UE Message Retransmission After Radio Link Failure
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Solution Overview
Problem
In wireless communication systems, user equipment (UE) initiated messages, such as MBMS interest indications, IDC indications, and power preference indications, are not reliably retransmitted after a radio link failure or handover failure, leading to incomplete message transmission and user experience issues.
Innovation Solution
A method where the UE submits messages to the PDCP and RLC layers, detects radio link or handover failures, checks for acknowledgement from the network, reestablishes the connection, and retransmits the message upon successful reconnection if no acknowledgement is received, ensuring reliable message delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs reestablishment procedure upon detecting radio link failure or handover failure, then the connection is restored, but the previously transmitted message is lost and cannot be retransmitted
Solution Approach 1:
The UE stores the message in the RLC layer before transmission and maintains it after reestablishment, allowing the message to be retransmitted if ACK is not received. This preliminary storage action ensures the message survives the reestablishment process.
Solution Approach 2:
The UE checks whether the RLC layer receives ACK for the transmitted message after reestablishment. If ACK is not received, the UE retransmits the message. This feedback mechanism ensures reliable delivery despite connection failures.
2Reliability
If the L2 performs ARQ and HARQ retransmissions to reliably carry the message, then message delivery is improved, but upon reestablishment the L2 cannot retransmit the message anymore
Solution Approach 1:
The RLC layer acts as an intermediary that stores the message between the RRC layer and the L2 retransmission mechanisms. This intermediary storage allows the message to persist through reestablishment and enables coordinated retransmission across different protocol layers.
3Reliability
If the UE retransmits the message upon reestablishment, then complete message transmission is ensured, but additional transmission overhead and time are required
Solution Approach 1:
The UE performs selective retransmission only when necessary (when ACK is not received after reestablishment), rather than always retransmitting. This partial action approach ensures reliability when needed while avoiding unnecessary time loss when the message was already successfully transmitted.
Data Source
AI summary
A method and apparatus for transmitting a message in a wireless communication system is provided. A user equipment (UE) submits a message to a packet data convergence protocol (PDCP) layer and a radio link control (RLC) layer, detects a radio link failure or a handover failure, checks whether the RLC layer receives acknowledgement (ACK) to the message from the network, reestablishes the connection with the network, and retransmits the message upon the reestablishment if the RLC layer does not receive the ACK to the message.