FR2804214A1 - Mobile telephone station DECT wire less telecommunications position network having processing determining base station positions and where base stations insufficient mobile station/base station converting. - Google Patents

Abstract

The method of positioning a mobile station (SM) has processing determining base station locations. When insufficient base stations are found, a unit functioning in mobile station mode is transferred to function as a base station.

Description

The present invention relates to a method and device for locating wireless equipment in a telecommunications network, and to systems implementing them.

More specifically, the present invention relates to a procedure for wireless communication equipment to measure its position relative to other wireless communication equipment in its environment.

The invention belongs to the field of wireless local area networks.

The European standard EN 301 649, 1999, DECT DPRS <I> ("Enhanced Cordless Telecommunications, DECT Packet Radio Service", Advanced Digital Wireless Telecommunications, Radio Packet Service) describes procedures for establishing communication. between two mobile stations, by switching one of the two mobile stations into base station operating mode.

Some known systems provide a wireless "tracker" or tracker for locating in an office environment. However, such a wireless "tracker" is usually only used for localization purposes and can not be used for wireless communication purposes. It therefore represents additional specific equipment, increasing the complexity and cost of the system. In addition, a number of wireless "trackers" must be positioned in an office to obtain a sufficiently accurate measurement of the position.

No. 5,862,477 also discloses a procedure for verifying the topology of a wireless communication system, based on a measurement of the power of the received radio signal. However, this procedure does not allow to obtain a very precise position; it merely indicates whether there is a significant change in the topology of the system.

The present invention aims to overcome the above disadvantages.

For this purpose, the present invention proposes a method of locating a mobile station in a wireless telecommunications network, according to which the position of a processing device is determined, which is remarkable in that, when there is not enough base stations to determine this position, at least one station operating in the mobile station mode is switched to the base station operating mode.

Thus, the present invention makes it possible to locate a device connected to a wireless communication module or integrating such a module, without adding an additional electronic component.

Indeed, the invention allows to reuse wireless communication adapters to perform a location procedure; it is therefore not necessary to add specific electronic component to implement the location function. This reduces the cost of the wireless communication module.

In a particular embodiment, according to which - a search operation is performed, consisting in searching for the presence of at least one base station in the environment of this mobile station; if the presence of at least one base station is detected, for each detected base station, a measurement operation is performed, consisting of measuring the position of the mobile station and determining the accuracy of the measurement made; the method is remarkable in that, if the accuracy of the measurement performed is less than a predetermined value - at least one request operation is performed, consisting, for the mobile station, of signaling to the base station that it needs at least one new base station to measure its position; a mode change request operation is performed, consisting, for the base station, of requesting a hybrid station operating in a mobile station mode to switch to a base station operating mode; and a switching operation is performed for the hybrid station to switch from the mobile station operating mode to the base station operating mode to form the new base station.

Thus, the present invention provides an adaptable procedure for specifying the accuracy with which position measurement is to be performed.

In addition, the present invention makes it possible to obtain the position of a mobile device, either dynamically, at specific times, such as switching on or off or after changing the cell (in English "handover"), either periodically, at regular times or intervals of time.

According to a particular characteristic, during the measurement operation, the position of the mobile station is measured from a plurality of information transmitted by the detected base station.

This plurality of information makes it possible to obtain, in a simple and rapid manner, information on the location of the mobile station.

According to a particular characteristic, during the query operation, the mobile station sends a message to the base station to signal to it that it needs at least one new base station.

According to a particular characteristic, during the mode change request operation, the base station sends a message to the hybrid station to request it to switch to base station operating mode.

According to a particular characteristic, during the switching operation, the hybrid station switches to base station operating mode upon receiving the message from the base station. The three preceding characteristics make it possible to reconfigure the network for the purposes of the location procedure, automatically and transparently for the user.

According to a particular characteristic, during the measuring operation, the above-mentioned plurality of information comprises a value of the power of the radio signal received from the base station, and / or a value of a mobility parameter diffused by the base station and / or a value of a position parameter broadcast by the base station.

Each of these parameters makes it possible to obtain quickly and easily important information on the location. In particular, the mobility parameter makes it possible to determine the accuracy of the measurement: the lower the mobility, the more reliable the measurement.

According to a particular characteristic, at the end of the query operation, an incrementation operation is performed, consisting, for the base station, in incrementing by one unit a parameter representing the number of hybrid stations already interrogated by the base station to become a new base station.

According to a particular characteristic, a list is stored in the base station listing all the hybrid stations operating in mobile station mode and synchronized with the base station.

Both of the above features allow the base station to systematically survey its environment to find a new base station.

According to a particular characteristic, prior to the measurement operation - a location request operation is performed, consisting, for the base station, in sending to the mobile station a message requesting it to return information on its location; and performing a location operation, consisting, for the mobile station, of returning to the base station a message containing the value of a position parameter, the value of a distance parameter and the value of a parameter mobility. This feature makes it easier to locate. For the same purpose as that indicated above, the present invention also proposes a device for locating a mobile station in a wireless telecommunications network, comprising a module for determining the position of a processing device, remarkable in that it further comprises a switching module, for switching at least one station operating in mobile station mode to the base station operating mode when there are not enough base stations to determine the aforementioned position.

Still for the same purpose, the present invention also proposes a mobile station in a wireless telecommunications network, comprising or connected to a radio adapter having means adapted to implement a location method as above.

The present invention also relates to a mobile station in a wireless telecommunications network, comprising or connected to a radio adapter comprising a location device as above.

Still for the same purpose, the present invention further proposes a base station in a wireless telecommunications network, comprising or connected to a radio adapter having means adapted to implement a location method as above.

The present invention also relates to a base station in a wireless telecommunications network, comprising or connected to a radio adapter comprising a location device as above.

