System, control method thereof, control device, and program

Abstract

To allow joint beamforming (JB) to be used efficiently.SOLUTION: A system including a plurality of access points includes: acquisition means for acquiring received signal strength at a station of signals transmitted from the plurality of access points; and determination means for determining information indicating whether the plurality of access points communicate with the station in joint beamforming. The determination means determines not to use joint beamforming for communication between the plurality of access points and the station if the received signal strength at the station of the signal transmitted from any one of the plurality of access points exceeds a first threshold.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to control of communications using joint beamforming. [Background technology]

[0002] The IEEE802.11 series of standards is known as one of the communication standards for wireless local area networks (WLANs). Patent Document 1 proposes a technology that can ensure high frequency utilization efficiency while suppressing interference in communications using IEEE802.11ax.

[0003] To further improve throughput, the IEEE established the Extreme High Throughput (EHT) Study Group (SG) in 2018. The EHTSG has proposed a technology called Joint Beamforming (JB). JB is a technology that aims to improve the signal reach by coordinating the operation of multiple access points (APs). Specifically, it transmits the same data at the same time and on the same frequency channel while adjusting the phase for the same station (STA). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-50133 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, when multiple APs are installed in different locations, the received strength of radio waves from each AP observed at a certain STA will differ. If the received strength of radio waves from only one AP is relatively strong, the use of JB cannot be expected to improve the reach, and there is a problem that the resources of the entire system will be wasted.

[0006] The present invention has been made in view of the above problems, and aims to enable efficient use of joint beamforming (JB). [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the system according to the present invention has the following configuration: That is, a system including a plurality of access points, Received signal strength at a station of signals transmitted from multiple access points Received Signal Strength Indicator (RSSI) and an acquisition means for acquiring the a determination means for determining information indicating whether or not the plurality of access points will communicate with the station using joint beamforming, which is a communication method in which the plurality of access points transmit the same data to the station on the same frequency channel at the same time; and The determining means determines whether the station receives a signal transmitted from any one of the plurality of access points. RSSI determines not to use the joint beamforming for communication between the plurality of access points and the station when the first threshold exceeds a first threshold. [Effects of the Invention]

[0008] According to the present invention, joint beamforming (JB) can be efficiently utilized. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a diagram illustrating the overall configuration of a wireless network system. [Figure 2] FIG. 2 is a diagram illustrating the hardware configuration of each device. [Figure 3] 10 is a flowchart of the operation in the STA. [Figure 4] 10 is a flowchart of the operation of the AP control device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] (First embodiment) A first embodiment of a control device according to the present invention will be described below by taking as an example a communication system configured to be able to use joint beamforming (JB).

[0012] <System configuration and device configuration> Fig. 1 is a diagram showing the overall configuration of a wireless network system including an AP control device 101, which is a control device according to the first embodiment. STA 104 is a communication device that plays the role of a station (STA) that participates in the wireless network. APs 102 and 103 are communication devices that play the role of access points (APs) that build the wireless network. Fig. 1 exemplifies a wireless network configured with two APs and one STA, but the number of APs and STAs is not limited to this.

[0013] Each communication device supports communication using joint beamforming (hereinafter referred to as JB) and can communicate via a wireless network. Each communication device can communicate in the 2.4 GHz, 5 GHz, and 6 GHz frequency bands. Each communication device can also communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz.

[0014] Each communication device can perform OFDMA communication to realize multi-user (MU) communication, which multiplexes signals from multiple users. In OFDMA communication, a portion of the divided frequency band (RU: Resource Unit) is assigned to each STA so that they do not overlap, and the carrier waves of each STA are orthogonal. This allows an AP to communicate with multiple STAs in parallel.

[0015] As described above, each communication device is configured to be able to use JB. That is, two APs 102 and 103 can cooperate and communicate with a STA 104. The AP control device 101 controls the APs 102 and 103, as will be described later, and controls communication using JB. In FIG. 1, an example is shown in which the APs 102 and 103 are communicatively connected to the AP control device 101 via a backhaul line so that they can communicate with each other for cooperative operation. However, the functions of the AP control device may be configured to be incorporated into any one of the multiple APs.

