Patent Publication Number: US-2017359821-A1

Title: Method and apparatus for reusing over obss txop

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to co-pending U.S. Provisional Patent Application No. 62/348,517, entitled “METHOD AND APPARATUS FOR REUSING OVER OBSS TXOP”, filed Jun. 10, 2016, the disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Field 
     The following relates generally to wireless communication and more specifically to reusing over overlapping basic service set (OBSS) frame(s) in a transmission opportunity (TXOP). 
     Background 
     Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). A wireless network, for example a wireless local area network (WLAN), such as a Wi-Fi (i.e., IEEE 802.11) network may include access point (AP) that may communicate with one or more stations (STAs) or mobile devices. The AP may be coupled to a network, such as the Internet, and may enable a mobile device to communicate via the network (or communicate with other devices coupled to the access point). A wireless device may communicate with a network device bi-directionally. For example, in a WLAN, an STA may communicate with an associated AP via downlink (DL) and uplink (UL). The DL (or forward link) may refer to the communication link from the AP to the station, and the UL (or reverse link) may refer to the communication link from the station to the AP. 
     A group of STAs that are communicating with an AP may be known as a basic service set (BSS). In some cases, the area of one BSS may overlap with the area of another BSS, which may be known as an OBSS. Transmissions from different devices within the OBSS may interfere with one another. Techniques used by each device to limit this interference, such as OBSS frame reusing rules, may limit the efficiency of communications within the OBSS. 
     SUMMARY 
     In one aspect of the disclosure, a method of wireless communication includes obtaining spatial reuse (SR) information from one or more nodes, performing a reuse check based on the obtained SR information for a transmission opportunity, wherein the performing includes determining whether the reuse check passes for at least one overlapping basic service set (OBSS) frame in the transmission opportunity based on at least one predetermined level in the obtained SR information, and reusing one or more remaining OBSS frames of the transmission opportunity after the at least one OBSS frame and any portion of the at least one OBSS frame after the determining the reuse check passes in response to the determining that the reuse check passes for the at least one OBSS frame. 
     In an additional aspect of the disclosure, an apparatus configured for wireless communication includes means for obtaining SR information from one or more nodesr, means for performing a reuse check based on the obtained SR information for a transmission opportunity, wherein the means for performing includes means for determining whether the reuse check passes for at least one OBSS frame in the transmission opportunity based on at least one predetermined level in the obtained SR information, and means for reusing one or more remaining OBSS frames of the transmission opportunity after the at least one OBSS frame and any portion of the at least one OBSS frame after the means for determining the reuse check passes in response to determination that the reuse check passes for the at least one OBSS frame. 
     In an additional aspect of the disclosure, a non-transitory computer-readable medium having program code recorded thereon. The program code further includes code to obtain SR information from one or more nodes, code to perform a reuse check based on the obtained SR information for a transmission opportunity, wherein the code to perform includes code to determine whether the reuse check passes for at least one OBSS frame in the transmission opportunity based on at least one predetermined level in the obtained SR information, and code to reuse one or more remaining OBSS frames of the transmission opportunity after the at least one OBSS frame and any portion of the at least one OBSS frame after execution of the code to determine the reuse check passes in response to determination that the reuse check passes for the at least one OBSS frame. 
     In an additional aspect of the disclosure, an apparatus configured for wireless communication is disclosed. The apparatus includes at least one processor, and a memory coupled to the processor. The processor is configured to obtain SR information from one or more nodes, to perform a reuse check based on the obtained SR information for a transmission opportunity, wherein the configuration to perform includes configuration of the at least one processor to determine whether the reuse check passes for at least one OBSS frame in the transmission opportunity based on at least one predetermined level in the obtained SR information, and to reuse one or more remaining OBSS frames of the transmission opportunity after the at least one OBSS frame and any portion of the at least one OBSS frame after execution of the configuration to determine the reuse check passes in response to determination that the reuse check passes for the at least one OBSS frame. 
     The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description, and not as a definition of the limits of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of the present disclosure may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
         FIG. 1  illustrating details of a WLAN for wireless communications. 
         FIG. 2  illustrates an example of a wireless communications system with OBSS. 
         FIG. 3  illustrates details of a TXOP. 
         FIG. 4  is a block diagram illustrating example blocks executed to implement one aspect of the present disclosure regarding reusing over OBSS TXOP. 