Still for the same purpose, the present invention also proposes a wireless telecommunications network, comprising means adapted to implement a location method as above.

The present invention also relates to a wireless telecommunications network, comprising a location device as above.

The invention also aims at - a computer-readable information storage means or a microprocessor retaining instructions of a computer program, allowing the implementation of a location method as above, and - a means partially or totally removable information storage device readable by a computer or a microprocessor retaining instructions from a computer program, allowing the implementation of a location method as above.

The invention also relates to a computer program comprising sequences of instructions for implementing a location method as above.

The particular characteristics and the advantages of the location device, the mobile stations, the base stations, the information storage means and the computer program being the same as those of the localization method according to the invention, they are not not remembered here.

Other particular features and advantages of the invention will appear on reading the following detailed description of particular embodiments, given as non-limiting examples. The description refers to the accompanying drawings, in which - Figure 1 schematically shows the overall structure of an electronic circuit included in a wireless communication device using the DECT standard according to the present invention and adapted to operate in base station mode; FIG. 2 schematically represents the overall structure of an electronic circuit included in a communication device according to the present invention and adapted to operate in mobile station mode, in relation with the communication device illustrated in FIG. 1, in a particular embodiment; FIG. 3 is a flowchart illustrating the steps performed by a mobile station to determine its position according to the present invention, in a particular embodiment; FIG. 4 is a flowchart illustrating the steps performed by a base station to determine its position according to the present invention, in a particular embodiment; FIG. 5 is a flowchart illustrating the steps performed by a mobile station in order to find new base stations in order to be able to determine its position according to the invention, in a particular embodiment; FIG. 6 is a flowchart illustrating the steps performed by a mobile station following those illustrated in FIG. 5, in order to measure its position with respect to a new base station according to the invention, in a particular embodiment; FIG. 7 is a flowchart illustrating the steps performed by a mobile station on receiving a location request from a base station, in accordance with the present invention, in a particular embodiment; FIG. 8 is a flowchart illustrating the steps performed by a base station on receiving a request for new base stations from a mobile station, in accordance with the present invention, in a particular embodiment; and FIG. 9 is a flowchart illustrating the steps performed by a hybrid station operating in a mobile station mode, upon receipt of a change of operating mode request from a base station, in accordance with the present invention, in a particular embodiment.

FIG. 1 represents the electronic circuit of a wireless communication device 100 using the European DECT standard (specified by ETSI, ETS 300 175, 1991), which can be connected to a network 110 of the RTC (Switched Telephone Network) type. , Ethernet, or other.

The device 100 may be either a DECT base station or a DECT hybrid station. In particular, a DECT base station is responsible for providing system synchronization. A hybrid station is a communication station that can alternatively operate as a base station or as a mobile station.

In the following, the term "base station" will include, on the one hand, the communication stations which can only operate according to the operating mode of base station and, on the other hand, the hybrid communication stations, operating temporarily in base station mode. Also, in the following, the term "mobile station" will include, on the one hand, the communication stations which can only operate according to the mobile station operating mode and, on the other hand, the hybrid communication stations operating temporarily in mobile station mode.

Generally speaking, a station is synchronized with a base station, either when operating in mobile station mode and synchronized with a base station, or when operating itself in station mode. based.

The communication device 100 can be integrated into a computer, printer, fax, etc. type of equipment. or connected to one of the aforementioned equipment.

The electronic circuit 100 comprises, interconnected by an address and data bus 102 - a radio unit 101, provided with an antenna 103, - an input / output controller 107, - a network controller 108 (optional) a central processing unit 106, a ROM 105, and a random access memory RAM 104.

Moreover, a power supply 109 is provided to supply all the components of the electronic circuit 100 (the electrical connections relating to the power supply 109 are not shown).

The network controller 108 manages the interface with an external network 110.

The input / output controller 107 is connected to a source of information such as, for example, a sensor for images, sounds, texts or graphics, a telephone, a fax machine, a computer, a camera, a video camera, a camcorder, etc. and / or to a recipient of information such as, for example, a television, monitor, music channel, telephone, fax machine, printer, computer, VCR, etc.

All the components illustrated in FIG. 1 are well known to those skilled in the field of processor communication circuits and, more generally, information processing circuits. They are not detailed here.

The electronic circuit 100 and, in particular, the central unit 106, are adapted to exploit all the capabilities of the DECT standard known before the present invention.

The central unit 106 is further adapted to implement the method of the invention and, in particular, the flow charts illustrated in Figures 4 and 8.

The RAM 104 includes registers which, for convenience, each have the same name as the data they contain <I> - "Position </ I> interm" <I>: </ I> temporary variable used to store a intermediate result of the calculation of the parameter <I> "Position". </ I> On power-up, <I> "Position </ I> interm" takes the value 0; <I> - "List <B> SU '</ B>: </ I> temporary variable containing the list of mobile stations that can hear base station 100. When powered on, <I>" List </ I> <B> SU '</ B> does not contain any elements <B>; <I> - </ I> "Mobility-SU": temporary variable containing the list of mobility parameters associated with mobile stations contained in <I> "List </ I> SM." On power-up, <I> "Mobility </ I> SU 'does not contain any element; <I> - "Position </ I> SM" <I>: </ I> temporary variable containing the list of <I> "Position" </ I> parameters associated with mobile stations contained in <I> "List < / I> <B> SU '. </ B> On power-up, <I> "Position </ I> SM" contains no element; <I> - "Distance </ I> SM" <I> : </ I> temporary variable containing the list of calculated distances between the device 100 and the mobile stations contained in <I> "List </ I> SM." On power-up, <I> "Distance <B> SU </ B> </ I> does not contain any element; - N: temporary variable to count the number of mobile stations listed by <I> "List </ I> SM". On power up, N takes the value 0; - N REQ: list of temporary variables allowing to know, for each mobile station, what is the number of hybrid stations already interrogated to become a new base station; <I> - "List </ I> H ': list for listing all the hybrid stations operating in mobile station mode and synchronized with the base station 100. This list is further classified according to the mobility parameter associated with each hybrid station The constitution of this list can be done using the means described in patent application number 98 09628. - NH: variable for counting the number of elements of the list <I> "List H '; </ I> <I> - "Precision </ I> interm" <I>: </ I> temporary variable used to calculate the precision obtained in the measurement of the position performed by the calculation of <I> " Position </ I> interm ". On power-up, <I> "Precision </ I> interm" is 0; <I> - "Time </ I> Der" <I>: </ I> variable containing the time at which the last position measurement was performed.

