Selective FTM Access Point Scanning to Reduce WLAN Congestion
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Solution Overview
Problem
Existing FTM protocols in WLANs face issues with APs being overloaded by multiple ranging requests, leading to channel congestion, denial of service, and inefficient ranging measurements due to increased management traffic from both associated and non-associated client devices, impacting the performance of responders.
Innovation Solution
An enhanced FTM scanning method where a wireless station selects a set of target APs based on scanning parameter values and weights, reducing the burden on responders by scanning only a subset of APs in each cycle, thereby optimizing resource utilization and improving scan efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all APs are scanned for FTM measurements, then measurement completeness is improved, but channel congestion and AP overload increase
Solution Approach 1:
The patent divides the FTM scanning process into multiple scan cycles, where each cycle scans only a subset of target APs selected based on weights. This segmentation reduces the number of simultaneous scanning operations, thereby decreasing channel congestion while maintaining measurement completeness over time through multiple cycles.
Solution Approach 2:
Instead of scanning all APs in each FTM scan cycle, the patent performs partial scanning by selecting only a subset of target APs based on weight calculations. This partial action reduces the burden on APs and channel congestion while still achieving comprehensive coverage across multiple cycles.
2Adaptability or versatility
If multiple ranging requests are processed simultaneously, then service coverage is improved, but AP performance deteriorates due to overload
Solution Approach 1:
The patent dynamically adjusts the set of target APs scanned in each FTM cycle based on weight calculations that consider current network conditions and AP performance. This dynamic selection ensures that APs with better performance are scanned more frequently, while overloaded APs are temporarily excluded, maintaining both service coverage and AP reliability.
Solution Approach 2:
The patent changes the parameter of target AP selection by calculating weights based on scanning parameter values and using these weights to determine which APs to scan in each cycle. This parameter-based selection adapts to changing network conditions and AP performance levels, balancing service coverage with AP reliability.
3Measurement precision
If FTM scanning is performed frequently, then location accuracy is improved, but resource utilization decreases due to increased management traffic
Solution Approach 1:
The patent implements periodic FTM scanning with multiple cycles, where each cycle scans a different subset of target APs based on weight calculations. This periodic approach maintains location accuracy by repeatedly scanning all APs over time while improving resource utilization by distributing the scanning load across multiple periods rather than performing frequent comprehensive scans.
Data Source
AI summary
Examples of performing selective Fine Timing Measurement (FTM) are described. For an FTM scan cycle, a first AP (i.e., an initiator) may determine scanning parameter values of a plurality of second APs (i.e., potential responders) based on previously performed FTM scans. The first AP may determine weights of the plurality of second APs based on the scanning parameter values and select a set of target APs based on the weights. The first AP may then scan the set of target APs for the FTM scan so that the rest of the plurality of second APs are relieved from participating in the FTM scan thereby reducing the performance impact on the rest of the plurality of second APs. After the FTM scan cycle is completed, the first AP may update the weights and select another set of target APs based on the updated weights to perform another FTM scan cycle.