METHOD AND SYSTEM FOR LOCATIONING SUBSCRIBER TERMINAL IN CELLULAR RADIO NETWORK

Abstract: The invention relates to a method and a system of locationing a subscriber terminal. The network sends (402) to the terminal a short message with type zero, the protocol conveying the short message commanding the terminal to wait for the next short message, whereby the radio link between the network and the terminal remains active for a given time. The terminal rejects (408) the payload of the received short message without measures taken by the user, since the type of the short message is zero. The terminal (414) sends automatically, without measures taken by the user, an acknowledgement message to the network having received the short message. The terminal is located (416) by retrieving the identifier of the cell serving the terminal from the network while the radio link between the network and the terminal is active because the terminal is waiting for the next short message.

Description: METHOD AND SYSTEM FOR LOCATIONING SUBSCRIBER TERMINAL IN CELLULAR RADIO NETWORK FIELD The invention relates to a method of locationing a subscriber termi- nal in a cellular radio system and to a system for locationing a subscriber terminal in a cellular radio system. BACKGROUND Location Services (LCS) refer to a service enabled by the infrastructure of the network of a cellular radio system, allowing a subscriber terminal's location to be determined. The information provided by the location services is usable for example in providing a location-dependent value added service. Examples of value added services include local weather forecasts, information on local entertainment services, timetables, traffic, the nearest service points (e.g. a pharmacy or the police), and locationing the user of a subscriber terminal when he makes an emergency call. The location may be determined at several different accuracies. The locationing of a subscriber terminal at the accuracy of the serving cell is sufficient for most purposes. For example, in the GSM system (Global System for Mobile Com- munications), location information on a subscriber terminal may be inquired of the network by means of the mobile application part protocol (MAP) ATI function (Any Time Interrogation) or SRI function (Send Routing Information). If the inquiry takes place when there is no active radio link between the network and the subscriber terminal, the location information obtained only comprises the location area code (LAC), which is not real-time information. If the inquiry takes place when there is an active radio link between the network and the subscriber terminal, the location information obtained comprises a much more accurate identifier of the serving cell, which is real-time information. If the subscriber terminal to be located has no active radio link to the network because of a call, an active radio link can be achieved by sending, from the network to the subscriber terminal, an SMS message (SMS = Short Message Service), which will hereinafter be called short message. The problem here is that the radio link is active only a short time as the subscriber terminal receives or sends short messages, which makes the success of a loca- tion information inquiry uncertain. Another problem is that a short message sent for locationing purposes requires activity of the user of the subscriber terminal, e.g. reading and deleting the message. BRIEF DESCRIPTION The object of the invention is to provide an improved method of lo- cationing a subscriber terminal in a cellular radio system and an improved system for locationing a subscriber terminal in a cellular radio system. An aspect of the invention is the method of locationing a subscriber terminal as claimed in claim 1. An aspect of the invention is the system for locationing a subscriber terminal in a cellular radio system as claimed in claim 15. Other preferred em- bodiments of the invention are disclosed in the dependent claims. The invention is based on the network sending, to a subscriber terminal, a short message whose type is set to type zero. Furthermore, the protocol conveying the short message commands the subscriber terminal to wait for the next short message, whereby the radio link between the network and the subscriber terminal remains active for a given time. The subscriber terminal rejects the payload of the received short message without measures taken by the user of the subscriber terminal, since the type of the short message is zero. The subscriber terminal is located by retrieving the identifier of the cell serving the subscriber terminal from the network while the radio link between the net- work and the subscriber terminal is active. The radio link is active because the subscriber terminal is waiting for the next short message. The invention provides two significant advantages. The reliability of locationing a subscriber terminal improves, since the radio link remains active sufficiently long in order for the location information inquiry to succeed. How- ever, the user does not have to take any measures because of the locationing, since the subscriber terminal automatically rejects the payload of the received short message. In fact, in an ideal case, the user of the subscriber terminal receives no indication that locationing was performed. LIST OF THE FIGURES The preferred embodiments of the invention will be described by way of example with reference to the accompanying drawings, of which Figure 1 is a basic view of the locationing service; Figure 2 is a simplified block diagram of a system for locationing a subscriber terminal in a cellular radio system; Figure 3 shows cells in a cellular radio system; Figure 4 is a flow diagram illustrating a method of locationing a subscriber terminal in a cellular radio system; Figures 5, 6 and 7 are signal sequence diagrams illustrating the implementation of a location-dependent service in a cellular radio system; Figure 8 illustrates an embodiment wherein a new component is created in the system of Figure 2; Figure 9 is a signal sequence diagram illustrating different ways to perform locationing; Figure 10 is a flow diagram illustrating locationing in the GPRS sys- tern; Figure 11 is a flow diagram illustrating locationing in the UMTS system; Figure 12 is a simplified block diagram of the structure of the UMTS system. DESCRIPTION OF THE EMBODIMENTS The general principle of the locationing service is shown with reference to Figure 1. A client 100 of the locationing service sends a subscriber terminal locationing request 106 to a locationing server 102. The client 100 of the locationing service may be any part of a cellular radio system, including a subscriber terminal 104 to be located or an entity external to the cellular radio system. The locationing server 102 is composed of hardware and software components required to implement the locationing service, and necessary data links. Thus, the locationing