| With the development of the next generation mobile communication system,low earth orbit(LEO)satellite network has become an indispensable and important part of the future mobile network.However,compared with the terrestrial network,LEO satellite network has the characteristics of long delay,high bit error and high dynamic network topology.The TCP congestion control algorithm widely used in the terrestrial network has poor performance when transmitted through LEO satellite network.Aiming at the long delay,high bit error and high dynamic network topology characteristics of LEO satellite network,this paper proposes packet loss discrimination algorithm and congestion control algorithm,hoping to improve the transmission efficiency of TCP Congestion Control Algorithm in LEO satellite network.Due to the long delay,high bit error and high dynamic network topology characteristics of LEO satellite network,the accuracy of TCP packet loss discrimination algorithm is not high,which reduces the transmission efficiency of TCP congestion control algorithm.To solve the above problems,this paper proposes a TCP shn-ld packet loss discrimination algorithm,which is composed of the following two contributions:first,based on cross layer technology,a satellite handover flag bit(SHN)is proposed.The SHN flag bit can be set by the satellite node responsible for the handover after the satellite handover occurs.After receiving the message segment with SHN flag bit information,both ends of TCP communication can perceive the handover of satellite link,And take corresponding control measures to maintain the efficient and reliabletransmission of subsequent message segments.Secondly,a packet loss discrimination algorithm based on satellite handover flag bit(shn-ld)is proposed.Considering that the estimated bottleneck queue length is greatly affected by satellite handover reroute,a packet loss discrimination decision parameter called bottleneck queue proportion deviation is designed,and the parameter is updated after satellite handover.Finally,simulation results show that shn-ld algorithm has 10%～20%improvement in packet loss discrimination accuracy compared with other packet loss discrimination algorithms,and can improve throughput performance on the premise of ensuring friendliness.LEO satellite network has the characteristics of long delay,so it is a large bandwidth delay product network.The performance of TCP cubic algorithm commonly used in large bandwidth delay product networks in LEO satellite networks is limited by high bit error and high dynamic network topology.To solve this problem,this paper proposes a cross layer TCP congestion control algorithm(cubic-shn)for LEO satellite network,which mainly has the following three contributions:first,a link sensing technology based on SHN flag bit is proposed,which enables the two ends of TCP communication to estimate the parameter difference of the link before and after satellite switching through the message segment,and then update the parameters of the old link,so as to provide conditions for subsequent efficient and reliable TCP transmission.Second,the adaptive function is added to the slow start threshold and congestion window function.During satellite switching,the TCP sender estimates the parameters of the new link through link sensing technology.The slow start threshold and congestion window function are updated according to these parameters to match the new link and maintain the efficient and reliable TCP transmission of the new link.Thirdly,combined with shn-ld packet loss discrimination algorithm,cubic-shn algorithm is proposed,and the overall process of cubic-shn algorithm is described in detail.Finally,simulation experiments show that cubic-shn algorithm has good throughput,fairness and friendliness. |
