Modeling, analysis and enhancement of transmission control protocol

Transmission control protocol (TCP) is one of the core protocols of the Internet protocol (IP) suite, which provides congestion control and reliable end-to-end connections in the Internet. In wireless environment, due to the random packet loss, many previous TCP variants primarily designed for wired networks may not perform well. In this thesis, we first analyze the impact of random packet loss on the throughput performance of TCP CUBIC. Then, by incorporating online network coding, we propose a new TCP variant called TCP Vegas with online network coding (TCP VON), which can be efficiently applied in wireless networks. In the first part of this thesis, we propose a Markov chain model to determine the steady state throughput of TCP CUBIC in wireless environment. The proposed model considers both congestion loss and random packet loss caused by the wireless environment. We derive the stationary distribution of the Markov chain and obtain the average throughput based on the stationary distribution. Simulations are carried out to validate the analytical model. In the second part of this thesis, we propose TCP Vegas with online network coding (TCP VON), which incorporates online network coding into TCP. TCP VON includes two mechanisms, namely congestion control and online network coding control. The congestion control is extended from TCP Vegas. For the online network coding control, the sender transmits redundant coded packets when packet losses happen. Otherwise, it transmits innovative coded packets. As a result, all the packets can be decoded consecutively and the average decoding delay is small. We establish a Markov chain model to compute the analytical delay performance of TCP VON. We also conduct ns-2 simulations to validate the proposed analytical models. Finally, we compare the average delay and throughput performance of TCP VON and automatic repeat request (ARQ) network coding based TCP (TCP ARQNC) for different topologies. Results show that TCP VON outperforms TCP ARQNC.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat