Research On Cross-layer Security Approaches In Future Wireless Communication System

Massive MIMO,non-orthogonal modulation and other novel wireless communication technologies meet the surging demands of transmission rate,resource utilization,quality of service,coverage and so on,thus greatly enriched the application scenarios and user experience compared with the existing 4G communication system.However,high security requirements,large capacity,fast access,Internet of things and heterogeneous networks of 5G challenge the security of future communications networks a lot.Traditional security based on computing is at stake due to the dramatic cracking efficiency of high-speed computer and cloud computing;meanwhile,statistic-based physical security which takes advantage of channel diversity has gained attention as a novel solution.Indeed,it over-relies on the channel conditions,sacrifices system complexity and transmission efficiency,such a probabilistic security technology cannnot guarantee security at the probability of 1 in short frame transmission,which means a serious constraint to application environment.Setting out the above background,this thesis studies the cross-layer secrecy transmission technology combining physical layer security with traditional cryptography security based on the crucial physical layer technology of 5G to solve its secrecy communications problem.Firstly,for SCMA system,two cross-layer secure transmission schemes based on random codebook sets and distorted codewords are proposed respectively.Through sharing the upper layer stream cipher,the legal parties control the codebook set selection or codeword deformation in the SCMA modulation process,as sparse codebook mapping and MPA detection depend heavily on codewords and codebook,illegal eavesdroppers fail decoding.According to BER and security capacity in simulation results,a hierarchical security strategy is proposed that different cross-layer security schemes are selected under specific SNR to ensure secure transmission requirements with minimal complexity.Both schemes we introduced break through the limitations of the channel characteristics with small extra system overhead.Secondly,chapter four develops two MIMO cross-layer secure transmission schemes based on spatial modulated OFDM.Now,the upper layer stream cipher shared between the legitimate communicating parties has following functions: in the polymorphic spatial modulation scheme,it controls the code domain modulation / demodulation;in the cross-layer precoding scheme,it constructs the secret precoding matrix and its inverse matrix;and it controls the antenna mapping/de-mapping in both ones.In addition to the physical layer security caused by the difference of channel distribution,hopping of the modulated signal and the fast random phase offeset of OFDM symbols safeguard against eavesdroppers' secret information interception.The security analysis and simulation results demonstrate that the my solutions provide reliable decoding for legal one in several APM modulation modes,on the contrary,the eavesdropper's bit error rate is close to 0.5 as well as frame error rate driven to 100%.Furthermore,the system security capacity is effective to ensure the communication security.Finally,the USRP-Lab VIEW platform is used to implement and verify the performance of precoding MIMO-OFDM cross-layer secure transmission scheme.After the design of link functional modules and frame structure,a complete downlink communication system is built in the hardware and software environment,this paper realizes and verifies enhancement to the system security by the cross-layer precoding scheme in 2.5GHz / 3.5GHz / 5GHz frequency band.Several tests have confirmed that the reliability and security of the proposed cross-layer security scheme can fulfill the unconditional security transmission.