Video transmission method and related apparatus

Abstract

A video transmission method for transmitting video data through multiple links includes: dynamically allocating multiple Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate multiple Physical Protocol Data Units (PPDUs) to be transmitted through the multiple links when at least one predetermined condition associated with the multiple links is met, wherein the sequence numbers of the multiple MPDUs in each PPDU are non-sequential; and transmitting the multiple PPDUs through the multiple links.

Description

A video transmission method and related apparatus This invention generally relates to multi-link transmission, and more particularly, to a video transmission method and related apparatus for dynamically distributing MPDUs on multiple links for transmitting video data. Video streaming over wireless networks is attractive for a wide range of applications, from home entertainment to surveillance and search and rescue operations. However, technical challenges arise when the unpredictability of wireless radio frequency channels meets the high data rate and low latency requirements of video transmission. Most video streams use prediction-based coding standards (such as H.264 / AVC) for compression to reduce data rate. Loss of video packets leads to degraded video quality. Due to the loss of consecutive video blocks, some video blocks may not even be successfully decoded or recovered. The following summary is illustrative only and is not intended to be limiting in any way. That is, it provides an overview to introduce the concepts, key points, benefits, and advantages of the novel and non-obvious techniques described herein. Selected embodiments are further described in the detailed description below. Therefore, the following summary is neither intended to identify the essential features of the claimed subject matter nor to define the scope of the claimed subject matter. One embodiment provides a video transmission method for transmitting video data through multiple links, comprising: when at least one predetermined condition associated with the multiple links is met, assigning multiple Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate multiple Physical Protocol Data Units (PPDUs) to be transmitted through the multiple links, wherein the sequence numbers of the multiple MPDUs assigned in each PPDU are non-sequential; and transmitting the multiple PPDUs through the multiple links. In some embodiments, the method further includes encapsulating a plurality of MAC Service Data Units (MSDUs) corresponding to a single video slice into a single MPDU. In some embodiments, when at least one predetermined condition associated with the plurality of links is met, the step of assigning a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when the difference in transmission conditions between the plurality of links exceeds a threshold, assigning the MPDU corresponding to a high-priority video slice among the plurality of MPDUs to the link with relatively better transmission conditions. In some embodiments, when at least one predetermined condition associated with the plurality of links is met, the step of allocating a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when the difference in transmission conditions between the plurality of links is less than a threshold, uniformly allocating MPDUs corresponding to high-priority video slices among the plurality of MPDUs on the plurality of links. In some embodiments, the transmission conditions include packet error rate (PER) and / or received signal strength indicator (RSSI). In some embodiments, the video slice includes an intra-frame (I) slice, a prediction (P) slice, and a bidirectional prediction (B) slice, wherein the I slice has a higher priority than the P slice, and the P slice has a higher priority than the B slice. In some embodiments, when the remaining transmission time of the plurality of links is insufficient to transmit all of the plurality of MPDUs in the current frame exchange, at least one MPDU corresponding to a low-priority video slice is not generated in the plurality of PPDUs. In some embodiments, when at least one predetermined condition associated with the plurality of links is met, the step of assigning a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when at least one of the plurality of links is detected to contain a continuous error, alternately assigning the plurality of MPDUs containing video data to different PPDUs, wherein the sequence numbers of the plurality of MPDUs assigned to each PPDU are alternately arranged. In some embodiments, the method further includes: when a discrete error is detected on the plurality of links, generating a PPDU sequentially according to the sequence number of the plurality of MPDUs. In some embodiments, the method further includes: estimating the playback time of a video frame of the receiving device, and sending a block acknowledgment request (BAR) frame before the playback time of the video frame to request the receiving device to force refresh its reordering buffer. Another embodiment provides an apparatus for transmitting video data over multiple links. The apparatus includes a transceiver configured for wireless communication and a processor coupled to the transceiver. The processor is configured to perform operations including: dispatching multiple Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate multiple Physical Protocol Data Units (PPDUs) to be transmitted over the multiple links when at least one predetermined condition associated with the multiple links is satisfied, wherein the sequence numbers of the multiple MPDUs dispatched in each PPDU are non-sequential; and transmitting the multiple PPDUs via the transceiver over the multiple links. In some embodiments, the processor is also configured to perform the following operation: encapsulate multiple MAC Service Data Units (MSDUs) corresponding to a single video slice into a single MPDU. In some embodiments, when at least one predetermined condition associated with the plurality of links is met, the operation of assigning a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when the difference in transmission conditions between the plurality of links exceeds a threshold, assigning the MPDU corresponding to a high-priority video slice among the plurality of MPDUs to the link with relatively better transmission conditions. In some embodiments, when at least one predetermined condition associated with the plurality of links is met, the operation of distributing a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when the difference in transmission conditions between the plurality of links is less than a threshold, uniformly distributing the MPDUs corresponding to high-priority video slices among the plurality of MPDUs on the plurality of links. In some embodiments, the transmission conditions include packet error rate (PER) and / or received signal strength indicator (RSSI). In some embodiments, the video slice includes an intra-frame (I) slice, a prediction (P) slice, and a bidirectional prediction (B) slice, wherein the I slice has a higher priority than the P slice, and the P slice has a higher priority than the B slice. In some embodiments, when the remaining transmission time of the plurality of links is insufficient to transmit all of the plurality of MPDUs in the current frame exchange, at least one MPDU corresponding to a low-priority video slice is not generated in the plurality of PPDUs. In some embodiments, when