Patent Description:
A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations/access points and/or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and/or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet. In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station or access point, and transmit and/or receive communications on the carrier.

The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (<NUM> radio). Another example of an architecture that is known as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. Another example communication system is so called <NUM> radio or NR (new radio) access technology.

3GPP TS <NUM>, version <NUM>. <NUM>, discloses, in its subclause U. x, conditions to perform emergency services in <NUM> NR and in other RATs. <CIT> discloses a handover of an emergency call from a non-3GPP network to a 3GPP network.

In the following certain embodiments are explained with reference to mobile communication devices capable of communication via a wireless cellular system and mobile communication systems serving such mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system, access systems thereof, and mobile communication devices are briefly explained with reference to <FIG> and <FIG> to assist in understanding the technology underlying the described examples.

A communication device <NUM> or terminal such as shown in <FIG> can be provided wireless access via cells, base stations or similar wireless transmitter and/or receiver nodes providing access points of a radio access system.

Access points and hence communications there through are typically controlled by at least one appropriate controller apparatus so as to enable operation thereof and management of mobile communication devices in communication therewith. <FIG> shows an example of a control apparatus for a node, for example to be integrated with, coupled to and/or otherwise for controlling the access points. The control apparatus <NUM> can be arranged to allow communications between a user equipment and a core network. For this purpose the control apparatus comprises at least one memory <NUM>, at least one data processing unit <NUM>, <NUM> and an input/output interface <NUM>. Via the interface the control apparatus can be coupled to relevant other components of the access point. The control apparatus can be configured to execute an appropriate software code to provide the control functions. It shall be appreciated that similar components can be provided in a control apparatus provided elsewhere in the network system, for example in a core network entity. The control apparatus can be interconnected with other control entities. The control apparatus and functions may be distributed between several control units. In some embodiments, each base station can comprise a control apparatus. In alternative embodiments, two or more base stations may share a control apparatus.

Access points and associated controllers may communicate with each other via a fixed line connection and/or via a radio interface. The logical connection between the base station nodes can be provided for example by an X2 or the like interface. This interface can be used for example for coordination of operation of the stations and performing reselection or handover operations.

The communication device or user equipment (UE) <NUM> may comprise any suitable device capable of at least receiving wireless communication of data. For example, the device can be handheld data processing device equipped with radio receiver, data processing and user interface apparatus. Non-limiting examples include a mobile station (MS) such as a mobile phone or what is known as a 'smart phone', a portable computer such as a laptop or a tablet computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like. Further examples include wearable wireless devices such as those integrated with watches or smart watches, eyewear, helmets, hats, clothing, ear pieces with wireless connectivity, jewellery and so on, universal serial bus (USB) sticks with wireless capabilities, modem data cards, machine type devices or any combinations of these or the like.

<FIG> shows a schematic, partially sectioned view of a possible communication device. More particularly, a handheld or otherwise mobile communication device (or user equipment UE) <NUM> is shown. A mobile communication device is provided with wireless communication capabilities and appropriate electronic control apparatus for enabling operation thereof. Thus, the communication device <NUM> is shown being provided with at least one data processing entity <NUM>, for example a central processing unit and/or a core processor, at least one memory <NUM> and other possible components such as additional processors <NUM> and memories <NUM> for use in software and hardware aided execution of tasks it is designed to perform. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board <NUM> and/or in chipsets. Data processing and memory functions provided by the control apparatus of the communication device are configured to cause control and signalling operations in accordance with certain embodiments as described later in this description. A user may control the operation of the communication device by means of a suitable user interface such as touch sensitive display screen or pad <NUM> and/or a key pad, one of more actuator buttons <NUM>, voice commands, combinations of these or the like. A speaker and a microphone are also typically provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The communication device may communicate wirelessly via appropriate apparatus for receiving and transmitting signals. <FIG> shows schematically a radio block <NUM> connected to the control apparatus of the device. The radio block can comprise a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the communication device.

The communication device may operate in an SR mode wherein the communication device is registered to a single radio access technology core network (e.g. EPC or 5GCN) or in a DR mode wherein the communication device is registered to two radio access technology core networks (e.g. EPC and 5GCN).

