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LTE CSFB and Legacy Interworking Procedures

This hub groups the LTE procedures that leave pure EPS packet service and move into fallback or legacy interworking behavior.

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This category covers LTE fallback and interworking procedures that involve legacy voice or legacy radio continuity.

Common nodes include the UE, eNB, MME, and legacy access or core domains.

These procedures matter when LTE service hands over voice or mobility handling to non-EPS paths.

Procedures that move service from LTE into legacy voice handling.

LTE CSFB Procedure — Main LTE circuit-switched fallback path.
LTE CSFB to 3G — Fallback path from LTE to UMTS.
LTE CSFB to 2G — Fallback path from LTE to GSM.
LTE 1xCSFB / CDMA2000 Fallback Procedure — Fallback path from LTE to CDMA2000 voice handling.

Procedures that prepare or transfer signaling for legacy interworking.

LTE Handover From E-UTRA Preparation Request — Preparation signaling for legacy interworking handover.
LTE UL Handover Preparation Transfer — Uplink preparation transfer for interworking mobility.

Procedures that preserve or prepare voice continuity during legacy transition.

LTE PS Handover / SRVCC Preparation Flows — Voice continuity and legacy preparation paths.