Research On Real-Time Control Algorithm Of Multimedia Stream Based On DCCP

The transmission of real-time multimedia stream not only need to solve the traditional Internet inherent network congestion problem,but also need to meet its real-time requirements.Therefore,solving the problem of real-time multimedia stream transmission has a high theoretical significance and engineering practice significance.Based on the research of multimedia streaming theory and network congestion control,Firstly,the mathematical model of TCP/AQM system is researched,and an H-infinite PI control algorithm based on TCP/AQM system model is proposed.Secondly,a proportional controller based on TCP-like window is proposed in the TCP-like congestion control mechanism.Finally,in order to realize the real-time transmission of multimedia streaming,a real-time control algorithm of TCP-like window based on Calman filter is proposed.The main work is as follows:(1)In order to improve the robust stability of AQM algorithm in a dynamic network environment,applying H-infinity control to TCP/AQM system model to improve AQM algorithm.Based on the dynamic TCP network model in classical fluid theory,and after mathematical derivation,the TCP/AQM closed-loop transfer function is obtained,and the H-infinity PI mathematical model of controller is established.The TCP/AQM system model is transformed into a controlled object that can be manipulated by the H-infinity PI controller using Pade approximation.After obtaining the PI controller with H-infinity performance,the parameters of the PI controller are adjusted by using the linear matrix inequality method.The simulation results show that the algorithm with better stability and network efficiency.(2)In order to realize the real-time perception of the source network status,a TCP-like window model based on proportional controller is proposed,which can adjusts the window size in real time by calculating the round trip delay(RTT)and the length of the buffer queue.Firstly,a network model of a single bottleneck link with n DCCP connections is proposed,and the instantaneous buffer queue length q in the bottleneck router is calculated in time v,and the obtained queue length q is used as the input variable with the feedback factor ki to construct the transmission rate proportional controller.Secondly,the TCP-like window size is calculated by RTT and the transmission rate proportional controller.The mathematical analysis verifies that the proposed window model can guarantee the stability and fairness of the system.(3)In order to meet the real-time requirements of multimedia streaming,a new TCP-like window model is proposed.Firstly,the Calman filter algorithm is used to approximate the TCP-like window based on the proportional controller.Then,The initial state value of the window xk is obtained by the TCP window model,combine xk and the predicted value xk of the previous time to obtain the estimated error covariance Pk+1.Finally,the real-time control of multimedia streaming is achieved by predicting-correcting the values of TCP-like window.The simulation results show that the proposed algorithm has better real-time stability than traditional TFRC mechanism.