In this paper, we propose the approach of employing circulant permutation matrices to construct quantum quasicyclic （QC） low-density parity-check （LDPC） codes. Using the proposed approach one may construct some ne...In this paper, we propose the approach of employing circulant permutation matrices to construct quantum quasicyclic （QC） low-density parity-check （LDPC） codes. Using the proposed approach one may construct some new quantum codes with various lengths and rates of no cycles-length 4 in their Tanner graphs. In addition, these constructed codes have the advantages of simple implementation and low-complexity encoding. Finally, the decoding approach for the proposed quantum QC LDPC is investigated.展开更多
Present study provides a simple analytical formula,the“Klingel-like formula”or“Pascal’s Formula”that can be used as a reference to test some results of existing railway codes and specifically those using rigid co...Present study provides a simple analytical formula,the“Klingel-like formula”or“Pascal’s Formula”that can be used as a reference to test some results of existing railway codes and specifically those using rigid contact.It develops properly the 3D Newton-Euler equations governing the 6 degrees of freedom(DoF)of unsuspended loaded wheelsets in case of zero wheel-rail friction and constant conicity.Thus,by solving numerically these equations,we got pendulum like harmonic oscillations of which the calculated angular frequency is used for assessing the accuracy of the proposed formula so that it can in turn be used as a fast practical target for testing multi-body system(MBS)railway codes.Due to the harmonic property of these pendulum-like oscillations,the squareω2 of their angular frequency can be made in the form of a ratio K/M where K depends on the wheelset geometry and load and M on its inertia.Information on K and M are useful to understand wheelsets behavior.The analytical formula is derived from the first order writing of full trigonometric Newton-Euler equations by setting zero elastic wheel-rail penetration and by assuming small displacements.Full trigonometric equations are numerically solved to assess that the formula providesω2 inside a 1%accuracy for usual wheelsets dimensions.By decreasing the conicity down to 1×10^(−4) rad,the relative formula accuracy is under 3×10^(−5).In order to test the formula reliability for rigid contact formulations,the stiffness of elastic contacts can be increased up to practical rigidity(Hertz stiffness×1000).展开更多
Decoding by alternating direction method of multipliers(ADMM) is a promising linear programming decoder for low-density parity-check(LDPC) codes. In this paper, we propose a two-step scheme to lower the error floor of...Decoding by alternating direction method of multipliers(ADMM) is a promising linear programming decoder for low-density parity-check(LDPC) codes. In this paper, we propose a two-step scheme to lower the error floor of LDPC codes with ADMM penalized decoder.For the undetected errors that cannot be avoided at the decoder side, we modify the code structure slightly to eliminate low-weight code words. For the detected errors induced by small error-prone structures, we propose a post-processing method for the ADMM penalized decoder. Simulation results show that the error floor can be reduced significantly over three illustrated LDPC codes by the proposed two-step scheme.展开更多
Frequency Hopping Spread Spectrum (FHSS) system is often deployed to protect wireless communication from jamming or to preclude undesired reception of the signal. Such themes can only be achieved if the jammer or unde...Frequency Hopping Spread Spectrum (FHSS) system is often deployed to protect wireless communication from jamming or to preclude undesired reception of the signal. Such themes can only be achieved if the jammer or undesired receiver does not have the knowledge of the spreading code. For this reason, unencrypted M-sequences are a deficient choice for the spreading code when a high level of security is required. The primary objective of this paper is to analyze vulnerability of linear feedback shift register (LFSRs) codes. Then, a new method based on encryption algorithm applied over spreading codes, named hidden frequency hopping is proposed to improve the security of FHSS. The proposed encryption security algorithm is highly reliable, and can be applied to all existing data communication systems based on spread spectrum techniques. Since the multi-user detection is an inherent characteristic for FHSS, the multi-user interference must be studied carefully. Hence, a new method called optimum pair “key-input” selection is proposed which reduces interference below the desired constant threshold.展开更多
This paper proposes a cross-layer dual adaptive coded modulation architecture using turbo codes for mobile multimedia communication, which adapts to both the varying channel characteristics and the QoS of various mult...This paper proposes a cross-layer dual adaptive coded modulation architecture using turbo codes for mobile multimedia communication, which adapts to both the varying channel characteristics and the QoS of various multimedia services simultancously to increase the average system throughput substantially. A pragmatic channeladaptive turbo coded modulation schcme, which comes within 2.5 dB of the Shannon limit, is optimally designed, and then a QoS-adaptive scheme is superimposed to build the dual adaptive architecture. Simulation results show that the novel dual adaption reduces the gap from the fading channel capacity to 2 dB when assuming different services occur in equal probability and the service duration follows exponential distribution.展开更多
