In this paper, the prediction of received power in the out-of-zone of a dedicated short range communications (DSRC) system operating inside a typical arched highway tunnel is discussed. By conducting wideband directional channel sounding inside the tunnel, the gain, angle-of-arrival and delay of each propagation path are estimated by means of a multidimensional maximum likelihood estimation algorithm from the measured data. Using these estimated parameters and by employing simulations of application antennas according to the DSRC standard, the received power in the out-of-zone is predicted for 2 roadside unit (RSU) antenna positions. The dominant scatterers causing the over-reach of radiated power to the out-of- zone were identified and attributed to the ground and sidewalk. These scatterers can affect the received power level in the out- of-zone by as much as 10 dB. It can therefore be concluded that suppressing ground and sidewalk scatterings in the vicinity of RSU by installing composite pavement materials are needed to increase the electromagnetic absorption in order to guarantee DSRC services.

To analyze the radio propagation channel inside a tunnel, a wideband directional measurement campaign was managed inside an arched tunnel which was constructed to be used for a highway. Using a wideband channel sounder equipped with a cylindrical dual polarized array at the receiver (Rx), the spatio-temporal characteristics of the received propagation paths could be estimated by means of a super-resolution estimation algorithm. The dominant scatterers are classified into 5 classes based on the structure of the tunnel as follows: ceiling, light-frames, walls, sidewalk or ground. The power contribution and cross polarization ratio for different Rx positions along the tunnel are compared