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This paper analyzes what is mitigated as spoofing attack using the U-Blox Receiver and GPS RF signal generator developed at ETRI. Generally the spoofing attack made the target receiver to be wrong navigation solution by providing false measurement of code and carrier. So we analyzed the impact of spoofing attack through the signal strength and navigation solution. In oder to test of effect of anti-spoofing signal, we consider the signal with antiphase code to spoofing signal and generated GPS normal signal and spoofing signal and anti-spoofing signal using GPS RF signal generator. This paper analyzed that the GPS receiver was responded to the spoofing attack according to code phase difference between spoofing and anti-spoofing signal. We confirmed that the spoofing signal was disappeared by anti-spoofing signal if code phase is an exact match.

In this paper, an adaptive signal tracking loop for a GPS L1/L2C/L5 receiver is designed. The design parameters is adjusted according to the receiver`s operating conditions such as the signal strength and the receiver dynamics by using the different characteristics of GPS L1, L2C and L5 signal. Simulation results show that the tracking accuracy of the proposed signal tracking loop is better than those of L1, L2C and L5 only signal tracking loop.

Today Global Navigation Satellite Systems (GNSS) are widely used for determining position. Within the city environment, however, in which there are many tall buildings, GNSS signals are frequently interrupted, making it difficult for users to obtain information on their exact position. This paper analyzed the availability and positioning performance of a GPS augmented system within the Seoul urban area using the Japanese QZSS (Quasi-Zenith Satellite System) and a geostationary satellite. A 3-dimensional reproduction of Seoul that was based on the 3D GIS (Geographic Information System) Digital Map and a satellite tracking algorithm using Ray-Triangle Intersection algorithm were discussed. A satellite tracking algorithm was verified through filed testing and the QZSS orbit simulator was realized using Keplerian parameter. DOP (Dilution of Precision) and availability in the urban area of Seoul were analyzed using a GPS/QZSS/geostationary satellite separately and simultaneously.

This paper analyzes the availability and Dilution Of Precision (DOP) of GPS, widely used in positioning, with and without augmentation using QZSS (Quasi-Zenith Satellite System). Orbit simulator for QZSS is developed using Kepler‘s orbital parameters. Also 3D modeling technique based on three-Dimensional GIS digital map and satellite tracking algorithm for visible satellite simulation system are discussed. Performance improvement of the availability and DOP were achieved by combining GPS with QZSS at urban environment of Seoul.

Visibility of the satellite navigation is related to a environmental condition of a receiver. Obstacles like buildings and trees in urban areas can block signals and have effects on accuracy and reliability of positioning. This paper presents a method of creating 3D analysis model of urban canyon of Seoul using three-Dimensional digital map. Analysis techniques of visible satellites with Ray-Polygon Collision Detection and validation of algorithm through field tests are discussed. We have compared and analyzed the visibility of GPS and Galileo with respect to separate and simultaneous tracking in view of DOP (Dilution of Precision) using the 3D GIS digital map.

In this paper, we propose a novel L5 tracking scheme for QZSS satellite using L1/L5 synchronization characteristics in the L1/L5 receiver. The QZSS consists of a multiple number of satellites that fly in the orbit passing through the near zenith over Japan. The Michibiki, the first QZSS satellite, is transmitting all the positioning signals including the L1/L5 signals. As the code length of L5 signal is 10- times that of L1 signal, the L5 acquisition process takes too much time. To reduce this acquisition processing time, a higher number of correlators should be used in the acquisition module. These makes the hardware complexity and the computation power increase. As the proposed scheme uses the L1 tracking results such as the PRN, bit synchronization, and Doppler frequency, it doesn't need the extra L5 acquisition module and provides fast and stable tracking of L5 signal. The feasibility of the proposed scheme is demonstrated by processing L1/L5 signal transmitted from the QZSS satellite.

The GNSS(Global Navigation Satellite System) is used widely and generally these days. The satellite navigation system provides navigation service globally and doesn"t need an extra cost to use. Thus this system is portrayed as public service. But this system has a weak point. The satellite signal strength is very weak on the ground so this system is vulnerable against interference signal. When the GNSS interference signal is induced, the receiver cannot operate normally. The interference is presented by jamming or spoofing about GNSS signal. The effect of the interference can be done in various field from car navigation to national infrastructure like mobile communication, power plant, etc. ETRI(Electronics and Telecommunications Research Institute) developed GPS Jamming monitoring system for monitoring interference of GNSS signal. The developed GPS Jamming monitoring system has the functions which are jamming & spoofing detection and jamming location with direction finders. Among the technologies of GPS Jamming monitoring system, this paper describes spoofing detection module. This module monitors GPS signal and detects the spoofing signal with measurement and message of receiver. ETRI performed the functional test of developed spoofing detection module through the spoofing signal generation equipment. In this test, we confirm that the spoofing signal is induced in GPS receiver and verify the performance of spoofing detection.

GPS is widely used in the location based service and the telematics service. And communication systems, electrical power grids, and financial networks also rely on GPS for synchronization and operational efficiency. GPS applications are newly being developed and becomes very critical infrastructure. However, GPS couldn’t be used by intentional interference signal of even low power, low cost transmitters. In order to prevent the damage caused by illegal interference signal to GPS, GPS interference monitoring system(IMS) should be developed and operated. So, this paper presents the development and the test results of the GPS IMS which provides the detection, the direction finding and the location of GPS interference signal. The main functions are verified by test results of the interference test-bed environment.

