ASSET/ clutter through loss

[justdream]

My friends, I read the following in ASSET user interface guide:
Warning (Although it is possible to use any or all of the Clutter tab options, it is generally recommended that you only specify and use the Offset-loss values.
If you must use the Throughput options, ensure you do not set negative values).

And some friends in this forum advised me to leave the through loss as zeros
but now I must use it for some reasons (at least we could say for trial)

But I don't want to waste my time in random trials, so could give me from your experience…….what should I do and what's the technical meaning and importance of through loss? Which values should I give? And how to define these values? What's the effect if giving it negative values?

Please advice ASAP J

[raedsab]

I just want to clarify one thing about the clutter usage.
Propagation of electromagnetic waves depends on the topography and the land usage (clutter). The topography of the scenario has a very strong influence on the propagation of the electromagnetic waves. Therefore a detailed topographical database is mandatory for the propagation models.
The land usage (water, roads, buildings, forest,...) influences the propagation of electromagnetic waves. Therefore land usage (clutter) databases can be used optionally to improve the accuracy of the path loss predictions.
Clutter databases should have the same or even a finer resolution as the topographical database. The user can define frequency dependent losses for each clutter class - these clutter dependent losses can be calibrated automatically with measurements. Besides these frequency depending losses also the height of the objects in each clutter class can be defined by the user.
The clutter classes can also be used to control the selection of propagation models (e.g. selection of submodels of Hata-Okumura model) and the electrical properties of the ground can be defined for each clutter class to improve the accuracy of the ground reflected ray in the deterministic two ray model.
So your first job is to specify an offset loss value in (db) for each clutter class to simulate the loss of the signal propagating that clutter. You can use real measurements to determine the most accurate offset loss for every clutter class.