First wireless station and communication method

Abstract

The invention relates to a first wireless station belonging to a basic service set (BSS), the first wireless station comprising: a receiver that receives a trigger frame transmitted from an access point (AP) belonging to an overlapping BSS (OBSS), the trigger frame requesting an uplink multi-user signal from a plurality of wireless stations belonging to the OBSS; a transmitter that transmits a signal to a second wireless station belonging to the BSS in a spatial multiplexing operation when the uplink multi-user signal is transmitted, wherein the spatial multiplexing operation is limited based on a rank of the first wireless station, the rank indicating a received signal strength indicator (RSSI) measurement accuracy.

Description

[0001] This application is a divisional application of Chinese Patent Application No. CN201780022745.X, filed on March 14, 2017, entitled "Wireless Station and Communication Method". TECHNICAL FIELD

[0002] The present application relates to a wireless station and a communication method that perform appropriate wireless communication in an environment in which interference occurs between wireless stations. BACKGROUND

[0003] In IEEE (the Institute of Electrical and Electronics Engineers) 802.11 Task Group (TG) ax, as a next-generation standard of IEEE 802.11ac, development of a technical specification of IEEE 802.11ax (hereinafter, 11ax) is underway.

[0004] In IEEE 802.11 standards, as a set of wireless stations (also referred to as stations or STAs) that constitute a basic wireless network, a BSS (Basic Service Set) is defined. The BSS is constituted of one access point and a plurality of terminals (wireless stations other than the access point) in infrastructure mode, and is constituted of a plurality of terminals in point-to-point mode (Ad hoc mode). As a distinction from the BSS in infrastructure mode, the BSS in point-to-point mode is referred to as an IBSS (Independent BSS). A BSS other than the BSS to which the own terminal (or the access point) belongs is referred to as an OBSS (Overlapping BSS) or as an inter-BSS. In the OBSS, a plurality of communication cells overlap, and thus in communication between the OBSSs, interference occurs between the communication cells, and communication quality deteriorates.

[0005] In wireless communication, due to the influence of the distance between wireless stations and obstacles and the like, a state in which wireless signals of the wireless stations do not reach each other (a radio wave environment in which carrier sensing does not work) can occur. As a countermeasure against such an environment, that is, an environment in which a hidden terminal exists, in IEEE 802.11 standards, a function of preventing collision using a NAV (Network Allocation Vector) is prepared. If the access point and the terminal receive a wireless frame for setting the NAV at a level equal to or higher than a prescribed threshold, transmission is prohibited during the NAV set by the duration information, except for the case in which the wireless frame for setting the NAV is a frame addressed to the own terminal or the own access point. In the threshold used for determining whether to set the NAV, a value of the minimum reception sensitivity is generally used.

[0006] Further, in 11ax, it has been agreed to introduce SR (Spatial Reuse) that reuses wireless resources in use in OBSS (see Non-Patent Literature 1). The purpose of SR is to increase the utilization rate of wireless resources by increasing the transmission opportunity of a terminal (or access point) in a case where the given interference to OBSS (hereinafter, referred to as given interference) is small, thereby improving the communication performance in a wireless network. One method for implementing SR is to set the threshold value (hereinafter, referred to as OBSS_PD (Power Density)) for determining whether to set the NAV in a case where a wireless frame from OBSS is received to a value larger than the value of the minimum reception sensitivity normally used, under a specific condition.

[0007] Prior Art Documents

[0008] Non-Patent Literature

[0009] Non-Patent Literature 1: Robert Stacey, “Specification Framework for TGax”, IEEE 802.11-15 / 0132r15

[0010] Non-Patent Literature 2: Sigurd Schelstraete, “Multiple NAVs for Spatial Reuse”, IEEE 802.11-15 / 1348

[0011] Non-Patent Literature 3: Reza Hedayat, “TXOP Considerations for Spatial Reuse,” IEEE 802.11-15 / 1104 SUMMARY

[0012] However, in a case where the given interference level to OBSS is larger than the prescribed threshold value, if the terminal (or access point) erroneously estimates the size of the given interference and releases the regular NAV, there is a concern that the communication performance of the wireless network will decline, because the terminal in OBSS cannot correctly decode the received signal at a level of interference to the terminal in OBSS.

[0013] Therefore, one embodiment of the present application provides a wireless station and a communication method that prevent inappropriate release of a regular NAV and improve the communication performance.

[0014] The wireless station of one embodiment of the present application is a wireless station in a wireless network having a plurality of wireless stations, and includes a reception unit that receives a trigger signal transmitted from a first wireless station belonging to an interfering cell to a second wireless station belonging to the interfering cell, and a transmission prohibition period control unit that, after a transmission prohibition period to other wireless stations belonging to a communication cell to which the own station belongs is set, in a case where the trigger signal is received by the reception unit, makes a determination as to whether or not to release the transmission prohibition period based on a reception strength of the trigger signal.

[0015] Further, these general or specific description can be implemented not only by system, method, integrated circuit, computer program or recording medium, but also by any combination of system, apparatus, method, integrated circuit, computer program and recording medium.

[0016] According to one embodiment of the present application, inappropriate normal NAV release can be prevented, and the communication performance of a wireless network can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a diagram illustrating a positional relationship of an access point and a terminal in the first embodiment.

[0018] Figure 2 is a block diagram showing an example of a structure of a terminal in the first embodiment.

[0019] Figure 3 is a timing chart showing an example of an operation of a wireless network at the time of RTS / CTS frame transmission / reception in the first embodiment.

[0020] Figure 4 is a timing chart showing an example of an operation of a wireless network at the time of trigger frame transmission / reception in the first embodiment.

[0021] Figure 5 is a diagram illustrating a positional relationship of an access point and a terminal constituting a wireless network in the second embodiment.

[0022] Figure 6 is a block diagram showing an example of a structure of a terminal in the second embodiment.

[0023] Figure 7 is a diagram illustrating a positional relationship of an access point and a terminal constituting a wireless network in the third embodiment.

[0024] Figure 8 is a block diagram showing an example of a structure of a terminal in the third embodiment.

[0025] Figure 9 is a timing chart showing an example of an operation of a wireless network at the time of trigger frame transmission / reception in the third embodiment.

[0026] Figure 10 is a timing chart showing an example of the operation of the wireless network at the time of transmission and reception of the trigger frame in the fourth embodiment.

[0027] Figure 11 is a diagram illustrating a positional relationship of the access point and the terminal constituting the wireless network of the fifth embodiment.

[0028] Figure 12 is a block diagram showing a structure of the terminal of the fifth embodiment.

[0029] Figure 13 is a timing chart showing an example of the operation of the wireless network at the time of transmission and reception of the trigger frame in the fifth embodiment.

[0030] Figure 14 is a diagram illustrating a positional relationship of the access point and the terminal constituting the wireless network of the sixth embodiment.

[0031] Figure 15 is a block diagram showing an example of the structure of the terminal of the sixth embodiment.

[0032] Figure 16 is a timing chart showing an example of the operation of the wireless network at the time of transmission and reception of the RTS / CTS frame in the sixth embodiment. DETAILED DESCRIPTION

[0033] Hereinafter, each embodiment of the present application will be explained in detail with reference to the drawings. However, there are cases where detailed explanation, such as detailed explanation of known matters and repeated explanation of substantially the same structure, is omitted.

[0034] Further, the following explanation and the referenced drawings are provided in order for those skilled in the art to understand the present application, and are not intended to limit the scope of the claims of the present application.

[0035] <Reason for accomplishing the present application>

[0036] Hereinafter, the reason for accomplishing the present application will be explained simply.

[0037] In 11ax, in each of intra-BSS and OBSS, a separate management NAV is agreed (refer to Non-Patent Literature 2). Thereby, the situation that the NAV of intra-BSS is released by the NAV release request (CF-End: Contention Free-End) from OBSS, and the NAV of OBSS is released by the CF-End of intra-BSS is avoided. In 11ax, in order to simplify the SR processing, in the case where there are a plurality of OBSSs, the terminal (or access point) does not distinguish the NAV for each OBSS, but manages two NAVs of intra-BSS NAV and regular NAV (the NAV of OBSS, or the NAV in the case where it is not distinguished whether it is the OBSS of intra-BSS).