To accurately model flows with shock waves using staggered-grid Lagrangian hydrodynamics, the artificial viscosity has to be introduced to convert kinetic energy into internal energy, thereby increasing the entropy ac...To accurately model flows with shock waves using staggered-grid Lagrangian hydrodynamics, the artificial viscosity has to be introduced to convert kinetic energy into internal energy, thereby increasing the entropy across shocks. Determining the appropriate strength of the artificial viscosity is an art and strongly depends on the particular problem and experience of the researcher. The objective of this study is to pose the problem of finding the appropriate strength of the artificial viscosity as an optimization problem and solve this problem using machine learning (ML) tools, specifically using surrogate models based on Gaussian Process regression (GPR) and Bayesian analysis. We describe the optimization method and discuss various practical details of its implementation. The shock-containing problems for which we apply this method all have been implemented in the LANL code FLAG (Burton in Connectivity structures and differencing techniques for staggered-grid free-Lagrange hydrodynamics, Tech. Rep. UCRL-JC-110555, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1992, in Consistent finite-volume discretization of hydrodynamic conservation laws for unstructured grids, Tech. Rep. CRL-JC-118788, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1994, Multidimensional discretization of conservation laws for unstructured polyhedral grids, Tech. Rep. UCRL-JC-118306, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1994, in FLAG, a multi-dimensional, multiple mesh, adaptive free-Lagrange, hydrodynamics code. In: NECDC, 1992). First, we apply ML to find optimal values to isolated shock problems of different strengths. Second, we apply ML to optimize the viscosity for a one-dimensional (1D) propagating detonation problem based on Zel’dovich-von Neumann-Doring (ZND) (Fickett and Davis in Detonation: theory and experiment. Dover books on physics. Dover Publications, Mineola, 2000) detonation theory using a reactive burn model. We compare results for default (currently used values in FLAG) and optimized values of the artificial viscosity for these problems demonstrating the potential for significant improvement in the accuracy of computations.展开更多
Implementing check node(CN)update based on the minimum value(MV)and second MV of incoming message magnitudes is crucial for Min-Sum Algorithms(MSAs).In the category of bit-serial implementations,existing schemes suffe...Implementing check node(CN)update based on the minimum value(MV)and second MV of incoming message magnitudes is crucial for Min-Sum Algorithms(MSAs).In the category of bit-serial implementations,existing schemes suffer from decoding performance degradation,large hardware areas,and/or long latency.In this paper,we propose two efficient CN update functions based on the MV and an approximate second MV,and design bit-serial architectures to implement them.Simulation results show that our functions exhibit the minimum decoding performance degradation compared to the existing functions using approximate second MVs.Moreover,the applicationspecific integrated circuits(ASIC)implementation results demonstrate the advantages of our architectures in terms of area,latency,etc.展开更多
A general construction of inter-group complementary (IGC) codes is proposed based on perfect complementary (PC) codes,interleaving operation,and the orthogonal matrix.The correlation properties of the newly constructe...A general construction of inter-group complementary (IGC) codes is proposed based on perfect complementary (PC) codes,interleaving operation,and the orthogonal matrix.The correlation properties of the newly constructed IGC codes can be described as follows:(1) the autocorrelation sidelobes of the codes are zeros in the zero correlation zone (ZCZ);(2) the cross-correlation functions (CCFs) between any two different codes of the same group are zeros in the ZCZ;(3) the CCFs between any two codes of different groups are zeros everywhere.The key point of this construction is that the ZCZ length of the generated IGC codes can be chosen flexibly.It is well known that there is a limitation between the ZCZ length and the number of mates;that is,the smaller is the length of ZCZ,the more are the IGC codes that can be generated.Therefore,if we can choose the ZCZ length of the IGC codes flexibly according to the requirement of the system,more users can be accommodated in the system.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60773085 and 60801051)the NSFC-KOSEF International Collaborative Research Funds (Grant Nos 60811140346 and F01-2008-000-10021-0)
文摘In this paper, we propose the approach of employing circulant permutation matrices to construct quantum quasicyclic （QC） low-density parity-check （LDPC） codes. Using the proposed approach one may construct some new quantum codes with various lengths and rates of no cycles-length 4 in their Tanner graphs. In addition, these constructed codes have the advantages of simple implementation and low-complexity encoding. Finally, the decoding approach for the proposed quantum QC LDPC is investigated.
