WO2015020585A1

WO2015020585A1 - Handling of emergency call handover

Info

Publication number: WO2015020585A1
Application number: PCT/SE2014/050706
Authority: WO
Inventors: Lena MELIN; Martin Israelsson
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2013-08-08
Filing date: 2014-06-11
Publication date: 2015-02-12

Abstract

Embodiments herein relate to a method in a network node (17,18) for handling an emergency call from a wireless device (10) in a radio communications network (1). The network node generates a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology. Furthermore, the network node (17,18) adds an identity of the wireless device (10) to the message; and transmits the message to a radio access network node (16) of the second radio access technology.

Description

HANDLING OF EMERGENCY CALL HANDOVER

TECHNICAL FIELD

The embodiments herein relate to a network node, a radio access network node and methods therein and in a system. In particular embodiments herein relate to handle an emergency call in a radio communications network. BACKGROUND

In a typical radio communications network, wireless devices, also known as mobile stations and/or user equipments (UE), communicate via a Radio Access Network (RAN) to one or more core networks. The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a "NodeB" or "eNodeB". A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole radio communications network is also broadcasted in the cell. One base station may have one or more cells. A cell may be a downlink and/or an uplink cell. The base stations communicate over the air interface operating on radio frequencies with the mobile devices within range of the base stations.

Internet Protocol Multimedia (IPMM) services provide a dynamic combination of voice, video, messaging, data, etc, within the same session. By growing the numbers of basic applications and the media which it is possible to combine, the number of services offered to the end users will grow, and the inter-personal communication experience will be enriched. This will lead to a new generation of personalised, rich multimedia communication services, including so-called "combinational IP Multimedia" services.

IP Multimedia Subsystem (IMS) is the technology defined by the Third Generation

Partnership Project (3GPP) to provide IP Multimedia services over radio communications networks. IMS provides key features to enrich the end-user person-to-person

communication experience through the integration and interaction of services. IMS allows new rich person-to-person, or client-to-client, as well as person-to-content, or client-to- server, communications over an IP-based network. The IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between wireless devices, or wireless devices and application servers. The Session Description Protocol (SDP), carried by SIP signalling, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to-user protocol, IMS allows operators and service providers to control user access to services and to charge users accordingly. Other protocols are used for media transmission and control, such as Real-time Transport Protocol (RTP) and Real-time Transport Control Protocol (RTCP).

Existing radio communications network deployments are dominated by the second generation (2G) and third generation (3G) standards. The process of rolling out so-called fourth generation (4G) networks has just begun, and it will be many years before 4G network coverage is sufficient to allow 2G and 3G networks to be withdrawn completely. A fundamental requirement for real-time service provision is a seamless handover of services for subscribers roaming across cell boundaries of the RAN. Given the ongoing co-existence of 2G, 3G and 4G networks, it is particularly desirable to allow for the handover of real-time service connections such as voice calls between the different radio access technologies.

Considering further the 4G technology, this is being specified under the name Long Term Evolution (LTE) and System Architecture Evolution (SAE) in 3GPP. The LTE radio access network technology implements only a packet switched access, in contrast to 2G and 3G, using Global System for Mobile communication (GSM), Genera! Packet Radio Sen/ices (GPRS) and Enhanced Data rates for GSM Evolution (EDGE) Radio Access Network (GERAN) and Universal Terrestrial Radio Access Network (UTRAN) radio access network technologies respectively, which provide for both packet switched and circuit switched access. In 2G and 3G networks, packet switched connections are used to carry data whilst circuit switched connections are used for real-time services such as voice calls. In 4G networks, all services will be carried via packet switched

connections. In the case of a voice call initiated when a wireless device is attached to a LTE radio access network, termed Evolved UTRAN or E-UTRAN, that call will make use of a packet switched connection. If it is necessary for the call to be transferred to a 2G or 3G radio access network, e.g. because the wireless device roams out of the coverage area of the E-UTRAN and into that of a GERAN or UTRAN network, the call must be switched from a packet switched (PS) access to a circuit switched (CS) access, i.e. an Access Transfer is required. Of course, the process for implementing the handover must be seamless such that little or no disruption of the call is perceived by a user of the wireless device. An appropriate access handover mechanism is also required in the case of the handover of a call from a PS access using a 3G UTRAN, High Speed Packet Access (HSPA), access network to a CS call using either 3G UTRAN access or 2G GSM access.

A Universal Mobile Telecommunications System (UMTS) is a third generation radio communications system, which evolved from the 2G GSM. The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for wireless devices. In a forum known as the 3GPP, telecommunications suppliers propose and agree upon standards for e.g. third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some versions of the RAN as e.g. in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.

Specifications for the Evolved Packet System (EPS) have been completed within the 3^rd 3GPP and this work continues in the coming 3GPP releases. The EPS comprises the E-UTRAN, also known as the LTE radio access, and the Evolved Packet Core (EPC), also known as the SAE core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base stations are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially "flat" architecture comprising radio base stations without reporting to RNCs.

