Improvements in and relating to proximity services in a telecommunication network

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Disclosed is a method of managing a ProSe connection set up between a remote User Equipment, UE, a relay and a network, the connection using a Protocol Data Unit session, the PDU session being a Local Area Data Network, LADN, PDU session, wherein during a link establishment or modification procedure, between the remote UE and the relay, the relay verifies if it is inside or outside a defined LADN service area.

Description

IMPROVEMENTS IN AND RELATING TO PROXIMITY SERVICES IN A TELECOMMUNICATION NETWORK

[0001] The present application relates to wireless communication technologies, in particular to a method and a device for improving a proximity-based services (prose).

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] The principal object of the embodiments herein is to disclose methods and apparatus for improving a proximity-based services (prose).

[0009] It is an aim of certain examples of the present disclosure to address, solve and / or mitigate, at least partly, at least one of the problems and / or disadvantages associated with the related art, for example at least one of the problems and / or disadvantages described herein. It is an aim of certain examples of the present disclosure to provide at least one advantage over the related art, for example at least one of the advantages described herein.

[0010] The present disclosure is defined in the independent claims. Advantageous features are defined in the dependent claims. Embodiments or examples disclosed in the description and / or figures falling outside the scope of the claims are to be understood as examples useful for understanding the present disclosure.

[0011] Other aspects, advantages and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings.

[0012] Before undertaking the MODE FOR INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation; the term "or," is inclusive, meaning and / or; the phrases "associated with" and "associated therewith," as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term "controller" means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0013] Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code. The phrase "computer readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer readable medium" includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A "non-transitory" computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device.

[0014] Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0015] According to an embodiment of present disclosure, methods and apparatus are provided for improving a proximity-based services (prose).

[0016] Fig. 1 illustrates a representation of a system to which am embodiment of the invention applies;

[0017] Fig. 2 illustrates a message flow related to ProSe establishment;

[0018] Fig. 3 illustrates a problem associated with the prior art;

[0019] Fig. 4 shows a flowchart illustrating an embodiment of the invention;

[0020] Fig. 5 illustrates a block diagram of a user equipment (UE) according to the present disclosure.

[0021] Proximity services (ProSe) enable direct communications between devices where these devices can engage in ProSe discovery and / or ProSe communications using so called PC5 resources. Such Proximity Services are typically offered in Fifth Generation, 5G, and other telecommunication networks.

[0022] Figure 1 shows a schematic, illustrating certain entities, which will be referred to in the following. In particular, it shows: a remote User Equipment, UE, 10; a L3 UE to Network Relay 20; a Next Generation Radio Access Network, NG-RAN, 30; a Fifth Generation, 5G, Core, 5GC; and a Data Network 50. In essence, The L3 relay 20 provides connection to the remote UE 10 by establishing a PDU session and using the PDU session to transfer data between the remote UE 10 and the Data Network 50.

[0023] One of the use cases of ProSe is to provide relay services to so called remote User Equipments, UEs. A remote UE is a UE that is not in direct coverage of the network, whereas a relay UE is in coverage of the network and, hence, acts as a communication relay for the remote UEs. A Layer 3 UE-to-Network relay UE provides connectivity for remote UEs by establishing a Protocol Data Unit, PDU, session that is used for relay communication. More details about ProSe services can be found in 3GPP TS 23.304 amongst other specifications.

[0024] The procedure for communication of a remote UE with the network via a ProSe Layer-3 UE-to-Network relay UE, hereafter referred to as L3 relay UE, is described in section 6.5.1.1 of 3GPP TS 23.304 and is reproduced below:

[0025] A 5G ProSe Layer-3 UE-to-Network Relay registers to the network (if not already registered). 5G ProSe Layer-3 UE-to-Network Relay establishes a PDU Session(s) or modifies an existing PDU Session(s) in order to provide relay traffic towards 5G ProSe Layer-3 Remote UE(s). PDU Session(s) supporting 5G ProSe Layer-3 UE-to-Network Relay shall only be used for 5G ProSe Layer-3 Remote UE(s) relay traffic.

[0026] The PLMN serving the 5G ProSe Layer-3 UE-to-Network Relay and the PLMN to which the 5G ProSe Layer-3 Remote UE registers can be the same PLMN or two different PLMNs.

[0027] The following refers to Figure 2 of the drawings.

[0028] 1. Service authorization and provisioning are performed for the 5G ProSe Layer-3 UE-to-Network Relay 20 (step 1a) and 5G ProSe Layer-3 Remote UE (step 1b) as described in clause　6.2.

[0029] 2. The 5G ProSe Layer-3 UE-to-Network Relay 20 may establish a PDU Session for relaying. In the case of IPv6, the 5G ProSe Layer-3 UE-to-Network Relay obtains the IPv6 prefix via prefix delegation function from the network as defined in TS　23.501.

[0030] NOTE　1: 5G ProSe Layer-3 UE-to-Network Relay 20 can establish a PDU Session for any Relay Service Code (RSC) it supports before the connection is established with the 5G ProSe Layer-3 Remote UE 10.

[0031] 3. The 5G ProSe Layer-3 Remote UE 10 performs discovery of a 5G ProSe Layer-3 UE-to-Network Relay 20 as described in clause　6.3.2.3. As part of the discovery procedure the 5G ProSe Layer-3 Remote UE learns about the connectivity service the 5G ProSe Layer-3 UE-to-Network Relay provides.

