Method for TXOP aggregation of multiple links

Abstract

A method for multi-link transmission opportunity TXOP aggregation is provided. A method for providing multi-link operation channel access in a multi-link network includes: starting a first backoff countdown and a second backoff countdown associated with a first link and a second link of the multi-link network, respectively, and in response to the first backoff countdown reaching zero, determining whether the second backoff countdown is less than or equal to an aggregation threshold, and in response to determining that the second backoff countdown is less than or equal to the aggregation threshold, sending a first frame and a second frame on the first link and the second link.

Description

Technical Field

[0001] Aspects of the present disclosure relate to wireless network communications. Background Art

[0002] Typically, a basic service set (BSS) includes an access point (AP) such as a wireless router and one or more stations such as user devices (e.g., phones, laptops, TVs, etc.). The access point enables stations within the BSS to connect to a wired network. In a multi-link BSS (e.g., a wi-fi network), an access point (AP) may operate on multiple links whose operating channels may be on different frequency bands, but a subset of the operating channels of the multiple links may be on the same frequency band. An example of a multi-channel BSS may be 20 MHz operation in the 2.4 GHz band, 80 MHz operation in the 5 GHz band, and 160 MHz operation in the 6 GHz band, wherein two or more of the 20 MHz operation in the 2.4 GHz band, the 80 MHz operation in the 5 GHz band, and the 160 MHz operation in the 6 GHz band may be performed concurrently. The access point may announce the multi-link operation of the access point through a beacon, a probe response, etc. The station may inform the access point of the capabilities of the station or the station type during the association phase.

[0003] Stations participating in a multi-link BSS can generally be classified as follows: 1) legacy stations, compatible with 802.11ax, 802.11ac, 802.11n, etc., and associated with an access point on a single link operating through a baseline mechanism; 2) single-link stations (SL STAs), such as extremely high throughput stations (EHT STAs) operating on a single link (e.g., for power saving when no active actions are running, for coexistence, etc.); and 3) multi-link stations (ML STAs), which are extremely high throughput stations associated with access points on multi-link operations. This classification may change over time, and the same station may be a SL STA at time t0 and a ML STA at time t1, depending on the operating mode of the same station at time t0 and time t1 and the set of links it supports. In other words, the selection of the link on which the station operates may be time-varying. Therefore, it is desirable to design a mechanism that enables such dynamic operation.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute prior art. Summary of the invention

[0005] Aspects of example embodiments of the present disclosure are directed to a system and method for addressing some of the problems presented by the introduction of multi-link operations in the current revision of the IEEE 802.11 standard.

[0006] Aspects of example embodiments of the present disclosure are directed to enhancing medium utilization for non-STR STAs in asynchronous multi-channel operation. Further aspects of the present disclosure are directed to improving fairness of medium access for non-STR stations and legacy stations in a multi-link network, particularly in light of transmission opportunity aggregation by multi-link stations.

[0007] According to some embodiments of the present disclosure, a method for providing multi-link operation channel access in a multi-link network is provided, the method comprising: starting a first backoff countdown and a second backoff countdown respectively associated with a first link and a second link of the multi-link network; and in response to the first backoff countdown reaching zero, determining whether the second backoff countdown is less than or equal to an aggregation threshold; and in response to determining that the second backoff countdown is less than or equal to the aggregation threshold, sending a first frame and a second frame on the first link and the second link.

[0008] In some embodiments, the method further includes determining that the first link and the second link are idle.

[0009] In some embodiments, the method further comprises maintaining a contention window for the second link the same as the contention window prior to sending the second frame.

[0010] In some embodiments, the method further comprises: in response to determining that the second backoff countdown is less than or equal to the aggregation threshold: pausing the second backoff countdown before sending the second frame; and resuming the second backoff countdown after completing sending on the second link.

[0011] In some embodiments, the method further includes: in response to determining that the second backoff countdown is less than or equal to the aggregation threshold: pausing the second backoff countdown before sending the second frame; and generating a new start value for the second backoff countdown, wherein the new start value is a random value that is less than the contention window of the second link.

[0012] In some embodiments, the first frame and the second frame have time-aligned start times and time-aligned end times.

[0013] In some embodiments, the method further comprises padding a shorter one of the first frame and the second frame to equalize a frame duration of the first frame and a frame duration of the second frame.

[0014] In some embodiments, the method further comprises: in response to determining that the second backoff countdown is greater than the aggregation threshold, sending the first frame on the first link and not sending on the second link.

[0015] In some embodiments, the method further comprises: receiving the aggregation threshold from an access point of the multi-link network.

[0016] In some embodiments, at least one of the first frame and the second frame includes an encapsulation of a physical header, one or more MAC headers, and one or more data payloads.

[0017] According to some embodiments of the present disclosure, a method for providing multi-link operation channel access in a multi-link network is provided, the method comprising: starting a first backoff countdown and a second backoff countdown respectively associated with a first link and a second link of the multi-link network; and in response to the first backoff countdown reaching zero, identifying the second link as a restricted link or an unrestricted link; in response to identifying the second link as the unrestricted link, sending a first frame and a second frame on the first link and the second link, respectively; and in response to identifying the second link as the restricted link, sending the first frame on the first link and not sending on the second link.

[0018] In some embodiments, the step of transmitting the first frame and the second frame includes transmitting the first frame and the second frame simultaneously on the first link and the second link.

[0019] In some embodiments, the method further comprises: determining that the second link is idle before sending the second frame.

[0020] According to some embodiments of the present disclosure, a method for providing multi-link operation channel access in a multi-link network is provided, the method comprising: starting a first backoff countdown and a second backoff countdown respectively associated with a first link and a second link of the multi-link network; and in response to the first backoff countdown reaching zero, determining whether the second backoff countdown is less than or equal to an aggregation threshold; and in response to determining that the second backoff countdown is less than or equal to the aggregation threshold, sending a request to send frame on the first link and the second link; and in response to receiving a clear to send frame on both the first link and the second link, sending a first frame and a second frame on the first link and the second link.

[0021] In some embodiments, the method further comprises monitoring the first link and the second link for the clear to send frame from an access point of the multi-link network.

[0022] In some embodiments, the method further includes, in response to receiving a clear to send frame on the first link but not on the second link, sending the first frame on the first link and not sending on the second link.

[0023] In some embodiments, the method further includes limiting transmission on the first link and the second link in response to not receiving a clear to send frame on either of the first link and the second link.

[0024] In some embodiments, the method further comprises maintaining a contention window for the second link the same as the contention window prior to sending the second frame.

[0025] In some embodiments, at least one of the first frame and the second frame includes an encapsulation of a physical header, one or more mac headers, and one or more data payloads.

