Angle of Departure Estimation Using Cyclic Delay in Multi-Antenna Signals
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Solution Overview
Problem
Current wireless localization methods, such as GPS and cellular network triangulation, are unreliable indoors and in crowded urban environments, and existing WLAN-based methods face challenges in accurately determining the angle of arrival of signals with multiple antennas.
Innovation Solution
A method that processes signals from multiple antennas using a multi-carrier encoding scheme with a predefined cyclic delay to estimate the angle of departure, allowing for accurate localization even with a single omnidirectional antenna, by computing the phase delay and applying linear transformations to time-frequency bins or correlation functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS is used for localization, then location coordinates can be derived from satellite signals, but GPS works poorly indoors and in crowded urban environments due to dependence on weak satellite signals
Solution Approach 1:
The patent uses WiFi access points as intermediary objects to enable localization. Instead of relying directly on satellite signals that are blocked by buildings, the system uses locally available WiFi signals from access points as mediators to determine position, thereby resolving the contradiction between needing reliable localization and dealing with environmental signal blockage
Solution Approach 2:
The patent changes the fundamental parameter of signal type used for localization from satellite-based GPS signals to WiFi-based signals from access points. This parameter change allows the system to operate effectively in indoor and urban environments where satellite signals are blocked but WiFi signals are available
2Measurement precision
If cellular network triangulation is used, then telephone location can be determined based on signals between telephone and multiple cellular antennas, but the technique is inaccurate and unreliable
Solution Approach 1:
The patent changes the measurement parameter from signal strength-based triangulation to angle of arrival (AoA) estimation using phase difference measurements. This parameter change from measuring signal intensity to measuring phase relationships enables more accurate and reliable location determination
Solution Approach 2:
The patent replaces the traditional cellular triangulation method with a new approach using phase difference measurements and AoA estimation. This substitution introduces a fundamentally different measurement mechanism that achieves superior accuracy and reliability
3Measurement precision
If angle of arrival estimation is performed using existing WLAN methods, then location can be determined, but accurate determination of angle of arrival with multiple antennas faces challenges
Solution Approach 1:
The patent segments the complex AoA estimation problem into distinct processing stages: receiving signals from multiple antennas, computing phase differences, applying correlation functions, and estimating angles. This segmentation of the signal processing pipeline makes the complex task more manageable and implementable
Solution Approach 2:
The patent changes the approach to AoA estimation by using phase difference measurements between signals received at different antennas, combined with correlation functions. This parameter change from direct angle measurement to phase-based indirect measurement achieves accurate AoA determination while managing processing complexity
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 accurate determination of the angle of departure from wireless access points, enabling precise localization of mobile devices without the need for GPS or direct association with access points, improving indoor and urban location determination.
Implementation Method 1
The received first and second signals are processed, using the cyclic delay, in order to derive a measure of a phase delay between the first and second signals
Data Source
AI summary
A method for signal processing includes receiving at a given location at least first and second signals transmitted respectively from at least first and second antennas (34) of a wireless transmitter (24). The at least first and second signals encode identical data using a multi-carrier encoding scheme with a predefined cyclic delay between the transmitted signals. The received first and second signals are processed, using the cyclic delay, in order to derive a measure of a phase delay between the first and second signals. Based on the measure of the phase delay, an angle of departure (θ) of the first and second signals from the wireless transmitter to the given location is estimated.