at least one predetermined condition associated with the plurality of links is met, the operation of assigning a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when at least one of the plurality of links is detected to contain a continuous error, alternately assigning the plurality of MPDUs containing video data to different PPDUs, wherein the sequence numbers of the plurality of MPDUs assigned to each PPDU are alternately arranged. In some embodiments, the processor is further configured to perform the following operation: when a discrete error is detected on the plurality of links, to generate a PPDU sequentially according to the sequence number of the plurality of MPDUs. In some embodiments, the processor is also configured to perform the following operations: estimate the playback time of a video frame of the receiving device, and send a block acknowledgment request (BAR) frame before the playback time of the video frame to request the receiving device to force refresh its reordering buffer. The embodiments of the present invention can dynamically allocate MPDUs containing video data according to link-related conditions, thereby improving video transmission efficiency and quality. These and other objects of the invention will be readily understood by those skilled in the art upon reading the following detailed description of the preferred embodiments illustrated in the accompanying drawings. A detailed description will be given in the following embodiments with reference to the accompanying drawings. The following description illustrates preferred embodiments of the present invention. These embodiments are merely illustrative of the technical features of the invention and are not intended to limit the scope of the invention. Certain terms are used throughout this specification and the claims to refer to specific components. Those skilled in the art will understand that manufacturers may use different names to refer to the same components. This specification and the claims do not distinguish components by differences in name, but by differences in function. The scope of the invention should be determined with reference to the appended claims. The terms "comprising" and "including" used in the following description and claims are open-ended terms and should be interpreted as "comprising, but not limited to...". Furthermore, the term "coupled" refers to an indirect or direct electrical connection. Therefore, if a device is described as coupled to another device, it means that the device can be directly electrically connected to the other device, or indirectly electrically connected to the other device through other devices or connection means. The terms "basically" or "roughly" used in this text refer to a technical problem that can be solved and the desired technical effect achieved by someone with ordinary knowledge in the relevant technical field, within an acceptable range. For example, "roughly equal to" refers to a method that, without affecting the correctness of the result, is acceptable to someone with ordinary knowledge in the relevant technical field, with a certain margin of error compared to "exactly equal to". In video encoding and compression, a video stream typically consists of a sequence of frames, which can be further divided into smaller segments called slices. These slices are, understandably, groups of macroblocks that can be encoded independently. Slices are particularly useful for error recovery and parallel processing. In video codecs, such as those using H.264 / AVC (Advanced Video Coding) and H.265 / HEVC (High Efficiency Video Coding), three main types of slices are used: intra-slices (I-slices), predictive slices (P-slices), and bi-directional predictive slices (B-slices). Specifically, an I-slice contains macroblocks encoded using only information within the same slice. In other words, an I-slice can be decoded without referencing other frames or slices. Typically, I-slices serve as reference points for decoding subsequent slices and are crucial for random access points in the video stream (e.g., at the start of playback or when jumping to a new location). P-slices contain macroblocks that can be encoded using motion-compensated predictions from previous frames or slices. P-slices can reference blocks in one or more previously decoded I-slices or P-slices to predict the content of their macroblocks, which helps reduce the amount of data required to represent them. B-slices can use past and future frames or slices for motion-compensated predictions. This means that B-slices can reference macroblocks in earlier or later I-slices or P-slices in the video sequence to predict their content. During video transmission over multiple links, MAC service data units (MSDUs) containing video data (e.g., video slices) are transmitted from the network layer to the MAC layer. The transmitting device can then package multiple MSDUs into an aggregated-MSDU (A-MSDU) and encapsulate the MSDUs or A-MSDUs into a MAC protocol data unit (MPDU) at the MAC layer. Optionally, multiple MPDUs can also be packaged into an aggregated-MPDU (A-MPDU). Further, the transmitting device encapsulates the multiple MPDUs or A-MPDUs into a physical protocol data unit (PPDU) at the physical (PHY) layer and transmits the PPDU to the receiving device through multiple links. The key point of this invention is that, during the PPDU generation process, the MPDUs carrying video data are dynamically dispatched based on various conditions. Understandably, "dynamic dispatching" of MPDUs refers to allocating or scheduling different MPDUs to different entity layer processing flows (e.g., different links) according to corresponding rules for further encapsulation and modulation, ultimately forming PPDUs that can be transmitted over the wireless medium, rather than always sequentially scheduling MPDUs to generate PPDUs. For example, when at least one predetermined condition associated with multiple links is met, the transmitting device deliberately dispatches multiple MPDUs containing video data to generate multiple PPDUs to be transmitted through multiple links. In the generated multiple PPDUs, the sequence number (SN) of the multiple MPDUs assigned to each PPDU is non-sequential; that is, the multiple MPDUs within a single PPDU have non-sequential sequence numbers. The method proposed in this invention allows for flexible scheduling of transmission plans based on various conditions, rather than always generating PPDUs sequentially according to their MPDU sequence numbers, thereby improving the quality of video transmission and facilitating the effective recovery of failed video data. In one embodiment, once a continuous error pattern is detected on any of the multiple links, the transmitting device is configured to alternately dispatch the MPDU (which contains video data) to be transmitted into different PPDUs that will be transmitted on different links.Thus, the sequence numbers of the multiple MPDUs within each PPDU are arranged in an alternating or interleaving manner. In another embodiment, if a discrete error pattern is identified on multiple links, the transmitting device is configured to construct PPDUs directly and sequentially based on the MPDU sequence numbers, wherein the sequence numbers of the multiple MPDUs within each PPDU are sequentially arranged, i.e., the sequence numbers of the multiple MPDUs in a single PPDU are consecutive. Therefore, this adaptive strategy enables the transmitting device to optimize data transmission according to the