Patent Publication Number: US-2022232492-A1

Title: Data Processing Method and Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Patent Application No. 16/537,219, filed on Aug. 9, 2019, which is a continuation of International Application No. PCT/CN2018/094577, filed on Jul. 4, 2018. The International Application claims priority to Chinese Patent Application No. 201710537942.7, filed on Jul. 4, 2017. All of the afore-mentioned patent applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of communications technologies, and in particular, to a data processing method and apparatus. 
     BACKGROUND 
     In a wireless local area network (WLAN), starting from 802.11a/g, an orthogonal frequency division multiplexing (OFDM) modulation scheme is used for a data packet (also referred to as a physical layer protocol data unit (PPDU)), and an entire transmission bandwidth is allocated to one station (STA). 
     In 802.11ax, orthogonal frequency division multiple access (OFDMA) is further introduced based on OFDM, so that an entire bandwidth may be allocated to a plurality of STAs. 802.11ax defines four data packet types, including a single user (SU) data packet, an extended range single user (ER SU) data packet, a trigger-based (TB) data packet, and a multi-user (MU) data packet. 
     In a data transmission process in the wireless local area network, to resolve a problem of an excessively fast channel change caused by a Doppler scenario (a high-speed movement scenario), a middle preamble (Midamble) is inserted into a data field in the PPDU. To be specific, a midamble is inserted always every M symbols. 
     However, such a manner of inserting a midamble always every M symbols is difficult to accommodate different Doppler scenarios and data modulation and coding schemes. 
     SUMMARY 
     Embodiments of the present invention provide a data processing method and apparatus, to resolve a problem that an existing manner of inserting a midamble always every M symbols is difficult to accommodate different Doppler scenarios and data modulation and coding schemes. 
     According to a first aspect, an embodiment of the present invention provides a data processing method, including: generating a physical layer protocol data unit PPDU, where the PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and sending the PPDU. The insertion frequency of the middle preamble in the data field is indicated by using a specified field in the preamble. In this way, in different scenarios, the middle preamble may be inserted into the data field at different frequency, thereby reducing overheads of an inserted pilot and improving data transmission performance. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the SR field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the MCS field or the SIGB MCS field. 
     In a possible implementation, the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an MCS in the MCS field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the DCM field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using the combination of the SIGB MCS field and the SIGB DCM field. 
     In a possible implementation, the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an NSTS in the NSTS field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the NSTS field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     According to a second aspect, an embodiment of the present invention provides a data processing method, including: generating a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and sending the trigger frame. The insertion frequency of the middle preamble in the data field is indicated by using a specified field in the trigger frame. Based on the trigger frame, the TB PPDU may be triggered and the insertion frequency of the middle preamble in the data field in the TB PPDU may be indicated. In this way, in different scenarios, the middle preamble may be inserted into the data field at different frequency, thereby reducing overheads of an inserted pilot and improving data transmission performance in a PPDU transmission process. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, an HE-SIG-A field, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field, a combination of an MCS field and a DCM field, an RU allocation field, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and to indicate that the trigger-based TB PPDU uses a middle preamble structure, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the HE-SIG-A field. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, a midamble frequency indication field is added to the Trigger Dependent Common Info field in the trigger frame, and the insertion frequency of the middle preamble is indicated by using the midamble frequency indication field. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the MCS field. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the DCM field. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the SS allocation field. 
     In a possible implementation, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the combination of the SS allocation field and the MCS field. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1 to indicate that the TB PPDU uses a midamble structure, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the HE-SIG-A field in a common field. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1, a midamble frequency indication field is added to the Trigger Dependent Common Info field in the trigger frame in a common field, and the insertion frequency of the middle preamble is indicated by using the midamble frequency indication field. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the MCS field. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the DCM field. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1, and the SS allocation field is used to indicate the insertion frequency of the middle preamble while indicating an SS parameter. 
     In a possible implementation, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the combination of the SS allocation field and the MCS field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the HE-SIG-A field. 
     In a possible implementation, the insertion frequency of the middle preamble is indicated by using a reserved value of a Reserved field in a User Info field. 
     According to a third aspect, an embodiment of the present invention provides a data processing method, including: generating a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and sending the MAC frame. The insertion frequency of the middle preamble is indicated by using a specified field in the MAC frame. Based on the MAC frame, the TB PPDU may be triggered and the insertion frequency of the middle preamble in the data field in the TB PPDU may be indicated. In this way, in different scenarios, the middle preamble may be inserted into the data field at different frequency, thereby reducing overheads of an inserted pilot and improving data transmission performance in a PPDU transmission process. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     In a possible implementation, the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using a reserved value of the RU allocation field. 
     In a possible implementation, the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the UL MCS field. 
     In a possible implementation, the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the Reserved field. 
     According to a fourth aspect, an embodiment of the present invention provides a data processing method, including: receiving a physical layer protocol data unit PPDU. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     According to a fifth aspect, an embodiment of the present invention provides a data processing method, including: receiving a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the trigger frame includes information used to indicate an insertion frequency of a middle preamble in a data field in the PPDU, and the PPDU includes the data field and the middle preamble field; generating the PPDU based on the trigger frame; and sending the PPDU. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     According to a sixth aspect, an embodiment of the present invention provides a data processing method, including: receiving a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and generating and sending the PPDU based on the MAC frame. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     According to a seventh aspect, an embodiment of the present invention provides a data processing apparatus, including: a PPDU generation unit, configured to generate a physical layer protocol data unit PPDU, where the PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a sending unit, configured to send the PPDU. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     According to an eighth aspect, an embodiment of the present invention provides a data processing apparatus, including: a trigger frame generation unit, configured to generate a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a sending unit, configured to send the trigger frame. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     According to a ninth aspect, an embodiment of the present invention provides a data processing apparatus, including: a MAC frame generation unit, configured to generate a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a sending unit, configured to send the MAC frame. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     According to a tenth aspect, an embodiment of the present invention provides a data processing apparatus, including a receiving unit, configured to receive a physical layer protocol data unit PPDU. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     According to an eleventh aspect, an embodiment of the present invention provides a data processing apparatus, including: a receiving unit, configured to receive a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the trigger frame includes information used to indicate an insertion frequency of a middle preamble in a data field in the PPDU, and the PPDU includes the data field and the middle preamble field; a PPDU generation unit, configured to generate the PPDU based on the trigger frame; and a sending unit, configured to send the PPDU. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     According to a twelfth aspect, an embodiment of the present invention provides a data processing apparatus, including: a receiving unit, configured to receive a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; a PPDU generation unit, configured to generate the PPDU based on the MAC frame; and a sending unit, configured to send the PPDU. 
     In a possible implementation, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     According to a thirteenth aspect, an embodiment of the present invention provides a computer-readable storage medium. The computer-readable storage medium stores an instruction. When running on a computer, the instruction enables the computer to perform the methods according to the foregoing aspects. 
     According to a fourteenth aspect, an embodiment of the present invention provides a computer program product including an instruction. When running on a computer, the computer program product enables the computer to perform the methods according to the foregoing aspects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an application scenario according to an embodiment of the present invention; 
         FIG. 2  is a schematic structural diagram of an MU PPDU in the prior art; 
         FIG. 3  is a schematic diagram of a frame structure of a trigger frame in the prior art; 
         FIG. 4 a    is a schematic structural diagram of an SU/ER SU PPDU according to an embodiment of the present invention; 
         FIG. 4 b    is another schematic structural diagram of an SU/ER SU PPDU according to an embodiment of the present invention; 
         FIG. 4 c    is a schematic structural diagram of an MU PPDU according to an embodiment of the present invention; 
         FIG. 4 d    is another schematic structural diagram of an MU PPDU according to an embodiment of the present invention; 
         FIG. 5  is an interaction diagram of a data processing method according to an embodiment of the present invention; 
         FIG. 6  is a schematic diagram of a communications system according to an embodiment of the present invention; 
         FIG. 7  is a structural diagram of a data processing apparatus according to an embodiment of the present invention; 
         FIG. 8  is a structural diagram of hardware of a data processing apparatus according to an embodiment of the present invention; 
         FIG. 9  is a structural diagram of another data processing apparatus according to an embodiment of the present invention; 
         FIG. 10  is a structural diagram of hardware of another data processing apparatus according to an embodiment of the present invention; 
         FIG. 11  is an interaction diagram of a data processing method according to an embodiment of the present invention; 
         FIG. 12  is a schematic diagram of a first frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 13  is a schematic diagram of a second frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 14  is a schematic diagram of a third frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 15  is a schematic diagram of a fourth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 16  is a schematic diagram of a fifth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 17  is a schematic diagram of a sixth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 18  is a schematic diagram of a seventh frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 19  is a schematic diagram of an eighth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 20  is a schematic diagram of a ninth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 21  is a schematic diagram of a tenth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 22  is a schematic diagram of an eleventh frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 23  is a schematic diagram of a twelfth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 24  is a schematic diagram of a thirteenth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 25  is a schematic diagram of a fourteenth frame structure of a trigger frame according to an embodiment of the present invention; 
         FIG. 26  is a structural diagram of a data processing apparatus according to an embodiment of the present invention; 
         FIG. 27  is a structural diagram of hardware of a data processing apparatus according to an embodiment of the present invention; 
         FIG. 28  is a structural diagram of another data processing apparatus according to an embodiment of the present invention; 
         FIG. 29  is a structural diagram of hardware of another data processing apparatus according to an embodiment of the present invention; 
         FIG. 30  is an interaction diagram of a data processing method according to an embodiment of the present invention; 
         FIG. 31  is a schematic structural diagram of an HTC field in a MAC frame in the prior art; 
         FIG. 32  is a first schematic structural diagram of an HTC field in a MAC frame according to an embodiment of the present invention; 
         FIG. 33  is a second schematic structural diagram of an HTC field in a MAC frame according to an embodiment of the present invention; 
         FIG. 34  is a third schematic structural diagram of an HTC field in a MAC frame according to an embodiment of the present invention; 
         FIG. 35  is a structural diagram of a data processing apparatus according to an embodiment of the present invention; 
         FIG. 36  is a structural diagram of hardware of a data processing apparatus according to an embodiment of the present invention; 
         FIG. 37  is a structural diagram of another data processing apparatus according to an embodiment of the present invention; and 
         FIG. 38  is a structural diagram of hardware of another data processing apparatus according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following clearly describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. 
     To facilitate understanding of the embodiments of the present invention, the following further explains the specific embodiments with reference to the accompanying drawings, and the embodiments do not constitute a limitation on the embodiments of the present invention. 
     The embodiments of the present invention are mainly applied to data communication between one node and one or more other nodes, and in a data communication process, a Doppler scenario or a high-speed movement scenario occurs. For example, communication between an AP and a STA shown in  FIG. 1  is also applicable between an AP and an AP or between a STA and a STA. The data communication in  FIG. 1  includes two types of data: uplink data (data sent by the STA to the AP) and downlink data (data sent by the AP to the STA). An 802.11ax standard defines four data packet structures. For uplink and downlink single-user data transmission, an SU PPDU or an ER SU PPDU is usually used for transmission. For downlink multi-user data transmission, an MU PPDU is used for transmission. For uplink multi-user data transmission, first, the AP needs to send a trigger frame to the STA, and then the STA sends a TB PPDU to the AP based on the trigger frame.  FIG. 2  shows a form of an MU PPDU in the prior art. As shown in  FIG. 2 , the MU PPDU includes a preamble field, a data field Data, a middle preamble field Midamble, and a data packet extension field PE. 
     In a less desirable implementation, to resolve a problem of an excessively fast channel change caused by the Doppler scenario (the high-speed movement scenario), a middle preamble field (Midamble) is usually inserted into the data field Data always every M symbols. The middle preamble field (Midamble field) may be a combination of HE-STF and HE-LTF or only HE-LTF. In a data receiving process, a midamble may enable a receive end to re-estimate a channel after receiving data Data of every M symbols, and then continue to receive data Data of next M symbols, so as to effectively resolve the problem of the excessively fast channel change caused by Doppler. In the MU PPDU shown in  FIG. 2 , two midambles are inserted. 
     The preamble field includes a legacy preamble (L-Preamble), a repeated legacy signal field (RL-SIG), a high efficient signal field A (HE-SIG-A), a high efficient signal field B (HE-SIG-B), a high efficient short training field (HE-STF), and a high efficient long training field (HE-LTF). It should be noted that, HE in the foregoing fields represents a reference number of the 802.11ax standard. In the solutions of the present invention, these fields may alternatively use another reference number to represent signal fields in a PPDU in another standard, such as next generation (NG) and very high efficient (VHE). 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Field 
                 Full Name 
                 Meaning 
               
