An Improved TCP with Cross-layer Congestion Notification over Wired/Wireless Hybrid Networks

Different from wired networks, TCP over wireless networks needs to be cross-layer designed which depends on information of MAC. However, it is difficult to apply existing cross-layer design into hybrid networks. Based on researches of congestion metrics from MAC layer over wireless networks, this paper proposes an cross-layer ECN scheme that TCP sender will trigger congestion control by ECN if RTS count in its receiving packet exceeds a given thresh. This cross-layer design is an efficient enhancement to congestion control based on ECN, by which forms a model coupling existing TCP over wired/wirelessnetworks. To verify this new TCP model, WLAN including multi TCP flow and multi-hop wireless/wired hybrid networks are designed in NS2. Simulation results show that it can improve network performance and can be easily extended to other TCP variants.