Dual Bandwidth TDOA Location System Using UWB and WLAN Signals
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Solution Overview
Problem
Current IEEE 802.11a/b/g/n based Time Difference of Arrival (TDOA) location systems face limitations in accuracy due to the limited bandwidth of their signals, which affects the precision of Time of Arrival (TOA) measurements, especially in multipath environments, and are further constrained by the range limitations of Ultra-Wide Band (UWB) systems.
Innovation Solution
A dual bandwidth TDOA location system is developed, integrating UWB technology with narrower band WLAN/WPAN communication systems, allowing for the transmission and reception of dual bandwidth signals, where location transceivers can measure and process both WLAN and UWB signals synchronously, enabling improved location accuracy and range by utilizing the higher accuracy of UWB signals while maintaining the broader coverage of WLAN signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IEEE 802.11a/b/g/n based TDOA location systems use single bandwidth signals, then the system maintains simplicity and broader coverage, but location accuracy deteriorates due to limited bandwidth affecting TOA measurement precision
Solution Approach 1:
The patent combines UWB and WLAN communication systems into a hybrid TDOA location system. The system integrates UWB location transceivers with existing WLAN infrastructure, allowing the system to leverage the high measurement precision of UWB signals while maintaining the broader coverage and simpler deployment of WLAN networks. This merging resolves the contradiction by achieving high accuracy without requiring a complete system overhaul.
Solution Approach 2:
The location transceivers are designed to handle multiple signal types (UWB and WLAN) simultaneously, making them multi-functional devices. This universality allows the system to use UWB signals for high-precision TOA measurements when needed, while falling back to or supplementing with WLAN signals for broader coverage areas, thus improving location accuracy without proportionally increasing system complexity.
2Measurement precision
If UWB technology is used to improve TOA measurement accuracy, then location precision improves, but range limitations worsen the overall system coverage
Solution Approach 1:
The patent merges UWB and WLAN systems where UWB transceivers provide high-precision TOA measurements for short-range applications, while WLAN access points extend the overall system coverage to longer ranges. The hybrid architecture allows the system to achieve accurate location determination within UWB range while maintaining operational capability beyond that range through WLAN integration.
Solution Approach 2:
WLAN signals act as an intermediary to bridge the range gap of UWB systems. The system uses WLAN access points as intermediate nodes that can detect and report locations of tags beyond UWB range, while UWB provides precise measurements for tags within its shorter range. This intermediary approach resolves the range limitation without sacrificing UWB measurement accuracy.
3Measurement precision
If higher bandwidth signals are used to improve TOA accuracy, then measurement precision improves, but signal penetration and range deteriorate
Solution Approach 1:
The system combines UWB and WLAN signals, using UWB for high-precision TOA measurements where available and WLAN for more reliable coverage in environments with challenging propagation conditions. The hybrid system selects or combines measurements from both signal types, resolving the contradiction between precision and reliability by leveraging the complementary strengths of each signal type.
Data Source
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AI summary
A wireless location system has at least one wireless tag to be located by the wireless location system, wherein the at least one wireless tag transmits two wireless signals having a known time relationship and having different bandwidths. A plurality of receivers is provided wherein a first receiver receives and processes a first of the two wireless signals and estimates a time to arrive (TOA) of the first wireless signal, and a second receiver receives and processes a second of the two wireless signals and estimates a TOA of the second wireless signal at the second transceiver. The plurality of receivers is time synchronized based on a common timing signal. A location server is coupled to each of the plurality of receivers. The location server receives the TOA of the first wireless signal from the first receiver and the TOA of the second wireless signal from the second receiver. The location server calculating a TDOA of the two wireless signals and estimates a position of the at least one wireless tag based on the TDOA.