JPWO2009139263A1 - Calibration method and communication apparatus - Google Patents

Abstract

The present invention is a calibration method in a case where a radio device having a plurality of antennas that perform communication by the TDD system performs calibration of each antenna, and the first method is as follows. A first calibration step for calculating a correction coefficient; a second calibration step for calculating a second correction coefficient by performing antenna calibration using communication with another radio; and the first calibration step. A correction coefficient selection step of selecting either one of the correction coefficient and the second correction coefficient according to the situation and setting it as a final correction coefficient.

Description

  The present invention relates to a calibration method for performing calibration between a plurality of antennas with high efficiency in wireless communication, and a communication apparatus for realizing the calibration method.

  The demand for high-speed wireless communication is high, and high-speed wireless communication transmission technology is required. Therefore, recently, a technique in which a radio device performs high-speed signal transmission using a plurality of antennas has been widely studied. In future mobile communications, an environment in which a base station simultaneously performs spatial multiplexing transmission using a transmission beam to a plurality of terminals is also assumed. In addition, transmission power necessary for communication can be reduced by performing appropriate transmission beam forming in the terminal. Therefore, high-accuracy transmission beam forming technology is considered as an important issue in the future.

  Among them, in the TDD (Time Division Duplex) method in which the same frequency is alternately used in the uplink and the downlink, there is an expectation for an advantage that the propagation path reversibility can be used in forming the transmission beam. Usually, in order to appropriately control the transmission beam, channel information is required at the transmitter (transmitter-side radio). At this time, assuming that the ideal channel reversibility can be obtained in the TDD system, channel measurement is performed using a pilot signal from the receiver (receiver-side radio device) to the transmitter, thereby easily receiving from the transmitter. The channel status to the machine can be grasped.

  However, in reality, although the reversibility is established in the actual propagation path from the antenna end of the transmitter to the antenna end of the receiver, the propagation path measured in the digital domain (hereinafter referred to as the characteristic difference of analog devices in the transceiver circuit) (Referred to as measurement propagation path) does not hold complete reversibility. For this reason, the radio equipment measures the propagation path in the digital domain, but in order to use reversibility, it compensates for the analog characteristic difference between the transmitter and the receiver (transmission / reception system analog characteristic difference). Calibration that maintains the reversibility of the image is usually required.

  The conventional techniques for performing such calibration can be roughly divided into two. One is self-calibration disclosed in Patent Document 1 and Non-Patent Document 1 below. In this self-calibration, a transmission / reception system analog characteristic difference between a plurality of antennas is compensated by transmitting / receiving a test signal between the plurality of antennas in the wireless device.

  The other is calibration disclosed in Patent Document 2 below. In this method, a radio having a plurality of antennas transmits / receives test signals to / from other radios, so that a plurality of antennas can be obtained. Compensates for the difference in analog characteristics between the transmitting and receiving systems.

JP 2006-279668 A US Pat. No. 6,037,898 K. Nishimori, K. Cho, Y. Takatori, T. Hori, “A novel configuration for realizing automatic calibration of adaptive array using dispersed SPDT switches for TDD systems”, IEICE Trans. On Commun., Vol. E84-B, No .9, pp.2516-2522, Sept. 2001.

  The self-calibration described in Patent Document 1 and Non-Patent Document 1 has an advantage that a control signal is not required in the wireless system because a weak transmission power test signal is exchanged between a plurality of antennas in the wireless device. However, because the test signal transmission power is much lower than the transmission power during communication, the analog characteristics of the amplifier change between the test signal transmission and the communication signal transmission when the transmitter amplifier of the radio is power dependent. There is a case. In this case, even if self-calibration is performed using a test signal, phase matching between antennas cannot be sufficiently maintained during communication.

  On the other hand, in the method of performing calibration via another wireless device described in Patent Document 2, since the transmission power of the test signal is similar to the transmission power during communication, the transmission amplifier has power dependency. In addition, phase consistency between antennas can be maintained during communication. However, when performing calibration, in order to transmit / receive a test signal to / from another wireless device, it is necessary to transmit a control signal for controlling the other wireless device.