[0016] Each communication device may be compatible with the IEEE 802.11 series standards (802.11a / b / g / n / ac / ax / be). In addition to the IEEE 802.11 series standards, it may also be compatible with other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, and MBOA. Here, NFC stands for Near Field Communication, UWB stands for Ultra Wide Band, and MBOA stands for Multi Band OFDM Alliance. UWB includes Wireless USB, Wireless 1394, WiNET, and the like. It may also be compatible with a wired communication standard such as a wired LAN.

[0017] Specific examples of the APs 102 and 103 include, but are not limited to, a wireless LAN router and a PC. The APs 102 and 103 may also be wireless chips capable of performing wireless communication in accordance with the wireless LAN standard.

[0018] Specific examples of the STA 104 include, but are not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, etc. The STA 104 may also be a wireless chip capable of performing wireless communication in accordance with the wireless LAN standard.

[0019] 2 is a diagram showing the hardware configuration of each device. That is, the hardware configuration of the AP control device 101, APs 102 and 103, and STA 104 is shown as an example. Each device includes a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207. Note that the AP control device 101 may be configured to have only a communication unit 206 for wired communication without the antenna 207. Also, the APs 102 and 103 may be configured to have a communication unit 206 that supports both wired communication and wireless communication.

[0020] The storage unit 201 is configured with memories such as ROM and RAM, and stores various information such as computer programs for performing various operations described below and communication parameters for wireless communication. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. Note that, in addition to memories such as ROM and RAM, storage media such as flexible disks, hard disks, optical disks (CDs, DVDs, etc.), magneto-optical disks, magnetic tapes, and non-volatile memory cards may also be used as the storage unit 201. Furthermore, the storage unit 201 may be configured with multiple memories.

[0021] The control unit 202 is configured with one or more processors, such as a CPU or MPU, and controls the entire device by executing a computer program stored in the storage unit 201. Note that CPU stands for Central Processing Unit, and MPU stands for Micro Processing Unit. The control unit 202 may control the entire device in cooperation with the computer program stored in the storage unit 201 and an OS (Operating System). The control unit 202 may also generate data and signals to be transmitted in communication with other devices. The control unit 202 may also include multiple processors, such as a multi-core processor, and the entire device may be controlled by the multiple processors.

[0022] The functional unit 203 is hardware that enables the device to execute predetermined processes. The functional unit 203 realizes functions specific to each device through control by the control unit 202. For example, the STA 104 executes processes such as wireless communication, imaging, printing, and projection. The APs 102 and 103 also execute processes for transferring received data and for setting up communication, which will be described later. The AP control device 101 executes processes related to setting up communication in the APs 102 and 103.

[0023] The input unit 204 receives various operations from the user. The output unit 205 performs various outputs to the user via a monitor screen or a speaker. Here, the output by the output unit 205 may be display on the monitor screen, voice output by the speaker, vibration output, etc. Note that both the input unit 204 and the output unit 205 may be realized by one module like a touch panel. Also, the input unit 204 and the output unit 205 may be integrated with the device or separate from it, respectively.

[0024] The communication unit 206 communicates with other devices. The data to be communicated includes user data (such as image data, document data, video data, etc.) and control data (data related to communication settings). As described above, in the AP control device 101, it may have only the communication unit 206 for wired communication. Also, in the APs 102 and 103, they may have a communication unit 206 corresponding to both wired communication and wireless communication. The communication unit 206 for wireless communication controls the antenna 207 to transmit and receive wireless signals for wireless communication generated by the control unit 202. Note that if the device supports communication standards such as NFC standard or Bluetooth standard in addition to the wireless LAN standard, it may perform control of wireless communication compliant with these communication standards. Also, if the device can execute wireless communication compliant with multiple communication standards, it may have a configuration with separate communication units 206 and antennas 207 corresponding to each communication standard.

[0025] In this embodiment, it is assumed that the STA 104 is configured to be connectable to a wireless network constituted by either or both of the APs 102 and 103. Also, when the STA 104 is connected to a plurality of APs, it is assumed that the AP control device 101 controls each AP to perform the operation of JB.

