Apparatus and method for switching channels

Abstract

A method for switching channels in a wireless local area network is provided. A station, as a member of a Basic Service Set (BSS), receives information from an associated access point (AP) regarding the Non-Primary Channel Access (NPCA) primary channel within the BSS bandwidth of that BSS. The station receives inter-BSS Physical Layer Protocol Data Units (PPDUs) on the BSS primary channel and switches from the BSS primary channel to the NPCA primary channel to perform NPCA operations when the following conditions are met: (i) the channel occupied by the inter-BSS PPDU does not overlap with the NPCA primary channel, and (ii) the station maintains the value of the Network Allocation Vector (NAV) counter within the BSS at zero.

Description

Technical Field

[0001] This disclosure relates to wireless local area networks (WLANs), and more specifically, to an apparatus and method for switching channels in a WLAN. Background Technology

[0002] A wireless local area network (WLAN) can consist of one or more access points (APs) that provide a shared wireless communication medium for use by a number of client devices (also known as stations (STAs)).

[0003] A single access point (AP) and its associated set of STAs are called a basic service set (BSS). When two or more BSSs managed by different APs are close enough to listen to each other and are operating on the same frequency channel, an overlapping basic service set (OBSS) occurs. OBSS can lead to unnecessary waiting and lower speeds.

[0004] WLAN supports transmission at various bandwidths, such as 20MHz, 40MHz, 80MHz, 160MHz, and 320MHz. Wideband channels include multiple 20MHz channels, each of which can be classified as a primary or secondary channel. To access a wideband channel (>20MHz), the primary channel (e.g., the primary 20MHz channel) must be idle. If the primary channel is busy, the AP / STA cannot transmit on any idle secondary channel, even if one exists.

[0005] To address the OBSS problem, non-primary channel access is proposed. Since the AP / STA can utilize available secondary channels when the primary channel is busy but the secondary channel is available, spectrum utilization can be improved. Summary of the Invention

[0006] This disclosure provides a method for switching channels in a wireless local area network.

[0007] This disclosure also provides an apparatus for a wireless local area network.

[0008] In one embodiment, a method for switching channels in a wireless local area network is provided. The method is performed by a site that is a member of a Basic Service Set (BSS) and includes: receiving information about a Non-Main Channel Access (NPCA) primary channel within the BSS bandwidth of the BSS from an associated access point (AP) corresponding to the BSS; receiving inter-BSS Physical Layer Protocol Data Units (PPDUs) on the BSS primary channel, the BSS primary channel being a common working channel for all member sites within the BSS, the inter-BSS PPDU being transmitted by at least one of an inter-BSS site that is not a member of the BSS or an AP that does not correspond to the BSS; and switching from the BSS primary channel to the NPCA primary channel to perform NPCA operation when both of the following conditions (i) and (ii) are met: (i) the channel occupied by the inter-BSS PPDU does not overlap with the NPCA primary channel; and (ii) the site maintains a Network Allocation Vector (NAV) counter within the BSS at a value of zero, the BSS NAV counter being updated by the BSS PPDU being transmitted by at least one of an intra-BSS site that is a member of the BSS or the associated AP.

[0009] In another embodiment, a device for a wireless local area network is provided. The device, as a member of a basic service set (BSS), includes: a processor; and a memory operatively coupled to the processor and configured to store instructions that, when executed by the processor, cause the device to perform multiple functions. The functions include: receiving information about the non-primary channel access (NPCA) primary channel within the BSS bandwidth of the BSS from the associated access point (AP) corresponding to the BSS; receiving inter-BSS physical layer protocol data units (PPDUs) on the BSS primary channel, the BSS primary channel being a common working channel for all member sites within the BSS, the inter-BSS PPDU being transmitted by at least one of an inter-BSS site that is not a member of the BSS or an AP that does not correspond to the BSS; and switching from the BSS primary channel to the NPCA primary channel to perform NPCA operation when both of the following conditions (i) and (ii) are met: (i) the channel occupied by the inter-BSS PPDU does not overlap with the NPCA primary channel; and (ii) the device maintains the value of the intra-BSS network allocation vector (NAV) counter at zero, the intra-BSS NAV counter being updated by the intra-BSS PPDU being transmitted by at least one of an intra-BSS site that is a member of the BSS or the associated AP.

