EP2494373A1 - Method and system for assisting with the locating of a mobile terminal in a closed environment using pseudolite base stations. - Google Patents

Method and system for assisting with the locating of a mobile terminal in a closed environment using pseudolite base stations.

Info

Publication number
EP2494373A1
EP2494373A1 EP10787834A EP10787834A EP2494373A1 EP 2494373 A1 EP2494373 A1 EP 2494373A1 EP 10787834 A EP10787834 A EP 10787834A EP 10787834 A EP10787834 A EP 10787834A EP 2494373 A1 EP2494373 A1 EP 2494373A1
Authority
EP
European Patent Office
Prior art keywords
base stations
terminal
pseudolite base
signals
satellite
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10787834A
Other languages
German (de)
French (fr)
Inventor
Arnaud David Masson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Insiteo
Original Assignee
Insiteo
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Insiteo filed Critical Insiteo
Publication of EP2494373A1 publication Critical patent/EP2494373A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
    • G01S19/10—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing dedicated supplementary positioning signals
    • G01S19/11—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing dedicated supplementary positioning signals wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters

Definitions

  • the invention relates to assistance with the precise location of a mobile communication terminal equipped with satellite signal location functionality, in particular GPS (English initials set for Global Positioning System) in spaces. covered or closed in which the conventional satellite signals of the GPS type, for example, emitted by the satellites are little or not received.
  • satellite signal location functionality in particular GPS (English initials set for Global Positioning System) in spaces. covered or closed in which the conventional satellite signals of the GPS type, for example, emitted by the satellites are little or not received.
  • satellite tracking systems on which the invention can be applied such as Galileo, Glonass, Compass, QZSS systems for example.
  • GPS Galileo, Glonass, Compass, QZSS systems
  • mobile communication terminal is understood to mean any portable equipment equipped with a GPS receiver, such as a cell phone of a cellular telecommunication network, a laptop, a personal assistant or PDA (initials in English for Personal Digital Assistant), a portable music player, a simple portable GPS navigator ...
  • a GPS receiver such as a cell phone of a cellular telecommunication network, a laptop, a personal assistant or PDA (initials in English for Personal Digital Assistant), a portable music player, a simple portable GPS navigator ...
  • the GPS system makes it possible to provide terminals equipped with a GPS receiver with a location on a map in order, for example, to provide an indication of the route to take to arrive at a given location.
  • This system was initially used for the purpose of providing a navigation aid for vehicle drivers. More recently, portable terminals equipped with GPS receivers have been developed, making it possible to extend the navigation assistance service to pedestrians equipped with these terminals.
  • the SPS signals for civilian use are signals coded by a code called C / A (English initials set for Coarse / Acquisition) and broadcast on a carrier frequency L1 (1575.42 MHz).
  • the C / A code consists of a 1023-bit pseudo-random sequence with a 1.023MHz clock. It is repeated every millisecond. Its small size allows the GPS receiver to quickly capture satellite information.
  • Each satellite has its own pseudo-random code known as "Gold code”. This code has been studied to minimize the probability of confusing two different signals emitted by different satellites on the same frequency and to allow the measurement of a propagation time.
  • the C / A code is not encrypted and is thus accessible to all users.
  • the GPS system can provide a location with a horizontal accuracy ranging from 10 to 100 meters depending on the degradation or not of the signals received, a vertical accuracy of 156 meters, and a maximum error of 337 nanoseconds for UTC time.
  • US Pat. No. 6,256,475 discloses an auxiliary system making it possible to acquire information on the ephemerides of the satellites and to transmit this information to the terminal.
  • the wireless terminal has only to determine the distance signals, which can be achieved more quickly and cheaply.
  • A-GPS system English initials set for Assisted Global Positioning System
  • WA-GPS Wireless Assisted Global Positioning System
  • GPS receivers are used.
  • operator of a cellular radio network on which the mobile terminal is registered to help the mobile terminal determine the GPS satellites it must follow and acquire their signals.
  • an operator server includes an antenna coupled to a receiver that searches for information from satellites (also known as reference receiver), a platform (hardware and software) to perform positioning calculations, and a computer (or "Gateway”) that connects the server to the IP network.
  • the mobile terminal sends a request via the IP network to the A-GPS server to obtain the list of GPS signals that it must follow.
  • the terminal operates autonomously. If the phone loses any GPS signal, it may request assistance from the A-GPS server again. With this assistance, the signal search performed by the terminal is greatly reduced. Typically, the time required for a first connection or TTFF (imperial initials set for Time To First Fix) from several minutes to only a few seconds.
  • TTFF perial initials set for Time To First Fix
  • the A-GPS receiver integrated in the terminal is able to detect and demodulate signals of very small magnitude.
  • Previous GPS or A-GPS systems offer acceptable performance as long as the service user moves in an open environment with an unobstructed view to the sky.
  • mobile terminals with GPS or A-GPS location functionality have their ability to locate considerably reduced, or even zero, as the user moves in a closed or covered environment, for example inside. buildings of a company, a shopping center, an airport, a museum, or a basement parking.
  • the signals transmitted by the satellites are either undetected or received with power too low to be processed by the terminal.
  • knowing that a minimum number of received GPS signals are necessary to allow a precise localization the probability that the terminal manages to locate itself inside the buildings remains very weak.
  • pseudolites pseudo-satellites
  • pseudolite base stations even if they are conveniently placed inside buildings, must cover the total area of buildings in which the terminals can evolve, without being too numerous for obvious reasons of cost.
  • the power required for this causes a phenomenon of reception of signals tainted with a lot of interference for certain terminals operating in the immediate vicinity of a pseudolite base station. Indeed, for a terminal located near a pseudolite base station, the power level of the signal received from the latter may be too great compared to that received from a distant pseudolite base station. In this case, the strongest signal interferes with the measurement that the terminal makes of the most remote pseudolite base station.
  • the invention proposes to solve the problems related to the reception of signals of very different levels for a GPS receiver operating in an environment in which a set of pseudolite base stations has been installed.
  • This object is achieved according to the invention which has for its first object a method of assisting the location of a mobile communication terminal equipped with a satellite location receiver in a closed environment within which a set of stations base pseudolites has been installed, said satellite location receiver being adapted to receive coded signals transmitted by each of the pseudolite base stations of said set on a satellite communication link, the mobile communication terminal being further able to transmit signals on a wireless transmission link separate from said satellite communication link, the method being characterized in that it comprises the following steps:
  • the step of determining the list of pseudolite base stations to listen consists in excluding from said set the pseudolite base stations for which the theoretical power values of the signals received are less than the highest theoretical power minus one predetermined margin.
  • the margin is of the order of 24 dB for a signal transmitting a code broadcast at a frequency of 1575.42 MHz, and of the order of 20. dB in acquisition mode.
  • the wireless transmission link is a WiFi type short-range link between the mobile communication terminal and at least one WiFi terminal installed inside the closed environment to which it is connected. 'interested.
  • a Bluetooth short-range link may be used between the mobile communication terminal and at least one Bluetooth terminal installed within said environment.
  • the steps of determining the theoretical power values and the determination of the list of pseudolite base stations to be listened to can be carried out either at the level of the mobile communication terminal or at the level of a server to which the base stations pseudolites of the assembly and said terminal are connected. In the latter case, the list is then transmitted to the mobile communication terminal advantageously via the wireless transmission link.
  • the pre-location information can be used to calculate the distance D separating the mobile communication terminal and each of the pseudolite base stations from the set. It is then possible to deduce the theoretical value of the power received from the distance D and the power of the signals emitted by each of the radio stations. base pseudolites of the set using the law of radiofrequency wave propagation in free field.
  • measurements of the power received from each of the pseudolite base stations at different points in the closed environment are recorded and stored beforehand.
  • the theoretical values of the powers of the signals received by the satellite location receiver correspond to the values of the reading for the nearest point of the pre-location information, or these values are calculated by interpolation from the values of the statement.
  • a prior modeling of the topology of the closed environment comprising the locations of the pseudolite base stations of the set, the absorption and / or reflection coefficients likely to be involved in the path of the waves between each pseudolite base station and different points of the environment so as to simulate the power received from each of the pseudolite base stations at different points of the closed environment.
  • the theoretical values of the powers of the signals received by the satellite location receiver correspond to the values deduced from the modeling for the nearest point of the pre-location information, or calculated by interpolation from the data of the satellite location receiver. simulation.
  • the present invention also relates to a system for assisting the location of a mobile communication terminal in a closed environment, the system comprising a set of pseudolite base stations installed inside said environment, capable of transmitting signals. encoded on a satellite communication link to a satellite location receiver equipping the terminal, the mobile communication terminal being further able to exchange signals on a wireless transmission link separate from said satellite communication link, the system characterized in that it further comprises: At least one terminal capable of exchanging signals with said mobile communication terminal on said wireless transmission link so as to be able to determine pre-location information of said mobile communication terminal from the signals transmitted by said terminal on said link; wireless transmission;
