GB2440576A

GB2440576A - Emergency Call-Back in a Mobile Telecommunications Terminal without a Smart Card.

Info

Publication number: GB2440576A
Application number: GB0613281A
Authority: GB
Inventors: Craig Kelvin Bishop; Chen-Ho Chin
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2006-07-04
Filing date: 2006-07-04
Publication date: 2008-02-06
Also published as: GB0613281D0

Abstract

A method of performing an emergency call in a telecommunications network from a mobile terminal without a smart card activated therein, the method comprises the step of a network element allocating a local temporary telephone number to the mobile terminal. This enables emergency services to return a call to a mobile telecommunications terminal unregistered or unrecognised in the network. The temporary identity may be one of many reserved for such terminals. The invention may be applied to calls made over a packet switched or a circuit switched network. Such a mobile terminal is arranged to scan for response once an emergency call is made from it.

Description

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-Mobile Communications This invention relates to establishing communications associated with an emergency service between a mobile communications device and a communications network. More particularly, the present invention relates to establishing communications In mobile communications networks such as GSM, GPRS and UIMTS systems, calls to an emergency service can be established even for mobile terminals or smart card, such as a SIM card for GSM or a USIM!UICC for UMTS mobile terminals. A user identity can be invalid if it is blocked for use, for example because of attempted access by a wrong PIN-code or because no roaming agreements are in place for the particular location of the mobile terminal. A mobile terminal without or without a valid user identity will be referred to as a SIM-less' mobile terminal, independent of whether the terminal is a GSM, GPRS or UMTS terminal.

Currently the provision of eCall and EMC 1 are being discussed. eCall is a pan-European initiative to provide an in-vehicle emergency call service.

More information on eCall can be found for example under http://europa.eu. int/information_society/activities/esafety/doc/esafety library! mou/invehicle ecal lmou.pdf.

The Third Generation Partnership Project 3GPP is developing the functionalities to provide emergency calls not only via the circuit switched (CN) domain, but also through the PS domain. Specifically, the service is provided through the IP Multimedia (IM) Core Network (CN) subsystem, more commonly known as the IP Multimedia Subsystem (IMS). More details may for example be found in the 3GPP specification TR 23.867 "IP based IP Multimedia Subsystem emergency sessions".

Both eCall and EMCI are features that involve the originating, routing and maintaining of a mobile originated emergency voice call. eCall applies to the CS domain, i.e. it uses existing procedures to establish emergency calls.

In both eCall and EMCI all the requirements for originating, routing

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and maintaining a mobile originated emergency call are applicable to mobile terminals with a user identity and mobile terminals without. These are requirements set down by regulatory bodies and accepted by the GSM and 3GPP communities.

A further regulatOry requirement of both eCall and EMCI is the support of the co-called Callback feature. The Callback feature -in the terminology of emergency calls and emergency services -allows the person at the Public Safety Answering Point (PSAP) handling the incoming emergency call to decide that there is a need to the current emergency call and then to follow up by making a terminating call back to the mobile terminal that originated the emergency call.

However, while this requirement extends to both mobile terminal with SilvI and mobile terminals without a user identity such as SIMJILJCC, currently the emergency callback feature is limited to mobile terminals with a SIM/IJICC. Callback to mobile terminals without a SIMJIJICC or without a valid SIIvJi'IJICC is currently not supported.

It is thus an aim of the present invention to alleviate the disadvantages discussed above.

According to one aspect of the present invention there is provided a method of performing an emergency call in a CS domain of a telecommunications network from a mobile terminal without a smart card activated therein, the method comprising the step of a network element allocating a local temporary identity number to the mobile terminal.

According to another aspect of the present invention there is provided a method of performing an emergency call in a PS domain of a telecommunications network from a mobile terminal without a smart card activated therein, the method comprising the step of a network element allocating a local temporary identity number other than the P-TMSI to the mobile terminal.

According to another aspect of the present invention there is provided a method of performing an emergency call in a telecommunications network from a mobile terminal, the method comprising the step indicating, in the service request in the response to a paging signal, the service type as the paging response to an emergency callback.

According to another aspect of the present invention there is provided a method of performing an emergency call in a telecommunications network from a mobile terminal without a smart card activated therein, the method comprising the step of listening to a paging channel for paging signals directed to the mobile terminal.

These and other aspects, preferred features and embodiments will be described further, by way of example only, with reference to the accompanying drawings in which: Figures 1 and 2 are schematic outlines of a mobile communications network, in which the present invention can be incorporated; Figure 3 is a schematic outline of the architecture of a IMS network; Figure 4 is a schematic illustration of a signalling exchange for registration of a mobile terminal in the CS domain; Figure 5 is a schematic illustration of a signalling exchange for a terminating call to a mobile terminal in CS domain; Figure 6 is a schematic illustration of a signalling exchange for registration in the IM CN subsystem; Figure 7 is a schematic illustration of a signalling exchange for a terminating call in an IM CN system; Figure 8 is a schematic illustration of the operation of a circuit switched emergency call; Figure 9 is a schematic illustration of the process of allocating a temporary emergency E164IMSISDN by a MSC according to one embodiment of the present invention; Figures 1OA and B are schematic illustrations of the process of allocating a temporary emergency E164IMSISDN by a HLR according to two different embodiments of the present invention; Figure 11 is a schematic illustration of the process of providing the SIM-less mobile terminal with a temporary identity according to another embodiment of the present invention; Figure 12 is a schematic illustration of the process of providing an E-TMSI to the SIM-less mobile terminal in the PS domain according to another embodiment of the present invention; Figure 13 is a schematic illustration of the paging procedure for a SIM-less mobile terminal according to another embodiment of the present invention; Figure 14 is a schematic illustration of the paging response procedure according to another embodiment of the present invention; and Figure 15 is a schematic illustration of the paging procedure for a SIM-less mobile terminal for the PS domain according to yet another embodiment of the present invention.

