Wireless base station and wireless terminal

Abstract

Phase tracking is easily achieved when multiple wireless base stations transmit signals simultaneously. The wireless base stations coordinate with a coordinating wireless base station to transmit signals to the wireless terminal. Each wireless base station has a wireless control unit and a communication unit. The wireless control unit, in coordination with the coordinating wireless base station, determines a reference signal and generates the determined reference signal. The communication unit coordinates with the coordinating wireless base station to transmit the signal containing the reference signal to the wireless terminal. The wireless terminal estimates the frequency error between the coordinating wireless base stations based on the received reference signal.

Description

[Technical Field]

[0001] This technology relates to wireless base stations and wireless terminals. More specifically, it relates to wireless base stations and wireless terminals in a wireless system comprising a plurality of wireless base stations simultaneously transmitting signals. [Previous Technology]

[0002] In a wireless LAN, within a Basic Service Set (BSS), access points (APs or BSs) and terminals (STAs or UEs) autonomously acquire transmission rights within the BSS and communicate. When the transmitting terminal is equipped with multiple antennas, high-gain transmission to the desired destination terminal can be achieved by simultaneously using multiple antennas for transmission (BF: beamforming), thereby increasing the system throughput within the BSS. Generally, the gain obtained by beamforming is proportional to the number of antennas used simultaneously. By expanding this beamforming, the system throughput can be increased through the transmission caused by multiple APs (hereinafter referred to as multiple APs) working together.

[0003] There are several types of multiple access points (APs), including: Coherent Joint Transmission (CJT), where each AP acts as a virtual single AP with a shared number of antennas; Non-Coherent Joint Transmission (NCJT), where each AP forms its own beam to transmit to a common receiving terminal; and Coordinated Nulling, where each AP forms its own beam to communicate with different terminals without interfering with each other's communication. These methods achieve higher system throughput in environments with multiple APs compared to uncoordinated scenarios. Among these, CJT, where each AP acts as a virtual single access point with a shared number of antennas, achieves the highest throughput among multiple APs. However, for CJT to function as a virtual single access point among multiple APs, the carrier frequencies of the access points must be synchronized with high precision. Furthermore, frequency synchronization is also required between multiple access points (APs) and terminals. However, in actual systems, it is difficult to achieve complete synchronization of their carrier frequencies, resulting in residual frequency errors, also known as residual carrier frequency offset (CFO).

[0004] In OFDM (Orthogonal Frequency Division Multiplexing) modulation, a widely used modulation method in wireless communication systems, although different data sequences can be inserted for each subcarrier, a known sequence (hereinafter referred to as pilot signal) is inserted for specific subcarriers within each OFDM symbol. The sequence inserted into each subcarrier by means of the residual CFO will generate a common composite phase rotation over time, but the terminal performs correction (phase tracking) to compensate for the phase rotation of the pilot signal. In CJT, for the terminal, since the residual CFO of each access point constituting multiple APs is different, it is necessary to estimate the residual CFO of each access point to perform phase tracking. However, if the pilot signal is inserted into the same subcarrier among multiple APs, the different pilot signals due to the residual CFO will be multiplexed, which will lead to the problem of difficulty in correctly performing phase tracking. Therefore, for example, a system for separating pilot signals using a quasi-orthogonal sequence inherent to each base station and allocating such pilot signals has been proposed (see, for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2010 / 079985 [Summary of the Invention]

[0006] [The problem the invention aims to solve]

[0007] In the aforementioned prior art, a pseudo-orthogonal sequence inherent to each base station is used to achieve pilot signal separation. However, due to the nature of the pseudo-orthogonal sequence, it is difficult for the terminal to estimate the residual CFO for each access point, which leads to the problem of phase tracking in CJT.

[0008] This technology was developed in view of this situation, and its purpose is to easily achieve phase tracking when multiple wireless base stations are transmitting signals simultaneously. [Means used to solve the problem]

[0009] This technology was developed to solve the above-mentioned problems. Its first aspect is a wireless base station comprising: a wireless control unit that generates a reference signal determined between itself and a coordinating wireless base station; and a communication unit that coordinates the transmission of a signal containing the aforementioned reference signal with the aforementioned coordinating wireless base station and transmits it to a wireless terminal. This achieves the function of coordinating the transmission of a signal containing the reference signal determined between itself and a coordinating wireless base station (e.g., a secondary access point) with the coordinating wireless base station to the wireless terminal.

[0010] Furthermore, in the first aspect, the aforementioned reference signal may also be transmitted using at least one of different frequencies, different times, and different sequences. This achieves the effect of guaranteeing the orthogonality of the reference signal, thereby facilitating separation at the receiving end.

[0011] Furthermore, in the first aspect, it is also possible that the aforementioned communications unit exchanges information regarding the supported coordination methods between the aforementioned coordination wireless base station and the aforementioned wireless terminal before the aforementioned coordination communication is sent. This achieves the goal of confirming the functionality of the supported coordination methods before coordination communication is sent.

[0012] Furthermore, in the first aspect, the aforementioned radio control unit may, before the generation of the aforementioned reference signal, determine the allocation of the aforementioned reference signal in the coordinated transmission between itself and the aforementioned coordinated radio base station. This achieves the function of determining the allocation of the reference signal in the coordinated transmission before the generation of the reference signal.

[0013] Furthermore, in the first aspect, the aforementioned radio control unit may determine the information of each frequency channel and the information about the aforementioned frequency channel within the frequency band used in the aforementioned coordination method. Alternatively, the aforementioned radio control unit may determine at least one of the following: information including the number of the aforementioned coordinated radio base stations, information for identifying the aforementioned coordinated radio base stations, and information assigned to the aforementioned coordinated radio base stations. Alternatively, the aforementioned radio control unit may determine, for each of the aforementioned coordinated radio base stations, at least one of the following: information indicating the presence or absence of the aforementioned reference signal insertion, information indicating the symbol of the inserted aforementioned reference signal, and a sequence required for separating the reference signal in the aforementioned radio terminal.

[0014] Furthermore, in the first aspect, it is also possible that the aforementioned communication unit sends information about the aforementioned coordinated wireless base station to the aforementioned wireless terminal during the aforementioned coordinated communication. This achieves the function of notifying the wireless terminal of information about the coordinated wireless base station during the coordinated communication.

