Wireless communication device, wireless communication system, wireless communication method, and wireless communication program

Abstract

The present disclosure relates to a wireless communication device, a wireless communication system, a wireless communication method, and a wireless communication program. This wireless communication device carries out wireless communication with other devices and has a plurality of interfaces, an environment change detection unit, a correlation DB, and a CSI estimation unit. The plurality of interfaces include a CSI measurement interface and a data transmission interface. The environment change detection unit is configured to carry out, with respect to at least some of the links served by the interfaces, a process for acquiring CSI, a process for calculating a change of CSI, and a process for adjusting a CSI acquisition interval on the basis of the change. The correlation DB is configured to hold the CSI correlation between a CSI measurement link served by the CSI measurement interface and a data transmission link served by the data transmission interface. The CSI estimation unit is configured to carry out a CSI measurement process for measuring the CSI of the CSI measurement link, a process for acquiring the CSI correlation from the correlation DB, and a CSI estimation process for estimating the CSI of the data transmission link on the basis of the CSI correlation and the CSI obtained in the CSI measurement process. The data transmission interface is configured to carry out wireless communication with other devices on the basis of the CSI obtained in the CSI estimation process.

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication device, a wireless communication system, a wireless communication method, and a wireless communication program. [Background technology]

[0002] MIMO (Multiple-input Multiple-output) technology, which uses spatial multiplexing with multiple antennas, is known as a method for increasing communication capacity. As MIMO technology becomes more sophisticated and broader in bandwidth, there is an increasing demand for more frequent acquisition of CSI (Channel State Information).

[0003] Acquiring CSI requires one and a half round-trip packet exchanges. In particular, when using a time-varying channel where the channel environment changes over time, there is a large difference in the environment between when CSI is acquired and when actual data is transmitted, which poses a problem of inaccurate information transmission.

[0004] To solve the above-mentioned problems, Non-Patent Document 1 discloses a technique for improving communication performance of MIMO eigenmode transmission in a time-varying channel by performing channel prediction on the transmitting side and the receiving side. Also, Non-Patent Document 2 discloses a technique for improving communication performance of MIMO eigenmode transmission in a time-varying channel by simulation using a time-varying channel model. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Dorai, et al., "A method for improving communication performance degradation of MIMO eigenmode transmission in time-varying channels by performing channel prediction at the transmitter and receiver," IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J99-B, No. 10, pp. 938-965, July 1, 2016. [Non-patent document 2] Dorai, et al., "A method to improve communication performance degradation due to feedback delay in MIMO eigenmode transmission in time-varying channels without channel prediction," IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J99-B, No. 2, pp. 60-77, July 1, 2016. Summary of the Invention [Problem to be solved by the invention]

[0006] However, in systems using MLD (Multi Link Device) with multiple links, CSI estimation is required according to the number of links. This increases the overhead associated with CSI estimation. In other words, the environmental difference between when CSI is acquired and when actual data is transmitted increases, making accurate information transmission difficult.

[0007] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a wireless communication device that can reduce the overhead associated with CSI estimation and transmit actual data at close or overlapping timing, thereby reducing the influence of a time-varying channel and enabling accurate information transmission. [Means for solving the problem]

[0008] A first aspect of the present disclosure is preferably a wireless communication device that performs wireless communication with another device, the wireless communication device having a plurality of interfaces, an environmental change detection unit, a correlation DB, and a CSI estimation unit, wherein the plurality of interfaces include an interface for CSI measurement and an interface for data transmission, the environmental change detection unit is configured to perform a process of acquiring CSI for at least some of the links handled by the interfaces, a process of calculating CSI fluctuations, and a process of adjusting the CSI acquisition interval based on the fluctuations, the correlation DB is configured to hold a CSI correlation between the CSI measurement link handled by the CSI measurement interface and the data transmission link handled by the data transmission interface, the CSI estimation unit is configured to perform a CSI measurement process of measuring the CSI of the CSI measurement link, a process of acquiring the CSI correlation from the correlation DB, and a CSI estimation process of estimating the CSI of the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement process, and the data transmission interface is configured to perform wireless communication with the other device based on the CSI obtained by the CSI estimation process.

