Communication device, control method, and program

Abstract

To allow appropriate control to be executed depending on situations in systems in which cooperative communication can be used.SOLUTION: A communication device for communicating wirelessly with an opposite device determines whether or not to execute null steering to reduce effects of interference between communication between the communication device and the opposite device and communication of another communication device based on information related to communication quality between the other communication device and the opposite device, and controls the communication based on determination results.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to communication control technology in a wireless communication system capable of using cooperative communication.

Background Art

[0002] With the increase in the amount of data communicated in recent years, the development of communication technologies such as wireless LAN (Local Area Network) has been promoted. As the main communication standards for wireless LAN, the IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard series is known. The IEEE 802.11 standard series includes standards such as IEEE 802.11a / b / g / n / ac / ax. For example, in the IEEE 802.11ac standard and the IEEE 802.11ax standard, advanced communication technologies using MIMO (Multi-Input Multi-Output) have been standardized.

[0003] Currently, for further improvement of communication performance, a Task Group for formulating a standard called IEEE 802.11be has been established as a successor standard to IEEE 802.11ax. As a system throughput improvement technology in the IEEE 802.11be standard, a Multi-AP Coordination configuration in which a plurality of access points (APs) cooperate to communicate is being considered.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 describes a wireless LAN compliant with the IEEE 802.11 standard in which multiple access points (APs) and stations (STAs) communicate while reducing interference between devices using MIMO-based coordinated beamforming. In such a system, for example, to reduce interference between the first AP and its communication partner STA, the second AP can control the signals transmitted from its multiple antennas so that the antenna gain in the direction of the STA becomes zero or a very small value. This prevents the signal transmitted from the second AP from reaching the STA with sufficient power, and also prevents the second AP from receiving the signal transmitted from the STA with sufficient power. This type of antenna control is called null steering. While null steering can suppress interference with specific devices, using it even when interference conditions are not severe may result in insufficient performance, such as communication speed. [Means for solving the problem]

[0006] This invention provides a technology for performing appropriate control in a system that can utilize cooperative communication, depending on the situation.

[0007] A communication device according to one aspect of the present invention is a communication device that operates as an access point, and communicates with a first station in a first network managed by the communication device, and includes a first acquisition means for acquiring first channel information relating to a first channel state that the first station feeds back based on a Null Data packet (NDP) transmitted by the communication device, The first station provides feedback based on the NDP transmitted by other access points. Regarding channel status Second channel Information The aforementioned communication device The signal to acquire To the aforementioned other access point The means of transmission, The aforementioned The first station provides feedback based on the NDP transmitted by other access points. The aforementioned Regarding the second channel state The aforementionedThe system includes a second acquisition means for acquiring second channel information, a determination means for determining whether to perform null steering to reduce the effects of interference between the first communication between the communication device and the first station and the second communication between the other access point and the second station in the second network managed by the other access point, based on the second channel information, and a control means for performing downlink communication to the first station based on the first channel information and the second channel information when it is determined that null steering should be performed, wherein the communication device transmits an NDP to acquire the first channel information, and the other access point transmits an NDP to acquire the second channel information, in sequence. [Effects of the Invention]

[0008] According to the present invention, in a system capable of cooperative communication, appropriate control can be performed depending on the situation. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a system configuration. [Figure 2] This is a diagram showing an example of a communication device configuration. [Figure 3] This figure shows an example of the functional configuration of a communication device. [Figure 4] This diagram shows an example of the processing flow performed by a communication device. [Figure 5] This diagram shows an example of the processing flow executed by the system. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] (System Configuration) Figure 1 shows an example configuration of a wireless communication system according to this embodiment. This wireless communication system, in one example, includes wireless LAN AP102, AP105, STA103, and STA106 compliant with the IEEE 802.11 standard series (IEEE 802.11a / b / g / n / ac / ax / be standards, etc.). AP is an abbreviation for wireless LAN access point, and STA is an abbreviation for wireless LAN station. For the sake of simplicity, two APs and two STAs are shown here, but of course, there may be three or more of these communication devices, or there may be only one.