[0010] When the primary channel is occupied by BSS inter-service traffic, the STA can access the radio medium on the alternative primary channel. Attached Figure Description

[0011] Figure 1A block diagram of an exemplary wireless communication network is shown.

[0012] Figure 2 A block diagram of an exemplary wireless communication device is shown.

[0013] Figure 3 An example of a wireless channel that includes multiple sub-channels is shown.

[0014] Figure 4 This shows an example of an NPCA operation.

[0015] Figure 5 An example of NPCA operation according to an embodiment of the present invention is shown.

[0016] Figure 6 An example of NPCA operation according to another embodiment of the present invention is shown.

[0017] Figure 7 A method for switching channels according to an embodiment of the present invention is shown.

[0018] Figure 8 An NPCA operation method according to an embodiment of the present invention is shown.

[0019] Figure 9 An example of NPCA operation according to an embodiment of the present invention is shown.

[0020] Figure 10 An example of NPCA operation according to an embodiment of the present invention is shown.

[0021] Figure 11 An example of NPCA operation according to an embodiment of the present invention is shown.

[0022] Figure 12 An example of NPCA operation according to an embodiment of the present invention is shown. Detailed Implementation

[0023] The following description is directed to certain embodiments and is intended to describe the inventive aspects of this disclosure. However, those skilled in the art will readily recognize that the teachings in this disclosure can be applied in a variety of different ways. The embodiments can be implemented in any apparatus, system, or network capable of transmitting and receiving radio frequency (RF) signals in accordance with one or more of the following standards: IEEE 802.11, IEEE 802.15, the Bluetooth® standard defined by the Bluetooth Special Interest Group (SIG), or the Long Term Evolution (LTE), 3G, 4G, or 5G (New Radio (NR)) standards developed by the 3GPP. The embodiments can also be implemented using one or more of the following techniques or methods: Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal FDMA (OFDMA), Single Carrier FDMA (SC-FDMA), Single User (SU) Multiple Input Multiple Output (MIMO), and Multi User (MU) MIMO. The implementation scheme may also employ other wireless communication protocols or RF signals suitable for one or more of the following: Wireless Personal Area Network (WPAN), Wireless Local Area Network (WLAN), Wireless Wide Area Network (WWAN), or Internet of Things (IoT) networks.

[0024] Figure 1 A block diagram of an exemplary wireless communication network is shown.

[0025] Depending on some aspects, the wireless communication network 10 may be an example of a wireless local area network (WLAN), such as a Wi-Fi network (hereinafter also referred to as WLAN 10). For example, WLAN 10 may be a network implementing at least one of the IEEE 802.11 family of wireless communication protocol standards (e.g., as defined by the IEEE 802.11-2016 specification or its revisions (including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11be, and 802.11bn)). WLAN 10 may include multiple wireless communication devices, such as access points (APs) 11 and multiple stations (STAs) 12. Although only one AP 11 is shown in the figure, WLAN 10 may also include multiple APs.

[0026] Each STA 12 may also be referred to as a mobile site (MS), mobile device, mobile handheld device, wireless handheld device, access terminal (AT), user equipment (UE), subscriber station (SS), or subscriber unit, etc. STA 12 can represent various devices, such as mobile phones, personal digital assistants (PDAs), other handheld devices, netbooks, laptops, tablets, portable computers, display devices (e.g., televisions, computer monitors, navigation systems, etc.), music or other audio / stereo devices, remote control devices (“remote controllers”), printers, kitchen appliances, or other household appliances, etc.

[0027] A single AP 11 and its associated group of STAs 12 can be referred to as a Basic Service Set (BSS), which is managed by the respective AP 11. The BSS can be identified to users by a Service Set Identifier (SSID), and also to other devices by a Basic Service Set Identifier (BSSID), which can be the Media Access Control (MAC) address of the AP 11. The AP 11 periodically broadcasts beacon frames (“beacons”) including the BSSID to enable any STA 12 within the AP 11's wireless coverage area to “associate” or reassociate with the AP 11, thereby establishing or maintaining a communication link with the AP 11 (hereinafter also referred to as a “Wi-Fi link”). For example, the beacon may include an identifier of the primary channel used by the respective AP 11, and a timing synchronization function for establishing or maintaining time synchronization with the AP 11. The AP 11 can provide access to external networks to each STA 12 in the WLAN via their respective communication links.

