Patent ID: 12245334

DETAILED DESCRIPTION

Certain terms are used throughout the following description and claims, which refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the 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 . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

FIG.1is a diagram illustrating a wireless fidelity (WiFi) system according to an embodiment of the present invention. For brevity and simplicity, it is assumed that the WiFi system100includes one access point (AP)102and two non-AP stations (STAs)104and106. In this embodiment, AP102and non-AP STAs104and106are wireless fidelity (WiFi) multi-link devices (MLDs) that support multi-link operation (MLO). For example, AP102may own K links L1-LKat different channels (radio frequency bands), may communicate with non-AP STA104via N links L11-L1N(which are selected from links L1-LK), and may communicate with non-AP STA106via M links L21-L2M(which are selected from links L1-LK), where K, M and N are positive integers, N is not smaller than 2, M is not smaller than 2, and K is not smaller than any of M and N. In some embodiments of the present invention, non-AP STAs104and106may be dual-radio STAs (M=N=2), and AP102may be a tri-band AP (K=3). For example, links owned by AP102may include a channel in 5 GHz, a channel in 6 GHz, and a channel in 2.4 GHz. However, this is for illustrative purposes only, and is not meant to be a limitation of the present invention. Any WiFi system using the proposed physical protocol data unit (PPDU) alignment mechanism falls within the scope of the present invention. In addition to MLO, the AP102may support other features such as multi-User multiple-input multiple-output (MU-MIMO) and orthogonal frequency-division multiple access (OFDMA) for multi-user transmission.

In certain cases, the PPDUs' starting time instants may not be synchronized due to the fact that transmission opportunity (TXOP) timing of multiple links may be different and/or the transmitter needs to check clear channel assessment (CCA) for a certain period before medium access. The proposed PPDU alignment mechanism is capable of synchronizing ending time instants of transmission of PPDUs transmitted over multiple links to help the acknowledgement (ACK) receiving and the follow-up transmission to be synchronized. In this present invention, ending time instants of transmission of PPDUs transmitted over multiple links may be regarded as aligned with each other when mismatch between the ending time instants falls within a predefined tolerance range. For example, the predefined tolerance range may be set by short interframe space (SIFS)±aSlotTime*10%. In practice, the predefined tolerance range may be adjusted, depending upon actual design considerations.

FIG.2is a diagram illustrating a first PPDU ending time alignment mechanism according to an embodiment of the present invention. In accordance with the first PPDU ending time alignment mechanism, one WiFi MLD (e.g., AP102shown inFIG.1) aligns parameters of a plurality of links (e.g., links L11-L1Nor links L21-L2M) for constraining the links to have the same capacity for PPDU transmission, and transmits PPDUs via the links, where highest capacity supported by one of the links is different from highest capacity supported by another of the links, and each of the PPDUs is generated and transmitted under the same parameters. For example, the parameters may include BW, NSS, and MCS. In this embodiment, one WiFi MLD (e.g., AP102) communicates with another WiFi MLD (e.g., Non-AP STA104or Non-AP STA106) via a first link (denoted by “Link 1”) and a second link (denoted by “Link 2”), where the first link supports BW=40 MHz (denoted by “BW40”), NSS=1, and best MCS=MCS3, and the second link supports BW=80 MHz (denoted by “BW80”), NSS=1, and best MCS=MCS7. Hence, the highest capacity supported by the second link is higher than the highest capacity supported by the first link.

In accordance with the first PPDU ending time alignment mechanism, the PPDU transmission for each of the first link and the second link may use BW=40 MHz, NSS=1, and best MCS=MCS3. The first PPDU ending time alignment mechanism may be applicable to the duplicate transmission scenario with synchronized PPDU starting time. As shown inFIG.2, one PPDU202is transmitted via the first link, and one PPDU204is transmitted via the second link, where the WiFi MLD (e.g., AP102) transmits the PPDUs202and204to the same user (e.g., non-AP STA104or non-AP STA106), and the PPDU204is a duplicate of the PPDU202such that the PPDUs202and204carry the same content. As shown inFIG.2, the ending time instants of transmission of PPDUs202and204are aligned.

Since the highest capacity supported by the second link is higher than the highest capacity supported by the first link and parameters of the first link and the second link are constrained to be the same for PPDU transmission, the available capacity of the second link is not fully utilized by PPDU transmission. As a result, links capable of allowing more data transmission may lose efficiency. As shown inFIG.2, a half of the capacity supported by the second link is unused during a transmission period of the PPDU204. To address this issue, the present invention proposes a second PPDU ending time alignment mechanism.

