IEEE 802.11 Preamble Phase Offset Locationing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing locationing technologies in indoor wireless communication networks face challenges in achieving sufficient accuracy without requiring highly stable clocks and synchronization between receivers, making them impractical for smaller environments.
Innovation Solution
The use of differential phase measurements of IEEE 802.11 preambles, where fixed access points measure phase offsets of the 1.25 MHz preamble cycles to determine the position of a mobile device, utilizing a local clock synchronized with a global phase reference, eliminating the need for precise timing and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TDOA (Time Difference of Arrival) techniques are used for locationing, then locationing capability is provided, but precise timing measurements and infrastructure with highly stable clocks and synchronization between receivers are required
Solution Approach 1:
The patent replaces the mechanical timing-based TDOA system with a phase measurement system. Instead of measuring time differences of arrival which require precise clock synchronization, the system measures phase offsets of received preamble signals at each receiver independently. This substitution eliminates the need for complex clock synchronization infrastructure while maintaining locationing capability through phase-based measurements combined with signal strength information.
Solution Approach 2:
The patent uses the phase information copied from the received preamble signals as a proxy for time measurement. Rather than directly measuring arrival times which would require synchronized clocks, the system copies phase characteristics from the received signals and uses these phase offsets in conjunction with signal strength to determine location, thereby avoiding the need for precise timing infrastructure.
2Measurement precision
If GPS receivers are used for locationing, then locationing capability is provided, but the solution is expensive and not practical for smaller networks
Solution Approach 1:
The patent employs standard IEEE 802.11 wireless receivers and transmitters that are inexpensive and widely available, replacing expensive GPS receivers. The system uses ordinary Wi-Fi hardware components rather than specialized GPS equipment, making the locationing solution cost-effective for small networks while maintaining sufficient accuracy through phase and signal strength measurements.
Solution Approach 2:
The patent makes existing IEEE 802.11 wireless infrastructure serve dual purposes: both communication and locationing. Instead of requiring separate GPS receivers for locationing, the system enables standard Wi-Fi access points and stations to perform both data communication and position determination functions, thereby eliminating the need for expensive dedicated locationing hardware.
3Reliability
If TDOA techniques are used for locationing, then locationing capability is provided, but highly stable clocks and synchronization between receivers are required which may not be available for smaller environments
Solution Approach 1:
The patent replaces the clock synchronization mechanism with independent phase measurement at each receiver. Instead of requiring receivers to be synchronized in time, each receiver independently measures the phase offset of received preamble signals relative to its own local clock. This substitution eliminates the synchronization requirement while maintaining reliable locationing through the combination of phase offset and signal strength data.
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
This method provides accurate locationing within indoor environments with reduced demands on clock stability and synchronization, enabling effective locationing in smaller networks without the need for expensive infrastructure.
Implementation Method 1
determining a phase offset between the local clock and any nearest cycle of a preamble in the received packets in each of the receivers
Data Source
AI summary
A method and apparatus for locationing using differential phase measurements of IEEE 802.11 preambles. A first step includes providing a local clock at the same frequency as the IEEE 802.11 preambles. This step includes synchronizing the local clocks at multiple receivers with a reference clock, for example, using Synchronous Ethernet. A next step includes receiving IEEE 802.11 packets from a transmitter by at least three fixed receivers. A next step includes determining a phase offset between the local clock and any nearest cycle of a preamble in the received packets in each of the receivers. A next step includes locating the transmitter using each of the phase offsets.