               
                   
               
             
            
               
                 UL/DL 
                 Uplink/ 
                 Used to indicate whether a data 
               
               
                   
                 Downlink 
                 packet is used for uplink 
               
               
                   
                   
                 transmission or downlink 
               
               
                   
                   
                 transmission 
               
               
                 SIGB MCS 
                 HE-SIG-B 
                 High efficient signal field B 
               
               
                   
                 Modulation and 
                 modulation and coding scheme 
               
               
                   
                 Coding Scheme 
                   
               
               
                 SIGB DCM 
                 HE-SIG-B  
                 Used to indicate whether dual 
               
               
                   
                 Dual Coding 
                 carrier modulation is used for a 
               
               
                   
                 Modulation 
                 high efficient signal field B 
               
               
                 BSS color 
                 Basic Service 
                 Used to identify a color of a 
               
               
                   
                 Set Color 
                 basic service set 
               
               
                 Spatial reuse 
                   
                 Used to indicate a parameter 
               
               
                   
                   
                 related to spatial reuse 
               
               
                 Bandwidth 
                   
                 Used to indicate a bandwidth 
               
               
                   
                   
                 of a data packet 
               
               
                 Number of HE- 
                 MU MIMO: 
                 Used to indicate a quantity of 
               
               
                 SIG-B symbols or 
                 Multiple User 
                 symbols in a high efficient signal 
               
               
                 MU-MIMO users 
                 Multiple Input 
                 field B or a quantity of users for 
               
               
                   
                 Multiple Output 
                 multi-user multiple-input 
               
               
                   
                   
                 multiple-output 
               
               
                 SIGB compression 
                   
                 Used to indicate whether a high 
               
               
                   
                   
                 efficient signal field B is 
               
               
                   
                   
                 compressed 
               
               
                 GI + LTF size 
                 Guard  
                 Used to indicate a 
               
               
                   
                 Interval + High 
                 guard interval and a size of a 
               
               
                   
                 Efficient 
                 high efficient long 
               
               
                   
                 Long Training 
                 training field 
               
               
                   
                 Field size 
                   
               
               
                 Doppler 
                   
                 Used to indicate whether 
               
               
                   
                   
                 a Doppler mode is used for 
               
               
                   
                   
                 a data packet 
               
               
                 TXOP 
                 Transmit 
                 Used to indicate a transmit 
               
               
                   
                 Opportunity 
                 opportunity 
               
               
                 Reserved 
                   
                 Reserved bit, which is set to 1 
               
               
                 Number of HE-LTF 
                   
                 Used to indicate a quantity of 
               
               
                 Symbols 
                   
                 symbols in a high efficient long 
               
               
                   
                   
                 training field 
               
               
                 LDPC Extra 
                 LDPC: Low 
                 Used to indicate whether an 
               
               
                 Symbol Segment 
                 Density Parity 
                 extra symbol segment 
               
               
                   
                 Code 
                 exists in a case of a 
               
               
                   
                   
                 low density parity code 
               
               
                 STBC 
                 Space Time 
                 Indicate whether space time 
               
               
                   
                 Block Code 
                 coding is used 
               
               
                 Pre-FEC Padding 
                 FEC: forward 
                 Used to indicate a padding factor 
               
               
                 Factor 
                 error control 
                 before forward error control 
               
               
                 PE Disambiguity 
                 PE: 
                 Data packet extension 
               
               
                   
                 Packet Extension 
                 disambiguation bit 
               
               
                 CRC 
                 Cyclic 
                 Cyclic redundancy code 
               
               
                   
                 redundancy code 
                   
               
               
                 Tail 
                   
                 Tail bit 
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, Table 1 shows fields included in the HE-SIG-A in the MU PPDU. The fields included in the HE-SIG-A include common information, for example, identification information of a basic service set, indication information of a transmit opportunity, indication information of a spatial reuse parameter, and allocation information of some resources on a physical layer. The allocation information of some resources on the physical layer includes related indication information of a size of the HE-LTF, a quantity of HE-LTFs, a size of a guard interval, an LDPC, and an STBC, and related information of the HE-SIG-B. The related information of the HE-SIG-B includes an MCS and a length of the HE-SIG-B. 
     The HE-SIG-B following the HE-SIG-A includes a common field and a User Info field. The common field is used to indicate resource unit allocation (RU Allocation). The RU allocation is used to indicate allocation of all resource units in frequency domain and a quantity of STAs in each resource unit. In 802.11ax, if the quantity of STAs in the resource unit is 1, a non-MU-MIMO mode is used, and if the quantity of STAs in the resource unit is greater than 1, a MU-MIMO mode is used. Depending on whether MU-MIMO is used for a resource unit, two different indication methods are used for the User Info field in the HE-SIG-B. 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 STA-ID 
                 STA Identifier 
                 The station identifier is usually 
               
               
                   
                   
                 used to indicate an 
               
               
                   
                   
                 association identifier of a STA. 
               
               
                 NSTS 
                 Number of Space 
                 Used to indicate a quantity of 
               
               
                   
                 Time Stream 
                 space time streams of a single user 
               
               
                 Tx 
                 Transmit 
                 Used to indicate whether a 
               
               
                 Beamforming 
                 Beamforming 
                 beamforming technology is used 
               
               
                 MCS 
                 Modulation and 
                 Modulation and 
               
               
                   
                 Coding Scheme 
                 coding scheme 
               
               
                 DCM 
                 Dual Coding 
                 Dual carrier modulation 
               
               
                   
                 Modulation 
                   
               
               
                 Coding 
                   
                 Indicate a coding type 
               
               
                   
               
            
           
         
       
     
     Table 2 shows fields included in the User Info field in the HE-SIG-B in a case of the non-MU-MIMO mode. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
             
            
               
                   
                 STA-ID 
                 STA Identifier 
                 The station identifier is 
               
               
                   
                   
                   
                 usually used to indicate an 
               
               
                   
                   
                   
                 association identifier of a STA. 
               
               
                   
                 Spatial 
                 Number of 
                 A table is used to indicate 
               
               
                   
                 Configuration 
                 Spatial Stream 
                 a quantity of space time 
               
               
                   
                   
                   
                 streams of an MU-MIMO unit. 
               
               
                   
                 MCS 
                 Modulation and 
                 Modulation and coding scheme 
               
               
                   
                   
                 Coding Scheme 
                   
               
               
                   
                 DCM 
                 Dual Coding 
                 Dual carrier modulation 
               
               
                   
                   
                 Modulation 
                   
               
               
                   
                 Coding 
                   
                 Indicate a coding type 
               
               
                   
                   
               
            
           
         
       
     
     Table 3 shows fields included in the User Info field in the HE-SIG-B in a case of the MU-MIMO mode. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Doppler Condition/MCS 
                 MCS 0   
                 MCS 1   
                 MCS 3   
                 MCS 5   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 60 Km/h 
                 50 
                 30 
                 15 
                 8 
               
               
                   
                 on 2nd/3rd tap 
                   
                   
                   
                   
               
               
                   
                 60 Km/h 
                 30 
                 20 
                 10 
                 5 
               
               
                   
                 on all taps 
                   
                   
                   
                   
               
               
                   
                 30 Km/h 
                 60 
                 40 
                 20 
                 10 
               
               
                   
                 on all taps 
                   
                   
                   
                   
               
               
                   
                 15 Km/h 
                 120 
                 80 
                 40 
                 20 
               
               
                   
                 on all taps 
                   
                   
                   
                   
               
               
                   
                   
               
            
           
         
       
     
     Table 4 shows suggested midamble insertion frequency in cases of different rates and different MCSs. It can be learned from Table 4 that in different Doppler scenarios and MCSs, a manner of inserting a midamble always every M symbols cannot be applied to different scenarios. 
     
       
         
           
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Field 
                 Full Name 
                 Meaning in Chinese 
               
               
                   
               
             
            
               
                 Format 
                   
                 Used to indicate whether a format 
               
               
                   
                   
                 of a data packet is an SU format or 
               
               
                   
                   
                 a TB format 
               
               
                 Beam change 
                   
                 Indicate whether a beam change 
               
               
                   
                   
                 is used 
               
               
                 UL/DL 
                 Uplink/Downlink 
                 Used to indicate whether a data 
               
               
                   
                   
                 packet is used for uplink 
               
               
                   
                   
                 transmission or downlink 
               
               
                   
                   
                 transmission 
               
               
                 MCS 
                 Modulation and  
                 Modulation and coding scheme 
               
               
                   
                 Coding Scheme 
                 for a data part 
               
               
                 DCM 
                 Dual Coding  
                 Used to indicate whether dual 
               
               
                   
                 Modulation 
                 carrier modulation is used for a 
               
               
                   
                   
                 data part 
               
               
                 BSS color 
                 Basic Service  
                 Used to identify a color of a basic 
               
               
                   
                 Set Color 
                 service set 
               
               
                 Reserved 
                   
                 Reserved bit, which is set to 1 
               
               
                 Spatial reuse 
                   
                 Used to indicate a parameter 
               
               
                   
                   
                 related to spatial reuse 
               
               
                 Bandwidth 
                   
                 Used to indicate a bandwidth of a 
               
               
                   
                   
                 data packet 
               
               
                 GI + LTF size 
                 Guard Interval +  
                 Used to indicate a guard interval 
               
               
                   
                 High Efficient Long 
                 and a size of a high efficient long 
               
               
                   
                 Training Field size 
                 training field 
               
               
                 NSTS 
                 Number of Space  
                 Used to indicate a quantity of 
               
               
                   
                 Time Stream 
                 space time streams 
               
               
                 TXOP 
                 Transmit  
                 Used to indicate a transmit 
               
               
                   
                 Opportunity 
                 opportunity 
               
               
                 Coding 
                   
                 Indicate a coding type 
               
               
                 LDPC Extra  
                 LDPC: Low Density  
                 Used to indicate whether an extra 
               
               
                 Symbol  
                 Parity Code 
                 symbol segment exists in a case of 
               
               
                 Segment 
                   
                 a low density parity code 
               
               
                 STBC 
                 Space Time  
                 Indicate whether space time 
               
               
                   
                 Block Code 
                 coding is used 
               
               
                 Pre-FEC  
                 FEC: forward  
                 Used to indicate a padding factor 
               
               
                 Padding 
                 error control 
                 before forward error control 
               
               
                 Factor 
                   
                   
               
               
                 PE  
                 PE: Packet  
                 Data packet extension 
               
               
                 Disambiguity 
                 Extension 
                 disambiguation bit 
               
               
                 Reserved 
                   
                 Reserved bit, which is set to 1 
               
               
                 Doppler 
                   
                 Used to indicate whether a 
               
               
                   
                   
                 Doppler mode is used for a data 
               
               
                   
                   
                 packet 
               
               
                 CRC 
                 Cyclic redundancy  
                 Cyclic redundancy code 
               
               
                   
                 code 
                   
               
               
                 Tail 
                   
                 Tail bit 
               
               
                   
               
            
           
         
       
     
