Wireless Station No. 1

Abstract

To achieve prevention of inappropriate regular NAV (Network Allocation Vector: transmission prohibition period) release, and improvement of communication performance.SOLUTION: A first radio station includes: an antenna belonging to a first communication cell and receives a trigger frame transmitted from an access point belonging to a second communication cell, the trigger frame requesting an uplink multiple-user response signal from a plurality of terminals belonging to the second communication cell and including desired signal strength (Target RSSI: received signal strength indicator) of the uplink multiple-user response signal at the access point; a controller which determines whether an estimated receiving signal strength indication to be measured at the access point when the access point receives a signal transmitted from the first radio station is higher or not than a value obtained by adding an allowable interference amount to the target RSSI, and sets a temporary transmission allowed state that allows transmitting a signal to a second radio station belonging to the first communication cell; and an antenna which transmits the signal when response signals are transmitted from the multiple terminals and when the first radio station is in the set temporary transmission allowed state.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present disclosure relates to a wireless station that performs suitable wireless communication in an environment where interference occurs between wireless stations. [Background technology]

[0002] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 Task Group (TG) ax is currently developing the technical specifications for IEEE 802.11ax (hereinafter referred to as 11ax) as the next-generation standard after IEEE 802.11ac.

[0003] The IEEE 802.11 standard defines a Basic Service Set (BSS) as a set of wireless stations (also called stations or STAs) that make up a basic wireless network. In infrastructure mode, a BSS consists of one access point and multiple terminals (wireless stations other than an access point), and in ad-hoc mode, it consists of multiple terminals. The ad-hoc mode BSS is called an Independent BSS (IBSS) to distinguish it from the infrastructure mode BSS. BSSs other than the BSS (intra-BSS) to which the terminal (or access point) belongs are called Overlapping BSS (OBSS) or inter-BSS. In an OBSS, multiple communication cells overlap, so communication between OBSSs causes interference between the communication cells, degrading communication quality.

[0004] In wireless communication, a situation may occur where wireless signals between wireless stations do not reach each other (a radio wave environment where carrier sense does not function) due to the distance between wireless stations or the presence of obstacles. As a measure against such an environment, i.e. an environment where hidden terminals exist, the IEEE 802.11 standard provides a collision prevention function using NAV (Network Allocation Vector: transmission inhibition period). When an access point or terminal receives a wireless frame for setting NAV at a level above a certain threshold, it prohibits transmission during the NAV period set in the duration information, except when the wireless frame for setting NAV is addressed to the own terminal or access point. The threshold value for determining whether to set NAV is usually the minimum receiving sensitivity value.

[0005] In addition, in 11ax, the introduction of SR (Spatial Reuse), which reuses radio resources used by OBSS, has been agreed upon (see Non-Patent Document 1). The purpose of SR is to increase the transmission opportunities of terminals (or access points) and improve the utilization rate of radio resources when the interference to OBSS (hereinafter referred to as interference) is small, thereby improving the communication performance in a wireless network. One method for realizing SR is to set a threshold value (hereinafter referred to as OBSS_PD (Power Density)) for determining whether or not to set NAV when a wireless frame is received from an OBSS under specific conditions to a value greater than the minimum receiving sensitivity value normally used. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Robert Stacey, “Specification Framework for TGax”, IEEE 802.11-15 / 0132r15 [Non-Patent Document 2] Sigurd Schelstraete, “Multiple NAVs for Spatial Reuse”, IEEE 802.11-15 / 1348 [Non-Patent Document 3] Reza Hedayat, “TXOP Considerations for Spatial Reuse,” IEEE 802.11-15 / 1104 Summary of the Invention

[0007] However, if the level of interference to the OBSS is greater than a specified threshold and a terminal (or access point) misestimates the level of interference and cancels regular NAV, interference will occur to the terminal (or access point) in the OBSS at a level that prevents the terminal in the OBSS from correctly decoding the received signal, which may result in a degradation of the communications performance of the wireless network.

[0008] Therefore, one aspect of the present disclosure provides a wireless station and a communication method that prevent inappropriate cancellation of regular NAV and improves communication performance.

[0009] A first wireless station according to one embodiment of the present disclosure is a first wireless station belonging to a first communication cell, and includes an antenna that receives a trigger frame transmitted from an access point belonging to a second communication cell, the trigger frame requesting uplink multi-user response signals from multiple terminals belonging to the second communication cell and including a desired signal strength (Target RSSI: received signal strength indicator) of the uplink multi-user response signal at the access point; a controller that determines whether an estimated received signal strength that can be measured at the access point when the access point receives a signal transmitted from the first wireless station exceeds a value obtained by adding an allowable interference amount to the Target RSSI, and sets a temporary transmission permission state that allows transmission of a signal to a second wireless station belonging to the first communication cell; and the antenna that transmits the signal when the uplink multi-user response signals are being transmitted from the multiple terminals and when the first wireless station is in the set temporary transmission permission state.

[0010] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0011] According to one embodiment of the present disclosure, it is possible to prevent inappropriate cancellation of regular NAV and improve the communication performance of a wireless network. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a positional relationship between an access point and a terminal according to a first embodiment; [Diagram 2] FIG. 1 is a block diagram showing an example of a configuration of a terminal according to a first embodiment; [Diagram 3] FIG. 1 is a sequence diagram showing an example of the operation of a wireless network when transmitting and receiving an RTS / CTS frame in the first embodiment; [Figure 4]FIG. 1 is a sequence diagram showing an example of an operation of a wireless network when a trigger frame is transmitted and received in the first embodiment; [Diagram 5] FIG. 13 is a diagram illustrating a positional relationship between access points and terminals constituting a wireless network according to a second embodiment; [Figure 6] FIG. 11 is a block diagram showing an example of a configuration of a terminal according to a second embodiment; [Figure 7] FIG. 13 is a diagram illustrating a positional relationship between access points and terminals constituting a wireless network according to a third embodiment; [Figure 8] FIG. 13 is a block diagram showing an example of a configuration of a terminal according to a third embodiment. [Figure 9] FIG. 13 is a sequence diagram showing an example of an operation of a wireless network when transmitting and receiving a trigger frame in the third embodiment. [Figure 10] FIG. 13 is a sequence diagram showing an example of an operation of a wireless network when transmitting and receiving a trigger frame in the fourth embodiment. [Figure 11] FIG. 13 is a diagram illustrating the positional relationship between access points and terminals constituting a wireless network according to a fifth embodiment; [Figure 12] FIG. 13 is a block diagram showing a configuration of a terminal according to a fifth embodiment. [Figure 13] FIG. 13 is a sequence diagram showing an example of an operation of a wireless network when transmitting and receiving a trigger frame in the fifth embodiment. [Figure 14] FIG. 13 is a diagram illustrating the positional relationship between access points and terminals constituting a wireless network according to a sixth embodiment; [Figure 15] FIG. 13 is a block diagram showing an example of a configuration of a terminal according to a sixth embodiment. [Figure 16] FIG. 13 is a sequence diagram showing an example of the operation of a wireless network when transmitting and receiving an RTS / CTS frame in the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. However, more detailed explanation than necessary, for example, detailed explanation of already well-known matters and duplicate explanation of substantially the same configuration, may be omitted.

[0014] It should be noted that the following description and the referenced drawings are provided to enable those skilled in the art to understand the present disclosure, and are not intended to limit the scope of the claims of the present disclosure.

[0015] <Background to this disclosure> The background to this disclosure will be briefly described below.

[0016] In 11ax, it has been agreed that NAVs should be managed separately for intra-BSS and OBSS (see Non-Patent Document 2). This avoids a situation in which the intra-BSS NAV is cancelled by a NAV cancellation request (CF-End: Contention Free-End) from the OBSS, or the OBSS NAV is cancelled by the intra-BSS CF-End. In 11ax, in order to simplify SR processing, when there are multiple OBSSs, the terminal (or access point) does not distinguish between NAVs for each OBSS, but manages two NAVs, the intra-BSS NAV and the regular NAV (the NAV for the OBSS or the NAV for the intra-BSS when it is not possible to distinguish between them).

