Wireless base station

Abstract

The present invention pertains to, in multiple APs which each carry out cooperative transmission, increasing an effective rate for executing cooperative transmission by changing weight again after first execution of cooperative transmission .　This wireless base station is provided with: a wireless control unit; and a communication unit. The wireless control unit generates, from a first weight for past execution of cooperative transmission with another wireless base station, weight update information for updating a second weight for executing cooperative transmission thereafter. The communication unit notifies the other wireless base station of the weight update information.

Description

[Technical field]

[0001] The present technology relates to a radio base station and a radio terminal, and more particularly to a radio base station and a radio terminal in a radio system including a plurality of radio base stations that perform coordinated transmission. [Background technology]

[0002] In wireless LAN, within one basic service set (BSS), an access point (AP or BS) and a user terminal (STA or UE) autonomously acquire the right to transmit within the BSS and communicate. When a transmitting terminal is equipped with multiple antennas, in transmission using multiple antennas simultaneously (MIMO: Multiple Input Multiple Output), the formation of directivity in the desired direction (hereinafter, BF: Beamforming) can be realized by multiplying appropriate weights (hereinafter, weights) at the transmitting antenna and the receiving antenna. This not only enables high-gain transmission to the desired destination terminal, but also enables communication to multiple terminals at the same time, improving the system throughput within the BSS.

[0003] To implement beamforming, it is necessary to determine in advance the weight to be multiplied at the transmitting antenna based on the propagation path information between the transmitting antenna of the transmitting terminal and the receiving antenna of the receiving terminal. To achieve this, the AP implementing beamforming needs to estimate the propagation path information in advance.

[0004] As an example of a framework for determining weights at the AP, "IEEE 802.11-2016" specifies explicit feedback beamforming and implicit feedback beamforming. In explicit feedback beamforming, the AP transmits a known signal or a reference signal to the STA (hereinafter referred to as "sounding"), while in implicit feedback beamforming, the STA performs sounding to the AP. In "IEEE 802.11-2016", the weights are also called the matrix of steering vectors or steering matrix.

[0005] In explicit feedback beamforming, the STA receives the aforementioned known signal or reference signal and estimates the channel information. The STA then feeds back the estimated channel information to the AP, which calculates the weights to be used in beamforming based on the fed back information. On the other hand, in implicit feedback beamforming, the AP directly estimates the channel information through sounding of the STA and calculates the weights. However, strictly speaking, it is difficult to obtain the channel information directly in sounding, and the channel information is estimated including the influence of the circuit, so the weights are also calculated including the influence of the circuit. In beamforming, the AP uses the transmission circuit and the STA uses the reception circuit, while in implicit feedback beamforming sounding, the AP uses the reception circuit and the STA uses the transmission circuit, so the circuits affected are different. For this reason, implicit feedback beamforming requires a separate calibration to correct the influence of the circuit.

[0006] In explicit feedback beamforming, the amount of propagation path information (hereafter referred to as overhead) fed back from the STA to the AP is large, so even if the peak rate is improved by beamforming, the overhead makes it difficult to improve the effective rate. However, it is not necessary to feedback propagation path information every time beamforming is performed. This is because, for example, in a propagation environment with little time fluctuation, it is possible to obtain the same peak rate as when the latest weights are used by reusing propagation path information that has been fed back in the past and performing weight calculation and beamforming without feeding back propagation path information and calculating weights for each beamforming.

[0007] By extending this type of beamforming and implementing joint transmission (JT: Joint Transmission) using beamforming coordinated by multiple APs (hereafter referred to as multi-AP) that cooperate with each other, the peak rate can be further improved. There are several methods for joint transmission, but in particular, Coherent Joint Transmission (CJT), which transmits as a virtual single AP with antennas equal to the sum of the antennas of each AP, can achieve the highest peak rate.

[0008] When performing such coordinated transmission, it has been proposed to transmit a trigger immediately before sounding (for example, see Non-Patent Document 1). This conventional technology also mentions feeding back channel information estimated by the STA to the AP, which is the main body that determines the weights. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Kosuke Aio, et al., "Consideration on Multi-AP Sounding," doc.: IEEE 802.11-19 / 1134r1 9th Aug. 2019 Summary of the Invention [Problem to be solved by the invention]

[0010] In the above-mentioned cooperative transmission, it is assumed that the AP (Sharing AP) that decides the weight will notify the multi-AP (Shared AP) other than the Sharing AP that performs CJT of the weight. If conventional technology is used as a method for notifying this weight, there is a concern that the effective rate will decrease due to the overhead of notifying the weight. In particular, if the weight applied by each AP that makes up the multi-AP is changed when CJT is performed again after it has been performed once, the Shared AP will need to be notified of the changed weight from the Sharing AP each time.

[0011] As a specific example, when transmitting simultaneously to multiple STAs by CJT (hereinafter referred to as "CJT DL MU MIMO": CJT Downlink Multi User Multiple Input Multiple Output), the number of destination users may change for each communication, or the transmission power allocated to the users may change. Generally, in "CJT DL MU MIMO", weights must be applied to the destination users to reduce interference between users, so if the weights are not reconfigured appropriately, interference cannot be suppressed and communication quality will deteriorate, especially when the destination user is changed.

[0012] In the case of MIMO transmission with one AP, the AP can calculate and change the weight for each beamforming based on the estimated propagation path information and execute beamforming, but in the case of CJT, if the weight is not notified from the sharing AP, the CJT cannot change the beamforming. Therefore, with CJT, overhead occurs due to weight notification every time the weight is changed, which causes a problem of a decrease in the effective rate.

[0013] This technology was developed in light of these circumstances, and its purpose is to improve the effective rate in multi-AP cooperative transmission when cooperative transmission is performed once and then the weights are changed again to perform cooperative transmission. [Means for solving the problem]

[0014] The present technology has been made to solve the above-mentioned problems, and a first aspect thereof is a radio base station including a radio control unit that generates weight update information for updating a first weight used when cooperative transmission with another radio base station has been performed in the past to a second weight for performing the cooperative transmission thereafter, and a communication unit that notifies the other radio base station of the weight update information, thereby providing an effect of notifying the other radio base station of the weight update information for updating the first weight to the second weight.

[0015] In addition, in the first aspect, the radio control unit may generate capability information regarding whether or not coordinated transmission is possible in the radio base station and an algorithm that can be used to update the weight from the first weight to the second weight, and the communication unit may notify the other radio base station of the capability information. This brings about an effect of notifying the other radio base station of the capability information before notifying the weight update information.

[0016] In addition, in the first aspect, the radio control unit may generate target data for the cooperative transmission using the second weight, and the communication unit may include the target data in the weight update information and transmit the weight update information to the other radio base station. This provides an effect of simultaneously notifying the weight update information and sharing data.

[0017] In addition, in this first aspect, the weight update information may include information indicating that the target data is included, thereby providing an effect of causing another radio base station to determine whether or not the target data is included.

[0018] In addition, in this first aspect, the weight update information may include information for updating to the second weight for each of the other radio base stations and the destination terminal of the coordinated transmission, and may further include index information for identifying each of them. This provides an effect of individually identifying the information for updating to the second weight.

[0019] In addition, in the first aspect, the index information may include the number of the other radio base stations and information for identifying each of the other radio base stations, thereby providing an effect of identifying information for updating to the second weight for each radio base station.

[0020] In addition, in the first aspect, the weight update information may include information for identifying the number of the destination terminals and each of the destination terminals, and information on the communication streams to be individually assigned to the destination terminals. This provides an effect of identifying information for updating to the second weight for each terminal.

[0021] In addition, in this first aspect, the weight update information may include at least one of the first weight, a parameter for converting the first weight to the second weight, and the second weight, thereby providing an effect of appropriately selecting and transmitting information to be transmitted as the weight update information.

[0022] In addition, in the first aspect, the weight update information may further include mode information indicating which of the first weight, a parameter for converting the first weight to the second weight, and the second weight is included, thereby providing an effect of allowing information included as the weight update information to be determined in another radio base station.

[0023] In addition, in this first aspect, the parameters may include information on transmission power for the cooperative transmission, thereby providing an effect that the transmission power in the cooperative transmission is determined in the other radio base station.

[0024] In addition, in this first aspect, the parameter may include information on an eigenvector of a propagation path for a terminal that is a destination of the cooperative transmission using the first weight but is not a destination of the cooperative transmission using the second weight, thereby providing an effect of causing another radio base station to determine a transmission direction when the number of terminals decreases from the previous time in the cooperative transmission.

