A complete mesh free adaptive algorithm (MFAA), with solution adaptation and geometric adaptation, is developed to improve the resolution of flow features and to replace traditional global refinement techniques in s...A complete mesh free adaptive algorithm (MFAA), with solution adaptation and geometric adaptation, is developed to improve the resolution of flow features and to replace traditional global refinement techniques in structured grids. Unnecessary redundant points and elements are avoided by using the mesh free local clouds refinement technology in shock influencing regions and regions near large curvature places on the boundary. Inviscid compressible flows over NACA0012 and RAE2822 airfoils are computed. Finally numerical results validate the accuracy of the above method.展开更多
yTwo exotic species, Sonneratia caseolaris (L.) Engl. and S. apetala B. Ham., were introduced to Futian Mangrove Forest Nature Reserve, Shenzhen Bay, in 1993 for afforestation. Winter cold caused frigid harm but did n...yTwo exotic species, Sonneratia caseolaris (L.) Engl. and S. apetala B. Ham., were introduced to Futian Mangrove Forest Nature Reserve, Shenzhen Bay, in 1993 for afforestation. Winter cold caused frigid harm but did not appear to be an obstacle to the introduction. The cold tolerance of the parental and filial generation increased in several years. The two Sonneratia spp. could propagate by seeds and disperse in Shenzhen Bay. While the two species grew faster than indigenous species, at the same time they promoted the growth of indigenous species, but they could not replace indigenous mangrove species. Suitable habitat was more important than the distance from the source in the natural spreading for the two species. The niche of the two species did not overlap with the niche of indigenous species. The two species did not self regenerate, although they could disperse on localized area in Shenzhen Bay. Therefore, it was unlikely that the two species would pose ecological disaster.展开更多
In term of the features of 3G system, a novel AMR link adaptation strategy for 3G system is proposed. The impacts of AMR codec modes and power control on traffic quality of service are taken into account in the strate...In term of the features of 3G system, a novel AMR link adaptation strategy for 3G system is proposed. The impacts of AMR codec modes and power control on traffic quality of service are taken into account in the strategy at the same time. By synthetically comparing the signal-to-interference ratio value with the switching threshold and comparing the transmission power with its threshold, radio resource management can always keep each link on its proper codec mode with the corresponding optimal power level to achieve both robust speech quality and link capacity enhancement. Based on the WCDMA FDD uplink link-level simulation platform, AMR link adaptation platform is constructed. Simulation results show that the algorithm can track the fast change of channel conditions and select the most robust codec mode, thus the synthetic speech quality of AMR is better than that of signal mode during a wide range of channel conditions. The result will provide a reference strategy for AMR link adaptation of 3G system.展开更多
To overcome nonlinear and 6-DOF(degrees of freedom)under-actuated problems for the attitude and position of quadrotor UAVs,an adaptive backstepping sliding mode method for flight attitude of quadrotor UAVs is proposed...To overcome nonlinear and 6-DOF(degrees of freedom)under-actuated problems for the attitude and position of quadrotor UAVs,an adaptive backstepping sliding mode method for flight attitude of quadrotor UAVs is proposed,in which an adaptive law is designed to online estimate the parameter variations and the upper bound of external disturbances and the assessments is utilized to compensate the backstepping sliding mode control.In addition,the tracking error of the design method is shown to asymptotically converge to zero by using Lyapunov theory.Finally,based on the numerical simulation of quadrotor UAVs using the setting parameters,the results show that the proposed control approach can stabilize the attitude and has hover flight capabilities under the parameter perturbations and external disturbances.展开更多
A novel anti-collision algorithm in RFID wireless network is proposed.As it is put forward on the basis of collision tree(CT)and improved collision tree(lCT) anti-collision protocols,we call it adaptive collision tree...A novel anti-collision algorithm in RFID wireless network is proposed.As it is put forward on the basis of collision tree(CT)and improved collision tree(lCT) anti-collision protocols,we call it adaptive collision tree protocol(ACT).The main novelty of this paper is that the AD strategy is introduced and used in ACT to decrease collisions and improve the tag system throughput.AD strategy means that query strings will divide into two or four branches adaptively according to the label quantity.This scheme can decrease both depth of query and collision timeslots,and avoid producing too much idle timeslots at the same time.Both theoretical analysis and simulation results indicate that the novel proposed anticollision protocol ACT outperforms the previous CT and ICT protocols in term of time complexity,system throughput,and communication complexity.展开更多