server 102 locates 108 the subscriber terminal 104 as specified in the locationing request 106 in accordance with the quality of service defined in the locationing request 106. The quality of service specifies the locationing method used. After the locationing 108, the locationing server 102 sends a locationing response 110 to the client 100 of the locationing service. The locationing response 110 indicates the location of the subscriber terminal 104 in a manner suited to the quality of the service subscribed, e.g. as coordinates, identifier of the serving cell or postal code of the area involved. The locationing service can be implemented for example in the GSM system, in systems developed further from the GSM system or third generation mobile systems, however, with the proviso that in locationing the radio link can be activated in the system by the use of the short message service or in a manner resembling the short message service for sending discrete text messages between a network and a subscriber terminal. A system for locationing a subscriber terminal in a cellular radio network is next described with reference to Figure 2. In the example, the cellu- lar radio system used is the GSM system, but the system is also applicable to other cellular radio systems wherein the short message or like service is known. Figure 2 only shows the blocks essential to the explanation of the embodiments, but it is obvious to a person skilled in the art that a conventional cellular radio system also comprises other functions and structures that need not be described in detail herein, since further information upon them is easily available. The assumption in the example is that the subscriber terminal is located at the request of a service provider 200 external to the cellular radio system, but it is apparent that locationing can also be performed at the request of a part of the cellular radio system. From the point of view of the locationing service, the service provider 200 acts as the client 100. If need be, further information on the short message service is available in the following documents, which are incorporated herein by reference: Digital cellular telecommunications system (Phase 2+); Technical Realization of the Short Message Service (SMS); Point-to-Point (PP). GSM 03.40 version 5.8.1 Release 1996. ETS 300 901 December 1998 Fifth Edition, Digital cellular telecommunications system (Phase 2+); Alphabets and language-specific information. GSM 03.38 version 6.0.1 Release 1997. ETSI TS 100 900 V6.0.1 07-1998. The service provider 200 has a data link to both an intelligent network service control point (SCP) 204 and a short message centre 206. The intelligent network service control point 204 is a component in an intelligent network that provides an interface for the locationing service. From the point of view of the locationing service, the intelligent network service control point 204 and the short message centre 206 provide a functionality corresponding to the locationing server 102. From both the intelligent network service control point 204 and the short message centre 206, there is a connection to a signalling transfer point (STP) 230, which routes the signalling in the direction of both a mobile switch- ing centre 208 and a home location register 212. The subscriber data of said operator are permanently stored in the home location register 212. A visitor location register 210 comprises data on the subscriber terminals 104 located in the service area of the mobile switching centre 208 at a given time. From the mobile switching centre 208, there is a connection to a base station controller 214, which monitors and controls base stations 216. The tasks of the base station controller 214 mainly include frequency management and base station 216 control. The base station 216 and its antennas are usually located in the middle of the coverage area, i.e. cell. If the cell is divided into sectors, then the base station 216 is located at the edge of a sector. The transmission powers of the transceivers of the base station 216 determine the size of the cell. A base station 216 typically comprises one to sixteen transceivers, each of which implements eight radio channels in both uplink and downlink. The above-described fixed infrastructure of a cellular radio system may be called a network 202. In the example, the service provider 200 is not part of the network 202, but such an alternative is feasible since, as was stated earlier, the client 100 of the locationing service, i.e. the service provider 200, may also be a part of the cellular radio system. There is a bi-directional radio link 218 from the base station 216 to the subscriber terminal 104. The subscriber terminal 104 is typically portable, but it may also be fixedly placed in a vehicle or a building. The subscriber terminal 104 comprises an antenna 220, a transceiver 222, and a control part 224. The control part 224 is typically implemented by a microprocessor and software. In addition, the subscriber terminal 104 comprises a power supply and a user interface. A user interface typically comprises at least a display, a keyboard, a microphone and an earpiece. Figure 3 illustrates cells in a cellular radio system. Cells are usually modelled theoretically as hexagons, although real coverage areas naturally overlap and do not have very distinct boundaries. The example shows seven cells 300, 302, 304, 306, 308, 310, 312. In cell 312, the base station 216 has a radio link 218 to the subscriber terminal 104, i.e. cell 312 is the cell serving the subscriber terminal 104. The object of the locationing service is to find out the identifier of the cell serving a given subscriber terminal 104. In the system of Figure 2, this is accomplished by the system comprising means 232 for sending a short mes- sage to the subscriber terminal 104, setting the type of the short message to type zero, and making the protocol conveying the short message command the subscriber terminal 104 to wait for the next short message, whereby the radio link 218 between the network 202 and the subscriber terminal 104 remains active for a given time. In the GSM system, type zero is set in the TP-PID field of a short message. In the GSM system, the subscriber terminal 104 is com- manded to wait for the next message by setting a 'More Messages to Send (MMS)' flag on in the mobile application part protocol conveying the short message. The MAP protocol belongs to the seventh layer, i.e. the application layer of the OSI model (Open Systems Interconnection). The means 232 can be implemented as software run in a processor, whereby e.g. each necessary function is implemented as a separate program module. The means 232 can also be implemented as a hardware solution, e.g. an application specific integrated circuit (ASIC) or operations logic built of separate components. In selecting the way to implement the means 232, a person skilled in the art will pay