Matthias Wildemeersch

Erik Steinmetz, Matthias Wildemeersch, Tony Q. S. Quek et al.

Vehicular networks allow vehicles to share information and are expected to be an integral part in future intelligent transportation system (ITS). In order to guide and validate the design process, analytical expressions of key performance metrics such as packet reception probabilities and throughput are necessary, in particular for accident-prone scenarios such as intersections. In this paper, we analyze the impact of interference in an intersection scenario with two perpendicular roads using tools from stochastic geometry. We present a general procedure to analytically determine the packet reception probability and throughput of a selected link, taking into account the geographical clustering of vehicles close to the intersection. We consider both Aloha and CSMA MAC protocols, and show how the procedure can be used to model different propagation environments of practical relevance. We show how different path loss functions and fading distributions can be incorporated in the analysis to model propagation conditions typical to both rural and urban intersections. Our results indicate that the procedure is general and flexible to deal with a variety of scenarios. Thus, it can serve as a useful design tool for communication system engineers, complementing simulations and experiments, to obtain quick insights into the network performance.

Wai Hong Ronald Chan, Matthias Wildemeersch, Tony Q. S. Quek

Diffusion processes are instrumental to describe the movement of a continuous quantity in a generic network of interacting agents. Here, we present a probabilistic framework for diffusion in networks and propose to classify agent interactions according to two protocols where the total network quantity is conserved or variable. For both protocols, our focus is on asymmetric interactions between agents involving directed graphs. Specifically, we define how the dynamics of conservative and non-conservative networks relate to the weighted in-degree Laplacian and the weighted out-degree Laplacian. Our framework allows the addition and subtraction of the considered quantity to and from a set of nodes. This enables the modeling of stubborn agents with time-invariant quantities, and the process of dynamic learning. We highlight several stability and convergence characteristics of our framework, and define the conditions under which asymptotic convergence is guaranteed when the network topology is variable. In addition, we indicate how our framework accommodates external network control and targeted network design. We show how network diffusion can be externally manipulated by applying time-varying input functions at individual nodes. Desirable network structures can also be constructed by adjusting the dominant diffusion modes. To this purpose, we propose a Markov decision process that learns these network adjustments through a reinforcement learning algorithm, suitable for large networks. The presented network control and design schemes enable flow modifications that allow the alteration of the dynamic and stationary behavior of the network in conservative and non-conservative networks.