Control circuit

Abstract

The present invention relates to a control circuit for controlling a radio station belonging to a communication cell. The control circuit controls the following steps: a step of receiving a trigger frame transmitted from an access point belonging to an interference cell; and a step of determining whether transmission from the radio station to another radio station belonging to the communication cell is possible based on at least one parameter included in the trigger frame and a reception signal strength of the trigger frame in the radio station. The at least one parameter includes a target reception signal strength and a transmission power value of the trigger frame transmitted from the access point.

Description

[0001] This application is a divisional application of a Chinese patent application with the application number CN201780022745.X, titled "Wireless Station and Communication Method", which was filed on March 14, 2017. Technical Field

[0002] The present invention relates to a wireless station and a communication method for performing appropriate wireless communication in an environment where interference between wireless stations occurs. Background Art

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

[0004] In the IEEE 802.11 standard, a BSS (Basic Service Set) is defined as a set of wireless stations (also referred to as stations or STAs) that constitute a basic wireless network. In the infrastructure mode, the BSS consists of one access point and multiple terminals (wireless stations other than the access point), and in the ad hoc mode, it consists of multiple terminals. As a difference from the BSS in the infrastructure mode, the BSS in the ad hoc mode is called an IBSS (Independent BSS). A BSS other than the BSS (intra-BSS) to which this terminal (or access point) belongs is called an OBSS (Overlapping BSS) or inter-BSS. Since multiple communication cells overlap in the OBSS, interference occurs between the communication cells during communication between OBSSs, deteriorating the communication quality.

[0005] In wireless communication, due to the influence of the distance between wireless stations and obstacles, etc., a state may occur where the wireless signals between wireless stations do not reach each other (a radio wave environment where carrier sensing does not work). As a countermeasure for such an environment, that is, an environment with hidden terminals, in the IEEE 802.11 standard, a collision prevention function using NAV (Network Allocation Vector: transmission prohibition period) is prepared. If an access point and a terminal receive a wireless frame for NAV setting at a level equal to or higher than a specified threshold, except when the wireless frame for NAV setting is a frame sent to this terminal or this access point, transmission is prohibited during the NAV period set with the duration information. As the threshold for determining whether to set NAV, the minimum reception sensitivity value is usually used.

[0006] In addition, in 11ax, it has been agreed to introduce SR (Spatial Reuse) that reuses the wireless resources in use for OBSS (refer to Non-Patent Document 1). The purpose of SR is to increase the transmission opportunities of terminals (or access points) and improve the utilization rate of wireless resources when the interference given to OBSS (hereinafter referred to as the given interference) is small, thereby improving the communication performance in the wireless network. One method for implementing SR is to set the threshold for determining whether to set NAV when receiving a wireless frame from OBSS (hereinafter referred to as OBSS_PD (Power Density)) to a value larger than the minimum reception sensitivity value usually used under specific conditions.

[0007] Prior Art Documents

[0008] Non-Patent Documents

[0009] Non-Patent Document 1: Robert Stacey, “Specification Framework for TGax”, IEEE802.11-15 / 0132r15

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

[0011] Non-Patent Document 3: Reza Hedayat, “TXOP Considerations for Spatial Reuse,” IEEE802.11-15 / 1104 Summary of the Invention

[0012] However, when the given interference level to OBSS is greater than a specified threshold, if a terminal (or access point) erroneously estimates the magnitude of the given interference and releases the regular NAV, interference at a level where the terminal (or access point) in OBSS cannot correctly decode the received signal is generated, and there is a concern that the communication performance of the wireless network will deteriorate.

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

[0014] One mode of the wireless station of the present invention is a wireless station in a wireless network having a plurality of wireless stations, including: a receiving unit that receives a trigger signal transmitted from a first wireless station belonging to an interfering cell to a second wireless station belonging to the interfering cell; and a transmission prohibition period control unit that, after setting a transmission prohibition period for other wireless stations within the communication cell to which the own station belongs, determines whether to release the transmission prohibition period based on the reception intensity of the trigger signal when the receiving unit receives the trigger signal.

[0015] Furthermore, these general or specific modes can be implemented by a system, method, integrated circuit, computer program, or recording medium, or can also be implemented by any combination of a system, device, method, integrated circuit, computer program, and recording medium.

[0016] According to one mode of the present invention, inappropriate conventional NAV release can be prevented, and the communication performance of the wireless network can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0019] Figure 3 It is a timing diagram showing an example of the operation of the wireless network when RTS / CTS frames are transmitted and received in the first embodiment.

[0020] Figure 4 It is a timing diagram showing an example of the operation of the wireless network when trigger frames are transmitted and received in the first embodiment.

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

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

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

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

[0025] Figure 9 It is a timing diagram showing an example of the operation of the wireless network when trigger frames are transmitted and received in the third embodiment.

[0026] Figure 10 It is a timing chart showing an example of the operation of a wireless network when a trigger frame is transmitted and received in the fourth embodiment.

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

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

[0029] Figure 13 It is a timing chart showing an example of the operation of a wireless network when a trigger frame is transmitted and received in the fifth embodiment.

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

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

[0032] Figure 16 It is a timing chart showing an example of the operation of a wireless network when an RTS / CTS frame is transmitted and received in the sixth embodiment. Detailed Embodiments

[0033] Hereinafter, each embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, there are cases where detailed descriptions such as those of known matters and repeated descriptions of substantially the same structures are omitted.

[0034] Furthermore, the following descriptions and the accompanying drawings are provided for those skilled in the art to understand the present invention, and do not limit the scope of the claims of the present invention.

[0035] <Completion Reason of the Present Invention>

[0036] Hereinafter, the reason for completing the present invention will be briefly described.

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

[0038] Moreover, in 11ax, as one of the methods of SR, it has been proposed that the regular NAV is released even when it is not in the case of receiving a CF - End frame (NAV release request frame) under specified conditions (Non - Patent Document 3). In this method, by using a combination of a trigger signal and a response signal, the magnitude of a given interference to the terminal (or access point) of the OBSS is estimated, and the regular NAV is released. In the case where the magnitude of the given interference of the OBSS is suppressed to be less than, for example, a specified threshold empirically derived, according to this method, the effect of SR is further improved.

[0039] In the following Reference Non - Patent Document 1, it is disclosed that the terminal (or access point) releases the regular NAV when the following conditions are met. The first condition is a condition such that when receiving an inter - BSS RTS (Request To Send) frame, the RSSI (Received Signal Strength Indicator) is higher than OBSS_PD (a threshold applicable to the case where the object is OBSS). The second condition is a condition such that when receiving an inter - BSS CTS (Clear To Send) frame, the RSSI is lower than a specified NAV release threshold.

[0040] Reference Non - Patent Document 1: Reza Hedayat, “Recipient - aware Spatial Reuse,” IEEE802.11 - 16 / 0060

[0041] In addition, in Reference Non-Patent Document 2 described below, it is disclosed that when the RSSI of a trigger frame is lower than OBSS_PD, a terminal (or an access point) releases a regular NAV when detecting a UL MU PPDU (UpLink Multi-User Physical layer convergence Protocol Data Unit; uplink multi-user physical layer convergence protocol data unit) transmitted following the trigger frame.

[0042] Reference Non-Patent Document 2: Geonjung Ko, “Improving Spatial Reuse During OBSS ULMU Procedure”, IEEE 802.11-15 / 1338

[0043] However, in cases where the measurement accuracy of the RSSI of a terminal is low, or the distance between terminals is short, etc., the regular NAV is sometimes released erroneously. As a result, for a terminal (or an access point) of an OBSS, interference above OBSS_PD, for example, may be generated and a desired signal may not be received correctly. For this reason, it is desired to prevent inappropriate release of the regular NAV. In the embodiments of the present invention described below, a radio station and a communication method for preventing inappropriate release of the regular NAV and improving the communication performance of a wireless network will be described. Furthermore, the terminal or the access point in each of the following embodiments corresponds to the radio station.

[0044] <First Embodiment>

[0045] Figure 1 FIG. is a diagram illustrating the positional relationship between an access point and terminals constituting a wireless network 100 according to the first embodiment. In the wireless network 100, as Figure 1 shown, 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).

[0046] [Description of Structure]

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

[0048] may be the same as the structure of the terminal 200 shown in Figure 2As shown, the terminal 200 includes: a transmitting and receiving antenna 201, a wireless transmitting and receiving unit 202, a transmission signal generating unit 203, a received 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. In addition, an 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 transmitting and receiving antenna 201 is at least one antenna and performs transmission or reception of wireless signals.

[0050] At the time of transmission, the wireless transmitting and receiving 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 generating unit 203, and transmits the transmission signal through the transmitting and receiving antenna 201. At the time of reception, the wireless transmitting and receiving unit 202 performs predetermined wireless reception processing such as down-conversion and A / D conversion on the wireless signal received through the transmitting and receiving antenna 201, and outputs the received wireless signal to the received signal demodulating and decoding unit 204 and the RSSI measuring unit 205.

[0051] The transmission signal generating unit 203 encodes and modulates the MAC frame input from the MAC frame generating unit 209, adds control signals (also referred to as preambles) such as pilot signals for frequency synchronization and timing synchronization on the receiving side, and channel estimation signals, etc., to generate a wireless frame (also referred to as PPDU), and outputs it to the wireless transmitting and receiving unit 202.

[0052] The received signal demodulating and decoding unit 204 performs autocorrelation processing, etc. on the wireless signal after wireless reception processing input from the wireless transmitting and receiving unit 202 to extract the wireless frame, and demodulates and decodes the wireless frame. In addition, the received signal demodulating 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 transmitting and receiving unit 202, 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 measures the RSSI based on the wireless signal after wireless reception processing input from the wireless transmitting and receiving unit 202, and outputs RSSI information including the measurement result to the transmission prohibition state setting unit 210.

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

[0055] Based on the transmission prohibition state information (information indicating that transmission is prohibited, that is, information indicating whether NAV is set) input from the transmission prohibition state setting unit 210 and the buffer state information (information indicating whether there is transmission data) input from the transmission buffer 208, the transmission control unit 207 performs transmission control. 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.

[0056] The transmission buffer 208 stores the transmission data transmitted by the terminal 200 to other terminals (or access points). In addition, the transmission buffer 208 outputs buffer state information indicating whether there is transmission data to the transmission control unit 207.

[0057] Based on the transmission data generation instruction input from the transmission control unit 207, 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. The MAC frame generation unit 209 outputs the generated MAC frame to the transmission signal generation unit 203.

[0058] Based on the RSSI information input from the RSSI measurement unit 205, the MAC frame input from the received signal demodulation and decoding unit 204, the RSSI measurement accuracy information input from the terminal information setting unit 211, and the BSS class information input from the BSS class determination unit 206, the transmission prohibition state setting unit 210 sets NAV.

[0059] Specifically, the transmission prohibition state setting unit 210 sets NAV when it is a MAC frame for which NAV setting such as an RTS / CTS frame is indicated. In addition, the transmission prohibition state setting unit 210 releases NAV when the set NAV period expires and when a CF-End frame indicating NAV release is received.

[0060] Furthermore, when setting the NAV, the transmission inhibition state setting unit 210 differentiates the states 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, when receiving an intra-BSS MAC frame, the transmission inhibition state setting unit 210 performs intra-BSS setting, and when receiving an OBSS MAC frame, performs regular NAV setting.

[0061] However, the transmission inhibition 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, even if it is other than the above (when the set NAV period expires, or when a CF-End frame is received), the regular NAV is also released. The transmission inhibition state setting unit 210 outputs transmission inhibition state information related to NAV setting or NAV release to the transmission control unit 207.

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

[0063] According to such a configuration, in the first embodiment, by setting the threshold value for the NAV release determination 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 due to the measurement error of the RSSI, causing a large given interference to the OBSS. Hereinafter, a specific operation example of the wireless network 100 of the first embodiment will be described.

[0064] [Operation Example]

[0065] Figure 3 It is a timing chart showing an operation example of the wireless network 100 at the time of transmission and reception of RTS / CTS frames in the first embodiment. As Figure 3 shown, first, terminal B performs the transmission process (ST101) of an RTS (Request to Send: trigger signal for CTS) frame requesting the transmission of CTS to access point A. Terminal C performs the RTS frame reception process (ST102) from terminal B. The RTS frame reception process includes the RSSI measurement of the RTS frame. Furthermore, regarding the measurement method of the RSSI, there is no particular limitation in the present invention, and a known RSSI measurement method can be used. Terminal C sets the regular NAV according to the RTS (ST103).

