AP Self-Positioning With FTM Pairing and Multipath Outlier Removal

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Solution Overview

Problem

Fine Time Measurement (FTM) for Access Point (AP) self-positioning is inaccurate in multipath environments due to phase variations and low Received Signal Strength Indicator (RSSI), leading to high ranging errors and communication failures.

Innovation Solution

APs generate an AP graph based on Received Signal Strength Indicator (RSSI) to determine accurate AP pairs, use multiple TX and RX antennas with constant Cyclic Shift Delay (CSD) to send and receive FTM action frames, and remove outlier signals with low RSSI to improve positioning accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If FTM is used for AP self-positioning in multipath environments, then positioning capability is provided, but phase variations and low RSSI cause high ranging errors and measurement inaccuracy

Engineering Contradiction:

ImproveFTM ranging accuracyVSAvoidphase variations and multipath interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent segments the FTM measurement process into multiple components: separating direct signals from multipath signals, dividing the measurement into multiple hops through intermediate APs, and segmenting the signal processing into distinct stages (signal reception, RSSI calculation, outlier removal, position determination). This segmentation allows the system to isolate and eliminate harmful multipath interference while maintaining positioning capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces intermediate APs as mediators in the FTM measurement process. Instead of direct AP-to-AP measurements that are susceptible to multipath interference, the system uses intermediate APs to relay measurements, creating a multi-hop path that avoids direct line-of-sight requirements and reduces the impact of phase variations and signal strength fluctuations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If APs operate at standard power, then power efficiency is improved, but Rate over Range limitations reduce communication performance

Engineering Contradiction:

ImproveAP power consumptionVSAvoidcommunication rate

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent performs preliminary position determination using FTM measurements at lower power levels before establishing full-rate communication. By pre-calculating positions and characterizing the radio environment during low-power measurement phases, the system can optimize communication parameters and establish efficient data transmission paths without requiring continuous high-power operation, thus achieving both power efficiency and adequate communication performance.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12526764B2Fine time measurement improvement for access point self-positioning

Publication Date: 2026.01.13 CISCO TECHNOLOGY INC

AI summary

Fine Time Measurement (FTM) improvement for AP self-positioning may be provided. First, an Access Point (AP) graph may be generated. An AP pair may be determined for FTM AP self-positioning based on the AP graph, A plurality of Transmit (TX) signals may be sent to a paired AP of the AP pair using two more TX antennas, wherein the plurality of TX signals include FTM action frames and have a first constant Cyclic Shift Delay (CSD). A plurality of Receive (RX) signals may be received from the paired AP using two or more RX antennas, wherein the plurality of RX signals include FTM action frames and have a second constant CSD, Outlier RX signals having a low Received Signal Strength Indicator (RSSI) may be removed from the plurality of RX signals. An AP position may be determined based on the plurality of RX signals.