WO2025190777A1

WO2025190777A1 - Secondary connection selection as new primary connection

Info

Publication number: WO2025190777A1
Application number: PCT/EP2025/056150
Authority: WO
Inventors: Brajesh Soni; Bharath Ramesh KASHYAP
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2024-03-13
Filing date: 2025-03-06
Publication date: 2025-09-18
Anticipated expiration: 2026-09-13

Abstract

There is provided a first user equipment, UE, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first UE at least to: establish a primary connection to a wireless communication network via a second UE; establish at least one secondary connection to the wireless communication network via at least one third UE; after the at least one secondary connection is established, determine a termination of the primary connection; and based on determining the termination of the primary connection, select one of the established at least one secondary connection as a new primary connection.

Description

SECONDARY CONNECTION SELECTION AS NEW PRIMARY CONNECTION

TECHNICAL FIELD

Various example embodiments relate generally to wireless communication. More particularly, the present solution relates to selecting established secondary connection as a new primary connection based on determining a termination of a primary connection.

BACKGROUND

Network access for a remote user equipment (UE) may be enhanced by using one or more relaying UEs to relay data between the remote UE and the network. Thus, UEs that are located, for example, at cell edge or beyond may connect to the network via a relaying UE. As with all communication, there may be service interruptions or connection terminations associated with the relay connection which need to be handled one way or another.

BRIEF DESCRIPTION

According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The embodiments that do not fall under the scope of the claims are to be interpreted as examples useful for understanding the disclosure.

LIST OF THE DRAWINGS

In the following, the invention will be described in greater detail with reference to the embodiments and the accompanying drawings, in which

Figure 1 presents a network to which one or more embodiments are applicable;

Figure 2 illustrates a scenario in which relay UE experiences outage and service for a remote UE may be interrupted;

Figures 3 and 4 illustrate flow diagrams according to some embodiments;

Figure 5 illustrates some examples of secondary connections for a remote UE;

Figures 6A, 6B, 7A, 7B, 8, and 9 illustrate signalling diagrams according to some embodiments; and

Figures 10 and 11 illustrate apparatuses according to some embodiments. DESCRIPTION OF EMBODIMENTS

The following embodiments are exemplary. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. For the purposes of the present disclosure, the phrases “at least one of A or B”, “at least one of A and B”, “A and/or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrases “A or B” and “A and/or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C). It is also to be noted that element(s) may be used herein to refer to one or more elements. For example, embodiment(s) may refer to one or more embodiments.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments.

Embodiments described may be implemented in a radio system, such as one comprising at least one of the following radio access technologies (RATs): Worldwide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and enhanced LTE (eLTE). Term ‘eLTE’ here denotes the LTE evolution that connects to a 5G core. LTE is also known as evolved UMTS terrestrial radio access (EUTRA) or as evolved UMTS terrestrial radio access network (EUTRAN). A term “resource” may refer to radio resources, such as a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term “transmission” and/or “reception” may refer to wirelessly transmitting and/or receiving via a wireless propagation channel on radio resources

The embodiments are not, however, restricted to the systems/RATs given as an example but a person skilled in the art may apply the solution to other communication systems/networks provided with necessary properties. Some examples of a suitable communication networks include a 5G network and/or a 6G network. The 3GPP solution to 5G is referred to as New Radio (NR). 6G is envisaged to be a further development of 5G. NR has been envisaged to use multiple-input- multiple-output (M1M0) multi-antenna transmission techniques, more base stations or nodes than the current network deployments of LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller local area access nodes and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates. 5G will likely be comprised of more than one radio access technology / radio access network (RAT /RAN), each optimized for certain use cases and/or spectrum. 5G mobile communications may have a wider range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and being integrable with existing legacy radio access technologies, such as the LTE.

The current architecture in LTE networks is distributed in the radio and centralized in the core network. The low latency applications and services in 5G may require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time- critical control, healthcare applications). Edge cloud may be brought into RAN by utilizing network function virtualization (NVF) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. Network slicing allows multiple virtual networks to be created on top of a common shared physical infrastructure. The virtual networks are then customised to meet the specific needs of applications, services, devices, customers or operators.

In radio communications, node operations may in be carried out, at least partly, in a central/centralized unit, CU, (e.g. server, host or node) operationally coupled to distributed unit, DU, (e.g. a radio head/node). It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of work between core network operations and base station operations may vary depending on implementation. Thus, 5G networks architecture may be based on a so-called CU-DU split. One gNB- CU controls several gNB-DUs. The term ‘gNB’ may correspond in 5G to the eNB in LTE. The gNBs (one or more) may communicate with one or more UEs. The gNB- CU (central node) may control a plurality of spatially separated gNB-DUs, acting at least as transmit/receive (Tx/Rx) nodes. In some embodiments, however, the gNB- DUs (also called DU) may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the gNB-CU (also called a CU) may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too. It is considered that skilled person is familiar with the OS1 model and the functionalities within each layer.

In an embodiment, the server or CU may generate a virtual network through which the server communicates with the radio node. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Such virtual network may provide flexible distribution of operations between the server and the radio head/node. In practice, any digital signal processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

Some other possible technology advancements to be used are Software- Defined Networking (SDN), Big Data, and all-lP, to mention only a few non-limiting examples. For example, network slicing may be a form of virtual network architecture using the same principles behind software defined networking (SDN) and network functions virtualisation (NFV) in fixed networks. SDN and NFV may deliver greater network flexibility by allowing traditional network architectures to be partitioned into virtual elements that can be linked (also through software). Network slicing allows multiple virtual networks to be created on top of a common shared physical infrastructure. The virtual networks are then customised to meet the specific needs of applications, services, devices, customers or operators.

The plurality of gNBs (access points/nodes), each comprising the CU and one or more DUs, may be connected to each other via the Xn interface over which the gNBs may negotiate. The gNBs may also be connected over next generation (NG) interfaces to a 5G core network (5GC), which may be a 5G equivalent for the core network of LTE. Such 5G CU-DU split architecture may be implemented using cloud/server so that the CU having higher layers locates in the cloud and the DU is closer to or comprises actual radio and antenna unit. There are similar plans ongoing for LTE/LTE-A/eLTE as well. When both eLTE and 5G will use similar architecture in a same cloud hardware (HW), the next step may be to combine software (SW) so that one common SW controls both radio access networks/technologies (RAN/RAT). This may allow then new ways to control radio resources of both RANs. Furthermore, it may be possible to have configurations where the full protocol stack is controlled by the same HW and handled by the same radio unit as the CU.

It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Big Data and all-lP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well.

