RSTD Measurement Using PRS in MBSFN Subframes
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Solution Overview
Problem
In current wireless communication systems, User Equipment (UE) devices face challenges in performing Reference Signal Time Difference (RSTD) measurements for Observed Time Difference Of Arrival (OTDOA) positioning due to the absence of Cell Specific Reference Signals (CRS) in Multimedia Broadcast Multicast Service (MBMS) Single Frequency Network (MBSFN) subframes, which hinders accurate UE location determination.
Innovation Solution
The proposed solution involves configuring the UE to decode MBSFN subframe configuration information and Positioning Reference Signal (PRS) configuration, determining the existence of CRS and PRS in specific subframes, and using these signals for RSTD measurements, even in scenarios where CRS is not transmitted in MBSFN regions, by signaling MBSFN subframe configurations for all cells or assuming alignment across cells to reduce overhead and enhance positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If CRS is not transmitted in MBSFN regions to reduce signaling overhead, then signaling overhead is reduced, but RSTD measurement accuracy deteriorates
Solution Approach 1:
The patent introduces PRS (Positioning Reference Signal) as an intermediary signal specifically for positioning measurements. Instead of relying on CRS which is absent in MBSFN subframes, the UE uses PRS configured in these subframes to perform RSTD measurements. This mediator signal enables positioning functionality without requiring CRS transmission in MBSFN regions.
Solution Approach 2:
The patent changes the parameter of reference signal type from CRS to PRS for positioning measurements in MBSFN subframes. By configuring PRS with specific parameters (resource elements, subframe patterns) in MBSFN subframes, the system enables RSTD measurements without CRS while maintaining measurement accuracy.
2Productivity
If CRS is not transmitted in MBSFN subframes, then resource utilization for MBSFN service is improved, but UE positioning capability deteriorates
Solution Approach 1:
The patent segments the reference signal functionality by separating CRS (for general channel estimation) and PRS (for positioning). This segmentation allows CRS to be absent in MBSFN subframes while PRS is specifically configured for positioning, enabling both MBSFN service and positioning to coexist without interference.
Solution Approach 2:
The PRS signal serves multiple functions: it enables RSTD measurements for positioning, works in MBSFN subframes, and maintains compatibility with existing positioning protocols. This multi-functional signal ensures positioning capability is maintained while supporting MBSFN service.
3Measurement precision
If MBSFN subframe configuration is signaled for all cells to ensure reference signal availability, then positioning accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent applies partial signaling by configuring PRS only in the necessary MBSFN subframes for positioning measurements, rather than signaling all MBSFN subframe configurations. The UE is provided with specific PRS configuration information (resource elements, subframe patterns) only for cells where positioning measurements are required, reducing overall signaling overhead while maintaining positioning accuracy.
Data Source
AI summary
Technology for a UE configured to perform RSTD measurements for OTDOA positioning is disclosed. The UE can decode a MBSFN subframe configuration information for one or more cells in a plurality of cells. The UE can decode PRS configuration information for one or more cells in the plurality of cells. The UE can determine, for the one or more cells in the plurality of cells, an existence of a CRS for selected subframes of a plurality of subframes based on the MBSFN subframe configuration information. The UE can determine for the one or more cells in the plurality of cells, an existence of a PRS for selected subframes of the plurality of subframes based on the PRS configuration information. The UE can measure the RSTD for the one or more cells in the plurality of cells using the CRS and the PRS.