The read-only memory 105 has registers which, for convenience, each have the same name as the data they contain <I> - </ I> "Programl" <I>: </ I> register in which the program is kept operating the central unit 106; <I> - "Position": </ I> variable containing the position of the device 100. On power up, <I> "Position" </ I> returns to the same value as before the power was turned off. The radio unit 101 must periodically broadcast on the radio the value of <I> "Position", </ I> so that the mobile stations synchronized with this base station can determine their own position, as explained below; <I> - "Mobility": </ I> parameter containing information on the mobility of the device 100. Like the parameter <I> "Position", </ I> the parameter <I> "Mobility" </ I > must be broadcast on the radio by any base station. This <I> "Mobility" </ I> parameter can take three values - the "FIXED" value for fixed equipment, such as a bulky printer, for example. In this case, if the equipment is moved, for example during a move, the administrator must change the value of the parameter <I> "Position"; </ I> - the value "PORTABLE", as in the case a small printer for example. The value of <I> "Position" </ I> is then recalculated automatically each time the power is turned on; - the value "MOBILE", as in the case of a phone for example. The value of <I> "Position" </ I> must be calculated automatically each time the power is turned on and each cell change.

Devices with the <I> "Mobility" </ I> parameter equal to "FIXED" will thus be able to serve as a reference for portable or mobile equipment; - T2: value of the maximum time to detect the presence of a mobile station not already listed in "List-SU" By way of non-limiting example, T2 may be worth 30 seconds, - T3: value of the maximum time to wait for reception of a message of "LOCATION INFO" type after the transmission of a message of the "REQ PROC_LOCATION" type, as described below with the help of FIG. 4. By way of non-limiting example, T3 may be worth 5 minutes; - T6: value of the maximum time to wait for the reception of an "ACCEPT CHANGE MODE" message, after the transmission of a "REQ CHANGE MODE" type message, as described below using the FIG. 8. As a non-limiting example, T6 may be worth 5 seconds; T7: value of the maximum time to wait to reset the variable N REQ after receiving a message of the type "REQ NEWS SB {LOCATION}", as described later with the help of Figure 8. By way of example not lim itative, T7 can be worth 10 minutes.

FIG. 2 schematically represents the architecture of an electronic circuit 200 incorporated in a communication device according to the present invention and adapted to operate in mobile station mode, in relation with the electronic circuit 100 illustrated in FIG.

The device 200 may be either a DECT mobile station or a DECT hybrid station. This communication device can be integrated into a computer, printer, fax, etc. type of equipment. or connected to one of the aforementioned equipment.

The electronic circuit 200 comprises, connected to each other by an address and data bus 202 - a radio unit 201, equipped with an antenna 203, - an input / output controller 207, - a central processing unit 206, a screen 210 (optional), a keyboard 211 (optional), a ROM 205, and a RAM RAM 204.

Furthermore, a power supply 209 is provided for supplying all the components of the electronic circuit 200 (the electrical connections relating to the power supply 209 are not shown).

The input / output controller 207 is connected to a source of information such as, for example, an image, sound, text or graphics sensor, a telephone, a fax machine, a computer, a camera, a video camera, a camcorder, etc. and / or to a recipient of information such as, for example, a television, monitor, computer, music channel, telephone, fax machine, printer, VCR, etc.

All the components illustrated in FIG. 2 are well known to those skilled in the field of processor communication circuits and, more generally, information processing circuits. They are not detailed here.

The electronic circuit 200 and, in particular, the central unit 206, are adapted to exploit all the capabilities of the DECT standard known before the present invention.

The central unit 206 is further adapted to implement the method of the invention and, in particular, the flow charts illustrated in Figures 3, 5, 6, 7 and 9.

The RAM 204 has registers which, for convenience, each have the same name as the data they contain <I> - "Position </ I> interm" <I>: </ I> temporary variable used to store a intermediate result of the calculation of the <I> "Position" parameter. When </ I> is powered up, <I> "Position </ I> interm" is 0; <I> - "Accuracy </ I> interm" <I>: </ I> temporary variable used to calculate the accuracy obtained in the measurement of position, by calculating <I> "Position </ I> interm" . <I> A </ I> power up, <I> "Accuracy </ I> interm" is 0; - N: temporary variable to count the number of base stations that can hear the device 200. On power up, N is 0; <I> - "List </ I> SB": temporary variable containing the list of base stations heard by the device 200. On power-up, <I> "List </ I> SB" does not contain any element; - M: temporary variable for indexing the list of base stations <I> "List </ I> SB". On power up, M is 0; - X: Temporary variable for indexing hybrid stations that have been switched to base station mode and listed in <I> "SB List". On power up, X is 0; <I> - "Received Power" </ I>: A temporary variable used to store the value of a measurement of the power of the received radio signal. On power up, <I> "Received power" </ I> is 0; <I> - "Mobility </ I> SB" <I>: </ I> temporary variable containing the list of mobility parameters associated with the base stations contained in the list. <I> "List </ I> SB". On power-up, <I> "Mobility </ I> SB" does not contain any element; <I> - "Position </ I> SB" <I>: </ I> temporary variable containing the list of position parameters associated with the base stations contained in <I> "SB List" </ I>. On power up, <I> "Position </ I> SB" does not contain any items; <I> - "Distance SB": </ I> temporary variable containing the list of calculated distances between the device 200 and the base stations contained in <I> "List </ I> SB". On power-up, <I> "Distance </ I> SB" does not contain any element; <I> - "Distance": </ I> temporary variable used to store the value of a distance calculation between the mobile station and a base station; <I> - "Time </ I> Der" <I>: </ I> variable containing the time at which the last position measurement was performed.

