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CMAS

 

In LTE, there are three main components getting involved in sending CMAS as follows.

    i) Paging : CMAS Notification.

    ii) SIB 12 : Message Format and Contents

 

Following is Paging, SIB12  showing the field (IEs) related to CMAS. (For the details of ETWS, refer to 3GPP TS23.828 and TS22.268 and TS 36.523 18.1 CMAS on LTE)

 

PCCH-Message ::= SEQUENCE

  +-message ::= CHOICE [c1]

    +-c1 ::= CHOICE [paging]

      +-paging ::= SEQUENCE [0001]

        +-pagingRecordList ::= SEQUENCE OF OPTIONAL:Omit

        +-systemInfoModification ::= ENUMERATED OPTIONAL:Omit

        +-etws-Indication ::= ENUMERATED OPTIONAL:Omit

        +-nonCriticalExtension ::= SEQUENCE [01] OPTIONAL:Exist

          +-lateNonCriticalExtension ::= OCTET STRING OPTIONAL:Omit

          +-nonCriticalExtension ::= SEQUENCE [10] OPTIONAL:Exist

            +-cmas-Indication-r9 ::= ENUMERATED [true] OPTIONAL:Exist

            +-nonCriticalExtension ::= SEQUENCE OPTIONAL:Omit

 

 

BCCH-DL-SCH-Message ::= SEQUENCE

  +-message ::= CHOICE [c1]

    +-c1 ::= CHOICE [systemInformation]

      +-systemInformation ::= SEQUENCE

        +-criticalExtensions ::= CHOICE [systemInformation-r8]

          +-systemInformation-r8 ::= SEQUENCE [0]

            +-sib-TypeAndInfo ::= SEQUENCE OF SIZE(1..maxSIB[32]) [1]

            | +- ::= CHOICE [sib12-v920]

            |   +-sib12-v920 ::= SEQUENCE [10]

            |     +-messageIdentifier-r9 ::= BIT STRING SIZE(16) [0001000100010010]

            |     +-serialNumber-r9 ::= BIT STRING SIZE(16) [0011000000000000]

            |     +-warningMessageSegmentType-r9 ::= ENUMERATED [lastSegment]

            |     +-warningMessageSegmentNumber-r9 ::= INTEGER (0..63) [0]

            |     +-warningMessageSegment-r9 ::= OCTET STRING SIZE(ALIGNED)

                                                  [01C576597E2EBBC7F950A8D168341A8D46A3D168341

                                                   A8D46A3D168341A8D46A3D168341A8D46A3D168341A

                                                   8D46A3D168341A8D46A3D168341A8D46A3D168341A8

                                                   D46A3D168341A8D46A3D168341A8D46A3D1000A]

            |     +-dataCodingScheme-r9 ::= OCTET STRING SIZE(1) [01] OPTIONAL:Exist

            |     +-lateNonCriticalExtension ::= OCTET STRING OPTIONAL:Omit

            |     +-EXTENSION ::= SEQUENCE

            +-nonCriticalExtension ::= SEQUENCE OPTIONAL:Omit

 

 

Example >

 

Step

Direction

Message

Comments

1

UE <-- NW

SIB1

Indicate SIB12 is scheduled

2

UE <-- NW

SIB12

Transmit CMAS message

3

UE <-- NW

Paging

CMAS indication is present

4

UE

 

Detect the Paging with CMAS Indication

5

UE

 

Decode SIB1 and find SIB12 is scheduled

6

UE

 

Decode SIB12

 

Step 1 : SIB 1

    BCCH-DL-SCH-Message

        message: c1 (0)

            c1: systemInformationBlockType1 (1)

                systemInformationBlockType1

                    cellAccessRelatedInfo

                        plmn-IdentityList: 1 item

                            Item 0

                                PLMN-IdentityInfo

                                    plmn-Identity

                                        mcc: 3 items

                                            Item 0

                                                MCC-MNC-Digit: 0

                                            Item 1

                                                MCC-MNC-Digit: 0

                                            Item 2

                                                MCC-MNC-Digit: 1

                                        mnc: 2 items

                                            Item 0

                                                MCC-MNC-Digit: 0

                                            Item 1

                                                MCC-MNC-Digit: 1

                                    cellReservedForOperatorUse: notReserved (1)

                        trackingAreaCode: 0000 [bit length 16, 0000 0000  0000 0000 decimal value 0]

                        cellIdentity: 00000000

                        cellBarred: notBarred (1)

                        intraFreqReselection: notAllowed (1)

                        .... ..0. csg-Indication: False

                    cellSelectionInfo

                        q-RxLevMin: -110dBm (-55)

                    p-Max: 23dBm

                    freqBandIndicator: 4

                    schedulingInfoList: 3 items

                        Item 0

                            SchedulingInfo

                                si-Periodicity: rf16 (1)

                                sib-MappingInfo: 0 items

                        Item 1

                            SchedulingInfo

                                si-Periodicity: rf32 (2)

                                sib-MappingInfo: 1 item

                                    Item 0

                                        SIB-Type: sibType3 (0)

                        Item 2

                            SchedulingInfo

                                si-Periodicity: rf32 (2)

                                sib-MappingInfo: 1 item

                                    Item 0

                                        SIB-Type: sibType12-v920 (9)

                    si-WindowLength: ms20 (5)

                    systemInfoValueTag: 0

                    nonCriticalExtension

                        nonCriticalExtension

                            ims-EmergencySupport-r9: true (0)

 

Step 2 : SIB 12

    BCCH-DL-SCH-Message

        message: c1 (0)

            c1: systemInformation (0)

                systemInformation

                    criticalExtensions: systemInformation-r8 (0)

                        systemInformation-r8

                            sib-TypeAndInfo: 1 item

                                Item 0

                                    sib-TypeAndInfo item: sib12-v920 (10)

                                        sib12-v920

                                            messageIdentifier-r9: CMAS Identifier for CMAS Presidential Level Alerts (4370)

                                            serialNumber-r9: 3000 [bit length 16, 0011 0000  0000 0000 decimal value 12288]

                                                00.. .... .... .... = Geographical Scope: Display mode immediate, cell wide (0)

                                                ..11 0000 0000 .... = Message Code: 768

                                                .... .... .... 0000 = Update Number: 0

                                            warningMessageSegmentType-r9: lastSegment (1)

                                            warningMessageSegmentNumber-r9: 0

                                            warningMessageSegment-r9: 0154747a0e4acf416137a8d82ecbcf65f7388...

                                            dataCodingScheme-r9: 01

                                                0000 .... = Coding Group: Coding Group 0

                                                                 (Language using the GSM 7 bit default alphabet) (0)

                                                .... 0001 = Language: English (1)

 

Step 3 : Paging

    PCCH-Message

        message: c1 (0)

            c1: paging (0)

                paging

                    nonCriticalExtension

                        nonCriticalExtension

                            cmas-Indication-r9: true (0)

                                [Expert Info (Warn/Sequence): Commercial Mobile Alert System Indication!]

                                    [Commercial Mobile Alert System Indication!]

                                    [Severity level: Warn]

                                    [Group: Sequence]