JP2013046278A - Radio communication device and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of improving transmission performance when communicating using a plurality of antennas.SOLUTION: A transmission weight acquisition unit 124 obtains a plurality of transmission weights to perform null steering in regard to transmission directivity by a plurality of antennas 110a provided in a communication unit 11. An interference intensity acquisition unit 160 obtains the intensity of an interference wave component included in a reception signal received in the communication unit 11. A transmission weight adjustment unit 122 makes greater amplitude of at least one transmission weight out of the plurality of transmission weights, as the intensity of the interference wave component obtained in the interference intensity acquisition unit 160 is smaller.

Description

  The present invention relates to a communication technique using a plurality of antennas.

  Conventionally, various techniques relating to wireless communication have been proposed. For example, Patent Literature 1 discloses a technique for controlling transmission directivities related to a plurality of antennas for a wireless communication apparatus that communicates using the plurality of antennas.

Japanese Patent No. 3956739

  Now, in a wireless communication device, it is desired to improve its transmission performance.

  Therefore, the present invention has been made in view of the above-described points, and an object thereof is to provide a technique capable of improving transmission performance when communicating using a plurality of antennas.

  In order to solve the above problem, a wireless communication apparatus according to the present invention includes a communication unit that performs communication using a plurality of antennas, and a plurality of transmission weights for performing null steering with respect to transmission directivity at the plurality of antennas. A transmission weight obtaining unit to be obtained, a transmission weight setting unit for setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas, and interference included in a reception signal received by the communication unit An interference intensity acquisition unit that obtains the intensity of the wave component; and a transmission weight adjustment unit that increases the amplitude of at least one transmission weight of the plurality of transmission weights as the intensity of the interference wave component decreases.

  In addition, a wireless communication apparatus according to the present invention includes a communication unit that performs communication using a plurality of antennas, and a transmission weight acquisition unit that calculates a plurality of transmission weights for performing null steering with respect to transmission directivity at the plurality of antennas. A transmission weight setting unit that sets the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas; and an intensity of an interference wave component included in the reception signal received by the communication unit. When the interference intensity acquisition unit to be obtained and the intensity of the interference wave component are smaller than a threshold, the amplitude of at least one transmission weight of the plurality of transmission weights is increased, and the intensity of the interference wave component is A transmission weight adjusting unit that does not adjust the plurality of transmission weights when the threshold is larger than the threshold;

  In the wireless communication apparatus according to the aspect of the invention, the plurality of antennas may be N (N ≧ 2) antennas, and the transmission weight adjustment unit may have an amplitude of 1 in the plurality of transmission weights. The amplitude of at least one other transmission weight is increased without adjusting the amplitude of the transmission weight that is Mth (1 ≦ M <N) from the largest transmission weight.

  Further, in one aspect of the wireless communication apparatus according to the present invention, the transmission weight adjustment unit does not adjust the amplitude of the transmission weight having the largest amplitude from the transmission weight having the largest amplitude in the plurality of transmission weights. The amplitude of the at least one other transmission weight is increased so that the amplitude of the other at least one transmission weight approaches the transmission weight having the Mth largest amplitude.

  Also, in one aspect of the wireless communication apparatus according to the present invention, the plurality of antennas are N (N ≧ 2) antennas, and receive N received signals respectively received by the N antennas. A reception level acquisition unit for obtaining a level is further provided, and the transmission weight adjustment unit receives, in the N reception signals, the reception signal whose reception level is Mth (1 ≦ M <N) from the reception signal having the highest reception level. The amplitude of at least one other transmission weight is increased without adjusting the M transmission weights set for the transmission signals transmitted from the M antennas that receive the signals.

  Further, in one aspect of the wireless communication apparatus according to the present invention, the transmission weight adjustment unit increases the transmission weight amplitude, the transmission weight before the amplitude is increased, and the transmission weight after the amplitude is increased. The phase of the transmission weight after increasing the amplitude is adjusted so that the correlation between the transmission weight and the frequency becomes higher.

  In addition, the wireless communication method according to the present invention includes (a) a step of performing communication using a plurality of antennas, and (b) a plurality of transmission weights for performing null steering with respect to transmission directivity at the plurality of antennas. (C) setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas in the step (a); and (d) receiving the signals in the step (a). And (e) increasing the amplitude of at least one transmission weight of the plurality of transmission weights as the intensity of the interference wave component is smaller.

  In addition, the wireless communication method according to the present invention includes (a) a step of performing communication using a plurality of antennas, and (b) a plurality of transmission weights for performing null steering with respect to transmission directivity at the plurality of antennas. (C) setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas in the step (a); and (d) receiving the signals in the step (a). (E) when the intensity of the interference wave component is smaller than a threshold value, the amplitude of at least one transmission weight of the plurality of transmission weights is determined. And a step of not adjusting the plurality of transmission weights when the intensity of the interference wave component is larger than the threshold value.

  According to the present invention, transmission performance can be improved.

It is a figure which shows the structure of a radio | wireless communications system. It is a figure which shows the structure of a base station. It is a figure which shows an example of the transmission directivity of a base station. It is a figure which shows the relationship between CIR and the adjustment coefficient of a transmission weight. It is a figure which shows an example of a reference coefficient acquisition table. It is a figure which shows the structure of the modification of a base station.

  FIG. 1 is a diagram illustrating a configuration of a wireless communication system 100 including a wireless communication apparatus according to the present embodiment. The radio communication apparatus according to the present embodiment is, for example, a base station that communicates with a communication terminal. Hereinafter, the radio communication apparatus according to the present embodiment is referred to as “base station 1”.

  As shown in FIG. 1, the wireless communication system 100 includes a plurality of base stations 1, and each base station 1 communicates with a plurality of communication terminals 2. The service area 10 of each base station 1 partially overlaps the service area 10 of the neighboring base station 1. The plurality of base stations 1 are connected to a network (not shown) and can communicate with each other through the network. Further, a server device (not shown) is connected to the network, and each base station 1 can communicate with the server device through the network.

  FIG. 2 is a diagram showing the configuration of each base station 1. The base station 1 has an array antenna as a transmission / reception antenna, and can control the directivity of the array antenna using an adaptive array antenna system.

