Base station and communication method

Abstract

Achieving appropriate shared control in cooperative communication. [Solution] The base station includes a receiving circuit that receives control information regarding the sharing of channel state information in inter-base station cooperative communication, and a control circuit that controls the transmission of the channel state information to other base stations based on the control information.When the control information indicates a combination of another base station involved in inter-base station cooperative communication that does not receive channel state information and the source of the channel state information, the control circuit determines to transmit the channel state information from the source to the other base station.

Description

[Technical Field]

[0001] The present disclosure relates to a base station and a communication method. [Background technology]

[0002] The Institute of Electrical and Electronics Engineers (IEEE) is currently studying the IEEE 802.11be (hereinafter referred to as "11be") standard for next-generation wireless local area networks (LANs), which will be the successor to the IEEE 802.11ax (hereinafter referred to as "11ax"). For example, IEEE 802.11ax is also known as High Efficiency (HE), and IEEE 802.11be is also known as Extremely High Throughput (EHT). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] IEEE 802.11-20 / 1935r15, Compendium of straw polls and potential changes to the Specification Framework Document - Part 2 [Non-patent document 2] IEEE 802.11-19 / 1097r0, Sounding procedure in AP collaboration [Non-patent document 3] IEEE 802.11-19 / 1554r1, Data Sharing for Multi-AP Coordination [Non-patent document 4] IEEE P802.11ax / D8.0 [Non-patent document 5] IEEE P802.11-REVmd / D5.0 Summary of the Invention

[0004] However, there is room for further study on shared control during cooperative communication in wireless communication such as wireless LAN.

[0005] Non-limiting examples of the present disclosure contribute to providing a base station and a communication method that can achieve appropriate shared control in cooperative communication.

[0006] A base station according to one embodiment of the present disclosure includes a receiving circuit that receives control information related to the sharing of channel state information in inter-base station cooperative communication, and a control circuit that controls transmission of the channel state information to other base stations based on the control information.

[0007] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0008] According to an embodiment of the present disclosure, appropriate shared control can be achieved in cooperative communication.

[0009] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0010] [Figure 1] A diagram showing an example of a Multi-AP (multi-access point, MAP) configuration [Figure 2] FIG. 1 is a diagram illustrating an example of a communication environment in which downlink and uplink coverage are different. [Figure 3] A diagram showing an example of a MAP control sequence. [Figure 4] A diagram showing an example of a MAP control sequence. [Figure 5] FIG. 1 is a block diagram showing a configuration example of a part of an AP according to a first embodiment; [Figure 6] FIG. 1 is a block diagram showing an example of the configuration of an AP according to a first embodiment; [Figure 7] FIG. 1 is a block diagram showing an example of the configuration of an STA according to a first embodiment; [Figure 8] FIG. 10 is a diagram showing an example of a control sequence of MAP according to the first embodiment. [Figure 9] An example of a Channel State Information request (CSI Req) frame is shown in Figure 1. [Figure 10] Figure showing an example of a CSI request definition in the Frame Control field [Figure 11] Figure showing an example of a CSI request definition in the Trigger Type subfield [Figure 12] Figure showing an example of specifying the BFRP (Beamforming Report Poll) Trigger frame format and providing a CSI request subfield [Figure 13] Figure 1 shows an example of a CSI Share Request (CSI ShareReq) frame. [Figure 14] Figure showing an example of specifying the BFRP Trigger frame format and providing a CSI sharing request subfield [Figure 15] Figure showing an example of a CSI sharing request definition in the Trigger Type subfield [Figure 16] Figure showing an example of specifying the BFRP Trigger frame format and providing a CSI sharing request subfield [Figure 17] An example of a CSI Share frame [Figure 18] Figure showing an example of CSI sharing definition in the Frame Control field [Figure 19]Diagram showing an example of the definition of the HE / EHT Compressed Beamforming / Channel Quality Indicator (CQI) frame [Figure 20] FIG. 10 is a diagram showing an example of a control sequence of MAP according to the second embodiment. [Figure 21] Figure 1 shows an example of a CSI sharing request frame. [Figure 22] Figure showing an example of a CSI sharing request definition in the Frame Control field [Figure 23] Figure showing an example of a CSI sharing request definition in the Trigger Type subfield [Figure 24] Figure showing an example of specifying the BFRP Trigger frame format and providing a CSI sharing request subfield [Figure 25] Figure 1 shows an example of a CSI sharing frame [Figure 26] Figure showing an example of CSI sharing definition in the Frame Control field [Figure 27] Diagram showing an example of HE / EHT Compressed Beamforming / CQI frame definition [Figure 28] FIG. 10 is a diagram showing an example of a control sequence of MAP according to the third embodiment. [Figure 29] Figure 1 shows Example 1 of including a CSI sharing request in a MAP Null Data Packet Announcement (NDPA) frame. [Figure 30] Figure 2 shows Example 2 of including a CSI sharing request in a MAP NDPA frame [Figure 31] Figure 3 shows Example 3 of including a CSI sharing request in a MAP NDPA frame [Figure 32] Figure 1 shows an example of a CSI sharing frame [Figure 33] Figure showing an example of CSI sharing definition in the Frame Control field [Figure 34] Diagram showing an example of HE / EHT Compressed Beamforming / CQI frame definition [Figure 35]FIG. 13 is a diagram showing an example of a control sequence of MAP according to the fourth embodiment. [Figure 36] A diagram showing an example of including a CSI share request flag (CSI ShareReq Flag) in a MAP NDPA frame. [Figure 37] Diagram showing an example of a line configuration between Shared APs [Figure 38] FIG. 13 is a diagram showing an example of a control sequence of MAP according to the fifth embodiment. [Figure 39] FIG. 13 shows an example of the configuration of a MAP NDPA frame in the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings.

[0012] [Multi-Access Point coordination] In 11be, for example, the application of Multi-AP (hereinafter referred to as "MAP") coordination (hereinafter also referred to as "cooperative communication" or "cooperative communication between base stations") has been considered, in which multiple access points (APs: Access Point, also called "base stations") cooperate to send and receive data between each terminal (STAs: Station, also called "non-AP STA") (see, for example, Non-Patent Documents 1 to 3).

[0013] In 11be, multiple MAP coordination schemes (Multi-AP coordination schemes) are considered. For example, the following schemes are considered: Coordinated Spatial Reuse (hereinafter referred to as "C-SR") Coordinated OFDMA (hereinafter referred to as "C-OFDMA") Joint Transmissions (hereinafter referred to as "JT") ·Coordinated Beamforming (hereinafter referred to as “CBF”)

[0014] The MAP coordination scheme may be interchangeably referred to as other terms, such as "communication type" or "MAP type." In this definition, JT may include a method of transmitting the same signal from multiple cooperating APs and a method of transmitting different transmission streams from multiple cooperating APs. The latter is called Distributed Multi-User - Multiple Input Multiple Output (hereinafter sometimes referred to as "D-MIMO").

[0015] JT is sometimes defined as a method of transmitting the same signal from multiple cooperating APs, and is therefore different from D-MIMO. For convenience, this specification will be explained under the latter definition.

[0016] FIG. 1 is a diagram showing an example of the configuration of APs and STAs (an example of the configuration of MAPs) that perform cooperative communication.

[0017] 1, a "Sharing AP" may be, for example, an AP that acquires a channel use (or transmission) period (e.g., a TXOP (transmission opportunity)) and initiates (or controls) cooperative communication. Also, a "Shared AP" may be an AP that is instructed to perform cooperative communication by the Sharing AP.

[0018] In the example shown in FIG. 1, one of the Shared APs (for example, AP1) also functions as a Sharing AP, but the present invention is not limited to this, and the Sharing AP and the Shared AP may be different APs.

[0019] 1, STA a is associated (may also be referred to as "connected") to Sharing AP (AP1) and performs cooperative communication between Sharing AP (AP1) and Shared AP (AP2). Also, in the example of FIG. 1, STA b is associated with Shared AP (AP2) and performs cooperative communication between Sharing AP (AP1), Shared AP (AP2), and Shared AP (AP3).

[0020] To optimize the throughput or quality of cooperative communication, each Shared AP transmits an NDP, estimates propagation channel state information (CSI), and reports it to each Shared AP. The CSI reported to each Shared AP is aggregated by an AP, such as a Sharing AP, that determines the aforementioned MAP cooperation scheme (see, for example, Non-Patent Document 2).

[0021] [Retransmission control in MAP coordination] 2 is a diagram showing an example of a communication environment in which the coverage (communicable range) differs between the downlink and the uplink. Note that the connection relationship between AP1, AP2, AP3, STA a, and STA b shown in FIG. 2 may be the same as the connection relationship between the APs and STAs shown in FIG.

[0022] As shown in Figure 2, STA a exists (or is located) within the downlink coverage of each of Sharing AP (AP1) and Shared AP (AP2; the same applies below). In addition, Sharing AP (AP1) and Shared AP (AP2) exist within the uplink coverage of STA a. Therefore, STA a can simultaneously respond with CSI for downlink data to Sharing AP (AP1) and Shared AP (AP2).

[0023] On the other hand, STA b is present within the downlink coverage of each of the Sharing AP (AP1), Shared AP (AP2), and Shared AP (AP3). Meanwhile, the Shared AP (AP2) and Shared AP (AP3) are present within the uplink coverage of STA b, but the Sharing AP (AP1) is outside the uplink coverage of STA b. Therefore, STA b may not be able to simultaneously respond with CSI for downlink data to the Sharing AP (AP1), Shared AP (AP2), and Shared AP (AP3). For example, the Sharing AP (AP1) may not receive CSI from STA b.

