CSFB Failure Rate

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,…