[0009] A second aspect of the present disclosure is preferably a wireless communication system that performs wireless communication between a wireless communication device and another device, wherein links carried by the wireless communication device include a CSI measurement link and a data transmission link, and the wireless communication system is configured to perform, for at least a part of the link, a process of acquiring CSI, a process of calculating CSI fluctuations, a process of adjusting a CSI acquisition interval based on the fluctuations, a process of measuring CSI on the CSI measurement link, a process of acquiring CSI correlation between the CSI measurement link and the data transmission link, a process of estimating CSI on the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement, and a process of performing wireless communication using the data transmission link based on the CSI obtained by CSI estimation.

[0010] A third aspect of the present disclosure is preferably a wireless communication method for performing wireless communication between a wireless communication device and another device, wherein links carried by the wireless communication device include a CSI measurement link and a data transmission link, and the wireless communication method is configured to perform the following: acquiring CSI for at least a portion of the link; calculating CSI fluctuations; adjusting a CSI acquisition interval based on the fluctuations; measuring CSI for the CSI measurement link; acquiring CSI correlation between the CSI measurement link and the data transmission link; estimating CSI for the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement; and performing wireless communication using the data transmission link based on the CSI obtained by the CSI estimation.

[0011] A fourth aspect of the present disclosure is preferably a wireless communication program to be executed by a wireless communication device that performs wireless communication with another device, the wireless communication program including a program for causing a computer to execute the following processes: a process for acquiring CSI for at least a part of the link; a process for calculating CSI fluctuations; a process for adjusting the CSI acquisition interval based on the fluctuations; a process for measuring CSI for the CSI measurement link; a process for acquiring CSI correlation between the CSI measurement link and the data transmission link; a process for estimating CSI for the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement; and a process for performing wireless communication using the data transmission link based on the CSI obtained by CSI estimation. [Effects of the Invention]

[0012] According to the first to fourth aspects of the present disclosure, the overhead associated with CSI estimation can be reduced, and the timing of CSI acquisition and actual data transmission can be brought closer together or overlapped, thereby reducing the influence of time-varying channels and enabling accurate information transmission. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a conceptual diagram showing an environment in which channel fluctuations are severe. [Figure 2] FIG. 1 is a conceptual diagram showing an environment with mild channel fluctuations. [Figure 3] 1 is a diagram illustrating a wireless communication system according to a first embodiment of the present disclosure. [Figure 4] FIG. 10 is a diagram showing the effects of the invention according to the first embodiment of the present disclosure. [Figure 5] 4 is a flowchart showing a correlation calculation process according to the first embodiment of the present disclosure. [Figure 6] 4 is a flowchart showing a CSI estimation process according to the first embodiment of the present disclosure. [Figure 7] 4 is a flowchart showing an environmental change detection process according to the first embodiment of the present disclosure. [Figure 8] FIG. 10 is a diagram illustrating a wireless communication system according to a modified example of the first embodiment of the present disclosure. [Figure 9] FIG. 10 is a functional block diagram illustrating a wireless communication system according to a modified example of the first embodiment of the present disclosure. [Figure 10] FIG. 10 is a functional block diagram illustrating an interface according to a modification of the first embodiment of the present disclosure. [Figure 11] FIG. 10 is a functional block diagram showing an environmental change detection unit according to a modified example of the first embodiment of the present disclosure. [Figure 12] FIG. 10 is a diagram illustrating a hardware configuration of a CSI estimator according to a modification of the first embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Embodiment 1 Figure 1 is an image of an environment with severe channel fluctuations. The graph on the left in the speech bubble shows the changes over time for two channels used in wireless communication. The thick and thin lines show the waveforms of two different channels. The solid and dotted lines show the channel waveforms before and after the changes over time. In other words, in this environment, the channel changes over time rapidly.

[0015] For example, in the case of communications using wideband signals such as band 5a, channel fluctuations become severe, making CSI estimation more difficult.

