Communication device, communication method, and program

Abstract

To provide a mechanism that enables maintaining or improving transmission efficiency by performing precoding processing when communication propagation conditions change.SOLUTION: A communication device that communicates with another communication device, includes a state detection unit that detects a change in state in the communication device, a transmission unit that, when a change in state in the communication device is detected, transmits a message to the other communication device requesting that precoding be performed, and a reception unit that receives precoded data from the other communication device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In recent years, the 3GPP (3rd Generation Partnership Project) has been formulating specifications for LTE (Long Term Evolution) and next-generation (NR).

[0003] The specifications under development include precoding technology, which generates signals that take into account current propagation path information on the transmitting side to improve transmission efficiency. Specifically, the specifications for communications in which a base station controls user communication devices (User Equipment, hereafter referred to as UE) (hereafter referred to as Uu communications) are as follows:

[0004] That is, the UE receives a reference signal emitted by the base station and returns the received signal to the base station as a Channel State Information (CSI) report. The UE is instructed by the base station to send a CSI report, and the UE follows this instruction to return the CSI report to the base station.

[0005] The CSI report includes a Channel Quality Indicator (CQI), a Precoding Matrix Index (PMI), etc. The base station can improve transmission efficiency by forming a transmission signal based on the CSI report.

[0006] On the other hand, a standard specification called Sidelink communication (hereinafter referred to as Sidelink) has been developed, which does not go through a base station. This specification enables direct wireless communication between UEs using an interface called PC5, without going through a mobile communication network (core network).

[0007] Patent Document 1 discloses a method for returning CSI to a UE that has transmitted a reference signal in a sidelink. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2022-526741 Summary of the Invention [Problem to be solved by the invention]

[0009] In the case of Sidelink communication, it is expected that both UEs will move. In other words, it is expected that communication propagation conditions will fluctuate more frequently than in Uu communication. For example, if a UE connected via Sidelink moves significantly, the communication propagation conditions will fluctuate significantly. Therefore, to improve transmission efficiency between UEs, it is desirable to perform precoding processing to generate signals that take propagation path information into account. Note that similar problems may occur not only in Sidelink communication but also in Uu communication.

[0010] The present invention has been made in consideration of at least one of the above-mentioned problems, and an object of the present invention is to provide a mechanism that enables maintaining or improving transmission efficiency by performing a precoding process when communication propagation conditions change. [Means for solving the problem]

[0011] A communication device according to one aspect of the present invention is a communication device that communicates with another communication device, and includes a state detection unit that detects a change in state in the communication device, a transmission unit that, when it detects a change in state in the communication device, transmits a message to the other communication device requesting that precoding be performed, and a reception unit that receives precoded data from the other communication device. [Effects of the Invention]

[0012] According to the present invention, when a UE moves significantly, the UE notifies the UE of the start of precoding processing. The UE then performs precoding processing upon receiving the notification, thereby maintaining or improving transmission efficiency. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the configuration of a communication device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing an example of the functional configuration of UE A101 and UE B102 according to the present embodiment. [Figure 3] FIG. 4 is a flowchart showing the processing of UE A101 in this embodiment. [Figure 4] FIG. 4 is a flowchart showing the processing of UE A101 in this embodiment. [Figure 5] FIG. 10 is a flowchart showing the processing of a UE B102 in this embodiment and other embodiments. [Figure 6] FIG. 10 is a flowchart showing the processing of a UE A101 according to another embodiment. [Figure 7] FIG. 4 is a sequence diagram showing the processing performed by UE A101 and UE B102 in this embodiment. [Figure 8] FIG. 10 is a sequence diagram showing processing performed by UE A101 and UE B102 in another embodiment. [Figure 9] FIG. 10 is a diagram showing a message format of NotificationMessageSidelink in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted. First Embodiment

[0015] [System Configuration] Fig. 1 is a diagram showing an example of the configuration of a system according to this embodiment. The system according to Fig. 1 includes UE A101 and UE B102. In Fig. 1, it is assumed that connection processing for sidelink communication between UE A101 and UE B102 has been completed, and sidelink communication is possible between UE A101 and UE B102. Completion of connection processing for sidelink communication means that various settings required for communication by transmitting and receiving control signals between UEs have been completed, and user data can be transmitted and received.

