WO2024001724A1

WO2024001724A1 - User equipment, network node and methods for rlf handling

Info

Publication number: WO2024001724A1
Application number: PCT/CN2023/099400
Authority: WO
Inventors: Min Wang; Jan Christoffersson; Zhang Zhang
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ); Zhang Zhang
Priority date: 2022-06-27
Filing date: 2023-06-09
Publication date: 2024-01-04

Abstract

User equipment, network node and methods for RLF handling are provided for a multi-path connection scenario. A method in a first User Equipment (UE) (100) includes detecting or being informed (402) of a Radio Link Fault (RLF) event on at least one of multiple connection paths between the first UE (100) and a network node (200); and performing (406) a RLF-handling operation in response to the detected or informed RLF event. The multiple connection paths comprise at least one indirect path between the first UE (100) and the network node (200), on which the first UE (100) is connected to the network node (200) via at least one relay UE.

Description

User Equipment, Network Node and Methods for RLF Handling

INTRODUCTION

Technical Field

The present disclosure relates to Radio Link Fault (RLF) handling in a multi-path connection scenario of a User Equipment (UE) and a network node.

Background

New Radio (NR) SideLink (SL) communication is specified by 3GPP in Rel-16. The NR SL is an evolution of the LTE (Long-Term Evolution) sidelink, in particular of features introduced in Rel-14 and Rel-15 for V2X (Vehicle-to-anything) communication. Some of the features of the NR SL include:

- support for unicast and groupcast transmissions, in addition to broadcast transmissions which were already supported in LTE;

- support for HARQ (Hybrid Automatic Repeat request) feedback over the SL for unicast and groupcast; this feedback is conveyed by the receiver UE to the transmitter UE using physical sidelink feedback channel (PSFCH) ; this functionality is new in NR compared to LTE;

- to alleviate resource collisions among different sidelink transmissions launched by different UEs, it enhances channel sensing and resource selection procedures, which also lead to a new design of physical channels carrying sidelink control information (SCI) ; the new design of the SCI simplifies coexistence between releases by grouping together all the information related to resource allocation (which is critical for coexistence) in a single channel with a robust, predefined format; other control information is carried by other means, in a more flexible manner;

- grant-free transmissions, which are supported in NR uplink transmissions, are also provided in NR SL transmissions, to improve the latency performance;

- to achieve a high connection density, congestion control and thus QoS (Quality of Service) management is supported in NR SL transmissions.

SL relay is being standardized in NR Rel-17, which enables a remote UE to be able to connect to a gNB (next generation Node B) via a relay UE. All UP (User Plane) data and CP (Control Plane) signaling between the remote UE and the gNB are exchanged between each other via the relay UE in a transparent fashion. During the Rel-17 time frame, the remote UE may be in coverage (IC) or out of coverage (OOC) of the gNB. For the remote UE in IC and having both direct connection and indirect connection with the gNB, the remote UE is allowed to use only a single connectivity to transmit data. Due to this restriction, it would be reasonable and straightforward for the remote UE to only use the indirection connection to transmit data to the gNB. With this restriction i.e., the remote UE only uses a single connectivity for data transmission and reception, it is beneficial to simplify design efforts in NR Rel-17. However, the drawback is that the remote UE is not able to utilize the other connection although it is available. In case of high data volume, it would be very helpful if the remote UE in IC can utilize both direct connection and indirect connection to achieve aggregated data rate over both connections.

In the R18 SI/WI on NR sidelink relay enhancements (i.e., RP-213585) , the following study objective has been defined to be studied in 3GPP Rel-18 time frame:

1. Study the benefit and potential solutions for multi-path support to enhance reliability and throughput (e.g., by switching among or utilizing the multiple paths simultaneously) in the following scenarios [RAN2, RAN3] :

A. UE is connected to the same gNB using one direct path and one indirect path via Layer-2 UE-to-Network (L2 U2N) relay,

In the above objective, a UE is allowed to connect to the same gNB using both a direct path (i.e., direct connection to the gNB via a Uu link) and an indirect path via a L2 U2N relay UE (i.e., indirect connection to the gNB via at least one relay UE) , and switch among or utilize the multiple paths simultaneously for data transmission and reception with the gNB.

Further, a UE may be configured with multiple paths connected to a gNB, which include more than one indirect path.

In the above cases, the UE may be configured with Radio Link Monitoring (RLM) and RLF on each path. The UE may then operate RLM/RLF independently for each of the paths. Either of the paths may trigger RLF. UE/gNB behaviors of RLF handling in such case would be unclear, which might cause problems.

Therefore, it is required to develop solutions for solving the above issues.

Summary

Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. User equipment, network node and methods for RLF handling are provided for a multi-path connection scenario.

In some embodiments, a method in a first User Equipment (UE) may include: detecting or being informed of a Radio Link Fault (RLF) event on at least one of multiple connection paths between the first UE and a network node; and performing a RLF-handling operation in response to the detected or informed RLF event. The multiple connection paths comprise at least one indirect path between the first UE and the network node, on which the first UE is connected to the network node via at least one relay UE.

In some embodiments, a method in a first User Equipment (UE) may include: detecting or being informed of a Radio Link Fault (RLF) event on at least one of multiple connection paths between a second UE and a network node; and performing a RLF-handling operation in response to the detected or informed RLF event. The multiple connection paths comprise at least one indirect path between the second UE and the network node, on which the second UE is connected to the network node via at least one relay UE including the first UE.

In some embodiments, a method in a network node is provided. The method may include: being informed of a Radio Link Fault (RLF) event on at least one of multiple connection paths between a first User Equipment (UE) and the network node; and performing a RLF-handling operation in response to the informed RLF event. The multiple connection paths comprises at least one indirect path between the first UE and the network node, in which the first UE is connected to the network node via at least one relay UE.

In some embodiments, a UE may include one or more processors, and memory storing instructions that, when executed by the one or more processors, cause the UE to perform the method of the above embodiments.

In some embodiments, a network node may include one or more processors, and memory storing instructions that, when executed by the one or more processors, cause the network node to perform the method of the above embodiments.

In some embodiments, a computer readable storage medium is provided. The computer readable storage medium has computer program instructions stored thereon. The computer program instructions, when executed by a processor in a UE, cause the UE to perform the method according to the above embodiments.

In some embodiments, a computer readable storage medium is provided. The computer readable storage medium has computer program instructions stored thereon. The computer program instructions, when executed by a processor in a network node, cause the network node to perform the method according to the above embodiments.

Certain embodiments may provide one or more of the following technical advantage (s) . With the solutions provided in the present disclosure, UE/gNB behaviors of RLF handling in a multi-path connection scenario are defined to enable a clear, fast and reliable recovery from RLF. For example, it is feasible for UE to recover from RLF on a path without going to inactive or idle RRC state, and to avoid interruption to services due to RLF on a path.

Brief Description of the Drawing

The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

Figure 1 shows multi-path connection scenarios including remote UE, relay UE and network node, in which embodiments of the present disclosure may be applied;

Figure 2 is a schematic block diagram of a UE according to some embodiments of the present disclosure;

Figure 3 is a schematic block diagram of a network node according to some embodiments of the present disclosure;

Figure 4 is a flowchart illustrating a method performed in a remote UE according to some embodiments of the present disclosure;

Figure 5 is a flowchart illustrating a method performed in a relay UE according to some embodiments of the present disclosure;

Figure 6 is a flowchart illustrating a method performed in a network node according to some embodiments of the present disclosure;

Figure 7 shows examples of RLF handing operations according to some embodiments of the present disclosure;

Figure 8 shows an example of a communication system QQ100 in accordance with some embodiments;

Figure 9 shows a UE QQ200 in accordance with some embodiments;

Figure 10 shows a network node QQ300 in accordance with some embodiments;

Figure 11 is a block diagram of a host QQ400, which may be an embodiment of the host QQ116 of Figure 8, in accordance with various aspects described herein;

Figure 12 is a block diagram illustrating a virtualization environment QQ500 in which functions implemented by some embodiments may be virtualized; and

Figure 13 shows a communication diagram of a host QQ602 communicating via a network node QQ604 with a UE QQ606 over a partially wireless connection in accordance with some embodiments.

Detailed Description

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

In this disclosure a term “node” is used which can be a network node or a UE. Examples of network nodes are NodeB, base station (BS) , multi-standard radio (MSR) radio node such as MSR BS, eNodeB (Evolved Node B, or eNB) , gNB, MeNB (Master eNodeB) , SeNB (Secondary eNodeB) , integrated access backhaul (IAB) node, network controller, radio network controller (RNC) , base station controller (BSC) , relay, donor node controlling relay, base transceiver station (BTS) , Central Unit (e.g. in a gNB) , Distributed Unit (e.g. in a gNB) , Baseband Unit, Centralized Baseband, C-RAN (Centralized Radio Access Network) , access point (AP) , transmission points, transmission nodes, RRU (Remote Radio Unit) , RRH (Remote Radio Head) , nodes in distributed antenna system (DAS) , core network nodes (e.g. MSC (Mobile Switching Center) , MME (Mobility Management Entity) etc) , O&M (Operations &Maintenance) , OSS (Operation Support Systems) , SON (Self-Organizing Network) , positioning node (e.g. E-SMLC (Evolved Serving Mobile Location Center) ) , etc.

Another example of a node is User Equipment (UE) , which is a non-limiting term and refers to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UE are target device, device-to-device (D2D) UE, vehicular to vehicular (V2V) , machine type UE, MTC (Machine Type Communication) UE or UE capable of machine to machine (M2M) communication, PDA (Personal Digital Assistant) , Tablet, mobile terminals, smart phone, laptop embedded equipment (LEE) , laptop mounted equipment (LME) , USB (Universal Serial Bus) dongles etc.

In some embodiments, generic terminology, “radio network node” or simply “network node (NW node) ” , is used. It can be any kind of network node which may comprise base station, radio base station, base transceiver station, base station controller, network controller, evolved Node B (eNB) , Node B, gNodeB (gNB) , relay node, access point, radio access point, Remote Radio Unit (RRU) , Remote Radio Head (RRH) , Central Unit (e.g. in a gNB) , Distributed Unit (e.g. in a gNB) , Baseband Unit, Centralized Baseband, C-RAN, access point (AP) , etc.

The term “radio access technology” , or RAT, may refer to any RAT e.g. UTRA (Universal Terrestrial Radio Access) , E-UTRA (Evolved-UTRA) , narrow band internet of things (NB-IoT) , WiFi, Bluetooth, next generation RAT, New Radio (NR) , 4G, 5G, etc. Any of the equipment denoted by the terminology node, network node or radio network node may be capable of supporting a single or multiple RATs.