[0026] In some embodiments, the method further comprises: in response to the first backoff countdown reaching zero, identifying the state of the second link as idle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] These and other features of some example embodiments of the present disclosure will be appreciated and understood with reference to the specification, claims, and drawings, in which:

[0028] Figure 1 is a block diagram of a communication network according to some embodiments of the present disclosure;

[0029] FIG. 2A to FIG. 2C shows possible conflicts in asynchronous multilink operation with non-STR stations, where medium access on each channel is completely independent;

[0030] Figure 3 illustrates a multi-link operation using the above-mentioned baseline strategy according to some embodiments of the present disclosure;

[0031] Figure 4 The effect of opportunistic backoff restart in improving medium access utilization according to some embodiments of the present disclosure is shown;

[0032] Figure 5 illustrates collisions that may occur at an access point due to concurrent transmissions by both non-STR STA stations and single-link stations on different channels according to some examples;

[0033] Figure 6 The effects of opportunistic backoff restart and multi-link busy status indication in avoiding collisions and improving medium access utilization in a network with non-STR STAs, STR STAs and SL STAs according to some embodiments of the present disclosure are shown;

[0034] Figure 7 is a flow chart illustrating a process of providing multi-link operating channel access in a multi-link network according to some embodiments of the present disclosure;

[0035] Figure 8 is a flow chart illustrating a process for providing multi-link operating channel access by utilizing access point acknowledgement in a multi-link network according to some embodiments of the present disclosure;

[0036] Fig. 9 Performing transmission opportunity (TXOP) aggregation on a pair of idle links according to some examples of the present disclosure is shown;

[0037] Fig.10 The effect of the aggregation threshold according to some embodiments of the present disclosure in preventing TXOP aggregation and improving fairness in a multi-link BSS is shown;

[0038] FIG. 11A to FIG. 11B illustrates an aggregated link backoff process performed by a multi-link station according to some embodiments of the present disclosure;

[0039] Fig.12 illustrates multi-link channel access operation in restricted aggregation mode according to some embodiments of the present disclosure;

[0040] Fig.13A An example scenario of multi-link TXOP aggregation with RTS-CTS handshake according to some embodiments of the present disclosure is shown;

[0041] Fig. 13B and Fig. 13C Two different scenarios of TXOP aggregation when RTS on one of the links fails according to some embodiments of the present disclosure are shown;

[0042] Fig.14A shows TXOP aggregation without alignment in the STR STA case according to some embodiments of the present disclosure;

[0043] Fig. 14B shows TXOP aggregation without alignment in case of non-STR STA according to some embodiments of the present disclosure;

[0044] Fig.15 illustrates a process of TXOP aggregation using an aggregation threshold in a multi-link network according to some embodiments of the present disclosure;

[0045] Fig.16 illustrates a process for TXOP aggregation utilizing restricted links and unrestricted links in a multi-link network according to some embodiments of the present disclosure;

[0046] Fig.17 illustrates a process of TXOP aggregation utilizing RTS-CTS handshake in a multi-link network according to some embodiments of the present disclosure; and

[0047] Fig.18 A multi-link access mode announcement frame including access mode definitions for all link pairs according to some embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0048] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of some example embodiments of the system and method for channel estimation provided according to the present disclosure, and is not intended to represent the only form in which the present disclosure can be constructed or utilized. The description sets forth the features of the present disclosure in conjunction with the illustrated embodiments. However, it should be understood that the same or equivalent functions and structures may be implemented by different embodiments that are also intended to be encompassed within the scope of the present disclosure. As shown elsewhere herein, the same element numbers are intended to indicate the same elements or features.

[0049] Figure 1 is a block diagram of a communication network 100 according to some embodiments of the present disclosure.

[0050] According to some embodiments, a communication network 100 (e.g., a wireless network) includes an access point (AP) 110 and one or more stations (STA) 120, wherein the communication network 100 may be a basic service set (BSS). The access point 110 is a wireless network device that is connected to the wired network 10 and acts as a portal for the stations 120 within the BSS 100. Therefore, the access point 110 may convert a wired signal into a wireless signal and vice versa. The access point 110 may include a router or may be coupled to the wired network 10 through a router. Each station 120 within the BSS 100 may be a wireless terminal device (e.g., a client device), such as a mobile phone, a tablet, a computer, a television, a wireless sensor, etc.

[0051] In some examples, the access point 110 is a multi-antenna system and can communicate with each station 120 within the BSS 100 via two or more channels / links 130. The access point 110 can establish operating channels 130 for the stations 120 within the BSS 100. Therefore, the access point 110 can select operating channels 130 so that the access point 110 has simultaneous transmit-receive (STR) capability on each pair of links in its BSS 100. As used herein, STR capability refers to the ability to support reception on one link 130 while transmitting on another link 130 (e.g., concurrent reception and transmission on two links). The STR capability of a device (e.g., an access point 110 or a station 120) can depend on multiple factors, such as RF design and operating parameters, wherein the RF design and operating parameters include channel location, bandwidth of each channel, antenna distribution, etc. Throughout this disclosure, the terms "link", "channel", and medium can be used interchangeably to refer to the frequency band used by the wireless network 100 to send and receive data.

[0052] In order to realize the full potential of multi-channel operation, it is desirable for participating access points 110 / stations 120 to have simultaneous bidirectional communication capabilities on multiple channels 130. With this capability, uplink and downlink communications can occur simultaneously in an asynchronous manner between access points 110 and stations 120. However, even stations 120 that are multi-radio devices may lack such capabilities due to in-device power leakage caused by insufficient operating frequency spacing.

[0053] According to some examples, the constraints on multi-link operation may include STR constraints, simultaneous transmit-transmit (STT) constraints, and simultaneous receive-receive (SRR) constraints. When operating in the STR constraint, the station 120 may not be able to detect the physical preamble / header of the frame (e.g., 802.11PHY preamble) or decode the physical header on link A when transmitting on link B. For example, this may occur when link A operates on the lower 5GHz band and link B operates on the higher 5GHz band. When operating in the STT constraint, the multi-link station 120 may not be able to transmit simultaneously on a specific combination of channels / links 130 due to intermodulation problems. In addition, for some channel combinations, the multi-link station 120 may not be able to transmit simultaneously on those channels with a single antenna due to RF limitations. In addition, when operating in the SRR constraint, the multi-link station 120 may not be able to receive simultaneously on some channels 130 with a single antenna due to RF limitations. In such a case, since station 120 may not be able to detect / decode packets simultaneously on link 130, it may not maintain a network allocation vector (NAV) on link 130. Therefore, multi-link station 120 with SRR constraints on a pair of links 130 may fall back to single link operation. In IEEE 802.11, NAV may represent the amount of time that a sending station intends to keep the medium busy.

[0054] Based on these multi-link operation constraints, the stations 120 may be classified as: simultaneous transmit-receive stations (STR STAs), which are capable of STR, STT, and SRR on a link pair; non-simultaneous transmit-receive stations (non-STR STAs), which may not be capable of STR, but are capable of STT and SRR on a link pair; non-simultaneous transmit-transmit stations (non-STT STAs), which may not be capable of STR or STT, but are capable of SRR on a link pair; and single-link stations (SL STAs), which operate on only one link in a link pair. SL STAs may include traditional stations as well as very high throughput stations that operate on a single link due to SRR constraints, are in power saving mode, etc. A single device 110 / 120 may have STR capability on a pair of links and not have STR capability on another link pair.

[0055] According to some examples, each frame (or data frame) may be a physical protocol data unit (PPDU), wherein the PPDU includes (e.g., encapsulates) a physical (PHY) preamble / header (e.g., a PHY layer header) and one or more medium access control (MAC) protocol data units (MPDUs). Each MPDU may include a MAC header (e.g., a MAC layer header) and a data payload.