In this paper, we compared and analyzed the performance of generated GPS signal by GPS L1 signal generator with Live GPS signal using the U-Blox receiver. Generally GPS Receiver calculates the position of the satellite by using the ephemeris data received from GPS satellites, and calculates the position of the receiver using the pseudorange. GPS satellites, so it is synchronized, it will then transmit the same data at the same time but the pseudorange because the distance between each satellite and receiver is different. However, For the same signal as the GPS provides the receiver, signal generator is required to generate the RF signal that reflects the pseudorange that different are measured to the same signal as the GPS, not the GPS satellites. This paper provides an overview of a device which can generate an L1 GPS signal at the same time as the GPS signal, and compared with Live GPS signal performance verification for this. As a result, we can check that the navigation of the GPS signals generated in synchronization with the GPS signal can be maintained in the same manner as Live GPS, and the relative pseudorange error between channels are kept constant when generating signals of the long.

Galileo system is being under the in-orbit validation (IOV) and and its constellation consists of Proto Flight Model (PFM) and Flight Model 2 (FM2) launched in October 2011 and FM3 and FM4 launched in October 2012. The researchers of the NAVIS Centre and the European Space Agency (ESA) have announced the signal tracking of all the four satellites and the first determination of a ground location, respectively. This paper for the first time, presents E1 acquisition and tracking results using our own receiver after receiving the signals of all the four Galileo satellites at the same time, in Korea. The simulation results show that the SW based Galileo E1 receiver of ETRI successfully processes the signals of all the four Galileo satellites.

The Michibiki is the first QZSS satellite, which was launched by a H-IIA rocket departing from the Tanegashima in Japan on 11 September, 2010 and technical and application verification of the satellite is being carried out. This paper presents the results obtained from processing of the L5 signal transmitted from the QZSS satellite. The QZSS L5 signal is collected in ETRI, Korea. And then, the acquisition and tracking are performed by the L5 software receiver implemented by ETRI. The tracking loop of FLL, PLL, and DLL, the EPL correlator output, and the C/No output results show that the QZSS L5 signal is normally processed. Finally, the paper demonstrates that the QZSS L5 signal could be used as GPS satellite based augmentation system in Korea as well as Japan.

Pseudolite system is good alternative for indoor navigation in where GPS signal can not reach. There are two types of pseudolite system. The one is synchronous system and the other is asynchronous system. For the asynchronous system, user requires RF link to be provided augmentation data for timing and reference station for monitoring timing offsets of pseudolites. For the synchronous system, User does not require RF link for augmentation data but it still need reference station for monitoring timing offsets of pseudolites and the reference station need RF link with pseudolites for providing timing offset information for synchronizing slave pseudolites with master pseudolite. A synchronous pseudolite system with single clock which can cut down cost for the pseudolite system is presented in this paper. Also we will present configuration, operation concept, and preliminary simulation result for it.

This paper proposes the advanced fine-acquisition scheme using the E5a signal transmitted from the Galileo GIOVE-B satellite. The proposed approach is based on the code phase changes which occur during the acquisition processing time originating in the Doppler frequency. The proposed scheme detects a fast code phase within about 1 chip near the estimated code phase and improves the accuracy of the Doppler frequency in comparison with the conventional scheme. The feasibility of the proposed schemes is demonstrated through simulation

COSPAS-SARSAT system which consists of space segment and ground segment provides a distress alert and the position information for a distressed ship or airplane with beacon equipment. Currently, COSPAS-SARSAT system provides the LEOSAR service which is called to the first generation, and the GEOSAR service as the second generation. The GEOSAR service provides position accuracy better than the LEOSAR service because the second generation 406 MHz beacon allows for the encoding of position data in the transmitted 406 MHz message, thus providing for quasi-real time alerts and position information through the GEOSAR service. ETRI developed emergency position indicating radio beacon (EPIRB) as the second generation 406 MHz beacon for use in maritime applications. Design and implementation aspects of the EPIRB developed by ETRI are presented. Also, performance is presented through the experiment.

Modernized GPS and Galileo system will be available to civil users, thus there is a need for unified platform that can receive multi-frequency signals of Galileo/GPS to develop and test a variety of applications. ETRI involved in developing technologies of GNSS ground infrastructure and next generation search and rescue beacon from 2007 up to 2010. We are going to develop high performance S/W receiver for feasibility study on developing a receiver for GNSS ground sensor station for the program. In order to test and verify S/W receiver prototype digitized IF signal generator is developed. The experimental result for the S/W receiver is presented in future.

GNSS Digitized IF Signal Simulator (GDISS) is being developed by ETRI as a part of development of software- based Test & Evaluation Facility which will provide test and evaluation environment for various software level application and navigation algorithm in GNSS. GDISS will provide digitized IF data of GPS and Galileo signals. In this paper, GDISS prototype for L1, L2C, and E1(B&C) is developed and verified. The proposed prototype has good modularity and flexibility to add conveniently various modelings like ionospheric model, tropospheric model, multipath model, satellite clock model, etc. It will be verified by the commercial S/W receiver, Nordnav, and the S/W receiver implemented by CNU(Chungnam National University).