WO2005029902A1

WO2005029902A1 - Method and telecommunications system for positioning accuracy negotiation between a location service client and a target user equipment of a subscriber

Info

Publication number: WO2005029902A1
Application number: PCT/IT2003/000515
Authority: WO
Inventors: Alessandro Lala; Enrico De Luca; Maurizio Iovieno
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2003-08-22
Filing date: 2003-08-22
Publication date: 2005-03-31
Anticipated expiration: 2006-02-22
Also published as: AU2003264875A1

Abstract

A method is provided for positioning accuracy negotiation between a Location Service (LCS) client and a target User Equipment (UE) of a subscriber to be positioned within a network for cellular communications, the method comprising the steps of receiving a positioning request from the LCS client for the target UE at a Gateway Mobile Location Center (GMLC); sending a message comprising the positioning request from the GMLC to a Mobile Switching Center (MSC) or a Serving GPRS Support Node (SGSN) and comprising information about a preferred positioning accuracy level required by the LCS client; checking whether the LCS client-required positioning accuracy level information complies with a maximum positioning accuracy level allowed by the subscriber; and, in response to a determination that the LCS client-required positioning accuracy level information complies with the subscriber-allowed maximum positioning accuracy level, returning the location information of the mobile station to the LCS client according to the subscriber-allowed maximum positioning accuracy level.

Description

METHOD AND TELECOMMUNICATIONS SYSTEM FOR POSITIONING ACCURACY NEGOTIATION BETWEEN A LOCATION SERVICE CLIENT AND A TARGET USER EQUIPMENT OF A SUBSCRIBER

Field of the Invention The present invention relates to a method and a telecommunications system for the negotiation of positioning accuracy between a Location Service (LCS) client and a target user equipment (UE) of a subscriber, particularly suited for a network for cellular communications .

Background of the Invention The positioning of UE (User Equipment) is a service provided by the Access Network. In particular, all Radio Access Networks, for example GSM (Global System for Mobile communication) and UMTS (Universal Mobile

Telecommunication System), that facilitate determination of the locations of User Equipment, are able to exchange location information with the core network. 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 associated with the UE, or by a client within or attached to the core network. The positioning feature may be used internally by^' the access 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, it is explained in document 3 GPP TS 23.271 N6.4.0, 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects, Functional stage 2 description of LCS, Release 6, which is hereby incorporated by reference, there are generally four categories of usage of the location service. These are the Commercial LCS, the Internal LCS, the

Emergency LCS and the Lawful Intercept LCS. The definition of these services and their categories is outside the scope of the present document. The Commercial LCS (or Value Added Services) will typically be associated with an application that provides a value-added service to the subscriber of the service, through knowledge of the 'UE location and, if available, and at the operator's discretion, the positioning method used to obtain location information. This may be, for example, a directory of restaurants in the local area of the UE, together with directions' for reaching them from the current UE location. The Internal LCS will typically be developed to make use of the location information of the UE for Access Network internal operations. This may include, for example, location assisted handover and traffic and coverage measurement. This may also include support for certain O&M^' related tasks, supplementary services, Intelligent Network related services and GSM bearer services and teleservices. The Emergency LCS will typically be part of a service provided to assist subscribers who place emergency calls. In this service, the location of the UE caller and, if available, the positioning method used to obtain the location information is provided to the emergency service provider to assist them in their response. This service may be mandatory in some jurisdictions. In the United