[0017] Furthermore, in 11ax, as one of the SR methods, it is proposed to cancel the regular NAV even when a CF-End frame (NAV cancellation request frame) is not received under specific conditions (Non-Patent Document 3). In this method, the magnitude of interference to the terminal (or access point) of the OBSS is estimated by using a combination of a trigger signal and a response signal, and the regular NAV is cancelled. If the magnitude of interference of the OBSS can be suppressed to less than a predetermined threshold value derived empirically, for example, this method further improves the effect of SR.

[0018] The following reference non-patent document 1 discloses that a terminal (or an access point) cancels regular NAV when the following conditions are met. The first condition is that when an inter-BSS RTS (Request To Send) frame is received, the RSSI (Received Signal Strength Indicator) is higher than OBSS_PD (a threshold applied when the target is OBSS). The second condition is that when an inter BSS CTS (Clear To Send) frame is received, the RSSI is lower than a predetermined NAV cancellation threshold. [Reference non-patent document 1] Reza Hedayat, “Recipient-aware Spatial Reuse,” IEEE 802.11-16 / 0060

[0019] In addition, the following reference non-patent document 2 discloses that if the RSSI of the trigger frame is lower than OBSS_PD, the terminal (or the access point) cancels the regular NAV upon detecting a UL MU PPDU (UpLink Multi-User Physical layer convergence Protocol Data Unit) transmitted following the trigger frame. [Reference non-patent document 2] Geonjung Ko, “Improving Spatial Reuse During OBSS UL MU Procedure”, IEEE 802.11-15 / 1338

[0020] However, when the measurement accuracy of the terminal's RSSI is low or when the terminals are close to each other, the regular NAV may be cancelled erroneously. This may cause interference of, for example, OBSS_PD or more to the terminal (or access point) of the OBSS, making it impossible to receive the desired signal correctly. In view of this, there is a demand for preventing the cancellation of the regular NAV inappropriately. In the embodiments of the present disclosure described below, a wireless station and a communication method that prevent the cancellation of the regular NAV inappropriately and improve the communication performance of a wireless network will be described. Note that the terminal or access point in each of the following embodiments corresponds to a wireless station.

[0021] <First embodiment> Fig. 1 is a diagram illustrating the positional relationship of access points and terminals constituting wireless network 100 according to the first embodiment. As shown in Fig. 1, wireless network 100 includes access point A, terminal B, terminal C, and access point D. Access point A and terminal B belong to BSS1 (OBSS), and terminal C and access point D belong to BSS2 (intra-BSS).

[0022] [Configuration Description] Fig. 2 is a block diagram showing an example of the configuration of terminal 200 according to the first embodiment. Terminal 200 shown in Fig. 2 corresponds to terminal C shown in Fig. 1. Note that the configurations of access points A and D and terminal B shown in Fig. 1 may also be similar to the configuration of terminal 200 shown in Fig. 1.

[0023] 2, the terminal 200 has a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generating unit 203, a received signal demodulating / decoding unit 204, an RSSI measuring unit 205, a BSS type determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a terminal information setting unit 211. The BSS type determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the terminal information setting unit 211 configure an access control unit 212 (MAC).

[0024] The transmitting / receiving antenna 201 is at least one antenna, and transmits or receives radio signals.

[0025] During transmission, the wireless transceiver unit 202 performs predetermined wireless transmission processing such as D / A conversion and up-conversion to a carrier frequency on the transmission signal input from the transmission signal generation unit 203, and transmits the transmission signal via the transmission / reception antenna 201. During reception, the wireless transceiver unit 202 performs predetermined wireless reception processing such as down-conversion and A / D conversion on the wireless signal received via the transmission / reception antenna 201, and outputs the received wireless signal to the reception signal demodulation and decoding unit 204 and the RSSI measurement unit 205.

[0026] The transmission signal generation unit 203 encodes and modulates the MAC frame input from the MAC frame generation unit 209, and adds control signals (also called preambles) such as a pilot signal used for frequency synchronization and timing synchronization on the receiving side and a channel estimation signal to generate a wireless frame (also called PPDU), which it outputs to the wireless transmission / reception unit 202.

[0027] The received signal demodulation / decoding unit 204 extracts radio frames by performing autocorrelation processing and the like on the radio signal after radio reception processing input from the radio transmission / reception unit 202, and demodulates and decodes the radio frames. The received signal demodulation / decoding unit 204 also extracts preamble information (control signal for the radio frame) and a MAC frame from the radio signal input from the radio transmission / reception unit 202, and outputs the preamble information to the BSS type determination unit 206 and the MAC frame to the transmission prohibition state setting unit 210.

[0028] The RSSI measurement section 205 measures the RSSI based on the radio signal after radio reception processing input from the radio transmission / reception section 202 , and outputs RSSI information including the measurement result to the transmission prohibition state setting section 210 .

[0029] The BSS type determination unit 206 extracts BSS identifier information (hereinafter referred to as BSS color) included in the preamble information input from the received signal demodulation and decoding unit 204, and determines the type of BSS to which the terminal (or access point) that transmitted the received wireless signal belongs. If the BSS color included in the preamble information is the same as the BSS color of the BSS to which the terminal 200 belongs, the BSS type determination unit 206 determines the BSS to be intra-BSS, and if not, determines the BSS to be OBSS. The BSS type determination unit 206 outputs the determination result as BSS type information (information indicating whether the type is intra-BSS or not) to the transmission prohibition state setting unit 210.

[0030] The transmission control unit 207 performs transmission control based on the transmission prohibition state information (information indicating whether transmission is prohibited, i.e., whether or not the NAV is set) input from the transmission prohibition state setting unit 210 and the buffer state information (information indicating the presence or absence of transmission data) input from the transmission buffer 208. Specifically, when the NAV is not set and the transmission buffer 208 has transmission data, the transmission control unit 207 outputs a transmission data generation instruction to the transmission data generation unit.

[0031] The transmission buffer 208 stores transmission data to be transmitted from the terminal 200 to another terminal (or an access point). The transmission buffer 208 also outputs to the transmission control unit 207 buffer status information indicating the presence or absence of transmission data.

[0032] The MAC frame generation unit 209 performs MAC frame generation processing such as adding a MAC header to the transmission data input from the transmission buffer 208 based on a transmission data generation instruction input from the transmission control unit 207. The MAC frame generation unit 209 outputs the generated MAC frame to the transmission signal generation unit 203.

[0033] The transmission prohibition state setting unit 210 sets the NAV based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the received signal demodulation and decoding unit 204, the RSSI measurement accuracy information input from the terminal information setting unit 211, and the BSS type information input from the BSS type determination unit 206.

[0034] Specifically, the transmission prohibition state setting unit 210 sets the NAV when it receives a MAC frame that instructs NAV setting, such as an RTS / CTS frame, etc. Also, the transmission prohibition state setting unit 210 cancels the NAV when the set NAV period expires or when it receives a CF-End frame that instructs NAV cancellation.

[0035] When setting the NAV, the transmission prohibition state setting unit 210 distinguishes between intra-BSS NAV and regular NAV states, and the above-mentioned NAV setting and NAV cancellation are performed for each NAV. Specifically, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, for example, it sets the intra-BSS, and when it receives an OBSS MAC frame, it sets the regular NAV.

[0036] However, the transmission prohibition state setting unit 210 judges whether or not to cancel the NAV using a NAV cancellation judgment method described later, and if it judges that the NAV should be cancelled, it cancels the regular NAV even in cases other than the above (when the set NAV period expires or when a CF-End frame is received). The transmission prohibition state setting unit 210 outputs transmission prohibition state information relating to the NAV setting or NAV cancellation to the transmission control unit 207.

