Vehicles Receive Beacon Messages outside RSU Range

I am working on Veins framework, inside OMNET++. I set the property of RSU inside .ned file as follow:

 @display("p=150,140;b=10,10,oval;r=90");

The tkenv shows a circle around RSU, but the vehicles received beacons outside the range (circle).

How can I adjust the transmission range of RSU to the Circle?

Adding a display string tag of r is just adding a circle to the graphical output; it does not influence the simulation.

If you define the "transmission range" as the point where the probability of reception is zero, you can calculate this point based on the transmission power at the antenna and the sensitivity of the radio (both set in omnetpp.ini), as well as the used path loss and fading models (set in config.xml). If you change these parameters and models, you are changing this "transmission range".

Note, however, that this range has only little relevance to frame reception probability. Veins employs the MiXiM suite and approach to model transmissions as two-dimensional (time and frequency) functions of signal power that are modified by path loss and fading effects (both stochastic and deterministic, e.g., due to buildings). If a frame's receive power is above the sensitivity threshold, its reception probability is computed based on dividing these functions for signal, interference, and noise to derive the SINR and, from that, the bit error rate. Even at moderate interference levels, this means that most frames cannot be decoded even though they are well above the sensitivity threshold (simply because their SINR was too low).

Just to repeat: I am warning against calculating a "transmission range" for anything other than purely informational purposes. How far you can send in theory has absolutely no relation to how far you can send on a moderately busy channel. This effect is modeled in Veins!