Lte sib messages and their jobs

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                                                   LTE SIB Messages and Their Jobs

 

 

SIB1 in LTE

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
cellAccessRelatedInfo   

  PLMN_Identity 

     mcc[0] 

     mcc[1] 

     mcc[2] 

     mnc[0] 

     mnc[1] 

 cellReservedForOperatorUse
 trackingAreaCode
 cellIdentity
 cellBarred 

intraFreqReselection 

cellSelectionInfo 

    q_RxLevMin 

    q_RxLevMinOffset  

p_Max  

freqBandIndicator 

schedulingInfoList[0] 

    si_Periodicity 

    sib_MappingInfo[0] 

si_WindowLength 

systemInfoValueTag 

 

Field Descriptions:

PLMN-Identity

Consists of MCC and MNC. The first listed one is the Primary PLMN

p-Max

Value 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_RxLevMinOffset

Actual 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.

freqBandIndicator

indicates the E-UTRA operating band

schedulingInfoList

information regarding the presence of SIB type; other than SIB1

  si_Periodicity

Periodicity of the SI-message in radio frames (SI will be transmitted within the specified radio frame)

  sib_MappingInfo

carries the List of the SIBs mapped. SIB2 is always present in the first element of schedulingInfoList

  si_WindowLength

specifies 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.

systemInfoValueTag

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.

Common for all SIBs other than MIB, SIB1, SIB10, SIB11 and SIB12

 

SIB2 in LTE

SIB-2: an IMPORTANT SIB

  • The IE SystemInformationBlockType2 contains radio resource configuration information that is common for all UEs.
  • It carries Common and shared channel configuration, RACH related configuration, Timers, UL Power controls.
  • Without this SIB UE cannot initiate ATTACH procedure.
  • SIB2 is not specifically included in the scheduling information in SIB1 but it is always mapped to the SI message that corresponds to the first entry in the list of SI messages in schedulingInfoList in SIB1

Signalling radio bearer: N/A 
RLC-Mode: TM
Logical channel: BCCH
Direction: E‑UTRAN to UE 
 

Important contents of SystemInformationBlockType2
rach_ConfigCommon
radioResourceConfigCommon
  numberOfRA_Preambles
    preamblesGroupAConfig_exist
    powerRampingParameters
    powerRampingStep
    preambleInitialReceivedTargetPower
    ra_SupervisionInfo
    preambleTransMax
    ra_ResponseWindowSize
  mac_ContentionResolutionTimer
  maxHARQ_Msg3Tx 4
bcch_Config
pcch_Config
prach_Config
pdsch_ConfigCommon
pusch_ConfigCommon
pucch_ConfigCommon

soundingRS_UL_ConfigCommon
uplinkPowerControlCommon
ue_TimersAndConstants
freqInfo
timeAlignmentTimerCommon
   

Field Descriptions:

ac-BarringInfo

Access Class Barring configuration

radioResourceConfig

used to specify common radio resource configurations in the system information and in the mobility control information

 numberOfRA_Preambles

Number of non-dedicated random access preambles 

  preamblesGroupAConfig_exist

Provides the configuration for preamble grouping. If the field is not signalled, the size of the random access preambles group A is equal to numberOfRA-Preambles

  powerRampingParameters 

 

  powerRampingStep

Power ramping factor 

  preambleInitialReceivedTargetPower

Initial preamble power 

  ra_SupervisionInfo

 

  preambleTransMax

Maximum number of preamble transmission 

 ra_ResponseWindowSize

Duration of the RA response window. Value in subframes. Value sf2 corresponds to 2 subframes

 mac_ContentionResolutionTimer

Timer for contention resolution. Value in subframes. Value sf8 corresponds to 8 subframes

 maxHARQ_Msg3Tx 4

Maximum number of Msg3 HARQ transmissions, used for contention based random access

bcch_Config

 

 modificationPeriodCoeff

Actual modification period, expressed in number of radio frames= modificationPeriodCoeff * defaultPagingCycle. n2 corresponds to value 2

pcch_Config

 

 defaultPagingCycle

Default paging cycle, used to derive ‘T’. Value rf32 corresponds to 32 radio frames

 nB

is used as one of parameters to derive the Paging Frame and Paging Occasion

prach_Config

used to specify the PRACH configuration in the system information and in the mobility control information

 rootSequenceIndex

 

  prach_ConfigIndex

mentions the:
Preamble format: 0-4 (For frame structure 1 preamble format is 0-3 and for frame structure 2 it is 0-4) 
SFN: whether it will be EVEN no. frmae OR any frame
subframe number: carrier the subframe no. within the SFN 
(Look for the table in TS36.211 - Table 5.7.1-2)

  highSpeedFlag

TRUE corresponds to Restricted set and FALSE to Unrestricted set

  zeroCorrelationZoneConfig

used for Preamble generation

pdsch_Config

used to specify the common and the UE specific PDSCH configuration 

pusch_Config

used to specify the common PUSCH configuration and the reference signal configuration for PUSCH and PUCCH

pucch_Config

used to specify the common and the UE specific PUCCH configuration 

 soundingRS_UL_Config

used to specify the uplink Sounding RS configuration

uplinkPowerControl

used to specify parameters for uplink power control in the system information and in the dedicated signalling

ue_TimersAndConstants   

Timer values

freqInfo   

UL carrier frequency and bandwidth

timeAlignmentTimerCommon 

used to control how long the UE is considered uplink time aligned. Value in subframes

 

 

                                                                



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