[0037] The terminal information setting unit 211 outputs the RSSI measurement accuracy information of the terminal 200 to the transmission prohibition state setting unit 210. In 11ax, two types of terminal classes (also called STA Classes) with different required accuracy such as RSSI measurement accuracy are supported, and the RSSI measurement accuracy information is information that is set based on the terminal class of the terminal 200.

[0038] With this configuration, in the first embodiment, by setting a threshold value for determining whether to cancel the regular NAV in consideration of the accuracy of RSSI measurement, it is possible to prevent a terminal with low accuracy of RSSI measurement from inappropriately canceling its NAV based on an error in RSSI measurement, which would cause significant interference to the OBSS. A specific example of the operation of the wireless network 100 in the first embodiment will be described below.

[0039] [Example] Fig. 3 is a sequence diagram showing an example of the operation of the wireless network 100 when transmitting and receiving an RTS / CTS frame in the first embodiment. As shown in Fig. 3, first, terminal B performs a transmission process of an RTS (Request to Send: CTS trigger signal) frame requesting access point A to transmit a CTS (ST101). Terminal C performs a reception process of the RTS frame from terminal B (ST102). The RTS frame reception process includes measuring the RSSI of the RTS frame. Note that the RSSI measurement method is not particularly limited in this disclosure, and any known RSSI measurement method may be used. Terminal C sets a regular NAV in accordance with the RTS (ST103).

[0040] Next, in response to the RTS frame from terminal B, access point A transmits a CTS (Clear to Send) frame, which is a response signal (ST104). When terminal C receives the CTS from access point A, it measures the RSSI (ST105). Based on the RSSI of the CTS frame, terminal C determines whether or not to cancel the regular NAV (ST106). The method of determining whether to cancel the regular NAV in ST106 will be described in detail later.

[0041] 3 illustrates an example in which it is determined in ST106 not to cancel the regular NAV. In this case, terminal C updates the regular NAV in response to the CTS frame (ST107). Next, terminal B transmits data to access point A (ST108). At this time, because the regular NAV is set in terminal C, terminal C does not transmit to access point D.

[0042] On the other hand, Fig. 4 is a sequence diagram showing an example of the operation of the wireless network 100 when transmitting and receiving a trigger frame in the first embodiment. In Fig. 4, it is assumed that a regular NAV is set in advance for a terminal C.

[0043] As shown in FIG. 4, first, access point A performs trigger frame transmission processing to terminal B (ST201). Terminal C performs trigger frame reception processing from access point A (ST202). The trigger frame reception processing includes measuring the RSSI of the trigger frame. Terminal C determines whether or not to cancel the regular NAV based on the result of measuring the RSSI of the trigger frame (ST203). The method of determining the regular NAV in ST203 will be described in detail later.

[0044] 4 illustrates an example in which it is determined in ST203 not to cancel the regular NAV. In this case, terminal C updates the regular NAV in response to the trigger frame (ST204). Next, terminal B transmits data to access point A (ST205). At this time, since the regular NAV is set in terminal C, terminal C does not transmit to access point D.

[0045] [NAV cancellation determination method 1] The following describes in detail the method of determining whether or not to cancel the regular NAV in ST106 shown in FIG. 3 or ST203 shown in FIG.

[0046] NAV cancellation determination method 1 described below corresponds to the determination method in ST106 in Fig. 3. In NAV cancellation determination method 1, terminal C sets thresholds used for determining NAV cancellation based on its own terminal's RSSI measurement accuracy information or terminal classes (STA Classes). Terminal C sets a threshold for a trigger signal (first threshold) and a threshold for a response signal (second threshold). Here, the trigger signal is, for example, an RTS frame, and the response signal is, for example, a CTS frame. The first and second thresholds are set higher than the threshold for an intra-BSS signal.

[0047] 11ax supports two types of device classes that require different accuracy such as RSSI measurement accuracy. Class A is a high-function device, and RSSI measurement accuracy must be within ±2 dB. On the other hand, Class B is a low-function device, and RSSI measurement accuracy must be within ±5 dB. In other words, Class B devices are allowed to have a maximum RSSI measurement error of 3 dB compared to Class A devices.

[0048] Therefore, in order to keep interference caused to other terminals due to RSSI measurement errors of Class B terminals within the same range as Class A, it is necessary to set a threshold value for Class B terminals different from that for Class A. Specifically, the first threshold value for Class B terminals is set 3 dB higher than the first threshold value for Class A, and the second threshold value for Class B terminals is set 3 dB lower than the second threshold value for Class A. This value of 3 dB is based on the difference in RSSI measurement accuracy required for the above-mentioned Class A terminals and Class B terminals. Also, the first threshold value is set to be equal to or higher than the second threshold value.

[0049] Then, when terminal C receives a trigger signal (RTS frame) from the OBSS (ST102 in FIG. 3), it measures the RSSI of the RTS frame and determines whether it is higher than a first threshold. Furthermore, terminal C subsequently measures the RSSI of a response signal (CTS frame) transmitted from the OBSS and determines whether it is lower than a second threshold. If the RSSI of the RTS frame is higher than the first threshold and the RSSI of the CTS frame is lower than the second threshold, terminal C cancels the regular NAV. Note that terminal C may determine whether to cancel the regular NAV based only on the result of the determination of whether the RSSI of the RTS frame is higher than the first threshold, without determining whether the RSSI of the RTS frame is higher than the first threshold.

[0050] With this determination method, even if terminal C is a Class B terminal, i.e., a terminal with relatively low RSSI measurement accuracy, it is possible to determine whether to cancel the regular NAV based on a threshold value set in consideration of the measurement accuracy. Therefore, even if terminal C is a Class B terminal, i.e., a terminal with relatively low RSSI measurement accuracy, it is possible to reduce interference with OBSS terminals (or access points). Therefore, it is possible to prevent inappropriate cancellation of regular NAV and improve the communication performance of the wireless network. The first or second threshold value for Class A terminals may be, for example, OBSS_PD.

[0051] [NAV cancellation determination method 2] NAV cancellation determination method 2 described below corresponds to the determination method in ST203 in Fig. 4. In NAV cancellation determination method 2, terminal C sets a threshold value used for determining NAV cancellation based on its own terminal's RSSI measurement accuracy information or terminal class. Terminal C sets a threshold value for a trigger signal. Here, the trigger signal is, for example, a trigger frame. This threshold value is set higher than the threshold value for an intra-BSS signal.

[0052] NAV cancellation determination method 2 differs from determination method 1 in that the determination is made using the RSSI of the trigger frame. When terminal C receives a trigger frame from the OBSS, it determines whether the RSSI of the trigger frame is lower than a threshold value. If the RSSI of the trigger frame is lower than the threshold value, terminal C cancels the regular NAV. Note that the method of setting the threshold value may be the same as the method of setting the second threshold value in the above-mentioned NAV cancellation determination method 1 (i.e., set 3 dB lower than OBSS_PD), or a different setting method may be adopted.

[0053] With this determination method, like NAV cancellation determination method 1, even if terminal C is a terminal with relatively low RSSI measurement accuracy, it is possible to determine whether to cancel regular NAV based on a threshold value set in consideration of measurement accuracy. Therefore, even if terminal C is a terminal with relatively low RSSI measurement accuracy, it is possible to reduce interference with terminals (or access points) in the OBSS. Therefore, it is possible to prevent inappropriate cancellation of regular NAV and improve the communication performance of the wireless network.

[0054] <Second embodiment> The second embodiment will be described below. Fig. 5 is a diagram illustrating the positional relationship of access points and terminals constituting a wireless network 100' according to the second embodiment. As shown in Fig. 5, in the wireless network 100', access point A and terminal B belong to BSS1 (OBSS), and terminal C and access point D belong to BSS2 (intra-BSS), which is similar to the first embodiment shown in Fig. 1, but the distance between terminals B and C is closer than in the first embodiment.

