Characterising the Impact of Antenna Beamwidth on the Performance of Vehicle-to-Infrastructure (V2I) Millimetre Wave Communication

Autonomous vehicles require vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. Fifth-generation (5G) and beyond wireless networks enable such infrastructure through beamforming techniques at millimetre-wave (mm-wave) frequencies. This paper characterises the impact of antenna beamwidth on the Doppler shift, cross-polarisation ratio (XPR) and the channel attenuation for the 26GHz mm-wave V2I line-of-sight (LoS) channel. It is proven that the received Doppler power spectrum is proportional to the probability density function (PDF) of the Doppler Shift. This indicates that Doppler power reduces with the Doppler shift. It has also been established that a wider antenna half power beamwidth (HPBW) of 20° instead of 17° reduces the XPR by 20dB whilst increasing the channel attenuation by 10dB in a mm-wave LoS channel with dynamic blockage. Therefore, a trade-off between the XPR and channel attenuation can be introduced by employing different antenna HPBWs.