     Comparing with a format of the MU PPDU, formats of the SU PPDU, the ER SU PPDU, and the TB PPDU lack the HE-SIG-B field. For example, Table 5 shows fields included in the HE-SIG-A in the SU PPDU or the ER SU PPDU. For details, refer to the foregoing descriptions of the MU PPDU, and details are not described herein again. 
       FIG. 3  is a schematic diagram of a frame structure of a trigger frame in the prior art. For uplink multi-user transmission, first, an AP sends a trigger frame to a plurality of STAs. The trigger frame may indicate resource for performing uplink transmission by a STA. After receiving the trigger frame, the STA performs uplink multi-user transmission based on the resource indication information in the trigger frame. The uplink multi-user transmission is performed based on the trigger frame. Therefore, a PPDU sent by the STA is referred to as a trigger-based data packet structure (TB PPDU). The frame structure of the trigger frame defined in 802.11ax is shown in  FIG. 3 , and includes a common field and a User Info field. The common field includes a trigger frame type used to indicate trigger frames of different subtypes and carrier sensing (CS) required used to indicate whether the STA needs to perform carrier sensing after receiving a trigger frame. Data is sent when a channel is idle. Depending on different trigger frame types, common information or station information based on the trigger frame type carries corresponding indication information. The User Info field includes RU Allocation, MCS, DCM, and SS Allocation. 
     The embodiments of the present invention provide a data processing method. The method relates to PPDU transmission. The method is applicable to downlink data transmission (for example, the AP transmits data to the STA in  FIG. 1 ) and uplink single user transmission (for example, one STA transmits data to the AP in  FIG. 1 ), and more specifically, to transmission of an HE SU PPDU, an HE ER SU PPDU, and an HE MU SU PPDU. Specifically, the following content is included: 
       FIG. 5  is an interaction diagram of a data processing method according to an embodiment of the present invention. The method is applicable to a Doppler scenario or a high-speed movement scenario. A STA generates a PPDU (a Doppler bit field in a preamble in the PPDU needs to be set to 1 in a PPDU generation process).  FIG. 4 a    is a schematic structural diagram of an SU/ER SU PPDU according to an embodiment of the present invention. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble field in the PPDU includes information used to indicate an insertion frequency of the middle preamble field inserted in the data field in the PPDU. In this embodiment of the present invention, a midamble is inserted every M symbols (herein, the M symbols do not include the midamble) in the data field. In the PPDU generation process, the STA first generates a preamble field part of the PPDU, and generates a data field part in the foregoing manner of inserting a midamble every M symbols in the data field, so as to generate the entire PPDU. The STA sends the generated PPDU to an AP. The AP receives the PPDU sent by the STA. When the AP receives the PPDU, the AP first receives the preamble field part of the PPDU, next obtains information M of the insertion frequency of the middle preamble field inserted in the data field based on the preamble field part, and then receives the data field part based on M. Specifically, the AP first receives data of M symbols in the data field based on HE-STF and HE-LTF in the last part of the preamble field, and then re-estimates a channel based on the midamble (HE-LTF or a combination of HE-STF and HE-LTF), and further receives data of next M symbols. In this way, the AP receives the data field in the entire PPDU. 
       FIG. 4 b    is another schematic structural diagram of an SU/ER SU PPDU according to an embodiment of the present invention. The PPDU includes a preamble field, a data field, and a middle preamble field. In the data field Data, for every M symbols (herein, the M symbols include a midamble), that is, the M symbols include data and a midamble, the midamble has two formats: HE-LTF or a combination of HE-STF and HE-LTF. HE-LTF is one symbol, and a quantity of symbol in HE-STF is determined based on the preamble. In this embodiment, it is assumed that HE-STF is N symbols. When the midamble is HE-LTF, the M symbols include data of M-1 symbols and HE-LTF of one symbol. When the midamble is a combination of HE-STF and HE-LTF, the M symbols include data of M-N-1 symbols, HE-STF of N symbols, and HE-LTF of one symbol. 
       FIG. 4 c    is a schematic structural diagram of an MU PPDU according to an embodiment of the present invention. For the PPDU, a midamble is inserted every M symbols (herein, the M symbols do not include the midamble) in the data field Data. For details, refer to related descriptions of  FIG. 4   a,  and details are not described herein again. 
       FIG. 4 d    is another schematic structural diagram of an MU PPDU according to an embodiment of the present invention. For the PPDU, a midamble is inserted every M symbols (herein, the M symbols include the midamble) in the data field Data. For details, refer to related descriptions of  FIG. 4   b,  and details are not described herein again. 
     It should be noted that in this embodiment of the present invention, insertion of the middle preamble into the data field Data based on symbols is described. Herein, in addition to symbol-based division, the middle preamble may be inserted into the data field according to another rule, and details are not further described in this embodiment. 
     The information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in a spatial reuse (SR for short below) field in the HE-SIG-A (the HE SU PPDU, the HE ER SU PPDU, and the HE MU SU PPDU). For details, refer to Table 6. In an 802.11ax standard, the SR field includes four bits, and may indicate 16 cases (SR values are 0 to 15). When an SR value is o, it indicates SRP_DISALLOW, representing that SR transmission based on a spatial reuse parameter (Spatial Reuse Parameter, SRP) is prohibited. When SR values are 1 to 12, the values are reserved values. When an SR value is 13, it indicates SR_RESTRICTED, representing that SR transmission is restricted. When an SR value is 14, it indicates SR_DELAY, representing that SR transmission is delayed. When an SR value is 15, it indicates SRP_AND_NON-SRG_OBSS-PD_PROHIBITED, representing that overlapping basic service set (OBSS)-data packet detection for SRP and a non-SR group (Group) is prohibited. 
     
       
         
           
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 SR Value 
                 Meaning 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 SRP_DISALLOW 
               
               
                 1-12 
                 Reserved 
               
               
                 13 
                 SR_RESTRICTED 
               
               
                 14 
                 SR_DELAY 
               
               
                 15 
                 SRP_AND_NON-SRG_OBSS-PD_PROHIBITED 
               
               
                   
               
            
           
         
       
     
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using one or more of reserved values of the SR field. That is, the insertion frequency of the middle preamble is indicated by using one or more of the reserved values (1 to 12) of the SR field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 SR Value 
                 Meaning 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 SRP_DISALLOW 
               
               
                 1 
                 M = M1 
               
               
                 2 
                 M = M2 
               
               
                 3-12 
                 Reserved 
               
               
                 13 
                 SR_RESTRICTED 
               
               
                 14 
                 SR_DELAY 
               
               
                 15 
                 SRP_AND_NON-SRG_OBSS-PD_PROHIBITED 
               
               
                   
               
            
           
         
       
     
     For example, Table 7 is an example of the foregoing indication method. The SR value 1 indicates M (the insertion frequency of the middle preamble in the data field, that is, a middle preamble is inserted every M symbols)=M1. The SR value 2 indicates M=M2. For example, M1=5, and M2=10. A specific quantity of values in the SR values 1 to 12 that are used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is implicitly indicated by using a parameter used to indicate SR in SR. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 SR Value 
                 Meaning 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 SRP_DISALLOW, M = M1 
               
               
                 1 
                 SRP_DISALLOW, M = M2 
               
               
                 2 
                 M = M1 
               
               
                 3 
                 M = M2 
               
               
                 4-9 
                 Reserved 
               
               
                 10 
                 SR_RESTRICTED, M = M2 
               
               
                 11 
                 SR_DELAY, M = M2 
               
               
                 12 
                 SRP_AND_NON-SRG_OBSS-PD_PROHIBITED, M = M2 
               
               
                 13 
                 SR_RESTRICTED, M = M1 
               
               
                 14 
                 SR_DELAY, M = M1 
               
               
                 15 
                 SRP_AND_NON-SRG_OBSS-PD_PROHIBITED, M = M1 
               
               
                   
               
            
           
         
       
     
     For example, Table 8 is an example of the foregoing indication method. When the SR value is 0, 13, 14, or 15, the SR value indicates M=M1 while indicating a corresponding SR parameter. Four values are randomly selected from the SR values 1 to 12, and the four values each are used to indicate M while indicating a corresponding parameter M=when the SR values are 0, 13, 14, and 15. For example, when the SR value is 1, it indicates SRP_DISALLOW and M=M2. The SR value 2 indicates M=M1. The SR value  3  indicates M=M2. When the SR value is 2 or 3 only M is indicated, and the SR parameter is not indicated. When the SR value is 10, it indicates SR_RESTRICTED and M=M2. When the SR value is 11, it indicates SR_DELAY and M=M2. When the SR value is 12, it indicates SRP_AND_NON-SRG_OBSS-PD_PROHIBITED and M=M2. A specific quantity of values in the SR values 0 to 15 that are used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     In this embodiment of the present invention, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in one of the following fields: an MCS field in the HE-SIG-A (the HE SU PPDU), an MCS field in the HE-SIG-B (the HE MU SU PPDU), or a SIGB MCS field in the HE-SIG-A (the HE MU SU PPDU). The MCS field includes four bits, and may indicate 16 cases (MCS values are 0 to 15). Currently, 802.11ax supports 12 MCSs: MCS0 to MCS11. MCS12 to MCS15 are reserved values. For details, refer to Table 9. 
     
       
         
           
               
               
             
               
                 TABLE 9 
               
               
                   
               
               
                 MCS Value 
                 Meaning 
               
               
                   
               
             
            
               
                  0-11 
                 Indicate MCS0 to MCS11 respectively 
               
               
                 12-15 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using one or more of reserved values of the MCS field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                 MCS Value 
                 Meaning 
               
               
                   
               
             
            
               
                  0-11 
                 Indicate MCS0 to MCS11 respectively 
               
               
                 12 
                 M = M1 
               
               
                 13 
                 M = M2 
               
               
                 14-15 
                 Reserved 
               
               
                   
               
            
           
         
       
     
     For example, Table 10 is an example of the foregoing indication method. When the MCS values are 0 to 11, the MCS values indicate corresponding MCS parameters. One or more values are randomly selected from the MCS values 12 to 15 to indicate M. For example, the MCS value 12 indicates M=M1, and the MCS value 13 indicates M=M2. A specific quantity of values in the MCS values 12 to 15 that are used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is implicitly indicated by using a parameter used to indicate an MCS in the MCS field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
             
               
                 TABLE 11 
               
               
                   
               
               
                 MCS Value 
                 Meaning 
               
               
                   
               
             
            
               
                 0-11 
                 Indicate MCS0 to MCS11 respectively, and M = M1 
               
               
                 12 
                 MCS0, M = M2 
               
               
                 13 
                 MCS1, M = M2 
               
               
                 14 
                 MCS2, M = M2 
               
               
                 15 
                 MCS3, M = M2 
               
               
                   
               
            
           
         
       
     
     For example, Table 11 is an example of the foregoing indication method. When the MCS values are 0 to 11, the MCS values indicate M=M1 while indicating corresponding MCS parameters. One or more values are randomly selected from the MCS values 12 to 15 to indicate M. For example, when the MCS value is 12, it indicates MCS0 and M=M2. When the MCS value is 13, it indicates MCS1 and M=M2. When the MCS value is 14, it indicates MCS2 and M=M2. When the MCS value is 15, it indicates MCS3 and M=M2. A specific quantity of values in the MCS values 12 to 15 that are used to indicate MCS0 to MCS11, M, and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     It should be noted that the MCS field in the HE-SIG-A in the HE ER SU PPDU has only MCS0 to MCS2 used. One or more of the reserved values 3 to 15 of the MCS field may be used to indicate M. For details, refer to the foregoing descriptions of the HE SU PPDU. For brevity of description, details are not described herein again. 
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using one or more of the reserved values of the SIGB MCS field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
             
               
                 TABLE 12 
               
               
                   
               
               
                 SIGB MCS Value 
                 Meaning 
               
               
                   
               
             
            
               
                 0-5 
                 Indicate MCS0 to MCS5 respectively 
               
               
                 6 
                 M = M1 
               
               
                 7 
                 M = M2 
               
               
                   
               
            
           
         
       
     
     For example, Table 12 is an example of the foregoing indication method. The HE-SIG-A of the HE MU PPDU further includes SIGB MCS and SIGB DCM. SIG-B MCS has three bits, and may indicate eight cases. SIG-B MCS values 0 to  5  are used. SIG-B MCS values 6 and  7  are reserved values, and may be used to indicate M. The SIGB MCS values 0 to 5 indicate corresponding MCS parameters. One or two values are selected from the MCS values 6 and 7 to indicate M. For example, the SIGB MCS value 6 indicates M=M1. For example, the SIGB MCS value 7 indicates M=M2. A specific quantity of values in the SIGB MCS values 6 and 7 that are used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     In this embodiment of the present invention, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in one of the following fields: a combination of an MCS field and a DCM field in the HE-SIG-A (the HE SU PPDU or the HE ER SU PPDU), a combination of an MCS field and a DCM field in the HE-SIG-B (the HE MU SU PPDU), or a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A (the HE MU SU PPDU). In 802.11ax, the DCM field/the SIGB DCM field is applicable to only MCS0, MCS1, MCS3, and MCS4. Other MCS values or SIGB MCS values cannot be indicated simultaneously. An unsupported combination may be escaped to indicate M. 
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using the combination of the MCS field and the DCM field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
               
             
               
                 TABLE 13 
               
               
                   
               
               
                 MCS Value 
                 DCM Value 
                 Meaning 
               
               
                   
               
             
            
               
                 0, 1, 3, 4 
                 0/1 
                 Indicate MCS0, MCS1, MCS3,  
               
               
                   
                   
                 and MCS4 respectively for which 
               
               
                   
                   
                 DCM is not used/used 
               
               
                 2, 5-11 
                 0 
                 Indicate MCS2 and MCS5 to  
               
               
                   
                   
                 MCS11 for which DCM is not used 
               
               
                 2 
                 1 
                 Indicate M = M1 
               
               
                 5 
                 1 
                 Indicate M = M2 
               
               
                 . . . 
                 . . . 
                 . . . 
               
