METHOD AND APPARATUS FOR TRANSMITTING TRAFFIC DIRECTED TO A MULTI-LINK GROUP

Abstract

This application applies to a multi-link group-directed traffic transmission method and a device. Group-directed traffic indication information sent by the first AP of an MLD AP indicates whether an AP within the MLD AP has group-directed traffic. The AP is either the first AP or another AP within the MLD AP, and the first STA of the MLD STA can learn whether the first AP or another AP has group-directed traffic. This improves the flexibility of AP group-directed traffic notification. The group-directed traffic indication information indicates whether each AP in multiple or all APs within the MLD AP has group-directed traffic, so the first STA can learn if multiple APs have group-directed traffic. In this way, each STA within the MLD STA does not need to monitor whether each AP has group-directed traffic. This reduces the power consumption of the MLD STA.This application can be applied to a wireless local area network system that supports a next-generation IEEE 802.11ax Wi-Fi EHT protocol, for example, 802.11 serial protocols such as 802.11be.

Description

METHOD AND APPARATUS FOR TRANSMITTING TRAFFIC DIRECTED TO A MULTI-LINK GROUP FIELD OF INVENTION This application relates to the field of communication technologies and, in particular, to a method and apparatus for transmitting traffic directed to a multi-link group. BACKGROUND OF THE INVENTION To significantly increase the service transmission speed of a wireless local area network (WLAN), the 802.11ax standard from the Institute of Electrical and Electronics Engineers (IEEE) adopts Orthogonal Frequency Division Multiplexing (OFDMA) technology, building upon existing Orthogonal Frequency Division Multiple Access (OFDM) technology. OFDMA supports multiple nodes sending and receiving data simultaneously, achieving multi-station diversity gains. Additionally, the Federal Communications Commission (FCC) released a new unlicensed frequency band from 5925 to 7125 MHz, which will be referred to as the 6 GHz band.Therefore, the operating range of an 802.11ax-compatible device expands from 2.4 GHz and 5 GHz to 2.4 GHz, 5 GHz, 6 GHz, and so on. Extremely high throughput (EHT) next-generation IEEE 802.11 Wi-Fi devices need to be forward-compatible. Therefore, these devices also support the operating spectrum of 802.11ax-compatible devices, specifically the 2.4 GHz, 5 GHz, and 6 GHz frequency bands. Extremely high throughput IEEE 802.11ax devices perform channel division based on the latest available 6 GHz frequency band. A supported bandwidth of, for example, 320 MHz, exceeds the maximum bandwidth of 160 MHz supported at 5 GHz. Peak throughput for an IEEE 802.11ax next-generation Wi-Fi device can be increased by using ultra-large bandwidth and by increasing the number of streams, for example, by increasing the number of streams to 16, by using multiple frequency bands (2.4 GHz, 5 GHz, and 6 GHz), and so on. Within a single frequency band, peak throughput can be further increased by using multiple channels or other methods. This reduces service transmission latency. In this specification, multiple frequency bands or multiple channels are collectively referred to as multiple links. The IEEE 802.11ax Wi-Fi protocol device, using the next-generation EHT protocol, employs multi-link cooperation technology to aggregate multiple consecutive links, creating an ultra-large bandwidth. In addition to increasing bandwidth, multi-link cooperation technology can also be used to simultaneously send data packets of the same traffic to the same station. It can be observed that multi-link cooperation technology greatly improves transmission speed. However, for downlink group traffic transmission, because each station in a station multi-link device needs to periodically remain in an operational state to monitor whether each access point in a multi-link access point device is sending downlink group traffic, more power is consumed. BRIEF DESCRIPTION OF THE INVENTION This application provides a method for transmitting traffic directed to a multilink group and an apparatus, to help reduce the power consumption of a station multilink device. According to the first aspect, this application provides a method for transmitting multi-link group-directed traffic. In this method, the first access point (AP) of a multi-link access point device (MLD) generates group-directed traffic indication information, where the group-directed traffic indication information indicates whether one or more APs of the MLD have group-directed traffic. The first AP then sends the group-directed traffic indication information. In one implementation, the group-directed traffic indication information shows whether an AP in the AP MLD has group-directed traffic, and whether that AP is the first AP or another AP in the AP MLD. Compared to a method where a station managed by the first AP can only learn if the first AP has group-directed traffic, this implementation improves the flexibility of group-directed traffic notification. In another implementation, group-directed traffic indication information shows whether each AP in the multiple APs of the MLD has group-directed traffic. Compared to a system where a station managed by the first AP can only learn if the first AP has group-directed traffic, in this implementation, each STA in an MLD does not need to periodically monitor whether a corresponding AP has group-directed traffic. In other words, in this implementation, a station in the MLD can learn whether multiple APs have group-directed traffic. This reduces the power consumption of the MLD. In yet another implementation, the group-directed traffic indication information shows whether each AP in the MLD has group-directed traffic. In contrast to a system where a station managed by the first AP can only learn if the first AP has group-directed traffic, in this implementation, each STA in the MLD does not need to periodically check if a corresponding AP has group-directed traffic. In other words, in this implementation, a station in the MLD can learn whether each AP has group-directed traffic. This reduces the MLD's power consumption. In one implementation, each bit of the Group-Directed Traffic Indication Information corresponds to each AP in the one or more APs of the AP MLD. Each bit indicates whether the AP corresponding to the bit has group-directed traffic, or a value of the bit indicates whether the AP corresponding to the bit has group-directed traffic. In one implementation, each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD. Each bit indicates whether the AP corresponding to the bit has group-directed traffic, or a bit value indicates whether the AP corresponding to the bit has group-directed traffic. In one implementation, a mapping between each bit of the group-directed traffic indication information and each AP of the AP MLD, or a mapping between each bit of the group-directed traffic indication information and each AP in the one or more APs of the AP MLD, can be configured by using an association response frame or a management frame between the STA MLD and the AP MLD. In another implementation, a mapping is predefined between each bit of the group-directed traffic indication information and each AP in the AP MLD, or a mapping between each bit of the group-directed traffic indication information and each AP in the one or more APs of the AP MLD. In yet another implementation, the group-directed traffic indication information is a bit portion in a partial virtual bitmap field in a TIM traffic indication map element. In one implementation, group-directed traffic indication information is a portion of consecutive bits in the partial virtual bitmap field. For example, if the group-directed traffic indication information is bits 1 through 7 in the partial virtual bitmap field, bits 1 through 7 in the partial virtual bitmap field can indicate whether each AP in the AP MLD has group-directed traffic. In another implementation, group-directed traffic indication information is a portion of non-consecutive bits in the partial virtual bitmap field. For example, if the group-directed traffic indication information is bits 1, 2, and 4 in the partial virtual bitmap field, bits 1, 2, and 4 can indicate whether each AP in the AP MLD has group-directed traffic. In one implementation, the first AP in the AP MLD generates Association Identifier configuration information, where the Association Identifier configuration information indicates a corresponding Association Identifier for each AP in the AP MLD. The first AP sends the Association Identifier configuration information. The Association Identifier configuration information for each AP corresponds to each bit of the Group-Directed Traffic Indication information. That is, each bit of the Group-Directed Traffic Indication information indicates whether the AP with the corresponding AID is carrying group-directed traffic. The Association Identifier configuration information can be sent to the STA MLD in an Association Response frame or a Management frame. In another implementation, an AID corresponding to a first bit or a start bit in the consecutive bits portion of the group-directed traffic indication information is predefined. In other words, the first bit or the start bit of the consecutive bits portion is predefined. Alternatively, a start bit location for the group-directed traffic indication information is predefined in the partial virtual bitmap field of the TIM element. Alternatively, the AIDs of the APs in the AP MLD are assigned consecutively starting from AID x, where AID x is predefined. In this implementation, the group-directed traffic indication information is the consecutive bits portion in the partial virtual bitmap field of the TIM traffic indication map element. The association identifier assigned to each AP in the AP MLD is different from the association identifier assigned to a station associated with that AP. In other words, the association identifier assigned to each AP in the AP MLD cannot be assigned by the AP to a station it manages. However, the association identifiers assigned by different APs to stations they manage are relatively independent. In other words, the association identifiers assigned by different APs to stations they manage can be the same. Furthermore, if one or more APs in the AP MLD are APs that operate in a multi-BSSID mode and are broadcast AP BSSIDs, in the two previous implementations, the AP AIDs of the APs in the AP MLD are assigned consecutively starting from AID x, where x is equal to max{2A(Ni), 2λ(N2), ..., 2A(Ny), ..., 2A(Nn)}. n is a number of broadcast AP BSSIDs in the AP MLD and Ny is a value of a max BSSID indicator field in a multi BSSID (multiple BSSID) broadcast by a yth AP that is a broadcast AP BSSID from the AP MLD. Alternatively, the AP AIDs of the AP MLD are assigned consecutively starting from AID x, where x equals max{2A(Ni), 2A(N2), ..., 2A(Ny), ..., 2L(NΠ)}. n is the number of APs in the AP MLD, and Ny is the value of a max BSSID indicator field in a multi-BSSID broadcast by the yth AP MLD. A max BSSID indicator field value for a default non-broadcast AP or an AP that does not operate in multi-BSSID mode is 0. In other words, the start bit, or the first bit of the consecutive bits in the partial virtual bitmap field corresponding to group-directed traffic indication information, is bit x, where x equals max{2A(Ni), 2Λ(N2), 2A(Ny), 2A(Nn)}. Alternatively, an AID corresponding to the start bit, or the first bit of the consecutive bits in the partial virtual bitmap field corresponding to group-directed traffic indication information, is AID x, where x equals max{2A(Ni), 2A(N2), 2A(Ny), ..., 2A(Nn)}. For the physical meanings of ny, see the preceding description. No further details are described herein. Furthermore, the group-directed traffic indication information corresponds to the portion of bits in the partial virtual bitmap field of the TIM element. Therefore, the first AP determines an offset field and a length field in the TIM element based on a start byte Ni and an end byte N2 in a virtual bitmap field of the group-directed traffic indication information. The first AP can then send the offset and length fields. This helps a station associated with the first AP and located in the STA MLD to determine, based on the group-directed traffic indication information, the offset field, and the length field, whether the AP corresponding to each bit of the group-directed traffic indication information has group-directed traffic. Optionally, in this version of the application, the group-directed traffic indication information can be compressed using an offset. In one implementation, it is assumed that the AP corresponding to each bit of the group-directed traffic indication information is assigned sequentially based on the size of a link identifier on which each AP in the AP MLD operates, and none of the multiple APs with consecutive link identifiers carry group-directed traffic. In this case, the group-directed traffic indication information can include only bits corresponding to APs other than the multiple APs; that is, the group-directed traffic indication information sent by the first AP can include the bits corresponding to APs other than the multiple APs. For ease of description, the group-directed traffic indication information generated by the first AP is known as the first group-directed traffic indication information, and the group-directed traffic indication information sent by the first AP is known as the second group-directed traffic indication information. The second group-directed traffic indication information may be the same as the first group-directed traffic indication information, or the second group-directed traffic indication information may be a bit portion of the first group-directed traffic indication information. An offset of the second group-directed traffic indication information relative to the first group-directed traffic indication information is referred to simply as the second group-directed traffic indication information offset. It is assumed that none of the APs corresponding to bits before byte Ni and all bits after byte N2 of the first group-directed traffic indication information have group-directed traffic, where Ni is greater than or equal to 0, and N2 is greater than or equal to 1. In this case, the second group-directed traffic indication information consists of all bits starting from byte Ni of the first group-directed traffic indication information and ending in byte N2. In this case, the length of the second group-directed traffic indication information sent by the first AP is N2-N1+I, and the offset of the second group-directed traffic indication information is N1 / 2. Furthermore, the station managed by the first AP in the STA MLD receives the length and offset, and can determine whether the second group-directed traffic indication information received indicates whether the APs corresponding to bits NΓ8 to bits ((N2+1)*8-1) have group-directed traffic, determine whether the APs corresponding to all bits from bit 0 to bit NΓ8-1 do not have group-directed traffic, and determine whether the APs corresponding to bit (N2+IΓ8 and all subsequent bits) do not have group-directed traffic. The bit 'a' described in this request is an th bit. For example, bit 0 is a 0 bit. It is assumed that none of the APs corresponding to bits N0*8-1 through N / 8-1 of the first group-directed traffic indication information have group-directed traffic, and none of the APs corresponding to bits N2*8 and a subsequent bit have group-directed traffic. In this case, the second group-directed traffic indication information consists of bits starting from byte 0 of the first group-directed traffic indication information and ending with byte N0-1, and bits starting from byte Ni of the first group-directed traffic indication information and ending with byte N2. In this case, the length of the second group-directed traffic indication information sent by the first AP is NO+N2-N1+I, and the offset of the second group-directed traffic indication information is Ni-NO.In addition, the station managed by the first AP in the STA MLD receives the length and offset, and can determine that the second group-directed traffic indication information received indicates bits 0 to bits (N0-1)*8-1, determine if the APs corresponding to bit (Ni-1)*8+1 to bit N2*8+1 have group-directed traffic, and determine that none of the APs corresponding to bit (N0-1)*8 to bit (Ni-1)*8 have group-directed traffic. In another implementation, when none of multiple APs with consecutive association IDs has group-directed traffic, the partial virtual bitmap field may not carry bits corresponding to these association IDs. That is, a number of bits of the group-directed traffic indication information in the partial virtual bitmap field are reduced by using an offset in the TIM element. The group-directed traffic indication information is assumed to be the partial virtual bitmap field in the TIM element. If none of the AID APs corresponding to a bit before byte Ni and all bits after byte N2 in the traffic indication virtual bitmap field have group-directed traffic, where Ni is greater than or equal to 0, and N2 is greater than or equal to 1, the group-directed traffic indication information consists of all bits starting from byte Ni in the traffic indication virtual bitmap field and ending with byte N2. In this case, the length of the TIM element sent by the first AP is N2-Ni+1+3, and the offset of the TIM element is (1 / 2)Ni.Furthermore, the station managed by the first AP in the STA MLD determines, based on the received length and offset, that the group-directed traffic indication information indicates whether APs with AIDs corresponding to bits NJ8 to ((N2+1)*8-1)) have group-directed traffic, determines that APs with AIDs corresponding to all bits from bit 0 to bit NG8-1 do not have group-directed traffic, and determines that APs with AIDs corresponding to bits (N2+1)*8 and all subsequent bits do not have group-directed traffic. If none of the APs in the AIDs corresponding to all bits from byte NO to byte Ni-1 of the traffic indication virtual bitmap field have group-directed traffic, the group-directed traffic indication information consists of bits starting from byte 0 of the traffic indication virtual bitmap field and ending in byte N0-1, and bits starting from byte Ni of the traffic indication virtual bitmap field and ending in byte N2. In this case, the length of the TIM element sent by the first AP is N0+N2-Ni+1+3, and the offset of the TIM element is (N1-NO) 1 / 2.Furthermore, the station managed by the first AP in the STA MLD can determine, based on the length field and the offset of the received TIM element, that the received group-directed traffic indication information indicates bit 0 to bit (N0-1)*8-1, determine if the AID APs corresponding to bit (Ni-1)*8+1 to bit N2*8+1 have group-directed traffic, and determine that the AID APs corresponding to bits (N0-1)*8 to bits (Ni-1)*8 do not have group-directed traffic. Optionally, the group-directed traffic indication information sent by the first AP is carried in a Delivery Traffic Indication Map (DTIM) beacon frame. Additionally, the first AP forwards the group-directed traffic after sending the DTIM beacon frame. Optionally, for a beacon frame, the group-directed traffic indication information can be carried only in the DTIM beacon frame. Optionally, the group-directed traffic indication information can also be carried in another frame, such as a frame MA / a / 2U22 / U1 04 1J of TIM beacon, a management frame, a data frame or a control frame. Optionally, if the group-directed traffic indication information is carried in the TIM beacon frame, management frame, data frame, or control frame, and if the first AP has an AP that provides group-directed traffic, the first AP can also send the DTIM delivery traffic indication map beacon frame and group-directed traffic after the DTIM beacon frame. According to a second aspect, this application also provides a method for transmitting multi-link group-directed traffic. The method is described from the perspective of a multi-link STA MLD device. In this method, a first STA station of the STA MLD receives group-directed traffic indication information from an AP MLD, where the group-directed traffic indication information indicates whether one or more APs of the AP MLD are carrying group-directed traffic. Optionally, the first STA can determine or learn, based on group-directed traffic indication information, whether one or more APs have group-directed traffic. In one implementation, the group-directed traffic indication information shows whether an AP in the AP MLD has group-directed traffic, and whether that AP is the first AP or another AP in the AP MLD. In this implementation, the first STA can learn whether the first AP or another AP in the AP MLD has group-directed traffic. This improves the flexibility of group-directed traffic notification. In another implementation, the group-directed traffic indication information shows whether each AP in the multiple APs of the AP MLD has group-directed traffic. In this implementation, the first STA can learn if multiple APs have group-directed traffic, so each STA in the STA MLD doesn't need to periodically listen for group-directed traffic from a corresponding AP. This reduces the power consumption of the STA MLD. In yet another implementation, the group-directed traffic indication information shows whether each AP in the AP MLD has group-directed traffic. In this implementation, the first STA can learn whether each AP in the AP MLD has group-directed traffic, so each STA in the STA MLD doesn't need to periodically listen for group-directed traffic from a corresponding AP. This reduces the power consumption of the STA MLD. In one implementation, the first STA of the STA MLD is a station that operates on a primary link, and that a first STA of the STA MLD receives group-directed traffic indication information from an AP MLD includes: The first STA of the STA MLD listens, on the primary link, for group-directed traffic indication information from an AP of the AP MLD. Optionally, for a beacon frame, group-directed traffic indication information can be carried only in the DTIM beacon frame. Optionally, group-directed traffic indication information can be carried in another frame such as a TIM beacon frame, a management frame, a data frame, or a control frame. Optionally, group-directed traffic indication information is carried in another frame, such as a TIM beacon frame, a management frame, a data frame, or a control frame. The first STA can receive the DTIM beacon frame and then receive the group-directed traffic after receiving the DTIM beacon frame. Consequently, if another STA in the STA MLD learns, based on the group-directed traffic indication information, that a corresponding AP also has group-directed traffic, the other STA can receive the DTIM beacon frame and then receive the group-directed traffic after receiving the DTIM beacon frame. Optionally, group-directed traffic is carried in a DTIM beacon frame, and the first STA can receive group-directed traffic after receiving the DTIM beacon frame. Consequently, if another STA in the STA MLD learns, based on group-directed traffic indication information, that a corresponding AP also has group-directed traffic, the other STA can receive the DTIM beacon frame and receive the group-directed traffic after receiving the DTIM beacon frame. In another implementation, if it is determined that an AP on the link on which the first STA operates has group-directed traffic, the first STA can receive, on the link, a DTIM Delivery Traffic Indication Map beacon frame from the AP and group-directed traffic after receiving the DTIM beacon frame. In one implementation, each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD. A bit's value indicates whether the corresponding AP has group-directed traffic. For a related description of this implementation, see the related content in the first aspect. Details are not described again here. In another implementation, group-directed traffic indication information is a bit portion in a partial virtual bitmap field within a TIM traffic indication map element. For a related description of this implementation, see the related content in the first aspect. Details are not described