Wireless communication system and wireless communication method

Abstract

The present invention relates to a wireless communication system and a wireless communication method. The format in which the BSS identifier of the transmission source is included in the preamble of a frame is set as the HE format, and the format in which the BSS identifier is not included in the preamble but is included in the MAC header is set as the Non HE format. The wireless station of the BSS includes a control unit, and the control unit confirms the format of the received frame received above a predetermined reception sensitivity. When the format of the received frame is the HE format and the BSS identifier of the received frame is the same as its own BSS, the control unit continues to demodulate the received frame. When the format of the received frame is the HE format and the BSS identifier of the received frame is different from its own BSS, the control unit performs a process of stopping demodulating the received frame.

Description

[0001] This divisional application is a divisional application of a patent application for an invention titled "Wireless Communication System and Wireless Communication Method" with application number 201680057714.3, filing date October 5, 2016, and applicant Nippon Telegraph and Telephone Corporation. Technical Field

[0002] The present invention relates to a wireless communication system and a wireless communication method for improving the reduction in throughput caused by CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) control of each wireless station in a dense environment of a wireless LAN (Local Area Network). Background Art

[0003] In recent years, due to the spread of high-performance wireless terminals such as personal computers and smartphones, wireless LANs based on the IEEE802.11 standard are widely used not only in enterprises and public places but also in ordinary households. Among wireless LANs based on the IEEE802.11 standard, there are wireless LANs based on the IEEE802.11b / g / n standard using the 2.4 GHz band and wireless LANs based on the IEEE802.11a / n / ac standard using the 5 GHz band.

[0004] Here, in a dense environment of a wireless LAN where the number of channels that can be used simultaneously at a certain location is less than the number of BSSs (Basic Service Set), multiple BSSs use the same channel. In this case, due to the influence of interference between BSSs using the same channel, the throughput of this BSS and the system as a whole decreases. Therefore, autonomous distributed access control is used in the wireless LAN, and this autonomous distributed access control uses CSMA / CA control to send data only when the channel is idle through carrier sensing.

[0005] However, even with CSMA / CA control, in a dense environment of a wireless LAN using the same channel, since the frequency at which the channel becomes busy through carrier sensing is high, the transmission opportunity (the opportunity to obtain the right to use the channel) decreases, and the throughput decreases.

[0006] Here, a CCA (Clear Channel Assessment) threshold is set. When the radio station performs carrier sensing, the received power value (RSSI) of the received signal is used to determine whether the channel is idle or busy. The following methods are discussed in Non-Patent Documents 1, 2, and 3: By dynamically controlling the DSC (Dynamic Sensitivity Control) of the CCA threshold, the state of unnecessarily waiting to transmit is eliminated, and the transmission opportunity is increased. Hereinafter, taking the downlink communication from the AP to the STA as an example, a control example of the CCA threshold will be described with the radio base station being the AP and the radio terminal being the STA.

[0007] Figure 14A and Figure 14B Shows a control example of the conventional CCA threshold.

[0008] In Figure 14A AP1, STA1, AP2, STA2, and AP3 respectively form different BSSs. AP1 can select the default CCA threshold (i.e., -82 dBm) and the CCA threshold for Non-WLAN (Non-Wireless Local Area Network) frames (i.e., -62 dBm). When the signal detected by carrier sensing corresponding to the default CCA threshold is, for example, a signal other than a wireless LAN, AP1 controls to the CCA threshold for Non-WLAN frames to narrow the carrier sensing range and perform control to increase the transmission opportunity. Here, an example is shown where AP2 is located between the carrier sensing ranges corresponding to the two CCA thresholds of AP1, and AP3 is located outside the carrier sensing range corresponding to the default CCA threshold.

[0009] AP1 starts carrier sensing with the default CCA threshold (i.e., -82 dBm) (S100). If the received power value of the received signal is a value greater than or equal to the reception sensitivity of -82 dBm or less (S101: Yes), the preamble of the received signal is detected (S102). When the preamble is normally detected (S103: Yes), the default CCA threshold at the time of successful detection of the preamble is maintained to determine the channel state (S104). Here, if the channel is busy (S105: Yes), the received signal is continuously demodulated (S106), and if the channel is idle (S105: No), the demodulation of the received signal is stopped (S107). On the other hand, when the preamble is not normally detected (S103: No), it is changed to the CCA threshold for Non-WLAN frames (i.e., -62 dBm), and the carrier sensing range is narrowed to determine the channel state, thereby increasing the transmission opportunity (S108).

[0010] In the above CCA threshold control, in AP1, even if the signal of AP3 is above the reception sensitivity and the preamble can be normally detected, it is judged that the channel is idle due to the default CCA threshold being set, so that demodulation can be stopped to increase the transmission opportunity. That is, AP1 and AP3 can transmit simultaneously as base stations with little interference between them. On the other hand, regarding the signal of AP2, the channel becomes busy due to the default CCA threshold being set, and AP1 continues to demodulate the signal of AP2 and waits for transmission. At this time, even if it is possible to transmit from AP1 to STA1 and from AP2 to STA2 simultaneously, AP1 becomes waiting for transmission because it has detected the signal of AP2, becoming a so-called exposed terminal state. Therefore, for example, it is possible for AP1 to detect the signal of another BSS. If the CCA threshold is controlled to be higher to narrow the corresponding carrier sense range, AP1 can transmit simultaneously even when AP2 is transmitting, improving the system throughput.

[0011] However, when STA1 is located close to AP2 and the interference signal from AP2 is large, even if the transmission opportunity of AP1 is increased by controlling the CCA threshold in AP1, STA1 may experience reception failure due to the interference signal from AP2, and conversely, the throughput may decrease.

[0012] In addition, it can be said that in AP1, when receiving the signal transmitted by the controlled STA1 or when receiving the beacon frame transmitted by AP2, rather than controlling the CCA threshold to increase the transmission opportunity, it is better for AP1 to suppress transmission and perform reception. That is, it is preferable that AP1 distinguishes between the signal of STA1 from its own BSS and the signal of AP2 from another BSS, and even for the signal of AP2 from another BSS, it can select whether to control the CCA threshold according to whether demodulation is required to enable simultaneous transmission.

