Managing extended discontinuous reception and emergency call back in a radio telecommunications network

Abstract

User equipment, core network entity, radio access network entity or Managing extended discontinuous reception and emergency call back in a radio telecommunications network. If UE is in inactive state and has an emergency Packet Data Unit (PDU) session, use DRX not eDRX. The core network entity, after being informed of completion of an emergency service, maintains the PDU session and does not deactivate a user plane connection of the emergency PDU session. The radio access network uses DRX (not eDRX) to page a UE having radio access network user plane resources associated with an emergency ARP value. The radio access network entity, uses DRX (not eDRX) to page a UE, in the inactive state, when paging triggered by a message comprises an emergency Allocation and Retention Priority (ARP) value.

Description

[0001] TITLE

[0002] Managing extended discontinuous reception and emergency call back in a radio telecommunications network

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to Managing extended discontinuous reception and emergency call back in a radio telecommunications network..

[0005] BACKGROUND

[0006] The current 3GPP 5G standard provides for emergency call back to a user equipment that has originated an emergency call. Emergency call back is sometimes referred to as “Public Safety Answering Point Callback”.

[0007] The current 3GPP 5G standard provides for both discontinuous reception and extended discontinuous reception.

[0008] There is scope for management of extended discontinuous reception and emergency call back in a radio telecommunications network to be improved.

[0009] BRIEF SUMMARY

[0010] According to various, but not necessarily all, embodiments there are provided examples as claimed in the appended claims.

[0011] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function

[0012] BRIEF DESCRIPTION

[0013] Some examples will now be described with reference to the accompanying drawings in which:

[0014] FIG 1 illustrates an example of a cellular radio network;

[0015] FIG2 illustrates an example of a current architecture for a cellular radio network;

[0016] FIG 3 illustrates an example of a control plane protocol stack for a cellular radio network; FIG 4 illustrates an example of a user plane protocol stack for a cellular radio network;

[0017] FIG 5 illustrates an example of emergency call establishment;

[0018] FIG 6 illustrates an example of an emergency service (ES) and supporting layers;

[0019] FIG 7 illustrates an example of a state machine;

[0020] FIG 8 illustrates an innovative example of emergency service termination and supporting layers according to a first embodiment;

[0021] FIG 9 illustrates an innovative example of emergency service termination and paging according to the first embodiment;

[0022] FIG. 10 illustrates an example of a controller; and

[0023] FIG. 11 illustrates an example of a computer program.

[0024] The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0025] DETAILED DESCRIPTION

[0026] The additional latency when the UE is in eDRX can be very long: In RRC-lnactive the UE can be configured with an eDRX cycle length up to 2.91 hours, provided that the UE is configured with CN eDRX .

[0027] Fig. 1 illustrates an example of a network 100 comprising a plurality of network entities including terminal apparatus 110, node apparatus 120 and one or more network apparatus 130. The terminal apparatus 110 and node apparatus 120 communicate 124 with each other. The one or more network apparatus 130 communicate 128 with the node apparatus 120.

[0028] In some examples the one or more network apparatus 130 communicate with the terminal apparatus 110. The one or more network apparatus 130 can, in some examples, communicate with each other. The one or more node apparatus 120 can, in some examples, communicate 126 with each other.

[0029] The network 100 can be a cellular network comprising a plurality of cells 122 each served by a node apparatus 120. In this example, the interface between the terminal apparatus 110 and a node apparatus 120 defining a cell 122 is a wireless interface 124.

[0030] The node apparatus 120 comprises one or more cellular radio transceivers. The terminal apparatus 110 comprises one or more cellular radio transceivers. In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal apparatus 110 are user equipment (UE) and the node apparatus 120 can be access nodes such as base stations.

[0031] A user equipment comprises a mobile equipment. Where reference is made to user equipment that reference includes and encompasses, wherever possible, a reference to mobile equipment.

[0032] In some examples, during operation, a user equipment 110 comprises a mobile equipment comprising a smart card for authentication / encryption etc. such as a Subscriber Identity Module (SIM). In some examples, during operation, a user equipment 110 comprises mobile equipment comprising circuitry embedded as part of the user equipment 110 for authentication / encryption such as software SIM.

[0033] The node apparatus 120 can be any suitable access node such as a base station or transmission reception point. The node apparatus 120 can be a network element responsible for radio transmission and reception in one or more cells 122, to or from the UE 110. The node apparatus 120 can be a network element in a Radio Access Network (RAN), an Open-Radio Access Network (O-RAN) or any other suitable type of network.

[0034] The network apparatus 130 can be part of a core network. The network apparatus 130 can be configured to manage functions relating to connectivity for the UEs 110. For example, the network apparatus 130 can be configured to manage functions such as connectivity, mobility, authentication, authorization, and / or other suitable functions. In some examples the network apparatus 130 can comprise an Access and Mobility management Function (AMF) and / or a User Plane Function (UPF) or any other suitable entities.

[0035] In the example of Fig. 1 the network apparatus 130 is shown as a single entity. In some examples the network apparatus 130 could be distributed across a plurality of entities. For example, the network apparatus 130 could be cloud based or distributed in any other suitable manner. The network apparatus 130 can be a core network node.

[0036] The network 100 can be a 4G or 5G network, for example. It can for example be a New Radio (NR) network that uses gNB or eNB as access nodes 120. New Radio is the 3GPP name for 5G technology. In such cases the node apparatus 120 can comprise gNodeBs (gNBs) 120 configured to provide user plane and control plane protocol terminations towards the UE 110 and / or to perform any other suitable functions. The gNBs 120 are interconnected with each other by means of an Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the network apparatus 130. The gNBs can be connected to an AMF or any other suitable network apparatus 130. Other types of networks and interfaces could be used in other examples. Other types of network could comprise next generation mobile and communication network, for example, a 6G network. FIG 2 illustrates the NR architecture including the core network (CN) 130, the access network (AN) (for example, the Radio Access Network (RAN) which includes base stations 120), and the user equipment 110.

[0037] The User Plane Function (UPF), handles the user plane (user data and the associated signalling).

[0038] The Session Management Function (SMF), handles a PDU Session, and contacts the UPF accordingly. The SMF collects all the information related to Packet Data Unit (PDU) session management from various network components (e.g, UPF, vPCF, UDM).

[0039] FIG 3 illustrates a control plane protocol stack. The FIG includes a user equipment (UE) 110, the access network 120, the core network (CN) 130 providing the Access and Mobility management Function (AMF) and Session Management Function (SMF).

[0040] The Key Functions of 5G Network Access Stratum (NAS) Protocol are: Connection Management (CM); Mobility Management (MM); Session Management (SM); Security. Session Management (SM) includes: Session Establishment, Session Modification, Session Release. Session Establishment manages the establishment of user plane connections for data transfer. Session Modification handles modifications to existing sessions, such as changes in Quality of Service (QoS) parameters. Session Release manages the release of user plane connections.

[0041] NAS-SM: supports the handling of Session Management between the UE and the SMF. It supports user plane PDU Session Establishment, modification, and release. It is transferred via the AMF, and transparent to the AMF.

