基于Wi-Fi信号的成像与压缩波束形成定位研究

发布时间：2018-02-11 11:03

本文关键词： Wi-Fi成像二维扫描射频定位信号到达角压缩波束形成　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

【摘要】：Wi-Fi(Wireless Fidelity)信号通常使用2.4 GHz或5 GHz两个射频频段,带宽通常为20 MHz或40 MHz。与传统光学成像、红外成像、太赫兹成像等成像方法相比较,Wi-Fi信号在非视距或不可见等恶劣成像条件下成像具有巨大优势。尤其是对于墙壁等障碍物,Wi-Fi信号在穿透性和传输距离方面都强于红外、毫米波和太赫兹波。因此基于Wi-Fi信号的成像技术在室内穿墙成像定位、城市反恐和室内人员监测及抗震救灾等领域具有美好的应用前景;另一方面,Wi-Fi信号也可用于室内定位或Wi-Fi热点附近区域定位。虽然全球定位系统GPS、北斗和格洛纳斯能够提供实时定位导航服务,但是对于地下室或大型建筑物内这些导航信号难以覆盖或提供更为精确的定位信息,因此基于Wi-Fi信号的定位技术,可以弥补它们在室内环境下定位的不足。Wi-Fi定位可为大型商场、学校、车站或停车场等公共场所提供更为便捷、精确和低成本的定位服务。另外,基于该Wi-Fi定位技术也可实现大型仓储货物定位、家中老人小孩的安全监测、刑侦案件破获以及生命体搜救等。在Wi-Fi成像方面,本文基于合成孔径雷达(SAR)成像技术,使用线性调频信号即chirp信号,采用距离-多普勒算法,利用MATLAB进行了Wi-Fi信号SAR成像仿真。由于Wi-Fi信号频率相对较低,其相应的SAR成像精度不高,难以满足室内传感和定位的要求。因此针对Wi-Fi信号的特点提出天线阵列成像和二维扫描成像的方法,利用定向天线通过二维机械扫描成像方式,获取成像目标的各像素点的反射信号值,最后重构出目标图像。该研究结果表明:主动式Wi-Fi信号成像技术可以实现物体的低分辨率成像。对于金属物体的目标物,在像素点采集数目较低的情况下,依然可识别出金属目标物及其相应的大致轮廓。最后本文对该实验所存在的问题及成像的局限性进行了讨论。在Wi-Fi定位方面,本文介绍对比了目前常用的几种定位方法:基于到达方向监测的信号到达角(AOA)定位、基于信号到达时间的(TOA)定位和基于信号传播时间差的(TDOA)定位,以及用于距离估计的接收信号强度基(RSSI)定位方法。由于它们本身定位原理的限制,以及定位性能仍存在不足。如CBF算法对噪声鲁棒性强,但其分辨率低,MUSIC和MVDR算法依赖于频谱矩阵特征值,所以当出现采样数量少,频谱矩阵轶不足以及信号子空间少时,定位性能会大大降低。为解决定位性能问题,提高定位精度,本文提出了一种基于压缩传感(CS)波束成形算法应用于射频无线定位研究。本文分别通过软件仿真和实验验证分析了该定位算法的性能。根据仿真结果讨论了各算法定位的效果,通过改变采样次数和阵元数目计算定位的误差率,分析算法的性能。上述研究表明:压缩传感波束形成算法在较小的采样次数下,仍能够较高精度的定位目标方位。另外,在多目标方向定位中,CS算法有更强的指向性,定位性能稳定。在实验方面,通过对定位系统的系统参数分析,探究实验所用信号频率、均匀线阵阵元间距和非均匀线阵对定位结果的影响。研究结果表明:当天线阵列采用半波布阵时,信号的频率对定位结果影响不大,而天线阵列的阵元间距对实验的稳定性有较大影响,在均匀线阵非半波布阵下和非均匀线阵定位效果皆不理想。基于AOA定位的压缩传感波束形成算法,结合压缩传感理论,突破了传统定位算法的局限性,对室内定位设计有着重要的指导意义。
[Abstract]:Wi-Fi (Wireless Fidelity) signal usually use 2.4 GHz or 5 GHz two radio frequency band, bandwidth is 20 MHz or 40 MHz. with traditional optical imaging, infrared imaging, compared to terahertz imaging and imaging method, Wi-Fi signal has a huge advantage in the non line of sight or not visible and poor imaging conditions especially for wall imaging. Other obstacles, Wi-Fi signal in the penetration and transmission distance are strong in infrared, millimeter wave and terahertz wave. Therefore based on Wi-Fi signal imaging technology in indoor positioning through wall imaging, has a good application prospect of the city on terror and indoor personnel monitoring and earthquake relief and other fields; on the other hand, the Wi-Fi signal can also be used indoor positioning or Wi-Fi hotspot area near the location. Although the GPS global positioning system, Beidou and GLONASS can provide real-time positioning and navigation services, but for the basement or large buildings in the Some navigation signal can not cover or provide more accurate location information, so based on the positioning technology of Wi-Fi signal, can make up for their lack of.Wi-Fi positioning positioning in indoor environment for the large shopping malls, schools, bus station or parking lot and other public places to provide more convenient, accurate positioning and low cost services. In addition, the Wi-Fi technology can realize the large-scale storage of goods based on the location of the elderly child safety monitoring, criminal investigation and case cracked life rescue. In Wi-Fi imaging, this paper based on synthetic aperture radar (SAR) imaging technology, the use of linear FM signal chirp signal, using the range Doppler algorithm, the Wi-Fi signal SAR imaging simulation by MATLAB. The