Domain selection for terminating voice call

Field

The present invention relates to domain selection for terminating voice call. More specifically, the present invention exemplarily relates to measures (including methods, apparatuses and computer program products) for realizing domain selection for terminating voice call.

Background

The present specification generally relates to terminating access domain selection (T- ADS).

Currents T-ADS functionality takes into account only the access network's capabilities including the information whether internet protocol (IP) multimedia subsystem (IMS) voice over packet switched (PS) session is supported by the 3rd Generation Partnership Project (3GPP) access network, that had the most recent radio contact with the user equipment (UE) being the target of a terminating voice call.

Based on this information, the service centralization and continuity application server (SCC-AS) decides to use the packet domain (i.e. voice over packet switched (VoPS) or the circuit switched (CS) domain (i.e. CS voice) for a terminating voice call.

Currently, T-ADS service logic defined by the 3GPP may deliver fuzzy information to the SCC-AS.

Hence, the problem arises that as a consequence of such fuzzy information calls may fail. Namely, in a first example of a scenario, the PS domain is represented by a serving general packet radio service (GPRS) support node (SGSN) which is connected to the global system for mobile communication(GSM) enhanced radio access network (GERAN) and/or universal terrestrial radio access network (UTRAN), and does not support IMS voice over PS session. The T-ADS feature is not supported. In this scenario, further, the evolved packet system (EPS) domain is represented by a mobility management entity (MME) which is connected to the evolved universal terrestrial radio access network (E-UTRAN), and supports IMS voice over PS session in all tracking areas (TA). In addition, in this scenario, the UE is currently located in the E-UTRAN.

As a consequence of the assumed situation, the SCC-AS receives from the HSS an indication that IMS voice over PS session support is unknown, although it might be provided/served in the E-UTRAN.

In a second example of a scenario, the PS is represented by the SGSN which is connected to GERAN/UTRAN, and which does not support IMS voice over PS session. The T-ADS feature is supported.

In this scenario, further the EPS domain is represented by the MME which is connected to E-UTRAN and which supports IMS voice over PS session in all TA's, and this radio access technology (RAT) type has the freshest timestamp. In addition, in this scenario, the UE is currently located in the GERAN/UTRAN.

As a consequence of the assumed situation, the SCC-AS receives the indication that IMS voice over PS session is supported with the most recent RAT-type (i.e. RAT-type = E- UTRAN). Thus, since the UE is actually in the GERAN/UTRAN, the mobile terminating call (VoPS) will fail. Hence, there is a need to provide for domain selection for terminating voice call. Summary

Various exemplary embodiments of the present invention aim at addressing at least part of the above issues and/or problems and drawbacks.

Various aspects of exemplary embodiments of the present invention are set out in the appended claims.

According to an exemplary aspect of the present invention, there is provided a method in a terminating access domain selection scenario, said method comprising transmitting a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, receiving information indicative of whether a first switching domain is available for said terminating voice call, and deciding, based on said information, which switching domain of said first switching domain and a second switching domain is to be used for said terminating voice call.

According to an exemplary aspect of the present invention, there is provided a method in a terminating access domain selection scenario, said method comprising receiving a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, transmitting a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed, determining, based on an outcome of said query, whether a first switching domain is available for said terminating voice call, and transmitting information indicative of a result of said determining.

According to an exemplary aspect of the present invention, there is provided a method in a terminating access domain selection scenario, said method comprising receiving a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed, checking whether a first switching domain for a terminating voice call is provided in a recent tracking area and/or routing area of said terminal, and if said first switching domain is provided transmitting a paging message for said terminal.

According to an exemplary aspect of the present invention, there is provided a method in a terminating access domain selection scenario, said method comprising receiving a paging message including a service indication related to packet switched services, transmitting a paging response, and establishing a user plane for receiving a terminating voice call utilizing voice over packet switching.

According to an exemplary aspect of the present invention, there is provided an apparatus in a terminating access domain selection scenario, said apparatus comprising a transmitting device configured to transmit a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, a receiving device configured to receive information indicative of whether a first switching domain is available for said terminating voice call, and a deciding device configured to decide, based on said information, which switching domain of said first switching domain and a second switching domain is to be used for said terminating voice call.

According to an exemplary aspect of the present invention, there is provided an apparatus in a terminating access domain selection scenario, said apparatus comprising a receiving device configured to receive a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, a transmitting device configured to transmit a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed, and a determining device configured to determine, based on an outcome of said query, whether a first switching domain is available for said terminating voice call, wherein said transmitting device is configured to transmit information indicative of a result of said determining device.

