Access point

Abstract

To prevent inappropriate cancellation of regular NAV (Network Allocation Vector: transmission prohibited period) and improve communication performance.SOLUTION: An access point belonging to an OBSS that partially overlaps with a BSS includes: a signal generation unit that generates a trigger frame to request a response signal from a plurality of terminals belonging to the OBSS, where the trigger frame includes an AP Tx power subfield indicating a transmission power value of the trigger frame and a target RSSI subfield indicating a desired received signal strength of the response signal at the access point, where the AP Tx power subfield and the Target RSSI subfield are used by a first terminal belonging to the BSS that has received the trigger frame to determine whether it is allowed to transmit to a second terminal belonging to the BSS; and an antenna that transmits the generated trigger frame.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present disclosure relates to an access point that performs suitable wireless communication in an environment where interference occurs between wireless stations.

Background Art

[0002] In IEEE (the Institute of Electrical and Electronics Engineers) 802.11 Task Group (TG) ax, as the next-generation standard of IEEE 802.11ac, the formulation of the technical specifications of IEEE 802.11ax (hereinafter, 11ax) is in progress.

[0003] In the IEEE 802.11 standard, a BSS (Basic Service Set) is defined as a set of wireless stations (also called stations or STAs) that constitute a basic wireless network. In infrastructure mode, a BSS is composed of one access point and multiple terminals (wireless stations other than the access point), and in ad hoc mode, it is composed of multiple terminals. The ad hoc mode BSS is distinguished from the infrastructure mode BSS and is called an IBSS (Independent BSS). A BSS other than the BSS (intra-BSS) to which the own terminal (or access point) belongs is called an OBSS (Overlapping BSS) or inter-BSS. Since multiple communication cells overlap in the OBSS, interference occurs between communication cells in OBSS-to-OBSS communication, and the communication quality deteriorates.

[0004] In wireless communication, due to factors such as distance between radio stations and obstacles, conditions can arise where radio signals cannot reach each other (a radio environment where carrier sense does not function). To address such environments, i.e., environments where hidden terminals exist, the IEEE 802.11 standard provides a collision prevention function using NAV (Network Allocation Vector: transmission blackout period). When an access point or terminal receives a wireless frame for NAV setting at a level above a predetermined threshold, it will prohibit transmission for the NAV period set in the duration information, unless the wireless frame for NAV setting is destined for its own terminal or access point. The threshold value used to determine whether or not to set NAV is usually the minimum reception sensitivity value.

[0005] Furthermore, in 11ax, the introduction of Spatial Reuse (SR), which reuses radio resources used by OBSS, has been agreed upon (see Non-Patent Document 1). The purpose of SR is to improve communication performance in the wireless network by increasing the transmission opportunities by terminals (or access points) when the interference to OBSS (hereinafter referred to as interference) is small, thereby improving the utilization rate of radio resources. One way to realize SR is to set a threshold value (hereinafter referred to as OBSS_PD (Power Density)) used to determine whether or not to set NAV when a radio frame is received from OBSS under specific conditions to a value greater than the value of the minimum reception sensitivity 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 [Overview of the project]

[0007] However, if the level of interference to OBSS exceeds a predetermined threshold, and the terminal (or access point) mistakenly estimates the magnitude of the interference and disables regular NAV, interference may occur to the terminal (or access point) in OBSS that prevents the terminal in OBSS from correctly decoding the received signal, potentially degrading the communication performance of the wireless network.

[0008] Therefore, one aspect of this disclosure provides a radio station and a communication method that prevent improper regular NAV deactivation and improve communication performance.

[0009] An access point according to one aspect of the present disclosure is an access point belonging to an OBSS (Overlapping Basic Service Set) that partially overlaps with a BSS (Basic Service Set), and generates a trigger frame for requesting response signals from a plurality of terminals belonging to the OBSS, wherein the trigger frame includes an AP Tx power subfield indicating the transmit power value of the trigger frame and a Target RSSI (Target received signal strength indicator) subfield indicating the desired received signal strength of the response signal at the access point, and the AP Tx power subfield and the Target RSSI subfield are used by the first terminal belonging to the BSS that receives the trigger frame to determine whether or not to transmit it to a second terminal belonging to the BSS, comprising a signal generation unit and an antenna for transmitting the trigger frame.

[0010] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium, or as any combination of a system, device, method, integrated circuit, computer program, and recording medium.

[0011] According to one aspect of this disclosure, it is possible to prevent improper regular NAV deactivation and improve the communication performance of the wireless network. [Brief explanation of the drawing]

[0012] [Figure 1] A diagram illustrating the positional relationship between the access point and the terminal in the first embodiment. [Figure 2] Block diagram showing an example of the configuration of a terminal according to the first embodiment. [Figure 3] A sequence diagram showing an example of wireless network operation during RTS / CTS frame transmission and reception in the first embodiment. [Figure 4] A sequence diagram showing an example of wireless network operation during trigger frame transmission and reception in the first embodiment. [Figure 5] A diagram illustrating the positional relationship between access points and terminals constituting a wireless network according to the second embodiment. [Figure 6] Block diagram showing an example of the configuration of a terminal according to the second embodiment. [Figure 7] A diagram illustrating the positional relationship between access points and terminals constituting a wireless network according to the third embodiment. [Figure 8] Block diagram showing an example of the configuration of a terminal according to the third embodiment. [Figure 9] In the third embodiment, a sequence diagram showing an example of wireless network operation during trigger frame transmission and reception. [Figure 10] In the fourth embodiment, a sequence diagram showing an example of wireless network operation during trigger frame transmission and reception. [Figure 11]Figure illustrating the positional relationship between an access point and a terminal constituting a wireless network according to the fifth embodiment [Figure 12] Block diagram showing the configuration of a terminal according to the fifth embodiment [Figure 13] Sequence diagram showing an example of the operation of a wireless network during the transmission and reception of a trigger frame in the fifth embodiment [Figure 14] Figure illustrating the positional relationship between an access point and a terminal constituting a wireless network according to the sixth embodiment [Figure 15] Block diagram showing an example of the configuration of a terminal according to the sixth embodiment [Figure 16] Sequence diagram showing an example of the operation of a wireless network during the transmission and reception of an RTS / CTS frame in the sixth embodiment

Embodiments for Carrying Out the Invention

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

[0014] Note that the following description and the drawings referred to are provided for 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 Leading to the Present Disclosure> Hereinafter, the background leading to the present disclosure will be briefly described.

