Adaptive Inactivity Timeout for Wireless Power Saving
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Solution Overview
Problem
Wireless devices face challenges in power management, particularly in minimizing power consumption while maintaining performance, due to the tradeoff between idle listening time and data reception, especially in WLAN systems where channel congestion and hidden nodes can lead to inaccurate packet arrival rate determination and increased latency.
Innovation Solution
The system adjusts the inactivity time interval (ITO) based on channel congestion metrics, using look-up tables and adaptive methods to optimize power saving, and employs speculative polling to mitigate errors in congestion estimation and hidden node issues, ensuring efficient power management and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device keeps the STA awake for a fixed period of time after the last received/transmitted frame, then performance is maintained, but power consumption increases
Solution Approach 1:
The patent implements dynamic adjustment of the inactivity time interval (ITO) based on channel congestion conditions. Instead of using a fixed ITO value, the system adapts the ITO duration according to real-time channel metrics such as channel busy ratio (CBR) and packet error rate (PER). This allows the device to extend the awake period when channel conditions indicate potential data arrivals, while reducing the awake period when the channel is clear, thereby dynamically optimizing the tradeoff between power consumption and data reception performance.
Solution Approach 2:
The patent changes the parameter of inactivity time interval from a fixed value to a variable value that depends on channel congestion metrics. The system measures channel conditions (CBR, PER) and adjusts the ITO parameter accordingly, selecting from multiple predefined ITO values or calculating an optimal ITO based on the measured parameters. This parameter adaptation resolves the contradiction by allowing the system to maintain performance when needed while reducing power consumption when possible.
2Use of energy by moving object
If the device frequently enters sleep mode to save power, then power consumption is reduced, but data reception opportunities are lost
Solution Approach 1:
The patent employs feedback mechanisms where the device continuously monitors channel congestion metrics (CBR, PER) and uses this feedback to adjust the ITO value. The feedback loop ensures that the device only enters sleep mode when channel conditions indicate low probability of data arrivals, thereby maintaining data reception performance while achieving power savings. The system feedback from channel measurements directly influences the decision to extend or reduce the awake period.
Solution Approach 2:
The patent performs preliminary assessment of channel conditions before the device enters sleep mode. By measuring CBR and PER in advance and predicting the likelihood of data arrivals, the system makes informed decisions about ITO adjustment. This preliminary action prevents premature sleep mode transitions that would result in missed data, while still enabling power savings when channel conditions warrant early sleep entry.
3Use of energy by moving object
If the device uses packet arrival rate to adjust ITO, then power saving is optimized, but estimation errors occur due to channel congestion
Solution Approach 1:
The patent introduces intermediary metrics (CBR and PER) that mediate between the difficult-to-measure packet arrival rate and the ITO adjustment decision. Instead of directly measuring packet arrival rate which is error-prone under channel congestion, the system uses CBR (channel busy ratio) and PER (packet error rate) as intermediate indicators that are more reliably measurable. These intermediary metrics provide a more accurate basis for ITO adjustment, reducing estimation errors while still enabling power optimization.
Solution Approach 2:
The patent substitutes the direct measurement approach (mechanically counting packets to determine arrival rate) with an indirect measurement approach using channel metrics. Instead of relying on packet counting which is susceptible to congestion-related errors, the system uses radio frequency measurements of channel busy status and error rates. This substitution replaces a fragile measurement mechanism with a more robust one that is less affected by channel congestion conditions.
4Use of energy by moving object
If the device sends null-data frames to enter sleep mode, then power saving is achieved, but transmission power is consumed due to retries from channel congestion
Solution Approach 1:
The patent performs preliminary assessment of channel congestion conditions (using CBR and PER metrics) before the device attempts to enter sleep mode via null-data frame transmission. By evaluating channel conditions in advance, the system predicts the likelihood of successful sleep mode entry versus the likelihood of requiring retries due to congestion. This preliminary action prevents unnecessary null-data frame transmissions in congested conditions, avoiding the energy waste associated with retry attempts while still enabling power savings when channel conditions are favorable.
Data Source
AI summary
Power saving for wireless communication devices by adjusting the amount of time, after a last transmission/reception of data, that the device remains in an awake mode listening for more data before the device enters a sleep mode. This time period may be referred to as inactivity time interval or inactivity timeout (ITO). The described features may be employed to improve power savings by taking metrics of channel congestion into account for determining the ITO. The appropriate ITO may be determined to be commensurate with ongoing transmission and/or reception activity. Because error may occur in estimating channel congestion and/or transmission/reception activity, latency bounds based on estimation errors may be managed by classifying the operational mode into multiple regions and employing techniques for mitigating error in congestion estimation based at least in part on the operational mode.