According to an exemplary aspect of the present invention, there is provided an apparatus in a terminating access domain selection scenario, said apparatus comprising a receiving device configured to receive a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed, a checking device configured to check whether a first switching domain for a terminating voice call is provided in a recent tracking area and/or routing area of said terminal, and a transmitting device, wherein if said first switching domain is provided said transmitting device configured to transmit a paging message for said terminal. According to an exemplary aspect of the present invention, there is provided an apparatus in a terminating access domain selection scenario, said apparatus comprising a receiving device configured to receive a paging message including a service indication related to packet switched services, a transmitting device configured to transmit a paging response, and an establishing device configured to establish a user plane for receiving a terminating voice call utilizing voice over packet switching.

According to an exemplary aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code which, when the program is run on a computer (e.g. a computer of an apparatus according to any one of the aforementioned apparatus-related exemplary aspects of the present invention), is configured to cause the computer to carry out the method according to any one of the aforementioned method-related exemplary aspects of the present invention.

Such computer program product may comprise (or be embodied) a (tangible) computer- readable (storage) medium or the like on which the computer-executable computer program code is stored, and/or the program may be directly loadable into an internal memory of the computer or a processor thereof.

Any one of the above aspects enables an efficient improvement of terminating voice over packet handling to thereby solve at least part of the problems and drawbacks identified in relation to the prior art. By way of exemplary embodiments of the present invention, there is provided domain selection for terminating voice call. More specifically, by way of exemplary embodiments of the present invention, there are provided measures and mechanisms for realizing domain selection for terminating voice call.

Thus, improvement is achieved by methods, apparatuses and computer program products enabling/realizing domain selection for terminating voice call.

Brief description of the drawings

In the following, the present invention will be described in greater detail by way of non- limiting examples with reference to the accompanying drawings, in which

Figure 1 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 2 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention, Figure 3 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 4 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 5 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 6 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention,

Figure 7 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention, Figure 8 is a schematic diagram of a procedure according to exemplary embodiments of the present invention,

Figure 9 is a schematic diagram of a procedure according to exemplary embodiments of the present invention, Figure 10 is a schematic diagram of a procedure according to exemplary embodiments of the present invention,

Figure 1 1 is a schematic diagram of a procedure according to exemplary embodiments of the present invention, and Figure 12 is a block diagram alternatively illustrating apparatuses according to exemplary embodiments of the present invention.

Detailed description of drawings and embodiments of the present invention

The present invention is described herein with reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present invention. A person skilled in the art will appreciate that the invention is by no means limited to these examples, and may be more broadly applied.

It is to be noted that the following description of the present invention and its embodiments mainly refers to specifications being used as non-limiting examples for certain exemplary network configurations and deployments. Namely, the present invention and its embodiments are mainly described in relation to 3GPP specifications being used as non- limiting examples for certain exemplary network configurations and deployments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the invention in any way. Rather, any other communication or communication related system deployment, etc. may also be utilized as long as compliant with the features described herein.

Hereinafter, various embodiments and implementations of the present invention and its aspects or embodiments are described using several variants and/or alternatives. It is generally noted that, according to certain needs and constraints, all of the described variants and/or alternatives may be provided alone or in any conceivable combination (also including combinations of individual features of the various variants and/or alternatives).

According to exemplary embodiments of the present invention, in general terms, there are provided measures and mechanisms for (enabling/realizing) domain selection for terminating voice call. Figure 1 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. The apparatus may be a network node 10 such as a SCC-AS comprising a transmitting device 1 1 , a receiving device 12, and a deciding device 13. The transmitting device 1 1 transmits a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed. The receiving device 12 receives information indicative of whether a first switching domain is available for said terminating voice call. The deciding device 13 decides, based on said information, which switching domain of said first switching domain and a second switching domain is to be used for said terminating voice call. Figure 8 is a schematic diagram of a procedure according to exemplary embodiments of the present invention. The apparatus according to Figure 1 may perform the method of Figure 8 but is not limited to this method. The method of Figure 8 may be performed by the apparatus of Figure 1 but is not limited to being performed by this apparatus.

As shown in Figure 8, a procedure according to exemplary embodiments of the present invention comprises an operation of transmitting (S81 ) a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, an operation of receiving (S82) information indicative of whether a first switching domain is available for said terminating voice call, and an operation of deciding (S83), based on said information, which switching domain of said first switching domain and a second switching domain is to be used for said terminating voice call.

