Packet Switched Handover Protocol Parameter Negotiation
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Solution Overview
Problem
In packet switched handover in mobile communication systems, particularly in 2nd and 3rd generation mobile phone systems using GPRS, there is a significant service interruption due to the need for negotiation of new LLC/SNDCP parameters after handover, which increases the interruption time as the target SGSN can only initiate the negotiation after successful access to the new cell, adding additional round trip times.
Innovation Solution
Negotiating protocol parameters before the mobile moves to the new cell by including an exchange identification data command in a packet switched handover request, allowing downlink data transfer to continue and reducing service interruption time by completing the negotiation while the terminal is still connected to the source node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target SGSN waits until the mobile successfully accesses the new cell to initiate protocol parameter negotiation, then the negotiation can be completed with confirmed connectivity, but the service interruption time increases due to additional round trip times
Solution Approach 1:
The patent applies preliminary action by initiating the XID command and protocol parameter negotiation before the mobile station completes handover to the target cell. The source SGSN sends the XID command to the mobile station while it is still connected to the source cell, allowing the negotiation to start in advance. This reduces service interruption time because the negotiation does not have to wait for successful handover completion, eliminating the need for additional round trip times after handover.
2Reliability
If the negotiation procedure is conducted after handover completion, then the mobile is guaranteed to be connected to the new cell, but downlink data transfer must be paused during negotiation
Solution Approach 1:
The patent initiates the XID command and negotiation procedure before handover completion, allowing downlink data transfer to continue during the negotiation process. The source SGSN can forward downlink data to the mobile station through the source cell while the negotiation is ongoing, maintaining data transfer continuity that would otherwise be interrupted by waiting for post-handover negotiation.
Solution Approach 2:
The source SGSN acts as an intermediary by relaying the XID command from the target SGSN to the mobile station before handover completion. This intermediary role allows the negotiation to proceed while the mobile is still connected to the source cell, enabling data transfer to continue through the source SGSN during the negotiation process without requiring the mobile to be fully established in the target cell first.
Data Source
AI summary
A method of packet switched handover in a mobile communication system comprising a terminal, a source node and a destination node comprises negotiating protocol parameters for the destination node on behalf of a new network entity, by communicating with an old network entity whilst the terminal is still connected to the source node; and completing the packet switched handover, such that service interruption on handover is reduced.