Inter-Vehicle Data Dissemination in Sparse Equipped Traffic

We address the following question: How can data be disseminated in an inter-vehicle communications (IVC) network when the traffic of IVC-equipped vehicles is very sparse (e.g., one IVC-equipped vehicle every few minutes), using minimal extra-vehicular infrastructure? We present a data-dissemination scheme that uses wireless dead drops (dead letter boxes) as intermediaries between vehicles. These dead drops are simple transceivers with storage and are not connected to other dead drops, the Internet, or other networks. An important question is the placement of such dead drops. We formulate the corresponding optimization problem and prove that it is NP-hard. We present an optimal greedy approximation algorithm for solving the optimization problem. Our algorithm is based on mapping the dead-drop placement problem to the problem of computing a minimum-weight spanning sub-hypergraph