Research On Cooperative Spectrum Sensing Security Strategy

Cognitive radio(CR)technology allows secondary users(SUs)to opportunistcally access the idle spectrum without harmful interference to the primary user(PU).Compared with the fixed spectrum allocation scheme,CR makes the implementation of the dynamic spectrum allocation strategy possible,greatly improving the spectrum utilization and solving the spectrum shortage problem.As a key technology in cognitive radio networks(CRNs),spectrum sensing is responsible for detecting the availability of spectrum.In order to overcome the shadow fading,multipath effect and receiver uncertainty of wireless channels,cooperative spectrum sensing(CSS)further improves the spectrum sensing performance by exploting multiuser spatial diversity.Meanwhile,due to the openness of CRNs,CSS also suffers from various security threats,especially Byzantine attack,resulting in a decline in the spectrum sensing performance,which not only causes a waste of spectrum,but also casues harmful interference to the primary network.This dissertation provides more in-depth analysis of the impact of Byzantine attack on CSS in CRNs,while securing CSS and improving the spectrum sensing performance and efficiency.It mainly includes: analysis of the impact of Byzantine attack on CSS;sequential detection-based secure sequential cooperative spectrum sensing(SCSS)method;Byzantine attack strategy in CSS;Byzantine defense strategy based on game theory in CSS.The main contributions of this dissertation are as follows:1.Aiming at the impact of Byzantine attack on CSS,the performance expression under the user characteristics and Byzantine attack are derived respectively,the performance optimization scheme based DDTED and the anti-Byzantine attack method based TSCT are also proposed.Firstly,the dissertation analyzes the impact of the user characteristics(including the SU mobility and the sensing range,the PU activity and the protection range)on the CSS performance in the spatial-temporal CRN without malicious users(MUs).On the basis of the double threshold energy detection,DDTED is proposed to optimize the miss detection probability and the false alarm probability via a dynamic threshold factor.Secondly,the impact of Byzantine attack on the CSS performance in the mesh CRN with MUs is analyzed,TSCT is proposed for different attack scenarios,which utilizes the received signal strength(RSS),location information and credit to check consistency,and gradually excludes malicous users from the SU stage and the cell stage.Finally,simulation results show the impact of user characteristics and Byzantine attack on the CSS performance;In contrast to other schemes without the performance optimization,DDTED has obvious optimization effect on the CSS performance,and TSCT is also superior to other anti-Byzantine attack methods.2.Concerning sophisticated Byzantine behaviors in CSS,a generic Byzantine attack model based hard-combining technology is established,a secure sequential cooperative spectrum sensing(SCSS)scheme is proposed,which not only improves the cooperative sensing performance,but also reduces the sample size.Firstly,by analyzing malicious behaviors in the process of CSS,a generic Byzantine attack model based hard-combining technology is proposed,the secenario where Byzantine attack may make the FC blind is analyzed,and the blind condition is aslo derived.Secondly,through a detailed analysis on conventional data fusion techniques,a sequential detection-based CSS scheme is proposed.This scheme makes use of data transmission mechanism to check consistency of the local sensing result,thereby solving the dilemma that the fusion center(FC)is unreliable,and reuses the Byzantine sensing information through a novel weight allocation method,and proceeds with the sequential test according to the reputation ranking.Finally,compared to other data fusion technologies,simulation results show that SCSS not only gurantees the security of CSS,but also requires a small sample size in support of the more accurate global decision,even in the blind scenario.3.For the strategic Byzantine attack in CSS,the optimal attack strategies to maximize Bayes risk in the context of various fusion rules are determined,and Byzantine attack tradeoff and risk in a generic Byzantine attack model based soft-combining technology are further studied.Firstly,on the basis of the hard Byzantine attack model,the optimal attack strategies to achieve the maximal Bayes risk in the context of unknown/majority fusion rule are analzed.Secondly,considering that the fusion rule esimates Byzantine attack strategy by an estimation algorithm and adopts the optimal fusion rule minimizes Bayes risk,the optimal attack stratey to maximize Bayes risk under the optimal fusion rule,and the closed expression is given.Furthermore,in the generic Byzantine attack model based soft-combinging technology,the cost and benefit of the false alarm attack and the miss detection attack are considered,and two attack tradeoff problems are put forward,the existence of the attack tradeoff is mathematically collaborated.Finally,simulation results verify the theoretical analysis and estimation algorithm of the attack strategy.The attack risk is evaluated in the reputation-based spectrum sensing algorithm.4.Considering the dynamic process of Byzantine attack and defense in CSS,the noncooperative game framework of Byzantine attack and defense is proposed,Nash equilibrium(NE)related to the benefit ratio and penalty rate is determined,which effectively defends against Byzantine attack and saves defense cost.Firstly,according to the periodic spectrum sensing frame structure in the CRN,Byzantine attack and defense in the process of CSS is analyzed,correspondingly,the defined cost and benefit,which are further introduced into game theory.Consequently,in the non-cooperative game framework,the individual best reponse is analyzed according to individual strategy,then NE related to the benefit ratio and the penalty rate are determined in different cases.Finally,numerical simulation results analyze the impact of the benefit ratio and the penalty rate on the dynamic game process of Byzantine attack and defense,and collaborate that game theory can effectively defend against Byzatine attack and save the defense cost.