WO2000003556A1

WO2000003556A1 - System for locating mobile telephones

Info

Publication number: WO2000003556A1
Application number: PCT/FR1999/001693
Authority: WO
Inventors: François Caseau
Original assignee: Caseau Francois
Priority date: 1998-07-10
Filing date: 1999-07-09
Publication date: 2000-01-20
Also published as: PL345419A1; EP1097599A1; AU4627699A; FR2781073B1; BR9911974A; IL140689A0; ID28843A; CN1308827A; CA2337814A1; TR200100015T2; FR2781073A1; ZA200100513B

Abstract

The invention concerns a system for locating mobile telephones capable of communicating with a first reception terminal of a reception terminal network supervised by an operational management centre. The mobile telephone comprises means for estimating at least one parameter representing position relative to a terminal, and means for transmitting data concerning said parameter to a server via the first reception terminal, and the server comprises means for comparing data concerning said parameter with a pre-established mapping of said parameter, and estimate therefrom the mobile telephone location.

Description

Mobile phone location system.

The present invention relates to the field of cellular digital radiocommunication with mobile stations, for example according to the GSM standard (Global System of Mobile Communications). The invention relates more particularly to a system for locating mobile stations communicating by means of a fixed reception terminal belonging to a network.

This type of system generally implements time multiplexing consisting in dividing the time into frames of fixed and predetermined duration, themselves divided into time intervals. This technique is called "Time Division Multiple Access" (TDMA). The recurrence of a particular time interval in each frame constitutes a physical channel. This structure is used both for the uplink from a mobile station to a reception terminal and for the downlink from a reception terminal to a mobile station.

The data exchanged by a mobile station and the reception terminals are transmitted in the form of packets which are each placed in a time interval. The different logical channels, for example the TCH traffic channels, and the control channels are multiplexed on the physical channels. Consequently, the time intervals of a given physical channel are distributed between several logical channels, thus giving rise to a new structure, called multiframe.

The GSM communication protocol is described in the book "The GSM System for Mobile Communications" by M. Mouly and MB. Pautet, 1992, the content of which is incorporated herein by reference. On the GSM Protocol, it will be recalled that the mobile telephone network knows in real time a rough location of a mobile station on standby, in the sense that it knows the reception area communicating with the mobile station at the place where it is located. The reception area is represented by several contiguous reception terminals.

If the mobile station leaves an area served by a reception area, it transmits an update message to indicate this change to the network. The network's knowledge of this location of a mobile station enables it to be able to be called at any time. In addition, the network knows the global identification parameter of the CGI cell of attachment of a mobile station in communication, a cell being a portion of land served by the same radio terminal.

A communicating mobile station transmits, at given time intervals, a measurement report message to its home reception terminal. These messages are sent on a service radio channel, the SACCH channel. This information allows the network to choose at any time the best reception terminal capable of carrying communication with the mobile station.

Knowledge of the time taken to travel the distance between the mobile station and the radio terminal, or time advance TA, allows the mobile station to transmit to the radio terminal at a selected time so that said radio terminal is able to receive the transmission of the mobile station without interference with the emissions of other mobile stations. The time advance TA therefore reflects the distance traveled by the radio wave between the mobile station and the radio terminal. An increment of 1 of this time advance TA corresponds to a distance of approximately 550 meters.

In the measurement report message sent by the mobile station to the radio terminal, a parameter RXLEV is provided which corresponds to the level of reception by the mobile station of the radio terminal with which it communicates and at most the best six neighboring reception terminals . The measurement report message also includes a parameter RXQUAL which corresponds to the quality of reception by the mobile station of the radio terminal with which it communicates.

An SMS short message service allows the sending or receiving of text messages between the mobile station and the network. They are transmitted either on the SACCH channel if the mobile station is in communication, or on the TCH / 8 signaling channel (or SDCCH) if the mobile station is on standby. The mobile telephone operator can be provided with a radio planning tool which allows the calculation of the level of reception and the quality of reception at a given geographical point as a function of the geographical positioning of the radio terminal, of the neighboring radio terminals, their transmission power, their type, the frequencies used, etc.

We know from the technical specifications phase 2 + GSM 1 1.1 1 and GSM 1 1.14, interface specifications between a mobile device and the SIM card of a subscriber. It is known in particular that a SIM card can request a measurement report from the mobile equipment, that it can cause the sending of short SMS messages and that it can store the content of incoming short messages. Document EP-AO 398 773 discloses a method of geographic location of a mobile station of a time-division multiplex communication network, comprising steps of transmitting a value measured at the first station mobile station for the offset of reception of the synchronization signals originating from the first and from at least one second fixed station, for measuring at the first fixed station the propagation time of the synchronization signal from the first fixed station to the mobile station, and of the offset in reception of the BCCH channel, of calculation at the first fixed station of the propagation times of the synchronization signal from the second fixed station to the mobile station using the transmission offset stored previously, and of calculation of the position of the mobile from propagation times and geographic coordinates of the first and second fixed stations.

WO-9635306 describes a method for determining the location of a mobile station of a cellular radio system including a plurality of base stations. Time differences between base station transmissions as measured by the mobile unit are determined. From these time differences, the differences in distance between the mobile station and each of the base stations are determined. We deduce the location of the mobile unit. The time division structures of the control channels of at least some of the base stations which are within range of the mobile station are synchronized and said mobile station determines the time differences of an element characteristic of the broadcasting of the time division structure through the control channel of each base station.