A cellular communications system includes mobile user equipment (UEs), a radio access network (RAN) and one or more core networks (CNs), as illustrated in Figure 1 for the IJMTS case. A detailed overview over the architecture of a cellular telecommunications system of the third generation may be found in the 3GPP specification "UTRAN Overall Description' 3GPP TS25.40l and related specifications. Communication between the UEs and the UTRAN is provided via the Uu interface (Uu), whereas the communication between the UTRAN and the core networks is done via the lu interface (hi).

Referring now to Figure 2, the architecture of a circuit switched domain is illustrated. The R.AN comprises base stations, such as the so-called Node B's for the UTRAN, and radio network controllers (RNC) , also referred to as base station controllers (BSC). The base stations handle the actual communication across the radio interface, covering a specific geographical area also referred to as a cell. The RNCs control the base stations connected to it, and also include other functionality for tasks such as the allocation of radio

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resources, i.e. the local mobility. An RNC is connected to one or more core networks via the lu interface, to a number of base stations via the lub interface and possibly to one or more other RNCs via the lur interface.

In a UMTS network, the Radio Resource Control (RRC) protocol is used to across the radio interface, i.e. between the UE and UTRAN. These protocol end points interact by exchanging protocol parameters, by sending messages comprising of one or more information elements.

As can be seen from Figure 2, the core network includes a serving GPRS (General Packet Radio Service) support node (SGSN), Circuit Switched Media Gateway Functions (CS-MGW), a Gateway MSC Server (GMSC), a Gateway GPRS Support Node (GGSN), and a Home Subscriber Server (HSS) including Home Location Register (HLR) and an Authentication Centre (AuC).

The CN also includes the 1P Multimedia Subsystem (IMS). Fig. 3 illustrates the architecture of an IMS. The IMS related elements include a Call Session Control Function (CSCF), a Media Gateway Control Function (MGCF), a MS Media Gateway function (MS-MGW), a Multimedia Resource Function Controller (MRFC), a Multimediate Resource Function Processsor (MIRFP), a Breakout Gateway Control Function (BGCF), and a Home Subscriber Server (HSS). The IJE is connected to the IMS via a Proxy CSCF (P-CSCF). The MRFP and the BGCF are connected to a IP Multimedia Network, whereas the IMS-MGF and MGCF are connected to a Public Switched Telephone Network (PSTN). More details may be found in the

3GPP Specification TS 23.002 "Network Archicture".

In a network including both a CS domain and an IMS, a mobile terminal can connect to the network either via the CS domain or the IMS.

Both networks provide call related services, also known as supplementary services. Supplementary Services for example include call forwarding, call redirecting, call holding, and call re-routing.

In the following the current registration procedure and call termination procedure for a mobile terminal with and without a SIM are described.

Referring now to Fig. 4, a signalling exchange is described for registration of a mobile terminal in the CS domain. The process starts in step 101 with radio access procedures between the mobile station (MS) and the RAN. In step 103 the MS sends an location updating request including a mobile identity to the MSC/VLR. In step 105 the MSCIVLR sends the update location request including the mobile identity to the HLR. The HLR responds in step 107 with transmitting the subscriber data to the MSC/VLR. In step 109 the transmission of step 107 is acknowledged by the MSC/VLR, and the HLR responds in step 111 with an update location acknowledgment to the MSC/VLR. In step 113 the authentication, security checks and setting up procedures follow. In step 115 the MSC/VLR sends an location updating accept message to the MS including an temporary MS identity (TMSI).

Referring now to Figure 5, a signalling exchange for a terminating call to a mobile terminal in CS domain are described. In step 121 the GMSC sends a request for routing information to the HLR, including the MSISDN. In step 123 the HLR sends a message to the MSC/VLR requesting a roaming number and including the mobile identity. The MSC/VLR responds in step 125 by providing a roaming number result and including the Mobile Subscriber Roaming Number (MSRN). The HLR sends in step 127 the routing information result including the MSRN to the GMSC, and the GMSC provides in step 129 the initial address message including the MSRN to the MSC/VLR. In step 131 the MSCNLR pages the RAN using the mobile station's TMSI, and subsequently the RAN pages the MS in step 133. In step the radio access procedures are carried out and the terminating call signalling procedures are carried out in step 137.

The above described example illustrates the MSCIVLR initiating the page to the called liE only when the MSC/VLR receives the 1AM (MSRN) from the GMSC. However, there is an existing option in GMSILTMTS whereby the MSCNLR initiates the paging procedure towards the liE even before the JAM (MSRN) arrives from the GMSC. This option is called Pre-Paging. Pre-Paging can be initiated after MSCIVLR receives and accepts the Provide Routing Number message from the HLR. Details of Pre-Paging can be found in 3GPP TS 23.108.

From the signalling examples described above with reference to Figure 4 and 5 it is particularly noted, that when a mobile terminal makes a registration, the mobile terminal has to provide some identity to allow a check to be made back towards the HLR. Also, in the course of registration, the mobile terminal is provided a temporary identity. Later in a terminating call, the mobile terminal is paged with that temporary identity. For a terminating call to a UMTS or GSM network, the first point of entry for a terminating call is the GMSC.

When an incoming call arrives at the UMTS or GSM network, the Called Number is a MSISDN number. The MSISDN number is of the internationally recognised E164 numbering structure as defined by ITU. This El 64IMSTSDN number is then used in the UMTS or GSM network to be remapped to a temporary MSRN.

Referring now to Figure 6, a signalling exchange for registration in the JIM CN subsystem is described. The process starts in step 141 by registration of the UE in a visited network at the Proxy Call Session Control Function (P-CSCF) of the visited network. In step 143 the P-CSCF registers at the Interrogating Call Session Control Function (I-CSCF) of the home network.

