WO2001050150A2

WO2001050150A2 - Radioelectric device for tracking people

Info

Publication number: WO2001050150A2
Application number: PCT/FR2000/003724
Authority: WO
Inventors: Serge Hethuin; Françoise MARTIN
Original assignee: Serge Hethuin; Martin Francoise
Priority date: 1999-12-30
Filing date: 2000-12-28
Publication date: 2001-07-12
Also published as: AU2861401A; FR2803390A1; WO2001050150A3

Abstract

The invention concerns a device for near and distant tracking of people through a cellular radio communication system comprising a specific number of portable electronic objects, each object comprising a device for transmitting/receiving long range radio-frequency waves (1) provided with display means and communication means for communicating with the network base stations and enable their being tracked in the network through a monitoring station. The transmitter/receiver device (1) is programmed to listen to signals coming from other transmitter/receiver devices of other portable objects, and to display on the display means data concerning the portable objects and signals received from each of them enabling their location. The invention is useful for tracking people in distress.

Description

Radio device for locating individuals.

The present invention relates to a radioelectric device for locating individuals.

It mainly applies to rescue, to aid in medical diagnosis and prevention against imminent dangers such as avalanche threats in the mountains.

Current positioning techniques make extensive use of satellite positioning systems of the type known by the acronym

GPS which is the abbreviation of the Anglo-Saxon word "Global Positioning

System "and to cellular radiotelephone systems such as the GSM system which is the abbreviation of the English term" Global System For

Mobile Communication "which allow mobiles to communicate by radio with other mobiles or the public switched telephone network via base stations located in the center of each cell of the cellular network. In a satellite tracking system GPS type, the geographical position of a GPS receiver is determined by a triangulation of the pseudo-distances that separate the receiver from a cluster of satellites. With such a system, any individual carrying a GPS receiver cannot make known his position to distant emergency services, only if he also has a radio communication means putting him in contact with a surveillance center.

In a GSM type communication system, a description of which can be found in the book entitled "GSM-DCS Networks" by the authors Xavier Lagrange, Philippe Godlewski and Sami Tabbane published by HERMES Science Publications Paris France, 1999, the localization of mobiles is also obtained by a triangulation of pseudodistances measured between the mobile to be identified and the base stations, and the initiative for the measurement of pseudo-distances returns to the base stations neighboring the cell in which the mobile circulates. However, a problem arises when the position of the mobile has not yet been identified or has been lost after an interruption in the operation of its transmitter. receiver for example, while it has moved a relatively large distance. In this case, a large number of network base stations are required to search for the new position of the mobile when the transceiver is restarted. When several mobiles are to be located simultaneously, congestion in the interconnection network of the base stations occurs. This loss of time can be detrimental in certain circumstances to the delivery of aid to people or individuals in difficulty equipped with GSM transmitter-receiver stations.

According to a more recent process, the initiative for measuring pseudo-distances in a GSM network is left to the mobile. This process leaves the choice to the mobile to be identified or not during its various activities. The mobile acquires the pseudo-distances between it and the closest stations which, unlike the previous case, has the effect of limiting the number of measurements and reducing the inconvenience on the GSM network. The mobile then sends the measurements to a master station which performs the triangulation and thus determines the position of the mobile.

However, the location accuracy of these systems does not appear sufficient in the mountains, especially in the case of an avalanche, where rescuers must be able to locate very quickly and to the nearest meter the presence of individuals buried under a snow cover. At best, the location accuracy on horizontal ground, with a good distribution of base stations, is of the order of a hundred meters. We understand that in the mountains the conditions to obtain this precision are difficult to meet. Anyway, this precision remains largely insufficient and does not allow research on soils with significant differences in level.

The object of the invention is to overcome in particular the aforementioned drawbacks.

To this end, the subject of the invention is a device for the short and long distance localization of individuals through a cellular radio communication system comprising a determined number of portable electronic objects comprising at least one transmission device - reception of long-range radio waves, provided, on the one hand, with a display means and, on the other hand, with a communication means for communicating with network base stations and enabling their location in the network by a monitoring station. It is characterized in that the transceiver device is programmed to listen to signals from other transceiver devices of portable objects located nearby, and display on the display means information specific to portable objects and signals received from them to allow location. The communication device can listen to other devices of the same type on its own.

