| Along with the continuous development of mobile Internet, the civil aviationonboard Internet accessing appears. At present, the civil aviation aircraft access Internetin two ways: one is through the earth base-station directly connected to the groundnetwork(ground-to-air network); the other is through synchronous satellite connected toground network when aircraft flying across the ocean and the polar(satellite relayingnetwork). Due to the fact that civil aviation mobile communication network hascharacteristics of large delay jitter, high packet loss rate and large delay in satellitesubnetwork, the performance of TCP in this network is very low, which affect thedevelopment of onboard Internet and the experience of users.In this paper, the civil aviation mobile communication network is considered as asubnet of Internet, and do research according to the characteristics of satellite relayingsubnet and ground-to-air subnet, at last, one solution called TCP Hybrid-Hybla is putforward, which is good at fairness and adaptability, and solved the network transmissionproblem brought by the heterogeneous network and mobile aircraft, then thetransmission efficiency of TCP in aviation mobile network is improved. The mainworks are as follows:①According to the characteristics of satellite relaying subnet and ground-to-airsubnet and the link switch between these networks, one delay-based link switchjudgment method is proposed, then sender adjust congestion control strategy by thisnetwork type judgment method；②When aircraft communication link is switched to different network, someimportant TCP parameters(timeout threshold RTO, receiving window size) aresuggested to be adjusted self-adaptively, which can avoid the TCP performance problemby fault timeout and maximum window limitation;③In order to solve the problem of serious packet loss caused by the fastexponential growth during slow start phase in long delay network, the adaptive slowstart exit mechanism is put forward to avoid this serious network congestion, by thismechanism the network robustness is enhanced;④Due to the serious packet loss under satellite link and sometimes under wirelesslink, the timestamp-based available bandwidth estimation algorithm (TABE) isintroduced to solve this problem and achieve the goal of fast recovery, but TABE has one problem that it is too conservative in congestion backoff, to solve this problem theTABE parameter decaying mechanism is proposed, which can achieve the balance ofimproving transmission rate and avoiding congestion, and enhance the practicability andrationality of the algorithm.Through the OPNET simulation platform, the performance characteristics andpractical problem of TCH Hybla is simulated, and the performance of TCP Hybla andTCP Hybrid-Hybla is simulated contrastively. The experiment in aviation mobilenetwork scenario has shown that the throughput performance of TCP Hybrid-Hyblaincreased about32%on the base of TCP Hybla, and increased about61%on the base ofTCP Reno. |
