A new principle for grounding fault feeder detection based on negative sequence current variation and energy dissipated in the fault point is presented. It has high precision in both isolated systems and resonance ear...A new principle for grounding fault feeder detection based on negative sequence current variation and energy dissipated in the fault point is presented. It has high precision in both isolated systems and resonance earthed systems, even in full compensated systems. And it can be installed at the local control unit of feeder in distribution automation systems, such as field terminal unit (FTU). This principle is verified by EMTP simulator and experimentation.展开更多
Physical-layer network coding(PNC) promises substantial theoretical gain to achieve the maximum system throughput in cooperative relay transmission. However, with the increasing global warming, how to reduce power con...Physical-layer network coding(PNC) promises substantial theoretical gain to achieve the maximum system throughput in cooperative relay transmission. However, with the increasing global warming, how to reduce power consumption while satisfy system throughput requirement is becoming a vital issue. In this paper, we investigate energy-efficiency resource allocation(RA) based on PNC with amplify-and-forward(AF) protocol in orthogonal frequency division multiple(OFDM) bidirectional transmission. To minimize the overall transmit power consumption with required system throughput requirement, we consider joint subcarriers and power allocation and formulate the objective task into a constrained optimization problem where the best relay node is selected to minimize total transmit power. The closed form optimization power allocation solutions are acquired by analytical derivation. Based on derivation, we propose a novel optimal energy-efficient power allocation(OE-PA). Numerical results are given to evaluate the performance of the derived scheme as compared to other schemes and show that our scheme has signifi cant improvement to energy saving.展开更多
Newton's polynomial interpolation may be the favorite linear interpolation,associated continued fractions interpolation is a new type nonlinear interpolation.We use those two interpolation to construct a new kind of ...Newton's polynomial interpolation may be the favorite linear interpolation,associated continued fractions interpolation is a new type nonlinear interpolation.We use those two interpolation to construct a new kind of bivariate blending rational interpolants.Characteristic theorem is discussed.We give some new blending interpolation formulae.展开更多
In order to optimize power utilization of relay nodes in cooperative communication,a power allocation algorithm with objective function to maximize system capacity is proposed.Based on the convex optimization theory,a...In order to optimize power utilization of relay nodes in cooperative communication,a power allocation algorithm with objective function to maximize system capacity is proposed.Based on the convex optimization theory,an ellipsoid algorithm is used to solve this problem,which could simplify the subgradient choosing steps and improve convergence stability,so that an optimized power allocation algorithm is presented.Theoretical analysis and simulation results show that the algorithm can effectively distribute the power of each node with lower complexity,and ensure the transmission capability of relay nodes in cooperative communication.展开更多
It has been demonstrated that either Channel Allocation (CA) or Relay Selection (RS) can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi...It has been demonstrated that either Channel Allocation (CA) or Relay Selection (RS) can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi-cell uplink scenarios. In this paper, we investigate the issue which considers the CA and RS to optimize the system transmission rate in an uplink scenario, while maintaining the resource distribution fairness among users. This is first formulated as an optimization problem for a linear cellular system, where the same frequency channels can be reused in different cells. Based on the link and co-channel interference conditions, two low-complexity CA and RS schemes are then proposed with different decomposition se quences. Finally, numerical results are con ducted to verify the effectiveness of the pro posed CA and RS methods. Simulations re suits show that the proposed methods can yield significant improvements in system per formance in terms of average sum rate.展开更多
