Method, apparatus and computer program product for managing a sidelink-based relay

Abstract

A method, an apparatus, and a computer program product for relay communication between a source user equipment and a target user equipment are disclosed. According to an embodiment, the method comprises: determining whether a transmitting user equipment of user equipment-to-user equipment relay communication is allowed to request a relay user equipment to establish at least one relay channel on a communication link for user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the transmitting user equipment; according to the determination, generating at least one control message to indicate a result of the determination to the transmitting user equipment; and transmitting the at least one control message to the transmitting user equipment.

Description

Technical Field

[0001] This invention relates to the management of sidelink-based relays. Background Technology

[0002] This section is intended to provide background or context for the invention as set forth in the claims. The description herein may include concepts that may be explored, but are not necessarily concepts that have been previously conceived or explored. Therefore, unless otherwise stated herein, the content described in this section is not prior art to the specification and claims of this application, and is not acknowledged as prior art by virtue of its inclusion in this section.

[0003] Sidelinks (SLs) are tools used for direct communication (UE-to-UE communication) between user equipment in various use cases. In some use cases, solutions including New Radio (NR) sidelinks are primarily geared towards vehicle-to-everything (V2X) communication; however, they can also be used for public safety and commercial applications where service requirements can be met.

[0004] In Layer 2 (L2) UE-to-UE (U2U) relay based on New Radio (NR) sidelinks (SL), the transmitting UE (Tx UE) may need to establish an SL Relay Radio Link Control (RLC) channel to transmit end-to-end (E2E) radio bearers (RBs), including signaling RBs (SRBs) and data RBs (DRBs), to the U2U relay UE for relaying to the receiving UE (Rx UE). The Tx UE may also be referred to as Tx UE in this document, and the Rx UE may also be referred to as Rx UE in this document.

[0005] In NR SL-based L2 UE-to-Network (U2N) relay, the serving gNB has complete control over the establishment and mapping of the SL relay RLC channel between the remote UE and the L2 U2N relay UE, as well as the Uu relay RLC channel between the L2 U2N relay UE and the serving gNB, for relaying the remote UE's (multiple) Uu SRBs and (multiple) DRBs via the L2 U2N relay UE. This may not work in L2 U2U relay scenarios because the UEs involved in L2 U2U relay do not need to be in a Radio Resource Control (RRC) connection state to the serving gNB. Summary of the Invention

[0006] A method, apparatus, and computer program product are provided for managing sidelink-based relays, i.e., utilizing a relay device in communication between two other devices (e.g., between a remote user equipment (UE) and a network node or between two remote user equipments) to transmit data via the relay device (e.g., a relay user equipment).

[0007] The scope of protection sought by the various embodiments of the present invention is set forth in the independent claims. Embodiments, examples, and features (if any) described in this specification that do not fall within the scope of the independent claims are to be interpreted as examples useful for understanding the various embodiments of the invention.

[0008] The subject matter of the independent claims is provided according to several aspects. Additional aspects are defined in the dependent claims. Embodiments not falling within the scope of the claims are to be interpreted as examples useful for understanding this disclosure.

[0009] According to a first aspect, a relay user equipment is provided for user equipment-to-user equipment relay communication, comprising components for: Determine whether the sending user equipment in the user equipment-to-user equipment relay communication is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the sending user equipment. Based on the determination, at least one control message is generated to indicate the determination result to the sending user equipment; Send at least one control message to the sending user equipment.

[0010] According to the second aspect, a method for user equipment-to-user equipment relay communication is provided, comprising: The relay user equipment determines whether the sending user equipment is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the sending user equipment. Based on the determination, the relay user equipment generates at least one control message to indicate the determination result to the transmitting user equipment; and The relay user equipment sends at least one control message to the transmitting user equipment.

[0011] According to a third aspect, a relay user equipment is provided, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured, together with the at least one processor, to cause the relay user equipment to perform the following for user equipment-to-user equipment relay communication: Determine whether the sending user equipment in the user equipment-to-user equipment relay communication is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the sending user equipment. Based on the determination, at least one control message is generated to indicate the determination result to the transmitting user equipment; and Send at least one control message to the sending user equipment.