The ROM 205 has registers which, for convenience, each have the same name as the data they contain. the operation of the central unit 206; <I> - "Position": </ I> variable containing the position of the device 200. On power-up, <I> "Position" </ I> returns to the same value as before the power was turned off; <I> - "Mobility": </ I> parameter containing information on the mobility of the device 200. This parameter is identical to the parameter <I> "Mobility" </ I> described for the device 100; <I> - "Accuracy": </ I> value indicating the accuracy with which position measurement is to be performed. On power-up, <I> "Accuracy" </ I> returns to the same value as before the power was turned off. By default, <I> "Accuracy" </ I> is 3, which corresponds to the use of the triangulation method, known to those skilled in the art, for the location; - T1: Maximum time value to search for the presence of a base station not already listed in <I> "SB List". For example, T1 is 30 seconds; - T4: value of the maximum time to wait between the transmission of a message of the type "REQ_NOV SB" and the reception of a message of the type "CHANGE SB", as described further with the aid of FIG. for example, T4 is 5 seconds; - T5: value of the maximum time to wait to search for the presence of a new base station not already listed in <I> "SB List", </ I> among hybrid stations that have switched from mobile station mode to base station mode. For example, T5 is 60 seconds; - T8: value of the maximum time to wait for the reception of a message of the "LOC_FINI" type, as described later with the aid of FIG. 6, after having switched into base station mode. For example, T8 is 2 minutes; - Barter: value of the periodicity with which the localization procedure shown in Fig. 3 must be executed. If Troc is 0, then the localization procedure must not be initiated periodically. For a fixed type of equipment, Troc will be worth 0. For a portable type of equipment, Troc can be worth 4 hours, whereas for a mobile type of equipment, Troc can be worth 1 hour for example; - TDER: time value to decide if the last position measurement performed is still valid or not. For example, TDER can be equal to TLocJ2.

Fig. 3 is a flowchart showing the succession of steps performed by a mobile station to determine its position.

This procedure can be initiated - in case the <I> "Mobility" </ I> parameter is equal to "FIXED": at the request of the system administrator; - in the case where the parameter <I> "Mobility" </ I> is equal to "PORTABLE": at each power-up, at the request of the administrator, at the request of another communication device (sending a radio message type "REQ_PROC-LOCATION", as described later with the help of Figure 4) or periodically (the periodicity is fixed by the value of Troc). If the location procedure of the mobile station is initiated as a result of the receipt of a "REQ PROC LOCALIZATION" message, the mobile station must then communicate the new calculated position in a "LOCATION INFO" radio message to the source station the message "REQ PROC_LOCALISATION"; - in the case where the parameter <I> "Mobility" </ I> is equal to "MOBILE": in the same circumstances as in the previous case where the parameter <I> "Mobility" </ I> is "PORTABLE" , and in addition to each cell change detection (i.e. a change of the base station with which the mobile station is synchronized).

The localization procedure starts with the initialization, during a step 301, of the variable N at 0, of <I> "Position </ I> interm" <I> to </ I> 0, of <I > "Precision </ I> interm" to 0. In step 301, <I> "List </ I> SB" does not contain any base stations. In a step 302, a clock timer (in English "timer") is initialized to an integer value and positive then activated. Its value decreases by one unit at each pulse of a clock or a clock divider (i.e. a time counter whose pulse frequency is lower than that of the clock). The duration T1 during which its value is positive is known in advance. When its value reaches 0, its operation is automatically stopped.

During a step 303, the mobile station 200 then searches, by listening to the DECT radio frequency band, which extends between 1880 MHz and 1900 MHz, the presence of at least one base station not yet recorded in <I > "List </ I> SB".

If no base station not already recorded in <I> "List </ I> SB", is found before the lapse of time T1, ie, if test 304 is negative and the test 305 is positive, or if the tests 304, then 309 and 305 are positive, the processing unit 206 then tests if <I> "List </ I> SB" is empty, that is to say if N is zero (test 306).

If <I> "List </ I> SB" is empty and if the station 200 is a hybrid station, that is, if the tests 306 and 307 are positive, the station 200 then switches to station mode. base (step 308) and the succession of steps shown in Fig. 4 is executed.

If <I> "List </ I> SB" is empty and the station is not a hybrid station, i.e., if the test 306 is positive and the test 307 is negative, the location procedure failed because the communication station has no other station in its environment allowing it to locate itself.

If <I> "List </ I> SB" is not empty (test 306 negative), the succession of steps shown in FIG. 5 is executed.

