CN110572238B

CN110572238B - Wireless communication method and device

Info

Publication number: CN110572238B
Application number: CN201910482866.3A
Authority: CN
Inventors: 胡昇泉; 伍天宇; 刘剑函; 皮尔二世汤姆士艾德华
Original assignee: MediaTek Singapore Pte Ltd
Current assignee: MediaTek Singapore Pte Ltd
Priority date: 2018-06-06
Filing date: 2019-06-04
Publication date: 2022-03-22
Anticipated expiration: 2039-06-04
Also published as: DE102019114851A1; CN110572238A

Abstract

The invention provides a wireless communication method and equipment, wherein the wireless communication method comprises the following steps: allocating a plurality of frequency channels to a plurality of stations, respectively, for downlink multi-user orthogonal frequency division multiple access transmission; generating a multi-user packet comprising a plurality of payloads to be transmitted in the plurality of frequency channels, respectively, wherein the generating comprises: in response to determining that the frequency channels for a first set of payloads are time-varying, inserting midambles in the first set of payloads, wherein each midamble comprises training symbols for channel estimation by one of the plurality of stations; and in response to determining that the frequency channel for the second set of payloads is time invariant, not inserting a midamble in the second set of payloads; and transmitting the multiuser packet to the plurality of stations in the downlink multiuser orthogonal frequency division multiple access transmission. The embodiment of the invention can improve the transmission efficiency and the throughput.

Description

Wireless communication method and device

Technical Field

The present invention relates generally to the field of wireless network communication technology, and more particularly, to a wireless communication method and apparatus.

Background

Wireless channels (wireless channels) in WLANs are typically affected by Doppler effects (Doppler effects), caused for example by movement of the associated wireless Station (STA) or by fast moving objects around the STA. Some other changes in the environment may also cause the wireless channel to change over time during packet (packet) transmissions. Performance in WLAN systems tends to be adversely affected if such channel variations are not taken into account when sending or receiving packets.

A method of combating the temporal channel variation problem involves inserting a "mid-amble" (or so-called "doppler midamble") in the data (data) field of the packet, which includes training symbols (training symbols) used by the receiving device to perform channel estimation, thereby tracking the channel conditions in real time. The midamble may be a repetition of a high efficiency-long training field (HE-LTF) contained in a preamble (preamble). Typically, the midamble is inserted after a predefined data length (referred to herein as a "midamble update interval" or "midamble period" in the IEEE802.11ax protocol), e.g., after each predefined transmission time or after each predefined number of Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

In Orthogonal Frequency Division Multiple Access (OFDMA) transmission, a multi-user (MU) data packet includes a payload (payload) that is directed to Multiple stations (STAs or "users" herein) and carried in different Frequency channels (also referred to simply as "channels"), e.g., Resource Units (RUs). Traditionally, the midamble setting for OFDMA MU packages is consistent across the entire bandwidth. In particular, no midamble is available for any STA's packet, or all STAs involved in the transmission have the same midamble update interval. Typically, the midamble update interval is set to a relatively high value to ensure that each STA can correctly receive the packet.

In practice, however, it is unlikely that all frequency channels in an OFDMA transmission will vary together, let alone to the same extent. Unnecessary midambles waste transmission time that may be used for data transmission. Therefore, using a common (common) midamble update interval for all channels tends to reduce transmission efficiency and overall system throughput.

In general, the midamble is neither needed nor supported in Downlink (DL) multi-user (MU) multiple-input multiple-output (MIMO) transmission. In OFDMA transmission, if one frequency channel is allocated for downlink multiuser multiple-input multiple-output mode, the entire bandwidth is prohibited from using the midamble due to the constraint set by the common midamble. This may result in incorrect channel estimates on other channels at the receiving STA.

Disclosure of Invention

The present invention provides a wireless communication method and apparatus with improved transmission efficiency and throughput.

The invention provides a wireless communication method, which can comprise the following steps: allocating a plurality of frequency channels to a plurality of stations, respectively, for downlink multi-user orthogonal frequency division multiple access transmission; generating a multi-user packet comprising a plurality of payloads to be transmitted in the plurality of frequency channels, respectively, wherein the generating comprises: in response to determining that the frequency channels for a first set of payloads are time-varying, inserting midambles in the first set of payloads, wherein each midamble comprises training symbols for channel estimation by one of the plurality of stations; and in response to determining that the frequency channel for the second set of payloads is time invariant, not inserting a midamble in the second set of payloads; and transmitting the multiuser packet to the plurality of stations in the downlink multiuser orthogonal frequency division multiple access transmission.