  As described above, the self-calibration has a problem of the power dependency of the signal amplifier, while the calibration performed through another radio device has a problem of increasing the amount of control signal.

  The accuracy of the correction coefficient obtained by each of the above methods also varies depending on the reception quality (SNR and SINR) of the test signal. It is desirable to exchange test signals in an environment where the influence of noise and interference is small. However, in actuality, there are cases where the transmitted signal is weak in self-calibration, and in the calibration performed via other radios, antennas are used. Due to the wide distance, the correction coefficient is not always obtained with sufficient reception quality, and there is a problem that a test signal that is long in time must be used to ensure calibration accuracy.

  The present invention has been made in view of the above, and realizes a calibration method for efficiently compensating for an analog characteristic difference between antennas by solving the problem of power dependency and control signal amount. An object of the present invention is to obtain a communication device that performs the above.

  In order to solve the above-described problems and achieve the object, the present invention is a calibration method in a case where a radio apparatus having a plurality of antennas that perform communication by the TDD method calibrates each antenna, A first calibration step for calculating a first correction coefficient by performing antenna calibration by the radio alone, and a second correction coefficient by performing antenna calibration using communication with other radios A second calibration step to be calculated; and a correction coefficient selection step of selecting one of the first correction coefficient and the second correction coefficient depending on the situation to obtain a final correction coefficient. It is characterized by that.

  According to the present invention, it is possible to obtain a calibration method that efficiently compensates for an analog characteristic difference between antennas.

FIG. 1 is a diagram illustrating the concept of Method A (self-calibration). FIG. 2 is a diagram illustrating the concept of Method B (calibration performed via another wireless device). FIG. 3 is a diagram showing the concept of the calibration method of the present embodiment. FIG. 4 is a flowchart illustrating an example of a control procedure of the calibration method according to the present embodiment. FIG. 5 is a diagram illustrating a signal correction operation during signal transmission. FIG. 6 is a diagram illustrating a control signal transmission / reception operation between the wireless device and the base station in the calibration by the method B. FIG. 7 is a diagram illustrating a configuration example of a wireless device that realizes the calibration method according to the second embodiment. FIG. 8 is a diagram illustrating an operation procedure of the method B used in the calibration method according to the third embodiment. FIG. 9 is a diagram illustrating an operation procedure of the method B used in the calibration method according to the third embodiment. FIG. 10 is a diagram illustrating an operation procedure of method B used in the calibration method of the third embodiment.

1 Radio 2 Base station (other radio)
DESCRIPTION OF SYMBOLS 11 Transmission / reception control part 12 Electric power measurement part 13 Reception quality prediction part 14 Test signal sequence length determination part 15 Parameter control part

  Embodiments of a calibration method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In the following description, for the sake of simplicity, self-calibration will be referred to as method A, and calibration performed via another wireless device will be referred to as method B.

Embodiment 1 FIG.
Here, first, the prerequisite technology used in the calibration method of the present embodiment will be described. In the calibration method of the present embodiment, the calibration of the method A and the method B is used. FIG. 1 is a conceptual diagram of calibration of Method A. In this method A, the wireless device 1 transmits / receives a test signal between two antennas, and calculates an analog characteristic difference between the antennas from the result. In the wireless device 1, the component with T _i is a transmission processing unit (transmitter) corresponding to the i-th (i = 1,..., M) antenna, and the component with R _i is i. A reception processing unit (receiver) corresponding to the th antenna. FIG. 1 shows the case where the number of antennas is 2. However, when the number of antennas is 3, any one antenna is used as a reference antenna, and the test signal is transmitted between the reference antenna and another antenna. Transmission / reception is performed, and an analog characteristic difference between the reference antenna and each antenna is calculated from the obtained result. FIG. 2 is a conceptual diagram of the calibration of the method B. In the method B, the wireless device 1 transmits / receives a test signal between each antenna and another wireless device (for example, the base station 2), and calculates an analog characteristic difference between the antennas from the result. In the base station 2, component transmission processing unit T _BS is attached (transmitter), the components R _BS is attached is a reception processing unit (receiver).