         FIG. 5  illustrates details of a TXOP in accordance with one aspect of the present disclosure. 
         FIG. 6  illustrates details of a TXOP in accordance with one aspect of the present disclosure. 
         FIG. 7  illustrates details of a TXOP in accordance with one aspect of the present disclosure. 
         FIG. 8  illustrates details of a TXOP in accordance with one aspect of the present disclosure. 
         FIG. 9  illustrates details of a TXOP in accordance with one aspect of the present disclosure. 
         FIG. 10  illustrates a block diagram of a reusing node in accordance with one aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In some wireless communications systems, a transmitting wireless device such as a station (STA) or an access point (AP) that is part of a basic service set (BSS) may perform a clear channel assessment (CCA) procedure to determine the availability of the radio frequency spectrum used for communication. Multiple BSSs can be in relative close proximity, and transmissions from an overlapping BSS (OBSS) may impact the ability of a device to obtain access to, or “win,” the channel. For example, if an STA detects a packet (e.g., a preamble) from another device, the STA may abstain from transmitting for the duration of the detected packet if the receive power of the packet is above a threshold. However, if the STA detects a packet from another device, it may still transmit if the received power of the packet is less than a threshold. In some cases, an STA may increase the threshold if the STA&#39;s transmission (TX) power is correspondingly decreased by some amount. 
     During a transmission opportunity (TXOP) that includes one or more OBSS frames, transmissions from multiple transmitting wireless devices may overlap. Conventionally, in order to reduce interferences, a transmitting wireless device (i.e., reusing device) may perform a CCA procedure for each OBSS frame to determine whether it is reusable. After performing such a reuse check, the reusing node may be able to use the remaining time of the “checked” OBSS frame. However, if a TXOP includes more than one OBSS frame, the transmitting wireless device may have to perform a reuse check, perform the reuse, and terminate reusing for each of the OBSS frames in TXOP. In this case, inefficiencies result, and a time gap between termination of reuse and start of reusing a following OBSS frame may further reduce a reuse gain. The present disclosure addresses this problem by enabling more than one OBSS frame to be reused based on a reuse check of one OBSS frame within a TXOP. By reusing the remaining OBSS TXOP instead of performing a reuse check per OBSS frame, the reuse gain can be improved due to longer continuous reuse time since the reuse check may be bypassed for remaining OBSS frames in the TXOP. 
       FIG. 1  illustrating details of a WLAN  100  for wireless communications. WLAN  100  may be a Wi-Fi network. WLAN  100  may include an AP  105  and multiple associated STAs  115 , which may represent devices such as mobile stations, personal digital assistants (PDAs), other handheld devices, netbooks, notebook computers, tablet computers, laptops, display devices (e.g., TVs, computer monitors, etc.), printers, etc. AP  105  and the associated STAs  115  may represent a BSS or an extended service set (ESS). The various STAs  115  in the network are able to communicate with one another through AP  105 . Also shown is a coverage area  110  of the AP  105 , which may represent a basic service area (BSA) of WLAN  100 . An extended network station (not shown) associated with WLAN  100  may be connected to a wired or wireless distribution system that may allow multiple APs  105  to be connected in an ESS. 
     Although not shown in  FIG. 1 , STA  115  may be located in the intersection of more than one coverage area  110  and may associate with more than one AP  105 . A single AP  105  and an associated set of STAs  115  may be referred to as a BSS. An ESS is a set of connected BSSs. A distribution system (not shown) may be used to connect APs  105  in an ESS. In some cases, coverage area  110  of AP  105  may be divided into sectors (also not shown). WLAN  100  may include APs  105  of different types (e.g., metropolitan area, home network, etc.), with varying and overlapping coverage areas  110 . Two STAs  115  may also communicate directly via a direct wireless link  125  regardless of whether both STAs  115  are in the same coverage area  110 . Examples of direct wireless links  125  may include Wi-Fi Direct connections, Wi-Fi Tunneled Direct Link Setup (TDLS) links, and other group connections. STAs  115  and APs  105  may communicate via a wireless link  120  according to the WLAN radio and baseband protocol for physical (PHY) and medium access control (MAC) layers from IEEE 802.11 and versions including, but not limited to, 802.11b, 802.11g, 802.11a, 802.11n, 802.11ac, 802.11ad, 802.11ah, etc. In other implementations, peer-to-peer connections or ad hoc networks may be implemented within WLAN  100 . In further implementations, WLAN  100  may be controlled by wide wireless access network (WWAN), such as a LTE network. 
