Wan-Sik Choi

One-way ranging technique for CSS-based indoor localization

In this paper we are seeking a real-time one-way ranging technique for the chirp spread spectrum (CSS) based indoor localization. The motivation of this research is to overcome some technical disadvantage inherent to the existing symmetric double side two way ranging (SDS-TWR) technique. It is our aim to establish a ranging technique that has the following features: (i) The mobile device only acts as a transmitter (it only broadcasts RF signal to other devices); (ii) Low-power consumption at the mobile device; and (iii) The clock drift and the variation of the reply time are calibrated online so that it reflects the effects of environmental variation.

The development of modularized post processing GPS software receiving platform

Modularized GPS software defined radio (SDR) software platform has many advantages of applying and modifying algorithm. Hardware based GPS receiver uses many hardware parts (such as RF front, correlators, CPU and others) that process tracked signal and navigation data to calculate user position, while SDR uses software modules, which run on general purpose CPU platform, to implement same function. SDR needs not change hardware part and it is not limited by hardware capability when new processing algorithm is required. The weakness of SDR is that software correlation takes lots of processing time. However, in these days the evolution of MPU and DSP, and the size minimization of general purpose CPU increase the competitiveness of SDR against the hardware GPS receiver. This paper presents a study of modulization of GPS SDR software platform and development of the GNSS SDR software platform using MATLAB Simulinktrade. We focus on especially post processing SDR platform which is usually adapted in research area. The main functions of SDR are GPS signal acquisition, signal tracking, decoding navigation data and calculating stand alone user position from stored data that was intermediate frequency (IF) down converted and sampled. Each module of SDR platform is categorized by function for applicability. The developed SDR software platform was tested using stored data that IF down converted and sampled. The test results present that the SDR software platform calculates user position properly.

Paradigm Shift and the State of the Art of LBS in the Advent of Smartphone

This paper presents the paradigm shift and the state of the art of LBS(Location Based Service) in the recent mobile environment. The advent of smartphone, especially, HW(Hardware) for localization, the middleware for LBS and map DB(Database), leads a big step towards LBS as a killer application. The LBS grows very fast with various smartphone applications. In feature phone, the service area of LBS was limited and the main usage was finding buddy. However, in smartphone, LBS merges other killer applications such as SNS(Social Network Service), AR(Augmented Reality), game, mobile commerce and so on. The abrupt evolution of technology and service requires appropriate laws and systems for the future development.

The Development of Modularized Post Processing GPS Software Receiving Platform using MATLAB Simulink

Modularized GPS software defined radio (SDR) software platform has many advantages of applying and modifying algorithm. Hardware based GPS receiver uses many hardware parts (such as RF front, correlators, CPU and others) that process tracked signal and navigation data to calculate user position, while SDR uses software modules, which run on general purpose CPU platform, to implement same function. SDR needs not change hardware part and it is not limited by hardware capability when new processing algorithm is required. The weakness of SDR is that software correlation takes lots of processing time. However, in these days the evolution of MPU and DSP, and the size minimization of general purpose CPU increase the competitiveness of SDR against the hardware GPS receiver. This paper presents a study of modulization of GPS SDR software platform and development of the GNSS SDR software platform using MATLAB Simulinktrade. We focus on especially post processing SDR platform which is usually adapted in research area. The main functions of SDR are GPS signal acquisition, signal tracking, decoding navigation data and calculating stand alone user position from stored data that was intermediate frequency (IF) down converted and sampled. Each module of SDR platform is categorized by function for applicability. The developed SDR software platform was tested using stored data that IF down converted and sampled. The test results present that the SDR software platform calculates user position properly.

The effect on tracking loop performance when using the efficient search method for fast fine frequency acquisition

When implementing real-time software based GNSS receiver, the accurate and fast signal acquisition and tracking method is more necessary than the hardware based receiver owing to lots of computation time. Generally, in the software based GNSS receiver, parallel code phase signal acquisition method using FFT has been used. But it has the defect of the limited frequency resolution according to input datas length. Considering the carrier frequency resolution must be about tens of Hz in order to perform the tracking loop correctly, the fine frequency acquisition method to minimize the computation time should be necessary to overcome this limitation. Also the examination whether the method will enhance the tracking loops performance and cause the reduction of computation time should be necessary. To evaluate these necessities, in this paper, the efficient search method for fine frequency acquisition will be suggested and tested. Furthermore, the effect on signal tracking loop, when the result of signal acquisition obtained by the suggested method is applied, will be analyzed.

Improving the Performance of DR/GPS Integrated System For Land Navigation Using Sigma Point Based RHKF Filter

This paper describes a DR construction for land navigation and the sigma point based receding horizon Kalman FIR (SPRHKF) filter for DR/GPS hybrid navigation system. A simple DR construction is adopted to improve the performance both of the pure DR navigation and the DR/GSP hybrid navigation system. In order to overcome the flaws of the EKF, the SPKF is merged with the receding horizon strategy. This filter has several advantages over the EKF, the SPKF, and the RHKF filter. The advantages include the robustness to the system model uncertainty, the initial estimation error, temporary unknown bias, and etc. The computational burden is reduced. Especially, the proposed filter works well even in the case of exiting the unmodeled random walk of the inertial sensors, which can be occurred in the MEMS inertial sensors by temperature variation. Therefore, the SPRHKF filter can provide the navigation information with good quality in the DR/GPS hybrid navigation system for land navigation seamlessly.