Research On Physical Layer Security Technology Of Underwater Acoustic OFDM Communication

The development of high communication rate,energy efficiency,stability,security and low-cost underwater acoustic network has very important practical significance and economic value for research fields such as ocean monitoring,exploration and resource development.Because the underwater acoustic network is limited by its own characteristics and communication environment,the underwater acoustic communication often faces serious security attacks and threats.Therefore,it is of great practical significance to design underwater acoustic communication security technology and security system for the security threats and security requirements faced by underwater acoustic communication.This thesis mainly studies the physical layer security(PLS)security technology of underwater acoustic communication,aiming to realize the secure communication in the underwater acoustic environment.The main research contents of this thesis as follows:Firstly,the related technologies of PLS are expounded,and their development and principles are introduced in detail.Then,compare and introduce some underwater acoustic safety communication technologies and some common PLS technologies in underwater acoustic OFDM scenarios.On this basis,a key encryption algorithm is given in the OFDM system,setting a highspeed communication scenario,and using the phase rotation technique to affect the modulated constellation diagram,so as to achieve the purpose of concealing the modulation method.Considering the Doppler effect caused by the relative motion of high-speed communication,it is assumed that the channel has no effect on the frequency offset,and the Doppler effect produces a frequency offset of a certain size,and the similar relationship between the Doppler frequency offset and the phase rotation is considered,When the receiving end decrypts the received signal,the Doppler frequency offset is compensated by the cyclic prefix(CP)method.Then,an underwater acoustic OFDM key encryption algorithm is presented.Under the underwater acoustic multipath Doppler channel,the sub-carriers in the OFDM system are encrypted in phase by using the chaotic phase rotation encryption matrix generated by the one-dimensional chaotic system.Aiming at the similar characteristics of Doppler effect and frequency offset between the proposed algorithms in underwater acoustic communication,linear equalization(LE)technology is used at the receiver to perform Doppler compensation and at the same time physically decrypt to recover valid signals.Finally,in the OFDM scenario of underwater acoustic communication,a directional modulation combined with artificial noise security communication algorithm is presented.When the user is located close to the legal user,the system security will not be guaranteed.This thesis analyzes the application of the frequency diverse array(FDA)with both distance and direction correlation in the underwater acoustic safety communication.The effect on the FDA in the Doppler-consistent scenario is considered,the SINR closed expression of eavesdropping is deduced,and the security communication indicators such as secrecy rate and interruption probability are deduced and analyzed.