CN118019025A - Wi-Fi device and associated transmission control method - Google Patents

Abstract

Wi-Fi devices and associated transmission control methods are provided. The Wi-Fi device selectively transmits at least a data portion of the transmit data over the low-performance link based on a plurality of parameters. The parameters include a starting point in time of a backoff process for the low-performance link, duration information associated with another Wi-Fi device on the high-performance link, and some predefined exception conditions. By listening to the status of another Wi-Fi device on the high performance link, the Wi-Fi device attempts to acquire duration information. If duration information is available, the Wi-Fi device calculates the collaborative residual duration accordingly. The Wi-Fi device then determines whether the transmit data should be transmitted immediately on the low-performance link, later on the high-performance link, or sequentially in the low-high-performance link and the high-performance link.

Description

Wi-Fi device and associated transmission control method

The present application is a continuation-in-part application of U.S. application Ser. No.17/964,045, filed 10/12 at 2022. The continuation-in-this section claims the benefit of U.S. provisional application No.63/383,114, filed on 10 at 11/2022, the subject matter of which is incorporated herein by reference.

Technical Field

The present disclosure relates generally to Wi-Fi devices and associated transmission control methods, and more particularly to Wi-Fi devices and associated transmission control methods capable of enhancing throughput through multi-link interoperation.

Background

In Wi-Fi multi-link operation (MLO), there may be multiple links between two MLDs that occupy different Radio Frequency (RF) bands, including an Access Point (AP) and a non-AP Station (STA). These links may operate independently to increase overall throughput and/or to improve connection stability. However, each link has its own capacity based on a number of parameters including Bandwidth (BW), number of Spatial Streams (NSS), modulation and Coding Scheme (MCS), etc. Furthermore, each link has its own conditions based on a number of parameters, including load, interference, etc. The capacity and conditions of the links may be very different. It is therefore desirable to optimally utilize these asymmetric links to maximize overall system performance.

Disclosure of Invention

The present disclosure relates to Wi-Fi devices, wi-Fi, and associated transmission control methods capable of enhancing throughput through multilink interoperation.

According to one embodiment, a Wi-Fi apparatus is provided. The Wi-Fi device is in an overlapping Basic Service Set (BSS) with another Wi-Fi device, and the other Wi-Fi device transmits a first physical layer protocol data unit (PPDU) frame on a first link between a first-first point in time and a third-first point in time. The Wi-Fi device includes: a medium access control address (MAC) module, and the MAC module comprises: the device comprises a receiving circuit, a first transmitting circuit corresponding to the first link, a second transmitting circuit and a link selecting module. The receiving circuit obtains duration information associated with a first payload portion of the first PPDU frame at a second-first time point, wherein the second-first time point is between the first-first time point and the third-first time point. The second transmission circuit selectively transmits a second PPDU frame over a second link between a first-second point in time and a second-second point in time, wherein a performance of the second link is lower than a performance of the first link. The link selection module is electrically connected to the receiving circuit, the first transmitting circuit, and the second transmitting circuit. The link selection module selectively controls the first transmission circuit and the second transmission circuit to perform transmission according to states of the first link and the second link.

According to another embodiment, a transmission control method employed by a Wi-Fi device is provided. The transmission control method comprises the following steps: first, duration information associated with a first payload portion of the first PPDU frame is acquired at a second-first point in time. The second-first time point is between the first-first time point and the third-first time point. Then, a second PPDU frame is selectively transmitted over the second link between the first-second time point and the second-second time point. The Wi-Fi device is in an overlapping basic service set with another Wi-Fi device, and the performance of the second link is lower than the performance of the first link.

These and other objects of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures and drawings.

Drawings

Fig. 1 is a schematic diagram illustrating a case when a plurality of access points and a plurality of stations simultaneously select the same link for frame exchange processing.

Fig. 2 is a schematic diagram illustrating a Wi-Fi system according to an embodiment of the present disclosure.

Fig. 3 is a schematic diagram illustrating classification of a transmission configuration according to an embodiment of the present disclosure.

Fig. 4 is a flowchart illustrating a transmission control method capable of adaptively selecting a transmission mode in response to a predefined quality condition being met, according to an embodiment of the present disclosure.

Fig. 5 is a schematic diagram illustrating an exemplary structure of a ppdu_22 frame.

Fig. 6A and 6B are diagrams illustrating an exemplary structure of an a-MPDU sub-frame subF m.

Fig. 7 is a schematic diagram illustrating that the Wi-Fi device STA2 obtains access to the high-performance link l_hi, and the Wi-Fi device STA2 performs a frame exchange process on the high-performance link l_hi.

Fig. 8 is a block diagram illustrating a MAC module according to an embodiment of the present disclosure.

Fig. 9 is a flowchart illustrating an exemplary implementation of step S455 in fig. 4.

Fig. 10 is a flowchart illustrating a frame exchange process performed by STA2 on the low-performance link l_lo when any one of predefined exception conditions is satisfied.

Fig. 11A and 11B are diagrams illustrating that the high performance channel l_hi has been occupied by STA1, and STA2 determines to perform ppdu_22 frame exchange processing on the low performance link l_lo.

Fig. 12A is a schematic diagram illustrating a case when STA2 cannot estimate the end time point of the ppdu_11 frame on the high performance link l_hi.

Fig. 12B is a schematic diagram illustrating another case when STA2 cannot estimate the end time point of the ppdu_11 frame on the high performance link l_hi.

Fig. 13 is a schematic diagram illustrating different results reflecting a comparison between a minimum PPDU duration min DUR _PPDU and a synergistic remaining duration Trmn.

Fig. 14 is a schematic diagram illustrating that the cooperative remaining duration Trmn is shorter than the minimum PPDU duration min DUR _PPDU.

Fig. 15 is a flowchart illustrating an exemplary implementation of step S4555g in fig. 9.

Fig. 16A and 16B are diagrams illustrating that when the cooperative remaining duration Trmn is longer than the duration of the ppdu_22 frame exchange process (DUR _{PPDU_22}), the number of a-MPDU sub-frames subF [1] to subF [ M ] of the payload portion of the ppdu_22 frame is equal to the number of data subsets subDAT [ N ] to subDAT [ N ] (m=n).

Fig. 17 is a schematic diagram illustrating that when the cooperative remaining duration Trmn is longer than the duration of the ppdu_22 frame exchange process (DUR _{PPDU_22}), the link selection module controls the link-specific MAC (low) to perform cooperative transmission.

Fig. 18A and 18B are diagrams illustrating that when the cooperative remaining duration Trmn is shorter than the duration of the ppdu_22 frame exchange process (DUR _{PPDU_22}), the number of a-MPDU sub-frames subF [1] to subF [ M ] of the payload portion of the ppdu_22 frame is smaller than the number of data subsets subDAT [ N ] to subDAT [ N ] (M < N).

Fig. 19 is a schematic diagram illustrating that when the cooperative remaining duration Trmn is shorter than the duration of the ppdu_22 frame (DUR _{PPDU_22}), the link selection module controls the link-specific MAC (low) to perform cooperative transmission.

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawings.

Detailed Description

Certain terms are used throughout the following description and claims to refer to particular components. As will be appreciated by those skilled in the art, electronic device manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. Furthermore, the term "coupled" is intended to mean an indirect or direct electrical connection. Thus, if one device couples to another device, that connection may be through a direct electrical connection or through an indirect electrical connection via other devices and connections.

To a frame exchange process between a station device (STA) and an access point (STA) in an environment with asymmetric multilinks. To improve transmission efficiency EMLSR is a solution proposed in the 802.11 specification. However, the conventional EMLSR proposed in the 802.11 specification is not suitable for environments with unbalanced links, and thus a EMLXR-based txOnRx alignment is proposed in U.S. patent application (application number: 17/964,045). Briefly, EMLXR-based txOnRx alignment aims to acquire the duration information reported by the header portion and simultaneously utilize the low-performance link l_lo before the PPDU frame exchange process of other Wi-Fi devices accessing the l_hi is completed. However, EMLXR-based txOnRx alignment has limitations on low-to-medium Overlapping Basic Service Set (OBSS) loads, and further improvements are needed. In this specification EMLXR may represent an enhanced multilink single radio (EMLSR) and/or an enhanced multilink multiradio (EMLMR).

For a better understanding of the technical features of the proposed multi-link co-operation, the following embodiments assume that the asymmetric multi-link comprises a high-performance link l_hi with higher throughput and a low-performance link l_lo with lower throughput. The two links do not interfere with each other. The core concept of multi-link cooperative transmission is that STAs only transmit data to their corresponding AP on the low-performance link l_lo, while the high-performance link l_hi is used by another pair of AP and STA.

The performance of the link is determined by a combination of different link capabilities (e.g., bandwidth (BW), modulation Coding Scheme (MCS), and/or Number of Spatial Streams (NSS)) and conditions (e.g., load and/or interference). The high-performance link l_hi and the low-performance link l_lo may represent two channels in the same frequency band (one of the 2.4GHz, 5GHz, and 6GHz frequency bands) or in different frequency bands (two of the 2.4GHz, 5GHz, and 6GHz frequency bands).

Fig. 1 is a schematic diagram illustrating a case when a plurality of access points and a plurality of stations simultaneously select the same link for frame exchange processing. In fig. 1, frame exchange processing between Wi-Fi multilink devices (MLDs) 151, 171, and frame exchange processing between MLDs 153, 173 are performed. For illustration, MLD 151 is considered an access point (AP 1), MLD 153 is considered an access point (AP 2), MLD 171 is considered a station device (STA 1), and MLD 173 is considered a station device (STA 2).

