Radio Link Failure Criteria for Low-Latency RLC Retransmissions
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Solution Overview
Problem
Current radio link failure (RLF) procedures in wireless communications systems waste resources and consume battery life in low-latency applications like extended reality (XR) due to excessive retransmissions after packets become obsolete.
Innovation Solution
Implementing RLF criteria tailored for low-latency applications, such as XR, where a UE removes PDUs from the retransmission buffer after a certain number of retransmissions and triggers RLF based on time-window or counter-based conditions to initiate RRC connection reestablishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional RLF procedures are used with excessive retransmission attempts, then packet delivery reliability is improved, but resource waste and battery consumption increase significantly
Solution Approach 1:
The patent applies dynamics by making the retransmission threshold adaptive rather than fixed. The threshold is dynamically adjusted based on packet age and priority levels, allowing the system to optimize between reliability and energy consumption in real-time based on actual traffic conditions and packet characteristics.
Solution Approach 2:
The patent changes the parameter of retransmission threshold from a static value to a dynamic value that varies with packet age and priority. This parameter change enables the system to declare RLF earlier for old packets (reducing energy waste) while maintaining longer retransmission attempts for high-priority packets (maintaining reliability).
2Reliability
If retransmission attempts continue indefinitely, then packet delivery reliability is improved, but time loss increases due to obsolete packets consuming resources
Solution Approach 1:
The patent applies preliminary action by establishing packet age tracking and priority level assignment before retransmission decisions are made. The system pre-establishes the criteria for when to stop retransmitting based on packet age thresholds and priority levels, enabling timely RLF declaration without needing to analyze every packet in detail at decision time.
Solution Approach 2:
The patent makes the retransmission decision process dynamic by continuously monitoring packet age and adjusting the retransmission threshold accordingly. This dynamic approach ensures that time is not wasted on excessively old packets while maintaining the ability to retransmit recently arrived packets if needed.
3Loss of time
If RLF is declared immediately after first retransmission failure, then time loss is reduced, but reliability deteriorates due to premature connection reestablishment
Solution Approach 1:
The patent applies dynamics by making the RLF declaration threshold adaptive based on packet priority and age. High-priority packets require multiple retransmission failures before triggering RLF, while low-priority or old packets trigger RLF after fewer failures. This dynamic threshold prevents premature RLF for transient failures while enabling timely RLF for persistent problems.
Solution Approach 2:
The patent changes the RLF threshold parameter from a fixed low value to a variable value that depends on packet characteristics. This parameter change allows the system to tolerate more retransmission failures for high-priority packets (maintaining reliability) while being more aggressive with low-priority packets (reducing time loss).
4Device complexity
If uniform RLF criteria are applied to all traffic types, then device complexity is reduced, but adaptability deteriorates for low-latency applications like XR
Solution Approach 1:
The patent applies local quality by treating different traffic types differently based on their characteristics. The system assigns different RLF thresholds and packet age criteria to high-priority low-latency traffic (like XR) versus standard traffic. This localized differentiation enables optimized performance for latency-sensitive applications without requiring a completely new RLF mechanism.
Solution Approach 2:
The patent segments the RLF criteria into distinct rules based on packet priority levels and traffic types. By segmenting the handling logic into priority-based categories, the system achieves adaptability for different applications while maintaining manageable complexity through structured, hierarchical decision rules.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described that provide radio link failure (RLF) in accordance with RLF criteria associated with relatively low-latency applications. The RLF criteria may provide that when a radio link control (RLC) protocol data unit (PDU) of a low-latency RLC entity has been transmitted for a threshold quantity of times a transmitter may remove the PDU from a retransmission buffer and record one retransmission failure. RLF may be triggered by the transmitter based on a time-window associated with recorded retransmission failures, or based on a counter-based condition associated with the recorded retransmission failures. For the time-window-based condition, if there are at least a threshold quantity of retransmission failures with a time window, RLF may be triggered. For the counter-based condition, if a count of retransmission failures reaches a configured threshold value prior to expiration of a timer, RLF may be triggered.