The I-CSCF sends in step 145 Cx-Query/Cx-Select Pull message to the HSS, and the HSS responds with a Cx-Query/Cx-Select Pull Response message (step 147). In step 149 the I-CSCF registers with the Serving Call Session Control Function (S-CSCF). In step 151, the S-CSCF sends a Cx-put/Cx-pull message to the HSS and the HSS responds in step 153 with a Cx-put response/Cx-pull response to the S-CSCF. In step 155 service control is established as the S-CSCF. In step 157, 159 and 161 a confirmation message of successful registration (200 Ok) is sent from the S-CSCF to the I-CSCF, from the 1-CSCF to the P-CSCF and from the P-CSCF to the liE, respectively.

Referring now to Figure 7, the signalling exchange for a terminating call in an IM CN system will be described.

In step 201 an Initial SDP offer is sent from the originating network to the S-CSCF of the terminating network, and the S-CSCF establishes service control in step 202. In steps 203 and 204 the S-CSCF sends an Initial SDP offer to the P-CSCF, and the P-CSCF to the UE, respectively. The UE responds in step 205 and thus the P-CSCF authorises Quality of Service resources in step 206. In steps 207 and 208 the P-CSCF sends an offer response to the S-CSCF, and the S-CSCF to the originating network, respectively.

In steps 209, 210 and 211 the response confirmation for the option SDP is sent from the originating network via the S-CSCF and P-CSCF to the UE. In step 212 the UE acknowledges receipt of the confirmation message and reserves resources for the call in step 213. Subsequently in step 214 and 215 the SCSCF and the S-CSCF acknowledge receipt of the confirmation messages.

In steps 216, 217 and 218 the reservation confirmation is sent from the originating network via the S-CSCF and P-CSCF to the UE. The user is alerted of the call in step 219, and reservation confirmation messages are sent back from the UE via the P-CSCF and the S-CSCF to the originating network (steps 220 to 222). In the same way ringing signals are sent in steps 223 to 225 from the user to the originating network. A 200 ok' confirmation message is send from the liE to the P-CSCF in step 226. The P-CSCF approves in step 227 of the QoS commitment and the transmission of media data to the liE starts in step 228. A 200 ok confirmation message is send from the P-CSCF to the S-CSCF in step 229 and from the S-CSCF to the originating network in step 230.

In steps 231, 232 and 233 acknowledgement messages are sent from the originating network via the S-CSCF and P-CSCF to the IJE.

It is noted that in the procedures described above with reference to Figures 6 and 7 the identities used by the mobile terminal and the IM CN subsystem for registration purposes (and later call origination and terminating purposes at IMS level) are not the same as the identities used by the underlying network identities. However, there exists a relationship between the identities used.

In order for the P-CSCF to send the INVITE message to the UE a paging procedure may be required at the radio interface. Whilst the P- CSCF and indeed the JIM CN subsystem may view the IJE's user agent (UA) as always ON' in UMTS terms, there might not be a radio connection or even a logical PMM connection. Therefore, in order to allow the INVITE message to be forwarded to the UE's UA, the UE has to be paged.

Furthermore, it is noted that the identity that the UE is paged on is not that of the Request uniform resource identifier (URI) in the INVITE message.

However, there exists a relationship between these two identities internally in the network -from the IM CN subsystem to the supporting PS domain in the form of the GPRS network to the underlying RAN -and thus there might be several transformed but linked identities.

Referring now to Figure 8, the operation of a circuit switched emergency call is described. It can be seen that a mobile communication device, such as a mobile terminal or user equipment (UE), is initiated to make an emergency call (step 251). A radio connection is established between the UE and the radio access network (step 252). hi step 253 a request for service (CM_service_request message) is then forwarded to the mobile switching centre from the UE. In step 254 the core network determines from the received service request message that the circuit switched call is an emergency call, and so skips the authentication and security procedures. This mechanism is built into the circuit switched domain of the core network.

Further steps follow which allow the user plane resources to be allocated and for the UE and core network to complete the emergency call.

In step 255 an emergency setup message is sent from the terminal to the MSC, and a call proceeding message is sent back from the MSC to the terminal. In step 257 resources are allocated for the emergency. It is noted that the CN realises that the call is an emergency call and priority is given to the emergency call. In step 258 an alerting message is sent from the MSC to the terminal and the call is connected in step 259.

It can be seen from Figure 8 that because the terminal has no SIIM/UICC, the CN does not execute a registration procedure and so the SIM-less mobile terminal, even when allowed the extra-ordinary service of making an originating emergency call to a PSAP, is not seen to "exist".

The provision of emergency call carried out by a SlIM-less mobile terminal via the PS domain is currently discussed in 3GPP working groups SA2 and CTI. More details can be found in the documents 3GPP reports TR 23.867 "IP based IP Multimedia Subsystem emergency sessions" and TS 23.167, v.7.0.0 "IMS emergency sessions".

From the signalling examples described above with reference to figures 4 th 8, it can be see that the following features need to be considered in order to provide a callback function for emergency calls carried out from a SliMless mobile terminal:- 1) The SIMless mobile terminal needs to register with the network. If the network allows the SiMless mobile terminal to be registered such an extra-ordinary registration can occur for example in parallel with establishment of the mobile originating emergency call so as not to delay the emergency call.

2) During SIMless registration the SiMless mobile terminal is provided with a registration identity. In this way the network can subsequently page the SiMless mobile terminal in order to provide the callback and deliver the terminating call or other features. This identity can be purely of local network significance and roaming considerations need not be considered.

3) Security checks and authentications and over the air protection will not be performed for emergency calls.

4) The PSAP is notified of a number for calling back the SiMless mobile terminal. This number may for example be a notional or a temporary E164IMSISDN number (might be fictitious, might be temporary,, or a predetermined number of a preserved range of E164/MS1SDN numbers just for such emergency call back use). In this way the network elements can remap that EI64IMSISDN to a temporary MSRN that the network can use to route and subsequently identify so as to page the SIM-less mobile terminal.