States, for example, this service is mandated for all mobile voice subscribers. The Lawful Intercept LCS will use the location information to support various legally required or sanctioned services. The position information shall be 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 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. The present invention is directed to such UE. The UE informs the core network and radio access network about its LCS capabilities in this respect. Current standardised 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 signalling capabilities of the Access Network. Clients submit their requests to an LCS server for receiving information about positioning a UE. At present, methods are known and defined i which privacy checks are performed in response to a positioning request by an LCS client. Particularly, it is known that an LCS client can specify the required level of accuracy for the positioning request and a location information or and error code can be returned to the LCS client, depending on whether the LCS client request complies with the required Quality of Service (QoS) or not. Unfortunately, in the known methods the subscriber is not aware of the accuracy that is used in the positioning request: accordingly, due to privacy reasons, the subscriber could decide to be not positioned at all. To this purpose, a mobile subscriber defines a Subscriber Location Privacy Profile (SLPP) stating which LCSs are allowed to request and obtain positioning information from the mobile subscriber or user equipment and in which areas. Unfortunately, an LCS is either allowed or denied access to receive positioning information concerning a certain mobile subscriber, so that many times mobile subscribers simply deny access to an LCS out of caution in order to preserve the desired level of privacy. However, this is a major drawback which implies important loss of profit and disadvantages both for the operator, since the subscribers are not encouraged in taking advantage of their services, and for the subscribers, who deny themselves of useful services in which they may enroll if their privacy were more under their control.

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 the subscriber to choose the level of accuracy of the location information to be returned to LCS clients. 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 is to meet the needs of both the UE subscribers and the LCS client users, through appropriate customization of the allowed and required privacy levels, respectively. This aim, these objects and other which will become better apparent hereinafter are achieved by a method for positioning accuracy negotiation between a Location Service client (LCS) and a target User Equipment (UE) of a subscriber to be positioned within a network for cellular communications, the method comprising the steps of: receiving a positioning request from the Location Service client for the target User' Equipment at a Gateway Mobile Location

Center (GMLC), the request comprising information about a Location Service preferred positioning accuracy level; sending a message comprising the positioning request from the Gateway Mobile Location Center to a Mobile Switching Center (MSC) or a Serving General Packet Radio Service Support Node (SGSN) and comprising the information about the Location Service preferred positioning accuracy level; initiating a checking whether the Location Service preferred positioning accuracy level information complies with a maximum positioning accuracy level allowed by the subscriber; and in response to a determination that the Location Service preferred positioning accuracy level information complies with the subscriber-allowed maximum positioning accuracy level, returning the location information of the User Equipment to the Location Service client according to the subscriber-allowed maximum positioning accuracy level. Moreover, the aim and the objects of the invention are also achieved by a service node for positioning accuracy negotiation between a Location Service

(LCS) client and a target User Equipment (UE) of a subscriber to be positioned within a network for cellular communications, characterized in that the service node comprises means for communicating with a Gateway Mobile Location Center (GMLC) supporting Location Service functionality and with the target User Equipment, so as to manage a positioning request provided to the Gateway

Mobile Location Center by a Location Service client; and in that the service node comprises: memory means storing a maximum positioning accuracy level allowed by the subscriber; and privacy-checking means for checking whether a preferred positioning accuracy level required by the' Location Service client complies with the maximum positioning accuracy level allowed by the subscriber and for allowing returning of location information of the target User Equipment to the Location Service client according to the subscriber-allowed maximum positioning accuracy level. According to preferred embodiments of the invention, the service node is selected from the group comprising MSCs and SGSNs. The aim and the objects of the invention are also achieved by a telecommunications system for positioning accuracy negotiation between a Location Service (LCS) client and a target User Equipment (UE) of a subscriber to be positioned within a network for cellular communications, the system comprising: a Gateway Mobile Location Center (GMLC) for supporting Location Service functionality and connected to at least one Location Service client for providing positioning requests to the Gateway Mobile Location Center; a Mobile Switching Center (MSC) or a Serving General Packet Radio Service Support Node (SGSN) for communicating with the Gateway Mobile Location Center and a User Equipment and for managing positioning requests; characterized in that the system comprises memory means for storing a maximum positioning accuracy level allowed by the subscriber and privacy-checking means for checking whether a preferred positioning accuracy level required by a Location Service client complies with the maximum positioning accuracy level allowed by the subscriber and for allowing returning of the location information of the target User

Equipment to the Location Service client according to the subscriber-allowed maximum positioning accuracy level. The positioning request may advantageously comprise information about a minimum positioning accuracy level required by the LCS client, below which a returned location of the UE would be too imprecise to be acceptable by the LCS.

