Patent Publication Number: US-2005124356-A1

Title: Method and telecommunications system for positioning a target user equipment using a mobile originating-location request procedure

Description:
FIELD OF THE INVENTION  
      The present invention relates to a method and telecommunications system for positioning a target User Equipment (UE) of a subscriber within a network for cellular communications using a mobile originating-location request procedure.  
     BACKGROUND OF THE INVENTION  
      The positioning of User Equipment (UE) is a service provided by cellular networks. In particular, for example, the Global System for Mobile communication (GSM) and the Universal Mobile Telecommunication System (UMTS) networks, that facilitate determination of the locations of User Equipment, are able to determine location information. Location information may also be communicated between Gateway Mobile Location Centers (GMLCs), located in the same or a different Public Land Mobile Network (PLMN), via a known GMLC to GMLC interface.  
      By making use of radio signals, the capability to determine the geographic location of the user equipment is well known in the art. The location information may be requested by and reported to a client application within or attached to the core network of a cellular network. The positioning feature may be used internally by the access network of a cellular network or attached networks, e.g. for location assisted. handover or to support other features such as home location billing, by value-added network services, by the UE itself or through the network, and by “third party” services. The positioning feature may also be used by an emergency service, which may be mandated or “value-added”, but the position service is not exclusively for emergencies.  
      More in detail, as explained in document 3GPP TS 23.271 V6.4.0, 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Functional stage 2 description of LoCation Service (LCS), Release 6, there are generally four location services procedures for allowing a subscriber to be positioned. The subscriber may be positioned from an external entity (mobile terminating positioning), or after a request from the network (network induced positioning), or may be informed of his own position after an own positioning request (mobile originating positioning), or may inform an external entity of his position after an own request (mobile originating positioning).  
      The position information is preferably reported in standard co-ordinates, for instance geographical co-ordinates, together with the time-of-day and the estimated errors or uncertainty of the location of the UE.  
      It shall be possible for the majority of UEs within a network, both active or idle, to use the positioning feature without compromising the radio transmission or signaling capabilities of the access networks.  
      The UE and the network may support a number of different positioning methods. Moreover, the UE may support privacy invocation request and response.  
      Current standardized architectures of a Location Service in GSM and UMTS networks provide for LCS entities, such as LCS clients and servers, which communicate between themselves by the messaging and signaling capabilities of the Access Network. Clients submit their requests to an LCS server for receiving information about positioning a UE.  
      In the known architectures, if a subscriber wishes to position a third party subscriber, the location must be requested by passing through a service provider, which is external to the network.  
      Moreover, in order to position a third party user equipment, a subscriber must have access to an LCS client, which in turn starts a terminating positioning procedure. Unfortunately, in most cases the LCS client may not be easily accessible by a subscriber, for instance because the particular user equipment of the subscriber requesting location services does not support LCS client functionality. This drawback may be troublesome for a user, especially if he needs a quick response.  
     SUMMARY OF THE INVENTION  
      Aim of the present invention is to overcome the above mentioned drawbacks, particularly by providing a method, a service node and a telecommunications system for allowing a user equipment of a requesting subscriber to retrieve location information of a target user equipment of another subscriber, within the same or in a different PLMN.  
      User equipment in the context of the invention may be a mobile station, a computing device comprising or connected to means for wireless telecommunications, or a handset adapted to provide mobile telecommunications.  
      Within the scope of this aim, an object of the present invention is to preserve the standard architecture of the networks without affecting the communications standards among the various entities interacting over the network.  
      Another object of the present invention is to benefit of both existing standard Mobile Originating Location Request (MO-LR) and Mobile Terminating Location Request (MT-LR) procedures without changing the standard communication interfaces.  
      A further object is to meet the target user equipment privacy settings, through appropriate customization of the privacy settings by the target subscriber.  
      This aim, these objects and other which will become apparent hereinafter are achieved by a method for positioning a target user equipment of a first subscriber within a network for cellular communications, characterized in that it comprises the steps of: at a first service node connected to a Gateway Mobile Location Center, receiving a Mobile Originating Location Services invoke from a requesting User Equipment of a second subscriber, the invoke comprising a target identifier of the target user equipment; initiating a checking whether an identifier associated with the requesting user equipment is comprised within a list of allowable identifiers of respective user equipments which are allowed to position the target user equipment; in response to a determination that the identifier associated with the requesting user equipment is comprised within the list of allowable identifiers, initiating a positioning of the target user equipment and returning location information resulting from the positioning to the requesting user equipment.  
