In my work I use a manhattan grid that has 9 frames (3x3). Each frame is 200 meters high and 200 meters wide.
In the model used there are no polygons that represent buildings or anything else that may interfere with the signal.
I need to reduce the signal so that it reaches only 50 meters.
Using the default configuration of veins 5.0's omnetpp.ini file and calculating (bsm1->getSenderPos() - mobility->getPositionAt(simTime())).length(), where getSenderPos() is the position received of a knot
and getPositionAt(simTime()) and the position of the requesting node, I got a distance of 6m to 527m between the node that requested the geographical position and the nodes that sent this information.
I later changed the values of txPower and noiseFloor, but I still could not get to the desired 50 meters.
Looking at this link Reduce the coverage area between vehicles, it has been said that changingmaxInterfDist can help.
What adjustments could I make or what would I need to understand better to make these adjustments?
Sounds like you are looking to model radio communication much more abstractly than Veins currently does: rather than calculating a receive probability (i.e., 25%) based on how well a vehicle receives a transmission (particularly when compared with sources of noise and interference), it seems you want to 100% receive anything transmitted within 50m, and definitely not receive anything further away than that. Such a simple model is currently not offered in Veins, but you can approximate it by simply discarding any information further than 50m away, for example, in your application -- or by setting the maxInterfDist of your ConnectionManager, as this defines the maximum distance at which two radios will interact (desired or undesired). See https://github.com/sommer/veins/blob/veins-4.7.1/src/veins/base/connectionManager/ConnectionManager.ned#L28 for details