[0015] Furthermore, in the first aspect, it is also possible that the aforementioned communication unit transmits information about each of the arbitrary frequency channels to be used in the aforementioned coordinated communication as information about the aforementioned coordinated wireless base station to the aforementioned wireless terminal. Alternatively, it is also possible that the aforementioned communication unit transmits the identification number assigned to the aforementioned coordinated wireless base station as information about the aforementioned coordinated wireless base station to the aforementioned wireless terminal. Furthermore, it is also possible that the information about the aforementioned coordinated wireless base station, together with the codebook determined between the aforementioned coordinated wireless base station and the aforementioned coordinated wireless base station, serves as the information required to determine the allocation of the aforementioned reference signal.

[0016] Furthermore, the first side may also include: a signal processing unit that performs frequency error correction based on frequency synchronization information received from the aforementioned wireless terminal during the aforementioned coordinated communication. This achieves the function of correcting frequency errors based on frequency synchronization information received from the wireless terminal.

[0017] Furthermore, a second aspect of this technology is a wireless base station comprising: a wireless control unit that receives reference information from a coordinating wireless base station that coordinates the transmission; and a communication unit that coordinates with the coordinating wireless base station to transmit a signal containing the aforementioned reference information to a wireless terminal. This achieves the function of coordinating with the coordinating wireless base station (e.g., a master access point) to transmit a signal containing reference information received from the coordinating wireless base station to the wireless terminal.

[0018] Furthermore, in the second aspect, it is also possible that the aforementioned communication unit sends information about the aforementioned coordinated wireless base station to the aforementioned wireless terminal during the aforementioned coordinated communication. This achieves the purpose of notifying the wireless terminal of information about the coordinated wireless base station during the coordinated communication.

[0019] Furthermore, in the second aspect, it is also possible that the aforementioned communication unit transmits information about each of the arbitrary frequency channels to be used in the aforementioned coordinated communication as information about the aforementioned coordinated wireless base station to the aforementioned wireless terminal. Alternatively, it is also possible that the aforementioned communication unit transmits the identification number assigned to the aforementioned coordinated wireless base station as information about the aforementioned coordinated wireless base station to the aforementioned wireless terminal. Furthermore, it is also possible that the information about the aforementioned coordinated wireless base station, together with the codebook determined between the aforementioned coordinated wireless base station and the aforementioned coordinated wireless base station, is used as the information required to determine the allocation of the aforementioned reference signal.

[0020] Furthermore, the second side may also include: a signal processing unit that performs frequency error correction based on the frequency synchronization information received from the aforementioned wireless terminal during the aforementioned coordinated communication. This achieves the function of correcting frequency errors based on the frequency synchronization information received from the wireless terminal.

[0021] Furthermore, a third aspect of this technology is a wireless terminal comprising: a channel estimation unit that separates a reference signal from signals coordinated and transmitted from a plurality of wireless base stations based on reference information, and estimates the frequency error between the plurality of wireless base stations; and a signal processing unit that performs phase shift correction on the coordinated and transmitted signals based on the estimated frequency error. This achieves the function of estimating the frequency error and performing phase shift correction based on the coordinated and transmitted signals.

[0022] Furthermore, in this third aspect, the aforementioned channel estimation unit may also separate the aforementioned reference signal based on the codebook determined among the aforementioned plurality of wireless base stations and the aforementioned information. This achieves the effect of further separating the reference signal based on the codebook.

[0023] Furthermore, the third aspect may also include: a communication unit that transmits information regarding the estimated frequency error mentioned above to at least one of the plurality of wireless base stations mentioned above. This achieves the function of notifying the wireless base stations of the estimated frequency error.

Implementation Method

[0024] The following describes the form in which this technology is implemented (hereinafter referred to as the embodiment). The description is performed in the following order: 1. Embodiment 2. Variation

[0025] <1. Embodiment> [Wireless Network System] Figure 1 is a diagram illustrating an example of the configuration of a wireless network system in an embodiment of the present technology.

[0026] Here, it is assumed that simultaneous transmission (JT) is performed by a plurality of access points 11 and 12 in coordination. The access points 11 and 12 performing this simultaneous transmission are collectively referred to as multiple APs. Three or more access points constitute a multiple AP. Furthermore, in this example, although wireless terminal 201 is shown as the transmission target for simultaneous transmission, it can also communicate with a plurality of wireless terminals simultaneously.

[0027] To determine the coordination method of multiple APs, the entity that determines the coordination method is defined as the primary AP, and the access points that implement the coordination method through notification from the primary AP are defined as secondary APs. Furthermore, the primary AP is also called the sharing AP, and the secondary AP is also called the shared AP. The primary AP can also participate in the coordination method of multiple APs. For example, in the same diagram, access point 11 can be set as the primary AP, and access point 12 as the secondary AP. Although access point 11 is referred to as primary AP 101 and access point 12 as secondary AP 102 below, there can be multiple secondary APs. Furthermore, the primary AP and secondary APs are not fixed to each AP, but are dynamically determined within the multiple APs. For example, at a certain time t1, AP1 is the primary AP and AP2 is the secondary AP, while at a different time t2, AP1 becomes the secondary AP and AP2 becomes the primary AP.

[0028] [Device Configuration] Figure 2 is a diagram illustrating an example of the configuration of a wireless communication device 300 in an embodiment of the present technology. The wireless communication device 300 here includes a main AP 101, a secondary AP 102, and a wireless terminal 201. Alternatively, the wireless communication device 300 may also be a wireless communication module or integrated circuit mounted in these APs or terminals.

[0029] The wireless communication device 300 includes: a communication unit 310, a control unit 321, a power supply unit 322, and an antenna 319. The communication unit 310 may also exist in multiples.

[0030] The communication unit 310 includes: a wireless control unit 311, a data processing unit 312, a demodulation unit 313, a signal processing unit 314, a channel estimation unit 315, a wireless interface 316, and an amplification unit 317. The wireless interface 316, the amplification unit 317, and the antenna 319 form a group, or more than one group can be used as constituent elements. Furthermore, the function of the amplification unit 317 can also be built into the wireless interface 316. The communication unit 310 is implemented by, for example, LSI (Large Scale Integration).