     In some cases, STA  115  or AP  105  may operate in a shared or unlicensed frequency spectrum. These devices may perform a CCA prior to communicating in order to determine whether the channel is available. A CCA may include an energy detection procedure to determine whether there are any other active transmissions. For example, the device may infer that a change in a received signal strength indication (RSSI) of a power meter indicates that a channel is occupied. Specifically, signal power is that is concentrated in a certain bandwidth and exceeds a predetermined noise floor may indicate another wireless transmitter. A CCA may also include detection of specific sequences that indicate use of the channel. For example, another device may transmit a specific preamble prior to transmitting a data sequence. 
       FIG. 2  illustrates an example of a wireless communications system  200  with OBSS. Wireless communications system  200  may include AP  105 - a  and STA  115 - a  associated with a first BSS with a coverage area  110 - a . Wireless communications system  200  may also include AP  105 - b  and STA  115 - b , which may be associated with an OBSS having a coverage area  110 - b  that overlaps coverage area  110 - a . AP  105 - a , AP  105 - b , STA  115 - a , and STA  115 - b  may all communicate with one another and may be examples of the corresponding devices described with reference to  FIG. 1 . The examples described below with reference to STA  115  may be performed by any number of wireless devices. 
     In wireless communications system  200 , a transmitting wireless device (e.g., STAs  115 - a ,  115 - b  or AP  105 - a ,  105 - b ) may perform a CCA procedure to determine the availability of the radio frequency spectrum used for communication. In some cases, multiple BSSs can be in relative close proximity, and interference from STA  115 - b  may affect the transmission of STA  115 - a . STA  115 - a  may detect a preamble from STA  115 - b  and determine whether to transmit. The preamble may include spatial reuse (SR) information. SR information may be obtained by decoding the detected preamble. SR information may include a predetermined CCA level, or a predetermined interference level. If STA  115 - a  detects the SR information from STA  115 - b , STA  115 - a  may refrain from transmitting if a received RSSI is above the predetermined CCA level, and/or if an estimated interference to STA  115 - b  is above the predetermined interference level. The interference to STA  115 - b  may be estimated based on path loss measured by STA  115 - a . However, STA  115 - a  may proceed with transmitting if a received RSSI is below the predetermined CCA level, and/or if an estimated interference to STA  115 - b  is below the predetermined interference level. 
       FIG. 3  illustrates details of a transmission opportunity (TXOP)  300 . TXOP  300  may include one or more OBSS frames  305 - a ,  305 - b ,  305 - c  . . . . During TXOP  300 , transmissions from multiple transmitting wireless devices may overlap. Conventionally, in order to reduce interferences, a transmitting wireless device may perform a CCA procedure for each of OBSS frames  305 - a ,  305 - b ,  305 - c  . . . to determine whether to transmit in such OBSS frame. In other words, a transmitting wireless device may perform a CCA procedure for each of frames  305 - a ,  305 - b ,  305 - c  . . . to determine whether it is reusable. Accordingly, a transmitting wireless device may also be referred to as a reusing node herein. After performing a CCA procedure/reuse check, a transmitting wireless device/reusing node may be able to use the remaining time of such “checked” OBSS frame. For example, if a reuse check is performed for OBSS frame  305 - a , and such reuse check is completed at T 1    315 , a reusing node may be only able to reuse a time period  310  between T 1    315  and T 2    320  within OBSS frame  305 - a . Still further, if a TXOP includes more than one OBSS frame, such as TXOP  300  in  FIG. 3 , the transmitting wireless device may have to perform a reuse check, perform the reuse, and terminate reusing for each of the OBSS frames in TXOP, further compounding the inefficiencies associated with limited reuse time period due to performing reuse check. A time gap between termination of reuse and start of reusing a following OBSS frame may reduce a reuse gain. As a result, overall communication efficiency may degrade. 
     In some instances, as described in further detail below with respect to  FIG. 4 , more than one OBSS frame may be reused based on a reuse check of one OBSS frame within a TXOP. In other words, a reusing node may perform a reuse check of one OBSS frame within a TXOP, and reuse the entire remaining OBSS TXOP instead of reusing just the one OBSS frame for which the reuse check was performed. In other instances, one or more reuse checks may be performed for one or more OBSS frames, but any number of OBSS frames after completion of the reuse check(s) remaining within the TXOP may be reused. By reusing the remaining OBSS TXOP instead of performing a reuse check per OBSS frame, the reuse gain can be improved due to longer continuous reuse time since the reuse check may be bypassed for remaining OBSS frames in the TXOP. 
