Patent Description:
In wireless networks such as a wireless local area network (WLAN) operating in accordance with the Institute of Electrical and Electronics Engineers (IEEE) <NUM> standard(s), a multi-link device (MLD) is a device that supports multi-link operation yet is susceptible to in-device coexistence (IDC) interference when two or more of the multiple links are close to each other. The MLD operating on two links with IDC interference cannot support simultaneous transmission and reception on the two links, which are referred to as a non-simultaneous-transmit-and-receive (NSTR) pair of links. In such cases, the MLD is referred to as an NSTR MLD.

An access point (AP) MLD that has IDC interference and operates on an NSTR pair of links is referred to as an NSTR AP MLD. For an NSTR AP MLD, synchronous transmission between the NSTR AP MLD and an STR/NSTR non-AP MLD can be applied to avoid the IDC interference by performing contention based channel access on the NSTR pair of links respectively and start transmission at the same time with the following constraints. Firstly, the NSTR AP MLD may designate one link of an NSTR link pair as a primary link, with the other link of the NSTR link pair being a non-primary link or a secondary link. In this case, the NSTR AP MLD may transmit Beacon frames and Probe Response frames on the primary link but not on the non-primary link. Further, the non-primary link may initiate a physical layer protocol data unit (PPDU) transmission only if a station (STA) affiliated with the same MLD in the primary link is also initiating the PPDU as a TXOP holder with the same start time.

However, when channel switch operation is required for one or both of the primary link and the non-primary link of the NSTR link pair, there are challenges as a result of the constraints. For example, since there is no Beacon frames and Probe Response frames transmitted on the non-primary link, the non-AP MLD may have difficulties knowing when the AP on the non-primary link resumes the basic service set (BSS) operation on the new channel. Further, when both the primary link and the non-primary link are needed to switch from the current operating channels to either another new operating channels together or swap the operating channel with each other, there is a need to efficiently designate a new primary link and non-primary link or perform the channel switching. Moreover, the associated non-AP MLD also needs a way to efficiently perform primary link and non-primary link channel switching.

Therefore, there is a need for a solution of the NSTR link pair channel switch operation scheme in wireless communications to address aforementioned issues. IEEE P802.11be™/D2. <NUM> defines a channel switch on the primary link.

IEEE <NUM>-<NUM>/1018r47 discloses indication of beacon frame related information.

A method and an apparatus according to the invention are defined in the independent claims. The dependent claims define preferred embodiments thereof.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be an access point (AP) multi-link device (MLD). In certain configurations, the AP MLD establishes a primary link on a first channel and a non-primary link on a second channel. The AP MLD determines to perform a channel switch operation to switch a first link of the primary link and the non-primary link to operating on a different channel. The AP MLD transmits, on the primary link and prior to the switching of the first link, a first management frame including a first element indicating a target switching time for the switching of the first link. The AP MLD transmits, on the primary link after the switching of the first link, a second management frame indicating that an AP on the first link is in operation.

In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a non-AP MLD. In certain configurations, the non-AP MLD associates, at the non-AP MLD, with an AP MLD on a primary link that is operating on a first channel and on a non-primary link that is operating on a second channel. The non-AP MLD receives, on the primary link, a first management frame including a first element indicating a target switching time for switching a first link of the primary link and the non-primary link to operating on a different channel. The non-AP MLD receives, on the primary link after switching of the first link, a second management frame indicating that an AP on the first link is in operation. The non-AP MLD resumes communication on the first link based on the second management frame, where the first link is operating on the different channel.

Several aspects of telecommunications systems will now be presented with reference to various apparatus and methods.

Accordingly, in one or more example aspects, the functions described may be implemented in hardware, software, or any combination thereof.

<FIG> is a diagram illustrating an exemplary network environment <NUM>. The network environment <NUM> may involve at least a NSTR AP MLD <NUM> and a non-AP MLD <NUM> communicating wirelessly with each other in accordance with the IEEE <NUM> standards. The NSTR AP MLD <NUM> has a first AP <NUM> and a second AP <NUM>, and each of the APs <NUM> and <NUM> may be an AP station (STA) affiliated with the NSTR AP MLD <NUM>. The non-AP MLD <NUM> has a first STA <NUM> and a second STA <NUM>, and each of the STAs <NUM> and <NUM> may be a non-AP STA affiliated with the non-AP MLD <NUM>. Further, the NSTR AP MLD designates a link pair between the NSTR AP MLD <NUM> and the non-AP MLD <NUM>. Specifically, the AP <NUM> and the STA <NUM> are communicate with each other on a primary link <NUM> on a corresponding first channel, and the AP <NUM> and the STA <NUM> communicate with each other on a non-primary link <NUM> on a corresponding second channel.

In certain embodiments of the present disclosure, under a scheme with respect to the NSTR link pair channel switch operation, the NSTR AP MLD <NUM> may schedule a channel switch operation for the primary link <NUM> and/or the non-primary link <NUM> by including information related to a target switching time (which indicates the time of the non-primary link <NUM> being switched to a new channel or suspended) and an estimated channel switch time that the AP <NUM> operating on the non-primary link <NUM> resumes a basic service set (BSS) operation on the new channel in a management frame, such as a Beacon frame or a Probe Response frame, that the AP <NUM> affiliated with the NSTR AP MLD <NUM> and operating on the primary link <NUM>, such that the AP <NUM> affiliated with the NSTR AP MLD <NUM> on the non-primary link <NUM> may suspend and resume the BSS operation based on the information carried in the management frame (i.e., the Beacon frame or the Probe Response frame) on the primary link <NUM>.