[0056] FIG. 2A to FIG. 2C Illustrates possible collisions that may occur in asynchronous multi-link operation with non-STR STAs, where medium access on each channel is completely independent. Figure 2A shows the collision caused by non-STR STA transmission, Figure 2B shows the collision caused by the access point's transmission, and Figure 2C Figure 2 shows a conflict caused by a packet detection failure of a non-STR STA. FIG. 2A to FIG. 2C The STR conflict shown in shows the timeline from the perspective of a non-STR STA represented by STA 1.

[0057] Figure 2A The situation that the non-STR STA contends on channel B after it becomes idle and transmits after winning the contention is shown, wherein BUSY indicates other communications on the link. On channel A, the access point is transmitting to the non-STR STA, which fails to receive successfully due to its own transmission on channel B.

[0058] Figure 2B The situation in which the access point contends on link B after link B becomes idle and transmits after winning the contention is shown. On link A, the non-STR STA is transmitting to the AP. Therefore, the non-STR STA fails to receive the AP's transmission on link B.

[0059] Figure 2CA situation is shown where a non-STR STA completes transmission on link A and resumes contention on both links. Just after the non-STR STA completes transmission on link A, the non-STR STA may fail to detect an ongoing intra-BSS transmission on link B (i.e., a transmission from another station (STA2) within the same BSS). This detection failure may occur due to the following reasons: (a) the non-STR STA fails to receive the physical header (e.g., of a frame from the second station to the access point) on link B because the non-STR STA is transmitting on link A at the time, or (b) the energy of the ongoing transmission on link B received by the non-STR STA is below the energy detection threshold defined in the 802.11 standard. The ongoing transmission on link B may be an uplink transmission (e.g., a frame sent to the access point) or a downlink transmission (e.g., a frame sent from the access point). If the non-STRSTA continues to attempt medium access and transmit on link B, there will be a collision in the BSS at (a) the access point (assuming the ongoing transmission is an uplink frame) or (b) another station (STA 2) within the BSS (if the ongoing transmission is a downlink frame intended for (e.g., to) that station). In either case, the transmission failure may cause the size of the backoff window of the transmitter following the IEEE802.11 standard backoff procedure to increase, thereby reducing throughput utilization and overall system performance.

[0060] According to some examples, when a non-STR STA or access point is busy on another channel (e.g., link B), the problem can be solved by suspending transmission attempts from the non-STR STA to the access point and from the access point to the non-STR STA on the channel (e.g., link A). FIG. 2A to FIG. 2C For example, at a non-STR STA, in order to resolve Figure 2A As shown in the situation shown in , whenever a station is in a transmitting or receiving state on one channel (e.g., on channel A), the backoff process (e.g., 802.11 backoff process) for medium access on another channel (e.g., channel B) can be suspended. In addition, in order to prevent Figure 2B In the situation shown in , when the access point is receiving a BSS intraframe on one channel / link (e.g., channel A), since the BSS intraframe may come from a non-STR STA, the access point may not attempt to transmit to any non-STR STA on another channel / link (e.g., channel B).

[0061] Figure 3 The multi-link operation using the above baseline strategy according to some embodiments of the present disclosure is shown. Figure 3In the embodiment of the present invention, when the non-STR STA (i.e., STA 1) is in a receiving state on link A, the non-STR STA suspends its backoff process on link B. Here, the backoff suspension is indicated by a backoff countdown (e.g., 9, 8, 7), wherein the backoff countdown (e.g., 9, 8, 7) is suspended when there is an uplink transmission in the same BSS (e.g., indicated by a frame from STA 2 to the access point), and the backoff countdown is suspended again when there is a transmission appearing on link A in a neighboring BSS (e.g., a frame from an overlapping BSS (OBSS)). However, in both cases, these suspensions may be unnecessary for the following reasons: even if the non-STR STA has resumed its contention on link B and has transmitted, there will be no STR conflict because the transmission on link A is not intended (e.g., not designated) for the non-STR STA. This may result in insufficient medium utilization, and therefore, it may be desirable to increase the medium utilization of the non-STR STA to exceed the baseline policy.

[0062] According to some embodiments, non-STR STA medium utilization is improved by utilizing opportunistic backoff restarts.

[0063] Typically, it may take some time (e.g., more than 100 μS) for a station to decode the MAC header of a frame on a link to identify the intended receiver of the frame (e.g., the station itself or another station within the BSS). However, reading the physical header of a frame may take significantly less time (e.g., on the order of 20 μS to 50 μS). Thus, in some embodiments, the physical header of a frame sent by an access point on a link (e.g., link A) includes an indication of another link (e.g., link A). Figure 3 The station observing the transmission on the link can quickly interpret the information in the physical header and determine whether to resume medium access (e.g., resume the backoff countdown).

[0064] Figure 4 The effect of opportunistic backoff restart according to some embodiments of the present disclosure on improving medium access utilization is shown.

[0065] exist Figure 4In the example of , a non-STR STA is competing for access on both link A and link B. This is indicated by independent countdown timers on the two links (i.e., "9, 8, 7" on link A and "4, 3, 1..." on link B). However, the non-STR STA receives a frame on link A and suspends the countdown on both link A and link B to avoid any conflict. The non-STR STA reads the physical header of the frame received through link A and determines that the frame is not intended / not designated for the non-STR STA, and the physical header does not identify any transmission on link B. Therefore, the non-STR STA resumes the countdown on link B (as indicated by "1, 0") after a short time (e.g., about 20μS to 50μS). Once the countdown of link B reaches zero, the non-STR STA transmits on link B. Therefore, according to some embodiments, opportunistic backoff restart enables the non-STRSTA to improve (e.g., maximize) access utilization while avoiding conflicts.

[0066] At a non-STR STA, the key STR conflict situation to be avoided is when the frame being received on link A is a downlink frame for this non-STR STA and the non-STR STA resumes the backoff countdown on link B (see e.g. Figure 2A ). In other cases, such as Figure 4 As shown, the backoff countdown on link B may be resumed. Thus, according to some embodiments, after pausing the backoff countdown due to the presence of a frame on a link (e.g., channel A), the non-STR STA resumes the backoff on another link (e.g., channel B) when the non-STR STA receives a frame on channel A that is a neighboring BSS frame, an intra-BSS uplink frame (i.e., a frame intended for an access point of the BSS), or an intra-BSS downlink frame intended for another station. The neighboring BSS frame may be a frame from another neighboring wireless network that has high enough energy to be detected as a data frame by the non-STR STA.