The MLD (AP 1) 151 and the MLD (STA 1) perform frame exchange processing on the high-performance link l_h1 and the low-performance link l_lo 1. The MLD (AP 2) 153 and the MLD (STA 2) 173 perform frame exchange processing on the high-performance link l_h2 and the low-performance link l_lo2. Since channel (link) contention is referred to in the specification, l_h1=l_h2=l_hi and l_lo1=l_lo2=l_lo are assumed.

Since OBSS distribution in the environment changes from time to time, a flexible transmission control method applied to MLD (e.g., STA 2) is provided. According to embodiments of the present disclosure, wi-Fi MLD involves a number of parameters, including the link state and attributes of which data is transmitted. Various transmission configurations are provided to enable Wi-Fi MLD to adaptively select an appropriate and efficient configuration for data transmission.

According to embodiments of the present disclosure, wi-Fi MLD may transmit packets on one of the high-performance link l_hi and the low-performance link l_lo, suspend packet transmission, or transmit a portion of packets on the low-performance link l_lo and leave another portion of packets for later transmission. The following describes different embodiments to explain how the transmission control method selects an appropriate transmission configuration.

Fig. 2 is a schematic diagram illustrating a Wi-Fi system according to an embodiment of the present disclosure. For simplicity and simplicity, it is assumed that Wi-Fi system 2 includes MLDs 21, 23. The MLD 21 is a station apparatus (STA), and the MLD 23 is an Access Point (AP).

The MLD 21 includes a functional circuit 217, a wireless control circuit, a medium access control address (MAC) module 211, a physical layer (PHY) module 24, and a plurality of antennas. The wireless control circuit 215 is electrically connected to the MAC module 211 and the functional circuit 217. The wireless control circuit 215 executes Wi-Fi related programs at an upper layer. Further, the wireless control circuit 215 communicates and cooperates with the functional circuit 217. The PHY module 24 is electrically connected to the MAC module 211 and the antenna.

The MAC module 211 includes a Control Register (CR) 218, a link selection module 211a, and a plurality of link-specific MACs. The Control Register (CR) is configured according to the number of cooperative links used by the MLD 21, and the number of link-specific MACs may vary. For illustration, the following embodiments are shown on a dual link basis. Thus, in fig. 2, a link-specific MAC (high) 26 corresponding to the high-performance link l_hi and a link-specific MAC (low) 28 corresponding to the low-performance link l_lo are shown.

The link-specific MAC (high) 26 includes a collision avoidance module (high) 261, a TxMAC (high) 263, and an RxMAC (high) 265, and is electrically connected to the link selection module 211a. The collision avoidance module (high) 261 is electrically connected to a TxMAC (high) 263.TxMAC (high) 263 and RxMAC (high) 265 are electrically connected to PHY module 24.

The link-specific MAC (high) 28 includes a collision avoidance module (low) 281, txMAC (low) 283, and RxMAC (low) 285, and is electrically connected to the link selection module 211a. The collision avoidance module (low) 281 is electrically connected to the TxMAC (low) 283.TxMAC (low) 283 and RxMAC (low) 285 are electrically connected to PHY module 24.

It is assumed that in the embodiment, the collision avoidance module (high) 261 includes a back-off counter corresponding to the high-performance link l_hi (i.e., back-off counter cnt_hi), and the collision avoidance module (low) 281 includes a back-off counter corresponding to the low-performance link l_lo (i.e., back-off counter cnt_lo). The link selection module 211a refers to the count values of the back-off counters cnt_hi, cnt_lo to determine how to control the TxMAC (high) 263 and TxMAC (low) 283.

The MLD 21 utilizes a carrier sense mechanism to determine whether any channel activity is present/occurring at its respective link. If there is no media activity in its corresponding link, the backoff counter (cnt_hi or cnt_lo) corresponding to that link is decremented in units of time slots. On the other hand, if any media activity is present/occurring in one of the other links, the back-off counter (cnt_hi or cnt_lo) maintains its count value. The count value (i.e., the remaining back-off count value) held by the back-off counter (cnt_hi or cnt_lo) will decrease later once there is no media activity in the link corresponding to MLD 21. The link corresponding to the back-off counter (cnt_hi or cnt_lo) counted to zero will start transmitting data. Briefly, the back-off counter cnt_hi is used to determine whether the high performance link l_hi is accessible by the MLD 21, and the back-off counter cnt_lo is used to determine whether the low performance link l_hi is accessible by the MLD 21.

In some embodiments, the MLDs 21, 23 may have M links L1-LM, and may communicate with each other via N links L1-LN. The variables M and N are positive integers, N is not less than 2, and M is greater than or equal to N. In this embodiment, each of the links L1-LN may be defined by a channel of the frequency band. For example, links L1-LN may include different channels of the same frequency band (e.g., 2.4GHz, 5GHz, or 6GHz bands) and/or channels of different frequency bands (e.g., 2.4GHz, 5GHz, and/or 6GHz bands).

Fig. 3 is a schematic diagram illustrating classification of data transmission modes selected by a link selection module according to an embodiment of the present disclosure. For illustration, the frame exchange process described below is based primarily on the perspective of STA2. Unless otherwise indicated, the operations and components mentioned below belong to STA2.

In fig. 3, a combination of different types of OBSS distribution and unbalanced links is involved. As a station device, STA2 dynamically adjusts its transmission configuration to effectively respond to the real-time status of the asymmetric link. The details about classification in fig. 3 are shown with other figures, as shown in brackets.

Fig. 4 is a flowchart illustrating a transmission control method capable of adaptively selecting a transmission mode in response to a predefined quality condition being met, according to an embodiment of the present disclosure. Please refer to fig. 2, fig. 3 and fig. 4 together. First, the link selection module 211a checks whether a predefined quality condition is satisfied (step S41). Note that the predefined quality condition is not limited, but is freely defined in practical applications.

Exemplary predefined quality conditions relate to OBSS loading. For example, if the OBSS load in the environment is lower than or equal to a predefined OBSS threshold, the predefined quality condition is considered to be met, and vice versa. The predefined OBSS threshold may be, for example, between 40% and 50%.

If the result of the determination of step S41 is negative, the link selection module 211a controls one of the TxMAC (high) 263 and the TxMAC (low) 283 to perform the frame exchange process using the conventional EMLXR depending on which one of the backoff processes corresponding to the collision avoidance module (low) and the collision avoidance module (high) ends first (step S43). In step S43, if the backoff process of the low-performance link BOL ends before the backoff process of the high-performance link BOH ends, the link selection module 211a notifies the link-specific MAC (low) 28 to perform EMLXR frame exchange processing, and vice versa.

If the result of the determination of step S41 is affirmative, the link selection module 211a dynamically changes its transmission configuration based on the comprehensive consideration (step S45). Factors influencing the decision made by link selection module 211a include the listening result, the backoff procedure of low-performance link BOL and high-performance link BOH, and the inherent characteristics of transmit data txDAT _sta 2. The dashed box FM1 in fig. 3 covers the classification of the transmission configuration related to step S45.

Step S45 further includes the following steps. The link selection module 211a checks the back-off counter cnt_hi in the collision avoidance module (high) 261 to clarify whether the link-specific MAC (high) 26 can obtain access rights on the high-performance link l_hi (step S451). If the count value of the back-off counter cnt_hi reaches "0", the determination result of step S451 is affirmative, and the link selection module 211a controls the link-dedicated MAC (high) 26 to perform frame exchange processing on the high-performance link l_hi (the situation shown in fig. 5) (step S453). In step S453, the duration length of the frame exchange process performed by the link-dedicated MAC (high) 26 is directly governed by the data length txDAT _sta2 of the transmission data.

If the determination result of step S451 is negative, the link selection module 211a knows that the link-specific MAC (high) 26 has not been able to perform the frame exchange process. Nevertheless, the link selection module 211a does not control the link-specific MAC (L0) 28 to immediately perform the frame exchange process. In contrast, the link selection module 211a needs to consider more factors (step S455). In step S455, the link selection module 211A may control the link-dedicated MAC (low) 28 to perform the frame exchange process on the low-performance link l_lo (the case shown in fig. 11A and 11B), control the link-dedicated MAC (low) 28 not to perform the frame exchange process (the case shown in fig. 12A to 12B and 14), or control the link-dedicated MAC (low) 28 to perform the frame exchange process in a coordinated manner (the case shown in fig. 17 and 19). The dashed-line box FM2 in fig. 3 covers the classification of the transmission configuration related to step S455.

In the specification, frame exchange processing representing different situations is illustrated. Each frame exchange process includes multiple timing axes to represent the course of the frame exchange process on the high-performance link l_hi and the low-performance link l_lo. The rectangle above the timing axis represents frames transmitted from the STA to the AP (e.g., STA1 to AP1, or STA2 to AP 2), while the rectangle below the timing axis represents frames transmitted from the AP to the STA (e.g., AP1 to STA1, or AP2 to STA 2).

In these frame exchange processes, rectangles use different screen styles to represent their source devices and their destination devices. The horizontal screen style represents a frame exchange process between MLDs (e.g., AP2 and STA 2) whose reaction and operation are described by the specification, and the dotted screen style represents a frame exchange process between other MLDs (e.g., AP1 and STA 1) whose reaction is not described in the specification.

In addition, a relatively dense screen style (above the timing axis) is used to represent signals transmitted from STAs to their corresponding APs, while a relatively loose screen style (below the timing axis) is used to represent signals transmitted from APs to their corresponding STAs. For example, the horizontal screen style representing the frame exchange process from STA2 to AP2 is relatively dense, while the horizontal screen style representing the frame exchange process from AP2 to STA2 is relatively loose.

