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Analysis of RAN procedures for MBS Multicast Inactive

Acquiring PLMN and RAN Information
Obtain MIB
Obtain SIB1 (points to SIB24)
SIB24 contains configuration of MCCH
Demodulation of MCCH (PDSCH) via PDCCH (with MCCH-RNTI = FFFD)
MCCH contains MBSMulticastConfiguration
Obtain configuration of MTCH within MBSMulticastConfiguration
Demodulation of MTCH (PDSCH) with G-RNTI

Acquiring PLMN and RAN Information

For information on the MBS Broadcast Pre-Configuration Management Object (MO) refer to 3GPP TS 24.575.

A UE can support MBS to deliver content from a single source entity to users in a multicast group (MBS multicast communication), as defined in 3GPP TS 23.247. If the UE is pre-configured with information related to services using MBS, the UE can discover and receive data for services by using the provisioned configuration. The UE may support pre-configuration of information for services using MBS, which contains a list of PLMNs. for each PLMN, the following information is included:

PLMN ID of the PLMN for which the configuration applies;
default DNN and S-NSSAI pair for PDU sessions that can be used to join MBS multicast sessions (as specified in 3GPP TS 24.501) for which no other information is available.

Obtention of MIB/SIB signaling

For definitions refer to 3GPP TS 38.331 Clause 6.2.2

SIB 24 - Acquisition MCCH/MTCH for MBS multicast reception in RRC_INACTIVE

SIB24 contains the information required to acquire the multicast MCCH/MTCH configuration for MBS multicast reception in RRC_INACTIVE.

-- ASN1START 
-- TAG-SIB24-START 
SIB24-r18 ::= SEQUENCE { 
 multicastMCCH-Config-r18 MCCH-Config-r17 OPTIONAL, -- Need S 
 cfr-ConfigMCCH-MTCH-r18 CFR-ConfigMCCH-MTCH-r17 OPTIONAL, -- Need S 
 lateNonCriticalExtension OCTET STRING OPTIONAL, 
 ... 
} 
-- TAG-SIB24-STOP 
-- ASN1STOP

RRC - MulticastMCCH-Message

-- ASN1START 
-- TAG-MULTICASTMCCH-MESSAGE-START 
MulticastMCCH-Message-r18 ::= SEQUENCE { 
 message MulticastMCCH-MessageType-r18 
} 
MulticastMCCH-MessageType-r18 ::= CHOICE { 
 c1 CHOICE { 
 mbsMulticastConfiguration-r18 MBSMulticastConfiguration-r18, 
 spare1 NULL
 }, 
 messageClassExtension SEQUENCE {} 
} 
-- TAG-MULTICASTMCCH-MESSAGE-STOP 
-- ASN1STOP 

-- ASN1START 
-- TAG-MBSMULTICASTCONFIGURATION-START 
MBSMulticastConfiguration-r18 ::= SEQUENCE { 
 criticalExtensions CHOICE { 
 mbsMulticastConfiguration-r18 MBSMulticastConfiguration-r18-IEs, 
 criticalExtensionsFuture SEQUENCE {} 
 } 
} 
MBSMulticastConfiguration-r18-IEs ::= SEQUENCE { 
 mbs-SessionInfoListMulticast-r18 MBS-SessionInfoListMulticast-r18 OPTIONAL, -- Need R 
 mbs-NeighbourCellList-r18 MBS-NeighbourCellList-r17 OPTIONAL, -- Need S 
 drx-ConfigPTM-List-r18 SEQUENCE (SIZE (1..maxNrofDRX-ConfigPTM-r17)) OF DRX-ConfigPTM-r17 OPTIONAL, -- Need R 
 pdsch-ConfigMTCH-r18 PDSCH-ConfigBroadcast-r17 OPTIONAL, -- Need S 
 mtch-SSB-MappingWindowList-r18 MTCH-SSB-MappingWindowList-r17 OPTIONAL, -- Need R 
 thresholdMBS-List-r18 SEQUENCE (SIZE (1..maxNrofThresholdMBS-r18)) OF ThresholdMBS-r18 OPTIONAL, -- Need R 
 lateNonCriticalExtension OCTET STRING OPTIONAL, 
 nonCriticalExtension SEQUENCE {} OPTIONAL
} 
ThresholdMBS-r18 ::= SEQUENCE { 
 rsrp-r18 RSRP-Range OPTIONAL, -- Need R 
 rsrq-r18 RSRQ-Range OPTIONAL -- Need R 
} 
-- TAG-MBSMULTICASTCONFIGURATION-STOP 
-- ASN1STOP 

TO BE REVIEWED

Control Plane Procedures

RRC: MBS Multicast

Acquisition of MBS Broadcast information via MCCH

Procedures in 3GPP TS 38.331 Clause 5.10
- Acquisition of MCCH: via SIB20, included in SIBTypeInfo in SIB1. MCCH transmission indicated via PDCCH (MCCH-RNTI)
- Configuration information in MCCH via MBSBroadcastConfiguration
SIB20 in 3GPP TS 38.331 Clause 6.2.2: SIB20 contains the information required to acquire the MCCH/MTCH configuration for MBS broadcast. Go to ASN.1.
MBSBroadcastConfiguration in 3GPP TS 38.331 Clause 6.2.2: The MBSBroadcastConfiguration message contains the control information applicable for MBS broadcast services transmitted via broadcast MRB. Go to ASN.1.
MBS information elements in 3GPP TS 38.331 Clause 6.3.6

Broadcast MRB configuration

Procedures in 3GPP TS 38.331 Clause 5.9.3
Broadcast MRB establishment in 3GPP TS 38.331 Clause 5.9.3.3
- Upon a broadcast MRB establishment, the UE shall:
  - establish a PDCP entity and an RLC entity in accordance with MRB-InfoBroadcast for this broadcast MRB included in the MBSBroadcastConfiguration message and the configuration specified in 3GPP TS 38.331 Clause 9.1.1.7;
  - configure the MAC layer in accordance with the mtch-SchedulingInfo (if included);
  - configure the physical layer in accordance with the mbs-SessionInfoList, searchSpaceMTCH, and pdsch-ConfigMTCH, applicable for the broadcast MRB;
  - receive DL-SCH on the cell where the MBSBroadcastConfiguration message was received for the established broadcast MRB using g-RNTI and mtch-SchedulingInfo (if included) in this message for this MBS broadcast service;
  - if an SDAP entity with the received mbs-SessionId does not exist:
    - establish an SDAP entity as specified in 3GPP TS 37.324 clause 5.1.1.
    - indicate the establishment of the user plane resources for the mbs-SessionId to upper layers.
Broadcast MRB release in 3GPP TS 38.331 Clause 5.9.3.4
- Upon broadcast MRB release for MBS broadcast service, the UE shall:
  - release the PDCP entity, RLC entity as well as the related MAC and physical layer configuration;
  - if the SDAP entity associated with the corresponding mbs-SessionId has no associated MRB:
    - release the SDAP entity, as specified in 3GPP TS 37.324 clause 5.1.2;
    - indicate the release of the user plane resources for the mbs-SessionId to upper layers.

PDCP: MBS Broadcast

Procedures in 3GPP TS 38.323 Clause 5
- A PDCP entity associated with MRB can be configured by upper layers 3GPP TS 38.331 to use header compression.
- Protocol data units, formats, and parameters in 3GPP TS 38.323 Clause 6
- State variables, constants, and timers in 3GPP TS 38.323 Clause 7

RLC: MBS Broadcast

Procedures in 3GPP TS 38.322
- UM RLC entity in 3GPP TS 38.322 Clause 4.2.1.2
- Variables, constants, and timers in 3GPP TS 38.322 Clause 7

MAC: MBS Broadcast

MCCH within DL-SCH in 3GPP TS 38.321 Clause 5.3
Value of LCID for MBS broadcast on DL-SCH in 3GPP TS 38.321 Table 6.2.1-1c
RNTI values MCCH-RNTI = FFFD in 3GPP TS 38.321 Table 7.1-1