In this paper, a novel adaptive transmit-receive scheme is presented for indoor Direct Se- quence Ultra-WideBand (DS-UWB) systems. In the proposed scheme, a simple switch module is in- troduced to improve the system t...In this paper, a novel adaptive transmit-receive scheme is presented for indoor Direct Se- quence Ultra-WideBand (DS-UWB) systems. In the proposed scheme, a simple switch module is in- troduced to improve the system throughput. Furthermore, adaptive detection is implemented via an improved Least Mean Squares (LMS) algorithm. The convergence behavior and the Bit Error Rate (BER) performance of the proposed scheme are examined under the realistic channel models. Simu- lation results show that, nearly without loss of the BER performance, the proposed scheme can obtain at least 2/3 improvement in training overhead compared with the conventional approach.展开更多
Adaptive flight control technology, feedback linearization, model inversion theory are reviewed and the error dynamic characteristics are analyzed, and an adaptive on-line neural network attitude control system is pre...Adaptive flight control technology, feedback linearization, model inversion theory are reviewed and the error dynamic characteristics are analyzed, and an adaptive on-line neural network attitude control system is presented. The model inversion is under the hover condition. And the adaptive control law based on the neural network is designed to guarantee the boundedness of tracking error and control signals. Simulation results demonstrate that the nonlinear neural network augmented model inversion can self-adapt to the uncertainty and modeling errors of unmanned helicopters. Results are compared while the parameters of PD controller and robustness items are changed.展开更多
To regulate the transmit-power and enhance the total throughput, a novel Transmit Power Control Game (TPCG) algorithm and an adaptive Modulation TPCG (M-TPCG) algorithm which combine bandwidth allocation, adaptive mod...To regulate the transmit-power and enhance the total throughput, a novel Transmit Power Control Game (TPCG) algorithm and an adaptive Modulation TPCG (M-TPCG) algorithm which combine bandwidth allocation, adaptive modulation and transmit-power control based on Space Time Block Coding (STBC) OFDM-CDMA system are designed and a cross-layer framework of database sharing is proposed. Simulation results show that the TPCG algorithm can regulate their transmitter powers and enhance the total throughput effectively, M-TPCG algorithm can achieve maximal system throughput. The performance of the cognitive radio system is improved obviously.展开更多
In times of global changes and turbulence like ours, more than anything, firms need some pillars of stability. By this paper we would like to develop a comprehensive and adaptive managerial approach of corporate reput...In times of global changes and turbulence like ours, more than anything, firms need some pillars of stability. By this paper we would like to develop a comprehensive and adaptive managerial approach of corporate reputation. This is based on the premise that intangible assets (in general) and corporate reputation (in particular) are more and more recognized and managed as sources of (unique) sustainable competitive advantages and as core determinants of firm competitiveness, which are relatively hard to build and very easy to loose.展开更多
Wireless Mesh Networks(WMNs) are envisioned to support the wired backbone with a wireless Backbone Networks(BNet) for providing internet connectivity to large-scale areas.With a wide range of internet-oriented applica...Wireless Mesh Networks(WMNs) are envisioned to support the wired backbone with a wireless Backbone Networks(BNet) for providing internet connectivity to large-scale areas.With a wide range of internet-oriented applications with different Quality of Service(QoS) requirement, the large-scale WMNs should have good scalability and large bandwidth.In this paper, a Load Aware Adaptive Backbone Synthesis(LAABS) algorithm is proposed to automatically balance the traffic flow in the WMNs.The BNet will dynamically split into smaller size or merge into bigger one according to statistic load information of Backbone Nodes(BNs).Simulation results show LAABS generates moderate BNet size and converges quickly, thus providing scalable and stable BNet to facilitate traffic flow.展开更多
Efficient data visualization techniques are critical for many scientific applications. Centroidal Voronoi tessellation(CVT) based algorithms offer a convenient vehicle for performing image analysis,segmentation and co...Efficient data visualization techniques are critical for many scientific applications. Centroidal Voronoi tessellation(CVT) based algorithms offer a convenient vehicle for performing image analysis,segmentation and compression while allowing to optimize retained image quality with respect to a given metric.In experimental science with data counts following Poisson distributions,several CVT-based data tessellation algorithms have been recently developed.Although they surpass their predecessors in robustness and quality of reconstructed data,time consumption remains to be an issue due to heavy utilization of the slowly converging Lloyd iteration.This paper discusses one possible approach to accelerating data visualization algorithms.It relies on a multidimensional generalization of the optimization based multilevel algorithm for the numerical computation of the CVTs introduced in[1],where a rigorous proof of its uniform convergence has been presented in 1-dimensional setting.The multidimensional implementation employs barycentric coordinate based interpolation and maximal independent set coarsening procedures.It is shown that when coupled with bin accretion algorithm accounting for the discrete nature of the data,the algorithm outperforms Lloyd-based schemes and preserves uniform convergence with respect to the problem size.Although numerical demonstrations provided are limited to spectroscopy data analysis,the method has a context-independent setup and can potentially deliver significant speedup to other scientific and engineering applications.展开更多