The backoff process of the low-performance link BOL represents a process in which the backoff counter cnt_lo counts down from a random value to 0. The backoff process of the high-performance link BOH means a process in which the backoff counter cnt_hi counts down from a random value to 0. In the frame exchange process, acknowledgement frame ACK, distributed inter-frame space DIFS, and short inter-frame space SIFS are shown. The generation and duration control related to the backoff procedure BOH, BOL, distributed inter-frame space DIFS, short inter-frame space SIFS, and acknowledgement frame ACK may be referred to the 802.11 specification.

In the frame exchange process, a data frame is marked with a physical layer protocol data unit (PPDU) together with a number indicating the start and destination of the PPDU frame. For example, a ppdu_11 frame represents a data frame to be transmitted by STA1 to AP1, and a ppdu_22 frame represents a data frame to be transmitted by STA2 to AP 2.

Fig. 5 is a schematic diagram illustrating an exemplary structure of a ppdu_22 frame. In fig. 5, the ppdu_22 frame includes a header portion hd_22 and a payload portion pl_22, and the duration of the ppdu_22 frame is equal to the duration of the header portion hd_22 and the duration of the payload portion pl_22. In some applications, the ppdu_22 frame may also include one or more padding bits.

In the present disclosure, in most cases, it is assumed that the payload portion pl_22 of the ppdu_22 frame is an aggregate MAC protocol data unit (a-MPDU). Thus, the payload portion pl_22 of the ppdu_22 frame may be denoted as a-mpdu_22 (pl_22=a-mpdu_22), and the a-mpdu_22 includes M a-MPDU sub-frames subF [1] to subF [ M ]. In practical applications, the internal structure of the header portion hd_22 and the payload portion pl_22 of the ppdu_22 frame may vary with different versions of the 802.11 specification. With appropriate modification, the concepts of the present disclosure may be applied to other types of ppdu_22 frames having various configurations of header portions hd_22 and payload portions pl_22.

Each a-MPDU sub-frame subF [1] to subF [ M ] carries one of N data sequences subDAT [ N ], where n=1 to M and 1+.m+.n. For example, A-MPDU sub-frame subF [ M ] carries a subset of data subDAT [ n ].

Since the format of the header portion hd_22 is specified in the 802.11 specification, the duration (T _hd) of the header portion hd_22 is known. On the other hand, the duration of the payload portion pl_22 varies with the number of a-MPDU subframes (i.e. M). According to the 802.11 specification, duration information durINFO _{PL_22}(T_{PL_22}＝T_{A-MPDU_22} associated with the payload portion of the ppdu_22 frame is reported in the header portion hd_22 of the ppdu_22 frame.

Fig. 6A and 6B are diagrams illustrating an exemplary structure of an a-MPDU sub-frame subF m. In fig. 6A and 6B, the a-MPDU sub-frame subF m includes a MPDU header MPDUhd m and a MPDU payload MPDUpl m.

In fig. 6A, MPDU payload MPDUp [ m ] includes MPDU data field subDAT [ n ]. Thus, the duration of the a-MPDU sub-frame subF [ m ] in fig. 6A (i.e., T _subF[m]) corresponds to the sum of the duration of the MPDU header MPDUhd [ m ] (i.e., T _MPDUhd) and the duration of the data subset subDAT [ n ] (i.e., T _subDAT[n]). I.e., T _subF[m]＝T_MPDUhd[n]+T_subDAT[m].

In fig. 6B, MPDU payload MPDUp [ m ] also includes MPDU data field subDAT [ n ] and MPDU padding MPDUpad [ m ]. Thus, the duration of the a-MPDU sub-frame subF [ m ] in fig. 6B (i.e., T _subF[m]) corresponds to the sum of the duration of the MPDU header MPDUhd [ m ] (i.e., T _MPDUhd), the duration of the data subset subDAT [ n ] (i.e., T _subDAT[n]), and the duration of MPDU padding (i.e., T _MPDUpad[m]). I.e., T _{subF_22[m]}＝T_{MPDUhd_22[m]}+T_{subDAT_22[n]}+T_MPDUpad[m].

According to fig. 6A and 6B, MPDU padding MPDUpad m is optionally added. In practical applications, MPDU padding MPDUpad m is inserted into MPDU payload MPDUp m as needed, and the exact format and length of MPDU padding MPDUpad m is not limited. Basically, MPDU padding MPDUpad [ m ] is used to dynamically adjust the duration T _{PL_22} of the payload portion.

Before the STA starts the frame exchange process, it senses (listens to) the media to determine if the link is idle (if the media is occupied by others). If the medium is idle, the STA (e.g., STA 2) starts a backoff procedure (BOH or BOL) to wait for a duration. Thus, the STA may listen to the header portion of PPDU frames transmitted by other MLDs and know the media status in the environment. Based on the listening result, STA2 knows how to dynamically configure its data transmission.

More specifically, by sharing the header portion of the PPDU frame, the MLD can know whether the link is in progress. Alternatively, the MLD will know how long the link will be occupied by another MLD and manage its frame exchange process better. With this listening mechanism, the chance of collisions can be reduced and throughput can be increased.

Fig. 7, 11A, 11B, 12A to 12B, 14, 17, and 19 are examples illustrating how the link selection module 211A reacts and adjusts its frame exchange process according to different listening results.

Fig. 7 is a schematic diagram illustrating that the Wi-Fi device STA2 obtains access to the high-performance link l_hi, and the Wi-Fi device STA2 performs a frame exchange process on the high-performance link l_hi. Please refer to fig. 4 and fig. 7 together. Fig. 7 corresponds to step S453 in fig. 4. In this embodiment, the high performance channel l_hi is not occupied by MLDs other than STA2 and AP 2.

As shown in fig. 7, the count value of the backoff counter cnt_hi of STA2 reaches 0 at time point t 1. Thus, STA2 obtains access to the high-performance link l_hi, and performs ppdu_22 frame exchange processing, i.e., DUR _{PPDU_22} = (t 3-t 1), on the high-performance link l_hi between the time points t1 and t 3. As outlined in fig. 3, the link selection module 211a selects the high-performance link l_hi for data transmission when the high-performance link l_hi is not accessed by other MLDs (e.g., AP1 and STA 1). In fig. 7, all transmit data txDAT _sta2 is transmitted in a single ppdu_22 frame, so N data subsets subDAT [1] to subDAT [ N ] are carried by a-MPDU subframes subF [1] to subF [ M ] in the payload pl_22, where m=n. Thus, the duration of the ppdu_22 frame exchange process (DUR _{PPDU_22}) corresponds to the sum of the duration of the header portion hd_22 (T _hd) and the duration of the M a-MPDU sub-frames (T _subF[1]+...T_subF[M]). I.e., DUR _{PPDU_22}＝T_hd+T_{PL_22}＝T_hd+T_{A-MPDU_22}＝T_hd+(T_subF[1]+...T_subF[M]).

Fig. 7 shows an ideal case where the high performance link l_hi is freely accessible. However, the situation in fig. 7 may not always occur, and STA2 needs to share or contend for use of the high-performance link l_hi and the low-performance link l_lo with other Wi-Fi devices. Thus, a listening function is provided in the 802.11 specification. In practical applications, the state of the link is always changed, and the monitoring result may dynamically reflect the state. According to embodiments of the present disclosure, different transmit configurations are provided to accommodate various states of the link.

In general, according to embodiments of the present disclosure, link selection module 211a preferably performs frame exchange processing on high performance link L_HI. However, as shown in the classification in fig. 3, there are some cases where the link selection module 211a needs to adjust its transmission configuration. Embodiments in accordance with the present disclosure illustrate how a transmit configuration should be adjusted in response to a state change of an unbalanced link.

Fig. 8 is a block diagram illustrating a MAC module according to an embodiment of the present disclosure. The MAC module 81 is electrically connected to the wireless control circuit 85 and the PHY module 24.

PHY module 24 also includes TxPHY module 243 and RxPHY module 241.RxPHY module 241 includes a receive PHY (RxPHY (high)) 2411 corresponding to a high-performance link l_hi and a receive PHY (RxPHY (low)) 2413 corresponding to a low-performance link l_lo. TxPHY module 243 includes a transmit PHY (TxPHY (high)) 2431 corresponding to high-performance link l_hi and a transmit PHY (TxPHY (low)) 2433 corresponding to low-performance link l_lo.

The MAC module 81 includes a link selection module 89, a Control Register (CR), a link-specific MAC (high) 86 corresponding to the high-performance link l_hi, and a link-specific MAC (low) 88 corresponding to the low-performance link l_lo. The control register CR is electrically connected to the link selection module 89. The internal components of the link-specific MAC (low) 88 and their interconnections are briefly described below.

The link-specific MAC (high) 86 includes collision avoidance modules 861, txMAC (high) 863, and RxMAC (high) 865. The internal components of the collision avoidance modules 861, txMAC (high) 863, and RxMAC (high) 865 are described separately.

The collision avoidance module 861 also includes a SIFS timer 8611, a back-off counter 8613, and a DIFS timer 8615 corresponding to the high performance link l_hi. SIFS timer 8611, back-off counter (cnt_hi) 8613, and DIFS timer 8615 are electrically connected to TxMAC (high) 863 and link selection module 89.

TxMAC (high) 863 also includes a Tx buffer (high) 8633 and a frame constructor (high) 8631. The Tx buffer (high) 8633 is electrically connected to TxPHY (high) 2431 and the frame constructor (high) 8631. The frame constructor (high) 8631 is electrically connected to the link selection module 89 and the collision avoidance module 861.

SIFS timer 8611, back-off counter (cnt_hi) 8613, and DIFS timer 8615 send their states to frame constructor 8631. The frame constructor 8631 organizes and constructs frames in the Tx packet based on the states of the SIFS timer 8611, the back-off counter (cnt_hi) 8613, and the DIFS timer 8615, the transmission data TxDAT received from the wireless control circuit 85, and the transmission configuration transmitted from the link selection module 89. After the frame constructor 8631 constructs the Tx packet, the Tx packet is temporarily stored in a Tx buffer (high) 8633. The Tx buffer (high) 8633 then sends the Tx packet to TxPHY (high) 2431 at the appropriate point in time.

