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 the IEEE (the Institute of Electrical and Electronics Engineers) 802.11 Task Group (TG) ax, the technical specifications of IEEE 802.11ax (hereinafter, 11ax) are being developed as the next-generation standard of IEEE 802.11ac.

[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. The BSS is composed of one access point and a plurality of terminals (wireless stations other than the access point) in the infrastructure mode, and is composed of a plurality of terminals in the ad hoc mode. The ad hoc mode BSS is called an IBSS (Independent BSS) to distinguish it from the infrastructure mode 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 a plurality of communication cells overlap in the OBSS, interference occurs between the communication cells in the OBSS-to-OBSS communication, and the communication quality deteriorates.

[0004] In wireless communication, due to factors such as the distance between wireless stations and obstacles, a situation may occur where the wireless signals between wireless stations cannot reach each other (a radio environment where carrier sense does not function). As a countermeasure for such an environment, that is, an environment where hidden terminals exist, the IEEE 802.11 standard provides a collision prevention function using NAV (Network Allocation Vector: transmission prohibition period). When an access point and a terminal receive a wireless frame for NAV setting at a level equal to or higher than a predetermined threshold, except when the wireless frame for NAV setting is a frame addressed to the local terminal or the local access point, transmission is prohibited during the NAV period set by the duration information. Usually, the value of the minimum reception sensitivity is used as the threshold for determining whether to set NAV.

[0005] Also, in 11ax, the introduction of SR (Spatial Reuse) that reuses the wireless resources in use by OBSS has been agreed upon (see Non-Patent Document 1). The purpose of SR is to increase the transmission opportunity by a terminal (or an access point) and improve the utilization rate of wireless resources when the interference given to OBSS (hereinafter referred to as interference) is small, thereby improving the communication performance in the wireless network. One method for realizing SR is to set the threshold (hereinafter referred to as OBSS_PD (Power Density)) for determining whether to set NAV when receiving a wireless frame from OBSS under specific conditions to a value larger than the value of the usually used minimum reception sensitivity.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

[0007] However, when the interference level to the OBSS is greater than a predetermined threshold, if a terminal (or an access point) erroneously releases the regular NAV by estimating the magnitude of the interference, interference at a level where the terminal (or an access point) in the OBSS cannot correctly decode the received signal may occur to the terminal (or an access point) in the OBSS, and the communication performance of the wireless network may deteriorate.

[0008] Therefore, one aspect of the present disclosure provides a wireless station and a communication method that prevent inappropriate regular NAV release 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 a response signal from a plurality of terminals belonging to the OBSS. The trigger frame includes an AP Tx power subfield indicating a transmission power value of the trigger frame and a Target RSSI (Target received signal strength indicator) subfield indicating a 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 the first terminal belonging to the BSS that has received the trigger frame to determine whether to transmit to a second terminal belonging to the BSS, and includes a signal generation unit and an antenna for transmitting the trigger frame.

[0010] In addition, these general or specific aspects may be implemented in a system, method, integrated circuit, computer program, or recording medium, or may be implemented in any combination of a system, apparatus, method, integrated circuit, computer program, and recording medium.

[0011] According to one aspect of the present disclosure, it is possible to prevent inappropriate regular NAV release and improve the communication performance of a wireless network.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

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 detailed than necessary, for example, detailed descriptions of well-known matters and duplicate descriptions of substantially the same configurations, may be omitted.

[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 to manage NAV separately for each of intra-BSS and OBSS (see Non-Patent Document 2). This avoids situations where the intra-BSS NAV is released by a NAV release request (CF-End: Contention Free-End) from the OBSS, or the OBSS NAV is released by the intra-BSS CF-End. In 11ax, to simplify the SR process, when there are multiple OBSSs, a terminal (or access point) manages two NAVs: the intra-BSS NAV and the regular NAV (the NAV of the OBSS or the NAV when there is no distinction between OBSS and non-OBSS within the intra-BSS), without distinguishing the NAV for each OBSS.

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

[0018] In the following Reference Non-Patent Document 1, it is disclosed that a terminal (or access point) releases the 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 (the threshold applicable when the target is the 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 release threshold. [Reference Non-Patent Document 1] Reza Hedayat, “Recipient-aware Spatial Reuse,” IEEE 802.11-16 / 0060

[0019] Also, in the following Reference Non-Patent Document 2, it is disclosed that when the RSSI of the trigger frame is lower than OBSS_PD, the terminal (or access point) releases the regular NAV when detecting the 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 RSSI of the terminal is low, or when the distance between terminals is short, etc., the regular NAV may be incorrectly released. As a result, for example, interference equal to or higher than OBSS_PD may occur to the terminal (or access point) of the OBSS, and the desired signal may not be received correctly. For these reasons, it is desired to prevent inappropriate release of the regular NAV. In the embodiments of the present disclosure described below, a wireless station and a communication method for preventing inappropriate release of the regular NAV and improving the communication performance of the wireless network will be described. Note that the terminal or access point in each of the following embodiments corresponds to the wireless station.