               
                 11 
                 1 
                 Indicate M = M8 
               
               
                 Other 
                   
                 Reserved 
               
               
                   
               
            
           
         
       
     
     For example, Table 13 is an example of the foregoing indication method. (MCS0, DCM0/MCS1, DCM0/MCS3, DCM0/MCS4, DCM0) indicate MCS0, MCS1, MCS3, and MCS4 for which dual carrier modulation is not used. (MCS0, DCM1/MCS1, DCM1/MCS3, DCM1/MCS4, DCM1) indicate MCS0, MCS1, MCS3, and MCS4 for which dual carrier modulation is used. (MCS2/MCS5 to MCS11, DCM0) indicate MC2 and MCS5 to MCS11 for which dual carrier modulation is not used. (MCS2, DCM1) indicates M=M1. (MCS5, DCM1) only indicates M=M2 (and does not indicate any other meaning than this). A specific quantity of values in combinations of MCS values and DCM values (MC2/MCS5 to MCS11, DCM1) that are used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using the combination of the SIGB MCS field and the SIGB DCM field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
               
             
               
                 TABLE 14 
               
               
                   
               
               
                 SIGB MCS Value 
                 SIGB DCM Value 
                 Meaning 
               
               
                   
               
             
            
               
                 0, 1, 3, 4 
                 0/1 
                 Indicate MCS0, MCS1, MCS3,  
               
               
                   
                   
                 and MCS4 respectively for 
               
               
                   
                   
                 which DCM is not used/used 
               
               
                 2, 5-7 
                 0 
                 Indicate MCS2 and MCS5 for  
               
               
                   
                   
                 which DCM is not used 
               
               
                 2, 5-7 
                 1 
                 Indicate M 
               
               
                 Other 
                   
                 Reserved 
               
               
                   
               
            
           
         
       
     
     For example, Table 14 is an example of the foregoing indication method. (SIGB MCS0, SIGB DCM0/SIGB MCS1, SIGB DCM0/SIGB MCS3, SIGB DCM0/SIGB MCS4, SIGB DCM0) indicate SIGB MCS0, SIGB MCS1, SIGB MCS3, and SIGB MCS4 for which dual carrier modulation is not used. (SIGB MCS0, SIGB DCM1/SIGB MCS1, SIGB DCM1/SIGB MCS3, SIGB DCM1/SIGB MCS4, SIGB DCM1) indicates SIGB MCS0, SIGB MCS1, SIGB MCS3, and SIGB MCS4 for which dual carrier modulation is used. (SIGB MC2/SIGB MCS5 to SIGB MCS7, SIGB DCM0) indicate SIGB MC2 and SIGB MCS5 to SIGB MCS7 for which dual carrier modulation is not used. (SIGB MC2/SIGB MCS5 to SIGB MCS7, SIGB DCM0) indicate M. A specific quantity of values in combinations of SIGB MCS values and SIGB DCM values (SIGB MC2/SIGB MCS5 to SIGB MCS7, SIGB DCM1) that are used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     In this embodiment of the present invention, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in an NSTS field in the HE-SIG-B (the HE MU SU PPDU). The NSTS field includes three bits, and indicates one space time stream (STS) to eight STSs. For details, refer to Table 15. 
     
       
         
           
               
               
             
               
                 TABLE 15 
               
               
                   
               
               
                 NSTS 
                 Corresponding Quantity of Space Time Streams 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 A quantity of space time streams is equal to 1. 
               
               
                 1 
                 A quantity of space time streams is equal to 2. 
               
               
                 2 
                 A quantity of space time streams is equal to 3. 
               
               
                 3 
                 A quantity of space time streams is equal to 4. 
               
               
                 4 
                 A quantity of space time streams is equal to 5. 
               
               
                 5 
                 A quantity of space time streams is equal to 6. 
               
               
                 6 
                 A quantity of space time streams is equal to 7. 
               
               
                 7 
                 A quantity of space time streams is equal to 8. 
               
               
                   
               
            
           
         
       
     
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is implicitly indicated by using a parameter used to indicate an NSTS in the NSTS field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
             
               
                 TABLE 16 
               
               
                   
               
               
                 NSTS 
                 Corresponding Quantity of Space Time Streams and M 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 A quantity of space time streams is equal to 1, and M = M1. 
               
               
                 1 
                 A quantity of space time streams is equal to 2, and M = M1. 
               
               
                 2 
                 A quantity of space time streams is equal to 1, and M = M2. 
               
               
                 3 
                 A quantity of space time streams is equal to 2, and M = M2. 
               
               
                 4 
                 A quantity of space time streams is equal to 1, and M = M3. 
               
               
                 5 
                 A quantity of space time streams is equal to 2, and M = M3. 
               
               
                 6 
                 A quantity of space time streams is equal to 1, and M = M4. 
               
               
                 7 
                 A quantity of space time streams is equal to 2, and M = M4. 
               
               
                   
               
            
           
         
       
     
     For example, Table 16 is an example of the foregoing indication method. The NSTS value 0 indicates that the quantity of space time streams is equal to 1 and M=M1. The NSTS value 1 indicates that the quantity of space time streams is equal to 2 and M=M1. The NSTS value 2 indicates that the quantity of space time streams is equal to 1 and M=M2. The NSTS value 3 indicates that the quantity of space time streams is equal to 1 and M=M2. The NSTS value 4 indicates that the quantity of space time streams is equal to 1 and M=M3. The NSTS value 5 indicates that the quantity of space time streams is equal to 3 and M=M3. The NSTS value 6 indicates that the quantity of space time streams is equal to 1 and M=M4. The NSTS value 7 indicates that the quantity of space time streams is equal to 2 and M=M4. 
     In the Doppler scenario or the high-speed movement scenario, a channel condition is relatively poor. Usually, the scenario is a light of sight scenario (LOS), and does not allow a relatively large quantity of space time streams. In this embodiment, the quantity of space time streams may be limited to 1 or 2, and four types of M are limited. In addition, a plurality of cases such as four quantities (1, 2, 3 or 4) of space time streams and two types of M (M1 or M2) may alternatively be set. The quantity of space time streams and M may be set according to a specific Doppler scenario or high-speed movement scenario. This is not specifically limited in this embodiment. 
     In this embodiment of the present invention, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in a combination of an MCS field and an NSTS field. The combination of the MCS field and the NSTS field may be a function of an MCS value and an NSTS value. In addition, the MCS value and the NSTS value have an association mapping table. It should be noted that in this embodiment, an NSTS and an MCS respectively indicate a quantity of space time streams and a modulation and coding scheme used for the data part. In addition, a corresponding mapping relationship is used to implicitly indicate the insertion frequency of the middle preamble. 
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using the combination of the MCS field and the NSTS field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     When data is downlink data (for example, the AP transmits data to the STA in  FIG. 1 ) and the Doppler scenario or the high-speed movement scenario occurs, the Doppler field in the HE-SIG-A is set to 1 (that is, a transmission scenario of the PPDU is the Doppler scenario or the high-speed movement scenario). The function of the MCS value and the NSTS value is used to indicate the insertion frequency of the middle preamble. For example, a function of an MCS value and an NSTS value in the HE SU PPDU, the HE ER SU PPDU, or the HE MU SU PPDU is used to indicate the insertion frequency of the middle preamble in the corresponding data field. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 17 
               
               
                   
               
               
                 NSTS/MCS 
                 0 
                 1 
                 2 
                 3 
                 4 
                 5 
               
               
                   
               
             
            
               
                 0 
                 M1 
                 M1 
                 M1 
                 M1 
                 M2 
                 M2 
               
               
                 1 
                 M1 
                 M1 
                 M1 
                 M2 
                 M2 
                 M2 
               
               
                 2 
                 M1 
                 M1 
                 M2 
                 M2 
                 M2 
                 M2 
               
               
                   
               
            
           
         
       
     
     For example, Table 17 is an example of a mapping table in the foregoing indication method. (NSTS0, MCS0) indicates M=M1, (NSTS0, MCS1) indicates M=M1, (NSTS0, MCS2) indicates M=M1, (NSTS0, MCS3) indicates M=M1, (NSTS0, MCS4) indicates M=M2, (NSTS0, MCS5) indicates M=M2, and so on. A specific function relationship between an MCS value and an NSTS value used to indicate M and a specific numerical value of M may be set according to a specific Doppler scenario or high-speed movement scenario, and this embodiment imposes no specific limitation thereon. 
     In this embodiment of the present invention, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in an RU allocation field in the HE-SIG-B (the HE MU SU PPDU). The RU allocation field includes a plurality of reserved parts. For details, refer to Table 18. 
     
       
         
           
               
               
               
             
               
                 TABLE 18 
               
               
                   
               
               
                 8-bit RU Allocation Indication 
                 RU Distribution 
                 Quantity of Entries 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 . . . 
               
            
           
           
               
               
               
            
               
                 01110100-01110111 
                 Reserved value 
                 4 
               
               
                 01111000-01111111 
                 Reserved value 
                 8 
               
            
           
           
               
            
               
                 . . . 
               
            
           
           
               
               
               
            
               
                 11100000-11111111 
                 Reserved value 
                 32 
               
               
                   
               
            
           
         
       
     
     Optionally, in an example of the present invention, the insertion frequency of the middle preamble in the data field in the PPDU is indicated by using a reserved value of the RU allocation field. This may be applicable to a downlink data transmission solution (for example, the AP transmits data to the STA in  FIG. 1 ). 
     
       
         
           
               
               
               
               
             
               
                 TABLE 19 
               
               
                   
               
               
                 8-bit RU Allocation 
                   
                   
                 Quantity 
               
               
                 Indication 
                 RU Distribution 
                 M 
                 of Entries 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 . . . 
               
            
           
           
               
               
               
               
               
            
               
                 01110100 
                 242 
                 242 
                 M = M1 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 01110101 
                 242 
                 242 
                 242 
                 242 
                 M = M1 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 01110110 
                 242 
                 242 
                 242 
                 242 
                 242 
                 242 
                 242 
                 242 
                 M = M1 
                 1 
               
            
           
           
               
               
               
               
            
               
                 01110111 
                 Reserved value 
                   
                 1 
               
            
           
           
               
               
               
               
               
            
               
                 01111000 
                 242 
                 242 
                 M = M2 
                 1 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 01111001 
                 242 
                 242 
                 242 
                 242 
                 M = M2 
                 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 01111010 
                 242 
                 242 
                 242 
                 242 
                 242 
                 242 
                 242 
                 242 
                 M = M2 
                 1 
               
            
           
           
               
               
               
               
            
               
                 01111011-01111111 
                 Reserved value 
                   
                 8 
               
            
           
           
               
            
               
                 . . . 
               