5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future rail- way/maritime/aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). Each satellite in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on- ground cells may be created through an on-ground relay node or by a gNB located on-ground or in a satellite.

The embodiments may be also applicable to narrow-band (NB) Internet-of-things (loT) systems which may enable a wide range of devices and services to be connected using cellular telecommunications bands. NB-loT is a narrowband radio technology designed for the Internet of Things (loT) and is one of technologies standardized by the 3rd Generation Partnership Project (3GPP). Other 3GPP loT technologies also suitable to implement the embodiments include machine type communication (MTC) and eMTC (enhanced Machine-Type Communication). NB-loT focuses specifically on low cost, long battery life, and enabling a large number of connected devices. The NB-loT technology is deployed “in-band” in spectrum allocated to Long Term Evolution (LTE) - using resource blocks within a normal LTE carrier, or in the unused resource blocks within an LTE carrier’s guard-band - or “standalone” for deployments in dedicated spectrum.

The embodiments may be also applicable to device-to-device (D2D), machine-to-machine, peer-to-peer (P2P) communications. The embodiments may be also applicable to vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V21), infrastructure-to-vehicle (12V), or in general to V2X or X2V communications.

Figure 1 illustrates an example of a wireless communication system to which embodiments of the invention may be applied. The system may comprise a control node 110 providing one or more cells, such as cell 100, and a control node 112 providing one or more other cells, such as cell 102. Each cell may be, e.g., a macro cell, a micro cell, femto, or a pico cell, for example. In another point of view, the cell(s) may define a coverage area or a service area of the corresponding access node. The control node 110, 112 may be an evolved Node B (eNB) as in the LTE and LTE-A, ng-eNB as in eLTE, gNB of 5G, or any other apparatus capable of controlling radio communication and managing radio resources within a cell. The control node 110, 112 may be called a base station, network node, or an access node. The wireless communication system may be understood to comprise user devices, as discussed below, and at least wireless communication network that may include one or more access nodes (e.g. 110, 112).

The described wireless communication system may be a cellular communication system. For example, the cellular communication system may comprise a radio access network of access nodes, each controlling a respective cell or cells. The access node 110 (i.e. access node 110 of the cellular communication system or any other similar wireless communication system) may provide user equipment (UE) 120 (one or more UEs) with wireless access to other networks such as the Internet. The wireless access may comprise downlink (DL) communication from the control node to the UE 120 and uplink (UL) communication from the UE 120 to the control node. Another example may device to device communication (D2D) as explained below.

Additionally, although not shown, one or more local area access nodes may be arranged such that a cell provided by the local area access node at least partially overlaps the cell of the access node 110 and/or 112. The local area access node may provide wireless access within a sub-cell. Examples of the sub-cell may include a micro, pico and/or femto cell. Typically, the sub-cell provides a hot spot within a macro cell. The operation of the local area access node may be controlled by an access node under whose control area the sub-cell is provided. In general, the control node for the small cell may be likewise called a base station, network node, or an access node.

There may be a plurality of UEs 120, 122 in the system. Each of them may be served by the same or by different control nodes 110, 112. The UEs 120, 122 may communicate with each other, in case D2D communication interface is established between them. One example of D2D communication may be sidelink communication.

The term “terminal device” or “UE” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

In the case of multiple access nodes in the communication network, the access nodes may be connected to each other with an interface. LTE specifications call such an interface as X2 interface. For IEEE 802.11 network (i.e. wireless local area network, WLAN, WiFi), a similar interface may be provided between access points. An interface between an LTE access point and a 5G access point, or between two 5G access points may be called Xn. Other communication methods between the access nodes may also be possible. The access nodes 110 and 112 may be further connected via another interface to a core network 116 of the cellular communication system. The LTE specifications specify the core network as an evolved packet core (EPC), and the core network may comprise a mobility management entity (MME) and a gateway node. The MME may handle mobility of terminal devices in a tracking area encompassing a plurality of cells and handle signalling connections between the terminal devices and the core network. The gateway node may handle data routing in the core network and to/from the terminal devices. The 5G specifications specify the core network as a 5G core (5GC), and there the core network may comprise e.g. an access and mobility management function (AMF) and a user plane function/gateway (UPF), to mention only a few. The AMF may handle termination of non-access stratum (NAS) signalling, NAS ciphering & integrity protection, registration management, connection management, mobility management, access authentication and authorization, security context management. The UPF node may support packet routing & forwarding, packet inspection and QoS handling, for example.

Further, the wireless communication system may be configured to support UE relaying. For example, UE 120 may be configured act as a UE-to- network (U2N) relay UE that relays data (or simply information) between UE 122 and wireless communication network. In this scenario, UE 122 may be referred to as a remote UE 122 as it utilizes relay connection for data transfer with the network. Data transfer may be uplink and/or downlink data transfer. This U2N relaying, by U2N relay UE 120, enables the remote UE 122 to be connected with the network at cell edge or even beyond service area of a cell (e.g. cell 100). Or at least power may be saved as UE 122 may user lower power to communicate via the U2N relay UE 120. The relay connection between the UE 122 and the network may comprise two components with the assumption that relay is single hop relay: one connection (e.g., PC5 connection, may also be referred to as a sidelink connection) between the UEs 120, 122 and one connection (e.g., Uu connection) between the U2N relay UE 120 and the network. The term network (or more precisely, wireless communication network) is used herein to encompass one or more access nodes 110, 112. It is clear for the skilled person that communication with the network involves an entity at the radio access network side, wherein the entity is, for example, an access node such as gNB in NR/5G system.

One open question with respect to relay connections is service continuity. If the relay connection is terminated, RUE 122 may experience service outage. Figure 2 shows such example.

Block 202 represents RUE 122 being connected to the network via relay UE 120. This may require discovery process to establish the connection with the relay UE 120 by the RUE 122, and connection establishment (e.g., radio resource control (RRC) setup, or simply connection setup) with the network. The relay connection may be used to provide one or more services for the RUE 122 by the network (e.g., network node 110).

In block 204, the relay UE 120 may experience outage or be subject to an outage, failure or interruption. That is, the outage may at least affect the relay connection between the RUE 122 and the network. Outage may be caused by either or both of the following connections: connection between RUE 122 and relay UE 120 or connection between the relay UE 120 and the network node 110. For example, such outage may be caused by radio link failure (RLF) or by radio link quality being below an acceptable level/threshold. Another example is that the relay UE 120 determines to stop acting as a relay due to one or more reasons, such as low battery level or switching off.

Block 206 represents service interruption for the remote UE 122 that is caused by the outage of block 204.