In the following solution will be described for the routing of the terminating call from the point of entry into the PLMN network to the CN entity to whom the SIM-less mobile terminal is temporarily allowed to register and get access and the paging procedure to a SIM-less mobile terminal It is noted that when a mobile terminal makes a CS emergency call, that CS emergency call is made to the network the mobile terminal is registered in. If for example a U.K. user is in Germany and he dials 112, he is connected to the German PSAP. This is by nature of the way the CS emergency call has been designed to work.

Therefore, for the CS domain, any callback to a CS emergency caller with a roaming SIM-less mobile terminal is handled by the HLR of the network from which the user originated the emergency call.

For the PS domain, the IM CN subsystem entities through UICC_less emergency registration procedures specified in TS 24.229 can route a PS callback through the IM CN subsystem.

A further reason for only involving the HLR of the network the SIM-less mobile terminal is currently located in is that the user without a SlIM does not have his/her own HLR, as there is no subscription. ) I.

It is noted that possibilities to provide a callback feature for SIMless mobile terminals via the PS domain have been discussed in previous 3GPP working group meetings of the groups SA2 and CT1. A possible solution allowing the routing of an emergency callback in the IMSIPS domain which has been discussed in the CT1 meeting number 42 proposes to tag an emergency un to the emergency call while being routed to the PSAP. This un can be used by the PSAP to call back the mobile terminal. More details can for example be found at the 3gpp servers at http://www.3gpp.orglftpltsg ctfWG I mm-cc-sm_ex-CN 1/TSGC l_42/. Such solutions when finally agreed will be documented in TS 24.229.

Network Routine of Callback in the CS Domain As described above with reference to Figure 5, a call enters a PLMN at the GMSC and the HLR with the identification of a called telephone number, i.e. a MSISDN or E164 number. With that EI64IMSISDN number the GMSC queries the HLR, knowing the last registered location of the mobile terminal provides the GMSC with a routing number, the MSRN. Internal network signalling is required between the HLR and the involved CN entities to derive this MSRN. With this MSRN the GMSC routes the call directly to that MSC serving the mobile terminal and from there the MSC will instruct the access network to initiate the paging procedure and when the mobile terminal answers to the paging the MSC delivers the terminating call.

Therefore, if the HLR knows of a mobile terminal without SIMIIJICC, the translation procedure to a local routing identity (i.e. the MSRN) as described above can be left unchanged. In this way the reuse of existing signalling can be maximised.

Also, the E164IMSISDN number can be used from outside the PLMN to address the SIM-less mobile terminal.

Allocation of a temporary emergency EI64IMSISDN In the following the allocation of a temporary emergency E164/ MSISDN will be described. This can be performed for example by the MSC or by the HLR.

When a SIM-less mobile terminal makes an emergency call it needs to gain access and service from the network. The main CN entity that deals with accepting and provision of that service is the MSC. According to a first embodiment the MSC allocates a temporary emergency E164/MSISDN number when the MSC allows the mobile terminal originated emergency call.

This E164IMSISDN number can for example be of a predetermined range reserved to emergency calls. In this way the temporarily provided numbers do not clash with any existing EI64IMSISDN number in use.

Referring now to Figure 9, the process of allocation of a temporary emergency E164IMSISDN by a MSC is described.

In step 301 the SIM-less mobile tenninals initiates a CS based emergency call. In step 302 a radio connection is established between the mobile terminal and the RAN. An originating conversational call is given as the establishment cause for the signaling connection. In step 303 the mobile terminal sends an CM_service_request message to the MSC.VLR, identifying the service type as an emergency call and the mobile identity as the [MEl. In step 304 the MSCJVLR sends a location update message to the HLR, giving the temporary emergency EI64IMSISDN number as the mobile identity. In step 305 the HLR sends an insert subscriber data message to the MSCIVLR, and in step 306 the MSC/VLR sends an insert subscriber data acknowledgment message to the HLR.

By sending the insert subscriber data as described in step 305 the HLR provides subscriber related information, including security related information, to the MSC. However, in the above described embodiment steps 305 and 306 or optional, the procedure can also be carried outwithout steps 305 and 306. j

In step 307 the HLR sends an update location acknowledgement message to the MSC/VLR.

An alternative solution is the allocation of the temporary emergency E164/MSISDN by the HLR. As described above, there is not a normal registTation procedure performed for a the SJM-less mobile terminal attempting a mobile originated emergency call. However, there is still in a sense an authorization decision by the MSC. The MSC and the HLR adapt the normal registration procedure wherein the MSC contacts the HLR as described above. However, the MSC shall provide an indication that a SliM-less emergency call is performed and thus performs an extraordinary' registration.

The MSC can for example provide an Emergency Indicator in the Update Location message to HLR.

Referring now to Figure 1 OA, the process of allocating a temporary emergency El 64fMSISDN by a HLR is described.

Steps 311 to 313 are equivalent to steps 301 to 303 described above with reference to Figure 9. In step 314, however, the MSC/VLR sends a location update message to the HLR, specifying the IMSI number as the mobile identity number and including an indication to the HLR that the call is an emergency call. In step 315 the HLR then allocates a temporary El 54IMSISDN number to the SIM-less mobile terminals and sends an insert subscriber data message to the MSC/VLR, including the allocated temporary emergency EI64IMSISDN. In step 316 the MSC/VLR sends an insert subscriber data acknowledgment message to the HRL. In step 317 the HLR sends an update location acknowledgement message to the MSCIVLR.

An alternative solution is illustrated in Figure 1 OB. Steps 321 to 324 are the same as steps 311 to 314 of Figure 1 OA. However, the HLR sends the allocated temporary emergency E164IMSISDN in step 327 in the update location acknowledgement message rather than in the insert subscriber data message of steps 325. Steps 325 and 326 are equivalent to steps 305 and 306 described above with reference to Figure 9. In this way the insert subscriber data procedure of steps 325 and 326 are not necessarily required for this embodiment. The insert subscriber date procedure is thus optional.

