An algorithm for improving Sliding window Network Coding in TCP

Abstract

Sliding-window Network Coding (NC) is a variation of Network Coding that is an addition to TCP/IP and improves the throughput of TCP on wireless networks. In this article, two implementations of a new algorithm are proposed in order to decrease the total transmission time, and to increase the decoding throughput throughout the transmission. The algorithm's main process identifies then retransmits the number of outstanding lost packets and is implemented in two different ways. The End of Transmission (EOT) implementation applies the process only once at the end of the transmission, whereas the “Pseudo-block” (PB) implementation applies the process at regular intervals throughout file transmission. The discrete event simulator ns-2 is used to implement and test the benefits of the proposed algorithm. Our extensive simulation results show that both implementations provide a sizeable decrease in average transmission time. For the first implementation (EOT), the average time to receive data decreased by 8.04% for small files (under 1 MB) compared to TCP/NC. The second implementation, PB, reduces file transmission times by up to 70% for larger files (GB range). Furthermore, PB creates a more even decoding throughput and allows for a smoother transmission. In this work, PB is shown to decrease the average standard deviation of the decoding throughput by over 60%. This decrease in decoding delay demonstrates the potential of sliding window NC in future streaming applications.