Different schemes, which performed channel, power and time allocation to enhance the network performance of overall end-to-end throughput for cooperative cognitive radio network, were investigated. Interference temper...Different schemes, which performed channel, power and time allocation to enhance the network performance of overall end-to-end throughput for cooperative cognitive radio network, were investigated. Interference temperature limit of corresponding primary users was considered. Due to the constraints caused by multiple dual channels, the power allocation problem is non-convex and NP-hard. Based on geometric programming (GP), a novel and general algorithm, which turned the problem into a series of GP problems by logarithm approximation (LASGP), was proposed to efficiently solve it. Numerical results verify the efficiency and availability of the LASGP algorithm. Solutions of LASGP are provably convergent and globally optimal point can be observed as well as the channel allocation always outperforms power or timeslot allocation from simulations. Compared with schemes without any allocation, the scheme with joint channel, power and timeslot allocation significantly increases the overall end-to-end throughput by no less than 70% under same simulation conditions. This scheme can not only maximize the throughput by increasing total maximum power of relay node, but also outperform other resource allocation schemes when lower total maximum power of source and relay nodes is restricted. As the total maximum power of source node increases, the scheme with joint channel and timeslot allocation performs best in all schemes.展开更多
This paper presents a wavelet-based technique for detection and classification of normal and abnormal conditions that occur on power distribution lines. The proposed technique depends on a sensitive fault detection pa...This paper presents a wavelet-based technique for detection and classification of normal and abnormal conditions that occur on power distribution lines. The proposed technique depends on a sensitive fault detection parameter (denoted DET) calculated from the wavelet multi-resolution decomposition of the three phase currents only. This parameter is fast and sensitive to any small changes in the current signal since it uses the square of the first and second details of the decomposed signals. The simulation results of this study clearly show that the proposed technique can be successfully used to detect and classify not only low-current faults that could not be detected by conventional overcurrent relays but also normal transients like load switching and inrush currents.展开更多
This paper presents an integrated protection technique for power distribution systems. A novel integrated protection scheme based on overcurrent protection technique for distribution system is described, in which a sp...This paper presents an integrated protection technique for power distribution systems. A novel integrated protection scheme based on overcurrent protection technique for distribution system is described, in which a specially designed protection relay is installed at each substation of a network and responsible for the protection of every line sections connected to the substation busbar The conventional directional overcurrent and the new adaptive accelerated protection algorithms with multiple settings are implemented into the relay to cover all the protected line sections. The paper includes studies of a typical multi section distribution network to demonstrate the principle of the scheme. Studies show that the new scheme not only offer the new protection features for individual power line section, but also provide the characteristics of integrated protection.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
For a single-relay amplify-and-forward (AF) non-cooperative system,an optimal power proportionbetween source and relay is considered.Aiming to minimize end-to-end bit error rate (BER) and maximizeattainable rate,both ...For a single-relay amplify-and-forward (AF) non-cooperative system,an optimal power proportionbetween source and relay is considered.Aiming to minimize end-to-end bit error rate (BER) and maximizeattainable rate,both large-scale path loss and small-scale Rayleigh fading are taken into account.Aclosed form expression to allocate power in optimal proportion at source is obtained.Simulation resultsshow that the proposed scheme to distribute power can minimize BER under any channel conditions.展开更多
A resource allocation scheme with the considerations of user fairness and load balancing is proposed in orthogonal frequency division multiple access (OFDMA)-based relay networks. The optimal resource allocation sch...A resource allocation scheme with the considerations of user fairness and load balancing is proposed in orthogonal frequency division multiple access (OFDMA)-based relay networks. The optimal resource allocation scheme is formulated mathematically to maximize the minimum achievable rate among all user equipments (UEs) for fairnegs improvement. The optimal problem has been proved to be N-P-hard and it is prohibitive to find the optimal solution for its computational complexity. Accordingly, this paper proposes a suboptimal scheme which considers not only user fairness but also load balancing among base stations (BS) and relay stations (RSs) during resource allocation procedure. The suboptimal scheme takes the traffic load of access nodes (BS and RSs) into consideration to balance the system traffic load, which would prevent them from overloading and throughput degradation. Simulation results show that the suboptimal scheme performs similarly to the optimal solution and can enhance the system fairness and load balancing performance significantly compared with the traditional schemes.展开更多