  • a third subject of the invention concerns a mobile communication terminal equipped with a satellite location receiver able to receive, on a satellite communication link, coded signals transmitted by a set of pseudolite base stations of a satellite system. assisting the localization, and exchanging signals over a wireless transmission link separate from said satellite communication link, characterized in that it comprises means for acquiring and monitoring the coded signals transmitted by a list of pseudolite base stations selected from the set of pseudolite base stations according to a pre-location information of the terminal obtained from the signals transmitted on said wireless transmission link and the power of the signals transmitted by each of the pseudolites base stations of said together.
  • the present invention further relates to a communication server characterized in that it is capable of being connected to a set of pseudolite base stations able to communicate with a satellite location receiver of a mobile communication terminal by a satellite communication link and at least one terminal capable of communicating with said terminal via a wireless communication link separate from said satellite communication link, and in that it comprises software means for determining the theoretical power values and the list according to the method.
  • FIG. 1 schematically illustrates a possible architecture of a location assistance system according to the invention
  • FIG. 2 illustrates, in the form of a simplified block diagram, the various steps implemented in a localization method according to the invention.
  • the reference 1 indicates a location assistance system intended to provide, in a closed environment within which the system is implanted, a location aid to a mobile communication terminal 2 when this last enters the system cover.
  • the location aid uses the coded signals transmitted by a predetermined number N of pseudolite base stations constituting a set of the system 1, of which four are visible in FIG. 1 and referenced PSI to PS4, these signals being able to be all or partly received by a GPS receiver (not shown) equipping the mobile communication terminal 2, depending on where the terminal is located at a given time.
  • the assistance system 1 is coupled to the satellite navigation system represented by the general reference 3. In a variant, the assistance system 1 is completely autonomous, that is to say that the basic values used are known to the system 1 without the latter being connected to the satellite navigation system 3.
  • the principle of the invention consists in allowing the elaboration of a preferred list of pseudolite base stations chosen from the set of pseudolite base stations included in the assistance system 1, so as to avoid the risks of interference. between the signals actually received by the GPS receiver of the mobile communication terminal 2. It proposes for this purpose to provide a particular signal processing that allows to exclude if necessary base stations pseudolites likely to emit a signal that would be received by the receiver with interference.
  • the assistance system 1 preferably comprises a plurality of terminals, in the example represented, a number P of Wifi terminals of which only three, referenced WF1 to WF3, are visible on the figure. It should be noted that the invention is applicable in the case where only one terminal is used. These terminals are able to receive or transmit, automatically or on request, signals respectively transmitted or received by the mobile communication terminal 2 on a wireless transmission link 11 distinct from the GPS communication link 10 when the terminal 2 passes nearby. . Of course, the terminal 2 must also be equipped with means (not shown) for transmitting such WiFi signals.
  • other short-range communication links such as a Bluetooth-type link
  • the Wifi terminals then being replaced by appropriately placed Bluetooth terminals.
  • Localization through these terminals can be calculated both by the terminal and then transmitted to the system than by the system after recovery of power measurements terminals WF1 to WF3 made by the terminal according to known methods (triangulation, fingerprinting, ). Since the terminal has already been located by the method described, it is also possible to use the localization provided by the location calculated by the valid pseudolite signals received by the terminal. In this case, the mobile terminal can transmit via the wireless transmission link 11, a signal comprising the pre-location calculated by the terminal. It is recalled that a combination of use of these means can be used.
  • the reception of the signals by one or more of the terminals of the system makes it possible to determine, either by determining the terminal or terminals having received the signals, or by analyzing the contents of these signals (in which case the terminal transmits the location information), a minimum coarse location of the mobile terminal called in the following description prelocation information.
  • the pre-location information is determined in all cases from the signals that are transmitted on the wireless transmission link 11.
  • the pre-location information Once the pre-location information has been obtained, it is sought to determine, for this pre-location, the values of the powers 3 ⁇ 4 of the signals that would be theoretically received by the GPS receiver of the mobile communication terminal 2 from each of the radio stations. pseudolites base of said set (step S2 in Figure 2). This determination is performed using, on the one hand, the pre-location information, and, on the other hand, the power 3 ⁇ 4 of the signals emitted by each of the pseudolite base stations of the set, which is moreover known. To do this, several methods can be used:
  • a first method consists in determining the values 3 ⁇ 4 by using the law of propagation of radio waves in free field expressed by the relation
  • Z 2 is the distance separating the terminal 2 from each Psi pseudolite base station, estimated from the pre-location information and the knowledge of the positions of each of the pseudolite base stations of the system;
  • P Ei is the power emitted by each psi pseudolite base station, known from the system.
  • each pseudolite base station Psi point corresponding to the pre-location point of the terminal 2.
  • a source of 10 W will produce a field E of 1 mV / m at a distance of 30 km, which, in radio, is not a negligible field.
  • the determination step S2 will essentially consist of:
  • a second method consists in carrying out a preliminary step of recording and storing measurements of the power received from each of the pseudolite base stations of said set at different points of the closed environment.
  • the step of determining the theoretical values P Ri of the powers of the signals received by the GPS receiver consists in choosing in the reading the value of the power for the most close to the pre-location information.
  • step S2 it is also possible to provide an interpolation calculation of the theoretical values of the powers of the signals received by the satellite location receiver after having chosen the known power values for the points closest to the pre-information information. location.
  • a prior modeling of the topology of the closed environment including in particular the locations of the pseudolite base stations of the set, the absorption and / or reflection coefficients likely to take place in the path is carried out. waves between each pseudolite base station and different points of the environment. In the latter case, it is necessary to know all the materials used to define the walls, walls, ceiling ... existing in the closed environment. This modeling can then be used in real time to simulate the theoretical value P Ri of power received from each of the pseudolite base stations at different points of the closed environment, and in particular at the point given by the information of pre- location.
  • the method according to the invention may advantageously comprise an additional step in which the terminal determines its location using the signals it receives from the base stations of the list, and measures the power of the signals that it actually receives pseudolite base stations, so as to allow dynamic update of the survey or modeling.
  • the assistance method provides a step of determining a list of pseudolite base stations that the GPS receiver.
  • the mobile communication terminal 2 must listen among the pseudolite base stations of the set from the theoretical values of the powers of the signals received (step S3 in FIG. 2).
  • reception interference is likely to occur between the signals received from two pseudolite base stations when the ratio of the powers received by the terminal of these two stations is greater than one.
  • threshold which is expressed in decibels, is around 24 dB in the tracking mode. This threshold can even go down to 20 dB in acquisition mode.
  • the step S3 for determining the list preferably consists in excluding pseudolite base stations from said set for which the theoretical power values of the received signals are lower than the highest theoretical power minus a predetermined margin. , this margin being preferably of the order of 24 dB for a GPS type signal transmitting a code broadcast at a frequency of 1575.42 MHz in tracking mode, and of the order of 20 dB in acquisition mode.
  • margins can be adjusted according to the characteristics of the location receiver used in the terminal.
  • value of these margins is indicated here in the context of GPS signals, but other values must be used for other satellite tracking systems.
  • the steps S2 and S3 can be implemented at the level of the assistance system 1, and more specifically by software means at a server 12 to which the different base stations pseudolites and Wifi or Bluetooth terminals are connected.
  • the server 12 has been shown as implanted in the closed location to which the assistance system is dedicated.
  • this server may be at another location, connected to the various elements of the system by a network 13 of the LAN type.
  • the same server can also be used to work with different sets of pseudolites installed in different places, for example separate buildings.
  • the Wifi terminals WF1 to WF3 made it possible to pre-locate the terminal 2 roughly and, according to the method according to the invention, one of the pseudolite base stations, here the PS3 station. , is excluded from all pseudolite base stations.
  • the list developed in accordance with the method of the invention contains in this case only the stations PSI, PS2 and PS4.
  • the system transmits this list to the terminal which can then continue its localization process based on the list.
  • the means making it possible to transmit this list are the same as those which made it possible to receive the pre-location of the terminal, namely the WiFi or Bluetooth terminals of the system 1.
  • the assistance system checks beforehand that the terminal 2 is entitled to the service. If this condition is met, the server will execute the algorithm to create the list of optimal pseudolite base stations. Then this list created is possibly stored by the server next to the terminal concerned so as to be able to update it according to the precise location of the terminal that could be transmitted regularly by the terminal to the server, according to the self-learning step described. previously. This control is optional, because we can imagine that this service would be in certain situations free and available for everyone.
  • the terminals can advantageously be controlled in the system so that the sending of the list of base stations pseudolites optimal to the terminal is regular or caused by events.
  • the frequency of this sending may be temporal or the sending may be caused by a displacement in the closed location, or after a specific request for an application of the terminal.