If a base station, which will be designated later by SB, is detected (test 304 positive), and it is not yet contained in "SB list" (test 309 negative), it is then added in this list at the position N, during a step 310. In a step 311, performed for each base station thus detected, the processing unit 206 can then calculate an intermediate position value as follows - the radio unit 201 measures the power of the radio signal received from the base station <I> "List </ I> SB [N]" and stores the measured value in the variable "Power <I> received"; </ I> - the radio unit 201 listens to the value of the parameter <I> "Mobility" </ I> broadcast by the base station <I> "List </ I> SB [N]" and stores it in the variable <I> " Mobility </ I> SB [N] "<I>; </ I> - the radio unit 201 listens to the value of the parameter <I>" Position "</ I> broadcast by the base station <I>" List </ I> SB [N] "and stores it in the variable <I>" Position </ I> SB [ N] "<I>; </ I> - the processing unit 206 calculates the distance between the mobile station 200 and the base station SB from the value of <I>" Received power "</ I> and stores the calculated value in <I> "Distance </ I> SB [N]" <I>; </ I> - from the parameters <I> - "Position </ I> SB [Z]", Z = 0 to N, <I> - "Distance </ I> SB [Z]", Z = 0 to N, <I> - "Mobility </ I> SB [Z]", Z = 0 to N, the processing unit 206 can determine, for example by triangulation, an intermediate position <I> "Position </ I> interm", from the position and distance information, and define a confidence index from the information of mobility, this confidence index being stored in <I> "Accuracy </ I> interm", determining if other distance measurements must be made: when the mobility information is "FIXED" or "PORTABLE", it is incremented <I> "Precision </ I> interm" of a unit; otherwise, <I> "Precision </ I> interm" keep the same value.

Then N is incremented by one. The variable X has the same value as N and will be used later (see Figure 6 described later).

- P, représente la valeur de la puissance reçue<I>("Puissance reçue"),</I> - k est un facteur proportionnel, - X représente la longueur d'onde radio, - y représente la perte de propagation, et vaut 2 dans un espace ouvert, 3 dans un espace de type zone sous-urbaine, et 3,5 dans une zone urbaine, - Pt représente la puissance transmise et vaut 24dBm dans le cas d'une station de base DECT, et - D représente la distance entre la station mobile et la station de base, soit ici<I>"Distance</I> SB[N]". The following relation exists between the power of the received radio signal and the distance between the mobile station receiving this signal and the base station transmitting the signal

- P, represents the value of the received power <I>("Receivedpower"),</I> - k is a proportional factor, - X represents the radio wavelength, - y represents the loss of propagation, and is 2 in an open space, 3 in a suburban area, and 3.5 in an urban area, - Pt is the transmitted power and is 24dBm in the case of a DECT base station, and - D represents the distance between the mobile station and the base station, here <I>"Distance</I> SB [N]".

If the intermediate position obtained is sufficiently precise, that is to say if the test 312 is negative, this position is then written in the read-only memory 205 in the <I> "Position" </ I> variable during a step 313. This completes the location procedure. The time at which the value of <I> "Position" </ I> was obtained is then stored in <I> "Hour </ I> Der".

If the location procedure had been initiated as a result of the receipt of a "REQ-PROC_LOCATION" message, the mobile station 200 must then issue a location information message "LOCALIZATION_INFO" containing the variable <I> "Position" < / I> and the distance between the mobile station and the base station initiating the message "REQ PROC LOCALIZATION".

<B> Figure 4 </ B> represents the sequence of steps performed by a station operating in base station mode to measure its position. During a step 401, the processing unit 106 initializes the variable N to 0; in step 401, <I> "List </ I> SU" does not refer to any mobile station In a next step 402, the processing unit 106 starts a clock pulse down timer which must remain active for a time T2, and the radio unit 101 tries to detect the presence of mobile stations.To this, several known solutions of the state of the art are possible.For example, the radio unit can broadcast a message requesting mobile stations that hear it to contact the base station.

If no mobile station not already listed in <I> "List <B> SU '</ I> </ I> is found before time T2 has elapsed (ie, if the test 403 is negative and the test 404 is positive, ie if the tests 403, then 405 and 404 are positive), the localization procedure is then terminated without having been able to obtain a position measurement with the required precision, but the calculated intermediate position <I> ("Position </ I> interm") can be used if the accuracy of this result, given by <I> "Accuracy </ I> intenm", is not too bad.

When a new mobile station, which will be designated later by SM, is detected (test 403 positive), if SM is not already registered in <I> "SU List </ B> </ I > (test 405 negative), it is then added in <I> "List <B> SU '</ B> </ I> to the position N, during a step 406.

At the step 406, the radio unit 101 then sends a location request "REQ-PROC_LOCALISATION" message to the mobile station <I> "List </ I> SM [N]". Figure 7 describes how a mobile station responds to this type of message.

In a next step 407, the processing unit 106 then activates a pulse down timer T3. If the mobile station <I> "List </ I> SM [N]" did not return a LOCATION <B> "LOCATION </ B> -INFO" message prior to the lapse of time T3 (408 negative test and 409 positive test), the radio unit then tries to detect a new mobile station by repeating the process from step 402.

On the other hand, if the test 408 is positive, that is to say if the processing unit 106 received before the lapse of time T3 a message <B> "LOCATION </ B> _INFO {PO, DI, MO} "location information, (where the first term PO represents the position of the mobile station transmitting the message, where the second term DI represents its distance from the device 100, and where the third term MO represents the mobility of this mobile station), then during a step 410, the processing unit 109 writes in the random access memory 104 the three preceding parameters, namely, PO in <I> "Position </ I> SM [N]", DI in <I> "Distance </ I> SMN]" and MO in <I> "Mobility - <B> SM </ B> </ I> N]".

Then, again during step 410, the processing unit 106 performs an intermediate calculation of its position and the associated precision from all the data collected in the <I> "Position </ I> SNl" tables, <I> "Distance </ I> SV and <I>" Mobility </ I> Sh1 ".

Then N is incremented by one.