again here. In yet another implementation, group-directed traffic indication information is a portion of consecutive bits in a partial virtual bitmap field within a TIM traffic indication map element. For a related description of this implementation, see the related content in the first aspect. Details are not described again herein. Because the AIDs corresponding to some bits in the partial virtual bitmap field are assigned to a station, and these bits separately indicate whether a corresponding station has unicast traffic, in this implementation, an association identifier assigned to each AP of the AP MLD is different from an association identifier assigned to a station associated with each AP. In other words, the association identifier assigned to each AP of the AP MLD cannot be assigned by the AP to a station managed by the AP. However, the AIDs assigned by different APs to stations managed by the APs are relatively independent. In other words, the AIDs assigned by different APs to stations managed by the APs can be the same. In one implementation, the first STA of the MLD STA receives Association Identifier configuration information, where the Association Identifier configuration information indicates an Association Identifier (AID) corresponding to each AP of the MLD AP. The AP's AID corresponds to each bit of the Group-Directed Traffic Indication information. Based on the Association Identifier configuration information, the first STA determines the AID corresponding to the AP of the MLD AP. For a related description of this implementation, see the related content in the first aspect. Details are not described again here. In another implementation, an AID is predefined corresponding to the first bit of the consecutive bits in the partial virtual bitmap field that correspond to the group-directed traffic indication information. For a related description of this implementation, see the related content in the first aspect. Details are not described again here. In yet another implementation, an AID corresponding to the first bit of the consecutive bit portion is AID x, where x equals max{2A(Ni), 2L(N2),..., 2A(Ny),..., 2L(Nη)}. n is the number of Basic Service Set Identifier APs transmitted on the MLD AP, and N is the value of a maximum Basic Service Set Identifier BSSID indicator field in a multiple Basic Service Set Identifier BSSID broadcast by a transmitted APy BSSID. The transmitted APy BSSID is the th AP BSSID transmitted on the MLD AP. For a related description of this implementation, see the related content in the first aspect. No further details are described herein. Optionally, in this version of the application, the group-directed traffic indication information can be compressed using an offset. In one implementation, it is assumed that the AP corresponding to each bit of the group-directed traffic indication information is assigned sequentially based on the size of a link identifier on which each AP in the AP MLD operates, and none of the multiple APs with consecutive link identifiers carry group-directed traffic. In this case, the group-directed traffic indication information can include only bits corresponding to APs other than the multiple APs; that is, the group-directed traffic indication information sent by the first AP can include the bits corresponding to APs other than the multiple APs. For a related description of this implementation, see the related content in the first aspect.No further details are described herein. According to a third aspect, this application provides an access point for a multi-link access point device. The multi-link access point device has some or all of the functions of the first AP, which is the MLD AP and is implemented in the method example in the first aspect. For example, the multi-link access point device may have functions in some or all of the modes of this application, or it may have a function implemented independently of any mode of this application. The function may be implemented by hardware, or it may be implemented by hardware running the corresponding software. The hardware or software includes one or more units or modules corresponding to the functions. In one implementation, a multi-link access point architecture may include a processing unit and a communication unit. The processing unit is configured to support the multi-link access point in performing a corresponding function as described in the previous method. The communication unit is configured to support communication between the multi-link access point and another device. The multi-link access point may also include a storage unit. The storage unit may be coupled to the processing unit and a transmitting unit, and it stores a computer program and data required by the multi-link access point. In one implementation, the access point multi-link device includes: the processing unit, configured to generate group-directed traffic indication information, where the group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic; and the communication unit, configured to send the group-directed traffic indication information. It can be learned that, at the access point of a multi-link access device (MLD), the group-directed traffic indication information generated by the processing unit can indicate whether the access point or another AP has group-directed traffic. The communication unit then sends this group-directed traffic indication information to a station multi-link device. In this way, any station on the station multi-link device can listen to the group-directed traffic indication information. This improves the flexibility of group-directed traffic notification. Furthermore, if the group-directed traffic indication information shows whether each AP or multiple APs on the MLD have group-directed traffic, any station on the station multi-link device can learn whether the multiple APs have group-directed traffic.Therefore, not all stations on the station multilink device need to listen for group-directed traffic on a given link. This reduces the power consumption of the station multilink device. In one example, the processing unit could be a processor, the communication unit could be a transceiver or a communication interface, and the storage unit could be memory. In another implementation, the access point multi-link device includes: the processor, configured to generate group-directed traffic indication information, where the group-directed traffic indication information indicates whether one or more APs of an AP MLD have group-directed traffic; and the transceiver, configured to send the group-directed traffic indication information. It can be learned that, at the access point of a multi-link access device (MLD), the group-directed traffic indication information generated by the processor can indicate whether the access point or another AP has group-directed traffic. The transceiver then sends this group-directed traffic indication information to a station multi-link device. In this way, any station on the station multi-link device can listen to the group-directed traffic indication information. This improves the flexibility of group-directed traffic notification. Furthermore, if the group-directed traffic indication information shows whether each AP or multiple APs on the MLD have group-directed traffic, any station on the station multi-link device can learn whether the multiple APs have group-directed traffic.Therefore, not all stations on the station multilink device need to listen for group-directed traffic on a given link. This reduces the power consumption of the station multilink device. Optionally, the access point of the multi-link access point device may also implement one or more of the first aspect. Details are not described again herein. According to a fourth aspect, this request further provides a station of a station multilink device. The station of the station multilink device has some or all of the functions of the first STA, which is of the STA MLD and implements the method example in the second aspect. For example, the station of the station multilink device may have functions in some or all of the modes of this request, or it may have a function that is independent of any mode of this request. The function may be implemented by hardware, or it may be implemented by hardware running the corresponding software. The hardware or software includes one or more units or modules corresponding to the functions. In one implementation, a station multilink device structure may include a processing unit and a communication unit. The processing unit is configured to support the station multilink device in performing a corresponding function as described above. The communication unit is configured to support communication between the station multilink device and another device. The station multilink device may also include a storage unit. The storage unit may be coupled to the processing unit and a transmitting unit, and it stores a computer program and data required by the station multilink device. In one implementation, the station multilink device station includes: the communication unit, configured to receive group-directed traffic indication information from an MLD AP, where the group-directed traffic indication information indicates whether one or more of the MLD APs have group-directed traffic. Optionally, the station of the multi-link device also includes the processing unit. The processing unit is configured to determine, based on group-directed traffic indication information, whether one or more APs have group-directed traffic. It can be learned that, at the station multilink device station, the processing unit can learn, based on group-directed traffic indication information, whether one or more access points (APs) are carrying group-directed traffic. Specifically, the station multilink device station can learn not only if an AP associated with the station is carrying group-directed traffic, but also if another AP in the AP MLD is carrying group-directed traffic. This enhances the flexibility of group-directed traffic notification. Furthermore, the group-directed traffic indication information shows whether multiple APs, or each AP in the AP MLD, are carrying group-directed traffic. In other words, any station multilink device station can learn whether multiple APs, or each AP in the AP MLD, are carrying group-directed traffic.Therefore, not all STAs in the STA MLD need to listen for group-directed traffic from a corresponding AP. This reduces resource consumption. IVIA / a / ZUZZ / UI 04 1 J STA MLD energy. In one example, the processing unit could be a processor, the communication unit could be a transceiver or a communication interface, and the storage unit could be memory. In another implementation, the station multilink device station includes: the transceiver, configured to receive group-directed traffic indication information from an MLD AP, where the group-directed traffic indication information indicates whether one or more of the MLD APs have group-directed traffic. Optionally, the station's multi-link device also includes a processor. The processor is configured to determine, based on group-directed traffic indication information, whether one or more APs have group-directed traffic. It can be learned that, at the station multilink device (STA), the processor can learn, based on group-directed traffic indication information, whether one or more access points (APs) are carrying group-directed traffic. Specifically, the station multilink device can learn not only if an AP associated with the station is carrying group-directed traffic, but also if another AP within the AP MLD is carrying group-directed traffic. This enhances the flexibility of group-directed traffic notification. Furthermore, the group-directed traffic indication information shows whether multiple APs, or each AP within the AP MLD, are carrying group-directed traffic. In other words, any STA within the AP MLD can learn whether multiple APs, or each AP within the AP MLD, are carrying group-directed traffic. Therefore, not all STAs within the AP MLD need to monitor whether a corresponding AP is carrying group-directed traffic.This reduces the energy consumption of the STA MLD. Optionally, the station multilink device can also implement one or more of the second aspect. Details are not described again herein. According to a fifth aspect, one embodiment of the present invention provides a computer-readable storage medium configured to store a computer program. When the computer program is executed on a communication apparatus, the communication apparatus performs the multilink group-directed traffic transmission method according to the first aspect. According to a sixth aspect, one embodiment of the present invention provides a computer-readable storage medium configured to store a computer program. When the computer program is executed on a communication apparatus, the communication apparatus performs the multilink group-directed traffic transmission method according to the second aspect. According to a seventh aspect, this application further provides a computer program product that includes a computer program. When the computer program product is executed on a communication apparatus, the communication apparatus is activated to perform the multilink group-directed traffic transmission method according to the first aspect. According to an eighth aspect, this application further provides a computer program product that includes a computer program. When the computer program product is executed on a communication apparatus, the communication apparatus is activated to perform the multilink group-directed traffic transmission method according to the second aspect. According to a ninth aspect, this application provides a system-on-a-chip. The system-on-a-chip includes at least one processor and an interface, configured to support any AP of an AP MLD, for example, a first AP, to implement a function in the first aspect, for example, a function to determine or process at least one of the data and information in the preceding method. In a possible design, the system-on-a-chip further includes memory, and the memory is configured to store a computer program and data that are required for an AP of the AP MLD. The system-on-a-chip may include a single chip, or it may include a chip and another discrete component. According to a tenth aspect, this application provides a system-on-a-chip. The system-on-a-chip includes at least one processor and an interface, configured to support any STA of a STA MLD, for example, a first STA, to implement a function in the second aspect, for example, a function to determine or process at least one of the data and information in the preceding method. In a possible design, the system-on-a-chip further includes memory, and the memory is configured to store a computer program and data that are required for an STA of the STA MLD. The system-on-a-chip may include a single chip, or it may include a chip and another discrete component. BRIEF DESCRIPTION OF THE FIGURES FIGURE 1 is a schematic diagram of structures of an AP MLD and a STA MLD according to one modality of this application; FIGURE 2 is a schematic diagram of a TIM element frame format according to a modality of this application; FIGURE 3(a) is a schematic diagram of a communication system structure 100 according to one modality of this application; FIGURE 3(b) is a schematic diagram of a communication system structure 200 according to one modality of this application; IVIA / a / ZUZZ / UI 041 J communication 300 in accordance with a modality of this request; and FIGURE 14 is a schematic diagram of a chip structure according to one modality of this application. DETAILED DESCRIPTION OF THE INVENTION The following clearly and completely describes the technical solutions in the modalities of this application with reference to the attached figures in the modalities of this application. To better understand a multilink group-directed traffic transmission method and related apparatus disclosed in modalities of this application, related concepts are first described in modalities of this application. 1. Multi-link device A wireless communication system applicable to the modalities of this application can be a wireless local area network (WLAN) or a cellular network. A group-directed traffic transmission method can be implemented using a communication device within the wireless communication system or a chip or processor within the communication device. The communication device can be a wireless communication device that supports concurrent transmission over multiple links. For example, the communication device is known as a multi-link device or a multi-band device. Compared to a device that supports only single-link transmission, the multi-link device has higher transmission efficiency and throughput. The multilink device includes one or more affiliated STAs. An affiliated STA is a logical station and can operate on a link. The affiliated station can be an access point (AP) or a non-access point (non-AP) STA. For ease of description, in this application, a multilink device whose affiliated station is an AP may be referred to as a multilink AP, a multilink AP device, or an AP multi-link device (AP MLD). A multilink device whose affiliated station is a non-AP STA may be referred to as a multilink STA, a multilink STA device, or a STA multi-link device (STA MLD). For ease of description, the multilink device that includes an affiliated STA is also briefly described as the multilink device that includes an STA in the modalities of this application. It should be noted that the multi-link device includes multiple logical stations, and each logical station operates on one link, but multiple logical stations are allowed to operate on the same link. The multi-link device can implement wireless communication according to 802.11 serial protocols. For example, a station that meets Extremely High Performance (EHT) standards, or a station that complies with or supports 802.11be, communicates with another device. This other device may or may not be a multi-link device. For example, the multilink device in this application modality can be a single-antenna device or a multi-antenna device. For example, the multilink device can have more than two antennas. The number of antennas included in the multilink device is not limited in the application modality. In the application modality, the multilink device can allow traffic of the same access type to be transmitted over different links, or even allow the same data packets to be transmitted over different links. Alternatively, the multilink device may not allow traffic of the same access type to be transmitted over different links, but may allow traffic of different access types to be transmitted over different links. For example, a multi-link device is an appliance with a wireless communication function, and the appliance can be a device itself, or it can be a chip, a processing system, or something similar installed within the device. The device in which the chip or processing system is installed can implement methods and functions in the modes described in this application under the control of the chip or processing system. For example, a multi-link device (MLD) in the modes described in this application has a wireless transceiver function, can support the 802.11 serial protocols, and can communicate with an MLD access point (AP), another MLD, or a single-link device. For example, an MLD is any user communication device that allows a user to communicate with an access point (AP) and also with a wireless network (WLAN).For example, the STA MLD can be a user device that can connect to a network, such as a tablet computer, desktop computer, laptop computer, notebook computer, ultra-mobile personal computer (UMPC), notebook computer, netbook, personal digital assistant (PDA), or mobile phone; it can be an Internet of Things node in an Internet of Things; or it can be a vehicle-mounted communication device in an Internet of Vehicles. Alternatively, the STA MLD can be a chip and processing system in the aforementioned terminals. The AP MLD in the modalities of this application is a device that serves the STA MLD and can support the 802.11 serial protocols. For example, the AP MLD can be a communication entity such as a communication server, router, switch, or bridge, or it can include various forms of macro base stations, micro base stations, and relay stations. The AP MLD can also be a chip and processing system in various device forms, implementing the method and function described in this application. Furthermore, the multi-link device can support high-speed, low-latency transmission. With the continuous evolution of wireless local area network application scenarios, the multi-link device can be applied to even more scenarios, for example, serving as a sensor node (e.g., a smart water meter).A smart electricity meter or a smart air sensing node in a smart city; a smart device (e.g., a smart camera, projector, display screen, television, stereo, refrigerator, or washing machine) in a smart home; an Internet of Things node; an entertainment terminal (e.g., AR, VR, or other interactive device); a smart device (e.g., a printer or projector) in a smart office; an Internet of Vehicles device; or infrastructure (e.g., a vending machine, self-service navigation console, self-checkout device, or self-service food machine) in everyday life scenarios. The specific forms of STA MLD and AP MLD are not specifically limited in the modalities of this application.These are merely examples for the purposes of this description. The 802.11 protocol can be a protocol that supports 802.11be or is compatible with 802.11be. The frequency bands in which the multi-link device operates may include, but are not limited to, sub-1 GHz, 2.4 GHz, 5 GHz, 6 GHz and a high frequency of 60 GHz. For example, the multilink device in the modes of this application can be a single-antenna device or a multi-antenna device. For instance, the multilink device in the modes of this application can have more than two antennas. The number of antennas included in the multilink device is not limited in this mode of this application. Figure 1 is a schematic diagram of a structure in which an AP MLD has multiple antennas and a STA MLD has a single antenna. An 802.11 standard focuses on the Physical Layer (PHY) and Media Access Control (MAC) layers in the AP MLD and the STA MLD. 2. Link identifier A link identifier represents a station operating on a link. In other words, if there is more than one station on a link, more than one link identifier is required to represent the more than one station. A link mentioned later sometimes also represents a station operating on that link. During data transmission, an AP MLD and a STA MLD can use a link identifier to identify a link or a station on a link. Before communication, the AP MLD and STA MLD may first negotiate or communicate with each other to establish a mapping between a link identifier and a link or station on a link. Therefore, during data transmission, the link identifier is carried without transmitting a large amount of signaling information to indicate a link or a station on a link. This reduces signaling overhead and improves transmission efficiency. In one example, a management frame sent by the AP MLD when establishing a basic service set (BSS), such as a beacon frame, carries an element. This element includes multi-link identifier information fields. The link identifier information field can indicate a mapping between a link identifier and a station operating on a link corresponding to that link identifier. The link identifier information field not only includes the link identifier but also one or more pieces of the following information: a Media Access Control (MAC) address, an operational class, and a channel number. One or more of the MAC address, operational class, and channel number can indicate a link. For an AP, an AP's MAC address is its BSSID (Basic Service Set Identifier).In another example, during a multi-link device association process, the AP MLD and the multi-link STA negotiate multi-link identifier information fields. Multi-link device association means that one AP of the AP MLD is associated with one STA of the STA MLD once. This association can allow multiple STAs of the STA MLD to associate with multiple APs of the AP MLD, where one STA is associated with one AP. In subsequent communication, the AP MLD or the STA multilink device identifies or represents a station on the STA multilink device by using a Link Identifier. The Link Identifier can also represent one or more attributes of a station's MAC address, operational class, and channel number. The MAC address can be replaced with an association identifier of the associated AP MLD. Optionally, if multiple stations operate on a link, the meanings represented by a Link Identifier (which is a numeric ID) include not only the operational class of the link and a channel number, but also an identifier of a station operating on the link, such as a station's MAC address or association identifier (AID). 