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LTE: Which network node converts PS call to CS call in the LTE network ?

+2 votes
LTE: Which network node converts PS call to CS call in the LTE network ?
posted Sep 30, 2016 by Rupam

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2 Answers

+2 votes


For CS Fallback, MME will convert PS to CS switching.

The flow goes like following :
MO cal :

UE sends ESR to mme, mme gives the switchover command to ENB, ENB make UE to other technology fallback(handover). Then the call continous in other tech (3G or 2G).After call finishes it is upper layer job to reselect the ENB.

Terminated call :

MSC send the paging request to MME via SG interface. MME forwards to UE, Then UE will start ESR to MME, Then same flow contineous as per above flow.

answer Oct 4, 2016 by Jaganathan
0 votes


Serving Gateway will initiate the trigger to CS call.

answer Sep 30, 2016 by Bhagyashree R
Similar Questions
+4 votes

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.

+1 vote

In TS 23.221 7.2a, there is a note describe that "Whether to perform combined EPS/IMSI attach/combined TA/LA Update or EPS attach/TAU for the case of "IMS PS Voice preferred" is to be evaluated in each release of the specifications.", but I can not find any information about that.

+1 vote

Suppose MME is getting CS call notification for MSC then How MME will notify to UE when
1. UE is idle mode. ?
2. UE is in connected mode?

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