cooja_transmission_model.txt

from the sender's point of view. the tx range is the range in which the
transmitted packet can be received correctly by any node within this range.
while the interference range, is the range in which the transmission can be
heard but the transmitted packet cannot be received correctly. outside of
these two ranges, the packet can not be heard.

tx and rx ratios are just random variables that are added to the sending or
reception of a packet to allow the simulation of random errors in tx or rx
respectively.

a collision will be sensed if a node tries to transmit while it lies in the
tx or int range of a node that is sending at the same time.
if you are using csma, the packet will be retransmitted after a random
back-off time. if not, then the packet will be dropped.