WLAN Power Save Mechanism With Target Wake Time Slots
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Solution Overview
Problem
In WLAN environments with multiple stations, the aggregate throughput level typically drops with the number of stations served, and existing power save mechanisms require significant overhead and new signaling messages.
Innovation Solution
Implementing a 'no service' schedule where stations can enter a deep sleep state for a defined duration, aligned with target wakeup time slots, and wake up only to listen at slot boundaries if serviced, reducing unnecessary wake-ups and maintaining stable throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If initiated scheduled access with TWT groups is used to enable power saving, then stations can enter sleep states, but aggregate throughput drops with increasing number of stations
Solution Approach 1:
The service period is segmented into multiple TWT slots, with each slot dedicated to specific STAs. This segmentation allows the AP to efficiently manage multiple sleeping STAs without requiring all of them to wake up simultaneously, thereby maintaining aggregate throughput while enabling power saving for each individual STA.
Solution Approach 2:
STAs wake up periodically at scheduled TWT slot boundaries rather than remaining continuously active. This periodic wake-up pattern enables power saving by keeping STAs in sleep mode between wake-ups, while the AP schedules transmissions to occur during these periodic wake-up moments, maintaining throughput efficiency.
2Use of energy by moving object
If initiated scheduled access with TWT groups is implemented, then power saving is enabled, but signaling overhead increases due to new messages required
Solution Approach 1:
The TWT setup mechanism is designed to serve multiple functions simultaneously: it establishes wake-up schedules for power saving, allocates TWT slots for resource management, and provides a framework for efficient data transmission. This multi-functionality reduces the need for separate signaling messages for each function, thereby reducing overall signaling overhead.
Solution Approach 2:
The AP performs preliminary scheduling of TWT slots and wake-up times before actual data transmission occurs. By pre-establishing the TWT structure and wake-up patterns, the system avoids the need for dynamic negotiation and signaling during active transmission periods, reducing signaling overhead while maintaining power saving benefits.
3Reliability
If stations wake up frequently to check for data, then data reception reliability is maintained, but power consumption increases
Solution Approach 1:
The system dynamically adjusts STA wake-up behavior based on whether data is actually available. STAs wake up at TWT slot boundaries to check for data, and if no data is present, they return to sleep mode. This dynamic adaptation ensures reliable data reception when needed while minimizing power consumption during idle periods.
Solution Approach 2:
STAs autonomously determine whether to wake up or remain in sleep mode based on their own data reception needs and the scheduled TWT slots. Each STA independently manages its wake-up pattern according to the pre-established schedule, eliminating the need for continuous polling or centralized control, thereby reducing power consumption while maintaining reliability.
Data Source
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AI summary
Methods, systems, and devices are described for saving power in wireless communications. One aspect includes providing an indication of a sleep duration for transmission to a wireless node, communicating with the wireless node during a target wakeup time (TWT), wherein the communication comprises at least one of providing data for transmission to the wireless node or obtaining data received from the wireless node, and refraining from providing data for transmission to the wireless node for at least the indicated sleep duration based at least in part on timing of the communication. Another aspect includes receiving an indication of a sleep duration from a wireless node, communicating with the wireless node during a time slot of a TWT, and entering a sleep mode for the indicated sleep duration based at least in part on timing of the communication with the wireless node during the time slot of the TWT.