If the number of base stations detected by the mobile station is too low, the time advance required for communication with the serving base station is used to deduce the distance between the mobile station and the serving base station. However, the various methods proposed allow localization of the mobile station without the knowledge of its user and are cumbersome and expensive to implement.

The object of the present invention is to propose a system in which the location of a mobile station can only be carried out on the command of its user or using an ad hoc SIMToolkit application.

SIMToolkit applications can cause automatic transmission of short messages. These SIMToolkit applications can only send these messages when a specific telephone number has been dialed.

Another object of the present invention is to propose a system for locating a mobile station which does not require modification of the GSM communication protocol.

The location system according to the invention is provided for mobile stations able to communicate with a first radio terminal of a network of radio terminals supervised by an operational management center. The mobile station comprises means for estimating at least one parameter representative of the position relative to a radio terminal, and means for transmitting information relating to said parameter to a server via the first radio terminal.

The server comprises means for comparing the information relating to said parameter with a pre-established map of said parameter, and deducing therefrom an estimate of the location of the mobile station.

In one embodiment of the invention, the system comprises means for estimating the distance between a mobile station and the first radio terminal, with a margin of imprecision Δdb _m as a function of the time taken by a wave to travel said distance.

In one embodiment of the invention, the system comprises means for estimating the reception levels of the first radio terminal and of the neighboring radio terminals. In one embodiment of the invention, the system comprises means for estimating the quality of reception of the emissions from the first radio terminal and, advantageously, from the neighboring radio terminals.

Advantageously, the mobile station comprises means for comparing the instants of reception by the mobile station of the emissions of the other radio terminals with the instants of reception r of the emissions of the first radio terminal and of deducing therefrom the value of the offset Δ of the reception instants, and means for transmitting to the server via the first radio terminal the value of each offset Δq, and the server comprises means for estimating the distance between the mobile telephone and each other radio terminal as a function of the offset Δq, and of the offset Δe ^ between the transmission times e ^ from the other radio terminals and the transmission times e from the first radio terminal.

In one embodiment of the invention, the system comprises means for specifying the location of the mobile telephone by cross-checking the location estimates obtained by at least two parameters.

Localization can be carried out on command of the user of the mobile station.

The server may include means for transmitting information to the user depending on the location of the mobile phone. This information can be either audio messages or messages intended for display.

Advantageously, the transmission of information between a mobile station and a radio terminal taking place on a logical service channel and on a logical traffic channel, the transmission of information relating to said parameter to the first radio terminal is carried out on the logical channel traffic, for example the short message service.

The mapping can be adapted to the transmission power levels of the different radio terminals by linear interpolation.

The cartography can be recalculated according to the evolution of parameters likely to modify the values brought up towards the geographic information server, for example depending on whether or not the frequency hopping is activated on the different radio frequencies.

The mapping can be recalculated depending on whether or not the Enhanced Full Rate EFR is activated on the different radio frequencies.

The cartography can be recalculated as a function of the transmission power levels of the different radio terminals, of the change in topology of the cards recorded, for example due to the construction of a building, and of the activation of the frequency hopping. In one embodiment of the invention, the parameter representative of the position is the NB -correlation parameter corresponding to the number of correlations on the BCCH frequency.

The mobile station can be provided with means for comparing location data with a prerecorded area, for specific pricing, for example near the user's home, the location data being stored in a SIM card of the station. mobile.

The mobile station may include means for transmitting pricing data by short message service. In one embodiment of the invention, the mobile station transmits pricing data if a call is made or received near the preregistered area, if the mobile station enters or leaves said preregistered area during a communication.

In one embodiment of the invention, the mobile station comprises means for transmitting a transfer message on the fixed network if said mobile station is in the preregistered area, causing a modification of the call routes so that any incoming call is notified on the fixed station (s) and on the mobile station.

In such a system, a mobile station can be used for many uses, for example to launch a distress signal, to provide the user with information relating to his location.

The user can thus be put in communication with a database containing geographic information for guidance, or tourist comprising comments on what the user can see from where he is. This communication with a database can be created using a specific telephone number and unchanged regardless of location. The language in which the information is supplied to the user can also be selected, either automatically through the information transmitted to the location server, or on the order of said user, or be associated with the telephone number.

The present invention will be better understood on studying the detailed description of a few embodiments taken by way of non-limiting examples and illustrated by the appended drawings, in which: FIG. 1 is a diagram illustrating the operation of a network mobile phone, according to the invention; Figure 2 shows a variant of Figure 1; FIG. 3 is a diagram showing the capture of the number of correlations of a radio wave in the geographic information server; and FIG. 4 is a diagram illustrating the entry of a particular time profile.

In the following description, mobile equipment is understood to mean a "blank" mobile telephone without an operational SIM card inserted. Mobile equipment cannot make calls other than an emergency call.

A SIM card - "Subscriber Identity Module" has the function of identifying a subscriber to a given mobile network. A mobile station is the set made up of mobile equipment and a SIM card. A mobile station thus formed can make or receive telephone calls.

A logical service channel carries all the information necessary for the proper functioning of a mobile network: making calls, receiving calls, Handovers ...

A service channel is based on different types of physical channels such as BCCH or SDCCH channels.