       FIG. 4  is a block diagram illustrating example blocks executed to implement one aspect of the present disclosure regarding reusing over OBSS TXOP. The example blocks may be implemented by a reusing node, such as APs  105  and STAs  115  in  FIGS. 1, 2 and 10 . The reusing node, as illustrated in  FIG. 10 , may include a processor  1025 , which operates to execute logic, computer instructions, software  1020  stored in a memory  1015 , an antenna  1005  to transmit/receive signals, and a transceiver  1010  to process signals. At block  400 , spatial reuse (SR) information may be obtained from one or more nodes, which may be an access point, or a station, such as APs  105  and STAs  115  in  FIGS. 1 and 2 . At block  405 , a reuse check may be performed based on the obtained SR information for a transmission opportunity. The reuse check may help a reusing node to determine one or more distances with respect to soliciting and responding nodes, and determine whether to transmit/reuse OBSS frames in TXOP accordingly. Performing the reuse check may include determining whether the reuse check passes for at least one overlapping basic service set (OBSS) frame in the transmission opportunity based on at least one predetermined level in the obtained SR information. At block  410 , in response to the determining that the reuse check passes for the at least one OBSS frame, one or more remaining OBSS frames of the transmission opportunity after the at least one OBSS frame and any portion of the at least one OBSS frame after the determining the reuse check passes may be reused. 
     The predetermined level may be one or more of: a clear channel assessment (CCA) level, or an interference level. Accordingly, determining whether the reuse check passes for the at least one OBSS frame may include determining a received signal strength indicator (RSSI), and/or determining an estimated interference to one or more neighboring nodes by a reusing node, and comparing them with the predetermined level. In some cases, a reuse check may pass when an RSSI is below a predetermined CCA level. In other cases, a reuse check may pass when an estimated interference is below a predetermined interference level. Oppositely, a reuse check may not pass when an RSSI is above a predetermined CCA level, or when an estimated interference is above a predetermined interference level. 
       FIG. 5  illustrates details of a TXOP  500  in accordance with one aspect of the present disclosure. The same as TXOP  300  in  FIG. 3 , TXOP  500  also includes one or more OBSS frames  305 - a ,  305 - b ,  305 - c  . . . . In some aspects of the present disclosure, the duration of TXOP  500  may be determined based on a network allocation vector (NAV). The NAV may be obtained by a reusing node from the received SR information. In TXOP  500 , reusing procedures as provided in  FIG. 4  are implemented. As a result, the entire duration of TXOP  510  after a reuse check is completed at T 1    515  may be reused by a reusing node. Such duration  510  may include one or more OBSS frames after the “checked” OBSS frame, such as frame  305 - c , and any remaining time of the OBSS frame after the completion of reuse check, such as remaining time of frame  305 - b  after T 1    515 . The reuse check may include one or more reuse checks for one or more OBSS frames in TXOP  500 . Accordingly, a reusing node may have longer continuous reuse time. 
     The reusing methods and concepts as provided above and  FIGS. 4 and 5  may be applicable to different types of communication structure, such as single user communications, or multiple users communications. Single user communications may involve two different nodes that exchange transmissions in OBSS frames, such as a soliciting node, which is also referred to as a transmitter, and a responding node, which is also referred to as a receiver. Multiple user communications may involve more nodes that exchange transmissions in OBSS frames, such as multiple soliciting nodes and multiple responding nodes, a soliciting node and multiple responding nodes, or multiple soliciting nodes and a responding node. A reusing node may detect and measure signals simultaneously transmitted from multiple nodes. The reusing methods and concepts as provided above and  FIGS. 4 and 5  may be also applicable to different types of transmission modes. Exemplary transmission modes and corresponding reusing methods are illustrated below with  FIGS. 6-9 . 
