UMTS SRNS Relocation Call Drop Prevention
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Solution Overview
Problem
Call drops occur during SRNS relocation in UMTS terrestrial radio access networks due to exceptional cases such as RLC reset or incorrect serial numbers during UMI or RBR message delivery, which existing technologies do not adequately address.
Innovation Solution
A method and apparatus that involve receiving control messages during SRNS relocation, performing RLC configuration, transmitting complete messages, and retransmitting these messages if an RLC reset occurs, ensuring proper ACK serial numbers are received to prevent call drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RLC reset is performed during UMI message delivery in SRNS relocation, then data loss prevention is improved, but call stability deteriorates due to call drop
Solution Approach 1:
The source RNC performs preliminary actions by transmitting information concerning unidentified data and serial numbers to the target RNC before the actual SRNS relocation is completed. This preliminary data transfer enables the target RNC to properly handle RLC reset scenarios without causing call drop, as the necessary information is already available in advance.
Solution Approach 2:
The patent implements a feedback mechanism where the source RNC provides information about unidentified data and serial numbers to the target RNC. This feedback loop ensures that the target RNC can correctly process RLC reset scenarios by having advance knowledge of the data state, thereby preventing call drop while maintaining data loss prevention.
2Speed
If incorrect serial numbers are transmitted during RBR message delivery, then message transmission speed is improved, but communication reliability deteriorates due to call drop
Solution Approach 1:
The source RNC transmits information concerning unidentified data and corresponding serial numbers to the target RNC before the RBR message delivery is completed. This preliminary action ensures that the target RNC has the correct serial number information in advance, preventing the transmission of incorrect serial numbers while maintaining efficient message delivery.
Solution Approach 2:
A feedback mechanism is established where the source RNC provides serial number information to the target RNC. This feedback ensures that the target RNC uses the correct serial numbers when transmitting RBR messages, thereby maintaining both transmission speed and communication reliability.
3Reliability
If RLC configuration procedure is performed during SRNS relocation, then data integrity is improved, but relocation completion time increases
Solution Approach 1:
The RLC configuration information and unidentified data are transmitted from the source RNC to the target RNC as preliminary actions before the SRNS relocation is finalized. This allows the RLC configuration procedure to be performed more efficiently during relocation, reducing the overall completion time while maintaining data integrity.
Data Source
AI summary
A method of preventing call drop in a mobile terminal when a serving radio network subsystem SRNS relocation to a target RNC from a source RNC is performed includes (a) receiving a control message in accordance with start of the SRNS relocation from the target RNC, (b) performing a RLC configuration procedure, (c) transmitting a complete message in accordance with the RLC configuration procedure to the target RNC, and (d) retransmitting the complete message to the target RNC in case that RLC reset is performed after the complete message is transmitted. As a result, call drop by exceptional case while the SRNS relocation is performed may be prevented.