[0038] Further, in 11ax, as one of the methods of SR, it is proposed that the regular NAV is released even in the case other than the case where the CF-End frame (NAV release request frame) is received under the specified condition (Non-Patent Literature 3). In this method, by using the combination of the trigger signal and the response signal, the size of the given interference to the terminal (or access point) of OBSS is estimated, and the release of the regular NAV is performed. In the case where the size of the given interference to OBSS is suppressed to be smaller than the prescribed threshold value derived empirically, for example, according to this method, the effect of SR is further improved.

[0039] In the following reference Non-Patent Literature 1, it is disclosed that the terminal (or access point) releases the regular NAV in the case where the following conditions are satisfied. The 1st condition is the condition that the RSSI (Received Signal Strength Indicator) is higher than OBSS_PD (the threshold value applicable to the case where the object is OBSS) when the inter-BSS RTS (Request To Send) frame is received. The 2nd condition is the condition that the RSSI is lower than the prescribed threshold value for NAV release when the inter-BSS CTS (Clear To Send) frame is received.

[0040] Reference Non-Patent Literature 1: Reza Hedayat, “Recipient-aware Spatial Reuse,” IEEE 802.11-16 / 0060

[0041] Further, in the following reference non-patent literature 2, it is disclosed that the terminal (or access point) releases the regular NAV at the time of detection of the UL MU PPDU (UpLink Multi-User Physical layer convergence Protocol Data Unit) transmitted in succession to the trigger frame, in a case where the RSSI of the trigger frame is lower than OBSS_PD.

[0042] Reference non-patent literature 2: Geonjung Ko, "Improving Spatial Reuse During OBSS UL MU Procedure", IEEE 802.11-15 / 1338

[0043] However, in a case where the measurement accuracy of the RSSI of the terminal is low, or in a case where the distance between terminals is close, etc., there are cases where the regular NAV is released erroneously. Due to this, there are cases where the terminal (or access point) of the OBSS generates interference of, for example, OBSS_PD or more, and cannot correctly receive the desired signal. From such a reason, it is desirable to prevent the release of the inappropriate regular NAV. In the embodiments of the present application described below, a wireless station and a communication method that prevent the release of the inappropriate regular NAV and improve the communication performance of the wireless network are described. Further, the terminal or the access point in each of the embodiments below corresponds to the wireless station.

[0044] <1st Embodiment>

[0045] Figure 1 is a diagram illustrating the positional relationship of the access point and the terminal that constitute the wireless network 100 of the 1st embodiment. In the wireless network 100, as shown in Figure 1 , there are the access point A, the terminal B, the terminal C, and the access point D. The access point A and the terminal B belong to the BSS1 (OBSS), and the terminal C and the access point D belong to the BSS2 (intra-BSS).

[0046] [Description of Structure]

[0047] Figure 2 is a block diagram showing an example of the structure of the terminal 200 of the 1st embodiment. Figure 2 The terminal 200 illustrated in Figure 1 corresponds to the terminal C shown in Figure 1 Further, the structures of the access points A and D and the terminal B shown in Figure 1 The terminal 200 shown in

[0048] As shown in Figure 2As shown, the terminal 200 has a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generating unit 203, a reception signal demodulating and decoding unit 204, an RSSI measuring unit 205, a BSS category determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a terminal information setting unit 211. Further, the access control unit 212 (MAC) is constituted by the BSS category determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the terminal information setting unit 211.

[0049] The transmission / reception antenna 201 is at least one antenna, and performs transmission or reception of a wireless signal.

[0050] In transmission, the wireless transmission / reception unit 202 performs prescribed wireless transmission processing such as D / A conversion and up-conversion to a carrier frequency on a transmission signal input from the transmission signal generating unit 203, and transmits the transmission signal via the transmission / reception antenna 201. In reception, the wireless transmission / reception unit 202 performs prescribed wireless reception processing such as down-conversion and A / D conversion on a wireless signal received via the transmission / reception antenna 201, and outputs the received wireless signal to the reception signal demodulating and decoding unit 204 and the RSSI measuring unit 205.

[0051] The transmission signal generating unit 203 encodes and modulates a MAC frame input from the MAC frame generating unit 209, and generates a wireless frame (also referred to as a PPDU) by attaching a pilot signal for frequency synchronization and timing synchronization in the reception side, and a control signal (also referred to as a preamble) such as a signal for channel estimation, and outputs the wireless frame to the wireless transmission / reception unit 202.

[0052] The reception signal demodulating and decoding unit 204 extracts a wireless frame by performing autocorrelation processing or the like on a wireless signal input from the wireless transmission / reception unit 202 after wireless reception processing, and performs demodulation and decoding of the wireless frame. Further, the reception signal demodulating and decoding unit 204 extracts preamble information (a control signal of the wireless frame) and a MAC frame from the wireless signal input from the wireless transmission / reception unit 202, and outputs the preamble information to the BSS category determining unit 206, and outputs the MAC frame to the transmission prohibition state setting unit 210.

[0053] The RSSI measuring unit 205 performs measurement of RSSI based on a wireless signal input from the wireless transmission / reception unit 202 after wireless reception processing, and outputs RSSI information including the measurement result to the transmission prohibition state setting unit 210.

[0054] The BSS category determination unit 206 extracts the identifier information (hereinafter, referred to as BSS color) of the BSS included in the preamble information input from the reception signal demodulation and decoding unit 204, and determines the category of the BSS to which the terminal (or access point) that transmitted the received wireless signal belongs. The BSS category determination unit 206 determines that it is intra-BSS in the case where the BSS color included in the preamble information and the BSS color of the BSS to which the own terminal 200 belongs are the same, and determines that it is OBSS in the case where it is not. The BSS category determination unit 206 outputs the determination result as BSS category information (information indicating whether it is intra-BSS) to the transmission prohibition state setting unit 210.

[0055] The transmission control unit 207 performs transmission control based on the transmission prohibition state information (information indicating that transmission is prohibited, i.e., information indicating whether the NAV is set) input from the transmission prohibition state setting unit 210 and the buffer state information (information indicating the presence or absence of transmission data) input from the transmission buffer 208. Specifically, in the case where the 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.

[0056] The transmission buffer 208 holds transmission data for which the terminal 200 transmits to other terminals (or access points). In addition, the transmission buffer 208 outputs the buffer state information indicating the presence or absence of transmission data to the transmission control unit 207.

[0057] The MAC frame generation unit 209 performs a MAC frame generation process of attaching a MAC header or the like 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.

[0058] The transmission prohibition state setting unit 210 performs setting of the NAV based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the reception signal demodulation and decoding unit 204, the RSSI measurement accuracy information input from the terminal information setting unit 211, and the BSS category information input from the BSS category determination unit 206.

[0059] Specifically, the transmission prohibition state setting unit 210 performs setting of the NAV in the case where the MAC frame is a frame indicating setting of the NAV such as an RTS / CTS frame. In addition, the transmission prohibition state setting unit 210 releases the NAV in the case where the period of the set NAV expires and in the case where a CF-End frame indicating release of the NAV is received.

[0060] Further, in setting the NAV, the transmission prohibition state setting unit 210 distinguishes the state of the intra-BSS NAV and the regular NAV, and performs the above-described NAV setting and NAV release for each NAV. Specifically, for example, in a case where the MAC frame of the intra-BSS is received, the transmission prohibition state setting unit 210 performs the setting of the intra-BSS, and in a case where the MAC frame of the OBSS is received, the setting of the regular NAV is performed.

[0061] However, the transmission prohibition state setting unit 210 performs the determination of whether to release the NAV using the NAV release determination method described later, and in a case where the determination to release the NAV is made in the determination, the release of the regular NAV is performed even in addition to the above-described (in a case where the set NAV period expires, or in a case where the CF-End frame is received). The transmission prohibition state setting unit 210 outputs the transmission prohibition state information related to the NAV setting or the NAV release to the transmission control unit 207.

[0062] The terminal information setting unit 211 outputs the RSSI measurement accuracy information of the terminal 200 to the transmission prohibition state setting unit 210. In 11ax, two categories of terminal levels (also referred to as ST levels A) having different required accuracies such as RSSI measurement accuracy are supported, and the RSSI measurement accuracy information is information set based on the terminal level of the terminal 200.

[0063] According to such a configuration, in the first embodiment, by setting the threshold value of the release determination of the regular NAV in consideration of the RSSI measurement accuracy, it is possible to prevent a terminal having low RSSI measurement accuracy from releasing the NAV based on the measurement error of the RSSI, and to prevent the situation where the OBSS is caused to have large given interference. Hereinafter, a specific example of the operation of the wireless network 100 of the first embodiment will be described.