[0016] [Functional configuration of communication device] Next, a functional configuration example of a Sidelink UE as a communication device according to this embodiment will be described. Note that the functional block configuration described below is merely an example. Some or all of the functional blocks described below may be replaced with other functional blocks that perform similar functions. Also, some functional blocks may be omitted, or additional functional blocks may be added. Furthermore, one functional block described below may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block.

[0017] FIG. 2 is a functional block diagram showing an example of the functional configuration of UE A101 and UE B102 as communication devices according to this embodiment.

[0018] 2, the control unit 201 controls each unit of the UE A101 and the UE B102 in accordance with input signals and a program described later. Note that instead of the control unit 201 controlling the entire device, the entire device may be controlled by multiple hardware devices sharing the processing. The control unit 201 also controls the communication establishment means.

[0019] The storage unit 202 stores a control program executed by the control unit 201, information related to communication, parameter values ​​for determining whether or not the UE can operate, etc. The various operations described below are performed by the control unit 201 executing the control program stored in the storage unit 202.

[0020] An RRC (Radio Resource Control) message generation processor 203 generates messages used in the RRC protocol, which is a protocol used for control signals between a communication partner UE and a base station (not shown).

[0021] The RRC message analysis processing unit 204 analyzes the received RRC message.

[0022] The state change detection unit 205 detects a change in the state of the UE, as will be described in detail later.

[0023] The Sidelink processing unit 206 performs various processes related to Sidelink connection and communication in the UE.

[0024] The communication unit 207 is an interface for communicating with external devices including UE. Specific examples include sidelink communication conforming to the 3GPP standard and uplink / downlink communication with a base station (not shown here). Furthermore, when a signal is received from an external device, the communication unit 207 may acquire the signal strength and / or reception quality of the received signal. The communication unit 207 may notify the control unit 201 of information indicating the acquired signal strength and / or reception quality.

[0025] The communication unit 207 also performs processing for transmitting messages generated by the RRC message generation processing unit 203, and processing for receiving RRC messages from the base station and the UE, as well as other necessary radio signals. The communication unit 207 also transmits and receives pre-coded data to and from the UE of the other communication partner.

[0026] The pre-coding processing unit 208 performs a process of pre-coding a signal when transmitting data. The process will be described below.

[0027] There are two types of precoding. One is the "wideband" type, which performs the same precoding process for the entire channel band (multiplying the entire band with the same precoding matrix). The other is the "subband" type, which performs precoding for each subband into which the channel is divided (multiplying each subband with the same or different precoding matrix). For example, it is conceivable to perform wideband precoding when there is little change in the radio wave environment, and perform subband precoding when there is a large change in the radio wave environment.

[0028] A UE requesting a counterpart UE to perform precoding transmits a message requesting the counterpart UE to perform precoding. The message may be a Notification Message Sidelink message (described later). The message may include information requesting either subband precoding or wideband precoding.

[0029] Upon receiving the message requesting the implementation of precoding, the RRC message generation processing unit 203 of the UE generates an RRC message specifying a method for reporting a CSI report. Furthermore, the communication unit 207 transmits the generated RRC message and a reference signal for indexing the radio wave environment to the UE of the other party. This RRC message may be called a CSI report transmission instruction.

[0030] Upon receiving the RRC message and reference signal, the UE measures the reference signal and generates a CSI report in accordance with the settings specified in the RRC message using precoding processing unit 208. The CSI report includes a Channel Quality Indicator (hereinafter referred to as CQI), a Precoding Matrix Index (hereinafter referred to as PMI), etc. Communication unit 207 transmits the generated CSI report to the UE of the other party.

[0031] Upon receiving the CSI report, the UE performs precoding suitable for the UE of the communicating party on the signal at the time of data transmission, based on the CQI, PMI, etc. included in the CSI report. Note that the control unit 201 is configured with one or more processors such as a CPU or an MPU, and controls the entire communication device by executing a control program read into the RAM, which is the storage unit 202. Note that the processes performed by the control unit 201, which will be described in the flowcharts below, can also be realized using various hardware circuits. The various hardware circuits include an ASIC (Application Specific Integrated Circuit) and an FPGA (Field Programmable Gate Array). Furthermore, the processes described in the flowcharts below can also be realized by the hardware circuits cooperating with a processor such as a CPU or an MPU.