       FIG. 6  illustrates details of a TXOP  600  in accordance with one aspect of the present disclosure. TXOP  600  may include one or more OBSS frames. In TXOP  600 , a node may transmit a frame  615 , and another node may transmit a frame  620 . The nodes may be APs  105 , or STAs  115  as provided in  FIGS. 1 and 2 , or any other network devices capable of transmitting and receiving signals, information, or data. In Mode 1, frame  615  may be an enhanced request to send (e-RTS) frame, and frame  620  may be an enhanced clear to send (e-CTS) frame. Compared with legacy RTS/CTS, e-RTS/e-CTS carries spatial reuse (SR) information to guide reusing node for reuse decision. In an e-RTS frame, a soliciting node may transmit SR information at the transmitter side. In e-CTS frame, a responding node may transmit SR information at receiver side. In order to determine whether to transmit in TXOP  600 , a reusing node for Mode 1 may obtain SR information from both nodes on frame  615  and frame  620 , and perform a reuse check for both frame  615  and frame  620 . A reusing node may reuse a duration  610  in response to the determining the reuse check passes for both frame  615  and frame  620 . Duration  610  may start from T 1    630 , at which a reuse check is determined to pass, and end at the end of TXOP  600 . Alternatively, duration  610  may end before the end of TXOP  600  in accordance with the obtained SR information. Duration  610  may include the remaining time period in frame  620  after completion of the reuse check at T 1    630 , and any subsequent OBSS frames in TXOP  600 , such as frame  625  and OBSS frames after frame  625 . In some cases, the reuse check may only pass for frame  620 . In response to such reuse checking results, a reusing node may only reuse OBSS frames transmitted by the soliciting node, which is typically right after frame  620 , such as frame  625 . 
     In Mode 2, frame  615  may be a trigger frame, and frame  620  may be a legacy clear to send (L-CTS) frame, or a data frame. In the trigger frame, a soliciting node may transmit information to another node to solicit the receiver&#39;s response or data transmissions. A trigger frame may be an e-RTS frame, a frame trigger data transmissions, or a data frame. In the L-CTS frame, the responding node may transmit L-CTS information, which does not include the SR information. In order to determine whether to transmit in TXOP  600 , a reusing node for Mode 2 may obtain SR information from the soliciting node on frame  615 , perform a reuse check for frame  620 , and perform an additional check for frame  615 . 
     The additional check may be performed by obtaining at least one threshold, such as a CCA threshold, or an interference threshold, and comparing such threshold to an RSSI of the trigger frame, or an estimated interference to the sender of frame  615 . In some cases, an additional check for frame  615  may pass when an RSSI of frame  615  is below a predetermined CCA threshold. In other cases, an additional check for frame  615  may pass when an estimated interference to the sender of frame  615  is below a predetermined interference threshold. Oppositely, an additional check may not pass when an RSSI of frame  615  is above a predetermined CCA threshold, or when an estimated interference to the sender of frame  615  is above a predetermined interference threshold. The threshold may be obtained from received SR information, or a preamble of frame  615 , or determined by a reusing node. 
     A reusing node may reuse duration  610  in response to the determining the reuse check passes for frame  620 , and the additional check passes for frame  615 . Duration  610  may start from T 1    630 , at which a reuse check is determined to pass, and end at the end of TXOP  600 . Alternatively, duration  610  may end before the end of TXOP  600  in accordance with the obtained SR information. Duration  610  may include the remaining time period in frame  620  after the completion of reuse check, and any subsequent OBSS frames in TXOP  600 , such as frame  625  and OBSS frames after frame  625 . In some aspects of the present disclosure, a reusing node may simultaneously receive L-CTS frames from multiple nodes. Accordingly, the reusing mode may perform a reuse check for all of such multiple L-CTS frames from multiple nodes. 
       FIG. 7  illustrates details of a TXOP  700  in accordance with one aspect of the present disclosure. TXOP  700  may include one or more OBSS frames. In TXOP  700 , a soliciting node (Txer) may transmit a frame  715 , a first responding node (Rxer 1) and a second responding node (Rxer 2) may transmit frames  720  and  730  simultaneously. Txer, Rxer 1, and Rxer 2 may be APs  105 , or STAs  115  as provided in  FIGS. 1 and 2 , or any other network devices capable of transmitting and receiving signals, information, or data. In Mode 3, frame  715  may be a trigger frame, and frames  720  and  730  may be solicited frames. A trigger frame may be an e-RTS frame, a frame trigger data transmissions, or a normal data frame. A solicited frame may be a L-CTS frame, a legacy acknowledge frame, or a data frame. In order to determine whether to transmit in TXOP  700 , a reusing node for Mode 3 may obtain SR information from the soliciting node on frame  715 , perform a reuse check for the frame  715 , and perform an additional check for frames  720  and  730 . 
