CSFB Failure Rate

4G LTE
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1

What are the possible reasons that causes CSFB to fail?

2

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,…
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3

Dear Hainm, What are your thoughts about the following scenario? It might be happening because of the CSFB failure.
Scenario: When the SMS transfer is on 2G or 3G and someone or MNO wants to send SMSs after 5 or 10 minutes, he is in one place, but when we see his record in the system, his location is showing in different provinces of the country.

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Very good explanation.
But about neighbor definition i want to know if the LTE cell SHOULD BE neighbor of the 2G/4G cell to work ??
Thanks in advance…

5

Hi Nemo,
I suppose you have a 4G LTE network for data and a 3G network for voice.Then to have optimum CSFB performance need to impliment dual attach.I suppose this is already implimented to Impliment dual attach you need to impliment SGsAP interface between MME and MSC.If not Its better if your network can impliment this and it will boost CSFB success rate significantly.
Thank you

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