PRS-to-RACH Occasion Mapping for Idle-State UE Positioning
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Solution Overview
Problem
User Equipment (UE) in RRC_IDLE or RRC_INACTIVE state cannot perform positioning reference signal (PRS) measurements due to the lack of defined methods for interpretation by the base station, necessitating a transition to RRC_CONNECTED state for PRS operations, which limits positioning capabilities.
Innovation Solution
Enabling PRS measurements in RRC_IDLE or RRC_INACTIVE states by defining a method for UE to map positioning reference signals to random access channel occasions (ROs), allowing the base station to interpret these measurements without requiring a state transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If UE transitions to RRC_CONNECTED state to perform PRS measurements, then positioning capability is enabled, but signaling overhead and latency increase
Solution Approach 1:
The patent enables PRS measurements to be performed in advance while the UE is in RRC_IDLE or RRC_INACTIVE state. The UE measures PRS signals and reports measurements to the base station before transitioning to RRC_CONNECTED state, allowing positioning to occur preliminarily without requiring state transition for measurement purposes.
Solution Approach 2:
The patent extracts the PRS measurement function from the RRC_CONNECTED state requirement and makes it available in RRC_IDLE and RRC_INACTIVE states. By separating the measurement capability from the connected state dependency, the system allows positioning measurements to be performed independently of the RRC connection state.
2Loss of time
If UE performs PRS measurements in RRC_IDLE or RRC_INACTIVE state, then latency is reduced, but base station interpretation capability is lacking
Solution Approach 1:
The patent introduces an intermediary mechanism where the base station receives PRS measurement reports from UEs in idle or inactive states and uses pre-configured mapping information to interpret these measurements. The mapping between PRS resources and random access occasions serves as the intermediary that enables the base station to understand measurements taken outside connected state.
Solution Approach 2:
The patent makes the base station's measurement interpretation capability universal across different RRC states. By configuring mapping information that links PRS resources to random access occasions, the base station gains the ability to interpret PRS measurements regardless of whether the UE is in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state.
3Device complexity
If UE remains in RRC_IDLE or RRC_INACTIVE state for positioning, then device complexity is reduced, but positioning accuracy may be compromised
Solution Approach 1:
The patent changes the operational parameters by enabling PRS measurement functionality in RRC_IDLE and RRC_INACTIVE states, which were traditionally restricted to RRC_CONNECTED state. This parameter change allows UEs to perform positioning measurements with simpler state management while maintaining measurement accuracy through proper configuration of PRS resources and mapping information.
Data Source
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AI summary
Disclosed are various techniques for wireless communication. In some aspects, a method of wireless communication performed by a user equipment (UE) includes determining a positioning reference signal (PRS) to random access channel (RACH) occasion (RO) mapping that defines specific ROs during which the UE should at least transmit a RACH sequence based on specific PRS measurements. The method also includes performing at least one PRS measurement. The method also includes transmitting a RACH sequence on at least one RO according to the PRS to RO mapping and based on the specific PRS measurement. The method optionally includes reporting a result of the PRS measurement to the base station according to the PRS to RO mapping based on the PRS measurements.