Comparison of Ray Tracing and Channel-Sounder Measurements for Vehicular Communications

This paper presents the results of an accuracy study of a deterministic channel model for vehicle-to-vehicle (V2V) communications. Channel simulations obtained from the ray-tracing model developed by TU Braunschweig are compared to data gathered during the DRIVEWAY V2V channel measurement campaign at 5.6 GHz in the city of Lund in summer 2009. The analysis focuses on PDP and channel gains in an urban four-way intersection scenario. Despite of some implementation-based limitations of the ray-tracing model, a very good agreement between simulation and measurement results is achieved. Most relevant power contributions arising from multiple-bounce specular reflections as well as single-bounce non-specular reflections are captured by the deterministic model. We also discuss the question to what extent roadside obstacles like traffic signs, parked cars or lamp posts have to be considered when characterizing the V2V channel

Delay and Doppler Spreads of Non-Stationary Vehicular Channels for Safety Relevant Scenarios

Abstract in UndeterminedVehicular communication channels are characterized by a nonstationary time-frequency-selective fading process due to rapid changes in the environment. The nonstationary fading process can be characterized by assuming local stationarity for a region with finite extent in time and frequency. For this finite region, the wide-sense stationarity and uncorrelated scattering assumption approximately holds, and we are able to calculate a time-frequency-dependent local scattering function (LSF). In this paper, we estimate the LSF from a large set of measurements collected in the DRIVEWAY'09 measurement campaign, which focuses on scenarios for intelligent transportation systems (ITSs). We then obtain the time-frequency-varying power delay profile (PDP) and the time-frequency-varying Doppler power spectral density (DSD) from the LSF. Based on the PDP and the DSD, we analyze the time-frequency-varying root-mean-square (RMS) delay spread and the RMS Doppler spread. We show that the distribution of these channel parameters follows a bimodal Gaussian mixture distribution. High RMS delay spread values are observed in situations with rich scattering, whereas high RMS Doppler spreads are obtained in drive-by scenarios

Measurements Based Channel Characterization for Vehicle-to-Vehicle Communications at Merging Lanes on Highway

This paper presents results for vehicle-to-vehicle channel characterization based on measurements conducted for the merging lane scenarios on a highway. We present power delay profiles as well as channel gains and analyze important propagation mechanisms to see the impact of line-of-sight (LOS) and the antenna radiation pattern on the total received power. It is found that the absence of LOS and strong scattering objects, close to the point where the ramp merges with a highway, may result in poor received signal strength. The probability of dropping packets also increases where there is LOS between TX and RX but the antenna pattern is not omni-directional. A dip in the antenna pattern affects the received signal strength severely which poses a challenge for vehicle-to-vehicle communication in safety critical situations

Directional Analysis of Vehicle-to-Vehicle Propagation in Different Traffic Environments

This paper presents a double directional analysis of vehicle-to-vehicle channel measurements conducted in two different traffic environments. Using a high-resolution algorithm, we derive channel parameters like angle-of- arrival, angle-of-departure, propagation delay and Doppler’s spread and identify underlying propagation mechanisms by combining these estimates with maps of the measurement sites. The results show that single-bounce interaction with static objects is the dominating effect in the absence of line-of-sight, and that the contribution from other vehicles is small. We also find that in the absence of line-of-sight the direction spread at both sides of link is large which indicates possible diversity gain using multi-antenna arrangements