[0066] Next, the access point A responds to the RTS frame from the terminal B by sending a response signal, i.e., a CTS (Clear to Send) frame (ST104). If the terminal C receives the CTS from the access point A, it measures the RSSI (ST105). The terminal C determines whether to release the regular NAV based on the RSSI of the CTS frame (ST106). Details of the method for determining the release of the regular NAV in ST106 will be described later.

[0067] In Figure 3 an example is shown of the case where it is determined in ST106 not to release the regular NAV. In this case, the terminal C updates the regular NAV according to the CTS frame (ST107). Next, the terminal B sends 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 send to the access point D.

[0068] On the other hand, Figure 4 is a timing diagram showing an example of the operation of the wireless network 100 when triggering frame transmission and reception in the first embodiment. In Figure 4 it is assumed that the terminal C has a regular NAV set in advance.

[0069] As Figure 4 shown, first, the access point A performs a triggering frame transmission process for the terminal B (ST201). The terminal C performs a triggering frame reception process from the access point A (ST202). The triggering frame reception process includes RSSI measurement of the triggering frame. The terminal C determines whether to release the regular NAV based on the RSSI measurement result of the triggering frame (ST203). Details of the method for determining the regular NAV in ST203 will be described later.

[0070] In Figure 4 an example is shown of the case where it is determined in ST203 not to release the regular NAV. In this case, the terminal C updates the regular NAV according to the triggering frame (ST204). Next, the terminal B sends 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 send to the access point D.

[0071] [NAV Release Determination Method 1]

[0072] Hereinafter, Figure 3 shown in Figure 4 the details of the method for determining whether to release the regular NAV in ST106 or

[0073] shown in Figure 3The determination method in ST106. In NAV release determination method 1, terminal C sets the threshold for NAV release determination based on the RSSI measurement accuracy information of this terminal or the terminal class (STA Classes). Terminal C sets the threshold for the trigger signal (the first threshold) and the threshold for the response signal (the second threshold). Here, the trigger signal is, for example, an RTS frame, and the response signal is, for example, a CTS frame. The first threshold and the second threshold are set higher than the threshold for intra-BSS signals.

[0074] In 11ax, two categories 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 Class B terminals, a maximum RSSI measurement error of 3 dB is allowed for Class A terminals.

[0075] Therefore, in order to keep the interference given to other terminals due to the RSSI measurement error of Class B terminals within the same level as that of Class A, it is necessary to set different thresholds in Class B terminals. Specifically, the first threshold in Class B terminals can be set 3 dB higher than the first threshold in Class A, and the second threshold in Class B terminals can be set 3 dB lower than the second threshold in Class A. The 3 dB value is based on the difference in RSSI measurement accuracy required for Class A terminals and Class B terminals respectively. In addition, the first threshold can be set to be greater than or equal to the second threshold.

[0076] Then, when receiving a trigger signal (RTS frame) from an OBSS ( Figure 3 in ST102), terminal C measures the RSSI of the RTS frame and determines whether it is higher than the first threshold. Moreover, terminal C measures the RSSI of the subsequent response signal (CTS frame) sent 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, terminal C releases the regular NAV. Furthermore, terminal C can also 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.

[0077] According to such a determination method, even when terminal C is a terminal of class B, that is, a terminal with relatively low RSSI measurement accuracy, it is possible to perform a determination for releasing the regular NAV based on a threshold set in consideration of the measurement accuracy. Therefore, even when terminal C is a terminal of class B, that is, a terminal with relatively low RSSI measurement accuracy, it is possible to reduce the interference caused to the terminals (or access points) of the OBSS. Therefore, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved. Furthermore, the first threshold or the second threshold in the class A terminal 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 Figure 4 the determination method in ST203. In the NAV release determination method 2, terminal C sets a threshold for determining the release of the NAV based on the RSSI measurement accuracy information of this terminal or the terminal class. Terminal C sets a threshold for the trigger signal. Here, the trigger signal is, for example, a trigger frame. This threshold is set higher than the threshold for the intra-BSS signal.

[0080] In the NAV release determination method 2, it is different from the determination method 1 in terms of using the RSSI determination of the trigger frame. When receiving a trigger frame from the OBSS, terminal C determines whether the RSSI of the trigger frame is lower than the threshold. When the RSSI of the trigger frame is lower than the threshold, terminal C releases the regular NAV. Furthermore, as the method for setting the threshold, the same method as the method for setting the second threshold in the above-described NAV release determination method 1 (that is, set 3 dB lower than OBSS_PD) can be adopted, or a different setting method can be adopted.

[0081] According to 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, it is possible to perform a determination for releasing the regular NAV based on a threshold set in consideration of the measurement accuracy. Therefore, even when terminal C is a terminal with relatively low RSSI measurement accuracy, it is possible to reduce the interference caused to the terminals (or access points) of the OBSS. Therefore, 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 between the access points and terminals constituting the wireless network 100' of the second embodiment. As Figure 5As shown, in the wireless network 100', 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) in the same way as Figure 1 shown in the first embodiment, but the distance between the terminal B and the terminal C has become closer compared to the first embodiment.

[0084] In this way, when the distance between the terminal B and the terminal C is relatively close, the RSSI of the transmission signal from the terminal C to the terminal B is of a strength close 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 deteriorates due to the interference of the terminal C. In such a case, the possibility of reception failure from the access point A at the terminal B increases. In the second embodiment, a wireless network 100' will be described in which communication can be appropriately performed without reducing the communication quality even in such a situation.

[0085] [Description of the 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 Figure 5 corresponds to the terminal C shown in Figure 5 Furthermore, the structures of the access points A and D and the terminal B shown in Figure 6 can also be the same as the structure of the terminal 200' shown in

[0087] As Figure 6 shown, the terminal 200' has a transmission and reception antenna 201, a wireless transmission and reception unit 202, a transmission signal generation unit 203, a reception signal demodulation and decoding unit 204, an RSSI measurement unit 205, a BSS category 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. In addition, the access control unit 212' (MAC) is composed of the BSS category 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, in terms of not having the terminal information setting unit 211, the structure of the terminal 200' in the second embodiment is different from that of the terminal 200 in Figure 2 shown in the first embodiment. In addition, the operation of the transmission prohibition state setting unit 210 is somewhat different from that of the first embodiment.