Therefore, in case that in response to a determination that the LCS client-required positioning accuracy level information does not in general comply with the subscriber-allowed maximum positioning ' accuracy level, for instance if the preferred accuracy desired by the LCS does not match the subscriber's settings, it is checked whether such LCS client-minimum positioning accuracy level complies with the maximum positioning accuracy level allowed by the subscriber; and, if so, a location information of the UE is returned to the LCS client according to the maximum positioning accuracy level allowed by the subscriber. The LCS client may be associated with any one of the GSM or UMTS networks, either in a Circuit Switching (CS) or in a Packet Switching (PS) domain. Conveniently, a location information of the UE according to the positioning accuracy level required by the LCS client is in any case returned to the LCS if the LCS is an Emergency Services or a Lawful Interception Services client, thus leaving existing constraints and methods, concerning particular situations, unaffected by the additional functionality introduced by the present invention. Preferably, the step of checking whether the LCS client-required positioning accuracy level information complies with a maximum positioning accuracy level allowed by the subscriber is performed at the MSC or at the SGSN or, according to another aspect of the present invention, at the GMLC. The maximum positioning accuracy level allowed by the subscriber may be defined through a first parameter in a Subscriber LCS Privacy Profile stored in at least one of the MSC, SGSN or GMLC or in a Home Location Register (HLR) or in a Visitor Location Register (VLR) or in any external entity of the network communicating with the GMLC. If the parameter is stored at an HLR, it is then transferable to the VLR by ' means of a conventional Mobile Application Part (MAP) service used for inserting subscriber data. The skilled in the art appreciates that the subscriber may define a different maximum positioning accuracy level for each LCS 'client or groups of LCS clients, further to a maximum accuracy level that it may set as a default value against all positioning requests. Similarly, the minimum positioning accuracy level required by the LCS client may be forwarded from the GMLC to the MSC or SGSN by means of a Mobile Application Part (MAP) service. If the checking procedure according to which it is checked whether the LCS client's preferred positioning accuracy level information complies with a maximum positioning accuracy level allowed by the subscriber is performed at the GMLC itself which initiates the checking procedure, the GMLC may receive the UE positioning accuracy level information from the HLR HSS and then (if the checking steps according to the invention reveal that the LCS request can be met) forward the LCS request to the MSC/SGSN, which accordingly duly returns the location information according to the maximum positioning accuracy level. 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 method and the telecommunication system for positioning accuracy negotiation between an LCS client and a target UE, illustrated by way of non-limitative embodiments in the accompanying drawings, wherein: Figure 1 is a block diagram of a conventional cellular network; Figure 2 is a block diagram of a conventional Positioning System architecture; Figure 3 is a block diagram of a Positioning System architecture according to the present invention; Figure 4 is a flow chart illustrating the steps involved in positioning a UE according to the present invention when a positioning request is submitted by an LCS; Figure 5 is a flow chart illustrating second steps involved in positioning a UE according to the present invention when a response is returned to the LCS. Detailed Description of the Invention A typical and conventional mobile cellular network 10 is shown in Figure 1. The network 10 is for instance a second generation Global System for Mobile Communications (GSM) Public Land Mobile Network (PLMN) or a third generation UMTS network. However, the same inventive concept may apply to any existing or forthcoming new generation networks, as long as the general architecture of the positioning system remains the same. The cellular network 10 comprises areas 11, hereby identified as Geographical Areas, each of which is handled by a Mobile Switching Center (MSC) 20 and preferably comprises a Visitor Location Register (VLR). Each Geographical Area comprises in turn a plurality of cellular areas or cells 12. Each cell 12 is provided with a Base Transceiver Station (BTS) 13 which allows a UE located within the radio coverage of the cell to communicate with a corresponding cellular network 10 or Radio Access Network. Figure 2 displays a conventional positioning architecture showing two different kinds of Radio Access Networks,' particularly a GSM Radio Access network 120 and a UMTS Radio Access Network 130, each of which is provided with Serving Mobile Location Center (SMLC) functionality. The GSM Radio Access Network 120 is connected to a 2G (2^nd generation) Mobile Switching Center (2G-MSC) 121 arid to a 2G-Serving GPRS support node