[0016] In 11ax, it is agreed that NAVs should be managed separately for intra-BSS and OBSS (see Non-Patent Document 2). This prevents situations where an intra-BSS NAV is deactivated by a NAV deactivation request (CF-End: Contention Free-End) from an OBSS, or where an OBSS NAV is deactivated by an intra-BSS CF-End. In 11ax, to simplify SR processing, if multiple OBSSs exist, the terminal (or access point) does not distinguish between NAVs for each OBSS, but manages two NAVs: intra-BSS NAV and regular NAV (NAV for OBSS, or NAV for when it is not possible to distinguish between an OBSS and an intra-BSS OBSS).

[0017] Furthermore, in 11ax, one method of signal rescission (SR) has been proposed to deactivate regular NAV even when a CF-End frame (NAV deactivation request frame) is not received under specific conditions (Non-Patent Literature 3). This method uses a combination of trigger and response signals to estimate the magnitude of interference from OBSS to the terminal (or access point) and deactivates regular NAV. If the magnitude of interference from OBSS can be kept below, for example, a predetermined threshold derived empirically, this method further improves the effectiveness of SR.

[0018] Reference Non-Patent Document 1 below discloses that a terminal (or access point) can deactivate 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 deactivation threshold. [Reference non-patent document 1] Reza Hedayat, “Recipient-aware Spatial Reuse,” IEEE 802.11-16 / 0060

[0019] Furthermore, reference non-patent document 2 below discloses that when the RSSI of the trigger frame is lower than OBSS_PD, the terminal (or access point) will deactivate regular NAV upon detecting an 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, if the measurement accuracy of the terminal's RSSI is low, or if the terminals are close together, the regular NAV may be mistakenly deactivated. This can cause interference, such as OBSS_PD or higher, to the OBSS terminal (or access point), preventing the correct reception of the desired signal. For this reason, there is a need to prevent inappropriate deactivation of the regular NAV. The embodiments of this disclosure described below describe a radio station and communication method that prevent inappropriate deactivation of the regular NAV and improve the communication performance of the wireless network. In each of the embodiments described below, the terminal or access point corresponds to the radio station.

[0021] <First Embodiment> Figure 1 is a diagram illustrating the positional relationship of access points and terminals constituting a wireless network 100 according to the first embodiment. As shown in Figure 1, the 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] [Explanation of the structure] Figure 2 is a block diagram showing an example of the configuration of terminal 200 according to the first embodiment. The terminal 200 illustrated in Figure 2 corresponds to terminal C shown in Figure 1. Note that the configurations of access points A and D and terminal B shown in Figure 1 may be the same as those of terminal 200 shown in Figure 1.

[0023] As shown in Figure 2, terminal 200 includes a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generation unit 203, a received signal demodulation / decoding unit 204, an RSSI measurement unit 205, a BSS type determination unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generation unit 209, a transmission prohibition state setting unit 210, and a terminal information setting unit 211. Furthermore, the BSS type determination unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generation unit 209, the transmission prohibition state setting unit 210, and the terminal information setting unit 211 constitute an access control unit 212 (MAC).

[0024] The transmitting / receiving antenna 201 is at least one antenna that transmits or receives wireless signals.

[0025] During transmission, the wireless transceiver unit 202 performs predetermined wireless transmission processing, such as D / A conversion and upconversion to the carrier frequency, on the transmission signal input from the transmission signal generation unit 203, and transmits the transmission signal via the transceiver antenna 201. During reception, the wireless transceiver unit 202 performs predetermined wireless reception processing, such as downconversion and A / D conversion, of the wireless signal received via the transceiver antenna 201, and outputs the received wireless signal to the received signal demodulation / 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, 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 a PPDU), which is then output to the wireless transceiver unit 202.

[0027] The received signal demodulation / decoding unit 204 extracts wireless frames by performing autocorrelation processing on the wireless signal that has been processed by the wireless reception unit 202, and then demodulates and decodes the wireless frames. The received signal demodulation / decoding unit 204 also extracts preamble information (control signals for wireless frames) and MAC frames from the wireless signal input from the wireless reception unit 202, and outputs the preamble information to the BSS type determination unit 206 and the MAC frames to the transmission prohibition state setting unit 210.

[0028] The RSSI measurement unit 205 measures the RSSI based on the wireless signal after wireless reception processing input from the wireless transceiver unit 202, and outputs the RSSI information, including the measurement result, to the transmission disable state setting unit 210.

[0029] The BSS type determination unit 206 extracts the BSS identifier information (hereinafter referred to as BSS color) contained in the preamble information input from the received signal demodulation / decoding unit 204 and determines the type of BSS to which the terminal (or access point) that transmitted the received wireless signal belongs. The BSS type determination unit 206 determines it to be intra-BSS if the BSS color contained in the preamble information is the same as the BSS color of the BSS to which the terminal 200 belongs, and determines it to be OBSS otherwise. The BSS type determination unit 206 outputs the determination result as BSS type information (information indicating whether it 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 status information (information indicating whether transmission is prohibited, i.e., whether NAV is set or not) input from the transmission prohibition status setting unit 210 and the buffer status information (information indicating whether or not there is transmission data) input from the transmission buffer 208. Specifically, if NAV is not set and there is transmission data in the transmission buffer 208, the transmission control unit 207 outputs a transmission data generation instruction to the transmission data generation unit.

[0031] The transmit buffer 208 stores the data that terminal 200 sends to other terminals (or access points). The transmit buffer 208 also outputs buffer status information to the transmit control unit 207 indicating whether or not there is data to transmit.

[0032] The MAC frame generation unit 209 performs MAC frame generation processing, such as adding a MAC header, on the transmission data input from the transmission buffer 208, based on the 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 disable 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 / 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 disable setting unit 210 sets the NAV if it is a MAC frame that instructs NAV settings, such as an RTS / CTS frame. The transmission disable setting unit 210 also cancels the NAV when the set NAV period expires or when it receives a CF-End frame that instructs the cancellation of the NAV.