[0012] According to the fourth aspect, a computer program product including computer-readable program code is provided, the computer-readable program code being configured, together with at least one processor, to cause a relay user equipment to perform at least the following for user equipment-to-user equipment relay communication: Determine whether the sending user equipment in the user equipment-to-user equipment relay communication is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the sending user equipment. Based on the determination, at least one control message is generated to indicate the determination result to the transmitting user equipment; and Send at least one control message to the sending user equipment.

[0013] According to a fifth aspect, a transmitting user equipment is provided for user equipment-to-user equipment relay communication, comprising components for: A relay user equipment (SUE) receiving at least one control message from a user equipment for user equipment-to-user equipment relay communication indicates whether the transmitting user equipment is permitted to request the relay SUE to establish at least one relay channel on the communication link for user equipment-to-user equipment relay communication, the communication link being between the relay SUE and the transmitting user equipment; and Based on the control message, determine whether to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication.

[0014] According to the sixth aspect, a method for user equipment-to-user equipment relay communication is provided, comprising: A transmitting user equipment (User Equipment) for User Equipment-to-User Equipment (User Equipment) relay communication receives at least one control message from a relay user equipment (Retrieval User Equipment). The control message indicates whether the transmitting User Equipment is permitted to request the Retrieval User Equipment to establish at least one relay channel on the communication link for User Equipment-to-User Equipment (User Equipment) relay communication between the Retrieval User Equipment and the transmitting User Equipment. Based on the control message, determine whether to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication.

[0015] According to a seventh aspect, a transmitting user equipment is provided, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code being configured, together with the at least one processor, to enable the transmitting user equipment to: A relay user equipment (SUE) receiving at least one control message from a user equipment for user equipment-to-user equipment relay communication indicates whether the transmitting user equipment is permitted to request the relay SUE to establish at least one relay channel on the communication link for user equipment-to-user equipment relay communication, the communication link being between the relay SUE and the transmitting user equipment; and The control message determines whether to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication.

[0016] According to the eighth aspect, a computer program product including computer-readable program code is provided, the computer-readable program code being configured, together with at least one processor, to cause a transmitting user equipment to perform at least the following: A relay user equipment (SUE) receiving at least one control message from a user equipment for user equipment-to-user equipment relay communication indicates whether the transmitting user equipment is permitted to request the relay SUE to establish at least one relay channel on the communication link for user equipment-to-user equipment relay communication, the communication link being between the relay SUE and the transmitting user equipment; and Based on the control message, determine whether to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication. Attached Figure Description

[0017] To gain a more complete understanding of exemplary embodiments of the present invention, reference is now made to the following description taken in conjunction with the accompanying drawings, in which: Figure 1 A portion of an exemplary wireless communication access network according to at least some embodiments of the present invention is shown; Figure 2a Examples of communication configurations that can implement some of the embodiments are shown; Figure 2b Another example of a communication configuration that can implement some of the embodiments is shown; Figure 3a The user plane protocol stack for Layer 2 UE-to-UE relay is described according to a certain method; Figure 3b The control plane protocol stack for Layer 2 UE-to-UE relay is described according to a certain method; Figure 4 A signaling diagram depicting the process of configuring the maximum number of SL trunk RLC channels from a U2U trunk UE to a Tx-end UE according to a certain method; Figure 5a A flowchart of a method according to an embodiment is depicted; Figure 5b A flowchart depicts a method for relaying user equipment; Figure 5c A flowchart depicts a method for transmitting data from a user equipment; and Figure 6 An apparatus according to an embodiment is shown. Detailed Implementation

[0018] The following embodiments are exemplary. Although the specification may refer to "a," "an," or "some" (or more) embodiments in several places, this does not necessarily mean that each such reference refers to the same (or more) embodiments, or that the feature applies only to a single embodiment. Individual features of different embodiments may also be combined to provide other embodiments.