[0025] In addition, in this first aspect, the parameter may include information on an eigenvector of a propagation path for a terminal that is a destination of the cooperative transmission using the second weight but is not a destination of the cooperative transmission using the first weight. This brings about an effect that a transmission direction when a terminal is added since the previous time in the cooperative transmission is determined by another radio base station.

[0026] Also, a second aspect of the present technology is a radio base station including a communication unit that receives weight update information from another radio base station that has previously performed cooperative transmission using a first weight, and a radio control unit that updates the first weight to a second weight for performing the cooperative transmission thereafter based on the weight update information. This provides an effect of receiving weight update information for updating the first weight to a second weight from another radio base station and updating to the second weight.

[0027] In addition, in the second aspect, the radio control unit may generate capability information regarding whether or not coordinated transmission is possible in the radio base station and an algorithm that can be used to update the weight from the first weight to the second weight, and the communication unit may notify the other radio base station of the capability information, thereby providing an effect of notifying the other radio base station of the capability information before performing weight updating.

[0028] In addition, in the second aspect, the radio control unit may extract target data for which the cooperative transmission is performed using the second weight when the target data is included in the weight update information, thereby achieving an effect of simultaneously notifying the weight update information and sharing data.

[0029] In addition, in the second aspect, the radio control unit may extract the target data when the weight update information includes information indicating that the target data is included, thereby achieving an effect of extracting the target data when the target data is included.

[0030] In addition, in this second aspect, the weight update information may include information for updating to the second weight for each of the other radio base stations and the destination terminal of the coordinated transmission, and may further include index information for identifying each of them. This provides an effect of individually identifying the information for updating to the second weight.

[0031] In addition, in the second aspect, the index information may include the number of the other radio base stations and information for identifying each of the other radio base stations, thereby providing an effect of identifying information for updating to the second weight for each radio base station.

[0032] In addition, in this second aspect, the weight update information may include information for identifying the number of the destination terminals and each of the destination terminals, and information on the communication streams to be individually assigned to the destination terminals. This provides the effect of identifying information for updating to the second weight for each terminal.

[0033] In addition, in this second aspect, the weight update information may include at least one of the first weight, a parameter for converting the first weight to the second weight, and the second weight, thereby providing an effect of appropriately selecting and transmitting information to be transmitted as the weight update information. [Brief description of the drawings]

[0034] [Figure 1] 1 is a diagram illustrating an example of a configuration of a wireless network system according to an embodiment of the present technology. [Diagram 2] 1 is a diagram illustrating an example of a configuration of a wireless communication device 300 according to an embodiment of the present technology. [Diagram 3] 1 is a sequence diagram showing an example of an operation of a wireless network system according to an embodiment of the present technology; [Figure 4] 8 is a diagram showing an example of the structure of a frame notified in capability exchange 811 and 812 according to the embodiment of the present technology. FIG. [Diagram 5] 11 is a diagram showing an example of the structure of a frame notified by weight update information 828 according to the embodiment of the present technology. FIG. [Figure 6] 11 is a diagram illustrating an example of the structure of a frame notified in weight update information performed immediately before an L2-th coordinated transmission in a first example of an embodiment of the present technology. FIG. [Figure 7] 13 is a diagram showing an example of the structure of a frame notified in weight update information performed immediately before an L2-th coordinated transmission in a second and third example of the embodiment of the present technology. FIG. [Figure 8]13 is a diagram illustrating an example of the structure of a frame notified in weight update information performed immediately before an L2-th coordinated transmission in a fourth example of an embodiment of the present technology. FIG. [Figure 9] 11 is a flowchart showing an example of a processing procedure when selecting each example of the embodiment of the present technology. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, modes for carrying out the present technology (hereinafter, referred to as embodiments) will be described. The description will be made in the following order. 1. Overall processing 2. Example of weight update

[0036] <1. Overall processing> [Wireless network system] FIG. 1 is a diagram showing an example of a configuration of a wireless network system according to an embodiment of the present technology.

[0037] In this wireless network system, multiple access points AP#1 (101) and AP#2 (102) are connected to multiple communication terminals STA#1 (201), STA#2 (202), STA#3 (203), STA#4 (204), and STA#5 (205). The access points AP#1 (101) and AP#2 (102) function as a multi-AP 100 and perform cooperative transmission to any multiple communication terminals.

[0038] To simplify the following explanation, the communication terminal groups grouped into an arbitrary number of communication terminals STAs are called STAs. In the figure, STA#1 to STA#3 are STAs#1, and STA#4 and STA#5 are STAs#2, but the components of each communication terminal group and the number of communication terminal groups are not limited to this. Also, the same communication terminal may belong to multiple communication terminal groups. Similarly, in the figure, two APs, AP#1 (101) and AP#2 (102), are shown as APs constituting the multi-AP 100, but there may be three or more APs.

[0039] The APs constituting the multi-AP 100 are called sharing APs if they have acquired the transmission right before the implementation of the cooperative transmission, and shared APs if they have not, and may play the following roles. That is, when the sharing AP cooperates with the shared AP as the multi-AP, after acquiring the transmission right, it notifies the shared AP that it will cooperate within the transmission time it has acquired. The sharing AP may be called a master AP, and the shared AP may be called a slave AP. The sharing AP and the shared AP may not be fixedly determined by the AP, but may be dynamically determined within the multi-AP. For example, at a certain time t1, AP1 may be a sharing AP and AP2 may be a shared AP, and at a different time t2, AP1 may be a shared AP and AP2 may be a sharing AP.

[0040] In addition, when performing cooperative transmission, the sharing AP and the shared AP share data and notify each other of weights, but the sharing AP may also notify the shared AP of data sharing and weights, and similarly, the shared AP may notify the sharing AP and other shared AP of data sharing and weights.

[0041] The frequency channels used for communication between the multi-APs and communication between the multi-APs and the communication terminals may be different. For example, communication between the multi-APs may be performed in the 6 GHz band, and communication between the multi-APs and the communication terminals may be performed in the 2.4 GHz band and the 5 GHz band. In this case, it is possible to prevent communication between the multi-APs and communication between the multi-APs and the communication terminals from interfering with each other. Communication between the multi-APs may be performed by wired communication such as optical fiber or power line.

[0042] In addition, the frequency channels used in the cooperative transmission between the multi-AP and the group of communication terminals may be completely the same, or may be only partially the same. For example, when two frequency channels B1 and B2 are used between AP#1 and the group of communication terminals, and two frequency channels B2 and B3 are used between AP#2 and the group of communication terminals, cooperative transmission may be performed only on the frequency channel B2.

[0043] [Device configuration] 2 is a diagram showing a configuration example of a wireless communication device 300 according to an embodiment of the present technology. The wireless communication device 300 includes the above-mentioned access points AP#1 (101) and AP#2 (102) and communication terminals STA#1 (201) to STA#5 (205). For example, the wireless communication device 300 may be a wireless communication module or an integrated circuit mounted on these APs or terminals.

[0044] The wireless communication device 300 includes a communication unit 310, a control unit 321, a power supply unit 322, and an antenna 319. There may be multiple communication units 310.

[0045] The communication unit 310 includes a radio control unit 311, a data processing unit 312, a modulation / demodulation unit 313, a signal processing unit 314, a channel estimation unit 315, a radio interface unit 316, and an amplifier unit 317. The radio interface unit 316, the amplifier unit 317, and the antenna 319 form a set, and one or more sets may be components. The function of the amplifier unit 317 may be included in the radio interface unit 316. The communication unit 310 is realized by, for example, an LSI (Large Scale Integration).

[0046] During transmission when data is input from an upper layer, the data processing unit 312 generates packets for wireless transmission from the data, performs processing such as adding a header for media access control (MAC) and adding an error detection code, and supplies the processed data to the modem unit 313. On the other hand, during reception when there is input from the modem unit 313, it performs analysis of the MAC header, detection of packet errors, reordering processing, and provides the processed data to its own protocol upper layer.

[0047] The wireless control unit 311 transfers information between the various units. It also sets parameters for the modem unit 313 and the signal processing unit 314, schedules packets in the data processing unit 312, and sets parameters and controls transmission power for the modem unit 313, the signal processing unit 314, the wireless interface unit 316, and the amplifier unit 317.

[0048] During transmission, the modem unit 313 performs encoding, interleaving, and modulation on input data from the data processing unit 312 based on the encoding method and modulation method set by the radio control unit 311, generates a data symbol stream, and supplies it to the signal processing unit 314. During reception, the modem unit 313 performs processing on the input from the signal processing unit 314 that is the reverse of that during transmission, and supplies the data to the data processing unit 312 or the radio control unit 311.

