Idle Mode UE Positioning via UL-PRS and AMF Triggering
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Solution Overview
Problem
Existing positioning methods in cellular networks are inefficient for user equipment (UE) in idle or inactive mode, as they require transitioning to connected mode for signaling and data exchange, leading to latency and power inefficiency, and lack support for UE-assisted positioning operations.
Innovation Solution
The implementation of signaling and protocol methods that allow UE-based and UE-assisted positioning operations in idle or inactive modes using downlink and uplink measurements, with uplink positioning reference signals (UL-PRS) embedded in the RACH procedure and positioning operations triggered through the Access and Mobility Management Function (AMF), enabling measurements and location requests without transitioning to connected mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UE transitions to connected mode for positioning operations, then positioning accuracy and network control are improved, but power consumption increases and latency is introduced
Solution Approach 1:
The patent applies partial action by allowing UEs in idle or inactive mode to perform positioning measurements using downlink signals without transitioning to connected mode. The UE can measure downlink positioning reference signals and report results partially, without establishing full RRC connected state, thus reducing power consumption while maintaining acceptable positioning accuracy.
Solution Approach 2:
The network performs preliminary actions by pre-configuring positioning parameters, assistance data, and measurement opportunities while the UE is in idle or inactive mode. The gNB prepares positioning configurations and stores them for later use, enabling the UE to perform measurements without needing to transition to connected mode, thereby reducing power consumption and latency.
2Reliability
If a UE transitions to connected mode for positioning operations, then signaling support and measurement reporting are improved, but latency is introduced due to mode transition
Solution Approach 1:
The network performs preliminary configuration of positioning parameters, assistance data, and measurement opportunities while the UE is in idle or inactive mode. The gNB prepares positioning configurations and stores them for later use, enabling the UE to perform measurements without needing to transition to connected mode, thereby reducing power consumption and latency.
Solution Approach 2:
The patent uses copying by allowing the UE to use stored assistance data and configuration information that was previously provided and cached during idle or inactive mode. Instead of requiring full signaling exchange in connected mode, the UE can utilize copied configuration data to perform measurements and report results, reducing the time required for positioning operations.
3Use of energy by moving object
If positioning operations are performed in standalone mode using external signals, then power efficiency is improved, but positioning accuracy deteriorates due to lack of cellular system assistance
Solution Approach 1:
The patent merges standalone positioning with cellular system assistance by enabling UEs in idle or inactive mode to perform positioning using downlink signals from the cellular network. The UE can measure downlink positioning reference signals transmitted by gNBs and combine these measurements with cached assistance data, achieving accurate positioning while maintaining power efficiency through idle mode operation.
Solution Approach 2:
The downlink positioning reference signals serve multiple functions: they enable positioning measurements for UEs in idle mode, provide synchronization information, and assist in cell identification. This multi-functionality allows the cellular system to support positioning operations without requiring UEs to transition to connected mode, maintaining power efficiency while providing accurate positioning.
4Measurement precision
If UE-assisted positioning is implemented for idle or inactive UEs, then positioning capability is improved, but device complexity increases due to additional signaling requirements
Solution Approach 1:
The patent extracts the essential positioning functionality from the full connected mode signaling sequence. The UE can perform downlink measurements and report results using simplified signaling procedures that do not require full RRC connected state. The network extracts and caches necessary assistance data in advance, reducing the signaling complexity required for UE-assisted positioning in idle or inactive mode.
Data Source
AI summary
Signalling and protocol methods are proposed to allow positioning operations with signals of the cellular system for a UE in idle or inactive mode. In one novel aspect, UL-PRS is embedded in the RACH procedure: a set of RACH preambles with the functionality of UL-PRS are defined. These preambles are sent by the UE to the serving gNB to initiate a RACH procedure, and the following signalling could convey the measurement results. In another novel aspect, positioning operations on the network side are triggered through an AMF. The AMF may elect not to bring the UE to connected mode before transferring the location request to an LMF; instead, the AMF may indicate that the UE is in idle mode and it expects to page the UE with a subsequent message from the LMF.