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CS IRAT HO

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  • 10th September 2012 at 11:02 #68557
    anh
    Guest

    Pls help,
    Drivetest log shows many cases that MS failed to HO from 3G to 2G although 2G Rxlev is very strong.
    2G’s KPIs(CSSR~99.3%, CDR~0.81%, HOSR~99.1%)are all good.
    From log file, the HO failed if after DL-HandoverFromUTRANCommand-GSM msg, MS sends Undecoded SACCH msg.

    What can be the root cause for this problem? How to improve CS IRAT HO?

    Many thanks,

    10th September 2012 at 18:46 #68558
    pix
    Guest

    hi,

    Undecoded SACCH means the MS did not succeed in decoding the DL SACCH msg.

    After the “HO Command from UTRAN” the MS should send HO ACCESS in UL to the GSM channel. Do you see those ? Right after that, you should expect a handshake in the layer 2 (SABM, UA)

    Does the info in the HO COMMAND FROM UTRAN is correct ? Is the 2G frequency (ARFCN) provided in the msg the good one ?

    If HOSR is 99%, then there is no reason that your MS is not able to succesfully go to the 2G cell during drive test. Can you trace your DT mobile call on your OMCR 3G and OMCR 2G ? Then you will have aclear picture of what’s going on.

    regards
    pix

    11th September 2012 at 07:52 #68559
    anh
    Guest

    Hi pix,

    I don’t see the Handover Access in UL in both successful and failed cases.
    I post here the failure case.
    Pls have a look and advice. Thanks,

    263480 19:51:07.820 L3 DL RR Handover Command DL-DCCH HandoverFromUTRANCommand-GSM
    Information Elements:

    Altitude (m): 65534
    Heading (deg): 228
    Speed (km/h): 27
    Speed (mph): 17
    —
    Message:

    Uu_RRC: DL_DCCH_Message
    – . .integrityCheckInf
    – . . .messageAuthenticationCode: 1461609585
    – . . .rrc-MessageSequenceNumber: 7
    – . .message:- handoverFromUTRANCommand-GSM:- r3
    – . . . . .handoverFromUTRANCommand-GSM-r3
    – . . . . . .rrc-TransactionIdentifier: 3
    – . . . . . .toHandoverRAB-Info
    – . . . . . . .rab-Identity:- gsm-MAP-RAB-Identity: 1
    – . . . . . . .cn-DomainIdentity: 0 ( cs_domain)
    – . . . . . . .nas-Synchronisation-Indicator: 6
    – . . . . . . .re-EstablishmentTimer: 0 ( useT314)
    – . . . . . .frequency-band: 0 ( dcs1800BandUsed)
    – . . . . . .gsm-message:- gsm-MessageList
    – . . . . . . . .gsm-Messages

    BCCH: 9 BSIC: 03(dec) 03(oct)
    Channel Type: TCH/F + FACCH/F and SACCH/F
    TimeSlot: 0 TrainingSeq: 3
    Hopping: No, ARFCN: 29
    HandoverRef: 28 OrderedPowerLevel: 5
    Channel Mode: Speech full rate or half rate version 2 (GSM EFR)
    —————————————————————————-
    263482 19:51:07.820 L3 DL RR Handover Command
    Information Elements:

    Altitude (m): 65534
    Heading (deg): 228
    Speed (km/h): 27
    Speed (mph): 17
    —
    Message:

    BCCH: 9 BSIC: 03(dec) 03(oct)
    Channel Type: TCH/F + FACCH/F and SACCH/F
    TimeSlot: 0 TrainingSeq: 3
    Hopping: No, ARFCN: 29
    HandoverRef: 28 OrderedPowerLevel: 5
    Channel Mode: Speech full rate or half rate version 2 (GSM EFR)
    —————————————————————————-
    263481 19:51:07.820 RRC Event Report
    263484 19:51:07.820 Tx Power Report
    —————————————————————————-
    263491 19:51:07.980 RR State Report
    Information Elements:

    Altitude (m): 65534
    Heading (deg): 228
    Speed (km/h): 27
    Speed (mph): 17
    —
    Message:
    RR State: Wait for physical information from BS
    …
    …
    —————————————————————————-
    263492 19:51:07.980 Undecoded SACCH Message
    Information Elements:

    Altitude (m): 65534
    Heading (deg): 228
    Speed (km/h): 27
    Speed (mph): 17
    —
    Message:
    —————————————————————————-
    263499 19:51:08.200 MPH Cell
    Information Elements:

    Altitude (m): 65534
    Heading (deg): 227
    Speed (km/h): 27
    Speed (mph): 17
    —
    Message:

    Cell CGI Description: empty
    —————————————————————————-
    263518 19:51:08.400 UL-DCCH HandoverFromUTRANFailure
    Information Elements:

    Altitude (m): 65534
    Heading (deg): 227
    Speed (km/h): 27
    Speed (mph): 17
    —
    Events:
    —————————————————————————-
    Handover From UTRAN Failure:
    —
    Message:

    Uu_RRC: UL_DCCH_Message
    – . .integrityCheckInfo
    – . . .messageAuthenticationCode: 2497688090
    – . . .rrc-MessageSequenceNumber: 9
    – . .message:- handoverFromUTRANFailure
    – . . . .rrc-TransactionIdentifier: 3
    – . . . .interRAT-HO-FailureCause:- physicalChannelFailure: null

    20th September 2012 at 02:15 #68560
    Ater
    Guest

    What vendor?

    depending on the vendor there are some counters that you can check to see where is the problem

    If you are not making IRAT at all you probably need to trace at core or RNC level and not at Uu

    other things to verify
    1-data mismach at rnc level of external gsm cells (bcch, lac, ect)
    2-data mismach at 3g msc level of outer gsm cell (if 2g and 3g are in diferents mscs)
    3-xudt activated in both MSCs (if 2g and 3g are in diferents mscs)
    4-in some vendors multi rab connections are not supported for irat

    20th September 2012 at 08:00 #68561
    anh
    Guest

    Thanks Ater,
    3G vendor: Huawei, 2G vendor: ALU, Motorola
    Item 1: Checked OK.
    Item 2: only external LAC at both MSC 3G and MSC 2G need declaring?
    Item 3,4: pls let me know more.
    BR,

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