  Note that self-calibration conventionally used generally has a problem of power dependency, but the method A used in the present embodiment may be any conventional self-calibration method. In addition, in the method of performing calibration through another wireless device that has been used conventionally, the amount of control signal generally increases, but the method B used in the present embodiment is the conventional method performed through another wireless device. Any calibration method may be used.

  FIG. 3 is a diagram showing the concept of the calibration method of the present embodiment. As shown in the figure, this embodiment is characterized in that calibration is performed by selectively or adaptively using the method A and the method B depending on the situation. Hereinafter, the calibration operation of the present embodiment will be described based on FIG. 4 which is a flowchart showing an example of the control procedure of the calibration method of the present embodiment.

In the calibration method according to the present embodiment, the radio (communication device) 1 first calculates the correction coefficient u _A by the method A (see FIG. 1) and the method B (see FIG. 1) within a time in which the temperature characteristics can be regarded as equivalent. 2), the correction coefficient u _B is calculated (step S1).

Next, the wireless device 1 compares the two calculated correction coefficients u _A and u _B and confirms whether they are similar (step S2).

If the two correction coefficients are similar (step S2, Yes), it is determined that the influence of the power dependency of the transmission amplifier in the method A is small and the method A can be applied, and the correction coefficient u _A calculated by the method A is determined. Is adopted (step S3). A method for determining whether the correction coefficients are similar will be described later. Further, in order to compensate for the temperature change, the correction coefficient is calculated by the method A when a certain time has elapsed, and the correction coefficient u _A is updated (step S4). Further, it is confirmed whether or not it is necessary to reselect the correction coefficient calculation method (step S5). If reselection is necessary (step S5, Yes), the process proceeds to step S1. On the other hand, if there is no need for reselection (step S5, No), the correction coefficient is calculated by the method A when a predetermined time has passed and the correction coefficient u _A is updated (step S4). Thereafter, the processes in steps S4 and S5 are repeated until it is determined in step S5 that the correction coefficient calculation method needs to be selected again.

On the other hand, when the two correction coefficients are not similar but greatly different (step S2, No), it is determined that the influence of the power dependency of the transmission amplifier in the method A is large and the method A is not applicable. Then, the correction coefficient u _B calculated by the method B is employed (step S6). Further, in order to compensate for the temperature change, the correction coefficient is calculated by the method B when a certain time has elapsed, and the correction coefficient u _B is updated (step S7). Further, it is confirmed whether or not it is necessary to reselect the correction coefficient calculation method (step S8). If reselection is necessary (step S8, Yes), the process proceeds to step S1. On the other hand, if there is no need for reselection (step S8, No), the correction coefficient is calculated by the method B when a fixed time has passed and the correction coefficient u _B is updated (step S7). Thereafter, the processes in steps S7 and S8 are repeated until it is determined in step S8 that the correction coefficient calculation method needs to be selected again.

Here, the correction coefficient is a value that is individually set for each antenna in order to compensate for a transmission / reception system analog characteristic difference. Also, as shown in FIG. 5, the first antenna (antenna # 1) is normally used as a reference, and the correction coefficient is set to 1 for the reference antenna. The other antenna (antenna #m) corrects the transmission signal or the reception signal using the correction coefficient so that the same transmission / reception analog characteristics as the reference antenna are obtained. In the above-described control, the calibration between the two antennas is assumed, and the correction coefficients at the second antenna (antenna #m) are shown as u _A and u _B. This is just an example, and the same concept can be applied to the case of three or more antennas.

