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 another device and comprises a plurality of interfaces, a correlation DB, and a CSI estimation unit. The plurality of interfaces include an interface for CSI measurement and an interface for data transmission. The correlation DB is configured to hold CSI correlation between a CSI measurement link which the interface for CSI measurement is responsible for and a data transmission link which the interface for data transmission is responsible for. The CSI estimation unit is configured to carry out CSI measurement processing for measuring the CSI of the CSI measurement link, processing for acquiring the CSI correlation from the correlation DB, and CSI estimation processing for estimating the CSI of the data transmission link on the basis of the CSI correlation and the CSI obtained by the CSI measurement processing. The interface for data transmission is configured to carry out wireless communication with another device on the basis of the CSI obtained by the CSI estimation processing.

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 Art

[0002] As a method for increasing communication capacity, a MIMO (Multiple-input multiple-output) technique that performs spatial multiplexing transmission using multiple antennas is known. With the advancement and broadbandization of this MIMO technology, the demand for high-frequency CSI (Channel State Information) acquisition has been increasing.

[0003] For CSI acquisition, packet exchange of one and a half round trips is required. In particular, when using a time-varying channel where the channel environment changes over time, the difference in the environment becomes large between the CSI acquisition time and the actual data transmission time, resulting in a problem that accurate information transmission cannot be achieved.

[0004] To solve the above problems, Non-Patent Document 1 discloses a technique for improving the communication performance of MIMO eigenmode transmission in a time-varying channel by performing channel prediction on the transmission side and the reception side. Further, Non-Patent Document 2 discloses a technique for improving the communication performance of MIMO eigenmode transmission in a time-varying channel by simulation using a time-varying channel model.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

[0006] However, in systems using MLDs (Multi-Link Devices) with multiple links, CSI estimation is required according to the number of links. This further increases the overhead associated with CSI estimation. In other words, the discrepancy between the environment at the time of CSI acquisition and the time of actual data transmission becomes even greater, leading to the problem of inaccurate information transmission.

[0007] The primary objective of this disclosure is to provide a wireless communication device that can accurately transmit information by reducing the overhead associated with CSI estimation and by bringing the timing of CSI acquisition and actual data transmission closer together or overlapping, thereby mitigating the effects of time-varying channels, in order to solve the aforementioned problems. [Means for solving the problem]

[0008] A first aspect of this disclosure is preferably a wireless communication device that performs wireless communication with other devices, comprising a plurality of interfaces, a correlation database, and a CSI estimation unit, wherein the plurality of interfaces include an interface for CSI measurement and an interface for data transmission, the correlation database is configured to maintain the CSI correlation between a CSI measurement link handled by the interface for CSI measurement and a data transmission link handled by the interface for data transmission, the CSI estimation unit is configured to perform a CSI measurement process to measure the CSI of the CSI measurement link, a process to obtain the CSI correlation from the correlation database, and a CSI estimation process to estimate the CSI of the data transmission link based on the CSI correlation and the CSI obtained in the CSI measurement process, and the interface for data transmission is configured to perform wireless communication with other devices based on the CSI obtained in the CSI estimation process.

[0009] A second aspect of this disclosure is a wireless communication system for performing wireless communication between a wireless communication device and another device, wherein the link carried out by the wireless communication device includes a CSI measurement link and a data transmission link, and the wireless communication system is configured to perform a process for measuring the CSI of the CSI measurement link, a process for obtaining the CSI correlation between the CSI measurement link and the data transmission link, a process for estimating the CSI of the data transmission link based on the CSI correlation and the CSI obtained from the CSI measurement, and a process for performing wireless communication using the data transmission link based on the CSI obtained from the CSI estimation.

[0010] A third aspect of this disclosure is preferably a wireless communication method for performing wireless communication between a wireless communication device and another device, wherein the link carried out by the wireless communication device includes a CSI measurement link and a data transmission link, and the method is configured to perform CSI measurement on the CSI measurement link, obtain a CSI correlation between the CSI measurement link and the data transmission link, estimate the CSI of the data transmission link based on the CSI correlation and the CSI obtained from the CSI measurement, and perform wireless communication using the data transmission link based on the CSI obtained from the CSI estimation.

