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International audience; In order to address the Global Navigation Satellite Systems (GNSS) signal data rate increase challenge, as well as the GNSS signal data availability in urban environments issue, this paper proposes a new designed GNSS signal. Code-Shift Keying (CSK) modulation has been chosen as an alternative to current Binary PhaseShift Keying (BPSK) since it allows increased data rates and non-coherent demodulation. In addition, the new CSK-modulated signal is protected by a Low-Density Parity-Check (LDPC) channel code, as in the latest GNSS designed signal, GPS III L1C. Firstly, an asymptotic analysis is done via EXtrinsic Information Transfer (EXIT) charts in an Additive White Gaussian Noise (AWGN) propagation channel, to show that bitinterleaved iterative decoding for a CSK-modulated signal (consisting in adding a soft feedback between the LDPC decoder and the CSK demodulator) can significantly outperform non-iterative decoding. Based on this analysis, an asymptotic optimization is performed in order to design the optimized LDPC channel code profiles, for a CSK-modulated signal, in an AWGN propagation channel and for iterative decoding. From these results, finite length parity-check matrices have been generated thanks to state of the art algorithms such as the Progressive Edge Growth (PEG) algorithm, and simulation results are presented. Finally, in an AWGN context, the current GPS L1C subframe 2 (used as a benchmark) demodulation performance is compared to the demodulation performance obtained for CSK-modulated signals with 2 bits and 6 bits per CSK symbol, protected by different optimized LDPC channel codes and iteratively decoded. The results show that a CSK-modulated signal iteratively decoded and implementing the LDPC codes optimized in this work, exhibits a decoding gain of 0.6 dB for 2 bits per CSK symbol and of 1.2 dB for 6 bits per CSK symbol with respect to the current GPS L1C subframe 2 LDPC code. The study has been made in an AWGN propagation channel as a first step, but results are really promising for urban propagation channels.

Satellite navigation signals demodulation performance is historically tested and compared in the Additive White Gaussian Noise propagation channel model which well simulates the signal reception in open areas. Nowadays, the majority of new applications targets dynamic users in urban environments; therefore the GNSS signals demodulation performance has become mandatory to be provided in urban environments. The GPS L1C signal demodulation performance in urban environments is thus provided in this paper. To do that, a new methodology adapted to provide and assess GNSS signals demodulation performance in urban channels has been developed. It counteracts the classic method limitations which are the fluctuating received C/N0 in urban environments and the fact that each received message is taken into account in the error rate computation whereas in GNSS it is not necessary. The new methodology thus proposes to provide the demodulation performance for "favorable" reception conditions together with statistical information about the occurrence of these favorable reception conditions. To be able to apply this new methodology and to provide the GPS L1C signal demodulation performance in urban environments, a simulator SiGMeP (Simulator for GNSS Message Performance) has been developed. Two urban propagation channel models can be tested: the narrowband Perez-Fontan/Prieto model and the wideband DLR model. Moreover, the impact of the received signal phase estimation residual errors has been taken into account (ideal estimation is compared with PLL tracking).

Satellite navigation signals demodulation performance is historically tested and compared in the Additive White Gaussian Noise propagation channel model which well simulates the signal reception in open areas. Nowadays, the majority of new applications targets dynamic users in urban environments; therefore the implementation of a simulation tool able to provide realistic GNSS signal demodulation performance in obstructed propagation channels has become mandatory. This paper presents the simulator SiGMeP (Simulator for GNSS Message Performance), which is wanted to provide demodulation performance of any GNSS signals in urban environment, as faithfully of reality as possible. The demodulation performance of GPS L1C simulated with SiGMeP in the AWGN propagation channel model, in the Prieto propagation channel model (narrowband Land Mobile Satellite model in urban configuration) and in the DLR channel model (wideband Land Mobile Satellite model in urban configuration) are computed and compared one to the other. The demodulation performance for both LMS channel models is calculated using a new methodology better adapted to urban environments, and the impact of the received signal phase estimation residual errors has been taken into account (ideal estimation is compared with PLL tracking). Finally, a refined figure of merit used to represent GNSS signals demodulation performance in urban environment is proposed.

International audience; Satellite navigation signals demodulation performance is historically tested and compared in the Additive White Gaussian Noise propagation channel model which well simulates open areas. Nowadays, the majority of new applications targets dynamic users in urban environments; therefore the implementation of a simulation tool able to provide realistically GNSS signal demodulation performance in obstructed propagation channels has become mandatory . This paper presents the simulator SiGMeP (Simulator for GNSS Message Performance) which is wanted to provide demodulation performance of any GNSS signals in urban environment , as faithfully of reality as possible . The demodulation performance of GPS L1C/A, GPS L2C, GPS L1C and Galileo E1 OS signals simulated with SiGMeP in the AWGN channel model configuration is firstly showed . Then, the demodulation performance of GPS L1C simulated with SiGMeP in urban environments is presented using the Prieto channel model with two signal carrier phase estimation configurations: perfect signal carrier phase estimation and PLL tracking

http://www.ion.org/publications/abstract.cfm?articleID=9229; International audience; GNSS-based Road User Charging (RUC) systems have recently attracted special attention because of their flexibility and reduced roadside infrastructure. For instance, German and Slovak motorways already perform truck toll collection by means of GPS receivers installed on the vehicles. Road toll belongs to the so-called liability critical applications, which are characterized by the fact that they must use trustful positioning data in order to control the navigation errors and their negative legal or economical consequences. Consequently, integrity monitoring of GNSS signals plays a key role in such systems. Nevertheless, the design of GNSS integrity algorithms like RAIM requires a deep knowledge of the characteristics of the application, the received signals and the environment effects on them. This paper analyzes and provides the required parameters to develop RAIM algorithms for road tolling applications in urban and rural environnements.

