It has been proven that carrier smoothing and differential global positioning system(DGPS)are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode err...It has been proven that carrier smoothing and differential global positioning system(DGPS)are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode errors between the ground station and user.However,another issue coming with local area augmentation system(LAAS)is how to find an adaptive smoothing window width to minimize the error on account of ionosphere delay and multipath.Based on the errors analysis in carrier smoothing process,a novel algorithm is formulated to design adaptive Hatch filter whose smoothing window width flexibly varies with the characteristic of ionosphere delay and multipath in the differential carrier smoothing process.By conducting the simulation in LAAS and after compared with traditional Hatch filers,it reveals that not only the accuracy of differential correction,but also the accuracy and the robustness of positioning results are significantly improved by using the designed adaptive Hatch filter.展开更多
The GPS multipath signal model is presented,which indicates that the coherent DLL outputs in multipath environment are the convolution between the ideal DLL outputs and the channel responses.So the channel responses c...The GPS multipath signal model is presented,which indicates that the coherent DLL outputs in multipath environment are the convolution between the ideal DLL outputs and the channel responses.So the channel responses can be estimated by a least square method using the observed curve of the DLL discriminator.In terms of the estimated multipath channels,two multipath mitigation methods are discussed,which are equalization filtering and multipath subtracting,respectively.It is shown,by computer simulation,that the least square method has a good performance in channels estimation and the multipath errors can be mitigated almost completely by either of the methods.However,the multipath subtracting method has relative small remnant errors than equalization filtering.展开更多
We propose a new multipath mitigation technique based on cross-correlation function for the new cosine phased binary off-set carrier （cosine-BOC） modulated signals, which will most likely be employed in both Europea...We propose a new multipath mitigation technique based on cross-correlation function for the new cosine phased binary off-set carrier （cosine-BOC） modulated signals, which will most likely be employed in both European Galileo system and Chinese Compass system. This technique is implemented to create an optimum cross-correlation function via designing the modulated symbols of the local signal. And the structure of the code tracking loop for cosine-BOC signals is quite simple including only two real correlators. Results demonstrate that the technique efficiently eliminates the ranging errors in the medium and long multipath regions with respect to the conventional receiver correlation techniques.展开更多
This paper proposes an efficient scheme to reduce the pre-correlation bandwidth effect in the global navigation satellite system(GNSS)receiver filtering process.It is mainly based on the application of a spectral tran...This paper proposes an efficient scheme to reduce the pre-correlation bandwidth effect in the global navigation satellite system(GNSS)receiver filtering process.It is mainly based on the application of a spectral transformation to the satellite-emitted signal that effectively reduces its band.At the receiver's end,this operation causes the spreading of noise over a much wider band than that used by the radio frequency stage.Consequently,the resulting auto-correlation function in the acquisition process acquires properties that enhance considerably the performance of the receiver in the presence of the multipath and noise disturbing phenomena.The simulation results demonstrate that the proposed method is a plausible solution for both multipath and noise problems in the GNSS applications for any limited value of the pre-correlation bandwidth in the receiver filter.展开更多
Because the intrinsic characteristics of mobile ad hoc networks（MANETs） cause several vulnerabilities,anonymous routing protocols attract much more attention in secure mobile ad hoc networks for the purposes of secu...Because the intrinsic characteristics of mobile ad hoc networks（MANETs） cause several vulnerabilities,anonymous routing protocols attract much more attention in secure mobile ad hoc networks for the purposes of security and privacy concerns.Until recently,lots of anonymous routing protocols have been proposed.However,most of them are single path or use one path at a time,and the multipath schemes can not thwart both the passive attacks and active attacks simultaneously.Thus an anonymous multipath routing protocol based on secret sharing is proposed.The protocol provides identity anonymity,location anonymity,data and traffic anonymity by employing cryptograph technology and secret sharing in MANET communication process.Meanwhile,a hash function is introduced to detect active attacks in the data transmission process.The protocol can effectively thwart various passive attacks and reduce the successful probability of active attacks（such as interception and physical destroy attacks）.Simulation results show that the proposed scheme provides a reasonably good level of network security and performance.展开更多
An optimized detection model based on weighted entropy for multiple input multiple output (MIMO) radar in multipath environment is presented. After defining the multipath distance difference (MDD), the multipath recei...An optimized detection model based on weighted entropy for multiple input multiple output (MIMO) radar in multipath environment is presented. After defining the multipath distance difference (MDD), the multipath received signal model with four paths is built systematically. Both the variance and correlation coefficient of multipath scattering coefficient with MDD are analyzed, which indicates that the multipath variable can decrease the detection performance by reducing the echo power. By making use of the likelihood ratio test (LRT), a new method based on weighted entropy is introduced to use the positive multipath echo power and suppress the negative echo power, which results in better performance. Simulation results show that, compared with non-multipath environment or other recently developed methods, the proposed method can achieve detection performance improvement with the increase of sensors.展开更多