attention to the required processing capacity and manufacturing costs, for example. Various hybrid implementations involving software and hardware are also feasible. Although Figure 2 shows the means 232 as a separate block divided among the client 100 of the locationing service and the locationing server 102, it is obvious to a person skilled in the art that the functionality implemented with the means 232 can also be placed in the service provider 200 and the intelligent network control point 204, the methods of implementation being said software and/or hardware implementations. The subscriber terminal 104 comprises means 224 for rejecting the payload of the received short message without measures taken by the user of the subscriber terminal 104 since the type of the short message is zero, and for automatically, without measures taken by the user, sending an acknowledgement message to the network 202 on the reception of the short message. The means 224 can be implemented in the same way as the means 232, as software and/or hardware. The means 232 also comprise a functionality for locationing the subscriber terminal 104 by retrieving the identifier of the cell 312 serving the subscriber terminal 104 from the network 202 when the radio link 218 between the network 202 and the subscriber terminal 104 is active as the subscriber terminal 104 waits for the next short message. Next, preferred embodiments of the locationing system will be described. An embodiment allows for the possibility that the subscriber terminal 104 does not support processing a short message of type zero. The system then comprises means 232 for setting the class of the short message to class zero. In this case, if the subscriber terminal 104 does not support processing a short message of type zero, then the subscriber terminal comprises means 224 for showing the payload on the display of the subscriber terminal 104 without measures taken by the user of the subscriber terminal 104 and without automatically storing the short message in the memory of the subscriber terminal 104, since the class of the short message is zero. Consequently, the user sees the short message received, whose contents are, for example, 'You are being located' on the display of the subscriber terminal. A class zero short message typically arrives directly at the display of the subscriber terminal 104 without any of it being stored in the memory of the subscriber terminal 104 or in the SIM (Subscriber Identity Module). A class zero short message is typically simpler to delete than a conventional short message, naturally depending on the implementation of the user interface. The simplest way to delete a class zero short message is to press one button at the user interface of the subscriber terminal 104. In the GSM system, class zero is set in the TP-DCS field of a short message. In an embodiment of the GSM system, the system comprises means 232 for retrieving the identifier of the serving cell 312 from the home location register 212 of the cellular radio system, which retrieves the information from the visitor location register 210 of the cellular radio system. In the GSM system, this is carried out by the above-mentioned ATI or SRI function. In an embodiment, the system comprises means 232 for deactivating the radio link 218 between the network and the subscriber terminal 104 after locationing is completed. This brings about the advantage that the system does not remain in an undetermined state when the subscriber terminal 104 waits a given period for a short message that never arrives. The system natu- rally recovers from an error condition anyway, but that may take some dozens of seconds, for example. In an embodiment, the radio link 218 is deactivated by sending, to the subscriber terminal 104, a short message, whose type is set to type zero and class to class zero, and the protocol conveying the short message com- mands the subscriber terminal 104 to abort the wait for the next short message. This provides the advantage that, in an ideal case, the user does not have to do anything, since he does not detect the incident at all. In the GSM system, the subscriber terminal 104 is notified that new short messages will no longer arrive by setting the 'More Messages to Send (MMS)' flag off in the mobile application part protocol conveying the short message. In an embodiment, the radio link is inactivated by aborting an ongoing MAP dialog. In the GSM system, this is preferably carried out by the MAP- P-ABORT service, which is described in the part of the ETSI specification to be incorporated herein by reference: Digital cellular telecommunications system (Phase 2+); Mobile Application Part (MAP) specification. GSM 09.02 version 6.1.1 Release 1997. ETS TS 100 974 V6.1.1 08-1998. Chapter 7.3.5. MAP-P- ABORT Service. In an embodiment, a new component is created in the network 202, and certain properties of the short message centre 206, intelligent network control point 204 and/or mobile switching centre 208, and the functionality of the means 232 are associated with the component. If the new component comprises functionalities of both the intelligent network control point 204 and the mobile switching centre 208, then the new component is easier to adapt to different networks 202. Figure 8 shows the placement of a new component 800 in the system of Figure 2. In practice, the new component 800 implements the functionality of the locationing server 102 in the network 202, and is thus an alternative to the manner of implementing the locationing service shown in Figure 2. The means 232 are included in the new component 800. In this embodiment, the division of responsibilities between the client 100 of the locationing service and the locationing server 102 is clearer than in the embodiment of Figure 2, wherein the functionality of the means 232 was divided between both the client 100 of the locationing service and the locationing server 102. The new component 800 is aware of how the events proceed, resulting in less need for signalling between the different components in the network. Furthermore, fewer components are needed if the new component is so constructed that it is able to also process locationing service requests originating from a subscriber terminal. The active radio link can be disconnected immediately after a response is received to the ATI or SRI inquiry. To summarize, the use of this embodiment facilitates managing the whole and enhances the use of resources. A database can be associated with the new component 800 for modifying the location information, i.e. the identifier of the serving cell into in- formation to be notified to the user, e.g. a postal code or coordinates. In the GSM system, the new component 800 has an SS7 interface (Signalling System 7) to the network 202 and another interface to the service provider 200. In the GSM system, the new component implements at least the MAP operations: 'Any Time