[0049] During transmission, the signal processing unit 314 performs signal processing for spatial separation on the input from the modulation / demodulation unit 313 as necessary, and supplies the obtained one or more transmission symbol streams to each of the wireless interface units 316. Note that, without spatial separation, an arbitrary delay amount may be applied to each antenna 319 for transmission (hereinafter, cyclic shift delay (CSD)). During reception, the signal processing unit 314 performs signal processing on the reception symbol streams input from each of the wireless interface units 316, and performs spatial decomposition of the streams as necessary, and supplies the streams to the modulation / demodulation unit 313.

[0050] The channel estimation unit 315 calculates complex channel gain information of the propagation path from the preamble portion and the training signal portion of the input signal from each of the wireless interface units 316. The calculated complex channel gain information is used for demodulation processing in the modem unit 313 and spatial processing in the signal processing unit 314 via the wireless control unit 311.

[0051] During transmission, the wireless interface unit 316 converts the input from the signal processing unit 314 into an analog signal, performs filtering, up-conversion to a carrier frequency, and phase control, and sends the signal to the antenna 319 or the amplifier unit 317. During reception, the wireless interface unit 316 performs the reverse processing on the input from the antenna 319 or the amplifier unit 317, and supplies data to the signal processing unit 314 and the channel estimation unit 315.

[0052] During transmission, the amplifier unit 317 amplifies an analog signal input from the wireless interface unit 316 to a predetermined power and sends it to the antenna 319. During reception, the amplifier unit 317 amplifies a signal input from the antenna 319 to a predetermined power and outputs it to the wireless interface unit 316. At least one of the functions of the amplifier unit 317 during transmission and reception may be entirely or partially included in the wireless interface unit 316. Furthermore, at least one of the functions of the amplifier unit 317 during transmission and reception may be entirely or partially a component external to the communication unit 310.

[0053] The control unit 321 controls the wireless control unit 311 and the power supply unit 322. Furthermore, the control unit 321 may carry out at least a part of the operation of the wireless control unit 311 in place of the wireless control unit 311.

[0054] The power supply unit 322 is constituted by a battery power source or a fixed power source, and supplies power to each unit of the wireless communication device 300 .

[0055] Also, a plurality of communication units 310 may be installed and configured to be connected to one control unit. In this case, at least one of the plurality of communication units 310 may be used for communication only with other APs. For example, when communication occurs between APs, it may be used as a communication interface for a dedicated backhaul, and may be operated on a frequency channel different from that for communication with communication terminals.

[0056] Of these components, radio control unit 311 and control unit 321 control each unit to perform the following operations.

[0057] [Operation] FIG. 3 is a sequence diagram showing an example of operation of the wireless network system according to the embodiment of the present technology.

[0058] Here, there are two APs, AP#1 and #2, constituting a multi-AP, and there are multiple communication terminal groups, STAs#1 and #2. Although the figure shows a case where capability exchange 811 is performed by AP#1, it may be performed by AP#2 first. Similarly, the figure shows a case where trigger 823, data sharing 814, weight update information 828, and cooperative transmission trigger 821 are performed by AP#1, but some or all of them may be performed by AP#2.

[0059] For example, data sharing 814 may be performed from AP#2 to AP#1, while weight update 828 may be performed from AP#1 to AP#2. Also, update generation 827 and weight update 830 are performed in AP#1 and AP#2, respectively, but may also be performed in AP#2 and AP#1, respectively.

[0060] In addition, in the figure, cooperative transmission is performed twice, and the first cooperative transmission is performed for STAs#1 and STAs#2, and the second cooperative transmission is performed only for STAs#1, but this order may be reversed and may not be as shown in the destination diagram. That is, the first cooperative transmission may be performed only for STAs#2, and the second cooperative transmission may be performed for STAs#1 and STAs#2, or both cooperative transmissions may be performed for STAs#1 only or for both STAs#1 and STAs#2.

[0061] In addition, each sequence may be implemented by combining parts of the sequences into one sequence as necessary, or parts of the sequences may be omitted. For example, the trigger 823 may not be present, and the weight update information 828 may be implemented simultaneously with the data sharing 825. In addition, for example, the capability exchange 811 may be implemented simultaneously with the weight update information 828.

[0062] Furthermore, when performing coordinated transmission, sounding may be performed in advance. This is because, in order to calculate weights for performing CJT, APs #1 and #2 constituting the multi-AP need to acquire propagation path information with a group of communication terminals when each is treated as a single virtual AP. Therefore, in sounding, a reference signal that is a known sequence is transmitted from each antenna of the multi-AP, and at this time, a sequence that is orthogonal between each antenna is used.

[0063] Also, just before sounding, information notification regarding sounding may be performed between the multi-APs. This is because, since adjustment of transmission timing and frequency synchronization are required between the multi-APs in coordinated transmission, sounding for obtaining feedback for calculating weights in coordinated transmission also requires adjustment of transmission timing and frequency synchronization between the multi-APs. Therefore, just before sounding, it is necessary to notify the time to start sounding between the multi-APs, notify parameters for orthogonalizing reference signals transmitted between the antennas, and transmit a signal for performing frequency synchronization. Just before sounding, a frame that can perform these simultaneously may be transmitted between the multi-APs.

[0064] When the above-mentioned sounding-related information notification and sounding are performed, they may be performed immediately before weight sharing 818. Each communication terminal that receives a reference signal by sounding estimates a propagation path with the multi-AP by the reference signal, and notifies the multi-AP of information regarding the propagation path. The information regarding the propagation path at this time may be a complex matrix that directly indicates the propagation path, or may be information regarding an eigenvector for a propagation path matrix as indicated in the compressed feedback of "IEEE 802.11-2016".

[0065] The Ack shown in the figure indicates a notification of information indicating a reception result for the information notification performed immediately before. The notification method here may be an Ack or a block Ack as specified in "IEEE 802.11-2016."

[0066] [Capability exchange] First, AP#1 and #2 notify each other of their own capabilities. This is called capability exchange 811 and 812. The capabilities here include, but are not limited to, whether or not coordinated transmission 822 and 832 can be performed, whether or not weight update 830 can be performed, and the type of algorithm when weight update 830 is performed.

[0067] The weight update algorithm may be implemented or not implemented depending on the AP. Therefore, an implemented algorithm among commonly known algorithms such as ZF (Zero Forcing) and MMSE (Minimize Maximum Square Error) may be notified by the capability exchange 811 and 812. Also, an algorithm implemented by a vendor may be notified instead of the commonly known algorithms described above.

[0068] The capability exchanges 811 and 812 may be executed, for example, by being included in a beacon signal periodically transmitted by each AP, or in information notification (association) for connecting the APs to operate as a multi-AP.

[0069] FIG. 4 is a diagram showing an example of the structure of a frame notified in capability exchanges 811 and 812 according to the embodiment of the present technology.

[0070] The notification frames of the capability exchanges 811 and 812 are composed of, but not limited to, a "frame control", a "destination address", a "source address" and an "EHT (Extremely High Throughput) capability".

[0071] “Frame Control” includes information indicating that this frame is a frame notified in capability exchanges 811 and 812 .

[0072] The "destination address" (RA: Receiver Address) includes information indicating the terminal to which this frame is addressed. For example, it may include information indicating the MAC (Media Access Control) address of the destination terminal, but if the destination terminals are multiple specific terminals or all terminals capable of receiving this frame, it may include information indicating that the frame may be received by those terminals. The "source address" (TA: Transmitter Address) includes information indicating the terminal that is the sender of this frame. Like the "destination address," it may include information indicating the MAC address of the sender.

[0073] The “EHT Capabilities” element includes information indicating the capabilities of the wireless communication device transmitting this frame, in particular information indicating whether simultaneous transmission is possible, and information regarding whether weight update 830 (described below) can be performed and the algorithm that can be performed.

[0074] The "EHT Capability" element contains at least one of the following fields: "Element ID", "Length", "Cooperative Transmission" and "Weight Update".

[0075] "Element ID" includes information indicating that this element is "EHT Capability". "Length" includes information indicating the bit length of the information stored as "EHT Capability". "Joint Transmission" includes information regarding whether or not joint transmission can be performed in the terminal notifying this frame.

[0076] The "Weight Update" includes information regarding whether or not the terminal notifying this frame can perform weight update 830 and the algorithm that can be performed, and may include, for example, information indicating whether or not to use the "Gram-Schmidt orthonormalization method."

