Characterising Vehicle Suspension Variations in Millimetre Wave V2I System

This paper investigates the effects of antenna vibration occurring due to suspension variation during the movement for vehicle-to-infrastructure (V2I) communication by developing a two dimensional (2D) model. With highly directional antennas fitted on a car's rear bumper and at a base station (BS), different beamwidths from 10° to 50° are investigated for a moving vehicle at 70mph. The gain sensitivity of the radiation pattern and the micro-Doppler shift are modelled for suspension variations between 5cm and 20cm. The analysis has been performed based on the observed angle of arrivals (AoA) at the receiver antenna in the elevation plane. The gain sensitivity represents the BSs’ main lobes' misalignments and receiver antennas’ radiation patterns at 26GHz. The results reveal a significant impact on gain sensitivity during the first 200m of movement away from the BS. Furthermore, the total Doppler shift increases due to the micro-Doppler with vertical displacements from the suspension variation. However, this can be mitigated if the beamwidth increases relative to the link budget or the BS height increases. The 2D model is validated by utilising accelerometer data recorded whilst the vehicle is moving at 70mph on a motorway, by extracting the displacements and computing the gain sensitivity.