Development of Seamless Positioning System for Urban areas by Combining Satellite-based and Pseudolite-based Positioning Systems.

1.研制了包括发射机和接收机在内的伪卫星系统样机。发射机是在现有GPS模拟器的基础上开发的，而接收机除了接收天线和A/D转换器外，都是基于软件开发的。基于软件的接收器能够实现一种算法，以减轻来自发射机或卫星的多程信号所引起的误差。此外，软件接收器作为进一步研究的平台向研究人员开放。2.使用原型接收器，提出了一种抑制多通误差的方法。利用多个相关器计算相关峰的形状，并根据该形状对直达信号和反射信号进行估计和分离。描述反射信号的参数有延迟、信号强度比和相位差。3.为了估计伪卫星与卫星组合后定位精度的提高程度，对原项目开发的仿真系统进行了改进，使之能够利用三维城市数据来模拟信号的反射和绕射。此外，通过将数据输入软件GPS接收器，我们可以估计在给定伪卫星和卫星分布的情况下预计会有多大误差。仿真结果表明，通过去除反射信号的污染，可以提高定位精度。

1.Prototype of pseudolite system including transmitter and receiver are developed. The transmitter is based on the existing GPS simulator, while the receiver was developed based on software except the receiving antenna and A/D converter. The software-based receiver enables to implement an algorithm to mitigate errors caused by multi-pass signal from the transmitter or the satellites. In addition, the software receiver was made open to researchers as a platform for further research.2.Using the prototype receiver, a method of mitigating the multi-pass errors. A number of correlators are implemented to compute the shape of the correlation peak, and with the detailed shape, direct signal and reflected signal are estimated and separated. Parameters describing the reflected signal is the delay, the ratio of signal strength and the phase difference. Through the experiment, it is demonstrated that the multi-path errors are mitigated using the actual reflected GPS signals.3.To estimate how much the positioning accuracy will be improved by the combination of pseudolites and the satellites, the simulation system, which was originally developed by the previous project, was improved to represent the reflection and the diffraction of the signal using the 3D urban data. In addition, by inputting the data into the software GPS receiver, we can estimate how much errors will be expected with a given distribution of pseudolites and satellites. It also demonstrated with the simulator that by removing the contaminated signal by the reflection, the positioning accuracy can be improved.