     The additional check may be performed by obtaining at least one threshold, such as a CCA threshold, or an interference threshold, and comparing such threshold with an aggregated RSSI of frames  720  and  730 , or an estimated individual or total interference to the senders of frames  720  and  730 . In some cases, an additional check for frames  720  and  730  may pass when the aggregated RSSI of frames  720  and  730  are below a predetermined CCA threshold. In other cases, an additional check for frames  720  and  730  may pass when an estimated individual or total interference to the senders of the frames  720  and  730  are below a predetermined interference threshold. Oppositely, an additional check may not pass when the aggregated RSSI of frames  720  and  730  are above a predetermined CCA threshold, or when an estimated interference to the senders of frames  720  and  730  is above a predetermined interference threshold. The threshold may be obtained from received SR information, a preamble of frame  715 , or preambles of frames  720  and  730 , or determined by a reusing node. 
     A reusing node my reuse duration  710  in response to the determining the reuse check passes for frame  715 , and the additional check passes for frames  720  and  730 . Duration  710  may start from T 1    735 , at which both a reuse check and an additional check are determined to pass, and end at the end of TXOP  700 . Alternatively, duration  710  may end before the end of TXOP  700  in accordance with the obtained SR information. Duration  710  may include the remaining time period in frames  720  and  730  after the completion of reuse check and additional check, and any subsequent OBSS frames in TXOP  700 , such as frame  725  and OBSS frames after frame  725 . 
     In Mode 3, since multiple nodes may transmit solicited frames at the same time, such as second frames  720  and  730 , a reusing node may calculate an RSSI, and/or estimate an individual or total interference to such nodes based on the aggregated RSSI received from such nodes, and/or path loss of signals from such nodes. 
       FIG. 8  illustrates details of a TXOP  800  in accordance with one aspect of the present disclosure. TXOP  800  may include one or more OBSS frames. In TXOP  800 , a soliciting node (Txer) may transmit a frame  815 , a responding node (Rxer) may transmit a frame  820 , and the Txer may further transmit a frame  825 . Txer and Rxer may be APs  105 , or STAs  115  as provided in  FIGS. 1 and 2 , or any other network devices capable of transmitting and receiving signals, information, or data. In Mode 4, frame  815  may be a legacy request to send (L-RTS) frame, or a legacy data frame, frame  820  may be a L-CTS frame or a legacy acknowledge frame, and third frame  825  may be an enhanced frame. The enhanced frame may be an 802.11ax frame, or other frames under 802.11 standards. In the L-RTS frame, a soliciting node may transmit L-RTS information. In the L-CTS frame, a responding node may transmit L-CTS information. In the legacy data frame, a soliciting node may transmit legacy data. In the legacy acknowledge frame, a soliciting node may transmit acknowledge message in response to the status of receiving data transmissions. However, L-RTS frame, L-CTS frame, legacy data frame, or legacy acknowledgment frame may not carry SR information. As such, in Mode 4, a reusing node may obtain SR information on the enhanced frame. 
     In order to determine whether to transmit in TXOP  800 , a reusing node for Mode 4 may obtain SR information from the soliciting node on frame  825 , perform a reuse check for frame  820 , and perform an additional check for frames  815  and  825 . The additional check may be performed by obtaining at least one threshold, such as a CCA threshold, or an interference threshold, and comparing such threshold with an RSSI of frames  815  and  825 , or an estimated interference to the senders of frames  815  and  825 . In some cases, an additional check for frames  815  and  825  may pass when RSSIs of frames  815  and  825  are below a predetermined CCA threshold. In other cases, an additional check for frames  815  and  825  may pass when estimated interferences to the senders of frames  815  and  825  are below a predetermined interference threshold. Oppositely, an additional check may not pass when RSSIs of frames  815  and  825  are above a predetermined CCA threshold, or when estimated interferences to the senders of frames  815  and  825  are above a predetermined interference threshold. The threshold may be obtained from received SR information in frame  825 , a preamble of frame  815  or a preamble of frame  820 , or determined by a reusing node. 