SL physical channels

In NR SL, the following physical layer (PHY) channels are defined.

- PSCCH (Physical Sidelink Common Control Channel) : this channel carries sidelink control information (SCI) including part of the scheduling assignment (SA) that allows a receiver to further process and decode the corresponding PSSCH (e.g., demodulation reference signal (DMRS) pattern and antenna port, Modulation and Coding Scheme (MCS) , etc) . In addition, PSCCH indicates future reserved resources. This allows a RX to sense and predict the utilization of the channel in the future. This sensing information is used for the purpose of UE-autonomous resource allocation (Mode 2) , which is described below.

- PSSCH (Physical Sidelink Shared Channel) : the PSSCH is transmitted by a sidelink transmitter UE, which conveys sidelink transmission data (i.e., the SL shared channel SL-SCH) , and a part of the sidelink control information (SCI) . In addition, higher layer control information may be carried using the PSSCH (e.g., MAC (Media Access Control) CE (Control Element) , RRC (Radio Resource Control) signaling, etc. ) . For example, channel state information (CSI) is carried in MAC CE over PSSCH instead of PSFCH.

- PSFCH (Physical Sidelink feedback channel) : the PSFCH is transmitted by a sidelink receiver UE for unicast and groupcast. It conveys the SL HARQ acknowledgement (ACK) , which may consist of ACK/NACK (used for unicast and groupcast option 2) or NACK-only (used for groupcast option 1) .

- Physical Sidelink Broadcast Channel (PSBCH) : the PSBCH conveys information related to synchronization, such as the direct frame number (DFN) , indication of the slot and symbol level time resources for sidelink transmissions, in-coverage indicator, etc. The SSB is transmitted periodically at every 160 ms. The PSBCH is transmitted along with the S-PSS/S-SSS as a sidelink synchronization signal block (S-SSB) . Sidelink Primary/Secondary Synchronization Signal (S-PSS/S-SSS) are used by UEs to establish a common timing references among UEs in the absence of another reference such as GNSS (Global Navigation Satellite System) time of NW time

Along with the different physical channels, reference signals (RS) are transmitted for different purposes, including demodulation (DM-RS) , phase tracking RS (PT-RS) , or RS for channel state information acquisition (CSI-RS) .

Another new feature is the two-stage sidelink control information (SCI) . A first part (first stage) of the SCI is sent on the PSCCH. This part is used for channel sensing purposes (including the reserved time-frequency resources for transmissions, demodulation reference signal (DMRS) pattern and antenna port, etc. ) and can be read by all UEs while the remaining part (second stage) of the SCI carries the remaining scheduling and control information such as a 8-bits source identity (ID) and a 16-bits destination ID, NDI (Network Device Interface) , RV (redundancy version) and HARQ process ID is sent on the PSSCH to be decoded by the receiver UE.

Resource allocation

NR SL supports the following two modes of resource allocation:

- Mode 1: Sidelink resources are scheduled by a gNB;

- Mode 2: UE autonomously selects sidelink resources from a configured/preconfigured sidelink resource pool; to avoid collisions between UEs a procedure based on the channel sensing and resource reservation is used.

An in-coverage UE can be configured by a gNB to use Mode 1 or Mode 2. For the out-of-coverage UE, only Mode 2 can be used.

Like in LTE, scheduling over the sidelink in NR is done in different ways for Mode 1 and Mode 2.

In Mode 1, the grant is provided by the gNB. The following two kinds of grants are supported:

- Dynamic grants are provided for one or multiple transmissions of a single packet (i.e., transport block (TB) ) . When the traffic to be sent over sidelink arrives at a transmitter UE (i.e., at the corresponding TX buffer) , the UE initiates the four-message exchange procedure to request sidelink resources from a gNB (SR (Status Report) on UL, grant, BSR (Buffer Status Report) on UL, grant for data on SL sent to UE) . A gNB indicates the resource allocation for the PSCCH and the PSSCH in the downlink control information (DCI) conveyed by PDCCH with CRC (Cyclic Redundancy Check) scrambled with the SL-RNTI (Radio Network Temporary Identity) of the corresponding UE. A UE receiving such a DCI, assumes that it has been provided a SL dynamic grant only if the detects that the CRC of DCI has been scrambled with its SL-RNTI. A transmitter UE then indicates the time-frequency resources and the transmission scheme of the allocated PSSCH in the PSCCH, and launches the PSCCH and the PSSCH on the allocated resources for sidelink transmissions. When a grant is obtained from a gNB, a transmitter UE can only transmit a single TB. As a result, this kind of grant is suitable for traffic with a loose latency requirement.

- Configured grant: for the traffic with a strict latency requirement, performing the four-message exchange procedure to request sidelink resources may induce unacceptable latency. In this case, prior to the traffic arrival, a transmitter UE may perform the four-message exchange procedure and request a set of resources. If a grant can be obtained from a gNB, then the requested resources are reserved in a periodic manner. Upon traffic arriving at a transmitter UE, this UE can launch the PSCCH and the PSSCH on the upcoming resource occasion. This kind of grant is also known as grant-free transmissions.

Note that only the transmitter UE is scheduled by the gNB. The receiver UE does not receive any information directly from the gNB. Instead, it is scheduled by the transmitter UE by means of the SCI. Therefore, a receiver UE should perform blind decoding to identify the presence of PSCCH and find the resources for the PSSCH through the SCI.

In Mode 2 resource allocation, the grant is generated by the UE itself. When traffic arrives at a transmitter UE (i.e., at the corresponding TX buffer) , this transmitter autonomously selects resources for the PSCCH and the PSSCH. To further enhance the probability of successful TB decoding at one shot and thus suppress the probability to perform retransmissions, a transmitter UE may repeat the TB transmission along with the initial TB transmission. These retransmissions may be triggered by the corresponding SL HARQ feedback or may be sent blindly by the transmitter UE. In either case, to minimize the probability of collision for potential retransmissions, the transmitter UE may also reserve the corresponding resources for PSCCH/PSSCH for retransmissions. That is, the transmitter UE selects resources for:

- PSCCH/PSSCH corresponding to the first transmission;

- PSCCH/PSCCH corresponding to the retransmissions. Resources for up to two retransmissions may be reserved. These reserved resources are always used in case of blind retransmissions. If SL HARQ feedback is used, the used of the reserved resources is conditional on a negative SL HARQ acknowledgement

Since each transmitter UE in sidelink transmissions should autonomously select resources for its own transmissions, preventing the different transmitter UEs from selecting the same resources turns out to be a critical issue in Mode 2. A particular resource selection procedure is therefore imposed to Mode 2 based on channel sensing. The channel sensing algorithm involves detecting the reservations transmitted by other UEs and performing power measurements (i.e., reference signal received power (RSRP) ) on the incoming transmissions.

In the following, embodiments are described in the context of NR. The embodiments are applicable to L2 relay scenarios. Herein, the terms “path” and “connection path” is used interexchangeably to refer to connection between UE and network node. The term “direct path” refers to a direct connection from a remote UE (i.e., transmitter or TX UE) to a network node (e.g., gNB via NR air interface) . The term “indirect path” refers to an indirect connection between a remote UE and a network node via at least one intermediate node (also known as relay UE) . In the following embodiments, we assume that an indirect path contains two hops i.e., PC5 hop between the remote UE and a relay UE, and Uu hop between the relay UE and the network node. However, Embodiments are not limited to two hops. For an indirect path containing more than two hops, the embodiments are also applicable.

In some embodiments, a remote UE may connect to a gNB via both a direct path (i.e., the remote UE connects to the gNB via a Uu link directly) and an indirect path (e.g., the remote UE also connects to the same gNB via a relay UE) . In some embodiments, a remote UE may connect to a gNB via more than on indirect path with more than one relay UEs. The referred UEs may be under a full or partial coverage of the same or different gNBs. Under full-coverage, all the UEs are under the coverage of a gNB. Under partial-coverage, the UEs may be under the coverage of at least a gNB. They may be served by different gNBs, or some of them may be not served by any gNB. The Uu connections between the remote UE and the gNB as well as between the relay UE and the gNB may be LTE Uu or NR Uu. The connection between the remote UE and the relay UE is not limited to PC5 connection or sidelink. Any short-range communication technology such as Wifi is equally applicable.

In some embodiments, one of the paths between the remote UE and the gNB may be defined as a primary path on which the remote UE transmits and/or receives control plane signaling (including RRC signaling and/or lower layer signaling. e.g., MAC CE or L1 signaling) . The other paths different from the primary path may be referred to as secondary paths on which the remote UE transmits and/receives user plane data. The remote UE may also transmit and/or receive control plane signaling via the secondary paths. The embodiments are not limited by any of the terms. Other similar terms including primary and/or secondary connection/connectivity, master cell group (MCG) and/or secondary cell group (SCG) , master and/or secondary connection/connectivity may interchangeably applicable.

Embodiments are also applicable to the case where a remote UE connects to different gNBs via two different paths, wherein either of the two paths may be a direct path or an indirect path.

Embodiments are also applicable to the case where a remote UE connects to different gNBs via more than two paths, wherein any one of the paths may be a direct path or an indirect path.

Figure 1 shows multi-path connection scenarios including remote UE, relay UE and network node, in which embodiments of the present disclosure may be applied. As shown in part (a) of Figure 1, the remote UE may connect to the gNB via two paths including a direct path and an indirect path with a relay UE. In part (b) of Figure 1, the remote UE may connect to the gNB via two indirect paths each having a relay UE. NR sidelink is assumed on the PC5 interface between the Remote UE and the relay UE (s) , and the Uu interface is assumed between the UEs and the gNB. The remote UE may switch among or utilize the multiple paths simultaneously for data transmission and reception with the gNB.

Although not shown, one or more of the UEs in Figure 1 may be in coverage of a cell/network/gNB. For example, some of the coverage scenarios considered may be listed in the following:

- All UEs (Remote UE, Relay UE) are in coverage of a cell;

- Some of the UEs (Remote UE, Relay UE) are out-of-coverage;

- Partial coverage whereby at least one of the UEs involved in relaying (Remote UE, Relay UE) is in-coverage, and at least one of the UEs involved in relaying is out-of-coverage;

- UEs (Remote UE, Relay UE) are in coverage of different cells.

Although not shown, there may be more than two paths between the remote UE and the gNB.