[0035] The transmission prohibition state setting unit 210 distinguishes between the intra-BSS NAV and the regular NAV when setting the NAV, and the above NAV setting and NAV deactivation are performed for each respective NAV. Specifically, for example, if the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it sets the intra-BSS settings, and if it receives an OBSS MAC frame, it sets the regular NAV settings.

[0036] However, the transmission prohibition state setting unit 210 determines whether or not to cancel NAV using the NAV cancellation determination method described later, and if the determination determines that NAV should be canceled, it cancels regular NAV even in cases other than those mentioned 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 regarding 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 its own terminal 200 to the transmission disable state setting unit 210. In 11ax, two types of terminal classes (also called STA Classes) with different required accuracies such as RSSI measurement accuracy are supported, and the RSSI measurement accuracy information is information set based on the terminal class of its own terminal 200.

[0038] With this configuration, in the first embodiment, by setting a threshold for the regular NAV deactivation determination considering the RSSI measurement accuracy, it is possible to prevent terminals with low RSSI measurement accuracy from inappropriately deactivating NAV based on RSSI measurement errors, thereby causing significant interference to OBSS. Below, a specific example of the operation of the wireless network 100 in the first embodiment will be described.

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

[0040] Next, access point A responds to the RTS frame from terminal B by sending 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 deactivate regular NAV (ST106). Details of the method for determining whether to deactivate regular NAV in ST106 will be described later.

[0041] Figure 3 illustrates the case where ST106 determines that the regular NAV should not be deactivated. In this case, terminal C updates the regular NAV according to the CTS frame (ST107). Next, terminal B transmits data to access point A (ST108). At this time, since the regular NAV is set on terminal C, terminal C does not transmit to access point D.

[0042] On the other hand, Figure 4 is a sequence diagram showing an example of the operation of the wireless network 100 during trigger frame transmission and reception in the first embodiment. In Figure 4, terminal C is assumed to have regular NAV set in advance.

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

[0044] Figure 4 illustrates the case where ST203 determines that the regular NAV should not be deactivated. In this case, terminal C updates the regular NAV according to the trigger frame (ST204). Next, terminal B transmits data to access point A (ST205). At this time, since the regular NAV is set on terminal C, terminal C does not transmit data to access point D.

[0045] [NAV cancellation determination method 1] The following section details the method for determining whether or not to disable regular NAV in ST106 shown in Figure 3, or ST203 shown in Figure 4.

[0046] The NAV deactivation determination method 1 described below corresponds to the determination method in ST106 in Figure 3. In the NAV deactivation determination method 1, terminal C sets thresholds used for determining NAV deactivation based on its own RSSI measurement accuracy information or terminal class (STA Classes). Terminal C sets a threshold for the trigger signal (first threshold) and a threshold for the 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 thresholds for the intra-BSS signals.

[0047] 11ax supports two types of terminal classes with different required accuracy levels, such as RSSI measurement accuracy. Class A terminals are high-performance terminals, requiring an RSSI measurement accuracy of within ±2dB. On the other hand, Class B terminals are low-performance terminals, requiring an RSSI measurement accuracy of within ±5dB. In other words, Class B terminals are allowed an RSSI measurement error of up to 3dB compared to Class A terminals.

[0048] Therefore, in order to keep the interference caused to other terminals by RSSI measurement errors in Class B terminals to the same level as in Class A terminals, it is necessary to set different thresholds for Class B terminals than for Class A terminals. Specifically, the first threshold for Class B terminals should be set 3 dB higher than the first threshold for Class A terminals, and the second threshold for Class B terminals should be set 3 dB lower than the second threshold for Class A terminals. This 3 dB value is based on the difference in the required RSSI measurement accuracy for Class A terminals and Class B terminals, as described above. Alternatively, the first threshold should be set to be higher than or equal to the second threshold.

[0049] When terminal C receives a trigger signal (RTS frame) from OBSS (ST102 in Figure 3), it measures the RSSI of the RTS frame and determines whether it is higher than the first threshold. Terminal C then measures the RSSI of the response signal (CTS frame) transmitted from OBSS and determines whether it is lower than the 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 regular NAV. Alternatively, terminal C may decide whether to cancel regular NAV based only on the result of determining whether the RSSI of the CTS frame is lower than the second threshold, without determining whether the RSSI of the RTS frame is higher than the first threshold.

[0050] This determination method allows for the deactivation of regular NAV based on a threshold set considering the measurement accuracy, even if terminal C is a Class B terminal, i.e., a terminal with relatively low RSSI measurement accuracy. Therefore, even if terminal C is a Class B terminal, i.e., a terminal with relatively low RSSI measurement accuracy, interference to OBSS terminals (or access points) can be reduced. Consequently, inappropriate deactivation of regular NAV can be prevented, and the communication performance of the wireless network can be improved. The first or second threshold for Class A terminals can be, for example, OBSS_PD.

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

[0052] NAV Deactivation Determination Method 2 differs from Determination Method 1 in that it uses the RSSI of the trigger frame for determination. When terminal C receives a trigger frame from OBSS, it determines whether the RSSI of the trigger frame is lower than the threshold. If the RSSI of the trigger frame is lower than the threshold, terminal C deactivates the regular NAV. The method for setting the threshold may be the same as the method for setting the second threshold in NAV Deactivation Determination Method 1 described above (i.e., set 3dB lower than OBSS_PD), or a different setting method may be adopted.

[0053] This determination method, similar to NAV deactivation determination method 1, allows for the deactivation of regular NAV based on a threshold set considering the measurement accuracy, even when terminal C is a terminal with relatively low RSSI measurement accuracy. Therefore, even when terminal C is a terminal with relatively low RSSI measurement accuracy, interference to OBSS terminals (or access points) can be reduced. Consequently, inappropriate deactivation of regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0054] <Second Embodiment> The second embodiment will now be described. Figure 5 is a diagram illustrating the positional relationship of access points and terminals constituting the wireless network 100' according to the second embodiment. As shown in Figure 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), similar to the first embodiment shown in Figure 1. However, the distance between terminal B and terminal C is closer compared to the first embodiment.