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

[0089] Furthermore, when setting the NAV, the transmission inhibition state setting unit 210 differentiates between the states of intra-BSS NAV and regular NAV, and performs the above-mentioned NAV setting and NAV release for each respective NAV. Specifically, for example, when a MAC frame of intra-BSS is received, the transmission inhibition state setting unit 210 performs the intra-BSS setting, and when a MAC frame of OBSS is received, the regular NAV setting is performed.

[0090] However, the transmission inhibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. In the case where a determination to release the NAV is made in this determination, even in addition to the above, the regular NAV is also released. The transmission inhibition state setting unit 210 outputs transmission inhibition state information related to NAV setting or NAV release to the transmission control unit 207.

[0091] [Operation Example]

[0092] The operation example of the wireless network 100' in the second embodiment is the same as Figure 3 or Figure 4 the operation example shown, so the description is omitted. However, Figure 3 the NAV release determination method in ST106 of Figure 4 or the NAV release determination method in ST203 of

[0093] [NAV Release Determination Method]

[0094] The NAV release determination method described below corresponds to Figure 3 the determination method in ST106 of

[0095] In the case of receiving a trigger signal (RTS frame) from the OBSS ( Figure 3 ST102), the terminal C measures the RSSI of the RTS frame, determines whether it is higher than the third threshold, and determines whether it is lower than the fourth threshold. That is, the terminal C determines whether the RSSI of the RTS frame is within the specified range defined by the third threshold and the fourth threshold.

[0096] Moreover, the terminal C measures the RSSI of the response signal (CTS frame) subsequently sent from the OBSS, and determines whether it is lower than the second threshold. When the RSSI of the RTS frame is within the specified range and the RSSI of the CTS frame is lower than the second threshold, the terminal C releases the regular NAV.

[0097] For example, the third threshold can be set to OBSS_PD. In addition, the fourth threshold can be set to a specified threshold larger than the third threshold. For example, the fourth threshold is set to the value obtained by adding a positive compensation value to the third threshold. Thereby, the amount of signaling required for the notification of the fourth threshold can be reduced.

[0098] In this way, in the second embodiment, when the RSSI of the trigger signal from the OBSS is within the specified range (the range higher than the third threshold and lower than the fourth threshold), and only when the RSSI of the response signal is lower than the second threshold, the NAV is released in the terminal C. Therefore, in the case where the distance between the access point A and the terminal C is relatively close, etc., in the case where the reception quality in the terminal B is expected to deteriorate due to the interference of the terminal C, by preventing the NAV release when the RSSI of the trigger signal is not within the specified range, the degradation of the communication performance in the wireless network 100' can be reduced. Therefore, inappropriate regular NAV release can be prevented, and the communication performance of the wireless network can be improved.

[0099] Furthermore, in the operation example of the second embodiment described above, the operation example at the time of sending and receiving RTS / CTS frames is described, but the present invention is not limited thereto. That is, the second embodiment can also be applied to the sending and receiving of trigger frames.

[0100] <Third Embodiment>

[0101] Hereinafter, the third embodiment will be described. Figure 7 It is a diagram illustrating the positional relationship between the access point and the terminal constituting the wireless network 100" of the third embodiment. As Figure 7 shown, in terms of the presence of the terminal E belonging to BSS1 (OBSS), it is different from the Figure 1 wireless network 100 of the first embodiment shown.

[0102] In such a structure, the access point A sometimes sends a trigger frame that requests the transmission of MU-BA (Multi-User Block Ack) to multiple terminals such as terminal B and terminal E. The Block Ack is defined by IEEE802.11e and responds to multiple received data in one frame. In addition, MU-BA is multiplexed among multiple users through MU (Multi-User) multiplexing to perform Block Ack transmission. In addition, MU multiplexing refers to frequency multiplexing and spatial multiplexing of multiple terminals.

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

[0104] [Description of the structure]

[0105] Figure 8 It is a block diagram showing an example of the structure of the terminal 200” of the third embodiment. Figure 8 The terminal 200” illustrated in the example corresponds to Figure 7 the terminal C shown. Furthermore, Figure 7 the structures of the access points A and D, and terminals B and E shown may also be the same as the structure of the terminal 200” shown in Figure 8 In the aspect where there is no RSSI measurement unit and terminal information setting unit 211 but there is a trigger information analysis unit 213, the terminal 200” in the third embodiment is different from the structure of the terminal 200 in the first embodiment shown in

[0106] As shown in Figure 8 the terminal 200” has a transmit-receive antenna 201, a wireless transmit-receive unit 202, a transmit signal generation unit 203, a receive signal demodulation and decoding unit 204, a BSS category determination unit 206, a transmit control unit 207, a transmit buffer 208, a MAC frame generation unit 209, a transmit prohibition state setting unit 210, and a trigger information analysis unit 213. In addition, an access control unit 212” (MAC) is constituted by the BSS category determination unit 206, the transmit control unit 207, the transmit buffer 208, the MAC frame generation unit 209, the transmit prohibition state setting unit 210, and the trigger information analysis unit 213. That is, Figure 2 the structure of the terminal 200” in the third embodiment is different from that of the terminal 200 in the first embodiment shown. In addition, the operation of the transmit prohibition state setting unit 210 is different from that 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 performs NAV setting based on the MAC frame input from the reception signal demodulation and decoding unit 204, the BSS class information input from the BSS class determination unit 206, and the trigger type input from the trigger information analysis unit 213. In addition, when the set NAV period expires and when a CF-End frame indicating NAV release is received, the transmission prohibition state setting unit 210 releases the NAV.

[0109] Furthermore, when setting the NAV, the transmission prohibition state setting unit 210 differentiates between the states of intra-BSS NAV and normal NAV, and performs the above-mentioned 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, and when a MAC frame of OBSS is received, it performs normal NAV setting.

[0110] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. In the case where it is determined to release the NAV in this determination, even in addition to the above, the normal NAV is also released. 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.

[0111] [Operation Example]

[0112] Figure 9 is a timing chart showing an operation example of the wireless network 100 at the time of trigger frame transmission and reception in the third embodiment. In Figure 9 it is assumed that the terminal C has previously set a normal NAV.

