Communication device, communication method, and program

Abstract

To improve the efficiency of use of a radio medium.SOLUTION: A communication device performing radio communication conforming to the IEEE802.11 standard, acquires information on a first transmission signal intensity of a first radio frame included in the first radio frame transmitted from first another communication device of an overlapping basic service set (OBSS), acquires a reception signal intensity when the first radio frame is detected, specifies propagation loss between the first another communication device and the communication device from the first transmission signal intensity and the reception signal intensity, when a second radio frame transmitted from second another communication device of the OBSS as a destination of the first another communication device permits spatial reuse (SR), determines a second transmission signal intensity used in transmitting a third radio frame using the SR on the basis of the specified propagation loss, and transmits the third radio frame by using the SR while the second radio frame is being transmitted by using the second transmission signal intensity.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a technique for improving the efficiency of wireless communication.

Background Art

[0002] As a communication standard for wireless local area network (LAN), the IEEE (Institute of Electrical and Electronics Engineers) 802.11 series standards are known. In the IEEE 802.11 series standards, a technique for improving the communication efficiency in an Overlapping BSS (OBSS) environment where the communication ranges of a plurality of networks (Basic Service Set (BSS)) overlap with each other has been studied. Patent Document 1 describes a technique for increasing communication opportunities in an OBSS environment using a BSS Color for identifying a BSS.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a Spatial Reuse (SR) technique that allows communication using the same frequency channel as that OBSS in response to a specific condition being satisfied while communication is being performed in an OBSS. The present invention provides a technique for efficiently using the SR technique to improve the utilization efficiency of a wireless medium.

Means for Solving the Problems

[0005] A communication device according to one aspect of the present invention is a communication device that performs wireless communication compliant with the IEEE 802.11 standard, and acquires information on a first transmission signal strength of a first wireless frame included in a first wireless frame transmitted from a first other communication device in an Overlapping Basic Service Set (OBSS), and an acquisition unit that acquires a reception signal strength when the first wireless frame is detected; a specifying unit that specifies a propagation loss between the first other communication device and the communication device from the first transmission signal strength and the reception signal strength; and when a second wireless frame transmitted from a second other communication device in the OBSS to the first other communication device allows Spatial Reuse (SR), a determination unit that determines a second transmission signal strength to be used when transmitting a third wireless frame using SR based on the specified propagation loss; and a transmission unit that transmits the third wireless frame using SR while the second wireless frame is being transmitted using the second transmission signal strength.

Effects of the Invention

[0006] According to the present invention, the utilization efficiency of the wireless medium can be improved.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential for the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and redundant explanations are omitted.

[0009] (System Configuration) FIG. 1 shows a configuration example of a wireless communication system according to this embodiment. This wireless communication system is configured using, for example, a wireless LAN compliant with the IEEE802.11 series standards. Note that IEEE is an abbreviation for Institute of Electrical and Electronics Engineers, and LAN is an abbreviation for Local Area Network. In FIG. 1, as an example, two access points (APs) and two stations (STAs) compliant with the IEEE802.11 series standards are shown, but the wireless communication system may naturally include more than four communication devices.

[0010] In the wireless communication system of FIG. 1, it is assumed that STA111 participates in the network (Basic Service Set (BSS), not shown) constructed by AP101, and communication is performed between AP101 and STA111. Also, it is assumed that STA112 participates in the BSS (not shown) constructed by AP102, and communication is performed between AP102 and STA112. Note that these communication devices can communicate at frequencies in the 2.4 GHz band, 5 GHz band, and 6 GHz band. Note that the frequency bands used by the communication devices are not limited to this, and other frequency bands such as the 60 GHz band may be used. Also, each communication device can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz. However, these are merely examples, and bandwidths such as 240 MHz or 4 MHz may be used.

[0011] Each communication device is configured to be able to perform communication compliant with the IEEE802.11ax (HE) standard in which Spatial Reuse (SR) described later is adopted, for example, among the IEEE802.11 series standards. Note that in addition to the IEEE802.11ax standard, each communication device may support a legacy standard (for example, at least any one of the IEEE802.11a / b / g / n / ac standards) standardized before the IEEE802.11ax standard. Also, each communication device may support a standard standardized after IEEE802.11ax, such as the IEEE802.11be standard or the IEEE802.11bn standard. Further, in addition to the IEEE802.11 series standards, each communication device may support other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, and MBOA. Note that UWB is an abbreviation for Ultra Wide Band, and MBOA is an abbreviation for Multi Band OFDM Alliance. Here, OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. Also, NFC is an abbreviation for Near Field Communication. UWB includes wireless USB, wireless 1394, WiNET, and the like. Also, each communication device may support a communication standard for wired communication such as a wired LAN.

[0012] AP101 and AP102 can be, for example, a wireless LAN router or a personal computer (PC), but are not limited thereto. Also, STA111 to STA112 can be, for example, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, a wearable device such as a headset or smart glasses, or a printer, but are not limited thereto. AP101 to AP102 and STA111 to STA112 may be information processing devices such as a wireless chip that supports a standard such as IEEE802.11ax.

[0013] In this embodiment, as described above, each communication device (AP101 to AP102 and STA111 to STA112) can perform communication compliant with a standard that enables Spatial Reuse (SR). SR is a communication technology for efficiently utilizing a wireless medium in an Overlapping BSS (OBSS) environment where a plurality of BSSs are arranged to overlap geographically. In SR, during a period in which a predetermined frequency channel is being used for communication in any one BSS, communication is performed by spatially reusing that frequency channel in the OBSS for that BSS. That is, in SR, communication at a position that does not affect the communication in any one BSS is allowed to be performed in parallel. As a result, communication can be performed using a common frequency channel among a plurality of BSSs, enabling effective utilization of the wireless medium.