[0042] NAS-MM: supports registration management functionality, connection management functionality and user plane connection activation and deactivation. It is also responsible of ciphering and integrity protection of NAS signalling.

[0043] 5G-AN Protocol layer is set of AN-dependent protocols / layers.

[0044] 5G Session Management includes the authentication and authorization, establishment, modification, and release of PDU sessions. Each PDU session represents a PDU session established between the UE and an Data Network. PDU sessions can remain established even if the radio and network resources constituting the corresponding PDU session between the UE and the UPF are temporarily released.

[0045] 5G Session Management procedures can be performed only if a 5GMM context has been established between the UE and the AMF.

[0046] FIG 4 illustrates a user plane protocol stack. In a network, the data plane is sometimes known as the user plane, forwarding plane, carrier plane, data path or bearer plane. It refers to all the processes that are responsible for forwarding packets from one interface (source) to another (destination) based on the control plane's logic. The primary function of the user plane is to carry the network's user traffic, or data packets, and transit the packets while, optionally, applying some action to them.

[0047] A user plane connection comprises a connection from the user plane function (UPF) to the Radio Access Network (RAN) and a connection from the Radio Access Network (RAN) to the user equipment (UE).

[0048] The user plane connection from the user plane function (UPF) to the Radio Access Network (RAN) can be referred to as a RAN-CN user plane connection, N3 user plane connection or NG-U user plane connection, for example. The user plane connection from the Radio Access Network (RAN) to the user equipment (UE) can be referred to as a user equipment user plane connection, or UE-RAN user plane connection. The user plane connection from the user plane function (UPF) to the user equipment (UE) via the Radio Access Network (RAN) can be referred to as the UE-CN user plane connection.

[0049] The activation of a UP connection of an existing PDU Session causes activation of its UE-CN User Plane connection (i.e. data radio bearer and N3 tunnel).

[0050] FIG 4 includes a user equipment (UE) 110, the access network 120, the core network (CN) 130 providing the User Plane Function (UPF) . The User Plane Function (UPF), handles the user data. The PDU layer corresponds to the PDU carried between the UE and the Data Network (DN) over the PDU Session. GPRS T unnelling Protocol for the user plane (GTP-U) supports tunnelling user data over N3 (i.e. between the 5G-AN node and the UPF) and N9 (i.e. between different UPFs of the 5GC) in the backbone network. GTP shall encapsulate all end user PDUs. It provides encapsulation on a per PDU Session level. This layer carries also the marking associated with a QoS Flow.

[0051] The UE initiates the PDU Session Establishment process by sending a request to the 5G core network. The request includes information about the type of service that the UE wants to use, and the type of traffic.

[0052] The preservation of bearer resources for ES, means that a corresponding emergency PDU session can operate as ‘always-on PDU Session. Configuring PDU Session as 'always-on' is just one form of preservation of bearer resources for ES.

[0053] A PDU session is a logical connection between the UE and a data network. Always-on PDU session is about establishment of a corresponding data radio bearers (DRBs) and N3 tunnel each time the UE goes to RRC-Connected / CM-Connected (even if no data) and keeping N3 tunnel and DRBs (as active or suspended) till it goes to CM-ldle. In other words, the UE having always-on PDU session still can go to RRC-ldle / CM-ldle and then it is not possible to say that the connection is active.

[0054] Based on an indication from upper layers, a UE may request to establish a PDU Session as an always-on PDU Session (or modifiy an established PDU session , to an always-on PDU Session). The SMF decides whether the PDU Session can be established as (or modified to) an always-on PDU Session.

[0055] The UE shall request activation of User Plane resources for always-on PDU Sessions even if there are no pending uplink data for this PDU Session or when the Service Request is triggered for signalling only or when the Service Request is triggered for paging response only.

[0056] If the UE has one or more established PDU Sessions which are not accepted by the network as always-on PDU Sessions and the UE has no uplink user data pending to be sent for those PDU Sessions, the UE shall not request for activating User Plane resources for those PDU sessions.

[0057] The deactivation of the UP connection of an existing PDU Session causes the corresponding data radio bearer and N3 tunnel of the user plane to be deactivated. The UP connection of different PDU Sessions can be deactivated independently when a UE is in CM-Connected state. If a PDU Session is an always-on PDU Session, the SMF should not deactivate a UP connection of this PDU Session due to inactivity.

[0058] The Session Initiation Protocol (SIP), which runs over the user plane, is a signalling protocol used for initiating, maintaining, and terminating communication sessions that include voice, video, and messaging applications. A signalling protocol is a type of communications protocol for encapsulating the signalling between communication endpoints.

[0059] FIG 5 illustrates an emergency call establishment. The PDU Session Establishment Request comprises a Request Type for an emergency call (initial emergency request 2). PDU Session Establishment Request goes to SMF and may trigger some other actions towards IMS. When emergency service is required and an Emergency PDU Session is not already established, a UE shall initiate the UE Requested PDU Session Establishment procedure with a Request Type indicating " initial emergency request ".

[0060] The 3GPP and GSMA standards use many synonymous terms to describe a PDU Session used to provide emergency services including: Emergency PDU Session, PDU Session associated with emergency services, PDU Session for emergency services, PDU Session serving the IMS Emergency session. Hereinafter, for uniformity and simplicity, we use the term emergency PDU Session.

[0061] An emergency PDU Session is a PDU session established with the request type "initial emergency request" or "existing emergency PDU session".

[0062] Since, the above-mentioned request type “initial emergency type” is visible only for the UE and AMF and the ResumeCause = emergency is visible to gNB and Establishment = emergency can be visible to gNB, , the emergency PDU Session is also characterized by the usage of Allocation and Retention Priority (ARP) value that is reserved for emergency services.

[0063] The IP Multimedia Core Network Subsystem (IMS) 200, is part of the Core Network (CN) 130, and defines an architecture of logical elements using SIP for call signalling between network elements and provides a layered approach with defined service, control, and transport planes. A control layer that isolates the access network (transport) from the application layer. IMS emergency service is defined in 3GPP TS 23.167.

[0064] Emergency service supports enhanced emergency call functions. This can include the ability to transmit the caller's location information and provide priority call handling.

[0065] The IMS is designed to support emergency service and priority communications, ensuring that critical calls receive a high enough level of service quality and reliability.

[0066] IMS supports emergency service and priority communications through a combination of access prioritization, resource management, location services, call continuity, and security measures. These capabilities ensure that communications are delivered with a high enough level of reliability and quality for emergency response.

[0067] Emergency calls made through IMS are given priority over some other but not necessarily all other types of traffic.

[0068] Quality of Service (QoS) Management: . This ensures that critical communications, such as those by emergency service are transmitted with higher reliability.

[0069] Resource Reservation: IMS can reserve network resources for priority communications, ensuring that these communications can be initiated and carried out even during times of high network congestion.

[0070] An emergency call can be to an emergency number. An emergency call can be established by dialling a number or by other means e.g. event detection or using a user- activated “red button” at the UE, without the need to dial.