[0064] [Example of Operation]

[0065] Figure 3 is a timing chart showing an example of the operation of the wireless network 100 at the time of transmission and reception of the RTS / CTS frame in the first embodiment. As shown in Figure 3 first, the terminal B performs the transmission process of the RTS (Request to Send: trigger signal of CTS) frame requesting the CTS transmission to the access point A (ST101). The terminal C performs the reception process of the RTS frame from the terminal B (ST102). The reception process of the RTS frame includes the RSSI measurement of the RTS frame. Further, the measurement method of the RSSI is not particularly limited in the present application, and a known RSSI measurement method can be used. The terminal C sets the regular NAV based on the RTS (ST103).

[0066] Next, the access point A transmits a response signal, that is, a CTS (Clear to Send) frame, in response to the RTS frame from the terminal B (ST104). If the terminal C receives the CTS from the access point A, it measures the RSSI (ST105). The terminal C makes a determination as to whether or not to release the regular NAV based on the RSSI of the CTS frame (ST106). Details of the release determination method of the regular NAV in ST106 will be described later.

[0067] In Figure 3 , a case where it is determined not to release the regular NAV in ST106 is exemplified. In this case, the terminal C updates the regular NAV based on the CTS frame (ST107). Next, the terminal B transmits data to the access point A (ST108). At this time, since the regular NAV is set in the terminal C, the terminal C does not transmit to the access point D.

[0068] On the other hand, Figure 4 is a timing chart showing an example of the operation of the wireless network 100 at the time of reception of the trigger frame in the first embodiment. In Figure 4 , it is assumed that the terminal C sets the regular NAV in advance.

[0069] As shown in Figure 4 , first, the access point A performs a trigger frame transmission process to the terminal B (ST201). The terminal C performs a trigger frame reception process from the access point A (ST202). The trigger frame reception process includes RSSI measurement of the trigger frame. The terminal C makes a determination as to whether or not to release the regular NAV based on the RSSI measurement result of the trigger frame (ST203). Details of the determination method of the regular NAV in ST203 will be described later.

[0070] In Figure 4 , a case where it is determined not to release the regular NAV in ST203 is exemplified. In this case, the terminal C updates the regular NAV based on the trigger frame (ST204). Next, the terminal B transmits data to the access point A (ST205). At this time, since the regular NAV is set in the terminal C, the terminal C does not transmit to the access point D.

[0071] [NAV Release Determination Method 1]

[0072] Details of the determination method of whether or not to release the regular NAV in ST106 shown in Figure 3 or ST203 shown in Figure 4 will be described below.

[0073] The NAV release determination method 1 described below corresponds to the case where it is determined to release the regular NAV in ST106 shown in Figure 3the ST106. In the NAV release determination method 1, the terminal C sets the threshold for the determination of the NAV release based on the RSSI measurement accuracy information of the terminal itself or the terminal classes (STA Classes). The terminal C sets the threshold for the trigger signal (1st threshold) and the threshold for the response signal (2nd threshold). Here, the trigger signal is, for example, an RTS frame, and the response signal is, for example, a CTS frame. The 1st threshold and the 2nd threshold are set to be higher than the threshold for the signal within the BSS.

[0074] In 11ax, two classes of terminal classes are supported, which have different required accuracies of RSSI measurement accuracy and the like. Class A is a high-function 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-function terminal, and the RSSI measurement accuracy is required to be within an error of ±5 dB. That is, in the terminal of Class B, a maximum RSSI measurement error of 3 dB is allowed for the terminal of Class A.

[0075] Therefore, in order to accommodate the given interference to other terminals due to the RSSI measurement error of the terminal of Class B within the same as Class A, it is necessary to set a threshold different from that of Class A in the terminal of Class B. Specifically, it is sufficient to set the 1st threshold in the terminal of Class B to be 3 dB higher than the 1st threshold in Class A and to set the 2nd threshold in the terminal of Class B to be 3 dB lower than the 2nd threshold in Class A. The value of 3 dB is a value based on the difference in the required RSSI measurement accuracy in each of the terminal of Class A and the terminal of Class B. Further, it is sufficient to set the 1st threshold to be higher than the 2nd threshold.

[0076] Then, in the case where the trigger signal (RTS frame) from the OBSS is received (ST102) of the ST106, Figure 3 the terminal C measures the RSSI of the RTS frame and determines whether it is higher than the 1st threshold. Also, the terminal C measures the RSSI of the response signal (CTS frame) subsequently transmitted from the OBSS and determines whether it is lower than the 2nd threshold. In the case where the RSSI of the RTS frame is higher than the 1st threshold and the RSSI of the CTS frame is lower than the 2nd threshold, the terminal C releases the regular NAV. Further, the terminal C can not perform the determination of whether the RSSI of the RTS frame is higher than the 1st threshold, but can perform the determination of whether to release the regular NAV based only on the determination result of whether the RSSI of the CTS frame is lower than the 2nd threshold.

[0077] According to such a determination method, even in a case where the terminal C is a terminal of class B, i.e., a terminal with low RSSI measurement accuracy, the release determination of the regular NAV can be made based on the threshold value set in consideration of the measurement accuracy. Therefore, even in a case where the terminal C is a terminal of class B, i.e., a terminal with low RSSI measurement accuracy, the interference caused to the terminal (or access point) of the OBSS can be reduced. Thus, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved. Further, the first threshold value or the second threshold value in the terminal of class A can be set to OBSS_PD, for example.

[0078] [NAV release determination method 2]

[0079] The NAV release determination method 2 described below corresponds to the determination method in ST203. Figure 4 In the NAV release determination method 2, the terminal C sets the threshold value for the determination of the release of the NAV based on the RSSI measurement accuracy information of the terminal or the class of the terminal. The terminal C sets the threshold value for the trigger signal. Here, the trigger signal is a trigger frame, for example. The threshold value is set to be higher than the threshold value for the signal of the intra-BSS.

[0080] In the NAV release determination method 2, the RSSI determination using the trigger frame is different from the determination method 1. In a case where the trigger frame is received from the OBSS, the terminal C determines whether the RSSI of the trigger frame is lower than the threshold value. In a case where the RSSI of the trigger frame is lower than the threshold value, the terminal C releases the regular NAV. Further, the method of setting the threshold value can be the same as the method of setting the second threshold value in the NAV release determination method 1 described above (i.e., set to be 3 dB lower than OBSS_PD), or a different method can be employed.

[0081] According to such a determination method, as in the NAV release determination method 1, even in a case where the terminal C is a terminal with low RSSI measurement accuracy, the release determination of the regular NAV can be made based on the threshold value set in consideration of the measurement accuracy. Therefore, even in a case where the terminal C is a terminal with low RSSI measurement accuracy, the interference caused to the terminal (or access point) of the OBSS can be reduced. Thus, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0082] <Second embodiment>

[0083] Hereinafter, the second embodiment will be described. Figure 5 is a diagram illustrating the positional relationship of the access points and the terminals constituting the wireless network 100' of the second embodiment. As Figure 5In the wireless network 100', as shown, the access point A and the terminal B belong to the BSS 1 (OBSS), and the terminal C and the access point D belong to the BSS 2 (intra-BSS) in terms of Figure 1 The first embodiment shown is the same, but the distance between the terminal B and the terminal C is closer than in the first embodiment.

[0084] Thus, in the case where the distance between the terminal B and the terminal C is close, the RSSI of the transmission signal from the terminal C to the terminal B is close in strength to the RSSI of the transmission signal from the access point A to the terminal B, and there is a case where the reception quality of the transmission signal from the access point A to the terminal B is degraded due to the interference of the terminal C. In such a case, the possibility of failure in reception from the access point A in the terminal B increases. In the second embodiment, the wireless network 100' in which communication can be properly performed without degrading the communication quality even in such a case is explained.

[0085] [Explanation of Structure]

[0086] Figure 6 is a block diagram showing an example of the structure of the terminal 200' of the second embodiment. Figure 6 The terminal 200' exemplified in the second embodiment corresponds Figure 5 to the terminal C shown in the first embodiment. Also, Figure 5 The structure of the access points A and D and the terminal B shown in the second embodiment can be the same structure as Figure 6 the terminal 200' shown in the first embodiment.