The information transmitted on a logical service channel is managed by the infrastructure of the mobile operator. As opposed to logical service channels, a logical channel traffic is a channel carrying information intended for the correspondent of the mobile subscriber. A logical traffic radio channel is based on one or more physical channels such as the TCH, SDCCH (TCH / 8) channels or even a half of the TCH channel if the telephone operator has activated the half speed option or Half rate. It should be noted that the physical channel SDCCH (TCH / 8) can carry service information or traffic information. The information carried on a traffic channel is not intended for the mobile operator and is subject to billing. This information can be either audio information or "data" information intended for display, transported either by SMS short message services, or by messages of the USSD - Unstructured Supplementary Services type.

Data - or via GPRS messages - Global Packet Radio Switch.

The GPRS - Global Packet Radio Switch - is a radio communication protocol allowing data transmissions following the IP protocol - Internet Protocol - via a GSM telephony infrastructure.

If we refer to the communication layers defined by rOSI, GPRS interfaces between the IP communication layer and the physical layer.

Thus, GPRS allows a mobile station to communicate according to the IP format: access to Internet servers, transmission + reception of electronic messages ...

The term fixed / mobile convergence means all the techniques which make it possible to bring together and possibly confuse fixed and mobile telephone subscriptions.

This is in order to offer the advantages of the fixed telephone in the residential area, in particular in terms of voice quality and broadband while allowing mobility. Other advantages linked to fixed / mobile convergence are the single invoicing, the differentiation of costs according to the place of call, the possible use of the same telephone handset.

As can be seen in FIG. 1, the mobile telephone network comprises a plurality of radio bay systems 1 each comprising several transmitting and receiving terminals, not shown, and called radio terminals, each capable of communicating with several mobile stations, not shown. Each radio bay system 1 is linked to an operational management center 2. Each operational management center 2 manages several radio bay systems 1. The operational management centers 2 are themselves linked to a network management center 3. The network management center is connected to a geographic information server 4 capable of exchanging information with a radio planning tool 5 and with a mobile switching center 6 which makes it possible to interface with a non-wired telephone network. represented.

FIG. 2 illustrates a variant in which the operational management centers 2 are directly connected to the geographic information server 4.

In order for the geographic information server 4 to be able to calculate the position of a mobile station, it is necessary to allow the transmission of a certain amount of information from the mobile station to the geographic information server 4. A For this purpose, the location parameters are forwarded to the geographic information server 4 using the logical traffic channel. The geographic information server 4 is able to receive messages from the speech channel in the SMS short message service format or in IP format (in the case where the information leaves the mobile station in GPRS format)

The service information that the mobile station can send to the geographic information server 4 are parameters that help in locating:

- the global CGI cell identifier of the serving cell,

- the binomials BSIC, BCCH of the cells neighboring the server cell, the mobile station sending this information up for all the BCCH channels which it is capable of interpreting, the number of which may be greater than six,

- information relating to the RXLEV reception levels of all the aforementioned cells,

information relating to the quality of reception RXQUAL of the serving cell and advantageously of its neighboring cells, - the DIR reception instant difference attribute of all the above cells,

- the attribute NB -correlation indicating the number of correlations of the BCCH frequencies of the aforementioned cells, - the difference in reception time DTR of the synchronization bursts SCH of each of the aforementioned cells, and an attribute linked to the time elapsed since the start of the takes measurement by the mobile station,

- the attribute linked to the distance from the waitress radio terminal. The parameters for the global identification of CGI cells as well as the binomials BSIC and BCCH are the most useful for locating the mobile station. These parameters are used to identify the cells involved in locating the mobile station. They are already known and processed by the mobile station and can therefore be transmitted by the latter to the geographic information server 4 in a simple manner. In special cases, in particular for emergency calls, provision may be made for the mobile station to transmit service information relating to cells belonging to another mobile telephone network. In fact, in the GSM 05.08 ETS 300578 recommendations, it specifies that a mobile station must be able to scan all GSM frequencies to identify BCCH frequencies in order to calculate their reception power. In this case, the geographic information server 4 knows the location of the cells of the different networks and therefore knows the cells adjacent to a given cell.

In the following, the message containing the information necessary for the geographic location will be designated by "measures for location".

A mobile station is already performing calculations of the RXLEV parameter on the carrier frequency (RXLEV-FULL-SERVING-CELL and RXLEV-SUB-SERVING-CELL) and the BCCH frequencies of the adjacent cells (RXLEV-NCELL) and of the RXQUAL parameter of the frequency carrier (RXQUAL-FULL-SERVING-CELL and RXQUAL-SUB-

SERVΓNG-CELL).

Advantageously, the mobile station can calculate the parameter RXQUAL on the BCCH frequencies of the adjacent cells. In addition, to unify the measurements reported to the system geographic information 4, it may be decided to calculate the RXLEV and RXQUAL parameters of the server frequency not on all (or part) of the TDMA frames, but only on the BCCH multiframe. However, there are still inaccuracies in the RXLEV and RXQUAL parameters corresponding to the different radio terminals, these inaccuracies being mainly related to diversity and interference with other radio waves.

The time advance parameter TA is calculated as follows. A mobile station is synchronized with the BCCH frequency of the radio serving terminal using the FCCH and SCH channels. In the case of multi-transmission, which takes place mainly in urban environments where there are many obstacles, the mobile station synchronizes with the strongest received signal. When it goes into communication, the radio bay system 1 estimates the distance traveled by the radio wave between the mobile station and the serving radio terminal and transmits the parameter TA to the mobile station.

