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

TL;DR

This paper investigates the non-stationary characteristics of vehicular communication channels by estimating local scattering functions from measurements, analyzing delay and Doppler spreads, and revealing their bi-modal distribution in safety-critical scenarios.

Contribution

It introduces a method to estimate time-frequency-varying channel parameters from measurements and characterizes their distribution in vehicular environments.

Findings

High RMS delay spreads occur in rich scattering scenarios.

High RMS Doppler spreads are observed in drive-by scenarios.

Channel parameters follow a bi-modal Gaussian mixture distribution.

Abstract

Vehicular communication channels are characterized by a non-stationary time- and frequency-selective fading process due to rapid changes in the environment. The non-stationary 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 (WSSUS) assumption holds approximately and we are able to calculate a time and 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. 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 bi-modal Gaussian mixture distribution. High RMS delay spread values are observed in situations with rich scattering, while high RMS Doppler spreads are obtained in drive-by scenarios.