[0087] As Figure 6 shown, the terminal 200' has a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generating unit 203, a reception signal demodulation and decoding unit 204, an RSSI measuring unit 205, a BSS category determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, and a transmission prohibition state setting unit 210. Further, the access control unit 212' (MAC) is constituted by the BSS category determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, and the transmission prohibition state setting unit 210. That is, in terms of the absence of the terminal information setting unit 211, the terminal 200' in the second embodiment is different from the structure of the terminal 200 in the first embodiment shown in Figure 2 Further, the operation of the transmission prohibition state setting unit 210 is somewhat different from the first embodiment.

[0088] The transmission prohibition state setting unit 210 sets the NAV based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the received signal demodulation and decoding unit 204, and the BSS category information input from the BSS category determination unit 206. Furthermore, the transmission prohibition state setting unit 210 releases the NAV when the set NAV period expires or when a CF-End frame indicating NAV release is received.

[0089] Furthermore, when setting the NAV, the transmission prohibition state setting unit 210 distinguishes the states of the intra-BSS NAV and the regular NAV, and performs the aforementioned NAV setting and NAV release for each NAV. Specifically, for example, when a MAC frame of intra-BSS is received, the transmission prohibition state setting unit 210 performs intra-BSS setting; when a MAC frame of OBSS is received, the regular NAV is set.

[0090] However, the transmission prohibition state setting unit 210 uses the NAV release determination method described later to determine whether to release the NAV. If the determination to release the NAV is made in this determination, the normal NAV release will still be performed even if there are no other reasons mentioned above. 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.

[0091] [Action Examples]

[0092] An example of the operation of the wireless network 100' in the second embodiment and Figure 3 or Figure 4 The examples of actions shown are the same, so explanations are omitted. However, Figure 3 ST106, or Figure 4 The NAV release determination method in ST203 differs in several ways from the NAV release determination methods 1 and 2 described in the first embodiment. Hereinafter, the NAV release determination method in the second embodiment will be described.

[0093] [NAV Release Determination Method]

[0094] The NAV release determination method described below corresponds to Figure 3 The determination method in ST106. In the NAV release determination method of the second embodiment, terminal C sets a threshold for the upper limit value of the trigger signal (third threshold), a threshold for the lower limit value 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 threshold, the fourth threshold, and the second threshold are set higher than the threshold for the intra-BSS signal.

[0095] In a case where the trigger signal (RTS frame) from the OBSS is received (ST102), the terminal C measures the RSSI of the RTS frame, determines whether it is higher than the 3rd threshold value, and determines whether it is lower than the 4th threshold value. That is, the terminal C determines whether the RSSI of the RTS frame is within a prescribed range prescribed by the 3rd threshold value and the 4th threshold value. Figure 3

[0096] Further, the terminal C measures the RSSI of the response signal (CTS frame) subsequently transmitted from the OBSS, and determines whether it is lower than the 2nd threshold value. In a case where the RSSI of the RTS frame is within the prescribed range, and the RSSI of the CTS frame is lower than the 2nd threshold value, the terminal C releases the regular NAV.

[0097] The 3rd threshold value is set to OBSS_PD, for example. Further, the 4th threshold value is set to a prescribed threshold value larger than the 3rd threshold value. For example, the 4th threshold value is set to a value obtained by adding a positive compensation value to the 3rd threshold value. Thereby, the amount of signaling required for notification of the 4th threshold value can be reduced.

[0098] Thus, in the 2nd embodiment, the RSSI of the trigger signal from the OBSS is within a prescribed range (a range higher than the 3rd threshold value and lower than the 4th threshold value), and the release of the NAV is performed in the terminal C only in a case where the RSSI of the response signal is lower than the 2nd threshold value. Therefore, in a case where the distance between the access point A and the terminal C is relatively close, or in a case where the reception quality in the terminal B is expected to be degraded due to the interference of the terminal C, by preventing the release of the NAV in a case where the RSSI of the trigger signal is not within the prescribed range, the degradation 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.

[0099] Further, in the operation example of the above-described 2nd embodiment, the operation example at the time of transmission and reception of the RTS / CTS frame is described, but the present application is not limited thereto. That is, the 2nd embodiment can be applied even to the time of transmission and reception of the trigger frame.

[0100] <3rd Embodiment>

[0101] Hereinafter, the 3rd embodiment will be described. Figure 7 is a diagram illustrating the positional relationship of the access point and the terminals constituting the wireless network 100" of the 3rd embodiment. As Figure 7 indicated, in terms of the presence of the terminal E belonging to the BSS1 (OBSS), the wireless network 100 differs from the wireless network 100 of the 1st embodiment as Figure 1 indicated.

[0102] ​In such a structure, the access point A sometimes transmits a trigger frame that requests a MU-BA (Multi-User Block Ack) transmission to a plurality of terminals such as the terminal B and the terminal E. The block Ack is defined by IEEE 802.11e, and responses to a plurality of data received are made in one frame. Further, the MU-BA is multiplexed in a plurality of users by MU (Multi-User) multiplexing to make a block Ack transmission. Further, the MU multiplexing means frequency multiplexing and spatial multiplexing of a plurality of terminals.

[0103] In such a case, the MU-BA transmission from the terminal B and the terminal E that received the trigger frame can not be received by the access point A due to interference by the terminal C, for example. If such an event occurs, the access point A retransmits a trigger frame that requests the MU-BA transmission to the terminal B and the terminal E again, so the traffic increases, and the communication performance of the wireless network 100" can be degraded. In the third embodiment, a wireless network 100" that can appropriately perform communication without degrading the communication quality even in such a case is described.

[0104] [Description of Structure]

[0105] Figure 8 is a block diagram showing an example of the structure of the terminal 200" of the third embodiment. Figure 8 The terminal 200" exemplified in Figure 7 is the terminal C shown in Figure 7 The structures of the access points A and D, the terminals B and E shown in Figure 8 may be the same as the terminal 200" shown in

[0106] As shown in Figure 8 , the terminal 200" has a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generating unit 203, a reception signal demodulating and decoding unit 204, a BSS category determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a trigger information analyzing unit 213. Further, the access control unit 212" (MAC) is constituted by the BSS category determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the trigger information analyzing unit 213. That is, in the aspect in which there is no RSSI measuring unit and the terminal information setting unit 211, and there is the trigger information analyzing unit 213, the terminal 200" in the third embodiment is different from the structure of the terminal 200 in the first embodiment shown in Figure 2 . Further, the operation of the transmission prohibition state setting unit 210 is different from those in the first and second embodiments.

[0107] The trigger information analysis unit 213 extracts trigger type information related to the trigger type from the trigger frame input from the reception signal demodulation and decoding unit 204, and outputs it to the transmission prohibition state setting unit 210.

[0108] The transmission prohibition state setting unit 210 sets the NAV based on the MAC frame input from the reception signal demodulation and decoding unit 204, the BSS category information input from the BSS category determination unit 206, and the trigger type input from the trigger information analysis unit 213. Further, in the case where the set NAV period expires and in the case where a CF-End frame indicating the release of the NAV is received, the transmission prohibition state setting unit 210 releases the NAV.

[0109] Further, in setting the NAV, the transmission prohibition state setting unit 210 distinguishes the state of the intra-BSS NAV and the regular NAV, and performs the above-described NAV setting and NAV release for each of the NAVs. Specifically, for example, in the case where the MAC frame of the intra-BSS is received, the transmission prohibition state setting unit 210 performs the setting of the intra-BSS, and in the case where the MAC frame of the OBSS is received, the transmission prohibition state setting unit 210 performs the setting of the regular NAV.

[0110] However, the transmission prohibition state setting unit 210 performs the determination of whether to release the NAV using the NAV release determination method described later, and in the case where the determination to release the NAV is made in the determination, the release of the regular NAV is performed even in addition to the above. The transmission prohibition state setting unit 210 outputs the transmission prohibition state information related to the NAV setting or the NAV release to the transmission control unit 207.

[0111] [Action Example]

[0112] Figure 9 is a timing chart showing an action example of the wireless network 100" at the time of the reception of the trigger frame in the third embodiment. In Figure 9 , it is assumed that the terminal C has set the regular NAV in advance.

[0113] As shown in Figure 9 , first, the access point A transmits the trigger frame requesting the MU-BA transmission to the terminal B and the terminal E (ST301).

[0114] If the terminal C receives the trigger frame from the access point A, it identifies the trigger type (ST302). The terminal C performs the determination of whether to release the regular NAV based on the result of the identification in ST302 (ST303). The details of the determination method of the regular NAV in ST303 will be described later.

[0115] In Figure 9In the case where it is determined in ST303 that the regular NAV is not released, the terminal C continues the regular NAV and maintains the transmission prohibition state.

