Wave propagation in tunnels for vehicle-to-vehicle (V2V) communications scenarios is characterized by multiple diffuse reflections on tunnel surfaces as well as specular reflections on other objects inside the tunnel, leading to a non-stationary fading process. Such a fading process is difficult to model by ray tracing (RT), requiring a prohibitively high computational complexity due to the large number of diffuse reflections. In this work we propose two new ideas for modeling diffuse reflections in a non-stationary scenarios: (i) We partition the non-stationary fading process into multiple stationarity regions with a given extent in time and frequency for which approximate wide-sense stationarity can be assumed; (ii) we propose a hybrid model, tightly interlinking RT with a propagation graph, such that vertices for the propagation graph are obtained from interaction points calculated by RT for each stationarity region. We compare our hybrid model with measurement data in terms of the timevariant power-delay and the Doppler-power spectral-density as well as the root-mean square delay-and Doppler-spread. This analysis shows, that our hybrid model is the first numerical simulation model that is able to model diffuse reflections inside a tunnel with correct non-stationary (i.e. time-variant) temporal correlation for a non-stationary V2V communication link.
Abstract-In the vehicular communication channels, the mobility of the receiver (RX) and the transmitter (TX) along with the movements of interacting objects in the propagation environment result in significant non-stationary channel fading. The channel impulse response exhibits not just significant delay-and Doppler spreads, but also the delay-and Doppler spreads themselves are changing over the time-and frequency axes. In other words: the channel statistics change as the geometry of RX, TX, and interacting objects evolve over time. To account for this, the local stationary regions in time and frequency are specified and each one is modeled by a distinct local scattering function. We present an architecture for a real-time emulator capable of reproducing the input/output behavior of a non-stationary n-tap wireless vehicular propagation channel. The architecture is implemented as a virtual instrument on LabView and we benchmark the packet error ratio (PER) of a commercial off the shelf (COTS) vehicular IEEE 802.11p modem. The emulator architecture aims at a hardware implementation which features optimised hardware complexity while providing the required flexibility for calculating the non-stationary channel responses by reconfiguring the scattering model for each local stationary region. The National Instrument USRP-Rio 2953R is used as the Software-Defined Radio platform for implementation, however the results and considerations reported are general-purpose and can be applied to other platforms. Finally, we discuss the PER performance of a COTS modem for a vehicular non-stationary channel model derived for highway obstructed line of sight (LOS) scenario in the DRIVEWAY'09 measurement campaign.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.