Multi-path Mitigation in RF Tracking Using Digital Signal Processing
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Solution Overview
Problem
Conventional RF-based identification and location-finding systems face inaccuracies in indoor and outdoor environments due to RF signal propagation issues like multipath phenomena, which current methods struggle to mitigate effectively, especially when using narrow-bandwidth ranging signals at VHF or lower frequencies.
Innovation Solution
A method and system employing a multi-path mitigation processor using digital signal processing and software-defined radio technologies to enhance the accuracy of RF-based tracking and locating systems, capable of operating on various frequency bands including VHF, UHF, and higher frequencies, by processing narrow-bandwidth ranging signals and mitigating multipath effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If narrow-bandwidth ranging signals are used at VHF or lower frequencies, then signal attenuation and scattering are reduced, but multi-path phenomena remain severe enough to compromise location accuracy
Solution Approach 1:
The system changes the parameter of signal bandwidth from wide to narrow, and operates at VHF or lower frequencies to reduce signal attenuation and scattering. This allows the signal to propagate further with less energy loss while maintaining a manageable level of multi-path interference through digital signal processing mitigation techniques.
Solution Approach 2:
The patent replaces traditional hardware-based multi-path mitigation approaches with digital signal processing methods. The multi-path mitigation processor uses software-defined radio technologies to digitally separate direct path signals from reflected signals, substituting mechanical or hardware solutions with computational processing to achieve location accuracy.
2Measurement precision
If wide bandwidth ranging signals are used for multi-path mitigation, then location accuracy improves, but bandwidth requirements exceed available spectrum and regulatory limits
Solution Approach 1:
The system inverts the traditional approach by changing the bandwidth parameter from wide to narrow. Instead of using wide bandwidth signals to achieve multi-path mitigation, the system uses narrow-bandwidth signals at VHF frequencies combined with digital signal processing to achieve both spectrum efficiency and location accuracy within regulatory bandwidth limits.
Solution Approach 2:
The patent substitutes hardware-based wide bandwidth processing with software-defined narrow bandwidth processing. The multi-path mitigation is achieved through digital signal processing algorithms rather than requiring excessive RF bandwidth, allowing the system to operate within regulatory spectrum allocations while maintaining measurement precision.
3Reliability
If spatial diversity or antenna diversity techniques are used for multi-path mitigation, then location reliability improves, but infrastructure complexity and device portability are compromised
Solution Approach 1:
The patent replaces physical antenna diversity systems with a virtual diversity approach using software-defined radio and digital signal processing. The multi-path mitigation processor digitally creates multiple signal paths and processes them to achieve location reliability without requiring multiple physical antennas or complex infrastructure, thereby maintaining device portability and reducing system complexity.
4Object-affected harmful factors
If antenna arrays are used at VHF frequencies for multi-path mitigation, then multi-path effects are reduced, but antenna size becomes too large for portable devices
Solution Approach 1:
The patent substitutes physical antenna arrays with digital signal processing-based multi-path mitigation. The system uses a single or small number of antennas combined with software-defined radio technologies and digital processing algorithms to mitigate multi-path effects, avoiding the need for large physical antenna structures that would be required at VHF frequencies for traditional array-based solutions.
Solution Approach 2:
The system changes the approach from physical parameter-based mitigation (antenna size and spacing) to digital parameter-based mitigation (signal processing algorithms). By operating at VHF frequencies with narrow-bandwidth signals and using digital processing, the system achieves multi-path mitigation with compact antenna sizes suitable for portable devices.
Data Source
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AI summary
Methods for determining a LOB of one or more user equipment (UE) in a wireless system employing Time Difference of Arrival (TDOA) is described. TDOA techniques are based on estimating the difference in the arrival times of reference signals from multiple receivers or from multiple emitters to a receiver. A particular value of the time difference estimate defines a hyperbola between the two receivers on which the handset may exist. When the distance between the receiving antennas is small relative to the distance of the emitter source (the handset) being located, then the TDOA is equivalent to the angle between the baseline of the sensors (receivers antennas) and the incident RF energy from the emitter. If the angle between the baseline and true North is known, then the line of bearing (LOB) and/ or angle of arrival (AoA), can be utilized to determine the location of the UE.