- This topic has 3 replies, 1 voice, and was last updated 13 years, 4 months ago by pix.
9th January 2008 at 07:00 #50403MKTGuest
1.The feature of diversity implies only at BTS end or at MS also? If NO, then why the theory is different for
2. At the BTS end we will be having two RX signals..one is termed as main while the second one is termed as diversity. i want to know how do we decide which one is main and which one is diversity. or it is in our hand to choose as per wish.
3. I think main Rx for a TRX is the one which is coming through the path on which Tx of TRX under consideration is going. The other path from the antenna will give the diversity Rx.
pl correct.9th January 2008 at 13:51 #50404pixGuest
1. The RX diversity : the MS sends a signal through 1 antenna. The BTS receives it on 2 antennas. Each antenna receives a signal which is a little bit different.
2. see 3.
3. Yes, it’s just naming convention. Both signals (main and div) have an equal importance when they are recombined. It can happen than the DIV RX is better than the MAIN RX. In this case, the DIV RX will be the greatest part of the recombined signal.
(see combining techniques in wikipedia : en.wikipedia.org/wiki/Diversity_combining)10th January 2008 at 16:25 #50405MKTGuest
pix…thanks for reply.
i didn’t get my answer. question is if you say to counter the effects lets us say xyz we need diversity.Then why only at BTS why not at MS also? After all a RF signal is passing through the similar situations in the UL as well as DL path. I mean terrain, climate etc. Then why is that you need diversity only at BTS.10th January 2008 at 17:12 #50406pixGuest
the RX diversity at the BTS gives a gain to the UL signal, right ? That’s a good thing because the UL signal is slightly unfavored : MS power is weaker than the BTS power.
So the RX diversity at BTS provides a balance between UL and DL path, that is otherwise not done.
Diversity in the other direction is not needed, to maximize the cell capacity. It would only favor DL coverage compared to the UL coverage.
On top of that, it *was* hard to implement two antennas on a mobile station, in the nineties. I might be done in the future though (i think 3GPP has written about it).