[0013] Prior art documents

[0014] Non-patent documents

[0015] Non-patent document 1: “Proposed Specification Framework for TGax,” Robert Staceyet al., doc.: IEEE 802.11-14 / 1453r2, 5 November 2014;

[0016] Non-Patent Document 2: The LAN / MAN Standards Committee, “IEEE Std 802.11TM2012 IEEE standard for Information Technology - Telecommunications and information exchange between systems - Local and metropolitan area networks Specific requirements Part 11: Wireless LAN Medium Access Contral (MAC) and Physical Layer (PHY);

[0017] Non-Patent Document 3: Graham Smith, “Dynamic Sensitivity Control Practical Usage,” doc.: IEEE 802.11 - 14 / 0779r2. Summary of the Invention

[0018] However, the following technique has been discussed: By using the HE (High Efficiency) format with a field containing the BSS identifier in the PHY (Physical Layer) preamble of a wireless LAN frame, determining whether it is a signal of its own BSS or another BBS, and performing simultaneous transmission to maximize throughput.

[0019] Here, a wireless station AP or STA capable of transmitting and receiving HE - format frames is defined as an HE terminal. On the other hand, the conventional format that does not contain a field for the BSS identifier but contains preambles such as L - SIG, L - STF, and L - LTF is set as the Non - HE format, and a wireless station AP or STA that does not have the function of transmitting and receiving HE - format frames but can transmit and receive Non - HE - format frames is defined as a Non - HE terminal.

[0020] Figure 15 Fig. shows a configuration example of a wireless communication system in which a variety of terminals coexist. Figure 15Among them, the sending terminal 11 is set as a HE terminal, and the destination terminals 12 and 13 of the same BSS as the sending terminal 11 are set as HE terminals and Non-HE terminals. That is, the sending terminal 11 sends HE format frames or Non-HE format frames in accordance with the standards of the destination terminals. The interfering terminal 14 that becomes an interference source for the sending terminal 11 and the destination terminal 12 is set as a HE terminal, and the interfering terminal 15 that becomes an interference source for the sending terminal 11 and the destination terminal 13 is set as a Non-HE terminal.

[0021] Here, the sending terminal 11 differentiates between HE format frames sent from the interfering terminal 14 and Non-HE format frames sent from the interfering terminal 15. And, in the case of HE format frames, it detects the BSS identifier and determines whether it can transmit simultaneously or whether to suppress simultaneous transmission and receive the frame based on whether it is consistent with its own BSS.

[0022] For example, the sending terminal 11 can recognize HE format frames sent from the interfering terminal 14. In the case of determining that it is a signal from another BSS, it aborts demodulation and transmits to the destination terminals 12 and 13. At this time, if the destination terminal 12 that can recognize HE format frames also aborts demodulation in the same way, it can receive from the sending terminal 11. However, since the destination terminal 13 cannot recognize HE format frames, it continues to receive as it is. In this case, even if the sending terminal 11 recognizes HE format frames from the interfering terminal 14 and aborts demodulation, and transmits Non-HE format frames to the destination terminal 13, there is a possibility of reception failure in the destination terminal 13 that continues to receive frames from the interfering terminal 14. That is, the sending terminal 11 effectively performs the following control: it determines whether it can transmit simultaneously based on the signals from the interfering terminal 14 and the standards of the destination terminals 12 and 13, and sets that it can transmit simultaneously for the destination terminal 12 as a HE terminal, and sets that it cannot transmit simultaneously for the destination terminal 13 as a Non-HE terminal.

[0023] An object of the present invention is to provide a wireless communication system and a wireless communication method as follows: in a dense environment of a wireless LAN where HE terminals and Non-HE terminals coexist, it is possible to effectively obtain a transmission opportunity and improve system throughput through the control of the CCA threshold, and it is also possible to effectively acquire management frames such as beacon frames required for information collection.

[0024] The first invention is a wireless communication system in which multiple BSSs exist adjacent to each other. The BSSs are composed of multiple wireless stations that use a predetermined channel to transmit and receive frames. The transmitting stations of each BSS use a Clear Channel Assessment (CCA) threshold to perform wireless communication through access control based on Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA). The CCA threshold takes into account the interference power value from interfering stations using the predetermined channel. The format that includes the BSS identifier of the transmission source within the preamble of the frame is set as the HE format, and the format that does not include the BSS identifier within the preamble but includes the BSS identifier in the MAC header is set as the Non HE format. The wireless stations of the BSS include a control unit that confirms the format of the received frame received above a predetermined reception sensitivity. When the format of the received frame is the HE format and the BSS identifier of the received frame is the same as its own BSS, the control unit continues to demodulate the received frame. When the format of the received frame is the HE format and the BSS identifier of the received frame is different from its own BSS, the control unit performs the process of stopping demodulating the received frame.

[0025] In the wireless communication system of the first invention, the control unit is configured as follows: when the received frame is in the HE format and the BSS identifier of the received frame is different from its own BSS, the control unit changes the CCA threshold from the default value to the CCA threshold for the HE format and performs carrier sensing.

[0026] In the wireless communication system of the first invention, the control unit is configured as follows: when the format of the received frame is the Non HE format, the control unit changes the CCA threshold from the default value to the CCA threshold for the Non HE format and performs carrier sensing. If the predetermined channel is busy, the control unit continues to demodulate the received frame. If the predetermined channel is idle, the control unit performs the process of stopping demodulating the received frame.

[0027] In the wireless communication system of the first invention, the control unit is configured as follows: when the format of the received frame is the Non HE format, the control unit confirms the BSS identifier included in the received frame. If it is the same as its own BSS, the control unit continues to demodulate the received frame. If it is different from its own BSS, the control unit performs the process of stopping demodulating the received frame. Also, the control unit is configured as follows: when the received frame is in the Non HE format and the BSS identifier is different from its own BSS, the control unit changes the CCA threshold from the default value to the CCA threshold for the Non HE format and performs carrier sensing.

[0028] In the wireless communication system of the first invention, the control unit is configured as follows: when the format of the received frame is the Non HE format, the control unit confirms the type of the received frame. If the type is the frame type or frame subtype required for the communication control of each wireless station, the control unit performs the process of continuing demodulation.

[0029] In the wireless communication system of the first invention, the control unit is configured as follows: It confirms the destination terminal of the frame to be transmitted as scheduled. When the own station and the destination terminal are capable of performing the process of stopping demodulating the received frame, it performs control to change the CCA threshold to a value higher than the default value. When the own station and the destination terminal are not capable of performing the process of stopping demodulating the received frame, it does not control the CCA threshold or controls it to a CCA threshold capable of detecting the received frame.

[0030] In the wireless communication system of the first invention, the control unit is configured as follows: It confirms the format of the frame to be transmitted as scheduled. When the format is the HE format, it performs control to change the CCA threshold to a value higher than the default value. When the format is the Non HE format, it does not control the CCA threshold or controls it to a CCA threshold capable of detecting the received frame.