FIG.3is a diagram illustrating a second PPDU ending time alignment mechanism according to an embodiment of the present invention. In accordance with the second PPDU ending time alignment mechanism, one WiFi MLD (e.g., AP102shown inFIG.1) aligns parameters of a plurality of links (e.g., links L11-L1Nor links L21-L2M) for constraining the links to have the same capacity for PPDU transmission, and transmits PPDUs via the links, where highest capacity supported by one of the links is different from highest capacity supported by another of the links, each of the PPDUs is generated and transmitted under the same parameters (which may include BW, NSS, and MCS), and more than one PPDU is transmitted via one link that supports higher capacity. For example, one WiFi MLD (e.g., AP102) communicates with another WiFi MLD (e.g., non-AP STA104or non-AP STA106) via a first link (denoted by “Link 1”) and a second link (denoted by “Link 2”), where the first link supports BW=40 MHz (denoted by “BW40”), NSS=1, and best MCS=MCS3, and the second link supports BW=80 MHz (denoted by “BW80”), NSS=1, and best MCS=MCS7. Hence, the highest capacity supported by the second link is higher than the highest capacity supported by the first link.

In accordance with the second PPDU ending time alignment mechanism, the PPDU transmission for each of the first link and the second link may use BW=40 MHz, NSS=1, and best MCS=MCS3. The second PPDU ending time alignment mechanism may be applicable to the duplicate transmission scenario with synchronized PPDU starting time. As shown inFIG.3, one PPDU302is transmitted via the first link, and one PPDU304and one duplicate PPDU306(which is a duplicate of PPDU304) are transmitted via the second link. In this embodiment, the WiFi MLD (e.g., AP102) transmits the PPDUs302,304, and306to the same user (e.g., non-AP STA104or non-AP STA106), and the PPDU304is a duplicate of the PPDU302such that the PPDUs302,304, and306carry the same content. As shown inFIG.3, the ending time instants of transmission of PPDUs302,304, and306are aligned. Duplicated transmission in extra BW of a high capacity link (e.g., second link) further increases transmission robustness. In addition, extra signaling about the duplicate PPDU in the extra BW of the high capacity link (e.g., second link) may be required.

FIG.4is a diagram illustrating a third PPDU ending time alignment mechanism according to an embodiment of the present invention. In accordance with the third PPDU ending time alignment mechanism, one WiFi MLD (e.g., AP102shown inFIG.1) sets parameters of each of links for enabling the links to have different capacity for PPDU transmission, sets a content that is carried by a first PPDU transmitted via one of the links to ensure that an ending time instant of transmission of the first PPDU transmitted via one of the links and an ending time instant of transmission of a second PPDU transmitted via another of the links are aligned, and transmits PPDUs (which include the first PPDU and the second PPDU) via the links. Parameters of each link may include BW, NSS, and MCS. In this embodiment, parameters of one of the links are different from parameters of another of the links, highest capacity supported by one of the links is higher than highest capacity supported by another of the links, and one PPDU is transmitted via each of the links. Each link may use its best parameters to generate and transmit the PPDU. For example, one WiFi MLD (e.g., AP102) communicates with another WiFi MLD (e.g., non-AP STA104or non-AP STA106shown inFIG.1) via a first link (denoted by “Link 1”) and a second link (denoted by “Link 2”), where the first link supports BW=40 MHz (denoted by “BW40”), NSS=1, and best MCS=MCS3, and the second link supports BW=80 MHz (denoted by “BW80”), NSS=1, and best MCS=MCS7. Hence, the highest capacity supported by the second link is higher than the highest capacity supported by the first link. The first link is configured to use best parameters, including BW=40 MHz, NSS=1, and best MCS=MCS3, for PPDU transmission, and the second link is configured to use best parameters, including BW=80 MHz, NSS=1, and best MCS=MCS7, for PPDU transmission.

Since the capacity provided by the second link is higher than the capacity provided by the first link, partial duplication can be enabled to align PPDU lengths for achieving PPDU ending time alignment. The third PPDU ending time alignment mechanism may be applicable to all of the aforementioned scenarios. As shown inFIG.4, one PPDU402is transmitted via the first link, and one PPDU404is transmitted via the second link, where the WiFi MLD (e.g., AP102) transmits PPDUs402and404to the same user (e.g., non-AP STA104or non-AP STA106), and the PPDU404transmitted via the second link includes a partial PPDU406(which includes one or more media access control protocol data units (MPDUs)407), one or more duplicate MPDUs408, and optional padding bits410. The duplicate MPDU(s)408may be derived from duplication of MPDU(s)407, and one or more duplicate MPDUs may be obtained from the same source MPDU. The optional padding bits410may be set by 0's. In this embodiment, the duplicate MPDU(s)408are appended to the partial PPDU406, and the optional padding bits410are appended to the duplicate MPDU(s)408. In an alternative design, source MPDU(s)407and duplicate MPDU(s)408may be interleaved in the PPDU404to increase diversity. As shown inFIG.4, the ending time instants of transmission of PPDUs402and404are aligned. Signaling of MPDU duplication may be required, and MPDUs with the same content can be decoded individually or jointly to reduce error possibility. It should be noted that PPDU starting time alignment is not necessarily required by the third PPDU ending time alignment mechanism.