User Plane Procedures

SDAP: MBS Broadcast

SDAP architecture in 3GPP TS 37.324 Clause 4.2
- The SDAP sublayer is configured for MRBs by RRC. The SDAP sublayer maps MBS QoS flows to MRBs (mapping between an MBS QoS flow and an MRB for DL).
Data transfer DL in 3GPP TS 37.324 Clause 5.2.2
- At the reception of an SDAP data PDU from lower layers for a QoS flow, the receiving SDAP entity shall:
  - if this SDAP data PDU is received from an MRB, retrieve the SDAP SDU from the DL SDAP data PDU as specified in 3GPP TS 37.324 Clause 6.2.2.1
Data PDU without SDAP header in 3GPP TS 37.324 Clause 6.2.2.1

PDCP: MBS Broadcast

Other RRC Messagges

-- ASN1START
-- TAG-CFR-CONFIGMCCH-MTCH-START

CFR-ConfigMCCH-MTCH-r17 ::= SEQUENCE {
    locationAndBandwidthBroadcast-r17          LocationAndBandwidthBroadcast-r17  OPTIONAL,  -- Need S
    pdsch-ConfigMCCH-r17                       PDSCH-ConfigBroadcast-r17          OPTIONAL,  -- Need S
    commonControlResourceSetExt-r17            ControlResourceSet                 OPTIONAL   -- Cond NotSIB1CommonControlResource
}

LocationAndBandwidthBroadcast-r17 ::= CHOICE {
    sameAsSib1ConfiguredLocationAndBW          NULL,
    locationAndBandwidth                       INTEGER (0..37949)
}

-- TAG-CFR-CONFIGMCCH-MTCH-STOP
-- ASN1STOP

-- ASN1START
-- TAG-PDSCH-CONFIGBROADCAST-START

PDSCH-ConfigBroadcast-r17 ::= SEQUENCE {
    pdschConfigList-r17                    SEQUENCE (SIZE (1..maxNrofPDSCH-ConfigPTM-r17) ) OF PDSCH-ConfigPTM-r17,
    pdsch-TimeDomainAllocationList-r17     PDSCH-TimeDomainResourceAllocationList-r16                          OPTIONAL,   -- Need R
    rateMatchPatternToAddModList-r17       SEQUENCE (SIZE (1..maxNrofRateMatchPatterns)) OF RateMatchPattern   OPTIONAL,   -- Need R
    lte-CRS-ToMatchAround-r17              RateMatchPatternLTE-CRS                                             OPTIONAL,   -- Need R
    mcs-Table-r17                          ENUMERATED {qam256, qam64LowSE}                                     OPTIONAL,   -- Need S
    xOverhead-r17                          ENUMERATED {xOh6, xOh12, xOh18}                                     OPTIONAL    -- Need S
}

PDSCH-ConfigPTM-r17 ::= SEQUENCE {
    dataScramblingIdentityPDSCH-r17        INTEGER (0..1023)         OPTIONAL,   -- Need S
    dmrs-ScramblingID0-r17                 INTEGER (0..65535)        OPTIONAL,   -- Need S
    pdsch-AggregationFactor-r17            ENUMERATED {n2, n4, n8}   OPTIONAL    -- Need S
}

-- TAG-PDSCH-CONFIGBROADCAST-STOP
-- ASN1STOP

MBSBroadcastConfiguration

-- ASN1START
-- TAG-MBSBROADCASTCONFIGURATION-START

MBSBroadcastConfiguration-r17 ::= SEQUENCE {
    criticalExtensions                CHOICE {
        mbsBroadcastConfiguration-r17     MBSBroadcastConfiguration-r17-IEs,
        criticalExtensionsFuture          SEQUENCE {}
    }
}

