Extended U-APSD Trigger Frames for Wi-Fi Power Save
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Solution Overview
Problem
Non-AP STAs with small battery capacities face reduced battery life due to the need to wake up regularly to listen for beacons and receive group-addressed frames, as per the existing Unscheduled Automatic Power Save Delivery (U-APSD) protocol, which is inefficient and shortens their operational time.
Innovation Solution
The implementation of an Extended U-APSD mechanism that allows non-AP STAs to send trigger frames to APs for group-addressed frames, enabling them to stay in power save mode longer without waking up at regular intervals, using an AC_GR subfield in communication frames to indicate support for trigger/delivery-enabled group-addressed frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-AP STAs wake up every DTIM time period to listen for beacons and receive group-addressed frames according to existing U-APSD protocol, then frame delivery reliability is ensured, but battery life is reduced
Solution Approach 1:
The AP performs preliminary actions by buffering group-addressed frames before the STA wakes up. The AP receives and stores frames in a buffered units (BU) list during the STA's sleep period, then delivers them all at once when the STA wakes up and sends a trigger frame, eliminating the need for the STA to wake up at every DTIM interval.
Solution Approach 2:
The AP acts as an intermediary by maintaining a buffered units list that mediates between frame arrival and frame delivery. This intermediary structure allows frames to be stored and managed by the AP until the STA is ready to receive them, decoupling the frame delivery timing from the STA's wake-up schedule.
2Use of energy by moving object
If non-AP STAs remain in power save mode longer to extend battery life, then power efficiency is improved, but frame delivery timing becomes unsynchronized
Solution Approach 1:
The STA provides feedback by sending a trigger frame (such as a QoS Null frame) when it wakes up, indicating to the AP that it is ready to receive buffered frames. The AP uses this feedback signal to initiate frame delivery, ensuring synchronization between the STA's wake-up time and the frame delivery timing.
Solution Approach 2:
The system transitions from a static DTIM-based wake-up schedule to a dynamic trigger-based mechanism. The STA can wake up at flexible intervals and initiate frame delivery dynamically by sending trigger frames, allowing the system to adapt to the STA's actual power save needs while maintaining delivery synchronization.
3Adaptability or versatility
If existing U-APSD protocol is used with separate AC configurations, then QoS requirements are met, but complexity increases for small battery STAs
Solution Approach 1:
The trigger frame mechanism serves multiple functions: it acts as a wake-up signal, a readiness indicator, and a frame delivery trigger. The same QoS Null frame structure is used across different ACs with unified handling at the AP, reducing the operational complexity for STAs while maintaining QoS differentiation through the buffering mechanism.
Data Source
AI summary
A device for communicating in a wireless network, such as, for example, a non-AP STA, is adapted to send a trigger frame to an AP for group-addressed frames. In addition, an AP may be adapted to be triggered for group-addressed frames to deliver the group-addressed frame to a non-AP STA. The group-addressed frames could include data frames or management frames or both. Such a device or non-AP STA can advantageously stay in a power save mode until it is ready to wake up to send a trigger frame to the AP, and does not need to wake up at regular intervals, such as at every DTIM time interval, to listen for beacons from the AP and to receive any group-addressed frames destined for it and buffered at the AP. In this way, the battery life of the device may be extended.