In certain configurations, the Beacon frame or the Probe Response frame may include a channel switch announcement element or an extended channel switch announcement element indicating the target switching time of the non-primary link <NUM> being suspended, and a max channel switch time element indicating the estimated time that the AP <NUM> operating on the non-primary link <NUM> resumes the BSS operation after the target switching time. The corresponding elements may be included in a per STA profile sub-element in the multi-link element carried in the Beacon frames or the Probe Response frames on the primary link.

In certain configurations, the per STA profile sub-element of each of the Beacon frames or the Probe Response frames transmitted before the target switching time includes the channel switch announcement element or the extended channel switch announcement element. In other words, the Beacon frames or the Probe Response frames transmitted after the target switching time do not include the channel switch announcement element or the extended channel switch announcement element. In certain configurations, the per STA profile sub-element of each of the Beacon frames or the Probe Response frames transmitted before the AP <NUM> operating on the non-primary link <NUM> resumes the BSS operation includes the max channel switch time element. In other words, the Beacon frames or the Probe Response frames transmitted after the AP <NUM> operating on the non-primary link <NUM> resumes the BSS operation do not include the max channel switch time element.

<FIG> and <FIG> are diagrams illustrating exemplary designs of corresponding elements in a Beacon frame under the scheme. Referring to <FIG>, the channel switch announcement element <NUM> is used by an AP or STA, such as the AP <NUM> as shown in <FIG>, to advertise when the AP <NUM> operating on the primary link <NUM> and/or the AP <NUM> operating on the non-primary link <NUM> is changing to a new channel and the channel number of the new channel. As shown in <FIG>, the channel switch announcement element <NUM> includes an element ID field <NUM>, a length field <NUM>, a channel switch mode field <NUM>, a new channel number field <NUM>, and a channel switch count field <NUM>, and each field is a <NUM>-octet field. Specifically, the channel switch announcement element <NUM> may refer to a primary link channel switching announcement and/or a non-primary link channel switching announcement. Further, the target switching time may be represented in the channel switch count field <NUM> of the channel switch announcement element <NUM> in the form of the channel switch count (CSC), which is applied in reference to the most recent target beacon transmission time (TBTT) and the beacon interval (BI) indicated in the corresponding elements of the AP <NUM> operating on the primary link <NUM>. For example, the channel switch count field <NUM> is set to the number of TBTTs until the STA (e.g., the AP <NUM>) sending the channel switch announcement element <NUM> switches to the new channel. In particular, the value of the channel switch count field <NUM> being <NUM> indicates that the switch occurs at the next TBTT. In this case, the AP <NUM> affiliated with the NSTR AP MLD <NUM> on the non-primary link <NUM> may suspend the BSS operation at and after the target switch time (i.e., the channel switch count) indicated in the channel switch announcement element <NUM>.

Referring to <FIG>, the extended channel switch announcement element <NUM> is used by an AP or STA, to advertise when the BSS is changing to a new channel in the same or a new operating class. The extended channel switch announcement element <NUM> is present only when an extended channel switch is pending. As shown in <FIG>, the extended channel switch announcement element <NUM> includes an element ID field <NUM>, a length field <NUM>, a channel switch mode field <NUM>, a new operating class field <NUM>, a new channel number field <NUM>, and a channel switch count field <NUM>, and each field is a <NUM>-octet field. Specifically, the extended channel switch announcement element <NUM> may refer to a primary link channel switching announcement and/or a non-primary link channel switching announcement. Further, the target switching time may be represented in the channel switch count field <NUM> of the extended channel switch announcement element <NUM> in the form of the CSC, which is applied in reference to the most recent TBTT and the BI indicated in the corresponding elements of the AP <NUM> operating on the primary link <NUM>. For example, the channel switch count field <NUM> is set to the number of TBTTs until the STA (e.g., the AP <NUM>) sending the extended channel switch announcement element <NUM> switches to the new channel. In particular, the value of the channel switch count field <NUM> being <NUM> indicates that the switch occurs at the next TBTT. In this case, the AP <NUM> affiliated with the NSTR AP MLD <NUM> on the non-primary link <NUM> may suspend the BSS operation at and after the target switch time (i.e., the channel switch count) indicated in the extended channel switch announcement element <NUM>.

Referring to <FIG>, the max channel switch time element <NUM> indicates the estimated time delta between the target switching time (i.e., the time the last Beacon frame carrying the target switching time is transmitted by the AP <NUM> operating on the primary link <NUM> in the current channel) and the expected time when the AP <NUM> on the non-primary link <NUM> resumes the BSS operation on the new channel after the channel switch operation has occurred (i.e., the expect time of the first Beacon frame not including the max channel switch time element transmitted by the AP <NUM> on the primary link <NUM>). In certain embodiments, the max channel switch time element <NUM> is optionally present in a Basic Multi-Link element carried by the Beacon frame when a channel switch announcement element <NUM> or an extended channel switch announcement element <NUM> is also present.

