Beam Tracking Based on Variable Step Beam for Millimeter Wave Massive MIMO

In this letter, a beam tracking scheme based on variable step beam (VSB) is proposed for millimeter wave (mmWave) massive MIMO. Firstly, a design method for VSB is proposed, where a small portion of the beam energy is taken to track the movement of user equipment (UE) and the large portion of the beam energy is used to keep the quality of current mmWave communication link. Then based on the beam sweeping using VSBs, the angle-of-departure (AoD) of the UE is estimated by iteratively updating the posterior probability together with the range prediction of the fading coefficient of the mmWave channel, where the mainlobe of the VSBs is iteratively updated by Gaussian process regression to cover the movement of the UE. Simulation results verify the effectiveness of the proposed scheme and show that it has larger achievable rate than the existing schemes.