What are the possible reasons that causes CSFB to fail?
Some possible reasons of CSFB 4G-3G failures as:
- enodeB setting did not enable CSFB service correctly
- enodeB not configure neighboring UMTS frequency for voice
- lack of license RRC connected users at enodeB
- 3G cell coverage is week, UE can not search for UMTS network
- neighboring 3G cells configured highest priority not have strongest signal quality.
- CSFB service request while UE is doing PS handover in LTE
- MME configure mapping TAC (4G) - LAC (3G) incorrectly
- some terminal incompatibility issues
- RAN issues, transmission issues,…