[0024] FIG. 3 is a diagram showing an example of a control sequence of MAP (in other words, CSI measurement and feedback) in the communication environment shown in FIG.

[0025] In FIG. 3, for example, the Sharing AP (AP1) transmits a MAP NDPA (NDP Announcement for MAP) to the Shared APs (AP2, AP3) and STAs (STA a, STA b). The MAP NDPA may include information such as Shared AP information related to CSI measurement, communication parameters for each Shared AP and STA pair, and identifiers (IDs) of STAs participating in cooperative communication. In this control sequence example, the MAP NDPA is transmitted from the Sharing AP (AP1) that shares transmission data, but the MAP NDPA may be transmitted by any of the Shared APs (AP2, AP3) other than the Sharing AP (AP1).

[0026] After transmitting the MAP NDPA, for example, the designated Shared AP transmits a MAP NDP (NDP for MAP), and each STA measures CSI. The Sharing AP (AP1) transmits, for example, a MAP Poll Trigger frame instructing each STA to feedback the measured CSI. The STA that receives the MAP Poll Trigger frame feedbacks the CSI using, for example, a MAP BFR (Beamforming Report for MAP) frame.

[0027] The control sequence shown in Figure 3 is an example in which each Shared AP transmits a MAP NDP simultaneously (or in parallel; the same applies below), and each STA also feeds back a MAP BFR in parallel. Alternatively, there is a method in which a MAP NDP is transmitted sequentially for each Shared AP, and a MAP BFR is also fed back sequentially, as in the control sequence example shown in Figure 4.

[0028] Depending on the MAP coordination scheme, the control sequence of parallel transmission as shown in Fig. 3 or the control sequence of sequential transmission as shown in Fig. 4 may be changed (in other words, selected or switched). In addition, the control sequence configuration of MAP NDPA and MAP NDP may be matched to the control sequence configuration of MAP trigger and data transmission. For example, when timing and phase synchronization between APs is required as in the case of JT MAP coordination scheme, the control sequence of parallel transmission of MAP NDP as shown in Fig. 3 may be used.

[0029] Also, for example, the Shared APs (AP2, AP3) may correct the carrier frequency and phase of the MAP NDP based on the MAP NDPA of the Sharing AP (AP1). Similarly, in JT data transmission in the Shared APs (AP2, AP3), the carrier frequency, phase, and symbol frequency of the JT data may be corrected based on the MAP trigger of the Sharing AP (AP1).

[0030] When the MAP cooperation scheme is JT and a sequential transmission control sequence is applied, the following measures may be required to grasp the absolute phase of the MAP NDP, for example. The Sharing AP (AP1) transmits a MAP NDPA immediately before each MAP NDP, and the Shared APs (AP2, AP3) use this as a reference to correct the phase or frequency of the MAP NDP. The STA measures the NDP by correcting the reference phase or frequency based on the MAP NDPA immediately preceding each MAP NDP. In this case, the entire NDPA information may be transmitted first, and then an NDPA with relatively less information (for example, simply serving as a trigger) may be transmitted before transmitting the individual NDPs.

[0031] If there is a Shared AP that cannot receive CSI from each STA, appropriate cooperative communication control may not be possible. For example, as shown in Figure 2, STA b does not receive MAP BFR (CSI feedback) because the Sharing AP (AP1) is outside of its uplink coverage. Since the Sharing AP (AP1) does not receive CSI, cooperative communication control may fail. Furthermore, methods for sharing CSI information of each STA between Shared APs (or between a Sharing AP and a Shared AP) have not been fully studied.

[0032] Therefore, in one embodiment of the present disclosure, a method for specifying a CSI sharing method to realize appropriate MAP cooperative communication control (and ultimately, improvement of the quality of MAP cooperative communication) will be described. For example, during MAP operation, a CSI sharing phase for CSI sharing is provided after a MAP BFR (CSI feedback) from each STA, thereby allowing the Sharing AP and each Shared AP to share CSI.

[0033] It should be noted that the term "phase" may be interchangeably read as other terms such as "period," "sequence," or "procedure."

[0034] [Wireless communication system configuration] The wireless communication system according to this embodiment may include, for example, a plurality of APs 100 and STAs 200. The AP 100 may have the functions of both a Sharing AP and a Shared AP, or may have the functions of only one of them.

[0035] 5 is a block diagram illustrating a configuration example of a portion of an AP 100 according to an embodiment of the present disclosure. In the AP 100 illustrated in FIG. 5, a wireless transceiver 105 (e.g., a receiver circuit) receives control information related to CSI sharing in inter-base station cooperative communication (e.g., MAP coordination). A controller 101 (e.g., a control circuit) controls transmission of the CSI to other base stations (e.g., other APs 100) based on the received control information.

[0036] (Embodiment 1) [AP100 configuration example] Fig. 6 is a block diagram showing an example configuration of AP 100. AP 100 shown in Fig. 6 may include, for example, a control unit 101, a STA-directed control signal generation unit 102, an AP-directed control signal generation unit 103, a transmission signal generation unit 104, a wireless transmission / reception unit 105, and a received signal demodulation / decoding unit 106.

[0037] The control unit 101 may control the setting of frames (or signals) such as a MAP NDPA frame, a MAP NDA frame, and a MAP Poll Trigger frame, and may also control the sharing of CSI. For example, when the AP is a Sharing AP, the control unit 101 may control the generation of control signals (for example, a MAP NDPA frame) for other APs 100 (for example, a Shared AP) or STAs 200. Furthermore, when the control unit 101 receives CSI from each STA 200, for example, the control unit 101 may determine whether to control the sharing of CSI and control the sharing of CSI between APs.

[0038] Furthermore, the control unit 101 may set, for example, control information for the STA 200 or another AP 100. For example, the control unit 101 may set resource allocation information for each STA 200 and scheduling information such as a modulation and coding scheme (MCS). Furthermore, the control unit 101 may determine parameters related to cooperative communication control based on, for example, information input from the received signal demodulation and decoding unit 106 (for example, control information notified from the Sharing AP to the Shared AP). Furthermore, the control unit 101 may output, for example, control information including the determined cooperative communication control parameters to the STA-directed control signal generation unit 102 and the AP-directed control signal generation unit 103.

[0039] The STA-directed control signal generating unit 102 may generate a control signal (for example, a MAP NDPA frame) directed to the STA 200 and output the generated control signal to the transmission signal generating unit 104, for example.

[0040] The AP-directed control signal generating unit 103 may generate, for example, a control signal for the AP 100. The control signal for the AP 100 may include, for example, a MAP NDPA frame or a control frame that controls CSI sharing. The AP-directed control signal generating unit 103 may generate the control signal based on, for example, at least one of control information input from the control unit 101 and information input from the received signal demodulating and decoding unit 106. The AP-directed control signal generating unit 103 may output the generated control signal to the transmission signal generating unit 104, for example.

[0041] The transmission signal generating unit 104 may perform transmission processing on, for example, a control signal or data input from the STA-directed control signal generating unit 102 or the AP-directed control signal generating unit 103, and generate a wireless frame that is a transmission signal. The transmission signal generating unit 104 may output the generated transmission signal to the wireless transmitting and receiving unit 105.

[0042] The radio transmission / reception unit 105 performs radio transmission processing such as D / A conversion and up-conversion to a carrier frequency on the transmission signal input from the transmission signal generation unit 104, and transmits the signal after radio transmission processing via an antenna.

[0043] For example, when the AP 100 receives an uplink signal transmitted from the STA 200 or a control signal transmitted from another AP 100, the AP 100 may operate as follows.

[0044] A radio signal received via an antenna is input to, for example, radio transmission / reception unit 105. Radio transmission / reception unit 105 performs radio reception processing, such as down-conversion of the carrier frequency, on the received radio signal, and outputs the signal after radio reception processing to received signal demodulation / decoding unit 106.

[0045] The received signal demodulation and decoding unit 106 may, for example, perform processing such as autocorrelation processing on the signal input from the wireless transceiver unit 105 and extract the received wireless frame. The received signal demodulation and decoding unit 106 may also decode and demodulate, for example, an uplink signal from the STA 200 (e.g., a response signal, feedback information) or a control signal from another AP 100 (e.g., a MAP NDPA frame) included in the extracted wireless frame. The demodulated and decoded control signal may be output to, for example, the control unit 101, the STA-directed control signal generation unit 102, and the AP-directed control signal generation unit 103.

[0046] [STA200 configuration example] 7 is a block diagram showing an example configuration of STA 200 according to this embodiment. STA 200 shown in FIG. 7 may include, for example, a radio transmission / reception unit 201, a received signal demodulation / decoding unit 202, and a transmission signal generation unit 203.

[0047] The radio transmission / reception unit 201 receives, for example, a signal transmitted from the AP 100 via an antenna, and performs radio reception processing such as down-conversion and A / D conversion on the received signal. The signal after the radio reception processing may be output, for example, to the received signal demodulation and decoding unit 202. The radio transmission / reception unit 201 also performs radio transmission processing such as D / A conversion and up-conversion to a carrier frequency on a signal input from the transmission signal generation unit 203. The signal after the radio transmission processing is transmitted, for example, via an antenna.

