T h eG A RDAP r o j e c t Building a Galileo Receiver GARDAconsortium at the Final Presentation The long history of the Galileo program’s development has tended to focus on the design, construction, and launch of the system’s satellites. But an equally important activity is the development of Galileo-capable user equipment. Leaders of an engineering team that has developed a multi- frequency Galileo receiver describe their efforts and the results. LIVIO MaRRADI, GianlUCA FRanZOni, Framework Program to study, design, Galileo receiver products and prepare LUCIO FOGLIA, DaRIO FOssati and develop the essential technologies, the way for user receivers to be “ready ALCatEL ALENIA SpaCE Italia components, applications, and services on the market” when the Galileo system CaRLO CORNACCHINI for the Galileo user segment. becomes operational. The design flexi- SpaCE ENGINEERING, ItalY In response to the first call, Alcatel bility also allows a quick reaction to the MaRC LE GOFF, LUC DUCHESNE, LARS FOGED Alenia Space Italia (AASI) was selected evolution and changes in the Galileo SatiMO, FRANCE to lead a consortium responsible for signal specification. ANTONIOJ. FER NANDEZ,AU GUSTOCa RAMagnO developing Galileo receiver technologies In particular, the GARDA design is DEIMOS, Spain within the (GAlileo user Receiver Devel- the basis for the on-going development opment Activities (GARDA) program. of a safety-of-life (SoL) receiver within ROBERT SCHWEIKERT, THOMAS WOERZ Table 1 lists consortium members and the GJU’s Galileo Integrity Receiver for AUDENS ACT, GERMANY their responsibilities in GARDA. Advanced Safety Of Life Equipment VINCENT GABagliO Within the GARDA project, AASI (GIRASOLE) project. Further, GARDA GALILEO JOINT UNDERtaKING has developed a prototype receiver receivers are going to be used within capable of processing L1, E5a/E5b, and the Galileo receiver chain of the ground E6 Galileo signals in addition to GPS L1. mission segment sensor stations to feed s Galileo satellites begin reach- This represents one of the first GPS/Gali- data to the Galileo orbit determination, ing orbit and transmitting their leo receivers. In developing this proto- integrity and timing facilities. signals, a critical complement type receiver, efforts have been made to The GARDA project has also pro- needs to be in place for the user define the architecture of the RF front- vided the opportunity to analyze future Acommunity: Galileo-capable receivers. end and baseband sections to be as flex- market of Galileo applications, to study In the frame of Europe’s development, ible as possible. some core receiver processing tech- of Galileo, the Galileo Joint Undertaking The aim of the GARDA project was niques and also to develop two impor- (GJU) has issued three calls since 2003 to develop a modular architecture that tant components such as the Galileo RF under the European Commission’s 6th could be the basis for future AASI GPS/ signal simulator as well as a complete 40 InsideGNSS NOVEMBER/DECEMBER 2006 www.insidegnss.com Galileo receiver and environment SW structure providing maximum com- Company/Institute Activity simulation tool. monality with corresponding GPS pro- Alcatel Alenia Space Receiver& C oreTechnologies This article will describe the design cessing. Italia and testing of the receiver technology Multipath mitigation. In particular, Deimos Space GRANADA SW Simulator developed under the GARDA program. professional and safety-of-life applica- Audens Act Core Technologies We will begin by describing the design tions with requirements for high accu- Space Engineering Galileo RF Signal Simulator challenges and core technologies identi- racy will benefit from effective multipa- fied as crucial for receiver development. th mitigation techniques. In GARDA, Satimo Antenna Then we will address the receiver archi- the performance of various multipath BoozH allenH amilton Market Analysis & Rx tecture, functions, and designs devel- mitigation strategies on signal process- Development Plan oped and tested in a prototype system ing level has been extensively studied, Politecnico diTorino Core Technologies before implementation in the final prod- with specific focus on techniques that Prague Technical Core Technologies uct. A section of the article addresses the adequately support multipath mitiga- Univ. development of two GNSS simulators tion for the BOC(1,1) signal on Galileo ST Microelectronics Consumer applications as part of the GARDA initiative. These L1. As a result, these efforts determined Advanced Aviation Certification and Safety simulators were used to help in test- that a combination of a “narrow corre- Tech. bench design and development of the lator” discriminator with a multipath TABLE 1. GARDA consortium partners and tasks receivers