conditions of the communication link between the transmitting device and the corresponding receiving device. Furthermore, this invention proposes a method for encapsulating a single video slice's MSDU into a single MPDU, thereby enabling the assignment of a corresponding priority to each MPDU. The priority of an MPDU is related to the characteristics of the video slice it encapsulates / contains. For example, an MPDU encapsulating slice I has a higher priority than an MPDU encapsulating slice B. This priority setting allows for more rational and dynamic allocation of MPDUs based on their transmission priorities, thereby further improving the transmission quality and recovery rate of video data. For instance, this priority setting facilitates the dynamic allocation of MPDUs based on their corresponding transmission priorities and the transmission conditions of the link, thereby improving overall transmission quality and increasing the feasibility of successfully recovering video data. For illustrative purposes, the transmission method of the present invention is illustrated using a dual-link (i.e., two-link) configuration. However, it should be noted that the scope of the present invention is not limited to this dual-link configuration. The innovative concept of the present invention can be easily extended to systems comprising three or more communication links. For example, these links can operate in various frequency bands, including but not limited to the 2.4 GHz, 5 GHz, and 6 GHz bands. Figure 1 illustrates a first example allocation 100 of multiple MPDUs according to an embodiment of the present invention. In this invention, an MPDU, also referred to as a packet, is the basic unit constituting data transmission within a Physical Protocol Data Unit (PPDU). For example, a single PPDU can encapsulate / comprise multiple MPDUs. It should be noted that, for illustrative purposes, the accompanying drawings only show the payload portion of each PPDU, and numbers (e.g., 1, 2, ..., 7, 8) are used to represent the sequence number (SN) of the MPDU. In the first example allocation 100 shown in Figure 1, each MPDU is constructed to contain an equal amount of video data. It is noteworthy that the division of these MPDUs is independent of the boundaries of video slices (as can be seen in Figure 1, the boundaries of the MPDUs do not coincide with the boundaries of the slices). Understandably, video slices typically include: intra-frame slices (I-slices, labeled "I-Slice" in the accompanying figure for ease of explanation), predictive slices (P-slices, labeled "P-Slice" in the accompanying figure for ease of explanation), and bidirectional predictive slices (B-slices, labeled "B-Slice" in the accompanying figure for ease of explanation). As mentioned above, given the dependencies between video codes, the relative importance of these slices in video transmission can be ranked as follows: I-slices are the most critical, followed by P-slices, and then B-slices. Therefore, the importance of each slice in video transmission is I-slice > P-slice > B-slice. In Figure 1, the division / boundary of MPDUs is independent of the type / boundary of video slices. Moreover, in conventional transmission schemes, MPDUs with consecutive (sequential or continuous) sequence numbers are always aggregated into a single PPDU. It is evident that this conventional MPDU generation and transmission method does not consider the segmentation of the underlying video content. Figure 2 illustrates a second example allocation 200 of multiple MPDUs according to an embodiment of the present invention. In the second example allocation 200 of Figure 2, the boundaries of the MAC Protocol Data Units (MPDUs) are the same as the boundaries of the video slices. Therefore, each MPDU can be assigned a corresponding transmission priority. In this way, the transmission and allocation of MPDUs can be based on the type or priority of the video slices. In this embodiment, multiple MAC Service Data Units (MSDUs) corresponding to a single video slice are encapsulated into the same (single) MPDU. That is, a group of MSDUs associated with the same video slice are aggregated and encapsulated into a single MPDU. This encapsulation process can be performed by a transmission mechanism, which can be embodied in a Wi-Fi driver or similar module within a transmitting device. In particular, the construction of MPDUs can be based on the boundaries of the video slices and / or the average size of the video slices, wherein the boundaries of the video slices define the start and end points of the slices in the video stream. To determine these boundaries, the MSDU itself can contain metadata specifying slice boundary information. This metadata is crucial for the receiving device to accurately reconstruct the video content. Therefore, information about the slice boundaries can be obtained from the MSDU. Furthermore, the transmitting device can optimize the encapsulation process using the average size of the video slices. For example, the average size of the video slices can be determined based on the size metric available after decoding by the video receiving device. Once the receiving device has decoded the video slices and determined their size, it can feed this information back to the transmitting device. This feedback allows the transmitting device to dynamically adjust the MPDU generation process to take into account the actual size of the slices received and decoded by the receiving device. By employing this feedback, the transmitting device can improve the efficiency of data transmission, ensuring that the MPDU is constructed in a manner consistent with the current characteristics of the video stream (i.e., a single MPDU corresponds to the data of a single video slice), thereby promoting more reliable and efficient video communication. As described above, it is understandable that the importance of each slice in video transmission should be I-slice > P-slice > B-slice. Therefore, in one embodiment, if the video slices include I-slices, P-slices, and B-slices, the priority categories for MPDUs (or video slices) can include high, medium, and low. In other words, MPDUs corresponding to I-slices can be assigned high priority, MPDUs corresponding to P-slices can be assigned medium priority, and MPDUs corresponding to B-slices can be assigned low priority, but the invention is not limited to this. For example, in another embodiment, two priority categories, high and low, can also be assigned. For example, MPDUs corresponding to relatively high-priority video slices (such as I-slices) are assigned high priority, and MPDUs corresponding to relatively low-priority video slices (such as P-slices and B-slices) are assigned low priority. In one embodiment, when the transmission conditions of multiple links differ significantly (e.g., when the difference in transmission conditions between multiple links exceeds a threshold), MPDUs with relatively high priority are assigned to links with better transmission conditions, while MPDUs with relatively low priority are assigned to links with poorer transmission conditions. In another embodiment, when the transmission conditions of multiple links are relatively consistent or similar (e.g., when the difference in transmission conditions between multiple links is less than a threshold), high-priority MPDUs are evenly distributed among the multiple links. Parameters used to evaluate transmission conditions include, but are not limited to, packet error rate (PER) and / or received signal strength