MBOC The new optimized spreading modulation

MBOC: The New Optimized SpreadingModulation Recommended for GALILEOL1 OS and GPS L1CGuenter W. Hein, Jose-Angel Avila-Rodriguez,Stefan Wallner, Anthony R. Pratt, John Owen,Jean-Luc IsslerJohn W. Betz, Chris J. Hegarty, Lt Sean Lenahan,Joseph J. Rushanan, Andrea L. Kraay,Thomas A. StansellGuenter W. Hein is Full Professor and Director of theInstitute of Geodesy and Navigation at the UniversityFAF Munich. He is responsible for research andteaching in the fields of high-precision GNSS positioning and navigation, physical geodesy and satellitemethods.

He has been working in the field of GPS since1984 and is author of numerous papers on kinematicpositioning and navigation as well as sensor integration.In 2002 he received the prestigious “Johannes KeplerAward“ from the US Institute of Navigation (ION) for”sustained and significant contributions to satellitenavigation“. Presently he is heavily involved in theGALILEO program.Christopher J. Hegarty is a Senior Principal Engineerwith The MITRE Corporation's Center for AdvancedAviation System Development.

He received a D.Sc. inElectrical Engineering from The George WashingtonUniversity. He is a member of RTCA's ProgramManagement Committee and co-chair of RTCA SpecialCommittee 159. He was a recipient of the 1998 IONEarly Achievement Award and the 2005 JohannesKepler Award. He currently serves the ION as Editor ofNAVIGATION: Journal of the Institute of Navigationand as Eastern Region Vice President.Stefan Wallner studied at the Technical University ofMunich and graduated in 2003 with a Diploma inTechno-Mathematics. He is now research associate atthe Institute of Geodesy and Navigation at the Universityof the Federal Armed Forces Germany in Munich.

Hismain topics of interests can be denoted as the SpreadingCodes and the Signal Structure of GALILEO.John W. Betz is a Fellow of The MITRE Corporation.His PhD in Electrical and Computer Engineering is fromNortheastern University. He contributed to the design ofthe GPS M-code signal, led the Modulation andAcquisition Design Team, and developed the binaryoffset carrier (BOC) modulation.

He has contributed tomany aspects of GNSS engineering, and has participatedin international efforts to achieve compatibility andinteroperability between GPS and other satellitenavigation systems. He received the ION Burka Awardin 2001, and is a member of the US Air Force ScientificAdvisory Board, and a Fellow of the ION.Anthony R.

Pratt graduated with a B.Sc. and Ph.D. inElectrical and Electronic Engineering from BirminghamUniversity, UK. He joined the teaching staff atLoughborough University, UK in 1967 and remaineduntil 1980. He held visiting professorships at YaleUniversity, IIT New Delhi and at the University ofCopenhagen. In 1980, he joined Navstar Ltd, asTechnical Director. In 1991, he joined Peek acting inseveral roles including running Tollstar, a road tollingopportunity. He left Peek in 1997 and joined NavstarSystems Ltd as Technical Consultant. He is nowTechnical Director (GPS) with Parthus.

He is also aSpecial Professor at the IESSG, University ofNottingham, UK. He acts as Consultant to the UKGovernment in the development of GALILEO SatelliteSystem.José-Ángel Ávila-Rodríguez is research associate at theInstitute of Geodesy and Navigation at the University ofthe Federal Armed Forces Munich. He is responsible forresearch activities on GNSS signals, including BOC,BCS, and MBCS modulations. He is involved in theGALILEO program, in which he supports the EuropeanSpace Agency, the European Commission, and theGALILEO Joint Undertaking, through the GALILEOSignal Task Force. He studied at the TechnicalUniversities of Madrid, Spain, and Vienna, Austria, andhas an M.S. in electrical engineering. His major areas ofinterest include the GALILEO signal structure, GNSSreceiver design and performance, and GALILEO codes.0-7803-9454-2/06/$20.00/©2006 IEEELt Lawrence S.