3. Traffic indication map element A traffic indication map (TIM) beacon frame and a delivered traffic indication map (DTIM) beacon frame each carry a traffic indication map (TIM) element. A frame format of a TIM element field is shown in FIGURE 2. Element identifier field (identifier, ID): The element identifier field is used to identify that the element shown in FIGURE 2 is a TIM element. Length field: The length field indicates a TIM element length and counts a total length of fields after the length field; to be specific, it counts, in bytes, a total length of a DTIM count field, a DTIM period field, a bitmap control field, and a partial virtual bitmap field. DTIM Count Field: The DTIM count field indicates the number of TIM beacon frames remaining between the current beacon frame carrying the TIM element and the arrival of the next DTIM beacon frame. In other words, the DTIM count field is a count value, and the count value is variable. When the DTIM count field value is 0, it indicates that the current beacon frame is a DTIM beacon frame. When the DTIM count field value is not 0, it indicates that the current beacon frame is a TIM beacon frame. DTIM Period Field: The DTIM period field indicates the period length of a DTIM beacon frame, i.e., an arrival interval. The arrival interval uses a TIM beacon frame period as its unit. For example, if a DTIM period is set to 1, a DTIM count in each TIM element field is equal to 0; in other words, each beacon frame is a DTIM beacon frame. Bitmap Control Field: As shown in Figure 2, bit 0 in the bitmap control field indicates whether an access point (AP) forwards group-directed data traffic after sending a DTIM beacon frame. In other words, bit 0 in the bitmap control field in the DTIM beacon frame indicates whether the AP buffers group-directed traffic and indicates that group-directed traffic is not forwarded when using a group-directed AID. Bits 1 through 7 in the bitmap control field indicate a partial virtual bitmap offset; the offset is one byte (i.e., 8 bits). Partial virtual bitmap: Each bit in the partial virtual bitmap field corresponds to an association identifier (AID), indicating whether a station corresponding to the AID has unicast traffic. Alternatively, each bit in the partial virtual bitmap field corresponds to a group-directed AID, indicating whether a group of stations corresponding to the group-directed AID has downlink traffic. The partial virtual bitmap field is a bit portion of a traffic indication virtual bitmap field, where the traffic indication virtual bitmap field is 251 bytes in size, and indicates whether stations corresponding to AID 0 through AID 2007 have downlink traffic. The Item ID field, Length field, DTIM Count field, DTIM Period field, and Bitmap Control field each occupy 1 byte. Although the methods for this request are mainly described when using a network IVIA / a / ZUZZ / UI 04 1 J, which implements IEEE 802.11 as an example, a person skilled in the art readily understands that several aspects of this application can be extended to other networks using various standards or protocols, such as Bluetooth, a high-performance radio LAN (HIPERLAN) (a wireless standard similar to IEEE 802.11 and primarily used in Europe), a wide area network (WAN), a wireless local area network (WLAN), a personal area network (PAN), or any other known or subsequently developed network. Therefore, the various aspects provided in this application are applicable to any suitable wireless network, regardless of coverage or wireless access protocol. A wireless local area network in FIGURE 3(a) is used as an example to describe a communication system 100 to which one modality of this application applies. The communication system 100 includes a station 101 and a station 102. Station 101 can communicate with station 102 over multiple links to improve performance. Station 101 can be a multi-link device, and station 102 can be a single-link device, a multi-link device, or similar. In one scenario, station 101 is an MLD AP, and station 102 is an MLD STA or a station (e.g., a single-link station). In another scenario, station 101 is an MLD STA, and station 102 is an AP (e.g., a single-link AP) or an MLD AP. In yet another scenario, station 101 is an MLD AP, and station 102 is either an MLD AP or an AP.In yet another scenario, station 101 is an MLD STA and station 102 is either an MLD STA or an STA (for example, a single-link station). Certainly, the wireless local area network may also include other devices. The number and type of devices shown in Figure 3(a) are merely examples. FIGURE 3(b) and FIGURE 3(c) show schematic diagrams of the structures of a communication system 200 and a communication system 300. In communication system 200 and communication system 300, an example is used in which a multi-link device in a wireless local area network communicates with another device through multiple links. Figure 3(b) is a scenario in which an AP MLD communicates with an STA MLD. The AP MLD includes an affiliate AP 1 and an affiliate AP 2. The STA MLD includes an affiliate STA 1 and an affiliate STA 2. The AP MLD and the STA MLD communicate in parallel through a link 1 and a link 2.Figure 3(c) shows a scenario in which an AP MLD 601 communicates with an STA MLD 602, an STA MLD 603, and an STA 604. AP MLD 601 includes an affiliated AP 601-1 and an affiliated AP 601-3. STA MLD 602 ​​includes three affiliated STAs: STA 602-1, STA 602-2, and STA 602-3. STA MLD 603 includes two affiliated STAs: STA 603-1 and STA 603-2. STA 604-1 and STA 604 are single-link devices. The AP MLD 601 can separately use link 1, link 2, and link 3 to communicate with STA MLD 602, link 2 and link 3 to communicate with STA MLD 603, and link 1 to communicate with STA 604. In one example, STA 604 operates in the 2.4 GHz frequency band. In STA MLD 603, STA 603-1 operates in the 5 GHz frequency band, and STA 603-2 operates in the 6 GHz frequency band. In STA MLD 602, STA 602-1 operates in the 2 GHz frequency band.The STA 602-2 operates in the 5 GHz frequency band, and the STA 602-3 operates in the 6 GHz frequency band. The AP 601-1, operating in the 2.4 GHz frequency band on the AP MLD 601, can perform uplink or downlink data transmission via link 1 with the STA 604 and the STA 602-2 on the STA MLD 602. The AP 601-2, operating in the 5 GHz frequency band on the AP MLD 601, can perform uplink or downlink data transmission via link 2 with the STA 603-1, which operates in the 5 GHz frequency band on the STA MLD 603, and can also perform uplink or downlink data transmission via link 2 with the STA 602-2. of 5 GHz frequencies at the STA MLD 602.The AP 601-3 operating in the 6 GHz frequency band at the AP MLD 601 can perform, via link 3, uplink or downlink data transmission with the STA 602-3 operating in the 6 GHz frequency band at the STA MLD 602, and can also perform, over link 3, uplink or downlink data transmission with the STA 603-2 at the STA MLD. It should be noted that FIGURE 3(b) only shows that the MLD AP supports two frequency bands. FIGURE 3(c) shows only one example where the MLD 601 AP supports three frequency bands (2.4 GHz, 5 GHz, and 6 GHz). Each frequency band corresponds to a link, and the MLD 601 AP can operate on one or more links of Link 1, Link 2, or Link 3. On the AP or STA side, the link in this example can also be understood as a station operating on the link. In actual application, the MLD AP and MLD STA may support more or fewer frequency bands. In other words, the MLD AP and MLD STA may operate on more or fewer links. This is not a limitation in this application. Currently, a single-link device, such as a station in power-saving mode, periodically listens for a traffic indication map (TIM) beacon frame and determines, based on the 0 bit in a bitmap control field within the TIM beacon frame, whether group-directed traffic follows a delivery traffic indication map (DTIM) beacon frame. However, in a multi-link device scenario, it is assumed that the 0 bit in a bitmap control field is also used to determine whether group-directed traffic follows a DTIM beacon frame.In this case, in the communication systems shown in Figure 3(a) through Figure 3(c), each STA in the MLD STAs needs to periodically listen for a TIM beacon frame on a link. It learns whether an AP on the link sends group-directed traffic after sending a DTIM beacon frame based on a 0 bit value in the bitmap control field of the TIM beacon frame listened to by the STA. If group-directed traffic is present, the STA receives the group-directed traffic sent by the AP after receiving the corresponding DTIM beacon frame. The group-directed traffic is sent immediately after the DTIM beacon frame, for example, after a short inter-frame space (SIFS) following the DTIM beacon frame. In an 802.11 protocol, a STA typically has two operating modes: a non-power-saving mode and a power-saving mode. When the STA is operating in power-saving mode, it is in an active state (also referred to as a standby state) regardless of whether there is data to be transmitted. The STA can be in an active state when data is being transmitted with an access point (AP). When there is no data transmission between the STA and the AP, the STA can be in a doze state to reduce power consumption. The STA can send a frame to the AP to notify it whether it is in power-saving mode. If a power-saving bit in a frame control field in a frame's MAC header is set to 1, the AP is notified that the STA is in power-saving mode.If the power saving bit in the frame control field in the frame MAC header is set to 0, the AP is notified that the STA is in non-power saving mode. In one group, the directed traffic transmission method 100 shown in FIGURE 4, communication between AP MLD 601 and STA MLD 602 ​​in FIGURE 3(c) is used as an example. STA 602-1 of STA MLD 602 ​​needs to listen to a TIM 1 beacon frame on link 1 to learn, by using bit 0 in a bitmap control field in the TIM 1 beacon frame, whether AP 601-1 sends traffic directed to group 1 after sending a DTIM 1 beacon frame. STA 602-2 of STA MLD 602 ​​needs to listen to a TIM 2 beacon frame on link 2 to learn, by using bit 0 in a bitmap control field in the TIM 2 beacon frame, whether AP 601-2 sends traffic directed to group 2 after sending a DTIM 2 beacon frame.The STA 602-3 of the STA MLD 602 ​​needs to listen to a TIM 3 beacon frame on link 3 to learn, by using bit 0 in a bitmap control field in the TIM 3 beacon frame, whether the AP 601-3 sends traffic directed to group 3 after sending a DTIM 3 beacon frame. It can be learned that if the number of links of the STA MLD 602 ​​continues to increase, the power consumption of the STA MLD 602 ​​increases greatly. Therefore, the way in which the energy consumption of the STA MLD is reduced becomes an urgent problem that must be solved. According to a multilink group traffic transmission method provided in the modalities of this application, the energy consumption of an MLD STA can be reduced. Detailed descriptions with reference to the attached figures follow. In this application, Mode 1 and Mode 2 are described separately. One difference between Mode 1 and Mode 2 is that Mode 1 is described using an example where each bit of group-directed traffic indication information indicates whether an AP corresponding to that bit has group-directed traffic, and Mode 2 is described using an example where the group-directed traffic indication information is a portion of bits in a partial virtual bitmap field in a TIM element. Mode 1 Figure 5 shows a multilink group 200 traffic transmission method according to one modality of this application. The multilink group 200 traffic transmission method is described using an example in which the 200 method is implemented in a communication system that includes an AP MLD and an STA MLD. The AP MLD includes one or more APs, and a first AP is any AP within the one or more APs. The STA MLD includes one or more STAs, and a first STA is any STA within the one or more STAs. As described above, a multilink association can be established between the AP MLD and the STA MLD. The multilink group 200 traffic transmission method may include, but is not limited to, the following steps. Step S201: The first AP of the AP MLD generates group-directed traffic indication information. The first AP is any AP of the AP MLD. The group-directed traffic indication information may be called the group-directed traffic indication field or group-directed traffic indication. This is not limited in this application. The description of the group-directed traffic indication information includes the following two expressions: (1) The group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic. (2) The group-directed traffic indication information indicates whether one or more APs of the AP MLD send group-directed traffic after sending a DTIM beacon frame. For another example, the description of the group-directed traffic indication information includes the following two expressions: (3) The group-directed traffic indication information indicates whether one or more APs of the AP MLD buffer have group-directed traffic. (4) The IVIA / a / ZUZZ / UI 041 J Group-Directed Traffic Indication Information indicates that group-directed traffic from one or more APs of the MLD AP is not sent in the form of a group-directed AID. In this version of this request, expression (1) is used as an example for further description. On one hand, group-directed traffic can include a group-directed management frame and a group-directed data frame, where the frame type is indicated by a type identifier in a frame control field in a MAC header. On the other hand, group-directed traffic can be classified into broadcast traffic and multicast traffic. In other words, group-directed traffic sent by the AP is sent to a station associated with the AP, or to a station associated with the AP, in either a broadcast or group-directed manner. Within a single MLD access point (AP), each AP independently sends a group-directed management frame on the link where it operates. On this link, the AP then sends the same group-directed data frame to each corresponding station (STA) of an MLD STA associated with the AP. This group-directed management frame operates at the link layer and does not require reception by a conventional station on another link or an MLD STA that has not established an association on the link. This reduces the power consumption of the corresponding station. Each AP in the MLD AP sends the same group-directed data frame on each link, ensuring that a station on a single-radio MLD STA does not lose the group-directed data frame, and that a station on a single-radio MLD STA does not need to frequently switch a link to receive the group-directed data frame.In an optional implementation, group-directed traffic indication information shows whether an AP within the AP MLD has group-directed traffic. The AP can be the first AP, or it can be a different AP within the AP MLD than the first AP. For example, in Figure 3(c), the first AP is AP 601-1, and the group-directed traffic indication information generated by AP 601-1 can indicate whether AP 601-2 within AP MLD 601 has group-directed traffic. Alternatively, the group-directed traffic indication information generated by AP 601-1 can indicate whether AP 601-1 within AP MLD 601 has group-directed traffic. In another optional implementation, the group-directed traffic indication information shows whether multiple APs of the MLD AP have group-directed traffic. The multiple APs can be some of the APs of the MLD AP, or they can be all the APs of the MLD AP. For example, in Figure 3(c), the first AP is AP 601-1, and AP 601-1 generates group-directed traffic indication information. The group-directed traffic indication information can show whether AP 601-1 of MLD AP 601 has group-directed traffic and whether AP 601-2 has group-directed traffic. Alternatively, the group-directed traffic indication information can show whether AP 601-1 of MLD AP 601 has group-directed traffic, whether AP 601-2 has group-directed traffic, and whether AP 601-3 has group-directed traffic. IVIA / a / ZUZZ / UI 04 1 J In an optional implementation, each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD. The value of each bit indicates whether an AP corresponding to that bit has group-directed traffic, or vice versa. Optionally, each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD based on the size of a link identifier on which the AP in the AP MLD operates. In other words, a bit order in the group-directed traffic indication information corresponds to a link identifier, and the link identifier is the identifier of a link on which each AP in the AP MLD operates. In another implementation, the group-directed traffic indication (GDI) bits are one-to-one mapped to links (or APs of the MLD AP). For example, each GDI bit is used in conjunction with each link identifier. Optionally, each GDI bit is located in a target beacon transmission time (TBTT) field within a Reduced Neighbor Report (RNR) element.Specifically, a multi-link device (MLD) parameters subfield (MLD parameters subfield) shown in Figure 5a is added to the TBTT information field. This MLD parameters subfield includes a multi-link device identifier (MLD ID), a link identifier (link ID), a change sequence, and a group-directed traffic indication. The multi-link device identifier identifies an MLD in which a reported AP is located. The link identifier identifies a sequence number of the reported AP within the MLD. The change sequence number indicates an updated count value of a key BSS parameter of the reported AP. The group-directed traffic indication indicates whether the reported AP has group-directed traffic. The group-directed traffic indication can occupy 1 bit.Optionally, group-directed traffic can include group-directed management frame traffic and group-directed data frame traffic. In one implementation, group-directed management frame traffic and group-directed data frame traffic are indicated by two fields. For example, each field occupies 1 bit. Specifically, an indication of group-directed management frame traffic and an indication of group-directed data frame traffic respectively indicate whether the reported AP has corresponding group-directed management frame traffic or corresponding group-directed data frame traffic. In another implementation, only one of group-directed management frame traffic and one of group-directed data frame traffic can be indicated, using a single field.For example, a group-directed management frame traffic indication field indicates whether the reported AP has corresponding group-directed management frame traffic, or a group-directed data frame traffic indication field indicates whether the reported AP has corresponding group-directed data frame traffic. Optionally, the AP sending group-directed traffic indication information can still indicate, by using an existing method, i.e., bit 0 in a bitmap control field in a TIM element, whether the AP has downlink group-directed traffic. Generally, the RNR element is used to allow a non-associated station to discover an element from a surrounding AP, but an associated station can ignore the interpretation of the RNR element. Therefore, this application provides a method to indicate whether there is an indication of group-directed traffic in the RNR element. Specifically, the method is implemented by using a capability information field in a beacon frame or a probe response frame. A group-directed traffic flag is added to the capability information field to indicate whether at least one reported AP has group-directed traffic in the RNR element. The group-directed traffic flag can be indicated by using 1 bit. For example, if 1 bit of the group-directed traffic flag is set to 1, it indicates that at least one reported AP has group-directed traffic.In an equivalent workaround, 1 bit can be set to 0 to indicate that at least one reported AP has group-directed traffic. As shown in Figure 5b, the group-directed traffic flag is added to the capacity information field in the probe response frame. When the capacity information field indicates group-directed traffic, the associated or non-associated station can be specified to interpret the RNR element. The capacity information field shown in Figure 5b can also include a change sequence number (CSN) updated flag, which indicates whether a change sequence number field value for the reported AP has changed.When the updated CSN flag indicates that a change sequence number field value of at least one reported AP has changed, the associated station or non-associated station can be indicated to interpret the RNR element. Alternatively, in another implementation, as shown in FIGURE 5c, an RNR flag is added to a capability element to indicate whether a change sequence number field value from at least one reported AP changes, or whether there is group-directed traffic; in other words, it indicates a station to interpret the RNR element. The RNR flag can be indicated by 1 bit. When the RNR flag is set to 1, it indicates that at least one reported AP has group-directed traffic, or that a change sequence number field value from at least one reported AP changes, indicating the associated or non-associated station to interpret the RNR element. Indeed, in an equivalent alternative solution, the RNR flag value is set to IVIA / a / ZUZZ / UI 04 1J 1. Alternatively, the RNR flag value can be set to 0 to indicate that at least one reported AP has group-directed traffic or to indicate that a change sequence number field value of at least one reported AP has changed. In the two implementations shown in Figure 5b and Figure 5c, the capacity information field also includes an ESS (Extended Service Set) field, an IBSS (Independent Basic Service Set) field, a privacy field, a short preamble field, a spectrum management field, a QoS (Quality of Service) field, a short slot time field, an APSD (Automatic Power Saving Delivery) field, a radio measurement field (wireless management), and an EPD (Ethertype Protocol Discrimination) field. For details, see the 802.1 IREVmd D 3.0 protocol.At one station end, for example, an associated station or an associated station MLD, either the RNR element to be analyzed can be selected when using a beacon frame, the 1-bit group-directed traffic flag, or the 1-bit RNR flag added to the capability element in the probe response frame, or the RNR element is always being analyzed by default. For a better understanding of this form of this application, the RNR element mentioned in the previous form is described as follows: Reduced Neighbor Report Element: An AP includes the Reduced Neighbor Report Element in a management frame, such as a beacon frame or a poll response frame. During scanning, a STA receives a management frame sent by the AP, obtains information about surrounding APs based on the Reduced Neighbor Report Element in the management frame, and then selects an appropriate AP for association. Specifically, the RNR element typically carries one or more Neighbor AP info fields to describe information about one or more neighboring APs and BSSs to which the neighboring APs belong. This information is referred to as Neighbor AP reduced information later on. Figure 5d shows an example format. The fields included in the Neighbor Reduced Report element are shown in the figure. A TBTT information header (a target beacon transmission time (TBTT) info header) carries the following information: TBTT info Field Type: The TBTT info field type indicates a TBTT info type. The TBTT info field type specifies a format for a TBTT info field along with a TBTT info length field. Filtered neighbor AP field: The filtered neighbor AP field