Research On Physical Layer Security Performance Of Multi-antenna And SWIPT Wireless Systems

As a complement scheme to traditional encryption technology,physical layer security of multiple-input multiple-output(MIMO)wireless systems,has been widely used in multiple access,relay systems,cognitive networks,millimeter wave communication,simultaneous wireless information and power transfer(SWIPT),etc.,which is a research hotspot in the field of current wireless communication.The physical layer security of code division multiple access(CDMA)systems,MIMO wireless systems and SWIPT systems were investigated in this thesis respectively.A brief review of physical layer security of optical CDMA systems and wireless CDMA systems,MIMO wireless systems,wireless systems with randomly located eavesdroppers and SWIPT systems were presented in chapter 1.The physical layer security performance of CDMA system with space-time spreading over time-correlated Rayleigh block fading channels was investigated in chapter 2.The system consists of a transmitter which uses space-time spreading CDMA signal,a legitimate receiver and an eavesdropper.The exact closed-form expressions for non-zero secrecy capacity probability,secrecy outage probability and asymptotic secrecy outage probability of the above system over timecorrelated Rayleigh block fading channels were derived.The physical layer security performance of space-time spreading CDMA system with correlation coefficients as parameters was investigated by numerical and simulation experiments.Aiming at the feedback delay can deteriorate the physical layer security performance of space-time coding wireless system,an orthogonal space-time block coding(OSTBC)scheme using channel prediction and transmit antenna selection to enhance its physical layer security was proposed in chapter 3.The scheme selects transmit antennas based on predictive channel matrix and the maximization criterion of the signal-to-noise ratio at the receiver,then the signal is encoded using OSTBC and transmitted by the selected antennas,the secret signal is recovered after maximum ratio combining,maximum likelihood decoding and demodulation at the receiver,the exact closed-form expressions for non-zero secrecy capacity probability,secrecy outage probability and asymptotic secrecy outage probability of OSTBC wireless system with channel prediction and transmit antenna selection were derived by using moment generating function.Numerical and simulation results show that the proposed scheme can obtain a larger secrecy array gain to enhance the physical layer security performance of OSTBC wireless system with transmit antenna selection under low normalized delay.Aiming at the problem that the number and location information of eavesdroppers in SWIPT system are difficult to determine in the actual scenario,modeling the number and location distribution of eavesdroppers as a Poisson point process was presented in chapter 4.Considering independent and collusion two eavesdropping scenarios,the expressions for secrecy outage probability of SWIPT system with power split and time switch strategies,the expression for secrecy throughput of SWIPT system with time switch strategy were derived,respectively.The effects of different system parameters on the physical layer security performance of SWIPT system were investigated by numerical and simulation experiments.Chapter 5 is the conclusion of this thesis.