Modelling and performance optimisation of micro-Doppler effects in millimetre wave vehicular applications for 5G and beyond communications

5G communications are exploiting millimetre wave (mmWave) spectrum designed to provide a high data rate and low latency. Applications with vehicular communications are subject to many challenges due to the dynamic channel characteristics, which should be addressed whilst developing the hardware. Therefore, the need to understand the impact of motion on the communications bearer necessities unlocking the parameters causing antenna's depointing. The vibrations produced from moving on uneven roads induce a Doppler power spectrum which causes a change of the composite amplitude and phase of the antenna's radiation pattern. This will degrade the fidelity of the link and the information caring capacity. Therefore, this thesis presents several measurement methodologies to characterise a mmWave vehicular channel and unlock one more parameter that characterises a vehicular channel by investigating the reflectivity that causes phase changes and the antenna's vibration resulting from a vehicle's suspension variations and causing antenna's depointing. The unlocked parameter is the micro-Doppler shift which is not limited to applications of the Radar Cross-Section. The contributions to the design methodologies include: • Investigation of the system functions in conjunction with the condensed parameters that characterise a vehicular channel by performing novel outdoor measurements to reflect simple V2V or V2I communication channels using the 26 GHz phased array antenna at the transmitter and a horn antenna at the receiver. • Develop novel theoretical and geometrical models that reflect mmWave vehicular communication channel with vibrations to investigate the gain sensitivity and the observed micro-Doppler shift with the Doppler power spectrum considering the antennas' heights and beamwidths. • Validate the theoretical model by performing novel reflectivity measurements in the Anechoic chamber. A narrow beamwidth shows a significant impact of suspension variations rather than a wider one for a height of 5G base station for macro-cell operating at mmWave over a maximum distance the system's dynamic range could cope. A metal reflector changes the phase response and induces a micro-Doppler shift whilst it moves. Furthermore, a 2.6휆 vertical displacement due to vibration of the receiver's antenna with 17° − 23° beamwidth results in a 2 dB difference in the average amplitude of the Doppler power spectrum.