The display means is for example a display screen and the transmission-reception device is programmed to display on the display screen the identification codes of the other portable objects and the information of the electromagnetic fields received from each of them. to allow localization.

Each portable object can additionally comprise a guidance device comprising a short-range radio transmitter / receiver device for randomly transmitting bursts of information on a determined carrier frequency F1, or for collecting the signals transmitted by other objects. portable to locate transmitting on the frequency F1, allowing to locate. these portable objects and coupled to the transmission-reception device for viewing on the screen.

The guide device is for example interconnected to the device by wire link or by very short range wireless link. _' According to one embodiment, the guide device comprises, for example:

radio means for generating a frequency ramp for a portable object to be located when the portable object is operating in a locating terminal, means for retransmitting the frequency ramp which it receives from a portable locating object offset by a frequency interval F when the portable object is placed in the role of a terminal to be located,

measurement means for measuring the frequency offset of the offset frequency ramp received from a portable object to be located with the frequency ramp emitted when the portable object is placed in the role of a locating terminal,

- And calculation means to determine the distance separating the portable locator object from the localized portable object from the result of the measurement of the frequency offset of the two ramps provided by the measuring means.

The main advantage of the device according to the invention is that it allows emergency assistance to arrive at the precise places where accident victims or people in difficulty are found as soon as possible, while leaving the possibility for rescuers to come into contact with the people to be rescued.

Other characteristics and advantages of the invention will become apparent from the following description given with reference to the appended drawings which represent: FIG. 1 a first embodiment of a device for implementing the method according to the invention. 'invention.

Figure 2 a second embodiment of a device according to the invention.

FIG. 3 is a time graph representing the signals transmitted and received by the transponder-transmitter-receiver device TER.

Figure 4 an embodiment of a guide device implemented in a portable object according to the invention.

The device according to the invention allows users carrying electronic portable objects, on the one hand, to enter into communication with a central monitoring station (not shown) located remotely in a GSM network in order to be located at the inside a network cell and other On the other hand, to carry out a fine localization of other people located nearby using substantially identical portable objects.

According to a first embodiment which is shown in FIG. 1, each portable object is composed of a first set 1 of long-distance communication and location coupled to a second set 2 of incident detection and short-range location , the assemblies 1 and 2 being represented respectively inside closed dotted lines.

The assembly 1 comprises a communication module 3 comprising at least one radio wave transmitter and receiver coupled to an antenna 4 and a long-distance location module 5 which can be integrated into the communication module 3 or coupled thereto by a link 6.

The assembly 2 includes an incident detection module 7 and a location and terminal guidance module 8, comprising a radio wave emission device coupled to an antenna 9.

A link 10 connects the incident detection module 7 to the communication module 3, and a bidirectional link 11 connects the communication module 3 to the location and terminal guidance module 8. This connection can be made either by cable or wireless. In the latter case, the link (preferably radio) is very short range since it consists in connecting two accessories to the same individual; this radio link provides the advantage of mechanical and electrical independence between the two accessories.

Incidentally a keyboard 12 can be connected to the communication module 3 to transmit the requests of a user.

The communication module 3 can also be programmed to go into a so-called scanning mode of portable objects located in its periphery. This enables the portable scanner object to listen to the signaling signals from the communication modules of the other portable objects located in its area and to display the identification codes and the amplitude of the received field on the screen. This possibility allows the portable object to operate in simplified mode without using the assembly 2 comprising the location and terminal guidance module 8. This operation, however, suffers from a lack of directivity but makes it possible to draw up a first assessment of people in the area concerned and give an indication of the research to be undertaken.

In the same spirit, the module 8 of the assembly 2 can be used independently of the assembly 1. In this context, the module 3 is then connected to a terminal of the Palm Pilot type or other pocket equipment provided with a serial interface and allowing to visualize the data received on its screen.