            
           
           
               
               
               
               
            
               
                 11100000-11111111 
                 Reserved value 
                   
                 32 
               
               
                   
               
            
           
         
       
     
     For example, Table 19 is an example of the foregoing indication method. If the RU Allocation is 01110100, (242, 242) means that an entire bandwidth is divided into two resource blocks each having 242 subcarriers, and M=M1 is indicated. If the RU Allocation is 01111000, (242, 242) means that an entire bandwidth is divided into two resource blocks each having 242 subcarriers, and M=M2 is indicated. 
     According to the data transmission method provided in this embodiment of the present invention, the insertion frequency of the middle preamble in the data field is indicated by using a specified field in the preamble, so as to generate and send the PPDU. In this way, in different scenarios, the middle preamble may be inserted into the data field at different frequency, thereby reducing overheads of an inserted pilot and improving data transmission performance. 
       FIG. 6  is a schematic diagram of a communications system according to an embodiment of the present invention. The communications system may include at least one network device  100  (only one network device is shown) and one or more terminal devices  200  connected to the network device  100 . 
     The network device  100  may be a device that can communicate with the terminal device  200 . The network device  100  may be any device having a wireless transmission and receiving function. The network device  100  includes, but is not limited to, a base station (for example, a NodeB, an evolved NodeB, eNodeB, a base station in a fifth-generation (5G) communications system, a base station or a network device in a future communications system, or an access node, a wireless relay node, or a wireless backhaul node in a Wi-Fi system) or the like. Alternatively, the network device  100  may be a radio controller in a cloud radio access network (CRAN) scenario. Alternatively, the network device  100  may be a network device in a 5G network or a network device in a future evolved network, and may also be a wearable device, an in-vehicle device, or the like. Alternatively, the network device  100  may be a small cell, a transmission reference point (transmission reference point, TRP), or the like. Certainly, this application is not limited thereto. 
     The terminal device  200  is a device having a wireless transmission and receiving function. The terminal device  200  may be deployed on land, including an indoor or outdoor device, a handheld device, a wearable device, or an in-vehicle device, may be deployed at a water surface (for example, in a ship), or may be deployed in air (for example, on an airplane, in a balloon, or on a satellite). The terminal device may be a mobile phone, a tablet computer (Pad), a computer having a wireless transmission and receiving function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal related to industrial control, a wireless terminal related to self-driving, a wireless terminal related to remote medical, a wireless terminal related to a smart grid, a wireless terminal related to transportation safety, a wireless terminal related to a smart city, a wireless terminal related to a smart home, or the like. This embodiment of this application imposes no limitation on an application scenario. The terminal device sometimes may also be referred to as user equipment (UE), an access terminal device, a UE unit, a UE station, a mobile station, a mobile console, a remote station, a remote terminal device, a mobile device, a UE terminal device, a terminal device, a wireless communications device, a UE agent, a UE apparatus, or the like. 
     It should be noted that in this embodiment of the present invention, terms “system” and “network” may be used interchangeably. “A plurality of” refers to two or more. In view of this, “the plurality of” in this embodiment of the present invention may also be understood as “at least two”. The term “and/or” describes an association relationship for describing associated objects and represents that three relationships may exist. For example, A and/or B may represent the following three cases: Only A exists, both A and B exist, and only B exists. In addition, the character “/” usually indicates an “or” relationship between the associated objects unless specified otherwise. 
     The foregoing describes the solutions provided in the embodiments of the present invention mainly from the perspective of interaction between the STA and the AP. It may be understood that to implement the foregoing functions, the STA/AP or the like includes corresponding hardware structures and/or software modules for implementing the various functions. A person of ordinary skill in the art should be easily aware that, with reference to the units and algorithm steps in the examples described in the embodiments disclosed in this specification, the present invention may be implemented by hardware or a combination of hardware and computer software. Whether a function is performed by hardware or computer software driving hardware depends on particular applications and design constraint conditions 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 should not be considered that the implementation goes beyond the scope of the present invention. 
     In the embodiments of the present invention, functional unit division may be performed on the STA and the AP according to the examples of the foregoing method. For example, various functional units may be divided according to the corresponding functions, or two or more functions may be integrated into one processing unit. The integrated unit may be implemented in a form of hardware, or may be implemented in a form of a software functional unit. It should be noted that the unit division in the embodiments of the present invention is an example, and is merely logical function division. There may be another division manner in an actual implementation. 
     When an integrated unit is used,  FIG. 7  is a possible schematic structural diagram of a data processing apparatus in the foregoing embodiments. As shown in  FIG. 7 , a data processing apparatus  700  may include a PPDU generation unit  701  and a sending unit  702 . 
     The PPDU generation unit  701  is configured to generate a physical layer protocol data unit PPDU. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. The sending unit  702  is configured to send the PPDU. 
     The data processing apparatus  700  in this embodiment has a function of the STA in  FIG. 5 , and may implement an action completed by the STA in  FIG. 5 , so as to achieve a technical effect of the corresponding data processing method. For details, refer to related descriptions of  FIG. 5 . For brevity of description, details are not described herein again. 
       FIG. 8  is a schematic structural diagram of a data processing apparatus (for example, a communications apparatus such as an access point, a base station, a station, or a terminal, or a chip in the foregoing communications apparatus) according to an implementation of the present invention. As shown in  FIG. 8 , a data processing apparatus  800  may be implemented by using a bus  801  as a general bus system structure. Depending on specific application and an overall design constraint condition of the data processing apparatus  800 , the bus  801  may include any quantity of interconnection buses and bridges. The bus  801  connects various circuits together. The circuits include a processor  802 , a storage medium  803 , and a bus interface  804 . Optionally, the data processing apparatus  800  connects a network adapter  805  and the like by using the bus interface  804  and the bus  801 . The network adapter  805  may be configured to: implement a signal processing function of a physical layer in a wireless communications network, and send and receive a radio frequency signal by using an antenna  807 . A user interface  806  may connect to a user terminal, such as a keyboard, a display, a mouse, or a joystick. The bus  801  may also connect other various circuits, such as a timing source, a peripheral device, a voltage regulator, or a power management circuit. The circuits are well-known in the art, and are not described in detail. 
     Alternatively, the data processing apparatus  800  may also be configured as a general-purpose processing system, for example, known as a chip. The general-purpose processing system includes one or more microprocessors providing a processor function and a peripheral memory providing at least a part of the storage medium  803 . All the circuits are connected to other supporting circuits by using a peripheral bus system structure. 
     Alternatively, the data processing apparatus  800  may be implemented by an ASIC (application-specific integrated circuit) having the processor  802 , the bus interface  804 , and the user interface  806  and at least a part of the storage medium  803  that is integrated into a single chip. Alternatively, the data processing apparatus  800  may be implemented by one or more FPGAs (field programmable gate array), PLDs (programmable logic device), controllers, status machines, logic gates, discrete hardware components, any other suitable circuits, or any combination of circuits that can implement various functions described in the present invention. 
     The processor  802  is responsible for bus management and general processing (including executing software stored in the storage medium  803 ). The processor  802  may be implemented by one or more general-purpose processors and/or special-purpose processors. Examples of the processor include a microprocessor, a microcontroller, a DSP processor, and another circuit that can execute the software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     In the following figure, the storage medium  803  is separate from the processor  802 . However, a person skilled in the art will readily appreciate that the storage medium  803  or any part of the storage medium  803  may be located outside the data processing apparatus  800 . For example, the storage medium  803  may include a transmission line, a carrier waveform modulated by using data, and/or a computer product separate from a wireless node. The media may be accessed by the processor  802  through the bus interface  804 . Alternatively, the storage medium  803  or any part of the storage medium  803  may be integrated into the processor  802 . For example, the storage medium  803  may be a cache and/or a general-purpose register. 
     The processor  802  may perform the following step: generating a physical layer protocol data unit PPDU. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     The antenna  807  may perform the following step: sending the PPDU. 
     Alternatively, all or some of the procedures or functions may be implemented by using software, hardware, firmware, or any combination thereof. When software is used for implementation, all or some of the procedures or functions may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or some of the procedures or functions according to the embodiments of the present invention are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid state disk Solid State Disk, (SSD)), or the like. 
     When an integrated unit is used,  FIG. 9  is a possible schematic structural diagram of a data processing apparatus in the foregoing embodiments. As shown in  FIG. 9 , a data processing apparatus  900  may include a receiving unit  901 . 
     The receiving unit  901  is configured to receive a physical layer protocol data unit PPDU. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     The data processing apparatus  900  in this embodiment has a function of the STA in  FIG. 5 , and may implement an action completed by the STA in  FIG. 5 , so as to achieve a technical effect of the corresponding data processing method. For details, refer to related descriptions of  FIG. 5  . For brevity of description, details are not described herein again. 
       FIG. 10  is a schematic structural diagram of a data processing apparatus (for example, a communications apparatus such as an access point, a base station, a station, or a terminal, or a chip in the foregoing communications apparatus) according to an implementation of the present invention. As shown in  FIG. 10 , a data processing apparatus  1000  may be implemented by using a bus  1001  as a general bus system structure. Depending on specific application and an overall design constraint condition of the data processing apparatus  1000 , the bus  1001  may include any quantity of interconnection buses and bridges. The bus  1001  connects various circuits together. The circuits include a processor  1002 , a storage medium  1003 , and a bus interface  1004 . Optionally, the data processing apparatus  1000  connects a network adapter  1005  and the like by using the bus interface  1004  and the bus  1001 . The network adapter  1005  may be configured to: implement a signal processing function of a physical layer in a wireless communications network, and send and receive a radio frequency signal by using an antenna  1007 . A user interface  1006  may connect to a user terminal, such as a keyboard, a display, a mouse, or a joystick. The bus  1001  may also connect other various circuits, such as a timing source, a peripheral device, a voltage regulator, or a power management circuit. The circuits are well-known in the art, and are not described in detail. 
     Alternatively, the data processing apparatus  1000  may also be configured as a general-purpose processing system, for example, known as a chip. The general-purpose processing system includes one or more microprocessors providing a processor function and a peripheral memory providing at least a part of the storage medium  1003 . All the circuits are connected to other supporting circuits by using a peripheral bus system structure. 
     Alternatively, the data processing apparatus  1000  may be implemented by an ASIC (application-specific integrated circuit) having the processor  1002 , the bus interface  1004 , and the user interface  1006  and at least a part of the storage medium  1003  that is integrated into a single chip. Alternatively, the data processing apparatus  1000  may be implemented by one or more FPGAs (field programmable gate array), PLDs (programmable logic device), controllers, status machines, logic gate, discrete hardware components, any other suitable circuits, or any combination of circuits that can implement various functions described in the present invention. 
     The processor  1002  is responsible for bus management and general processing (including executing software stored in the storage medium  1003 ). The processor  1002  may be implemented by one or more general-purpose processors and/or special-purpose processors. Examples of the processor include a microprocessor, a microcontroller, a DSP processor, and another circuit that can execute the software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     In the following figure, the storage medium  1003  is separate from the processor  1002 . However, a person skilled in the art will readily appreciate that the storage medium  1003  or any part of the storage medium  1003  may be located outside the data processing apparatus  1000 . For example, the storage medium  1003  may include a transmission line, a carrier waveform modulated by using data, and/or a computer product separate from a wireless node. The media may be accessed by the processor  1002  through the bus interface  1004 . Alternatively, the storage medium  1003  or any part of the storage medium  1003  may be integrated into the processor  1002 . For example, the storage medium  1003  may be a cache and/or a general-purpose register. 
     The antenna  1007  may perform the following step: receiving a physical layer protocol data unit PPDU. The PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     Alternatively, all or some of the procedures or functions may be implemented by using software, hardware, firmware, or any combination thereof. When software is used for implementation, all or some of the procedures or functions may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or some of the procedures or functions according to the embodiments of the present invention are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid state disk Solid State Disk, (SSD)), or the like. 
     An embodiment of the present invention provides a data processing method. Transmission related to a PPDU in the method may be applicable to a Doppler scenario or a high-speed movement scenario (for example, the STA transmits data to the AP in  FIG. 1 ) occurred during uplink multi-user data transmission. That is, a trigger frame is needed to trigger and instruct TB PPDU transmission. 
       FIG. 11  is an interaction diagram of the data processing method according to this embodiment of the present invention. The method is applicable to the Doppler scenario or the high-speed movement scenario. An AP generates a trigger frame. The trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU. The PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. The AP sends the trigger frame to a STA. The AP receives the PPDU sent by the STA. 
     For a manner of generating the trigger frame by the AP, refer to the foregoing manner of generating the PPDU by the STA. That is, information indicating M is added to the trigger frame when the trigger frame is generated. Further, after receiving the trigger frame, the STA may generate the PPDU based on the information indicating M, and further send the PPDU to the AP. 
     In this embodiment, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU may be added in one of the following fields: a Trigger Type field, a Doppler field, an HE-SIG-A field, a Trigger Dependent Common Info field, an MCS field, a combination of an MCS field and a DCM field, an RU allocation field, or an SS allocation field. 
     A core idea of this embodiment is setting the trigger frame as a trigger frame used in the Doppler scenario or the high-speed movement scenario. Therefore, the Trigger Type field or the Doppler field is mainly used to set a type of the trigger frame, and then another specified field is used to indicate M. 
     Optionally, in an example of the present invention, referring to  FIG. 12 , one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame (the Trigger Type field includes four bits, and may indicate 16 cases, where currently values 0 to 7 have been used, values 8 to 15 are reserved values, and any one or more of the values 8 to 15 may be set to indicate that the trigger frame is a Doppler trigger frame), and to indicate that the TB PPDU uses a midamble structure. The insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the HE-SIG-A field in a common field. For example, two bits  00  are used to indicate M=M1, 01 are used to indicate M=M2, 10 are used to indicate M=M3, and 11 are used to indicate M=M4. 
     For another example, two bits  00  are used to indicate M=M1, 01 are used to indicate M=M2, 10 are used to indicate M=M3, and 11 are used to indicate that no midamble is inserted. In a default state, a bit in the Reserved field in the HE-SIG-A is set to 1. Therefore, if all bits are set to 1, it indicates a default state. That is, no midamble is inserted. 
     Optionally, in an example of the present invention, referring to  FIG. 13 , one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, a midamble frequency indication field is added to the Trigger Dependent Common Info field in the trigger frame in a common field, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using the midamble frequency indication field. Similarly, the midamble frequency indication field may be added to a Trigger Dependent User Info field in a User Info field, to indicate the insertion frequency of the middle preamble in the data field in the TB PPDU. The foregoing two manners are similar. For brevity of description, details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 14 , one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the MCS field. For details, refer to related descriptions of Table 10, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 15 , one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using the combination of the MCS field and the DCM field. For details, refer to related descriptions of Table 13, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 16 , one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using a reserved value of the RU allocation field. For details, refer to related descriptions of Table 19, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 17 , one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble in the data field in the TB PPDU is implicitly indicated by using a parameter used to indicate an SS in the SS allocation field. The SS allocation field has three bits, and indicates 8 SSs. For details, refer to Table 20. 
     