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

[0022] [Description of Configuration] FIG. 2 is a block diagram showing an example of the configuration of the terminal 200 according to the first embodiment. The terminal 200 illustrated in FIG. 2 corresponds to the terminal C shown in FIG. 1. Note that the configurations of the access points A and D and the terminal B shown in FIG. 1 may be the same as those of the terminal 200 shown in FIG. 1.

[0023] As shown in FIG. 2, the terminal 200 includes a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generation unit 203, a reception 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. Further, an access control unit 212 (MAC) is configured by 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.

[0024] The transmission / reception antenna 201 is at least one antenna and transmits or receives a wireless signal.

[0025] At the time of transmission, the wireless transmission / reception 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. At the time of reception, the wireless transmission / reception unit 202 performs predetermined wireless reception processing such as down-conversion of the wireless signal received via the transmission / reception antenna 201 and A / D conversion, and outputs the received wireless signal to the reception signal demodulation / decoding unit 204 and the RSSI measurement unit 205.

[0026] The transmission signal generation unit 203 performs encoding and modulation on 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, etc., generates a wireless frame (also called a PPDU), and outputs it to the wireless transmission / reception unit 202.

[0027] The received signal demodulation and decoding unit 204 performs autocorrelation processing, etc. on the wireless signal after wireless reception processing input from the wireless transmission / reception unit 202 to extract a wireless frame, and performs demodulation and decoding of the wireless frame. Also, the received signal demodulation and decoding unit 204 extracts preamble information (control signal of the wireless frame) and the MAC frame from the wireless signal input from the wireless 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, respectively.

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

[0029] The BSS type determination unit 206 extracts the identifier information of the BSS (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 the BSS to which the terminal (or access point) that transmitted the received wireless signal belongs. The BSS type determination unit 206 determines that it is intra-BSS when the BSS color included in the preamble information is the same as the BSS color of the BSS to which the own terminal 200 belongs, and determines that it is 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 state information (information indicating whether transmission is prohibited, i.e., whether 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 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 transmission buffer 208 stores transmission data that the terminal 200 transmits to other terminals (or access points). Also, the transmission buffer 208 outputs buffer state information indicating the presence or absence of transmission data to the transmission control unit 207.

[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 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 prohibition state setting unit 210 sets NAV based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the reception 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 prohibition state setting unit 210 sets NAV when it is a MAC frame instructing the setting of NAV such as an RTS / CTS frame. Also, the transmission prohibition state setting unit 210 releases NAV when the set NAV period has expired or when a CF-End frame instructing the release of NAV is received.

[0035] Note that when setting the NAV, the transmission prohibition state setting unit 210 distinguishes between the states of the intra-BSS NAV and the regular NAV, and the above NAV setting and NAV release are performed for each NAV. Specifically, for example, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it performs intra-BSS setting, and when it receives an OBSS MAC frame, it performs regular NAV setting.

[0036] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. When it is determined to release the NAV in this determination, the regular NAV is released even outside the above cases (when the set NAV period has expired 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 release to the transmission control unit 207.

[0037] The terminal information setting unit 211 outputs the RSSI measurement accuracy information of the own terminal 200 to the transmission prohibition 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 the own terminal 200.

[0038] With such a configuration, in the first embodiment, by setting the threshold for releasing the regular NAV in consideration of the RSSI measurement accuracy, it is possible to prevent a situation where a terminal with low RSSI measurement accuracy inappropriately releases the NAV based on the measurement error of the RSSI and causes a large interference to the OBSS. Hereinafter, a specific operation example of the wireless network 100 of the first embodiment will be described.

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

[0040] Next, the access point A responds to the RTS frame from terminal B and transmits a CTS (Clear to Send) frame, which is a response signal (ST104). When terminal C receives the CTS from the access point A, it measures the RSSI (ST105). Terminal C determines whether to cancel the regular NAV based on the RSSI of the CTS frame (ST106). Details of the method for canceling the regular NAV in ST106 will be described later.

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

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

[0043] As shown in Fig. 4, first, access point A performs trigger frame transmission processing on terminal B (ST201). Terminal C performs trigger frame reception processing from access point A (ST202). The trigger frame reception processing includes RSSI measurement of the trigger frame. Terminal C determines whether to cancel the regular NAV based on the RSSI measurement result of the trigger frame (ST203). Details of the regular NAV determination method in ST203 will be described later.

[0044] Fig. 4 illustrates the case where it is determined not to cancel the regular NAV in ST203. 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 Release Determination Method 1] Hereinafter, details of the determination method for whether to cancel the regular NAV in ST106 shown in Fig. 3 or ST203 shown in Fig. 4 will be described.

