针对风力助航船舶航线优化中存在的风能利用效率量化不足、油耗预测精度受限以及多目标协同优化机制缺失等问题,提出1种融合动态风帆控制与混合驱动预测的多目标航线优化方法。通过建立基于流体力学特性的动态风帆控制策略模型,实现风...针对风力助航船舶航线优化中存在的风能利用效率量化不足、油耗预测精度受限以及多目标协同优化机制缺失等问题,提出1种融合动态风帆控制与混合驱动预测的多目标航线优化方法。通过建立基于流体力学特性的动态风帆控制策略模型,实现风帆辅助推力的空间矢量解析,该模型突破传统静态攻角设定的局限性,可即时动态调整帆角参数,使风能转化效率处于较高水平。为解决传统物理模型环境适应性差与数据驱动方法物理可解释性弱的双重局限,构建物理约束下的人工神经网络分层融合架构,通过船舶运动学方程构建特征空间基底,采用注意力机制引导的人工神经网络进行残差学习。该方法在保留能耗物理机理的同时,实现数据特征与流体力学方程的双向耦合,经北大西洋航线的验证表明,其油耗预测平均绝对百分比误差(mean absolute percentage error,MAPE)较纯物理模型降低21.9%,较纯数据驱动方法的可解释性也大大提升。在此基础上,建立包含时间成本和燃油消耗的多目标优化模型,设计基于非支配排序遗传算法(non-dominated sorting genetic algorithm,NSGA-Ⅱ)和逼近理想解排序法(technique for order preference by similarity to ideal solution,TOPSIS)的协同优化算法,其非劣解集收敛速度较标准算法得以提升。以“新伊敦”轮为对象的实证研究表明:优化后的航线在北大西洋典型航次中,风帆有效工作效率提升,相较于传统推荐航线,优化航线的单航次航行时间缩短5%左右,油耗成本和固定成本分别降低9.1%和4.95%,总成本降低超过7.2%,有效的提高了风力助航船的经济效益并较少了对环境的污染。展开更多
针对高误码率及高中断率对无线TCP(Transport Control Protocol)的影响,提出了OFDM(Orthogonal Frequency Division Multiplexing)系统跨层TCP增强技术CLTCP(Cross-Layer TCP)。CLTCP利用链路级恢复和TCP冻结技术,提高了无线TCP性能;对...针对高误码率及高中断率对无线TCP(Transport Control Protocol)的影响,提出了OFDM(Orthogonal Frequency Division Multiplexing)系统跨层TCP增强技术CLTCP(Cross-Layer TCP)。CLTCP利用链路级恢复和TCP冻结技术,提高了无线TCP性能;对于出错的无线帧,链路层能给予有限次的重传,以屏蔽TCP层对高误码率的感知;同时,为了保证出错帧在有限重传次数内被正确递交对端,链路层联合物理层采用自适应调制编码技术来提高重传帧的可靠性。对于无线链路长时间断连,CLTCP利用TCP源端冻结技术冻结RTO(Retransmission Time Out)值,以避免数据包连续超时造成的极大RTO,由此保证无线链路恢复连接后,TCP层能及时恢复工作。通过NS2(Network Semulation 2)软件仿真了多种无线TCP增强技术,并对仿真结果进行了比较和分析。仿真结果表明,CLTCP的吞吐量较Snoop技术最多可提升33%,并同时节省约38%的带宽。展开更多
Motivated by the objective of pursuing revenue, improvement in coverage and reduction in energy cost for wireless communication networks have been of great significance for mobile operators. Therefore, heterogeneous c...Motivated by the objective of pursuing revenue, improvement in coverage and reduction in energy cost for wireless communication networks have been of great significance for mobile operators. Therefore, heterogeneous cellular networks(HCNs) and Coordinated Multipoint(Co MP) transmission are considered as promising solutions to enhance the performances of wireless communication systems. This paper analyzed the K-tier HCNs with a dynamic downlink Co MP scheme, in which the flexible clusters of cooperative stations are determined by a connecting threshold θ. Using stochastic geometry, the coverage probability(CP) and energy efficiency(EE) of a K-tier HCN operating under this scheme are derived, based on which the trade-off between CP and EE is discovered and discussed. Simulation results show the validity of our derivations. The proposed schememay significantly reduce energy consumption sacrificing a small amount of CP, and outperforms the fixed scheme as well. The CP-EE trade-off are also revealed, whichsuggests suitable trade-off points between CP and EE that will deliver the maximum economic profitability. Tendencies discovered in this paper may provide the operators with opportunities for further optimization in pursuit of economic profitability.展开更多
To reinforce the coverage and QoS(quality of service) of on-ground cellular communication system, unmanned aerial vehicles which are carrying small cells are deployed in some emergency and disaster areas. Although ASC...To reinforce the coverage and QoS(quality of service) of on-ground cellular communication system, unmanned aerial vehicles which are carrying small cells are deployed in some emergency and disaster areas. Although ASCs(aerial small cells) can provide a higher probability of LoS(line-of-sight) transmission, the wireless backhaul link will bring extra interference to the whole system if not well designed. Therefore, in this paper, we study the backhaul scheme for UAV-assist cellular network. We first analyze the interference environments of UAV-assist cellular network considering the IBOG(In-Band to On-Ground), OBOG(Out-of-Band to On-Ground) and IBTU(In-Band to Tethered-UAV) backhauling mode, and give the descriptions of the performance metrics for each mode. Then, the considered problem is formulated as an optimization of achievable rate. We derive the optimal solutions for the involved three backhauling modes for ASCs respectively, and closed-form optimal value for each mode is acquired with proof. We also give a pseudo-code form of our proposed optimal access/backhaul spectrum allocation algorithm. The simulation results indicate that the proposed scheme can deliver a significant gain, while IBTU performs best among proposed backhauling modes.展开更多
