Abstract: Described herein is a method for improving the reception of a satellite navigation message divided in several pages and transmitted by one or several satellites. A satellite navigation message M of k pages is encoded inn pages, and any k retrieved pages from any satellite enables decoding of the original satellite navigation message M. An implementation of the method uses parallel block encoding for a binary erasure channel with high parity and zero overhead, where symbols at a fixed position of all pages are encoded in parallel into shorter codes. This method achieves full page interchangeability in the message transmission, optimizes message reception and reduces decoding cost.

Abstract: A method carried out in a radionavigation system (2), the radionavigation system (2) comprising a receiver (4) and a radionavigation infrastructure (6), the radionavigation infrastructure comprising a plurality of satellite-borne transmitters (8, 8?, 8?, 8??), and encryption component (10) configured for communication with the transmitters (8, 8?, 8?, 8??) and the receiver (4). The method comprises the following, for one or more given transmitters (8) of the plurality of satellite-borne transmitters (8, 8?, 8?, 8??). In the radionavigation infrastructure (6), a series of keys k2,i are generated in respect of a predetermined authentication interval [0,T] of duration T and commencing at t=0 and a spreading code-encrypted signal e(t) is generated from a first radionavigation signal s1(t) using a keystream K1(t), the keystream K1(t) being generated with a secret key k1 of the radionavigation infrastructure (6).

Abstract: Described herein is a method for improving the reception of a satellite navigation message divided in several pages and transmitted by one or several satellites. A satellite navigation message M of k pages is encoded in n pages, and any k retrieved pages from any satellite enables decoding of the original satellite navigation message M. An implementation of the method uses parallel block encoding for a binary erasure channel with high parity and zero overhead, where symbols at a fixed position of all pages are encoded in parallel into shorter codes. This method achieves full page interchangeability in the message transmission, optimizes message reception and reduces decoding cost.

Abstract: A radio navigation system (100; 400), comprising a plurality of satellite-borne transmitters (110, 114, 118, 122) and at least one ground-based receiver (104), the receiver (104) being adapted to receive radionavigation signals (112, 116, 120, 124; 412, 416, 420, 424) from each of a plurality of the transmitters (110, 114, 118, 122). Each of the transmitters (110, 114, 118, 122) and the receiver (104) being adapted to access a predetermined first key chain, the first key chain comprising a first encryption key (K; Kj) and one or more further encryption keys (K; Kj,1, Kj,2, Kj,3, Kj,4).

Abstract: A method carried out in a radionavigation system (2), the radionavigation system (2) comprising a receiver (4) and a radionavigation infrastructure (6), the radionavigation infrastructure comprising a plurality of satellite-borne transmitters (8, 8?, 8?, 8??), and encryption component (10) configured for communication with the transmitters (8, 8?, 8?, 8??) and the receiver (4). The method comprises the following, for one or more given transmitters (8) of the plurality of satellite-borne transmitters (8, 8?, 8?, 8??). In the radionavigation infrastructure (6), a series of keys k2,i are generated in respect of a predetermined authentication interval [0, T] of duration T and commencing at t=0 and a spreading code-encrypted signal e(t) is generated from a first radionavigation signal s (t) using a keystream K1(t), the keystream K1(t) being generated with a secret key k1 of the radionavigation infrastructure (6).

Abstract: The invention introduces “crossed” navigation message authentication, which comprises a) generation and transmission of unpredictable bits periodically from satellites currently not connected to the ground mission segment and b) generation of digital signatures for the data from these satellites, and the transmission thereof through satellites that currently are connected to the ground mission segment. An attacker cannot spoof the navigation message as it contains an unpredictable bit pattern that is verified a few seconds later through a digital signature.

Abstract: The present invention describes a method and a system to compute the time (t1) and the position (P1) of a receiver (102, 805, 901) based on satellite radiofrequency signals without accurate, a priori time or position information and without the need for demodulating data from the signals received by the satellites (103, 800). In particular, the present invention computes the receiver time (t1) and position (P1) by estimating the time offset between the actual time (t1) and an initial time (t0), which can be defined arbitrarily and even have an error of hours or days. The estimation of this time offset is performed by updating Doppler estimations (D(t0), D(t1)) between different times using Doppler change rates.

Abstract: A radio navigation system (100; 400), comprising a plurality of satellite-borne transmitters (110, 114, 118, 122) and at least one ground-based receiver (104), the receiver (104) being adapted to receive radionavigation signals (112, 116, 120, 124; 412, 416, 420, 424) from each of a plurality of the transmitters (110, 114, 118, 122). Each of the transmitters (110, 114, 118, 122) and the receiver (104) being adapted to access a predetermined first key chain, the first key chain comprising a first encryption key (K; Kj) and one or more further encryption keys (K; Kj,1, Kj,2, Kj,3, Kj,4).

Abstract: The invention introduces “crossed” navigation message authentication, which comprises a) generation and transmission of unpredictable bits periodically from satellites currently not connected to the ground mission segment and b) generation of digital signatures for the data from these satellites, and the transmission thereof through satellites that currently are connected to the ground mission segment. An attacker cannot spoof the navigation message as it contains an unpredictable bit pattern that is verified a few seconds later through a digital signature.

Abstract: The present invention belongs to the field of positioning applications, particularly those requiring or benefiting from the use of geographic information and needing a high service or integrity guarantee, such as positioning by means of a satellite navigation system for users and ground vehicles circulating through a network of streets and highways for example. The invention can be used both for critical safety applications and for those entailing legal or contractual responsibilities.

Abstract: The invention relates to a method for determining a set of passable roads or areas traveled by a user with a minimum associated probability or integrity which comprises: receiving from a GNSS system respective position solutions PVT of said user in respective instants of time ta and tb, respectively, and respective position integrity ellipses, Ia and Ib (201), with respective minimum associated probabilities, Pa and Pb, that the user is located in each of them in ta and in tb, respectively, and a position increase ?ab between ta and tb with its position increase integrity ellipse Iab (204) and its associated probability Pab; obtaining from a GIS system respective passable areas corresponding to said PVT solutions, determining a first passable integral area Sa=Ia?TGIS (202) and a second passable integral area Sb=Ib?TGIS (203) as an intersection for each instant of time of said position integrity ellipses with said passable areas; propagating said first passable integral area to the subsequent instant tb by