Lawful interception monitoring for multi-device service

Abstract

The present disclosure provides a method for performing International Mobile Equipment Identity (IMEI) based Lawful Interception (LI) monitoring for multi-device service performed by a Point of Interception (POI) function device (202) associated with a Serving Call Session Control Function (S-CSCF) (104) of an Internet Protocol Multimedia Subsystem (IMS) core network (510). The method can include examining (302) a header of a message (116) received by the S-CSCF to determine whether the first header comprises an IMEI that matches a target IMEI, and if so initiate (304) monitoring of the first session. The method can also include examining (306) a request field of a second message (120) sent by the S-CSCF (104) to the first UE (108-1) to determine whether the request field of the second message (120) comprises an identifier that corresponds to the target IMEI, and if so, initiate (308) monitoring of the first session.

Description

LAWFUL INTERCEPTION MONITORING FOR MULTI-DEVICE SERVICETECHNICAL FIELD[OOO1] The present disclosure relates to a method for performing International Mobile Equipment Identity (IMEI) based Lawful Interception monitoring for multi-device service. The disclosure also relates to a network node, a computer program and a carrier containing a computer program.BACKGROUND

[0002] The Internet Protocol (IP) Multimedia Subsystem (IMS) introduces a big change into telecommunication networks by separating the access network from service network, and so providing a set of services regardless of used access technology.

[0003] This new architecture is completely based on IP and allows a faster introduction of new services compared to the circuit switched (CS) legacy world, where the Mobile Switching Center (MSC) was controlling both service and access.

[0004] IMS services meet flexibility, easy deployment and customization needs coming from both Telco operators and end-users.

[0005] In addition, from a lawful interception (LI) point of view a network operator can provide access to the intercepted Content of Communications (CC) and the Intercept Related Information (IRI) of the mobile target and services related to the target (e.g., Call Forwarding) on behalf of Law Enforcement Agencies (LEAs). The LEA provides the intercept request (e.g., lawful authorization or warrant) to the Communication Service Provider (CSP). The intercept request identifies, at a minimum, the target, the type of intercept (I.e., IRI-only, or IRI and CC) that is authorized, the authorized period for interception, and the LEA delivery address(es) for the intercepted information.

[0006] The Third Generation Partnership Project (3GPP) standards require IMS to support the International Mobile Equipment Identity (IMEI) and Permanent Equipment Identifier IMEI (PEIIMEI) target type, which is received during the registration.

[0007] In particular, for a terminating session, TS 33.128 V18.2.0, chapter 7.12.2.8.2.2 specifies: l / V7?en an IMS session is terminated at an IMS UE (using SIP INVITE), the IRI-POI / CC-TF examines the following to verify for a target match:[...] +sip. instance-id of Contact header received in the SIP REGISTER request when the target identity is PEI I MEI or I MEI.

[0008] The Multi-Device (MuD) service is an operator specific service which enables a user to use different User Equipments (UEs) that are registered under the same public user identity, see 3GPP TS 24.174 V17.6.0, chapter 4.1). When a call is initiated to a subscriber with an active MuD service, the call is forked to all UEs that are registered in the network under the IMS Public User Identity (IMPU) of the subscriber. The first UE answering will be the one that handles the multimedia session. This forking is done in the Application Server (AS) serving the terminating party.

[0009] The 3GPP LI standards do not specify how IMEI base interception shall be performed in the multi-device scenario. The standard being not specific enough allows implementations that are not acceptable in some jurisdictions.

[0010] A problematic case regarding IMEI based interception is the following:• the IMPU of the terminating party is not a target,• one of the IMEIs registered under the IMPU is a target, while• the other IMEIs I devices are not targets.

[0011] In such conditions, when the IMS Point of Interception (POI) in the a Serving Call Session Control Function (S-CSCF) receives the INVITE, it will apply the method described in TS 33.128 V18.2.0. If one of the IMEI received with the SIP REGISTER is a target for interception, the entire session will be monitored.

[0012] Note that at the point when the monitoring starts, no actual UE is involved in the call. The first UE that answers the call may or may not be the one that registered the IMEI which is a target for the interception.

