DTM Handover Command Forwarding in GSM-3GPP Networks
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Solution Overview
Problem
Current dual transfer mode (DTM) handover procedures in GSM and 3GPP networks experience unnecessary delays and connection losses due to the requirement of receiving acknowledgments from both circuit-switched and packet-switched domains before sending the DTM handover command, and fail if only one copy of the message is received.
Innovation Solution
The method involves sending the DTM handover command to a mobile device as soon as a positive acknowledgement is received from one domain, with the option to proceed with the handover without confirmation from the second domain, and using a 'Wait' or 'Proceed' indicator to manage the handover process, allowing the handover to continue in the valid domain even if one message is lost or timed out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source BSS waits to receive both copies of the DTM handover command before forwarding to the mobile station, then the reliability of the handover command is improved, but the handover delay increases
Solution Approach 1:
The source BSS forwards the DTM handover command to the mobile station as soon as the first copy is received, before receiving the second copy. This preliminary action reduces handover delay while maintaining reliability through subsequent validation mechanisms.
Solution Approach 2:
The mobile station sends a handover confirm message back to the source BSS after receiving the handover command. This feedback mechanism allows the source BSS to validate the command execution and detect any issues, compensating for the early forwarding before both copies are received.
2Speed
If the DTM handover command is sent as soon as the first acknowledgement is received, then the handover speed is improved, but the risk of connection loss increases
Solution Approach 1:
The source BSS initiates the handover command transmission immediately upon receiving the first acknowledgement, performing the critical action in advance before all validation information is available. This reduces the window for connection loss while maintaining reliability through the feedback mechanism.
Solution Approach 2:
The handover confirm message from the mobile station provides real-time feedback on whether the handover command was successfully received and executed. This allows the source BSS to detect connection issues early and take corrective action, mitigating the risks of early command transmission.
3Measurement precision
If the procedure is cancelled when only one copy of the DTM handover command is received, then the message accuracy is improved, but the productivity of handover is reduced
Solution Approach 1:
Instead of cancelling the procedure upon receiving only one copy, the source BSS forwards the command preliminarily and allows the handover to proceed. This maintains message accuracy through feedback validation while significantly improving handover productivity by avoiding unnecessary cancellations.
Solution Approach 2:
The handover confirm message provides accuracy validation after the command is executed. This feedback mechanism ensures that even if only one copy is received, the system can verify whether the handover was successful, maintaining measurement precision while improving productivity.
Data Source
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AI summary
A method of dual transfer mode (DTM) handover in a communication system comprising at least one mobile device, a source node and a target node; the method comprising sending a handover request from a source node to a target node, in a first domain and a second domain; returning an acknowledgement in both the first and second domains, the acknowledgements including a DTM handover command; and when a first positive acknowledgement is received from the first domain, forwarding to a mobile device, all or part of the DTM handover command.