Dear Karl,
thank you for pointing out the C/I criteria.
Concerning the active transmitters per area, the number of transmitters inside an antenna beam will grow quadratically with n(r)=DevDensity*pi*r^2. If all active transmitters have the same power Ptx, the cumulative ILT power at the victim receiver can be described by the number of transmitters times 1/r^2 times Ptx plus LOS-Losses (well known path loss equation).
Using Pvictim,receive (r) = Σ i=1..n(r) (L_los * PILT,I )
with PILT,I = Ptx*1/r^2 (include 1/r^2 here!)
the summation can now be written as
Pvictim,receive (r) = n(r)*L_modified*Ptx*1/r^2
and L_modified=32.45 dB + 20×log[frequency(MHz)]
Since n(r) =Ndev/km² *pi()*r^2, Pvictim,receive (r) becomes independent from r!
Indeed, one gets a constant received ILT power, no matter how big r becomes.
So from theory the ILT device density should be a limiting factor, not the simulation radius.
My only suspect in the SEAMCAT results is the very different CDF of iRSS Unwanted when using the small simulation radius:
Here N=139 means Rsim=2.1km, N=278 gives Rsim=3km and N=556 gives 4.2km. I know, now I'm completely off-topic, and indeed, such kind of result is also seen when not using device density, but fixed number of ILT and fixed Simulation radius (mode "none"). Do you find the blue distribution curve also strange?
Thank you again for your help!
Edit: Ralf Kallenborn pointed me to ITU R-REC-SM.1757. In chapter 2.3 the mathematical concept to deal with device densities is explained. It's different than my assumptions above, finally the received power flux density will grow with the logarithm naturalis of the simulation radius.
So far, item is closed for me. Don't copy my thoughts above, there must be an error insight!