CiteULike: dcastro's gnss

Challenges for GNSS-based high precision positioning - some geodetic aspects

S Schon — 2008-07-24T15:41:08-00:00

Positioning, Navigation and Communication, 2007. WPNC '07. 4th Workshop on (2007), pp. 229-237.

In geodesy, GNSS-based methods are widely used for positioning and navigation. Since the precision (< some mm) and accuracy (< 1 cm) requirements are very high, sophisticated correction models and analysis strategies were developed, e.g. like the network RTK concept realised in different active permanent reference station networks. However, multipath and signal diffraction as well as the incomplete stochastic model for GNSS observations limits still the attainable accuracy and precision, especially for real time applications. In this paper, we focus on multipath and diffraction mitigation. The state of the art procedures for mitigation are revisited as well as the challenges for new strategies are addressed and explained using examples from the Satellite Positioning Service of the German National Survey (SAPOS) and from typical geodetic monitoring networks. Finally the importance of a complete stochastic model for GPS observations for statistically tests and meaningful interpretations of the results is underlined.

A Multi-Objective Approach in GNSS Code Discriminator Design

Jyh-Ching Juang — 2008-07-24T15:40:28-00:00

Position, Location, And Navigation Symposium, 2006 IEEE/ION (2006), pp. 223-234.

Performance analysis of a stand-alone high-sensitivity receiver

Macgougan — 2008-07-24T11:47:54-00:00

GPS Solutions, Vol. 6, No. 3. (24 December 2002), pp. 179-195.

Abstract. The use of GPS for personal location using wireless devices requires satellite signal measurements both outdoors and indoors. In the outdoor environment propagation paths may range from line-of-sight to shaded or blocked. The indoor environment may range from single-floor wooden constructions to high-rise buildings and underground facilities. In this paper, a high-sensitivity receiver which operates in unaided stand-alone mode is tested under a range of shaded and blocked signal environments, ranging from residential outdoor areas to urban canyons and residential houses. The measurement analysis is performed in both the observation and position domains. The results show that the receiver tested is able to yield measurements with C/N0 degradations in excess of 20 dB-Hz, as compared to line-of-sight measurements. Position results are a function of the geometry of the remaining satellites, which in turn is a function of the environment.

Galileo RF Constellation Simulator Design Verification and Testing

P Boulton — 2008-07-17T15:34:29-00:00

Frequency Control Symposium, 2007 Joint with the 21st European Frequency and Time Forum. IEEE International (2007), pp. 511-516.

The characterisation and certification of Galileo Ground Receiver Chain (GRC) elements for the Galileo satellite-based navigation system is a critical programme activity, particularly for the In-Orbit Verification phase (IOV). Spirent has been contracted by the European Space Agency (ESA) via Thales Alenia Space to provide reference test equipment in the form of RF Constellation Simulators (RFCS) to support certification of the GRC and test user receiver elements. These RFCS are able to support all the Galileo frequencies and services, including open service, commercial service, safety-of-life service and public regulated service (PRS). This paper begins by presenting a brief technical description of the RCFS design and architecture and proceeds to describe the scope of and approach to the formal verification process. Where appropriate, further detail of some of the verification techniques used are presented including a statement of the requirement, the test equipment and procedures involved and a summary of the results obtained. Most specific PRS aspects are excluded from this paper due to their classified status. Initial conclusions are drawn and future work is described.

Loser: Geopositioning - No Payoff For Galileo Navigation System

W Sweet — 2008-06-22T14:52:37-00:00

Spectrum, IEEE, Vol. 45, No. 1. (2008), pp. 48-49.

The idea of a European geopositioning system similar to the U.S. Global Positioning System originated a decade ago. Today the system is five years behind schedule and, in terms of public funding, at least a couple of billion euros over budget.

Joint Bayesian positioning and multipath mitigation in GNSS

Bernhard Krach — 2008-06-15T13:58:25-00:00

Acoustics, Speech and Signal Processing, 2008. ICASSP 2008. IEEE International Conference on (2008), pp. 3437-3440.

A sequential Bayesian estimation algorithm for joint positioning and multipath mitigation within satellite navigation receivers is presented. The underlying process model is especially designed for dynamic user scenarios and dynamic channel conditions. To demonstrate its capabilities simulation results are presented.

Gating Functions for Multipath Mitigation in GNSS BOC Signals

FD Nunes — 2008-03-28T23:04:21-00:00

Aerospace and Electronic Systems, IEEE Transactions on, Vol. 43, No. 3. (2007), pp. 951-964.

