Analysis and Modeling of Dsrc Service Over-reach inside an Arched Transportation Tunnel

The prediction of received power in the adjacent zone of a Dedicated Short Range Communications (DSRC) system operating inside an arched transportation tunnel is discussed. Wideband directional channel sounding was conducted inside the tunnel, and the gain, angleof-arrival and delay of each propagation path were estimated from the measured data. By simulating application antennas according to the DSRC standard, the received power was predicted for 2 road-side unit antenna positions. The dominant scatterers causing the overreach of radiated power to the adjacent zone were identified and attributed to the ground and sidewalk. The effect of these scatterers were modeled using their scattering losses. INTRODUCTION Dedicated Short Range Communications (DSRC) is a short to medium range communication service intended to improve public safety on the road and also to exchange high speed duplex data between road-side units (RSU) and onboard units (OBU) installed inside vehicles [1]. DSRC applications for intervehicular communications include highway cooperative collision avoidance whereas vehicle-roadside applications include automatic equipment identification and electronic toll collection (ETC) [2], among others. Simultaneous to the development of more components [3] and complex applications for DSRC, the reliability of the system has to be assessed as well [4]-[5]. Specifically, to analyze the DSRC service zone, the radio channel of the deployment scenario has to be characterized. Among applications of DSRC is the so called location awareness or verification service which can be used in collision avoidance systems as well as security applications [6]. To deploy such services, it is required to limit the radiated power in the service zone to prevent undesired communication by over-reach of the radiated power to the adjacent zone. Inside transportation tunnels, the implementation of such application becomes an even more demanding task. This is because the propagation of radio waves inside tunnels are confined in the tunnel space which can increase the received power in the adjacent zone.