Two-way relay networks have received lots of attention, thanks to its ability to overcome the loss in the spectral efficiency due to half-duplex transmission. Asymptotic performance analysis can provide valuable insig...Two-way relay networks have received lots of attention, thanks to its ability to overcome the loss in the spectral efficiency due to half-duplex transmission. Asymptotic performance analysis can provide valuable insights in- to practical system designs. However, this is a gap in two-way relay network. In this paper, the asymptotic performance is studied for multi-branch dual-hop two-way amplify-and-forward （AF） relaying networks in independently but not necessarily identically distributed （i.n.i.d.） Nakagami-m fading channels, with arbitrary m 〉 5. The approximate prob- ability density function （PDF） of the instantaneous dual-hop link power at high SNR region is derived. Then we present the asymptotic outage probability expression, and analyze the diversity order and coding gain. Simulations are per- formed to verify the tightness of the presented analysis at medium and high SNR regions.展开更多
In this paper,we investigate the performance of the two-way Amplify-and-Forward(AF) relaying systems in an interference-limited Rayleigh fading environment.More specifically,assuming the presence of Rayleigh faded mul...In this paper,we investigate the performance of the two-way Amplify-and-Forward(AF) relaying systems in an interference-limited Rayleigh fading environment.More specifically,assuming the presence of Rayleigh faded multiple interferers at the AF relay and noisy sources,an approximate closed-form expression for the Overall Outage Probability(OOP) and an integral expression for the average Symbol Error Probability(SEP) are derived.The analysis results are verified through com-parison with the Monte Carlo simulation results.展开更多
This letter analyzes the outage probability of opportunistic amplify-and-forward relaying over asymmetric and independent but non-identically distributed (i.n.d) fading environments. The work investigates the scenario...This letter analyzes the outage probability of opportunistic amplify-and-forward relaying over asymmetric and independent but non-identically distributed (i.n.d) fading environments. The work investigates the scenarios where cooperative nodes are located at different geographical locations. As a result, the different signals are affected by different i.n.d fading channels, one may undergo Rician fading distribution and others may undergo Rayleigh fading distribution. In this letter, a lower bound of the outage probability for various asymmetric fading environments is derived at high SNR by applying the initial value theorem. The analytical model is validated through Monte-Carlo simulation results.展开更多
Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted m...Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. Based on the AUB, we propose a criterion for the parameter optimization in the PSAM scheme. We discuss how the pilot spacing and the length of the Wiener ?lter should be chosen under the constraint of a tradeoff between pilot overhead, estimation accuracy, and receiver complexity. We also formulate an power allocation problem for the considered system. It is shown that the power allocation problem can optimally be solved by means of a gradient search method. Numerical simulations are presented to verify the correctness of the theoretical results and to demonstrate the benefits of the parameter optimization.展开更多
We propose two novel power control policies for a two-way amplify-and-forward (AF) relaying system,in which each node (two sources and one relay) is assumed to operate under bothminimum and peak power constraints.Thro...We propose two novel power control policies for a two-way amplify-and-forward (AF) relaying system,in which each node (two sources and one relay) is assumed to operate under bothminimum and peak power constraints.Through the exploitation of instantaneous channel gains,the first policy can maximize the sum rate of the system.However,the instantaneous channel gains may be unavailable in a rapid time-varying system,where the first policy is inoperable.Consequently,a robust power control policy which requires only mean channel gains is proposed to maximize the upper bound of the average sum rate,and the properties of this policy are investigated.Simulation results show that,by comparison with the policy in which all the nodes use their peak transmit power,the proposed power control policies can provide considerable system performance improvement.Furthermore,the performance difference between the two proposed policies is negligible when the relay is close to one source.展开更多