[0116] Next, the terminal B and the terminal E perform MU-BA transmission to the access point A (ST304 and ST305). At this time, the regular NAV is set in the terminal C, so the terminal C does not perform transmission to the access point D.

[0117] [NAV release determination method]

[0118] Hereinafter, details of the determination method of whether to release the regular NAV in ST303 shown in FIG. 12 will be described. Figure 9

[0119] In 11ax, the MU-BA is transmitted in the UL MU PPDU. As described above, when receiving the MU-BA from a plurality of terminals, if reception on the access point A side fails due to interference, the traffic increases due to retransmission of the trigger frame and the MU-BA, and the communication performance of the wireless network 100 deteriorates. Therefore, it is desirable that no interference occurs. In addition, the PPDU length is short in the MU-BA, so the effect of the regular NAV release is small.

[0120] Therefore, in the third embodiment, if the terminal C receives the trigger frame, the trigger type information is extracted and the trigger type is discriminated, and in the case where the trigger type is MU-BAR (Multi-User Block Ack Request) which requests MU-BA transmission, the regular NAV is not released.

[0121] Thus, in the third embodiment, the determination of whether to release the regular NAV is made based on the trigger type, and the regular NAV is not released in the case where the trigger type is the MU-BAR. Thereby, the MU-BA is preferentially transmitted and received, it is possible to prevent deterioration of the communication performance of the wireless network 100 due to retransmission of the trigger frame and the MU-BA, and it is possible to maintain the effect of the SR. Further, in the case where it is determined 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, it is possible to prevent inappropriate regular NAV release and improve the communication performance of the wireless network.

[0122] Further, 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 the trigger frame including the MU-BAR to the terminal B and the terminal E is described, but the present application is not limited to this. For example, even in the case where more terminals belong to the OBSS and the access point A transmits the MU-BAR to these terminals, the third embodiment can be applied.

[0123] <Fourth Embodiment>​

[0124] The following describes the fourth embodiment. The positional relationship of the access point and the terminal constituting the wireless network 100" of the fourth embodiment is the same as that of the wireless network 100" of the third embodiment exemplified in Figure 7 The wireless network 100" of the third embodiment exemplified in

[0125] In the wireless network 100" exemplified in Figure 7 In the wireless network 100" exemplified in

[0126] [Description of Configuration]

[0127] The configuration of the terminal 200" in the fourth embodiment is also the same as that of the terminal 200" of the third embodiment exemplified in Figure 8 However, the operation of the transmission prohibition state setting unit 210 and the trigger information analysis unit 213 is somewhat different from that of the third embodiment.

[0128] The trigger information analysis unit 213 extracts the multiplexing number information on the MU multiplexing number included in the trigger frame input from the reception signal demodulation and decoding unit 204, and outputs it to the transmission prohibition state setting unit 210.

[0129] The transmission prohibition state setting unit 210 performs the NAV setting based on the MAC frame input from the reception signal demodulation and decoding unit 204, the BSS category information input from the BSS category determination unit 206, and the multiplexing number information input from the trigger information analysis unit 213. Further, in the case where the set NAV period expires and in the case where the CF-End frame indicating the NAV release is received, the transmission prohibition state setting unit 210 releases the NAV.

[0130] Further, at the time of setting the NAV, the transmission prohibition state setting unit 210 distinguishes the state of the intra-BSS NAV and the regular NAV, and performs the above-described NAV setting and NAV release for each of the NAVs. Specifically, for example, in the case where the MAC frame of the intra-BSS is received, the transmission prohibition state setting unit 210 performs the setting of the intra-BSS, and in the case where the MAC frame of the OBSS is received, the transmission prohibition state setting unit 210 performs the setting of the regular NAV.

[0131] However, the transmission prohibition state setting unit 210 uses the NAV release determination method described later to determine whether to release the NAV, and in a case where the determination to release the NAV is made in the determination, the regular NAV is released even if it is not described above. The transmission prohibition state setting unit 210 outputs transmission prohibition state information related to the NAV setting or the NAV release to the transmission control unit 207.

[0132] [Action Example]

[0133] Figure 10 is a timing chart showing an action example of the wireless network 100" at the time of reception of the trigger frame in the fourth embodiment. In Figure 10 , it is assumed that the terminal C sets the regular NAV in advance.

[0134] As shown in Figure 10 , first, the access point A transmits a trigger frame requesting data transmission to the terminal B and the terminal E (in a case where more terminals exist within the OBSS, the terminals can also be included in them) (ST401).

[0135] If the terminal C receives the trigger frame from the access point A, it extracts information related to the number of MU multiplexes (ST402). The information related to the number of MU multiplexes is, for example, included in the trigger frame.

[0136] The terminal C makes a determination as to whether to release the regular NAV based on the information related to the number of MU multiplexes extracted in ST402 (ST403). Details of the determination method of the regular NAV in ST403 will be described later.

[0137] In Figure 10 , a case where it is determined not to release the regular NAV in ST403 is exemplified. In this case, the terminal C continues the regular NAV, and maintains the transmission prohibition state.

[0138] Next, the terminal B and the terminal E perform transmission of data to the access point A (ST404 and ST405). At this time, the regular NAV is set in the terminal C, so the terminal C does not perform transmission to the access point D.

[0139] [NAV Release Determination Method]

[0140] Details of the determination method of whether to release the regular NAV in ST403 shown in Figure 10 will be described below. That is, in a case where the number of MU multiplexes notified by the trigger frame is higher than a prescribed threshold value, the terminal C does not release the regular NAV.

[0141] Thus, in the fourth embodiment, it is determined whether or not to release the normal NAV according to the number of MUs, and the normal NAV is not released in a case where the number of MUs is higher than a predetermined threshold. Thus, it is possible to prevent a decrease in the communication performance of the wireless network 100" caused by retransmission of data, and it is possible to maintain the effect of SR. Further, in a case where the number of MUs is lower than the predetermined threshold, the terminal C can maintain the effect of SR by performing the conventional NAV control. Thus, it is possible to prevent inappropriate release of the normal NAV, and improve the communication performance of the wireless network.

[0142] <5th Embodiment>

[0143] The fifth embodiment will be described below. Figure 11 is a diagram illustrating a positional relationship of an access point and terminals constituting the wireless network 100"'of the fifth embodiment. As Figure 11 indicated in the diagram, in the wireless network 100" ', the distance from the terminal B to the access point A is almost equal to the distance from the terminal C to the access point A, or converges within a predetermined difference.

[0144] In this case, the RSSI of the transmission signal from the terminal B to the access point A is close to the RSSI of the transmission signal from the terminal C to the access point A. This is because, in the access point A, the strength of the transmission signal from the terminal B (desired signal) and the transmission signal from the terminal C (interference signal) is almost the same, and thus the reception quality in the access point A sometimes decreases. In the fifth embodiment, a wireless network 100"'capable of appropriately performing communication without decreasing the communication quality even in such a case will be described.

[0145] [Description of Configuration]

[0146] Figure 12 is a block diagram showing the configuration of the terminal 200"'of the fifth embodiment. Figure 12 The terminal 200"'illustrated in the diagram corresponds to Figure 11 the terminal C shown in the diagram. Further, Figure 11 the configurations of the access points A and D and the terminal B shown in the diagram can also be the same configuration as the terminal 200"'shown in the diagram. Figure 12

[0147] Figure 12 ​As shown, the terminal 200"' has a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generating unit 203, a reception signal demodulating and decoding unit 204, an RSSI measuring unit 205, a BSS category determining unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a trigger information analyzing unit 213. Further, the access control unit 212"' (MAC) is constituted by the BSS category determining unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the trigger information analyzing unit 213. That is, the terminal 200"' in the fifth embodiment differs from the terminal 200 in the first embodiment in that the terminal 200"' does not have the terminal information setting unit 211 but has the trigger information analyzing unit 213. Figure 2 The structure of the terminal 200 in the first embodiment shown differs. Further, the operation of the transmission prohibition state setting unit 210 differs somewhat from that of the first embodiment.

[0148] The trigger information analyzing unit 213 extracts the target RSSI and the AP Tx power included in the trigger frame input from the reception signal demodulating and decoding unit 204 and outputs them to the transmission prohibition state setting unit 210.

