MSC Pool Call Forwarding for LTE CSFB Connectivity Failures
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Solution Overview
Problem
In mobile telecommunications networks, when connectivity between a 3G radio network controller (RNC) or 2G base station center (BSC) and a mobile switching center (MSC) is lost, LTE subscribers experience lost calls as the 3GPP standards do not cover this scenario, leading to failed mobile terminating calls that are redirected to voice mail.
Innovation Solution
Implementing techniques at a telecommunications device, such as an MSC, to forward mobile terminating calls to another MSC within a pool, allowing call setup continuation even if the initial MSC's connectivity with the RNC/BSC is down, using Network Resource Identifier (NRI) information and supporting Mobile Terminating Roaming Forwarding (MTRF) to identify and redirect calls within the MSC pool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LTE subscribers use CSFB to make and receive calls, then voice service is enabled on LTE network, but mobile terminating calls are lost when connectivity between RNC/BSC and MSC is failed
Solution Approach 1:
The patent introduces an intermediary mechanism where the RNC/BSC detects MSC connectivity failure and acts as a mediator to redirect mobile terminating calls to an alternate MSC. The RNC/BSC receives the paging message from the failed MSC, determines the failure condition, and forwards the call to a different MSC that can successfully establish connectivity with the UE, thus maintaining call delivery reliability while preserving CSFB voice service capability
Solution Approach 2:
The patent implements dynamic call routing where the system adaptively changes the MSC destination based on real-time connectivity conditions. When the primary MSC connection fails, the system dynamically redirects the call to an alternate MSC, making the call routing flexible and adaptive to changing network conditions rather than following a static routing path
2Adaptability or versatility
If 3GPP standards are followed for CSFB, then LTE to 2G/3G fallback is standardized, but no solution exists for MSC connectivity failure scenarios
Solution Approach 1:
The patent implements preliminary failure detection and handling mechanisms where the RNC/BSC proactively monitors MSC connectivity status and prepares alternate routing paths before call failure occurs. When connectivity is lost, the pre-prepared redirection mechanism immediately activates to forward calls to alternate MSCs, preventing call loss without requiring changes to the standardized CSFB flow
3Reliability
If call forwarding to alternate MSC is implemented, then mobile terminating call delivery is maintained, but additional signaling and processing are required
Solution Approach 1:
The RNC/BSC serves as an intermediary that simplifies the overall system complexity by centralizing the failure detection and redirection logic. Rather than requiring complex interactions between multiple network elements, the RNC/BSC alone handles the failure detection, alternate MSC selection, and call forwarding, reducing signaling overhead and processing complexity while maintaining high call delivery reliability
Data Source
AI summary
Techniques pertaining to mobile terminating network failure forwarding for LTE circuit-switched fallback (CSFB) are described. In one aspect, a method includes a first telecommunications device of a pool of telecommunications devices receiving a reply message from a mobile user device forwarded to the first telecommunications device by a radio access device. The reply message is provided by the mobile user device in response to the mobile user device receiving a request message from a second telecommunications device of the pool of telecommunications devices. The method also includes the first telecommunications device establishing a voice call for the mobile user device based at least in part on information in the reply message.