R8-UE request CSFB service in LTE cell enabled flash CSFB based on RIM

Hi all experts,

Flash CSFB based on RIM feature has benefit of reducing CSFB setup time, this is due to RRC-conn-release message that enb sent to UE also contain PSC + SI of UMTS cell.
This feature require enb/CN and UE support R9 and later.
Have anyone ever seen how a R8-UE request CSFB service in a LTE cell enabled flash CSFB?

  • CSFB will be failed.
  • or enb checked UE capability and just send UMTS-frequency only to UE and UE continue with normal CSFB

2019 I saw many cases where flash csfb was zero. and S1 was R8. …
today I was checking the same but to my surprise… I have sites (many . like 1k) with R8 and flash csfb happening (?) unfortunately Im overloaded with bureaucracy enough to investigate interesting matters but if I find time I would lalso ike to know how is that possible…

R8 MME/SGSN can not support flash CSFB, at least R9.
Can you check: DSP UTRANRIM, DSP S1INTERFACE to check whether enb can obtain UTRAN SI and which version of core network?

yes, my mistake. checked again. there was 2 S1 created. one was R8 for another CN operator… so my dynamic table was bugged.(that is what happens when you check thousands elements on a hurry hahah! ) As we know, R8 is not having flash csfb…
on the other hand. the best proof that it is working (through redirection) is that we dont receive complains… customers were very sensible to this problem in the last years.

site with no FLASH:
image

Second option!