In order to improve the data transmission reliability of mobile ad hoc network, a routing scheme called integrated forward error correction multipath routing protocol was proposed, which integrates the techniques of p...In order to improve the data transmission reliability of mobile ad hoc network, a routing scheme called integrated forward error correction multipath routing protocol was proposed, which integrates the techniques of packet fragmenting and forward error correction encoding into multipath routing. The scheme works as follows: adding a certain redundancy into the original packets; fragmenting the resulting packets into exclusive blocks of the same size; encoding with the forward error correction technique, and then sending them to the destination node. When the receiving end receives a certain amount of information blocks, the original information will be recovered even with partial loss. The performance of the scheme was evaluated using OPNET modeler. The experimental results show that with the method the average transmission delay is decreased by 20% and the transmission reliability is increased by 30%.展开更多
The influence of pulse repetition frequency(PRF) on performance of wireless digital time hopping spread spectrum(THSS) ultrawide bandwidth(UWB) radio systems with PPM in dense multipath fading environments is firstly ...The influence of pulse repetition frequency(PRF) on performance of wireless digital time hopping spread spectrum(THSS) ultrawide bandwidth(UWB) radio systems with PPM in dense multipath fading environments is firstly investigated. The receiver used in this UWB system is a hybrid selection/maximal-ratio combining(H-S/MRC) diversity receiver in which L strongest multipath components out of N multipath diversity branches are selected and combined using maximal-ratio combining. The exact expressions for the bit error rate(BER) of this UWB system are firstly derived by using the virtual branch technique in term of PRF, the number of multipath components selected and combined L, and multipath spread of the channel and then this BER performance is evaluated. With the computer simulation for impulses having different pulse shapes, numerical results show that PRF, as well as pulse shape and the number of multipath diversity branches selected and combined L, has much effect on the BER performance of this UWB system in dense multipath fading environments. As PRF increases, the BER performance of this UWB system is much degraded under the conditions of fixed L and pulse shape.展开更多
Concurrent multipath transfer(CMT)using stream control transmission protocol(SCTP)multihoming has become an appealing option to increase the throughput and improve the performance of increasingly bandwidth-hungry appl...Concurrent multipath transfer(CMT)using stream control transmission protocol(SCTP)multihoming has become an appealing option to increase the throughput and improve the performance of increasingly bandwidth-hungry applications.To investigate the rate allocation for applications in CMT,this paper analyzes the capacities of paths shared by competing sources,then proposes the rate allocation model for elastic flows based on the framework of network utility maximization(NUM).In order to obtain the global optimum of the model,a distributed algorithm is presented which depends only on local available information.Simulation results confirm that the proposed algorithm can achieve the global optimum within reasonable convergence times.展开更多
This study presents an interdisciplinary framework to enhance the radar cross-section(RCS)reduction of next-generation long-range cruise missiles by integrating Mn Zn ferrite/epoxy-based radar-absorbing materials(RAM)...This study presents an interdisciplinary framework to enhance the radar cross-section(RCS)reduction of next-generation long-range cruise missiles by integrating Mn Zn ferrite/epoxy-based radar-absorbing materials(RAM),electromagnetic simulation,and multipath-aware flight profiles.The best-performing RAM exhibited a reflection loss of-23 d B at 9.8 GHz with a 3.4 GHz effective absorption bandwidth,supported by complex permittivity/permeability analysis and Lorentz-based dispersion modeling.When applied to realistic missile geometries,simulations showed RCS reductions exceeding 25 d B.Furthermore,integrating this material into a dynamic radar detection algorithm shows how sea-surface multipath effects can increase the generation of null channels,reducing reaction time by up to 94 s under simulated conditions.Results underscore the effectiveness of integrating RAM with adaptive trajectory profiles to develop new doctrines for future radio-frequency(RF)low-observable,long-range cruise missiles.展开更多
基金supported by the National Natural Science Foundationof China(60974104)the National Defense Technical Foundation of Shipbuilding Industry(08J3.8.8)
文摘It has been proven that carrier smoothing and differential global positioning system(DGPS)are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode errors between the ground station and user.However,another issue coming with local area augmentation system(LAAS)is how to find an adaptive smoothing window width to minimize the error on account of ionosphere delay and multipath.Based on the errors analysis in carrier smoothing process,a novel algorithm is formulated to design adaptive Hatch filter whose smoothing window width flexibly varies with the characteristic of ionosphere delay and multipath in the differential carrier smoothing process.By conducting the simulation in LAAS and after compared with traditional Hatch filers,it reveals that not only the accuracy of differential correction,but also the accuracy and the robustness of positioning results are significantly improved by using the designed adaptive Hatch filter.