Subclause U. <NUM> of 3GPP TS <NUM> describes how the UE in SR mode operates according to the EMC and EMF indicators and UE's support of ESFB when a UE is in a cell of a specific access technology. However, there are several incomplete or inaccurate descriptions in the subclause. One or more of the following embodiments address these issues.

In summary, if the EMC indicates "Emergency services not supported", the UE supports ESFB, and the ESFB is N, it may be desirable that:.

If the EMC indicates that the emergency services are supported in RAT only and if the UE does not support ESFB or the ESFB is N, it may be desirable that:.

The UE's attempt to select a RAT cell connected to 5GCN may fail. In the failure case, the UE may attempt to select an E-UTRAN cell.

The UE's attempt to select an E-UTRAN cell may fail. Even if there is no need to address the failure case because it is outside the scope of the subclause, the specification should not be described as if the success is guaranteed.

Establishment of the emergency call via E-UTRAN may be performed if the EMC BS is set to "emergency bearer services in S1 mode supported". If the EPS does not support emergency bearer services, the UE might try e.g. CS, but it is outside of the scope of the subclause.

It is proposed to reflect these changes by amending subclause U. <NUM> of 3GPP TS <NUM> to recite:
"U. <NUM> Emergency service in single registration mode
NOTE: This subclause covers only the case where the UE selects the IM CN subsystem in accordance with the conventions and rules specified in 3GPP TS <NUM> [4B] and describes the IP-CAN specific procedure. It does not preclude the use of CS domain and the use of CS domain is outside the scope of this subclause.

When the UE operates in single registration mode as described in 3GPP TS <NUM> [<NUM>] and the UE recognises that a call request is an emergency call, if:.

then the following treatment is applied:.

Subclause U. <NUM> of 3GPP TS <NUM> is silent as to how the UE in DR mode operates according to the EMC and EMF indicators and UE's support of ESFB when a UE is in a cell of a specific access technology. One or more of the following embodiments address this issue.

In summary, if the EMC indicates "Emergency services not supported", the UE may perform an IP-CAN specific procedure as described in annex L to establish the emergency call.

If the UE is in an NR cell connected to 5GCN, the EMC may indicate that emergency services are supported only via E-UTRA connected to 5GCN, the UE supports ESFB, ESFB is Y, and the UE is capable of accessing 5GCN via E-UTRA, the UE may perform ESFB.

If the UE is in an E-UTRA cell connected to 5GCN, the EMC indicates that emergency services are supported only via NR connected to 5GCN, the UE supports ESFB, ESFB is Y, and the UE is capable of accessing 5GCN via NR, the UE may perform an IP-CAN specific procedure as described in annex L to establish the emergency call.

If the EMC indicates that emergency services are supported only via the different RAT to the RAT of the cell that the UE is camping in, ESFB is not available in the UE or network, and the UE is capable of accessing 5GCN via the different RAT, the UE may attempt to perform emergency call by triggering PDU session establishment for emergency service via the different RAT.

If the attempt fails, the UE may perform an IP-CAN specific procedure as described in annex L to establish the emergency call.

If the EMC indicates that emergency services are supported only via the different RAT to the RAT of the cell that the UE is camping in and the UE is not capable of accessing 5GCN via the different RAT, the UE may perform an IP-CAN specific procedure as described in annex L to establish the emergency call.

If the emergency services are supported in the current RAT, the UE may attempt emergency call by triggering PDU session establishment for emergency service.

It is proposed to reflect these changes by adding a subclause U. x to 3GPP TS <NUM>.

x Emergency service in dual registration mode
NOTE: This subclause covers only the case where the UE selects the IM CN subsystem in accordance with the conventions and rules specified in 3GPP TS <NUM> [4B] and describes the IP-CAN specific procedure. It does not preclude the use of CS domain and the use of CS domain is outside the scope of this subclause.

When the UE operates in dual registration mode as described in 3GPP TS <NUM> [<NUM>] and the UE recognises that a call request is an emergency call, if:.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE operates in SR mode.

In step <NUM>, the UE receives a call request from a user.

In step <NUM>, the UE determines that the call request is an emergency call request.