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

[0047] In 11ax, two types of terminal classes with different required accuracies such as RSSI measurement accuracy are supported. Class A is a high-performance terminal, and the RSSI measurement accuracy is required to be within an error of ±2 dB. On the other hand, Class B is a low-performance terminal, and the RSSI measurement accuracy is required to be within an error of ±5 dB. That is, in the Class B terminal, an RSSI measurement error of up to 3 dB with respect to the Class A terminal is allowed.

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

[0049] When the terminal C receives a trigger signal (RTS frame) from the OBSS (ST102 in FIG. 3), the terminal C measures the RSSI of the RTS frame and determines whether it is higher than the first threshold. Further, the terminal C subsequently measures the RSSI of the response signal (CTS frame) transmitted from the OBSS and determines whether it is lower than the second threshold. When 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, the terminal C releases the regular NAV. Note that the terminal C may determine whether to release the regular NAV based only on the determination result of 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] With such a determination method, even when terminal C is a Class B terminal, that is, a terminal with relatively low RSSI measurement accuracy, it is possible to perform a regular NAV release determination based on a threshold value set in consideration of the measurement accuracy. Therefore, even when terminal C is a Class B terminal, that is, a terminal with relatively low RSSI measurement accuracy, the interference given to an OBSS terminal (or access point) can be reduced. Accordingly, inappropriate regular NAV release can be prevented, and the communication performance of the wireless network can be improved. Note that the first or second threshold value in a Class A terminal may be, for example, OBSS_PD.

[0051] [NAV Release Determination Method 2] The NAV release determination method 2 described below corresponds to the determination method in ST203 of FIG. 4. In the NAV release determination method 2, terminal C sets a threshold value used for the NAV release determination based on the RSSI measurement accuracy information of its own terminal or the terminal class. Terminal C sets a threshold value for the trigger signal. Here, the trigger signal is, for example, a trigger frame. This threshold value is set higher than the threshold value for the intra-BSS signal.

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

[0053] With such a determination method, similar to the NAV release determination method 1, even when terminal C is a terminal with relatively low RSSI measurement accuracy, the release determination of the regular NAV can be performed based on the threshold value set considering the measurement accuracy. Therefore, even when terminal C is a terminal with relatively low RSSI measurement accuracy, the interference imposed on the OBSS terminal (or access point) can be reduced. Consequently, inappropriate regular NAV release can be prevented, and the communication performance of the wireless network can be improved.

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

[0055] When the distance between terminal B and terminal C is relatively close in this way, the RSSI of the transmission signal from terminal C to terminal B becomes close in intensity to the RSSI of the transmission signal from access point A to terminal B, and the reception quality of the transmission signal from access point A to terminal B may deteriorate due to the interference of terminal C. In such a case, the possibility of reception failure from access point A at terminal B becomes high. In the second embodiment, the wireless network 100' that can suitably perform communication without degrading the communication quality even in such a case will be described.

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

[0057] As shown in FIG. 6, the terminal 200' includes a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generation unit 203, a reception 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. Further, an access control unit 212' (MAC) is constituted by 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. That is, the terminal 200' in the second embodiment is different from the configuration of the terminal 200 in the first embodiment shown in FIG. 2 in that it does not have a terminal information setting unit 211. Also, 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 performs NAV setting based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the reception signal demodulation / decoding unit 204, and the BSS type information input from the BSS type determination unit 206. Also, the transmission prohibition state setting unit 210 releases the NAV when the set NAV period expires or when a CF-End frame instructing NAV release is received.

[0059] Note that the transmission prohibition state setting unit 210 distinguishes between the states of intra-BSS NAV and regular NAV when setting the NAV, and the above NAV setting and NAV release are performed for each NAV. Specifically, for example, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it performs intra-BSS setting, and when it receives an OBSS MAC frame, it performs regular NAV setting.

[0060] However, the transmission prohibition state setting unit 210 determines whether to cancel the NAV using the NAV cancellation determination method described later. When it is determined to cancel the NAV in this determination, the regular NAV is also cancelled even in other cases. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV cancellation to the transmission control unit 207.

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

[0062] [NAV Cancellation Determination Method] The NAV cancellation determination method described below corresponds to the determination method in ST106 of FIG. 3. In the NAV cancellation determination method in the second embodiment, the terminal C sets a threshold value (third threshold value) for the upper limit value of the trigger signal, a threshold value (fourth threshold value) for the lower limit value of the trigger signal, and a threshold value (second threshold value) for the response signal. 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 values for intra-BSS signals.

[0063] When the 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, the 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] Furthermore, terminal C continuously measures the RSSI of the response signal (CTS frame) transmitted from OBSS, and determines whether it is lower than a second threshold. When the RSSI of the RTS frame is within a predetermined range and the RSSI of the CTS frame is lower than the second threshold, terminal C releases the regular NAV.

[0065] The third threshold may be, for example, OBSS_PD. Also, the fourth threshold may be a predetermined threshold larger than the third threshold. For example, the fourth threshold is a value obtained by adding a positive offset value to the third threshold. Thereby, the signaling amount required for notifying the fourth threshold can be reduced.

