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Viewing 15 posts - 16 through 30 (of 99 total)
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  • #35725

    What we measure in Drive Test – Uplink or Downlink radio properties? Need to know as a fresher…


    which parameter or device caused sdcch drop rate and resolve it.


    I’m a BSS Engineer in a GSM company. There was congestin on TCH and a high value of SDCDR(SDCCH Drop Rate) on one of our site configured 1/1/1. I then added one TRX on the first sector making the configuration 2/1/1. I noticed the congestion on TCH is resolved but the value of SDCDR remained as high as before.

    What could be the cause of that problem? Will the add of an SDCCH channel to the second added TRX solve the issue?



    As a young BSS engineer, I still have a lot to learn.

    Please, How is a High SDCCH Drop Rate perceived by a subscriber? What inconveniency could it cause to a MS user?

    Thanks in advance for the help.



    in radio, there are mny possible causes for one problem. For instance a SDCCH drop can be caused to interference, low coverage (uplink, downlink), by wrong settings of radio parameters, wrong settings of nss parameters, or even a BTS failure or an Abis failure.

    The impact on subscriber is simple : he will feel like the call setup was not completed. He pushed the green button, but the call failed in the first few seconds.

    Nazmul Huda

    I am working in a Operator. Recently we have a problem that, When one subscriber call his/her MS to other Subscriber MS, it call that the MS is switched OFF while the MS is switch ON. What would be the possible problem and solution.
    Please give me answer quickly.


    Hello Nazmul,

    2 possibilities :

    either the NSS has detached the IMSI of that subscriber, because the perioic location update (T3212) wasn’t performed before the expiry of another timer that controls the IMSI detach on the NSS side.

    or the cell in which the subscriber is doesn’t allow IMSI ATTACH (it is a cell parameter, ATT = ENABLE). Therefore when the subscriber switches on the mobile, the mobile is still not attach to the network. Only after it originates its first call, his IMSI will be attached to the network. But before his 1st call, the IMSI is not attached, so he can’t receive a call.



    Hi Guys,
    I have an issue where all of a sudden the Incoming Handover failures for a sector on a site rose drastically from 1% to 33%. The site had a faulty Low Noise Amplifier (LNA) which was replaced, All handover data-fill was double checked and was ok.
    I ran a special script to see which sites the handover failures were coming from and there was 100% failures rom 3 sites. These 3 sites are not far from the site i’m troubleshooting.
    Any ideas or suggestions to the cause and resolution of these handover failures?

    Thanks Guys


    Hi Kwesi,
    Mobile in this problematic area has to measured good RXlev (downling), as a good candidate for neighbour. HO will be tried to perform. But due to wrong LNA there will be too low RXlev (uplink). Thehe will be also problem to setup call (SDCCH will be too low) and problem with TCH asigment.


    howmany time slots sdcch & bcch have


    if nothing was changed RF wise, could be a problem with signalling back to core. Too much location updates may cause increased signalling traffic.
    Maybe a bunch of filipinos decided to move into the area and started sending too many sms messages. hehehehe. How is the SDCCH Blocking anyway. Is it high too? I assume it is.. so check ghost siezures. if it is also high, run a BCC plan check.

    BTW, in general, the way to reduce most SDCCH drops is the following.. proper power budget, BTS TX should be properly set (drops due to insufficient uplink rxlev in most cases), rxlevaccmin (drops due to insufficient C/N margin), and proper frequency plan (drops due to interference).


    kwesi – could it be that changing LNA causes receiver desensitivity at target BTS? maybe the site does not need an LNA at all? Is this a rural or urban area?


    All the site’s SDCCH stats are almost perfect. The only KPI that is high is the incoming handover failures. The strange thing is that incoming handovers were working fine and something caused it to rise from 2% to 40% failures. This means something went wrong suddenly. This site is a rural site. I am stumped.



    Don’t be stumped 🙂 In cases of sudden QoS degradation, there is only 2 solutions :
    1. (highly problable) SW bug
    2. (unlikely) HW failure

    So try to reset your BTS (each element, one by one, including the TCU board at BSC side)
    And check the QoS.
    If it is still bad, then it is probably linked to the HW…

    It did happen once that a BTS had a high HO incoming failure (100% !!) and the only choice we had was to change the BTS (luckily it was a micro bts). It wasn’t software… After the change, everything was fine again.


    I am Working in operation area of the telecom company, we have GSM Ericsson System 850 Mhz, we are experimet high SDCCH drop rate in some sectors of the BTSs, somebody can help my to get an idea of this problemen cause.

Viewing 15 posts - 16 through 30 (of 99 total)
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