[0012] AP102 and AP105 may be configured to communicate with each other, for example, via a backhaul 100. The backhaul 100 may be configured as a wired communication line such as Ethernet® or a telephone line. Alternatively, the backhaul 100 may be configured as a wireless communication line such as LTE (Long Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access). Furthermore, AP102 and AP105 may communicate with each other via wireless communication compliant with the IEEE 802.11 standard series, either without communicating via a separately configured backhaul 100 or in addition to this. In this case, the wireless channel used between AP102 and AP105 may be the same as or different from the wireless channel used for communication between AP102 or AP105 and STA103 or STA106.

[0013] AP102 configures and manages the first network 101 and can communicate with STAs (or other APs) participating in this first network 101. AP105 also configures and manages the second network 104 and can communicate with STAs participating in this second network 104. AP102 and AP105 have a Multi-AP Coordination function. The Multi-AP Coordination function is a function that allows APs to communicate with connected STAs in cooperation with other APs. For example, by AP102 coordinating with AP105 to communicate with STA103 and STA106, AP102 can achieve faster communication and improved communication stability compared to when AP102 communicates with these STAs alone. Communication stability is evaluated by indicators such as whether the signal-to-noise ratio (SNR) reaches a predetermined level, whether the interference power level is lower than a predetermined level, whether the delay and jitter are less than predetermined values, and combinations of these indicators and the magnitude of their fluctuations. In the following, the Multi-AP Coordination function may be referred to as the cooperative communication function.

[0014] The cooperative communication function includes, for example, a communication function using the null steering method. In this null steering method, for example, when AP102 communicates with STA103 and AP105 communicates in parallel with STA106, AP102 uses antenna control to sufficiently reduce its antenna gain in the direction of STA106 (e.g., to zero). Similarly, AP105 uses antenna control to sufficiently reduce its antenna gain in the direction of STA103 (e.g., to zero). Hereafter, this process of sufficiently reducing the antenna gain in a predetermined direction may be referred to as forming a null in that predetermined direction. The method in which AP102 and AP105 cooperate to use the null steering method may be called Coordinated null steering. Furthermore, this method can also be called Coordinated Beamforming (BF) because it performs beamforming to appropriately set the null point of the beam radiated from each AP. In addition, this method may be called Coordinated BF and Nulling. Antenna control for null steering is performed by varying the phase (and possibly amplitude) of the radio signals transmitted by multiple antennas of the AP, but since the specific method is well known, a detailed explanation will be omitted. This makes it possible to prevent interference between communication between AP102 and STA103 and between AP105 and STA106. The cooperative communication function may also include a function that improves the reception quality of radio signals at STA103 and STA106 and provides high-speed wireless communication by controlling the radio signals transmitted from the antennas of AP102 and AP105, respectively. In this embodiment, null steering is used as the cooperative communication function, and other cooperative communication functions are not used.

[0015] STA103 and STA106 are configured to establish a connection with, for example, AP102 or AP105 and perform wireless communication. Note that these STAs can establish a connection with AP102 and also establish a connection with AP105 in parallel, and can communicate in parallel with these APs when these APs cooperate to communicate.

[0016] When using a method to reduce the impact of interference as a cooperative communication function, the performance of communication such as throughput may decrease. For example, when an AP uses null steering, as a result of forming a null for interference suppression, the antenna gain with respect to the direction of the communication partner STA may decrease. Therefore, in this embodiment, the AP is made not to use null steering unnecessarily, so as to improve the communication performance of the entire system. Hereinafter, a configuration example of a device that executes such processing and an example of the processing flow will be described.

[0017] (Configuration of the device) FIG. 2 shows a hardware configuration example of a communication device (AP and STA). As an example of its hardware configuration, the communication device has a storage unit 201, a control unit 202, a functional unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0018] The storage unit 201 is composed of both a ROM (read-only memory) and a RAM (random access memory), or either one of them, and stores programs for performing various operations described later and various information such as communication parameters for wireless communication. Note that, as the storage unit 201, in addition to memories such as ROM and RAM, storage media such as a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, and a DVD may be used.

[0019] The control unit 202 is composed of, for example, one or more processors such as a CPU or MPU, an ASIC (Application-Specific Integrated Circuit), a DSP (Digital Signal Processor), or an FPGA (Field-Programmable Gate Array). Here, CPU is an acronym for Central Processing Unit, and MPU is an acronym for Micro Processing Unit. The control unit 202 controls the entire device by executing a program stored in the memory unit 201. Alternatively, the control unit 202 may control the entire device in cooperation with the OS (Operating System) and the program stored in the memory unit 201.

