Ki-Won Song

Performance Analysis of WADGPS System for Improving Positioning Accuracy

ABSTRACT The Wide Area Differential Global Positioning System (WADGPS) that uses a number of Global Navigation Satellite System (GNSS) reference stations are implemented with various types and provide services as it can service a wide range of areas relatively. This paper discusses a constellation design of reference stations and performance analysis of the WADGPS. It presented performance results of static and dynamic users when wide area correction algorithm was applied using eight reference stations. Keywords: GNSS, WADGPS, DGPS, SBAS been implemented and serviced as shown in the Wide Area Augmentation System in the U.S. and European Geostationary Navigation Overlay Service in Europe. In South Korea, Korean SBAS implementation project has been under way under the sponsorship of the Ministry of Land, Infrastructure, and Transport.Along with them, there is a project called Exploitation of DGPS for Guidance Enhancement (EDGE) in the U.S. (Carlo 2015). The EDGE is a WADGPS using reference stations that have a long baseline. It employed four DGPS reference stations and has been known to achieve the performance goal (3 m) of correction accuracy of user receivers. Other than above examples, there are other technical study examples such as Wide Area GPS Enhancement and Talon NAMATH that are broadcasted at the GPS P (Y) code.This paper discussed the performance analysis results about WADGPS for the purpose of improvements on GPS positioning accuracy. The target system consists of eight reference stations and one master station. Real-time user correction performance was verified.This paper is organized as follows. In Section 2, configuration of the implemented system is discussed. In Section 3, performance results of post-processing of collected data are presented in order to verify the performance of GPS observation data at the implemented reference station. In Section 4, correction performance of

Performance Analysis of Pseudorange Error in STAP Beamforming Algorithm for Array Antenna

The most effective method to overcome GPS jamming problem is to use an adaptive array antenna which has the capability of beamforming or nulling to a certain direction. In this paper, Space Time Adaptive Processing (STAP) beamforming algorithm of four elements array antenna will be designed and the anti-jamming performance will be analyzed. According to the analysis, the signal to noise ratio (SNR) and anti-jamming performance can be enhanced by beamforming algorithm. Also, the time tap effect of STAP algorithm will be analyzed theoretically and verified with array antenna modeling and simulation. Specially, the cautious selection of reference time tap in STAP can prevent the degradation of position accuracy performance.

Deadzone Elimination of Closed-Loop Fiber Optic Gyro using Pulse Dithering

Gyroscope`s deadzone is a region where can not detect the rate even though the actual rotation is applied. This paper analyzed the cause of deadzone by modeling/simulation and introduced pulse dithering method to overcome. From the testing of 3-axis fiber optic gyro system using 900m fiber, it confirmed deadzone could be effectively eliminated by combination of three factors, dither amplitude, dither frequency, and gyro loop gain.

Design of Fiber Optic Gyroscope for Sensing High Rotation

We studied the design of fiber optic gyroscope that enables to sense high rotation by extending the limit of rotation sensibility of fiber optic interferometer. Based on the digital serrodyne modulation technique, the signal processing of fiber optic gyroscope was designed and the prototype fiber optic gyroscope showed the high rotation sensibility up to and scale factor performance of about 150[ppm] by the experiments. Accordingly, we confirmed that the design of fiber optic gyroscope was valid for high rotation.

A Fast GPS Signal Acquisition Method for High Speed Vehicles Using INS Velocity and Multiple Correlators

GPS/INS integrated navigation systems have been used for guided munitions. By adding the navigation system into unguided munitions, accuracy can be highly improved. In these applications, GPS receivers have to meet certain requirements such as gun-hardening, fast signal acquisition and jammer tolerance. Especially, the signal should be acquired as fast as possible since mission time is very short. Several methods have been proposed for fast acquisition. These methods make it possible to reduce acquisition time by searching code phases in parallel. However, in military applications, the Doppler frequency range to be searched should be reduced since the Doppler frequency range is wider than conventional vehicle. This paper proposes a fast acquisition method using INS velocity and multiple correlators for high speed vehicles. In order to reduce acquisition time, range of the Doppler frequency is reduced using INS velocity and number of code phase to be searched is reduced using multiple correlators. Monte-Carlo simulation was carried out to show performance of the proposed method.

Initial Alignment Algorithm for the SDINS Using an Attitude Determination GPS Receiver

Since the stationary alignment process of the SDINS is not completely observable, some furls of the aided alignment have been applied. The purpose of this paper is to propose a new initial alignment algorithm, which utilizes the attitude output from the AGPS(Attitude Determination GPS) receiver and to demonstrate the feasibility of the proposed algorithm with several experimental results. A Kalman filter is designed for utilizing the attitude output as well as the zero velocity information. Also analyzed is the observability of the SDINS error model. To show the feasibility of the proposed scheme, we implement an alignment system where HG1700AE IMU (Inertial Measurement Unit) from Honeywell and an AGPS receiver designed at Chungnam National University are used. Test trials are done to evaluate the performance of the proposed alignment scheme. The proposed algorithm provides as good initial alignment performance as a high accurate navigation system, MAPS(Modular Azimuth Positioning System) INS.