This paper investigates secure transmission for non-orthogonal multiple access(NOMA)systems where the imperfect successive interference cancellation(SIC)is considered at both legitimate users and eavesdropper(Eve).A p...This paper investigates secure transmission for non-orthogonal multiple access(NOMA)systems where the imperfect successive interference cancellation(SIC)is considered at both legitimate users and eavesdropper(Eve).A power allocation scheme is designed for the legitimate users to mitigate the effect of the SIC error caused by imperfect SIC.For characterizing the secrecy performance of the NOMA system,the closed-form expressions for connection outage probability(COP),secrecy outage probability(SOP),and effective secrecy throughput(EST)are derived over Nakagami-m fading channels in both NOMA and benchmark orthogonal multiple access(OMA)systems.We also provide security and reliability trade-off results(SRT)for the users in the NOMA and OMA systems.Simulation results verify our analysis and show that the strong users achieve better secrecy performance but worse reliability performance and NOMA outperforms OMA in terms of SRT.展开更多
To address the problems of network congestion and spectrum resources shortage in multi-user large-scale scenarios,this paper proposes a twice random access OFDMA-NOMA-RA protocol combining the advantages of orthogonal...To address the problems of network congestion and spectrum resources shortage in multi-user large-scale scenarios,this paper proposes a twice random access OFDMA-NOMA-RA protocol combining the advantages of orthogonal frequency division multiple access(OFDMA)and non-orthogonal multiple access(NOMA).The idea of this protocol is that OFMDA is used to divide the entire frequency field into multiple orthogonal resource units(RUs),and NOMA is used on each RU to enable more users to access the channel and improve spectrum efficiency.Based on the protocol designed in this paper,in the case of imperfect successive interference cancellation(SIC),the probability of successful competition subchannels and the outage probability are derived for two scenarios:Users occupy the subchannel individually and users share the subchannel.Moreover,when two users share the channel,the decoding order of the users and the corresponding probabilities are considered.Then,the system throughput is obtained.To achieve better outage performance in the system,the optimal power allocation algorithm is proposed in this paper,which enables the optimal power allocation strategy to be obtained.Numerical results show that the larger the imperfect SIC coefficient,the worse the outage performance of weak users.Compared with pure OFDMA and NOMA,OFDMA-NOMA-RA always maintains an advantage when the imperfect SIC coefficient is less than a specific value.展开更多
In order to improve the reliability and resource utilization efficiency of vehicle-to-vehicle(V2V)communication system,in this paper,the fairness optimization and power allocation for the cognitive V2V network that ta...In order to improve the reliability and resource utilization efficiency of vehicle-to-vehicle(V2V)communication system,in this paper,the fairness optimization and power allocation for the cognitive V2V network that takes into account the realistic three-dimensional(3D)channel are investigated.Large-scale and small-scale fading are considered in the proposed channel model.An adaptive non-orthogonal multiple access(NOMA)/orthogonal multiple access(OMA)scheme is proposed to reduce the complexity of successive-interference-cancellation(SIC)in decoding and improve spectrum utilization.Also,a fairness index that takes into account each user's requirements is proposed to indicate the optimal point clearly.In the imperfect SIC,the optimization problem of maximizing user fairness is formulated.Then,a subgradient descent method is proposed to solve the optimization problem with customizable precision.And the computational complexity of the proposed method is analyzed.The achievable rate,outage probability and user fairness are analyzed.The results show that the proposed adaptive NOMA/OMA(A-NOMA/OMA)outperforms both NOMA and OMA.The simulation results are compared with validated analysis to confirm the theoretical analysis.展开更多
