Spatial diversity plays a significant role in wireless communication systems,including the Fourth Generation(4G)and Fifth Generation(5G)systems,and it is expected to be a fundamental part of the future wireless commun...Spatial diversity plays a significant role in wireless communication systems,including the Fourth Generation(4G)and Fifth Generation(5G)systems,and it is expected to be a fundamental part of the future wireless communication systems as well.The Multiple-Input Multiple-Output(MIMO)technology,which is included in the IEEE 802.16j standard,still holds the most crucial position in the 4G spectrum as it promises to improve the throughput,capacity,spectral,and energy efficiency of wireless communication systems in the 2020s.This makes MIMO a viable technology for delay constrained medical and health care facilities.This paper presents an approximate closed-form expression of the ergodic capacity for the Decode-and-Forward(DF)protocol MIMO-Orthogonal Frequency Division Multiplexing(OFDM)relaying network.Although MIMO-OFDM is highly valuable for modern high-speed wireless communication systems,especially in the medical sciences,its performance degrades in multi-hop relay networks.Therefore,in this paper,an approximate closed-form expression is derived for an end-to-end ergodic capacity of multi-hop DF MIMO-OFDM wireless communication system has been presented.Monte-Carlo simulations are conducted to verify the performance of the presented analysis regarding the capacity(bits/s/Hz)for different SNR-dB values for single,2×2,4×4,and multi-hop DF MIMOOFDM systems.The presented results provide useful insights for the research on the end-to-end ergodic capacity evaluation.展开更多
This paper focuses on analyzing the ergodic capacity performance of limited feedback (LFB) beamforming in multi-user distributed antenna system (DAS). In such a system, multi-user interference (MUI) is inevitably due ...This paper focuses on analyzing the ergodic capacity performance of limited feedback (LFB) beamforming in multi-user distributed antenna system (DAS). In such a system, multi-user interference (MUI) is inevitably due to the channel uncertainties caused by quantization error. Considering this, we propose a parameter named effective ergodic capacity rate (EECR), which denotes the capacity offset between finite rate feedback and perfect channel state information (CSI). The simulation results show that the derived approximated EECR is very tight to actual EECR. Based on the approximated EECR, an adaptive minimum bit feedback scheme is proposed, which can effectively reduce the overhead of feedback channel and the complexity of the system. The simulation results verify the effectiveness of the proposed scheme.展开更多
In this paper,we consider the spectrum sharing Cognitive Radio(CR) system,wherein Single-Input Multi-Output(SIMO) cognitive fading channel is assumed.Subject to the average in-terference constraint of primary user,the...In this paper,we consider the spectrum sharing Cognitive Radio(CR) system,wherein Single-Input Multi-Output(SIMO) cognitive fading channel is assumed.Subject to the average in-terference constraint of primary user,the ergodic capacity of cognitive user involving joint beamforming and power control is analyzed.We derive the optimal joint beamforming and power control strategy and deduce the general integral expression for ergodic capacity.Furthermore,under different channel fadings including Raleigh fading,Nakagami-m fading and Lognormal shadowing fading,the specific expressions of ergodic capacity for SIMO cognitive channel are exhibited.Most of the expressions are presented in closed-form or with some special integral functions.Large amount of simulations are conducted to corroborate our theoretical results.展开更多
Switch-and-examine combining (SEC) is an interesting diversity technique that is simpler than selection combining (SC), whereas its performances is similar in terms of bit error rate (BER) and diversity order. A...Switch-and-examine combining (SEC) is an interesting diversity technique that is simpler than selection combining (SC), whereas its performances is similar in terms of bit error rate (BER) and diversity order. As ergodic capacity is also a key performance index in modem wireless systems, this article analyzes the ergodic capacity of the SEC system. The numerical results show that the ergodic capacity of SEC with optimal threshold is similar to that of SC for arbitrary number of diversity branches.展开更多
Intelligent reflecting surface(IRS)is a newly emerged and promising paradigm to substantially improve the performance of wireless communications by constructing favorable communication channels via properly tuning mas...Intelligent reflecting surface(IRS)is a newly emerged and promising paradigm to substantially improve the performance of wireless communications by constructing favorable communication channels via properly tuning massive reflecting elements.This paper considers a distributed IRS aided decode-and-forward(DF)relaying system over Nakagami-m fading channels.Based on a tight approximation for the distribution of the received signalto-noise ratio(SNR),we first derive exact closed-form expressions of the outage probability,ergodic capacity,and energy efficiency for the considered system.Moreover,we propose the optimal IRS configuration considering the energy efficiency and pilot overhead.Finally,we compare the performance between the distributed IRS-aided DF relaying and multi-IRS-only systems,and verify the analytical results by using monte carlo simulations.展开更多
