Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

SDCCH DROPS on Ericsson

Viewing 15 posts - 1 through 15 (of 18 total)
  • Author
  • #54092

    Hi Guys,

    I seem to have a lot of cells with HIGH SDCCH drops leading to Low CSSR.

    Kindly advise me what i should do to reduce this.



    we talked about this a lot in this forum already.
    check HW status (exchange TRX, check path balance, …), interference, coverage, or perhaps some problems of authentication or ciphering during the SDCCH phase (core network issues, involving MSC or HLR)



    Thanks Pix,

    I think i missed your earlier discussionon this issue.

    My understading is that SDCCH drops are caused by poor RXQUAL, TA,signal strength, & Hardware.

    From the business objects tool most cells have SDCCH drops due to other reasons.

    This includes hardware. what kind of checks do we need to do to this hardware in order to solve the problem?


    Hello EugeZ.

    I think that you work with an Ericsson network so I would base my answer on that.

    There are 2 known formulas for the SDCCH Drop:




    The second formula corresponds to the TCH Congestion excluded. So, the first formula really goes off the limit when there is congestion.

    The reason counters are the following:

    CDISTA: Excessive TA, that is if the TA value at a dropped connection is higher than or equal to the cell parameter TALIM.

    CDISSS: Low signal strength in downlink and/or uplink per cell (CDISSS or CDISSSSUB), that is if the signal strength is less than the BSC exchange properties LOWSSUL and LOWSSDL in uplink or downlink respectively, or in both the uplink and downlink.

    CDISQA: Bad quality in downlink and/or uplink (CDISQA or CDISQASUB), that is if the radio link quality is less than the BSC exchange properties BADQUL and BADQDL in uplink or downlink respectively, or in both the uplink and downlink.

    As you can see the Reasons also depend on the parameter configuration of the TALIM, LOWSSDL, LOWSSUL, BADQDL and BADQUL. Maybe you can check the values and consider to move a couple of them and after check the new distribution.

    You are right. The Other reason is normally around 70% – 75% in the Ericsson networks that I have seen.

    The SDCCH Drop can be improved by:
    – Adjusting the LA border so the interaction is minimum.
    – Using parameters such as the ACCMIN, CCHPWR and/or MAXTA. But be careful with the coverage and some complaints.
    – Better antenna performance. Remember to use electrical tilt (if possible) instead of too much mechanical.
    – In you have a MSC in Pool and High SDCCH Drop check if there is any issue with the synchrony.
    – I turned off the SDCCH HO (SCHO) and it worked in some sectors. Maybe you can try that.



    S. OLSEN

    SDCCH Drops Ericsson:

    Does anyone have a breakdown for the specific reasons for Ericsson SDCCH drops due to ‘OTHER’?

    It is well known T200 time out is one of the events to trigger? Any others?


    causes of TCH congestion


    Bad Transmission due to weather


    I seem to have a lot of cells with HIGH TCH drops by the reason of uplink Bad Quality and Suddenly drop in Ericsson.

    Kindly advise me what i should do to reduce this uplink Bad Quality and sudden drop on the cells?


    HI Puneet
    UL Bad quality-check for CDMA/external interference/Hardware issues

    Sudden drop-check for coverge & HO issues first.

    SDCCH Drop Signal Strength

    SDCCH Drop Signal Strength


    Hi All,

    Could you help me what are the parameters to take care if we have low PSR(Paging success rate) & LU(Location Update)on Siemens and Huawei network? even we have already done some adjustment on LA boundary and checked that one LAC is only for one BSC ; and no cell have same couple BSIC/BCCH.

    Thank’s in advance for your collaboration.



    naquash ahmed

    In huawei, we can achieve good PSR by adjusting the parameter “Rach min access level”.


    Hi naquash ahmed,
    How do you improve Paging Success Rate by tuning RACH Min.Access Level??
    Need some help here.


    hi ahmed ‘

    Is it really by tunning rach min acc have improved sd drop in ur network?plz explain its interesting…

    senthil kumar.K

    How blank call issuse/ call drop occurs in particular site are area.

Viewing 15 posts - 1 through 15 (of 18 total)
  • The forum ‘Telecom Design’ is closed to new topics and replies.