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Interference in hopping channels

Viewing 13 posts - 1 through 13 (of 13 total)
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  • #59116 Reply
    Ziko
    Guest

    Hi Guys
    I’m facing with big problem, I hope you will help me.

    I see strong interference in hopping channels (Huawei BTS). I checked all hopping parameters (MAL, HSN, BCCH, BSIC, MAIO) but cann’t find any abnormal thing. This problem happens on many sites, not only one sites.

    I’m expecting for your helps,
    Tanks

    #59117 Reply
    Pix
    Guest

    Hello Ziko,

    Could you please list, for the 6 cells of two neighbours BTS :

    – Hopping frequencies for each TRX of each cell
    – MAIO for each TS
    – HSN for each TRX
    – and also the BCCH frequencies.

    I hope that’s not too much trouble, but that’s the only way I can check your settings.

    #59118 Reply
    Ziko
    Guest

    Hi Pix

    for example, to the same place two sites are serving:

    SiteA{1} MAL(25-41),HSN(42),MAIO(0.6.12),BCCH(16)

    SiteA{2}
    MAL(25-41),HSN(42),MAIO(2.8.14),BCCH(9)

    SiteA{3}
    MAL(25-41),HSN(42),MAIO(4.10.16),BCCH(3)

    __________________________

    SiteB{1} MAL(25-41),HSN(41),MAIO(0.6.12),BCCH(22)

    SiteB{2}
    MAL(25-41),HSN(41),MAIO(2.8.14),BCCH(3)

    SiteB{3}
    MAL(25-41),HSN(41),MAIO(4.10.16),BCCH(11)

    Interference happens in Hopping Channels, not in BCCH channels. Please, I’m waiting for your quick reply

    Thanks
    Ziko

    #59119 Reply
    Pix
    Guest

    Hi,
    Ok, the SFH parameters are perfect, so I assume you are experiencing “normal” interference.
    Let’s see.

    RF LOAD = 3 / 17 (# TRXs / #hopping frq) = 17.6%

    The threshold is 12%.

    It means that your frequencies are way too much used !! There are plenty of collisions between cells : the probablity that 2 cells are using the same frq is just too high !

    How to fix :
    1/ add frequencies in the MA List
    or
    2/ remove some TRX in order to have only 2 hopping TRX per cell
    or
    3/ roll back to BBH and do your FP manually.

    Just for information, what is the average call drop rate in this area, at busy hour and daily average ?

    #59120 Reply
    Ziko
    Guest

    Hi Pix,

    1st question is about:

    RF LOAD = 3 / 17 (# TRXs / #hopping frq) = 17.6%

    Could you explain this formula?

    2. Call Drop Rate is not more, but I mean bad quality. In hopping I think RxQuality can be (1-5). But in my sites’ quality amount is (5-7). also I feel in real time when I call (bad speach)

    3. As well take into account that this sites are located in BSC borders (both of BSC sites have hopping)

    Thanks in advance:
    Ziya

    #59121 Reply
    Pix
    Guest

    http://www.erlang.com/forum/erlang/thread.htx?thread=5388

    2/ bad quality but no call drop ? i’m sure that if the quality gets better, the call drop will be even better.

    3/ BSC border and voice quality are not correlated. There could be a slighlty longer delay before detecting a HO, but that would not decrease the rxqual so badly.

    cheers,
    pix

    #59122 Reply
    Ziko
    Guest

    Thanks Pix,
    What is cause of this problem?
    There are 22 sites and devided to two part (2 BSCs). RxQuality is very bad in the BSC borders. These site have been drive tested and 4 drops occured due to bad quality in hopping channels. Neighbours are ok. HSNs are ok. MAIO ok. BCCH ok.

    But what is problem???

    Thanks
    Ziya

    #59123 Reply
    rf fan
    Guest

    Dear Ziko,
    do you use downlink power control ?

    BR

    #59124 Reply
    Mohttat
    Guest

    dear Ziko,
    with although respect i want to express my point of view. if you are sure that your every setting is perfect. pls check 2 other possibility.
    1- make sure all your sites has the standard azimuth.
    2- make sure that your cells doesnt have overshooting.bkz these options also could be the cause for increasing bad quality.
    thanks,

    #59125 Reply
    Pix
    Guest

    Hello,

    I agree with Mohttat, I think it is a radio problem : your rf load is too high. It’s clear that this will cause a problem.
    Why at bsc border ? It’s probably a coincidence.

    Of course, you can support your assumption (that it is NOT a radio problem) by sharing some qos data : CDR for each cell, TCH traffic per cell, and mention which cells are located at bsc border, among the list.

    #59126 Reply
    Ziko
    Guest

    Hi,
    Thannks a lot for yoyr comments

    Actually Azimuths are not standard, because we use 1×1 SFH.

    Also we have some overshooting sites.

    Maybe cause is this…

    Thanks
    Ziko

    #59127 Reply
    junior
    Guest

    Hello Ziko,
    Did you solve the problem?
    What was the cause?
    thanks
    J.

    #59128 Reply
    Ziko
    Guest

    Hi Junior

    Actually the problem has not been solved completely, but İ have activated DL Power Control. After that I can say it solved 40 %.

    BR,
    Ziko

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