[0067] According to the 802.11ax protocol, the physical header of the frame has a BSS color indicator to identify which BSS the frame comes from. The BSS color indicator can be a 6-bit identifier that is attached to the physical header of each frame and enables the non-STR STA to determine whether the frame on the link is a BSS intra-frame or from an adjacent BSS. In some examples, the access point can identify which frames are from other networks based on the BSS color indicator and ignore them to improve spatial multiplexing with signals within the BSS. In addition, the 802.11ax physical header also includes an uplink / downlink bit to indicate whether the frame (e.g., a BSS intra-frame) is an uplink frame or a downlink frame. In addition, according to some embodiments, the physical header of at least all downlink frames (e.g., all downlink single-user transmissions from an access point) includes station identifier information, wherein the station identifier information enables the non-STRSTA to identify whether the frame is intended for a non-STR STA or another station. In some examples, the station identifier can be small and can be 48 bits or less. In some embodiments, the station identifier in the physical header is different from (e.g., shorter than) the station address of the MAC header. For example, the station identifier in the physical header may be 12 bits long, while the MAC address may be 48 bits long. Two different networks (BSSs) may use the same station identifier to identify two different devices; however, the station identifier and the BSS color indicator together may uniquely identify a particular station. Therefore, according to some embodiments, by reading the BSS color indicator, uplink / downlink bit, and station identifier of the physical header of the frame, a non-STR STA may determine whether a frame on the link is an adjacent BSS frame, an intra-BSS uplink frame, or an intra-BSS downlink frame intended for another station, and therefore determine whether to resume the backoff countdown. In some embodiments, both the station and the access point are capable of encoding the station identifier in the physical header.

[0068] In some embodiments, decoding the physical header is significantly faster than decoding the MAC header (e.g., 40 μS vs. 150 μS or a few milliseconds). Therefore, making contention decisions based on information encoded in the physical header compared to MAC header information can substantially improve medium access efficiency and increase medium utilization for non-STR STAs. To further reduce decoding time, in some embodiments, when a non-STR STA identifies a frame as an inter-network frame or an intra-network uplink frame, the non-STR STA does not decode the station identifier in the physical header.

[0069] At the access point, a key STR collision situation to be avoided is when the access point is receiving a frame from a non-STR STA on one link while the access point is attempting to transmit to a non-STR STA on another link (see e.g. Figure 2BAs described above, in some embodiments, the access point has STR capabilities, and the multi-link stations indicate their STR capabilities to the access point (e.g., during the association phase). The access point can use this knowledge to improve medium utilization.

[0070] According to some embodiments, the physical header of the frame generated by the station (i.e., the uplink frame) includes a station identifier. Therefore, in some embodiments, when the access point determines that the frame being received on one link is from a specific non-STR STA, the access point does not transmit to the STA when obtaining medium access on another link. In this way, the access point can transmit to a non-STR STA on one link (e.g., link A) while receiving from another non-STR STA on another link (e.g., link B).

[0071] In the case of an 802.11 frame with a legacy physical header (i.e., a physical header that does not include a BSS color indicator, an uplink / downlink bit, and a station identifier), which is common in control frames / management frames and transmissions of legacy devices, according to some embodiments, information used by a non-STR STA to resume a backoff countdown at the earliest time is not available. Therefore, according to some embodiments, when a non-STR STA and an access point determine that the physical header does not include a BSS color indicator, an uplink / downlink bit, or a station identifier, the non-STR STA and the access point wait to decode the 802.11 MAC header information to determine the receiver of the frame. After doing so, the access point and the non-STR STA follow the above-described method. Decoding an 802.11 MAC header may take longer (e.g., 3 times longer or more) time than decoding a physical header, thereby potentially reducing medium utilization; however, avoiding collisions by adopting this method may improve medium access efficiency compared to prior art solutions.

[0072] In some examples, the non-STR STA may negotiate with the access point a physical protocol data unit (PPDU) format for individually addressed frames and group addressed frames intended for (e.g., destined for) the non-STR STA. Thus, if the detected frame does not belong to the negotiated format, the backoff may be restarted. For example, the non-STR STA may negotiate only an extremely high throughput (EHT) format and a non-high throughput (non-HT) format with the access point. Thus, when the PPDU type of the frame is not one of the EHT format or the non-HT format, the non-STR STA may restart the backoff countdown. For example, the PPDU type of the frame may be one of the high throughput (HT) format, the very high throughput (VHT) format, or the high efficiency (HE) format.

[0073] Figure 5Collisions that may occur at an access point due to concurrent transmissions by both non-STR STAs and single-link stations (SL STAs) on different channels are shown according to some examples.

[0074] exist Figure 5 In the example of , a non-STR STA (STA 1) is transmitting on link A, during which a single-link station (STA 2) that is only capable of receiving and transmitting on a single link starts transmitting on link B. The non-STR STA cannot receive / sense the transmission on link B, and may find link B to be idle due to the low received power from the single-link STA (hidden terminal). RTS-CTS (Request to Send / Clear to Send: helps reduce frame collisions in the 802.11 protocol) cannot solve this problem. Since the non-STR STA is busy transmitting on the link A single link when the single-link station starts transmitting on link B, the non-STR STA will not receive the Clear to Send (CTS) broadcast from the access point on link B, and will not be aware of the transmission on link B. In this situation, if the non-STR STA gains access to link B and transmits, it may cause a conflict at the access point, resulting in failure of the transmission of the single-link station and reception of the transmission of the non-STR STA.

[0075] Since the STR constraint is indicated by the non-STR STA when it starts operating on the link pair, the conflict can be resolved by utilizing the access point's acknowledgement of the non-STR STA with the STR constraint. In some embodiments, the conflict is resolved by one or more of a pause countdown timer at the non-STR STA, energy detection at the non-STR STA, and broadcasting of the remaining TXOP by the access point.

[0076] According to some embodiments, the access point may provide a Figure 5 The access point may indicate to non-STR STAs in an acknowledgement (ACK or Block ACK) as shown in FIG. 1 that the access point is receiving a BSS intra-frame on another link (e.g., Figure 5Frames from STA2 to AP on link B in ). In some embodiments, upon receiving the indication, the non-STR STA may pause its backoff countdown on another link (e.g., link B) and start a pause countdown timer (the pause countdown timer may be similar to the multi-user enhanced distributed channel access (MU EDCA) timer in the 2019802.11ax draft standard). In some examples, the pause countdown may be up to 5.43ms. Once the pause countdown reaches zero, the non-STR STA returns to normal operation by resuming the backoff countdown on the link (e.g., link B). During the pause countdown on the link, if the non-STR STA receives a BSS intra-frame, it stops the pause countdown timer and resumes the backoff process. Using the pause countdown timer ensures that the non-STR STA does not suspend the backoff countdown for a long time when the channel becomes idle without other BSS intra-frame transmissions. The pause countdown value may be announced by the access point in the same frame (e.g., beacon) in which the access point announces the multi-link channel access mode information, or a default value of 5.43 mS may be used (5.43 mS may be the duration of the longest PPDU). The access point may broadcast beacons to stations within the BSS at startup and at regular intervals (e.g., every 100 mS).

[0077] As an alternative to or in addition to using a pause countdown timer, in some embodiments, a non-STR STA utilizes a pause mode energy detection threshold to determine whether it can transmit on link B when the non-STR STA has just completed transmission on link A. According to some embodiments, the new energy detection threshold used to enable the non-STR STA to detect transmissions from other stations on link B in this particular situation is different from (e.g., less than) the frame detection threshold used under normal operation. For example, the pause mode energy detection threshold can be about -72dBm to about -82dBm, which is lower than the energy detection threshold during normal operation (e.g., -62dBm). When the detected energy is greater than or equal to the pause mode energy detection threshold, the non-STR STA determines that there is a transmission on link B (i.e., link B is busy), and the non-STR STA does not attempt to perform any transmission on the link. However, according to some embodiments, when the detected energy is less than the pause mode energy detection threshold, the non-STR STA can resume the backoff countdown on link B even if the pause countdown timer has not yet reached zero. Using this frame detection scheme during the pause countdown allows non-STR STAs to resume transmission on link B without having to wait for the entire duration of the pause countdown, thereby further improving medium access efficiency.