indicates whether the SSIDs of all BSSs ported in the Neighbor AP info field match the SSIDs in a probe request frame. Reserved field (Reserved) (1 bit). TBTT info count field: The TBTT info count field indicates the number of TBTT info fields included in a TBTT info set. TBTT Info Length Field: The TBTT Info Length field indicates the length of each TBTT info field. Table 1 shows IVIA / a / ZUZZ / UI 04 1 J the specific information formats cover of different lengths. Table 1 TBTT Information Length (bytes) Content Carried in a TBTT Information Field 1 Neighbor TBTT AP Offset Field 2 Neighbor TBTT AP Offset Field and BSS Parameter Field 5 Neighbor TBTT AP Offset Field and Short SSID Field 6 Neighbor TBTT AP Offset Field, Short SSID Field and BSS Parameter Field 7 Neighbor TBTT AP Offset Field and BSSID Field 8 Neighbor TBTT AP Offset Field, BSSID Field and BSS Parameter Field 11 Neighbor TBTT AP Offset Field, BSSID Field and Short SSID Field 12 Neighbor TBTT AP Offset Field, BSSID Field, Short SSID Field and BSS Parameter Field 13 Neighbor TBTT AP Offset Field, BSSID Field, Short SSID Field, BSS Parameter Field and 20 MHz Power Spectrum Density Field 0, 9 and 10 Reserved 14 to 255 Reserved, but the information on the first 13 bytes is the same as the fields carried when The length of the TBTT information is 13. The following provides a specific format for the TBTT information field (TBTT info) when the TBTT information length is 12 bytes, as shown in FIGURE 5e. Neighbor AP TBTT Offset: The Neighbor AP TBTT offset field indicates a beacon transmission time offset between a Neighbor AP and a reporting AP. BSS Identifier Field (BSSID): The BSS identifier field indicates a BSS identifier corresponding to the neighboring AP. Short Service Set Identifier (Short SSID) field: The Short Service Set Identifier field indicates a service set identifier to which the neighboring AP belongs. The 20 MHz power spectrum density indicates the predetermined transmission power, which is the equivalent isotropically radiated power (EIRP) at power spectrum density (PSD), the unit of which is dBm / MHz. BSS Parameter Field: The BSS parameter field indicates a related parameter of the neighboring AP. As shown in FIGURE 5e, the BSS parameter field includes the following information: Recommended Channel Tunneling Mechanism Field (Recommended OCT): The recommended channel tunneling mechanism indicates that the neighboring AP expects to exchange a management-type MPDU with the reporting AP when using the OCT mechanism. Same Service Set Identifier (Same SSID) field: The same service set identifier indicates whether the neighbor AP and the reporting AP have the same SSID. Multiple Basic Service Set Identifier (Multiple BSSID) Field: The Multiple Basic Service Set Identifier indicates whether the neighboring AP belongs to a part of a multiple BSSID set. Transmitted BSSID field: The transmitted BSSID indicates whether the neighbor AP is a transmitted BSSID or a non-transmitted BSSID if the neighbor AP is part of the multiple BSSID set. Extended Service Set Member with 2.4 / 5 GHz Co-Located AP (Member Of ESS With 2.4 / 5 GHz Co-Located AP) field: The Extended Service Set Member with 2.4 / 5 GHz Co-Located AP field indicates whether the neighbor AP shares a location with a 2.4 / 5 GHz AP (in other words, whether the neighbor AP is a 6 GHz only AP) and indicates that the neighbor AP is a member of an extended service set. Unsolicited Probe Response Active field: The Unsolicited Probe Response Active field indicates whether the neighboring AP allows an active probe response. Co-located AP field: The Co-located AP field indicates whether the neighboring AP and the reporting AP are co-located. For example, AP MLD 601 includes three APs. The group-directed traffic indication information has 3 bits, and these 3 bits correspond respectively to the three APs in descending order of the link identifiers on which the three APs operate. It is assumed that the link identifiers on which the three APs operate are as follows: If the link identifier of AP 601-1 is 3, the link identifier of AP 601-2 is 2, and the link identifier of AP 601-3 is 1, the first bit of the group-directed traffic indication information corresponds to AP 601-1, the second bit corresponds to AP 601-2, and the third bit corresponds to AP 601-3. If the group-directed traffic indication information is 011, it indicates that AP 601-1 has no group-directed traffic, and AP 601-2 and AP 601-3 have group-directed traffic.Certainly, the 3 bits can also correspond respectively to the three APs in ascending order of the link identifiers on which the three APs operate. In an optional implementation, a number of bits in the group-directed traffic indication information can be a fixed value. In the fixed number of bits, one bit other than those corresponding to a number of APs can be set to zero by default. For example, the fixed number of bits is 4 bits, where the three most significant bits correspond to three APs in the AP MLD, and one subsequent bit is set to zero. That is, the fixed number of bits can be greater than the number of APs in the AP MLD. S202: The first AP sends the group-directed traffic indication information. S203: The first STA of the STA MLD receives the group-directed traffic indication information. The first STA is either a station managed by the first AP or a surrounding station. Stations surrounding the first AP include the station managed by the first AP and a non-associated station. The following describes the group-directed traffic transmission method in this application mode, using the AP-managed station as an example. Optionally, the first STA can be any station in the STA MLD, and it can learn whether each AP or a portion of APs in the AP MLD has group-directed traffic. Therefore, any station in the STA MLD can receive group-directed traffic indication information from an AP associated with the station. S204: The first STA determines, based on the group-directed traffic indication information, whether one or more APs in the AP MLD have group-directed traffic. In one implementation, the multi-link group-directed traffic transmission method further includes the following: For an AP with group-directed traffic from the MLD AP, the AP can forward the group-directed traffic after sending a subsequent DTIM beacon frame, which is sent after the group-directed traffic indication information. Consequently, a station operating on a link from the MLD STA AP can receive the DTIM beacon frame on the link and receive the subsequent group-directed traffic. Specifically, the MLD STA station operating on the AP link can receive and analyze a group-directed management frame after the DTIM beacon frame on the link, and discard a group-directed data frame after a DTIM beacon frame on a different link—one on which the first STA is located.In this case, the first STA of the STA MLD has received a corresponding group-directed data frame on the first STA link. Optionally, the DTIM frame is a subsequent DTIM beacon frame following the group-directed traffic indication information. Alternatively, if the first AP also has group-directed traffic, it can send the group-directed traffic after sending a subsequent DTIM beacon frame. Consequently, the first STA can receive the DTIM beacon frame following the group-directed traffic indication information and receive the group-directed traffic following the DTIM beacon frame. In this embodiment of the present invention, the group-directed traffic indication information can be carried in a management frame, for example, a beacon frame, a TIM frame, a data frame, a control frame, or another frame. Optionally, the group-directed traffic indication information can be placed within a DTIM beacon frame, and the beacon frame is a DTIM beacon frame containing the group-directed traffic indication information. In other words, for the beacon frame, the group-directed traffic indication information sent by the first AP can only be found within the DTIM beacon frame. Specifically, for an AP carrying group-directed traffic that is part of the MLD AP, the AP can send the group-directed traffic after sending a subsequent DTIM beacon frame, which is sent after the group-directed traffic indication information.Consequently, a station corresponding to the AP learns, based on group-directed traffic indication information, that the AP has group-directed traffic and can receive the DTIM beacon frame and group-directed traffic after receiving the DTIM beacon frame. Specifically, the MLD STA station operating on the AP link can receive and analyze a group-directed management frame after the DTIM beacon frame on the link, and discard a group-directed data frame after a DTIM beacon frame on a different link—one on which the first STA is located. In this case, the first STA of the MLD STA has received a corresponding group-directed data frame on the first STA's link.Optionally, if the first AP also has group-directed traffic, it can send the group-directed traffic after the DTIM beacon frame that carries the group-directed traffic indication information. Consequently, the first STA can receive the group-directed traffic after the DTIM beacon frame that carries the group-directed traffic indication information. For example, it is assumed that in the communication system 300 shown in FIGURE 3(c), the group-directed traffic indication information sent by AP 601-2 on AP MLD 601 is 111. The first bit of the group-directed traffic indication information corresponds to AP 601-1, the second bit corresponds to AP 601-2, and the third bit corresponds to AP 601-3. As shown in FIGURE 3(c), AP 601-2 communicates with STA 603-1 on STA MLD 603 and STA 602-2 on STA MLD 602 ​​via link 2. Therefore, STA 603-1 and STA 602-2 can listen and detect that the group-directed traffic indication information sent by AP 601-2 is 111. In one implementation, STA 602-2 can determine that AP 601-1, AP 601-2, and AP 601-3 each have group-addressed traffic. Furthermore, STA 602-1, operating on link 1 of AP 601-1 in STA MLD 602, listens for a DTIM 1 beacon frame and subsequent group-addressed traffic 1. STA 602-2, operating on link 2 of AP 601-2 in STA MLD 602, listens for a DTIM 2 beacon frame and subsequent group-addressed traffic 2. STA 602-3, operating on link 3 of AP 601-3 in STA MLD 602, listens for a DTIM 3 beacon frame and subsequent group-addressed traffic 3. In another implementation, if group-directed traffic indication information is carried in a DTIM beacon frame, STA 602-2 receiving the DTIM beacon frame can receive group-directed traffic after the DTIM beacon frame. Another STA in STA MLD 602 ​​also needs to receive a DTIM beacon frame and subsequent group-directed traffic on its respective link. Optionally, STA 604 can listen for group-directed traffic indication information on link 1. However, if STA 604 is indifferent to whether other APs indicated by the group-directed traffic indication information are carrying group-directed traffic, STA 604 may choose not to receive group-directed traffic from these APs. If STA 604 is concerned about whether other APs indicated by the group-directed traffic indication information are carrying group-directed traffic—for example, if STA 604 has a frequency band selection and reception capability—STA 604 can learn, based on the group-directed traffic indication information, whether the other APs are carrying group-directed traffic. For STA MLD 603, STA 603-1 can determine that AP 601-1, AP 601-2, and AP 601-3 each have group-directed traffic, where STA MLD 603 does not have a station operating on link 1 of AP 601-1. Therefore, STA 603-1, operating on link 2 of AP 601-2 in STA MLD 603, hears a DTIM 2 beacon frame and subsequent group-directed traffic 2. STA 603-2, operating on link 3 of AP 601-3 in STA MLD 603, hears a DTIM 3 beacon frame and subsequent group-directed traffic 3. In another implementation, if group-directed traffic indication information is carried in a DTIM beacon frame, STA 603-1 receiving the DTIM beacon frame can receive group-directed traffic after the DTIM beacon frame. Another STA in STA MLD 603 also needs to receive a DTIM beacon frame and subsequent group-directed traffic on its respective link. It is noted that the listening mentioned in the present invention can also be understood as reception. Figure 6 illustrates a multilink group-directed traffic transmission method between AP MLD 601 and STA MLD 602 ​​in this example. As shown in Figure 6, STA MLD 602 ​​can use STA 602-2 to listen for group-directed traffic indication information sent by AP 601-2 to determine if AP 601-1 and AP 601-3 have group-directed traffic. In the group-directed traffic transmission method shown in Figure 4, each STA in STA MLD 602 ​​needs to listen for a TIM beacon frame sent by AP MLD 601 on a respective link to learn, using the TIM beacon frame, whether AP MLD 601 is sending group-directed traffic after the DTIM beacon frame. Compared to method 100, this method greatly reduces the energy consumption of the STA MLD 602. It can be learned that in this mode of this request, a first AP of an MLD AP can generate and send group-directed traffic indication information, where the group-directed traffic indication information can show whether an AP of the MLD AP has group-directed traffic. The AP can be the first AP or a different AP of the MLD AP, so that a STA of an MLD STA can learn if an AP associated with the STA has group-directed traffic, or if another AP of the MLD AP has group-directed traffic. Compared to a mode where each STA of the MLD STA can only listen for whether an AP associated with the STA has group-directed traffic, in this mode of this request, the flexibility of reporting group-directed traffic by the MLD AP can be improved. In this mode of this request, the first AP of the AP MLD can generate and send group-directed traffic indication information. This group-directed traffic indication information can show whether each AP, or a portion of APs across multiple APs in the AP MLD, is carrying group-directed traffic, allowing a station in the STA MLD to learn if multiple APs are carrying group-directed traffic. Compared to a mode where each STA in the STA MLD can only listen for group-directed traffic from an AP associated with that STA, this mode of the request can reduce the power consumption of the STA MLD. In this mode of this request, one or more APs in the AP MLD can send group-directed traffic indication information, and one or more STAs in the STA MLD can listen for group-directed traffic indication information. The following describe optional implementations. Case 1: An AP sending group-directed traffic indication information and a STA listening for group-directed traffic indication information In an optional implementation, each AP in the AP MLD sends group-directed traffic indication information, and any STA in the STA MLD can listen for group-directed traffic indication information on a link. Alternatively, any of the multiple STAs in the STA MLD listen for group-directed traffic indication information on a link where each STA is operating. For example, in Figure 3(c), AP 601-1 and AP 601-3 can also perform steps S201 and S202, and each sends group-directed traffic indication information. Any one or more STAs in the STA 602 MLD can listen for group-directed traffic indication information on a corresponding link. A corresponding AP is assigned to each bit in the group address indication information sent by each AP.If multiple STAs in STA MLD 602 ​​listen for group-directed traffic indication information on a corresponding link, these multiple STAs can all be STAs or a portion of STAs within STA MLD. This implementation greatly improves the flexibility of STA MLD in listening for group-directed traffic indication information. Furthermore, since one or more STAs within STA MLD listen for group-directed traffic indication information, the power consumption of STA MLD can also be reduced to some extent. In another optional implementation, the first STA in steps S203 and S204 can be a station operating on a primary link in the STA MLD, and the first STA of the STA MLD listens for group-directed traffic indication information sent by an AP operating on the primary link. In yet another optional implementation, the first STA in steps S203 and S204 is a station operating on a primary link in the STA MLD. Optionally, the STA MLD can notify the AP MLD of a primary link on which the STA MLD operates. For example, the station on the primary link in the STA MLD notifies, using a station link identifier, a corresponding AP to the STA in the AP MLD. In this way, one AP operating on the primary link in the AP MLD sends group-directed traffic indication information, while another AP may not send group-directed traffic indication information. This helps reduce the power consumption of the AP MLD or helps the AP MLD send group-directed traffic indication information more efficiently, for example, by repeatedly sending group-directed traffic indication information across multiple links. The following describes an implementation of how the AP MLD learns the primary link on which the STA MLD operates. In one implementation, the AP MLD can obtain primary link identifier information determined by the STA MLD. For example, the primary link identifier information might include one or more of the following: an operational class and channel number corresponding to the primary link, or a MAC address (or BSSID) of the primary link, or an identifier (ID) of the primary link. The specific content included in the primary link identifier information is not limited in this modality of this request. Any information that can be used to uniquely identify a station operating on the primary link may be the primary link identifier information described in this modality of this request.The primary link MAC address can be the MAC address of a STA operating on the primary link, or the MAC address of an AP operating on the primary link. When the primary link MAC address is the MAC address of the AP operating on the primary link, the primary link MAC address can also be referred to as a BSSID. In one implementation, if the AP MLD is not associated with the STA MLD, the AP MLD can obtain primary link identifier information in the following ways: The AP MLD receives an association request frame from the STA MLD. The link used by the AP MLD to receive the association request frame is the primary link determined by the STA MLD. Alternatively, the association request frame received by the AP MLD carries link identifier information for the primary link determined by the STA MLD. That is, the AP MLD can determine a station on a link through which the association request frame is received (or a station sending the association request frame) as the primary link identifier. Alternatively, the AP MLD obtains the primary link identifier information carried in the association request frame. In another implementation, if the AP MLD is associated with the STA MLD, the AP MLD obtaining link identifier information from the primary link may involve the following: The AP MLD receives a message frame from the STA MLD, where the message frame carries the link identifier information of the primary link determined by the STA MLD. The message frame is a management frame, a data frame, a control frame, or similar. In this implementation, the message frame is used to notify the AP MLD of a primary link change in the STA MLD. In other words, the primary link identifier information carried in the message frame is the link identifier information for the changed primary link. Optionally, the management frame may also include a change count, indicating a countdown before the primary link is changed. Optionally, the AP MLD can select a link as the primary link, and the primary link's link identifier indicates that the AP operates on that link. The AP needs to send the primary link identifier to a station associated with the AP or a nearby station. In step S201, the first AP is a The first AP operating on the primary link carries group-directed traffic. Therefore, the group-directed traffic indication information sent by the first AP can indicate whether the first AP operating on the primary link carries group-directed traffic. Alternatively, the group-directed traffic indication information can indicate whether an AP operating on a secondary link carries group-directed traffic. The secondary link is a link on which an AP other than the first AP of the MLD operates, or the secondary link includes a link other than the primary link across multiple links. In this mode of this request, the group-directed traffic indication information sent by the first AP can be part or all of the bits of the group-directed traffic indication information generated by the first AP. If the group-directed traffic indication information sent by the first AP is a portion of the bits of the group-directed traffic indication information generated by the first AP, signaling overhead can be reduced. The following describes this implementation. Each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD. If none of the APs corresponding to bits before the nth bit of the group-directed traffic indication information has group-directed traffic, and none of the APs corresponding to bits after the N2nd bit has group-directed traffic, the group-directed traffic indication information sent by the first AP may include only the nth bit through the N2nd bit. N1 may be greater than or equal to 0 and less than a total number of bits of the generated group-directed traffic indication information. N2 may be greater than N1 and less than or equal to a total number of bits of the generated group-directed traffic indication information. This implementation helps reduce signaling overhead.Furthermore, in this case, the group-directed traffic information also includes an offset field and a length field. The offset indicates Ni, and the length indicates N2-N1+I of the group-directed traffic information. For ease of description, in what follows, the group-directed traffic indication information generated by the first AP is referred to as the first group-directed traffic indication information, and the group-directed traffic indication information sent by the first AP is referred to as the second group-directed traffic indication information. The second group-directed traffic indication information may be the same as the first group-directed traffic indication information, or the second group-directed traffic indication information may be a bit portion of the first group-directed traffic indication information. If the second group-directed traffic indication (GDI) is a portion of the bits of the first GDI, the first AP also needs to send an offset and a length. The offset and length are used by the first STA of the STA MLD to determine which AP the second GDI corresponds to. An offset of the second GDI relative to the first GDI is referred to simply as the second GDI offset. If the second GDI consists of all the bits of the first GDI, the first AP can either send the offset and length or not. The first group-directed traffic indication (GDI) includes a bit corresponding to each AP in the MLD AP. A mapping between each bit of the GDI and each AP in the MLD AP can be established using the management frame above, or it can be predefined based on the size of a link identifier on which each AP operates. Specifically, the total number of bits in the GDI can equal the total number of APs in the MLD AP. Alternatively, the MLD AP can determine, based on the size of the link identifier on which each AP operates, that each bit of the GDI is in a one-to-one correspondence with each AP. There are two more cases. That is, case 2.1 and case 2.2 analyze that the second group-directed traffic indication information is a bit portion of the first group-directed traffic indication information. Case 2.1: The second group-directed traffic indication information consists of all bits starting from byte Ni of the first group-directed traffic indication information and ending in byte N2, where Ni is greater than or equal to O, and N2 is greater than or equal to Ni. It is assumed that none of the APs corresponding to all bits from bit 0 to bit NΓ81 of the first group-directed traffic indication information has group-directed traffic, and none of the APs corresponding to bit (N2+1)*8 and all subsequent bits have group-directed traffic. In this