[0055] When terminal B and terminal C are relatively close, the RSSI of the transmission signal from terminal C to terminal B becomes close in strength to the RSSI of the transmission signal from access point A to terminal B, and interference from terminal C can degrade the reception quality of the transmission signal from access point A to terminal B. In such cases, terminal B is more likely to fail to receive signals from access point A. In the second embodiment, a wireless network 100' that can communicate effectively without degrading communication quality even in such cases will be described.

[0056] [Explanation of the structure] Figure 6 is a block diagram showing an example of the configuration of terminal 200' according to the second embodiment. Terminal 200' illustrated in Figure 6 corresponds to terminal C shown in Figure 5. Note that the configurations of access points A and D and terminal B shown in Figure 5 may be the same as those of terminal 200' shown in Figure 6.

[0057] As shown in Figure 6, terminal 200' includes a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generation unit 203, a received signal demodulation / decoding unit 204, an RSSI measurement unit 205, a BSS type determination unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generation unit 209, and a transmission prohibition state setting unit 210. Furthermore, the BSS type determination unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generation unit 209, and the transmission prohibition state setting unit 210 constitute the access control unit 212' (MAC). In other words, terminal 200' in the second embodiment differs from the configuration of terminal 200 in the first embodiment shown in Figure 2 in that it does not have a terminal information setting unit 211. Also, the operation of the transmission prohibition state setting unit 210 differs slightly from that of the first embodiment.

[0058] The transmission disable 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 / decoding unit 204, and the BSS type information input from the BSS type determination unit 206. The transmission disable state setting unit 210 also cancels the NAV when the set NAV period expires or when it receives a CF-End frame instructing it to cancel the NAV.

[0059] The transmission prohibition state setting unit 210 distinguishes between the intra-BSS NAV and the regular NAV when setting the NAV, and the above NAV setting and NAV deactivation are performed for each respective NAV. Specifically, for example, if the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it sets the intra-BSS settings, and if it receives an OBSS MAC frame, it sets the regular NAV settings.

[0060] However, the transmission prohibition state setting unit 210 determines whether or not to disable NAV using the NAV disabling determination method described later, and if the determination determines that NAV should be disabled, it will also disable regular NAV in addition to the above. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV disabling to the transmission control unit 207.

[0061] [Example of operation] The operation example of the wireless network 100' in the second embodiment is the same as the operation example shown in Figure 3 or Figure 4, so its explanation will be omitted. However, the NAV deactivation determination method in ST106 in Figure 3 or ST203 in Figure 4 is slightly different from the NAV deactivation determination methods 1 and 2 described in the first embodiment. The NAV deactivation determination method in the second embodiment will be described below.

[0062] [NAV cancellation determination method] The NAV deactivation determination method described below corresponds to the determination method in ST106 in Figure 3. In the NAV deactivation determination method of the second embodiment, terminal C sets a threshold for the upper limit of the trigger signal (third threshold), a threshold for the lower limit of the trigger signal (fourth threshold), and a threshold for the 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 third, fourth, and second thresholds are set higher than the thresholds for the intra-BSS signal.

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

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

[0065] The third threshold can be, for example, OBSS_PD. The fourth threshold can be a predetermined threshold that is greater than the third threshold. For example, the fourth threshold can be the third threshold plus a positive offset value. This reduces the amount of signaling required to notify the fourth threshold.

[0066] In the second embodiment, NAV is deactivated at terminal C only when the RSSI of the trigger signal from OBSS is within a predetermined 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, when the distance between access point A and terminal C is short, and a decrease in reception quality at terminal B is expected due to interference from terminal C, the degradation of communication performance in the wireless network 100' can be reduced by preventing NAV deactivation when the RSSI of the trigger signal is outside the predetermined range. Thus, inappropriate regular NAV deactivation can be prevented, and the communication performance of the wireless network can be improved.

[0067] While the above-described example of operation in the second embodiment describes an example of operation during the transmission and reception of RTS / CTS frames, this disclosure is not limited thereto. In other words, the second embodiment can also be applied to the transmission and reception of trigger frames.

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

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

[0070] In such a case, MU-BA transmissions from terminals B and E, which have received the trigger frame, may not be received by access point A due to interference from terminal C, for example. When this occurs, access point A resends a trigger frame requesting MU-BA transmission to terminals B and E, which increases the amount of communication and can degrade the communication performance of the wireless network 100''. In the third embodiment, a wireless network 100'' that can communicate suitably without degrading communication quality even in such a case will be described.

[0071] [Explanation of the structure] Figure 8 is a block diagram showing an example of the configuration of terminal 200'' according to the third embodiment. Terminal 200'' illustrated in Figure 8 corresponds to terminal C shown in Figure 7. Note that the configurations of access points A and D and terminals B and E shown in Figure 7 may be the same as those of terminal 200'' shown in Figure 8.

[0072] As shown in Figure 8, terminal 200'' includes a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generation unit 203, a received signal demodulation / decoding unit 204, a BSS type determination unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generation unit 209, a transmission prohibition state setting unit 210, and a trigger information analysis unit 213. Furthermore, the BSS type determination unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generation unit 209, the transmission prohibition state setting unit 210, and the trigger information analysis unit 213 constitute the access control unit 212'' (MAC). In other words, terminal 200'' in the third embodiment differs from the configuration of terminal 200 in the first embodiment shown in Figure 2 in that it does not have an RSSI measurement unit and a terminal information setting unit 211, but does have a trigger information analysis unit 213. Also, the operation of the transmission prohibition state setting unit 210 differs from that of the first and second embodiments.

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

[0074] The transmission disable state setting unit 210 sets the NAV based on the MAC frame input from the received signal demodulation / 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. The transmission disable state setting unit 210 also cancels the NAV when the set NAV period expires or when it receives a CF-End frame instructing it to cancel the NAV.

[0075] The transmission prohibition state setting unit 210 distinguishes between the intra-BSS NAV and the regular NAV when setting the NAV, and the above NAV setting and NAV deactivation are performed for each respective NAV. Specifically, for example, if the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it sets the intra-BSS settings, and if it receives an OBSS MAC frame, it sets the regular NAV settings.

[0076] However, the transmission prohibition state setting unit 210 determines whether or not to disable NAV using the NAV disabling determination method described later, and if the determination determines that NAV should be disabled, it will also disable regular NAV in addition to the above. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV disabling to the transmission control unit 207.