[0020] Furthermore, the control unit 202 controls the functional unit 203 to execute predetermined processes such as AP functions, STA functions, imaging, printing, and projection. The functional unit 203 is hardware that enables the device to execute predetermined processes. For example, if the communication device is an AP, the functional unit 203 is configured to execute AP functions including cooperative communication functions. If the communication device is an STA, the functional unit 203 establishes a connection with the AP and performs communication. Also, for example, if the communication device is a camera, the functional unit 203 is the imaging unit and performs imaging processing. Also, for example, if the communication device is a printer, the functional unit 203 is the printing unit and performs printing processing. Also, for example, if the communication device is a projector, the functional unit 203 is the projection unit and performs projection processing. The data processed by the functional unit 203 may be data stored in the storage unit 201, or data communicated with other APs or STAs via the communication unit 206, which will be described later.

[0021] The input unit 204 receives various operations from the user. The output unit 205 provides various outputs to the user. Here, the output from the output unit 205 includes at least one of the following: display on the screen, audio output from a speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be implemented in a single module, such as a touch panel.

[0022] The communication unit 206 controls wireless communication compliant with the IEEE 802.11 standard series and IP communication. The communication unit 206 is a so-called wireless chip and may include one or more processors and memory itself. In this embodiment, the communication unit 206 can perform processing compliant with at least the IEEE 802.11be standard. The communication unit 206 also controls the antenna 207 to transmit and receive wireless signals for wireless communication. The communication device communicates content such as image data, document data, and video data with other communication devices via the communication unit 206. The antenna 207 is, for example, an antenna capable of transmitting and receiving at least one of the sub-GHz band, 2.4GHz band, 5GHz band, and 6GHz band. The frequency bands (and their combinations) that the antenna 207 can handle are not particularly limited. The antenna 207 may be a single antenna or a set of two or more antennas for MIMO (Multi-Input and Multi-Output) transmission and reception. For example, antenna 207 may be configured to include 16 antenna elements to support MIMO communication with 16 spatial streams as per the IEEE 802.11be standard.

[0023] Figure 3 shows an example of the functional configuration of APs (AP102 and AP105). The AP includes, for example, a wireless LAN control unit 301, a UI control unit 302, a storage unit 303, a method selection unit 304, a Single-AP control unit 305, and a null steering control unit 306. These functional units are realized when the AP's control unit 202 executes a program containing instructions that define the operation of each functional unit stored in the storage unit 201. Some or all of the functional units shown below may be realized by dedicated hardware.

[0024] The wireless LAN control unit 301 is configured to include circuits for sending and receiving wireless signals with other devices (e.g., other APs or STAs) and programs for controlling them, compliant with, for example, the IEEE 802.11 standard series. The wireless LAN control unit 301 generates and transmits frames according to the procedures specified in the IEEE 802.11 standard series, and performs communication control such as receiving wireless frames from other devices and extracting information. The UI control unit 302 is configured to include hardware related to the user interface (UI), such as a touch panel or buttons for accepting operations on the AP by the AP user (not shown), and programs for controlling them. The UI control unit 302 also has functions for presenting information to the user, such as displaying images or outputting audio. The storage unit 303 is configured to include functions for storing programs executed by the AP and various data.

[0025] The method selection unit 304 selects whether or not to use the cooperative communication function based on factors such as whether or not there are surrounding APs, the capabilities of the surrounding APs, the connection status between the surrounding APs and the STA, and a value corresponding to the distance between the surrounding APs and the communication partner device of the device itself. For example, the method selection unit 304 decides whether to use the null steering method, which is a cooperative communication function, or the Single-AP method, which is a non-cooperative communication function. This method selection method will be described later. When the Single-AP method is selected by the method selection unit 304, the Single-AP control unit 305 performs communication control to connect to the STA alone without using the cooperative communication function, that is, without cooperating with other APs. For example, the Single-AP control unit 305 can control the multiple antennas of the AP so that the antenna gain in the direction of the communication partner STA is sufficiently large without considering interference. This can improve the communication performance when cooperative communication is not performed. When the null steering method is selected by the method selection unit 304, the null steering control unit 306 performs communication by cooperating with other APs and performing control to reduce interference. For example, the null steering control unit 306 controls the antenna to form a null in the direction of the STA of another AP's communication partner when it is possible to interfere with that STA, and performs cooperative communication control to communicate in parallel with the communication of that other AP. Furthermore, if the communication of another AP may interfere with the STA of the device's communication partner, the null steering control unit 306 performs cooperative communication control to cause the other AP to perform null steering.