[0077] As a specific example, when "cooperative transmission" is two bits long, the information may be indicated as follows. For example, when "cooperative transmission" is "00", it may indicate that neither NCJT (Non Coherent Joint Transmission) nor CJT can be implemented in cooperative transmission. When it is "01", it may indicate that NCJT can be implemented but CJT cannot be implemented in cooperative transmission. When it is "10", it may indicate that both NCJT and CJT can be implemented in cooperative transmission. In addition to these two bits of information, information indicating the maximum transmission power that the AP transmitting this frame can allocate to CJT may be included.

[0078] [Data sharing and weight sharing] When CJT is implemented as part of coordinated transmission, data sharing 814 of data to be transmitted by CJT and weight sharing 818 of weights to be applied by CJT are implemented in advance between multiple APs. In the figure, an example is shown in which AP#1, as a sharing AP, implements data sharing 814 and weight sharing 818 with AP#2, but AP#2 may also implement data sharing 814 and weight sharing 818 as a sharing AP.

[0079] On the other hand, when data sharing or weight notification is not required between multiple APs, such as in NCJT, data sharing 814 and weight sharing 818 do not need to be performed.

[0080] [Cooperative transmission trigger] The multi-APs, which have been notified of the ability to perform cooperative transmission by the capability exchanges 811 and 812, perform a cooperative transmission trigger (JT Trigger) 821, which is an information notification for inducing cooperative transmission, immediately before performing cooperative transmission 822. However, before performing cooperative transmission 822, sounding needs to be performed between the multi-AP and the communication terminal, and they need to hold a weight for performing cooperative transmission with each other. Also, when performing CJT among cooperative transmissions, the data to be transmitted by CJT needs to be shared in advance between the multi-APs.

[0081] The coordinated transmission trigger 821 includes information indicating that the frame notified by the coordinated transmission trigger 821 is the frame notified by the coordinated transmission trigger 821. Also, information indicating the time to perform coordinated transmission may be included, but is not necessarily included. For example, this is the case when it is implicitly understood between multiple APs that coordinated transmission 822 will be performed after a set time has elapsed after receiving the coordinated transmission trigger 821.

[0082] Although the cooperative transmission trigger 821 before cooperative transmission 822 is performed has been described above, the cooperative transmission trigger 831 before cooperative transmission 832 is performed is similar.

[0083] [Cooperative transmission] The AP that received the cooperative transmission trigger 821 and the AP that transmitted the cooperative transmission trigger 821 perform cooperative transmission (Joint Transmission) 822 .

[0084] The same is true for coordinated transmission 832, but the number of destination terminals may be different from that of coordinated transmission 822.

[0085] [Trigger] After the coordinated transmission 822 is performed, the communication terminal that was the destination of the coordinated transmission 822 returns Ack 824 to the multi-AP. In addition, the communication terminal that performs Ack 824 may perform Ack 824 from the communication terminal that has acquired the transmission right, but Ack 824 may also be performed by frequency multiplexing such as OFDMA (Orthogonal Frequency Division Multiple Access) as defined in IEEE 802.11. In this case, immediately before performing Ack 824 by OFDMA, a trigger 823 must be performed as information notification for notifying the transmission time, transmission power, and frequency to be assigned to each communication terminal.

[0086] Update Weights When a multi-AP that has once performed cooperative transmission 822 performs cooperative transmission 832 again, if the destination communication terminal changes, the sharing AP generates update information 827 to change the CJT weight, the power to be allocated to the transmission stream, the stream identification number, and the coding scheme (MCS: Modulation and Coding Scheme) accordingly.

[0087] Furthermore, the sharing AP notifies the shared AP of weight update information (Weight Update Info) 828 relating to the changed weight, the power to be allocated to the stream, the stream identification number, and the MCS.

[0088] FIG. 5 is a diagram showing an example of a structure of a frame notified by the weight update information 828 according to the embodiment of the present technology.

[0089] The notification frame of this update information notification 828 is composed of "frame control", "destination address", "source address", "action", "MIMO control", "CJT weight update information" and "data", but the components are not limited to these.

[0090] The "Frame Control", "Destination Address" and "Source Address" are the same as those in the above-mentioned capability exchanges 811 and 812. However, if the destination is multiple shared APs, the "Destination Address" may contain information indicating those APs.

[0091] "Action" includes information indicating whether this frame contains subsequent "CJT weight update information" and "Data". "MIMO Control" includes information for interpreting the information contained in the subsequent "CJT weight update information". "CJT Weight Update Information" includes information regarding the weights to be applied in the immediately following CJT. "Data" includes data to be transmitted in the CJT.

[0092] As a specific example of the information contained in "Action", when Action is expressed as a 2-bit length, for example, the following information may be included. That is, "00" indicates that this frame contains both "CJT weight update information" and "data". Also, "01" indicates that this frame does not contain "CJT weight update information", but does contain "data". Also, "01" indicates that this frame contains "CJT weight update information", but does not contain "data". Also, "11" indicates that this frame does not contain either "CJT weight update information" or "data".

[0093] "MIMO control" includes at least one of the subfields "Nc index", "Nr index", "Frequency band", "Grouping", "Coefficient size", and "Codebook information".

[0094] The "Nc Index" and "Nr Index" include information regarding the AP and destination communication terminal to which the CJT weights indicated in the "CJT Weight Update Information" are applied. That is, the "Nc Index" includes the "Number of APs (AP Num)", "AP Identifier (AP ID)" and "Terminal Identifier (Nc ID)". The same is true for the "Nr Index". The "Frequency Band (BW)" and "Grouping" include information indicating the frequencies to which the weights included in the "CJT Weight Update Information" are applied. The "Coefficient Size" and "Codebook Information" include information regarding the resolution of the weights included in the "CJT Weight Update Information".

[0095] For example, if the "CJT weight update information" contains information indicating a matrix W that represents the CJT weight, then the transposed matrix W T In contrast, the "Nc index" may include information indicating which column the weight of each AP that applies the CJT weight corresponds to, and the "Nr index" may include information indicating which row the weight for each communication terminal that is the destination in the CJT corresponds to.

[0096] Furthermore, when the transmission method is an OFDM (Orthogonal Frequency Domain Multiplexing) modulation method and the matrix W is sent to only some of the subcarriers used in OFDM, the "frequency band" may include information indicating the frequency band to which the CJT weights are applied, and the "grouping" may include information indicating which subcarrier weights are included in the "CJT weight update information" among the frequency bands indicated by the "frequency band". In other words, although it is possible to send the weight update information for every frequency, adjacent frequencies may be thinned out, for example, at intervals of three, and the "grouping" indicates the correspondence of the weight update information when such thinning is performed.

[0097] Further, when the matrix W is represented by parameters derived by operations such as Givens Rotation on the matrix H representing the propagation path information, the "codebook information" may include information indicating how many bits each parameter is represented by.

[0098] Similarly, when the matrix W is directly represented as a complex matrix, the "coefficient size" may include information indicating how many bits the complex numbers that are the elements of the matrix are represented by.

[0099] <2. Example of Weight Update> Hereinafter, the parameter calculation in the update information generation 827 and the calculation method of the weights in the weight update 830 will be described, and examples will be described for the details of the information included in the "CJT weight update information".

[0100] [First Embodiment] In this first embodiment, the APs constituting the multi-AP 100 are two APs, AP#1 (101) and AP#2 (102), and the communication terminals connected to the multi-AP 100 are three terminals, STA#1 to STA#3. Then, a case where STA#1 to STA#3 are the destinations in the L1-th cooperative transmission and STA#1 and STA#2 are the destinations in the L2-th cooperative transmission will be described. However, 1 ≤ L1 < L2. That is, this first embodiment shows an example where the number of terminals that are destinations in the L2-th cooperative transmission is less than the number of terminals that are destinations in the L1-th cooperative transmission.

[0101] First, for generalization, the weight (hereinafter referred to as the CJT weight) implemented by CJT at the k-th frequency in the l-th round is shown in Equation 1.

Equation

[0102] However, W (k、l) The matrix w that is an element ij (k,l)represents the weight that the jth AP applies to the i-th communication terminal in the l-th CJT at the k-th frequency. (NSTA,c) (k,l) In N STA represents the number of communication terminals that are the destinations of the lth CJT at the kth frequency, and similarly, N AP Let k denote the number of APs that perform the l-th CJT at the k-th frequency.