Although not shown, there may be more than one relay UE in an indirect path between the remote UE and the gNB.

Signaling exchanged between the UEs via the PC5 interface may transmitted via at least one of the following signaling alternatives:

- RRC signaling (e.g., PC5-RRC) ,

- PC5-S signaling,

- Discovery signaling,

- MAC CE,

- Control PDU of a protocol layer (e.g., SDAP, PDCP, RLC, or an adaptation layer in case of SL relay) , and

- L1 signaling on channels such as PSSCH, PSCCH, or PSFCH.

Signaling exchanged between UE and the gNB via Uu interface may be transmitted via at least one of the following signaling alternatives:

- RRC signaling,

- MAC CE,

- Paging message,

- L1 signaling on channels such as PRACH, PUCCH, PDCCH.

The above listed signaling alternatives are merely examples, and any suitable signaling mechanism may be used.

The remote UE, relay UE and gNB in Figure 1 may perform RLF-handling operations as described above with reference to Figures 4 to 6 which will be described later.

Figure 2 is a schematic block diagram of UE according to some embodiments of the present disclosure. It may be used as any of the remote and relay UEs in Figure 1. As illustrated, the UE 100 includes one or more processors 102 (e.g., CPUs, ASICs, FPGAs, and/or the like) , memory 104, and one or more transceivers 106 each including one or more transmitters and one or more receivers coupled to one or more antennas 112. The transceiver (s) 106 includes radio-front end circuitry connected to the antenna (s) 112 that is configured to condition signals communicated between the antenna (s) 112 and the processor (s) 102, as will be appreciated by on of ordinary skill in the art. The processors 102 are also referred to herein as processing circuitry. The transceivers 106 are also referred to herein as radio circuitry. In some embodiments, the functionality of the UE 100 described herein may be fully or partially implemented in software that is, e.g., stored in the memory 104 and executed by the processor (s) 102. Note that the UE 100 may include additional components not illustrated in Figure 2 such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker (s) , and/or the like and/or any other components for allowing input of information into the UE 100 and/or allowing output of information from the UE 100) , a power supply (e.g., a battery and associated power circuitry) , etc.

In some embodiments, a computer program is provided to include instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the UE 100 according to any of the embodiments described herein, for example, one or more of the steps included in a method shown in Figure 4 or Figure 5 to be described later. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory) .

In some embodiments, the UE 100 may include one or more modules, each of which is implemented in software. The module (s) provide the functionality of the UE 100 according to any of the embodiments described herein.

Figure 3 is a schematic block diagram of a network node according to some embodiments of the present disclosure. As illustrated, the network node 200 includes one or more processors 202 (e.g., CPUs, ASICs, FPGAs, and/or the like) , memory 204, one or more transceivers 206 each including one or more transmitters and one or more receivers coupled to one or more antennas 212, and network interface 214. The transceiver (s) 206 includes radio-front end circuitry connected to the antenna (s) 212 that is configured to condition signals communicated between the antenna (s) 212 and the processor (s) 202, as will be appreciated by on of ordinary skill in the art. The processors 202 are also referred to herein as processing circuitry. The transceivers 206 are also referred to herein as radio circuitry. The network interface 214 may be configured to provide communications with other network nodes and/or core network. In some embodiments, the functionality of the network node 200 described herein may be fully or partially implemented in software that is, e.g., stored in the memory 204 and executed by the processor (s) 202. Note that the network node 200 may include additional components not illustrated in Figure 3, such as a power supply and associated power circuitry, etc.

In some embodiments, a computer program is provided to include instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node 200 according to any of the embodiments described herein, for example, one or more of the steps included in methods shown in Figure 6 to be described later. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory) .

In some embodiments, the network node 200 includes one or more modules, each of which is implemented in software. The module (s) provide the functionality of the network node 200 according to any of the embodiments described herein.

User equipment, network node and methods therein for RLF handling are provided for a multi-path connection scenario, for example, as shown in Figure 1, in which the remote UE may switch among or utilize the multiple paths simultaneously for data transmission and reception with the gNB. According to embodiments herein, UE/gNB behaviors of RLF handling in such a multi-path connection scenario are defined to enable a clear, fast and reliable recovery from RLF. For example, it is feasible for UE to recover from RLF on a path without going to inactive or idle RRC state, and to avoid interruption to services due to RLF on a path.

Figure 4 is a flowchart illustrating a method performed in a remote UE for RLF handling according to some embodiments of the present disclosure. The remote UE may be implemented with UE 100 in Figure 2, and may operate as the remote UE in Figure 1. Herein, it may also be referred to as UE1. There may be multiple connection paths between the remote UE and a network node, including at least one indirect path on which the remote UE is connected to the network node (e.g., gNB) via at least one relay UE. The method may include detecting or being informed of a RLF event on at least one of the multiple connection paths between the remote UE and a network node (step 402) . In some embodiment, by referring to Figure 1, the remote UE may detect a RLF event on the PC5 sidelink/hop with the relay UE, or on the direct Uu link with the gNB. In some embodiment, a RLF event on the Uu sidelink/hop between the relay UE and the gNB may be detected by the relay UE, and then informed to the remote UE via the PC5 hop.

For a direct path (i..e, an Uu connection between the remote UE and the gNB) , a RLF event may be detected or declared by the remote UE when one of the following conditions is met (the conditions are same as the conditions captured in clause 9.2.7 of TS 38.300 v17.0.0) :

- expiry of a radio problem timer started after indication of a radio problem from a physical layer (if radio problems are recovered before the timer is expired, the UE may stop the timer) ;

- expiry of a timer started upon triggering a measurement report for a measurement identity for which the timer has been configured while another radio problem timer is running;

- random access procedure failure;

- Radio Link Control (RLC) failure;

- detection of consistent uplink Listen-Before-Talk (LBT) failures for operation with shared spectrum channel access; and

- for integrated access backhaul Machine Type (IAB-MT) node, a backhaul (BH) RLF indication being received from its parent node.

For an indirect path, a RLF event may be declared or detected because either of the following failure events has occurred. In some embodiments, SL RLF event may be detected or declared by the remote UE on the PC5 hop (between the remote UE and the relay UE) when one of the following conditions is met:

- a maximum number of out-of-sync instances for the PC5 hop being reached; (The remote UE may monitor the radio channel quality based on a specific reference symbol. The remote UE may compare the measured channel quality with out-of-sync and in-sync thresholds, Qout and Qin respectively. The physical channel may evaluate the channel quality and periodically send indication on out-of-sync or in-sync to layer 3. The layer 3 then may evaluate the radio link failure based on the in-sync and out-of-sync indications that output from the layer 3 filter. For RLM on the link, a counter and/or a timer may be defined. In an example, when the consecutively received out-of-sync indications are beyond a configured counter, a timer is started. While the timer is running, the radio link considered to be recovered if the remote UE consecutively receives a configured number of in-sync indications from the physical layer. )

- a maximum number ofRLC retransmissions being reached;

- a configuration or reconfiguration error occurring upon reception of a Radio Resource Control (RRC) configuration or reconfiguration signaling message;

- a maximum number of consecutive HARQ DTX being reached;

- no expected acknowledgement being received within a specified period of time; (For instance, when the remote UE sends an RRCReconfigurationSidelink message but do not receive an RRCReconfigurationSidelinkComplete message in response by the relay UE within a certain time. )

- no acknowledgement on RLC transmission being received within a specified period of time.

(For instance, the remote UE does not get an acknowledgement on the RLC transmission within a certain amount of time. This means that the remote UE keep on retransmitting RLC Packet Data Units (PDUs) as far as a timer is running; and if it gets no acknowledgement from the relay UE, it may declare a RLF event. )

Regarding the condition of the maximum number of consecutive HARQ DTX being reached, it may be the same as HARQ-based Sidelink RLF detection described in 5.22.1.3.3 of TS 38.321 V 16.6.0. The HARQ-based Sidelink RLF detection procedure is used to detect Sidelink RLF based on a number of consecutive DTX on PSFCH reception occasions for a PC5-RRC connection. RRC configures the following parameter to control HARQ-based Sidelink RLF detection:

- sl-maxNumConsecutiveDTX.

The following UE variable is used for HARQ-based Sidelink RLF detection.

- numConsecutiveDTX, which is maintained for each PC5-RRC connection

The Sidelink HARQ Entity shall (re-) initialize numConsecutiveDTX to zero for each PC5-RRC connection which has been established by upper layers, if any, upon establishment of the PC5-RRC connection or (re) configuration of sl-maxNumConsecutiveDTX. For each PSFCH reception occasion associated to the PSSCH transmission:

1> if PSFCH reception is absent on the PSFCH reception occasion:

2> increment numConsecutiveDTX by 1;

2> if numConsecutiveDTX reaches sl-maxNumConsecutiveDTX:

3> indicate HARQ-based Sidelink RLF detection to RRC.

1> else:

2> re-initialize numConsecutiveDTX to zero.

In some embodiments, a RLF event on the PC5 hop may be detected by the relay UE in conditions similar to the above conditions.

In some embodiments, a RLF event may detected on the Uu hop (between the relay UE and the gNB) by the relay UE when one of conditions the same as the above conditions described for the direct path is met. Then, the relay UE may inform the remote UE of the RLF event via the PC5 hop therebetween.

Back to Figure 4, the method may further include performing, by the remote UE, a RLF-handling operation in response to the detected or informed RLF event (step 406) .

In some embodiments, the remote UE may handle the RLF event by performing a Radio Resource Control (RRC) connection reestablishment procedure if the at least one path with the RLF event includes a primary path on which control plane signaling is transmitted between the remote UE and the network node. In this case, the remote UE may need to tear down/remove/de-configure the other paths (i.e., secondary paths) before initiating the RRC connection reestablishment procedure.

In some embodiments, the remote UE may handle the RLF event by performing a RRC connection reestablishment procedure only when the at least one path with the RLF event includes all of the multiple connection paths between the remote UE and the gNB.

In some embodiments, before performing a RLF-handling operation in response to the detected or informed RLF event (step 406) , the method may also optionally include, as shown in dashed-line blocks in Figure 4, informing the gNB of the RLF event on the at least one connection path by sending a first signaling to the gNB via one of the multiple connection paths where no RLF occurs (step 404) . The first signaling contains at least one of:

- an identifier (ID) of the remote UE;

- information of the at least one connection path where the RLF occurs;

- an indicator indicating that the RLF has been detected on the at least one connection path;

- a cause of the RLF;

- in case that the at least one connection path is an indirect path comprising a relay UE, a list of potential other relay UEs and corresponding measurements of PC5 link radio conditions to the other relay UE; and

- in case that the at least one connection path comprises an unlicensed sidelink, measurements of channel occupancy or Listen-Before-Talk (LBT) failure statistics.

