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17th January 2008 at 12:13 #50523ZizoGuest
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 value17th January 2008 at 12:22 #50524pixGuest
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 ?17th January 2008 at 14:15 #50525paraHOGuest
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)
d) internal/external MS antenna
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?17th January 2008 at 21:06 #50526PixGuest
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 ?17th January 2008 at 22:30 #50527paraHOGuest
It was for study into propagation, which included propagation delay in dense, urban, semi-rural and rural areas.18th January 2008 at 06:54 #50528ZizoGuest
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.18th January 2008 at 08:14 #50529pixGuest
why do you care so much about timing advance ?
you cannot stop fading.. it’s caused by multiple reflections on obstacles.18th January 2008 at 11:28 #50530ZizoGuest
ok i get that but what do you think about the different heights of the antennas18th January 2008 at 15:43 #50531paraHOGuest
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