In step <NUM>, the UE determines whether the UE is camping in an NR cell or in an E-UTRA cell. If the UE is camping in an NR cell, the method goes to step <NUM>. If the UE is camping in an E-UTRAN the method goes to step <NUM>.

In step <NUM> (i.e. the UE is camping in an NR cell), the UE determines whether emergency services are supported by NR cells connected to 5GCN, for example based on an EMC. The EMC may be provided by an access and mobility management function (AMF) in 5GCN to the UE via non-access stratum (NAS) signalling in a REGISTRATION ACCEPT message. Likewise, the UE determines whether emergency services are supported by E-UTRAN cells connected to 5GCN, for example based on the EMC.

If the EMC indicates that emergency services are supported by none of NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step A (linking <FIG>). If the EMC indicates that emergency services are supported by E-UTRAN cells connected to 5GCN only, the method proceeds to step B (linking <FIG>). If the EMC indicates that emergency services are supported by NR cells connected to 5GCN only or both NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step C (linking <FIG>).

In step <NUM> (i.e. the UE is camping in an E-UTRAN cell), the UE determines whether emergency services are supported by NR cells connected to 5GCN, for example based on the EMC. Likewise, the UE determines whether emergency services are supported by E-UTRAN cells connected to 5GCN, for example based on the EMC.

If the EMC indicates that emergency services are supported by none of NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step D (linking <FIG>). If the EMC indicates that emergency services are supported by NR cells connected to 5GCN only, the method proceeds to step E (linking <FIG>). If the EMC indicates that emergency services are supported by E-UTRAN cells connected to 5GCN only or both NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step F (linking <FIG>).

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in SR mode and emergency services are supported neither by E-UTRA cells connected to the 5GCN nor by NR cells connected to the 5GCN.

In step <NUM>, the UE determines whether the UE supports an emergency services fallback procedure. If the UE supports the emergency services fallback procedure, the method goes to step <NUM>. If the UE does not support the emergency services fallback procedure, the method goes to <NUM>.

In step <NUM>, the UE determines whether the emergency services fallback procedure is available, for example based on an ESFB. If the ESFB indicates the emergency services fallback procedure is available, the method goes to step <NUM>. If the ESFB indicates that the emergency services fallback procedure is not available, the method goes to <NUM>.

In step <NUM> (i.e. the emergency services fallback procedure is available), the UE attempts to perform an emergency call by triggering an emergency services fallback procedure.

In step <NUM> (i.e. the emergency services fallback procedure is not available), the UE determines whether the emergency service fallback procedure is supported by E-UTRA cells connected to 5GCN only, for example based on an EMF. The EMF may be provided by an access and mobility management function (AMF) in 5GCN to the UE via non-access stratum (NAS) signalling in a REGISTRATION ACCEPT message. If the EMF indicates that the emergency service fallback procedure is supported by E-UTRA cells connected to 5GCN only, the method goes to step <NUM>. If the EMF indicates that the emergency service fallback procedure is not supported by E-UTRA cells connected to 5GCN only, the method goes to step <NUM>.

In step <NUM> (i.e. the emergency service fallback procedure is supported by E-UTRA cells connected to 5GCN only), the UE determines whether the UE supports accessing 5GCN via an E-UTRA cell and whether there is a suitable E-UTRA cell connected to 5GCN accessible by the UE. For example, the UE may determine whether the UE has a E-UTRA radio stack, whether the UE is within the coverage area of an E-UTRA cell connected to 5GCN, whether the load of the E-UTRA cell connected to 5GCN meets a predefined requirement, whether radio link between the UE and the E-UTRA cell connected to 5GCN meets a predefined requirement, or other.

In general, a suitable cell for a UE may be defined as a cell that the UE may camp. More detailed criteria include (non-exhaustive): the cell is part of either the selected PLMN or a PLMN of the equivalent PLMN list; the cell selection criteria are fulfilled; a cell is served by the selected/registered PLMN and not barred; in multi-beam operations, measurement quantity of a cell is derived amongst the beams corresponding to the same cell (applicable to NR only), etc..

If there is a suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM> or <NUM>.

In step <NUM>, the UE attempts to select the suitable E-UTRA cell connected to 5GCN accessible by the UE and trigger an emergency services fallback procedure.