The cause of the RLF may be any cause the same as any of the conditions described above.

In some embodiments, the information of the at least one connection path may indicate at least one of:

- whether the at least one connection path with the RLF event is a primary path for transmitting control plane signaling;

- whether the at least one connection path is a secondary path different from a primary path for transmitting control plane signaling;

- an ID of the at least one connection path;

- an ID of a relay UE in the at least one connection path, in case that the at least one connection path is an indirect path comprising the relay UE; and

- which hop has the RLF event, in case that the at least one connection path is an indirect path comprising at least two hops between the remote UE and the network node.

With such signaling information, it is possible to clearly define UE/gNB behaviors of RLF handling in the multi-path connection scenario, and to enable a clear, fast and reliable recovery from RLF.

In some embodiments, the remote UE may send the first signaling to the gNB on a direct path among the multiple connection paths via at least one of the following signaling alternatives.

(1) Dedicated RRC signaling, which may be an existing RRC signaling or a new RRC signaling.

(2) MAC CE based signaling, which may be an existing MAC CE or a new MAC CE for indicating that the UE has declared/detected RLF.

(3) The remote UE may initiate a RACH procedure to carry the signaling.

In one embodiment, a 4-step RA may be triggered to carry the signaling. In an example, Msg1 may be used to carry the signaling. A dedicated preamble or dedicated RACH occasions may be allocated to the UE for indicating the above signaling information. The allocation may be pre-defined, determined based on a pre-defined rule, or configured by another node. In an example, Msg3 may be extended to carry the signaling information. In Msg3, the UE may supplie a UE identifier, e.g. C-RNTI MAC CE, and an indicator indicating the above signaling information. The indicator may be a field in the MAC subheader or carried in a MAC CE.

In another embodiment, a 2-step RA may be triggered to carry the signaling. A dedicated preamble or dedicated RACH occasions or dedicated PUSCH occasions/resources may be allocated to the UE for indicating the signaling information. Alternatively, indicators may be included in MsgA payload such as described above for Msg3. The indicator may be a field in the MAC subheader or carried in a MAC CE. Alternatively, an RRC message (partly or fully) may be included in a RACH message, which includes the above signaling information from the remote UE.

(4) The remote UE may initiate a PUCCH transmission for indicting the signaling information. Separate dedicated PUCCH resources may be configured accordingly.

(5) The remote UE may initiate a configured grant-based transmission for carrying the signaling. Separate dedicated configured grant resources may be configured accordingly. Alternatively, the signaling information may be included in the CG-UCI (configured grant uplink control information) .

As an additional example to (4) and (5) , the remote UE may transmit the first signaling in the PUCCH-UCI which may be carried in the PUCCH or multiplexed with PUSCH.

In some embodiments, the remote UE may send the first signaling to the network node on an indirect path via at least one of the following signaling alternatives.

(2) MAC CE based signaling, which may be an existing MAC CE or a new MAC CE for indicating that the UE has declared/detected RLF. For this alternative, a SL MAC CE for indicating RLF may need to be defined for SL. Meanwhile, a MAC CE for indicating RLF on Uu connection may also need to be defined.

In some embodiments, if the relay UE detects a RLF event on the PC5 hop between it and the remote UE, the relay UE may inform the occurrence of RLF on the indirect path to the gNB via the Uu interface with the gNB.

In some embodiments, in step 406, the remote UE may handle the RLF event by receiving a second signaling transmitted from the gNB to inform the remote UE of at least one of the following actions.

● Deactivate the path with the RLF event. Deactivation of a SL path may be a temporary state, in other words, the SL path/carrier may be reactivated again after a while. If the path contains multiple hops, deactivation of the path would affect each hop of the path. In other words, each hop may be also deactivated for a while.

● De-configure/remove the path with the RLF event. De-configuration of a path is a hard decision. In other words, the path will not be configured for the remote UE.

● Add a new connection path between the remote UE and the network node to replace the path with the RLF event. The gNB may use a direct or indirect path to replace the path.

● Reconfigure the path with the RLF event. In an example, if the path is an indirect path, a new SL Band Width Part (BWP) for the SL carrier may be added or configured, meanwhile the SL BWP on which SL RLF is detected may be deactivated or de-configured. In another example, the gNB may order the remote UE to use a different Uu BWP if the path with the RLF event is a direct path.

● Fall-back to one of the multiple connection paths without the RLF event. If there are two paths between the remote UE and the gNB, the gNB may instruct the remote UE to fallback to a single path operation.

● Request the remote UE to send an updated/fresh measurement report.

● Reconfigure radio bearer (RB) transmission on the path with the RLF event to one of the multiple connection paths without the RLF event, and continue the RB transmission on the one path.

● Send RRC release to the remote UE for releasing RRC connection of the remote UE.

The gNB may send the second signaling to the remote UE via at least one of the following signaling alternatives:

- system information;

- dedicated RRC signaling;

- MAC CE based signaling based signaling; and

- Layer 1 (L1) signaling.

In some embodiments, in step 406, the remote UE may handle the RLF event by further performing at least one of the following actions in response to receiving the second signaling from the gNB:

- stopping using the path with the RLF event for a specified period in response to being informed of deactivation of the path;

- stopping using the path with the RLF event in response to being informed of de-configuration of the path;

- using a new connection path between the first UE and the network node to replace the path with the RLF event in response to being informed of addition of the new connection path;

- using a sidelink BWP or Uu BWP different from a sidelink BWP or Uu BWP on which the RLF event is detected for the path, in response to being informed of reconfiguration of the path;

- falling back to one of the multiple connection paths without the RLF event in response to being informed of an instruction of fallback to the one connection path;

- sending an updated measurement report to the gNB in response to being informed of a request for the updated measurement report;

- switching RB transmission on the path with the RLF event to one of the multiple connection paths without the RLF event, in response to being informed of reconfiguration of the RB transmission; and

- releasing RRC connection of the remote UE in response to being informed of RRC release.

In some embodiments, in step 406, the remote UE may handle the RLF event by automatically or based on an instruction sent from the gNB via a lower layer signaling, switching RB transmission on the path with the RLF event to one of the multiple connection paths without the RLF event. For an RB, the gNB may configure multiple RB to Logic Channel (LCH) mappings (e.g., the RB may be mapped to multiple LCHs belonging to different paths, or multiple mappings configured to the UE, wherein each mapping indicating how the RB is mapped to a LCH; the remote UE may apply a mapping at a time) where the LCH is associated with different paths, e.g., one RB to Uu LCH mapping on the direct path and one RB to PC5 LCH mapping on the indirect path. In case that the RB is being transmitted on one path and that path is failed, the remote UE may switch the transmission/reception of the RB to another path whereno RLF is detected (i.e., without RRC reconfiguration) , automatically or based on an instruction from the gNB, where the instruction is sent via a lower layer (e.g., L1/L2) signaling.

With the RLF-handling actions described above, it is feasible for the remote UE to, for example, recover from RLF on a path without going to inactive or idle RRC state, and to avoid interruption to services due to RLF on a path.

Figure 5 is a flowchart illustrating a method performed in a relay UE for RLF handling according to some embodiments of the present disclosure. The relay UE may be implemented with UE 100 in Figure 2, and may operate as any of the relay UE in Figure 1. Herein, it may also be referred to as UE2. There may be multiple connection paths between the remote UE and a network node, including at least one indirect path on which the remote UE is connected to the network node (e.g., gNB) via at least one relay UE. The method implemented in the relay UE may include detecting or being informed of a RLF event on at least one of the multiple connection paths between the remote UE and a network node (step 502) . In some embodiment, by referring to Figure 1, the relay UE may detect a RLF event on the PC5 sidelink/hop with the remote UE, or on the Uu sidelink/hop with the gNB. In some embodiment, a RLF event on a direct path between the remote UE and the gNB may be detected by the remote UE as described above, and then informed to the relay UE via the PC5 hop therebetween.

In some embodiments, the relay UE may detect a RLF event on the PC5 sidelink/hop with the remote UE in the same conditions as those for the remote UE to detect a RLF event on the PC5 hop. Repeated description thereof will be omitted here.

In some embodiments, the relay UE may detect a RLF event on the Uu sidelink/hop with the gNB in the same conditions as those for the remote UE to detect a RLF event on the direct Uu connection to the gNB. Repeated description thereof will be omitted here.

As shown in Figure 5, the method implemented in the relay UE may further include performing a RLF-handling operation in response to the detected or informed RLF event (step 504) . In some embodiment, if the relay UE detects the RLF event on the Uu hop, it may handle the RLF event by informing, via the PC5 hop, the remote UE of the RLF event on the Uu hop, so that the remote UE may further inform the RLF event to the gNB via a connection path without RLF. In some embodiments, if the relay UE detects the RLF event on the PC5 hop, it may handle the RLF event by informing, via the Uu hop, the gNB of the RLF event on the PC5 hop, so that the gNB may know the RLF event and perform actions for handling or recovery. In some embodiments, if the remote UE detects a RLF event on a direct path between the remote UE and the gNB, the remote UE may inform the relay UE of the RLF event via a PC5 hop therebetween. In response to the informed RLF event, the relay UE may handle the RLF event by informing, via the Uu hop, the gNB of the RLF event on the direct path, so that the gNB may know the RLF event and perform actions for handling or recovery. The relay UE may inform the gNB of the RLF event by sending a signaling to the gNB via the Uu hop therebetween, and the signaling may be similar to or the same as the first signaling sent by the remote UE to the gNB, which is described above with reference to Figure 4. The relay UE may send the signaling by, for example, including the signaling in a dedicated RRC signaling (e.g., an existing or new RRC signaling) , or including the signaling in MAC CE based signaling (e.g., an existing MAC CE or a new MAC CE) , in which an MAC CE for indicating the RLF event is defined for each of sidelinks/links on PC5 and Uu ports.

Figure 6 is a flowchart illustrating a method performed in a network node according to some embodiments of the present disclosure. The network node may be implemented with the network node 200 in Figure 3. The network node may have a coverage in which one or more of the UEs (remote and relay UEs as described above) is covered. The network node may operate as the gMN in Figure 1. There may be multiple connection paths between the remote UE and the gNB, including at least one indirect path on which the remote UE is connected to gNB via at least one relay UE. In some embodiments, the method performed by the network node may include: being informed of a RLF event on at least one of multiple connection paths between the remote UE and the network node (step 602) ; and performing a RLF-handling operation in response to the informed RLF event (step 604) .