To improve spectrum utilization and minimize interference to Primary User (PU), an adaptive spectrum decision method is proposed for Secondary User (SU), while taking traffic load balancing and spectrum heterogeneity ...To improve spectrum utilization and minimize interference to Primary User (PU), an adaptive spectrum decision method is proposed for Secondary User (SU), while taking traffic load balancing and spectrum heterogeneity into consideration. Long-term statistics and current sensing results are integrated into the proposed decision method of spectrum access. Two decision methods, namely probability based and sensing based, are presented, compared and followed by performance analysis in terms of delay. For probability based spectrum decision, Short-Time-Job-First (STJF) priority queuing discipline is employed to minimize average residual time and theoretical conclusion is derived in a novel way. For sensing based decision we treat the interrupted service of SU as newly incoming and re-decision process is initialized to find available spectrum in a First-Available-First-Access (FAFA) fashion. Effect of sensing error in PHY layer is also analyzed in terms of extended average residual time. Simulation results show that, for relatively low arriving rate of SU traffic, the proposed spectrum decision method yields at least a delay reduction of 39.5% compared with non-adaptive method. The proposed spectrum decision can significantly improve delay performance even facing sensing errors, which cause performance degeneration to both PU and SU.展开更多
A distributed local adaptive transmit power assignment (LA-TPA) strategy was proposed to construct a topology with better performance according to the environment and application scenario and prolong the network lifet...A distributed local adaptive transmit power assignment (LA-TPA) strategy was proposed to construct a topology with better performance according to the environment and application scenario and prolong the network lifetime.It takes the path loss exponent and the energy control coefficient into consideration with the aim to accentuate the minimum covering district of each node more accurately and precisely according to various network application scenarios.Besides,a self-healing scheme that enhances the robustness of the network was provided.It makes the topology tolerate more dead nodes than existing algorithms.Simulation was done under OMNeT++ platform and the results show that the LA-TPA strategy is more effective in constructing a well-performance network topology based on various application scenarios and can prolong the network lifetime significantly.展开更多
Sensor localization is crucial for the configuration and applications of wireless sensor network (WSN). A novel distributed localization algorithm, MDS-DC was proposed for wireless sensor network based on multidimensi...Sensor localization is crucial for the configuration and applications of wireless sensor network (WSN). A novel distributed localization algorithm, MDS-DC was proposed for wireless sensor network based on multidimensional scaling (MDS) and the shortest path distance correction. In MDS-DC, several local positioning regions with reasonable distribution were firstly constructed by an adaptive search algorithm, which ensures the mergence between the local relative maps of the adjacent local position regions and can reduce the number of common nodes in the network. Then, based on the relationships between the estimated distances and actual distances of anchors, the distance estimation vectors of sensors around anchors were corrected in each local positioning region. During the computations of the local relative coordinates, an iterative process, which is the combination of classical MDS algorithm and SMACOF algorithm, was applied. Finally, the global relative positions or absolute positions of sensors were obtained through merging the relative maps of all local positioning regions. Simulation results show that MDS-DC has better performances in positioning precision, energy efficiency and robustness to range error, which can meet the requirements of applications for sensor localization in WSN.展开更多
Inherent flaws in the extended Kalman filter(EKF) algorithm were pointed out and unscented Kalman filter(UKF) was put forward as an alternative.Furthermore,a novel adaptive unscented Kalman filter(AUKF) based on innov...Inherent flaws in the extended Kalman filter(EKF) algorithm were pointed out and unscented Kalman filter(UKF) was put forward as an alternative.Furthermore,a novel adaptive unscented Kalman filter(AUKF) based on innovation was developed.The three data-fusing approaches were analyzed and evaluated in a mathematically rigorous way.Field experiments conducted in lake further demonstrate that AUKF reduces the position error approximately by 65% compared with EKF and by 35% UKF and improves the robust performance.展开更多
