Standard Global Positioning System Receiver Research Articles

High-Performance Time Server Core for FPGA System-on-Chip

This paper presents the complete design and implementation of a low-cost, low-footprint, network time protocol server core for field programmable gate arrays. The core uses a carefully designed modular architecture, which is fully implemented in hardware using digital circuits and systems. Most remarkable novelties introduced are a hardware-optimized timekeeping algorithm implementation, and a full-hardware protocol stack and automatic network configuration. As a result, the core is able to achieve similar accuracy and performance to typical high-performance network time protocol server equipment. The core uses a standard global positioning system receiver as time reference, has a small footprint and can easily fit in a low-range field-programmable chip, greatly scaling down from previous system-on-chip time synchronization systems. Accuracy and performance results show that the core can serve hundreds of thousands of network time clients with negligible accuracy degradation, in contrast to state-of-the-art high-performance time server equipment. Therefore, this core provides a valuable time server solution for a wide range of emerging embedded and distributed network applications such as the Internet of Things and the smart grid, at a fraction of the cost and footprint of current discrete and embedded solutions.

Design and Development of In-Vehicle Lane Departure Warning System using Standard Global Positioning System Receiver

A lane departure warning system is a critical element among advanced driver-assistance systems functions, which has significant potential to reduce crashes. Generally, lane departure warning systems use image processing or optical scanning techniques to detect a lane departure. These systems have some limitations, however, such as harsh weather or irregular lane markings having a negative influence on their performance. Integrating global positioning system (GPS) and digital maps of lane-level resolution with an image processing based lane detection system can improve its efficiency but make the overall system more complex and expensive. In this paper, a lane detection method is proposed which uses a standard GPS receiver without any lane-level resolution maps. The proposed algorithm determines the lateral shift of a vehicle by comparing the vehicle’s trajectory acquired by standard GPS receiver to the reference road direction. The reference road direction is extracted from a standard digital mapping database commonly available in any navigational device containing maps with only road-level information. Extensive field tests were performed to evaluate the efficiency of the proposed system. The field test results show that the proposed system can detect a true lane departure with an accuracy of almost 100%. Although no true lane departure was left undetected, occasional false lane departures were detected when the vehicle did not actually depart its lane. Furthermore, a modification in the proposed algorithm was also tested which has significant potential to reduce the frequency of false alarms.

Indoor positioning based on global positioning system signals

AbstractThe Global Positioning System (GPS) is highly reliable and accurate when used outdoors.However, in indoor environments, due to the additional signal loss incurred by the walls of the buildings, the detection and decoding of GPS signals becomes a difficult task. As a solution to the indoor area coverage problem, an indoor positioning system based on GPS repeaters and a modified positioning algorithm is proposed, designed, and tested. A prototype indoor positioning system for 1D/2D positioning is built using directional GPS antennas and low‐noise amplifiers (LNA). The modified positioning algorithm is used for the real time processing of captured live GPS data. All the system components are integrated and positioning is obtained for the evaluation of the system performance. Results of the experiments show that the proposed system can be used for indoor positioning in locations where there is no GPS signal reception. The proposed system facilitates the continuation of GPS services indoors with hardware additions to the buildings and only a software update to a standard GPS receiver. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1091–1097, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27520

Performance analysis of advanced GPS receiver technique in radio frequency difficult environment

Global Positioning System (GPS) is widely used in many applications, especially on its position, velocity and timing (PVT) services. In general, a GPS receiver performs accurately and smoothly under open-sky environment. However, under urban canyon and dense foliage environments, a GPS receiver could not provide PVT services adequately due to GPS signal blockage or multipath. As a result, this paper develops and implements an advance GPS receiver technique, the Vector Tracking (VT) technique, to compare its performance with the conventional standard GPS receiver design under radio frequency difficult environments. The VT technique is based on an Extended Kalman Filter (EKF) to track all GPS satellites simultaneously and to estimate the user's position, velocity, and clock bias. The VT technique takes the advantage of the user's dynamic to predict the associated changes in the GPS signal, and it could thus facilitate the GPS receiver to bridge the temporary signal outages. Additionally, the tuning of the EKF is the key performance factor of the VT technique, and two algorithms to estimate the noise covariance, namely the correlation method and the empirical setting method, are discussed in this paper as well. Finally, this paper presents the performance gained from the developed VT technique in comparison to the conventional GPS receiver under various Radio Frequency (RF) difficult environments.

Indoor Positioning Based on GPS-Repeaters: Performance Enhancement using an Open Code Loop Architecture

Indoor localization systems are now increasingly needed in supporting location-based services (LBS). We carry out a theoretical study of an indoor positioning technique based on sequential switching. It uses available global positioning System (GPS) signals and simple deployment of so-called "GPS repeaters." The delay-lock loop (DLL) architecture of a GPS receiver has been modified into an open DLL to improve indoor positioning performance. A comparison study between simulation results using a standard GPS receiver and an improved one shows that the latter allows submetrical accuracy to be achieved.