International audience; This paper presents the simulation results of a hybrid positioning system based on a pedestrian navigation system that takes advantage of very few measurements of different types as well as map constraints. The data fusion is achieved at infrastructure and user level. Particle and extended Kalman filters are implemented and tested against different beacon density scenarios. Results show that metric accuracy (below 3 meters) is achievable in structured areas of low beacons and WiFi AP density.

Land vehicle navigation in urban areas, where masking effects are very frequent, is a major challenge for both the accuracy and the integrity of GPS-only solution. Several strong effects linked to urban canyon environments can seriously degrade the final position solution. Thus, the sole use of a GPS to navigate in urban areas has been proven to be challenging when high performances are expected in terms of accuracy and integrity of the computed solution.

First driven by the regulation on emergency calls in the United States (E-911), Location Based Services (LBS) are currently gaining more and more importance in everyday life. Numerous positioning technologies are foreseen to allow the location of one user whether he is indoors or outdoors. Among these techniques, GPS and even more GNSS are well adapted to applications requiring accurate positioning whatever the environment (urban or rural). Such a positioning technique requires no extra infrastructure but a chipset to decode and process GPS signals. As a consequence, this makes it very suitable to fulfil the location requirements of applications such as emergency services (US E911), guidance of rescue teams, in-vehicle navigation, e-tourism

First driven by the regulation on emergency calls in the United States (E-911), Location Based Services (LBS) are currently gaining more and more importance in everyday life. Numerous positioning technologies are foreseen to allow the location of one user whether he is indoors or outdoors. Among these techniques, GPS and even more GNSS are well adapted to applications requiring accurate positioning whatever the environment (urban or rural). Such a positioning technique requires no extra infrastructure but a chipset to decode and process GPS signals. As a consequence, this makes it very suitable to fulfil the location requirements of applications such as emergency services (US E911), guidance of rescue teams, in-vehicle navigation, e-tourism

International audience; The Galileo E5 signal is of particular interest to the civil aviation community. Indeed, it will be broadcast in an Aeronautical Radio Navigation Services (ARNS). Moreover, combined with the Galileo E1 signal, Galileo E5 will allow dual-frequency ionosheric-free pseudoranges combinations supporting a dramatic increase of accuracy. In addition, one of its components, E5b, will carry the Galileo integrity message needed by the user to benefit from the Safety-of-Life service (SoL). Civil aviation users have specific requirements in terms of performance of future Galileo receivers. Those requirements are provided by EUROCAE in the interim Minimum Operational Performance Specification (MOPS) document as developed by the Working Group 62. One important minimum requirement is for the receiver to process independently Galileo E5a and E5b signals mainly in order to reduce interference impact and to benefit from the Safety-of-Life (SoL) service. There are different possible signal processing techniques to build a civil aviation receiver achieving the performance requirements which are stated in terms of accuracy and robustness to interference, for instance. This paper presents an overview of the different signal processing techniques expected to be implemented in future Galileo E5 receivers to meet civil aviation requirements. Most of the presented techniques were considered by EUROCAE WG62 to derive requirements. Some new techniques which could provide increased performance, at the cost of an increased complexity in general, are presented as well. The levels of performance achieved by all those techniques are indicated. In the first section of this paper, the Galileo E5 signal, as described in the Galileo SIS ICD, is shortly presented. Then, the architecture of the receiver is described along with the main functions involved and their respective performance for Galileo E5 signal. These functions are: RF/IF filtering, the blanker system (temporal and frequency-based: FDAF), the acquisition process (temporal and frequency-based), tracking process and interference detection techniques.