To recover from the service interruption, the RUE 122 may need to again start (i.e., in a sense, restart) seeking for a new relay UE. This may require new discovery procedure, selection of new relay, and connection establishment as depicted by block 208. Problem is that this causes delay and thus the service interruption may be prolonged. For example, the service may be critical for the UE 122, and any delay may cause undesired effects. Hence, it may be beneficial to provide solutions at least for reducing these negative effects. Figures 3 and 4 illustrate flow diagrams of methods according to some embodiments. Referring first to Figure 3, a method for an apparatus is shown, wherein the method comprises: establishing a primary connection to a wireless communication network via a second UE (block 302); establishing at least one secondary connection to at least one third UE (304); determining a termination of the primary connection (block 306); and based on determining the termination of the primary connection, selecting one of the established at least one secondary connection as a new primary connection (block 308).

In an embodiment, the at least one secondary connection is to the wireless communication network via the at least one third UE.

In an embodiment, the termination of the primary connection is determined after the at least one secondary connection is established.

The method of Figure 3 and any associated embodiments may be performed by an apparatus. The apparatus may be a UE (e.g. UE 122 which can be referred to also as RUE 122) or comprised in a UE (e.g. UE 122).

The second UE may be, for example, UE 120. The at least one third UE may comprise one or more UEs capable of acting as a relay for RUE 122. For example, the at least one third UE may comprise UE 130 and/or UE 132.

Referring first to Figure 4, a method for an apparatus is shown, wherein the method comprises: broadcasting a message indicating a capability of the UE to act as a secondary communication relay between another UE and a wireless communication network (block 402); and maintaining, based on a request from said another UE, a secondary connection to said another UE (block 404).

In an embodiment, the secondary connection is maintained between said another UE and the wireless communication network.

The method of Figure 4 and any associated embodiments may be performed by an apparatus. The apparatus may be a UE or comprised in a UE. The UE may refer to UE that is capable of acting as a relay UE. That is, as an U2N relay UE.

At this point it is noted that secondary connection may also be referred to as auxiliary connection. Similarly, secondary communication relay may be referred to as auxiliary communication relay.

Figure 5 illustrates an example embodiment of applying one or more secondary connections (i.e., relay connections) by the RUE 122. Apart from a primary connection (e.g. PC5) with UE 120 (also referred to as U2N1 in Figure 5), the RUE 122 will also have a secondary connection (e.g., PC5) established with one or more UEs 130, 132 (also referred to as U2N2, U2N3 respectively) so that during or based on a service interruption (e.g. outage in the primary connection), one of the secondary connections can be converted in to a primary connection.

Two different secondary connection routes can be seen in Figure 5: intra-gNB route and inter-gNB route (gNB used herein as an example of NR/5G system, but other network nodes may be used e.g. in future networks such as 6G). Intra-gNB route refers to using the UE 130 (U2N2) that is connected to same network node 110 as UE 120 (U2N1). Inter-gNB route refers to using UE 130 (U2N3) that is connected to a different network node 112. Both network nodes 110, 112 may be comprised in the same wireless communication network and connected to each other (e.g., via Xn interface) to enable transfer of UE context between the nodes. Depending on implementation, the remote UE 122 may take into account, when selecting the secondary connection(s), to which network node the candidate secondary UE 130, 132 is connected.

Primary connection should be understood as a relay connection that is enabled by a communication relay such as UE 120 between RUE 122 and the wireless communication network (or simply network). Particularly, the relay connection is between RUE 122 and network node of the wireless communication network. Primary connection may be set up using, for example, RRC signalling. Primary connection may be used to transfer data between RUE 122 and the network. Once established, primary connection may be ready to be used for transferring data.

Secondary connection, which can also be referred to as a secondary or auxiliary relay connection, may differ from a primary connection. For example, the secondary connection may be understood to be dormant in the sense that it is not used to transmit data. That is, after establishment of the secondary connection, the secondary connection may not yet be ready for transferring data before connection setup is performed with the network. For example, a heartbeat signal or similar may be used to keep the secondary connection alive depending on requirements set by device implementation or by specifications. The secondary connection may stay dormant with bare minimal exchange of messages to keep the connection alive until it is converted to a primary connection. Thus, the secondary connection or connections may be kept alive and ready to be used as a primary connection, but at the same time using communication resources as little as possible. The secondary connection, promoted as the new primary connection, may be used to transmit data, for example, after performing connection setup with the network. Performing connection setup with the network may implicitly indicate that the secondary connection is promoted as the new primary connection.

According to an example embodiment, secondary connection (e.g. the at least one secondary connection discussed with reference to Figure 3) is established between RUE 122 and a relay UE (e.g. UE 130). Thus, the secondary connection may comprise PC5 (or sidelink) connection established between RUE 122 and the relay UE. In this example, the secondary connection may not extend to the wireless communication network (e.g., to the network node). However, if the secondary connection is promoted to a primary connection, the connection may then extend (after connection setup) from RUE 122 via relay UE 130 to the wireless communication network. It is noted that UE 130 may or may not be connected to the wireless communication network during it working as a secondary communication relay. In the case that it is connected to the network, the secondary connection may still not logically extend to the wireless communication network. In this example, heartbeat signal may be transmitted between RUE 122 and relay UE 130.

In another example embodiment, secondary connection (e.g. the at least one secondary connection discussed with reference to Figure 3) is established between RUE 122 and wireless communication network via a relay UE (e.g. UE 130). In this example, both PC5 and Uu connections may be formed already for the secondary connection and the secondary connection may logically extend from RUE 122 to the wireless communication network. Also in this example, heartbeat signal may be transmitted between RUE 122 and relay UE 130 as connection between relay UE 130 and the network may already be in use for other communication purposes. In an embodiment, the secondary connection is not used to transmit user plane data.

According to an embodiment, the remote UE 122 is caused to detect a deterioration or a radio link failure (RLF) of the primary connection, wherein the remote UE 122 is caused to determine the termination of the primary connection based on detecting the deterioration or the RLF of the primary connection. As discussed herein, RLF or deterioration of the connection may be caused in a radio link between the RUE 122 and the UE 120 and/or in a radio link between the UE 120 and the network node 110.

In an embodiment, the remote UE 122 is caused to determine the termination of the primary connection based on not receiving communication via the primary connection for a specified time period. For example, the time period may be preconfigured for the remote UE 122 or the remote UE 122 may receive information indicating the time period from the network. For example, a timer is provisioned to wait for configured period, if there is no response from serving U2U relay up to indicated time period set by the timer, remote UE 122 can start promoting to one of secondary connection as primary connection. After the waiting of said time period, remote UE 122 may start the promotion of secondary connection to primary connection.