MBSBroadcastConfiguration-r17-IEs ::= SEQUENCE {
    mbs-SessionInfoList-r17               MBS-SessionInfoList-r17                                              OPTIONAL,   -- Need R
    mbs-NeighbourCellList-r17             MBS-NeighbourCellList-r17                                            OPTIONAL,   -- Need S
    drx-ConfigPTM-List-r17                SEQUENCE (SIZE (1..maxNrofDRX-ConfigPTM-r17)) OF DRX-ConfigPTM-r17   OPTIONAL,   -- Need R
    pdsch-ConfigMTCH-r17                  PDSCH-ConfigBroadcast-r17                                            OPTIONAL,   -- Need S
    mtch-SSB-MappingWindowList-r17        MTCH-SSB-MappingWindowList-r17                                       OPTIONAL,   -- Need R
    lateNonCriticalExtension              OCTET STRING                                                         OPTIONAL,
    nonCriticalExtension                  SEQUENCE {}                                                          OPTIONAL
}

-- TAG-MBSBROADCASTCONFIGURATION-STOP
-- ASN1STOP

-- ASN1START
-- TAG-MBS-SESSIONINFOLIST-START

MBS-SessionInfoList-r17 ::=      SEQUENCE (SIZE (1..maxNrofMBS-Session-r17)) OF MBS-SessionInfo-r17

MBS-SessionInfo-r17 ::=          SEQUENCE {
    mbs-SessionId-r17                TMGI-r17,
    g-RNTI-r17                       RNTI-Value,
    mrb-ListBroadcast-r17            MRB-ListBroadcast-r17,
    mtch-SchedulingInfo-r17          DRX-ConfigPTM-Index-r17                      OPTIONAL, -- Need S
    mtch-NeighbourCell-r17           BIT STRING (SIZE(maxNeighCellMBS-r17))       OPTIONAL, -- Need S
    pdsch-ConfigIndex-r17            PDSCH-ConfigIndex-r17                        OPTIONAL, -- Need S
    mtch-SSB-MappingWindowIndex-r17  MTCH-SSB-MappingWindowIndex-r17              OPTIONAL  -- Cond MTCH-Mapping
}

DRX-ConfigPTM-Index-r17 ::=          INTEGER (0..maxNrofDRX-ConfigPTM-1-r17)

PDSCH-ConfigIndex-r17  ::=           INTEGER (0..maxNrofPDSCH-ConfigPTM-1-r17)

MTCH-SSB-MappingWindowIndex-r17  ::= INTEGER (0..maxNrofMTCH-SSB-MappingWindow-1-r17)

MRB-ListBroadcast-r17 ::=            SEQUENCE (SIZE (1..maxNrofMRB-Broadcast-r17)) OF MRB-InfoBroadcast-r17

MRB-InfoBroadcast-r17 ::=            SEQUENCE {
    pdcp-Config-r17                      MRB-PDCP-ConfigBroadcast-r17,
    rlc-Config-r17                       MRB-RLC-ConfigBroadcast-r17,
    ...
}

MRB-PDCP-ConfigBroadcast-r17 ::=     SEQUENCE {
    pdcp-SN-SizeDL-r17                   ENUMERATED {len12bits}                   OPTIONAL, -- Need S
    headerCompression-r17                CHOICE {
        notUsed                              NULL,
        rohc                                 SEQUENCE {
            maxCID-r17                           INTEGER (1..16)               DEFAULT 15,
            profiles-r17                         SEQUENCE {
                profile0x0000-r17                    BOOLEAN,
                profile0x0001-r17                    BOOLEAN,
                profile0x0002-r17                    BOOLEAN
           }
        }
    },
    t-Reordering-r17                     ENUMERATED {ms1, ms10, ms40, ms160, ms500, ms1000, ms1250, ms2750}    OPTIONAL -- Need S
}

MRB-RLC-ConfigBroadcast-r17 ::=      SEQUENCE {
    logicalChannelIdentity-r17           LogicalChannelIdentity,
    sn-FieldLength-r17                   ENUMERATED {size6}                       OPTIONAL, -- Need S
    t-Reassembly-r17                     T-Reassembly                             OPTIONAL  -- Need S
}

-- TAG-MBS-SESSIONINFOLIST-STOP
-- ASN1STOP