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Abrupt nature of SDCCH blocking in n/w

Viewing 15 posts - 1 through 15 (of 16 total)
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  • #59818 Reply
    pridey
    Guest

    Hi,

    we r facing very abnormal nature in nokia network regarding SDCCH blocking.

    Avg %SDCCH blk during N/w BH never goes below 1% without TRX sof reset everyday before BH.

    Around 10/15 cells giving a tot of 4 lacks sdblocks out of 1 cr sd attempts, each cell around 1 lacs sdblk sometimes. But the fact is , those bad cells never repeat next day, but some other 10/15 cells do the same. hence the typical nature “who is when” is not predictable , not even before start of busy hour.

    Due to inconsistancy of the bad performing cells , we cant guess any s/w or h/w issue.

    Although , enough sdcch augmentation done after weekly sd dimensioning, sdcch is in excess in the n/w. So lack of sd is not an issue.

    What could be the issue/how to handle it, just running out of ideas.

    keenly looking for suggestions.

    #59819 Reply
    Bijoy
    Guest

    Hi Pridey
    1.Are you guys using 16 KBPS LAPD links?
    2.Is there Signalling overload in BSC’s?

    Br\\
    Bijoy

    #59820 Reply
    pridey
    Guest

    Thanks for your reply.

    1.yes. But now a days we r upgrading to 32 kbps LAPD for BCCH TRX only and for entire n/w.

    2. By Signalling overload in BSC’s, do u mean Abis TRXSIG load ? If not, then pls explain once more.

    If we change MAXRET from 4 to 2 and also reduce DMAX, will it help?
    what are the parameters are directly related to sdblock?

    #59821 Reply
    Bijoy
    Guest

    Hi Pridey
    1.16 KBPS LAPD Links can support upto 12 SDCCH channels & a maximum of 18 channels at any time.So,if in a particular TRX if you are using 2 SDCCH & rest are TCHD,there is every possibility of TCH/SDCCH blocking & drop.
    In non-BCCH TRX also,take care of this fact & keep only 1 SDCCH & at max 3 TCHD.
    2.Check with the command “ZOLT;” in BSC,if TX/RX Erlang >0.2 in BH,need to add SL(if < 16 SL) or augment(64 KBPS to 128 KBPS). Yes,reducing MAXRET will help. Reducing DMAX is a cynical way of reducing SDCCH Blocking Br\\ Bijoy

    #59822 Reply
    pridey
    Guest

    Thanks a lot.

    In nonBCCH TRX if we keep 1 sdcch & 3 TCHD, then what will be rest 4 timeslots? provided LAPD is 16 kbps.

    #59823 Reply
    raman
    Guest

    Hi Bijoy Sir ,
    you are saying that “in BSC,if TX/RX Erlang >0.2 in BH,need to add SL(if < 16 SL) or augment(64 KBPS to 128 KBPS)." ...... But our switch team is saying that on LSL if on any SL greater than 0.7 eRL. than only they can go for C7 augmentation is there any doc ...for support for that or calculation in support for that ..... plz tell

    #59824 Reply
    Bijoy
    Guest

    Pridey
    Remaining RTSL will be TCHF
    Raman
    This is a NOKIA system recommendation for 64 KBPS SL with 25 merl/sub.Refer NED for details.

    Br\\
    Bijoy

    #59825 Reply
    raman
    Guest

    Bijoy Sir,
    I am in Eric/// system agreed concept would be same in that system also plz give any doc regarding E./// …
    plz give NED doc any help would be highly helpful for network ….plz mail to
    job.raman@gmail.com

    #59826 Reply
    Bijoy
    Guest

    Hi Raman.
    In ericsson,its a bit complex
    Let me know if you are talking about TCAP load or TRH Load?
    Can you provide me the sample data.

    #59827 Reply
    Bijoy
    Guest

    Raman
    In Ericsson too
    The maximum traffic load per 64 kbit/s link is:
    0.3 Erlang under normal conditions
    0.6 Erlang under failure situations
    and for a 56 kbit/s link or HSL the maximum traffic load is:
    0.4 Erlang under normal conditions
    0.8 Erlang under failure situations
    Please go through “BSC/TRC Dimensioning” chapter in Alex for details.

    Br\\
    Bijoy

    #59828 Reply
    raman
    Guest

    i am not able to find plz can you give specifically exact where it is written ……thank a lot ///

    #59829 Reply
    pridey
    Guest

    Hi Bijay, thanks a lott.

    We hv 1800 cabex also, so “1 sdcch per 3 tchd max” rule should count 1800 trx aslongwith 900 trx or applicable for 900 only.

    point 2 is: what are the parameters to ‘fetch’ calls from HR to FR.

    lastly,
    what % of total call should be HR out of total voice traffic, to reduce sd blocking at minimum.

    and , does “total HR traffic” = “Non AMR HR + “AMR HR”

    #59830 Reply
    Bijoy
    Guest

    Pridey
    If you are using Common BCCH with 1800 as non-BCCH band,you are not defining SDCCH on 1800 TRX,do you??
    In that case all RTSL’s can be configured as TCHD.

    Well,if you are using Dual band N/w(BCCH in both 1800 & 900),the same rule of 900 applies for 1800 too.
    Point2.

    FRL & FRU is the most primitive one to do so.

    Lastly,your HR% should be 20-30% ideally.

    Br\\
    Bijoy

    #59831 Reply
    Bijoy
    Guest

    Yes Pridey
    “Total HR traffic” = “Non AMR HR” + “AMR HR”

    Raman
    In alex,there is a chapter called”BSC/TRC domensioning”,you can find it there.

    Br\\
    Bijoy

    #59832 Reply
    pridey
    Guest

    Hi Bijay,

    Thanks you very much. Its really works for me.

    Just want to clarify the following.

    we hv common bcch for 900 & 1800
    “In that case all RTSL’s can be configured as TCHD.
    “. So it means all 1800 rtsl are tchd.

    An expl: In a segment w, say both 900& 1800 exist, with common BCCH in 900. Also 900 has 3 TRX & 1800 has 2 TRX in the same segment under common BCCH.
    All TRX lapd are 16 kbps.
    So ,

    TRX 1 in 900: MBCCH, SDCCB, TCHD,TCHD,TCHD,TCHF,TCHF,TCHF.

    TRX 2in 900: SDCCH,TCHD,TCHD,TCHD,TCHF,TCHF,TCHF,TCHF.

    TRX 3 in 900: SDCCH,TCHD,TCHD,TCHD,TCHF,TCHF,TCHF,TCHF.

    TRX 4 in 1800: all TCHD
    TRX 5 in 1800: all TCHD

    Does such a config do well with % sdcch blocking? (I hv kept “1 sdcch per 3 tchd max” rule valid)

    OR all the 1800 RTSL should be TCHF?

    Is there any other parameter other than FRU,FRL?

    What are the parameters values to set for minimum % SDCCH Blocking?
    MAXRET to 02 from 04? any other?

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