[0011] A fourth aspect of this disclosure is a wireless communication program to be implemented by a wireless communication device that performs wireless communication with another device, wherein the link carried out by the wireless communication device includes a CSI measurement link and a data transmission link, and the program preferably includes a program to cause a computer to perform the following: a process of measuring the CSI of the CSI measurement link; a process of obtaining the CSI correlation between the CSI measurement link and the data transmission link; a process of estimating the CSI of the data transmission link based on the CSI correlation and the CSI obtained from the CSI measurement; and a process of performing wireless communication using the data transmission link based on the CSI obtained from the CSI estimation. [Effects of the Invention]

[0012] According to the first to fourth aspects of this 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 overlap, thereby reducing the impact of time-varying channels and enabling accurate information transmission. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows a wireless communication system according to Embodiment 1 of the present disclosure. [Figure 2] This is a flowchart showing the correlation calculation process according to Embodiment 1 of this disclosure. [Figure 3] This is a flowchart showing the CSI estimation process according to Embodiment 1 of this disclosure. [Figure 4] This figure shows a wireless communication system according to a modified example of Embodiment 1 of the present disclosure. [Figure 5] This is a functional block diagram showing a wireless communication system according to a modified example of Embodiment 1 of the present disclosure. [Figure 6] This is a functional block diagram showing an interface related to a modified example of Embodiment 1 of the present disclosure. [Figure 7] This figure shows the hardware configuration of the CSI estimation unit according to a modified example of Embodiment 1 of the present disclosure.

Best Mode for Carrying Out the Invention

[0014] Embodiment 1 FIG. 1 is a diagram showing a wireless communication system according to Embodiment 1 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.

[0015] The wireless communication in the wireless communication system 100 will be described. First, the acquisition of CSI correlation to be performed in advance will be described.

[0016] The wireless communication system 100 includes MLD2. MLD2 performs wireless communication with devices 4a and 4b as communication partners. Here, a multi-user MIMO environment using an MLD having a plurality of interfaces is assumed. Also, each interface is responsible for a different frequency channel.

[0017] MLD2 has one or more interfaces. Here, an embodiment having interfaces 6a, 6b, 6c, and 6d is shown. Among these four interfaces, the links carried by interfaces 6a and 6b are used as data transmission links. In particular, the frequency band of the link carried by interface 6b is the same as that of devices 4a and 4b. Also, the links carried by interfaces 6c and 6d are used as CSI measurement links.

[0018] First, CSI measurement is performed at the interface responsible for each link. The data measured at each interface is transmitted to the CSI estimation unit 8.

[0019] Subsequently, CSI correlation between the link for data transmission and the link for CSI measurement is obtained. This CSI correlation acquisition is performed by the CSI estimation unit 8. In the present disclosure, an environment is assumed in which the phase of CSI in each link cannot be estimated due to large environmental fluctuations. That is, the CSI estimated here is the channel amplitude for each subcarrier in each link. The obtained CSI correlation is stored in the correlation DB 10.

[0020] Next, CSI estimation for the data transmission link will be described. The interface responsible for the CSI measurement link always performs CSI measurement. And when there is a variation in CSI, the variation information is transmitted to the CSI estimation unit 8. The CSI estimation unit 8 estimates the CSI of the data transmission link based on the variation information and the information in the correlation DB 10.

[0021] Based on the estimated CSI, the CSI estimation unit 8 determines a resource unit to be used in the wireless communication with the devices 4a and 4b so that the channel amplitude becomes the largest. This resource unit may be one carrier of the OFDM signal or a unit combining a plurality of carriers. Then, the determined information is transmitted to the interface responsible for the data transmission link. Here, it is transmitted to the interface 6b responsible for the link in the same frequency band as the devices 4a and 4b.