[0071] The UE detects the request for the establishment of an emergency session.

[0072] If the UE has insufficient resources or capabilities to establish an emergency call due to other ongoing sessions then the UE will terminate the ongoing communication and release reserved bearer resources. If bearer registration is required and has not been performed, the UE shall perform bearer registration

[0073] If bearer resources for the transport of the IMS related signalling are required to be reserved, the UE shall reserve the resources

[0074] If the UE has sufficient credentials to authenticate with the IMS network, it shall initiate an IMS emergency registration by providing its IP address The IMS registration request shall include an emergency indication. The implicit registration set of the SIP URI used in the emergency registration request used by the UE when the UE performs a nonemergency registration shall contain an associated TEL-URI that is used to call back the UE.

[0075] The UE shall initiate the IMS emergency session establishment using the IMS session establishment procedures containing an emergency service indication.

[0076] When an emergency service is established there are two Quality of Service (QoS) flows. One is for IMS signalling via SIP (5QI5 IMS Signalling). The other is for telephone service (5QI1 -Conversational Voice. 5QI stands for 5G QoS Identifier.

[0077] Packets are classified and marked using QFI (Quality of Service Flow Identifier).

[0078] A QoS profile of a QoS flow contains QoS parameters including

[0079] 5QI (5G QoS Identifier) and ARP (Allocation and Retention Priority).

[0080] The 5QI is a reference to specific QoS forwarding behavior. For example, packet delay budget which can be multiple (2) orders of magnitude (e.g. 5ms to 500ms). For example, packet error rate which can be multiple (6) orders of magnitude (from 10-8 to 10-2).

[0081] The ARP value of a subscriber’s bearer determines whether or not it can replace an existing bearer that has a lower ARP precedence or be replaced by new bearer with a higher ARP precedence. ARP enables network operators to prioritize and allocate network resources to different users and services. The ARP priority ranges from 1 (highest) to 15 (lowest), where a lower ARP value indicates higher priority. ARP enables network operators to prioritize critical services, such as emergency services, over less critical services,

[0082] A QoS flow associated with the default QoS rule must be created by the network when the UE creates the emergency PDU session, as defined in 3GPP specifications. A standardised 5QI value of five (5) and an ARP value that is reserved for emergency services must be used for the QoS flow associated with the default QoS rule. The default QoS flow is used for IMS SIP signalling. ARP values reserved for emergency services are saved in the local configuration of the network entity (i.e. they are not fully standardized).

[0083] Preventing deactivation of a user plane connection of an emergency PDU Session comprises preservation of bearer services for the emergency PDU Session on the interface between the user plane function and the radio access network. In FIG 4, the user plane connection from the user plane function (UPF) to the Radio Access Network (RAN) is the N3 connection. Preventing deactivation of a user plane connection of an emergency PDU Session comprises preservation of the RAN-CN user plane connection including N3 tunnel.

[0084] After the release of the emergency call (i.e. 5QI=1 (conversational voice) is released, but 5QI=5 (IMS signal ling)is kept) for the purpose of eventual subsequent emergency callback.

[0085] FIG 6 illustrates an emergency service 10 and supporting layers 20, 30. Bearer Resources 30 for emergency PDU session supports emergency PDU session 20 which supports emergency service (ES) 10.

[0086] The emergency service can have two Quality of Service (QoS) flows. One is for IMS signalling via SIP (5QI5 IMS Signalling). The other is for telephone service (5QI1- Conversational Voice). The emergency telephony service (tele-service requires both 5QI5 and 5QI1). The emergency PDU session can survive with just one QoS Flow 5QI5.

[0087] The gNB is aware of: Bearer Resources for emergency PDU session 30. While this is maintained, it is indirectly aware of the existence of a emergency PDU session 10. A the lack of Bearer Resources for emergency PDU session 30 does not indicate the lack of emergency PDU session 20.

[0088] The ARP (Allocation and Retention Priority) used belongs to the ARP range configured in the network element as emergency (but restricted to values 1-8). A similar configuration parameters exists in other Network Elements.

[0089] RAN / gNB is aware of the Bearer Resources for emergency PDU session 30 via ARP (Allocation and Retention Priority). The PDU Session Resource Setup Request (received by RAN) includes ARP priority level, pre-emption capability and pre-emption vulnerability which can be used to identify the requests as a PDU Session Resource Setup Request (for emergency service).

[0090] The IE id-QosFlowSetupRequestList includes IE qosFlowldentifier which includes qosFlowLevelQosParameters including 5QI, ARP, pre-emptionCapability.

[0091] FIG 7 illustrates an example of state machine for Connection management (CM) and an example of a state machine for Radio Resource Control (RRC). The RRC state machine has three states: RRC-ldle, RRC-lnactive and RRC- Connected. It is possible that states will be renamed in future. It is possible that states will be added or removed in future. A transition from RRC-ldle to RRC-Connected is at least via connection establishment.

[0092] A transition from RRC-Connected to RRC-ldle is at least via connection release’. A transition from RRC-Connected to RRC-lnactive is at least via Suspend’. A transition from RRC-lnactive to RRC-Connected is at least via Resume. A transition from RRC-lnactive to RRC-ldle is at least via Release. There is no transition from RRC-ldle to RRC-lnactive.

[0093] In the example illustrated, a transition from RRC-ldle to RRC-Connected is only via connection establishment. A transition from RRC-Connected to RRC-ldle is only via connection release. A transition from RRC-Connected to RRC-lnactive is at least only via Suspend. A transition from RRC-lnactive to RRC-Connected is at least only via Resume. A transition from RRC-lnactive to RRC-ldle is at least only via Release. There is no transition from RRC-ldle to RRC-lnactive.

[0094] ‘Release’ does not necessary mean that the ‘RRCRelease’ message is transmitted, e.g. unsuccessful resume or reception of CN paging in RRC-lnactive changes state to RRC-ldle and is considered ‘Release’ procedure. The RRCRelease message can be used for transition to RRC-ldle or RRC-lnactive depending on parametrization (presence of suspendConfig).

[0095] The CM state machine has two states: CM-ldle and CM- Connected. It is possible that states will be renamed in future. It is possible that states will be added or removed in future. A transition from CM-ldle to CM-Connected is at least via connection establishment. A transition from CM-Connected to CM-ldle is at least via Connection Release (from RRC- Connected) or from Release from RRC-lnactive.

[0096] In the example illustrated, a transition from CM-ldle to CM-Connected is only via connection establishment. A transition from CM-Connected to CM-ldle is only via Connection Release (from RRC-Connected) or from Release from RRC-lnactive.

[0097] Connection Management (CM) includes the functions to establish and release a NAS signalling connection between a UE and the Access and Mobility Management Function (AMF) over the N1 interface. This signalling connection enables the NAS signalling exchange between the UE and the core network. The CM states determine the NAS signalling connection of the UE with the AMF. The following are the CM states:

[0098] CM-ldle — When a UE is in the CM-ldle state, the UE has no NAS signalling connection established with the AMF over the N1 interface. The AN signalling connection, N2 connection, and N3 connection do not exist in this state.

[0099] CM-Connected — When a UE is in the CM-Connected state, the UE has a NAS signalling connection with the AMF over the N1 interface. A NAS signalling connection comprises an RRC Connection between the UE and the NG-RAN and an NGAP UE association between the AN and the AMF for the 3GPP access. SMF supports network-initiated messages when a UE is either in the CM-ldle state or in the CM-Connected state.

[0100] In the RRC-Connected state, RRC connection is active and CM state is CM-Connected. In the RRC-lnactive state, RRC connection is suspended and CM-CM state is Connected. Core network (CN) Paging or Radio Access Network (RAN) Paging is possible.

[0101] In the RRC-ldle state, there is no RRC connection and CM state is CM-ldle. Core network (CN) Paging is possible but Radio Access Network (RAN) Paging is not possible.

[0102] In the following the term ‘Inactive state’ will be used to refer to a state that has a suspended state at lower layers (e.g. RRC) and a connected state at higher layers (e.g. CM-connected).

[0103] RAN paging is needed for UE in the RRC-lnactive CM-Connected state. Since a UE in the RRC-lnactive Connected state is in the CM-Connected state in the core network’s viewpoint, the core network simply forwards the data or the signaling message to the RAN when the data or signaling message arrives. Therefore, RAN itself generates the paging message and performs paging to find the exact location of the UE, and then to send the data or signaling to the UE.

[0104] UE monitors the PCCH for CN paging using the 5G-S-TMSI and RAN paging using the l-RNTI.

[0105] Paging allows the network to reach UEs in RRC-ldle and in RRC-lnactive state through Paging messages, and to notify UEs in RRC-ldle, RRC-lnactive and RRC- Connected state of, for example, system information change. While in RRC-ldle the UE monitors the paging channels for CN-initiated paging. While in RRC-lnactive the UE monitors paging channels for RAN-initiated paging and CN-initiated paging.

[0106] Paging DRX (Discontinuous Reception) is defined where the UE in RRC-ldle or RRC- lnactive is only required to monitor paging channels during one Paging Occasion (PO) per DRX cycle. The Paging DRX cycles are configured by the network:

[0107] 1) For CN-initiated paging, a default cycle is broadcast in system information;

[0108] 2) For CN-initiated paging, a UE specific cycle can be configured via NAS signalling;

[0109] 3) For RAN-initiated paging, a UE-specific cycle is configured via RRC signalling;

[0110] The UE uses the shortest of the DRX cycles applicable. The term DRX will be used to refer to paging DRX.

[0111] In a DRX cycle, the UE get into a reception sleeping mode for a certain period of time and wakes up again, temporarily, to check if there is any paging / data coming from the network before going back into sleeping mode again if there is no data. This periodic repetition of "sleep mode and wake up mode" is called DRX (Discontinuous Reception". The UE may be configured by upper layers and / or RRC with an extended DRX (eDRX) cycle.

[0112] The UE operates in eDRX for CN paging in RRC-ldle or RRC-lnactive states if the UE is configured for eDRX by upper layers and eDRX-Allowedldle is signalled in SIB1.

[0113] The UE operates in eDRX for RAN paging in RRC-lnactive state if the UE is configured for eDRX by RAN and eDRX-Allowedlnactive is signalled in SIB1.

[0114] . The maximum non-extended DRX cycle is 2.56s.

[0115] With eDRX, the DRX cycle can be extended to several hours or possibly, in future, even days. It can also be 2.56s. 2.56s belongs to both DRX cycles set and eDRX cycle set.. eDRX and DRX requires synchronization between UE and Network.

[0116] The CN eDRX cycle is an eDRX cycle for UE RRC-ldle (or UE RRC-lnactive) controlled at CN.

[0117] The INACTIVE or RAN eDRX cycle is an eDRX cycle for UE RRC-lnactive controlled at RAN.

[0118] A gNB may configure INACTIVE / RAN eDRX cycle only if IDLE / CN eDRX is configured and RAN eDRX is equal or shorter then CN eDRX.

[0119] Since CN informs gNB about IDLE / CN eDRX cycle, and gNB may configure INACTIVE / RAN eDRX cycle only if IDLE / CN eDRX is configured and RAN eDRX is equal or shorter then CN eDRX, CN knows that if it has not informed gNB about CN eDRX, RAN eDRX cannot be configured and otherwise it can be configured but not longer than CN eDRX. The CN knows of possibility but not actuality of INACTIVE / RAN eDRX being configured.

[0120] The current 3GPP 5G standard does not prevent usage of eDRX for RAN initiated paging in the RRC-lnactive state during the period in which an emergency call back call may be initiated, which may result in the inability to establish emergency call back calls.

[0121] It may be helpful to clarify what entities have what knowledge / awareness:

[0122] The UE is aware of the configuration of INACTIVE / RAN eDRX. The RAN is aware of the configuration of INACTIVE / RAN eDRX. RAN configures INACTIVE / RAN eDRX. The CN is aware of the possibility (not actuality) of configuration of INACTIVE / RAN eDRX. CN informs gNB about IDLE / CN eDRX cycle. gNB may configure INACTIVE / RAN eDRX cycle only if IDLE / CN eDRX is configured and RAN eDRX cycle is equal or shorter then CN eDRX cycle. CN knows that if it has not informed gNB about CN eDRX, RAN eDRX cannot be configured and otherwise it can be configured but not longer than CN eDRX.

[0123] The UE is aware of the existence / termination of an emergency service. The RAN is not aware of the of the emergency service. It is transparent to the RAN. The CN (IMS) is aware of the emergency service. The UE is aware of the UE RRC State. The RAN is aware of the UE RRC state. The gNB can control UE RRC state transitions. The CN is not aware of the UE RRC State except when optional RRC Inactive Transition Report is implemented full visibility is possible.

[0124] The fact that the network element knows a UE state does not mean that this known state is ‘correct’. State desynchronizations is possible and procedures are designed in such a way that the state machines resynchronize at the next radio contact or contact attempt. For example, RRC state is known by UE / gNB as outcome of RRCSetupRequest / RRCSetup / RRCSetupComplete messaging or RRCRelease or RRCResumeRequest / RRCResumeRequestl / RRCResume / RRCResumeComplete.

[0125] The UE is aware of the UE CM State. The CN is aware of the UE CM State. If UE- associated logical connection exists across NG-C / N2 interface the UE is in CM-Connected.

[0126] CM state is known by gNB and CN / AMF as outcome of the procedures initiated by UL NGAP Initial UE Message or UL NGAP UE CONTEXT RELEASE REQUEST or DL NGAP UE CONTEXT RELEASE COMMAND .

[0127] CM state is known by UE and AMF based on outcome of the procedures initiated by NAS UE initial messages (these are the NAS messages that are always sent as first messages in the UL direction on a newly established radio connection and are piggybacked on RRCSetupComplete messages and piggybacked on NGAP Initial UE message, example of such message is NASServiceRequest or NASRegistrationRequest). The actual transition of the state is not done by ‘response’ kind of the NAS message send in DL direction, but rather indication from the lower layer, e.g. on UE side the RRC lower layer informs the NAS upper layer that the connection exists, similarly on AMF side NGAP lower layer informs NAS upper layer that NG-C connection is established.