[0014] Currently, in the IEEE 802.11 standard, two types of SR processing methods (Parameterized Spatial Reuse (PSR)-based SR and OBSS Power Detect (PD) based SR) are defined. In PSR-based SR, in the communication device of the BSS, parameters are read from the trigger frame transmitted in the OBSS. From the trigger frame, as parameters, the target transmission signal strength of the trigger frame transmitted by the AP, the strength of the signal received from the AP, the signal strength of the allowable interference wave, and the period of a series of radio frames to be executed subsequently following the trigger frame are obtained. And in PSR-based SR, on the same frequency channel as the radio frame transmitted in the OBSS in response to the trigger frame, the radio frame of the BSS is transmitted with the transmission signal strength determined using those parameters. In PSR-Based SR, since it is necessary to read the above-mentioned parameters from the trigger frame, SR cannot be used when communication not using the trigger frame is performed in the OBSS. In other words, in the BSS, PSR-based SR cannot be applied unless a Trigger Based (TB) Physical layer Protocol Data Unit (PPDU) is transmitted in the OBSS.

[0015] In OBSS PD based SR, regardless of the type of the wireless frame transmitted by the OBSS, the transmission signal strength is determined according to the detected signal strength of the detected OBSS signal, and the BSS signal is transmitted using the transmission signal strength. Note that the determination as to whether the wireless frame is the one transmitted by the OBSS is made using the BSS Color. OBSS PD based SR can perform SR regardless of the type of the wireless frame transmitted in the OBSS. On the other hand, OBSS PD based SR is executed without considering the state of the receiver of the wireless frame of the OBSS for which SR is permitted. For this reason, when the BSS signal is transmitted with the transmission signal strength determined as described above, depending on the position of the receiver of the OBSS, the BSS signal may be strongly received at the position of the receiver, and there may be a case where the communication of the OBSS cannot be appropriately performed.

[0016] In this embodiment, in view of such circumstances, a method is provided to reduce the impact on OBSS communication while making SR applicable even when a wireless frame other than a TB PPDU is transmitted in OBSS by using the OBSS PD based SR method. For example, when transmitting a wireless frame that allows the application of OBSS PD based SR and its Ack in OBSS, information on the transmission signal strength of the transmitted signal is included. As a result, when the communication device in the BSS executes communication using OBSS PD based SR, it becomes possible to specify the magnitude of the impact on the transmitter and receiver of the wireless frame that allows OBSS PD based SR. More specifically, when a wireless frame using SR is transmitted, the wireless frame reaches the receiver in OBSS with a received signal strength reduced by only the propagation loss amount from the transmission signal strength of the wireless frame. A communication device attempting to transmit a wireless frame using SR estimates the propagation loss from the transmission signal strength of the wireless signal transmitted from other communication devices in OBSS and the received signal strength when the wireless signal is received. Here, it can be considered that the propagation loss in the signal transmitted from other communication devices in OBSS and arriving at the communication device also occurs in the propagation of the wireless frame transmitted by the device itself and reaching other communication devices. Therefore, by specifying the propagation loss between the communication device and other communication devices in OBSS, the communication device can estimate the received signal strength at which the wireless frame reaches other communication devices when assuming that the wireless frame is transmitted using SR. In this way, when the communication device transmits a wireless frame using SR, it can estimate the magnitude of the impact on the reception processing by other communication devices in OBSS based on the propagation loss as described above. Then, based on the magnitude of the propagation loss, the communication device can determine the transmission signal strength that does not affect the communication of the wireless frame for which SR is allowed in that OBSS. In this way, it becomes possible to perform communication using SR while sufficiently suppressing the impact on the communication in OBSS that allows SR, and it becomes possible to effectively utilize the wireless medium.

[0017] (Device Configuration) Using FIG. 2, a configuration example of the communication devices (AP101 to AP102 and STA111 to STA112) according to this embodiment will be described. FIG. 2 shows a hardware configuration example of the communication device. As shown in FIG. 2, as its hardware configuration, the communication device includes, for example, 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 configured to include one or more memories such as ROM and RAM, and stores various computer programs for performing various operations described later, and various information such as communication parameters for wireless communication. Note that ROM is an abbreviation for Read Only Memory, and RAM is an abbreviation for Random Access Memory. In addition to or instead of memories such as ROM and RAM, the storage unit 201 may include 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. Further, the storage unit 201 may include a Solid State Drive (SSD). Also, the storage unit 201 may include a plurality of memories and the like.

[0019] The control unit 202 is composed of one or more processors such as a CPU or an MPU, and controls the entire communication device by executing a computer program stored in the storage unit 201, for example. Note that CPU is an abbreviation for Central Processing Unit, and MPU is an abbreviation for Micro Processing Unit. In addition to controlling the entire communication device, the control unit 202 can be configured to execute a process of generating data and signals (radio frames) to be transmitted in communication with other communication devices. Note that the control unit 202 may be configured to execute processes such as controlling the entire communication device in cooperation with a computer program stored in the storage unit 201 and an OS (Operating System), for example. Further, the control unit 202 may include a plurality of processors such as a multi-core, and execute processes such as controlling the entire communication device by the plurality of processors. Further, the control unit 202 may be composed of an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

[0020] Further, the control unit 202 controls the functional unit 203 to execute predetermined processes such as imaging, printing, and projection. The functional unit 203 is hardware for the communication device to execute predetermined processes. For example, when the communication device is a camera such as a digital still camera or a smartphone having a camera, the functional unit 203 is an imaging unit that performs imaging processing of surrounding images. Also, for example, when the communication device is a printer, the functional unit 203 is a printing unit that performs printing processing on a sheet such as paper based on print data stored in the storage unit 201 or acquired from the outside via wireless communication or the like. Also, for example, when the communication device is a projector or smart glasses, the functional unit 203 is a projection unit that performs projection processing of image data or video data stored in the storage unit 201 or acquired from the outside via wireless communication or the like. In the case of smart glasses, the projection surface is the retina of the end user or the like. The data processed by the functional unit 203 may be data stored in the storage unit 201 or data communicated with other communication devices via the communication unit 206 described later. Furthermore, the communication device can also provide a network storage function such as a NAS (Network Attached Storage). This function is provided to other communication devices as a web service such as a network storage service. For example, another communication device connects to the network storage service provided by the communication device using a protocol such as SMB, FTP, or WebDAV. Then, another communication device can upload a file to the storage service or download a file in the storage.