[0013] Many jurisdictions do not allow to monitor a multimedia session when the target identity is not directly included in the session. In most cases is possible to start monitoring since the call is routed to the UE with the target IMEI, however the monitoring should stop as soon as a different UE answers the call and the signaling leg to the UE with the target IMEI is closed down.

[0014] In the past it was generally accepted to over-deliver due to technical reasons. However, with the more stringent privacy laws and regulations being adopted in many markets, this is no longer the case.

[0015] In the best case this problem prevents IMEI monitoring to be used in many markets, which deprives law enforcement of an important tool. In the worst case thisaspect may be missed by our customer, resulting in a privacy violation which could tarnish our customer and / or Ericson reputation, and possible also result in steep fines.SUMMARY

[0016] An object of the invention is to improve privacy when performing International Mobile Equipment Identity (IMEI) based Lawful Interception (LI) monitoring for multi-device service.

[0017] The present disclosure provides a method for performing IMEI based LI monitoring for multi-device service performed by a Point of Interception (POI) function device associated with a Serving Call Session Control Function (S-CSCF) of an Internet Protocol Multimedia Subsystem (IMS) network. The method can include examining a first header of a first message received by the S-CSCF from an Application Server (AS) to determine whether the first header comprises an IMEI that matches a target IMEI, wherein the first message is associated with a first User Equipment (UE) of the multidevice service. The method can also include initiating monitoring of a first session associated with the first UE in response to the first header of the first message comprising the IMEI that matches the target IMEI. The method can also include examining a request field of a second message sent by the S-CSCF to the first UE to determine whether the request field of the second message comprises an identifier that corresponds to the target IMEI. The method can also include initiating monitoring of the first session associated with the first UE in response to the request field comprising the identifier that corresponds to the target IMEI.

[0018] In an embodiment, a network node implements a POI function device associated with a S-CSCF of an IMS network that is configured to perform IMEI based LI monitoring for multi-device service. The network node can include processing circuitry that can cause the network node to examine a first header of a first message received by the S-CSCF from an AS to determine whether the first header comprises an IMEI that matches a target IMEI, wherein the first message is associated with a first UE of the multi-device service. The processing circuitry can also cause the network node to initiate monitoring of a first session associated with the first UE in response to the first header of the first message comprising the IMEI that matches the target IMEI. The processing circuitry can also cause the network node to examine a request field of a second message sent by the S-CSCF to the first UE to determine whether the requestfield of the second message comprises an identifier that corresponds to the target IMEI. The processing circuitry can also cause the network node to initiate monitoring of the first session associated with the first UE in response to the request field comprising the identifier that corresponds to the target IMEI.

[0019] In another embodiment, a computer program can be provided that includes instructions that when executed on at least one processor cause the processor to perform the methods above. Additionally, a carrier can be provided that contains the computer program, where the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

[0020] One of the advantages provided by the techniques disclosed herein is that privacy regulations can be complied with in more countries, and it reduces the risk of privacy violations.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0022] Figure 1 illustrates a call flow for a multi-device terminating case according to some embodiments of the present disclosure;

[0023] Figure 2 illustrates a block diagram schematic of a multi-device system according to some embodiments of the present disclosure;

[0024] Figure 3 illustrates a flow chart of a method for performing International Mobile Equipment Identity (IMEI) based Lawful Interception (LI) monitoring for multidevice service according to some embodiments of the present disclosure;

[0025] Figure 4 illustrates a flow chart of another method for performing IMEI based LI monitoring for multi-device service according to some embodiments of the present disclosure;

[0026] Figure 5 illustrates another flow chart of another method for performing IMEI based LI monitoring for multi-device service according to some embodiments of the present disclosure;

[0027] Figure 6 illustrates one example of a cellular communications system according to some embodiments of the present disclosure;

[0028] Figure 7 is a schematic block diagram of a network node according to some embodiments of the present disclosure;

[0029] Figure 8 is a schematic block diagram that illustrates a virtualized embodiment of the network node of Figure 6 according to some embodiments of the present disclosure; and

