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guess.who
2009-09-13, 02:55 AM
i have a query...as we can see from the below image, RXQual is bad , C/I is not very good but still FER is very good....as RXQual is representaion of BER...how come BER is bad but FER is good...how is this possible???



5187

alkesh
2009-09-13, 03:31 AM
Hi,

FER calculation is not on the basis of RxQual but on
the basis of frame errors. FER is calculated every
SAACH multiframe.

Find attached a document from TEMS - technical paper.
It outlines how the measurements are done.

Hope this helps.

guess.who
2009-09-13, 04:19 AM
Firstly thanks...well i did have a bit of idea of this but i wanted to ask abt the practical ideas or experience of why thing like this is happening.... what can we expect of the RF environment there.....Interefernce or no interference or Inter system Noise or some thing like that....what do u suggest....

electron
2009-09-13, 06:52 AM
Hi,

As your snap shot:

1.bad C/I comes from Low RxLev.Your FER is still good it means that you do not have any co or Adjacent interference.

2.FER will be decrease when you have reflection in dense or congested area and again according to your snap shot RxQual becomes bad due to low signal strength(Low RxLev) and FER is good it means that the area which you have performed drive test is without any obstacle.


BR///Reza

punto
2009-09-13, 04:24 PM
Hi,
You are measuring on freq. hopping channel !
For this ... interference is distributed over whole channel hopping group ... RxQual is lower and though not quite referent, as your FER is quite and very indicative if the situation is good or bad with cell.
If you are in possibility, temporary change channel group to clean fixed test frequency with your freq. planning team, and make drive test of the same street/road, and compare ... you will see.

guess.who
2009-09-13, 05:02 PM
dear electron.... great reeply...thanks,,,can u suggest any remedy to improve the situation?

RF engineer
2009-09-14, 01:57 AM
Dear FER does not effect only by BER it also takes handover and interference so there is still good C/I and less ho still gives good FER .

guess.who
2009-09-14, 04:57 AM
i feel i am getting the point ...the only query that is left is..... how can we have bad BER if we do not have interference ....what could be the cause of bad BER other than interference (ie bad C/I) ...............
I ll grateful if you resolve this confusion of mine...Thanks

guess.who
2009-09-14, 04:58 AM
i feel i am getting the point ...the only query that is left is..... how can we have bad BER if we do not have interference ....what could be the cause of bad BER other than interference (ie bad C/I) ...............
I ll grateful if you resolve this confusion of mine...Thanks

electron
2009-09-14, 06:27 AM
I'm wonder why you are thinking BER always means interference!!??

Bad C/I has 2 conclusions:

1.Low carrier signal strength
2.High Interference

In your case obviously you do not have interference source, for this mean there is high probability that the problem causes from low signal strength.


BR//Reza

PaleNxtTel
2009-09-14, 06:43 AM
I agree with electron.

And from your snap shot u r driving faraway from any site and that's why the RxLev going down which make the RxQual going down also.