Research On Secure Transmission Of Information In Wireless Heterogeneous Networks Under Uncertain Channel Envirenment

In order to provide wireless user equipment with seamless coverage,high transmission rate and high reliability,5G network will develop towards layered heterogeneous network in the future.It can improve network coverage,reduce blind area and increase network capacity.As a typical representative,two-tier heterogeneous network basically cover all the technologies and challenges of layered heterogeneous network.There are mainly:(1)the serious signal interference;(2)the uncertainty of the real-time channel gain;(3)the eavesdropping risk.Therefore,considering various uncertainties in the channel environment,the robust communication and information secrecy transmission scheme for two-tier heterogeneous network is designed in this paper,which is suitable for more complex 5G communication environment.The main work and innovations of this paper are as follows:First of all,for two-tier heterogeneous network with single user and single eavesdropper,the information secrecy transmission schemes are proposed to maximize the secrecy rate while constraining user's communication quality in two uncertain channel environments.One is instantaneous channel state information(CSI)scenario considering the reliable estimates of CSI can be obtained;the other is the statistical CSI scenario in which reliable estimates of CSI can not be obtained and it is considered to obey Rayleigh distribution.The difficult and non-convex optimization problem is transformed by chance-constrained method.And the optimal solution acquisition algorithm is given,which realizes the robust communication of user and the information secrecy transmission of network.Then,for two-tier heterogeneous network with multi-user and multi-eavesdropper,considering instantaneous CSI scenario and statistical CSI scenario obeying Exponential distribution,the reliable communication and secrecy transmission schemes are proposed,which ensures user's robust communication at the same time stimulates Femtocell to assist Macrocell to suppress information eavesdropping.The Bernstein approximation method is utilized to transform the original problem into convex optimization problem.The application scope of the Bernstein approximation method is widened in statistical CSIscenario.After that,the iterative algorithm of obtaining the optimal solution is given,which realizes the robust communication and information secrecy transmission in the actual communication environment.At last,for two-tier heterogeneous network contains energy receivers,the robust communication and secrecy transmission schemes with the energy harvesting are proposed,considering the statistical CSI scenario obeying Truncated Gaussian distribution.The optimization problem maximizing the secrecy rate and constraining the users' quality of service and energy receivers' energy harvesting is established.The convex transformation of the problem is completed by using chance-constrained method.And the iterative algorithm of obtaining the optimal solution is given,which improves the communication environment of the network,avoids the waste of energy,and further improves the secrecy transmission performance of the heterogeneous network.