SIB1 in LTE

After initial synchronization of UE with the network and obtaining the MIB, the UE starts to listen System Information Block Type 1 (SIB1) which is carrying cell access related information. SIB1 is transmitted through BCCH -> DL-SCH -> PDSCH channels. It is always sent in sub-frame #5 of the Radio-Frame, and continues re-transmitting the same message in each 20 ms with different redundancy versions. Each 80ms a new SIB1 is transmitted.

Here the list of carried information from the network to UE through SIB1:

PLMN Identity List: up to 6 PLMN can be identified in the list. First one is primary PLMN.
PLMN Identity: identifies operator global identity, combination of MCC and MNC.
Cell Reserved For Operator Use: Reserved or notReserved. In case of multiple PLMNs indicated in SIB1, this field is specified per PLMN inverse of *Cell Barred.
Tracking Area Code: identifies a tracking area for paging the users.
Cell Identity: identifies a cell within PLMN.

*Cell Barred: identifies the cell access status, if it is barred then it is not allowed the user to access to the cell. In case of multiple PLMNs listed in SIB1, this field is common for all PLMNs.
Intra Frequency Reselection: identifies the intra-frequency reselection permission status if it is allowed or not.
CSG Indication: False or True, identifies Closed Subscriber Group.
CSG Identity: is a limited set of users with connectivity access, in case of “true” only those UEs can access to the CSG cell which are in the group.
q_RxLevMin: minimum required received RSRP level for cell selection. Actual value in dBm is obtained by multiplying by two.
q_RxLevMinOffset: indicates the offset to the minimum required signal level.
p-Max: defines the maximum allowed uplink transmit power for the UE.
Freq Band Indicator: indicates LTE frequency band.
SI Periodicity: periodicity of System Information Blocks except than SIB1.
SIB Mapping Info: list of mapped SIBs.
SIB Type: type of transmitted SIB message in the list.
SI Window Length: a window is defined to enable multiple transmissions of the SI message within the window. SI Window Length can be set to 1, 2, 5 10, 15, 20 or 40 ms.
System Info Value Tag: if a change has occurred in the SI messages. UEs can use System Info Value Tag to verify if the previously stored SI messages are still valid.

SIB1 carried information:

Example for SIB1, taken from drive-test tool:

plmn-IdentityList
PLMN-IdentityList :
[0 ] :
plmn-Identity
mcc
MCC :
[0 ] : 1
[1 ] : 1
[2 ] : 1
mnc
MNC :
[0 ] : 0
[1 ] : 2
cellReservedForOperatorUse : notReserved
trackingAreaCode : 38441 (0x9629)
cellIdentity : 113491462 (0x6C3BE06)
cellBarred : notBarred
intraFreqReselection : allowed
csg-Indication : False
q-RxLevMin : -60
p-Max : 23
freqBandIndicator : 3
schedulingInfoList
SchedulingInfoList :
[0 ] :
si-Periodicity : rf16
sib-MappingInfo
SIB-MappingInfo :
[0 ] :
extensionBit0 : 0
Optionalitem : sibType3
[1 ] :
si-Periodicity : rf32
sib-MappingInfo
SIB-MappingInfo :
[0 ] :
extensionBit0 : 0
Optionalitem : sibType5
si-WindowLength : ms40
systemInfoValueTag : 8