[0016] Figure 2 is an image of an environment with gentle channel fluctuations. The graph on the left in the speech bubble shows the changes over time for two channels used in wireless communication. The thick and thin lines show the waveforms of two different channels. The solid and dotted lines show the channel waveforms before and after changes over time. In other words, in this environment, the channel changes over time gently.

[0017] For example, in the case of communications using narrowband signals, such as band 5b, channel fluctuations are moderate. This disclosure is intended for use in such environments.

[0018] 3 is a diagram illustrating a wireless communication system according to a first embodiment of the present disclosure. The wireless communication system 100 achieves the object of the present disclosure by estimating the CSI of a data transmission link based on the CSI of a link not used for data transmission.

[0019] A description will be given of wireless communication in the wireless communication system 100. First, a description will be given of the detection of environmental changes that is performed in advance.

[0020] The wireless communication system 100 includes an MLD 2. The MLD 2 communicates wirelessly with an MLD 4 as its communication partner. Here, an environment where the CSI time variation is gentle and an MLD with multiple interfaces is used is assumed. Examples of environments where the CSI time variation is gentle include IoT, closed environments, and outdoor long-distance communications. Each interface handles a different frequency channel.

[0021] The MLD2 has one or more interfaces. Here, an embodiment having interfaces 6a, 6b, 6c, and 6d is shown. Of these four interfaces, the links handled by interfaces 6a and 6b are assumed to be links for data transmission. In particular, the frequency band of the link handled by interface 6b is assumed to be the same as that of the MLD4. Furthermore, the links handled by interfaces 6c and 6d are assumed to be links for CSI measurement.

[0022] First, CSI measurement is performed at the interface handling each link. This CSI measurement is performed continuously. Alternatively, this CSI measurement may be performed simultaneously at the interfaces of the MLD 4. The data measured at each interface is sent to the CSI estimation unit 8.

[0023] The CSI estimation unit 8 calculates the CSI variation based on the measured CSI. For example, it compares the CSI obtained from the previously received data with the CSI obtained from the newly received data, and obtains the difference. This CSI includes amplitude and phase information.

[0024] Then, based on the CSI fluctuation, it is determined whether the channel changes smoothly over time, specifically, whether the CSI amplitude fluctuation is below a threshold or whether the phase fluctuation is below a threshold or linear.

[0025] If the channel changes slowly over time, the system proceeds to acquire CSI correlation. If the channel changes slowly over time, the system either notifies the MLD4 of the CSI or requests re-measurement of the CSI. The system then calculates the CSI variability, estimates the channel coherence time, and adjusts the CSI measurement interval based on the estimated coherence time.

[0026] In addition, when links with large channel fluctuations and links with small channel fluctuations are mixed, only pairs of links for which CSI correlation calculation is possible may be presented.

[0027] The above-described environmental variation detection process can calculate CSI variations, which can determine the conditions under which link-to-link CSI estimation is possible depending on parameters such as the number of streams, received power, and PER.

[0028] Next, we will explain how to obtain CSI correlation. First, CSI measurement is performed at the interface that handles each link. This CSI includes amplitude and phase information.

[0029] Next, the CSI correlation between the data transmission link and the CSI measurement link is acquired. This CSI correlation acquisition is performed by the CSI estimation unit 8. The acquired CSI correlation is stored in the correlation DB 10.

[0030] Next, we will explain how to estimate the CSI of a data transmission link. The interface that handles the link for CSI measurement constantly measures the CSI. When there is a change in the CSI, it transmits the change information to the CSI estimation unit 8. The CSI estimation unit 8 estimates the CSI of the data transmission link based on the change information and the information in the correlation DB 10.

[0031] Based on the estimated CSI, the CSI estimation unit 8 determines a resource unit to be used in wireless communication with the MLD 4. This resource unit may be one carrier of an OFDM signal or a unit that aggregates multiple carriers. The determined information is then transmitted to an interface that serves as a data transmission link.

[0032] The interface serving as the data transmission link performs wireless communication with the MLD 4 using the resource unit determined by the CSI estimation unit 8.