Abstract

The invention relates to a method of assisting with the locating of a mobile communication terminal (2) equipped with a satellite receiver in a closed environment inside which a set of pseudolite base stations (PS1-PS4) has been installed, the satellite receiver being able to receive coded signals emitted by each of the pseudolite base stations of the set on a satellite communication link-up (10), the terminal (2) being able to exchange signals on a wireless transmission link (11) distinct from the satellite communication link-up (10). According to the invention, a pre-location cue for the terminal (2) is determined on the basis of signals transmitted on the wireless transmission link (11); then the theoretical values of the powers of the signals received by the satellite receiver and emitted by each of the pseudolite base stations (PS1-PS4) of the set, are determined on the basis of the pre-location cue and of the power of the signals emitted by each of the pseudolite base stations (PS1-PS4) of the set; finally, there is deduced therefrom a list (PS1, PS2, PS4) of pseudolite base stations that the satellite receiver must listen to from among the stations of the set. Advantage: reduces the risks of listening for signals undergoing interference on reception.

Description

PROCEDE ET SYSTEME D'ASSISTANCE A LA LOCALISATION D'UN TERMINAL MOBILE DANS UN ENVIRONNEMENT FERME UTILISANT DES METHOD AND SYSTEM FOR ASSISTING THE LOCATION OF A MOBILE TERMINAL IN A CLOSED ENVIRONMENT USING
STATIONS DE BASE PSEUDOLITES L'invention concerne l'assistance à la localisation précise d'un terminal de communication mobile équipé d'une fonctionnalité de localisation par signaux satellite, notamment le GPS (Initiales anglo-saxonnes mises pour Global Positioning System) dans des espaces couverts ou fermés dans lesquels les signaux classiques satellite de type GPS par exemple émis par les satellites sont peu, voire pas reçus. Il existe d'autres systèmes de localisation par satellite sur lesquelles l'invention peut s'appliquer comme les systèmes Galileo, Glonass, Compass, QZSS par exemple. Par abus de langage dans la suite de l'exposé on utilise le terme GPS pour désigner de tels systèmes de localisation ce dernier étant le plus connu. The invention relates to assistance with the precise location of a mobile communication terminal equipped with satellite signal location functionality, in particular GPS (English initials set for Global Positioning System) in spaces. covered or closed in which the conventional satellite signals of the GPS type, for example, emitted by the satellites are little or not received. There are other satellite tracking systems on which the invention can be applied such as Galileo, Glonass, Compass, QZSS systems for example. Abuse of language in the rest of the presentation we use the term GPS to designate such location systems, the latter being the best known.
Dans la suite de l'exposé, on entend par terminal de communication mobile tout équipement portatif équipé d'un récepteur GPS, tel qu'un téléphone portable d'un réseau de télécommunication cellulaire, un ordinateur portable, un assistant personnel ou PDA (initiales anglo-saxonnes mises pour Personal Digital Assistant), un lecteur de musique portable, un simple navigateur GPS portatif...  In the remainder of the disclosure, mobile communication terminal is understood to mean any portable equipment equipped with a GPS receiver, such as a cell phone of a cellular telecommunication network, a laptop, a personal assistant or PDA (initials in English for Personal Digital Assistant), a portable music player, a simple portable GPS navigator ...
Le système GPS permet de fournir à des terminaux équipés d'un récepteur GPS une localisation sur une carte en vue de délivrer par exemple une indication sur l'itinéraire à prendre pour arriver à un lieu donné. Ce système a dans un premier temps été utilisé dans le but de fournir une aide à la navigation pour les conducteurs de véhicules. Plus récemment, des terminaux portatifs dotés de récepteurs GPS ont été développés, permettant d'élargir le service d'aide à la navigation à des piétons munis de ces terminaux.  The GPS system makes it possible to provide terminals equipped with a GPS receiver with a location on a map in order, for example, to provide an indication of the route to take to arrive at a given location. This system was initially used for the purpose of providing a navigation aid for vehicle drivers. More recently, portable terminals equipped with GPS receivers have been developed, making it possible to extend the navigation assistance service to pedestrians equipped with these terminals.
On rappelle que le service de positionnement standard ou SPS est à la disposition de tous les utilisateurs de GPS du monde entier et ce, sans aucune charge directe. Les signaux du SPS à usage civil sont des signaux codés par un code dit C/A (initiales anglo-saxonnes mises pour Coarse/Acquisition) et diffusés sur une fréquence porteuse Ll (1575,42 MHz). Le code C/A consiste en une suite pseudo-aléatoire de 1023 bits avec une horloge de 1,023MHz. Il est ainsi répété chaque milliseconde. Sa petite taille permet au récepteur GPS de capter rapidement les informations satellites. Chaque satellite possède son propre code pseudo-aléatoire connu sous la dénomination anglo-saxonne "Gold code". Ce code a été étudié pour minimiser les probabilités de confondre deux signaux différents émis par des satellites différents sur la même fréquence et permettre la mesure d'un temps de propagation. Le code C/A n'est pas crypté et est ainsi accessible à tous les utilisateurs. Le système GPS permet de fournir une localisation avec une précision horizontale variant de 10 à 100 mètres en fonction de la dégradation ou non des signaux reçus, une précision verticale de 156 mètres, et une erreur maximale de 337 nanosecondes pour l'heure UTC. We remind you that the standard positioning service or SPS is available to all GPS users around the world without any direct charge. The SPS signals for civilian use are signals coded by a code called C / A (English initials set for Coarse / Acquisition) and broadcast on a carrier frequency L1 (1575.42 MHz). The C / A code consists of a 1023-bit pseudo-random sequence with a 1.023MHz clock. It is repeated every millisecond. Its small size allows the GPS receiver to quickly capture satellite information. Each satellite has its own pseudo-random code known as "Gold code". This code has been studied to minimize the probability of confusing two different signals emitted by different satellites on the same frequency and to allow the measurement of a propagation time. The C / A code is not encrypted and is thus accessible to all users. The GPS system can provide a location with a horizontal accuracy ranging from 10 to 100 meters depending on the degradation or not of the signals received, a vertical accuracy of 156 meters, and a maximum error of 337 nanoseconds for UTC time.
Plus récemment, des systèmes d'assistance utilisant la navigation GPS ont été développés pour permettre à des terminaux sans fil, et par conséquent d'autonomie limitée, d'acquérir plus rapidement les signaux des satellites nécessaires à leur localisation.  More recently, assistance systems using GPS navigation have been developed to allow wireless terminals, and therefore limited autonomy, to acquire faster satellite signals necessary for their location.
On connaît par exemple du document US 6 256 475 un système auxiliaire permettant d'acquérir une information sur les éphémérides des satellites et de transmettre cette information au terminal . Le terminal sans fil n'a plus qu'à déterminer les signaux de distance, ce qui peut être réalisé plus rapidement et à moindre coût.  US Pat. No. 6,256,475 discloses an auxiliary system making it possible to acquire information on the ephemerides of the satellites and to transmit this information to the terminal. The wireless terminal has only to determine the distance signals, which can be achieved more quickly and cheaply.
On connaît par ailleurs le système A-GPS (initiales anglo-saxonnes mises pour Assisted Global Positioning System), ou WA-GPS (initiales anglo- saxonnes mises pour Wireless Assisted Global Positioning System), dans lequel on utilise des récepteurs GPS d'un opérateur d'un réseau cellulaire de radiocommunication sur lequel le terminal mobile est inscrit, pour aider le terminal mobile à déterminer les satellites GPS qu'il doit suivre et à acquérir leurs signaux. Plus précisément, un serveur de l'opérateur comporte une antenne couplée à un récepteur qui cherche les informations venant des satellites (aussi connue comme receveur de référence), une plate-forme (matérielle et logicielle) pour effectuer des calculs de positionnement, et un ordinateur (ou « Gateway ») qui connecte le serveur au réseau IP. Lors de sa mise en route, le terminal mobile envoie une requête via le réseau IP au serveur A-GPS pour obtenir la liste des signaux GPS qu'il doit suivre. Une fois cette liste acquise, il cherche alors à acquérir les signaux des satellites indiqués par le serveur pour déterminer sa position . Dès lors, le terminal fonctionne de manière autonome. Si le téléphone perd tout signal GPS, il peut demander à nouveau l'assistance du serveur A-GPS. Grâce à cette assistance, la recherche de signal effectuée par le terminal est grandement réduite. Typiquement, la durée nécessaire pour une première connexion ou TTFF (initiales anglo-saxonnes mises pour Time To First Fix) passe de plusieurs minutes à seulement quelques secondes. De plus, contrairement aux récepteurs GPS traditionnels, le récepteur A-GPS intégré dans le terminal est en mesure de détecter et démoduler des signaux de très faible magnitude. Also known is the A-GPS system (English initials set for Assisted Global Positioning System), or WA-GPS (English initials set for Wireless Assisted Global Positioning System), in which GPS receivers are used. operator of a cellular radio network on which the mobile terminal is registered, to help the mobile terminal determine the GPS satellites it must follow and acquire their signals. More specifically, an operator server includes an antenna coupled to a receiver that searches for information from satellites (also known as reference receiver), a platform (hardware and software) to perform positioning calculations, and a computer (or "Gateway") that connects the server to the IP network. When it is started up, the mobile terminal sends a request via the IP network to the A-GPS server to obtain the list of GPS signals that it must follow. Once this list acquired, it then seeks to acquire the satellite signals indicated by the server to determine its position. As a result, the terminal operates autonomously. If the phone loses any GPS signal, it may request assistance from the A-GPS server again. With this assistance, the signal search performed by the terminal is greatly reduced. Typically, the time required for a first connection or TTFF (imperial initials set for Time To First Fix) from several minutes to only a few seconds. In addition, unlike traditional GPS receivers, the A-GPS receiver integrated in the terminal is able to detect and demodulate signals of very small magnitude.
Les systèmes GPS ou A-GPS précédents offrent des performances acceptables tant que l'utilisateur du service se déplace dans un environnement ouvert avec une vue dégagée vers le ciel .  Previous GPS or A-GPS systems offer acceptable performance as long as the service user moves in an open environment with an unobstructed view to the sky.
Néanmoins, les terminaux mobiles disposant d'une fonctionnalité de localisation par GPS ou A-GPS voient leur capacité de localisation considérablement réduite, voire nulle, dès lors que l'utilisateur se déplace dans un environnement fermé ou couvert, par exemple à l'intérieur des bâtiments d'une entreprise, d'un centre commercial, d'un aéroport, d'un musée, ou d'un parking en sous-sol. Dans de telles configurations, les signaux transmis par les satellites sont soit non détectés, soit reçus avec une puissance trop faible pour pouvoir être traités par le terminal . De plus sachant qu'il faut un nombre minimum de signaux GPS reçus pour permettre une localisation précise, la probabilité que le terminal arrive à se localiser à l'intérieur des bâtiments reste très faible.  Nevertheless, mobile terminals with GPS or A-GPS location functionality have their ability to locate considerably reduced, or even zero, as the user moves in a closed or covered environment, for example inside. buildings of a company, a shopping center, an airport, a museum, or a basement parking. In such configurations, the signals transmitted by the satellites are either undetected or received with power too low to be processed by the terminal. Moreover knowing that a minimum number of received GPS signals are necessary to allow a precise localization, the probability that the terminal manages to locate itself inside the buildings remains very weak.
Pour pallier cet inconvénient et améliorer la continuité et la disponibilité du service de positionnement, certains organismes publics ou privés ont mis en place dans leurs bâtiments un certain nombre de stations de base dites pseudolites (pseudo-satellites) capables d'émettre chacune, à destination des terminaux mobiles, un signal similaire à ceux transmis par les satellites. To overcome this drawback and to improve the continuity and availability of the positioning service, some public or private bodies have set up a number of radio stations in their buildings. base called pseudolites (pseudo-satellites) capable of transmitting each, to mobile terminals, a signal similar to those transmitted by satellites.
Il est connu selon les documents US 7 251 562 et US 6 597 988 de pouvoir transmettre les codes PRN des stations pseudolites.  It is known from documents US Pat. No. 7,251,562 and US Pat. No. 6,597,988 to be able to transmit the PRN codes of pseudolite stations.
