WO2023020742A1

WO2023020742A1 - Network-initiated connection establishment for remote device

Info

Publication number: WO2023020742A1
Application number: PCT/EP2022/068691
Authority: WO
Inventors: Ling Yu; György Tamás Wolfner; Vinh Van Phan; Lianghai JI; Faranaz SABOURI-SICHANI
Original assignee: Nokia Technologies Oy
Priority date: 2021-08-20
Filing date: 2022-07-06
Publication date: 2023-02-23
Also published as: CN117882454A; EP4388804A1

Abstract

According to an example aspect of the present invention, there is provided a method comprising: receiving, by a network entity, a paging message associated to a paging identifier of a remote device, determining, by the network entity, that the remote device is connected to a relay device, and in response to receiving the paging message and said determining, transmitting, by the network entity to the relay device, a radio resource control connection management message for setting up or resuming a radio resource control connection with the remote device, without receiving a radio resource control connection management request message.

Description

NETWORK-INITIATED CONNECTION ESTABLISHMENT FOR REMOTE DEVICE

FIELD

[0001] Various example embodiments relate to controlling network-initiated remote device connection establishment, and in particular for relaying communication scenarios.

BACKGROUND

[0002] Relaying may be used to enhance coverage, capacity and/or power savings by having a relay device between a transmitting device and a receiving device, thereby creating a multi-hop communication link. Relaying may be used, for example, in various communication networks, such as, in cellular communication networks operating according to 5G radio access technology. User equipment (UE)-to-network relay may refer to a relaying architecture where a relay UE relays the traffic between a remote UE and the network. UE-to-network relay enables coverage extension and power saving for the remote UE. For UE-to-network relay, the remote UE may be paged via the relay UE.

SUMMARY

[0003] According to some aspects, there is provided the subject matter of the independent claims. Some embodiments for some or all of the aspects are defined in the dependent claims.

[0004] According to a first aspect, there is provided a method for a network entity, such as a node of a radio access network, comprising: receiving, by a network entity, a paging message associated to a paging identifier of a remote device, determining, by the network entity, that the remote device is connected to a relay device, and in response to receiving the paging message and said determining, transmitting, by the network entity to the relay device, a radio resource control connection management message for setting up or resuming a radio resource control connection with the remote device, without receiving a radio resource control connection management request message.

[0005] According to a second aspect, there is provided a method for a relay device, such as a user device, comprising: receiving, by a relay device from a network entity, a paging message associated to a paging identifier of a remote device, determining, by the relay device, at least one link quality condition of a connection between the relay device and the remote device, and in response to receiving the paging message and the at least one link quality condition satisfying at least one link quality requirement, transmitting by the relay device to the network entity, a radio resource control connection management request message on behalf of the remote device, without first receiving a corresponding radio resource control connection management request message from the remote device.

[0006] According to some further aspects, there is provided an apparatus, comprising means configured for performing the method of the first aspect or the second aspect, or an embodiment thereof. The means may comprise one or more processors and memory comprising instructions, when executed by the one or more processors, cause the apparatus to perform the method.

[0007] According to some further aspects, there is provided an apparatus, comprising one or more processors and memory comprising instructions, when executed by the one or more processors, cause the apparatus for performing the method of the first aspect, the second aspect, or an embodiment thereof.

[0008] The relay device may be a relay terminal and the remote device may be a remote terminal. The apparatus performing the first aspect may be a radio access network device or for/comprised by a radio access network device, in some embodiments a base station, such as a gNodeB . The apparatus performing the second aspect may be a user device or terminal, such as a user equipment configured to access a Third Generation Partnership Project (3GPP) network.

[0009] According to still further aspects, there is provided a computer program product, a computer readable medium, or a non-transitory computer readable medium comprising program instructions for causing, when executed in a processor of an apparatus, the apparatus to perform the method according to any one of the above aspects or embodiments thereof.

[0010] In an embodiment, the paging message is received by the relay device in a radio resource control (RRC) message dedicated to the relay device in RRC connected state.

[0011] In some embodiments, the RRC connection management message is or comprises an RRC connection setup or resume message, and the RRC connection management request message is or comprises an RRC connection setup or resume request message.

[0012] In an embodiment, the relay device includes, in the RRC connection setup message, an identifier of the remote device received from the remote device or a random identifier generated by the relay device in response to failing to receive an identifier of the remote device.

[0013] In an embodiment, the relay device may include, in the RRC connection resume request message, an identifier of the remote device and security context information received from the remote device. [0014] In an embodiment, the relay device, in RRC idle or inactive state, may transmit, to the network entity, an RRC connection management request message of the relay device together with the RRC connection management request message on behalf of the remote device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIGURE 1 illustrates an example of a wireless communications system;

[0016] FIGURE 2 illustrates signalling for RRC connection establishment for a remote device being paged;

[0017] FIGURE 3 illustrates a method in accordance with at least some embodiments;

[0018] FIGURE 4 illustrates 5G NR RRC states;

[0019] FIGURE 5 illustrates a signalling example for controlling RRC connection establishment for a remote device being paged;

[0020] FIGURE 6 illustrates a method in accordance with at least some embodiments;

[0021] FIGURE 7 illustrates a signalling example for controlling RRC connection establishment for a remote device being paged; and

[0022] FIGURE 8 illustrates an example apparatus capable of supporting at least some embodiments.