The present invention also provides a wireless communication device, which may include: a memory; a processor coupled to the memory; and a transceiver comprising a signal processor, wherein the signal processor is configured to: for executing the wireless communication method provided by the invention.

The method and the device provided by the embodiment of the invention use the intermediate code on the basis of each user or each channel, and can favorably improve the transmission efficiency and the throughput.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 shows an example of usage of a midamble per user in OFDMA transmission according to an embodiment of the present invention.

Fig. 2 depicts a flowchart of an exemplary computer-implemented process 200 for setting an indication related to midamble usage per user of an OFDMA transmission in accordance with an embodiment of the present invention.

Fig. 3 illustrates a format of an exemplary trigger frame 300 for triggering transmission of a TB PPDU in UL OFDMA according to an embodiment of the present invention.

Fig. 4A illustrates a format of an exemplary Downlink (DL) High Efficiency (HE) MU PPDU 400 for OFDMA transmissions according to an embodiment of the present invention.

Fig. 4B shows the format of the "HE-SIG-B" field 412 in an exemplary DL PPDU 400 according to an embodiment of the present invention.

Fig. 5 is a block diagram illustrating a configuration of an exemplary wireless communication device 500 according to an embodiment of the present invention.

Detailed Description

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. By "substantially" it is meant within an acceptable error range, within which one skilled in the art would be able to solve the technical problem to substantially achieve the technical result. Furthermore, the term "coupled" is intended to include any direct or indirect electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. The following is a preferred embodiment of the invention for the purpose of illustrating the spirit of the invention and not for the purpose of limiting the scope of the invention, which is defined in the appended claims.

The following description is of the best embodiments contemplated by the present invention. The description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention should be determined with reference to the claims that follow.

PER-USER MIDAMBLE in MU PPDU

Embodiments of the present invention are described in detail with reference to the Physical Layer Convergence Protocol (PLCP) Protocol data unit (PPDU) structure defined in the IEEE802.11 series of specifications and standards. However, the present invention is not limited to any particular packet format or structure, nor to any particular industry standard or specification.

Embodiments of the present invention provide a mechanism for OFDMA transmission that uses per-user based midamble for channel variation adaptation. The multiple channels used in OFDMA transmission may use different midamble settings based on their respective channel characteristics. In particular, some channels may have a midamble, while some channels may not have a midamble, and the midamble update interval may vary between channels. For Trigger-Based (TB) Uplink (UL) OFDMA transmission, the Access Point (AP) may signal (signal) per-user midamble (per-user mid-amble) information in the user information field of the Trigger frame. For Downlink (DL) OFDMA transmissions, the AP may signal the midamble information per user in a high efficiency signal B (HE-SIG-B) field.

Fig. 1 shows an example of usage of a midamble per user in OFDMA transmission according to an embodiment of the present invention. In this example, the entire bandwidth is divided into four frequency channels 101-104, each channel consisting of one or more Resource Units (RUs). Channels 101-103 are allocated to STA1, STA2 and STA3, respectively. These channels are therefore used for transmission in Single User (SU) mode during OFDMA transmission. Channel 104 is allocated to STA4 and STA5 for transmission in a multi-user multiple-input multiple-output mode during OFDMA and MU-MIMO hybrid transmission.

According to embodiments of the present invention, whether a midamble is needed for each individual channel is determined independently on a per-user or per-channel basis, e.g., based on a set of doppler metrics or other relevant channel characteristics. If the channel requires a midamble, the appropriate midamble update interval pattern is selected. Thus, in OFDMA transmission, the payloads carried in multiple channels may have different midamble update interval patterns, and some of them may not have any midamble.

As shown,

channels

101 and 103 have a midamble inserted between the data symbols ("data") of STA1 and STA3, but have different midamble update intervals. The reason for using different midamble update intervals is, for example, that the channel is detected to experience different degrees of channel variation in time. Channel 102 has no midamble, e.g., because it is determined that channel 102 is time-invariant for OFDMA transmission. Channel 104 has no midamble because it is used for DL MU MIMO mode.

Because the midamble is used on a per-STA (or per-user) or per-channel basis, the choice of midamble mode can be tailored to the characteristics of the particular channel. In contrast to conventional approaches that only allow common midamble settings, per-user midamble usage can advantageously and efficiently avoid unnecessary midambles and can also enable necessary channel variation adaptation in transmission. As a result, transmission throughput and efficiency can be advantageously improved. In addition, in OFDMA transmission, even if some frequency channels used in DL MU MIMO mode do not support midamble usage, midambles are still allowed on other channels.