In the case of multi-transmission, the mobile station makes several correlations on the same signal. To synchronize, it will choose the signal which corresponds to the best path in terms of power and reception quality, this signal being received at an instant T2. However, the mobile station also knows the instant T1 at which the first correlation of the signal has been received. We can thus define a new parameter called the distance of the direct path DCD between the mobile station and its radio terminal waiter: DCD = D (TA) - cx (T2-T1), D (TA) being the distance calculated from indication transmitted by the radio server terminal of the time advance TA, and c being the speed of light.

The DCD parameter better represents the actual distance between the serving radio terminal and the mobile station than the TA time advance. Indeed, the power of the first correlation received from the signal may have been weakened by various obstacles, for example trees, being on its propagation path. The strongest correlation received may have been reflected by other types of obstacles, for example the flat facade of a building.

It is also possible to use the difference in time of reception -DIR- of signals from the different radio terminals (see GSM recommendations 05.10 - phase 2+). The mobile station will be able to calculate as a value the difference in reception time, that corresponding to the shortest time taken by each radio wave to propagate and not the time taken by the signal received with the strongest power, to avoid related inaccuracies to multi-transmission. The mobile station can thus calculate the DIR parameter for each of the neighboring radio terminals.

If the radio terminals are synchronized or if the RTD transmission offset between the different radio terminals is known to it, the geographic information server 4 will be able to calculate the distance from the neighboring radio terminal in question. However, this DIR parameter only allows a precise location calculation if the radio terminals are strictly synchronized or if the RTD transmission offset is known and does not drift over time. A mobile station listening to a mobile telephone network needs to synchronize with each of the BCCH frequencies of the serving cell and of the neighboring cells. To do this, it synchronizes with the synchronization burst SCH of the channel BCCH. A radio wave can take different paths between a radio terminal and a mobile station. This phenomenon is called multitransmission. In this case, the mobile station correlates to what corresponds to the best path in terms of power and quality, but not necessarily to the shortest path. A count of the number of correlations of a BCCH frequency received by the mobile station is carried out. The mobile station can thus calculate the value of the parameter NB -correlation for each of the BCCH frequencies received and transmit it in the message "measurements for localization". Of course, a filter can be provided to eliminate the correlations corresponding to a very poor reception quality.

A mobile station may be able to estimate whether it is moving and, if so, its approximate speed of movement. The measurement of the reception time difference DTR is carried out thanks to the difference in the reception time of the same burst SCH of a multiframe of the channel BCCH. A BCCH multiframe contains five SCH bursts. Inside the BCCH multiframe, a SCH burst is emitted every 10x8 periods of BP burst, or 11x8 periods at the end of the BCCH multiframe. A period of BP burst lasting exactly 15/26 ms, a mobile station not moving, receives each SCH burst every (10x8xl5) / 26 ms and once in five every (Hx8xl5) / 26 ms. A BCCH multiframe is transmitted cyclically. Its transmission duration is: 51x8x15 / 26 = 235.38 ms. Let tl be the instant of reception by the mobile station of a SCH burst of a BCCH multiframe and t2 the instant of reception by the mobile station of the same SCH burst of a BCCH multiframe transmitted for example five cycles later, the difference in reception time DTR is written: DTR = t2-tl-t with: t = 5x51x8x15 / 26 = 1.17692 s. The minimum speed of movement will then be the maximum value of the DTR parameter calculated on each of the BCCH frequencies received. If a BCCH frequency has not been received continuously on five multiframes, the mobile station indicates this in the message "measurements for localization".

There are several possibilities for activating the feedback of the "measurements for location" message to the geographic information server 4, by automatic activation after dialing the telephone number of the geographic information server 4 or by manual activation by the user. . The telephone number of the geographic information server 4 can be contained either in the SIM card of the user's mobile station, or in the software of the mobile station.

The user can save the telephone number of the geographic information servers authorized to locate it. Once the telephone number of the geographic information server has been dialed, the mobile station begins to measure the above parameters. The mobile station can also transmit to the geographic information server the reception levels of the different BCCH frequencies of the cells of the mobile network picked up by the mobile station before the establishment of the call in order to initiate the location calculation as quickly as possible. possible. With regard to the frequency of transmission of the message "measurements for localization" by the mobile station, several possibilities exist. The mobile station may only issue a "measurements for location" message when it considers it appropriate to do so, for example if the DTR parameter reaches a large value. The mobile station may also not issue "measurement" messages for location "only upon receipt of a request for location information sent by the geographic information server in the form of a short SMS message or via GPRS technology. The frequency of reporting of" measurements for location "can be carried out at intervals fixed in advance, for example 30 seconds Finally, the frequency of reporting of "measurements for localization" can be specified in a message sent by the geographic information server.

These different possibilities can advantageously be combined. For example, the mobile station may issue "location measurements" immediately after the telephone number of the geographic information server has been dialed or when said mobile station has moved, and upon receipt of a request message location information. This can be particularly interesting if the geographic information server has not succeeded in estimating the positioning of the mobile station, in particular in the event of erroneous or inconsistent data.

