Airborne WLAN Geo-Location Range Extension via Signal Correlation
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Solution Overview
Problem
The range of an airborne measuring station for geo-locating wireless devices is limited due to the fixed sensitivity of the receiver, which is restricted by the noise figure and the need to receive packets without errors, especially in environments with significant obstruction losses.
Innovation Solution
The method involves correlating raw bits of a received sequence with an expected sequence to achieve a significant processing gain, allowing for a longer range of location determination by transmitting a ranging signal, receiving a direct sequence spread spectrum signal, and comparing the correlation value to a predetermined threshold to determine the geo-location of the wireless device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the receiver sensitivity is increased to extend the geo-location range, then the range of location determination is improved, but the noise figure and error rate worsen due to receiving signals in noisy conditions
Solution Approach 1:
The patent combines multiple received signal sequences through correlation processing to form a composite signal representation. By merging information from multiple transmissions and applying correlation with expected sequences, the system accumulates signal energy while averaging out random noise, thereby extending detection range without sacrificing reliability
Solution Approach 2:
The patent converts the harmful effect of noise into a benefit by using correlation processing. Known noise components that are correlated with the expected sequence pattern are distinguished from random noise, allowing the system to extract useful signal information even in noisy conditions and transform the noisy environment into an acceptable operating condition for extended range detection
2Measurement precision
If correlation processing is applied to improve signal detection sensitivity, then the receive sensitivity is enhanced, but the processing complexity increases
Solution Approach 1:
The patent performs preliminary correlation processing on received sequences before final decision making. By pre-computing correlation values with expected sequences and making decisions based on these preliminary results, the system achieves high detection sensitivity while avoiding the need for more complex post-processing algorithms
Solution Approach 2:
The patent replaces complex mechanical or hardware-based signal processing with computational correlation methods. Instead of using sophisticated analog signal processing circuits, the system uses digital correlation algorithms that can be implemented through software or simple logic circuits, achieving high sensitivity with reduced hardware 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
This approach enhances the sensitivity of geo-location determination, increasing the effective receive sensitivity of the airborne measuring station and extending the range of active geo-location by improving the accuracy and reliability of signal detection even in noisy conditions.
Implementation Method 1
A correlator is provided which correlates raw bits of the received sequence with raw bits of the expected sequence to determine a correlation value
Implementation Method 2
receiving a direct sequence spread spectrum signal transmitted from a second wireless device in response to the ranging signal
Data Source
AI summary
A method and devices are disclosed that increase the range of active geo-location from the airborne measuring station as compared with known methods by increasing the effective receive sensitivity of the airborne measuring station. In one embodiment this may be accomplished by transmitting a predetermined ranging packet and correlating the raw received bit stream of the response packet with the predetermined bit stream. In one embodiment, the disclosed method applies to the reception of IEEE 802.11 direct sequence spread spectrum DSSS ACK and DSSS CTS packets in response to DSSS data null and DSSS RTS packets respectively, in the 2.4 GHz band.