In contrast with orthogonal multiple access(OMA)technologies,non-orthogonal multiple access(NOMA)technology can achieve higher spectral effi-ciency and support more users simultaneously.Multiple relays can be deployed...In contrast with orthogonal multiple access(OMA)technologies,non-orthogonal multiple access(NOMA)technology can achieve higher spectral effi-ciency and support more users simultaneously.Multiple relays can be deployed in NOMA networks,in order to combat fading and thus increase the transmission reliability.In the existing works on cooperative NOMA networks with multiple relays,the decoding error at the relays and the imperfect successive interference cancellation(SIC)are not taken into account simultaneously.In this work,we consider the bit error rate(BER)analysis of relay-aided NOMA networks,where max-min relay selection is employed.Particularly,closed-form BER expressions are derived for NOMA networks with Rayleigh fading,in the existence of the relay decoding error and imperfect SIC.The asymptotic BER performance is then obtained to provide some useful insights into the system design such as the diversity order.Finally,simulation results illustrate the correctness of the derived expressions.The presented results reveal the effects of imperfect SIC and relay decoding error on the performance of cooperative NOMA networks.展开更多
Hardware impairments(HI)are always present in low-cost wireless devices.This paper investigates the outage behaviors of intelligent reflecting surface(IRS)assisted non-orthogonal multiple access(NOMA)networks by takin...Hardware impairments(HI)are always present in low-cost wireless devices.This paper investigates the outage behaviors of intelligent reflecting surface(IRS)assisted non-orthogonal multiple access(NOMA)networks by taking into account the impact of HI.Specifically,we derive the approximate and asymptotic expressions of the outage probability for the IRS-NOMA-HI networks.Based on the asymptotic results,the diversity orders under perfect self-interference cancellation and imperfect self-interference cancellation scenarios are obtained to evaluate the performance of the considered network.In addition,the system throughput of IRS-NOMA-HI is discussed in delay-limited mode.The obtained results are provided to verify the accuracy of the theoretical analyses and reveal that:1)The outage performance and system throughput for IRS-NOMA-HI outperforms that of the IRS-assisted orthogonal multiple access-HI(IRS-OMA-HI)networks;2)The number of IRS elements,the pass loss factors,the Rician factors,and the value of HI are pivotal to enhancing the performance of IRS-NOMAHI networks;and 3)It is recommended that effective methods of reducing HI should be used to ensure system performance,in addition to self-interference cancellation techniques.展开更多
基金supported by the National Key R&D Program of China(No.2018YFB1801103)the National Natural Science Foundation of China(No.61771487).
文摘This paper investigates secure transmission for non-orthogonal multiple access(NOMA)systems where the imperfect successive interference cancellation(SIC)is considered at both legitimate users and eavesdropper(Eve).A power allocation scheme is designed for the legitimate users to mitigate the effect of the SIC error caused by imperfect SIC.For characterizing the secrecy performance of the NOMA system,the closed-form expressions for connection outage probability(COP),secrecy outage probability(SOP),and effective secrecy throughput(EST)are derived over Nakagami-m fading channels in both NOMA and benchmark orthogonal multiple access(OMA)systems.We also provide security and reliability trade-off results(SRT)for the users in the NOMA and OMA systems.Simulation results verify our analysis and show that the strong users achieve better secrecy performance but worse reliability performance and NOMA outperforms OMA in terms of SRT.
基金funded in part by the National Natural Science Foundation of China under Grant 61663024in part by the Hongliu First Class Discipline Development Project of Lanzhou University of Technology(25-225305).
文摘To address the problems of network congestion and spectrum resources shortage in multi-user large-scale scenarios,this paper proposes a twice random access OFDMA-NOMA-RA protocol combining the advantages of orthogonal frequency division multiple access(OFDMA)and non-orthogonal multiple access(NOMA).The idea of this protocol is that OFMDA is used to divide the entire frequency field into multiple orthogonal resource units(RUs),and NOMA is used on each RU to enable more users to access the channel and improve spectrum efficiency.Based on the protocol designed in this paper,in the case of imperfect successive interference cancellation(SIC),the probability of successful competition subchannels and the outage probability are derived for two scenarios:Users occupy the subchannel individually and users share the subchannel.Moreover,when two users share the channel,the decoding order of the users and the corresponding probabilities are considered.Then,the system throughput is obtained.To achieve better outage performance in the system,the optimal power allocation algorithm is proposed in this paper,which enables the optimal power allocation strategy to be obtained.Numerical results show that the larger the imperfect SIC coefficient,the worse the outage performance of weak users.Compared with pure OFDMA and NOMA,OFDMA-NOMA-RA always maintains an advantage when the imperfect SIC coefficient is less than a specific value.