Toutefois, les stations de bases pseudolites, même si elles sont judicieusement placées à l'intérieur des bâtiments, doivent couvrir la surface totale des bâtiments dans lesquels peuvent évoluer les terminaux, sans pour autant être trop nombreuses pour des raisons évidente de coût. La puissance requise pour cela entraîne un phénomène de réception de signaux entachés de beaucoup d'interférences pour certains terminaux évoluant dans le voisinage immédiat d'une station de base pseudolite. En effet, pour un terminal se trouvant à proximité d'une station de base pseudolite, le niveau de puissance du signal reçu de cette dernière peut être trop important par rapport à celui reçu d'une station de base pseudolite lointaine. Dans ce cas en effet, le signal le plus fort crée des interférences sur la mesure que le terminal effectue de la station de base pseudolite la plus lointaine. Ces différences peuvent être acceptées par le terminal, mais, d'après le constat de la Demanderesse, la structure même des codes utilisés par les satellites limite la valeur relative de ces différences, notamment à 24 dB pour le GPS C/A diffusé en fréquence Ll en mode poursuite, et même à 21 dB en mode acquisition. En effet, au-delà de cette valeur, les codes des signaux avec le plus de puissance provoquent des interférences sur la réception des codes des signaux reçus avec le moins de puissance. Cette situation est peu probable quand il s'agit de signaux reçus directement des satellites de positionnement car, vu du terminal, le niveau des signaux d'entrée des satellites est faible et la problématique dans cette situation est bien de pouvoir recevoir un minimum de signaux plutôt que d'avoir peur de la réception de signaux qui se brouillent entre eux de part leur écart de puissance. Ainsi dans la situation courante en extérieur, les terminaux équipés d'un récepteur GPS ne sont pas confrontés au phénomène d'interférences cité plus avant. L'invention se propose de résoudre les problèmes liés à la réception de signaux de niveaux très différents pour un récepteur GPS évoluant au sein d'un environnement à l'intérieur duquel un ensemble de stations de base pseudolites a été installé. However, pseudolite base stations, even if they are conveniently placed inside buildings, must cover the total area of buildings in which the terminals can evolve, without being too numerous for obvious reasons of cost. The power required for this causes a phenomenon of reception of signals tainted with a lot of interference for certain terminals operating in the immediate vicinity of a pseudolite base station. Indeed, for a terminal located near a pseudolite base station, the power level of the signal received from the latter may be too great compared to that received from a distant pseudolite base station. In this case, the strongest signal interferes with the measurement that the terminal makes of the most remote pseudolite base station. These differences may be accepted by the terminal, but, according to the finding of the Applicant, the very structure of the codes used by the satellites limits the relative value of these differences, in particular to 24 dB for the GPS C / A broadcast in frequency Ll in tracking mode, and even at 21 dB in acquisition mode. In fact, beyond this value, the codes of the signals with the most power cause interference on the reception of the codes of the signals received with the least power. This situation is unlikely when it comes to signals received directly from the positioning satellites because, given the terminal, the level of satellite input signals is low and the problem in this situation is to be able to receive a minimum of signals rather than being afraid of the reception of signals that are blurred between them because of their power deviation. Thus in the current outdoor situation, terminals equipped with a GPS receiver are not confronted with the phenomenon of interference mentioned above. The invention proposes to solve the problems related to the reception of signals of very different levels for a GPS receiver operating in an environment in which a set of pseudolite base stations has been installed.
Ce but est atteint selon l'invention qui a pour premier objet un procédé d'assistance à la localisation d'un terminal de communication mobile équipé d'un récepteur de localisation par satellite dans un environnement fermé à l'intérieur duquel un ensemble de stations de bases pseudolites a été installé, ledit récepteur de localisation par satellite étant apte à recevoir des signaux codés émis par chacune des stations de bases pseudolites dudit ensemble sur un lien de communication satellite, le terminal de communication mobile étant apte en outre à transmettre des signaux sur une liaison de transmission sans fil distincte dudit lien de communication satellite, le procédé étant caractérisé en ce qu'il comporte les étapes suivantes :  This object is achieved according to the invention which has for its first object a method of assisting the location of a mobile communication terminal equipped with a satellite location receiver in a closed environment within which a set of stations base pseudolites has been installed, said satellite location receiver being adapted to receive coded signals transmitted by each of the pseudolite base stations of said set on a satellite communication link, the mobile communication terminal being further able to transmit signals on a wireless transmission link separate from said satellite communication link, the method being characterized in that it comprises the following steps:
- Déterminer une information de pré-localisation dudit terminal de communication mobile à partir de signaux transmis sur ladite liaison de transmission sans fil;  - Determining pre-location information of said mobile communication terminal from signals transmitted on said wireless transmission link;
- Déterminer des valeurs théoriques des puissances des signaux reçus par le récepteur de localisation par satellite du terminal de communication mobile et émis par chacune de stations de base pseudolites dudit ensemble, à partir de l'information de pré-localisation et de la puissance des signaux émis par chacune des stations de base pseudolites dudit ensemble;  Determining theoretical values of the powers of the signals received by the satellite location receiver of the mobile communication terminal and transmitted by each of the pseudolite base stations of said set, from the pre-location information and the signal strength. issued by each of the pseudolite base stations of said set;
- Déterminer une liste de stations de bases pseudolites que le récepteur de localisation par satellite du terminal de communication mobile doit écouter parmi les stations de base pseudolites dudit ensemble à partir des valeurs théoriques des puissances des signaux reçus.  - Determining a list of pseudolite base stations that the satellite location receiver of the mobile communication terminal must listen among the pseudolite base stations of said set from the theoretical values of the powers of the received signals.
Avantageusement, l'étape de détermination de la liste de stations de base pseudolites à écouter consiste à exclure dudit ensemble les stations de bases pseudolites pour lesquelles les valeurs théoriques de puissance des signaux reçus sont inférieures à la puissance théorique la plus forte diminuée d'une marge prédéterminée. De préférence, dans le cas où on utilise un système de localisation de type GPS, la marge est de l'ordre de 24 dB pour un signal transmettant un code diffusé à une fréquence de 1575,42 MHz, et de l'ordre de 20 dB en mode acquisition. Advantageously, the step of determining the list of pseudolite base stations to listen consists in excluding from said set the pseudolite base stations for which the theoretical power values of the signals received are less than the highest theoretical power minus one predetermined margin. Preferably, in the case where a GPS-type location system is used, the margin is of the order of 24 dB for a signal transmitting a code broadcast at a frequency of 1575.42 MHz, and of the order of 20. dB in acquisition mode.
Dans un mode de réalisation préféré de l'invention, la liaison de transmission sans fil est une liaison courte portée du type WiFi entre le terminal de communication mobile et au moins une borne WiFi installée à l'intérieur de l'environnement fermé auquel on s'intéresse.  In a preferred embodiment of the invention, the wireless transmission link is a WiFi type short-range link between the mobile communication terminal and at least one WiFi terminal installed inside the closed environment to which it is connected. 'interested.
En variante, on peut utiliser une liaison courte portée de type Bluetooth entre le terminal de communication mobile et au moins une borne Bluetooth installée à l'intérieur dudit environnement.  Alternatively, a Bluetooth short-range link may be used between the mobile communication terminal and at least one Bluetooth terminal installed within said environment.
Dans une autre variante si le terminal a déjà utilisé les pseudolites pour se localiser, on utilisera cette méthode de localisation.  In another variant, if the terminal has already used the pseudolites to locate itself, this method of localization will be used.
Dans une variante supplémentaire il est possible d'utiliser une combinaison des méthodes précitées.  In a further variant it is possible to use a combination of the above methods.
Les étapes de détermination des valeurs théoriques de puissances et de détermination de la liste des stations de base pseudolites à écouter peuvent être réalisées soit, au niveau du terminal de communication mobile, soit, au niveau d'un serveur auquel les stations de base pseudolites de l'ensemble et ladite borne sont reliées. Dans ce dernier cas, la liste est alors transmise au terminal de communication mobile avantageusement via la liaison de transmission sans fil.  The steps of determining the theoretical power values and the determination of the list of pseudolite base stations to be listened to can be carried out either at the level of the mobile communication terminal or at the level of a server to which the base stations pseudolites of the assembly and said terminal are connected. In the latter case, the list is then transmitted to the mobile communication terminal advantageously via the wireless transmission link.
Plusieurs algorithmes peuvent être utilisés pour la détermination des valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite:  Several algorithms can be used for the determination of the theoretical values of the powers of the signals received by the satellite location receiver:
Selon une première variante, l'information de pré-localisation peut être utilisée pour calculer la distance D séparant le terminal de communication mobile et chacune des stations de base pseudolites de l'ensemble. Il est alors possible de déduire la valeur théorique de la puissance reçue à partir de la distance D et de la puissance des signaux émis par chacune des stations de base pseudolites de l'ensemble en utilisant la loi de propagation des ondes radiofréquence en champ libre. According to a first variant, the pre-location information can be used to calculate the distance D separating the mobile communication terminal and each of the pseudolite base stations from the set. It is then possible to deduce the theoretical value of the power received from the distance D and the power of the signals emitted by each of the radio stations. base pseudolites of the set using the law of radiofrequency wave propagation in free field.
Selon une deuxième variante, on relève et mémorise au préalable des mesures de la puissance reçue en provenance de chacune des stations de bases pseudolites en différents points de l'environnement fermé. Dans ce cas, les valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite correspondent aux valeurs du relevé pour le point le plus proche de l'information de pré-localisation, ou ces valeurs sont calculées par interpolation à partir des valeurs du relevé.  According to a second variant, measurements of the power received from each of the pseudolite base stations at different points in the closed environment are recorded and stored beforehand. In this case, the theoretical values of the powers of the signals received by the satellite location receiver correspond to the values of the reading for the nearest point of the pre-location information, or these values are calculated by interpolation from the values of the statement.
Selon encore une autre variante, on établit une modélisation préalable de la topologie de l'environnement fermé comprenant les emplacements des stations de base pseudolites de l'ensemble, les coefficients d'absorption et/ou de réflexion susceptibles d'intervenir dans le trajet des ondes entre chaque station de base pseudolite et différents points de l'environnement de manière à simuler la puissance reçue en provenance de chacune des stations de bases pseudolites en différents points de l'environnement fermé. Dans ce cas, les valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite correspondent aux valeurs déduites de la modélisation pour le point le plus proche de l'information de pré-localisation, ou calculées par interpolation à partir des données de simulation.  According to yet another variant, a prior modeling of the topology of the closed environment comprising the locations of the pseudolite base stations of the set, the absorption and / or reflection coefficients likely to be involved in the path of the waves between each pseudolite base station and different points of the environment so as to simulate the power received from each of the pseudolite base stations at different points of the closed environment. In this case, the theoretical values of the powers of the signals received by the satellite location receiver correspond to the values deduced from the modeling for the nearest point of the pre-location information, or calculated by interpolation from the data of the satellite location receiver. simulation.
Il est entendu que, pour l'homme de l'art, ces méthodes peuvent être utilisées de manière statistique et/ou par une combinaison d'entre elles.  It is understood that those skilled in the art can use these methods statistically and / or by a combination of them.
La présente invention a également pour objet un système d'assistance à la localisation d'un terminal de communication mobile dans un environnement fermé, le système comportant un ensemble de stations de bases pseudolites installées à l'intérieur dudit environnement, aptes à transmettre des signaux codés sur un lien de communication satellite à destination d'un récepteur de localisation par satellite équipant le terminal, le terminal de communication mobile étant en outre apte à échanger des signaux sur une liaison de transmission sans fil distincte dudit lien de communication satellite, le système étant caractérisé en ce qu'il comporte en outre: - Au moins une borne apte à échanger des signaux avec ledit terminal de communication mobile sur ladite liaison de transmission sans fil de façon à pouvoir déterminer une information de pré-localisation dudit terminal de communication mobile à partir des signaux transmis par ledit terminal sur ladite liaison de transmission sans fil; The present invention also relates to a system for assisting the location of a mobile communication terminal in a closed environment, the system comprising a set of pseudolite base stations installed inside said environment, capable of transmitting signals. encoded on a satellite communication link to a satellite location receiver equipping the terminal, the mobile communication terminal being further able to exchange signals on a wireless transmission link separate from said satellite communication link, the system characterized in that it further comprises: At least one terminal capable of exchanging signals with said mobile communication terminal on said wireless transmission link so as to be able to determine pre-location information of said mobile communication terminal from the signals transmitted by said terminal on said link; wireless transmission;
- Des moyens de détermination des valeurs théoriques des puissances des signaux reçus par le récepteur de localisation par satellite du terminal de communication mobile et émis par lesdites stations de base pseudolites dudit ensemble, à partir de l'information de pré-localisation et de la puissance des signaux émis par chacune des stations de base pseudolites dudit ensemble, et de détermination d'une liste de stations de bases pseudolites que le récepteur de localisation par satellite du terminal de communication mobile doit écouter parmi l'ensemble des stations de base pseudolites à partir des valeurs théoriques des puissances des signaux reçus.  Means for determining the theoretical values of the powers of the signals received by the satellite location receiver of the mobile communication terminal and transmitted by said pseudolite base stations of said set, from the pre-location information and the power; signals emitted by each of the pseudolite base stations of said set, and of determining a list of pseudolite base stations that the satellite location receiver of the mobile communication terminal must listen among all the pseudolite base stations from theoretical values of the powers of the received signals.