[0048] The received signal demodulation and decoding unit 202 may, for example, perform processing such as autocorrelation processing on the signal input from the radio transmission and reception unit 201 to extract the received radio frame. Furthermore, the received signal demodulation and decoding unit 202 may, for example, demodulate and decode a control signal (e.g., a MAP Poll Trigger frame) included in the extracted radio frame to obtain uplink transmission control parameters. The obtained uplink transmission control parameters may be output to the transmission signal generation unit 203, for example.

[0049] The transmission signal generating unit 203 may perform transmission signal processing on an uplink signal (e.g., feedback information) based on the uplink transmission control parameters input from the received signal demodulating and decoding unit 202, and generate a radio frame as a transmission signal. The generated transmission signal may be output to the radio transmitting and receiving unit 201, for example.

[0050] [Example of AP100 and STA200 operation] Next, an example of the operation of the AP 100 and the STA 200 according to this embodiment will be described.

[0051] In this embodiment, for example, an AP that controls the sharing of CSI is defined as a CSI-controlled AP, and CSI information is aggregated in this CSI-controlled AP, and then the CSI sharing is controlled for the Sharing AP and each Shared AP.

[0052] The CSI-Controlled AP is an AP that controls the sharing of CSI between APs, and may be, for example, a Sharing AP or a Shared AP that can receive CSI transmitted from STA 200 under the control of a MAP. AP 100 that plays the role of the CSI-Controlled AP may be set (defined or changed) periodically or irregularly depending on, for example, the propagation environment. This allows, for example, the AP 100 that plays the role of the CSI-Controlled AP to be dynamically set depending on the propagation environment, thereby enabling adaptive optimization of CSI sharing control.

[0053] In this embodiment, for example, in a phase after the process in which each STA 200 transmits MAP BFR (CSI feedback) (which may be referred to as a "CSI sharing phase"), the following control steps (A1), (B1), and (C1) may be provided. Note that "step" may be interpreted as other terms such as "process" or "procedure."

[0054] (A1) When a shared AP does not receive CSI, it transmits a signal (for example, referred to as a "CSI request frame") requesting CSI to the CSI-controlling AP. (B1) When the CSI control AP receives the CSI request frame, it transmits a signal (for example, referred to as a "CSI sharing request frame") to each Shared AP to instruct it to share CSI. (C1) When the Shared AP receives a CSI sharing request frame, it transmits a CSI sharing frame.

[0055] The channel usage period called TXOP may be set, for example, in a MAP NDPA frame, which is a trigger for starting CSI measurement, and a CSI sharing phase including the above-mentioned control steps (A1), (B1), and (C1) may be set in the TXOP.

[0056] FIG. 8 is a diagram showing an example of a MAP control sequence (in other words, a control sequence of CSI measurement and feedback) in this embodiment.

[0057] Similar to Fig. 3, Fig. 8 is a diagram showing an example of a control sequence of MAP in the communication environment shown in Fig. 2. For example, Fig. 8 shows an example in which, regarding CSI for MAP NDP transmitted from the Sharing AP (AP1) and Shared APs (AP2, AP3), CSI from STA b does not reach the Sharing AP (AP1).

[0058] In the case of Fig. 8, for example, a Shared AP (AP2) that is an AP that can receive CSI from both STA a and STA b may be set (or defined) as the CSI-controlled AP. Note that the setting (or designation) of the CSI-controlled AP may be performed within a MAP NDPA frame, which is an example of a trigger (or signal) that starts CSI measurement, or may be performed in a phase prior to the MAP NDPA frame (for example, a phase in which setup or channel estimation related to MAP is performed).

[0059] For example, in the control step (A1), a Sharing AP (for example, AP1) that did not receive CSI may transmit a CSI request frame to a Shared AP (AP2) that is a CSI-controlling AP.

[0060] In control step (B1), for example, when a Shared AP (AP2), which is a CSI-controlled AP, receives a CSI request frame from a Sharing AP (AP1) that did not receive CSI, it may transmit a CSI sharing request frame to each Shared AP (e.g., AP1 and AP3) instructing them to share CSI (e.g., transmit CSI to AP1).

[0061] In the control step (C1), for example, the designated Shared AP transmits a CSI sharing frame in response to a CSI sharing request frame from the CSI-control AP. In the example of Fig. 8, the Shared APs (AP2 and AP3) that have received CSI from STA b may transmit a CSI sharing frame to the Sharing AP (AP1) that has not received the CSI, thereby notifying the Sharing AP of the CSI. As a result, AP1, AP2, and AP3 share the CSI from STA b.

[0062] In this way, the AP 100 that controls CSI sharing is defined as a CSI-controlled AP, and CSI information is aggregated in this CSI-controlled AP, and then CSI sharing control is performed for the Sharing AP and each Shared AP. This allows the Sharing AP and each Shared AP to share CSI information for each STA 200 under the MAP. Therefore, appropriate cooperative communication control can be implemented in the MAP. Furthermore, appropriate cooperative communication control can improve the quality of MAP cooperative communication.

[0063] In addition, the control sequence (e.g., determining the MAP Scheme) illustrated in FIG. 8 may include a phase in which, in the case of JT, the CSI-controlled AP determines the steering matrix (or precoding codebook, etc.) for the entire MAP and distributes the precoding information for which each AP is responsible to the other APs.

[0064] If the MAP Scheme has already been determined to be JT, the operation after MAP BFR may be performed, for example, as follows. If there is no CSI that the CSI-controlled AP cannot receive (in other words, if there is no CSI shortage), the precoding information distribution phase is entered and the precoding information is transmitted to the shared AP. If CSI is insufficient, a CSI request is sent at that time.

[0065] Also, after determining the MAP Scheme as JT, JT may be in an inappropriate state. In such a case, for example, when making a CSI request after determining the MAP Scheme as JT, it may be an operation to change the MAP Scheme instead of determining it.

[0066] Next, a configuration example of the frame used in the above-described control steps (A1), (B1), and (C1) will be described.

[0067] <CSI Request Frame (Control Step (A1))> The CSI request frame used in control step (A1) may be configured to include, for example, the address field of the Shared AP that is the source of the CSI request frame (in other words, the Shared AP that did not receive CSI, which is AP1 in FIG. 8).

[0068] FIG. 9 is a diagram showing a configuration example of a CSI request (CSI Req) frame.

[0069] As shown in FIG. 9, the CSI request frame may include, for example, the address of the Shared AP that is its source (for example, CSI Req Address). This address (CSI Req Address) may be, for example, the Medium Access Control (MAC) address of AP100 or a virtual Basic Service Set (BSS) address. As the virtual BSS address, for example, one identifier (ID) may be assigned to a plurality of AP100s targeted for MAP operation, or a plurality may be assigned within a specific ID value range.

[0070] Also, the designation (or display) of "frame type" indicating that the wireless frame is a CSI request frame may be based on, for example, at least one of the following definitions (or settings). ·Type value and Subtype value of the Frame Control field New Trigger Type (Trigger Type subfield value) Specify the BFRP Trigger frame format and set the CSI Req (CSI request) subfield

[0071] Fig. 10 is a diagram showing an example of specifying a frame type by the Type value and Subtype value of the Frame Control field in the CSI request frame shown in Fig. 9. Fig. 10 shows an example in which the type of the CSI request frame is defined to "0000," which is an undefined Subtype value (e.g., Reserved) in 11ax (e.g., Control type in Table 9-1 Valid type and subtype combinations of the 11ax specification). Note that Fig. 10 shows an example in which the type of the CSI request frame is defined to "0000," but is not limited to this and may be defined to another undefined value.

[0072] Also, FIG. 10 shows an example in which three subtypes, CSI Req (CSI request), CSI ShareReq (CSI sharing request), and CSI Share (CSI sharing), are defined, but this is not limited to this. For example, one CSI sharing subtype may have three variants to indicate three types.

[0073] Fig. 11 is a diagram showing an example in which a CSI request frame is specified by a new Trigger Type (Trigger Type subfield value). Fig. 11 shows an example in which the type of the CSI request frame is defined to "8," which is an undefined Trigger Type subfield value (e.g., Reserved) in 11ax (e.g., Table 9-29c Trigger Type subfield encoding of the 11ax specification). Note that Fig. 11 shows an example in which the type of the CSI request frame is defined to "8," but is not limited to this and may be defined to another undefined value.

[0074] Figure 12 shows the case where the BFRP Trigger frame format is specified and a CSI Req (CSI request) subfield is provided. In Figure 12, an example is shown where the BFRP Trigger frame format is specified by the Trigger Type, and a CSI Req (CSI request) subfield is provided within the User Info List of the frame. In this CSI Req (CSI request) subfield, for example, the presence or absence of a CSI request may be indicated. Also, as shown in Figure 12, the Association ID (AID) 12 subfield may be assigned as an identifier (ID) for CSI Req (CSI request).

[0075] <CSI Sharing Request Frame (Control Step (B1))> The CSI sharing request frame used in the control step (B1) may be configured to include, for example, the address field of the Sharing AP or Shared AP (in the example of Figure 8, AP1) that requests CSI.

[0076] Figure 13 is a diagram showing a configuration example of a CSI sharing request (CSI ShareReq) frame.

[0077] As shown in Figure 13, the CSI sharing request frame may include at least one address (for example, CSI ShareReq Address) of the Sharing AP or Shared AP (for example, the AP that requests sharing of CSI) that requests CSI. For example, the address (CSI ShareReq Address) included in the CSI sharing request frame may include the address (CSI Req Address) in the CSI request frame used in the control step (A1).

