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What are the possible reason of CSFB Failure in LTE network?

+2 votes
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What are the possible reason of CSFB Failure in LTE network?
posted Jan 12, 2016 by anonymous

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2 Answers

+1 vote

when CSFB is triggered UE is released from LTE network through RRC message stating the frequency of legacy network and in case of RIM exact cell information is provided. So first thing first, you have define the correct frequencies of legacy network.
Now UE can reselect the cell based on measurements or blindly. Your 3G cells should be defined properly. You can check 3G cell own speech performance that it does not have any issue.

answer Sep 24, 2018 by Ammar Qadir
0 votes

I think only during the "mo" and "mt" voice call , LTE UE moves to CSFB .

answer Jan 12, 2016 by Harshita
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CSFB: How signalling messages are exchanged in CSFB when UE moves from LTE to Legacy network ?

Assuming one case when UE was in LTE network and data transmission was ongoing. Due to incoming voice call, UE leaves LTE network and moves to legacy network to finish voice call. I want to know what will happen with ongoing data session in LTE network.
Does the LTE network deletes UE context ? Does the LTE network buffers UE data coming in downlink direction ? Or UE establishes voice as well as data session is legacy network and he continues voice and data services (less through due to legacy network speed) in case UE and legacy network both support DTM (Dual transmission mode) ?

+4 votes
When CSFB call end while PS session ongoing then which procedure will be performed to move again LTE Network?

If UE doesn't have any PS session and any CSFB call initiated then UE redirected to WCDMA or GSM and after ending CS session UE moved to LTE network by performing Tracking area update.

But in case PS session is on going and CS call have to be initiated then Handover to WCDMA will be performed. But when CS call finished and PS session is also still ongoing then which procedure will be performed to move again LTE Network? If its Handover then how measurement reporting will be done.

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