The RxMAC (high) 865 also includes a frame detector (high) 8653 and a frame parser (high) 8651. The frame detector (high) 8653 is electrically connected to RxPHY (high) 2411 and the frame parser (high) 8651. The frame parser (high) 8651 is electrically connected to the link selection module 89. The frame detector (high) 8653 receives the Rx data from RxPHY (high) 2411 and passes the Rx packet to the frame parser (high) 8651. Then, a frame parser (high) 8651 parses the fields in the Rx packet.

Similarly, link-specific MAC (low) 88 includes collision avoidance modules 881, txMAC (low) 883, and RxMAC (low) 885.TxMAC (low) 883 is electrically connected to TxPHY (low) 2433, and RxMAC (low) 885 is electrically connected to RxPHY (low) 2413. Since the internal components in the link-specific MAC (low) 88 are similar to those in the link-specific MAC (high) 86, detailed description of the internal components in the link-specific MAC (low) 88 and interconnections thereof is omitted.

The link selection module 89 also includes boundary analysis circuits 891 and EMLXR Tx configuration circuits 893. The boundary analysis circuit 891 is electrically connected EMLXR Tx to the configuration circuit 893 and the wireless control circuit 85. The Tx configuration circuit 893 is electrically connected to the wireless control circuit 85 and the frame constructor (high) 8631 and the frame constructor (low) 8831.EMLXR Tx the configuration circuit 893 informs TxMAC (high) 863 and TxMAC (low) 883 whether they should both wait for the next transmission opportunity or one of them should immediately perform the frame exchange process.

Fig. 9 is a flowchart illustrating an exemplary implementation of step S455 in fig. 4. EMLXR Tx the configuration circuit 893 checks if the transmit data (txDAT) meets any predefined exception conditions (step S4551). Step S4551 corresponds to the flowchart in fig. 10. If the determination result of step S4551 is affirmative, then EMLXR Tx configuration circuit 893 notifies link-specific MAC (low) 88 to perform frame exchange processing on low-performance link l_lo (step S4553), as shown in fig. 11A and 11B.

In some applications, steps S4451 and S4553 may be skipped. Or in some applications, step S4451 may be performed after step S4555e with some modifications. Details concerning this alternative design are omitted. In practical applications, the order of the steps may be adjusted by appropriate modifications.

If the determination result of step S4551 is negative, then EMLXR Tx configuration circuit 893 controls link-specific MAC (low) 88 to temporarily ignore transmission data txDAT _sta2 (see the opposite example in fig. 12A to 12B and fig. 14); transmitting the complete transmission data txDAT _stas 2 using the ppdu_22 frame (see fig. 17); or transmits a portion of the transmission data txDAT _sta2 (see fig. 19) using the ppdu_22 frame (step S4555). Step S4555 further includes the following steps.

First, the frame detector (high) 8653 listens to the high-performance link l_hi, and the frame parser (high) 8651 attempts to acquire a field in the header of the frame transmitted on the high-performance link l_hi (step S4555 a). Then, the frame parser (high) 8651 parses a field in the header portion of the ppdu_11 frame, and successfully acquires the duration information durINFO _{PL_11} (i.e., durINFO _{PL_11}＝T_{PL_11}) associated with the payload portion of the ppdu_11 frame transmitted by the STA1 (step S4555 c).

If the determination result of step S4555c is negative, the EMLXR Tx configuration circuit 893 does not control the link-specific MAC (low) 88 to perform ppdu_22 frame exchange processing. Fig. 12A and 12B present a problem caused by the conventional EMLXR when the determination result of step S4555c is negative.

Fig. 14, 17, and 19 correspond to the case when the determination result of step S4555c is affirmative. If the result of the determination of step S4555c is affirmative, the boundary analysis circuit 891 further verifies whether there is a sufficient duration to transmit at least a portion of the transmission data txDAT _sta2 with the ppdu_22 frame (step S4555 e).

If the determination result of step S4555e is negative, the EMLXR Tx configuration circuit 893 does not control the link-specific MAC (low) 88 to perform ppdu_22 frame exchange processing. Fig. 14 is an exemplary case when the determination result of step S4555e is negative.

If the determination result of step S4555e is affirmative, then EMLXR Tx configuration circuit 893 notifies link-specific MAC (low) 88 to perform ppdu_22 frame exchange processing (see fig. 17 and 19) in a coordinated manner (step S4555 g).

Please refer to fig. 5. The transmission data txDAT _sta2 is divided into N data subsets subDAT [1] to subDAT [ N ]. The difference between fig. 17 and 19 is whether the cooperative remaining duration Trmn is sufficient to transmit the N data subsets subDAT [1] to subDAT [ N ] using the M a-MPDU sub-frames subF [1] to subF [ M ]. If the cooperative remaining duration Trmn is sufficient to transmit N data subsets subDAT [1] through subDAT [ N ] (m=n) using M a-MPDU sub-frames subF [1] through subF [ M ], the link-specific MAC (low) 88 transmits the entire transmission data txDAT _sta2 using ppdu_22 frames (see fig. 17). In contrast, if the cooperative remaining duration Trmn is insufficient to transmit N data subsets subDAT [1] through subDAT [ N ] (M < N) with M a-MPDU sub-frames subF [1] through subF [ M ], the link-specific MAC (low) 88 transmits a portion of the transmit data txDAT _sta2 with ppdu_22 frames (see fig. 19).

Fig. 10 is a flowchart illustrating a frame exchange process performed by STA2 on the low-performance link l_lo when any one of predefined exception conditions is satisfied. Fig. 10 corresponds to step S4551 in fig. 9. Please refer to fig. 8 and fig. 10 together.

The link selection module 89 verifies whether the transmission data txDAT _sta2 has a high priority (step S61). If the result of the determination of step S61 is affirmative, the link selection module 89 notifies the link-specific MAC (high) 86 to perform frame exchange processing on the low-performance link l_lo (step S63).

If the result of the determination of step S61 is negative, the link selection module 89 verifies whether the transmission data txDAT _sta2 requires a short delay (step S65). If the result of the determination of step S65 is affirmative, step S63 is executed. Otherwise, the link selection module 89 verifies whether the transmission data txDAT _sta2 is unsuitable for aggregation or population (step S67). Steps S61, S65, and S67 are examples of predefined exception conditions. In practical applications, the type of predefined exception condition is not limited.

If the result of the determination of step S67 is affirmative, step S63 is executed.

In summary, predefined exception conditions may include, for example, when transmit data txDAT _sta2 has a high priority, when transmit data txDAT _sta2 requires a short delay, and/or when transmit data txDAT _sta2 is not suitable for aggregation. In practical applications, the predefined exception conditions are not limited to the examples mentioned herein.

An exemplary procedure of the ppdu_22 frame exchange process related to step S63 is shown in fig. 11A and tu 11B. In short, fig. 11A and 11B correspond to a case where the low performance link l_lo is directly selected for the frame exchange process when the ppdu_22 satisfies any one of the predefined exception conditions. These predefined exceptions represent the case where the transmit data txDAT _stas 2 needs to be transmitted as soon as possible. Therefore, in step S63, STA2 chooses to immediately perform frame exchange processing on the low-performance link l_lo without waiting for an access opportunity on the high-performance link l_hi. In step S63, the duration length of the frame exchange process performed on the low-performance link l_lo is governed by the data length of the transmission data txDAT _sta 2.

On the other hand, if the determination result of step S67 is negative, the link selection module 89 needs to further analyze the listening result of the high performance channel l_hi, the count value of the backoff counter cnt_l of STA2, and the duration (DUR _{PPDU_22}) of the ppdu_22 frame (step S69). Step S69 corresponds to step S4555 in fig. 9, and more details regarding the case related to step S69 are described in fig. 12A, 12B, 14, and 17 to 19.

Fig. 11A and 11B are diagrams illustrating that STA1 has accessed the high-performance channel l_hi and STA2 determines to perform frame exchange processing on the low-performance link l_lo. In fig. 11A and 11B, it is assumed that data to be transmitted by STA2 (i.e., txDAT _sta 2) satisfies at least one of the predefined exception conditions, and STA2 needs to immediately perform a frame exchange process.

In fig. 11A and 11B, the backoff procedure BOH of the high-performance link ends at a time point t1 (defined as a first-first time point tp 11), and the STA1 performs ppdu_11 frame exchange processing on the high-performance channel l_hi between time points t1 and t4 (defined as a third-first time point tp31 in fig. 11A) or between time points t1 and t5 (defined as a third-first time point tp31 in fig. 11B). The header portion of the ppdu_11 frame reporting duration information durINFO _{PL_11} associated with the payload portion of the ppdu_11 frame is transmitted from STA1 to AP1 at time point t2 (defined as second-first time point tp 21).

Since STA2 is not busy at time point t2, STA2 may listen for duration information durINFO _{PL_11} on high performance link l_hi when STA1 transmits duration information durINFO _{PL_11} to AP 1. In other words, STA2 knows the point in time at which the ppdu_11 frame is scheduled to end before the backoff procedure BOL of the low performance link ends at point in time t 3. For example, the ppdu_11 frame ends at time point t4 in fig. 11A and ends at time point t5 in fig. 11B.