With its rapid development in the wireless markets, IEEE 802.11 WLAN is experiencing a huge popularity. However, due to the limitation of frequency bandwidth of WLANs, it is essential that the available radio resource...With its rapid development in the wireless markets, IEEE 802.11 WLAN is experiencing a huge popularity. However, due to the limitation of frequency bandwidth of WLANs, it is essential that the available radio resource should be fully utilized to offer different services to multiple users. In order to maximize system throughput while still guaranteeing the fairness among users, a proportional fairness based algorithm is proposed in this work. Since most of the previous resource allocation algorithms were simply based on the channel conditions without taking into account user's demand, in this paper, we introduce the theory of fuzzy synthetic evaluation(FSE) which also allows us to consider user's demand as an important factor. As such, the fairness among users can be improved based on different users' requirements for services. In addition, a channel state information based rate adaptation scheme is also proposed. Through simulation studies, the results clearly validate that our proposed scheme shows advantages on providing user fairness while still improving the system throughput.展开更多
The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameter...The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameters, when the number of stations increases, the probability of different stations in the same AC choosing the same values will increase, which will result in collisions. Random adaptive MAC (medium access control) parameters scheme (RAMPS) is proposed, which uses random adaptive MAC differentiation parameters instead of the static ones used in the 802.11e standard. The performance of RAMPS is compared with that of enhanced distributed coordination access (EDCA) using NS2. The results show that RAMPS can reduce collision rate of the AC and improve the throughput by using adaptive random contention window size and inter-frame spacing values. RAMPS ensures that at any given time, several flows of the same priority have different MAC parameter values. By using the random offset for the inter-frame spacing value and the backoff time, RAMPS can provide intra-AC differentiation. The simulation results show that RAMPS outperforms EDCA in terms of both throughput and end-to-end delay irrespective of the traffic load.展开更多
文摘A complete mesh free adaptive algorithm (MFAA), with solution adaptation and geometric adaptation, is developed to improve the resolution of flow features and to replace traditional global refinement techniques in structured grids. Unnecessary redundant points and elements are avoided by using the mesh free local clouds refinement technology in shock influencing regions and regions near large curvature places on the boundary. Inviscid compressible flows over NACA0012 and RAE2822 airfoils are computed. Finally numerical results validate the accuracy of the above method.
文摘yTwo exotic species, Sonneratia caseolaris (L.) Engl. and S. apetala B. Ham., were introduced to Futian Mangrove Forest Nature Reserve, Shenzhen Bay, in 1993 for afforestation. Winter cold caused frigid harm but did not appear to be an obstacle to the introduction. The cold tolerance of the parental and filial generation increased in several years. The two Sonneratia spp. could propagate by seeds and disperse in Shenzhen Bay. While the two species grew faster than indigenous species, at the same time they promoted the growth of indigenous species, but they could not replace indigenous mangrove species. Suitable habitat was more important than the distance from the source in the natural spreading for the two species. The niche of the two species did not overlap with the niche of indigenous species. The two species did not self regenerate, although they could disperse on localized area in Shenzhen Bay. Therefore, it was unlikely that the two species would pose ecological disaster.
文摘In term of the features of 3G system, a novel AMR link adaptation strategy for 3G system is proposed. The impacts of AMR codec modes and power control on traffic quality of service are taken into account in the strategy at the same time. By synthetically comparing the signal-to-interference ratio value with the switching threshold and comparing the transmission power with its threshold, radio resource management can always keep each link on its proper codec mode with the corresponding optimal power level to achieve both robust speech quality and link capacity enhancement. Based on the WCDMA FDD uplink link-level simulation platform, AMR link adaptation platform is constructed. Simulation results show that the algorithm can track the fast change of channel conditions and select the most robust codec mode, thus the synthetic speech quality of AMR is better than that of signal mode during a wide range of channel conditions. The result will provide a reference strategy for AMR link adaptation of 3G system.
