A smart 3GDT schema has been disclosed, in detail, a method for controlling the communication of a network system has been disclosed. The network system comprises a UE, a NodeB, a RNC, a SGSN, and a GW. The UE is arranged to be in communication with the RNC via the NodeB, and the RNC is arranged to be in communication with the SGSN which in turn being arranged to be in communication with the GW for non-3GDT communication of the network system, or the RNC is arranged to be in communication with the GW for 3GDT communication of the network system. In this method, statistics of payload transferred between the UE and the GW has been monitored, and if the statistics of payload within a predetermined time period exceeds a first threshold, and the UE is in the non-3GDT communication, then switching the non-3GDT communication to the 3GDT communication. The present application has also disclosed the SGSN, GW, and the network system adaptive to perform the method.