[0021] The input unit 204 receives various operations from the user. The output unit 205 performs various outputs to the user. Here, the output by the output unit 205 includes at least one of, for example, display on the screen, audio output by the speaker, vibration output, and the like. Note that both the input unit 204 and the output unit 205 may be realized by one module such as a touch panel. Also, the input unit 204 and the output unit 205 may be incorporated in the communication device respectively, or may be configured as external devices connected to the communication device.

[0022] The communication unit 206 controls wireless communication compliant with the IEEE 802.11 series standards and controls Internet Protocol (IP) communication. For example, the communication unit 206, in cooperation with the antenna 207, executes transmission and reception of HE PPDUs compliant with the IEEE 802.11ax standard. Note that the communication unit 206 can execute transmission and reception processing compliant with at least the standard in which SR is adopted, in addition to or instead of the IEEE 802.11 standard. The antenna 207 is an antenna capable of transmitting and receiving signals in at least any one of the frequency bands, such as the sub-GHz band, 2.4 GHz band, 5 GHz band, 6 GHz band, 7 GHz band, and 60 GHz band. In this embodiment, one antenna 207 is shown, but the number of antennas may be two or more. In one example, different antennas may be prepared for each frequency band. Further, when the communication device has a plurality of antennas, it may have a plurality of communication units 206 respectively corresponding to the plurality of antennas. Note that when the communication device supports the above-described NFC standard, Bluetooth (registered trademark) standard, or wired communication standard, etc., a communication unit 206 configured to control communication compliant with these communication standards may be provided. Note that the communication unit 206 and the antenna 207 may be provided as an integrated component, or may be prepared as separate components respectively.

[0023] Fig. 3 shows an example of the functional configuration of the communication device. The communication device includes, as its functional configuration, a wireless LAN control unit 301, a frame processing unit 302, an SR management unit 303, a UI control unit 304, and a memory control unit 305. These functions can be realized, for example, by the control unit 202 executing a program stored in the storage unit 201, or by a processing functional unit in the communication unit 206. Note that Fig. 3 is a diagram for explaining the main functions of the present embodiment, and other functions are omitted. Therefore, the communication device can naturally have functions for establishing a connection with a counterpart device and for communication control, such as a normal AP or STA, and functions that a communication device generally has. Also, a plurality of functional blocks in Fig. 3 may be integrated into one functional block, or one functional block may be divided into a plurality of functional blocks.

[0024] The wireless LAN control unit 301 is configured to include an antenna and circuits for transmitting and receiving wireless signals to and from other wireless LAN devices, and a program for controlling them. Note that the communication device may have a plurality of wireless LAN control units 301. The wireless LAN control unit 301 executes communication control of the wireless LAN in accordance with the provisions of the IEEE802.11 series standards. The frame processing unit 302 performs processes such as generation and analysis of wireless frames transmitted and received in the wireless LAN control unit 301. The content of generation and analysis of wireless control frames in the frame processing unit 302 may be restricted by settings stored in the storage unit 305, or may be changed by user settings from the UI control unit 304. The frame generated in the frame processing unit 301 is transferred to the wireless LAN control unit 301 and transmitted via the wireless LAN control unit 301. Also, the frame received in the wireless LAN control unit 301 is transferred to the frame processing unit 302 and analyzed in the frame processing unit 302. When it is necessary to transmit a wireless frame, the SR management unit 303 determines whether SR can be used for transmitting the wireless frame based on the parameters collected so far via the frame processing unit 302. When the SR management unit 303 determines that SR can be used for transmitting a wireless frame, it determines parameters such as the signal strength, modulation order, and packet length at the time of transmitting the wireless frame, and notifies the wireless LAN control unit 301 and the frame generation unit 302 of the parameters. The frame generation unit 302 generates a wireless frame to be transmitted using the notified parameters, and the wireless LAN control unit 301 transmits the generated wireless frame with a transmission power based on the notified parameters. The UI control unit 304 is configured to include hardware related to a user interface such as a touch panel or buttons for receiving operation inputs to the communication device by a user (not shown) of the communication device, and a program for controlling them. Also, the UI control unit 304 may be configured to include hardware related to functions for presenting information to the user, such as display of an image or the like and audio output, and a program for controlling the same. The storage control unit 305 performs control for storing programs and data for operating the communication device in a storage device such as a ROM or a RAM.

[0025] (Processing flow) FIG. 4 shows an example of the communication processing flow in the present embodiment. Here, the relative positional relationship among AP101, AP102, STA111, and STA112 is assumed to be in the state shown in FIG. 1. Also, each communication device (AP101, AP102, STA111, and STA112) performs wireless communication using a common frequency channel. Further, AP101 and AP102 each form a different BSS, and these BSSs are in an OBSS relationship with each other. That is, as seen from AP101 and STA111, the BSS formed by AP102 is an OBSS, and as seen from AP102 and STA112, the BSS formed by AP101 is an OBSS.