(2G-SGSN) 122. Similarly, the UMTS Radio Access Network is connected to a 3G (3^rd generation)-MSC (3G-MSC) 131" and to a 3G-SGSN 132. The SGSNs contain functionality responsible for managing positioning requests of a Locations Service (LCS) client 2. The LCS functions of SGSNs and/or MSCs are related to charging and billing, LCS 'co-ordination, authorisation and operation of the LCS services and, most particularly, with regard to present invention, location request. The 2G-MSC 121, 3G-MSC 131, 2G-SGSN 122 and 3G-SGSN 132 are connected to a Gateway Mobile Location Center (GMLC) 30, which contains functionality required to support Locations Services. Of course, more than one GMLC may be present in each network 10. The GMLC 30 is the first node that an external LCS client 2 accesses in a mobile network, and may request routing information from the Home Location Register or Home Subscriber Server (HLR/HSS) 40. The HLR/HSS also contains the address to the Privacy Profile Register (PPR), which is used for privacy checks. The skilled in the art easily appreciates that the HLR/HSS 40, which is shown in Figure 2 as a separate entity, may be also positioned within a MSC/VLR 121, 131 and, as it is in the illustrative example of Figure 2, may serve several MSCs. With reference now to Figure 3, a block diagram is shown illustrating a Positioning System according to the present invention. More in detail, Figure 3 displays a User Equipment 1, a Radio Access Network 100, which generically identifies any kind of mobile access networks, like the GSM RAN 120 and UMTS RAN 130 of Figure 2 and their SMLC functionality, a service node 20 (briefly referred to as "MSC" in the figures) which generically identifies both MSCs and SGSNs, for instance 2G-MSC 121, 3G-MSC

131, 2G-SGSN 122 and 3G-SGSN 132 with added functionality according to the present invention. A conventional GMLC 30, HLR HSS 40 and LCS client 2 are also shown. Finally, a database 25 is shown, accessible by the service node 20, providing additional Privacy Information. The operation of the system according to the present invention will be now described with reference to the flow diagrams of Figures 4 and 5. At step 400 an LCS client 2 sends to the GMLC 30 a Positioning Request concerning UE 1. At step 405, the GMLC 30 conventionally requests to the HLR HSS 40 routing information required to reach the UE 1. As soon as the routing information is received by the GMLC 30, the GMLC 30 sends a Positioning Request to the service node 20 (step 410), which sets the value of a new FIXED_ACCURACY_LENEL parameter to an initial value. Typically, the FIXED_ACCURACY_LENEL is set to the value indicated in the positioning request sent by the LCS 2 as a preferred value. For illustrative purposes, such value is deemed to be initially set to INFINITE, wherein INFINITE is an exemplary value indicating that the value of FIXED_ACCURACY_LEVEL does not influence, so far, the conventional positioning procedure, and may correspond, for instance, to a value that is greater than or equal to the maximum accuracy level that can be handled in the cellular network 10. In this case, a value of "0" may be considered to be the lowest possible accuracy level or no accuracy at all, while increasing values identify increasing accuracy. However, the skilled in the art appreciates that the accuracy may be expressed through any convention. For instance, by way of example and for illustrative purposes only, Accuracy Level