[0032] The storage unit 202 may include a main storage unit and an auxiliary storage unit. The main storage unit is, for example, a read-only memory (ROM) or a random access memory (RAM). The main storage unit is basic software executed by the control unit 201. It may store or temporarily save programs and data such as an operating system (OS) or application software. The auxiliary storage unit is, for example, a hard disk drive (HDD) or a solid state drive (SSD), and may store data related to application software. For example, a control program stored in a non-volatile storage area is expanded into a random access memory (RAM) and executed by a processor constituting the control unit 201. In this way, the control unit 201 and the storage unit 202 may function as a so-called computer.

[0033] The storage unit 202 may include a recording medium that stores a predetermined program. The program stored in this recording medium may be installed via a drive device or the like, and the installed predetermined program may be executable by the control unit 201. Various types of recording media can be used. For example, the recording medium may be a recording medium that records information optically, electrically, or magnetically, such as a CD (Compact Disc)-ROM, a flexible disk, or a magneto-optical disk. The recording medium may also be a semiconductor memory that records information electrically, such as a ROM or a flash memory. Note that the recording medium does not include a carrier wave.

[0034] The status change detection unit 205 is an example of a status detection unit. The communication unit 207 is an example of a transmission unit, a reception unit, a message reception unit, and a report reception unit. The above is an example of a block diagram showing an example of the functional configuration of a communication device in this embodiment.

[0035] [Processing example] An example of the operation of this embodiment will be described using an example of an operation sequence shown in FIG. 7 and example flowcharts shown in FIGS.

[0036] UE A101 and UE B102 in FIG. 1 are connected by a sidelink method that does not involve a base station, and are performing data communication (S301, S501, F701).

[0037] Here, it is assumed that some state change occurs in UE A101 and this state change is detected (S302, F702). The state change here refers to, for example, the detection of movement of the device itself, a change in the received radio wave strength, an increase in the number of retransmissions of data, etc. Details of process A (S303) performed when such a state change is detected will be described with reference to FIG. 4.

[0038] When UE A101 detects a state change, it checks the details of the detected state change (S401). First, movement detection will be described (S404). The state change detection unit 205 of UE A101 may detect a state change when the movement speed of UE A101 exceeds a predetermined threshold or when UE A101 moves a predetermined distance. When a UE performing data communication moves, the propagation path changes, and therefore the radio wave environment is expected to change significantly. Therefore, if each UE performing data communication performs precoding processing using a precoding setting set for the propagation path before the movement, it may not lead to an improvement in transmission efficiency. To improve transmission efficiency, each UE performing data communication needs to perform precoding processing again based on the propagation path after the movement.

[0039] Therefore, in this embodiment, when UE A101 detects the movement of its own device (S404), it requests the UE with which it is communicating to perform precoding corresponding to, for example, the subband, since it is expected that the radio wave environment of the propagation path will change significantly as described above.

[0040] As an example of a method for realizing this, a method using NotificationMessageSidelink, which is one of the RRC messages, will be described. NotificationMessageSidelink is shown in Fig. 9. In this embodiment, information elements pmi-subband-request and pmi-wideband-request are newly added to NotificationMessageSidelink. When requesting precoding compatible with subband from the communication partner terminal, pmi-subband-request is set in NotificationMessageSidelink. Also, when requesting precoding compatible with wideband from the communication partner terminal, pmi-wideband-request is set in NotificationMessageSidelink. Returning to Fig. 4, the description will continue.

[0041] Here, it is assumed that UE A101 requests precoding corresponding to the subband. The precoding processing unit 208 instructs the RRC message generation processing unit 203 to generate a NotificationMessageSidelink in which pmi-subband-request is set (S408). Thereafter, the precoding processing unit 208 instructs the RRC message generation processing unit 203 to transmit the NotificationMessageSidelink in which pmi-subband-request is set to the remote UE (S304, F703). This process requests the remote UE to perform precoding corresponding to the subband.

[0042] When UE B102 receives NotificationMessageSidelink in which pmi-subband-request is set (S502), UE B102 analyzes the message using RRC message analysis processing unit 204. That is, UE B102 detects that UE A101 is requesting precoding corresponding to the subband (S503).