Alternatively to the embodiments described above with reference to Figures 1 OA and 1 OB in which an emergency indicator is provided to the HLR, the MSC may provide the ll%4EI as the mobile identity to the HLR inthe Update Location message (steps 314 or 324). In this way the HLR sees that the mobile identity 1MEI is being used and deduces that this a SIM-less emergency call.

A yet other possibility is that the MSC provides both the IMEI as the mobile identity and an Emergency Indicator to the HLR in the Update Location message (steps 314 or 324).

It is noted that in the above described embodiments the MSC performs an extra-ordinary update to the HLR (steps 304, 314 and 324). The extra-ordinary update indicates that there is a SIM-less emergency call and specifies the MSC allocated temporary emergency E164/MSISDN. The HLR can use this information to locate the MSC when a terminating call arrives for that temporary emergency El 64IMSISDN number. This will be described in more detail below.

After having allocated the temporary emergency E164/MSISDN (either by -the MSC or by the HLR), the MSC indicates this El 64/MSISDN number as the calling number to the PSAP. The MSC then uses the ISUP SS7 signaling for providing the PSAP with the E164IMSISDN number. The MSC can provide this temporary emergency E164IMSISDN for example as the Calling Party Number of the ISUP lAM message.

In this way the PSAP is provided with a telephone number for the SIM-less mobile terminal. This E164fMSISDN number can then be used for calling back the SIM-less mobile terminal that was originating the emergency call.

PaEing a mobile terminal without SIMIUICC The key to the paging procedure is for both the Network and the UE to have an identity that is commonly known, so that the NW can page the UE and where the HE can listen on the paging channels to know if the HE is paged.

Having an identity for a UE with a SIM is one of the key features of the UMTS, GPRS, GSM systems. The SIM allows for security procedures to be performed and once authonsed the mobile terminal is then provided a temporary identity through which the HE can be paged. Even if the mobile terminal is not provided with a temporary identity or does not have a temporary identity (for example if the mobile terminal or the network has lost the temporary identity) paging the mobile terminal can still be performed using the IMSI. However, SIM-less mobile terminals do not have an IMSI.

Allocation of the E-TMSI In the following the paging procedure of a SIM-less mobile terminal is discussed. In embodiments of the present the network provides the SIM-less terminal with a temporary local identity number when the SIM-less mobile terminal initiates an originating emergency call. This temporary local identity number may for example be an emergency temporary mobile subscriber identity, referred to as E-TMSI in the following. The E-TMSI is a local temporary identity number which is only used for providing SIM-less mobile terminals initiating an emergency call with a temporary identity. In this way the SIM-less mobile terminals can be paged as will be described in more detail below. The E-TMSI numbers have the same format as conventional TMS1 numbers for the CS domain or P-TMS1 numbers for the PS domain. In this way the RRC paging messages can be used in the same way for paging a SIM-less mobile terminal as paging a liE in the prior art.

Although the paging procedures for paging SIM-less mobile terminals using the E-TMSIs are the same as for paging liEs using TMSI or P-TMSI numbers, it is advantageous for the network element to use a separate local j identity as the E-TMSI for handling emergency calls of Silvi-less mobile terminals. In this way the E-TMSI numbers are identified as exceptional identities and the extra-ordinary registration and paging procedures can be logically and clearly distinguished from existing procedures.

The network may for example reserve a range of predetermined numbers of the TMSI format for use as E-TMSI numbers.

It is noted that the E-TMSI numbers are temporary identities, and therefore have a limited life span. In this way it can be ensured that there is no misuse of the E-TMSIs.

This lifespan can for example be a predefined time period. It can also be a time period chosen by the network and provided to the SIM-less mobile tenrnnal as part of the procedure providing the E-TMSI. Other possibilities are to limit the lifespan to one or a predefined number of successful paging responses within a fixed period of time, to a predetermined or dynamically fixed number of successful pages received or number of paging cycles, to one or a fixed or dynamically determined number of successful completions of terminating calls or to any combination of the above.

When the SIM-less mobile terminal makes an emergency call it has to be provided temporary exceptional access to the network. In order to gain exceptional access, a form of an exceptional registration procedure may be run or the registration procedure may be by-passed all together.

Referring now to Figure 11 it will be described how the SlIM-less mobile terminal is provided with a temporary identity, the E-TMSI, when the exceptional access to the network is provided.

In step 401 the SIM-less mobile terminals initiates a CS based emergency call. In step 402 a radio connection is established between the mobile terminal and the RAN. An originating conversational call is given as the establishment cause for the signaling connection. In step 403 the mobile terminal sends an CM service request to the MSC/VLR, identifying the service type as an emergency call and the mobile identity as the lIME!.

In step 404 an extra-ordinary registration procedure is carried out between the MSCNLR and the HLR. In step 405 the MSCNLR sends and CM_SERVICE_ACCEPT message to the SIM-less mobile terminal and includes in this message the E_TMSI assigned to the SlIM-less mobile terminal.

In the process described above with reference to Figure 11 in step 404 a form of registration-like process is carried out between the MSC and the HLR. However, it is appreciated that this step of an extra-ordinary registration procedure is optional and it is not a condition to the sending of the E-TMSI in the CM_SERVICE_ACCEPT message Also, in the embodiment described above the extra-ordinary registration procedure of step 404 has been carried out prior to the MSC sending the CM_SERVICE_ACCEPT back to the mobile terminal with the B-TMSI in step 405. Alternatively the extra-ordinary registration procedure of step 404 can be carried out simultaneously to or after the MSC sending the CM_SERVICE_ACCEPT back to the mobile terminal with the E-TMSI in step 405.

Referring now to Figure 12, the process of providing an E-TMSI to the SlIM-less mobile terminal of the PS domain will be described.

