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The MBOC Modulation

A Final Touch for the Galileo Frequency and Signal Plan


A 2004 agreement between the European Union and the United States — an unprecedented cooperation in GNSS affairs — established a common baseline signal BOC(1,1) for the Galileo Open Service and the modernized civil GPS signal on the L1 frequency (L1C). The agreement also allowed the opportunity for improvements on that signal design, which a bilateral working group subsequently proposed in 2006: the multiplexed BOC or MBOC. Under the terms of the 2004 pact, the EU had the right to decide whether to implement the BOC(1,1) or MBOC as the common baseline. This article describes the process leading up to the recent decision to implement MBOC and provides an overview of the final Galileo signal and frequency plan.

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As emphasized in the European Commission (EC) “white paper” on European transport policy for 2010, the European Union (EU) needs an independent satellite navigation system. Galileo is Europe’s contribution to the global navigation satellite system of systems (GNSS) and has committed itself from the very beginning to developing a signal plan that would provide sufficient independence from GPS, while also being compatible and interoperable with it.

The historic Agreement on the Promotion, Provision, and Use of Galileo and GPS Satellite-Based Navigation Systems and Related Applications between the United States and the European Commission (EC) signed in 2004, wherein both parties agreed to work together, affected the originally planned Galileo signals but has intensified the cooperation on interoperability and compatibility issues between Galileo and GPS for the maximum benefit of GNSS users worldwide.

The final touch to the Galileo signal plan was achieved in 2006 when the Working Group on GPS and Galileo compatibility and interoperability, under the auspices of the 2004 agreement, finally settled on a new modulation for the common signal in the E1/L1 frequency, namely the multiplex binary offset carrier, or MBOC for short. This decision was pursuant to efforts mainly driven by the European side and fully recognized by the U.S. representatives.

The journey to the signals Galileo has today for its baseline has been tedious and long, but from the outset the journey has followed a consistent logic. At the very beginning, one of the main challenges that Galileo set for itself was to offer three wideband signals, satisfying at the same time the requirements of the mass market and pushing the potential performance of the navigation signals to their natural limits.

This article will try to shed some light on the long process that has led to the signal baseline we have today. Special care will be placed on describing all the modulations of the final Galileo Signal Plan.

(For the rest of this story, please download the complete article using the link above.)

Author Profiles

José-Ángel Ávila-Rodríguez is a research associate at the Institute of Geodesy and Navigation at the University FAF Munich. He is responsible for research activities on GNSS signals, including BOC, BCS, and MBCS modulations. Ávila-Rodríguez is involved in the Galileo program, in which he supports the European Space Agency, the European Commission, and the Galileo Joint Undertaking, through the Galileo Signal Task Force. He studied at the Technical Universities of Madrid, Spain, and Vienna, Austria, and has an M.S. in electrical engineering. His major areas of interest include the Galileo signal structure, GNSS receiver design and performance, and Galileo codes. 

Günter W. Hein is Full Professor and Director of the Institute of Geodesy and Navigation at the University FAF Munich. He is responsible for research and teaching in the fields of high-precision GNSS positioning and navigation, physical geodesy and satellite methods. He has been working in the field of GPS since 1984 and is author of numerous papers on kinematic positioning and navigation as well as sensor integration. In 2002 he received the prestigious “Johannes Kepler Award” from the U.S. Institute of Navigation (ION) for “sustained and significant contributions to satellite navigation.” Presently he is heavily involved in the Galileo program.

Stefan Wallner studied at the Technical University of Munich and graduated with a diploma in technomathematics. He is now research associate at the Institute of Geodesy and Navigation at the University FAF Munich. Wallner’s main topics of interests are the spreading codes and the signal structure of Galileo and also interference and interoperability issues involving GNSS systems.

Jean-Luc Issler is head of the Transmission Techniques and Signal Processing Department of CNES (the French Space Agency), whose main tasks are signal processing, air interfaces and equipment in radionavigation; tracking, telemetry, and control; propagation, and spectrum survey. He has been involved in the development of several spaceborne receivers in Europe, as well as in studies on the European radionavigation projects, such as GALILEO and pseudolite networks. With the Direction de la Recherche et des Affaires Scientifiques et Techniques (DRAST), he represents France in the Galileo Signal Task Force of the European Commission. In 2004, with Lionel Ries and Laurent Lestarquit, he received the Astronautic Prize of the AAAF (French aeronautical and space association) for his technical work on Galileo signals and space borne GNSS equipment.