Interrogation' and/or 'Send Routing Info', 'Forward Short Message (MT-SM mobile terminating short message)', and 'Send Routing Info for SM'. If the new component 800 makes a 'Provide Subscriber Info' inquiry directly to the visitor location register 210, then the address of the mobile switching centre 208 obtained by a 'Send Routing Info for SM' operation is used. If the intention is for the new component 800 to receive service requests directly from the SS7 network, then a MAP operation 'Forward Short Message (MO-SM, mobile originating short message) has also to be imple- mented therein. A method of locationing a subscriber terminal in a cellular radio system will be illustrated next with reference to the flow diagram of Figure 4. At the same time, reference is made to the signal sequence diagram of Figure 5, which illustrates the implementation of a location-dependent service in a cellu- lar radio system, although the reason why locationing is to be performed is irrelevant to the locationing method. Figure 5 shows two ways of initiating the implementation of a location-dependent service. The signal sequence in area 500A shown with a dashed line is executed when a subscriber terminal MS itself requests for a location-dependent service, and signal 500B initiates the execution of a location-dependent service requested by some other party than the subscriber terminal. The subscriber terminal MS sends, to a short message centre SMSC, a service request message 502, requesting for a location-dependent service. The short message centre SMSC relays a service request message 504 to a service provider SP and sends an acknowledgement message 506 to the subscriber terminal MS. In Figure 5, the acknowledgement messages are denoted by a dashed arrow for the sake of clarity. The service provider SP sends, to the short message centre SMSC, a wait message 508 including an MMS bit to be set in the MAP protocol to keep the radio channel active. Instead of the above-described signal sequence 500A, locationing may be initiated by the service provider SP sending an initiate message 500B to the short message centre SMSC. At this stage, the execution of the method according to the flow diagram in Figure 4 also starts. The method starts in block 400. In block 402, the network, i.e. the short message centre SMSC sends, to the subscriber terminal MS, a short message 510, whose type is set to type zero and the protocol conveying the short message commands the subscriber terminal to wait for the next short message in order for the radio link between the network and the subscriber terminal to remain active for a given time. Optionally, the class of the short message is set to class zero in block 402. In block 404, a selection is made as to whether the subscriber terminal MS supports the processing of messages of type zero. If so, arrow 406 is taken to block 408, wherein the subscriber terminal MS rejects the payload of the received short message without measures taken by the user of the sub- scriber terminal, since the type of the short message is zero. If the subscriber terminal does not support the processing of messages of type zero, then arrow 410 is taken to an optional block 412, wherein the payload is showed on the display of the subscriber terminal without measures taken by the user of the subscriber terminal and without automatically storing the short message in the memory of the subscriber terminal, since the class of the short message is zero. From both block 408 and block 412, the process proceeds next to block 414, wherein the subscriber terminal MS, having received the short message 510, sends automatically, without measures taken by the user, an ac- knowledgement message 512 to the network, i.e. the short message service centre SMSC. The short message service centre SMSC transfers an acknowledgement 513 to the service provider SP. Then, in block 416, the subscriber terminal is located by retrieving the identifier of the cell serving the subscriber terminal MS from the network while the radio link between the network and the subscriber terminal is active as the subscriber terminal is waiting for the next short message. This can be carried out for example in the manner shown in Figure 5 by signals 514 to 524. The service provider SP sends a location information request message 514 to the intelligent network control point SCP. The intelligent network control point SCP sends an ATI message (Any Time Interrogation) 516 to the home location register HLR. The home location register HLR sends a PSI message (Provide Subscriber Info) 518 to the visitor location register VLR, which replies by a PSI message 520 to the home location register HLR. The home location register HLR replies by an ATI message 522 to the intelligent network control point SCP. The intelligent network control point SCP returns the location information 524 to the service provider. Then, in block 418, the radio link is deactivated by sending, to the subscriber terminal, a short message whose type is set to type zero and class to class zero, and the protocol conveying the short message commands the subscriber terminal to abort the wait for the next short message. This is ac- complished for example in the manner described above by the service provider SP requesting 526 the short message service centre SMSC to send, to the subscriber terminal MS, a short message 528, in which the MMS flag is in the off position. The subscriber terminal MS sends an acknowledgement message 530 to the short message service centre SMSC. The service provider SP implements a location-dependent service 532. If the service requires measures with the subscriber terminal MS, the service provider SP requests 534 that the short message service centre SMSC send a short message 536 to the subscriber terminal MS, which sends an acknowledgement message 538. The method of locationing a subscriber terminal in a cellular radio system can be modified in accordance with the attached dependent claims. Since their contents were described above in association with the system for locationing a subscriber terminal in a cellular radio system, the description is not repeated here. For the sake of clarity, Figures 6 and 7 show two more examples of a signalling sequence usable when functionalities of a short message service centre SMSC, an intelligent network control point SCP and/or a mobile switching centre MSC are combined with a new component NEW shown in Figure 8. In the example of Figure 6, functionalities of a short message service centre and a mobile switching centre, and, in Figure 7, functionalities of a mobile switching centre and an intelligent network control point are combined with a new component NEW. A comparison between Figures 6 and 7 and Figure 5 reveals that managing signal timing becomes easier by using the new component NEW, and signalling between the service provider SP and other compo- nents decreases. This is advantageous since IP