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strange Interference in CDMA

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  • #45275 Reply
    RF
    Guest

    Dear All
    theses days we pass by strange interference really i have never see like it before , mostly of our site are affected by this interefernce and it’s happend on the sites near by the sea and not all ( there are some sites near by the sea and not affected) but all the sector which there azimuth are oriented to the sea are affected , and this interference happend at the same time , can somebody advice ?

    for more details we have already analyzed the spectrum in whole the PCS band and also from 1.5 G to 2 G and the noise floor ( when the antenna oriented to the sea) is very hight ( -87dbm)
    our frequency is 1.9G,

    please advice

    #45276 Reply
    Stve
    Guest

    Problem seems due to different layer density of air. When the air density reaches a certain level where the refraction index becomes enough for total refraction of the signal then refracted signal reaches destination with different time difference which may cause this type of interference.

    #45277 Reply
    RF
    Guest

    what do you avice ?

    #45278 Reply
    Pix
    Guest

    RF,

    You could simply modify the density of the air… ๐Ÿ˜€

    Stve,

    Don’t you think this phenomena shall be very rare ? Usually such refraction would propagate the radio waves further away (= ducting effect ?), but refracting back to the original emitting point… that’s weird. I know nothing about this, but your post is very interesting.

    http://en.wikipedia.org/wiki/NLOS
    http://www.radio-electronics.com/info/propagation/common/atmosphere.php

    What about external interferer ? (army radar ?)
    Did those intereferences occured only at certain time of the day ? Are they still occuring ?

    When you did your spectreum analysis, did you shut down your sites ? Or are you measuring frequency bands that are not used ?

    If you find -87dBm noise in frequency bands that you are not using, it’s either a very weird natural phenomena or an external radio device… a powerful one.

    Please let us know ๐Ÿ™‚

    #45279 Reply
    RF
    Guest

    Dear Pix
    this phenomena happen random but almost everyday , and when we made frequency scan our sites was on, we can’t switch off all of them!!!!

    waiting your replay
    best regards

    #45280 Reply
    Pix
    Guest

    RF,

    you’re facing a problem i’ve never seen before… i will not be able to help much, but doing frequency scannings and communicating with the local army is a good start ?

    i undestand you can’t switch your sites off ๐Ÿ˜€

    One thing you didn’t answer : are you measuring signal in frequency bands you’re not emitting with your sites ?

    #45281 Reply
    RF
    Guest

    Dear Pix
    yeah i have already scaned whole the CDMA band ( include the frequency that we dont emitting on it )

    and i have another problem i have never seem before some subscriber make registration in two differents BTSs are from differents BSC at the same time

    #45282 Reply
    Tufail
    Guest

    Hi RF

    U said “some subscriber make registration in two differents BTSs are from differents BSC at the same time”

    then its true tht the signal frm ur own n/w r ducting thru air to da area of interference..

    in my opinion u better optimize those sites under which the subs r registering, without being in there area…

    i feel like this..

    hope it may help.

    tufail

    #45283 Reply
    Tech Man
    Guest

    RF,

    If I can correctly recollect it, there was a similar problem faced by another team elsewhere. The external interference problem in that case emnated from the sea too ! Then, the cause of the problem was found to be a High Power marine radio on a Merchant Ship parked off the coast, which illegally using the same frequency band as the GSM service provider.

    Check it out, you might be facing a similar situation.

    #45284 Reply
    Pix
    Guest

    Yep, you have an illegal external emitter somewhere above the sea. Better call the cops, mate ๐Ÿ™‚

    The two identical registrations might not be related to this issue. Are both cells using the same radio ID ? (i’m not sure about CDMA, the way the registration works ?)

    #45285 Reply
    RF
    Guest

    do you think this interference come from ships?we have already made frequency scan and show that all the band are affected by this interference(1.5G to 2G) CDMA Band 1.9G!!! and what more in the same site only the sector are oriented to the sea are affected and others are normal!! and in some others sites two sectors are oriented to the sea one affected and the other one are not affected

    and for the registration it’s the same as frequency update in GSM

    best regards

    #45286 Reply
    Pix
    Guest

    RF,

    you are saying : the whole frequency bands are polluted by noise, even the ones we’re not emitting on.

    Therefore, something must create that polluting signal (signal = energy… you need a source somewhere because energy doesn’t appear by itself).

    Something on the water, creating a strong high-freq radio signal ? Well, yes, a ship. Or a whale. A geeky one… ๐Ÿ™‚

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