[0032] 4. The 5G ProSe Layer-3 Remote UE 10 selects a 5G ProSe Layer-3 UE-to-Network Relay 20 and establishes a connection for unicast mode communication as described in clause　6.4.3.6. If there is no PDU Session associated with the Relay Service Code or a new PDU Session for relaying is needed, the 5G ProSe Layer-3 UE-to-Network Relay initiates a new PDU Session establishment procedure for relaying before completing the PC5 connection establishment.

[0033] When the 5G ProSe Layer-3 Remote UE 10 sends the Direct Communication Request message including the dedicated emergency RSC, the 5G ProSe Layer-3 UE-to-Network Relay 20 sets up an emergency PDU session for relaying the emergency service if there is not an emergency PDU Session established in step　2.

[0034] NOTE　2: If the 5G ProSe Layer-3 UE-to-Network Relay 20 has its own emergency service ongoing, how to handle the conflict case is specified in clause　5.4.4.3.

[0035] The network decides that the PDU Session to be established is for relay traffic, and then generates the QoS rules and QoS Flow level QoS parameters to 5G ProSe Layer-3 UE-to-Network Relay 20 with relay consideration and can initiate the setup of QoS flows as specified in clause　5.6.2.1. The Remote UE 10 can also initiate the setup of QoS flows by providing PC5 QoS info and (optionally) PC5 QoS rule(s) to the 5G ProSe Layer-3 UE-to-Network Relay 20 during connection setup, according to the procedure as specified in clause　5.6.2.1.

[0036] The 5G ProSe Layer-3 UE-to-Network Relay 20 determines the PDU Session type for relaying as specified in clause　5.4.1.1.

[0037] According to the PDU Session Type for relaying, the 5G ProSe Layer-3 UE-to-Network Relay 20 performs relaying function at the corresponding layer as follows:

[0038] - When the IP type PDU Session is used for IP traffic over PC5 reference point, the 5G ProSe Layer-3 UE-to-Network Relay 20 acts as an IP router. For IPv4, the 5G ProSe Layer-3 UE-to-Network Relay 20 performs IPv4 NAT between IPv4 addresses assigned to the 5G ProSe Layer-3 Remote UE and the IPv4 address assigned to the PDU Session used for the relay traffic.

[0039] - When the Ethernet type PDU Session is used for Ethernet traffic over PC5 reference point, the 5G ProSe Layer-3 UE-to-Network Relay 20 acts as an Ethernet switch.

[0040] - When the Unstructured type PDU Session is used for Unstructured traffic over PC5 reference point, the 5G ProSe Layer-3 UE-to-Network Relay 20 performs traffic relaying based on a mapping between the PC5 Link Identifier and the PDU Session ID, and a mapping between PFI for PC5 Layer-2 link and the QFI for the PDU Session. These mappings are created when the Unstructured type PDU Session is established for the 5G ProSe Layer-3 Remote UE 10.

[0041] - When the IP type PDU Session is used for Ethernet or Unstructured traffic over PC5 reference point, the 5G ProSe Layer-3 UE-to-Network Relay 20 uses IP tunneling. For this IP tunnelling, the 5G ProSe Layer-3 UE-to-Network Relay 20 locally assigns an IP address / prefix for the 5G ProSe Layer-3 Remote UE 10 and uses it on the Uu reference point to encapsulate and decapsulate the uplink and downlink traffic for the 5G ProSe Layer-3 Remote UE 10. The tunnelled traffic over Uu reference point is transported over the PC5 reference point as Ethernet or Unstructured traffic.

[0042] 5. For IP PDU Session Type and IP traffic over PC5 reference point, IPv6 prefix or IPv4 address (including NAT case) is allocated for the 5G ProSe Layer-3 Remote UE as defined in clause　5.5.1.3.

[0043] 6. The 5G ProSe Layer-3 Remote UE 10 may provide PC5 QoS Info and PC5 QoS rule(s) to the 5G ProSe Layer-3 UE-to-Network Relay using Layer-2 link modification procedure as specified in clause　6.4.3.4. The 5G ProSe Layer-3 UE-to-Network Relay generates the Packet Filters used over Uu interface based on the received PC5 QoS Info and QoS Rule(s) as described in clause　5.6.2.1, and may perform the UE requested PDU Session Modification as defined in TS　23.502　 clause　4.3.3 to setup a new QoS Flow or bind the traffic to an existing QoS Flow.

[0044] From this point the uplink and downlink relaying can start. For downlink traffic forwarding, the PC5 QoS Rule is used to map the downlink packet to the PC5 QoS Flow. For uplink traffic forwarding, the 5G QoS Rule is used to map the uplink packet to the Uu QoS Flow.

[0045] 7. The 5G ProSe Layer-3 UE-to-Network Relay shall send a Remote UE Report (Remote User ID, Remote UE info) message to the SMF 32 for the PDU Session associated with the relay. The Remote User ID, as defined in TS　33.503, is an identity of the 5G ProSe Layer-3 Remote UE 10 user that was successfully connected in step　4. The Remote UE info is used to assist identifying the 5G ProSe Layer-3 Remote UE in the 5GC. For IP PDU Session Type, the Remote UE info is Remote UE IP info. For Ethernet PDU Session Type, the Remote UE info is Remote UE MAC address which is detected by the 5G ProSe Layer-3 UE-to-Network Relay. For Unstructured PDU Session Type, the Remote UE info is not included. The SMF 32 stores the Remote User IDs and the related Remote UE info in the 5G ProSe Layer-3 UE-to-Network Relay's SM context for this PDU Session associated with the relay.