In step <NUM>, the UE determines the UE supports accessing EPC via an E-UTRA cell and whether there is a suitable E-UTRA cell connected to EPC accessible by the UE. For example, the UE may determine whether the UE has a E-UTRA radio stack, the UE may determine whether the UE is within the coverage area of an E-UTRA cell connected to EPC, whether the load of the E-UTRA cell connected to EPC meets a predefined requirement, whether radio link between the UE and the E-UTRA cell connected to EPC meets a predefined requirement, or other. If the UE determines that the UE supports accessing EPC via an E-UTRA cell and there is a suitable E-UTRA cell connected to EPC accessible by the UE, the method goes to step <NUM>.

In step <NUM> (i.e. there is a suitable E-UTRA cell connected to EPC accessible by the UE), the UE determines whether emergency bearer services are supported, for example based on an EMC BS. The EMC BS may be provided by the mobility management entity (MME) in EPC via NAS signalling in a TRACKING AREA UPDATE ACCEPT message or an ATTACH ACCEPT message.

If the EMC BS indicates that emergency bearer services in S1 mode are supported, the method goes to step <NUM>.

In step <NUM> (i.e. emergency bearer services in S1 mode are supported), the UE attempts to select the suitable E-UTRA cell connected to EPC and perform an emergency call by performing an IP-CAN procedure.

In step <NUM> (i.e. the UE does not support the emergency services fallback procedure or the emergency services fallback procedure is not supported by E-UTRA cells connected to 5GCN only or there is no suitable E-UTRA cell connected to 5GCN), the UE disables <NUM> capability, for example the UE disables N1 mode capability. The method then goes to step <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in SR mode and emergency services are supported by E-UTRA cells connected to the 5GCN only.

In step <NUM>, the UE determines whether the emergency services fallback procedure is available, for example based on the ESFB. If the ESFB indicates the emergency services fallback procedure is available, the method goes to step <NUM>. If the ESFB indicates that the emergency services fallback procedure is not available, the method goes to <NUM>.

In step <NUM> (i.e. the UE does not support the emergency services fallback procedure or the emergency services fallback procedure is not available), the UE determines whether the UE supports accessing 5GCN via a E-UTRA cell and whether there is a suitable E-UTRA cell connected to 5GCN accessible by the UE. If there is a suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM> or <NUM>.

In step <NUM>, the UE attempts to select the suitable E-UTRA cell connected to 5GCN accessible by the UE and trigger a PDU session establishment procedure.

In step <NUM>, the UE determines whether the UE supports accessing EPC via an E-UTRA cell and whether there is a suitable E-UTRA cell connected to EPC accessible by the UE. If the UE determines that there is a suitable E-UTRA cell connected to EPC accessible by the UE, the method goes to step <NUM>.

In step <NUM> (i.e. there is a suitable E-UTRA cell connected to EPC accessible by the UE), the UE determines whether emergency bearer services are supported, for example based on an EMC BS. The EMC BS may be provided by the mobility management entity (MME) in EPC via NAS signalling in a TRACKING AREA UPDATE ACCEPT message or an ATTACH ACCEPT message. If the EMC BS indicates that emergency bearer services in S1 mode are supported, the method goes to step <NUM>.

In step <NUM> (i.e. there is no suitable E-UTRA cell connected to 5GCN), the UE disables <NUM> capability, for example the UE disables N1 mode capability. The method then goes to step <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in SR mode and emergency services are supported by NR cells connected to the 5GCN only or supported by both NR cells and E-UTRA cells connected to the 5GCN.

In step <NUM> the UE attempts to perform an emergency call by triggering a PDU session establishment procedure.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an E-UTRA cell operates in SR mode and emergency services are supported neither by E-UTRA cells connected to the 5GCN nor by NR cells connected to the 5GCN.

In step <NUM> (i.e. the emergency services fallback procedure is not available), the UE determines whether the emergency service fallback procedure is supported by NR cells connected to 5GCN only, for example based on an EMF. If the EMF indicates that the emergency service fallback procedure is supported by NR cells connected to 5GCN only, the method goes to step <NUM>. If the EMF indicates that the emergency service fallback procedure is not supported by NR cells connected to 5GCN only, the method goes to step <NUM>.

