Analytic throughput model for TCP-NC

Network coding improves TCP's performance in lossy wireless networks. However, the complex congestion window evolution of network coded TCP (TCP-NC) makes the analysis of end-to-end throughput challenging. This paper analyzes the evolutionary process of TCP-NC against lossy links. An analytic model is established by applying a two-dimensional Markov chain. With maximum window size, end-to-end erasure rate and redundancy parameter as input parameters, the analytic model can reflect window evolution and calculate end-to-end throughput of TCP-NC precisely. The key point of our model is the novel definition for the states of Markov chain. It substantially reduces related states and much lower complexity is obtained. Our work helps understand the factors that affect TCP-NC's performance and lay the foundation of optimization. Extensive simulations on NS2 show that the analytic model features fairly high accuracy.