[0078] Furthermore, the frame type that specifies (or indicates) that a radio frame is a CSI sharing request frame may be based on at least one of the following definitions (or settings), for example. Frame Control field Type value and Subtype value New Trigger Type (Trigger Type subfield value) Specify the BFRP Trigger frame format and set the CSI Req (CSI request) subfield

[0079] Fig. 14 is a diagram showing an example of specifying a frame type by the Type value and Subtype value of the Frame Control field in the CSI sharing request frame shown in Fig. 13. Fig. 14 shows, as an example, an example in which the type of the CSI sharing request (CSI ShareReq) frame is defined to "0001," which is an undefined Subtype value (e.g., Reserved) in 11ax (e.g., the Control type in Table 9-1 Valid type and subtype combinations of the 11ax specification). Note that Fig. 14 shows an example in which the type of the CSI sharing request frame is defined to "0001," but is not limited to this and may be defined to another undefined value.

[0080] Fig. 15 shows an example of specifying the frame type by a new Trigger Type (Trigger Type subfield value). Fig. 15 shows, as an example, an example in which the type of the CSI sharing request frame is defined as "9," which is an undefined Trigger Type subfield value (e.g., Reserved) in 11ax (e.g., Table 9-29c Trigger Type subfield encoding of the 11ax specification). In this example, the type of the CSI sharing request frame is defined as "9," but the type of the CSI sharing request frame may also be defined as another undefined value.

[0081] FIG. 16 shows an example of specifying a BFRP Trigger frame format and providing a CSI Req (CSI request) subfield. In FIG. 16, it is shown that the BFRP Trigger frame format is specified by the Trigger Type, and a CSI ShareReq (CSI shared request) subfield is provided within the user information (User Info List) of the frame. In this CSI ShareReq (CSI shared request) subfield, for example, the presence or absence of a CSI shared request may be indicated. Also, as shown in FIG. 16, the AID12 subfield may be assigned as an identifier (ID) for the CSI ShareReq (CSI shared request).

[0082] <CSI shared frame (control step (C1))> The CSI shared frame used in the control step (C1) may be configured to include CSI information, for example.

[0083] FIG. 17 is a diagram showing a configuration example of a CSI share frame.

[0084] The Compressed Beamforming Report field included in the CSI share frame shown in FIG. 17 may include, for example, a HE / EHT Compressed Beamforming Report field.

[0085] Also, the frame type that specifies (or indicates) that the wireless frame is a CSI share frame may be based on, for example, at least one of the following definitions (or settings). · Type value and Subtype value of the Frame Control field Newly defined in the Action field values ​​of the HE / EHT Compressed Beamforming / CQI frame, or in the Feedback Type or undefined (Reserved) area in the HE / EHT MIMO Control field

[0086] Fig. 18 is a diagram illustrating an example of specifying a frame type by a Type value and a Subtype value in a Frame Control field in the CSI sharing frame illustrated in Fig. 17. In Fig. 18, as an example, the type of the CSI sharing frame is defined to "1111", which is an undefined Subtype value (e.g., Reserved) in 11ax (e.g., Control type in Table 9-1 Valid type and subtype combinations of the 11ax specification). Note that Fig. 18 illustrates an example in which the type of the CSI sharing frame is defined to "1111", but is not limited to this and may be defined to another undefined value.

[0087] FIG. 19 is a diagram showing an example in which the type of CSI-sharing frame is defined in the Action field values ​​of the HE / EHT Compressed Beamforming / CQI frame, or is newly defined in the Feedback Type or undefined (Reserved) area in the HE / EHT MIMO Control field.

[0088] 19 shows an example in which the type of a CSI Share frame is defined to "3," which is an undefined value (e.g., Reserved) in 11ax (e.g., Table 9-526a HE Action field values ​​of the 11ax specifications). Note that, although FIG. 19 shows an example in which the type of a CSI Share frame is defined to "3," this is not limitative and the type may be defined to another undefined value (e.g., any one of 4 to 255).

[0089] 19 also shows that the type of CSI Share frame may be defined as "3", which is an undefined value (e.g., Reserved) of Feedback Type in 11ax (e.g., Figure 9-144a MIMO Control field format of the 11ax specification). Additionally, FIG. 19 shows, as an example, that the Reserved field in 11ax (e.g., Figure 9-144a MIMO Control field format of the 11ax specification) is newly defined as a CSI Share subfield, with "1" indicating a CSI Share frame and "0" indicating a non-CSI Share frame.

[0090] Note that the type setting (or type indication) of the CSI-sharing frame shown in FIG. 19 is merely a non-limiting example, and may be realized using other undefined values ​​or undefined regions.

[0091] The above has described examples of various frame configurations related to CSI sharing used in control steps (A1), (B1), and (C1).

[0092] As described above, in this embodiment, AP100 receives control information (radio frames) regarding the sharing of feedback information (e.g., CSI information) for downlink signals in inter-base station cooperative communication, and controls the transmission of CSI to other APs based on the received control information.

[0093] For example, in this embodiment, when control information (e.g., a CSI request frame) received from another AP 100 indicates a CSI request, the AP 100 that is the CSI-controlled AP instructs an AP 100 other than the other AP 100 (the AP transmitting the CSI request frame) among the base stations involved in the inter-base station cooperative communication to transmit CSI to the other AP 100 (in other words, requests CSI sharing). Also, for example, in this embodiment, when the AP 100 other than the CSI-controlled AP 100 receives control information (e.g., a CSI sharing request frame) indicating a request for CSI sharing, it determines to transmit CSI (e.g., a CSI sharing frame) to the other AP 100 indicated in the control information.

[0094] This CSI sharing control allows multiple APs 100 (e.g., Sharing AP and Shared AP) to share CSI from STA 200 under MAP. Therefore, for example, even if AP 100 does not receive CSI from STA 200, it can obtain the CSI by sharing the CSI with other APs 100, enabling appropriate cooperative communication control. Therefore, according to this embodiment, for example, it is possible to optimize the throughput or quality of MAP cooperative communication and improve the quality of MAP cooperative communication.

[0095] Note that the CSI request frame may include, for example, the address of the source AP 100 (in other words, the AP 100 from which the CSI does not reach) and also the address of the source STA 200 of the CSI. This allows the CSI shared among multiple APs 100 to be set to the CSI not received by the source AP 100 of the CSI request frame, and other CSI does not need to be shared, thereby reducing overhead in CSI sharing control.

[0096] (Embodiment 2) Next, a description will be given of embodiment 2. The configuration examples of the AP 100 and the STA 200 according to embodiment 2 may be the same as those of embodiment 1.

[0097] In the first embodiment, for example, a case has been described in which AP 100, which is a CSI control AP, controls sharing of CSI from STA 200 for multiple APs 100. In the second embodiment, a case in which AP 100 individually controls CSI sharing will be described. For example, when AP 100 does not receive CSI from STA 200, AP 100 may individually request other APs 100 to share CSI.

[0098] Therefore, in the second embodiment, for example, in a phase after the process in which each STA 200 transmits a MAP BFR (CSI feedback), the following control steps (A2) and (B2) may be provided as a CSI sharing phase.

[0099] (A2) If the Shared AP does not receive CSI, it sends a CSI share request (CSI ShareReq) frame to the Shared AP associated with the STA 200 that sent the CSI. (B2) When the Shared AP receives a CSI sharing request frame, it sends a CSI sharing frame.

[0100] The channel usage period called TXOP may be set in a MAP NDPA frame, which is an example of a trigger for starting CSI measurement, and the CSI sharing phase including the above-mentioned control steps (A2) and (B2) may be set in the TXOP.

[0101] FIG. 20 is a diagram showing an example of a MAP control sequence (in other words, a control sequence of CSI measurement and feedback) in this embodiment.

[0102] Similar to Fig. 3, Fig. 20 is a diagram showing an example of a control sequence of MAP in the communication environment shown in Fig. 2. For example, Fig. 20 shows an example in which, regarding CSI for MAP NDP transmitted from the Sharing AP (AP1) and Shared APs (AP2, AP3), CSI from STA b does not reach the Sharing AP (AP1).

[0103] For example, in control step (A2), the Sharing AP (AP1) that did not receive CSI from STA b may transmit a CSI sharing request frame to the Shared AP (AP2) to which STA b is associated.

[0104] In control step (B2), the Shared AP (AP2) that has received the CSI sharing request frame may transmit a CSI sharing frame to the Sharing AP (AP1).

[0105] Note that if each Shared AP successfully receives CSI through MAP BFR (in other words, if there is no Shared AP that did not receive CSI), the CSI sharing phase may not be performed.

[0106] The Shared AP (AP2) that receives the CSI sharing request frame from the Sharing AP (AP1) may transmit a CSI sharing frame to the Sharing AP (AP1) based on the CSI sharing request frame, for example.

[0107] 20, the Shared AP (AP2) associated with STA b transmits a CSI sharing frame to the Sharing AP (AP1) that does not receive the CSI, thereby notifying the CSI from STA b. As a result, AP1 and AP2 share the CSI from STA b.

[0108] In this manner, in this embodiment, AP 100 controls CSI sharing by individually requesting CSI sharing for APs 100 that do not receive CSI. This control allows the Sharing AP and the Shared AP to share CSI information from each STA 200 under the MAP, and enables appropriate cooperative communication control in the MAP.

[0109] In addition, in the present embodiment, for example, compared with Embodiment 1, the setting of the CSI control AP and the control steps related to the CSI request for the CSI control AP do not need to be performed (or can be omitted), so that the overhead related to the shared control of CSI can be reduced.

[0110] Next, a configuration example of the frame used in the above-described control steps (A2) and (B2) will be described.