文摘Present study provides a simple analytical formula,the“Klingel-like formula”or“Pascal’s Formula”that can be used as a reference to test some results of existing railway codes and specifically those using rigid contact.It develops properly the 3D Newton-Euler equations governing the 6 degrees of freedom(DoF)of unsuspended loaded wheelsets in case of zero wheel-rail friction and constant conicity.Thus,by solving numerically these equations,we got pendulum like harmonic oscillations of which the calculated angular frequency is used for assessing the accuracy of the proposed formula so that it can in turn be used as a fast practical target for testing multi-body system(MBS)railway codes.Due to the harmonic property of these pendulum-like oscillations,the squareω2 of their angular frequency can be made in the form of a ratio K/M where K depends on the wheelset geometry and load and M on its inertia.Information on K and M are useful to understand wheelsets behavior.The analytical formula is derived from the first order writing of full trigonometric Newton-Euler equations by setting zero elastic wheel-rail penetration and by assuming small displacements.Full trigonometric equations are numerically solved to assess that the formula providesω2 inside a 1%accuracy for usual wheelsets dimensions.By decreasing the conicity down to 1×10^(−4) rad,the relative formula accuracy is under 3×10^(−5).In order to test the formula reliability for rigid contact formulations,the stiffness of elastic contacts can be increased up to practical rigidity(Hertz stiffness×1000).
基金supported in part by National Nature Science Foundation of China under Grant No.61471286,No.61271004the Fundamental Research Funds for the Central Universitiesthe open research fund of Key Laboratory of Information Coding and Transmission,Southwest Jiaotong University(No.2010-03)
文摘Decoding by alternating direction method of multipliers(ADMM) is a promising linear programming decoder for low-density parity-check(LDPC) codes. In this paper, we propose a two-step scheme to lower the error floor of LDPC codes with ADMM penalized decoder.For the undetected errors that cannot be avoided at the decoder side, we modify the code structure slightly to eliminate low-weight code words. For the detected errors induced by small error-prone structures, we propose a post-processing method for the ADMM penalized decoder. Simulation results show that the error floor can be reduced significantly over three illustrated LDPC codes by the proposed two-step scheme.
文摘Frequency Hopping Spread Spectrum (FHSS) system is often deployed to protect wireless communication from jamming or to preclude undesired reception of the signal. Such themes can only be achieved if the jammer or undesired receiver does not have the knowledge of the spreading code. For this reason, unencrypted M-sequences are a deficient choice for the spreading code when a high level of security is required. The primary objective of this paper is to analyze vulnerability of linear feedback shift register (LFSRs) codes. Then, a new method based on encryption algorithm applied over spreading codes, named hidden frequency hopping is proposed to improve the security of FHSS. The proposed encryption security algorithm is highly reliable, and can be applied to all existing data communication systems based on spread spectrum techniques. Since the multi-user detection is an inherent characteristic for FHSS, the multi-user interference must be studied carefully. Hence, a new method called optimum pair “key-input” selection is proposed which reduces interference below the desired constant threshold.
基金This work is supported by the High Technology Research and Development Program of China(No. 2001AA121031)the National Natural Science Foundation of China (No. 60072028)
文摘This paper proposes a cross-layer dual adaptive coded modulation architecture using turbo codes for mobile multimedia communication, which adapts to both the varying channel characteristics and the QoS of various multimedia services simultancously to increase the average system throughput substantially. A pragmatic channeladaptive turbo coded modulation schcme, which comes within 2.5 dB of the Shannon limit, is optimally designed, and then a QoS-adaptive scheme is superimposed to build the dual adaptive architecture. Simulation results show that the novel dual adaption reduces the gap from the fading channel capacity to 2 dB when assuming different services occur in equal probability and the service duration follows exponential distribution.