[0033] As described above, in this disclosure, CSI estimation is performed using redundant links that are not data transmission links. This allows CSI estimation of data transmission links without packet switching, which is required in conventional CSI estimation. Therefore, overhead associated with CSI estimation is reduced, and by aligning or overlapping the timing of CSI acquisition and actual data transmission, the effects of time-varying channels are reduced, enabling accurate information transmission.

[0034] The CSI measured in this disclosure may use either upload or download, or may use both. However, it is preferable to directly measure download.

[0035] 4 is a diagram illustrating the effect of the invention according to the first embodiment of the present disclosure. The graph on the left shows the waveforms of two channels before change over time. The graph on the right shows the waveforms of two channels before and after change over time. The thick line shows the waveform of the channel that changes rapidly over time. The thin line shows the waveform of the channel that changes slowly over time. The solid and dotted lines show the waveforms of the channel before and after change over time.

[0036] In this embodiment, CSI estimation is performed for a channel that changes slowly over time based on the CSI of the CSI estimation link and the correlation DB10. That is, by using a redundant link different from the data transmission link, CSI estimation can be performed while reducing the overhead associated with packet switching in the data transmission link. This allows channel estimation to be performed immediately before or simultaneously with the transmission of the beamformed actual data frame. That is, it is possible to achieve more sophisticated and accurate beams.

[0037] 5 is a flowchart showing a correlation calculation process according to the first embodiment of the present disclosure. First, in step 100, the CSI of all links is acquired.

[0038] Next, in step 102, the CSI correlation between each link is calculated and recorded. This process is performed, for example, by the CSI estimation unit 8. The CSI estimation unit 8 calculates the CSI correlation between each link and records the calculation results in the correlation DB 10. The CSI correlation is, for example, a difference. This completes the correlation calculation process performed in advance for CSI estimation.

[0039] The subsequent steps 104 to 108 represent a correlation calculation process that is repeatedly performed as an update whenever an environmental change occurs. First, in step 104, the occurrence of an environmental change is confirmed. This environmental change may be a natural occurrence, or may be an active occurrence caused by a change in transmission power, etc.

[0040] Next, in step 106, the CSI of all links is acquired. Subsequently, in step 108, the CSI correlation between each link is calculated and recorded. This process is performed, for example, by the CSI estimation unit 8. The calculation of this CSI correlation includes time variation. That is, in addition to the CSI correlation between each link, the CSI variation of each link is recorded. This also calculates the correlation in the time-varying direction, that is, how the CSI changes at each link. Then, the CSI estimation unit 8 records the calculation result in the correlation DB 10.

[0041] As described above, in addition to the correlation calculation process performed in advance, the process of repeatedly updating the data in response to environmental changes is performed, allowing CSI estimation to be performed according to the environment.

[0042] 6 is a flowchart showing a CSI estimation process according to Embodiment 1 of the present disclosure. First, a data transmission link and a CSI estimation link are determined in step 110. This determination is performed, for example, by a CSI estimation unit.

[0043] The subsequent steps 112 to 120 represent the CSI estimation process that is repeatedly performed. First, the CSI of the link for estimation is measured in step 112. CSI measurement is performed on this link for estimation as needed or at all times.

[0044] Next, in step 114, the CSI of the data transmission link is estimated. This process is performed, for example, by the CSI estimation unit 8. This estimation is performed based on the correlation calculation results for each link stored in the correlation DB 10. Next, in step 116, the CSI of the data transmission link is measured.

[0045] In step 118, it is confirmed whether information in the correlation DB is insufficient. First, the CSI measured in step 116 is compared with the CSI estimated in step 114, and the difference is obtained as error information. Then, based on this error information, it is determined whether information in the correlation DB is insufficient. For example, if the value of the error information is greater than a certain value, it is determined that information in the correlation DB is insufficient. In other words, if there is a discrepancy between the CSI measured in step 116 and the CSI estimated in step 114, it is determined that information in the correlation DB is insufficient. If there is insufficient information, the process proceeds to step 120. If there is no insufficiency, the CSI estimation process ends.

[0046] Next, the correlation DB is updated in step 120. That is, the error information acquired in step 118 is stored in the correlation DB 10, thereby updating the correlation calculation results held in the correlation DB 10.