[0026] Since STA is a communication device that functions as a general wireless LAN station compliant with the IEEE 802.11 standard series, we will omit a detailed explanation of its functions here.

[0027] (Process flow) Next, using Figure 4, an example of the process flow for determining whether the APs (AP102 and AP105) use the Single-AP method or the null steering method will be explained. This process is implemented, for example, by the AP's control unit 202 executing a program stored in the memory unit 201. The AP can perform this selection process, for example, when configuring the network such as when powering on, or at any time while the network is in operation.

[0028] In this process, the AP first searches for APs in the vicinity (S401). The AP searches for APs in the vicinity, for example, by receiving Beacons transmitted from other APs via wireless functionality, or by receiving broadcast / multicast signals from other APs via a wired connection. The AP may transmit Beacons wirelessly or broadcast / multicast signals via a wired connection to notify other APs in the vicinity of its presence. Alternatively, the AP may identify the presence of a specific other AP in the vicinity by sending an inquiry frame to that AP and receiving a response to that frame. In this embodiment, AP102 and AP105 recognize each other as neighboring APs.

[0029] If the AP detects a nearby AP (YES in S401), it determines whether that nearby AP has cooperative communication capabilities (S402). This determination may be based, for example, on capability information indicating whether or not the AP supports cooperative communication capabilities, which may be included in the Beacon or response signals to query signals received wirelessly from nearby APs, or in signals received via wired connections. Alternatively, this determination may be based on other information, such as the version of the standard that the nearby APs comply with. If there are no nearby APs with cooperative communication capabilities (NO in S401, NO in S402), the AP selects the Single-AP method to use, which communicates with the STA (Station) alone without performing cooperative communication control with other APs (S405).

[0030] On the other hand, if the AP determines that the surrounding APs have cooperative communication capabilities (YES in S402), it then determines whether the distance between its communication partner STA and the surrounding APs with cooperative communication capabilities is sufficiently large (S403). If the AP determines that the distance between the communication partner STA and the surrounding APs is not large (NO in S403), it selects the null steering method as the method to use (S404). On the other hand, if the AP determines that the distance between the communication partner STA and the surrounding APs is large (YES in S403), it selects the Single-AP method as the method to use (S405). In other words, when the distance between the communication partner STA and the surrounding APs is sufficiently large, interference from the surrounding APs to the communication partner STA is not considered when transmitting the wireless signal, as the effect of interference is sufficiently suppressed by the distance attenuation of radio waves. For this reason, in this case there is no need to cooperate with the surrounding APs, so the Single-AP method is selected. On the other hand, when the distance between the communication partner STA and surrounding APs is relatively close, the effects of interference are expected to be significant. Therefore, the null steering method is selected to reduce the effects of such interference. In this case, the AP causes other APs to perform null steering, thereby reducing the interference it causes to the communication partner device. The AP may also perform null steering on its own device based on a request from another AP, or based on the distance to the communication partner device of another AP, etc.

[0031] Whether the distance between the communicating STA and the surrounding AP is too great is determined, for example, based on the RSSI (Received Signal Strength Indicator) when the communicating STA receives beacons from the surrounding APs. For example, the STA measures the received strength of the surrounding AP beacons and notifies the AP of the RSSI value. If the notified RSSI is above a predetermined value, the AP determines that the distance between the communicating STA and the surrounding AP is sufficiently close, and if the RSSI is below the predetermined value, it may determine that the distance between the communicating STA and the surrounding AP is too great.