[0066] In the second embodiment, in this way, the NAV is released at terminal C only when the RSSI of the trigger signal from 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, when the distance between access point A and terminal C is short and the reception quality at terminal B is expected to deteriorate due to interference from terminal C, by preventing the release of the NAV when the RSSI of the trigger signal is not within the predetermined range, the degradation of the communication performance in wireless network 100’ can be reduced. Accordingly, inappropriate regular NAV release can be prevented and the communication performance of the wireless network can be improved.

[0067] Note that in the operation example of the second embodiment described above, the operation example during the transmission and reception of RTS / CTS frames has been described, but the present disclosure is not limited thereto. That is, the second embodiment can also be applied to the transmission and reception of trigger frames.

[0068] <The Third Embodiment> Next, a third embodiment will be described. FIG. 7 is a diagram illustrating the positional relationship between the access points and terminals constituting the wireless network 100'' according to the third embodiment. As shown in FIG. 7, at the point where the terminal E belonging to BSS1 (OBSS) exists, it is different from the wireless network 100 of the first embodiment shown in FIG. 1.

[0069] In such a configuration, the access point A may transmit a trigger frame that requests MU-BA (Multi-User Block Ack) transmission to a plurality of terminals such as the terminal B and the terminal E. Block Ack is defined in IEEE 802.11e and is for responding to a plurality of received data in one frame. Also, MU-BA performs Block Ack transmission multiplexed by a plurality of users through MU (Multi-User) multiplexing. Also, MU multiplexing multiplexes a plurality of terminals in frequency and space.

[0070] In such a case, the MU-BA transmission from the terminals B and E that have received the trigger frame may not be received by the access point A due to the interference of, for example, the terminal C. When such a situation occurs, the access point A retransmits a trigger frame that requests MU-BA transmission to the terminals B and E again, so the traffic increases and the communication performance of the wireless network 100'' may deteriorate. In the third embodiment, the wireless network 100'' that can perform communication suitably without degrading the communication quality even in such a case will be described.

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

[0072] As shown in FIG. 8, the terminal 200'' includes a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generation unit 203, a reception signal demodulation / decode 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. Further, 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 an access control unit 212'' (MAC). That is, the terminal 200'' in the third embodiment does not include an RSSI measurement unit and a terminal information setting unit 211, and is different from the configuration of the terminal 200 in the first embodiment shown in FIG. 2 in that it has a trigger information analysis unit 213. Also, the operation of the transmission prohibition state setting unit 210 is different from that in the first and second embodiments.

[0073] The trigger information analysis unit 213 extracts trigger type information regarding the trigger type from the trigger frame input from the reception signal demodulation / decode unit 204 and outputs it to the transmission prohibition state setting unit 210.

[0074] The transmission prohibition state setting unit 210 performs NAV setting based on the MAC frame input from the reception signal demodulation / decode 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. Also, the transmission prohibition state setting unit 210 releases the NAV when the set NAV period expires or when a CF-End frame instructing NAV release is received.

[0075] Note that the transmission prohibition state setting unit 210 distinguishes between the states of intra-BSS NAV and regular NAV when setting the NAV, and the above NAV setting and NAV release are performed for each NAV. Specifically, for example, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it performs intra-BSS setting, and when it receives an OBSS MAC frame, it performs regular NAV setting.

[0076] However, the transmission prohibition state setting unit 210 determines whether to cancel the NAV using the NAV cancellation determination method described later. When it is determined to cancel the NAV in this determination, the regular NAV is also cancelled even if it is not the above case. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV cancellation to the transmission control unit 207.

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

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

[0079] When the terminal C receives the trigger frame from the access point A, it identifies the trigger type (ST302). Based on the identification result in ST302, the terminal C determines whether to cancel the regular NAV (ST303). Details of the regular NAV determination method in ST303 will be described later.

[0080] In FIG. 9, the case where it is determined not to cancel the regular NAV in ST303 is illustrated. In this case, the terminal C continues the regular NAV and maintains the transmission prohibition state.

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

[0082] [NAV Cancellation Determination Method] Hereinafter, details of the determination method of whether to cancel the regular NAV in ST303 shown in FIG. 9 will be described.

[0083] In 11ax, the MU-BA is transmitted in the UL MU PPDU. As described above, when receiving MU-BAs from a plurality of terminals, if the reception on the access point A side fails due to interference, the communication volume increases due to the retransmission of the trigger frame and the MU-BA, and the communication performance of the wireless network 100’’ deteriorates. Therefore, it is desirable to prevent interference from occurring. Also, since the MU-BA has a short PPDU length, the effect of regular NAV release is small.

