively, calibration measurements are performed with all the distributed antennas DA by moving one external antenna. Multiple external antennas EA or multiple measurements by moving the position can be handled in the same way as when the calibration antenna number k in the first embodiment is changed.

[0088] In the second embodiment, the calibration method using the external antenna EA in the D-MIMO device has been described as an example, but the present invention is not limited to this. The calibration method according to the second embodiment can also be applied to a C-MIMO device.

[0089] [Embodiment 3] FIG. 13 is a block diagram illustrating a configuration of a D-MIMO apparatus according to the third embodiment.

[0090] D-MIMO apparatus 11 according to the third embodiment differs from D-MIMO apparatus 31 according to the first embodiment in that a radio unit RU and a distributed antenna unit DU are connected by an optical cable.

[0091] As shown in Figure 13, the DL signal generated by the digital front-end DFE in the radio unit RU is converted to an optical signal together with a transmit / receive switching signal and transmitted to the distributed antenna unit DA via an optical cable. The optical signal transmitted to the distributed antenna unit DA is converted to an electrical signal, then converted to an RF signal and transmitted from the antenna. The UL signal undergoes the reverse processing of the DL signal.

[0092] It is assumed that the reference clocks serving as the reference for the radio unit RU and each distributed antenna unit DA are synchronized. However, even if the reference clocks are synchronized, the transmission and reception characteristics of the distributed antenna units DA differ from one another due to variations in analog circuit characteristics such as skew of the reference clock and the phase of the local oscillator. According to the third embodiment, the difference in the transmission and reception characteristics of the distributed antenna units DA can be calibrated in the same manner as in the first embodiment.

[0093] In the above embodiment, the present invention has been described as being configured as hardware, but the present invention is not limited to this. The present invention can also be realized by having a CPU (Central Processing Unit) execute a computer program to process each component.

[0094] In the above embodiment, the program can be stored and supplied to the computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include magnetic recording media (specifically, flexible disks, magnetic tapes, and hard disk drives), magneto-optical recording media (specifically, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, semiconductor memories (specifically, mask ROMs, PROMs (Programmable ROMs), and EPROMs (Erasable PROMs)), flash ROMs, and RAMs (Random Access Memory). The program may also be supplied to the computer by various types of transitory computer readable media. Examples of the transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The transitory computer readable media can supply the program to the computer via wired communication paths such as electric wires and optical fibers, or wireless communication paths.

[0095] Additionally, although operations are depicted in a particular order, this should not be understood as requiring such operations to be performed in the particular order or sequential order depicted, or that all of the depicted operations be performed, to achieve desirable results. In certain situations, multitasking and parallel processing may be advantageous. Similarly, although details of several specific embodiments are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable combination.

[0096] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

[0097] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention.

[0098] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

[0099] This application claims priority to Japanese Patent Application No. 2020-209739, filed on December 17, 2020, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0100] 11: Wireless communication equipment, D-MIMO equipment 111: Calibration control unit 112: Calibration coefficient calculation unit 113: Calibration application section 1141, 1142, 1143, 1144: Transmitter / Receiver 1141t, 1142t, 1143t, 1144t: Transmitters 1141r, 1142r, 1143r, 1144r: Receiver 1151: Layer mapper section 1152: Precoding section 1153:OFDM signal generation section 1154: OFDM signal demodulation section 1155: Channel estimation unit 1156: Precoding weight calculation unit DA, DA1, DA2, DA3, DA4: Distributed antenna, distributed antenna section EA, EA1, EA2, EA3: External antennas RU: Radio Department DFE: Digital Front End MODEM: Modulator / Demodulator