Lenahan is the L1C Project MilitaryCo-Chair and works for the GPS Joint Program Office inits Engineering and Advanced Technology Branch, after3 years with the 2d Space Operations Squadron as its883S.M. and Engineer’s degree in Electrical Engineeringand Computer Science from the Massachusetts Instituteof Technology and Woods Hole OceanographicInstitution in 2003. From 1997 until 2000 she worked asan engineer for Digital Systems Resources, Inc. inFairfax, Virginia developing and testing algorithms forunderwater target detection and classification.

From2000 to 2003 she was a research assistant at MIT’sOcean Engineering Acoustics Laboratory in Cambridge,Massachusetts where she conducted research in reducedrank adaptive array processing techniques forinterference cancellation and improved power estimationin non-stationary environments. She is currently a seniorengineer in the Signal Processing Group at the MITRECorporation in Bedford, Massachusetts working in radar,navigation, and communications system design.Engineer On-Call for Spacecraft Anomalies.

Lt Lenahanreceived a B.S. degree from the United States Air ForceAcademy in Astronautical Engineering and is currently amember of ION and AIAA.John I. R. Owen is Leader of Navigation Systems, AirSystems Department, DSTL. He is a DSTL SeniorFellow, a Fellow of the Royal Institute of Navigation.He gained a BSc (Hons) in Electrical and ElectronicEngineering, Loughborough University, and joined theRoyal Aircraft Establishment to research aspects ofaircraft antennas. He helped develop the first GPSadaptive antenna system.

He moved to the satellitenavigation research group in 1982 and was responsiblefor the technical development of GPS receivers, antennasystems and simulators in the UK. Following theformation of DERA, he was responsible for the satellitenavigation aspects of UK MOD’s research programmesfor aircraft and missiles. He is technical adviser to UKGovernment Departments for GPS and the EuropeanGALILEO programme, where he is active on the SignalWorking Group, the Security Board and the EuropeanSpace Agency Programme Board for Navigation. Hechaired the ICAO Global Navigation Satellite Systemsspectrum subgroup.Tom Stansell heads Stansell Consulting, after 8 yearswith the Johns Hopkins Applied Physics Laboratory, 25years with Magnavox (Staff VP), and 5 years with Leica(VP), pioneering Transit and GPS navigation and surveyproducts.

He served on the WAAS Independent ReviewBoard (2000); led technical development of the GPSL2C signal (2001); and is coordinator of the GPS L1Cproject. ION and other awards: Weems Award (1996),Fellow (1999), Kershner (PLANS-2000), GPS JPONavstar Award (2002), and Johannes Kepler (2003). Hewas technical chair (’84, ’86, and ’88) and general chair(’94, ’96, and ’98) of PLANS conferences, technicalchair of ION GPS-91, and general chair of ION GPS-92.He also is Western Regional VP of the ION.Jean-Luc Issler is head of the Transmission Techniquesand signal processing department of CNES, whose maintasks are signal processing, air interfaces and equipmentsin Radionavigation, TT&C, Image telemetry,propagation and spectrum survey. With DRAST andDGA, he represents France in the GALILEO SignalTask Force of the European Commission.

Lionel Ries,Antoine DeLatour and Laurent Lestarquit, from histeam, were deeply involved in the design of CBOC, oneof the recommended optimized GALILEO OS signal. Heis involved in the development of several spacebornereceivers in Europe. He received the “AstronauticalPrize” from the “Association Aeronautique etAstronautique de France” for his involvement in theGALILEO frequency choice and signal designABSTRACTThis paper describes the Multiplexed Binary Offset Carrier(MBOC) spreading modulation that has been recommended bythe GPS-GALILEO Working Group on Interoperability andCompatibility.