[0103] At this time, the L1th and L2nd CJT weights W (k,L1 ) and W (k,L2 ) are expressed as Equation 2 and Equation 3 below, respectively.

number

number

[0104] At this time, the L2th CJT weight W (k,L2 ) Compared to the L1th CJT, the transmission power allocated to STA#3 can be used for transmissions by STA#1 and STA#2, so the weights for STA#1 and STA#2 are set to W (k,L1 ) For i and j, we can use weights that change only the transmission power of each stream. ij (k,L1) And w ij (k,L2) satisfies the relationship shown in the following formula 4.

number

[0105] where n(i) is w ij (k,L1) Also, the real number γ m (k,i,L1,L2) , w ij (k,L2) w for the m-th stream CJT weightij (k,L1) represents the power ratio of the m-th stream to the CJT weight of N STA (L2) represents the number of communication terminals that are the destinations of the L2-th CJT at the k-th frequency.

[0106] In the update information generation 827, as shown in Equation 4, γ1 (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) By defining W (k,L2) is required.

[0107] γ1 (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) may be determined so that the transmission power of either AP#1 or AP#2 is equal to or less than the threshold value. At this time, it may be determined based on information notified in the capability exchanges 811 and 812, and may be determined so that the transmission power is equal to or less than the maximum transmission power that AP#1 and AP#2 can mutually allocate to the CJT.

[0108] FIG. 6 is a diagram illustrating an example of a frame structure notified in weight update information performed immediately before the L2th coordinated transmission in the first example of the embodiment of the present technology.

[0109] The notification frame for this update information notification is composed of "frame control", "destination address", "source address", "action", "MIMO control", "CJT weight update information" and "data", but the components are not limited to these. Also, "data" does not have to be present, and "frame control", "destination address", "source address", "action" and "MIMO control" are the same as those described above.

[0110] "CJT Weight Update Information" includes the fields of "Mode", "Base Weight", "SIG Shared AP" and "Update Parameters". "Mode" includes information for identifying the information included in the following. "Base Weight" includes information indicating the number L1 of coordinated transmissions. "SIG Shared AP" includes information on the communication terminal that is the destination in the L2th CJT. "Update Parameters" includes information on "Magnitude". This "Magnitude" subfield includes γ1 in Equation 4. (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) That is, this "magnitude" includes information regarding the transmission power.

[0111] As a specific example of information included in the "mode", when the "mode" has a length of 2 bits, it may include "01" which indicates that the frame corresponds to the first embodiment.

[0112] In addition, the "SIG Shared AP" may include one or more subfields of "Number of Terminals", "AID" and "SS Index". "Number of Terminals (STA Num)" is the number of communication terminals that are the destinations in the L2th CJT, N STA Contains information indicating the AID (AID#1 to AID#N STA "SS Index (SS Index#1 to SS Index#N)" includes information for identifying each communication terminal that is the destination in the CJT. STA )" includes information indicating the number of streams to be transmitted in the L2 CJT to the communication terminals indicated by the AIDs.

[0113] Note that "SIG Shared AP" and "Update Parameter" do not necessarily have to be present. For example, if the CJT weights used for STA#1 and STA#2 in the L2th iteration are equal to the CJT weights used in the L1st iteration, only "Mode" and "Reference Weight" may be present. In this case, the information included in "Mode" may include "00", which indicates no change, when "Mode" is 2 bits long.

[0114] For any number p, the "magnitude #p" of the "update parameters" may include information indicating:

number

[0115] However, N fr denotes an arbitrary number of subcarriers. Also, N r may be determined by the values ​​indicated in "Frequency Band" and "Grouping" in "MIMO Control". For example, in the frequency band indicated in "Frequency Band", the number of subcarriers used in the OFDM modulation method is N F , a natural number N that is a "grouping" g If indicated, N fr may be defined by Equation 6 below.

number

[0116] Here, min(a,b) represents the smallest number for any real numbers a and b. F / N g The " part represents the ceiling function for real numbers.

[0117] Furthermore, p, i, and m may satisfy the relationship shown in the following formula 7.

number

[0118] At this time, particularly N SS , N STA satisfies the relationship shown in the following Equation 8, and for any (m, s), p may be a bijective relationship. [Equation]

[0119] The shared AP notified of the weight update information 828 may calculate its own CJT weight at the L2 - th time using the following Equations 9 and 10 in the weight update 830. However, "magnitude" includes the information shown in Equation 5. Also, N fr in Equation 9 may satisfy Equation 6. Note that the weight in this case is calculated at the shared AP, and a tilde symbol is added to distinguish it from the weight calculated at the above - mentioned sharing AP. diag[x] represents a diagonal matrix with each element of the vector x as a diagonal component. [Equation] [Equation]

[0120] [Second Embodiment] In this second embodiment, similar to the above - mentioned first embodiment, the APs constituting the multi - AP 100 are two APs, AP#1 (101) and AP#2 (102), and the communication terminals connected to the multi - AP 100 are three terminals, STA#1 to STA#3. Then, the case where STA#1 and STA#2 are destinations in the L1 - th and L2 - th cooperative transmissions will be described. However, 1 ≦ L1 < L2. However, different from the above - mentioned first embodiment, in this second embodiment, W (k,L1) and W (k,L2) do not satisfy the relational expression of Equation 4.

[0121] In the first embodiment described above, in the L2 CJT, transmission is not performed to STA#3, which was the destination in the L1 CJT, so the method is to effectively use the power allocated in the L1 CJT. However, in "CJT DL MU MIMO", by not transmitting to STA#3, the degree of freedom of space available for transmission of STA#1 and STA#2 is increased compared to the L1 transmission. For this reason, in this second embodiment, a method is presented that effectively uses not only the power but also the degree of freedom of space.

[0122] Here, W (k,L1) and W (k,L2) By using Schmidt's orthonormalization method, the relationship shown in Equation 11 can be obtained.

number

[0123] However, for STA#1 and STA#2, which are communication terminals common to the destination terminal in the L1 CJT and the destination terminal in the L2 CJT, (k,L1) and W (k,L2) When it is assumed that the column numbers of the CJT vectors used for STA#1 and STA#2 in STA (L2∩L1) indicates a set of column numbers of the CJT vectors used for STA#1 and STA#2.

[0124] In addition, N(i) is w i (k,L2) Also, the real number γ m (k,i,L1,L2) , w i (k,L2) w for the m-th stream CJT weight i (k,L1) represents the power ratio of the m-th stream to the CJT weight.

[0125] Also, the matrix U - (k)represents a matrix (kernel vector) whose column vectors are eigenvectors whose eigenvalues ​​are not zero for the propagation path matrix of multi-AP and STA#3 in the vector space that serves as the kernel space for the propagation path matrix of multi-AP, STA#1, and STA#2 for the kth frequency.

[0126] matrix U - (k) can be calculated based on the feedback of channel information from the communication terminal. For example, the explicit feedback beamforming of "IEEE 802.11-2016" defines CSI (Channel State Information) feedback, which returns the channel matrix as a complex number, and compressed feedback, which returns the eigenvector of the channel matrix. For both of them, the calculation method shown in "Mirette Sadek, et al., "A Leakage-Based Precoding Scheme for Downlink Multi-User MIMO Channels," IEEE Transactions on Wireless Communications, Vol. 6, No. 5, pp.1711-1721 May 2007" can be used to calculate U - (k) can be sought.

[0127] In this case, by transforming Equation 11, we obtain W as shown in Equation 12. (k,L1) From W (k,L2) We can obtain the update formula to derive

number

[0128] Based on the feedback of propagation path information from the communication terminal, - (k) Also, γ1 is determined by the sharing AP. (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2)Thus, in the update information generation 827, the square root of W is determined by the formula 12. (k,L2) can be sought.

[0129] FIG. 7 is a diagram illustrating an example of a frame structure notified in weight update information performed immediately before the L2-th coordinated transmission in the second example of the embodiment of the present technology.

[0130] The notification frame for this update information notification is composed of "frame control", "destination address", "source address", "action", "MIMO control", "CJT weight update information" and "data", but the components are not limited to these. Also, "data" does not have to be present, and "frame control", "destination address", "source address", "action" and "MIMO control" are the same as those described above.

[0131] "CJT weight update information" includes the fields of "mode", "reference weight", "SIG shared AP" and "update parameters". "Mode" includes information for identifying the information included thereafter. "Reference weight" includes information indicating the number L1 of coordinated transmissions. "SIG shared AP" includes information regarding the communication terminal that is the destination in the L2th CJT.

[0132] The "update parameters" include information on the "Kernel Vector" in addition to the "magnitude".

[0133] As a specific example of information included in the "mode", when the "mode" has a length of 2 bits, it may include "10" which indicates that the frame corresponds to the second embodiment.