FIG.5is a diagram illustrating a fourth PPDU ending time alignment mechanism according to an embodiment of the present invention. In accordance with the fourth PPDU ending time alignment mechanism, one WiFi MLD (e.g., AP102shown inFIG.1) sets parameters of links for enabling the links to have different capacity for PPDU transmission, and transmits PPDUs via the links. Parameters of each link may include BW, NSS, and MCS. In this embodiment, parameters of one of the links are different from parameters of another of the links, highest capacity supported by one of the links is higher than highest capacity supported by another of the links, one PPDU is transmitted via one link, and multiple PPDUs are transmitted via another link to ensure that an ending time instant of transmission of one PPDU on one link and an ending time instant of transmission of multiple PPDUs on another link are aligned.

Each link may use its best parameters to generate and transmit the PPDU. For example, one WiFi MLD (e.g., AP102) communicates with another WiFi MLD (e.g., non-AP STA104) via multiple links including a first link (denoted by “Link 1”) and a second link (denoted by “Link 2”), and further communicates with yet another WiFi MLD (e.g., non-AP STA106) via multiple links including the second link (denoted by “Link 2”), where the first link supports BW=40 MHz (denoted by “BW40”), NSS=1, and best MCS=MCS3, and the second link supports BW=80 MHz (denoted by “BW80”), NSS=1, and best MCS=MCS7. Hence, the highest capacity supported by the second link is higher than the highest capacity supported by the first link. The first link is configured to use best parameters, including BW=40 MHz, NSS=1, and best MCS=MCS3, for PPDU transmission, and the second link is configured to use best parameters, including BW=80 MHz, NSS=1, and best MCS=MCS7, for PPDU transmission.

Since the capacity provided by the second link is higher than the capacity provided by the first link, the second link is allowed to transmit multiple PPDUs during a transmission period of one PPDU that is transmitted via the first link. The fourth PPDU ending time alignment mechanism may be applicable to all of the aforementioned scenarios. As shown inFIG.5, one PPDU502is transmitted via the first link, and one PPDU504and at least one padding PPDU506are transmitted via the second link, where the WiFi MLD (e.g., AP102) transmits the PPDUs502and504to the same user (e.g., non-AP STA104), and transmits padding PPDU(s)506to a different user (e.g., non-AP STA106). The multiple PPDUs504and506transmitted via the second link are separated by SIFS to ensure medium occupation. As shown inFIG.5, an ending time instant of transmission of PPDU502and an ending time instant of transmission of multiple PPDUs504and506(particularly, an ending time instant of transmission of the last one of PPDUs504and506) are aligned. It should be noted that PPDU starting time alignment is not necessarily required by the fourth PPDU ending time alignment mechanism.

In a case where the fourth PPDU ending time alignment mechanism is applied to the duplicate transmission scenario, the PPDU504is a duplicate of the PPDU502, and an ending time instant of transmission of the PPDU504is earlier than an ending time instant of transmission of the PPDU502. If immediate acknowledgement (ACK) is required by duplicate transmission and an ACK message is sent over the second link, the ACK message receiving interferes with transmission of padding PPDU(s)506. To address this issue, the present invention proposes sending the ACK message over the first link that occupies the longer period to avoid interfering with transmission of the padding PPDU(s)506on the second link. Alternatively, a block ACK mechanism may be adopted to collect acknowledgement later after the transmission, and/or signaling can be adopted to delay the acknowledgement until the end of transmission.

FIG.6is a diagram illustrating a fifth PPDU ending time alignment mechanism according to an embodiment of the present invention. In accordance with the fifth PPDU ending time alignment mechanism, one WiFi MLD (e.g., AP102shown inFIG.1) sets parameters of links for enabling the links to have different capacity for PPDU transmission, sets a content that is carried by a first PPDU transmitted via one of the links to ensure that an ending time instant of transmission of the first PPDU transmitted via one of the links and an ending time instant of transmission of a second PPDU transmitted via another of the links are aligned, and transmits PPDUs (which include the first PPDU and the second PPDU) via the links. Parameters of each link may include BW, NSS, and MCS. In this embodiment, parameters of one of the links are different from parameters of another of the links, highest capacity supported by one of the links is higher than highest capacity supported by another of the links, and one PPDU is transmitted via each of the links. Each link may use its best parameters to generate and transmit PPDU. For example, one WiFi MLD (e.g., AP102) communicates with another WiFi MLD (e.g., non-AP STA104or non-AP STA106) via a first link (denoted by “Link 1”) and a second link (denoted by “Link 2”), where the first link supports BW=40 MHz (denoted by “BW40”), NSS=1, and best MCS=MCS3, and the second link supports BW=80 MHz (denoted by “BW80”), NSS=1, and best MCS=MCS7. Hence, the highest capacity supported by the second link is higher than the highest capacity supported by the first link. The first link is configured to use best parameters, including BW=40 MHz, NSS=1, and best MCS=MCS3, for PPDU transmission, and the second link is configured to use best parameters, including BW=80 MHz, NSS=1, and best MCS=MCS7, for PPDU transmission.

