As one of the key technologies for the fifth generation(5G) wireless networks,device-to-device(D2D) communications allow user equipment(UE) in close proximity to communicate with each other directly.Forwarded by a rel...As one of the key technologies for the fifth generation(5G) wireless networks,device-to-device(D2D) communications allow user equipment(UE) in close proximity to communicate with each other directly.Forwarded by a relay,the relay-aided D2D(RA-D2D) communications can not only be applied to communications in much longer distance but also achieve a high quality of service(Qo S) .In this paper,we first propose a two-layer system model allowing RA-D2 D links to underlay traditional cellular uplinks.Then we maximize the energy efficiency of the RA-D2 D link while satisfying the minimum data-rate of the cellular link.The optimal transmit power at both D2 D transmitter and D2 D relay sides is obtained by transforming the nonlinear fractional programming into a nonlinear parameter programming.Simulation results show that our proposed power allocation method is more energy efficient than the existing works,and the proposed RA-D2 D scheme outperformed direct D2 D scheme when the distance between two D2 D users is longer.展开更多
This paper studies the achievable spectral efficiency(SE)of downlink multiuser multiple-input-multiple-output(MIMO)system,where the base station(BS)is deployed an arbitrary finite antenna number and communicates simul...This paper studies the achievable spectral efficiency(SE)of downlink multiuser multiple-input-multiple-output(MIMO)system,where the base station(BS)is deployed an arbitrary finite antenna number and communicates simultaneously with many users. We assume that the BS has accurate channel state information(CSI)and adopt maximum ratio transmission(MRT)precoding. An accurate analytical result for the achievable SE is obtained. Based on the analytical result on the achievable SE,we further study the achievable energy efficiency(EE)of multiuser MIMO system by considering an energy consumption model. Results indicate that the increasing number of BS antennas can boost the achievable SE of system,whilst the achievable SE tends to a saturated rate in the high signal-tonoise ratios(SNR)regime. Furthermore,an important conclusion is that the increasing number of users is beneficial for the achievable EE and there is an optimal antenna number to maximize the EE of system.展开更多
Cooperation allows wireless network users to benefit from various gains such as an in- crease in the achieved rate or an improvement in the bit error rate. In the paper, we propose a distributed Hierarchical Game (HG...Cooperation allows wireless network users to benefit from various gains such as an in- crease in the achieved rate or an improvement in the bit error rate. In the paper, we propose a distributed Hierarchical Game (HG) theoretic framework over multi-user cooperative communication networks to stimulate cooperation and improve the network performance. First, we study a two- user decision making game in the OFDMA based subscriber cooperative relaying network, in which subscribers transmit their own data in the first phase, while helping to retransmit their partner's or choosing to freeride in the second phase. Instead of consulting to a global optimal solution, we decouple the cooperation resource allocation into two level subproblems: a user level Nash game for distributed cooperation decision and a Base Station (BS) level coalition game for centralized resource allocation. In the proposed HG algorithm, where mutual cooperation is preferred and total payoff is transferable, we prove it converges to a unique optimal equilibrium and resolve the subcarrier as-signment and power allocation among the couples. Besides, we discuss the existence of the publishing and rewarding coefficients in order to encourage cooperation. Then, we extend the HG to multi-user cases by coupling among subscribers according to the location information. The simulation results show that the proposed scheme with the distributed HG game achieves a well tradeoff between fairness and efficiency by improving the transmission efficiency of adverse users and outperforms those employing centralized schemes.展开更多
Switch policy is essential for small cells to properly serve variable number of users in an energy efficient way.However,frequently switching small cell base stations(SBSs) may increase the network operating cost,espe...Switch policy is essential for small cells to properly serve variable number of users in an energy efficient way.However,frequently switching small cell base stations(SBSs) may increase the network operating cost,especially when there is an nonnegligible start-up energy cost.To this end,by observing the variety of user number,we focus on the design of a switch policy which minimize the cumulative energy consumption.A given user transmission rate is guaranteed and the capability of SBSs are limited as well.According to the knowledge on user number variety,we classify the energy consumption problem into two cases.In complete information case,to minimize the cumulative energy consumption,an offline solution is proposed according to critical segments.A heuristic algorithm for incomplete information case(HAIIC) is proposed by tracking the difference of cumulative energy consumption.The upper bound of the Energy Consumption Ratio(ECR) for HAIIC is derived as well.In addition,a practical Q-learning based probabilistic policy is proposed.Simulation results show that the proposed HAIIC algorithm is able to save energy efficiently.展开更多