Un troisième objet de l'invention concerne un terminal de communication mobile équipé d'un récepteur de localisation par satellite apte à recevoir, sur un lien de communication satellite, des signaux codés transmis par un ensemble de stations de bases pseudolites d'un système d'assistance à la localisation, et à échanger des signaux sur une liaison de transmission sans fil distincte dudit lien de communication satellite, caractérisé en ce qu'il comporte des moyens pour acquérir et suivre les signaux codés transmis par une liste de stations de bases pseudolites choisies parmi l'ensemble de stations de base pseudolites en fonction d'une information de pré-localisation du terminal obtenue à partir des signaux transmis sur ladite liaison de transmission sans fil et de la puissance des signaux émis par chacune des stations de base pseudolites dudit ensemble.  A third subject of the invention concerns a mobile communication terminal equipped with a satellite location receiver able to receive, on a satellite communication link, coded signals transmitted by a set of pseudolite base stations of a satellite system. assisting the localization, and exchanging signals over a wireless transmission link separate from said satellite communication link, characterized in that it comprises means for acquiring and monitoring the coded signals transmitted by a list of pseudolite base stations selected from the set of pseudolite base stations according to a pre-location information of the terminal obtained from the signals transmitted on said wireless transmission link and the power of the signals transmitted by each of the pseudolites base stations of said together.
La présente invention a en outre pour objet un serveur de communication caractérisé en ce qu'il est apte à être connecté à un ensemble de stations de base pseudolites aptes à communiquer avec un récepteur de localisation par satellite d'un terminal de communication mobile par un lien de communication satellite et à au moins une borne apte à communiquer avec ledit terminal via une liaison de communication sans fil distincte dudit lien de communication satellite, et en ce qu'il comporte des moyens logiciels de détermination des valeurs théoriques de puissance et de la liste conformément au procédé. The present invention further relates to a communication server characterized in that it is capable of being connected to a set of pseudolite base stations able to communicate with a satellite location receiver of a mobile communication terminal by a satellite communication link and at least one terminal capable of communicating with said terminal via a wireless communication link separate from said satellite communication link, and in that it comprises software means for determining the theoretical power values and the list according to the method.
La présente invention, ainsi que les avantages qu'elle procure, seront mieux compris au vu de la description suivante d'un exemple de système de localisation implémentant l'invention, faite en description aux figures annexées dans lesquelles :  The present invention, as well as the advantages that it provides, will be better understood in view of the following description of an example of a location system implementing the invention, described in the appended figures in which:
- la figure 1 illustre schématiquement une architecture possible d'un système d'assistance à la localisation selon l'invention ;  - Figure 1 schematically illustrates a possible architecture of a location assistance system according to the invention;
- la figure 2 illustre sous forme de synoptique simplifié, les différentes étapes mises en œuvre dans un procédé de localisation conforme à l'invention.  FIG. 2 illustrates, in the form of a simplified block diagram, the various steps implemented in a localization method according to the invention.
Sur la figure 1 annexée, la référence 1 indique un système d'assistance à la localisation destiné à fournir, dans un environnement fermé à l'intérieur duquel le système est implanté, une aide à la localisation à un terminal 2 de communication mobile lorsque ce dernier entre dans la couverture du système.  In FIG. 1 appended, the reference 1 indicates a location assistance system intended to provide, in a closed environment within which the system is implanted, a location aid to a mobile communication terminal 2 when this last enters the system cover.
L'aide à la localisation utilise les signaux codés transmis par un nombre N prédéterminé de stations de base pseudolites constituant un ensemble du système 1, dont quatre sont visibles sur la figure 1 et référencées PSI à PS4, ces signaux étant aptes à être tous ou en partie reçus par un récepteur GPS (non représenté) équipant le terminal 2 de communication mobile, selon l'endroit où se trouve le terminal à un instant donné. Le système 1 d'assistance est couplé au système de navigation par satellite représenté par la référence générale 3. En variante, le système 1 d'assistance est totalement autonome, c'est à dire que les valeurs de bases utilisées sont connues du système 1 sans pour autant que celui-ci soit relié au système de navigation par satellite 3. Dans tous les cas, les stations de base pseudolites PSi (i= 1 à N) transmettent sur un lien de communication GPS radiofréquence 10 des signaux de puissances déterminées du même type que ceux émis par les satellites du système GPS 3, à savoir des signaux codés selon le code C/A et diffusés sur une fréquence porteuse Ll égale à 1575,42 MHz. The location aid uses the coded signals transmitted by a predetermined number N of pseudolite base stations constituting a set of the system 1, of which four are visible in FIG. 1 and referenced PSI to PS4, these signals being able to be all or partly received by a GPS receiver (not shown) equipping the mobile communication terminal 2, depending on where the terminal is located at a given time. The assistance system 1 is coupled to the satellite navigation system represented by the general reference 3. In a variant, the assistance system 1 is completely autonomous, that is to say that the basic values used are known to the system 1 without the latter being connected to the satellite navigation system 3. In all cases, the pseudolite base stations PSi (i = 1 to N) transmit on a radio frequency GPS communication link 10 signals of certain powers of the same type as those issued by satellites of the GPS system 3, namely signals coded according to the C / A code and broadcast on a carrier frequency Ll equal to 1575.42 MHz.
Le principe de l'invention consiste à permettre l'élaboration d'une liste préférée de stations de base pseudolites choisies parmi l'ensemble des stations de base pseudolites comprises dans le système 1 d'assistance, de façon à éviter les risques d'interférences entre les signaux effectivement reçus par le récepteur GPS du terminal 2 de communication mobile. Elle propose à cet effet de fournir un traitement particulier des signaux qui permette d'exclure si besoin les stations de base pseudolites susceptibles d'émettre un signal qui serait reçu par le récepteur avec des interférences.  The principle of the invention consists in allowing the elaboration of a preferred list of pseudolite base stations chosen from the set of pseudolite base stations included in the assistance system 1, so as to avoid the risks of interference. between the signals actually received by the GPS receiver of the mobile communication terminal 2. It proposes for this purpose to provide a particular signal processing that allows to exclude if necessary base stations pseudolites likely to emit a signal that would be received by the receiver with interference.
Pour ce faire, le procédé selon l'invention comprend essentiellement les étapes décrites ci-après, résumées sur la figure 2 annexée :  To do this, the process according to the invention essentially comprises the steps described below, summarized in the appended FIG. 2:
On commence par déterminer une information de pré-localisation du terminal de communication mobile par des moyens distincts de ceux utilisés pour la navigation GPS (Etape SI sur la figure 2). Pour ce faire, et comme illustré sur la figure 1, le système 1 d'assistance comporte de préférence une pluralité de bornes, dans l'exemple représenté, un nombre P de bornes Wifi dont trois seulement, référencées WF1 à WF3, sont visibles sur la figure. Il convient de noter que l'invention est applicable au cas où une seule borne est utilisée. Ces bornes sont aptes à recevoir ou à émettre, automatiquement ou sur requête, des signaux respectivement transmis ou reçus par le terminal 2 de communication mobile sur une liaison 11 de transmission sans fil distincte du lien 10 de communication GPS lorsque le terminal 2 passe à proximité. Bien entendu, le terminal 2 doit être équipé lui aussi de moyens (non représentés) lui permettant de transmettre de tels signaux Wifi. En variante, d'autres liaisons de communication à courte portée, telles qu'une liaison de type Bluetooth, peuvent être utilisées, les bornes Wifi étant alors remplacées par des bornes Bluetooth judicieusement placées. La localisation grâce à ces bornes peut être calculée aussi bien par le terminal puis transmise au système que par le système après récupération des mesures de puissances des bornes WF1 à WF3 effectuées par le terminal selon des méthodes connues (triangulation, fingerprinting,...). Le terminal ayant déjà été localisé par la méthode décrite, on peut également utiliser la propre localisation fournie par la localisation calculée grâce aux signaux pseudolites valides reçus par le terminal. Dans ce cas, le terminal mobile peut transmettre via la liaison 11 de transmission sans fil, un signal comportant la pré-localisation calculée par le terminal. On rappelle qu'une combinaison d'utilisation de ces moyens peut- être utilisée. Dans tous les cas, la position des bornes étant connue du système, la réception des signaux par une ou plusieurs des bornes du système permet de déterminer, soit par détermination de la ou des bornes ayant reçu les signaux, soit par analyse du contenu de ces signaux (cas où le terminal transmet l'information de localisation), une localisation au minimum grossière du terminal mobile appelée dans la suite de la description information de prélocalisation. Ainsi, l'information de pré-localisation est déterminée dans tous les cas à partir des signaux qui sont transmis sur la liaison de transmission sans fil 11. We first determine a pre-location information of the mobile communication terminal by means different from those used for GPS navigation (Step SI in Figure 2). For this purpose, and as illustrated in FIG. 1, the assistance system 1 preferably comprises a plurality of terminals, in the example represented, a number P of Wifi terminals of which only three, referenced WF1 to WF3, are visible on the figure. It should be noted that the invention is applicable in the case where only one terminal is used. These terminals are able to receive or transmit, automatically or on request, signals respectively transmitted or received by the mobile communication terminal 2 on a wireless transmission link 11 distinct from the GPS communication link 10 when the terminal 2 passes nearby. . Of course, the terminal 2 must also be equipped with means (not shown) for transmitting such WiFi signals. As a variant, other short-range communication links, such as a Bluetooth-type link, can be used, the Wifi terminals then being replaced by appropriately placed Bluetooth terminals. Localization through these terminals can be calculated both by the terminal and then transmitted to the system than by the system after recovery of power measurements terminals WF1 to WF3 made by the terminal according to known methods (triangulation, fingerprinting, ...). Since the terminal has already been located by the method described, it is also possible to use the localization provided by the location calculated by the valid pseudolite signals received by the terminal. In this case, the mobile terminal can transmit via the wireless transmission link 11, a signal comprising the pre-location calculated by the terminal. It is recalled that a combination of use of these means can be used. In any case, since the position of the terminals is known to the system, the reception of the signals by one or more of the terminals of the system makes it possible to determine, either by determining the terminal or terminals having received the signals, or by analyzing the contents of these signals (in which case the terminal transmits the location information), a minimum coarse location of the mobile terminal called in the following description prelocation information. Thus, the pre-location information is determined in all cases from the signals that are transmitted on the wireless transmission link 11.
Une fois l'information de pré-localisation obtenue, on cherche à déterminer, pour cette pré-localisation, les valeurs des puissances ¾ des signaux qui seraient théoriquement reçus par le récepteur GPS du terminal 2 de communication mobile en provenance de chacune des stations de base pseudolites dudit ensemble (étape S2 sur la figure 2). Cette détermination est effectuée en utilisant d'une part, l'information de pré-localisation, et d'autre part, la puissance ¾ des signaux émis par chacune des stations de base pseudolites de l'ensemble, connue par ailleurs. Pour ce faire, plusieurs méthodes peuvent être utilisées :  Once the pre-location information has been obtained, it is sought to determine, for this pre-location, the values of the powers ¾ of the signals that would be theoretically received by the GPS receiver of the mobile communication terminal 2 from each of the radio stations. pseudolites base of said set (step S2 in Figure 2). This determination is performed using, on the one hand, the pre-location information, and, on the other hand, the power ¾ of the signals emitted by each of the pseudolite base stations of the set, which is moreover known. To do this, several methods can be used:
Une première méthode consiste à déterminer les valeurs ¾ en utilisant la loi de propagation des ondes radio en champ libre exprimée par la relation  A first method consists in determining the values ¾ by using the law of propagation of radio waves in free field expressed by the relation
Di D i
dans laquelle : - Z^ est la distance séparant le terminal 2 de chaque station de base pseudolite Psi, estimée à partir de l'information de pré localisation et de la connaissance des positions de chacune des stations de base pseudolite du système ; in which : Z 2 is the distance separating the terminal 2 from each Psi pseudolite base station, estimated from the pre-location information and the knowledge of the positions of each of the pseudolite base stations of the system;
- PEi est la puissance émise par chaque station de base pseudolite Psi, connue du système ; et P Ei is the power emitted by each psi pseudolite base station, known from the system; and
- E, est le champ électrique rayonné en un point situé à la distance - E, is the electric field radiated at a point situated at a distance
D, de chaque station de base pseudolite Psi, point correspondant au point de pré-localisation du terminal 2. D, of each pseudolite base station Psi, point corresponding to the pre-location point of the terminal 2.
Cette relation n'est valable que pour une distance Di beaucoup plus grande que la longueur d'onde du signal . This relation is valid only for a distance D i much larger than the wavelength of the signal.
Ainsi, une source de 10 W produira un champ E de 1 mV /m à une distance de 30 km, ce qui, en radioélectricité, n'est pas un champ négligeable.  Thus, a source of 10 W will produce a field E of 1 mV / m at a distance of 30 km, which, in radio, is not a negligible field.