[0055] In this way, when the distance between terminal B and terminal C is relatively short, the RSSI of the signal transmitted from terminal C to terminal B will be close to the strength of the RSSI of the signal transmitted from access point A to terminal B, and interference from terminal C may degrade the reception quality of the signal transmitted from access point A to terminal B. In such a case, there is a high possibility that terminal B will fail to receive the signal from access point A. In the second embodiment, a wireless network 100' that can perform communication favorably without degrading communication quality even in such a case will be described.

[0056] [Configuration Description] Fig. 6 is a block diagram showing an example of the configuration of terminal 200' according to the second embodiment. Terminal 200' shown in Fig. 6 corresponds to terminal C shown in Fig. 5. Note that access points A and D and terminal B shown in Fig. 5 may have the same configuration as terminal 200' shown in Fig. 6.

[0057] As shown in FIG. 6, the terminal 200′ includes a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generating unit 203, a reception signal demodulating / decoding unit 204, an RSSI measuring unit 205, a BSS type determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, and a transmission prohibition state setting unit 210. In addition, the BSS type determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, and the transmission prohibition state setting unit 210 configure an access control unit 212′ (MAC). That is, the terminal 200′ in the second embodiment differs from the terminal 200 in the first embodiment shown in FIG. 2 in that it does not include the terminal information setting unit 211. In addition, the operation of the transmission prohibition state setting unit 210 is slightly different from that in the first embodiment.

[0058] The transmission prohibition state setting unit 210 sets the NAV based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the received signal demodulation and decoding unit 204, and the BSS type information input from the BSS type determination unit 206. Furthermore, the transmission prohibition state setting unit 210 cancels the NAV when the set NAV period expires or when a CF-End frame instructing to cancel the NAV is received.

[0059] When setting the NAV, the transmission prohibition state setting unit 210 distinguishes between intra-BSS NAV and regular NAV states, and the above-mentioned NAV setting and NAV cancellation are performed for each NAV. Specifically, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, for example, it sets the intra-BSS, and when it receives an OBSS MAC frame, it sets the regular NAV.

[0060] However, the transmission prohibition state setting unit 210 judges whether or not to cancel the NAV using a NAV cancellation judgment method described later, and if it is judged that the NAV should be cancelled, it cancels the regular NAV in other cases as well. The transmission prohibition state setting unit 210 outputs transmission prohibition state information relating to the NAV setting or NAV cancellation to the transmission control unit 207.

[0061] [Example] An example of the operation of wireless network 100' in the second embodiment is similar to the example of operation shown in Fig. 3 or Fig. 4, and therefore a description thereof will be omitted. However, the NAV cancellation determination method in ST 106 in Fig. 3 or ST 203 in Fig. 4 is slightly different from NAV cancellation determination methods 1 and 2 described in the first embodiment. The NAV cancellation determination method in the second embodiment will be described below.

[0062] [NAV cancellation determination method] The NAV release determination method described below corresponds to the determination method in ST106 in Fig. 3. In the NAV release determination method in the second embodiment, terminal C sets a threshold value for the upper limit value of the trigger signal (third threshold value), a threshold value for the lower limit value of the trigger signal (fourth threshold value), and a threshold value for the response signal (second threshold value). Here, the trigger signal is, for example, an RTS frame, and the response signal is, for example, a CTS frame. The third, fourth, and second threshold values ​​are set higher than the threshold value for intra-BSS signals.

[0063] When terminal C receives a trigger signal (RTS frame) from the OBSS (ST102 in FIG. 3), it measures the RSSI of the RTS frame and determines whether it is higher than the third threshold value and whether it is lower than the fourth threshold value. That is, terminal C determines whether the RSSI of the RTS frame is within a predetermined range defined by the third threshold value and the fourth threshold value.

[0064] Terminal C then measures the RSSI of the response signal (CTS frame) transmitted from the OBSS and determines whether it is lower than the second threshold. If the RSSI of the RTS frame is within a predetermined range and is lower than the second threshold, terminal C cancels the regular NAV.

[0065] The third threshold may be, for example, OBSS_PD. The fourth threshold may be a predetermined threshold greater than the third threshold. For example, the fourth threshold may be a value obtained by adding a positive offset value to the third threshold. This can reduce the amount of signaling required to notify the fourth threshold.

[0066] In the second embodiment, the NAV is cancelled in terminal C only when the RSSI of the trigger signal from the OBSS is within a predetermined range (a range higher than the third threshold and lower than the fourth threshold) and the RSSI of the response signal is lower than the second threshold. Therefore, in cases where a decrease in reception quality in terminal B is expected due to interference from terminal C, such as when the distance between access point A and terminal C is short, it is possible to reduce degradation of communication performance in wireless network 100' by preventing NAV cancellation when the RSSI of the trigger signal is not within the predetermined range. Therefore, it is possible to prevent inappropriate cancellation of regular NAV and improve the communication performance of the wireless network.

[0067] In the above-described operation example of the second embodiment, an operation example when transmitting and receiving an RTS / CTS frame has been described, but the present disclosure is not limited to this. That is, the second embodiment can also be applied to when transmitting and receiving a trigger frame.

[0068] <Third embodiment> The third embodiment will be described below. FIG. 7 is a diagram illustrating the positional relationship of access points and terminals constituting a wireless network 100'' according to the third embodiment. As shown in FIG. 7, the third embodiment differs from the wireless network 100 of the first embodiment shown in FIG. 1 in that a terminal E belonging to BSS1 (OBSS) is present.

[0069] In such a configuration, access point A may transmit a trigger frame requesting MU-BA (Multi-User Block Ack) transmission to multiple terminals, such as terminal B and terminal E. Block Ack is defined in IEEE 802.11e and is a response to multiple received data in one frame. MU-BA is a method of multiplexing multiple users using MU (Multi-User) multiplexing to transmit a Block Ack. MU multiplexing is a method of frequency and spatial multiplexing of multiple terminals.

[0070] In such a case, it may happen that the MU-BA transmission from terminals B and E that have received the trigger frame is not received by access point A due to interference from terminal C, for example. If such a case occurs, access point A will resend the trigger frame requesting another MU-BA transmission to terminals B and E, which may increase the amount of communication and degrade the communication performance of wireless network 100''. In the third embodiment, a wireless network 100'' that can perform communication favorably without degrading communication quality even in such a case will be described.

[0071] [Configuration Description] FIG. 8 is a block diagram showing an example of the configuration of a terminal 200″ according to the third embodiment. The terminal 200″ shown in FIG. 8 corresponds to the terminal C shown in FIG. 7. The access points A and D and the terminals B and E shown in FIG. 7 may also have the same configuration as the terminal 200″ shown in FIG. 8.

[0072] As shown in FIG. 8, the terminal 200″ includes a transmitting / receiving antenna 201, a radio transmitting / receiving unit 202, a transmission signal generating unit 203, a reception signal demodulating / decoding unit 204, a BSS type determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a trigger information analyzing unit 213. In addition, the BSS type determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the trigger information analyzing unit 213 configure an access control unit 212″ (MAC). That is, the terminal 200″ in the third embodiment differs from the terminal 200 in the first embodiment shown in FIG. 2 in that it does not include an RSSI measuring unit and a terminal information setting unit 211, but includes a trigger information analyzing unit 213. In addition, the operation of the transmission prohibition state setting unit 210 differs from that in the first and second embodiments.

[0073] The trigger information analysis unit 213 extracts trigger type information relating to the trigger type from the trigger frame input from the received signal demodulation and decoding unit 204 , and outputs the information to the transmission prohibition state setting unit 210 .

[0074] The transmission prohibition state setting unit 210 sets the NAV based on the MAC frame input from the received signal demodulation and decoding unit 204, the BSS type information input from the BSS type determination unit 206, and the trigger type input from the trigger information analysis unit 213. Furthermore, the transmission prohibition state setting unit 210 cancels the NAV when the set NAV period expires or when a CF-End frame instructing to cancel the NAV is received.