[0030] Figure 9 is a schematic block diagram of the network node of Figure 6 according to some other embodiments of the present disclosure.DETAILED DESCRIPTION

[0031] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

[0032] Network Node: As used herein, a "network node" can be any type of apparatus / device in an Internet Protocol (IP) Multimedia Subsystem (IMS) network, e.g., in an IMS core network, or any apparatus / device that implements a network function. Some examples of an IMS network node include, a computer or server host for e.g., a Serving Call Session Control Function (S-CSCF), Application Server (AS), IMS network node that hosts Point of Interception (POI) Function, in this application termed POI Function device, or the like. In the following description, when stating that any of these functions, such as an S-CSCF, AS, or POI function device, perform an action, such as examining / initiating / monitoring, etc., then it is to be understood that it is in practice the network node / computer / server host / POI Function device that hosts the S-CSCF and POI Function, respectively, that performs the action. One or both of the S-CSCF and the AS may be part(s) of the IMS core network.

[0033] Note that the description given herein focuses on a Third Generation Partnership Project (3GPP) cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0034] The present disclosure provides a method for performing International Mobile Equipment Identity (IMEI) based Lawful Interception (LI) monitoring for multidevice service performed by a POI function device associated with a S-CSCF of an IMS core network. The method can include examining a first header of a first message received by the S-CSCF from an AS to determine whether the first header comprises an IMEI that matches a target IMEI, wherein the first message is associated with a first User Equipment (UE) of the multi-device service. The method can also include initiating monitoring of a first session associated with the first UE in response to the first header of the first message comprising the IMEI that matches the target IMEI. The method can also include examining a request field of a second message sent by the S-CSCF to the first UE to determine whether the request field of the second message comprises an identifier that corresponds to the target IMEI. The method can also include initiating monitoring of the first session associated with the first UE in response to the request field comprising the identifier that corresponds to the target IMEI.

[0035] In order to meet the most stringent regulations, IMEI based interception in the POI function device of the S-CSCF can be triggered only on the call leg where the contact that the IMEI has been associated to is already selected. If the Multi-Device service in the provider's network is implemented by using caller preferences, then the S- CSCF POI function device shall examine the Accept-Contact header to determine whether the value of the -i-sip.instance-id parameter matches an IMEI entry in a target list. Caller preferences can determine in advance the outcome of contact selection, and thus can be a trigger for IMEI interception if the preferences exclude the possibility of the call leg being terminated to a device with a non-matching instance ID.

[0036] One of the advantages provided by this method is that privacy regulations can be complied with in more countries, and it reduces the risk of privacy violations.

[0037] In an embodiment, at registration (Session Initiation Protocol (SIP) REGISTER) the S-CSCF POI shall keep track of the association between the IMEI in the 4-sip. instance-id of the Contact header and the SIP Uniform Resource Identifier (URI) included in the contact header. At session setup (INVITE) the S-CSCF POI function device serving the terminating user can:• Examine the Request URI and the to header for IMPU target matching. If a match is found, then follows standard procedures (not in the scope of the invention). If no match is found, then;• Examines the +sip-instance parameter of the Accept-Contact header - if present - for IM El target matching. If a match is found, then the POI function device starts monitoring the session;• Select the contact the INVITE will be routed to, e.g., as described in TS 24.229 V18.0.0, chapter 5.4.3.3). Before the INVITE is sent out, the POI function device examines the +sip-instance-id that has been associated to the selected contact URI for IMEI target matching. If a match is found, then the POI function device starts monitoring the session if it has not already started doing so.

[0038] In an alternate embodiment, the POI function device can examine whether there is any contact of the terminating user that has been registered with an IMEI that is a target. If so, the POI function device can start monitoring the communications. At 200 OK answer to the INVITE for a call that is monitored based on IMEI, the POI function device shall use the Contact header in the 200 OK to lookup the actual IMEI used by the UE that answered the call. If the UE is not a target for interception, the monitoring shall stop.

[0039] Figure 1 depicts a call flow for a multi-device, terminating case and is adapted from 3GPP TS 24.174 V17.6.0, annex A.3.2.