In some embodiments, the network node may be informed of the RLF event by receiving a signaling from the remote UE via one of the multiple connection paths where no RLF occurs (a direct path or an indirect path) , as described above with reference to Figure 4. In some embodiments, the RLF event may be detected on the PC5 hop by the relay UE, and the network node is informed of the RLF event by the relay UE, as described above with reference to Figure 5.

In some embodiments, in response to being informed of the RLF event, the gNB may handle the RLF event by sending a signaling to inform the remote UE of at least one of the actions as described above with reference to Figure 4, so that the remote UE may act correspondingly to handle the RLF. Repeated description is thus omitted here.

In some embodiments, in response to being informed of the RLF event, the gNB may handle the RLF event by sending the remote UE via a lower layer signaling, an instruction of switching RB transmission on the path with the RLF event to one of the multiple connection paths without the RLF event.

So far, the methods performed by the UEs and network node have been described. In the following, these methods will be further explained with reference to Figure 7 which shows examples of RLF handing operations according to some embodiments of the present disclosure. As shown in parts (a) and (b) of Figure 7, a RLF event may occur on the indirection path. In part (a) , the RLF event is detected on the Uu hop by the relay UE, and the relay UE may inform the Remote UE of the detected RLF event. After that, the remote UE may signal the gNB of the RLF event via the direct path. Although not shown, the remote UE may signal the gNB of the RLF event via another indirect path. In response to being informed of the RLF event, the gNB may send a signaling, via the direct path or another indirect path, to inform the remote UE how to handle the RLF event.

In part (b) of Figure 7, the remote UE may detect a RLF event on the PC5 hop, and may inform the gNB of the RLF event via the direct path. Although not shown, the relay UE may also detect the RLF event on the PC5 hop, and may inform the gNB of the RLF event via the Uu hop. In response to being informed of the RLF event, the gNB may send a signaling, via the direct path or another indirect path, to inform the remote UE how to handle the RLF event.

As shown in part (c) of Figure 7, a RLF event may occur on the direct path. In this case, the remote UE may detect the RLF event, and inform to the gNB via the indirect path. The RLF event may be signaled by the remote UE to the gNB via the relay UE on the indirect path. In response to being informed of the RLF event, the gNB may send a signaling, via the indirect path or another indirect path (if any) , to inform the remote UE how to handle the RLF event.

Figure 8 shows an example of a communication system QQ100 in accordance with some embodiments.

In the example, the communication system QQ100 includes a telecommunication network QQ102 that includes an access network QQ104, such as a radio access network (RAN) , and a core network QQ106, which includes one or more core network nodes QQ108. The access network QQ104 includes one or more access network nodes, such as network nodes QQ110a and QQ110b (one or more of which may be generally referred to as network nodes QQ110) , or any other similar 3rd Generation Partnership Project (3GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network QQ102 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network QQ102 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network QQ102, including one or more network nodes QQ110 and/or core network nodes QQ108.

Examples of an ORAN network node include an open radio unit (O-RU) , an open distributed unit (O-DU) , an open central unit (O-CU) , including an O-CU control plane (O-CU-CP) or an O-CU user plane (O-CU-UP) , a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp) , or any combination thereof (the adjective “open” designating support of an ORAN specification) . The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1, F1, W1, E1, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes QQ110 facilitate direct or indirect connection of user equipment (UE) , such as by connecting UEs QQ112a, QQ112b, QQ112c, and QQ112d (one or more of which may be generally referred to as UEs QQ112) to the core network QQ106 over one or more wireless connections.

Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system QQ100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system QQ100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

The UEs QQ112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes QQ110 and other communication devices. Similarly, the network nodes QQ110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs QQ112 and/or with other network nodes or equipment in the telecommunication network QQ102 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network QQ102.

In the depicted example, the core network QQ106 connects the network nodes QQ110 to one or more hosts, such as host QQ116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network QQ106 includes one more core network nodes (e.g., core network node QQ108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node QQ108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC) , Mobility Management Entity (MME) , Home Subscriber Server (HSS) , Access and Mobility Management Function (AMF) , Session Management Function (SMF) , Authentication Server Function (AUSF) , Subscription Identifier De-concealing function (SIDF) , Unified Data Management (UDM) , Security Edge Protection Proxy (SEPP) , Network Exposure Function (NEF) , and/or a User Plane Function (UPF) .

The host QQ116 may be under the ownership or control of a service provider other than an operator or provider of the access network QQ104 and/or the telecommunication network QQ102, and may be operated by the service provider or on behalf of the service provider. The host QQ116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

As a whole, the communication system QQ100 of Figure 8 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM) ; Universal Mobile Telecommunications System (UMTS) ; Long Term Evolution (LTE) , and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G) ; wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi) ; and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax) , Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

In some examples, the telecommunication network QQ102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network QQ102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network QQ102. For example, the telecommunications network QQ102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC) /Massive IoT services to yet further UEs.

In some examples, the UEs QQ112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network QQ104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network QQ104. Additionally, a UE may be configured for operating in single-or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC) , such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio -Dual Connectivity (EN-DC) .

In the example, the hub QQ114 communicates with the access network QQ104 to facilitate indirect communication between one or more UEs (e.g., UE QQ112c and/or QQ112d) and network nodes (e.g., network node QQ110b) . In some examples, the hub QQ114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub QQ114 may be a broadband router enabling access to the core network QQ106 for the UEs. As another example, the hub QQ114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes QQ110, or by executable code, script, process, or other instructions in the hub QQ114. As another example, the hub QQ114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub QQ114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub QQ114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub QQ114 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub QQ114 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy IoT devices.

The hub QQ114 may have a constant/persistent or intermittent connection to the network node QQ11Ob. The hub QQ114 may also allow for a different communication scheme and/or schedule between the hub QQ114 and UEs (e.g., UE QQ112c and/or QQ112d) , and between the hub QQ114 and the core network QQ106. In other examples, the hub QQ114 is connected to the core network QQ106 and/or one or more UEs via a wired connection. Moreover, the hub QQ114 may be configured to connect to an M2M service provider over the access network QQ104 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes QQ110 while still connected via the hub QQ114 via a wired or wireless connection. In some embodiments, the hub QQ114 may be a dedicated hub -that is, a hub whose primary function is to route communications to/from the UEs from/to the network node QQ110b. In other embodiments, the hub QQ114 may be a non-dedicated hub -that is, a device which is capable of operating to route communications between the UEs and network node QQ110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.

Figure 9 shows a UE QQ200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA) , wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , smart device, wireless customer-premise equipment (CPE) , vehicle, vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP) , including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.

A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC) , vehicle-to-vehicle (V2V) , vehicle-to-infrastructure (V2I) , or vehicle-to-everything (V2X) . In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller) . Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter) .

The UE QQ200 includes processing circuitry QQ202 that is operatively coupled via a bus QQ204 to an input/output interface QQ206, a power source QQ208, a memory QQ210, a communication interface QQ212, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 9. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

The processing circuitry QQ202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory QQ210. The processing circuitry QQ202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs) , application specific integrated circuits (ASICs) , etc. ) ; programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP) , together with appropriate software; or any combination of the above. For example, the processing circuitry QQ202 may include multiple central processing units (CPUs) .

In the example, the input/output interface QQ206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE QQ200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc. ) , a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

In some embodiments, the power source QQ208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet) , photovoltaic device, or power cell, may be used. The power source QQ208 may further include power circuitry for delivering power from the power source QQ208 itself, and/or an external power source, to the various parts of the UE QQ200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source QQ208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source QQ208 to make the power suitable for the respective components of the UE QQ200 to which power is supplied.

The memory QQ210 may be or be configured to include memory such as random access memory (RAM) , read-only memory (ROM) , programmable read-only memory (PROM) , erasable programmable read-only memory (EPROM) , electrically erasable programmable read-only memory (EEPROM) , magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory QQ210 includes one or more application programs QQ214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data QQ216. The memory QQ210 may store, for use by the UE QQ200, any of a variety of various operating systems or combinations of operating systems.

The memory QQ210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID) , flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM) , synchronous dynamic random access memory (SDRAM) , external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs) , such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC) , integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card. ’ The memory QQ210 may allow the UE QQ200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory QQ210, which may be or comprise a device-readable storage medium.

The processing circuitry QQ202 may be configured to communicate with an access network or other network using the communication interface QQ212. The communication interface QQ212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna QQ222. The communication interface QQ212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network) . Each transceiver may include a transmitter QQ218 and/or a receiver QQ220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth) . Moreover, the transmitter QQ218 and receiver QQ220 may be coupled to one or more antennas (e.g., antenna QQ222) and may share circuit components, software or firmware, or alternatively be implemented separately.

In the illustrated embodiment, communication functions of the communication interface QQ212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA) , Wideband Code Division Multiple Access (WCDMA) , GSM, LTE, New Radio (NR) , UMTS, WiMax, Ethernet, transmission control protocol/internet protocol (TCP/IP) , synchronous optical networking (SONET) , Asynchronous Transfer Mode (ATM) , QUIC, Hypertext Transfer Protocol (HTTP) , and so forth.

Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface QQ212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature) , random (e.g., to even out the load from reporting from several sensors) , in response to a triggering event (e.g., when moisture is detected an alert is sent) , in response to a request (e.g., a user initiated request) , or a continuous stream (e.g., a live video feed of a patient) .

As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

A UE, when in the form of an Internet of Things (IoT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR) , a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal-or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV) , and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an IoT device comprises circuitry and/or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE QQ200 shown in Figure 9.

As yet another specific example, in an IoT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

Figure 10 shows a network node QQ300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points) , base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs) ) , O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU) .

Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and/or remote radio units (RRUs) , sometimes referred to as Remote Radio Heads (RRHs) . Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS) .

Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs) , base transceiver stations (BTSs) , transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs) , Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs) ) , and/or Minimization of Drive Tests (MDTs) .

The network node QQ300 includes a processing circuitry QQ302, a memory QQ304, a communication interface QQ306, and a power source QQ308. The network node QQ300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc. ) , which may each have their own respective components. In certain scenarios in which the network node QQ300 comprises multiple separate components (e.g., BTS and BSC components) , one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node QQ300 may be configured to support multiple radio access technologies (RATs) . In such embodiments, some components may be duplicated (e.g., separate memory QQ304 for different RATs) and some components may be reused (e.g., a same antenna QQ310 may be shared by different RATs) . The network node QQ300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node QQ300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node QQ300.

