Analysis Of Security Performance In Collaborative Spectrum Sharing Network

The combined application of cooperative diversity technology and spectrum sharing technology can effectively combat multi-path fading and improve spectrum utilization so as to ease the contradiction between the shortages of spectrum resources;physical layer security technology can improve the transmission security of wireless communication network.However,most researches on cooperative spectrum sharing technology mostly aim at maximizing the channel capacity or spectrum sharing strategy,without considering the system energy efficiency and secure transmission problems;In the aspect of physical layer security,most of them are aimed at the optimal security capacity or the minimum total transmit power.However,with the rapid development of wireless communications,data transmission is expected to be faster,safer,more efficient and more stable.Therefore,the integrated application of different technologies has become an inevitable trend of the times.Based on this,this thesis makes a research on the energy efficiency and outage probability of the system under the cooperative spectrum sharing mechanism,the specific contents include:1.In the proposed cooperative spectrum sharing mechanism,the relay node acted as the secondary user transmitter combine the decoded primary signal with secondary signal by assigning fractions ?and 1-? of the available power to the correspond destination receiver of the primary and secondary network.At the same time,the eavesdropper node disguised as a legitimate user can also receive the superimposed signal.Based on this mechanism,this thesis studies the optimal power allocation algorithm with the relay nodes using decode and forward protocol.For the non convex problem of objective function,the original problem is decomposed and solved iteratively by fractional programming and DC programming theory.Simulation results show that the proposed algorithm can achieve higher security efficiency than the maximum secrecy rate;however,there is a certain loss of secrecy rate because of the compromise between the secrecy rate and the safety efficiency.2.Based on the proposed mechanism,the optimal power allocation algorithm is studied with the constraint of peak power and secrecy rate when the relay node employs amplified and forward protocol.By jointly using fractional programing,penalty function,alternating search and DC programming theory,the original objective function is solved by equivalent and decomposition means.The performance gap between the proposed algorithms with the ergodic algorithm is compared,and the convergence performance of the proposed algorithm is verified.This paper analyzes the influence of the change of the node position on the energy efficiency of the system,and verifies that the compromise of the secrecy rate and the energy efficiency still exists in the physical layer secure communication network.3.We consider the case that the licensed network uses spectrum sharing opportunity as a decoy to wiretap the confidential data of cognitive networks.In this section,the expressions and the closed form solution of the outage probability for the primary network and the security outage probability for the secondary network under the relay node employs decode-and-forward and amplify-and-forward protocols respectively is derived with considering the primary transmitter as eavesdropper.The range of power allocation factor and its influence on system outage probability are analyzed and verified by simulation results.