Performance of TCP in Intermittently Connected Wireless Networks: Analysis and Improvement

Intermittently Connected Wireless Networks (ICWN) or Delay/Disruption Tolerant Networks (DTN), have attracted attention from researchers because of their inherent characteristics, including long latency, low data rate, and intermittent connectivity. Extensive research has been conducted on ICWN, including the architecture, and routing. However, few researchers have investigated the performance of TCP in ICWN, especially when Epidemic Routing is used. In this paper, we first evaluate the performance of TCP in ICWN with Epidemic Routing. Our results show that the Epidemic Routing in ICWN degrades the performance of TCP because multicopy data packets cause duplicate ACKs, and in turn reduce the transmitting rate of TCP. Then an enhanced algorithm for TCP, named A-TCP/Reno is proposed to solve the above problem. A-TCP/Reno can avoid the duplicate ACK problem which is caused by Epidemic Routing. The simulation results show that A-TCP/Reno outperforms the TCP/Reno in ICWN with Epidemic Routing protocol.