In micro-cell and micromicro-cell environment for 3G mobile communication, the probability of call handover dropping due to mobile users or congestion of new calls becomes an important parameter that determines the QoS of the system. 在第三代系统环境的微小区和微微小区中,用户的移动造成交换通话掉话的概率和新建通话被拥塞概率是决定系统QoS的重要参数。