To reduce energy consumption while maintaining users' Quality of Service (QoS) in Orthogonal Frequency Division Mul- tiplex Access (OFDMA) relay-enhanced net- works, an adaptive energy saving subcarrier, bit and ...To reduce energy consumption while maintaining users' Quality of Service (QoS) in Orthogonal Frequency Division Mul- tiplex Access (OFDMA) relay-enhanced net- works, an adaptive energy saving subcarrier, bit and power allocation scheme is presented. The optimal subcarrier, bit and power alloca- tion problems based on discrete adaptive modula- tion and coding scheme have been previously formulated for relay-enhanced networks, and have been reformulated into and solved by integer programming in optimization theory. If the system still has a surplus of subcarriers after resource allocation, we carry out Band- width Exchange (BE) to enable more subcar- riers to participate in transmission to save en- ergy. In addition, as the relay selection scheme is closely linked with heuristic energy saving resource allocation, a relay selection scheme is proposed. Simulation results indicate that the proposed algorithm consumes less energy when transmitting the same number of bits than greedy energy saving schemes, although its spectrum efficiency is worse.展开更多
Two-way decode-and-forward(DF) relay technique is an efficient method to improve system performance in 5G networks.However,traditional orthogonal frequency division multiplexing(OFDM) based two-way relay systems only ...Two-way decode-and-forward(DF) relay technique is an efficient method to improve system performance in 5G networks.However,traditional orthogonal frequency division multiplexing(OFDM) based two-way relay systems only consider a per-subcarrier relay strategy,which treats each subcarrier as a separate channel,which results in significant sum rate loss,especially in fading environments.In this paper,a joint coding scheme over multiple subcarriers is involved for multipair users in two-way relay systems to obtain multiuser diversity.A generalized subcarrier pairing strategy is proposed to permit each user-pair to occupy different subcarriers during the two transmission phases,i.e.,the multiple access and broadcast phases.Moreover,a low complexity joint resource allocation scheme is proposed to improve the spectrum efficiency with an additional multi-user diversity gain.Some numerical simulations are finally provided to verify the efficacy of our proposal.展开更多
To achieve an optimal trade-off between video quality and energy efficiency in the uplink streaming of multi-user Scalable Video Coding (SVC) videos in relay-based Orthogonal Frequency Division Multiple Access (OFDMA)...To achieve an optimal trade-off between video quality and energy efficiency in the uplink streaming of multi-user Scalable Video Coding (SVC) videos in relay-based Orthogonal Frequency Division Multiple Access (OFDMA) cellular networks, a cross-layer design framework that jointly selects the Transmission Policy (TP) for SVC video frames, assigns OFDMA subcarriers, and allocates power for each subcarrier is proposed. We apply the dual decomposition method to the problem, and obtain a TP selection subproblem for each SVC video adaptation and a resource allocation subproblem of Joint Subcarrier, Relay and Power Allocation (JSRPA). A second level of dual decomposition is used to divide the JSRPA problem into independent subcarrier subproblems. The proposed Crosslayer Trade-off Optimization (CTO) algorithm is sub-distributed with significantly low complexity. A performance evaluation with typical SVC video traces demonstrates that the proposed algorithm is able to converge and efficiently achieve the optimal trade-off between the video quality and energy consumption at the MSs for uplink SVC streaming.展开更多
The optimization of the network throughput and transmission range is one of the most important issues in cognitive relay networks (CRNs). Existing research has focused on the dual-hop network, which cannot be extend...The optimization of the network throughput and transmission range is one of the most important issues in cognitive relay networks (CRNs). Existing research has focused on the dual-hop network, which cannot be extended to a triple-hop network due to its shortcomings, including the limited transmission range and one-way communication. In this paper, a novel, triple-hop relay scheme is proposed to implement time-division duplex (TDD) transmission among secondary users (SUs) in a three-phase transmission. Moreover, a superposition coding (SC) method is adopted for handling two-receiver cases in triple-hop networks with a cognitive relay. We studied a joint optimization of time and power allocation in all three phases, which is formulated as a nonlinear and concave problem. Both analytical and numerical results show that the proposed scheme is able to improve the throughput of SUs, and enlarge the transmission range of primary users (PUs) without increasing the number of hops.展开更多
文摘A new principle for grounding fault feeder detection based on negative sequence current variation and energy dissipated in the fault point is presented. It has high precision in both isolated systems and resonance earthed systems, even in full compensated systems. And it can be installed at the local control unit of feeder in distribution automation systems, such as field terminal unit (FTU). This principle is verified by EMTP simulator and experimentation.