[0022] The interface 6b performs wireless communication with the devices 4a and 4b using the resource unit determined by the CSI estimation unit 8. For example, when the channel amplitude in the device 4a is shown in the graph on the right side of the device 4a, the subcarrier band of the allocated resource unit is the band 5a. Similarly, when the channel amplitude in the device 4b is shown in the graph on the right side of the device 4b, the subcarrier band of the allocated resource unit is the band 5b.

[0023] As described above, this disclosure performs CSI estimation using a surplus link that is not a data transmission link. This makes it possible to perform CSI estimation on a data transmission link without performing packet switching, which was required in conventional CSI estimation. Therefore, the overhead associated with CSI estimation is reduced, and by bringing the timing of CSI acquisition and actual data transmission closer together or overlapping, the impact of time-varying channels is reduced, and accurate information transmission can be achieved.

[0024] Figure 2 is a flowchart showing the correlation calculation process according to Embodiment 1 of this disclosure. First, in step 100, the CSI of all links is obtained.

[0025] 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 result in the correlation DB 10. The CSI correlation is, for example, the difference. This completes the correlation calculation process performed in advance for CSI estimation.

[0026] Steps 104 through 108 describe the 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 occur naturally or be actively generated by changing the transmission power, etc.

[0027] Next, in step 106, the CSI of all links is obtained. 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. This calculation of CSI correlation includes time variation. That is, in addition to the CSI correlation between each link, the variation in the CSI of each link is recorded. This allows for the calculation of the correlation in the direction of time variation, showing how the CSI changes at each link. The CSI estimation unit 8 then records the calculation results in the correlation DB 10.

[0028] As described above, in addition to the pre-calculated correlation process, the system undergoes repeated updates in response to environmental changes. This enables CSI estimation tailored to the environment.

[0029] Figure 3 is a flowchart showing the CSI estimation process according to Embodiment 1 of this disclosure. First, in step 110, the data transmission link and the CSI estimation link are determined. This determination is performed, for example, by the CSI estimation unit.

[0030] Steps 112 to 120 that follow describe a repeated CSI estimation process. First, in step 112, the CSI of the estimation link is measured. The CSI of this estimation link is measured as needed or continuously.

[0031] 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 also 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.

[0032] Step 118 checks if there is insufficient information in the correlation database. 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 there is insufficient information in the correlation database. For example, if the value of the error information is greater than a certain value, it is determined that there is insufficient information in the correlation database. 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 there is insufficient information in the correlation database. If there is insufficient information, the process proceeds to step 120. If there is no insufficient information, the CSI estimation process is terminated.

[0033] Next, in step 120, the correlation database is updated. Specifically, the error information obtained in step 118 is stored in the correlation database 10, thereby updating the correlation calculation results held in the correlation database 10.

[0034] Furthermore, if the signal-to-noise ratio (SNR) of the data transmission link's CSI is low, that 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.

[0035] As described above, this disclosure performs CSI estimation using a surplus link that is not a data transmission link. This makes it possible to perform CSI estimation on a data transmission link without performing packet switching, which was required in conventional CSI estimation. In other words, it reduces the overhead associated with CSI estimation and reduces the impact of time-varying channels by bringing the timing of CSI acquisition and actual data transmission closer together or overlapping, thereby enabling accurate information transmission.

[0036] Figure 4 shows a wireless communication system according to a modified embodiment 1 of the present disclosure. Wireless communication system 100a differs from wireless communication system 100 in that the communication partners of MLD2 are MLDs 12a and 12b, which have multiple interfaces.

[0037] The wireless communication system 100a includes MLDs 12a and 12b. Like MLD2, MLDs 12a and 12b are MLDs with multiple interfaces. That is, in the CSI correlation calculation process, it is necessary to obtain correlations corresponding to each interface of each terminal.

