Target Wake Time

Target Wake Time

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), and beacons containing the Delivery Traffic Indication Map (DTIM), a bit-map, indicates that the AP has downlink traffic buffered for transmission to particular clients.

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.

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. 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.


Note

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.

Extended Power-Savings Using Target Wake Time

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.

TWT capable STA can either negotiate an individual TWT agreement with TWT-scheduling AP, or it can elect to be part or member of Broadcast TWT agreement existing on the AP. An STA does not need to be aware that a TWT service period (SP) can be used to exchange frames with other STAs. Frames transmitted during a TWT SP can be carried in any PPDU format supported by the pair of STAs that have established the TWT agreement corresponding to that TWT SP, including High Efficiency Multi-User Physical Protocol Data Unit (HE MU PPDU), High Efficiency Trigger-Based Physical Protocol Data Unit (HE TB PPDU), and so on.

Following are the TWT Agreement Types:

Individual TWT

Single TWT session is negotiated between AP and an STA. This ensures a specific service period of DL and UL between AP and STA with expected traffic to be limited within the negotiated SP of 99% accuracy. The service period starts at specific offset from the target beacon transmission time (TBTT) and runs for the SP duration and repeats every SP interval.

TWT Requesting STA communicates the Wake Scheduling information to its TWT responding AP, which then devises a schedule and delivers the TWT values to the TWT requesting STA when a TWT agreement has been established between them.

Solicited TWT

STA initiates the TWT session with the AP.

Unsolicited TWT

AP initiates TWT setup with STA. AP sends TWT response with service period which is accepted by STA.

Broadcast TWT

High-Efficiency AP requests the STA to participate in the broadcast TWT operation, either on-going broadcast SP or new SP.

Configuring Target Wake Time at the Radio Level (CLI)

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

ap dot11 { 24ghz | 5ghz | 6ghz} shutdown

Example:

Device(config)#ap dot11 24ghz shutdown

Disables the 802.11a, 802.11b, or 802.11 6-GHz network.

Step 3

ap dot11 { 24ghz | 5ghz| 6ghz} dot11ax

Example:

Device(conf)#ap dot11 24ghz dot11ax

Configures the 802.11ax parameters.

802.11ax cannot be disabled on the 6-GHz band.

Step 4

[no] ap dot11 { 24ghz | 5ghz| 6ghz} dot11ax target-wakeup-time

Example:

Device(config)#ap dot11 24ghz dot11ax target-wakeup-time

Configures 802.11 6-GHz dot11ax target wake-up time.

Step 5

[no] ap dot11 { 24ghz | 5ghz| 6ghz} dot11ax twt-broadcast

Example:

Device(config)#ap dot11 24ghz dot11ax twt-broadcast

Configures 802.11 6-GHz dot11ax target wake-up time broadcast.

Note

 

By default TWT is disabled on the controller. You can enable TWT by running this command.

Step 6

no ap dot11 { 24ghz | 5ghz | 6ghz} shutdown

Example:

Device(config)#no ap dot11 24ghz shutdown

Enables the 802.11a or 802.11b network.

Enables the 802.11a, 802.11b, or 802.11 6-GHz network.

Step 7

show ap dot11 { 24ghz | 5ghz| 6ghz} network

Example:

Device(config)#show ap dot11 24ghz network

Displays the 802.11ax network configuration details, which includes information about Target Wakeup Time and Target Wakeup Broadcast.

Configuring Target Wake Time on WLAN

Enabling Target Wake Time on WLAN (CLI)

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

wlan wlan-profile

Example:

Device(config)# wlan wlan-profile

Enters WLAN configuration submode. The wlan-profile is the profile name of the configured WLAN.

Step 3

shutdown

Example:

Device(conf-wlan)#shutdown

Disables the WLAN network

Step 4

dot11ax target-waketime

Example:

Device(conf-wlan)#dot11ax target-waketime

Configures target wake time mode on WLAN.

Step 5

dot11ax twt-broadcast-support

Example:

Device(conf-wlan)#dot11ax twt-broadcast-support

Configures the TWT broadcast support on WLAN.

Step 6

no shutdown

Example:

Device(conf-wlan)#no shutdown

Enables WLAN.

Step 7

show wlan { all | id | name | summary}

Example:

Device# show wlan all
Device# show wlan id
Device# show wlan name

Displays the details of the configured WLAN, including Target Wakeup Time and Target Wakeup Time Broadcast.

Disabling Target Wakeup Time on WLAN (CLI)

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

wlan profile-name

Example:

Device(config)# wlan wlan-profile

Enters WLAN configuration submode. The wlan-profile is the profile name of the configured WLAN.

Step 3

shutdown

Example:

Device(conf-wlan)#shutdown

Disables the WLAN network

Step 4

no dot11ax target-waketime

Example:

Device(conf-wlan)#no dot11ax target-waketime

Disables the target wake time mode on WLAN.

Step 5

no dot11ax twt-broadcast-support

Example:

Device(conf-wlan)#no dot11ax twt-broadcast-support

Disables the TWT broadcast support on WLAN.

Step 6

no shutdown

Example:

Device(conf-wlan)#no shutdown

Enables WLAN.

Configuring Target Wake Time (GUI)

Procedure

Step 1

Choose Configuration > Radio Configurations > Parameters.

The parameters page is displayed where you can configure global parameters for 5 GHz Band and 2.4 GHz Band radios.

Step 2

In the 11ax Parameters section, check the Target Wakeup Time check box and the Target Wakeup Time Broadcast check box to configure target wakeup time and broadcast target wakeup time.

Verifying Target Wakeup Time

To verify Target Wakeup Time and Target Wakeup Time Broadcast, use the following command:

show ap dot11 24ghz network

The following is a sample output:

Device#show ap dot11 24ghz network
.
.
.
802.11ax                                : Enabled
Target Wakeup Time                      : Enabled 
Target Wakeup Time Broadcast            : Enabled
.
.
.