An IMS anchored emergency call that is started within LTE/EPC might, if coverage becomes bad, have to be transferred to WCDMA using the Single Radio Voice Call Continuity (SRVCC), handover from Packet Switched (PS) to Circuit Switched (CS), procedure. During a SRVCC procedure a speech component of the call is transformed from PS to CS, however the session within LTE normally also includes packet bearers, supposed to be transferred to WCDMA with Packet Switched handover (PSHO).

At the WCDMA side a request for a combined CS and PS handover is then received. The RNC of the WCDMA side may e.g. receive Radio Access Network

Application Part (RANAP) Relocation Request messages over interface lu-PS as well as interface lu-CS and the Information Element (IE) 'Number of lu instances' within container IE 'Source RNC to Target RNC Transparent Container', defined in section 9.2.1.28, in 3GPP TS 25.413 version 1 1.0.0, is set to '2'.

The co-ordination of requests from both CN instances is done by using a unique identity of the wireless device received over RANAP, this identity is the International Mobile Subscriber Identity number (IMSI) included in IE 'Permanent Non Access Stratum (NAS) UE Identity'.

For an emergency call the IMSI might not be known. Therefore a co-ordination of the CS and PS domain is currently not possible in case of emergency call. The RNC or another radio access network node could in this case choose to reject the relocation request completely - or - in the SRVCC case - accept the CS component only. An attempted SRVCC for an emergency call will thus have to drop the PS components, leading to a reduced performance of the radio communications network.

SUMMARY

An object of embodiments herein is to provide a mechanism that supports handover of an emergency call without reduced performance of the radio communications network.

The object is achieved by a method in a network node for handling an emergency call from a wireless device in a radio communications network. The network node, e.g. a Mobile Switching Centre (MSC) server or a Serving GPRS Support Node (SGSN), generates a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The network node adds an identity of the wireless device to the message, and transmits the message to a radio access network node, e.g. an RNC, of the second radio access technology.

The object is further achieved by a method in a radio access network node for handling an emergency call from a wireless device in a radio communications network. The radio access network node receives a message, from a network node, indicating a handover of the emergency call from a first radio access technology to a second radio access technology, the radio access network node being of the second radio access technology. The message comprises an identity of the wireless device. The radio access network node determines how to handle the handover based on the identity in the received message.

The object is additionally achieved by a network node for handling an emergency call from a wireless device in a radio communications network. The network node is configured to generate a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The network node is further configured to add an identity of the wireless device to the message. The network node is configured to transmit the message to a radio access network node of the second radio access technology.

The object is furthermore achieved by a radio access network node for handling an emergency call from a wireless device in a radio communications network. The radio access network node is configured to receive a message, from a network node, indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The radio access network node is of the second radio access technology and the message comprises an identity of the wireless device. The radio access network node is further configured to determine how to handle the handover based on the identity in the received message.

The object is also achieved by a method in a system comprised in a radio communications network for handling an emergency call from a wireless device. The system comprises one or more network nodes and a radio access network node. The one or more network nodes transmits to the radio access network node, a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The message or messages comprise an identity of the wireless device and the radio access network node is of the second radio access technology. The radio access network node determines how to handle the handover based on the identity in the received message or messages.

Embodiments herein suggest that the identity of the wireless device, e.g.

International Mobile Equipment Identity (IMEI), is transferred from e.g. LTE to WCDMA during a handover process, such as the SRVCC, to enable co-ordination of the handover signalling for e.g. the PS and CS domains. An advantage of embodiments herein is that it is made possible to handover both CS call and any PS components during an SRVCC of an emergency session as the identity is added into the message. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described in more detail in relation to the enclosed drawings, in which:

Fig. 1 is a schematic overview depicting a wireless communication network according to embodiments herein. Fig. 2 shows a schematic combined flowchart and signalling scheme in a radio communications network according to embodiments herein.

Fig. 3 is a schematic flowchart depicting a method in network node according to embodiments herein.

Fig. 4 is a schematic flowchart depicting a method in radio access network node according to embodiments herein.

Fig. 5 is a block diagram depicting a network node according to embodiments herein. Fig. 6 is a block diagram depicting a radio access network node according to

embodiments herein.

DETAILED DESCRIPTION

Embodiments herein relate to radio communications networks in general. Fig. 1 is a schematic overview depicting a radio communications network 1 , also referred to as a wireless communication network or mobile network. The radio communications network 1 comprises one or more RANs and one or more CNs. The radio communications network 1 may use a number of different technologies, such as Long Term Evolution (LTE), LTE- Advanced, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. The radio communications network 1 is exemplified herein to comprise an LTE network and a WCDMA network.

In the radio communications network 1 , a wireless device 10, also known as a mobile station, a user equipment and/or a wireless terminal, communicates via a Radio Access Network (RAN) to one or more core networks (CN). It should be understood by the skilled in the art that "wireless device" is a non-limiting term which means any wireless terminal, user equipment, Machine Type Communication (MTC) device, a Device to Device (D2D) terminal, or node e.g. Personal Digital Assistant (PDA), laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within respective cell.