As the radio communications technology widely used,wireless location technology plays a more important role in maintaining the order of the air waves.However concretely effective symbol calibration method with regard ...As the radio communications technology widely used,wireless location technology plays a more important role in maintaining the order of the air waves.However concretely effective symbol calibration method with regard to Chinese DTMB signal of different frame mode is quite under research due to the multiple structure of DTMB signal.In this paper,we propose a Time Difference of Arrival(TDOA)-based passive location scheme using least square principle.Utilizing the large number of anchor nodes in wireless monitoring network,a novel algorithm is formulated to solve the None-LineOf-Sight problem.The derived Cramer Rao Lower Bound of the localization method guides to the accuracy of the position outcome with regards to the calibration precision.In contrast with traditional multi-terminal location schemes,our location scheme can reduce calculation complexity and location costs abruptly.A twostep NLOS identification algorithm is proposed.Computer simulation is employed to verify the well performance of the calibration method of3-4 dB superiority than normal method and also the whole localization scheme for less than 50 meters through channel of SNR lower than dB.Simulation also shows that our algorithm can effectively identify NLOS path and improve positioning accuracy.展开更多
In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into s...In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into small meshes,and all meshes are clustered into highly related groups using the spatial correlation among them. In each group,some representative meshes are selected as detecting meshes(DMs)using a multi-center mesh(MCM)clustering algorithm,while other meshes(EMs)are estimated according to their correlations with DMs and the Markov modeled dependence on history by MAP principle. Thus,detecting fewer meshes saves the sensing consumption. Since two independent estimation processes may provide contradictory results,minimum entropy principle is adopted to merge the results. Tested with data acquired by radio environment mapping measurement conducted in the downtown Beijing,our scheme is capable to reduce the consumption of traditional sensing method with acceptable sensing performance.展开更多
Beyond 3G(B3G)system,the future mobile communication system,is envisioned as a user-centric,open,and convergent information infrastructure capable of providing personalized services.It is extremely important to develo...Beyond 3G(B3G)system,the future mobile communication system,is envisioned as a user-centric,open,and convergent information infrastructure capable of providing personalized services.It is extremely important to develop service models and architectures for B3G system.A three-dimension service model is proposed.The dimensions are identified as service support scope,service capability definition,and adaptive feature elements.Then,the hierarchical service architecture for B3G is introduced.The enabling technologies for B3G service architecture are discussed in this paper,such as Virtual Home Environment(VHE),service support environment,service openness,distributed computing,intelligent technology,and profile.展开更多
To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobi...To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobile Telecommunication System (UMTS) and perform the Random Access (RA) procedure simultaneously, a comprehensive RA analysis model of RA is proposed in this paper. Further, a power ramping strategy based on the logarithm for M2M is proposed. The efficiency of both the existing and proposed scheme is assessed through a simulation across several metrics, including average target power, throughput, blocking probability, and delay statistics. Numerical results show that the proposed algorithm can ensure a minimal impact on H2H communication while maintaining the throughput of the M2M communication. Meanwhile, because of its low energy consumption, this algorithm has a significant guide value for real-world applications.展开更多