[0043] Next, UE B102 instructs RRC message generation processing unit 203 to generate an RRC message instructing transmission of a CSI report for performing precoding corresponding to the subband in precoding processing unit 208. This RRC message may be called a CSI report transmission instruction. This RRC message may include information on the radio resource location of the reference signal transmitted in F705, information instructing whether the CSI report corresponding to the subband or the wideband should be transmitted, and the like.

[0044] Specifically, when UE B102 receives NotificationMessageSidelink with pmi-subband-request configured, it performs the following: That is, UE B102 generates an RRC message including information indicating whether to transmit a CSI report corresponding to the subband. Also, when UE B102 receives NotificationMessageSidelink with pmi-wideband-request configured, it performs the following: That is, UE B102 generates an RRC message including information indicating whether to transmit a CSI report corresponding to the wideband.

[0045] UE B102 transmits the generated RRC message to UE A101 (S504, F704). UE B102 also transmits a reference signal to UE A101 (F705). The reference signal may be, for example, a Channel State Information Reference Signal (CSI-RS).

[0046] When UE A101 receives an RRC message instructing transmission of a CSI report corresponding to a subband (S305, F704), the process is as follows. That is, UE A101 receives a reference signal transmitted by UE A101 (F705), and generates a CSI report in precoding processing unit 208 (S306). When the RRC message includes information instructing transmission of a CSI report corresponding to a subband, UE A101 generates a CSI report including CQI and PMI for each subband. When the RRC message includes information instructing transmission of a CSI report corresponding to wideband, UE A101 generates a CSI report including CQI and PMI for the entire band.

[0047] Furthermore, UE A101 transmits the generated CSI report to UE B102 (S307, F706).

[0048] When UE B102 receives the CSI report (S505, F706), the process is as follows: UE B102 performs optimal precoding for the communication partner UE on the signal when transmitting data to UE A101 based on the CSI report in precoding processing unit 208 (S506, F711). Note that performing precoding means, for example, transmitting a radio signal multiplied by precoding information (precoding matrix) determined based on the CSI report.

[0049] For example, when UE B102 receives a CSI report including CQI and PMI for each subband, it may perform precoding corresponding to the subband on a signal to be transmitted to UE A101. That is, UE B102 may transmit to UE A101 a radio signal multiplied by precoding information for each subband. Furthermore, when UE B102 receives a CSI report including CQI and PMI for the entire band, it may perform precoding corresponding to the wideband on a signal to be transmitted to UE A101. That is, UE B102 may transmit to UE A101 a radio signal multiplied by the same precoding information for the entire band.

[0050] Meanwhile, UE B102 can also detect that a change has occurred in the radio wave environment between UE B102 and UE A101 by receiving a NotificationMessageSidelink from UE A101 requesting precoding processing. Therefore, it is desirable that UE B102 also transmits a similar NotificationMessageSidelink to UE A101 to request precoding processing from UE A101 (F707). That is, when a communication unit of UE B102 receives a NotificationMessageSidelink (a message requesting the execution of precoding) from UE A101 (F703), the communication unit of UE B102 may be configured as follows. That is, the communication unit of UE B102 may transmit a NotificationMessageSidelink (a message requesting the execution of precoding) to UE A101 (F707).

[0051] The precoding process performed by UE A101 is the same as the process performed by UE B102 (that is, F704 to F706, F711), and therefore a description thereof will be omitted (F708 to F711).

[0052] As described above, when a UE in a Sidelink connection moves, the UE that detects the movement requests a precoding process from the other UE. The other UE that receives the request performs a precoding process, thereby performing a precoding process that corresponds to the change in the radio wave environment. This makes it possible to maintain or improve transmission efficiency even when the radio wave environment between UEs changes.

[0053] Although the present embodiment has been described using a sidelink connection as an example, the same effect can be expected for a connection between a base station and a UE. That is, when a UE connected to a base station moves, the UE detects the movement and requests the base station to perform precoding processing, thereby achieving the same effect as a sidelink connection. Second Embodiment In this embodiment, a case where there is a change in radio wave strength at UE A101 or where a retransmission of data occurs at UE A101 will be described. The system configuration in this embodiment is the same as that in Fig. 1, and the configuration of the devices that make up the system is also the same as that in Fig. 2, so a description thereof will be omitted.

[0054] (Processing example) An example of the operation of this embodiment will be described using an example of an operation sequence shown in FIG. 7 and example flowcharts shown in FIGS.

