Abstract:
A technique for locating equipment connected via a high-speed line to a distributor device of fixed and predetermined position. The technique involves measuring signal attenuation between the equipment and the distributor device, and estimating the position of the equipment relative to the distributor device, deduced from this attenuation measurement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national phase of the International Patent Application No. PCT/FR2011/052293 filed Oct. 3, 2011, which claims the benefit of French Application No. 1058231 filed Oct. 11, 2010, the entire content of which is incorporated herein by reference. 
     FIELD 
     The invention relates to determining the location of equipment, based on the IP address of this equipment (IP for “Internet Protocol”). 
     BACKGROUND 
     There is increasing demand for reliable techniques which allow obtaining the location of a user of a telecommunications terminal. In fact, with the marked expansion in location-based services (LBS), we are seeing increased user demand for a rapid determination of their location in a precise manner and with a low failure rate. 
     Frequently used location solutions are:
         those based on satellite systems,   those based on mobile networks, and   those based on the Internet.       

     Location solutions based on satellite systems, such as the American GPS (Global Positioning System) system, are used by terminals equipped with GPS receiving means that can decode the synchronization signals sent by the satellites in order to deduce their position, subject to visibility by at least three satellites. Due to this, although this method is effective in terms of accuracy, it only works in certain types of environments (where the sky is directly visible) and with a limited number of terminals. 
     In location solutions based on mobile networks (GSM, UMTS, etc.) or local area networks (WLAN, for example WiFi), determining the location of the mobile terminals is based solely on two principal mechanisms such as:
         using indications of the strength of the signals received, and   using the identifier for the cell to which the terminal is connected.       

     In the first technique given above, indications of the strength of the signals received from fixed transmitters or access points or base stations (RSS technique, for “Received Signal Strength”) are used. Several location methods have been developed that are based on this received signal information. The most common is based on creating a database of RSS vectors corresponding to a spatial discretization. The principle of this method, commonly called calibration (or fingerprinting) or sampling, is:
         to find the best correspondence between the RSS vector measured by the mobile terminal (signal level measured at a given location) and those stored in a database, then   estimating the location based on this correspondence.       

     This method must necessarily be accompanied by a continuous exchange between the terminal and the dedicated server hosting the correspondence database in the network. 
     The second of said location techniques uses the identifier of the cell to which the mobile terminal to be located is connected. In fact, each mobile terminal “grabs” a cell in order to exchange data or send/receive voice calls via the mobile network. Each cell corresponds to a base station or access point for which the coordinates are only known by the equipment in the network. Due to this, in order to find out its location, a mobile terminal must send the cell identifier (for the cell where it is located) to a dedicated platform in the network. This platform returns the position associated with the base station to the mobile terminal. Several disadvantages result from this arrangement:
         imprecision (compared to other location techniques), and   high latency times (due in particular to the response time of said platform).       

     Internet-based location solutions, which use the IP address associated with the user terminal (PC or mobile), make use of mechanisms which allow associating an IP address with the location of the last public router for which the location is known in the Internet wide area network. Due to this, the accuracy is clearly still less precise than values obtained by techniques such as those presented above. The level of accuracy typically is regional (or departmental in France), in cases where the location can even be obtained. 
     SUMMARY 
     The invention aims to improve this situation. 
     In particular, it proposes improving the precision of this last type of location determination, based on the IP address of the user equipment (particularly a terminal). For this purpose, the invention relates to a method for determining the location of equipment connected via a high-speed line to a distributor device of fixed and predetermined position, said method comprising:
         a measurement of signal attenuation between the equipment and the distributor device, and   an estimation of the position of the equipment relative to the distributor device, deduced from this attenuation measurement.       

     The invention therefore proposes the use of measurements on signals, for example xDSL or ADSL (Asynchronous Digital Subscriber Line), between said equipment (for example but not necessarily the terminal of a user) and a distributor device such as, for example, a DSLAM multiplexer (Digital Subscriber Line Access Multiplexer) which serves a subscriber using an ADSL line with an identified IP address. 
     As the location (geographical position) of DSLAM type equipment is known and fixed, it is possible to determine the rough position of the subscriber. However, in the meaning of the invention, the precision of the location is advantageously improved by using attenuation measurement mechanisms. In particular, as described below as an example, speed measurements are obtained, which allows fine-tuning the estimation of the distance between the equipment of the subscriber and the geographical position of the distributor device. Thus in one example embodiment, the attenuation measurement comprises measuring the speed on a high-speed line established between the distributor device and the equipment. 
     One thus obtains a location within a thin ring (a ring width of only a few hundred meters) instead of a location within a disk-like region around the distributor having a radius of several kilometers, as we will see below with reference to  FIG. 1 . In one embodiment, this location can be further reduced to one sector of the ring, with the precision corresponding to a limited region due to using information on the approach angle between the DSLAM distributor and the equipment using the ADSL line. This approach angle information may, for example, be deduced from the directions of the trenches made when installing the local loop (pair of copper wires) between the distributor and the residence of a given user. Typically one can make use of a map of these trenches, or of tests conducted on site. In addition, the local loop may also, in certain cases, comprise a local loop using radiofrequencies, therefore without wired connections between the distributor and the home of the subscriber. In this case, said angle measurements can be deduced from a sector that covers a transmitting antenna used to broadcast the radiofrequency signals from the distributor to a receiving antenna near the home of the subscriber. This is therefore a possible variant for mapping the approach angle measurements. 
     In one possible embodiment, in order to pinpoint a location to within a sector, the method can then generally comprise:
         mapping beforehand the signal attenuation around at least one distributor device, and   determining the current location of the equipment within a sector around the distributor, by said attenuation measurement.       

