We propose to use Vehicular ad hoc networks
(VANET) as the infrastructure for an urban cyber-physical
system for gathering up-to-date data about a city, like traffic
conditions or environmental parameters. In this context, it
is critical to design a data collection protocol that enables
retrieving the data from the vehicles in almost real-time in
an efficient way for urban scenarios.
We propose Back off-based Per-hop Forwarding (BPF), a
broadcast-based receiver-oriented protocol that uses the destination
location information to select the forwarding order
among the nodes receiving the packet. BFP does not require
nodes to exchange periodic messages with their neighbors
communicating their locations to keep a low management
message overhead. It uses geographic information about the
final destination node in the header of each data packet to
route it in a hop-by-hop basis. It takes advantage of redundant
forwarding to increase packet delivery to a destination, what is
more critical in an urban scenario than in a highway, where the
road topology does not represent a challenge for forwarding.
We evaluate the performance of the BPF protocol using ns-3
and a Manhattan grid topology and compare it with well-known
broadcast suppression techniques. Our results show that BPF
achieves significantly higher packet delivery rates at a reduced
redundancy cost.