[0019] A wireless device can be a device configured to communicate over radio waves via a wireless radio link (i.e., a wireless link). Communication can include user traffic and / or signaling. User traffic can include data, voice, video, and / or audio. Examples of wireless links include point-to-point wireless links and point-to-multipoint wireless links. A wireless link can be provided between two wireless devices. It should be understood that wireless devices can vary. For example, wireless devices connected via a wireless link can include one or more of user equipment (UE), access nodes, access points, relay nodes, user terminals, and Internet of Things (IoT) devices.

[0020] The radio equipment can be a radio access device configured to serve multiple other radio devices (e.g., user radio devices) and provide radio access to the communication system for the user radio devices. The radio equipment can also be a radio station that acts as a relay node or provides wireless backhaul for one or more radio access nodes. Examples of radio access devices include at least access nodes, access points, base stations, and (e / g) NodeBs. Examples of user radio devices include at least user terminals and user equipment (UEs). The radio equipment can be airborne radio equipment and / or non-terrestrial radio equipment configured to operate above the ground without being fixed at a specific altitude. Examples of non-terrestrial radio equipment include at least satellites and spacecraft configured to conduct radio communications in a communication system that includes both terrestrial and non-terrestrial radio equipment. Examples of airborne radio equipment include at least High Altitude Platform Stations (HAPS) and Unmanned Aerial Vehicles (UAVs) (such as drones). The radio access device can have one or more cells to which user radio devices can connect to access the services of the communication system via the radio access device. Cells can include cells of different sizes, such as macrocells, microcells, picocells, and femtocells. A macrocell can be a cell configured to provide coverage over a large coverage area within the service area of ​​a communication system (e.g., in a rural area or along a highway). A microcell can be a cell configured to provide coverage over a smaller coverage area than a macrocell, such as in a densely populated urban area. A picocell can be a cell configured to provide coverage over an area smaller than a microcell, such as in a large office, shopping mall, or train station. A femtocell can be a cell configured to provide coverage over an area smaller than a picocell, such as in a home or small office. For example, a macrocell provides coverage for user radio equipment passing through a city on a highway / road, and a local cell (e.g., a microcell or smaller) provides coverage for user radio equipment within the city. In another example, a macrocell provides coverage for airborne and / or non-terrestrial radio equipment, and a local cell (e.g., a microcell or smaller) provides coverage for airborne and / or non-terrestrial radio equipment located at an elevated position relative to one or more radio access devices of the communication system. Therefore, airborne or non-ground radio equipment can connect to the microcell of the radio access equipment, and when the airborne or non-ground radio equipment is above a certain altitude, it can switch to a macrocell, for example, through a handover process.

[0021] Figure 1An example of a simplified system architecture is depicted, showing only a few components and functional entities. All components and functional entities are logical units, and their implementation may differ from that shown. Figure 1 The connections shown are logical connections; the actual physical connections may differ. It will be apparent to those skilled in the art that the system typically includes, in addition to... Figure 1 Other functions and structures besides those shown.

[0022] Figure 1 The example illustrates a portion of an exemplary radio access network.

[0023] Figure 1 User equipment 100 and 102 are illustrated, configured to wirelessly connect to an access node (e.g., (e / g)NodeB) 104 providing the cell on one or more communication channels within a cell. The physical link from the user equipment to the (e / g)NodeB is referred to as an uplink or reverse link, and the physical link from the (e / g)NodeB to the user equipment is referred to as a downlink or forward link. It should be understood that the (e / g)NodeB, or its functionality, can be implemented using any entity suitable for this purpose, such as a node, host, server, or access point. The access node provides access via radio frequency (RF) signal communication and may be referred to as a radio access node. It should be understood that a radio access network may include more than one access node, thereby enabling the handover of a user equipment's wireless connection from one cell of an access node (e.g., the source cell of the source access node) to another cell of another node (e.g., the target cell of the target access node).

