Dual-Mode Device Operating Window Adjustment for Clock Drift
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Solution Overview
Problem
Dual-mode devices operating in time division multiplexed WLAN modes face challenges in adjusting operating windows due to clock drift, leading to potential packet loss and inefficiencies in time allocation between access point and station modes.
Innovation Solution
The dual-mode device computes the expected time instances of beacon arrival and adjusts its operating windows by recalculating the sequence of future time instances and scheduling station and access point windows based on the variance, ensuring that each mode operates within pre-configured time periods to prevent packet loss and maintain optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dual-mode device uses fixed operating windows for AP and station modes, then the time allocation is simple and stable, but packet loss occurs due to clock drift and timing variations
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual beacon reception time and comparing it with the expected beacon time. Based on this feedback, the device dynamically adjusts the operating window boundaries to compensate for clock drift and timing variations, ensuring reliable packet transmission without requiring overly complex adjustment mechanisms
Solution Approach 2:
The patent changes the time parameters of the operating windows dynamically. Specifically, it adjusts the start and end boundaries of AP mode and station mode operating windows based on the measured variance between actual and expected beacon times, allowing the system to adapt to timing variations while maintaining simple operation
2Measurement precision
If the operating window duration is extended to accommodate clock drift variations, then timing accuracy is improved, but time allocation efficiency between AP and station modes deteriorates
Solution Approach 1:
The patent makes the operating window duration dynamic rather than fixed. It calculates the actual operating window duration based on the measured beacon timing variance and adjusts the window boundaries accordingly. This allows the system to extend timing accuracy when needed while maintaining efficient time allocation when conditions are stable
Solution Approach 2:
The patent applies partial adjustment to the operating windows based on the actual timing variance observed. Instead of always extending windows maximally, it only adjusts them to the extent necessary to accommodate the measured clock drift, thereby maintaining time allocation efficiency while achieving sufficient timing accuracy
3Reliability
If the device frequently adjusts operating windows to compensate for clock drift, then packet loss is prevented, but processing overhead and operational complexity increase
Solution Approach 1:
The patent implements self-service by having the dual-mode device automatically monitor its own beacon timing and adjust its operating windows without external intervention. The device independently measures the variance between actual and expected beacon times and autonomously recalculates the operating window boundaries, preventing packet loss while avoiding complex manual management
Data Source
AI summary
A dual-mode device may compute an expected time instance of arrival of a first beacon based on prior received beacons. If the first beacon is received at an actual time instance which is in variance with the expected time instance, the device re-computes a sequence of future time instances of arrival of respective future beacons and schedules a sequence of station windows, with each station window to cover the corresponding future time instance of the sequence of future time instances and to have a desired first period. The dual-mode device operates in station mode in the sequence of station windows and in the AP mode in a sequence of AP windows, wherein each station window of the sequence of station windows is operated alternately with each AP window of the sequence of AP windows in a TDM manner, with each AP window having a desired second period.