[0075] When setting the NAV, the transmission prohibition state setting unit 210 distinguishes between intra-BSS NAV and regular NAV states, and the above-mentioned NAV setting and NAV cancellation are performed for each NAV. Specifically, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, for example, it sets the intra-BSS, and when it receives an OBSS MAC frame, it sets the regular NAV.

[0076] However, the transmission prohibition state setting unit 210 judges whether or not to cancel the NAV using a NAV cancellation judgment method described later, and if it is judged that the NAV should be cancelled, it cancels the regular NAV in other cases as well. The transmission prohibition state setting unit 210 outputs transmission prohibition state information relating to the NAV setting or NAV cancellation to the transmission control unit 207.

[0077] [Example] FIG. 9 is a sequence diagram showing an example of the operation of the wireless network 100'' when transmitting and receiving a trigger frame in the third embodiment. In FIG. 9, it is assumed that a regular NAV is set in advance for a terminal C.

[0078] As shown in FIG. 9, first, access point A transmits a trigger frame requesting MU-BA transmission to terminal B and terminal E (ST301).

[0079] When terminal C receives the trigger frame from access point A, it identifies the trigger type (ST302). Based on the identification result in ST302, terminal C determines whether or not to cancel the regular NAV (ST303). The method of determining the regular NAV in ST303 will be described in detail later.

[0080] 9 illustrates a case where it is determined not to cancel the regular NAV in ST 303. In this case, terminal C continues the regular NAV and maintains the transmission prohibited state.

[0081] Next, terminal B and terminal E perform MU-BA transmission to access point A (ST304 and ST305). At this time, regular NAV is set in terminal C, so terminal C does not perform transmission to access point D.

[0082] [NAV cancellation determination method] The following describes in detail the method of determining whether or not to cancel the regular NAV in ST303 shown in FIG.

[0083] In 11ax, MU-BA is transmitted in UL MU PPDU. As described above, when receiving MU-BA from multiple terminals, if reception at access point A fails due to interference, the traffic increases due to retransmission of trigger frame and MU-BA, and the communication performance of wireless network 100'' deteriorates. For this reason, it is desirable to prevent interference. Also, since MU-BA has a short PPDU length, the effect of canceling regular NAV is small.

[0084] Therefore, in the third embodiment, when terminal C receives a trigger frame, it extracts the trigger type information and determines the trigger type. If the trigger type is MU-BAR (Multi-User Block Ack Request), which requests MU-BA transmission, it does not cancel the regular NAV.

[0085] In this way, in the third embodiment, a determination is made as to whether or not to cancel the regular NAV based on the trigger type, and if the trigger type is MU-BAR, the regular NAV is not canceled. This allows MU-BA to be preferentially transmitted and received, making it possible to prevent a decrease in the communication performance of the wireless network 100'' due to retransmission of the trigger frame and MU-BA, and to maintain the effect of SR. Note that, when terminal C determines that the received trigger frame is of a trigger type other than MU-BAR, it is possible to maintain the effect of SR by performing conventional NAV control. Therefore, it is possible to prevent inappropriate cancellation of the regular NAV and improve the communication performance of the wireless network.

[0086] In the third embodiment, a case has been described in which access point A, terminal B, and terminal E belong to an OBSS, and access point A transmits a trigger frame including an MU-BAR to terminals B and E, but the present disclosure is not limited to this. For example, the third embodiment can also be applied to a case in which many terminals belong to an OBSS, and access point A transmits an MU-BAR to these terminals.

[0087] <Fourth embodiment> The fourth embodiment will be described below. The positional relationship between the access points and terminals constituting a wireless network 100″ according to the fourth embodiment is similar to that of the wireless network 100″ according to the third embodiment illustrated in FIG.

[0088] In a wireless network 100'' as shown in FIG. 7, when the number of terminals multiplexed by access point A and SR (MU multiplexing number) increases, the probability of failure of reception by SR increases due to the influence of the positional relationship between the terminals and the accuracy of RSSI measurement. Furthermore, when the multiplexing number is large, noise increases and the influence of interference by terminal C becomes greater. For this reason, in the fourth embodiment, a wireless network 100'' that can perform communication favorably without degrading communication quality even when the multiplexing number is large will be described.

[0089] [Configuration Description] The configuration of the terminal 200'' in the fourth embodiment is also similar to that of the terminal 200'' in the third embodiment shown in FIG. 8. However, the operations of the transmission inhibition state setting unit 210 and the trigger information analysis unit 213 are slightly different from those in the third embodiment.

[0090] The trigger information analyzer 213 extracts multiplex number information relating to the number of multiplexed MUs included in the trigger frame input from the received signal demodulator / decoder 204 , and outputs this to the transmission prohibition state setting unit 210 .

[0091] The transmission prohibition state setting unit 210 sets the NAV based on the MAC frame input from the received signal demodulation and decoding unit 204, the BSS type information input from the BSS type determination unit 206, and the multiplex number information input from the trigger information analysis unit 213. Furthermore, the transmission prohibition state setting unit 210 cancels the NAV when the set NAV period expires or when a CF-End frame instructing to cancel the NAV is received.

[0092] When setting the NAV, the transmission prohibition state setting unit 210 distinguishes between intra-BSS NAV and regular NAV states, and the above-mentioned NAV setting and NAV cancellation are performed for each NAV. Specifically, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, for example, it sets the intra-BSS, and when it receives an OBSS MAC frame, it sets the regular NAV.

[0093] However, the transmission prohibition state setting unit 210 judges whether or not to cancel the NAV using a NAV cancellation judgment method described later, and if it is judged that the NAV should be cancelled, it cancels the regular NAV in other cases as well. The transmission prohibition state setting unit 210 outputs transmission prohibition state information relating to the NAV setting or NAV cancellation to the transmission control unit 207.

[0094] [Example] FIG. 10 is a sequence diagram showing an example of the operation of the wireless network 100'' when transmitting and receiving a trigger frame in the fourth embodiment. In FIG. 10, it is assumed that a regular NAV is set in advance for a terminal C.

[0095] As shown in FIG. 10, first, access point A transmits a trigger frame requesting data transmission to terminal B and terminal E (which may include terminals B and E if more terminals exist in the OBSS) (ST401).

[0096] When terminal C receives the trigger frame from access point A, it extracts information relating to the number of MUs multiplexed (ST402). The information relating to the number of MUs multiplexed is included in the trigger frame, for example.

[0097] Terminal C determines whether or not to cancel the regular NAV based on the information on the number of multiplexed MUs extracted in ST402 (ST403). The method of determining the regular NAV in ST403 will be described in detail later.

[0098] 10 illustrates a case where it is determined not to cancel the regular NAV in ST 403. In this case, terminal C continues the regular NAV and maintains the transmission prohibited state.

[0099] Next, terminal B and terminal E transmit data to access point A (ST404 and ST405). At this time, regular NAV is set in terminal C, so terminal C does not transmit data to access point D.

[0100] [NAV cancellation determination method] The following describes in detail the method of determining whether or not to cancel the regular NAV in ST403 shown in Fig. 10. That is, terminal C does not cancel the regular NAV if the number of MUs multiplexed notified by the trigger frame is higher than a predetermined threshold value.

[0101] In this way, in the fourth embodiment, a decision is made as to whether or not to cancel the regular NAV depending on the MU multiplexing number, and if the MU multiplexing number is higher than a predetermined threshold, the regular NAV is not canceled. This makes it possible to prevent a decrease in the communication performance of the wireless network 100'' due to data retransmission, and to maintain the effects of SR. Note that, when the MU multiplexing number is equal to or lower than a predetermined threshold, terminal C can maintain the effects of SR by performing conventional NAV control. This makes it possible to prevent inappropriate cancellation of the regular NAV and improve the communication performance of the wireless network.

[0102] <Fifth embodiment> The fifth embodiment will be described below. FIG. 11 is a diagram illustrating the positional relationship between access points and terminals constituting a wireless network 100'' according to the fifth embodiment. As shown in FIG. 11, in the wireless network 100'' the distance from terminal B to access point A and the distance from terminal C to access point A are approximately equal or fall within a predetermined difference.