In limited feedback-based CloudRAN(C-RAN) systems,the inter-cluster and intra-cluster interference together with the quantification error can seriously deteriorates the system spectral efficiency.We,in this paper,prop...In limited feedback-based CloudRAN(C-RAN) systems,the inter-cluster and intra-cluster interference together with the quantification error can seriously deteriorates the system spectral efficiency.We,in this paper,propose an efficient three-phase framework and corresponding algorithms for dealing with this problem.Firstly,a greedy scheduling algorithm based on the lower bound of the ergodic rate is performed for generating an elementary cluster in the first phase.And then the elementary cluster is divided into many small clusters according to the following proposed algorithms based on the short term instantaneous information in the second phase.In the end,based on the limited feedback two zero-forcing(ZF) precoding strategies are adopted for reducing the intra-cluster interference in the third phase.The provided Monte Carlo simulations show the effectiveness of our proposed algorithms in the respect of system spectral efficiency and average user rate.展开更多
Staircase is an important means of vertical transportation. Staircase design exerts a great influence on the aesthetics, transportation efficiency, user comfort and experience level. In this paper, a survey on the sta...Staircase is an important means of vertical transportation. Staircase design exerts a great influence on the aesthetics, transportation efficiency, user comfort and experience level. In this paper, a survey on the staircase rotation preference was conducted, based on the environment behavior studies. Different user frequencies of a pair of scissors stairs in the 2nd teaching building of North China University of Technology were analyzed. The psychological effect was evaluated and quantified, and the user preference on the two staircase rotations was then withdrawn. The survey found that the type of staircase with clockwise upstairs was much more preferred (78%) than the other staircase rotation anti-clock upstairs. Considering different genders, the female shows a 66% higher preference inclination of this type of staircase rotation than the male. To improve the transportation efficiency of the staircase in case of fire, the result of this paper can be very constructive for the evacuation staircase rotation choice for the high-rise buildings.展开更多
In the network environment, changes of resources structure, information technology and users requirements of standards library cause series of problems such as unobvious effect of services, low efficiency of resource ...In the network environment, changes of resources structure, information technology and users requirements of standards library cause series of problems such as unobvious effect of services, low efficiency of resource utilization, poor innovation ability, etc. And we point out the problems and challenges faced by traditional standards library in the network environment. The standards library must redesign the organization structure and business process radically so that standards library could improve the service model, enhance the service quality and utilization rate of various document resources.展开更多
Social tagging systems are widely applied in Web 2.0.Many users use these systems to create,organize,manage,and share Internet resources freely.However,many ambiguous and uncontrolled tags produced by social tagging s...Social tagging systems are widely applied in Web 2.0.Many users use these systems to create,organize,manage,and share Internet resources freely.However,many ambiguous and uncontrolled tags produced by social tagging systems not only worsen users' experience,but also restrict resources' retrieval efficiency.Tag clustering can aggregate tags with similar semantics together,and help mitigate the above problems.In this paper,we first present a common co-occurrence group similarity based approach,which employs the ternary relation among users,resources,and tags to measure the semantic relevance between tags.Then we propose a spectral clustering method to address the high dimensionality and sparsity of the annotating data.Finally,experimental results show that the proposed method is useful and efficient.展开更多
Compared with standard logit-based stochastic user equilibrium assignment model,the C-logit model describes route choice behavior in a more realistic way by considering the overlapping effect between routes.This paper...Compared with standard logit-based stochastic user equilibrium assignment model,the C-logit model describes route choice behavior in a more realistic way by considering the overlapping effect between routes.This paper investigates the inefficiency upper bounds of this model against the deterministic system optimum and the C-logit stochastic system optimum in terms of the total network travel time.It is found that the commonality factor of overlapping routes significantly affects the inefficiency bound,besides link congestion degree,total demand and the number of feasible routes.If the commonality factor is not considered,the efficiency loss resulting from selfishly stochastic travel behavior will be to large extent underestimated.展开更多
基金supported by the ZTE Corp under Grant CON1412150018the Natural Science Foundation of China under Grant 61572389 and 61471361
文摘As one of the key technologies for the fifth generation(5G) wireless networks,device-to-device(D2D) communications allow user equipment(UE) in close proximity to communicate with each other directly.Forwarded by a relay,the relay-aided D2D(RA-D2D) communications can not only be applied to communications in much longer distance but also achieve a high quality of service(Qo S) .In this paper,we first propose a two-layer system model allowing RA-D2 D links to underlay traditional cellular uplinks.Then we maximize the energy efficiency of the RA-D2 D link while satisfying the minimum data-rate of the cellular link.The optimal transmit power at both D2 D transmitter and D2 D relay sides is obtained by transforming the nonlinear fractional programming into a nonlinear parameter programming.Simulation results show that our proposed power allocation method is more energy efficient than the existing works,and the proposed RA-D2 D scheme outperformed direct D2 D scheme when the distance between two D2 D users is longer.