[0134] Although not shown in the figure, the "SIG Shared AP" may include one or more subfields of "Number of Terminals", "AID" and "SS Index" as in the first embodiment. The "Number of Terminals (STA Num)" is the number of communication terminals that are destinations in the L2th CJT. STAContains information indicating the AID (AID#1 to AID#N STA "SS Index (SS Index#1 to SS Index#N)" includes information for identifying each communication terminal that is the destination in the CJT. STA )" includes information indicating the number of streams to be transmitted in the L2 CJT to the communication terminals indicated by the AIDs.

[0135] The "magnitude" of the "update parameter" is γ1 in Eq. (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) The “kernel vector” of the “update parameters” is the matrix U - (k) That is, this "kernel vector" includes information about the eigenvectors of the propagation paths.

[0136] For any number p, the "magnitude #p" of the "update parameters" may include information indicating a value obtained by Equation 5. Similarly, for any number u, the "kernel vector #U" may include information indicating a vector obtained by Equation 13.

number

[0137] Here, N r may be determined by the values ​​indicated in "Frequency Band" and "Grouping" in "MIMO Control". u represents a number determined by u. For example, in the frequency band shown in "frequency band", the number of subcarriers used in the OFDM modulation method is N F , a natural number N that is a "grouping" g is shown, n u is determined according to the following Equation 14.

number

[0138] Here, min(a,b) represents the smallest number for any real numbers a and b. F / N g " represents the ceiling function for real numbers.

[0139] The shared AP that has been notified of the weight update information 828 performs weight update 830 by using the weights w i (k,L2) The weight update information 828 may calculate the weight of the L2th iteration and determine its own CJT weight based on the calculated weight. However, the "magnitude" and "kernel vector" in the frame notified by the weight update information 828 include the information shown in the formulas 5 and 13, respectively. fr may satisfy Equation 6 above.

number

[0140] However, U (tilde) in formula 15 - (k) satisfies Equation 16, and G and D in Equation 16 satisfy Equation 17.

number

number

[0141] However, n u - is the maximum n that does not exceed k u , n u + is the smallest n that exceeds k u and Equation 17 essentially represents U - nu+ , and U - nu+ This is an equation that describes the relationship between the two using Givens Rotation.

[0142] [Third Example] In this third embodiment, the APs that make up the multi-AP 100 are two APs, AP#1 (101) and AP#2 (102), and the communication terminals connected to the multi-AP 100 are four terminals, STA#1 to STA#4. Then, a case will be described where, in the L1-th cooperative transmission, three terminals, STA#1 to STA#3, are the destinations, and in the L2-th cooperative transmission, four terminals, STA#1 to STA#4, are the destinations. However, let 1 ≤ L1 < L2. That is, this third embodiment shows an example where, unlike the above-described second embodiment, the number of terminals that are destinations in the L2-th cooperative transmission is larger than the number of terminals that are destinations in the L1-th cooperative transmission.

[0143] At this time, for W (k,L1) and W (k,L2) the relationship shown in Equation 18 can be established by using the Schmidt orthogonalization method.

Equation

[0144] However, U + (k) (i) represents the i-th row of U + (k) (i) Also, N1 is the number of columns of w i (k,L1) and N2 is the number of columns of w i (k,L2) and N STA (L2 ∩ L1) represents the set of all communication terminals that are common destinations in the L1-th and L2-th cooperative transmissions.

[0145] Also, for j ∈ N STA (L2 ∩ L1), the real number γ m (k,i,L1,L2) represents the power ratio of the CJT weight of the m-th stream of w i (k,L2) with respect to the CJT weight of the m-th stream of w i (k,L1) and for j ∉ N STA (L2 ∩ L1), w i (k,L2)represents the transmission power for the CJT weight of the m-th stream.

[0146] Also, U + (k) represents a matrix whose column vectors are eigenvectors whose eigenvalues ​​for the propagation path matrix of multi-AP and STA#4 are not zero, in the vector space that serves as the kernel space for the propagation path matrices of multi-AP and STA#1 to STA#3 for the kth frequency.

[0147] U + (k) can be calculated based on feedback of channel information from the communication terminal, as in the second embodiment.

[0148] In this case, the above equation 18 becomes W (k,L1) From W (k,L2) This can be seen as an update equation to derive

[0149] Based on the feedback of propagation path information from the communication terminal, + (k) Also, γ1 is determined by the sharing AP. (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) Thus, in the update information generation 827, the square root of W is determined by the formula 18. (k,L2) can be sought.

[0150] The frame structure notified in the L2 update information notification in the third embodiment of the present technology is the same as that in the second embodiment. However, the contents of the included values ​​are different as shown below.

[0151] The "magnitude" of the "update parameter" is γ1 in Eq. (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) The “kernel vector” of the “update parameters” is U + (k) Includes information about.

[0152] For any number p, the "magnitude #p" of the "update parameter" is γ1 (k,i,L1,L2) ,…,γ n(i) (k,i,L1,L2) For an arbitrary number u, "kernel vector #U" may include information indicating a value obtained by applying formula 5. Similarly, for an arbitrary number u, "kernel vector #U" may include information indicating a vector obtained by formula 19.

number

[0153] Here, N r may be determined by the values ​​indicated in "Frequency Band" and "Grouping" in "MIMO Control". For example, in the frequency band indicated in "Frequency Band", the number of subcarriers used in the OFDM modulation method is N F , a natural number N that is a "grouping" g is shown, and N defined in Eq. fr When using, it may be determined to follow Equation 14.

[0154] The shared AP that has been notified of the weight update information 828 performs weight update 830 by using the weights w i (k,L2) The weight update information 828 may calculate the weight of the L2th iteration and determine its own CJT weight based on the calculated weight. However, the "magnitude" and "kernel vector" in the frame notified by the weight update information 828 include the information shown in the formulas 5 and 19, respectively. In addition, N fr may satisfy Equation 6 above.

number

[0155] However, U (tilde) in formula 20 + (k) satisfies Equation 21, and G and D in Equation 21 satisfy Equation 22.

number

Number

[0156] However, n u - is the largest n that does not exceed k u , n u + is the smallest n that exceeds k u represents, and Equation 22 is essentially an equation that describes the relationship between U + nu+ , and U + nu+ using Givens Rotation.

[0157] [Fourth Embodiment] In this fourth embodiment, the APs that make up the multi-AP 100 are two APs, AP#1 (101) and AP#2 (102), and the number of communication terminals connected to the multi-AP 100 is any number including STA#1. Then, in the L1-th cooperative transmission, any communication terminal is the destination, and the case where STA#1 is the destination in the L2-th cooperative transmission will be described. However, 1 ≦ L1 < L2. Note that in this fourth embodiment, in the L2-th cooperative transmission, not only STA#1 but also a plurality of communication terminals may be the destination.

[0158] Similar to the first embodiment described above, the CJT weight W (k,L2) at the L2-th time in the k-th frequency can be expressed as in Equation 3, respectively.

[0159] In the update information generation 827, W (k,L2) is obtained based on the feedback of the propagation path information from the communication terminal.

[0160] FIG. 8 is a diagram showing a configuration example of a frame notified by weight update information performed immediately before the L2-th cooperative transmission in the fourth embodiment of the embodiment of the present technology.

[0161] In the other embodiments described above, "update parameters" are transmitted, but in the frame configuration of the fourth embodiment, "weight information" is transmitted. This "weight information" is (k,L2) The other fields are the same as in the other embodiments described above.

[0162] As a specific example of information contained in the "mode", when the "mode" has a length of 2 bits, it may contain "11" which indicates that the frame corresponds to the fourth embodiment.

[0163] In addition, the "weight information" may include subfields for "SNR" and "Beamforming FBCK matrix."

[0164] The “SNR (signal-to-noise ratio)” includes information about the transmission power with respect to the CJT weight. For example, it includes information indicating Γ in Equation 23.

number

[0165] Beamforming FBCK Matrix #1~#N f )" is an arbitrary natural number p, and "Beamforming FBCK matrix #p" is W in Equation 24 (Nfr,L2) Also, as shown in Equation 25, W (Nfr,L2) The normalized matrix U (Nfr,L2) may be also possible.

number

number

[0166] In Equation 23 and Equation 25, ||a|| for any vector a represents the Frobenius norm or the Hilbert-Schmidt norm.i (Nfr,L2) is W (Nfr,L2) It represents the i-th row of .