[0128] In at least some of the following examples, when the UE is in inactive state (RRC- Inactive) and has emergency PDU session, the UE and network follow regular discontinuous reception (cycle of less than or equal to 2.56s) and shall not use a longer INACTIVE / RAN eDRX cycle.

[0129] FIG 8 and FIG 9 illustrate an example where the RAN (gNB 120) is aware of user plane (UP) resources 30 associated with an emergency Allocation and Retention Priority (ARP) value and is therefore aware of the existence of an emergency PDU session 20.

[0130] The resources used, from the perspective of the RAN (gNB 120) are user plane (UP) resources 30 associated with an emergency Allocation and Retention Priority (ARP) value and, from the perspective of the CN 130 are Bearer Resources 30 for emergency PDU session 20. The CN 130 does not release Bearer Resources 30 for emergency PDU session 20. This is known to the RAN (gNB 120) because UP resources 30 associated with an emergency ARP value are not released.

[0131] In FIG 8, the CN 130 maintains (does not release) CN-RAN Bearer Resources 30 for emergency PDU session 20. The RAN (gNB 120) is consequentially aware of the maintenance of the emergency PDU session 20.

[0132] When the emergency service / call 10 ends, the CN 130 does not release Bearer Resources 30 for emergency PDU session 20 (the UP resources 30 associated with an ARP value). The RAN (gNB) 120 is consequently aware of emergency PDU session 20. The RAN (gNB) 120 is aware of the emergency PDU session 20 but is not aware of ending of emergency service / call 10, as the RAN (gNB) 120 is transparent to SIP.

[0133] The RAN (gNB) 120 uses DRX (DRX cycle of <2.56s) while Bearer Resources for emergency PDU session exists (the UP resources 30 associated with an emergency ARP value exist). This implies emergency PDU session 20 exists.

[0134] In at least some examples, the RAN (gNB) 120 uses DRX (DRX cycle of <2.56s) while Bearer Resources for emergency PDU session exists (the UP resources 30 associated with an emergency ARP value exist) even though UE 110 is configured for eDRX (eDRX cycle of >2.56s).

[0135] The Bearer Resources 30 for emergency PDU session (the UP resources 30 associated with an emergency ARP) and the emergency PDU session 20 are maintained as long as an emergency call back is possible, i.e. as long as the emergency PDU session 20 exist and call back is possible (timer based). The most likely implementation is a single timer to control release of emergency PDU session 20 (and automatically resources 30 are released at the same time), but two separate timers are possible.

[0136] After a timeout time period, Emergency PDU Session is released, so its resources on RAN-CN interface are also released.

[0137] If call back is required during the timeout time period, the CN 130 causes RAN paging 40 according to DRX schedule (DRX cycle of <2.56s). The CN sends SIP INVITE request over existing 5QI5 or CN sends PDU SESSION RESOURCE MODIFY REQUEST to add 5QI1 to the existing PDU Session. Generally, both are required at a certain point, but the order depends on implementation / configuration.

[0138] The CN 130 is caused to not release Bearer Resources for emergency PDU session after the end of an emergency call. This can be realized as an always-on PDU Session (UE requests andnetwork configures during original UE originated emergency service establishment or SMF modifies to always-on if call back is enabled). The network entity 130, for example a network entity providing a session management function (SMF), comprises means for: maintaining an emergency Packet Data Unit (PDU) session 20; and being informed of completion of an emergency service 10; wherein the network entity 130 comprises means for ensuring that the radio access network (RAN) 120 is aware of possibility of emergency call back establishment by not initiating deactivation of a user plane connection 32 of an emergency Packet Data Unit session 20 while maintaining the emergency Packet Data Unit session 20, after being informed of completion of the emergency service (e.g. release of service flow for conversational voice).

[0139] In at least some examples , to ensure timely emergency call back establishment in eDRX capable mobile networks for eDRX capable UEs, the CN / SMF ensures that the RAN / gNB is aware of possibility of emergency call back establishment, so that RAN / gNB does not configure UE with RAN eDRX or does not use RAN eDRX even if configured.

[0140] In at least some examples, preventing deactivation of a user plane connection 32 of an emergency Packet Data Unit session 20 comprises preservation of bearer services 30 for the emergency Packet Data Unit session 20 on an interface (N3) between a user plane function (UPF) and a radio access network (RAN) 120.

[0141] In at least some examples, an emergency service 10 comprises multiple quality of service flows and completion of an emergency service comprises release of one or more but not all quality of service flows. In at least some examples, completion of an emergency service comprises release of the telephone service flow of the emergency service quality of service flows.

[0142] In at least some examples, maintaining the emergency Packet Data Unit session 20 comprises maintaining an IMS signalling flow used for IMS signalling. In at least some examples, completion of an emergency service comprises maintenance of only the IMS signalling flow used for IMS signalling.

[0143] In at least some examples,, a standardised 5QI value of five (5) and an ARP value that is reserved for emergency services are used for the QoS flow associated with the default QoS rule. The default QoS flow is used for IMS SIP signalling.

[0144] In at least some examples, completion of an emergency service maps to “PCF (vPCF) removes all PCC Rules with a 5QI other than the default 5QI and the 5QI used for IMS signalling”

[0145] In at least some examples, the network entity 130 comprises means for: receiving a request from a user equipment 110, during session establishment or session modification; evaluating the request to determine whether or not to grant session establishment or session modification in accordance with the request, wherein, when the request is that an emergency Packet Data Unit (PDU) session 20 be configured as an always-on PDU session it is evaluated with more favorable criteria than, when the request is that a non-emergency Packet Data Unit (PDU) session 20 be configured as an always- on PDU session. In at least some examples, the more favorable evaluation is conditionally dependent upon emergency call back and / or Radio Access Network extended Discontinuous Reception being enabled in the network. In some examples, when CN / SMF accepts emergency Packet Data Unit session establishment or modification and the UE requests the emergency Packet Data Unit session 20 to be configured as an always-on PDU Session, CN / SMF configures the emergency Packet Data Unit session 20 as an always-on PDU session even if configuration of the emergency Packet Data Unit session 20 as an always-on PDU Session is not required due to some other reasons (e.g. requested QoS characteristics apart from ARP). In some examples, the CN / SMF is aware of emergency call back and / or RAN eDRX being enabled in the network based on local configuration (configuration parameters of the network entity 130 and not information obtained via C-plane or U-plane interfaces).

[0146] In at least some examples, the network entity 130 comprises means for identifying a request from a user equipment 110 as a request during session establishment or session modification that an emergency Packet Data Unit (PDU) session 20 be configured as an always-on PDU session, the request being a NAS PDU SESSION ESTABLISHMENT REQUEST and / or a NAS PDU SESSION MODIFICATION REQUEST messages with always-on PDU session requested information element set to the value always-on PDU session requested.

