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High SD drop

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #51816

    Can anyone help me. Actyually there is high SD drop rate due to the reason OTHER (according to Ericsson applications).HW was checked,transmission was checked as well.What can cause SD drops?


    just assuming :
    expiry of the authentication/ciphering phase between HLR and MS
    lost messages on RSL link (Abis congested) or BSC board (processor congestion)
    faulty board in the BTS (called “SUM” card in alcatel)

    well, that’s all… i guess all other possibilities woul be counted in proper ericsson counters.



    We had the same situation. We checked everything, and everything seem working fine. Finally we replaced the dTRUs, and everything start working fine.



    Thanx for your comments.
    pix,if your first assumption is right (expire of a timer)how can i detect the very subcriber(s)(IMSI) that can cause SD drops assuming that SD drop rate is around 15-30 percents and as it is not 100 percents so there are some subcribers that increase SD drop rate,how to find them.

    Da Architect

    Hey Nick7!

    Hello there everyone!
    intresting points as always presented by pix.

    Nick i think your problem may be solved in a consistency check, perhaps it is missdefinition of the cells between bss and nss.
    On the other hand, it could be related to SCLD feature.

    What is the value of SCLDSC in your problematic cells?


    i’d go with MNoor solution first : try to reset or replace the dTRU. Most of the time, a really poor QoS is due to hardware issues.

    Nick7 : you can perform a A-interface trace, and collect the IMSI’s which fail. You can even do it manually, it should be quite obvious. However, you should favor other assumptions than this one… you might be more succesful with a hardware check. Yet, a A interface trace will always lead you to the root problem in the end.

    Da Architect : hello 🙂 what is the SCLD ?

    Da Architect

    SCLD: Sub Cell Load Distribution
    an intresting feature from Ericsson, with it you balance the load between UL and OL (outer and inner) by monitoring the idle timeslots capacity in each of the subcells.


    Thanx for your inputs.
    OL&UL feature is not used in my network.As for inconsistency,checked.It seems to me that if there could be inconsistency i would have much more SD drop rate.
    Pix,you mean A-bis interface.I will do that.


    da architect,

    okay, there is something like this in alcatel also, but with a fixed value of 50% inner / 50% outer load

    but i guess that SDCCH can only be defined in the outer zone, so why this feature would generate SDCCH drops ?

    Da Architect

    Hello Pix,

    would you kindly remind me of this smilira feature name in alacatel, which parameter do you mean. As for SCLD versus CNDROP, in my network we discovered that we can’t make SCLD prefer OL because of high cndrop generated, perhaps it conflict with another feature immediate assignment on tch. but mostly it is a weak point in ericsson, I contacted them lately, and still waiting for their reply. if their reply was logical, i will let you know ofcourse!


    Dears all
    please , I have in my network
    the paging success rate less than 70 % per LAC(Location Area Code)

    what I can do?
    please help me about this

    Thanks in advance


    da architect,

    great, thanks 🙂
    in alcatel : en_load_balance = enable –>
    if radio conditions allow it,
    and if there is traffic_load_inner < traffic_load_outer (traffic_load = busy_ts / defined_ts) 1) tch is allocated in inner zone (during call setup or incoming ho) 2) intrazone ho outer-->inner is trigerred

    Da Architect

    THX PIX!


    you may chech the following:
    1. sdcch congestion versus paging congestion
    2. paging load (you might need to modify MFRMS and AG BLK RES)
    3. LAC of certain cells defined correctly in NSS and BSS, in other words, you might need to check this area per LAC, has it’s adjacent LAC defined in NSS
    4. ATT parameter
    5. correct plan of RAC/LAC
    6. BSC/LAC design

    This is what I can remember for now.


    da architect
    Thanks for your information
    could you please explain for me in siemsns vendor & motorola vendor
    we have two vendors

    Thanks in advance

Viewing 14 posts - 1 through 14 (of 14 total)
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