To improve the capacity of initial ranging(IR)users simultaneously accessing into network and enhance the performance of the IR,a novel IR algorithm is presented for the orthogonal frequency division multiple access systems with the smart antenna.The beamforming weight vectors provided by the antenna array are introduced for the IR users,and the procedures of the multiuser parameter estimation and the interference cancellation are designed.The proposed method can improve the accuracy of the channel estimation of active paths and efficiently reduce the residual multiple access interference.Simulation results show that the proposed method has a much better performance than the available successive multiuser detection and interference cancellation algorithm and accommodates more active ranging users simultaneously accessing into a cell. To improve the capacity of initial ranging (IR) users sequentially accessing into network and enhance the performance of the IR, a novel IR algorithm is presented for the orthogonal frequency division multiple access systems with the smart antenna. Beamforming weight vectors provided by the antenna array are introduced for the IR users, and the procedures of the multiuser parameter estimation and the interference cancellation are are. the proposed method can improve the accuracy of the channel estimation of active paths and efficiently reduce the residual multiple access interference. Simulation results show that that the proposed method has a much better performance than the available previous multiuser detection and interference cancellation algorithm and accommodates more active ranging users successively accesses into a cell.