[0047] If the SNR of the CSI of the data transmission link is low, the CSI may be stored separately as low-reliability information. In this case, adjustments may be made, such as shortening the interval at which step 118 is performed.

[0048] 7 is a flowchart showing the environmental change detection process according to the first embodiment of the present disclosure. Here, the environmental change detection process is performed by repeating the update process shown in steps 120 to 128.

[0049] First, CSI is measured and recorded in step 120. Next, CSI variation is calculated in step 122. This process is performed, for example, by the CSI estimation unit 8. Here, by calculating the time variation of the CSI, for example, the propagation environment change degree is calculated.

[0050] Next, in step 124, it is determined whether the channel is changing significantly over time. This determination can be made, for example, based on whether the CSI amplitude fluctuation is below a threshold or whether the phase fluctuation is subphase or linear. If so, proceed to step 126. If not, end the update process.

[0051] In step 126, it is determined whether a parameter has deteriorated. Examples of parameters include the number of streams or SN. If it has deteriorated, the process proceeds to step 128. If it has not deteriorated, the update process ends.

[0052] In step 128, an adjustment of the CSI acquisition interval is requested, i.e., the interval between update processes is shortened to increase the frequency of CSI acquisition, thereby improving the accuracy of CSI estimation.

[0053] As described above, in the present disclosure, CSI estimation is performed using redundant links that are not data transmission links. This allows CSI estimation of data transmission links without packet switching, which is required in conventional CSI estimation. In other words, the overhead associated with CSI estimation is reduced, and by aligning or overlapping the timing of CSI acquisition and actual data transmission, the effects of time-varying channels are reduced, enabling accurate information transmission.

[0054] 8 is a diagram illustrating a wireless communication system according to a variation of the first embodiment of the present disclosure. The wireless communication system 100a differs from the wireless communication system 100 in that the communication partners of the MLD 2 are MLDs 12a and 12b, which have multiple interfaces.

[0055] The wireless communication system 100a includes MLDs 12a and 12b. The MLDs 12a and 12b are MLDs having multiple interfaces, similar to the MLD 2. That is, in the CSI correlation calculation process, it is necessary to obtain correlations corresponding to each interface of each terminal.

[0056] Therefore, it is determined in advance which interface each interface of the MLD 2 corresponds to. For example, it is determined in advance that interface 6b corresponds to the interface of the MLD 12a, and interface 6d corresponds to the interface of the MLD 12b. Then, the above-described correlation calculation process and CSI estimation process are performed for each corresponding interface.

[0057] As a result, even when the communication partner is an MLD, CSI estimation can be performed using a redundant link that is not a data transmission link. That is, as in the first embodiment, the overhead associated with CSI estimation can be reduced, and the timing of CSI acquisition and actual data transmission can be made close to or overlapped, thereby reducing the influence of time-varying channels and enabling accurate information transmission.

[0058] 9 is a functional block diagram showing a wireless communication system according to a modification of the first embodiment of the present disclosure. Here, wireless communication performed between the MLD2 and the MLD12a in the wireless communication system 100a will be described. Here, interfaces 6a and 6b of the MLD2 are defined as links for data transmission, and interfaces 6c and 6d are defined as links for CSI measurement. Furthermore, interfaces 14a and 14b of the MLD12a are defined as links for data transmission, and interfaces 14c and 14d are defined as links for CSI measurement. Note that there may be one or more links for data transmission and one or more links for CSI measurement, and the present invention is not limited to this example.

[0059] The processing flow in the functional block diagram of Figure 9 will be described. First, CSI measurements are performed at interfaces 6a to 6d and interfaces 14a to 14d. The measured data is transmitted to CSIDB 16. CSIDB 16 stores the transmitted CSI data between each link. Note that CSIDB 16 may store SNR data at the time of measurement in order to adjust the re-measurement interval when re-performing the correlation calculation process.

[0060] The CSIDB 16 transmits the transmitted CSI data between each link to the correlation calculation unit 18. When the correlation calculation unit 18 receives the CSI data between each link for each time period, it outputs CSI correlation information for each link. Examples of this CSI correlation information include the CSI correlation at each time period or the correlation of fluctuations between links over time.

