Study of TCP Available Bandwidth Using NS2 and Its Forecasting Based on Genetic Algorithm

Abstract: On the one hand, the available bandwidth in a bandwidth-limited medium as the wireless medium is a highly demanded topic of study. On the other hand, the Transport Control Protocol (TCP) is one of the most used transport protocols on the Internet. The available bandwidth study and TCP constitute the most typical scenario in the Wireless Local Area Networks (WLAN). This Thesis locates the study in the 2.4GHz frequency band where Primary Users can be present modifying the behaviour of the WLAN medium. This band is unlicensed and, as a consequence of this, the congestion is considerable. Nowadays, several studies of this band are related to Cognitive Users operating in this band. However, this thesis studies the impact of Primary Users in the TCP available bandwidth in a classic IEE 802.11g WLAN network. The second part of the dissertation takes a step forward, a tool to forecast the TCP available bandwidth for WLAN based on a genetic algorithm has been developed. This tool is able to estimate the future available bandwidth finding the best function that will fit better to the future behaviour of the network. A genetic algorithm programmed specifically for this purpose finds this function. A significant number of tests have been carried out in the study. The TCP available bandwidth study shows a relation between MAC busy time and available bandwidth in some cases. In addition, the study shows that the TCP available bandwidth increases if the idle periods are longer. Reliable results in the forecasting have been achieved with a limitation in some specific scenarios.