In step <NUM> (i.e. the emergency service fallback procedure is supported by NR connected to 5GCN only), the UE determines whether the UE supports accessing 5GCN via an NR cell and whether there is a suitable NR cell connected to 5GCN accessible by the UE. For example, the UE may determine whether the UE has an NR radio stack, whether the UE is within the coverage area of an NR cell connected to 5GCN, whether the load of the NR cell connected to 5GCN meets a predefined requirement, whether radio link between the UE and the NR cell connected to 5GCN meets a predefined requirement, or other. If there is a suitable NR cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable NR cell connected to 5GCN accessible by the UE, the method goes to step <NUM> or <NUM>.

In step <NUM>, the UE determines whether the UE supports accessing EPC via an E-UTRA cell and whether there is a suitable E-UTRA cell connected to EPC accessible by the UE. For example, the UE may determine whether the UE has an E-UTRA radio stack, whether the UE is within the coverage area of an E-UTRA cell connected to EPC, whether the load of the E-UTRA cell connected to EPC meets a predefined requirement, whether radio link between the UE and the E-UTRA cell connected to EPC meets a predefined requirement, or other. If the UE determines that there is a suitable E-UTRA cell connected to EPC accessible by the UE, the method goes to step <NUM>.

In step <NUM> (i.e. there is a suitable E-UTRA cell connected to EPC accessible by the UE), the UE determines whether emergency bearer services are supported, for example based on an EMC BS in a TRACKING AREA UPDATE ACCEPT message. If the EMC BS indicates that emergency bearer services in S1 mode are supported, the method goes to step <NUM>.

In step <NUM> (i.e. the UE does not support the emergency services fallback procedure or the emergency services fallback procedure is not supported by NR cells connected to 5GCN only or there is no suitable NR cell connected to 5GCN), the UE disables <NUM> capability, for example the UE disables N1 mode capability. The method then goes to step <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in SR mode and emergency services are supported by NR cells connected to the 5GCN only.

In step <NUM> (i.e. the UE does not support the emergency services fallback procedure or the emergency services fallback procedure is not available), the UE determines whether the UE supports accessing 5GCN via an NR cell and whether there is a suitable NR cell connected to 5GCN accessible by the UE. If there is a suitable NR cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM> or <NUM>.

In step <NUM>, the UE attempts to select the suitable NR cell connected to 5GCN accessible by the UE and trigger a PDU session establishment procedure.

In step <NUM>, the UE determines whether there is a suitable NR cell connected to EPC accessible by the UE. If the UE determines that there is a suitable NR cell connected to EPC accessible by the UE, the method goes to step <NUM>.

In step <NUM> (i.e. emergency bearer services in S1 mode are supported), the UE attempts to select the suitable NR cell connected to EPC and perform an emergency call by performing an IP-CAN procedure.

In step <NUM> (i.e. there is no suitable NR cell connected to 5GCN), the UE disables <NUM> capability, for example the UE disables N1 mode capability. The method then goes to step <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a user equipment when the user equipment operates in DR mode.

In step <NUM> (i.e. the UE is camping in an NR cell), the UE determines whether emergency services are supported by NR cells connected to 5GCN, for example based on an EMC. Likewise, the UE determines whether emergency services are supported by E-UTRAN cells connected to 5GCN, for example based on the EMC.

If the EMC indicates that emergency services are supported by none of NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step G (linking <FIG>). If the EMC indicates that emergency services are supported by E-UTRAN cells connected to 5GCN only, the method proceeds to step H (linking <FIG>). If the EMC indicates that emergency services are supported by NR cells connected to 5GCN only or both NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step I (linking <FIG>).

If the EMC indicates that emergency services are supported by none of NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step J (linking <FIG>). If the EMC indicates that emergency services are supported by NR cells connected to 5GCN only, the method proceeds to step K (linking <FIG>). If the EMC indicates that emergency services are supported by E-UTRAN cells connected to 5GCN only or both NR cells connected to 5GCN and E-UTRAN cells connected to 5GCN, the method proceeds to step K (linking <FIG>).

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in DR mode and emergency services are supported neither by E-UTRA cells connected to the 5GCN nor by NR cells connected to the 5GCN.