Selon cette première méthode, l'étape de détermination S2 consistera donc essentiellement à :  According to this first method, the determination step S2 will essentially consist of:
- Calculer la distance Di séparant le terminal 2 de communication mobile et chacune des stations de base pseudolites de l'ensemble à partir de l'information de pré-localisation et de la localisation connue de chaque station de base pseudolites; Calculating the distance D i separating the mobile communication terminal 2 and each of the pseudolite base stations from the set from the pre-location information and the known location of each pseudolite base station;
- En déduire la valeur théorique de la puissance reçue à partir de la distance D, et de la puissance PEi des signaux émis par chacune des stations de base pseudolites dudit ensemble en utilisant la loi de propagation des ondes radiofréquence en champ libre. - Deduce the theoretical value of the power received from the distance D, and the power P Ei of the signals emitted by each of the pseudolite base stations of said set using the law of radiofrequency wave propagation in free field.
Une deuxième méthode consiste à réaliser une étape préalable de relevé et mémorisation de mesures de la puissance reçue en provenance de chacune des stations de bases pseudolites dudit ensemble en différents points de l'environnement fermé. Dans ce cas, l'étape de détermination des valeurs théoriques PRi des puissances des signaux reçues par le récepteur GPS consiste à choisir dans le relevé la valeur de la puissance pour le point le plus proche de l'information de pré-localisation. On peut en outre prévoir dans l'étape S2 un calcul par interpolation des valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite après avoir choisi les valeurs de puissance connues pour les points les plus proches de l'information de pré-localisation. A second method consists in carrying out a preliminary step of recording and storing measurements of the power received from each of the pseudolite base stations of said set at different points of the closed environment. In this case, the step of determining the theoretical values P Ri of the powers of the signals received by the GPS receiver consists in choosing in the reading the value of the power for the most close to the pre-location information. In step S2, it is also possible to provide an interpolation calculation of the theoretical values of the powers of the signals received by the satellite location receiver after having chosen the known power values for the points closest to the pre-information information. location.
Selon une troisième méthode possible, on effectue une modélisation préalable de la topologie de l'environnement fermé comprenant notamment les emplacements des stations de base pseudolites de l'ensemble, les coefficients d'absorption et/ou de réflexion susceptibles d'intervenir dans le trajet des ondes entre chaque station de base pseudolite et différents points de l'environnement. Dans ce dernier cas, il est nécessaire de connaître l'ensemble des matériaux utilisés pour définir les parois, murs, plafond... existant dans l'environnement fermé. Cette modélisation peut alors être utilisée en temps réel pour simuler la valeur théorique PRi de puissance reçue en provenance de chacune des stations de bases pseudolites en différents points de l'environnement fermé, et en particulier au point donné par l'information de pré-localisation. According to a third possible method, a prior modeling of the topology of the closed environment including in particular the locations of the pseudolite base stations of the set, the absorption and / or reflection coefficients likely to take place in the path is carried out. waves between each pseudolite base station and different points of the environment. In the latter case, it is necessary to know all the materials used to define the walls, walls, ceiling ... existing in the closed environment. This modeling can then be used in real time to simulate the theoretical value P Ri of power received from each of the pseudolite base stations at different points of the closed environment, and in particular at the point given by the information of pre- location.
Les deuxième et troisième méthodes explicitées ci-avant peuvent donner des résultats très précis. Néanmoins, elles souffrent de nécessiter des nouveaux relevés ou modélisations à chaque fois que l'implantation des stations de base pseudolites est modifiée. Pour pallier cet inconvénient et tenir compte de l'évolution du nombre, des positions ou des puissances émises des stations de base pseudolites, on peut prévoir avantageusement, en complément de ces méthodes, une étape additionnelle d'auto apprentissage permettant de mettre à contribution les terminaux déjà localisés par la réception des signaux des pseudolites. Un échange régulier des mesures de puissances perçues par ces terminaux et de l'endroit où elles ont été faites permet dynamiquement de mettre à jour la base de données les valeurs théoriques de puissances déterminées par relevé ou modélisation. Ainsi, le procédé selon l'invention peut avantageusement comporter une étape additionnelle dans laquelle le terminal détermine sa localisation à l'aide des signaux qu'il reçoit des stations de base de la liste, et mesure la puissance des signaux qu'il reçoit effectivement des stations de base pseudolites, de façon à permettre une mise à jour dynamique du relevé ou de la modélisation. The second and third methods explained above can give very precise results. Nevertheless, they suffer from requiring new readings or models every time the implementation of pseudolite base stations is modified. To overcome this drawback and to take into account the evolution of the number, the positions or the transmitted powers of the pseudolite base stations, it is advantageous to provide, in addition to these methods, an additional self-learning step making it possible to use the terminals already located by the reception of pseudolites signals. A regular exchange of the power measurements perceived by these terminals and the place where they have been made dynamically makes it possible to update the database the theoretical values of powers determined by reading or modeling. Thus, the method according to the invention may advantageously comprise an additional step in which the terminal determines its location using the signals it receives from the base stations of the list, and measures the power of the signals that it actually receives pseudolite base stations, so as to allow dynamic update of the survey or modeling.
Une fois que les valeurs de puissances théoriques reçues ont été déterminées, selon l'une quelconque des méthodes décrites précédemment, le procédé d'assistance selon l'invention prévoit une étape de détermination d'une liste de stations de bases pseudolites que le récepteur GPS du terminal 2 de communication mobile doit écouter parmi les stations de base pseudolites de l'ensemble à partir des valeurs théoriques des puissances des signaux reçus (étape S3 sur la figure 2).  Once the received theoretical power values have been determined, according to any of the methods described above, the assistance method according to the invention provides a step of determining a list of pseudolite base stations that the GPS receiver. the mobile communication terminal 2 must listen among the pseudolite base stations of the set from the theoretical values of the powers of the signals received (step S3 in FIG. 2).
De plus, les études de la Demanderesse ont montré que des interférences à la réception étaient susceptibles d'intervenir entre les signaux reçus de deux stations de base pseudolites dès lors que le rapport des puissances reçues par le terminal de ces deux stations est supérieur à un seuil, qui exprimé en décibels, se trouve aux alentours de 24 dB en mode poursuite. Ce seuil peut même descendre à 20 dB en mode acquisition.  Moreover, the Applicant's studies have shown that reception interference is likely to occur between the signals received from two pseudolite base stations when the ratio of the powers received by the terminal of these two stations is greater than one. threshold, which is expressed in decibels, is around 24 dB in the tracking mode. This threshold can even go down to 20 dB in acquisition mode.
Dès lors, l'étape S3 de détermination de la liste consiste de préférence à exclure les stations de bases pseudolites dudit ensemble pour lesquelles le les valeurs théoriques de puissance des signaux reçus sont inférieures à la puissance théorique la plus forte diminuée d'une marge prédéterminée, cette marge étant de préférence de l'ordre de 24 dB pour un signal de type GPS transmettant un code diffusé à une fréquence de 1575,42 MHz en mode poursuite, et de l'ordre de 20 dB en mode acquisition.  Therefore, the step S3 for determining the list preferably consists in excluding pseudolite base stations from said set for which the theoretical power values of the received signals are lower than the highest theoretical power minus a predetermined margin. , this margin being preferably of the order of 24 dB for a GPS type signal transmitting a code broadcast at a frequency of 1575.42 MHz in tracking mode, and of the order of 20 dB in acquisition mode.
On notera que les marges ci-dessus peuvent être ajustées en fonction des caractéristiques du récepteur de localisation utilisé dans le terminal. En outre, la valeur de ces marges est indiquée ici dans le cadre de signaux GPS, mais d'autres valeurs doivent être utilisées pour d'autres systèmes de localisation par satellite.  Note that the above margins can be adjusted according to the characteristics of the location receiver used in the terminal. In addition, the value of these margins is indicated here in the context of GPS signals, but other values must be used for other satellite tracking systems.
Les étapes S2 et S3 peuvent être mises en œuvre au niveau du système 1 d'assistance, et plus précisément par des moyens logiciels au niveau d'un serveur 12 auquel les différentes stations de base pseudolites et bornes Wifi ou Bluetooth sont reliées. Sur la figure 1, le serveur 12 a été représenté comme implanté dans l'emplacement fermé auquel le système d'assistance est dédié. Bien entendu, ce serveur peut être à un autre endroit, relié aux différents éléments du système par un réseau 13 de type LAN. Un même serveur peut d'ailleurs être utilisé pour fonctionner avec différents ensembles de pseudolites installés en différents endroits, par exemple des bâtiments distincts. The steps S2 and S3 can be implemented at the level of the assistance system 1, and more specifically by software means at a server 12 to which the different base stations pseudolites and Wifi or Bluetooth terminals are connected. In FIG. 1, the server 12 has been shown as implanted in the closed location to which the assistance system is dedicated. Of course, this server may be at another location, connected to the various elements of the system by a network 13 of the LAN type. The same server can also be used to work with different sets of pseudolites installed in different places, for example separate buildings.
Dans l'exemple représenté sur la figure 1, les bornes Wifi WF1 à WF3 ont permis de pré-localiser grossièrement le terminal 2, et, conformément au procédé selon l'invention, l'une des stations de base pseudolite, ici la station PS3, est exclue de l'ensemble des stations de base pseudolites. La liste élaborée conformément au procédé de l'invention contient dans ce cas uniquement les stations PSI, PS2 et PS4.  In the example shown in FIG. 1, the Wifi terminals WF1 to WF3 made it possible to pre-locate the terminal 2 roughly and, according to the method according to the invention, one of the pseudolite base stations, here the PS3 station. , is excluded from all pseudolite base stations. The list developed in accordance with the method of the invention contains in this case only the stations PSI, PS2 and PS4.
Une fois que le serveur a déterminé la liste des stations de base devant être écoutées par le terminal 2, le système transmet alors cette liste au terminal qui peut alors continuer son processus de localisation sur la base de la liste. Avantageusement, les moyens permettant de transmettre cette liste sont les mêmes que ceux qui ont permis de recevoir la pré-localisation du terminal, à savoir les bornes WiFi ou Bluetooth du système 1.  Once the server has determined the list of base stations to be listened to by the terminal 2, the system then transmits this list to the terminal which can then continue its localization process based on the list. Advantageously, the means making it possible to transmit this list are the same as those which made it possible to receive the pre-location of the terminal, namely the WiFi or Bluetooth terminals of the system 1.
On peut prévoir en outre que le système d'assistance vérifie au préalable que le terminal 2 a droit au service. Si cette condition est remplie, le serveur va exécuter l'algorithme permettant de créer la liste des stations de bases pseudolites optimale. Ensuite cette liste créée est éventuellement mémorisée par le serveur en regard du terminal concerné afin de pouvoir la mettre à jour en fonction de la localisation précise du terminal qui pourrait être transmise régulièrement par le terminal au serveur, selon l'étape d'auto apprentissage décrite précédemment. Ce contrôle est optionnel, car on peut imaginer que ce service serait dans certaines situations gratuit et disponible pour tout le monde.  It can further be provided that the assistance system checks beforehand that the terminal 2 is entitled to the service. If this condition is met, the server will execute the algorithm to create the list of optimal pseudolite base stations. Then this list created is possibly stored by the server next to the terminal concerned so as to be able to update it according to the precise location of the terminal that could be transmitted regularly by the terminal to the server, according to the self-learning step described. previously. This control is optional, because we can imagine that this service would be in certain situations free and available for everyone.
Les bornes peuvent avantageusement être contrôlées dans le système de manière à ce que l'envoi de la liste de stations de base pseudolites optimale vers le terminal soit régulière ou provoquée par des événements. La fréquence de cet envoi peut être temporelle ou bien l'envoi peut être provoqué par un déplacement dans l'emplacement fermé, ou encore après une demande spécifique d'une application du terminal . The terminals can advantageously be controlled in the system so that the sending of the list of base stations pseudolites optimal to the terminal is regular or caused by events. The frequency of this sending may be temporal or the sending may be caused by a displacement in the closed location, or after a specific request for an application of the terminal.
Bien que l'utilisation d'un serveur soit préférée du fait qu'il permet de ne pas venir grever l'autonomie du terminal par des charges de calcul supplémentaires, on peut également envisager que les étapes S2, S3 soient mises en ouvre au niveau du terminal 2. Dans ce cas, toutes les informations nécessaires sont transmises par le système 1 au terminal 2.  Although the use of a server is preferred because it makes it possible not to burden the autonomy of the terminal with additional computing loads, it is also conceivable that the steps S2, S3 are implemented at the level of the server. of the terminal 2. In this case, all the necessary information is transmitted by the system 1 to the terminal 2.

