5G SRS Positioning Fallback for Failed Neighbor-Cell QCL References
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Solution Overview
Problem
In 5G wireless communication systems, the failure of path loss or spatial transmit quasi-collocation (QCL) reference from neighboring cells for sounding reference signals (SRS) poses challenges for accurate positioning, particularly when signal quality falls below a threshold, necessitating fallback procedures for uplink reference signal processing.
Innovation Solution
The proposed method involves configuring a user equipment (UE) to switch from an unusable first downlink reference signal to a second downlink reference signal from a neighboring or serving cell for estimating path loss or determining an uplink spatial transmit beam, based on signal quality thresholds, and transmitting uplink reference signals accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE uses the first downlink reference signal from a neighboring cell for estimating path loss or determining uplink spatial transmit beam, then positioning accuracy is improved, but when the signal quality falls below a threshold, the positioning reliability deteriorates
Solution Approach 1:
The patent changes the parameter being measured from simple signal quality to a composite metric that includes signal quality and timing advance information. When the first downlink reference signal quality deteriorates, the system transitions to using alternative reference signals (second downlink reference signal from neighboring cell or third downlink reference signal from serving cell) based on comparing composite metrics, thereby maintaining positioning reliability while preserving accuracy where possible
Solution Approach 2:
The patent performs preliminary evaluation of multiple downlink reference signals before actual positioning measurement. The UE measures signal quality and timing advance for both the first and alternative reference signals in advance, compares their composite metrics, and pre-determines which signal to use for positioning. This preliminary action prevents positioning failures when the primary signal deteriorates, ensuring continuous reliability
2Reliability
If the UE switches to alternative downlink reference signals when the first reference signal fails, then positioning reliability is improved, but the device complexity increases due to multiple signal monitoring and switching mechanisms
Solution Approach 1:
The patent segments the reference signal selection process into distinct phases: measurement phase (evaluating first and alternative reference signals), comparison phase (comparing composite metrics including signal quality and timing advance), and selection phase (choosing the reference signal with the better composite metric). This segmentation makes the complex switching mechanism more manageable and implementable through structured algorithms
Solution Approach 2:
The patent enables the UE to autonomously perform reference signal evaluation, comparison, and switching without continuous network control. The UE independently measures signal quality and timing advance, compares composite metrics of multiple reference signals, and self-determines which signal to use for positioning. This self-service approach reduces signaling overhead and simplifies network-UE coordination while maintaining reliability
Data Source
AI summary
Disclosed are techniques for wireless communication. In an aspect, a UE receives a positioning configuration, the positioning configuration including at least an identifier of a first downlink reference signal from a neighboring cell to be used for estimating a downlink path loss or determining an uplink spatial transmit beam, determines that a first downlink reference signal received from the neighboring cell cannot be used for estimating the downlink path loss or determining the uplink spatial transmit beam, in response to the determination, estimating the downlink path loss or determining the uplink spatial transmit beam based on a second downlink reference signal received from the neighboring cell or a serving cell, and transmits an uplink reference signal for positioning based on the estimated downlink path loss, the determined uplink spatial transmit beam, or a combination thereof.