[0147] The radio access network entity 120 comprises means for: monitoring user plane resources 30 associated with an emergency Allocation and Retention Priority (ARP) value; and for a user equipment 110 having radio access network user plane resources 30 associated with an emergency ARP value, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment 110.

[0148] In some examples, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment 110 comprises preventing configuration of Radio Access Network extended Discontinuous Reception (eDRX) for the user equipment 110 having radio access network user plane resources 30 associated with an emergency ARP value.

[0149] In some examples, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment 110 comprises following Radio Access Network Discontinuous Reception (DRX) when Radio Access Network paging the user equipment 110, even if the user equipment 110 is configured with Radio Access Network extended Discontinuous Reception (eDRX).

[0150] In some examples, the means for monitoring user plane resources 30 associated with an emergency ARP value comprises means for monitoring user plane resources 30 associated with an emergency ARP value across an interface to a core network.

[0151] In some examples, if user plane resources 30 across RAN-CN interface (N3 tunnel) associated with emergency ARP values are allocated in the RAN / gNB 120 for a given UE110, RAN / gNB 120 does not configure this UE 110 with RAN eDRX (i.e. RAN eDRX configured by gNB 120 via RRC).

[0152] In some examples, if user plane resources 30 across RAN-CN interface (N3 tunnel) associated with emergency ARP values are allocated in the RAN / gNB 120 for a given UE 110, RAN / gNB 120 follows a regular RAN DRX when paging this UE 110, even if this UE is configured with RAN eDRX.

[0153] In some examples, using Radio Access Network Discontinuous Reception (DRX) for radio access network paging of the user equipment 110 comprises using a cycle less than or equal to 2.56s (a DRX cycle), and using extended Radio Access Network Discontinuous Reception (eDRX) for radio access network paging of the user equipment 110 comprises using a cycle greater than or equal to 2.56s (an eDRX cycle).

[0154] In some examples, if user plane resources 30 across the RAN-CN interface associated with emergency ARP values are allocated in the RAN / gNB 120 for a given UE 110, RAN / gNB 120 does not configure this UE 110 with RAN eDRX cycle longer than 2.56s (i.e. longer than the maximum regular RAN DRX cycle).

[0155] In some examples, the radio access network entity 120 comprises means for, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment 110 for user equipment 110 having radio access network user plane resources 30 associated with an emergency ARP value, if the Radio Access Network extended Discontinuous Reception (eDRX) is configured to operate with a cycle longer than 2.56s. The radio access network entity 120 comprises means for: receiving from a core network a message 42 that causes radio access network paging 40 of a user equipment 110; in dependence upon the received message 42, performing radio access network paging 40 of the user equipment 110, wherein, if the received message 42 comprises an emergency Allocation and Retention Priority (ARP) value and the user equipment 110 is in the inactive state, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment 110.

[0156] In some examples, if the gNB 120 receives from the CN signalling message 42 that includes emergency ARP values and the further processing of this message or procedure related to this message require RAN paging 40 of the UE in RRC-lnactive state, gNB 120 follows a regular RAN DRX even if the UE 110 is configured with RAN eDRX (this does not prevent the gNB from employing a paging strategy in which paging is repeated such that paging occasions associated with both RAN DRX and RAN eDRX are utilized).

[0157] In some examples, if the gNB 120 receives from the CN signalling message 42 that includes emergency ARP values and the further processing of this message or procedure related to this message require RAN paging of the UE in RRC-lnactive state, gNB 120 follows a regular RAN DRX if the UE 110 is configured with RAN eDRX cycle longer than 2.56s (i.e. longer than the maximum regular RAN DRX cycle). This does not prevent the gNB from employing a paging strategy in which paging is repeated such that paging occasions associated with both RAN DRX and RAN eDRX are utilized).

[0158] The user equipment 110 comprises means for: maintaining an inactive state; monitoring an emergency Packet Data Unit (PDU) session 20; being configured to operate in a Radio Access Network (RAN) Discontinuous Reception (DRX) mode; being configured to operate in a Radio Access Network (RAN) extended Discontinuous Reception (eDRX) mode different to the Radio Access Network (RAN) Discontinuous Reception (DRX) mode; wherein the user equipment 110 comprises means for, when in an inactive state, if the user equipment 110 has an emergency Packet Data Unit (PDU) session 20, operating in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode.

[0159] In at least some examples, the user equipment 110 comprises means for, when in an inactive state, if the user equipment 110 has an emergency Packet Data Unit (PDU) session 20, operating in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode with an eDRX cycle longer than 2.56s. For example, when the UE is in RRC-lnactive state and has an emergency Packet Data Unit session 20 it follows regular RAN / INACTIVE DRX if it is configured with RAN eDRX cycle longer than 2.56s (i.e. longer than the maximum regular RAN DRX cycle).

[0160] In at least some examples the user equipment 110 comprises means for, when in an inactive state, if the user equipment 110 has an emergency Packet Data Unit (PDU) monitoring paging according to Radio Access Network Discontinuous Reception (DRX) cycle even if the user equipment 110 is configured to monitor paging according to the Radio Access Network extended Discontinuous Reception (eDRX) cycle.

[0161] In at least some examples, the user equipment 110 comprises means for, when in an inactive state and configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode, if the user equipment 110 has an emergency Packet Data Unit (PDU) session 20, operating in the Radio Access Network Discontinuous Reception (DRX) mode instead of the Radio Access Network extended Discontinuous Reception (eDRX) mode.

[0162] In at least some examples, whenever the user equipment 110 requests emergency Packet Data Unit (PDU) session 20, it requests an always-on PDU session. The request can be for establishment or modification. For example, when the UE requests establishment of an emergency Packet Data Unit session 20, it request the emergency Packet Data Unit session 20 to be configured by the CN / SMF as an always-on PDU Session. For example, when UE has an ongoing emergency Packet Data Unit session 20, it requests emergency Packet Data Unit session 20 modification to an always-on PDU Session if it has not already been configured as such.

[0163] In at least some examples, the user equipment 110 comprises means for requesting, during session establishment or session modification, the emergency Packet Data Unit (PDU) session 20 to be configured as an always-on PDU session, said requesting comprising sending NAS PDU SESSION ESTABLISHMENT REQUEST and / or NAS PDU SESSION MODIFICATION REQUEST messages with always-on PDU session requested information element (IE) set to the value always-on PDU session requested. In at least some examples, the user equipment 110 comprises means for requesting activation of user plane resources 30 for the emergency Packet Data Unit session 20 during Service Request and Registration procedures even if there are no pending uplink data for this PDU Session. For example the UE 110 requests activation of user plane resources 30 when there is no pending uplink data for this PDU Session because, for example, Service Request procedure is triggered for signaling only. For example, the UE 110 requests activation of user plane resources 30 when there is no pending uplink data for this PDU Session because, for example, Service Request procedure is triggered for paging response only. In some examples, the UE 110 includes Uplink data status IE with the bit corresponding to the emergency Packet Data Unit session set to one in NAS SERVICE REQUEST, NAS CONTROL PLANE SERVICE REQUEST and NAS REGISTRATION REQUEST messages.

