Wireless Device Positioning During RAT Handover
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Solution Overview
Problem
Current position determination methods for wireless devices, especially during emergency calls, face delays due to the need for RAT changes and interruptions in scenarios like CS fallback and SRVCC, which hinder accurate and timely location determination.
Innovation Solution
The method allows wireless devices to initiate and complete position determination while connected to a source RAT and continue it after being handed over to a target RAT, ensuring continuous positioning procedures even during handovers and SRVCC events, utilizing existing GNSS assistance information and network support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wireless device performs RAT change from LTE to WCDMA or GSM for emergency call setup, then the emergency call can be established in the target RAT, but the position determination procedure is delayed because it is triggered only after the wireless device is redirected to the new RAT
Solution Approach 1:
The patent applies preliminary action by triggering the position determination procedure in the source RAT (LTE) before the wireless device is handed over to the target RAT (WCDMA/GSM). The location request is sent and positioning measurements are initiated while the device is still connected to LTE, so that positioning information is already available or nearly available when the emergency call is established in the target RAT, thereby eliminating the delay caused by waiting for RAT change completion before starting positioning.
2Measurement precision
If the position determination procedure is triggered after RAT change, then the positioning can be performed in the target RAT, but the overall position determination time is increased due to the sequential nature of RAT change and positioning
Solution Approach 1:
The patent initiates the position determination procedure in advance in the source RAT before the handover to target RAT is completed. This allows the positioning measurements and calculations to start earlier, reducing the total duration while maintaining the required position accuracy through proper handover of positioning context between RATs.
Solution Approach 2:
The patent ensures continuity of the position determination procedure across RAT boundaries by maintaining positioning context information during handover. The location request and measurement procedures continue seamlessly from source RAT to target RAT, preventing interruption and reducing total positioning time while preserving measurement precision.
3Measurement precision
If the wireless device waits for NILR request with GNSS assistance information after RAT change, then the positioning can be performed with proper assistance data, but the location determination is delayed until the entire CS fallback procedure is complete
Solution Approach 1:
The patent sends the location request and initiates GNSS assistance data reception in the source RAT before the CS fallback procedure completes. This preliminary action allows the wireless device to receive and process positioning assistance information earlier, so that position determination can proceed in parallel with the RAT change process rather than waiting sequentially, thereby improving location determination speed while maintaining accuracy through proper assistance data.
Data Source
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AI summary
There is provided a method for position determination of a wireless device. The method is performed by the wireless device. The method comprises detecting, whilst being operatively connected to a source radio access technology (RAT) an indicator requiring a handover of the wireless device to a target RAT. The method comprises starting a positioning detection procedure of the wireless device before being handed over to the target RAT, the positioning detection procedure involving processing of positioning measurements. The method comprises keeping the positioning measurements of the positioning detection procedure whilst the wireless device being handed over from the source RAT to the target RAT. The method comprises continuing the positioning detection procedure using the positioning measurements whilst being operatively connected to the target RAT.