The Research On DiffServ Model In UMTS Core Networks

It is in the period from the 2nd generation to the 3rd generation for the development of wireless communication network. The wireless communication system based on circuit exchange will become an all-IP network consisting of IP core cable and radio access network. UMTS is a main standard for the 3G. With the maturity of the radio access technology and the extension of multimedia real-time services, it has been an emphasis to research the QoS mechanism in UMTS core network for the network designers and service providers.Focusing on the realization of DiffServ model in UMTS core network,the paper introduces the Qos structure and services classification in UMTS at first. Further, IntServ and DiffServ, two Qos models based on IP provided by IETF, are researched in this paper. We consider that DiffServ is of excellent scalability without difficult signaling, which fits UMTS core networks surrounding well.The algorithm of queue management is an important component in the realizing DiffServ model. The RIO algorithm widely used at present has some problems in setting parameters and keeping stable queue size. A self-adaptive algorithm is provided to solve the delay sensitivity for the real-time applications in UMTS. It is proved by experiments that the average queue size is influenced slightly by the congestion of network and the proportion of different packets in our scheme. The algorithm can also alleviate the "bandwidth skew" phenomenon, protect the packets with high priority and improve the fairness.A QoS control model based on Diffserv is designed for the QoS requirement of different services in UMTS, and the correlative schemes of service mapping, queue scheduling, traffic conditioning are also provided. We design a new queue scheduling scheme, which can satisfy the delay requirements for conversational and stream class, and guarantee the bandwidth for interactive and background class using priority and queue dividing mechanism. The performance of the scheduling scheme is assessed by a mathematics model. At last, the validity of the model at the core of the new scheduling scheme is proved by experiments.