[0103] In such a case, the RSSI of a signal transmitted from terminal B to access point A becomes close to the RSSI of a signal transmitted from terminal C to access point A. This is because, at access point A, the strengths of the signal transmitted from terminal B (desired signal) and the signal transmitted from terminal C (interference signal) become almost the same, which may result in a deterioration in the reception quality at access point A. In the fifth embodiment, a wireless network 100''' that can perform favorable communication without degrading communication quality even in such a case will be described.

[0104] [Configuration Description] FIG. 12 is a block diagram showing the configuration of a terminal 200'' according to the fifth embodiment. The terminal 200'' shown in FIG. 12 corresponds to the terminal C shown in FIG. 11. The access points A and D and the terminal B shown in FIG. 11 may also have the same configuration as the terminal 200''' shown in FIG. 12.

[0105] As shown in FIG. 12, the terminal 200''' has a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generating unit 203, a reception signal demodulating / decoding unit 204, an RSSI measuring unit 205, a BSS type determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a trigger information analyzing unit 213. In addition, the BSS type determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the trigger information analyzing unit 213 configure an access control unit 212''' (MAC). That is, the terminal 200''' in the fifth embodiment differs from the terminal 200 in the first embodiment shown in FIG. 2 in that it does not have the terminal information setting unit 211, but has the trigger information analyzing unit 213. In addition, the operation of the transmission prohibition state setting unit 210 is slightly different from that in the first embodiment.

[0106] The trigger information analysis unit 213 extracts the target RSSI and AP Tx power contained in the trigger frame input from the received signal demodulation and decoding unit 204 , and outputs them to the transmission prohibition state setting unit 210 .

[0107] The transmission prohibition state setting unit 210 sets the NAV based on the MAC frame input from the received signal demodulation and decoding unit 204, the BSS type information input from the BSS type determination unit 206, and the target RSSI and AP Tx power input from the trigger information analysis unit 213. Furthermore, the transmission prohibition state setting unit 210 cancels the NAV when the set NAV period expires or when a CF-End frame instructing to cancel the NAV is received.

[0108] When setting the NAV, the transmission prohibition state setting unit 210 distinguishes between intra-BSS NAV and regular NAV states, and the above-mentioned NAV setting and NAV cancellation are performed for each NAV. Specifically, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, for example, it sets the intra-BSS, and when it receives an OBSS MAC frame, it sets the regular NAV.

[0109] However, the transmission prohibition state setting unit 210 judges whether or not to cancel the NAV using a NAV cancellation judgment method described later, and if it is judged that the NAV should be cancelled, it cancels the regular NAV in other cases as well. The transmission prohibition state setting unit 210 outputs transmission prohibition state information relating to the NAV setting or NAV cancellation to the transmission control unit 207.

[0110] [Example] FIG. 13 is a sequence diagram showing an example of the operation of the wireless network 100'''' when transmitting and receiving a trigger frame in the fifth embodiment. In FIG. 13, it is assumed that a regular NAV is set in advance for a terminal C.

[0111] As shown in FIG. 13, first, access point A transmits a trigger frame to terminal B (ST501). Terminal C performs trigger frame reception processing from access point A (ST502). The trigger frame reception processing includes extracting target RSSI and AP Tx power, and measuring RSSI. Based on the RSSI of the trigger frame and the AP Tx power extracted from the trigger frame, terminal C estimates the RSSI that may be measured at access point A when terminal C transmits data (ST503). Terminal C then determines whether or not the RSSI estimated in ST503 is higher than a value obtained by adding a predetermined allowable interference amount to the target RSSI, and determines whether or not to cancel the regular NAV based on the determination result (ST504). The method of determining the regular NAV in ST504 will be described in detail later.

[0112] 13 illustrates a case where it is determined not to cancel the regular NAV in ST 503. In this case, terminal C continues the regular NAV and maintains the transmission prohibited state.

[0113] Next, terminal B transmits data to access point A (ST505). At this time, since regular NAV is set in terminal C, terminal C does not transmit data to access point D.

[0114] [NAV cancellation determination method] The following describes in detail the method of determining whether or not to cancel the regular NAV in ST504 shown in FIG.

[0115] As described above, when terminal C receives a trigger frame from the OBSS, it estimates the RSSI that may be measured at access point A of the OBSS when terminal C transmits data, based on the RSSI of the trigger frame and the AP Tx power extracted from the trigger frame. Based on this, terminal C determines whether the estimated RSSI is higher than the value obtained by adding a predetermined allowable interference amount to the target RSSI. If the estimated RSSI is higher than the value obtained by adding the predetermined allowable interference amount to the target RSSI, terminal C does not cancel the regular NAV. Note that the predetermined allowable interference amount is a preset margin.

[0116] In the fifth embodiment, the strength (target RSSI) of the transmission signal (desired signal) from terminal B at access point A is compared with the strength (estimated RSSI) of the transmission signal (interference signal) from terminal C, and if the estimated RSSI is higher than the target RSSI plus a predetermined allowable interference amount, terminal C does not cancel the regular NAV. This makes it possible to reduce degradation of communication performance in wireless network 100'''. Therefore, it is possible to prevent inappropriate cancellation of regular NAV and improve the communication performance of the wireless network.

[0117] Sixth embodiment The third embodiment will be described below. FIG. 14 is a diagram illustrating the positional relationship of access points and terminals constituting a wireless network 100'''' according to the sixth embodiment. As shown in FIG. 14, in the sixth embodiment, there are access point A, terminal B, terminal C, access point D, terminal E, and access point F. Also, access point A and terminal B belong to BSS1 (OBSS), terminal C and access point D belong to BSS2 (intra-BSS), and terminal E and access point F belong to BSS3 (OBSS).

[0118] In this way, when multiple OBSSs exist, in 11ax, terminal C does not distinguish between and manage the NAVs of multiple OBSSs, and therefore canceling the NAV of one OBSS may cause relatively large interference to other OBSSs. In the sixth embodiment, a wireless network 100'''' that can perform communication favorably without degrading communication quality even in such a case will be described.

[0119] [Configuration Description] FIG. 15 is a block diagram showing an example of the configuration of terminal 200'''' according to the sixth embodiment. Terminal 200'''' shown in FIG. 15 corresponds to terminal C shown in FIG. 14. Note that access points A, D, and F and terminals B and E shown in FIG. 14 may also have the same configuration as terminal 200'''' shown in FIG. 15.

[0120] 15, the terminal 200'''' has a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generating unit 203, a received signal demodulating / decoding unit 204, an RSSI measuring unit 205, a BSS type determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a target BSS information storage unit 214. Furthermore, the BSS type determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the target BSS information storage unit 214 configure an access control unit 212'''' (MAC).

[0121] The transmission prohibition state setting unit 210 performs NAV setting based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the received signal demodulation and decoding unit 204, the BSS type information input from the BSS type determination unit 206, and the target BSS information input from the target BSS information storage unit 214. Details of the target BSS information will be described later. Furthermore, the transmission prohibition state setting unit 210 cancels the NAV when the set NAV period expires or when a CF-End frame instructing cancellation of the NAV is received.

[0122] When setting the NAV, the transmission prohibition state setting unit 210 distinguishes between intra-BSS NAV and regular NAV states, and the above-mentioned NAV setting and NAV cancellation are performed for each NAV. Specifically, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, for example, it sets the intra-BSS, and when it receives an OBSS MAC frame, it sets the regular NAV.

[0123] However, the transmission prohibition state setting unit 210 judges whether or not to cancel the NAV using a NAV cancellation judgment method described later, and if it is judged that the NAV should be cancelled, it cancels the regular NAV in other cases as well. The transmission prohibition state setting unit 210 outputs transmission prohibition state information relating to the NAV setting or NAV cancellation to the transmission control unit 207.

[0124] Furthermore, if the target BSS information needs to be updated, the transmission prohibition state setting unit 210 generates new target BSS information and outputs it to the target BSS information storage unit 214 .

