In this study,a solution based on deep Q network(DQN)is proposed to address the relay selection problem in cooperative non-orthogonal multiple access(NOMA)systems.DQN is particularly effective in addressing problems w...In this study,a solution based on deep Q network(DQN)is proposed to address the relay selection problem in cooperative non-orthogonal multiple access(NOMA)systems.DQN is particularly effective in addressing problems within dynamic and complex communication environ-ments.By formulating the relay selection problem as a Markov decision process(MDP),the DQN algorithm employs deep neural networks(DNNs)to learn and make decisions through real-time interactions with the communication environment,aiming to minimize the system’s outage proba-bility.During the learning process,the DQN algorithm progressively acquires channel state infor-mation(CSI)between two nodes,thereby minimizing the system’s outage probability until a sta-ble level is reached.Simulation results show that the proposed method effectively reduces the out-age probability by 82%compared to the two-way relay selection scheme(Two-Way)when the sig-nal-to-noise ratio(SNR)is 30 dB.This study demonstrates the applicability and advantages of the DQN algorithm in cooperative NOMA systems,providing a novel approach to addressing real-time relay selection challenges in dynamic communication environments.展开更多
The performance of interfered cooperative ad-hoc networks is analyzed by stochastic geometry analysis and a selection region of relay is presented. First, assuming that the distribution of nodes in the random network ...The performance of interfered cooperative ad-hoc networks is analyzed by stochastic geometry analysis and a selection region of relay is presented. First, assuming that the distribution of nodes in the random network follows the Poisson point process （PPP）, a closed-form expression of the outage probability is derived for the best relay selection （BRS） scheme. Secondly, the capacity of the network is presented for this scheme. Finally, a performance factor is defined to evaluate the performance gain obtained from the BRS. By using this factor, a relay selection region is found to guarantee the performance gain from the BRS. The analysis and simulation results show that the performance of the BRS not only depends on the densities of source nodes and relay nodes but also on the factors of networks such as the path loss factor and the decoding threshold. And the BRS has a greater advantage than direct transmission （DT） in hush environments such as the long transmission distances, much interference and the high decoding thresholds.展开更多
In order to save energy and make more efficient use of wireless channel, this article puts forward an energy saving cooperative relaying scheme which actuates the cooperative transmis- sion only when the feedback from...In order to save energy and make more efficient use of wireless channel, this article puts forward an energy saving cooperative relaying scheme which actuates the cooperative transmis- sion only when the feedback from the destination indicates failure of the direct transmission. The proposed scheme selects the optimal relay and its corresponding transmission power in each time slot based on channel condition and residual ener- gy with the objective of minimizing energy con- sumption and extending network lifetime. In the study, the f＇mite-state Markov channel model is used to characterize the correlation structure of channel fading in wireless networks, and the pro- cedure of relay selection and transmission power decision is formulated as a M arkov decision process. Numerical and simulation results show that the proposed scheme consumes less energy and prolongs the network lifetime.展开更多
Non-orthogonal multiple access(NOMA)technique is an expert on channel differences exploiting.In this paper,a dual-hop NOMA-based cooperative relaying network where a best relay is selected as an active node to accompl...Non-orthogonal multiple access(NOMA)technique is an expert on channel differences exploiting.In this paper,a dual-hop NOMA-based cooperative relaying network where a best relay is selected as an active node to accomplish the communication between a source and a destination is discussed.We assume that both decode-and-forward(DF)and amplify-and-forward(AF)protocols are applied to the selected relay.The metrics that ergodic sum-rate and outage probability are investigated,and the closed-form expressions of the latter for DF and AF protocols are derived.Numerical and simulation results are conducted to verify the validity of the theoretical analysis,in which we can see that the NOMA based DF relaying is better than the NOMA based AF relaying and other existing NOMA-based cooperative communication schemes.展开更多
A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary u...A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary users （SUs） communicate with each other via an assist relay. The main point is to provide the best system performance to SUs while maintaining the interference power at primary user （PU） under a certain level. Using convex optimization, a closed-form solution is obtained when optimizing the power allocation among the two nodes and relay. Based on this result, a joint power control and relay selection scheme with fewer variable dimensions is proposed to maximize the achievable rate of the secondary system. Simulation results demonstrate that the sum rate of the cognitive two-way relay network increases compared with a random relay selection and fixed power allocation.展开更多
Cloud computing is always adopted to enhance the computing capability of mobile systems, especially when the mobile users prefer to use some computation intensive applications. Consequently, the distributed wireless r...Cloud computing is always adopted to enhance the computing capability of mobile systems, especially when the mobile users prefer to use some computation intensive applications. Consequently, the distributed wireless relay infrastructure should be deployed to aid the traffic transmission. To further enhance the QoS provisioning goals of wireless cooperative network, this paper puts forward a multi-objective approach for distributed optimal relay selection, which takes Bit Error Rate (BER) and Secrecy Capacity (SC) into account simultaneously. Firstly, our proposal partitions the channel state into several levels according to the received signal-to-noise ratio (SNR) and describes the time-varying Rayleigh fading channel characteristics by using first order finite-state Markov model. Secondly, we model the relay selection as Restless Multi-armed Bandit optimal solution problem with respect to the channel state and the state transition probability. Finally, simulation results demonstrate the efficiency of the proposed approach which outperforms the existing ones.展开更多
Single-relay selection techniques based on themax-min criterion can achieve the highest bit error rate(BER)performance with full diversity gain as compared to the state-of-the-art single-relay selection techniques.The...Single-relay selection techniques based on themax-min criterion can achieve the highest bit error rate(BER)performance with full diversity gain as compared to the state-of-the-art single-relay selection techniques.Therefore,in this work,we propose a modified max-min criterion by considering the differences among the close value channels of all relays while selecting the best relay node.The proposed criterion not only enjoys full diversity gain but also offers a significant improvement in the achievable coding gain as compared to the conventional one.Basically,in this article,an improved bi-directional three-phase single-relay selection technique using the decodeand-forward protocol for wireless cooperative communication networks that enhances the overall network performance in terms of BER is proposed and its performance is proved analytically and through Monte-Carlo simulations.More specifically,the proposed criterion is first used to select the best relaynode.After that the selected relay-node forwards the information symbols of the communicating terminals after performing a digital network coding to minimize power consumptions.In our simulations,we show that our proposed technique outperforms the best-known single relay selection techniques.Furthermore,we prove that the BER results obtained from our conducted simulations perfectly match those obtained from the theoretical analysis.展开更多
As the installation of small cells increases,the use of relay also increases.The relay operates as a base station as well as just an amplifier.As the roles and types of relays become more diverse,appropriate relay sel...As the installation of small cells increases,the use of relay also increases.The relay operates as a base station as well as just an amplifier.As the roles and types of relays become more diverse,appropriate relay selection technology is an effective way to improve communication performance.Many researches for relay selection have been studied to secure the reliability of relay communication.In this paper,the relay selection scheme is proposed for a cooperative system using decode-and-forward(DF)relaying scheme in the mobile communication system.To maintain the transmission rate,the proposed scheme classifies a candidate group considering the outage probability of multiple relays.For the applicable candidate group,the proposed scheme selects the relay considering the amount of data allocated to each user.Therefore,the proposed scheme defines the unit transmission time through each user’s data and relay capacity.Finally,the proposed scheme selects a relay that minimizes the total transmission time through the relay transmission time that calculates the unit transmission time for all users.With this adaptive relay selection scheme,an optimal relay can be assigned for each user.For the same transmission rate and the amount of data,the proposed scheme improves the performance of transmission time and reliability.Simulation results show that the proposed scheme reduces the total transmission time for the same amount of data and signal to noise ratio(SNR).展开更多
This paper investigates the relay selection and resource allocation problem in multiuser orthogonal frequency division multiplexing （OFDM） based cooperative cellular networks, in which user nodes could relay informa...This paper investigates the relay selection and resource allocation problem in multiuser orthogonal frequency division multiplexing （OFDM） based cooperative cellular networks, in which user nodes could relay information for each other using the decode-and-forward （DF） protocol to achieve spatial diversity gain. Specifically, the paper proposes an optimal joint relay selection and resource allocation （0RSRA） algorithm whose objective is to maximize system total achievable data rate with the constraints of each user＇ s individual quality of service （QoS） requirement and transmission power. Due to being a mixed binary integer programming （MBIP） problem, a novel two-level Lagrangian dual-primal decomposition and subgradient projection approach is proposed to not only select the appropriate cooperative relay nodes, but also allocate subcarries and power optimally. Simulation re- suits demonstrate that our proposed scheme can efficiently enhance overall system data rate and guarantee each user＇ s QoS requirement. Meanwhile, the fairness among users can be improved dramatically.展开更多
In this article,we introduce a new bi-directional dual-relay selection strategy with its bit error rate(BER)performance analysis.During the first step of the proposed strategy,two relays out of a set of N relay-nodes ...In this article,we introduce a new bi-directional dual-relay selection strategy with its bit error rate(BER)performance analysis.During the first step of the proposed strategy,two relays out of a set of N relay-nodes are selected in a way to optimize the system performance in terms of BER,based on the suggested algorithm which checks if the selected relays using the maxmin criterion are the best ones.In the second step,the chosen relay-nodes perform an orthogonal space-time coding scheme using the two-phase relaying protocol to establish a bi-directional communication between the communicating terminals,leading to a significant improvement in the achievable coding and diversity gain.To further improve the overall system performance,the selected relay-nodes apply also a digital network coding scheme.Furthermore,this paper discusses the analytical approximation of the BER performance of the proposed strategy,where we prove that the analytical results match almost perfectly the simulated ones.Finally,our simulation results show that the proposed strategy outperforms the current state-of-the-art ones.展开更多
We derive closed-form expressions for outage probability and symbol error rate （SER） of opportunistic relaying （OR） and selection cooperation （SC）. For the amplify-and-forward relay selection scheme, comparison ...We derive closed-form expressions for outage probability and symbol error rate （SER） of opportunistic relaying （OR） and selection cooperation （SC）. For the amplify-and-forward relay selection scheme, comparison between two selection strategies over independent non-identically distributed Nakagami-rn fading channels via analytical and simulation results is given in terms of the outage probability and SER. Simulation results show that OR performs better than SC.展开更多
An improved distributed turbo coding （DTC） scheme, namely, systematic-bit-selection DTC, is proposed for a two-hop relay network implementing selective-relaying （SR）. In the scheme, source broadcasts a punctured t...An improved distributed turbo coding （DTC） scheme, namely, systematic-bit-selection DTC, is proposed for a two-hop relay network implementing selective-relaying （SR）. In the scheme, source broadcasts a punctured turbo code in order to increase the successful decoding rate of relay. The relay forwards systematic-bit to the destination in case of successful cyclic redundancy check （CRC）. From the two versions of systematic-bit coming from relay and source respectively, the des- tination selects the one with higher signal-to-noise ratio （SNR） for turbo decoding. Simulation re- suits show the improved bit error rate （BER） performance of our scheme.展开更多
A novel photocatalytic energy transfer-driven radical relay strategy has been introduced for the chemoand regioselective 1,4-difunctionalization of carbon-sulfur double bonds.This represents the first instance of radi...A novel photocatalytic energy transfer-driven radical relay strategy has been introduced for the chemoand regioselective 1,4-difunctionalization of carbon-sulfur double bonds.This represents the first instance of radical-mediated dual-functionalization of X-Y type unsaturated bonds,enabling the synthesis of complex linear molecules with C–O,C–N,and C-S bonds in a single operation.The method surpasses traditional approaches by avoiding the need for thiourea intermediates and the harsh conditions typically associated with them.The developed strategy exemplifies versatility,being applicable to 1,4-oxyamination,1,4-diamination,and 1,4-sulfonamination reactions,and has demonstrated compatibility with over 60 different substrates.The research also elucidates the role of electronic complementarity between radicals and receptors in achieving high selectivity in 1,4-difunctionalization reactions.This study significantly advances the field of bifunctionalization and remote difunctionalization reactions,with profound implications for the development of pharmaceuticals and materials science.展开更多
In this paper, we present a special spectrum sharing scheme that is a joint optimization of relay selection and power allocation at the secondary transmitter, where the primary user is incapable of supporting its targ...In this paper, we present a special spectrum sharing scheme that is a joint optimization of relay selection and power allocation at the secondary transmitter, where the primary user is incapable of supporting its target signal-to-noise ratio(SNR). Specifically, the selected secondary transmitter assists the primary user with achieving its target SNR via two-phase cooperative amplify-and-forward relaying. By searching for the candidate secondary transmitters which have already satisfied the primary user's target SNR, we can select the optimal secondary transmitter. This optimal secondary transmitter not only satisfies the primary user's target SNR,but also maximizes the throughput of the secondary user. We study this joint optimization problem such that the secondary user's throughput is maximized under the constraint that satisfies the primary user's target SNR.Numerical results show that our scheme can maximize the throughput of the secondary user, and can obtain the win-win solution for the primary and secondary systems.展开更多
In this paper, we consider an amplify-and-forward （AF） cooperative communication system when the channel state information （CSI） used in relay selection differs from that during data transmission, i.e., the CSI us...In this paper, we consider an amplify-and-forward （AF） cooperative communication system when the channel state information （CSI） used in relay selection differs from that during data transmission, i.e., the CSI used in relay selection is outdated. The selected relay may not be actually the best for data transmission and the outage performance of the cooperative system will deteriorate. To improve its performance, we propose a relay selection strategy based on maximum a posteriori （MAP） estimation, where relay is selected based on predicted signal-to-noise ratio （SNR）. To reduce the computation complexity, we approximate the a posteriori probability density of SNR and obtain a closed-form predicted SNR, and a relay selection strategy based on the approximate MAP estimation （RS-AMAP） is proposed. The simulation results show that this approximation leads to trivial performance loss from the perspective of outage probability. Compared with relay selection strategies given in the literature, the outage probability is reduced largely through RS-AMAP for medium-to-large transmitting powers and medium-to-high channel correlation coefficients.展开更多
Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward （AF） mode with a low complexity is easy to be imp...Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward （AF） mode with a low complexity is easy to be implemented. Under the consideration of cooperative communication systems, the scenario includes one information source, M relay stations and N destinations. This work proposes a relay selection algorithm in the Raleigh fading channel. Based on the exhaustive search method, easily to realize, the optimal selection scheme can be found with a highly complicated calculation. In order to reduce the computational complexity, an approximate optimal solution with a greedy algorithm applied for the relay station selection is proposed. With different situations of the communication systems, the performance evaluation obtained by both the proposed algorithm and the exhaustive search algorithm are given for comparison. It shows the proposed algorithm could provide a solution approach to the optimal one.展开更多
A distributed best-relay node selection scheme is investigated for cooperative communications with adaptive modulation and coding （MAC） strategy over underlay-paradigm based cognitive radio （CR） networks. The sche...A distributed best-relay node selection scheme is investigated for cooperative communications with adaptive modulation and coding （MAC） strategy over underlay-paradigm based cognitive radio （CR） networks. The scheme aims to maximize the average spectral efficiency and meanwhile to guarantee that the primary link is provided with a minimum-rate for a certain percentage of time. Simulation results demonstrate that the proposed scheme can significantly improve the spectral efficiency compared with other existing schemes.展开更多
In this paper,we derive the Symbol Error Probability(SEP)of cooperative systems with incremental relaying and Distributed Relay Selection(DRS).The relays remain idle when the Signal to Noise Ratio(SNR)between the sour...In this paper,we derive the Symbol Error Probability(SEP)of cooperative systems with incremental relaying and Distributed Relay Selection(DRS).The relays remain idle when the Signal to Noise Ratio(SNR)between the source and destination is larger than T.Otherwise,we activate a relay using DRS.Relay nodes transmit only if their SNR is larger than thresholdβ.If the SNRs of more than two relays is larger thanβ,there is a collision and the destination uses only the received signal from the source.If all relays have SNR less thanβ,no relay is chosen.Thresholdβis optimized to yield the lowest SEP at the destination.Our results are compared to centralized relay selection using opportunistic Amplify and Forward(OAF),Partial and Reactive Relay Selection(PRS and RRS).We compare our results to computer simulations for Rayleigh fading channels.展开更多
In cognitive radio (CR) relay networks,most previous work concentrates on maximizing physical layer quality of service (QoS),e.g.,spectral efficiency and achievable data rate,as relay selection criteria.However,the re...In cognitive radio (CR) relay networks,most previous work concentrates on maximizing physical layer quality of service (QoS),e.g.,spectral efficiency and achievable data rate,as relay selection criteria.However,the residual energy state of relay nodes is largely ignored,which has significant effects on the average network lifetime for those battery-limited wireless networks.In this paper,an opportunistic distributed best-relay node selection scheme is proposed for cooperative transmissions over underlay-paradigm based CR networks,and meanwhile guarantee that the primary link is provided with a minimum-rate for a certain percentage of time.The objective is to increase achievable data rate as well as prolong average network lifetime.Specifically,both the instantaneous channel state information (ICSI) and residual energy of candidate relay nodes are taken as weighted metric,and the relay node with the optimal weighted metric is selected as the best one.Simulation results are presented to demonstrate the effectiveness of the proposed scheme.展开更多
Based on the existing incremental selection algorithm for Decode-and-Forward (DF) Multiple Input Multiple Output (MIMO) systems, a faster one which combines the incremental selection with the decremental exclussion is...Based on the existing incremental selection algorithm for Decode-and-Forward (DF) Multiple Input Multiple Output (MIMO) systems, a faster one which combines the incremental selection with the decremental exclussion is proposed. Firstly, the algorithm selects one antenna which makes the increment of the capacity greatest in every step. Then, excludes the antennas whose contribution to the capacity is less than μ% of that of the best antenna. Simulations show that the proposed algorithm achieves comparable performance to the existing one and has obviously decreased complexity under the appropriate threshold μ% .展开更多
基金supported by the National Natural Science Foundation of China(Nos.61841107 and 62061024)Gansu Natural Sci-ence Foundation(Nos.22JR5RA274 and 23YFGA0062)Gansu Innovation Foundation(No.2022A-215).
文摘In this study,a solution based on deep Q network(DQN)is proposed to address the relay selection problem in cooperative non-orthogonal multiple access(NOMA)systems.DQN is particularly effective in addressing problems within dynamic and complex communication environ-ments.By formulating the relay selection problem as a Markov decision process(MDP),the DQN algorithm employs deep neural networks(DNNs)to learn and make decisions through real-time interactions with the communication environment,aiming to minimize the system’s outage proba-bility.During the learning process,the DQN algorithm progressively acquires channel state infor-mation(CSI)between two nodes,thereby minimizing the system’s outage probability until a sta-ble level is reached.Simulation results show that the proposed method effectively reduces the out-age probability by 82%compared to the two-way relay selection scheme(Two-Way)when the sig-nal-to-noise ratio(SNR)is 30 dB.This study demonstrates the applicability and advantages of the DQN algorithm in cooperative NOMA systems,providing a novel approach to addressing real-time relay selection challenges in dynamic communication environments.
基金The National Science and Technology Major Project(No. 2011ZX03005-004-03 )the National Natural Science Foundation of China (No. 61171081)the Science and Technology Support Program of Jiangsu Province (No. BE2011187)
文摘The performance of interfered cooperative ad-hoc networks is analyzed by stochastic geometry analysis and a selection region of relay is presented. First, assuming that the distribution of nodes in the random network follows the Poisson point process （PPP）, a closed-form expression of the outage probability is derived for the best relay selection （BRS） scheme. Secondly, the capacity of the network is presented for this scheme. Finally, a performance factor is defined to evaluate the performance gain obtained from the BRS. By using this factor, a relay selection region is found to guarantee the performance gain from the BRS. The analysis and simulation results show that the performance of the BRS not only depends on the densities of source nodes and relay nodes but also on the factors of networks such as the path loss factor and the decoding threshold. And the BRS has a greater advantage than direct transmission （DT） in hush environments such as the long transmission distances, much interference and the high decoding thresholds.
基金The authors would like to thank the reviewers for their de-tailed reviews and constructive comments, which have helped improve the quality of this paper. This work was supported by the National Natural Science Foundation of China under Grant No. 61101107 the Scientific Research and Innovation Plan for the Youth of BUPT under Grant No. 2011RC0305 the National International Science and Technology Cooperation Project under Grant No. 2010DFA11320.
文摘In order to save energy and make more efficient use of wireless channel, this article puts forward an energy saving cooperative relaying scheme which actuates the cooperative transmis- sion only when the feedback from the destination indicates failure of the direct transmission. The proposed scheme selects the optimal relay and its corresponding transmission power in each time slot based on channel condition and residual ener- gy with the objective of minimizing energy con- sumption and extending network lifetime. In the study, the f＇mite-state Markov channel model is used to characterize the correlation structure of channel fading in wireless networks, and the pro- cedure of relay selection and transmission power decision is formulated as a M arkov decision process. Numerical and simulation results show that the proposed scheme consumes less energy and prolongs the network lifetime.
基金supported in part by the National Natural Science Foundation of China under Grants 61971149,61431005,and 61971198in part by the Natural Science Foundation of Guangdong Province under Grant 2016A030308006+1 种基金in part by the Guangdong Basic and Applied Basic Research Foundation under Grant 2019A1515011040in part by the Young Innovative Talents Project of Guangdong Province under Grant 2018GkQNCX118.
文摘Non-orthogonal multiple access(NOMA)technique is an expert on channel differences exploiting.In this paper,a dual-hop NOMA-based cooperative relaying network where a best relay is selected as an active node to accomplish the communication between a source and a destination is discussed.We assume that both decode-and-forward(DF)and amplify-and-forward(AF)protocols are applied to the selected relay.The metrics that ergodic sum-rate and outage probability are investigated,and the closed-form expressions of the latter for DF and AF protocols are derived.Numerical and simulation results are conducted to verify the validity of the theoretical analysis,in which we can see that the NOMA based DF relaying is better than the NOMA based AF relaying and other existing NOMA-based cooperative communication schemes.
基金supported by the National Natural Science Foundation of China (61250005)Jiangxi Postdoctoral Science Foundation(2013KY07)
文摘A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary users （SUs） communicate with each other via an assist relay. The main point is to provide the best system performance to SUs while maintaining the interference power at primary user （PU） under a certain level. Using convex optimization, a closed-form solution is obtained when optimizing the power allocation among the two nodes and relay. Based on this result, a joint power control and relay selection scheme with fewer variable dimensions is proposed to maximize the achievable rate of the secondary system. Simulation results demonstrate that the sum rate of the cognitive two-way relay network increases compared with a random relay selection and fixed power allocation.
基金supported by National Natural Science Foundation of China under Grant No.60971083Science Technology Innovation Foundationfor Young Teachers in BUPT under Grant No.2011RC0306+1 种基金State Major Science and Technology Special Projects under Grant No.2011ZX03005-002-02 National International Science and Technology Cooperation Project of China under Grant No.2010DFA11320
文摘Cloud computing is always adopted to enhance the computing capability of mobile systems, especially when the mobile users prefer to use some computation intensive applications. Consequently, the distributed wireless relay infrastructure should be deployed to aid the traffic transmission. To further enhance the QoS provisioning goals of wireless cooperative network, this paper puts forward a multi-objective approach for distributed optimal relay selection, which takes Bit Error Rate (BER) and Secrecy Capacity (SC) into account simultaneously. Firstly, our proposal partitions the channel state into several levels according to the received signal-to-noise ratio (SNR) and describes the time-varying Rayleigh fading channel characteristics by using first order finite-state Markov model. Secondly, we model the relay selection as Restless Multi-armed Bandit optimal solution problem with respect to the channel state and the state transition probability. Finally, simulation results demonstrate the efficiency of the proposed approach which outperforms the existing ones.
基金This work was supported by College of Engineering and Technology,the American University of the Middle East,Kuwait.Homepage:https://www.aum.edu.kw.
文摘Single-relay selection techniques based on themax-min criterion can achieve the highest bit error rate(BER)performance with full diversity gain as compared to the state-of-the-art single-relay selection techniques.Therefore,in this work,we propose a modified max-min criterion by considering the differences among the close value channels of all relays while selecting the best relay node.The proposed criterion not only enjoys full diversity gain but also offers a significant improvement in the achievable coding gain as compared to the conventional one.Basically,in this article,an improved bi-directional three-phase single-relay selection technique using the decodeand-forward protocol for wireless cooperative communication networks that enhances the overall network performance in terms of BER is proposed and its performance is proved analytically and through Monte-Carlo simulations.More specifically,the proposed criterion is first used to select the best relaynode.After that the selected relay-node forwards the information symbols of the communicating terminals after performing a digital network coding to minimize power consumptions.In our simulations,we show that our proposed technique outperforms the best-known single relay selection techniques.Furthermore,we prove that the BER results obtained from our conducted simulations perfectly match those obtained from the theoretical analysis.
基金This research was supported by the MSIT(Ministry of Science and ICT),Korea,under the ITRC(Information Technology Research Center)support program(IITP-2019-2018-0-01423)supervised by the IITP(Institute for Information&communications Technology Promotion)was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2020R1A6A1A03038540).
文摘As the installation of small cells increases,the use of relay also increases.The relay operates as a base station as well as just an amplifier.As the roles and types of relays become more diverse,appropriate relay selection technology is an effective way to improve communication performance.Many researches for relay selection have been studied to secure the reliability of relay communication.In this paper,the relay selection scheme is proposed for a cooperative system using decode-and-forward(DF)relaying scheme in the mobile communication system.To maintain the transmission rate,the proposed scheme classifies a candidate group considering the outage probability of multiple relays.For the applicable candidate group,the proposed scheme selects the relay considering the amount of data allocated to each user.Therefore,the proposed scheme defines the unit transmission time through each user’s data and relay capacity.Finally,the proposed scheme selects a relay that minimizes the total transmission time through the relay transmission time that calculates the unit transmission time for all users.With this adaptive relay selection scheme,an optimal relay can be assigned for each user.For the same transmission rate and the amount of data,the proposed scheme improves the performance of transmission time and reliability.Simulation results show that the proposed scheme reduces the total transmission time for the same amount of data and signal to noise ratio(SNR).
基金Supported by the National Natural Science Foundation for Distinguished Young Scholar （ No. 61001115 ） and the Beijing Municipal Natural Science Foundation （ No. 4102044）.
文摘This paper investigates the relay selection and resource allocation problem in multiuser orthogonal frequency division multiplexing （OFDM） based cooperative cellular networks, in which user nodes could relay information for each other using the decode-and-forward （DF） protocol to achieve spatial diversity gain. Specifically, the paper proposes an optimal joint relay selection and resource allocation （0RSRA） algorithm whose objective is to maximize system total achievable data rate with the constraints of each user＇ s individual quality of service （QoS） requirement and transmission power. Due to being a mixed binary integer programming （MBIP） problem, a novel two-level Lagrangian dual-primal decomposition and subgradient projection approach is proposed to not only select the appropriate cooperative relay nodes, but also allocate subcarries and power optimally. Simulation re- suits demonstrate that our proposed scheme can efficiently enhance overall system data rate and guarantee each user＇ s QoS requirement. Meanwhile, the fairness among users can be improved dramatically.
基金This work was supported by College of Engineering and Technology,the American University of the Middle East,Kuwait.Homepage:https://www.aum.edu.kw.
文摘In this article,we introduce a new bi-directional dual-relay selection strategy with its bit error rate(BER)performance analysis.During the first step of the proposed strategy,two relays out of a set of N relay-nodes are selected in a way to optimize the system performance in terms of BER,based on the suggested algorithm which checks if the selected relays using the maxmin criterion are the best ones.In the second step,the chosen relay-nodes perform an orthogonal space-time coding scheme using the two-phase relaying protocol to establish a bi-directional communication between the communicating terminals,leading to a significant improvement in the achievable coding and diversity gain.To further improve the overall system performance,the selected relay-nodes apply also a digital network coding scheme.Furthermore,this paper discusses the analytical approximation of the BER performance of the proposed strategy,where we prove that the analytical results match almost perfectly the simulated ones.Finally,our simulation results show that the proposed strategy outperforms the current state-of-the-art ones.
基金the National Natural Science Foundation of China(No.60972050)the National Basic Research Program (973) of China(No.2009CB3020402)the Jiangxi Province Science Foundation for Youths(No.20122BAB211041)
文摘We derive closed-form expressions for outage probability and symbol error rate （SER） of opportunistic relaying （OR） and selection cooperation （SC）. For the amplify-and-forward relay selection scheme, comparison between two selection strategies over independent non-identically distributed Nakagami-rn fading channels via analytical and simulation results is given in terms of the outage probability and SER. Simulation results show that OR performs better than SC.
文摘An improved distributed turbo coding （DTC） scheme, namely, systematic-bit-selection DTC, is proposed for a two-hop relay network implementing selective-relaying （SR）. In the scheme, source broadcasts a punctured turbo code in order to increase the successful decoding rate of relay. The relay forwards systematic-bit to the destination in case of successful cyclic redundancy check （CRC）. From the two versions of systematic-bit coming from relay and source respectively, the des- tination selects the one with higher signal-to-noise ratio （SNR） for turbo decoding. Simulation re- suits show the improved bit error rate （BER） performance of our scheme.
基金the National Natural Science Foundation of China(No.22101059)the financial support from Guangxi Science and Technology Program of China(No.2023GXNSFBA026275)Guangxi Normal University。
文摘A novel photocatalytic energy transfer-driven radical relay strategy has been introduced for the chemoand regioselective 1,4-difunctionalization of carbon-sulfur double bonds.This represents the first instance of radical-mediated dual-functionalization of X-Y type unsaturated bonds,enabling the synthesis of complex linear molecules with C–O,C–N,and C-S bonds in a single operation.The method surpasses traditional approaches by avoiding the need for thiourea intermediates and the harsh conditions typically associated with them.The developed strategy exemplifies versatility,being applicable to 1,4-oxyamination,1,4-diamination,and 1,4-sulfonamination reactions,and has demonstrated compatibility with over 60 different substrates.The research also elucidates the role of electronic complementarity between radicals and receptors in achieving high selectivity in 1,4-difunctionalization reactions.This study significantly advances the field of bifunctionalization and remote difunctionalization reactions,with profound implications for the development of pharmaceuticals and materials science.
基金the National High Technology Research and Development Program(863) of China(No.2014AA01A706)the National Major Science and Technology Special Project of China(Nos.2012ZX03001021 and 2012ZX03005008)+3 种基金the National Natural Science Foundation of China(No.61379159)the Chongqing City College Innovation Team(2013)the Chongqing Municipal Education Commission Science and Technology Research Project(No.KJ130513)the Chongqing Basic and Cutting-Edge Project(No.cstc2013jcyj A40020)
文摘In this paper, we present a special spectrum sharing scheme that is a joint optimization of relay selection and power allocation at the secondary transmitter, where the primary user is incapable of supporting its target signal-to-noise ratio(SNR). Specifically, the selected secondary transmitter assists the primary user with achieving its target SNR via two-phase cooperative amplify-and-forward relaying. By searching for the candidate secondary transmitters which have already satisfied the primary user's target SNR, we can select the optimal secondary transmitter. This optimal secondary transmitter not only satisfies the primary user's target SNR,but also maximizes the throughput of the secondary user. We study this joint optimization problem such that the secondary user's throughput is maximized under the constraint that satisfies the primary user's target SNR.Numerical results show that our scheme can maximize the throughput of the secondary user, and can obtain the win-win solution for the primary and secondary systems.
基金National Basic Research Program of China(No.2010CB731803)
文摘In this paper, we consider an amplify-and-forward （AF） cooperative communication system when the channel state information （CSI） used in relay selection differs from that during data transmission, i.e., the CSI used in relay selection is outdated. The selected relay may not be actually the best for data transmission and the outage performance of the cooperative system will deteriorate. To improve its performance, we propose a relay selection strategy based on maximum a posteriori （MAP） estimation, where relay is selected based on predicted signal-to-noise ratio （SNR）. To reduce the computation complexity, we approximate the a posteriori probability density of SNR and obtain a closed-form predicted SNR, and a relay selection strategy based on the approximate MAP estimation （RS-AMAP） is proposed. The simulation results show that this approximation leads to trivial performance loss from the perspective of outage probability. Compared with relay selection strategies given in the literature, the outage probability is reduced largely through RS-AMAP for medium-to-large transmitting powers and medium-to-high channel correlation coefficients.
基金supported by National Science Council under Grant No.101-2221-E-029-020-MY3
文摘Using a relaying system to provide spatial diversity and improve the system performance is a tendency in the wireless cooperative communications. Amplify-and-forward （AF） mode with a low complexity is easy to be implemented. Under the consideration of cooperative communication systems, the scenario includes one information source, M relay stations and N destinations. This work proposes a relay selection algorithm in the Raleigh fading channel. Based on the exhaustive search method, easily to realize, the optimal selection scheme can be found with a highly complicated calculation. In order to reduce the computational complexity, an approximate optimal solution with a greedy algorithm applied for the relay station selection is proposed. With different situations of the communication systems, the performance evaluation obtained by both the proposed algorithm and the exhaustive search algorithm are given for comparison. It shows the proposed algorithm could provide a solution approach to the optimal one.
基金Supported by Beijing Municipal Natural Science Foundation(4102044)the National Natural Science Funds for Young Scholar (61001115)the National Major Science & Technology Project (2011ZX03001-007-03)
文摘A distributed best-relay node selection scheme is investigated for cooperative communications with adaptive modulation and coding （MAC） strategy over underlay-paradigm based cognitive radio （CR） networks. The scheme aims to maximize the average spectral efficiency and meanwhile to guarantee that the primary link is provided with a minimum-rate for a certain percentage of time. Simulation results demonstrate that the proposed scheme can significantly improve the spectral efficiency compared with other existing schemes.
文摘In this paper,we derive the Symbol Error Probability(SEP)of cooperative systems with incremental relaying and Distributed Relay Selection(DRS).The relays remain idle when the Signal to Noise Ratio(SNR)between the source and destination is larger than T.Otherwise,we activate a relay using DRS.Relay nodes transmit only if their SNR is larger than thresholdβ.If the SNRs of more than two relays is larger thanβ,there is a collision and the destination uses only the received signal from the source.If all relays have SNR less thanβ,no relay is chosen.Thresholdβis optimized to yield the lowest SEP at the destination.Our results are compared to centralized relay selection using opportunistic Amplify and Forward(OAF),Partial and Reactive Relay Selection(PRS and RRS).We compare our results to computer simulations for Rayleigh fading channels.
基金Sponsored by the National Major Science&Technology Project(Grand No.2009ZX03002-014)the National Nature Science Foundation(Grant No.60832009)+1 种基金the Beijing Municipal Natural Science Foundation(Grand No.4102044)the National Natural Science Foundation for Distinguished Young Scholar(Grand No.61001115)
文摘In cognitive radio (CR) relay networks,most previous work concentrates on maximizing physical layer quality of service (QoS),e.g.,spectral efficiency and achievable data rate,as relay selection criteria.However,the residual energy state of relay nodes is largely ignored,which has significant effects on the average network lifetime for those battery-limited wireless networks.In this paper,an opportunistic distributed best-relay node selection scheme is proposed for cooperative transmissions over underlay-paradigm based CR networks,and meanwhile guarantee that the primary link is provided with a minimum-rate for a certain percentage of time.The objective is to increase achievable data rate as well as prolong average network lifetime.Specifically,both the instantaneous channel state information (ICSI) and residual energy of candidate relay nodes are taken as weighted metric,and the relay node with the optimal weighted metric is selected as the best one.Simulation results are presented to demonstrate the effectiveness of the proposed scheme.
基金Supported by the National Natural Science Foundation of Jiangsu Province(No.08KJB510015)
文摘Based on the existing incremental selection algorithm for Decode-and-Forward (DF) Multiple Input Multiple Output (MIMO) systems, a faster one which combines the incremental selection with the decremental exclussion is proposed. Firstly, the algorithm selects one antenna which makes the increment of the capacity greatest in every step. Then, excludes the antennas whose contribution to the capacity is less than μ% of that of the best antenna. Simulations show that the proposed algorithm achieves comparable performance to the existing one and has obviously decreased complexity under the appropriate threshold μ% .