In fig. 11A and 11B, the backoff procedure BOL of the low-performance link ends at time point t3 (defined as first-second time point tp 12). Then, STA2 immediately starts transmitting ppdu_22 frames. The duration length (DUR _{PPDU_22}) of the ppdu_22 frame is related to the data length of the mpdu_22 payload, which is directly determined by the data length of the transmit data txDAT _sta 2. Fig. 11A and 11B are similar except that the payload portion pl_22 of the ppdu_22 frame in fig. 11A is longer than that in fig. 11B.

In fig. 11A, the ppdu_22 frame on the low performance link l_lo starts at time point t3 and ends at time point t5 (defined as second-second time point tp 22). I.e. DUR _{PPDU_22} =t5-t 3. In fig. 11B, the ppdu_22 frame on the low performance link l_lo starts at time point t3 and ends at time point t4 (defined as second-second time point tp 22). I.e. DUR _{PPDU_22} =t4-t 3.

According to fig. 11A and 11B, if its transmission data (txDAT _sta 2) satisfies at least one of the predefined exception conditions, the STA2 starts to transmit the ppdu_22 frame regardless of the end time point of the ppdu_11 frame (time point t4 in fig. 11A and time point t5 in fig. 11B). Examples of predefined exception conditions may refer to steps S61, S65, and S67 in fig. 10.

Since the transmission data txDAT _sta2 is encapsulated in the ppdu_22, the duration of the ppdu_22 frame (DUR _{PPDU_22}) varies with the data length of the transmission data txDAT _sta 2. The longer the transmission data txDAT _sta2, the longer the duration of the required ppdu_22 frame (PD _{PPDU_22}). In fig. 11A, the ppdu_22 frame (between time points t3 and t 5) ends later than the ppdu_11 frame (between time points t1 and t 4) because the data length of the transmission data txDAT _sta2 is longer. In fig. 11B, since the data length of the transmission data txDAT _sta2 is short, the ppdu_22 frame (between time points t3 and t 4) ends earlier than the ppdu_11 frame (between time points t2 and t 5).

When the predefined quality condition is not satisfied, the link selection module 211a selects the legacy EMLXR for data transmission (step S43 in fig. 4). When the predefined quality condition is satisfied, the link selection module 211a dynamically switches its transmission configuration based on consideration of different timing combinations (step S45 in fig. 4). Various transmission configurations are exemplified below.

Based on the illustrations in fig. 4, 9, 10, 11A, and 11B, the link selection module 89 provides the following transmission configuration. When the predefined quality condition is met, STA2 first checks if it can obtain access rights on the high performance link l_hi. If the predefined quality condition is met and the link selection module 89 knows from the back-off counter cnt_hi that the link-specific MAC (high) can obtain access rights on the high-performance link l_hi, STA2 directly selects the high-performance link l_hi for data transmission (step S453 in fig. 4). On the other hand, when the predefined quality condition is satisfied and the link selection module 89 learns from the back-off counter cnt_lo that the link-specific MAC (low) can obtain the access rights on the low-performance link l_lo, the STA2 needs to consider more problems before selecting its transmission configuration (step S455 in fig. 4).

Fig. 12A is a schematic diagram illustrating an example case in which STA2 cannot estimate the end time point of the ppdu_11 frame on the high performance link l_hi. In fig. 12A, when STA1 transmits the duration information durINFO _{PL_11} on the high-performance link l_hi at time point t5 (defined as second-first time point tp 21), STA2 cannot acquire the duration information durINFO _{PL_11} on the high-performance link l_hi because STA2 is busy performing ppdu_22 frame exchange processing on the low-performance link l_lo. Therefore, STA2 cannot estimate/calculate the end time point of the ppdu_11 frame based on the duration information durINFO _{PL_11}.

The DIFS duration of the high performance link l_hi for STA1 starts at time point t1 and ends at time point t3. Therefore, STA2 cannot utilize the high-performance link l_hi until time point t3. At time point t2 (defined as first-second time point tp 12), the backoff procedure for the low-performance link BOL of STA2 ends. Then, the ppdu_22 frame starts at time point t2 and ends at time point t6 (defined as second-second time point tp 22). I.e. DUR _{PPDU_22} =t6-t 2.

The backoff procedure BOH for the high-performance link l_hi of STA1 starts at time point t3 and ends at time point t4 (defined as first-first time point tp 11). Then, ppdu_11 frames are transmitted between time points t4 and t7 (defined as third-first time point tp 31). Namely, DUR _{PPDU_11} = (t 7-t 4). During the ppdu_11 frame (DUR _{PPDU_11}), duration information durINFO _{PL_11} is transmitted at time point t5 (defined as second-first time point tp 21).

By the time STA1 transmits the duration information durINFO _{PL_11} (time point t 5), STA2 is already transmitting the ppdu_22 frame (DUR _{PPDU_22} = (t 6-t 2)). Therefore, STA2 cannot listen to the state of the high performance link l_hi. Without the duration information durINFO _{PL_11}, STA2 cannot estimate the end time point of the ppdu_11 frame (i.e., time point t 7).

Fig. 12B is a schematic diagram illustrating another example case in which STA2 cannot estimate the end time point of the ppdu_11 frame on the high performance link l_hi. In fig. 12B, STA2 cannot estimate the end time point of the ppdu_11 frame on the high-performance link l_hi because when STA1 transmits the duration information durINFO _{PL_11} on the high-performance link l_hi at time point t4 (defined as second-first time point tp 21), STA2 is already transmitting the ppdu_22 frame (DUR _{PPDU_22} = (t 6-t 3)).

At time point t2 (defined as first-first time point tp 11), the backoff procedure BOH for the high-performance link of STA1 ends, and AP1 starts transmitting ppdu_11 frames. A ppdu_11 frame (DUR _{PPDU_11}) is transmitted between time points t2 and t5 (defined as third-first time point tp 31), and a header portion having duration information durINFO _{PL_11} is transmitted at time point t4 (defined as second-first time point tp 21).

The backoff counter cnt_lo of STA2 starts counting down at time point t1 and ends at 0 at time t3 (defined as first-second time point tp 12). Therefore, at the moment (time point t 4) when the AP1 transmits the duration information durINFO _{PL_11}, the STA2 is already transmitting the ppdu_22 frame (DUR _{PPDU_22} = (t 6-t 3)). Therefore, when STA1 transmits the duration information durINFO _{PL_11} at the time point t4, STA2 cannot listen to the state of the high-performance link l_hi at the time point.

Please refer to fig. 3 and fig. 12A to fig. 12B together. Fig. 12A and 12B show a case where the STA2 cannot successfully detect the duration information durINFO _{PL_11a}、durINFO_{PL_11b} according to the classification in fig. 3.

In contrast to fig. 12A and 12B, there are cases where STA2 can successfully acquire the duration information durINFO _{PL_11}. For these cases, the link selection module 89 calculates the collaborative residual duration Trmn based on the acquired duration information durINFO _{PL_11}. The synergy remaining duration Trmn is then compared to the minimum duration of a single MPDU (min_pd _MPDU). For more details on the minimum duration of a single MPDU (min_pd _MPDU) reference may be made to fig. 13.

The cooperative remaining duration Trmn is a time difference between an end time point of a PPDU frame performed by STA1 on the high-performance link l_hi and an end time point of a backoff procedure BOL of the low-performance link of STA2 (i.e., trmn = (tp 31-tp 12)). Since the transmission operations of STA1 and STA2 are independent, the actual duration of the cooperative remaining duration Trmn is not a constant value.

In order to calculate the cooperative remaining duration Trmn, STA2 needs to estimate the end time point of the PPDU frame on the high performance link l_hi from the duration information durINFO _{PL_11}. Therefore, STA2 needs to detect the state of the high performance link l_hi to acquire the duration information durINFO _{PL_11}. In some applications, the collaborative residual duration Trmn may not be calculated if the duration information durINFO _{PL_11} cannot be successfully obtained by listening.

Based on the definition of the cooperative remaining duration Trmn, the length of the cooperative remaining duration Trmn varies with the end time point of the PPDU frame on the high-performance link l_hi (i.e., the third-first time point tp 31) and the end time point of the backoff procedure BOL of the low-performance link (i.e., the first-second time point tp 12). For the situation shown in fig. 12A and 12B, the cooperative remaining duration Trmn is not available to STA2 because STA2 has no opportunity to listen to the state on the high-performance link l_hi. Therefore, the end time point (i.e., the third-first time point tp 31) of the PPDU frame on the high-performance link l_hi cannot be successfully acquired.

In some applications, STA2 may listen for duration information durINFO _{PL_11} on the high-performance link l_hi and estimate the end time point (i.e., third-first time point tp 31) of the PPDU frame on the high-performance link l_hi accordingly. When the end time point (i.e., the third-first time point tp 31) of the PPDU frame on the high performance link l_hi can be successfully calculated/estimated, the cooperative remaining duration Trmn can be calculated. The boundary analysis circuit 891 then also compares the synergistic remaining duration Trmn to the minimum PPDU duration (min DUR _PPDU).

After the comparison, the comparison result is sent to EMLXR Tx configuration circuit 893.EMLXR Tx the configuration circuit 893 references the comparison to determine which transmission configuration is better suited for ppdu_22 frames.

To improve the throughput of the transmission, the payload portion of the ppdu_22 frame is preferably constructed by aggregating one or more a-MPDU sub-frames subF [1] to subF [ M ]. The duration of the first a-MPDU sub-frame subF [1] eligible for the next transmission defines a minimum PDDU duration min DUR _PPDU. In other words, the minimum PDDU duration min_dur _PPDU refers to the duration of a PPDU that contains only the first a-MPDU sub-frame that is eligible to be transmitted.

Fig. 13 illustrates a schematic diagram reflecting different results of a comparison between a minimum PPDU duration min DUR _PPDU and a synergistic remaining duration Trmn. The duration of the minimum PPDU duration min_DUR_PPDU is between time points t1 and t3 (min_DUR_PPDU＝t3-t1).