case, the second group-directed traffic indication information sent by the first AP can be all the bits starting from byte Ni of the first group-directed traffic indication information and ending with byte N2. In this case, the length of the second group-directed traffic indication information sent by the first AP is N2-Ni+1, and the offset of the second information is IVIA / a / ZUZZ / UI 041 J Group-directed traffic indication is Ni. In addition, the station managed by the first AP in the STA MLD receives the length and offset, and can determine that the second group-directed traffic indication information received indicates whether the APs corresponding to bits NG8 to bits ((N2+I )*8—1) have group-directed traffic, determine that the APs corresponding to all bits from bit 0 to bit NG8-1 do not have group-directed traffic, and determine that the APs corresponding to bit (N2+1)*8 and all subsequent bits do not have group-directed traffic. For example, assume the first group-directed traffic indication piece is 3 bytes long, where none of the APs corresponding to bits in byte 0 have group-directed traffic, and none of the APs corresponding to bits in byte 2 have group-directed traffic. In this case, the second group-directed traffic indication piece can include only bits in byte 1. Therefore, the length of the second group-directed traffic indication piece is 1 byte, and the offset is 1 byte.In this way, after receiving the second group-directed traffic indication information, the length and offset, the first STA can learn that the bits in the second group-directed traffic indication information indicate whether the APs corresponding to bits 8 through 15 have group-directed traffic, learn that none of the APs corresponding to bits in byte 0 have group-directed traffic, and learn that none of the APs corresponding to bits in byte 2 have group-directed traffic. In another implementation, to reduce the signaling overhead required to send the offset—in other words, to reduce the number of bits required to indicate the offset—the offset of the second group-directed traffic indication information can be set to N1 / 2. In this case, Ni is required to be an even number of bytes. For example, if the offset sent by the first AP is 0 and the length is 1 byte, the second group-directed traffic indication sent by the first AP includes bits 0 through 7. This allows the first STA to learn, based on the values ​​of bits 0 through 7, whether the APs corresponding to bits 0 through 7 have group-directed traffic. If the offset sent by the first AP is 1 and the length is 1 byte, the second group-directed traffic indication sent by the first AP includes byte 2, that is, bits 16 through 22. This allows the first STA to learn, based on the values ​​of bits 16 through 22, whether the APs corresponding to bits 16 through 22 have group-directed traffic. For another example, assume that the offset sent by the first AP is 0, the length is 1 byte, the second group-directed traffic indication is 01100110, and bits 0 through 7 correspond to AP 1 through AP 8 of the AP MLD, respectively. In this case, the first STA can learn that AP 1, AP 4, AP 5, and AP 8 do not have group-directed traffic, and AP 2, AP 3, AP 6, and AP 7 do. Optionally, if bit 0 is predefined as irrelevant (i.e., bit 0 does not correspond to any AP), bits 1 through 7 correspond to AP 1 through AP 7 of the AP MLD, respectively, and the first STA can learn that AP 1, AP 2, AP 5, and AP 6 have group-directed traffic, and AP 3, AP 4, and AP 7 do not. It can be learned that in case 1, the correspondence between each AP in the AP MLD and each bit in the first group-directed traffic indication information is determined by predefinition or notification when using a management frame. Furthermore, the second group-directed traffic indication information is a portion of bits from the first group-directed traffic indication information, to reduce signaling overhead. Case 2.2: The second group-directed traffic indication information consists of bits starting from byte 0 and ending at byte N0-1 of the first group-directed traffic indication information, and bits starting from byte Ni of the first group-directed traffic indication information and ending at byte N2. In this case, it is assumed that none of the APs corresponding to bit N0*8-1 through bit N / 8-1 of the first group-directed traffic indication information have group-directed traffic, and none of the APs corresponding to bit N2*8 and a subsequent bit have group-directed traffic. In this case, the second group-directed traffic indication information sent by the first AP consists of bits starting from byte 0 of the first group-directed traffic indication information and ending with byte N0-1, and bits starting from byte N0 of the first group-directed traffic indication information and ending with byte N2. Accordingly, the length of the second group-directed traffic indication information sent by the first AP is NO+N2-N1+I, and the offset of the second group-directed traffic indication information is Ni - NO. Furthermore, the station managed by the first AP in the STA MLD receives the length and offset, and can determine that the second group-directed traffic indication information received indicates bits 0 to bits (N01)*8-1, determine if the APs corresponding to bit Ni*8+1 to bit N2*8-1 have group-directed traffic, and determine that none of the APs corresponding to bit (N0-1)*8 to bit (N11)*8 have group-directed traffic. In one implementation, to reduce the number of bits required for offset, the offset of the second group-directed traffic indication information sent by the first AP is half of the actual offset. Therefore, in this case, the offset sent by the first AP is (Ni - N0) / 2, and its length is N0 + N2 - N1 + I bytes. Furthermore, because the offset is (Ni - N0) / 2, if N0 is an odd number, then Ni is also an odd number. If N0 is an even number, then Ni is also an even number. Mode 2 Figure 7 is a schematic diagram of a multilink 400 group-directed traffic transmission method. In the multilink 400 group-directed traffic transmission method, the group-directed traffic indication information is a bit portion in a partial virtual bitmap field within a TIM traffic indication map element. Specifically, the group-directed traffic indication information is a bit portion in the partial virtual bitmap field shown in Figure 2. As shown in Figure 7, the multilink 400 group-directed traffic transmission method includes, but is not limited to, the following steps. S401: A first AP of an MLD AP generates the group-directed traffic indication information. S402: The first AP sends the TIM element. The TIM element can be carried in a beacon frame, or it can be carried in another management frame, for example, a TIM frame. The partial virtual bitmap field in the TIM element includes the group-directed traffic indication information. Specifically, the group-directed traffic indication information is the portion of the bits in the partial virtual bitmap field of the TIM traffic indication map element. Furthermore, as described in Mode 1, optionally, for the beacon frame, the group-directed traffic indication information can be carried only in a DTIM beacon frame. Optionally, the group-directed traffic indication information can be carried in another frame, such as a management frame, a data frame, or a control frame. For example, FIGURE 8 shows bits from the partial virtual bitmap field in FIGURE 2. For example, the partial virtual bitmap field has 251 bytes, and each byte includes 8 bits. As shown in FIGURE 8, byte 0 includes bits 0 through 7, byte 1 includes bits 8 through 15, and so on, and the rest can be deduced by analogy. Byte 250 includes bits 2000 through 2007. In one implementation, the group-directed traffic indication information is a portion of consecutive bits in the partial virtual bitmap field. For example, if the group-directed traffic indication information is bits 1 through 7 in the partial virtual bitmap field in FIGURE 8, bits 1 through 7 in the partial virtual bitmap field can indicate whether each AP in the AP MLD has group-directed traffic. In another implementation, group-directed traffic indication information is a IVIA / a / ZUZZ / UI 04 1 J part of non-consecutive bits in the partial virtual bitmap field in FIGURE 8. For example, if the group-directed traffic indication information is bit 1, bit 2, and bit 4 in the partial virtual bitmap field, then bit 1, bit 2, and bit 4 in the partial virtual bitmap field can indicate whether each AP of the AP MLD has group-directed traffic. S403: A first STA of an MLD STA receives the TIM element. S404: The first STA reads the group-directed traffic indication information in the partial virtual bitmap field from the TIM element, and determines if one or more APs of the AP MLD have group-directed traffic. For the related description of step S401, reference is made to the description of step S201 in the traffic transmission method directed to group 200 shown in FIGURE 5. Details are not described again herein. Optionally, the multilink 400 group-directed traffic transmission method also includes: For an AP that is determined to have group-directed traffic, the STA operating on the AP link in the STA MLD receives group-directed traffic after a DTIM beacon frame. For example, group-directed traffic indication information can be carried in any beacon frame, including both a TIM beacon frame and a DTIM beacon frame. In this case, the DTIM beacon frame is either a DTIM beacon frame following the TIM beacon frame, or it is a DTIM beacon frame that carries the group-directed traffic indication information. In another example, group-directed traffic indication information is carried only in a DTIM beacon frame within a beacon frame. In this case, the DTIM beacon frame is a DTIM beacon frame that carries the group-directed traffic indication information. Optionally, the group-directed traffic indication information can be carried in another frame such as a management frame, a data frame, or a control frame. Specifically, to learn how to operate another AP of the AP MLD and another STA of the STA MLD, refer to the description in one of the modalities. Details are not described again herein. As described in Figure 2, the partial virtual bitmap is a portion of a traffic indication virtual bitmap field, with each bit corresponding to an AID. Therefore, in this application mode, the AP MLD assigns AIDs to APs within the AP MLD and also uses bits corresponding to the AIDs in the partial virtual bitmap field to separately indicate whether the APs with those AIDs carry group-directed traffic. In other words, the group-directed traffic indication information consists of the bits corresponding to the AIDs. An AID assigned to an AP cannot be used by any AP within the AP MLD to assign to a station associated with that AP. Furthermore, an AID explicitly or implicitly assigned to the AP cannot be used by the STA MLD that establishes a multilink association with the AP MLD in which the AP is located. The AIDs assigned to all stations within the STA MLD are the same.“Explicitly means that a management frame sent by the AP carries an association identifier of each AP or an association identifier of each AP other than the first AP of the AP MLD in which the AP is located, as mentioned in Method 1 below. “Implicitly refers to AIDs that correspond to bits occupied by the AP in the partial virtual bitmap field in the TIM element, as mentioned in Method 2 below. It can be learned that, in the 400 multi-link group-directed traffic transmission method, group-directed traffic indication information is carried in the partial virtual bitmap field of the beacon frame, thus improving the flexibility of group-directed traffic notification. Furthermore, when group-directed traffic indication information shows whether multiple access points (APs) are carrying group-directed traffic, the power consumption of the STA MLD can also be reduced. It is assumed that in the communication system 300 shown in FIGURE 3(c), the AIDs of AP 601-1 through AP 601-3 in AP MLD 601 are AID 1, AID 2, and AID 3. In this case, AID 1, AID 2, and AID 3 each correspond to one of the three bits in the partial virtual bitmap field in the TIM beacon frame. In a multilink group-directed traffic transmission method 500 shown in FIGURE 9, an AP 601-2 sends a beacon frame 2, where a partial virtual bitmap field in the beacon frame 2 carries group-directed traffic indication information. An STA 602-1 listens to beacon frame 2 on link 2 and reads, from the partial virtual bitmap field in beacon frame 2, 3 bits corresponding to AID 1, AID 2, and AID 3 as 111. In this case, STA 602-1 can learn that an AP 601-1 to an AP 601-3 each has group-directed traffic following a corresponding DTIM beacon frame.Furthermore, STA 602-1 and STA 602-3 can each listen separately for group-directed traffic on a link where both operate. It can be learned that in this implementation, STA 602-1 and STA 602-3 on an MLD STA 602 do not periodically listen for beacon frames to determine if a corresponding AP has group-directed traffic. This reduces the power consumption of the MLD STA 602. Optionally, for the beacon frame, if the group-directed traffic indication information is carried only in a DTIM beacon frame, STA 602-1 receiving the DTIM beacon frame can receive group-directed traffic after the DTIM beacon frame. Another STA in STA MLD 602 ​​also needs to receive a DTIM beacon frame and subsequent group-directed traffic on its respective link. IVIA / a / ZUZZ / UI 04 1 J The following discusses two AID configuration methods. Specifically, in Method 1, an MLD AP explicitly assigns an AID to each AP included in the MLD AP, and the MLD AP assigns the AID to each AP using association identifier configuration information. In Method 2, an MLD AP implicitly assigns an AID to each AP included in the MLD AP. Specifically, an AID is predefined corresponding to the first bit of a string of consecutive bits located in a partial virtual bitmap field, which corresponds to group-directed traffic indication information. The method may also include two cases. Case 3.1 describes how to predefine an AID corresponding to an AP when the MLD AP's AP is not operating in multi-BSSID (Basic Service Set Identifier) ​​mode. Case 3.2 describes how to assign the AID to each AP in the MLD AP when one or more APs in the MLD AP are operating in multi-BSSID mode.In this case, within a partial virtual bitmap field of a TIM element, the AIDs also need to be assigned to multiple APs in a multiple basic service set identifier set. Therefore, the AID assigned to each AP of the AP MLD cannot be the same as the AIDs assigned to the multiple APs in the multiple basic service set identifier set. In other words, the bits corresponding to each AP of the AP MLD in the partial virtual bitmap field are not repeated with the bits corresponding to multiple non-transmitted APs in the multiple basic service set identifier set established in the partial virtual bitmap field. Method 1: The AP MLD explicitly assigns the AID to each AP included in the AP MLD. Optionally, the AID configuration method includes, but is not limited to, the following steps: A first AP in the AP MLD generates association identifier configuration information, where the association identifier configuration information indicates an association identifier corresponding to each AP in the AP MLD. Specifically, the association identifier configuration information includes one or more pieces of association identifier subconfiguration information, each piece of association identifier subconfiguration information corresponding to an AP, and the association identifier subconfiguration information includes an AP AID and an AP AID. Optionally, the association subconfiguration information can be ported into a subelement or field that stores information about a single AP and is located in an MLD element used for information about one or more APs in the MLD.The first AP sends the association identifier configuration information. Each bit of the group-directed traffic indication information indicates whether an AP with an AID corresponding to that bit has group-directed traffic. Each AP's AID corresponds to each bit of the group-directed traffic indication information. The first AP that generates and sends the association identifier configuration information and the first AP that generates and sends the group-directed traffic indication information in step S201 can be the same AP of the MLD AP, or they can be different APs of the MLD AP. In one implementation, if the AP MLD is not associated with the STA MLD, the association identifier configuration information can be carried in an association response frame sent by the STA MLD. In another implementation, if the AP MLD is associated with the STA MLD, the association identifier configuration information can be carried in a management frame sent by the STA MLD. In this implementation, because the AP MLD assigns the AID to each AP of the AP MLD, the group-directed traffic indication information can be a bit portion in a partial virtual bitmap, and the bit portion can be consecutive or non-consecutive. Furthermore, because the AIDs corresponding to some bits in the partial virtual bitmap field are assigned to a station, and these bits separately indicate whether a corresponding station has unicast traffic, in this implementation, an association identifier assigned to each AP of the AP MLD is different from an association identifier assigned to a station associated with each AP. In other words, the association identifier assigned to each AP of the AP MLD cannot be assigned by the AP to a station managed by the AP. However, the AIDs assigned by different APs to stations managed by the APs are relatively independent. In other words, the AIDs assigned by different APs to stations managed by the APs can be the same. For example, in the communication system 300 shown in FIGURE 3(c), it is assumed that the AIDs assigned from AP 601-1 to AP 601-3 of AP MLD 601 are AID 1, AID 2, and AID 3.In this case, AID 1, AID 2, and AID 3 cannot be assigned to stations associated with AP 601-1 and AP 601-3, for example, a STA of STA MLD 602, a STA of STA MLD 603, and STA 604. However, the AID assigned by AP 601-1 to STA 602-1 of STA MLD 602 ​​can be the same as the AID assigned by AP 601-2 to STA 602-2 of STA MLD 602. Even if the AID of STA 602-1 is the same as the AID of STA 602-2, STA 602-1 and STA 602-2 operate on different links, namely link 1 and link 2. Therefore, STA 602-1 and STA 602-2 with The same AIDs are not confusing. It can also be understood that an AID explicitly or implicitly assigned to the AP of the MLD AP cannot be used for the MLD STA that establishes a multi-link association with the MLD AP where the AP is located. The AIDs assigned to all stations of the MLD STA are the same.“It implicitly refers to AIDs that correspond to bits occupied by the AP in the partial virtual bitmap field in the TIM element, as mentioned in the following method 2. Optionally, because each STA in the STA MLD is located in a different Basic Service Set (BSS), the AP MLD can assign an AID to each STA MLD. In other words, the STAs in the STA MLD share one AID, and confusion does not occur. Alternatively, the AP MLD can assign an AID to each STA within the STA MLD. In other words, each STA within the STA MLD has its own AID. It can be learned that, in this implementation, the AID is assigned to each AP in the AP MLD, and the partial virtual bitmap field in the TIM element is used to notify the STA MLD if each AP in the AP MLD has group-directed traffic. Compared to the notification method of using bit 0 in the bitmap control field in the TIM beacon frame on each link, where the AP on each link indicates whether there is group-directed traffic in the group-directed traffic processing method 100, this implementation improves the flexibility of group-directed traffic notification. Furthermore, when group-directed traffic indication information shows whether multiple APs have group-directed traffic, the power consumption of the STA MLD can also be reduced. For example, it is assumed that in the communication system 300 shown in FIGURE 3(c), the AIDs assigned to AP 601-1 to AP 601-3 of AP MLD601 are AID 1, AID 2, and AID 3. In this case, AID 1, AID 2, and AID 3 each correspond to one of the 3 bits of the partial virtual bitmap field in the TIM element. Optionally, multiple AIDs assigned to multiple APs of the AP MLD are consecutive. Optionally, the partial virtual bitmap field may not carry group-directed traffic indication information from an AP (referred to as the reporting AP) that sends the partial virtual bitmap field, but instead carry group-directed traffic indication information from another AP in the MLD where the reporting AP is located. The group-directed traffic indication information from the reporting AP is still indicated by bit 0 in a bitmap control field. There are two implementations without portability in the present invention. One is that the partial virtual bitmap field carries a bit corresponding to the reporting AP, but the bit is reserved and irrelevant. The other is that the partial virtual bitmap field does not carry a bit corresponding to the reporting AP. This is applicable to another embodiment of the present invention, and details are not described again. Method 2: The AP MLD implicitly assigns the AID to each AP included in the AP MLD. When the AP MLD implicitly assigns the AID to each AP included in the AP MLD, it must be considered whether any AP in the AP MLD is operating in a multiple Basic Service Set Identifier (BSS) mode, and if so, whether the AP operating in BSS mode is a broadcast AP. Therefore, Method 2 is analyzed in two cases. Specifically, Case 3.1 analyzes how to assign the AID to each AP included in the AP MLD when no AP in the AP MLD is operating in BSS mode, and Case 3.2 analyzes when one or more APs in the AP MLD are operating in BSS mode. IVIA / a / ZUZZ / UI 04 1 J in the multiple basic service set identifier mode and at least one AP is an AP broadcast in the multiple basic service set identifier set. To facilitate understanding, a related concept of a Basic Service Set Identifier (BSSID) is first described. In one implementation, the set of multiple Basic Service Set identifiers (multiple BSSID set, which may be referred to as a multiple BSSID set) can be understood as a set of several cooperative access points (APs). All cooperative APs use the same operating class, channel number, and antenna interface. Within the multiple BSSID set, only one AP BSSID is transmitted, and the other APs are non-transmitted. Information about the multiple BSSID set (i.e., a multiple BSSID element) is carried in a beacon frame, polling response frame, or neighbor report sent by the transmitted AP BSSID. Information about a non-transmitted AP BSSID is derived by a station based on the beacon frame, polling response frame, multiple BSSID element in the neighbor report, or similar sources.The BSSID of the non-broadcast AP BSSID is calculated using a BSSID of the broadcast AP BSSID and a BSSID index field in a multiple BSSID index element in a non-broadcast BSSID profile of the broadcast AP BSSID. For a specific method, see the 802.11 REVmdD 3.0 protocol draft. In another implementation, the multiple BSSID set can be understood as including multiple APs. Each AP manages a BSS, and different APs can have different SSIDs and permissions, such as a security mechanism or a broadcast occasion. In a multiple BSSID set, only an AP whose BSSID is a broadcast BSSID can send a beacon frame and a probe response frame. Therefore, if a probe request frame sent by an STA is sent to an AP whose BSSID is not broadcast in the multiple BSSID set, the AP whose BSSID is the broadcast BSSID in the multiple BSSID set needs to assist in responding to the probe request frame by sending a probe response frame. A BSSID of one AP within a multiple AP in a multiple BSSID set is configured as the Transmitted BSSID, and a transmitted AP BSSID can be referred to as a Transmitted AP. A BSSID of another AP is configured as the Nontransmitted BSSID, and a nontransmitted AP BSSID can be referred to as a Nontransmitted AP. A frame format for the multiple BSSID element is shown in FIGURE 10. The multiple BSSID element includes an element ID field, a length field, a maximum BSSID indicator field, and an