RRC Success Rate Degrade after Adding the Second SCCPCH

[mounir34]

The RRC success rate degrades to 94% for 6 hours after adding the second SCCPCH
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After adding the second SCCPCH, UE will not recognize till it update the system information message. In this period, when UE send RRC request to RNC, RNC may send the RRC request setup message to UE on the second SCCPCH. For UE did not recognize the second SCCPCH, the RRC attempt will be fail.

According to protocol 25.331, UE must re-read the system information message for at least one time in 6 hours. So in theory, the RRC connection setup success rate should recover in 6 hours after adding second SCCPCH. All the traffic will be affect till UE re-read the system information message, and also reset UE can recover problem happened in the UE.After adding the second SCCPCH, UE will not recognize till it update the system information message. In this period, when UE send RRC request to RNC, RNC may send the RRC request setup message to UE on the second SCCPCH. For UE did not recognize the second SCCPCH, the RRC attempt will be fail.

According to protocol 25.331, UE must re-read the system information message for at least one time in 6 hours. So in theory, the RRC connection setup success rate should recover in 6 hours after adding second SCCPCH. All the traffic will be affect till UE re-read the system information message, and also reset UE can recover problem happened in the UE.

the below switch is recommended to open and close it beofre and after add 2nd SCCPCH,

SET UNBMPARA: RELIABILITYSWITCH=CELL_SIB_NOT_UPD_NCELL_CHG_SWITCH-1 and 0.



When the switch is turned on, activating and deactivating neighboring cells does not trigger an update of local cell's system information. This switch needs to be turned on before the second SCCPCH is added to multiple cells and needs to be turned off after the addition.

In system information message, there is a value tag. If the UE find the value tag is the same as before, it will not update system information message immediately. The value tag is in loop from 0~6, when activating and deactivating neighboring cells, the value tag will change.

When add the second SCCPCH, there are many operation of activating and deactivating neighboring cells and the value tag will change frequently. After adding the SCCPCH, the value tag may be the same as before. In this case, the UE will cannot update system information message immediately. So it suggests turning the switch on before adding second SCCPCH, and turning the switch off after adding second SCCPCH. The value tag will change at the same time when switch turn off, and the value tag will be different with before in all the cells.