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SIB Change Notification

 

Most UE decodes all the MIB/SIBs during cell selection. However once they decoded all the MIB/SIBs and perform registration, they may not try to decode all the SIBs. So if you change any information in SIB after UE get camped on and stay in idle mode, the UE may not recognize those changes. So there should be some mechanism for Network to explicitely tell UE to update all the SIBs.

 

3GPP 25.331 8.1.1.5 describes all the possible situations how SIB change should be notified and recognized by UE.

The most common case of SIB change detection on UE side would be as follows :

 

    If ( he value tag in the master information block

           is different from the value tag stored for this cell and this PLMN in the variable VALUE_TAG ) {

    • store the value tag into the variable VALUE_TAG for the master information block;
    • read and store scheduling information included in the master information block

    }

     

    If ( no IEs for the master information block are stored) {

    • store the value tag into the variable VALUE_TAG for the master information block;
    • read and store scheduling information included in the master information block

    }

     

    If ( he value tag in the master information block

           is same as the value tag stored for this cell and this PLMN in the variable VALUE_TAG ) {

    • store the value tag into the variable VALUE_TAG for the master information block;
    • read and store scheduling information included in the master information block

    }

 

Normally this 'update request' is done by three steps (6,7,8,9) in the following sequence.

 

    1) UE <--  NW : MIB Transmission

    2) UE <--  NW : SIB Transmission

    3) UE <--> NW : < Registration >

    4) UE <--> NW : < Idle >

    5)    < Make changes in SIB >

    6) UE <--  NW : MIB Transmission with changed Valuetag

    7) UE <--  NW : SIB Transimssion with changed parameter

    8) UE <--  NW : Paging Type 1 with bcch-Modification Info

    9) UE             : Decode all the SIBs again and update the changes

If you have UE logging tool and check the decoded SIBs on UE side, you can easily confirm the newly decoded SIBs on UE side.

If you do not have any UE logging tool, you can indirectly confirm this behavior in the following way.

1) UE <--  NW : MIB Transmission

    MasterInformationBlock

        mib-ValueTag: 1

        plmn-Type: gsm-MAP (0)

            gsm-MAP

                plmn-Identity

                    mcc: 3 items

                        Item 0

                            Digit: 0

                        Item 1

                            Digit: 0

                        Item 2

                            Digit: 1

                    mnc: 2 items

                        Item 0

                            Digit: 0

                        Item 1

                            Digit: 1

        sibSb-ReferenceList: 5 items

            Item 0

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType1 (0)

                        sysInfoType1: 1

                    scheduling

                        scheduling

                            sib-Pos: rep32 (3)

                                rep32: 2

            Item 1

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType3 (2)

                        sysInfoType3: 1

                    scheduling

                        scheduling

                            sib-Pos: rep32 (3)

                                rep32: 3

            Item 2

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType5 (4)

                        sysInfoType5: 1

                    scheduling

                        scheduling

                            segCount: 4

                            sib-Pos: rep64 (4)

                                rep64: 5

                            sib-PosOffsetInfo: 3 items

                                Item 0

                                    SibOFF: so2 (0)

                                Item 1

                                    SibOFF: so2 (0)

                                Item 2

                                    SibOFF: so28 (13)

            Item 3

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType7 (6)

                        sysInfoType7: NULL

                    scheduling

                        scheduling

                            sib-Pos: rep64 (4)

                                rep64: 10

            Item 4

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType11 (10)

                        sysInfoType11: 1

                    scheduling

                        scheduling

                            segCount: 9

                            sib-Pos: rep128 (5)

                                rep128: 11

                            sib-PosOffsetInfo: 8 items

                                Item 0

                                    SibOFF: so4 (1)

                                Item 1

                                    SibOFF: so2 (0)

                                Item 2

                                    SibOFF: so2 (0)

                                Item 3

                                    SibOFF: so22 (10)

                                Item 4

                                    SibOFF: so2 (0)

                                Item 5

                                    SibOFF: so4 (1)

                                Item 6

                                    SibOFF: so2 (0)

                                Item 7

                                    SibOFF: so2 (0)

 

2) UE <--  NW : SIB Transmission

 

: I will list only one SIB that will be changed later. In real test, several other SIBs are transmitted as well.

    SysInfoType1

        cn-CommonGSM-MAP-NAS-SysInfo: 0000

        CN Common GSM-MAP NAS system information

            Location Area Code (LAC): 0x0000 (0)

        cn-DomainSysInfoList: 2 items

            Item 0

                CN-DomainSysInfo

                    cn-DomainIdentity: ps-domain (1)

                    cn-Type: gsm-MAP (0)

                        gsm-MAP: 8001

                        PS domain specific system information

                            Routing Area Code (RAC): 0x80 (128)

                            0000 00.. = Spare bit(s): 0

                            .... ..0. = NMO I: Network Mode of Operation indicated in Bit 1 (NMO)