[0031] The data processing unit 312 generates packets required for wireless transmission from the data received from the upper layer, performs processing such as adding headers or error detection codes required for Media Access Control (MAC), and supplies the processed data to the modulation and demodulation unit 313. On the other hand, when there is a received signal from the modulation and demodulation unit 313, it performs MAC header parsing, packet error detection, and rearrangement processing, and provides the processed data to its own protocol upper layer.

[0032] The wireless control unit 311 is responsible for receiving and transmitting information between various units. It also performs parameter settings in the demodulation unit 313 and the signal processing unit 314, packet scheduling in the data processing unit 312, parameter settings and transmission power control for the demodulation unit 313, the signal processing unit 314, the wireless interface unit 316 and the amplification unit 317.

[0033] The modulation and demodulation unit 313, during transmission, takes the input data from the data processing unit 312 and generates a data symbol stream based on the relevant parameters of the physical layer (PHY) set by the radio control unit 311, and supplies it to the signal processing unit 314. Specifically, based on the encoding and modulation methods set by the radio control unit 311, it performs encoding, interleaving, and modulation to generate a data symbol stream and supplies it to the signal processing unit 314. During reception, the input from the signal processing unit 314 is processed in the opposite way to that during transmission, and data is supplied to the data processing unit 312 or the radio control unit 311.

[0034] During transmission, the signal processing unit 314 performs spatial separation signal processing on the input from the modulation / demodulation unit 313 as needed, and supplies the resulting transmission symbol stream to each wireless interface 316. In addition, it performs additional text on the physical layer or inserts pilot signals based on the relevant parameters of the physical layer set by the wireless control unit 311. Furthermore, it can generate pilot signals as needed. During reception, the signal processing unit 314 performs signal processing on the reception symbol stream input from each wireless interface 316, performing phase tracking with reference to the received pilot signal or spatial decomposition of the stream as needed, and then supplies it to the modulation / demodulation unit 313.

[0035] The channel estimation unit 315, based on the preceding section and the training signal section, performs estimation of the frequency error between the terminal and the received signal, and calculation of composite channel gain information of the propagation path from the input signals from each wireless interface 316. The estimated frequency error or the calculated composite channel gain information is used by the wireless control unit 311 in the demodulation processing of the modulation and demodulation unit 313 and the signal processing of the signal processing unit 314.

[0036] The wireless interface 316, when transmitting a signal, converts the input from the signal processing unit 314 into an analog signal, performs filtering, upscaling to the carrier frequency, and phase control, and then sends it to the antenna 319 or the amplification unit 317. When receiving a signal, it performs the opposite processing on the input from the antenna 319 or the amplification unit 317, and supplies data to the signal processing unit 314 and the channel estimation unit 315.

[0037] The amplification unit 317 amplifies the analog signal input from the wireless interface 316 to a predetermined power during transmission and sends it to the antenna 319. During reception, it amplifies the signal input from the antenna 319 to a predetermined power and then outputs it to the wireless interface 316. At least one or more of the transmission and reception functions of the amplification unit 317 may also be built into the wireless interface 316. Furthermore, at least one or more of the transmission and reception functions of the amplification unit 317 may also be a component other than the communication unit 310.

[0038] The control unit 321 controls the wireless control unit 311 and the power supply unit 322. Furthermore, the control unit 321 can also perform the operation of at least one part of the wireless control unit 311 in place of the wireless control unit 311.

[0039] The power supply unit 322 is composed of a battery power supply or a fixed power supply and supplies power to various parts of the wireless communication device 300.

[0040] In these configurations, the wireless control unit 311 and the control unit 321 control each unit by performing the following operations.

[0041] [Action] Figure 3 is a sequence diagram of an example of the operation of a wireless network system in an embodiment of this technology.

[0042] Here it is assumed that a wireless terminal 201 exists, and the main AP 101 and the secondary AP 102 that can simultaneously transmit signals to the wireless terminal 201 exist in a multi-AP manner.

[0043] [Capability Exchange] First, whether simultaneous transmission due to multiple APs is feasible is mutually notified among the main AP 101, secondary AP 102, and wireless terminal 201. This is called Capability Exchange 810. Specifically, it is notified that the main AP 101 and secondary AP 102 can perform simultaneous transmission, and that the wireless terminal 201 can receive signals transmitted through simultaneous transmission. In addition, during joint transmission, information indicating whether transmission and reception are possible for CJT (Coherent Joint Transmission) and NCJT (Non-Coherent Joint Transmission), respectively, is also notified.

[0044] Furthermore, the ability to perform simultaneous transmission can also be indirectly interpreted as the ability to perform frequency synchronization with the precision required for simultaneous transmission. For example, it can also be interpreted as the inability to perform high-precision frequency synchronization when only NCJT can be implemented, but the ability to perform high-precision frequency synchronization when CJT can be implemented.

[0045] Furthermore, the capability exchange 810 is one example of a communication unit described in the scope of the patent application.

[0046] [Pilot Allocation Negotiation] After being notified by the multiple APs and the wireless terminal 201 that simultaneous transmission is possible via capability exchange 810, the primary AP 101, which decides to implement simultaneous transmission using multiple APs, notifies the secondary AP 102 of the information required to determine the allocation of pilot signals (821). The secondary AP 102, having received notification 821 from the primary AP 101, notifies the primary AP 101 of the information required to determine the allocation of pilot signals (822). These negotiations are called Pilot Allocation Negotiation 820.

[0047] For example, the main AP101 may notify (821) of the allocation of pilot signals being transmitted simultaneously, and the secondary AP102 may notify (822) of the approval information. Alternatively, the main AP101 may similarly notify (821) of information indicating a plurality of candidates, and the secondary AP102 may reply with the candidate selected from among them (822).

[0048] Pilot signal allocation negotiation 820 can be conducted before each simultaneous signal transmission by multiple APs, but it does not necessarily have to be conducted every time simultaneous signal transmission is implemented. For example, if the pilot signal allocation method used when the APs have been assigned as primary AP101 and secondary AP102 is common among the multiple APs, then the access points constituting the multiple APs can also have their pilot signal allocation determined by default when they have been assigned as primary AP101 and secondary AP102. In this case, as long as the allocation of primary AP101 and secondary AP102 has not been changed, the allocation method can be inherited.