indicator (RSSI). For ease of illustration, the following embodiments use PER as an example criterion, but the invention is not limited to this example. For example, a single parameter or a weighted sum of multiple parameters can be used as an indicator for evaluating transmission conditions. Figure 3 illustrates a schematic diagram of a transmission example 300 of dynamically distributing MPDUs across multiple links according to an embodiment of the present invention. In one embodiment, when the remaining transmission time on multiple links is deemed insufficient to transmit all MPDUs to be transmitted, at least one MPDU corresponding to a low-priority video slice (e.g., the lowest-priority B slice) can be discarded. That is, this low-priority MPDU is not generated in the PPDU to be transmitted (or is not assigned to any link for transmission), ensuring that as many other higher-priority MPDUs as possible are transmitted during the current frame exchange. In Figure 3, the packet error rate (PER) of link 1 is 25%, and the PER of link 2 is 45%. Understandably, in embodiments where PER is used as an indicator of link transmission conditions, a lower PER indicates better link transmission conditions. Assuming a predetermined threshold of 15%, the difference in transmission conditions between the two links (which is 20%) exceeds the predetermined threshold. Therefore, MPDUs corresponding to higher-priority video slices are preferentially assigned to better links (such as link 1). In this embodiment, due to insufficient remaining transmission (TX) time for the current frame exchange, MPDUs corresponding to low-priority video slices (e.g., B-Slice[5] and B-Slice[6]) are not generated in the PPDU and are discarded to ensure that other higher-priority MPDUs can be transmitted in the remaining short time. Figure 3 shows the first PPDU transmitted on link 1 and the second PPDU transmitted on link 2. It can be understood that, as described above, the payload portion of the first PPDU includes the first MPDU corresponding to I-Slice[1] and the third MPDU corresponding to I-Slice[3]. The payload portion of the second PPDU includes the second MPDU corresponding to P-Slice[2], the fourth MPDU corresponding to P-Slice[4], and the seventh MPDU corresponding to P-Slice[7]. Among these, the MPDUs corresponding to the lowest-priority B-Slice[5] and B-Slice[6] are actively discarded. As shown in Figure 3, the current frame exchange ends shortly after the transmission of the second I-slice content (i.e., the third MPDU), and the two B-slices are discarded. However, it should be noted that in some cases, these two B-slices can be recovered from other slices that have been sent.In a preferred embodiment, after the generated PPDU is transmitted, a block acknowledgement request (BAR) frame can be deliberately sent on a better link (e.g., link 1) to force the receiving device to refresh its reorder buffer and end the transmission of MPDU in the current frame exchange (avoiding continuous attempts to retransmit due to the failure to receive MPDUs of B-Slice[5] and B-Slice[6]), thereby entering the next frame exchange. The information carried by the P slice is more important than that of the B slice but not as important as that of the I slice. Therefore, the MPDU corresponding to the P slice can be assigned to a worse link (e.g., link 2). In the example of Figure 3, the transmission of the P slice can be completed in the remaining transmission time. In this way, the important information (high-priority MPDU) carried by the I slice and P slice is transmitted, while the MPDU of the B slice carrying less important information is discarded during transmission due to insufficient TX time. In addition, in this case, a BAR frame can be deliberately sent on a better link. Figure 4A illustrates a schematic diagram of a transmission example 400 of dynamically distributing MPDUs among multiple links according to another embodiment of the present invention. Similar to Figure 3, the PERs of Link 1 and Link 2 are 25% and 45%, respectively, indicating that the differences in transmission conditions among the multiple links exceed the aforementioned thresholds (15% as an example). Therefore, MPDUs corresponding to high-priority video slices or the most important slices (such as I slices) should be assigned to Link 1, which has a lower PER (i.e., relatively better transmission conditions). At least one MPDU corresponding to a low-priority video slice or a less important slice (such as P slices) can also be assigned to Link 1 (if more slice data / MPDUs can be transmitted on Link 1) or to Link 2 (if Link 1 cannot transmit more data). If Link 1 cannot transmit more data (such as P slices) after assigning I slices, then P slices are assigned to Link 2. If, after allocating I and P slices, links 1 and 2 do not have the capacity (time) to transmit additional data (such as B slices), the remaining slice data (such as B slices) will not be generated on links 1 and / or 2, as they will be discarded on links 1 and / or 2. B slice data can be allocated based on the remaining capacity of links 1 and 2. If, after allocating I and P slices, link 2 still has the capacity to transmit more data, then B slice data can be allocated on link 2. If, after allocating I and P slices, neither link 1 nor link 2 can transmit more data (such as B slices), then B slices will not be generated on links 1 and / or 2; instead, low-priority B slices will be discarded directly. In this way, the attributes of successfully received I and P slices can be used to recover MPDUs lost during transmission (which correspond to B slices). In another embodiment, as shown in FIG4B, if the PER of link 1 and link 2 are similar, indicating that the difference in transmission conditions is less than the above threshold, then the MPDU corresponding to the high-priority video slice (such as I slice) is evenly distributed in link 1 and link 2, because the probability of MPDU loss in link 1 and link 2 is similar or almost the same. It should be noted that in the embodiments depicted in Figures 3 and 4A / 4B, the data of each video slice is encapsulated in an independent Media Access Control Protocol Data Unit (MPDU). That is, each slice shown in the figures corresponds to one MPDU. Furthermore, the numbers presented in the figures can be used as examples of MPDU serial numbers. For example, in Figure 4A, I-Slice[1] can represent MPDU 1, which has serial number 1 and carries the corresponding data of I-Slice[1], P-Slice[2] can represent MPDU 2, which has serial number 2 and carries the corresponding data of P-Slice[2], I-Slice[3] can represent MPDU 3, which has serial number 3 and carries the corresponding data of I-Slice[3], and so on. Furthermore, it can be observed from Figures 3 and 4A / 4B that the sequence numbers of multiple MPDUs within a single PPDU are non-sequential. For example, in the second PPDU transmitted on link 2 shown in Figure 3, the sequence numbers of the MPDUs included are 2, 4, and 7, respectively. In the embodiment shown in Figure 3, although MPDUs 5 and 6 are not transmitted, the data of B-Slice[5] and B-Slice[6] may be recovered from the data of other slices. In another embodiment, considering that the amount of data in B slices is usually small, it is possible to aggregate / encapsulate MSDUs corresponding to multiple B slices into a single MPDU. For example, the data of B-Slice[5] and B-Slice[6] can be combined to encapsulate into a single MPDU. Therefore, in another embodiment, the data of a single I slice is