DETAILED DESCRIPTION

[0023] Fig. 1 illustrates a simplified example wireless communications system. A user device, herein referred to as a user equipment (UE) 10 communicates wirelessly with a wireless radio or access network entity or node, hereafter also referred to as AN, 20, such as a NodeB, an evolved NodeB (eNB), a Next Generation (NG) NodeB (gNB), a base station, an access point, or other suitable wireless/radio access network (RAN) device or system.

[0024] The UE 10 may attach or register to the AN 20 for wireless communications. The air interface between UE and AN may be configured in accordance with a Radio Access Technology, RAT, which both the UE 10 and AN 20 are configured to support.

[0025] Examples of cellular RATs include Long Term Evolution, LTE, New Radio, NR, which is also known as fifth generation, 5G, and MulteFire. On the other hand, an example of a non-cellular RATs includes Wireless Local Area Network, WLAN. Principles of the present disclosure are not limited to a specific RAT though. For example, in the context of NR, AN 20 may be a gNB, but in the context of another RAT, AN 20 may be another type of base station, access node or nodeB.

[0026] The AN 20 may comprise one or more operationally and/or physically separate sub-units or nodes referred to below as nodes or logical RAN nodes. The controlling node 22 may be a central unit (CU) and the controlled node(s) may be distributed unit(s) (DU), such as the gNB-CU and gNB- DU connected over Fl interface of 3GPP 5G RAN, respectively.

[0027] The AN 20 may be connected, directly or via at least one intermediate node, with one or more devices or elements 32 of a core network 30, such as a Next Generation core network, Evolved Packet Core (EPC), or other network management element. The core network 30 may comprise a set of network functions. A network function may refer to an operational and/or physical entity. The core network element 32 may be a network function or be configured to perform one or more network functions. The network function may be a specific network node or element, or a specific function or set of functions carried out by one or more entities, such as virtual network elements. Examples of such network functions include an access control or management function, mobility management or control function, session management or control function, interworking, data management or storage function, authentication function or a combination of one or more of these functions.

[0028] For example, a 3GPP 5G core network comprises Access and Mobility Management Function (AMF) which may be configured to terminate RAN control plane (N2) interface and perform registration management, connection management, reachability management, mobility management, access authentication, access authorization, Security Anchor Functionality (SEAF), Security Context Management (SCM), and support for interface for non-3GPP access. The AMF is in charge i.a. for managing handovers between gNBs and initiating core-network paging by a paging message to a gNB.

[0029] The core network 30 may be, in turn, coupled with another network (not shown), via which connectivity to further networks may be obtained, for example via a worldwide interconnection network. The AN 20 may be connected with at least one other AN as well via an inter-base station interface, particularly for supporting mobility of the UE 10, e.g. by 3GPP X2 or similar NG interface.

[0030] The UE 10 may be referred to as a user device or wireless terminal in general. Hence, without limiting to 3GPP User Equipment, the term user equipment is to be understood broadly to cover various mobile/wireless terminal devices, mobile stations and user devices for user communication and/or machine to machine type communication. The UE 10 may be or be comprised by, for example, a smartphone, a cellular phone, a Machine-to-Machine, M2M, node, machine-type communications node, an Internet of Things, loT, node, a wearable, a car telemetry unit, a laptop computer, a tablet computer or, indeed, another kind of suitable user device or mobile station, i.e., a terminal. [0031] Additionally, although the apparatuses have been depicted as single entities, different units, processors and/or memory units (not all shown in Fig. 1) may be implemented inside these apparatuses, to enable the functioning thereof. The system may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service. The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

[0032] Edge cloud may be brought into radio access network (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. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. For example, in a 5G cloud RAN, the DU’s server and relevant software could be hosted on a site itself or can be hosted in an edge cloud (datacenter or central office) depending on transport availability and fronthaul interface. The CU’s server and relevant software can be co-located with the DU or hosted in a regional cloud data center. One of the concepts for 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0033] The depicted system is only an example of a part of a system and in practice, the system may comprise further access nodes, e.g. with the split CU-DU architecture, the user device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other core network functions or elements, etc. A cellular radio system may be implemented as a multilayer network including several kinds of cells, such as macrocells, microcells and picocells, for example. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of NodeBs are required to provide such a network structure. 5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling.