[0049] Furthermore, the pilot signal allocation negotiation 820 is an example of a wireless control unit described in the claims.

[0050] After the pilot signal allocation negotiation 820 has been implemented, each access point constituting multiple APs allocates the pilot signal that has been determined by the pilot signal allocation negotiation 820 during the implementation of simultaneous signal transmission (830).

[0051] In addition, the pilot signal allocation 830 is an example of a wireless control unit described in the claims.

[0052] [Simultaneous transmission] The multiple APs that have had their pilot signal allocation determined through pilot signal allocation negotiation 820 allocate pilot signals according to the determined pilot signal allocation, and then perform simultaneous transmission (e.g., CJT) (840) on the wireless terminal 201.

[0053] In addition, prior to the implementation of simultaneous transmission, the sharing of data to be transmitted to the wireless terminal 201 or frequency synchronization among multiple APs can also be implemented among multiple APs.

[0054] In addition, the simultaneous transmission of information 840 is one example of a communication unit described in the scope of the patent application.

[0055] [Phase Tracking] The wireless terminal 201, upon receiving signals simultaneously transmitted from multiple APs, performs frequency synchronization with the multiple APs and performs phase tracking 850 based on the assigned pilot signals. At this time, the codebook already determined among the multiple APs can also be referenced.

[0056] Various methods exist for implementing phase tracking. For example, a simple algorithm applicable to pilot signal allocation as specified in IEEE 802.11, where the composite phase rotation of the pilot signal is small, has been proposed (A. Troya, M. Krstic, and K. Maharatna, “Simplified residual phase correction mechanism for the IEEE 802.11a standard,” in Proc. IEEE VTC-Fall, Oct. 2003, vol. 2, pp. 1137-1141.). The algorithm presented here, while for phase tracking of a single transmitter, can also be applied to multiple access points (APs). In this case, if the access points constituting the multiple APs are not perfectly frequency synchronized, phase tracking can be performed for a single access point. Alternatively, phase tracking can be performed for the average frequency across multiple access points. This reduces the impact of residual frequency errors on multiple APs.

[0057] Furthermore, the phase tracking 850 is an example of the channel estimation unit and signal processing unit described in the claims.

[0058] [Ack] When a wireless terminal 201 determines that the reception of a signal caused by simultaneous signal transmission from multiple APs has been completed, it notifies the multiple APs of the Ack (Acknowledgement) 860 indicating normal reception. At this time, the wireless terminal 201 can estimate the residual CFO between the primary AP 101 and the secondary AP 102 by means of the pilot signal, and can also notify the multiple APs together with the information indicating the residual CFO (Residual CFO Feedback).

[0059] In addition, Ack860 is one example of a communication unit described in the scope of the patent application.

[0060] Upon receiving the Ack860, the main AP101 corrects the frequency error (870) in a manner that reduces the residual CFO among multiple APs, based on the notified information representing the residual CFO.

[0061] In addition, the frequency error correction 870 is one example of the signal processing unit described in the claims.

[0062] [Frame Structure] The following details the structure of each frame as illustrated in the sequence diagram above.

[0063] [Capability Exchange] Figure 4 is an illustration of an example of the configuration of the notification frame in capability exchange 810 in an embodiment of the present technology.

[0064] The notification frame of the capability exchange 810 is used to notify the wireless terminal 201 that it can transmit signals simultaneously. This frame consists of "destination address", "transmission source address", "frame control" and "EHT (Extremely High Throughput) capability", but is not limited to these. Furthermore, the same information regarding "destination address", "transmission source address" and "frame control" will also be notified in the frames shown in the following figures, so the explanation in the following frames is omitted.

[0065] The "Destination Address" (TA) contains information indicating the terminal that is the destination of this frame. For example, it may also contain information indicating the MAC address of the destination terminal. However, if the destination terminal is a specific plurality of terminals or all terminals that can receive this frame, it may also contain information indicating that it is acceptable even if the message is received by these terminals. The "Sending Source Address" (RA) contains information indicating the terminal that is the sending source of this frame. Similar to the "Destination Address," it may also contain information indicating the MAC address of the sending source.

[0066] "Frame Control" contains information indicating that this frame is a frame notified in capability exchange 810. However, it is not necessarily only included in "Frame Control", but can also be configured to indicate, in conjunction with other information in this frame, that this frame is a frame notified as capability exchange 810.

[0067] "EHT Capabilities" contains information indicating the capabilities of the wireless communication device that sends this frame, and in particular, information indicating whether simultaneous transmission is possible. The "EHT Capabilities" contain at least one of "Element ID", "Length" and "EHT Capability Information", but its constituent elements are not limited to these.

[0068] The "Element ID" contains information indicating that this element is an "EHT capability". The "Length" contains information indicating the length of the information stored as an "EHT capability". The "EHT Capability Information" contains information indicating the capabilities of the terminal that sent this frame. Although the "EHT Capability Information" contains information on "simultaneous transmission", its constituent elements are not limited to these.

[0069] The "Joint Transmission" in "EHT Capability Information" contains information indicating whether joint transmission is possible. Furthermore, "Joint Transmission" may also contain detailed information indicating whether it is possible for several methods. For example, if "Joint Transmission" is represented by 3 bits, it can be configured as follows: "000" indicates that joint transmission is not possible under any method; "010" indicates that only NCJT reception is possible during joint transmission; "011" indicates that both NCJT transmission and reception are possible during joint transmission; "100" indicates that only transmission is possible under both CJT and NCJT; "101" indicates that both parties can perform transmission and reception under both CJT and NCJT.

[0070] [Pilot Signal Allocation Negotiation] Figure 5 is an illustration of an example of the configuration of the notification frame in the pilot signal allocation negotiation 820 of this embodiment of the technology.

[0071] The frame notified in the pilot signal allocation negotiation 820 is used among multiple APs capable of simultaneous transmission when notifying each other of the information required to determine the allocation of pilot signals in simultaneous transmission. This frame consists of a "destination address", a "transmission source address", a "frame control", a "simultaneous transmission control element", and a "simultaneous transmission notification element", but its constituent elements are not limited to these.