optional subelement field. The maximum BSSID indicator field indicates a maximum number n of BSSIDs included in the multiple BSSID set, and the optional subelement field includes information about a BSSID of the untransmitted AP BSSID. The maximum number of APs allowed in the multiple BSSID set is 2Λ(Nη), where Nn is a value indicated by a MaxBSSID indicator field in the multiple BSSID element in Figure 7. Therefore, bits 1 through 2Λ(Nη)-1 of a traffic indication virtual bitmap field can be assigned to non-transmitted BSSID APs in the multiple BSSID set, respectively, to indicate whether non-transmitted BSSID APs with NonTxBSS IDs (identifiers) from 1 to 2n-1 have group-directed traffic. A NonTxBSS ID value is equal to a value in the BSSID index field in the multiple BSSID index element of the non-transmitted BSSID profile in the multiple BSSID element. The non-transmitted BSSID profile is located in the optional sub-element field. Case 3.1: No AP of the AP MLD is operating in multiple basic service set identifier mode. In one implementation, each bit of the group-directed traffic indication information described in S201 corresponds to each AP of the AP MLD. Therefore, a starting bit location for the group-directed traffic indication information in the partial virtual bitmap field in the TIM element can be determined in a predefined manner. In other words, the AP AIDs of the AP MLD are assigned sequentially starting from AID x, for example. The AIDs are assigned sequentially in descending or ascending order of the link identifier sizes on which the APs operate. AID x is predefined. Alternatively, a first bit or a start bit of the group-directed traffic indication information is predefined in the partial virtual bitmap field in the TIM element. In this implementation, a portion of the bits in the partial virtual bitmap field of the TIM element, corresponding to the group-directed traffic indication information, are consecutive. In other words, the group-directed traffic indication information corresponds to the portion of consecutive bits in the partial virtual bitmap field of the TIM element. For example, the AP MLD implicitly assigns AIDs to multiple APs within the AP MLD; that is, it assigns a segment of predetermined consecutive AIDs to all APs within the AP MLD. For example, the AIDs to all APs within the AP MLD are assigned consecutively, starting with AID 1 by default. It is assumed that the AP MLD has three APs: AP 1, AP 2, and AP 3. In this case, AID 1, AID 2, and AID 3 are assigned to AP 1, AP 2, and AP 3, respectively, by default. AIDs are assigned by default in a sequence of link identifiers on which the APs operate. If the link identifiers of AP 1, AP 2, and AP 3 are respectively Link Identifier 3, Link Identifier 2, and Link Identifier 1, then AID 3, AID 2, and AID 1 are assigned to AP 1, AP 2, and AP 3 respectively by default. It can be learned that in this implementation, an AID corresponding to each AP does not need to be communicated, when using the association response frame, management frame, or similar frames described in the previous implementation, to a station managed by the AP, since it is known by the default station. This helps reduce signaling overhead. Furthermore, because non-transmitting APs in the multi-BSSID set cannot send the beacon frame, this implementation is also applicable to a scenario where one or more APs in the MLD AP set operate in multi-BSSID mode, but those APs are non-transmitting APs. In other words, none of the MLD APs are transmitting APs in the multi-BSSID set. Optionally, the partial virtual bitmap field may not carry group-directed traffic indication information from an AP (referred to as the reporting AP) that sends the partial virtual bitmap field, but instead carry group-directed traffic indication information from another AP in the MLD where the reporting AP is located. The group-directed traffic indication information of the reporting AP is still indicated by bit 0 in a bitmap control field. In this case, the bits corresponding to the group-directed traffic indication information in the partial virtual bitmap field remain consecutive, and only the group-directed traffic indication information of the reporting AP is omitted. For example, AID 1, AID 2, and AID 3 are implicitly assigned to AP 1, AP 2, and AP 3 of the MLD AP, respectively, or AP 1, AP 2, and AP 3 correspond to bits 1 through 3 in the traffic indication virtual bitmap field.If AP 1 sends group-directed traffic indication information, the group-directed traffic indication information includes only group-directed traffic indications from AP 2 and AP 3, and bits 1 and 2 are used in the partial virtual bitmap field. If AP 2 sends group-directed traffic indication information, the group-directed traffic indication information includes only group-directed traffic indications from AP 1 and AP 3, and bits 1 and 2 are used in the partial virtual bitmap field. Case 3.2: One or more APs of the AP MLD operate in multi-BSSID mode, and at least one AP is a broadcast AP in the multiple BSSID set. It is assumed that there are a total of n BSSID APs broadcast on the AP MLD, and a value indicated by a MaxBSSID indicator field of the multiple BSSID set in which a broadcast AP BSSID is located is Ny. The AP bit configuration or predefinition of the AP MLD starts from bit x of the traffic indication virtual bitmap field. Alternatively, it is assumed that there are n APs on the AP MLD in total, where n APs belong to the multiple BSSID set. Ny for an AP that does not operate in multi-BSSID mode is equal to 0, Ny for an AP that operates in multi-BSSID mode and is a non-broadcast AP BSSID is equal to 0, and Ny for an AP that operates in multi-BSSID mode and is a broadcast AP BSSID is equal to a value indicated by a MaxBSSID indicator field of the multiple BSSID set in which the AP is located. In one implementation, the group addressed the traffic indication information starting with the x bit of the virtual traffic indication bitmap field, yx equals max{2A(Ni),2(N2), ..., 2A(Ny), ..., 2A(Nn)}. In other words, an AID corresponding to the first bit of a set of consecutive bits in the partial virtual bitmap field that corresponds to group-directed traffic indication information is AID x. Alternatively, the AP AIDs of the AP MLD are assigned consecutively starting from AID x. x equals max{2A(Ni), 2A(N2), ..., 2A(Ny), ..., 2A(Nn)}. Alternatively, the configuration or predefinition of bits in the traffic indication virtual bitmap that corresponds to APs of the AP MLD starts from bit x. x equals max{2A(Ni), 2A(N2), ..., 2A(Ny),..., 2A(Nn)}. For example, AP MLD has two APs: AP 1 and AP 2. Both AP 1 and AP 2 operate in multiple BSSID mode and transmit AP BSSIDs. The maximum BSSID flag field in a multiple BSSID element sent by AP 1 is 3, and the maximum BSSID flag field in a multiple BSSID element sent by AP 2 is 2. In this case, the maximum number of untransmitted AP BSSIDs in a multiple BSSID set supported by AP 1 is 7, and the maximum number of untransmitted AP BSSIDs in a multiple BSSID set supported by AP 2 is 3. Therefore, the starting AID in the AIDs assigned by AP MLD to AP 1 and AP 2 is AID 8, or the starting bit for AP 1 and AP 2 in the traffic indication virtual bitmap field is bit 8. Furthermore, this implementation is also applicable to a scenario where one or more APs in the AP MLD operate in multi-BSSID mode. Optionally, the partial virtual bitmap field may not carry group-directed traffic indication information from the AP (referred to as the reporting AP) sending the partial virtual bitmap field, but rather group-directed traffic indication information from another AP in the MLD where the reporting AP is located. The group-directed traffic indication information from the reporting AP is still indicated by bit 0 in a bitmap control field. In this case, the bits corresponding to the group-directed traffic indication information in the partial virtual bitmap field remain consecutive, and only the group-directed traffic indication information from the reporting AP is omitted.In the previous example, a start bit for AP 1 and AP 2 in the traffic indication virtual bitmap field is bit 8, and AP 1 and AP 2 in the AP MLD correspond to bits 8 and 9 in the traffic indication virtual bitmap field. If AP 1 sends group-directed traffic indication information, the group-directed traffic indication information includes only one group-directed traffic indication from AP 2, and bit 8 is used in the partial virtual bitmap field. If AP 2 sends the... MA / a / ZUZZ / UI 04 1J Group-directed traffic indication information, the group-directed traffic indication information includes only one group-directed traffic indication from AP 1, and bit 8 is used in the partial virtual bitmap field. Similarly, the Multilink 400 and Multilink 500 group-directed traffic transmission methods can be alternatively implemented as described in the Multilink 200 group-directed traffic transmission method, where one or more APs of the AP MLD send a beacon frame carrying the group-directed traffic indication information, and one or more STAs of the STA MLD listen to the beacon frame. A difference is that, in the Multilink 400 and Multilink 500 group-directed traffic transmission methods, the group-directed traffic indication information is carried in the partial virtual bitmap field of the TIM element. Correspondingly, one or more APs in the AP MLD can send the beacon frame, and any of the multiple STAs of the STA MLD can listen to the beacon frame.It can be learned that this implementation greatly improves the flexibility of the STA MLD in listening to group-directed traffic indication information. Furthermore, one or more STAs within the STA MLD listen to the group-directed traffic indication information, thus reducing the STA MLD's power consumption. Optionally, the group-directed traffic indication information can be carried only within a DTIM beacon frame. In another implementation, the first STA in steps S203 and S204 can be a station operating on a primary link in the STA MLD, and the first STA of the STA MLD listens for a beacon frame sent by an AP operating on the primary link. In yet another implementation, the first STA in steps S203 and S204 is a station operating on a primary link in the STA MLD. Optionally, the STA MLD can notify the AP MLD of a primary link on which the STA MLD operates. For example, the station on the primary link in the STA MLD notifies, using a station link identifier, a corresponding AP to the STA in the AP MLD. In this way, the AP operating on the primary link in the AP MLD sends the beacon frame, while another AP may choose not to send the beacon frame. This helps reduce the power consumption of the AP MLD or helps the AP MLD send grouped traffic indication information more efficiently, for example, by repeatedly sending grouped traffic indication information across multiple links. Furthermore, for an implementation of how the AP MLD learns the primary link on which the STA MLD operates, refer to the previous description. Details are not described again herein. Similarly, in the Multi-Link 400 and Multi-Link 500 Group-Directed Traffic Transmission Methods, the group-directed traffic indication information sent by the first AP can include bits corresponding to the AID of a portion of the AP, or bits corresponding to the AID of a portion of the stations, to reduce the bit overhead required by the TIM element. The group-directed traffic indication information is assumed to be the partial virtual bitmap field in the TIM element, and the partial virtual bitmap field is a portion of the bits in the traffic indication virtual bitmap field. The AP's traffic indication virtual bitmap field is neither sent nor ported in the TIM element.The following analyzes a length field, an offset, and the partial virtual bitmap field (i.e., group-directed traffic indication information) in the TIM element in two cases, i.e., case 4.1 and case 4.2. Case 4.1: This case is applicable to case 3.1 in method 1 and method 2. In other words, the related content of case 4.1 applies to a scenario where each AP in the AP MLD does not operate in multi-BSSID mode, or a scenario where each AP operates in multi-BSSID mode but is a non-broadcasting AP. Optionally, this may also apply to another scenario. Group-directed traffic indication information consists of all bits starting from byte Ni of the traffic indication virtual bitmap field and ending in byte N2, where Ni is greater than or equal to 0, and N2 is greater than or equal to Ni. In this case, a compression method is used in a protocol. When none of multiple access points with consecutive association identifiers carries group-directed traffic, the partial virtual bitmap field may not carry bits corresponding to these association identifiers. That is, a number of bits of the group-directed traffic indication information in the partial virtual bitmap field are reduced by using an offset in the TIM element. It is assumed that the AID stations corresponding to a bit preceding a larger even byte Ni and all bits following a smaller byte N2 in the traffic indication virtual bitmap field have no received downlink traffic, or the APs of the corresponding AIDs have no sent group-directed traffic. In this case, the group-directed traffic indication information consists of all bits starting from byte Ni in the traffic indication virtual bitmap field and ending with byte N2. To reduce the signaling overhead required to send the offset—in other words, to reduce the number of bits required to indicate the offset—the offset of the second group-directed traffic indication information can be set to Ni / 2. That is, Ni is an even number of bytes. In this case, the length field of the TIM element sent by the first AP is N2-Ni+1+3, and the offset of the TIM element is (1 / 2)Ni. Furthermore, a station managed by the first AP in the STA MLD receives the length and offset, and determines that the group-directed traffic indication information indicates that stations with AIDs corresponding to bits NG8 to ((N2+1)*8-1)) have no downlink traffic received or APs with the corresponding AIDs have no group-directed traffic sent, determines that APs with AIDs corresponding to all bits from bit 0 to bit NU8-1 have no group-directed traffic, and determines that APs with AIDs corresponding to bits (N2+1)*8 and all subsequent bits have no group-directed traffic. For example, if the offset in the TIM element sent by the first AP is 0 and the length field is 4 bytes (i.e., the partial virtual bitmap is 1 byte), the group-directed traffic indication information sent by the first AP is bits 0 through 7 in the partial virtual bitmap field. Thus, if an AP's AID falls within the range of AIDs corresponding to bits 16 through 23, the first STA can learn, based on the values ​​of bits 0 through 7, whether APs with AIDs corresponding to bits 0 through 7 are sending group-directed traffic. If an AP's AID does not fall within the range of AIDs corresponding to bits 0 through 7, the AP is not sending group-directed traffic to a station associated with the AP or to a surrounding station. As another example, if the offset sent by the first AP is 1 and the length is 4 bytes (i.e., the partial virtual bitmap is 1 byte), the group-directed traffic indication information sent by the first AP is byte 2 in the partial virtual bitmap field, i.e., bits 16 through 23. Thus, if an AP's AID falls within the range of AIDs corresponding to bits 16 through 23, the first STA can learn, based on the values ​​of bits 16 through 23, whether APs with AIDs corresponding to bits 16 through 23 are sending group-directed traffic. If an AP's AID does not fall within the range of AIDs corresponding to bits 16 through 23, the AP is not sending group-directed traffic to a station associated with the AP or to a surrounding station. For another example, assume that the offset sent by the first AP is 0, the length is 4 bytes, the partial virtual bitmap field is 01100110, and bits 0 through 7 correspond to AP 1 through AP 8 of the AP MLD, respectively. In this case, the first STA can learn that AP 1, AP 4, AP 5, and AP 8 have no group-directed traffic, and AP 2, AP 3, AP 6, and AP 7 have group-directed traffic. Optionally, if bit 0 is predefined to be irrelevant (i.e., bit 0 does not correspond to any AP), bits 1 through 7 correspond to AP 1 through AP 7 of the AP MLD, respectively, and the first STA can learn that AP 1, AP 2, AP 5, and AP 6 have group-directed traffic, and AP 3, AP 4, and AP 7 do not. Case 4.2: This case is applicable to case 3.2 in method 2. In other words, the related content of case 4.2 applies to a scenario where one or more APs of the AP MLD operate in multi-BSSID mode and one AP is a broadcast AP. Optionally, this may also apply to other scenarios. Method A: The group-directed traffic indication information is located in the partial virtual bitmap field, where the partial virtual bitmap field consists of bits starting from byte 0 of the traffic indication virtual bitmap field and ending with byte N2. N2 is a minimum byte number, so the bit values ​​(N2+1)*8 to bit 2007 in the traffic indication virtual bitmap field are all 0, the maximum byte number of the traffic indication virtual bitmap field is 251, and the corresponding maximum AID is 2Λ251 -1=2007. In this case, the offset is 0, and the field length is N2+1+3. Method B: Group-directed traffic indication information is located in the partial virtual bitmap field, where the partial virtual bitmap field consists of bits starting from byte 0 of the traffic indication virtual bitmap field and ending in byte N0-1, and bits starting from byte Ni of the traffic indication virtual bitmap field and ending in byte N2. The maximum number of bytes in the traffic indication virtual bitmap field is 251 bytes, and the corresponding maximum AID is AID 2007. In this case, stations with AIDs corresponding to bits N0*8-1 through Ni*8-1 of the traffic indication virtual bitmap field have no downlink traffic received, or the APs of the corresponding AIDs have no group-directed traffic sent. Similarly, stations with AIDs corresponding to bits N2*8 through 2007 have no downlink traffic received, or the APs of the corresponding AIDs have no group-directed traffic sent. In this case, the group-directed traffic indication information sent by the first AP may include bits starting from byte 0 of the traffic indication virtual bitmap field and ending with byte N0-1, and may include bits starting from byte Ni of the traffic indication virtual bitmap field and ending with byte N2.Furthermore, it is required that if it is NOT an odd number, then Ni is also an odd number; if it is NOT an even number, then Ni is also an even number. In this case, the TIM element offset is (Ni -N0) / 2, and the length field is N0+N2-Nn-4 bytes. Furthermore, the offset is (Ni-N0) / 2. Furthermore, it is assumed that the AP MLD has one AP operating in multi-BSSID mode and that it is a transmitted AP BSSID, and a larger value indicated by a MaxBSSID flag field for each AP operating in multi-BSSID mode and that it is a transmitted AP BSSID is n. In this case, a minimum number of bytes of NO must satisfy N0*8-2nN_AP<8, where N_AP is the number of APs included in the AP MLD or the number of APs minus 1. In this case, the offset is (Ni - N0) / 2 bytes, and the length is N0+N2- Nn-4 bytes. In the aforementioned modalities provided in this application, the methods provided are described separately from the perspectives of the AP MLD and the STA MLD. To implement functions in the methods provided in the aforementioned modalities, the AP MLD and the STA MLD may each include a hardware structure and a software module, implementing the aforementioned functions in the form of the hardware structure, the software module, or a combination of the hardware structure and the software module. A function in the aforementioned modalities may be implemented in the form of the hardware structure, the software module, or a combination of the hardware structure and the software module. The following describes in detail the communication devices in the modalities of this application with reference to Figures 11 through 14.The communication device is an access point in an access point multilink device or a station in a station multilink device. Additionally, the communication device can be a device in an AP MLD or a device in a STA MLD. FIGURE 11 is a schematic block diagram of a communication appliance 100. The communication appliance 100 corresponds to the MLD AP, or any AP of the MLD AP described in any of the multilink group-directed traffic transmission methods above 200 to multilink group-directed traffic transmission method 500. Optionally, the communication appliance 100 is an AP or an appliance of the MLD AP in FIGURE 3(a) to FIGURE 3(c). The 100 communication device includes: a processing unit 101, configured to generate group-directed traffic indication information, wherein the group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic; and a communication unit 102, configured to send the group-directed traffic indication information. It can be learned that, in communication apparatus 100, the group-directed traffic indication information generated by processing unit 101 can indicate whether the access point or another AP has group-directed traffic, and then communication unit 102 sends the group-directed traffic indication information to a station multilink device. In this way, any station on the station multilink device can listen to the group-directed traffic indication information. This improves the flexibility of group-directed traffic notification. Furthermore, if the group-directed traffic indication information indicates whether each AP or multiple APs of the AP MLD have group-directed traffic, any station on the station multilink device can learn whether the multiple APs have group-directed traffic.Therefore, not all stations on the station multilink device need to listen for group-directed traffic on a given link. This reduces the power consumption of the station multilink device. In one implementation, each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD. A bit value indicates whether the AP corresponding to that bit has group-directed traffic. For details, refer to the related content in the modalities shown in Figure 5 and Figure 6 in the preceding method modalities. Furthermore, the group-directed traffic indication information sent by a transceiver may be a bit portion of the group-directed traffic indication information generated by a processor, for example, related content described in Case 2.1 to Case 2.2. Details are not described again herein. In another implementation, group-directed traffic indication information is a bit portion in a partial virtual bitmap field in a TIM traffic indication map element. Alternatively, group-directed traffic indication information is a consecutive bit portion in the partial virtual bitmap field in the TIM traffic indication map element. It can be learned that, in this implementation, the AP MLD assigns AIDs to APs included within the AP MLD, and also uses bits corresponding to the AIDs in the partial virtual bitmap field to separately indicate whether the APs with the AIDs have group-directed traffic. That is, the group-directed traffic indication information is contained in the bits corresponding to the AIDs. For details, refer to the related content shown in Figures 7 through 9 in the preceding method modes. Furthermore, to determine whether the AID corresponding to each AP of the AP MLD is explicitly assigned or implicitly predefined, or to determine the AID corresponding to each AP of the AP MLD when the AP MLD has an AP that operates in a multi-BSSID mode and that is a transmitted AP BSSID, reference is made to Method 1 and Method 2 in the previous method modalities. Details are not described again herein. For example, if the AID corresponding to each AP in the AP MLD is explicitly assigned, in the communication appliance, processing unit 101 is further configured to generate association identifier configuration information, where the association identifier configuration information indicates the association identifier (AID) corresponding to each AP in the AP MLD. The AP's AID corresponds to each bit of the group-directed traffic indication information. Communication unit 102 is further configured to send the association identifier configuration