The proposed core network for the third-generation (3G) mobile telecommunication has the all IP architecture that IP protocol is used for transporting all user data and signaling traffic within the network. While this architecture can bring many benefits (e.g. providing various IP-based multi-media services), it is also noted that the QoS problems still exist since it provides the multi-media services using ordinary IP packets and routing. Especially, for the operator, it is necessary to manage the network resources and capabilities according to their business requirements. As a solution for this problem, the policy-based network management (PBNM) would be suggested by 3GPP. In this paper, we obtain the comparative performance results of specific cases of the network with the policy-based QoS management and with the existing QoS mechanism through ns-2 simulation. Simulation results show that the proposed PBNM architecture can guarantee the required quality of service to meet the business requirements better.