The radio communications network 1 covers a geographical area which is divided into cell areas, e.g. a cell 11 being served by a radio base station 12. The radio base station 12 may also be referred to as a first radio base station and e.g. a NodeB, an evolved Node B (eNB, eNode B), a base transceiver station, Access Point Base Station, base station router, or any other network unit capable of communicating with a wireless device within the cell served by the radio base station depending e.g. on the radio access technology and terminology used. The radio base station 12 may serve one or more cells, such as the cell 1 1.

A cell is a geographical area where radio coverage is provided by radio base station equipment at a base station site or at remote locations in Remote Radio Units (RRU). The cell definition may also incorporate frequency bands and radio access technology used for transmissions, which means that two different cells may cover the same geographical area but using different frequency bands. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell 11 uniquely in the whole radio communications network 1 is also broadcasted in the cell 11. The radio base station 12 communicates over the air or radio interface operating on radio frequencies with the wireless device 10 within range of the radio base station 12. The wireless device 10 transmits data over the radio interface to the radio base station 12 in Uplink (UL) transmissions and the radio base station 12 transmits data over an air or radio interface to the wireless device 10 in Downlink (DL) transmissions.

Furthermore, the radio communications network 1 comprises a core network node such as a Mobility Management Entity (MME) 13.

The radio base station 12 serving the wireless device 10 is herein denoted as a first node. A node providing a second cell 14 is denoted as a second node 15 or second radio base station herein. The second node 15 is a radio access network node e.g. a radio base station of a different radio access technology such as the WCDMA than the radio base station 12. A radio access network node 16, such as a radio network controller (RNC), a radio base station, or a base station controller (BSC), supervises and coordinates various activities of the second node 15 connected thereto. It should be noted that the second node 15 may be implemented in the radio access node 16 e.g. in an eNB. The radio access network node 16 is typically connected to one or more core networks (CN). A Mobile (Services) Switching Centre (MSC) server 17 is comprised in a circuit switched Core Network. The MSC server 17 is a telephone exchange that makes a voice connection between wireless devices within the radio access network and other radio access networks. A Serving GPRS Support Node (SGSN) 18 is comprised in a packet Switched Core network. The SGSN 18 handles all packet switched data within the network, e.g. the mobility management and authentication of wireless devices. The MSC server 17 and the SGSN 18 being referred to as network nodes 19 herein.

An Sv interface is an interface between the MME 13 or the SGSN 18 and MSC server 17 enhanced for SRVCC. Sv interface is used to support Inter-RAT handover from IMS based voice service over EPS to CS domain over 3GPP UTRAN/GERAN access or from UTRAN (HSPA) to 3GPP UTRAN/GERAN access and to support Inter-RAT handover from IMS based voice and video service over EPS to CS domain over 3GPP UTRAN access. Sv interface is also used to support Inter-RAT handover from voice service in CS domain over 3GPP UTRAN/GERAN access to IMS based service over LTE or UTRAN (HSPA).

Embodiments herein relate to a Relocation and Inter Radio Access Technology (I RAT) handover, i.e. a handover between a first and a second radio access technology, in particular Single Radio Voice Call Continuity (SRVCC) between LTE and WCDMA, but the first and second radio access technologies may also be the same radio access technology. In some examples, the first radio access technology supports a packet switched call and the second radio access technology supports a circuit switched call, or the first radio access technology supports a circuit switched call and the second radio access technology supports a packet switched call.

When Voice over LTE (VoLTE) is implemented in LTE/EPS, emergency calls will be possible to perform within LTE. However, LTE is a relative new system and other radio access technologies, such as WCDMA or similar, is needed as a complement in areas where radio coverage is not yet offered.

When emergency calls are started within e.g. LTE/EPS but the wireless device 10 loses radio coverage a handover to another radio access technology is required in order not to drop the call. This means that a SRVCC procedure, a mechanism to handover a call from PS to CS, is required to support also emergency calls.

The MME 13 knows that the SRVCC is for emergency purposes and when the SRVCC is initiated the MME 13 sends a SRVCC CS to PS request, defined in 3GPP TS 29.280 section 5.2.2 v. 1 1 ,4,0. This includes some vital Information Elements, seen below: e.g. the Mobile Equipment Identity (MEI) as well as the Emergency Indicator.

I ES within the SRVCC CS to PS Request, sent on the Sv interface:

ME Identity This IE is included in the message for the MEI

(MEI) following cases:

• The wireless device 10 is emergency

attached and it is Universal Integrated

Circuit Card-less (UlCCIess), i.e. without a

Subscriber Identity Module (SIM) card

• The wireless device 10 is emergency

attached and the I MSI is not authenticated This IE is included for all SRVCC calls if

0 available in the MME 13 or SGSN 18(NOTE 2).

Sv Flags This IE is included if any one of the Sv applicable flags is set to 1. Flags

The following flags are applicable:

• 'Emlnd': this flag is sent if this session is for

an emergency call.