[0046] The Remote UE Report is N1 SM NAS message sent with the PDU Session ID to the AMF 31, in turn delivered to the SMF 32.

[0047] NOTE　3: The privacy protection for Remote User ID is specified in TS　33.503.

[0048] For IP info the following principles apply:

[0049] - for IPv4, the 5G ProSe Layer-3 UE-to-Network Relay shall report TCP / UDP port ranges assigned to individual 5G ProSe Layer-3 Remote UE(s) (along with the Remote User ID);

[0050] - for IPv6, the 5G ProSe Layer-3 UE-to-Network Relay shall report IPv6 prefix(es) assigned to individual 5G ProSe Layer-3 Remote UE(s) (along with the Remote User ID).

[0051] If the PDU Session for relaying is released by the UE-to-Network Relay or the network as described in clause　4.3.4 of TS　23.502, the UE-to-Network Relay should initiate the release of the layer-2 links associated with the released PDU Session using the procedure defined in clause　6.4.3.3.

[0052] The PDU Session(s) used for relaying should be released as described in clause　4.3.4 of TS　23.502　[5] (e.g. by 5G ProSe Layer-3 UE-to-Network Relay), if the service authorization for acting as a 5G ProSe Layer-3 UE-to-Network Relay in the serving PLMN is revoked.

[0053] The 5G ProSe Layer-3 UE-to-Network Relay shall send the Remote UE Report message when the 5G ProSe Layer-3 Remote UE disconnects from the 5G ProSe Layer-3 UE-to-Network Relay (e.g. upon explicit layer-2 link release or based on the absence of keep alive messages over PC5) to inform the SMF 32 that the 5G ProSe Layer-3 Remote UE(s) have left.

[0054] NOTE　4: In order for the SMF 32 to have the 5G ProSe Layer-3 Remote UE(s) information, the HPLMN and the VPLMN where the 5G ProSe Layer-3 UE-to-Network Relay is authorised to operate, needs to support the transfer of the 5G ProSe Layer-3 Remote UE related parameters if the SMF 32 is in the HPLMN.

[0055] It is up to 5G ProSe Layer-3 UE-to-Network Relay implementation how PDU Session(s) used for relaying are released or QoS Flow(s) used for relaying are removed by the 5G ProSe Layer-3 UE-to-Network Relay when 5G ProSe Layer-3 Remote UE(s) disconnect from the 5G ProSe Layer-3 UE-to-Network Relay.

[0056] As can be seen from the above, when a remote UE establishes a link with the L3 relay UE, the latter may perform a PDU session modification procedure with the network.

[0057] It should be noted that a PC5 connection between two 5G ProSe enabled UEs will be subject to keep-alive messages so as to ensure that the link is maintained and is actually active. It is expected that such keep-alive messages will consume resources especially battery / power at the UEs.

[0058] The Fifth Generation System, 5GS, provides access to local area data network (LADN) via a PDU session for LADN. As the data network is local, the UE can only have access to it if the UE is inside the LADN service area. The PDU session for LADN is identified by an LADN Data Network Name (DNN), or LADN DNN and slice (Single - Network Slice Selection Assistance Information, S-NSSAI). It is possible that the UE attempts to establish or modify a PDU session, but the UE is now outside the LADN area e.g. the UE is just moving from inside the LADN area to outside the LADN area as it sends a NAS message for an LADN PDU session (establishment or modification).

[0059] According to 3GPP TS 24.501 V18.3.0, the network (e.g. Session Management Function, SMF) may reject a UE's request to modify a PDU session if the session is for LADN and the UE is not inside the LADN service area. For example, section 6.4.2.4.3 of 3GPP TS 24.501 V18.3.0 specifies the following when this scenario occurs:

[0060] ... SKIP ...

[0061] If the 5GSM cause value is #46 "out of LADN service area", the UE shall ignore the Back-off timer value IE and Re-attempt indicator IE provided by the network, if any. If the UE is not located inside the LADN service area, the UE shall not send another PDU SESSION ESTABLISHMENT REQUEST message or another PDU SESSION MODIFICATION REQUEST message except for indicating a change of 3GPP PS data off UE status for the LADN DNN provided by the UE during the PDU session establishment procedure until the LADN information for the specific LADN DNN or the extended LADN information for the specific LADN DNN and S-NSSAI is updated as described in subclause　5.4.4 and subclause　5.5.1. If the UE is not located inside the LADN service area, the UE shall not indicate the PDU session(s) for the LADN DNN provided by the UE during the PDU session establishment procedure in the Uplink data status IE included in the SERVICE REQUEST message until the LADN information for the specific LADN DNN or the extended LADN information for the specific LADN DNN and S-NSSAI is updated as described in subclause　5.4.4 and subclause　5.5.1.

[0062] ... SKIP ...

[0063] As set out above, it is clear that the UE's request will be rejected when it is for an LADN PDU session and the UE is outside the LADN area. Furthermore, the UE is not allowed to initiate another request until the LADN information is updated.

[0064] A problem experienced in the prior art is that the rejection of a 5GSM request due to the UE being outside the LADN area and how it impacts a PC5 connection has not been addressed.