[0111] <CSI Sharing Request Frame (Control Step (A2))> The CSI sharing request frame used in control step (A2) may have a configuration including at least one address field of AP100 related to the sharing of CSI (for example, the Sharing AP or Shared AP that is the destination of the CSI sharing request, and in the example of FIG. 20, AP2), similar to the CSI sharing request frame in control step (B1) of Embodiment 1.

[0112] FIG. 21 is a diagram showing a configuration example of a CSI sharing request (CSI ShareReq) frame.

[0113] As shown in FIG. 21, the CSI sharing request frame may include at least one address (for example, CSI ShareReq Address) of the Sharing AP or Shared AP that is the destination of the CSI request (for example, the AP that is requested to share the CSI). The address (CSI ShareReq Address) may be shared, for example, in a MAP NDPA frame that is an example of a trigger for starting CSI measurement, or may be shared in a phase of performing processing (for example, setup related to MAP or channel estimation) that is earlier in time than the MAP NDPA frame.

[0114] In addition, the frame type for designating (or indicating) that the wireless frame is a CSI sharing request frame may be based on at least one of the following definitions (or settings). Frame Control field Type value and Subtype value New Trigger Type (Trigger Type subfield value) Specify the BFRP Trigger frame format and set the CSI Req (CSI request) subfield

[0115] Fig. 22 is a diagram showing an example of specifying a frame type by the Type value and Subtype value of the Frame Control field in the CSI sharing request frame shown in Fig. 21. Fig. 22 shows, as an example, an example in which the type of the CSI sharing request (CSI ShareReq) frame is defined to "0000," which is an undefined Subtype value (e.g., Reserved) in 11ax (e.g., the Control type in Table 9-1 Valid type and subtype combinations of the 11ax specification). Note that Fig. 22 shows an example in which the type of the CSI sharing request frame is defined to "0000," but is not limited to this and may be defined to another undefined value.

[0116] Fig. 23 is a diagram illustrating an example of specifying the type of a CSI sharing request frame by a new Trigger Type (Trigger Type subfield value). Fig. 23 illustrates an example in which the type of a CSI sharing request (CSI ShareReq) frame is defined to "8," which is an undefined Trigger Type subfield value (e.g., Reserved) in 11ax (e.g., Table 9-29c Trigger Type subfield encoding of the 11ax specification). Note that Fig. 23 illustrates an example in which the type of the CSI sharing request frame is defined to "8," but is not limited to this and may be defined to another undefined value.

[0117] FIG. 24 is a diagram showing an example of specifying the BFRP Trigger frame format and specifying the type of CSI sharing request frame by providing a CSI Req (CSI request) subfield. In FIG. 24, an example is shown in which the BFRP Trigger frame format is specified by the Trigger Type, and a CSI ShareReq (CSI sharing request) subfield is provided in the user information (User Info List) of the frame. In this CSI ShareReq (CSI sharing request) subfield, for example, the presence or absence of a CSI sharing request may be indicated. Also, as shown in FIG. 24, the AID12 subfield may be assigned as an identifier (ID) for the CSI ShareReq (CSI sharing request).

[0118] <CSI sharing frame (control step (B2))> The CSI sharing frame used in the control step (B2) may have a configuration including CSI information, for example, similar to the CSI sharing frame in the control step (C1) of Embodiment 1.

[0119] FIG. 25 is a diagram showing a configuration example of a CSI sharing (CSI Share) frame.

[0120] The Compressed Beamforming Report field included in the CSI sharing frame shown in FIG. 25 may include, for example, a HE / EHT Compressed Beamforming Report field.

[0121] <00,00500>Also, for the frame type that specifies (or indicates) that the wireless frame is a CSI sharing frame, it may be based on, for example, at least one of the following definitions (or settings). ·Type value and Subtype value of the Frame Control field Newly defined in the Action field values ​​of the HE / EHT Compressed Beamforming / CQI frame, or in the Feedback Type or undefined (Reserved) area in the HE / EHT MIMO Control field

[0122] Figure 26 is a diagram showing an example of specifying a frame type by the Type value and Subtype value of the Frame Control field in the CSI sharing frame shown in Figure 25. Figure 26 shows an example of defining the type of the CSI sharing frame to "0001", which is an undefined Subtype value (e.g., Reserved) in 11ax (e.g., Control type in Table 9-1 Valid type and subtype combinations of the 11ax specification). Note that Figure 26 shows an example in which the type of the CSI sharing frame is defined to "0001", but is not limited to this and may be defined to another undefined value.

[0123] FIG. 27 is a diagram showing an example in which the type of CSI-sharing frame is defined in the Action field values ​​of the HE / EHT Compressed Beamforming / CQI frame, or is newly defined in the Feedback Type or undefined (Reserved) area in the HE / EHT MIMO Control field.

[0124] 27 shows an example in which the type of a CSI Share frame is defined to "3", which is an undefined value (e.g., Reserved) in 11ax (e.g., Table 9-526a HE Action field values ​​of the 11ax specification). Note that, although FIG. 27 shows an example in which the type of a CSI Share frame is defined to "3", this is not limitative and the type may be defined to another undefined value (e.g., any one of 4 to 255).

[0125] 27 also shows that the type of CSI Share frame may be defined as "3", which is an undefined value (e.g., Reserved) of Feedback Type in 11ax (e.g., Figure 9-144a MIMO Control field format of the 11ax specification). Additionally, FIG. 27 shows, as an example, that the Reserved field in 11ax (e.g., Figure 9-144a MIMO Control field format of the 11ax specification) is newly defined as a CSI Share subfield, with "1" indicating a CSI Share frame and "0" indicating a non-CSI Share frame.

[0126] Note that the type setting (or type indication) of the CSI-sharing frame shown in FIG. 27 is merely a non-limiting example, and may be realized using other undefined values ​​or undefined regions.

[0127] The above has described an example of the structure of the frame used in the control steps (A2) and (B2) in the second embodiment.

[0128] As described above, in the second embodiment, AP 100 receives control information (radio frame) regarding CSI sharing for downlink signals in inter-base station cooperative communication, and, based on the received control information, controls transmission of CSI to other APs 100. For example, when control information (e.g., a CSI sharing request frame) received from another AP 100 indicates a request for sharing CSI of STA 200 associated with that AP 100, AP 100 determines to transmit CSI to that other AP 100.

[0129] This CSI sharing control allows multiple APs 100 (e.g., Sharing AP and Shared AP) to share CSI from STAs 200 under the control of a MAP. Therefore, even if an AP 100 does not receive CSI from a STA 200, the AP 100 can obtain the CSI by sharing the CSI with other APs 100, enabling appropriate cooperative communication control. Therefore, for example, the throughput or quality of MAP cooperative communication can be optimized, and the quality of MAP cooperative communication can be improved.

[0130] (Embodiment 3) Next, a description will be given of embodiment 3. The configurations of the AP and STA according to embodiment 3 may be the same as those in embodiment 1.

[0131] In the third embodiment, for example, a Shared AP related to CSI sharing may be specified in a MAP NDPA frame, which is an example of a trigger for starting CSI measurement.

[0132] For example, in the phase after the transmission process of the MAP NDPA frame and the MAP BFR (CSI feedback) from each STA 200, the following control steps (A3) and (B3) may be provided as a CSI sharing phase.

[0133] (A3) The MAP NDPA frame, which is an example of a trigger to start CSI measurement, specifies the combination of the Shared AP requesting CSI sharing and the STA transmitting CSI. (B3) The designated Shared AP transmits a CSI shared frame after the MAP BFR.

[0134] The channel usage period called TXOP may be set in a MAP NDPA frame, which is an example of a trigger for starting CSI measurement, and the CSI sharing phase including the above-mentioned control step (B3) may be set in the TXOP.

[0135] FIG. 28 is a diagram showing an example of a control sequence of MAP (in other words, a control sequence of CSI measurement and feedback) in the third embodiment.

[0136] Like Fig. 3, Fig. 28 is a diagram showing an example of a control sequence of MAP in the communication environment shown in Fig. 2. For example, Fig. 28 shows an example in which, regarding CSI for MAP NDP transmitted from the Sharing AP (AP1) and Shared APs (AP2, AP3), CSI from STA b does not reach the Sharing AP (AP1).

[0137] For example, in the above-described control step (A3), the Sharing AP (AP1) may specify a combination of a Shared AP requesting CSI sharing and a STA 200 transmitting the CSI. In other words, the Sharing AP (AP1) may specify a combination of an AP 100 that may not receive CSI from a STA 200 and the STA 200.

[0138] For example, the Sharing AP (AP1) may determine the uplink coverage of each STA 200 based on the propagation loss or channel estimation value between each STA 200 and each Shared AP collected in the Multi-AP Channel sounding phase. Then, the Sharing AP (AP1) may determine, for example, a combination of a Shared AP located outside the uplink coverage of each STA 200 and the STA 200. In the example of FIG. 28, for example, a combination of STA b and AP1 located outside the uplink coverage of STA b may be specified.

[0139] The above-mentioned combination designation may be updated periodically or irregularly, which allows the combination of AP 100 and STA 200 to be dynamically set (or changed) depending on the propagation environment, for example, thereby enabling adaptive optimization of CSI sharing control.

[0140] Also, for example, in the above-described control step (B3), the Shared AP (AP2) specified in the MAP NDPA frame in control step (A3) may transmit a CSI sharing frame to the Sharing AP (AP1) indicated in the combination.