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

[0085] In the third embodiment, in this way, it is determined whether to release the regular NAV based on the trigger type, and when the trigger type is a MU-BAR, the regular NAV is not released. Thereby, the MU-BA is preferentially transmitted and received, and it is possible to prevent the communication performance of the wireless network 100’’ from deteriorating due to the retransmission of the trigger frame and the MU-BA, and the effect of the SR can be maintained. Note that when the terminal C determines that the received trigger frame is a trigger type other than the MU-BAR, the terminal C can maintain the effect of the SR by performing the conventional NAV control. Therefore, inappropriate regular NAV release can be prevented, and the communication performance of the wireless network can be improved.

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

[0087] <Fourth Embodiment> The following describes the fourth embodiment. The positional relationship between the access point and the 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 FIG. 7.

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

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

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

[0091] The transmission prohibition state setting unit 210 performs NAV setting 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 number information input from the trigger information analysis unit 213. Also, the transmission prohibition state setting unit 210 releases the NAV when the set NAV period has elapsed or when a CF-End frame instructing NAV release is received.

[0092] Note that when setting the NAV, the transmission prohibition state setting unit 210 differentiates between the states of the intra-BSS NAV and the regular NAV, and the above NAV setting and NAV release are performed for each respective NAV. Specifically, for example, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it performs the intra-BSS setting, and when it receives an OBSS MAC frame, it performs the regular NAV setting.

[0093] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. If it is determined to release the NAV in this determination, it releases the regular NAV even in other cases. The transmission prohibition state setting unit 210 outputs transmission prohibition state information related to NAV setting or NAV release to the transmission control unit 207.

[0094] [Operation Example] FIG. 10 is a sequence diagram showing an operation example of the wireless network 100'' during the transmission and reception of trigger frames in the fourth embodiment. In FIG. 10, it is assumed that terminal C has previously set a regular NAV.

[0095] As shown in FIG. 10, first, the access point A transmits a trigger frame requesting data transmission to terminal B and terminal E (when more terminals exist within the OBSS, those terminals may also be included) (ST401).

[0096] When terminal C receives the trigger frame from access point A, it extracts information regarding the MU multiplicity (ST402). The information regarding the MU multiplicity is included in the trigger frame, for example.

[0097] Based on the information regarding the MU multiplicity extracted in ST402, terminal C determines whether to release the regular NAV (ST403). Details of the regular NAV determination method in ST403 will be described later.

[0098] FIG. 10 illustrates a case where it is determined not to cancel the regular NAV in ST403. In this case, terminal C continues the regular NAV and maintains the transmission prohibition state.

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

[0100] [NAV Cancellation Determination Method] Hereinafter, details of the determination method of whether to cancel the regular NAV in ST403 shown in FIG. 10 will be described. That is, terminal C does not cancel the regular NAV when the MU multiplicity notified by the trigger frame is higher than a predetermined threshold.

[0101] In the fourth embodiment, in this way, it is determined whether to cancel the regular NAV according to the MU multiplicity, and when the MU multiplicity is higher than a predetermined threshold, the regular NAV is not canceled. Thereby, it is possible to prevent a decrease in the communication performance of the wireless network 100″ due to retransmission of data, and the effect of SR can be maintained. Note that when the MU multiplicity is equal to or less than a predetermined threshold, terminal C can maintain the effect of SR by performing the conventional NAV control. Therefore, inappropriate cancellation of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0102] <Fifth Embodiment> Hereinafter, the fifth embodiment will be described. FIG. 11 is a diagram illustrating the positional relationship between the access point and the terminals constituting the 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 substantially 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 intensities of the transmission signal from terminal B (desired signal) and the transmission signal from terminal C (interference signal) are almost the same, which may result in a decrease in the reception quality at access point A. In the fifth embodiment, a wireless network 100''' that can suitably perform communication without degrading the communication quality even in such a case will be described.

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

[0105] As shown in FIG. 12, terminal 200''' includes a transmission / reception antenna 201, a wireless transmission / reception 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. Further, an access control unit 212''' (MAC) is configured by 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. That is, terminal 200''' in the fifth embodiment differs from the configuration of terminal 200 in the first embodiment shown in FIG. 2 in that it does not include a terminal information setting unit 211 and includes a trigger information analysis unit 213. Also, 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 included in the trigger frame input from the received signal demodulation / decoding unit 204 and outputs them to the transmission prohibition state setting unit 210.

[0107] The transmission prohibition state setting unit 210 performs NAV setting based on the MAC frame input from the reception 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. Also, when the set NAV period expires or when a CF-End frame instructing NAV release is received, the transmission prohibition state setting unit 210 releases the NAV.

[0108] Note that when setting the NAV, the transmission prohibition state setting unit 210 distinguishes between the states of intra-BSS NAV and regular NAV, and the above NAV setting and NAV release are performed for each NAV. Specifically, for example, when receiving an intra-BSS MAC frame, the transmission prohibition state setting unit 210 performs intra-BSS setting, and when receiving an OBSS MAC frame, the transmission prohibition state setting unit 210 performs regular NAV setting.

