5G/NR - MIB / SIB                                           Home : www.sharetechnote.com

 

 

 

 

MIB / SIB

 

Overall functionality and structure of MIB / SIB  of NR is almost same as LTE, but there is one major differeces between NR and LTE. In LTE (actually all other techology except NR), all the SIBs are broadcast periodically regardless of whether UE want it or not. However, in NR there are two different types of SIBs. One type is the one being transmitted periodically like SIBs in LTE and the other type is the one being transmitted only when there is the request from UE.  

 

 

 

Overall MIB/SIB Transmission Flow

 

Overall MIB / SIB transmission and relationships among SIBs is illustrated as below (38.331 - 5.2 System information)  

 

 

 

 

MIB/SIB Aquisition Process

 

MIB / SIB acquisition process would vary depending on cases. I will describe the overall MIB/SIB acquisition process with various cases.

 

 

< Case 1 : Upon Power On and No Stored SIB in UE, No-OnDemand SI indication >

    i) Power On

    ii) Search Cell and Decode MIB

    iii) Store the decoded MIB

    iv) Check if CellBarred = barred, stop there and if not, move to next step.

    v) Using the parameters in MIB, try decoding SIB1.

    vi) [if SIB1 decoding is successful] store the infromation and then move to next step.

    vii) [assuming that SIB1 indicate No On-Demand SI] Decode Other SIBs (SI)

 

 

< Case 2 : Upon Power On and No Stored SIB in UE, OnDemand SI indication >

    i) Power On

    ii) Search Cell and Decode MIB

    iii) Store the decoded MIB

    iv) Check if CellBarred = barred, stop there and if not, move to next step.

    v) Using the parameters in MIB, try decoding SIB1.

    vi) [if SIB1 decoding is successful] store the infromation and then move to next step.

    vii) [assuming that SIB1 indicate On-Demand SI] Check the RRC Status (NOTE : Based on 38.331-5.2.2.3.3]

      a) if RRC Status is in RRC_IDLE or RRC_INACTIVE

      • Trigger lower layer to initiate preamble transmission procedure
      • Aquire the requiested SI messages when Acknowledgement for SI request is received

      b) if RRC Status is in RRC_CONNECTED

      • [Process is not defined yet.]

 

 

 

MasterInformationBlock

 

 

Followings are the overall characteristics of MIB (MasterInformationBlock)

  • Transmitted over BCH / PBCH
  • Transmitted with the periodicity of 80 ms and within this 80 ms repeatative transmission happens
  • Includes the parameters that are required to decode SIB1 (SystemInformationType1)

 

  

MIB ::= SEQUENCE {

    systemFrameNumber                   BIT STRING (SIZE (6)),

    subCarrierSpacingCommon             ENUMERATED {scs15or60, scs30or120},

    ssb-SubcarrierOffset                INTEGER (0..15),

    dmrs-TypeA-Position                 ENUMERATED {pos2, pos3},

    pdcch-ConfigSIB1                    INTEGER (0..255),

    cellBarred                          ENUMERATED {barred, notBarred},

    intraFreqReselection                ENUMERATED {allowed, notAllowed},

    spare                               BIT STRING (SIZE (1))

}

 

 

subCarrierSpacingCommon : Indicates the Subcarrier spacing for SIB1, Msg.2/4 for initial access and SI-messages. Values 15 and 30 kHz are applicable for carrier frequencies < 6GHz; Values 60 and 120 kHz are applicable for carrier frequencies > 6GHz

 

ssb-subcarrierOffset : Indicates the frequency domain offset between SSB and the overall resource block grid in number of subcarriers.

 

dmrs-TypeA-Position : Indicates Position of (first) DL DM-RS.

 

pdcchConfigSIB1: Determines a bandwidth for PDCCH/SIB, a common ControlResourceSet (CORESET), a common search space and necessary PDCCH parameters. This corresponds to RMSI-PDCCH-Config.

