For finite number of users, the performance degradation occurs due to multiuser interference in conventional scheme. To improve the system performance, orthonormal beam set selection using Q mini-time slots is considered in this thesis. Among the Q sets of orthonormal random beams, the best one is selected and then data are transmitted using these random beams. We determine the number of mini-time slots by optimizing the trade-off between the selection diversity gain and reduction of data time slot. We also analyze the throughput of the proposed scheme. Simulation results show that the proposed scheme improves the throughput performance and the optimum number of Q is two.