[0072] The "Joint Transmission Control element" is used to estimate the length of the subsequent "Joint Transmission Notification element," but its purpose is not limited to this. Furthermore, the "Joint Transmission Control element" can also be defined as a single element together with the "Joint Transmission Notification element." This "Joint Transmission Control element" contains at least one of the following: "Element ID," "Length," and "Number of Terminals Sending Transmissions Simultaneously," but its constituent elements are not limited to these.

[0073] "Element ID" contains information indicating that this element is a "Simultaneous Sending Control Element". "Length" contains information indicating the length of this element. "Number of Simultaneous Sending Terminals" (JT STA Num) contains information indicating the number of "Terminal Information" fields in the subsequent "Simultaneous Sending Notification Element".

[0074] The "Joint Transmission Announcement element" contains, in addition to announcing the allocation of pilot signals in the joint transmission, information indicating the frequency band used for transmission to the destination wireless terminal 201 during the joint transmission. The "Joint Transmission Announcement element" contains at least one of "element ID", "length", "pilot signal allocation" and "terminal information", but the constituent elements are not limited to these.

[0075] The "Element ID" contains information indicating that this element is a "simultaneous signal transmission notification element". The "Length" contains information indicating the length of this element. The "Pilot Allocation" contains information indicating the allocation of pilot signals according to each access point constituting the multiple APs. The "STA Info" contains information indicating the frequency band allocated to the wireless terminal 201 at the destination of the simultaneous signal transmission.

[0076] The “Pilot Signal Allocation” contains at least one of the subfields “Number of Channels” and “Channel”. “Number of Channels” contains information indicating the number of subsequent “Channel” subfields. “Channel” contains information indicating the allocation of pilot signals to any access point constituting multiple APs within the frequency band indicated by each channel.

[0077] Furthermore, each "channel" stores information of "channel ID" and "allocation type". The "channel ID" contains information indicating the frequency band of the object shown in the "channel" sub-field. The "allocation type" contains information indicating the allocation of pilot signals to any access point constituting multiple APs within the frequency band indicated by the "channel ID".

[0078] The "Allocation Type" contains information about "AP Number", "BSSID#i", and "Allocation Type #i". "AP Number" (AP Num) contains information indicating the number of access points mentioned in the "Allocation Type". "BSSID#i" contains information that individually represents each different access point. "Allocation Type #i" (Allocation Type #i) contains information indicating the allocation of pilot signals for each access point corresponding to each BSSID. Here, i is an integer from 1 to NAP(1). For example, "AP Number" may contain information indicating NAP(1), or it may contain information determined by the MAC address of the access point specified in "BSSID#i".

[0079] The “allocation type #i” may also contain any one of the following information indicating the allocation. Specifically, in the frequency band indicated by “channel ID”, the access point indicated by “BSSID#i” (1) indicates whether a pilot signal is inserted, (2) indicates in which OFDM symbol the pilot signal is inserted, and (3) in the case of inserting a pilot signal across multiple subcarriers and OFDM symbols, indicates the orthogonal sequence required in the wireless terminal 201 to separate the pilot signal.

[0080] In this case, phase tracking can be easily performed in the wireless terminal 201 by allocating pilot signals that ensure the orthogonality of the pilot signals for each access point. The orthogonality referred to here means using at least one of different frequencies, different times, and different sequences.

[0081] The “Terminal Information” contains at least one of the subfields “BSSID” and “Channel”. The “BSSID” contains information indicating the different wireless terminals. The “Channel” contains information indicating the bandwidth allocated to the wireless terminals indicated by the “BSSID” when transmitting signals simultaneously.

[0082] [Simultaneous transmission] Figure 6 is a diagram illustrating an example of the configuration of the data unit (PPDU: Physical-layer-convergence-Protocol Data Unit) notified in the simultaneous transmission 840 of this embodiment of the technology.

[0083] The data unit notified in the simultaneous transmission 840 is used by multiple APs that have had their pilot signal allocation determined through pilot signal allocation negotiation 820 when transmitting data to the wireless terminal 201. This data unit is composed of "Legacy", "EHT-SIG", "EHT-STF", "EHT-LTF", "transmission source address", "destination address" and "data", but the constituent elements are not limited to these.

[0084] "Legacy" is a field that allows the wireless terminal 201 receiving this frame to demodulate subsequent data, and contains sequences required for frame detection, AGC (Auto Gain Control), frequency synchronization, time synchronization, and propagation path estimation. "EHT-SIG" contains information about the pilot signals allocated among the multiple APs. "EHT-STF" and "EHT-LTF" contain sequences required to further improve the accuracy of AGC, frequency synchronization, time synchronization, or propagation path estimation compared to "Legacy". "Send Source Address" contains information indicating the multiple APs from which the signal is sent. "Destination Address" contains information indicating the wireless terminal 201 as the destination. "Data" contains data to be sent from the multiple APs to the wireless terminal 201.

[0085] Here, "Legacy" may not be a single field, but rather a combination of multiple fields. For example, it may be divided into: fields for frame detection, AGC, coarser timing synchronization, frequency synchronization, and fields for finer timing synchronization. Furthermore, in addition to the pilot signal information mentioned above, "EHT-SIG" may also contain bandwidth information that can be used subsequently, but its constituent elements are not limited to these.

[0086] Furthermore, "EHT-SIG" may also contain one or more subfields for "Channel Number" and "Channel #i", but the constituent elements are not limited to these. "Channel Number" contains information indicating the number (Nc) of the subsequent "Channel #i" subfield. That is, i in "Channel #i" is an integer from 1 to Nc. "Channel #i" contains information indicating the allocation of pilot signals for multiple APs in the frequency band indicated by the "Channel ID" within the "Channel #i" subfield.

[0087] The “Channel #i” subfield contains one or more subfields, including “Channel ID” and “Allocation Type”, but the constituent elements are not limited to these. “Channel ID” contains information indicating the channel mentioned in the subsequent “Allocation Type”. “Allocation Type” contains information regarding the allocation of pilot signals for multiple APs in the frequency band indicated by “Channel ID”.

[0088] Thus, in the simultaneous transmission 840 of this embodiment, the transmission is performed together with information indicating the allocation of pilot signals for multiple APs.

[0089] [Ack] Figure 7 is an illustration of an example of the configuration of the notification frame in Ack860 in an embodiment of the present technology.

