Research On Physical Layer Security For Heterogeneous Cellular Network With Limited Feedback

With the continuous development of heterogeneous cellular networks,the security threats brought by heterogeneous deployment and complex interference become more serious.The physical layer security technology uses the fingerprint characteristics of the wireless channel to act as an effective supplement to high-level encryption to ensure the secure communication of heterogeneous cellular networks.Existing physical layer security technologies need to be designed based on accurate channel state information(CSI).In the transmission process of heterogeneous cellular networks,the limited feedback technology can provide more effective and reliable CSI compared with the direct use of channel reciprocity.The existing physical layer security technology with limited feedback has two main ideas,one is to improve the CSI quality by designing the corresponding transmission scheme,the other is to design a robust transmission scheme with CSI error which provides reliable security performance.However,due to the limit of nodes and the wireless environment,it is difficult to directly apply the physical layer security scheme in the traditional network into the heterogeneous cellular network.Specifically,the following problems still need to be solved urgently: 1)Lack of analysis framework for physical layer security of heterogeneous cellular networks with limited feedback;2)Lack of limited feedback transmission scheme for improving CSI accuracy in heterogeneous cellular networks 3)Existing robust transmission schemes with limited feedback cannot guarantee the safety performance when there are multiple eavesdroppers.Motivated by these facts,this paper is devoted to the security transmission technology of the heterogeneous cellular network physical layer security with limited feedback.Considering the characteristics of diverse types,huge numbers,and dynamic topology in heterogeneous cellular networks,the reliability,safety,and effectiveness of the limited feedback system have to be studied.The specific research content and results of this article are summarized as follows:1.The physical layer security analysis framework of heterogeneous cellular network with limited feedback is established.Aiming at the situation of heterogeneous cellular network with various types of nodes and complex topological structure,a random geometry tool is used to model the node position.Combined with a joint error model of channel estimation error and feedback error,the coverage probability and secrecy outage probability are used as evaluation indicators.The transmission model of K-layer heterogeneous cellular network with limited feedback is presented.The influence of parameters such as the number of antennas,feedback length,estimation accuracy and base station distribution density on the security performance of heterogeneous cellular networks are analyzed.The correctness of theoretical derivation is verified through the simulation.2.For base stations with different numbers and distribution densities,a variable feedback length security transmission scheme for the heterogeneous cellular network is designed,and a search algorithm that maximizes the system security throughput within feedback length and coding parameters is given.Firstly,the entire limited feedback transmission process is improved,and the safety throughput expression of the system is given based on the previous framework.At the same time,under the constraints of coverage probability and secrecy outage probability,a joint search algorithm is used to search the optimal feedback length and coding parameters of the network.The simulation results verify that the scheme can maintain a high safety throughput at various antenna numbers,and the maximum safety throughput can be increased by about 15% compared with the less feedback length scheme.3.For a heterogeneous cellular network with a large number of nodes and eavesdroppers,a robust and secure transmission scheme for multiple eavesdroppers with limited feedback is proposed.The scheme uses energy harvesting to improve the energy efficiency of the system.Under the constraints of transmitting and receiving power,the optimization problem is going to maximize the minimum safety energy efficiency of the system.Through designing information and energy beamforming matrix,the convex optimization algorithm is used to solve the optimization problem.Simulation results show that our scheme can reduce the loss of security efficiency by about 35% and 10% respectively when the eavesdropper and error increases.