A new multipath mitigation technique is proposed for binary offset carrier (BOC) signals in global navigation satellite systems (GNSS) using the concept of gating function originally conceived for the GPS coarse-acquisition (C/A) code. Specially-tailored pulses are utilized to diminish the number of false-lock points of the code discriminator response and to improve the multipath mitigation capability. The code loop includes only four real correlators (two extra correlators are required for the simplified bump-jumping algorithm with BOC(n,n) signals). Results obtained with BOC(n,n) and BOC(2n,n) signals show that this technique eliminates the multipath ranging errors for reflected rays with relative delays typically above twenty percent of the spreading code chip duration, thus comparing favorably with the conventional receiver correlation techniques.

A modular architecture for the real-time reconfigurability of GNSS receivers

F Dovis — 2008-06-11T20:26:39-00:00

Electronics in Marine, 2004. Proceedings Elmar 2004. 46th International Symposium (2004), pp. 336-341.

The increased interest for the design of applications based on both navigation and communication systems, represents an important driver for the design and implementation of innovative receivers architectures. The realization of civil GPS applications, the advent of the European navigation system Galileo, and the integration of localization services in communication network, make the reconfigurability an indispensible requirement for the development of innovative Global Navigation Satellite systems (GNSS) platforms. In addition, it must be pointed out that several problem as indoor positioning and multipath recovery, are pushing the research activity in order to provide users of flexible devices able to adapt their functionalities according to the environment. From this standpoint, the Software Defined Radio (SDR) approach constitutes an interesting perspective to develop modular architectures. In this paper, the implementation of a reconfigurable user terminal integrating both navigation and communication capabilities will be discussed. The work will be presented focusing the attention on the real-time reconfigurability, based on a set of software-designed functionalities. In particular, the reconfigurable module for multipath mitigation in the tracking phase will be discussed as an example of adaptability of the receiver to the operating environment.

A Novel Unambiguous Multipath Mitigation Scheme for BOC(kn, n) Tracking in GNSS

Sanghun Kim — 2008-06-03T18:59:27-00:00

Applications and the Internet Workshops, 2007. SAINT Workshops 2007. International Symposium on (2007), pp. 57-57.

Binary offset carrier (BOC) signal tracking is one of the challenging problems in future global navigation satellite systems (GNSS) including Galileo and global positioning system (GPS), because false lock could be generated in the tracking procedure due to multiple side-peaks in BOC autocorrelation. Multipath mitigation is another challenging problem in GNSS systems, because the presence of multi-path signals gives a range error. Recently, a novel tracking scheme for the BOC signal was proposed by Garin [8]. However, it can not completely resolve the ambiguity problem due to the false lock and has not enough multipath mitigation performance. Moreover, Garin¿s scheme is applicable to only BOC(n, n). In this paper, we propose a novel unambiguous multipath mitigation scheme. The proposed scheme is applicable to various BOC signals (i.e., BOC(kn, n)) and does not incur false lock point in the tracking procedure. In addition, the proposed scheme has appropriate multipath mitigation performance than traditional and Garin¿s schemes.

THE VALUE OF POSITIONING INTEGRITY FOR GNSS- BASED ELECTRONIC FEE COLLECTION SYSTEMS

Paulo Gomes — 2008-05-19T19:41:19-00:00

Fading Channel Models for the Assessment of GNSS Receivers

R Prieto-Cerdeira — 2008-05-08T08:45:14-00:00

Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on (2007), pp. 1-5.

Applications based on Global Navigation Satellite System (GNSS) positioning for difficult environments, such as indoor, the urban canyon or low Earth orbiting satellites, have become very attractive in recent years. For a rigorous assessment of receiver performances in controlled laboratory conditions with respect to their objective environment, a precise knowledge of the electromagnetic radio channel is required. Different propagation mechanisms (diffraction, reflection and scattering) are combined together originating signal variations that affect receiver performance. Shadowing and blockage due to obstacles, frequency selective fading due to multipath, large building penetration losses or strong fading due to ionospheric scintillation are some examples of the impairments that GNSS receivers may encounter. In this paper, fading channel models that generate time-series are analysed for establishing procedures to assess the performance of GNSS receivers in different environments by, first setting error bounds in software implementations, and later, using RF signal simulators.

Novel fast GPS/GLONASS code-acquisition technique using low update rate FFT

AJRM Coenen — 2008-05-07T06:45:02-00:00

Electronics Letters, Vol. 28, No. 9. (1992), pp. 863-865.

