Combining GA and iterative searching DOA estimation for CDMA signals

This paper deals with direction-of-arrival (DOA) estimation based on iterative searching technique for code-division multiple access signals. It has been shown that the iterative searching technique is more likely to converge to a local maximum, causing errors in DOA estimation. In conjunction with a genetic algorithm for selecting initial search angle, we present an efficient approach to achieve the advantages of iterative DOA estimation with fast convergence and more accuracy estimate over existing conventional spectral searching methods. Finally, several computer simulation examples are provided for illustration and comparison.     

Combining genetic algorithm and iterative MUSIC searching DOA estimation for the CDMA system

This paper deals with direction-of-arrival (DOA) estimation based on iterative MUSIC searching technique for the code division multiple access (CDMA) system. It has been shown that the iterative searching technique suffers from the local maximum searching problem, causing acquisition errors in DOA estimation. In conjunction with a genetic algorithm (GA) for selecting initial search angle, we present an efficient approach to achieve the advantages of iterative DOA estimation with fast convergence and more accuracy estimate over existing conventional spectral searching methods. Finally, several computer simulation examples are provided for illustration and comparison.     

ADSP21160实现CDMA信号波达方向估计

本文针对CDMA系统,提出使用DSP器件ADSP21160实现对感兴趣用户的波达方向和估计的算法。该算法是对传统MUSIC方法的推广与变形,克服了要求接收信号数小于阵元数的局限,算法运算量小,能有效估计CDMA信号的到达方向。     

基于UKF的CDMA系统信道参数估计

CDMA系统信道时间延迟估计是一个非线性的迭代过程。UKF算法能够避免EKF由于线性化非线性系统而带来的误差过大等问题,比EKF估计的更加精确。利用UKF算法对CDMA系统信道的幅度衰减参数与延时参数进行了估计。在研究中考虑到了多址干扰和远近效应对信道参数的影响,仿真结果表明UKF算法能有效地抑制远近效应及多址干扰,估计出无线信道参数。     

基于自适应迭代学习算法的一类非线性系统故障检测与估计

针对迭代学习算法在非线性系统故障检测与估计过程中存在估计误差较大和收敛速度较慢等不足的问题,提出了一种基于龙格–库塔故障估计观测器模型的自适应迭代学习算法,有效降低了故障估计误差;并引入H∞性能指标,提高了故障估计观测器的收敛速度.该算法首先设计故障检测观测器对故障进行检测,然后设计故障估计观测器,并将自适应算法与迭代学习策略相结合,使得估计故障逐渐逼近真实故障,从而实现对非线性系统中多种常见故障的精确检测与估计.最后,通过机械臂旋转关节驱动电机的执行器故障仿真验证了所提算法的有效性.     

基于前后相关阵的CDMA信号DOA估计及DSP实现

本文针对CDMA系统,提出使用DSP器件TMS320-C6701实现对CDMA信号的波达方向估计。该算法基于对解扩前后相关阵相减,去除了干扰相关阵是,然后使用传统MUSIC或ESPRIT算法进行DOA估计,克服了要求接收信号数小于阵元数的局限,能有效估计波达方向相差很小的多径信号的参数。     

基于前后相关阵的CDMA信号DOA估计及DSP实现

本文针对CDMA系统,提出使用DSP器件TMS320-C6701实现对CDMA信号的波达方向估计.该算法基于对解扩前后相关阵相减,去除了干扰相关阵是,然后使用传统MUSIC或ESPRIT算法进行DOA估计,克服了要求接收信号数小于阵元数的局限,能有效估计波达方向相差很小的多径信号的参数.     

Robust and fast iterative sparse recovery method for space-time adaptive processing

Conventional space-time adaptive processing (STAP) requires large numbers of independent and identically distributed (i.i.d) training samples to ensure the performance of clutter suppression, which is hard to be achieved in practical complex nonhomogeneous environment. In order to improve the performance of clutter suppression with small training sample support, a robust and fast iterative sparse recovery method for STAP is proposed in this paper. In the proposed method, the sparse recovery of clutter spatial-temporal spectrum and the calibration of space-time overcomplete dictionary are achieved iteratively. Firstly, the robust solution of sparse recovery is derived by regularized processing, which can be calculated recursively based on the block Hermitian matrix property, afterwards the mismatch of space-time overcomplete dictionary is calibrated by minimizing the cost function. The proposed method can not only alleviate the effect of noise and dictionary mismatch, but also reduce the computational cost caused by direct matrix inversion. Finally, the proposed method is verified based on the simulated and the actual airborne phased array radar data, which shows that the proposed method is suitable for practical complex nonhomogeneous environment and provides better performance compared with conventional STAP methods.     