[0034] Fig. 1 further illustrates that the UE 10 may operate as a relay device to another device 12, which may operate as remote device. Devices 10 and 12 may be terminal devices and referred to as relay terminal and remote terminal, respectively. Since the devices 10, 12 may be UEs, such as 3GPP 5G UEs, they may also be referred to as relay UE/eRelay-UE and remote UE/eRemote-UE, respectively. Indirect 3 GPP communication may refer to signalling and communication between a UE and 3 GPP network, where there is a relay UE between the remote UE and the 3GPP network.

[0035] A sidelink (SL) may be established between the relay UE 10 and the remote UE 12 to establish UE-to-network (U2N) relayed communication. In case of 3GPP NR, an NR sidelink over PC5 interface or a non-3GPP link may be established between the relay UE 10 and the remote UE 12. The remote UE 12 may be out of cell coverage or in cell coverage. The UEs 10, 12 may be in the same cell or in different cells when a remote connection via the relay UE 10 is established.

[0036] For paging the remote UE 12, the relay UE 10 may be arranged to monitor the remote UE's paging occasion(s) in addition to its own paging occasion(s). Such paging relaying solution may be applied to both CN paging and RAN paging.

[0037] For example, as illustrated in 5G NR based signalling example of Fig. 2, in case of detecting a paging message 200 from gNB (e.g. AN 20) to the remote UE (e.g. UE 12), the relay UE (e.g. UE 10) forwards the paging message to the remote UE by an SL transmission 202. The remote UE then initiates RRC connection setup with the gNB by transmitting RRC request message 204 over the SL. The relay UE may forward the received RRC request by an uplink connection message 206. The gNB responds to the RRC request of the remote UE by transmitting an RRC message to setup RRC connection with the remote UE as downlink (DL) transmission 208 to the relay UE. The relay UE forwards the received RRC setup message to the remote UE 12 by SL transmission 210. The RRC connection setup between the remote UE and the gNB is completed by RRC setup complete message. The RRC setup complete is transferred by SL message 212 to the relay UE 10, which then forwards the RRC setup by uplink message 214 to the gNB.

[0038] Due to relayed or two-hop transmission of paging and RRC signaling messages of RRC connection establishment between gNB and remote UE, additional delay is caused between remote UE’s paging message arrival to gNB and remote UE’s RRC connection established between remote UE and gNB, as compared to paging using direct communication. For instance, let us assume that one direction SL transmission latency over PC5 interface is at the range of 5-10 ms, there is one paging message and three RRC connection setup related RRC signaling messages relayed over PC5 interface. Thus, the total additional delay caused by the relayed message transmission may be in the range of 20 - 40 ms. If assuming the total RRC connection establishment procedure latency to be between 70 - 80 ms for direct connection establishment between UE and base station, or around 50 ms with latency improvement features, the additional delay of 20 - 40 ms due to relayed message transmission over the PC5 interface may be significant for RRC connection establishment between remote UE and gNB.

[0039] There are now provided improvements to reduce delay for network-initiated connection establishment with a remote device communicating via a relay device.

[0040] Fig. 3 is a flow graph of a method for controlling RRC connection management, such as RRC connection setup or resume, in accordance with at least some embodiments. The method may be performed by a network entity, such as the AN 20, e.g. a gNB, or by a control device configured to control the functioning thereof. It is to be noted that an action, such as transmitting, in a given block of any of the methods disclosed herein may refer to controlling or causing such action in another apparatus or unit.

[0041] Block 300 comprises receiving, by the network entity, a paging message associated to a paging identifier of a remote device.

[0042] Block 310 comprises determining, by the network entity, that the remote device is connected to a relay device.

[0043] Block 320 comprises transmitting, in response to receiving the paging message and said determining, by the network entity to the relay device, an RRC connection management message for setting up or resuming an RRC connection with the remote device, without receiving an RRC connection management request message.

[0044] Before entering block 300, the network entity may receive, from the relay device, the paging identifier of the remote device connected to the relay device, and store the received paging identifier in association to the relay device. Block 310 may comprise detecting that a paging identifier in the paging message matches with the stored paging identifier associated with the relay device.

[0045] The RRC connection management request message may be associated with, or correspond to, the RRC connection management message. The network entity may independently initiate RRC connection establishment or resume on behalf of the remote UE. The network entity may initiate the RRC connection management by transmitting the RRC connection management message instantly upon detecting the match between the paging identifier in the received paging message and the paging identifier in the pre stored information associated with the relay device served by the network entity. The network entity may thus transmit the RRC connection management message independent of, and without requiring and waiting for preceding associated or corresponding request from the relay device or the remote device.

[0046] Hence, gNB may directly initiate remote UE’s RRC connection establishment/resume procedure upon receiving and identifying the remote UE’s paging message from CN or other RAN node. This reduces signalling and associated delay, since further paging messages to the relay UE and further to the remote UE, as well as RRC setup request messages from the remote UE to the relay UE and from the relay UE to the gNB are avoided.

