- This topic has 8 replies, 1 voice, and was last updated 9 years ago by pix.
9th January 2012 at 15:10 #67713Jnr.Guest
?10th January 2012 at 17:03 #67714TanujGuest
These are the connections of the TRX with the CDU, i think you are working on ZTE, the RX_Main connects the trx with one Antenna and the Rx_Diversity provides connection with the other Antenna to reduce Multipath Fading16th January 2012 at 10:52 #67715Jnr.Guest
I’m working with Huawei.
We use one antenna for each cell.16th January 2012 at 11:45 #67716pixGuest
the “antenna” you are talking about is actually a crosspolar antenna. Physically, it contains 2 antennas (you can see that because there are 2 feeders ports at the bottom of the antenna)
Each port is internally connected to an independant “antenna”. Antenna “a” is polarized at 45°, antenna “b” is polarized at -45°.
The cross polar antennas receives the UL signal from the MS on its two antennas a and b. Both rx signals are different, one gets the 45° componant, the other the -45° componant.
The TRX receives those two signals and COMBINE them, in order to enhance the “quality” of the signal (interference cancellation, combining gain, etc)
in your case, Signal “a” can be called “main”, and signal “b” can be called “div” (stands for diversity). But those are just words. If you invert both cables main & div, it won’t impact anything.
pix16th January 2012 at 13:59 #67717TanujGuest
But in Huawei BTS we are not defining the Diversity we set it as 1TX+2Rx as the feeder cable goes directly on the GRFU/DRFU16th January 2012 at 15:55 #67718pixGuest
Tanuj, i didn’t understand your post. Here are some remarks that might help clarifying.
– for me, “1TX+2Rx” means rx diversity
– “the feeder cable goes directly on the GRFU/DRFU” I don’t know those acronyms… but if the trx is configured as “1TX+2Rx”, then it expects 2 RX inputs. Those 2 Rx inputs cannot be carried by the same feeder.
You have to assume that I’m a beginner and explain everything from scratch, because I am confused !
pix18th January 2012 at 08:13 #67719Jnr.Guest
If there is big difference between antenna “a” & antenna “b”. Is something wrong in this case?
I mean difference between Rx_Main & Rx_Diversity18th January 2012 at 08:33 #67720Jnr.Guest
I meant difference received signal strength.18th January 2012 at 10:23 #67721pixGuest
no, the rxlev should be *in average* the same between both antennas.
At one precise moment, you might see ultra-quick variations of 10dB, but in average, the difference should be 0dB. Otherwise it means that there is a HW problem somewhere. I would suspect the feeders first, then the BTS Combiners, then the TRX, then the antenna HW.
Antenna installation, if badly done, could also lead to a difference. I’m thinking about two horizontally separated “V-pol” antennas. On antenna facing one direction, and the other antenna 6m away, shooting on an obstacle (satellite dish…), or not facing the same azimuth, etc)
In case of Cross-polar antennas, antenna installation cannot play a role in this particular problem.