中文摘要：

由于网络的时变性和异构性，流媒体系统往往不能很好地适应网络带宽的变化。为此，结合Darwin streaming server（DSS）的源代码对其拥塞控制方法进行分析，同时运用TCP Westwood（TCPW）的带宽估计算法来改进DSS的拥塞控制策略，并搭建了实际的视频流传输系统对该策略进行验证。实验结果表明，改进后的拥塞控制策略不仅能有效地提高接收端的视频质量，而且带宽利用率也有明显的提高。

英文摘要：

Due to time-variable and heterogeneous network, streaming media system always can not adapt to the network bandwidth well. Based on analyzing the strategy of congestion control of Darwin Streaming Server, using TCP Westwood to estimate the bandwidth, an improved congestion control strategy is proposed in this paper and validated in a real-time video transport system. Experimental result shows that the improved strategy not only improves the video quality in the receiver, but also improves the bandwidth utility.