[0047] The network entity may transmit, in or together with the RRC connection management message of block 320, configuration information of a data or signaling radio bearer of the relay device. The configuration information may be transmitted in addition to including configuration information of a data or signaling radio bearer of the remote device. [0048] In some embodiments, at least some of the presently disclosed features are applied for 5G NR systems, some further such example embodiments being illustrated below with references to NR RAN entities, without limiting application of the features to such RANs.

[0049] First, Fig. 4 illustrates RRC states or modes of 5G NR. A third independent RRC state, referred to as RRC_INACTIVE, is complementing earlier existing connected and idle states, RRC CONNECTED and RRC IDLE. A UE is either in RRC CONNECTED state or in RRC INACTIVE state when an RRC connection has been established. If this is not the case, i.e. no RRC connection is established, the UE is in RRC IDLE state. The RRC INACTIVE state enables to quickly resume the RRC connection and start the transmission of small or sporadic data with a much lower initial access delay and associated signalling overhead as compared to the RRC IDLE state.

[0050] In some embodiments, the RRC connection management message of block 320 is transmitted to the relay device when the remote device is in RRC IDLE state. Thus, the RRC connection management message is or comprises an RRC connection setup message and the RRC connection management request message is or comprises an RRC connection setup request message. The RRC connection setup message may be transmitted to the relay device in response to the relay device being in RRC_CONNECTED state.

[0051] A serving gNB of RRC CONNECTED relay UE needs to have the up-to-date information of the connected remote UEs and their paging IDs. For example, the stored paging identifiers may include SAE temporary mobile subscriber identity (S-TMSI), 5G-S-TMSI, or inactive radio network temporary identifier (I-RNTI) for RRC INACTIVE state.

[0052] To enable the relay UE to monitor the paging occasion(s) of the remote UE, the relay UE is also provided with and stores the paging ID of the remote UE. The remote device may be connected to the relay device via an SL interface, such as the 3GPP PC5 interface. The paging identifier may be received in an SL update message, for example. The relay UE may provide the paging ID of the remote UE to the gNB when the relay UE is in RRC_CONNECTED state. Whenever there is a change of SL connections between the remote UEs and relay UE, e.g. new remote UE established SL connection with relay UE for layer 2 U2N relay, or SL connection of existing remote UE is released/failed, the relay UE sends associated update information to gNB.

[0053] Fig. 5 illustrates a signalling example in case the relay UE is in RRC CONNECTED state and the remote UE is in RRC IDLE state.

[0054] In order to identify remote UE’s paging message, gNB hence stores 500 a received paging ID of the remote UE that has a SL connection over PC5 interface to the relay UE in RRC CONNECTED state. [0055] Based on the stored information of paging ID(s) of remote UE(s) that are connected to the relay UE, the serving gNB of the relay UE is able to identify 502 there is paging message of the remote UE connected to the relay UE, by checking the paging ID in a received paging message from CN or other RAN node.

[0056] Upon identifying 502 the paging message of the remote UE, and based on the stored information indicative of the remote UE being connected via SL to the relay UE served by the gNB, the gNB is triggered to initiate RRC connection establishment procedure. Hence, the gNB generates RRCSetup message for/of the remote UE, and includes the RRCSetup in a DL message 504 to the relay UE, without receiving the corresponding request message from remote UE.

[0057] The gNB may include configuration information for an SRB or DRB of the relay UE in the message 504 in addition to configuration information of RRC connection setup message for the remote UE, such as signalling radio bearer (SRB) and/or data radio bearer (DRB) configuration for the remote UE in the RRCSetup. Alternatively, such configuration information for the relay UE may be transmitted in a separate message to the relay UE. Such configuration information for the relay UE may comprise adaptation layer configuration, such as remote UE’s local ID, radio bearer ID used in adaptation layer, and mapping of relay UE’s Uu bearer and PC5 bearer for the relayed SRB and/or DRB.

[0058] When the relay UE receives the remote UE’s RRCSetup in the DL message 504 from the gNB, the relay UE forwards the RRCSetup to the remote UE by an SL transmission 506.

[0059] Upon completing the RRC setup, the remote UE may transmit an RRCSetupComplete by an SL transmission 508. The relay UE forwards the RRCSetupComplete to the gNB in an UL transmission 510.