[0065] Assume an L3 relay UE which is providing a relay service to remote UEs such that the PDU session is an LADN PDU session. As set out in the foregoing, it is possible that the L3 relay UE attempts to modify a PDU session after a link has been established with a remote UE. However, the network may then reject the request due to the L3 relay UE being outside the LADN service area. As has been seen, the L3 relay UE is not allowed to send another request towards the network until the LADN information is updated. If this does not happen, then the PC5 link which has been established is basically useless, as the remote UE will not be able to get any service. Therefore, the maintenance of the PC5 link will lead to unnecessary resource usage at the L3 relay UE and, furthermore, both the remote UE and the L3 relay UE will waste power to maintain the PC5 link which will not be used. There is no behaviour that has been defined for the L3 relay UE to address this scenario and so avoid the issue of an unnecessary link and power usage at the L3 relay UE and the remote UE. Note that the problem can also occur when the relay UE is trying to establish a first PDU session to serve a remote UE and then the network rejects the request. In this case, there is no point in actually establishing the PC5 connection as it will be useless and will waste UE power.

[0066] Note that the problem can also occur for a Layer 2 (L2) remote UE which uses a L2 relay UE (referring to a Layer 2 UE-to-network relay UE) to connect with a network. In this case, the L2 remote UE uses a PC5 connection with the L2 relay UE to connect with the network. However, the L2 remote UE has its own NAS signalling connection with the network i.e. the NAS signalling connection is directly between the L2 remote UE and the network. It is also possible that the L2 remote UE may attempt to establish an LADN PDU session, but the UE gets rejected with the same 5GSM cause #46. The behaviour of the L2 remote UE is not defined.

[0067] The problem can be illustrated, as shown in Figure 3. Here there is shown a UE 10 located in a different area as indicated by the different tracking area identities - TAI - where TAI 1 supports LADN PDU session but TAI 2 does not support LADN PDU session. The UE 10 in TAI 1 can establish a PDU session for LADN. If, however, the UE moves to TAI 2 and attempts to establish a PDU session for LADN, then the network (via SMF 32) will reject the request.

[0068] It is an aim of an embodiment of the present invention to address these and other shortcomings in the prior art, whether mentioned herein or not.

[0069] According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

[0070] According to a first aspect of the present invention, there is provided a method of managing a ProSe connection set up between a remote User Equipment, UE, a relay and a network, the connection using a Protocol Data Unit session, the PDU session being a Local Area Data Network, LADN, PDU session, wherein during a link establishment or modification procedure, between the remote UE and the relay, the relay verifies if it is inside or outside a defined LADN service area.

[0071] In an embodiment, during a link establishment procedure, if the relay determines it is outside the LADN service area, then the relay rejects the link establishment by means of a PROSE DIRECT LINK ESTABLISHMENT REJECT message.

[0072] In an embodiment, the relay rejects the link establishment with a PC5 cause value #111 "protocol error, unspecified".

[0073] In an embodiment, during a link modification procedure, the relay verifies if either:

[0074] the relay is outside a service area of the LADN; or

[0075] a NAS 5GSM procedure fails due to reception of 5GSM cause value #46 "out of LADN service area" in a PDU SESSION MODIFICATION REJECT message, and if either is true, the relay rejects the modification.

[0076] In an embodiment, the relay rejects the link modification procedure by sending a PROSE DIRECT LINK MODIFICATION REJECT message.

[0077] In an embodiment, if the relay verifies that there is a remote UE which is served on an LADN PDU session and the relay is outside the LADN service area or if the relay verifies if there is a remote UE which is served on an LADN PDU session and the relay receives 5GSM cause value #46 "out of LADN service area" in a PDU SESSION MODIFICATION REJECT message, then the relay releases the ProSe connection with the remote UE.

[0078] According to a second aspect of the present invention, there is provided apparatus arranged to perform the method of the first aspect.

[0079] In an embodiment, the L3 relay UE should perform an action on the PC5 link with a remote UE after a 5GSM request is rejected due to the L3 relay UE being outside an LADN service area. For example, the L3 relay UE should reject a new PC5 link or release a PC5 link for any remote UE which is being served over the PDU session in question.

[0080] As such, receiving the 5GSM cause value #46 "out of LADN service area" by a L3 relay UE should lead to a modification of (e.g. rejection of a connection or release of a connection on) a PC5 link between the L3 relay UE and at least one remote UE (e.g. which is a layer 3 remote UE)

[0081] Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0082] For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which:

[0083] Figure 1 shows a representation of a system to which am embodiment of the invention applies;

[0084] Figure 2 shows a message flow related to ProSe establishment;

[0085] Figure 3 illustrates a problem associated with the prior art; and

[0086] Figure 4 shows a flowchart illustrating an embodiment of the invention.

[0087] Note that the embodiments described herein will be explained using the 5GSM cause value #46 "out of LADN service area". However, all the details apply for other 5GSM causes such as #37 "5GS QoS not accepted", #44 "Semantic errors in packet filter(s)", #45 "Syntactical error in packet filter(s)", #59 "unsupported 5QI value", #67 "insufficient resources for specific slice and DNN", #69 "insufficient resources for specific slice", #83 "Semantic error in the QoS operation", and #84 "Syntactical error in the QoS operation".