[0109] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. When it is determined to release the NAV in this determination, the regular NAV is released even in other cases. The transmission prohibition state setting unit 210 outputs transmission prohibition state information regarding NAV setting or NAV release to the transmission control unit 207.

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

[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 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 a value obtained by adding a predetermined allowable interference amount to the target RSSI, and based on the determination result, determines whether to release the regular NAV (ST504). Details of the method for determining the regular NAV in ST504 will be described later.

[0112] FIG. 13 illustrates the case where it is determined not to release the regular NAV in ST503. In this case, terminal C continues the regular NAV and maintains the transmission prohibition state.

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

[0114] [NAV Release Determination Method] Hereinafter, details of the method for determining whether to release the regular NAV in ST504 shown in FIG. 13 will be described.

[0115] As described above, when the terminal C receives a trigger frame from the OBSS, it estimates the RSSI that can be measured at the access point A of the OBSS when the 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, the 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 a predetermined allowable interference amount to the target RSSI, the terminal C does not release the regular NAV. Note that the predetermined allowable interference amount is a preset margin.

[0116] In the fifth embodiment, as described above, the intensity (target RSSI) of the transmission signal (desired signal) from the terminal B at the access point A and the intensity (estimated RSSI) of the transmission signal (interference signal) from the terminal C are compared. If the estimated RSSI is higher than the value obtained by adding a predetermined allowable interference amount to the target RSSI, the terminal C does not release the regular NAV. Thereby, the deterioration of the communication performance in the wireless network 100’’’ can be reduced. Therefore, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

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

[0118] When there are multiple OBSSs as described above, in 11ax, since terminal C does not distinguish and manage the NAVs of multiple OBSSs, releasing 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 suitably without degrading communication quality even in such a case will be described.

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

[0120] As shown in FIG. 15, the terminal 200'''' includes a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generation unit 203, a reception signal demodulation / decode 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. Further, an access control unit 212'''' (MAC) is configured by 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.

[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 reception signal demodulation / decode 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. Also, the transmission prohibition state setting unit 210 releases the NAV when the set NAV period expires or when a CF-End frame instructing NAV release is received.

[0122] Note that when setting the NAV, the transmission prohibition state setting unit 210 distinguishes between the states of the intra-BSS NAV and the regular NAV, and the above NAV setting and NAV release are performed for each NAV. Specifically, for example, when the transmission prohibition state setting unit 210 receives an intra-BSS MAC frame, it performs the intra-BSS setting, and when it receives an OBSS MAC frame, it performs the regular NAV setting.

[0123] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. When it is determined to release the NAV in this determination, the regular NAV is released even in other cases. The transmission prohibition state setting unit 210 outputs transmission prohibition state information related to NAV setting or NAV release to the transmission control unit 207.

[0124] In addition, when it is necessary to update the target BSS information, 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. In addition, the target BSS information storage unit 214 outputs the stored target BSS information to the transmission prohibition state setting unit 210 as necessary.

[0126] [Operation Example] FIG. 16 is a sequence diagram showing an operation example of the wireless network 100'''' when transmitting and receiving RTS / CTS frames 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 RTS frame reception processing from access point F (ST602). The RTS frame reception processing includes extraction of the BSS color from the RTS frame and measurement of the RSSI of the RTS frame. Terminal C sets a regular NAV according to 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 an OBSS for which the NAV is set. That is, 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 CTS frame reception processing from terminal E (ST606). The CTS frame reception processing includes extraction of the BSS color from the CTS frame and measurement of the RSSI of the CTS frame.

[0130] Then, terminal C 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, 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 to release the regular NAV (ST608). Details of the method for determining the regular NAV in ST608 will be described later.

[0132] In FIG. 16, the case where it is determined that the regular NAV is not released in ST608 is illustrated. In this case, the terminal C continues the regular NAV and maintains the transmission prohibition state.

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

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

[0135] The terminal C determines whether to release the regular NAV (ST612). Details of the method for determining the regular NAV in ST612 will be described later.

[0136] In FIG. 16, the case where it is determined that the regular NAV is not released in ST612 is illustrated. In this case, the terminal C continues the regular NAV and maintains the transmission prohibition state. If the regular NAV is not released in ST612, the terminal C compares the stored RSSI with the current RSSI, and if the current RSSI is higher, updates the target BSS information (ST613). Here, assume that the stored RSSI (RSSI from the terminal E) is higher than the current RSSI (RSSI from the terminal B), and the terminal C does not update the target BSS information.

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

[0138] The terminal C determines whether to cancel the regular NAV (ST616). Details of the regular NAV determination method in ST616 will be described later.

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

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

[0141] [NAV Cancellation Determination Method] Hereinafter, details of the determination method for whether to cancel the regular NAV in ST608, ST612, and ST616 shown in FIG. 16 will be described.