[0164] In at least some examples, the user equipment 110 comprises means for: after the emergency Packet Data Unit session 20 is released, the user equipment 110 in inactive state follows Radio Access Network extended Discontinuous Reception if it is configured.

[0165] In at least some examples, the user equipment 110 comprises means for, when in an inactive state, enabling upper (protocol) layers of the user equipment 110 to inform lower (protocol) layers of the user equipment 110 whether eDRX or DRX should be followed depending on whether the user equipment 110 has an emergency Packet Data Unit session 20.

[0166] In examples, if the UE 110 is in inactive state and has an emergency Packet Data Unit (PDU) session 20, use DRX not eDRX. In examples, the core network entity 130, after being informed of completion of an emergency service 10, does not deactivate a user plane connection of the emergency PDU session. The radio access network 120 uses DRX (not eDRX) to page a UE110 having radio access network user plane resources associated with an emergency ARP value. The radio access network entity 120, uses DRX (not eDRX) to page a UE 110, in the inactive state, when paging triggered by a message comprising an emergency Allocation and Retention Priority (ARP) value.

[0167] The mechanism of UP connection preservation proposed is for the purpose of emergency call back. The solution can be implemented with or without always-on PDU Session feature being supported or used by the UE. In at least some examples, the emergency Packet Data Unit session 20 does not have to be requested as an always-on PDU Session nor does it have to be accepted / configured as an always-on PDU Session by the CN / SMF. An example of a possible addendum to 3GPP 38.304 at : 7.1 Discontinuous Reception for paging in light of this description: “ In RRC-lnactive state, the UE shall not operate in eDRX, instead the UE shall use Discontinuous Reception (DRX) if the UE has a PDU Session for emergency services. NOTE: When UE is allocated with resources for PDU Session for emergency services RAN does not configure the UE with eDRX.”

[0168] In FIGs 8 & 9, the emergency PDU session 20 is maintained after the emergency service 10 (emergency call) is terminated and paging is used according to the DRX (not eDRX) cycle. In FIGs 8 & 9, bearer resources for the emergency PDU session 20 are maintained after the emergency service 10 (emergency call) is terminated. The RAN (gNB) 120 is aware of the emergency PDU session 20 and RAN paging 40 is used according to the DRX (not eDRX) cycle (e.g. 2.56s).

[0169] FIG. 10 illustrates an example of a controller 400 suitable for use in an apparatus (UE 110, RAN entity 120, CN entity 130). Implementation of a controller 400 may be as controller circuitry. The controller 400 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

[0170] As illustrated in FIG. 10 the controller 400 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions 406 in a general-purpose or special-purpose processor 402 that may be stored on a machine readable storage medium (disk, memory etc.) to be executed by such a processor 402.

[0171] The processor 402 is configured to read from and write to the memory 404. The processor 402 may also comprise an output interface via which data and / or commands are output by the processor 402 and an input interface via which data and / or commands are input to the processor 402.

[0172] The memory 404 stores instructions, program, or code 406 that controls the operation of the apparatus (UE 110, RAN entity 120, CN entity 130) when loaded into the processor 402. The computer program instructions, program or code am 406, provide the logic and routines that enables the apparatus (UE 110, RAN entity 120, CN entity 130) to perform the methods illustrated in the accompanying FIGs. The processor 402 by reading the memory 404 is configured to load and execute the instructions, program, or code 406.

[0173] The apparatus (UE 110) comprises: at least one processor 402; and at least one memory 404 storing instructions that, when executed by the at least one processor 402, cause the apparatus at least to: operate in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode, on a condition that the user equipment has an emergency Packet Data Unit (PDU) session.

[0174] The apparatus (CN entity 130) comprises: at least one processor 402; and at least one memory 404 storing instructions that, when executed by the at least one processor 402, cause the apparatus at least to: not initiating deactivation of, a user plane connection of an emergency packet data unit session while maintaining the emergency packet data unit session, after being informed of completion of an emergency service.

[0175] The apparatus (RAN entity 120) comprises: at least one processor 402; and at least one memory 404 storing instructions that, when executed by the at least one processor 402, cause the apparatus at least to: monitor user plane resources associated with an emergency Allocation and Retention Priority (ARP) value; and for a user equipment having radio access network user plane resources associated with an emergency ARP value, use Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

[0176] The apparatus (RAN entity 120) comprises: at least one processor 402; and at least one memory 404 storing instructions that, when executed by the at least one processor 402, cause the apparatus at least to: receive from a core network a message that causes radio access network paging of a user equipment; if the received message comprises an emergency Allocation and Retention Priority (ARP) value and the user equipment is in the inactive state, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

[0177] As illustrated in FIG. 11 , the instructions, program, or code 406 may arrive at the apparatus (UE 110, RAN entity 120, CN entity 130) via any suitable delivery mechanism 408. The delivery mechanism 408 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD-ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the computer program 406. The delivery mechanism may be a signal configured to reliably transfer the computer program 406. The apparatus (UE 110, RAN entity 120, CN entity 130) may propagate or transmit the computer program 406 as a computer data signal.

[0178] The term “non-transitory” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal ) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0179] In some examples there is provided a computer program that when run by one or more processors of a user equipment 110, causes the user equipment 110, when in an inactive state, to: operate in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode, on a condition that the user equipment has an emergency Packet Data Unit (PDU) session.

[0180] In some examples there is provided a computer program that when run by one or more processors of a core network entity 130, causes the core network entity 130 to:_maintain, and not initiating deactivation of, a user plane connection of an emergency packet data unit session while maintaining the emergency packet data unit session, after being informed of completion of an emergency service.

[0181] In some examples there is provided a computer program that when run by one or more processors of a radio access network entity 120, causes the radio access network entity 120to: monitor user plane resources associated with an emergency Allocation and Retention Priority (ARP) value; and for a user equipment having radio access network user plane resources associated with an emergency ARP value, use Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

[0182] In some examples there is provided a computer program that when run by one or more processors of a radio access network entity 120, causes the radio access network entity 120 to: receive from a core network a message that causes radio access network paging of a user equipment; if the received message comprises an emergency Allocation and Retention Priority (ARP) value and the user equipment is in the inactive state, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

[0183] The computer program instructions may be comprised in a computer program, a non- transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program.

[0184] Although the memory 404 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0185] Although the processor 402 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 402 may be a single core or multi-core processor.

[0186] References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

[0187] As used in this application, the term ‘circuitry’ may refer to one or more or all the following:

[0188] (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and

[0189] (b) combinations of hardware circuits and software, such as (as applicable): i. a combination of analog and / or digital hardware circuit(s) with software / firmware and ii. any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory or memories that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation.

[0190] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0191] The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the computer program 406. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

[0192] As used here ‘module’ refers to a unit or apparatus that excludes certain parts / components that would be added by an end manufacturer or a user. The user equipment 110 can, for example be a module. A controller 400 of the user equipment 110 can, for example be a module.

[0193] Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

[0194] The above-described examples find application as enabling components of: automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services.

