一种基于圆环模型的网格搜索定位算法

为了降低非视距(Non-Line-of-Sight,NLOS)误差对定位精度的不利影响,提出了一种基于圆环模型的到达时间(Time of Arrival,TOA)/到达角(Angle of Arrival,AOA)混合定位算法。假设各基站(Base Station,BS)接收的多径信号都经历了散射体的单次散射,首先利用圆环模型的几何特征搜索圆环的半径,再根据圆环的半径、TOA信息和AOA信息确定散射体的位置;然后将散射体作为虚拟基站规划移动台(Mobile Station,MS)的可能位置范围,并使用网格搜索和约束判断来获得多个MS可能的估计位置;最后根据误差目标函数的大小进行选择性平均。在不同NLOS场景下的仿真结果表明,与现有算法相比,所提算法取得了更好的定位性能。     

小波分析法解决无线定位跟踪问题

无线定位中,信号的非视距传播（NLoS）很大程度上决定了移动台的定位精度,而小波分析理论在信号处理中有较为明显的优点,提出了一种在蜂窝网络中非视距环境下对移动台（MS）的定位及跟踪算法。利用小波变换对信号的分解和重构,实现了对TDOA测量值误差的修正,再利用经典Chan算法对移动台位置进行估计,配合相应的距离门限值对移动台的位置进行跟踪定位。仿真结果表明,该算法能够有效地实现对移动台位置的静态定位和动态跟踪,并明显优于同等环境下经典算法的仿真结果,有效提高了定位精度。     

Dual‐mode multiple‐target tracking in wireless sensor networks based on sensor grouping and maximum likelihood estimation

The problem of tracking multiple mobile targets, using a wireless sensor network, is investigated in this paper. We propose a new sensor grouping algorithm, based on the maximum sensor separation distances (G‐MSSD), for estimating the location of multiple indistinguishable targets, either jointly or individually, depending on the distances between the generated groups. The joint tracking algorithm is formulated as a maximum likelihood (ML) estimator and solved through a modified version of the well‐known Gauss‐Newton (MGN) iterative method. We propose two candidate initial guesses for MGN based on G‐MSSD in joint tracking mode, while for the individual mode, the information of each group is used to estimate the location of only the corresponding target. The Cramer‐Rao lower bound (CRLB) for the variance of the proposed ML estimator is derived, and the potential conditions for reducing the CRLB are presented. Since tracking efficiency is affected by poor estimates, we present two criteria to evaluate the quality of estimates and detect the poor ones. An approach is also proposed for correcting the poor estimates, based on additional initial guesses. We demonstrate the effectiveness and accuracy of our proposed dual‐mode algorithm via simulation results and compare our results with the Multi‐Resolution search algorithm.     

LFM/BPSK混合调制信号盲处理结果可信性评估:一种简化的似然比算法

针对以相关谱最大值作为统计量对线性调频/二相编码（LFM/BPSK,Linear Frequency Modulation/Binary Phase Shift Keying）混合调制信号盲处理结果进行可信性检验时,存在概率密度函数复杂,难以得到似然比检验闭合表达式的问题,提出了一种基于极值分布理论（EVT,Extreme Value Theory）的简化处理算法.利用相关谱最大值的极限分布替代其精确分布,基于纽曼-皮尔逊（NP,Neyman-Pearson）准则得到简化的似然比检验,给出了相应判决式及其判决门限的解析表达式.文中给出了不同假设下相关谱最大值的极限分布形式.计算机仿真结果表明：本算法与已有的恒虚警方法相当,但优于基于分组极值模型及超阈值模型的两种分布拟合检验法,且具有较低的计算复杂度.     

Geometrical statistical channel model arisen from scatterers around the mobile with an inverted-parabolic spatial distribution

In this paper,firstly presented a geometrically based statistical channel model with scatterers that are with an inverted parabolic spatial distribution around mobile station(MS) within a circle wherein the base station(BS) and MS are included.This paper proposed a technique to simply derive probability density functions(PDFs) of angle of arrival(AOA),time of arrival(TOA) and Doppler spectra to characterize the outdoor macrocell and microcell environments by employing various distances between BS and MS,or different size of circular region.Employing this channel model,we analyze the impacts of a directional antenna at BS with the main-lobe width 2 on the fading and the Doppler spectra.     

无线传感网中NLoS环境下的ToA/AoA改进混合定位算法(英文)

An improved hybrid Time of Arrival (ToA)/ Angle of Arrival (AoA) location algorithm by adopting Gauss-Newton iterative algorithm is proposed. It is with the advantage of fast convergence and combining with the grid-search-based method to optimize the initial object coordinates of the iteration, meanwhile, under the condition of small measurement errors caused by noises of ToA and AoA, the algorithm performance can be improved effectively. In the Non-Line-of-Sight (NLoS) environments of the Wireless Sensor N...     

一种基于单次散射体定位的TOA/AOA混合定位算法

为了降低非视距(Non-Line-of-Sight,NLOS)误差对定位精度的不利影响,提出了一种基于散射体定位的到达时间(Time of Arrival,TOA)/到达角(Angle of Arrival,AOA)混合定位算法.假设各基站(Base Station,BS)接收的多径信号都经历了散射体单次散射,首先利用...     