In the first case (case 1), it is assumed that the cooperative remaining duration Trmn is between the time points t1 and t4 (Trmn =t4-t 1), and that the cooperative remaining duration Trmn is longer than the minimum PPDU duration min_dur _PPDU (i.e., trmn > min_dur _PPDU). In the second scenario (scenario 2), it is assumed that the collaborative residual duration Trmn lasts between time points t1 and t3 (Trmn=t3-t1), and the collaborative residual duration Trmn is equal to the minimum PPDU duration (i.e., Trmn＝min_DUR_PPDU).

For classification of scenes belonging to the first case and the second case according to an embodiment of the present disclosure, please refer to fig. 15, 16A, 16B, 17, 18A, 18B and 19.

For the third case (case 3), assume that the remaining duration of collaboration, Trmn, lasts between time points t1 and t2 (Trmn=t2-t1), and that the cooperative remaining duration Trmn is shorter than the minimum PPDU duration min_dur _PPDU (i.e., trmn < min_dur _PPDU). In this case, the link selection module 89 knows that the cooperative remaining duration Trmn is too short for any of the a-MPDU sub-frames subF [1] to subF [ M ] that the link-specific MAC (low) 88 transmission is eligible to be transmitted first. According to an embodiment of the present disclosure, for the third case (case 3), txMAC (L0) does not transmit transmission data of any part of transmission data txDAT _sta 2.

Fig. 14 is an example showing that the synergy remaining duration Trmn is shorter than the minimum PPDU duration min_dur _PPDU (Trmn < min_dur _PPDU). In fig. 14, the cooperative remaining duration Trmn is too short for any PPDU frame. In this case, STA2 suspends transmission on the low-performance link l_lo.

The backoff process of the high-performance link ends at time point t1 (defined as the first to first time point tp11), and PPDU_11 frames continue between time points t1 and t4 (defined as the third to first time point tp31). Namely, DUR _{PPDU_11} = (t 4-t 1). The header of ppdu_11 reports duration information durINFO _{PL_11} at time point t2 (defined as second-first time point tp 21).

Since STA2 is unoccupied at time point t2, STA2 may listen to the state of the high performance link l_hi and successfully acquire duration information durINFO _{PL_11}. Using the duration information durINFO _{PL_11}, STA2 may calculate/estimate that ppdu_11 frame (DUR _{PPDU_11}) will end at time point t 4.

On the low-performance link l_lo, the count value of the back-off counter cnt_lo of STA2 reaches 0 at time point t 3. Therefore, the STA2 can calculate the cooperative remaining duration Trmn based on the end time point (time point t3, i.e., the first-second time point tp 12) of the backoff process of the low-performance link BOL and the estimated end time point (time point t4, i.e., the third-first time point tp 31) of the ppdu_11 frame. I.e. Trmn =t4-t3=tp31-tp 12.

In fig. 14, BOL ends at time point t3 (defined as first-second time point tp 12), and STA2 obtains access rights on the low-performance link l_ho. On the other hand, the high-performance link l_hi is still used by STA 1. Accordingly, the legacy STA2 transmits ppdu_22 frames between time points t3 and t5 (defined as second-second time point tp 22).

Fig. 14 shows that the available cooperative remaining duration Trmn = (t 4-t 3) is insufficient for STA2 to complete transmission of the minimum PPDU duration (min_pdppdu) on the low performance link l_lo. In fig. 14, a dashed circle CR2 is shown. The frame exchange process enclosed in the dashed circle CR2 is performed in the conventional method, but is removed according to the embodiment of the present disclosure. When STA2 encounters a situation in which the cooperative remaining duration Trmn is too short, as in fig. 14, the emlxr Tx configuration circuit 893 should control the link specific MAC (low) 88 to skip the ppdu_22 frame exchange process.

Please refer to fig. 9, 12A, 12B and 14 together. Basically, fig. 12A and 12B show a case when the determination result of step S4555c is negative, and fig. 14 shows a case when the determination result of step S4555e is negative. For the case similar to fig. 12A, 12B and 14, STA2 assumes that direct access on the low-performance link l_lo is inefficient and preferably waits for the next access opportunity of the high-performance link l_hi. Thus, it is shown that transmission is suspended, and the problems described in fig. 12A, 12B, and 14 will not occur when employing the embodiments of the present disclosure.

When the cooperative remaining duration Trmn is sufficient for the PPDU frame having the minimum PPDU duration min_dur _PPDU, STA2 needs to further compare the length of the cooperative remaining duration Trmn with the duration DUR _{PPDU_22} of the ppdu_22 frame to know whether the transmission data txDAT _sta2 can be transmitted using one PPDU frame. Fig. 15, 16A, 16B, 17, 18A, 18B, and 19 provide further analysis regarding the situation when the link selection module 89 controls the link-specific MAC (low) 88 to transmit all or only part of the transmission data txDAT _sta 2.

When the cooperative remaining duration Trmn is longer than or equal to the minimum PPDU duration (min DUR _PPDU) and the minimum PPDU duration (min DUR _PPDU), the EMLXR Tx configuration circuit 893 may inform the link-specific MAC (low) 88 to prepare to transmit the PPDU in a cooperative manner. Then, fig. 15 is performed.

Fig. 15 is a flowchart illustrating an exemplary implementation of step S4555g in fig. 9. Fig. 15 corresponds to a case where the link selection module 89 selects to perform cooperative transmission. When co-transmitting, STA1 and STA2 are transmitting their respective frames on the high-performance link l_hi and the low-performance link l_lo, respectively, in parallel during the co-ordinated remaining duration Trmn. That is, during the cooperative remaining duration Trmn, STA2 transmits a ppdu_22 frame on the low-performance link l_lo and STA1 transmits a ppdu_11 frame on the high-performance link l_hi.

First, EMLXR Tx the configuration circuit 893 verifies whether the synergistic remaining duration Trmn is longer than the duration of the ppdu_22 frame or equal to the duration of the ppdu_22 frame (Trmn. Gtoreq. DUR _{PPDU_22}) (step S71). Therefore, EMLXR Tx configuration circuit 893 needs to know whether transmit data txDAT _sta2 can be completely transmitted.

If the result of the determination of step S71 is affirmative, then EMLXR Tx configuration circuit 893 notifies link-specific MAC (low) 88 to directly perform ppdu_22 frame exchange processing on low-performance link l_lo (step S73). Details concerning step S73 can be found in fig. 16A, 16B, and 17.

If the result of the determination of step S71 is negative, the boundary analysis circuit 891 reports to EMLXR Tx configuration circuit 893 that ppdu_22 frame (DUR _{PPDU_22}) is too long for the cooperative remaining duration Trmn, and EMLXR Tx configuration circuit 893 notifies link specific MAC (low) 88 to perform EMLXR-based txOnRx alignment (step S75). Details concerning step S75 can be found in fig. 18A, 18B, and 19.

In practical applications, instead of sending the boundary analysis result to EMLXR Tx configuration circuit 893, boundary analysis circuit 891 may directly notify link-specific MAC (L0) 88 to proceed to step S75. Alternative designs may be implemented in practical applications.

Fig. 16A and 16B are diagrams illustrating that M a-MPDU sub-frames subF [1] to subF [ M ] of the payload portion of a ppdu_22 frame can carry all N data subsets subDAT [ N ] to subDAT [ N ] (m=n) when the cooperative remaining duration Trmn is longer than the duration of the ppdu_22 frame (DUR _{PPDU_22}). Fig. 16A and 16B are generally similar except that a padding bit (dummy bit) is further added in fig. 16B.

In fig. 16A, the cooperative remaining duration Trmn is equal to the sum of the duration of the header portion hd_22 and the duration of all M a-MPDU sub-frames subF [1] to subF [ M ]. I.e., trmn =t _hd+(T_subF[1]+...T_subF[M]). Thus, the ppdu_22 frame is constructed from the header portion hd_22 and a-MPDU sub-frames subF [1] to sub [ M ].

In fig. 16B, the cooperative remaining duration Trmn is longer than the sum of the duration of the header portion hd_22 and the duration of all M a-MPDU sub-frames subF [1] to subF [ M ]. I.e., trmn > T _hd+(T_subF[1]+...T_subF[M]). Thus, one or more padding bits are added to extend the duration of the payload portion pl_1122 of the ppdu_22 frame. Thus, the ppdu_22 frame is comprised of a header portion hd_22, a payload portion including a-MPDU sub-frames subF [1] to sub [ M ], and one or more PAD bits pad_22.

In both fig. 16A and 16B, the number M of a-MPDU subframes is equal to the number of data subsets subDAT [1] to subDAT [ N ]. Thus, each of the data subsets subDAT [1] to subDAT [ N ] is carried by one of the A-MPDU subframes subF [1] to subF [ M ].

Fig. 17 is a schematic diagram illustrating that when the cooperative remaining duration Trmn is longer than the duration of the ppdu_22 frame (DUR _{PPDU_22}), the link selection module controls the link-specific MAC (low) to perform cooperative transmission.

When the duration DUR _{PPDU_22} of the ppdu_22 frame is shorter than the cooperative remaining duration Trmn or equal to the cooperative remaining duration Trmn (DUR _{PPDU_22}. Ltoreq. Trmn), the TxMAC (low) 883 may end transmitting the ppdu_22 frame at an end time point (defined as a third-first time point tp 31) of the ppdu_11 frame. In other words, the end time point of the ppdu_22 frame may be earlier than the time point t5 or aligned with the time point t 5.