[0195] The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

[0196] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

[0197] In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. , to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components.

[0198] As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database, or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine / determining" can include resolving, selecting, choosing, establishing, and the like.

[0199] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

[0200] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0201] Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

[0202] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0203] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0204] The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus.

[0205] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0206] The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0207] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0208] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

[0209] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0210] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon, l / we claim:

Claims

1. 29CLAIMS1. A user equipment comprising means for: maintaining an inactive state; monitoring an emergency Packet Data Unit (PDU) session; being configured to operate in a Radio Access Network Discontinuous Reception (DRX) mode; being configured to operate in a Radio Access Network extended Discontinuous Reception (eDRX) mode different to the Radio Access Network Discontinuous Reception (DRX) mode; wherein the user equipment comprises means for, when in an inactive state, if the user equipment has an emergency Packet Data Unit (PDU) session, operating in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode.

2. A user equipment as claimed in claim 1 , wherein the user equipment comprises means for, when in an inactive state, if the user equipment has an emergency Packet Data Unit (PDU) session, operating in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode with an eDRX cycle longer than 2.56s.

3. A user equipment as claimed in claim 1 or 2, wherein whenever the user equipment requests emergency Packet Data Unit (PDU) session, it requests an always-on PDU session.

4. A user equipment as claimed in claim 3, comprising means for requesting, during session establishment or session modification, the emergency Packet Data Unit (PDU) session to be configured as an always-on PDU session, said requesting comprising sending NAS PDU SESSION ESTABLISHMENT REQUEST and / or NAS PDU SESSION MODIFICATION REQUEST messages with Always-on PDU session requested IE set to the value Always-on PDU session requested.

5. A user equipment as claimed in any preceding claim, wherein the user equipment comprises means for requesting activation of user plane resources for the emergency PDU Session during Service Request and Registration procedures even if there are no pending uplink data for this PDU Session; and / or30 wherein the user equipment comprises means for, when in an inactive state, enabling upper layers of the user equipment to inform lower layers of the user equipment whether eDRX or DRX should be followed depending on whether the user equipment has an emergency PDU Session; and / or wherein the user equipment comprises means for, when in an inactive state and configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode, if the user equipment has an emergency Packet Data Unit (PDU) session, operating in the Radio Access Network Discontinuous Reception (DRX) mode instead of the Radio Access Network extended Discontinuous Reception (eDRX) mode.

6. A user equipment as claimed in any preceding claim comprising means for: after the emergency PDU Session is released, the user equipment in inactive state follows Radio Access Network extended Discontinuous Reception if it is configured.

7. A network entity, for example a network entity providing a session management function, comprising means for: maintaining an emergency packet data unit (PDU) session; and being informed of completion of an emergency service; wherein the network entity comprises means for ensuring that the radio access network (RAN) is aware of possibility of emergency call back establishment by not initiating deactivation of a user plane connection of an emergency PDU session while maintaining the emergency PDU Session after being informed of completion of the emergency service.

8. A network entity as claimed in claim 7, wherein an emergency service comprises multiple quality of service flows and completion of an emergency service comprises release of one or more but not all quality of service flows; and / or wherein preventing deactivation of a user plane connection of an emergency PDU Session comprises preservation of bearer services for the emergency PDU Session on an interface between a user plane function and a radio access network.

9. A network entity as claimed in claim 7 or 8, wherein completion of an emergency service comprises release of the telephone service flow of the emergency service quality of service flows; and / or wherein completion of an emergency service comprises maintenance of only the IMS signalling flow used for IMS signalling. and / or wherein maintaining the emergency PDU session comprises maintaining an IMS signalling flow used for IMS signalling.

10. A network entity as claimed in any of claims 7 to 9, wherein the network entity comprises means for: receiving a request from a user equipment, during session establishment or session modification; evaluating the request to determine whether or not to grant session establishment or session modification in accordance with the request, wherein, when the request is that an emergency Packet Data Unit (PDU) session be configured as an always-on PDU session it is evaluated with more favorable criteria than, when the request is that a non-emergency Packet Data Unit (PDU) session be configured as an always-on PDU session, wherein optionally, more favorable evaluation is conditionally dependent upon emergency call back and / or Radio Access Network extended Discontinuous Reception being enabled in the network; and / or.

11. A radio access network entity comprising means for: monitoring user plane resources associated with an emergency Allocation and Retention Priority (ARP) value; and for a user equipment having radio access network user plane resources associated with an emergency ARP value, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

12. A radio access network entity as claimed in claim 11, wherein using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment comprises preventing configuration of Radio Access Network extended DiscontinuousReception (eDRX) for the user equipment having radio access network user plane resources associated with an emergency ARP value. and / or wherein using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment comprises following Radio Access Network Discontinuous Reception (DRX) when Radio Access Network paging the user equipment, even if the user equipment is configured with Radio Access Network extended Discontinuous Reception (eDRX); and / or wherein the means for monitoring user plane resources associated with an emergency ARP value comprises means for monitoring user plane resources associated with an emergency ARP value across an interface to a core network.

13. A radio access network entity as claimed in any of claims 11 or 12, wherein using Radio Access Network Discontinuous Reception (DRX) for radio access network paging of the user equipment comprises using a cycle less than or equal to 2.56s.

14. A radio access network entity as claimed in any of claims 11 to 13, wherein the radio access network entity comprises means for, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment for user equipment having radio access network user plane resources associated with an emergency ARP value, if the Radio Access Network extended Discontinuous Reception (eDRX) is configured to operate with a cycle longer than 2.56s.

15. A radio access network entity comprising means for: receiving from a core network a message that causes radio access network paging of a user equipment; in dependence upon the received message, radio access network paging the user equipment, wherein, if the received message comprises an emergency Allocation and Retention Priority (ARP) value and the user equipment is in the inactive state, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.3316. A computer program that when run by one or more processors of a user equipment, causes the user equipment, when in an inactive state, to:Operate in the Radio Access Network Discontinuous Reception (DRX) mode even if configured to operate in the Radio Access Network extended Discontinuous Reception (eDRX) mode, on a condition that the user equipment has an emergency Packet Data Unit (PDU) session.

17. A computer program that when run by one or more processors of a core network entity, causes the core network entity to: maintain, and not initiating deactivation of, a user plane connection of an emergency packet data unit session while maintaining the emergency packet data unit session, after being informed of completion of an emergency service.

18. A computer program that when run by one or more processors of a radio access network entity, causes the radio access network entity to: monitor user plane resources associated with an emergency Allocation and Retention Priority (ARP) value; and for a user equipment having radio access network user plane resources associated with an emergency ARP value, use Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

19. A computer program that when run by one or more processors of a radio access network entity, causes the radio access network entity to: receive from a core network a message that causes radio access network paging of a user equipment; if the received message comprises an emergency Allocation and Retention Priority (ARP) value and the user equipment is in the inactive state, using Radio Access Network Discontinuous Reception (DRX), not Radio Access Network extended Discontinuous Reception (eDRX), for radio access network paging of the user equipment.

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