文摘The GPS multipath signal model is presented,which indicates that the coherent DLL outputs in multipath environment are the convolution between the ideal DLL outputs and the channel responses.So the channel responses can be estimated by a least square method using the observed curve of the DLL discriminator.In terms of the estimated multipath channels,two multipath mitigation methods are discussed,which are equalization filtering and multipath subtracting,respectively.It is shown,by computer simulation,that the least square method has a good performance in channels estimation and the multipath errors can be mitigated almost completely by either of the methods.However,the multipath subtracting method has relative small remnant errors than equalization filtering.
基金supported by the National Natural Science Foundation of China(6117900461179005)
文摘We propose a new multipath mitigation technique based on cross-correlation function for the new cosine phased binary off-set carrier （cosine-BOC） modulated signals, which will most likely be employed in both European Galileo system and Chinese Compass system. This technique is implemented to create an optimum cross-correlation function via designing the modulated symbols of the local signal. And the structure of the code tracking loop for cosine-BOC signals is quite simple including only two real correlators. Results demonstrate that the technique efficiently eliminates the ranging errors in the medium and long multipath regions with respect to the conventional receiver correlation techniques.
文摘This paper proposes an efficient scheme to reduce the pre-correlation bandwidth effect in the global navigation satellite system(GNSS)receiver filtering process.It is mainly based on the application of a spectral transformation to the satellite-emitted signal that effectively reduces its band.At the receiver's end,this operation causes the spreading of noise over a much wider band than that used by the radio frequency stage.Consequently,the resulting auto-correlation function in the acquisition process acquires properties that enhance considerably the performance of the receiver in the presence of the multipath and noise disturbing phenomena.The simulation results demonstrate that the proposed method is a plausible solution for both multipath and noise problems in the GNSS applications for any limited value of the pre-correlation bandwidth in the receiver filter.
基金supported by the National Basic Research Program of China(973 Program)(2011CB302903)the Key Program of Natural Science for Universities of Jiangsu Province(10KJA510035)+2 种基金the Science and Technology Innovation Group Foundation of Jiangsu Province ("Qing and Lan" Project)the Postgraduate Innovation Project Foundation of Jiangsu Province(CX10B 194ZCX09B 152Z)
文摘Because the intrinsic characteristics of mobile ad hoc networks（MANETs） cause several vulnerabilities,anonymous routing protocols attract much more attention in secure mobile ad hoc networks for the purposes of security and privacy concerns.Until recently,lots of anonymous routing protocols have been proposed.However,most of them are single path or use one path at a time,and the multipath schemes can not thwart both the passive attacks and active attacks simultaneously.Thus an anonymous multipath routing protocol based on secret sharing is proposed.The protocol provides identity anonymity,location anonymity,data and traffic anonymity by employing cryptograph technology and secret sharing in MANET communication process.Meanwhile,a hash function is introduced to detect active attacks in the data transmission process.The protocol can effectively thwart various passive attacks and reduce the successful probability of active attacks（such as interception and physical destroy attacks）.Simulation results show that the proposed scheme provides a reasonably good level of network security and performance.