As shown in <FIG>, the max channel switch time element <NUM> includes an element ID field <NUM>, a length field <NUM>, an element ID extension field <NUM>, and a switch time field <NUM>, in which the first three fields are <NUM>-octet fields and the switch time field <NUM> is a <NUM>-octet field. Specifically, the switch time field <NUM> indicates an estimated time when the AP <NUM> on the non-primary link <NUM> resumes the BSS operation on the new channel after the channel switch operation has occurred. Specifically, the estimated time indicated by the switch time field <NUM> may be a maximum time delta between the target switching time (i.e., the time the last Beacon frame carrying the target switching time is transmitted by the AP <NUM> on the primary link <NUM>) and the expected time when the AP <NUM> on the non-primary link <NUM> resumes the BSS operation on the new channel after the channel switch operation has occurred (i.e., the expected time of the first Beacon frame not including the max channel switch time element <NUM> transmitted by the AP <NUM> on the primary link <NUM>). In certain embodiments, the estimated time that the AP <NUM> operating on the non-primary link <NUM> resumes the BSS operation after the target switching time is included in the switch time field <NUM> in the max channel switch time element <NUM>. In this case, the AP <NUM> affiliated with the NSTR AP MLD <NUM> on the non-primary link <NUM> may resume the suspended BSS operation based on the estimated time indicated in the switch time field <NUM> of the max channel switch time element <NUM>. In certain embodiments, the estimated time indicated by the switch time field <NUM> may be a maximum time delta between a time when the Beacon frame carrying the Basic Multi-Link element containing the max channel switch time element is transmitted by the AP <NUM> operating on the primary link <NUM> and the expected time when the AP <NUM> operating on the non-primary link <NUM> resumes the BSS operation on the new channel after the channel switch has occurred. It should be noted that, while the channel switch count in the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> is applied in reference to the most recent TBTT and the BI on the primary link <NUM>, the switch time field <NUM> is not tied to the TBTT on the primary link <NUM>, and the estimated time in the switch time field <NUM> is generally expressed in time units (TUs).

In certain embodiments, in addition to the estimated time indicated in the max channel switch time element, an additional disabled link indication subfield may be used to indicate disablement or enablement of the AP <NUM> on the non-primary link <NUM>. Specifically, the NSTR AP MLD <NUM> may indicate the disablement of the non-primary link at and after the target switching time until the reported AP (i.e., the AP <NUM> on the non-primary link <NUM>) resumes its BSS operation in the TBTT Information field corresponding to the non-primary link <NUM> in a reduced neighbor report (RNR) element transmitted in the Beacon frames on the primary link <NUM>. In certain embodiments, the RNR element is also included in a per STA profile sub-element in the multi-link element carried in the Beacon frames or the Probe Response frames on the primary link. Referring to <FIG>, the RNR element <NUM> contains channel and other information related to neighbor APs. As shown in <FIG>, the RNR element <NUM> includes an element ID field <NUM>, a length field <NUM>, and the neighbor AP information fields <NUM>, in which the first two fields are <NUM>-octet fields, and the neighbor AP information fields <NUM> contain one or more of the neighbor AP information fields. In other words, the neighbor AP information fields <NUM> include variable fields.

Referring to <FIG>, in certain embodiments, the neighbor AP information field <NUM> (which corresponds to the neighbor AP information fields <NUM>) specifies TBTT and other information related to a group of neighbor APs on one channel. As shown in <FIG>, the neighbor AP information field <NUM> includes a TBTT information header field <NUM>, an operating class field <NUM>, a channel number field <NUM>, and the TBTT information field <NUM>. The TBTT information header field <NUM> is a <NUM>-octet subfield which identifies the format of the TBTT information field <NUM>. The TBTT information field <NUM> includes one or more TBTT information fields, namely, a set of subfields. In certain embodiments, the TBTT information header field <NUM> includes, among other things, a TBTT information field type subfield and a TBTT information length subfield, where the values of the TBTT information field type subfield and the TBTT information length subfield are used to determine the set of subfields in the TBTT information field <NUM>. In one embodiment, the TBTT information field <NUM> may include a MLD parameters subfield, which is a <NUM>-octet subfield.

Referring to <FIG>, in certain embodiments, an exemplary MLD parameters subfield <NUM> includes an <NUM>-bit AP MLD ID subfield <NUM>, a <NUM>-bit link ID subfield <NUM>, an <NUM>-bit BSS parameters change count <NUM>, a <NUM>-bit all updates included subfield <NUM>, a <NUM>-bit disabled link indication subfield <NUM>, and <NUM> bits reserved. Specifically, the disabled link indication subfield <NUM> is set to <NUM> at and after the target switching time to disable the AP on the non-primary link, and to <NUM> to indicate that the reported AP <NUM> resumes its BSS operation on the non-primary link <NUM> (i.e., enabling the AP <NUM> on the non-primary link <NUM>).

Referring to <FIG>, in certain embodiments, when the non-AP MLD <NUM> receives a primary link channel switching announcement in the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> of a Beacon frame, the non-AP MLD <NUM> shall not transmit any more frames on the non-primary link <NUM> at and after the target switch time indicated in the timing field (e.g., the channel switch count field <NUM>) until it receives a Beacon frame on the new channel of the primary link <NUM>. In certain embodiments, the non-AP MLD <NUM> shall not transmit any more frames on the non-primary link <NUM> at and after the target switch time until it receives a Beacon frame on the new channel of the primary link and the non-primary link is indicated as enabled by the disabled link indication subfield <NUM> in the RNR element <NUM>.

Referring to <FIG>, in certain embodiments, when the non-AP MLD <NUM> receives a non-primary link channel switching announcement in the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> of a Beacon frame, the non-AP MLD <NUM> shall not transmit any more frames on the non-primary link <NUM> at and after the target switch time indicated in the timing field until it receives a Beacon frame indicating that the non-primary link resumes the BSS operation by at least one of the following ways. On one hand, the non-primary link <NUM> is indicated as being enabled on the new channel by the disabled link indication subfield <NUM> in the RNR element <NUM> of the most recently received Beacon frame on the primary link <NUM>. On the other hand, in the most recently received Beacon frame transmitted on the primary link <NUM>, the per-STA profile corresponding to the non-primary link <NUM> stops including the max channel switch time element <NUM>.

<FIG> is a diagram illustrating an exemplary communication system <NUM>, which has two apparatuses <NUM> and <NUM>. Each of the apparatus <NUM> and the apparatus <NUM> may perform various functions to implement schemes, techniques, processes and methods described herein pertaining to the channel switch operation, including the scheme described above with respect to various proposed designs, concepts, schemes, systems and methods described above as well as processes described below. For instance, the apparatus <NUM> may be implemented in the NSTR AP MLD <NUM> as shown in <FIG> and the apparatus <NUM> may be implemented in the non-AP MLD <NUM> as shown in <FIG>.

