Research On Congestion Control Of Internet Streaming Media Transmission

With the rapid increase of networks, users and various applications of Internet, the network congestion is becoming more and more serious. The streaming media business has special requirements in quality of service(QoS) such as bandwidth, packet loss, latency and jitter compared with traditional data business, so the reduced bandwidth, increased packet loss and jitter caused by the network congestion will seriously impact the user’s subjective feeling. Because the current Internet only supports the "best-effort" service and does not provide reliable transmission and bandwidth guarantee, so the congestion control at appropriate levels and particle size is required in order to ensure network stability and improve quality of service. After years of study on the congestion control of Internet streaming media transmission, the gratifying results have achieved, but far from being able to meet the streaming media needs of quality of service. At the same time, as the diversification of user’s needs, it will face growing challenges of wireless link environment, network heterogeneity and time-varying.At present, the wireless access network has gradually become an important part of the Internet. For the issues such as throughput and TCP-friendly reducing of cable network congestion control mechanism for streaming media caused by high bit-error characteristics of wireless links, this thesis considers the two packet loss events on the impact of congestion window size according to statistics probability characteristics of congestion and wireless packet loss, then model the TCP behavior in accordance with the congestion windows variation of TCP flow of wireless links, and obtain the long-term steady-state throughput model of wireless link for streaming media transmission. Based on this model, a unicast congestion control mechanism for streaming media of wireless access network is present, it has good throughput, TCP-friendly and smooth sending rate.In heterogeneous network environment, the steaming media transmission is more suitable way of using IP multicast. For the issues existed in multi-rate multicast congestion control such as complexity of protocol, rough granularity adjustment of sending rate, TCP-friendly which is difficult to ensure, stability, response speed and so on, this thesis presents a IP multicast multi-rate congestion control mechanism based on windows, the mechanism uses fixed rate coding for each layer according to non-integer index allocation scheme in order to take into account the granularity of layer rate adjustment and the frequency of operation of multicast’s add and left, it avoids the feedback implosion problem and complexity caused by the dynamic rate, and improves the scalability. At the same time, it adjusts congestion window and estimates rate expectations by two-stage congestion window adjustment algorithm, so obtains the stability, response speed and TCP-friendly.Internet steaming media transmission can not separated from the support of routers, the routers are direct perception of network congestion, and its congestion control performance decide the quality of service of streaming media transmission at a great extent, as an effective congestion control mechanism of router, active queue management(AQM) can provide a small packet loss, high bandwidth utilization of the bottleneck, low latency and so on. For the issues existed in active queue management of time-varying network such as stability, robustness, high packet loss rate, low bandwidth utilization and so on, this thesis proposes a rate-based active queue management mechanism for steaming media, this mechanism stabilizes the queue length and decides the sending rate of source by phase margin-based adaptive PI(proportional-integral) controller, it enhances the system stability and robustness and obtain a high bandwidth utilization and low packet loss.