Demodulation Performance Assessment of New GNSS Signals in Urban Environments

International audienceSatellite navigation signals demodulation performance ishistorically tested and compared in the Additive WhiteGaussian Noise propagation channel model which wellsimulates the signal reception in open areas. Nowadays,the majority of new applications targets dynamic users inurban environments; therefore the GNSS signalsdemodulation performance has become mandatory to beprovided in urban environments. The GPS L1C signaldemodulation performance in urban environments is thusprovided in this paper. To do that, a new methodologyadapted to provide and assess GNSS signalsdemodulation performance in urban channels has beendeveloped. It counteracts the classic method limitationswhich are the fluctuating received C/N0 in urbanenvironments and the fact that each received message istaken into account in the error rate computation whereasin GNSS it is not necessary. The new methodology thusproposes to provide the demodulation performance for‘favorable’ reception conditions together with statisticalinformation about the occurrence of these favorablereception conditions. To be able to apply this newmethodology and to provide the GPS L1C signaldemodulation performance in urban environments, asimulator SiGMeP (Simulator for GNSS MessagePerformance) has been developed. Two urbanpropagation channel models can be tested: thenarrowband Perez-Fontan/Prieto model and the widebandDLR model. Moreover, the impact of the received signalphase estimation residual errors has been taken intoaccount (ideal estimation is compared with PLL tracking)

GNSS Signal Demodulation Performance in Urban Environments

International audienceSatellite 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 trackin

Optimizing GNSS Navigation Data Message Decoding in Urban Environment

Nowadays, the majority of new GNSS applications targets dynamic users in urban environments; therefore the decoder input in GNSS receivers needs to be adapted to the urban propagation channel to avoid mismatched decoding when using soft input channel decoding. The aim of this paper consists thus in showing that the GNSS signals demodulation performance is significantly improved integrating an advanced soft detection function as decoder input in urban areas. This advanced detection function takes into account some a priori information on the available Channel State Information (CSI). If no CSI is available, one has to blindly adapt the detection function in order to operate close to the perfect CSI case. This will lead to avoid mismatched decoding due to, for example, the consideration by default of the Additive White Gaussian Noise (AWGN) channel for the derivation of soft inputs to be fed to soft input decoders. As a consequence the decoding performance will be improved in urban areas. The expressions of the soft decoder input function adapted for an urban environment is highly dependent on the available CSI at the receiver end. Based on different model of urban propagation channels, several CSI contexts will be considered namely perfect CSI, partial statistical CSI and no CSI. Simulation results will be given related to the GPS L1C demodulation performance with these different advanced detection function expressions in an urban environment. The results presented in this paper are valid for any kind of soft input decoders, such as Viterbi decoding for trellis based codes, the MAP/BCJR decoding for turbo-codes and the Belief Propagation decoding for LDPC codes

New GNSS Signals Demodulation Performance in Urban Environments

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

Optimized low-cost HSGPS/IMU/WSS land vehicle navigation system for urban navigation

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

Multi―sensor fusion for localization. Concept and simulation results

International audienceThis 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

Multi―sensor fusion for localization. Concept and simulation results

International audienceThis 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

LDPC Channel Code Optimization for a GNSS CSK-Modulated Signal

International audienceIn 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