Fig. 2 depicts a flowchart of an exemplary computer-implemented process 200 for setting an indication related to midamble usage per user of an OFDMA transmission in accordance with an embodiment of the present invention. Process 200 may be performed by the AP after allocating frequency channels to the plurality of STAs when generating a trigger frame to trigger UL OFDMA transmission or when generating a PPDU for DL OFDMA transmission. STA X and corresponding channels are used as examples in the flow chart. It should be appreciated that steps 201-206 are repeated for each STA or each allocated channel involved in the OFDMA transmission.

At 201, it is determined whether the channel is used for DL MU MIMO mode. If so, no midamble should be added for this channel for DL MU-MIMO. Thus, at 203, the "per user doppler mode" for STA X is set to "0". If not, at 202, it is determined whether the Doppler metric for the channel is greater than a predetermined threshold. If not, the "per user Doppler mode" for STA X is set to "0", meaning that there is no midamble in the channel.

The present invention is not limited to any particular doppler metric or any other type of metric that may be used to indicate the state of channel variation. The metric may integrate one or more channel characterization parameters. For example, the doppler metric may be generated from channel estimation performed based on the OFDM symbols and fixed positioning pilots in a packet previously received by the transmitting device. In some embodiments, the doppler metric is defined as a normalized difference (normalized difference) of channel estimates between a plurality of OFDM symbols. In some other embodiments, the doppler metric is defined as the energy difference of a constant modulus modulated subcarrier, such as a Binary Phase Shifting Key (BPSK) modulated fixed positioning pilot. Various exemplary doppler metric definition and metric determination processes are described in more detail in co-owned, co-pending U.S. patent application No.15/342,299, entitled "signaling and feedback scheme for time varying channels in high efficiency WLANs," the contents of which are incorporated herein by reference.

In this example, if the doppler metric indicates that the channel is time-varying (e.g., the doppler metric is greater than a predetermined threshold), it is further determined (at 204) whether a midamble is inserted for STA X. It should be appreciated that this determination process is specific to STA X and independent of another STA. The determination may be based on any suitable factor (factor), such as the length of the data packet. If the midamble is not inserted, the "per-user Doppler mode" of STA X is set to "0". Otherwise, it is set to "1" 205. At 206, the midamble update interval mode of STAX is selected and the indication is set accordingly. At 207, an indication is set to indicate whether at least one midamble is used in the OFDMA transmission.

It is necessary to inform the receiving device of the presence of the midamble and the update interval. Traditionally, the packet preamble has a dedicated field to indicate the presence of a midamble in the packet. For example, as in the ieee802.11ax series of standards and specifications, a one-bit "doppler mode" field in the high efficiency signal a (HE-SIG-a) field of the preamble is defined to indicate whether any doppler mode midamble is included in the packet. A single bit is not sufficient for the use of the midamble per user.

Fig. 3 shows a format of an exemplary 300 for triggering transmission of a TB ul pdu in OFDMA and the trigger frame 300 includes an indication of the midamble usage per user according to an embodiment of the present invention. As shown, the trigger frame 300 includes a frame control field (e.g., "frame control"), a transmission duration field ("duration"), receiver address and transmission address fields ("RA" and "TA"), a common information field ("common information") 310 and one or more user information fields ("user information", e.g., 320), padding ("padding") and a Frequency Check Sequence ("FCS").

The common information field 310 has a sub-field "doppler bit" (not explicitly shown). In some embodiments, if at least one STA is to use doppler mode in the subsequent TB PPDU transmission, then the bit is set to "1", meaning that the PPDU will include at least one midamble; otherwise, it is set to "0".

In addition, the presence of the midamble and the update interval pattern of each STA indicated in the user information field (e.g., 320) by the trigger frame. Each user information field may specify an ID of one STA to trigger (e.g., "AID 12"), an assigned RU ("RU assignment"), an assigned spatial stream ("SS assignment random access RU information") 331, reserved bits ("reserved") 332, and other information needed for UL PPDU transmission, such as coding type, modulation and coding scheme ("MCS"), dual carrier modulation ("DCM"), a target received signal strength indicator ("target RSSI"), and trigger dependent user information 340.