       
         
           
               
               
             
               
                 TABLE 20 
               
               
                   
               
               
                 Number of SS 
                 Corresponding Quantity of Space Time Streams 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 A quantity of space time streams is equal to 1. 
               
               
                 1 
                 A quantity of space time streams is equal to 2. 
               
               
                 2 
                 A quantity of space time streams is equal to 3. 
               
               
                 3 
                 A quantity of space time streams is equal to 4. 
               
               
                 4 
                 A quantity of space time streams is equal to 5. 
               
               
                 5 
                 A quantity of space time streams is equal to 6. 
               
               
                 6 
                 A quantity of space time streams is equal to 7. 
               
               
                 7 
                 A quantity of space time streams is equal to 8. 
               
               
                   
               
            
           
         
       
     
     Table 20 shows indication parameters and indicated meanings of the SS allocation field. An SS value in the SS allocation field is used to indicate a quantity of space time streams. A function of the SS allocation field is similar to a function of the NSTS field (Table 15), and both are used to indicate a quantity of space time streams in a standard. In this embodiment of the present invention, the SS allocation field is escaped to indicate the insertion frequency of the middle preamble. This is similar to the NSTS field. The SS value indicates the insertion frequency of the middle preamble while indicating the quantity of space time streams. For details, refer to Table 21. 
     
       
         
           
               
               
             
               
                 TABLE 21 
               
               
                   
               
               
                 Number  
                   
               
               
                 of SS 
                 Corresponding Quantity of Space Time Streams and M 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 0 
                 A quantity of space time streams is equal to 1, and M = M1. 
               
               
                 1 
                 A quantity of space time streams is equal to 2, and M = M1. 
               
               
                 2 
                 A quantity of space time streams is equal to 1, and M = M2. 
               
               
                 3 
                 A quantity of space time streams is equal to 2, and M = M2. 
               
               
                 4 
                 A quantity of space time streams is equal to 1, and M = M3. 
               
               
                 5 
                 A quantity of space time streams is equal to 2, and M = M3. 
               
               
                 6 
                 A quantity of space time streams is equal to 1, and M = M4. 
               
               
                 7 
                 A quantity of space time streams is equal to 2, and M = M4. 
               
               
                   
               
            
           
         
       
     
