针对车地传输TCP协议优化的TTI-RTT拥塞控制算法

TTI-RTT Congestion Control Algorithm Optimized for Train-Ground Transmission TCP Protocol

为适应铁路5G专用移动通信系统动态易变的网络环境,解决现有算法中存在的吞吐量减少、传输时延增加、检测数据车地传输可靠性难以保证的问题,在分析传输控制协议(TCP)传输拥塞控制过程,以及对比TCP-Reno,TCP-Vegas和TCP-Westwood 3种基础拥塞控制算法存在问题的基础上,提出一种联合传输时间间隔(TTI)和往返时延(RTT)的拥塞控制算法——TTI-RTT算法,即将RTT的成对比较测试统计量和网络当前拥塞因子联合起来作为网络拥塞判断标准,根据反映网络拥塞程度的拥塞因子动态调节加性和乘性因子,并在传输控制协议拥塞控制的不同条件下灵活调整传输时间间隔。采用NS-3仿真软件,构建考虑高速铁路5G-R无线信道误码影响的点对点通信网络拓扑结构,对TTI-RTT拥塞控制算法进行仿真验证,并与3种基础算法进行性能比较。结果表明:不同丢包率下所提算法的平均吞吐量均保持在9 Mb·s^(-1)以上,较基础算法中吞吐量最高且最稳定的TCP-Reno算法增加了约5.9%,且实时吞吐量稳定性具有显著改善。

To adapt to the dynamic and variable network environment of the 5th Generation Mobile Communication System-Railway,and to address issues such as decreased throughput,increased transmission delay,and difficulty in ensuring the reliability of detection data transmission between train and ground,this paper analyzes the transmission control protocol(TCP)congestion control process and compares the existing problems with three basic congestion control algorithms:TCP-Reno,TCP-Vegas,and TCP-Westwood.Based on this analysis,a congestion control algorithm that combines transmission time interval(TTI)and round-trip time(RTT)called the TTI-RTT algorithm is proposed.This algorithm calculates the test statistic for pairwise comparison and the current network congestion factor based on the RTT measurement value,using both as a criterion for judging network congestion.It dynamically adjusts the additive and multiplicative factors based on the congestion factor reflecting the degree of network congestion.Additionally,the transmission time interval is flexibly adjusted during different conditions of congestion control.Using the NS-3 simulation software,a point-to-point communication network topology is constructed considering the error code impact of high-speed railway 5G-R wireless channel,the TTI-RTT congestion control algorithm is validated through simulation and compared with the three basic algorithms in terms of performance.The results show that under different packet loss rates,the average throughput of the proposed algorithm remains above 9 Mb·s^(-1),which is an increase of about 5.9%over the highest and most stable throughput of the basic TCP-Reno algorithm,with significant improvements in real-time throughput stability.