Passive IoT Localization Technology Based on SD-PDOA in NLOS and Multi-Path Environments

Addressing the challenges of passive Radio Frequency Identification(RFID)indoor localization technology in Non-Line-of-Sight(NLoS)and multipath environments,this paper presents an innovative approach by introducing a combined technology integrating an improved Kalman Filter with Space Domain Phase Difference of Arrival(SD-PDOA)and Received Signal Strength Indicator(RSSI).This methodology utilizes the distinct channel characteristics in multipath and NLoS contexts to effectively filter out interference and accurately extract localization information,thereby facilitating high precision and stability in passive RFID localization.The efficacy of this approach is demonstrated through detailed simulations and empirical tests conducted on a custom-built experimental platform consisting of passive RFID tags and an R420 reader.The findings are significant:in NLoS conditions,the four-antenna localization system achieved a notable localization accuracy of 0.25 m at a distance of 5 m.In complex multipath environments,this system achieved a localization accuracy of approximately 0.5 m at a distance of 5 m.When compared to conventional passive localization methods,our proposed solution exhibits a substantial improvement in indoor localization accuracy under NLoS and multipath conditions.This research provides a robust and effective technical solution for high-precision passive indoor localization in the Internet of Things(IoT)system,marking a significant advancement in the field.

A Revisit of Orbital Angular Momentum Multiplexing in Multipath Environment

It is commonly believed that orbital an-gular momentum(OAM)multiplexing is only suitable for short-range communications in line-of-sight(LoS)scenario and multipath propagation would be detrimental for OAM communications.It has been demonstrated very recently that OAM multiplexing could work in rich isotropic multipath environment when the conventional spatial equalization is used for data detection.Moreover,the resulting channel capacity is comparable to that of a conventional multiple-input multiple-output system.Nev-ertheless,the rich isotropic multipath environment is an ideal multipath scenario.In this paper,we investigate the performance of OAM multiplexing in arbitrary multipath environment.Contrary to the common belief,it is shown that multipath can be beneficial for OAM multiplexing in terms of channel capacity.Particularly,the OAM capacity increases with enlarged angular spread of the channel and reaches its maximum when the angular spread is comparable to the divergence angle of the OAM beam.Based on the study,the OAM multiplexing is further investigated for base station(BS)applications.It is shown that OAM based BS antennas are comparable to(or even outperform)the conventional BS antennas in terms of channel capacity.

Beamspace maximum likelihood algorithm based on sum and difference beams for elevation estimation

Beamspace super-resolution methods for elevation estimation in multipath environment has attracted significant attention, especially the beamspace maximum likelihood(BML)algorithm. However, the difference beam is rarely used in superresolution methods, especially in low elevation estimation. The target airspace information in the difference beam is different from the target airspace information in the sum beam. And the use of difference beams does not significantly increase the complexity of the system and algorithms. Thus, this paper applies the difference beam to the beamformer to improve the elevation estimation performance of BML algorithm. And the direction and number of beams can be adjusted according to the actual needs. The theoretical target elevation angle root means square error(RMSE) and the computational complexity of the proposed algorithms are analyzed. Finally, computer simulations and real data processing results demonstrate the effectiveness of the proposed algorithms.

GNSS基准站环境质量分析系统设计与实现

在利用全球导航卫星系统GNSS(GPS,GLONASS,Galileo等)进行精密定位时,多路径效应是影响其精度和准确度的主要误差源之一,但不能通过差分方法消除,故对GNSS基准站环境质量监测至关重要。在阐述GNSS基准站环境分析原理的基础上,对GNSS基准站环境质量分析软件进行了系统设计,利用VB编程实现了该分析软件。该软件界面良好,人机交互能力强,功能全面,能从多方面对基准站的环境进行分析,因此在进行数据质量分析方面有较好的实用价值。

削弱GNSS多路径效应的半天球格网点建模方法

多路径效应与测站观测环境相关,无法利用差分的方式消除或削弱,是GPS精密数据处理时的主要误差源。为此,本文提出了一种利用半天球格网点模型削弱测站多路径误差影响的新方法MHGM(multi-point hemispherical grid model)。该方法对以测站为球心的半天球进行格网点划分,通过格网点的参数化描述,实现测站处多路径误差建模,可适用于现有各类GPS数据处理的软硬件设备和观测环境。本文算例的测试结果表明,采用新方法建模后双差观测值残差的RMS均值改善率平均在73.9%左右,较传统恒星日滤波方法的改善效果平均可提升26.9%,对于静态观测数据,按实时动态相对定位处理模式可获得平面精度约1.7 mm,高程精度约3.0 mm的定位结果。此外,MHGM模型还可进一步用于对测站周边可能存在的多路径误差源进行方位评估,对从物理意义上消除多路径误差源的影响给出一定的指导性意见。

基于模型的环境修正匹配滤波算法

由于主动声呐发射信号经过浅海多途信道传播后,回波信号与参考信号相关性降低,进而导致匹配滤波器检测性能下降。针对此问题,本文对基于模型的环境修正匹配滤波器进行了研究。通过修正匹配滤波器的参考信号,改善匹配滤波器受多径效应影响时处理性能下降的问题。同时,本文进一步对比了2种信道估计算法。仿真分析和试验数据处理结果表明:验证了算法可在去除目标周围相关峰的同时,对噪声进行一定程度的抑制。本文算法改善了经典匹配滤波器因环境影响而使得其处理性能下降的问题。

对航管二次雷达干扰现象的分析

论文主要针对航管二次雷达的几种干扰现象进行了分析及思考,以期解决对航管二次雷达的几种干扰现象。在对航管二次雷达原理阐述的基础上,对"扰环效应"、"多径效应"、大气波导环境影响等几种干扰现象进行了分析,并进一步思考,提出采用双通道、改进天线、单脉冲测向技术等方法解决干扰现象。结果表明:解决方法客观、有效,能为解决此类问题提供有力支撑。