Similarly to the process described above for the circuit switched case, in step 411 the SlIM-less mobile terminals initiates a PS based emergency call.

In step 412 a radio connection is established between the mobile terminal and the RAN. In step 413 the mobile terminal sends a service request to the SGSN, identifying the service type as an emergency session establishment and the mobile identity as the lIME!. In step 414 the SGSN sends an SERVICE_ACCEPT message to the SlIM-less mobile terminal, including the E-TMSI as described above.

Alternatively to sending the SERVICE_REQUEST message in step 413, an ATTACH_REQUEST message may be send in step 413. In this message the mobile identity is specified as the lIME! and the call is indicated as an emergency call. The SGSN then responds by sending an ATTACH_ACCEPT message in step 414, including the E-TMSI as described above.

A further alternative to the two solutions described above is to send an EMERGENCY_ATTACH_REQUEST message in step 413. Again, in this message the mobile identity is specified as the IMEI. The SGSN then responds by sending an EMERGENCY_ATTACH_ACCEPT message in step 414, including the E-TMSI as described above.

As has been described above a temporary, local and exceptional' mobile identity is allocated to the SIM-less mobile terminal when that SIM-less mobile terminal make an access to initiate an emergency call as part of an extra-ordinary registration-like procedure. This identity has been referred to a the E-TMSI.

However, it is appreciated that other forms of mobile identities can be used for such an extra-ordinary registration-like procedure. Also, by using other identities the SIM-less mobile terminal can be paged. However, the mobile identity needs to be uniquely known by both the network side and the SIM-less mobile side. Alternatives to using the E-TMSI may for example be the use of P-TMSI, TMSI or IMEI. By using any of the above mobile identities the SIM-less mobile terminal can be provided with an identity which can-be used for paging the SIM-less mobile terminal.

However, it is noted that the above described E-TMSI is advantageous to the other described mobile identities as will be discussed below.

In current mobile communications systems such as UMTS, GPRS or GSM the allocated TMSI and/or P-TMSI is/are never sent unprotected, i.e. non-integrity protected or non-encrypted or both. Although it is possible to make an exception and send the mobile identity in unprotected form in the case that a SlIM-less mobile terminal initiates an emergency and the callback feature is required, it is noted that such exceptions only complicates specifications and implementations. Therefore, the provision of a new, separate and special local identity avoids the requirements of not sending existing local identities unprotected. )

If a SIM-less mobile terminal physically moves from one area served by one CN to another area served by another CN, it is advantageous to introduce the requirement that, apart from the lifespan of the E-TMSI discussed above, a valid existing E-TMSI is superseded if and when a new E-TMSI is provided.

Any form of identity, particularly temporary identities, in a mobile system comes with mobility management considerations and even roaming considerations. As described above, the E-TMSI is an identity of only local significance. Thus, the E-TMSI is only valid within the area of the CN allocating the E-TMSI. If the Silvi-less mobile terminal moves out of the area of the CN that allocated the E-TMSI, the SIM-less mobile terminal does not need to perform any mobile management procedures to declare its new location. Neither can it be paged by this CN, as the CN only pages within its own area.

Thus for the SIM-less mobile terminal no mobility management considerations and no roaming considerations are necessary.

Also the CN does not generally consider mobility management or roaming for the SIM-less mobile terminal which has been provided an E-TMSI. However, as long as an assigned E-TMSI is valid, the CN does not need to consider allocating a new E-TMSI (and a new El 64IMSISDN) even if the SIM-less mobile terminal initiates another mobile originated emergency call. So if a SIM-less mobile terminal makes a second or subsequent mobile originated emergency call after having been assigned a E-TMSI on its first emergency call, the CN can be sufficiently aware that there is no need to assign another E-TMSI. This can be done by the CN matching an IMEI has an allocated E-TMSI.

Also, even if the CN assigns a different E-TMSI on subsequent mobile originating emergency calls by a Silvi-less mobile terminal, the CN should take care not to assign a new EI64IMSISDN as this is used as the telephone number and communicated to the PSAP in order to initiate the callback, if required.

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In the following the paging procedures using the different mobile identities will be described.

Paging with the E-TMSI Once there is a common identity known on both sides of the radio interface, this temporary identity can then be used by the network to page the mobile terminal and for the mobile terminal to listen to the paging channels for incoming calls.

Referring now to Figure 13 the paging procedure for a SIM-less mobile terminal is described after a mobile identity has been allocated in a mobile originating emergency call.

In steps 501 and 502 the PSAP initiates a call back to the SilvI-less mobile terminal via an external telecommunications network indicating the allocated E164/MSISCN number as the telephone number of the SIM-less mobile terminal. In step 503 the GMSC sends routing information including the MSIDSN to the HLR. In step 504 the HLR provides the MSC/VLR with the roaming number and includes the allocated mobile identity number. In step 505 the MSC/VLR sends a roaming number result to the HLR and includes the MSRN number. Subsequently, the HLR sends the routing information results including the MSRN to the GMSC (step 506). In step 507 the GMSC sends an initial address message to the MSC/VLR and specifies the MSRN. In steps 508 and 509 the MSC/VLR initiates paging of the SIM-less mobile terminal via the RAN using the E-TMSI number. In step 510 the radio access procedures are carried out in order to set up the emergency callback.

As described above it is advantageous to use a E-TMSI of the same length and structure as a TMSI as then the paging identity within the Paging message can identify a TMSI structure while still indicating the E-TMSL Thus the paging identity of the TMSI can easily be re-used by the network in the paging messages towards the mobile terminal, and no other paging identifier needs to be defined.

Paging with the IMEI It is well known that every mobile terminal, and thus also a SIM-less mobile terminal, has an IMEI. Alternatively to the E-TMSI as described above, the IMEI can be used as the identity for paging. In this case the network needs to obtain the IMEI from the SIM-less mobile terminal before the paging procedure starts. This can for example be achieved through the Identity Request procedure run by the network when the SIM-less mobile terminal makes an access request to attempt an emergency call.