Also, a device for measuring physical and psychological data 13 of the type described in the applicant's patent application FR 9700175, can be coupled to the incident detection device 7 and to the localization and guidance device 8. In this case , the device for measuring physical and psysiological data 13, receives data from physiological sensors placed on the body of the person carrying the portable object. As the portable object can be attached to the belt, or in the pocket of a jacket or even on the wrist and that the heart rate, temperature, etc. sensors are on the other hand housed in different places on the body, such as for example the thorax, it is desirable for the approval of the person to have short-range radio links between the physiological sensors and the portable object. The data obtained can then pass through the location module 8 or be multiplexed with the other short-range signals of the radio link between the module 8 and the module 3.

According to another mode of use not shown of the device according to the invention, it is also possible to connect a specific vocoder for the hearing impaired on the GSM. The disabled can then be put in communication like everyone else and can also be located in the event of an incident, fire for example.

According to another embodiment of the invention, represented in FIG. 2 where the elements homologous to those of FIG. 1 bear the same references, the assembly 1 can be a portable GSM commercial handset optionally coupled to a GPS receiver. In this case, the communication of long distance messages between a central monitoring station and the device is carried out through the GSM network and the location of the device in the network takes place in a known manner either by measuring pseudoranges between several network base stations and the user mobile of the device then triangulation by a main station or by the GPS module.

In one or other of the embodiments described above, a fine localization can be carried out by the assembly 2 by the random transmission by each transmitter on a first carrier frequency F1 of information burst, corresponding for example to device described in the aforementioned patent application FR 97 00175.

This procedure allows one or more of the portable objects (locator object) to switch to "listening and searching" mode on the frequency F1 and makes it possible to collect the levels of the signals received (RSSI) from the various other portable objects to be located. The information collected by a locator object is then displayed (not shown for reasons of clarity) on the GSM display screen if set 1 is used or on a Palm or equivalent when set 1 is not used . In this embodiment, the module 8 is only a transmitter or receiver and not a transponder. Several locators can coordinate by choosing to search for distinct individuals in the case of multiple searches.

This operating mode makes it possible to quickly give an assessment of the people located within the radio perimeter and then give an indication of the position of the person sought. The approach is for example progressively refined by new measures.

In one or other of the embodiments described above, a fine localization can also be carried out by the assembly 2 by the random emission by each transmitter on a first carrier frequency F1 of information burst by making them follow d 'Listening on a second frequency F2 for a determined time interval.

This procedure also allows one of the portable objects (locator object) to collect incidentally the levels of the received signals (RSSI) on the frequency F1 of the various other portable objects to be located.

This systematic listening phase makes it possible to collect specific requests from other transmitting TER portable objects and in particular, a request for distance measurement. The listening phase makes it possible to isolate a particular portable transmitting object and to carry out an operation of frequency calibration, which has the advantage of avoiding the complexity of very fine synchronization thereon.

More generally, the portable object to which is assigned a role of locating terminal sends, during the listening phase which follows the burst of information sent by a portable TER object, a message containing and confirming the identity of the object TER portable of an individual to be located who alone is allowed to continue the distance measurement procedure.

This procedure consists in transmitting by the portable locating object TER, a frequency ramp whose amplitude is variable over time, in a determined frequency band and in re-transmitting in another frequency band the same signal shifted by 'an interval of frequency F determined from the portable object TER of the individual to be located. The offset signal received by the locating portable object TER is compared with the signal sent but offset by the same frequency value or by a different frequency F ¹ to give a frequency difference FF ′ as shown in FIGS. 3A and 3B.

For the implementation of this process, it is convenient to use a ramp frequency f (t) which varies linearly over time, of the form: f (t) = f0 + pt (1) where p = ΔF / T is the slope of the ramp, ΔF is the frequency excursion and T is the duration of an elementary ramp.

Under these conditions the instantaneous phase is written to the nearest constant value:. . - - ^• - φ (t) = 2 π [f0.t + ^_1/2 pt ^2] (2)

The representation of the different signals exchanged is then as follows:

By calling S1 (t) the signal emitted by the portable locator object, this can be represented by a relation of the form:

S1 (t) = ai cos [φ (t)] = ai .cos {2π [fO.t + 1 / 2.pt ² ]} (3)

The signal received by the portable object of the individual to be located is then of the form:

S1 (t - τ) = b1.cos {2 π [f0 (t -t) + 1 / 2.p. (T - τ) ² ]} (4) where τ represents the signal transit time between the locating portable object TER and the portable object TER of the individual to be located.

