Idle UE Location via Time Fingerprint Lookup Tables
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Solution Overview
Problem
Traditional methods for determining the location of user equipment (UE) in wireless networks, such as cell ID, enhanced cell ID, and assisted GPS, often result in significant errors due to propagation delays, especially in distributed antenna systems and low-power wireless radio cells, which can be substantial and affect the accuracy of UE location calculations.
Innovation Solution
The system determines the location of UEs by calculating differential time values based on observed time values and reference differential time values, even when UEs are in idle mode, using time fingerprint locating (TFL) measurements to compensate for signal propagation delays caused by mismatches, stray capacitances, and other factors, thereby improving location accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional location methods (CGI+TA, CGI+RTT, TOA) are used to determine UE location, then location services can be provided, but significant errors occur due to propagation delays in distributed antenna systems and low-power wireless radio cells
Solution Approach 1:
The patent introduces an intermediary measurement approach by using observed time difference (OTD) measurements as a mediator between the UE and base station timing. Instead of directly measuring propagation delay which is affected by network timing delays, the system uses OTD measurements from the UE perspective to eliminate the impact of base station internal timing variations and propagation delays in distributed antenna systems.
Solution Approach 2:
The patent creates a virtual reference timing system by having multiple base stations synchronize to a common reference clock. This copying of the reference timing to multiple base stations allows the system to eliminate timing variations and focus on measuring only the propagation delay component, thereby improving location accuracy despite network timing delays.
2Measurement precision
If propagation delay is measured with improved accuracy using traditional methods, then UE location calculations improve, but errors remain >1 km for RTT and UTDOA methods
Solution Approach 1:
The patent enables the UE to perform self-measurement of OTD values using its own receiver timing. The UE autonomously measures the time difference between receiving signals from different base stations without requiring complex specialized receivers at the base station side, thereby achieving accurate propagation delay measurement with reduced system complexity.
Solution Approach 2:
Instead of having base stations measure uplink timing (as in UTDOA which requires specialized receivers), the patent inverts the approach by having the UE measure downlink timing differences. This inversion simplifies the base station equipment while maintaining or improving measurement accuracy.
3Ease of operation
If timing advance is used for location determination, then location can be estimated within an arc from the base site, but errors remain multiple km
Solution Approach 1:
The patent merges multiple measurement approaches by combining OTD measurements from multiple base station pairs. By merging the hyperbolic location lines from different base station pairs, the system achieves precise two-dimensional location determination, overcoming the limitation of single-arc positioning and reducing errors from multiple km to much smaller values.
4Measurement precision
If signal propagation delay is compensated for using pre-computed values and lookup tables, then location accuracy improves to median errors <70 meters, but computational complexity increases
Solution Approach 1:
The patent performs preliminary computation of propagation delay values and stores them in lookup tables before actual location determination. By pre-computing and storing timing correction values for different base station pairs and locations, the system achieves high location accuracy (<70m median error) while keeping real-time computational complexity low, as the actual location determination only requires table lookup and simple interpolation.
Data Source
AI summary
A user equipment (UE) location in a wireless network can be determined by leveraging geometric calculations for an overlaid bin grid framework mapping the wireless network area to store differential values for each frame of the bin grid framework for each pair of relevant NodeBs. A timing offset can be determined, such that when a time value from a target UE is accessed, the location can be quickly determined with minimal real time computation. In an aspect, the time value from an idle-state target UE can be accessed. The target UE time value can be searched among pre-computed differential value data sets indexed by relevant NodeB site pairs to return sets of frames that can facilitate converging on a location for the target UE. Intersecting frames can represent the geographic location of the UE in the wireless network. Further, the data can be leveraged to correct timing in the network.