[0060] In an embodiment allowing further optimization and delay reduction, if the relay UE has appropriate information of the remote UE to form the RRC connection setup complete message, the relay UE may be triggered after message 506 to send the corresponding complete message 510 on behalf of remote UE without explicit complete message 508 from the remote UE. The complete message may be triggered by relay UE after getting hybrid automatic repeat request (HARQ) acknowledgement (ACK) feedback (not shown) on the SL transmission of RRC connection setup message 508, to ensure the relayed RRCSetup is received by remote UE over PC5 interface. For example, sufficient remote UE’s information to form RRCSetupComplete message on behalf of the remote UE may include at least some of a registered AMF, Single - Network Slice Selection Assistance Information (S-NSSAI) list, and S-TMSI. [0061] Similar latency analysis and procedure may also be applied for the remote UE in RRC INACTIVE state to transit to RRC CONNECTED state using RRC connection resume procedure. Hence, the RRC connection management message is or comprises an RRC connection resume message and the RRC connection management request message is or comprises an RRC connection resume request message. Messages 504 and 506 may thus instead comprise 5G NR RRCResume and messages 508 and 510 may comprise RRCResumeComplete. Above-illustrated optimization features may thus be applied for 5G NR U2N relay when SL connection over the PC5 interface is maintained between the relay UE and the remote UE when the remote UE is in RRC IDLE or RRC_INACTIVE state and CN or RAN initiated paging is applied for the remote UE.

[0062] According to an aspect, the relay device 10 reduces RRC setup or resume related signalling by transmitting RRC setup or complete message on behalf of a paged remote UE 12 in response to link quality of a connection between the relay device and the remote device satisfying a predefined condition or requirement.

[0063] Fig. 6 is a flow graph of a method for controlling RRC connection setup or resume in accordance with at least some embodiments. The method may be performed by a relay device, such as the (relay) UE 10, or by a control device configured to control the functioning thereof. The method of Fig. 6 and embodiments thereof may be applied in a wireless system for optimizing network-initiated connection establishment in addition to, or separately from the above-illustrated features performed by the network entity.

[0064] Block 600 comprises receiving, by the relay device from a network entity, a paging message associated to a paging identifier of a remote device.

[0065] Block 610 comprises determining, by the relay device, at least one link quality condition of a connection between the relay device and the remote device.

[0066] Block 620 comprises transmitting, in response to receiving the paging message and the at least one link quality condition satisfying at least one link quality requirement, by the relay device to the network entity, an RRC connection management request message on behalf of the remote device, without first receiving a corresponding RRC connection management request message from the remote device. The relay device may thus independently transmit the RRC connection management request message on behalf of the remote device. The relay device may thus be triggered to generate and transmit the RRC connection management request message in response to the paging message and outcome of block 610. The relay device may perform this instead of being triggered by the corresponding RRC connection management request (corresponding to the RRC connection management request now initiated in block 620 by the relay device) from the remote device (to simply forward the received RRC connection management request to the network entity). [0067] In response to the at least one link quality condition satisfying at least one link quality requirement, the relay device may prevent transmitting a second paging message, corresponding to the first paging message, to the remote device. This may be a further block between block 610 and 620, for example.

[0068] In response to the at least one link quality condition of block 610 not satisfying the at least one link quality requirement, the relay device may, instead of entering block 620, transmit a second paging message, corresponding to the first paging message, to the remote device. The relay device may forward or relay the first paging message as such as the second paging message. However, although the second paging message is corresponding to the first paging message, they do not have to be equal.

[0069] The relay device performing the method of Fig. 6 may further receive an acknowledgement message from the remote device in response to said transmitting the second paging message. The relay device may transmit the RRC connection management request message to the network entity in block 620 further in response to the acknowledgement message.

[0070] Before entering block 620, there may thus be a further block of checking if the at least one link quality condition satisfies at least one link quality requirement, or such check may be included in block 610. If yes, block 620 is entered. If no, the second paging message is transmitted. The check may comprise comparing the at least one link quality condition, such as one or more SL quality or condition parameter measured by the relay UE, to at least one link respective quality requirement or condition threshold value. The at least one link quality condition may comprise a quality parameter of a sidelink connection maintenance related message, such as a sidelink channel state information message, a reference signal received power reporting message, or a keep alive message.

[0071] The at least one link quality condition and requirement may be based on reception power of messages from the remote UE. The link quality condition may require and indicate that a reception power of message(s) received via the sidelink connection is above a reception power threshold. In another example embodiment, time between reception of periodical messages is applied as the condition for entering block 620. The link quality condition may require that an interval for receiving periodical messages via the sidelink connection is below a maximum interval threshold. Such periodical messages may include channel state information reports, messages comprising reference signal received power (RSRP), and/or non-access stratum (NAS) level keep alive messages, for example. However, it will be appreciated that these are just some examples, and various other messages and/or parameters of communication between the relay device and the remote device may be applied.

[0072] Some further example embodiments are illustrated below in connection with 5G NR signalling example of Fig. 7 and with reference to 5G NR entities. This example is applicable in case the remote UE is in RRC IDLE state. [0073] The relay UE stores the paging ID of the remote UE and is configured to monitor for paging messages comprising the paging ID of the remote UE. The relay UE receives a paging message 700 to a paging ID of the remote UE. The paging message 700 may be received (in block 600) in an RRC message dedicated to the relay device in RRC CONNECTED state.

