How do UE read modified SI by NW

Below are the steps how do UE read when there is a modification of sib from NW side.

This we can get from below test case according 3GPP spec TS-36.523-1
8.1.1.2 RRC / Paging for notification of BCCH modification in idle mode


According the Test Case Below is the steps included for the Test case,


Main Steps in this test cases are 1,5,6,7 and 7a.

Step 1 verifies whether the UE is able respond to paging or not after the attach which is without any SI modification. In-fact this during this attach whatever SI has been transmitted are the scale to determine about the SI changes done by NW.

Step 5 NW transmits a paging like below,

Air Message: AIR_MSG_TYPE_PCCH
        paging Paging
          systemInfoModification PagingsystemInfoModification_true
          pagingRecordList_exist         0
          systemInfoModification_exist 1
          etws_Indication_exist                 0
          nonCriticalExtension_exist         0
As this is applicable to all the UE on that eNB so this kind of Paging doesn't include any UE identity.

Step 6 ensures that UE receive's the changed system information.
         This will be done by in this test scenario,
          First UE will go and read SIB1 - which will have SystemInfoValueTag as 1 in this case.
          Then UE will go and read SIB2 according scheduling Info provided by the new SIB1.
           This test case includes only PRACH CONFIG INDEX changed in SIB2 as below,

Previously:
prach_ConfigIndex 3
Now:
prach_ConfigIndex 10


Step 7  and 7a is just for checking whether UE is able to setup RRC Connection with NW or not?
         This steps will not be happening in case of live NW.
          Here NW pages (Step 7) UE with Paging message as below with S-Tmsi and UE establishes Rrc Connection Successfully (Step 7a).

Air Message: AIR_MSG_TYPE_PCCH

 

          pagingRecordList_exist         1

          systemInfoModification_exist 0

          etws_Indication_exist                 0

          nonCriticalExtension_exist         0

        pagingRecordList[0] PagingRecord

            ue_Identity PagingUE_Identity_

              s_TMSI S_TMSI

                mmec MMEC

                  buff[0..0] 01 

                TMSI S_TMSIm_TMSI

                  buff[0..3] c2 34 56 78 

       

St	Procedure	Message Sequence		TP	Verdict
		U - S	Message
1	The SS transmits a Paging message including a matched identity.	<--	Paging	-	-
2	Check: Does the UE transmit an RRCConnectionRequest message?	-->	RRCConnectionRequest	1	P
3	The SS transmits an RRCConnectionSetup message.	<--	RRCConnectionSetup	-	-
3A	The UE transmits an RRCConnectionSetupComplete message. This message includes a SERVICE REQUEST message.	-->	RRCConnectionSetupComplete	-	-
3B	The SS transmits a SecurityModeCommand message.	<--	SecurityModeCommand	-	-
3C	The UE transmits a SecurityModeComplete message.	-->	SecurityModeComplete	-	-
3D	The SS transmits an RRCConnectionReconfiguration message.	<--	RRCConnectionReconfiguration	-	-
3E	The UE transmits an RRCConnectionReconfigurationComplete message.	-->	RRCConnectionReconfigurationComplete	-	-
3F	The SS transmits an RRCConnectionRelease message.	<--	RRCConnectionRelease	-	-
3G	Wait for 5 s for the UE to enter E-UTRA RRC_IDLE state.	-	-	-	-
4	The SS changes the prach-ConfigIndex in the system information	-	-	-	-
5	The SS transmits a Paging message including a systemInfoModification.	<--	Paging	-	-
6	Wait for 15s for the UE to receive system information.	-	-	-	-
7	The SS transmits a Paging message including a matched identity.	<--	Paging	-	-
7A	Check: Does the UE re-transmit a random access using prach-ConfigIndex given in step 4?	-	-	1	P
8	The UE transmit an RRCConnectionRequest message.	-->	RRCConnectionRequest	-	-
9	The SS transmits an RRCConnectionSetup message.	<--	RRCConnectionSetup	-	-
9A	The UE transmits an RRCConnectionSetupComplete message. This message includes a SERVICE REQUEST message.	-->	RRCConnectionSetupComplete	-	-
9B	The SS transmits a SecurityModeCommand message.	<--	SecurityModeCommand	-	-
9C	The UE transmits a SecurityModeComplete message.	-->	SecurityModeComplete	-	-
9D	The SS transmits an RRCConnectionReconfiguration message.	<--	RRCConnectionReconfiguration	-	-
9E	The UE transmits an RRCConnectionReconfigurationComplete message.	-->	RRCConnectionReconfigurationComplete	-	-
9F	The SS transmits an RRCConnectionRelease message.	<--	RRCConnectionRelease	-	-
9G	Wait for 5 s for the UE to enter E-UTRA RRC_IDLE state.	-	-	-	-
10	Check: Does the test result of generic test procedure in TS 36.508 subclause 6.4.2.2 indicate that the UE is in E-UTRA RRC_IDLE state on Cell 1?	-	-	1	-