Each of the apparatus <NUM> and the apparatus <NUM> may be a part of an electronic apparatus, which may be a non-AP MLD or an AP MLD, such as a portable or mobile apparatus, a wearable apparatus, a wireless communication apparatus or a computing apparatus. When implemented in a non-AP MLD, each of the apparatus <NUM> and the apparatus <NUM> may be implemented in a smartphone, a smart watch, a personal digital assistant, a digital camera, or a computing equipment such as a tablet computer, a laptop computer or a notebook computer. Each of the apparatus <NUM> and the apparatus <NUM> may also be a part of a machine type apparatus, which may be an Internet of things (IoT) apparatus such as an immobile or a stationary apparatus, a home apparatus, a wire communication apparatus or a computing apparatus. For instance, each of the apparatus <NUM> and the apparatus <NUM> may be implemented in a smart thermostat, a smart fridge, a smart door lock, a wireless speaker or a home control center. When implemented in or as a network apparatus, the apparatus <NUM> and/or the apparatus <NUM> may be implemented in a network node, such as an AP MLD in a WLAN.

In certain embodiments, each of the apparatus <NUM> and the apparatus <NUM> may be implemented in the form of one or more integrated-circuit (IC) chips such as, for example and without limitation, one or more single-core processors, one or more multi-core processors, one or more reduced-instruction set computing (RISC) processors, or one or more complex-instruction-set-computing (CISC) processors. In the scheme described above, each of the apparatus <NUM> and the apparatus <NUM> may be implemented in or as a non-AP MLD or an AP MLD. Each of the apparatus <NUM> and the apparatus <NUM> may include at least some of those components shown in <FIG>, such as a processor <NUM> and a processor <NUM>, respectively, for example. Each of the apparatus <NUM> and the apparatus <NUM> may further include one or more other components not pertinent to the proposed scheme of the present disclosure (e.g., internal power supply, display device and/or user interface device), and, thus, such component(s) of the apparatus <NUM> and the apparatus <NUM> are neither shown in <FIG> nor described below in the interest of simplicity and brevity.

In certain embodiments, the processor <NUM> and the processor <NUM> may be implemented in the form of one or more single-core processors, one or more multi-core processors, one or more RISC processors or one or more CISC processors. That is, even though a singular term "a processor" is used herein to refer to the processor <NUM> and the processor <NUM>, the processor <NUM> and the processor <NUM> may include multiple processors in some implementations and a single processor in other implementations in accordance with the present disclosure. In certain embodiments, the processor <NUM> and the processor <NUM> may be implemented in the form of hardware (and, optionally, firmware) with electronic components including, for example and without limitation, one or more transistors, one or more diodes, one or more capacitors, one or more resistors, one or more inductors, one or more memristors and/or one or more varactors that are configured and arranged to achieve specific purposes in accordance with the present disclosure. In other words, in certain embodiments, the processor <NUM> and the processor <NUM> is a special-purpose machine specifically designed, arranged and configured to perform specific tasks including those pertaining to system parameters transmission scheme in wireless communications in accordance with various implementations of the present disclosure.

In certain embodiments, the apparatus <NUM> may further include a memory <NUM> coupled to the processor <NUM> and capable of being accessed by the processor <NUM> and storing data therein. In some implementations, the apparatus <NUM> may further include a memory <NUM> coupled to the processor <NUM> and capable of being accessed by the processor <NUM> and storing data therein. Each of the memory <NUM> and the memory <NUM> may include a type of random-access memory (RAM) such as dynamic RAM (DRAM), static RAM (SRAM), thyristor RAM (T-RAM) and/or zero-capacitor RAM (Z-RAM). Alternatively, or additionally, each of the memory <NUM> and the memory <NUM> may include a type of read-only memory (ROM) such as mask ROM, programmable ROM (PROM), erasable programmable ROM (EPROM) and/or electrically erasable programmable ROM (EEPROM). Alternatively, or additionally, each of the memory <NUM> and the memory <NUM> may include a type of non-volatile random-access memory (NVRAM) such as flash memory, solid-state memory, ferroelectric RAM (FeRAM), magnetoresistive RAM (MRAM) and/or phase-change memory.

In certain embodiments, the apparatus <NUM> may also include a transceiver <NUM> coupled to the processor <NUM>. The transceiver <NUM> may include a transmitter capable of wirelessly transmitting and a receiver capable of wirelessly receiving data. In certain embodiments, the apparatus <NUM> may also include a transceiver <NUM> coupled to the processor <NUM>. The transceiver <NUM> may include a transmitter capable of wirelessly transmitting and a receiver capable of wirelessly receiving data.

Each of the apparatus <NUM> and the apparatus <NUM> may be a communication entity capable of communicating with each other using various proposed schemes in accordance with the present disclosure. In certain embodiments, the apparatus <NUM> may function as the NSTR AP MLD <NUM>, and the apparatus the <NUM> may function as the non-AP MLD <NUM> to perform the methods, processes and schemes as described.

<FIG> is a diagram illustrating a first example of an NSTR AP MLD scheduling operating channel switch only for the primary link <NUM> and no change to the non-primary link <NUM>. Specifically, the AP operating on the primary link <NUM> transmits a plurality of Beacon frames <NUM>, which may include the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM>, the max channel switch time element <NUM>, and the RNR element <NUM>. The corresponding elements are carried in the Beacon frames <NUM> on the primary link <NUM>, and may be included in the per STA profile sub-element in the multi-link element carried in the Beacon frames <NUM> on the primary link <NUM>. In certain embodiments, instead of the Beacon frames <NUM>, the frames carrying the elements may be the Probe Response frames.