[0040] In the call flow, the Serving Call Session Control Function (S-CSCF) 104 can receive at step 110 from the originating network 102 (e.g., a Public Land Mobile Network (PLMN)) an INVITE message. The INVITE message can include a Request URI that identifies a user of UE 108-1 and 108-2 as a native, and the at step 112 the S- CSCF 104 can forward the INVITE message to the AS 106.

[0041] At step 114, the AS 106 determines that it shall forward the request towards UE 108-1 and UE 108-2 for which the identity in Request Uniform Resource Identifier (URI) is the native identity of the called user.

[0042] At steps 116 and 118, the AS 106 can forward the INVITE message to the S- CSCF 104, and the S-CSCF 104 can replace the identity of the user with the UE 108-1 contact and UE 108-2 contact, respectively, in the Request-URI and adds a P-Called- Party-ID header field.

[0043] At steps 120 and 122 the S-CSCF 104 forwards the INVITE message to both UEs associated with the user, and in the example shown in Figure 1, UE 108-2 responds with 200 (OK) at step 124, thus answering the call.

[0044] Figure 2 illustrates a block diagram schematic of a multi-device system with messages sent between components of the system according to some embodiments of the present disclosure. The messages in Figure 2 will also be referenced with respect to the call flow in Figure 1.

[0045] In Figure 2, UE 108-1 can be registered with a first IMEI and UE 108-2 can be registered with a second IMEI. The first IMEI of UE 108-1 can be provisioned as an LI target in the S-CSCF 104, while the second IMEI of UE 108-2 and an IMS public user identity (IMPU) that is associated with a subscriber that owns, uses, or is otherwise associated with UE 108-1 and UE 108-2, are not identified as targets in the S-CSCF 104.

[0046] The standards do not mandate specifically which message shall be provided as Intercept Related Information (IRI) for the session initiation. Any of the messages passing the logical points denoted 206, 208, and 210 on Figure 2 could be candidates.

[0047] The logical points are 206 - An INVITE message 110 incoming from the originating network 102. 208 is the INVITE messages 114 and 116 coming back from the AS 106 after the AS has been invoked by the S-CSCF 104. 210 is the INVITE messages 120 and 122 being sent out towards the terminating UEs 108-1 and 108-2.

[0048] Note that it's only at point 210 where the contact is selected in the S-CSCF 104. IMEI based interception strictly speaking does not make sense before point 210.

[0049] The S-CSCF 104 can receive the INVITE request at 110 which originates from originating network 102. The IMPU is bound to multiple contacts, one of which was registered with the first IMEI of UE 108-1 that is a target. The terminating UE contact is not known at this stage however as that will be selected only after the last AS 106 has been invoked.

[0050] Based on the service profile, the S-CSCF 104 invokes one or more application servers (e.g., AS 106).

[0051] As a back to back user agent, a multi-device service in the AS 106 creates new dialogs, one toward each registered UE 108-1 and 108-2. The AS 106 uses caller preferences in order to have the S-CSCF 104 select a single terminating contact (e.g., either UE 108-1 or UE 108-2) for each dialog, and inserts the Accept-Contact header with the following content into each of INVITE messages in steps 116 and 118 that are sent from the AS 106 back to the S-CSCF 104:Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp- service.ims.icsi.mmtel",*;+sip.instance="<urn:gsma:imei:IMEI l>";require;explicit

[0052] After the AS 106 has been invoked, the terminating contact is selected in the S-CSCF 104. The Request URI is changed to the contact URI, and the INVITE messages are routed towards UE 108-1 and UE 108-2 in steps 120 and 122 respectively. Both devices ring, but UE 108-2 answers the call, and a 200 OK message is sent back to the S-CSCF at step 124. The dialog towards UE 108-1 is cancelled, whereas the session with UE 108-2 is established.

[0053] In an embodiment, the INVITE message received by the S-CSCF 104 from the originating network 102 does not trigger monitoring, and neither does the message received at step 118 but the INVITE message from AS 106 to S-CSCF 104 at step 116 does trigger monitoring by matching in Accept-Contact: The POI function device 202 matches the IMEI in the Accept-Contact against the entries in the target list. The first IMEI of UE 108-1 matches, and the request is intercepted. Although the terminating contact is not yet selected the LI POI can infer from the caller preferences which UE contact will be selected for this dialog. The POI function device 202 can thus start monitoring the IRI related communications with the first dialog associated with UE 108- 1.