      The aim and the objects of the invention are also achieved by a telecommunications system for positioning a target user equipment of a first subscriber within a network for cellular communications, the system comprising a service node connected to a Gateway Mobile Location Center and to means for positioning user equipments, characterized in that the service node comprises means for receiving a Mobile Originating Location Services invoke from a requesting User Equipment of a second subscriber, the invoke comprising a target identifier of the target user equipment, and in that the system comprises: memory means for storing a list of allowable identifiers of respective user equipments which are allowed to position the target user equipment, checking means for checking whether an identifier associated with the requesting user equipment is comprised within the list of allowable identifiers, and means for returning location information resulting from the positioning to the requesting user equipment in response to a determination that the identifier associated with the requesting user equipment is comprised within the list of allowable identifiers.  
      Moreover, the aim and the objects of the invention are also achieved by a service node for positioning a target user equipment of a first subscriber within a network for cellular communications, the service node comprising means for communicating with a Gateway Mobile Location Center supporting positioning functionality and with the target user equipment, characterized in that the service node comprises: means for receiving a Mobile Originating positioning request from a requesting User Equipment of a second subscriber, the request comprising a target identifier of the target user equipment, means for initiating a checking whether an identifier associated with the requesting user equipment is comprised within the list of allowable identifiers, and means for initiating a positioning of the target user equipment, in response to a determination that the requesting identifier is comprised within the list of allowable identifiers.  
      The list of allowable identifiers is stored in a database which is preferably comprised in the SLPP (Subscriber Location service Privacy Profile) of the Home Location Register or the Home Subscriber Server. The list can be alternatively stored in any other centralized home operator&#39;s subscriber database of the target subscriber, as it is clear to the skilled in the art.  
      The checking is preferably performed at the MSC/SGSN serving the target UE, but it may be also performed at the GMLC as well, once it has accessed the target subscriber&#39;s information stored in the HLR/HSS. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Further characteristics and advantages of the invention will become better apparent from the following description of preferred but not exclusive embodiments of the invention, illustrated by way of non-limitative embodiments in the accompanying drawings, wherein:  
       FIG. 1  is a block diagram of a conventional cellular network;  
       FIG. 2  is a block diagram of a standard LCS architecture for positioning a target user equipment;  
       FIG. 3  is a block diagram of an architecture for allowing a user equipment to be positioned by a second user equipment, according to an embodiment of the present invention;  
       FIG. 4  is a flow chart illustrating the steps involved for handling requests by a second subscriber for positioning a target user equipment;  
       FIG. 5  is a flow chart illustrating the steps involved for returning location information about the target user equipment to the requesting user equipment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A typical GSM network  10  comprises a plurality of cells  12 , which are associated with at least one Base Transceiver Station  13  (briefly represented by a tower antenna) and which are grouped so as to form larger areas  11  associated with a particular geographical zone. Such areas are served by at least one Mobile Switching Center (MSC)  20  which preferably comprises or is connected to a Visitor Location Register (VLR) (MSCNLR).  
      The basic function of MSC/VLR is to switch speech and data connections between Base Station Controllers (BSCs), other MSCs, other networks and external non-mobile-networks. The MSC also handles a number of functions associated with mobile subscribers, among others registration, location updating and handover between a UE and the PLMN.  
      In the area served by a certain MSC, the UE does not need to send update information about its location.  
      The VLR stores data about all customers who are roaming within the location area of the corresponding MSC. This data is updated with the location update procedure initiated from the UE through the MSC, or directly from the subscriber&#39;s Home Location Register (HLR) or Home Subscriber Server (HSS).  
      The HLR/HSS is the home register of the subscriber, which particularly stores information about the subscription, the services which are allowed by the subscriber and his location. When the subscriber roams into the location area of an MSC different from the home MSC, the HLR/HSS is updated accordingly. It is therefore clear that the role of HLR/HSS is very important for handling positioning procedures.  
      The HLR/HSS may be co-located with a given MSC/VLR, integrated with the MSC/VLR, or alternatively can service multiple MSC/VLRs. The HLR may be also in a network different from the network in which the UE is roaming.  
      With reference to  FIG. 2 , a typical and conventional architecture supporting location-based services and UE positioning comprises at least one User Equipment (UE)  1  interfacing with a Radio Access Network (RAN), comprising any one of a Global System for Mobile Communications (GSM) Public Land Mobile Network (PLMN)  120  and a Universal Mobile Telecommunications System (UMTS) access network  130 .  
       FIG. 2  further shows a Gateway Mobile Location Center (GMLC)  30 , which usually interfaces a plurality of LCS clients  2  and the mobile network, and contains functionality required to support Location Services. The GMLC  30  sends positioning requests to Service Nodes and may receive in answer location information about the target UE  1 . In the particular embodiment shown, the HLR/HSS  40  is connected to the GMLC  30 .  