• 'ICS': this flag is sent to request IMS

Centralized Service support.

• VHO': this flag is sent if the MME 13

requests the Single Radio Voice Call

Continuity (vSRVCC) Handover (HO).

According to embodiments herein a message is transferred from e.g. the MSC server 17 to the radio access network node 16 e.g. a RANAP Relocation Request, defined in 3GPP TS 25.413 section 9.1.10 v 1 1.4.0 but with a modification. An identity, a unique identity, of the wireless device 10 such as IMEI and in some embodiments also an emergency indicator is included into the message. New Information Elements may be used for this. The two lEs may be independent and embodiments herein cover cases where both lEs are added in the specification, and also cases where only one of the proposed lEs is added to the specification. These lEs are marked bold and italic in the tables below.

An IE element may be added denoted IMEI to identify the wireless device 10 of the handover. The presence may be optional and the IE type may comprise an octet string of 8 bits. The semantics description may state

- hexadecimal digits 0 to F, two hexadecimal digits per octet,

- each hexadecimal digit encoded 0000 to 1111,

- 1111 used as filler for bits 8 to 5 of last octet

- bit 4 to 1 of octet n encoding digit 2n-1

- bit 8 to 5 of octet n encoding digit 2n

Number of hexadecimal digits may be e.g. 15.

In some embodiments also an IE for indicating an emergency call is added. This IE may be called Emergency call' and the IE type may be an enumerated type indicating emergency call or not. An alternative solution to enable inclusion of the identity e.g. the IMEI would be to extend the choice in the Permanent NAS UE Identity IE to enable inclusion of the IMEI, as shown in the table below. A sub-IE to Permanent NAS UE Identity IE is denoted below as IMEI and comprises an octet string with size (8). The sematic description of the IMEI may be:hexadecimal digits 0 to F, two hexadecimal digits per octet; each hexadecimal digit encoded 0000 to 11 11 ^'; 1 11 1 used as filler for bits 8 to 5 of last octet; bit 4 to 1 of octet n encoding digit 2n-1 ; bit 8 to 5 of octet n encoding digit 2n. Number of hexadecimal digits shall be 15.

The radio access network node 16 then determines how to handle the handover based on the identity in the received message or messages.

Fig. 2 is a schematic signaling diagram depicting some embodiments wherein the MSC server 17 transmits, action 201 , e.g. a RANAP Relocation Request message comprising the identity of the wireless device 10 to the Radio Access Network Node 16.

Action 202. The SGSN 18 also transmits e.g. a RANAP Relocation Request message comprising the identity of the wireless device 10 to the Radio Access Network Node 16. One or both RANAP Relocation Request messages may further comprise an indication that it is an emergency call. According to embodiments herein a definition of an IE for the identity of the wireless device 10 in the Relocation Request message and additionally in some embodiments a definition of an IE for the Emergency call indication in the Relocation Request message is provided. A mandate to include the identity if IMSI is not available and one may set the IE indicating Emergency call to "emergency call" in case of an emergency call. As an alternative solution may be where the Emergency call IE may be defined in the RANAP Relocation Request message, and where the choice in the Permanent NAS UE Identity IE is extended to enable inclusion of e.g. the IMEI. And a mandate to include the IMEI if IMSI is not available and the Emergency call IE may be set to "emergency call" in case of an emergency call.

Action 203. The Radio Access Network Node 16 then determines how to handle the handover based on one identity or identities in each of the requests, and/or indication that it is an emergency call. The Radio Access Network Node 16 may coordinate the CN domains by comparing the identities comprised in the different RANAP Relocation Request messages, and when a positive match is found determines that these RANAP Relocation Request messages are for the same session.

Some embodiments herein suggest, alternatively or additionally, that an emergency indication is sent to the Radio Access Network Node 16 from the network node 19, such as the MSC server 17, within the Relocation Request message in case the SRVCC is initiated for an emergency call. In case the Radio Access Network Node 16 receives an indication that the relocation is initiated for an emergency call, the Radio Access Network Node 16 have the option of immediately proceed with the handover of the CS component and not waiting for the Relocation Request for the PS component, in case of emergency call. Moreover, the emergency indicator would enable separate observability of emergency calls.

Action 204. The Radio Access Network Node 16 may then transmit a RANAP Relocation Request Acknowledgement to the MSC server 17.

Action 205. The Radio Access Network Node 16 may also transmit a RANAP Relocation Request Acknowledgement to the SGSN 18.

Embodiments herein relate to a method in a system comprised in the radio communications network 1 for handling an emergency call from the wireless device 10. The system comprises one or more network nodes 17, 18 and the radio access network node 16. The one or more network nodes 17, 18 transmits to the radio access network node 16, a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The radio access network node 16 being of the second radio access technology. The message or messages comprise an identity of the wireless device 10, and the radio access network node 16 determines how to handle the handover based on the identity in the received message/or messages.