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

[0143] When the terminal C updates the regular NAV by receiving 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, the terminal C updates the target BSS information using the BSS color and RSSI of the received signal. However, the cancellation of the regular NAV due to the expiration of the NAV period may be performed regardless of the target BSS.

[0144] In the sixth embodiment, as described above, the regular NAV is canceled based on the signal received from the target BSS, but not based on the signals received from other BSSs. Therefore, even when there are multiple OBSSs, it is possible to avoid a situation where canceling the NAV of one OBSS causes relatively large interference to other OBSSs. Accordingly, inappropriate cancellation of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0145] As described above, various embodiments have been described with reference to the drawings. Needless to say, the present disclosure is not limited to such examples. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that they also belong to the technical scope of the present disclosure. Also, within the scope not departing from the gist of the disclosure, the components in the above embodiments may be arbitrarily combined.

[0146] In the first to sixth embodiments described above, when the terminal C received the CF-End frame, it released the NAV. However, for example, when there are multiple OBSSs, the RSSI of the CF-End frame is measured, compared with the RSSI of the target BSS information in which the measured RSSI is stored, and the terminal C may release the regular NAV only when the RSSI of the CF-End frame is higher. With such a configuration, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0147] The method for releasing the transmission prohibition state in the above embodiment is not limited to releasing the NAV. For example, it is also applicable when temporarily setting the transmission permission state without releasing the NAV (managing the time of the transmission permission state and returning to the transmission prohibition state again if the original NAV period is still valid after that time has passed).

[0148] Also, in the above embodiment, instead of releasing the transmission prohibition state, an operation of reducing the interference by reducing the transmission power may be performed.

[0149] In the above embodiment, when the transmission prohibition state cannot be released, there may be a case where an ACK for data reception cannot be returned. In that case, an operation of transmitting an ACK after releasing the NAV may be performed.

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

[0151] Also, 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 formed into one chip, or may be formed into one chip so as to include some or all of them. Here, it has been described as an LSI, but depending on the degree of integration, it may also be referred to as an IC, a system LSI, a super LSI, or an ultra LSI.

[0152] Also, the method of integrating circuits is not limited to LSI, and it may be realized by an application-specific circuit or a general-purpose processor. After manufacturing the LSI, an FPGA (Field Programmable Gate Array) that can be programmed, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may be used.

[0153] Furthermore, if a technology for integrating circuits that replaces LSI appears due to the progress of semiconductor technology or other derived technologies, naturally, the integration of functional blocks may be performed using that technology. The application of biotechnology, etc. may be possible.

[0154] <Summary of the Present Disclosure> The wireless station of the present disclosure 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 interference cell to a second wireless station belonging to the interference cell, and after setting a transmission prohibition period for other wireless stations belonging to the communication cell to which the own station belongs, when the receiving unit receives the trigger signal, based on the reception intensity of the trigger signal, a transmission prohibition period control unit that determines whether to cancel the transmission prohibition period.

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

[0156] In the wireless station of the present disclosure, the communication cell to which the own 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 wireless station of the present disclosure, the transmission prohibition period control unit determines whether to cancel the transmission prohibition period based on a threshold value set based on the reception intensity measurement accuracy of the own station and the reception intensity of the trigger signal.

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

[0159] In the wireless station of the present disclosure, when the transmission prohibition period control unit receives a response signal from the second wireless station to the trigger signal, it determines whether to cancel the transmission prohibition period based on the threshold set based on the reception strength measurement accuracy of its own station, the reception strength of the trigger signal, and the reception strength of the response signal.

[0160] In the wireless station of the present disclosure, the transmission prohibition period control unit cancels the transmission prohibition period when the reception strength of the trigger signal is within a predetermined range set based on the reception strength measurement accuracy of its own station.

[0161] In the wireless station of the present disclosure, the transmission prohibition period control unit discriminates the type of the trigger signal, and when the trigger signal is a trigger signal that requests responses from a plurality of wireless stations in the interference cell, it does not cancel the transmission prohibition period.

[0162] In the wireless station of the present disclosure, when the trigger signal is a trigger signal that requests responses from a plurality of wireless stations in the interference cell, the transmission prohibition period control unit extracts information regarding the number of wireless stations that the trigger signal requests responses from the trigger signal, and determines whether to cancel the transmission prohibition period based on the extracted information.

[0163] In the wireless station of the present disclosure, the transmission prohibition period control unit compares the strength of the response signal from the second wireless station to the first wireless station extracted from the trigger signal with the estimated reception strength of the signal transmitted from its own station to the first wireless station at the first wireless station estimated in advance, and does not cancel the transmission prohibition period when the difference is smaller than a predetermined value.

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

[0165] The communication method of the present disclosure is a communication method in a wireless network having a plurality of terminals or wireless stations that are access points. After one of the plurality of wireless stations sets a transmission prohibition period for other wireless stations belonging to the communication cell to which the own station belongs, when receiving a trigger signal transmitted from a first wireless station belonging to an interference cell to which the own station does not belong to a second wireless station belonging to the interference cell, the one wireless station determines whether to release the transmission prohibition period based on the reception intensity of the trigger signal.

