Random Beamforming (RBF) is considered one of the most promising beamforming techniques especially for Massive MIMO mmWave systems. It has been proven to achieve optimal sumrate capacity for downlink MIMO systems for many applications. In this paper, the RBF is implemented in a mmWave MIMO systems with mobile users and the effect of this mobility is studied. Beside that, some parameters of the system have been optimized for different realistic scenarios. The mathematical derivation of the system model and the simulation using some practical values have been conducted. The resulted degradation in system throughput as a consequence of beamforming outage that results from users mobility is calculated. Many factors that affect the system throughput were considered in the derivation. The second part of the paper is going a further step in optimizing the network parameters for different operation scenarios. These parameters include the frame duration and beam width. Taking in consideration that the outage probability is a Convex optimization problem, the optimal values of these parameters were derived. for the walking and running users cases.