[0024] A communication system typically includes more than one (e / g)NodeB. In this case, the (e / g)NodeBs can also be configured to communicate with each other via wired or wireless links designed for this purpose. These links can be used for signaling purposes. The (e / g)NodeB is a computing device configured to control the radio resources of the communication system to which it is connected. A NodeB can also be referred to as a base station, access point, or any other type of interface device, including relay stations capable of operating in a wireless environment. The (e / g)NodeB includes or is connected to a transceiver. From the transceiver of the (e / g)NodeB, a connection is provided to the antenna element that establishes a bidirectional radio link to the user equipment. The antenna element may include multiple antennas or antenna elements. The (e / g)NodeB is also connected to the core network 110 (CN, or next-generation core NGC). Depending on the system, the CN-side counterpart may be a serving gateway (S-GW for routing and forwarding user data packets), a packet data network gateway (P-GW) for providing connectivity between (multiple) user equipment (UEs) and external packet data networks, or a mobility management entity (MME), etc.

[0025] User equipment (also known as UE, user equipment, user terminal, terminal equipment, wireless equipment, communication equipment, etc.) exemplifies a type of apparatus to which resources on the air interface are allocated and assigned, and thus any features described herein with respect to user equipment can be implemented by a corresponding apparatus (such as a relay node). An example of such a relay node is a Layer 3 relay (self-backhaul relay) toward a base station.

[0026] User equipment (UE) generally refers to a portable computing device that includes wireless mobile communication devices with or without a Subscriber Identity Module (SIM), including but not limited to the following types of devices: mobile stations (mobile phones), smartphones, personal digital assistants (PDAs), cell phones, devices using wireless modems (such as alarm or measuring devices), laptop and / or touchscreen computers, tablet computers, game consoles, laptop computers, vehicle equipment, UEs installed in vehicles, and multimedia devices. It should be understood that UE can also be a virtually exclusive uplink-only device, examples of which include cameras or camcorders that load images or video clips onto a network. UE can also be a device capable of operating in an Internet of Things (IoT) network, a scenario in which the ability to transmit data over a network to objects is provided without human-to-human or human-to-computer interaction is required. UE can also utilize the cloud. In some applications, UE may include a small portable device with radio components (such as a watch, earphones, or glasses), and computation is performed in the cloud. UE (or, in some embodiments, a Layer 3 relay node) is configured to perform one or more UE functions. User equipment can also be referred to as subscriber unit, mobile station, remote terminal, access terminal, user terminal, or user equipment (UE). Only some of these names or devices are mentioned here.

[0027] The various techniques described in this article can also be applied to cyber-physical systems (CPS) (systems that control collaborative computing elements of physical entities). CPS can enable the implementation and utilization of a large number of interconnected ICT devices (sensors, actuators, processors, microcontrollers, etc.) embedded in physical objects in different locations. Mobile cyber-physical systems, which are inherently mobile physical systems, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robots and electronic devices transported by humans or animals.

[0028] Furthermore, although the device has been described as a single entity, different units, processors, and / or memory units can be implemented. Figure 1 (Not all are shown in the image).

[0029] 5G enables the use of multiple-input multiple-output (MIMO) antennas, more base stations or nodes than LTE (the so-called small cell concept), macro sites that cooperate with smaller stations, and a variety of radio technologies depending on service requirements, use cases, and / or available spectrum. 5G mobile communications support a wide range of use cases and related applications, including video streaming, augmented reality, different data sharing methods, and various forms of machine-type applications (e.g., massive machine-type communications (mMTC), including vehicle safety, various sensors, and real-time control). 5G is expected to have multiple radio interfaces: sub-6GHz, cmWave, and mmWave, and will also be able to integrate with existing legacy radio access technologies such as LTE. Integration with LTE (at least initially) can be implemented as a system where macro coverage is provided by LTE, and 5G radio interface access is obtained from small cells via aggregation to LTE. In other words, 5G is planned to support inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as sub-6GHz-cmWave and sub-6GHz-cmWave-mmWave). One of the concepts believed to be used in 5G networks is network slicing, in which multiple independent and dedicated virtual sub-networks (network instances) can be created within the same infrastructure to run services with different requirements for latency, reliability, throughput, and mobility.

