Impact of Big Vehicle Shadowing on Vehicle-to-Vehicle Communications

Vehicle to vehicle (V2V) communications using dedicated short-range communications (DSRC) are considered a promising technology for enhancing road safety. However, in V2V communications, passenger cars suffer from obstruction of bigger vehicles such as buses or trucks. Based on our measurement, a big vehicle can cause a signal loss from 10 to 15 dB due to shadowing. This results in a shorter communication range and reduces the safety message dissemination capability. In this paper, we analyze the impact of shadowing caused by multiple big vehicles on the V2V communication of passenger cars. We propose a model that takes into account both geometric and stochastic shadowing of multiple big vehicles. In order to cope with the physical size of vehicles and safety distance between them in the real world, we propose to use a repulsive point process called hardcore repulsive Poisson point process (PPP) to model the locations of vehicles. Generating procedure and some basic properties of this process are introduced. Based on the proposed model, we derive the average length of the shadow region and the shadowing loss caused by multiple big vehicles. We show that when the number of big vehicles increases from 10% to 80% of total vehicles in one lane, the shadow region increases from 50 m to 450 m on the road. Furthermore, the shadowing loss causes the relative number of cars within communication range of a typical car to reduce from 90% to between 15% and 50%, depending on whether the big vehicles are in the same or the adjacent lane of the consider car. We analyse the packet collision probability while taking into consideration the big vehicle shadow region and observe significant packet collisions without dedicated bus lanes.