[0032] In addition, an AP may decide whether or not to perform cooperative communication, including null steering, based on various information related to the distance between its communication partner device and other APs. For example, an AP may assume that the communication partner's STA is located near a nearby AP and determine whether the distance between its own device and the nearby AP is large, thereby determining whether the distance between the communication partner's STA and the nearby AP is large. That is, if the distance between its own device and the nearby AP is large, the AP estimates that the distance between the communication partner's STA and the nearby AP is also likely to be large. Conversely, if the distance between its own device and the nearby AP is small, the AP may estimate that the distance between the communication partner's STA and the nearby AP is also likely to be small. For this reason, the AP measures the received strength of beacons transmitted from nearby APs. Then, if this received strength falls below a predetermined value, the AP determines that the distance between its own device and the nearby AP is large, and therefore, the distance between the communication partner's STA and the nearby AP is also large. Furthermore, if the reception strength of beacons from surrounding APs is above a predetermined value, the AP determines that the distance between its own device and the surrounding APs is short, and therefore, the distance between the communication partner STA and the surrounding APs is also short.

[0033] Furthermore, if the communication partner STA and a nearby AP are communicating, the AP may use channel status information (CSI) regarding the communication between the communication partner STA and the nearby AP to make the above determination. For example, if the SNR value included in the CSI is below a predetermined value, the AP estimates that there is a high probability that the distance between the communication partner STA and the nearby AP is large. Conversely, if the SNR value included in the CSI is above a predetermined value, the AP estimates that there is a high probability that the distance between the communication partner STA and the nearby AP is small. In this case, the AP may make this determination by obtaining CSI information from the nearby AP or the communication partner STA. CSI information can be obtained, for example, by the AP sending a request signal to at least one of the nearby AP and the communication partner STA. Also, the signal received when the AP discovers a nearby AP in S401 may include CSI information between that nearby AP and the STA that is communicating (connected).

[0034] Furthermore, if the communication partner's STA and the surrounding AP each have positioning functions such as GPS (Global Positioning Satellite), the AP may determine whether the communication partner's STA and the surrounding AP are far apart based on the positioning results. In this case, the AP may perform this determination by obtaining positioning information from the communication partner's STA and the surrounding APs, for example. For example, if the surrounding AP is communicating (connected) with the communication partner's STA, the AP may obtain not only the positioning results of the surrounding AP but also the positioning results of the communication partner's STA from the surrounding AP. In addition, it may be determined in S403 whether the distance between the communication partner's STA and the surrounding AP is greater than or equal to a predetermined distance, and this predetermined distance may be determined, for example, by the frequency band used. That is, since distance attenuation is expected to differ depending on the frequency used, the predetermined distance that serves as the determination criterion may be appropriately determined according to the frequency band used.

[0035] Furthermore, the determination in S403 may be made based on information that combines multiple types of distance-related information, as described above.

[0036] Next, an example of the processing flow performed in the wireless communication system according to this embodiment will be explained using Figure 5. In the following example, AP102 and AP105 are connected to / communicating with STA103 and STA106, respectively, and each AP acquires the CSI with each STA and determines the method to use based on that CSI.

[0037] First, AP102 checks the channel status with STA103 and STA106 (S501, S503), and AP105 also checks the channel status with STA103 and STA106 (S502, S504). For example, AP102 and AP105 send a Null Data Packet (NDP) that does not contain data, and STA103 and STA106 measure the channel status based on the NDP from these APs. Then, STA103 and STA106 feed back the CSI to the AP that sent the NDP based on the measurement results. After that, AP102 and AP105 exchange and share the CSIs they each acquired (S505). Through this information exchange, AP102 and AP105 can also perform DownLink MultiUser (DL MU) operations from AP to multiple STAs in parallel. In addition, when acquiring CSI, the channel status when a signal is sent from STA to AP may also be checked. This information may be used when performing Uplink MultiUser (UL MU) operation from multiple STAs to APs. Here, AP102 and AP105 are assumed to have selected the null steering method. Note that the processing in S501 to S505 is executed periodically, for example.

[0038] Next, AP102 sends a null steering trigger frame (TF) to AP105. This TF is used to determine the timing of the next transmission operation. Here, it may be decided by negotiation whether AP102 or AP105 will be responsible for sending this TF, and this negotiation may take place, for example, when sharing the CSI of S505.