  According to the calibration method of the present embodiment, the method A with a small amount of control signal is used when the problem of the power dependency of the amplifier is small in the method A, and the power dependency when the influence of the power dependency is large. Method B that is not affected by the above is used. As described above, the method A and the method B are properly used depending on the situation. As a result, the conventional method using only the method A has a problem of power dependency of the amplifier. However, in the method of the present embodiment, the method A is used only when the power dependency of the amplifier does not matter. There is no power dependency problem. Compared with the conventional method using only method B, the amount of control signal can be suppressed by appropriately using method A in the present embodiment.

  Normally, the analog characteristics of the transmission / reception system change with time. Therefore, as described above, the calibration is repeatedly executed to follow the characteristic variation. In particular, the analog characteristics are likely to change according to the temperature change, but can usually be regarded as constant for about 1 minute. Accordingly, in steps S4 and S7, the selected method (method A in step S4, method B in step S7) is repeatedly executed, for example, in a time period of about 1 minute, and the correction coefficient is updated. On the other hand, the process of steps S1 and S2, that is, the process of selecting the method to be applied is a period (for example, 1 hour period, 1 day period, etc.) sufficiently longer than the period of updating the correction coefficient in steps S4 and S7. Execute. Therefore, in steps S5 and S8, it is confirmed whether or not a predetermined period (one hour period, one day period, etc. sufficiently longer than 1 minute) has elapsed after the method selection is performed, and the transition destination is determined according to the confirmation result. To decide. In addition, the process of selecting the method to be applied may be performed when the radio power has moved and the transmission power used for communication has changed greatly, instead of determining the elapsed time since the process was executed. Alternatively, determination based on elapsed time and determination based on transmission power may be used in combination. As described above, when the method of the present embodiment is used, it is possible to perform calibration without being affected by the power dependency of the amplifier while suppressing the control signal amount as compared with the conventional method B.

  In the calibration method of the present embodiment, it is necessary to notify information for switching between method A and method B to another wireless device (for example, base station 2) as shown in FIG. For example, when the wireless device 1 having a plurality of antennas performs calibration with the base station 2, the wireless device 1 first transmits a request signal for requesting the calibration by the method B to the base station 2, and the base station 2 transmits the wireless device. When the request signal from 1 is received, calibration by the method B is executed between the wireless device 1 and the base station 2. Further, the wireless device 1 also performs calibration by the method A independently. Thereafter, the wireless device 1 compares the two correction coefficients obtained by the method A and the method B, and selects one of them (corresponding to the processing in steps S1 and S2 in FIG. 4). When the correction coefficient obtained by the method A is selected, that is, when the method A is used thereafter (when steps S3 to S5 in FIG. 4 are executed), calibration control that requests the base station 2 to stop calibration control. Send a stop signal. When the base station 2 receives the calibration control stop signal, the base station 2 stops the calibration by the method B, and thereafter, the radio device 1 performs the calibration by the method A at regular intervals. When the correction coefficient obtained by the method B is selected, that is, when the method B is subsequently used (when steps S6 to S8 in FIG. 4 are executed), the radio device 1 controls the base station 2 to perform calibration control. A calibration control continuation signal for requesting continuation of is transmitted. When the base station 2 receives the calibration control continuation signal, the base station 2 continues the calibration by the method B, so that the test signal is exchanged with the wireless device 1 at a specific cycle, and the calibration by the method B is executed.

  As described above, the wireless device 1 notifies the base station 2 of the calibration control stop signal or the continuation signal in accordance with the selection of the method A and the method B. Although the control of the base station 2 and the wireless device 1 is shown here as an example, the above-described control may be performed between any two wireless devices.

Next, a method for determining whether the correction coefficients u _A and u _B are similar or greatly different in step S2 described above will be described below. Various methods can be used as this determination method. For example, the determination can be made using the following equation (1).

| u _A / u _B −1 | <T (1)
Here, T is a threshold value. Normally, u _A and u _B are complex numbers, but if the ratio is close to 1, the correction coefficients u _A and u _B can be regarded as similar. Therefore, if the expression (1) is satisfied, it is determined that the correction coefficients are similar, and the control shown in steps S3 to S5 is executed. If not satisfied, the control shown in steps S6 to S8 is executed. In addition, in the present embodiment, a method of determining the similarity between the correction coefficients u _A and u _B based on various criteria can be considered.