[0026] Also, in this processing example, it is assumed that the wireless frame transmitted from STA112 to AP102 is a wireless frame that permits communication using OBSS PD based SR by an OBSS. Therefore, in the wireless frame transmitted from STA112 to AP102, information permitting OBSS PD based SR is included in the PHY header and transmitted. Here, AP101 identifies from the PHY header of the wireless frame transmitted by STA112 that OBSS PD based SR is permitted, and attempts to use SR in the transmission of the wireless frame addressed to STA112. At this time, the AP101 according to the present embodiment can suppress the transmission signal strength of the wireless frame so as not to affect the reception result of the wireless frame from STA112 in AP102 by the wireless frame transmitted by its own device.

[0027] When transmitting a wireless frame, for example, AP101 suppresses the signal strength (transmission power) of the wireless frame so that when the wireless frame reaches AP102, it is suppressed to the level of the noise floor due to the thermal noise of AP102. According to this, it is possible to prevent the signal-to-noise ratio (SNR) of the wireless frame received at AP102 from deteriorating. In other words, if the wireless frame transmitted by AP101 reaches AP102 with a signal strength higher than the thermal noise, the SNR of the signal frame received by AP102 may deteriorate to a non-negligible extent. In order to calculate at what signal strength the wireless frame transmitted by AP101 reaches AP102, AP101 needs to identify the propagation loss between its own device and AP102. And in order to identify this propagation loss, AP101 needs to be able to identify the transmission signal strength (transmission power) of the wireless frame transmitted from AP102 and the received signal strength (received power) of that wireless frame at its own device. That is, the difference between the transmission signal strength and the received signal strength is the propagation loss between AP101 and AP102. The wireless frame transmitted from AP101 will be received at AP102 with a signal strength obtained by subtracting the magnitude of the propagation loss from the transmission signal strength of the wireless frame. Therefore, AP101 can, for example, identify the value obtained by adding the magnitude of the propagation loss to the noise floor level of AP102 as the transmission signal strength, thereby enabling communication while suppressing the impact on the reception of the wireless frame at AP102.

[0028] On the other hand, in a conventional IEEE 802.11 standard-compliant wireless frame other than some trigger frames used in PSR-based SR, information on the signal strength output by the communication device on the transmission side of the wireless frame is not included. Therefore, for example, it is not possible to identify the propagation loss between the communication device on the transmission side and the communication device attempting to transmit a wireless frame using SR. Thus, in this embodiment, when transmitting a wireless frame that permits SR and other wireless frames related to the wireless frame, information on the transmission signal strength of those wireless frames is included in the wireless frames and transmitted. That is, the AP 102 may transmit the transmission signal strength of the wireless frame in a wireless frame for transmitting a wireless frame that permits SR or in a response (e.g., ACK) when receiving the wireless frame. As a result, the AP 101 can acquire information on the transmission signal strength from the wireless frame, and can identify the propagation loss based on the information and the measurement result of the reception signal strength of the wireless frame.

[0029] When a wireless frame that permits SR is transmitted, information on the transmission signal strength of the wireless frame can be included in the header of the wireless frame. That is, in a wireless frame including a header and data, the information on the transmission signal strength can be included in the header part instead of the data part. This is because in the data part, a modulation method with a large modulation order is likely to be used, whereas in the header part, a modulation method with a low modulation order (for example, the one with the minimum modulation order among available modulation methods) is likely to be used to reduce the error rate. That is, since the modulation order of the data part of the wireless frame can be adjusted to be high based on the reception quality of the wireless frame in the communication device on the reception side and then transmitted, there may be a case where a communication device that transmits a wireless frame using SR cannot demodulate the data part. In contrast, the header part has a low modulation order so that the communication device on the reception side can surely demodulate its content, and the communication device that transmits a wireless frame using SR can also perform demodulation. For this reason, by including the information on the transmission signal strength in the header part, a communication device that transmits a wireless frame using SR can acquire the information, and the probability of specifying the propagation loss can be increased. Note that this is an example, and the information on the transmission signal strength may be included in the data part of the wireless frame.

[0030] Also, not only the wireless frame for data transmission that permits SR but also the reception response frame (ACK) for the wireless frame can be transmitted with the information on the transmission signal strength included therein. According to this, a communication device that transmits a wireless frame using SR can specify the propagation loss between itself and the communication device on the reception side of the wireless frame for data transmission that permits SR.

[0031] In addition, a communication device that may transmit or receive a wireless frame for data transmission that permits SR may, for example, send information indicating the transmission signal strength to the surroundings in a wireless frame separate from, for example, a wireless frame for data transmission or a reception response frame. In one example, the communication device may use a management frame such as a Beacon frame to send information indicating the transmission signal strength to the surroundings. Further, the communication device may include information indicating the transmission signal strength to be used in subsequent communication in a Request To Send (RTS) frame or a Clear To Send (CTS) frame and send it. The communication device can identify the propagation loss with other communication devices in the OBSS by receiving those wireless frames transmitted from other communication devices in the OBSS and acquiring the information on the transmission signal strength. Then, when the other communication devices in the OBSS send and receive wireless frames that permit SR, the communication device can identify the transmission signal strength in communication using SR based on the propagation loss.