[0031] In the wireless communication system of the first invention, the control unit is configured as follows: It confirms the type of the frame to be transmitted as scheduled. When the type is a frame type or frame subtype required for communication control of each wireless station, it does not control the CCA threshold or controls it to a CCA threshold capable of detecting the received frame. When the type is not a frame type or frame subtype required for communication control of each wireless station, it performs control to change the CCA threshold to a value higher than the default value.

[0032] A second invention is a wireless communication method. There are a plurality of basic service sets (BSS) adjacent to each other. The BSS is composed of a plurality of wireless stations that use a predetermined channel to transmit and receive frames. The transmitting station of each BSS uses the clear channel assessment (CCA) threshold to perform wireless communication through access control based on carrier sense multiple access with collision avoidance (CSMA / CA). The CCA threshold takes into account the interference power value from interfering stations using the predetermined channel. In the wireless communication method, the format in which the BSS identifier of the transmission source is included in the preamble of the frame is set as the HE format, and the format in which the BSS identifier is not included in the preamble but is included in the MAC header is set as the Non HE format. The wireless stations of the BSS have: Step 1, confirm the format of the received frame received above a predetermined reception sensitivity; and Step 2, when the format of the received frame is the HE format and the BSS identifier of the received frame is the same as that of its own BSS, continue to demodulate the received frame. When the format of the received frame is the HE format and the BSS identifier of the received frame is different from that of its own BSS, perform the process of stopping demodulating the received frame.

[0033] In the wireless communication method of the second invention, step 2 also changes the CCA threshold from the default value to the CCA threshold for the HE format and performs carrier sensing when the received frame is in the HE format and the BSS identifier of the received frame is inconsistent with its own BSS.

[0034] In the wireless communication method of the second invention, step 2 also changes the CCA threshold from the default value to the CCA threshold for the Non HE format and performs carrier sensing when the format of the received frame is the Non HE format. If the predetermined channel is busy, continue demodulating the received frame. If the predetermined channel is idle, perform the process of stopping demodulating the received frame.

[0035] In the wireless communication method of the second invention, step 2 also confirms the BSS identifier included in the received frame when the format of the received frame is the Non HE format. If it is consistent with its own BSS, continue demodulating the received frame. If it is inconsistent with its own BSS, perform the process of stopping demodulating the received frame. Step 2 also changes the CCA threshold from the default value to the CCA threshold for the Non HE format and performs carrier sensing when the received frame is in the Non HE format and the BSS identifier is not consistent with its own BSS.

[0036] In the wireless communication method of the second invention, step 2 also confirms the type of the received frame when the format of the received frame is the Non HE format. If the type is the frame type or frame subtype required for the communication control of each wireless station, perform the process of continuing demodulation.

[0037] In the wireless communication method of the second invention, there is also step 3, which confirms the destination terminal of the frame to be transmitted. When its own station and the destination terminal can perform the process of stopping demodulating the received frame, perform the control of changing the CCA threshold to a value higher than the default value. When its own station and the destination terminal cannot perform the process of stopping demodulating the received frame, do not control the CCA threshold or control it to the CCA threshold capable of detecting the received frame.

[0038] In the wireless communication method of the second invention, there is also step 4, which confirms the format of the frame to be transmitted. When the format is the HE format, perform the control of changing the CCA threshold to a value higher than the default value. When the format is the Non HE format, do not control the CCA threshold or control it to the CCA threshold capable of detecting the received frame.

[0039] In the wireless communication method of the second invention, there is also step 5 of confirming the type of the frame to be transmitted. When the type is a frame type or frame subtype required for communication control of each wireless station, the CCA threshold is not controlled or is controlled to a CCA threshold capable of detecting the received frame. When the type is not a frame type or frame subtype required for communication control of each wireless station, control is performed to change the CCA threshold to a value higher than the default value.

[0040] The present invention dynamically controls the CCA threshold corresponding to the interference power value, thereby increasing the transmission opportunity, and aborting the demodulation process of the interference frame so that transmission processing and reception processing can be performed. Thus, simultaneous transmission with the interference frame can be actively executed, and throughput improvement can be achieved.

[0041] In addition, simultaneous transmission can be actively and effectively utilized through control of the CCA threshold and control of continuation / abortion of the demodulation process, and the type of the received frame is judged. When it is not a data frame, the demodulation process is continued, thereby reliably receiving management frames such as beacon frames.

[0042] In addition, simultaneous transmission can be actively and effectively utilized through control of the CCA threshold and control of continuation / abortion of the demodulation process. In the case of a Non-HE terminal where control of aborting the demodulation process cannot be performed for the interference frame, the CCA threshold is not controlled or is controlled to a CCA threshold capable of detecting the interference frame. Thus, simultaneous transmission to the Non-HE terminal can be avoided and throughput reduction can be avoided.

[0043] In addition, simultaneous transmission is actively and effectively utilized through control of the CCA threshold and control of continuation / abortion of the demodulation process. When the transmitted frame is not in the HE format, the CCA threshold is not controlled or is controlled to a CCA threshold capable of detecting the interference frame. Thus, simultaneous transmission to the Non-HE terminal can be avoided and throughput reduction can be avoided.

[0044] In addition, simultaneous transmission can be actively and effectively utilized through control of the CCA threshold and control of continuation / abortion of the demodulation process. When the transmitted frame is a management frame, the CCA threshold is not controlled or is controlled to a CCA threshold capable of detecting the interference frame. Thus, simultaneous transmission can be avoided and throughput reduction can be avoided. Description of the Drawings

[0045] Figure 1 is a diagram showing a configuration example of the wireless communication system of the present invention;

[0046] Figure 2 is a flowchart showing an example of the reception processing steps of AP1 in Embodiment 2 of the present invention;

[0047] Figure 3 is a timing diagram showing the operation examples of steps S8 and S12;

[0048] Figure 4 is a timing diagram showing operation example 1 of steps S14 and S15;

[0049] Figure 5 is a timing diagram showing operation example 2 of steps S14 and S15;

[0050] Figure 6 is a flowchart showing operation example 2 of the reception processing steps of AP1 in Embodiment 2 of the present invention;

[0051] Figure 7 is a timing diagram showing the operation examples of steps S21, S23, and S24;

[0052] Figure 8 is a flowchart showing the reception processing steps example of AP1 in Embodiment 3 of the present invention;

[0053] Figure 9 is a timing diagram showing the operation examples of steps S10 to S13, S31 to S32;

[0054] Figure 10 is a flowchart showing the transmission processing steps example of AP1 in Embodiment 4 of the present invention;

[0055] Figure 11A and Figure 11B is a timing diagram showing the operation examples of steps S44 and S45;

[0056] Figure 12 is a flowchart showing transmission processing steps example 1 of AP1 in Embodiment 5 of the present invention;

[0057] Figure 13 is a flowchart showing transmission processing steps example 2 of AP1 in Embodiment 5 of the present invention;

[0058] Figure 14A and Figure 14B is a diagram showing a control example of a conventional CCA threshold;

[0059] Figure 15 is a diagram showing a configuration example of a wireless communication system in which various terminals coexist; Detailed implementation manners

[0060] Figure 1 shows a configuration example of the wireless communication system of the present invention.

