Access Point Priority Scheduling for WLAN Service Delay
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Solution Overview
Problem
In wireless local area networks (WLANs) using IEEE 802.11 power save mode, high-priority Quality of Service (QoS) stations experience service delays due to the current unscheduled automatic power save delivery (U-APSD) mechanism, where lower-priority QoS stations are serviced before high-priority ones, leading to increased delay for high-priority data transmission.
Innovation Solution
The method involves holding off transmission of lower-priority buffered downlink data and prioritizing higher-priority data by using a hold-off configuration frame to indicate the delay in transmission, ensuring that high-priority data is transmitted first, and duplicating the switch point duration for efficient data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If lower-priority QoS stations are serviced before high-priority ones in U-APSD mechanism, then power save mode operation is maintained, but service delay for high-priority stations increases
Solution Approach 1:
The patent changes the transmission parameter by introducing a priority-based scheduling mechanism that modifies the service order of stations. High-priority stations are identified and scheduled for service before lower-priority stations, fundamentally altering the time parameter for data transmission and reducing service delay for critical traffic.
Solution Approach 2:
The patent implements dynamic priority-based scheduling where the AP can adaptively adjust the service order of stations based on their QoS requirements. This dynamic mechanism allows the system to respond to changing traffic conditions by prioritizing high-priority stations when needed, thereby reducing their service delay without compromising overall system operation.
2Loss of time
If high-priority data is prioritized for transmission, then service delay is reduced, but transmission scheduling complexity increases
Solution Approach 1:
The patent segments the station population into different priority groups (high-priority and lower-priority QoS stations). This segmentation allows the AP to apply different scheduling rules to different groups, simplifying the overall scheduling complexity while still achieving priority-based service. Instead of managing all stations uniformly, the system divides them into manageable segments with distinct handling rules.
Solution Approach 2:
The patent employs feedback mechanisms where the AP monitors station priorities and adjusts transmission scheduling accordingly. The AP receives information about station QoS requirements and uses this feedback to dynamically adjust the service order, ensuring high-priority stations are serviced first. This feedback-driven approach manages scheduling complexity by using real-time information to make localized scheduling decisions.
3Use of energy by moving object
If power save mode is used to reduce power consumption, then energy efficiency is improved, but frame transmission and reception capability is lost
Solution Approach 1:
The patent implements periodic wake-up intervals where STAs in power save mode periodically wake up to check for buffered data at the AP. During these periodic awake intervals, the STA can receive beacon frames containing TIM information and engage in data transmission. This periodic action allows the STA to maintain power save mode for most of the time while still providing opportunities for reliable frame transmission when needed.
Solution Approach 2:
The patent uses preliminary actions by having the AP buffer downlink data for power-saving STAs before the STAs wake up. The AP stores incoming frames in its buffer and waits for the STA's next awake interval to transmit them. This preliminary buffering action ensures that data is ready for immediate transmission when the STA becomes active, maintaining reliability without requiring the STA to remain continuously awake.
Data Source
AI summary
Disclosed are a method and an apparatus for operating based on a power save mode in a wireless LAN. The method for operating based on the power save mode in a wireless LAN may comprise the steps of: an AP receiving, from a first STA, a first trigger frame for triggering the transmission of first downlink data which has been buffered for the first STA; the AP determining a temporary halt of the transmission the first downlink data, which is transmitted as a response to the first trigger frame, based on a first priority rank of the first downlink data which has been buffered for the first STA, a second priority rank of second downlink data which has been buffered for a second STA, and a point when the second STA is switched to an awake state; and the AP transmitting, to the first STA, a temporary halt setting frame for indicating the temporary halt.