The method actions in the network node 19, exemplified as MSC server 17 and SGSN 18 herein, for handling an emergency call form the wireless device 10 according to some embodiments will now be described with reference to a flowchart depicted in Fig. 3. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes. The network node may be comprised in a packet switched core network such as the SGSN 18, or a circuit switched core network, such as the MSC server 17.

Action 301. The network node 19 generates a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology.

Action 302. The network node 19 adds an identity an identity of the wireless device 10 to the message. The network node 19 may further add an indication to the message indicating that the message relates to an emergency call, e.g. an emergency indicator.

Some embodiments herein provide a definition of the identity as the IMEI IE in the

Relocation Request message., and a mandate to include the IMEI if IMSI is not available e.g. in case the emergency call is made without a SIM card. As an alternative solution the choice in the Permanent Non Access Stratum (NAS) UE Identity IE is extended to enable inclusion of the IMEI, and a mandate to include the IMEI if IMSI is not available. Some embodiments herein may also provide a definition of an Emergency call IE in the

Relocation Request message, and a mandate to set the Emergency call IE to "emergency call" in case of an emergency call. The message may be a request for a combined circuit switched and packet switched handover, such as a RANAP relocation request. The identity may be the IMEI of the wireless device 10. The IMEI may be added when

International Mobile Subscriber Identity is not available and/or an Emergency call information element is set to "emergency call".

Action 303. The network node 19 then transmits the message to a radio access network node 16 of the second radio access technology. This is exemplified above in Action 201 and Action 202. Action 304. The network node 19 may further receive a response message such as an acknowledgment acknowledging relocation or similar.

The first radio access technology may support a packet switched call and the second radio access technology may support a circuit switched call. Alternatively, the first radio access technology may support a circuit switched call and the second radio access technology may support a packet switched call. It should also be note that the first radio access technology may be the same as the second radio access technology.

The method actions in the radio access network node 16 for handling an emergency call form the wireless device 10 in the radio communications network 1 according to some embodiments will now be described with reference to a flowchart depicted in Fig. 4. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes.

Action 401. The radio access network node 16 receives the message, may also be referred to as a first message, from the network node 19, such as the MSC server 17, indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The message comprises the identity of the wireless device 10 and the radio access network node 16 is of the second radio access

technology. The message may further comprise an indication that the message relates to an emergency call. The indication may be an Emergency call information element set to "emergency call". The message may be a request for a combined circuit switched and packet switched handover. The identity may be an IMEI.

Action 402. The radio access network node 16 may receive a second message from a second network node, such as the SGSN 18, indicating a handover of the emergency call from the first radio access technology to the second radio access technology. The second message comprises an identity of the wireless device 10.

Action 403. The radio access network node 16 determines how to handle the handover based on the identity in the received message. In some embodiments the radio access network node 16 further takes the identity in the second message into account when determining how to handle the handover. E.g. the radio access network node 16 may coordinate the handover by matching the different relocation requests with the identity of the wireless device 10 comprised in each relocation message. Thus, a relocation request for a packet switched component is associated with a relocation request for a circuit switched component. The radio access network node 16 may determine to handle the handover according to at least one of the following: handover both circuit switched call and any packet switched component of the emergency call during an Single Radio Voice Call Continuity, SRVCC, of an emergency session; perform a Core network hard handover (CNHHO) of the emergency call within the second radio 5 access technology, wherein the first radio access technology is the same as the second radio access technology; and immediately proceed with a handover of a circuit switched component and not waiting for a Relocation Request of a packet switched component. Hence, some embodiments herein enable a CNHHO of emergency sessions within e.g. WCDMA, wherein the first radio access technology is the same as the second radio

10 access technology. The radio access network node 19 may further take the indication of the emergency call into account when determining how to handle the handover.

The first radio access technology may support a packet switched call and the second radio access technology may support a circuit switched call, or vice versa, i.e. the first radio access technology may support a circuit switched call and the second radio

15 access technology may support a packet switched call. The first radio access technology may be the same as the second radio access technology. This corresponds to the action 203 in Fig. 2.

Action 404. The radio access network node 16 may further transmit a response message to each of the network nodes such as a RANAP Relocation Request

20 Acknowledge upon successful handover.

In order to perform the method the network node 19 or a core network node, such as the MSC server 17 or the SGSN 18 is provided. Fig. 5 discloses a block diagram depicting the network node 19. The network node 19 comprises a transmitting circuit 25 501 configured to transmit e.g. a SRVCC associated message, e.g. RANAP Relocation Request, comprising identity of the user equipment 10 and/or an Emergency call indication. The network node 19 may also be referred to as the transmitting network node.

The network node 19 may further comprise a generating module 502 or circuit configured to generate the message.

30 The network node further comprises a receiving circuit 503 that may be

configured to receive acknowledgment from the RAN node 16, e.g. an RNC.

The embodiments herein for handling an emergency call may be implemented through one or more processors, a processing circuit 504 or processing means in the network node 19 depicted in Fig. 5, together with computer program code for performing 35 the functions and/or method actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing embodiments herein when being loaded into the network node. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The 5 computer program code may furthermore be provided as pure program code on a server and downloaded to the network node.