[0088] As such, for all the details which follow, which assume (or which is based on the UE receiving) 5GSM cause #46 "out of LADN service area", corresponding scenarios can also apply when the 5GSM cause value received is any other value such as, but not limited to, #37 "5GS QoS not accepted", #44 "Semantic errors in packet filter(s)", #45 "Syntactical error in packet filter(s)", #59 "unsupported 5QI value", #67 "insufficient resources for specific slice and DNN", #69 "insufficient resources for specific slice", #83 "Semantic error in the QoS operation", and #84 "Syntactical error in the QoS operation", or any other new 5GSM cause value that may be defined in future iterations of the standard.

[0089] Note that a general solution is as follows. A well-known Relay Service Code (RSC) may be associated with a PDU session for LADN. As such, all the 5G ProSe capable UEs may be configured with information about the association of an RSC with an LADN PDU session or LADN information, where for example the LADN information may be LADN DNN, or LADN DNN and slice (S-NSSAI). As such, a 5G ProSe capable UE e.g. a remote UE, may select a relay UE for an LADN PDU session based on an RSC value where the remote UE may be configured with the set of RSCs that are for LADN PDU sessions. As such, a selection of a relay UE may be based on the RSC if the selecting UE needs a PDU session for LADN and the RSC is known to provide service for LADN PDU session or provides a PDU session for LADN. Therefore, the 5G ProSe discovery procedure (on the direct link, or the PC5 link) may use an RSC value which is associated with an LADN PDU session. The advertising UE (e.g. a relay UE) may advertise that it supports a connection to an LADN PDU session (or LADN information) by using an RSC which is associated with an LADN PDU session in its discovery messages. Similarly, a UE which is discovering a service may determine that a service is associated with an LADN PDU session, or that an LADN PDU session can be obtained, based on an RSC value which is known to be associated with an LADN PDU session or LADN information.

[0090] A first embodiment relates to modifying a procedure on a PC5 link based on receiving the 5GSM cause value #46 "out of LADN service area".

[0091] A L3 relay UE may have a PDU session for LADN which is being used to serve at least one remote UE. The at least one remote UE may be a layer 3 (L3) remote UE. The L3 relay UE may use a particular Relay Service Code (RSC) value to indicate that an LADN PDU session is supported, where the RSC may be used as part of the discovery procedure (which may be standalone or integrated with another procedure such as link establishment procedure).

[0092] The L3 relay UE may receive a PC5 request, optionally from at least one remote UE (which optionally may be a L3 remote UE) where the request may be any of the following - a PROSE DIRECT LINK ESTABLISHMENT REQUEST message, or a PROSE DIRECT LINK MODIFICATION REQUEST message, or any other PC5 procedure or message. Note that for simplicity, all of these messages or procedure will be referred to as a 'PC5 request'. It should be noted that other PC5 direct messages may also be used or covered by the embodiments described herein, although they have not been listed. As such the messages listed above are not to be considered as limitations, but simply as examples.

[0093] Optionally, the PC5 request (received by the L3 relay UE) may require the L3 relay UE to perform a 5GSM procedure (optionally on the Uu interface) with the network (e.g. with the SMF). The 5GSM procedure may be a PDU session establishment procedure (for which the UE may send a PDU SESSION ESTABLISHMENT REQUEST message) or a PDU session modification procedure (for which the UE may send a PDU SESSION MODIFICATION REQUEST message). Hereafter, any of these messages (or other messages) are referred to as a 5GSM message. The L3 UE may receive a rejection from the network (e.g. from the SMF) where the rejection is a NAS reject message such as any of a - PDU SESSION ESTABLISHMENT REJECT message, or a PDU SESSION MODIFICATION REJECT message, where the NAS reject message may contain a 5GSM cause value #46 "out of LADN service area" (e.g. as described in 3GPP TS 24.501 V18.3.0). The reject message may be a response to the 5GSM message that the L2 relay sent.

[0094] The L3 relay UE may already be aware that it is outside the LADN service area (or not inside the LADN service area) for a particular LADN DNN (or LADN DNN and S-NSSAI), where the L3 relay may also be aware that the RSC being advertised is associated with an LADN PDU session. In this case, when the L3 relay UE receives a PC5 request, optionally from at least one remote UE (which optionally may be a L3 remote UE) and the request is determined to be associated with an LADN PDU session for which the L3 relay UE is aware that it is outside the LADN service area (or not inside the LADN service area), the L3 relay UE may take any of the actions set out below e.g. the L3 relay UE may reject the request by sending a PROSE DIRECT LINK ESTABLISHMENT REJECT message (in case the initial PC5 request was to establish a new direct link) or by sending a PROSE DIRECT LINK MODIFICATION REJECT message (in case the initial PC5 request was to modify a PC5 link), or the UE can initiate the release of a PC5 connection with any remote UE which is being served on a PDU session for LADN (e.g. the L3 relay sends the PROSE DIRECT LINK RELEASE REQUEST message). As such, the L3 relay UE in this case can take the action on the PC5 link (towards the L3 remote UE) without necessarily needing to send any 5GSM message towards the network and without waiting for any 5GSM message to be rejected with 5GSM cause value #46 "out of LADN service area". Note that the RSC being advertised can mean that the remote UE is requesting a PC5 link establishment in association to the RSC which corresponds to an LADN PDU session, and this information is known at the L3 relay UE. The L3 relay UE may be aware that is it outside of an LADN area (or not inside the LADN area) by comparing the Tracking Area Identity (TAI) of the cell on which the L3 relay UE is currently camping with the TAI for the LADN service area information. Therefore, if the L3 relay UE is aware that it is outside the LADN area (or not inside the LADN area) for an LADN PDU session, and the L3 relay receives a PC5 request which is associated with this LADN PDU session, e.g. by means of an RSC which is known to be associated to an LADN PDU session (or by means of a DNN and / or S-NSSAI which is associated with the RSC), then the UE should reject the request as described herein without necessarily sending a message towards the network or without necessarily receiving a 5GSM cause value e.g. #46, from the network.