[0077] [Example of operation] Figure 9 is a sequence diagram showing an example of the operation of the wireless network 100'' during trigger frame transmission and reception in the third embodiment. In Figure 9, terminal C is assumed to have regular NAV pre-configured.

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

[0079] When terminal C receives a 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 regular NAV (ST303). Details of the method for determining regular NAV in ST303 will be described later.

[0080] Figure 9 illustrates the case where ST303 determines that regular NAV should not be deactivated. In this case, terminal C continues regular NAV and maintains the transmission-prohibited state.

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

[0082] [NAV cancellation determination method] The following section details the method for determining whether or not to disable the regular NAV in ST303, as shown in Figure 9.

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

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

[0085] In the third embodiment, a determination is made as described above whether or not to deactivate regular NAV based on the trigger type, and if the trigger type is MU-BAR, regular NAV is not deactivated. As a result, MU-BA is preferentially transmitted and received, preventing a decrease in the communication performance of the wireless network 100'' due to retransmission of trigger frames and MU-BA, and maintaining the effect of SR. Furthermore, if terminal C determines that the received trigger frame is of a trigger type other than MU-BAR, it can maintain the effect of SR by performing conventional NAV control. Therefore, inappropriate deactivation of regular NAV can be prevented, and the communication performance of the wireless network can be improved.

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

[0087] <Fourth Embodiment> The fourth embodiment will now be described. The positional relationship between the access points and terminals constituting the wireless network 100'' according to the fourth embodiment is the same as that of the wireless network 100'' of the third embodiment illustrated in Figure 7.

[0088] In a wireless network 100'' as illustrated in Figure 7, as the number of terminals performing multiplexing by access point A and SR (MU multiplexing count) increases, the probability of reception failure by SR increases due to factors such as the relative positions of terminals and the accuracy of RSSI measurement. Furthermore, a high number of multiplexing counts increases noise, and the influence of interference from terminal C becomes greater. For this reason, the fourth embodiment describes a wireless network 100'' that can suitably perform communication without degrading communication quality even when the number of multiplexing counts is high.

[0089] [Explanation of the structure] The configuration of terminal 200'' in the fourth embodiment is the same as that of terminal 200'' in the third embodiment shown in Figure 8. However, the operation of the transmission prohibition state setting unit 210 and the trigger information analysis unit 213 differs slightly from that of the third embodiment.

[0090] The trigger information analysis unit 213 extracts multiplexing information related to the MU multiplexing count included in the trigger frame input from the received signal demodulation / decoding unit 204 and outputs it to the transmission disable state setting unit 210.

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

[0092] The transmission prohibition state setting unit 210 distinguishes between the intra-BSS NAV and the regular NAV when setting the NAV, and the above NAV setting and NAV deactivation are performed for each respective NAV. Specifically, for example, if the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it sets the intra-BSS settings, and if it receives an OBSS MAC frame, it sets the regular NAV settings.

[0093] However, the transmission prohibition state setting unit 210 determines whether or not to disable NAV using the NAV disabling determination method described later, and if the determination determines that NAV should be disabled, it will also disable regular NAV in addition to the above. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV disabling to the transmission control unit 207.

[0094] [Example of operation] Figure 10 is a sequence diagram showing an example of the operation of the wireless network 100'' during trigger frame transmission and reception in the fourth embodiment. In Figure 10, terminal C is assumed to have regular NAV pre-configured.

[0095] As shown in Figure 10, first, access point A sends a trigger frame (ST401) to terminals B and E (and may include terminals if there are more terminals in OBSS) requesting them to transmit data.

[0096] When terminal C receives a trigger frame from access point A, it extracts information about the MU multiplexing count (ST402). This information is included, for example, in the trigger frame.

[0097] Terminal C determines whether or not to deactivate regular NAV based on the MU multiplexing information extracted by ST402 (ST403). Details of the method for determining regular NAV in ST403 will be described later.

[0098] Figure 10 illustrates the case where ST403 determines that regular NAV should not be deactivated. In this case, terminal C continues regular NAV and maintains the transmission-prohibited state.

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

[0100] [NAV cancellation determination method] The following describes in detail the method for determining whether or not to cancel regular NAV in ST403, as shown in Figure 10. Specifically, terminal C does not cancel regular NAV if the number of MU multiplexings notified by the trigger frame is higher than a predetermined threshold.

[0101] In the fourth embodiment, a determination is made as described above whether or not to deactivate the regular NAV depending on the number of MU multiplexings, and if the number of MU multiplexings is higher than a predetermined threshold, the regular NAV is not deactivated. This prevents a decrease in the communication performance of the wireless network 100'' due to data retransmission and maintains the effect of SR. Terminal C can maintain the effect of SR by performing conventional NAV control when the number of MU multiplexings is below a predetermined threshold. Therefore, it is possible to prevent inappropriate deactivation of the regular NAV and improve the communication performance of the wireless network.

[0102] <Fifth Embodiment> The fifth embodiment will now be described. Figure 11 is a diagram illustrating the positional relationship between access points and terminals constituting the wireless network 100'' according to the fifth embodiment. As shown in Figure 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 within a predetermined difference.

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

[0104] [Explanation of the structure] Figure 12 is a block diagram showing the configuration of terminal 200''' according to the fifth embodiment. Terminal 200''' illustrated in Figure 12 corresponds to terminal C shown in Figure 11. Note that the configurations of access points A and D and terminal B shown in Figure 11 may be the same as those of terminal 200''' shown in Figure 12.

[0105] As shown in Figure 12, terminal 200''' includes a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generation unit 203, a received signal demodulation / decoding unit 204, an RSSI measurement unit 205, a BSS type determination unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generation unit 209, a transmission prohibition state setting unit 210, and a trigger information analysis unit 213. Furthermore, the BSS type determination unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generation unit 209, the transmission prohibition state setting unit 210, and the trigger information analysis unit 213 constitute the access control unit 212''' (MAC). In other words, terminal 200''' in the fifth embodiment differs from the configuration of terminal 200 in the first embodiment shown in Figure 2 in that it does not have a terminal information setting unit 211, but does have a trigger information analysis unit 213. Also, the operation of the transmission prohibition state setting unit 210 is slightly different from that of 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 / decoding unit 204 and outputs them to the transmission disable state setting unit 210.

