Research On Physical-layer Security In Successive Relaying Networks

Successive relaying technology can overcome half-duplex constraint of relay nodes by arranging multiple relay nodes alternatively help relaying,and has received much attention since it can effectively promote communication efficiency of network.But introduction of multiple relay nodes enlarged secrecy signal range and increased risks of relay channel being eavesdropped.However,the existing research in successive relaying only paid attention to promotion of spectrum efficiency and few attached importance to security problem.Physical-layer security utilizes the inherent nature of wireless channel including randomness,time variability,diversity and reciprocity to solve security problem in wireless communication networks and had attracted great research interest.When outside or inside eavesdropper exists in networks,there is no performance analysis and solution yet.To solve security problems in successive relaying networks,this thesis studies physical-layer security in successive relaying networks based on the National Natural Science Foundation of China and the Natural High Technology Research and Development Program of China.Successive relaying physical-layer security models including outside and inside eavesdroppers are first established and performance analysis is conducted.Based on this,successive relaying secure transmission scheme with trusted relay,secure-oriented relay selection scheme in successive relaying networks were proposed to combat outside eavesdropping,successive relaying secure transmission scheme with untrusted relay was proposed to deal with inside eavesdropping.The concrete research content includes:1.To solve eavesdropping problem in successive relaying systems,a physical-layer security scheme based on inter-relay interference iterative elimination was proposed.Inter-relay interference was exploited as artificial noise to degrade eavesdropper's channel quality,and was eliminated at user by making use of correlation between adjacent receiving signals,then a quick power allocation algorithm at transmitter was proposed to maximize secrecy rate.Simulation results showed that the proposed scheme improved secrecy rate of successive relaying system at least 3 bit/s/Hz.2.Security-oriented relay selection schemes in successive relaying systems are proposed to maximize secrecy rate in multiple-relay systems with an outside eavesdropper.First,optimal relay selection(OPRS)scheme through general search was proposed and theoretical secrecy rate was deduced.To lower complexity,three different two-stage relay selection schemes which first narrows the scope of relays was proposed from aspects of maximizing main channel(K-MMRS)and maximizing interference between relays(K-MIRS),respectively.K-MIRS scheme had the lowest computation complexity,while K-MMRS scheme had the lowest CSI overhead.Simulation results showed that K-MMRS scheme can achieve optimal secrecy rate with lower complexity.3.A secure scheme based on inter-relay interference cancellation was proposed to combat untrusted relay eavesdropping problem in successive relaying systems.First inter-relay interference between trusted relay and untrusted relay was exploited as artificial noise to degrade untrusted relay's eavesdropping condition,then beamforming and inter-relay interference iterative cancellation method were adapt to improve signal quality received by legitimate user.Base on this,a quick power allocation algorithm aiming to minimize untrusted relay's sum rate was proposed.Theoretical analysis and simulation results showed that the proposed scheme can improved security of successive relaying systems,and a promotion of at least 2 bit/s/Hz in secrecy rate can be observed.