[0032] In FIG. 4, first, assume that AP101 has not specified or memorized the propagation loss between itself and each of AP102 and STA112. Here, assume that STA112 executes Clear Channel Acessment (CCA) and determines that the frequency channel to be used is idle, and then transmits a wireless frame 404 including a header portion 402 and a data portion 403. Note that in CCA in the IEEE802.11 standard, a backoff period 401, which is a random waiting time, is provided. Since this backoff period is different for each communication device attempting to transmit a wireless frame, the probability of a collision occurring due to multiple communication devices transmitting wireless frames simultaneously can be reduced. STA112 includes in the header portion 402 of the wireless frame 404 information indicating that OBSS PD based SR is allowed and that the destination is AP102, and information on the transmission signal strength of this wireless frame 404, and then transmits it. AP101 demodulates the header portion 402 and recognizes that OBSS PD based SR is allowed and that the destination is AP102. Also, AP101 specifies the propagation loss between itself and STA112 based on the information on the transmission signal strength included in the header portion 402 and the reception strength of the wireless frame 404, and stores it in the storage unit 201. Based on the conventional SR, AP101 can start transmitting a wireless frame using SR in response to specifying that OBSS PD based SR is allowed. On the other hand, in this embodiment, AP101 does not execute SR when the information on the destination of the wireless frame allowing OBSS PD based SR and the propagation loss between that destination and AP101 are unknown. For this reason, AP101 does not transmit a wireless frame using SR within the transmission period of the wireless frame 404.

[0033] After STA112 finishes transmitting the wireless frame 404, the AP102, which is the destination of the wireless frame 404, transmits an acknowledgment frame (ACK405) to STA112 after the SIFS (Short Inter Frame Space) period. This ACK405 includes information on the transmission signal strength. AP102 demodulates the ACK405, obtains the information on the transmission signal strength, determines the propagation loss between itself and STA112 based on this information and the reception strength of the ACK405, and stores it in the storage unit 201.

[0034] Note that, in order for an AP of a wireless LAN to be able to receive a wireless frame addressed to itself at any timing when the frame arrives, the receiving state can be maintained at all times during periods other than when a wireless frame is being transmitted. For this reason, AP102 can always receive wireless frames transmitted by AP102 or STA112 operating on the same frequency channel. Therefore, AP101 can determine both the propagation loss between itself and STA112 and the propagation loss between itself and AP102. Also, AP101 can maintain the propagation loss at the latest value by constantly observing wireless frames from other communication devices and updating the value of the propagation loss.

[0035] After the communication by STA112 ends, AP101 starts CCA to transmit a wireless frame to STA111. Also, at this time, it is assumed that STA112 also starts CCA to transmit a wireless frame to AP102. Here, STA111 has set a backoff period 406, and AP101 has set a backoff period 411. Then, as a result of their CCA, it is assumed that STA111 starts transmitting a wireless frame 409 including a header part 407 and a data part 408. Note that, similar to the wireless frame 404, the wireless frame 409 includes, in the header part 407, information indicating that OBSS PD based SR is allowed and that the destination is AP102, and information on the transmission signal strength of this wireless frame 409.

[0036] When the AP101 detects the wireless frame 409 sent by the STA111 during the execution of the CCA, it determines that normal transmission cannot be performed, and attempts to transmit the wireless frame using the SR. First, the AP101 demodulates the header portion 407 of the wireless frame 409 that collided in the CCA to identify the source (STA112) and destination (AP102) of the wireless frame 409. The AP101 can calculate the transmission signal strength of the wireless frame used by the AP101 in the SR based on the value of the propagation loss, provided that at least the value of the propagation loss between the destination (AP102) and the AP101 is stored.

[0037] In the IEEE802.11 standard, it is stipulated that a communication device must be able to receive a 6Mbps OFDM signal using BPSK with a received signal strength of -80dBm or more. In other words, it is acceptable that signals with an intensity of less than -80dBm may not be received. From this, in one example, the AP101 adjusts the transmission signal strength of the wireless frame to be transmitted so that the intensity is less than -80dBm at the STA112 and the AP102. By doing so, it is assumed that the AP101 can transmit the wireless frame without affecting the communication between the STA112 and the AP102. However, there are actually wireless LAN communication devices that can demodulate signals with an intensity of less than -80dBm. Therefore, in another example, the AP101 can adjust and transmit the transmission signal strength of the wireless frame so that the received signal strength is less than -100dBm per 20MHz at the STA112 and the AP102.

[0038] In this embodiment, the AP 101 can calculate the transmission signal strength such that the received signal strengths at both the AP 102 and the STA 112 are less than -80 dBm. Then, when communication with the STA 111 is possible with the calculated transmission signal strength, the AP 101 starts transmitting a wireless frame. For example, assume that the propagation loss between the AP 101 and the AP 102 is 90 dB and the propagation loss between the AP 101 and the STA 112 is 70 dB. In this case, for the received signal strength at the AP 102 to be less than -80 dBm, the transmission signal strength at the AP 101 needs to be less than -80 + 90 = 10 [dBm]. Similarly, for the received signal strength at the STA 112 to be less than -80 dBm, the transmission signal strength at the AP 101 needs to be less than -80 + 70 = -10 [dBm]. The AP 101 can specify less than -10 dBm, which is the lower of these transmission signal strengths, as the transmission signal strength that can be used for transmitting the wireless frame. Note that the AP 101 may specify the transmission signal strength by calculation, or for example, may store a table defining the relationship between the propagation loss and the transmission signal, and may specify the transmission signal strength by referring to that table. Then, when the AP 101 transmits a wireless frame with that transmission signal strength, it determines whether communication with the STA 111 is possible by determining whether the wireless frame is received at a sufficient received signal strength at the STA 111, which is the communication partner device. For example, the AP 101 can determine whether the received signal strength at the STA 111 is -80 dBm or more. The AP 101 can determine that communication with the STA 111 is possible when the received signal strength at the STA 111 is -80 dBm or more. In one example, the AP 101 can set the largest possible transmission signal strength within the range that is less than -10 dBm and the received signal strength at the STA 111 is -80 dBm or more.