The count value of the backoff counter cnt_hi of STA1 reaches 0 at time point t1, and ppdu_11 frames are transmitted between time points t1 (defined as first-first time point tp 11) and t5 (defined as third-first time point tp 31). Namely, DUR _{PPDU_11} = (t 5-t 1). The header portion hd_11 of the ppdu_11 frame carrying duration information durINFO _{PL_11} is transmitted at time point t2 (defined as second-first time point tp 21).

Since duration information durINFO _{PL_11} is listened to by STA2 at time point t2, boundary analysis circuit 891 knows that ppdu_11 frame will end at time point t 5. Therefore, the boundary analysis circuit 891 calculates the cooperative remaining duration Trmn based on the difference between the end time point (time point t 5) of the ppdu_11 frame and the end time point (time point t3, as the first-second time point tp 12) of the backoff process BOL of the low-performance link. That is, trmn = (t 5-t 3) in fig. 17.

Meanwhile, the boundary analysis circuit 891 receives the transmission data txDAT _sta2 from the wireless control circuit 85 and knows the duration required to transmit the transmission data txDAT _sta2 (DUR _{PPDU_22}). In fig. 17, since the duration of the ppdu_22 frame is shorter than the synergy remaining duration Trmn (DUR _{PPDU_22} < Trmn = (t 5-t 3)), the boundary analysis circuit 891 knows that the ppdu_22 frame will end at time point t4 (i.e., before time point t 5). In fig. 17, one or more padding bits are added in the duration between time points t4 and t 5. The boundary analysis circuit 891 notifies EMLXR Tx the configuration circuit 893 of the duration comparison result. Then EMLXR Tx configuration circuit 893 controls the frame constructor (low) to construct the ppdu_22 frame accordingly.

Therefore, once the count value of the back-off counter cnt_lo of STA2 reaches 0 at time point t3, the emlxr Tx configuration circuit 893 controls TxMAC (low) 883 to immediately transmit the ppdu_22 frame. Then, the ppdu_22 frame is transmitted between time points t3 and t4, and one or more pad bits are transmitted between time points t4 and t 5.

In fig. 17, it is assumed that the ppdu_22 frame further includes padding bits (dummy bits) added between time points t4 and t 5. The duration between time points t4 and t5 is the extended padding duration Tpad (Tpad = (t 5-t 4)) to align the end time point of the padded ppdu_22 frame with the end time point of the ppdu_11 frame.

Fig. 18A and 18B are diagrams illustrating that a-MPDU sub-frames subF [1] to subF [ N ] of the payload portion of a ppdu_22 frame cannot carry all N data subsets subDAT [ N ] to subDAT [ N ] (M < N) when the cooperative remaining duration Trmn is shorter than the duration DUR _{PPDU_22} of the ppdu_22 frame. Fig. 18A and 18B are generally similar, except that a padding bit (dummy bit) is further added in fig. 18B.

In fig. 18A, the cooperative remaining duration Trmn is equal to the sum of the durations of p a-MPDU sub-frames subF [1] to subF [ p ], where p is a positive number and 1+.p < N. Details concerning the construction of the p a-MPDU sub-frames subF [1] to subF [ p ] are omitted. Briefly, p a-MPDU sub-frames subF [1] to subF [ p ] are constructed by selecting p of N subDAT [1] to subDAT [ N ]. Note that the ordering (1 to p) of the selected a-MPDU subframes is not required to be the same as the ordering (1 to N) of the data subsets subDAT [1] to subDAT [ N ].

In fig. 18B, the cooperative remaining duration Trmn is longer than the sum of the durations of the p a-MPDU subframes subF [1] to subF [ p ] and shorter than the sum of the durations of the p+1 a-MPDU subframes subF [1] to subF [ p+1 ]. In other words, txMAC (L0) 883 cannot transmit more than p MPDU subF [1] to subF [ p ]. Accordingly, the payload of the ppdu_22 frame may contain only m=p a-MPDU sub-frames subF [1] to subF [ M ].

In fig. 18A and 18B, the number of a-MPDU subframes (M) is set equal to p (set m=p). This means that the payload portion of the ppdu_22 frame (pl_22=a-mpdu_22) cannot transmit the data subsets subDAT [1] to subDAT [ N ] using the a-MPDU sub-frames subF [1] to subF [ M ] in fig. 18A and 18B. If the payload portion of the ppdu_22 frame (pl_22=a-mpdu_22) also includes any of a-MPDU subframes subF [ m+1] to subDAT [ N ], the duration of the ppdu_22 frame DUR _{PPDU_22} will exceed the cooperative remaining duration Trmn, which is undesirable in cooperative transmission.

In fig. 18A, it is assumed that the sum of the duration T _hd of the header portion and the duration T _subF[1]+…T_subF[m+1] of the a-MPDU sub-frame is exactly the same as the cooperative remaining duration Trmn. Thus, the ppdu_22 frame includes hd_22 and p a-MPDU sub-frames subF [1] to sub [ p ].

In fig. 18B, the ppdu_22 frame includes a header portion hd_22, a payload portion including a-MPDU sub-frames subF [1] to sub [ M ], and one or more PAD bits pad_22. One or more PAD bits pad_22 are inserted to extend the duration DUR _{PPDU_22} of the ppdu_22 frame such that the end time point of the ppdu_22 frame is aligned with the end time point of the co-ordinated remaining duration Trmn.

The payload portion of the ppdu_22 frame in fig. 18A and 18B includes fewer a-MPDU sub-frames than the payload portion of the ppdu_22 frame in fig. 16A and 16B because not all transmission data txDAT _sta2 is carried in the payload portion of the ppdu_22 frame. By not transmitting all transmit data txDAT _sta2, EMLXR Tx configuration circuit 893 knowing that the link-specific MAC (high) 86 may get a better opportunity to transmit the remaining data subsets subDAT [ m+1] through subDAT [ N ] on the high performance link l_hi shortly after the ppdu_11 frame and ppdu_22 frame end.

Fig. 19 is a schematic diagram illustrating that when the cooperative remaining duration Trmn is shorter than the duration DUR _{PPDU_22} of the ppdu_22 frame, the link selection module controls the link-specific MAC (low) to perform cooperative transmission.

Please refer to fig. 15, fig. 18B and fig. 19 together. When the duration required for the ppdu_22 frame to transmit all of the data subsets subDAT [1] to subDAT [ M ] is longer than the cooperative remaining duration Trmn (DUR _{PPDU_22} > Trmn), txMAC (low) 883 cannot end transmission of the ppdu_22 frame before the end time point (defined as the third-first time point tp 31) of the ppdu_11 frame. That is, if N > M and N a-MPDU subframes are required, the ppdu_22 frame (DUR _{PPDU_22}) is too long for the cooperative remaining duration Trmn. Therefore, the EMLXR Tx configuration circuit notifies the frame constructor (low) that only a part of the transmission data txDAT _sta2 is transmitted, and the ppdu_22 frame includes only a part of the transmission data txDAT _sta2 (txDAT _pc [1] to txDAT _pc [ m ]) (step S751 in fig. 15).

After the backoff procedure BOH of the high-performance link ends at time point t1 (defined as first-second time point tp 12), STA1 transmits ppdu_11 frames between time points t1 and t4 (defined as second-second time point tp 22). Namely, DUR _{PPDU_11} = (t 4-t 1). At a time point t2 (defined as a second-first time point tp 21), the frame detector 571 detects the state of the high-performance link l_hi, and the frame parser 571 acquires the duration information durINFO _{PL_11}. The frame parser 571 then passes the duration information durINFO _{PL_11} to the boundary analysis circuit 891. Based on the duration information durINFO _{PL_11}, the boundary analysis circuit 891 may estimate an end time point (defined as a third-first time point tp 31) of the ppdu_11 frame. For example, a time point t4 (defined as a third-first time point tp 31) in fig. 19.

On the other hand, from the backoff counter cnt_lo, the boundary analysis circuit 891 knows that the backoff process BOL of the low-performance link ends at time point t3 (defined as first-second time point tp 12). Thus, the boundary analysis circuit 891 may calculate the collaborative residual duration Trmn as the duration between time points t3 and t 4. I.e. Trmn = t4-t3.

Further, the boundary analysis circuit 891 receives the transmission data txDAT _sta2 from the wireless control circuit 85. Based on the data length of the transmission data txDAT _sta2, the boundary analysis circuit 891 knows that the transmission data txDAT _sta2 cannot be completely transmitted within the cooperative remaining duration Trmn (between the time points t3 and t 4). Therefore, EMLXR Tx configuration circuit 893 should configure link-specific MAC (low) 88 to perform ppdu_22 frame exchange processing along with EMLXR based txOnRx alignment (step S753 in fig. 15).

According to an embodiment of the present disclosure, EMLXR Tx configuration circuit 893 informs link-specific MAC (low) 88 that transmit data txDAT _sta2 cannot be completely transmitted at the end of cooperative remaining duration Trmn, so link selection module 89 controls link-specific MAC (low) 88 to perform PPDU frame exchange processing in which not all transmit data txDAT _sta2 is transmitted.

More specifically, the duration DUR _{PPDU_22} of the ppdu_22 frame is specifically set equal to the cooperative remaining duration Trmn to ensure that the end time point (defined as the second-second time point tp 22) of the ppdu_22 frame is aligned with the end time point (defined as the third-first time point tp 31) of the ppdu_11 frame. For example, time point t4 in fig. 19.

Step S753 in fig. 15 corresponds to the ppdu_22 frame described in fig. 18A, 18B, and 19. In fig. 19, a ppdu_22 frame is constructed based on fig. 18B. EMLXR Tx the configuration circuit 893 controls TxMAC (low) 883 to send ppdu_22 frames over the low performance link l_lo during time points t3 and t 4. Namely, DUR _{PPDU_22} = (t 4-t 3). As shown in fig. 19, the time point t4 is the end time point of the ppdu_11 frame and the end time point of the ppdu_22 frame. In other words, the ppdu_11 frame and the ppdu_22 frame end synchronously.

