LTE to 2G/3G Fallback Using Pre-Allocated TMSI
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Solution Overview
Problem
In current communication systems, when a user equipment (UE) transitions from an LTE network to a 2G/3G network, the process often results in significant delays due to the need for a location update, affecting voice service continuity and user experience.
Innovation Solution
A method and system that involve an access network device and a mobility management entity coordinating to notify the UE of the target 2G/3G cell's location area information, requesting a location update from the corresponding mobile switching center, and providing the UE with a temporary mobile station identity (TMSI) before connecting, allowing direct communication without the need for an additional location update process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE initiates a location update process after connecting to the 2G/3G network, then the location area information is updated correctly, but the voice service is delayed by several seconds
Solution Approach 1:
The patent applies preliminary action by having the access network device send the location area information of the target 2G/3G cell to the MME before the UE connects to the network. The MME then proactively sends this information to the UE in advance, so that when the UE connects, it already possesses the correct location area information and can immediately communicate with the MSC without initiating a location update process, thereby eliminating the several-second delay while ensuring location information accuracy
2Speed
If the UE connects to the target 2G/3G cell without prior location update information, then the connection is established quickly, but the UE cannot communicate with the MSC until location update is completed
Solution Approach 1:
The patent resolves this contradiction by performing preliminary action where the location area information is delivered to the UE before connection. The access network device sends the target cell's location area information to the MME, which then includes it in a message to the UE prior to connection. This allows the UE to establish connection quickly while already having the necessary location information to communicate immediately with the MSC, maintaining both speed and communication continuity
Data Source
AI summary
Embodiments of the present invention provides a method for falling back to a 2G/3G network, a relevant device and a system. The embodiments of the present invention includes: receiving, by a mobility management entity, a first message from an access network device, where the first message carries location area information of a target 2G/3G cell to which a user equipment UE prepares to connect; sending a second message for requesting to perform a location update on the UE to a mobile switching center MSC corresponding to a location area of the target 2G/3G cell; receiving a third message from the MSC, where the third message carries a temporary mobile station identity TMSI allocated to the UE by the MSC; and sending, to the UE, a fourth message carrying the TMSI, so that the UE, after being connected to the target 2G/3G cell, communicates with the MSC by using the TMSI.