The twt of wifi is an extension of u-apsd. And u-apsd is an upgrade to ps-poll.
The ps-poll is really very inefficient. It requires clients to always use ps-poll (control frame) to poll the AP, and it will not stop until the AP sets More Data (Frame Control) to 0.
But u-apsd is different. The client uses a null frame or data frame to trigger the AP. If the AP caches its frames, it will send all the cached data to the client in a burst, otherwise it will reply with a null frame. u- The difference between apsd and ps-poll is that u-apsd does not need to wake up every listen interval, but AP nego wakes up in advance. u(nscheduled) is what it means. This reduces the number of opening rx path. In addition, ps-poll is no longer repeated, which reduces overhead and tx power consumption. Moreover, the IFS of each burst frame is SIFS, which will not be contend by other clients, which improves efficiency.
twt is divided into itwt, awake twt, btwt. itwt is similar to u-apsd. btwt is the broadcast twt.