基金supported by the National Natural Science Foundation of China(62001166,62172139)the Open Subject of Hebei Key Laboratory of Power Internet of Things Technology(2023KFKT002)the Natural Science Foundation of Hebei Province of China(F2022201055).
文摘In order to improve the reliability and resource utilization efficiency of vehicle-to-vehicle(V2V)communication system,in this paper,the fairness optimization and power allocation for the cognitive V2V network that takes into account the realistic three-dimensional(3D)channel are investigated.Large-scale and small-scale fading are considered in the proposed channel model.An adaptive non-orthogonal multiple access(NOMA)/orthogonal multiple access(OMA)scheme is proposed to reduce the complexity of successive-interference-cancellation(SIC)in decoding and improve spectrum utilization.Also,a fairness index that takes into account each user's requirements is proposed to indicate the optimal point clearly.In the imperfect SIC,the optimization problem of maximizing user fairness is formulated.Then,a subgradient descent method is proposed to solve the optimization problem with customizable precision.And the computational complexity of the proposed method is analyzed.The achievable rate,outage probability and user fairness are analyzed.The results show that the proposed adaptive NOMA/OMA(A-NOMA/OMA)outperforms both NOMA and OMA.The simulation results are compared with validated analysis to confirm the theoretical analysis.
基金This work was supported by the National Natural Science Foundation of China under Grants 61971360 and 61871139.
文摘In contrast with orthogonal multiple access(OMA)technologies,non-orthogonal multiple access(NOMA)technology can achieve higher spectral effi-ciency and support more users simultaneously.Multiple relays can be deployed in NOMA networks,in order to combat fading and thus increase the transmission reliability.In the existing works on cooperative NOMA networks with multiple relays,the decoding error at the relays and the imperfect successive interference cancellation(SIC)are not taken into account simultaneously.In this work,we consider the bit error rate(BER)analysis of relay-aided NOMA networks,where max-min relay selection is employed.Particularly,closed-form BER expressions are derived for NOMA networks with Rayleigh fading,in the existence of the relay decoding error and imperfect SIC.The asymptotic BER performance is then obtained to provide some useful insights into the system design such as the diversity order.Finally,simulation results illustrate the correctness of the derived expressions.The presented results reveal the effects of imperfect SIC and relay decoding error on the performance of cooperative NOMA networks.
基金supported by the National Natural Science Foundation of China under Grants 62071052,61901043the R&D Program of Beijing Municipal Education Commission under Grant KM202011232003+1 种基金supported by Talent Engineering Training Funds of Hebei Province under Grant A202101106Science and Technology Project of Hebei Education Department under Grant QN2020508.
文摘Hardware impairments(HI)are always present in low-cost wireless devices.This paper investigates the outage behaviors of intelligent reflecting surface(IRS)assisted non-orthogonal multiple access(NOMA)networks by taking into account the impact of HI.Specifically,we derive the approximate and asymptotic expressions of the outage probability for the IRS-NOMA-HI networks.Based on the asymptotic results,the diversity orders under perfect self-interference cancellation and imperfect self-interference cancellation scenarios are obtained to evaluate the performance of the considered network.In addition,the system throughput of IRS-NOMA-HI is discussed in delay-limited mode.The obtained results are provided to verify the accuracy of the theoretical analyses and reveal that:1)The outage performance and system throughput for IRS-NOMA-HI outperforms that of the IRS-assisted orthogonal multiple access-HI(IRS-OMA-HI)networks;2)The number of IRS elements,the pass loss factors,the Rician factors,and the value of HI are pivotal to enhancing the performance of IRS-NOMAHI networks;and 3)It is recommended that effective methods of reducing HI should be used to ensure system performance,in addition to self-interference cancellation techniques.