The processing circuitry QQ302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node QQ300 components, such as the memory QQ304, to provide network node QQ300 functionality.

In some embodiments, the processing circuitry QQ302 includes a system on a chip (SOC) . In some embodiments, the processing circuitry QQ302 includes one or more of radio frequency (RF) transceiver circuitry QQ312 and baseband processing circuitry QQ314. In some embodiments, the radio frequency (RF) transceiver circuitry QQ312 and the baseband processing circuitry QQ314 may be on separate chips (or sets of chips) , boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry QQ312 and baseband processing circuitry QQ314 may be on the same chip or set of chips, boards, or units.

The memory QQ304 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM) , read-only memory (ROM) , mass storage media (for example, a hard disk) , removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD) ) , and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry QQ302. The memory QQ304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry QQ302 and utilized by the network node QQ300. The memory QQ304 may be used to store any calculations made by the processing circuitry QQ302 and/or any data received via the communication interface QQ306. In some embodiments, the processing circuitry QQ302 and memory QQ304 is integrated.

The communication interface QQ306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface QQ306 comprises port (s) /terminal (s) QQ316 to send and receive data, for example to and from a network over a wired connection. The communication interface QQ306 also includes radio front-end circuitry QQ318 that may be coupled to, or in certain embodiments a part of, the antenna QQ310. Radio front-end circuitry QQ318 comprises filters QQ320 and amplifiers QQ322. The radio front-end circuitry QQ318 may be connected to an antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry may be configured to condition signals communicated between antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry QQ318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry QQ318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters QQ320 and/or amplifiers QQ322. The radio signal may then be transmitted via the antenna QQ310. Similarly, when receiving data, the antenna QQ310 may collect radio signals which are then converted into digital data by the radio front-end circuitry QQ318. The digital data may be passed to the processing circuitry QQ302. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

In certain alternative embodiments, the network node QQ300 does not include separate radio front-end circuitry QQ318, instead, the processing circuitry QQ302 includes radio front-end circuitry and is connected to the antenna QQ310. Similarly, in some embodiments, all or some of the RF transceiver circuitry QQ312 is part of the communication interface QQ306. In still other embodiments, the communication interface QQ306 includes one or more ports or terminals QQ316, the radio front-end circuitry QQ318, and the RF transceiver circuitry QQ312, as part of a radio unit (not shown) , and the communication interface QQ306 communicates with the baseband processing circuitry QQ314, which is part of a digital unit (not shown) .

The antenna QQ310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna QQ310 may be coupled to the radio front-end circuitry QQ318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna QQ310 is separate from the network node QQ300 and connectable to the network node QQ300 through an interface or port.

The antenna QQ310, communication interface QQ306, and/or the processing circuitry QQ302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna QQ310, the communication interface QQ306, and/or the processing circuitry QQ302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

The power source QQ308 provides power to the various components of network node QQ300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component) . The power source QQ308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node QQ300 with power for performing the functionality described herein. For example, the network node QQ300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source QQ308. As a further example, the power source QQ308 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

Embodiments of the network node QQ300 may include additional components beyond those shown in Figure 10 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node QQ300 may include user interface equipment to allow input of information into the network node QQ300 and to allow output of information from the network node QQ300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node QQ300.

Figure 11 is a block diagram of a host QQ400, which may be an embodiment of the host QQ116 of Figure 13, in accordance with various aspects described herein. As used herein, the host QQ400 may be or comprise various combinations hardware and/or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host QQ400 may provide one or more services to one or more UEs.

The host QQ400 includes processing circuitry QQ402 that is operatively coupled via a bus QQ404 to an input/output interface QQ406, a network interface QQ408, a power source QQ410, and a memory QQ412. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures QQ2 and QQ3, such that the descriptions thereof are generally applicable to the corresponding components of host QQ400.

The memory QQ412 may include one or more computer programs including one or more host application programs QQ414 and data QQ416, which may include user data, e.g., data generated by a UE for the host QQ400 or data generated by the host QQ400 for a UE. Embodiments of the host QQ400 may utilize only a subset or all of the components shown. The host application programs QQ414 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC) , High Efficiency Video Coding (HEVC) , Advanced Video Coding (AVC) , MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC) , MPEG, G. 711) , including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems) . The host application programs QQ414 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host QQ400 may select and/or indicate a different host for over-the-top services for a UE. The host application programs QQ414 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP) , Real-Time Streaming Protocol (RTSP) , Dynamic Adaptive Streaming over HTTP (MPEG-DASH) , etc.

Figure 12 is a block diagram illustrating a virtualization environment QQ500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments QQ500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host) , then the node may be entirely virtualized. In some embodiments, the virtualization environment QQ500 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface.

Applications QQ502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc. ) are run in the virtualization environment Q400 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

Hardware QQ504 includes processing circuitry, memory that stores software and/or instructions executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers QQ506 (also referred to as hypervisors or virtual machine monitors (VMMs) ) , provide VMs QQ508a and QQ508b (one or more of which may be generally referred to as VMs QQ508) , and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer QQ506 may present a virtual operating platform that appears like networking hardware to the VMs QQ508.

The VMs QQ508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer QQ506. Different embodiments of the instance of a virtual appliance QQ502 may be implemented on one or more of VMs QQ508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV) . NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, a VM QQ508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs QQ508, and that part of hardware QQ504 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs QQ508 on top of the hardware QQ504 and corresponds to the application QQ502.

Hardware QQ504 may be implemented in a standalone network node with generic or specific components. Hardware QQ504 may implement some functions via virtualization. Alternatively, hardware QQ504 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration QQ510, which, among others, oversees lifecycle management of applications QQ502. In some embodiments, hardware QQ504 is coupled to one or more radio units that each includes one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system QQ512 which may alternatively be used for communication between hardware nodes and radio units.

Figure 13 shows a communication diagram of a host QQ602 communicating via a network node QQ604 with a UE QQ606 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE QQ112a of Figure 8 and/or UE QQ200 of Figure 9) , network node (such as network node QQ110a of Figure 8 and/or network node QQ300 of Figure 10) , and host (such as host QQ116 of Figure 8 and/or host QQ400 of Figure 11) discussed in the preceding paragraphs will now be described with reference to Figure 13.

Like host QQ400, embodiments of host QQ602 include hardware, such as a communication interface, processing circuitry, and memory. The host QQ602 also includes software, which is stored in or accessible by the host QQ602 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE QQ606 connecting via an over-the-top (OTT) connection QQ650 extending between the UE QQ606 and host QQ602. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection QQ650.

The network node QQ604 includes hardware enabling it to communicate with the host QQ602 and UE QQ606. The connection QQ660 may be direct or pass through a core network (like core network QQ106 of Figure 8) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

The UE QQ606 includes hardware and software, which is stored in or accessible by UE QQ606 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE QQ606 with the support of the host QQ602. In the host QQ602, an executing host application may communicate with the executing client application via the OTT connection QQ650 terminating at the UE QQ606 and host QQ602. In providing the service to the user, the UE′s client application may receive request data from the host′s host application and provide user data in response to the request data. The OTT connection QQ650 may transfer both the request data and the user data. The UE′s client application may interact with the user to generate the user data that it provides to the host application through the OTT connection QQ650.

The OTT connection QQ650 may extend via a connection QQ660 between the host QQ602 and the network node QQ604 and via a wireless connection QQ670 between the network node QQ604 and the UE QQ606 to provide the connection between the host QQ602 and the UE QQ606. The connection QQ660 and wireless connection QQ670, over which the OTT connection QQ650 may be provided, have been drawn abstractly to illustrate the communication between the host QQ602 and the UE QQ606 via the network node QQ604, without explicit reference to any intermediary devices and the precise routing of messages via these devices.

As an example of transmitting data via the OTT connection QQ650, in step QQ608, the host QQ602 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE QQ606. In other embodiments, the user data is associated with a UE QQ606 that shares data with the host QQ602 without explicit human interaction. In step QQ610, the host QQ602 initiates a transmission carrying the user data towards the UE QQ606. The host QQ602 may initiate the transmission responsive to a request transmitted by the UE QQ606. The request may be caused by human interaction with the UE QQ606 or by operation of the client application executing on the UE QQ606. The transmission may pass via the network node QQ604, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step QQ612, the network node QQ604 transmits to the UE QQ606 the user data that was carried in the transmission that the host QQ602 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step QQ614, the UE QQ606 receives the user data carried in the transmission, which may be performed by a client application executed on the UE QQ606 associated with the host application executed by the host QQ602.

In some examples, the UE QQ606 executes a client application which provides user data to the host QQ602. The user data may be provided in reaction or response to the data received from the host QQ602. Accordingly, in step QQ616, the UE QQ606 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE QQ606. Regardless of the specific manner in which the user data was provided, the UE QQ606 initiates, in step QQ618, transmission of the user data towards the host QQ602 via the network node QQ604. In step QQ620, in accordance with the teachings of the embodiments described throughout this disclosure, the network node QQ604 receives user data from the UE QQ606 and initiates transmission of the received user data towards the host QQ602. In step QQ622, the host QQ602 receives the user data carried in the transmission initiated by the UE QQ606.

One or more of the various embodiments improve the performance of OTT services provided to the UE QQ606 using the OTT connection QQ650, in which the wireless connection QQ670 forms the last segment. More precisely, the teachings of these embodiments may enable network nodes and wireless devices to invalidate at least part of their activities, such as unnecessary measurements, signal monitoring, reporting, and other transmissions, and thus save power. Network nodes and wireless devices may also improve resource utilization by, for example, optimizing PDSCH and/or PUSCH transmission. These, in the end, will increase possibility for network nodes and wireless devices to gain more sleep time and save power. In UL direction, as a result of wireless device’s transmission cancellations, the network nodes may create reception gaps during which they can reduce receiver-related activities, for example, utilizing various sleep states depending on gap length, and thereby save energy.

In an example scenario, factory status information may be collected and analyzed by the host QQ602. As another example, the host QQ602 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host QQ602 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights) . As another example, the host QQ602 may store surveillance video uploaded by a UE. As another example, the host QQ602 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host QQ602 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices) , or any other function of collecting, retrieving, storing, analyzing and/or transmitting data.

In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection QQ650 between the host QQ602 and UE QQ606, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host QQ602 and/or UE QQ606. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection QQ650 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection QQ650 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node QQ604. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host QQ602. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection QQ650 while monitoring propagation times, errors, etc.

Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and/or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and/or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing (s) .
● 3GPP     Third Generation Partnership Project
● 5G          Fifth Generation
● 5GC         Fifth Generation Core
● 5GS         Fifth Generation System
● ACK         Acknowledgement
● ACK/NACK    Acknowledgement/Negative Acknowledgement
● AF          Application Function
● AMF         Access and Mobility Function
● AN          Access Network
● AP          Access Point
● AUSF        Authentication Server Function
● CE          Control Element
● CORESET     Control Resource Set
● CPU         Central Processing Unit
● CSI         Channel State Information
● CSI-RS      Channel State Information Reference Signal
● CQI         Channel Quality Index
● DCI         Downlink Control Information
● DL          Downlink
● DMRS        Demodulation Reference Signal
● DN          Data Network
● DSP         Digital Signal Processor
● eMBB        Enhanced Mobile Broadband
● eNB         Enhanced or Evolved Node B
● FDD         Frequency Division Duplex
● GEO         Geostationary Earth Orbit
● gNB         next Generation NodeB
● HARQ        Hybrid Automatic Repeat Request
● HSS         Home Subscriber Server
● IoT         Internet of Things
● IP          Internet Protocol
● ITS         In-the-Sky
● LEO         Low Earth Orbit
● LTE     Long Term Evolution
● MAC     Medium Access Control
● MEO     Medium Earth Orbit
● MIMU    Multiple-Input Multiple-Output
● MME     Mobility Management Entity
● MU-MIMU Multi-User Multiple-Input Multiple-Output
● MTC     Machine Type Communication
● NACK    Negative Acknowledgement
● NEF     Network Exposure Function
● NF      Network Function
● NR      New Radio
● NRF     Network Function Repository Function
● NSSF    Network Slice Selection Function
● NTN     Non-Terrestrial Network
● OTT     Over-the-Top
● PC      Personal Computer
● PCF     Policy Control Function
● PDSCH   Physical Downlink Shared Channel
● PDCCH   Physical Downlink Control Channel
● P-GW    Packet Data Network Gateway
● PHY     Physical Layer
● PMI     Precoder Matrix Index
● PRACH   Physical Random Access Channel
● PUCCH   Physical Uplink Control Channel
● RACH    Random-Access Channel
● RAM     Random Access Memory
● RAN     Radio Access Network
● RI      Rank Index
● ROM     Read Only Memory
● RRC     Radio Resource Control
● RRH     Remote Radio Head
● RTT     Round Trip Time
● SAW       Stop-and-Wait
● SCEF      Service Capability Exposure Function
● sCell     Secondary Cell
● SCS       Subcarrier Spacing
● SIB       System Information Block
● SMF       Session Management Function
● SNR       Signal-to-Noise Ratio
● SRS       Sounding Reference Signal
● SSB       Synchronization Signal Block
● SU-MIMU   Single-User Multiple-Input Multiple-Output
● TBS       Transport Block Size
● TCI       Transmission Configuration Indicator
● TDD       Time Division Duplex
● TDL       Tapped Delay Line
● UDM       Unified Data Management
● UE        User Equipment
● UL        Uplink
● UPF       User Plane Function
● URLLC     Ultra Reliable and Low Latency Communication
● ZP        Zero Power

Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

A method in a first User Equipment (UE) (100) , the method comprising:

detecting or being informed (402) of a Radio Link Fault (RLF) event on at least one of multiple connection paths between the first UE (100) and a network node (200) ; and

performing (406) a RLF-handling operation in response to the detected or informed RLF event,

wherein the multiple connection paths comprise at least one indirect path between the first UE (100) and the network node (200) , on which the first UE (100) is connected to the network node (200) via at least one relay UE.
The method of claim 1, further comprising:

before performing the RLF-handling operation, informing (404) the network node of the RLF event on the at least one connection path by sending a first signaling to the network node via one of the multiple connection paths where no RLF occurs.
The method of claim 2, wherein the first signaling contains at least one of:

- an identifier (ID) of the first UE;

- information of the at least one connection path where the RLF occurs;

- an indicator indicating that the RLF has been detected on the at least one connection path;

- a cause of the RLF;

- in case that the at least one connection path is an indirect path comprising a relay UE, a list of potential other relay UEs and corresponding measurements of PC5 link radio conditions to the other relay UE; and

- in case that the at least one connection path comprises an unlicensed sidelink, measurements of channel occupancy or Listen-Before-Talk (LBT) failure statistics.
The method of claim 3, wherein the information of the at least one connection path indicates at least one of:

- whether the at least one connection path is a primary path for transmitting control plane signaling;

- whether the at least one connection path is a secondary path different from a primary path for transmitting control plane signaling;

- an ID of the at least one connection path;

- an ID of a relay UE in the at least one connection path, in case that the at least one connection path is an indirect path comprising the relay UE; and

- which hop has the RLF event, in case that the at least one connection path is an indirect path comprising at least two hops between the first UE and the network node.
The method of claim 3 or 4, wherein in case that among the multiple connection paths, the first UE sends the first signaling to the network node on a direct path between the first UE and the network node, on which the first UE is connected to the network node without relay, the first signaling is sent to the network node via at least one of:

- including the first signaling in a dedicated RRC signaling comprising an existing or new RRC signaling;

- including the first signaling in a Media Access Control (MAC) Control Element (CE) based signaling comprising an existing MAC CE or a new MAC CE;

- initiating a Radom Access Channel (RACH) procedure for carrying the first signaling;

- initiating a Physical Uplink Control Channel (PUCCH) transmission for carrying the first signaling;

- initiating a configured grant-based transmission for carrying the first signaling;

- including the first signaling in a configured grant uplink control information (CG-UCI) ; and

- including the first signaling in a PUCCH uplink control information (PUCCH -UCI) carried in PUCCH or multiplexed with Physical Uplink Shared Channel (PUSCH) .
The method of claim 5, wherein the RACH procedure comprises a 4-step RACH procedure in which:

Msg1 is used to carry the first signaling, and a dedicated preamble or RACH occasion is allocated to the first UE for indicating the first signaling; or

Msg3 is used to carry the first signaling by supplying an ID of the first UE and an indicator indicating the first signaling in Msg3.
The method of claim 5, wherein the RACH procedure comprises a 2-step RACH procedure in which:

a dedicated preamble or RACH occasion or PUSCH occasion is allocated to the first UE for indicating the first signaling; or

MsgA is used to carry the first signaling by supplying an indicator indicating the first signaling in MsgA.
The method of claim 6 or 7, wherein the indicator indicating the first signaling comprises a field in an MAC subheader or carried in an MAC CE.
The method of claim 5, wherein an RRC message is partly or fully included in a RACH message in the RACH procedure to include the first signaling.
The method of claim 3 or 4, wherein in case that the first UE sends the first signaling to the network node on one of the at least one indirect path between the first UE and the network node, the first signaling is sent to the network node via at least one of:

- including the first signaling in a dedicated RRC signaling comprising an existing or new RRC signaling; and

- including the first signaling a Media Access Control (MAC) Control Element (CE) based signaling comprising an existing MAC CE or a new MAC CE, in which an MAC CE for indicating the RLF event is defined for each of links on PC5 and Uu ports between the first UE and the network node.
The method of any of claims 2 to 10, wherein in case that the at least one connection path is an indirect path comprising at least a PC5 hop between the first UE and a relay UE and a Uu hop between the relay UE and the network node,

informing the network node of the RLF event on the at least one connection path comprises:

if the RLF event is detected on the Uu hop by the relay UE, informing the network node of the RLF event on the Uu hop by the first UE in response to being informed of the RLF event on the Uu hop by the relay UE via the PC5 hop; and

if the RLF event is detected on the PC5 hop by the first UE, informing the network node of the RLF event on PC5 hop by the first UE via one of the multiple connection paths without RLF event.
The method of any of claims 2 to 10, wherein in case that the at least one connection path is a direct path between the first UE and the network node, on which the first UE is connected to the network node without relay:

informing the network node of the RLF event on the at least one connection path comprises: when the first UE detects the RLF event on the direct path, informing the network node of the RLF event on the direct path via a relay UE on one of the at least one indirection path.
The method of any of claims 1 to 12, wherein performing the RLF-handling operation comprises:

performing a Radio Resource Control (RRC) connection reestablishment procedure when the at least one connection path with the RLF event comprises a primary path on which control plane signaling is transmitted between the first UE and the network node.
The method of claim 13, wherein performing the RLF-handling operation further comprises:

de-configuring all of the rest of the multiple connection paths other than the primary path before performing the RRC connection reestablishment procedure.
The method of claim 1, wherein performing the RLF-handling operation comprises:

performing a Radio Resource Control (RRC) connection reestablishment procedure when the at least one connection path with the RLF event comprises all of the multiple connection paths.
The method of any of claims 2 to 10, wherein performing the RLF-handling operation comprises receiving a second signaling transmitted from the network node to inform the first UE of at least one of the following:

- deactivation of the at least one connection path with the RLF event for a specified period before reactivation;

- de-configuration of the at least one connection path with the RLF event for the first UE;

- addition of a new connection path between the first UE and the network node to replace the at least one connection path with the RLF event;

- reconfiguration of the at least one connection path with the RLF event;

- an instruction of fall-back to one of the multiple connection paths without the RLF event;

- a request for an updated measurement report;

- reconfiguration of radio bearer (RB) transmission on the at least one connection path with the RLF event to one of the multiple connection paths without the RLF event; and

- Radio Resource Control (RRC) release for releasing RRC connection of the first UE.
The method of claim 16, wherein in case that the at least one connection path with the RLF event is one of the at least one indirection path, and the RLF event is detected on a sidelink bandwidth part (BWP) of the one indirection path,

the reconfiguration of the at least one connection path with the RLF event comprises: addition or configuration of a different sidelink BWP for the indirection path while the SL BWP with the RLF event is deactivated or de-configured;

in case that the at least one connection path with the RLF event is a direct path with a Uu port between the first UE and the network node, on which the first UE is connected to the network node without relay, and the RLF event is detected on a Uu BWP of the direct path,

the reconfiguration of the at least one connection path with the RLF event comprises: ordering the first UE to use a different Uu BWP for the direct path.
The method of claim 16 or 17, wherein performing the RLF-handling operation further comprises: in response to receiving the second signaling from the network node, performing at least one of the following actions:

- stopping using the at least one connection path with the RLF event for a specified period in response to being informed of deactivation of the at least one connection path;