based (Internet Protocol) data links are typically used between a service provider SP and a network, whereas SS7 based data links are used within a network. SS7 based links are faster and securer than IP based links. Furthermore, IP/SS7 conversions are eliminated when signalling only uses SS7 based data links. A comparison between for example Figures 5 and 6 shows that, in Figures 6 and 7, actual locationing only requires two IP based signallings 508, 524 instead of the five IP based signallings 500B, 513, 514, 524, 526 of Figure 5. In Figure 6, a subscriber terminal MS sends a service request message 502 requesting for a location-dependent service, to a short message service centre SMSC. The short message service centre SMSC relays a service request message 504 to a service provider SP and sends an acknowledgement message 506 to the subscriber terminal MS. The service provider SP sends a wait message 508 to the new component NEW. The new component NEW then sends, to the subscriber terminal MS, a short message 510, whose type is set to type zero, and the protocol conveying the short message commands the subscriber terminal to wait for the next short message, whereby the radio link between the network and the subscriber terminal remains active for a given time. Having received the short message 510, the subscriber terminal MS sends automatically, without measures taken by the user, an acknowledgement message 512 to the new compo- nents NEW. Next, the subscriber terminal is located by retrieving the identifier of the cell serving the subscriber terminal MS from the network while the radio link between the network and the subscriber terminal is active, as the subscriber terminal is waiting for the next short message. The new component NEW sends a SRI message (Send Routing Info) 600 to the home location register HLR. The home location register HLR sends a PSI message (Provide Subscriber Info) 518 to a visitor location register VLR, which responds with a PSI message 520 to the home location register HLR. The home location register HLR responds with a SRI message 602 to the new component NEW. The radio link is then deactivated by sending, to the subscriber terminal MS, a short message, whose type is set to type zero and class to class zero, the short message commanding the subscriber terminal MS to abort the wait for the next short message. This is accomplished by the new component NEW sending, to the subscriber terminal MS, a short message 528 wherein the MMS flag is in the off position. The subscriber terminal MS sends an acknowledgement message 530 to the new component NEW. The new component NEW then returns the location information 524 to the service provider. The service provider SP implements a location-dependent service 532. The service provider SP requests 534 the short message service centre SMSC to send at least one short message 536 including the service to the subscriber terminal MS, which sends an acknowledgement message 538. The example of Figure 7 corresponds to Figure 6 with the following exceptions: actual locationing is carried out with an ATI message 516 instead of a SRI message 600, i.e. the new component NEW sends the ATI message 516 to the home location register HLR, and the home location register HLR responds with an ATI message 522 to the new component NEW; the radio link is deactivated using the MAP-P-ABORT service instead of sending an MMS flag in the off position, i.e. the new component NEW sends, to the mobile switching centre MSC, a message 700 requesting MAP- P-ABORT, and the mobile switching centre MSC sends an error message 702 to the new component NEW only in an error condition. For the sake of clarity, short message transmission is shown in Figures 5, 6 and 7 in a simplified manner, i.e., in reality, short messages 510, 512, 528, 530, 536, 538 are conveyed between the short message service centre SMSC and the subscriber terminal MS via a mobile switching centre (not shown in Figures 5 and 6). The above describes the embodiments mainly in the GSM system. Figure 12 shows a UMTS system (Universal Mobile Telecommunication Sys- tem) using the direct sequence wideband code division multiple access method. The main parts of the mobile system comprise a core network CN, a UMTS terrestrial radio access network UTRAN and user equipment UE. The interface between the core network CN and the UTRAN is called lu, and the air interface between the UTRAN and the UE is called Uu. The user equipment UE comprises two parts: mobile equipment ME comprises a radio terminal used to establish a radio link over the interface Uu. A UMTS Subscriber Identity Module USIM is a smart card comprising information on the identity of the subscriber and typically performing identification algorithms, storing encryption parameters and subscriber data. The UTRAN is composed of a radio network subsystem RNS. The RNS is composed of a radio network controller RNC and one or more nodes B. In practice, node B refers to a base station. The coverage area of node B, i.e. a cell is denoted by C in Figure 8. The radio network controller RNC manages radio resources via base stations connected thereto. The core network CN is composed of several parts. A home location register HLR is a database in a subscriber's home system and maintains a user service profile. The home location register also maintains information on the location of a user at the accuracy of a mobile switching centre. A mobile switching centre MSC/VLR is a switch (MSC) and a database (VLR) serving the user equipment as far as circuit switched (CS) services are concerned. The MSC switches circuit switched services and the VLR maintains information on user profile and location. A gateway MSC (GMSC) is a switch connecting the UMTS to external services or networks. All circuit switched connections pass via the GMSC. The functionality of a serving general packet radio service support node (SGSN) corresponds to the functionality of the MSC/VLR, except that packet switched (PS) connections pass through it. Similarly, a gateway GPRS support node (GGSN) corresponds functionally to the GMSC as far as packet switched connections are concerned. External networks can be divided into two types: circuit switched networks, e.g. existing telephone networks, and packet switched networks, such as the Internet. The UMTS comprises several specified interfaces. A Cu interface exists between the smart card USIM and the mobile telephone ME. The Uu interface exists between a terminal and a base station. The interface between the core network CN and the UTRAN is called lu. The interface between radio network subsystems RNS is called lur. This enables soft handover between radio network controllers of different manufacturers. The interface between the radio network controller RNC and a base station B is called lub. Accordingly, the embodiments can be implemented in the GSM system or the UMTS system, in both of which packet switched