基金supported by the National Natural Science Foundation of China under Grants 61531011 and 61450110445the International Science and Technology Cooperation Program of China under Grant 2014DFT10300 and China Scholarship Council
文摘This paper studies the achievable spectral efficiency(SE)of downlink multiuser multiple-input-multiple-output(MIMO)system,where the base station(BS)is deployed an arbitrary finite antenna number and communicates simultaneously with many users. We assume that the BS has accurate channel state information(CSI)and adopt maximum ratio transmission(MRT)precoding. An accurate analytical result for the achievable SE is obtained. Based on the analytical result on the achievable SE,we further study the achievable energy efficiency(EE)of multiuser MIMO system by considering an energy consumption model. Results indicate that the increasing number of BS antennas can boost the achievable SE of system,whilst the achievable SE tends to a saturated rate in the high signal-tonoise ratios(SNR)regime. Furthermore,an important conclusion is that the increasing number of users is beneficial for the achievable EE and there is an optimal antenna number to maximize the EE of system.
基金Acknowledgements This work is supported by the National Natural Science Foundation of China under Grant No. 60971083, National High-Tech Research and Development Plan of China under Grant No. 2009AA01Z206 and National International Science and Technology Cooperation Project under Granted NO.2008DFA12090.
文摘Cooperation allows wireless network users to benefit from various gains such as an in- crease in the achieved rate or an improvement in the bit error rate. In the paper, we propose a distributed Hierarchical Game (HG) theoretic framework over multi-user cooperative communication networks to stimulate cooperation and improve the network performance. First, we study a two- user decision making game in the OFDMA based subscriber cooperative relaying network, in which subscribers transmit their own data in the first phase, while helping to retransmit their partner's or choosing to freeride in the second phase. Instead of consulting to a global optimal solution, we decouple the cooperation resource allocation into two level subproblems: a user level Nash game for distributed cooperation decision and a Base Station (BS) level coalition game for centralized resource allocation. In the proposed HG algorithm, where mutual cooperation is preferred and total payoff is transferable, we prove it converges to a unique optimal equilibrium and resolve the subcarrier as-signment and power allocation among the couples. Besides, we discuss the existence of the publishing and rewarding coefficients in order to encourage cooperation. Then, we extend the HG to multi-user cases by coupling among subscribers according to the location information. The simulation results show that the proposed scheme with the distributed HG game achieves a well tradeoff between fairness and efficiency by improving the transmission efficiency of adverse users and outperforms those employing centralized schemes.