International audience; This paper presents a real time pedestrian navigation system that combines different type of GPS receivers (namely High Sensitivity GPS and Assisted GPS) with several low-cost inertial sensors to face GPS outages and provide a reliable and continuous position solution. The off-the-shelf inertial module from Xsens is made of several low-cost MEMS type sensors contained in a very small package (58×58×22 mm W×L×H). This unit is composed of a triad of gyroscopes, a triad of accelerometers and a triad of magnetometers as well as a temperature sensor. The measurements of the different sensors are combined to provide an autonomous Pedestrian Navigation System that does not rely on GPS measurements. This navigation method is based on the analysis of the dynamic of the pedestrian, as performed in [1], in order to limit the impact of accelerometer biases that systematically degrades the position accuracy. The remaining gyro drifts are estimated and compensated dynamically through the implementation of an attitude filter that combines the different sensors data. The magnetic interference issue is also addressed with a mitigation technique based on gyros measurements. The Assisted GPS or High Sensitivity GPS receiver and the Pedestrian Navigation System are combined in real time to provide more reliable position solutions and also augment the overall availability especially in deep urban canyons and indoor environments. The coupling methodology follows a loose integration scheme. The Integrated Navigation System is software implemented on an ultra portable PC. The inertial unit is connected to the ultra Portable PC using the serial RS-232 link through the USB serial port. Results show that the real time combination of both navigation systems improves tremendously the availability of the position solution, especially in harsh environments. The accuracy of the position solution during GPS outages is also augmented, and stays within acceptable limits according the trials that are exercised during long GPS outages. It is also shown that the analysis of the coefficients used to model the velocity of the pedestrian allows the detection of bad GPS measurements that prevent the Pedestrian Navigation System from being inaccurately initialized for further standalone navigation.

International audience; The land vehicle navigation using very few GPS updates is studied in this paper using a low-cost MEMS sensors assembly integrated with a conventional GPS receiver. The sensors assembly is composed of triad of accelerometers, gyrometers, magnetometers as well as a pressure sensor, and can easily be taken in or off the car. Since in most of cities, downtown areas block GPS signals, conventional receivers may not be able to compute 3D or even 2D fixes. Therefore, to augment the availability of the position solution in harsh environments, pseudorange and pseudorange rate measurements are fused in a Kalman Filter (KF) with the Dead Reckoning (DR) solution provided by the sensors assembly following a tight integration scheme. In the developed vehicular navigation algorithm, the MEMS sensors are used to provide reliable attitude information of the vehicle. It also propagates the position of the vehicle in three dimensions. A conventional GPS receiver gives pseudorange and pseudorange rate measurements for the tight integration. External ephemeredes are used to estimate the satellite Doppler contribution in the user-to-satellite Line Of Sight (LOS). Results show that as soon as two satellites are tracked, the overall accuracy of the integrated positioning system increases. Moreover, the availability of the position solutions is also augmented. Depending on the type of harsh environments, namely classical or deep urban canyons, heavy map-matching algorithms are not required with such low-cost sensors integration. However, the integration scheme is dependent on the satellite geometry with respect to the user's heading. When a bad satellite configuration is detected, the Integrated Navigation System (INS) relies exclusively on the IMU data. As a consequence, the INS may experience systematic drift for long periods (>1min) without any GPS updates.

International audience; First driven by the regulation on emergency call, several methods are studied to enable the location of one user whether he is outdoors or indoors. Moreover, location based services take more and more importance, and as a consequence, the ability of providing such a location becomes a great challenge. Assisted satellite navigation solutions are investigated, but they encounter big issues in indoor environment. The main reason is the weak power of the signals to acquire and process. Therefore, complementary techniques shall be developed to supply or enhance GPS based positioning solutions when GPS reception is disrupted. MEMS based techniques are promising ones. In this paper, the performance of a MEMS based Pedestrian Navigation System (PNS) is studied. As the PNS is assumed to be used during GPS outages, only the navigation using exclusively MEMS sensors is addressed. The Pedestrian Navigation Module (PNM) relies on four components: a three axes accelerometer, a three axes gyro and a three axes magnetometer, as well as a pressure sensor. The four sensors are low-cost ones.

International audience; The efforts of the semiconductor industry to produce small, low consumption and powerful chipsets bear fruit, and many portable devices are now equipped with them. Indeed, the miniaturized chipsets with increasing processing power make them suitable for supporting software-based applications. On the other hand, demand for indoor navigation and location based services applications, whose interoperability with GNSS technology is being more and more obvious, is expected to grow rapidly in the next few years. In this context, because of their maximum flexibility and minimum hardware modifications, software-based positioning techniques embedded in portable devices become very interesting. The remaining key point is the time needed to acquire these rare and weak indoor signals and give a position solution. The aim of this study is to present results on the time needed to acquire one satellite for such embedded GPS applications, and more specifically, for Assisted-GPS ones. In this paper, an RF front-end chipset combined with a processor embedded in a portable device is considered. Only the acquisition process using FFT correlations will be studied here. The classical structure for L1 code FFT acquisition is first described and acquisition performance, such as the mean acquisition time, is discussed. A statistical process is used to simulate acquisition procedures, according to probabilities of detection, acquisition structure and the implemented acquisition strategy. The estimated times are then deduced from these tests. A special study is carried out to measure the impact of the Doppler affecting the GPS signal. An analysis of the effect of the computational power is also conducted, as well as the influence of the signal-to-noise ratio on the acquisition procedure, mostly dedicated to indoor and deep indoor environments. Results point out the fact that to achieve the requirements of the application supporting the software-based acquisition process, a trade-off has to be found between performance relative to the acquisition of weak signals, and the rapidity of the processing, especially in deep indoor environments. The evaluation of the Doppler component due to user dynamics and the acquisition strategy are also key points that would speed up the process.