[0054] If neither of messages from AS 106 at steps 116 or 118 trigger monitoring, the POI function device 202 can also determine from the contact URIs in the messages at steps 120 and 122 whether to start monitoring. In this case, the message at step 120 from the S-CSCF 104 to the UE 108-1 triggers monitoring. After contact selection, the S-CSCF 104 intercepts the outgoing request at step 120 as the first IMEI associated with UE 108-1 is associated to a contact URI in the registration data that was saved during the registration that is also associated to UE 108-1. The result is that only the messages that belong to the dialog directed towards UE 108-1 are provided as IRI by the POI function device 202 to Mediation and Delivery Function (MDF) 204.

[0055] In an alternative embodiment, the message received at step 110 by S-CSCF 104 can trigger monitoring, and then when the UE 108-2 answers the call, and the 200 OK message is received by S-CSCF 104 at step 124, that message can trigger the POI function device 202 to stop monitoring. The result of this alternative embodiment is that all the dialogs towards both UE 108-1 and 108-2 are provided as IRI to MDF 204.If UE 108-1 (the target device) answers, then monitoring of the dialogs towards UE 108-1 continue, while the monitoring of dialog towards UE 108-2 stops. If UE 108-2 (not a target) answers, then monitoring of all dialogs stops.

[0056] Figure 3 illustrates a flow chart of a method for performing International Mobile Equipment Identity (IMEI) based Lawful Interception (LI) monitoring for multidevice service by the POI function device 202 according to some embodiments of the present disclosure.

[0057] At step 302, the method includes examining a first header of a first message (116) received by the S-CSCF 104 from AS 106 to determine whether the first header comprises an IMEI that matches a target IMEI, wherein the first message 116 is associated with UE 108-1 of the multi-device service.

[0058] At step 304, the method includes initiating monitoring of the first session (or dialog) associated with the first UE 108-1 if the Accept Contact header of the first message 116 include the IMEI that matches the target IMEI.

[0059] At step 306, the method includes examining (306) a request field of a second message 120 sent by the S-CSCF 104 to the first UE 108-1 to determine whether the request field of the second message 120 comprises an identifier (e.g., Contact URI) that corresponds to the target IMEI, and if there is a match, initiating, at step 308, monitoring of the first session associated with the first UE 108-1.

[0060] During a registration procedure, the S-CSCF 104 builds an internal database in the S-CSCF / S-CSCF host that contains a mapping between the IMPU and the Contact URI(s) of the UE(s) being registered, where the database comprises an ad hoc address in the form of a SIP URI where the device is reachable at the time. The S-CSCF 104 also receives the IMEI during registration (the value of the +sip. instance parameter of the Contact header in the REGISTER message) and saves the IMEI to the internal database and associates it to the Contact URI in the internal database.

[0061] When at call setup, and the INVITE message is routed from the S-CSCF 104 to the terminating UE, the contact is selected and the Request-URI of the message is changed to the Contact URI, and the POI function device 202 and S-CSCF 104 know the IMEI that is associated to the selected Contact URI from the internal database. The POI function device 202 has access to the internal database at the S-CSCF 104 as the POI function device 202 is an internal part of the S-CSCF 104, and has access to the S- CSCF's internal database using internal application programming interfaces (APIs). Ifthe IM El that is associated to the selected Contact URI matches the target IM El, the POI function device 202 can determine there is a match and proceed with step 308 described above. The target IMEI in the target list has typically previously been provided to the POI function device / S-CSCF as a target identifier over an XI interface according to European Telecommunications Standard Institute TS 103 221-1, e.g., version 1.14.1, from an LI administration function, ADMF.

[0062] At step 310 the UE 108-1 can answer the call associated with the first session, and the POI function device 202 at step 312 can then collect and provide the IRI with the session to the MDF 204.

[0063] In an embodiment, an IMPU associated with the first message 116 does not match a target IMPU.