基金supported by the Science Instrument Special Funds of the National Natural Science Foundation of China under Grant No.61027003the National High Technology Research and Development Program of China under Grant No.2012AA01A50604
文摘Physical-layer network coding(PNC) promises substantial theoretical gain to achieve the maximum system throughput in cooperative relay transmission. However, with the increasing global warming, how to reduce power consumption while satisfy system throughput requirement is becoming a vital issue. In this paper, we investigate energy-efficiency resource allocation(RA) based on PNC with amplify-and-forward(AF) protocol in orthogonal frequency division multiple(OFDM) bidirectional transmission. To minimize the overall transmit power consumption with required system throughput requirement, we consider joint subcarriers and power allocation and formulate the objective task into a constrained optimization problem where the best relay node is selected to minimize total transmit power. The closed form optimization power allocation solutions are acquired by analytical derivation. Based on derivation, we propose a novel optimal energy-efficient power allocation(OE-PA). Numerical results are given to evaluate the performance of the derived scheme as compared to other schemes and show that our scheme has signifi cant improvement to energy saving.
基金Supported by the Project Foundation of the Department of Education of Anhui Province(KJ2008A027,KJ2010B182,KJ2011B152,KJ2011B137)Supported by the Grant of Scientific Research Foundation for Talents of Hefei University(11RC05)Supported by the Grant of Scientific Research Foundation Hefei University(11KY06ZR)
文摘Newton's polynomial interpolation may be the favorite linear interpolation,associated continued fractions interpolation is a new type nonlinear interpolation.We use those two interpolation to construct a new kind of bivariate blending rational interpolants.Characteristic theorem is discussed.We give some new blending interpolation formulae.
基金Supported by the National High Technology Research and Development Programme of China(No.2008AA01A322)National Science andTechnology Major Projects(No.2011ZX03001-007-03)
文摘In order to optimize power utilization of relay nodes in cooperative communication,a power allocation algorithm with objective function to maximize system capacity is proposed.Based on the convex optimization theory,an ellipsoid algorithm is used to solve this problem,which could simplify the subgradient choosing steps and improve convergence stability,so that an optimized power allocation algorithm is presented.Theoretical analysis and simulation results show that the algorithm can effectively distribute the power of each node with lower complexity,and ensure the transmission capability of relay nodes in cooperative communication.
基金supported by the Key Project of State Key Laboratory of Rail Traffic and Control under Grant No.RCS2012ZZ004the Fundamental Research Funds for the Central Universities under Grant No. 2013YJS025
文摘It has been demonstrated that either Channel Allocation (CA) or Relay Selection (RS) can improve the performance in relaying networks separately. However, there is little work concerning their combination in multi-cell uplink scenarios. In this paper, we investigate the issue which considers the CA and RS to optimize the system transmission rate in an uplink scenario, while maintaining the resource distribution fairness among users. This is first formulated as an optimization problem for a linear cellular system, where the same frequency channels can be reused in different cells. Based on the link and co-channel interference conditions, two low-complexity CA and RS schemes are then proposed with different decomposition se quences. Finally, numerical results are con ducted to verify the effectiveness of the pro posed CA and RS methods. Simulations re suits show that the proposed methods can yield significant improvements in system per formance in terms of average sum rate.
基金Project(60902092) supported by the National Natural Science Foundation of China
文摘Different schemes, which performed channel, power and time allocation to enhance the network performance of overall end-to-end throughput for cooperative cognitive radio network, were investigated. Interference temperature limit of corresponding primary users was considered. Due to the constraints caused by multiple dual channels, the power allocation problem is non-convex and NP-hard. Based on geometric programming (GP), a novel and general algorithm, which turned the problem into a series of GP problems by logarithm approximation (LASGP), was proposed to efficiently solve it. Numerical results verify the efficiency and availability of the LASGP algorithm. Solutions of LASGP are provably convergent and globally optimal point can be observed as well as the channel allocation always outperforms power or timeslot allocation from simulations. Compared with schemes without any allocation, the scheme with joint channel, power and timeslot allocation significantly increases the overall end-to-end throughput by no less than 70% under same simulation conditions. This scheme can not only maximize the throughput by increasing total maximum power of relay node, but also outperform other resource allocation schemes when lower total maximum power of source and relay nodes is restricted. As the total maximum power of source node increases, the scheme with joint channel and timeslot allocation performs best in all schemes.