[0078] According to some embodiments, in addition to the busy status indication by the acknowledgement (ACK or block ACK), the access point also provides the remaining transmission opportunities (TXOP) on the other link. The TXOP defines the duration for which a station can send a frame after it has contended for the transmission medium. Therefore, the non-STR STA can accurately determine the time to suspend the backoff countdown.

[0079] Using the pause countdown timer, the broadcast of the remaining TXOPs described above, and / or the lower energy detection mechanism may improve medium utilization of non-STR STAs in asynchronous multi-channel operations.

[0080] Figure 6 The effect of opportunistic backoff restart and multi-link busy status indication in avoiding collision and improving medium access utilization in a network with non-STR STA, STR STA and SL STA according to some embodiments of the present disclosure is shown. Figure 6 In , the first station STA 1 is a non-STR STA, the second station STA 2 is a STR STA, and the third station STA 3 is a SLSTA. Figure 6 The examples shown in are from the perspective of a non-STR STA.

[0081] According to some embodiments, following a transmission from a non-STR STA to the access point on link A, the access point provides multi-channel busy status feedback in a corresponding acknowledgment (ACK or block ACK) indicating that the access point is receiving (a frame from a second station, STA 2) on link B. As a result of the busy status indication, in some embodiments, the non-STR STA defers contending for medium access on link B until synchronizing its contention status with a BSS intra-frame on link B. In this case, the BSS intra-frame is an acknowledgment from the access point for the second station, STA 2 transmission on link B to the access point.

[0082] After both link A and link B become idle, the non-STR STA contends for medium access on both link A and link B (as indicated by the backoff countdown "9, 8, 7" on link A and "6, 5" on link B), and begins receiving a frame on link A, wherein the frame is a transmission from the access point to the second station STA2. In some embodiments, upon detecting the frame on link A, the non-STR STA pauses / interrupts the countdown on link B and reads the physical header of the frame. Upon identifying that the frame is an intra-BSS downlink frame intended for another station (e.g., based on the BSS color indicator, uplink / downlink bit, and station identifier in the physical header), the non-STR STA resumes the backoff countdown on link B.

[0083] exist Figure 6In the example of , similar to the access point, the second station STA 2 has STR capability and can therefore perform simultaneous transmission and reception. Figure 6 In the example of FIG. 1 , the second station STA 2 wins the contention on link B and transmits to the access point. The non-STR STA senses (eg, identifies) the transmission from the second station STA 2 (eg, by decoding the physical header) and does not transmit on link B.

[0084] Next, the non-STR STA starts the backoff countdown on both links again after the corresponding link becomes idle. Then, the non-STR STA detects the frame it starts receiving on link A (i.e., the third station STA 3 transmission to the access point), and suspends the backoff countdown in link B. The non-STR STA reads the physical header of the frame detected on link A and identifies the frame as an intra-BSS uplink frame. Accordingly, the non-STR STA resumes the backoff countdown on link B, and after the backoff countdown reaches zero, the non-STR STA sends on link B.

[0085] Thus, the non-STR STA avoids any collisions on channel A and channel B while also improving (eg, increasing) its medium utilization.

[0086] Figure 7 is a flow chart illustrating a process 200 of providing multi-link operating channel access in a multi-link network according to some embodiments of the present disclosure.

[0087] In some embodiments, a multi-link station (e.g., a non-STR STA) starts a first backoff countdown and a second backoff countdown associated with a first link and a second link of a multi-link network, respectively (202). The multi-link station receives a first frame on the first link (204) and thus suspends the second backoff countdown (206). The multi-link station decodes the first frame (e.g., decodes a physical header of the first frame) to identify the first frame as one of an inter-network frame, an intra-network uplink frame, or an intra-network downlink frame (208). In response to identifying the first frame as an inter-network frame or an intra-network uplink frame (210), the multi-link station resumes the second backoff countdown (212). When the first frame is an intra-network downlink frame, the multi-link station identifies the receiver of the first frame as the multi-link station or another station (214). When the designated receiver of the first frame is another station, the multi-link station resumes the second backoff countdown (212). However, when the designated receiver is the multi-link station itself, the multi-link station stops / pauses the second backoff countdown on the second link (218).

[0088] Figure 8is a flow chart illustrating a process 300 for providing multi-link operating channel access by utilizing access point acknowledgement in a multi-link network in accordance with some embodiments of the present disclosure.

[0089] In some embodiments, a multi-link station (e.g., a non-STR STA) receives an acknowledgment (an ACK of a block ACK) from an access point on a first link due to completion of transmission to the access point on a first link (302). The multi-link station starts a first backoff countdown and a second backoff countdown associated with the first link and the second link of the multi-link network, respectively (304). The multi-link station decodes the acknowledgment to determine whether the access point is receiving a first intra-network frame on the second link (306). When the acknowledgment indicates that the access point is receiving on the second link (308), the multi-link station pauses the second backoff countdown (310) and starts a pause countdown (312). When the pause countdown reaches zero, the multi-link station resumes the backoff countdown (314). If the acknowledgment indicates that the access point is not receiving on the second link (308), the multi-link station continues the second backoff countdown and the normal backoff process (316).

[0090] TXOP aggregation

[0091] Transmission opportunity (TXOP) aggregation is a mechanism by which a multi-link station can synchronize (align in time) its transmissions on a pair of links that are idle (i.e., not busy). In some embodiments, when two or more channels are idle, the multi-link station starts transmissions on the two or more channels simultaneously once the first of the corresponding two or more backoff countdowns reaches zero. Thereafter, the earliest link whose backoff countdown reaches zero is referred to as the primary link, and the links participating in multi-link aggregation if the backoff countdown of the link has not yet reached zero are referred to as aggregated links.

[0092] Fig. 9 Performing TXOP aggregation on a pair of idle links according to some examples of the present disclosure is shown. Fig. 9 It is shown from the perspective of a multi-link station, TXOP indicates the transmission of the multi-link station, and BUSY indicates other traffic on the link.

[0093] exist Fig. 9 In the example of , the multi-link station contends for access on both link A and link B as soon as both channels become idle. Here, the backoff countdown for link B reaches zero before the backoff countdown for link A, and the multi-link station begins transmitting on link B. In the prior art, transmission on link A does not begin until after the corresponding backoff countdown reaches zero. However, according to some embodiments, the multi-link station begins transmission on both idle channels (i.e., even link A) as soon as the countdown on one channel (i.e., link B) reaches zero. Fig. 9In the example of , link B is the primary link and link A is the aggregated link. In some embodiments, frames (eg, PPDUs) on the primary link and the aggregated link have aligned start and end times.

[0094] While TXOP aggregation may facilitate channel / medium access for aggregated multi-link stations, it may reduce channel access for single-link stations (e.g., legacy stations) competing on the same channel as the multi-link stations. Fig. 9 In the example of , a single-link station competing for access to link A may fail due to the early aggregated transmission of the multi-link station on link A. Therefore, some embodiments of the present disclosure provide a mechanism for addressing fairness for single-link stations and legacy stations in a multi-link BSS with aggregation mode enabled.