In some embodiments, reserved bits 332 (as a "per user doppler mode" field) may be used to indicate the presence of a midamble for the corresponding STA. For example, the bit is set to "1" to instruct the STA to insert a midamble in the following TB PPDU; a setting to "0" indicates other meanings.

In some embodiments, the "SS allocation random access RU information" 331 may be redefined to indicate a midamble update interval mode selected for the STA. When reserved bit 332 is set to "1," the STA will be the only one assigned to the channel, and therefore the "start spatial stream" 333 subfield is not needed since it always starts from 1. The maximum number of spatial streams for a STA will also be limited to a small value, e.g., 4, and thus the "number of spatial streams" 334 sub-field may not require 3 bits to achieve this. Accordingly, some bits in the "SS allocation random access RU information" field 331 may be redefined to indicate a midamble update interval selected for the STA, e.g., every 10 symbols or every 20 symbols.

In some other embodiments, reserved bits 341 in the trigger dependent user information subfield 340 may be used to indicate the midamble update interval mode selected for the STA. It is to be understood that other suitable bits in the user information field may be used or reused for the midamble interval pattern per user without departing from the scope of the invention. By way of example, the numbers below the table in fig. 3 represent exemplary numbers of bits allocated for the respective fields, e.g., the "frame control" field comprises 2 bytes (octets), each user information field comprises 5 or more bytes, and the "reserved bits" 332 comprise 1 bit (bit).

Fig. 4A illustrates a format of an exemplary Downlink (DL) High Efficiency (HE) MU PPDU 400 for OFDMA transmissions operable to signal per-user midamble usage in accordance with an embodiment of the present invention. The PPDU 400 includes a preamble 410 and a payload 420 encoded and modulated in different channels 401-404. The payload 420 is directed to STAs 1-5 in the same manner as the example shown in fig. 1. The channels 401-404 can be contiguous or non-contiguous RUs and can have different sizes. The preamble 410 includes a short training field (L-STF), a long training field (L-LTF), a high efficiency short training field (HE-STF), a high efficiency long training field (HE-LTF), a signaling field (legacy signal (L-SIG), a repeated legacy signal (RL-SIG), a high efficiency signal a (HE-SIG-a), and a high efficiency signal B (HE-SIG-B)).

The midamble (e.g., 421 and 422) carries training symbols for use by receiving STAs to perform channel estimation to track channel conditions in real time. Each midamble may be a repetition of one or more "HE-LTF" fields in the preamble. However, the present invention is not limited to the specific information contained in the middle.

According to embodiments of the invention, the "HE-SIG-a" field 411 may carry an indication of overall midamble usage in the entire PPDU, and the "HE-SIG-B" field may carry an indication of per-user midamble usage.

The "HE-SIG-a" 411 includes a one-bit "doppler mode" subfield (or "field"). Conventionally, this bit is used to indicate whether a doppler mode midamble is contained in the payload. As described above, conventionally, a single bit is sufficient to indicate midamble usage for the entire PPDU because all channels use the same midamble setting.

According to an embodiment of the present invention, the "doppler mode" field in the "HE-SIG-a" 411 is redefined to carry two alternative sets of information depending on whether the per-user doppler mode is used or not. In particular, if the per-user doppler mode is signaled in the "HE-SIG-B" user field, the "doppler mode" field in the "HE-SIG-a" 411 may be set to "1" to indicate a doppler mode for at least one STA and to "0" to indicate that the doppler mode is not used. On the other hand, if the per-user doppler mode is not signaled in the "HE-SIG-B" user field, the "doppler mode" field in the "HE-SIG-a" 411 may be set to "1" to indicate that the doppler mode is used for all STAs allocated on a single user channel (e.g., having a common midamble update interval mode) and to "0" to indicate that the doppler mode is not used for any STA.

Thus, the "doppler mode" field in the PPDU is redefined to be used as a dual-purpose field to indicate two sets of information. This advantageously extends the range of information available for provision to the receiving device by using the current preamble structure.

Fig. 4B illustrates the format of the "HE-SIG-B" field 412 in an exemplary DL PPDU 400, where the per-user midamble information is signaled in a user-specific field, in accordance with an embodiment of the present invention. The "HE-SIG-B" field 412 includes a "common field" 430 and a "user-specific field" 440. As described above, since the midamble is used in the PPDU, the "doppler field" in the "common field" is set to 1.

