  Driven by both safety concerns and commercial interests, vehicular ad hoc
networks (VANETs) have recently received considerable attentions. In this
paper, we address popular content distribution (PCD) in VANETs, in which one
large popular file is downloaded from a stationary roadside unit (RSU), by a
group of on-board units (OBUs) driving through an area of interest (AoI) along
a highway. Due to high speeds of vehicles and deep fadings of
vehicle-to-roadside (V2R) channels, some of the vehicles may not finish
downloading the entire file but only possess several pieces of it. To
successfully send a full copy to each OBU, we propose a cooperative approach
based on the coalition formation games, in which OBUs exchange their possessed
pieces by broadcasting to and receiving from their neighbors. Simulation
results show that our proposed approach presents a considerable performance
improvement relative to the non-cooperative approach, in which the OBUs
broadcast randomly selected pieces to their neighbors as along as the spectrum
is detected to be unoccupied.