The co-channel interference modeling is vital for evaluating the secrecy performance in random wireless networks,where the legitimate nodes and eavesdroppers are randomly distributed.In this paper,a new interference m...The co-channel interference modeling is vital for evaluating the secrecy performance in random wireless networks,where the legitimate nodes and eavesdroppers are randomly distributed.In this paper,a new interference model is proposed from the userdominant perspective.The model can provide a better analytical assessment of secrecy performance with interference coordination for the presence of eavesdroppers.The typical legitimate is assumed to be located at the origin,and chooses the closest base station(BS) as its serving BS.The field of interferers is obtained by excluding the desired BSs(including the serving BS and its cooperative BS(s)).In contract with the exiting interference model,it is assumed that desired BSs and interferers belong to the same Poisson Point Process(PPP),and eavesdroppers are distributed according to another independent PPP.Based on this model,the average secrecy transmission capacity is derived in simply analytical forms with interference coordination.Analysis and simulation results show that the secrecy performance can be significantly enhanced by exploiting interference coordination.Furthermore,the average secrecy transmission capacity increases with increasing number of cooperative BSs.展开更多
In order to make full use of advanced technologies for future mobile communications systems such as Space Time Code(STC),Joint Transmission(JT)and Multiple Input Multiple Output(MIMO),and to meet the requirements of h...In order to make full use of advanced technologies for future mobile communications systems such as Space Time Code(STC),Joint Transmission(JT)and Multiple Input Multiple Output(MIMO),and to meet the requirements of high-bit-rate multimedia services,new network topologies should be studied.Generalized distributed multicell architecture can take full advantage of multi-antenna technologies and solve the problem of frequent handover caused by higher carrier frequencies.Group handover,the handover policy based on the architecture,can eliminate the cell edge effect.Furthermore,by applying the concept of group handover to 3G mobile communication systems,the Fast Cell Group Selection(FCGS)scheme can effectively improve the data rate for cell edge users.展开更多
文摘针对风力助航船舶航线优化中存在的风能利用效率量化不足、油耗预测精度受限以及多目标协同优化机制缺失等问题,提出1种融合动态风帆控制与混合驱动预测的多目标航线优化方法。通过建立基于流体力学特性的动态风帆控制策略模型,实现风帆辅助推力的空间矢量解析,该模型突破传统静态攻角设定的局限性,可即时动态调整帆角参数,使风能转化效率处于较高水平。为解决传统物理模型环境适应性差与数据驱动方法物理可解释性弱的双重局限,构建物理约束下的人工神经网络分层融合架构,通过船舶运动学方程构建特征空间基底,采用注意力机制引导的人工神经网络进行残差学习。该方法在保留能耗物理机理的同时,实现数据特征与流体力学方程的双向耦合,经北大西洋航线的验证表明,其油耗预测平均绝对百分比误差(mean absolute percentage error,MAPE)较纯物理模型降低21.9%,较纯数据驱动方法的可解释性也大大提升。在此基础上,建立包含时间成本和燃油消耗的多目标优化模型,设计基于非支配排序遗传算法(non-dominated sorting genetic algorithm,NSGA-Ⅱ)和逼近理想解排序法(technique for order preference by similarity to ideal solution,TOPSIS)的协同优化算法,其非劣解集收敛速度较标准算法得以提升。以“新伊敦”轮为对象的实证研究表明:优化后的航线在北大西洋典型航次中,风帆有效工作效率提升,相较于传统推荐航线,优化航线的单航次航行时间缩短5%左右,油耗成本和固定成本分别降低9.1%和4.95%,总成本降低超过7.2%,有效的提高了风力助航船的经济效益并较少了对环境的污染。
文摘针对高误码率及高中断率对无线TCP(Transport Control Protocol)的影响,提出了OFDM(Orthogonal Frequency Division Multiplexing)系统跨层TCP增强技术CLTCP(Cross-Layer TCP)。CLTCP利用链路级恢复和TCP冻结技术,提高了无线TCP性能;对于出错的无线帧,链路层能给予有限次的重传,以屏蔽TCP层对高误码率的感知;同时,为了保证出错帧在有限重传次数内被正确递交对端,链路层联合物理层采用自适应调制编码技术来提高重传帧的可靠性。对于无线链路长时间断连,CLTCP利用TCP源端冻结技术冻结RTO(Retransmission Time Out)值,以避免数据包连续超时造成的极大RTO,由此保证无线链路恢复连接后,TCP层能及时恢复工作。通过NS2(Network Semulation 2)软件仿真了多种无线TCP增强技术,并对仿真结果进行了比较和分析。仿真结果表明,CLTCP的吞吐量较Snoop技术最多可提升33%,并同时节省约38%的带宽。
基金supported by the National Natural Science Foundation of China under Grant No.61231009the National High-tech Research and Development Program of China under Grant No.2014AA01A701the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No.NCET 12-0795