If the result of the computation of <I> "Position </ I> interm" gives a precision <I> "Precision </ I> interm" satisfactory (test 411 negative), during a step 412, the value of <I > "Position </ I> interm" is copied to <I> "Position" </ I> in ROM 105 and the time at which the value of <I> "Position" </ I> was obtained is stored in <I> "Hour </ I> Der". The localization procedure is then complete.

In the case where the base station was in mobile station mode before performing this procedure (see Figure 3), the radio operating mode can then return to the mobile mode.

If the intermediate result of the calculation of the position does not give a satisfactory accuracy (test 411 positive), the radio unit 101 then tries to detect a new mobile station by repeating the process from step 402.

Figure 5 shows the sequence of steps performed by a station operating in mobile station mode to find new base stations to measure its position. This succession of steps is performed when the number of measurements obtained from the base stations already present in the system does not allow to obtain a sufficiently precise position measurement (see Figure 3).

A first step 501 consists in initializing the variable M to 0. Then, during a step 502, the processing unit 206 activates a clock pulse counter T1. Then, during a step 503, the processing unit 206 tries to synchronize, by scanning the radio frequencies reserved for the DECT, with the base station corresponding to <I> "List </ I> SB [M]" .

If the synchronization with the base station <I> "List </ I> SB [M]" is not carried out before the lapse of time T1 (test 507 negative then test 504 positive), the processing unit 206 then try to synchronize with another base station in the <I> List </ I> SB [M] list. For this, during a test 505, it tests whether the value of M is equal to N-1. If M is not equal to N-1 (test 505 negative), M is then incremented by one unit (step 506) and the synchronization procedure with another base station <I> "List </ I> SB [M] "is reiterated from step 502. Otherwise the procedure ends.

If the synchronization with the base station <I> "List </ I> SB [M]" is carried out before the lapse of the time T1 (test 507 positive), the mobile station 200 sends then a request of the type "REQ_NOUV SB {LOCALIZATION} of a base station request, during a step 508, meaning that the mobile station needs the presence of a new base station, the term "LOCATION" indicating the reason for this request (see FIG. 8 for a description of the steps of the base station side). The new base station requested is to be searched for among the hybrid stations.

The processing unit 206 then activates the clock pulse down timer T4 during a step 509, in order to wait for a base station change message, of the type "CHANGE-SB (NEW SB)", from the base station <I> "List </ I> SB [M]".

If the message "CHANGE SB {NEW SB"} is received before the lapse of time T4 (test 510 positive), the sequence of steps shown in Fig. 6 is then executed. This message indicates to the mobile station 200 that it must seek to synchronize with the base station whose identity corresponds to "NEW SB".

Otherwise, or if a rejection message "REJ_NOUV SB" is received, indicating that the interrogated base station can not satisfy the request (test 511 positive), the processing unit 206 then tries to synchronize with another base station . For this, in the test 505, it tests whether the value of M is equal to N-1. If M is not equal to N-1 (test 505 negative), M is then incremented by one unit (step 506), and the search procedure for synchronization with a base station contained in <I> "List < / I> SB [M] "is reiterated from step 502. Otherwise the procedure is terminated.

Figure 6 shows the sequence of steps performed by a station operating in mobile station mode to measure its position with respect to a new base station (see Figure 5). During a first step 601, a clock pulse down timer T5 is activated. Then during a step 602, the radio unit 201 scans the DECT radio channel in order to detect the signal broadcast by the base station "NEW SB". If no signal from the base station "NEW SB" is detected before the lapse of time T5 (test 603 negative and test 604 positive), the mobile station 200 will then be able to request the base station <I> "List </ I> SB [M]" to find a new base station by sending a new base station request message "REQ_NEW SB {LOCATION}", which corresponds to step 508 in Figure 5.

T5 is greater than T1 because it must include the switching time from the mobile station mode to the base station mode for "NEW SB" (Hybrid Station).

If the base station "NEW SB" is detected before the lapse of time T5 (test 603 positive), during a step 605, it is added to the list of base stations already recorded, to the position <I > X ("List </ I> SB [X]" <I≥ </ I> "NEW SB"). During a step 606, the processing unit 206 can then calculate a new intermediate position similarly to the step 311 illustrated in FIG.

The variable X is then incremented by one unit and the base station "NEW SB" is informed, by sending an end of localization procedure message "LOC_FINI", during a step 607, that the procedure measurement is complete.

If this new intermediate position makes it possible to obtain a sufficient precision, that is to say if <I> "Precision </ I> interm" <I >> _ "Precision" </ I> (test 608 negative), this intermediate position then becomes the final position measured by this procedure (step 609). The time at which the value of <I> "Position" </ I> was obtained is then stored in <I> "Hour </ I> Der".

If not (test 608 positive), the mobile station 200 must look for a new base station to be able to make a new measurement. For this purpose, it can again request the base station <I> "List </ I> SB [M]" to find a new base station by sending a new base station request message "REQ NEW SB {LOCATION}". FIG. 7 represents the succession of steps executed by a mobile station having received a location request "REQ_PROC_LOCALISATION" message (step 701) from a base station which will be designated subsequently by SB.

The mobile station first tests (test 702) if the value of its <I> Mobility </ I> parameter is equal to "FIXED". If this is the case, during a step 703, the mobile station then makes a measurement of the power received from the radio signal from SB and calculates from this measurement its distance from SB. Then, during a step 704, it sends back to the base station SB a message of the type <B> "LOCATION </ B> -INFO {PO, DI, MO}" of location information, where the first PO term takes the value of <I> "Position" </ I> stored in ROM 205 (Figure 2), the second term DI takes the value of <I> "Distance" </ I> stored in the RAM 204, and the last term MO takes the value of <I> "Mobility" </ I> stored in ROM 205.