[0064] In an embodiment, the first session and second session are forked sessions associated with an invite message (e.g., 110) received from an originating network 102.

[0065] In an embodiment, the first message 116 of the first session and the first message 118 of the second session are received by the S-CSCF 104 in response to the S-CSCF 104 forwarding an invite message 112 received from an originating network 102 to the AS 106.

[0066] Figure 4 illustrates a flow chart of another method for performing International Mobile Equipment Identity (IMEI) based Lawful Interception (LI) monitoring for multi-device service according to some embodiments of the present disclosure.

[0067] In the embodiment depicted in Figure 4, the POI function device 202 examines the first header of the first message 118 received from AS 106 at step 302 and examines the request field of the second message 122 sent by the S-CSCF to the UE 108-2 at step 304.

[0068] The method further includes, at step 402 determining that a first header of a first message 118 of a second session associated with a second UE 108-2 of the multidevice service does not comprise the IMEI that matches the target IMEI.

[0069] The method further includes at step 402 determining that a request field of a second message (122) associated with a second UE (108-2) of the multi-device service that is sent by the S-CSCF (104) to the second UE (108-2) does not comprise the identifier that corresponds to the target IMEI.

[0070] As a result of unsuccessful matching, the POI in the S-CSCF does not start monitoring at step 404 of the dialog towards the second UE (108-2)

[0071] Alternatively, as shown in Figure 5, the POI function device 202 examines the invite message 110 received from the originating network at step 502.

[0072] At step 504, the POI function device 202 initiates monitoring if the IMPU in the Request URI of the invite message 110 is associated with a target IMEI (e.g., the first UE 108-1).

[0073] At step 506, the method includes ceasing monitoring if the Contact URI is not associated with the IMEI of the device that answers the call. So, in this example, if the second session associated with second UE 108-2 answers, the POI function device 202 will cease monitoring.

[0074] Figure 6 illustrates one example of a cellular communications system 600 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 600 is a 5G system (5GS) including a Next Generation RAN (NG-RAN) and a 5G Core (5GC) or an Evolved Packet System (EPS) including an Evolved Universal Terrestrial RAN (E-UTRAN) and an Evolved Packet Core (EPC). In this example, the RAN includes base stations 602-1 and 602-2, which in the 5GS include NR base stations (gNBs) and optionally next generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC) and in the EPS include eNBs, controlling corresponding (macro) cells 604-1 and 604-2. The base stations 602- 1 and 602-2 are generally referred to herein collectively as base stations 602 and individually as base station 602. Likewise, the (macro) cells 604-1 and 604-2 are generally referred to herein collectively as (macro) cells 604 and individually as (macro) cell 604. The RAN may also include a number of low power nodes 606-1 through 606-4 controlling corresponding small cells 608-1 through 608-4. The low power nodes 606-1 through 606-4 can be small base stations (such as pico or femto base stations) or RRHs, or the like. Notably, while not illustrated, one or more of the small cells 608-1 through 608-4 may alternatively be provided by the base stations 602. The low power nodes 606-1 through 606-4 are generally referred to herein collectively as low power nodes 606 and individually as low power node 606. Likewise, the small cells 608-1 through 608-4 are generally referred to herein collectively as small cells 608 and individually as small cell 608. The cellular communications system 600 also includes an IMS corenetwork 610. The base stations 602 (and optionally the low power nodes 606) are connected to the IMS core network 610.

[0075] The base stations 602 and the low power nodes 606 provide service to wireless communication devices 612-1 through 612-5 in the corresponding cells 604 and 608. The wireless communication devices 612-1 through 612-5 are generally referred to herein collectively as wireless communication devices 612 and individually as wireless communication device 612. In the following description, the wireless communication devices 612 are oftentimes UEs, but the present disclosure is not limited thereto.

[0076] Figure 7 is a schematic block diagram of a network node 700 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node 700 may for example implement S-CSCF 104 or POI function device 202. As illustrated, the network node 700 includes a control system 702 that includes one or more processors 704 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and / or the like), memory / computer readable storage medium 706, and a network interface 708. The one or more processors 704 are also referred to herein as processing circuitry. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 606 and executed by the one or more processors 704.

