Evaluation Of Transmission Performance For Cognitive Radio Networks Based On Network Coding

With the rapid development of wireless communication technology,spectrum resources has become scarce increasingly, under the current system ofspectrum allocation, the utilization of spectrum resource is very low. In order tosolve these problems, one kind of intelligent communications network which canrecognize the communication environment comes into being. Because the birth ofa new network, there must be have some suitable new network transportprotocols to support the reliable transport, but the previous communicationprotocol mechanism is still not perfect now.This thesis focuses on the TCP of cognitive radio networks (CRNs). Thereare some features in CRNs, such as spectrum sensing, spectrum switching,licensed user activity, the external varied communication environment etc. Weanalyze the impact of these characteristics on TCP performance, and thenpropose a new transmission control protocol (CR-NCTCP) based on networkcoding. For accurately calculating the throughput in CRNs, a model is presentedfor the licensed users. And then we calculate the collision probability betweenthe licensed users and un-licensed users. Moreover, the end-to-end throughputalso is calculated according to the three stages, normal state, spectrum sensingand spectrum switching.We evaluate the performance of the CR-NCTCP protocol by simulationunder different network settings, e.g., sensing time, using NS2with cognitiveradio network module. The simulation results show that CR-NCTCP can ensurelarger value of CWND under different number of occurrences of licensed users.Moreover, the CR-NCTCP can improve the performance of CRNs, whichachieves a higher throughput in terms of various numbers of occurrences oflicensed users, communication time of licensed users and sensing time ofun-licensed users.