Congestion exposure enabled TCP with network coding for hybrid wired-wireless network

TCP with network coding (TCP/NC) makes the packet loss, which is caused by wireless transmission error, have no effect on congestion control. Current proposals prefer to use delay-based congestion control aspect(congestion avoidance phase) of TCP Vegas to deal with the congestion problem of TCP/NC. However, it is oversimplified and may lead to unfairness when both TCP flow and TCP/NC flow coexist in the congested wired bottleneck link in hybrid wired-wireless network. In this paper, congestion exposure enabled TCP/NC, named CEE-TCP/NC, is proposed to make TCP/NC be friendlier to TCP protocols in the case of congestion. CEE-TCP/NC replaces TCP´s loss-based congestion indicator with a method based on analyzing gaps in the ACK stream that arrive at the TCP sender. Further, different levels of congestion can be detected and actions against congestion are taken accordingly. By theoretic analysis and simulation, we show that the scheme not only inherits the advantage of network coding to eliminate the effect of wireless transmission error, but also avoids damaging the performance of other competing flows.