"0" may indicate that no positioning is allowed, Accuracy Level "1" may indicate that the accuracy level refers to a first group of Geographical Areas 11, Accuracy Level "2" may indicate that the accuracy level refers to a second group of Geographical Areas 11 which is a subset of the first group, Accuracy Level "3" may indicate that the accuracy level refers to a third group of Geographical Areas 11 which is a subset of the second group, Accuracy Level "4" may indicate that the accuracy level refers to a single Geographical Area 11, Accuracy Level "5" may indicate that the accuracy level refers to a group of cells 12 within a Geographical Area 11, and so forth, until the best available level of accuracy is reached, down to a single cell 12 or to even more precise area positioning which may be available in the art. At step 415 it is conventionally checked whether the UE 1 allows positioning or not. If not, at step 420 it is checked whether the LCS client 2 requesting positioning information is nevertheless authorised to bypass the UE's SLPP, for instance in case that the LCS client 2 is an Emergency LCS or a Lawful Intercept LCS client. If so, a conventional positioning procedure is performed starting from step 500. Otherwise, the Positioning Request is rejected, the LCS client 2 is notified accordingly (step 425) and the procedure is terminated. The new preferred procedural steps according to the present invention are now described starting from block 430. In fact, if the conditional statement of block 415 is true, i.e. if the UE 1 allows positioning, the service node 20 according to the invention checks in database 25 whether a Maximum Accuracy Level has been set by the UE 1. The Maximum Accuracy Level could be part of the Subscriber LCS

Privacy Profile stored in at least one of the MSC, SGSN or GMLC or in a Home Location Register (HLR) or in a Visitor Location Register (VLR) or in any external entity of the network communicating with the GMLC. With reference to the state of art SLPP structure, the subscriber may define the Maximum Accuracy Level against a specific LCS Client in the External LCS Client list or as a common value against a specific class of LCS Clients. If no Maximum Accuracy Level is set, then the value of FIXED_ACCURACY_LENEL remains unchanged and set to INFINITE, and a conventional positioning is carried out starting at block 500. On the other hand, if a Maximum Accuracy Level is set, then service node

20 retrieves this value from the database 25 and FIXED_ACCURACY_LENEL is updated accordingly (step 435). At step 440 a further check is optionally carried out, so as to verify whether the LCS's positioning request indicates a minimum value below which the accuracy level is deemed to be pointless or useless for the LCS 2, i.e. the positioning information is deemed to be too imprecise and is not acceptable. If no minimum value was set by the LCS 2, then the positioning procedure is carried on from step 500. However, in this case, it is to be noted that the remaining steps of the positioning procedure will be influenced by the value of FIXED_ACCURACY_LENEL, which is now set to the Maximum Accuracy

Level allowed by the UE. If the conditional statement of block 440 indicates that a Minimum Accuracy Level was actually set by the LCS 2, then the corresponding value is retrieved by the MSC at step 445. It shall be noted that such value is preferably stored in the Positioning Request submitted by the LCS 2, but may likewise be stored or integrated with further information stored in a database accessible by the MSC, for instance if an LCS wishes to set a Minimum Accuracy Level to be used against any UE or a Minimum Accuracy Level which is to be used any time he requests positioning of a registered UE 1. Additionally, the minimum positioning accuracy level may be defined in the GMLC and transferred to the MSC upon receiving of a positioning request. At step 450 the MSC checks whether the Minimum Accuracy Level indicated by the LCS 2 is compatible with the Maximum Accuracy Level set by the UE 2. It shall be noted that, although the check is preferably performed at the MSC node, it could be likewise performed at an SGSN node or GMLC node or in any accessible external entity of the network. More in detail, in order for the positioning to be allowable, the Minimum Accuracy Level requested by the LCS 2 must be equal to or lower than the Maximum Accuracy Level set by the UE. If so, the value of FIXED_ACCURACY_LEVEL remains unchanged, i.e. set to the Maximum

Accuracy Level as set at step 435, and the positioning procedure is carried on from step 500. Also in this case, the remaining steps of the positioning procedure will be influenced by the value of FIXED_ACCURACY_LEVEL. If the Minimum Accuracy level set by the LCS 2 is greater than the Maximum Accuracy Level set by the UE 1, then the positioning procedure is carried on from step 420. The remaining steps of positioning procedure following step 500 will be now described with reference to Figure" 5. ' At step 505, UE paging, authentication and ciphering is conventionally carried out between the service node 20 and the UE 1, so as to determine the cell

