Access Point Station Classification for Wi-Fi Power Savings
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Solution Overview
Problem
In IEEE 802.11 compliant communications systems, stations that receive little or no downlink traffic consume excessive power by monitoring for traffic indicators, leading to reduced battery life and increased energy consumption, especially in sensor devices with low duty cycle traffic.
Innovation Solution
Implementing a method to categorize stations into TIM and non-TIM types based on their downlink and uplink data usage, allowing non-TIM stations to ignore traffic indication maps (TIM) and sleep for extended periods, with the access point automatically detecting or negotiating station types and adjusting their operation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stations monitor for traffic indicators in beacons, then they can receive downlink traffic timely, but power consumption increases and battery life decreases
Solution Approach 1:
The patent applies local quality by differentiating station types (TIM stations vs. non-TIM stations) based on their downlink traffic characteristics. TIM stations monitor beacons for traffic indicators, while non-TIM stations ignore TIM elements and sleep longer. This localized differentiation allows each station type to operate optimally for its specific traffic pattern, resolving the contradiction between reliable downlink reception and power consumption.
Solution Approach 2:
The patent implements dynamics by making the station operation mode adaptive rather than static. Stations dynamically adjust their beacon monitoring behavior based on whether they have downlink traffic to receive. The access point dynamically assigns TIM or non-TIM status based on observed traffic patterns, allowing the system to adapt to changing conditions and optimize the balance between traffic reception reliability and power consumption.
2Use of energy by moving object
If stations sleep for extended periods to save power, then battery life increases, but ability to receive downlink traffic decreases
Solution Approach 1:
The patent applies preliminary action by having the access point proactively manage downlink traffic delivery to non-TIM stations. Before a non-TIM station goes to sleep, the access point can buffer incoming downlink traffic and deliver it when the station wakes up. This preliminary preparation ensures that no downlink traffic is lost even though the station sleeps for extended periods, resolving the contradiction between power savings and traffic reception reliability.
Solution Approach 2:
The access point acts as an intermediary between the external network and sleeping non-TIM stations. It receives downlink traffic from the network, buffers it, and forwards it to stations when they are awake. This intermediary role allows stations to sleep without missing traffic, as the access point mediates the delivery timing, resolving the contradiction between extended sleep periods and reliable traffic reception.
3Reliability
If all stations monitor TIM in beacons, then downlink traffic can be indicated to all stations, but device complexity and processing overhead increase
Solution Approach 1:
The patent applies taking out by extracting the TIM monitoring requirement from non-TIM stations. Instead of all stations needing to process TIM elements in beacons, the system extracts this requirement and applies it only to TIM stations. Non-TIM stations ignore TIM elements entirely, reducing their processing complexity while TIM stations continue to monitor for traffic indicators, thus resolving the contradiction between comprehensive traffic indication and reduced device complexity.
4Reliability
If stations with low duty cycle traffic monitor beacons continuously, then they can receive traffic immediately, but energy efficiency decreases
Solution Approach 1:
The patent applies local quality by tailoring the beacon monitoring behavior to the specific traffic characteristics of each station. Stations with low duty cycle traffic (sensor devices) are classified as non-TIM stations and configured to ignore TIM elements and sleep longer, matching their low traffic patterns. This localized optimization ensures that energy is not wasted on continuous monitoring for stations that don't need it, while still maintaining responsiveness for stations that do have traffic, resolving the contradiction between responsiveness and energy efficiency.
Data Source
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AI summary
A method for operating an access point includes receiving information from a first station configured to operate in a non- transmit-indicator-map (TIM) mode, and determining if downlink data intended for the first station is available at the access point. The method also includes transmitting at least one of the downlink data intended for the first station to the first station, a data indicator indicating that the downlink data intended for the first station is available at the access point, information indicating downlink data is available for the first station, and a time indicator indicating a specific time when the downlink data intended for the first station will be sent to the first station.