Claims

REVENDICATIONS
Procédé d'assistance à la localisation d'un terminal (2) de communication mobile équipé d'un récepteur de localisation par satellite dans un environnement fermé à l'intérieur duquel un ensemble de stations de bases pseudolites (PS1-PS4) a été installé, ledit récepteur étant apte à recevoir des signaux codés émis par chacune des stations de bases pseudolites dudit ensemble sur un lien (10) de communication satellite, le terminal (2) de communication mobile étant apte en outre à transmettre des signaux sur une liaison (11) de transmission sans fil distincte dudit lien (10) de communication satellite le procédé étant caractérisé en ce qu'il comporte les étapes suivantes : Method for assisting in the location of a mobile communication terminal (2) equipped with a satellite location receiver in a closed environment inside which a set of pseudolite base stations (PS1-PS4) has been installed , said receiver being able to receive coded signals transmitted by each of the pseudolite base stations of said set on a satellite communication link (10), the mobile communication terminal (2) also being able to transmit signals on a link ( 11) of wireless transmission distinct from said satellite communication link (10), the method being characterized in that it comprises the following steps:
- Déterminer (SI) une information de pré-localisation dudit terminal (2) de communication mobile à partir de signaux transmis sur ladite liaison (11) de transmission sans fil; - Determine (SI) pre-location information for said mobile communication terminal (2) from signals transmitted on said wireless transmission link (11);
- Déterminer (S2) des valeurs théoriques des puissances des signaux reçus par le récepteur de localisation par satellite du terminal - Determine (S2) theoretical values of the powers of the signals received by the satellite location receiver of the terminal
(2) de communication mobile et émis par chacune des stations de base pseudolites (PS1-PS4) dudit ensemble, à partir de l'information de prélocalisation et de la puissance des signaux émis par chacune des stations de base pseudolites (PS1-PS4) dudit ensemble; (2) of mobile communication and transmitted by each of the pseudolite base stations (PS1-PS4) of said set, from the prelocation information and the power of the signals transmitted by each of the pseudolite base stations (PS1-PS4) of said set;
- Déterminer - Determine
(S3) une liste (PSI, PS2, PS4) de stations de base pseudolites que le récepteur de localisation par satellite du terminal (2) de communication mobile doit écouter parmi les stations de base pseudolites (PS1-PS4) dudit ensemble à partir des valeurs théoriques des puissances des signaux reçus. (S3) a list (PSI, PS2, PS4) of pseudolite base stations that the satellite location receiver of the mobile communication terminal (2) must listen to among the pseudolite base stations (PS1-PS4) of said set from the theoretical values of the powers of the signals received.
Procédé selon la revendication 1, caractérisé en ce que l'étape (S2) de détermination des valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite consiste à : - Calculer la distance Dt séparant le terminal (2) de communication mobile et chacune des stations de base pseudolites (PS1-PS4) dudit ensemble à partir de l'information de pré-localisation et de la localisation connue de chaque station de base pseudolite (PS1-PS4); Method according to claim 1, characterized in that the step (S2) of determining the theoretical values of the powers of the signals received by the satellite location receiver consists of: - Calculate the distance D t separating the mobile communication terminal (2) and each of the pseudolite base stations (PS1-PS4) of said set from the pre-location information and the known location of each pseudolite base station (PS1-PS4);
- En déduire la valeur théorique de la puissance reçue à partir de la distance Di et de la puissance des signaux émis par chacune des stations de base pseudolites (PS1-PS4) dudit ensemble en utilisant la loi de propagation des ondes radiofréquence en champ libre. - Deduce the theoretical value of the power received from the distance D i and the power of the signals transmitted by each of the pseudolite base stations (PS1-PS4) of said set using the law of propagation of radiofrequency waves in a free field .
Procédé selon la revendication 1, caractérisé en ce que le procédé comporte en outre une étape préalable de relevé et mémorisation de mesures de la puissance reçue en provenance de chacune des stations de bases pseudolites (PS1-PS4) dudit ensemble en différents points de l'environnement fermé, et en ce que l'étape (S2) de détermination des valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite consiste à choisir dans le relevé la valeur de la puissance pour le point le plus proche de l'information de prélocalisation. Method according to claim 1, characterized in that the method further comprises a preliminary step of recording and storing measurements of the power received from each of the pseudolite base stations (PS1-PS4) of said set at different points of the closed environment, and in that the step (S2) of determining the theoretical values of the powers of the signals received by the satellite location receiver consists of choosing in the reading the value of the power for the point closest to the prelocation information.
4. Procédé selon la revendication 3, caractérisé en ce que le procédé comporte en outre, dans l'étape (S2), un calcul par interpolation des valeurs théoriques des puissances des signaux reçues par le récepteur satellite après avoir choisi les valeurs de puissance connues pour les points les plus proches de l'information de pré-localisation. 4. Method according to claim 3, characterized in that the method further comprises, in step (S2), a calculation by interpolation of the theoretical values of the powers of the signals received by the satellite receiver after having chosen the known power values for the closest points to the pre-location information.
Procédé selon la revendication 1, caractérisé en ce que l'étape (S2) de détermination des valeurs théoriques des puissances des signaux reçues par le récepteur de localisation par satellite consiste à utiliser une modélisation préalable de la topologie de l'environnement fermé comprenant les emplacements des stations de base pseudolites dudit ensemble, les coefficients d'absorption et/ou de réflexion susceptibles d'intervenir dans le trajet des ondes entre chaque station de base pseudolite et différents points de l'environnement de manière à simuler la puissance reçue en provenance de chacune des stations de bases pseudolites (PS1-PS4) en différents points de l'environnement fermé. Method according to claim 1, characterized in that the step (S2) of determining the theoretical values of the powers of the signals received by the satellite location receiver consists of using a prior modeling of the topology of the closed environment including the locations pseudolite base stations of said set, the absorption and/or reflection coefficients likely to intervene in the path of the waves between each base station pseudolite and different points in the environment so as to simulate the power received from each of the pseudolite base stations (PS1-PS4) at different points in the closed environment.
6. Procédé selon l'une quelconque des revendications 4 ou 5, caractérisé en ce qu'il comporte en outre une étape additionnelle dans laquelle le terminal détermine sa localisation à l'aide des signaux qu'il reçoit des stations de base de ladite liste, et mesure la puissance des signaux qu'il reçoit des stations de base pseudolites, de façon à mettre à jour dynamiquement ledit relevé ou ladite modélisation. 6. Method according to any one of claims 4 or 5, characterized in that it further comprises an additional step in which the terminal determines its location using the signals it receives from the base stations of said list , and measures the power of the signals that it receives from the pseudolite base stations, so as to dynamically update said survey or said modeling.
7. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que l'étape (S3) de détermination de la liste de stations de base pseudolites à écouter consiste à exclure les stations de bases pseudolites dudit ensemble pour lesquelles les valeurs théoriques de puissance des signaux reçus sont inférieures à la puissance théorique la plus forte diminuée d'une marge prédéterminée. 7. Method according to any one of the preceding claims, characterized in that the step (S3) of determining the list of pseudolite base stations to listen to consists of excluding the pseudolite base stations from said set for which the theoretical values of power of the signals received are lower than the highest theoretical power reduced by a predetermined margin.
8. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le système de localisation par satellite est l'un des systèmes suivants : GPS, Galileo, Glonass, Compass, QZSS. 8. Method according to any one of the preceding claims, characterized in that the satellite location system is one of the following systems: GPS, Galileo, Glonass, Compass, QZSS.
9. Procédé selon la revendication 7, caractérisé en ce que, le système de localisation par satellite est de type GPS, et en ce que ladite marge est de l'ordre de 24 dB pour un signal transmettant un code diffusé à une fréquence de 1575,42 MHz en mode poursuite, et de l'ordre de 20 dB en mode acquisition. 9. Method according to claim 7, characterized in that the satellite location system is of the GPS type, and in that said margin is of the order of 24 dB for a signal transmitting a code broadcast at a frequency of 1575 .42 MHz in tracking mode, and around 20 dB in acquisition mode.
10. Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que ladite liaison (11) de transmission sans fil est une liaison courte portée du type WiFi ou Bluetooth entre le terminal (2) de communication mobile et au moins une borne WiFi (WF1-WF3) ou Bluetooth installée à l'intérieur dudit environnement. 10. Method according to any one of the preceding claims, characterized in that said wireless transmission link (11) is a short-range connection of the WiFi or Bluetooth type between the mobile communication terminal (2) and at least one WiFi terminal (WF1-WF3) or Bluetooth installed within said environment.
11. Procédé selon la revendication 10, caractérisé en ce que les étapes de détermination (S2) des valeurs théoriques de puissances et de détermination (S3) de la liste des stations de base pseudolites à écouter sont réalisées : 11. Method according to claim 10, characterized in that the steps of determining (S2) the theoretical power values and determining (S3) the list of pseudolite base stations to listen to are carried out:
- soit, au niveau du terminal (2) de communication mobile, - either, at the level of the mobile communication terminal (2),
- soit, au niveau d'un serveur (12) auquel les stations de base pseudolites (PS1-PS4) et ladite borne sont reliées, auquel cas le procédé comporte en outre une étape de transmission de ladite liste au terminal (2) de communication via la liaison (11) de transmission sans fil. - either, at the level of a server (12) to which the pseudolite base stations (PS1-PS4) and said terminal are connected, in which case the method further comprises a step of transmitting said list to the communication terminal (2) via the wireless transmission link (11).
12. Système d'assistance à la localisation d'un terminal (2) de communication mobile dans un environnement fermé, le système comportant un ensemble de stations de bases pseudolites (PS1-PS4) installées à l'intérieur dudit environnement, aptes à transmettre des signaux codés sur un lien (10) de communication satellite à destination d'un récepteur de localisation par satellite équipant le terminal, le terminal (2) de communication mobile étant en outre apte à transmettre des signaux sur une liaison (11) de transmission sans fil distincte dudit lien de communication satellite le système étant caractérisé en ce qu'il comporte en outre : 12. System for assisting in the location of a mobile communication terminal (2) in a closed environment, the system comprising a set of pseudolite base stations (PS1-PS4) installed inside said environment, capable of transmitting signals coded on a satellite communication link (10) intended for a satellite location receiver fitted to the terminal, the mobile communication terminal (2) further being capable of transmitting signals on a transmission link (11) wireless distinct from said satellite communication link, the system being characterized in that it further comprises:
- au moins une borne (WF1-WF3) apte à échanger des signaux avec ledit terminal (2) de communication mobile sur ladite liaison de transmission sans fil de façon à pouvoir déterminer une information de pré-localisation dudit terminal (2) de communication mobile obtenue à partir des signaux transmis par le terminal (2) sur ladite liaison de transmission sans fil; - at least one terminal (WF1-WF3) capable of exchanging signals with said mobile communication terminal (2) on said wireless transmission link so as to be able to determine pre-location information of said mobile communication terminal (2) obtained from the signals transmitted by the terminal (2) over said wireless transmission link;
- Des moyens (2 ; 10) de détermination des valeurs théoriques des puissances des signaux reçus par le récepteur de localisation par satellite du terminal (2) de communication mobile et émis par lesdites stations de base pseudolites (PS1-PS4) dudit ensemble, à partir de l'information de pré-localisation et de la puissance des signaux émis par chacune des stations de base pseudolites (PS1-PS4) dudit ensemble, et de détermination d'une liste de stations de bases pseudolites que le récepteur de localisation par satellite du terminal (2) de communication mobile doit écouter parmi l'ensemble des stations de base pseudolites (PSI, PS4) à partir des valeurs théoriques des puissances des signaux reçus. - Means (2; 10) for determining the theoretical values of the powers of the signals received by the satellite location receiver of the mobile communication terminal (2) and transmitted by said pseudolite base stations (PS1-PS4) of said set, from the pre-location information and the power of the signals transmitted by each of the pseudolite base stations (PS1-PS4) of said together, and determining a list of pseudolite base stations that the satellite location receiver of the mobile communication terminal (2) must listen to among all the pseudolite base stations (PSI, PS4) from the theoretical values of the powers of the signals received.
13. Système selon la revendication 12, caractérisé en ce que lesdits moyens de détermination comportent un serveur (12) auquel les stations de base pseudolites (PS1-PS4) de l'ensemble et la borne (WF1- WF3) sont reliées. 13. System according to claim 12, characterized in that said determination means comprise a server (12) to which the pseudolite base stations (PS1-PS4) of the assembly and the terminal (WF1-WF3) are connected.
14. Système selon la revendication 12, caractérisé en ce que ladite au moins une borne est apte à transmettre ladite liste au terminal (2) de communication mobile via ladite liaison (11) de transmission sans fil. 14. System according to claim 12, characterized in that said at least one terminal is capable of transmitting said list to the mobile communication terminal (2) via said wireless transmission link (11).
15. Système selon la revendication 12, caractérisé en ce que lesdits moyens de détermination font partie du terminal (2) de communication mobile. 15. System according to claim 12, characterized in that said determination means form part of the mobile communication terminal (2).
16. Terminal (2) de communication mobile équipé d'un récepteur de localisation par satellite apte à recevoir, sur un lien (10) de communication satellite, des signaux codés transmis par un ensemble de stations de bases pseudolites (PS1-PS4) d'un système d'assistance à la localisation, et à échanger des signaux sur une liaison (11) de transmission sans fil distincte dudit lien de communication satellite, caractérisé en ce qu'il comporte des moyens pour acquérir et suivre les signaux codés transmis par une liste (PSI, PS2, PS4) de stations de bases pseudolites choisies parmi l'ensemble de stations de base pseudolites (PS1-PS4) en fonction d'une information de pré-localisation du terminal obtenue à partir des signaux transmis sur ladite liaison (11) de transmission sans fil et de la puissance des signaux émis par chacune des stations de base pseudolites (PS1-PS4) dudit ensemble. 16. Mobile communication terminal (2) equipped with a satellite location receiver capable of receiving, on a satellite communication link (10), coded signals transmitted by a set of pseudolite base stations (PS1-PS4) d 'a location assistance system, and for exchanging signals on a wireless transmission link (11) distinct from said satellite communication link, characterized in that it comprises means for acquiring and tracking the coded signals transmitted by a list (PSI, PS2, PS4) of pseudolite base stations chosen from the set of pseudolite base stations (PS1-PS4) according to pre-location information of the terminal obtained from the signals transmitted on said link (11) of wireless transmission and the power of the signals transmitted by each of the pseudolite base stations (PS1-PS4) of said set.
17. Terminal (2) de communication mobile selon la revendication 16, caractérisé en ce qu'il est apte à recevoir ladite liste d'un serveur (12) du système d'assistance à la localisation. 17. Mobile communication terminal (2) according to claim 16, characterized in that it is capable of receiving said list from a server (12) of the location assistance system.
18. Terminal selon l'une des revendications 16 ou 17, caractérisé en ce que le récepteur de localisation par satellite est apte à fonctionner avec l'un des systèmes de localisation par satellite suivants : GPS, Galileo, Glonass, Compass, QZSS. 18. Terminal according to one of claims 16 or 17, characterized in that the satellite location receiver is capable of operating with one of the following satellite location systems: GPS, Galileo, Glonass, Compass, QZSS.
19. Serveur (12) de communication caractérisé en ce qu'il est apte à être connecté à un ensemble de stations de base pseudolites (PS1-PS4) aptes à communiquer avec un récepteur de localisation par satellite d'un terminal (2) de communication mobile par un lien (10) de communication satellite et à au moins une borne (WF1-WF3) apte à communiquer avec ledit terminal (2) via une liaison (11) de communication sans fil distincte dudit lien de communication satellite, et en ce qu'il comporte des moyens logiciels de détermination des valeurs théoriques de puissance et de la liste conformément au procédé de la revendication 1. 19. Communication server (12) characterized in that it is capable of being connected to a set of pseudolite base stations (PS1-PS4) capable of communicating with a satellite location receiver of a terminal (2) of mobile communication by a satellite communication link (10) and at least one terminal (WF1-WF3) capable of communicating with said terminal (2) via a wireless communication link (11) distinct from said satellite communication link, and in what it includes software means for determining the theoretical power values and the list in accordance with the method of claim 1.
EP10787834A 2009-10-26 2010-10-22 Method and system for assisting with the locating of a mobile terminal in a closed environment using pseudolite base stations. Withdrawn EP2494373A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0957496A FR2951832B1 (en) 2009-10-26 2009-10-26 METHOD AND SYSTEM FOR ASSISTING THE LOCATION OF A MOBILE TERMINAL IN A CLOSED ENVIRONMENT USING PSEUDOLITE BASE STATIONS
PCT/FR2010/052265 WO2011051604A1 (en) 2009-10-26 2010-10-22 Method and system for assisting with the locating of a mobile terminal in a closed environment using pseudolite base stations.

Publications (1)

Publication Number Publication Date
EP2494373A1 true EP2494373A1 (en) 2012-09-05

Family

ID=42799915

Family Applications (1)

Application Number Title Priority Date Filing Date
EP10787834A Withdrawn EP2494373A1 (en) 2009-10-26 2010-10-22 Method and system for assisting with the locating of a mobile terminal in a closed environment using pseudolite base stations.

Country Status (3)

Country Link
EP (1) EP2494373A1 (en)
FR (1) FR2951832B1 (en)
WO (1) WO2011051604A1 (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6118977A (en) 1997-09-11 2000-09-12 Lucent Technologies, Inc. Telecommunications-assisted satellite positioning system
US6597988B1 (en) 2000-09-22 2003-07-22 Sirf Technology, Inc. Network assisted pseudolite acquisition for enhanced GPS navigation
GB2396985B (en) * 2001-09-12 2005-05-11 Data Fusion Corp Gps near-far resistant receiver
US7933612B2 (en) * 2006-02-28 2011-04-26 Microsoft Corporation Determining physical location based upon received signals

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2011051604A1 *

Also Published As

Publication number Publication date
FR2951832A1 (en) 2011-04-29
WO2011051604A1 (en) 2011-05-05
FR2951832B1 (en) 2011-12-23

Similar Documents

Publication Publication Date Title
CA2736917C (en) Processing of radionavigation signals using a wide-lane combination
EP1503220B1 (en) Position determination of mobile terminals by means of assistance data transmitted on request
EP1804071B1 (en) Method for optimising positioning data processing where there are several satellite positioning constellations
EP1836507B1 (en) Positioning device and method
CA2682278C (en) Method of processing radionavigation signals
EP2626723B1 (en) Method for estimating the incoming direction of navigation signals in a receiver after reflecting off walls in a satellite positioning system
EP1804070B1 (en) Method for fast acquisition of satellite signals
FR3023922A1 (en) POSITIONING AND NAVIGATION RECEIVER WITH CONFIDENCE INDICATOR
FR2936669A1 (en) METHOD FOR OPTIMIZING ACQUISITION OF A SPECTRA SIGNAL FROM A SATELLITE BY A MOBILE RECEIVER
WO2007074266A1 (en) Pre-location method and system for assisting satellite radio-navigation systems
EP1628139B1 (en) Process for determining the position of a Radio Frequency Receiver without knowledge of the initial position, and receiver for carrying it out
EP1544636A1 (en) Determination device by filtering of integrity data in a differential positioning system, for a mobile terminal
FR2858510A1 (en) Mobile terminal e.g. mobile phone, position determining method, involves selecting hypothesis couple corresponding to signal reply presenting correlation with signal received during time interval to determine pseudo-random code
EP2494373A1 (en) Method and system for assisting with the locating of a mobile terminal in a closed environment using pseudolite base stations.
FR3090848A1 (en) SURVEYING NAIL, TOPOGRAPHIC MESH, TOPOGRAPHIC SURVEYING SYSTEM AND METHOD
FR3068140A1 (en) METHOD FOR UPDATING A SET OF ORBITAL PARAMETERS STOCKETED IN A GEOLOCATION BEACON, COMPUTER PROGRAM PRODUCT, CORRESPONDING UPDATING DEVICE AND BEAM.
EP2406661A1 (en) Geopositioning method using assistance data
WO2021240119A1 (en) Cloud-offloaded gnss positioning method
EP2259643A2 (en) Method for transmitting position information by a mobile device
FR2907556A1 (en) METHOD FOR ASSISTING A GPS RECEIVER TO IMPROVE ALTITUDE CALCULATION
FR2924848A1 (en) Vehicle's localization indicating system, has CPU with data transmission units that transmit data towards data reception units, where data includes characteristic latitude and longitude of position of vehicle
EP2006705A1 (en) Method and system for precise pre-location of a satellite navigation signal receiver operating in assisted mode by a mobile telecommunication network
FR2966924A1 (en) Reliable telematic location system for locating motor vehicle in case of failure or accident, has communication unit communicating with remote geolocation service for transmitting calculated current position of system

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20120503

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

DAX Request for extension of the european patent (deleted)
17Q First examination report despatched

Effective date: 20130906

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

INTG Intention to grant announced

Effective date: 20150721

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20151201