TCP performance in wireless networks with delay spike and different initial congestion window sizes

Previous research indicates that increasing the initial congestion window size in transmission control protocol (TCP) from one segment to roughly 4 KB can significantly improve its performance for file transfers that are small compared to the link bandwidth-delay product in wireless cellular networks. However, these networks are also likely to experience delay spikes exceeding the typical round-trip-time (RTT) figures, which can cause spurious timeouts that lead to unnecessary retransmissions and reduction of the TCP sender's transmission rate. Consequently, additional unnecessary retransmissions are needed for a large initial congestion window and thus the throughput of the TCP is degraded. This paper presents the research results on using large initial windows over wireless cellular networks. It has been shown that the throughput of TCP connection over a single bottleneck link with first-in-first-out (FIFO) transmission is degraded with enlarging initial window in the presence of delay spikes. Furthermore, TCP throughput performance is kept unchanged in the simple network topology when there is no burst delay. All these findings should be considered while setting up initial congestion window.