as well as in testing and perfor- estimation unit leads to promising per- mance verification, along with commer- formance. cial simulators. The article will conclude Cross-Correlation Mitigation. Depend- Core Technology Receiver Types with a discussion of key results from test ing on the application, future GNSS Code & Carrier Phase all evaluations of the GARDA receiver. navigation receiver performance may be Tracking affected by quite different interference Code Acquisition all Core Technologies sources. While for aeronautical applica- Multipath Mitigation professional, safety- Due to the new Galileo signal-in-space tions the terrestrial radio navigation sys- of-life (SIS) structure, Galileo receivers will tem DME/TACAN and a military com- Cross-Correlation consumer/massmarket have to operate and process naviga- munication system JTIDS may represent Mitigation tion signals that differ substantially major interference sources, navigation Positioning with limited consumer/massmarket from GPS C/A code by different chip- receivers using signals on E6 may be signal ping rates, introduction of pilot signal mainly affected by pulsed interference Hybrid PVT consumer/massmarket components or different signal formats, from L-band radar. Measurements Quality professional, safety- such as binary offset carrier or BOC(1,1) For terrestrial mobile applications Control of-life on in the L1 frequency band and Alt- using consumer/mass market receivers TABLE 2. CoreTechnological Topics studied by BOC(15,10) on the E5a and E5b bands. that operate in environments character- GARDA Consequently, GARDA identified core ized by severe shadowing, navigation per- technological areas considered essential formance — in particular, the receiver’s for future Galileo receivers, including a acquisition capability — will most likely subset of selected topics with respect to suffer from intra-system interference. Advanced positioning with limited sig- signal processing. Table 2 summarizes This will arise from cross-correlation nals and hybrid PVT. User equipment tar- these focus technologies together with interference due to substantially different geting the consumer mass market will the corresponding receiver types tar- received GNSS signal power levels. mainly take the form of small, low-cost geted for application of them.. GARDA studies on cross-correla- navigation-only receivers using single- Code acquisition and code & carrier tion mitigation have consequently been frequency Galileo and/or GPS L1 signals, phase tracking. Code acquisition, as well focused on consumer/mass market or will be integrated into handheld com- as code & carrier phase tracking, are receivers employing Galileo L1 signals munication user terminals. Particularly fundamental signal processing functions only. As those receivers commonly use for combined navigation/communica- of any navigation receiver. The GARDA 1-bit analog/digital convertors (ADCs), a tions (NAV/COM) mobile terminals, studies have focused on various acquisi- multipath mitigation approach has been positioning may be only required if, for tion and tracking strategies that exploit proposed that can still operate assum- example, a location-based service (LBS) the properties of the new Galileo signal ing 1-bit input quantization. As could be is initiated. In this case “one-shot” posi- structures, particularly, on L1 and E5. shown for a quite severe interference sce- tioning is apparently preferable, because Our efforts placed special empha- nario, by using the proposed mitigation of the savings in power consumption. sis on the development of algorithms technique, the effect of cross-correlation In GARDA, researchers extensively that lead not only to good performance on the acquisition performance may be studied the performance of various figures but also to a required hardware reduced to an almost negligible level. approaches to advanced positioning with www.insidegnss.com NOVEMBER/DECEMBER 2006 InsideGNSS 41 gaRDA PROJECT FIGURE 1 Receiver Block Diagram limited signals, with a focus on adapting an extended Kalman filter as well as an Digital section. AASI designed and promising techniques to the new Gali- alternative. developed a new proprietary digital leo L1 signal structure. Combined NAV/ channel specifically to process Galileo COM mobile terminals may achieve a Receiver Architecture and GPS signals. The channel, named higher integration of navigation and ter- and Functions GALVANI, was designed and simulated restrial communications by basing posi- Three main modules comprise the through a Simulink design process and tioning/velocity/timing (PVT) solutions GARDA receiver architecture designed ported to Very High Speed Integrated not only on GNSS signals-in-space but by AASI. Circuit Hardware Description