文摘This paper presents a wavelet-based technique for detection and classification of normal and abnormal conditions that occur on power distribution lines. The proposed technique depends on a sensitive fault detection parameter (denoted DET) calculated from the wavelet multi-resolution decomposition of the three phase currents only. This parameter is fast and sensitive to any small changes in the current signal since it uses the square of the first and second details of the decomposed signals. The simulation results of this study clearly show that the proposed technique can be successfully used to detect and classify not only low-current faults that could not be detected by conventional overcurrent relays but also normal transients like load switching and inrush currents.
文摘This paper presents an integrated protection technique for power distribution systems. A novel integrated protection scheme based on overcurrent protection technique for distribution system is described, in which a specially designed protection relay is installed at each substation of a network and responsible for the protection of every line sections connected to the substation busbar The conventional directional overcurrent and the new adaptive accelerated protection algorithms with multiple settings are implemented into the relay to cover all the protected line sections. The paper includes studies of a typical multi section distribution network to demonstrate the principle of the scheme. Studies show that the new scheme not only offer the new protection features for individual power line section, but also provide the characteristics of integrated protection.
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Supported by the National High Technology Research and Development Progranmme of China (No. 2009AA01Z246,2009AA01Z211 )
文摘For a single-relay amplify-and-forward (AF) non-cooperative system,an optimal power proportionbetween source and relay is considered.Aiming to minimize end-to-end bit error rate (BER) and maximizeattainable rate,both large-scale path loss and small-scale Rayleigh fading are taken into account.Aclosed form expression to allocate power in optimal proportion at source is obtained.Simulation resultsshow that the proposed scheme to distribute power can minimize BER under any channel conditions.
基金) Supported by the National Natural Science Foundation of China (No. 61001115), the National Major Science and Technology Project (No. 2011ZX03001- 007-03), and the Natural Science Foundation of Beijing (No. 4102044).
文摘A resource allocation scheme with the considerations of user fairness and load balancing is proposed in orthogonal frequency division multiple access (OFDMA)-based relay networks. The optimal resource allocation scheme is formulated mathematically to maximize the minimum achievable rate among all user equipments (UEs) for fairnegs improvement. The optimal problem has been proved to be N-P-hard and it is prohibitive to find the optimal solution for its computational complexity. Accordingly, this paper proposes a suboptimal scheme which considers not only user fairness but also load balancing among base stations (BS) and relay stations (RSs) during resource allocation procedure. The suboptimal scheme takes the traffic load of access nodes (BS and RSs) into consideration to balance the system traffic load, which would prevent them from overloading and throughput degradation. Simulation results show that the suboptimal scheme performs similarly to the optimal solution and can enhance the system fairness and load balancing performance significantly compared with the traditional schemes.
基金supported partially by the 973 Program under Grant No. 2012CB316100National Natural Science Foundation of China under Grants No. 61071108, No. 61032002the Central Universities Basic Scientific Research Special Fund under Grant No.SWJTU12CX097
文摘To reduce energy consumption while maintaining users' Quality of Service (QoS) in Orthogonal Frequency Division Mul- tiplex Access (OFDMA) relay-enhanced net- works, an adaptive energy saving subcarrier, bit and power allocation scheme is presented. The optimal subcarrier, bit and power alloca- tion problems based on discrete adaptive modula- tion and coding scheme have been previously formulated for relay-enhanced networks, and have been reformulated into and solved by integer programming in optimization theory. If the system still has a surplus of subcarriers after resource allocation, we carry out Band- width Exchange (BE) to enable more subcar- riers to participate in transmission to save en- ergy. In addition, as the relay selection scheme is closely linked with heuristic energy saving resource allocation, a relay selection scheme is proposed. Simulation results indicate that the proposed algorithm consumes less energy when transmitting the same number of bits than greedy energy saving schemes, although its spectrum efficiency is worse.