[0030] The current architecture in LTE networks is entirely distributed across radios and entirely centralized in the core network. Low-latency applications and services in 5G require bringing content closer to the radio, leading to local outages and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the data source. This approach requires leveraging resources that may be discontinuously connected to the network, such as laptops, smartphones, tablets, and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content near cellular subscribers for faster response times. Edge computing encompasses a wide range of technologies, such as wireless sensor networks, mobile data acquisition, mobile signature analytics, collaborative distributed peer-to-peer self-organizing networking and processing, and can also be categorized as local cloud / fog computing as well as grid / raster computing, dew computing, mobile edge computing, micro-cloud, distributed data storage and retrieval, autonomous self-healing networks, remote cloud services, augmented and virtual reality, data caching, the Internet of Things (IoT) (massive connectivity and / or latency critical), and critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0031] The communication system can also communicate with other networks, such as the public switched telephone network or the Internet, or utilize services provided by them. The communication network may also be able to support the use of cloud services; for example, at least a portion of the core network operation can be performed as a cloud service (this is in...). Figure 1 (Depicted in “Cloud” 114). Communication systems may also include a central control entity, operations and maintenance manager, or similar entities that provide facilities for collaboration between networks of different operators (e.g., in spectrum sharing).

[0032] Edge cloud can be introduced into the radio access network (RAN) by leveraging Network Functions Virtualization (NFV) and Software-Defined Networking (SDN). Using edge cloud means that access node operations are performed, at least partially, in servers, hosts, or nodes operationally connected to a remote radio head or base station, including the radio portion. Node operations can also be distributed across multiple servers, nodes, or hosts. The application of a cloud RAN architecture enables the execution of real-time RAN functions on the RAN side (in the distributed unit DU104) and non-real-time functions in a centralized manner (in the centralized unit CU 108).

[0033] It should also be understood that the division of labor between core network operations and base station operations may differ from, or even not exist in, LTE. Other technological advancements that can be used include big data and all-IP, which can change how networks are built and managed. 5G (or New Radio, NR) networks are designed to support multiple tiers, where MEC servers can be placed between the core and base stations or NodeBs (gNBs). It should be understood that MEC can also be applied to 4G networks.

[0034] 5G can also leverage satellite communications to enhance or supplement 5G service coverage, for example, by providing backhaul. Possible use cases include providing service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on transportation, or ensuring service availability for critical communications and future rail / sea / air communications. Satellite communications can utilize geostationary Earth orbit (GEO) satellite systems, but can also utilize low Earth orbit (LEO) satellite systems, particularly mega-constellations (systems deploying hundreds of (nano) satellites). Each satellite 106 in a mega-constellation can cover several network entities supporting the satellites, which create ground cells. Ground cells can be created via ground relay nodes 104 or by gNBs located on the ground or within satellites.

[0035] It will be apparent to those skilled in the art that the depicted system is merely an example of a portion of a radio access system, and in practice, the system may include multiple (e / g)NodeBs, user equipment may access multiple radio cells, and the system may also include other devices such as physical layer relay nodes or other network elements. At least one of the (e / g)NodeBs may be a home (e / g)NodeB. Furthermore, multiple different types of radio cells and multiple radio cells may be provided within the geographical area of ​​the radio communication system. Radio cells may be macrocells (or umbrella cells) that are large cells typically with diameters of up to tens of kilometers, or smaller cells such as microcells, femtocells, or picocells. Figure 1 The (e / g)NodeB can provide any type of these cells. Cellular radio systems can be implemented as multi-layer networks comprising several types of cells. Typically, in a multi-layer network, one access node provides one or more types of cells, thus requiring multiple (e / g)NodeBs to provide this network structure.