Such examples may refer to abrupt termination of the primary connection, l.e., the connection is terminated suddenly without previous knowledge about the termination.

Another example of termination of the primary connection is known or predetermined termination. According to an embodiment, the RUE 122 is caused to receive, from the UE 120, an indication indicating the termination of the primary connection, wherein the RUE 122 is caused to determine the termination of the primary connection based on the indication. For example, the indication may indicate a time period after which the primary connection will be terminated or the indication may indicate that the primary connection is already terminated or terminated immediately after the indication is received. Based on the indication, the RUE 122 may determine the termination of the primary connection and start promoting one of the secondary connection(s) as the new primary connection. The relay UE (e.g. UE 120) may be caused to indicate termination of the primary connection (and also terminate the connection) based on battery level of UE 120, mobility of UE 120, and/or data usage policy to name a few examples. The indication may be, for example, a message NotificationMessageSidelink(mdicationType-rl7=’relayUE-Termination’) that is transmitted from UE 120 to UE 122. It is noted that the indication about the termination of the primary connection may also be transmitted from UE 120 to the network node 110. For example, based on this indication the network node 110 may indicate to the RUE 122 that it needs to select one of its secondary connections as the new primary connection. Alternatively or in addition, the network node 110 may indicate which of the secondary connections should be selected as the new primary connection.

Let us now draw our attention to Figures 6A and 6B illustrating some embodiments. Steps 600-608 are the same in both Figures and they are now explained with reference to both Figures 6A and 6B.

In step 602, RUE 122 receives, from a plurality of UEs 120, 130, 132, at least one message indicating a capability of plurality of UEs to act as a communication relay between RUE and the wireless communication network. One example of these messages are discovery messages. For example, each UE that is capable of acting as a relay may broadcast message indicating such capability and RUE 122 may receive one or more of those messages.

In an example embodiment, the relay UEs 120, 130, 132 transmit the messages without any transmission trigger from RUE 122. That is, such broadcasting mode may sometimes be referred to as model A discovery.

In an alternative example, RUE 122 broadcasts (step 600) a request a communication relay between RUE 122 and the wireless communication network, wherein the messages of step 602 received as a response to the request. That is, the UEs 120, 130, 132 may receive the request and start broadcasting messages of step 602 based on the request. This can be sometimes referred to as a model B discovery.

In step 604, RUE 122 may select a UE for a primary connection based on the messages of step 602.

In step 606, the primary connection (e.g. PC5) may be established between RUE 122 and UE 120. In this example, RUE 122 has selected UE 120 for the primary connection but as skilled person understands, the selection may differ based on the messages of step 602.

Step 608 represents that a connection between RUE 122 and the network is established via the relaying UE 120. The connection may be established using RRC connection establishment procedure. Thus, RUE 122 may utilize a network service(s) using said connection.

Now referring to Figure 6A, in step 614, RUE 122 may select one or more UEs for one or more secondary connections. In an embodiment, the selecting is performed based on the message(s) received from the UEs in step 602. Hence, the selection of UEs for primary connection and for the one or more secondary connections may be based on messages received at the same time or at least during same step or process. The selection of the secondary connection by RUE 122 or by network is discussed later in more detail. However, using the embodiment of Figure 6A may require less signalling than some other solutions. Furthermore, the selection of UEs for primary and secondary connection(s) may happen concurrently and thus it may be rather fast and simple.

In step 616, one or more secondary connections are established by RUE 122, for example based on the selection of step 614. Now RUE 122 may have primary connection and one or more secondary connections established.

Figure 6B illustrates an embodiment in which a further messaging between candidate secondary relaying UEs and RUE 122 is performed to establish the one or more secondary connections after the primary connection has already been established (see steps 606 and 608). This may be beneficial to enable further flexibility for the secondary connection establishment.

In step 622, RUE 122 may select one or more candidate UEs for secondary connections. This selection may be based on the messages of step 602. For example, RUE 122 may rank UE(s) that are left after one of the UEs is selected as the primary relaying UE (e.g., UE 120 in the example of Fig. 6B). In this example, UEs 130 and 132 have indicate that they may act as relaying UEs and thus may be selected as candidate UEs. However, RUE 122 may determine to select only some of the remaining relaying UEs and for this purpose ranking may be performed. For example, a certain number of highest ranking UEs may be selected as candidate UEs in step 622.

In step 624, RUE 122 may broadcast a request for secondary connections.

In step 626, one or more UEs may respond by broadcasting a response to the request of block 624. Steps 624, 626 may be performed, for example, according to model B discovery process.

In step 628, RUE 122 may select one or more UEs for one or more secondary connections. This selection may be based on the messages received in step 626 by the RUE 122 from the UEs 130, 132.

In step 630, RUE 122 may establish one or more secondary connections with one or more selected UEs based on step 628. In this example, secondary connection is established at least with UE 130. The dotted arrow between RUE 122 and 132 may mean that further secondary connection(s) are optional.

Thus, RUE 122 may have primary connection and one or more secondary connections established.

According to an embodiment, at least one message (e.g. message of step 602 and/or 626) indicating a capability of the at least one UE to act as a communication relay between RUE 122 and the wireless communication network may be indicating ability to act as a secondary communication relay. For instance, a message (e.g. discovery message broadcasted by UE 130, 132) may comprise information element which indicates a capability to act as a secondary relay UE (e.g., Relay Service Code = ‘Auxiliary Connection’).

Similarly, in an embodiment, the request by RUE 122 may indicate that RUE 122 requests UE(s) for secondary connection. For example, such may be indicated by message of step 624.

In an embodiment, the message(s) (block 602 and/or 626) indicate or comprise further information for selecting the UEs for secondary connection(s). That is, relay UE candidate may indicate information that is characteristic to the relay UE candidate (e.g. UE 130, 132) or more particularly UE specific information. Such further information may include at least one of an indication of a time period for which the UE can act as a communication relay between RUE 122 and the wireless communication network, battery level information of the UE, or mobility state information of the UE. This information may further enhance the selection of UE(s) for secondary connection(s).

U2N capable UEs (i.e. capable of providing secondary connection and maintaining keep-alive messages) may thus publish its secondary connections capabilities and offering over discovery messages. This allows the remote UE 122 to select (prioritise) a U2N relay which offers secondary connection.

Figures 7A and 7B illustrate signalling diagrams according to some embodiments that relate to the selection of UE(s) for secondary connection(s). Steps 700 and 702 may be same in both Figures and they may correspond to steps 600, 602 of Figures 6A and 6B.