If the parameter <I> "Mobility" </ I> is different from "FIXED" (test 702 negative), the processing unit 206 then tests (test 705) whether the last position measurement carried out goes back to more than TDER or no. If the last position measurement is too old (test 705 positive), a new position measurement must be made before returning the message "LOCATION INFO {PO, DI, MO}" of location information, executing the succession of steps defined in Figure 3.

FIG. 8 represents the succession of steps executed by a base station 100 having received a "base station request" type request (step 801) from a mobile station which will be subsequently designated by SM.

When the base station 100 receives a message of the type "REQ NEW SB {LOCATION}", it increments by one unit the parameter N_REQ associated with the mobile station SM (step 802).

This parameter N REQ [SMJ is reset to 0 when no message of the type "REQ NEW SB {LOCATION}" is received from SM during a time T7. Then, during a test 803, the processing unit 106 tests whether the value of NH, which indicates the number of hybrid stations synchronized with the base station 100, is strictly less than N REQ [SM]. If the result of the 803 test is positive, then there is no longer a hybrid station available to become a base station. The base station 100 then responds to the mobile station SM by a rejection message "REJ NOUV SB" (step 804).

If there is at least one available hybrid station (test 803 negative), the base station then sends a message of the type "REQ CHANGE MODE {LOCATION, SM}" request for change of operating mode (step 805), the first term indicating the reason for this change of operating mode request, the second term SM indicating which is the mobile station that wishes to locate.

The base station 100 then activates (step 806) a clock pulse counter to wait for a maximum duration T6 the response to the message "REQ ÇHANGE_MODE {LOCALIZATION, SM}".

If no "ACCEPT CHANGE MODE" operating mode change acceptance message is received before time T6 has elapsed, or if a "REJ CHANGE MODE" mode change refusal message is received before In the course of time T6 (test 807 negative and test 808 positive), the base station then tries to find another hybrid station to become a base station.

If a message of the type "ACCEPT CHANGE MODE is received before the lapse of time T6 (test 807 positive), the base station then sends to the station SM a message of type" CHANGE SB {List H {N REQ [SM] } "(step 809), indicating to the mobile station SM that it must synchronize with the base station whose identity is indicated in this message, ie <I>" List </ I> H [N_REQ [SM] Step 510 in Figure 5 indicates receipt of this message by the SM station.

FIG. 9 represents the succession of steps executed by a hybrid station operating in mobile station mode having received, during a step 901, a change of operating mode request "REQ CHANGE MODE (LOCATION, SM)" of the from a base station which will subsequently be designated by SB.

During a test 902, the hybrid station tests whether switching to the base station mode is allowed. For example, the hybrid station considers that switching is not possible if it is in communication with SB or with another mobile station through the base station SB.

If switching to the base station mode is not possible (test 902 negative), the hybrid station then returns to the base station SB a message of the type "REJ_CHANGE_MODE" of refusal of change of operating mode, during of a step 903. The procedure is then completed.

In the opposite case (ie if the test 902 is positive), the hybrid station sends to the base station SB a message of the type "ACCEPT CHANGE MODE" of acceptance of change of operating mode (step 904). Then the hybrid station switches to base station mode (step 905). It will remain in base station mode until it receives a "LOC FINI" end of locating procedure message from mobile station SM (test 907 positive), or until the flow of a time T8 (test 907 negative and test 908 positive) (a clock timer timer T8 having been activated during a step 906).

The procedure ends with switching to the mobile station mode, in a step 909.

Thus, the present invention enables a mobile station to determine its position by listening to and analyzing the radio signal from the base stations in its environment. If the number of base stations present is not sufficient to obtain a satisfactory position measurement, the invention makes it possible to switch one or more mobile stations in base station operating mode. A method of locating a mobile station (SM) in a wireless telecommunications network, wherein the position of a processing device is determined, characterized in that, when there are not enough stations In order to determine said position, at least one station operating in mobile station mode is switched to the base station operating mode.

2. The method of claim 1, wherein - performing a search operation (303) of searching for the presence of at least one base station (SB) in the environment of said mobile station (SM); - if the presence of at least one base station (SB) is detected, for each detected base station, a measurement operation (311) is performed, consisting of measuring the position of said mobile station (SM) and determining the precision <I> ("Precision </ I> interm") of the measurement made; said method being characterized in that, if the accuracy <I> ("Precision </ I> intenm") of the measurement made is less than a predetermined value <I> ("Accuracy") </ I> - it is carried out at minus a request operation (508), consisting, for said mobile station (SM), in signaling to the base station (SB) that it needs at least one new base station to measure its position; a mode change request operation (805) is performed, requesting a hybrid station operating in a mobile station mode to switch to a base station operating mode; and a switching operation (905) is performed, for said hybrid station, to switch from the mobile station operating mode to the base station operating mode, to constitute said new base station.

3. Method according to claim 2, characterized in that, during said measuring operation (311), the position of said mobile station (SM) is measured from a plurality of information transmitted by the detected base station. (SB).