[0036] To meet the needs of improved communication system deployment and performance, the concept of "plug-and-play" (e / g) NodeBs has been introduced. Typically, in addition to home (e / g) NodeBs (H(e / g) NodeBs), networks capable of using "plug-and-play" (e / g) NodeBs also include home NodeB gateways or HNB-GWs ( Figure 1 (Not shown in the image). HNB gateways (HNB-GWs), typically installed within a carrier's network, can aggregate traffic from a large number of HNBs and send it back to the core network.

[0037] However, the embodiments are not limited to the system given as an example, and those skilled in the art can apply the solution to other communication systems that provide the desired properties.

[0038] The nature of a sidelink (SL) is directional based on the sending user equipment (Tx UE), where the receiving user equipment (Rx UE) may need to continuously monitor all possible PSCCH (Physical Sidelink Control Channel) instances to receive sidelink transmissions on one or more pre-configured resource pools (RPs). At least two allocation modes exist for sidelink transmissions. The first mode (Mode 1) is a base station (BS) scheduling mode, where the serving base station allocates resources for sidelink transmissions to the user equipment, and the second mode (Mode 2) is an autonomous UE selection mode, where the user equipment can select resources for sidelink transmissions without base station intervention. These modes are indistinguishable from receiving Rx UEs in terms of receiving sidelinks, regardless of whether the sidelink is used for broadcast, multicast, or unicast. Sidelinks can be applied in both in-coverage and out-of-coverage scenarios and provide support for multiple PLMNs (Tx UEs and Rx UEs from different serving PLMNs).

[0039] Figure 2a An example of communication established according to a certain method is shown. Figure 2a In the example, there is a base station 200, which can operate as an access point for user equipment 204, 206, and 208 to access the communication network 202. User equipment 204, 206, and 208 have wireless communication capabilities with other user equipment and / or base stations. For example, in... Figure 2a In this setup, one user equipment 204 acts as a relay between some other user equipments 206, 208 and base station 200. However, some of user equipments 204, 206, 208 can also have direct communication connections with each other without any relay user equipment or base station. Figure 2a In the example, the second user equipment 206 and the third user equipment 208 communicate with each other, while the first user equipment 204 communicates with the base station 200, the second user equipment 206 and the third user equipment 208.

[0040] For example, user equipment that has a direct connection to each other can use a side link connection 210.

[0041] exist Figure 2aIn the diagram, User Equipment 204 communicates with Base Station 200 using both downlink (DL) and uplink (UL), while User Equipment 206 communicates with Base Station 200 using only the downlink (DL), meaning it only receives signals from Base Station 200 and communicates with the other two User Equipments 204 and 208 via a sidelink. User Equipment 208 communicates with User Equipments 204 and 206 only via a sidelink. However, User Equipment 204, which can communicate with Base Station 200, can forward messages from other User Equipments 206 and 208 to Base Station 200, and vice versa. Therefore, User Equipment 204 operates as a relay UE between the other (multiple) User Equipments 206 and 208 and Base Station 200.

[0042] In the following text, see references Figure 3a and Figure 3b The protocol stack presented here serves as an example of a Layer 2 UE-to-UE relay architecture. Figure 3a The user plane (UP) protocol stack for Layer 2 UE-to-UE relay according to a certain method is described, and Figure 3b The control plane (CP) protocol stack for Layer 2 UE-to-UE relay is described according to a certain method.

[0043] For the L2 UE-to-UE relay architecture, the protocol stack is similar to that of L2 UE-to-network relay, except that the termination points are two remote UEs. At the two PC5 interfaces, the Sidelink Relay Adaptation Protocol (SRAP) sublayer sits above the RLC sublayer for both CP and UP. The Sidelink Serving Data Adaptation Protocol (SDAP), Packet Data Convergence Protocol (PDCP), and Radio Resource Control (RRC) layers terminate between the two L2 U2U remote UEs, while SRAP, Radio Link Control (RLC), Media Access Control (MAC), and Physical Layer (PHY) terminate in each PC5 link, between the L2 U2U remote UE and the L2 U2U relay UE. The U2U remote UE is also referred to as the terminal UE. PC5 stands for Direct Radio Interface on SL in the 3GPP standard.