Figure 2 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. In particular, Figure 2 illustrates a variation of the apparatus shown in Figure 1 . The apparatus according to Figure 2 may thus further comprise a determining device 21 . According to a variation of the procedure shown in Figure 8, exemplary details of the deciding operation (S83) are given, which are inherently independent from each other as such.

Such exemplary deciding operation (S83) according to exemplary embodiments of the present invention may comprise, if said information is indicative of that said first switching domain is not supported, an operation of determining, that said second switching domain is to be used for said terminating voice call, and if said information is indicative of that said first switching domain is supported, an operation of determining, that said first switching domain is to be used for said terminating voice call. According to further exemplary embodiments of the present invention, said first switching domain is a packet switching domain, said second switching domain is a circuit switching domain, said information indicative of that said first switching domain is not supported is internet protocol multimedia subsystem voice over packet switching not supported information, and said information indicative of that said first switching domain is supported is internet protocol multimedia subsystem voice over packet switching supported information and includes a radio access technology type accessed by said terminal.

Figure 3 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. The apparatus may be a network node 30 such as a HSS comprising a receiving device 31 , a transmitting device 32, and a determining device 33. The receiving device 31 receives a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed. The transmitting device 32 transmits a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed. The determining device 33 determines, based on an outcome of said query, whether a first switching domain is available for said terminating voice call. The transmitting device 32 further transmits information indicative of a result of said determining device 33.

Figure 9 is a schematic diagram of a procedure according to exemplary embodiments of the present invention. The apparatus according to Figure 3 may perform the method of Figure 9 but is not limited to this method. The method of Figure 9 may be performed by the apparatus of Figure 3 but is not limited to being performed by this apparatus.

As shown in Figure 9, a procedure according to exemplary embodiments of the present invention comprises an operation of receiving (S91 ) a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, an operation of transmitting (S92) a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed, an operation of determining (S93), based on an outcome of said query, whether a first switching domain is available for said terminating voice call, and an operation of transmitting (S94) information indicative of a result of said determining. Figure 4 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. In particular, Figure 4 illustrates a variation of the apparatus shown in Figure 3. The apparatus according to Figure 4 may thus further comprise a deciding device 41 . According to a variation of the procedure shown in Figure 9, exemplary details of the determining operation (S93) are given, which are inherently independent from each other as such.

Such exemplary determining operation (S93) according to exemplary embodiments of the present invention may comprise, if, as said outcome of said query, a paging success indication, an indication that said first switching domain is supported, and a radio access technology type, are received, an operation of deciding, that said first switching domain is supported in combination with said radio access technology type, and otherwise an operation of deciding that said first switching domain is not supported. According to further exemplary embodiments of the present invention, said first switching domain is a packet switching domain, if said result of said determining is that said first switching domain is not supported, said information indicative of said result is internet protocol multimedia subsystem voice over packet switching not supported information, and if said result of said determining is that said first switching domain is not supported, said information indicative of said result is internet protocol multimedia subsystem voice over packet switching supported information and includes a radio access technology type accessed by said terminal.

Figure 5 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. The apparatus may be a network node 50 such as a SGSN, a MME or an authentication, authorization and accounting (AAA) entity comprising a receiving device 51 , a checking device 52, and a transmitting device 53. The receiving device 51 receives a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed. The checking device 52 checks whether a first switching domain for a terminating voice call is provided in a recent tracking area and/or routing area of said terminal. The transmitting device 53, if said first switching domain is provided, transmits a paging message for said terminal.

Figure 10 is a schematic diagram of a procedure according to exemplary embodiments of the present invention. The apparatus according to Figure 5 may perform the method of Figure 10 but is not limited to this method. The method of Figure 10 may be performed by the apparatus of Figure 5 but is not limited to being performed by this apparatus.

As shown in Figure 10, a procedure according to exemplary embodiments of the present invention comprises an operation of receiving (S101 ) a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed, an operation of checking (S102) whether a first switching domain for a terminating voice call is provided in a recent tracking area and/or routing area of said terminal, and if said first switching domain is provided (YES in Fig. 10 between steps S102 and S103), an operation of transmitting (S103) a paging message for said terminal. Figure 6 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. In particular, Figure 6 illustrates a variation of the apparatus shown in Figure 5. The apparatus according to Figure 6 may thus further comprise a determining device 61 .