The network node 19 further comprises a memory 505 configured to be used to store data on such as I M El, emergency call indicator, applications to perform the methods herein, and/or the like.

10 Hence, Fig. 5 discloses a block diagram depicting the network node for handling an emergency call from the wireless device 10 in the radio communications network 1. The network node 19 may be the MSC server 17 or the SGSN 18.

The network node 19, the generating module 502 and/or the processing circuit 504 is configured to generate the message indicating a handover of the emergency call from

15 the first radio access technology to the second radio access technology. The network node 19, the generating module 502 and/or the processing circuit 504 is further configured to add the identity of the wireless device 10 to the message. The network node 19, the generating module 502 and/or the processing circuit 504 may further be configured to add an indication to the message indicating that the message relates to an

20 emergency call. The first radio access technology may support a packet switched call and the second radio access technology may support a circuit switched call, or the other way around, the first radio access technology may support a circuit switched call and the second radio access technology may support a packet switched call. The message may be a request for a combined circuit switched and packet switched handover, such as a

25 relocation request e.g. a RANAP relocation request. The added identity may an

International Mobile Equipment Identity, IMEI, and the network node 19, the generating module 502 and/or the processing circuit 504 may be configured to add the IMEI when International Mobile Subscriber Identity is not available and/or an Emergency call information element is set to "emergency call". The first radio access technology may be

30 the same as the second radio access technology.

The network node 19, the transmitting circuit 501 , and/or the processing circuit 504 is configured to transmit the message to the radio access network node 16 of the second radio access technology.

The methods according to the embodiments described herein for the network node

35 19 and/or the radio access network node 16, described below, may respectively be implemented by means of e.g. a computer program 506 or a computer program product, comprising instructions, i.e., software code portions, which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the network node 19 and/or the radio access network node 16. The computer program 506 may be stored on a computer-readable storage medium 507, e.g. a disc or similar. The computer-readable storage medium 507, having stored thereon the computer program 506, may comprise the instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the network node 19 and/or the radio access network node 16. In some embodiments, the computer-readable storage medium may be a non-transitory computer-readable storage medium.

In order to perform the method the RAN node 16 is provided. Fig. 6 discloses a block diagram depicting the RAN node 16. The RAN node 16 comprises a receiving circuit 601 configured to receive the message e.g. an SRVCC associated message such as RANAP Relocation Request, comprising the identity of the wireless device 10 and in some embodiments also an Emergency call indication.

The radio access network node 16 may further comprise a determining circuit 602 configured to determine how to handle the handover based on information in the request, i.e. the identity e.g. IMEI and in some embodiments also the indication that it is an emergency call. E.g. to handover both CS call and any PS components during an SRVCC of an emergency session, perform a Core network hard handover (CNHHO) of emergency sessions within WCDMA, immediately proceed with the handover of the CS component and not waiting for the Relocation Request from PS, in case of emergency call.

The radio access network node 16 further comprises a transmitting circuit 603 that may be configured to transmit an acknowledgement of the message to the network node 19.

The embodiments herein for handling an emergency call may be implemented through a processing circuit 604, one or more processors or processing means in the radio access network node 16 depicted in Fig. 6, together with computer program code for performing the functions and/or method actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing embodiments herein when being loaded into the radio access network node. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the radio access network node.

The radio access network node 16 further comprises a memory 605 configured to 5 be used to store data on such as I M El of wireless devices, relocation requests,

emergency call indicator, applications to perform the methods herein, and/or the like.

Thus, Fig. 6 shows a block diagram depicting the radio access network node 16 for handling an emergency call from the wireless device 10 in the radio communications network 1.

10 The radio access network node 16, the receiving circuit 601 and/or the processing circuit 604 is configured to receive a message, from the network node 19, indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The message comprises the identity of the wireless device 10 and the radio access network node 16 is of the second radio access technology. The message

15 may be a request for a combined circuit switched and packet switched handover, and the identity is an International Mobile Equipment Identity, IMEI.

The radio access network node 16, the determining module 602 and/or the processing circuit 604 is configured to determine how to handle the handover based on the identity in the received message. The message may further comprise an indication

20 that the message relates to an emergency call, and the radio access network node 16, the determining module 602 and/or the processing circuit 604 may further be configured to take the indication into account when determining how to handle the handover. The indication may be an Emergency call information element set to "emergency call". The radio access network node 16, the determining module 602 and/or the processing circuit

25 604 may be configured to determine to handle the handover according to at least one of the following: handover both circuit switched call and any packet switched component of the emergency call during an Single Radio Voice Call Continuity, SRVCC, of an emergency session; perform a Core network hard handover, CNHHO, of the emergency call within the second radio access technology, wherein the first radio access technology

30 is the same as the second radio access technology; and immediately proceed with a handover of a circuit switched component and not wait for a Relocation Request of a packet switched component. The first radio access technology may support a packet switched call and the second radio access technology may support a circuit switched call, or the other way around, the first radio access technology may support a circuit switched call and the second radio access technology may support a packet switched call. The first radio access technology may be the same as the second radio access technology.