Lionel Ries has been a navigation engineer in the Transmission Techniques and Signal Processing Department at CNES since June 2000. He is responsible for research activities on GNSS2 signal, including BOC modulations and GPS IIF L5, and software receivers. He is involved in the Galileo program in which he supports the European Space Agency, the European Commission, and the Galileo Joint Undertaking through the Galileo Signal Task Force. He graduated from the Ecole Polytechnique de Bruxelles, at Brussels Free University (Belgium) and received an M.S. degree from the Ecole Nationale Supérieure de l’Aéronautique et de l’Espace (SUPAERO) in Toulouse (France).

Laurent Lestarquit graduated from the Ecole Polytechnique of Paris and then specialized in space telecommunication systems at the Ecole Nationale de l’Aéronautique et de l’Espace (SUPAERO) in Toulouse, France. Since 1996, he has been collaborating on several projects related to GPS space receivers (HETE2 and STENTOR). He is now involved in the Galileo program and supports the EC and ESA through the Galileo Signal Task Force. He invented the AltBOC 8 PSK signal proposed for Galileo on the E5 frequency. From now on he will be involved in Galileo orbit determination and time synchronization.

Antoine de Latour has been a navigation engineer in the CNES Transmission Techniques and Signal Processing Department since 2003. He is involved in the Galileo Program in which he supports the European Space Agency and the European Commission. De Latour is involved in the design of the Galileo signals, in the use of GNSS for space applications, in the GPS/Galileo radio frequency compatibility assessment, and in the development of a GNSS RF signal simulator. In particular, he studied in depth the CBOC Galileo signal definition and the PRS signal. De Latour proposed new tracking signal techniques for generic receivers and spaceborne receivers. He was graduated from the Ecole Supérieure d´Electricité (Supélec) in Paris and obtained a master’s degree from the University of Stuttgart.

Jérémie Godet is the chairman of the Galileo Signal Task Force and has security and frequency responsibility in the Galileo Unit of the European Commission. He is in charge of compatibility and interoperability discussions with GPS, GLONASS, and QZSS for the Galileo program. He graduated from the Ecole Nationale Supérieure des Télécommunications de Bretagne (Télécom Bretagne, France) and received an M.S. degree from the International Space University.

Frédéric Bastide is working at the European GNSS Supervisory Authority (GSA) where he is in charge of Galileo signals. He is also involved in coordination activities with other GNSSes. He graduated as an electronics engineer at the ENAC in 2001 and obtained a Ph.D. in GNSS studies from the Institut National Polytechnique de Toulouse.

Tony (A. R.) Pratt graduated with a B.Sc. and Ph.D. in electrical and electronic engineering from Birmingham University, UK. He joined the teaching staff at Loughborough University, UK, in 1967 and remained until 1980. He held visiting professorships at Yale University, Indian Institute of Technology (IIT) New Delhi and at the University of Copenhagen. In 1980, he joined Navstar Ltd., as technical director. In 1991, he joined Peek acting in several roles including running Tollstar, a road tolling opportunity. He left Peek in 1997 and joined Navstar Systems Ltd. as a technical consultant. He is now technical director (GPS) with Parthus. He is also a special professor at the IESSG, University of Nottingham, UK. He acts as consultant to the UK government in the development of the Galileo satellite system.

John I. R. Owen is Leader of Navigation Systems, Air Systems Department, Dstl. He is a Dstl senior fellow, a fellow of the Royal Institute of Navigation. He gained a BSc (Hons) in electrical and electronic engineering, Loughborough University, and joined the Royal Aircraft Establishment to research aspects of aircraft antennas. He helped develop the first GPS adaptive antenna system. He moved to the satellite navigation research group in 1982 and was responsible for the technical development of GPS receivers, antenna systems, and simulators in the UK. Following the formation of the Defense Establishment Research Agency (DERA), he was responsible for the satellite navigation aspects of UK Ministry of Defense’s research programs for aircraft and missiles. He is technical adviser to the UK Government Departments for GPS and the European Galileo program, where he is active on the Signal Working Group, the Security Board, and the European Space Agency Program Board for Navigation. He chairs the ICAO Global Navigation Satellite Systems spectrum subgroup.

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