Evaluation of stationarity regions in measured non-WSSUS 60 GHz mmWave V2V channels

TL;DR

This paper investigates the stationarity regions of measured 60 GHz V2V channels, revealing how LOS and NLOS conditions affect the size of these regions in time and frequency, with implications for channel modeling.

Contribution

It introduces a method to estimate local scattering functions and define stationarity regions in measured V2V mmWave channels, comparing LOS and NLOS scenarios.

Findings

Large stationarity regions for LOS channels with no relative movement.

NLOS channels dominated by specular reflections have a stationarity bandwidth of 270 MHz.

NLOS channels with rich multipath have shorter stationarity times around 5 ms.

Abstract

Due to high mobility in multipath propagation environments, vehicle-to-vehicle (V2V) channels are generally time and frequency variant. Therefore, the criteria for wide-sense stationarity (WSS) and uncorrelated scattering (US) are just satisfied over very limited intervals in the time and frequency domains, respectively. We test the validity of these criteria in measured vehicular 60 GHz millimeter wave (mmWave) channels, by estimating the local scattering functions (LSFs) from the measured data. Based on the variation of the LSFs, we define time-frequency stationarity regions, over which the WSSUS assumption is assumed to be fulfilled approximately. We analyze and compare both line-of-sight (LOS) and non-LOS (NLOS) V2V communication conditions. We observe large stationarity regions for channels with a dominant LOS connection, without relative movement between the transmitting and receiving vehicle. In the same measured urban driving scenario, modified by eliminating the LOS component in the post-processing, the channel is dominated by specular components reflected from an overpassing vehicle with a relative velocity of 56 km/h. Here, we observe a stationarity bandwidth of 270 MHz. Furthermore, the NLOS channel, dominated by a single strong specular component, shows a relatively large average stationarity time of 16 ms, while the stationarity time for the channel with a rich multipath profile is much shorter, in the order of 5 ms.