The MultiCarrier Code Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence (DS-) CDMA systems due to serious InterChip Interference (ICI) and MultiUser Interf...The MultiCarrier Code Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence (DS-) CDMA systems due to serious InterChip Interference (ICI) and MultiUser Interference (MUI) in high-data-rate wireless communication systems. In this paper, the Uniform Linear Array (ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment. A joint space-frequency multiuser symbol sequence detector is developed for all active users within one macrocell without space-frequency channel estimation. Simultaneously, Directions-Of-Arrivals (DOAs) of all active users can also be estimated. By dividing the ULA into two identical overlapping subarrays, a specific auxiliary matrix is constructed, which includes both symbol sequence and DOA information of all active users. Then, based on the subspace method, performing the eigen decomposition on such auxiliary matrix, the closed-form solution of symbol sequences and DOAs for all active users can be obtained. In comparison with schemes based on channel estimation, our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity. Extensive computer simulations demonstrate the overall performance of this novel scheme.展开更多
In traditional system identification (SI), actual values of system parameters are concealed in the input and output data;hence, it is necessary to apply estimation methods to determine the parameters. In signal proces...In traditional system identification (SI), actual values of system parameters are concealed in the input and output data;hence, it is necessary to apply estimation methods to determine the parameters. In signal processing, a signal with N elements must be sampled at least N times. Thus, most SI methods use N or more sample data to identify a model with N parameters;however, this can be improved by a new sampling theory called compressive sensing (CS). Based on CS, an SI method called compressive measurement identification (CMI) is proposed for reducing the data needed for estimation, by measuring the parameters using a series of linear measurements, rather than the measurements in sequence. In addition, the accuracy of the measurement process is guaranteed by a criterion called the restrict isometric principle. Simulations demonstrate the accuracy and robustness of CMI in an underdetermined case. Further, the dynamic process of a DC motor is identified experimentally, establishing that CMI can shorten the identification process and increase the prediction accuracy.展开更多
In this paper, we consider the perturbation analysis of linear time-invariant systems, which arise from the linear optimal control in continuous-time. We provide a method to compute condition numbers of continuous-tim...In this paper, we consider the perturbation analysis of linear time-invariant systems, which arise from the linear optimal control in continuous-time. We provide a method to compute condition numbers of continuous-time linear time-invariant systems. It solves the perturbed linear time-invariant systems via Riccati differential equations and continuous-time algebraic Riccati equations in finite and infinite time horizons. We derive the explicit expressions of measuring the perturbation bounds of condition numbers with respect to the solution of the linear time-invariant systems. Furthermore, condition numbers and their upper bounds of Riccati differential equations and continuous-time algebraic Riccati equations are also discussed. Numerical simulations show the sharpness of the perturbation bounds computed via the proposed methods.展开更多
A new concept is presented to express the damping property of linear time-invariant systems, by the Lyapunov theorem in view of quadratic form-defined energy. Two definitions are introduced: damping energy function D...A new concept is presented to express the damping property of linear time-invariant systems, by the Lyapunov theorem in view of quadratic form-defined energy. Two definitions are introduced: damping energy function D（X<sub>0</sub>, X）=Ci∫<sub>x<sub>0</sub>, x</sub> x<sub>i</sub>dx<sub>i-1</sub>and comprehensive damping coefficient η-min(Ci/a<sub>n-i</sub>). It is concluded that （ⅰ） of the Hurwitz determinants, △<sub>x-1</sub> is proportional to the damping effect of oscillating systems, （ⅱ） the comprehensive damping coefficients of linear time-invariant systems are derived as. piecewise rational fractions which can be easily calculated and （ⅲ） the damping torque coefficient obtained for synchronous machines is independent of ω.展开更多
We investigate the type of singularity and qualitative structure of solutions to a time-invariant linear dynamic system on time scales. The results truly unify the qualitative behaviors of the system on the continuous...We investigate the type of singularity and qualitative structure of solutions to a time-invariant linear dynamic system on time scales. The results truly unify the qualitative behaviors of the system on the continuous and discrete times with any step size.展开更多