So, based on broadcasting a request (step 700) or without broadcasting the request, RUE 122 may receive messages from a plurality of UEs 120, 130, 132 that indicate capability of the respective UE to act as a relay for secondary connection or simply for relay connection.

In the embodiment shown in Figure 7A, RUE 122 may determine ranking (step 704) for UEs that are suitable for secondary connections. For instance, if primary connection is established with one of the UEs (e.g. UE 120) that UE may be left out of the ranking.

In step 706, RUE 122 may select UE(s) for secondary connection(s) based on the ranking.

In step 708, RUE 122 may indicate to the network the selected UE(s) for the secondary connection(s). For example, the primary connection may be used to convey the information to the network. Hence, the network (or more particularly, network node 110) may determine to which UE(s) the secondary connection is established. Alternatively, the network node 110 may be configured to accept or decline the selection by RUE 122. If accepted, the network node 110 may indicate the acceptance to RUE 122 and RUE 122 may establish the secondary connection(s). If declined, the network node 110 may indicate that the selection is declined and thus RUE 122 may not establish secondary connection(s) with the selected UE(s). In such case, an alternative selection may be provided by the network node 110, for example.

The secondary connection(s) may be established, e.g. as discussed with reference to Figs. 6A and 6B, with the selected UE(s). Thus, RUE may be caused to establish the at least one secondary connection based on the at least one message (i.e., message(s) of step 702).

In the embodiment shown in Figure 7B, the ranking for UEs may be determined at the network side instead of ranking by RUE 122. In step 712, RUE 122 is caused to forward the at least one message (i.e., message(s) received in step 702), transmit information regarding the at least one message, or transmit information indicating the UE(s) capable of acting as relays to the wireless communication network.

For example, message of step 712 may be an RRC message (e.g. RRCSLAuxiliaryConnlnfolnd) from RUE 122 to network node 110. The message may, for example, comprise a list of target candidates U2N relay UEs for secondary connection. For instance, all UEs from which message, indicating capability to act as a secondary relay UE, is received in step 702 may be added to the list and indicated to the network node 110. Additionally, the message may comprise information for the ranking. For instance, the ranking may be performed similarly at the network side as at RUE 122. Hence, the information may comprise at least one of an indication of a time period for which the UE can act as a communication relay between RUE 122 and the wireless communication network, battery level information of the UE, or mobility state information of the UE. This information may be provided per UE, and for each UE from which such information is received by RUE 122 in step 702.

Based on the information received from RUE 122, the network node 110 may determine a ranking of the UEs for secondary connections (step 714). The network node 110 may have additional information (e.g. from other similar connections or RUE(s)) which it may utilize in the ranking (i.e., base the ranking on the information from RUE 122 and on said additional information). Hence, the ranking may be even further enhanced.

In step 716, RUE 122 may receive the ranking or information indicating the ranking from the network node 110. Thus, RUE 122 may receive, from the wireless communication network, information for selecting at least one UE to which at least one secondary connection is to be established. For example, the ranking may be indicated using an RRC message (e.g. RRCSLAuxiliaryConnlnfoCnf) which comprises a ranked list of candidates U2N relay(s) and assistance information like time period of secondary connection (i.e., how long the connection can be provided), mobility state information, battery level information which are received from U2U relay(s). In some examples, it may be even possible that network node 110 receives the assistance information from the candidate relay UEs directly. E.g., a candidate relay UE may be acting as a relay to another remote UE and thus network node 110 may already be aware of the assistance information based on the earlier connection(s).

Steps 718 and 720 may be similar as steps 706 and 708 in which RUE 122 may select (steps 706, 718) the UE(s) for one or more secondary connection(s) and transmit (steps 708, 720) the indication about the selection to the network.

Figure 8 illustrates a signalling diagram according to an embodiment. Referring to Figure 8, RUE 122 has a primary connection via UE 120 to the network.

In step 812, RUE 122 selects one or more UEs for one or more secondary connections. This selection may be based on, for example, information received from the UEs 130, 132 and possibly additionally on information received from the network.

In step 814, one or more secondary connections (e.g. PC5) are established by RUE 122 with UEs 130, 132.

In step 816, RUE 122 indicates, after establishing the one or more secondary connections, a list of UEs to the network. This list of UEs may be a ranked list of UEs. In an embodiment, the list of UEs indicates all UEs that RUE 122 identified to be able to act as a relay for secondary connection. In this case, in some examples, the list may also indicate UE(s) to which secondary connection has been established. Thus, network may determine all possible relay UEs for secondary connection(s) and also determine which UEs are already acting as relays for secondary connection(s).

In an embodiment, the list of UEs indicates all UEs, but not the UE(s) to which secondary connection has already been established, that RUE 122 identified to be able to act as a relay for secondary connection.

Step 818 represents that the list of UEs is conveyed by UE 120 to the network according to the U2N relaying principles. The network, e.g. by the network node 110, may perform ranking decision based on the list of UEs and indicate the ranking decision to RUE 122. Thus, for example, the list of UEs may be understood as a proposal of secondary relay UEs based on which the network node 110 may make decision(s). The ranking decision may indicate which one or more UEs the RUE 122 should use to establish one or more secondary connections. In this example, the network may perform the final decision on which UE(s) to use for the secondary connection(s). However, in some embodiments RUE 122 may itself make the decision and inform the decision to the network.

As discussed, a remote UE establishes and maintains secondary connection with other U2N relay(s). In case of outage of main PC5 connection, remote UE uses an existing secondary connection to access the network and continue to avail the services. That is, the remote UE may promote (one of) the secondary connections to primary connection. Figure 9 illustrates a signalling diagram of an embodiment in which the primary connection is terminated. As shown in the Figure, primary connection 912 is established between RUE 122 and network node 110 via UE 120, and secondary connection 914 between RUE 122 and network node 112 via UE 132. For the sake of clarity, only one secondary connection is shown, but there may be more than one depending on implementation and/or scenario.

In step 916, service is interrupted due to termination of the primary connection. That is, the primary connection is abrupted or it is knowingly terminated.

Without the present solution, RUE 122 would need to start discovery process to obtain a new connection to the network via a relay UE. However, as secondary connection is already established at the time of the service interruption, RUE 122 may simply promote the secondary connection as a new primary connection. In other words, the secondary connection may be selected as a new primary connection. Block 918 represents that RUE 122 may start using the secondary connection. For example, one of one or more secondary connections of RUE 122 may be started using by RUE 122.