基金This work was performed under the auspices of the National Nuclear Security Administration of the US Department of Energy at Los Alamos National Laboratory under Contract No.89233218CNA000001The Authors gratefully acknowledge the support of the US Department of Energy National Nuclear Security Administration Advanced Simulation and Computing Program.LA-UR-22-33159.
文摘To accurately model flows with shock waves using staggered-grid Lagrangian hydrodynamics, the artificial viscosity has to be introduced to convert kinetic energy into internal energy, thereby increasing the entropy across shocks. Determining the appropriate strength of the artificial viscosity is an art and strongly depends on the particular problem and experience of the researcher. The objective of this study is to pose the problem of finding the appropriate strength of the artificial viscosity as an optimization problem and solve this problem using machine learning (ML) tools, specifically using surrogate models based on Gaussian Process regression (GPR) and Bayesian analysis. We describe the optimization method and discuss various practical details of its implementation. The shock-containing problems for which we apply this method all have been implemented in the LANL code FLAG (Burton in Connectivity structures and differencing techniques for staggered-grid free-Lagrange hydrodynamics, Tech. Rep. UCRL-JC-110555, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1992, in Consistent finite-volume discretization of hydrodynamic conservation laws for unstructured grids, Tech. Rep. CRL-JC-118788, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1994, Multidimensional discretization of conservation laws for unstructured polyhedral grids, Tech. Rep. UCRL-JC-118306, Lawrence Livermore National Laboratory, Livermore, CA, 1992, 1994, in FLAG, a multi-dimensional, multiple mesh, adaptive free-Lagrange, hydrodynamics code. In: NECDC, 1992). First, we apply ML to find optimal values to isolated shock problems of different strengths. Second, we apply ML to optimize the viscosity for a one-dimensional (1D) propagating detonation problem based on Zel’dovich-von Neumann-Doring (ZND) (Fickett and Davis in Detonation: theory and experiment. Dover books on physics. Dover Publications, Mineola, 2000) detonation theory using a reactive burn model. We compare results for default (currently used values in FLAG) and optimized values of the artificial viscosity for these problems demonstrating the potential for significant improvement in the accuracy of computations.
基金supported by National Natural Science Foundation of China(NSFC)under Grant 62571455,Grant 62371401,and Grant 62331002supported by the SingaporeMinistry of Education Academic Research Fund Tier 2 T2EP50221-0036.
文摘Implementing check node(CN)update based on the minimum value(MV)and second MV of incoming message magnitudes is crucial for Min-Sum Algorithms(MSAs).In the category of bit-serial implementations,existing schemes suffer from decoding performance degradation,large hardware areas,and/or long latency.In this paper,we propose two efficient CN update functions based on the MV and an approximate second MV,and design bit-serial architectures to implement them.Simulation results show that our functions exhibit the minimum decoding performance degradation compared to the existing functions using approximate second MVs.Moreover,the applicationspecific integrated circuits(ASIC)implementation results demonstrate the advantages of our architectures in terms of area,latency,etc.
基金Project supported by the National Natural Science Foundation of China (Nos. 61001110,60773074,and 60903004)the China Post-doctoral Science Foundation (No. 20100470204)+1 种基金the Beijing Municipal Natural Science Foundation (No. 4082020)the National High-Tech R & D Program of China (Nos. 2007AA01Z213 and 2009AA01Z209)
文摘A general construction of inter-group complementary (IGC) codes is proposed based on perfect complementary (PC) codes,interleaving operation,and the orthogonal matrix.The correlation properties of the newly constructed IGC codes can be described as follows:(1) the autocorrelation sidelobes of the codes are zeros in the zero correlation zone (ZCZ);(2) the cross-correlation functions (CCFs) between any two different codes of the same group are zeros in the ZCZ;(3) the CCFs between any two codes of different groups are zeros everywhere.The key point of this construction is that the ZCZ length of the generated IGC codes can be chosen flexibly.It is well known that there is a limitation between the ZCZ length and the number of mates;that is,the smaller is the length of ZCZ,the more are the IGC codes that can be generated.Therefore,if we can choose the ZCZ length of the IGC codes flexibly according to the requirement of the system,more users can be accommodated in the system.