As shown in <FIG>, the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> indicates the target switching time, which may be represented in the timing field (e.g., the channel switch count field <NUM> or <NUM>) in the form of the channel switch count (CSC). The CSC is applied in reference to the most recent TBTT and the BI indicated in the corresponding elements of the AP operating on the primary link, and the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> may determine whether the BSS operation on the initial channel should be suspended based on the CSC value. When the CSC is <NUM> (indicating the target switching time), the AP affiliated with the NSTR AP MLD on the primary link <NUM> starts performing the channel switch operation to switch from the initial channel to the new channel, and the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> shall suspend the BSS operation on the initial channel at and after the target switch time. In this case, when the primary link <NUM> performs the channel switch operation, there is no transmission on the non-primary link <NUM> although there is no channel switch operation on the non-primary link.

The NSTR AP MLD may further include the max channel switch time element <NUM> in the Beacon frame <NUM> transmitted on the primary link <NUM> to indicate the estimated time that the first Beacon frame <NUM> is transmitted on the new channel of the primary link <NUM> after the channel switch occurs at the target switch time. In other words, the estimated time that the AP operating on the non-primary link <NUM> resumes the BSS operation after the target switching time is included in the switch time field <NUM> in the max channel switch time element <NUM>. It should be noted that the switch time field <NUM> in the max channel switch time element <NUM> carried in the per-STA profile of the AP is not tied to a TBTT on the affected link (i.e., the primary link <NUM>). Instead, the switch time field <NUM> provides an estimated time that the AP operating on the non-primary link <NUM> resumes the BSS operation on the new channel (i.e., the estimated time when the first Beacon frame <NUM> will be transmitted on the new channel of the primary link <NUM> after the channel switch has occurred). In certain embodiments, when the channel switch operation on the primary link <NUM> is complete, the AP operating on the new channel starts transmitting the Beacon frames <NUM> on the primary link <NUM>. In this case, in the first Beacon frame <NUM> on the new operating class/channel, there is no max channel switch time element <NUM>. In this case, the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> resumes the BSS operation on the initial channel of the non-primary link <NUM>.

<FIG> is a flow chart of methods of suspending and resuming the non-primary link <NUM> according to the channel switch announcement element <NUM>, the extended channel switch announcement element <NUM> and the max channel switch time element <NUM>. As shown in <FIG>, in the method <NUM>, the suspension of the non-primary link <NUM> is controlled by the timing field (e.g., the channel switch count field <NUM> or <NUM>) in the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM>, which indicates the target switching time (e.g., in the form of the CSC). At operation <NUM>, a Beacon frame <NUM> is transmitted on the primary link <NUM>. At operation <NUM>, it is determined based the value of the timing field (e.g., the channel switch count field <NUM> or <NUM>) in the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> as to whether the channel switch count is <NUM> (i.e., whether CSC = <NUM>). If CSC is not <NUM>, the non-primary link <NUM> maintains enabled, and the system returns to operation <NUM> to wait for a next Beacon frame <NUM> to be transmitted. If CSC = <NUM>, at operation <NUM>, the AP on the non-primary link <NUM> is controlled to suspend the BSS operation on the non-primary link <NUM>.

As shown in <FIG>, in the method <NUM>, the enablement of the non-primary link <NUM> is controlled by the switch time field <NUM> in the max channel switch time element <NUM>, which indicates the estimated time that the AP operating on the non-primary link <NUM> resumes the BSS operation. At operation <NUM>, a Beacon frame <NUM> is transmitted on the primary link <NUM>. At operation <NUM>, it is determined whether the Beacon frame <NUM> includes the max channel switch time element <NUM>. If the Beacon frame <NUM> includes the max channel switch time element <NUM>, the non-primary link <NUM> maintains suspended, and the system returns to operation <NUM> to wait for a next Beacon frame <NUM> to be transmitted. If the Beacon frame <NUM> does not include the max channel switch time element <NUM>, at operation <NUM>, the AP on the non-primary link <NUM> is controlled to resume the BSS operation on the non-primary link <NUM>.

In an alternative embodiment, the RNR element <NUM> includes the disabled link indication subfield <NUM> to indicate the disablement or enablement of the AP on the non-primary link <NUM>. Specifically, before the target switch time, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>) before the last Beacon frame <NUM> on the initial operating class/channel (in which CSC = <NUM>), and in the last Beacon frame <NUM> on the initial operating channel, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>), indicating the AP on the non-primary link <NUM> to suspend/disable the transmission. Further, when the channel switch operation on the primary link <NUM> is complete, the AP operating on the new channel starts transmitting the Beacon frames <NUM> on the primary link <NUM>. In this case, in the first Beacon frame <NUM> on the new operating class/channel, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>), indicating the AP on the non-primary link <NUM> to resume/enable the transmission. In this case, the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> resumes the suspended BSS operation on the initial channel of the non-primary link <NUM>.

<FIG> is a flow chart of methods of suspending and resuming the non-primary link according to the reduced neighbor report element <NUM>. As shown in <FIG>, in the method <NUM>, the suspension/disablement of the non-primary link <NUM> is controlled by the disabled link indication subfield <NUM> in the reduced neighbor report element <NUM>. At operation <NUM>, a Beacon frame <NUM> is transmitted on the primary link <NUM>. At operation <NUM>, it is determined based the value of the disabled link indication subfield <NUM> in the reduced neighbor report element <NUM> as to whether the disabled link indication is <NUM> (i.e., whether DLI = <NUM>). If DLI = <NUM>, the non-primary link <NUM> maintains enabled, and the system returns to operation <NUM> to wait for a next Beacon frame <NUM> to be transmitted. If DLI = <NUM>, at operation <NUM>, the AP on the non-primary link <NUM> is controlled to suspend the BSS operation on the non-primary link <NUM>.

