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International audience ; GALILEO, the major contribution of the European Union to the Global Navigation Satellite System (GNSS), will be both independent and complementary to the current GPS. It is still in its design phase, and while the signals have to be finalized, the main specifications have already been confirmed. The Binary Offset Carrier (BOC) modulation is part of the current GALILEO signal plan. A BOC modulation multiplies a spreading code with a square wave sub-carrier that has a frequency multiple of the code rate. It creates a split spectrum with two main lobes shifted from the center frequency by the frequency of the sub-carrier. This modulated signal induces better tracking in white noise and better inherent multipath mitigation compared to the spreading code alone. However, it also makes acquisition more challenging and tracking potentially ambiguous due to its multiple peak autocorrelation function. As a result, an evaluation of its performance under different conditions and research on advanced tracking techniques are necessary to assess its robustness and advantages before final selection. This paper focuses on a specific BOC signal: the BOC(1,1). Working on a given signal, instead of trying to find a generic solution, offers the possibility to fully exploit this signal's characteristics to find a more relevant way to improve its performance and cancel its bias threat. A new innovative tracking technique dedicated to BOC(n,n) signals has therefore been developed using a synthesized local correlation function. It completely removes the sidepeak threat and allows clean acquisition and tracking of any BOC(n,n) signal while keeping the same sharp correlation main peak. Consequently, it does not need to check if tracking is done on the main peak. It also offers a good resistance to long-delay multipath. The particular case of BOC(1,1) is taken as an example throughout the paper due to the strong probability that it will be used by the L1 GALILEO civil signal. Both acquisition and tracking are ...

International audience ; GALILEO, the major contribution of the European Union to the Global Navigation Satellite System (GNSS), will be both independent and complementary to the current GPS. It is still in its design phase, and while the signals have to be finalized, the main specifications have already been confirmed. The Binary Offset Carrier (BOC) modulation is part of the current GALILEO signal plan. A BOC modulation multiplies a spreading code with a square wave sub-carrier that has a frequency multiple of the code rate. It creates a split spectrum with two main lobes shifted from the center frequency by the frequency of the sub-carrier. This modulated signal induces better tracking in white noise and better inherent multipath mitigation compared to the spreading code alone. However, it also makes acquisition more challenging and tracking potentially ambiguous due to its multiple peak autocorrelation function. As a result, an evaluation of its performance under different conditions and research on advanced tracking techniques are necessary to assess its robustness and advantages before final selection. This paper focuses on a specific BOC signal: the BOC(1,1). Working on a given signal, instead of trying to find a generic solution, offers the possibility to fully exploit this signal's characteristics to find a more relevant way to improve its performance and cancel its bias threat. A new innovative tracking technique dedicated to BOC(n,n) signals has therefore been developed using a synthesized local correlation function. It completely removes the sidepeak threat and allows clean acquisition and tracking of any BOC(n,n) signal while keeping the same sharp correlation main peak. Consequently, it does not need to check if tracking is done on the main peak. It also offers a good resistance to long-delay multipath. The particular case of BOC(1,1) is taken as an example throughout the paper due to the strong probability that it will be used by the L1 GALILEO civil signal. Both acquisition and tracking are studied and compared with the standard tracking algorithm, first theoretically and then using simulations.

International audience ; This paper will show how frequency diversity improves the availability of accurate navigation solution of GNSS receivers, in the case of aeronautical applications for instance. Therefore, frequency diversity is a mean to mitigate jamming and interferences, to consider among others. It is very important for civil aviation to handle a probabilistic theory related to involuntary jamming of GNSS receivers, with and without the use of frequency diversity. As a preliminary hypothesis, we assume that the GNSS link budgets has been equally balanced for each considered band Bi, even if a band is provided with more interferers than an other. In this later case, this would mean that the GNSS power is higher in the band provided with more interferers. This first assumption can be translated in probabilistic terms. The second assumption made is a jamming probability much smaller than 1. These assumptions are used to derive: - The probability to lose the navigation solution of a monosystem dual frequency receiver, like a L1/L5 GPS or GALILEO receiver. - The probability to lose the navigation solution of a monosystem tri-frequency receiver, like a L1/L2/L5 GPS receiver or a GALILEO E5a/E5b/L1 or E5b/E6/L1 receiver. An application is computed, for a jamming probability of 1/10000 during a full flight. In such a case, the probability to loose the dual frequency navigation function is 15000 times lower in the case of a tri-frequency monosystem receiver instead of a dual frequency monosystem receiver, and this makes this event an improbable case. Intermediate conclusions has been drawn : Frequency diversity has an enormous potential as an interference mitigation mean, which can be at least as efficient as beam forming reception GNSS antennas. - To have an efficient ionospheric correction, the availability of two frequencies among a single system is necessary - The use of L1C/A, L2C, and L5 is interesting for a more robust GPS receiver. The L2C channel can be considered as a backup ; L2C is the mitigation mean. - The use of E5a, E5b, and L1BOC(1,1) is also very interesting for an aeronautic GALILEO receiver, since all these 3 bands are ARNS. The E6 Galileo frequency (provided with integrity) could even be a backup to one E5 signal componant if necessary. The capabability to process ionospheric corrections using only E5a and E5b GALILEO signal componants will be discussed, thanks to code/carrier divergence observations. The paper will also show that E5b C/No degradation due to military radar spurious is low and acceptable.