[0061] The CSI correlation information output by the correlation calculation unit 18 is transmitted to the correlation DB 10. The correlation DB 10 stores the CSI correlation information. Note that the correlation DB 10 may also store correction information based on the actual link measurements, as described in the processing of steps 116 to 120.

[0062] The CSI correlation information held in the correlation DB 10 is transmitted to the CSI estimation unit 8. Upon receiving the CSI information of the CSI measurement link and the received CSI correlation information, the CSI estimation unit 8 outputs CSI estimation data of the data transmission link.

[0063] The CSI estimation data output by the CSI estimation unit 8 is transmitted to the interfaces 6a and 6b, which serve as data transmission links. The interfaces 6a and 6b perform wireless communication with the interfaces 14a and 14b based on the CSI estimation data.

[0064] The MLD 2 may also include a correction information calculation unit 20. The correction information calculation unit 20 has a function to perform the processes described in steps 116 to 120. That is, the correction information calculation unit 20 has a function to perform correction processing of the correlation DB based on CSI measurements in the data transmission link.

[0065] The flow of the above-mentioned correction process will be described below with reference to the functional block diagram in Figure 9. The correction information calculation unit 20 receives both the CSI estimation data output by the CSI estimation unit 8 and the CSI measurement data output by the interfaces 6a and 6b, which serve as the data transmission link. The correction information calculation unit 20 then compares the received data and obtains error information.

[0066] Subsequently, the correction information calculation unit 20 transmits the acquired error information to the correlation DB 10. By storing this error information, the correlation DB 10 can update the correlation calculation results stored in the correlation DB 10.

[0067] The wireless communication system 100a also includes an environmental change detection unit 28. The environmental change detection unit 28 will be described later.

[0068] 10 is a functional block diagram showing an interface according to a modification of the first embodiment of the present disclosure. The interface 6a includes a CSI measurement unit 22. The CSI measurement unit 22 performs CSI measurement. The interface 6a also includes a CSI reporting unit 24. The CSI reporting unit reports CSI data measured by the CSI measurement unit to the CSIDB 16.

[0069] 11 is a functional block diagram showing an environmental change detection unit according to a variation of the first embodiment of the present disclosure. The environmental change detection unit 28 includes a transceiver 29. The transceiver 29 receives the CSI measurement results via a receiver 30. The received CSI measurement results are input to a CSI calculation unit 32.

[0070] The CSI calculation unit 32 calculates CSI from the input CSI measurement results and transmits it to the fluctuation calculation unit 34. The fluctuation calculation unit 34 calculates the CSI fluctuation and transmits it to the measurement interval determination unit 36. The measurement interval determination unit determines whether the channel changes smoothly over time based on the transmitted CSI fluctuation and the TRx parameters of the transceiver 29. Examples of the TRx parameters include the transmission and reception power, PER, MCS, and the number of streams.

[0071] 12 is a diagram illustrating a hardware configuration of a CSI estimation unit according to a variation of the first embodiment of the present disclosure. The CSI estimation unit 8 includes a CPU 118. The CPU 118 is connected to a bus line 120. Memory devices such as a ROM 122, a RAM 124, and a storage 126 are connected to the bus line 120. A wireless communication program executed by the CPU 118 is stored in the memory device. The CSI estimation unit 8 can realize functions specific to this embodiment by the CPU 118 executing the wireless communication program.

[0072] A communication interface 128 is also connected to the bus line 120. The CSI estimation unit 8 communicates with a network via the communication interface 128. An operation unit 130 and a display unit 132 are also connected to the bus line 120. The operation unit 130 and the display unit 132 function as a user interface for operating the CSI estimation unit 8.

