What is eCSFB?

 

Enhanced Circuit Switched Fallback (eCSFB) is an LTE to 1xRTT fallback mechanism used to provide voice and other important services like SMS, E911 and Location based services (LBS) to LTE users using a single radio device.

eCSFB Architecture

Where to activate eCSFB?

eCSFB will be activated at sites only where NV LTE and NV CDMA both are on air

TAC has already activated all the sites where NV LTE and NV CDMA are on air.Sites where NV CDMA is already on air but LTE was not on air, RAN commissioning is responsible for activating eCSFB whenever LTE comes on air for those sites.

Sites where NV LTE is already on air but CDMA was not on air, Samsung TAC 4G is responsible for activating eCSFB whenever CDMA comes on air for those sites.

 

Troubleshooting eCSFB

 

If eCSFB success rate is 0% (with non zero attempts), good possibility is that parameter/neighbor configuration is incorrect or does not match. i.e PN and BTS/Sector id in ECSFB nbr list do not correspond.

If eCSFB success rate is low, it could be due to BH/HW/Radio resource shortage at the handin target BTS’s 1X carrier. Look for BH/Core CFC’s and alarms on 3G side.

eCSFB success rate can be low due to poor 3G coverage overlap with that of 4G or due to ECSFB attempts being made out to less than optimum neighbors (3G BTSs) which may happen due to missing own (collocated) and/or1st tier neighbors and or target FA (ARFCN of first FA) for significant nbr is down.

If Ec/Io for CDMA is less than -12 dB, then the device will do blind re-direction towards 1x configured in the NBR list. In case of missing NBR config, the call drops.