基金supported by the Natural Science Foundation Research Project of Shaanxi Province(2016JQ6020)
文摘An optimized detection model based on weighted entropy for multiple input multiple output (MIMO) radar in multipath environment is presented. After defining the multipath distance difference (MDD), the multipath received signal model with four paths is built systematically. Both the variance and correlation coefficient of multipath scattering coefficient with MDD are analyzed, which indicates that the multipath variable can decrease the detection performance by reducing the echo power. By making use of the likelihood ratio test (LRT), a new method based on weighted entropy is introduced to use the positive multipath echo power and suppress the negative echo power, which results in better performance. Simulation results show that, compared with non-multipath environment or other recently developed methods, the proposed method can achieve detection performance improvement with the increase of sensors.
基金Projects(2003CB314802) supported by the State Key Fundamental Research and Development Programof China project(90104001) supported by the National Natural Science Foundation of China
文摘In order to improve the data transmission reliability of mobile ad hoc network, a routing scheme called integrated forward error correction multipath routing protocol was proposed, which integrates the techniques of packet fragmenting and forward error correction encoding into multipath routing. The scheme works as follows: adding a certain redundancy into the original packets; fragmenting the resulting packets into exclusive blocks of the same size; encoding with the forward error correction technique, and then sending them to the destination node. When the receiving end receives a certain amount of information blocks, the original information will be recovered even with partial loss. The performance of the scheme was evaluated using OPNET modeler. The experimental results show that with the method the average transmission delay is decreased by 20% and the transmission reliability is increased by 30%.
文摘The influence of pulse repetition frequency(PRF) on performance of wireless digital time hopping spread spectrum(THSS) ultrawide bandwidth(UWB) radio systems with PPM in dense multipath fading environments is firstly investigated. The receiver used in this UWB system is a hybrid selection/maximal-ratio combining(H-S/MRC) diversity receiver in which L strongest multipath components out of N multipath diversity branches are selected and combined using maximal-ratio combining. The exact expressions for the bit error rate(BER) of this UWB system are firstly derived by using the virtual branch technique in term of PRF, the number of multipath components selected and combined L, and multipath spread of the channel and then this BER performance is evaluated. With the computer simulation for impulses having different pulse shapes, numerical results show that PRF, as well as pulse shape and the number of multipath diversity branches selected and combined L, has much effect on the BER performance of this UWB system in dense multipath fading environments. As PRF increases, the BER performance of this UWB system is much degraded under the conditions of fixed L and pulse shape.
基金supported by the National Natural Science Foundation of China(60833002)the National Basic Research Program of China(973 Program)(2007CB307100)+2 种基金the National High Technology Research and Development Program of China(863 Program)(2007AA01Z202)the Program for Changjiang Scholars and Innovative Research Team in University(IRT0707)the Program of Introducing Talents of Discipline to Universities(111 Project)(B08002)
文摘Concurrent multipath transfer(CMT)using stream control transmission protocol(SCTP)multihoming has become an appealing option to increase the throughput and improve the performance of increasingly bandwidth-hungry applications.To investigate the rate allocation for applications in CMT,this paper analyzes the capacities of paths shared by competing sources,then proposes the rate allocation model for elastic flows based on the framework of network utility maximization(NUM).In order to obtain the global optimum of the model,a distributed algorithm is presented which depends only on local available information.Simulation results confirm that the proposed algorithm can achieve the global optimum within reasonable convergence times.
文摘This study presents an interdisciplinary framework to enhance the radar cross-section(RCS)reduction of next-generation long-range cruise missiles by integrating Mn Zn ferrite/epoxy-based radar-absorbing materials(RAM),electromagnetic simulation,and multipath-aware flight profiles.The best-performing RAM exhibited a reflection loss of-23 d B at 9.8 GHz with a 3.4 GHz effective absorption bandwidth,supported by complex permittivity/permeability analysis and Lorentz-based dispersion modeling.When applied to realistic missile geometries,simulations showed RCS reductions exceeding 25 d B.Furthermore,integrating this material into a dynamic radar detection algorithm shows how sea-surface multipath effects can increase the generation of null channels,reducing reaction time by up to 94 s under simulated conditions.Results underscore the effectiveness of integrating RAM with adaptive trajectory profiles to develop new doctrines for future radio-frequency(RF)low-observable,long-range cruise missiles.