[0026] <Problems of Communication Using JB> JB is a technology that aims to improve the signal reach by having multiple access points (APs) transmit the same data at the same time and on the same frequency channel while adjusting the phase to the same station (STA). Each of the multiple APs can transmit using the maximum transmission power regulated by each country's radio wave regulations. Therefore, by transmitting in coordination with other APs (by adjusting the phase), the radiation intensity in a specific direction can be increased beyond what a single AP can output. For example, if two APs operate in coordination, under ideal circumstances, the signal strength can be expected to increase by up to approximately 6 dB, approximately doubling the reach. However, depending on the relative positions of the multiple APs and STAs, JB may not be used effectively, and the reach may not be extended.

[0027] For example, to actually improve signal strength by approximately 6 dB, the signals from each AP must reach the target STA with the same strength. If the signal strength from each AP differs by 10 dB, JB can only be expected to improve signal strength by about 1 dB. One method to equalize the signal strengths would be to lower the signal strength of the AP with the stronger signal, but this would have limited effect compared to when the AP with the stronger signal sends a signal to the STA alone. Therefore, if the signal strengths from each AP differ significantly, it is considered more efficient in terms of resource consumption not to implement JB.

[0028] Also, if the STA is close to one of the APs and is in a position where the signal-to-noise ratio (SNR) is sufficiently secured, the maximum effective communication speed may be achieved without JB. In such cases, it is better not to implement JB.

[0029] An example of a situation in which the use of JB is effective is when APs 102 and 103 are relatively close to each other, and APs 102 and 103 are far away from STA 104. Because STA 104 is far from both APs, it is unable to ensure a sufficient effective communication speed. On the other hand, because the difference between the distance from STA 104 to AP 102 and the distance from STA 104 to AP 103 is relatively small, the signal strength from each AP at STA 104 is approximately equal.

[0030] <Device Operation> Next, the operation of communication connection in this embodiment will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a flowchart of the operation in the STA 104, and Fig. 4 is a flowchart of the operation in the AP control device 101.

[0031] In S301, the STA 104 connects to the wireless network configured by the AP control device 101. Specifically, the STA 104 connects to the wireless network formed by the AP 102 or the AP 103. Note that, in this example, the STA 104 is described as establishing a connection with one AP (AP 102). This enables the STA 104 to communicate with the AP control device 101 via the AP 102.

[0032] In S302, the STA 104 periodically measures a received signal strength indicator (RSSI) as reception information of signals from the AP 102 and the AP 103. For example, the STA 104 measures the RSSI of beacon signals transmitted from the AP 102 and the AP 103. Here, it is assumed that the RSSI of signals from one or more connectable APs (here, the AP 102 and the AP 103) is measured, but the STA 104 may also be configured to measure the RSSI of signals from other APs.

[0033] In S303, the STA 104 notifies the AP control device 101 of the RSSI measurement result. For example, the notification is made when it is detected that the beacon transmitted from the AP 102 contains information indicating that the AP is available for use by JB. The STA 104 may be configured to transmit the measurement result (RSSI notification) to the address of the AP control device 101 notified in advance. Alternatively, the STA 104 may be configured to transmit the RSSI notification to the currently connected AP 102, and the AP 102 may transfer the RSSI notification to the AP control device 101.

[0034] In S401, the AP control device 101 receives and acquires an RSSI notification, which is information received at the STA 104, from the STA 104, which is the communication partner. That is, the RSSI notification transmitted from the STA 104 in S303 is received via the AP 102, which has previously been connected to and communicated with the STA 104. Note that a beacon or the like contains, as an IP address, sender information indicating which AP the signal is from. Therefore, the STA 104 can know which AP the RSSI is between the STA 104 and the AP. Here, when the STA 104 notifies the AP control device 101 of which AP the RSSI is between the STA 104 and the AP.

[0035] In S402, the AP control device 101 determines the maximum RSSI from one or more RSSIs included in the received RSSI notification. It also determines whether the determined maximum RSSI is equal to or less than a predetermined threshold (equal to or less than the threshold RSSI) at which a predetermined communication speed can be achieved. Here, it is assumed that the threshold RSSI is set in advance in the AP control device 101. If the determined maximum RSSI exceeds the threshold RSSI (S402 → No), the process proceeds to S405, and if it is equal to or less than the threshold RSSI (S402 → Yes), the process proceeds to S403.