[0039] AP102 and AP105 transmit data frames after a SIFS (Short Inter Frame Space) time has elapsed from the timing of TF transmission and reception, or after another predetermined time has elapsed. Here, AP102 transmits a data frame to STA103 while performing null steering to point the null toward STA106 (S507). AP105 also transmits a data frame to STA106 while performing null steering to point the null toward STA103 (S508). As a result, communication between AP102 and STA103 and communication between AP105 and STA106 can be performed in parallel without mutual interference. Note that if the SNR in the CSI between AP102 and STA106 is sufficiently small and the SNR in the CSI between AP105 and STA103 is large, only AP105 may perform null steering. Similarly, if the SNR in the CSI between AP102 and STA106 is sufficiently large, and the SNR in the CSI between AP105 and STA103 is small, only AP102 may perform null steering. In other words, in these cases, if the SNR with the STA that is not the communication partner is sufficiently small, and interference is considered to be small even without null steering, the AP does not need to use null steering. This means that in environments where interference can be sufficiently suppressed, the reduction in throughput caused by using null steering can be suppressed by not using it.

[0040] AP102 may also transmit TF to AP105 (S509) and then transmit a data frame to STA106 while performing null steering to point the null toward STA103 (S510). Alternatively, AP105 may transmit a data frame to STA103 while performing null steering to point the null toward STA106 (S511).

[0041] This null steering method allows communication while suppressing interference. However, when the distance between an AP and the STA of another AP is large, the interference between this other AP and this STA is expected to be of sufficiently low power. Therefore, in this embodiment, when the distance between the interfering AP and the interfered STA is large, communication with the STA is performed without coordinating with other surrounding APs. That is, when it is not necessary to coordinate with surrounding APs and have them perform interference suppression control, communication with the STA is performed independently without performing coordinated communication. This makes it possible to improve communication efficiency without attempting to mitigate interference, which may reduce communication efficiency in environments where interference is unlikely to occur. Also, when the distance between the interfering AP and the interfered STA is small, communication is performed while reducing interference by coordinating with other surrounding APs and having them perform interference suppression control, thereby tolerating a decrease in communication efficiency. In this way, according to this embodiment, it is possible to perform efficient communication while considering the distance between communication devices.

[0042] In this embodiment, the AP decided whether to perform cooperative communication that causes the other AP to perform null steering, based on the distance between the AP's communication partner device's STA and the other AP. From the perspective of the other AP, the AP may decide whether to perform cooperative communication with the other AP in a form that causes its own device to perform null steering, based on the distance between the other AP's communication partner device's STA and the AP's own device. The AP may also decide whether to perform null steering based on the distance between the other AP's communication partner device's STA and the AP's own device. When the first AP causes the second AP to perform null steering, for example, when sharing the channel state in S505, an instruction may be sent from the first AP to the second AP. Similarly, when the second AP causes the first AP to perform null steering, for example, when sharing the channel state in S505, an instruction may be sent from the second AP to the first AP. This ensures that null steering is performed only when necessary, improving communication efficiency. Furthermore, for example, an AP that transmits a TF may instruct an AP that receives the TF to use null steering in that TF, while the AP transmitting the TF may independently decide whether or not to use null steering itself. In other words, when communicating in cooperation with other APs, an AP may have other APs perform a predetermined process (e.g., null steering) while communicating itself without receiving instructions from other APs.

[0043] The above example shows an AP compliant with the IEEE 802.11 standard series coordinating with other APs to transmit signals, but it is not limited to this. For example, when multiple STAs transmit signals in parallel, an AP may coordinate with other APs to perform receive control in a similar manner to the process described above. For example, an AP may cause the other AP to perform receive antenna control by pointing a null towards the STA when the distance between the AP's communication partner STA and the other AP is short. In this case, for example, the AP coordinates by causing the other AP's communication partner STA and the AP's communication partner STA to transmit signals in parallel, and at that time, the other AP performs receive antenna control. Furthermore, the above control may also be performed when cooperative communication occurs between STAs. Moreover, not limited to wireless LANs, when multiple communication devices communicate with their respective communication partner devices, a communication device may decide whether or not to perform cooperative communication with other communication devices based on the distance between its communication partner device and the other communication device. This prevents a decrease in communication efficiency caused by unnecessarily performing coordinated control when the interference between communication devices and communication by other communication devices is sufficiently small and coordinated control is not required.