The radio access network node 16, the receiving circuit 601 and/or the processing circuit 604 may be configured to receive a second message from a second network node, such as the MSC server 17 or the SGSN 18, indicating a handover of the emergency call from the first radio access technology to the second radio access technology. The message comprises an identity of the wireless device 10. , The radio access network node 16, the determining module 602 and/or the processing circuit 604 may be configured to take the identity in the second message into account when determining how to handle the handover. E.g. the radio access network node 16, the determining module 602 and/or the processing circuit 604 may coordinate requests based on a match of identities comprised in the message and the second message.

As will be readily understood by those familiar with communications design, that functions from other circuits or modules may be implemented using digital logic and/or one or more microcontrollers, microprocessors, or other digital hardware. In some embodiments, several or all of the various functions or modules may be implemented together, such as in a single application-specific integrated circuit (ASIC), or in two or more separate devices with appropriate hardware and/or software interfaces between them. Several of the functions or modules may be implemented on a processor shared with other functional components of a wireless terminal or network node, for example.

Alternatively, several of the modules or functional elements of the processing circuits or means discussed may be provided through the use of dedicated hardware, while others are provided with hardware for executing software, in association with the appropriate software or firmware. Thus, the term "processor" or "controller" as used herein does not exclusively refer to hardware capable of executing software and may implicitly include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random-access memory for storing software and/or program or application data, and non-volatile memory. Other hardware, conventional and/or custom, may also be included. Designers of communications receivers will appreciate the cost, performance, and maintenance tradeoffs inherent in these design choices. The receiving circuits 503, 601 and transmitting circuits 501 ,603 may be implemented as receivers and transmitters but also as transceivers.

Embodiments exemplified herein disclose a method in the network node 19 for handling an emergency call from the wireless device 10 in the radio communications network 1. The network node 19 generates a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology. The network node 19 adds an identity of the wireless device 10 to the message and may add an indication that the message relates to an emergency call. The network node 19 further transmits the message to the radio access network node 16 of the second radio access technology. The message may be a request for a combined CS and PS handover, such as a Relocation request or a SRVCC request. Furthermore, a method in the radio access network node 16 for handling an emergency call from the wireless device 10 in the radio communications network 1 is disclosed. The radio access network node 16 receives a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology; the message comprises an identity of the wireless device 10 and may further comprise an indication that the message relates to an emergency call. Furthermore, a network node and a radio access network node is provided to perform the methods.

Modifications and other embodiments of the disclosed embodiments will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. It will be appreciated that the foregoing description and the accompanying drawings represent non-limiting examples of the methods and

apparatus taught herein. As such, the inventive apparatus and techniques taught herein are not limited by the foregoing description and accompanying drawings.

Instead, the embodiments herein are limited only by the following claims and their legal equivalents.

Claims

A method in a network node (17, 18, 19) for handling an emergency call from a wireless device (10) in a radio communications network (1), comprising

generating (301) a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology; adding (302) an identity of the wireless device (10) to the message; and transmitting (201 ,202,303) the message to a radio access network node (16) of the second radio access technology.

A method according to claim 1 , wherein the adding (302) further comprises to add an indication to the message indicating that the message relates to an emergency call.

A method according to any of the claims 1-2, wherein first radio access technology supports a packet switched call and the second radio access technology supports a circuit switched call, or the first radio access technology supports a circuit switched call and the second radio access technology supports a packet switched call.

A method according to any of the claims 1-3, wherein the message is a request for a combined circuit switched and packet switched handover.

A method according to any of the claims 1-4, wherein the identity is an International Mobile Equipment Identity, IMEI.

A method according to claim 5, wherein the IMEI is added when International Mobile Subscriber Identity is not available and/or an Emergency call information element is set to "emergency call".

A method according to any of claims 1-6, wherein the network node (17, 18, 19) is comprised in a packet switched core network or a circuit switched core network.

8. A method according to any of the claims 1-7, wherein the first radio access technology is the same as the second radio access technology. A method in a radio access network node (16) for handling an emergency call from a wireless device (10) in a radio communications network (1), comprising receiving (401) a message, from a network node (17, 18, 19), indicating a handover of the emergency call from a first radio access technology to a second radio access technology, wherein the message comprises an identity of the wireless device (10) and wherein the radio access network node (16) is of the second radio access technology, and

determining (203,403) how to handle the handover based on the identity in the received message.

10. A method according to claim 9, wherein the message further comprises an indication that the message relates to an emergency call, and the determining (203,403) takes the indication into account.

1 1. A method according to claim 10, wherein the indication is an Emergency call information element set to "emergency call".