International audience ; Because of the limited availability of the spectrum allocated for navigation systems, the numerous navigation signals broadcast by Modernized GPS and Galileo system will have to be combined and employ bandwidth-efficient modulations. Indeed, the GPS modernization scheme entails the addition of the new military signal (M-code) to the established C/A and P(Y) codes at the same carrier frequency. One of the most important questions is how to combine this new signal with the legacy ones at the payload level, while maintaining good performance at reception. This problem also exists for Galileo since: - in the L1 band, the Open Service (OS) signal (two channels) and the Public Regulated Service (PRS) signal must be transmitted on the same carrier. - in the E6 band, the Commercial Service (CS) signal must be transmitted with the PRS signal. The Interplex modulation, a particular phase-shiftedkeyed/ phase modulation (PSK/PM), was chosen to transmit all these signals because it is a constant-envelope modulation, thereby allowing the use of saturated power amplifiers with limited signal distortion ([STF, 2002; Rajan and Irvine, 2005]). The main objective of this paper is to study the Interplex modulation, as it is used for the GPS and Galileo signals. In a first part we will present the Interplex modulation, its general formulation and its application for the multiplexing of three signals. Then, we will be interested in the application of this modulation to the GPS L1 signals and the Galileo L1 signals. We will give the general expression of the GPS L1 Interplex signal and show the modification which must be made on the general expression of the Interplex modulation to apply it to the case of the combination of the C/A and P(Y) codes with the new M-code. With regards to the Galileo signals we will study two different cases. In the first case we will consider that the OS signal is a classical BOC(1,1). In the second case we will make the study, assuming that the OS signal is the new signal called ...

International audience ; Because of the limited availability of the spectrum allocated for navigation systems, the numerous navigation signals broadcast by Modernized GPS and Galileo system will have to be combined and employ bandwidth-efficient modulations. Indeed, the GPS modernization scheme entails the addition of the new military signal (M-code) to the established C/A and P(Y) codes at the same carrier frequency. One of the most important questions is how to combine this new signal with the legacy ones at the payload level, while maintaining good performance at reception. This problem also exists for Galileo since: - in the L1 band, the Open Service (OS) signal (two channels) and the Public Regulated Service (PRS) signal must be transmitted on the same carrier. - in the E6 band, the Commercial Service (CS) signal must be transmitted with the PRS signal. The Interplex modulation, a particular phase-shiftedkeyed/ phase modulation (PSK/PM), was chosen to transmit all these signals because it is a constant-envelope modulation, thereby allowing the use of saturated power amplifiers with limited signal distortion ([STF, 2002; Rajan and Irvine, 2005]). The main objective of this paper is to study the Interplex modulation, as it is used for the GPS and Galileo signals. In a first part we will present the Interplex modulation, its general formulation and its application for the multiplexing of three signals. Then, we will be interested in the application of this modulation to the GPS L1 signals and the Galileo L1 signals. We will give the general expression of the GPS L1 Interplex signal and show the modification which must be made on the general expression of the Interplex modulation to apply it to the case of the combination of the C/A and P(Y) codes with the new M-code. With regards to the Galileo signals we will study two different cases. In the first case we will consider that the OS signal is a classical BOC(1,1). In the second case we will make the study, assuming that the OS signal is the new signal called ...

