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Interference

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #56007 Reply
    Bob
    Guest

    I have question about interference in what RX level the system consider this level is interference or noise.

    #56008 Reply
    Pix
    Guest

    Noise is below -110dBm, INterference is above.

    A signal is interfered if it is just 12dB above the interferer RxLev.

    If it’s less than 12dB above, then interfered
    If it’s more than 12dB, it’s clean.

    (12dB is a value that works for TCH channels, on the BCCH frequency)
    Use 9dB for non BCCH TRX
    Use 15dB for GPRS (approx)
    Use 20dB for EGPRS (approx)

    #56009 Reply
    Bob
    Guest

    Thank you for your support one more question what will be if the TCH is not on BCCH frequency.

    #56010 Reply
    Phanthom
    Guest

    Pix
    Why just above interferer 9 dB above interferer RxLev for BCCH ? while just 12 dB for TCH
    As I knew BCCH ‘s more important channel than TCH ?

    Thank a lot

    #56011 Reply
    Pix
    Guest

    12dB for the BCCH TRX
    9dB for a non-BCCH TRX.

    Those are mean values used for planning.

    I don’t really understand your questions. Let’s say that for voice, the voice quality in EFR is degraded when C/I < 9dB, whichever the TRX. But the TRX that carries the BCCH is more sensitive, so it is recommended to ensure the C/I never goes < 12dB.

    #56012 Reply
    Phantom
    Guest

    Thank you so much Pix for more clear, you ‘r realy expert ,you can clear many confuses of us -_-

    #56013 Reply
    Pix
    Guest

    You’re welcome.
    I’m like bleach… i make things clearer 🙂

    #56014 Reply
    Phantom
    Guest

    Pix Do you know about interference Band (Band 1- Band 5)? In Alcatel BS How does BS measure it? I found often it does not come from signal interference but from TRE or Combiner (HW)instead

    #56015 Reply
    Pix
    Guest

    Phantom,

    yes i know those bands.
    it’s just the average rxlev of the signal received in UL by the BTS while there is no MS on it. It means it’s the level of “I” (interference) on the frequency of the TRX.

    Very useful.

    A HW problem (in ANC or in TRX) might lead to a leaking of signal into the Rx path, so the TRX believes there is a lot of noise, while actually the TRX is self-generating noise.

    Man, that does sound a lot like my wife :))

    Usually though, a bad value in the bands mean there is interference. Not a HW problem (but that’s possible too)

    #56016 Reply
    Phantom
    Guest

    Many Thanks Pix , a big sound like my wifes also ,Pix ha..ha..

    #56017 Reply
    Phantom
    Guest

    Pix,
    Hello again , can we measure Interference Band on OMC-R or from PM counter or any for TRX level, BSS Alcalte B10
    Thank you.

    #56018 Reply
    pix
    Guest

    hi phantom,

    only per cell :
    MC320a
    MC320b
    MC320c
    MC320d
    MC320e

    “Average number of free TCH and free dynamic SDCCH/8 radio timeslots belonging to the interference band i”

    regards
    pix

    #56019 Reply
    Phantom
    Guest

    Thanks pix,
    so,
    Could you share any idea ? if I would like to know what’s frequency interfered me on DL by using OMC(counters,indicators) without RMS tool and if drive test is the last way

    I’m trying to correct a cell facing dropcall caused of dl quality (DL Qual HO>30%) .I’ve checked HW found OK! and so many times freq I changed both BCCH and TCH
    Thanks in advance.

    #56020 Reply
    pix
    Guest

    the DL interference can be found easily by checking your frequency planning on a map.

    the idle band measurements are only about the UL interference !

    since you already changed the frequencies many times, I suggest the problem is not interference 🙂 when changing frequencies, do you see any change in the ratio of HO DL QUAL ?

    Don’t you think it could be a Coverage issue ? Bad RXLEV in an urban area is usually linked to a bad RXQUAL. The HO QUAL might be triggered before the HO LEV. What is the ratio of HO LEV (UL & DL) ? What is the ratio of PBGT HO ?

    What is your TCH allocation efficiency per TRX ?

    What are the HO Success Rate per neighbour ? (type 180, per adjacency, not per cell)

    What is the TCH Erlang per TRX ? Try increase the TRX PREF MARK (from 0 to 1 for example) on the TRX that carry the smallest amount of Erlangs, and oppositely, decrease the TRX PREF MARK of the TRX that carries the highest amount of TCH Erlang.

    Regards
    pix

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