[0073] As described above, the CSI estimation unit 8 can realize the functions specific to this embodiment by the CPU 118 executing a wireless communication program. That is, the CSI estimation unit 8 can also be realized by a computer and the program. The program can also be recorded on a recording medium or provided via a network. [Explanation of symbols]

[0074] 6a Interface 6b Interface 6c Interface 6d interface 8 CSI estimation part 10 Correlation DB 14a Interface 14b interface 14c interface 14d Interface 20 Correction information calculation unit 28 Environmental change detection unit 100 Wireless Communication System 100a Wireless Communication System

Claims

1. A wireless communication device that performs wireless communication with another device, The apparatus includes a plurality of interfaces, an environmental change detection unit, a correlation DB, and a CSI estimation unit, The plurality of interfaces: An interface for CSI measurement and an interface for data transmission, The environmental change detection unit obtaining CSI for at least some of the links carried by the interface; A process of calculating a variation in the CSI; a process of adjusting a CSI acquisition interval based on the fluctuation; configured to perform The correlation DB is a CSI correlation between a CSI measurement link carried by the CSI measurement interface and a data transmission link carried by the data transmission interface; The CSI estimation unit a CSI measurement process for measuring CSI of the CSI measurement link; A process of acquiring the CSI correlation from the correlation DB; a CSI estimation process for estimating a CSI of the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement process; configured to perform The data transmission interface is configured to perform wireless communication with the other device based on the CSI obtained by the CSI estimation process. Wireless communication device.

2. The interface: The CSI estimation unit is configured to acquire a CSI of a link carried by the interface and transmit the CSI to the CSI estimation unit; The CSI estimation unit a CSI correlation calculation process for calculating a CSI correlation for the combination of links; A process of recording the CSI correlation in the correlation DB. is configured to implement The wireless communication device according to claim 1 .

3. The CSI correlation calculation process includes: The interface: When an environmental change occurs, a process of reacquiring CSI of the link handled by the interface and transmitting it to the CSI estimation unit; The CSI estimation unit recalculating the CSI correlation for the link combination; Including, The recalculated CSI correlation includes the correlation in the time-varying direction. The wireless communication device according to claim 2 .

4. Further comprising a correction information calculation unit, The correction information calculation unit measuring a CSI of the data transmission link; A process of acquiring error information between the measured CSI of the data transmission link and the CSI obtained by the CSI estimation process; storing the error information in the correlation DB and updating the correlation calculation results stored in the correlation DB; is configured to implement The wireless communication device of claim 1 .

5. The interface for the CSI measurement and the interface for the data transmission are determined based on the result of the CSI correlation calculation process. The wireless communication device according to claim 2 .

6. A wireless communication system for performing wireless communication between a wireless communication device and another device, the links carried by the wireless communication device include a CSI measurement link and a data transmission link; obtaining CSI for at least some of the links; A process of calculating a variation in the CSI; adjusting a CSI acquisition interval based on the variation; a process of measuring CSI of the CSI measurement link; A process of obtaining a CSI correlation between the CSI measurement link and the data transmission link; a process of estimating CSI of the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement; a process of performing wireless communication using the data transmission link based on the CSI obtained by the CSI estimation; 1. A wireless communication system configured to implement

7. A wireless communication method for performing wireless communication between a wireless communication device and another device, the links carried by the wireless communication device include a CSI measurement link and a data transmission link; obtaining CSI for at least some of the links; Calculating the variance of the CSI; adjusting a CSI acquisition interval based on the variation; and measuring CSI of the CSI measurement link; obtaining a CSI correlation between the CSI measurement link and the data transmission link; estimating a CSI of the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement; performing wireless communication using the data transmission link based on the CSI obtained by the CSI estimation; A wireless communication method configured to perform the steps of:

8. A wireless communication program for causing a wireless communication device that performs wireless communication with another device to perform the program, the links carried by the wireless communication device include a CSI measurement link and a data transmission link; obtaining CSI for at least some of the links; A process of calculating a variation in the CSI; adjusting a CSI acquisition interval based on the variation; a process of measuring CSI of the CSI measurement link; A process of obtaining a CSI correlation between the CSI measurement link and the data transmission link; a process of estimating CSI of the data transmission link based on the CSI correlation and the CSI obtained by the CSI measurement; a process of performing wireless communication using the data transmission link based on the CSI obtained by the CSI estimation; A wireless communication program including a program for causing a computer to execute the above.

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