Indoor Positioning Carrier Frequency Offset Cancellation

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Solution Overview

Problem

Indoor positioning systems using Bluetooth low energy (BLE) devices face inaccuracies due to carrier frequency offset (CFO) and frequency drift caused by oscillator frequency mismatch between transmitters and receivers, affecting phase difference measurements and positioning estimation.

Innovation Solution

A method and system for carrier frequency offset and frequency drift cancellation in indoor position estimation, which involves receiving wireless signals, calculating phase differences, and applying compensation techniques based on antenna switching patterns to generate accurate direction estimates of mobile devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase difference measurement is performed using BLE devices, then positioning capability is provided, but measurement precision deteriorates due to carrier frequency offset and frequency drift

Engineering Contradiction:

Improvephase difference measurement accuracyVSAvoidpositioning estimation accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by estimating and compensating for carrier frequency offset and frequency drift before performing phase difference measurements. The system performs frequency offset estimation using reference signals and applies compensation algorithms to correct the phase differences, thereby eliminating the harmful frequency mismatch effects before positioning calculations are performed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback mechanisms where the system continuously monitors frequency offset and drift conditions, estimates these parameters from received signals, and adjusts the phase difference measurements accordingly. The feedback loop ensures that frequency compensation is dynamically adapted to changing oscillator conditions, maintaining measurement precision throughout the positioning operation.

Inventive Principle:

Principle #23Feedback

2Ease of operation

If oscillator frequency mismatch occurs between BLE transmitter and receiver, then device operation is maintained, but measurement precision deteriorates due to carrier frequency offset

Engineering Contradiction:

Improvedevice operation continuityVSAvoidphase difference measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent converts the harmful frequency offset into a measurable and compensable parameter. By intentionally measuring the frequency offset using reference signals and known transmission patterns, the system transforms the oscillator mismatch from an uncontrollable error source into a correctable parameter that can be compensated through mathematical adjustment of phase difference measurements.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting the frequency compensation parameters based on estimated offset values. The system modifies the phase difference measurements through frequency compensation algorithms that adapt to the actual oscillator mismatch conditions, thereby maintaining measurement precision despite varying frequency offset conditions.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If frequency drift is present due to oscillator mismatch, then signal reception is maintained, but measurement precision deteriorates affecting positioning estimation

Engineering Contradiction:

Improvesignal reception continuityVSAvoidpositioning estimation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent performs preliminary frequency drift estimation and compensation before positioning calculations. The system estimates drift parameters from reference signals and applies compensation algorithms to correct phase differences in advance, eliminating time-varying frequency errors before they can affect positioning accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamic frequency compensation that adapts to changing drift conditions. The system continuously estimates frequency drift parameters and adjusts compensation values in real-time, allowing the positioning system to maintain accuracy despite time-varying oscillator characteristics and signal reception conditions.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9860096B1Systems and methods for carrier frequency offset and drift cancellation based indoor position estimation

Publication Date: 2018.01.02 NXP USA INC

AI summary

Embodiments described herein provide a method for carrier frequency offset and frequency drift cancellation based indoor position estimation. A wireless signal including a plurality of data samples is received at a receiving antenna and from a mobile device. Information relating to an antenna switching pattern for transmitting or receiving the wireless signal may then be obtained from the wireless signal. A phase difference is calculated associated with each data sample of plurality of data samples. Carrier frequency offset and frequency drift cancellation may be applied to the phase difference to obtain a compensated phase difference. A direction estimate of the mobile device may then be generated based at least in part on the compensated phase difference.