Further, it is possible that the link-dedicated MAC (high) 86 utilizes the availability of the high-performance link l_hi to transmit the remaining transmission data after the ppdu_11 frame exchange process and the ppdu_22 frame exchange process are ended. The remaining transmission data (i.e., data subsets subDAT [ m+1] to subDAT [ N ]) are the differences between the full transmission data txDAT _sta2 and the transmission data actually transmitted by the ppdu_22 frame (i.e., data subsets subDAT [1] to subDAT [ M ]). The transmission process of the remaining transmission data (i.e., data subsets subDAT [ m+1] to subDAT [ N ]) requires another execution cycle of fig. 4, and details are omitted.

As illustrated above, fig. 17 and 19 are examples showing that STA2 performs ppdu_22 frame exchange processing in a cooperative manner when the cooperative remaining duration Trmn is longer than the minimum PPDU duration min_dur _PPDU or equal to the minimum PPDU duration min_dur _PPDU. That is Trmn. Gtoreq.min_DUR _PPDU.

The embodiments shown in fig. 17 and 19 represent the duration of the existence of STA1 and STA2 performing their respective PPDU frame exchange processes on the high-performance link l_hi and the low-performance link l_lo, respectively, in parallel and simultaneously. Thus, this scheme is referred to as cooperative transmission in the specification. The difference between fig. 17 and 19 is that the ppdu_22 frame in fig. 17 carries all transmission data txDAT _sta2, and the ppdu_22 frame in fig. 19 transmits only a portion of the transmission data txDAT _sta 2.

If DUR _{PPDU_22} is less than or equal to Trmn (see FIGS. 16A, 16B, and 17), both STA1 and STA2 complete their data transmissions at the point in time when the cooperative remaining duration Trmn ends. On the other hand, if DUR _{PPDU_22} > Trmn (see fig. 18A, 18B, and 19), STAs 1 and ST2 cooperatively transmit their transmission data to their respective APs (AP 1 and AP2, respectively) during the cooperative remaining duration Trmn, and some of the transmission data txDAT _sta2 (i.e., the data subsets subDAT [ m+1] to subDAT [ N ]). Later, the link selection module 89 will determine how the remaining a-MPDU sub-frames subF [ m+1] to subF [ M ] should be transmitted by performing the steps in fig. 4 again.

In some applications, the functions, operations, and connections associated with boundary analysis circuits 891 and EMLXR Tx configuration circuit 893 may be modified, exchanged, or integrated together. Alternative implementations of the components in link selection module 89 are not limited.

For example, the link selection module performs a transmission control method for transmitting data using the proposed multilink cooperative operation. STA1 transmits ppdu_11 between the first-first time point tp11 and the third-first time point tp31, and duration information associated with the payload portion pl_11 of ppdu_11 is transmitted at the second-first time point tp 21. When STA2 can listen for status on the high pre-performance link l_hi, STA2 attempts to acquire duration information durINFO _{PL_11} by listening for status on the high pre-performance link l_hi. Further, STA2 selectively transmits ppdu_22 over the low performance link l_lo between the first-second time point tp12 and the second-second time point tp 22.

As demonstrated in the above embodiment, the relationship between the time points tp11, tp21, tp31, tp12, and tp22 may be changed, and thus the transmission control method adaptively selects an appropriate transmission configuration in response to different situations in the environment. The above exemplified transmission configurations, their respective appropriate cases and the associated drawings are summarized in table 1.

TABLE 1

Wi-Fi devices rely on OBSS traffic to dynamically switch their transmit configurations for uplink use. Note that according to an embodiment of the present application, the transmission configuration only needs to be adjusted at the local side MLD (e.g., STA2 itself), and no handshake with other MLDs (e.g., AP 2) is required. Thus, the MLD is free to react to state changes in asymmetric links in an efficient and appropriate manner.

When the predefined quality condition is not satisfied, the MAC module 81 performs a frame exchange process based on the legacy EMLXR. According to an embodiment of the present disclosure, the MAC module 81 freely changes its transmission configuration when a predefined quality condition is satisfied.

As illustrated above, the MAC module 81 may perform ppdu_22 frame exchange processing on the high performance link l_hi (fig. 7) or the low performance link l_lo (fig. 11A, 11B, and 17), wherein the payload portion of the ppdu_22 frame includes all transmission data txDAT _sta2. Or the MAC module 81 may temporarily ignore or skip the transmission operation (fig. 12A, 12B, and 14). Alternatively, the MAC module 81 may perform ppdu_22 frame exchange processing on the low performance link l_lo, wherein the payload portion of the ppdu_22 frame does not include all transmission data txDAT _sta2 (fig. 19). According to the simulation result, the Wi-Fi device and the associated transmission control method can realize higher throughput and reduce time delay no matter how the environmental quality changes.

Various modifications and variations of the disclosed embodiments will be apparent to those skilled in the art. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.

Claims (18)

1. A Wi-Fi apparatus, wherein the Wi-Fi apparatus is in an overlapping basic service set with another Wi-Fi apparatus, and the other Wi-Fi apparatus transmits a first physical layer protocol data unit, PPDU, frame on a first link between a first-first point in time and a third-first point in time, wherein the Wi-Fi apparatus comprises:

a medium access control address, MAC, module comprising:

A receiving circuit configured to obtain duration information associated with a first payload portion of the first PPDU frame at a second-first point in time, wherein the second-first point in time is between the first-first point in time and the third-first point in time;

a first transmitting circuit, the first transmitting circuit corresponding to the first link;

a second transmission circuit configured to selectively transmit a second PPDU frame over a second link between a first-second point in time and a second-second point in time, wherein a performance of the second link is lower than a performance of the first link; and

A link selection module electrically connected to the receiving circuit, the first transmitting circuit, and the second transmitting circuit, the link selection module configured to selectively control the first transmitting circuit and the second transmitting circuit to perform transmission according to states of the first link and the second link.

2. A transmission control method employed by a Wi-Fi device in an overlapping basic service set with another Wi-Fi device that transmits a first physical layer protocol data unit, PPDU, frame on a first link between a first-first point in time and a third-first point in time, the transmission control method comprising the steps of:

Obtaining duration information associated with a first payload portion of the first PPDU frame at a second-first time point, wherein the second-first time point is between the first-first time point and the third-first time point; and

A second PPDU frame is selectively transmitted over the second link between the first-second point in time and the second-second point in time,

Wherein the performance of the second link is lower than the performance of the first link.

3. The transmission control method of claim 2, wherein the Wi-Fi apparatus stops performing transmission on the first link when the other Wi-Fi apparatus transmits the first PPDU frame.

4. The transmission control method of claim 2, wherein the Wi-Fi apparatus stops transmitting the second PPDU frame if the Wi-Fi apparatus cannot acquire the duration information.

5. The transmission control method according to claim 4, wherein

The Wi-Fi device cannot acquire the duration information if the second-first time point is earlier than the first-second time point.

6. The transmission control method of claim 4, wherein the Wi-Fi apparatus cannot acquire the duration information if the first-second time point is within a duration of a distributed inter-frame interval on the first link.

7. The transmission control method according to claim 2, wherein

The Wi-Fi apparatus refers to the duration information to obtain the third-first time point, wherein a cooperative remaining duration is defined as a difference between the third-first time point and the first-second time point.

8. The transmission control method according to claim 7, wherein

If the cooperative remaining duration is shorter than a minimum PPDU frame duration, the Wi-Fi device stops transmitting the second PPDU frame, and

The Wi-Fi device transmits the second PPDU frame on the second link for the cooperative remaining duration if the cooperative remaining duration is longer than or equal to the minimum PPDU frame duration.

9. The transmission control method according to claim 8, wherein

The second PPDU frame includes a second header portion and a second payload portion, wherein

The duration of the second header portion starts at the first-second point in time and the duration of the second payload portion ends at the second-second point in time.

10. The transmission control method according to claim 9, wherein

The second payload portion carries at least a portion of the transmission data for the access point device.

11. The transmission control method according to claim 10, wherein

The second payload portion includes M subframes, the transmission data includes N data subsets, and each of the M subframes includes a subframe header and a subframe payload carrying one of the N data subsets, where M and N are positive integers and M is less than or equal to N.

12. The transmission control method of claim 11, wherein the second payload portion is an aggregate MAC protocol data unit a-MPDU and the M subframes are a-MPDU subframes.

13. The transmission control method according to claim 11, wherein

The minimum PPDU frame duration represents the duration of one PPDU containing only the first a-MPDU sub-frame that is eligible to be transmitted.

14. The transmission control method according to claim 11, wherein

M is less than N, and if the cooperative remaining duration is shorter than the sum of the duration of the second header portion and the duration required to transmit all of the N data subsets, the second payload portion transmits M data subsets of the N data subsets with the M subframes.

15. The transmission control method according to claim 14, wherein

The second payload portion further includes at least one padding bit if a sum of a duration of the second header portion and a duration of the M subframes is shorter than the cooperative remaining duration.

16. The transmission control method according to claim 13, wherein

M is equal to N and the second payload portion transmits all of the N data subsets using the M subframes if the cooperative remaining duration is longer than or equal to the sum of the duration of the second header portion and the duration required to transmit all of the N data subsets.

17. The transmission control method according to claim 16, wherein

The second payload portion further includes at least one padding bit if a sum of a duration of the second header portion and a duration of the M subframes is shorter than the cooperative remaining duration.

18. The transmission control method of claim 2, wherein the first PPDU frame includes a first header portion and the first payload portion, and further comprising the steps of:

detecting the first header portion on the first link; and

And analyzing the duration time information according to the first header part.