[0038] Therefore, it is decided in advance which interface each interface of MLD2 corresponds to. For example, it is decided in advance that interface 6b corresponds to the interface of MLD12a, and interface 6d corresponds to the interface of MLD12b. Then, the correlation calculation process and CSI estimation process described above are performed for each corresponding interface.

[0039] This allows CSI estimation to be performed using a surplus link that is not a data transmission link, even when the communication partner is an MLD. In other words, similar to Embodiment 1, the overhead associated with CSI estimation is reduced, and the timing of CSI acquisition and actual data transmission is brought closer together or overlaps, thereby reducing the impact of time-varying channels and enabling accurate information transmission.

[0040] Figure 5 is a functional block diagram showing a modified wireless communication system according to Embodiment 1 of this disclosure. Here, we will describe the wireless communication between MLD2 and MLD12a in the wireless communication system 100a. In this example, interfaces 6a and 6b of MLD2 are used as data transmission links, and interfaces 6c and 6d are used as CSI measurement links. Similarly, interfaces 14a and 14b of MLD12a are used as data transmission links, and interfaces 14c and 14d are used as CSI measurement links. Note that there may be one or more data transmission links and CSI measurement links, and this example is not limited to this one.

[0041] The processing flow in the functional block diagram of Figure 5 is explained below. First, CSI measurements are performed between interfaces 6a to 6d and interfaces 14a to 14d. The measured data is transmitted to CSIDB16. CSIDB16 holds the transmitted CSI data between each link. CSIDB16 may also retain the signal-to-noise ratio data at the time of measurement in order to adjust the remeasurement interval when the correlation calculation process is repeated.

[0042] CSIDB16 transmits the CSI data between each transmitted 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 point, or the correlation of fluctuations between links over time.

[0043] The CSI correlation information output by the correlation calculation unit 18 is sent to the correlation DB 10. The correlation DB 10 stores the CSI correlation information. The correlation DB 10 may also store correction information based on actual link measurements, as described in steps 116 to 120.

[0044] The CSI correlation information held by the correlation DB10 is transmitted to the CSI estimation unit 8. When the CSI estimation unit 8 receives the CSI information of the CSI measurement link and the received CSI correlation information as input, it outputs the CSI estimation data for the data transmission link.

[0045] The CSI estimation data output by the CSI estimation unit 8 is transmitted to interfaces 6a and 6b, which are responsible for the data transmission links. Based on the CSI estimation data, interfaces 6a and 6b conduct wireless communication with interfaces 14a and 14b.

[0046] Furthermore, MLD2 may include a correction information calculation unit 20. The correction information calculation unit 20 has the function of performing the processing described in steps 116 to 120. That is, it has the function of performing a correction process for the correlation DB based on CSI measurement in the data transmission link.

[0047] The following describes the flow of the correction process as shown in the functional block diagram of Figure 5. 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 interfaces 6a and 6b, which are responsible for the data transmission link. It then compares the received data and obtains the error information.

[0048] Next, 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 it holds.

[0049] Figure 6 is a functional block diagram showing an interface according to a modified embodiment 1 of the present disclosure. Interface 6a has a CSI measurement unit 22. The CSI measurement unit 22 performs CSI measurement. Interface 6a also has a CSI notification unit 24. The CSI notification unit notifies the CSIDB 16 of the CSI data measured by the CSI measurement unit.

[0050] Figure 7 shows the hardware configuration of a modified CSI estimation unit according to Embodiment 1 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, RAM 124, and storage 126 are connected to the bus line 120. The memory devices store a wireless communication program executed by the CPU 118. The CSI estimation unit 8 can realize functions specific to this embodiment by having the CPU 118 execute its wireless communication program.

[0051] A communication interface 128 is also connected to the bus line 120. The CSI estimation unit 8 communicates with the network via the communication interface 128. An operation unit 130 and a display unit 132 are further 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.