  As described above, in the present embodiment, the calibration method of the method A in which the calibration accuracy is deteriorated when the power dependency is present, but the test signal does not need to be transmitted to and received from another wireless device, and the power Although there is no deterioration in calibration accuracy due to dependency, the calibration method of Method B, which requires a control signal for transmitting and receiving test signals to and from other wireless devices and is complicated, is used depending on the situation. Specifically, when there is no power dependency, the self-calibration (method A) that is easy to process is adopted, and when there is power dependency and sufficient correction performance cannot be obtained by method A, the processing is The calibration (method B), which is complicated but does not degrade the correction accuracy due to the influence of power dependency, is performed using communication with other wireless devices (method B). As a result, a calibration method that efficiently compensates for the difference in analog characteristics between antennas can be obtained.

In the present embodiment, the antenna calibration assuming two antennas has been described. However, in the case of N antennas (N ≧ 3), the correction coefficient vector U _A = [1, u _A (2), u _A (3), ..., u _A (N)] ^T , U _B = [1, u _B (2), u _B (3), ..., u _B (N)] ^T On the other hand, equivalent control is applied. In this case, the similarity between the vectors U _A and U _B can be determined by the following equation (2), for example.

| U _A ^H U _B | / (| U _A | ・ | U _B |)> V (2)
Here, superscript T ( ^T ) and superscript H ( ^H ) represent transposition and transposition conjugate, respectively, and V represents a threshold value.

The value of the left side of the above equation (2) increases when the directions of the vectors U _A and U _B are close. Therefore, when the left side of Equation 2 is larger than a certain threshold value V, the vectors U _A and U _B can be regarded as similar states.

  As described above, the calibration method according to the present embodiment can also be applied to the case of performing calibration with three or more antennas.

Embodiment 2. FIG.
Next, the calibration method according to the second embodiment will be described. The calibration method described in the first embodiment has been described assuming that any method may be used without particularly mentioning the method A (self-calibration) to be used. An example of Method A will be described. Specifically, a calibration method is described in which the reception quality of the test signal to be used is predicted, and the method A is performed while changing the length of the test signal according to the prediction result.

  FIG. 7 is a diagram illustrating a configuration example of a radio that realizes the calibration method according to the second embodiment. In the method A described above, reception quality prediction is performed and the length of a test signal used for calibration is controlled. The example of a structure of the radio | wireless machine 1a to perform is shown. The wireless device 1a includes a transmission / reception control unit 11 that performs signal transmission / reception processing, a power measurement unit 12 that measures the power of a reception signal, a reception quality prediction unit 13 that predicts reception quality of a test signal, and a test signal to be transmitted. A test signal sequence length determination unit 14 that determines the length of the signal, and a parameter control unit 15 that sets various parameters when executing the calibration operation.

  Hereinafter, the method A (self-calibration) performed by the wireless device 1a will be described with reference to FIG. The overall calibration operation is as described in the first embodiment.

