  Future automation and control units for advanced driver assistance systems
(ADAS) will exchange sensor and kinematic data with nearby vehicles using
wireless communication links to improve traffic safety. In this paper we
present an accurate real-time system-level simulation for multi-vehicle
communication scenarios to support the development and test of connected ADAS
systems. The physical and data-link layer are abstracted and provide the frame
error rate (FER) to a network simulator. The FER is strongly affected by the
non-stationary doubly dispersive fading process of the vehicular radio
communication channel. We use a geometry-based stochastic channel model (GSCM)
to enable a simplified but still accurate representation of the non-stationary
vehicular fading process. The propagation path parameters of the GSCM are used
to efficiently compute the time-variant condensed radio channel parameters per
stationarity region of each communication link during run-time. Five condensed
radio channel parameters mainly determine the FER forming a parameter vector:
path loss, root mean square delay spread, Doppler bandwidth, $K$-factor, and
line-of-sight Doppler shift. We measure the FER for a pre-defined set of
discrete grid points of the parameter vector using a channel emulator and a
given transmitter-receiver modem pair. The FER data is stored in a table and
looked up during run-time of the real-time system-level simulation. We validate
our methodology using empirical measurement data from a street crossing
scenarios demonstrating a close match in terms of FER between simulation and
measurement.