基金Project(61203021)supported by the National Natural Science Foundation of ChinaProject(2011216011)supported by the Scientific and Technological Project of Liaoning Province,China+1 种基金Project(2013020024)supported by the Natural Science Foundation of Liaoning Province,ChinaProjects(LJQ2015061,LR2015034)supported by the Program for Liaoning Excellent Talents in University,China
文摘To overcome nonlinear and 6-DOF(degrees of freedom)under-actuated problems for the attitude and position of quadrotor UAVs,an adaptive backstepping sliding mode method for flight attitude of quadrotor UAVs is proposed,in which an adaptive law is designed to online estimate the parameter variations and the upper bound of external disturbances and the assessments is utilized to compensate the backstepping sliding mode control.In addition,the tracking error of the design method is shown to asymptotically converge to zero by using Lyapunov theory.Finally,based on the numerical simulation of quadrotor UAVs using the setting parameters,the results show that the proposed control approach can stabilize the attitude and has hover flight capabilities under the parameter perturbations and external disturbances.
基金This work is supported by the National Natu ral Science Foundation of China under grant No.61071073 and No. 61371092, Doctoral Fund of Ministry of Education of China (No.20090061110043).
文摘A novel anti-collision algorithm in RFID wireless network is proposed.As it is put forward on the basis of collision tree(CT)and improved collision tree(lCT) anti-collision protocols,we call it adaptive collision tree protocol(ACT).The main novelty of this paper is that the AD strategy is introduced and used in ACT to decrease collisions and improve the tag system throughput.AD strategy means that query strings will divide into two or four branches adaptively according to the label quantity.This scheme can decrease both depth of query and collision timeslots,and avoid producing too much idle timeslots at the same time.Both theoretical analysis and simulation results indicate that the novel proposed anticollision protocol ACT outperforms the previous CT and ICT protocols in term of time complexity,system throughput,and communication complexity.
基金Supported by the National Natural Science Foundation of China (No.60372055)the National Doctoral Foun-dation of China (No.20030698027).
文摘In this paper, a novel adaptive transmit-receive scheme is presented for indoor Direct Se- quence Ultra-WideBand (DS-UWB) systems. In the proposed scheme, a simple switch module is in- troduced to improve the system throughput. Furthermore, adaptive detection is implemented via an improved Least Mean Squares (LMS) algorithm. The convergence behavior and the Bit Error Rate (BER) performance of the proposed scheme are examined under the realistic channel models. Simu- lation results show that, nearly without loss of the BER performance, the proposed scheme can obtain at least 2/3 improvement in training overhead compared with the conventional approach.
文摘Adaptive flight control technology, feedback linearization, model inversion theory are reviewed and the error dynamic characteristics are analyzed, and an adaptive on-line neural network attitude control system is presented. The model inversion is under the hover condition. And the adaptive control law based on the neural network is designed to guarantee the boundedness of tracking error and control signals. Simulation results demonstrate that the nonlinear neural network augmented model inversion can self-adapt to the uncertainty and modeling errors of unmanned helicopters. Results are compared while the parameters of PD controller and robustness items are changed.
基金Supported by National Natural Science Foundation of China (No.60772062)the Key Projects for Science and Technology of MOE (No.206055)the Key Basic Re-search Projects for the Natural Science of Jiangsu Colleges (No.06KJA51001).
文摘To regulate the transmit-power and enhance the total throughput, a novel Transmit Power Control Game (TPCG) algorithm and an adaptive Modulation TPCG (M-TPCG) algorithm which combine bandwidth allocation, adaptive modulation and transmit-power control based on Space Time Block Coding (STBC) OFDM-CDMA system are designed and a cross-layer framework of database sharing is proposed. Simulation results show that the TPCG algorithm can regulate their transmitter powers and enhance the total throughput effectively, M-TPCG algorithm can achieve maximal system throughput. The performance of the cognitive radio system is improved obviously.