The MBOC(6,1,1/11) power spectral density isa mixture of BOC(1,1) spectrum and BOC(6,1) spectrum, thatwould be used by GALILEO for its Open Service (OS) signalat L1 frequency, and also by GPS for its modernized L1 Civil(L1C) signal. A number of different time waveforms canproduce the MBOC(6,1,1/11) spectrum, allowing flexibility inimplementation, although interoperable waveforms remains anobjective for GALILEO and GPS. The time-multiplexed BOC(TMBOC) implementation interlaces BOC(6,1) and BOC(1,1)spreading symbols in a regular pattern, whereas compositeBOC (CBOC) uses multilevel spreading symbols formed fromthe weighted sum of BOC(1,1) and BOC(6,1) spreadingsymbols, interplexed to form a constant modulus compositesignal.

This paper provides information on the history,motivation, and construction of MBOC signals. It then showsvarious performance characteristics, and summarizes theirstatus in GALILEO and GPS signal design.Joseph J. Rushanan is a Principal Mathematician in theSignal Processing Section of the MITRE Corporation.His expertise includes discrete mathematics, includingbinary sequences, and general security engineering. Hehas a BS and MS in 1982 from the Ohio State Universityand a Ph. D. from the California Institute of Technologyin 1986, all in mathematics.

He has been with MITREsince 1986.Andrea L. Kraay received a B.S. in ElectricalEngineering from George Mason University in 1999, a884-60On June 26th, 2004, the United States of America and theEuropean Community established the "Agreement on thePromotion, Provision and Use of GALILEO and GPSSatellite-Based Navigation Systems and Related Applications"[1]. One aspect of the Agreement was to adopt a commonbaseline signal to be transmitted in the future by GALILEOand GPS at the L1 center frequency of 1575.42 MHz.Although the Agreement established BOC(1,1) as the baselinefor GALILEO L1 OS and GPS future L1C signals, it alsostated that the Parties shall work together toward achievingoptimization of that modulation for their respective systems,within the constraints of the Agreement.-65Power Spectral Density (dBW/Hz)INTRODUCTION-70BOC(1,1)-75-80-85-90-95-100-20A recent joint design activity involving experts from theUnited States and Europe has produced a recommendedoptimized spreading modulation for the L1C signal and theGALILEO L1 OS signal [2, 3].

The spreading modulationdesign places a small amount of additional power at higherfrequencies in order to improve signal tracking performance.This paper describes the spreading modulation’s powerspectral density (PSD), as well as alternative spreading timeseries and their autocorrelation functions. In addition, variousmeasures are used to assess the performance benefits of theoptimized modulation compared to those of othermodulations.

The status and way ahead are then summarized.-15-10-50510Offset from Center Frequency (MHz)1520Fig. 1. Unit Power PSD of BPSK-R(1) and BOC(1,1)Spreading Modulations, Showing BOC(1,1)’s AdditionalPower at Higher FrequenciesMBOC(6,1,1/11)’s resulting increase in higher frequencypower, compared to that of BOC(1,1), is evident in Fig. 2. Aswill be seen, the improvement in high frequency power forsignal tracking can be even greater than what is shown inFig. 2 by placing all or most of the BOC(6,1) symbols, whichprovide the additional high frequency power, in the pilotcomponent of the signal.MBOC POWER SPECTRAL DENSITY-60-65Power Spectral Density (dBW/Hz)The spreading modulation for the legacy civil signal at1575.42 MHz, the GPS C/A code, is based on binary phaseshift keyed signal with a rectangular pulse shape and aspreading code chip rate of 1.023 MHz, denoted BPSK-R(1).While very good performance can be obtained with the C/Acode signal, it has been recognized that better performance canbe obtained using spreading modulations that provide morepower at high frequencies away from the center frequency.Binary offset carrier (BOC) spreading modulations [4] are oneway to accomplish this, and a BOC(1,1) spreading modulationwas selected as the baseline for the future GALILEO L1 OSand GPS L1C signals.