Ground to vehicles transmissions using natural propagation in tunnels

The problem of providing data communications between ground and vehicles in tunnels has received considerable attention, and it seems to be more and more important with the Spreading out of fully automated, driverless, urban transportation systems. Ground to vehicles links using natural propagation of electro-magnetic microwaves in tunnel seem to be a rather effective and inexpensive method. The deep cancellations of the microwave carrier combined with the speed program of the vehicles moving in the tunnels imply that the transmission errors arise by packets correlated with this fading. Theoretical and experimental results are given showing the relation ships between electric field attenuations and bit error rate for different kinds of directive receiving antennas.