Claims

1. a calibration control means for performing, for each of the plurality of antennas, DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of the plurality of antennas and receiving the calibration DL signal at one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal at the antenna other than the one antenna; calculating a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver connected to each of the antennas based on the calibration DL signals transmitted from the plurality of antennas and the calibration DL signals received by the plurality of antennas in the DL control, and the calibration UL signals transmitted from the plurality of antennas and the calibration UL signals received by the plurality of antennas in the UL control; a calibration coefficient calculation means for calculating a calibration coefficient for calibrating a wireless DL signal based on the DL channel coefficient and the UL channel coefficient; a calibration application means for adjusting a phase and an amplitude of the wireless DL signal transmitted from each of the plurality of antennas based on the calibration coefficient; Equipped with The calibration coefficient calculation means calculating, for each of a plurality of antennas, a plurality of DL channel coefficients corresponding to the antenna other than the one based on the calibration DL signal at the time of transmission transmitted from the antenna other than the one and the calibration DL signal at the time of reception received by the one antenna; calculating, for each of a plurality of antennas, a plurality of UL channel coefficients corresponding to the antenna other than the one based on the calibration UL signal at the time of transmission transmitted from the one antenna and the calibration UL signal at the time of reception received by the antenna other than the one; calculating the calibration coefficient for calibrating the wireless DL signal based on the DL channel coefficient and the UL channel coefficient calculated from a plurality of calibration measurements obtained by the DL control and the UL control; The calibration coefficient calculation means calculating a ratio of the DL channel coefficient to the UL channel coefficient calculated from a plurality of the calibration measurements as a UL / DL channel coefficient ratio; selecting one of the UL / DL channel coefficient ratios of the plurality of calibration measurements as a reference channel coefficient ratio; Calculating a ratio of the reference channel coefficient ratio to the UL / DL channel coefficient ratio of the plurality of calibration measurements as a correction coefficient between the plurality of calibration measurements; correcting a ratio of the DL channel coefficient to the UL channel coefficient for the plurality of calibration measurements using the correction coefficient between the plurality of calibration measurements; The calibration coefficient calculation means performing the calibration measurement a plurality of times, and when a plurality of the DL channel coefficients and the UL channel coefficients are obtained for the one antenna, determining a weighting coefficient based on the received power of the calibration DL signal or the calibration UL signal; calculating a ratio of the DL channel coefficient to the UL channel coefficient for each of the calibration measurements from the DL channel coefficient and the UL channel coefficient as the UL / DL channel coefficient ratio; performing a correction between the calibration measurements on the UL / DL channel coefficient ratio using the correction coefficient for each of the calibration measurements; calculating a weighted average UL / DL channel coefficient ratio by weighting and averaging the UL / DL channel coefficient ratio for each of the plurality of calibration measurements based on the weighting coefficients, for each of the plurality of antennas; The weighted average UL / DL channel coefficient ratio is set as the new calibration coefficient. Wireless communication device.

2. The calibration coefficient calculation means Calculating an average correction factor by averaging the correction factors calculated for the plurality of calibration measurements; The average correction coefficient is set as the new correction coefficient. The wireless communication device of claim 1 .

3. The calibration control means controls the plurality of antennas to transmit the calibration DL signals having different frequencies.

3. A wireless communication device according to claim 1 or 2.

4. the calibration application means readjusts a phase and an amplitude of the wireless DL signal when a difference between a temperature of any one of the plurality of antennas and a temperature at the time of the previous calibration is equal to or greater than a predetermined temperature, or when a difference between an average temperature of all the antennas and a temperature at the time of the previous calibration is equal to or greater than the predetermined temperature; 4. A wireless communication device according to claim 1.

5. performing DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of the plurality of antennas and receiving the calibration DL signal at one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal at the antenna other than the one antenna, for each of the plurality of antennas; calculating a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver connected to each of the antennas based on the calibration DL signals transmitted from the plurality of antennas and the calibration DL signals received by the plurality of antennas in the DL control, and the calibration UL signals transmitted from the plurality of antennas and the calibration UL signals received by the plurality of antennas in the UL control; calculating a calibration coefficient for calibrating a wireless DL signal based on the DL channel coefficient and the UL channel coefficient; adjusting a phase and an amplitude of the wireless DL signal transmitted from each of the plurality of antennas based on the calibration coefficient; calculating, for each of a plurality of antennas, a plurality of DL channel coefficients corresponding to the antenna other than the one based on the calibration DL signal at the time of transmission transmitted from the antenna other than the one and the calibration DL signal at the time of reception received by the one antenna; calculating, for each of a plurality of antennas, a plurality of UL channel coefficients corresponding to the antenna other than the one based on the calibration UL signal at the time of transmission transmitted from the one antenna and the calibration UL signal at the time of reception received by the antenna other than the one; calculating the calibration coefficients for calibrating the wireless DL signal based on the DL channel coefficients and the UL channel coefficients calculated from a plurality of calibration measurements obtained by the DL control and the UL control; calculating a ratio of the DL channel coefficient to the UL channel coefficient calculated from a plurality of the calibration measurements as a UL / DL channel coefficient ratio; selecting one of the UL / DL channel coefficient ratios of a plurality of the calibration measurements as a reference channel coefficient ratio; calculating a ratio of the reference channel coefficient ratio to the UL / DL channel coefficient ratio of the plurality of calibration measurements as a correction coefficient between the plurality of calibration measurements; correcting a ratio of the DL channel coefficient to the UL channel coefficient for the plurality of calibration measurements using the correction coefficient between the plurality of calibration measurements; performing the calibration measurement a plurality of times, and when a plurality of the DL channel coefficients and the UL channel coefficients are obtained for the one antenna, determining a weighting coefficient based on the received power of the calibration DL signal or the calibration UL signal; calculating a ratio of the DL channel coefficient to the UL channel coefficient for each calibration measurement from the DL channel coefficient and the UL channel coefficient as the UL / DL channel coefficient ratio; performing a correction between the calibration measurements on the UL / DL channel coefficient ratio for each of the calibration measurements using the correction coefficient; calculating a weighted average UL / DL channel coefficient ratio by weighting and averaging the UL / DL channel coefficient ratio for each of the plurality of calibration measurements based on the weighting coefficients for the plurality of calibration measurements for each of the plurality of antennas; determining the weighted average UL / DL channel coefficient ratio as a new calibration coefficient; A wireless communication device method comprising:

6. performing DL control for transmitting a calibration DL (Down Link) signal from an antenna other than one of the plurality of antennas and receiving the calibration DL signal at one antenna, and UL control for transmitting a calibration UL (Up Link) signal from the one antenna and receiving the calibration UL signal at the antenna other than the one antenna, for each of the plurality of antennas; calculating a DL channel coefficient of a transmitter and a UL channel coefficient of a receiver connected to each of the antennas based on the calibration DL signals transmitted from the plurality of antennas and the calibration DL signals received by the plurality of antennas in the DL control, and the calibration UL signals transmitted from the plurality of antennas and the calibration UL signals received by the plurality of antennas in the UL control; calculating a calibration coefficient for calibrating a wireless DL signal based on the DL channel coefficient and the UL channel coefficient; adjusting a phase and an amplitude of the wireless DL signal transmitted from each of the plurality of antennas based on the calibration coefficient; calculating, for each of a plurality of antennas, a plurality of DL channel coefficients corresponding to the antenna other than the one based on the calibration DL signal at the time of transmission transmitted from the antenna other than the one and the calibration DL signal at the time of reception received by the one antenna; calculating, for each of a plurality of antennas, a plurality of UL channel coefficients corresponding to the antenna other than the one based on the calibration UL signal at the time of transmission transmitted from the one antenna and the calibration UL signal at the time of reception received by the antenna other than the one; calculating the calibration coefficients for calibrating the wireless DL signal based on the DL channel coefficients and the UL channel coefficients calculated from a plurality of calibration measurements obtained by the DL control and the UL control; calculating a ratio of the DL channel coefficient to the UL channel coefficient calculated from a plurality of the calibration measurements as a UL / DL channel coefficient ratio; selecting one of the UL / DL channel coefficient ratios of a plurality of the calibration measurements as a reference channel coefficient ratio; calculating a ratio of the reference channel coefficient ratio to the UL / DL channel coefficient ratio of the plurality of calibration measurements as a correction coefficient between the plurality of calibration measurements; correcting a ratio of the DL channel coefficient to the UL channel coefficient for the plurality of calibration measurements using the correction coefficient between the plurality of calibration measurements; performing the calibration measurement a plurality of times, and when a plurality of the DL channel coefficients and the UL channel coefficients are obtained for the one antenna, determining a weighting coefficient based on the received power of the calibration DL signal or the calibration UL signal; calculating a ratio of the DL channel coefficient to the UL channel coefficient for each calibration measurement from the DL channel coefficient and the UL channel coefficient as the UL / DL channel coefficient ratio; performing a correction between the calibration measurements on the UL / DL channel coefficient ratio for each of the calibration measurements using the correction coefficient; calculating a weighted average UL / DL channel coefficient ratio by weighting and averaging the UL / DL channel coefficient ratio for each of the plurality of calibration measurements based on the weighting coefficients for the plurality of calibration measurements for each of the plurality of antennas; determining the weighted average UL / DL channel coefficient ratio as a new calibration coefficient; A program that causes a computer to execute the following.

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