文摘Motivated by the objective of pursuing revenue, improvement in coverage and reduction in energy cost for wireless communication networks have been of great significance for mobile operators. Therefore, heterogeneous cellular networks(HCNs) and Coordinated Multipoint(Co MP) transmission are considered as promising solutions to enhance the performances of wireless communication systems. This paper analyzed the K-tier HCNs with a dynamic downlink Co MP scheme, in which the flexible clusters of cooperative stations are determined by a connecting threshold θ. Using stochastic geometry, the coverage probability(CP) and energy efficiency(EE) of a K-tier HCN operating under this scheme are derived, based on which the trade-off between CP and EE is discovered and discussed. Simulation results show the validity of our derivations. The proposed schememay significantly reduce energy consumption sacrificing a small amount of CP, and outperforms the fixed scheme as well. The CP-EE trade-off are also revealed, whichsuggests suitable trade-off points between CP and EE that will deliver the maximum economic profitability. Tendencies discovered in this paper may provide the operators with opportunities for further optimization in pursuit of economic profitability.
基金supported in part by the National Natural Science Foundation of China under Grant 61631003in part by the National Science Fund for Distinguished Young Scholars under Grant 61525101
文摘To reinforce the coverage and QoS(quality of service) of on-ground cellular communication system, unmanned aerial vehicles which are carrying small cells are deployed in some emergency and disaster areas. Although ASCs(aerial small cells) can provide a higher probability of LoS(line-of-sight) transmission, the wireless backhaul link will bring extra interference to the whole system if not well designed. Therefore, in this paper, we study the backhaul scheme for UAV-assist cellular network. We first analyze the interference environments of UAV-assist cellular network considering the IBOG(In-Band to On-Ground), OBOG(Out-of-Band to On-Ground) and IBTU(In-Band to Tethered-UAV) backhauling mode, and give the descriptions of the performance metrics for each mode. Then, the considered problem is formulated as an optimization of achievable rate. We derive the optimal solutions for the involved three backhauling modes for ASCs respectively, and closed-form optimal value for each mode is acquired with proof. We also give a pseudo-code form of our proposed optimal access/backhaul spectrum allocation algorithm. The simulation results indicate that the proposed scheme can deliver a significant gain, while IBTU performs best among proposed backhauling modes.
基金supported by National BeiDou Special ProjectNational Science & Technology planning project of China(Grant No. 2014BAK12B04)
文摘As the radio communications technology widely used,wireless location technology plays a more important role in maintaining the order of the air waves.However concretely effective symbol calibration method with regard to Chinese DTMB signal of different frame mode is quite under research due to the multiple structure of DTMB signal.In this paper,we propose a Time Difference of Arrival(TDOA)-based passive location scheme using least square principle.Utilizing the large number of anchor nodes in wireless monitoring network,a novel algorithm is formulated to solve the None-LineOf-Sight problem.The derived Cramer Rao Lower Bound of the localization method guides to the accuracy of the position outcome with regards to the calibration precision.In contrast with traditional multi-terminal location schemes,our location scheme can reduce calculation complexity and location costs abruptly.A twostep NLOS identification algorithm is proposed.Computer simulation is employed to verify the well performance of the calibration method of3-4 dB superiority than normal method and also the whole localization scheme for less than 50 meters through channel of SNR lower than dB.Simulation also shows that our algorithm can effectively identify NLOS path and improve positioning accuracy.