According to a variation of the procedure shown in Figure 10, exemplary additional operations are given, which are inherently independent from each other as such. According to such variation, an exemplary method according to exemplary embodiments of the present invention may comprise an operation of determining, based on an outcome of said paging message, whether said first switching domain is supported.

According to a variation of the procedure shown in Figure 10, exemplary details of the determining operation are given, which are inherently independent from each other as such.

Such exemplary determining operation according to exemplary embodiments of the present invention may comprise, if, as said outcome of said paging message, a paging response is received, an operation of transmitting a paging success indication, an indication that said first switching domain is supported, and a radio access technology type accessed by said terminal, and otherwise, an operation of transmitting a paging failure indication and an indication that said first switching domain is not supported.

According to further exemplary embodiments of the present invention, said first switching domain is a packet switching domain, said indication that said first switching domain is not supported is internet protocol multimedia subsystem voice over packet switching not supported information, and said indication that said first switching domain is supported is internet protocol multimedia subsystem voice over packet switching supported information and includes said radio access technology type accessed by said terminal.

According to a still further variation of the procedure shown in Figure 10, said paging message for said terminal includes a service indication related to packet switched services. Figure 7 is a block diagram illustrating an apparatus according to exemplary embodiments of the present invention. The apparatus may be a terminal 70 such as a UE comprising a receiving device 71 , a transmitting device 72, and an establishing device 73. The receiving device 71 receives a paging message including a service indication related to packet switched services. The transmitting device 72 transmits a paging response. The establishing device 73 establishes a user plane for receiving a terminating voice call utilizing voice over packet switching.

Figure 1 1 is a schematic diagram of a procedure according to exemplary embodiments of the present invention. The apparatus according to Figure 7 may perform the method of Figure 1 1 but is not limited to this method. The method of Figure 1 1 may be performed by the apparatus of Figure 7 but is not limited to being performed by this apparatus.

As shown in Figure 1 1 , a procedure according to exemplary embodiments of the present invention comprises an operation of receiving (S1 1 1 ) a paging message including a service indication related to packet switched services, an operation of transmitting (S1 12) a paging response, and an operation of establishing (S1 13) a user plane for receiving a terminating voice call utilizing voice over packet switching.

In the following, the above mentioned exemplary embodiments are described in more specific details.

Namely, according to exemplary embodiments of the present invention, the T-ADS handling supports a pre-paging option, that is, an option to page a terminal in advance.

In case the SCC-AS (e.g. network node 10) has set this pre-paging option in a Sh request towards the HSS (e.g. network 30), the HSS triggers a T-ADS query (if supported) including the pre-paging option towards the appropriate network nodes (e.g. SGSN, MME, AAA 50). If IMS voice over PS session is supported in the UE's (i.e. terminal 70) recent TA/routing area (RA), the serving node triggers a paging message with a service indication "PS services" to the UE.

In the case the UE (i.e. terminal) is not located in this radio access network (RAN), the paging fails. The related serving network node delivers, to the HSS, an "IMS voice over PS session" not supported indication including the RAT type, a time stamp of the latest radio contact (e.g. latest processed RA update message), and a paging failed indication. In the other case, namely, in case the UE is located in the RAN, the UE triggers a paging response to the serving network node and establishes the user plane to receive the VoPS call. With such behavior according to aspects of the present invention, a faster VoPS call establishment can be achieved. Namely, currently the user plane might need to be re- established, after the SCC-AS has decided to use the packet domain for the VoPS call. However, with the approach according to the present invention, the user plane is already established during this phase.

In the other case, i.e., in case the UE is located in the RAN and triggered the paging response to the serving network node, the serving node delivers, to the HSS, an "IMS voice over PS session" supported indication including the RAT type, the time stamp of the last radio contact (related to the paging response message), and a paging success indication.

The HSS takes the first response with a paging success indication and delivers this information to the SCC-AS. In all other scenarios (e.g. the response including the paging failed indication is received, no response is received, since e.g. the serving node detects that IMS voice over PS session is not supported in the UE's recent TA/RA), the HSS delivers an "IMS voice over PS session" not supported to the SCC-AS.

Upon receipt of the response from the HSS at the SCC-AS, the SCC-AS triggers the voice call either using the packet domain (IMS voice over PS sessions supported) using the still/already established user plane (VoPS), or using the circuit domain (IMS voice over PS sessions not supported).