[0090] The Ack860 is used to enable a wireless terminal 201 that receives a frame notified by simultaneous transmission 840 to notify multiple APs of the received response and the residual CFO of the access point with the inserted pilot signal. The frame consists of "frame control", "length", "transmission source address", "residual CFO feedback" and "FCS", but the constituent elements are not limited to these.

[0091] "Frame Control" contains information indicating that this frame is a frame notified by Ack860. "Length" contains information indicating the length of this frame. "Sending Source Address" (RA) contains information indicating the wireless terminal 201 from which the signal is sent. "Residual CFO Feedback" contains information indicating the residual CFO for any access point constituting multiple APs. "FCS" (Frame Check Sequence) contains the sequence required for error detection or error correction of the received frame.

[0092] The “Residual CFO Feedback” contains one or more sub-fields, namely “Multiple APs” and “Residual CFO AP#i”.

[0093] "Multi AP Number" contains information indicating the number of access points for which the residual CFO mentioned in the "Residual CFO Feedback" is represented. "Residual CFO AP#i" contains information indicating the residual CFO of each access point. Here, i is an integer from 1 to MAP. For example, "Multi AP Number" contains information including MAP, and "Residual CFO AP#i" contains the BSSID of the access points constituting the multi AP and the value of the residual CFO of the access points of the wireless terminal 201.

[0094] Thus, according to the embodiment of this technology, by transmitting information indicating the allocation of pilot signals among multiple APs in the simultaneous transmission 840, phase tracking 850 can be performed in the receiving wireless terminal 201. Furthermore, by notifying the residual CFO generated in the wireless terminal 201 along with Ack 860, frequency error correction 870 can be performed among the multiple APs.

[0095] <2. Variations> [Variations in Pilot Signal Allocation Negotiation] In the above-described embodiment, the allocation of pilot signals for access points is individually represented using the "allocation type" of "pilot signal allocation" in pilot signal allocation negotiation 820. In contrast, in this variation, it is assumed that the allocation of pilot signals will be determined according to the size of the MAC address. Therefore, the explicit specification of the "allocation type" is not required.

[0096] Figure 8 is a diagram illustrating a modified example of the signal frame notified in the pilot signal allocation negotiation 820 in an embodiment of the present technology.

[0097] Here, the difference between the pilot signal allocation negotiation 820 and the above-described embodiment, namely the "simultaneous signal notification element", will be explained. The "simultaneous signal notification element" in this variation contains at least one of "element ID", "length" and "pilot signal allocation", but the constituent elements are not limited to these.

[0098] "Element ID" contains information indicating that this element is a "simultaneous notification element". "Length" contains information indicating the length of this element. "Pilot Allocation" contains information regarding the allocation of pilot signals to any access point constituting multiple APs.

[0099] The “Pilot Signal Allocation” contains one or more subfields, including “AP Number”, “BSSID#i” and “AP#iID”.

[0100] "AP Number" contains information indicating the number of access points targeted in Pilot Allocation. "BSSID#i" contains information indicating the identification number of the access point. "AP#iID" contains information regarding the allocation of pilot signals for each access point indicated by "BSSID#i". Here, i is an integer from 1 to NAP. For example, "AP Number" contains information indicating NAP, "BSSID#i" contains information indicating the value determined based on the MAC address, and "AP#iID" contains information indicating a natural number below NAP.

[0101] In this variation, it is assumed that the access point shown by "BSSID#i" is determined by referring to the information shown by "AP#iID" and the codebook for the allocation of pilot signals that has been determined in advance among multiple APs.

[0102] [Modification of Simultaneous Communication] Figure 9 is an illustration of a modification of the data unit configuration in the simultaneous communication 840 of this embodiment.

[0103] Although the above-described embodiment represents the "allocation type" information for each channel, in this variant, each access point represents the information regarding the allocation of pilot signals.

[0104] Here, the difference between the simultaneous transmission of signal 840 and the above-described embodiment, namely "EHT-SIG", will be explained. In this variation, "EHT-SIG" contains at least one of "multiple APs" and "AP information #i", but the constituent elements are not limited to these.

[0105] "Multi AP Number" contains information indicating the number (NAP) of the subsequent "AP Information #i" subfield. "AP Information #i" contains information about the allocation of pilot signals for each access point constituting the multiple APs. Here, i is an integer from 1 to NAP.

[0106] Hereinafter, as a specific example, we will explain the case in which the "Data" part of the data unit is transmitted in OFDM modulation mode due to a variation of the simultaneous transmission 840.

[0107] Figure 10 is a diagram illustrating an example of pilot signal allocation in an embodiment of this technology. The same figure illustrates a plurality of OFDM symbols constituting the "data" section.

[0108] The wireless terminal 201 cuts out each OFDM symbol and demodulates the symbols that have been inserted into each subcarrier by frequency conversion. At this time, in order to ensure that all the delayed waves observed in the OFDM symbol are delayed waves caused by the symbols used in the same OFDM symbol, a CP (Cyclic Prefix) is inserted at the beginning. In the CP, any time domain waveform of the OFDM symbol immediately following it can also be used, but it is not limited to this.

[0109] In the same diagram, it is assumed that multiple access points (APs) are formed by three access points (AP#1, AP#2, and AP#3). Although pilot signals are inserted into each OFDM symbol, this is implemented by inserting pilot signals into different subcarriers and OFDM symbols between access points. However, it is not necessary to insert all access point pilot signals into all OFDM symbols.

[0110] indicates that the information of AP#1, AP#2 and AP#3 is included in "AP Information #1" and even "AP Information #3". If the information of the number of access points "3" constituting the multiple APs is included in "Number of Multiple APs", then assuming that the information is used, the distribution method of the pilot signal is known between the multiple APs and the wireless terminal 201.

[0111] In this case, the wireless terminal 201 can determine, by using the information represented by "Number of Multiple APs" and "AP Information #1" and even "AP Information #3" in "EHT-SIG", where the access point constituting the multiple APs inserts the pilot signal. Then, the wireless terminal 201 can determine the residual CFO of each access point.

[0112] Furthermore, in the above-described embodiment, the wireless terminal 201 can determine where the access points constituting multiple APs will insert pilot signals by using the information shown in the "allocation type" of each "channel #i" in "EHT-SIG", and can also determine the residual CFO of each access point.