This paper investigates the performance of a two-way amplify-and-forward （AF） relay system with adaptive modulation over independent and non-identical Nakagami-m fading channels. The tight closed-form cumulative dis...This paper investigates the performance of a two-way amplify-and-forward （AF） relay system with adaptive modulation over independent and non-identical Nakagami-m fading channels. The tight closed-form cumulative distribution function （CDF） expression of the instantaneous end-to-end signal-to-noise ratio （SNR） is provided. Further, approximate closed-form expression for the average spectral efficiency of the two-way AF system with adaptive modulation is obtained. Then, a tight lower bound of outage probability is derived. Finally, we use numerical simulations to verify the tightness of our analytical results.展开更多
This article analyzed multi-user diversity performance for multiple input single output （MISO） amplify-and-forward （AF） relaying network with selection combiner, and the closed-form outage probabilities for variab...This article analyzed multi-user diversity performance for multiple input single output （MISO） amplify-and-forward （AF） relaying network with selection combiner, and the closed-form outage probabilities for variable gain relaying and fixed gain relaying network are derived. Based on these results, diversity order is presented for variable gain relaying network. Simulation results validate the derived theoretical results, and the diversity order of variable gain relaying network with Nr available relays is K （Nt ＋ Nr） in K users＇ scenario, where Nt is the number of source transmitter antennas.展开更多
Linear transceiver designs are investigated for distributed two-way relaying networks,which aim at minimising the WeightedMean Square Error(WMSE) of data detections.The forwarding matrices at relays andequalization ma...Linear transceiver designs are investigated for distributed two-way relaying networks,which aim at minimising the WeightedMean Square Error(WMSE) of data detections.The forwarding matrices at relays andequalization matrices at destinations are jointly optimised.To overcome the challenginglimitations introduced by individual powerconstraints,a Semi-Definite Relaxation(SDR)called element-wise relaxation is proposed,which can transform the original optimizationproblem into a standard convex optimizationproblem.In this research,two-way relaying isunderstood from a pure signal processing perspective which can potentially simplify thetheoretical analysis.Finally,simulation resultsare used for assessing the performance advantage of the proposed algorithm.展开更多
In this paper, the problem of cubature Kalman fusion filtering(CKFF) is addressed for multi-sensor systems under amplify-and-forward(AaF) relays. For the purpose of facilitating data transmission, AaF relays are utili...In this paper, the problem of cubature Kalman fusion filtering(CKFF) is addressed for multi-sensor systems under amplify-and-forward(AaF) relays. For the purpose of facilitating data transmission, AaF relays are utilized to regulate signal communication between sensors and filters. Here, the randomly varying channel parameters are represented by a set of stochastic variables whose occurring probabilities are permitted to exhibit bounded uncertainty. Employing the spherical-radial cubature principle, a local filter under AaF relays is initially constructed. This construction ensures and minimizes an upper bound of the filtering error covariance by designing an appropriate filter gain. Subsequently, the local filters are fused through the application of the covariance intersection fusion rule. Furthermore, the uniform boundedness of the filtering error covariance's upper bound is investigated through establishing certain sufficient conditions. The effectiveness of the proposed CKFF scheme is ultimately validated via a simulation experiment concentrating on a three-phase induction machine.展开更多
