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 Working Papers This regular Inside GNSS column explores the technical and scientific themes that underpin Global Navigation Satellite System programs and applications. It appears in Inside GNSS six times a year. It features analyses and discussions by engineers and researchers on topics ranging from GNSS interoperability to preferred technologies for GNSS receivers to antispoofing tools for GNSS signals. The column is coordinated by Prof. Dr.-Ing Günter Hein, a member of the European Commission’s Galileo Signal Task Force and organizer of the annual Munich Satellite Navigation Summit in Germany. He has been a professor and director of the Institute of Geodesy and Navigation at the University FAF Munich since 1983. Regular contributors include three research associates at the Institute of Geodesy and Navigation: Dipl. Ing. José-Angel Ávila-Rodriguez is responsible for research activities on GNSS signals. Dipl. Math. Techn. Stefan Wallner works on the interoperability of GNSS signals, spreading codes and the signal structure of Galileo. Thomas Pany’s areas of interest include GPS/Galileo software receiver design, Galileo signal structure and GPS science. If you have questions or comments, or would like to contribute to “Working Papers,” contact Professor Hein. Columns
March/April 2008
GNSS Indoors — Fighting The Fading, Part 1The ability to receive low-power GNSS signals inside buildings wins the gold medal for product designers and manufacturers who can achieve it. The authors share results of a new test that creates an original model of signal behavior in indoor spaces of different shapes and material. <em>First of two parts.</em>
January/February 2008
Unmanned Air VehiclesImagine yourself in the middle of a battlefield with only one truly compelling objective: to maneuver yourself from one point to another and execute your mission — with the reward of your own survival. One eye on the threat, one eye on the horizon! Tension, perhaps a deep fear, seizes you as you confront mortal danger. This is your last shot! Wouldn’t you rather make it while seated behind a desk at a mission control station far from the raging conflict, directing an aerial vehicle without a human on board? A powered, aerial vehicle that can do more for than you could personally on the battlefield yourself?
November/December 2007
Active GNSS Networks and the Benefits of Combined GPS + Galileo PositioningOver the past 10 years, GNSS reference networks have simplified and extended the range of high-precision positioning over longer distances with the aid of differential corrections. However, a number of operational and environmental factors continue to limit the full realization of these techniques’ potential. Access to and use of additional satellite signals from multiple GNSS systems could help address these limitations. This column examines the potential benefit of GPS + Galileo positioning under a variety of ionospheric conditions.
September/October 2007
Authenticating GNSS: Proofs against Spoofs, Part 2Securing GNSS systems against unauthorized use and false signals (spoofing) is a matter of growing concern for GNSS operators and users. In this column, the second and final part of a series, the authors explore a variety of methods for user and signal authentication and discuss their application in GNSS.
July/August 2007
Authenticating GNSS: Proofs against Spoofs, Part 1Concerns about the authenticity and security of GNSS signals are usually associated with military applications. On the one hand, military GNSS users need to detect and avoid spoofing — the generation of false ranging signals by an adversary to mislead a foe — while on the other preventing the exploitation of one’s own GNSS broadcasts by an enemy. This two-part column explores the realm of cryptographic tools that can be used to ensure that only authorized users have access to GNSS services and that the positioning information they use — and report — is the real thing.
May/June 2007
Envisioning a Future: GNSS System of Systems, Part 3Radio frequency is a scarce commodity. No one’s making any more of it. L-band, the home for most GNSS signals, is particularly crowded. Some suggest that C-band, where Europe has filed for an allocation, could be an upscale solution. But will it cause more problems than it solves?
March/April 2007
Envisioning a Future: GNSS System of Systems, Part 2For reasons of political sovereignty, technological competition, policy differences, operational control, and perhaps just plain old national prestige, the planet Earth may have four complete global navigation satellite systems within five or six years. Let’s assume that happens. Are users and manufacturers destined to work through a labyrinth of competing technical specifications and management regimes in order to take advantage of the rich GNSS signal resource coming into existence? Or can we shape a better world of GNSS interoperability and cooperation?
January/February 2007
Envisioning a Future: GNSS System of Systems, Part 1It's not too early to begin thinking about what a multisystem GNSS might look like and mean for users, receiver manufacturers, and service providers.
July/August 2006
GNSS Software Defined Radio: Real Receiver or Just a Tool for Experts?The ability to replace some hardware components in a GNSS receiver with software-based signal-processing techniques has already produced benefits for prototyping new equipment and analyzing signal quality and performance. Now some developers are attempting to extend the flexibility and cost-benefits of software defined radios to commercial end-user products, including mobile devices incorporating GNSS functionality. This column takes a look at the history of GNSS software receivers, the opportunities and practical engineering challenges that they pose for manufacturers, and the state of the art and related applications of them.
May/June 2006
MBOC: The New Optimized Spreading ModulationThis article introduces the multiplexed binary offset carrier (MBOC) spreading modulation recently recommended by the GPS-Galileo Working Group on Interoperability and Compatibility for adoption by Europe’s Galileo program for its Open Service (OS) signal at L1 frequency, and also by the United States for its modernized GPS L1 Civil (L1C) signal. The article provides information on the history, motivation, and construction of MBOC signals. It then shows various performance characteristics and summarizes their status in Galileo and GPS signal design.
April 2006
GNSS Meteorology on Moving PlatformsOver the years, researchers have advanced the use of GPS receivers to measure water vapor content in the troposphere and model its effects on signal propagation. However, these techniques typically employ stationary GPS receivers. This column describes a method for measuring water vapor by GPS receivers on moving platforms and determining the associated atmospheric effects.
March 2006
Platforms for a Future GNSS ReceiverSince introduction of the first GPS receivers more than a quarter century ago, GNSS equipment has changed profoundly – from racks of computers and 25-pound “manpacks” into tiny integrated circuit chipsets suitable for inclusion in mobile phones and other portable devices. But the evolution of GNSS form factors is far from ended. Indeed, the appearance of new GPS and GLONASS signals and the arrival of Galileo has injected new vitality into design of GNSS products. This installment of Working Papers traces the trajectory – past, present, and future – of that technological evolution.
January/February 2006
GNSS InteroperabilityPart of the rationale for building additional GNSS systems, in addition to the motive of political sovereignty, is the argument that a single system is not able to meet all the requirements for use in challenging application environments such as large cities and mountainous terrain. In the end, our answer to the question of GNSS compatibility and interoperability also answers the question of whether GNSSes are complementary or competitive and mutually exclusive systems.
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