The geographic information server may need measurements related to a given radio terminal. It then sends an SMS or GPRS type message "specific measurement request" to the mobile station, specifying the BSIC, BCCH pair of the radio terminal. The mobile station then transmits a "measurement for a terminal" message relating to the radio terminal specified in the "specific measurement request" message. These measurements contain the pair BSIC, BCCH of the radio terminal, as well as the values RXLEV, RXQUAL, NB -correlation, DTR, NB-cycle and, possibly, parameters relating to the distance if the radio terminal in question is a waiter or if the mobile station knows how to calculate the DIR parameter with respect to the serving cell. The data passing between a mobile station and a radio terminal are subject to encryption, which preserves a certain confidentiality. In addition, these data are not sufficient to calculate the positioning of the mobile station, because the positioning of the radio terminals is information which does not pass over the network, but is known to the geographic information server.

The mobile station only issues "measures for location" messages in the following cases: - upon dialing a specific telephone number corresponding to a geographic location server;

- upon receipt of an "authenticated" message corresponding to a location request; - periodically, to a server identified by the mobile station.

In the latter two cases, the transmission of "measurements for location" messages is managed by the subscriber's SIM card. Indeed, some subscriptions may provide that the mobile station is located periodically by a location server. In this case, an ad hoc SIMToolkit application has been developed and the SIM card holder will have been informed that the switched on mobile station can be located.

In order to avoid any unwanted localization, security mechanisms can be implemented. For example, the list of telephone numbers of the various geographic information servers that can be saved in the SIM card or in the mobile equipment itself.

For better confidentiality, a user's SIM card may contain an encryption key K, equal to or different from the key used for encryption according to the GSM recommendation. The mobile station checks the identity of the geographic information server. When the call is established, the mobile station transmits a RAND code number to the GIS. The geographic information server, which contains the user's key K, then calculates the SRES code which it transmits in the message "request for location information". On receipt of this message, the mobile station checks whether the SRES code corresponds to that which it calculated itself. In the positive case, the mobile station transmits the message "measurements for location". Otherwise, the mobile station does not transmit and warns the user that an unsuccessful location attempt has been attempted.

The mobile station can also, instead of directly transmitting the "location measurements", transmit only the BSIC and BCCH pair from the serving cell. The geographic information server which will have retrieved the LAI parameter for identifying the reception area of the serving cell by interrogating a VLR visitor database covering the area from which the call was made, will then be able to know the setting CGI of the waiter cell as well as all the BSIC couples, BCCH from neighboring cells and transmit them to the mobile station. The mobile station then checks the accuracy of the information transmitted.

The geographic information server 4 is an expert system which estimates the most probable position or location area of a mobile station by correlation between parameter values which are fed back to it, and values recorded in its database. The parameters saved in the geographic information server database are associated with fixed geographic points. The parameters which the geographic information server can use to estimate the positioning of a mobile station are the reception level, the quality of reception, the distance, the different paths taken by a radio wave between a radio terminal and a given point, the movement of the mobile station and the hourly communication profile of the cell.

The RXLEV parameter corresponds to the reception level between the radio terminals, waitresses or neighbors, and the mobile station. In fact, the mobile station knows the downward parameter RXLEV, that is to say the level of reception which it receives from a transmission from a serving or neighboring radio terminal. Even for a mobile station that does not move from a given location, the RXLEV parameter can be subject to many variations, mainly due to fading phenomena of radio waves. A wave of given frequency is very often the result of several signals received at different phases.

The reception quality parameter corresponds to a reception quality level between the radio server terminal and possibly the neighbors, and the mobile station. Again, this reception quality parameter can be subject to many variations, mainly due to the interference between different signals of the same frequency, this being caused by the reuse by other radio terminals of the same radio frequency, or the phenomenon of fading. Thus, the higher the number of communications at a given time, the poorer the quality of a communication.

In addition, the frequency hopping makes it possible to increase the quality of reception by pseudo-randomly changing the frequencies used except that of the BCCH channel. It may be necessary to take this change in frequency into account in the mapping. The distance between the mobile station and its serving radio terminal is estimated either by the time advance TA or by the distance from the direct path DCD. The distance to neighboring radio terminals can possibly be estimated by the DIR reception time difference parameter, if the radio terminals are synchronized or if the RTD transmission offset between each radio terminal is known by the information server geographic. In this case, the GIS geographic information server will be able to calculate the observed time difference parameter OTD = DIR + RTD. The distance to neighboring cells can be calculated by the formula D = Do + Cx (OTD) with Do = distance calculated using the parameter TA or Do = DCD, and C: speed of light.

For each of the geographic points and each of the cells, the parameter NB -correlation is associated corresponding to the number of correlations of the BCCH frequency between a radio terminal and a mobile station. The value of this parameter depends greatly on the topology of the terrain. This value, entered in the database of the geographic information server, can come from a calculation carried out by the radio planning tool 5, supplemented or not by physical measurements, see figure 3. In the case of values coming from 'network planning tool, the relevance of the calculated values depends on the quality of the digital topology, which can be improved by comparing actual measurements with calculated measurements.

For a given call, the value of the RXLEV parameters and especially RXQUAL depends on the number of simultaneous calls on the waiter radio terminal and on its neighboring radio terminals. It is possible to establish hourly traffic profiles based on location, day and time. Thanks to the statistics processed by the different operational management centers 2, the network operators can establish an hourly traffic profile on the different sites processed by the geographic information server 4. For example, the traffic on the radio terminals covering a stadium football will be much more important on a match day.

