Heterogeneous Networks(HetNets)and cell densification represent promising solutions for the surging data traffic demand in wireless networks.In dense HetNets,user traffic is steered toward the Low-Power Node(LPN)when ...Heterogeneous Networks(HetNets)and cell densification represent promising solutions for the surging data traffic demand in wireless networks.In dense HetNets,user traffic is steered toward the Low-Power Node(LPN)when possible to enhance the user throughput and system capacity by increasing the area spectral efficiency.However,because of the transmit power differences in different tiers of HetNets and irregular service demand,a load imbalance typically exists among different serving nodes.To offload more traffic to LPNs and coordinate the Inter-Cell Interference(ICI),Third-Generation Partnership Project(3GPP)has facilitated the development of the Cell Range Expansion(CRE),enhanced Inter-Cell Interference Coordination(eICIC)and Further enhanced ICIC(FeICIC).In this paper,we develop a cell clustering-based load-aware offsetting and an adaptive Low-Power Subframe(LPS)approach.Our solution allows the separation of User Association(UA)functions at the User Equipment(UE)and network server such that users can make a simple cell-selection decision similar to that in the maximum Received Signal Strength(max-RSS)based UA scheme,where the network server computes the load-aware offsetting and required LPS periods based on the load conditions of the system.The proposed solution is evaluated using system-level simulations wherein the results correspond to performance changes in different service regions.Results show that our method effectively solves the offloading and interference coordination problems in dense HetNets.展开更多
Tube hydroforming technology has shown the attention of the automotive industry due to its advantages over conventional stamping and welding methods.In this study,the tube hydroforming process including tube bending,p...Tube hydroforming technology has shown the attention of the automotive industry due to its advantages over conventional stamping and welding methods.In this study,the tube hydroforming process including tube bending,preforming and hydroforming process for an automobile subframe is analyzed and designed by the simulation software AutoForm of a finite element method (FEM) program.A parametric study is carried out to obtain the effect of the forming parameters such as initial tube size and loading path on the forming results.The simulation results are also compared with experiment results.The research indicates that the multiple forming operation of the tube hydroforming process can be simulated accurately by using the implicit code AutoForm,and the formability of tube hydroforming can be improved by designing suitable forming parameters.展开更多
The tube hydroforming technology is used today in the mass production of lightweight components for the automotive industries due to its advantages over conventional stamping methods. A typical tube hydroforming proce...The tube hydroforming technology is used today in the mass production of lightweight components for the automotive industries due to its advantages over conventional stamping methods. A typical tube hydroforming process is usually a multiple forming operation process. The tube preforming and hydroforming process of an automobile subframe were analyzed by finite element method (FEM), and a parametric study was also carried out to obtain the effect of the forming parameters such as the die closing, the internal pressure and the axial feeding. The simulation results were also compared with industrial products in respect to the thickness distribution of some typical and key cross-sections. The study indicates that the internal pressure and the axial feeding should be set correctly and the multiple forming operations of tube hydroforming process can be simulated well by using the explicit code Ls-Dyna.展开更多
A 5G network must be heterogeneous and support the co-existence of multilayer cells, multiple standards, and multiple applica- tion systems. This greatly improves link performance and increases link capacity. A networ...A 5G network must be heterogeneous and support the co-existence of multilayer cells, multiple standards, and multiple applica- tion systems. This greatly improves link performance and increases link capacity. A network with co-existing macro and pico cells ean alleviate traffic congestion caused by muhicast or unicast subscribers, help satisfy huge traffic demands, and further extend converge. In order to practically implement advanced 5G technology, a number of technical problems have to be solved, one of which is inter-cell interference. A method called Almost Blank Subframe （ABS） has been proposed to mitigate interference; howev- er, the reference signal in ABS still causes interference. This paper describes how interference can be cancelled by using the in- formation in the ABS. First, the interference-signal model, which takes into account channel effect, time and frequency error, is presented. Then, an interference-cancellation scheme based on this model is studied. The timing and carrier frequency offset of the interference signal is compensated. Afterwards, the reference signal of the interfering cell is generated locally and the channel response is estimated using channel statistics. Then, the interference signal is reconstructed according to previous estimation of channel, timing, and carrier frequency offset. The interference is mitigated by subtracting the estimated interference signal. Com- puter simulation shows that this interference-cancellation algorithm significantly improves performance under different channel conditions.展开更多
WiMAX distributed scheduling can be modeled as two procedures：three-way handshaking procedure and data subframe scheduling procedure.Due to manipulating data transmission directly,data subframe scheduling has a close...WiMAX distributed scheduling can be modeled as two procedures：three-way handshaking procedure and data subframe scheduling procedure.Due to manipulating data transmission directly,data subframe scheduling has a closer relationship with user Quality of Service（QoS） satisfaction,and has more severe impact on network performance,compared with handshaking procedure.A QoS guaranteed Throughput-Efficiency Optimal distributed data subframe Scheduling scheme,named as QoS-TEOS,is proposed.QoS-TEOS achieves QoS guarantee through modeling services into different ranks and assigning them with corresponding priorities.A service with higher priority is scheduled ahead of that with lower priority and offered with high QoS quality.Same kinds of services that request similar QoS quality are classified into one service set.Different service sets are scheduled with different strategies.QoS-TEOS promotes network performance through improving network throughput and efficiency.Theoretical analysis shows that the scheduled data transmission should balance data generation rate from upper layer and transmission rate of physical layer,to avoid network throughput and efficiency declining.Simulation results show that QoS-TEOS works excellently to achieve throughput-efficiency optimization and guarantee a high QoS.展开更多
