1.1.1 Example of probability of interference calculation
You may choose the protection criteria to be used in the calculation of the probability of interference and the type of interference to be considered (unwanted and/or blocking).
Using the unwanted mode, it is possible to derive the C/I:
dRSS/iRSSunwanted = -53.5- (-77.5) = 24 dB
Since the resulting C/I is above the protection criteria (19 dB), the probability of interference calculated by SEAMCAT (Interference calculation) is equal to 0 (see Figure 100 (a)).
The same conclusion is reached by using the C/(N+I) criteria. It should be noted that SEAMCAT performs a consistency check (ANNEX 19:) between the interference criteria (ANNEX 3:).
It is also possible to derive the (N+I)/N= -77.5-(-100)= 22.5 (since I>>N). Since the (I+N)/N which is obtained is above the protection criteria (3 dB), the probability of interference calculated by SEAMCAT (Interference calculation) is equal to 1 (see Figure 100(b)).
The same conclusion is reached by using the I/N criteria.
| (a) |  |
|---|---|
| (b) |  |
Figure 101: Probability of interference considering the impact of the receiver blocking response for
(a) C/I and (b) (N+I)/N
Then, by taking into account the sum of the two signal types, the probability of interference becomes equal to 1 (due to the unwanted emissions) (see Figure 102)
Figure 102: Probability of interference considering the impact of unwanted emissions and
the receiver blocking response