[0028] To establish a communication link with AP 11, each STA 12 is configured to perform passive or active scanning operations on frequency channels in one or more frequency bands (e.g., 2.4 GHz, 5 GHz, 6 GHz, or 60 GHz bands). For passive scanning, STA 12 listens for beacons (measured in units of time (TU), where one TU can be equal to 1024 microseconds (μs)) transmitted by each AP 11 at periodic time intervals called Target Beacon Transmission Time (TBTT). For active scanning, STA 12 generates and sequentially transmits probe requests on each channel to be scanned and listens for probe responses from AP 11. Each STA 12 can be configured to identify or select an AP 11 to associate with based on the scanning information obtained through passive or active scanning, and perform authentication and association operations to establish a communication link with the selected AP 11. AP 11 assigns an Association Identifier (AID) to STA 12 upon completion of the association operation, and AP 11 uses this AID to track STA 12.

[0029] AP 11 and STA 12 can operate and communicate according to the IEEE 802.11 series of wireless communication protocol standards (via their respective communication links). These standards define the radio and baseband protocols for the physical layer (PHY) and media access control (MAC) layers of WLAN. AP 11 and STA 12 in WLAN 10 can transmit frames on frequency bands such as 2.4 GHz, 5 GHz, 60 GHz, 3.6 GHz, and 900 MHz.

[0030] Each frequency band can include multiple channels (which can be used as sub-channels of a larger bandwidth channel). For example, a Physical Layer Protocol Data Unit (PPDU) can be transmitted in the 2.4 GHz and 5 GHz frequency bands, each band being divided into multiple 20 MHz channels. Therefore, the PPDU is transmitted on a physical channel with a minimum bandwidth of 20 MHz, but wider channels can be formed through channel bonding. For example, a PPDU can be transmitted on physical channels with bandwidths of 40 MHz, 80 MHz, 160 MHz, or 320 MHz by bonding multiple 20 MHz channels (which may be called sub-channels) together.

[0031] Uplink (UL) indicates that a signal (or message or PPDU) is transmitted from a STA to an AP; downlink (DL) indicates that a signal (or message or PPDU) is transmitted from an AP to one or more STAs.

[0032] Figure 2 A block diagram of an exemplary wireless communication device is shown.

[0033] In some implementations, the wireless communication device 50 may be for STA (such as the reference above). Figure 1 One example is a device (such as one of the STA12s described above). In some embodiments, the wireless communication device 50 may also be for an AP (such as those described above). Figure 1 An example of the device described in AP 11. The wireless communication device 50 is capable of transmitting (or outputting for transmission) and receiving wireless communications (e.g., in the form of wireless packets). For example, the wireless communication device 50 may be configured to transmit and receive packets in the form of PPDUs and / or MAC Protocol Data Units (MPDUs) conforming to the IEEE 802.11 wireless communication protocol standards—such as the IEEE 802.11-2016 specification or its revisions (including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11be, 802.11bn).

[0034] The wireless communication device 50 may be or may include a chip, system-on-a-chip (SoC), chipset, package, or device, which includes one or more processors 51. Processor 51 may include intelligent hardware modules or devices, such as a processing core, processing module, central processing unit (CPU), microprocessor, microcontroller, digital signal processor (DSP), application-specific integrated circuit (ASIC), programmable logic device (PLD) (e.g., field-programmable gate array (FPGA)), discrete gate or transistor logic, discrete hardware components, or any combination thereof used to perform the functions described herein. Processor 51 processes information received via transceiver 53 and processes information to be output via transceiver 53 through a wireless medium. For example, processor 51 may implement a physical layer (PHY) and / or a MAC layer and is configured to perform various operations related to the generation and transmission of PPDUs, MPDUs, frames, or packets.