[0095] If the 5G ProSe direct link establishment request is for 5G ProSe layer-3 UE-to-network relaying, the PDU session for relaying the service is an LADN PDU session, and the target UE acting as a 5G ProSe layer-3 UE-to-network relay UE is outside the LADN service area, the target UE shall send a PROSE DIRECT LINK ESTABLISHMENT REJECT message containing PC5 signalling protocol cause value #111 "protocol error, unspecified".

[0096] If the target UE is a 5G ProSe layer-3 UE-to-network relay UE, the PDU session for relaying the service is an LADN PDU and:

[0097] 1) the target UE is outside the LADN service area; or

[0098] 2) the 5G ProSe direct link modification requires a PDU session modification procedure which fails due to reception of the 5GSM cause value #46 "out of LADN service area" in the PDU SESSION MODIFICATION REJECT message as specified in as specified in 3GPP TS 24.501 clause 6.4.2.4.1;

[0099] the target UE shall send a PROSE DIRECT LINK MODIFICATION REJECT message with PC5 signalling protocol cause value #111 "protocol error, unspecified".

[0100] If the initiating UE is a 5G ProSe layer-3 UE-to-network relay UE, the PDU session for relaying the service is an LADN PDU and:

[0101] 1) the target UE is outside the LADN service area; or

[0102] 2) the UE receives the 5GSM cause value #46 "out of LADN service area" in the PDU SESSION MODIFICATION REJECT message as specified in as specified in 3GPP TS 24.501 clause 6.4.2.4.1;

[0103] and there is at least one 5G ProSe layer-3 remote UE which is served on the PDU session, then the UE should initiate the 5G ProSe direct link release procedure.

[0104] When this occurs, the L3 relay UE should take any of the following actions, where the action may be performed on, or in relation to, a PC5 procedure optionally towards a L3 remote UE:

[0105] - The L3 relay UE should send a PROSE DIRECT LINK ESTABLISHMENT REJECT message. Optionally this action is taken by the L3 relay if the PC5 request which was received is a PROSE DIRECT LINK ESTABLISHMENT REQUEST message. In this option, the L3 relay basically rejects the establishment of the direct link because a 5GSM message was rejected with a 5GSM value #46 "out of LADN service area"

[0106] - The L3 relay UE should send a PROSE DIRECT LINK MODIFICATION REJECT message. Optionally this action is taken by the L3 relay if the PC5 request which was received is a PROSE DIRECT LINK MODIFICATION REQUEST message. In this option, the L3 relay basically rejects the modification of the direct link because a 5GSM message was rejected with a 5GSM value #46 "out of LADN service area"

[0107] - For any other remote UE which is served by the L3 relay UE and served on (or with) the PDU session for which the L3 relay UE received the 5GSM cause value #46 "out of LADN service area", the L3 relay UE may initiate a 5G ProSe direct link release procedure towards the remote UE which is being served on this PDU session (where optionally the remote UE is a L3 remote UE). The L3 relay UE should send the PROSE DIRECT LINK RELEASE REQUEST message optionally to the L3 remote UE. In this option, the L3 relay basically rejects the establishment of the direct link because the 5GSM message was rejected with a 5GSM value #46 "out of LADN service area". The L3 relay UE may take this action towards any remote UE which is served by / om the PDU session in question even if the 5GSM reject message is not for the particular remote UE i.e. it suffices to get the 5GSM reject message such that the L3 relay UE can then take the actions proposed herein towards any (other) remote UE which is served by / on this PDU session (for which the cause value was received) even though the 5GSM reject message was not related to all remote UEs.

[0108] When the L3 relay UE sends a PC5 message, where the message may be any of those listed above, the L3 relay UE may include any PC5 signalling protocol cause value where this may be a new value or an existing value. For example, the L3 relay UE may use the PC5 signalling protocol cause value #13 "congestion situation", or #5 "lack of resources for 5G ProSe direct link", or #111 "protocol error, unspecified", or #NN "out of LADN service area" where '#NN' may be any integer that can be defined.

[0109] The L3 relay UE may also include a back-off timer in the PC5 response message (or PC5 message e.g. the message to release a connection) that is sent to the remote UE (e.g. the L3 remote UE).

[0110] The remote UE may be a 5G ProSe layer-3 remote UE. The relay UE may be a 5G ProSe layer-3 UE-to-network relay UE.

[0111] The following demonstrates exemplary changes that may be made to the relevant specifications based on the embodiments described herein.