12 ID and Timing Advance (TA) value, if allowed by the specific positioning method, for the serving BTS from the serving Base Station Controller (BSC), depending on whether the UE 1 is in idle mode or it is in dedicated mode, for instance busy in a telephone conversation. At step 510, the service node 20, depending on the privacy option set in the subscriber SLPP, may send to the UE an LCS Location Notification Invoke and waits for the LCS Location Notification Return Result (step 515). At step 520 a Location Request message is then submitted by the service node 20 to the RAN 100, including the FIXED_ACCURACY_LEVEL indication as set or modified through the above described positioning steps of the data flow of Figure 4. At step 525, the RAN 100 communicates with the UE 1 to determine the positioning method to be used and to instigate the particular message sequence for that method. At step 530, when a location information best satisfying the requested QoS and subject to the maximum accuracy level set by the UE 1 has been obtained, the RAN 100 returns it to the service node 20 server in a Location Report message. The information about the positioning method used may be returned with the location information. If a location information could not be obtained, the RAN 100 returns a Location Report message containing a failure cause and no location information. In turn, the service node 20 returns the location information to the GMLC 30, which eventually returns the location information to the LCS 2. Therefore, the positioning accuracy negotiation returned to the LCS does not exceed the positioning accuracy allowed by the subscribers, thus preserving their privacy to the desired extent, and is no less than the minimum required accuracy accepted by the LCS client. The skilled in the art easily understands that the above described steps may be performed by any computer hardware and/or software and telecommunication means programmed through conventional techniques in order to take into account the additional information data needed by the present invention. A combination of CPU, memory and communications means is required in order to check the availability of the a maximum accuracy level allowed by a UE and a minimum accuracy level required by the LCS, together with comparing means, preferably implemented through software, for comparing the two parameters and returning a result. The invention is therefore preferably implemented by introducing new functionality in existing systems, which enhancements are clearly in the reach of the average technician and 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. Where technical features mentioned in any claim are followed by reference signs, those reference signs have 'been included for the sole purpose of increasing the intelligibility of the claims and, accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. Method for positioning accuracy negotiation between a Location Service client (2) and a target User Equipment (1) of a subscriber to be positioned within a network for cellular communications, the method comprising the steps of: a) receiving a positioning request from the Location Service client (2) for the target User Equipment (1) at a Gateway Mobile Location Center (30), the request comprising information about a Location Service preferred positioning accuracy level; b) sending (410) a message comprising the positioning request from the

Gateway Mobile Location Center (30) to a Mobile Switching Center (121, 131) or a Serving General Packet Radio Service Support Node (122, 132) and comprising the information about the Location Service preferred positioning accuracy level; c) initiating a checking (430) whether the Location Service preferred positioning accuracy level information complies with a maximum positioning accuracy level allowed by the subscriber; and d) in response to a determination that the Location Service preferred positioning accuracy level information complies with the subscriber-allowed maximum positioning accuracy level, returning (530) the location information of the User Equipment (1) to the Location Service client (2) according to the subscriber-allowed maximum positioning accuracy level.

2. The method of claim 1, characterized in that said positioning request further comprises information about a minimum positioning accuracy level required by the Location Service client (2).

3. The method of claims 1 or 2, further comprising the steps of: e) in response to a determination that the Location Service client-required positioning accuracy level information does not comply with the subscriber- allowed maximum positioning accuracy level, initiate checking (450) whether the

Location Service client-minimum positioning accuracy level complies with the maximum positioning accuracy level allowed by the subscriber; and f) in response to a determination that the minimum positiomng accuracy level information required by the Location Service client (2) complies with the maximum positioning accuracy level allowed by the subscriber, returning (530) the location information of the User Equipment (1) to the Location Service client (2) according to the maximum positioning accuracy level allowed by the subscriber.