After selecting the new primary connection, RUE 122 may transmit a connection request message to the network in order to start using the new primary connection (i.e., secondary connection of block 914) for using the interrupted service. The connection request may be, for example, RRC setup request transmitted to the network node 112. Network may respond to the connection request with connection setup message (e.g. RRC setup from network node 112 to RUE 122).

RUE 122 may further respond with setup complete message (e.g., RRC setup complete). Thus, the secondary connection may be setup for use as the new primary connection as indicated by block 940.

In the example of Figure 9, the new primary connection is via a UE 132 that is served by a second access node 112 different than a first access node 110 serving the UE 120 that provides the original primary connection. In such case, context retrieval procedure (block 930) may be used to retrieve context of RUE 122 by network node 112 from network node 110. For example, this context retrieval procedure may work as currently defined in the 3GPP specifications. However, in some cases same network node may serve both the original and the new UEs that act as relays for RUE 122. In this case, the context may already be available at the network node and thus no context retrieval may be needed.

According to an embodiment, after secondary connection is selected as new primary connection, RUE 122 may be further caused to establish one or more new secondary connections. For example, if the only established secondary connection is promoted as the new primary connection, RUE 122 may determine to establish one or more new secondary connections as a backup. For example, if the number of established secondary connections is below a threshold number, RUE 122 may determine to establish one or more new secondary connections as a backup. Establishing new secondary connection(s) may be performed similarly as described above, for example.

In an embodiment, RUE 122 is caused to: receive, respectively from each of a plurality of UEs, a message indicating a capability of the respective UE to act as a secondary communication relay between RUE 122 and the wireless communication network; and based on the messages, determine a ranking for the plurality of UEs.

In an embodiment the RUE 122 is caused to: receive, respectively from each of a plurality of UEs, a message indicating a capability of the respective UE to act as a secondary communication relay between RUE 122 and the wireless communication network; forward the messages, transmit information regarding the messages, or transmit information indicating the plurality of UEs to the wireless communication network; and receive, from the wireless communication network, a ranking for the plurality of UEs.

In an embodiment, the message comprises at least one of an indication of a time period for which the respective UE can act as a communication relay between RUE 122 and the wireless communication network, battery level information of the respective UE, or mobility state information of the respective UE.

In an embodiment, RUE 122 is caused to select the at least one UE, to which the at least one secondary connection is to be established, amongst the plurality of UEs based on the ranking of the plurality of UEs.

In an embodiment, RUE 122 is caused to: indicate, to the wireless communication network, the selected at least one UE.

In an embodiment, RUE 122 is caused to select an established secondary connection via a highest ranking UE, according to the ranking, as the new primary connection. That is, highest ranking UE or highest ranking secondary connection may be selected as the new secondary connection.

An embodiment, as shown in Figure 10, provides an apparatus 10 comprising a control circuitry (CTRL) 12, such as at least one processor, and at least one memory 14 storing instructions that, when executed by the at least one processor, cause the apparatus at least to carry out any one of the above-described processes. In an example, the at least one memory and the instructions (e.g. computer program code (software)), are configured, with the at least one processor, to cause the apparatus to carry out any one of the above-described processes. The memory may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The memory may comprise a database for storing data.

In an embodiment, the apparatus 10 may comprise UE of the wireless communication system, e.g. a user terminal (UT), a computer (PC), a laptop, a tabloid computer, a cellular phone, a mobile phone, a communicator, a smart phone, a palm computer, a mobile transportation apparatus (such as a car), a household appliance, or any other communication apparatus, commonly called as UE in the description. Alternatively, the apparatus is comprised in such a UE. Further, the apparatus may be or comprise a module (to be attached to the UE) providing connectivity, such as a plug-in unit, an “USB dongle”, or any other kind of unit. The unit may be installed either inside the UE or attached to the UE with a connector or even wirelessly.

In an embodiment, the apparatus 10 is or is comprised in the UE 122 (also referred to as RUE 122 or remote UE 122). The apparatus may be caused to execute some of the functionalities of the above described processes, such as the steps of Figure 3.

The apparatus may further comprise a radio interface (TRX) 16 comprising hardware and/or software for realizing communication connectivity according to one or more communication protocols. The TRX may provide the apparatus with communication capabilities to access the radio access network, for example.

The apparatus may also comprise a user interface 18 comprising, for example, at least one keypad, a microphone, a touch display, a display, a speaker, etc. The user interface may be used to control the apparatus by the user.

The control circuitry 12 may comprise a first establishing circuitry 20 for performing the step 302 of Figure 3 according to any of the embodiments; a second establishing circuitry 22 for performing the step 304 of Figure 3 according to any of the embodiments; a determining circuitry 24 for performing the step 306 of Figure 3 according to any of the embodiments; and a selecting circuitry 26 for performing the step 308 of Figure 3 according to any of the embodiments.

An embodiment, as shown in Figure 11, provides an apparatus 50 comprising a control circuitry (CTRL) 52, such as at least one processor, and at least one memory 54 storing instructions that, when executed by the at least one processor, cause the apparatus at least to carry out any one of the above-described processes. In an example, the at least one memory and the instructions (computer program code (software)), are configured, with the at least one processor, to cause the apparatus to carry out any one of the above-described processes. The memory may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The memory may comprise a database for storing data.

In an embodiment, the apparatus 50 may be or be comprised in a UE of the wireless communication system. In an embodiment, the apparatus is or is comprised in the UE 120, UE 130, or UE 132. That is, the apparatus may be or be comprised in a UE capable of relaying data between apparatus 10 or RUE 122 and the wireless communication network. The apparatus may be caused to execute some of the functionalities of the above-described processes, such as the steps of Figure 4.

The apparatus may further comprise communication interface (TRX) 56 comprising hardware and/or software for realizing communication connectivity according to one or more communication protocols. The TRX may provide the apparatus with communication capabilities with at least one user equipment, for example.

The apparatus may also comprise a user interface 58 comprising, for example, at least one keypad, a microphone, a touch display, a display, a speaker, etc. The user interface may be used to control the apparatus by the user.

The control circuitry 52 may comprise a broadcasting circuitry 60 for performing the step 402 of Figure 4 according to any of the embodiments; and a maintaining circuitry 62 for performing the step 404 of Figure 4 according to any of the embodiments.

In an embodiment, an apparatus carrying out at least some of the embodiments described comprises at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the functionalities according to any one of the embodiments described. According to an aspect, when the at least one processor executes the computer program code, the computer program code causes the apparatus to carry out the functionalities according to any one of the embodiments described. According to another embodiment, the apparatus carrying out at least some of the embodiments comprises the at least one processor and at least one memory including a computer program code, wherein the at least one processor and the computer program code perform at least some of the functionalities according to any one of the embodiments described. Accordingly, the at least one processor, the memory, and the computer program code form processing means for carrying out at least some of the embodiments described. According to yet another embodiment, the apparatus carrying out at least some of the embodiments comprises a circuitry including at least one processor and at least one memory including computer program code. When activated, the circuitry causes the apparatus to perform the at least some of the functionalities according to any one of the embodiments described.