  As shown in FIG. 2, the base station 1 includes a communication unit 11 and a control unit 12 that controls the communication unit 11. The communication unit 11 includes an array antenna 110 including a plurality of antennas 110a. In the example of FIG. 2, the array antenna 110 includes four antennas 110a. Hereinafter, the four antennas 110a may be referred to as a first antenna 110a to a fourth antenna 110a, respectively. The number of antennas 110a constituting the array antenna 110 is not limited to four, and may be two or more.

  The communication unit 11 performs amplification processing, down-conversion, A / D conversion processing, and the like on each of the plurality of reception signals received by the array antenna 110, and generates and outputs a plurality of baseband reception signals. .

  In addition, the communication unit 11 performs D / A conversion processing, up-conversion, amplification processing, and the like on each of the plurality of baseband transmission signals generated by the control unit 12, and thereby transmits the plurality of transmission signals in the carrier band. Is generated. Then, the communication unit 11 inputs the generated plurality of transmission signals in the carrier band to the plurality of antennas 110a configuring the array antenna 110, respectively. Thereby, a transmission signal is wirelessly transmitted from each antenna 110a.

  The control unit 12 includes a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a memory, and the like. In the control unit 12, the CPU and the DSP execute various programs in the memory, so that the transmission weight processing unit 120, the reception weight processing unit 130, the transmission signal generation unit 140, the reception data acquisition unit 150, the interference strength acquisition unit 160, and the like. A plurality of functional blocks are formed.

  The transmission signal generation unit 140 generates transmission data to be transmitted to the communication target communication terminal 2 (hereinafter referred to as “communication target terminal 2”), which is a communication partner device of the base station 1. Then, the transmission signal generation unit 140 generates a baseband transmission signal including the generated transmission data. This transmission signal is generated by the number of the plurality of antennas 110a constituting the array antenna 110.

  The transmission weight processing unit 120 includes a transmission weight setting unit 121, a transmission weight adjustment unit 122, a transmission weight normalization unit 123, and a transmission weight acquisition unit 124.

  The transmission weight acquisition unit 124 calculates a plurality of transmission weights for controlling the transmission directivity at the array antenna 110 based on the plurality of reception weights calculated by the reception weight processing unit 130.

  The transmission weight normalization unit 123 normalizes the plurality of transmission weights calculated by the transmission weight acquisition unit 124. The transmission weight adjustment unit 122 adjusts a plurality of transmission weights normalized by the transmission weight normalization unit 123. The operations of the transmission weight normalization unit 123 and the transmission weight adjustment unit 122 will be described in detail later.

  Transmission weight setting section 121 sets a plurality of transmission weights adjusted by transmission weight adjustment section 122 for the plurality of transmission signals generated by transmission signal generation section 140, respectively. Then, transmission weight setting section 121 outputs a plurality of transmission signals, each having a plurality of transmission weights set, to communication section 11.

  Reception weight processing section 130 calculates a plurality of reception weights for controlling the reception directivity at array antenna 110. The reception weight processing unit 130 sets the calculated plurality of reception weights for the plurality of reception signals input from the communication unit 11. The reception weight processing unit 130 combines a plurality of reception signals each having a plurality of reception weights to generate a new reception signal.

  The reception data acquisition unit 150 performs equalization processing, demodulation processing, and the like on the new reception signal generated by the reception weight processing unit 130, and acquires control data and user data included in the reception signal.

  Base station 1 according to the present embodiment communicates with communication terminal 2 while adaptively controlling the directivity of array antenna 110 by the functions of communication unit 11, transmission weight processing unit 120, and reception weight processing unit 130. . The base station 1 controls each of the reception directivity and transmission directivity of the array antenna 110 when communicating with the communication terminal 2. Specifically, the reception weight processing unit 130 controls the reception directivity at the array antenna 110 by adjusting the reception weight to be multiplied to the reception signal. Also, the transmission weight processing unit 120 controls the transmission directivity at the array antenna 110 by adjusting the transmission weight to be multiplied with the transmission signal. The transmission weight can be obtained from the reception weight, and the reception weight can be obtained based on a known signal such as a pilot signal output from the communication terminal 2. In the base station 1, the reception weight processing unit 130 and the transmission weight acquisition unit 124 constitute a calculation unit that obtains a plurality of transmission weights based on known signals received by the communication unit 11.

  Further, the base station 1 according to the present embodiment relates to control of the reception directivity of the array antenna 110 when receiving a signal from the communication target terminal 2 (hereinafter sometimes referred to as “array reception control”). Both beamforming and null steering are performed simultaneously. In addition, the base station 1 performs beam forming and null steering with respect to control of the transmission directivity of the array antenna 110 when transmitting a signal to the communication target terminal 2 (hereinafter sometimes referred to as “array transmission control”). Do both at the same time. As a method for obtaining the reception weight, a least square error method (MMSE) such as SMI (Sample Matrix Inversion) or LMS (Least Mean Square) is known, and reception is performed using this least square error method. By calculating the weight, both null steering and beamforming can be performed simultaneously during reception. Also, by calculating the transmission weight based on the reception weight obtained using this least square error method, both null steering and beamforming can be performed simultaneously during transmission.

  The transmission weight acquisition unit 124 according to the present embodiment corrects the reception weight obtained by the reception weight processing unit 130 based on the calibration information, and uses the corrected reception weight as the transmission weight. The calibration information is information generated based on a difference in characteristics between the transmission system circuit and the reception system circuit in the base station 1. The transmission weight acquisition unit 124 can acquire the transmission weight by directly using the reception weight obtained by the reception weight processing unit 130 as the transmission weight. However, since there is a difference in the characteristics of the transmission system circuit and the reception system circuit (for example, the difference in the characteristics of the amplifying units of the transmission system circuit and the reception system circuit), a highly accurate transmission weight is acquired in this embodiment. Therefore, the transmission weight acquisition unit 124 uses the calibration information to correct the reception weight so as to absorb the difference, and uses the corrected reception weight as the transmission weight.

  The interference intensity acquisition unit 160 obtains the intensity of the interference wave component included in the received signal from the communication target terminal 2 received by the communication unit 11 (hereinafter referred to as “interference intensity”). In the present embodiment, for example, the relative intensity of the interference wave component included in the received signal with respect to the intensity of the desired wave component included in the received signal from the communication target terminal 2 is obtained. Specifically, a CIR (Carrier-to-Interference Ratio) indicating a signal power ratio between a desired wave component and an interference wave component included in a received signal from the communication target terminal 2 is obtained. For CIR, the smaller the value, the greater the intensity of the interference wave component relative to the intensity of the desired wave component. Below, an example of the calculation method of CIR is demonstrated.