      A service node may be any one of a 2G (2nd generation) Mobile Switching Center (2G-MSC)  121 , a 2G-Serving GPRS Support Node (2G-SGSN)  122 , in the case of a GSM network. Similarly, if the RAN is a UMTS Radio Access Network  130 , the service node may be a 3G (3rd generation)-MSC (3G-MSC)  131  as well as a 3G-SGSN  132 . Obviously, the same RAN may be simultaneously connected to a plurality of MSCs and SGSNs.  
      The GMLC usually interfaces with the LCS clients by means of an Application Programming Interface to allow third party service providers access to the mobile network. Moreover, the GMLC usually communicates with both the service node and the HLR/HSS by means of Mobile Application Part (MAP) messages. A typical MAP message which is of particular interest for the present invention is the MAP  PROVIDE   —   SUBSCRIBER   —   LOCATION  message, which is used by the GMLC to request the position of the UE from the Visited Mobile Switching Center (VMSC).  
      An MSC and a UE communicate (e.g., exchange mobility management messages) via Direct Transfer Application Part (DTAP) messages.  
      An architecture for allowing a user equipment to be positioned by a second user equipment, according to an embodiment of the present invention, is shown in  FIG. 3 .  
      The architecture comprises a first User Equipment  1  to be positioned, which interfaces with a Radio Access Network  100 . RAN  100  generically identifies any kind of mobile access networks, for instance the GSM RAN  120  and UMTS RAN  130  of  FIG. 2  (with their SMLC functionality) or a RAN based on a Code Division Multiple Access (CDMA), which is not shown in the figures but which is known to the skilled in the art.  
      A service node  25  (generically identifying either an MSC or an SGSN), for instance 2G-MSC  121 , 3G-MSC  131 , 2G-SGSN  122  and 3G-SGSN  132 , a GMLC  35  and a HLR/HSS  45  have enhanced functionality according to the present invention and are reciprocally connected in a conventional manner.  
      According to a particular embodiment of the present invention, the service node  25  is a 2G-MSC and the GMLC  35  accesses an external network  50  serving a second user equipment  3 . For example, the GMLC  35  communicates with the external network  50  by a standard GMLC to GMLC interface.  
      Either UE  1  or UE  3  may be in their respective home location area, or in areas different from the respective home location area, according to standard arrangements which are known to the skilled in the art.  
      In another embodiment of the present invention (not shown in the figures), the second user equipment is comprised in the same network in which the first user equipment is located and they communicate with the same RAN  100 . Many other arrangements are clear to the skilled in the art without departing from the scope of the present invention, as will become apparent hereinafter.  
      According to the invention, a new privacy list is stored in memory means within the network, preferably in the target Subscriber LCS Privacy Profile (SLPP) of the HLR/HSS  45 . This new information is needed to define a list of UE subscribers which are authorized to request the own location, in terms of geographical coordinates, for location services usage.  
      The privacy list comprises a number of allowable identifiers, each one associated with a respective user equipment. Such identifiers are, in a preferred embodiment of the invention, phone numbers associated to the authorized UEs.  
      When the target UE roams into a location area which is not directly served by the home MSC, the privacy list is downloaded to the MSC/VLR visited by the target subscriber through the MAP message conventionally called  INSERT   —   SUBSCRIBER   —   DATA,  which message is duly modified so as to carry information about such privacy list.  
      In order to allow the UE  1  to be positioned by the UE  3 , the particular procedure shown in  FIG. 4  is preferably followed. The procedure concerns in particular the case of a GSM Circuit Switched (CS) network, but it is straightforward to apply the teachings of the invention to a GSM Packet Switched (PS) or to UMTS networks, either CS or PS.  
      At the beginning  400  of the procedure, if the subscriber of UE  3  is in idle mode, the UE  3  requests a radio connection setup and sends a Connection Management (CM) service request indicating a request for a call independent supplementary service to his RAN. Instead, if the UE  3  is in dedicated mode, the UE  3  sends a CM service request on the already established radio connection.  
      At step  410 , the RAN connected to the UE  3  receives the CM service request and forwards it to the core network, in particular to the MSC of the requesting UE&#39;s location area.  
      At step  415 , the MSC server instigates authentication and ciphering if the UE was in idle mode or returns a Direct Transfer CM Service Accept if the UE was in dedicated mode.  
      At step  420  the UE  3  sends to the MSC a DTAP message, which is based on a conventional MO-LR Location Services invoke, but is modified according to the invention. The modification to the standard invoke mainly consists in including an identifier of the target subscriber in the invoke. In the illustrative embodiment hereby described such identifier is advantageously the phone number of the UE  1 .  
