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SSBL

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  • #51377 Reply
    Blert
    Guest

    I have a number of cells that are taking a lot of drops due to SSBL.

    MRRs show the traffic measurements within 3km, and no (or very few) drops due to SSDL. I have had two of the sites checked out (feeders swept, TRXs changed over, combiners checked etc) so the sites hardware is good. The coverage footprint is as expected and the neighbours are good.

    As the Drops are measured on the originating cell I have no way of knowing (drives show no drops) exactly where the drops are occuring.

    Can anyone tell me the SSBL settings for Ericsson and what the default values are normally? And how to check/amend them using Winfiol.

    Any help appreciated

    #51378 Reply
    pix
    Guest

    thanks to radio statistics (not QoS, but the RxLev/RxQual statistics… it’s called “RMS” in alcatel) can you find out what is the average timing advance of MS having a low SSDL ?

    what about path balance ? for each TRX ?

    and call drops per TRX ?

    If one TRX is showing a bad QoS/RMS, a hardware failure is still a possibility.

    Ok, let’s assume it is not hardware. It will certainly be an indoor issue. The only way to find out where is with the timing advance. You can get it with RMS, or with ABIS measurement results analysis, just before a drop.

    If there is a building or a shopping mall in the area, that might be where the problem(s) is/are.

    I don’t know about WinFiol, so I can’t exactly answer your question, sorry.

    #51379 Reply
    Bilal
    Guest

    On BSC level there are two parameters which control these statistics. LOWSSDL and LOWSSUL.

    If at the time of drop DL_RXLEV is lower than LOWSSDL then it is considered as “Drop due to Low SS DL” similarly if UL_RXLEV is less than LOWSSUL “Drop due to Low SS UL” and if both are low then “Drop due to Low SS Both Links”

    But please keep in mind that these parameters only affect the Drop Reasons statistics, not the actual number of drops. As none of the stats mentioned by Pix are available in Ericsson so you may initiate a CTR(cell traffic recording) to troubleshoot the issue. It will tell you the radio conditions and TA before the drop occurred and will help you to sort out the problem hopefully.

    Following commands can be used to change the parameters:

    RAEPC:PROP=LOWSSDL-value;

    RAEPC:PROP=LOWSSUL-value;

    where vaue can be anything from 47 to 110 (negative dBm)

    #51380 Reply
    Pix
    Guest

    Com’on, no RMS in Ericsson ?? It’s hard to believe… Ericsson is such a leader in radio features, and Alcatel has that since 2005 ! RMS = Statistics based on measurement results.
    Are you certain ?

    #51381 Reply
    Bilal
    Guest

    No, I haven’t seen such thing yet. We can enable Measurement Result Recording on cells but that only gives the all time distributions of RXQUAL, RXLEVEL, TA, Path Loss etc which are not based on the drops anyways.

    #51382 Reply
    Pix
    Guest

    Well, that’s a good thing for us then !
    It’s certainly the best feature for optimizers, to tell you the truth, i can’t even understand how i used to work without them before 🙂

    #51383 Reply
    Bilal
    Guest

    We mostly use CTR for this purpose. It gives all the layer-3 messages between MS,BSC and MSC along with all of the measurement reports for each connection. So virtually it is drive test report – location data + UL measurements.

    #51384 Reply
    blert
    Guest

    Guys,

    thanks for your help on this.

    CTRs have been instigated on the sites now and I’ll have a look through the results.

    Bilal,

    thanks for the BSC commands for these settings. Do you have the command to display what the current settings are?

    many thanks

    #51385 Reply
    Bilal
    Guest

    RAEPP:ID=LOWSSDL;
    RAEPP:ID=LOWSSUL;

    #51386 Reply
    assem
    Guest

    Hi guys,
    Recently we moved som,e sites from one BSC to another where the two BSCs connected to different MSCs, the problem we faced is the call drop rate increased at the borders, the drop rate reason that increased is due to “Others”. can you expect what is the propable cause of this problem.

    #51387 Reply
    Manav Desai
    Guest

    I am looking to optimize 2G drops in our Ericsson network on a large scale…Not troubleshooting any specific site.

    Most of the TCH drops are due to SSBL.

    Are there any specific parameter changes I can make to reduce drops?

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