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

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

[0115] In Figure 9In this case, an example where it is determined in ST303 not to release the regular NAV is illustrated. In this case, the terminal C keeps the regular NAV and maintains the transmission prohibition state.

[0116] Next, the terminals B and 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.

[0117] [NAV Release Determination Method]

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

[0119] In 11ax, MU - BA is transmitted in the UL MU PPDU. As described above, when receiving MU - BA from multiple terminals, if the reception on the access point A side fails due to interference, the traffic increases due to the retransmission of the trigger frame and MU - BA, and the communication performance of the wireless network 100” deteriorates. Therefore, it is desirable not to generate interference. In addition, since the PPDU length in MU - BA is short, the effect of releasing the regular NAV is small.

[0120] Therefore, in the third embodiment, if the terminal C receives a trigger frame, it extracts the trigger type information and discriminates the trigger type. When the trigger type is MU - BAR (Multi - User Block Ack Request; multi - user block Ack request) for requesting MU - BA transmission, the regular NAV is not released.

[0121] In this way, in the third embodiment, the determination of whether to release the regular NAV is based on the trigger type, and the regular NAV is not released when the trigger type is MU - BAR. Thereby, MU - BA is preferentially transmitted and received, the deterioration of the communication performance of the wireless network 100” caused by the retransmission of the trigger frame and MU - BA can be prevented, and the SR effect can be maintained. Furthermore, when it is determined that the received trigger frame is a trigger type other than MU - BAR, the terminal C can maintain the SR effect by performing the NAV control as before. Therefore, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0122] Furthermore, in the third embodiment, it is described that the access point A, the terminals B and E belong to the OBSS, and the access point A transmits a trigger frame including MU - BAR to the terminals B and E, but the present invention is not limited thereto. For example, even when more terminals belong to the OBSS and the access point A transmits MU - BAR to these terminals, the third embodiment can be applied.

[0123] <Fourth Embodiment>

[0124] Hereinafter, the fourth embodiment will be described. The positional relationship between the access point and the terminal of the wireless network 100” constituting the fourth embodiment is the same as that of the wireless network 100” of the third embodiment exemplified in Figure 7 .

[0125] In the wireless network 100” exemplified in Figure 7 , if the number of terminals (MU multiplexing number) performing SR-based multiplexing with the access point A is large, the probability of reception failure due to SR increases due to the influence of the positional relationship between terminals and the RSSI measurement accuracy. In addition, if the multiplexing number is large, the noise increases, and the influence of interference caused by terminal C becomes large. Therefore, in the fourth embodiment, a wireless network 100” that can appropriately communicate without degrading the communication quality even when the multiplexing number is large will be described.

[0126] [Description of Structure]

[0127] Regarding the structure of the terminal 200” in the fourth embodiment, it is also the same as the terminal 200” of the third embodiment shown in Figure 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.

[0128] The trigger information analysis unit 213 extracts the multiplexing number information related to 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 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. In addition, when the set NAV period expires and when a CF-End frame indicating the release of the NAV is received, the transmission prohibition state setting unit 210 releases the NAV.

[0130] Furthermore, when setting the NAV, the transmission prohibition state setting unit 210 differentiates between the states of intra-BSS NAV and normal NAV, and performs the above NAV setting and NAV release for each NAV. Specifically, for example, when an intra-BSS MAC frame is received, the transmission prohibition state setting unit 210 performs intra-BSS setting, and when an OBSS MAC frame is received, it performs normal NAV setting.

[0131] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. In the case where it is determined to release the NAV in this determination, the normal NAV is released even in addition to the 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.

[0132] [Operation Example]

[0133] Figure 10 is a timing diagram showing an operation example of the wireless network 100” at the time of trigger frame transmission and reception in the fourth embodiment. In Figure 10 it is assumed that the terminal C has previously set the normal NAV.

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

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

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

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

[0138] Next, the terminal B and the terminal E transmit data to the access point A (ST404 and ST405). At this time, since the normal NAV is set in the terminal C, the terminal C does not transmit to the access point D.

[0139] [NAV Release Determination Method]

[0140] Hereinafter, details of the determination method of whether to release the normal NAV in ST403 shown in Figure 10 will be described. That is, when the MU multiplexing number notified by the trigger frame is higher than a specified threshold, the terminal C does not release the normal NAV.

[0141] Thus, in the fourth embodiment, it is determined whether to release the regular NAV based on the MU multiplexing number. When the MU multiplexing number is higher than a specified threshold, the regular NAV is not released. Thereby, it is possible to prevent a degradation in the communication performance of the wireless network 100” caused by retransmission of data, and the effect of SR can be maintained. Furthermore, when the MU multiplexing number is equal to or less than the specified threshold, the terminal C can maintain the effect of SR by performing NAV control as in the past. Therefore, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0142] <Fifth Embodiment>

[0143] Hereinafter, the fifth embodiment will be described. Figure 11 is a diagram illustrating the positional relationship between the access point and the terminals constituting the wireless network 100”’ of the fifth embodiment. As Figure 11 shown, 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 specified difference.

[0144] In such a 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 intensity of the transmission signal from the terminal B (desired signal) and the transmission signal from the terminal C (interference signal) is almost the same, so sometimes the reception quality in the access point A deteriorates. In the fifth embodiment, a wireless network 100”’ that can appropriately communicate without degrading the communication quality even in such a case will be described.

[0145] [Description of Structure]

[0146] Figure 12 is a block diagram showing the structure of the terminal 200”’ of the fifth embodiment. Figure 12 The terminal 200”’ illustrated in Figure 11 corresponds to Figure 11 the terminal C shown in Figure 12 Furthermore,

[0147] Figure 12As shown, the terminal 200''' has a transmitting and receiving antenna 201, a wireless transmitting and receiving unit 202, a transmission signal generation unit 203, a received signal demodulation and decoding unit 204, an RSSI measurement unit 205, a BSS category 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. In addition, an access control unit 212''' (MAC) is constituted by the BSS category 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, the terminal 200''' in the fifth embodiment is different from the structure of the terminal 200 in the first embodiment shown in Figure 2 in that it does not have a terminal information setting unit 211 but has a trigger information analysis unit 213. In addition, the operation of the transmission prohibition state setting unit 210 is somewhat different from that in the first embodiment.