[0113] Furthermore, the above-described embodiments are examples of what is necessary to realize this technology, and the matters in the embodiments and the specific matters of the invention in the claims are respectively related. Similarly, the specific matters of the invention in the claims and the matters in the embodiments of this technology that bear the same name are respectively related. However, this technology is not limited to the embodiments, and various modifications can be made to the embodiments to realize it without departing from its spirit.

[0114] Furthermore, the processing procedure described in the above embodiments can be regarded as a method having these series of programs, and also as the program required to enable the computer to execute these series of programs, or even the recording medium for storing the program. Such recording medium may include, for example, CD (Compact Disc), MD (Mini Disc), DVD (Digital Versatile Disc), memory card, Blu-ray Disc, etc.

[0115] In addition, the effects described in this specification are only illustrative and not limited, and there may be other effects as well.

[0116] In addition, the present technology can also be regarded as the following configuration. (1) A wireless base station, comprising: a wireless control unit that generates a reference signal determined between itself and a coordinating wireless base station for coordinated transmission; and a communication unit that coordinates a signal containing the aforementioned reference signal with the aforementioned coordinating wireless base station and transmits it to a wireless terminal. (2) The wireless base station as described in (1) above, wherein the aforementioned reference signal is transmitted using at least one of different frequencies, different times, and different sequences. (3) The wireless base station as described in (1) or (2) above, wherein the aforementioned communication unit exchanges information about the supported coordination methods between the aforementioned coordinating wireless base station and the aforementioned wireless terminal before the aforementioned coordinated transmission. (4) As described in any of (1) to (3) above, the aforementioned wireless control unit determines the allocation of the aforementioned reference signal in the aforementioned coordinated transmission and the aforementioned coordinated wireless base station before the generation of the aforementioned reference signal. (5) As described in (4) above, the aforementioned reference signal allocation decision unit determines the information of each frequency channel and the information about the aforementioned frequency channel in the frequency band used in the aforementioned coordination method. (6) As described in (4) or (5) above, the aforementioned wireless control unit determines at least one of the following: information about the number of the aforementioned coordinated wireless base stations, information used to identify the aforementioned coordinated wireless base stations, and information about the numbers allocated to the aforementioned coordinated wireless base stations. (7) As described in any of the preceding items (4) to (6), the preceding wireless control unit determines for each preceding coordinated wireless base station information including information indicating the presence or absence of the preceding reference signal insertion, information indicating the symbol of the preceding reference signal insertion, and at least one of the following: information for separating the reference signal in the preceding wireless terminal. (8) As described in any of the preceding items (1) to (7), the preceding communication unit transmits information about the preceding coordinated wireless base station to the preceding wireless terminal during the preceding coordinated transmission. (9) As described in the preceding item (8), the preceding communication unit transmits information about each of any frequency channels to be used in the preceding coordinated transmission as information about the preceding coordinated wireless base station to the preceding wireless terminal. (10) The wireless base station as described in (8) or (9) above, wherein the communication unit of the above shall send the identification number assigned to the above coordinating wireless base station as information about the above coordinating wireless base station to the above wireless terminal.(11) The wireless base station described in any of the preceding items (8) to (10), wherein the information regarding the preceding coordinating wireless base station, together with the codebook determined between the preceding coordinating wireless base station, is used as information required to determine the allocation of the preceding reference signal. (12) The wireless base station described in any of the preceding items (1) to (11), further comprising: a signal processing unit that performs frequency error compensation based on frequency synchronization information notified from the preceding wireless terminal during the preceding coordination transmission. (13) A wireless base station comprising: a wireless control unit that receives reference information from the coordinating wireless base station performing the coordination transmission; and a communication unit that coordinates a signal containing the preceding reference information with the preceding coordinating wireless base station and transmits it to a wireless terminal. (14) As described in the preceding (13) wireless base station, wherein the preceding communication unit transmits information about the preceding coordinated wireless base station to the preceding wireless terminal during the preceding coordinated transmission. (15) As described in the preceding (14) wireless base station, wherein the preceding communication unit transmits information about each of any frequency channels to be used in the preceding coordinated transmission as information about the preceding coordinated wireless base station to the preceding wireless terminal. (16) As described in the preceding (14) or (15) wireless base station, wherein the preceding communication unit transmits the identification number assigned to the preceding coordinated wireless base station as information about the preceding coordinated wireless base station to the preceding wireless terminal. (17) The wireless base station described in any of (14) to (16) above, wherein the information regarding the coordinated wireless base station mentioned above, together with the codebook determined between the coordinated wireless base station mentioned above, is used as the information required to determine the allocation of the reference signal mentioned above. (18) The wireless base station described in any of (13) to (17) above, further comprising: a signal processing unit that performs frequency error compensation based on frequency synchronization information notified from the wireless terminal mentioned above during the coordinated transmission of the aforementioned signal. (19) A wireless terminal comprising: a channel estimation unit that separates a reference signal from signals transmitted in coordination from a plurality of wireless base stations based on reference information and estimates the frequency error between the plurality of wireless base stations mentioned above; and a signal processing unit that performs phase shift compensation of the signals transmitted in coordination above based on the estimated frequency error mentioned above. (20) In the wireless terminal described in (19) above, the aforementioned channel estimation unit separates the aforementioned reference signal based on the codebook determined among the aforementioned plurality of wireless base stations and the aforementioned information. (21) In the wireless terminal described in (19) or (20) above, the aforementioned unit further comprises: a communication unit that transmits information about the frequency error estimated in the aforementioned to at least one of the aforementioned plurality of wireless base stations. [Simplified Explanation of the Diagram]

[0118] [Figure 1] Illustration of a configuration example of a wireless network system in an embodiment of the present technology. [Figure 2] Illustration of a configuration example of a wireless communication device 300 in an embodiment of the present technology. [Figure 3] Sequence diagram of an operation example of a wireless network system in an embodiment of the present technology. [Figure 4] Illustration of a configuration example of a frame notified in capability exchange 810 in an embodiment of the present technology. [Figure 5] Illustration of a configuration example of a frame notified in pilot signal allocation negotiation 820 in an embodiment of the present technology. [Figure 6] Illustration of a configuration example of a data unit notified in simultaneous transmission 840 in an embodiment of the present technology. [Figure 7] Illustration of a configuration example of a frame notified in Ack 860 in an embodiment of the present technology. [Figure 8] Illustration of a modified configuration example of a frame notified in pilot signal allocation negotiation 820 in an embodiment of the present technology. [Figure 9] Illustration of a modified configuration example of a data unit notified in simultaneous transmission 840 in an embodiment of the present technology. [Figure 10] A diagram illustrating an example of pilot signal allocation in an embodiment of this technology.