[0061] In Figure 1Among them, AP1, AP2, AP3, and AP4 form different BSSs respectively, and AP1 and STA1-1, STA1-2, STA1-3 form the same BSS. The CCA threshold of AP1 can be selected as the default value of -82 dBm, -76 dBm when used for Non HE format, -66 dBm when used for HE format, and -62 dBm when used for Non WLAN frames. The carrier sensing range of AP1 corresponds to the CCA threshold, which is shown as a circle for simplicity here, and the receiving sensitivity is set to a predetermined value below -82 dBm. In addition, the numerical values of the CCA threshold and the receiving sensitivity, including their default values, are all examples.

[0062] Relative to AP1, STA1-1 and STA1-3 are within the carrier sensing range corresponding to the CCA threshold for Non WLAN frames (i.e., -62 dBm). Relative to AP1, AP3 is between the carrier sensing ranges corresponding to the CCA threshold for Non WLAN frames (i.e., -62 dBm) and the CCA threshold for HE format (i.e., -66 dBm). Relative to AP1, AP2 and STA1-2 are between the carrier sensing ranges of the CCA threshold for HE format (i.e., -66 dBm) and the CCA threshold for Non HE format (i.e., -76 dBm). Relative to AP1, AP4 is between the carrier sensing ranges of the CCA threshold for Non HE format (i.e., -76 dBm) and the default CCA threshold (i.e., -82 dBm). In AP1, the interference from AP2 to AP4 is observed according to the set CCA threshold.

[0063] Here, AP1, STA1-1, and STA1-2 are set as HE terminals, and STA1-3 is set as a Non HE terminal. Therefore, AP1 sends HE format frames to the destination STA1-1 and STA1-2, and AP1 sends Non HE format frames to the destination STA1-3. Assume that there are frames destined for STA1-1 and STA1-3 in the transmission queue of AP1.

[0064] Next, control examples for effectively obtaining a transmission opportunity and improving system throughput in AP1 are shown, and control examples for effectively acquiring frames required for information collection such as beacon frames are also shown. Embodiment 1 shows a control example of the communication area based on the setting of the receiving sensitivity, Embodiment 2 shows a control example according to each received frame format, Embodiment 3 shows a control example according to each received frame type, Embodiment 4 shows a control example according to the criteria and functions of each destination terminal, and Embodiment 5 shows a control example according to each transmission frame format and type.

[0065] (Embodiment 1)

[0066] Example 1 assumes a situation where all terminals to communicate are configured within a few meters for tethering etc. of AP1. For example, in Figure 1 , when only STA1-1 and STA1-3 exist near AP1, the reception sensitivity of AP1 is set to, for example, -62 dBm or more. Thus, AP1 can perform simultaneous transmission to STA1-1 and STA1-3 more simply than by controlling the CCA threshold.

[0067] The reception sensitivity corresponding to the communication area controlled by each AP can be set in the control server connected by wire or wirelessly to each AP. In Figure 1 , AP1 measures the reception power values of the reception signals from STA1-1 and STA1-3 and the reception power values of the wireless signals transmitted from the surrounding APs AP2 to AP4, and notifies the control server. When the reception power values of STA1-1 and STA1-3 measured by AP1 are high enough, the control server determines that the terminal is near AP1 and controls the reception sensitivity. This reception sensitivity is, for example, a value below the reception power values of STA1-1 and STA1-3, and is set higher than the reception power values of the surrounding APs AP2 to AP4 measured by AP1.

[0068] In addition, when the transmission power values or antenna gains of each STA and each AP are known, these values can be used to correct the reception power values from each STA and each AP. However, when it is determined that the reception power value of AP1 observed in AP2 to AP4 causes interference in any of AP2 to AP4 and thus the throughput decreases, the reception sensitivity of AP1 is not controlled.

[0069] (Example 2)

[0070] The feature of Example 2 is to control the CCA threshold according to each reception frame format in AP1. Here, for frames in the HE format, the CCA threshold is controlled to a high value, for example, Figure 1 shown as -66 dBm, in order to actively perform simultaneous transmission. For frames in the Non HE format, from the viewpoint of fairness, the CCA threshold is controlled to the default, for example, Figure 1 shown as -82 dBm, or is controlled to a value lower than the CCA threshold for the HE format, for example, Figure 1 shown as -76 dBm. In addition, the CCA threshold for the HE format can be set to a fixed relationship with respect to the CCA threshold for the Non HE format, for example, 10 dB higher.

[0071] Figure 2Example 1 of the reception processing steps of AP1 in Embodiment 2 of the present invention is shown. The same applies to other APs and STAs as well.

[0072] In Figure 2 , AP1 starts carrier sensing (S0) with the default CCA threshold (i.e., -82 dBm). If the received power value of the received frame is greater than or equal to the receive sensitivity (i.e., -82 dBm) or a value below it (S1: Yes), the preamble of the received frame is detected (S2). In the case where the preamble is normally detected (S3: Yes), it is confirmed whether the frame format is HE format or Non-HE format (S4). If the frame format is HE format (S5: Yes), the BSS identifier located in the preamble is confirmed (S6). If the BSS identifier of the received frame is the BSS identifier of AP1 (S7: Yes), the received frame is continuously demodulated (S8).

[0073] In addition, in step S3, in the case where the preamble of the received frame is not normally detected (S3: No), it is determined that it is not a wireless LAN frame, the CCA threshold for Non-WLAN frames (i.e., -62 dBm) is set, and the channel state is determined (S9). This control is the same as Figure 14B the step S108 shown, and the carrier sensing range is narrowed to determine the channel state, thereby increasing the transmission opportunity.