[0036] In S403, the AP control device 101 determines whether or not there is another AP in the received RSSI notification whose strength difference is within a predetermined range, using the maximum RSSI determined in S402 as a reference. Here, it is assumed that the predetermined range is set in advance in the AP control device 101. If there is another AP whose strength difference is within the predetermined range (S403 → Yes), the process proceeds to S404; if there is not another AP whose strength difference is within the predetermined range (S403 → No), the process proceeds to S405.

[0037] In S404, the AP control device 101 determines that JB is expected to improve communication speed and communication distance. Therefore, the AP control device 101 decides to use JB for communication with the STA 104, and controls each AP (here, AP 102 and AP 103) so that communication is performed via the APs. Specifically, the AP control device 101 notifies each AP to perform JB using multiple APs whose RSSI strength difference is within a predetermined range.

[0038] In S405, the AP control device 101 determines that JB cannot be expected to improve communication speed or communication distance. Therefore, the AP control device 101 decides not to use JB for communication with the STA 104, and notifies each AP to communicate via one AP (here, AP 102). In other words, if the process proceeds from S402 to S405, it is expected that a sufficient communication speed can be ensured without using JB, and further improvement in communication efficiency by JB is limited. Also, if the process proceeds from S403 to S405, it is because the improvement in communication efficiency by JB is limited with the combination of available APs.

[0039] In S304, the STA 104 waits for a signal from the AP control device 101 notifying it of a transition to JB. If it has been notified (Yes in S304), the process proceeds to S305, and if it has not been notified (No in S304), the process proceeds to S306. Here, the case where it has not been notified of a transition to JB includes the case where it has been notified of independent communication.

[0040] In S305, the STA 104 transitions to communication using JB. Specifically, the AP 102 and the AP 103 receive the transfer functions estimated by the AP control device 101 and start communication with the STA 104. To implement JB, it is necessary to calculate the transfer functions between each AP and the STA 104. To calculate the transfer functions, channel state information (CSI) between each AP and the STA 104 is required.

[0041] Therefore, prior to implementing JB, STA 104 transmits a sounding frame, which is a frame for calculating CSI. By receiving the sounding frame, AP 102 and AP 103 can calculate CSI between STA 104 and AP 103. Alternatively, AP 102 and AP 103 transmit a sounding frame. By receiving the sounding frame, STA 104 can calculate CSI between AP 102 and AP 103.

[0042] When AP 102 and AP 103 calculate CSI, AP 102 and AP 103 notify AP control device 101 of the calculated CSI. On the other hand, when STA 104 calculates CSI, STA 104 notifies AP control device 101 of the calculated CSI. This allows AP control device 101 to estimate transfer functions between each AP (AP 102 and AP 103) and STA 104, and AP control device 101 notifies each AP of the estimated transfer functions. AP 102 and AP 103 each start communication with STA 104 using the notified transfer functions. This realizes communication using JB.

[0043] In S306, the STA 104 communicates via one AP. Here, it is assumed that communication via the currently connected AP 102 is continued, but communication may be switched to communication via another AP designated by the AP control device 101.

[0044] As described above, according to this embodiment, the RSSI of signals transmitted from multiple APs is measured at the STA, and parameters for JB communication are determined based on the RSSI measurement results. This configuration makes it possible to achieve more efficient communication. Specifically, when the effect of using JB is limited, it is possible to suppress the consumption of resources in the entire system by controlling not to use JB. Furthermore, when using JB, it is possible to clearly determine the combination of APs that can maximize the effect.

[0045] Although this embodiment does not mention whether MIMO (Multiple-Input and Multiple-Output) is implemented, similar effects can be obtained by performing the same processing as in this embodiment even when MIMO is implemented. Both single-user (SU)-MIMO and multi-user (MU)-MIMO can be used as MIMO operations.

