WLAN Reception Window Timing for Airborne Geo-Location
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Solution Overview
Problem
Existing geo-location methods for WLAN devices face challenges in accurately determining the reception window timing due to varying distances and altitudes of airborne measuring stations, leading to false signal detections and performance issues.
Innovation Solution
A method and apparatus that determine reception window timing using a directional antenna, calculating far and near projection angles and ranges based on antenna beam width, tilt angle, and altitude, to precisely define the start and end times of the reception window for accurate signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reception window timing is used for geo-location, then the device complexity is reduced, but the measurement precision deteriorates due to varying distances and altitudes causing false signal detections
Solution Approach 1:
The reception window timing is made dynamic by calculating it based on the measured round-trip time (RTT) from ranging packets. The end time of the reception window is set to TOA + RTT/2, and the start time is set to TOA + RTT/2 - window_duration, where TOA is the time of arrival and window_duration is calculated based on the speed of light and a distance threshold. This allows the reception window to adapt automatically to varying distances and altitudes, preventing false signal detections while maintaining reasonable device complexity.
Solution Approach 2:
The reception window parameters (start time, end time, duration) are changed based on the measured RTT and calculated distance. The window duration is dynamically adjusted as min(window_duration, (Ttmax - tSIFS) - (TOA - TOD - tSIFS)), where Ttmax is the maximum allowed reception window end time. This parameter adaptation ensures accurate signal detection across varying geo-location conditions without requiring complex manual configuration.
2Adaptability or versatility
If the reception window is extended to cover larger distance ranges, then the adaptability is improved, but the loss of time increases due to waiting for potential distant responses
Solution Approach 1:
The reception window timing is preliminarily calculated based on the measured RTT before actually opening the window. The end time is set to TOA + RTT/2, which is the expected time for a response from the calculated distance. This preliminary calculation ensures the window is opened only for the necessary duration to receive responses from devices within the relevant distance range, avoiding unnecessary waiting time while maintaining adaptability to different ranges.
Solution Approach 2:
The reception window duration is dynamically adjusted based on the calculated distance and RTT. The actual window duration is set to min(window_duration, (Ttmax - tSIFS) - (TOA - TOD - tSIFS)), which automatically scales the window size according to the measured conditions. This dynamic adjustment allows the system to adapt to larger or smaller distance ranges without always incurring maximum time loss.
Data Source
AI summary
A method for determining reception window timing using a measuring station receiving an antenna beam width, receiving an antenna tilt angle, receiving an altitude A, determining a far projection angle Δf, determining a near projection angle Δn, and determining a far projection range corresponding to the far projection angle Δf and based at least upon the values of Δf and A. The method further includes determining a near projection range corresponding to the near projection angle Δn and based at least upon the values of Δn and A, determining an end time of a reception window based at least upon the value of the far projection range the reception window being a window of time in which a response from the target station is expected to be received, and determining a start time of the reception window based at least upon the value of the near projection range.