A Reconfigurable Intelligent Surface(RIS)can relay signals from the transmitter to the receiver.In this regard,RISs operate similarly to traditional relays.We design a Multiple-Input-Multiple-Output(MIMO)system with a...A Reconfigurable Intelligent Surface(RIS)can relay signals from the transmitter to the receiver.In this regard,RISs operate similarly to traditional relays.We design a Multiple-Input-Multiple-Output(MIMO)system with a hybrid network of RIS and Half-Duplex(HD)Amplify-and-Forward(AF)relay.We model the system’s signal propagation and propose a new algorithm to get the system’s Achievable Rate(AR)value.We complete simulations to evaluate the performance of the RIS and HD-AF relay hybrid network system compared to the system assisted by either the RIS or HD-AF relay.The simulations indicate that many factors can considerably influence the system performance.Selecting an optimal placement for the RIS and relay can result in the best performance for the RIS and HD-AF relay hybrid network system in situations where the direct link between the receiver and transmitter is absent.展开更多
In Power Line Communications(PLC),there are regulatory masks that restrict the transmit power spectral density for electromagnetic compatibility reasons,which creates coverage issues despite the not too long distances...In Power Line Communications(PLC),there are regulatory masks that restrict the transmit power spectral density for electromagnetic compatibility reasons,which creates coverage issues despite the not too long distances.Hence,PLC networks often employ repeaters/relays,especially in smart grid neighborhood area networks.Even in broadband indoor PLC systems that offer a notable data rate,relaying may pave the way to new applications like being the backbone for wireless technologies in a cost-effective manner to support the Internet-of-things paradigm.In this paper,we study Multiple-Input Multiple-Output(MIMO)PLC systems that incorporate inband full-duplex functionality in relaying networks.We present several MIMO configurations that allow end-to-end half-duplex or full-duplex operations and analyze the achievable performance with state-of-the-art PLC systems.To reach this analysis,we get channel realizations from random network layouts for indoor and outdoor scenarios.We adopt realistic MIMO channel and noise models and consider transmission techniques according to PLC standards.The concepts discussed in this work can be useful in the design of future PLC relay-aided networks for different applications that look for a coverage extension and/or throughput:smart grids with enhanced communications in outdoor scenarios,and“last meter”systems for high-speed connections everywhere in indoor ones.展开更多
Physical layer security methods based on joint relay and jammer selection(JRJS)have been widely investigated in the study of secure wireless communications.Different from current works on JRJS schemes,which assumed th...Physical layer security methods based on joint relay and jammer selection(JRJS)have been widely investigated in the study of secure wireless communications.Different from current works on JRJS schemes,which assumed that the global channel state information(CSI)of the eavesdroppers(Eves)was known beforehand,then the optimal relaying and jamming relays were determined.More importantly,the time complexity of selecting optimal jamming relay is O(N^(2)),where N is the maximum number of relays/Eves.In this paper,for the scenario where the source wants to exchange the message with the destination,via relaying scheme due to longer communication distance and limited transmission power,in the presence of multiple Eves,with the assumption of Eves'perfect CSI and average CSI,we propose two kinds of JRJS methods.In particular,the time complexity of finding the optimal jammer can be reduced to O(N).Furthermore,we present a novel JRJS scheme for no CSI of Eves by minimizing the difference between expected signal and interfering signal at the destination.Finally,simulations show that the designed methods are more effective than JRJS and other existing strategies in terms of security performance.展开更多