[0166] In the communication method of the present disclosure, the wireless station is a wireless station compliant 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-BSS (Basic Service Set), and the interference cell is an OBSS (Overlapping Basic Service Set) or an inter-BSS.

[0168] In the communication method of the present disclosure, the one wireless station determines whether to release the transmission prohibition period based on a threshold set based on the reception intensity measurement accuracy of the own station and the reception intensity of the trigger signal.

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

[0170] In the communication method of the present disclosure, when the first radio station receives a response signal from the second radio station to the trigger signal, it determines whether to cancel the transmission prohibition period based on a threshold value set based on the reception strength measurement accuracy of its own station, the reception strength of the trigger signal, and the reception strength of the response signal.

[0171] In the communication method of the present disclosure, the first radio station cancels the transmission prohibition period when the reception strength of the trigger signal is within a predetermined range set based on the reception strength measurement accuracy of its own station.

[0172] In the communication method of the present disclosure, the first radio station discriminates the type of the trigger signal, and when the trigger signal is a trigger signal that requests a response from a plurality of radio stations in the interference cell, the first radio station does not cancel the transmission prohibition period.

[0173] In the communication method of the present disclosure, when the trigger signal is a trigger signal that requests a response from a plurality of radio stations in the interference cell, the first radio station extracts information regarding the number of radio stations that the trigger signal requests a response from the trigger signal, and determines whether to cancel the transmission prohibition period based on the extracted information.

[0174] In the communication method of the present disclosure, the first radio station 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 reception strength of the signal transmitted from the first radio station to the first radio station at the first radio station estimated in advance, and does not cancel the transmission prohibition period when the difference is smaller than a predetermined value.

[0175] In the communication method of the present disclosure, when the wireless station of 1 sets the transmission prohibition period triggered by a trigger signal from any of the wireless stations belonging to the interference cell, the identifier of the interference cell to which the wireless station that transmitted the trigger signal that triggered the setting of the transmission prohibition period belongs, and the reception intensity of the trigger signal that triggered the setting of the transmission prohibition period are stored. When a new trigger signal from an interference cell is received, if the reception intensity of the newly received trigger signal is higher than the reception intensity of the stored trigger signal, the transmission prohibition period is released.

Industrial Applicability

[0176] The present disclosure is suitable for a wireless station that performs suitable wireless communication in an environment where interference occurs between wireless stations.

Explanation of Signs

[0177] 100, 100’, 100’’, 100’’’, 100’’’’ Wireless network 200, 200’, 200’’, 200’’’, 200’’’’ Terminal 201 Transmission / reception antenna 202 Wireless transmission / reception unit 203 Transmission signal generation unit 204 Received signal demodulation / decoding unit 205 RSSI measurement unit 206 BSS type determination unit 207 Transmission control unit 208 Transmission buffer 209 MAC frame generation unit 210 Transmission prohibition state setting unit 211 Terminal information setting unit 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 overlapping basic service set (OBSS) that partially overlaps with a basic service set (BSS), a signal generator that generates a trigger frame for requesting response signals from a plurality of terminals belonging to the OBSS, the trigger frame including an AP Tx power subfield indicating a transmission power value of the trigger frame and a Target received signal strength indicator (Target RSSI) subfield indicating a desired received signal strength of the response signal at the access point, the AP Tx power subfield and the Target RSSI subfield being used by a first terminal belonging to the BSS that has received the trigger frame to determine whether or not to transmit to a second terminal belonging to the BSS; an antenna for transmitting the trigger frame; An access point comprising:

2. An estimated received power value when the access point receives a signal transmitted from the first terminal is calculated based on the value of the AP Tx power subfield and the value of the Target RSSI subfield. The access point of claim 1 .

3. The transmission permission is determined based on whether or not the estimated reception power value is higher than a value obtained by adding an allowable interference amount to the value of the Target RSSI subfield.

3. The access point of claim 2.

4. A communication method for an access point that belongs to an overlapping basic service set (OBSS) that partially overlaps with a basic service set (BSS), comprising: generating a trigger frame for requesting response signals from a plurality of terminals belonging to the OBSS, the trigger frame including an AP Tx power subfield indicating a transmission power value of the trigger frame and a Target received signal strength indicator (Target RSSI) subfield indicating a desired received signal strength of the response signal at the access point, the AP Tx power subfield and the Target RSSI subfield being used by a first terminal belonging to the BSS that has received the trigger frame to determine whether or not transmission to a second terminal belonging to the BSS is possible; transmitting the trigger frame; Communication methods.

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

6. The transmission permission is determined based on whether or not the estimated reception power value is higher than a value obtained by adding an allowable interference amount to the value of the Target RSSI subfield. The communication method according to claim 5.

Images