12. A method according to any of the claims 9-1 1 , wherein the determining (403) comprises to determine to handle the handover according to at least one of the following:

handover both circuit switched call and any packet switched component of the emergency call during an Single Radio Voice Call Continuity, SRVCC, of an emergency session;

perform a Core network hard handover, CNHHO, of the emergency call within the second radio access technology, wherein the first radio access technology is the same as the second radio access technology; and

immediately proceed with a handover of a circuit switched component and not waiting for a Relocation Request of a packet switched component.

13. A method according to any of claims 9-12, wherein first radio access

technology supports a packet switched call and the second radio access technology supports a circuit switched call, or the first radio access technology supports a circuit switched call and the second radio access technology supports a packet switched call.

14. A method according to any of the claims 9-13, wherein the message is a request for a combined circuit switched and packet switched handover.

15. A method according to any of the claims 9-14, wherein the identity is an

International Mobile Equipment Identity, IMEI.

16. A method according to any of the claims 9-15, wherein the first radio access technology is the same as the second radio access technology.

17. A method according to any of the claims 9-16, further comprising

receiving (402) a second message from a second network node (18, 17, 19) indicating a handover of the emergency call from the first radio access technology to the second radio access technology, wherein the message comprises an identity of the wireless device (10), and wherein the determining (203,403) further takes identity in the second message into account when determining how to handle the handover.

18. A network node (17,18, 19) for handling an emergency call from a wireless device (10) in a radio communications network (1), being configured to:

generate a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology;

add an identity of the wireless device (10) to the message; and transmit the message to a radio access network node (16) of the second radio access technology.

19. A network node (17,18, 19) according to claim 18, further being configured to add an indication to the message indicating that the message relates to an emergency call.

20. A network node (17, 18, 19) according to any of the claims 18-19, wherein first radio access technology supports a packet switched call and the second radio access technology supports a circuit switched call, or the first radio access technology supports a circuit switched call and the second radio access technology supports a packet switched call.

21. A network node (17,18, 19) according to any of the claims 18-20, wherein the message is a request for a combined circuit switched and packet switched handover.

22. A network node (17, 18, 19) according to any of the claims 18-21 , wherein the identity is an International Mobile Equipment Identity, IMEI.

23. A network node (17,18, 19) according to claim 22, being configured to add the IMEI when International Mobile Subscriber Identity is not available and/or an Emergency call information element is set to "emergency call".

24. A network node (17,18, 19) according to any of claims 18-23, wherein the

network node (19) is a Mobile Switching Centre, MSC, server (17) or a Serving General Packet Radio Services Support Node, SGSN, (18).

25. A network node (17,18, 19) according to any of the claims 18-24, wherein the first radio access technology is the same as the second radio access technology.

26. A radio access network node (16) for handling an emergency call from a

wireless device (10) in a radio communications network (1), being configured to:

receive a message, from a network node (17, 18, 19), indicating a handover of the emergency call from a first radio access technology to a second radio access technology, wherein the message comprises an identity of the wireless device (10) and wherein the radio access network node (16) is of the second radio access technology; and to

determine how to handle the handover based on the identity in the received message.

27. A radio access network node (16) according to claim 26, wherein the message further comprises an indication that the message relates to an emergency call, and the radio access network node (16) is further configured to take the indication into account when determining how to handle the handover.

28. A radio access network node (16) according to claim 27, wherein the indication is an Emergency call information element set to "emergency call".

29. A radio access network node (16) according to any of the claims 26-28, being configured to determine to handle the handover according to at least one of the following:

immediately proceed with a handover of a circuit switched component and not wait for a Relocation Request of a packet switched component.

30. A radio access network node (16) according to any of claims 26-29, wherein first radio access technology supports a packet switched call and the second radio access technology supports a circuit switched call, or the first radio access technology supports a circuit switched call and the second radio access technology supports a packet switched call.

31. A radio access network node (16) according to any of the claims 26-30,

wherein the message is a request for a combined circuit switched and packet switched handover.

32. A radio access network node (16) according to any of the claims 26-31 ,

wherein the identity is an International Mobile Equipment Identity, IMEI.

33. A radio access network node (16) according to any of the claims 26-32,

wherein the first radio access technology is the same as the second radio access technology.

34. A radio access network node (16) according to any of the claims 26-33, further being configured to:

receive a second message from a second network node (18, 17, 19) indicating a handover of the emergency call from the first radio access technology to the second radio access technology, wherein the message comprises an identity of the wireless device (10), and being configured to take the identity in the second message into account when determining how to handle the handover.

35. A method in a system comprised in a radio communications network (1) for handling an emergency call from a wireless device (10), wherein the system comprises one or more network nodes (17, 18, 19) and a radio access network node (16), the method comprising

transmitting (201 ,202,303) from one or more network nodes (17,18, 19) to the radio access network node (16), a message indicating a handover of the emergency call from a first radio access technology to a second radio access technology, wherein the message comprises an identity of the wireless device (10) and wherein the radio access network node (16) is of the second radio access technology; and

determining (203) in the radio access network node (16), how to handle the handover based on the identity in the received message or messages.