基金supported in part by National Natural Science Foundation of China under Grants(61525101,61227801 and 61601055)in part by the National Key Technology R&D Program of China under Grant 2015ZX03002008
文摘In this paper,a space-time correlation based fast regional spectrum sensing(RSS)scheme is proposed to reduce the time and energy consumption of traditional spatial spectrum sensing. The target region is divided into small meshes,and all meshes are clustered into highly related groups using the spatial correlation among them. In each group,some representative meshes are selected as detecting meshes(DMs)using a multi-center mesh(MCM)clustering algorithm,while other meshes(EMs)are estimated according to their correlations with DMs and the Markov modeled dependence on history by MAP principle. Thus,detecting fewer meshes saves the sensing consumption. Since two independent estimation processes may provide contradictory results,minimum entropy principle is adopted to merge the results. Tested with data acquired by radio environment mapping measurement conducted in the downtown Beijing,our scheme is capable to reduce the consumption of traditional sensing method with acceptable sensing performance.
基金Project ofNational"863"Plan of China(No.2004AA119030)
文摘Beyond 3G(B3G)system,the future mobile communication system,is envisioned as a user-centric,open,and convergent information infrastructure capable of providing personalized services.It is extremely important to develop service models and architectures for B3G system.A three-dimension service model is proposed.The dimensions are identified as service support scope,service capability definition,and adaptive feature elements.Then,the hierarchical service architecture for B3G is introduced.The enabling technologies for B3G service architecture are discussed in this paper,such as Virtual Home Environment(VHE),service support environment,service openness,distributed computing,intelligent technology,and profile.
基金supported in part by the National Natural Science Foundation of Chinaunder Grants No.60971125, No.61121001Major National S&T Project under Grant No. 2012ZX03005010 the project under Grant No.201105
文摘To analyze and reduce the impact of Machine-to-Machine (M2M) Devices (MDs) on the traditional Human-to-Human (H2H) users for the blending scenario, where both M2M and H2H services coexist in the current Universal Mobile Telecommunication System (UMTS) and perform the Random Access (RA) procedure simultaneously, a comprehensive RA analysis model of RA is proposed in this paper. Further, a power ramping strategy based on the logarithm for M2M is proposed. The efficiency of both the existing and proposed scheme is assessed through a simulation across several metrics, including average target power, throughput, blocking probability, and delay statistics. Numerical results show that the proposed algorithm can ensure a minimal impact on H2H communication while maintaining the throughput of the M2M communication. Meanwhile, because of its low energy consumption, this algorithm has a significant guide value for real-world applications.
基金This work is supported by the National Natural Science Foundation for Distinguished Young Scholar of China under Grant No. 61325006 and the National High-tech Research and Development Program of China under Grant No. 2014AA01A701.
文摘The co-channel interference modeling is vital for evaluating the secrecy performance in random wireless networks,where the legitimate nodes and eavesdroppers are randomly distributed.In this paper,a new interference model is proposed from the userdominant perspective.The model can provide a better analytical assessment of secrecy performance with interference coordination for the presence of eavesdroppers.The typical legitimate is assumed to be located at the origin,and chooses the closest base station(BS) as its serving BS.The field of interferers is obtained by excluding the desired BSs(including the serving BS and its cooperative BS(s)).In contract with the exiting interference model,it is assumed that desired BSs and interferers belong to the same Poisson Point Process(PPP),and eavesdroppers are distributed according to another independent PPP.Based on this model,the average secrecy transmission capacity is derived in simply analytical forms with interference coordination.Analysis and simulation results show that the secrecy performance can be significantly enhanced by exploiting interference coordination.Furthermore,the average secrecy transmission capacity increases with increasing number of cooperative BSs.
基金Program ofNational Natural Science Foundation of China(No.60496312)Program of Beijing NaturalScience Foundation(No.4042021)
文摘In order to make full use of advanced technologies for future mobile communications systems such as Space Time Code(STC),Joint Transmission(JT)and Multiple Input Multiple Output(MIMO),and to meet the requirements of high-bit-rate multimedia services,new network topologies should be studied.Generalized distributed multicell architecture can take full advantage of multi-antenna technologies and solve the problem of frequent handover caused by higher carrier frequencies.Group handover,the handover policy based on the architecture,can eliminate the cell edge effect.Furthermore,by applying the concept of group handover to 3G mobile communication systems,the Fast Cell Group Selection(FCGS)scheme can effectively improve the data rate for cell edge users.