[0112] The following changes (shown in square brackets) can be made to the section 7.2.2.5 '5G ProSe direct link establishment procedure not accepted by the target UE' in 3GPP TS 24.554:

[0113] [ If the 5G ProSe direct link establishment request is for 5G ProSe layer-3 UE-to-network relaying, the request required the establishment of a PDU session by the 5G ProSe layer-3 UE-to-network relay UE which is a target UE, and the PDU session establishment was unsuccessful due to the reception of 5GSM cause #8 "maximum number of PDU sessions reached", #27 "Missing or unknown DNN", #28 "Unknown PDU session type", #29 "user authentication or authorization failed", #31 "request rejected, unspecified", #32 "service option not supported", #33 "requested service option not subscribed", #46 "out of LADN service area", or #65 "maximum number of PDU sessions reached" as specified in 3GPP TS 24.501

[0011] , the target UE shall send a PROSE DIRECT LINK ESTABLISHMENT REJECT message containing PC5 signalling protocol cause value #111 "protocol error, unspecified". ]

[0114] The following changes (shown in square brackets) can be made to the section 7.2.3.5 '5G ProSe direct link modification procedure not accepted by the target UE' in 3GPP TS 24.554:

[0115] [ If the target UE is a 5G ProSe layer-3 UE-to-network relay UE and the 5G ProSe direct link modification requires a PDU session modification procedure which fails due to reception of the 5GSM cause value #46 "out of LADN service area" in the PDU SESSION MODIFICATION REJECT message as specified in as specified in 3GPP TS 24.501

[0011] clause 6.4.2.4.1, the target UE shall send a PROSE DIRECT LINK MODIFICATION REJECT message with PC5 signalling protocol cause value #111 "protocol error, unspecified". ]

[0116] The following changes (shown in square brackets) can be made to the section 7.2.6.2 '5G ProSe direct link release procedure initiation by initiating UE' in 3GPP TS 24.554:

[0117] [If the initiating UE which is acting as 5G ProSe layer-3 UE-to-network relay UE receives the 5GSM cause value #46 "out of LADN service area" in the PDU SESSION MODIFICATION REJECT message as specified in as specified in 3GPP TS 24.501

[0011] clause 6.4.2.4.1, and there is at least one 5G ProSe layer-3 remote UE which is served on the PDU session, then the UE should initiate the 5G ProSe direct link release procedure.]

[0118] A second embodiment relates to a new UE behaviour for Layer 2 remote UE after receiving the same 5GSM cause value from the network.

[0119] A new behaviour is provided for the L2 remote UE such that the details which have been described earlier would also apply in this case. Here the L2 remote UE can take the role of the L3 relay UE and the L2 relay UE (when the L2 remote UE is served by the L2 relay UE) takes the role of the L3 remote UE described above. Further description of this solution is provided below.

[0120] When a L2 remote UE, optionally which has already established a PC5 link or connection with a L2 relay UE, receives a (5GSM) NAS reject message (where this may by any of the messages listed earlier e.g. PDU SESSION ESTABLISHMENT REJECT message, or a PDU SESSION MODIFICATION REJECT message) which may contain the 5GSM cause value #46 "out of LADN service area", the L2 remote UE may then send any of the PC5 messages listed earlier e.g. the PROSE DIRECT LINK RELEASE REQUEST message. The L2 remote UE may include any of the previously listed PC5 signalling protocol cause value (either new or existing).

[0121] The remote UE (e.g. the L2 remote UE) may also include a back-off timer in the PC5 message that is sent to the relay UE (e.g. the L2 relay UE).

[0122] The remote UE may be a 5G ProSe layer-2 remote UE. The relay UE may be a 5G ProSe layer-2 UE-to-network relay UE.

[0123] The following demonstrates exemplary changes that may be made to the specifications based on the solutions herein.

[0124] The following changes (shown in square brackets) can be made to the section 7.2.6.2 '5G ProSe direct link release procedure initiation by initiating UE' in 3GPP TS 24.554:

[0125] [If the initiating UE which is acting as 5G ProSe layer-2 remote UE receives the 5GSM cause value #46 "out of LADN service area" in the PDU SESSION MODIFICATION REJECT message as specified in as specified in 3GPP TS 24.501 clause 6.4.2.4.1, then the UE should initiate the 5G ProSe direct link release procedure optionally towards the 5G ProSe layer-2 UE-to-network relay UE.]

[0126] For completeness, Figure 4 shows a flowchart illustrating an embodiment of the invention.

[0127] At S401, A ProSe connection procedure is commenced. This may be an establishment or modification procedure.

[0128] At S402, the relay UE identify whether the relay UE is within an LADN service area.

[0129] At S403, in case that the relay UE determines that the relay UE is not in the LADN service area, then the link establishment process is rejected, with a defined cause value.

[0130] Figure 5 is a block diagram of an exemplary terminal that may be used in examples of the present disclosure. For example, a relay user equipment and / or a remote user equipment in the examples of figures 1-4 may comprise a terminal of figure 5. The skilled person will appreciate that a terminal may be implemented, for example, as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, and / or as a virtualised function instantiated on an appropriate platform, e.g., on a cloud infrastructure.

[0131] The entity 500 comprises a processor (or controller) 501, a transmitter 503 and a receiver 505. The receiver 505 is configured for receiving one or more messages from one or more other network entities, for example as described above.

[0132] According to one embodiment, the receiver 505 is configured to receive a PDU session modification reject message including a 5GSM cause value associated with an out of LADN service area.

[0133] The transmitter 503 is configured for transmitting one or more messages to one or more other network entities, for example as described above.

[0134] According to one embodiment, the transmitter 503 is configured to transmit a reject message including a PC5 signalling protocol cause value associated with a protocol error.