[0052] As described above, the CSI estimation unit 8 can realize functions specific to this embodiment by having the CPU 118 execute a wireless communication program. In other words, the CSI estimation unit 8 can also be realized by a computer and the program. Furthermore, the program can be recorded on a recording medium or provided via a network. [Explanation of symbols]

[0053] 4a Device 4b device 6a Interface 6b Interface 6c interface 6D Interface 8 CSI estimation part 10. Correlation Database 14a Interface 14b Interface 14c interface 14d interface 20 Correction Information Calculation Unit 100 Wireless Communication Systems 100a wireless communication system

Claims

1. A wireless communication device that performs wireless communication with other devices, It has multiple interfaces, a correlation database, and a CSI estimation unit. The aforementioned multiple interfaces, It includes an interface for CSI measurement and an interface for data transmission. The aforementioned correlation DB, The interface for CSI measurement is configured to maintain the CSI correlation between the CSI measurement link and the data transmission link handled by the interface for data transmission. The CSI estimation unit, A CSI measurement process for measuring the CSI of the CSI measurement link, The process of obtaining the CSI correlation from the correlation DB, A CSI estimation process is performed to estimate the CSI of the data transmission link based on the CSI correlation and the CSI obtained in the CSI measurement process. It is configured to implement, The data transmission interface is configured to perform wireless communication with the other device based on the CSI obtained in the CSI estimation process. Wireless communication device.

2. The aforementioned interface, The interface is configured to acquire the CSI of the link it handles and transmit it to the CSI estimation unit. The CSI estimation unit, For the aforementioned combination of links, a CSI correlation calculation process is performed to calculate the CSI correlation, The process of recording the CSI correlation in the correlation DB, It is configured to implement The wireless communication device according to claim 1.

3. The CS1 correlation calculation process described above is: The aforementioned interface, When there is a change in the environment, the interface reacquires the CSI of the link it handles and transmits it to the CSI estimation unit. The CSI estimation unit, For the aforementioned combination of links, a process is performed to recalculate the CSI correlation. Includes, The recalculated CSI correlation includes the correlation in the time-varying direction. The wireless communication device according to claim 2.

4. It is further equipped with a correction information calculation unit, The correction information calculation unit, A process for measuring the CSI of the data transmission link, A process for obtaining error information between the measured CSI of the data transmission link and the CSI obtained in the CSI estimation process, The process involves storing the aforementioned error information in the correlation database and updating the correlation calculation results held in the correlation database. It is configured to implement The wireless communication device according to claim 1.

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

6. A wireless communication system that performs wireless communication between a wireless communication device and other devices, The link operated by the wireless communication device includes a CSI measurement link and a data transmission link. The process of performing CSI measurement on the aforementioned CSI measurement link, A process for obtaining the CSI correlation between the CSI measurement link and the data transmission link, A process for estimating the CSI of the data transmission link based on the CSI correlation and the CSI obtained from the CSI measurement, Based on the CSI obtained from the CSI estimation, a process is performed to conduct wireless communication using the data transmission link. A wireless communication system configured to perform the following actions.

7. A wireless communication method for performing wireless communication between a wireless communication device and another device, The link operated by the wireless communication device includes a CSI measurement link and a data transmission link. The CSI measurement link is to be subjected to CSI measurement, To obtain the CSI correlation between the CSI measurement link and the data transmission link, Based on the CSI correlation and the CSI obtained from the CSI measurement, the data transmission link is estimated by CSI, Based on the CSI obtained from the CSI estimation, wireless communication is performed using the data transmission link. A wireless communication method configured to perform the following actions.

8. A wireless communication program to be implemented by a wireless communication device that performs wireless communication with other devices, The link operated by the wireless communication device includes a CSI measurement link and a data transmission link. The process of performing CSI measurement on the aforementioned CSI measurement link, A process for obtaining the CSI correlation between the CSI measurement link and the data transmission link, A process for estimating the data transmission link's CSI based on the CSI correlation and the CSI obtained from the CSI measurement, Based on the CSI obtained from the CSI estimation, a process is performed to conduct wireless communication using the data transmission link. A wireless communication program that includes a program to cause a computer to perform a certain action.

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