[0095] Typically, the links of a multi-link BSS operate independently, and therefore the network busyness status may be independent between the links.It is possible that at a given time, the aggregated link may be busy with a higher average backoff countdown value than the primary link.

[0096] According to some embodiments, a multi-link station transmits using an aggregated link only when the backoff countdown of the aggregated link is less than or equal to a predefined aggregation threshold. This threshold may be set by the access point and announced via periodically broadcast beacons (similar to 802.11ax MU EDCA). In some examples, the access point may dynamically set the aggregation threshold for each link based on the number of associated single-link stations on each link to maintain fairness.

[0097] Fig.10 The effect of the aggregation threshold according to some embodiments of the present disclosure in preventing TXOP aggregation and improving fairness in a multi-link BSS is shown. Fig.10 It is shown from the perspective of a multi-link station, with TXOP indicating a transmission by the multi-link station and BUSY indicating other communications on the link.

[0098] exist Fig.10 In the example of , a multi-link station contends for access on both link A and link B after the channel becomes idle, and runs a separate backoff countdown for each link. The backoff countdown for link B reaches zero before the backoff countdown for link A, and the multi-link station starts transmission on link B at time t0. However, since the backoff countdown for link A (which is 7 at time t0) is not below the aggregation threshold (e.g., 4), the multi-link station does not aggregate link A and does not start transmission on the link. In this example, the backoff countdown on link A may continue to count down, however, another station wins the contention on link A, and from the perspective of the multi-link station, the link becomes busy. Therefore, preventing aggregation in this case improves fairness to other competing devices on link A.

[0099] According to some embodiments, a multi-link station performs a specific aggregate link backoff process to ensure fairness of channel access. In the baseline 802.11 specification, a typical backoff process after a successful transmission is to reset the contention window (CW) to the CW minimum parameter announced by the access point, and generate a new random count to which the backoff countdown is reset. Performing this same operation on an aggregated link may result in significant unfairness to a single-link station, especially in congested situations. As used herein, a backoff countdown is a number randomly selected between 0 and a maximum value called a contention window. The minimum contention window value may depend on the access category, and each link may have an independent contention window parameter for each access category. According to some examples, each count of the countdown may represent a single time slot, wherein a single time slot may be approximately 9 μS or approximately 20 μS.

[0100] Thus, according to some embodiments, after a successful transmission on an aggregated link, the multi-link station does not reset the contention window, but maintains the same contention window as before the transmission opportunity (TXOP) obtained by aggregation on the aggregated link. In some embodiments, the backoff countdown is restored to its value before the TXOP aggregation, and in other embodiments, a new backoff countdown value is selected for the aggregated link (e.g., randomly). After a transmission failure on an aggregated link (e.g., caused by another station winning the contention), the backoff process can behave in the same manner as the existing 802.11 specification.

[0101] FIG. 11A to FIG. 11B An aggregated link backoff procedure performed by a multi-link station according to some embodiments of the present disclosure is shown. Fig.11A shows that the backoff countdown remains the same after TXOP aggregation, and Fig. 11B The backoff countdown is shown to be reset to a new random count after TXOP aggregation.

[0102] refer to FIG. 11A to FIG. 11B , the multi-link station contends for access on both link A and link B. At time t1, the backoff countdown on link B reaches zero, and the backoff countdown on link A is less than the aggregation threshold. Therefore, according to some embodiments, the multi-link station aggregates link A and transmits on both channels simultaneously. Fig.11A Once the transmission on link A ends, at time t2, the multi-link stations compete for access to link A again. In some embodiments, the backoff countdown is restored to its value before TXOP aggregation (e.g., 6). Fig. 11B , at time t2, the multi-link station selects a new random backoff countdown value with the same contention window as before TXOP aggregation.

[0103] In a multi-link BSS, there may be a situation where single-link stations and legacy stations mainly operate on specific links. In order to address fairness in this situation, as an alternative to the aggregated link backoff process, some embodiments of the present disclosure impose restrictions on the aggregation of links. Thereafter, an unrestricted link represents an aggregateable link, and a restricted link is a non-aggregable link.

[0104] According to some embodiments, when in restricted aggregation mode, the multi-link station restricts aggregation to one direction. In other words, when the backoff countdown of the restricted link drops to zero, the multi-link station can aggregate the unrestricted link if it is idle, and when the backoff countdown of the unrestricted link drops to zero, the multi-link station cannot aggregate the restricted link even if the restricted link is idle. According to some embodiments, the access point determines which link is marked as a restricted link and which link is unrestricted, and broadcasts it to the stations within the BSS, for example, through a beacon.

[0105] Fig.12 A multi-link channel access operation in restricted aggregation mode according to some embodiments of the present disclosure is illustrated.

[0106] exist Fig.12 In the embodiment, link A is mainly operated by inter-BSS single link and traditional stations. Therefore, the access point has identified link A as a restricted link and link B as an unrestricted link. At time t1, the backoff countdown of restricted link A has reached zero, and unrestricted link B is idle. Therefore, in some embodiments, the multi-link station aggregates unrestricted link B and transmits on two channels simultaneously. At time t2, the backoff countdown of unrestricted link B has reached zero. However, since link A is restricted from aggregation, the multi-link station does not aggregate link A and transmits only on link B.

[0107] According to some embodiments, the multi-link TXOP aggregation process may be performed in conjunction with the RTC / CTS (ie, Request to Send / Clear to Send) mechanism of 802.11.

[0108] Fig.13A An example scenario of multi-link TXOP aggregation with RTS-CTS handshake according to some embodiments of the present disclosure is shown. Fig. 13B and Fig. 13C Two different scenarios of TXOP aggregation when RTS on one of the links fails according to some embodiments of the present disclosure are shown.

[0109] refer to FIG. 13A to FIG. 13C In some embodiments, assuming that the aggregated link is idle, a multi-link station (eg, non-STR STA) may aggregate an RTS frame when the backoff countdown on one of the links it is contending for reaches zero. In this example, link A is the aggregated link.

[0110] According to some embodiments, when a CTS frame is received on both links (e.g., from an access point), transmission is performed on both links. When a CTS frame is received only on a link where the backoff countdown is 0 (e.g., link B), transmission is performed only on that link, and the other link (e.g., link A) is not aggregated (see, e.g., Fig. 13B ). In addition, when a CTS is received only on the aggregated link (eg, link A), no transmission is performed (see, e.g. Fig. 13C ). Since no data transmission will be performed, a Contention Free Period End (CF-End) frame may be sent on the aggregated link to reset the NAV of all devices on the aggregated link and inform the devices that they are free to contend for access on the channel. The normal backoff process applies to link B.

[0111] In the example of TXOP aggregation provided above, the transmission opportunities (TXOPs) on the primary link and the aggregated link are equal and fully aligned (i.e., start and end at the same time). In some examples, this can help avoid conflicts on the aggregated link with transmissions in the opposite direction. However, in some cases, the padding frames used to align the TXOPs can result in inefficient multi-link utilization. To improve operational efficiency, according to some embodiments, the TXOP used on the aggregated link can be smaller than the primary link when the backoff countdown reaches zero.