As a consequence, the voice call succeeds in any case.

Namely, returning to the above mentioned scenario examples, the SCC-AS according to the present invention receives the following, upon which the appropriate decision on the used domain can be made.

In the first example of a scenario, the SCC-AS receives IMS voice over PS session supported with RAT type = "E-UTRAN", and can thus exploit the providing in the E- UTRAN.

In the second example of a scenario, the SCC-AS receives the indication that IMS voice over PS session is not supported. Accordingly, the mobile terminating call will not fail, since, based on this correct information, the SCC-AS decides that the mobile terminal call shall use the CS domain, which is supported. Thus, an SCC-AS which, according to the present invention utilizes the pre-paging option, receives the IMS voice over PS session supported indication including the RAT type only in case the UE is located in the corresponding RAN and the area is capable of VoPS.

Of course, in case that VoPS sessions are supported/not supported homogeneously in all areas of the packet domain, the query of the serving network nodes is not required (specified in an operator policy).

It is again be noted that the foregoing description of the present invention and its embodiments mainly refers to specifications being used as non-limiting examples for certain exemplary network configurations and deployments, and in particular has been described in relation to VoPS in mobile networks as non-limiting examples. However, the present invention is likewise applicable for voice over Wifi (VoWifi) and other radio access technologies (which might be capable for VoPS).

The above-described procedures and functions may be implemented by respective functional elements, processors, or the like, as described below.

In the foregoing exemplary description of the network entity, only the units that are relevant for understanding the principles of the invention have been described using functional blocks. The network entity may comprise further units that are necessary for its respective operation. However, a description of these units is omitted in this specification. The arrangement of the functional blocks of the devices is not construed to limit the invention, and the functions may be performed by one block or further split into sub- blocks.

When in the foregoing description it is stated that the apparatus, i.e. network node (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that a (i.e. at least one) processor or corresponding circuitry, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured circuitry or means for performing the respective function (i.e. the expression "unit configured to" is construed to be equivalent to an expression such as "means for"). In Figure 12, an alternative illustration of apparatuses according to exemplary embodiments of the present invention is depicted. As indicated in Figure 12, according to exemplary embodiments of the present invention, the apparatus (network node) 10' (corresponding to the network node 10) comprises a processor 1201 , a memory 1202 and an interface 1203, which are connected by a bus 1204 or the like. Further, according to exemplary embodiments of the present invention, the apparatus (network node) 30' (corresponding to the network node 30) comprises a processor 121 1 , a memory 1212 and an interface 1213, which are connected by a bus 1214 or the like. Further, according to exemplary embodiments of the present invention, the apparatus (network node) 50' (corresponding to the network node 50) comprises a processor 1221 , a memory 1222 and an interface 1223, which are connected by a bus 1224 or the like. Further, according to exemplary embodiments of the present invention, the apparatus (terminal) 70' (corresponding to the terminal 70) comprises a processor 1231 , a memory 1232 and an interface 1233, which are connected by a bus 1234 or the like,, and the apparatuses may be connected via links 1241/1242/1243, respectively.

The processor 1201/121 1 /1221 /1231 and/or the interface 1203/1213/1223/1233 may also include a modem or the like to facilitate communication over a (hardwire or wireless) link, respectively. The interface 1203/1213/1223/1233 may include a suitable transceiver coupled to one or more antennas or communication means for (hardwire or wireless) communications with the linked or connected device(s), respectively. The interface 1203/1213/1223/1233 is generally configured to communicate with at least one other apparatus, i.e. the interface thereof.

The memory 1202/1212/1222/1232 may store respective programs assumed to include program instructions or computer program code that, when executed by the respective processor, enables the respective electronic device or apparatus to operate in accordance with the exemplary embodiments of the present invention.

In general terms, the respective devices/apparatuses (and/or parts thereof) may represent means for performing respective operations and/or exhibiting respective functionalities, and/or the respective devices (and/or parts thereof) may have functions for performing respective operations and/or exhibiting respective functionalities.

When in the subsequent description it is stated that the processor (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that at least one processor, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured means for performing the respective function (i.e. the expression "processor configured to [cause the apparatus to] perform xxx-ing" is construed to be equivalent to an expression such as "means for xxx-ing"). According to exemplary embodiments of the present invention, an apparatus representing the network node 10 comprises at least one processor 1201 , at least one memory 1202 including computer program code, and at least one interface 1203 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 1201 , with the at least one memory 1202 and the computer program code) is configured to perform transmitting a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed (thus the apparatus comprising corresponding means for transmitting), to perform receiving information indicative of whether a first switching domain is available for said terminating voice call (thus the apparatus comprising corresponding means for receiving), and to perform deciding, based on said information, which switching domain of said first switching domain and a second switching domain is to be used for said terminating voice call (thus the apparatus comprising corresponding means for deciding).