[0074] In addition, in step S5, in the case where the received frame is not in HE format (S5: No), the CCA threshold for Non-HE format (i.e., -76 dBm) is set, and the channel state is determined (S10). Here, if the channel is busy (S11: Yes), the received frame is continuously demodulated (S12), and waiting for simultaneous transmission. On the other hand, if the channel is idle (S11: No), the demodulation of the received frame is stopped (S13), and it is set to a state where simultaneous transmission is possible.

[0075] In addition, in step S7, if the BSS identifier of the received frame does not match the BSS identifier of AP1 (S7: No), since a HE format frame from another BSS is received, the CCA threshold for HE frames (i.e., -66 dBm) is set, and the channel state is determined (S14). And regardless of whether the channel is busy or idle, the demodulation of the received frame is stopped (S15), and it is set to a state where simultaneous transmission is possible.

[0076] Figure 3 Examples of the operations of steps S6 - S8, S10 - S12 are shown. Here, examples of the operations when AP1 receives a HE format frame sent by STA1-2 and a Non-HE format frame sent by AP2 are shown.

[0077] In Figure 3Among them, at time t1, AP1 detects a received power value higher than the reception sensitivity and starts frame reception. At time t2, it normally receives the preamble of the received frame, confirms that it is in HE format, and confirms that the BSS identifier is the same as its own BSS, and continues demodulation. At time t3, frame demodulation is completed. In this case, since it is determined that the frame of STA1-2 of its own BSS that needs to be demodulated, demodulation is continued without performing simultaneous transmission.

[0078] In addition, in the case of receiving HE format frames sent from Figure 1 AP2 to AP4 among them, through the process of step S15, demodulation is stopped in order to perform simultaneous transmission after preamble reception. For details, refer to Figure 4 and Figure 5 for separate description.

[0079] At time t4, AP1 detects a received power value higher than the reception sensitivity and starts frame reception. At time t5, it normally receives the preamble of the received frame, confirms that it is in Non HE format, and sets the CCA threshold for Non HE format (i.e., -76 dBm) through the process of step S10. In this operation example, since it is a received frame from AP2 and the received power value is higher than this CCA threshold, the channel is determined to be busy, and demodulation is continued, and frame demodulation is completed at time t6. In this case, since it is a Non HE format frame sent by AP2 of other BSS, it is determined that it may need demodulation such as a beacon frame, etc., and demodulation is continued without performing simultaneous transmission. Thus, even when the CCA threshold is increased but the channel is busy, by avoiding simultaneous transmission, the influence of interference in other BSS that are receiving this frame can be reduced.

[0080] On the other hand, once AP1 that has received a Non HE format frame from Figure 1 AP4 among them sets the CCA threshold for Non HE format (i.e., -76 dBm) through the process of step S10, since the received power value from AP4 is lower than this CCA threshold, the channel is determined to be idle, and demodulation is stopped through the process of step S13 and becomes capable of simultaneous transmission. In addition, for the reception of Non HE format frames such as beacon frames sent by AP4 among Figure 1 them, it can be dealt with through the steps shown in Embodiment 3 described later.

[0081] Figure 4 Shows operation example 1 of steps S14 and S15. Here, shows the operation example when AP1 receives a HE format frame sent from AP2.

[0082] In Figure 4Among them, STA1-1 and AP1 detect received power values higher than the reception sensitivity at times t7 and t8 and start frame reception, and normally receive the preamble of the received frame at times t9 and t10 and confirm that it is in the HE format. Here, since the BSS identifier is AP2 of another BSS, the CCA threshold for the HE format (i.e., -66 dBm) is set through the process of step S14, and demodulation is stopped through the process of step S15. In this operation example, once AP1 identifies a frame from AP2 and increases the CCA threshold, since the received power value is lower than this CCA threshold, the channel is judged to be idle, demodulation is stopped, and transmission can be performed simultaneously.

[0083] If the channel is idle until time t11, which is the fixed time + random time, AP1 transmits a frame destined for STA1-1. STA1-1 stops demodulation at time t9 and detects a received power value higher than the reception sensitivity at time t12 and starts frame reception.

[0084] Thus, since AP1 sets a high CCA threshold for the HE format and stops demodulation after detecting the preamble of the HE format frame transmitted by AP2 of another BSS, it is easy to acquire the right of transmission and perform simultaneous transmission with AP2. On the other hand, STA1-1 also stops demodulation after detecting the preamble of another BSS, and can normally demodulate the frame transmitted from AP1 even when AP2 is in the process of transmitting a frame.

[0085] Figure 5 An operation example 2 of steps S14 and S15 is shown. Here, an operation example of receiving the HE format frame transmitted by receiving STA1-2 after receiving the HE format frame transmitted from AP3 in AP1 is shown.

[0086] In Figure 5 AP1 detects a received power value higher than the reception sensitivity at time t13 and starts frame reception, and normally receives the preamble of the received frame at time t14 and confirms that it is in the HE format. Here, since the BSS identifier is AP3 of another BSS, the CCA threshold for the HE format (i.e., -66 dBm) is set through the process of step S14, and demodulation is stopped through the process of step S15. In this operation example, even if AP1 identifies a frame from AP3 and increases the CCA threshold, since the received power value is higher than its CCA threshold, it is judged that the channel is busy and waits for simultaneous transmission.

[0087] On the other hand, STA1-1 and STA1-2 receive HE format frames from AP3 and stop demodulation. If the channel is idle, they can transmit. Here, if the received power value from AP3 in STA1-2 is lower than the CCA threshold for the HE format (i.e., -66 dBm), it is determined that the channel is idle, and frames destined for AP1 are transmitted. AP1 stops demodulating frames from AP3 at time t14, detects a received power value higher than the reception sensitivity at time t15, and starts receiving frames from STA1-2.

[0088] In this way, after detecting the preamble of the HE format frame transmitted by AP3 of another BSS, AP1 sets a high CCA threshold for the HE format and stops demodulation. However, since the received power value of the frame from AP3 is higher than this CCA threshold, the channel becomes busy and simultaneous transmission is not performed, and it waits. On the other hand, STA1-2 also increases the CCA threshold after detecting the preamble of another BSS and stops demodulation. If the channel is idle, it can transmit frames. Therefore, even during the process of AP3 transmitting frames, if STA1-2 can transmit frames, AP1 can normally demodulate the frames.

