Zheng N.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research |
Zheng N.,Beijing Institute of Satellite Information Engineering |
Lu F.,Beijing Institute of Satellite Information Engineering
Lecture Notes in Geoinformation and Cartography | Year: 2012
Traditional solutions to shortest path problems on time-varying transportation networks use traffic information only at precise moments regardless of considering the fact that the travel time through any link is dependent on the time entering that link. In this study, travel speed rather than travel time on each link is used as the time period dependent parameter to model time-dependent transportation networks, and a First-In-First-Out (FIFO) condition satisfied computational function of link travel time is then deduced based on kinematics. Finally, a temporally adaptive A* shortest path algorithm on this FIFO network is presented, where the time factor is introduced into the evaluation function, and the Euclidean distance divided by the maximum possible travel speed is used as a heuristic evaluator. An experiment on a real road network shows that the proposed algorithm is capable of foreseeing and bypassing forthcoming traffic congestion, at a cost only about 10% more in computational time than the traditional algorithm. In addition, frequent path reoptimization required with use of the traditional algorithm is effectively avoided.©Springer-Verlag Berlin Heidelberg 2012.
Tian L.,Beijing Institute of Satellite Information Engineering |
Fan S.-M.,Beijing Institute of Satellite Information Engineering |
Zhao W.,Beijing Institute of Satellite Information Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010
This paper proposes a parallel computing method of multi-thread technology replacing the former serial-execution one according to the analysis of the radar imaging, the processing flow of NCS algorithm and the characteristic of multiprocessor and multi-core system, considering of the hard demand of high speed in imaging of raw spaceborne SAR data. A multi-thread program based on Linux and the pthread encapsulated is also provided. Through the experiments on HP Proliant DL580, it is proved that, compared with traditional serial NCS algorithm, the method of multi-thread presented in this paper makes use of system resource effectively and is good for parallel expansibility of imaging as well as achieving nice resolution. © 2010 Copyright SPIE - The International Society for Optical Engineering.
Zhang L.,University of Science and Technology Beijing |
Zhang F.-C.,University of Science and Technology Beijing |
Wang B.,Beijing Institute of Satellite Information Engineering
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013
Aiming to improve the performance of transmitted reference(TR) UWB system and mitigate external interference in multipath channel, time reversal(TiR) is employed. The BER performance of TR-UWB systems with and without TiR technology are investigated respectively, and the results imply that the SNR of TR-UWB system is improved about 10dB in multi-path channel with TiR pre-filter than that without TiR pre-filter whilst BER=1E-3. The impacts of the notch filter's parameters on performance of TiR TR-UWB system are investigated. The simulation results show that every increase of 528MHz in the width of notch filter causes 5dB degradation in the performance whilst the depth of notch filter has little influence on it. Finally, BER performance of this system with notch filter is studied in the case of MB-OFDM-UWB interference. Results indicate that with ultra-wideband notch filter technology, strong ultra-wideband interference within a bandwidth of 3×528MHz can be mitigated. For BER=1E-2, the signal-to-interference ratio(SIR) of TR-UWB improves 25dB with a notch filter comparing to that without a notch filter. The present work is expected to be useful for the design of the simple and advanced TR-UWB system. © 2013 Springer-Verlag Berlin Heidelberg.
Xia J.,Beijing Institute of Satellite Information Engineering |
Yue F.,Beijing Institute of Satellite Information Engineering |
Wang P.,Beijing Institute of Satellite Information Engineering |
Wang S.,Beijing Institute of Satellite Information Engineering
International Conference on Signal Processing Proceedings, ICSP | Year: 2014
Ionospheric scintillation can cause GNSS (Global Navigation Satellite System) signal with severe random fluctuations, leading to the loss of tracking loop, which makes the GNSS receiver unable to provide normal positioning service. This paper proposes a robust GNSS signal tracking algorithm based on vector delay/frequency lock loop (VDFLL) under ionospheric scintillation, in order to accomplish information sharing between all channels and adaptive regulation of loop noise bandwidth by using a Kalman filter, which allows it to adapt to ionospheric scintillation. Firstly it presents the basic theory of VDFLL. Then introduces the VDFLL into the anti-scintillation loop and completes the design of the anti-scintillation loop. Lastly the robust tracking algorithm based on VDFLL is implemented in a software receiver. The simulation results show that: when the scintillation index S4 is 0.9, the Doppler frequency standard deviation of the traditional scalar tracking loop (STL) is 0.4204, however, the Doppler frequency standard deviation of the anti-scintillation tracking algorithm based on VDFLL proposed in this paper is 10.6188. It can be seen that the anti-scintillation algorithm proposed in this paper has a better tracking performance under strong ionospheric scintillation situation. © 2014 IEEE.
Liu H.,Beijing Institute of Satellite Information Engineering |
Li J.,Beijing Institute of Satellite Information Engineering |
Hao X.,Beijing Institute of Satellite Information Engineering |
Zou G.,Beijing Institute of Satellite Information Engineering
2014 IEEE International Conference on Communication Problem-Solving, ICCP 2014 | Year: 2014
In multicast communication based on LKH, when a group member is added or evicted from the communication group, the system needs to update the group key to ensure the security of communication. In order to further reduce the rekey overhead, LKH is modified into a new key tree structure, which is constructed by heuristic search algorithm based on the number of group members. Compared to the LKH key tree structure, the branching factor of the new one can take on different value at each level. The experimental results showed the scheme proposed could efficiently reduce the encryption overhead, transmission overhead and the storage of keys during the rekey process. © 2014 IEEE.