International audience ; Under the 2004 Agreement on the Promotion, Provision, and Use of Galileo and GPS Satellite-Based Navigation Systems and Related Applications, the member states of the European Union and the United States agreed on working together, intensifying thus the cooperation on interoperability and compatibility issues between Galileo and GPS. Among other topics, one important focus was the E1/L1 frequency band, centred at 1575.42 MHz, where the Galileo E1 Open Service (OS) signal and the modernized GPS L1 civil (L1C) signal are going to be transmitted along with many other RNSS signals. Recent efforts made by US and European experts identified a common optimized Power Spectral Density (PSD) frame, known as Multiplexed BOC (MBOC), in which both the Galileo E1 OS and the GPS L1C signals would fit. This normalized MBOC PSD is actually formed by the sum of 10/11 of the normalized BOC(1,1) PSD and 1/11 of the normalized BOC(6,1) PSD. Because the MBOC is defined in the frequency domain, the time representation cannot be uniquely defined, and at least two different implementations that would still comply with the MBOC spectrum exist: CBOC and TMBOC. Indeed, the latest developments indicate that the main Galileo E1 OS and GPS L1C candidates will exhibit different features [3],[4]: - The current GPS L1C main candidate will have a pure BOC(1,1) data channel gathering 25% of the total signal power while the pilot channel will use a Time- Multiplexed BOC (TMBOC) modulation with 75% of the total civil signal power. - The current Galileo E1 OS main candidate will equally share its power between its data and pilot channels, with the important difference with respect to TMBOC that in both channels a Composite BOC (CBOC) modulation with BOC(6,1) will be used. It is well-understood that the definition of a common PSD for the GPS and Galileo civil signals on E1/L1 calls for an increased interoperability and compatibility of these signals at the user level. However, to really promote the use of GPS/Galileo E1/L1 ...

International audience ; Under the 2004 Agreement on the Promotion, Provision, and Use of Galileo and GPS Satellite-Based Navigation Systems and Related Applications, the member states of the European Union and the United States agreed on working together, intensifying thus the cooperation on interoperability and compatibility issues between Galileo and GPS. Among other topics, one important focus was the E1/L1 frequency band, centred at 1575.42 MHz, where the Galileo E1 Open Service (OS) signal and the modernized GPS L1 civil (L1C) signal are going to be transmitted along with many other RNSS signals. Recent efforts made by US and European experts identified a common optimized Power Spectral Density (PSD) frame, known as Multiplexed BOC (MBOC), in which both the Galileo E1 OS and the GPS L1C signals would fit. This normalized MBOC PSD is actually formed by the sum of 10/11 of the normalized BOC(1,1) PSD and 1/11 of the normalized BOC(6,1) PSD. Because the MBOC is defined in the frequency domain, the time representation cannot be uniquely defined, and at least two different implementations that would still comply with the MBOC spectrum exist: CBOC and TMBOC. Indeed, the latest developments indicate that the main Galileo E1 OS and GPS L1C candidates will exhibit different features [3],[4]: - The current GPS L1C main candidate will have a pure BOC(1,1) data channel gathering 25% of the total signal power while the pilot channel will use a Time- Multiplexed BOC (TMBOC) modulation with 75% of the total civil signal power. - The current Galileo E1 OS main candidate will equally share its power between its data and pilot channels, with the important difference with respect to TMBOC that in both channels a Composite BOC (CBOC) modulation with BOC(6,1) will be used. It is well-understood that the definition of a common PSD for the GPS and Galileo civil signals on E1/L1 calls for an increased interoperability and compatibility of these signals at the user level. However, to really promote the use of GPS/Galileo E1/L1 combined receivers, it is of greatest importance to find GPS L1C and Galileo E1 OS tracking architectures that minimize the receiver complexity while maintaining high quality measurements. This is particularly true since the main candidates for implementation of MBOC for GPS L1C and Galileo E1 OS are already baseline of their respective systems [3]. The purpose of this article is to thoroughly investigate possible GPS/Galileo receiver architectures that could be adapted to CBOC, TMBOC or both waveforms and to assess their performance. The first step of the proposed analysis is to assess the interference that both GPS and Galileo signals will cause on each other. This step is necessary in order to evaluate the degradation that Galileo and GPS signals will cause on each other, and thus, to assess precisely the quality of the forthcoming tracking loops. In a second part, several CBOC/TMBOC tracking architectures meant to minimize the complexity of a combined GPS/Galileo receiver will be presented and their performances in terms of resistance to thermal noise and multipath, as well as their complexity, will be compared to optimal architectures dedicated to CBOConly or TMBOC-only receivers. This part aims at giving an insight on which key parameters can be modified to find a relevant trade-off between receiver complexity and performance for the general user. Finally, in the last section, different multipath mitigation techniques will be tested according to different receiver configurations - BOC(1,1) or MBOC receiver - and flexibility in the number of correlators available for each channel - pilot or data + pilot tracking. In particular, innovative multipath mitigation techniques based on a multi-correlator receiver are also investigated.