[0141] 28, the Shared AP (AP2) designated for the combination of AP1 and STA b transmits a CSI sharing frame to the Sharing AP (AP1) that does not receive CSI from STA b, thereby notifying the CSI from STA b. As a result, the CSI from STA b is shared between AP1 and AP2.

[0142] In this way, in the third embodiment, the MAP NDPA frame controls the sharing of CSI by specifying a combination of AP 100 and STA 200 that do not receive CSI. This control enables the Sharing AP and the Shared AP to share CSI information from each STA 200 under the MAP, and enables appropriate cooperative communication control.

[0143] Furthermore, in the third embodiment, for example, compared to the first or second embodiment, the control steps related to the configuration of the CSI control AP and the CSI sharing request in the CSI sharing phase can be eliminated, thereby reducing overhead related to CSI sharing control.

[0144] Next, an example of the structure of a frame used in the above-mentioned control steps (A3) and (B3) will be described.

[0145] <map ndpaフレーム> The MAP NDPA frame used in the control step (A3) may be configured to include information about the STA 200 with which CSI is shared in a field of information for each AP 100 (for example, "Per AP Info").

[0146] FIG. 29 is a diagram illustrating Example 1 in which a CSI sharing request (CSI ShareReq) is included in a MAP NDPA frame.

[0147] 29, a CSI sharing request (CSI ShareReq) subfield may be provided in the information (AP Info) field for each AP 100. At least one identifier (STA ID) of the STA 200 related to CSI sharing may be set in this CSI sharing request subfield.

[0148] For example, in the example shown in FIG. 29, the ID of STA b may be set in the CSI sharing request subfield of the AP Info 1 field corresponding to the Sharing AP (AP1).

[0149] The STA ID may use a MAC address (for example, 48 bits), or may define an STA identifier called a Short ID. The Short ID may be defined as part of the Association ID (AID) specified in the 11ax specifications, or may be assigned to the Reserved area of ​​AID12. Using a Short ID can reduce overhead compared to using a MAC address.

[0150] FIG. 30 is a diagram illustrating Example 2 in which a CSI sharing request (CSI ShareReq) is included in a MAP NDPA frame.

[0151] As shown in FIG. 30, a CSI sharing request (CSI ShareReq) subfield may be provided within the STA info field for each STA200 in the MAP NDPA frame. Information indicating whether to request sharing of CSI (e.g., a CSI sharing request flag) may be set within this CSI sharing request subfield. The CSI sharing request flag may be, for example, 1-bit information.

[0152] For example, in the example shown in FIG. 28, in the Per STA info 1 field corresponding to STA b within the Per AP Info 1 field corresponding to the Sharing AP (AP1), it may be indicated by the CSI sharing request flag that the CSI sharing request is enabled.

[0153] FIG. 31 is a diagram showing Example 3 including a CSI sharing request (CSI ShareReq) in the MAP NDPA frame.

[0154] In FIG. 31, in the MAP NDPA frame, an example is shown in which a CSI sharing request (CSI ShareReq) subfield is provided within the STA info for each STA200, and the ID of AP100 related to the sharing of CSI is set within this CSI sharing request subfield. This frame configuration is an example of defining information indicating the presence or absence of a CSI sharing request in the undefined region (Reserved) of the HE NDPA frame, and an existing frame type can be used.

[0155] Note that in the examples shown in FIGS. 29 to 31, an example of providing a CSI sharing request (CSI ShareReq) subfield in the MAP NDPA frame is shown, but information indicating the presence or absence of a CSI sharing request may be similarly defined in the MAP Poll Trigger frame that indicates the feedback of the CSI measured by each STA200.

[0156] <CSI Sharing Frame (Control Step (B3))> The CSI sharing frame used in control step (B3) may be configured to include CSI information, for example, similarly to the CSI sharing frame in control step (C1) of the first embodiment.

[0157] 32 is a diagram illustrating an example of a CSI Share frame. In FIG. 32, the Compressed Beamforming Report field may include, for example, an HE / EHT Compressed Beamforming Report field.

[0158] The frame type that specifies (or indicates) that a radio frame is a CSI-sharing frame may be based on at least one of the following definitions (or settings), for example. Frame Control field Type value and Subtype value Newly defined in the Action field values ​​of the HE / EHT Compressed Beamforming / CQI frame, or in the Feedback Type or undefined (Reserved) area in the HE / EHT MIMO Control field

[0159] Figure 33 is a diagram showing an example of specifying a frame type by the Type value and Subtype value of the Frame Control field in the CSI sharing frame shown in Figure 32. Figure 33 shows an example of defining the type of the CSI sharing frame to "0001", which is an undefined Subtype value (e.g., Reserved) in 11ax (e.g., Control type in Table 9-1 Valid type and subtype combinations of the 11ax specification). Note that Figure 33 shows an example in which the type of the CSI sharing frame is defined to "0001", but is not limited to this and may be defined to another undefined value.

[0160] Fig. 34 shows a case where a CSI-sharing frame is defined in an undefined (reserved) area of ​​an HE / EHT Compressed Beamforming / CQI frame. Fig. 34 shows an example in which the type of CSI-sharing frame is defined by one of the following definitions, similar to the example of Fig. 27. Undefined value of HE Action field values ​​(e.g., "3") -Undefined value of Feedback Type in the HE MIMO Control field (e.g., "3") - New definition for undefined subfields in the HE MIMO Control field

[0161] FIG. 34 shows an example in which the type of a CSI Share frame is defined to "3", which is an undefined value (e.g., Reserved) in 11ax (e.g., Table 9-526a HE Action field values ​​of the 11ax specifications). Note that while FIG. 34 shows an example in which the type of a CSI Share frame is defined to "3", this is not limitative and the type may be defined to another undefined value (e.g., any one of 4 to 255).

[0162] FIG. 34 also shows that the type of CSI Share frame may be defined as "3", which is an undefined value (e.g., Reserved) of Feedback Type in 11ax (e.g., Figure 9-144a MIMO Control field format of the 11ax specification). Additionally, FIG. 34 shows, as an example, that the Reserved field in 11ax (e.g., Figure 9-144a MIMO Control field format of the 11ax specification) is newly defined as a CSI Share subfield, with "1" indicating a CSI Share frame and "0" indicating a non-CSI Share frame.

[0163] Note that the type setting (or type indication) of the CSI-sharing frame shown in FIG. 34 is merely a non-limiting example, and may be realized using other undefined values ​​or undefined regions.

[0164] The above has described examples of the frame configurations used in the control steps (A3) and (B3).

[0165] As described above, in the third embodiment, AP 100 receives control information (radio frame) regarding sharing of CSI for downlink signals in cooperative communication, and, based on the received control information, controls transmission of CSI to other APs 100. For example, when the received control information (e.g., MAP NDPA frame) indicates a combination of another AP 100 involved in cooperative communication that does not receive CSI and the source STA 200 of the CSI, AP 100 determines to transmit CSI from the source STA 200 to the other AP 100.

[0166] This CSI sharing control allows multiple APs 100 (e.g., Sharing AP and Shared AP) to share CSI from each STA 200 under a MAP. Therefore, for example, even if an AP 100 does not receive CSI from a STA 200, it can acquire the CSI by sharing the CSI with other APs 100. This enables appropriate MAP cooperative communication and improves the quality of MAP cooperative communication.

[0167] (Fourth embodiment) Next, a description will be given of embodiment 4. The configurations of the AP and STA according to embodiment 4 may be the same as those in embodiment 1.

[0168] In the fourth embodiment, for example, each Shared AP may transmit a CSI sharing frame regardless of the CSI reception state at each Shared AP.

[0169] For example, in the phase after processing of the MAP NDPA frame and the MAP BFR (CSI feedback) transmitted by each STA 200, the following control steps (A4) and (B4) may be provided as a CSI sharing phase.

[0170] (A4) The Sharing AP instructs multiple Shared APs (e.g., all Shared APs) to share CSI using a MAP NDPA frame, which is an example of a trigger to start CSI measurement. (B4) After receiving the MAP BFR from STA200, the Shared AP transmits a CSI shared frame.

[0171] In addition, the channel usage period called TXOP may be set in a MAP NDPA frame, which is an example of a trigger to start CSI measurement, and a CSI sharing phase including the above-mentioned control step (B4) may be set in the TXOP.

[0172] FIG. 35 is a diagram showing an example of a control sequence of MAP (in other words, a control sequence of CSI measurement and feedback) in the fourth embodiment.

[0173] Similar to Fig. 3, Fig. 35 is a diagram showing an example of a control sequence of MAP in the communication environment shown in Fig. 2. For example, Fig. 35 shows an example in which, regarding CSI for MAP NDP transmitted from the Sharing AP (AP1) and Shared APs (AP2, AP3), CSI from STA b does not reach the Sharing AP (AP1).

[0174] For example, in the above-described control step (A4), the Sharing AP (AP1) may set information instructing (or requesting) multiple Shared APs (AP2 and AP3) to share CSI. The information instructing CSI sharing may be, for example, a 1-bit CSI sharing request flag (CSI ShareReqFlag). For example, when the CSI sharing request flag is set to enable (e.g., when CSI sharing is instructed), each Shared AP may operate assuming that the CSI sharing phase of control step (B4) is set. On the other hand, when the CSI sharing request flag is set to disable (e.g., when CSI sharing is not instructed), each Shared AP may operate assuming that the CSI sharing phase of control step (B4) is not set.

