Research On Physical Layer Security In Distributed Antenna System And System Building

Security and capacity are important metrics for wireless communication systems.In terms of security,physical layer security can provide "absolute security" independent of computational complexity at the bottom layer,and has attracted more and more attention.In terms of capacity,distributed antenna systems can achieve higher system capacity while using the same spectrum resources.Therefore,how to ensure the communication security of distributed antenna systems is an important research direction.Most of the physical layer security techniques are aimed at centralized antenna system.Only a few of them study distributed antenna system,and their feature considerations are not enough.Aiming at the above problems,the physical layer security of distributed antenna system is studied in this thesis.The specific research contents are as follows.Aiming at the problem of eavesdropping in distributed antenna system,based on the differential time-delay distribution among distributed antennas,this thesis proposed a physical layer security modulation scheme,and its demodulation method.The scheme can map part of the information to time domain,the modulated information is covered by the time-space randomness of wireless channel,and the eavesdropper's difficulty in cracking information is increased without increasing the difficulty of demodulation for legitimate users.Theoretical and simulation analyses show that this scheme can effectively guarantee information security.Aiming at the problem of identity impersonation in distributed antenna system,a lightweight region-oriented physical layer authentication framework is proposed.The framework can estimate the probability of an attacker in a specific area by using the received signal strength,and then give the evaluation methods of the security area and the dangerous area.In order to verify the effectiveness of the framework,the probability of successful authentication of legitimate users and the probability of successful attack of attackers are deduced in three scenarios.Theoretical deduction and simulation analysis show that the authentication framework can effectively identify the legitimacy of transmitting antennas.Aiming at the problem of building distributed antenna system,a distributed antenna system supporting multi-antenna cooperative parallel transmission is built based on Netfilte technique.The system consists of multiple remote antenna units(RAU)and multiple users;each user can automatically connect to the RAU with the strongest signal intensity.The RAU in the system has two working modes.When each RAU communicates with the target user separately,the maximum transmission rate of the system can reach 13Gbits/s.When all RAUs communicate with the target user cooperatively,the system will distribute data packages according to the status of each link,and the robustness of this system will be improved.