International audience ; Jamming situations taking place as part of anti-drone struggle or military exercises are a threat for civil aviation. During these jamming operations, in order to protect civil aviation operations, segregation zones (also called protection zone in this article) are elaborated in which GNSS ICAO minimum requirements are not guaranteed. Segregation zones refer to the area, determined by the regulator, in which pilots are warned of a potential GNSS service failure because of the jamming. Currently, these protection areas are deduced from the ITU standardized interference mask but it appears that these protection areas are much larger than the observed impacted zone, highlighting thus the inefficiency of the current method. In this article, first a clarification on the interpretation of the interference mask is proposed, in order to explain the difference between the size of the protection zone and the impacted area. Second, a new method is proposed to compute a new protection zone, and this method estimates the true impacted zone considering local RFI situation. The main innovation of this new method is to take into account the situation of the jammer in terms of aeronautical interference level in its local surroundings. The main advantage of this method is the protection area size reduction while still guaranteeing that minimum GNSS ICAO requirements are respected.

International audience ; Jamming situations taking place as part of anti-drone struggle or military exercises are a threat for civil aviation. During these jamming operations, in order to protect civil aviation operations, segregation zones (also called protection zone in this article) are elaborated in which GNSS ICAO minimum requirements are not guaranteed. Segregation zones refer to the area, determined by the regulator, in which pilots are warned of a potential GNSS service failure because of the jamming. Currently, these protection areas are deduced from the ITU standardized interference mask but it appears that these protection areas are much larger than the observed impacted zone, highlighting thus the inefficiency of the current method. In this article, first a clarification on the interpretation of the interference mask is proposed, in order to explain the difference between the size of the protection zone and the impacted area. Second, a new method is proposed to compute a new protection zone, and this method estimates the true impacted zone considering local RFI situation. The main innovation of this new method is to take into account the situation of the jammer in terms of aeronautical interference level in its local surroundings. The main advantage of this method is the protection area size reduction while still guaranteeing that minimum GNSS ICAO requirements are respected.

International audience ; Under the 2004 Agreement on the Promotion, Provision, and Use of GALILEO and GPS Satellite-Based Navigation Systems and Related Applications, the member states of the European Union and the United States agreed on working together, intensifying thus the cooperation on interoperability and compatibility issues between GALILEO and GPS. Among other topics, one important focus was the E1/L1 frequency band, centred at 1575.42 MHz, where the GALILEO Open Service (OS) signal and the modernized L1 civil (L1C) signal are going to be transmitted along with many other RNSS signals. The opportunity to design new signals in this preeminent radionavigation frequency band has significant importance to future users worldwide. Recent joint efforts by United States and European experts have identified MBOC (multiplexed BOC) [1][2][3][4][5] as a promising joint solution for E1 OS and L1C, along with multiple sets of spreading waveforms that yield this optimized spectrum. The resulting optimized E1 OS and L1C spreading modulations enable receivers to obtain significantly better performance in multipath than with previously considered spreading modulations, along with other potential benefits. The optimized spreading modulation provides considerable flexibility for receiver designers, and simpler receivers that employ only BOC(1,1)-based processing, experience very modest performance degradation, compared to the baseline BOC(1,1) spreading modulation.

International audience ; Under the 2004 Agreement on the Promotion, Provision, and Use of GALILEO and GPS Satellite-Based Navigation Systems and Related Applications, the member states of the European Union and the United States agreed on working together, intensifying thus the cooperation on interoperability and compatibility issues between GALILEO and GPS. Among other topics, one important focus was the E1/L1 frequency band, centred at 1575.42 MHz, where the GALILEO Open Service (OS) signal and the modernized L1 civil (L1C) signal are going to be transmitted along with many other RNSS signals. The opportunity to design new signals in this preeminent radionavigation frequency band has significant importance to future users worldwide. Recent joint efforts by United States and European experts have identified MBOC (multiplexed BOC) [1][2][3][4][5] as a promising joint solution for E1 OS and L1C, along with multiple sets of spreading waveforms that yield this optimized spectrum. The resulting optimized E1 OS and L1C spreading modulations enable receivers to obtain significantly better performance in multipath than with previously considered spreading modulations, along with other potential benefits. The optimized spreading modulation provides considerable flexibility for receiver designers, and simpler receivers that employ only BOC(1,1)-based processing, experience very modest performance degradation, compared to the baseline BOC(1,1) spreading modulation.