[0039] In addition, AP101 checks the length of the wireless frame 409 and determines (calculates) the timing at which the wireless frame 409 ends. Also, AP101 determines (calculates) the timing at which the ACK 410 sent by AP102 to STA112 ends. Then, AP101 determines the length of the wireless frame 415 to be transmitted so that the timing at which AP102 completes the transmission of ACK 410 and the time at which AP101 completes the transmission of the wireless frame approximately coincide. In one example, in the wireless frame 415 including the header portion 412 and the data portion 413, AP101 can adjust the length by inserting padding 414 using dummy data. This can be done to prevent the timing of ACK 416 by STA111 from overlapping with the wireless frame 409 and ACK 410. Then, AP101 transmits the wireless frame 415 with the adjusted length to STA111 at the transmission signal strength determined as described above. By determining the transmission signal strength of the wireless frame 415 as described above, it is possible to prevent the transmission of the wireless frame 415 from strongly affecting both the reception of the wireless frame 409 by AP102 and the reception of ACK 410 by STA112.

[0040] Note that the padding 414 may not be inserted. For example, AP101 may notify STA111 by including information indicating that the wireless frame 415 is communication using SR for communication between AP102 and STA112 in the header portion 412 or the data portion 413. STA111 may determine the transmission signal strength of ACK 416 in the same manner as AP101 based on, for example, the propagation loss between AP102 and STA112 specified in advance in the same manner as the above-mentioned AP101 and the information included in the wireless frame 415. When such transmission of ACK 416 is possible, the insertion of the padding 414 may be omitted.

[0041] In the above example, the case where AP101 sets the transmission signal strength so as not to affect either STA112 or AP102 has been described. However, the transmission signal strength may be set so as not to affect only the reception operation of AP102. For example, in the above example, when the transmission signal strength of AP101 is 10 dBm, the received signal strength at AP102 is -80 dBm. In this case, AP101 can adjust the length of the wireless frame 415 to be transmitted so that the transmission ends at the timing when the transmission of STA112 ends. This is because the wireless frame 415 may strongly affect STA112, which is the communication device on the receiving side of ACK410. In this case, it is important that ACK416 transmitted by STA111 to AP101 is transmitted with a transmission signal strength that does not affect the reception of ACK410 by STA112. Also, when the wireless frame 415 transmitted by AP101 is a wireless frame in a form such as broadcast or multicast that does not require the reception of ACK416, it is not necessary to consider the signal strength of ACK416 transmitted by STA111. As a result, since AP101 transmits the wireless frame 415 with a higher transmission signal strength, communication using SR can be performed with higher efficiency.

[0042] Fig. 5 shows an example of the flow of processing executed by a communication device (AP101 in the example of Fig. 4) that communicates using SR. This processing can be realized, for example, when a control unit 202 in the communication device executes a program stored in a storage unit 201, or by a processing functional unit in a communication unit 206. In the following, the case where the communication device performing the processing is AP101 will be described, but this processing may be performed by other communication devices such as STA111. It is assumed that AP101 has established a link so as to be able to perform wireless communication with STA111.

[0043] AP101 observes the wireless frames of OBSS being transmitted and received in the vicinity and demodulates the header portion of the wireless frames. By this demodulation, AP101 detects, for example, a wireless frame whose source is STA112, destination is AP102, and SR is permitted (S501). AP101 determines whether information on the propagation loss between AP102 and STA112 is stored in the storage unit 201 (S502). If such propagation loss information is not stored (NO in S502), AP101 identifies and records the propagation loss with STA112 based on the wireless frame detected in S501 (S507). That is, AP101 calculates the propagation loss between its own device and STA112 from the information on the transmission signal strength included in the wireless frame detected in S501 and the reception signal strength when the wireless frame is received, and stores it in the storage unit 202. Further, AP101 receives an ACK from AP102 for the wireless frame transmitted from STA112, and similarly calculates the propagation loss with AP102 and stores it in the storage unit 202 (S508). Then, the process returns to S501.

[0044] When AP101 determines that the information on the propagation loss between AP101 and AP102 and STA112 is stored in the storage unit 201 (YES in S502), it determines the transmission signal strength of the wireless frame to be transmitted using SR based on the information on the propagation loss (S503). That is, AP101 can calculate the transmission signal strength of the wireless frame to be transmitted so that the received signal strength at least in AP102 is equal to or lower than a predetermined level. Further, AP101 may calculate the transmission signal strength of the wireless frame to be transmitted so that the received signal strengths in both AP102 and STA112 are equal to or lower than a predetermined level. Then, when AP101 transmits a wireless frame with the determined transmission signal strength, it determines whether STA111 can receive the wireless frame (S504). For example, AP101 determines that STA111 can receive the wireless frame when the received signal strength of the transmitted wireless frame at STA111 is equal to or higher than a predetermined level. When AP101 determines that STA111 cannot receive the wireless frame (NO in S504), it decides not to transmit the wireless frame using SR (S509). By transmitting the wireless frame even though STA111 cannot receive the wireless frame transmitted by AP101, an increase in unnecessary interference to the surroundings can be suppressed. On the other hand, when AP101 determines that STA111 can receive the wireless frame with the determined transmission signal strength (YES in S504), it determines the length of the wireless frame using SR (S505). For example, AP101 obtains information on the frame length from the header portion of the wireless frame detected in S501 and determines the length of the wireless frame to be transmitted according to the frame length. Then, AP101 transmits a wireless frame with the determined frame length to STA111 at the determined transmission signal strength (S506).