     This mapping can be established by test measurements around the distributor device or by the topology configuration of the network around the distributor device. 
     The equipment of the user can be a terminal using an IP address attributed for at least one given communication. Thus, at least one IP address is assigned to the equipment and the equipment, in communications, then uses this IP address, the method comprising an attenuation measurement for this IP address currently being used, in order to determine the location of the equipment. 
     In one particular embodiment (specifically when the equipment is a gateway between a local area network to which at least one terminal is connected and a wide area network), a set of predetermined IP addresses can be assigned to the equipment, and the equipment, in operation, uses at least one of these predetermined IP addresses, said method then comprising:
         a dynamic determination of the IP address currently being used by the equipment, and   an attenuation measurement, for this IP address currently being used, in order to determine the location of the equipment.       

     Known location technologies based on the Internet IP use a database containing a correspondence between an IP address and the location of the last Internet router for which the location is known. This type of database, essentially static, limits the possibilities of providing location information that is up to date and of acceptable precision. Advantageously, in this embodiment of the invention, an approach based on dynamically collected IP address data allows reducing the uncertainty in the location determination. 
     In an example embodiment in which the equipment comprises a gateway to a short-range local area network, it is additionally possible to determine the location of a terminal connected to this short-range network. The method then additionally comprises determining the location of a terminal connected by the short-range network to the equipment. In particular, the location of the terminal is comparable to that of the gateway. In fact, the location of the gateway is determined first. Thus any terminal then identified by its IP address in the short-range network around the gateway is determined as being located within a zone in immediate proximity to the gateway, because the network has a short range (several dozen meters). The position of the terminal is then considered as corresponding to that of the gateway, with a low degree of uncertainty (corresponding to these few dozen meters). 
     In such an embodiment where a plurality of terminals can be connected to the equipment by the short-range network, a set of predetermined IP addresses is assigned to the equipment and the equipment assigns to each terminal one of said predetermined IP addresses. The method then comprises:
         a dynamic determination of each IP address in the set currently being used by a terminal, and   an attenuation measurement, for each IP address currently being used, in order to determine the location of each terminal connected to the equipment by the short-range network.       

     The invention also relates to an element of a wide area telecommunications network, intended to be connected to a distributor device of the type mentioned above. In particular, the network element comprises means for measuring the signal attenuation between telecommunications equipment connected via a high-speed line to this distributor device, in order to implement the method presented above. This network element in the meaning of the invention may additionally comprise means for estimating the location of the equipment, deduced from the attenuation measurements, particularly in the case where the network element is in the form of a dedicated service platform as described below in an example embodiment. 
     The invention also relates to a computer program comprising instructions which, when run by a processor, implement the method presented above. In one example embodiment, this program can be installed on a platform of the abovementioned type.  FIG. 2 , which is presented below, can be a flowchart of the general algorithm for such a program. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the invention will be apparent from reading the following description of some possible example embodiments, and from examining the attached drawings, in which: 
         FIG. 1  schematically illustrates equipment  11  connected to a distributor  10  and which can thus be located within a ring portion LOC, in the meaning of the invention, 
         FIG. 2  illustrates the main steps of the method according to the invention, in an example embodiment, 
         FIG. 3  illustrates the determination of a terminal&#39;s location when it is in a mobile situation. 
     
    
    
     DETAILED DESCRIPTION 
     A distributor device  10  is represented in  FIG. 1 , for example a DSLAM (Digital Subscriber Line Access Multiplexer), to which is connected the equipment  11  of a user  16  (for example a PC computer) that has a connection to the Internet  14  and which therefore has an assigned IP address. The equipment  11  is then connected to the distributor device  10  by a high-speed connection, for example xDSL or ADSL (Asynchronous Digital Subscriber Line), via a gateway  12  between a local area network and the Internet  14  in the example represented. 
     The distributor device  10  is connected to the Internet  14  via a server  13  (for example a BRAS—Broadcast Remote Access Server) in the example represented, and possibly via one or more IP routers (not represented). 
     In particular, one can see a region D in  FIG. 1  representing the range of the distributor  10  for providing a high-speed connection for all the telecommunications equipment contained in this region D. The region in question resembles a disk. 
     To locate specific equipment  11 , the invention proposes reducing the uncertainty of the location within the disk D, by a proposed IP-DSLAM location solution based on the equipment in the ADSL network. By applying the invention, this uncertainty disk D is reduced to a precision ring characterized by a minimum radius R in  and a maximum radius R out  where:
         R in  corresponds to the minimum distance estimated using a measurement of the speed between the user terminal (PC or mobile) and the DSLAM equipment of the network, and   R out  corresponds to the maximum distance estimated using a measurement of the speed between the user terminal (PC or mobile terminal) and the DSLAM equipment of the network.       

