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 :
- 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
- 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
- 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 different from the value tag stored for this cell and this PLMN in the variable VALUE_TAG ) {
}
If ( no IEs for the master information block are stored) {
}
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 ) {
}
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
2) UE <-- NW : SIB Transmission
3) UE <--> NW : < Registration >
4) UE <--> NW : < Idle >
5) < Make LAC changes in SIB1 : In this test, I changed LAC from 0 to 1>
6) UE <-- NW : MIB Transmission with changed Value tag
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
10) < UE should go through following process for Location Updating for new LAC >
12) UE <--> NW : < RRC Connection Setup >
13) UE <--> NW : < Perform Location Area Updating >
14) UE <--> NW : < Perform Routing Area Updating >
15) UE <--> NW : < RRC Connection Release >
16) UE <--> NW : < Idle >
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