在高斯噪声背景下,针对互耦条件下的均匀线阵(Uniform Linear Array,ULA),该文提出了一种联合多用户波达方向(Direction Of Arrival,DOA)估计与互耦误差自校正算法。该算法首先利用特征矩阵联合相似对角化(Joint Approximative Diagonal...在高斯噪声背景下,针对互耦条件下的均匀线阵(Uniform Linear Array,ULA),该文提出了一种联合多用户波达方向(Direction Of Arrival,DOA)估计与互耦误差自校正算法。该算法首先利用特征矩阵联合相似对角化(Joint Approximative Diagonalization of Eigen matrix,JADE)方法估计出各用户广义空间特征矢量,然后定义了一个将各用户广义空间特征矢量转换为只与部分阵元相关的转换矩阵,进而在斜投影及前后向空间平滑的基础上,实现了多用户相干信源DOA估计,最后以多用户相干信源DOA及广义空间特征矢量估计值为基础,给出一种互耦自校正方法。仿真结果表明:该算法具有较高的DOA估计精度及DOA估计成功率,而且对高斯白噪声/色噪声背景,阵列互耦误差已知/未知情形,均具有普适性。展开更多
基金Partially supported by the National Natural Science Foundation(No.69872029)and the Research Fund for Doctoral Program of Higher Education(No.19990690808)of China
文摘The MultiCarrier Code Division Multiple Access (MC-CDMA) scheme is promising for relieving capacity limit problems of Direct Sequence (DS-) CDMA systems due to serious InterChip Interference (ICI) and MultiUser Interference (MUI) in high-data-rate wireless communication systems. In this paper, the Uniform Linear Array (ULA) is applied to the base station of macrocellular MC-CDMA systems in a frequency-selective fading channel environment. A joint space-frequency multiuser symbol sequence detector is developed for all active users within one macrocell without space-frequency channel estimation. Simultaneously, Directions-Of-Arrivals (DOAs) of all active users can also be estimated. By dividing the ULA into two identical overlapping subarrays, a specific auxiliary matrix is constructed, which includes both symbol sequence and DOA information of all active users. Then, based on the subspace method, performing the eigen decomposition on such auxiliary matrix, the closed-form solution of symbol sequences and DOAs for all active users can be obtained. In comparison with schemes based on channel estimation, our algorithm need not explicitly estimate the space-frequency channel for each active user,so it has lower computation complexity. Extensive computer simulations demonstrate the overall performance of this novel scheme.
基金Supported by the National Natural Science Foundation of China(61605218)National Defense Science and Technology Innovation Foundation of Chinese Academy of Sciences(CXJJ-17S023)
文摘In traditional system identification (SI), actual values of system parameters are concealed in the input and output data;hence, it is necessary to apply estimation methods to determine the parameters. In signal processing, a signal with N elements must be sampled at least N times. Thus, most SI methods use N or more sample data to identify a model with N parameters;however, this can be improved by a new sampling theory called compressive sensing (CS). Based on CS, an SI method called compressive measurement identification (CMI) is proposed for reducing the data needed for estimation, by measuring the parameters using a series of linear measurements, rather than the measurements in sequence. In addition, the accuracy of the measurement process is guaranteed by a criterion called the restrict isometric principle. Simulations demonstrate the accuracy and robustness of CMI in an underdetermined case. Further, the dynamic process of a DC motor is identified experimentally, establishing that CMI can shorten the identification process and increase the prediction accuracy.
文摘In this paper, we consider the perturbation analysis of linear time-invariant systems, which arise from the linear optimal control in continuous-time. We provide a method to compute condition numbers of continuous-time linear time-invariant systems. It solves the perturbed linear time-invariant systems via Riccati differential equations and continuous-time algebraic Riccati equations in finite and infinite time horizons. We derive the explicit expressions of measuring the perturbation bounds of condition numbers with respect to the solution of the linear time-invariant systems. Furthermore, condition numbers and their upper bounds of Riccati differential equations and continuous-time algebraic Riccati equations are also discussed. Numerical simulations show the sharpness of the perturbation bounds computed via the proposed methods.
文摘A new concept is presented to express the damping property of linear time-invariant systems, by the Lyapunov theorem in view of quadratic form-defined energy. Two definitions are introduced: damping energy function D（X<sub>0</sub>, X）=Ci∫<sub>x<sub>0</sub>, x</sub> x<sub>i</sub>dx<sub>i-1</sub>and comprehensive damping coefficient η-min(Ci/a<sub>n-i</sub>). It is concluded that （ⅰ） of the Hurwitz determinants, △<sub>x-1</sub> is proportional to the damping effect of oscillating systems, （ⅱ） the comprehensive damping coefficients of linear time-invariant systems are derived as. piecewise rational fractions which can be easily calculated and （ⅲ） the damping torque coefficient obtained for synchronous machines is independent of ω.
文摘We investigate the type of singularity and qualitative structure of solutions to a time-invariant linear dynamic system on time scales. The results truly unify the qualitative behaviors of the system on the continuous and discrete times with any step size.
文摘在高斯噪声背景下,针对互耦条件下的均匀线阵(Uniform Linear Array,ULA),该文提出了一种联合多用户波达方向(Direction Of Arrival,DOA)估计与互耦误差自校正算法。该算法首先利用特征矩阵联合相似对角化(Joint Approximative Diagonalization of Eigen matrix,JADE)方法估计出各用户广义空间特征矢量,然后定义了一个将各用户广义空间特征矢量转换为只与部分阵元相关的转换矩阵,进而在斜投影及前后向空间平滑的基础上,实现了多用户相干信源DOA估计,最后以多用户相干信源DOA及广义空间特征矢量估计值为基础,给出一种互耦自校正方法。仿真结果表明:该算法具有较高的DOA估计精度及DOA估计成功率,而且对高斯白噪声/色噪声背景,阵列互耦误差已知/未知情形,均具有普适性。
