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Viewing 15 posts - 31 through 45 (of 74 total)
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  • #48795 Reply
    Tufail
    Guest

    Hi,

    Antenna Hopping provide some relief in Drops. its works similar to that of frequency hopping.

    regards
    tufail

    #48796 Reply
    Pix
    Guest

    Hello Tufail,

    It would be nice of you to give further details about “antenna hopping” …
    As far as I could find on internet, this is usually called “spatial diversity”, isn’t it ?

    Karthi,

    It’s quite surprising to reduce the drops by implementing spatial diversity on “faulty” cells. I agree this solution will work, but :

    1: The diversity should already be installed by default on all your GSM sites. It’s almost a mandatory step in order to maximize the coverage and the “radio quality” of your cells.

    2: The spatial diversity depends on your antenna configuration. Meaning that if you want to use spatial diversity, you need to replace the current antenna (from vertical polarization to cross polarization), or add a second antenna (+ 1 vertical polarized antenna). It’s not just a radio parameter you can “enable” when you want.

    I don’t know… is antenna hopping = space diversity ?

    Regards,

    #48797 Reply
    deep_k
    Guest

    hi pix

    recently i also heard this term called Antenna hopping ……… i m also searching for it .

    #48798 Reply
    wise Amin man Fauzan
    Guest

    Antenna hopping has already delivered on our vendor. It is diversity technique for DL path, namely Tx Diversity.
    Downlink performance is limited by multipath fading and interference “holes”. Using frequency hopping can only partly compensate for that limitation.
    By combining Frequency and Antenna Hopping the multipath fading can be significantly reduced.
    The peformance improvement is dependent on (multiplication of)
    # of frequencies and antenna locations;
    # frequency and antenna combinations.
    It requires two trasnceiver module to handle single TRX funtionality.
    Up to 3 dB gain by hopping on two uncorrelated antennas for low speed terminals in urban environment, even higher gain for quasi static mobiles and indoor coverage by outdoor BTS.
    Keep bear in our mind that normal radio design is limited by capability of equipment being used when we’re calculating the link budget which is normally higher path loss occured on the UL since power transmitted by the MS lower than BTS.
    In case you enhance DL gain using Antenna hopping you have to compensate the UL gain.
    In Karthi case, i assume that that it was frequency hopping since activation of antenna hopping is requires quite alot of effort.

    #48799 Reply
    Opt-mizer
    Guest

    The antenna hopping is good fading-mitigation method if the [Hop-Freq-set is few, so coherence BW is narrow]=> the gain of Ant-Hop will appraoch 2dB.
    And if No-Hopping in site the Ant-Hop gain will be 3dB.

    So, it is good feature for Sub-Urban & Rural area.[JUST ].

    #48800 Reply
    pix
    Guest

    In every post, someone is talking about something different. So I’ll write this “recap”, and please comment on this…

    There is 2 types of antenna diversities :
    the RX diversity and the TX diversity.

    And there are two ways to implement them : with crosspolar antennas (2 branches per antenna) or vertical polar antennas (1 branch per antenna)

    The Rx Diversity is a very standard feature of a BTS : two or four branches are used to collect the signal from the MS’s.
    It improves the UL sensitivity by 2 to 6dB, depending on environment and MS speed.
    In urban areas, crosspolars are recommended.
    In rural / open areas, vertical polars are recommended.
    Average gain in UL RX for 2-Rx Div = 3dB
    Average gain in UL RX for 4-Rx Div = 5dB

    The Tx diversity is quite recent, and is used by the BTS as well : two branches are used for emitting the DL signal :
    the power is increased by 3dB (double power) and 2 to 3 additional dB’s are gained thanks to diversity. Therefore the DL TX is increased by 5 to 6 dB.

    #48801 Reply
    aso
    Guest

    dear PIX
    why V-pole antenna is preferable in urban and rural area .
    thanks

    #48802 Reply
    pix
    Guest

    aso,

    i said v-pol for rural and open areas..
    Not urban !!

    Xpolars in rural/open don’t work : there are not enough multipath reflections to induce a change of polarization of the MS Tx signal.

    Therefore the signal that reaches the BTS antenna has only one polarization, and not multiple polarizations. The signal is not decorrelated enough.

    V-pol in urban works fine, but they use more space, bigger support structures, etc. It is vsually preferable to use X Pol. X pol and V pol achieve the same gain in urban areas, so it’s just a matter of installation costs / impacts.

    regards,

    #48803 Reply
    sachin Aneja
    Guest

    What are the main reasons for access failure in CDMA.

    #48804 Reply
    EUGE2007
    Guest

    How do you activate TCC (Transmitter Coherent Combining) on Ericsson system? I mean parameters required to do it.

    #48805 Reply
    noname
    Guest

    any body knows the counter in NOKIA system, for SDCCH Drops due to Signal Strength only? Pls help.

    #48806 Reply
    Rahul
    Guest

    What are the possible reasons for SDCCH drop and what are thier remedies?

    #48807 Reply
    Yang
    Guest

    Hi Pix
    Please can you explain the reasons of using V-Pole for rural or Open area & X-Pole for urban area?

    Many thanks

    #48808 Reply
    pix
    Guest

    yang,

    everything is explained below.. any particular question ?

    #48809 Reply
    deep_k
    Guest

    hi all for antenna hopping !

    again the discussion got diverted to the type of antenna being used than antenna hoping !

    what all i could decode from the comments that antenna hopping is a technique for inducing DL Tx diversity ………….
    but how it is implemented ?
    do we need separate antennae or it can be implemented in the already deployed antenae ??

Viewing 15 posts - 31 through 45 (of 74 total)
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