[0149] The transmission prohibition state setting unit 210 performs the NAV setting based on the MAC frame input from the reception signal demodulating and decoding unit 204, the BSS category information input from the BSS category determining unit 206, and the target RSSI and the AP Tx power input from the trigger information analyzing unit 213. Further, in the case where the set NAV period expires and in the case where a CF-End frame indicating the release of the NAV is received, the transmission prohibition state setting unit 210 releases the NAV.

[0150] Further, at the time of setting the NAV, the transmission prohibition state setting unit 210 distinguishes the state of the intra-BSS NAV from that of the regular NAV and performs the above-described NAV setting and NAV release for each of the NAVs. Specifically, for example, in the case where the MAC frame of the intra-BSS is received, the transmission prohibition state setting unit 210 performs the setting of the intra-BSS, and in the case where the MAC frame of the OBSS is received, the transmission prohibition state setting unit 210 performs the setting of the regular NAV.

[0151] However, the transmission prohibition state setting unit 210 performs the determination of whether to release the NAV using the NAV release determining method described later, and in the case where the determination to release the NAV is made in the determination, the release of the regular NAV is performed even if it is not described above. The transmission prohibition state setting unit 210 outputs the transmission prohibition state information related to the NAV setting or the NAV release to the transmission control unit 207.

[0152] [Action Example]

[0153] Figure 13 is a timing chart showing an action example of the wireless network 100"'at the time of trigger frame transmission / reception in the fifth embodiment. In Figure 13 , it is assumed that the terminal C has set a regular NAV in advance.

[0154] As shown in Figure 13 , first, the access point A transmits a trigger frame to the terminal B (ST501). The terminal C performs trigger frame reception processing from the access point A (ST502). The trigger frame reception processing includes extraction of the target RSSI and the AP Tx power and measurement of the RSSI. The terminal C estimates the RSSI measurable by the access point A at the time of data transmission by the terminal C on the basis of the RSSI of the trigger frame and the AP Tx power extracted from the trigger frame (ST503). Then, the terminal C determines whether or not the RSSI estimated in ST503 is higher than a value obtained by adding a prescribed allowable interference amount to the target RSSI, and on the basis of the determination result, performs determination of whether or not to release the regular NAV (ST504). Details of the determination method of the regular NAV in ST504 will be described later.

[0155] In Figure 13 , a case where it is determined in ST503 not to release the regular NAV is exemplified. In this case, the terminal C continues the regular NAV, and maintains the transmission prohibition state.

[0156] Next, the terminal B performs data transmission to the access point A (ST505). At this time, the regular NAV is set in the terminal C, so the terminal C does not perform transmission to the access point D.

[0157] [NAV Release Determination Method]

[0158] Details of the determination method of whether or not to release the regular NAV in ST504 shown in Figure 13 will be described below.

[0159] As described above, if the trigger frame from the OBSS is received, the terminal C estimates the RSSI measurable by the access point A of the OBSS at the time of data transmission by the terminal C on the basis of the RSSI of the trigger frame and the AP Tx power extracted from the trigger frame. On the basis of this, the terminal C determines whether or not the estimated RSSI is higher than a value obtained by adding a prescribed allowable interference amount to the target RSSI. In a case where the estimated RSSI is higher than the value obtained by adding the prescribed allowable interference amount to the target RSSI, the terminal C does not release the regular NAV. Further, the prescribed allowable interference amount is a margin set in advance.

[0160] Thus, in the fifth embodiment, the strength (target RSSI) of the transmission signal (desired signal) from the terminal B in the access point A is compared with the strength (estimated RSSI) of the transmission signal (interference signal) from the terminal C, and the terminal C does not release the regular NAV in a case where the estimated RSSI is higher than a value obtained by adding the prescribed allowable interference amount to the target RSSI. Thereby, it is possible to reduce degradation of the communication performance in the wireless network 100' ". Thus, it is possible to prevent inappropriate release of the regular NAV and improve the communication performance of the wireless network.

[0161] <6th Embodiment>

[0162] The third embodiment will be described below. Figure 14 is a diagram illustrating a positional relationship of an access point and terminals constituting the wireless network 100' " of the sixth embodiment. As Figure 14 indicated, 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. In addition, the access point A and the terminal B belong to the BSS 1 (OBSS), the terminal C and the access point D belong to the BSS 2 (intra-BSS), and the terminal E and the access point F belong to the BSS 3 (OBSS).

[0163] Thus, in a case where there are a plurality of OBSSs, in 11ax, the terminal C does not distinguish the NAVs of the plurality of OBSSs, and thus, sometimes, a relatively large interference is caused to the other OBSSs due to release of the NAV of one OBSS. In the sixth embodiment, a wireless network 100' " in which communication is appropriately performed without degrading the communication quality even in such a case will be described.

[0164] [Description of Configuration]

[0165] Figure 15 is a block diagram showing an example of the configuration of the terminal 200' " of the sixth embodiment. Figure 15 The terminal 200' " illustrated in Figure 14 is the terminal C shown in Figure 14 , the terminal B and E can also have the same configuration as the terminal 200' " illustrated in Figure 15 .

[0166] As Figure 15As shown, the terminal 200'" has a transmission / reception antenna 201, a wireless transmission / reception unit 202, a transmission signal generating unit 203, a reception signal demodulating and decoding unit 204, an RSSI measuring unit 205, a BSS category judging unit 206, a transmission control unit 207, a transmission buffer 208, a MAC frame generating unit 209, a transmission prohibition state setting unit 210, and a target BSS information storage unit 214. Further, the access control unit 212'" (MAC) is constituted by the BSS category judging unit 206, the transmission control unit 207, the transmission buffer 208, the MAC frame generating unit 209, the transmission prohibition state setting unit 210, and the target BSS information storage unit 214.

[0167] The transmission prohibition state setting unit 210 performs the NAV setting based on the RSSI information input from the RSSI measuring unit 205, the MAC frame input from the reception signal demodulating and decoding unit 204, the BSS category information input from the BSS category judging 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. Further, in the case where the set NAV period expires or in the case where a CF-End frame indicating the NAV release is received, the transmission prohibition state setting unit 210 releases the NAV.

[0168] Further, in setting the NAV, the transmission prohibition state setting unit 210 distinguishes the state of the intra-BSS NAV and the regular NAV, and performs the above-described NAV setting and NAV release for each NAV. Specifically, for example, in the case where the MAC frame of the intra-BSS is received, the transmission prohibition state setting unit 210 performs the setting of the intra-BSS, and in the case where the MAC frame of the OBSS is received, performs the setting of the regular NAV.

[0169] However, the transmission prohibition state setting unit 210 performs the determination of whether to release the NAV using the NAV release judging method described later, and in the case where the determination to release the NAV is made in the determination, releases the regular NAV even if other than the above. The transmission prohibition state setting unit 210 outputs the transmission prohibition state information related to the NAV setting or the NAV release to the transmission control unit 207.

[0170] Further, in the case where the update of the target BSS information is required, the transmission prohibition state setting unit 210 generates new target BSS information and outputs it to the target BSS information storage unit 214.

[0171] The target BSS information storage unit 214 stores the target BSS information. If 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. Further, as necessary, the target BSS information storage unit 214 outputs the stored target BSS information to the transmission prohibition state setting unit 210.

[0172] [Action Example]

[0173] Figure 16 is a timing chart showing an action example of the wireless network 100" in the case where the RTS / CTS frame is transmitted and received in the sixth embodiment.

[0174] As shown in Figure 16 , first, the access point F transmits an RTS frame to the terminal E (ST601). The terminal C performs an RTS frame reception process from the access point F (ST602). The RTS frame reception process includes extraction of the BSS color from the RTS frame and RSSI measurement of the RTS frame. The terminal C sets a regular NAV based on the RTS frame (ST603).

[0175] If the regular NAV is set, the terminal C generates target BSS information (ST604). Here, the target BSS information is information indicating an OBSS whose NAV is set. That is, the target BSS information generated in ST604 is information indicating BSS3 as a target. Further, the target BSS information includes the BSS color of the target BSS and the RSSI of the RTS frame. Figure 14

[0176] Next, the terminal E transmits a CTS frame which is a response signal of the RTS frame to the access point F (ST605). The terminal C performs a CTS frame reception process from the terminal E (ST606). The CTS frame reception process includes extraction of the BSS color from the CTS frame and RSSI measurement of the CTS frame.