[0046] (Other Examples) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0047] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0048] 101 AP control device; 102, 103 Access point (AP); 104 Station (STA); 201 Memory unit; 202 Control unit; 203 Functional unit; 204 Input unit; 205 Output unit; 206 Communication unit; 207 Antenna

Claims

1. 1. A system including a plurality of access points, an acquiring means for acquiring a received signal strength indicator (RSSI) indicating a received signal strength at a station of signals transmitted from a plurality of access points; a determination means for determining information indicating whether or not the plurality of access points will communicate with the station using joint beamforming, which is a communication method in which the plurality of access points transmit the same data to the station on the same frequency channel at the same time; and The determination means determines not to use the joint beamforming for communication between the plurality of access points and the station when an RSSI at the station of a signal transmitted from any one of the plurality of access points exceeds a first threshold. A system characterized by:

2. When an RSSI at the station of a signal transmitted from any one of the plurality of access points does not exceed the first threshold, the decision means acquires an RSSI at the station of a signal transmitted from a first access point and an RSSI at the station of a signal transmitted from a second access point, and then determines to use the joint beamforming for communication between the first access point and the second access point and the station if a difference in strength between the two RSSIs does not exceed a second threshold, and determines not to use the joint beamforming for communication between the first access point and the second access point and the station if the difference in strength exceeds the second threshold.

2. The system of claim 1.

3. The wireless communication between the plurality of access points and the station is wireless communication conforming to the IEEE 802.11 standard series.

2. The system of claim 1.

4. The acquiring means acquires, as the RSSI, an RSSI of a beacon signal transmitted from an access point.

2. The system of claim 1.

5. the system includes a controller including the determining means; When the signal includes information indicating that the joint beamforming can be used, the station notifies the control device of information indicating the access point that transmitted the signal and the RSSI.

2. The system of claim 1.

6. a calculation unit configured to calculate, prior to performing the joint beamforming, channel state information (CSI) between each of the plurality of access points and the station; Initiating communication between the plurality of access points and the station using a transfer function estimated based on the channel state information calculated by the calculation means.

2. The system of claim 1.

7. The calculation means calculates the channel state information based on transmission and reception of a sounding frame between the station and any one of the access points. The system of claim 6 .

8. The acquiring means acquires the RSSI before the start of the joint beamforming.

2. The system of claim 1.

9. 1. A control method for controlling a system including a plurality of access points, comprising: an acquisition step of acquiring a received signal strength indicator (RSSI) indicating a received signal strength at a station of signals transmitted from a plurality of access points; a determination step of determining information indicating whether or not the plurality of access points will communicate with the station using joint beamforming, which is a communication method in which the plurality of access points transmit the same data to the station on the same frequency channel at the same time; and The determining step determines not to use the joint beamforming in communication between the plurality of access points and the station when an RSSI at the station of a signal transmitted from any one of the plurality of access points exceeds a first threshold. A control method comprising:

10. The decision step includes, when an RSSI at the station of a signal transmitted from any one of the plurality of access points does not exceed the first threshold, acquiring an RSSI at the station of a signal transmitted from a first access point and an RSSI at the station of a signal transmitted from a second access point, and determining to use the joint beamforming for communication between the first access point and the second access point and the station when a difference in strength between the two RSSIs does not exceed a second threshold, and determining not to use the joint beamforming for communication between the first access point and the second access point and the station when the difference in strength exceeds the second threshold.

10. The control method according to claim 9.

11. The wireless communication between the plurality of access points and the station is wireless communication conforming to the IEEE 802.11 standard series.

10. The control method according to claim 9.

12. an acquiring means for acquiring a received signal strength indicator (RSSI) indicating a received signal strength at a station of signals transmitted from a plurality of access points; a determination means for determining information indicating whether or not the plurality of access points will communicate with the station using joint beamforming, which is a communication method in which the plurality of access points transmit the same data to the station on the same frequency channel at the same time; and The determination means determines not to use the joint beamforming for communication between the plurality of access points and the station when an RSSI at the station of a signal transmitted from any one of the plurality of access points exceeds a first threshold. A control device characterized by:

13. When an RSSI at the station of a signal transmitted from any one of the plurality of access points does not exceed the first threshold, the decision means acquires an RSSI at the station of a signal transmitted from a first access point and an RSSI at the station of a signal transmitted from a second access point, and then determines to use the joint beamforming for communication between the first access point and the second access point and the station if a difference in strength between the two RSSIs does not exceed a second threshold, and determines not to use the joint beamforming for communication between the first access point and the second access point and the station if the difference in strength exceeds the second threshold.

13. The control device according to claim 12.

14. The wireless communication between the plurality of access points and the station is wireless communication conforming to the IEEE 802.11 standard series.

13. The control device according to claim 12.

15. A program for causing a computer to function as each of the means of the control device according to any one of claims 12 to 14.

Images