     For example, Table 21 is an example of the foregoing indication method. The SS value 0 indicates that the quantity of space time streams is equal to 1 and M=M1. The SS value 1 indicates that the quantity of space time streams is equal to 2 and M=M1. The SS value 2 indicates that the quantity of space time streams is equal to 1 and M=M2. The SS value 3 indicates that the quantity of space time streams is equal to 1 and M=M2. The SS value 4 indicates that the quantity of space time streams is equal to 1 and M=M3. The SS value 5 indicates that the quantity of space time streams is equal to 3 and M=M3. The SS value 6 indicates that the quantity of space time streams is equal to 1 and M=M4. The SS value 7 indicates that the quantity of space time streams is equal to 2 and M=M4. 
     In the Doppler scenario or the high-speed scenario, a channel condition is relatively poor. Usually, the scenario is a light of sight scenario (LOS), and does not allow a relatively large quantity of space time streams. In this embodiment, the quantity of space time streams may be limited to 1 or 2, and four types of M are limited. In addition, a plurality of cases such as two quantities (1 or 2) of space time streams and two types of M (M1 or M2) may alternatively be set. The quantity of space time streams and M may be set based on a specific Doppler scenario or high-speed movement scenario. This is not specifically limited in this embodiment. 
     Optionally, in an example of the present invention, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble in the data field in the TB PPDU is implicitly indicated by using a parameter used to indicate an SS in the combination of the SS allocation field and the MCS field. The SS allocation field and the NSTS field are substantially the same. For details, refer to related descriptions of Table 17, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 18 , the Doppler field in the trigger frame is set to 1 to indicate that the TB PPDU uses a midamble structure, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the HE-SIG-A field in a common field. For example, two bits  00  are used to indicate M=M1, 01 are used to indicate M=M2, 10 are used to indicate M=M3, and 11 are used to indicate M=M 4  (or ii are used to indicate that no midamble is inserted). 
     Optionally, in an example of the present invention, referring to  FIG. 19 , the Doppler field in the trigger frame is set to 1, a midamble frequency indication field is added to the Trigger Dependent Common Info field in the trigger frame in a common field, and the insertion frequency of the middle preamble is indicated by using the midamble frequency indication field. 
     Optionally, in an example of the present invention, referring to  FIG. 20 , the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the MCS field. For details, refer to related descriptions of Table 10, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 21 , the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using the combination of the MCS field and the DCM field. For details, refer to related descriptions of Table 13, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 22 , the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using a reserved value of the RU allocation field. For details, refer to related descriptions of Table 19, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 23 , the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble in the data field in the TB PPDU is implicitly indicated by using a parameter used to indicate an SS in the SS allocation field. For details, refer to related descriptions of Table 21, and details are not described herein again. 
     Optionally, in an example of the present invention, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble in the data field in the TB 
     PPDU is implicitly indicated by using a parameter used to indicate an SS in the combination of the SS allocation field and the MCS field. The SS allocation field and the NSTS field are substantially the same. For details, refer to related descriptions of Table 17, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 24 , the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of the HE-SIG-A field. For example, two bits  00  are used to indicate M=M1, 01 are used to indicate M=M2, 10 are used to indicate M=M3, and 11 are used to indicate that no midamble is inserted. 
     Optionally, in an example of the present invention, referring to  FIG. 25 , the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using a reserved value of the Reserved field (one bit) in a User Info field. For example, when the value of reserved field is equal to 1, it indicates M=M1. When the value of reserved field is equal to 0, it indicates M=M2. 
     According to the data processing method provided in this embodiment of the present invention, the insertion frequency of the middle preamble in the data field is indicated by using a specified field in the trigger frame. Based on the trigger frame, generation of the TB PPDU may be triggered and the insertion frequency of the middle preamble in the data field in the TB PPDU may be indicated. In this way, in different scenarios, the middle preamble may be inserted into the data field at different frequency, thereby reducing overheads of an inserted pilot and improving data transmission performance in a TB PPDU transmission process. 
     The foregoing describes the solutions provided in the embodiments of the present invention mainly from the perspective of interaction between the STA and the AP. It may be understood that to implement the foregoing functions, the STA/AP or the like includes corresponding hardware structures and/or software modules for implementing the various functions. A person of ordinary skill in the art should be easily aware that, with reference to the units and algorithm steps in the examples described in the embodiments disclosed in this specification, the present invention may be implemented by hardware or a combination of hardware and computer software. Whether a function is performed by hardware or computer software driving hardware depends on particular applications and design constraint conditions 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 should not be considered that the implementation goes beyond the scope of the present invention. 
     In the embodiments of the present invention, functional unit division may be performed on the STA and the AP according to the examples of the foregoing method. For example, various functional units may be divided according to the corresponding functions, or two or more functions may be integrated into one processing unit. The integrated unit may be implemented in a form of hardware, or may be implemented in a form of a software functional unit. It should be noted that the unit division in the embodiments of the present invention is an example, and is merely logical function division. There may be another division manner in an actual implementation. 
     When an integrated unit is used,  FIG. 26  is a possible schematic structural diagram of a data processing apparatus in the foregoing embodiments. As shown in  FIG. 26 , a data processing apparatus  2600  may include a trigger frame generation unit  2601  and a sending unit  2602 . 
     The trigger frame generation unit  2601  is configured to generate a trigger frame. The trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. The sending unit  2602  is configured to send the trigger frame. 
     The data processing apparatus  2600  in this embodiment has a function of the AP in  FIG. 11 , and may implement an action completed by the AP in  FIG. 11 , so as to achieve a technical effect of the corresponding data processing method. For details, refer to related descriptions of  FIG. 11 . For brevity of description, details are not described herein again. 
       FIG. 27  is a schematic structural diagram of a data processing apparatus (for example, a communications apparatus such as an access point, a base station, a station, or a terminal, or a chip in the foregoing communications apparatus) according to an implementation of the present invention. As shown in  FIG. 27 , a data processing apparatus  2700  may be implemented by using a bus  2701  as a general bus system structure. Depending on specific application and an overall design constraint condition of the data processing apparatus  2700 , the bus  2701  may include any quantity of interconnection buses and bridges. The bus  2701  connects various circuits together. The circuits include a processor  2702 , a storage medium  2703 , and a bus interface  2704 . Optionally, the data processing apparatus  2700  connects a network adapter  2705  and the like by using the bus interface  2704  and the bus  2701 . The network adapter  2705  may be configured to: implement a signal processing function of a physical layer in a wireless communications network, and send and receive a radio frequency signal by using an antenna  2707 . A user interface  2706  may connect to a user terminal, such as a keyboard, a display, a mouse, or a joystick. The bus  2701  may also connect other various circuits, such as a timing source, a peripheral device, a voltage regulator, or a power management circuit. The circuits are well-known in the art, and are not described in detail. 
     Alternatively, the data processing apparatus  2700  may also be configured as a general-purpose processing system, for example, known as a chip. The general-purpose processing system includes one or more microprocessors providing a processor function and a peripheral memory providing at least a part of the storage medium  2703 . All the circuits are connected to other supporting circuits by using a peripheral bus system structure. 
     Alternatively, the data processing apparatus  2700  may be implemented by an ASIC (application-specific integrated circuit) having the processor  2702 , the bus interface  2704 , and the user interface  2706  and at least a part of the storage medium  2703  that is integrated into a single chip. Alternatively, the data processing apparatus  2700  may be implemented by one or more FPGAs (field programmable gate array), PLDs (programmable logic device), controllers, status machines, gate logics, discrete hardware components, any other suitable circuits, or any combination of circuits that can implement various functions described in the present invention. 
     The processor  2702  is responsible for bus management and general processing (including executing software stored in the storage medium  2703 ). The processor  2702  may be implemented by one or more general-purpose processors and/or special-purpose processors. Examples of the processor include a microprocessor, a microcontroller, a DSP processor, and another circuit that can execute the software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     In the following figure, the storage medium  2703  is separate from the processor  2702 . However, a person skilled in the art will readily appreciate that the storage medium  2703  or any part of the storage medium  2703  may be located outside the data processing apparatus  2700 . For example, the storage medium  2703  may include a transmission line, a carrier waveform modulated by using data, and/or a computer product separate from a wireless node. The media may be accessed by the processor  2702  through the bus interface  2704 . Alternatively, the storage medium  2703  or any part of the storage medium 2703 may be integrated into the processor  2702 . For example, the storage medium  2703  may be a cache and/or a general-purpose register. 
     The processor  2702  may perform the following step: generating a trigger frame. The trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     The antenna  2707  may perform the following step: sending the trigger frame. 
     Alternatively, all or some of the procedures or functions may be implemented by using software, hardware, firmware, or any combination thereof. When software is used for implementation, all or some of the procedures or functions may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or some of the procedures or functions according to the embodiments of the present invention are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid state disk (SSD)), or the like. 
     When an integrated unit is used,  FIG. 28  is a possible schematic structural diagram of a data processing apparatus in the foregoing embodiments. As shown in  FIG. 28 , a data processing apparatus  2800  may include a receiving unit  2801 , a PPDU generation unit  2802 , and a sending unit  2803 . 
     The receiving unit  2801  is configured to receive a trigger frame. The trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the trigger frame includes information used to indicate an insertion frequency of a middle preamble in a data field in the PPDU, and the PPDU includes the data field and the middle preamble field. The PPDU generation unit  2802  is configured to generate the PPDU based on the trigger frame. The sending unit  2803  is configured to send the PPDU. 
     The data processing apparatus  2800  in this embodiment has a function of the STA in  FIG. 11 , and may implement an action completed by the STA in  FIG. 11 , so as to achieve a technical effect of the corresponding data processing method. For details, refer to related descriptions of  FIG. 11 . For brevity of description, details are not described herein again. 
       FIG. 29  is a schematic structural diagram of a data processing apparatus (for example, a communications apparatus such as an access point, a base station, a station, or a terminal, or a chip in the foregoing communications apparatus) according to an implementation of the present invention. As shown in  FIG. 29 , a data processing apparatus  2900  may be implemented by using a bus  2901  as a general bus system structure. Depending on specific application and an overall design constraint condition of the data processing apparatus  2900 , the bus  2901  may include any quantity of interconnection buses and bridges. The bus  2901  connects various circuits together. The circuits include a processor  2902 , a storage medium  2903 , and a bus interface  2904 . Optionally, the data processing apparatus  2900  connects a network adapter  2905  and the like by using the bus interface  2904  and the bus  2901 . The network adapter  2905  may be configured to: implement a signal processing function of a physical layer in a wireless communications network, and send and receive a radio frequency signal by using an antenna  2907 . A user interface  2906  may connect to a user terminal, such as a keyboard, a display, a mouse, or a joystick. The bus  2901  may also connect other various circuits, such as a timing source, a peripheral device, a voltage regulator, or a power management circuit. The circuits are well-known in the art, and are not described in detail. 
     Alternatively, the data processing apparatus  2900  may also be configured as a general-purpose processing system, for example, known as a chip. The general-purpose processing system includes one or more microprocessors providing a processor function and a peripheral memory providing at least a part of the storage medium  2903 . All the circuits are connected to other supporting circuits by using a peripheral bus system structure. 
     Alternatively, the data processing apparatus  2900  may be implemented by an ASIC (application-specific integrated circuit) having the processor  2902 , the bus interface  2904 , and the user interface  2906  and at least a part of the storage medium  2903  that is integrated into a single chip. Alternatively, the data processing apparatus  2900  may be implemented by one or more FPGAs (field programmable gate array), PLDs (programmable logic device), controllers, status machines, gate logics, discrete hardware components, any other suitable circuits, or any combination of circuits that can implement various functions described in the present invention. 
     The processor  2902  is responsible for bus management and general processing (including executing software stored in the storage medium  2903 ). The processor  2902  may be implemented by one or more general-purpose processors and/or special-purpose processors. Examples of the processor include a microprocessor, a microcontroller, a DSP processor, and another circuit that can execute the software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     In the following figure, the storage medium  2903  is separate from the processor  2902 . However, a person skilled in the art will readily appreciate that the storage medium  2903  or any part of the storage medium  2903  may be located outside the data processing apparatus  2900 . For example, the storage medium  2903  may include a transmission line, a carrier waveform modulated by using data, and/or a computer product separate from a wireless node. The media may be accessed by the processor  2902  through the bus interface  2904 . Alternatively, the storage medium  2903  or any part of the storage medium  2903  may be integrated into the processor  2902 . For example, the storage medium  2903  may be a cache and/or a general-purpose register. 
     The antenna  2907  may perform the following step: receiving a trigger frame. The trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the trigger frame includes information used to indicate an insertion frequency of a middle preamble in a data field in the PPDU, and the PPDU includes the data field and the middle preamble field. 
     The processor  2902  may perform the following step: generating the PPDU based on the trigger frame. 
     The antenna  2907  may perform the following step: sending the PPDU. 
     Alternatively, all or some of the procedures or functions may be implemented by using software, hardware, firmware, or any combination thereof. When software is used for implementation, all or some of the procedures or functions may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or some of the procedures or functions according to the embodiments of the present invention are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid state disk (SSD)), or the like. 
     An embodiment of the present invention provides a data processing method. Transmission related to a PPDU may be applicable to a Doppler scenario or a high-speed movement scenario (for example, the STA transmits data to the AP in  FIG. 1 ) occurred during uplink data transmission. In other words, a MAC frame is needed to trigger and instruct TB PPDU transmission. 
       FIG. 30  is an interaction diagram of the data processing method according to this embodiment of the present invention. The method is applicable to the Doppler scenario or the high-speed movement scenario. An AP generates a Media Access Control MAC frame. The MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU. The PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. The AP sends the MAC frame to the STA. The AP receives the PPDU sent by the STA. 
     For a process of interaction between the AP and the STA, refer to descriptions of  FIG. 11 , and details are not described herein again. 
     The information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control (HTC) field in the MAC frame. The HTC field includes the following fields. For details, refer to  FIG. 31 . 
     Optionally, in an example of the present invention, referring to  FIG. 32 , the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using a reserved value of an RU allocation field. For details, refer to related descriptions of Table 18, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 33 , the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of a UL MCS field. For details, refer to related descriptions of Table 10, and details are not described herein again. 
     Optionally, in an example of the present invention, referring to  FIG. 34 , the insertion frequency of the middle preamble in the data field in the TB PPDU is indicated by using one or more of reserved values of a Reserved field. For details, refer to related descriptions of  FIG. 17 , and details are not described herein again. 
     According to the data processing method provided in this embodiment of the present invention, the insertion frequency of the middle preamble is indicated by using a specified field in the MAC frame. Based on the MAC frame, the TB PPDU may be triggered and the insertion frequency of the middle preamble in the data field in the TB PPDU may be indicated. In this way, in different scenarios, the middle preamble may be inserted into the data field at different frequency, thereby reducing overheads of an inserted pilot and improving data transmission performance in a PPDU transmission process. 
     The foregoing describes the solutions provided in the embodiments of the present invention mainly from the perspective of interaction between the STA and the AP. It may be understood that to implement the foregoing functions, the STA/AP or the like includes corresponding hardware structures and/or software modules for implementing the various functions. A person of ordinary skill in the art should be easily aware that, with reference to the units and algorithm steps in the examples described in the embodiments disclosed in this specification, the present invention may be implemented by hardware or a combination of hardware and computer software. Whether a function is performed by hardware or computer software driving hardware depends on particular applications and design constraint conditions 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 should not be considered that the implementation goes beyond the scope of the present invention. 
     In the embodiments of the present invention, functional unit division may be performed on the STA and the AP according to the examples of the foregoing method. For example, various functional units may be divided according to the corresponding functions, or two or more functions may be integrated into one processing unit. The integrated unit may be implemented in a form of hardware, or may be implemented in a form of a software functional unit. It should be noted that the unit division in the embodiments of the present invention is an example, and is merely logical function division. There may be another division manner in an actual implementation. 
     When an integrated unit is used,  FIG. 35  is a possible schematic structural diagram of a data processing apparatus in the foregoing embodiments. As shown in  FIG. 35 , a data processing apparatus  3500  may include a MAC frame generation unit  3501  and a sending unit  3502 . 
     The MAC frame generation unit  3501  is configured to generate a Media Access Control MAC frame. The MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. The sending unit  3502  is configured to send the MAC frame. 
     The data processing apparatus  3500  in this embodiment has a function of the AP in  FIG. 30 , and may implement an action completed by the AP in  FIG. 30 , so as to achieve a technical effect of the corresponding data processing method. For details, refer to related descriptions of  FIG. 30 . For brevity of description, details are not described herein again. 