[0074] The relay device thus identifies that it has stored the paging ID and an association with the remote UE, and detects need to enter block 610 and potentially/conditionally request RRCSetup for the remote UE. The relay UE determines in block 702 the link quality and if it may transmit the RRCSetupRequest on behalf of the remote UE.

[0075] Sending of RRC connection management request message by the relay UE, in the present example RRCSetupRequest 704, may be triggered without relaying the paging message to remote UE over PC5 interface if SL connection maintenance over the PC5 interface is robust enough. For example, the link quality condition may require that the interval between SL channel state information (CSI) report messages, SL reference signal received power (SL-RSRP) report messages, SL discovery reference signal received power (SD-RSRP) report messages, or NAS level keeping alive messages is short enough to identify SL radio link failure or poor SL condition timely.

[0076] In the present example block 620 may be entered, and the RRC connection setup request message 704 is transmitted. The relay UE may include, in the RRC connection setup request message 704, an identifier of the remote UE received from the remote UE, or alternatively a random identifier generated by the relay UE in response to failing to receive an identifier of the remote UE. The procedure is continued by RRCSetup messages 706, 708 and associated RRCSetupComplete messages 710, 712.

[0077] The relay UE, e.g. the UE 10, in RRC IDLE or RRC INACTIVE state may also be able to perform the method of Fig. 6, when being aware of the paging ID of the remote UE, e.g. UE 12. The relay UE may thus be arranged to detect the paging message 700 to the remote UE. The relay UE may then transmit, to the gNB, an RRC connection management request message, in case of 5G NR RRCSetupRequest or RRCResumeRequest, of the relay UE together with the RRC connection management request message on behalf of the remote UE.

[0078] In case of the remote UE is in RRC INACTIVE state, messages 704 to 712 may comprise RRCResume messages, to transit the remote UE to RRC CONNECTED state using the RRC connection resume procedure. The relay UE may include, in the RRCResumeRequest message, an identifier of the remote UE and security context information received from the remote UE.

[0079] Similarly as illustrated in connection of Fig. 5, if the relay UE has all remote UE’s relevant information to form the RRC connection setup/resume complete message, the relay UE may be triggered to send the corresponding complete message 712 on behalf of remote UE without explicit complete message 710 from remote UE. The complete message may be triggered by relay UE after getting HARQ ACK feedback on the SL transmission of RRC connection setup/resume message.

[0080] In case of RRCResumeRequest message, I-RNTI of the remote UE is provided to facilitate the UE context retrieval at the gNB. The AS security configuration related information or calculated MAC-I may also be provided from the remote UE to relay UE to be included in the RRCResumeRequest message. Establishmentcause in the RRCSetupRequest message 704 or ResumeCause in RRCResumeRequest can be set to mt-Access as it is paging triggered setup/resume request.

[0081] An electronic device comprising electronic circuitries may be an apparatus for realizing at least some embodiments of the present invention. The apparatus may be or may be comprised in a computer, a user device, a base station, access point device, a RAN element or node, a RAN controller, or another apparatus capable for at least controlling RRC level data transmission. In another embodiment, the apparatus carrying out at least some of the above-described functionalities is comprised in such a device, e.g. the apparatus may comprise a circuitry, such as a chip, a chipset, a microcontroller, or a combination of such circuitries in any one of the above-described devices.

[0082] Fig. 8 illustrates an example apparatus capable of supporting at least some embodiments. Illustrated is device 800, which may comprise, for example, in applicable parts, a physical device running the network entity, such as the AN 20 or the gNB, or the relay device, such as the relay UE 10, for example. The device may be configured to to operate as the apparatus performing the method of Fig. 3 or 6, or an embodiment thereof.

[0083] Comprised in device 800 is processor 810, which may comprise, for example, a single- or multi -core processor wherein a single-core processor comprises one processing core and a multi -core processor comprises more than one processing core. Processor 810 may comprise, in general, a control device. Processor 810 may comprise more than one processor. Processor 810 may be a control device. Processor 810 may comprise at least one application-specific integrated circuit, ASIC. Processor 810 may comprise at least one field-programmable gate array, FPGA. Processor 810 may be means for performing method steps in device 800, such as receiving, transmitting and/or providing, for example. Processor 810 may be configured, at least in part by computer instructions, to perform actions.

[0084] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analogue and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analogue and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0085] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0086] Device 800 may comprise memory 820. Memory 820 may comprise random-access memory and/or permanent memory. Memory 820 may comprise at least one RAM chip. Memory 820 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 820 may be at least in part accessible to processor 810. Memory 820 may be at least in part comprised in processor 810. Memory 820 may be means for storing information. Memory 820 may comprise computer instructions that processor 810 is configured to execute. When computer instructions configured to cause processor 810 to perform certain actions are stored in memory 820, and device 800 overall is configured to run under the direction of processor 810 using computer instructions from memory 820, processor 810 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 820 may be at least in part comprised in processor 810. Memory 820 may be at least in part external to device 800 but accessible to device 800.