information. Furthermore, in this implementation, because the AIDs corresponding to some bits in the partial virtual bitmap field are station AIDs, there is an association identifier AID corresponding to each bit of the group-directed traffic indication information. IVIA / a / ZUZZ / UI 041 J is different from an AID of a station managed by each AP of the AP MLD. As another example, an AID is predefined corresponding to a first bit of the part of consecutive bits that are in the partial virtual bitmap field and that correspond to the group-directed traffic indication information. As another example, an AID corresponding to a first bit of the consecutive bit portion found in the partial virtual bitmap field in the TIM traffic indication map element and corresponding to group-directed traffic indication information is AID x. x is equal to max{2A(Ni), 2L(N2), ..., 2A(Ny), ..., 2L(Nη)}. n is a quantity of transmitted Basic Service Set Identifier (BSSID) APs in the MLD AP. Ny is a value of a maximum BSSID indication field in a Multiple BSSID element (Multiple BSSID) broadcast by a transmitted BSSID AP. The transmitted BSSID AP is the th BSSID AP transmitted from the MLD AP. In communication unit 100, communication unit 102 is further configured to send a DTIM (Delivery Traffic Indication Map) beacon frame and group-directed traffic following the DTIM beacon frame. When an AP in which communication unit 100 is located has group-directed traffic, communication unit 102 can perform this operation. It should be understood that the communication device 100 in this modality of this application can correspondingly perform the multilink group 200 traffic transmission method and the multilink group 500 traffic transmission method in the modalities of this application. Furthermore, the aforementioned operations or functions of the units in the communication device 100 are used separately to implement the corresponding procedures of the methods in FIGURE 5 and FIGURE 7. For the sake of brevity, details are not described again herein. FIGURE 12 is a schematic block diagram of a communication appliance 200. The communication appliance 200 corresponds to the MLD STA or any STA of the MLD STA, or an STA operating on a primary link of the MLD STA described in any of the multilink group-directed traffic transmission methods above 200 to multilink group-directed traffic transmission method 500. Optionally, the communication appliance 200 is the STA or an appliance of the MLD STA in FIGURE 1. Alternatively, the communication appliance 200 is the STA or an appliance of the MLD STA in FIGURE 3(a) to FIGURE 3(c). The 200 communication device includes: a communication unit 201, configured to receive group-directed traffic indication information from an MLD AP, wherein the group-directed traffic indication information indicates whether one or more APs of the MLD AP have group-directed traffic; and a processing unit 202, configured to determine, based on the group-directed traffic indication information, whether the one or more APs have group-directed traffic. It can be learned that, in communication apparatus 200, processing unit 202 can learn, based on group-directed traffic indication information, whether one or more APs have group-directed traffic. Specifically, communication apparatus 200 can learn not only if an AP associated with the station has group-directed traffic, but also if another AP in the AP MLD has group-directed traffic. This improves the flexibility of group-directed traffic notification. Furthermore, group-directed traffic indication information indicates whether multiple APs, or each AP in the AP MLD, have group-directed traffic. That is, any STA in the STA MLD where communication apparatus 200 is located can learn whether multiple APs, or each AP in the AP MLD, have group-directed traffic.Therefore, not all STAs in the STA MLD where communication device 200 is located need to listen for group-directed traffic from a corresponding AP. This reduces the power consumption of the STA MLD where communication device 200 is located. In one implementation, a STA corresponding to communication apparatus 200 is a station of the MLD STA operating on the primary link. Thus, communication unit 201 receives group-directed traffic indication information from the MLD AP specifically as follows: Communication unit 201 listens for group-directed traffic indication information from an MLD AP on the primary link. In this implementation, another STA of the MLD STA does not periodically listen for group-directed traffic indication information, thereby reducing the MLD STA's power consumption. For the manner in which the communication apparatus 200 determines the primary link, reference is made to the description in the previous method modalities. No further details are described herein. In one implementation, communication unit 201 is further configured to receive a DTIM traffic delivery indication map beacon frame and group-directed traffic following the DTIM beacon frame. In this implementation, when processing unit 202 determines that an AP corresponding to processing unit 202 has group-directed traffic, communication unit 201 can perform this operation. In one implementation, each bit of the group-directed traffic indication information corresponds to each AP in the AP MLD. A bit value indicates whether the AP corresponding to that bit has group-directed traffic. For details, refer to the related content in the modes shown in Figure 5 and Figure 6 in the method modes that IVIA / a / ZUZZ / UI 04 1 J above. Furthermore, the group-directed traffic indication information sent by a transceiver may be a bit portion of the group-directed traffic indication information generated by a processor, for example, related content described in Case 2.1 to Case 2.2. Details are not described again herein. In another implementation, group-directed traffic indication information is a bit portion in a partial virtual bitmap field in a TIM traffic indication map element. Alternatively, group-directed traffic indication information is a consecutive bit portion in the partial virtual bitmap field in the TIM traffic indication map element. It can be learned that, in this implementation, the AP MLD assigns AIDs to APs included within the AP MLD, and also uses bits corresponding to the AIDs in the partial virtual bitmap field to separately indicate whether the APs with the AIDs have group-directed traffic. That is, the group-directed traffic indication information is contained in the bits corresponding to the AIDs. For details, refer to the related content shown in Figures 7 through 9 in the preceding method modes. Furthermore, to determine whether the AID corresponding to each AP of the AP MLD is explicitly assigned or implicitly predefined, or to determine the AID corresponding to each AP of the AP MLD when the AP MLD has an AP that operates in a multi-BSSID mode and that is a transmitted AP BSSID, reference is made to Method 1 and Method 2 in the previous method modalities. Details are not described again herein. For example, if the AID corresponding to each AP of the AP MLD is explicitly assigned in communication appliance 200, communication unit 201 is further configured to receive association identifier configuration information, where the association identifier configuration information indicates the association identifier (AID) corresponding to each AP of the AP MLD. The AP AID corresponds to each bit of the group-directed traffic indication information. Processing unit 202 is further configured to determine, based on the association identifier configuration information, the AID corresponding to the AP of the AP MLD. Furthermore, in this implementation, because the AIDs corresponding to some bits in the partial virtual bitmap field are station AIDs, an association identifier AID corresponding to each bit of the group-directed traffic indication information is different from an AID of a station managed by each AP of the AP MLD. As another example, an AID is predefined corresponding to a first bit of the part of consecutive bits that are in the partial virtual bitmap field and that correspond to the group-directed traffic indication information. IVIA / a / ZUZZ / UI 04 1 J As another example, an AID corresponding to a first bit of the consecutive bit portion found in the partial virtual bitmap field in the TIM traffic indication map element and corresponding to group-directed traffic indication information is AID x. x is equal to max{2A(Ni), 2A(N2), ..., 2A(Ny), ..., 2L(NΠ)}. n is the number of APs that transmit a BSSID on the MLD AP, and Ny is the value of a max service set identifier BSSID indication field in a multiple service set identifier BSSID element broadcast by a transmitted AP BSSID. The transmitted AP BSSID is the yth AP BSSID transmitted from the MLD AP. It should be understood that the communication apparatus 200 in this modality of this application can correspondingly perform the multilink group 200 traffic transmission method and the multilink group 500 traffic transmission method in the modalities of this application. Furthermore, the aforementioned operations or functions of the units in the communication apparatus 200 are used separately to implement corresponding procedures of an STA or the first STA of the MLD STA in the methods shown in Figure 5 and Figure 7. For the sake of brevity, details are not described again herein. Figure 13 is a schematic block diagram of a communication device 300. In one implementation, the communication device 300 corresponds to the MLD AP, or any AP of the MLD AP described in any of the multilink group-directed traffic transmission methods 200 preceding the multilink group-directed traffic transmission method 500. Optionally, the communication device 300 may be an AP or an MLD AP device in Figure 1. Alternatively, the communication device 300 is the AP or an MLD AP device in Figure 3(a) through Figure 3(c). Optionally, the communication device 300 is a chip, system-on-a-chip, processor, or similar device that implements the preceding method modes. The communication device 300 may be configured to implement the methods described in the preceding method modes. For details, refer to the description in the preceding method modes. In another implementation, communication apparatus 300 corresponds to the MLD STA or any STA of the MLD STA, or an STA operating on a primary link of the MLD STA described in any of the preceding multilink group-directed traffic transmission methods 200 through 500. Optionally, communication apparatus 300 is the STA or an apparatus of the MLD STA shown in Figure 1. Alternatively, communication apparatus 300 is the STA or an apparatus of the MLD STA shown in Figure 3(a) through Figure 3(c). Optionally, communication apparatus 300 is a chip, system-on-a-chip, processor, or the like that implements the preceding method modalities. Communication apparatus 300 can be configured to implement the methods described in the preceding method modalities. For details, refer to the description in the preceding method modalities. The communication apparatus 300 may include one or more processors 301. The processor 301 may be a general-purpose processor, a dedicated processor, or similar. For example, the processor 301 may be a baseband processor or a central processing unit. The baseband processor may be configured to process a communication protocol and communication data, and the central processing unit may be configured to control a communication apparatus (for example, a base station, a baseband chip, a terminal, a terminal chip, a DU, or a CU) to execute a computer program or to process computer program data. The communication apparatus 300 may further include a transceiver 305. The transceiver 305 may be referred to as a transceiver unit, a transceiver machine, a transceiver circuit, or similarly, and is configured to implement a transceive function. The transceiver 305 may include a receiver and a transmitter. The receiver may be referred to as a receiver circuit, or similarly, and is configured to implement a receive function. The transmitter may be referred to as a transmitter circuit, or similarly, and is configured to implement a send function. Optionally, the communication apparatus 300 may further include an antenna 306. Optionally, the communication device 300 may include one or more memories 302, and memory 302 may store instructions 304. Instructions 304 may be a computer program. The computer program may be executed on the communication device 300, enabling the communication device 300 to perform the methods described in the preceding method modalities. Optionally, memory 302 may also store data. The communication device 300 and memory 302 may be separate or integrated. The communication apparatus 300 is configured to implement an AP function from the AP MLD in the multilink group traffic transmission method 200 to the multilink group traffic transmission method 500 in the preceding method modes. The 301 processor can be configured to perform step S201 in FIGURE 5, step S401 in FIGURE 7, and optional implementations of an AID corresponding to an AP in method 1 and method 2, for example, generating association identifier configuration information about a multi-link group traffic transmission method. The 305 transceiver is configured to perform step S202 in FIGURE 5, step S402 in FIGURE 7, and optional implementations of an AID corresponding to an AP in method 1 and method 2, e.g., sending association identifier configuration information. The communication apparatus 300 is configured to implement a function of an STA from the STA MLD in the multilink group traffic transmission method 200 to the multilink group traffic transmission method 500 in the preceding method modes. The 305 transceiver is configured to perform step S203 in FIGURE 5, step S403 in FIGURE 7, and optional implementations of an AID corresponding to an AP in method 1 and method 2, e.g., receiving association identifier configuration information. The 301 processor can be configured to perform step S204 in FIGURE 5 and step S404 in FIGURE 7 and optional implementations to determine the AP AID in the above method 1 and method 2, for example, determining the association identifier of each AP of the AP MLD based on the association identifier configuration information. In one implementation, the 301 processor may include a transceiver configured to implement a receive function and a send function. For example, the transceiver may be a transceiver circuit, an interface, or an interface circuit. The transceiver circuit, interface, or interface circuit configured to implement the receive and send functions may be separate or integrated together. The transceiver circuit, interface, or interface circuit may be configured to read and write code / data. Alternatively, the transceiver circuit, interface, or interface circuit may be configured to transmit or transfer a signal. In one implementation, processor 301 can store instructions 303. The instructions can be a computer program. Computer program 303 is executed on processor 301, enabling communication apparatus 300 to perform the methods described in the preceding method modalities. Computer program 303 can be fixed to processor 301, and in this case, processor 301 can be implemented in hardware. In one implementation, the communication apparatus 300 may include a circuit, and the circuit may implement a transmit, receive, or communicate function in the methods described above. The processor and transceiver described in this application may be implemented on an integrated circuit (IC), an analog IC, a radio frequency integrated circuit (RFIC), a mixed-signal IC, an application-specific integrated circuit (ASIC), or a printed circuit board (PCB), an electronic device, and the like. The processor and transceiver may be fabricated using various IC technologies, for example, a semiconductor The group information generated by the processor (IVIA / a / ZUZZ / UI 04 1 J) can indicate whether an access point or another AP has group-directed traffic. The transceiver then sends this group-directed traffic indication information to a station multilink device. This allows any station on the station multilink device to listen for the group-directed traffic indication. This improves the flexibility of group-directed traffic notification. Furthermore, if the group-directed traffic indication information shows whether each AP or multiple APs on the MLD AP have group-directed traffic, any station on the station multilink device can learn if the multiple APs have group-directed traffic. Therefore, not all stations on the station multilink device need to listen for group-directed traffic on a given link. This reduces the power consumption of the station multilink device. Optionally, the chip can also perform the function of an AP from the AP MLD in the multilink group 200 traffic transmission method to the multilink group 500 traffic transmission method. Details are not described again herein. The chip is configured to implement a function of an STA from the STA MLD in the multilink group 200 traffic transmission method to the multilink group 500 traffic transmission method in the preceding method modes. In one implementation, interface 402 is configured to receive group-directed traffic indication information from the AP MLD, where the group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic. Optionally, the 401 processor is configured to determine, based on group-directed traffic indication information, whether one or more APs have group-directed traffic. It can be learned that, on the chip, the processor can learn, based on group-directed traffic indication information, whether one or more access points (APs) are carrying group-directed traffic. Specifically, the chip can learn not only if an AP associated with the station is carrying group-directed traffic, but also if another AP within the MLD AP network is carrying group-directed traffic. This enhances the flexibility of group-directed traffic notification. Furthermore, the group-directed traffic indication information shows whether multiple APs, or each AP within the MLD AP network, are carrying group-directed traffic. In other words, any station within the MLD AP network where the chip is located can learn whether multiple APs, or each AP within the MLD AP network, are carrying group-directed traffic. Therefore, not all stations within the MLD AP network where the chip is located need to monitor for group-directed traffic.This reduces the power consumption of the STA MLD in which the chip is located. Optionally, the chip can also perform the function of an STA from the STA MLD in the multilink group 200 traffic transmission method to the multilink group 500 traffic transmission method. Details are not described again herein. A person skilled in the art may further understand that several illustrative logic blocks and steps listed in the modalities of this request can be implemented using electronic hardware, computer software, or a combination thereof. Whether the functions are implemented using hardware or software depends on the particular application and a design requirement of the entire system. A person skilled in the art may use various methods to implement the described functions for each particular application, but it is not necessary to consider that the implementation goes beyond the scope of the modalities of this request. This application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer-readable storage medium is executed by a computer, a function of any of the above method modalities is implemented. This application also provides a computer program product. When the computer program product is executed by a computer, the functions of any of the above method modalities are implemented. All or some of the above modalities can be implemented using software, hardware, firmware, or any combination thereof. When software is used to implement the modalities, all or part of the modalities can be implemented in the form of a computer program product. The computer program product includes one or more computer programs. When the computer program is loaded and executed on a computer, the procedures or functions according to the modalities of this application are generated, in whole or in part. The computer can be a general-purpose computer, a dedicated computer, a computer network, or other programmable devices. The computer program can be stored on a computer-readable storage medium or transmitted from one computer-readable storage medium to another.For example, a computer program can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired connection (e.g., coaxial cable, fiber optic cable, or digital subscriber line [DSL]) or wirelessly (e.g., infrared, radio, or microwave). The computer-readable storage medium can be any usable medium accessible by the computer, or a data storage device, such as a server or data center, that integrates one or more usable media. The usable medium can be magnetic (e.g., a floppy disk, hard drive, or magnetic tape), optical (e.g., a high-density digital video disc [DVD]), semiconductor (e.g., a solid-state drive [SSD]), or similar. A person skilled in the art may understand that the first, second, and several reference numbers in this application are distinguished simply for convenient description, and are not used to limit a scope of modalities of this application, and also indicate a sequence. “The ‘at least one’ in this application may alternatively be described as one or more, and ‘multiple’ means two, three, four, or more. This is not limited in this application. In the forms of this application, first, second, third, A, B, ‘C’, ‘D’, and the like are used to distinguish between the technical features described by them. There is no chronological order or size order among the technical features described by first, second, third, A, B, C, and D.” The mappings shown in the tables in this application can be configured or predefined. The values ​​in the tables are examples only, and other values ​​can be configured. This application does not limit this. When configuring a mapping between the information and each parameter, you do not need to configure all the mappings shown in the tables. For example, in the tables in this application, the mappings shown in some rows may not be configured. As another example, appropriate manipulations and adjustments such as splitting and merging can be performed based on the tables above.The parameter names shown in the headings of the preceding tables can be alternatively named and understood by a communication device. Similarly, the parameter values ​​or representations can also be understood by the communication device. During the implementation of the preceding tables, other data structures can be used, such as an array, queue, container, stack, linear table, pointer, linked list, tree, graph, structure, class, or hash table. Predefine in this application can be understood as define, predefine, store, pre-store, pre-negotiate, pre-configure, solidify or pre-burn. A person skilled in the art may be aware that, in combination with the examples described in the modalities disclosed in this specification, the algorithm units and steps can be implemented using electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on the particular applications and the design constraints of the technical solutions. A person skilled in the art may use different methods to implement the described functions for each particular application, but it is not necessary to consider that the implementation goes beyond the scope of this request. An expert in the technique can clearly understand that, for the purpose of a convenient and brief description, for a detailed operating process of the preceding system, apparatus and unit, reference is made to a corresponding process in the preceding modalities of method, and no details are described again herein. The descriptions above are merely specific implementations of this application; however, they are not intended to limit the scope of protection of this application. Any variation or replacement readily visualized by a person skilled in the art within the technical scope disclosed in this application should fall within the scope of protection of this application. Therefore, the scope of protection of this application should be subject to the scope of protection of the claims.

