Abstract The switched beam antenna is analyzed and its model in system level is presented. Based on analyzing the impact of multi-user detection (MUD) and switched beam antenna on the uplink capacity in TDD-CDMA systems, a novel uplink admission control algorithm is proposed. The theoretical and simulation results show that MUD and the number of antenna element have a great impact on uplink performance. The proposed scheme can provide higher gain for TDD-CDMA if the proper noise rise threshold is set.