| The transmission control mechanism of infrastructure-based vehicular networks has some special characteristics and transmission problems, besides the inherent problems of standard TCP in wireless links. For instance, TCP incorrectly adjusts congestion window when a message segment is lost due to transmission error. On one hand, with high speed moving, vehicles are so easily to move out of the communication range, so that communication link is short-lived; On the other hand, there are some asymmetry problems between wired and wireless links, such as limited bandwidth and transmission range, which lead to poor transmission performance. Therefore, improving the performance of end-to-end transmission in infrastructure-based vehicular network has become a hot research topic in this field.Based on the special network environment and application background, a Bottleneck Node based Transmission Control Protocol (BNTCP) is proposed. It aims to improving the end-to-end data throughput, avoiding congestion in bottleneck node and maintaining the fairness among data flows. At the sender, a congestion control mechanism with the packet-lost cause distinguishing based on the feedback information of bottleneck node and a flow control mechanism based on bottleneck link bandwidth are proposed. BNTCP solves the low bandwidth utilization problem caused by blindly reducing congestion window behavior in standard TCP, and it can avoid the oscillation of sending rate. Meanwhile, because of the short duration of communication in infrastructure-based vehicular network, BNTCP chooses to conduct data transmission with ideal transmission speed as soon as the connection is established instead of activating slow start algorithm.Experimental results show that BNTCP can provide better performance in infrastructure-based vehicular network than TCP Reno and TCP Westwood with less packet-lost rate, lower transmission delay, smaller delay jitter amplitude and higher throughput. |
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