encapsulated into a single MPDU, the data of a single P slice is encapsulated into a single MPDU, but the encapsulation of B slices is not subject to this limitation. Figure 5 illustrates a failed transmission scenario 500 where MPDUs are not dynamically distributed across multiple links. As shown in Figure 5, two Physical Protocol Data Units (PPDUs) are transmitted over two different links. Specifically, the first PPDU on link 1 comprises three Media Access Control Protocol Data Units (MPDUs), and the second PPDU on link 2 comprises five MPDUs. For ease of illustration and understanding, in the example, the numbers in the figures represent MPDU sequence numbers, which may correspond to the slice sequence numbers of the respective video slices in a scenario where each video slice is encapsulated into a single MPDU. For clarity, the embodiments described herein assume that the data of a video slice is encapsulated into one MPDU. However, in some embodiments, the scope of the invention is not limited to this configuration. In scenario 500, where the dynamic allocation strategy proposed in this invention is not employed, the sequence numbers of multiple MPDUs within a single PPDU are sequential. For example, MPDUs numbered 6, 7, and 8 (representing MPDU[6], MPDU[7], and MPDU[8], respectively) are generated in the first PPDU and transmitted via link 1, while MPDUs numbered 1 to 5 (representing MPDU[1] to MPDU[5], respectively) are generated in the second PPDU and transmitted via link 2. In this embodiment, each MPDU is associated with data from a different video slice. In some cases, it is assumed that the data within MPDU[6] (e.g., data from slice[6]) requires MPDU[2] (e.g., data from slice[2]), MPDU[5] (e.g., data from slice[5]), and MPDU[7] (e.g., data from slice[7]) to be successfully recovered. The data in MPDU[7] (e.g., the data in slice[7]) requires MPDU[3] (e.g., the data in slice[3]), MPDU[6] (e.g., the data in slice[6]), and MPDU[8] (e.g., the data in slice[8]) to be successfully recovered. Furthermore, the data in MPDU[8] requires MPDU[4] and MPDU[7] to be successfully recovered. However, as shown in Figure 5, due to interference, consecutive transmission errors may occur on link 1, causing MPDU[6], MPDU[7], and MPDU[8] to fail to be received. Therefore, the unavailability of MPDU[7] hinders the recovery of MPDU[6] and MPDU[8], and the absence of MPDU[6] and MPDU[8] also hinders the recovery of MPDU[7]. Thus, in the presented scenario 500, MPDU[6] to MPDU[8] cannot be recovered using successfully received MPDUs, resulting in a recovery rate of 0. Figure 6 illustrates a transmission example 600 of dynamically dispatching MPDUs across multiple links according to another embodiment of the present invention. In this embodiment, when at least one of the multiple links is detected to contain a continuous error, the multiple MPDUs to be transmitted are dispatched alternately across different PPDUs (i.e., alternately dispatched for transmission on different links), wherein the sequence numbers of the multiple MPDUs dispatched in each PPDU are arranged alternately or in an interleaved manner (non-contiguous). In Figure 6, the multiple MPDUs are dispatched alternately; for example, MPDUs 2, 4, and 5 (for constituting a first PPDU) are transmitted on link 1, and MPDUs 1, 3, 6, 7, and 8 (for constituting a second PPDU) are transmitted on link 2. Due to a high PER (e.g., a continuous error mode) in link 1, MPDUs 2, 4, and 5 are lost. However, MPDU 2 can be recovered from MPDUs 1, 3, and 6, MPDU 4 can be recovered from MPDUs 3 and 8, and MPDU 5 can be recovered from MPDUs 1 and 6. Therefore, these MPDUs are all available, with a recovery rate of 100%, which is much better than the 0% recovery rate in Figure 5. In this embodiment of the invention, when a continuous error pattern is detected in a link (as shown in Figure 6), the multiple MPDUs are alternately dispatched according to their sequence numbers, rather than being generated sequentially in the PPDUs. In another embodiment, when the error patterns in multiple links are discrete, the MPDUs are scheduled sequentially. That is, when discrete errors are detected on multiple links, the transmitting device can sequentially schedule the multiple MPDUs to be transmitted into different PPDUs, wherein the sequence numbers of the multiple MPDUs in each PPDU are continuous. Figure 7 is a flowchart illustrating a transmission method 700 for dynamically distributing MPDUs among multiple links according to an embodiment of the present invention. The transmission method 700 includes the following steps: Step S702: The transmitting device obtains a transmission opportunity, or, understandably, receives a transmission (TX) request. Step S704: Check whether to dynamically assign MPDU; if yes, proceed to step S706; otherwise, proceed to step S705. Step S705: Sequentially aggregate multiple MPDUs into each PPDU; proceed to step S716. Step S706: Check if the remaining transmission time in the current frame exchange is less than the PPDU time; if yes, proceed to step S708; otherwise, proceed to step S710. Step S708: Discard at least one low-priority MPDU. For example, discard at least one MPDU with the lowest priority, which may correspond to the lowest priority or least important video slice, such as slice B. Step S710: Check whether the PER (using PER as an example of transmission conditions, but the present invention is not limited to this example) between different links are similar; if they are (i.e., if the difference in transmission conditions between different links is less than a preset threshold), proceed to step S714; otherwise (i.e., if the difference in transmission conditions between different links is greater than a preset threshold), proceed to step S712. Step S712: During the generation of multiple PPDUs that will be transmitted through multiple links, high-priority MPDUs (e.g., corresponding I-slices) are preferentially assigned to low-PER links; that is, more I-slices are assigned to low-PER links. In this embodiment, a priority strategy is adopted to assign MPDUs by detecting the differences in transmission conditions (e.g., PER) between multiple communication links. Specifically, MPDUs containing high-priority video slices are preferentially assigned to links with relatively better or superior transmission characteristics / conditions. When all MPDUs cannot be transmitted on links with relatively better or superior transmission characteristics / conditions, MPDUs containing low-priority video slices are considered for assignment to links with relatively poorer transmission characteristics / conditions. This dynamic assignment method optimizes the use of available links by coordinating the priority of video content with the reliability of transmission paths, thereby improving the overall service quality of video streaming applications. Step S714: During the generation of PPDUs that will be transmitted through multiple links, high-priority MPDUs (e.g., corresponding I-slices) are evenly distributed across each link; that is, a similar number of I-slices are assigned to each link. In this embodiment, the difference in transmission conditions between multiple links is below a predetermined threshold—indicating similar link performance / conditions—and a fair allocation strategy is implemented to transmit MPDUs. This strategy evenly distributes MPDUs associated with high-priority video slices across multiple links. By employing this method, this embodiment ensures balanced utilization of links, thereby helping