The "user specific fields" 440 include one or more "user block fields" which may be followed by padding (padding). Each "user block field" includes a user field designed to contain information used by up to two STAs to decode their payloads (by way of example in fig. 4B, the user block fields except the last user block field include two user fields (denoted as "2 users" in the figure), and the last user block field includes one or two user fields (denoted as "1 or 2 users" in the figure)), and each user block field further includes a Cyclic Redundancy Check (CRC) sequence and Tail (Tail). Each user field may include a "STA-ID" field that indicates an identification of one STA (e.g., with STA1-STA5 as identifications of STA1-STA5, respectively). Each user field may include fields (not shown) for additional information related to the STA, such as RU allocation, number of spatial streams (e.g., "NSTS"), use of transmit beamforming (e.g., "TX beamforming"), modulation and coding scheme (e.g., "MCS"), dual carrier modulation (e.g., "DCM"), and coding scheme (e.g., "coding").

According to an embodiment of the invention, each user field contains a subfield (e.g. per user doppler mode) for the signaling of the midamble per user. For example, the subfield has one bit, where "1" indicates that at least one midamble exists for the corresponding STA, and "0" indicates that there is no midamble. For example, the doppler mode bit per user of STA1 and STA3 is "1", and the doppler mode bit per user of STA2, STA4 and STA5 is "0".

According to the IEEE802.11ax family of standards and specifications, there are no reserved bits in the "HE SIG-B" field. Thus, new bits can be introduced into each user field as per-user doppler mode bits. To keep the size of the user field for non-MU-MIMO allocations the same as the size of the user block allocation for MU-MIMO allocations, reserved bits may also be added to the user field for MU-MIMO allocations.

For a particular STA, the bits allocated for the STA to indicate the number of spatial streams ("NSTS") may be redefined to also indicate the selected midamble update interval pattern. This is because if its doppler bit per user is set to "1", the maximum number of spatial streams will be a relatively small number, e.g., at most 4, and thus 2 bits in the "NSTS" field can be used for sufficient indication. Thus, the remaining 1 bit may be reused to indicate the midamble interval pattern, e.g., every 10 symbols or every 20 symbols.

Fig. 5 is a block diagram illustrating a configuration of an exemplary wireless communication device 500, the exemplary wireless communication device 500 being operable to generate a trigger frame (TB PPDU as previously described) for an OFDMA transmission having a midamble per user and an indication thereof or to generate a DL PPDU for the OFDMA transmission in accordance with one embodiment of the present invention. Device 500 may be a wireless device configured as an AP station. As shown in the process described in more detail in fig. 1-4B, the device 500 is configured to generate a trigger frame or DL PPDU and assign values to several fields related to per-user doppler mode or per-user midamble usage.

Device 500 may be a router, a general purpose computer, or any other type of computing device having a network device. The device 500 includes a main processor 530, a memory 520, and a transceiver 540 coupled to an array of

antennas

501 and 504. The transceiver 540 includes a signal processor 510 having various modules of a transmit path configured to generate each portion of a PPDU, a trigger frame, or any other type of communication transmission message. For example, the signal processor 540 includes a transmit first-in-first-out (TXFIFO)511, an encoder 512, a scrambler 513, an interleaver 514, a constellation mapper (constellationmapper)515, an Inverse Discrete Fourier Transformer (IDFT)517, and a Guard Interval (GI) and window insertion module 516. The signal processor 540 further includes a doppler metric module 518 configured to calculate a doppler metric associated with a single channel and compare the calculated doppler metric to a threshold to determine whether the doppler metric is time-varying.

As shown in the process described in greater detail in fig. 1-4B, memory 530 stores a PPDU format 521 that includes a redefined dual-purpose field, such as "doppler mode" in "HE-SIG-a," SS-allocated random access RU information in a user information field in a trigger frame, "reserved bits and per-user doppler bits in" HE-SIG-B, "etc. PPDU generation module 522 stores processor-executable instructions for generating data and configuration of other portions of the PPDU according to PPDU format 521. As shown in the process described in more detail in fig. 1-4B, PPDU generation module 522 includes a per-user doppler decision module 524 that may decide whether a per-user doppler mode is enabled for PPDU transmissions, whether a single channel is time-varying and whether a midamble is inserted for the corresponding STA, and which midamble update interval to use for the STAs. The signal processor 510 generates a preamble and a midamble accordingly.

It should be understood that each of the signal processors 510 may include various other suitable components known in the art. The various components may be implemented in any suitable manner known in the art and may be implemented using hardware logic, firmware logic, software logic or combinations thereof. Furthermore, in some embodiments, the transceiver 540 in fig. 5 may also include components in the receive path.