The signal S2 (t) re-emitted by the portable object of the individual to be located is defined by the relation: S2 (t) = a2.cos {2 π [(f0 + F) (t -τ) +1 / 2 .p. (t - τ) ² ]} (5) where F represents the frequency offset.

Finally the signal which is received by the portable locator object is written:

S2 (t - τ) = b2.cos {2 π [(f0 + F) (t -2τ) + 1 / 2.p. (T - 2 τ) ² ]} (7)

On the other hand, the local reference signal generated by the portable locator object is of the form:

R (t) = ai .cos {2 π [(f0. + F ') t + 1 / 2.pt ² ]} (8)

The distance separating the two terminals is obtained by analyzing the product X (t) of the mixture between the signals R (t) and S2 (t -τ). This product checks the relation: X (t) = 1/2 ai .b2.cos {2 π [2 p τ t + (F - F) t + 2 (f0 + F) τ - 2.p.τ ² ] } (9)

The term (FF) represents a fixed frequency offset equal to zero if F 'is chosen equal to F. The term 2 p τ of equation (8) represents a frequency fb whose value is directly proportional to the transit time c 'is to say at the value of the distance d separating the two portable objects. The other terms represent unimportant phases thereafter. The distance d is obtained by the relation: d = c.τ where c represents the speed of light.

The precision obtained is expressed by the relationship:

Δd = y _2. (c. T / ΔF) Δfb The granularity of precision on the measurement of fb is related to the duration of emission of the burst. To obtain the desired precision, it is desirable to emit not a single ramp but several in succession from one another. Let N be the number of elementary ramps, the measurement granularity becomes Δfb = 1 / NT. The error on d becomes Δd = ¹ /2.(c. T / ΔF) / NT = ¹ /2.c / (ΔF.N) In the 860 MHz band, taking a spread ΔF = 600 kHz and N equal to 200, the granularity of distance measurement Δd is equal to 1.25 m. By taking T = 1 ms, the granularity of frequency analysis Δfb = 1 / NT = 5 Hz.

The frequency band to be analyzed corresponds to a maximum distance of 500 m, i.e. to a maximum value of fb = τΔF / T = 2.d.ΔF / T.c = 2kHz. The analysis FFT then comprises 512 points.

An embodiment of a terminal guide module 8 operating according to the method which has just been described is shown in Figure 4 where the elements homologous to those of Figures 1 and 2 are shown with the same references. This includes a commercial signal processing processor 15 suitably programmed to perform the distance calculation described above. The processor 15 is coupled by a first port 15ι to a transmission channel 16 and by a second port 15 ₂ to a reception channel 17. A bus 18 connects a third port of the processor 15 to the GSM handset 3 and a fourth port receives the physiological signals of the receiver 13 carried by the link 14 through the analog-digital converter 13bis.

The transmission channel 16 comprises a modulator 19, a mixer stage 20, a switching device 21, an amplifier 22 and a filter 23, these elements being connected in this order in series between the first port 15ι and the antenna 9. The mixer stage 20 mixes the signal supplied by the modulator 19 with that supplied by a frequency synthesizer 24 controlled in frequency by the ramp signal defined by relation (1) in the operating mode with transponder but which is controlled by the fixed frequency F1 for the emission of bursts when the portable object is in the operating mode of a portable object to be located, or controlled by the fixed frequency F2 for the emission of bursts on this frequency when the portable object is in locator mode.

The reception channel 17 comprises a filter 25, an amplifier 26, a switching device 27, a frequency mixer stage 28, and a demodulator 29, these elements being connected in this order in series between the antenna 9 and the second port 15 _2. The mixer stage 28 mixes the signal supplied by the amplifier 26 through the switching device 27 with that supplied by a frequency synthesizer 30 also controlled in frequency by the signal ramp defined by relation (1) in transponder mode but also by a fixed frequency when receiving bursts on frequency F1 in locator mode, and by a fixed frequency also when receiving bursts on frequency F2 when the portable object is in the operating mode of portable object to be located. A frequency transposition device 31 is coupled between the switching devices 21 and 27.