  The interference intensity acquisition unit 160 obtains the CIR based on a plurality of known signals (known complex signals) from the communication target terminal 2 respectively received by the plurality of antennas 110a constituting the array antenna 110. The interference intensity acquisition unit 160 outputs the correlation value between the known signal and the reference signal and the reference signal in the time direction for each of the plurality of known signals output from the communication unit 11 and received by the plurality of antennas 110a. And the maximum value of the calculated correlation value is specified. Here, the reference signal is a signal in an ideal state (a signal in an original state) for a known signal. Next, the interference intensity acquisition unit 160 obtains an average value of the maximum values of the plurality of calculated correlation values respectively corresponding to the plurality of antennas 110a. Then, the interference intensity acquisition unit 160 converts the obtained average value into a power value, and sets the value obtained thereby as CIR. The CIR (interference intensity) obtained in this way is used when the transmission weight adjustment unit 122 adjusts the transmission weight.

<Normalization of transmission weight>
In communication unit 11 according to the present embodiment, a plurality of transmission amplifiers (not shown) are provided corresponding to a plurality of antennas 110a, respectively. The plurality of transmission signals input to the communication unit 11 are respectively amplified by the plurality of transmission amplifiers and then input to the plurality of antennas 110a. In the base station 1, the transmission power of the transmission signal transmitted from each antenna 110a does not exceed the limit value (hereinafter referred to as “transmission power limit value”) according to the performance of each transmission amplifier of the communication unit 11 and the radio wave law. It is necessary to.

  On the other hand, if the transmission power of each antenna 110a is sufficiently smaller than the transmission power limit value, the transmission power of the base station 1 as a whole is reduced, so that the transmission performance of the base station 1 is lowered.

  Therefore, transmission weight normalization section 123 according to the present embodiment uses transmission weight acquisition section 124 so that the transmission power of antenna 110a having the maximum transmission power among the plurality of antennas 110a matches the transmission power limit value. Normalize the calculated plurality of transmission weights. Thereby, it can suppress that the transmission power of the whole base station 1 falls, suppressing the transmission power of each antenna 110a below a transmission power limit value. Hereinafter, the operation of the transmission weight normalization unit 123 will be described in detail. In the following description, for example, when a transmission signal in which a transmission weight having an amplitude square of “1” is set is transmitted from the antenna 110a, the transmission power of the antenna 110a matches the transmission power limit value (for example, 1W). It shall be. In this case, it can be said that the limit value (hereinafter referred to as “weight power limit value”) of the square of the amplitude of the transmission weight (hereinafter referred to as “weight power limit”) is set to “1”.

  The transmission weight normalization unit 123 obtains weight power of each of the plurality of transmission weights calculated by the transmission weight acquisition unit 124. Next, the transmission weight normalization unit 123 identifies a transmission weight having the maximum weight power (maximum amplitude) among the plurality of transmission weights. Hereinafter, among the plurality of transmission weights, the transmission weight with the maximum weight power, in other words, the transmission weight with the maximum amplitude is referred to as a “maximum transmission weight”.

  Next, transmission weight normalization section 123 divides each of the plurality of transmission weights by the amplitude of the maximum transmission weight (square root of weight power). Thereby, each transmission weight is normalized so that the weight power of the maximum transmission weight becomes the weight power limit value “1”. That is, each transmission weight is normalized so that the transmission power of the antenna 110a that transmits the transmission signal for which the maximum transmission weight is set, that is, the antenna 110a having the maximum transmission power matches the transmission power limit value.

  For example, the four transmission weights W1 to W4 calculated by the transmission weight acquisition unit 124 are W1 = 0.1 + j0.6, W2 = −0.1−j0.4, W3 = 0.3 + j0.7, W4 = 1 + j0. .6, the weight powers P1 to P4 are P1 = 0.37, P2 = 0.17, P3 = 0.58, and P4 = 1.36. Therefore, in this case, the transmission weight W4 is the maximum transmission weight, and the amplitude of the transmission weight W4 (the square root of the weight power P4) is “1.17”. When normalization is performed by dividing each of the four transmission weights W1 to W4 by “1.17”, the normalized transmission weights NW1 to NW4 that are the four transmission weights W1 to W4 after normalization are NW1 = 0.09 + j0. .51, NW2 = −0.09−j0.34, W3 = 0.26 + j0.6, and W4 = 0.86 + j0.51. The weight powers NP1 to NP4 of the normalized transmission weights NW1 to NW4 are NP1 = 0.27, NP2 = 0.12, NP3 = 0.43, and NP4 = 1. In this way, each transmission weight is normalized so that the weight power of the maximum transmission weight becomes the weight power limit value “1”.

<Adjustment of transmission weight based on interference intensity>
As can be understood from the above description, the transmission power of each antenna 110a can be increased to the transmission power limit value. Therefore, the maximum transmission power of the base station 1 is a value obtained by multiplying the number of antennas 110a included in the array antenna 110 by the transmission power limit value.

  Here, since the plurality of transmission weights are for controlling the transmission directivity of the array antenna 110 including the plurality of antennas 110a, the amplitude (weight power) of the plurality of transmission weights inevitably varies. Therefore, even if a plurality of transmission weights are normalized as described above, the transmission power of all the antennas 110a cannot be matched with the transmission power limit value. That is, the base station 1 cannot transmit a signal with the maximum transmission power, and the base station 1 cannot fully exhibit its transmission capability.

  On the other hand, if the transmission weight amplitude (weight power value) is increased in order to increase the transmission power of the base station 1, the transmission directivity of the array antenna 110 may change, and appropriate null steering is performed. May not be possible. That is, with respect to the transmission directivity of the array antenna 110, the gain at the null changes greatly when the amplitude of the transmission weight is changed, and there is a possibility that appropriate null steering cannot be performed.

  FIG. 3 is a diagram showing how the transmission directivity of the array antenna 110 changes when each transmission weight is changed. In FIG. 3, the horizontal axis indicates the direction around the array antenna 110 as an angle, and the vertical axis indicates the relative direction of the array antenna 110 with respect to a predetermined reference value in the direction (angle) indicated on the horizontal axis. Transmission gain is shown.

