NTN Timing Synchronization Using TA Reports and HARQ Feedback
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Solution Overview
Problem
Existing NTN systems face challenges in ensuring timely and reliable transmission of timing advance (TA) reports due to issues with HARQ processes without feedback and outdated satellite information, leading to potential scheduling failures and inefficiencies in RRC_CONNECTED states.
Innovation Solution
Implementing a UE that receives satellite assistance information and timing information to determine if a RACH-less synchronization operation is configured, and initiating synchronization operations based on this information, along with mechanisms for HARQ feedback-enabled TA report transmissions and NW-requested TA reports to ensure accurate and timely updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RACH-less synchronization operation is used, then device complexity is reduced, but reliability deteriorates due to lack of HARQ feedback
Solution Approach 1:
The system dynamically selects between RACH-less synchronization and traditional RACH-based synchronization based on whether HARQ feedback is configured. When HARQ feedback is available, the system uses RACH-less operation for reduced complexity; when HARQ feedback is unavailable, it falls back to RACH-based operation for guaranteed reliability through retransmission mechanisms.
2Measurement precision
If satellite assistance information is updated frequently, then measurement precision improves, but loss of time increases due to more synchronization operations
Solution Approach 1:
The system performs preliminary checks to determine whether satellite assistance information has actually changed before initiating synchronization operations. By comparing current satellite information with previously stored information, the system avoids unnecessary synchronization operations, thus reducing time loss while maintaining measurement precision when updates are truly needed.
3Reliability
If HARQ feedback is enabled for TA reports, then reliability improves, but device complexity increases
Solution Approach 1:
The system applies HARQ feedback selectively only to TA report transmissions where it provides value, rather than enabling it system-wide. The base station configures HARQ feedback for specific UEs or specific TA report scenarios based on network conditions and UE capabilities, thus improving reliability where needed while minimizing overall device complexity.
Data Source
AI summary
Methods and apparatuses for a timing advance report an NTN is provided. The method of UE comprises: receiving, from a BS, first information including satellite assistance information for a target satellite; receiving, from the BS, second information including timing information, wherein the timing information includes at least one of a start time and a time duration for a synchronization operation; determining whether a RACH-less synchronization operation is configured; and initiating, based on the satellite assistance information and the timing information, the synchronization operation by performing a RA procedure upon a determination that the RACH-less synchronization operation is not configured.