[0055] UE A101 and UE B102 are performing data communication in sidelink communication not via a base station (S301, F701).

[0056] Here, status change detection section 205 of UE A101 detects the occurrence of a status change. Here, the status changes to be detected are as follows: That is, whether the change in the received radio wave intensity of UE A102 (the absolute value of the difference between the previous measurement value and the current measurement value) is equal to or greater than a predetermined threshold (first threshold), or whether the number of retransmissions of data received from UE B102 is equal to or greater than a predetermined threshold (second threshold). In this case, UE A101 detects that a status change has occurred (S302, F702). When UE A101 detects a status change, it checks the details of the detected status change (S401).

[0057] When a change in radio wave strength or a retransmission of data transmission occurs, it is desirable to determine the content of the precoding process based on the magnitude of the change in radio wave strength and the number of retransmissions of the data transmission.As described above, the precoding process is performed using two types of methods: precoding corresponding to wideband and precoding corresponding to subband.

[0058] The sizes of the CSI reports generated by these two methods are different. Specifically, the processing load for precoding in the subband is greater than that in the wideband, and the size of the generated CSI report is also larger. Therefore, it is desirable to select precoding corresponding to the wideband when the radio wave environment changes little, and to select precoding corresponding to the subband when the radio wave environment changes greatly.

[0059] Therefore, when UE A101 detects a change in radio wave strength or the occurrence of a retransmission of data transmission, it makes a determination based on a threshold. That is, when the change in radio wave strength is equal to or greater than a first threshold and less than a third threshold (S403), it requests precoding corresponding to the wideband (S407). Or, when the number of retransmissions of data transmission is equal to or greater than a second threshold and less than a fourth threshold (S402), it requests precoding corresponding to the wideband (S407). Also, when the change in radio wave strength is equal to or greater than the first threshold and greater than a third threshold (S405), UE A101 requests precoding corresponding to the subband. Or, when the number of retransmissions of data transmission is equal to or greater than the second threshold and greater than a fourth threshold (S406), it requests precoding corresponding to the subband.

[0060] The method for requesting precoding is the same as in the first embodiment, and therefore a description thereof will be omitted here.

[0061] As described above, if there is a change in the signal strength between the UE and the other party during a Sidelink connection, or if a retransmission of data occurs between the UE and the other party, the following can be performed. That is, the UE that detects these changes can request the other party to perform a precoding process that is suitable for the current situation. Furthermore, the other party UE that receives the request can perform a suitable precoding process, thereby performing a precoding process that corresponds to the change in the signal environment, thereby maintaining or improving transmission efficiency. <Other embodiments> In the first embodiment, a method has been described in which, when UE A101 moves, UE B102, the communication partner, performs precoding processing.

[0062] In the second embodiment, a case has been described in which UE A101 detects that there has been a change in the radio wave strength between UE A101 and UE B102, or a case in which UE A101 detects that a retransmission of data has occurred between UE A101 and UE B102.

[0063] In another embodiment, the UE A101 and the UE B102 may request each other to perform precoding processing, assuming that a state change has occurred immediately after the sidelink communication connection is established.

[0064] The system configuration in this embodiment is the same as that in FIG. 1, and the configuration of the devices that make up the system is also the same as that in FIG. 2, so a description thereof will be omitted.

[0065] If the user of UE A101 determines that the communication conditions are poor, UE A101 may transmit a NotificationMessageSidelink to UE B102 based on a user instruction. UE A101 may have an interface unit for receiving instructions from the user. The interface unit may be a touch panel type or a push button type.

[0066] (Processing example) An example of the operation of another embodiment will be described using the example of the operation sequence shown in FIG. 8 and the example of the flowchart shown in FIG.

[0067] UE A101 and UE B102 in FIG. 8 are attempting to perform data communication using sidelink communication that does not go through a base station (S601, F801).

[0068] Immediately after the sidelink connection, the radio wave conditions between the two UEs are unknown, so it is considered preferable to apply precoding corresponding to the subband. Therefore, when the connection with UE B102 is completed, the state change detection unit 205 of UE A101 may assume that the state of UE A101 has changed and detect that the state has changed.