[0135] The processor 501 is configured for performing one or more operations, for example according to the operations as described above. According to one embodiment, the processor 501 is configured to identify whether the terminal is outside a local area data network (LADN) service area.

[0136] At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as 'component', 'module' or 'unit' used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of others.

[0137] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0138] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0139] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0140] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1.A method performed by a first user equipment (UE) associated with a proximity based service (prose) in a wireless communication system, the method comprising:identifying whether the first UE is outside a local area data network (LADN) service area, the first UE being associated with a 5G prose layer 3 UE-to-network relay UE; andtransmitting, to a second UE, a reject message including a PC5 signalling protocol cause value associated with a protocol error, in case that the first UE is outside the LADN service area.2.The method of claim 1, further comprising:identifying whether a 5G prose direct link establishment request is for a 5G prose layer-3 UE-to-network relay, and a protocol data unit (PDU) session for relaying a service is an LDAN PDU session,wherein, in case that the 5G prose direct link establishment request is for the 5G prose layer-3 UE-to-network relay, and the PDU session for relaying the service is the LDAN PDU session, the reject message is a prose direct link establishment reject message.3.The method of claim 1, further comprising:identifying whether a 5G prose direct link modification request is accepted,wherein, in case that the 5G prose direct link modification request is not accepted, and a PDU session for relaying a service is an LDAN PDU session, the reject message is a prose direct link establishment modification message.4.The method of claim 1, further comprising:receiving a PDU session modification reject message including a 5GSM cause value associated with an out of LADN service area; andidentifying that a 5G prose direct link modification requires a PDU session modification procedure which fails based on the PDU session modification reject message,wherein the reject message is a prose direct link establishment modification message based on the identification.5.The method of claim 1, further comprising:identifying whether the PDU session for relaying a service is an LADN PDU session and the first UE is outside the LADN service area;identifying whether at least one second UE is served on a PDU session, in case that the PDU session for relaying the service is the LADN PDU session and the first UE is outside the LADN service area; andinitiating a 5G prose direct link release procedure, in case that the at least one second UE is served on the PDU session.6.The method of claim 1, further comprising:identifying whether the PDU session for relaying a service is an LADN PDU session and a PDU session modification reject message includes a 5GSM cause value associated with an out of LADN service area is received;identifying whether at least one second UE is served on a PDU session, in case that the PDU session for relaying the service in the LADN PDU session and the PDU session modification reject message including the 5GSM cause value associated with the out of LADN service area is received; andinitiating a 5G prose direct link release procedure, in case that the at least one second UE is served on the PDU session.7.The method of claim 4,wherein the PC5 signalling protocol cause value associated with the protocol error is #111, andwherein the 5GSM cause value associated with the out of LADN service area is #46.8.A first user equipment (UE) associated with a proximity based service (prose) in a wireless communication system, the first UE comprising:a transceiver; andat least one processor configured to:identify whether the first UE is outside a local area data network (LADN) service area, the first UE being associated with a 5G prose layer 3 UE-to-network relay UE, andtransmit, to a second UE via the transceiver, a reject message including a PC5 signalling protocol cause value associated with a protocol error, in case that the first UE is outside the LADN service area.9.The first UE of claim 8, wherein the at least one processor is further configured to:identify whether a 5G prose direct link establishment request is for a 5G prose layer-3 UE-to-network relay, and a protocol data unit (PDU) session for relaying a service is an LDAN PDU session,wherein, in case that the 5G prose direct link establishment request is for the 5G prose layer-3 UE-to-network relay, and the PDU session for relaying the service is the LDAN PDU session, the reject message is a prose direct link establishment reject message.10.The first UE of claim 8, wherein the at least one processor is further configured to:identify whether a 5G prose direct link modification request is accepted,wherein, in case that the 5G prose direct link modification request is not accepted, and a PDU session for relaying a service is an LDAN PDU session, the reject message is a prose direct link establishment modification message.11.The first UE of claim 8, wherein the at least one processor is further configured to:receive, via the transceiver, a PDU session modification reject message including a 5GSM cause value associated with an out of LADN service area, andidentify that a 5G prose direct link modification requires a PDU session modification procedure which fails based on the PDU session modification reject message,wherein the reject message is a prose direct link establishment modification message based on the identification.12.The first UE of claim 8, wherein the at least one processor is further configured to:identify whether the PDU session for relaying a service is an LADN PDU session and the first UE is outside the LADN service area,identify whether at least one second UE is served on a PDU session, in case that the PDU session for relaying the service is the LADN PDU session and the first UE is outside the LADN service area, andinitiate a 5G prose direct link release procedure, in case that the at least one second UE is served on the PDU session.13.The first UE of claim 8, wherein the at least one processor is further configured to:identify whether the PDU session for relaying a service is an LADN PDU session and a PDU session modification reject message includes a 5GSM cause value associated with an out of LADN service area is received,identify whether at least one second UE is served on a PDU session, in case that the PDU session for relaying the service in the LADN PDU session and the PDU session modification reject message including the 5GSM cause value associated with the out of LADN service area is received, andinitiate a 5G prose direct link release procedure, in case that the at least one second UE is served on the PDU session.14.The first UE of claim 11, wherein the PC5 signalling protocol cause value associated with the protocol error is #111, andwherein the 5GSM cause value associated with the out of LADN service area is #46.

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