[0125] The target BSS information storage unit 214 stores the target BSS information. When new target BSS information is input from the transmission prohibition state setting unit 210, the target BSS information storage unit 214 updates the stored target BSS information with the new target BSS information. Furthermore, the target BSS information storage unit 214 outputs the stored target BSS information to the transmission prohibition state setting unit 210 as necessary.

[0126] [Example] FIG. 16 is a sequence diagram showing an example of the operation of the wireless network 100'''' when transmitting and receiving an RTS / CTS frame in the sixth embodiment.

[0127] As shown in Fig. 16, first, access point F transmits an RTS frame to terminal E (ST601). Terminal C performs processing to receive the RTS frame from access point F (ST602). The RTS frame reception processing includes extracting the BSS color from the RTS frame and measuring the RSSI of the RTS frame. Terminal C sets the regular NAV in accordance with the RTS frame (ST603).

[0128] When terminal C sets the regular NAV, it generates target BSS information (ST604). Here, the target BSS information is information indicating the BSS for which the NAV is set. In other words, the target BSS information generated in ST604 is information indicating that the target is BSS3 shown in FIG. 14. Note that the target BSS information includes the BSS color of the target BSS and the RSSI of the RTS frame.

[0129] Next, terminal E transmits a CTS frame, which is a response signal to the RTS frame, to access point F (ST605). Terminal C performs processing to receive the CTS frame from terminal E (ST606). The CTS frame reception processing includes extracting the BSS color from the CTS frame and measuring the RSSI of the CTS frame.

[0130] Terminal C then compares the RSSI stored in ST604 with the RSSI of the CTS frame received in ST606, and if the RSSI of the CTS frame is higher, it updates the target BSS information (ST607). Here, it is assumed that the current RSSI (RSSI from terminal E) is higher than the stored RSSI (RSSI from access point F), and terminal C updates the target BSS information. Note that in ST607, terminal C updates only the RSSI included in the target BSS information, and does not update the BSS color.

[0131] Terminal C determines whether or not to cancel the regular NAV (ST608). The method of determining the regular NAV in ST608 will be described later in detail.

[0132] 16 illustrates an example in which it is determined not to cancel the regular NAV in ST608. In this case, terminal C continues the regular NAV and maintains the transmission prohibited state.

[0133] Next, access point F transmits data to terminal E (ST609). At this time, since regular NAV is set in terminal C, terminal C does not transmit data to access point D.

[0134] Next, assume that terminal B transmits an RTS frame to access point A (ST610). Terminal C performs processing to receive the RTS frame from terminal B (ST611). The RTS frame reception processing includes extracting the BSS color from the RTS frame and measuring the RSSI of the RTS frame.

[0135] Terminal C determines whether or not to cancel the regular NAV (ST612). The method of determining the regular NAV in ST612 will be described later in detail.

[0136] 16 illustrates an example in which it is determined not to cancel regular NAV in ST612. In this case, terminal C continues regular NAV and maintains the transmission prohibited state. If regular NAV is not canceled in ST612, terminal C compares the stored RSSI with the current RSSI, and if the current RSSI is higher, updates the target BSS information (ST613). Here, it is assumed that the stored RSSI (RSSI from terminal E) is higher than the current RSSI (RSSI from terminal B), and terminal C does not update the target BSS information.

[0137] Next, access point A transmits a CTS frame, which is a response signal to the RTS frame, to terminal B (ST614). Terminal C performs processing to receive the CTS frame from access point A (ST615). The CTS frame reception processing includes extracting the BSS color from the CTS frame and measuring the RSSI of the CTS frame.

[0138] Terminal C determines whether or not to cancel the regular NAV (ST616). The method of determining the regular NAV in ST616 will be described later in detail.

[0139] 16 illustrates an example in which it is determined not to cancel regular NAV in ST616. In this case, terminal C continues regular NAV and maintains the transmission prohibited state. If regular NAV is not canceled in ST616, terminal C compares the stored RSSI with the current RSSI, and if the current RSSI is higher, updates the target BSS information (ST617). Here, it is assumed that the stored RSSI (RSSI from terminal E) is higher than the current RSSI (RSSI from terminal B), and terminal C does not update the target BSS information.

[0140] Next, terminal B transmits data to access point A (ST618). At this time, since regular NAV is set in terminal C, terminal C does not transmit data to access point D.

[0141] [NAV cancellation determination method] The following describes in detail the method of determining whether or not to cancel the regular NAV in ST608, ST612, and ST616 shown in FIG.

[0142] As described above, when terminal C sets the regular NAV (ST603 in FIG. 16), it stores target BSS information with the set BSS as the target BSS. Then, when determining whether to cancel the regular NAV (ST608, ST612, and ST616), it cancels the regular NAV based on a signal received from the target BSS, but does not cancel the regular NAV based on a signal received from any other BSS.

[0143] Then, when the regular NAV is updated due to the reception of an RTS / CTS frame or the like, if the RSSI of the received signal is higher than the RSSI stored as the target BSS information, terminal C updates the target BSS information using the BSS color and RSSI of the received signal. However, cancellation of the regular NAV due to the expiration of the NAV period may be performed regardless of the target BSS.

[0144] In this manner, in the sixth embodiment, the regular NAV is cancelled based on a signal received from the target BSS, but the regular NAV is not cancelled based on a signal received from any other BSS. Therefore, even when multiple OBSSs exist, it is possible to avoid a situation in which canceling the NAV of one OBSS causes relatively large interference to other OBSSs. Therefore, it is possible to prevent inappropriate cancellation of the regular NAV and improve the communication performance of the wireless network.

[0145] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or amended examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. In addition, the components in the above embodiments may be arbitrarily combined within the scope of the disclosure.

[0146] In the above-mentioned first to sixth embodiments, terminal C cancels the NAV when it receives a CF-End frame. However, for example, when multiple OBSSs exist, terminal C may measure the RSSI of the CF-End frame, compare the measured RSSI with the RSSI of the stored target BSS information, and cancel the regular NAV only when the RSSI of the CF-End frame is higher. With such a configuration, it is possible to prevent inappropriate cancellation of the regular NAV and improve the communication performance of the wireless network.

[0147] The method of releasing the transmission inhibition state in the above embodiment is not limited to releasing the NAV. For example, it is also possible to apply the method to a case where the transmission is temporarily permitted without releasing the NAV (managing the time during which the transmission is permitted, and returning to the transmission inhibition state if the original NAV period is still valid even after the time has passed).

[0148] In the above embodiment, instead of canceling the transmission inhibition state, the transmission power may be lowered to reduce interference.

[0149] In the above embodiment, if the transmission inhibition state cannot be released, it may become impossible to return an ACK for the data reception. In that case, an operation may be performed in which an ACK is transmitted after the NAV is released.

[0150] In each of the above embodiments, the present disclosure has been described taking as an example a case where the present disclosure is configured using hardware, but the present disclosure can also be realized using software in cooperation with hardware.

[0151] Furthermore, each functional block used in the description of each of the above embodiments is typically realized as an LSI, which is an integrated circuit. These may be individually integrated into one chip, or may be integrated into one chip that includes some or all of the functional blocks. Here, we refer to it as an LSI, but depending on the degree of integration, it may also be called an IC, a system LSI, a super LSI, or an ultra LSI.

[0152] The method of integration is not limited to LSI, but may be realized by a dedicated circuit or a general-purpose processor. It is also possible to use a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI.

[0153] Furthermore, if a new integrated circuit technology that can replace LSI appears due to the progress of semiconductor technology or a derivative technology, it is possible to integrate the functional blocks using that technology. The application of biotechnology is also a possibility.