[0069] The precoding processing unit 208 of UE A101 and UE B102, whose sidelink connection has been completed, respectively performs the following: In other words, it instructs the RRC message generation processing unit 203 to generate a NotificationMessageSidelink in which pmi-subband-request is set. Furthermore, UE A101 and UE B102 transmit a NotificationMessageSidelink requesting subband precoding (S602, F802, F806).

[0070] UE A101 and UE B102 receive an RRC message from a peer UE, the RRC message including information instructing whether to transmit a CSI report corresponding to the subband or the wideband (S603, F803, F807). Upon receiving the RRC message, UE A101 and UE B102 generate a CSI report (S604). UE A101 and UE B102 transmit a CSI report to the peer UE based on a reference signal received from the peer UE (F804, F808) (S605, F805, F809). UE A101 and UE B102 perform optimal precoding for the peer UE based on the CSI report (F810).

[0071] In this way, by transmitting the NotificationMessageSidelink from both UEs, it becomes possible to perform suitable precoding processing in both UEs and to achieve improved transmission efficiency. [Explanation of symbols]

[0072] 101 Terminal A (UE A) 102 Terminal B (UE B) 201 Control Unit 202 Storage section 203 RRC message generation processing unit 204 RRC message analysis processing unit 205 State change detection unit 206 Sidelink processing unit 207 Communications Department 208 Precoding processing unit

Claims

1. A communication device that communicates with another communication device, a state detection unit that detects a change in a state of the communication device; a transmitter that, when detecting a change in state in the communication device, transmits a message to the other communication device requesting execution of precoding; a receiving unit that receives precoded data from the other communication device; A communication device comprising:

2. The communication device according to claim 1 , wherein the receiving unit receives a CSI report transmission instruction transmitted from the other communication device in response to a message requesting the execution of the precoding.

3. The communication device according to claim 2 , wherein the CSI report transmission instruction is an RRC message.

4. The communication device according to claim 1 , wherein the message requesting the implementation of precoding includes information requesting either precoding corresponding to a subband or precoding corresponding to a wideband.

5. The communication device according to claim 1 , wherein the message requesting the execution of the precoding is a NotificationMessageSidelink message.

6. 2. The communication device according to claim 1, wherein the state detection unit detects that the state has changed when the communication device has moved a predetermined distance or when the speed of movement of the communication device has exceeded a predetermined threshold.

7. 2. The communication device according to claim 1, wherein the state detection unit detects that the state has changed when a change in received radio wave intensity from the other communication device is equal to or greater than a predetermined threshold.

8. 2. The communication device according to claim 1, wherein the state detection unit detects that the state has changed when the number of retransmissions of data received from the other communication device is equal to or greater than a predetermined threshold value.

9. 2. The communication device according to claim 1, wherein the state detection unit detects that the state has changed when the communication device has completed connection with the other communication device.

10. 2. The communication device according to claim 1, wherein when the transmission unit receives a message requesting the implementation of the precoding from the other communication device, the transmission unit transmits a message requesting the implementation of precoding to the other communication device.

11. A communication method executed by a communication device that communicates with another communication device, comprising: detecting a change of state in the communication device; When detecting a change in state in the communication device, transmitting a message to the other communication device requesting execution of precoding; receiving pre-coded data from the other communication device.

12. A communication device that communicates with other communication devices, detecting a change of state in the communication device; When detecting a change in state in the communication device, transmitting a message to the other communication device requesting execution of precoding; receiving pre-coded data from the other communication device; A program to execute.

13. A communication device that communicates with another communication device, a message receiving unit that receives a message requesting execution of precoding from the other communication device; a transmitter configured to transmit a CSI report transmission instruction to the other communication device in response to the message requesting the precoding; a report receiving unit that receives a CSI report from the other communication device.

14. A communication method executed by a communication device that communicates with another communication device, comprising: a message receiving step of receiving a message requesting execution of precoding from the other communication device; a transmitting step of transmitting a CSI report transmission instruction to the other communication device in response to the message requesting the precoding; a report receiving step of receiving a CSI report from the other communication device.

15. A communication device that communicates with other communication devices, a message receiving step of receiving a message requesting execution of precoding from the other communication device; a transmitting step of transmitting a CSI report transmission instruction to the other communication device in response to the message requesting the precoding; a report receiving step of receiving a CSI report from the other communication device; A program to execute.

Images