In step <NUM>, the UE determines whether the UE is attached for EPS services (i.e. whether the UE is registered to the EPS). If the UE is attached for EPS services, the method goes to step <NUM>. If the UE is not attached for EPS services, the method goes to <NUM>.

In step <NUM>, the UE determines whether emergency bearer services are supported, for example based on an EMC BS. If the EMC BS indicates that emergency bearer services in S1 mode are supported, the method goes to step <NUM>.

In step <NUM> (i.e. emergency bearer services in S1 mode are supported), the UE attempts to perform an emergency call by performing an IP-CAN procedure.

In step <NUM>, the UE determines whether the supports accessing EPC via an E-UTRA cell and whether there is a suitable E-UTRA cell connected to EPC accessible by the UE. If the UE determines that there is a suitable E-UTRA cell connected to EPC accessible by the UE, the method goes to step <NUM>.

In step <NUM> (i.e. there is suitable E-UTRA cell connected to EPC accessible by the UE) determines whether emergency bearer services are supported, for example based on an EMC BS. If the EMC BS indicates that emergency bearer services in S1 mode are supported, the method goes to step <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in DR mode and emergency services are supported by E-UTRA cells connected to the 5GCN only.

In step <NUM> (i.e. the UE supports the emergency services fallback procedure and the emergency services fallback procedure is available), the UE determines whether the UE supports accessing 5GCN via a E-UTRA cell and whether there is a suitable E-UTRA cell connected to 5GCN accessible by the UE. If there is a suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM>.

In step <NUM>, the UE attempts to select the suitable E-UTRA cell connected to 5GCN accessible by the UE and perform the emergency call by triggering an emergency services fallback procedure.

In step <NUM> (i.e. the UE supports the emergency services fallback procedure and the emergency services fallback procedure is available), the UE determines whether the UE is capable of accessing 5GCN via an E-UTRA cell. In other words, the UE determines whether there is a suitable E-UTRA cell connected to 5GCN accessible by the UE. If there is a suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable E-UTRA cell connected to 5GCN accessible by the UE, the method goes to step <NUM>.

In step <NUM>, the UE attempts to select the suitable E-UTRA cell connected to 5GCN accessible by the UE and perform the emergency call by triggering a PDU session establishment procedure.

In step <NUM> (i.e. there is no suitable E-UTRA cell connected to 5GCN accessible by the UE), the UE determines whether the UE is attached for EPS services. If the UE is attached for EPS services, the method goes to step <NUM>. If the UE is not attached for EPS services, the method goes to <NUM>.

In step <NUM> the UE determines whether emergency bearer services are supported, for example based on an EMC BS. If the EMC BS indicates that emergency bearer services in S1 mode are supported, the method goes to step <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an NR cell operates in DR mode and emergency services are supported by NR cells connected to the 5GCN only or supported by both NR cells and E-UTRA cells connected to the 5GCN.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an E-UTRA cell operates in DR mode and emergency services are supported neither by E-UTRA cells connected to the 5GCN nor by NR cells connected to the 5GCN.

In step <NUM>, the UE determines whether the UE is attached for EPS services. If the UE is attached for EPS services, the method goes to step <NUM>. If the UE is not attached for EPS services, the method goes to <NUM>.

<FIG> shows a schematic representation of a diagram of a method performed by a UE when the UE camping in an E-UTRA cell operates in DR mode and emergency services are supported by NR cells connected to the 5GCN only.

In step <NUM>, the UE determines whether the UE supports accessing 5GCN via a NR cell and whether there is a suitable NR cell connected to 5GCN accessible by the UE. If there is a suitable NR cell connected to 5GCN accessible by the UE, the method goes to step <NUM>. If there is no suitable NR-cell connected to 5GCN accessible by the UE, the method goes to step <NUM>.

In step <NUM> (i.e. there is a suitable NR cell connected to 5GCN accessible by the UE), the UE attempts to select the suitable NR cell connected to 5GCN and perform an emergency call by performing a PDU session establishment procedure.

In step <NUM> (i.e. there is no suitable NR cell connected to 5GCN accessible by the UE), the UE determines whether the UE is attached for EPS services. If the UE is attached for EPS services, the method goes to step <NUM>. If the UE is not attached for EPS services, the method goes to <NUM>.

