Indoor Wireless Device Location via Time Difference of Arrival
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Solution Overview
Problem
Existing methods for determining the location of wireless devices indoors, such as GPS and trilateration of mobile telephone signals, are ineffective due to interference and accuracy issues in indoor environments.
Innovation Solution
A method and system that utilize a digital transmitter and multiple receivers with synchronized antennas to calculate the time difference of arrival and bearing of a digital signal, allowing for the estimation of the direction of travel and location of a wireless device, even in environments with multipath interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS or trilateration of mobile telephone signals is used to determine wireless device location, then outdoor positioning can be achieved, but indoor positioning accuracy deteriorates due to interference and signal blockage
Solution Approach 1:
The patent segments the positioning system into multiple fixed receivers distributed throughout the indoor environment, each independently measuring signal arrival times. This segmentation allows the system to overcome signal blockage by having multiple measurement points, where at least some receivers can always detect the transmitted signal despite indoor interference and multipath effects.
Solution Approach 2:
The patent introduces a digital transmitter as an intermediary device that broadcasts known digital signals throughout the indoor space. This intermediary enables indirect positioning by having fixed receivers capture signal arrival times, which are then processed to calculate device location. The intermediary transmitter resolves the issue of direct GPS signal blockage by creating a localized signaling system adapted for indoor environments.
2Measurement precision
If multiple receivers are deployed to improve indoor positioning accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent implements self-service through automated signal processing where the system automatically performs time difference of arrival calculations, bearing estimations, and location determination without manual intervention. The processor automatically compares signals from multiple receivers, calculates positional information, and generates location data, reducing the need for complex manual configuration and operation procedures.
Solution Approach 2:
The fixed receivers are designed as multi-functional devices that simultaneously perform signal reception, time stamping, and data transmission functions. Each receiver unit serves multiple purposes within the positioning system, reducing overall system complexity by consolidating functions into unified components rather than requiring separate specialized devices for each function.
3Measurement precision
If signal processing is performed to filter unwanted signals and calculate time difference of arrival, then positioning accuracy improves, but processing time increases
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing all fixed receivers to a common time reference before signal arrival. This preliminary synchronization eliminates the need for complex post-processing time alignment, allowing receivers to directly record absolute arrival times without requiring extensive computational correction later. The digital transmitter also broadcasts known signal patterns that enable rapid correlation-based processing.
Solution Approach 2:
The patent replaces complex mechanical signal filtering methods with digital signal processing techniques. Instead of using physical filters or manual signal separation, the system uses digital correlation methods where the processor compares received digital signals with known transmitted patterns, efficiently identifying and measuring signal arrival times even in the presence of multipath interference and noise.
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 determination of wireless devices indoors by filtering out unwanted signals and accurately calculating the time difference of arrival and bearing, improving positioning accuracy in challenging indoor environments.
Implementation Method 1
A time difference of arrival of the first and second digital signals is determined at the processor based on the performed comparison
Implementation Method 2
The direction of travel of the digital transmit signal is estimated at the processor based on the determined time difference of arrival of the first and second digital signals. A bearing to the digital transmitter is determined based on the estimated direction of travel
Data Source
AI summary
A method for determining a location of a device in a wireless network includes transmitting a digital transmit signal from a digital transmitter including a first antenna. The first antenna is configured to transmit the digital transmit signal to two or more receivers. A first receiver including a second antenna and a second receiver including a third antenna receive the digital transmit signal from the digital transmitter. The digital transmit signal arrives at the receivers at two different time instances as a first digital signal and a second digital signal. A comparison of the digital signals is performed at the processor. A time difference of arrival of the digital signals is determined at the processor based on the performed comparison. The direction of travel of the digital transmit signal is estimated at the processor. A bearing to the digital transmitter is determined.