This paper investigates the secure communication between legitimate users in the presence of eavesdroppers, where the Intelligent Reflective Surface-Unmanned Aerial Vehicle (IRS-UAV) and Buffer-Aided (BA) relaying tec...This paper investigates the secure communication between legitimate users in the presence of eavesdroppers, where the Intelligent Reflective Surface-Unmanned Aerial Vehicle (IRS-UAV) and Buffer-Aided (BA) relaying techniques are utilized to enhance secrecy performance. By jointly optimizing the link selection strategy, the UAV position, and the reflection coefficient of the IRS, we aim to maximize the long-term average secrecy rate. Specifically, we propose a novel buffer in/out stabilization scheme based on the Lyapunov framework, which transforms the long-term average secrecy rate maximization problem into two per-slot drift-plus-penalty minimization problems with different link selection factors. The hybrid Particle Swarm Optimization-Artificial Fish Swarm Algorithm (PSO-AFSA) is adopted to optimize the UAV position, and the IRS reflection coefficient optimization problem is solved by iterative optimization in which auxiliary variables and standard convex optimization algorithms are introduced. Finally, the delay constraint is set to ensure the timeliness of information packets. Simulation results demonstrate that our proposed scheme outperforms the comparison schemes in terms of average secrecy rate. Specifically, the addition of BA improves the average secrecy rate by 1.37 bps/Hz, and the continued optimizations of IRS reflection coefficients and UAV positions improve the average secrecy rate by 2.46 bps/Hz and 3.75 bps/Hz, respectively.展开更多
卫星下行链路因其开放性、广域覆盖性而面临严峻的窃听威胁,传统以加密技术为核心的卫星下行链路防窃听方案在计算复杂度与抗量子攻击能力上存在双重瓶颈,且现有卫星下行链路物理层安全防窃听方案的应用场景存在局限性。针对以上问题,...卫星下行链路因其开放性、广域覆盖性而面临严峻的窃听威胁,传统以加密技术为核心的卫星下行链路防窃听方案在计算复杂度与抗量子攻击能力上存在双重瓶颈,且现有卫星下行链路物理层安全防窃听方案的应用场景存在局限性。针对以上问题,通过基于动态扩展因子的扰码与编码级联设计,提出一种基于信道状态信息(Channel State Information,CSI)和协作中继的卫星下行链路防窃听方案。首先,通过部署地面中继基站,建立基于协作中继的卫星下行链路通信模型,扩大合法链路与窃听链路的CSI随机性差异;其次,通过合法链路CSI对准循环低密度奇偶校验码扩展因子进行动态调控,增加编码随机性,进而增加窃听者译码难度;最后,通过动态扩展因子与合法链路CSI在卫星端与用户端构建加扰与解扰机制,使窃听者因缺乏合法链路CSI而无法解扰保密信息。仿真结果表明,在用户端误码率低至10-6的情况下,利用扰码对CSI的依赖性构建窃听者解扰壁垒,可使窃听者误码率接近0.5。所提方案凭借对CSI与地面协作中继的协同设计,既具备抵御量子计算攻击的潜在能力,又契合卫星通信网络工程部署对高效低耗的需求,能够有效平衡卫星下行链路信息传输可靠性与安全性的矛盾,可为未来6G空天地一体化场景下的信息安全传输提供具备工程实践价值的技术参考路径。展开更多
基金supported by the Major State Basic Research Development Program of China(973 Program No.2012CB316100)the National Natural Science Foundation of China(No.61032002)the Fundamental Research Funds for the Central Universities(No.2010XS21)
文摘Two-way relay networks have received lots of attention, thanks to its ability to overcome the loss in the spectral efficiency due to half-duplex transmission. Asymptotic performance analysis can provide valuable insights in- to practical system designs. However, this is a gap in two-way relay network. In this paper, the asymptotic performance is studied for multi-branch dual-hop two-way amplify-and-forward （AF） relaying networks in independently but not necessarily identically distributed （i.n.i.d.） Nakagami-m fading channels, with arbitrary m 〉 5. The approximate prob- ability density function （PDF） of the instantaneous dual-hop link power at high SNR region is derived. Then we present the asymptotic outage probability expression, and analyze the diversity order and coding gain. Simulations are per- formed to verify the tightness of the presented analysis at medium and high SNR regions.
基金Supported by the National Natural Science Foundation of China (No. 61001107)the Important National Science & Technology Specific Project (2010ZX03006-002-04)the Natural Science Foundation of Jiangsu Province (No.BK2010101)
文摘In this paper,we investigate the performance of the two-way Amplify-and-Forward(AF) relaying systems in an interference-limited Rayleigh fading environment.More specifically,assuming the presence of Rayleigh faded multiple interferers at the AF relay and noisy sources,an approximate closed-form expression for the Overall Outage Probability(OOP) and an integral expression for the average Symbol Error Probability(SEP) are derived.The analysis results are verified through com-parison with the Monte Carlo simulation results.
文摘This letter analyzes the outage probability of opportunistic amplify-and-forward relaying over asymmetric and independent but non-identically distributed (i.n.d) fading environments. The work investigates the scenarios where cooperative nodes are located at different geographical locations. As a result, the different signals are affected by different i.n.d fading channels, one may undergo Rician fading distribution and others may undergo Rayleigh fading distribution. In this letter, a lower bound of the outage probability for various asymmetric fading environments is derived at high SNR by applying the initial value theorem. The analytical model is validated through Monte-Carlo simulation results.