Claims

1. A first coordinating wireless base station, comprising: a communication unit, for exchanging first information with a second coordinating wireless base station among a plurality of coordinating wireless base stations; wherein, The aforementioned plurality of coordinated wireless base stations includes the aforementioned first coordinated wireless base station; each of the aforementioned plurality of coordinated wireless base stations performs coordinated signal transmission; and the aforementioned first information is used for the allocation of a reference signal; and a wireless control unit generates the aforementioned reference signal based on the aforementioned first information; the aforementioned communication unit further: in the aforementioned coordinated signal transmission, transmits a signal containing the aforementioned reference signal to a wireless terminal; and receives second information from the aforementioned wireless terminal based on the aforementioned transmitted signal; the aforementioned second information includes: third information indicating the frequency error associated with the aforementioned plurality of coordinated wireless base stations; and fourth information indicating the number of coordinated wireless base stations among the aforementioned plurality of coordinated wireless base stations; and also includes: a signal processing unit that corrects the aforementioned frequency error based on the aforementioned second information.

2. The first coordinating wireless base station as described in Request 1, wherein, Each of the aforementioned coordinating radio base stations further transmits the aforementioned reference signal using at least one of different frequencies, different times, and different sequences.

3. The first coordinating wireless base station as described in Request 1, wherein, The aforementioned communications department exchanges information 5 regarding the supported coordination methods between the aforementioned second coordination wireless base station and the aforementioned wireless terminal before the aforementioned coordination is sent.

4. The first coordinating wireless base station as described in request item 3, wherein, The first information in the foregoing contains: the sixth information about each of the plurality of frequency channels in the frequency band used in the foregoing coordination method, and the seventh information about the foregoing reference signal.

5. The first coordinating wireless base station as described in Request 1, wherein, The first information in the foregoing includes at least one of the following: the fifth information used to identify the plurality of coordinated radio base stations in the foregoing, or the sixth information including the number of each coordinated radio base station assigned to the plurality of coordinated radio base stations in the foregoing.

6. The first coordinating wireless base station as described in Request 1, wherein, The first piece of information in the foregoing contains: the fifth piece of information indicating whether the insertion of the foregoing reference signal is present or absent; the sixth piece of information indicating the symbol to be inserted for the foregoing reference signal; and the seventh piece of information containing the sequence required for separating the reference signal in the foregoing wireless terminal.

7. The first coordinating wireless base station as described in Request 1, wherein, The aforementioned communications department sends the fifth piece of information regarding the aforementioned second coordinated wireless base station to the aforementioned wireless terminal during the aforementioned coordinated communication process.

8. The first coordinating wireless base station as described in claim 7, wherein, Information 5 in the foregoing contains: Information 6 concerning each of the plurality of arbitrary frequency channels to be used in the coordinated transmission in the foregoing.

9. The first coordinating wireless base station as described in claim 7, wherein, Information 5 in the foregoing contains: Information 6, which indicates the identification number assigned to the coordinating wireless base station in the foregoing 2.

10. The first coordinating wireless base station as described in claim 7, wherein, Information 5 in the foregoing contains information 1 in the foregoing; the allocation of the reference signal in the foregoing is based on the codebook determined by the coordinating wireless base station in the foregoing.

11. A first coordinating wireless base station, comprising: a wireless control unit, which receives reference information from a second coordinating wireless base station among a plurality of coordinating wireless base stations, wherein... The aforementioned plurality of coordinated wireless base stations includes the aforementioned first coordinated wireless base station; each of the aforementioned plurality of coordinated wireless base stations performs coordinated signal transmission; and a communication unit, which transmits a signal containing the aforementioned reference information to a wireless terminal during the aforementioned coordinated signal transmission, and receives first information from the aforementioned wireless terminal based on the aforementioned transmitted signal; wherein the aforementioned first information includes: second information indicating the frequency error associated with the aforementioned plurality of coordinated wireless base stations; and third information indicating the number of coordinated wireless base stations among the aforementioned plurality of coordinated wireless base stations; and also includes: a signal processing unit that corrects the aforementioned frequency error based on the aforementioned first information.

12. The first coordinating wireless base station as described in claim 11, wherein, The aforementioned communications department sends the fourth information regarding the aforementioned second coordinated wireless base station to the aforementioned wireless terminal during the aforementioned coordinated communication process.

13. The first coordinated wireless base station as described in claim 12, wherein, Information 4 in the foregoing contains: Information 5 concerning each of the plurality of arbitrary frequency channels to be used in the coordinated transmission in the foregoing.

14. The first coordinated wireless base station as described in claim 12, wherein, Information 4 in the foregoing contains: Information 5, which indicates the identification number assigned to the coordinating wireless base station in the foregoing 2.

15. The first coordinating wireless base station as described in claim 12, wherein, Information 4 in the foregoing is information required for the allocation of reference signals; the allocation of reference signals in the foregoing is based on the codebook determined by the coordinating wireless base station in section 2 of the foregoing.

16. A wireless terminal comprising: a channel estimation unit that separates a reference signal from signals transmitted by a plurality of coordinated wireless base stations based on reference information, and estimates a frequency error associated with the plurality of coordinated wireless base stations based on the aforementioned reference signal; a signal processing unit that performs phase-shift correction on the aforementioned signals based on the estimated frequency error; and a communication unit that transmits first information to at least one of the plurality of coordinated wireless base stations to correct the estimated frequency error; the aforementioned first information comprising: second information indicating the estimated frequency error, and third information indicating the number of coordinated wireless base stations among the plurality of coordinated wireless base stations.

17. The wireless terminal as described in claim 16, wherein, The aforementioned channel estimation unit separates the aforementioned reference signal based on the codebook determined by the aforementioned multiple coordinated wireless base stations.

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