FR2888455A1 - Mobile telephone e.g. thuraya mobile telephone, detecting method for military field, involves determining position of mobile telephones from information transmitted by uplink signals, and representing position of telephones on map - Google Patents

Abstract

The method involves capturing uplink signals (Up) of mobile telephones (M1-M3) through an active geostationary satellite (S) in an observer`s environment using a broadband receiver (E). The positions of the mobile telephones are determined from position information transmitted by the uplink signals, and the positions of the mobile telephones are represented on geographical map (K), which is displayed in a screen of an electronic display. An independent claim is also included for an apparatus for implementing a method for detecting mobile phone.

Description

Method and apparatus for detecting mobile phones by satellite

  The invention relates to a method for detecting satellite mobile phones that are active in the environment of an observer. The invention also relates to a simple apparatus for implementing said method.

  For the protection of important objects or spaces, the provision of live information on the site itself is crucial. In this context, in global use, mobile-satellite telephones that simultaneously transmit position information have more and more often a role to play. A frequently used system is the mobile phone named "Thuraya", in which information on the position of the mobile phone according to the GPS system (global position system) is transmitted via the so-called rising data channel (return link from the mobile phone to the satellite ). This Thuraya mobile phone system uses geostationary satellites and covers, for example, North Africa, Europe, the Near East and parts of Asia, regardless of terrestrial mobile phone installations.

  It is known to determine in a centralized manner, by exploiting so-called downlink signals emitted by the satellite or C-bands leading to the base stations, the position of active mobile telephones in a given surveillance zone and to transmit this information, the if necessary supplemented with the number of the called telephone or the information content of the telephone conversation, to an observer stationed in the said surveillance zone (Thuraya detection system GSA600 Athos-1 or Athos 2/3 of the company Rohde & Schwarz). These systems based on a central detection device have the disadvantage that the routing of information for exploitation of information in a tactical commitment is too long and too complicated for an observer. Information about the situation in the field of action sent by the central post regularly arrives too late for the observer to take into account in his decision-making.

  From this, the present invention aims to provide a method that allows an observer to detect himself, directly on the site, the presence of mobile satellite phones active in his environment and determine their position. The present invention also relates to a simple device, portable, for carrying out said method.

  With the method according to the invention, an observer stationed far from a central station can locate directly, in real time and very quickly, active mobile satellite phones in his environment and therefore very quickly use this information in his decision-making for example for the protection of important objects or spaces. This allows effective protection of the objects, since a local operations manager can detect himself very quickly if a mobile phone is active in his protection zone and especially can know where is located mobile phone. This is interesting for example in the military field, because a tactical officer can obtain very quickly information on the surrounding activity during out-of-area commitments and react very quickly depending on it.

  In accordance with the method according to the invention, the uplink signals of active satellite mobile telephones in the observer's environment are picked up at the observer's site by means of a broadband receiver and, starting from position information transmitted via the uplink signals, the positions of said active satellite mobile telephones in the observer's environment are determined and shown on a geographical map.

  According to an advantageous characteristic of the invention, using a receiver for searching transmitters working in the frequency band, narrow beams assigned to the observer's site are sensed the downlink signals of the mobile-satellite telephones. in the observer environment and from said downlink signals the uplink channel information of the satellite mobile telephones is extracted which is then exploited in terms of the position information contained therein.

  According to another advantageous characteristic of the invention, in addition to the position, the duration of the activation of the mobile telephones by satellite is simultaneously determined and displayed.

  According to another advantageous feature of the invention, in addition to the position is simultaneously determined and displayed the telephone number called by a mobile phone satellite.

  According to another advantageous characteristic of the invention, in the environment of an observer, a given geographical area of alarm is defined and, in the presence of one or more mobile telephone activities in said alarm zone or in the presence of a call from a mobile phone from said alarm zone to given telephone numbers, an alarm is automatically triggered for the observer.

  According to another advantageous characteristic of the invention, from the broadcast channel (BCCH channel) downlink signals (Dn) from the satellite to the mobile telephone are determined the frequencies of the current uplink signals (Up) for the telephones concerned and from the random access channel (RACH) of said uplink signals (Up) the transmitted complementary GPS position information is determined and represented on a geographical map.

  An apparatus for carrying out the method according to the invention comprises a portable high-frequency broadband receiver with an omnidirectional receiving antenna for receiving the uplink signals (Up) of all active mobile phones in the environment of the d-point. installation, a device for the exploitation of the GPS position information transmitted via these uplink signals (Un), an electronic screen display device for the representation of a geographical map of the environment of the point of installation of the apparatus and for displaying the respective determined positions of mobile telephones on said map.

  According to a preferred embodiment of the invention, the portable high-frequency radio-frequency receiver can operate as a transmitter-seeking receiver and, with the aid of a directional characteristic antenna pointed at the satellite (S), during prior research, the downlink signals (Dn) of active mobile phones in the environment of the installation point are captured and exploited from the point of view of the current narrow beam, its environment and the frequencies of the link signals rising (Up) associated.

  The invention is described in detail in the following with the aid of an exemplary embodiment, with reference to the drawing.

  The single figure schematically shows the principle of a satellite mobile phone system.

  The figure shows the principle of the "Thuraya" mobile satellite telephone system, in which a mobile telephone M can, using a so-called L-band frequency range, anywhere in the world via geostationary satellites S, which in turn communicate in the so-called C-band frequency range with different base stations B distributed worldwide, where appropriate by using GSM telephone networks or fixed networks, establish telephone links with other subscribers. The communication with the subscribers' mobile telephones is organized into relatively narrow beams, commonly called "spot beams", which function as cells of the GSM system and work with different carrier frequencies in the L-band.

  Through the so-called "downlink" channels D of the L-bands between the satellite S and the mobile telephone M, data is continuously transmitted in signaling channels via the narrow beams assigned for the relevant position. Furthermore, the frequencies for so-called uplink channels Up associated with the mobile phones M concerned are transmitted for the connection between the mobile telephone and the satellite, as well as the type of modulation used and other temporal structures. When a mobile phone M is active and, through the L-band concerned, on the one hand receives information from the satellite via the downlink channel D "and transmits information from the mobile phone M to the satellite via the uplink channel Up, position information of the mobile phone M according to the GPS system is transmitted simultaneously via the uplink channel Up.

  This mode of operation of the mobile phone "Thuraya" is known as such. There are other equivalent mobile telephone systems, which work according to a similar principle and transmit position information via the uplink channel, where appropriate according to a different GPS location system, for example according to the future location system. European "Galileo".

  This possibility offered in the current mobile satellite telephone systems is used in accordance with the invention for the purpose of indicating directly on the site to an observer, for example to a troop leader on a field of action out of area or a local responsible for a protective action, using a handy reception device G, places in its close environment where mobile phones M are active. The receiver E receives via a small planar antenna F roughly pointed on the satellite S the downlink signals D of the satellite S and via a small broadband antenna H with an omnidirectional characteristic. Up uplink signals emitted in the direction of the satellite M by mobile phones M near. The reception of the uplink signals, due to the low transmission power of the mobile telephones M, is limited to mobile telephones located in the environment close to the receiver E, in practice within a radius of a few kilometers. This is nevertheless sufficient in practice for such uses.

  First, during a brief research phase of the receiver E, the narrow beam corresponding to the position of the receiver as well as the narrow beams in the environment thereof are determined. Then via the so-called BCCH broadcast channel of the downlink signal D emitted by the satellite S, the information associated with the surrounding mobile telephones M on the usable uplink channels (frequency, type of modulation, temporal structures and the like) is determined. ). A receiver broadband receiver module is then configured to receive all uplink signals from the active mobile phones M in the vicinity.

  From the so-called random access channel (RACH), uplink signals received in broadband are used to determine and exploit the position information according to the transmitted GPS system. The result of the determination of the position of mobile phones M active in the environment is presented on an electronic map K electronic on the receiving apparatus E, as shown in the example by three mobile phones M1, M2, M3 . The position T of the observer is also represented in the center of the small map K, which shows the immediate environment of the area of operation.

  In addition to the position of the mobile phone, it is also possible if necessary to determine each time the activity of the mobile phone and display it on the screen for the observer. In the case of a call from an active mobile phone, it would still be possible, if necessary, to determine the called telephone number via the RACH signal and display it.

  If the Thuraya operator uses multiple narrow beams at the observer's location, these are also detected. The receiving apparatus in this case is configured so that it can operate several sub-bands simultaneously.

  The receiver E is preferably designed as a digital receiver. In digital receiving parts, the carriers that contain the signaling channels are demodulated and decoded. The information extracted from signaling channel bursts is temporarily stored in a data store.

  The receiving apparatus E preferably has a very compact and robust construction, so that it can be installed very discreetly in a vehicle. The use of the device is very simple to use and the presentation of the result is done on a flat screen.

  The representation with preferably the own position at the center T of the geographical map is always centered even during a movement of the receiver E. The surveillance zone can be adapted according to the requirements encountered. Alarm functions can also be integrated into the receiving device. For example, it is possible to enter the receiver E which, as a priority, automatically monitors the activity of mobile telephones in a chosen zone A. If, for example, in this zone A an activity of a mobile phone is detected or if a large number of activities are detected or if a mobile phone in zone A calls a specific telephone number, or even certain zones, an alarm is automatically triggered in the receiving apparatus E and the observer is alerted. In the case of mobile phones that are moving, it is still possible to indicate the direction of travel.

  The invention is not limited to the embodiment shown and described. All the features described and shown can be combined with each other in any way.

Claims (8)

  1. A method of detecting mobile-satellite telephones which are active in the environment of an observer, characterized in that on the site (T) of the observer is picked up by means of a broadband receiver (E) the uplink signals (Up) of the mobile satellite telephones (M1, M2, M3) active in the observer's environment, from the position information transmitted via the uplink signals (Up) on determines the positions of the mobile satellite telephones (Ml, M2, M3) active in the observer's environment and is represented on a geographical map (K).   2. Method according to claim 1, characterized in that with the aid of a transmitter search receiver (E) working in the narrow beam frequency band assigned to the site (T) of the observer, the downlink signals (Dn) of the mobile satellite telephones (M1, M2, M3) active in the observer environment are received and, from said downlink signals (Dn), the channel information of uplink (Up) mobile satellite telephones (Ml, M2, M3) which are then exploited in terms of position information they contain.   3. Method according to any one of claims 1 or 2, characterized in that in addition to the position is simultaneously determined and displays the duration of the activation of mobile phones by satellite (Ml, M2, M3).   4. Method according to any one of claims 1 to 3, characterized in that in addition to the position is determined 2888455 10 simultaneously and displays the telephone number called by a mobile phone satellite (Ml, M2, M3).   5. Method according to any one of the preceding claims, characterized in that in the environment of an observer, a given alarm area (A) is defined and in the presence of one or more mobile telephone activities in said area. alarm zone or in the presence of a call from a mobile phone from said alarm zone to given telephone numbers, an alarm is automatically triggered for the observer.   6. Process according to any one of the claims   characterized in that from the broadcast channel (BCCH) of the downlink signals (Dn) of the satellite (S) to the mobile telephone the frequencies of the current uplink signals (Up) for the telephones are determined. the mobile (Ml, M2, M3) concerned and from the random access channel (RACH) of said uplink signals (Up) the complementary transmitted GPS position information is determined and represented on a geographical map (K).   7. Apparatus for implementing a method according to any one of the preceding claims, characterized in that it comprises a portable high frequency receiver (E) with an omnidirectional receiving antenna (H) for receiving the signals. of uplink (Up) all mobile phones (Ml, M2, M3) active in the environment of the installation point, a device for the exploitation of position information (GPS) transmitted via these signals uplink (Up), an electronic display device with a screen for the representation of a geographical map (K) of the environment of the installation point (T) of the apparatus (G) and for the display respective determined positions of mobile telephones (Ml, M2, M3) on said card (K).   8. Apparatus according to claim 7, characterized in that the portable high frequency radio receiver (E) can operate as a receiver looking for transmitters and using an antenna (F) with directional characteristic pointed at the satellite (S), during a preliminary search, the downlink signals (Du) of the mobile telephones (M1, M2, M3) active in the environment of the installation point (T) are picked up and exploited from the point of view of the current narrow beam, its environment and the frequencies of the associated uplink signals (Up).