A time profile system 7 (FIG. 4) can interface with the geographic information server to define the time profile concerning the simultaneous traffic on each of the radio terminals. The time profile system can take its information from the statistics of operational management centers or network management centers or from manual entries. For each radio terminal, the time profile depends on the day, work or holiday, the hour, exceptional days or other events. The geographic information server receives the calls made by it and processes the location parameters associated with this call.

Thanks to its interface with the operational management centers 2 or the network management center 3, the geographic information server knows the CGI parameter of the server cell and the correspondence of the pairs (BSIC, BCCH) of all the neighboring cells of the waiter cell with their respective CGI parameters, the exact geographic location of each radio terminal on the network and in three dimensions taking into account the height of the antenna of the radio terminal, the transmission power of each radio terminal of the network , the transmission frequency of each radio bay: GSM 900, Extended GSM, DCS

(or GSM) 1800, PCS 1900 or any other type of frequency, a parameter indicating whether frequency hopping and EFR (Enhanced Full Rate) is activated or not for each radio terminal, the exact geographical location of each fixed point modeled, in three dimensions. The option "Enhanced Full Rate" (EFR) allows to increase the quality of the transmission on the radio channel thanks to an improved transcoding of the radio channel. This transcoding has been standardized. It should be noted that, for each call, the EFR is activated only if the mobile station is capable of supporting this option. The EFR option is to be treated similarly to frequency hopping: the principle is the same: an activation of this option increases the quality on the radio channel.

Thanks to its interface with radio planning tools or through manual measurements, the geographic information server knows the estimated reception and quality levels of each of the BCCH frequencies received by a modeled geographic point, and the number of paths that a radio wave can travel between a radio terminal and a digitized point. The reception level, quality, interference values, as well as the number of estimated wave paths, are recorded in the geographic information server before the call of the mobile station. The geographic information server is used for its estimation of values calculated in deferred time. Nevertheless, it must take into account operational constraints, in particular for certain radio parameters which depend on the network, in particular the correspondences between the pair BSIC, BCCH and the CGI identifier, the power level of each radio terminal and the activation or not. frequency hopping.

Thanks to an interface with the network supervision means, preferably the standardized Q3 interface, the geographic information server is kept informed in real time of any changes to these parameters in order to take them into account in the evaluation. positioning of the mobile station. The geographic information server also takes into account the operational state of a radio terminal, in particular in the event of a breakdown. Similarly, in the event of a change in the transmission power of a radio terminal, the geographic information server can make a first approximation by considering that the ratio between the reception power at a given geographical point and the power of transmission from the radio terminal considered, is retained. On receipt of a "Measurements for location" message, the geographic information server calculates the CGI of all the cells involved in the measurement feedback thanks to the CGI of the waitress and the BSIC, BCCH pair of all the neighbors.

Then it estimates the most likely area for locating the mobile station using information on distance, reception level, reception quality level and number of correlations between the mobile station and the various neighboring radio terminals. This estimation is made by a comparison with prerecorded values thanks to rules defined by an expert system. In absolute terms, the information sent back to the geographic information server is too numerous. However, it should be taken into account that some of these parameters may be wrong. The expert system is able to discard the inconsistent parameters for the calculation of the location thanks to the values of the other parameters. When parameters are received, an interference engine starts a consultation and uses the rules of reasoning to make deductions and lead to the location of the mobile station. The location estimate by the geographic information server will be different if the mobile station is stationary or on the move. The degree of mobility of a mobile station can be assessed using a few indicators: change of radio waiter terminal, high frequency of reporting "measurements for location" message, DTR parameter, etc.

If the mobile station remains fixed, the geographic information server has time to calculate a more precise location and can use all the parameters at its disposal.

For a set of values available to the geographic information server corresponding to a call, either:

- {RXLEX} the set of geographic points of a topology corresponding to the RXLEV values for the different radio terminals concerned,

- {RXQUAL} the set of geographic points of a topology corresponding to the RXQUAL values for the different radio terminals concerned,

- {distance} the set of geographic points corresponding to the estimate of the distance from the radio waiter terminal.

The geographic information server will then follow reasoning rules, the following are given by way of example:

Rule 1: If the intersection between the three above-mentioned sets makes it possible to determine a point, then the location of the mobile station has been found.

Rule 2: If the intersection of the sets {RXLEV} and {RXQUAL} gives several points and if the distance estimated by the time advance TA gives a set of points further away from the radio terminal waiter than those found previously, then the TA time advance certainly corresponds to multi-transmission. The TA parameter must therefore not be taken into account. Rule 3:

If the distance parameter supplied to the geographic information server is the distance of the direct path DCD, then this estimate is more reliable than that made by the time advance TA. The geographic information server begins its search with the points corresponding to the DCD parameters and then correlates them to the points obtained with the RXLEV and RXQUAL parameters.

Rule 4:

If all of the geographic points found are located near a radio terminal and the latter does not appear in the "measurement for location" message, the geographic information server checks whether the radio terminal is active, and this through the interface with the operational management center or the network management center. If the radio terminal is inactive, then the location has been found. Otherwise, the geographic information server transmits to the mobile station a "request for specific measures" message while specifying the pair BSIC, BCCH, of the radio terminal in question. The mobile station transmits a "measurements for localization" message on the radio terminal in question. The geographic information server then determines whether the calculations are correct.