[0045] As described above, the communication device acquires information on the transmission signal strength of the wireless frame included in the wireless frame transmitted from the first other communication device on the receiving side of the OBSS, and specifies the propagation loss between the communication device and the first other communication device. Then, when the communication device transmits a wireless frame that allows the second other communication device on the transmission side of the OBSS to perform communication using SR, it can determine the transmission signal strength at a level that does not affect the first other communication device based on the propagation loss. When the communication device transmits a wireless frame that allows the second other communication device to perform communication using SR, it can transmit the wireless frame at the determined transmission signal strength using SR while sufficiently suppressing the influence on the first other communication device. Further, the communication device may similarly specify the propagation loss for the second other communication device and determine the transmission signal strength at a level that does not affect the second other communication device. In this case, for example, when a wireless frame such as an ACK is transmitted from the first other communication device to the second other communication device, the communication device can transmit the wireless frame at the determined transmission signal strength using SR while sufficiently suppressing the influence on the second other communication device.

[0046] In the above-described embodiment, when the STA 112 of the OBSS transmits a wireless frame that permits SR, it transmits including information on the transmission signal strength. Similarly, an example was described in which the AP 102 transmits including information on the transmission signal strength in the ACK for that wireless frame. However, it is not limited to this. That is, each communication device may always transmit including information on the transmission signal strength when transmitting a wireless frame. When the AP 101 of the BSS detects that wireless frame, it acquires information on the transmission signal strength and specifies and stores (or updates the stored information) the propagation loss from the information on the received signal strength of that wireless frame and its transmission signal strength. On the other hand, when the use of SR is not permitted in the wireless frame transmitted from the STA 112, the AP 101 does not transmit a wireless frame during the transmission of that wireless frame. Also, when the use of SR is permitted in the wireless frame transmitted from the STA 112, during the transmission of that wireless frame, the AP 101 determines the transmission signal strength from the stored propagation loss and can transmit a wireless frame at that transmission signal strength using SR. In this way, the propagation loss may be continuously updated while SR is not permitted, and when SR is permitted, a wireless frame can be immediately transmitted using SR. Note that in this case, the communication device does not have to specify the destination of the wireless frame when specifying the propagation loss based on the wireless frame received from another communication device. That is, since the communication device can specify the propagation loss from the transmission signal strength when the wireless frame is transmitted from another communication device and the received signal strength when that wireless frame is received, there is no need to specify the destination of the wireless frame. On the other hand, when performing communication using SR, the communication device checks the destination of the wireless frame for which SR is permitted and can determine the transmission signal strength that sufficiently suppresses the influence on the communication device of that destination based on the propagation loss for the communication device of that destination.

[0047] In the above example, in the case of OBSS, an example where STA112 attempts to transmit a wireless frame to AP102 and AP101 attempts to transmit a wireless frame to STA111 was described. However, this is only an example. That is, in OBSS, AP102 may transmit a wireless frame to STA112, or STA111 may attempt to transmit a wireless frame to AP101. Further, AP102 and STA112 may execute the processing executed by the above-described AP101, using AP101 and STA111 as OBSS.

[0048] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiment to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0049] (Summary of Embodiment) Summarizing at least a part of the above-described embodiment, it is as follows. (Item 1) A communication device that performs wireless communication compliant with the IEEE802.11 standard, an acquisition unit that acquires information on a first transmission signal strength of the first wireless frame included in the first wireless frame transmitted from a first other communication device of an Overlapping Basic Service Set (OBSS), and acquires a reception signal strength when the first wireless frame is detected; a specifying unit that specifies a propagation loss between the first other communication device and the communication device from the first transmission signal strength and the reception signal strength; a determination unit that determines a second transmission signal strength to be used when transmitting a third wireless frame using Spatial Reuse (SR) based on the specified propagation loss when a second wireless frame transmitted from a second other communication device of the OBSS to the first other communication device as a destination permits Spatial Reuse (SR); Transmission means for transmitting the third radio frame using SR while the second radio frame is being transmitted, using the second transmission signal strength; A communication device characterized by comprising the same. (Item 2) Determination means for determining whether or not a third other communication device, which is the destination of the third radio frame, can receive the third radio frame when the third radio frame is transmitted with the second transmission signal strength; The transmission means does not transmit the third radio frame when it is determined that the third other communication device cannot receive the third radio frame. The communication device according to item 1, characterized by the above. (Item 3) The communication device according to item 1 or 2, further comprising adjustment means for adjusting the length of the third radio frame so that the transmission of the third radio frame ends at the timing when the transmission of the second radio frame ends. (Item 4) The communication device according to any one of items 1 to 3, characterized in that the information on the first transmission signal strength is included in the header portion of the first radio frame. (Item 5) The acquisition means acquires information on the third transmission signal strength of the fourth radio frame included in the fourth radio frame transmitted from the second other communication device, and acquires the second reception signal strength when the fourth radio frame is detected. The specifying means specifies the propagation loss between the second other communication device and the communication device from the third transmission signal strength and the second reception signal strength. The determination means determines the second transmission signal strength based on both the propagation loss between the first other communication device and the communication device and the propagation loss between the second other communication device and the communication device. The communication device according to any one of items 1 to 4, characterized by the above. (Item 6) At the timing when the transmission of the reception response frame by the first other communication device for the second wireless frame is completed, further comprising adjustment means for adjusting the length of the third wireless frame so that the transmission of the third wireless frame is completed, the communication device according to item 5, characterized in that. (Item 7) A communication device that performs wireless communication compliant with the IEEE802.11 standard, When the use of Spatial Reuse (SR) is allowed in the wireless frame to be transmitted, including information on the transmission signal strength of the wireless frame in the wireless frame, or when receiving a wireless frame for which the use of SR is allowed, including information on the transmission signal strength of the reception response frame in the reception response frame, a communication device characterized by having transmission means for transmitting. (Item 8) The information on the transmission signal strength is included in the header part of the wireless frame and transmitted, the communication device according to item 7, characterized in that. (Item 9) The header part further includes information indicating that the use of the SR is allowed and is transmitted, the communication device according to item 8, characterized in that. (Item 10) A communication method executed by a communication device that performs wireless communication compliant with the IEEE802.11 standard, Obtaining information on the first transmission signal strength of the first wireless frame included in the first wireless frame transmitted from the first other communication device of the Overlapping Basic Service Set (OBSS), and obtaining the reception signal strength when the first wireless frame is detected; Identifying the propagation loss between the first other communication device and the communication device from the first transmission signal strength and the reception signal strength; When the second wireless frame transmitted from the second other communication device of the OBSS to the first other communication device allows Spatial Reuse (SR), determining the second transmission signal strength to be used when transmitting the third wireless frame using SR based on the identified propagation loss; Using the second transmission signal strength, while the second wireless frame is being transmitted, transmitting the third wireless frame using SR; A communication method characterized by including the above. (Item 11) A communication method executed by a communication device that performs wireless communication compliant with the IEEE802.11 standard, When the use of Spatial Reuse (SR) is allowed in a wireless frame to be transmitted, including information on the transmission signal strength of the wireless frame in the wireless frame, or when receiving a wireless frame in which the use of SR is allowed, including information on the transmission signal strength of the received response frame in the received response frame, and transmitting the same. A communication method characterized by including the above. (Item 12) A program for causing a computer to function as each means included in the communication device according to any one of Items 1 to 9.