transmission can be implemented using the GPRS (General Packet Radio Service). In the UMTS, the radio interface is thus implemented by a wideband code division multiple access method, and in the GSM system by a time division multiple access method using either normal GSM GMSK modulation (Gaussian Minimum-Shift Keying) or 8-PSK (8-Phase Shift Keying) modulation according to the EDGE technique (Enhanced Data Rates for GSM Evolution) on packet data channels. Accordingly, in the GSM system, the GPRS requires two new net- work components: SGSN and GGSN. The SGSN delivers packets to subscriber terminals within its area, sends inquiries to the home location register, detects new GPRS subscriber terminals within its area, processes the registration of new users and keeps a record of their location. The main task of the GGSN is to act as an interface to external packet data networks, i.e. the GGSN maintains routing information required for tunnelling protocol data units to SGSNs serving given subscriber terminals. Furthermore, the functionalities of existing GSM system network components have to be extended as follows: the base station system has to be able to identify and send user data to the SGSN serving the area, and the home location register has to be able to register GPRS user profiles and to respond to inquiries made by the SGSN regarding these profiles. An embodiment is also feasible, wherein the structure of the radio access network is outlined UMTS-style, but the radio interface is, however, a GSM based normal radio interface or a radio interface using EDGE modulation. In the GPRS, a terminal may be attached to both GPRS and GSM services, simultaneously supporting both GPRS and GSM services (class A) or the terminal may be attached to both GPRS and GSM services, only support- ing one kind of services at a time (GPRS or GSM) (class B) or the terminal may be attached to either GPRS or GSM services (class C). On the packet switched and circuit switched sides, a terminal may be located in various ways. On the circuit switched side, a terminal may be located in the above-described manner cell-specifically using the Any Time Interrogation MAP message, and, similarly, on the packet switched side, a terminal may be located cell-specifically by retrieving location information from the MM (Mobility Management) and PDP (Packet Data Protocol) contexts of the terminal. In present GPRS networks, location-dependent services cannot be implemented without LCS in the network, which also requires an MLC (Mobile Location Centre) and MAP messages associated with LCS in the network. Said additional features raise the price of a GPRS network thus rendering the implementation of location services dependent on the timetables of hardware suppliers. The solution described in the present application is independent of hardware manufacturers and of the terminal. Figure 10 illustrates locationing in a GPRS system. Reference is also made to Figure 9, which illustrates the signalling required between differ- ent network components. Once a locationing request is received, locationing starts in block 1000. Since both circuit and packet switched connections exist in a GPRS network, locationing is to be implemented on the side enabling it (class B and C terminal). A class A terminal may be located on both sides. In block 1002, a BSSAP+-MS-INFORMATION-REQUEST 900 (SGSN→VLR) is sent. In block 1004, the state of the terminal is received by a BSSAP+-MS-INFORMATION- RESPONSE message 902 (VLR→SGSN), wherein one parameter is Mobile Station State indicating the state of the terminal. This requires a connection between the VLR and the SGSN (Gs interface). In block 1006, the state of the terminal is checked. If the terminal is in IDLE mode, it can be located on the circuit switched side, i.e. arrow 1008 is taken to block 1012, wherein the radio path to the terminal is opened in the above-described manner by sending a short message 908. In block 1014, an ATI message 910 is then sent to the HLR, in response to which a response message 912 is received in block 1016. Next, in block 1018, the location of the subscriber terminal is obtained from the ATI response message at the accuracy of a cell. If the terminal is not in IDLE mode, arrow 1110 is taken from block 1006 to block 1020, wherein a check is made to see if the terminal is in READY mode. If the terminal is in READY mode, the terminal has an active GPRS connection (packet switched side), and arrow 1022 is taken to block 1026, wherein the cell-specific location information on the terminal is obtained from the SGSN from Cell Identity parameter 914 of the MM and PDP contexts of said terminal, the parameter being specified in specification 3GPP TS 23.060 chapter 13.2, which is incorporated herein by reference. In READY mode, the terminal can also be located from the circuit switched side by an ATI function 904, 906, cell information being obtained from the HLR, but Figure 10 does not show this option. If the terminal is not in READY mode, then arrow 1024 is taken from block 1020 to block 1028, wherein a check is made to see if the terminal is in STANDBY mode. If the GPRS connection (packet switched side) in the terminal has moved to STANDBY mode, cell information is not obtained from the MM and PDP contexts. In order to obtain cell information, the radio path to the terminal should be opened, i.e. arrow 1030 is taken from block 1028 to block 1034, wherein a short message 916 is sent to the subscriber terminal, whereby the terminal shifts to READY mode, and in block 1036 cell information is obtained from the MM and PDP contexts 918. Accordingly, if the terminal is in IDLE or STANDBY mode, the radio path can be opened for a moment by a short message, allowing the terminal to be located. Locationing a terminal can also be implemented using an intelligent network (IN), whereby the SGSN requires a gprsSSF feature, allowing the call to be directed to the intelligent network, wherein the terminal's location information can be recovered from an I NAP message. If the subscriber terminal is not in STANDBY mode either, it cannot be located, in which case arrow 1032 is taken from block 1028 to block 1038, wherein locationing is aborted. The execution of the locationing method is ended after either successful or failed locationing in block 1040. The procedure described above can be utilized for locationing ser- vices for example by the service using the MSISDN number to inquire location information, and the MSISDN and location information are returned to the service. In the UMTS system, a terminal may have both a packet switched and a circuit switched side (class A) or only either (classes B and C). On the circuit switched side, the terminal can be located cell-specifically and, correspondingly, on the circuit switched side the terminal can be located radio network controller-specifically utilizing MAP messages. In present UMTS systems, location-dependent