According to exemplary embodiments of the present invention, an apparatus representing the network node 30 comprises at least one processor 121 1 , at least one memory 1212 including computer program code, and at least one interface 1213 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 121 1 , with the at least one memory 1212 and the computer program code) is configured to perform receiving a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed (thus the apparatus comprising corresponding means for receiving), to perform transmitting a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed (thus the apparatus comprising corresponding means for transmitting), to perform determining, based on an outcome of said query, whether a first switching domain is available for said terminating voice call (thus the apparatus comprising corresponding means for determining), and to perform transmitting information indicative of a result of said determining (thus the apparatus comprising corresponding means for transmitting). According to exemplary embodiments of the present invention, an apparatus representing the network node 50 comprises at least one processor 1221 , at least one memory 1222 including computer program code, and at least one interface 1223 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 1221 , with the at least one memory 1222 and the computer program code) is configured to perform receiving a query for terminating access domain selection including an indication that a pre-paging of said terminal is to be performed (thus the apparatus comprising corresponding means for receiving), to perform checking whether a first switching domain for a terminating voice call is provided in a recent tracking area and/or routing area of said terminal (thus the apparatus comprising corresponding means for checking), and to perform transmitting a paging message for said terminal (thus the apparatus comprising corresponding means for transmitting).

According to exemplary embodiments of the present invention, an apparatus representing the terminal 70 comprises at least one processor 1231 , at least one memory 1232 including computer program code, and at least one interface 1233 configured for communication with at least another apparatus. The processor (i.e. the at least one processor 1231 , with the at least one memory 1232 and the computer program code) is configured to perform receiving a paging message including a service indication related to packet switched services (thus the apparatus comprising corresponding means for receiving), to perform transmitting a paging response (thus the apparatus comprising corresponding means for transmitting), and to perform establishing a user plane for receiving a terminating voice call utilizing voice over packet switching (thus the apparatus comprising corresponding means for establishing).

For further details regarding the operability/functionality of the individual apparatuses, reference is made to the above description in connection with any one of Figures 1 to 1 1 , respectively.

For the purpose of the present invention as described herein above, it should be noted that

- method steps likely to be implemented as software code portions and being run using a processor at a network server or network entity (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules therefore), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the embodiments and its modification in terms of the functionality implemented;

- method steps and/or devices, units or means likely to be implemented as hardware components at the above-defined apparatuses, or any module(s) thereof, (e.g., devices carrying out the functions of the apparatuses according to the embodiments as described above) are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field- programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components;

- devices, units or means (e.g. the above-defined network entity or network register, or any one of their respective units/means) can be implemented as individual devices, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, unit or means is preserved;

- an apparatus like the user equipment and the network entity /network register may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example. In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.

Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above-described concepts of methodology and structural arrangement are applicable.

In view of the above, there are provided measures for domain selection for terminating voice call. Such measures exemplarily comprise transmitting a request for a terminating voice call for a terminal including an indication that a pre-paging of said terminal is to be performed, receiving information indicative of whether a first switching domain is available for said terminating voice call, and deciding, based on said information, which switching domain of said first switching domain and a second switching domain is to be used for said terminating voice call. Even though the invention is described above with reference to the examples according to the accompanying drawings, it is to be understood that the invention is not restricted thereto. Rather, it is apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

List of acronyms and abbreviations

3GPP 3rd Generation Partnership Project

AAA authentication, authorization and accounting

CS circuit switched

E-UTRAN evolved universal terrestrial radio access network

EPS evolved packet system

GERAN GSM enhanced radio access network

GPRS general packet radio service

GSM global system for mobile communication

IMS IP multimedia subsystem

IP internet protocol

MME mobility management entity

PS packet switched

RA routing area

RAN radio access network

RAT radio access technology

SCC-AS service centralization and continuity application server

SGSN serving GPRS support node

TA tracking area

T-ADS terminating access domain selection

UE user equipment

UTRAN universal terrestrial radio access network VoPS voice over packet switched

VoWifi voice over Wifi