Modeling Network Coded TCP: Analysis of Throughput and Energy Cost

Abstract

We analyze the performance of TCP and TCP with network coding (TCP/NC) in lossy networks. We build upon the framework introduced by Padhye et al. and characterize the throughput behavior of classical TCP and TCP/NC as a function of erasure probability, round-trip time, maximum window size, and duration of the connection. Our analytical results show that network coding masks random erasures from TCP, thus preventing TCP’s performance degradation in lossy networks. It is further seen that TCP/NC has significant throughput gains over TCP. In addition, we study the cost of improving the goodput per user in a wireless network. We measure the cost in terms of number of base stations, which is highly correlated to the energy cost of a network provider. We show that increasing the available bandwidth may not necessarily lead to increase in goodput, particularly in lossy wireless networks using TCP. We show that using protocols such as TCP/NC, which are more resilient to erasures in the network, may lead to a goodput commensurate with the bandwidth dedicated to each user. By increasing goodput, users’ transactions are completed faster; thus, the resources dedicated to these users can be released to serve other requests, consequently reducing the cost for the network providers.