Various aspects of the devices and techniques described herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing description, and is therefore not limited in their application to the details of the foregoing components and arrangements or to the details shown in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

In some embodiments, the terms "about," "approximately," and "approximately" may be used to denote a range of ± 10% less than a target value and may include the target value. For example: less than + -5% of the target value and less than + -1% of the target value.

Use of ordinal terms such as "first," "second," "third," etc., in the claims to modify a claim element does not imply any priority or order, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name.

Although the present invention has been described with reference to particular embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method of wireless communication, comprising:

allocating a plurality of frequency channels to a plurality of stations, respectively, for downlink multi-user orthogonal frequency division multiple access transmission;

generating a multi-user packet comprising a plurality of payloads to be transmitted in the plurality of frequency channels, respectively, wherein the generating comprises:

in response to determining that the frequency channels for a first set of payloads are time-varying, inserting midambles in the first set of payloads, wherein each midamble comprises training symbols for channel estimation by one of the plurality of stations; and

in response to determining that the frequency channels for the second set of payloads are time-invariant, inserting no midambles in the second set of payloads; and

transmitting the multiuser packet to the plurality of stations in the downlink multiuser orthogonal frequency division multiple access transmission;

wherein the multi-user packet comprises a preamble comprising a plurality of user block fields in a high efficiency signal B field, wherein each user block field comprises at least one user field, the method further comprising setting a subfield in each user field to indicate whether a midamble is present in a payload of the first set of payloads.

2. The method of claim 1, wherein the first set of payloads comprise midambles having different midamble update intervals.

3. The method of claim 1, wherein the plurality of payloads comprises a downlink multiuser multiple-input multiple-output payload associated with a frequency channel and directed to a portion of the plurality of stations, wherein the generating further comprises determining not to insert a midamble in the downlink multiuser multiple-input multiple-output payload.

4. The method of claim 1, wherein the subfield is a new bit introduced in each of the user fields.

5. The method of claim 1, wherein the subfield is a first subfield, the method further comprising: a second subfield is set in each of the user fields to indicate a midamble update interval used in the payload.

6. The method of claim 5, wherein the second subfield is a number of spatial streams field indicating the number of spatial streams and the midamble update interval.

7. The method of claim 1, wherein the multi-user packet comprises a preamble, the preamble comprising a high efficiency signal A field, and the method further comprises: the doppler subfield in the high efficiency signal a field is set to indicate one of: a common midamble mode; and a per-user midamble mode of the multiuser packet.

8. The method of claim 1, wherein the plurality of stations is a first group of stations and the plurality of frequency signals is a first group of frequency signals, the method further comprising:

allocating a second set of frequency channels for uplink multi-user orthogonal frequency division multiple access transmission, respectively, to a second set of stations;

generating a trigger frame comprising at least one user information field, wherein for each of the plurality of user information fields, the generating comprises:

setting a first indication for a respective station to add one or more midambles in a trigger-based multi-user packet for the uplink multi-user orthogonal frequency division multiple access transmission; and

setting a second indication of a midamble update interval for the trigger-based multiuser packet,

wherein the midamble update intervals indicated in the at least one user information field are different and

the trigger frame is sent to the second set of stations to initiate the uplink multi-user orthogonal frequency division multiple access transmission.

9. The method of claim 8, wherein the at least one user information field is a first set of user information fields, the trigger frame further comprises a second set of user information fields, the second set of user information fields comprising one or more user information fields, and wherein the generating the trigger frame further comprises, for each of the second set of user information fields, setting an indication for a corresponding station to not insert any midamble in a trigger-based multi-user packet for the uplink multi-user orthogonal frequency division multiple access transmission.

10. The method of claim 8, wherein the trigger frame further comprises a common field comprising a sub-field, the sub-field of the common field specifying whether any midambles are to be inserted into the trigger based multi-user packet in the uplink multi-user orthogonal frequency division multiple access transmission.

11. The method of claim 8, wherein the first indication is included in reserved bits of the at least one user information field.

12. The method of claim 8, wherein the second indication is included in a reserved bit in an SS allocated random access RU information sub-field or a trigger dependent user information sub-field of the at least one user information field.

13. A wireless communication device, comprising:

a memory;

a processor coupled to the memory; and

a transceiver comprising a signal processor, wherein the signal processor is configured to: for performing the method of any one of claims 1-12.