Access Node Handover Logic for LTE to 2G3G Transitions
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Solution Overview
Problem
Existing solutions for handover between different radio access technologies (RATs) often result in failures of Single Radio Voice Call Continuity (SRVCC) or Packet Switched (PS) handover procedures, particularly when bearers cannot be handed over between LTE and 2/3G or 5G networks, leading to degraded user experience and service disruptions.
Innovation Solution
The method involves receiving information from a Mobility Management Entity (MME) about bearers that cannot be handed over to specific RATs, determining whether to perform a PS handover based on this information, and adjusting handover procedures to avoid failures by excluding unsupported bearers or using fake transaction identifiers, thereby ensuring successful handovers and maintaining service continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PS handover is performed for all bearers during SRVCC procedure, then service continuity is maintained, but handover failures occur when bearers cannot be handed over to 2/3G networks
Solution Approach 1:
The patent segments bearers into two categories: voice bearers that require handover to 2/3G for SRVCC, and data bearers that may not support handover to 2/3G. By treating different bearer types separately, the system performs PS handover only for compatible bearers, avoiding handover failures while maintaining service continuity for voice calls.
Solution Approach 2:
Instead of performing PS handover for all bearers (excessive action), the patent applies partial action by selectively performing PS handover only for bearers that support 2/3G handover. This partial approach prevents handover failures while still maintaining service continuity for critical voice services.
2Reliability
If SRVCC procedure is triggered for voice call continuity, then voice service is maintained during LTE to 2/3G transition, but data bearers may fail to hand over
Solution Approach 1:
The patent extracts and separates the voice bearer handover requirement from the data bearer handover process during SRVCC. By taking out the voice bearer handling and treating it separately from data bearers, the system ensures voice call continuity through mandatory 2/3G handover while allowing data bearers to be handled according to their individual capabilities.
Solution Approach 2:
The patent applies local quality by assigning different handover requirements to different bearer types. Voice bearers receive prioritized handling with mandatory 2/3G handover for SRVCC continuity, while data bearers receive differentiated treatment based on their specific capabilities, allowing some to handover and others to be switched off without affecting overall service.
3Reliability
If all bearers are switched off when PS handover fails, then handover failure impact is limited, but service continuity is degraded
Solution Approach 1:
Instead of switching off all bearers when handover fails (excessive action), the patent applies partial action by selectively switching off only the data bearers that cannot handover to 2/3G, while preserving voice bearers through SRVCC. This partial approach limits the impact of handover failure to only affected data services while maintaining critical voice service continuity.
Data Source
AI summary
Methods and apparatuses for handover between different radio access technologies (RATs) are disclosed. According to an embodiment, an access network node receives, from a mobility management entity (MME), information indicating that one or more bearers for a terminal device cannot be handed over to one or more RATs different than long term evolution (LTE). The access network node determines whether to perform a packet switched (PS) handover for the terminal device based on the information.