UE Packet Push Back for LTE RLF Latency Reduction
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Solution Overview
Problem
In mobile networks, particularly in LTE, latency and packet delay issues arise due to unacknowledged packets from the Radio Link Control (RLC) layer leading to packet loss and increased latency after a Radio Link Failure (RLF), where existing systems flush unacknowledged packets, causing important messages like SIP/UDP to be lost and leading to prolonged latency in resuming packet transfer.
Innovation Solution
The User Equipment (UE) is configured to push back unacknowledged Protocol Data Units (PDU) from the RLC layer and trigger a Tracking Area Update (TAU) procedure, ensuring immediate Radio Bearer assignment and preventing packet loss by storing and retransmitting packets until acknowledged or reaching a maximum retry count, and also pushing back processed Packet Data Convergence Protocol (PDCP) packets from the PDCP layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unacknowledged packets are flushed from the RLC layer after Radio Link Failure, then device complexity is reduced, but packet loss increases and latency increases
Solution Approach 1:
The patent applies preliminary action by triggering a Tracking Area Update (TAU) procedure immediately upon detecting unacknowledged packets in the RLC layer after RLF. This proactive approach ensures that packet transfer is resumed before the unacknowledged packets are lost, preventing packet loss while maintaining manageable device complexity through automated procedures.
2Reliability
If unacknowledged packets are pushed back and retained in the RLC layer, then packet loss is prevented, but device complexity increases
Solution Approach 1:
The patent implements self-service by enabling the UE to automatically trigger a TAU procedure when unacknowledged packets are detected in the RLC layer. This self-activating mechanism manages retained packets without requiring complex external control systems, thus preventing packet loss while keeping device complexity manageable through autonomous operation.
3Loss of time
If a Tracking Area Update procedure is triggered immediately upon detecting unacknowledged packets, then latency is reduced, but device complexity increases
Solution Approach 1:
The patent applies feedback by monitoring the acknowledgment status of packets in the RLC layer and using this feedback to automatically trigger a TAU procedure when unacknowledged packets are detected. This feedback-driven approach reduces packet transfer latency by initiating recovery actions only when necessary, rather than continuously, thereby managing device complexity efficiently through condition-based activation.
Data Source
AI summary
An apparatus for reducing latency in a User Equipment (UE), comprising a processor configured to push back a packet that is transmitted to but not acknowledged by a base station, from a Radio Link Control (RLC) layer; and trigger a Tracking Area Update (TAU) procedure based on the pushed back packet; and a radio frequency interface configured to transmit or receive the packet with the base station.