[0177] Then, the terminal C performs comparison of the RSSI stored in ST604 and the RSSI of the CTS frame received in ST606, and updates the target BSS information in the case where the RSSI of the CTS frame is high (ST607). Here, it is assumed that the current RSSI (RSSI from the terminal E) is higher than the stored RSSI (RSSI from the access point F), and the terminal C updates the target BSS information. Further, in ST607, the terminal C updates only the RSSI included in the target BSS information, and does not update the BSS color.

[0178] The terminal C performs determination of whether or not to release the regular NAV (ST608). Details of the method of determination of the regular NAV in ST608 will be described later.​

[0179] In Figure 16 , a case where it is determined not to release the regular NAV in ST608 is exemplified. In this case, the terminal C continues the regular NAV, and maintains the transmission prohibition state.

[0180] Next, the access point F performs transmission of data to the terminal E (ST609). At this time, the regular NAV is set in the terminal C, so the terminal C does not perform transmission to the access point D.

[0181] Next, it is assumed 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 RSSI measurement of the RTS frame.

[0182] The terminal C performs determination of whether to release the regular NAV (ST612). Details of the determination method of the regular NAV in ST612 will be described later.

[0183] In Figure 16 , a case where it is determined not to release the regular NAV in ST612 is exemplified. In this case, the terminal C continues the regular NAV, and maintains the transmission prohibition state. In a case where the regular NAV is not released in ST612, the terminal C performs comparison of the stored RSSI and the current RSSI, and in a case where the current RSSI is high, the target BSS information is updated (ST613). Here, it is assumed 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.

[0184] Next, the access point A transmits a CTS frame which is a response signal of 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.

[0185] The terminal C performs determination of whether to release the regular NAV (ST616). Details of the determination method of the regular NAV in ST616 will be described later.

[0186] In Figure 16The example illustrates a scenario where ST616 determines that the regular NAV should not be released. In this case, terminal C allows the regular NAV to continue, maintaining the transmission-prohibited state. If the regular NAV is not released in ST616, terminal C compares the stored RSSI with the current RSSI. If the current RSSI is higher, the target BSS information is updated (ST617). Here, it is assumed that the stored RSSI (from terminal E) is higher than the current RSSI (from terminal B), and terminal C does not update the target BSS information.

[0187] Next, terminal B sends data to access point A (ST618). At this time, a regular NAV is set in terminal C, so terminal C does not send data to access point D.

[0188] [NAV Release Determination Method]

[0189] The following is an explanation. Figure 16 Details of the methods for determining whether to release a conventional NAV in ST608, ST612, and ST616 are shown.

[0190] As mentioned above, when a regular NAV is set ( Figure 16 In ST603), terminal C stores the target BSS information of the BSS set as the target BSS. Then, when determining whether to release a regular NAV (ST608, ST612, and ST616), a regular NAV based on the signal received from the target BSS is released, but a regular NAV based on the signal received from other BSSs is not released.

[0191] Then, when there are regular NAV updates via RTS / CTS frame reception, if the RSSI of the received signal is higher than the RSSI stored as target BSS information, terminal C updates the target BSS information using the BSS color and RSSI of the received signal. However, the release of regular NAV due to the expiration of the NAV period can be implemented without relying on the target BSS.

[0192] Thus, in the sixth embodiment, a regular NAV release based on the signal received from the target BSS is performed, but a regular NAV release based on the signal received from other BSSs is not performed. Therefore, even in the presence of multiple OBSSs, a situation where releasing the NAV of one OBSS causes significant interference to other OBSSs can be avoided. Therefore, inappropriate regular NAV releases can be prevented, improving the communication performance of the wireless network.

[0193] The above is with reference to the appendix. Figure 1The present application is not limited to the above-described examples. Various modifications and alterations can be conceived as long as they are within the scope of the present application recited in the claims, and they are naturally included in the technical scope of the present application. In addition, the components in the above-described embodiments can be arbitrarily combined within the scope of the present application.

[0194] In the above-described first to sixth embodiments, the terminal C releases the NAV when receiving the CF-End frame. However, for example, in the case where there are a plurality of OBSSs, the RSSI of the CF-End frame is measured, the measured RSSI is compared with the RSSI of the stored target BSS information, and the terminal C can release the regular NAV only in the case where the RSSI of the CF-End frame is high. With such a configuration, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0195] The method of releasing the transmission prohibited state in the above-described embodiments is not limited to the NAV release. For example, the same can be applied in the case where the transmission prohibited state is temporarily released without releasing the NAV (the time during which the transmission permitted state is managed is managed, and even if the time elapses, if the original NAV period is valid, the transmission prohibited state is returned again).

[0196] In addition, in the above-described embodiments, instead of releasing the transmission prohibited state, the given interference action can also be reduced by lowering the transmission power.

[0197] In the above-described embodiments, in the case where the transmission prohibited state cannot be released, there is a case where the ACK to the data reception is not returned. In this case, the action of transmitting the ACK after the NAV release can also be performed.

[0198] In the above-described embodiments, the present application is described by way of example using a hardware configuration, but the present application can also be implemented in software in cooperation with the hardware.

[0199] In addition, each functional block used in the description of the above-described embodiments is generally implemented as an integrated circuit, that is, an LSI. These integrated circuits can be individually formed as single chips, or a part or all of them can be formed as a single chip. Here, although described as an LSI, depending on the degree of integration, it can also be referred to as an IC, a system LSI, a super LSI, or an ultra LSI.

[0200] Moreover, the method of the integrated circuit is not limited to the LSI and can be realized by using a special circuit or a general purpose processor. A FPGA (Field Programmable Gate Array) that can be programmed after the manufacture of the LSI, or a reconfigurable processor in which the connections and the settings of circuit cells included in the LSI can be reconfigured can be used.

[0201] Furthermore, with the advancement of semiconductor technology or other technology derived therefrom, if a technology that enables integration of an integrated circuit instead of an LSI appears, of course, the functional blocks can be integrated using this technology. There is also a possibility of applying biotechnology and the like.

[0202] <Summary of the Invention>

[0203] The wireless station of the present application is a wireless station in a wireless network having a plurality of wireless stations, comprising: a reception unit that receives a trigger signal transmitted from a first wireless station belonging to an interfering cell to a second wireless station belonging to the interfering cell; and a transmission prohibition period control unit that, after a transmission prohibition period to other wireless stations belonging to a communication cell to which the present station belongs is set, in a case where the reception unit receives the trigger signal, makes a determination of whether to release the transmission prohibition period based on a reception strength of the trigger signal.

[0204] In the wireless station of the present application, the wireless station is an IEEE 802.11ax-compliant wireless station.

[0205] In the wireless station of the present application, the communication cell to which the present station belongs is an intra-BSS (Basic Service Set), and the interfering cell is an OBSS (Overlapping Basic Service Set) or an inter-BSS.

[0206] In the wireless station of the present application, the transmission prohibition period control unit makes the determination of whether to release the transmission prohibition period based on a threshold value set in accordance with a reception strength measurement accuracy of the present station and the reception strength of the trigger signal.

[0207] In the wireless station of the present application, the transmission prohibition period control unit sets the threshold value based on STA classes specified in IEEE 802.11ax.

[0208] In the wireless station of the present application, the transmission prohibition period control unit makes a decision whether to release the transmission prohibition period based on a threshold value set in accordance with a reception strength measurement accuracy of the own station, a reception strength of the trigger signal, and a reception strength of the response signal, in a case where the response signal to the trigger signal from the second wireless station is received.

[0209] In the wireless station of the present application, the transmission prohibition period control unit releases the transmission prohibition period in a case where the reception strength of the trigger signal is within a prescribed range set based on a reception strength measurement accuracy of the own station.

[0210] In the wireless station of the present application, the transmission prohibition period control unit discriminates the category of the trigger signal, and does not release the transmission prohibition period in a case where it is a trigger signal requesting a response from a plurality of wireless stations in the interference cell.

[0211] In the wireless station of the present application, the transmission prohibition period control unit extracts information related to the number of wireless stations requested to respond by the trigger signal from the trigger signal in a case where the trigger signal is a trigger signal requesting a response from a plurality of wireless stations in the interference cell, and makes a decision whether to release the transmission prohibition period based on the extracted information.

[0212] In the wireless station of the present application, 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 and the estimated reception strength in the first wireless station of the signal transmitted from the own station to the first wireless station estimated in advance, and does not release the transmission prohibition period in a case where the difference is less than a prescribed value.

