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IEEE标准802.11ax-2021是一项针对信息技术、本地和城域网特定需求的标准，其中包括了无线局域网的介质访问控制和物理层规范的修订，以提供高效的无线局域网服务。其中第27条对高效（HE）物理层规范进行了详细说明，介绍了用于高效正交频分复用（OFDM）系统的物理层实体。该规范旨在通过一系列改进，提高其吞吐量和效率，以满足日益增长的无线网络需求。 IEEE 802.11ax标准的"High-efficiency (HE) PHY specification"（高效物理层规范）作为该标准的一个重要组成部分，主要是为了满足现代无线局域网对性能和效率的需求。在无线通信中，物理层是整个系统的基础，负责将数字数据转换成传输信号，并在接收端将信号转换回数据。通过对物理层的规范和改进，可以提高无线通信系统的传输速率、信道利用率和适应性。 HE PHY规范在技术层面通过对正交频分复用系统进行了详细说明，其中包括了一系列改进和优化。其中的技术难题之一是无线信道的多径衰落和干扰问题，针对这一问题，HE PHY规范使用了一系列现代信号处理技术和调制技术，例如波束成形和调制技术，以提高信道容量和减小干扰。此外，为了增强信道的使用效率，HE PHY还引入了一系列新的技术特性，如空时多址、灵活的调制和编码技术，以及更高效的信道访问机制等。总的来说，HE PHY规范旨在通过一系列的技术创新和改进，提高802.11ax标准的无线通信性能和效率，以满足未来无线通信系统对更高速率和更可靠连接的需求。这对于诸如物联网、5G移动通信等新兴应用领域而言，具有非常重要的意义。在未来的无线通信中，HE PHY规范可能会成为更多高效无线通信技术的基础，为更多的应用场景提供更可靠、更高速的无线连接，从而推动数字化社会的发展。值得期待的是，随着技术的不断发展和标准的进一步完善，无线通信技术将在更多的领域得到广泛的应用。

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480

IEEE Std 802.11ax-2021

IEEE Standard for Information Technology—Local and Metropolitan Area Networks—Specific Requirements—

Part 11: Wireless LAN MAC and PHY Specifications—

Amendment 1: Enhancements for High Efficiency WLAN

PARTIAL_AID

FORMAT is HE_SU,

HE_MU, HE_ER_SU, or

HE_TB

Not present N N

Otherwise See corresponding entry in Table 21-1.

TXOP_DURATION

FORMAT is HE_SU,

HE_MU, HE_ER_SU, or

HE_TB

Indicates the TXOP duration.

Enumerated type or integer:

UNSPECIFIED indicates no NAV value specified.

0–8448 indicates a value in units of 1 µs that is used to

update the NAV for this TXOP (see 26.2.4).

TXVECTOR parameter TXOP_DURATION is converted to a

value in the TXOP subfield of the HE-SIG-A field (see

Table 27-18, Table 27-20, and Table 27-21) as follows:

TXOP_DURATION = UNSPECIFIED: B0–B6 = 127.

TXOP_DURATION < 512: B0 = 0, B1–B6 = TXOP_

DURATION / 8

Otherwise: B0 = 1, B1–B6 = TXOP_DURATION – 512 / 8

RXVECTOR parameter TXOP_DURATION is determined

from the value in the TXOP subfield of the HE-SIG-A field

(see Table 27-18, Table 27-20, and Table 27-21) as follows:

B0–B6 = 127: TXOP_DURATION = UNSPECIFIED.

B0 = 0: TXOP_DURATION = 8 × B1-B6.

Otherwise: TXOP_DURATION = 512 + 128 × B1–B6.

See 26.11.5 for more details.

Otherwise Not present N N

SPATIAL_REUSE

FORMAT is HE_SU,

HE_MU, HE_ER_SU, or

HE_TB

Indicates the spatial reuse parameter value. There is one value

of the parameter for each of an HE SU PPDU, HE ER SU

PPDU, and HE MU PPDU. There are one to four values of the

parameter present for an HE TB PPDU, with the number of

values present dependent on the bandwidth of the PPDU. See

the Spatial Reuse field definition in 27.3.11.7.2.

See 26.5.2.3 and 26.11.6.

Otherwise Not present N N

DOPPLER

FORMAT is HE_SU,

HE_MU, HE_ER_SU, or

HE_TB

Set to 1 to indicate that either the midamble is present for the

PPDU or that the channel is with high Doppler. Set to 0

otherwise.

Otherwise Not present N N

Table 27-1—TXVECTOR and RXVECTOR parameters (continued)

Parameter

Condition Value

TXVECTOR

RXVECTOR

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IEEE Std 802.11ax-2021

IEEE Standard for Information Technology—Local and Metropolitan Area Networks—Specific Requirements—

Part 11: Wireless LAN MAC and PHY Specifications—

Amendment 1: Enhancements for High Efficiency WLAN

481

NUM_USERS

FORMAT is HE_SU,

HE_MU, HE_ER_SU, or

HE_TB

Not present

NOTE—The number of users for an HE SU PPDU, HE ER SU

PPDU, or HE TB PPDU is always 1. The number of users in

an RU in an HE MU PPDU is determined by RU_

ALLOCATION and STA_ID parameters for that RU.