As shown in <FIG>, in the method <NUM>, the enablement of the non-primary link <NUM> is controlled by the disabled link indication subfield <NUM> in the reduced neighbor report element <NUM>. At operation <NUM>, a Beacon frame <NUM> is transmitted on the primary link <NUM>. At operation <NUM>, it is determined based the value of the disabled link indication subfield <NUM> in the reduced neighbor report element <NUM> as to whether the disabled link indication is <NUM> (i.e., whether DLI = <NUM>). If DLI = <NUM>, the non-primary link <NUM> maintains suspended/disabled, and the system returns to operation <NUM> to wait for a next Beacon frame to be transmitted. If DLI = <NUM>, at operation <NUM>, the AP on the non-primary link <NUM> is controlled to resume/enable the BSS operation on the non-primary link <NUM>.

<FIG> is a diagram illustrating a second example of an NSTR AP MLD scheduling operating channel switches for both the primary link <NUM> and the non-primary link <NUM>. Specifically, in order to change the operating channels of the current NSTR link pair (both the primary link <NUM> and non-primary link <NUM>) to new operating channels respectively, the NSTR AP MLD shall perform channel switch for the primary link <NUM> and the non-primary link <NUM> at the same target switch time. Similar to <FIG>, the AP operating on the primary link <NUM> transmits a plurality of Beacon frames <NUM>, which may include the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM>, the max channel switch time element <NUM>, and the RNR element <NUM>. The corresponding elements are carried in the Beacon frames <NUM> on the primary link <NUM>, and may be included in the per STA profile sub-element in the multi-link element carried in the Beacon frames <NUM> on the primary link <NUM>. In certain embodiments, instead of the Beacon frames <NUM>, the frames carrying the elements may be the Probe Response frames.

As shown in <FIG>, the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> indicates the target switching time, which may be represented in the timing field (e.g., the channel switch count field <NUM> or <NUM>) in the form of the CSC. The CSC is applied in reference to the most recent TBTT and the BI indicated in the corresponding elements of the AP operating on the primary link <NUM>. As discussed, the NSTR AP MLD that intends to swap the operating channel used for its primary and non-primary links <NUM> and <NUM> respectively must simultaneously perform the (extended) channel switch operation on both the links. When the CSC is <NUM> (indicating the target switching time), both the AP affiliated with the NSTR AP MLD on the primary link <NUM> and the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> start performing the respective channel switch operation to switch from the initial channel to the new channel, and the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> shall suspend the BSS operation on the initial channel at and after the target switch time to start the channel switch operation. In this case, both the primary link <NUM> and the non-primary link <NUM> perform the channel switch operations simultaneously. In certain embodiments, the link IDs corresponding to the primary link <NUM> and the non-primary link <NUM> after the channel switching keep the same. The suspension of the non-primary link <NUM> is similar to the suspension of the non-primary link <NUM> in the method <NUM> as shown in <FIG>, and is thus not further elaborated herein.

The NSTR AP MLD may include the max channel switch time element <NUM> in the Beacon frame <NUM> transmitted on the primary link <NUM> to indicate the estimated time that the first Beacon frame <NUM> is transmitted on the new channel of the primary link <NUM> after the channel switch occurs at the target switch time. The estimated time that the AP operating on the non-primary link <NUM> resumes the BSS operation after the target switching time is included in the switch time field <NUM> in the max channel switch time element <NUM>. Specifically, since both the primary link <NUM> and the non-primary link <NUM> are intended to perform the channel switch, the Beacon frame <NUM> transmitted on the primary link <NUM> may carry two max channel switch time elements <NUM>. For the non-primary link channel switch, the max channel switch time element is included in the Per-STA profile sub-element of the basic multi-link element corresponding to the AP operating on the non-primary link <NUM> in the Beacon frame <NUM> transmitted on the primary link <NUM>. It should be noted that the switch time field <NUM> in the max channel switch time elements <NUM> for the primary link <NUM> and non-primary link <NUM> channel switch may be set to the same value (indicating the estimated time for the channel switch operation being the same on both links) or different values (indicating the estimated time for the channel switch operation being different on the primary link <NUM> and the non-primary link <NUM>). In certain embodiments, when the channel switch operation on the primary link <NUM> is complete, the AP operating on the new channel starts transmitting the Beacon frames <NUM> on the primary link <NUM>. In this case, in one of the subsequent Beacon frames <NUM> (which is not necessarily the first Beacon frame <NUM> transmitted by the AP operating on the new channel) on the new operating class/channel on the primary link <NUM>, there is no max channel switch time element <NUM>. In this case, the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> resumes the suspended BSS operation on the initial channel of the non-primary link <NUM>. The resuming/enablement of the non-primary link <NUM> is similar to the resuming/enablement of the non-primary link <NUM> in the method <NUM> as shown in <FIG>, and is thus not further elaborated herein.

