TDOA Reference Signal Hearability in LTE Positioning
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Solution Overview
Problem
Existing wireless communication systems face challenges in neighbor cell hearability, particularly when user equipment is located near the center of the serving cell site, leading to weak detection of reference signals from neighbor cell sites, which hinders accurate triangulation and location determination.
Innovation Solution
The introduction of a new reference signal, TDOA-RS, and an additional synchronization signal, TDOA-sync, with non-unity frequency reuse, allowing for improved hearability at low sensitivity and signal-to-noise ratios, and transmission in any resource blocks, including POSCH and MBSFN subframes, to enhance orthogonality between serving and neighbor cell sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If user equipment is located near the center of the serving cell site, then the serving cell signal strength is strong, but the neighbor cell reference signals become too weak for proper detection
Solution Approach 1:
The patent changes the parameter of reference signal configuration by introducing TDOA-RS with non-unity frequency reuse patterns. This allows neighbor cell reference signals to be transmitted on different resource blocks with reduced interference, improving detectability when user equipment is near the serving cell center where neighbor signals are typically too weak.
Solution Approach 2:
The patent introduces TDOA-RS as an intermediary reference signal that mediates between serving and neighbor cell transmissions. This new reference signal type facilitates time difference of arrival measurements by providing a standardized signal structure that can be detected even in high-interference environments near cell centers.
2Loss of energy
If reference signals from neighbor cell sites are transmitted with standard power, then network power consumption is optimized, but the signals are too weak for detection when user equipment is near the serving cell center
Solution Approach 1:
The patent applies local quality by implementing frequency-selective reference signal transmission where TDOA-RS are transmitted on specific resource blocks with non-unity frequency reuse. This allows neighbor cell signals to be enhanced locally in frequency domains where interference from the serving cell is minimal, improving detectability without requiring uniform power increases across all frequencies.
Solution Approach 2:
The patent introduces dynamic frequency reuse patterns for TDOA-RS transmission. The frequency allocation for neighbor cell reference signals is not static but varies according to the non-unity frequency reuse configuration, allowing the system to adaptively optimize signal detectability in different frequency regions based on interference conditions.
3Measurement precision
If additional reference signals are introduced to improve neighbor cell hearability, then positioning accuracy improves, but system complexity increases
Solution Approach 1:
The patent implements partial action by introducing TDOA-RS only in specific subframes and resource blocks rather than continuously across all resources. This selective deployment provides the necessary positioning information for improved accuracy while limiting the increase in processing complexity to only those specific time-frequency resources where TDOA-RS are present.
Data Source
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AI summary
Neighbor cell hearability can be improved by including an additional reference signal that can be detected at a low sensitivity and a low signal-to-noise ratio, by introducing non-unity frequency reuse for the signals used for a time difference of arrival (TDOA) measurement, e.g., orthogonality of signals transmitted from the serving cell sites and the various neighbor cell sites. The new reference signal, called the TDOA-RS, is proposed to improve the hearability of neighbor cells in a cellular network that deploys 3GPP EUTRAN (LTE) system, and the TDOA-RS can be transmitted in any resource blocks (RB) for POSCH and/or MBSFN subframe, regardless of whether the latter is on a carrier supporting both PMCH and POSCH or not. Besides the additional TDOA-RS reference signal, an additional synchronization signal (TDOA-sync) may also be included to improve the hearability of neighbor cells.