文摘In times of global changes and turbulence like ours, more than anything, firms need some pillars of stability. By this paper we would like to develop a comprehensive and adaptive managerial approach of corporate reputation. This is based on the premise that intangible assets (in general) and corporate reputation (in particular) are more and more recognized and managed as sources of (unique) sustainable competitive advantages and as core determinants of firm competitiveness, which are relatively hard to build and very easy to loose.
基金Supported in part by Natural Science Fundation of Jiangsu Province (No.06KJA51001)
文摘Wireless Mesh Networks(WMNs) are envisioned to support the wired backbone with a wireless Backbone Networks(BNet) for providing internet connectivity to large-scale areas.With a wide range of internet-oriented applications with different Quality of Service(QoS) requirement, the large-scale WMNs should have good scalability and large bandwidth.In this paper, a Load Aware Adaptive Backbone Synthesis(LAABS) algorithm is proposed to automatically balance the traffic flow in the WMNs.The BNet will dynamically split into smaller size or merge into bigger one according to statistic load information of Backbone Nodes(BNs).Simulation results show LAABS generates moderate BNet size and converges quickly, thus providing scalable and stable BNet to facilitate traffic flow.
基金supported by the grants DMS 0405343 and DMR 0520425.
文摘Efficient data visualization techniques are critical for many scientific applications. Centroidal Voronoi tessellation(CVT) based algorithms offer a convenient vehicle for performing image analysis,segmentation and compression while allowing to optimize retained image quality with respect to a given metric.In experimental science with data counts following Poisson distributions,several CVT-based data tessellation algorithms have been recently developed.Although they surpass their predecessors in robustness and quality of reconstructed data,time consumption remains to be an issue due to heavy utilization of the slowly converging Lloyd iteration.This paper discusses one possible approach to accelerating data visualization algorithms.It relies on a multidimensional generalization of the optimization based multilevel algorithm for the numerical computation of the CVTs introduced in[1],where a rigorous proof of its uniform convergence has been presented in 1-dimensional setting.The multidimensional implementation employs barycentric coordinate based interpolation and maximal independent set coarsening procedures.It is shown that when coupled with bin accretion algorithm accounting for the discrete nature of the data,the algorithm outperforms Lloyd-based schemes and preserves uniform convergence with respect to the problem size.Although numerical demonstrations provided are limited to spectroscopy data analysis,the method has a context-independent setup and can potentially deliver significant speedup to other scientific and engineering applications.
基金supported partially by China's National 863 Program under Grant No.2009AA01Z207
文摘To improve spectrum utilization and minimize interference to Primary User (PU), an adaptive spectrum decision method is proposed for Secondary User (SU), while taking traffic load balancing and spectrum heterogeneity into consideration. Long-term statistics and current sensing results are integrated into the proposed decision method of spectrum access. Two decision methods, namely probability based and sensing based, are presented, compared and followed by performance analysis in terms of delay. For probability based spectrum decision, Short-Time-Job-First (STJF) priority queuing discipline is employed to minimize average residual time and theoretical conclusion is derived in a novel way. For sensing based decision we treat the interrupted service of SU as newly incoming and re-decision process is initialized to find available spectrum in a First-Available-First-Access (FAFA) fashion. Effect of sensing error in PHY layer is also analyzed in terms of extended average residual time. Simulation results show that, for relatively low arriving rate of SU traffic, the proposed spectrum decision method yields at least a delay reduction of 39.5% compared with non-adaptive method. The proposed spectrum decision can significantly improve delay performance even facing sensing errors, which cause performance degeneration to both PU and SU.
基金Projects(61101104,61100213) supported by the National Natural Science Foundation of ChinaProject(NY211050) supported by Fund of Nanjing University of Posts and Telecommunications,China
文摘A distributed local adaptive transmit power assignment (LA-TPA) strategy was proposed to construct a topology with better performance according to the environment and application scenario and prolong the network lifetime.It takes the path loss exponent and the energy control coefficient into consideration with the aim to accentuate the minimum covering district of each node more accurately and precisely according to various network application scenarios.Besides,a self-healing scheme that enhances the robustness of the network was provided.It makes the topology tolerate more dead nodes than existing algorithms.Simulation was done under OMNeT++ platform and the results show that the LA-TPA strategy is more effective in constructing a well-performance network topology based on various application scenarios and can prolong the network lifetime significantly.