It will be understood that although the methods of <FIG> have been described in relation to <NUM> and E-UTRAN, the same concepts are applicable to other types of radio access technologies.

<FIG> is a schematic representation of a diagram of a method performed by a user equipment. It will be understood that the following steps may be performed in any suitable order.

In step <NUM>, the UE determines whether the UE operates in SR mode or DR mode.

In step <NUM>, the UE determines a first radio access technology of a cell the UE is camping on.

In step <NUM>, UE determines (i) whether both the first radio access technology and a second radio access technology support an emergency service or only the first radio access technology supports the emergency service, (ii) whether only the second radio access technology supports the emergency service or (iii) whether none of the first radio access technology and the second radio access technology supports the emergency service.

In step <NUM>, the UE determines at least one condition to attempt to switch the UE from using the first RAT to using the second RAT to access the first RAT core network or the second RAT core network and perform an emergency call. The least one condition is determined based on whether the UE operates in SR mode or DR mode, the first RAT and whether (i) both the first radio access technology and a second radio access technology support an emergency service or only the first radio access technology supports the emergency service, (ii) only the second radio access technology supports the emergency service or (iii) none of the first radio access technology and the second radio access technology supports the emergency service (e.g. see branches A to L on <FIG>).

In an example, the UE operates in SR mode, the UE camps on a <NUM> cell and none of <NUM> and E-UTRA supports the emergency service (branch A - <FIG>). At least one condition to attempt to switch from using a <NUM> cell to using an E-UTRA cell to access 5GCN and perform an emergency call by triggering an emergency fallback procedure comprise:.

In step <NUM>, in response to the at least one condition being met the UE ensures that the user equipment supports access to the first RAT core network or the second RAT core network via a cell of the second radio access technology.

In the above example, the UE determines that the UE supports access to 5GN via an E-UTRA cell (step <NUM>).

In step <NUM>, the UE also determines that there is a suitable cell of the second radio access technology accessible by the user equipment and connected to the first RAT core network or the second RAT core network.

In the above example, the UE determines that there is a suitable E-UTRA cell connected to 5GCN accessible by the UE (step <NUM>).

In step <NUM>, the UE attempts to switch from the first RAT to the second RAT to access the first RAT core network or the second RAT core network and perform an emergency call. If the switch is successful, the UE performs the emergency call.

In the above example, the UE performs the emergency call by triggering an emergency service fallback procedure (step <NUM>).

An advantage of the above method is that, the risk of failure when attempting the switch from the first RAT to the second RAT may be minimized. Indeed, unlike existing solutions the UE does not attempt to switch from the first RAT to the second RAT blindly.

The required data processing apparatus and functions may be provided by means of one or more data processors. The apparatus may be provided in the communications device, in the control apparatus and/or in the access point. The described functions at each end may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.

The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. In particular, it will be understood that one or more of the above embodiment may be combined. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as long as they fall within the terms of the appended claims.

Claim 1:
A user equipment, UE, comprising:
at least one processor; and
at least one memory including computer program code;
the at least one memory and the computer program code configured to, with the at least one processor, cause the UE at least to, when the UE operates in a dual registration mode:
- determine, when a call request is received from a user, whether the call request is an emergency call request;
- if the call request is an emergency call request, determine whether the UE is camping in a cell of a first radio access technology connected to a core network or in a cell of a second radio access technology connected to the core network;
- if the UE is camping in a cell of the first radio access technology connected to the core network, determine whether an emergency service is supported (i) in both the first radio access technology connected to the core network and the second radio access technology connected to the core network, , (ii) in only the first radio access technology connected to the core network, (iii) in only the second radio access technology connected to the core network , or (iv) in none of the first radio access technology connected to the core network and the second radio access technology connected to the core network;
- if the emergency service is supported in only the second radio access technology connected to the core network and if the UE does not support emergency services fallback, determine whether the UE supports access to the core network via a cell of the second radio access technology;
- if the UE supports access to the core network via a cell of the second radio access technology attempt to select a cell of the second radio access technology connected to the core network; and
- if the UE finds a suitable cell of the second radio access technology connected to the core network, perform an emergency call by triggering a packet data unit, PDU, session establishment for emergency service via the second radio access technology.