[0107] The transmission disable state setting unit 210 sets the NAV based on the MAC frame input from the received signal demodulation / 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. The transmission disable state setting unit 210 also cancels the NAV when the set NAV period expires or when it receives a CF-End frame instructing it to cancel the NAV.

[0108] The transmission prohibition state setting unit 210 distinguishes between the intra-BSS NAV and the regular NAV when setting the NAV, and the above NAV setting and NAV deactivation are performed for each respective NAV. Specifically, for example, if the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it sets the intra-BSS settings, and if it receives an OBSS MAC frame, it sets the regular NAV settings.

[0109] However, the transmission prohibition state setting unit 210 determines whether or not to disable NAV using the NAV disabling determination method described later, and if the determination determines that NAV should be disabled, it will also disable regular NAV in addition to the above. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV disabling to the transmission control unit 207.

[0110] [Example of operation] Figure 13 is a sequence diagram showing an example of the operation of the wireless network 100''' during trigger frame transmission and reception in the fifth embodiment. In Figure 13, terminal C is assumed to have regular NAV pre-configured.

[0111] As shown in Figure 13, first, access point A sends a trigger frame to terminal B (ST501). Terminal C performs trigger frame reception processing from access point A (ST502). Trigger frame reception processing includes extraction of target RSSI and AP Tx power, and measurement of RSSI. Terminal C estimates the RSSI that can be measured at access point A when terminal C transmits data, based on the RSSI of the trigger frame and the AP Tx power extracted from the trigger frame (ST503). Then, terminal C determines whether the RSSI estimated in ST503 is higher than the target RSSI plus a predetermined allowable interference amount, and based on the determination result, decides whether or not to deactivate regular NAV (ST504). Details of the method for determining regular NAV in ST504 will be described later.

[0112] Figure 13 illustrates the case where ST503 determines that regular NAV should not be deactivated. In this case, terminal C continues regular NAV and maintains the transmission-prohibited state.

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

[0114] [NAV cancellation determination method] The following section details the method for determining whether or not to disable the regular NAV in ST504, as shown in Figure 13.

[0115] As described above, when terminal C receives a trigger frame from OBSS, it estimates the RSSI that can be measured at OBSS access point A 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 target RSSI plus a predetermined allowable interference amount. If the estimated RSSI is higher than the target RSSI plus a predetermined allowable interference amount, terminal C does not deactivate regular NAV. The predetermined allowable interference amount is a pre-set margin.

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

[0117] <Sixth Embodiment> The third embodiment will be described below. Figure 14 is a diagram illustrating the positional relationship of access points and terminals constituting the wireless network 100'''' according to the sixth embodiment. As shown in Figure 14, in the sixth embodiment, there are access point A, terminal B, terminal C, access point D, terminal E, and access point F. Furthermore, 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 the case where multiple OBSSs exist as described above, in 11ax, terminal C does not distinguish and manage the NAVs of multiple OBSSs, so disabling the NAV of one OBSS may cause relatively large interference to other OBSSs. The sixth embodiment describes a wireless network 100'''' that can suitably perform communication without degrading communication quality even in such cases.

[0119] [Explanation of the structure] Figure 15 is a block diagram showing an example of the configuration of terminal 200'''' according to the sixth embodiment. Terminal 200'''' illustrated in Figure 15 corresponds to terminal C shown in Figure 14. Note that the configurations of access points A, D, and F, and terminals B and E shown in Figure 14 may be the same as those of terminal 200'''' shown in Figure 15.

[0120] As shown in Figure 15, terminal 200'''' includes a transmitting / receiving antenna 201, a wireless transmitting / receiving unit 202, a transmission signal generation unit 203, a received signal demodulation / decoding unit 204, an RSSI measurement unit 205, a BSS type determination unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generation unit 209, a transmission prohibition state setting unit 210, and a target BSS information storage unit 214. Furthermore, the BSS type determination unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generation unit 209, the transmission prohibition state setting unit 210, and the target BSS information storage unit 214 constitute the access control unit 212'''' (MAC).

[0121] The transmission disable 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 / 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. The transmission disable state setting unit 210 also cancels the NAV when the set NAV period expires or when it receives a CF-End frame instructing it to cancel the NAV.

[0122] The transmission prohibition state setting unit 210 distinguishes between the intra-BSS NAV and the regular NAV when setting the NAV, and the above NAV setting and NAV deactivation are performed for each respective NAV. Specifically, for example, if the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it sets the intra-BSS settings, and if it receives an OBSS MAC frame, it sets the regular NAV settings.

[0123] However, the transmission prohibition state setting unit 210 determines whether or not to disable NAV using the NAV disabling determination method described later, and if the determination determines that NAV should be disabled, it will also disable regular NAV in addition to the above. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV disabling to the transmission control unit 207.

[0124] Furthermore, if the transmission prohibition state setting unit 210 needs to update the target BSS information, it 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 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. The target BSS information storage unit 214 also outputs the stored target BSS information to the transmission prohibition state setting unit 210 as needed.

[0126] [Example of operation] Figure 16 is a sequence diagram showing an example of the operation of the wireless network 100'''' during the transmission and reception of RTS / CTS frames in the sixth embodiment.

[0127] As shown in Figure 16, first, access point F sends an RTS frame to terminal E (ST601). Terminal C performs RTS frame reception processing from access point F (ST602). RTS frame reception processing includes extracting the BSS color from the RTS frame and measuring the RSSI of the RTS frame. Terminal C sets up a regular NAV according to the RTS frame (ST603).

[0128] When terminal C sets a regular NAV, it generates target BSS information (ST604). Here, target BSS information is information indicating the OBSS on which the NAV is set. In other words, the target BSS information generated in ST604 indicates that the target is BSS3 as shown in Figure 14. 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 the CTS frame reception processing 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] Then, terminal C compares the RSSI stored in ST604 with the RSSI of the received CTS frame in ST606. If the RSSI of the CTS frame is higher, terminal C updates the target BSS information (ST607). Here, we assume 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 deactivate regular NAV (ST608). Details of the method for determining regular NAV in ST608 will be described later.