to maintain a consistent quality level for high-priority video data transmission and reducing the possibility of over-reliance on any single link. Step S716: Transmit the generated PPDU through multiple links. In step S704, for example, if the remaining transmission time is sufficient for dynamic MPDU allocation, if PER > M% (0 < M < 100) in at least one link, and / or if a continuous error pattern is observed on any link, dynamic MPDU allocation is considered, but the invention is not limited thereto. For example, if a series of MPDUs transmitted on a particular link are observed to fail over a time interval, this continuous transmission failure indicates a deterioration in link quality (unreliability), and a continuous error pattern is detected. If it is determined that dynamic MPDU allocation is not required, proceed to step S705. In step S705, PPDUs are generated using a conventional transmission scheme, wherein the sequence numbers of the MPDUs contained within each PPDU are consecutive. In other words, MPDUs are aggregated sequentially / in order in the PPDUs according to their assigned sequence numbers. If it is determined that dynamic MPDU allocation is required, method 700 proceeds to step S706. In step S706, it is checked whether the remaining transmission time is less than the PPDU time. If yes, proceed to step S708; otherwise, proceed to step S710. In step S708, data packets of low-priority slices, such as MPDUs corresponding to slice B, are discarded. In step S710, it is checked whether the packet error rates (PER, it should be noted that PER is an example of a transmission condition and the present invention is not limited to this example) of different links are similar. If so, proceed to step S714; otherwise, proceed to step S712. In step S712, during the generation of Physical Protocol Data Units (PPDUs), intra-frame slices (I-slices) (or MPDUs corresponding to I-slices) are assigned to links with low PER, provided that the links have sufficient capacity, while less important bidirectional prediction slices (B-slices) are considered for assignment to links with high PER. In step S714, since the PERs of different links are similar, a similar number of I-slices are assigned to the links. In step S716, the generated PPDUs are transmitted through multiple links. During data transmission, the transmitting device can determine or classify the error patterns associated with each link, such as discrete or continuous error patterns. In one example, the receiving device can return a Block Acknowledgement (BA) frame to the transmitting device to inform the transmitting device which packets (MPDUs) have been successfully received. Therefore, the transmitting device can determine the link error mode based on this feedback. However, it should be noted that the scope of the present invention is not limited to this method of determining the link error mode. Figure 8 is a schematic diagram illustrating a method for dynamically distributing MPDUs across multiple links according to an embodiment of the present invention. Multiple MPDUs are alternately distributed between link 1 and link 2. Link 1 is a link with a high packet error rate (PER) (e.g., PER above a first threshold), which may indicate a continuous error pattern, while link 2 is a link with a low packet error rate (PER) (e.g., PER below a second threshold, where the second threshold may be less than the first threshold). Before transmitting data, the transmitting device sends a request to send (RTS, abbreviated as "R" in the figure) frame 802 to the receiving device to signal that data transmission is imminent. Subsequently, the receiving device responds with a clear to send (CTS, abbreviated as "C" in the figure) frame 804, informing the receiving device that it is ready to receive data. After exchanging RTS frame 802 and CTS frame 804 (gaining a transmission opportunity), transmission of the alternately distributed MPDUs begins. As shown in Figure 8, after sending the corresponding Physical Protocol Data Units (PPDUs, four MPDUs are shown in Figure 8), a Block Acknowledgment Request (BA, referred to as "B" in the figure) frame 806 is transmitted to acknowledge data reception. In Figure 8, due to the high PER in Link 1, multiple MPDU transmissions on Link 1 fail. In one embodiment, when the time is close to the estimated video frame playback time (i.e., slightly ahead of the estimated video frame playback time by a preset time), a Block Acknowledgment Request (BAR) frame 808 is deliberately sent on Link 2, which has better transmission conditions, to force the receiving device to refresh its reordering buffer and terminate or end the MPDU transmission in the current frame exchange to proceed to the next frame exchange. The BAR frame 808 should be sent on Link 2, which has relatively better transmission conditions, rather than Link 1, because Link 1 has a high PER while Link 2 has a low PER. After the receiving device refreshes its reordering buffer, it reorders all successfully received MPDUs according to their sequence numbers, thereby determining that MPDUs 6, 8, 9, and 11 were lost in transmission (i.e., reception failed). However, in some cases, MPDU 6 can be recovered from MPDUs 2, 5, 7, and 10; MPDU 8 can be recovered from MPDUs 4, 7, and 12; MPDU 9 can be recovered from MPDUs 5, 10, and 13; and MPDU 11 can be recovered from MPDUs 7, 10, 12, and 15. Therefore, due to the alternating dispatch of MPDUs and the timely transmission of BAR frames 808 to refresh the reordering buffer, the recovery rate reaches 100%, effectively preventing useless retransmissions of failed MPDUs. In one embodiment, the BAR frame 808 is transmitted to the receiving device before the video frame playback time to enhance the smoothness of video playback, rather than because failed MPDUs are constantly being retransmitted.For example, BAR frame 808 can be transmitted for a predetermined duration before the estimated video frame playback time. Figure 9 illustrates an example system 900 according to an embodiment of the present invention, which includes at least example device 910 and example device 920. Each of device 910 and device 920 can perform various functions to implement the schemes, techniques and methods described herein related to video transmission over multiple links, including the various schemes related to the various proposed designs, concepts and schemes described above, as well as the processes described below. Devices 910 and 920 can be communication entities capable of communicating with each other using the various schemes proposed in this invention; for example, devices 910 and 920 can be multi-link devices (MLDs). Each of devices 910 and 920 may include at least some of the elements shown in FIG. 9, such as processor 912 and processor 922. Each of devices 910 and 920 may also include one or more other elements unrelated to the proposed solution of the present invention (e.g., internal power supply, display device and / or user interface device), therefore, for the sake of brevity, these elements of devices 910 and 920 are not shown in FIG. 9 and are not described below. In one aspect, processors 912 and 922 may be implemented as one or more single-core processors, one or more multi-core processors, one or more RISC processors, or one or more CISC processors. That is, even though the term "processor" is used herein to refer to processors 912 and 922, in this invention, each of processors 912 and 922 may include multiple processors in some embodiments and a single processor in other