[0167] Also, N fr may be determined by the values ​​indicated in "Frequency Band" and "Grouping" in "MIMO Control". For example, in the frequency band indicated in "Frequency Band", the number of subcarriers used in the OFDM modulation method is N F , a natural number N that is a "grouping" g If indicated, N fr may be determined to satisfy Equation 6.

[0168] In addition, when the "beamforming FBCK matrix" is expressed by Equation 24, the "SN ratio" field does not necessarily have to be present.

[0169] The format of the information shown in "Beamforming FBCK Matrix #p" may follow the format of the Compressed Beamforming Report or Non compressed Beamforming Report of "IEEE 802.11-2016" or the CSI report, and the same is true for the information shown in "SNR".

[0170] In a frame notified by the weight update information 828, when the "SN ratio" includes information indicating Γ in the formula 23 and the "beamforming FBCK matrix" includes information indicating the formula 25, the shared AP for which the weight update information 828 has been implemented performs weight update 830 by changing W to (k) may be calculated and used as the CJT weight for the L2th iteration. fr may satisfy Equation 6.

number

[0171] However, U in Eq. nr+ is assumed to satisfy Equation 27.

number

[0172] However, U (k) indicates a normal vector of the CJT weight for the multi-AP and STA#1 for the kth frequency, and Γ indicates a coefficient for correcting the CJT weight from the normal vector to a desired transmission power. r - is the maximum n that does not exceed k r , n r + is the smallest n that exceeds k r and Equation 27 represents U nr+ , and U nr- This is an equation that describes the relationship between the two using Givens Rotation.

[0173] [Selection criteria for each embodiment] FIG. 9 is a flowchart showing an example of a processing procedure when selecting each example of the embodiment of the present technology.

[0174] Here, a selection rule for generating "CJT weight update information" of a "weight update information" frame in a sharing AP when the weight update shown in the above-mentioned first to fourth embodiments is performed selectively will be described. In the first to fourth embodiments, an example of a "CJT weight update information" frame is also mentioned, but the amount of information notified in the "weight update information" and the communication quality of the L2-th cooperative transmission performed based on the notified information differ depending on the situation of the change in the communication terminal that is the destination in the L1-th cooperative transmission and the L2-th cooperative transmission. The following processing procedure shows an example of a selection rule for transmitting an optimal "weight update information" frame in consideration of these.

[0175] The sharing AP that has started the update information generation 827 judges whether or not to use the same weight as the most recently implemented "CJT DL MU MIMO" (step S911). Here, "most recently" may mean that the channel information held by the sharing AP was acquired within a certain threshold time. This threshold may be changed every time weight update 830 is performed, and for example, there may be cases where errors accumulate due to weight update 830. Note that the weight of the most recently implemented "CJT DL MU MIMO" is already held by the shared AP.

[0176] If the sharing AP determines to implement "CJT DL MU MIMO" with the same weight as the most recently implemented "CJT DL MU MIMO" (step S911: Yes), it generates and transmits the frame mentioned in the first embodiment by including information indicating that the frame mentioned in the first embodiment will be sent in the "mode" in the frame notified by the weight update information 828 (step S914). Here, if the "mode" is expressed in 2 bits, "00" may be stored. The shared AP notified of this frame updates the weight according to the "weight update information" shown in the first embodiment.

[0177] In this case, however, the fields "SIG Shared AP" and "Update Parameter" are not included in the "CJT Weight Update Information" in the frame notified by weight update information 828. The shared AP notified of this frame generates the weight at the past point in time indicated in "Reference Weight" as the weight for the next "CJT DL MU MIMO" based on the information included in "Mode" and "Reference Weight".

[0178] The information shown in the "reference weight" may be information indicating a weight having a small difference in the number of destination communication terminals among the weights used in the past when "CJT DL MU MIMO" is implemented in the next coordinated transmission. Similarly, it may be information indicating a weight having a small difference in the number of destination communication terminals among the weight update information 828 notified in the past.

[0179] The sharing AP that has determined not to use the most recently implemented "CJT DL MU MIMO" and weights determines whether to change the transmission power allocation to the most recently implemented weights (step S912). The criterion here may be, for example, that the communication traffic volume for each communication terminal held is different from the most recent one.

[0180] The sharing AP that has decided to change and implement the transmission power allocation (step S912: Yes) includes information indicating that the frame mentioned in the first embodiment will be sent in the "mode" in the frame notified in weight update information 828, and generates and transmits the frame mentioned in the first embodiment (step S915). Here, if the "mode" is expressed in 2-bit length, "01" may be stored, and the shared AP that has been notified of this frame updates its weight according to the "weight update information" shown in the first embodiment.

[0181] In this case, the fields "SIG Shared AP" and "Update Parameter" are included in the "CJT Weight Update Information" in the frame notified by weight update information 828. Based on the information included in the "Mode" and "Reference Weight", the frame notified of this frame generates a weight for the next "CJT DL MU MIMO" that results in a desired transmission power allocation based on the information indicated in the "Update Parameter" for the weight at the past point in time indicated in the "Reference Weight",.

[0182] A sharing AP that has determined not to use the most recently implemented "CJT DL MU MIMO" and weights and has determined not to change the transmission power allocation for the most recently implemented weights estimates the amount of information in the frame of the configuration examples shown in the second to fourth embodiments (step S913).

[0183] For example, if the weights most recently used were weights addressed to STA#1 to STA#3, but the communication terminals addressed to the next cooperative transmission are only STA#1 and STA#2 as shown in the second embodiment, the amount of information in the "update parameters" shown in the second embodiment and the "weight information" shown in the fourth embodiment is estimated.

[0184] Also, for example, if the weights most recently used were weights addressed to STA#1 to STA#3, but the communication terminals addressed in the next cooperative transmission are STA#1 to STA#4 as shown in the second embodiment, the amount of information in the "update parameters" shown in the third embodiment and the "weight information" shown in the fourth embodiment is estimated.

[0185] If it is determined that the amount of information sent using the "update parameters" is small (step S913: Yes), the weight to be stored in the "update parameters" is calculated (step S916). Then, information indicating that a frame mentioned in the second or third embodiment is to be sent is included in the "mode" in the frame notified by weight update information 828, and the frame mentioned in the second or third embodiment is generated and sent (step S917). Here, if the "mode" is expressed in 2-bit length, "10" may be stored, and the shared AP notified of this frame updates its weight according to the "weight update information" shown in the second or third embodiment.

[0186] On the other hand, if it is determined that the amount of information sent using "weight information" is small (step S913: No), the weight to be stored in "weight information" is calculated (step S918). Then, information indicating that the frame mentioned in the fourth embodiment will be sent is included in the "mode" in the frame notified by weight update information 828, and the frame mentioned in the fourth embodiment is generated and transmitted (step S919). Here, if the "mode" is expressed in 2 bits, "11" may be stored, and the shared AP notified of this frame updates its weight according to the "weight update information" shown in the fourth embodiment.

[0187] In addition, the shared AP to which this frame is notified may determine whether it is the second or third embodiment based on the information indicated in the "Reference Weight" and the information contained in the "SIG Shared AP".

[0188] For example, if the weight at a past point in time indicated by the "Reference Weight" is the weight for STA#1 to STA#3, and the AID included in the "SIG Shared AP" contains information indicating only STA#1 and STA#2, it may be determined that the frame is the one shown in the second embodiment.

[0189] Also, for example, if the weight at a past point in time indicated by the "Reference Weight" is the weight for STA#1 to STA#3, and the AID included in the "SIG Shared AP" includes information indicating STA#1 to STA#3 and other communication terminals, it may be determined that the frame is the one shown in the third embodiment.

[0190] In addition, if the AP that is the destination of capability exchange 811 and 812 has been notified in weight update 830 that it can only implement the first or fourth embodiment, it may be configured to send only other frames without sending frames of the configuration examples shown in the second or third embodiment.

[0191] In this case, the sharing AP that has decided not to use the most recently implemented "CJT DL MU MIMO" and weights, and has decided not to change the transmission power allocation for the most recently implemented weights, includes information indicating that the frame mentioned in the second embodiment will be sent in the "mode" in the frame notified in weight update information 828, and generates the frame mentioned in the fourth embodiment. Here, if the "mode" is expressed in 2 bits, "11" may be stored, and the shared AP that has been notified of this frame updates the weights according to the "weight update information" shown in the fourth embodiment.

[0192] Thus, according to an embodiment of the present technology, when multiple APs transmit cooperatively, the sharing AP sends an update information notification 828 to the shared AP, thereby enabling the sharing AP and the shared AP to transmit cooperatively using a common weight.