     A reusing node my reuse duration  810  in response to the determining the reuse check passes for frame  820 , and the additional check passes for frames  815  and  825 . Duration  810  may start from T 1    835 , at which both a reuse check and an additional check are determined to pass, and end at the end of TXOP  800 . Alternatively, duration  810  may end before the end of TXOP  800  in accordance with the obtained SR information. Duration  810  may include the remaining time period in frame  825  after the completion of reuse check and additional check, and any subsequent OBSS frames in TXOP  800 , such as frame  830  and OBSS frames after frame  830 . 
       FIG. 9  illustrates details of a TXOP  900  in accordance with one aspect of the present disclosure. TXOP  900  may include one or more OBSS frames. In TXOP  900 , a soliciting node may transmit a frame  915 . In Mode 5, frame  915  may be an enhanced frame that carriers SR information. The enhanced frame may be an 802.11ax frame, or other frames under 802.11 standards. In order to determine whether to transmit in TXOP  900 , a reusing node for Mode 5 may obtain SR information from the soliciting node on frame  915 , perform a reuse check for frame  915 , and determine whether a reusing indicator is signaled on frame  915 . The reusing indicator may be part of SR information of frame  915 . The reusing indicator may be one (1) bit in SR information field of HE-SIG-A. A reusing node may reuse duration  910  in response to the determining the reuse check passes for frame  915 , and the reusing indicator is signaled on frame  915 . Duration  910  may start from T 1    930 , at which a reuse check has been determined to pass and a reusing indicator has been determined to be signaled, and end at the end of TXOP  900 . Alternatively, duration  910  may end before the end of TXOP  900  in accordance with the obtained SR information. Duration  910  may include the remaining time period in frame  915  after T 1    930 , and any subsequent OBSS frames in TXOP  900 , such as frames  920  and  925  and OBSS frames after frame  925 . During frames  920  and  925 , a soliciting node, a responding node, or a reusing node may send transmissions. 
       FIG. 10  illustrate a block diagrams of a reusing node  1000  in accordance with one aspect of the present disclosure. Reusing node  1000  may be an access point, or a station, such as APs  105  and STAs  115  in  FIGS. 1 and 2 . Reusing node  1000  may include various components including an antenna  1005 , a transceiver  1010 , a memory  1015 , software  1020 , a processor  1025 , a SR information obtaining module  1030 , a reuse checking module  1035 , and a TXOP reusing module  1040 . Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses). Transceiver  1010  may communicate bi-directionally, via one or more antennas, wired, or wireless links, with one or more networks, as described above. For example, transceiver  1010  may communicate bi-directionally with an AP  105  or an STA  115 . Transceiver  1010  may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas. In some cases, Reusing node  1000  may include a single antenna  1005 . However, in some cases Reusing node  1000  may have more than one antennas  1005 , which may be capable of concurrently transmitting or receiving multiple wireless transmissions. 
     Memory  1015  may include RAM and ROM. Memory  1015  may store computer-readable, computer-executable software including instructions that, when executed, cause the processor to perform various functions described herein. For example, memory  1015  may store data and program codes for execution of SR information obtaining module  1030 , reuse checking module  1035 , and TXOP reusing module  1040 . SR information obtaining module  1030  may be executed to obtain SR information from a soliciting node and/or a responding node. Reuse checking module  1035  may be executed to perform a reuse check based on the obtained SR information for a transmission opportunity. Reuse checking module  1035  may be further executed to determine whether the reuse check passes for at least one OBSS frame in the transmission opportunity based on at least one predetermined level in the obtained SR information. TXOP reusing module may be executed to reuse one or more remaining OBSS frames of the transmission opportunity after the at least one OBSS frame and any portion of the at least one OBSS frame after the determining the reuse heck passes in response to the determining that the reuse check passes for the at least one OBSS frame. Processor  1025  may include an intelligent hardware device, (e.g., a CPU, a microcontroller, an ASIC, etc.) 
     Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     The functional blocks and modules in  FIGS. 4 and 10  may comprise processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof. 
     Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Skilled artisans will also readily recognize that the order or combination of components, methods, or interactions that are described herein are merely examples and that the components, methods, or interactions of the various aspects of the present disclosure may be combined or performed in ways other than those illustrated and described herein. 
     The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. 
     In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. Computer-readable storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, a connection may be properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL), then the coaxial cable, fiber optic cable, twisted pair, or DSL, are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
     As used herein, including in the claims, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of” indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) or any of these in any combination thereof. 
     The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.