As used in this application, the term ‘circuitry’ refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and soft- ware (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of ‘circuitry’ applies to all uses of this term in this application. As a further example, as used in this application, the term ‘circuitry’ would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware. The term ‘circuitry’ would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device.

In an embodiment, at least some of the processes described may be carried out by an apparatus comprising corresponding means for carrying out at least some of the described processes. Some example means for carrying out the processes may include at least one of the following: detector, processor (including dual-core and multiple-core processors), digital signal processor, controller, receiver, transmitter, encoder, decoder, memory, RAM, ROM, software, firmware, display, user interface, display circuitry, user interface circuitry, user interface software, display software, circuit, antenna, antenna circuitry, and circuitry. For example, apparatus, such as RUE 122 or relay UE, may comprise means for performing any of the described processes.

A 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).

As used herein the term “means” is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology “means for [performing A, B, C]”, is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology “means for performing A, means for performing B, means for performing C” is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C.

As used herein the phrase “one or more entities” may sometimes be replaced by the phrasing “entity(s)”. That is, for example one or more UEs may be referred to also as UE(s).

The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the apparatus(es) of embodiments may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chip set (e.g. procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit and executed by processors. The memory unit may be implemented within the processor or externally to the processor. In the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additionally, the components of the systems described herein may be rearranged and/or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

Embodiments as described may also be carried out in the form of a computer process defined by a computer program or portions thereof. Embodiments of the methods described may be carried out by executing at least one portion of a computer program comprising corresponding instructions. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. For example, the computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example. The computer program medium may be a non-transitory medium. Coding of software for carrying out the embodiments as shown and described is well within the scope of a person of ordinary skill in the art. Following is a list of some examples if the proposed solution.

Example 1. A first user equipment, UE, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first UE at least to: establish a primary connection to a wireless communication network via a second UE; establish at least one secondary connection to at least one third UE; after the at least one secondary connection is established, determine a termination of the primary connection; and based on determining the termination of the primary connection, select one of the established at least one secondary connection as a new primary connection.

Example 2. The first UE of example 1, wherein the at least one secondary connection is to the wireless communication network via the at least one third UE.

Example 3. The first UE of example 1 or 2, wherein first UE is caused to: detect a deterioration or a radio link failure, RLF, of the primary connection, wherein the first UE is caused to determine the termination of the primary connection based on detecting the deterioration or the RLF of the primary connection.

Example 4. The first UE of any preceding example 1 to 3, wherein the first UE is caused to determine the termination of the primary connection based on not receiving communication via the primary connection for a specified time period.

Example 5. The first UE of example 1 or 2, wherein the first UE is caused to: receive, from the second UE, an indication indicating the termination of the primary connection, wherein the first UE is caused to determine the termination of the primary connection based on the indication.

Example 6. The first UE of any preceding example 1 to 5, wherein the first UE is caused to: receive, from the at least one third UE, at least one message indicating a capability of the at least one third UE to act as a secondary communication relay between the first UE and the wireless communication network.

Example 7. The first UE of example 6, wherein the at least one message is a discovery message.

Example 8. The first UE of example 6 or 7, wherein the first UE is caused to: broadcast a request for a secondary communication relay between the first UE and the wireless communication network, wherein the at least one message is received as a response to the request.

Example 9. The first UE of any of examples 6 to 8, wherein the at least one message comprises at least one of an indication of a time period for which the at least one third UE can act as a communication relay between the first UE and the wireless communication network, battery level information of the at least one third UE, or mobility state information of the at least one third UE.

Example 10. The first UE of any of examples 6 to 9, wherein the first UE is caused to establish the at least one secondary connection based on the at least one message.

Example 11. The first UE of any of examples 6 to 9, wherein the first UE is caused to: forward the at least one message, transmit information regarding the at least one message, or transmit information indicating the at least one third UE to the wireless communication network; and receive, from the wireless communication network, information for selecting the at least one third UE to which the at least one secondary connection is to be established.

Example 12. The first UE of any of examples 1 to 5, wherein the first UE is caused to: receive, from each of a plurality of UEs, a message indicating a capability of the respective UE to act as a secondary communication relay between the first UE and the wireless communication network; and based on the messages, determine a ranking for the plurality of UEs.

Example 13. The first UE of any of examples 1 to 5, wherein the first UE is caused to: receive, from each of a plurality of UEs, a message indicating a capability of the respective UE to act as a secondary communication relay between the first UE and the wireless communication network; forward the messages, transmit information regarding the messages, or transmit information indicating the plurality of UEs to the wireless communication network; and receive, from the wireless communication network, a ranking for the plurality of UEs.

Example 14. The first UE of example 12 to 13, wherein the message comprises at least one of an indication of a time period for which the respective UE can act as a communication relay between the first UE and the wireless communication network, battery level information of the respective UE, or mobility state information of the respective UE.

Example 15. The first UE of example 12 to 14, wherein the first UE is caused to select the at least one third UE, to which the at least one secondary connection is to be established, amongst the plurality of UEs based on the ranking of the plurality of UEs.

Example 16. The first UE of example 15, wherein the first UE is caused to: indicate, to the wireless communication network, the selected at least one third UE.

Example 17. The first UE of example 12 to 16, wherein the first UE is caused to select an established secondary connection via a highest ranking UE, according to the ranking, as the new primary connection.

Example 18. The first UE of example 12, the first UE caused to: indicate the determined ranking to the wireless communication network.

Example 19. The first UE of example 18, the first UE caused to: receive a ranking decision as a response to the indicated ranking; wherein the first UE is caused to select the at least one third UE, to which the at least one secondary connection is to be established, amongst the plurality of UEs based on the ranking decision.

Example 20. The first UE according to any preceding example 1 to 19, wherein the new primary connection is via a UE that is served by a second access node different than a first access node serving the second UE, the first device is further caused to: transmit a setup request to the second access node via the UE associated with the new primary connection; and receive a response to the setup request.

Example 21. The first UE of any preceding example 1 to 20, wherein the at least one secondary connection is not used to transmit user plane data.

Example 22. A user equipment, UE, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to: broadcast a message indicating a capability of the UE to act as a secondary communication relay between another UE and a wireless communication network; and maintain, based on a request from said another UE, a secondary connection at least to said another UE.