[0193] The above-mentioned embodiment shows an example for realizing the present technology, and the matters in the embodiment and the matters specified in the claims correspond to each other. Similarly, the matters specified in the claims and the matters in the embodiment of the present technology having the same name correspond to each other. However, the present technology is not limited to the embodiment, and can be realized by applying various modifications to the embodiment within the scope of the gist of the technology.

[0194] The processing procedures described in the above embodiments may be regarded as a method having a series of these procedures, or as a program for causing a computer to execute the series of procedures or a recording medium for storing the program. For example, a CD (Compact Disc), an MD (MiniDisc), a DVD (Digital Versatile Disc), a memory card, a Blu-ray (registered trademark) Disc, etc. may be used as this recording medium.

[0195] It should be noted that the effects described in this specification are merely examples and are not limiting, and other effects may also be obtained.

[0196] The present technology can also be configured as follows. (1) a radio control unit that generates weight update information for updating a first weight used when cooperative transmission with another radio base station has been performed in the past to a second weight used for performing the cooperative transmission thereafter; a communication unit that notifies the other radio base station of the weight update information; A wireless base station comprising: (2) the radio control unit generates capability information regarding whether or not coordinated transmission is possible in the radio base station and an algorithm that can be used to update the weight from the first weight to the second weight; The communication unit notifies the other radio base station of the capability information. The wireless base station according to (1). (3) the radio control unit generates target data for the cooperative transmission using the second weight; The communication unit transmits the weight update information including the target data to the other radio base station. The wireless base station according to (1) or (2). (4) The weight update information includes information indicating that the target data is included. The wireless base station according to (3). (5) The weight update information includes information for updating to the second weight for each of the other radio base stations and each of the destination terminals of the cooperative transmission, and further includes index information for identifying each of the information. The wireless base station according to any one of (1) to (4). (6) The index information includes the number of the other wireless base stations and information for identifying each of the other wireless base stations. The wireless base station according to (5). (7) The weight update information includes the number of the destination terminals, information for identifying each of the destination terminals, and information regarding communication streams to be individually assigned to the destination terminals. The wireless base station according to (5) or (6). (8) The weight update information includes at least one of the first weight, a parameter for converting the first weight to the second weight, and the second weight. The wireless base station according to any one of (1) to (7). (9) The weight update information further includes mode information indicating which of the first weight, a parameter for converting the first weight to the second weight, and the second weight is included. The wireless base station according to (8). (10) The parameters include information regarding transmission power for the cooperative transmission. The wireless base station according to (8) or (9). (11) The parameter includes information regarding an eigenvector of a propagation path for a terminal that is a destination of the cooperative transmission using the first weight and is not a destination of the cooperative transmission using the second weight. The wireless base station according to any one of (8) to (10). (12) The parameter includes information regarding an eigenvector of a propagation path for a terminal that is a destination of the cooperative transmission using the second weight but is not a destination of the cooperative transmission using the first weight. The wireless base station according to any one of (8) to (10). (13) a communication unit that receives weight update information from another radio base station that has previously performed cooperative transmission using the first weight; a radio control unit that updates the first weight to a second weight for performing the cooperative transmission thereafter based on the weight update information; A wireless base station comprising: (14) The radio control unit generates capability information regarding whether or not coordinated transmission is possible in the radio base station and an algorithm that can be used to update the weight from the first weight to the second weight; The communication unit notifies the other radio base station of the capability information. The wireless base station according to (13). (15) The radio control unit extracts target data for which the cooperative transmission is to be performed using the second weight when the target data is included in the weight update information. The wireless base station according to (13) or (14). (16) The radio control unit extracts the target data when the weight update information includes information indicating that the target data is included. The radio base station according to (15). (17) The weight update information includes information for updating to the second weight for each of the other radio base stations and each of the destination terminals of the cooperative transmission, and further includes index information for identifying each of the other radio base stations and each of the destination terminals of the cooperative transmission; The radio control unit identifies each piece of information for updating to the second weight based on the index information. The radio base station according to any one of (13) to (16). (18) The index information includes the number of the other wireless base stations and information for identifying each of the other wireless base stations. The wireless base station according to (17). (19) The weight update information includes the number of the destination terminals, information for identifying each of the destination terminals, and information regarding communication streams to be individually assigned to the destination terminals. The wireless base station according to (17) or (18). (20) The weight update information includes at least one of the first weight, a parameter for converting the first weight to the second weight, and the second weight. The radio base station according to any one of (13) to (19). [Explanation of symbols]

[0197] 100 Multi-Access Point (Multi-AP) 101, 102 Access points (AP) 201~205 Communication terminal (STA) 210, 220 Communication terminals (STAs) 300 Wireless communication device 310 Communications Department 311 Radio control unit 312 Data Processing Unit 313 Modulation and demodulation section 314 Signal Processing Unit 315 Channel Estimation Unit 316 Wireless Interface Unit 317 Amplifier section 319 Antenna 321 Control Unit 322 Power supply section 811, 812 Capability Exchange 814, 825 Data sharing 818 Weight Sharing 821, 831 Cooperative transmission trigger 822, 832 Cooperative Transmission 823 Trigger 824 ACK 827 Update information generation 828 Update information notification 830 weight update

Claims

1. a radio control unit that generates weight update information for updating a first weight used when cooperative transmission with another radio base station has been performed in the past to a second weight used for performing the cooperative transmission thereafter, and capability information regarding whether cooperative transmission is possible in the radio base station and an algorithm that can be used to update the first weight to the second weight; a communication unit that notifies the other radio base station of the weight update information and the capability information; A wireless base station comprising:

2. the radio control unit generates target data for the cooperative transmission using the second weight; The communication unit transmits the weight update information including the target data to the other radio base station. The radio base station according to claim 1.

3. The weight update information includes information indicating that the target data is included. The radio base station according to claim 2.

4. The weight update information includes information for updating to the second weight for each of the other radio base stations and the destination terminal of the coordinated transmission, and further includes index information for identifying each of the other radio base stations and the destination terminal of the coordinated transmission. The radio base station according to claim 1.

5. The index information includes the number of the other radio base stations and information for identifying each of the other radio base stations. The radio base station according to claim 4.

6. The weight update information includes the number of the destination terminals, information for identifying each of the destination terminals, and information regarding communication streams to be individually assigned to the destination terminals. The radio base station according to claim 4.

7. The weight update information includes at least one of the first weight, a parameter for converting the first weight to the second weight, and the second weight. The radio base station according to claim 1.

8. The weight update information further includes mode information indicating which of the first weight, a parameter for converting the first weight to the second weight, and the second weight is included. The radio base station according to claim 7.

9. The parameters include information regarding transmission power for the cooperative transmission. The radio base station according to claim 7.

10. The parameter includes information regarding an eigenvector of a propagation path for a terminal that is a destination of the cooperative transmission using the first weight and is not a destination of the cooperative transmission using the second weight. The radio base station according to claim 7.

11. The parameter includes information regarding an eigenvector of a propagation path for a terminal that is a destination of the cooperative transmission using the second weight and is not a destination of the cooperative transmission using the first weight. The radio base station according to claim 7.

12. a communication unit that receives weight update information from another radio base station that has previously performed cooperative transmission using the first weight; a radio control unit that updates the first weight to a second weight for performing the cooperative transmission thereafter based on the weight update information; Equipped with the radio control unit generates capability information regarding whether or not coordinated transmission is possible in the radio base station and an algorithm that can be used to update the weight from the first weight to the second weight; The communication unit notifies the other radio base station of the capability information. Radio base station.

13. The radio control unit extracts target data for which the cooperative transmission is to be performed using the second weight when the target data is included in the weight update information. The radio base station according to claim 12.

14. The radio control unit extracts the target data when the weight update information includes information indicating that the target data is included. The radio base station according to claim 13.

15. the weight update information includes information for updating to the second weight for each of the other radio base stations and each of the destination terminals of the coordinated transmission, and further includes index information for identifying each of the other radio base stations and each of the destination terminals of the coordinated transmission; The radio control unit identifies each piece of information for updating to the second weight based on the index information. The radio base station according to claim 12.

16. The index information includes the number of the other radio base stations and information for identifying each of the other radio base stations. The radio base station according to claim 15.

17. The weight update information includes the number of the destination terminals, information for identifying each of the destination terminals, and information regarding communication streams to be individually assigned to the destination terminals. The radio base station according to claim 15.

18. The weight update information includes at least one of the first weight, a parameter for converting the first weight to the second weight, and the second weight. The radio base station according to claim 12.

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