[0112] Fig.14A TXOP aggregation without alignment (eg, without padding) in the STR STA case according to some embodiments of the present disclosure is shown. Here, each link has an acknowledgement from the receiving station or access point.

[0113] Fig. 14B FIG. 4 shows TXOP aggregation without alignment (eg, without padding) in the case of a non-STR STA according to some embodiments of the present disclosure. Fig. 14B In the example of , there is a unified ACK on the link (e.g., link B) where the backoff countdown is zero, where the ACK acts as an ACK for both channels. Here, packet extension can be used to account for processing overhead when preparing the unified block ACK on the primary link. In some examples, packet extension can be used when there is not enough time to process a received frame, whereby the station does not send anything on the medium, but does not expect any response.

[0114] Fig.15 A process 500 is shown for TXOP aggregation using an aggregation threshold in a multi-link network according to some embodiments of the present disclosure.

[0115] In some embodiments, a multi-link station initiates a first backoff countdown and a second backoff countdown associated with a first link and a second link of a multi-link network, respectively (502). In response to the first backoff countdown reaching zero (504), the multi-link station determines whether the second backoff countdown is less than or equal to an aggregation threshold (506). In response to determining that the second backoff countdown is less than or equal to the aggregation threshold, the multi-link station sends a first frame and a second frame on the first link and the second link (508). In response to determining that the second backoff countdown is greater than the aggregation threshold, the multi-link station sends the first frame on the first link and does not send on the second link (510).

[0116] Fig.16 A process 600 is shown for utilizing TXOP aggregation of restricted and unrestricted links in a multi-link network according to some embodiments of the present disclosure.

[0117] In some embodiments, a multi-link station initiates a first backoff countdown and a second backoff countdown associated with a first link and a second link of a multi-link network, respectively (602). In response to the first backoff countdown reaching zero (604), the multi-link station determines whether the second link is restricted or unrestricted (606). In response to identifying the second link as an unrestricted link, the multi-link station transmits a first frame and a second frame on the first link and the second link (608). In response to identifying the second link as a restricted link, the multi-link station transmits the first frame on the first link and does not transmit on the second link (610).

[0118] Fig.17 A process 700 is shown for TXOP aggregation utilizing RTS-CTS handshaking in a multi-link network according to some embodiments of the present disclosure.

[0119] In some embodiments, a multi-link station initiates a first backoff countdown and a second backoff countdown associated with a first link and a second link of a multi-link network, respectively (702). In response to the first backoff countdown reaching zero (704), the multi-link station determines whether the second backoff countdown is less than or equal to an aggregation threshold (706).

[0120] In response to determining that the second backoff countdown is less than or equal to the aggregation threshold, the multi-link station sends an RTS frame on the first link and the second link (708). The multi-link station then monitors the reception of CTS frames on the first link and the second link (710 and 712). In response to receiving a clear to send frame on both the first link and the second link, the multi-link station sends a first frame and a second frame on the first link and the second link, respectively (714). When the CTS frame is received only on the first link, the multi-link station sends the first frame on the first link and does not send on the second link (716). When the CTS frame is not received on the first link, the multi-link station restricts / cancels transmission on both links (i.e., does not send frames on either link) (718).

[0121] In response to determining that the second backoff countdown is greater than the aggregation threshold, the multi-link station sends an RTS frame only on the first link (and not on the second link) (720). When a CTS frame is received on the first link (722), the multi-link station sends the first frame on the first link and does not send on the second link (716). When a CTS frame is not received on the first link, the multi-link station restricts / cancels transmission on both links (i.e., does not send frames on either link) (718).

[0122] Typically, a multi-link access point establishes a BSS over multiple links distributed over multiple frequency bands. During a setup phase (e.g., during an association phase), a station of interest provides information about its STR capabilities to the access point of the BSS, and a multi-link setup is performed on a subset of links operated by the multi-link access point. Due to the different separation of frequency and spectrum locations, the STR capabilities may be independent (e.g., different) for each pair of links. The STR capabilities on a link pair may depend on the channel design, implementation, and operation. The channel design may, for example, include channel separation, operating bandwidth on each channel, operating frequency bands, antenna distribution across links (e.g., all antennas for all links, separate antennas for each link, etc.), and / or the like.

[0123] Table 1 shows a database storing STR capability information of different multi-link stations at an access point according to some embodiments of the present disclosure.

[0124] Table 1:

[0125]

[0126] In the example of Table 1, the setup links for each station indicate the links that are setup by the station during the initial association with the access point. Over time, and in a dynamic manner, only a subset of the setup links are enabled for frame exchanges (e.g., to save power). An example of the setup and enabled links is shown in Table 1. The database also maintains the STR capabilities for each pair of enabled links for each station in the BSS.

[0127] Because the channels and operating modes available to a station may change over time, the STR capabilities of a station may change dynamically over time.

[0128] In accordance with some embodiments, a multi-link station has the ability to indicate any changes to its support for simultaneous transmit and receive (STR) operations for enabled / setup link pairs, even after the initial multi-link setup. In some examples, this mechanism is similar to the operating mode (OM) indication defined in the IEEE (Institute of Electrical and Electronics Engineers) 802.11ax standard, and can be implemented by defining a new field similar to the 802.11ax OM control. Without this capability, the multi-link station would have to tear down the multi-link setup and redo the entire setup with updated support for STR operations, which would result in significant overhead and disruption in multi-link operations. This capability facilitates rapid transitions of the multi-link station from STR mode to non-STR mode, and vice versa. In some examples, such updates by the multi-link station to any pair of enabled / setup links would be allowed to be performed on any enabled link.

[0129] The multi-link channel access mode may be independent for each link pair, and for the same link pair, the STR capability may vary between the multi-link stations operating on the link pair. The access point is able to select a multi-link channel access mechanism for the link pair based on the STR capabilities of the associated multi-link stations operating on the link pair. According to some embodiments, the access point has the flexibility to select a multi-link channel access mechanism in a time-varying manner and announce the selection via the beacon. In some examples, this is similar to how the EDCA parameter set and the MU EDCA parameter set are announced in the beacon. As an example, as shown in the following table, for the multi-link channel access mechanism in the link pair, the STR capability may vary between the multi-link stations operating on the link pair. Figure 1 For the multi-link BSS shown, the access point can select a multi-link access mode for each link pair.

[0130] Table 2:

[0131] Link Pair Channel access mode AB Aggregation enabled for all STAs AC No aggregation BC Aggregation enabled only for non-STR STAs

[0132] In addition, in some embodiments, the access point can enable TXOP aggregation for specific types of stations or for specific services. For example, the access point can enable multi-link aggregation for non-STR STAs or for all stations.

[0133] Fig.18 A multi-link access mode announcement frame containing access mode definitions for all link pairs according to some embodiments of the present disclosure is shown. In some embodiments, each link pair has a corresponding frame indicating a channel access mode for the link pair.

