Physical Layer Security In 5G Millimeter Wave Networks

With the rapid development and popularization of the fifth-generation mobile communication system(5G),global wireless data traffic has been growing dramatically,which brings unprecedented challenges and pressures to the wireless networks.As one of the key techniques of 5G,millimeter wave(mm Wave)communication can use rich spectrum resources to significantly improve network capacity and transmission rate,and reduce transmission latency,thus effectively alleviating the above problems.On the other hand,the openness of wireless networks has laid a huge security risk,which makes the wireless transmission of data vulnerable to eavesdropping.How to effectively protect wireless secrecy has become a pain problem facing the wireless network designers.Fortunately,physical-layer security can achieve signal-level secure transmission at the physical layer by utilizing the inherent characteristics of wireless communication,such as channel fluctuation and noise randomness,thus providing a new method for solving the above problems which differs from traditional high-level cryptography encryption.Focusing on the issues of wireless secure transmission in 5G mm Wave networks,this thesis investigates the physical-layer security of two typical 5G application scenarios,namely,cacheenabled mm Wave heterogeneous networks and mm Wave C-V2 X networks,from the perspectives of system modeling,scheme design,performance analysis,and parameter optimization,etc.The main contributions of this thesis are summarized as follows:1)For the secure content delivery in cache-enabled two-tier mm Wave heterogeneous networks,this thesis propose a joint design of physical-layer transmission and cache allocation for maximizing the overall secrecy throughput.Firstly,based on the popularity of files,a cache resource allocation strategy is designed between the two network tiers.Secondly,physical-layer transmission schemes are proposed accordingly the file delivery in each tier.Based on this,the connection outage probability(COP)and secrecy outage probability(SOP)are analyzed,with analytical expressions derived.For maximizing the overall secrecy throughput,an optimization strategy by jointly designing the secrecy code rates and cache allocation is proposed,and a closed-form solution of the optimal cache allocation is obtained.Numerical results demonstrate that the proposed cache allocation strategy can significantly improve the secrecy throughput.Besides,the artificial noise technique is introduced for further improving network secrecy performance,and it is pointed out that artificial noise has a more significant advantage in improving the overall secrecy throughput under a more stringent SOP constraint.2)For the physical-layer security of uplink mm Wave transmission in C-V2 X networks,security association schemes based on distance and power are proposed,respectively,and a stochastic geometric analysis framework is established for studying the physical-layer security in the CV2 X network from the perspective of outage.Firstly,the spatial locations of roads,vehicles,pedestrians,road side units,and base stations are modeled leveraging the stochastic geometry theory.Secondly,For the uplink transmission,the smallest-distance association scheme(SDA)and the largest-power association scheme(LPA)are proposed,respectively,where network performance in aspects of association probability,COP,and SOP are analyzed for each association scheme,with analytical expressions derived.Finally,the influence of system parameters on network security performance is investigated for different association schemes.Simulation results show that the LPA scheme is always superior to the SDA scheme in improving the overall secrecy throughput.