     Advantageously, it is possible to additionally use information on the circle sector SA between the DSLAM distributor and the building where the ADSL line is operating in order to further refine the location to inside the intersection LOC of this circle sector and said ring. This circle sector information SA can be obtained from the personnel in charge of setting up the local loop (pair of copper wires between each residence in a building and the first element of the carrier&#39;s network). More generally, a map can be established by conducting test measurements around the distributor device or by the topology configuration of the network around the distributor device. These measurements are conducted by the technicians in charge of making the trenches when installing the local loop between the distributor and the residence of a given user. 
     In one example utilization, a user can then connect to an Internet content site and obtain, because of the location features of the invention, a list of addresses (restaurants, theaters, ATM machines, etc.) near his residence within an area typically several hundred meters across (corresponding to the difference between the radii R out  and R in , according to the tests conducted). Ultimately, the extent of this region corresponds to a portion of the uncertainty ring estimated using the location solution of the invention, based on the attenuation of the ADSL signal and expressed in one example embodiment by a decrease in speed. 
     The steps in an example method for such a location determination will now be described with reference to  FIG. 2 . First the connection of the equipment  11  is initiated, and in particular its IP address (or an IP address of the gateway  12 ) is identified in step  20 , and associated in step  21  (by elements of the ADSL access network) with a given DSLAM distributor  10 , in order to first determine a location within a disk D. In a next step  22 , a speed measurement is initiated by an element of the ADSL access network or by a remote platform dedicated to this purpose (denoted  15  in  FIG. 1 ). Once the speed has been measured, in step  23  an estimate of the distance is deduced from this, obtaining the radii R in  and R out  associated with the uncertainty ring estimated in this manner. In one example embodiment, this estimation of the radii can be obtained by measuring the speed and response time (or “ping”) of an IP test packet sent from the platform  15  to the equipment  11  (or to the gateway  12 ) and returned by the latter to the platform  15 , in said step  22 . For this purpose, the platform  15  sends a test packet by sending means C 1  and receives the return packet by receiving means C 2 , then measures the attenuation on the packet received which is expressed as a reduction in speed (possibly taking into account a ping response time), with the aid of measurement means MES, of course taking into account a typical speed loss between the distributor  10  and the platform  15 . 
     Of course, the ping time is a basic example of a speed measurement technique. Other more sophisticated and/or complementary variants can be envisaged. 
     Once the uncertainty ring is defined using the speed measurements, the next step  24  can consist of using the circle sector information SA to refine the location to a region of defined accuracy LOC in step  25 . As indicated above, the circle sector information SA can be stored in a database of correspondences between an ADSL line identifier and circle sector information determined by workers. 
     The equipment  11  connected to the gateway  12  may be fixed or mobile. In particular, when the equipment  11  is a terminal TER that is in a mobile situation, as represented in  FIG. 3 , in the context of a short-range wireless connection of the terminal TER to several successive gateways, it is possible to locate within a succession of short-range local area networks the movements of this terminal as it borrows a succession of IP addresses assigned by the successive gateways, doing so namely by said dynamic determination of the IP address currently being used by the mobile terminal. This situation is represented in  FIG. 3 , in which the mobile terminal TER is capable of communicating (telephone call via VoIP or data communication) with a plurality of successive gateways P 1 , P 2 , P 3  (via local area networks, for example using WiFi), by the respective assigned IP addresses @IP 1 , @IP 2 , @IP 3 . The first and second gateways P 1 , P 2  are connected to the DSLAM multiplexer  10 , but the second gateway P 2  is further away from the distributor  10 . One then detects a drop in the speed accessible to the terminal TER, which shows that the terminal is moving further away from the distributor  10 . Then, in the example represented, the terminal TER is connected by a local area network to a new gateway P 3  which assigns it the address @IP 3 . Here, the gateway P 3  is connected to a DSLAM distributor  10 ′ which is different from the distributor  10 , and a measurement of the attenuation between the gateway P 3  and this distributor  10 ′ allows determining the location of the terminal TER using the address @IP 3  within the immediate vicinity of the gateway P 3  (in a short-range local area network). 
     Of course, the invention is not limited to the embodiment described above as an example; it applies to other variants. 
     For example, an attenuation measurement performed by the platform  15  was described above. More generally, however, such a measurement can be conducted by any element of the wide area network connected to the distributor  10 . The invention then generally concerns an element of the wide area network which, for example, can be the platform  15 . 
     Also presented above was the case of a location within a region LOC several hundred meters across. However, depending on the precision of the attenuation mapping, it is possible to locate the exact address of the equipment connected to an ADSL line, which allows considering applications other than providing a list of relevant addresses near the equipment. For example, the user can connect to an online purchasing site in order to have a product or service delivered and it is then possible to determine the location of his ADSL line transparently in order to find the exact address corresponding to his current location.