Wi-Fi signal frequency is relatively low, the corresponding SAR imaging accuracy is not high, it is difficult to meet the requirements of indoor sensing and positioning. Therefore the needle of Wi-Fi signal The characteristics of proposed antenna array imaging and two-dimensional scanning imaging, using directional antennas by two-dimensional mechanical scanning imaging, the reflected signal of each pixel to obtain target value, finally reconstruct the target image. The results of this study showed that low resolution imaging active Wi-Fi signal imaging technology can achieve the target for metal objects. The object in the collection number of pixels is low, still can identify the metal target and its corresponding outline. The limitations of the existing problems and finally the imaging experiments are discussed. In the Wi-Fi position, this paper compared several common positioning methods: signal arrival direction based on the monitoring of the angle of arrival (AOA) location, time of arrival (TOA) based on the location and signal propagation time difference based on the (TDOA) position, and then used for distance estimation The received signal strength (RSSI) based localization method. Because of their own positioning principle, and the positioning performance is still insufficient. As to the noise robustness of CBF algorithm, but its resolution is low, MUSIC and MVDR algorithm depends on the spectrum of eigenvalues of a matrix, so when the sampling number is small, the spectrum matrix and signal sub Yi small space, performance will be greatly reduced. In order to solve performance problems, improve the positioning accuracy, this paper puts forward a kind of based on compressed sensing (CS) in a radio frequency wireless positioning algorithm. The application of beamforming by software simulation and experimental verification and analysis of the performance of the localization algorithm. According to the simulation results discussed the effect of localization algorithm, positioning error calculation by changing the sampling frequency and the number of array elements, performance analysis of the algorithm. The research shows that the compressed sensing beamforming algorithm in small sample Times, still can locate the target range and higher precision. In addition, in the positioning of multi targets direction, directivity has stronger CS algorithm, positioning and stable performance. In the experiment, through the analysis of the system parameters on the positioning system, explore the signal frequency used in the experiment, the uniform linear array element spacing and non uniform linear array to locate the effect. The results show that when the half wave antenna array array, the signal frequency has little influence on the positioning results, and has a great influence on the stability of the array element spacing of the antenna array in the experiment in uniform linear array non half wave arrays and non uniform linear array positioning effect are not ideal. AOA the positioning of the compressed sensing beamforming algorithm based on the combination of the compressed sensing theory, break through the limitations of traditional algorithms, has an important guiding significance for the design of indoor positioning.

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92;TN957.52

【相似文献】