  When the wireless device 1a performs self-calibration, first, the power measurement unit 12 collects power measurement data necessary for the reception quality prediction unit 13 in the subsequent stage to predict reception quality. For example, the power measurement unit 12 measures noise power (including interference power) in a silent section and calculates the magnitude of noise power. When power measurement data is collected by the power measurement unit 12, the reception quality prediction unit 13 next predicts reception quality such as SNR and SINR using the power measurement data. In the reception quality prediction operation, in addition to the noise power data calculated by the power measurement unit 12, the power level of the signal scheduled to be transmitted, and the literature “Noda, Hara, Yano, Kubo,“ bidirectional channel measurement in the TDD system are used. If the radio 1a is equipped with an attenuator (attenuator) described in "Antenna Array Self-Calibration Used", IEICE Technical Report RCS2008-12, May 2008, the attenuation ( The reception quality is predicted using the attenuation rate. In addition, since the attenuation amount utilized is hold | maintained, for example in the parameter control part 15, it is acquired. The received signal power can be estimated from, for example, a value obtained by subtracting the propagation loss between the plurality of antennas of the radio station 1a and the attenuation amount of the attenuator from the planned transmission power (power of the signal scheduled to be transmitted), The SNR can be predicted from this and the noise power measurement result described above. This prediction result is sent to the test signal sequence length determination unit 14, and the test signal sequence length determination unit 14 uses it in calibration based on the reception quality prediction result (for example, SNR) received from the reception quality prediction unit 13. Determine the number of symbols in the test signal. For the number of symbols, for example, a comparison table of the SNR and the required number of symbols is created and held in advance, and the number of symbols is determined by comparing this comparison table with the SNR received from the reception quality prediction unit 13. The determined number of symbols is held in the parameter control unit 15, and the test signal having the number of held symbols is used during calibration.

  When the number of antennas is 3 or more, the reception quality is predicted for each combination of the reference antenna and each antenna to be calibrated, and the test signal length (number of symbols) is determined for each combination. If you want to avoid complication of control, predict the reception quality and determine the test signal length for any one combination, and fix the test signal of the determined length in all combinations. It may be used.

  As described above, in the present embodiment, the radio that performs calibration predicts the reception quality of the test signal, and performs the calibration process using the test signal having a length corresponding to the prediction result. . As a result, for example, when the reception SNR of the test signal at the time of calibration is poor, the number of symbols of the test signal is correspondingly increased and the calibration process is performed, so that necessary accuracy can be ensured. Become. Further, when a sufficient reception SNR can be obtained, it is possible to obtain an effect such as suppressing transmission of an unnecessary number of symbols and shortening a communication disconnection time that occurs when the calibration process is performed.

  In addition, by changing the comparison table used in the test signal sequence length determination unit 14 according to the modulation method to be used, the accuracy of the necessary correction coefficient is changed depending on the modulation method used at the time of data communication after calibration. For example, even in a system that uses a modulation scheme that requires a small calibration distance and a higher calibration accuracy, and a system that uses adaptive modulation, the accuracy is controlled by the modulation scheme and the predicted reception quality, It is possible to prevent a decrease in communication efficiency due to calibration accuracy.

  In the present embodiment, the case where a method of predicting using the power measurement result of the silent section is applied as a method of predicting the reception quality has been described. However, in addition to this, a system that performs calibration periodically In the method of using the received power at the time of the previous calibration, the method of using the received power at the time of the most recent data communication, and receiving the received power and SNR from the wireless station that is the communication partner, and using it Method (for example, if communication is performed between the same model, the transmission power is known, and the propagation path reversibility between antennas is established, the reception power, noise power, SNR, etc. The reception quality of the station can be estimated), and the reception quality may be predicted by combining these.

Embodiment 3 FIG.
Next, the calibration method according to the third embodiment will be described. In the second embodiment, the case where the length of the test signal used in the method A is variable has been described. However, in the present embodiment, the test signal is used in the method B (calibration performed through another wireless device). A case where the length of the test signal to be made is variable will be described.

  Hereinafter, a method B (calibration performed via another wireless device) executed by the wireless device of the present embodiment will be described with reference to FIGS. 8 to 10 are diagrams illustrating an operation procedure of the method B used in the calibration method according to the third embodiment. In these drawings, as an example, a radio (method A) including a plurality of antennas is illustrated. FIG. 4 shows an operation procedure in the case where the radio apparatus) also executes the method B while regarding the base station as another radio apparatus. FIG. 8 shows a procedure when the reception quality prediction of the test signal and the determination of the test signal length are performed on the wireless device side, and FIG. 9 performs the reception quality prediction of the test signal on the wireless device side to determine the test signal length. FIG. 10 shows the procedure when the reception quality prediction of the test signal and the determination of the test signal length are performed on the base station side. 8 to 10, the same step number is assigned to the same process.