[0035] Memory 52 may include tangible storage media such as random access memory (RAM) or read-only memory (ROM), or combinations thereof. Memory 52 may also store non-transitory software code executable by a processor or computer, containing instructions that, when executed by processor 51, cause wireless communication device 50 to perform various wireless communication operations described herein, including the generation, transmission, reception, and interpretation of PPDU, MPDU frames, or packets. For example, the various functions of the components disclosed herein, or the various modules or steps of the methods, operations, processes, or algorithms disclosed herein, may be implemented as one or more modules of one or more computer programs.

[0036] Transceiver 53 typically includes at least one radio frequency (RF) transmitter (or “transmit link”) for transmitting radio signals and at least one RF receiver (or “receive link”) for receiving radio signals. For example, the RF transmitter and RF receiver may include various DSP circuitry, each including at least one power amplifier (PA) and at least one low-noise amplifier (LNA). The RF transmitter and RF receiver may be further coupled to one or more antennas. For example, in some embodiments, wireless communication device 50 may include multiple transmit antennas (each with a corresponding transmit link) and multiple receive antennas (each with a corresponding receive link) or coupled to said antennas.

[0037] A PPDU is a data block or data unit in a WLAN. A PPDU may include a preamble and a data portion. The data portion includes one or more PHY Service Data Units (PSDUs) following the preamble. The data portion may be referred to as the payload. The PPDU preamble may carry information necessary for interpreting the PPDU. The preamble may include bandwidth information indicating the transmit bandwidth of the PPDU. The preamble may include STA-specific scheduling information, such as MCS and RU (Resource Allocation) allocation. The preamble may include Transmitter Meeting (TXOP) information.

[0038] Figure 3 An example of a wireless channel that includes multiple sub-channels is shown.

[0039] Channel mapping for a specific frequency band (e.g., 2.5 GHz, 5 GHz, 6 GHz, etc.) can define multiple sub-channels. Each sub-channel can have a uniform channel width W = 20 MHz, but the techniques described in this specification are not limited to 20 MHz. The channel width W can be less than or greater than 20 MHz.

[0040] Some WLAN devices are capable of transmitting with higher bandwidth using a wireless channel composed of multiple sub-channels. When a WLAN device can transmit using an 80MHz BSS operating channel, it will use a group of four sub-channels (one primary 20MHz channel, one secondary 20MHz channel, and one secondary 40MHz channel). Figure 3 In the examples, the bandwidth of the BSS operating channel can be 20MHz, 40MHz, 80MHz, and 160MHz. Although the BSS operating channel is shown as contiguous in the channel mapping, in some implementations, the BSS operating channel may contain one or more sub-channels that are not adjacent in the channel mapping. Furthermore, in some implementations, larger groups of channels may be used. For example, the bandwidth of the operating channel may be 320MHz, 640MHz, or greater. A 320MHz bandwidth may be divided into sixteen 20MHz sub-channels.

[0041] The primary channel is the common operating channel for all STAs that are members of the BSS. Secondary channels are associated with the primary channel and are used to form a wider channel than the primary channel. For example, in an 80MHz BSS, the secondary 20MHz channel adjacent to the primary 20MHz channel, together with the primary 20MHz channel, forms the primary 40MHz channel of that 80MHz BSS; the secondary 40MHz channel adjacent to the primary 40MHz channel, together with the primary 40MHz channel, forms the 80MHz channel of that 80MHz BSS.

[0042] WLAN devices (APs or STAs) can classify received PPDUs into one of three types: inter-BSS PPDUs, intra-BSS PPDUs, and unknown PPDUs. Intra-BSS PPDUs can be PPDUs transmitted by STAs within their respective BSSs. Inter-BSS PPDUs can be PPDUs transmitted by STAs in neighboring BSSs.

[0043] A WLAN device may classify a received PPDU as an inter-BSS PPDU if any of the following conditions are met: (i) the received PPDU is transmitted by an AP not associated with the WLAN device; (ii) the received PPDU is transmitted by an AP that does not correspond to the BSS of the WLAN device; (iii) the received PPDU is transmitted by an inter-BSS STA that is not a member of the BSS of the WLAN device; (iv) the BSS of the received PPDU is not the BSS of the WLAN device; or (v) the received PPDU is a DLPPDU and the WLAN device is an AP.