[0077] In some embodiments, the function(s) are implemented in one or more computer programs 710 that are stored, e.g., in the memory 706 and executed by the one or more processors 704.

[0078] Figure 8 is a schematic block diagram that illustrates a virtualized embodiment of the network node 700 according to some embodiments of the present disclosure. This discussion is equally applicable to other types of network nodes. Further, other types of network nodes may have similar virtualized architectures. Again, optional features are represented by dashed boxes.

[0079] As used herein, a "virtualized" network node is an implementation of the network node 700 in which at least a portion of the functionality of the network node 700 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the network node 700 may include the control system 702. The network node 700 includes one or more processing nodes 800 coupled to or included as part of a network(s) 802.If present, the control system 702 or the radio unit(s) are connected to the processing node(s) 800 via the network 802. Each processing node 800 includes one or more processors 804 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 806, and a network interface 808.

[0080] In this example, functions 810 of the network node 700 described herein are implemented at the one or more processing nodes 800 or distributed across the one or more processing nodes 800 and the control system 702 in any desired manner. In some particular embodiments, some or all of the functions 810 of the network node 700 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 800. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) 800 and the control system 702 is used in order to carry out at least some of the desired functions 810.

[0081] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of network node 700 or a node (e.g., a processing node 800) implementing one or more of the functions 810 of the network node 700 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0082] Figure 9 is a schematic block diagram of the network node 700 according to some other embodiments of the present disclosure. The network node 700 includes one or more modules, each of which is implemented in software. The module(s) (e.g., S-CSCF 104 or POI function device 202) provide the functionality of the network node 700 described herein. This discussion is equally applicable to the processing node 800 of Figure 7 where the modules may be implemented at one of the processing nodes 800 or distributed across multiple processing nodes 800 and / or distributed across the processing node(s) 700 and the control system 702.

[0083] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of thesefunctional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processors (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.

[0084] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[0085] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

CLAIMS1. A method for performing International Mobile Equipment Identity, IMEI, based Lawful Interception, LI, monitoring for multi-device service performed by a Point of Interception, POI, Function device (202) associated with a Serving Call Session Control Function, S-CSCF, (104) of an Internet Protocol, IP, Multimedia Subsystem, IMS, network (610), the method comprising: examining (302) a first header of a first message (116) received by the S-CSCF (104) from an Application Server, AS, (106) to determine whether the first header comprises an IMEI that matches a target IMEI, wherein the first message (116) is associated with a first User Equipment, UE, (108-1) of the multi-device service; in response to the first header of the first message (116) comprising the IMEI that matches the target IMEI, initiating (304) monitoring of a first session associated with the first UE (108-1); examining (306) a request field of a second message (120) sent by the S-CSCF (104) to the first UE (108-1) to determine whether the request field of the second message (120) comprises an identifier that corresponds to the target IMEI; and in response to the request field comprising the identifier that corresponds to the target IMEI, initiating (308) monitoring of the first session associated with the first UE (108-1).

2. The method of claim 1, further comprising: in response to the first UE (108-1) answering (310) a call associated with the first session, collecting and providing (312) LI data associated with the first session to a Mediation and Delivery Function, MDF (204).

3. The method of claim 1, further comprising: determining (402) that a first header of a first message (118) of a second session associated with a second UE (108-2) of the multi-device service that is received from the AS (106) that the first header does not comprise the IMEI that matches the target IMEI; and determining (402) that a request field of a second message (122) of the second session associated with the second UE (108-2) of the multi-device service that is sent bythe S-CSCF (104) to the second UE (108-2) does not comprise the identifier that corresponds to the target IMEI.

4. The method of claim 3, further comprising: in response to the second UE (108-2) answering the call associated with the second session, ceasing (404) monitoring of the first session.

5. The method of claim 3, further comprising: in response to the S-CSCF (104) receiving an invite message (110) from an originating network (102), initiating (504) monitoring of the invite message (110) and subsequent messages; and in response to the second UE (108-2) answering the call associated with the second session, ceasing (506) monitoring of the first session and the second session.