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

[0149] The transmission prohibition state setting unit 210 performs NAV setting based on the MAC frame input from the received signal demodulation and decoding unit 204, the BSS category information input from the BSS category determination unit 206, and the target RSSI and the AP Tx power input from the trigger information analysis unit 213. In addition, when the set NAV period expires and when a CF-End frame indicating NAV release is received, the transmission prohibition state setting unit 210 releases the NAV.

[0150] Furthermore, when setting the NAV, the transmission prohibition state setting unit 210 differentiates the states of intra-BSS NAV and normal NAV and performs the above-mentioned 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, and when a MAC frame of OBSS is received, it performs normal NAV setting.

[0151] However, the transmission prohibition state setting unit 210 determines whether to release the NAV using the NAV release determination method described later. In the case where it is determined to release the NAV in this determination, even if there are other cases, the normal NAV is also released. 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.

[0152] [Operation Example]

[0153] Figure 13 This is a timing diagram showing the operation example of the wireless network 100''' when a trigger frame is sent and received in the fifth embodiment. In Figure 13 , it is assumed that the terminal C has a pre-set regular NAV.

[0154] As Figure 13 shown, first, the access point A sends a trigger frame (ST501) to the terminal B. The terminal C performs the trigger frame reception process from the access point A (ST502). The trigger frame reception process includes the extraction of the target RSSI and the AP Tx power and the measurement of the RSSI. The terminal C estimates the RSSI that can be measured by the access point A when the terminal C sends data based on the RSSI of the trigger frame and the AP Tx power extracted from the trigger frame (ST503). Then, the terminal C determines whether the RSSI estimated in ST503 is higher than the value obtained by adding the specified allowable interference amount to the target RSSI, and based on the determination result, determines whether to release the regular NAV (ST504). The details of the method for determining the regular NAV in ST504 will be described later.

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

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

[0157] [NAV Release Determination Method]

[0158] Hereinafter, the details of the method for determining whether to release the regular NAV in ST504 as Figure 13 shown will be described.

[0159] As described above, if a trigger frame from an OBSS is received, the terminal C estimates the RSSI that can be measured by the access point A of the OBSS when the terminal C sends 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 the specified allowable interference amount to the target RSSI. When the estimated RSSI is higher than the value obtained by adding the specified allowable interference amount to the target RSSI, the terminal C does not release the regular NAV. Furthermore, the specified allowable interference amount is a pre-set margin.

[0160] Thus, in the fifth embodiment, the intensity (target RSSI) of the transmission signal (desired signal) from terminal B in access point A is compared with the intensity (estimated RSSI) of the transmission signal (interference signal) from terminal C. When the estimated RSSI is higher than the value obtained by adding a specified allowable interference amount to the target RSSI, terminal C does not release the regular NAV. As a result, 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.

[0161] <Sixth Embodiment>

[0162] Hereinafter, the third embodiment will be described. Figure 14 It is a diagram illustrating the positional relationship between the access points and terminals that constitute the wireless network 100”” of the sixth embodiment. As Figure 14 shown, in the sixth embodiment, there are access point A, terminal B, terminal C, access point D, terminal E, and access point F. In addition, access point A and terminal B belong to BSS1 (OBSS), terminal C and access point D belong to BSS2 (intra - BSS), and terminal E and access point F belong to BSS3 (OBSS).

[0163] Thus, in the case where there are multiple OBSSs, in 11ax, terminal C does not distinguish and manage the NAVs of multiple OBSSs, so sometimes releasing the NAV of one OBSS causes relatively large interference to other OBSSs. In the sixth embodiment, a wireless network 100”” that can communicate appropriately without degrading the communication quality even in such a situation will be described.

[0164] [Description of Structure]

[0165] Figure 15 It is a block diagram showing an example of the structure of the terminal 200”” of the sixth embodiment. Figure 15 The terminal 200”” illustrated in corresponds to Figure 14 the terminal C shown in. Furthermore, Figure 14 the structures of the access points A, D, and F, and terminals B and E shown in can also be the same as the structure of the terminal 200”” shown 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 generation unit 203, a reception signal demodulation and decoding unit 204, an RSSI measurement unit 205, a BSS category 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. In addition, an access control unit 212 (MAC) is composed of the BSS category 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.

[0167] 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 BSS category information input from the BSS category determination unit 206, and the target BSS information input from the target BSS information storage unit 214, the transmission prohibition state setting unit 210 performs NAV setting. Details of the target BSS information will be described later. In addition, when the set NAV period expires and when a CF-End frame indicating NAV release is received, the transmission prohibition state setting unit 210 releases the NAV.

[0168] Furthermore, when setting the NAV, the transmission prohibition state setting unit 210 differentiates the states of intra-BSS NAV and regular NAV, and performs the above-mentioned 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 the intra-BSS setting, and when a MAC frame of OBSS is received, the regular NAV setting is performed.

[0169] However, the transmission prohibition state setting unit 210 uses the NAV release determination method described later to determine whether to release the NAV. When the determination to release the NAV is made in this determination, the regular NAV is released even in addition to the 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.

[0170] In addition, when 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. In addition, as needed, the target BSS information storage unit 214 outputs the stored target BSS information to the transmission prohibition state setting unit 210.

[0172] [Operation Example]

[0173] Figure 16 is a timing chart showing an operation example of the wireless network 100 during the transmission and reception of RTS / CTS frames in the sixth embodiment.

[0174] As Figure 16 shown, first, the access point F sends an RTS frame to the terminal E (ST601). The terminal C performs RTS frame reception processing from the access point F (ST602). The RTS frame reception processing includes extraction of the BSS color from the RTS frame and RSSI measurement of the RTS frame. The terminal C sets the normal NAV according to the RTS frame (ST603).

[0175] If the normal NAV is set, the terminal C generates target BSS information (ST604). Here, the target BSS information is information indicating the OBSS for which the NAV is set. That is, the target BSS information generated in ST604 is information indicating the target BSS3 as Figure 14 shown. Furthermore, the target BSS information includes the BSS color of the target BSS and the RSSI of the RTS frame.

