A Cognitive TCP Design for a Cognitive Radio Network with an Unstable-Bandwidth Link

In recent years, wireless network structures and mechanisms have been proposed to enhance the efficiency of communications. Regarding the upper-layer of protocol stacks, wireless transmission control protocols (WTCPs) are proposed to deal with transmission control protocol (TCP) performance problems on wireless networks. However, some new lower-layer solutions, e.g., cognitive radio (CR) systems, cause new throughput decay problems to TCPs, which existing WTCPs do not solve. In this paper, we study throughput decay issues in CR environments and discuss three events that cause these problems. Three event handlers are proposed to improve TCP throughput. The proposed solutions are designed by numerical analysis, and performance improvement is verified by NS2. We propose an event-driven CR-TCP that combines these event handlers, which can be combined with state-of-art CR-TCP solutions. Simulation results and analysis are presented to demonstrate the effectiveness of the proposed solution.