  In FIG. 3, the transmission directivity 200 indicated by a solid line indicates the transmission directivity when a plurality of transmission weights normalized by the transmission weight normalization unit 123 are respectively set to a plurality of transmission signals as they are. The transmission directivity 210 indicated by the wavy line indicates the transmission directivity when a plurality of transmission weights normalized by the transmission weight normalization unit 123 are respectively set to a plurality of transmission signals after changing their amplitudes. Show. The transmission directivity 220 indicated by the alternate long and short dash line is a transmission directivity when a plurality of transmission weights normalized by the transmission weight normalization unit 123 are respectively set to a plurality of transmission signals after changing their phases. Is shown. The transmission directivity 230 indicated by a two-dot chain line sets a plurality of transmission weights normalized by the transmission weight normalization unit 123 to a plurality of transmission signals after changing both their amplitude and phase. The transmission directivity is shown.

  As shown in FIG. 3, when the transmission weight is changed, with respect to the transmission directivity of the array antenna 110, the gain at the null changes more than the gain at the beam, and the gain at the null increases. Therefore, if the transmission weight is changed, appropriate null steering becomes difficult.

  As described above, it is desirable to increase the amplitude of the transmission weight in terms of increasing the transmission power of the base station 1, but it is not desirable to increase the amplitude of the transmission weight in terms of appropriately performing null steering.

  Therefore, the transmission weight adjustment unit 122 according to the present embodiment is set to a plurality of transmission signals transmitted from the plurality of antennas 110a to the communication target terminal 2 as the interference intensity in the reception signal from the communication target terminal 2 decreases. Increase the amplitude of at least one transmission weight of the plurality of transmission weights. Thereby, when the interference intensity in the received signal from the communication target terminal 2 is large, it is possible to appropriately perform null steering at the time of transmission while maintaining a plurality of transmission weight values as much as possible. On the other hand, when the interference intensity in the received signal from the communication target terminal 2 is small, the effect of null steering at the time of transmission may be reduced, but the amplitude of the transmission weight is increased and the transmission of the base station 1 is performed. Electric power can be increased.

  Here, in the direction in which an interference wave arrives at the base station 1 (hereinafter referred to as “interference direction”), an interference source such as a communication terminal 2 communicating with the neighboring base station 1 is located near the base station 1. Other communication devices (hereinafter, sometimes referred to as “interference source devices”) exist. Therefore, when the base station 1 transmits a signal in the interference direction, there is a possibility that interference is given to the interference source device.

  And when the interference intensity in the received signal from the communication target terminal 2 is large, there is a high possibility that the interference source device is located very close to the base station 1. Furthermore, as described above, by maintaining a plurality of transmission weight values and sufficiently exhibiting the effect of null steering during transmission to the communication target terminal 2, it is possible to reliably prevent interference source devices from being interfered with. can do.

  On the other hand, when the interference intensity in the received signal from the communication target terminal 2 is small, there is a high possibility that the interference source device does not exist so close to the base station 1. When the interference intensity is small, as described above, even if the amplitude of the transmission weight is increased to increase the transmission power of the base station 1 and the null steering effect is weakened at the time of transmission to the communication target terminal 2, the interference It can be said that the possibility of interference to the source device is low.

  As described above, as in the present embodiment, as the interference intensity in the received signal from the communication target terminal 2 is smaller, the plurality of transmissions set to the plurality of transmission signals transmitted from the plurality of antennas 110a to the communication target terminal 2 By increasing the amplitude of at least one transmission weight of the weights, the base station 1 can increase its transmission power while suppressing interference with surroundings. Therefore, the transmission performance of the base station 1 is improved. A specific example of the transmission weight adjustment method in the transmission weight adjustment unit 122 will be described below.

  In the present embodiment, among the plurality of normalized transmission weights obtained by transmission weight normalization section 123, for example, the normalized transmission weight having the second largest amplitude is the transmission weight to be adjusted in amplitude. Yes. Hereinafter, a transmission weight whose amplitude is to be adjusted may be referred to as an “adjustment target weight”. The transmission weight adjustment unit 122 uses the interference strength acquisition unit 160 to determine the amplitude of the normalized transmission weight having the second largest amplitude among the plurality of normalized transmission weights obtained by the transmission weight normalization unit 123. Is smaller, that is, the larger CIR is, the larger it is.

  In the present embodiment, the range that can be taken by the CIR obtained by the interference intensity acquisition unit 160 is divided into, for example, four stages (four ranges). These four stages are called stages 0 to 3, respectively. CIR increases in the order of stages 0 to 3. That is, the interference intensity decreases in the order of steps 0 to 3.

  In the present embodiment, the transmission weight adjustment unit 122 adjusts the weight to be adjusted (the amplitude is the second) when the CIR obtained by the interference intensity acquisition unit 160 belongs to stage 0 (when the interference intensity is large). When the CIR belongs to stage 1 (when the interference intensity is slightly high) without adjusting the amplitude of the large normalized transmission weight), when it belongs to stage 2 (when the interference intensity is slightly low), or belongs to stage 3 When the interference intensity is small, the amplitude of the adjustment target weight is adjusted. In other words, the transmission weight adjustment unit 122 does not adjust the amplitude of the normalized transmission weight having the second largest amplitude when the interference strength obtained by the interference strength acquisition unit 160 is larger than the threshold value. When the interference intensity is smaller than the threshold value, the amplitude of the normalized transmission weight having the second largest amplitude is adjusted.

  When the CIR obtained by the interference intensity acquisition unit 160 belongs to stage 1, the transmission weight adjustment unit 122 multiplies the adjustment target weight by the adjustment coefficient α1 to increase the amplitude. In addition, when the CIR obtained by the interference intensity acquisition unit 160 belongs to stage 2, the transmission weight adjustment unit 122 multiplies the adjustment target weight by the adjustment coefficient α2 to increase the amplitude. Then, when the CIR calculated by the interference intensity acquisition unit 160 belongs to stage 3, the transmission weight adjustment unit 122 multiplies the adjustment target weight by the adjustment coefficient α3 to increase the amplitude. The adjustment coefficients α1 to α3 increase in this order, and are calculated by the transmission weight adjustment unit 122. FIG. 4 is a diagram illustrating a correspondence relationship between CIR stages 1 to 3 and adjustment coefficients α1 to α3.