文摘Cooperative diversity is a promising technology for future wireless networks. In this paper, we consider a cooperative communication system operating in an amplify-and-forward (AF) mode with a pilot symbol as-sisted modulation (PSAM) scheme. It is assumed that a linear minimum mean square estimator (LMMSE) is used for the channel estimation at the receiver. A simple and easy-to-evaluate asymptotical upper bound (AUB) of the symbol-error-rate (SER) is derived for uncoded AF cooperative communication systems with quadrature amplitude modulation (QAM) constellations. Based on the AUB, we propose a criterion for the parameter optimization in the PSAM scheme. We discuss how the pilot spacing and the length of the Wiener ?lter should be chosen under the constraint of a tradeoff between pilot overhead, estimation accuracy, and receiver complexity. We also formulate an power allocation problem for the considered system. It is shown that the power allocation problem can optimally be solved by means of a gradient search method. Numerical simulations are presented to verify the correctness of the theoretical results and to demonstrate the benefits of the parameter optimization.
基金supported by the Sino-Swedish IMT-Advanced Cooperation Project (No.2008DFA11780)the Canada-China Scientific and Technological Cooperation (No.2010DFA11320)+1 种基金the National Natural Science Foundation of China (Nos.60802033 and 60873190)the National High-Tech R&D Program (863) of China (No.2008AA01Z211)
文摘We propose two novel power control policies for a two-way amplify-and-forward (AF) relaying system,in which each node (two sources and one relay) is assumed to operate under bothminimum and peak power constraints.Through the exploitation of instantaneous channel gains,the first policy can maximize the sum rate of the system.However,the instantaneous channel gains may be unavailable in a rapid time-varying system,where the first policy is inoperable.Consequently,a robust power control policy which requires only mean channel gains is proposed to maximize the upper bound of the average sum rate,and the properties of this policy are investigated.Simulation results show that,by comparison with the policy in which all the nodes use their peak transmit power,the proposed power control policies can provide considerable system performance improvement.Furthermore,the performance difference between the two proposed policies is negligible when the relay is close to one source.
基金supported by the China's Major Projects on Science and Technology for New-Generation Broadband Wireless Mobile Communications Network (2010ZX03001-001-03)
文摘This paper investigates the performance of a two-way amplify-and-forward （AF） relay system with adaptive modulation over independent and non-identical Nakagami-m fading channels. The tight closed-form cumulative distribution function （CDF） expression of the instantaneous end-to-end signal-to-noise ratio （SNR） is provided. Further, approximate closed-form expression for the average spectral efficiency of the two-way AF system with adaptive modulation is obtained. Then, a tight lower bound of outage probability is derived. Finally, we use numerical simulations to verify the tightness of our analytical results.
文摘This article analyzed multi-user diversity performance for multiple input single output （MISO） amplify-and-forward （AF） relaying network with selection combiner, and the closed-form outage probabilities for variable gain relaying and fixed gain relaying network are derived. Based on these results, diversity order is presented for variable gain relaying network. Simulation results validate the derived theoretical results, and the diversity order of variable gain relaying network with Nr available relays is K （Nt ＋ Nr） in K users＇ scenario, where Nt is the number of source transmitter antennas.