A Novel Architecture for Ultra-Tight HSGPS-INS Integration

Global Positioning System (GPS) currently fulfills the positioning requirements of many applications under Line-Of-Sight (LOS) environments. However, many Location-Based Services (LBS) and navigation applications such as vehicular navigation and personal location require positioning capabilities in environments where LOS is not readily available, e.g., urban areas, indoors and dense forests. Such environments either block the signals completely or attenuate them to a power level that is 10-30 dB lower than the nominal signal power. This renders it impractical for a standard GPS receiver to acquire and maintain signal tracking, which causes discontinuous positioning in such environments. In order to address the issue of GPS tracking and positioning in degraded signal environments, a novel architecture for ultra-tight integration of a High Sensitivity GPS (HSGPS) receiver with an inertial navigation system (INS) is proposed herein. By enhancing receiver signal tracking loops through the use of optimal estimators and with external aiding, the capabilities of the receiver can be substantially improved. The proposed approach is distinct from the commonly used ultra-tightly coupled GPS/INS approaches and makes use of different tracking enhancement technologies used in typical HSGPS receivers, multichannel cooperated receivers and the current ultra-tightly coupled GPS/INS methods. Furthermore, the effects of inertial measurement unit (IMU) quality, receiver oscillator noise and coherent integration time on weak signal tracking are also analyzed. Simulated test results in both static and dynamic testes show that, the designed INS-aided GPS receiver can track the incoming weak GPS signals down to 15 dB-Hz without carrier phase locked, or 25 dB-Hz with carrier phase locked. When there are multiple strong GPS signals in view, the other weak signals can be tracked down to 15 dB-Hz with carrier phase locked.

GPS profiling of the lower troposphere from space: Inversion and demodulation of the open‐loop radio occultation signals

Global Positioning System (GPS) radio occultation (RO) is a space‐borne remote sensing technique providing accurate, all‐weather, high vertical resolution atmospheric parameters, including pressure, temperature and humidity in the troposphere and stratosphere. In the moist lower troposphere (LT) RO encounters known problem related to the phase‐locked loop (PLL) tracking technique applied in standard GPS receivers and the complicated structure of LT RO signals. This problem has been overcome by developing an open‐loop (OL) tracking technique. This paper outlines post‐processing of OL RO data. In order to invert OL RO signals, the GPS navigation data modulation (NDM) has to be removed in post‐processing. This paper demonstrates that some tropical occultations are not accurately inverted (associated refractivity inversion errors exceed 5%) without the use of externally supplied NDM bit sequences. This result has important implications for the use of RO data from future RO missions for climate research and weather forecasting.

English

Real time mobile mapping is now a reality for natural resource professionals such as Abandoned Mine Land (AML) Reclamation Specialists, Mine Inspectors, and Permit Reviewers. During the early 1990's, lightweight global positioning system (GPS) receivers first opened the door for field professionals to accurately locate geographic features and environmental problems without traditional surveying crews and equipment. Further developments in GPS technology during the late 1990's enabled improvements in accuracy of GPS data with the introduction of real-time GPS correction equipment such as portable beacon receivers and Wide Area Augmentation System (WAAS) enabled GPS units. However, standard GPS receivers and even the higher-end GPS mapping equipment lacked the power and capabilities to seamlessly move from the office to the field and back without multiple data conversion and correction exercises. Recent innovations in Tablet computers, card type GPS receivers, integrated GPS technologies along with Geographic Information System (GIS) and Computer Aided Drafting and Design (CAD) software make it possible to use existing aerial photography, satellite imagery, and electronic permitting data to easily and accurately locate natural resource problem features, produce ready-to-use GIS data and maps, conduct in field CAD design, and seamlessly extract the data back in the office. The Office of Surface Mining (OSM) continues efforts in applying mobile computing devices and software to permitting and AML field work. This technology allows Inspectors to take maps and permit data to the field for inspection and verification of mining and permitting activities. The application of AML design and re-design in the field is also being applied along with traditional methods to eventually integrate mobile computing as a tool in AML and Regulatory work. This technology will result in a more efficient means of implementing the Surface Mining Control and Reclamation Act (SMCRA).

Assessing Reclamation Features and Estimating Reclamation Costs on Abandoned, Inactive, and Permitted Mines Using Real-Time GPS and Tablet Computers

Real time mobile mapping is now a reality for natural resource professionals such as Abandoned Mine Land (AML) Reclamation Specialists, Mine Inspectors, and Permit Reviewers. During the early 1990's, lightweight global positioning system (GPS) receivers first opened the door for field professionals to accurately locate geographic features and environmental problems without traditional surveying crews and equipment. Further developments in GPS technology during the late 1990's enabled improvements in accuracy of GPS data with the introduction of real-time GPS correction equipment such as portable beacon receivers and Wide Area Augmentation System (WAAS) enabled GPS units. However, standard GPS receivers and even the higher-end GPS mapping equipment lacked the power and capabilities to seamlessly move from the office to the field and back without multiple data conversion and correction exercises. Recent innovations in Tablet computers, card type GPS receivers, integrated GPS technologies along with Geographic Information System (GIS) and Computer Aided Drafting and Design (CAD) software make it possible to use existing aerial photography, satellite imagery, and electronic permitting data to easily and accurately locate natural resource problem features, produce ready-to-use GIS data and maps, conduct in field CAD design, and seamlessly extract the data back in the office. The Office of Surface Mining (OSM) continues efforts in applying mobile computing devices and software to permitting and AML field work. This technology allows Inspectors to take maps and permit data to the field for inspection and verification of mining and permitting activities. The application of AML design and re-design in the field is also being applied along with traditional methods to eventually integrate mobile computing as a tool in AML and Regulatory work. This technology will result in a more efficient means of implementing the Surface Mining Control and Reclamation Act (SMCRA).