  First, the procedure in the case where the test signal reception quality prediction and the test signal length determination shown in FIG.

  In the procedure shown in FIG. 8, first, the wireless device performs reception power measurement (step S11), then performs reception quality estimation based on this result (step S12), and further, a test signal based on the reception quality estimation result. A sequence length is determined (step S13). Note that the processing executed in each of these steps is the same as the processing executed by the power measurement unit 12, the reception quality prediction unit 13, and the test signal sequence length determination unit 14 described in the second embodiment. Thereafter, a signal designating the determined sequence length is transmitted to the base station (step S14), and the base station transmits a test signal having a length determined by the wireless device to the wireless device (step S15). Further, the radio transmits a test signal having a length determined in step S13 to the base station (step S16). Then, the base station feeds back the measurement result of the test signal transmitted from the radio device to the radio device (step S17), and the radio device returns the measurement result fed back and the test signal transmitted from the base station in step S15. The correction coefficient is calculated based on the reception result (step S18).

  By performing the method B according to the above procedure, the calibration performed with the test signal having a length corresponding to the reception quality is realized in the same manner as the calibration shown in the second embodiment. Even when the SNR at the time of reception is small, the test signal can be transmitted and received with the corresponding sequence length, and calibration can be performed with the required accuracy.

  In the procedure shown in FIG. 9, when performing steps S11 and S12 described above, the radio notifies the base station of the reception quality (reception quality estimation result) obtained by executing step S12 (step S21). Based on the notified reception quality, the base station determines the length of the test signal (test signal sequence length) (step S22). In this step S22, the base station determines the test signal sequence length in the same procedure as the test signal sequence length determination unit 14 shown in Embodiment 2 determines the test signal sequence length. After the base station determines the test signal sequence length, steps S15 to S18 already described are executed. In this case, the radio device performs a test such as having the base station notify the sequence length of the test signal to be received in advance, or defining the unique sequence included in the signal as the start and end points of the test signal. Operates by detecting the length of the signal.

  In the procedure shown in FIG. 9, the radio side estimates the reception quality from the reception power measurement result and notifies the base station of the obtained reception quality estimation result. The result may be transmitted to the base station as it is, and the base station may execute step S22 after estimating the reception quality based on the notified reception power measurement result.

  In the procedure shown in FIG. 10, the base station executes the same process as in step S11 above to measure the received power (step S31), and further executes the same process as in step S12 above to receive the reception quality. Is estimated (step S32). And a base station performs step S22 already demonstrated using the reception quality estimation result obtained by performing step S32. Thereafter, steps S15 to S18 are executed in the same manner as the procedure shown in FIGS.

  Although not shown, prior to step S31, the wireless device instructs the base station to start the calibration process of Method B after determining the test signal sequence length. On the contrary, the base station may autonomously determine the test signal sequence length and notify the radio device that the calibration process of method B is started, and then execute the above procedure. Similarly to the case of operating according to the procedure shown in FIG. 9, the radio apparatus notifies the base station of the sequence length of the test signal to be received in advance, or the unique sequence included in the signal is the starting point of the test signal. And, it operates by detecting the length of the test signal by a method such as prescribing as termination.

  When the base station and the radio antenna are reversible communication paths, and the noise level (noise power) and transmission power on the radio side are known on the base station side by some method, the base station measures the received power. Since the reception quality result of the radio can be predicted from the result, the procedure shown in FIG. 10 can be adopted.

  When the method B is performed according to the procedure shown in FIG. 9 or FIG. 10, the same effect as that obtained when the method B is performed according to the procedure shown in FIG.

  Of course, it is also possible to combine the calibration (method B) according to the procedure shown in the present embodiment and the calibration (method A) shown in the second embodiment. In both cases, the calibration can be performed with a required accuracy by using a test signal having a length corresponding to the reception quality. As a result, more efficient calibration becomes possible.