Alternatively, the IMEI can be obtained and cached by the network when the SJM-less mobile terminal provides that IMEI during access procedure to initiate the originating emergency call. These access procedures using IMEI have been described previously.

The paging procedure is then carried out analogous to the paging procedure described above with reference to Figure 13. However, in steps 508 and 509 the IMEI is given a the paging identity for the SIM-less mobile terminal.

It is noted that a disadvantage of using the IMEI is that the IMEI is of a length quite different from that of a TMSI or P-TMSI or even the IMSI.

Also, because the form of the IMEI is distinct from TMSI or P-TMSI, a new paging identity (ie. IMEI) would thus have to be introduced for the paging messages used to perform paging.

It is noted that in the paging procedure described above with reference to Figure 13 the network does not use pre-paging. However, it is noted that the paging procedure using either T-IIMSI or the IIMEI can be used in the same way including pre-paging. If pre-paging is used the MSCNLR will begin paging upon accepting the Provide Routing Number from the HLR and does not wait until the Initial Address Message arrives from the GMSC. )

Paging Identity and Cause over lu and A/Gb interfaces In the embodiments described above the CN may indicate when paging the SIN-less mobile terminal that it is paging to complete an emergency callback and/or that it pages a SIM-less mobile terminal.

In order to do this specific paging causes need to be introduced to the PAGING message over the lu interface, the PAGING over the A interfaces and the PAGING PS message or PAGING CS message over the Gb interface.

For instance paging causes such as the Paging Cause = "Emergency Callback" or "Paging to UICC-less mobile terminal" or a combination cause "Emergency Callback to UICC-less mobile terminal" can be introduced.

Connected Mode Paging In the same way as a normal mobile terminal (with a SIM), the SIM-less mobile terminal too can be paged in connected mode. For connected mode paging either the E-TMSI or the IMEI can be used as the Mobile Identity of the connected paging message i.e. PAGING TYPE 2 message.

SIM-less mobile terminal listening to the Paging Channels in order to allow a call placed from the emergency service to a SlIM-less mobile terminal, the terminal needs to listen to the paging channels of the PLMIN it is camped in.

In different embodiments of the present invention, the SIM-less mobile terminal may for example only listen to the paging if the SIM-less mobile terminal has a valid E-TMSI, or after the SlIM-less terminal has originated an emergency call or after the SIN-less terminal has originated an emergency call within a predetermined time period.

In order to allow paging of the SIN-less terminal, the network needs to know which paging group to use when paging the SIN-less mobile terminal and the SIN-less mobile terminal needs to listen to the correct Paging Group. In normal system working the paging group a mobile terminal

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listens to is a function of its IMSI. This formula is described 3GPP IS 25.304.

However, a SIM-less mobile terminal does not have a IMSI. However, it has already been suggested in 3GPP TS 25.304 that a mobile terminal without an SIM shall consider its IMSI to be zero. By using this the Network shall page the SlIM-less mobile terminal in Paging group 0 and the SIM-less mobile terminal shall listen to Paging Channel as a Paging Group 0 UE.

SIM-less mobile terminal responding to Pa2ing In the normal paging procedure, the UE answers to the paging from the Network with a Paging Response message canying the mobile identity on which the UE was paged.

If now a SIM-less mobile terminal is paged using the E-TMSI as described above, the Paging Response carries the E-TMSI as the mobile identity.

The procedure of the paging response is illustrated in Figure 14. In step 601 the radio access procedures for the callback of the emergency service to the SIM-less mobile terminal are carried out. In step 602 the SIM-Iess mobile terminal responds to the paging with a paging response, indicating the E-TMSI as the mobile identity. In step 603 the network can now carry out the terminating call signalling and resource assignment procedures in the normal way.

If the SIM-less mobile terminal was paged using the 1MEI, the mobile identity given in the Paging Response is the IMEI. The paging response procedure is thus analogous to the case discussed above with reference to Figure 14, except that in step 602 the SIM-less mobile terminal responds to the paging with a paging response, indicating the IMEI as the mobile identity.

The CN needs to support the reception and handling of a Paging Response that carries the E-TMSI or the IMEI as the mobile identity. Thus the CN needs to be able to correlate this mobile identity to the terminating emergency callback call for which the CN initiated the paging to the involved SlIM-less mobile terminal.

Therefore, if the CN recognises that in step 602 the E-TMSI or IMEI is given as the mobile identity the CN element deduces that this is an extra-ordinary paging response, that a SIM-less mobile terminal is involved and that it needs to correlate the paging response to the terminating call which arrived at the CN.

In this case the CN treats the paging response with the same degree of handling and management afforded to an originating emergency call by a SIM-less mobile terminal, and the CN skips security checks and run radio resource assignment procedures as for a normal originating emergency call.

Pa2in2 Procedure for the PS domain Referring now to Figure 15 the paging procedure for a SIM-less mobile terminal for the PS domain is described after a mobile identity has been allocated in a mobile originating emergency call.

In steps 701 and 702 the PSAP initiates a call back to the SlIM-less mobile terminal via an external telecommunications network indicating the allocated un provided during the original emergency call as previously described (or E164IMSISDN number) as the telephone number of the SlIM-less mobile terminal. In steps 703 and 704 the IM CN subsystem sends a PDU message or downlink signalling via the GGSN to the SGSN. In steps 705 and 706 the SGSN initiates paging of the SlIM-less mobile terminal specifying the E-TMSI number via the RAN. In step 707 a service request is transmitted to the SGSN, specifying the service type as a paging response and the mobile identity as the E-TMSI.

Compared to the CS procedure described above with reference to Figs. 13 and 14, the RAN still uses the Paging messages, but the uplink response from the mobile terminal is not the Layer 3 message Paging Response.