- stopping using the at least one connection path with the RLF event in response to being informed of de-configuration of the at least one connection path;

- using a new connection path between the first UE and the network node to replace the at least one connection path with the RLF event in response to being informed of addition of the new connection path;

- using a sidelink BWP or Uu BWP different from a sidelink BWP or Uu BWP on which the RLF event is detected for the at least one connection path, in response to being informed of reconfiguration of the at least one connection path;

- falling back to one of the multiple connection paths without the RLF event in response to being informed of an instruction of fallback to the one connection path;

- sending an updated measurement report to the network node in response to being informed of a request for the updated measurement report;

- switching radio bearer (RB) transmission on the at least one connection path with the RLF event to one of the multiple connection paths without the RLF event, in response to being informed of reconfiguration of the RB transmission; and

- releasing RRC connection of the first UE in response to being informed of RRC release.
The method of any of claims 16 to 18, wherein the second signaling is received from the network node via at least one of:

- system information;

- dedicated RRC signaling;

- Media Access Control (MAC) Control Element (CE) based signaling based signaling; and

- Layer 1 (L1) signaling.
The method of any of claims 1 to 12, wherein performing the RLF-handling operation comprises:

automatically or based on an instruction sent from the network node via a lower layer signaling, switching RB transmission on the at least one connection path with the RLF event to one of the multiple connection paths without the RLF event.
The method of any of claims 1 to 20, wherein in case that the at least one connection path with the RLF event is one of the at least one indirect path, the RLF event is detected on a PC5 hop between the first UE and the at least one relay UE when one of the following conditions is met:

- a maximum number of out-of-sync instances for the PC5 hop being reached;

- a maximum number of Radio Link Control (RLC) retransmissions being reached;

- a configuration or reconfiguration error occurring upon reception of a Radio Resource Control (RRC) configuration or reconfiguration signaling message;

- a maximum number of consecutive Hybrid Automatic Repeat Request (HARQ) Discontinuous Transmission (DTX) being reached;

- no expected acknowledgement being received within a specified period of time; and

- no acknowledgement on RLC transmission being received within a specified period of time.
The method of claim 21, wherein the maximum number of out-of-sync instances for the PC5 hop is considered to be reached when a number of out-of-sync indications for the PC5 hop consecutively received from a physical channel reaches a count value of a configured counter.
The method of claim 22, wherein the at least one connection path with the RLF event is considered to be recovered if a configured number of in-sync indications for the PC5 hop is consecutively received from the physical channel after the maximum number of out-of-sync instances for the PC5 hop is reached.
The method of claim 21, wherein a number ofRLC retransmissions is traced and stored for the PC5 hop, and

the maximum number ofRLC retransmissions is considered to be reached when the number ofRLC retransmissions reaches a count value of a configured counter.
The method of claim 21, wherein the expected acknowledgement comprises an RRCReconfigurationSidelinkComplete message sent from the at least one relay UE to the first UE, in response to an RRCReconfigurationSidelink message sent by the first UE on the PC5 hop.
The method of claim 21, wherein the acknowledgement on RLC transmission comprises an acknowledgement on RLC transmission sent from the at least one relay UE to the first UE, in response to retransmission of RLC Protocol Data Units (PDUs) by the first UE on the PC5 hop.
The method of any of claims 1 to 20, wherein in case that the at least one connection path with the RLF event is one of the at least one indirect path, the RLF event is detected on a Uu hop between the network node and the at least one relay UE when one of the following conditions is met:

- expiry of a radio problem timer started after indication of a radio problem from a physical layer;

- expiry of a timer started upon triggering a measurement report for a measurement identity for which the timer has been configured while another radio problem timer is running;

- random access procedure failure;

- RLC failure;

- consistent uplink Listen-Before-Talk (LBT) failures for operation with shared spectrum channel access being detected; and

- for integrated access backhaul Machine Type (IAB-MT) node, a backhaul (BH) RLF indication being received from its parent node.
A method in a first User Equipment (UE) (100) , the method comprising:

detecting or being informed (502) of a Radio Link Fault (RLF) event on at least one of multiple connection paths between a second UE and a network node (200) ; and

performing (504) a RLF-handling operation in response to the detected or informed RLF event,

wherein the multiple connection paths comprises at least one indirect path between the second UE and the network node (200) , in which the second UE is connected to the network node (200) via at least one relay UE including the first UE (100) .
The method of claim 28, wherein in case that the at least one connection path is an indirect path comprising at least a PC5 hop between the second UE and the first UE and a Uu hop between the first UE and the network node:

if the first UE detects the RLF event on the Uu hop, performing a RLF-handling operation comprises informing, via the PC5 hop, the second UE of the RLF event on the Uu hop;

if the first UE detects the RLF event on the PC5 hop, performing a RLF-handling operation comprises informing, via the Uu hop, the network node of the RLF event on the PC5 hop.
The method of claim 28, wherein in case that the at least one connection path is a direct path between the second UE and the network node, on which the second UE is connected to the network node without relay:

performing a RLF-handling operation comprises: informing the network node of the RLF event on the direct path in response to being informed by the second UE of the RLF event.
The method of any of claims 28 to 30, wherein in case that the at least one connection path with the RLF event is one of the at least one indirect path, detecting the RLF event comprises detecting the RLF event on a PC5 hop between the first UE and the second UE when one of the following conditions is met:

- a maximum number of out-of-sync instances for the PC5 hop being reached;

- a maximum number of Radio Link Control (RLC) retransmissions being reached;

- a configuration or reconfiguration error occurring upon reception of a Radio Resource Control (RRC) configuration or reconfiguration signaling message;

- a maximum number of consecutive Hybrid Automatic Repeat Request (HARQ) Discontinuous Transmission (DTX) being reached;

- no expected acknowledgement being received within a specified period of time; and

- no acknowledgement on RLC transmission being received within a specified period of time.
The method of any of claims 28 to 30, wherein in case that the at least one connection path with the RLF event is one of the at least one indirect path, detecting the RLF event comprises detecting the RLF event on a Uu hop between the network node and the second UE when one of the following conditions is met:

- expiry of a radio problem timer started after indication of a radio problem from a physical layer;

- expiry of a timer started upon triggering a measurement report for a measurement identity for which the timer has been configured while another radio problem timer is running;

- random access procedure failure;

- RLC failure;

- consistent uplink Listen-Before-Talk (LBT) failures for operation with shared spectrum channel access being detected; and

- for integrated access backhaul Machine Type (IAB-MT) node, a backhaul (BH) RLF indication being received from its parent node.
A method in a network node (200) , the method comprising:

being informed (602) of a Radio Link Fault (RLF) event on at least one of multiple connection paths between a first User Equipment (UE) (100) and the network node (200) ; and

performing (604) a RLF-handling operation in response to the informed RLF event,

wherein the multiple connection paths comprises at least one indirect path between the first UE (100) and the network node (200) , in which the first UE (100) is connected to the network node (200) via at least one relay UE.
The method of claim 33, wherein the network node is informed of the RLF event by receiving a first signaling from the first UE via one of the multiple connection paths where no RLF occurs.
The method of claim 34, wherein the first signaling contains at least one of:

- an identifier (ID) of the first UE;

- information of the at least one connection path where the RLF occurs;

- an indicator indicating that the RLF has been detected on the at least one connection path;

- a cause of the RLF;

- in case that the at least one connection path is an indirect path comprising a relay UE, a list of potential other relay UEs and corresponding measurements of PC5 link radio conditions to the other relay UE; and

- in case that the at least one connection path comprises an unlicensed sidelink, measurements of channel occupancy or Listen-Before-Talk (LBT) failure statistics.
The method of claim 33, wherein in case that the at least one connection path with the RLF event is one of the at least one indirection path having a PC5 hop between the first UE and a relay UE and a Uu hop between the relay UE and the network node, and the RLF event is detected on the PC5 hop by the relay UE, the network node is informed of the RLF event by the relay UE.
The method of any of claims 33 to 36, wherein performing the RLF-handling operation comprises sending a second signaling to inform the first UE of at least one of the following:

- deactivation of the at least one connection path with the RLF event for a specified period before reactivation;

- de-configuration of the at least one connection path with the RLF event for the first UE;

- addition of a new connection path between the first UE and the network node to replace the at least one connection path with the RLF event;

- reconfiguration of the at least one connection path with the RLF event;

- an instruction of fall-back to one of the multiple connection paths without the RLF event;

- a request for an updated measurement report;

- reconfiguration of radio bearer (RB) transmission on the at least one connection path with the RLF event to one of the multiple connection paths without the RLF event; and

- Radio Resource Control (RRC) release for releasing RRC connection of the first UE.
The method of claim 37, wherein in case that the at least one connection path with the RLF event is one of the at least one indirection path, and the RLF event is detected on a sidelink bandwidth part (BWP) of the one indirection path,

the reconfiguration of the at least one connection path with the RLF event comprises: addition or configuration of a different sidelink BWP for the indirection path while the SL BWP with the RLF event is deactivated or de-configured;

in case that the at least one connection path with the RLF event is a direct path with a Uu port between the first UE and the network node, on which the first UE is connected to the network node without relay, and the RLF event is detected on a Uu BWP of the direct path,

the reconfiguration of the at least one connection path with the RLF event comprises: ordering the first UE to use a different Uu BWP for the direct path.
The method of any of claims 37 or 38, wherein the second signaling is sent by the network node via at least one of:

- system information;

- dedicated RRC signaling;

- Media Access Control (MAC) Control Element (CE) based signaling based signaling; and

- Layer 1 (L1) signaling.
The method of any of claims 33 to 39, wherein performing the RLF-handling operation comprises:

sending, to the first UE via a lower layer signaling, an instruction of switching RB transmission on the at least one connection path with the RLF event to one of the multiple connection paths without the RLF event.
A User Equipment (UE) (100) , comprising:

one or more processors (102) ; and

memory (104) storing instructions that, when executed by the one or more processors (102) , cause the UE (100) to perform a method of any one of claims 1 to 32.
A network node (200) , comprising:

one or more processors (202) ; and

memory (204) storing instructions that, when executed by the one or more processors (202) , cause the network node (200) to perform a method of any one of claims 33 to 40.
A computer-readable storage medium having computer-readable instructions stored therein, the computer-readable instructions, when executed by a processor (102) of a User Equipment (UE) (100) , configure the UE (100) to perform a method of any one of claims 1 to 32, or when executed by a processor (202) of a network node (202) , configure the network node (200) to perform a method of any one of claims 33 to 40.