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

[0177] Then, the terminal C compares the RSSI stored in ST604 with the RSSI of the CTS frame received in ST606. If the RSSI of the CTS frame is high, the target BSS information is updated (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. Furthermore, in ST607, the terminal C only updates the RSSI included in the target BSS information and does not update the BSS color.

[0178] The terminal C determines whether to release the normal NAV (ST608). Details of the method for determining the normal NAV in ST608 will be described later.

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

[0180] 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 transmit 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 determines whether to release the regular NAV (ST612). Details of the method for determining the regular NAV in ST612 will be described later.

[0183] In Figure 16 it, a case where it is determined in ST612 not to release the regular NAV is illustrated. In this case, the terminal C continues the regular NAV and maintains the transmission prohibited state. In the case where the regular NAV is not released in ST612, the terminal C compares the stored RSSI and the current RSSI, and updates the target BSS information when the current RSSI is high (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 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.

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

[0186] In Figure 16In this case, an example where it is determined in ST616 not to release the regular NAV is illustrated. In this case, the terminal C continues the regular NAV and maintains the transmission prohibition state. When the regular NAV is not released in ST616, the terminal C compares the stored RSSI with the current RSSI. If the current RSSI is high, the target BSS information is updated (ST617). Here, assuming that the stored RSSI (the RSSI from the terminal E) is higher than the current RSSI (the RSSI from the terminal B), the terminal C does not update the target BSS information.

[0187] 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.

[0188] [NAV Release Determination Method]

[0189] Hereinafter, Figure 16 the details of the determination method for whether to release the regular NAV in ST608, ST612, and ST616 shown will be described.

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

[0191] Then, in the case of updating the regular NAV by receiving an RTS / CTS frame or the like, when 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 release of the regular NAV due to the expiration of the NAV period can be implemented regardless of the target BSS.

[0192] In this way, in the sixth embodiment, the regular NAV is released based on the signal received from the target BSS, but the regular NAV is not released based on the signal received from other BSSs. Therefore, even in the presence of multiple OBSSs, it is possible to avoid a situation where releasing the NAV of one OBSS causes relatively large interference to other OBSSs. Therefore, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0193] As above, while referring to the attached Figure 1The above describes various embodiments, but it goes without saying that the present invention is not limited to such examples. As long as those skilled in the art can obviously conceive of various modification examples or correction examples within the scope described in the claims and recognize that they naturally belong to the technical scope of the present invention. In addition, within the scope not departing from the gist of the invention, the constituent elements in the above embodiments can be arbitrarily combined.

[0194] In the above 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 multiple OBSSs, measure the RSSI of the CF-End frame, compare the measured RSSI with the RSSI of the stored target BSS information, and the terminal C can also release the regular NAV only when the RSSI of the CF-End frame is high. With such a structure, inappropriate release of the regular NAV can be prevented, and the communication performance of the wireless network can be improved.

[0195] The method for releasing the transmission prohibition state in the above embodiments is not limited to NAV release. For example, in the case of temporarily becoming a transmission permission state without releasing the NAV (managing the time as the transmission permission state, and if the original NAV period is still valid after this time, then returning to the transmission prohibition state again), it can also be applied in the same way.

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

[0197] In the above embodiments, in the case where the transmission prohibition state cannot be released, there is a case of not returning an ACK for data reception. In this case, it can also be an action of sending an ACK after releasing the NAV.

[0198] In the above embodiments, the present invention has been described by taking the case of using a hardware configuration as an example, but the present invention can also be implemented in cooperation with software and hardware.

[0199] In addition, each functional block in the description for the above embodiments is generally implemented as an integrated circuit, that is, an LSI. These integrated circuits can either be integrated into a single chip individually or a part or all of them can be integrated into a single chip. Here, although it is assumed to be an LSI, depending on the degree of integration, it is sometimes also referred to as an IC, a system LSI, a Super LSI, or an Ultra LSI.

[0200] In addition, the method for an integrated circuit is not limited to LSI, and can also be implemented using an application-specific circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connection and setting of circuit units inside the reconfigurable LSI can also be used.

[0201] Moreover, with the technological progress of semiconductors or other technologies derived therefrom, if a technology capable of replacing LSI for integrated circuit implementation emerges, of course, this technology can be utilized for the integration of functional blocks. There is also the possibility of applying biotechnology and the like.

[0202] <Summary of the present invention>

[0203] The wireless station of the present invention is a wireless station in a wireless network having a plurality of wireless stations, including: a receiving unit that receives a trigger signal transmitted from a first wireless station belonging to an interfering cell to a second wireless station belonging to the interfering cell; and a transmission prohibition period control unit that, after setting a transmission prohibition period for other wireless stations belonging to the communication cell to which the own station belongs, determines whether to release the transmission prohibition period based on the reception intensity of the trigger signal when the receiving unit receives the trigger signal.

[0204] In the wireless station of the present invention, the wireless station is a wireless station compliant with IEEE 802.11ax.

[0205] In the wireless station of the present invention, the communication cell to which the own 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 invention, the transmission prohibition period control unit determines whether to release the transmission prohibition period based on a threshold set according to the reception intensity measurement accuracy of the own station and the reception intensity of the trigger signal.

[0207] In the wireless station of the present invention, the transmission prohibition period control unit sets the threshold based on the terminal classes (STA classes) defined in IEEE 802.11ax.

[0208] In the radio station of the present invention, when a response signal to the trigger signal from the second radio station is received, the transmission prohibition period control unit determines whether to release the transmission prohibition period based on a threshold set according to the reception intensity measurement accuracy of this station, the reception intensity of the trigger signal, and the reception intensity of the response signal.

[0209] In the radio station of the present invention, the transmission prohibition period control unit releases the transmission prohibition period when the reception intensity of the trigger signal is within a specified range set based on the reception intensity measurement accuracy of this station.

[0210] In the radio station of the present invention, the transmission prohibition period control unit discriminates the category of the trigger signal, and does not release the transmission prohibition period when it is a trigger signal that requests responses from multiple radio stations in the interference cell.

[0211] In the radio station of the present invention, when the trigger signal is a trigger signal that requests responses from multiple radio stations in the interference cell, the transmission prohibition period control unit extracts information related to the number of radio stations that the trigger signal requests responses from the trigger signal, and determines whether to release the transmission prohibition period based on the extracted information.