6. The method of any of claims 1 to 5, wherein an Internet Protocol Multimedia Subsystem Public User Identify, IMPU, associated with the first message (116) does not match a target IMPU.

7. The method of any of claims 1 to 6, wherein the first header is an Accept-Contact header.

8. The method of any of claims 1 to 7, wherein the identifier in the request field is a contact Uniform Resource Identifier.

9. The method of claim 3, wherein the first session and second session are forked sessions associated with an invite message (110) received from an originating network (102).

10. The method of any of claims 1 to 3, wherein the first message (116) of the first session and the first message (114) of the second session are received by the S-CSCF (104) in response to the S-CSCF (104) forwarding an invite message (112) received from an originating network (102) to the AS (106).

11. A network node (700) that implements a Point of Interception, POI, Function device (202) associated with a Serving Call Session Control Function, S-CSCF, (104) of an Internet Protocol, IP, Multimedia Subsystem, IMS, network (610), that is configured to perform International Mobile Equipment Identity, IMEI, based Lawful Interception, LI, monitoring for multi-device service, the network node (700) comprising processing circuitry configured to cause the network node (700) to: examine (302) a first header of a first message (116) received by the S-CSCF (104) from an Application Server, AS, (106) to determine whether the first header comprises an IMEI that matches a target IMEI, wherein the first message (116) is associated with a first User Equipment, UE, (108-1) of the multi-device service; in response to the first header of the first message (116) comprising the IMEI that matches the target IMEI, initiate (304) monitoring of a first session associated with the first UE (108-1); examine (306) a request field of a second message (120) sent by the S-CSCF (104) to the first UE (108-1) to determine whether the request field of the second message (120) comprises an identifier that corresponds to the target IMEI; and in response to the request field comprising the identifier that corresponds to the target IMEI, initiate (308) monitoring of the first session associated with the first UE (108-1).

12. The network node (700) of claim 11, wherein the processing circuitry is further configured to: in response to the first UE (108-1) answering (310) a call associated with the first session, collect and provide (312) LI data associated with the first session to a Mediation and Delivery Function, MDF (204).

13. The network node (700) of claim 11, wherein the processing circuitry is further configured to: determine (402) that a first header of a first message (118) of a second session associated with a second UE (108-2) of the multi-device service that is received from the AS (106) that the first header does not comprise the IMEI that matches the target IMEI; anddetermine (402) that a request field of a second message (122) of the second session associated with the second UE (108-2) of the multi-device service that is sent by the S-CSCF (104) to the second UE (108-2) does not comprise the identifier that corresponds to the target IMEI.

14. The network node (700) of claim 13, wherein the processing circuitry is further configured to: in response to the second UE (108-2) answering the call associated with the second session, cease (404) monitoring of the first session.

15. The network node (700) of claim 13, wherein the processing circuitry is further configured to: in response to the S-CSCF (104) receiving an invite message (110) from an originating network (102), initiate (504) monitoring of the invite message (110) and subsequent messages; and in response to the second UE (108-2) answering the call associated with the second session, cease (506) monitoring of the first session and the second session.

16. The network node (700) of any of claims 11 to 15, wherein an Internet Protocol Multimedia Subsystem Public User Identify, IMPU, associated with the first message (116) does not match a target IMPU.

17. The network node (700) of any of claims 11 to 16, wherein the first header is an Accept-Contact header.

18. The network node (700) of any of claims 11 to 17, wherein the identifier in the request field is a contact Uniform Resource Identifier.

19. The network node (700) of claim 13, wherein the first session and second session are forked sessions associated with an invite message (110) received from an originating network (102).

20. The network node (700) of any of claims 11 to 13, wherein the first message (116) of the first session and the first message (114) of the second session are received by the S-CSCF (104) in response to the S-CSCF (104) forwarding an invite message (112) received from an originating network (102) to the AS (106).

21. A computer program (710) comprising instructions which, when executed on at least one processor (704), cause the processor (704) to carry out the method according to any of claims 1 to 10.

22. A carrier containing the computer program (710) of claim 21, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (706, 806).

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