In an alternative embodiment, the RNR element <NUM> includes the disabled link indication subfield <NUM> to indicate the disablement or enablement of the AP on the non-primary link <NUM>. Specifically, before the target switch time, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>) before the last Beacon frame <NUM> on the initial operating class/channel (in which CSC = <NUM>), and in the last Beacon frame <NUM> on the initial operating channel, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>), indicating the AP on the non-primary link <NUM> to suspend/disable the transmission. Further, when the channel switch operation on the primary link <NUM> is complete, the AP operating resumes its BSS operation on the new channel on the primary link <NUM>, and starts transmitting the Beacon frames <NUM> on the primary link <NUM>. In this case, in one of the subsequent Beacon frames <NUM> (which is not necessary the first Beacon frame <NUM> after the BSS operation on the new channel on the primary link <NUM> is resumed) on the new operating class/channel on the primary link <NUM>, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>), indicating the AP on the non-primary link <NUM> to resume/enable the transmission. For example, as shown in <FIG>, in the first Beacon frame <NUM> on the new operating class/channel of the primary link <NUM>, the DLI remains being <NUM>, indicating the AP on the non-primary link <NUM> to remain being suspended/disabled; and in the second Beacon frame <NUM> on the new operating class/channel, the DLI is <NUM>, indicating the AP on the non-primary link <NUM> to resume/enable the transmission. In this case, the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> resumes the suspended BSS operation on the initial channel of the non-primary link <NUM>. The suspension/disablement of the non-primary link <NUM> is similar to the suspension of the non-primary link <NUM> in the method <NUM> as shown in <FIG>, and the enablement of the non-primary link <NUM> is similar to the enablement of the non-primary link <NUM> in the method <NUM> as shown in <FIG>. Thus, details of the suspension/disablement and the enablement of the non-primary link <NUM> are thus not further elaborated herein.

<FIG> is a diagram illustrating a third example of an NSTR AP MLD scheduling operating channel switch for the non-primary link <NUM> and no change to the primary link <NUM>. Specifically, the AP operating on the primary link <NUM> transmits a plurality of Beacon frames <NUM>, which may include the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM>, the max channel switch time element <NUM>, and the RNR element <NUM>. The corresponding elements are carried in the Beacon frames <NUM> on the primary link <NUM>, and may be included in the per STA profile sub-element in the multi-link element carried in the Beacon frames <NUM> on the primary link <NUM>. In certain embodiments, instead of the Beacon frames <NUM>, the frames carrying the elements may be the Probe Response frames.

As shown in <FIG>, the channel switch announcement element <NUM> or the extended channel switch announcement element <NUM> indicates the target switching time, which may be represented in the timing field (e.g., the channel switch count field <NUM> or <NUM>) in the form of the CSC. The CSC is applied in reference to the most recent TBTT and the BI indicated in the corresponding elements of the AP operating on the primary link. When the CSC is <NUM> (indicating the target switching time), the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> starts performing the channel switch operation to switch from the initial channel to the new channel. Meanwhile, the AP affiliated with the NSTR AP MLD on the primary link <NUM> remains its the BSS operation on the initial channel at and after the target switch time. In other words, when the non-primary link <NUM> performs the channel switch operation, the primary link <NUM> keeps transmitting the Beacon frames <NUM>. The suspension of the non-primary link <NUM> is similar to the suspension of the non-primary link <NUM> in the method <NUM> as shown in <FIG>, and is thus not further elaborated herein.

The NSTR AP MLD may include the max channel switch time element <NUM> in the Beacon frame <NUM> transmitted on the primary link <NUM> to indicate the estimated time the AP on the non-primary link <NUM> resumes the BSS operation on the new channel after the channel switch occurs. In other words, the estimated time that the AP operating on the non-primary link <NUM> completes the channel switching and resumes the BSS operation after the target switching time is included in the switch time field <NUM> in the max channel switch time element <NUM>. It should be noted that the switch time field <NUM> in the max channel switch time element <NUM> carried in the per-STA profile of the AP is not tied to a TBTT on the affected link (i.e., the primary link <NUM>). Instead, the switch time field <NUM> provides an estimated time in TUs. In certain embodiments, when the channel switch operation on the non-primary link <NUM> is complete, the AP operating on the primary link <NUM> transmits a Beacon frame <NUM> without the max channel switch time element <NUM>. In this case, the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> resumes the suspended BSS operation on the new channel of the non-primary link <NUM>. The resuming/enablement of the non-primary link <NUM> is similar to the resuming/enablement of the non-primary link <NUM> in the method <NUM> as shown in <FIG>, and is thus not further elaborated herein.

In an alternative embodiment, the RNR element <NUM> includes the disabled link indication subfield <NUM> to indicate the disablement or enablement of the AP on the non-primary link <NUM>. Specifically, before the target switch time, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>) before the last Beacon frame <NUM> on the initial operating class/channel (in which CSC = <NUM>), and in the last Beacon frame <NUM> on the initial operating channel, the value of the disabled link indication subfield <NUM> is <NUM> (i.e., DLI = <NUM>), indicating the AP on the non-primary link <NUM> to suspend/disable the transmission and starts the channel switch operation. Further, when the channel switch operation on the non-primary link <NUM> is complete, the AP operating on the primary link <NUM> transmits a Beacon frame <NUM> with the value of the disabled link indication subfield <NUM> being <NUM> (i.e., DLI = <NUM>), indicating the AP on the non-primary link <NUM> to resume the BSS operation. In this case, the AP affiliated with the NSTR AP MLD on the non-primary link <NUM> resumes the suspended BSS operation on the new channel of the non-primary link <NUM>. The suspension/disablement of the non-primary link <NUM> is similar to the suspension of the non-primary link <NUM> in the method <NUM> as shown in <FIG>, and the enablement of the non-primary link <NUM> is similar to the enablement of the non-primary link <NUM> in the method <NUM> as shown in <FIG>. Thus, details of the suspension/disablement and the enablement of the non-primary link <NUM> are thus not further elaborated herein.