[0044] The WLAN device classifies a received PPDU as a BSS-internal PPDU if any of the following conditions are met: (i) the received PPDU is transmitted by an AP associated with the WLAN device; (ii) the received PPDU is transmitted by an AP corresponding to the BSS of the WLAN device; (iii) the received PPDU is transmitted by a BSS-internal STA that is a member of the BSS of the WLAN device; or (iv) the BSS of the received PPDU is the BSS of the WLAN device.

[0045] If it cannot be determined whether the received PPDU belongs to the intra-BSS PPDU or the inter-BSS PPDU, the WLAN device can classify it as an unknown PPDU.

[0046] Before sending a non-triggered transmission, a WLAN device performs a Clear Channel Assessment (CCA). CCA is a collision avoidance technique. Other similar techniques may be called Carrier Sense, Carrier Detection, or Listen-After-Speak. The WLAN device performs CCA to determine whether the wireless medium (e.g., a sub-channel group) is available or busy (occupied by another transmission). If the wireless medium is in use, the WLAN device can postpone the transmission until it performs CCA again and another device determines that the wireless communication medium is idle.

[0047] Transmission Opportunity (TXOP) is the time interval during which a STA has the right to initiate a frame exchange sequence on the WM (Wireless Medium). The NAV (Network Assignment Vector) is an indicator maintained by each STA to indicate that regardless of whether the STA's Free Channel Assessment (CCA) function detects WM busy, the STA will not initiate a transmission to the WM during this time interval. When the NAV counter is 0, the CS (Carrier Sense) indicates that the medium is free. When the counter is non-zero, it indicates busy. When the NAV counter is not zero (or the NAV indicates busy), the STA cannot access the channel. When a STA receives a PPDU that was not transmitted by or destined for that STA, the STA can update the NAV (or set / reset the NAV counter) based on the TXOP of the received PPDU.

[0048] The "backoff procedure" is a channel transmission (CS) process used to confirm that the radio medium (or channel) is idle. A STA wishing to initiate the transmission of data frames and / or management frames needs to invoke the CS mechanism to determine the busy / idle state of the medium. If the medium is busy, the STA postpones transmission until the medium is determined to have remained idle for a continuous period: this period equals a first interval (e.g., Extended Interframe Spacing (EIFS)) if the last transition to idle was due to a frame detected on the medium but not correctly received; otherwise, it equals a second interval (e.g., Distributed Interframe Spacing (DIFS)). After the medium idle time of this DIFS or EIFS, the STA generates a random backoff count to provide an additional delay before transmission, unless the backoff counter already contains a non-zero value, in which case random number selection is neither necessary nor performed. This process minimizes collisions when multiple STAs delayed due to the same event compete for the same data.

[0049] The proposed Non-Master Channel Access (NPCA) is described below.

[0050] NPCA is a mechanism that enables peer STAs to dynamically switch their operating channel from the BSS master channel to the NPCA master channel. NPCA allows STAs within the BSS to switch to an alternative channel for a period of time when OBSS activity is detected on a portion of the BSS operating channel.

[0051] When a STA receives an inter-BSS PPDU on the primary channel (e.g., primary 20 / 40 / 80 / 160 / 320 / 640MHz channel), the STA sets the primary channel's NAV counter and records the set of occupied primary channels. According to the traditional IEEE 802.11 protocol, when the primary channel is not idle, the STA cannot access the entire working channel regardless of whether any secondary channels are idle. TXOP is acquired solely based on the activity of the primary channel. Therefore, when the primary channel is busy, the STA cannot access the entire channel or initiate any transmissions.

[0052] Figure 4 This shows an example of an NPCA operation.

[0053] The AP can advertise a primary channel and / or an NPCA primary channel to the STA. The STA can receive frames (e.g., beacon frames) containing information about at least one of the primary channel and the NPCA primary channel. The frame may also contain information about at least one secondary channel associated with the NPCA primary channel. The primary channel may not overlap with the NPCA primary channel in the frequency domain. The NPCA primary channel is used for the NPCA mechanism according to the embodiments described in this disclosure.

[0054] The primary channel can also be called the BSS primary channel. The NPCA primary channel can also be referred to by various terms, such as supplementary primary channel, selected primary channel, alternative primary channel, etc. When the primary channel is called the first primary channel, the alternative primary channel can be called the second primary channel.

[0055] The NPCA primary channel can be located in a non-primary channel. The NPCA primary channel can also be located in a secondary channel associated with the primary channel. The bandwidth of the NPCA primary channel can be one of 20MHz, 40MHz, 80MHz, 160MHz, and 320MHz. The primary channel and the NPCA primary channel can be located in different frequency bands (e.g., different 80MHz segments) or different frequency zones.

[0056] When the NAV counter of the primary channel is set by an inter-BSS PPDU (or any PPDU not sent to the STA), the STA can switch from the primary channel to the NPCA primary channel. When the STA is able to switch to the NPCA primary channel to perform NPCA operations, the STA can initiate a backoff procedure on the NPCA primary channel.

[0057] After the STA moves to the NPCA main channel, it can switch back to the main channel when the main channel's NAV counter expires.

[0058] STAs supporting NPCA can access WM on the NPCA main channel when the main channel is occupied by BSS inter-service traffic. When a STA accesses WM on the NPCA main channel, the STA needs to maintain an NAV counter.

[0059] The STA and / or AP can maintain two NAVs: the intra-BSS NAV and the basic NAV. The intra-BSS NAV is updated by the intra-BSS PPDU. The basic NAV is updated by the inter-BSS PPDU or an unknown PPDU. The intra-BSS NAV counter can be set to a value obtained from the intra-BSS PPDU. The basic NAV counter can be set to a value obtained from the inter-BSS PPDU or an unknown PPDU. If both NAV counters are 0, CS indicates that the medium is idle; if at least one of the two NAV timers is non-zero, CS indicates that the medium is busy.

[0060] A STA may use the duration information indicated by a received PPDU to update the intra-BSV if any of the following conditions are met: (i) the received PPDU is an intra-BSV PPDU; (ii) the indicated duration is greater than the current intra-BSV value; and (iii) the recipient of the received PPDU is not the STA. A STA may use the duration information indicated by a received PPDU to update the basic NAV if any of the following conditions are met: (i) the received PPDU is an inter-BSV PPDU or an unknown PPDU; (ii) the indicated duration is greater than the current basic NAV value; and (iii) the recipient of the received PPDU is not the STA. A STA that is a TXOP holder will not use the duration information indicated in the received PPDU to update the intra-BSV.

[0061] Figure 5 An example of NPCA operation according to an embodiment of the present invention is shown.

[0062] When the STA accesses WM on the NPCA main channel, the STA can maintain the NAV counters of the main channel and the NPCA main channel.

[0063] The STA can receive inter-BSS PPDUs that occupy at least the main channel. The STA updates the NAV counter of the main channel. If the received inter-BSS PPDU occupies the NPCA main channel, the STA can also update the NAV counter of the NPCA main channel based on the received PPDU. When a STA accessing on the main channel receives an inter-BSS PPDU that occupies both the main channel and the NPCA main channel, the STA can update the NAV counters of both the main channel and the NPCA main channel simultaneously.

[0064] Figure 6 An example of NPCA operation according to another embodiment of the present invention is shown.

[0065] When both the NAV counters of the main channel and the NPCA main channel are non-zero, the STA receives a BSS-to-PPDU that does not occupy the NPCA main channel. Because the virtual CS of the NPCA main channel is busy, the STA will not switch to the NPCA main channel. This behavior helps to solve the blindness problem of NPCA.

[0066] Figure 7 A method for switching channels according to an embodiment of the present invention is illustrated. This method can be performed by a STA that is a member of a BSS managed by an AP.

[0067] In step S710, the STA, as a member of the BSS, receives NPCA operation information from the associated AP corresponding to the BSS. This information may include information about the NPCA main channel within the BSS bandwidth of the BSS.

[0068] In step S720, when the STA receives an inter-BSS PPDU on the BSS main channel, the STA can switch from the BSS main channel to the NPCA main channel. The bandwidth of the inter-BSS PPDU, determined based on the bandwidth information in the preamble of the inter-BSS PPDU, can be 20, 40, 80, 160, or 320 MHz.

