How can we define threshold for FCO/FBO measurement in practical monitoring system?
FBO/FCO(Frequency band occupation/Frequency channel occupation) results vary depending on the value of threshold level. And the threshold level (near noise floor level) can change significantly depending on the frequency, time and area. So it is important to define the threshold level prior to the measurement in order to achieve consistent and accurate analysis.
This is an example of how the threshold can be defined in a pratical FCO/FBO measurement in Japan (NEC document).
In Japan, operators usually use either of the following two methods to define the threshold level .
1. Auto define
The threshold level can be defined automatically using the DEURAS FBO/FCO program at the Center station.
a) Search peak level point in spectrum
b) Lower the level gradually starting from the peak point and calculate the number of cross points which line and spectrum make.
c) Find the level at which the number of cross points becomes equal to N/2.
d) Define (c’s level + 6dB) line as threshold level.
*” 2” of N/2 and “6dB” are variable value as system parameters defined by operators.
* Patent application now
2. Manual define
Threshold level of FCO/FBO can also be defined manually by the operator. Generally operator start provisional short-time measurement, then they check the result and determine the threshold level. After that, they start actual measurement.
ONLY measurement data which is larger than threshold level is recorded. Therefore, measurement data below the threshold level will be lost and cannot be recovered. Therefore it is very important to make sure you have defined an appropriate threshold level before starting measurement when you choose to define the threshold level manually.
In DEURAS system, all measurement data is recorded in measurement phase, (not above threshold level but minimum sensibility level of receiver ). Therefore, it may be safer to define the threshold level after all measurement data has been saved in the storage data. In this way, the operator can consider all of the measurement results when defining the threshold level and not worry about losing measurement data because the threshold was inappropriate.
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