Timing Advance Estimation for Layer 1/2 Triggered Mobility
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Solution Overview
Problem
Current serving cell changes in wireless communications systems, particularly handovers, involve lengthy latency, high overhead, and significant interruption times due to the use of Layer 3 (L3) signaling, which is inefficient compared to Layer 1 (L1)/Layer 2 (L2) signaling.
Innovation Solution
Implementing Layer 1/Layer 2 triggered mobility (LTM) techniques that allow for serving cell changes via L1/L2 signaling, reducing latency and overhead by minimizing interruptions during the mobility process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Layer 3 (L3) signaling is used for serving cell changes, then reliability of cell change confirmation is improved, but latency and interruption time increase significantly
Solution Approach 1:
The patent performs timing advance estimation and synchronization operations in advance during the preparation phase before the actual serving cell change. The UE estimates timing advance values for candidate target cells and reports them to the network entity, so that when the handover is executed, the timing synchronization is already established, eliminating the need for lengthy random access procedures and reducing handover latency while maintaining reliability
Solution Approach 2:
The patent divides the handover process into distinct phases: preparation phase (where timing advance is estimated and reported), synchronization phase (where early UL/DL synchronization is performed), and execution phase (where the actual cell change occurs). This segmentation allows timing synchronization to be prepared independently in advance, decoupling it from the critical path of the handover execution and reducing overall latency
2Reliability
If Layer 3 (L3) signaling is used for serving cell changes, then complete Layer 2 (L2) and Layer 1 (L1) resets can be performed, but overhead and interruption time increase
Solution Approach 1:
The patent extracts the timing synchronization function from the complete L1/L2 reset process. By performing timing advance estimation and early UL/DL synchronization separately during the preparation and synchronization phases, the patent eliminates the need for comprehensive L1/L2 resets during execution, reducing signaling overhead and interruption time while maintaining the essential timing synchronization required for reliable communication
3Loss of time
If timing advance estimation is performed without random access, then latency is reduced, but measurement precision may be insufficient
Solution Approach 1:
The patent implements a feedback mechanism where the UE estimates timing advance values based on downlink signals, reports these estimates to the network entity, and the network entity provides feedback (such as timing advance corrections or confirmation). This feedback loop allows the timing advance estimation to be refined and validated, ensuring measurement precision is sufficient even without traditional random access procedures
Solution Approach 2:
The patent performs timing advance estimation as a preliminary action before the actual handover execution. By estimating and reporting timing advance values in advance during the preparation phase, the patent has sufficient time to validate and refine these estimates through network feedback, ensuring accuracy is achieved before the critical handover execution phase
Data Source
AI summary
A user equipment (UE) may receive, from a first network entity, an indication of a configuration for the UE to report, to the first network entity, an estimate of a first timing advance value for a second network entity. The UE may determine the estimate of the first timing advance value. The UE may transmit, to the first network entity, the estimate of the first timing advance value for the second network entity or a reference signal time difference associated with the estimate of the first timing advance value. The UE may receive, from the first network entity, an indication of an error value associated with the estimate of the first timing advance value. The UE may determine a second timing advance value based on the estimate of the first timing advance value and the error value. The UE may transmit communications using the second timing advance value.