一种新的宽带DOA估计自聚焦算法

具有较高精度的宽带信号波达方向（DOA）快速估计算法是其实用化所要解决的重要问题。提出了一种新的相干子空间（CSM）类宽带DOA估计自聚焦算法。算法利用子空间投影变换将信号分离后分别处理,通过不断更新聚焦方向实现自聚焦。与已有算法相比,不受DOA初始值的影响,有更小的聚焦误差;不同目标在聚焦矩阵更新过程中无需再做奇异值分解,有较低的实时计算量。仿真实验表明,算法以较小的计算代价实现了近乎最优的聚焦性能,有较高的DOA估计精度。     

一种混合源环境下的波达方向估计方法

提出了一种基于均匀线阵的混合源波达方向DOA估计的新方法。该方法首先利用传统MUSIC方法估计出非相干信号源的DOA,然后对整个阵列数据协方差矩阵进行差分消除不相关源信号和噪声的影响,再对此差分矩阵进行特殊的空间平滑去相干,利用重建的数据协方差矩阵估计相干源的DOA。此方法的特点是分别估计不相关信号和相干信号的DOA,优点是在可估计出多于阵元数信号的前提下具有较高的DOA估计精度和稳健性。理论分析和仿真结果表明此方法的估计性能优于空间差分平滑算法。     

Covariance sparsity-aware DOA estimation for nonuniform noise

This paper reformulates the problem of direction-of-arrival (DOA) estimation for unknown nonuniform noise by exploiting a sparse representation of the array covariance vectors. In the proposed covariance sparsity-aware DOA estimator, the unknown noise variances can be eliminated by a linear transformation, and DOA estimation is reduced to a sparse reconstruction problem with nonnegativity constraint. The proposed method not only obtains an extended-aperture array with increased degrees of freedom which enables us to handle more sources than sensors, but also provides superiority in performance and robustness against nonuniform noise. Numerical examples under different conditions demonstrate the effectiveness of the proposed method.     

Optimized DOA estimation for an array antenna

Abstract—In this paper, we propose a Direction-of-Arrival (DOA) estimation technique that allows application of the signal subspace method. In the case when interference signals are coherent to the desired signals, the performance of the subspace method is reduced remarkably. As a solution to this problem, the spatial smoothing method has been proposed and applied. With the orthogonal element in the weighted spatial smoothing method being the calculation process to realize the MUSIC method, which is the most frequently used subspace, it becomes more complex. In order to solve this problem, we maximize the performance of DOA estimation by assigning a weight vector, which is directly orthogonal to the signal subspace. In this paper we compare the efficiency of the proposed algorithm with a modified spatial smoothing method via simulation results. The text was submitted by the authors in English.     

Robust DOA estimation and target docking for mobile robots

Direction of arrival (DOA) guided automated target acquisition and docking system is proposed for mobile robots employing the dual-directional antenna system. The dual-directional antenna estimates the DOA of the signal of interest using the ratio of the signal strengths between two adjacent antennas. In practice, DOA estimation poses a significant technical challenge, since the RF signal is easily distorted by the environmental conditions. Therefore, the robot often loses its way in an electromagnetically disturbed environment. To cope with this problem, a robust DOA estimation algorithm is developed based on Kalman filtering. This algorithm allows the robot to reduce the potential error in the estimated DOA, and adjust the robot’s heading to the target transponder without needing to know the positions of current and previous measurements in a global coordinate system. The simulation and experiment results clearly demonstrate that the mobile robot equipped with the developed system is able to dock to a target transponder in an indoor environment partially occupied by obstacles.     

Quality of service estimation for soft handoff region ratio and call admission control in CDMA cellular systems

In the operational stage of code division multiple access (CDMA) systems, the soft handoff region ratio (SHRR) is among the important parameters that guarantee the quality of service (QoS) and resource allocation. This paper analytically investigates the effects of the SHRR on QoS. In doing so, we simultaneously take into account the capacity increasing factor and traffic load variation. For this purpose, we propose a new traffic load estimation model using a semi-Markov chain in order to consider the call arrivals influenced by the SHRR under general resident time condition. We also present the calculation algorithm of the QoS measures such as the new call blocking probability (NBP) and forced termination probability (FTP) by applying the proposed model to the prioritized call admission control (CAC). The numerical result illustrates the effects of various soft handoff system parameters. Likewise, it shows that the value of SHRR has a significant impact of the QoS under the normal propagation conditions. Sensitivity analysis is also performed to show the effect of exponential cell resident time assumption. The proposed modeling is expected to provide a practical guide to improve the QoS of CDMA soft handoff systems.     

