Performance Analysis On Physical Layer Security Of Hybrid Satellite-Terrestrial Networks

Due to the open nature of hybrid satellite-terrestrial networks,the legitimate transmissions are vulnerable to eavesdropping attacks.It’s challenging to secure the transmission of hybrid satelliteterrestrial networks for their randomness and time-varying property.Based on the traditional cryptographic techniques,physical layer security relies on the unique and diversity characteristics of hybrid satellite-terrestrial network channels,which is designed from the perspective of information theory,as a promising paradigm for realizing the confidential transmission of hybrid satelliteterrestrial network.In the light of the Shannon security theory,cooperative relay and cooperative jamming are employed in this dissertation to improve the secrecy performance of hybrid satelliteterrestrial networks with jointly considering both the co-channel interference(CCI)and whether the channel state information(CSI)is known.Physical layer security is investigated in diverse hybrid satellite-terrestrial networks in this dissertation in terms of outage probability,intercept probability and secrecy outage probability.The main contributions and innovations are presented as follows.First,for a hybrid satellite-terrestrial relay network,the single-relay selection and multi-relay selection as well as round-robin scheduling schemes are presented to investigate the physical-layer security while the wiretap channels’ CSI is unavailable.A geostationary earth orbit(GEO)satellite,a terrestrial destination and multiple decode-and-forward relays are included in this considered hybrid satellite-terrestrial network,where communication is achieved by the satellite transmitting information to a destination through multiple relays at the appearance of an eavesdropper attempting to intercept the transmissions from both the satellite and relays.Moreover,with the assumption that only the main channels’ CSI is known,the secrecy performance is evaluated in accordance with secrecy outage probability by driving out the closed-form expressions for the single-relay selection and baseline round-robin scheduling schemes,as well as by computer simulations for multi-relay selection scheme.Numerical results show that the two relay selection schemes generally outperform the round-robin scheduling baseline scheme in the light of improving the secrecy performance even when the legitimate links are inferior to the wiretap links.Then,for a multi-relay multi-user hybrid satellite-terrestrial network,optimal and suboptimal relay-user pairing schemes are proposed to improve the physical layer security in two scenarios with regard to the CSI of wiretap links is known or not.A GEO satellite,multiple terrestrial relays and users are included in this considered hybrid satellite-terrestrial network in the presence of a terrestrial eavesdropper who attempts to tap legitimate information from both satellite and relays.Specifically,a relay-user pair maximizing the secrecy rate is chosen as the optimal one to participate in the transmission,where all links’ CSI is used to perform relay-user pairing.However,suboptimal relayuser pairing scheme is designed only relying on the main links’ CSI without requiring wiretap links’ CSI,where a relay-user pair with the maximal transmission rate of main link is selected.Also,closedform expressions of secrecy outage probability with both integer and rational fading severity parameter are derived in the case of satellite links undergo Shadowed-Rician fading and terrestrial links subject to Rayleigh fading.Furthermore,asymptotic secrecy outage probability analysis is conducted in the high signal-to-noise ratio region.Numerical results reveal that relay-user pairing is beneficial to further improve physical layer security of the hybrid satellite-terrestrial network.Next,for an uplink hybrid satellite-terrestrial network,two relay selection schemes are proposed to improve security-reliability trade-off performance,namely the partial CSI based relay selection(PCSI-RS)where the CSI of CCI links is absent,and the full CSI based relay selection(FCSI-RS)where the CSI of CCI links is known.A terrestrial source,multiple terrestrial relays,and a satellite are included in this considered hybrid satellite-terrestrial network,in the face of co-channel interference(CCI)and an eavesdropper.The conventional round-robin relay selection(RRRS)scheme is also employed as a benchmark for comparison purposes.Both the outage and intercept probability of the proposed PCSI-RS and FCSI-RS schemes as well as the RRRS scheme are derived in CCI environments by considering that the satellite-terrestrial links follow the Shadowed-Rician fading while the links between terrestrial nodes undergo the Rayleigh fading.Numerical results show that PCSI-RS and FCSI-RS schemes have better SRT performance than the RRRS scheme,where the FCSI-RS scheme can achieve the best SRT performance.With an increasing number of relays,SRT performance of the proposed PCSI-RS and FCSI-RS schemes improves obviously while that of the RRRS remains unchanged,which indicates the advantages of employing the proposed PCSI-RS and FCSI-RS schemes.Finally,for a hybrid satellite-terrestrial network,three friendly jammer aided transmission schemes are proposed to improve physical-layer security,namely the random jammer selection aided transmission(RJST)scheme,the optimal jammer selection aided transmission(OJST)scheme,and the multiple jammers aided transmission(MJT)scheme with equal power.A GEO satellite,a terrestrial destination,and multiple friendly jammers are included in this considered hybrid satelliteterrestrial network in the face of an eavesdropper.For comparison purposes,the non-jammer aided transmission(NJT)scheme is also presented as a baseline.Secrecy outage performance of the proposed RJST,OJST,and MJT schemes as well as the NJT scheme are analyzed by deriving their closed-form secrecy outage probability expressions,respectively.Numerical results show that the proposed RJST,OJST,and MJT schemes outperform the NJS scheme in terms of their secrecy outage probabilities,where the OJST scheme can achieve the best secrecy outage performance,showing the secrecy benefits of adopting friendly jammers aided transmission schemes against eavesdropping.Additionally,with an increase in the number of friendly jammers,the secrecy outage performance of the OJST and MJT schemes can be improved significantly,while that of the RJST scheme remains unchanged.