embodiments, and the invention is not limited thereto. In some embodiments, device 910 (e.g., the transmitting device described above) further includes a transceiver 916 coupled to processor 912. Transceiver 916 is capable of wirelessly transmitting and receiving data. In some embodiments, device 920 (e.g., the receiving device described above) may also include a transceiver 926 coupled to processor 922. Transceiver 926 is capable of wirelessly transmitting and receiving data. Transceivers 916 and 926 can wirelessly communicate with each other via one or more of a plurality of links (link 1 to link N, where N is a positive integer greater than 1, such as the first link and the second link). In some embodiments, device 910 may further include memory 914 coupled to processor 912 and accessible by processor 912 and storing data therein. In some embodiments, device 920 may further include memory 924 coupled to processor 922 and accessible by processor 922 and storing data therein. Figure 10 is a flowchart illustrating a transmission method 1000 for dynamically distributing MPDUs among multiple links according to an embodiment of the present invention. The transmission method 1000 includes the following steps: Step S1002: Check if at least one predetermined condition is met. If yes, proceed to step S1004; otherwise, proceed to step S1006. Step S1004: Dynamically assign multiple MPDUs containing video data to generate multiple PPDUs that will be transmitted through multiple links, wherein the sequence numbers of the multiple MPDUs assigned in each / corresponding PPDU are non-sequential. Step S1006: Generate multiple PPDUs sequentially according to the MPDU's serial number, wherein the serial numbers of the multiple MPDUs in each / corresponding PPDU are consecutive. Step S1008: Transmit multiple PPDUs on multiple links. In step S1002, it is checked whether at least one predetermined condition is met. For example, at least one predetermined condition may include: whether the remaining TX time for the current frame exchange is sufficient, whether the PER of the link is greater than M% (0 < M < 100), whether the transmission error mode is continuous, etc. If at least one of the conditions is met, proceed to step S1004 to dynamically assign multiple MPDUs containing video data to generate multiple PPDUs that will be transmitted through multiple links, wherein the sequence numbers of the multiple MPDUs assigned in each / corresponding PPDU are non-contiguous. If no predetermined condition is met, proceed to step S1006 to generate PPDUs sequentially according to the sequence numbers of the MPDUs. After executing step S1004 or step S1006, proceed to step S1008 to transmit the PPDUs on multiple links. In this invention, MPDUs are dynamically allocated based on the error mode on the link, the remaining transmission time for the current frame exchange, and / or transmission conditions. This improves the MPDU recovery rate. Therefore, this invention provides both quality and efficiency for video transmission by dynamically allocating MPDUs across multiple links. The use of ordinal terms such as “first,” “second,” and “third” in the scope of a patent application to modify patent elements does not in itself indicate any priority, order, or sequence of one patent element relative to another, or the temporal order of the execution of method actions, but is merely used as a marker to distinguish one patent element with the same name from another element with the same name. While the embodiments and advantages of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the present invention without departing from the spirit and scope defined by the claims. For example, new embodiments can be derived by combining several parts of different embodiments. The described embodiments are for illustrative purposes only and are not intended to limit the present invention. The scope of protection of the present invention is determined by the appended claims. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. The above descriptions are merely preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be included within the scope of the present invention. 100: First example allocation; 200: Second example allocation; 300, 400, 600: Transmission example of dynamically distributing MPDUs across multiple links; 500: Failed transmission scenario where MPDUs are not dynamically distributed across multiple links; S702, S704, S705, S706, S708, S710, S712, S714, S716: Steps; 910, 920: Devices; 912, 922: Processors; 914, 924: Memory; 916, 926: Transceiver; 700, 1000: Transmission method; S1002, S1004, S1006, S1008: Steps The accompanying drawings (in which the same numerals denote the same components) illustrate embodiments of the present invention. The included drawings are used to provide a further understanding of the embodiments of this disclosure, and are incorporated into and constitute a part of the embodiments of this disclosure. The drawings illustrate implementations of the embodiments of this disclosure and, together with the description, serve to explain the principles of the embodiments of this disclosure. It is understood that the drawings are not necessarily drawn to scale, as some components may be shown out of scale to clearly illustrate the concepts of the embodiments of this disclosure. Figure 1 is a first example allocation of multiple MPDUs according to an embodiment of the present invention. Figure 2 is a second example allocation of multiple MPDUs according to another embodiment of the present invention. Figure 3 is a schematic diagram illustrating an example of dynamic MPDU distribution transmission among multiple links according to an embodiment of the present invention. Figure 4A is a schematic diagram illustrating an example of dynamic MPDU distribution transmission among multiple links according to another embodiment of the present invention. Figure 4B is a schematic diagram illustrating an example of dynamic MPDU distribution transmission among multiple links according to another embodiment of the present invention. Figure 5 illustrates a failed transmission scenario where no dynamic MPDU distribution is performed among multiple links. Figure 6 is a schematic diagram illustrating an example of dynamic MPDU distribution transmission among multiple links according to another embodiment of the present invention. Figure 7 is a flowchart illustrating a method for dynamically distributing MPDUs among multiple links according to an embodiment of the present invention. Figure 8 is a schematic diagram illustrating the transmission of MPDUs dynamically distributed among multiple links according to an embodiment of the present invention. Figure 9 is a block diagram illustrating a video transmission system for dynamically distributing MPDUs among multiple links and used for transmitting video data according to an embodiment of the present invention. Figure 10 is a flowchart illustrating a method for dynamically distributing MPDUs among multiple links according to an embodiment of the present invention. In the following detailed description, numerous specific details are set forth for illustrative purposes so that those skilled in the art can more thoroughly understand the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details, and different embodiments or different features disclosed in different embodiments may be combined as needed, and should not be limited to the embodiments illustrated in the accompanying drawings. 1000: Transmission Method S1002, S1004, S1006, S1008: Steps

