TWT vs. R-TWT: Target Wake Time versions in WiFi 6 and WiFi 7

The difference between TWT (Target Wake Time) used in Wi-Fi 6 (802.11ax) and R-TWT (Restricted Target Wake Time) used in Wi-Fi 7 (802.11be) lies in how they manage scheduled access and power-saving, particularly in multi-user environments.

What is TWT (Target Wake Time) in Wi-Fi 6 (802.11ax)

The TWT mechanism was initially introduced in 802.11ah. In 802.11ax, it allows devices (i.e. STAs) to negotiate scheduled wake-up times with the AP (Access Point). In this mechanism, both AP and STA establish TWT aggrement and negotiate TWT service periods (SPs). Hence STA awake only within these schedules windows to transmit/receive data and sleep most of the time.

There are two TWT modes viz. individual TWT and broadcast TWT. In individual mode, both AP and STA negotiate one by one. In broadcast mode, TWT SPs are announced by AP and STAs send their requests to AP in order to join operation and consecutively to obtain SPs.

Application : It is ideal for IoT devices or mobile devices which require longer battery life.

What is R-TWT (Restricted TWT) in Wi-Fi 7 (802.11be)

It has been introduced for latency sensitive real time traffic. R-TWT inherits negotiation mechanism of broadcast TWT.

It extends TWT by enabling exclusive and contention free channel access during TWT schedule. In R-TWT, devices are granted exclusive access to the medium during SP (Service Period). AP enforces strict restrictions on medium access for other devices.

Application : Suitable for AR/VR, 4K/8K video, industrial automation etc.

Key differences between TWT and R-TWT

Conclusion

The Target Wake Time (TWT) mechanism in Wi-Fi 6 (802.11ax) optimizes power and network efficiency. Restricted TWT (R-TWT) in Wi-Fi 7 (802.11be) enhances timing guarantees, QoS and ultra-low latency.