基于空间相关性滤波和迭代最小余差剔除NLoS的ToA定位算法

To mitigate the Non-Line-of-Sight (NLoS) error which seriously affects the localization accuracy and robustness in complex indoor environment, a novel Iterative Minimum Residual (IMR) based on the consistency hypothesis of the residual and the error is proposed in this paper. It chooses the best subset of measurements to calculate the coordinates of the unknown node by comparing the residuals obtained with different subsets of beacons. To reduce the time complexity of the IMR algorithm, Spatial Correlation Filter (SCF) is also proposed, which can remove the most serious NLoS distance with low calculation cost. Combined with the proposed SCF and IMR algorithm, nodes can be localized with high accuracy and low time complexity. Experimental results with real dataset demonstrate that the proposed algorithm can identify the NLoS range effectively with about 50% time cost of employing SCF only.     

基于改进射线跟踪法和BP神经网络算法的室外微蜂窝毫米波信道特性研究

在28 GHz与39 GHz毫米波频段室外微蜂窝场景下,基于改进射线跟踪法和反向传播(back propagation, BP)神经网络算法对毫米波单发单收信道及单发多收信道进行建模仿真研究. 在得到的无线信道仿真数据基础上,研究分析了毫米波信道的路径损耗、均方根(root-mean-square, RMS)时延扩展(delay spread, DS)、接收功率等传播特性. 通过与现有文献的测量结果对比分析验证了改进射线跟踪法的正确性与有效性. 通过BP神经网络方法拟合得到的路径损耗模型参数结果与改进射线跟踪法仿真得到的路径损耗参数结果对比发现,两者吻合程度很高,验证了BP神经网络算法能很好地对室外微蜂窝毫米波信道大尺度参数进行预测. 同时,文中给出了一种普遍适用的用来表征室外微蜂窝视距(line-of-sight, LoS)与非视距(non-line-of-sight, NLoS)场景下28 GHz与39 GHz毫米波信道的路径损耗模型. 结果表明:LoS场景下的RMS DS和接收功率都小于NLoS场景下得到的结果;LoS场景与NLoS场景下RMS DS、水平方向到达角、多径簇的个数累积分布函数均服从高斯分布;RMS DS在毫米波频段微蜂窝场景下,随着频率的升高而增大,到达接收端的多径成簇呈现稀疏性.     

A geometrical-based microcell mobile radio channel model

In this paper we present a geometric multipath propagation model for a microcell mobile environment. The proposed model provides the statistics for the direction-of-arrival (DOA) of multipath components. These statistics are required to test adaptive array algorithms for cellular applications. The proposed model assumes that (1) a line-of-sight (LOS) path exists between the transmitter and the receiver, (2) the scatterers lie within a circle of radius R around the mobile station, and (3) the base station lies within this circle. The distances between the scatterers and the mobile station are subject statistically to a hyperbolic distribution. The model also provides the multipath power delay profiles (PDP), which are used to evaluate the bit error rate (BER) and the signal to interference ratio (SIR) for the direct-sequence code division multiple access (DS-CDMA). We derive and simulate the joint probability density functions (pdfs) of the power—DOA and the power—Doppler shift. Further we determine expressions for the BER performance and for the SIR of a DS-CDMA system over the proposed channel model. A simplified expression based on the improved Gaussian approximation (SEIGA) is used to evaluate the BER and the SIR in a wideband multipath channel. Although the proposed model is applicable for downlink as well, in this paper we will analyze the uplink environment only.     

一种码片内多径参数的最大似然估计算法

针对码分多址卫星移动通信中码片内两径参数估计问题,该文提出了基于最大似然的2维搜索算法。算法对两径时延进行2维搜索,同时对多径复振幅分别采用解相关和线性最小均方误差(LMMSE)算法进行估计,最后通过使似然函数最大化而找出最优的一组时延、复振幅估计值。仿真证明两径时延2维搜索结合采用近似的LMMSE算法进行多径复振幅估计具有良好的性能。     

一种天线阵列定位法及其仿真研究

为了克服CDMA移动台(MS)定位估计中面临的远近效应问题,该文提出了一种在服务基站(BS)附近布置一种天线阵列,采用TSOA/AOA混合定位技术对MS进行定位估计的方法,分析了采用不同定位法的GDOP分布, 并给出了相应的TSOA/AOA混合定位算法。不同条件下的仿真结果表明,只要AOA测量值达到一定精度,采用这种方法就能对MS进行准确定位。     

基于参数重构的非直达波混合定位算法

在蜂窝无线定位中,非视距(non-line-of-sight,NLOS)误差是影响定位精度的主要因素之一,故如何减轻NLOS误差影响是无线定位研究的热点。本文针对NLOS环境下的定位问题,提出基于参数重构的混合定位算法。首先利用波达角（angle-of-arrival,AOA）重构方法重构直达波AOA,随后充分利用AOA的重构结果,以最大似然估计法迭代估计直达波的波达时延（time-of-arrival,TOA）,最后利用这两个重构后的参数以视距（line-of-sight,LOS）混合定位方法估计出移动台的位置,以实现NLOS环境下的单基站定位,并获取较高的定位精度。这种方式无需视距与非视距识别,改进了传统的单目标参数重构模式。仿真结果验证了该算法的有效性。      