<FIG> is a flow chart <NUM> of a method (process) of wireless communication of an AP MLD according to the invention. The method may be performed by the AP MLD, e.g., the NSTR AP MLD <NUM> or the apparatus <NUM>. At operation <NUM>, the AP MLD establishes, at the AP MLD, a primary link on a first channel and a non-primary link on a second channel. At operation <NUM>, the AP MLD determines to perform a channel switch operation to switch a first link of the primary link and the non-primary link to operating on a different channel. At operation <NUM>, the AP MLD transmits, on the primary link and prior to the switching of the first link, a first management frame (e.g., a Beacon frame or a Probe Response frame) including a first element (e.g., a channel switch announcement element or an extended channel switch announcement element) indicating a target switching time for the switching of the first link. At operation <NUM>, the AP MLD transmits, on the primary link after the switching of the first link, a second management frame (e.g., a Beacon frame or a Probe Response frame) indicating that an AP on the first link is in operation.

the present invention, the first link is the non-primary link, and the second management frame further includes a second element (e.g., a RNR element) indicating that the non-primary link is resumed.

In certain configurations, the indication of the second management frame is by an absence of indication, in the second management frame, of an estimated time for the AP on the non-primary link to resume operation after the switching of the first link.

In certain configurations, the first link is the non-primary link, and the first management frame further includes a second element (e.g., a max channel switch time element) indicating an estimated time for the AP on the non-primary link to resume operation after the switching of the non-primary link.

In certain configurations, the estimated time is a maximum time difference (a) between the target switching time and an expected time when the AP on the non-primary link resumes operation after the switching of the non-primary link or (b) between the time the first management frame is transmitted on the primary link and an expected time when the AP operating on the non-primary link resumes operation after the switching of the non-primary link.

In certain configurations, the AP MLD switches the non-primary link to operating on the different channel at the target switching time. The AP MLD resumes, by the AP on the non-primary link, operation on the non-primary link after the switching of the non-primary link to operating on the different channel.

In certain configurations, the first link is the primary link. The AP MLD switches the primary link to operating on the different channel at the target switching time. The AP MLD suspends communication on the non-primary link from the target switching time until transmitting the second management frame.

In certain configurations, the first link is the primary link. The AP MLD switches the primary link to operating on the second channel at the target switching time. The AP MLD determines to switch the non-primary link to operating on the first channel, where the first management frame further includes a second element (e.g., a channel switch announcement element or an extended channel switch announcement element) indicating the same target switching time as the primary link for the switching of the non-primary link to operating on the first channel. The AP MLD switches the non-primary link to operating on the first channel at the target switching time.

In certain configurations, the first management frame further includes a third element (e.g., a max channel switch time element) indicating a first estimated time for an AP on the primary link to resume operation after the switching of the primary link and a fourth element (e.g., a max channel switch time element) indicating a second estimated time for an AP on the non-primary link to resume operation after the switching of the non-primary link.

In certain configurations, the second management frame is a first frame (e.g., a Beacon frame or a Probe Response frame) transmitted on the primary link after the switching of the primary link, and the second management frame further indicates that an AP on the non-primary link is in operation.

<FIG> is a flow chart <NUM> of a method (process) of wireless communication of a non-AP MLD. The method may be performed by a non-AP MLD, e.g., the non-AP MLD <NUM> or the apparatus <NUM>. At operation <NUM>, the non-AP MLD associates, at the non-AP MLD, with an AP MLD on a primary link that is operating on a first channel and on a non-primary link that is operating on a second channel. At operation <NUM>, the non-AP MLD receives, on the primary link, a first management frame (e.g., a Beacon frame or a Probe Response frame) including a first element (e.g., a channel switch announcement element or an extended channel switch announcement element) indicating a target switching time for switching a first link of the primary link and the non-primary link to operating on a different channel. At operation <NUM>, the non-AP MLD receives, on the primary link after switching of the first link, a second management frame (e.g., a Beacon frame or a Probe Response frame) indicating that an AP on the first link is in operation. At operation <NUM>, the non-AP MLD resumes communication on the first link based on the second management frame, where the first link is operating on the different channel.

In certain configurations, the first link is the non-primary link, and the second management frame includes a second element (e.g., a RNR element) indicating that the non-primary link is resumed, and the resuming communication is further based on the second element.

In certain configurations, the first link is the non-primary link. The non-AP MLD identifies, from the first management frame, a second element (e.g., a max channel switch time element) indicating an estimated time for the AP on the non-primary link to resume operation after the switching of the non-primary link, and the communication on the first link is resumed after the estimated time.

In certain configurations, the non-AP MLD suspends communication on the non-primary link at the target switching time, where the second management frame is received after the estimated time on the primary link. The non-AP MLD resumes communication on the non-primary link after receiving the second management frame.

In certain configurations, the first link is the primary link. The non-AP MLD suspends communication on the non-primary link from the target switching time until receiving the second management frame indicating the primary link is operational.

In certain configurations, the first link is the primary link and the different channel is the second channel. The non-AP MLD identifies, from the first management frame, a second element (e.g., a channel switch announcement element or an extended channel switch announcement element) indicating the target switching time for switching the non-primary link to operating on the first channel. The non-AP MLD resumes communication on the non-primary link after receiving the second management frame, where the non-primary link is operating on the first channel.

Claim 1:
A method of wireless communication of a non-simultaneous-transmit-and-receive access point multi-link device, NSTR AP MLD, comprising:
establishing (<NUM>), at the NSTR AP MLD, a primary link on a first channel and a non-primary link on a second channel;
determining (<NUM>) to perform a channel switch operation to switch a first link of the primary link and the non-primary link to operating on a different channel;
transmitting (<NUM>), on the primary link and prior to the switching of the first link, a first management frame including a first element indicating a target switching time for the switching of the first link; and
transmitting (<NUM>), on the primary link after the switching of the first link, a second management frame indicating that a NSTR AP on the first link is in operation,
characterized in that
the first link is the non-primary link, and the second management frame further includes a second element indicating that the non-primary link is resumed.