• Electronics and Telecommunications Trends
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• v.36 no.4
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• pp.61-71
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• 2021

Navigation satellite systems (GPS, GLONASS etc.) provide three main services, i.e., positioning for location based services, navigation for multi-modal transportation services, and timing for communication and critical infrastructure services. They were started as military systems but were extended to civil service. Navigation satellite navigation system began with GPS in the USA and GLONASS in Russia at nearly the same time. Indian NavIC and Chines BDS announced their FOCs in 2016 and 2020, respectively and European Galileo and Japanese QZSS are catching up others. In these days, Navigation Satellite System, Positioning, Navigation, and Timing services are part of our daily life very closely. They are required for autonomous driving car, Unmanned vehicles like UAV, UGV, and UMV, 5G/6G telecommunications, world financial system, power system, survey, agriculture, and so on. The services among navigation satellite systems are very competitive and also cooperative one another. This article describes the status of these systems and evolution in the technical and service senses, which may be helpful for planning korea positioning system(KPS).

• Journal of Positioning, Navigation, and Timing
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• v.11 no.2
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• pp.119-126
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• 2022

This paper presents a method to reduce the vibration-induced noise effect of an inertial measurement device mounted on a self-driving vehicle. The inertial sensor used in the GNSS/INS integrated navigation system of a self-driving vehicle is fixed directly on the chassis of vehicle body so that its navigation output is affected by the vibration of the vehicle's engine, resulting in the degradation of the navigational performance. Therefore, these effects must be considered when mounting the inertial sensor. In order to solve this problem, this paper proposes to use an in-house manufactured vibration suppression device and analyzes its impact on reducing the vibration effect. Experimental test results in a static scenario show that the vibration-induced noise effect is more clearly observed in the lateral direction of the vehicle, but can be effectively suppressed by using the proposed vibration suppression device compared to the case without it. In addition, the dynamic positioning test scenario shows the position, speed, and posture errors are reduced to 74%, 67%, and 14% levels, respectively.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.333-339
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• 2022

The satellite navigation system was developed for the purpose of calculating the location of local users, starting with the Global Positioning System (GPS) in the 1980s. Advanced countries in the space industry are operating Global Navigation Satellite System (GNSS) that covers the entire earth, such as GPS, GLONASS, Galileo, and BeiDou, by establishing satellite navigation systems for each country. Regional Navigation Satellite Systems (RNSS) such as QZSS and NavIC are also in operation. In the early 2010s, only GPS and GLONASS could calculate location using a single system for location determination. After 2016, the EU and China also completed the establishment of GNSS such as Galileo and BeiDou. As a result, satellite navigation users can benefit from improved availability of GNSS. In addition, before Galileo and BeiDou's Full Operational Capability (FOC) declaration, they used combined navigation algorithms to calculate the user's location by adding another satellite navigation system to the GPS satellites. Recently, it may be possible to calculate a user's location for each navigation system using the resources of a single system. In this paper, we evaluated the performance of single system navigation and combined navigation solutions of GPS, GLONASS, Galileo, BeiDou and QZSS individual navigation systems using high-performance GNSS receivers.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.229-238
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• 2022

This paper addresses on the International technical trends, standards, and development status of terrestrial radionavigation system to provide more accurate and fail-safe Positioning, Navigation, and Timing (PNT) Information available in maritime navigation environment. We analyze the performance result of pilot service in enhanced Long range navigation (eLoran) testbed environment using Low Frequency (LF) signal, and describe the development status of Ranging-Mode (R-Mode) system using Medium Frequency (MF) and Very High Frequency (VHF) to meet the Harbor Entrances and Approaches (HEA) requirement of International Maritime Organization (IMO) within 10m position accuracy. Furthermore, we present an architecture for integrated service of satellite-terrestrial navigation system and future maritime applicable fields. As the core information infrastructure of future navigation for 4th industrial revolution, this paper will be contributed to determining the direction of present and future to provide fail-safe PNT service with Global Navigation Satellite System (GNSS) based on the technical enhancement of terrestrial integrated navigation system.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.1
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• pp.1-13
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• 2024

