PLMN ID Provisioning for CSFB LTE Reconnection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE networks, when a wireless device transitions back from a 2G or 3G network to LTE after a Circuit Switched call, there is a high likelihood of service outage due to the inability to accurately determine available LTE frequencies with valid radio coverage, as existing methods either provide the last used PLMN ID too late or require unnecessary frequency measurements.
Innovation Solution
A method where a first network node provides the last used PLMN ID to a second network node during the setup of a CSFB procedure, allowing the second network node to request measurements on E-UTRAN frequencies associated with the last used PLMN ID, ensuring a successful return to LTE by selecting frequencies with valid radio coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the last used PLMN ID is provided to the network node after CSFB call setup, then the network can determine available LTE frequencies, but the service outage time increases due to delayed frequency information
Solution Approach 1:
The last used PLMN ID is provided to the network node during CSFB call setup, before the call is actually released back to LTE. This preliminary provision of frequency information allows the network to prepare the appropriate LTE frequencies in advance, eliminating the need for delayed frequency determination and reducing service outage time when returning to LTE.
2Reliability
If the network requests measurements on multiple E-UTRAN frequencies, then the wireless device can find available LTE frequencies, but unnecessary measurements increase device complexity and power consumption
Solution Approach 1:
Instead of requesting measurements on multiple E-UTRAN frequencies, the network uses the provided last used PLMN ID to directly determine the specific LTE frequency that the wireless device should connect to. This targeted approach based on local knowledge of the device's previous connection eliminates unnecessary broad measurements while ensuring reliable reconnection.
3Ease of operation
If the network uses generic frequency selection without PLMN ID information, then the procedure is simpler, but service outage time increases due to inability to accurately determine valid LTE frequencies
Solution Approach 1:
The last used PLMN ID is provided during CSFB call setup to enable preliminary determination of the appropriate LTE frequency. This allows the network to have the frequency information ready before the call release, maintaining a simple procedure while eliminating the time delay associated with post-release frequency determination.
Data Source
AI summary
A method performed by a first network node of providing a last used PLMN ID in LTE to a second network node, the first network node and the second network node operating in a wireless communications network. The method comprises providing the last used PLMN ID in LTE of a wireless device in the wireless communications network, to the second network node, as soon as a Circuit Switched, CS, call due to a CSFB procedure has been setup. The providing of the PLMN ID is performed by one of: adding information about the last used PLMN ID in LTE to an existing message from the first network node to the second network node, and defining a new message from the first network node to the second network node. The new message comprises the last used PLMN ID in LTE.