Since the capacity provided by the second link is higher than the capacity provided by the first link, different MPDUs can be allowed in the second link to align the PPDU lengths for achieving PPDU ending time alignment. The fifth PPDU ending time alignment mechanism may be applicable to the duplication transmission scenario with no PPDU starting time alignment. As shown inFIG.6, one PPDU602is transmitted via the first link, and one PPDU604is transmitted via the second link, where the WiFi MLD (e.g., AP102) transmits PPDUs602and604to the same user (e.g., non-AP STA104or non-AP STA106), and the PPDU604transmitted via the second link includes a partial PPDU606(which includes one or more media access control protocol data units (MPDUs)607), and one or more other MPDUs608that are not duplicate(s) of MPDU(s)607. The MPDU(s)608are appended to the partial PPDU606. As shown inFIG.6, an ending time instant of transmission of PPDU602and an ending time instant of transmission of PPDU604are aligned. The partial PPDU606may be a duplicate of the PPDU602. Hence, the MPDU(s)608carried in the second link are different from the MPDU(s) carried in the first link. In some embodiments of the present invention, the PPDU604may include optional padding bits (not shown) that are appended to the MPDU(s)608to make the PPDU length aligned.

FIG.7is a diagram illustrating a sixth PPDU ending time alignment mechanism according to an embodiment of the present invention. In accordance with the sixth PPDU ending time alignment mechanism, one WiFi MLD (e.g., AP102shown inFIG.1) sets parameters of links for enabling the links to have different capacity for PPDU transmission, sets a content that is carried by a first PPDU transmitted via one of the links to ensure that an ending time instant of transmission of the first PPDU transmitted via one of the links and an ending time instant of transmission of a second PPDU transmitted via another of the links are aligned, and transmits PPDUs (which include the first PPDU and the second PPDU) via the links. Parameters of each link may include BW, NSS, and MCS. In this embodiment, parameters of one of the links are different from parameters of another of the links, highest capacity supported by one of the links is higher than highest capacity supported by another of the links, and one PPDU is transmitted via each of the links. Each link may use its best parameters to generate and transmit the PPDU. For example, one WiFi MLD (e.g., AP102) communicates with another WiFi MLD (e.g., non-AP STA104) via multiple links including a first link (denoted by “Link 1”) and a second link (denoted by “Link 2”), and communicates with yet another WiFi MLD (e.g., non-AP STA106) via multiple links including the second link (denoted by “Link 2”), where the first link supports BW=40 MHz (denoted by “BW40”), NSS=1, and best MCS=MCS3, and the second link supports BW=80 MHz (denoted by “BW80”), NSS=1, and best MCS=MCS7. Hence, the highest capacity supported by the second link is higher than the highest capacity supported by the first link. The first link is configured to use best parameters, including BW=40 MHz, NSS=1, and best MCS=MCS3, for PPDU transmission, and the second link is configured to use best parameters, including BW=80 MHz, NSS=1, and best MCS=MCS7, for PPDU transmission.

Since the capacity provided by the second link is higher than the capacity provided by the first link, the second link can transmit a multi-user (MU) PPDU under a condition that the PPDU ending time alignment is met. The sixth PPDU ending time alignment mechanism may be applicable to all of the aforementioned scenarios. As shown inFIG.7, one PPDU702is transmitted via the first link, and one MU PPDU704is transmitted via the second link. The MU PPDU704accommodates data of different users (e.g., different WiFi MLDs) in a plurality of resource units (RUs), where each RU is a group of subcarriers (tones). For example, the MU PPDU704carries user data D_RU1 in a first RU of the MU PPDU704and user data D_RU2 in a second RU of the MU PPDU704, where the user data D_RU1 is transmitted to one user (e.g., non-AP STA104), and the user data D_RU2 is transmitted to another user (e.g., non-AP STA106). As shown inFIG.7, an ending time instant of transmission of PPDU702and an ending time instant of transmission of MU PPDU704are aligned. In some embodiments of the present invention, the PPDU702and the user data D_RU1 included in the MU PPDU704may be transmitted to the same user (e.g., non-AP STA104or non-AP STA106). In addition, padding in RUs for multiple users may be required. It should be noted that PPDU starting time alignment is not necessarily required by the sixth PPDU ending time alignment mechanism.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.