[0212] In the radio station of the present invention, the transmission prohibition period control unit compares the intensity of the response signal from the second radio station to the first radio station extracted from the trigger signal with the estimated reception intensity in the first radio station of the signal transmitted from this station to the first radio station estimated in advance, and does not release the transmission prohibition period when the difference is less than a specified value.

[0213] In the radio station of the present invention, when the transmission prohibition period is set by taking the trigger signal from any one radio station belonging to the interference cell as an opportunity, the identifier of the interference cell to which the radio station that transmitted the trigger signal as the opportunity for setting the transmission prohibition period belongs, and the reception intensity of the trigger signal as the opportunity for setting the transmission prohibition period are stored. When a new trigger signal from the interference cell is received, and when the reception intensity of the newly received trigger signal is higher than the reception intensity of the stored trigger signal, the transmission prohibition period control unit releases the transmission prohibition period.

[0214] The communication method of the present invention is a communication method in a wireless network having a plurality of terminals or access points, i.e., radio stations, and includes the following steps: After a transmission prohibition period for other radio stations belonging to the communication cell to which the present station belongs is set in one radio station among the plurality of radio stations, when a trigger signal transmitted to a second radio station belonging to the interference cell to which the present station does not belong is received from a first radio station belonging to the interference cell, the first radio station determines whether to release the transmission prohibition period based on the reception intensity of the trigger signal.

[0215] In the communication method of the present invention, the radio station is a radio station compliant with IEEE 802.11ax.

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

[0217] In the communication method of the present invention, the first radio station determines whether to release the transmission prohibition period based on a threshold set according to the reception intensity measurement accuracy of the present station and the reception intensity of the trigger signal.

[0218] In the communication method of the present invention, the first radio station sets the threshold based on the terminal classes (STA classes) specified in IEEE 802.11ax.

[0219] In the communication method of the present invention, when a response signal to the trigger signal is received from the second radio station, the first radio station determines whether to release the transmission prohibition period based on a threshold set according to the reception intensity measurement accuracy of the present station, the reception intensity of the trigger signal, and the reception intensity of the response signal.

[0220] In the communication method of the present invention, when the reception intensity of the trigger signal is within a specified range set based on the reception intensity measurement accuracy of the present station, the first radio station releases the transmission prohibition period.

[0221] In the communication method of the present invention, the first radio station discriminates the category of the trigger signal, and does not release the transmission prohibition period when it is a trigger signal requesting responses from a plurality of radio stations in the interference cell.

[0222] In the communication method of the present invention, when the trigger signal is a trigger signal for requesting responses from a plurality of radio stations in the interfering cell, the first radio station extracts information related to the number of radio stations for which the trigger signal requests responses from the trigger signal, and determines whether to release the transmission prohibition period based on the extracted information.

[0223] In the communication method of the present invention, the first radio station compares the intensity of the response signal from the second radio station to the first radio station, which is extracted from the trigger signal, with the estimated reception intensity in the first radio station of the signal transmitted from the first radio station itself, which is estimated in advance. When the difference is less than a specified value, the transmission prohibition period is not released.

[0224] In the communication method of the present invention, when the transmission prohibition period is set on the occasion of a trigger signal from any one radio station belonging to the interfering cell, the identifier of the interfering cell to which the radio station that transmitted the trigger signal as the occasion for setting the transmission prohibition period belongs, and the reception intensity of the trigger signal as the occasion for setting the transmission prohibition period are stored. When a new trigger signal is received from the interfering cell, if the reception intensity of the newly received trigger signal is higher than the reception intensity of the stored trigger signal, the first radio station releases the transmission prohibition period.

[0225] Industrial Applicability

[0226] The present invention is suitable for radio stations that perform appropriate wireless communication in an environment where interference occurs between radio stations.

[0227] Reference Signs Description

[0228] 100, 100’, 100”, 100”’, 100”” Wireless Network

[0229] 200, 200’, 200”, 200”’, 200”” Terminal

[0230] 201 Transmitting and Receiving Antenna

[0231] 202 Wireless Transmitting and Receiving Unit

[0232] 203 Transmitted Signal Generation Unit

[0233] 204 Received Signal Demodulation and Decoding Unit

[0234] 205 RSSI Measurement Unit

[0235] 206 BSS Class Judgment Unit

[0236] 207 Transmission Control Unit

[0237] 208 Transmission buffer

[0238] 209 MAC frame generation unit

[0239] 210 Transmission prohibition status 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 control circuit controls a radio station belonging to a communication cell. The control circuit controls the following steps: Receiving a trigger frame transmitted from an access point belonging to an interference cell; and Determining whether transmission from the radio station to another radio station belonging to the communication cell is possible based on at least one parameter included in the trigger frame and the received signal strength of the trigger frame in the radio station. The at least one parameter includes a target received signal strength and a transmission power value of the trigger frame transmitted from the access point. The control circuit controls the following steps: Based on the transmission power value of the trigger frame and the received signal strength, determining whether an estimated received signal strength that can be measured at the access point when the access point receives a signal transmitted from the radio station exceeds a value obtained by adding an allowable interference amount to the target received signal strength, and determining whether transmission from the radio station to the other radio station is possible.

2. The control circuit according to claim 1, wherein The control circuit controls the following steps: When there is data to be transmitted from the radio station to the other radio station in the transmission buffer and transmission permission from the radio station to the other radio station is determined, outputting a control signal indicating transmission from the radio station to the other radio station to the transmission unit.

3. The control circuit according to claim 1, wherein The control circuit controls the following steps: When transmission from the radio station to the other radio station is permitted, setting a period during which transmission from the radio station to the other radio station is permitted.

4. The control circuit according to claim 1, wherein The control circuit controls the following steps: During a period when multiple radio stations belonging to the interference cell transmit uplink response signals based on multi-user transmission in response to the trigger frame, performing transmission to another radio station belonging to the communication cell.

5. The control circuit according to claim 1, wherein The control circuit controls the following steps: Determining whether transmission from the radio station to the other radio station belonging to the communication cell is possible based on a terminal rank indicating RSSI measurement accuracy information of the radio station.

6. The control circuit according to claim 1, wherein The control circuit controls the following steps: Adjusting the transmission power for transmission from the radio station to another radio station belonging to the communication cell and performing transmission from the radio station to another radio station belonging to the communication cell.

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