Research On Multi-antenna Physical Layer Security Transmission Technology For Random Heterogeneous Networks

The deployment of the 5th generation mobile communication networks(5G)will be increasingly dense and heterogeneous.Heterogeneous wireless networks not only face the traditional threat of air interface,but also face more severe security challenges caused by the features of heterogeneous networks(HetNets),such as the diversification of node types,complexity of interference,and randomization of network topology.The multi-antenna physical layer security transmission technologies can make use of the characteristics of channel and the spatial freedom of multi-node and multi-antenna to guarantee the communication security of legitimate receivers in the stochastic HetNets.Recently,it has been widely studied in academia.However,the existing multi-antenna physical layer security researches in stochastic HetNets mainly focuse on the establishment of secrecy performance analysis framework and the design of secrecy transmission scheme for the traditional heterogeneous cellular networks.The related research is still in the initial stage.Specifically,the following research directions need to be expanded: 1)How to use these technologies to improve the secrecy performance of multi-hop aided stochastic HetNets and stochastic cognitive HetNets has not been studied;2)The air-to-ground communication scenario and indoor communication scenario in the stochastic HetNets have not been taken into consideration.Aiming at the above problems,according to the characteristics of different wireless communication systems and signal transmission scenarios,the multi-antenna physical layer security transmission technologies for different types of stochastic HetNets are studied respectively in this paper.Firstly,under the ground-to-ground communication scenario,the multi-antenna physical layer security transmission technologies are used for improving the secrecy performance of multi-hop HetNets as well as that of traditional cognitive HetNets,and a physical layer security transmission scheme for Non-Orthogonal Multiple Access(NOMA)aided cognitive HetNets is designed for improving network security.Then,under the air-to-ground communication scenario,the multi-antenna secrecy transmission technology is used for improving the secrecy energy efficiency of multi-type unmanned-aerial-vehicle(UAV)base stations(BSs)aided hovering HetNets.Finally,under the indoor communication scenario,a multi-access point(AP)cooperative secrecy transmission scheme is proposed according to the characteristics of multi-floor indoor HetNets.1.Aiming at the problems of uneven distribution of nodes,complexity of interference and possibly leakage of private information during multi-hop in single-antenna stochastic HetNets,the secrecy transmission based on multi-user Multi-Input Multi-Output(MU-MIMO)technology for multi-hop HetNets is analyzed.According to whether the user directly communicate with the BSs,a network can be regarded as the user in infrastructure mode or ad hoc mode.Based on stochastic geometry theory,a physical layer security analysis framework for MU-MIMO aided multi-hop HetNets is proposed.The MU-MIMO technology is introduced to multi-hop HetNets to improve the receive channel gain of users in infrastructure mode,and the service distance of the relay users working in infrastructure mode is restricted not greater than the given maximum single-hop distance,thus reducing the average distance of ad hoc users to its serving relay as well as the average path loss received by the users in ad hoc mode.Based on this framework,the secrecy performance of users in infrastructure mode and users in ad hoc mode are studied respectively,and the overall secrecy performance of multi-hop HetNets is analyzed.2.Aiming at the problems of high priority of primary users and weak secrecy performance of cognitive users in the stochastic cognitive HetNets,the secrecy transmission for stochastic cognitive HetNets is analyzed based on the multi-antenna technology combined with threshold-based access strategy and secrecy guard scheme.Utilizing the multi-antenna technology to serve the legitimate users in primary user networks as well as cognitive user networks(CUNs),the average received signal power is improved.In addition,utilizing the threshold-based access strategy to control the communications of CUNs,the interference of primary users caused by cognitive BSs(CBSs)is reduced.At the same time,the detection region is set around the CBSs to improve the security of CUNs.Once any eavesdropper is detected,the CBSs will terminate their communications.Based on stochastic geometry,an analysis framework for the average reliability and security of cognitive HetNets is given in this paper.3.Considering the multi-antenna primary BSs(PBSs)which use the NOMA technology to transmit the signals is faced with the problem that there is great differences in reliability and security among different users due to difference of allocated signal power,a secrecy transmission scheme for primary networks is proposed based on cooperative NOMA technology and secrecy guard scheme.Eavesdropper-exclusion zone is introduced around the PBSs for improving the secrecy performance of the primary networks.Then,the PBS transmit beamforming signal.After the primary user with better channel condition(NOMA-strong user)has stripped out his own signal,he uses NOMA technology to transmit other users' signals as a relay;After receiving signals from the PBS in the direct transmission slots and from the relay users in the cooperative slots,the NOMA-weak user uses selection combining scheme to handle the signals received in two slots.In this paper,the security and reliability of the cooperative NOMA aided primary networks are studied.Moreover,the above performance indicators are further conjointly analyzed based on the transmission secrecy outage probability.4.Considering the endurance of a hovering HetNet composed of UAV-BSs is limited by the power supply and the distance between the transmitter and the receiver will affect the energy efficiency as well as the communication security,a secrecy performance analysis framework for hovering HetNets is proposed based on multi-antenna technology and threshold-based access scheme.UAV-BSs use multi-antenna technology to improve the channel quality of legitimate receivers,and reduce low quality communications by threshold-based access scheme.As the communication between UAV-BS and ground receiver is air-to-ground communication,its message propagation includes line-of-sight(LoS)propagation and non-line-of-sight(NLoS)propagation.Modeling all nodes' distributions with Poisson point processes,the communication channel can be described by the probability of propagation mode.On this basis,the security,reliability and energy efficiency of the hovering HetNets are analyzed,and the access threshold as well as the transmission power of macro-BS are designed to maximize the secrecy energy efficiency in a given network.5.Aiming at the poor network secrecy performance caused by the features of multi-floor indoor HetNets such as the randomization of node distribution,restriction of transmit power,complexity of spatial structure,and diversification of loss types,a multi-AP cooperative secrecy transmission scheme for multi-floor indoor HetNets is proposed.This secrecy transmission method adopts the association scheme based on the average receiving signal power for all APs in different floors.A cooperative set of multiple APs which can provide the target user with the average receiving signal power greater than the given threshold value is selected for target user transmission.Distributed antenna array composed by multiple cooperative nodes is able to improve the secrecy performance of multi-floor indoor HetNets.Based on multi-floor Poisson point process and taking secrecy coverage probability as a secrecy performance evaluation index,the secrecy performance for cooperative transmissions in multi-floor indoor HetNets is analyzed.