       FIG. 36  is a schematic structural diagram of a data processing apparatus (for example, a communications apparatus such as an access point, a base station, a station, or a terminal, or a chip in the foregoing communications apparatus) according to an implementation of the present invention. As shown in  FIG. 36 , a data processing apparatus  3600  may be implemented by using a bus  3601  as a general bus system structure. Depending on specific application and an overall design constraint condition of the data processing apparatus  3600 , the bus  3601  may include any quantity of interconnection buses and bridges. The bus  3601  connects various circuits together. The circuits include a processor  3602 , a storage medium  3603 , and a bus interface  3604 . Optionally, the data processing apparatus  3600  connects a network adapter  3605  and the like by using the bus interface  3604  and the bus  3601 . The network adapter  3605  may be configured to: implement a signal processing function of a physical layer in a wireless communications network, and send and receive a radio frequency signal by using an antenna  3607 . A user interface  3606  may connect to a user terminal, such as a keyboard, a display, a mouse, or a joystick. The bus  3601  may also connect other various circuits, such as a timing source, a peripheral device, a voltage regulator, or a power management circuit. The circuits are well-known in the art, and are not described in detail. 
     Alternatively, the data processing apparatus  3600  may also be configured as a general-purpose processing system, for example, known as a chip. The general-purpose processing system includes one or more microprocessors providing a processor function and a peripheral memory providing at least a part of the storage medium  3603 . All the circuits are connected to other supporting circuits by using a peripheral bus system structure. 
     Alternatively, the data processing apparatus  3600  may be implemented by an ASIC (application-specific integrated circuit) having the processor  3602 , the bus interface  3604 , and the user interface  3606  and at least a part of the storage medium  3603  that is integrated into a single chip. Alternatively, the data processing apparatus  3600  may be implemented by one or more FPGAs (field programmable gate array), PLDs (programmable logic device), controllers, status machines, gate logics, discrete hardware components, any other suitable circuits, or any combination of circuits that can implement various functions described in the present invention. 
     The processor  3602  is responsible for bus management and general processing (including executing software stored in the storage medium  3603 ). The processor  3602  may be implemented by one or more general-purpose processors and/or special-purpose processors. Examples of the processor include a microprocessor, a microcontroller, a DSP processor, and another circuit that can execute the software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     In the following figure, the storage medium  3603  is separate from the processor  3602 . However, a person skilled in the art will readily appreciate that the storage medium  3603  or any part of the storage medium  3603  may be located outside the data processing apparatus  3600 . For example, the storage medium  3603  may include a transmission line, a carrier waveform modulated by using data, and/or a computer product separate from a wireless node. The media may be accessed by the processor  3602  through the bus interface  3604 . Alternatively, the storage medium  3603  or any part of the storage medium  3603  may be integrated into the processor  3602 . For example, the storage medium  3603  may be a cache and/or a general-purpose register. 
     The processor  3602  may perform the following step: generating a Media Access Control MAC frame. The MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     The antenna  3607  may perform the following step: sending the MAC frame. 
     Alternatively, all or some of the procedures or functions may be implemented by using software, hardware, firmware, or any combination thereof. When software is used for implementation, all or some of the procedures or functions may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or some of the procedures or functions according to the embodiments of the present invention are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid state disk (SSD)), or the like. 
     When an integrated unit is used,  FIG. 37  is a possible schematic structural diagram of a data processing apparatus in the foregoing embodiments. As shown in  FIG. 37 , a data processing apparatus  3700  may include a receiving unit  3701 , a PPDU generation unit  3702 , and a sending unit  3703 . 
     The receiving unit  3701  is configured to receive a Media Access Control MAC frame. The MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. The PPDU generation unit  3702  is configured to generate the PPDU based on the MAC frame. The sending unit  3703  is configured to send the PPDU. 
     The data processing apparatus  3700  in this embodiment has a function of the STA in  FIG. 30 , and may implement an action completed by the STA in  FIG. 30 , so as to achieve a technical effect of the corresponding data processing method. For details, refer to related descriptions of  FIG. 30 . For brevity of description, details are not described herein again. 
       FIG. 38  is a schematic structural diagram of a data processing apparatus (for example, a communications apparatus such as an access point, a base station, a station, or a terminal, or a chip in the foregoing communications apparatus) according to an implementation of the present invention. As shown in  FIG. 38 , a data processing apparatus  3800  may be implemented by using a bus  3801  as a general bus system structure. Depending on specific application and an overall design constraint condition of the data processing apparatus  3800 , the bus  3801  may include any quantity of interconnection buses and bridges. The bus  3801  connects various circuits together. The circuits include a processor  3802 , a storage medium  3803 , and a bus interface  3804 . Optionally, the data processing apparatus  3800  connects a network adapter  3805  and the like by using the bus interface  3804  and the bus  3801 . The network adapter  3805  may be configured to: implement a signal processing function of a physical layer in a wireless communications network, and send and receive a radio frequency signal by using an antenna  3807 . A user interface  3806  may connect to a user terminal, such as a keyboard, a display, a mouse, or a joystick. The bus  3801  may also connect other various circuits, such as a timing source, a peripheral device, a voltage regulator, or a power management circuit. The circuits are well-known in the art, and are not described in detail. 
     Alternatively, the data processing apparatus  3800  may also be configured as a general-purpose processing system, for example, known as a chip. The general-purpose processing system includes one or more microprocessors providing a processor function and a peripheral memory providing at least a part of the storage medium  3803 . All the circuits are connected to other supporting circuits by using a peripheral bus system structure. 
     Alternatively, the data processing apparatus  3800  may be implemented by an ASIC (application-specific integrated circuit) having the processor  3802 , the bus interface  3804 , and the user interface  3806  and at least a part of the storage medium  3803  that is integrated into a single chip. Alternatively, the data processing apparatus  3800  may be implemented by one or more FPGAs (field programmable gate array), PLDs (programmable logic device), controllers, status machines, gate logics, discrete hardware components, any other suitable circuits, or any combination of circuits that can implement various functions described in the present invention. 
     The processor  3802  is responsible for bus management and general processing (including executing software stored in the storage medium  3803 ). The processor  3802  may be implemented by one or more general-purpose processors and/or special-purpose processors. Examples of the processor include a microprocessor, a microcontroller, a DSP processor, and another circuit that can execute the software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     In the following figure, the storage medium  3803  is separate from the processor  3802 . However, a person skilled in the art will readily appreciate that the storage medium  3803  or any part of the storage medium  3803  may be located outside the data processing apparatus  3800 . For example, the storage medium  3803  may include a transmission line, a carrier waveform modulated by using data, and/or a computer product separate from a wireless node. The media may be accessed by the processor  3802  through the bus interface  3804 . Alternatively, the storage medium  3803  or any part of the storage medium  3803  may be integrated into the processor  3802 . For example, the storage medium  3803  may be a cache and/or a general-purpose register. 
     The antenna  3807  may perform the following step: receiving a Media Access Control MAC frame. The MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     The processor  3802  may perform the following step: generating the PPDU based on the MAC frame. 
     The antenna  3807  may perform the following step: sending the PPDU. 
     Alternatively, all or some of the procedures or functions may be implemented by using software, hardware, firmware, or any combination thereof. When software is used for implementation, all or some of the procedures or functions may be implemented in a form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or some of the procedures or functions according to the embodiments of the present invention are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or another programmable apparatus. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (DSL)) or wireless (for example, infrared, radio, or microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid state disk (SSD)), or the like. 
     A person skilled in the art may be further aware that, in combination with the examples described in the embodiments disclosed in this specification, units and algorithm steps may be implemented by electronic hardware, computer software, or a combination thereof. To clearly describe the interchangeability between the hardware and the software, the foregoing has described compositions and steps of each example in general according to functions. Whether the functions are performed by hardware or software depends on particular applications and design constraint conditions 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 should not be considered that the implementation goes beyond the scope of the present invention. 
     The steps in the method or algorithm described in the embodiments disclosed in this specification may be implemented by hardware, software module executed by the processor, or combination of hardware and software. The software module may reside in a random-access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. 
     In the foregoing specific implementations, the objective, technical solutions, and benefits of the present invention are further described in detail. It should be understood that the foregoing descriptions are merely specific implementations of the present invention, but are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, or improvement made without departing from the principle of the present invention should fall within the protection scope of the present invention. 
     An embodiment of the present invention discloses A1. A data processing method, including: generating a physical layer protocol data unit PPDU, where the PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and sending the PPDU. 
     A2. According to the method described in A1, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     A3. According to the method described in A2, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the SR field. 
     A4. According to the method described in A2, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the MCS field or the SIGB MCS field. 
     A5. According to the method described in A2, the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an MCS in the MCS field. 
     A6. According to the method described in A2, the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the DCM field. 
     A7. According to the method described in A2, the insertion frequency of the middle preamble is indicated by using the combination of the SIGB MCS field and the SIGB DCM field. 
     A8. According to the method described in A2, the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an NSTS in the NSTS field. 
     A9. According to the method described in A2, the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the NSTS field. 
     A10. According to the method described in A2, the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     A11. embodiment of the present invention further discloses B11. A data processing method, including: generating a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU, and the PPDU includes the data field and the middle preamble field; and sending the trigger frame. 
     B12. According to the method described in B11, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     B13. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and to indicate that the trigger-based PPDU uses a middle preamble midamble structure, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the HE-SIG-A field. 
     B14. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, a midamble frequency indication field is added to the Trigger Dependent Common Info field, and the insertion frequency of the middle preamble is indicated by using the midamble frequency indication field. 
     B15. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the MCS field. 
     B16. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the DCM field. 
     B17. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     B18. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the SS allocation field. 
     B19. According to the method described in B12, one or more of reserved values of the Trigger Type field in the trigger frame are set to indicate that the trigger frame is a Doppler trigger frame, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the combination of the SS allocation field and the MCS field. 
     B20. According to the method described in B12, the indicating the insertion frequency of the middle preamble in a data field by using a specified field in the trigger frame further includes: setting the Doppler field in the trigger frame to 1 to indicate that the TB PPDU uses a midamble structure, and indicating the insertion frequency of the middle preamble by using one or more of reserved values of the HE-SIG-A field. 
     B21. According to the method described in B12, the Doppler field in the trigger frame is set to 1, a midamble frequency indication field is added to the Trigger Dependent Common Info field, and the insertion frequency of the middle preamble is indicated by using the midamble frequency indication field. 
     B22. According to the method described in B12, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the MCS field. 
     B23. According to the method described in B12, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is indicated by using the combination of the MCS field and the DCM field. 
     B24. According to the method described in B12, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     B25. According to the method described in B12, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the SS allocation field. 
     B26. According to the method described in B12, the Doppler field in the trigger frame is set to 1, and the insertion frequency of the middle preamble is implicitly indicated by using a parameter used to indicate an SS in the combination of the SS allocation field and the MCS field. 
     B27. According to the method described in B11, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the HE-SIG-A field. 
     B28. According to the method described in B11, the insertion frequency of the middle preamble is indicated by using a reserved value of the Reserved field. 
     An embodiment of the present invention further discloses C29. A data processing method, including: generating a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and sending the MAC frame. 
     C30. According to the method described in C29, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     C31. According to the method described in C30, the insertion frequency of the middle preamble is indicated by using a reserved value of the RU allocation field. 
     C32. According to the method described in C30, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the UL MCS field. 
     C33. According to the method described in C30, the insertion frequency of the middle preamble is indicated by using one or more of reserved values of the Reserved field. 
     An embodiment of the present invention further discloses D34. A data processing method, including: receiving a physical layer protocol data unit PPDU, where the PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     D35. According to the method described in D34, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     An embodiment of the present invention further discloses E36. A data processing method, including: receiving a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the trigger frame includes information used to indicate an insertion frequency of a middle preamble in a data field in the PPDU, and the PPDU includes the data field and the middle preamble field; generating the PPDU based on the trigger frame; and sending the PPDU. 
     E37. According to the method described in E36, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     An embodiment of the present invention further discloses F38. A data processing method, including: receiving a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and generating and sending the PPDU based on the MAC frame. 
     F39. According to the method described in F38, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     An embodiment of the present invention further discloses G40. A data processing apparatus, including: a PPDU generation unit, configured to generate a physical layer protocol data unit PPDU, where the PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a sending unit, configured to send the PPDU. 
     G41. According to the apparatus described in G40, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     An embodiment of the present invention further discloses H42. A data processing apparatus, including: a trigger frame generation unit, configured to generate a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the trigger frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a sending unit, configured to send the trigger frame. 
     H43. According to the apparatus described in H42, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     An embodiment of the present invention further discloses I44. A data processing apparatus, including: a MAC frame generation unit, configured to generate a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a sending unit, configured to send the MAC frame. 
     I45. According to the apparatus described in I44, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved. 
     An embodiment of the present invention further discloses J46. A data processing apparatus, including a receiving unit, configured to receive a physical layer protocol data unit PPDU, where the PPDU includes a preamble field, a data field, and a middle preamble field, and the preamble in the PPDU includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU. 
     J47. According to the apparatus described in J46, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: an SR field used to indicate a parameter related to spatial reuse in a high efficient signal field A HE-SIG-A, an MCS field used to indicate a modulation and coding scheme in the HE-SIG-A, an MCS field in a high efficient signal field B HE-SIG-B, a SIGB MCS field used to indicate a high efficient signal field B modulation and coding scheme in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-A, a combination of an MCS field and a DCM field in the HE-SIG-B, a combination of a SIGB MCS field and a SIGB DCM field in the HE-SIG-A, an NSTS field used to indicate a quantity of space time streams of a single user in the HE-SIG-B, a combination of an MCS field and an NSTS field, or an RU allocation field used to indicate a resource unit in the HE-SIG-B. 
     An embodiment of the present invention further discloses K48. A data processing apparatus, including: a receiving unit, configured to receive a trigger frame, where the trigger frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the trigger frame includes information used to indicate an insertion frequency of a middle preamble in a data field in the PPDU, and the PPDU includes the data field and the middle preamble field; and a PPDU generation unit, configured to generate and send the PPDU based on the trigger frame. 
     K49. According to the apparatus described in K48, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in one of the following fields: a Trigger Type field used to indicate a trigger frame type, a Doppler field used to indicate whether a Doppler mode is used for a data packet, a high efficient signal field A HE-SIG-A, a Trigger Dependent Common Info field for indicating common information based on a trigger frame type, an MCS field used to indicate a modulation and coding scheme, a combination of an MCS field and a DCM field, an RU allocation field used to indicate a resource unit, an SS allocation field used to indicate a quantity of space time streams, or a combination of an SS allocation field and an MCS field in the trigger frame. 
     An embodiment of the present invention further discloses L50. A data processing apparatus, including: a receiving unit, configured to receive a Media Access Control MAC frame, where the MAC frame is used to instruct to generate and send a physical layer protocol data unit PPDU, the PPDU includes a data field and a middle preamble field, and the MAC frame includes information used to indicate an insertion frequency of the middle preamble in the data field in the PPDU; and a PPDU generation unit, configured to generate and send the PPDU based on the MAC frame. 
     L51. According to the apparatus described in L50, the information used to indicate the insertion frequency of the middle preamble in the data field in the PPDU is added in a high throughput control field HTC in the MAC frame, and the HTC field includes an RU allocation field used to indicate a resource unit, a UL MCS field used to indicate an uplink modulation and coding scheme, and a reserved value field Reserved.