  Traditional beam tracking methods have severe performance loss under the high
mobility and narrow beam scenario. To alleviate the tracking performance
degradation, we propose an adaptive beamwidth control for millimeter wave
(mmWave) beam tracking. The particle filter is applied to the beam tracking,
and the AoA estimation error is approximated with a posterior density function
constructed by the particles. The error approximation leads to the adaptive
beamwidth control which is implemented by the partial activation of the antenna
array. Simulation results show that the proposed algorithm aids the beam
tracking to yield a smaller AoA estimation error under the high mobility
environments.