Geometrical channel models for space-time systems

Based on the unified concept of space-time system field theory, a general space-time channel model can be constructed from the statistics of the space-time system field function (S-TSFF) for an arbitrary medium. This statistical characterization of the medium (channel) can be expressed in terms of the space-time correlation function, or, equivalently, the space-time power spectral density of the S-TSFF. The space-time correlation function of the S-TSFF generalizes the concept of the mutual coherence function (MCF) for a random electric field to an arbitrary space-time field. There are three different geometrical channel models depending on the choice of the coordinate systems, e.g. rectangular, cylindrical, and spherical. Using the notions of channel correlation time and correlation distance— i.e. doppler spread and delay spread—various geometrical tap-delay channel models are derived. From a system point of view, the space-time correlation parameters can be interpreted as a measure of the spatial and temporal memory of the channel. It is further demonstrated that the rectangular space-time channel model reduces to the two-dimensional randomly time-varying tap-delay line models introduced by Kailath (1961) and Bello (1963). A dual property for the S-TSFF is observed. This system duality principle shows that the channel response can manifest as a space-time filter put forth by linear system theory (convolution integral in space-time), or as a space-time aperture put forth by optics (convolution integral in space-time spectrum).     

Unified field theory for space-time systems

The communication efficiency associated with the problems of transmitting information in space and time is known to be dependent upon the characteristics of the transmission medium. Notably Turin (1977), Kailath (1961), and Bello (1963) have considered the temporal channel response as a function of the channel time and delay spread processes. The physics of the medium have not been considered. Middleton and Groginsky (1965) and Wittwer (1980) have attempted to incorporate the physics of the medium in a strictly temporal channel model. This paper presents a theory that generalizes the earlier work for characterizing medium-induced effects upon deterministic and random space-time fields, and the theory is applicable to any frequency band in the electromagnetic spectrum. For a linear medium, a space-time system field function (S-TSFF) is introduced as a system model for an arbitrary (turbulent or material) medium (Lo 1988). The unified system field theory states that the output space-time field is related to the input space-time field and the S-TSFF through a set of space-time superposition integrals. The geometry between the energy source, the medium, and the observed world-point area or volume is dependent on the chosen coordinate system, and is implicitly expressed by the space-time superposition integrals. (The term world-point was used by Minkowski (1908) to denote a point in a four-dimensional space-time coordinate system. To distinguish our approach from the analysis of arbitrary events in a space-time manifold, the terms world-area and world-volume are chosen to denote the ‘simultaneity in space’ as opposed to the notation of world-line and world-space used in the theory of relativity.) For a deterministic input space-time field, the statistics of the output field are solely dependent on the S-TSFF. For a random input space-time field, the statistics of the output field are related to the statistics of the input field and the S-TSFF. In either case, the statistical characterization can be expressed in terms of a space-time correlation function, or, equivalentIy, the space-time power spectral density of the input-output fields and of the S-TSFF. The space-time correlation function of the S-TSFF generalizes the concept of the mutual coherence function (MCF) used in statistical optics (Born and Wolf 1970). A dual property for the S-TSFF is observed and it is shown to be consistent with the duality principle in physics and the linear system theory in engineering. This space-time duality concept leads to the conclusion that fundamental properties of matter are imbedded in all physically realizable systems. This conclusion has far reaching implications in many detection, instrumentation, and measurement systems—for example, the uncertainty principle can be applied to analyse the stability of atomic clocks and trap ion frequency standards. The medium's response to an applied field is dependent upon whether the observed field is due to a space-time point source, a space-time plane wave, or something in-between. The space-time system field theory has numerous applications in system engineering, e.g. communications, radar, sonar, optics, and various imaging systems.     

DSP实现CDMA信号波达方向与多径时延联合估计

本文针对CDMA系统,提出使用DSP器件ADSP21160实现对感兴趣用户的波达方向和多径时延进行联合估计的算法。该算法是对传统MUSIC方法的推广与变形,克服了要求接收信号数小于阵元数的局限,能有效估计时延不同、波达方向相差很小的多径信号的参数。     

不同信号的DOA估计算法比较

波达方向(Direct of Arrival,DOA)估计技术渐渐成为移动通信中的研究热点,当用户的信号方向未知时,可以根据经典算法多重信号分类(Multiple Signal Classification,MUSIC)和旋转不变技术信号参数估计(Estimating Signal Parameters Viarotational Invariance Techniques,ESPRIT)等方法估计信号DOA。针对不同的信号采取不同的算法分析。对窄带信号,从信噪比、阵元数、快拍数等不同情况下对TLS-ESPRIT算法和MUSIC算法进行了仿真实验,并比较了TLS-ESPRIT算法与MUSIC算法的DOA性能。对宽带信号,主要重点分析了基于非相干信号处理算法(Incoherent Signal-subspace Method,ISM)的两种改进的方法,对低信噪比子带赋予低权重或舍弃。通过仿真实验,证明了改进算法的优越性,同时对两种改进算法的使用场合作了简单的分析。