基金Supported by National Natural Science Foundation of China (No60702037)Research Fund for the Doctoral Program of Higher Education of China (No20070056129)Natural Science Foundation of Tianjin (No09JCYBJC00800)
文摘Sensor localization is crucial for the configuration and applications of wireless sensor network (WSN). A novel distributed localization algorithm, MDS-DC was proposed for wireless sensor network based on multidimensional scaling (MDS) and the shortest path distance correction. In MDS-DC, several local positioning regions with reasonable distribution were firstly constructed by an adaptive search algorithm, which ensures the mergence between the local relative maps of the adjacent local position regions and can reduce the number of common nodes in the network. Then, based on the relationships between the estimated distances and actual distances of anchors, the distance estimation vectors of sensors around anchors were corrected in each local positioning region. During the computations of the local relative coordinates, an iterative process, which is the combination of classical MDS algorithm and SMACOF algorithm, was applied. Finally, the global relative positions or absolute positions of sensors were obtained through merging the relative maps of all local positioning regions. Simulation results show that MDS-DC has better performances in positioning precision, energy efficiency and robustness to range error, which can meet the requirements of applications for sensor localization in WSN.
基金Projects(2009AA093302,2002AA401003)supported by the National High-Tech Research and Development Program of ChinaProject(YYYJ-0917)supported by the Knowledge Innovation of Chinese Academy of Sciences+1 种基金Projects(61273334,61233013)supported by the National Natural Science Foundation of ChinaProject(2011010025-401)supported by the Natural Science Foundation of Liaoning Province,China
文摘Inherent flaws in the extended Kalman filter(EKF) algorithm were pointed out and unscented Kalman filter(UKF) was put forward as an alternative.Furthermore,a novel adaptive unscented Kalman filter(AUKF) based on innovation was developed.The three data-fusing approaches were analyzed and evaluated in a mathematically rigorous way.Field experiments conducted in lake further demonstrate that AUKF reduces the position error approximately by 65% compared with EKF and by 35% UKF and improves the robust performance.
基金partially supported by the Academy of Finland (Decision No. 284748, 288473)
文摘With its rapid development in the wireless markets, IEEE 802.11 WLAN is experiencing a huge popularity. However, due to the limitation of frequency bandwidth of WLANs, it is essential that the available radio resource should be fully utilized to offer different services to multiple users. In order to maximize system throughput while still guaranteeing the fairness among users, a proportional fairness based algorithm is proposed in this work. Since most of the previous resource allocation algorithms were simply based on the channel conditions without taking into account user's demand, in this paper, we introduce the theory of fuzzy synthetic evaluation(FSE) which also allows us to consider user's demand as an important factor. As such, the fairness among users can be improved based on different users' requirements for services. In addition, a channel state information based rate adaptation scheme is also proposed. Through simulation studies, the results clearly validate that our proposed scheme shows advantages on providing user fairness while still improving the system throughput.
基金Project(60673164) supported by the National Natural Science Foundation of ChinaProject(06JJ10009) supported by the Natural Science Foundation of Hunan Province, China+2 种基金Project(20060533057) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(2008CB317107) supported by the Major State Basic Research and Development Program of ChinaProject(NCET-05-0683) supported by the Program for New Century Excellent Talents in University
文摘The IEEE 802.11e standard is proposed to provide QoS support in WLAN by providing prioritized differentiation of traffic. Since all the stations in the same priority access category (AC) have the same set of parameters, when the number of stations increases, the probability of different stations in the same AC choosing the same values will increase, which will result in collisions. Random adaptive MAC (medium access control) parameters scheme (RAMPS) is proposed, which uses random adaptive MAC differentiation parameters instead of the static ones used in the 802.11e standard. The performance of RAMPS is compared with that of enhanced distributed coordination access (EDCA) using NS2. The results show that RAMPS can reduce collision rate of the AC and improve the throughput by using adaptive random contention window size and inter-frame spacing values. RAMPS ensures that at any given time, several flows of the same priority have different MAC parameter values. By using the random offset for the inter-frame spacing value and the backoff time, RAMPS can provide intra-AC differentiation. The simulation results show that RAMPS outperforms EDCA in terms of both throughput and end-to-end delay irrespective of the traffic load.