802.11ax Packet Formats

What is the packet format in IEEE 802.11ax?

It defines the structure of MAC and PHY frames optimized for high efficiency and multi-user operation.

How does 802.11ax packet format differ from 802.11ac?

It introduces new fields for OFDMA, MU-MIMO, and Target Wake Time scheduling while maintaining backward compatibility.

What are the main components of an 802.11ax MAC frame?

Frame Control, Duration/ID, Address fields, Sequence Control, QoS Control, HT Control, and Frame Body.

What is the significance of the HE (High Efficiency) Control field?

It carries control information related to new 802.11ax features like resource unit allocation and spatial reuse.

How is OFDMA reflected in the packet format?

OFDMA uses special trigger frames and control fields to indicate resource unit assignments for simultaneous transmissions.

What is the PPDU format in 802.11ax?

It includes a Legacy preamble, HE-LTF fields, HE-SIG-A and HE-SIG-B fields, followed by data symbols.

What role do the HE-SIG fields play?

HE-SIG-A and HE-SIG-B convey control information such as MCS, RU allocation, and transmission parameters.

How does 802.11ax support multiple spatial streams in the packet?

Packet format includes fields for MU-MIMO operation with spatial stream assignments and beamforming info.

Are there new frame types introduced in 802.11ax?

Yes, new control frames like Trigger Frames and Multi-User Block ACK frames support multi-user coordination.

What is a Trigger Frame?

A special control frame sent by the AP to schedule uplink transmissions from multiple stations simultaneously.

How does 802.11ax handle fragmentation in packet formats?

Similar to previous standards, fragmentation fields allow splitting large frames into smaller subframes.

Does 802.11ax support Quality of Service (QoS) in packet formats?

Yes, the QoS Control field is enhanced to support differentiated traffic handling.

What is the maximum size of an 802.11ax MAC frame?

Up to 7935 bytes, larger than previous standards to accommodate increased data and control info.

How are legacy devices supported in 802.11ax packet formats?

The Legacy preamble and fields ensure backward compatibility with older 802.11 devices.

What is the role of the PHY preamble in 802.11ax?

It enables synchronization, channel estimation, and signaling of packet format and rate.

How does 802.11ax handle encryption in packet formats?

Encryption headers and trailers are included per standard MAC layer security protocols like WPA3.

Are control frames shorter than data frames in 802.11ax?

Yes, control frames have minimal headers and fixed lengths for fast processing.

How does 802.11ax support target wake time (TWT) in packet formats?

TWT information is carried in specific management frames for scheduling device wake/sleep cycles.

Where can I find detailed 802.11ax packet format specifications?

In the IEEE 802.11ax standard document and related technical references from the Wi-Fi Alliance.

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