In the case of a mobile station in motion, the geographic information server does not have time to use all the parameters available to it. The geographic information server will estimate a displacement index DPT which is the maximum value of the reception time differences DTR, in order to be able to estimate the minimum speed at which the mobile station is moving. The geographic information server will use the identifiers, CGI and BSIC, BCCH pair, radio terminals received by the mobile station as well as the distance with the radio terminal server to make a first estimate of the location of the mobile station.

If no other location measurement has reached the geographic information server, the latter begins to perform the same location processing as for the mobile stations which are stopped. In the otherwise, the geographic information server will estimate the position of the mobile station using the difference between the values reported.

The parameters used will be the CGI identifier of the serving radio terminal, the identifier of the neighboring radio terminals (calculated from their

BSIC, BCCH), the distance from the radio terminal and the cartography of the geographic information server. A mobile station being able to move quickly only on road or rail axes, the geographic information server contains a vector map to take into account the different axes in its estimation of the location. The geographic information server uses expert system rules.

The following three rules are given as an example:

Rule 1:

In the case of a handover between two feedbacks of parameter values, the geographic information server can estimate the positioning of the mobile station by means of geographic cross-checks, vector mapping, the time interval between the two feedbacks. parameter values and the value of the DPT parameter. If the DPT parameter causes a speed of the mobile station to be estimated at least 40 krn / h, the time interval between two measurement feedbacks is 20 s, the arcs of a circle marking the distance between the mobile station and the two radio terminals at the time of the two value increases are contiguous, and if moreover a road exists at the place where the two arcs of circle are contiguous, then the mobile station is most likely to be located at this place .

Rule 2: According to the estimated speed of the mobile station by the parameter

DPT, the geographic information server knows the road or rail axes on which the mobile station is likely to be located. For example, if the estimated speed of the mobile station is around 250 km / h, the user is likely to be on a high-speed train, the route of which can be recognized by the server. information geographic.

Rule 3:

If no value has been returned for a sufficiently long time interval, for example 15 seconds, the geographic information server begins the location procedure for a fixed station.

This mobile phone location system can be used to distribute geographic information related to the exact location from which the call was made. This information will be disseminated after agreement with the publishers of geographic information and will only be available to subscribers to the mobile telephone network or to buyers of this service. A broadcast language can correspond to each telephone number, the telephone number being able to be unique on all networks. Geographic information can be of any kind, cultural, tourist, culinary, meteorological, commercial, etc. If the geographic information server considers that confusion between different locations is possible, it can offer comments relating to the different sites, at the user's choice, or even send a message "request for location information" to the mobile station. ".

This localization system can also be used for guidance or rescue operations. A probable location area of the highlighted mobile station can be displayed on a digital map of the geographic information server. An operator can thus either guide the user, or exchange information for display, or locate a distress call. The calculation of positioning with respect to radio terminals can be carried out with respect to radio terminals belonging to different mobile telephone networks.

The telephone operator can use this location system to offer fixed / mobile convergence services: either apply specific pricing for any call made near the subscriber's home, or converge mobile and fixed calls.

In the first case, the mobile station transmits, via the logical traffic radio channel, "measures for pricing" messages to a pricing center. The message "measurements for localization" contains the date and the start time of the call, its duration and the identifier of the mobile subscriber. If it cannot transmit its message, for example because of an excessive load of the network, it can store it in order to transmit it as soon as possible. During a conversation, the mobile station will only issue a "measurements for pricing" message in the following three cases: incoming or outgoing call made in the home area, leaving the mobile station from the home area during the conversion, entry of the mobile station into the home zone during the conversation. In the case of fixed / mobile convergence proper, a mobile station entering the perimeter of the subscriber's home transmits a "transfer to fixed" message via the logical traffic radio channel to a switching center. From this moment, an intelligent network system modifies the call routes so that the subscriber's mobile and landline "become one": any outgoing call can invariably be made from the landline or of the subscriber's mobile station and any incoming call causes a call notification on the subscriber’s landline and mobile station. Of course, the mobile station does not need to be in communication to transmit the message "transfer to landline" knowing that the GSM standard provides that any switched mobile station performs reception measurements in free or "idle" mode.

In the case of a family having several mobile subscriptions for a single fixed subscription, the mobile subscriptions can converge to a single fixed subscription. In the event of leaving the domiciliary zone of the domicile, the mobile transmits a message "transfer cancellation on landline" to the switching center. The effect of this message is to separate the convergence between the mobile station and the landline.

It is possible to manually deactivate the transmission of "landline transfer" messages.

There are two different methods for activating fixed / mobile convergence on a mobile station.

The first solution is as follows: when the processor of the mobile station is at his home, he can call a server in order to send a "measurements for location" message. The server receives the data and compares them to the values in its database. If the data is consistent, the server sends a message to the mobile station indicating that the transmitted data correspond to its home. The server also transmits the correspondences between the BSIC / BCCH pairs and the global identifier of the CGI cells of the neighboring cells. As provided in the GSM technical specifications 11, 11 and 1 1,14, the mobile station stores the global CGI cell identifiers of the cells that the subscriber's mobile station picks up at his home, their associated BSIC / BCCH pair as well as their calculated reception level in the subscriber's SIM card.

