Roaming Retry Mechanism for Pre-Paging Call Failures
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Solution Overview
Problem
Existing methods for roaming retry in pre-paging mode fail to handle call failures when a subscriber moves out of the current location area during the pre-paging period, leading to unsuccessful call connections.
Innovation Solution
Incorporating a Roaming Retry Indication field in the SRI and PRN messages to trigger a roaming retry procedure when pre-paging fails due to the subscriber's location change, allowing the GMSC to reselect routing and initiate a new call flow without additional messages like RCH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-paging is performed during roaming retry, then call success probability improves for high-mobility subscribers, but message flow complexity increases due to additional signaling interactions
Solution Approach 1:
The patent applies pre-paging as a preliminary action before the actual call setup. The GMSC sends a paging message to the VLR in advance to check if the subscriber is still in the same location area, before initiating the full call setup procedure. This preliminary check prevents call failures due to subscriber movement without requiring complex additional message flows during the actual call setup.
Solution Approach 2:
The patent extracts the location verification function from the main call setup flow by implementing it as a separate pre-paging step. This separation allows the system to check subscriber location independently before committing to full call setup, reducing the complexity of the main call flow while improving reliability through the preliminary check.
2Device complexity
If roaming retry is implemented without pre-paging, then message flow interactions are reduced, but call failure occurs when subscriber moves during routing acquisition
Solution Approach 1:
The pre-paging mechanism performs a preliminary location check before the subscriber moves during routing acquisition. By paging the subscriber in advance and verifying the location area code matches, the system ensures the subscriber is still in the same location area before proceeding with call setup, preventing call failures without adding complex message flows.
Solution Approach 2:
The pre-paging process provides feedback about the subscriber's current location area. The VLR compares the location area code received in the paging response with the stored location area code, and only proceeds with call setup if they match. This feedback mechanism ensures call success while maintaining simple message flow interactions.
3Device complexity
If traditional roaming retry without pre-paging support indication is used, then implementation is simpler, but it cannot handle cases where subscriber moves during the routing acquisition period
Solution Approach 1:
The pre-paging function performs a preliminary verification of subscriber location before call setup. By checking if the subscriber is still in the same location area through pre-paging, the system handles subscriber movement during routing acquisition without requiring complex additional implementations beyond the standard pre-paging capability.
Solution Approach 2:
The patent makes the GMSC and VLR multi-functional by enabling them to perform both traditional roaming retry and pre-paging operations. The pre-paging function, already present in the system for other purposes, is leveraged to also handle location verification during roaming retry, eliminating the need for separate complex implementation while improving call connection reliability.
Data Source
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AI summary
The present invention provides a method for roaming retry under pre-paging mode. The method comprises the following steps of: during a pre-paging period, a called Mobile Station (MS) moving to a new location area and sending a location update request to a new Visitor Mobile Switching Center/Visitor Location Register (New VMSC/VLR); after receiving the location update request, the New VMSC/VLR sending a location area update message to a Home Location Register (HLR); after receiving the location area update message, the HLR sending a Send Routing Information (SRI) Ack message including a Roaming Retry Indication identifier to a to a Gateway Mobile Switching Center (GMSC); after receiving the SRI Ack message, the GMSC triggering a roaming retry procedure according to the Roaming Retry Indication identifier, and completing the subsequent calling flow. The method of present invention can solve the problem of call failure that occurs when the location area of a user changes during the pre-paging period.