      At step  423 , the MSC checks if the requesting UE is authorized to use the MO-LR service for locating a target user equipment other than its own. If not, the request is rejected, an error code is generated at step  424  and the procedure is ended.  
      Otherwise, at step  425  a checking procedure is initiated according to the invention. In detail, the MSC forwards the request to the GMLC of the target subscriber through a new MAP message which is hereby referred to as  ORIGINATING   —   UE   —   LOCATION   —   REQUEST.    
      At this point the GMLC substantially handles the request as an ordinary Mobile Terminating (MT) positioning procedure, but new steps are performed according to the invention. In particular, at step  430 , the GMLC retrieves the MSC/VLR address at which the target subscriber is registered by contacting the HLR/HSS. Such “target” MSC/VLR may be also the same MSC/VLR from which the request started.  
      Then, at step  435 , the GMLC sends a  PROVIDE   —   SUBSCRIBER   —   LOCATION  MAP message which is modified so as to carry information about the requesting entity. In particular, an indication is provided so as to inform the target MSC that the location request is coming from an originating UE rather than from an LCS client. Such information comprises a unique identifier of the requesting UE, preferably its phone number.  
      In this case, privacy checks usually performed by the service node for handling requests by LCS clients are skipped, while a new check is performed.  
      Particularly, at step  440  it is checked whether the requesting UE&#39;s identifier, for instance its phone number, is comprised within the list of identifiers which are allowed to position the target UE.  
      If so, at step  500  the procedure enters substantially conventional MT-LR procedures, and positioning is initiated. In particular, at step  505  the target UE is positioned via RAN  100  and, at step  510 , the RAN  100  sends a standard Location report to the MSC  25 , which report may include a failure notification, should the location estimate be unsuccessful.  
      Then, at step  515 , the MSC  25  sends a MAP  SUBSCRIBER   —   LOCATION   —   REPORT  to the GMLC  35 , and no charging is performed in the MSC/VLR  25  which has performed the positioning.  
      At step  520 , the GMLC  35  forwards the report to the MSC of the requesting UE by means of a new MAP message  ORIGINATING   —   UE   —   LOCATION   —   RESPONSE.  Finally, at step  525 , the requesting UE  3  is notified about the location of the target UE  1  and the procedure ends at step  530 .  
      If, at step  440 , the requesting UE&#39;s identifier results not to be included in the privacy list, a further check is preferably performed at step  445 , so as to check whether the requesting UE is authorized to bypass the target UE&#39;s privacy settings, for example if the requesting UE is used for Legal Interception services.  
      If so, the procedures continues as in step  500 . If not, a privacy violation message is preferably returned to the requesting UE (step  450 ) and the procedure is terminated (step  460 ).  
      The actual checking is preferably performed at the “target” service node  25  itself, but it can be alternatively performed by other network elements which can access the list of allowable subscribers.  
      While a detailed description has been provided with reference to a CS GSM network, the person skilled in the art has no difficulty in applying the teachings of the present invention to other mobile networks, either CS or PS.  
      For example, in a UMTS CS network according to another embodiment of the present invention, a requesting UE sends the MO Location Services invoke to the 3G-MSC serving the location area of the requesting UE, which in turn sends the new  ORIGINATING   —   UE   —   LOCATION   —   REQUEST  MAP message to the GMLC. The target UE is then positioned after having passed the privacy checks according to the invention and the MSC serving the requesting UE is notified by the  ORIGINATING   —   UE   —   LOCATION   —   RESPONSE  MAP message, and so on.  
      The skilled in the art easily understands that the above described steps may be performed by any computer hardware and/or software and telecommunications means programmed through conventional techniques in order to take into account the additional information data needed by the present invention. A combination of processor, memory and communications means is required in order to check the availability of a list of allowable identifiers, together with checking means, preferably implemented through software, for comparing the identifiers or the phone numbers to the requesting UE&#39;s identifier or phone number and for returning a result.  
      The invention is therefore preferably implemented by introducing new functionality in existing systems, through conventional techniques which are clearly in the reach of the average technician and, therefore, are not hereby discussed in detail.  
      It has thus been shown that the present invention fulfils the proposed aim and objects. Clearly, several modifications will be apparent to and can be readily made by the skilled in the art without departing from the scope of the present invention. Therefore, the scope of the claims shall not be limited by the illustrations or the preferred embodiments given in the description in the form of examples, but rather the claims shall encompass all of the features of patentable novelty that reside in the present invention, including all the features that would be treated as equivalents by the skilled in the art.