[0087] Device 800 may comprise a transmitter 830. Device 800 may comprise a receiver 840. Transmitter 830 and receiver 840 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 830 may comprise more than one transmitter. Receiver 840 may comprise more than one receiver. Transmitter 830 and/or receiver 840 may be configured to operate in accordance with a suitable messaging protocol.

[0088] Device 800 may comprise user interface, UI, 850. UI 850 may comprise at least one of a display, a keyboard and a touchscreen. A user may be able to operate device 800 via UI 850, for example to configure operating parameters stored in the memory 820, such as parameter affecting an operation of the above described methods.

[0089] Processor 810 may be furnished with a transmitter arranged to output information from processor 810, via electrical leads internal to device 800, to other devices comprised in device 800. Such a transmiter may comprise a serial bus transmiter arranged to, for example, output information via at least one electrical lead to memory 820 for storage therein. Alternatively, to a serial bus, the transmiter may comprise a parallel bus transmiter. Likewise, processor 810 may comprise a receiver arranged to receive information in processor 810, via electrical leads internal to device 800, from other devices comprised in device 800. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 840 for processing in processor 810. Alternatively, to a serial bus, the receiver may comprise a parallel bus receiver. Device 800 may comprise further devices not illustrated in Fig. 8. In some embodiments, device 800 lacks at least one device described above.

[0090] Processor 810, memory 820, transmiter 830, receiver 840 and/or UI 850 may be interconnected by electrical leads internal to device 800 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 800, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0091] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0092] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0093] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention. [0094] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0095] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0096] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

Claims

CLAIMS:

1. A method, comprising

- receiving, by a network entity, a paging message associated to a paging identifier of a remote device,

- determining, by the network entity, that the remote device is connected to a relay device, and

- in response to receiving the paging message and said determining, transmitting, by the network entity to the relay device, a radio resource control connection management message for setting up or resuming a radio resource control connection with the remote device, without receiving a radio resource control connection management request message.

2. The method of claim 1, wherein the radio resource control connection management message comprises a radio resource control connection setup message transmitted to the relay device in response to the relay device being in radio resource control connected state and the remote device being in radio resource control idle state, or the radio resource control connection management message comprises a radio resource control connection resume message transmitted to the relay device in response to the relay device being in radio resource control connected state and the remote device being in radio resource control inactive state.

3. The method of claim 1 or 2, further comprising: receiving, by the network entity from the relay device, the paging identifier of the remote device connected to the relay device, and storing the received paging identifier in association to the relay device, and wherein said determining comprises detecting that a paging identifier in the paging message matches with the stored paging identifier associated with the relay device.

4. The method of any preceding claim, comprising transmitting, by the network entity in or together with the radio resource control connection management message, configuration information of a data or signaling radio bearer of the relay device.

5. A method, comprising:

- receiving, by a relay device from a network entity, a paging message associated to a paging identifier of a remote device,

- determining, by the relay device, at least one link quality condition of a connection between the relay device and the remote device, and - in response to receiving the paging message and the at least one link quality condition satisfying at least one link quality requirement, transmitting by the relay device to the network entity, a radio resource control connection management request message on behalf of the remote device, without first receiving a corresponding radio resource control connection management request message from the remote device.

6. The method of claim 5, comprising: in response to the at least one link quality condition satisfying at least one link quality requirement, preventing transmitting by the relay device a second paging message, corresponding to the first paging message, to the remote device.

7. The method of claim 5, comprising: in response to the at least one link quality condition not satisfying the at least one link quality requirement, transmitting a second paging message, corresponding to the first paging message, to the remote device.

8. The method of claim 7, further comprising receiving an acknowledgement message from the remote device in response to said transmitting the second paging message, and transmitting by the relay device to the network entity the radio resource control connection management request message in response to the acknowledgement message.

9. The method of any preceding claim 5 to 8, wherein the connection between the relay device and the remote device is a sidelink connection, and wherein the at least one link quality condition indicates that a reception power of at least one message received via the sidelink connection is above a reception power threshold and/or wherein an interval for receiving periodical messages via the sidelink connection is below a maximum interval threshold.

10. The method of claim 9, wherein the periodical messages are channel state information reports, messages comprising reference signal received power, and/or non-access stratum level keep alive messages.

11. The method of any preceding claim 5 to 10, wherein the relay device in a radio resource control connected state receives the paging message in a radio resource control message dedicated to the relay device, or the relay device in radio resource control idle or inactive state detects the paging message and transmits to the network entity a radio resource control connection management request message of the relay device together with the radio resource control connection management request message on behalf of the remote device.

12. The method of claim any preceding claim 5 to 11, further comprising:

- receiving, by the relay device from the network entity, a radio resource control connection management message after transmitting the radio resource control connection management request message,

- forwarding, by the relay device to the remote device, the radio resource control connection management message, and

- transmitting, by the relay device to the network entity, a response or complete message to the radio resource control connection management message on behalf of the remote device without receiving a radio resource control connection management response or complete message from the remote device.