  When the amplitude of the normalized transmission weight having the second largest amplitude is adjusted among the plurality of normalized transmission weights, the transmission weight adjusting unit 122 adjusts the normalized transmission weight and the remaining normalized transmission weight (the amplitude is adjusted). Output to the transmission weight setting unit 121. The transmission weight setting unit 121 transmits each of the plurality of normalized transmission weights (including the normalized transmission weight whose amplitude is adjusted) received from the transmission weight adjustment unit 122 from the antenna 110a corresponding to the normalized transmission weight. Set to the transmitted signal.

  Next, how to obtain the adjustment coefficients α1 to α3 will be described. When the transmission weight adjustment unit 122 multiplies the normalized transmission weight having the second amplitude in the plurality of normalized transmission weights by the coefficient α, the normalized transmission weight has the maximum amplitude normalized transmission weight. The coefficient α is calculated so as to match the amplitude of. That is, the coefficient α is a value obtained by dividing the amplitude of the normalized transmission weight having the maximum amplitude among the plurality of normalized transmission weights by the amplitude of the normalized transmission weight whose amplitude is the second. This coefficient α is a reference for determining the adjustment coefficients α1 to α3. Hereinafter, the coefficient α is referred to as “reference coefficient α”. A value obtained by subtracting “1” from the reference coefficient α is called an amplitude increase rate β. That is, β = α-1.

  For example, the transmission weight adjustment unit 122 sets the reference coefficient α as the adjustment coefficient α3. Therefore, when the interference intensity is low, when the normalized transmission weight with the second amplitude is multiplied by the adjustment coefficient α3, the amplitude of the normalized transmission weight matches the amplitude of the normalized transmission weight with the maximum amplitude. To come.

  For example, the transmission weight adjustment unit 122 sets a value obtained by adding “1” to 75% of the amplitude increase rate β as the adjustment coefficient α2. That is, α2 = 1 + β × 0.75.

  Then, for example, the transmission weight adjustment unit 122 sets the value obtained by adding “1” to 50% of the amplitude increase rate β as the adjustment coefficient α1. That is, α1 = 1 + β × 0.5.

  For example, if the amplitude of the normalized transmission weight having the maximum amplitude is “1” and the amplitude of the second normalized transmission weight is “0.8”, the reference coefficient α = 1 / 0.8. = 1.25, and the amplitude increase rate β = 0.25. Therefore, in this case, α1 = 1.125, α2 = 1.1875, and α3 = 1.25.

  By multiplying the adjustment target weight by any one of the adjustment coefficients α1 to α3 obtained in this way and increasing the amplitude of the adjustment target weight, the amplitude of the adjustment target weight becomes the normalized transmission weight having the maximum amplitude. Approaches the amplitude of.

  The adjustment coefficients α1 to α3 may be determined by other methods. In the above example, the transmission weight adjustment unit 122 adjusts the transmission weight normalized by the transmission weight normalization unit 123. However, the transmission weight normalization is performed because the performance of the transmission amplifier is sufficiently high. If there is no need to do this, the transmission weight calculated by the transmission weight acquisition unit 124 is directly adjusted.

  As described above, in base station 1 according to the present embodiment, the smaller the interference intensity, the larger the amplitude of at least one transmission weight of the plurality of transmission weights. While it is possible to perform appropriate null steering while maintaining the value of the transmission weight, it is not necessary to exert the effect of null steering. The transmission power of the station 1 can be increased. Therefore, the base station 1 can increase the transmission power while suppressing interference with the surroundings. As a result, the transmission performance of the base station 1 is improved.

  From another point of view regarding the base station 1 according to the present embodiment, the base station 1 does not adjust a plurality of transmission weights when the interference strength is high, and transmits when the interference strength is low. The weight amplitude is increased. Therefore, it is possible to execute appropriate null steering when the interference strength is high, but it is not necessary to exhibit the null steering effect so much. When the interference strength is low, the transmission power of the base station 1 is increased. can do. Therefore, the base station 1 can increase the transmission power while suppressing interference with the surroundings. As a result, the transmission performance of the base station 1 is improved.

  Further, in this embodiment, when increasing the amplitude of at least one transmission weight of a plurality of transmission weights, the transmission weight having the maximum amplitude is not adjusted, so at least one of the plurality of transmission weights is not adjusted. It is possible to prevent the transmission directivity of the array antenna 110 from changing greatly by adjusting the amplitude of the transmission weight. As a result, the null steering effect can be exhibited to some extent when the interference intensity is low. Therefore, it is possible to further suppress the interference to the surroundings.

  Also, in this embodiment, the transmission weight having the maximum amplitude is not adjusted in a plurality of transmission weights, and other transmission weights (in the above example, the amplitude is second) with respect to the amplitude of the transmission weight. Since the amplitude of the other transmission weight is increased so that the amplitude of the (large transmission weight) approaches, it is possible to further prevent the transmission directivity from changing by adjusting the amplitude of the transmission weight. As a result, the null steering effect can be further exhibited when the interference intensity is low. Therefore, it is possible to further suppress the interference to the surroundings.

  In the above example, the transmission weight having the second largest amplitude among the plurality of transmission weights is used as the adjustment target weight. However, the transmission weight having the third or larger amplitude may be used as the adjustment target weight. When the transmission weight having the third amplitude is set as the adjustment target weight, the amplitude of the transmission weight having the maximum amplitude is obtained by dividing the amplitude of the transmission weight having the third amplitude by the amplitude of the third transmission weight. Let the value be the reference coefficient α. Accordingly, when the transmission weight having the third amplitude is adjusted, the amplitude of the transmission weight comes closer to the transmission weight having the maximum amplitude. When the transmission weight having the amplitude of the fourth or subsequent amplitude is set as the adjustment target weight, the reference coefficient α is obtained in the same manner.

  In the above example, one of the plurality of transmission weights is set as the adjustment target weight. However, two or more transmission weights among the plurality of transmission weights may be set as the adjustment target weight. For example, a transmission weight having the second largest amplitude (hereinafter referred to as “second amplitude transmission weight”) and a transmission weight having the third largest amplitude (referred to as “amplitude third transmission weight”) are set as adjustment target weights. May be. In this case, adjustment coefficients α1 to α3 for adjusting the second amplitude transmission weight and adjustment coefficients α1 to α3 for adjusting the third amplitude transmission weight are obtained separately.

  In the above example, the transmission weight amplitude can be increased by three levels by multiplying the transmission weight by the three adjustment coefficients α1 to α3. However, the transmission weight amplitude is increased by two levels. The transmission weight amplitude may be increased by four or more levels.

