Receiving BCCH in Cell_DCH state (during a voice call) ?

**faisaladeem** · 2014-03-10, 06:55 AM

Hi,

I have observed a strange case where UE is receiving BCCH system information after active set update complete during a voice call. This is happening frequently after active cell update complete (but not all the time) with Huawei P1 handset. UE data was turned off during DT. The time-stamps show BCCH info being received from ~1s to ~5s and the voice call continues normally despite such gaps of no measurement reports in UL and call control signaling in DL. Any ideas what might be the reason ?
BCCH in Cell_DCH State.jpg

**Finetopix** · 2014-03-10 06:55 AM

**wolverine** · 2014-03-10, 07:20 AM

If this is an LTE capable handset?

**faisaladeem** · 2014-03-10, 07:26 AM

Yes it is an LTE capable handset in LTE capable network but it was locked on 3G during the DT

**khurrambilal01** · 2014-03-10, 06:35 PM

Normally when UE receives BCH information during a CS call it is considered to be drop call.

**wolverine** · 2014-03-10, 06:47 PM

What you are experiencing is a Qualcomm "enhancement" for LTE handsets. The UE will read SIB and store it in its SIB database to enable faster reselection to LTE (SIB19 required) following termination of a CSFB call.

Even though you locked the phone to 3G and obviously did not perform CSFB, the functionality is still there.

Originally Posted by faisaladeem

Yes it is an LTE capable handset in LTE capable network but it was locked on 3G during the DT

**faisaladeem** · 2014-03-11, 09:05 PM

Hi Wolverine, The concept seems similar to a feature in 2G/3G called "Fast return to LTE after call release" whereby LTE frequency or list of LTE cells is given to mobile at the time of call release to reselect LTE quickly. However as you mentioned in "Qualcomm enhancement for LTE handsets", the UE itself tries to read SIB19 to get LTE information during a voice call. This might impact in call KPIs. Can you kindly share any details of this Qualcomm enhancement for LTE handsets ?