[0175] In addition, the Shared AP (AP1) may specify a multiplexing method for transmitting the CSI shared frame in control step (B4). Examples of the multiplexing method for the CSI shared frame include time division multiplexing (TDMA: Time Division Multiple Access), frequency division multiplexing (e.g., OFDMA: Orthogonal Frequency Division Multiple Access), and space division multiplexing (e.g., MU-MIMO: Multi User - Multiple Input Multiple Output).

[0176] In control step (B4), the Shared AP may transmit the CSI sharing frame according to the multiplexing method specified in the MAP NDPA frame in control step (A4). Figure 35 shows an example of transmitting the CSI sharing frame by TDMA.

[0177] 35, multiple Shared APs (AP1, AP2, and AP3) that are instructed to share CSI in the MAP NDPA frame transmit CSI sharing frames. As a result, for example, the Shared APs (AP2 and AP3) notify the Sharing AP (AP1) that does not receive CSI from STA b of the CSI from STA b. Therefore, the CSI from STA b is shared among AP1, AP2, and AP3.

[0178] As described above, in the fourth embodiment, the MAP NDPA frame performs control to instruct multiple APs 100 to share CSI. This control enables the Sharing AP and the Shared AP to share CSI information from each STA 200 under the MAP, thereby enabling appropriate cooperative communication control.

[0179] Furthermore, in the fourth embodiment, for example, compared to the first or second embodiment, the control steps related to the configuration of the CSI control AP and the CSI sharing request in the CSI sharing phase can be eliminated, thereby reducing the overhead related to the CSI sharing control.

[0180] Next, an example of the structure of a frame used in the above-mentioned control steps (A4) and (B4) will be described.

[0181] <map ndpaフレーム> The MAP NDPA frame used in the control step (A4) may be configured to include information indicating sharing of CSI for a plurality of APs 100 (e.g., all Shared APs), for example.

[0182] FIG. 36 is a diagram showing an example of the configuration of the MAP NDPA frame.

[0183] FIG. 36 shows an example in which a CSI sharing request (CSI ShareReq) field for instructing CSI sharing for a plurality of Shared APs is provided in the common information (Common info) field shared by a plurality of APs 100. The CSI sharing request field may be, for example, a new field, or undefined bits in an existing field such as the Sounding Dialog Token field may be assigned.

[0184] Although FIG. 36 shows an example in which a CSI sharing request (CSI ShareReq) field is provided in the MAP NDPA frame, a field or bit value for requesting CSI sharing may be similarly defined in a signal (e.g., MAP Poll Trigger frame) for instructing the feedback of CSI measured by each STA 200.

[0185] <CSI Sharing Frame (Control Step (B4))> The CSI sharing frame used in the control step (B4) may be configured to include CSI information, for example, similarly to the CSI sharing frame in the control step (C1) of Embodiment 1. Also, examples of the configuration example and frame type designation of the CSI sharing frame may be the same as those of the CSI sharing frame in Embodiment 3, for example.

[0186] As described above, in the fourth embodiment, AP 100 receives control information (e.g., a radio frame) regarding the sharing of CSI for downlink signals in cooperative communication, and, based on the received control information, controls the transmission of CSI to other APs 100. For example, when the received control information (e.g., a MAP NDPA frame) instructs the sharing of CSI, AP 100 determines to transmit CSI to APs 100 involved in cooperative communication.

[0187] This CSI sharing control allows multiple APs 100 (e.g., Sharing AP and Shared AP) to share CSI from STAs 200 under a MAP. Therefore, for example, even if an AP 100 does not receive CSI from a STA 200, the AP 100 can acquire the CSI by sharing the CSI with other APs 100. This allows appropriate MAP cooperative communication control to be implemented, improving the quality of MAP cooperative communication.

[0188] (Embodiment 5) Next, a description will be given of embodiment 5. The configurations of the AP and STA according to embodiment 5 may be the same as those in embodiment 1.

[0189] In the fifth embodiment, for example, whether or not CSI is shared between the shared APs may be determined depending on the type of line between the shared APs (for example, whether it is wireless or wired).

[0190] The information determined by the AP 100 (for example, a Sharing AP) regarding the setting of sharing and whether or not to transmit may be, for example, at least one of the following. CSI sharing request frame in the first or second embodiment Information regarding combinations of AP 100 and STA 200 related to CSI sharing in the third embodiment Information regarding CSI sharing among multiple shared APs in the fourth embodiment

[0191] An example of a method for notifying information indicating whether to use a wired line or a wireless line is to notify by a frame including the following signaling. (a) Information on combinations that share CSI over wireless links (or do not share CSI over wired links) (b) Information on combinations that share CSI over wired links (or do not share CSI over wireless links) (c) Information combining (a) and (b) above (d) For each Shared AP, information indicating whether the sharing method is wireless or wired (e.g., a flag)

[0192] The AP 100 may acquire information about the type of line between the Shared APs, for example, during the Multi-AP Channel sounding phase or during another period.

[0193] Fig. 37 is a diagram showing an example of the configuration of lines between Shared APs. Fig. 37 shows an example in which a Sharing AP (AP1) and a Shared AP (AP2) are connected by a wired line, and the Sharing AP (AP1) and a Shared AP (AP3) and the Shared AP (AP2) and the Shared AP (AP3) are connected by wireless lines.

[0194] For example, if the relay line between shared APs (e.g., between AP1 and AP2 in Figure 37) is an ideal communication environment (e.g., a low-latency wired line such as Ethernet (registered trademark) or optical fiber), AP100 may transmit the CSI sharing request frame and at least one of the pieces of information regarding the combination of AP100 and STA200 for CSI sharing not wirelessly but in a wired frame such as an IEEE 802.3 Ethernet frame.

[0195] In contrast, for example, if the relay line between shared APs (e.g., between AP1 and AP3 in FIG. 37, or between AP2 and AP3) is not an ideal communication environment (e.g., in the case of a line such as a wireless line that tends to have larger delays than a wired line), AP100 may wirelessly transmit a CSI sharing request frame and a MAP NDPA frame that includes information regarding the combination of AP100 and STA200 related to CSI sharing.

[0196] Furthermore, in a relay circuit configuration in which wired and wireless are mixed (or used together), the AP 100 may transmit, for example, at least one of the CSI sharing request frame and information on the combination of the AP 100 and the STA 200 related to CSI sharing in a MAP NDPA frame on the wireless circuit path, and in a wired frame such as an IEEE 802.3 Ethernet frame on the wired circuit path. Note that the frames transmitted on the wired circuit and the wireless circuit are not limited to the above examples, and other frames may be used.

[0197] FIG. 38 is a diagram illustrating an example of a control sequence of MAP (in other words, a control sequence of CSI measurement and feedback) according to the fifth embodiment.

[0198] Figure 38 shows an example in which Sharing AP (AP1) and Shared AP (AP2) are connected by a wired line, and Sharing AP (AP1) and Shared AP (AP3), and Shared AP (AP2) and Shared AP (AP3) are connected by wireless lines.

[0199] 38 also shows an example in which CSI for a MAP NDPA frame transmitted from the Sharing AP (AP1) and Shared APs (AP2, AP3) does not reach the Sharing AP (AP1) from STA b. Note that the control sequence shown in FIG. 38 is an example in which a CSI sharing phase similar to the CSI sharing in each Shared AP is provided, as in the fourth embodiment, but the transmission and reception of CSI sharing frames between the Sharing AP (AP1) and Shared AP (AP2) that can be shared over a wired line is omitted.

[0200] For example, as shown in Fig. 38, between a Sharing AP (AP1) and a Shared AP (AP2) that are connectable via a wired line, at least one of the pieces of information related to CSI sharing may be transmitted in a wired frame and may not be transmitted wirelessly. Also, in Fig. 38, the CSI sharing frame from the Sharing AP (AP1) to the Shared AP (AP2) and the CSI sharing frame from the Shared AP (AP2) to the Sharing AP (AP1) may not be transmitted.

[0201] Fig. 39 is a diagram illustrating a configuration example of a MAP NDPA frame according to embodiment 5. Because a wired link is used between the Sharing AP (AP1) and the Shared AP (AP2), CSI sharing over a wireless link between AP1 and AP2 is not necessary. Therefore, as illustrated in Fig. 39, the elements of the CSI sharing request do not need to include information about AP2, but may include information about AP1 and AP3 that may share CSI over a wireless link.

[0202] According to the fifth embodiment, the AP 100 determines whether to share CSI with the other APs 100 (e.g., whether to request CSI sharing via wireless), based on the type of line to the other APs 100 (e.g., whether to request CSI sharing via wireless). The AP 100 can share CSI information of each STA 200 using both wired and wireless frames, thereby reducing the time required for CSI sharing. This reduces the time required for appropriate cooperative communication to be possible.

[0203] Note that, as an example, Figure 38 shows a control sequence based on the control sequence in embodiment 4, but this is not limited to this, and operations according to the line type in embodiment 5 may be applied to any of embodiments 1 to 3.

[0204] In addition, in embodiment 5, an example has been described in which CSI sharing is controlled depending on the line type, such as wireless or wired, between APs 100, but this is not limited to this, and CSI sharing may also be controlled depending on, for example, the communication performance (or communication method) between APs 100.

[0205] The embodiments of the present disclosure have been described above.

[0206] (Other embodiments) The operations (for example, control sequences) exemplified in the above-described embodiments may be applied selectively (in other words, switched).