Broadband channel measurement and analysis

1 Introduction A complete understanding of propagation characteristics of wireless channel is the key for designing a mobile wireless communication system as the outcomes of various researches on wireless channel are regarded as the basis of mobile wirele…     

Application of multiple channel estimators in MLSE detectors forfast time-varying and frequency selective channels

The authors propose a simplification of a maximum likelihood sequence estimator (MLSE) and multiple channel estimator algorithm used for equalising fast time-varying and frequency selective channels. The original algorithm suffers from a large computational burden when operating on typical mobile radio channels. The proposed algorithm reduces the number of channel estimators employed and the resulting performance/complexity tradeoff is simulated     

A novel ToA location algorithm using LoS range estimation for NLoS environments

One of the main problems facing accurate location in wireless communication systems is nonline-of-sight (NLoS) propagation. In this paper, we propose a novel location technique that estimates the true, or line-of-sight (LoS), ranges based on NLoS range measurements. This approach utilizes a constrained nonlinear optimization approach, when range measurements are available from three base stations (BSs) only. Bounds on the NLoS error and the relationship between the true ranges are extracted from the geometry of the cell layout and the measured range circles to serve as constraints. Simulations studying the performance of the algorithm for different NLoS error distributions and BS configurations show that the location accuracy is significantly improved over traditional algorithms, even under highly NLoS conditions.     

Wireless Fading Paradigm for Antenna Array Receiver for a Disk-Type Cluster of Scatterers

This correspondence presents a signal processing based alternate approach for simulating the flat fading narrowband wireless channels for the antenna array receivers under the time-varying environment, in which the discrete disk of scatterers is incorporated around the mobile wireless transmitter to model the spreading of azimuth. The disk-type cluster of scatterers continuously changes due to the movement of the mobile wireless transmitter. Under this time-varying environment, each scatterer, at the successive stages of the disk, is correlated with the scatterers at the preceding stages of the disk using the second-order autoregressive process AR(2). At the receiver, one signal waveform is associated with each element of the antenna array taking into account the spread in azimuth of the received signal. The correlation of the fading waveforms generated by using the presented paradigm is compared with the expected analytical correlation results, which clearly manifests that the simulation results are consistent with the findings based on Jakes’ model. Moreover, the presented discrete disk-type cluster of scatterers fading model may be used to generate/simulate the variable diameter ring-type cluster of scatterers fading paradigm. The proposed channel model may play a significant role in the emerging field of wireless signal processing for the latest mobile communication systems.     

Adaptive solution for blind identification/equalization usingdeterministic maximum likelihood

A deterministic maximum likelihood (DML) approach is presented for the blind channel estimation problem. It is first proposed in a block version, which consists of iterating two steps, each one solving a least-squares problem either in the channel or in the symbols. In the noiseless case and under certain conditions, this algorithm gives the exact channel and the exact symbol vector with a finite number of samples. It is shown that even if the DML method has a single global minimum, the proposed iterative procedure can converge to spurious local minima. This problem can be detected (under some channel diversity conditions) by using a numerical test that is proposed in the paper. Based on these considerations, we extend the maximum likelihood block algorithm (MLBA) to recursive implementations [maximum likelihood recursive algorithm (MLRA)]. The MLRA is able to track variations of the system by the introduction of an exponential forgetting factor in the DML criterion. The link between the adaptive algorithm and a soft decision feedback equalizer (SDFE) is emphasized. Low-complexity versions of the recursive and adaptive algorithm are presented     

Combined simplified maximum likelihood and sphere decoding algorithm for MIMO system

In this article, a new system model for sphere decoding （SD） algorithm is introduced. For the 2 × 2 multipleinput multiple-out （MIMO） system, a simplified maximum likelihood （SML） decoding algorithm is proposed based on the new model. The SML algorithm achieves optimal maximum likelihood （ML） performance, and drastically reduces the complexity as compared to the conventional SD algorithm. The improved algorithm is presented by combining the sphere decoding algorithm based on Schnorr-Euchner strategy （SE-SD） with the SML algorithm when the number of transmit antennas exceeds 2. Compared to conventional SD, the proposed algorithm has low complexity especially at low signal to noise ratio （SNR）. It is shown by simulation that the proposed algorithm has performance very close to conventional SD.     

一种基于RELAX的SAR自聚焦算法

该文提出了一种基于RELAX的自聚焦算法。根据多个特显点和杂波同时存在的模型,该算法交替迭代地进行相位校正和散射点参数估计,在精确估计出散射点子回波参数的同时估计出自聚焦所需的相位误差。由于该算法未对杂波和噪声模型作任何假设,可应用于绝大多数成像场景,同时该算法可用于估计任何类型的相位误差,因此是一种稳健的自聚焦算法。实际数据处理结果表明该方法是有效的。