Real-time vehicular channel emulator for future conformance tests of wireless ITS modems

Abstract

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.

Performance modelling and analysis for vehicle‐to‐anything connectivity in representative high‐interference channels

“…For evaluating single links and small networks, measurement campaigns are often conducted [8][9][10][11]. If this is not possible, emulation solutions are used instead [12][13][14]. These solutions, however, only evaluate small networks or single links.…”

Real‐Time Emulation of Nonstationary Channels in Safety‐Relevant Vehicular Scenarios

“…In our previous work in [17], we presented a general systematic approach to emulation of a geometry-based stochastic channel model. This structure or its subsets can serve as a platform for other classes of channel models, such as stochastic models and models formed by recorded impulse response.…”

“…For instance one cluster could represent different points of a single moving object which obviously exhibit similar delay and Doppler spreads. This model was used in [17] for benchmarking the set of commercial modems in V2V scenario on highway with obstructed line of sight.…”

IEEE 802.11p Performance for Vehicle-to-Anything Connectivity in Urban Interference Channels

“…Using the map data, we can show that around the point of most interference, there are no largescale obstructions, as it is surrounded by water on one side, and a large field on the other, and therefore we neglect the corresponding terms by setting X σ 2 and ζ to 0. We account for small-scale fading using a tapped-delay line based channel emulator [16], hence we use the delay line fading model which results in the time-variant impulse response where the parameters are set according to [17]. Specifically, we use a channel model defined for IEEE 802.11p, which uses 4 taps, and asymmetric half-bathtub shaped Doppler spectra.…”