基金supported in part by EricssonNational Science and Technology Major Project under Grant No.2010ZX03003-003-03+2 种基金Sino-Swedish IMT-Advanced and Beyond Cooperative Program under Grant No.2008DFA11780National Natural Science Foundation of China under Grant No.61101130the Excellent Young Scholar Research Funding of Beijing Institute of Technology under Grant No.2013CX04038
文摘Linear transceiver designs are investigated for distributed two-way relaying networks,which aim at minimising the WeightedMean Square Error(WMSE) of data detections.The forwarding matrices at relays andequalization matrices at destinations are jointly optimised.To overcome the challenginglimitations introduced by individual powerconstraints,a Semi-Definite Relaxation(SDR)called element-wise relaxation is proposed,which can transform the original optimizationproblem into a standard convex optimizationproblem.In this research,two-way relaying isunderstood from a pure signal processing perspective which can potentially simplify thetheoretical analysis.Finally,simulation resultsare used for assessing the performance advantage of the proposed algorithm.
基金supported in part by the National Natural Science Foundation of China(12171124,61933007)the Natural Science Foundation of Heilongjiang Province of China(ZD2022F003)+2 种基金the National High-End Foreign Experts Recruitment Plan of China(G2023012004L)the Royal Society of UKthe Alexander von Humboldt Foundation of Germany
文摘In this paper, the problem of cubature Kalman fusion filtering(CKFF) is addressed for multi-sensor systems under amplify-and-forward(AaF) relays. For the purpose of facilitating data transmission, AaF relays are utilized to regulate signal communication between sensors and filters. Here, the randomly varying channel parameters are represented by a set of stochastic variables whose occurring probabilities are permitted to exhibit bounded uncertainty. Employing the spherical-radial cubature principle, a local filter under AaF relays is initially constructed. This construction ensures and minimizes an upper bound of the filtering error covariance by designing an appropriate filter gain. Subsequently, the local filters are fused through the application of the covariance intersection fusion rule. Furthermore, the uniform boundedness of the filtering error covariance's upper bound is investigated through establishing certain sufficient conditions. The effectiveness of the proposed CKFF scheme is ultimately validated via a simulation experiment concentrating on a three-phase induction machine.
文摘A Reconfigurable Intelligent Surface(RIS)can relay signals from the transmitter to the receiver.In this regard,RISs operate similarly to traditional relays.We design a Multiple-Input-Multiple-Output(MIMO)system with a hybrid network of RIS and Half-Duplex(HD)Amplify-and-Forward(AF)relay.We model the system’s signal propagation and propose a new algorithm to get the system’s Achievable Rate(AR)value.We complete simulations to evaluate the performance of the RIS and HD-AF relay hybrid network system compared to the system assisted by either the RIS or HD-AF relay.The simulations indicate that many factors can considerably influence the system performance.Selecting an optimal placement for the RIS and relay can result in the best performance for the RIS and HD-AF relay hybrid network system in situations where the direct link between the receiver and transmitter is absent.
基金supported by the Spanish Government and EU,under project PID2019-109842RB-I00/AEI/10.13039/501100011033。
文摘In Power Line Communications(PLC),there are regulatory masks that restrict the transmit power spectral density for electromagnetic compatibility reasons,which creates coverage issues despite the not too long distances.Hence,PLC networks often employ repeaters/relays,especially in smart grid neighborhood area networks.Even in broadband indoor PLC systems that offer a notable data rate,relaying may pave the way to new applications like being the backbone for wireless technologies in a cost-effective manner to support the Internet-of-things paradigm.In this paper,we study Multiple-Input Multiple-Output(MIMO)PLC systems that incorporate inband full-duplex functionality in relaying networks.We present several MIMO configurations that allow end-to-end half-duplex or full-duplex operations and analyze the achievable performance with state-of-the-art PLC systems.To reach this analysis,we get channel realizations from random network layouts for indoor and outdoor scenarios.We adopt realistic MIMO channel and noise models and consider transmission techniques according to PLC standards.The concepts discussed in this work can be useful in the design of future PLC relay-aided networks for different applications that look for a coverage extension and/or throughput:smart grids with enhanced communications in outdoor scenarios,and“last meter”systems for high-speed connections everywhere in indoor ones.