                                         is used for MS configured for NMO_I_Behaviour

                            .... ...1 = NMO: Network Mode of Operation II

                    cn-DRX-CycleLengthCoeff: 8

            Item 1

                CN-DomainSysInfo

                    cn-DomainIdentity: cs-domain (0)

                    cn-Type: gsm-MAP (0)

                        gsm-MAP: 0001

                        CS domain specific system information

                            T3212: 0

                            0000 000. = Spare bit(s): 0

                            .... ...1 = ATT: MSs shall apply IMSI attach and detach procedure

                    cn-DRX-CycleLengthCoeff: 8

        ue-ConnTimersAndConstants

            t-305: noUpdate (0)

            t-308: ms320 (3)

            t-314: s0 (0)

            t-315: s0 (0)

            t-316: s-inf (6)

            t-317: infinity1 (1)

        ue-IdleTimersAndConstants

            t-300: ms2000 (10)

            n-300: 5

            t-312: 10

            n-312: s1 (0)

 

6) UE <--  NW : MIB Transmission with changed Valuetag

    MasterInformationBlock

        mib-ValueTag: 2

        plmn-Type: gsm-MAP (0)

            gsm-MAP

                plmn-Identity

                    mcc: 3 items

                        Item 0

                            Digit: 0

                        Item 1

                            Digit: 0

                        Item 2

                            Digit: 1

                    mnc: 2 items

                        Item 0

                            Digit: 0

                        Item 1

                            Digit: 1

        sibSb-ReferenceList: 5 items

            Item 0

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType1 (0)

                        sysInfoType1: 2

                    scheduling

                        scheduling

                            sib-Pos: rep32 (3)

                                rep32: 2

            Item 1

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType3 (2)

                        sysInfoType3: 1

                    scheduling

                        scheduling

                            sib-Pos: rep32 (3)

                                rep32: 3

            Item 2

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType5 (4)

                        sysInfoType5: 1

                    scheduling

                        scheduling

                            segCount: 4

                            sib-Pos: rep64 (4)

                                rep64: 5

                            sib-PosOffsetInfo: 3 items

                                Item 0

                                    SibOFF: so2 (0)

                                Item 1

                                    SibOFF: so2 (0)

                                Item 2

                                    SibOFF: so28 (13)

            Item 3

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType7 (6)

                        sysInfoType7: NULL

                    scheduling

                        scheduling

                            sib-Pos: rep64 (4)

                                rep64: 10

            Item 4

                SchedulingInformationSIBSb

                    sibSb-Type: sysInfoType11 (10)

                        sysInfoType11: 1

                    scheduling

                        scheduling

                            segCount: 9

                            sib-Pos: rep128 (5)

                                rep128: 11

                            sib-PosOffsetInfo: 8 items

                                Item 0

                                    SibOFF: so4 (1)

                                Item 1

                                    SibOFF: so2 (0)

                                Item 2

                                    SibOFF: so2 (0)

                                Item 3

                                    SibOFF: so22 (10)

                                Item 4

                                    SibOFF: so2 (0)

                                Item 5

                                    SibOFF: so4 (1)

                                Item 6

                                    SibOFF: so2 (0)

                                Item 7

                                    SibOFF: so2 (0)

 

7) UE <--  NW : SIB Transimssion with changed parameter

    SysInfoType1

        cn-CommonGSM-MAP-NAS-SysInfo: 0001

        CN Common GSM-MAP NAS system information

            Location Area Code (LAC): 0x0001 (1)

        cn-DomainSysInfoList: 2 items

            Item 0

                CN-DomainSysInfo

                    cn-DomainIdentity: ps-domain (1)

                    cn-Type: gsm-MAP (0)

                        gsm-MAP: 8001

                        PS domain specific system information

                            Routing Area Code (RAC): 0x80 (128)

                            0000 00.. = Spare bit(s): 0

                            .... ..0. = NMO I: Network Mode of Operation indicated in Bit 1

                                                   (NMO) is used for MS configured for NMO_I_Behaviour

                            .... ...1 = NMO: Network Mode of Operation II

                    cn-DRX-CycleLengthCoeff: 8

            Item 1

                CN-DomainSysInfo

                    cn-DomainIdentity: cs-domain (0)

                    cn-Type: gsm-MAP (0)

                        gsm-MAP: 0001

                        CS domain specific system information

                            T3212: 0

                            0000 000. = Spare bit(s): 0

                            .... ...1 = ATT: MSs shall apply IMSI attach and detach procedure

                    cn-DRX-CycleLengthCoeff: 8

        ue-ConnTimersAndConstants

            t-305: noUpdate (0)

            t-308: ms320 (3)

            t-314: s0 (0)

            t-315: s0 (0)

            t-316: s-inf (6)

            t-317: infinity1 (1)

        ue-IdleTimersAndConstants

            t-300: ms2000 (10)

            n-300: 5

            t-312: 10

            n-312: s1 (0)

     

 

8) UE <--  NW : Paging Type 1 with bcch-Modification Info

 

    message: pagingType1 (0)

        pagingType1

            bcch-ModificationInfo

                mib-ValueTag: 2