[0050] The invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the invention. Therefore, claims are attached to disclose the scope of the invention.

Description of Reference Numerals

[0051] 301: Wireless LAN control unit, 302: Frame processing unit, 303: SR management unit

Claims

1. A communication device that performs wireless communication compliant with the IEEE 802.11 standard, acquiring means for acquiring information on a first transmission signal strength of the first wireless frame included in the first wireless frame transmitted from a first other communication device of an Overlapping Basic Service Set (OBSS) and acquiring a reception signal strength when the first wireless frame is detected; specifying means for specifying a propagation loss between the first other communication device and the communication device from the first transmission signal strength and the reception signal strength; determining means for determining a second transmission signal strength to be used when transmitting a third wireless frame using Spatial Reuse (SR) based on the specified propagation loss when a second wireless frame transmitted from a second other communication device of the OBSS to the first other communication device as a destination permits Spatial Reuse (SR); transmission means for transmitting the third wireless frame using SR while the second wireless frame is being transmitted, using the second transmission signal strength; A communication device characterized by comprising the above.

2. further comprising determination means for determining whether a third other communication device, which is a destination of the third wireless frame, can receive the third wireless frame when the third wireless frame is transmitted with the second transmission signal strength; The transmission means does not transmit the third wireless frame when it is determined that the third other communication device cannot receive the third wireless frame. The communication device according to claim 1, characterized by the above.

3. The communication device according to claim 1, further comprising adjustment means for adjusting the length of the third wireless frame so that transmission of the third wireless frame ends at the timing when transmission of the second wireless frame ends.

4. The communication device according to claim 1, characterized in that the information on the first transmission signal strength is included in a header portion of the first wireless frame.

5. The acquisition means acquires information on a third transmission signal strength of the fourth wireless frame included in the fourth wireless frame transmitted from the second other communication device and acquires a second reception signal strength when the fourth wireless frame is detected. The specific means specifies the propagation loss between the second other communication device and the communication device from the third transmission signal strength and the second reception signal strength. The determination means determines the second transmission signal strength based on both the propagation loss between the first other communication device and the communication device and the propagation loss between the second other communication device and the communication device. The communication device according to claim 1, characterized in that.

6. The communication device according to claim 5, further comprising adjustment means for adjusting the length of the third radio frame so that the transmission of the third radio frame ends at the timing when the transmission of the reception response frame by the first other communication device for the second radio frame ends.

7. A communication device that performs wireless communication compliant with the IEEE 802.11 standard, characterized by having transmission means for including information on the transmission signal strength of the radio frame in the radio frame when the use of Spatial Reuse (SR) is allowed in the transmitted radio frame, or for including information on the transmission signal strength of the reception response frame in the reception response frame when a radio frame allowing the use of SR is received.

8. The communication device according to claim 7, characterized in that the information on the transmission signal strength is included in and transmitted in the header portion of the radio frame.

9. The communication device according to claim 8, characterized in that information indicating that the use of SR is allowed is further included in and transmitted in the header portion.

10. A communication method executed by a communication device that performs wireless communication compliant with the IEEE 802.11 standard, acquiring information on the first transmission signal strength of the first radio frame included in the first radio frame transmitted from a first other communication device of an Overlapping Basic Service Set (OBSS), and acquiring the reception signal strength when the first radio frame is detected; specifying the propagation loss between the first other communication device and the communication device from the first transmission signal strength and the reception signal strength. When a second radio frame transmitted from the second other communication device of the OBSS to the first other communication device as a destination permits Spatial Reuse (SR), based on the specified propagation loss, determining a second transmission signal strength to be used when transmitting a third radio frame using SR; Transmitting the third radio frame using SR while the second radio frame is being transmitted, using the second transmission signal strength; A communication method characterized by including the above. **Claim 11** A communication method executed by a communication device that performs wireless communication compliant with the IEEE 802.11 standard, the method comprising: When the use of Spatial Reuse (SR) is permitted in a radio frame to be transmitted, including information on the transmission signal strength of the radio frame in the radio frame, or when receiving a radio frame for which the use of SR is permitted, including information on the transmission signal strength of the received response frame in the received response frame and transmitting the received response frame. **Claim 12** A program for causing a computer to function as each means included in the communication device according to any one of claims 1 to 9.

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