[0069] If at least one of the following options is met, the STA can switch from the BSS primary channel to the NPCA primary channel.

[0070] As the first option, if (i) the channel occupied by the PPDU between BSSs does not overlap with the main channel of NPCA, and (ii) the NAV counter of the main channel of NPCA is zero, then the STA can switch to the main channel of NPCA.

[0071] As a second option, if (i) the channel occupied by the PPDU between BSSs does not overlap with the main channel of NPCA, and (ii) the STA maintains the value of the NAV counter within the BSS at zero, then the STA can switch to the main channel of NPCA.

[0072] As a third option, if (i) the channel occupied by the PPDU between BSSs does not overlap with the main channel of NPCA, and (ii) the STA maintains the value of the basic NAV counter at zero, then the STA may switch to the main channel of NPCA.

[0073] As a fourth option, if (i) the channel occupied by the PPDU between BSSs does not overlap with the main channel of NPCA, and (ii) the STA maintains the values ​​of the NAV counter and the basic NAV counter within the BSS at zero, then the STA can switch to the main channel of NPCA.

[0074] When a STA switches to the NPCA primary channel for NPCA operation, the STA must be ready to transmit and receive PPDUs on the NPCA primary channel no later than the end of the NPCA handover delay. The NPCA PPDU transmitted by the STA on the NPCA primary channel must include at least the NPCA primary channel within the BSS bandwidth. This NPCA PPDU does not include any channels occupied by the inter-BSS PPDUs that caused the STA to switch from the BSS primary channel to the NPCA primary channel.

[0075] In step S730, when operating on the NPCA primary channel, the STA switches back from the NPCA primary channel to the BSS primary channel. When the handover time expires, the STA may switch back to the BSS primary channel. The handover time may be determined based on the value derived from the inter-BSS PPDU that caused the STA to switch from the BSS primary channel to the NPCA primary channel. The handover time may include the TXOP duration derived from that inter-BSS PPDU. The following embodiments present various conditions for switching back to the BSS primary channel.

[0076] When the STA switches back to the BSS main channel, it replaces the current values ​​of the variables QSRC[AC], CW[AC], and backoff counters in each EDCAF with the values ​​stored when switching to the NPCA main channel. The STA then resumes the backoff process.

[0077] When a STA switches back to the BSS primary channel, it may initiate a backoff procedure. The STA initiates the backoff procedure if its backoff counter, stored when switching to the NPCA primary channel, is zero. Specifically, if the STA is currently performing a backoff procedure on the NPCA primary channel (i.e., the backoff counter on the NPCA primary channel is non-zero), the STA must initiate a backoff procedure after switching back to the primary channel. Otherwise, more than one STA resuming its backoff procedure (with a zero backoff counter) may collide.

[0078] Figure 8 An NPCA operation method according to an embodiment of the present invention is shown. This method can be performed by an AP managing the BSS.

[0079] In step S810, the AP transmits operational information for NPCA operation to the member STA, which is a member of the BSS. This operational information may include information about the NPCA primary channel within the BSS bandwidth of the BSS.

[0080] In step S820, the AP and member STA perform NPCA operation. The member STA can then... Figure 7 The STA mode is used in the illustrated embodiment.

[0081] Figure 9 An example of NPCA operation according to an embodiment of the present invention is shown.

[0082] After switching to the NPCA main channel, the STA can decode at least the PPDU that occupies the NPCA main channel. The STA receiving the PPDU can update the NAV counter of the NPCA main channel. If the received PPDU still occupies the main channel, the STA updates the NAV counter of the main channel based on the received PPDU.

[0083] A STA accessing the NPCA main channel receives PPDUs within the BSS that occupy the NPCA main channel but do not. In this case, the STA can update the NAV counter of the NPCA main channel.

[0084] Figure 10 An example of NPCA operation according to an embodiment of the present invention is shown.

[0085] A STA connected to the NPCA main channel receives a PPDU (Portable Component Distributed Duty Unit) within the BSS that is transmitted by its associated AP and simultaneously occupies both the BSS main channel and the NPCA main channel. If the PPDU within the BSS is received by the AP and the AP does not transmit a response PPDU, then the NAV (Network Access Device) can be discarded.

