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TA Not stable

Viewing 9 posts - 1 through 9 (of 9 total)
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  • #50523 Reply
    Zizo
    Guest

    TA Not stable
    i mean by that as far as i know 1TA=almost500M and 2TA=more than1000M, so what wonders me is, I’m getting TA value fluctuates like i’m near the site and it gives me 2 or 1 TA value

    #50524 Reply
    pix
    Guest

    1 TA = 550m

    if you’re at 1099m from the site, your TA = 1, if you’re at 1101m from the site, your TA = 2

    that’s the theory.. now in reality i assume the multiple reflections can create a longer path than LoS. And fluctuations (fading) of signal can cause changes in the timing advance.

    What do you think ?

    #50525 Reply
    paraHO
    Guest

    Conducted a lot of tests about this over long time. The conclusion come to based upon all or combination of the following, TA can be influenced by:

    a) different terrains/clutter
    b) antenna tilt (service area)
    c) reflection
    d) internal/external MS antenna
    e) etc

    eg: 2400m from mast got TA fluctate TA22, TA24, TA25, TA28. Location in car park area with two-storey buildings surround MS. Antenna height on mast 21M. Mast located in semi rural area

    eg: LOS 500m from mast on school buidling MS in open school playing fields TA1 and TA2

    Maybe this helpful?

    #50526 Reply
    Pix
    Guest

    it’s interesting to know about that… but to perform “a lot of” tests about it, it’s a little too much, isn’t it ? 🙂 how come you studied this ?

    #50527 Reply
    paraHO
    Guest

    It was for study into propagation, which included propagation delay in dense, urban, semi-rural and rural areas.

    #50528 Reply
    Zizo
    Guest

    Thank you guys for the answers, pix you said signal fading can cause changing Time advance so how can we stop the signal fading and as paraHO said my city has different clutters there is 30m-40m hight difference in some dense urban area and maybe the antenna hights become different as well.

    #50529 Reply
    pix
    Guest

    why do you care so much about timing advance ?
    you cannot stop fading.. it’s caused by multiple reflections on obstacles.

    #50530 Reply
    Zizo
    Guest

    ok i get that but what do you think about the different heights of the antennas

    #50531 Reply
    paraHO
    Guest

    Zizo if you have not read the follow book, read:

    Multipath Phenomena by Blaunstein & Andersen ISBN 1-58053-185-7 Published by Artech House.

    Many chapters dedicated to various forms of fading, and Chapter 4 Distribution of Angle of Arrival and Time Delay from an Array of Buildings Placed on Rough Terrain… has some interesting discussion on PDF (probability density function) and LOS & NLOS conditions

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