LTE: System Information Block Type 1

Direction: E-UTRAN => UE
Signalling Radio Bearer: N/A
RLC Mode: TM
Logical Channel: BCCH
Transport Channel: DL-SCH

SystemInformationBlockType1 (SIB1) contains information relevant when evaluating if a UE is allowed to access a cell. Also, it supplies the UE with the scheduling of other system information. SIBs other than SIB1 are carried in SystemInformation (SI) messages and mapping of SIBs to SI messages is flexibly configurable by schedulingInfoList included in SIB1

SIB1 uses a fixed schedule with a periodicity of 80ms and repetitions made within 80ms. The first transmission of SIB1 is scheduled in subframe #5 of radio frames for which the SFNmod8 = 0, and repetitions are scheduled in subframe #5 of all other radio frames for which SFNmod2 = 0

SIB1 contains cell access related information (e.g. a PLMN identity list, tracking area code, cell identity, etc.), information for cell selection (e.g. minimum required Rx level in the cell and offset), p-Max, frequency band indicator, scheduling information, TDD configuration, SI-window length and system information value tag etc...

Upon receiving the SIB1 message the UE shall check the IE freqBandIndicator. The UE shall consider the cell as barred if the frequency band indicated in the freqBandIndicator is not part of the frequency bands supported by the UE

Some of the IEs in SystemInformationBlockType1 message:
PLMN-IdentityList: List of PLMN identities. The first listed PLMN-Identity is the primary PLMN
TrackingAreaCode: A trackingAreaCode that is common for all the PLMNs listed
Cellidentity: Identity of the cell
CellBarred: 'barred’ means the cell is barred
IntraFreqReselection: Used to control cell reselection to intra-frequency cells when the highest ranked cell is barred, or treated as barred by the UE
CSG-Indication: If this IE is set to TRUE the UE is only allowed to access the cell if the CSG identity matches an entry in the CSG whitelist that the UE has stored
p-Max: Maximum power value applicable for the cell. If this IE is absent, then the UE applies the maximum power according to the UE capability
freqBandIndicator: Operating frequency band of the cell as defined in TS 36.101 [Table 5.5-1].
si-Periodicity: Periodicity of the SI-message in radio frames, such that rf8 denotes 8 radio frames, rf16 denotes 16 radio frames, and so on
sib-MappingInfo: List of the SIBs mapped to this SystemInformation message. There is no mapping information of SIB2; it is always present in the first SystemInformation message listed in the schedulingInfoList list.
si-WindowLength: Common SI scheduling window for all SIs. Unit in milliseconds, where ms1 denotes 1 millisecond, ms2 denotes 2 milliseconds and so on
systemInfoValueTag: Common for all SIBs other than MIB, SIB1, SIB10, SIB11 and SIB12. Change of MIB and SIB1 is detected by acquisition of the corresponding message
csg-Identity: Identity of the Closed Subscriber Group within the primary PLMN the cell belongs to. This field is present in a CSG cell
ims-EmergencySupport: Indicates whether the cell supports IMS emergency bearer services for UEs in limited service mode. If absent, IMS emergency call is not supported by the network in the cell for UEs in limited service mode

Reference: 3GPP TS 36.331

Example: SystemInformationBlockType1 message

24 comments:

  1. Hey... Kumar Swamy, i want to ask you,,.. how much bit needed to encode q-RxLevMin = -53 ?
    thanks...

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  2. Hello Kumar,

    In contrast with other SIBs the encoded message seems to be missing in the picture.

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  3. Hi kumar,

    What is the timer for system info value tag?


    ReplyDelete
    Replies
    1. Not sure what your question exactly means. But the following excerpt from 36.331 should help you with;

      SystemInformationBlockType1 includes a value tag, systemInfoValueTag, that indicates 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.

      Delete
  4. Hi i wanted to know how we distinguish SIB's in LTE? SIB's in LTE ARE decoded vi ASN.1 right? so these message have header or something?

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    Replies
    1. Yes, system information is encoded using ASN.1 in the similar way as other RRC messages. It is one of the choice values that decides the SIB type in BCCH-DL-SCH-MessageType. Please refer to 36.331 section 6.2.1

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  5. This comment has been removed by the author.

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  6. Just commenting to tell you about my appreciation for your blog. It's great!

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  7. Hi Kumar,
    Why does Source eNB send SIB1/SIB2 info . in handover context to Target eNB ?

    Thank You in Advance.

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    Replies
    1. There is no need for source eNodeB to send system information to the target eNodeB. It is the other way around. The source eNodeB needs information such as RACH preamble, access parameters, SIBs, etc. from target eNodeB

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    2. Hi Kumar,
      I meant, "HandoverPreparationInformation" message.
      Direction: source eNB/ source RAN to target eNB

      AS-Config {
      sourceMasterInformationBlock MasterInformationBlock,
      sourceSystemInformationBlockType1 SystemInformationBlockType1(WITH COMPONENTS
      {..., nonCriticalExtension ABSENT}),
      sourceSystemInformationBlockType2 SystemInformationBlockType2,
      }

      So in AS config, src eNB sends MIB/SIB1/SIB2 as well ?? I am wondering why 3GPP has included them ?

      Delete
  8. Hi Kumar,

    what is the Tdd configuration it is transmitting while the cell or network belongs to Tdd ?

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  9. Which SIB keep the information regarding TX mode in lte?

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  10. How RRC will get these parameter values to send to UE?

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  11. what is the difference between cellIdentity in sib1 and phy cell identity calculated with pss and sss?

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    Replies
    1. PCI from pss and sss is only for UE, its calculated as per field config taking consideration that neighbors reference signal don't fall at same RE's, while cellidentity in sib1 is decided by operator for its identitiy in the core network also

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  12. How does eNB select the value of parameters for SIB1 ?Is there any default values for SIB1 configuration ?

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    Replies
    1. Its configured by the operator depending on implementation.

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  15. How ue will get to know the sib information in power on procedure

    How ue will get know the location of pdcch

    How ue to know the pdsch location in resource grid

    How ue get to know the location of phich location

    ReplyDelete
  16. These blocks play a crucial role in enabling a mobile device to connect to and communicate with a cellular network effectively. How Audio Fix Different types of SIBs provide various sets of information for network configuration and optimization.

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