Otherwise See corresponding entry in Table 21-1.

RU_ALLOCATION

FORMAT is HE_MU and

SIG_B_COMPRESSION_

MODE is 0

For the TXVECTOR, indicates the RU Allocation subfield of

Common field in the HE-SIG-B field of the transmitted PPDU.

8 bits for a 20 MHz PPDU.

16 bits for a 40 MHz PPDU.

32 bits for an 80 MHz PPDU.

64 bits for a 160 MHz or 80+80 MHz PPDU.

See 27.3.11.8.3 for details.

For the RXVECTOR, 8 bits are used to indicate the RU

allocated in the whole bandwidth.

See 9.3.1.22 for details.

FORMAT is HE_TB 8 bits are used to indicate the RU allocated in the whole

bandwidth per user.

See 9.3.1.22 for details.

FORMAT is HE_SU, APEP_

LENGTH is 0, and CH_

BANDWIDTH is not CBW20

or CBW40

For the TXVECTOR, indicates the active RUs.

32 bits for 80 MHz PPDU.

64 bits for 160 MHz and 80+80 MHz PPDU.

For each 8 bits, only the following values are allowed:

113 (01110001 in binary representation).

192 (11000000 in binary representation).

See 27.3.11.8.3 for details.

FORMAT is NON_HT,

NON_HT_MODULATION is

NON_HT_DUP_OFDM, and

CH_BANDWIDTH is not

CBW20 or CBW40

Otherwise Not present N N

BEAMFORMED

FORMAT is HE_SU or

HE_ER_SU

Set to 1 if a beamforming steering matrix is applied to the HE

modulated fields. Set to 0 otherwise.

FORMAT is HE_MU or

HE_TB

For an RU with no more than 1 user allocated, set to 1 if a

beamforming steering matrix is applied to this non-MU-

MIMO allocation, and set to 0 otherwise.

For each user in an RU assigned to more than 1 user, always

set to 0.

Otherwise See corresponding entry in Table 21-1.

Table 27-1—TXVECTOR and RXVECTOR parameters (continued)

Parameter

Condition Value

TXVECTOR

RXVECTOR

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482

IEEE Std 802.11ax-2021

IEEE Standard for Information Technology—Local and Metropolitan Area Networks—Specific Requirements—

Part 11: Wireless LAN MAC and PHY Specifications—

Amendment 1: Enhancements for High Efficiency WLAN

CENTER_26_TONE_RU

FORMAT is HE_MU and

CH_BANDWIDTH is

CBW80,

CBW160,

CBW80+80,

HE-CBW-PUNC80-PRI,

HE-CBW-PUNC80-SEC,

HE-CBW-PUNC160-PRI20,

HE-CBW-PUNC80+80-

PRI20,

HE-CBW-PUNC160-SEC40,

HE-CBW-PUNC80+80-

SEC40.

Indicate the presence of the center 26-tone RU with regard to

bandwidth.

If the CH_BANDWIDTH parameter is CBW80, HE-CBW-

PUNC80-PRI or HE-CBW-PUNC80-SEC:

Set to 1 to indicate that a user is allocated to the center

26-tone RU (see Figure 27-7).

Set to 0 to indicate that no user is allocated to the center

26-tone RU.

If the CH_BANDWIDTH parameter is CBW160, CBW80+80,

HE-CBW-PUNC160-PRI20, HE-CBW-PUNC80+80-PRI20,

HE-CBW-PUNC160-SEC40, or HE-CBW-PUNC80+80-

SEC40:

Set to 0 to indicate that no user is allocated to either the

center 26-tone RU of the lower frequency 80 MHz or that

of the higher frequency 80 MHz.

Set to 1 to indicate that a user is allocated to the center

26-tone RU of the lower frequency 80 MHz.

Set to 2 to indicate that a user is allocated to the center

26-tone RU of the higher frequency 80 MHz.

Set to 3 to indicate that a user is allocated to each of the

center 26-tone RU of the lower frequency 80 MHz and

that of the higher frequency 80 MHz individually.

See 27.3.11.8.3.

Otherwise Not present N N

HE_LTF_TYPE

FORMAT is HE_SU,

HE_MU, HE_ER_SU, or

HE_TB

Indicates the type of HE-LTF.

Enumerated type:

1xHE-LTF indicates a 1x HE-LTF.

2xHE-LTF indicates a 2x HE-LTF.

4xHE-LTF indicates a 4x HE-LTF.

See 27.3.11.10.

Otherwise Not present N N

HE_LTF_MODE

FORMAT is HE_TB Integer:

Set to 0 to indicate that the transmitted PPDU uses HE

single stream pilot HE-LTF mode.

Set to 1 to indicate the transmitted PPDU uses HE masked

HE-LTF sequence mode.

Present for full-bandwidth MU-MIMO not using 1x HE-LTF

and not present otherwise.

See 27.3.11.10.

Otherwise Not present N N

Table 27-1—TXVECTOR and RXVECTOR parameters (continued)

Parameter

Condition Value

TXVECTOR

RXVECTOR

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