Before understanding the operation of TWT, it is important to understand the building blocks of the TWT framework. The below building blocks provide inputs on how the negotiation, setup and operation of a TWT is performed

The control field format for the TWT element is updated from 802.11-2020 as depicted

1. The Negotiation Type subfield indicates whether the information included in the TWT information element is for
   1. Negotiation of parameters of Broadcast TWT
   2. Negotiation of parameters of Individual TWT or
   3. Wake TBTT interval
2. The MSB of the Negotiation Type Subfield is the Broadcast field and if it is set to 1 – one or more broadcast parameter sets are contained in the TWT element.
3. The TWT Information Frame Disabled if set to 1 – indicates that the reception of TWT Information frames is disabled by the STA
4. The Wake Duration subfield depicts a value of 256 uS if set to 0 else it is a value in TUs

The TWT parameter information contains a single TWT parameter set field for an individual TWT setup when the broadcast bit is set to ‘0’ in the negotiation type subfield.

The TWT parameter information contains one or more Broadcast parameter set/s for a broadcast TWT setup when the broadcast bit is set to ‘1’ in the negotiation type subfield. The Broadcast TWT parameter set and the Individual TWT parameter set format is shown below

The Request Type sub-field is 2 octets long and is provided below for reference for a Broadcast TWT and Individual TWT. For information on each of the individual subfields – refer Section 9.4.2.199 TWT Element in the 802.11ax Standard

The Target Wake Time, the negotiation Type and the TWT wake Interval mantissa and Target Wake Interval Exponent group together to provide the below data

The TWT Request type sub-field indicates whether the station is a requester (set to 1) or a responder. The TWT setup command field indicates the type of TWT command. A Station or an AP can incorporate the TWT element in any frame during the association process. An 802.11ax station can also incorporate the TWT element in an action frame for TWT negotiation. For a broadcast TWT, AP can include the TWT element in the beacon.

TWT Setup Command and Flow Type description