Abstract: Aimming at the problems of traditional transmission control protocol (TCP) congestion control protocol in the wired/wireless heterogeneous networks, an innovative link equivalent noise model is proposed. In this method, the background traffic of TCP link is equivalent to the additive noise. The end-to-end link bandwidth estimation methods are researched based on the equivalent noise model. An improved TCP congestion control algorithm, TCP protocol based on noise model (N-TCP), is proposed. The results of simulation and theoretical analysis show that the proposed method is valid for bandwidth estimation and therefore suitable for the application since its good compatibility to the traditional TCP protocol and characteristics of fairness for allocating bandwidth and resisting random packet loss.