Analysis Of Security Region And Design Of Transmission Scheme Based On Security Outage Probability

Besides conventional informatic-encryption approaches,physical layer security(PLS)techniques,aiming to degrade the signal received by eavesdroppers,can further upgrade the security of wireless systems.As one of the most important indicators in PLS,security region can be utilized to not only protect the vulnerable areas for the given transmission scheme,but also enlarge the security region by optimizing the transmission scheme.So far,security region related research have still been at very early stage.The adopted channel models(normally Gaussian or Rayleigh channels)are relatively simple,resulting in a restriction on the application scenarios.To break this limitation,a general channel model,namely Rician fading channel,is considered in analyzing the security region in this thesis.Moreover,under the condition of partial location information of the eavesdropper,a novel transmission scheme for desired security region is also proposed.The main contributions of this thesis can be summarized as follows.By adopting the Rician fading channel model,we theoretically analyze the security region based on the security outage probability.Firstly,the probability distribution functions(PDF)of the signal-to-interference and noise ratio for both legitimate receiver(Bob)and the eavesdropper(Eve)are derived.Secondly,based on the obtained PDFs,the security outage probability when Eve at different positions is derived,while the security region is determined by the security outage probability threshold.Finally,simulation results verify the validity of the theoretical analysis.The effects of the transmit-antenna number,transmit power,and desired transmission rate on the shape of the security region are also investigated.According to different availability levels of the Eve's location information,the corresponding maximizing-security-region-oriented transmission schemes are proposed.Firstly,the security transmission scheme is modeled as an optimization problem with the objective function of security outage probability.By implementing an equivalently transformation of the optimization problem,a lower complexity problem is obtained.Secondly,two typical constraints are integrated in the optimization problem to design the corresponding artificial noise(AN)beamforming schemes.One is when the approximate Eve's direction information is known,the depth of the fan-shaped security region can be maximized.Another constrain is when no Eve's location information is available,the width of the security region can be maximized.Finally,we use the penalty function to transform the constrained optimizationinto an unconstrained one;then a searching algorithm can be applied to find out the final solution.Simulation results verify the validity of the proposed approaches for the different availability levels of the Eve's location information.