NDPA Frame Structure for Accurate WLAN Indoor Ranging

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Solution Overview

Problem

GPS technology is ineffective for providing accurate location information in indoor environments, and existing WLAN-based positioning techniques face challenges in accurately determining distances and angles for precise device location estimation.

Innovation Solution

A method involving the generation and exchange of null data packet announcement (NDPA) frames and null data packets (NDPs) between communication devices, including specific station information fields to facilitate ranging measurements, along with feedback packets for accurate distance and angle calculations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If GPS technology is used for location determination, then outdoor positioning accuracy is improved, but it becomes ineffective in indoor environments where GPS satellites are not visible

Engineering Contradiction:

Improvepositioning accuracyVSAvoidenvironmental adaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent introduces WLAN infrastructure (access points and communication devices) as an intermediary positioning system to replace GPS in indoor environments. The WLAN-based ranging measurement exchange uses null data packets and feedback mechanisms to determine distances and angles between devices, enabling location estimation without relying on GPS satellites.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a universal positioning solution that works across both outdoor and indoor environments. By developing WLAN-based triangulation and trilateration techniques using time of flight measurements, the system provides consistent positioning capability regardless of whether GPS is available, making the positioning system adaptable to different environmental conditions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If WLAN-based triangulation techniques are used for indoor positioning, then environmental adaptability is improved, but measurement precision for distance and angle determination deteriorates

Engineering Contradiction:

Improveindoor positioning capabilityVSAvoiddistance and angle measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where communication devices exchange null data packets and receive feedback information about signal characteristics. This feedback loop allows devices to refine their distance and angle calculations by analyzing signal strength, time of flight, and other measurements from multiple exchanges, thereby improving measurement precision through iterative refinement.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses multiple null data packet exchanges and collects measurements from multiple access points and communication devices. By gathering excessive measurement data points beyond the minimum required for triangulation, the system can average out errors and improve the precision of distance and angle determinations through statistical processing of multiple partial measurements.

Inventive Principle:

Principle #16Partial or excessive action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables precise location estimation of communication devices by determining distances and angles using WLAN technology, even in environments where GPS is unreliable, enhancing positioning accuracy.

Implementation Method 1

a distance between a first communication and a second communication device is determined by measuring a time of flight of WLAN transmissions between the first communication device and the second communication device

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS12554005B1Null data packet announcement frame for NDP ranging

Publication Date: 2026.02.17 MARVELL ASIA PTE LTD

AI summary

A first communication device generates a null data packet announcement (NDPA) frame for use in a ranging measurement exchange session with a second communication device. The NDPA frame includes a station information field corresponding to the second communication device, the station information field having i) an 11-bit association identifier (AID) subfield that includes an identifier of the second communication device, ii) a disambiguation subfield set to a value that prevents a third communication device operating according to a second communication protocol from improperly processing the NDPA frame, and iii) sixteen bits between the AID subfield and the disambiguation subfield. The first communication device transmits the NDPA frame to the second communication device as part of the ranging measurement exchange session. After transmitting the NDPA frame, the first communication device transmits a null data packet (NDP) to the second communication device as part of the ranging measurement exchange session.