[0132] Figure 16 illustrates the case where ST608 determines that regular NAV should not be deactivated. In this case, terminal C continues regular NAV and maintains the transmission-prohibited state.

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

[0134] Next, suppose terminal B sends an RTS frame to access point A (ST610). Terminal C performs RTS frame reception processing from terminal B (ST611). 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 deactivate regular NAV (ST612). Details of the method for determining regular NAV in ST612 will be described later.

[0136] Figure 16 illustrates the case where ST612 determines that regular NAV should not be deactivated. In this case, terminal C continues regular NAV and maintains the transmission-prohibited state. If regular NAV is not deactivated 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, we assume 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 the CTS frame reception process from access point A (ST615). The CTS frame reception process 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 deactivate regular NAV (ST616). Details of the method for determining regular NAV in ST616 will be described later.

[0139] Figure 16 illustrates the case where ST616 determines that regular NAV should not be deactivated. In this case, terminal C continues regular NAV and maintains the transmission-prohibited state. If regular NAV is not deactivated 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, we assume 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 sends data to access point A (ST618). At this time, since terminal C is set to regular NAV, terminal C does not send data to access point D.

[0141] [NAV cancellation determination method] The following section details the method for determining whether or not to disable Regular NAV in ST608, ST612, and ST616, as shown in Figure 16.

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

[0143] Then, if terminal C receives an RTS / CTS frame or the regular NAV is updated, and 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, the regular NAV can be deactivated due to the expiration of the NAV period regardless of the target BSS.

[0144] In the sixth embodiment, the regular NAV is deactivated based on the signal received from the target BSS, but not based on the signal received from other BSSs. Therefore, even when multiple OBSSs exist, it is possible to avoid situations where deactivating the NAV of one OBSS causes relatively large interference to other OBSSs. Thus, inappropriate deactivation of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0145] Although various embodiments have been described above with reference to the drawings, it goes without saying that this disclosure is not limited to such examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the disclosure.

[0146] In the first to sixth embodiments described above, terminal C deactivated NAV when it received a CF-End frame. However, for example, if there are multiple OBSSs, 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 deactivate regular NAV only if the RSSI of the CF-End frame is higher. Such a configuration can prevent inappropriate deactivation of regular NAV and improve the communication performance of the wireless network.

[0147] The method for releasing the transmission prohibition state in the above embodiment is not limited to releasing the NAV. For example, it can also be applied to cases where the transmission is temporarily allowed without releasing the NAV (the time for which the transmission is allowed is managed, and if the original NAV period is still valid after that time has elapsed, the transmission is returned to the transmission prohibition state).

[0148] Furthermore, in the above embodiment, instead of releasing the transmission disable state, the system may reduce interference by lowering the transmission power.

[0149] In the above embodiment, if the transmission prohibition state cannot be released, it may become impossible to send an ACK for data reception. In that case, the operation may be to send an ACK after releasing the NAV.

[0150] In the embodiments described above, the present disclosure was explained using the case where it is configured in hardware as an example, but the present disclosure can also be implemented in software in conjunction with hardware.

[0151] Furthermore, each functional block used in the description of the above embodiments is typically implemented as an integrated circuit (LSI). These may be individually integrated onto a single chip, or some or all of them may be integrated onto a single chip. Here, we refer to them as LSIs, but depending on the degree of integration, they may also be called ICs, system LSIs, super LSIs, or ultra LSIs.

[0152] Furthermore, the method of integrated circuit implementation is not limited to LSIs; it may also be implemented using dedicated circuits or general-purpose processors. After LSI manufacturing, FPGAs (Field Programmable Gate Arrays) that can be programmed, or reconfigurable processors that allow for the reconfiguration of the connections and settings of circuit cells inside the LSI, may also be used.

[0153] Furthermore, if advancements in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that replace LSIs, then naturally, it would be possible to use those technologies to integrate functional blocks. The application of biotechnology, for example, is a possibility.

[0154] <Summary of this disclosure> The radio station of this disclosure is a radio station in a radio network having multiple radio stations, and comprises: a receiving unit that receives a trigger signal transmitted from a first radio station belonging to an interference cell to a second radio station belonging to the interference cell; and a transmission prohibition period control unit that, after setting a transmission prohibition period for other radio stations belonging to the communication cell to which it belongs, determines whether or not to release the transmission prohibition period based on the received strength of the trigger signal when the receiving unit receives the trigger signal.

[0155] In the radio station described herein, the radio station is a radio station compliant with IEEE 802.11ax.

[0156] In the radio station of this disclosure, the communication cell to which the station belongs is an intra-BSS (Basic Service Set), and the interference cell is an OBSS (Overlapping Basic Service Set) or an inter-BSS.

[0157] In the radio station of this disclosure, the transmission prohibition period control unit determines whether or not to release the transmission prohibition period based on a threshold value set based on the station's reception strength measurement accuracy and the reception strength of the trigger signal.

[0158] In the radio station of this disclosure, the transmission prohibition period control unit sets the threshold value based on the terminal class (STA classes) defined in IEEE 802.11ax.

[0159] In the radio station of this disclosure, when the transmission prohibition period control unit receives a response signal from the second radio station to the trigger signal, it determines whether or not to release the transmission prohibition period based on a threshold set based on the station's reception strength measurement accuracy, the reception strength of the trigger signal, and the reception strength of the response signal.

[0160] In the radio station of this disclosure, the transmission prohibition period control unit releases the transmission prohibition period when the received strength of the trigger signal is within a predetermined range set based on the station's received strength measurement accuracy.

[0161] In the radio station of this disclosure, the transmission prohibition period control unit determines the type of the trigger signal and, if it is a trigger signal that requests a response from multiple radio stations in the interference cell, does not release the transmission prohibition period.

[0162] In the radio station of this disclosure, the transmission prohibition period control unit, if the trigger signal is a trigger signal that requests a response from multiple radio stations in the interference cell, extracts information from the trigger signal regarding the number of radio stations that the trigger signal requests a response from, and determines whether or not to release the transmission prohibition period based on the extracted information.

[0163] In the radio station of this disclosure, the transmission prohibition period control unit compares the intensity of the response signal from the second radio station to the first radio station, extracted from the trigger signal, with the estimated received intensity at the first radio station of the signal transmitted from the station to the first radio station, which has been estimated in advance. If the difference is smaller than a predetermined value, the transmission prohibition period is not released.