Claims (1)

<U> CLAIMS </ U> 4. A method according to claim 2 or 3, characterized in that, during said request operation (508), said mobile station (SM) sends a message ("REQ_NOUV SB_ {LOCATION}" ) to said base station to signal to it that it needs at least one new base station. 5. Method according to claim 2, 3 or 4, characterized in that, during said mode change request operation (805), said base station sends a message ("REQ CHANGE_MODE {LOCALIZATION, SMJ") to said hybrid station to ask it to switch to base station operating mode. 6. Method according to claim 5, characterized in that, during said switching operation (905), said hybrid station switches to base station operating mode on receipt of said message ("REQ CHANGE MODE (LOCATION, SM)"). ) from said base station (SB). 7. Method according to any one of claims 3 to 6, characterized in that, during said measuring operation (311), said plurality of information comprises a value of the power of the radio signal <I> ("Received power ") </ I> received from the base station (SB). 8. Method according to any one of claims 3 to 7, characterized in that said plurality of information further comprises a value of a mobility parameter ("Mobility") broadcast by the base station (SB). 9. Method according to any one of claims 3 to 8, characterized in that said plurality of information further comprises a value of a position parameter <I> ("Position") </ I> broadcast by the station Basic (SB). . Method according to one of the preceding claims, characterized in that, after said request operation (508), an incrementing operation (802), consisting of, for the base station (SB) is performed. ), to increment by one unit a parameter ("N_REQ [SM]") representing the number of hybrid stations already interrogated by the base station (SB) to become a new base station. 11. Method according to any one of the preceding claims, characterized in that stored in the base station (SB) a list <I> ("List </ I> N ') listing all the hybrid stations operating in mobile station mode and synchronized with the base station (SB) 12. A method according to any one of the preceding claims, characterized in that prior to said measuring operation (311) a request operation of a location (701), comprising, for said base station (SB), sending to said mobile station (SM) a message ("REQ_PROC_LOCATION") requesting it to return information about its location; and - performing a location operation (704), consisting of, for said mobile station (SM), returning to said base station (SB) a message <B> ("LOCATION </ B> _INFO {PO, DI, MO}") containing the value d 'a position parameter <I> ("Position"), </ I> the value of a parameter e of distance <I> ("Distance") </ I> and the value of a mobility parameter <I> ("Mobility"). </ I> 13. Device for locating a mobile station (SM) in a wireless telecommunications network, comprising means for determining the position of a processing device, characterized in that it further comprises switching means, for switching at least one station operating in mobile station mode to the base station operating mode when there are not enough base stations to determine said position. The device of claim 13 including - search means (206) for searching for the presence of at least one base station (SB) in the environment of said mobile station (SM); measuring means (206), for detecting the presence of at least one base station (SB), for each detected base station, measuring the position of said mobile station (SM) and for determining the accuracy <I> ("Accuracy </ I> interm") of the measurement performed; said device being characterized in that it further comprises - at least first request means (206), to allow said mobile station (SM), if the precision <I> ("Précision </ I> interm") of the measurement made is less than a predetermined value <I> ("Accuracy"), </ I> to signal to the base station (SB) that it needs at least one new base station to measure its position; mode change request means (106) for enabling the base station (SB) to request a hybrid station operating in a mobile station mode to switch to base station operating mode; and switching means for enabling said hybrid station to switch from the mobile station operating mode to the base station operating mode, to constitute said new base station. 15. Device according to claim 14, characterized in that said measuring means (206) measure the position of said mobile station (SM) from a plurality of information transmitted by said detected base station (SB). Device according to claim 14 or 15, characterized in that said request means (206) allow said mobile station (SM) to send a message ("REQ NEW SB (LOCATION)") to said base station ( SB) to point out that he needs at least one new base station. 17. Device according to claim 14, 15 or 16, characterized in that said mode change request means (106) allow said base station (SB) to send a message ("REQ CHANGE MODE {LOCALIZATION, SM } ") to said hybrid station to request it to switch to base station operating mode. 18. Device according to claim 17, characterized in that said switching means allow said hybrid station to switch to base station operating mode on receipt of said message ("REQ CHANGE MODE (LOCATION, SM)") from said base station (SB). 19. Device according to any one of claims 15 to 18, characterized in that said plurality of information comprises a value of the power of the radio signal <I> ("received power") </ I> received from the base station (SB). 20. Device according to any one of claims 15 to 19, characterized in that said plurality of information further comprises a value of a mobility parameter <I> ("Mobility") </ I> broadcast by the station Basic (SB). 21. Device according to any one of claims 15 to 20, characterized in that said plurality of information further comprises a value of a position parameter <I> ("Position") </ I> broadcast by the station Basic (SB). 22. Device according to any one of claims 14 to 21, characterized in that it further comprises incrementing means, to allow the base station (SB), after implementation of said request means (206). ), to increment by one unit a parameter ("N_REQ [SM]") representing the number of hybrid stations already interrogated by the base station (SB) to become a new base station. 23. Device according to any one of claims 14 to 22, characterized in that the base station (SB) contains a list <I> ("List </ I> H") listing all the hybrid stations operating in mobile station mode and synchronized with the base station (SB). 24. Device according to any one of claims 14 to 23, characterized in that it further comprises - locating request means (106), to allow said base station (SB) to send to said station mobile (SM) a message ("REQ PROC LOCALIZATION") asking him to return information on its location; and - location means (206) for enabling said mobile station (SM) to return to said base station (SB) a message <B> ("LOCATION </ B> _INFO {PO, DI, MO}" ) containing the value of a position parameter <I> ("Position"), </ I> the value of a distance parameter <I> ("Distance") </ I> and the value of a parameter of mobility <I> ("Mobility"). </ I> 25. Mobile station in a wireless telecommunications network, characterized in that it comprises or is connected to a radio adapter having means adapted to implement a locating method according to any one of claims 1 to 12. 26. Mobile station in a wireless telecommunications network, characterized in that it comprises or is connected to a radio adapter comprising a locating device according to any one Claims 13 to 24. 27. Base station in a wireless telecommunications network, characterized in that it comprises or is connected to a radio adapter having means adapted to implement a locating method according to any one of claims 1 to 12. 28. Base station in a wireless telecommunications network, characterized in that it comprises or is connected to a radio adapter comprising a locating device according to any one of claims 13 to 24. 29. Wireless telecommunications network, characterized in that it comprises means adapted to implement a localization method according to any one of claims 1 to 12. 30. Wireless telecommunications network, characterized in that it comprises a localization device according to any one of claims 13 to 24.