services cannot be implemented without LCS in the network, which also requires MLC (Mobile Location Centre) and MAP messages associated with LCS in the network. Said additional features raise the price of a UMTS network thus rendering the implementation of location services dependent on the timetables of hardware suppliers. The solution described in the present application is independent of hardware manufacturers and of the terminal. Figure 11 illustrates locationing in the UMTS system. Reference is also made to Figure 9, which illustrates signalling required between different network components. Once a locationing request is received, locationing is started in block 1100. Since both circuit and packet switched connections exist in a UMTS network, locationing is to be implemented on the side enabling it (class B and C terminal). A class A terminal may be located on both sides. In block 1102, a BSSAP+-MS-INFORMATION-REQUEST 900 (SGSN→VLR) is sent. In block 1104, the state of the terminal is received by a BSSAP+-MS-INFORMATION- RESPONSE message 902 (VLR→SGSN), wherein one parameter is Mobile Station State indicating the state of the terminal. This requires a connection between the VLR and the SGSN (Gs interface). In block 1106, the state of the terminal is checked. If the terminal's circuit switched side is in READY mode, block 1112 is entered wherein an ATI message 904 is sent to the HLR, in response to which a response message 906 is received in block 1114. Next, in block 1116, the location of the terminal is obtained from the ATI response message at the accuracy of a cell. If the terminal is not in READY mode, arrow 1110 is taken from block 1106 to block 1118, wherein a check is made to see if the terminal is in IDLE mode. If the terminal is in IDLE mode, arrow 1120 is taken to block 1124, wherein a short message 908 is sent to the subscriber terminal, after which the location of the subscriber terminal is found out in block 1126, 1128 and 1130 at the accuracy of a cell by an ATI inquiry 910, 912. If the terminal is not in IDLE mode, arrow 1122 is taken from block 1118 to block 1132, wherein a check is made to see if the GPRS connection is active, i.e. if the subscriber terminal is in PMM-CONNECTED mode. If the GPRS connection is active, arrow 1134 is taken to block 1138, wherein the location of the subscriber terminal is found out at the accuracy of a radio network controller from the RNC Address in Use parameter of the MM and PDP contexts of the SGSN of said terminal. If the GPRS connection is not active, arrow 1136 is taken from block 1132 to block 1140, wherein a check is made to see if the terminal is in PMM- IDLE mode. If the terminal is in PMM-IDLE mode, arrow 1142 is taken to block 1146, where the radio path is opened for a moment with a short message 916, allowing the terminal to be located radio network controller-specifically using the MM and PDP contexts 918. A terminal may also be located using an intelligent network (IN), in which case the SGSN requires a gprsSSF feature, allowing the call to be directed to the intelligent network, wherein the terminal's location information can be recovered from an INAP message. If the terminal is not in PMM-IDLE mode either, it cannot be located, and arrow 1144 is taken from block 1140 to block 1150, where locationing is aborted. The execution of the locationing method is ended after either sue- cessful or failed locationing in block 1152. Even though the invention is explained in the above with reference to the example according to the accompanying drawings, it is obvious that the invention is not restricted thereto but can be modified in many ways within the scope of the inventive idea disclosed in the attached claims.

Claims: CLAIMS 1. A method of locationing a subscriber terminal in a cellular radio system, characterized by (402) the network sending, to a subscriber terminal, a short mes- sage whose type is set to type zero, the protocol conveying the short message commanding the subscriber terminal to wait for the next short message, whereby the radio link between the network and the subscriber terminal remains active for a given time; (408) the subscriber terminal rejecting the payload of the received short message without measures taken by the user of the subscriber terminal, since the type of the short message is zero; (414) the subscriber terminal automatically, without measures taken by the user, sending an acknowledgement message to the network having received the short message; (416) locating the subscriber terminal by retrieving the identifier of the cell serving the subscriber terminal from the network while the radio link between the network and the subscriber terminal is active as the subscriber terminal is waiting for the next short message. 2. A method as claimed in claim ^characterized by setting type zero in the TP-PID field of the short message. 3. A method as claimed in any one of the preceding claims, characterized by commanding the subscriber terminal to wait for the next short message by setting a 'More Messages to Send' flag in the protocol conveying the short message. 4. A method as claimed in any one of the preceding claims, characterized by setting the class of the short message to class zero, and (404, 410) if the subscriber terminal does not support processing (412) a short message of type zero, showing the payload on the display of the subscriber terminal without measures taken by the user of the subscriber terminal and without automatically storing the short message in the memory of the subscriber terminal, since the class of the short message is zero. 5. A method as claimed in claim 4, characterized by setting class zero in the TP-DCS field of the short message. 6. A method as claimed in any one of the preceding claims, characterized by retrieving the identifier of the serving cell from a home location register in the cellular radio system, and the home location register retrieving the information from a visitor location register in the cellular radio system. 7. A method as claimed in any one of the preceding claims, characterized by deactivating the radio link between the network and the subscriber terminal after (418) performing the locationing (416). 8. A method as claimed in claim 7, characterized by deactivating (418) the radio link by sending, to the subscriber terminal, a short message whose type is set to type zero and class to class zero, and the protocol conveying the short message commanding the subscriber terminal to abort the wait for the next short message. 9. A method as claimed in claim 7, characterized by deactivating (418) the radio link by aborting an ongoing mobile application part dialog. 10. A method as claimed in claim 9, characterized by aborting the mobile application part dialog by the MAP-P-ABORT service. 11. A method as claimed in any one of the preceding claims, characterized by retrieving (416) the identifier of the serving cell from the network by an ATI (Any Time Interrogation) or SRI (Send Routing Info) function. 