A novel `differential' decoding technique is proposed which enables pre-averaging instead of postintegration for a substantially low update rate `FFT-IFT' correlation in spread-spectrum (navigational) receivers. <e1>N</e1>-channel code acquisition can be performed to monitor the time dispersion with FFT time left to analyse frequency dispersion in highly reflective areas (e.g. an urban environment)

The Research of Side-Band Acquisition for BOC-Modulated Signal

Li Yang — 2008-05-07T06:41:16-00:00

Wireless Communications, Networking and Mobile Computing, 2007. WiCom 2007. International Conference on (2007), pp. 645-648.

A Robust Statistical Approach to Non-Line-of-Sightmitigation

Chin-Heng Lim — 2008-05-07T06:40:03-00:00

Statistical Signal Processing, 2007. SSP '07. IEEE/SP 14th Workshop on (2007), pp. 428-432.

Mitigation of non-line-of-sight (NLoS) errors in the geolocation problem has received much attention. It is well-known that these errors degrade the robustness and accuracy of localization systems, whereby localization is performed using time-of-arrival (ToA) measurements. In this paper, we propose a robust approach to mitigate the NLoS effect in location estimation. The approach is based on modeling NLoS errors as contaminated Gaussian noise, which masks the unknown ToA. We then suggest a non-parametric estimate of the noise density, obtained from observations. It provides robustness against the outliers caused by the NLoS errors common in urban areas. Simulation results show an improvement over conventional approaches.

Design and practical implementation of multifrequency RF front ends using direct RF sampling

ML Psiaki — 2008-05-07T06:08:30-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 53, No. 10. (2005), pp. 3082-3089.

The use of direct RF sampling has been explored as a means of designing multifrequency RF front ends. Such front ends will be useful to multifrequency RF applications such as global navigation satellite system receivers that use global positioning system (GPS) L1, L2, and L5 signals and Galileo signals. The design of a practical multifrequency direct RF sampling front end is dependent on having an analog-to-digital converter whose input bandwidth accommodates the highest carrier frequency and whose maximum sampling frequency is more than twice the cumulative bandwidth about the multiple carrier signals. The principle of direct RF sampling is used to alias all frequency bands of interest onto portions of the Nyquist bandwidth that do not overlap. This paper presents a new algorithm that finds the minimum sampling frequency that avoids overlap. This design approach requires a multifrequency bandpass filter for the frequency bands of interest. A prototype front end has been designed, built, and tested. It receives a GPS coarse/acquisition code at the L1 frequency and GPS antispoofing precision code at both L1 and L2. Dual-frequency signals with received carrier-to-noise ratios in excess of 52 dB-Hz have been acquired and tracked using this system.

GPS receiver architectures and measurements

MS Braasch — 2008-02-11T09:58:35-00:00

Proceedings of the IEEE, Vol. 87, No. 1. (1999), pp. 48-64.

Although originally developed for the military, the Global Positioning System (GPS) has proven invaluable for a multitude of civilian applications. Each application demands specific performance from the GPS receiver and the associated requirements often vary widely. This paper describes the architectures and functions of civilian GPS receivers and then focuses on performance considerations. The fundamental receiver measurements are described and the quality of these measurements are related to the aforementioned receiver architectures

Receiver architecture synergies between future GPS/Galileo and UMTS/IMT-2000

G Heinrichs — 2008-02-11T09:41:27-00:00

Vehicular Technology Conference, 2002. Proceedings. VTC 2002-Fall. 2002 IEEE 56th, Vol. 3 (2002), pp. 1602-1606 vol.3.

The location requirements for emergency callers outside urban areas can hardly be fulfilled without Global Navigation Satellite Systems (GNSS). Consequently, interest in positioning techniques based on use of a GNSS such as GPS or on the cellular network infrastructure itself is growing rapidly in the mobile telephone community. The technical similarity based on the use of DS-CDMA spread-spectrum technology opens the door for the combination of GNSS with cellular network-based wireless location and positioning. The paper seeks to provide some initial answers to the question of whether mobile handset architecture synergies exist for the combination of GNSS with UMTS/cdma2000 cellular wireless networks. In this respect, we pay particular attention to the RAKE receiver architecture employed in mobile CDMA cellular handsets.

Numerical simulation of GNSS code tracking loops using Euler-Maruyama method

JL Garrison — 2008-02-03T22:58:07-00:00

Electronics Letters, Vol. 41, No. 15. (2005), pp. 868-869.

