| The interaction between TCP congestion control and MAC layer scheduling leads to low performance of TCP over next-generation mobile broadband networks,3GPP LTE. On the one hand, MAC Layer scheduling can have adverse effects on existing TCP congestion control mechanisms and lead to TCP spurious timeout, which causes unnecessarily low TCP goodput. On the other hand, TCP congestion controlaffects the delay of TCP packts, which reduce the porfermance of existing MAC scheduling algoritms.This thesis studies on the joint optimization of MAC layer scheduling algorithm and TCP congestion control over LTE networks to improve the porfermance of TCP over LTE networks.In this thesis, a cross-layer TCP congestion control algorithm, named TCP-MAC-CW is firstly proposed, to solve problems caused by spurious timeout. The proposed TCP-MAC-CW first detects spurious timeout according to the congestion warning sent by eNodeB MAC Layer, and then adjusts the TCP data rate to improve goodput. Simulation result shows that the proposed TCP-MAC-CW achieves much goodput gain compared to other existing mechanisms, while maintaining satisfied TCP-level fairness.LWADF scheduling algorithmis proposed in this thesis, considering the impact of TCP congestion control on TCP data delay. The propsed LWADF decideds the priority of users with the weighed average delay of TCP packets waiting in the MAC layer data queue, taking better control of users’TCP data delay. Simulation result shows that the proposed LWADF algorithm decreases the frequency of TCP spurious timeout and achieves much goodput gain compared to existing scheduling algorithms.A3GPP LTE simulation platform is implemented in this thesis to simulate above-mentioned algorithms. The design and development of this simulation platform is stated in detail. Other important researchs on this platform are also included。The research and implementation in this thesis is valuable to improve TCP performance in real LTE networks, and the thesis isuseful for reference. |
PDF Full Text Request