The switching devices 21 and 27 have two states A and B activated from the keyboard 12 of the GSM handset or by a monitoring station not shown in the GSM network, or from an internal controller depending on the current operating mode, they allow the guidance modules 8 to operate either as a transmitter-receiver interrogator) for the locating mobile, or as a transponder-answering machine for the mobiles to be located. In this operating mode, the switching devices 21 and 27 are positioned respectively in states A and B for module 8 of the mobile locator and those of the portable responder object of the mobile to be located in their state B. In state A of the switch 21 the portable object is in interrogator mode, it is then in the operating state of a central station, that is to say that it emits at the output of the transmission channel 16 the signal S1 (t ) to the portable object of the individual to be located, and that it receives at the input of the reception chain 17 the signal S2 (t-τ) coming from the portable object of the individual to be located.

This signal is transmitted through the switching device 27 placed in state B on a first input of the frequency transposition device 31 to be transposed from the offset frequency -F. The signal obtained at the output of the mixer stage 32 results from the mixing of the signal R (t) applied by the output of the switch 21 to the input of the amplifier 22 with the signal obtained at the output of the frequency transposition device 31. This signal which represents the cosine term of the signal X (t) is converted into a digital form by the analog-digital converter 33 before being transmitted to the processor 15 for the calculation of the frequency fb and the distance d. The calculated distance d is transmitted on the bus 18 in order to be displayed by the GSM handset with the identifier of the mobile located.

On the responder side, the switching devices 21 and 27 loop the output of the amplifier 26 back to the input of the amplifier 22 through the frequency transposition device 31 which is responsible for performing the frequency shift + F of the signal if (t-τ) received by the terminal to be located. As it is possible to verify in FIG. 4, different combinations of the states A and B of the switching devices 21 and 27 make it possible to place each of the portable objects indifferently in the standby state of a transmission from another portable object than these are found in the role of the locator object or the localized object. The device which has just been described can advantageously be supplemented by a device making it possible to indicate the direction from which the emissions of another detected portable object originate. This can be obtained by incorporating into the portable object an attenuator activated when the rescuer arrives near the person sought, within a radius of a few meters. The attenuator then makes it possible to greatly reduce the signal received and to re-center it in the unsaturated part of the distance / field characteristic received. Another possibility is to use a directive antenna 9 on the location module 8, for example secured to the rear face of the GSM; the user gradually turns with his mobile phone in front of him towards the direction presenting the maximum of signal received. Better yet, another possibility is to provide the portable object with two antennas and to program the location module 8 to analyze the phase shift of the signals received by the two antennas.

The use of a commercial GSM handset to carry out both the communication function and the long-distance location function which are directly associated with it is naturally recommended, given the low price of this equipment. Just connect it by bus 18 to the terminal guidance module (2) on its extension socket which is formed by a conventional RS232 interface.

To meet the constraints of autonomy linked to those of the batteries, because it is clear that currently the charge of the batteries of GSM portable devices does not last more than a few days in standby mode, from a full charge and provided meet normal environmental constraints at room temperature, it is advisable to provide the localization module and the communication module each with their own battery. The system which has just been described can be configured according to several operating modes depending on the circumstances of the searches.

In a first mode, the wearer of the portable object according to the invention can authorize the surveillance center to locate it permanently. Following the preliminary authorization given by the wearer of the portable object, the device sends a global monitoring request to the monitoring center and activates the long-distance location function. The carrier of the portable object can also, by manual action on the keyboard of the portable object, ask the emergency center to immediately initiate rescue, but this search can also be activated by the surveillance center at provided, however, that the holder of the portable object has previously authorized tracking. When, for example, the surveillance center finds that the wearer of the portable object remains static for too long with precision near the location system, in a dangerous or risky area, a search team can then be dispatched to the area concerned. Possibly a telephone contact, prior to the dispatch of the rescue team, is established.