  In the above example, the amplitude of the adjustment target weight is not adjusted when the CIR obtained by the interference intensity acquisition unit 160 belongs to stage 0. However, in this case, the adjustment coefficient is adjusted with respect to the adjustment target weight. The amplitude of the adjustment target weight may be slightly increased by multiplying an adjustment coefficient smaller than α1 (for example, a value obtained by adding “1” to 25% of the amplitude increase rate β).

<Various modifications>
<First Modification>
In the above example, the relative intensity of the interference wave component included in the received signal with respect to the intensity of the desired wave component included in the received signal from the communication target terminal 2 is obtained and transmitted based on the relative intensity. Although the weight is adjusted, the absolute intensity of the interference wave component included in the received signal from the communication target terminal 2 may be obtained, and the transmission weight may be adjusted based on the absolute intensity. For example, the absolute value of the power of the interference wave component included in the received signal from the communication target terminal 2 (hereinafter referred to as “absolute interference power”) is obtained, and the transmission weight is adjusted based on the absolute value of the power. Also good.

  The absolute interference power AIP for the received signal from the communication target terminal 2 can be expressed by the following equation (1) using the received power RP and CIR for the received signal.

  AIP = RP × (1 / (CIR + 1)) (1)

  However, AIP, RP, and CIR in the formula (1) are not expressed in decibels but are expressed as true numbers.

  For example, if the received power RP is 60 dBμV and the CIR is 30 dB, each is expressed as a true number, which is 1000000 and 1000. Therefore, in this case, the absolute interference power AIP≈1000 from Expression (1), and when expressed in decibels, the absolute interference power AIP is 30 dBμV.

  The received power RP can be calculated based on a known signal from the communication target terminal 2.

<Second Modification>
When increasing the amplitude of at least one transmission weight of the plurality of transmission weights, the maximum transmission weight and the second amplitude transmission weight may not be adjusted. As a result, it is possible to further prevent the transmission directivity from changing greatly by adjusting the amplitude of the transmission weight, and to further exhibit the null steering effect when the interference intensity is small.

  Also, when increasing the amplitude of at least one transmission weight of a plurality of transmission weights, the amplitude from the first largest transmission weight (maximum transmission weight) to the third largest transmission weight (amplitude third transmission weight) It is not necessary to adjust.

  Further, when the number of antennas 110a constituting the array antenna 110 is five or more, it is not necessary to adjust from the transmission weight having the first largest amplitude to the transmission weight having the fourth largest amplitude.

  Generalizing the above contents, assuming that the number of antennas 110a constituting the array antenna 110 is N (N ≧ 2), when the amplitude of at least one transmission weight of a plurality of transmission weights is increased, the amplitude is increased. Do not adjust from the first largest transmission weight to the Mth (1 ≦ M <N) largest transmission weight. Thereby, it is possible to prevent the transmission directivity from changing greatly by adjusting the amplitude of the transmission weight, and when the interference intensity is small, the effect of null steering can be exhibited.

  When M = 1, only the maximum transmission weight is not adjusted.

  In the above example, the amplitude of the maximum transmission weight is not adjusted in the plurality of transmission weights, and the amplitude of at least one other transmission weight is increased so as to approach the amplitude. The amplitude of at least one other transmission weight may be increased so as to approach the amplitude of the amplitude second transmission weight without adjusting the amplitude second transmission weight. Thereby, it is possible to further prevent the transmission directivity from changing due to the adjustment of the amplitude of the transmission weight, and to further exhibit the effect of null steering when the interference intensity is small.

  For example, when the amplitude of the third transmission weight is increased so as to approach the amplitude of the second transmission weight without adjusting the maximum transmission weight and the second transmission weight, the amplitude of the second transmission weight is used. A value obtained by dividing the value by the amplitude of the third transmission weight is set as a reference coefficient α. When the amplitude of the fourth transmission weight is increased so as to approach the amplitude of the second transmission weight without adjusting the maximum transmission weight and the second amplitude transmission weight, the amplitude of the second transmission weight is used. A value obtained by dividing the value by the amplitude of the fourth transmission weight is defined as a reference coefficient α.

  The maximum transmission weight and the second amplitude transmission weight are not adjusted, and the amplitudes of other transmission weights such as the third amplitude transmission weight and the fourth amplitude transmission weight are set so as to approach the amplitude of the second amplitude transmission weight. May be increased. In this case, adjustment coefficients α1 to α3 for adjusting the third amplitude transmission weight and adjustment coefficients α1 to α3 for adjusting the fourth amplitude transmission weight are obtained separately.

  Further, without adjusting from the transmission weight with the largest amplitude (maximum transmission weight) to the third largest transmission weight (amplitude third transmission weight), the amplitude approaches the amplitude of the transmission weight with the third largest amplitude. The amplitude of at least one other transmission weight may be increased.

  Further, when the number of antennas 110a constituting the array antenna 110 is five or more, the transmission having the fourth largest amplitude is performed without adjusting the transmission weight having the first largest amplitude to the fourth largest transmission weight. The amplitude of at least one other transmission weight may be increased so as to approach the amplitude of the weight.

  Generalizing the above contents, assuming that the number of antennas 110a constituting the array antenna 110 is N (N ≧ 2), transmission having the largest amplitude from the first largest transmission weight to Mth (1 ≦ M <N) Without adjusting the weight, the amplitude of at least one other transmission weight is increased so as to approach the amplitude of the Mth largest transmission weight. Thereby, it is possible to prevent the transmission directivity from changing greatly by adjusting the amplitude of the transmission weight, and when the interference intensity is small, the effect of null steering can be exhibited.

  When M = 1, the maximum transmission weight is not adjusted as in the above-described embodiment, and the amplitude of at least one other transmission weight is increased.

<Third Modification>
The reference coefficient α may be obtained using a table. FIG. 5 is a diagram showing a reference coefficient acquisition table 300 for obtaining the reference coefficient α. In the reference coefficient acquisition table 300, each value of the amplitude ratio γ between the maximum transmission weight and the adjustment target weight is associated with the value of the reference coefficient α used when adjusting the amplitude of the adjustment target weight. When the amplitude of the maximum transmission weight is AMm and the amplitude of the adjustment target weight is AMt, the amplitude ratio γ = AMt / AMm. The reference coefficient acquisition table 300 is stored in the transmission weight adjustment unit 122.