[0044] Furthermore, while the above-described embodiment explains the use of transmitting antenna control, it is not limited to this. For example, an AP may prevent interference between its own communication and the communication of other APs by performing predetermined coding (e.g., Dirty Paper Coding (DPC) or similar coding). For example, an AP may identify what data other APs transmit, predict in advance what waveform the signal transmitted from other APs will be received as by the communication partner device, and transmit a signal obtained by subtracting that waveform component from the signal to be transmitted from its own device. In this way, the communication partner device can receive a waveform in which the waveform received from the AP is added to the interference wave from other APs, and the signal that the AP should transmit is reconstructed. In this method, the AP can suppress the effects of interference by obtaining information on the data to be transmitted and the estimated channel value between the AP's communication partner STA and the other AP in advance from other APs, and by coordinating the signal transmission timing with each other. On the other hand, in environments where the distance between the AP's communication partner STA and the other AP is large, it is expected that errors in the channel estimate, etc. will increase, and using the above method in such an environment may actually degrade the communication performance. Therefore, whether or not to perform coordinated communication that works to reduce the effects of such interference may be determined based on information related to the distance between the AP's communication partner and other APs. This makes it possible to prevent degradation of communication performance by preventing the pre-subtraction of interference waveforms containing relatively large errors in environments where the effects of interference are not sufficiently strong and the interference waveform is buried in noise.

[0045] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0046] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0047] 201: Memory unit, 202: Control unit, 206: Communication unit, 207: Antenna, 301: Wireless LAN control unit, 304: Method determination unit, 305: Single-AP control unit, 306: Null steering control unit

Claims

1. A communication device that operates as an access point, the communication device that communicates with a first station in a first network managed by the communication device, A first acquisition means for acquiring first channel information relating to the first channel state that the first station feeds back based on the Null Data Packet (NDP) transmitted by the communication device, A transmitting means that transmits to the other access point a signal for the communication device to acquire second channel information relating to a second channel state that the first station feeds back based on an NDP transmitted by the other access point, A second acquisition means for acquiring the second channel information relating to the second channel state that the first station feeds back based on the NDP transmitted by the other access point, A determination means for determining whether to perform null steering to reduce the effects of interference between the first communication between the communication device and the first station and the second communication between the other access point and the second station in the second network managed by the other access point, based on the second channel information, A control means that performs control to perform downlink communication to the first station based on the first channel information and the second channel information when it is determined that null steering should be performed, It has, A communication device characterized in that the following steps are performed sequentially: the communication device transmits an NDP to obtain the first channel information, and the other access point transmits an NDP to obtain the second channel information.

2. The communication device according to claim 1, characterized in that the second channel information includes SNR information of the signal between the first station and the other access point.

3. The communication device according to claim 1, characterized in that the control means performs control to perform null steering to reduce interference to the second station when it is determined that null steering should be performed.

4. The communication device according to claim 1, characterized in that, when the control means determines that null steering should be performed, it controls the other access point to perform null steering to reduce interference to the first station.

5. The communication device according to any one of claims 1 to 4, characterized in that the communication device and the other access point are access points compliant with the IEEE 802.11 standard series.

6. A communication device operating as an access point, wherein the communication device communicates with a first station in a first network managed by the communication device, and the control method is performed by the communication device. The first station receives feedback of first channel information relating to the first channel state based on the Null Data Packet (NDP) transmitted by the communication device, The first station transmits a signal to the other access point for the communication device to acquire second channel information relating to the second channel state, which is fed back by the first station based on the NDP transmitted by the other access point. The first station receives feedback regarding the second channel state based on the NDP transmitted by the other access point, and the second channel information is obtained. Based on the second channel information, it is determined whether or not to perform null steering to reduce the effects of interference between the first communication between the communication device and the first station and the second communication between the other access point and the second station in the second network managed by the other access point, When it is determined that null steering should be performed, control is performed to perform downlink communication to the first station based on the first channel information and the second channel information. Includes, A control method characterized in that the following steps are performed sequentially: the communication device transmits an NDP to acquire the first channel information, and the other access point transmits an NDP to acquire the second channel information.

7. A program for causing a computer to function as a communication device according to any one of claims 1 to 5.

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