[0213] In the wireless station of the present application, in a case where the transmission prohibition period is set as an opportunity of a trigger signal from any one of the wireless stations belonging to the interference cell, in which the trigger signal that is the opportunity of setting the transmission prohibition period is stored, and the reception strength of the trigger signal that is the opportunity of setting the transmission prohibition period, the transmission prohibition period control unit releases the transmission prohibition period in a case where the reception strength of the trigger signal newly received from the interference cell is higher than the reception strength of the stored trigger signal.

[0214] The communication method of the present application is a communication method in a wireless network having a plurality of terminals or access points, i.e., wireless stations, including the steps of: after a transmission prohibition period is set for a wireless station other than a wireless station belonging to a communication cell to which the wireless station belongs, among the plurality of wireless stations, in a case where a trigger signal transmitted from a first wireless station belonging to an interfering cell other than the communication cell is received by a second wireless station belonging to the interfering cell, the first wireless station determines whether or not to release the transmission prohibition period based on a reception strength of the trigger signal.

[0215] In the communication method of the present application, the wireless stations are wireless stations conforming to IEEE 802.11ax.

[0216] In the communication method of the present application, the communication cell to which the wireless station belongs is an intra-BSS (Basic Service Set), and the interfering cell is an OBSS (Overlapping Basic Service Set) or an inter-BSS.

[0217] In the communication method of the present application, the first wireless station determines whether or not to release the transmission prohibition period based on a threshold value set in accordance with a reception strength measurement accuracy of the wireless station and the reception strength of the trigger signal.

[0218] In the communication method of the present application, the first wireless station sets the threshold value based on STA classes defined in IEEE 802.11ax.

[0219] In the communication method of the present application, in a case where a response signal to the trigger signal is received from the second wireless station, the first wireless station determines whether or not to release the transmission prohibition period based on a threshold value set in accordance with a reception strength measurement accuracy of the wireless station, the reception strength of the trigger signal, and a reception strength of the response signal.

[0220] In the communication method of the present application, in a case where the reception strength of the trigger signal is within a prescribed range set based on a reception strength measurement accuracy of the wireless station, the first wireless station releases the transmission prohibition period.

[0221] In the communication method of the present application, the first wireless station discriminates a category of the trigger signal, and in a case where it is a trigger signal requesting a response from a plurality of wireless stations in the interfering cell, does not release the transmission prohibition period.

[0222] In the communication method of the present application, in the case where the trigger signal is a trigger signal requesting response from a plurality of wireless stations in the interference cell, the first wireless station extracts information on the number of wireless stations requested to respond from the trigger signal, and makes a decision on whether to release the transmission prohibition period based on the extracted information.

[0223] In the communication method of the present application, the first wireless station compares the strength of the response signal from the second wireless station to the first wireless station extracted from the trigger signal with the estimated reception strength in the first wireless station of the signal transmitted from the first wireless station, which is estimated in advance, and in the case where the difference is smaller than a prescribed value, does not release the transmission prohibition period.

[0224] In the communication method of the present application, in the case where the transmission prohibition period is set as an opportunity from a trigger signal from any one of the wireless stations belonging to the interference cell, in the case where a trigger signal from an interference cell is newly received, in the case where the reception strength of the newly received trigger signal is higher than the reception strength of the stored trigger signal, the first wireless station releases the transmission prohibition period.

[0225] Industrial applicability

[0226] The present application is suitable for a wireless station that performs appropriate wireless communication in an environment where interference between wireless stations occurs.

[0227] Explanation of reference numerals

[0228] 100, 100', 100", 100"', 100"" wireless network

[0229] 200, 200', 200", 200"', 200"" terminal

[0230] 201 transmission / reception antenna

[0231] 202 wireless transmission / reception unit

[0232] 203 transmission signal generation unit

[0233] 204 reception signal demodulation and decoding unit

[0234] 205 RSSI measurement unit

[0235] 206 BSS category decision unit

[0236] 207 transmission control unit

[0237] 208 transmission buffer

[0238] 209 MAC frame generating unit

[0239] 210 transmission prohibition state setting unit

[0240] 211 terminal information setting unit

[0241] 212, 212', 212", 212"', 212"" access control unit

[0242] 213 trigger information analysis unit

[0243] 214 target BSS information storage unit

Claims

1. A first wireless station belonging to a basic service set (BSS), the first wireless station comprising: a receiver that receives a trigger frame transmitted from an access point (AP) belonging to an overlapping BSS (OBSS), the trigger frame requesting an uplink multi-user signal from a plurality of wireless stations belonging to the OBSS; a transmitter that transmits a signal to a second wireless station belonging to the BSS in a spatial multiplexing operation when the uplink multi-user signal is transmitted, wherein the spatial multiplexing operation is limited based on a class of the first wireless station, the class indicating a received signal strength indicator (RSSI) measurement accuracy.

2. The first wireless station according to claim 1, wherein the first wireless station includes a circuit that determines whether the first wireless station performs the spatial multiplexing operation based on the class of the first wireless station.

3. The first wireless station according to claim 1, wherein the class of the first wireless station indicates a transmission power accuracy.

4. The first wireless station according to claim 1, wherein the first wireless station includes a circuit that decodes the received trigger frame and extracts a plurality of parameters encoded in the trigger frame.

5. The first wireless station according to claim 4, wherein the circuit determines whether the first wireless station performs the spatial multiplexing operation based on the plurality of parameters.

6. The first wireless station according to claim 5, wherein one of the plurality of parameters is a target RSSI indicating a target received power value of the uplink multi-user signal measured at the access point, the circuit determines whether the first wireless station performs the spatial multiplexing operation based on the target RSSI.

7. The first wireless station according to claim 5, wherein one of the plurality of parameters is an AP transmission power indicating a transmission power of the trigger frame, the circuit determines whether the first wireless station performs the spatial multiplexing operation based on the AP transmission power.

8. The first wireless station according to claim 5, wherein one of the plurality of parameters is an allowed interference level, the circuit determines whether the first wireless station performs the spatial multiplexing operation based on the allowed interference level.

9. The first wireless station according to claim 5, wherein the circuit adjusts a transmission power of the signal based on the plurality of parameters.

10. The first wireless station according to claim 5, wherein the circuit sets a period during which the spatial multiplexing operation is allowed.

11. The first wireless station according to claim 6, wherein the circuit determines whether the first wireless station performs the spatial multiplexing operation based on the class of the first wireless station.

12. A first wireless station belonging to a basic service set (BSS), the first wireless station comprising: a receiver that receives a signal transmitted from another wireless station belonging to an overlapping BSS (OBSS); a transmitter that transmits a transmission signal to a second wireless station belonging to the BSS in a spatial multiplexing operation when wireless communication of the OBSS is in operation, wherein the spatial multiplexing operation is limited based on a class of the first wireless station, the class indicating a received signal strength indicator (RSSI) measurement accuracy. wherein the spatial reuse operation is limited based on the signal and a rank of the first wireless station, the rank indicating a received signal strength indicator (RSSI) measurement accuracy.

13. A communication method for a first wireless station, the first wireless station belonging to a basic service set (BSS), the communication method comprising: receiving a trigger frame transmitted from an access point (AP) belonging to an overlapping BSS (OBSS), the trigger frame requesting uplink multi-user signals from a plurality of wireless stations belonging to the OBSS; transmitting a signal to a second wireless station belonging to the BSS in a spatial reuse operation while the uplink multi-user signals are transmitted, wherein the spatial reuse operation is limited based on a rank of the first wireless station, the rank indicating a received signal strength indicator (RSSI) measurement accuracy.

14. A communication method for a first wireless station, the first wireless station belonging to a basic service set (BSS), the communication method comprising: receiving a trigger frame transmitted from an access point (AP) belonging to an overlapping BSS (OBSS), the trigger frame requesting uplink multi-user signals from a plurality of wireless stations belonging to the OBSS; transmitting a signal to a second wireless station belonging to the BSS in a spatial reuse operation while the uplink multi-user signals are transmitted, wherein the spatial reuse operation is limited based on a rank of the first wireless station, the rank indicating a received signal strength indicator (RSSI) measurement accuracy.

15. A communication method for a first wireless station, the first wireless station belonging to a basic service set (BSS), the communication method comprising: receiving a trigger frame transmitted from an access point (AP) belonging to an overlapping BSS (OBSS), the trigger frame requesting uplink multi-user signals from a plurality of wireless stations belonging to the OBSS; transmitting a signal to a second wireless station belonging to the BSS in a spatial reuse operation while the uplink multi-user signals are transmitted, wherein the spatial reuse operation is limited based on a rank of the first wireless

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