Effect of vehicle mobility on connectivity of vehicular ad hoc networks

Connectivity is a fundamental requirement in the planning, design and evaluation of vehicular ad hoc networks (VANET). In this paper, we propose a new equivalent speed parameter and develop an analytical model to explain the effect of vehicle mobility on the connectivity of highway segments in a VANET. We prove that the equivalent speed is different from the average vehicle speed and it decreases as the standard deviation of the vehicle speed increases. Using the equivalent speed we derive a novel analytical expression for the average number of vehicles on a highway segment, which allows us to accurately predict the network 1-connectivity. We verify the correctness of our analytical approach by comparing the numerical results with simulations. The results show that increasing the average vehicle speed increases the equivalent speed, which leads to a decrease in the average number of vehicles on a highway segment and consequently degrades connectivity. On the other hand increasing the standard deviation of the vehicle speed decreases the equivalent speed, which leads to an increase in the average number of vehicles on a highway segment and consequently improves connectivity. The results also show that vehicles in a VANET can adaptively choose their transmission range to ensure network connectivity in highway segments while minimising power consumption.