Random Access Timing for NTN Contention Resolution
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Solution Overview
Problem
In contention-based random access procedures in non-terrestrial networks (NTN), terminals erroneously determine that contention resolution has failed due to the premature expiration of the contention resolution timer, despite scheduled Msg3 retransmissions, leading to unnecessary retries.
Innovation Solution
Implement a method where terminals determine that contention resolution is unsuccessful only if specific conditions are met, such as the absence of Msg3 retransmission scheduling based on TC-RNTI on the PDCCH before the timer expires, particularly in NTN scenarios, and introduce an independent monitoring timer to manage blind retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the contention resolution timer is used to determine contention resolution success or failure, then the timer provides a mechanism to detect failed access attempts, but in NTN scenarios the timer expires prematurely before Msg3 retransmission scheduling is received, causing erroneous failure determination
Solution Approach 1:
The patent changes the timer duration parameter from a fixed value to a dynamic value that adapts to NTN scenarios. Specifically, it introduces a first duration for the contention resolution timer in NTN scenarios, which is longer than the second duration used in terrestrial scenarios. This parameter change allows the timer to accommodate the extended round-trip time in NTN, preventing premature expiration and erroneous failure determination while maintaining appropriate timing in terrestrial networks
Solution Approach 2:
The patent makes the contention resolution timer duration dynamic by selecting different timer values based on the network scenario. The terminal device determines whether it is in an NTN scenario and accordingly selects either the first duration (for NTN) or the second duration (for terrestrial networks). This dynamic adaptation resolves the contradiction by allowing the timer to be long enough for NTN while remaining appropriately short for terrestrial scenarios
2Reliability
If the terminal monitors for Msg3 retransmission scheduling on PDCCH after contention resolution timer expiration, then it can detect successful retransmission scheduling, but in NTN the timer expires before the scheduled retransmission is monitored, leading to unnecessary access retries
Solution Approach 1:
The patent applies preliminary action by extending the contention resolution timer duration before the actual Msg3 retransmission scheduling occurs in NTN scenarios. By setting the first duration to be sufficiently long, the timer remains active during the entire period when Msg3 retransmission scheduling might be received, including the extended propagation delay period in NTN. This prevents the terminal from erroneously determining contention failure before the retransmission scheduling is received, thereby improving reliability without causing unnecessary retries
3Ease of manufacture
If a fixed contention resolution timer duration is used, then the protocol is simple and easy to implement, but it cannot accommodate the varying propagation delays in NTN versus terrestrial networks
Solution Approach 1:
The patent introduces dynamics into the timer duration by making it scenario-dependent. The terminal device dynamically selects between a first duration (for NTN scenarios) and a second duration (for terrestrial scenarios) based on determining which scenario it is in. This dynamic approach maintains implementation simplicity by using a clear decision rule while achieving adaptability to different network scenarios with different propagation characteristics
Data Source
AI summary
A random access method, which is performed by a terminal, includes: determining that contention resolution is unsuccessful or not considering the contention resolution is unsuccessful, in a case where a contention resolution timer expires and a first condition is satisfied during a contention-based random access.