Example 23. The UE of example 22, wherein the message comprises at least one of an indication of a time period for which the UE can act as a communication relay between said another UE and the wireless communication network, battery level information of the UE, or mobility state information of the UE.

Example 24. A method for a first user equipment, UE, the method comprising: establishing a primary connection to a wireless communication network via a second UE; establishing at least one secondary connection to at least one third UE; after the at least one secondary connection is established, determining a termination of the primary connection; and based on determining the termination of the primary connection, selecting one of the established at least one secondary connection as a new primary connection.

Example 25. A method for a user equipment, UE, the method comprising: broadcasting a message indicating a capability of the UE to act as a secondary communication relay between another UE and a wireless communication network; and maintaining, based on a request from said another UE, a secondary connection at least to said another UE.

Example 26. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, such as a user equipment, execute the method according to example 24 or 25.

Example 27. A computer program product comprising program instructions which, when loaded into an apparatus, such as a user equipment, execute the method according to example 24 or 25.

Example 28. The method according to example 24, further comprising step(s) and/or definition(s) as indicated in any one of examples 2 to 21.

Example 29. The method according to example 25, further comprising step(s) and/or definition(s) as indicated in example 23.

Even though the invention has been described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.

Claims

1. A first user equipment, UE, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first UE at least to: establish a primary connection to a wireless communication network via a second UE; establish at least one secondary connection to at least one third UE; after the at least one secondary connection is established, determine a termination of the primary connection; and based on determining the termination of the primary connection, select one of the established at least one secondary connection as a new primary connection.

2. The first UE of claim 1, wherein the at least one secondary connection is to the wireless communication network via the at least one third UE.

3. The first UE of claim 1 or 2, wherein first UE is caused to: detect a deterioration or a radio link failure, RLF, of the primary connection, wherein the first UE is caused to determine the termination of the primary connection based on detecting the deterioration or the RLF of the primary connection.

4. The first UE of any preceding claim, wherein the first UE is caused to determine the termination of the primary connection based on not receiving communication via the primary connection for a specified time period.

5. The first UE of claim 1 or 2, wherein the first UE is caused to: receive, from the second UE, an indication indicating the termination of the primary connection, wherein the first UE is caused to determine the termination of the primary connection based on the indication.

6. The first UE of any preceding claim, wherein the first UE is caused to: receive, from the at least one third UE, at least one message indicating a capability of the at least one third UE to act as a secondary communication relay between the first UE and the wireless communication network.

7. The first UE of claim 6, wherein the at least one message is a discovery message.

8. The first UE of claim 6 or 7, wherein the first UE is caused to: broadcast a request for a secondary communication relay between the first UE and the wireless communication network, wherein the at least one message is received as a response to the request.

9. The first UE of any of claims 6 to 8, wherein the at least one message comprises at least one of an indication of a time period for which the at least one third UE can act as a communication relay between the first UE and the wireless communication network, battery level information of the at least one third UE, or mobility state information of the at least one third UE.

10. The first UE of any of claims 6 to 9, wherein the first UE is caused to establish the at least one secondary connection based on the at least one message.

11. The first UE of any of claims 6 to 9, wherein the first UE is caused to: forward the at least one message, transmit information regarding the at least one message, or transmit information indicating the at least one third UE to the wireless communication network; and receive, from the wireless communication network, information for selecting the at least one third UE to which the at least one secondary connection is to be established.

12. The first UE of any of claims 1 to 5, wherein the first UE is caused to: receive, from each of a plurality of UEs, a message indicating a capability of the respective UE to act as a secondary communication relay between the first UE and the wireless communication network; and based on the messages, determine a ranking for the plurality of UEs.

13. The first UE of any of claims 1 to 5, wherein the first UE is caused to: receive, from each of a plurality of UEs, a message indicating a capability of the respective UE to act as a secondary communication relay between the first UE and the wireless communication network; forward the messages, transmit information regarding the messages, or transmit information indicating the plurality of UEs to the wireless communication network; and receive, from the wireless communication network, a ranking for the plurality of UEs.

14. The first UE of claim 12 to 13, wherein the message comprises at least one of an indication of a time period for which the respective UE can act as a communication relay between the first UE and the wireless communication network, battery level information of the respective UE, or mobility state information of the respective UE.

15. The first UE of claim 12 to 14, wherein the first UE is caused to select the at least one third UE, to which the at least one secondary connection is to be established, amongst the plurality of UEs based on the ranking of the plurality of UEs.

16. The first UE of claim 15, wherein the first UE is caused to: indicate, to the wireless communication network, the selected at least one third UE.

17. The first UE of claim 12 to 16, wherein the first UE is caused to select an established secondary connection via a highest ranking UE, according to the ranking, as the new primary connection.

18. The first UE of claim 12, the first UE caused to: indicate the determined ranking to the wireless communication network.

19. The first UE of claim 18, the first UE caused to: receive a ranking decision as a response to the indicated ranking; wherein the first UE is caused to select the at least one third UE, to which the at least one secondary connection is to be established, amongst the plurality of UEs based on the ranking decision.

20. The first UE according to any preceding claim, wherein the new primary connection is via a UE that is served by a second access node different than a first access node serving the second UE, the first device is further caused to: transmit a setup request to the second access node via the UE associated with the new primary connection; and receive a response to the setup request.

21. The first UE of any preceding claim, wherein the at least one secondary connection is not used to transmit user plane data.

22. A user equipment, UE, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to: broadcast a message indicating a capability of the UE to act as a secondary communication relay between another UE and a wireless communication network; and maintain, based on a request from said another UE, a secondary connection at least to said another UE.

23. The UE of claim 22, wherein the message comprises at least one of an indication of a time period for which the UE can act as a communication relay between said another UE and the wireless communication network, battery level information of the UE, or mobility state information of the UE.

24. A method for a first user equipment, UE, the method comprising: establishing a primary connection to a wireless communication network via a second UE; establishing at least one secondary connection to at least one third UE; after the at least one secondary connection is established, determining a termination of the primary connection; and based on determining the termination of the primary connection, selecting one of the established at least one secondary connection as a new primary connection.

25. A method for a user equipment, UE, the method comprising: broadcasting a message indicating a capability of the UE to act as a secondary communication relay between another UE and a wireless communication network; and maintaining, based on a request from said another UE, a secondary connection at least to said another UE.

26. A computer program product embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, such as a user equipment, execute the method according to claim 24 or 25.

27. A computer program product comprising program instructions which, when loaded into an apparatus, such as a user equipment, execute the method according to claim 24 or 25.