Default Reference Signaling for NTN Handover Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In non-terrestrial networks (NTN), existing handover procedures face challenges in maintaining efficient and reliable communication due to the unique characteristics of satellite-based communication, such as long propagation delays and varying signal conditions, which affect the accuracy of handover decisions and lead to service disruptions.
Innovation Solution
The implementation of a default reference signal for handover procedures in NTN, which includes TCI activation/switching mechanisms and MAC-layer scheduling offsets, ensures seamless handovers by stabilizing downlink signals and optimizing communication during handover processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing handover procedures are used in NTN, then handover can be performed, but communication reliability deteriorates due to long propagation delays and varying signal conditions
Solution Approach 1:
The patent applies preliminary action by configuring a default reference signal before handover occurs. The source gNB configures the UE with a default TCI state and associated reference signal parameters in advance, so that when handover is needed, the UE can immediately use this pre-configured reference signal for downlink signal reception without waiting for target gNB signal configuration, thereby reducing propagation delay impact and improving communication reliability during handover transitions
2Reliability
If existing handover procedures are used in NTN, then handover can be performed, but service continuity deteriorates due to inaccurate handover decisions
Solution Approach 1:
The patent introduces an intermediary mechanism by using the default reference signal as a mediator between the source and target gNBs during handover. This reference signal serves as a common measurement benchmark that both network nodes can rely on, enabling more accurate handover decisions by providing a stable reference for signal quality assessment despite the dynamic NTN environment, thereby improving service continuity
3Reliability
If existing handover procedures are used in NTN, then handover can be performed, but communication quality deteriorates due to signal condition variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the TCI state configuration based on current signal conditions. The network can switch between different TCI states associated with the default reference signal depending on the measured signal quality and satellite position, allowing the system to adapt to varying signal conditions in NTN and maintain consistent communication quality during handover
Data Source
AI summary
A method may include receiving, by a wireless device and via a first cell, a layer 1/layer 2 trigger mobility (LTM) cell switch command indicating an LTM cell switch to a second cell and a random access channel (RACH)-less LTM cell switch to the second cell. The method may also include applying, after a time duration from a transmission occasion of a physical uplink control channel (PUCCH) for the LTM cell switch command, a first TCI state to the second cell. The time duration is based on a radio resource control (RRC) processing time; and synchronization signal block (SSB) measurement window for receiving, from the second cell, a first SSB transmission using the first TCI state. The method may also include transmitting, via the second cell, first uplink transmissions using the first TCI state until the wireless device receives an activation command indicating a second TCI state.