基金supported by the National Natural Science Foundation of China with Grants 62301076 and 62321001。
文摘Physical layer security methods based on joint relay and jammer selection(JRJS)have been widely investigated in the study of secure wireless communications.Different from current works on JRJS schemes,which assumed that the global channel state information(CSI)of the eavesdroppers(Eves)was known beforehand,then the optimal relaying and jamming relays were determined.More importantly,the time complexity of selecting optimal jamming relay is O(N^(2)),where N is the maximum number of relays/Eves.In this paper,for the scenario where the source wants to exchange the message with the destination,via relaying scheme due to longer communication distance and limited transmission power,in the presence of multiple Eves,with the assumption of Eves'perfect CSI and average CSI,we propose two kinds of JRJS methods.In particular,the time complexity of finding the optimal jammer can be reduced to O(N).Furthermore,we present a novel JRJS scheme for no CSI of Eves by minimizing the difference between expected signal and interfering signal at the destination.Finally,simulations show that the designed methods are more effective than JRJS and other existing strategies in terms of security performance.
基金co-supported by the National Natural Science Foundation of China(Nos.62271399,61901015,GNA22001 and GAA20024)the Zhejiang Provincial Natural Science Foundation of China(No.LQ24F010003).
文摘This paper investigates the secure communication between legitimate users in the presence of eavesdroppers, where the Intelligent Reflective Surface-Unmanned Aerial Vehicle (IRS-UAV) and Buffer-Aided (BA) relaying techniques are utilized to enhance secrecy performance. By jointly optimizing the link selection strategy, the UAV position, and the reflection coefficient of the IRS, we aim to maximize the long-term average secrecy rate. Specifically, we propose a novel buffer in/out stabilization scheme based on the Lyapunov framework, which transforms the long-term average secrecy rate maximization problem into two per-slot drift-plus-penalty minimization problems with different link selection factors. The hybrid Particle Swarm Optimization-Artificial Fish Swarm Algorithm (PSO-AFSA) is adopted to optimize the UAV position, and the IRS reflection coefficient optimization problem is solved by iterative optimization in which auxiliary variables and standard convex optimization algorithms are introduced. Finally, the delay constraint is set to ensure the timeliness of information packets. Simulation results demonstrate that our proposed scheme outperforms the comparison schemes in terms of average secrecy rate. Specifically, the addition of BA improves the average secrecy rate by 1.37 bps/Hz, and the continued optimizations of IRS reflection coefficients and UAV positions improve the average secrecy rate by 2.46 bps/Hz and 3.75 bps/Hz, respectively.
文摘卫星下行链路因其开放性、广域覆盖性而面临严峻的窃听威胁,传统以加密技术为核心的卫星下行链路防窃听方案在计算复杂度与抗量子攻击能力上存在双重瓶颈,且现有卫星下行链路物理层安全防窃听方案的应用场景存在局限性。针对以上问题,通过基于动态扩展因子的扰码与编码级联设计,提出一种基于信道状态信息(Channel State Information,CSI)和协作中继的卫星下行链路防窃听方案。首先,通过部署地面中继基站,建立基于协作中继的卫星下行链路通信模型,扩大合法链路与窃听链路的CSI随机性差异;其次,通过合法链路CSI对准循环低密度奇偶校验码扩展因子进行动态调控,增加编码随机性,进而增加窃听者译码难度;最后,通过动态扩展因子与合法链路CSI在卫星端与用户端构建加扰与解扰机制,使窃听者因缺乏合法链路CSI而无法解扰保密信息。仿真结果表明,在用户端误码率低至10-6的情况下,利用扰码对CSI的依赖性构建窃听者解扰壁垒,可使窃听者误码率接近0.5。所提方案凭借对CSI与地面协作中继的协同设计,既具备抵御量子计算攻击的潜在能力,又契合卫星通信网络工程部署对高效低耗的需求,能够有效平衡卫星下行链路信息传输可靠性与安全性的矛盾,可为未来6G空天地一体化场景下的信息安全传输提供具备工程实践价值的技术参考路径。