Claims

1. A multi-link group-directed traffic transmission method, characterized in that the method comprises: generating, by means of a first access point AP of a multi-link access point device (MLD), group-directed traffic indication information, wherein the group-directed traffic indication information indicates whether one or more APs of the MLD have group-directed traffic; and sending, by means of the first AP, the group-directed traffic indication information.

2. The method according to claim 1, characterized in that the group-directed traffic indication information indicates whether each AP of the AP MLD has group-directed traffic.

3. The method according to claim 1 or 2, characterized in that each bit of the group-directed traffic indication information corresponds to each AP of the AP MLD; and a bit value indicates whether the AP corresponding to the bit has group-directed traffic.

4. The method according to any of claims 1 to 3, characterized in that the Group-Directed Traffic Indication Information comprises a bit portion in a partial virtual bitmap field in a TIM traffic indication map element, wherein the bit portion in the partial virtual bitmap field in the TIM element indicates whether each AP of the MLD AP other than the first AP has group-directed traffic.

5. The method according to claim 4, characterized in that the bit portion in the partial virtual bitmap field in the TIM traffic indication map element are consecutive bits.

6. The method in accordance with any of claims 1 to 5, characterized in that an association identifier (AID) corresponding to each bit of the group-directed traffic indication information is different from an AID of a station managed by each AP of the AP MLD.

7. The method according to any of claims 1 to 3, characterized in that the group-directed traffic indication information comprises bit 0 of a bitmap control field in a TIM element, and bit 0 is used to indicate whether the first AP has group-directed traffic.

8. The method according to claim 1 or 2, characterized in that in the group-directed traffic indication information, a number of bits corresponding to each AP MLD is a fixed number of bits, and one bit in the fixed number of bits except for one bit corresponding to an AP is set to 0 by default.

9. The method according to claim 4 or 5, characterized in that in the group-directed traffic indication information, in the partial virtual bitmap field in the TIM element, AIDs corresponding to bits corresponding to an AP MLD are successively assigned in ascending or descending order of link identifiers of all APs except the first AP of the AP MLD.

10. A multilink group-directed traffic transmission method, characterized in that the method comprises: receiving, by means of a first STA station of a multilink STA MLD device, group-directed traffic indication information from an AP MLD, wherein the group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic.

11. The method according to claim 10, characterized in that the reception, by means of a first STA of an MLD STA, of group-directed traffic indication information from an MLD AP comprises: listening, by means of the first STA of the MLD STA, to group-directed traffic indication information from an AP of the MLD AP.

12. The method according to claim 10 or 11, characterized in that the group-directed traffic indication information is carried in a DTIM delivery traffic indication map beacon frame.

13. The method according to claim 12, characterized in that the method further comprises: receiving, by means of the first STA, group-directed traffic after the DTIM beacon frame.

14. The method according to any of claims 10 to 12, characterized in that the group-directed traffic indication information comprises a bit portion in a partial virtual bitmap field in a TIM traffic indication map element, wherein the bit portion in the partial virtual bitmap field in the TIM element indicates whether each AP of the MLD AP other than the first AP has group-directed traffic.

15. The method according to claim 14, characterized in that the bit portion in the partial virtual bitmap field in the TIM traffic indication map element are consecutive bits.

16. The method according to any of claims 10 to 12, characterized in that the group-directed traffic indication information comprises bit 0 of a bitmap control field in a TIM element, and bit 0 is used to indicate whether the first AP has group-directed traffic.

17. The method according to claim 10 or 11, characterized in that in the group-directed traffic indication information, a number of bits corresponding to each AP MLD is a fixed number of bits, and one bit in the fixed number of bits except for one bit corresponding to an AP is set to 0 by default.

18. The method according to claim 14 or 15, characterized in that in the group-directed traffic indication information, in the partial virtual bitmap field in the TIM element, AIDs corresponding to bits corresponding to an AP MLD are successively assigned in ascending or descending order of link identifiers of all APs except the first AP of the AP MLD.

19. An access point of an access point multilink device, characterized in that the access point of the access point multilink device comprises a transceiver and a processor, wherein the processor is configured to generate group-directed traffic indication information, wherein the group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic; and the transceiver is configured to send the group-directed traffic indication information.

20. The access point of the multi-link access point device according to claim 19, characterized in that the group-directed traffic indication information indicates whether each AP of the AP MLD has group-directed traffic.

21. The access point of the multi-link access point device according to claim 19 or 20, characterized in that each bit of the group-directed traffic indication information corresponds to each AP of the AP MLD; and a bit value indicates whether the AP corresponding to the bit has group-directed traffic.

22. The access point of the access point multilink device according to any of claims 19 to 21, characterized in that the group-directed traffic indication information is a bit part in a partial virtual bitmap field in a TIM traffic indication map element.

23. The access point of the multi-link access point device according to any of claims 19 to 22, characterized in that the group-directed traffic indication information is a portion of consecutive bits in the partial virtual bitmap field in the TIM traffic indication map element.

24. The access point of the multi-link access point device according to any of claims 19 to 23, characterized in that an association identifier (AID) corresponding to each bit of the group-directed traffic indication information is different from an AID of a station managed by each AP of the AP MLD.

25. The access point of the access point multilink device according to any of claims 19 to 21, characterized in that the group-directed traffic indication information comprises bit 0 of a bitmap control field in a TIM element, and bit 0 is used to indicate whether the first AP has group-directed traffic.

26. The access point of the access point multilink device according to claim 19 or 20, characterized in that in the group-directed traffic indication information, a number of bits corresponding to each AP MLD is a fixed number of bits, and one bit in the fixed number of bits except one bit corresponding to an AP is set to 0 by default.

27. The access point of the multi-link access point device according to claim 22 or 23, characterized in that in the group-directed traffic indication information, in the partial virtual bitmap field in the TIM element, AIDs corresponding to bits corresponding to an AP MLD are successively assigned in ascending or descending order of link identifiers of all APs except the first AP of the AP MLD.

28. A station of a station multilink device, characterized in that the station of the station multilink device comprises a transceiver; and the transceiver is configured to receive group-directed traffic indication information from an AP MLD, wherein the group-directed traffic indication information indicates whether one or more APs of the AP MLD have group-directed traffic.

29. The station multilink device station according to claim 28, characterized in that the station multilink device station operates on a primary link; and that the transceiver receives group-directed traffic indication information from an MLD AP is specifically: the transceiver is configured to listen, on the primary link, for group-directed traffic indication information from an MLD AP.

30. The station of the station multilink device according to claim 28 or 29, characterized in that the group-directed traffic indication information is carried in a Delivery Traffic Indication Map (DTIM) beacon frame.

31. The station of the station multilink device according to claim 30, characterized in that the transceiver is further configured to receive group-directed traffic after the DTIM beacon frame.

32. The station of the station multilink device according to any of claims 28 to 30, characterized in that the group-directed traffic indication information comprises a bit portion in a partial virtual bitmap field in a TIM traffic indication map element, wherein the bit portion in the partial virtual bitmap field in the TIM element indicates whether each AP of the MLD AP other than the first AP has group-directed traffic.

33. The station of the station multilink device according to claim 32, characterized in that the part of bits in the partial virtual bitmap field in the TIM traffic indication map element are consecutive bits.

34. The station of the station multilink device according to any of claims 28 to 30, characterized in that the group-directed traffic indication information comprises bit 0 of a bitmap control field in a TIM element, and bit 0 is used to indicate whether the first AP has group-directed traffic.

35. The station of the station multilink device according to claim 28 or 29, characterized in that in the group-directed traffic indication information, a number of bits corresponding to each AP MLD is a fixed number of bits, and one bit in the fixed number of bits except one bit corresponding to an AP is set to 0 by default.

36. The station of the station multi-link device according to claim 32 or 33, characterized in that in the group-directed traffic indication information, in the partial virtual bitmap field in the TIM element, AIDs corresponding to bits corresponding to an AP MLD are successively assigned in ascending or descending order of link identifiers of all APs except the first AP of the AP MLD.

37. A chip system, characterized in that it comprises at least one processor and one interface, wherein the processor is configured to generate group-directed traffic indication information, wherein the group-directed traffic indication information indicates whether one or more APs of an MLD AP have group-directed traffic; and the interface is configured to send the group-directed traffic indication information. MA / a / ZUZZ / UI 04 1J 38. A chip system, characterized in that it comprises at least one processor and an interface, wherein the interface is configured to receive group-directed traffic indication information from an MLD AP, wherein the group-directed traffic indication information indicates whether one or more APs of the MLD AP have group-directed traffic.

39. A computer-readable storage medium configured to store a computer program, characterized in that when the computer program is executed on a computer, the computer is activated to perform the method according to any one of claims 1 to 9, or to perform the method according to any one of claims 10 to 18.

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