The Euler-Maruyama (EM) method for the numerical integration of stochastic differential equations is applied to simulate tracking loops for Global Navigation Satellite System (GNSS) signals. Use of a large step size and two-point pseudorandom numbers allow for computationally efficient simulation of statistics such as the mean time to lose lock (MTLL). To demonstrate this method, non-coherent delay-lock loops are simulated using the EM method. The MTLL computed from an ensemble of 50 sample paths is compared to a numerical integration of the Fokker-Planck equation. The dependence of computational time and error on step size is evaluated.

An Open GNSS Receiver Platform Architecture

Frank Engel — 2007-12-06T16:58:31-00:00

In this paper we present the concept of an FPGA-based GPS receiver architecture with the aim of providing a framework for investigating new receiver architectures for current and upcoming GNSS standards. This development system facilitates researchers to prove new receiver concepts using real signals, which nowadays can only be simulated using tools such as Matlab. One will be able to work with the satellites as soon as they are operational, rather than having to wait for the availability ...

SIMD correlator library for GNSS software receivers

Heckler — 2006-12-29T16:56:32-00:00

GPS Solutions, Vol. 10, No. 4. (November 2006), pp. 269-276.

10 Hz or 10 s?

Schuler — 2007-04-05T05:53:49-00:00

GPS Solutions, Vol. 11, No. 2. (March 2007), pp. 77-83.

GPS/GNSS current bibliography

Tomás Soler — 2007-11-19T08:48:33-00:00

GPS Solutions, Vol. 11, No. 3. (31 July 2007), pp. 223-226.

Maximum Likelihood Estimation of Position in GNSS

P Closas — 2007-11-02T18:49:29-00:00

Signal Processing Letters, IEEE, Vol. 14, No. 5. (2007), pp. 359-362.

In this letter, we obtain the maximum likelihood estimator of position in the framework of global navigation satellite systems. This theoretical result is the basis of a completely different approach to the positioning problem, in contrast to the conventional two-step position estimation, consisting of estimating the synchronization parameters of the in-view satellites and then performing a position estimation with that information. To the authors' knowledge, this is a novel approach that copes with signal fading, and it mitigates multipath and jamming interferences. Besides, the concept of position-based synchronization is introduced, which states that synchronization parameters can be recovered from a user position estimation. We provide computer simulation results showing the robustness of the proposed approach in fading multipath channels. The root mean square error performance of the proposed algorithm is compared to those achieved with state-of-the-art synchronization techniques. A sequential Monte Carlo-based method is used to deal with the multivariate optimization problem resulting from the maximum likelihood solution in an iterative way

ML estimator and hybrid beamformer for multipath and interference mitigation in GNSS receivers

G Seco-Granados — 2007-10-25T08:59:08-00:00

Signal Processing, IEEE Transactions on [see also Acoustics, Speech, and Signal Processing, IEEE Transactions on], Vol. 53, No. 3. (2005), pp. 1194-1208.

This paper addresses the estimation of the code-phase (pseudorange) and the carrier-phase of the direct signal received from a direct-sequence spread-spectrum satellite transmitter. The signal is received by an antenna array in a scenario with interference and multipath propagation. These two effects are generally the limiting error sources in most high-precision positioning applications. A new estimator of the code- and carrier-phases is derived by using a simplified signal model and the maximum likelihood (ML) principle. The simplified model consists essentially of gathering all signals, except for the direct one, in a component with unknown spatial correlation. The estimator exploits the knowledge of the direction-of-arrival of the direct signal and is much simpler than other estimators derived under more detailed signal models. Moreover, we present an iterative algorithm, that is adequate for a practical implementation and explores an interesting link between the ML estimator and a hybrid beamformer. The mean squared error and bias of the new estimator are computed for a number of scenarios and compared with those of other methods. The presented estimator and the hybrid beamforming outperform the existing techniques of comparable complexity and attains, in many situations, the Crame/spl acute/r-Rao lower bound of the problem at hand.

CN/sub 0/ estimation and near-far mitigation for GNSS indoor receivers

G Lopez-Risueno — 2007-10-25T08:55:32-00:00

Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 4 (2005), pp. 2624-2628 Vol. 4.

This paper covers two key points in indoor and dense-urban positioning using Global Navigation Satellite Systems: CN/sub 0/ estimation, and near-far estimation problem. For the former, a novel CN/sub 0/ estimator adequate to deal with the low signal levels encountered in indoor and dense-urban environments is described. For the latter, the results of a novel near-far problem mitigation technique are presented. Both simulations and live data have been used to illustrate the advantages of the proposed algorithms.