[0164] In the radio station of this disclosure, when the transmission prohibition period control unit sets the transmission prohibition period triggered by a trigger signal from any of the radio stations belonging to the interference cell, it stores the identifier of the interference cell to which the radio station that transmitted the trigger signal that triggered the setting of the transmission prohibition period belongs, and the received intensity of the trigger signal that triggered the setting of the transmission prohibition period. When a new trigger signal is received from an interference cell, if the received intensity of the newly received trigger signal is higher than the received intensity of the stored trigger signal, the transmission prohibition period is released.

[0165] The communication method of this disclosure is a communication method in a wireless network having multiple terminal or access point radio stations, wherein one of the multiple radio stations sets a transmission prohibition period for other radio stations belonging to the communication cell to which it belongs, and then receives a trigger signal transmitted from a first radio station belonging to an interference cell to which it does not belong to a second radio station belonging to the interference cell, the first radio station determines whether or not to release the transmission prohibition period based on the received strength of the trigger signal.

[0166] In the communication method of this disclosure, the radio station is a radio station compliant with IEEE 802.11ax.

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

[0168] In the communication method of this disclosure, the radio station 1 determines whether or not to release the transmission prohibition period based on a threshold set based on the station's reception strength measurement accuracy and the reception strength of the trigger signal.

[0169] In the communication method of this disclosure, the radio station 1 sets the threshold based on the terminal classes (STA classes) defined in IEEE 802.11ax.

[0170] In the communication method of this disclosure, when the radio station 1 receives a response signal from the radio station 2 to the trigger signal, it determines whether or not to release the transmission prohibition period based on a threshold set based on the station's reception strength measurement accuracy, the reception strength of the trigger signal, and the reception strength of the response signal.

[0171] In the communication method of this disclosure, the radio station 1 releases the transmission prohibition period when the received strength of the trigger signal is within a predetermined range set based on the station's received strength measurement accuracy.

[0172] In the communication method of this disclosure, the radio station 1 determines the type of the trigger signal and, if it is a trigger signal that requests a response from multiple radio stations in the interference cell, does not release the transmission prohibition period.

[0173] In the communication method of the present disclosure, if the trigger signal is a trigger signal that requests a response from multiple radio stations in the interference cell, the radio station 1 extracts information from the trigger signal regarding the number of radio stations that the trigger signal requests a response from, and determines whether or not to release the transmission prohibition period based on the extracted information.

[0174] In the communication method of this disclosure, the radio station 1 compares the strength of the response signal from the second radio station to the first radio station, extracted from the trigger signal, with the estimated received strength at the first radio station of the signal transmitted from the radio station 1 to the first radio station, which has been estimated in advance, and does not release the transmission prohibition period if the difference is smaller than a predetermined value.

[0175] In the communication method of this disclosure, when the radio station 1 sets the transmission prohibition period triggered by a trigger signal from any of the radio stations belonging to the interference cell, it stores the identifier of the interference cell to which the radio station that transmitted the trigger signal that triggered the setting of the transmission prohibition period belongs, and the received intensity of the trigger signal that triggered the setting of the transmission prohibition period. When it receives a new trigger signal from the interference cell, if the received intensity of the newly received trigger signal is higher than the received intensity of the stored trigger signal, it releases the transmission prohibition period. [Industrial applicability]

[0176] This disclosure is suitable for radio stations that perform wireless communication suitable for environments where interference between radio stations occurs. [Explanation of Symbols]

[0177] 100, 100', 100'', 100''', 100'''' Wireless Network 200, 200', 200'', 200''', 200'''' terminal 201 Transmitting and Receiving Antenna 202 Wireless Transceiver Unit 203 Transmission signal generation unit 204 Received signal demodulation / decoding section 205 RSSI measurement section 206 BSS Type Determination Unit 207 Transmission Control Unit 208 transmit buffer 209 MAC Frame Generation Unit 210 Transmission Prohibition Status Setting Section 211 Terminal Information Settings Section 212, 212', 212'', 212'''', 212'''' Access Control Unit 213 Trigger Information Analysis Unit 214 Target BSS Information Storage Unit

Claims

1. An access point belonging to an OBSS (Overlapping Basic Service Set) that partially overlaps with a BSS (Basic Service Set), A signal generation unit generates a trigger frame for requesting response signals from multiple terminals belonging to the aforementioned OBSS, the trigger frame including an AP Tx power subfield indicating the transmit power value of the trigger frame and a Target RSSI (Target received signal strength indicator) subfield indicating the desired received signal strength of the response signal at the access point, the AP Tx power subfield and the Target RSSI subfield are used by a first terminal belonging to the aforementioned BSS that receives the trigger frame to determine whether or not to transmit to a second terminal belonging to the aforementioned BSS, and The antenna that transmits the trigger frame, An access point equipped with the following features.

2. Based on the values ​​of the AP Tx power subfield and the Target RSSI subfield, an estimated received power value is calculated when the access point receives a signal transmitted from the first terminal. The access point according to claim 1.

3. The decision on whether or not to transmit is made based on whether the estimated received power value is higher than the value of the Target RSSI subfield plus the allowable interference amount. The access point according to claim 2.

4. A communication method for access points belonging to an OBSS (Overlapping Basic Service Set) that partially overlaps with a BSS (Basic Service Set), A trigger frame is generated to request response signals from multiple terminals belonging to the OBSS, the trigger frame includes an AP Tx power subfield indicating the transmit power value of the trigger frame and a Target RSSI (Target received signal strength indicator) subfield indicating the desired received signal strength of the response signal at the access point, the AP Tx power subfield and the Target RSSI subfield are used by a first terminal belonging to the BSS that receives the trigger frame to determine whether or not to transmit it to a second terminal belonging to the BSS. The trigger frame is transmitted Communication method.

5. Based on the values ​​of the AP Tx power subfield and the Target RSSI subfield, an estimated received power value is calculated when the access point receives a signal transmitted from the first terminal. The communication method according to claim 4.

6. The decision on whether or not to transmit is made based on whether the estimated received power value is higher than the value of the Target RSSI subfield plus the allowable interference amount. The communication method according to claim 5.

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