A second solution is that a computer server downloads via a logical traffic channel to the mobile station, the global CGI cell identifiers of the cells that the subscriber's mobile station picks up at his home, their associated BSIC / BCCH pair as well as their estimated level of reception. As provided in the GSM technical specifications

1 1.11 and 1 1.14, the mobile station stores the values transmitted by the computer server in the subscriber's SIM card.

In the event of a change in frequency plan on the mobile network, the correspondence between the global CGI cell identifier and its associated BSIC / BCCH pair changes. In this case, the computer server downloads the values described in the previous paragraph before implementing the frequency plan and the subscriber's SIM card contains the two sets of calculations which can be used to calculate if the subscriber is located in the perimeter of the home. These values will have been calculated by the radio planning tool available to the operator.

Similarly, in the event of a change in the transmission power of a radio bay covering the subscriber's home, the computer server downloads "in real time" the new associated reception levels.

Finally, in the event of the addition, deletion or breakdown of a cell in the subscriber's perimeter, the computer server downloads "in real time" the new associated reception levels.

To make its calculations and estimate whether it can send a "measures for pricing", "fixed transfer" or "cancellation of fixed transfer" message, the mobile station has, for each cell located within the perimeter of the subscriber's home, the global identifier the CGI cell of the associated BSIC / BCCH pair as well as the associated reception level. It is important that the SIM card has all the global CGI cell identifiers since the cell carrying a communication, sent from the subscriber's home, will not necessarily always be the same. In fact, a mobile station only knows the global identifier of the cell carrying the communication, it only knows the identifier of neighboring cells by their relative identification, that is to say their BSIC / BCCH pair.

The software located on the SIM card of the mobile station calculates if it is within the perimeter of the home as follows: searches if the global CGI cell identifier carrying the current call is saved in the SIM card. If this is the case, comparison of the reception level values calculated by the mobile station with those recorded in the SIM card for the server cell and its neighboring cells identified by their BSIC / BCCH pair. Of course, the card software

SIM uses a margin of error in order to take into account the multiple inaccuracies already described. If more than one set of values is saved in the SIM card, the software located on the SIM card will compare with all of these value sets. Outside the perimeter of the home, no message related to fixed / mobile convergence is transmitted by the mobile station. Thus, the subscriber to the mobile network knows that he will be located "without his knowledge" only when he is within the perimeter of his home.

Claims

1. Mobile telephone location system capable of communicating with a first radio terminal of a network of radio terminals supervised by an operational management center, the mobile telephone comprising means for estimating at least one parameter representative of the position relative to a terminal, and means for transmitting information relating to said parameter to a server via the first radio terminal, and the server comprising means for comparing information relating to said parameter with a pre-established map of said parameter, and in deduce an estimate of the location of the mobile telephone, characterized in that, the transmission of information between a mobile telephone and a radio terminal taking place on a logical service channel and on a logical traffic channel, the transmission of information relating to said parameter at the first radio terminal is performed on the logical traffic channel .

2. System according to any one of the preceding claims, characterized in that it comprises means for estimating the distance between a mobile telephone and the first radio terminal, with a margin of imprecision Δd _lm as a function of the time taken by a wave to travel the said distance.

3. System according to any one of the preceding claims, characterized in that it comprises means for estimating the reception levels of the emissions from the first radio terminal and from neighboring radio terminals.

4. System according to any one of the preceding claims, characterized in that the mobile telephone comprises means for comparing the instants of reception q by the mobile telephone of the transmissions of the other radio terminals with the instants of reception r of the transmissions of the first radio terminal and deduce therefrom the value of the offset Δq of the reception instants, and means for transmitting to the server via the first radio terminal the value of each offset

Δq, and that the server comprises means for estimating the distance between the mobile telephone and each other radio terminal as a function of the offset Δq, and of the offset Δe ^ between the transmission times e ^ from the other terminals radio and the transmission times e of the first radio terminal.

5. System according to any one of the preceding claims, characterized in that it comprises means for specifying the location of the mobile telephone by cross-checking the location estimates obtained by at least two parameters.

6. System according to any one of the preceding claims, characterized in that the localization is carried out on command of the user of the mobile telephone.

7. System according to any one of the preceding claims, characterized in that the server comprises means for transmitting information to the user as a function of the location of the mobile telephone.

8. System according to any one of the preceding claims, characterized in that the mapping is adapted to the transmission power levels of the different radio terminals by linear interpolation.

9. System according to any one of the preceding claims, characterized in that the cartography is recalculated as a function of the evolution of parameters capable of modifying the values reported to the geographic information server.

10. System according to any one of the preceding claims, characterized in that the mobile station comprises means for comparing location data with a prerecorded area, for specific pricing, the location data being stored in a mobile station SIM card.

1 1. System according to claim 10, characterized in that the mobile station comprises means for transmitting pricing data via the logical traffic channel.

12. The system as claimed in claim 11, characterized in that the mobile station transmits pricing data if a call is made or received near the preregistered area, if the mobile station enters or leaves said preregistered area during 'a communication.

13. System according to claim 10 to 12, characterized in that the mobile station comprises means for transmitting a transfer message on the fixed network if said mobile station is in the area pre-recorded, causing a modification of the call routings so that any incoming call is notified on the fixed station (s) and on the mobile station.