13. The method of any preceding claim, wherein the radio resource control connection management message is or comprises a radio resource control connection setup or resume message and the radio resource control connection management request message is or comprises a radio resource control connection setup or resume request message.

14. The method of any preceding claim, wherein the remote device is connected to the relay device via a sidelink connection, such as a PC5 interface connection.

15. The method of any preceding claim, wherein the relay device is a relay user equipment, the remote device is a remote user equipment, and the network entity is a base station, such as a gNodeB.

16. An apparatus, comprising one or more processors and memory comprising instructions, when executed by the one or more processors, cause the apparatus to perform:

- receiving a paging message associated to a paging identifier of a remote device,

- determining that the remote device is connected to a relay device, and

- in response to receiving the paging message and said determining, transmitting to the relay device, a radio resource control connection management message for setting up or resuming a radio resource control connection with the remote device, without receiving a radio resource control connection management request message.

17. The apparatus of claim 16, wherein the radio resource control connection management message comprises a radio resource control connection setup message transmitted to the relay device in

19 response to the relay device being in radio resource control connected state and the remote device being in radio resource control idle state, or the radio resource control connection management message comprises a radio resource control connection resume message transmitted to the relay device in response to the relay device being in radio resource control connected state and the remote device being in radio resource control inactive state.

18. The apparatus of claim 16 or 17, wherein the apparatus is further caused to receive, from the relay device, the paging identifier of the remote device connected to the relay device, and storing the received paging identifier in association to the relay device, and wherein said determining comprises detecting that a paging identifier in the paging message matches with the stored paging identifier associated with the relay device.

19. The apparatus of claim 16, 17, or 18, wherein the apparatus is further caused to transmit configuration information of a data or signaling radio bearer of the relay device in or together with the radio resource control connection management message.

20. An apparatus, comprising one or more processors and memory comprising instructions, when executed by the one or more processors, cause the apparatus to perform:

- receiving, from a network entity, a paging message associated to a paging identifier of a remote device,

- determining at least one link quality condition of a connection between the relay device and the remote device, and

- in response to receiving the paging message and the at least one link quality condition satisfying at least one link quality requirement, transmitting a radio resource control connection management request message to the network entity on behalf of the remote device, without first receiving a corresponding radio resource control connection management request message from the remote device.

21. The apparatus of claim 20, wherein the apparatus is further caused to perform, in response to the at least one link quality condition satisfying at least one link quality requirement, preventing transmitting a second paging message, corresponding to the first paging message, to the remote device.

22. The apparatus of claim 20, wherein the apparatus is further caused to perform, in response to the at least one link quality condition not satisfying the at least one link quality requirement,

20 transmitting a second paging message, corresponding to the first paging message, to the remote device. The apparatus of claim 22, wherein the apparatus is further caused to receive an acknowledgement message from the remote device in response to said transmitting the second paging message, and transmitting by the relay device to the network entity the radio resource control connection management request message in response to the acknowledgement message. The apparatus of any preceding claim 20 to 23, wherein the connection between the apparatus and the remote device is a sidelink connection, and wherein the at least one link quality condition indicates that a reception power of at least one message received via the sidelink connection is above a reception power threshold and/or wherein an interval for receiving periodical messages via the sidelink connection is below a maximum interval threshold. The apparatus of claim 24, wherein the periodical messages are channel state information reports, messages comprising reference signal received power, and/or non-access stratum level keep alive messages. The apparatus any preceding claim 20 to 25, wherein the apparatus, when in a radio resource control connected state is caused to receive the paging message in a radio resource control message dedicated to the relay device, and the apparatus, when in a radio resource control idle or inactive state, is caused to detect the paging message and transmits to the network entity a radio resource control connection management request message of the relay device together with the radio resource control connection management request message on behalf of the remote device. The apparatus any preceding claim 20 to 26, wherein the apparatus is caused to perform: receiving, from the network entity, a radio resource control connection management message after transmitting the radio resource control connection management request message, forwarding the radio resource control connection management message to the remote device, and transmitting, to the network entity, a response or complete message to the radio resource control connection management message on behalf of the remote device without receiving a radio resource control connection management response or complete message from the remote device.

21 The apparatus any preceding claim, wherein the radio resource control connection management message is or comprises a radio resource control connection setup or resume message and the radio resource control connection management request message is or comprises a radio resource control connection setup or resume request message. The apparatus of any preceding claim, wherein the remote device is connected to the relay device via a side link, such as PC5 interface. The apparatus of any preceding claim, wherein the apparatus is or is comprised by a relay user equipment, the remote device is a remote user equipment, and the network entity is a base station. A computer program, comprising instructions for causing an apparatus to perform the method of any one of claims 1 to 15. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform the method of any one of claims 1 to 15.

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