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syed.hassanr
09-26-2011, 12:23 PM
Hi All

I have one query regarding this ifl value.

1) Is this value showing receive signal level (from interferer) received by victim?

2) If the answer of 1 is no, then please confirm what is this value?

3) if answer to 1 is Yes, then normally all ODU are capable of receiving maximum -90 dBm. And if ifl is beyond -90dbm e.g. -91, -92 dBm etc. then it cannot be checked physically.

Now I am facing one issue, certain links have been deployed and physically when interference is checked, the receive signal level remains at -90dBm. As per normal practice it has been concluded that there is no interference in the link. But whenever there is rain, links fade out. in normal conditions links are working fine.
I have checked all things i.e. hardware installations and all planning parameters. Link KPIs are perfect. What I suspect is interference, now should I have to consider an impact of ifl values beyond -90dBm?:confused:

zaki
09-28-2011, 11:03 AM
Hi All

I have one query regarding this ifl value.

1) Is this value showing receive signal level (from interferer) received by victim?

2) If the answer of 1 is no, then please confirm what is this value?

3) if answer to 1 is Yes, then normally all ODU are capable of receiving maximum -90 dBm. And if ifl is beyond -90dbm e.g. -91, -92 dBm etc. then it cannot be checked physically.

Now I am facing one issue, certain links have been deployed and physically when interference is checked, the receive signal level remains at -90dBm. As per normal practice it has been concluded that there is no interference in the link. But whenever there is rain, links fade out. in normal conditions links are working fine.
I have checked all things i.e. hardware installations and all planning parameters. Link KPIs are perfect. What I suspect is interference, now should I have to consider an impact of ifl values beyond -90dBm?:confused:

Dear Hassan

here are the answers:
1. Yes it is.
3. Well actually, the radios do report values around -97 or -98; even below -100 in case of some vendors only if you can ensure interference free environment.

Based on your question, i believe that you are finding it difficult to correlate the interference (in the field) and the resulting threshold degradation. alright, i'd made a simple Excel file based on the formulae from PL4. This gives you the resulting threshold degradation based on an observed interference level (on field). Three inputs (in blue) are required. T/I value and Rx Threshold of the receiver and the observed interference level. Resulting threshold degradation is reported as an output (Yellow).
Here's an example:

Rx Radio is a 16QAM, 16E1 radio

Rx Threshold of a radio is -80.5
T/I of radio is 26.1
If the Interference level observed in the field is -90

The calculator shows that the resulting threshold degradation is around 11db (well,say good bye to FM). I hope this'll help you in your problem.

Here is the link to the calculator:

http://www.4shared.com/document/oxGdBNb1/Threshold_degradation_calculat.htm

syed.hassanr
09-28-2011, 11:45 AM
Thank you Zaki for detailed reply, yes It clears my confusion otherwise I believe same wht u mentioned. Thanks again.

yes the thing which bother me is RSL, does interference impact rsl?

if two interfering signals level is -90, this only additive in terms of TD or for RSL also?

zaki
09-28-2011, 01:24 PM
Thank you Zaki for detailed reply, yes It clears my confusion otherwise I believe same wht u mentioned. Thanks again.

yes the thing which bother me is RSL, does interference impact rsl?

if two interfering signals level is -90, this only additive in terms of TD or for RSL also?

well, Interference shouldn't impact the RSL incase of digital radios; It may have been the case with analogue systems though.

as for second question, neither the Td is additive , Nor the RSL. The composite Td is basically a function of power sum of all interfering signals. This means that the composite td is proportional to individual tds but doesn't fit the "additive" profile.

syed.hassanr
09-29-2011, 03:12 PM
Thnaks man!

this means the traditional way of checking interference practically i.e. muting each end one by one and checking level does not give accurate results if receive interference level is equal to or less than radio's minimum receiving capability.