基金supported by the National Natural Science Foundation of China(NSFC)(No.61501527)State’s Key Project of Research and Development Plan(No.2016YFE0122900-3)+1 种基金the Fundamental Research Funds for the Central Universities,Basic Research Foundation of Science Technology and Innovation Commission of Shenzhen Municipality(No.JCYJ20150630153033410)SYSU-CMU Shunde International Joint Research Institute and 2016 Major Project of Collaborative Innovation in Guangzhou(Research and Application of Ground Satellite Communicaiton Systems for Space Broadband Information Networks)
文摘Two-way decode-and-forward(DF) relay technique is an efficient method to improve system performance in 5G networks.However,traditional orthogonal frequency division multiplexing(OFDM) based two-way relay systems only consider a per-subcarrier relay strategy,which treats each subcarrier as a separate channel,which results in significant sum rate loss,especially in fading environments.In this paper,a joint coding scheme over multiple subcarriers is involved for multipair users in two-way relay systems to obtain multiuser diversity.A generalized subcarrier pairing strategy is proposed to permit each user-pair to occupy different subcarriers during the two transmission phases,i.e.,the multiple access and broadcast phases.Moreover,a low complexity joint resource allocation scheme is proposed to improve the spectrum efficiency with an additional multi-user diversity gain.Some numerical simulations are finally provided to verify the efficacy of our proposal.
基金partially supported by the National Natural Science Foundation of China under Grants No. 610202380, No. 60932007Major Program of National Natural Science Foundation of China under Grant No. 60932007+2 种基金Tianjin Research Program of Application Foundation and Advanced Technology under Grant No. 12JCQNJC00300Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20110032120029the Innovation Foundation of Tianjin University
文摘To achieve an optimal trade-off between video quality and energy efficiency in the uplink streaming of multi-user Scalable Video Coding (SVC) videos in relay-based Orthogonal Frequency Division Multiple Access (OFDMA) cellular networks, a cross-layer design framework that jointly selects the Transmission Policy (TP) for SVC video frames, assigns OFDMA subcarriers, and allocates power for each subcarrier is proposed. We apply the dual decomposition method to the problem, and obtain a TP selection subproblem for each SVC video adaptation and a resource allocation subproblem of Joint Subcarrier, Relay and Power Allocation (JSRPA). A second level of dual decomposition is used to divide the JSRPA problem into independent subcarrier subproblems. The proposed Crosslayer Trade-off Optimization (CTO) algorithm is sub-distributed with significantly low complexity. A performance evaluation with typical SVC video traces demonstrates that the proposed algorithm is able to converge and efficiently achieve the optimal trade-off between the video quality and energy consumption at the MSs for uplink SVC streaming.
基金Project supported by the Zhejiang Provincial National Natural Science Foundation (No. LQ14F020005), the National Natural Science Foundation of China (Nos. 61379123 and 61402414), and the Research Program of the Educational Commission of Zhej iang Province, China (No. Y201431815)
文摘The optimization of the network throughput and transmission range is one of the most important issues in cognitive relay networks (CRNs). Existing research has focused on the dual-hop network, which cannot be extended to a triple-hop network due to its shortcomings, including the limited transmission range and one-way communication. In this paper, a novel, triple-hop relay scheme is proposed to implement time-division duplex (TDD) transmission among secondary users (SUs) in a three-phase transmission. Moreover, a superposition coding (SC) method is adopted for handling two-receiver cases in triple-hop networks with a cognitive relay. We studied a joint optimization of time and power allocation in all three phases, which is formulated as a nonlinear and concave problem. Both analytical and numerical results show that the proposed scheme is able to improve the throughput of SUs, and enlarge the transmission range of primary users (PUs) without increasing the number of hops.