Weibiao Z.,Beijing Institute of Satellite Information Engineering |
Tao D.,Beijing Institute of Satellite Information Engineering |
Xin W.,Beijing Institute of Satellite Information Engineering
Proceedings of 2016 IEEE Information Technology, Networking, Electronic and Automation Control Conference, ITNEC 2016 | Year: 2016
In order to solve crossover of lines in MMIC (Monolithic Microwave Integrated Circuits), a novel microstrip coupler has been presented. With a double-ring structure, the presented coupler achieves high isolation between adjacent ports. The size of coupler has been reduced by using an arc impedance transformer; Parameters influencing resonance loop and impedance matching of the coupler have been analyzed and the equations of theses parameters have been derived. Simulation, fabrication and measurement for the coupler have been done. Simulation of the relative bandwidth of reflectance, insertion loss and isolation is 18.61% (S11<-10dB), 7.31% (S12>-1dB) and 4.99% (S13<-15dB) respectively. Correspondingly measurement results is 17.94%,8.04% and 4.80%. Simulation and measurement results agree very well, which confirms the validity of the design. © 2016 IEEE.
Li H.-C.,Beijing Institute of Satellite Information Engineering |
Song H.-F.,Beijing Institute of Satellite Information Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011
The linear array CCD camera is the main sensor on the push-broom satellite. Because of the difference response among the CCD detectors, the striping noise is an obvious phenomenon in the remote sensing image along the scanning direction, which can seriously affect the image quality and quantitative application. The object of relative radiometric calibration is to eliminate them. As the state of satellite electronics varies from orbit to orbit, an automatic de-striping algorithm is needed that depends only on information that can be attained from the image data. There are many published techniques that are used to remove striping from images such as the histogram matching, histogram equalization, and Fourier transform filter methods. In order to decrease the effect we try to remove these stripes in CCD images using a relative radiometric correction algorithm based on the adaptive filtering pattern in this paper. Firstly, aiming at the characteristics of strip noise in push-broom scanner, the cause of strip noise formation is described. The suitable 1-D nonlinear filter is chosen to remove the obvious stripping based on the stripping distribution. Then, 1-D smoothing filtering is used to calculate the gain and offset coefficients. At last, the thin stripping is de-striped with the obtained coefficients. The final results indicate that the proposed method can effectively remove the stripping noise along the scanning direction effectively. Comparison of mean value and standard deviations obtained from the strip noise removed image by the proposed method and histogram equalization method suggested that the proposed method is evidently superior to the traditional histogram equalization method in preserving the image detail very well. The result of this study is applicable in striping removal of push-broom satellite's remote sensing data. © 2011 SPIE.
Li H.-C.,Beijing Institute of Satellite Information Engineering |
Hao S.-Y.,Beijing Institute of Satellite Information Engineering
Guangdian Gongcheng/Opto-Electronic Engineering | Year: 2011
Because of the difference response among the detectors in the pushbroom satellite, striping is an obvious phenomenon in the remote sensing image along the scanning direction. A relative radiometric correction algorithm is put forward based on the adaptive filtering pattern. Firstly, the suitable 1-D nonlinear filter is chosen to remove the obvious striping according to the image striping distribution. Then, the 1-D smoothing filter is used to calculate the gain and offset coefficients. At last, the thin stripping is destriped with the obtained coefficients. The comparison experiment proves that the algorithm can effectively improve the image quality, and remove the stripping along the scanning direction, at the same time it preserves the image detail.
Chen S.-S.,Beijing Institute of Satellite Information Engineering |
Liang Z.-G.,Beijing Institute of Satellite Information Engineering |
Zhang M.-Y.,Beijing Institute of Satellite Information Engineering
Xitong Fangzhen Xuebao / Journal of System Simulation | Year: 2014
The use of GPS receiver for high earth orbit (HEO) satellites which overcame the weak observation geometry from the earth could improve the orbit determination precision and also request high performance of receiver in weak signal processing. To lower the risk of engineering application, the simulation based on overall link analysis instead of geometrically visibility was needed. The simulation method estimated the GPS availability according to the signal power by link equation calculation and was developed by STK together with MATLAB, which made the result credible, reliable and flexible in theory and practice. Aimed at GEO application, the simulation result and the analysis for the large amount of available GPS number and proportion of side lobe signal in high sensitive receiver were proposed. And it is flexible for the proposed method to add the navigation constellation in order to be used for other navigation system receiver design.
Li H.,Beijing Institute of Satellite Information Engineering |
Hao S.,Beijing Institute of Satellite Information Engineering |
Zhu Q.,Beijing Institute of Satellite Information Engineering
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2011
A fast seamless mosaic algorithm for multiple remote sensing images was proposed to solve the problems of the high computation cost when mosaic processing and the obvious seam line existed in the mosaic result. Firstly, the original overlapping regions were determined according to the overlapping structure of the multi-chip CCD devices. Secondly, in order to reduce the computational burden, the original overlapping regions were decomposed into multi-resolution decomposition. Then the cross correlation matching method was used for the images mosaic, and the precise overlapping regions were obtained. At last, a new space interpolation mapping method was used to complete the histogram matching of overlapping regions, and the histogram look up table (LUT) was established to assign new values for the original image, which eliminated the mosaic seam caused by tone difference among the adjacent images. The experimental results show that this algorithm is practicable and can gain more satisfying mosaic images.