12. A method as claimed in any one of the preceding claims, characterized by the protocol conveying the short message being the mobile application part protocol. 13. A method as claimed in any one of claims 1 to 10, charac- t e r i z e d by retrieving the identifier of the serving cell from the network cell- specifically from the MM (Mobility Management) and PDP (Packet Data Protocol) contexts of an SGSN (Serving General Packet Radio Service Support Node). 14. A method as claimed in any one of claims 1 to10, charac- t e r i z e d by retrieving the identifier of the serving cell from the network radio network controller-specifically from the MM (Mobility Management) and PDP (Packet Data Protocol) contexts of an SGSN (Serving General Packet Radio Service Support Node). 15. A system for locationing a subscriber terminal (104) in a cellular radio system comprising a network (202), characterized in that: the system comprising means (232) for sending a short message to the subscriber terminal (104), setting the type of the short message to type zero, and making the protocol conveying the short message command the subscriber terminal (104) to wait for the next short message, whereby a radio link (218) between the network (202) and the subscriber terminal (104) remains active for a given time; the subscriber terminal (104) comprises means (224) for rejecting the payload of the received short message without measures taken by the user of the subscriber terminal (104) since the type of the short message is zero, and for automatically, without measures taken by the user, sending an acknowledgement message to the network (202) on the reception of the short message; the system comprises means (232) for locationing the subscriber terminal (104) by retrieving the identifier of a cell (312) serving the subscriber terminal (104) from the network (202) when the radio link between the network (202) and the subscriber terminal (104) is active as the subscriber terminal (104) waits for the next short message. 16. A system as claimed in claim 15, c h a r a c t e r i z e d in that type zero is set in the TP-PID field of the short message. 17. A system as claimed in any one of claims 15 to 16, c h a r a c t e r i z e d in that the subscriber terminal (104) is commanded to wait for the next message by setting a 'More Messages to Send' flag in the protocol conveying the short message. 18. A system as claimed in any one of claims 15 to 17, c h a r a c - t e r i z e d in that the system comprises means (232) for setting the class of the short message to class zero, and if the subscriber terminal (104) does not support processing a short message of type zero, then the subscriber terminal comprises means (224) for showing the payload on the display of the subscriber terminal (104) without measures taken by the user of the subscriber terminal (104) and without automatically storing the short message in the memory of the subscriber terminal (104), since the class of the short message is zero. 19. A system as claimed in claim 18, c h a r a c t e r i z e d in that class zero is set in the TP-DCS field of the short message. 20. A system as claimed in any one of claims 15 to 19, c h a r a c t e r i z e d in that the system comprises means (232) for retrieving the identi- fier of the serving cell (312) from a home location register (212) in the cellular radio system, which retrieves the information from a visitor location register (210) in the cellular radio system. 21. A system as claimed in any one of claims 15 to 20, c h a r a c - terized in that the system comprises means (232) for deactivating the radio link (214) between the network and the subscriber terminal (104) after locationing is completed. 22. A system as claimed in claim 21, characterized in that the radio link (214) is deactivated by sending, to the subscriber terminal (104), a short message, whose type is set to type zero and class to class zero, and the protocol conveying the short message commands the subscriber terminal (104) to abort the wait for the next short message. 23. A system as claimed in claim 21, characterized in that the radio link is deactivated by aborting an ongoing mobile application part dia- log. 24. A system as claimed in claim 23, characterized in that the mobile application part dialog is aborted by the MAP-P-ABORT service. 25. A system as claimed in any one of claims 15 to 24, c h a r a c - terized in that the system comprises a service provider (200) and an intel- ligent network control point (204), the means (232) comprised by the system being located in the service provider (200) and the intelligent network control point (204). 26. A system as claimed in any one of claims 15 to 24, c h a r a c - terized in that the means (232) comprised by the system are located in a new component (800) of the network (202), the new component comprising a short message centre (206), an intelligent network control point (204) and/or functionalities of a mobile switching centre (208). 27. A system as claimed in any one of claims 15 to 24, c h a r a c - terized in that the means (232) comprised by the system are located in a new component (800) of the network (202), the new component comprising the following functions of the protocol conveying the short message: 'Any Time Interrogation' and/or 'Send Routing Info', and 'Forward Short Message (MT-SM mobile terminating short message)', and 'Send Routing Info for SM'. 28. A system as claimed in any one of claims 15 to 27, c h a r a c - terized in that the identifier of the serving cell is retrieved from the network by the ATI (Any Time Interrogation) or SRI (Send Routing Info) function. 29. A system as claimed in any one of claims 15 to 28, c h a r a c - terized in that the protocol conveying the short message is a mobile application part protocol. 30. A system as claimed in any one of claims 15 to 27, c h a r a c - terized in that the identifier of the serving cell is retrieved from the network cell-specifically from the MM (Mobility Management) and PDP (Packet Data Protocol) contexts of an SGSN (Serving General Packet Radio Service Support Node). 31. A system as claimed in any one of claims 15 to 27, c h a r a c - terized in that the identifier of the serving cell is retrieved from the network radio network controller-specifically from the MM (Mobility Management) and PDP (Packet Data Protocol) contexts of an SGSN (Serving General Packet Radio Service Support Node).

Inventors: BLOMBERG OLAVI, KEISALA ILKKA, LAMMI TAPIO, NAULA MIKA, PAEIVAERINTA SANTTU, BLOMBERG, OLAVI, KEISALA, ILKKA, LAMMI, TAPIO, NAULA, MIKA, PAEIVAERINTA, SANTTU
Applicants: BLOMBERG OLAVI, KEISALA ILKKA, LAMMI TAPIO, NAULA MIKA, PAEIVAERINTA SANTTU, SONERA OYJ, BLOMBERG, OLAVI, KEISALA, ILKKA, LAMMI, TAPIO, NAULA, MIKA, PAEIVAERINTA, SANTTU
Application year: 2001
Main classification: H04Q7
IPC codes: H04W4, H04W64