[0207] Furthermore, in each of the above-described embodiments, an example has been described in which CSI is transmitted by an HE / EHT Compressed Beamforming Report. However, for example, CSI may be transmitted by any of the following signals or information. ·HE / EHT MU Exclusive Beamforming Report CSI Report ·Noncompressed Beamforming Report

[0208] Furthermore, in each of the above-described embodiments, an example has been described in which the information shared between APs 100 is CSI, but the information shared between APs 100 is not limited to CSI, and may be, for example, at least one of the candidates listed below in addition to or instead of CSI.

[0209] Acknowledgment from each STA 200 (e.g., ACK or Block ACK) -Transmission buffer status of each STA200: Buffer Status Report (BSR) Bandwidth occupancy status: Bandwidth (BW) Query Report (BQR) Information different from channel sounding from each STA200: NDP Feedback Report (NFR) Information used for Link Adaptation

[0210] Examples of information used for link adaptation include information or parameters such as MCS, DCM (Dual Sub-Carrier Modulation), RU (Resource Unit) Allocation, BW, NSS (Number of Spatial Streams), and Tx Beamforming. The type of Block Ack may be either Immediate Block Ack or Delayed Block Ack.

[0211] For example, one or a combination of two or more of the information used for CSI, ACK or Block ACK, BSR, BQR, NFR, and Link Adaptation may be subject to shared control between APs. In the format of a radio frame, individual definitions or a common definition may be assigned to a combination of two or more information elements. By adopting a common definition, it is possible to reduce the probability of exhaustion of resources, such as undefined fields or undefined values ​​that can be assigned to information elements related to shared control.

[0212] Alternatively, a signal (e.g., frame) format may be defined for each of the above information elements, or a signal (e.g., frame) format (e.g., a MAP shared frame) may be defined that handles at least part of each information element in a unified (or common) manner. Within this MAP shared frame, for example, a separate variant may be defined for each information element.

[0213] In addition, in each of the above-mentioned embodiments, an example has been described in which the CSI to be shared is CSI regarding CSI measurement and feedback by MAP NDP, but the CSI to be shared may also be CSI regarding CSI measurement and feedback during MAP data frame reception.

[0214] Furthermore, whether or not to perform CSI sharing control may be controlled by the MAP coordination scheme. For example, when the MAP coordination scheme is JT or CBF, AP 100 may perform CSI sharing control to aggregate CSI of coordinated APs, and when the MAP coordination scheme is neither JT nor CBF, AP 100 may not perform CSI sharing control.

[0215] Furthermore, the definitions of the information regarding CSI sharing in the Frame Control field, Trigger Type, and variant described in the above-described embodiments are merely examples, and other values ​​may be defined without being limited to these.

[0216] Furthermore, the configurations of the CSI request frame, CSI sharing request frame, CSI sharing frame, and MAP NDPA frame described in each of the above-mentioned embodiments are merely examples, and other configurations may be used without being limited to these. For example, in these frame configurations, some fields may not be set, and other fields may be set.

[0217] Furthermore, in each of the above-described embodiments, the AP that instructs cooperative communication and the AP that is instructed to perform cooperative communication are described as "Sharing AP" and "Shared AP," respectively, but this is not limited to these terms and other terms may be used.

[0218] Furthermore, although the above-described embodiments have been described based on the 11be format as a non-limiting example, the format to which an embodiment of the present disclosure can be applied is not limited to the 11be format. An embodiment of the present disclosure may be applied to, for example, IEEE 802.11bd (NGV (Next Generation V2X)), a next-generation standard of IEEE 802.11p, which is an in-vehicle standard.

[0219] The present disclosure can be realized by software, hardware, or software linked to hardware. Each functional block used in the description of the above embodiments may be partially or entirely realized as an LSI, which is an integrated circuit, and each process described in the above embodiments may be partially or entirely controlled by a single LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of a single chip that includes some or all of the functional blocks. The LSI may have data input and output. Depending on the degree of integration, the LSI may be called an IC, system LSI, super LSI, or ultra LSI.

[0220] The integrated circuit method is not limited to LSI, but may be realized by a dedicated circuit, a general-purpose processor, or a dedicated processor. Also, a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells within the LSI, may be used. The present disclosure may be realized as digital processing or analog processing.

[0221] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology can be used to integrate functional blocks. The application of biotechnology is also a possibility.

[0222] The present disclosure may be implemented in any type of apparatus, device, or system (collectively referred to as a communications apparatus) that has a communications function. The communications apparatus may include a wireless transceiver and processing / control circuitry. The wireless transceiver may include a receiver and a transmitter, or both functions. The wireless transceiver (transmitter and receiver) may include a radio frequency (RF) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of communication devices include telephones (e.g., cell phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (e.g., digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, communication-enabled vehicles or mobile transportation (e.g., cars, airplanes, ships), and combinations of the above devices.

[0223] Communications equipment is not limited to portable or mobile equipment, but also includes non-portable or fixed equipment, devices, and systems of any kind, such as smart home devices (such as appliances, lighting equipment, smart meters or metering devices, control panels, etc.), vending machines, and any other "things" that may exist on an IoT (Internet of Things) network.

[0224] Communications include data communications via cellular systems, wireless LAN systems, communications satellite systems, etc., as well as data communications via combinations of these.

[0225] A communications apparatus also includes devices such as controllers and sensors connected or coupled to a communications device that performs the communications functions described in this disclosure, such as controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications apparatus.

[0226] The communication apparatus also includes infrastructure facilities, such as base stations, access points, and any other apparatus, device, or system that communicates with or controls the various apparatuses listed above, but are not limited to these.

[0227] A base station according to one embodiment of the present disclosure may include a receiving circuit that receives control information regarding the sharing of channel state information in inter-base station cooperative communication, and a control circuit that controls the transmission of the channel state information to other base stations based on the control information.

[0228] In one embodiment of the present disclosure, when the control information indicates a request for the channel state information, the control circuit may instruct a base station other than the other base stations among the base stations involved in the base station-to-base station cooperative communication to transmit the channel state information to the other base stations.

[0229] In one embodiment of the present disclosure, when the control information indicates a request for sharing the channel state information, the control circuit may determine to transmit the channel state information to the other base station indicated in the control information.

[0230] In one embodiment of the present disclosure, the control circuit may determine to transmit the channel state information to the other base station when the control information indicates a request to share the channel state information for a terminal associated with the base station.

[0231] In one embodiment of the present disclosure, when the control information indicates a combination of a source of the channel state information and another base station involved in the base station-to-base station cooperative communication that does not receive the channel state information, the control circuit may determine to transmit the channel state information from the source to the other base station.

[0232] In one embodiment of the present disclosure, the control information may be included in a signal that triggers the start of measurement of the channel state information.

[0233] In one embodiment of the present disclosure, when the control information instructs sharing of the channel state information, the control circuit may determine to transmit the channel state information to base stations involved in the inter-base station cooperative communication.

[0234] In one embodiment of the present disclosure, the control information may be included in a signal that triggers the start of measurement of the channel state information.

[0235] In one embodiment of the present disclosure, the control circuit may determine whether to share the channel state information with the other base station based on the type of link to the other base station.

[0236] In one embodiment of the present disclosure, the control circuit may determine to share the channel state information when the line type is wireless, and may determine not to share the channel state information when the line type is wired.

[0237] In a communication method according to one embodiment of the present disclosure, a base station may receive control information regarding the sharing of channel state information in coordinated communication between base stations, and may control the transmission of the channel state information to other base stations based on the control information.

[0238] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2021-026256, filed on February 22, 2021, are incorporated herein by reference in their entirety. [Industrial Applicability]

[0239] One embodiment of the present disclosure is useful in wireless communication systems. [Explanation of symbols]

[0240] 100 AP 101 Control section 102 STA control signal generation unit 103 AP control signal generation unit 104,203 Transmission signal generator 105,201 Radio transmitter / receiver 106,202 Received signal demodulation and decoding unit 200 STA< / map> < / map>

Claims

1. a receiving circuit for receiving control information related to sharing of channel state information in cooperative communication between base stations; a control circuit that controls transmission of the channel state information to other base stations based on the control information; Equipped with When the control information indicates a combination of a source of the channel state information and another base station that does not receive the channel state information among base stations involved in the inter-base station cooperative communication, the control circuit determines to transmit the channel state information from the source of the channel state information to the other base station. Base station.

2. the control circuit determines, when the control information indicates a request for sharing the channel state information, to transmit the channel state information to the other base station indicated in the control information. The base station of claim 1 .

3. The control circuit determines, when the control information indicates a request for sharing the channel state information for a terminal associated with the base station, to transmit the channel state information to the other base station. The base station of claim 1 .

4. The control information is included in a signal that triggers the start of measurement of the channel state information. The base station of claim 1 .

5. the control circuit determines, when the control information instructs sharing of the channel state information, to transmit the channel state information to base stations involved in the inter-base station cooperative communication. The base station of claim 1 .

6. The control information is included in a signal that triggers the start of measurement of the channel state information. The base station according to claim 5.

7. the control circuit determines whether to share the channel state information with the other base station based on a type of a line to the other base station. The base station of claim 1 .

8. the control circuit determines whether to share the channel state information when the line type is wireless, and determines whether to not share the channel state information when the line type is wired. The base station of claim 7.

9. The base station is receiving control information regarding sharing of channel state information in cooperative communication between base stations; Controlling transmission of the channel state information to other base stations based on the control information; When the control information indicates a combination of the other base station that does not receive the channel state information and a source of the channel state information among the base stations involved in the inter-base station cooperative communication, determining transmission of the channel state information from the source to the other base station. Communication method.

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