The first SIB: SIB1
SIB1 contents assist the UE when it is evaluating cell access and also defines the scheduling of other system information.

Signalling radio bearer: N/A
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE
  • SIB1 is broadcasted at every 80 ms and is repeated are mabe within 80ms
  • The first transmission is made at SubFrame 5 for which SFN mod 8 = 0
  • Repetitions are scheduled in SubFRame 5 for which SFN mod 2 = 0
Important contents of SystemInformationBlockType1

Field Descriptions:
PLMN-IdentityConsists of MCC and MNC. The first listed one is the Primary PLMN
p-MaxValue applicable for the cell. If absent the UE applies the maximum power according to the UE capability. If eNB configures the value more than the value supported by the UE then UE will set the max value aupported by the UE capability. Example UE Catagory 3 supports max 23 db
cellReservedForOperatorUse As defined by operator (Reserved/Not_reserved)
trackingAreaCode   TAC which is common to the PLMN Identities
cellIdentity    Identifies a cell within the PLMN
cellBarred  If Barred then UE is not allowed to camp on the cell
intraFreqReselection If enabled, UE will be able to perform Cell-reselection to INTRA-frequency cells
q_RxLevMin  Minimum required RX level in the cell 
q_RxLevMinOffsetActual value Qrxlevminoffset = IE value * 2 [dB]. only applied when a cell is evaluated for cell selection as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN [5]. During this periodic search for higher priority PLMN the UE may check the S criteria of a cell using parameter values stored from a different cell of this higher priority PLMN. Affects the minimum required Rx level in the cell.
freqBandIndicatorindicates the E-UTRA operating band
schedulingInfoListinformation regarding the presence of SIB type; other than SIB1
  si_PeriodicityPeriodicity of the SI-message in radio frames (SI will be transmitted within the specified radio frame)
  sib_MappingInfocarries the List of the SIBs mapped. SIB2 is always present in the first element of schedulingInfoList
  si_WindowLengthspecifies that a SIB should be transmitted somewhere within the specified window length. Value is in ms. This window starts at the starting sub-frame of the mentioned si_periodicity. SIBs can be received in any of the sub-frame as mentioned in the WindowLength.
systemInfoValueTagindicates if a change has occurred in the SI messages. UEs may use systemInfoValueTag, e.g. upon return from out of coverage, to verify if the previously stored SI messages are still valid.
Additionally, the UE considers stored system information to be invalid after 3 hours from the moment it was successfully confirmed as valid, unless specified otherwise.
Common for all SIBs other than MIB, SIB1, SIB10, SIB11 and SIB12. 

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