Research On Physical Layer Security Strategies In Spectrum Sensing For Cognitive Radios

In cognitive radio(CR)spectrum sensing,all kinds of unknown wireless devices are allowed to access the licensed spectrum opportunistically,which inevitably cause secondary users(SU)particularly vulnerable to attacks launched by malicious users.These attacks include primary user emulation attack(PUEA),spectrum sensing data falsification attack(SSDF)and eavesdropping attack(EA).Cooperative spectrum sensing(CSS)can effectively solve wireless channel fading problem through information fusion or information sharing among SUs and obviously improve detection performance,which is often used to defense PUEA and SSDF attacks in spectrum sensing for CR.However,with the increasing of SU numbers,system energy consumption will significantly increase.Therefore,CSS puts forward higher requirements to energy efficiency because of the green CSS technology,which has become a research hotspot both in academia and industry.Based on the investigation on three common attacks in CRN,namely,PUEA,SSDF and eavesdropping attack,three kinds of defensive strategies are presented with the target of energy efficiency maximization.That is,to improve system energy efficiency while guarantee CR system security,and realize the trade-off between energy efficiency and security performance.Specific research works are provided as follows.1)Energy-efficiency priority based PUEA defensive scheme is investigated with performance analysis.In the proposed scheme,CSS energy efficiency is constructed as the optimum objective in the presence of PUEA with secure detection probability as the constraint conditions.Secure CSS model and PUEA defensive scheme are proposed to achieve energy efficiency based secure CSS.K-out-of-N criterion is set as global decision criterion in the scheme.Optimal fusion threshold K and optimal cooperative SUs N can be jointly determined in secure CSS with the guarantee of energy efficiency.Compared with the traditional maximum ratio combining(MRC)fusion rule,the proposed PUEA defensive scheme not only guarantees system energy efficiency,but also improves system detection performance.Namely,the proposed scheme can make a trade-off between energy efficiency and detection performance in the presence of PUEA.Numerical results also indicate that,the proposed scheme is immune to PUEA interference power,which shows that it is robustness to PUEA attack.2)Energy-efficient defensive strategy against SSDF attacks with multiple malicious users over Nakagami-m channels is studied.Secure CSS energy efficiency is set as the objective function under the constraint of message authentication code(MAC)length,reporting distance and reporting error rate.Hence,the optimal legitimate SUs and malicious users(MUs)can be jointly determined.In addition,we also considers the situation that MUs wiretap the reporting channel between fusion center(FC)and legitimate SUs to obtain the MAC.MU intercept performance is investigated over Nakagami-m fading channels.On the one hand,the proposed strategy can achieve a tradeoff between energy-efficiency and security.The achievable energy efficiency is almost immune to MU numbers.Simulation results show that,with the same MU numbers,the proposed scheme achieves higher energy-efficiency and requires fewer report bits(short MAC length).On the other hand,compared to conventional SSDF attack defensive strategy,the intercept probability of the proposed strategy can be reduced when the legitimate-to-malicious ratio(LMR)is high and the channel fading factor ratio is large.The dissertation initially designs and researches physical layer security strategies in spectrum sensing for CR.Research achievements provide significant value for the further related works.