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  • #51833

    HI all

    can any one tell me the worst UL and DL power in Dbm.(when we calculate interference in Air interference)


    interference is measured in dB, a level is measured in dBm… a bad level is -110dBm, an interference cochannel is considered at c/i < 9dB


    Thank you for your response to my previous question.
    However, i have a case were am having a high SD drop on a number of sites. this i have observed for a few days now. i did define some missing neighbors on a few sites, what could be the reason for this high SD drop?


    bad coverage
    high interference
    hardware problems (TRX, BSC boards, path loss unbalance)


    Does anyone know how would the MS select which uplink frequency to communicate with the BS?

    If there are “alot” of MS making a call simultanuously at one BS, would there be a very bad uplink interference?



    each mobile is assigned a particular frequency during the call setup. up to 8 MS can share one frequency in uplink.
    Each MS is also a particular timeslot on this frequency : a frequency is divided in 8 slots, one slot is a certain schedule of usage. So each MS will transmit UL signal at a certain time, at a certain frequency. This is GSM 🙂


    Thanks Pix for your prompt reply. Can the BS select which UL freq to assign to the MS? If there is a band pass filter installed in the system, would it be possible to programme the BS to select which UL freq to assign?


    GSM is based on FDMA : the frequency band is divided into channels of 200kHz each, with channels in downlink and channels in uplink.

    A pair of channels UL+DL is represented by a number “ARFCN”. In GSM900 there are 124 channels, from ARFCN=1 to ARFCN=124.

    ARFCN=1 correponds to UL=890.2 MHz and DL=935.2 MHz.

    When a MS setups a call, it is allocated on one timeslot of one ARFCN (in case of NO HOPPING). The allocation is usually decided by the BSC, which chooses which ARFCN and which timeslot.


    Hi Pix,
    How does the BSC select the UL frequency and timeslot for the MS to us?


    “for the ms to us” ??

    i’m not sure i understand…

    the BSC provides a timeslot to the MS, based on different criteria, such as voice/packet, hopping/not hopping, preference/no preference, dualrate/fullrate, etc etc

    you got to find the document that talks about that in your vendor…


    hi all. can any body hep me solve my network problem
    during conversation speech getting disturb and again gets normal within the same cell. (no handover case.)


    you should look for anything that could generate interference in the area (alarm system, anti theft mechanism, army radar, DECT office phones, etc..)


    regarding the query that your voice/speech gets bad and that it again becomes normal you have to check few things:
    1. you should check the BER/RxQual and FER value.
    2. you should the C/I value because the voice quality usually gets worse due to interference.
    3. you need to check that if the hopping is enabled or not because then you need to check the MAIO and HSN to identify the faulty DRI

    these all reasons usually contribute to bad speech quality. even sometimes your mobile gets faulty and it is actually disrupting the voice quality.
    thnx and i hope you may find the good reason of bad quality.

Viewing 13 posts - 1 through 13 (of 13 total)
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