[0086] Upon receiving the PPDU within the BSS, the STA can update the NAV counter of the main channel and switch back to the BSS main channel.

[0087] Figure 11 An example of NPCA operation according to an embodiment of the present invention is shown.

[0088] A STA accessing the NPCA main channel receives inter-BSS PPDUs that occupy the NPCA main channel but not the BSS main channel. The STA can update the NAV counter of the NPCA main channel. If the remaining time after the NAV expires on the NPCA main channel is less than the duration of OBSS activity on the BSS main channel, the STA can switch back to the BSS main channel. If the remaining time after the NAV expires on the NPCA main channel is greater than the duration of OBSS activity on the BSS main channel, the STA cannot switch back to the BSS main channel.

[0089] Figure 12 An example of NPCA operation according to an embodiment of the present invention is shown.

[0090] A STA accessing the NPCA main channel receives PPDUs that simultaneously occupy both the BSS main channel and the NPCA main channel. The STA can update the NAV counters for both the main channel and the NPCA main channel. If the remaining time after the NAV expires on the NPCA main channel is less than the duration of OBSS activity on the BSS main channel, the STA can switch back to the BSS main channel.

[0091] After switching back to the BSS main channel, the STA cannot access the BSS main channel because the virtual CS of the BSS main channel is busy.

Claims

1. A method for switching channels in a wireless local area network, performed by a site as a member of a basic serving set (BSS), comprising: Receive information about the non-primary channel access (NPCA) primary channel within the BSS bandwidth of the BSS from the associated access point (AP) corresponding to the BSS; Receive inter-BSS physical layer protocol data units (PPDUs) on the BSS main channel, whereby the BSS main channel is a common working channel for all stations that are members of the BSS, and the inter-BSS PPDUs are transmitted by at least one of the inter-BSS stations that are not members of the BSS or APs that do not correspond to the BSS; and If both of the following conditions (i) and (ii) are met, then the system switches from the BSS main channel to the NPCA main channel to perform NPCA operations: (i) The channel occupied by the inter-BSS PPDU does not overlap with the NPCA main channel; and (ii) The site maintains the value of the Network Allocation Vector (NAV) counter within the BSS at zero. The NAV counter within the BSS is updated by a PPDU within the BSS, which is sent by at least one of the BSS sites that are members of the BSS or the associated AP.

2. The method of claim 1, further comprising: When the handover time expires, the system switches back from the NPCA main channel to the BSS main channel, wherein the handover time is determined based on a value derived from the inter-BSS PPDU.

3. The method of claim 1, wherein, The bandwidth of the PPDU between BSSs is 20, 40, 80, 160 or 320 MHz.

4. A device for a wireless local area network, wherein the device is a member of a Basic Service Set (BSS), comprising: processor; as well as A memory operatively coupled to the processor and configured to store instructions, which, when executed by the processor, cause the device to perform the following functions: Receive information about the non-primary channel access (NPCA) primary channel within the BSS bandwidth of the BSS from the associated access point (AP) corresponding to the BSS; Receive inter-BSS physical layer protocol data units (PPDUs) on the BSS main channel, whereby the BSS main channel is a common working channel for all stations that are members of the BSS, and the inter-BSS PPDUs are transmitted by at least one of the inter-BSS stations that are not members of the BSS or APs that do not correspond to the BSS; and If both of the following conditions (i) and (ii) are met, then the system switches from the BSS main channel to the NPCA main channel to perform NPCA operations: (i) The channel occupied by the inter-BSS PPDU does not overlap with the NPCA main channel; and (ii) The device maintains the value of the Network Allocation Vector (NAV) counter within the BSS at zero. The NAV counter within the BSS is updated by a PPDU within the BSS, which is sent by at least one of the BSS sites that are members of the BSS or the associated AP.

5. The apparatus of claim 4, wherein, The functionality also includes: When the handover time expires, the system switches back from the NPCA main channel to the BSS main channel, wherein the handover time is determined based on a value derived from the inter-BSS PPDU.

6. The apparatus of claim 4, wherein, The bandwidth of the PPDU between BSSs is 20, 40, 80, 160 or 320 MHz.

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