[0134] Thus, as described above, embodiments of the present disclosure address some of the issues presented by the introduction of multi-link operation in the current revision of the IEEE 802.11 standard. Some aspects of the present disclosure are directed to enhancing medium utilization by non-STR STAs in asynchronous multi-channel operation. Other aspects of the present disclosure are directed to improving fairness of medium access to non-STR stations and legacy stations in a multi-link network, particularly in light of transmission opportunity aggregation by multi-link stations. As such, medium utilization by all stations within the network may be improved, thereby improving overall network performance.

[0135] The operations performed by each of the stations and access points of the multi-link network may be performed by a "processing circuit", which may include any combination of hardware, firmware, and software for processing data or digital signals. The processing circuit hardware may include, for example, an application-specific integrated circuit (ASIC), a general or dedicated central processing unit (CPU), a digital signal processor (DSP), a graphics processing unit (GPU), and a programmable logic device (such as a field programmable gate array (FPGA)). In the processing circuit, as used herein, each function is performed by hardware configured to perform the function (i.e., hard-wired), or by more general hardware (e.g., CPU) configured to execute instructions stored in a non-temporary storage medium. The processing circuit may be manufactured on a single printed wiring board (PWB) or distributed on several interconnected PWBs. The processing circuit may contain other processing circuits; for example, the processing circuit may include two processing circuits, an FPGA, and a CPU interconnected on a PWB.

[0136] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe various channels / links, elements, components and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish one channel / link, element, component or part from another channel / link, element, component or part. Therefore, without departing from the spirit and scope of the present invention, the first link, first element, first component or first part discussed below may be referred to as a second link, second element, second component, second region, second layer or second part.

[0137] As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form anyway.It will also be understood that when the terms "include" and / or "comprising" are used in this specification, the existence of the stated features, integers, steps, operations, elements and / or components is specified, but the existence or addition of the group of one or more other features, integers, steps, operations, elements, components and / or other features, integers, steps, operations, elements and components is not excluded.As used herein, the term "and / or" includes any and all combinations of one or more items in the associated listed items.In addition, when describing the embodiments of the present invention, the use of "can" refers to "one or more embodiments of the present disclosure".In addition, the term "exemplary" is intended to refer to examples or explanations.As used herein, the terms "use", "being used" and "used" can be considered to be synonymous with the terms "utilize", "being utilized" and "utilized" respectively.

[0138] For the purpose of the present disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be interpreted as only X, only Y, only Z, or any combination of two or more of X, Y, and Z, such as, for example, XYZ, XYY, YZ, and ZZ.

[0139] It should be understood that when an element or component is referred to as being "connected to," "coupled to," or "adjacent to" another element or component, it may be connected to, coupled to, or adjacent to the other element or component, or one or more intermediate elements or components may be present. When an element or component is referred to as being "directly connected to," "directly coupled to," or "immediately adjacent to" another element or component, there are no intermediate elements or components.

[0140] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than terms of degree, and are intended to account for the inherent variations in measurements or calculations that one of ordinary skill in the art would recognize. In addition, specific numbers or ranges recited in the written description or claims may also include the inherent variations in measurements or calculations that one of ordinary skill in the art would recognize.

[0141] In addition, any numerical range described herein is intended to include all sub-ranges of the same numerical precision contained in the range. For example, the range of "1.0 to 10.0" is intended to include all sub-ranges between the described minimum value 1.0 and the described maximum value 10.0 (and including the described minimum value 1.0 and the described maximum value 10.0), that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limit described herein is intended to include all lower numerical limits contained therein, and any minimum numerical limit described in this specification is intended to include all higher numerical limits contained therein. Therefore, the applicant reserves the right to modify this specification (including claims) to clearly describe any sub-range contained in the range clearly described here. All these ranges are intended to be inherently described in this specification.

[0142] While the present invention has been illustrated and described with reference to embodiments thereof, it will be apparent to those skilled in the art that various suitable changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims and their equivalents.

Claims

1. A method for providing multi-link operation channel access in a multi-link network, the method comprising: Initiating a first backoff countdown and a second backoff countdown respectively associated with a first link and a second link of the multi-link network; as well as In response to the first backoff countdown reaching zero: Determining whether a condition is satisfied, wherein the condition includes that the second backoff countdown is less than or equal to an aggregation threshold; as well as In response to determining that the condition is satisfied, a first frame and a second frame are transmitted on the first link and the second link, respectively.

2. The method according to claim 1, further comprising: It is determined that the first link and the second link are idle.

3. The method according to claim 1, further comprising: The contention window for the second link is maintained the same as the contention window before sending the second frame.

4. The method according to claim 1, further comprising: In response to determining that the second backoff countdown is less than or equal to the aggregation threshold: The second backoff countdown is paused before sending the second frame; as well as After the transmission on the second link is completed, the second backoff countdown is resumed.

5. The method according to claim 1, further comprising: In response to determining that the second backoff countdown is less than or equal to the aggregation threshold: The second backoff countdown is paused before sending the second frame; as well as generating a new start value for the second backoff countdown, The new start value is a random value that is smaller than the contention window of the second link.

6. The method according to claim 2, wherein: The first frame and the second frame have time-aligned start times and time-aligned end times.

7. The method according to claim 1, further comprising: A shorter one of the first frame and the second frame is padded to make the frame duration of the first frame and the frame duration of the second frame equal.

8. The method according to claim 1, further comprising: In response to determining that the second backoff countdown is greater than the aggregation threshold, the first frame is sent on the first link and is not sent on the second link.

9. The method according to claim 1, further comprising: The aggregation threshold is received from an access point of the multi-link network.

10. The method according to any one of claims 1 to 9, wherein: At least one of the first frame and the second frame includes an encapsulation of a physical header, one or more MAC headers, and one or more data payloads.

11. The method according to claim 1, wherein: The conditions also include the second link being identified as an unrestricted link, and, Wherein, the method further comprises: In response to the second link being identified as the restricted link, the first frame is transmitted on the first link and is not transmitted on the second link.

12. The method according to claim 11, wherein: The steps of sending the first frame and the second frame include: The first frame and the second frame are sent simultaneously on the first link and the second link.

13. The method according to claim 11, further comprising: The second link is determined to be idle before sending the second frame.

14. The method according to claim 1, wherein: In response to determining that the condition is satisfied, the steps of sending the first frame and the second frame on the first link and the second link, respectively, include: In response to determining that the second backoff countdown is less than or equal to the aggregation threshold: sending a request to send frame on the first link and the second link; and In response to receiving a clear to send frame on both the first link and the second link, the first frame and the second frame are sent on the first link and the second link, respectively.

15. The method according to claim 14, further comprising: The clear to send frame from an access point of the multi-link network is monitored for a first link and a second link.

16. The method according to claim 14, further comprising: In response to receiving a clear to send frame on the first link but not on the second link: The first frame is sent on the first link and is not sent on the second link.

17. The method according to claim 14, further comprising: In response to not receiving a clear to send frame on either the first link or the second link: Transmission on the first link and the second link is restricted.

18. The method according to claim 14, further comprising: The contention window for the second link is maintained the same as the contention window before sending the second frame.

19. The method according to any one of claims 14 to 18, wherein: At least one of the first frame and the second frame includes an encapsulation of a physical header, one or more MAC headers, and one or more data payloads.

20. The method of claim 14, further comprising: In response to the first backoff countdown reaching zero, a state of the second link is identified as idle.

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