[0089] Figure 4 and Figure 5 The example shown is as follows: In AP1, according to the BSS identifier detected by demodulating the preamble of the HE format frame in the processes of steps S6 and S7, when it is determined that the frame is from AP2 or AP3 of another BSS, in the process of step S14, the CCA threshold is increased from the default CCA threshold (i.e., -82 dBm) to the CCA threshold for the HE format (i.e., -66 dBm). Here, the frame of AP2 cannot be detected and the channel becomes idle, while the frame of AP3 remains detected and the channel becomes busy. However, in either case, AP1 stops demodulation. In the example of Figure 2 , AP1 becomes capable of transmitting, and in the example of Figure 2 , AP1 becomes capable of receiving. Figure 4 Figure 5 However, in AP1, when the received frame is in the HE format and it is determined that the frame is from another BSS in the processes of steps S6 and S7, depending on the form of the received frame, it is sometimes desired not to perform the process of controlling the CCA threshold shown in step S14 and to set the channel as busy.

[0090] Figure 2

[0091] ​​​For example, in the new wireless LAN standard, it is assumed that in multi-user MIMO (MU-MIMO) over the uplink (UL), multiple STAs that receive a trigger frame from an AP simultaneously transmit UL MU frames to the AP. When other APs start transmitting in response to this trigger frame, it is possible that an STA cannot transmit a UL MU frame, or even if it does transmit, the quality will be significantly degraded due to interference. To address this situation, signaling information is appended to a predetermined field within the preamble of the trigger frame. For example, in Figure 2 if, in the processes of steps S6 and S7, it is determined that the frame is from another BSS and this signaling information is detected from the preamble, the following control is performed: Without performing CCA threshold control, it is determined that the channel is busy, or even if a transmission opportunity is obtained through CCA threshold control, the transmission is restricted to within the period of the trigger frame. On the other hand, if the signaling information is not detected in the frame, then in Figure 2 the process of step S14, the CCA threshold for the HE format (i.e., -66 dBm) can be set, and the process proceeds to the determination of the channel state.

[0092] Figure 6 Example 2 of the receiving process steps of AP1 in Embodiment 2 of the present invention is shown. The same applies to other APs and STAs.

[0093] In Figure 6 the processes of steps S0 to S9, S14, and S15 are the same as those of Example 1 of the receiving process steps of AP1 shown in Figure 2 .

[0094] In step S5, when the received frame is not in the HE format (S5: No), AP1 confirms the BSSID (Basic Service Set Identifier) in the MAC (Media Access Control) header of the Non-HE format, determines whether it is the same as its own BSS (S21), and if it is the same as its own BSS, continues demodulation (S22) and waits for simultaneous transmission. On the other hand, if the BSSID of the received frame is not the same as its own BSS, the CCA threshold for the Non-HE format (i.e., -76 dBm) is set, the channel state for simultaneous transmission is determined (S23), and the demodulation of the received frame is stopped (S24).

[0095] Figure 7 An example of the operations of steps S21, S23, and S24 is shown. The following example of operations is shown: In AP1, after receiving a Non-HE format frame sent by AP3, a HE format frame sent by receiving STA1-2 is received.

[0096] In Figure 7Among them, at time t16, AP1 detects a received power value higher than the reception sensitivity and starts frame reception. At time t17, it normally receives the preamble of the received frame, confirms it is in the Non-HE format, and confirms the MAC header. Also, since at time t18 it is confirmed that the BSSID in the MAC header is another BSS, the CCA threshold for the Non-HE format (i.e., -76 dBm) is set through the process of step S23, and demodulation is stopped through the process of step S24. In this operation example, AP1 stops demodulation when receiving a frame from AP3. However, since the received power value is higher than the CCA threshold for the Non-HE format, the channel is judged to be busy and it waits for simultaneous transmission.

[0097] On the other hand, STA1-1 and STA1-2 also receive the Non-HE format frame from AP3 and stop demodulation. If the channel is idle, they become capable of transmission. Here, in STA1-2, if the received power value from AP3 is lower than the CCA threshold for the Non-HE format (i.e., -76 dBm), the channel is judged to be idle and a frame destined for AP1 is transmitted. AP1 stops demodulating the frame from AP3 at time t18 and detects a received power value higher than the reception sensitivity at time t19 and starts frame reception.

[0098] Thus, AP1 stops demodulation after detecting the BSSID of the Non-HE format frame sent by AP3 of another BSS and sets the CCA threshold for the Non-HE format. However, since the received power value of the frame sent by AP3 is higher than this CCA threshold, it does not perform simultaneous transmission but waits. On the other hand, STA1-2 also stops demodulation after receiving a frame from another BSS and becomes in a state capable of transmitting a frame. Therefore, even when AP3 is in transmission, AP1 can normally demodulate the frame sent from STA1-2.

[0099] In addition, when AP1 receives a Non-HE format frame sent by STA1-3 of its own BSS, since the BSSID is the same as its own BSS, it can continue demodulation through the processes of steps S21 and S22.

[0100] (Embodiment 3)

[0101] The features of Embodiment 3 are as follows: control is performed according to the type of received frames in each AP1. Here, when a frame is received, the frame type is read and the following selection is made: whether to directly receive, demodulate, or stop demodulating to enable simultaneous transmission. For example, the following control is performed: in the case of receiving a data frame, simultaneous transmission is actively performed; even if it is a frame of another BSS, but in the case of management frames such as an AP beacon frame or an STA association request frame, simultaneous transmission is suppressed and reception and demodulation are prioritized. In addition, for control frames such as RTS, CTS, and ACK, since the frame time length is short, the advantage of switching control to simultaneous transmission is small, and they can be directly received and demodulated to be effectively used for information collection.

[0102] Figure 8 An example of the reception processing steps of AP1 in Embodiment 3 of the present invention is shown. In addition, the same applies to other APs and STAs.

[0103] In Figure 8 the processing of steps S0 to S15 is the same as that of Figure 2 the example of the reception processing steps of AP1 in Embodiment 2 shown.

[0104] In step S5, when the received frame is not in HE format (S5: No), AP1 confirms the frame type and determines the frame type or frame subtype required for communication control in each radio station, for example, determines whether it is a management frame (S31). If it is a management frame, demodulation continues (S32), and waiting for simultaneous transmission. On the other hand, if it is a data frame, similar to Figure 2 Embodiment 2 shown, the CCA threshold for Non HE format (-76 dBm) is set, and the channel state is determined (S10). Here, if the channel is busy (S11: Yes), demodulation of the data frame continues (S12), and waiting for simultaneous transmission. On the other hand, if the channel is idle (S11: No), demodulation of the data frame is stopped (S13), and it is set to a state where simultaneous transmission is possible. That is, compared with Embodiment 2, Embodiment 3 is an embodiment in which, when it is a Non HE format frame and a management frame such as a beacon frame, a process of preferentially continuing demodulation is applied.