[0154] <Summary of this disclosure> The wireless station disclosed herein is a wireless station in a wireless network having a plurality of wireless stations, and includes a receiving unit that receives a trigger signal transmitted from a first wireless station belonging to an interfering cell to a second wireless station belonging to the interfering cell, and a transmission prohibition period control unit that sets a transmission prohibition period for other wireless stations belonging to a communication cell to which the wireless station belongs, and then, when the receiving unit receives the trigger signal, determines whether or not to cancel the transmission prohibition period based on the reception strength of the trigger signal.

[0155] In the wireless station of the present disclosure, the wireless station is a wireless station that complies with IEEE 802.11ax.

[0156] In the wireless station of the present disclosure, the communication cell to which the wireless station belongs is an intra-Basic Service Set (BSS), and the interfering cell is an overlapping Basic Service Set (OBSS) or an inter-BSS.

[0157] In the wireless station disclosed herein, the transmission inhibition period control unit determines whether to cancel the transmission inhibition period based on a threshold value set based on the reception strength measurement accuracy of the wireless station itself and the reception strength of the trigger signal.

[0158] In the wireless station according to the present disclosure, the transmission inhibition period control unit sets the threshold value based on terminal classes (STA classes) defined in IEEE 802.11ax.

[0159] In the wireless station disclosed herein, when the transmission inhibition period control unit receives a response signal from the second wireless station in response to the trigger signal, the transmission inhibition period control unit determines whether to cancel the transmission inhibition period based on a threshold value set based on the reception strength measurement accuracy of the wireless station, the reception strength of the trigger signal, and the reception strength of the response signal.

[0160] In the wireless station disclosed herein, the transmission inhibition period control unit releases the transmission inhibition period when the reception strength of the trigger signal is within a predetermined range set based on the reception strength measurement accuracy of the wireless station itself.

[0161] In the wireless station disclosed herein, the transmission inhibition period control unit determines the type of the trigger signal, and if the trigger signal is a trigger signal requesting a response from a plurality of wireless stations in the interfering cell, does not cancel the transmission inhibition period.

[0162] In the wireless station disclosed herein, when the trigger signal is a trigger signal requesting a response from a plurality of wireless stations in the interfering cell, the transmission inhibition period control unit extracts, from the trigger signal, information regarding the number of wireless stations for which the trigger signal requests a response, and determines whether to cancel the transmission inhibition period based on the extracted information.

[0163] In the wireless station disclosed herein, the transmission inhibition period control unit compares the strength of a response signal from the second wireless station to the first wireless station, extracted from the trigger signal, with an estimated reception strength at the first wireless station of a signal transmitted from the wireless station to the first wireless station, which has been estimated in advance, and does not release the transmission inhibition period if the difference between the strength and the strength is smaller than a predetermined value.

[0164] In the wireless station disclosed herein, when the transmission prohibition period control unit sets the transmission prohibition period in response to a trigger signal from any of the wireless stations belonging to the interfering cell, it stores an identifier of the interfering cell to which the wireless station that transmitted the trigger signal that triggered the setting of the transmission prohibition period belongs and the reception strength of the trigger signal that triggered the setting of the transmission prohibition period, and when a new trigger signal is received from the interfering cell, it releases the transmission prohibition period if the reception strength of the newly received trigger signal is higher than the reception strength of the stored trigger signal.

[0165] The communication method disclosed herein is a communication method in a wireless network having a plurality of terminals or wireless stations which are access points, and when one of the plurality of wireless stations sets a transmission prohibition period for other wireless stations which belong to a communication cell to which the wireless station belongs, and then receives a trigger signal transmitted from a first wireless station which belongs to an interfering cell to which the wireless station does not belong, to a second wireless station which belongs to the interfering cell, the one wireless station determines whether or not to release the transmission prohibition period based on the receiving strength of the trigger signal.

[0166] In the communication method disclosed herein, the wireless station is a wireless station that complies with IEEE 802.11ax.

[0167] In the communication method of the present disclosure, the communication cell to which the own station belongs is an intra-Basic Service Set (intra-BSS), and the interfering cell is an overlapping Basic Service Set (OBSS) or an inter-BSS.

[0168] In the communication method disclosed herein, the first wireless station determines whether to cancel the transmission inhibition period based on a threshold value set based on the reception strength measurement accuracy of the first wireless station and the reception strength of the trigger signal.

[0169] In the communication method of the present disclosure, the one wireless station sets the threshold value based on terminal classes (STA classes) defined in IEEE 802.11ax.

[0170] In the communication method disclosed herein, when the first wireless station receives a response signal from the second wireless station in response to the trigger signal, the first wireless station determines whether to cancel the transmission inhibition period based on a threshold value set based on the reception strength measurement accuracy of the first wireless station, the reception strength of the trigger signal, and the reception strength of the response signal.

[0171] In the communication method disclosed herein, the first wireless station releases the transmission inhibition period when the reception strength of the trigger signal is within a predetermined range that is set based on the reception strength measurement accuracy of the first wireless station.

[0172] In the communication method disclosed herein, the one wireless station determines the type of the trigger signal, and if the trigger signal is a trigger signal requesting a response from a plurality of wireless stations in the interfering cell, does not release the transmission inhibition period.

[0173] In the communication method disclosed herein, when the trigger signal is a trigger signal requesting a response from a plurality of wireless stations in the interfering cell, the one wireless station extracts information regarding the number of wireless stations for which the trigger signal requests a response from the one wireless station, and determines whether to cancel the transmission prohibition period based on the extracted information.

[0174] In the communication method disclosed herein, the first wireless station compares the strength of the response signal from the second wireless station to the first wireless station, extracted from the trigger signal, with an estimated reception strength at the first wireless station of the signal transmitted from the first wireless station to the first wireless station, which has been estimated in advance, and does not release the transmission prohibition period if the difference between the strength and the strength is smaller than a predetermined value.

[0175] In the communication method disclosed herein, when the one wireless station sets the transmission prohibition period in response to a trigger signal from any of the wireless stations belonging to the interfering cell, the one wireless station stores an identifier of the interfering cell to which the wireless station that transmitted the trigger signal that triggered the setting of the transmission prohibition period belongs and the reception strength of the trigger signal that triggered the setting of the transmission prohibition period, and when the one wireless station receives a new trigger signal from the interfering cell, if the reception strength of the newly received trigger signal is higher than the reception strength of the stored trigger signal, the one wireless station releases the transmission prohibition period. [Industrial Applicability]

[0176] The present disclosure is suitable for wireless stations that perform suitable wireless communication in an environment where interference occurs between wireless stations. [Explanation of symbols]

[0177] 100, 100', 100'', 100'''', 100'''' Wireless Network 200, 200', 200'', 200'''', 200'''' terminal 201 Transmitting and receiving antenna 202 Radio transmitter / receiver 203 Transmission signal generator 204 Received signal demodulation and decoding unit 205 RSSI measurement section 206 BSS type determination unit 207 Transmission control section 208 Send Buffer 209 MAC Frame Generation Unit 210 Transmission prohibition state setting section 211 Terminal information setting section 212, 212', 212'', 212'''', 212'''' Access control section 213 Trigger Information Analysis Unit 214 Target BSS information storage unit

Claims

1. A first wireless station belonging to a basic service set (BSS), An antenna for receiving a trigger frame transmitted from an access point belonging to an overlapping BSS (OBSS), the trigger frame requesting uplink multi-user response signals from a plurality of terminals belonging to the OBSS and including a target received signal strength indicator (RSSI) of the uplink multi-user response signal at the access point; a controller that extracts the Target RSSI from the received trigger frame, determines whether an estimated received signal strength that can be measured at the access point when the access point receives a signal transmitted from the first wireless station exceeds a value obtained by adding an allowable interference amount to the extracted Target RSSI, and sets a temporary transmission permission state that allows a second wireless station belonging to the BSS to transmit a signal; Equipped with the antenna transmits the signal when the uplink multi-user response signals are being transmitted from the multiple terminals and when the first wireless station is in the set temporary transmission allowed state; First radio station.

2. The controller sets a temporary transmission permission state based on a reception power value of the trigger frame at the first wireless station. The first wireless station according to claim 1 .

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