This paper considers how to obtain the maximum sum-rates by using the orthogonal random beamforming (ORBF) technique under the constraint on the average number of feedback users in the context of facing inter-beam interference scenarios.Aiming to solve this problem

a novel ORBF algorithm based on clustering and feedback threshold is proposed.The users are divided into multiple clusters according to their SNRs.The corresponding feedback threshold in each cluster is calculated by the tool of extreme value theory.Finally

the new ORBF algorithm is constructed based on clustering and multiple thresholds.We make some theoretical analysis on the algorithm and derive the upper bound of sum-rates loss;the scaling law of multiuser diversity gain is also exhibited.Simulation results not only verify the validity of our analysis but also show that

when compared with the classical ORBF technique

the proposed algorithm can considerably reduce the feedback load with a good sum-rates performance.