In this paper, we investigate the signal design of six (USA, EU, Russia, China, Japan, and India) countries for Global Navigation Satellite Systems (GNSS). Recently, a navigation satellite system that is capable of high-precision and reliable Positioning, Navigation, Timing (PNT) services has been developed. Prior to system design, a survey of the signal design for other GNSS systems should precede to ensure compatibility and interoperability with other GNSS. The signal design includes carrier frequency, Pseudorandom Noise (PRN) code, modulation, navigation service, etc. Specifically, GNSS is allocated L1, L2, and L5 bands, with recent additions of the L6 and S bands. GNSS uses PRN code (such as Gold, Weil, etc) to distinguish satellites that transmit signals simultaneously on the same frequency band. For modulation, both Binary Phase Shift Keying (BPSK) and Binary Offset Carrier (BOC) have been widely used to avoid collision in the frequency spectrum, and alternating BOCs are adopted to distinguish pilot and data components. Through the survey of other GNSS' signal designs, we provide insights for guiding the design of new satellite navigation systems.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.255-265
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• 2018

In this paper, the positioning performance index is proposed. The proposed index is used to find satellites that degrade positioning performance to improve the positioning performance. To do this, the proposed index is calculated using the code measurement quality and the DOP. And, through the experiment, the effectiveness of the proposed index is confirmed. In the experiment, the quality of the code measurements is analyzed, and the effectiveness of the proposed index is confirmed by comparing with the result of the precise float solution. Finally, it is shown that the precise float solution performance is improved by using the proposed index.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.49-54
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• 2021

Indoor positioning system becomes of increasing interests due to the demands for accurate indoor location information where Global Navigation Satellite System signal does not approach. Wi-Fi access points (APs) built in many construction in advance helps developing a Wi-Fi Received Signal Strength Indicator (RSSI) based indoor localization. This localization method first collects pairs of position and RSSI measurement set, which is called fingerprint database, and then estimates a user's position when given a query measurement set by comparing the fingerprint database. The challenge arises from nonlinearity and noise on Wi-Fi RSSI measurements and complexity of handling a large amount of the fingerprint data. In this paper, machine learning techniques have been applied to implement Wi-Fi based localization. However, most of existing indoor localizations focus on single position estimation. The main contribution of this paper is to develop multi-target localization by using deep neural, which is beneficial when a massive crowd requests positioning service. This paper evaluates the proposed multilocalization based on deep learning from a multi-story building, and analyses its learning effect as increasing number of target positions.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.21-28
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• 2021

In order to develop a Korea Positioning System (KPS) as part of key national infrastructure, independent navigation signal design is essential. The designed signal candidates must coexist with existing or planned GNSS signals within the limited frequency band. This requires a RF compatibility assessment, which can be performed using the Spectral Separation Coefficient (SSC) and Effective Carrier to Noise Density Ratio (Effective C/N0), for navigation signals. Thus, in this paper, the analysis of RF compatibility between the designed signal candidates and the existing GNSS signals is carried out based on analytical and numerical techniques.

• Journal of Positioning, Navigation, and Timing
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• v.5 no.2
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• pp.59-66
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• 2016

The International GNSS Service (IGS) provides the IGS-Real Time Service (IGS-RTS) corrections that can be used in stand-alone positioning in real time. In this study, the positioning accuracy before and after the application of the corrections to broadcast ephemeris by applying the IGS-RTS corrections at code pseudo-range based stand-alone positioning was compared with positioning result using precise ephemeris. The analysis result on IGS-RTS corrections showed that orbit error and clock error were 0.05 m and 0.5 ns compared to precise ephemeris and accuracy improved by about 8.5% compared to the broadcast ephemeris-applied result when the IGS-RTS was applied to positioning. Furthermore, regionally dispersed five observatories were selected to analyze the effect of external environments on positioning accuracy and positioning errors according to location and time were compared as well as the number of visible satellites and position dilution of precision by observatory were analyzed to verify a correlation with positioning error.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.2
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• pp.157-166
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• 2023

Several experiments were carried out to analyze the impact of the modernized Global Positioning System (GPS) L2C signal on pseudorange-based point positioning. Three dual-frequency positioning algorithms, ionosphere-free linear combination, ionospheric error estimation, and simple integration, were used, and the results were compared with those of Standard Point Positioning (SPP). An analysis was conducted to determine the characteristics of each dual-frequency positioning method, the impact of the magnitude of ionospheric error, and receiver grade. Ionosphere-free and ionospheric error estimation methods can provide improved positioning accuracy relative to SPP because they are able to significantly reduce the ionospheric error. However, this result was possible only when the ionospheric error reduction effect was greater than the disadvantage of these dual-frequency positioning algorithms such as the increment of multipath and noise, impact of uncertainty of unknown parameter estimation. The RMSE of the simple integration algorithm was larger than that of SPP, because of the remaining ionospheric error. Even though the receiver grade was different, similar results were observed.