Claims

1. A video transmission method for transmitting video data through multiple links, comprising: When at least one predetermined condition associated with the plurality of links is met, a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data are assigned to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links, wherein the sequence numbers of the plurality of MPDUs assigned in each PPDU are non-contiguous, and the plurality of links include a first link and a second link, the plurality of PPDUs include a first PPDU transmitted through the first link and a second PPDU transmitted through the second link, the sequence numbers of the first MPDU and the second MPDU consecutively encapsulated in the first PPDU are non-contiguous, and the sequence number of the third MPDU encapsulated in the second PPDU and the sequence number of one of the first MPDU and the second MPDU encapsulated in the first PPDU are contiguous; and the plurality of PPDUs are transmitted through the plurality of links.

2. The video transmission method as described in claim 1, wherein, The method also includes: encapsulating multiple MAC Service Data Units (MSDUs) corresponding to a single video slice into a single MPDU.

3. The video transmission method as described in claim 2, wherein, The step of assigning multiple Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate multiple Physical Protocol Data Units (PPDUs) to be transmitted through the multiple links when at least one predetermined condition associated with the multiple links is met includes: when the difference in transmission conditions between the multiple links exceeds a threshold, assigning the MPDU corresponding to a high-priority video slice among the multiple MPDUs to the link with relatively better transmission conditions.

4. The video transmission method as described in claim 2, wherein, The step of assigning multiple Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate multiple Physical Protocol Data Units (PPDUs) to be transmitted through the multiple links when at least one predetermined condition associated with the multiple links is met includes: uniformly assigning MPDUs corresponding to high-priority video slices among the multiple MPDUs on the multiple links when the difference in transmission conditions between the multiple links is less than a threshold.

5. The video transmission method as described in claim 4, wherein, The transmission conditions include Packet Error Rate (PER) and / or Received Signal Strength Indicator (RSSI).

6. The video transmission method as described in claim 2, wherein, The video slice includes an intra-frame (I) slice, a prediction (P) slice, and a bidirectional prediction (B) slice, wherein the I slice has a higher priority than the P slice, and the P slice has a higher priority than the B slice.

7. The video transmission method as described in claim 2, wherein, When the remaining transmission time of the multiple links is insufficient to transmit all of the multiple MPDUs in the current frame exchange, at least one MPDU corresponding to the low-priority video slice is not generated in the multiple PPDUs.

8. The video transmission method as described in claim 1, wherein, The step of assigning multiple Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate multiple Physical Protocol Data Units (PPDUs) to be transmitted through the multiple links when at least one predetermined condition associated with the multiple links is met includes: when at least one of the multiple links is detected to contain a continuous error, the multiple MPDUs containing video data are alternately assigned to different PPDUs, wherein the sequence numbers of the multiple MPDUs assigned to each PPDU are alternately arranged.

9. The video transmission method as described in claim 1, wherein, The method further includes: when a discrete error is detected on the multiple links, generating a PPDU sequentially according to the sequence number of the multiple MPDUs.

10. The video transmission method as described in claim 1, wherein, The method further includes: estimating the playback time of a video frame of the receiving device, and sending a block acknowledgment request (BAR) frame before the playback time of the video frame to request the receiving device to force refresh its reordering buffer.

11. An apparatus for transmitting video data through multiple links, comprising: The transceiver is configured for wireless communication. The transceiver, coupled to a processor, is configured to perform the following operations: when at least one predetermined condition associated with the plurality of links is satisfied, dispatching a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links, wherein the sequence numbers of the plurality of MPDUs dispatched in each PPDU are non-contiguous, and the plurality of links include a first link and a second link, the plurality of PPDUs include a first PPDU transmitted through the first link and a second PPDU transmitted through the second link, the sequence numbers of the first MPDU and the second MPDU consecutively encapsulated in the first PPDU are non-contiguous, and the sequence number of a third MPDU encapsulated in the second PPDU and the sequence number of one of the first MPDU and the second MPDU encapsulated in the first PPDU are contiguous; and transmitting the plurality of PPDUs through the plurality of links via the transceiver.

12. The apparatus as claimed in claim 11, wherein, The processor is also configured to perform the following operations: encapsulate multiple MAC Service Data Units (MSDUs) corresponding to a single video slice into a single MPDU.

13. The apparatus as claimed in claim 12, wherein, When at least one predetermined condition associated with the plurality of links is met, the operation of assigning a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when the difference in transmission conditions between the plurality of links exceeds a threshold, assigning the MPDU corresponding to a high-priority video slice among the plurality of MPDUs to the link with relatively better transmission conditions.

14. The apparatus as claimed in claim 12, wherein, When at least one predetermined condition associated with the plurality of links is met, the operation of distributing a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when the difference in transmission conditions between the plurality of links is less than a threshold, uniformly distributing the MPDUs corresponding to high-priority video slices among the plurality of MPDUs on the plurality of links.

15. The apparatus as claimed in claim 14, wherein, The transmission conditions include Packet Error Rate (PER) and / or Received Signal Strength Indicator (RSSI).

16. The apparatus as claimed in claim 12, wherein, The video slice includes an intra-frame (I) slice, a prediction (P) slice, and a bidirectional prediction (B) slice, wherein the I slice has a higher priority than the P slice, and the P slice has a higher priority than the B slice.

17. The apparatus as claimed in claim 12, wherein, When the remaining transmission time of the multiple links is insufficient to transmit all of the multiple MPDUs in the current frame exchange, at least one MPDU corresponding to the low-priority video slice is not generated in the multiple PPDUs.

18. The apparatus as claimed in claim 11, wherein, When at least one predetermined condition associated with the plurality of links is met, the operation of assigning a plurality of Media Access Control (MAC) Protocol Data Units (MPDUs) containing video data to generate a plurality of Physical Protocol Data Units (PPDUs) to be transmitted through the plurality of links includes: when at least one of the plurality of links is detected to contain a continuous error, the plurality of MPDUs containing video data are alternately assigned to different PPDUs, wherein the sequence numbers of the plurality of MPDUs assigned to each PPDU are alternately arranged.

19. The apparatus as claimed in claim 11, wherein, The processor is also configured to perform the following operations: when a discrete error is detected on the multiple links, generate a PPDU sequentially according to the sequence number of the multiple MPDUs.

20. The apparatus as claimed in claim 11, wherein, The processor is also configured to perform the following operations: estimate the playback time of a video frame of the receiving device, and send a Block Acknowledgment Request (BAR) frame before the playback time of the video frame to request the receiving device to force a refresh of its reordering buffer.

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