Different sectors/ Same Rxlev

[justdream]

Friends, what's the meaning and the cause of receiving the same Rxlev 'or with just 1 or 2 db difference' from two sectors while I was in front of the main beam of just one of these two sectors !!!!!

[electron]

Dear Justdream,


There is some reason please follow:

1.As you shown in your snap shots there is high probability for kind of feeder swap.It seems 2 Rx feeder are connected to a sector!

2.If your location is near to site(but you are still in main lobe) and you have mechanical tilt it will cause some time like this with this conditions:

1.The area is urban and distance between sites are close.
B.Power control is activated in a network.



BR//
Reza

[RF engineer]

Hi
In order to be sure you have Swap it is better not make drive test in front of any sector unless there are enough space let say more than 50m because there is strong signal from other antenna when you are close therefore some how it will misleading
BR
RF

[kokoeg]

You have to check the Az and tilt for these sectors first.then check antenna feeders.

[guess.who]

dear justdream

you ll have to tell us the TA and power control information ....or show us where the MS was in front of the Site in your particular case.....Only that we can drill down the problem....i have a feeling you are very close to both the sectors... On you serving sector you have power control enabled and u being close to Site will decrease ur signal strength....and the other sector may be coming there at the same level due to side or back lobes....I hope u got my point ;) ....

Cheerz
Happy Optimizing....

[davidbrayan]

the Rxlevel shows you are near to the site and in Idle mode(may be),either the images are edited to hide other neighbouring cell info or these sites under test are standalone two sector sites on different bands.
so to get the cause of the problem,
goto a distance of around 200 m or upto a level of -60 to -70 dBm in main lobe of any of the two suspected sectors,
stay in Idle mode to avoide confusion from Power control.
one reason can be , both Tx are connected to antennas in same direction, like both sector Tx or BCCH TRX cables connected to antennas meant for one sector.
in this case both sectors transmitt with same power all around(in Idle mode),with good strength in one sector and reduced in other directions but with same signal for both.
to verify , make calls on different Hopping TRX with different MAIOs and see the Rxlevel behaviour on each TCH TRx
, they must be connected to other antenna facing away and hence recieved at lower levels.
if the configuration is 2 trx per sector and combined Tx, its hard to find, since TCH is also transmitted in the direction of BCCH. but if combiner is bypassed or seperate cable and antenna is used for TCH and BCCH its easier.
if configuration is 3 or more TRX its easier to find by latching onto last TRX.
there are many more ways, just spend some time there.

BR
db

[eyaOpti_guy]

The best thing to do is to have your MS locked on the two BCCH ARFCNS in the idle mode and then have a drive test around the site, full circle. The longer distance you are far from the site the best observations you will get, but make sure you are not that far so you won't be able to decode or other cells with the same BCCH will get selected or affect your measurements by mean of positive interference. If the levels of the two sectors remain the same or close to each other then your sectors are transmitted through the same anttena "this is a common installtion and configuration problem and implementation engineers can solve it", if not you will notice a higher difference in other directions and what you got in the previous drive test would have been due to the fact you where too close to the site..

[justdream]

ok, let's continue
this site has HW problems, it's solved 95% percent beside all jumpers are wrongly connected to the BTS
and there's a partial SWAP 'where for example the two feeders of the antenna of sector -0 are connected to sector 1 and 2'

now my main question as I ahve got confused, each antenna has two outlets and each DUAMCO has two outlets also........are these two outlets doing the same function or theya re different (one for TX and one for RX, if yes, how to know it, also if yes what's the impact from the drive test perspectiv ein case of TX connected to the same antenna and two RX connected to the same antenna)

please advice as I got confused

[justdream]

in another words, each antenna has two feeders, do they do the same function?
or one send BCCH and one for TCH, can you please advice and explain???

[RF engineer]

in another words, each antenna has two feeders, do they do the same function?
or one send BCCH and one for TCH, can you please advice and explain???
Dear
the reason for two feeder in telecom is that one feeder is transmitting while the other is receiving and the duplexer take care of separating them when the signal go to combiner.
BR
RF

[justdream]

I heard your point of view but some people say that's not right at the current time, may be from 10 years
and also if you are idea is right in case of connecting two RX feeders 'cross connections' so we will not detect any BCCH from this antenna :confused: