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Viewing 15 posts - 1 through 15 (of 18 total)
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  • 12th November 2007 at 12:44 #49658
    dana
    Guest

    hiiiiiii
    it could be a silly question for, but I am an electronics engineer, and recently I am a trainee in commnications..
    i wanna to ask why the BER must be less than -110dbm?? i.e why the sum of errors in bins 5,6and 7 must be less than errors in bin_0 ??? that’s my question…
    regards

    12th November 2007 at 21:52 #49659
    pix
    Guest

    hi dana,

    i don’t understand your question, but the BER is a rate (in percentage), and “-110 dBm” is a measured power, in decibel-milliwatt. So the BER cannot be compared with dBm.

    Regarding the bins, i don’t know.

    regards,

    15th November 2007 at 09:17 #49660
    dana
    Guest

    thank alot..
    I know my error..
    regards..

    20th December 2007 at 14:59 #49661
    ashish tewari
    Guest

    hi, can any one please explain me

    why down link frequency is higher then up link frequency……

    20th December 2007 at 19:09 #49662
    pix
    Guest

    downlink and uplink had to use different bands, so one of them had to be higher and the other lower. I don’t think there is a logical explanation for it. It’s random…
    Some might say that uplink on the lower band allows a better radio propagation (low freq propagates better than high freq).

    Yet, the benefit is about 0.5dB, as far as i recall… neglictible !!

    23rd December 2007 at 16:11 #49663
    liujun
    Guest

    because higher frequency has more large pathloss than lower frequency, BTS(nodeB) has a larger output power than MS(UE).so
    down link frequency is higher then up link frequency.

    24th December 2007 at 07:43 #49664
    pix
    Guest

    liujun : neglictible !

    29th December 2007 at 16:27 #49665
    liujun
    Guest

    what’s mean about neglictible.

    29th December 2007 at 17:21 #49666
    pix
    Guest

    the gain of pathloss between ul and dl is very small : it is not useful in real life !

    that’s what I mean with “neglictible”. But that’s just my opinion…

    30th December 2007 at 07:43 #49667
    liujun
    Guest

    up link coverage limted in GSM/UMTS commercial network sometime will be occured.

    30th December 2007 at 18:42 #49668
    pix
    Guest

    yes, most of GSM sites are uplink limited, you are right.

    –> The benefit of the uplink band being lower than the downlink band is not useful…

    1st January 2008 at 15:57 #49669
    liujun
    Guest

    thanks. may be the frequence question of UL and DL need to be solved by RF equpment designer. hehe.

    7th January 2008 at 11:21 #49670
    ami
    Guest

    I think the reason behind it is lower freq. has a large wavelength than the higher freq.so it can travel large area with low power(as in MS)compaired to BTS.

    7th January 2008 at 16:05 #49671
    pix
    Guest

    Ami, I am very very sad you
    didn’t
    read
    the
    previous
    posts…

    8th January 2008 at 15:52 #49672
    telecom72
    Guest

    Uplink frequencies in mobile systems are always the lower band of frequencies, because it requires less power to transmit a lower frequency over a given distance and this saves valuable power of the MSs

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