The search can also be triggered automatically but it is still only possible if the user has previously authorized tracking. In the event of a fall and loss of consciousness of the person carrying a portable object according to the invention, the incident detection device sends automatically an alarm signal through the network to the surveillance center and instantly activates the terminal guidance module.

The incident detection sensor consists in detecting a fall by loss of verticality or by the appearance of excessive acceleration, the exceeding of thresholds on physiological parameters such as for example the heart rate or the temperature.

Naturally, the guide module can be actuated remotely. When, for example, a rescue team arrives at the site, in the area to be searched, the team leader can then launch an order on the network to activate the terminal guidance module, which will also have the effect of feeding it on its own battery. But it can also activate it directly to allow precise localization at short distance for the passage of dangerous areas such as avalanche corridors.

Claims

1 - Device for the short and long distance localization of individuals through a cellular radiocommunication system comprising a determined number of portable electronic objects comprising at least one device (1) for transmitting and receiving radio waves at long range provided on the one hand with a display means and on the other hand with a communication means for communicating with several base stations of the network and allowing the localization of portable objects in the network by a monitoring station characterized in that the transceiver is programmed to listen to signals from other transceivers of portable objects and display using the display means information specific to portable objects and signals received from each of them to allow location.

2- Device according to claim 1 characterized in that the display means is a display screen and in that the transmission-reception device is programmed to display on the display screen the identification codes of other portable objects and information about the electromagnetic fields received from each of them to enable location.

3- Device according to one of claims 1 and 2 characterized in that each portable object further comprises a guidance device (8) comprising a short range transmitter / receiver radio device for randomly transmitting bursts of information on a determined carrier frequency F1 or for collecting the signals transmitted by other portable objects to be located transmitting on the frequency F1, making it possible to locate these portable objects and coupled to the transceiver device (1) for display on the screen.

4- Device according to one of claims 1 and 2 characterized in that each portable object further comprises a guide device (8) comprising a short-range transponder-responder radio device coupled on the one hand, to a computing device (15) to determine the distance between it from another portable object located nearby and from other share, to the transceiver device (1) to transmit the calculated distance to the monitoring station and display it on the display screen.

5- Device according to one of claims 3 and 4 characterized in that each guide device (8) is used separately from the device (1) transceiver and coupled to a pocket PC equipment for viewing on screen.

6- Device according to one of claims 1 to 5 characterized in that the guide device (8) is interconnected to the device (1) by wire connection or by wireless link with very short range.

7- Device according to claims 1 to 6 characterized in that each portable object further comprises a receiver of signals from satellite navigation systems coupled to the communication means for transmitting to the monitoring station the geographic coordinates of the individual carrying portable object.

8- Device according to any one of claims 1 to 7 characterized in that each portable object comprises a physiological data receiving device (13) coupled to the calculation device (15).

9- Device according to any one of claims 1 to 8 characterized in that the guide device (8) comprises switching devices (21, 27) for assigning to each portable object a function of locator terminal or a terminal function to locate.

10- Device according to claim 9 characterized in that the guide device (8) comprising: - radio means (20 ... 24, 9) for generating a frequency ramp to a portable object to locate when the portable object works as a locator terminal,

- Means (21 ... 31) for retransmitting the frequency ramp which it receives from a portable locating object offset by a frequency interval F when the portable object is placed in the role of a terminal to be located , - measuring means (32, 33) for measuring the frequency offset of the offset frequency ramp received from a portable object to be located with the frequency ramp emitted when the portable object is placed in the role of a terminal locator, - and calculating means (15) for determining the distance which separates the locating portable object from the localized portable object from the result of the measurement of the frequency offset of the two ramps provided by the measuring means (32 , 33).

11- Device according to any one of claims 3 to 10 characterized in that the guide device (8) comprises means for randomly transmitting information bursts on a determined carrier frequency F1 and listening means and search to collect signals from other portable objects transmitting on a determined frequency F2 in order to initiate a localization procedure between a portable object to be located and a portable object.

12- Device according to any one of claims 1 to 11 characterized in that the device (1) for transmitting and receiving long-range radio waves is a GSM mobile terminal.