Instead, the Service_Request message is used for the service type of a paging response.

For the case of paging a SlIM-less mobile terminal the mobile identity is specified as the E-TMSI in the service request message of step 707. In case of paging using IMEI, in steps 705 and 706 the IMEI is given for paging and the service request carries the Mobile Identity E-TMSI.

Alternatively, a new Service Type, the paging response for an emergency callback, may be introduced.

It will be apparent from the foregoing that many other embodiments or variants of the above are possible. The present invention extends to any and all such variants, and to any novel subject matter or combination thereof disclosed in the foregoing.

Claims

CLAIMS: I. A method of performing an emergency call in a CS domain of a

telecommunications network from a mobile terminal without a smart card activated therein, the method comprising the step of a network element allocating a local temporary identity number to the mobile terminal.

2. A method according to claim 1, wherein the temporary identity is one of a predetermined number of temporary identity numbers reserved for the use of emergency calls from mobile terminals without a smart card activated therein.

3. A method according to claim br 2, wherein the temporary identity number is of the format of a TMSI number.

4. A method according to claim 1, 2 or 3, wherein the temporary identity number is a TMSI number.

5. A method according to any preceding claim, wherein the temporary identity number is allocated by a mobile switching centre.

6. A method according to any preceding claim, wherein the temporary identity number is transmitted to the mobile terminal in an CM_SERVICE_ATTACH message.

7. A method of performing an emergency call in a PS domain of a telecommunications network from a mobile terminal without a smart card activated therein, the method comprising the step of a network element allocating a local temporary identity number other than the P-TMSI to the mobile terminal.

8. A method according to claim 7, wherein the temporary identity is one of a predetermined number of temporary identity numbers reserved for the use of emergency calls from mobile terminals without a smart card activated therein.

9. A method according to claim 7, wherein the temporary identity number is of the format of a TMSI number.

10. A method according to any of claims 7 to 9, wherein the temporary identity number is allocated by a SGSN.

11. A method according to claim 10, wherein the temporary identity number is transmitted to the mobile terminal in an SERVICE_ACCEPT message.

12. A method according to claim 10, wherein the temporary identity number is transmitted to the mobile terminal in an ATTACH_ACCEPT message.

13. A method according to claim 10, wherein the temporary identity number is transmitted to the mobile terminal in an EMERGENCY_ATTACH_ACCEPT message.

14. A method according to any preceding claim, wherein the mobile terminal is adapted to listen to a paging channel for paging signals directed to the mobile terminal, without a smart card activated therein.

15. A method according to claim 14, wherein the mobile terminal listens to the paging channel if a valid temporary identity number is allocated to the terminal.

16. A method according to claim 14 or 15, wherein the mobile terminal listens to the paging channel if the terminal has initiated an emergency call.

17. A method according to claim 14, 15 or 16, wherein the mobile terminal listens to the paging channel if the terminal has initiated an emergency call within a predetermined time period.

18. A method according to any of claims 14 to 17, wherein a network element pages the mobile terminal without a smart card activated therein using the temporary identity number.

19. A method according to claim 18, wherein the mobile terminal transmits a paging response message indicating the temporary identity number as the mobile identity.

20. A method according to any of claims 14 to 17, wherein a network element pages the mobile terminal using the IMEI number.

21. A method according to claim 20, wherein the mobile terminal transmits a paging response message indicating the IMEI number as the mobile identity.

22. A method according to any of claims 14 to 21, wherein the paging response message is a service request in the PS domain.

23. A method according to any of claims 14 to 22, wherein paging in connected mode is performed using the temporary identity number or the IMEI number.

24. A method according to any of claims 14 to 23, wherein the core network arranges for the access network to page the mobile terminal.

25. A method according to claim 24, wherein the core network indicates to the access network that the paging is for a mobile terminal without a smart card activated therein.

26. A method according to claim 24 or 25, wherein the core network indicates to the access network that the paging is for an emergency callback.

27. A method according to claim 22, wherein the service request in the response to a paging signal indicates the service type as the paging response to an emergency callback.

28. A method of performing an emergency call in a telecommunications network from a mobile terminal, the method comprising the step indicating, in the service request in the response to a paging signal, the service type as the paging response to an emergency callback.

29. A method of performing an emergency call in a telecommunications network from a mobile terminal without a smart card activated therein, the method comprising the step of listening to a paging channel for paging signals directed to the mobile terminal.

30. A method according to claim 29, wherein the mobile terminal listens to the paging channel if a valid temporary identity number is allocated to the terminal.

31. A method according to claim 29 or 30, wherein the mobile terminal listens to the paging channel if the terminal has initiated an emergency call.

32. A method according to claim 29, 30 or 31, wherein the mobile terminal listens to the paging channel if the terminal has initiated an emergency call within a predetermined time period.

33. A method according to any of claims 29 to 32, wherein a network element pages the mobile terminal using a local temporary identity number allocated to the mobile terminal.

34. A method according to claim 33, wherein the mobile terminal transmits a paging response message indicating the temporary identity number as the mobile identity.

35. A method according to any of claims 29 to 32, wherein a network element pages the mobile terminal using the IMEI number.

36. A method according to claim 35, wherein the mobile terminal transmits a paging response message indicating the IMEI number as the mobile identity.

37. A method according to any of claims 29 to 36, wherein the paging response message is a service request in the PS domain.

38. A method according to any of claims 29 to 37, wherein paging in connected mode is performed using the temporary identity number or the IMEI number.

39. A method according to any of claims 29 to 38, wherein the core network arranges for the access network to page the mobile terminal.

40. A method according to claim 39, wherein the core network indicates to the access network that the paging is for a mobile terminal without a smart card activated therein.

41. A method according to claim 39 or 40, wherein the core network indicates to the access network that the paging is for an emergency callback.

42. A method according to claim 37, wherein the service request in the response to a paging signal indicates the service type as the paging response to an emergency callback.