Method for the accelerated acquisition of satellite signals
View Patent ↗The present invention proposes to use optimally a location method based on a WIFI type short-range telecommunication system and a satellite location system. The short-range telecommunication system is used to locate the terminal accurately within the building in which it is situated. The method uses a cartographic representation of the buildings in order to deduce from the position of the terminal a set of satellites that could be received by the terminal. The satellites are then acquired to synchronize the terminal to the satellite system. That synchronization is then used when the terminal leaves the building to acquire as quickly as possible the set of satellites of the satellite navigation constellation.
1. A method of accelerated acquisition ot positioning satellite signals from a satellite location system for a mobile terminal, wherein the mobile terminal moves from the interior to the exterior of a building, and the mobile terminal couples a transceiver capable of exchanging signals of a local range telecommunication system to a transceiver capable of exchanging positioning satellite signals of the satellite location system, the method comprising:
determining an approximate position of the mobile terminal by measuring a parameter of a signal from at least one access point of the local range telecommunication system, wherein the mobile terminal searches for location information and detects the at least one access point,
determining orientations of various satellites within the satellite location system which can be perceived from the determined position of the mobile terminal,
determining a probability of acquisition of signals from the various satellites, as a function of the azimuth and the elevation of each perceived satellite, and as a function of a radio wave attenuation coefficient for the determined position of the mobile terminal known to a system of cartographic representation of buildings and their internal architecture, wherein the system associates with each position within a building a distribution of probability of acquisition of a satellite signal from a given direction,
searching for satellite signals from each perceived satellite for which the probability of reception exceeds a certain threshold, and
synchronizing the mobile terminal to acquired satellite signals.
2. A method according to claim 1 , further comprising transmitting by the cartographic representation system a local map representing the building and the interior architecture of the building to the mobile terminal before the determining of the probability of acquisition of signals from the various satellites.
3. A hybrid location system for accelerated acquisition of positioning satellite signals for a mobile terminals, wherein the mobile terminal moves from the interior to the exterior of a building, the hybrid location system comprising:
a local range telecommunication system,
a satellite location system,
the mobile terminal which couples a transceiver capable of exchanging local telecommunication signals to a transceiver capable of exchanging positioning satellite signals,
a system of cartographic representation of buildings and of their interior architecture which associates with each position within a building a distribution of probability of acquisition of a satellite signal from a given direction,
means for determining a position of the mobile terminal by measuring a parameter of a signal from at least one access point of the local range telecommunication system, wherein the mobile terminal searches for location information and detects the at least one access point,
means for determining a probability of acquisition of signals from the various satellites, as a function of the azimuth and the elevation of various satellites of the satellite location system which can be perceived from the determined position of the mobile terminal, and as a function of a radio wave attenuation coefficient for the determined position of the mobile terminal known to the cartographic representation system,
means for searching for satellite signals from each perceived satellite for which the probability of reception exceeds a certain threshold, and
means for synchronizing the mobile terminal to acquired satellite signals.
4. A system according to claim 3 , wherein the system of cartographic representation of buildings and their interior architecture is integrated into a location server using an Assisted-GPS or Assisted-GNSS location technique.
5. A method according to claim 1 , wherein the cartographic representation system comprises a plurality of radio wave attenuation coefficients, each of which is associated with an element of the cartography of the building.