HE PPDU Structure

IEEE^® 802.11™¹ is a packet-based protocol. Each packet, also called a physical layer protocol data unit (PPDU), contains preamble and data fields. The preamble fields contain the transmission vector format information. The data field contains the user payload and higher layer headers, such as medium access control (MAC) fields and cyclic redundancy check (CRC). The transmission vector format and the PPDU structure vary between 802.11 versions. The transmission vector (TXVECTOR) format parameter is classified as:

HE to specify a high-efficiency (HE) physical layer (PHY) implementation.
- HE refers to fields formatted for association with 802.11ax™ data. Reference [1] defines and describes the HE PHY layer and PPDU.
- For HE, the TXVECTOR parameters, as defined in Table 27-1 of [1], determine the structure of PPDUs transmitted by an HE station (STA).

The table shows 802.11 versions that WLAN Toolbox™ supports, along with the supported TXVECTOR options and associated modulation formats.

802.11 Version	Transmission Vector Format	Modulation Format	Bandwidth/MHz
802.11b™	non-HT	DSSS/CCK	11
802.11a™	non-HT	OFDM only	5, 10, 20
802.11j™	non-HT	OFDM only	10
802.11p™	non-HT	OFDM only	5, 10
802.11g™	non-HT	OFDM	20
802.11g™	non-HT	DSSS/CCK	11
802.11n™ (Wi-Fi 4)	HT_MF, Non-HT	OFDM only	20, 40
802.11ac™ (Wi-Fi 5)	VHT, HT_MF, Non-HT	OFDM only	20, 40, 80, 160
802.11ah™	S1G	OFDM only	1, 2, 4, 8, 16
802.11ad™	DMG	Single Carrier and OFDM	2640
802.11ax (Wi-Fi 6)	HE	OFDMA	20, 40, 80, 160
802.11ba™	WUR	MC-OOK	20, 40, 80
802.11be™ (Wi-Fi 7)	EHT	OFDMA	20, 40, 80, 160, 320

For HE, there are four transmission modes: HE single-user (HE SU), HE extended-range SU (HE ER SU) HE multi-user (HE MU), and HE trigger-based (HE TB). The wlanHESUConfig, wlanHEMUConfig, and wlanHETBConfig objects enable you to create PPDUs and waveforms for all of them.

The field structure for HE PPDUs consists of preamble and data portions. The legacy preamble fields (L-STF, L-LTF, and L-SIG) are common to all four HE transmission modes, as well as the EHT, VHT, HT, and non-HT format preambles. HE preamble fields include additional format-specific signaling fields. Each format defines a data field for the transmission of user payload data.

The structures of the four kinds of HE PPDU

PPDU Field Abbreviation	Description
L-STF	Non-HT Short Training field
L-LTF	Non-HT Long Training field
L-SIG	Non-HT Signal field
RL-SIG	Repeated Non-HT Signal field
HE-SIG-A	HE Signal A field
HE-SIG-B	HE Signal B field
HE-STF	HE Short Training field
HE-LTF	HE Long Training field
HE-Data	Data field carrying the PSDUs
PE	Packet Extension field

The RL-SIG, HE-SIG-A, HE-STF, HE-LTF, and PE fields are present in all HE PPDU formats. The HE-SIG-B field is present only in the HE MU PPDU. For more information, see Section 27.3.4 of [1].

References

[1] IEEE Std 802.11ax-2021 (Amendment to IEEE Std 802.11-2020). “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 1: Enhancements for High Efficiency WLAN.” IEEE Standard for Information Technology — Telecommunications and Information Exchange between Systems. Local and Metropolitan Area Networks — Specific Requirements.