Target Wake Time details.
Target wakeup time (TWT) is a power-saving mechanism that
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allows an AP to schedule specific times for devices or stations (STAs) to wake up and communicate
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enables those devices to remain in a power-saving state for longer periods, and
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reduces overall network congestion.
Feature history
| Feature name |
Release information |
Feature description |
|---|---|---|
| Target wake time |
Cisco IOS XE 17.2.1 |
Target wake time (TWT) allows an AP to manage activity in the Wi-Fi network, in order to minimize medium contention between Stations (STAs), and to reduce the required amount of time that an STA in the power-save mode needs to be awake. This is achieved by allocating STAs to operate at non-overlapping times, and/or frequencies, and concentrate the frame exchanges in predefined service periods. |
Delivery traffic indication map
With 802.11e, the new power-saving mechanism was introduced that helps voice-capable Wi-Fi devices, as voice packets are transmitted at short time intervals, typically 20 ms/sec.
The existing Wi-Fi client power-saving mechanisms have been in use since 802.11b, where the client devices sleep between AP beacons or multiple beacons, waking up only when they have data to transmit (they can transmit at any time, as AP does not sleep).
A Delivery Traffic Indication Map (DTIM) is a bit-map that
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is contained within beacons
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indicates an AP has buffered downlink traffic, and
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specifies which particular clients are awaiting transmission.
If a client has a DTIM bit set, it can retrieve data from the AP by sending a Power-Save Poll (PS-Poll) frame to the AP. This power-save scheme is effective but only allows clients to doze for a small beacon interval. Clients still need to wake up several times per second to read DTIM from the beacon frame of the AP.
Unscheduled automatic power-save delivery (U-APSD) allows a power-save client to sleep at intervals within a beacon period. AP buffers the downlink traffic until the client wakes up and requests its delivery.
By default Target Wake Time (TWT) is disabled on the controller. To enable TWT, run the ap dot11 {24ghz | 5ghz| 6ghz} dot11ax twt-broadcast command.