  As described above, the calibration method according to the present invention is useful for wireless communication using a plurality of antennas, particularly when the wireless device efficiently compensates for a difference in transmission / reception system analog characteristics between antennas. Is suitable.

Claims (12)

A calibration method in a case where a radio device having a plurality of antennas that perform communication using the TDD method calibrates each antenna,
A first calibration step of calculating a first correction coefficient by performing antenna calibration by the radio alone;
A second calibration step of calculating a second correction coefficient by performing antenna calibration using communication with another wireless device;
A correction coefficient selection step of selecting any one of the first correction coefficient and the second correction coefficient depending on the situation, and setting it as a final correction coefficient;
A calibration method comprising:   2. The calibration according to claim 1, wherein in the correction coefficient selection step, the first correction coefficient and the second correction coefficient are compared, and one of the correction coefficients is selected based on the comparison result. Method.   3. The first correction coefficient is selected as a final correction coefficient when the comparison result indicates that the first correction coefficient and the second correction coefficient are similar to each other. Calibration method described in 1. According to the selection result in the correction coefficient selection step, the first calibration which is antenna calibration performed by the radio alone or the second calibration which is antenna calibration performed using communication with the other radio Periodically performing a correction coefficient updating step for updating the final correction coefficient,
The calibration method according to claim 1, further comprising:   When the first correction coefficient is selected in the correction coefficient selection step, the first calibration is periodically executed, and when the second correction coefficient is selected in the correction coefficient selection step The calibration method according to claim 4, wherein the second calibration is periodically executed.   In executing the correction coefficient update step, an operation for performing the second calibration is performed by transmitting a control signal corresponding to the selection result in the correction coefficient selection step to the other radio device. 6. The calibration method according to claim 4 or 5, wherein whether or not it is necessary is notified to the other wireless device. The first calibration step includes
A reception quality prediction step for predicting a signal reception quality when a test signal is transmitted and received between antennas for calibration;
A test signal length determination step for determining a length of a test signal used in calibration based on a prediction result in the reception quality prediction step;
A calibration execution step for performing calibration by transmitting and receiving the test signal of the length determined in the test signal length determination step between the antennas;
The calibration method according to claim 1, further comprising: The second calibration step includes
A reception quality prediction step of predicting a signal reception quality when transmitting / receiving a test signal to / from the other wireless device;
A test signal length determination step for determining a length of a test signal used in calibration based on a prediction result in the reception quality prediction step;
A calibration execution step of performing calibration by transmitting and receiving the test signal of the length determined in the test signal length determination step to and from the other wireless device;
The calibration method according to claim 1, further comprising: The second calibration step includes
A reception quality prediction step of predicting a signal reception quality when transmitting / receiving a test signal to / from the other wireless device;
Test signal length determination instruction step for notifying the other wireless device of the prediction result in the reception quality prediction step and instructing to determine the length of the test signal used in calibration based on the notified prediction result When,
A calibration execution step for performing calibration by transmitting / receiving a test signal having a length determined by the other wireless device according to the instruction to / from the other wireless device;
The calibration method according to claim 1, further comprising: The second calibration step includes
A power measurement step for measuring noise power necessary for predicting signal reception quality when transmitting / receiving a test signal to / from the other radio device;
A test signal length determination instruction step for notifying the other wireless device of the measured noise power and instructing to determine the length of the test signal used in calibration based on the notified noise power;
A calibration execution step for performing calibration by transmitting / receiving a test signal having a length determined by the other wireless device according to the instruction to / from the other wireless device;
The calibration method according to claim 1, further comprising: The second calibration step includes
Instructs the other wireless device to predict the signal reception quality when transmitting / receiving the test signal to / from itself and to determine the length of the test signal to be used for calibration based on the prediction result A test signal length determination instruction step;
A calibration execution step for performing calibration by transmitting / receiving a test signal having a length determined by the other wireless device according to the instruction to / from the other wireless device;
The calibration method according to claim 1, further comprising:   A communication apparatus that operates as a wireless device including the plurality of antennas according to claim 1.

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