 

 

 

SystemInformationBlockType1

 

 

Followings are the overall characteristics of SIB1 (SystemInformationBlockType1)

  • Transmitted over DL-SCH
  • Transmitted with the periodicity of [X] ms and within this [X] ms repeatative transmission happens
  • Includes information regarding the availability and scheduling (e.g. periodcity, SI-window size) of other SIB
  • Indicates whether they (i.e. other SIBs) are provided via periodic broadcast basis or only on-demand basis
  • (If other SIBs are provided on-demand then SIB1) Includes information for the UE to perform SI request   

 

 

SIB1 ::= SEQUENCE {

    frequencyOffsetSSB              ENUMERATED {khz-5, khz5}    OPTIONAL,   -- Need R

    ssb-PositionsInBurst            SEQUENCE {

        inOneGroup                          BIT STRING (SIZE (8)),

        groupPresence                       BIT STRING (SIZE (8))    OPTIONAL

                                                                     -- Cond above6GHzOnly

    },

    ssb-PeriodicityServingCell          ENUMERATED {ms5, ms10, ms20, ms40, ms80, ms160,

                                                    spare1, spare2},

    ss-PBCH-BlockPower                  INTEGER (-60..50),

 

    uplinkConfigCommon                  UplinkConfigCommon         OPTIONAL,

    supplementaryUplink                 SEQUENCE {

        uplinkConfigCommon              UplinkConfigCommon         OPTIONAL

    }             OPTIONAL, -- Cond SUL

 

    tdd-UL-DL-Configuration             TDD-UL-DL-ConfigCommon    OPTIONAL, -- Cond TDD

    tdd-UL-DL-configurationCommon2      TDD-UL-DL-ConfigCommon    OPTIONAL, -- Cond TDD

    pdcch-ConfigCommon                  PDCCH-ConfigCommon        OPTIONAL,

    pucch-ConfigCommon                  PUCCH-ConfigCommon        OPTIONAL,

    lateNonCriticalExtension            OCTET STRING          OPTIONAL,

    nonCriticalExtension               SEQUENCE{}                                                              OPTIONAL

}

 

 

PDCCH-ConfigCommon ::=                  SEQUENCE {

    commonControlResourcesSets      SEQUENCE (SIZE(1..2)) OF ControlResourceSet     OPTIONAL,

    commonSearchSpaces              SEQUENCE (SIZE(1..4)) OF SearchSpace            OPTIONAL, 

    searchSpaceSIB1                         SearchSpaceId             OPTIONAL, 

    searchSpaceOtherSystemInformation       SearchSpaceId             OPTIONAL,  

    pagingSearchSpace                       SearchSpaceId             OPTIONAL,  

    ra-ControlResourceSet                   ControlResourceSetId      OPTIONAL,   

    ra-SearchSpace                          SearchSpaceId             OPTIONAL,

    ...

 

}

 

commonControlResourcesSets : A list of common control resource sets. Only CORESETs with ControlResourceSetId = 0 or 1 are allowed. The CORESET#0 corresponds to the CORESET configured in MIB (see pdcch-ConfigSIB1) and is used to provide that information to the UE by dedicated signalling during handover and (P)SCell addition. The CORESET#1 may be configured an used for RAR

 

commonSearchSpaces :  A list of additional common search spaces

 

searchSpaceSIB1 : ID of the search space for SIB1 message. Corresponds to L1 parameter 'rmsi-SearchSpace'

 

searchSpaceOtherSystemInformation : ID of the Search space for other system information, i.e., SIB2 and beyond. Corresponds to L1 parameter 'osi-SearchSpace'. If the field is absent, the monitoring occasions are derived as described in PDCCH Type 0 Common Search Space page.

 

pagingSearchSpace : ID of the Search space for paging. Corresponds to L1 parameter 'paging-SearchSpace'. If the field is absent, the monitoring occasions are derived as described in PDCCH Type 0 Common Search Space page.

 

ra-ControlResourceSet : CORESET configured for random access. When the field is absent the UE uses the CORESET according to pdcch-ConfigSIB1 which is associated with ControlResourceSetId = 0. Corresponds to L1 parameter 'rach-coreset-configuration'

 

ra-SearchSpace : ID of the Search space for random access procedure. Corresponds to L1 parameter 'ra-SearchSpace'.  If the field is absent, the monitoring occasions are derived as described in PDCCH Type 0 Common Search Space page.

