| Multipath transmission can help to overcome bandwidth bottlenecks and improve the quality of transmission by distributing load to subflows. It is an important direction of network transmission technology. Multipath transmission of realtime media is still in the primary stage and there is no available scheme at present, especially in the aspect of related transmission control mechanism. This thesis mainly studies multipath realtime transmission control mechanism and protocol. Application relay sever forwarding media data in the application layer is a typical overlay network technology based on application layer routing. Actually it reduces the threshold of multipath transmission application. Multipath realtime transmission control mechanism and protocol have important application prospect in the aspect of promoting effection of IMS media transmission and IMS service innovation.Establishment of multipath transmission environment is only the basis of multipath transmission. Performance and efficiency of multipath transmission depend more on the multipath transmission control mechanism and protocol, especially for realtime transmission. Multiple factors such as business requirements and the dynamic chages of path QoS parameters need to be considered. At the same time, packet sequence needs to be ordered. To meet the demand of QoE, transmission control mechanism needs to balance the relationship between transmission efficiency and reliability. Message of transmission protocol should be concise and efficient.The thesis summarizes the existing multipath transmission protocols combined with the characteristics of relay path and the requirements of realtime transmission. The main contents are as follows:Firstly, a method of dynamic load allocation stratrgy is proposed and related algorithm of load allocation is designed. Transmission ability of each route is comprehensively assessed according to the business characteristics and path status. By analyzing parameter of each path and predicting QoE effect, transmission weight of each path is confirmed. The load is distributed according to the weight of each path. Secondly, a method of subflow recombination mechanism based on dynamic buffer is proposed and related recombination algorithm is designed. Subflows are recombined by setting a buffer at the reveiving end. By sorting the packets received from subflows in the buffer, we can mitigate the impact of delay jitter. By monitoring the packet loss rate and delay, we can adjust the length of buffer dynamically. Thirdly, MRTCP transmission control protocol is put forward, and related messages are designed. By designing the MRTCP protocol, end-to-end multipath realtime transmission control is realized.The results of simulation and test show that the load distribution algorithm, the subflow recombination algorithm and the MRTCP message proposed in the thesis is rational and available, which could be used in multipath realtime transmission control. |
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