  We investigate the evolution of line of sight (LOS) blockage over both time
and space for vehicle-to-vehicle (V2V) channels. Using realistic vehicular
mobility and building and foliage locations from maps, we first perform LOS
blockage analysis to extract LOS probabilities in real cities and on highways
for varying vehicular densities. Next, to model the time evolution of LOS
blockage for V2V links, we employ a three-state discrete-time Markov chain
comprised of the following states: i) LOS; ii) non-LOS due to static objects
(e.g., buildings, trees, etc.); and iii) non-LOS due to mobile objects
(vehicles). We obtain state transition probabilities based on the evolution of
LOS blockage. Finally, we perform curve fitting and obtain a set of
distance-dependent equations for both LOS and transition probabilities. These
equations can be used to generate time-evolved V2V channel realizations for
representative urban and highway environments. Our results can be used to
perform highly efficient and accurate simulations without the need to employ
complex geometry-based models for link evolution.