文摘Heterogeneous Networks(HetNets)and cell densification represent promising solutions for the surging data traffic demand in wireless networks.In dense HetNets,user traffic is steered toward the Low-Power Node(LPN)when possible to enhance the user throughput and system capacity by increasing the area spectral efficiency.However,because of the transmit power differences in different tiers of HetNets and irregular service demand,a load imbalance typically exists among different serving nodes.To offload more traffic to LPNs and coordinate the Inter-Cell Interference(ICI),Third-Generation Partnership Project(3GPP)has facilitated the development of the Cell Range Expansion(CRE),enhanced Inter-Cell Interference Coordination(eICIC)and Further enhanced ICIC(FeICIC).In this paper,we develop a cell clustering-based load-aware offsetting and an adaptive Low-Power Subframe(LPS)approach.Our solution allows the separation of User Association(UA)functions at the User Equipment(UE)and network server such that users can make a simple cell-selection decision similar to that in the maximum Received Signal Strength(max-RSS)based UA scheme,where the network server computes the load-aware offsetting and required LPS periods based on the load conditions of the system.The proposed solution is evaluated using system-level simulations wherein the results correspond to performance changes in different service regions.Results show that our method effectively solves the offloading and interference coordination problems in dense HetNets.
文摘Tube hydroforming technology has shown the attention of the automotive industry due to its advantages over conventional stamping and welding methods.In this study,the tube hydroforming process including tube bending,preforming and hydroforming process for an automobile subframe is analyzed and designed by the simulation software AutoForm of a finite element method (FEM) program.A parametric study is carried out to obtain the effect of the forming parameters such as initial tube size and loading path on the forming results.The simulation results are also compared with experiment results.The research indicates that the multiple forming operation of the tube hydroforming process can be simulated accurately by using the implicit code AutoForm,and the formability of tube hydroforming can be improved by designing suitable forming parameters.
文摘The tube hydroforming technology is used today in the mass production of lightweight components for the automotive industries due to its advantages over conventional stamping methods. A typical tube hydroforming process is usually a multiple forming operation process. The tube preforming and hydroforming process of an automobile subframe were analyzed by finite element method (FEM), and a parametric study was also carried out to obtain the effect of the forming parameters such as the die closing, the internal pressure and the axial feeding. The simulation results were also compared with industrial products in respect to the thickness distribution of some typical and key cross-sections. The study indicates that the internal pressure and the axial feeding should be set correctly and the multiple forming operations of tube hydroforming process can be simulated well by using the explicit code Ls-Dyna.
文摘A 5G network must be heterogeneous and support the co-existence of multilayer cells, multiple standards, and multiple applica- tion systems. This greatly improves link performance and increases link capacity. A network with co-existing macro and pico cells ean alleviate traffic congestion caused by muhicast or unicast subscribers, help satisfy huge traffic demands, and further extend converge. In order to practically implement advanced 5G technology, a number of technical problems have to be solved, one of which is inter-cell interference. A method called Almost Blank Subframe （ABS） has been proposed to mitigate interference; howev- er, the reference signal in ABS still causes interference. This paper describes how interference can be cancelled by using the in- formation in the ABS. First, the interference-signal model, which takes into account channel effect, time and frequency error, is presented. Then, an interference-cancellation scheme based on this model is studied. The timing and carrier frequency offset of the interference signal is compensated. Afterwards, the reference signal of the interfering cell is generated locally and the channel response is estimated using channel statistics. Then, the interference signal is reconstructed according to previous estimation of channel, timing, and carrier frequency offset. The interference is mitigated by subtracting the estimated interference signal. Com- puter simulation shows that this interference-cancellation algorithm significantly improves performance under different channel conditions.
基金Supported by Intel Project under Grant No.4507336215Huawei Project under Grant No.YBCB2007025the University of Science and Technology of China Innovation Foundation under Grant No.KD2008053.
文摘WiMAX distributed scheduling can be modeled as two procedures：three-way handshaking procedure and data subframe scheduling procedure.Due to manipulating data transmission directly,data subframe scheduling has a closer relationship with user Quality of Service（QoS） satisfaction,and has more severe impact on network performance,compared with handshaking procedure.A QoS guaranteed Throughput-Efficiency Optimal distributed data subframe Scheduling scheme,named as QoS-TEOS,is proposed.QoS-TEOS achieves QoS guarantee through modeling services into different ranks and assigning them with corresponding priorities.A service with higher priority is scheduled ahead of that with lower priority and offered with high QoS quality.Same kinds of services that request similar QoS quality are classified into one service set.Different service sets are scheduled with different strategies.QoS-TEOS promotes network performance through improving network throughput and efficiency.Theoretical analysis shows that the scheduled data transmission should balance data generation rate from upper layer and transmission rate of physical layer,to avoid network throughput and efficiency declining.Simulation results show that QoS-TEOS works excellently to achieve throughput-efficiency optimization and guarantee a high QoS.