[0105] Figure 9 Examples of the operations of steps S10 to S13 and S31 to S32 are shown. Here, examples of the operations when AP1 receives a Non HE format data frame and a beacon frame sent by AP4 are shown.

[0106] In Figure 9Among them, at time t20, AP1 detects a received power value higher than the reception sensitivity and starts frame reception. At time t21, it normally receives the preamble of the received frame and confirms that it is in the Non-HE format. And at time t22, it confirms that the frame type in the MAC header is data. Therefore, the CCA threshold for the Non-HE format is set through the processing of step S10 (i.e., -76 dBm). In this operation example, when AP1 receives a data frame from AP4, it stops demodulation. However, since the received power value is lower than the CCA threshold for the Non-HE format, the channel is judged to be idle, and thus it can transmit simultaneously.

[0107] If the channel is idle until time t23 after the fixed time + random time has elapsed, then AP1 transmits a frame destined for STA1-1. STA1-1 also stops demodulation, detects a received power value higher than the reception sensitivity, and starts frame reception.

[0108] At time t24, AP1 detects a received power value higher than the reception sensitivity and starts frame reception. At time t25, it normally receives the preamble of the received frame and confirms that it is in the Non-HE format, and confirms the frame type. At time t26, it is confirmed that the frame type in the MAC header is a management frame. Therefore, through the processing of step S32, demodulation continues, and at time t27, frame demodulation is completed. In the case where this frame is a beacon frame, the received power value can be recorded, or the BSS information of the transmitting source AP can be obtained from the information in the frame and recorded, etc.

[0109] As described above, in AP1, once the reception quality deteriorates due to simultaneous transmission for beacon frames and association frames, it will affect the connection of the wireless LAN itself. Therefore, the reception of this management frame is prioritized and simultaneous transmission is suppressed. In addition, since beacon frames, etc. generally do not use MIMO, they are suitable for measuring the received power value of frames transmitted from AP4. And the BSS information (performance, etc.) of AP4 can be obtained from the information in the beacon frame.

[0110] (Example 4)

[0111] The feature of Example 4 is that transmission control is performed according to each standard and function of the destination terminal in AP1. Here, since the conditions for successful frame reception are different according to the standard and function of the destination terminal, not only according to the state of the received frame as in the above-described examples, but also according to the information on the standard and function of the destination terminal to which transmission is desired, it is selected whether to perform simultaneous transmission. For example, if the destination terminal is a HE terminal, then even if a frame that becomes interference is received from another BSS, such as Figure 4Similar to STA1-1 shown, it is also possible to identify the BSS identifier and stop demodulation in advance. Therefore, in the destination terminal, even if an asynchronous interference frame is received before the desired frame, the demodulation of the interference frame can be stopped to normally receive the desired frame. On the other hand, in the case where the destination terminal is a Non HE terminal that does not have such a function, if the CCA threshold is controlled high to actively perform simultaneous transmission, and the desired frame arrives during the demodulation of the interference frame, the reception fails as a result.

[0112] Figure 10 Shows an example of the transmission processing steps of AP1 in Embodiment 4 of the present invention. In addition, in the AP and STA, it is assumed that the Figure 2 , Figure 6 , Figure 8 shown reception processing steps are executed. In Figure 10 , AP1 starts transmission preparation (S40) and confirms the destination of the frame to be transmitted (S41). Here, the standard and function of the frame that the destination terminal can correspond to are confirmed (S42), and it is judged whether the demodulation of the interference frame can be stopped (S43). For example, if the destination terminal is a HE terminal, a HE format frame is identified, and if the BSS identifier is identified in the preamble and the frame is identified as coming from another BSS, it is judged that the demodulation after the preamble of the interference frame can be stopped. If the destination terminal can stop demodulating the interference frame, CCA threshold control is implemented (S44), and the channel state is judged (S46). For example, as in the CCA threshold control in steps S10, S14, and S23 in the reception processing steps of the above embodiments, control is performed to make it a value higher than the default CCA threshold, increasing the chance that the channel becomes idle and implementing simultaneous transmission.

[0113] On the other hand, if the destination terminal is a Non HE terminal, since the demodulation of the interference frame cannot be stopped, AP1 does not implement CCA threshold control (S45), but judges the channel state (S46). For example, the CCA threshold control in steps S10, S14, and S23 in the reception processing steps of the above embodiments is not implemented, and it can be directly set to the default CCA threshold, or controlled to a CCA threshold that can detect the interference frame.

[0114] Figure 11A And Figure 11B Shows an example of the operations in steps S44 and S45. Here, it shows a control example in AP1 when judging whether to perform simultaneous transmission during the process of receiving a HE format frame from AP2, in the case where STA1-1 as a HE terminal is set as the destination and in the case where STA1-3 as a Non HE terminal is set as the destination.

[0115] In Figure 11AAmong them, at time t28, AP1 serving as an HE terminal and STA1-1 detect a received power value higher than the reception sensitivity and start frame reception. At time t29, they normally receive the preamble of the received frame, confirm it is in HE format, and confirm that the BSS identifier is another BSS, and set the CCA threshold (-66 dBm) for HE format. In this operation example, it is a received frame from AP2, and the received power value is lower than this CCA threshold, so it is determined that the channel is idle, demodulation is stopped, and simultaneous transmission is enabled. On the other hand, at time t28, STA1-3 serving as a Non HE terminal detects a received power value higher than the reception sensitivity and starts frame reception. At time t29, it normally receives the preamble of the received frame, but it cannot confirm that it is in HE format. Therefore, when the default CCA threshold (-82 dBm) is maintained, since the received power value of STA1-3 is higher than this CCA threshold, it is determined that the channel is busy, and demodulation continues.

[0116] If the channel is idle until time t30 after the fixed time + random time has elapsed, then AP1 sends a frame destined for STA1-1. STA1-1 stops demodulation at time t29 and can detect a received power value higher than the reception sensitivity at time t30 and start frame reception. In addition, STA1-3 of the Non HE terminal continues to demodulate the frame from AP2, but since this frame is in HE format and cannot be demodulated, it has no impact even if the reception of the HE format frame destined for STA1-1 overlaps.