The performance of Rayleigh fading channels is substantially impacted by the impacts of relays, antennas, and the number of branches. Opportunistic relaying is a potent technique for enhancing the effects of the afore...The performance of Rayleigh fading channels is substantially impacted by the impacts of relays, antennas, and the number of branches. Opportunistic relaying is a potent technique for enhancing the effects of the aforementioned factors while enhancing the performance of fading channels. Due to these issues, a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is taken into consideration in this study. So the investigation of a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is the focus of this paper. The primary goals of this study are to maximize security in wireless multicasting while minimizing security loss caused by the effects of relays, branches at destinations and wiretappers, as well as multicast users and wiretappers through opportunistic relaying. To comprehend the insight effects of prior parameters, the closed form analytical expressions are constructed for the probability of non-zero secrecy multicast capacity (PNSMC), ergodic secrecy multicast capacity (ESMC), and secure outage probability for multicasting (SOPM). The findings demonstrate that opportunistic relaying is a successful method for reducing the loss of security in multicasting.展开更多
In this paper,a novel opportunistic scheduling(OS)scheme with antenna selection(AS)for the energy harvesting(EH)cooperative communication system where the relay can harvest energy from the source transmission is propo...In this paper,a novel opportunistic scheduling(OS)scheme with antenna selection(AS)for the energy harvesting(EH)cooperative communication system where the relay can harvest energy from the source transmission is proposed.In this considered scheme,we take into both traditional mathematical analysis and reinforcement learning(RL)scenarios with the power splitting(PS)factor constraint.For the case of traditional mathematical analysis of a fixed-PS factor,we derive an exact closed-form expressions for the ergodic capacity and outage probability in general signal-to-noise ratio(SNR)regime.Then,we combine the optimal PS factor with performance metrics to achieve the optimal transmission performance.Subsequently,based on the optimized PS factor,a RL technique called as Q-learning(QL)algorithm is proposed to derive the optimal antenna selection strategy.To highlight the performance advantage of the proposed QL with training the received SNR at the destination,we also examine the scenario of QL scheme with training channel between the relay and the destination.The results illustrate that,the optimized scheme is always superior to the fixed-PS factor scheme.In addition,a better system parameter setting with QL significantly outperforms the traditional mathematical analysis scheme.展开更多
With increasing the demand for transmitting secure information in wireless networks,deviceto-device(D2D)communication has great potential to improve system performance.As a well-known security risk is eavesdropping in...With increasing the demand for transmitting secure information in wireless networks,deviceto-device(D2D)communication has great potential to improve system performance.As a well-known security risk is eavesdropping in D2D communication,ensuring information security is quite challenging.In this paper,we first obtain the closed-forms of the secrecy outage probability(SOP)and the secrecy ergodic capacity(SEC)for direct and decodeand-forward(DF)relay modes.Numerical results are presented to verify the theoretical results,and these results show the cases that the DF relay mode improves security performance compared to the direct mode at long distances between the transmitter and receiver nodes.Further,we look into the optimization problems of secure resource allocation in D2D communication to maximize the SEC and to minimize the SOP by considering the strictly positive secrecy capacity constraint as a mixed-integer non-linear programming(MINLP)problem.In the continue,we convert the MINLP to convex optimization.Finally,we solve this program with a dual method and obtain an optimal solution in the direct and DF relay modes.展开更多
An accurate, complete and realistic channel model is re- quired to accurately analyze the system performance of a multiple input multiple output (MIMO) broadband satellite mobile commu- nication system with dual-ort...An accurate, complete and realistic channel model is re- quired to accurately analyze the system performance of a multiple input multiple output (MIMO) broadband satellite mobile commu- nication system with dual-orthogonal polarized antennas (DPAs). In most current studies, the channel characteristic matrix (CCM) is always formed by an independent identical distribution (i.i.d) model of Rayleigh or Rice distribution and nevertheless incomplete and inaccurate to describe a broadband dual-orthogonal polarized MIMO land mobile satellite (BDM-LMS) channel. This paper fo- cuses on establishing the BDM-LMS channel statistical model, which combines the 4-state broadband LMS channel model, the time selective fading features, the channel covariance information (CCI) channel model and polarization correlations between an- tennas. The modeling steps of the channel model are introduced. The main emphasis is placed on the effects of the factors, such as antenna numbers, temporal correlations, terminal environments, elevation angles and polarization correlations between the DPAs, on the channel capacity in the BDM-LMS system. Many simulation results are provided to illustrate the effects of these factors through comparisons of the transmit rate, ergodic capacity and outage capacity with different factor values. Besides, the MIMO outage capacity advantages, which indicate the benefits of MIMO com- pared with a single input single output (SISO) system under the same channel condition, are also studied under i.i.d or BDM-LMS channel.展开更多
Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under ...Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint.An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approxi-mation is presented in closed form in Rayleigh fading channels.When the complete channel state in-formation is not available,a more practical transmitter-side joint access ratio and transmit power constraint is proposed.The new constraint guarantees the same impact on interference outage prob-ability at primary user receiver.Both the optimal power allocation and transmit rate under the new constraint are presented in closed form.Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.展开更多
This paper investigates a Multiple-Input Multiple-Output (MIMO) scheme combining Transmit Antenna Selection and receive Maximal-Ratio Combining (TAS/MRC) in time-varying Rayleigh fading channels. We first present new ...This paper investigates a Multiple-Input Multiple-Output (MIMO) scheme combining Transmit Antenna Selection and receive Maximal-Ratio Combining (TAS/MRC) in time-varying Rayleigh fading channels. We first present new closed-form expressions for optimal received Signal-to-Noise Ratio (SNR),which is expressed in polynomial form. These are used to analyze ergodic capacity,outage probability and Bit Error Rate (BER) of TAS/MRC systems. Numerical results are presented to validate the theoretical analysis.展开更多
In this paper</span><span style="font-family:"">,</span><span style="font-family:""> in order to attain the maximum ergodic capacity and signifi</span><sp...In this paper</span><span style="font-family:"">,</span><span style="font-family:""> in order to attain the maximum ergodic capacity and signifi</span><span style="font-family:"">cantly increase the spectral efficiency of wireless communication systems, novel linear beamforming is proposed for dual-hop amplify-and-forward (AF) multi-relay networks. The linear beamforming is designed based on the maximi<span>zation of the signal-to-interference-plus-noise ratio (SINR) and signal-to</span>-</span><span style="font-family:""> </span><span style="font-family:"">leakage-and-noise ratio (SLNR). The channel state information (CSI) is used <span>in applying this new design to multi-relay (MR) nodes between the source</span> and relays as well as relays and destination. The beamforming optimization <span>problem is solved by using the Fukunaga-Koontz Transform (FKT). The</span> scheme can achieve intra-node array and distributed gains by using multiple antennas and multi-relays (MRs). The performance of the proposed scheme demonstrates that by considering interference mitigation criteria the ergodic capaci<span>ty at a significant level is improved as compared to the conventional tech</span>niques. Therefore, the proposed techniques based on the maximization of the <span>signal-to-interference-plus-noise ratio (SINR) and sig</span>nal-to-leakage-and-noise ratio (SLNR) relay processing outperform other conventional techniques in case of a multi-relay dual-hop network in terms of ergodic.展开更多
To provide global service with low latency, the broadband low earth orbits (LEO) satellite constellation based communication systems have become one of the focuses in academic and industry. To allow for wideband acces...To provide global service with low latency, the broadband low earth orbits (LEO) satellite constellation based communication systems have become one of the focuses in academic and industry. To allow for wideband access for user links, the feeder link of LEO satellite is correspondingly required to support high throughput data communications. To this end, we propose to apply line-of-sight (LoS) multiple-input multiple-output (MIMO) transmission for the feeder link to achieve spatial multiplexing by optimizing the antenna arrangement. Unlike the LoS MIMO applications for static scenarios, the movement of LEO satellites make it impractical to adjust the optimal antenna separation for all possible satellite positions. To address this issue, we propose to design the antenna placement to maximize the ergodic channel capacity during the visible region of the ground station. We first derive the closed-form probability distribution of the satellite trajectory in visible region. Based on which the ergodic channel capacity can be then calculated numerically. The antenna placement can be further optimized to maximize the ergodic channel capacity. Numerical results verify the derived probability distribution of the satellite trajectory, and show that the proposed LoS MIMO scheme can significantly increase the ergodic channel capacity compared with the existing SISO one.展开更多
This work investigates the security issue of the energy-constrained untrusted relay network with imperfect channel reciprocity,where the relay without the built-in power supply can only scavenge energy from radio-freq...This work investigates the security issue of the energy-constrained untrusted relay network with imperfect channel reciprocity,where the relay without the built-in power supply can only scavenge energy from radio-frequency signals radiated by the source and destination.A hybrid power-splitting(PS)-and time-switching(TS)-based relaying(HPTR)protocol is presented to improve the degraded secrecy performance due to the incomplete self-interference cancellation at the destination.To evaluate the secrecy throughput(ST)of the studied system,the analytical expression of the secrecy outage probability under the delay-limited transmission mode and the closed-form lower bound of the ergodic secrecy capacity under delay-tolerant transmission mode are derived.Both linear and nonlinear models for the energy harvester at the relay are compared.The optimal PS and TS ratios are evaluated numerically.The theoretical derivations are validated by numerical results,revealing that the residual jamming has a negative effect on the secrecy performance of untrusted relay networks,which can be alleviated by the HPTR protocol.Besides,we compare the ST performance of the HPTR protocol with that of the PS and TS relaying schemes,and the results show that the HPTR protocol outperforms both PS and TS relaying protocols in terms of the ST.展开更多
This paper explores the ergodic channel capacity of multiple-input single-output(MISO)free-space optical(FSO)communication systems,assisted by(optical)re-configurable intelligent surfaces[(O)RIS],made of concave refle...This paper explores the ergodic channel capacity of multiple-input single-output(MISO)free-space optical(FSO)communication systems,assisted by(optical)re-configurable intelligent surfaces[(O)RIS],made of concave reflectors.On the one hand,RIS technology mitigates dead zones in communication systems.Additionally,it increases the data rate and communication range,enhances the communication channel by making it intelligent,and improves the system’s capacity.Finally,the RIS technology improves the spectrum and energy efficiencies of the considered systems.On the other hand,transmitting diversity mitigates deep fade and helps to achieve beamforming to regulate the beam sent in a specific direction.Finally,multiple light sources help to send different versions of the same information at other time slots.Furthermore,compared to flat reflectors,concave mirrors provide economic advantages enabled by their natural shape,which helps converge the impinging light beams into the same focal point.In this paper,we harness the full potential of ORIS and MISO technologies in an FSO system by exploiting the hollow of concave reflectors to focus the reflected beams on a single user.We derive an approximated closed-form expression,provide results of the proposed ORIS-aided FSO systems’ergodic channel capacity,and discuss the suitable type of concave reflector.These results show that all types of concave mirrors provide similar results except when the thickness of the reflector is large enough to impact the reflected light.展开更多
Femtocell is a promising technology to improve network performance with low-power and cost-beneficial small base stations. However, the interference-limited reality in femtocell networks makes interference and resourc...Femtocell is a promising technology to improve network performance with low-power and cost-beneficial small base stations. However, the interference-limited reality in femtocell networks makes interference and resource management the key to achieving the benefits of femtocell networks. In this paper, the following contributions are made step by step: first, on the basis of the interference temperature model (ITM) in cognitive radio (CR) technique and the network architecture of the third generation partnership project (3GPP) long term evolution advanced (LTE-A), the problem model of optimizing the capacity of the femtocell-reused subchannel is established under the frequency partitioning strategy, jointly considering the average interference constraint and the instantaneous interference constraint. Second, utilizing the convex theory, optimal power allocation of the femtocell-reused subchannel is derived. Third, under Rayleigh fading channel, closed-form expressions of the subchannel reusable probability and capacity are derived. At last, numerical results are conducted to confirming our analytical results, which could provide theoretical guidance for frequency resource allocation of femtocell network deployments.展开更多
This paper presents analytical expressions for the multiple-input multiple-output (MIMO) channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capac...This paper presents analytical expressions for the multiple-input multiple-output (MIMO) channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capacity for single-input multiple-output (SIMO) channels. The analysis shows that the SIMO channel capacity can be approximated by a Gaussian random variable and that the MIMO channel capacity can be approximated as the sum of multiple SIMO capacities. The SIMO channel results are used to derive approximate closed-form expressions for the MIMO channel ergodic capacity and the complementary cumulative distribution function (CCDF) of the MIMO channel capacity (outage capacity). Simulations show that these theoretical results are good approximations for MIMO systems with an arbitrary number of transmit or receive antennas. Moreover, these analytical expressions are relatively simple which makes them very useful for practical computations.展开更多
allocation (PA) plays an important role in capacity improvement for cooperative multiple-input multipleoutput (Co-MIMO) systems. Many contributions consider a total power constraint (TPC) on the sum of transmit ...allocation (PA) plays an important role in capacity improvement for cooperative multiple-input multipleoutput (Co-MIMO) systems. Many contributions consider a total power constraint (TPC) on the sum of transmit power from all nodes in addressing PA problem. However, in practical implementations, each transmit node is equipped with its own power amplifier and is limited by individual power constraint (IPC). Hence these PA methods under TPC are not realizable in practical systems. Meanwhile, the PA problem under IPC is essential, but it has not been studied. This paper extends the traditional non-cooperative water-filling PA algorithm to IPC-based Co-MIMO systems. Moreover, the PA matrix is derived based on the compound channel matrix from all the cooperative nodes to the user. Therefore, the cooperative gain of the IPC-based Co-MIMO systems is fully exploited, and further the maximal instantaneous capacity is achieved. Numerical simulations validate that, under the same IPC conditions, the proposed PA scheme considerably outperforms the non-cooperative water-filling PA and uniform PA design in terms of ergodic capacity.展开更多
Reconfigurable intelligent surfaces (RIS) play a vital role in meeting the growing demand for higher data rates and reliability in wireless systems. This study focuses on analyzing the performance of RIS systems to ga...Reconfigurable intelligent surfaces (RIS) play a vital role in meeting the growing demand for higher data rates and reliability in wireless systems. This study focuses on analyzing the performance of RIS systems to gain a deeper understanding of their potential.The paper presents a mathematical analysis of the RIS system,deriving closed-form formulae that express its characteristics including signal-to-noise ratio(SNR)distribution,ergodic and effective capacity,outage,and error probability. The obtained formulae are newly derived and unconditionally valid solutions. Numerical results demonstrate a close agreement between the derived formulae and MonteCarlo simulation outcomes.展开更多
文摘Spatial diversity plays a significant role in wireless communication systems,including the Fourth Generation(4G)and Fifth Generation(5G)systems,and it is expected to be a fundamental part of the future wireless communication systems as well.The Multiple-Input Multiple-Output(MIMO)technology,which is included in the IEEE 802.16j standard,still holds the most crucial position in the 4G spectrum as it promises to improve the throughput,capacity,spectral,and energy efficiency of wireless communication systems in the 2020s.This makes MIMO a viable technology for delay constrained medical and health care facilities.This paper presents an approximate closed-form expression of the ergodic capacity for the Decode-and-Forward(DF)protocol MIMO-Orthogonal Frequency Division Multiplexing(OFDM)relaying network.Although MIMO-OFDM is highly valuable for modern high-speed wireless communication systems,especially in the medical sciences,its performance degrades in multi-hop relay networks.Therefore,in this paper,an approximate closed-form expression is derived for an end-to-end ergodic capacity of multi-hop DF MIMO-OFDM wireless communication system has been presented.Monte-Carlo simulations are conducted to verify the performance of the presented analysis regarding the capacity(bits/s/Hz)for different SNR-dB values for single,2×2,4×4,and multi-hop DF MIMOOFDM systems.The presented results provide useful insights for the research on the end-to-end ergodic capacity evaluation.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.2006AA01Z272 and 2009AA02Z412)the Beijing Municipal Science & Technology Commission(Grant No.D08080100620802)
文摘This paper focuses on analyzing the ergodic capacity performance of limited feedback (LFB) beamforming in multi-user distributed antenna system (DAS). In such a system, multi-user interference (MUI) is inevitably due to the channel uncertainties caused by quantization error. Considering this, we propose a parameter named effective ergodic capacity rate (EECR), which denotes the capacity offset between finite rate feedback and perfect channel state information (CSI). The simulation results show that the derived approximated EECR is very tight to actual EECR. Based on the approximated EECR, an adaptive minimum bit feedback scheme is proposed, which can effectively reduce the overhead of feedback channel and the complexity of the system. The simulation results verify the effectiveness of the proposed scheme.
基金Supported by the National Basic Research Program (973) of China (No. 2009CB320400)the National High-Tech Research and Development Program (863) of China (No. 2009AA01Z243)+1 种基金the National Natural Science Foundation of China (No. 61072044)the Natural Science Fund of Jiangsu Province (BK2009056)
文摘In this paper,we consider the spectrum sharing Cognitive Radio(CR) system,wherein Single-Input Multi-Output(SIMO) cognitive fading channel is assumed.Subject to the average in-terference constraint of primary user,the ergodic capacity of cognitive user involving joint beamforming and power control is analyzed.We derive the optimal joint beamforming and power control strategy and deduce the general integral expression for ergodic capacity.Furthermore,under different channel fadings including Raleigh fading,Nakagami-m fading and Lognormal shadowing fading,the specific expressions of ergodic capacity for SIMO cognitive channel are exhibited.Most of the expressions are presented in closed-form or with some special integral functions.Large amount of simulations are conducted to corroborate our theoretical results.
基金supported by the National Natural Science Foundation of China (60602060)the Hi-Tech Research and Development Program of China (2007AA01Z211).
文摘Switch-and-examine combining (SEC) is an interesting diversity technique that is simpler than selection combining (SC), whereas its performances is similar in terms of bit error rate (BER) and diversity order. As ergodic capacity is also a key performance index in modem wireless systems, this article analyzes the ergodic capacity of the SEC system. The numerical results show that the ergodic capacity of SEC with optimal threshold is similar to that of SC for arbitrary number of diversity branches.
基金supported in part by National Natural Science Foundation of China under Grant 62371262 and 61971467in part by the Key Research and Development Program of Jiangsu Province of China under Grant BE2021013-1+1 种基金in part by the Qinlan Project of Jiangsu Provincein part by the Scientific Research Program of Nantong under Grant JC22022026
文摘Intelligent reflecting surface(IRS)is a newly emerged and promising paradigm to substantially improve the performance of wireless communications by constructing favorable communication channels via properly tuning massive reflecting elements.This paper considers a distributed IRS aided decode-and-forward(DF)relaying system over Nakagami-m fading channels.Based on a tight approximation for the distribution of the received signalto-noise ratio(SNR),we first derive exact closed-form expressions of the outage probability,ergodic capacity,and energy efficiency for the considered system.Moreover,we propose the optimal IRS configuration considering the energy efficiency and pilot overhead.Finally,we compare the performance between the distributed IRS-aided DF relaying and multi-IRS-only systems,and verify the analytical results by using monte carlo simulations.
文摘The performance of Rayleigh fading channels is substantially impacted by the impacts of relays, antennas, and the number of branches. Opportunistic relaying is a potent technique for enhancing the effects of the aforementioned factors while enhancing the performance of fading channels. Due to these issues, a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is taken into consideration in this study. So the investigation of a secure wireless multicasting scenario using opportunistic relaying over Rayleigh fading channel in the presence of multiple wiretappers is the focus of this paper. The primary goals of this study are to maximize security in wireless multicasting while minimizing security loss caused by the effects of relays, branches at destinations and wiretappers, as well as multicast users and wiretappers through opportunistic relaying. To comprehend the insight effects of prior parameters, the closed form analytical expressions are constructed for the probability of non-zero secrecy multicast capacity (PNSMC), ergodic secrecy multicast capacity (ESMC), and secure outage probability for multicasting (SOPM). The findings demonstrate that opportunistic relaying is a successful method for reducing the loss of security in multicasting.
基金supported in part by the National Natural Science Foundation of China under Grant 61720106003,Grant 61401165,Grant 61379006,Grant 61671144,and Grant 61701538in part by the Natural Science Foundation of Fujian Province under Grants 2015J01262+3 种基金in part by Promotion Program for Young and Middle-aged Teacher in Science and Technology Research of Huaqiao University under Grant ZQN-PY407in part by Science and Technology Innovation Teams of Henan Province for Colleges and Universities(17IRTSTHN014)in part by the Scientific and Technological Key Project of Henan Province under Grant 172102210080 and Grant 182102210449in part by the Collaborative Innovation Center for Aviation Economy Development of Henan Province。
文摘In this paper,a novel opportunistic scheduling(OS)scheme with antenna selection(AS)for the energy harvesting(EH)cooperative communication system where the relay can harvest energy from the source transmission is proposed.In this considered scheme,we take into both traditional mathematical analysis and reinforcement learning(RL)scenarios with the power splitting(PS)factor constraint.For the case of traditional mathematical analysis of a fixed-PS factor,we derive an exact closed-form expressions for the ergodic capacity and outage probability in general signal-to-noise ratio(SNR)regime.Then,we combine the optimal PS factor with performance metrics to achieve the optimal transmission performance.Subsequently,based on the optimized PS factor,a RL technique called as Q-learning(QL)algorithm is proposed to derive the optimal antenna selection strategy.To highlight the performance advantage of the proposed QL with training the received SNR at the destination,we also examine the scenario of QL scheme with training channel between the relay and the destination.The results illustrate that,the optimized scheme is always superior to the fixed-PS factor scheme.In addition,a better system parameter setting with QL significantly outperforms the traditional mathematical analysis scheme.
文摘With increasing the demand for transmitting secure information in wireless networks,deviceto-device(D2D)communication has great potential to improve system performance.As a well-known security risk is eavesdropping in D2D communication,ensuring information security is quite challenging.In this paper,we first obtain the closed-forms of the secrecy outage probability(SOP)and the secrecy ergodic capacity(SEC)for direct and decodeand-forward(DF)relay modes.Numerical results are presented to verify the theoretical results,and these results show the cases that the DF relay mode improves security performance compared to the direct mode at long distances between the transmitter and receiver nodes.Further,we look into the optimization problems of secure resource allocation in D2D communication to maximize the SEC and to minimize the SOP by considering the strictly positive secrecy capacity constraint as a mixed-integer non-linear programming(MINLP)problem.In the continue,we convert the MINLP to convex optimization.Finally,we solve this program with a dual method and obtain an optimal solution in the direct and DF relay modes.
基金supported by the National Natural Science Foundation of China(61301105)the China Postdoctoral Science Foundation Funded Project(2013M531351)
文摘An accurate, complete and realistic channel model is re- quired to accurately analyze the system performance of a multiple input multiple output (MIMO) broadband satellite mobile commu- nication system with dual-orthogonal polarized antennas (DPAs). In most current studies, the channel characteristic matrix (CCM) is always formed by an independent identical distribution (i.i.d) model of Rayleigh or Rice distribution and nevertheless incomplete and inaccurate to describe a broadband dual-orthogonal polarized MIMO land mobile satellite (BDM-LMS) channel. This paper fo- cuses on establishing the BDM-LMS channel statistical model, which combines the 4-state broadband LMS channel model, the time selective fading features, the channel covariance information (CCI) channel model and polarization correlations between an- tennas. The modeling steps of the channel model are introduced. The main emphasis is placed on the effects of the factors, such as antenna numbers, temporal correlations, terminal environments, elevation angles and polarization correlations between the DPAs, on the channel capacity in the BDM-LMS system. Many simulation results are provided to illustrate the effects of these factors through comparisons of the transmit rate, ergodic capacity and outage capacity with different factor values. Besides, the MIMO outage capacity advantages, which indicate the benefits of MIMO com- pared with a single input single output (SISO) system under the same channel condition, are also studied under i.i.d or BDM-LMS channel.
基金Supported by the National Natural Science Foundation of China (No. 60972008)
文摘Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint.An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approxi-mation is presented in closed form in Rayleigh fading channels.When the complete channel state in-formation is not available,a more practical transmitter-side joint access ratio and transmit power constraint is proposed.The new constraint guarantees the same impact on interference outage prob-ability at primary user receiver.Both the optimal power allocation and transmit rate under the new constraint are presented in closed form.Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.
文摘This paper investigates a Multiple-Input Multiple-Output (MIMO) scheme combining Transmit Antenna Selection and receive Maximal-Ratio Combining (TAS/MRC) in time-varying Rayleigh fading channels. We first present new closed-form expressions for optimal received Signal-to-Noise Ratio (SNR),which is expressed in polynomial form. These are used to analyze ergodic capacity,outage probability and Bit Error Rate (BER) of TAS/MRC systems. Numerical results are presented to validate the theoretical analysis.
文摘In this paper</span><span style="font-family:"">,</span><span style="font-family:""> in order to attain the maximum ergodic capacity and signifi</span><span style="font-family:"">cantly increase the spectral efficiency of wireless communication systems, novel linear beamforming is proposed for dual-hop amplify-and-forward (AF) multi-relay networks. The linear beamforming is designed based on the maximi<span>zation of the signal-to-interference-plus-noise ratio (SINR) and signal-to</span>-</span><span style="font-family:""> </span><span style="font-family:"">leakage-and-noise ratio (SLNR). The channel state information (CSI) is used <span>in applying this new design to multi-relay (MR) nodes between the source</span> and relays as well as relays and destination. The beamforming optimization <span>problem is solved by using the Fukunaga-Koontz Transform (FKT). The</span> scheme can achieve intra-node array and distributed gains by using multiple antennas and multi-relays (MRs). The performance of the proposed scheme demonstrates that by considering interference mitigation criteria the ergodic capaci<span>ty at a significant level is improved as compared to the conventional tech</span>niques. Therefore, the proposed techniques based on the maximization of the <span>signal-to-interference-plus-noise ratio (SINR) and sig</span>nal-to-leakage-and-noise ratio (SLNR) relay processing outperform other conventional techniques in case of a multi-relay dual-hop network in terms of ergodic.
基金supported by the National Key R&D Program of China under Grant 2019YFB1803102
文摘To provide global service with low latency, the broadband low earth orbits (LEO) satellite constellation based communication systems have become one of the focuses in academic and industry. To allow for wideband access for user links, the feeder link of LEO satellite is correspondingly required to support high throughput data communications. To this end, we propose to apply line-of-sight (LoS) multiple-input multiple-output (MIMO) transmission for the feeder link to achieve spatial multiplexing by optimizing the antenna arrangement. Unlike the LoS MIMO applications for static scenarios, the movement of LEO satellites make it impractical to adjust the optimal antenna separation for all possible satellite positions. To address this issue, we propose to design the antenna placement to maximize the ergodic channel capacity during the visible region of the ground station. We first derive the closed-form probability distribution of the satellite trajectory in visible region. Based on which the ergodic channel capacity can be then calculated numerically. The antenna placement can be further optimized to maximize the ergodic channel capacity. Numerical results verify the derived probability distribution of the satellite trajectory, and show that the proposed LoS MIMO scheme can significantly increase the ergodic channel capacity compared with the existing SISO one.
基金Special Foundation for Chongqing Science and Technology Talent(cstc2019yszx-jcyj X0006 and cstc2020yszx-jscx X0004)Advanced Research Project of Civil Aerospace Technologies in 13th Five-year Plan(D010201)。
文摘This work investigates the security issue of the energy-constrained untrusted relay network with imperfect channel reciprocity,where the relay without the built-in power supply can only scavenge energy from radio-frequency signals radiated by the source and destination.A hybrid power-splitting(PS)-and time-switching(TS)-based relaying(HPTR)protocol is presented to improve the degraded secrecy performance due to the incomplete self-interference cancellation at the destination.To evaluate the secrecy throughput(ST)of the studied system,the analytical expression of the secrecy outage probability under the delay-limited transmission mode and the closed-form lower bound of the ergodic secrecy capacity under delay-tolerant transmission mode are derived.Both linear and nonlinear models for the energy harvester at the relay are compared.The optimal PS and TS ratios are evaluated numerically.The theoretical derivations are validated by numerical results,revealing that the residual jamming has a negative effect on the secrecy performance of untrusted relay networks,which can be alleviated by the HPTR protocol.Besides,we compare the ST performance of the HPTR protocol with that of the PS and TS relaying schemes,and the results show that the HPTR protocol outperforms both PS and TS relaying protocols in terms of the ST.
文摘This paper explores the ergodic channel capacity of multiple-input single-output(MISO)free-space optical(FSO)communication systems,assisted by(optical)re-configurable intelligent surfaces[(O)RIS],made of concave reflectors.On the one hand,RIS technology mitigates dead zones in communication systems.Additionally,it increases the data rate and communication range,enhances the communication channel by making it intelligent,and improves the system’s capacity.Finally,the RIS technology improves the spectrum and energy efficiencies of the considered systems.On the other hand,transmitting diversity mitigates deep fade and helps to achieve beamforming to regulate the beam sent in a specific direction.Finally,multiple light sources help to send different versions of the same information at other time slots.Furthermore,compared to flat reflectors,concave mirrors provide economic advantages enabled by their natural shape,which helps converge the impinging light beams into the same focal point.In this paper,we harness the full potential of ORIS and MISO technologies in an FSO system by exploiting the hollow of concave reflectors to focus the reflected beams on a single user.We derive an approximated closed-form expression,provide results of the proposed ORIS-aided FSO systems’ergodic channel capacity,and discuss the suitable type of concave reflector.These results show that all types of concave mirrors provide similar results except when the thickness of the reflector is large enough to impact the reflected light.
基金The National Science and Technology Special Project,The National Natural Science Foundation of China
文摘Femtocell is a promising technology to improve network performance with low-power and cost-beneficial small base stations. However, the interference-limited reality in femtocell networks makes interference and resource management the key to achieving the benefits of femtocell networks. In this paper, the following contributions are made step by step: first, on the basis of the interference temperature model (ITM) in cognitive radio (CR) technique and the network architecture of the third generation partnership project (3GPP) long term evolution advanced (LTE-A), the problem model of optimizing the capacity of the femtocell-reused subchannel is established under the frequency partitioning strategy, jointly considering the average interference constraint and the instantaneous interference constraint. Second, utilizing the convex theory, optimal power allocation of the femtocell-reused subchannel is derived. Third, under Rayleigh fading channel, closed-form expressions of the subchannel reusable probability and capacity are derived. At last, numerical results are conducted to confirming our analytical results, which could provide theoretical guidance for frequency resource allocation of femtocell network deployments.
文摘This paper presents analytical expressions for the multiple-input multiple-output (MIMO) channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capacity for single-input multiple-output (SIMO) channels. The analysis shows that the SIMO channel capacity can be approximated by a Gaussian random variable and that the MIMO channel capacity can be approximated as the sum of multiple SIMO capacities. The SIMO channel results are used to derive approximate closed-form expressions for the MIMO channel ergodic capacity and the complementary cumulative distribution function (CCDF) of the MIMO channel capacity (outage capacity). Simulations show that these theoretical results are good approximations for MIMO systems with an arbitrary number of transmit or receive antennas. Moreover, these analytical expressions are relatively simple which makes them very useful for practical computations.
基金supported by the International Scientific and Technological Cooperation Program (S2010GR0902)the National Natural Science Foundation of China (61001119, 61027003)
文摘allocation (PA) plays an important role in capacity improvement for cooperative multiple-input multipleoutput (Co-MIMO) systems. Many contributions consider a total power constraint (TPC) on the sum of transmit power from all nodes in addressing PA problem. However, in practical implementations, each transmit node is equipped with its own power amplifier and is limited by individual power constraint (IPC). Hence these PA methods under TPC are not realizable in practical systems. Meanwhile, the PA problem under IPC is essential, but it has not been studied. This paper extends the traditional non-cooperative water-filling PA algorithm to IPC-based Co-MIMO systems. Moreover, the PA matrix is derived based on the compound channel matrix from all the cooperative nodes to the user. Therefore, the cooperative gain of the IPC-based Co-MIMO systems is fully exploited, and further the maximal instantaneous capacity is achieved. Numerical simulations validate that, under the same IPC conditions, the proposed PA scheme considerably outperforms the non-cooperative water-filling PA and uniform PA design in terms of ergodic capacity.
文摘Reconfigurable intelligent surfaces (RIS) play a vital role in meeting the growing demand for higher data rates and reliability in wireless systems. This study focuses on analyzing the performance of RIS systems to gain a deeper understanding of their potential.The paper presents a mathematical analysis of the RIS system,deriving closed-form formulae that express its characteristics including signal-to-noise ratio(SNR)distribution,ergodic and effective capacity,outage,and error probability. The obtained formulae are newly derived and unconditionally valid solutions. Numerical results demonstrate a close agreement between the derived formulae and MonteCarlo simulation outcomes.