基金partially supported by National Key Project of China under Grants No. 2013ZX03001007-004National Natural Science Foundation of China under Grants No. 61102052,61325012,61271219,91438115 and 61221001
文摘Switch policy is essential for small cells to properly serve variable number of users in an energy efficient way.However,frequently switching small cell base stations(SBSs) may increase the network operating cost,especially when there is an nonnegligible start-up energy cost.To this end,by observing the variety of user number,we focus on the design of a switch policy which minimize the cumulative energy consumption.A given user transmission rate is guaranteed and the capability of SBSs are limited as well.According to the knowledge on user number variety,we classify the energy consumption problem into two cases.In complete information case,to minimize the cumulative energy consumption,an offline solution is proposed according to critical segments.A heuristic algorithm for incomplete information case(HAIIC) is proposed by tracking the difference of cumulative energy consumption.The upper bound of the Energy Consumption Ratio(ECR) for HAIIC is derived as well.In addition,a practical Q-learning based probabilistic policy is proposed.Simulation results show that the proposed HAIIC algorithm is able to save energy efficiently.
基金supported by the National Natural Science Foundation of China(NSFC) under Grant(No. 61461136001)
文摘In limited feedback-based CloudRAN(C-RAN) systems,the inter-cluster and intra-cluster interference together with the quantification error can seriously deteriorates the system spectral efficiency.We,in this paper,propose an efficient three-phase framework and corresponding algorithms for dealing with this problem.Firstly,a greedy scheduling algorithm based on the lower bound of the ergodic rate is performed for generating an elementary cluster in the first phase.And then the elementary cluster is divided into many small clusters according to the following proposed algorithms based on the short term instantaneous information in the second phase.In the end,based on the limited feedback two zero-forcing(ZF) precoding strategies are adopted for reducing the intra-cluster interference in the third phase.The provided Monte Carlo simulations show the effectiveness of our proposed algorithms in the respect of system spectral efficiency and average user rate.
文摘Staircase is an important means of vertical transportation. Staircase design exerts a great influence on the aesthetics, transportation efficiency, user comfort and experience level. In this paper, a survey on the staircase rotation preference was conducted, based on the environment behavior studies. Different user frequencies of a pair of scissors stairs in the 2nd teaching building of North China University of Technology were analyzed. The psychological effect was evaluated and quantified, and the user preference on the two staircase rotations was then withdrawn. The survey found that the type of staircase with clockwise upstairs was much more preferred (78%) than the other staircase rotation anti-clock upstairs. Considering different genders, the female shows a 66% higher preference inclination of this type of staircase rotation than the male. To improve the transportation efficiency of the staircase in case of fire, the result of this paper can be very constructive for the evacuation staircase rotation choice for the high-rise buildings.
文摘In the network environment, changes of resources structure, information technology and users requirements of standards library cause series of problems such as unobvious effect of services, low efficiency of resource utilization, poor innovation ability, etc. And we point out the problems and challenges faced by traditional standards library in the network environment. The standards library must redesign the organization structure and business process radically so that standards library could improve the service model, enhance the service quality and utilization rate of various document resources.
基金supported by the National Natural Science Foundation of China(Nos.61273292,61303131,51474007,and 51374114)the MOE Humanities and Social Science Research on Youth Foundation of China(No.13YJCZH077)
文摘Social tagging systems are widely applied in Web 2.0.Many users use these systems to create,organize,manage,and share Internet resources freely.However,many ambiguous and uncontrolled tags produced by social tagging systems not only worsen users' experience,but also restrict resources' retrieval efficiency.Tag clustering can aggregate tags with similar semantics together,and help mitigate the above problems.In this paper,we first present a common co-occurrence group similarity based approach,which employs the ternary relation among users,resources,and tags to measure the semantic relevance between tags.Then we propose a spectral clustering method to address the high dimensionality and sparsity of the annotating data.Finally,experimental results show that the proposed method is useful and efficient.
基金supported by the National Basic Research Program of China under Grant No.2012CB725401the National Natural Science Foundation of China under Grant Nos.71271001 and 71401083the Program for New Century Excellent Talents in University under Grant No.NCET-13-0025
文摘Compared with standard logit-based stochastic user equilibrium assignment model,the C-logit model describes route choice behavior in a more realistic way by considering the overlapping effect between routes.This paper investigates the inefficiency upper bounds of this model against the deterministic system optimum and the C-logit stochastic system optimum in terms of the total network travel time.It is found that the commonality factor of overlapping routes significantly affects the inefficiency bound,besides link congestion degree,total demand and the number of feasible routes.If the commonality factor is not considered,the efficiency loss resulting from selfishly stochastic travel behavior will be to large extent underestimated.