Research On Physical Layer Security Encoding In Multi-user MIMO Power Line Communications

In the multi-user Multiple-Input Multiple-Output(MIMO)power line communication(PLC)networks,the channels of all users are linked together and form a small local area network.Because of the broadcast nature,the confidential signals are vulnerable to eavesdropping.With the increase of the number of users and the development of the computing abilities,the traditional cryptography is trapped in the dilemma of key management and brute forcing.In recent years,the physical layer security(PLS),which is defined from the perspective of information theory,has been proposed in the physical layer to complement and enhance the confidentiality provided by other layers.However,there are many differences between PLC and wireless communications in channel characteristics and MIMO configurations.As a result,the investigations on the PLS of MIMO-PLC networks are relatively fewer.Motivated by this situation,in this paper,the PLS coding of MIMOPLC networks are studied as follows:(1)The wiretap model of multi-user MIMO-PLC networks is built.Firstly,the fading,time-variant,and multi-path characteristics are analyzed,and the Single-Input Single-Output(SISO)PLC channel model based on the MK(Zimmermann M and Dostert K)model is built.Secondly,the SISO-PLC channel model is expanded to MIMO-PLC channel model by using statistical methods.Thirdly,the multi-user MIMO-PLC channel model is generated by increasing the user number of MIMO-PLC channel model.Finally,an active eavesdropper is added to the multi-user MIMO-PLC network,and the expressions of the secure rate and mean square error(MSE)of the wiretap link are deduced.(2)For the multi-user MIMO-PLC networks,a beamforming strategy is proposed to maximize the difference of MSE between the wiretap links and the legitimate links.We use the non-cooperative game frame to formulate the optimal problem.As a benefit,the number of variables and the complexity is reduced.The non-convex objective function is transformed into a convex form,and the closed-form solution of the coding matrices of each user are deduced.After that,an asynchronous iterative algorithm is proposed to obtain the Nash equilibrium solution,the existence and the uniqueness of which are also proved.(3)For the multi-user MIMO-PLC networks which contain cooperative jammers,a PLS coding combining the beamforming and the artificial noises is proposed to maximize the difference of MSE between the wiretap links and the legitimate links.In order to increase the efficiency of communication resource,the inactive transmitters are used to broadcast the artificial noises to jam the eavesdropper.Firstly,the optimal beamforming strategies of active pairs are solved while ignoring the interferences from inactive pairs.Secondly,the optimal power allocations of the artificial noises of inactive transmitters are solved by using linear programming.(4)For the multi-user MIMO-PLC networks which are aided by relay nodes,a PLS strategy jointly solves the optimal encoder matrices of transmitters,relays and receivers are proposed to maximize the difference of MSE between the wiretap links and the legitimate links.Multiple relay nodes are used to amplify and forward the signals from the transmitters,and the PLS coding strategy is formulated as an optimization problem.The non-convex optimal problem is divided into three convex sub-optimal problems which can be solved by using gradient descent.Finally,an iterated algorithm is proposed to obtain the optimal encoder matrices of transmitters,relays,and receivers.The proposed encoding algorithms are applied in different multi-user MIMO-PLC networks,and the simulation results show that the MSE performance and the secure rate are significantly improved.The effectiveness of the algorithms is verified,and the security performances of the networks are ensured.The proposed algorithms can be applied to communication scenarios such as centralized meter reading,smart home,and multimedia transmission of in-home users.It can protect private signals from eavesdropping,which has a certain practical significance.