Mechanism And Protocol Of Real-time Media Transmission Path QoS Estimation For IMS Overlay Networks

IP Multimedia Subsystem, IMS for short, introduced by3GPP in Release5at first, is a multimedia communication system, which is most likely to become the architecture of next generation telecommunication technology. The transmission technology in carrying network lags behind the need of service network development, which has become a serious constraint of application development and service innovation. In IMS overlay networks, real-time multi-path transmission which is mostly built based on the application-layer routing theorem, is a kind of upgrading method of IMS media transmission technology. Since path selection and switching will be done according to the path Quality of Service (QoS for short), how to measure and estimate the QoS has become a significant issue, which is mostly analyzed in the thesis.In single-path transmission, the elements of QoS (delay, delay jitter, bandwidth, packet loss, etc) could be estimated using RTCP in a statistical method. However, there are no available methods which could be used in multi-path real-time QoS estimation. Four significant unsettled issues about multi-path real-time QoS estimation are mainly analyzed in the thesis:how to describe the transmission path, how to describe the state of relaying nodes, how to estimate QoS dynamically, how to make an overall estimation of different QoS elements. Firstly, two methods which could be used in path description are proposed: description using nodes, description using subflow. Description using subflow is better than description using nodes. Secondly, a method which could be used in node-state description is proposed, and solutions according to different path description methods are proposed. Thirdly, a dynamical QoS estimation mechanism is proposed based on statistical method to report instantly when QoS changes. In IMS overlay networks, using "hot-backup" paths to transmit QoS estimation reports is also within the scope of dynamical QoS estimation, which makes the QoS estimation more robust, which also helps "hot-backup" paths keeping alive. Finally, the method how to make an overall estimation of QoS elements is proposed, according to which the QoS of paths could simply be determined. RTCP-E (Enhanced RTCP) is then proposed as a reference implementation of the content above.The results of simulation&test show that the solution proposed in the thesis is rational and available, which could be used in multi-path real-time QoS estimation.