  In the base station 1 according to the present modification, the transmission weight adjustment unit 122 includes a maximum transmission weight in the plurality of transmission weights normalized by the transmission weight normalization unit 123 and an adjustment target weight (for example, the plurality of transmission weights). Amplitude ratio γ of (amplitude second transmission weight) is obtained. Then, the transmission weight adjustment unit 122 specifies a value closest to the obtained value of the amplitude ratio γ among the plurality of values of the amplitude ratio γ described in the reference coefficient acquisition table 300. Then, the transmission weight adjustment unit 122 sets the value of the reference coefficient α associated with the identified value in the reference coefficient acquisition table 300 as the value of the reference coefficient α used for adjusting the adjustment target weight. For example, if the amplitude ratio γ between the maximum transmission weight in the plurality of transmission weights normalized by the transmission weight normalization unit 123 and the adjustment target weight in the plurality of transmission weights is “0.78”, the reference coefficient is acquired. Among a plurality of values of the amplitude ratio γ described in the table 300, the value closest to “0.78” is “0.8”, so the value “1” of the reference coefficient α associated therewith is “1”. .25 ″ is the value of the reference coefficient α used to adjust the adjustment target weight.

  Thus, even when the reference coefficient α is obtained using a table, the same effect as in the above example can be obtained.

<Fourth Modification>
There is a correlation between the reception level of the received signal received by one antenna 110a and the amplitude of one transmission weight obtained by the transmission weight acquisition unit 124 corresponding to the one antenna 110a. That is, the transmission weight acquisition unit that is set to the transmission signal transmitted from the one antenna 110a to the communication target terminal 2 as the reception level of the reception signal from the communication target terminal 2 received by the one antenna 110a is larger. The amplitude of one transmission weight obtained at 124 tends to increase.

  Therefore, in the present modification, among N reception signals received by the N antennas 110a that constitute the array antenna 110, M reception signals that receive the Mth reception signal from the reception signal having the first reception level that are the highest. The amplitude of at least one other transmission weight is increased without adjusting the M transmission weights corresponding to the respective antennas 110a. As a result, when the amplitude of at least one transmission weight of a plurality of transmission weights is increased, there is a higher possibility that the amplitude from the first largest transmission weight to the Mth largest transmission weight will not be adjusted. Similarly, it is possible to prevent the transmission directivity of the array antenna 110 from changing greatly. Therefore, the null steering effect can be exhibited to some extent when the interference intensity is low. This modification will be specifically described below.

  FIG. 6 is a diagram showing the configuration of the base station 1 according to this modification. In the base station 1 according to this modification, in the base station 1 shown in FIG. 2 described above, the control unit 12 further includes a reception level acquisition unit 170 as a functional block.

  The reception level acquisition unit 170 obtains a reception level for each of a plurality of reception signals respectively received by the plurality of antennas 110a. Specifically, the reception level acquisition unit 170 obtains the square of the amplitude of the reception signal for each of the plurality of baseband reception signals output from the communication unit 11, and calculates the square of the amplitude of the reception signal. The reception level.

  The transmission weight adjustment unit 122 receives the Mth received signal from the first received signal having the highest reception level among the N received signals respectively received by the N antennas 110a constituting the array antenna 110. The amplitude of at least one other transmission weight is increased without adjusting the M transmission weights respectively corresponding to the M antennas 110a.

  When determining the adjustment numbers α1 to α3 used to adjust the adjustment target weight, the transmission weight adjustment unit 122 uses the Mth largest reception level as the reception level of the reception signal at the antenna 110a corresponding to the adjustment target weight. Let the square root of the value obtained by dividing by the reference coefficient α. Then, the transmission weight adjustment unit 122 obtains the adjustment coefficients α1 to α3 for the adjustment target weight using the obtained reference coefficient α as described above.

  For example, a plurality of normalized transmission weights NW1 to NW4 respectively corresponding to the first antenna 110a to the fourth antenna 110a constituting the array antenna 110 are NW1 = 0.09 + j0.51, NW2 = −0.09−j0.34. , W3 = 0.26 + j0.6, W4 = 0.86 + j0.51, and the reception levels RL1 to RL4 for the plurality of received signals respectively received by the first antenna 110a to the fourth antenna 110a are RL1 = 0. 3. RL2 = 0.1, RL3 = 0.4, RL4 = 1, and M = 2. In such a case, the normalized transmission weight NW4 corresponding to the fourth antenna 110a that receives the reception signal having the first highest reception level and the third antenna that receives the reception signal having the second highest reception level. The normalized transmission weight NW3 corresponding to 110a is not adjusted. For example, when the normalized transmission weight NW1 corresponding to the first antenna 110a that receives the reception signal having the third highest reception level is the adjustment target weight, the reference coefficient α of the adjustment target weight is the second largest. The square root of the value “4/3” obtained by dividing the reception level “0.4” by the reception level “0.3” of the reception signal at the first antenna 110a. When the normalized transmission weight NW2 corresponding to the second antenna 110a that receives the received signal with the fourth highest reception level is the adjustment target weight, the reference coefficient α of the adjustment target weight is the second highest reception level. The square root of the value “4” obtained by dividing “0.4” by the reception level “0.1” of the reception signal at the second antenna 110a, that is, “2”.

  Although there is a correlation between the reception level and the amplitude of the transmission weight, there is a possibility that the transmission weight corresponding to the antenna 110a that receives the reception signal having the maximum reception level does not become the maximum transmission weight. Therefore, there is a possibility that the maximum transmission weight becomes the adjustment target weight. Therefore, in this modification, when adjusting the normalized transmission weight obtained by the transmission weight normalization unit 123, the weight power of the normalized transmission weight with the maximum amplitude does not exceed the weight power limit value. It is prohibited to set the normalized transmission weight of the maximum amplitude as the adjustment target weight. On the other hand, when there is no need to normalize the transmission weight, that is, there is no need to limit the transmission power of the base station 1 and the transmission weight calculated by the transmission weight acquisition unit 124 is directly adjusted, the maximum transmission weight is set. It is possible to set the adjustment target weight.