4. The method of claim 1 , further comprising the step of: e) returning to the Location Service client (2) the location information of the User Equipment (1) according to the positioning accuracy level required by the Location Service client (2), if the Location Service is selected from the group consisting of Emergency Services and Lawful Interception Services.

5. The method of claim 1, characterized in that the step of checking is performed at said Mobile Switching Center (121, 131) or Serving General Packet Radio Service Support Node (122, 132).

6. The method of claim 1 characterized in that the step of checking is performed at said Gateway Mobile Location Center (30).

7. The method of any one of the preceding claims, characterized in that the maximum positiomng accuracy level allowed by the subscriber is defined by a first parameter in a Subscriber Location Service Privacy Profile stored in at least one of said Mobile Switching Center (121, 131), Serving General Packet Radio Service Support Node (122, 132) or Gateway Mobile Location Center (30) or in a Home Location Register (40) or in a Visitor Location Register or in any external entity of the network communicating with the Gateway Mobile Location Center (30).

8. The method according to claim 7, further comprising the step of: transferring said first parameter from the Home Location Register (40) to the Visitor Location Register by means of a Mobile Application Part service used for inserting subscriber data.

9. The method of any one of the preceding claims, characterized in that the positioning accuracy level required by the' Location Service client (2) is defined by a second parameter generated by the Location Service client (2) and forwarded from the Gateway Mobile Location Center (30) to the Mobile Switching Center

(121, 131) or Serving General Packet Radio Service Support Node (122, 132) by means of a Mobile Application Part service.

10. A service node (20) for positioning accuracy negotiation between a Location Service client (2) and a target User Equipment (1) of a subscriber to be positioned within a network for cellular communications, characterized in that the service node (20) comprises means for communicating with a Gateway Mobile Location Center (30) supporting Location

Service functionality and with the target User Equipment (1), so as to manage a positioning request provided to the Gateway Mobile Location Center (30) by a

Location Service client; and in that the service node (20) comprises: a) memory means (25) storing a maximum positioning accuracy level allowed by the subscriber; and b) privacy-checking means for checking whether a preferred positioning accuracy level required by the Location Service client (2) complies with the maximum positioning accuracy level allowed by the subscriber and for allowing returning of location information of the target User Equipment (1) to the Location Service client (2) according to the subscriber-allowed maximum positioning accuracy level.

11. The service node of claim 10, characterized in that said service node is one of a Mobile Switching Center (121, 131) or a Serving General Packet Radio Service Support Node (122, 132)!

12. The service node of claim 10 or 11, further comprising means for comparing a minimum positioning accuracy level required by the Location Service client (2) and the maximum positioning accuracy level allowed by the subscriber.

13. The service node of any one of claims 10 to 12, characterized in that the privacy-checking means are set so as to return to the Location Service client (2) location information of the User Equipment (1) according to the positioning accuracy level required by the Location Service client (2), if the Location Service is one of a Emergency Service or a Lawful Interception Service.

14. The service node of any one of claims 10 to 13, characterized in that the maximum positioning accuracy level allowed by the subscriber is defined by a first parameter in a Subscriber Location Service Privacy Profile stored in said memory means (25).

15. A telecommunications system for positioning accuracy negotiation between a Location Service client (2) and a target User Equipment (l)of a subscriber to be positioned within a network for cellular communications, the system comprising: a Gateway Mobile Location Center (30) for supporting Location Service functionality and connected to at least one Location Service client (2) for providing positioning requests to the Gateway Mobile Location Center (30); a Mobile' Switching Center (121, 131) or a Serving General Packet Radio Service Support Node (122, 132) for communicating with the Gateway Mobile

Location Center (30) and a User Equipment (1) and for managing positioning requests; characterized in that the system comprises memory means (25) for storing a maximum positioning accuracy level allowed by the subscriber and privacy- checking means for checking whether a preferred positioning accuracy level required by a Location Service client (2) complies with the maximum positioning accuracy level allowed by the subscriber and for allowing returning of the location information of the target User Equipment (1) to the Location Service client (2) according to the subscriber-allowed maximum positioning accuracy level.