 

 

 

UplinkConfigCommon ::=      SEQUENCE {

    frequencyInfoUL             FrequencyInfoUL         OPTIONAL,

    initialUplinkBWP            BWP-UplinkCommon        OPTIONAL  

}

 

 

FrequencyInfoUL ::=                 SEQUENCE {

    frequencyBandList                   MultiFrequencyBandListNR        OPTIONAL,   

    absoluteFrequencyPointA             ARFCN-ValueNR                   OPTIONAL,   

    scs-SpecificCarriers                SEQUENCE (SIZE (1..maxSCSs)) OF SCS-SpecificCarrier,

    additionalSpectrumEmission          AdditionalSpectrumEmission      OPTIONAL,   

    p-Max                               P-Max                           OPTIONAL,   

    frequencyShift7p5khz                ENUMERATED {true}               OPTIONAL,   

    ...

}

 

 

BWP-UplinkCommon ::=                SEQUENCE {

    genericParameters                   BWP,

    rach-ConfigCommon                   SetupRelease { RACH-ConfigCommon }      OPTIONAL,   

    pusch-ConfigCommon                  SetupRelease { PUSCH-ConfigCommon }     OPTIONAL,

    pucch-ConfigCommon                  SetupRelease { PUCCH-ConfigCommon }     OPTIONAL,

    ...

}

 

 

RACH-ConfigCommon ::=  SEQUENCE {

    rach-ConfigGeneric              RACH-ConfigGeneric,

    totalNumberOfRA-Preambles       INTEGER (1..63)             OPTIONAL,   -- Need S

    ssb-perRACH-OccasionAndCB-PreamblesPerSSB   CHOICE {

        oneEighth  ENUMERATED {n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},

        oneFourth  ENUMERATED {n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},

        oneHalf    ENUMERATED {n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},

        one        ENUMERATED {n4,n8,n12,n16,n20,n24,n28,n32,n36,n40,n44,n48,n52,n56,n60,n64},

        two        ENUMERATED {n4,n8,n12,n16,n20,n24,n28,n32},

        four       INTEGER (1..16),

        eight      INTEGER (1..8),

        sixteen    INTEGER (1..4)

    }   OPTIONAL,   -- Need M

 

    groupBconfigured      SEQUENCE {

        ra-Msg3SizeGroupA      ENUMERATED {b56, b144, b208, b256, b282, b480, b640, b800, b1000,

                                          spare7, spare6, spare5, spare4, spare3, spare2, spare1},

        messagePowerOffsetGroupB   ENUMERATED { minusinfinity, dB0, dB5, dB8, dB10, dB12,

                                                dB15, dB18},

        numberOfRA-PreamblesGroupA          INTEGER (1..64)

    }   OPTIONAL,   -- Need R

 

    ra-ContentionResolutionTimer    ENUMERATED { sf8, sf16, sf24, sf32, sf40, sf48, sf56, sf64},

    rsrp-ThresholdSSB                       RSRP-Range          OPTIONAL,   -- Need R

    rsrp-ThresholdSSB-SUL                   RSRP-Range          OPTIONAL,   -- Need R

    prach-RootSequenceIndex                 CHOICE {

        l839                                    INTEGER (0..837),

        l139                                    INTEGER (0..137)

    },

    msg1-SubcarrierSpacing   SubcarrierSpacing,

    restrictedSetConfig      ENUMERATED {unrestrictedSet, restrictedSetTypeA, restrictedSetTypeB},

    msg3-transformPrecoding  ENUMERATED {enabled} OPTIONAL,  -- Need R

    ...

}

 

 

RACH-ConfigGeneric ::=          SEQUENCE {

    prach-ConfigurationIndex         INTEGER (0..255),

    msg1-FDM                         ENUMERATED {one, two, four, eight},

    msg1-FrequencyStart              INTEGER (0..maxNrofPhysicalResourceBlocks-1),

    zeroCorrelationZoneConfig        INTEGER(0..15),

    preambleReceivedTargetPower      INTEGER (-200..-74),

    preambleTransMax                 ENUMERATED {n3,n4,n5,n6,n7,n8,n10,n20,n50,n100,n200},

    powerRampingStep                 ENUMERATED {dB0, dB2, dB4, dB6},

    ra-ResponseWindow                ENUMERATED {sl1, sl2, sl4, sl8, sl10, sl20, sl40, sl80}

}

 

 

 

Other SIBs (Periodic SIBs)

 

 

Followings are the overall characteristics of other SIBs (i.e, SIBs other than SIB1) that are transmitted by periodic broadcast

  • Transmitted over DL-SCH
  • Transmitted within periodically occurring time-domain window called SI-Window

 

 

 

Reference

 

[1]