[0117] In Figure 11B the situation at times t28 and t29 is the same as in Figure 11A AP1 and STA1-1 immediately stop demodulation upon receiving the preamble of the frame from AP2, but STA1-3 continues to demodulate the frame from AP2. Here, when AP1 sends a Non HE format frame destined for STA1-3, a Non HE terminal, even if the CCA threshold is controlled to make the channel idle, as in Figure 11A it is sent at time t30, and demodulation cannot be performed in STA1-3 that continues to demodulate the frame of AP2. Therefore, when AP1 does not control the CCA threshold and maintains the default, or controls it to be able to detect the CCA threshold of the frame from AP2, since it becomes busy in AP1, it waits until time t31 when the transmission of AP2 ends and the channel becomes idle and then sends. Thus, normal reception can be performed in STA1-3.

[0118] (Embodiment 5)

[0119] The feature of Embodiment 5 is that transmission control is performed according to the format and type of the transmission frame in each of AP1.

[0120] In Embodiment 4, the criteria and functions of the destination terminal of the frame transmitted by AP1 select whether simultaneous transmission is possible based on whether demodulation of interfering frames can be stopped. However, the feature of Embodiment 5 is that when the frame transmitted by AP1 is in HE format, beacon frame, management frame, etc., the CCA threshold is controlled in the same manner as in Embodiment 4, and whether simultaneous transmission is possible is selected.

[0121] Figure 12 Example 1 of the transmission processing steps of AP1 in Embodiment 5 of the present invention is shown.

[0122] In Figure 12 , AP1 starts transmission preparation (S50), confirms the format of the frame to be transmitted (S51), and determines whether it is in HE format (S52). Here, if the frame to be transmitted is in HE format, since it is a frame destined for an HE terminal that can stop demodulating interfering frames, CCA threshold control is performed (S53), and the channel state is determined (S55). For example, as in the CCA threshold control in steps S10, S14, and S23 in the reception processing steps of the above embodiments, it is controlled to a value higher than the default CCA threshold to increase the chance that the channel becomes idle and simultaneous transmission is performed.

[0123] On the other hand, if the frame to be transmitted is in Non HE format, since there is a possibility that it is a frame destined for a Non HE terminal that cannot stop demodulating interfering frames, AP1 does not perform CCA threshold control (S54), but determines the channel state (S55). For example, the CCA threshold control in steps S10, S14, and S23 in the reception processing steps of the above embodiments may not be performed, the default CCA threshold may be maintained, or it may be controlled to a CCA threshold that can detect interfering frames.

[0124] That is, if the transmission frame is in HE format, similar to the transmission frame of STA1-1 destined for an HE terminal as shown in Figure 11A , it is assumed that CCA threshold control is performed and simultaneous transmission is possible. On the other hand, if the transmission frame is in Non HE format, similar to the transmission frame of STA1-3 destined for a Non HE terminal as shown in Figure 11B , the transmission of AP2 is ended, and after the channel becomes idle, transmission is performed.

[0125] Figure 13 Example 2 of the transmission processing steps of AP1 in Embodiment 5 of the present invention is shown. In Figure 13In the process, AP1 starts to prepare for transmission (S50), confirms the type of frame to be transmitted (S56), and determines whether it is a frame type or frame subtype required for communication control of each wireless station, such as whether it is a management frame (S57). Here, if it is not a management frame, such as a data frame, CCA threshold control is implemented (S53), and the channel state is determined (S55). For example, as in the CCA threshold control of steps S10, S14, and S23 in the receiving processing steps of each embodiment described above, control is performed to become a value higher than the default CCA threshold, increasing the chance of the channel becoming idle and implementing simultaneous transmission.

[0126] On the other hand, if it is a management frame, since even a Non HE terminal that cannot stop demodulating the interference frame needs to receive it, AP1 does not implement CCA threshold control (S54), but determines the channel state (S55). For example, the CCA threshold control of steps S10, S14, and S23 in the reception processing steps of the above-mentioned embodiments may not be implemented, and the default CCA threshold may be maintained, or the CCA threshold may be controlled to be a CCA threshold that can detect interference frames.

[0127] That is, if the transmitted frame is a data frame, then Figure 11A Similarly, the CCA threshold control is implemented for the transmission frame of STA1-1, which is the destination of the HE terminal, and the transmission is enabled at the same time. On the other hand, if the transmission frame is a management frame, Figure 11B Similarly, the transmission frames of STA1-3 whose destination is the Non-HE terminal are transmitted after AP2 finishes transmission and the channel becomes idle.

[0128] Explanation of symbols

[0129] AP wireless base station (access point)

[0130] STA Wireless Terminal

[0131] 11 Sending terminal (HE terminal)

[0132] 12 Destination terminal (HE terminal)

[0133] 13 Destination Terminal (Non HE Terminal)

[0134] 14 Interference Terminal (HE Terminal)

[0135] 15 Interference terminal (Non HE terminal).

Claims

1. A wireless communication terminal, wherein the wireless communication terminal performs transmission and reception of frames based on carrier sense multiple access with collision avoidance (CSMA / CA) access control. The format of the basic service set (BSS) identifier of the wireless communication terminal as the transmission source included in the preamble of the frame is set to the HE format. The wireless communication terminal has a control unit that confirms the format of a received frame, where, The received frame is a frame received above a predetermined clear channel assessment (CCA) threshold. When the format of the received frame is the HE format and the BSS identifier of the received frame is the same as its own BSS, the received frame is continuously demodulated. When the BSS identifier of the received frame is different from its own BSS, the channel state is judged using the CCA threshold for the HE format. When it is judged to be an idle state, transmission is performed. When the format of the received frame is the Non-HE format, the control unit performs carrier sensing using a CCA threshold lower than the CCA threshold for the HE format. When it is judged that the channel is idle, demodulation is stopped and transmission is performed.

2. A wireless communication method, wherein the wireless communication method performs transmission and reception of frames based on carrier sense multiple access with collision avoidance (CSMA / CA) access control. The format of the BSS identifier of the wireless communication terminal as the transmission source included in the preamble of the frame is set to the HE format. The wireless communication method includes: Step 1, a wireless station of the BSS confirms the format of the received frame, wherein the received frame is a frame received above a predetermined CCA threshold; and Step 2, the wireless station of the BSS continuously demodulates the received frame when the format of the received frame is the HE format and the BSS identifier of the received frame is the same as its own BSS. When the BSS identifier of the received frame is different from its own BSS, the channel state is judged using the CCA threshold for the HE format. When it is judged to be an idle state, transmission is performed. In Step 2, when the format of the received frame is the Non-HE format, carrier sensing is performed using a CCA threshold lower than the CCA threshold for the HE format. When it is judged that the channel is idle, demodulation is stopped and transmission is performed.

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