  Further, in this modification, since the reference coefficient α is determined based on the reception level, when the normalized transmission weight obtained by the transmission weight normalization unit 123 is adjusted using the adjustment coefficients α1 to α3 as they are, There is a possibility that the weight power of the normalized transmission weight after adjustment exceeds the weight power limit value. Therefore, in this modification, the upper limit value of the amplitude of the normalized transmission weight is limited to the square root of the weight power limit value so that the weight power of the adjusted normalized transmission weight does not exceed the weight power limit value. .

<Fifth Modification>
In the above example, the transmission weight adjustment unit 122 adjusts only the amplitude of the adjustment target weight, but may adjust both the amplitude and phase of the adjustment target weight. Hereinafter, the operation of the transmission weight adjustment unit 122 according to this modification will be described.

  When the amplitude of the adjustment target weight is increased as described above, the transmission weight adjustment unit 122 according to the present modification increases the adjustment target weight (hereinafter referred to as “weight before amplitude adjustment”) and the amplitude before increasing the amplitude. The phase of the adjustment target weight after increasing the amplitude is adjusted so that the correlation with the adjustment target weight (hereinafter referred to as “weight after amplitude adjustment”) is increased.

  For example, the transmission weight adjustment unit 122 stores a plurality of adjustment values different from each other with respect to the phase of the weight after amplitude adjustment. It is assumed that “0” is included in the plurality of adjustment values. For each of the plurality of adjustment values, the transmission weight adjustment unit 122 obtains a correlation value between the amplitude-adjusted weight whose phase has been changed by the adjustment value and the weight before amplitude adjustment. Thereby, a plurality of correlation values respectively corresponding to the plurality of adjustment values are obtained. Then, the transmission weight adjustment unit 122 uses the amplitude-adjusted weight after the phase adjustment, which is used when obtaining the maximum correlation value among the obtained correlation values, as the transmission weight setting unit 121. Use weights. Thereby, when the correlation between the weight before amplitude adjustment and the weight after amplitude adjustment is low, the phase of the weight after amplitude adjustment is adjusted so that the correlation becomes high.

  In this way, the transmission weight of the base station 1 is increased by adjusting the phase of the weight after amplitude adjustment so that the correlation between the weight before amplitude adjustment and the weight after amplitude adjustment becomes high. Even if the amplitude is increased, it is possible to prevent the transmission directivity of the array antenna 110 from changing greatly. Therefore, the null steering effect can be exhibited to some extent when the interference intensity is low.

<Other variations>
In the above example, the case where the present invention is applied to a base station has been described. However, any other wireless communication apparatus can be used as long as it is a wireless communication apparatus that controls transmission directivities of a plurality of antennas. Can be applied.

DESCRIPTION OF SYMBOLS 1 Base station 11 Communication part 110a Antenna 121 Transmission weight setting part 122 Transmission weight adjustment part 124 Transmission weight acquisition part 160 Interference strength acquisition part 170 Reception level acquisition part

Claims (8)

A communication unit that performs communication using a plurality of antennas;
A transmission weight obtaining unit for obtaining a plurality of transmission weights for performing null steering with respect to transmission directivity at the plurality of antennas;
A transmission weight setting unit for setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas;
An interference intensity obtaining unit for obtaining an intensity of an interference wave component included in a reception signal received by the communication unit;
A wireless communication apparatus comprising: a transmission weight adjustment unit that increases an amplitude of at least one transmission weight of the plurality of transmission weights as the intensity of the interference wave component is smaller. A communication unit that performs communication using a plurality of antennas;
A transmission weight obtaining unit for obtaining a plurality of transmission weights for performing null steering with respect to transmission directivity at the plurality of antennas;
A transmission weight setting unit for setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas;
An interference intensity obtaining unit for obtaining an intensity of an interference wave component included in a reception signal received by the communication unit;
When the intensity of the interference wave component is smaller than a threshold, the amplitude of at least one transmission weight of the plurality of transmission weights is increased, and when the intensity of the interference wave component is larger than the threshold Comprises a transmission weight adjusting unit that does not adjust the plurality of transmission weights. A wireless communication device according to any one of claims 1 and 2,
The plurality of antennas are N (N ≧ 2) antennas,
The transmission weight adjustment unit does not adjust the amplitude of the transmission weight having the largest amplitude from the first largest transmission weight to the Mth (1 ≦ M <N) in the plurality of transmission weights. A wireless communication device that increases the amplitude of a weight. The wireless communication device according to claim 3,
In the plurality of transmission weights, the transmission weight adjustment unit does not adjust the amplitude of the transmission weight having the largest amplitude from the transmission weight having the largest amplitude to the transmission weight having the largest amplitude. A wireless communication apparatus that increases the amplitude of at least one other transmission weight so that the amplitude of at least one transmission weight approaches. A wireless communication device according to any one of claims 1 and 2,
The plurality of antennas are N (N ≧ 2) antennas,
A reception level obtaining unit for obtaining a reception level for N reception signals respectively received by the N antennas;
The transmission weight adjustment unit transmits from the M antennas that receive the first reception signal having the highest reception level to the Mth reception signal (1 ≦ M <N) in the N reception signals. A wireless communication apparatus that increases the amplitude of at least one other transmission weight without adjusting M transmission weights set for each transmission signal. A wireless communication device according to any one of claims 1 to 5,
The transmission weight adjustment unit increases the amplitude of the transmission weight and increases the amplitude so that the correlation between the transmission weight before the amplitude is increased and the transmission weight after the amplitude is increased is increased. A wireless communication apparatus that adjusts the phase of the transmission weight after the transmission. (A) communicating using a plurality of antennas;
(B) obtaining a plurality of transmission weights for performing null steering with respect to transmission directivities at the plurality of antennas;
(C) setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas in the step (a);
(D) obtaining the intensity of the interference wave component included in the received signal received in the step (a);
(E) A step of increasing the amplitude of at least one of the plurality of transmission weights as the intensity of the interference wave component is smaller. (A) communicating using a plurality of antennas;
(B) obtaining a plurality of transmission weights for performing null steering with respect to transmission directivities at the plurality of antennas;
(C) setting the plurality of transmission weights to a plurality of transmission signals respectively transmitted from the plurality of antennas in the step (a);
(D) obtaining the intensity of the interference wave component included in the received signal received in the step (a);
(E) When the intensity of the interference wave component is smaller than a threshold value, the amplitude of at least one transmission weight of the plurality of transmission weights is increased, and the intensity of the interference wave component is larger than the threshold value. A wireless communication method comprising: adjusting the plurality of transmission weights when not larger.

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