[0044] For L2 UE-to-UE relay, the SRAP sublayer in both the L2 U2U remote UE and the L2 U2U relay UE performs bearer mapping to map the end-to-end SL bearers (SRB, DRB) of the L2 U2U remote UE to the PC5 U2U relay RLC channel. The PC5 SRAP sublayer in both the L2 U2U relay UE and the L2 U2U remote UE supports L2 U2U remote UE identification for sidelink traffic from the source L2 U2U remote UE to the destination L2 U2U remote UE.

[0045] The identifier of the L2 U2U remote UE end-to-end bearer and the remote UE ID contained in the SRAP header support the following arrangements: associating received packets with the RLC channel of the L2 U2U relay UE, associating transmitted packets with the PDCP entity associated with the end-to-end radio bearer and the destination L2 U2U remote UE ID, and associating received packets with the PDCP entity associated with the end-to-end radio bearer and the source L2 U2U remote UE ID.

[0046] The PC5 SRAP sublayer at the L2 U2U remote UE supports identification of the destination L2 U2U remote UE. The ID that can be mapped to the destination L2 U2U remote UE is included in the SRAP header of traffic from the source L2 U2U remote UE to the L2 U2U relay. The PC5 SRAP sublayer at the L2 U2U relay UE supports identification of the source L2 U2U remote UE. The ID that can be mapped to the source L2 U2U remote UE is included in the SRAP header of traffic from the L2 U2U relay UE to the destination L2 U2U remote UE.

[0047] For different end-to-end bearers, the SRAP sublayer at the L2 U2U relay UE can perform data multiplexing from multiple RLC channels of different source L2 U2U remote UEs to the same RLC channel of different destination L2 U2U remote UEs. For different end-to-end bearers, the SRAP sublayer at the L2 U2U relay UE can perform data demultiplexing from the same RLC channel of the source L2 U2U remote UE to multiple RLC channels of different destination L2 U2U remote UEs.

[0048] It should be noted that in the above description and the remainder of this specification, the remote UE is referred to as the terminal UE, source UE, target UE, Tx UE, or Rx UE.

[0049] In direct SL communication between the source UE or Tx UE and the destination UE or Rx UE, when the Tx UE is in RRC IDLE / INACTIVE or out-of-coverage state, the Tx UE is responsible for initiating and configuring the establishment of the SL logical channel (LC) for the SL SRB or SL DRB between the Tx UE and the Rx UE. Alternatively, when the Tx UE is in RRC connected state, the serving gNB of the Tx UE is responsible for initiating and configuring the establishment of the SL logical channel (LC) for the SL SRB or SL DRB between the Tx UE and the Rx UE. There is a 1:1 mapping between the SL logical channel and the SL radio bearer (RB), which can be either an SL SRB or an SL DRB.

[0050] U2U relay is used to extend SL coverage between a source UE and a target UE. When bidirectional communication exists between a source UE and a target UE via a U2U relay UE, either the source UE or the target UE can act as a Tx UE. For an end-to-end (E2E) SL RB between a Tx UE and an Rx UE, the Tx UE is the first-hop Tx UE between the Tx UE and the U2U relay UE, also known as the ingress hop of the U2U relay UE; the U2U relay UE is the second-hop Tx UE between the U2U relay UE and the Rx UE, also known as the egress hop of the U2U relay UE. An SL relay RLC channel is introduced to carry the E2E SL RB for SL relay connections on the first and second hops. The SL relay RLC channel allows either the Tx UE or the U2U relay UE to multiplex the E2E SL RB into a single SL relay RLC channel on the corresponding hop. Therefore, a one-to-many mapping can exist between the SL relay RLC channel and (multiple) E2E SL RBs. It should be noted that in multi-hop U2U relay, the intermediate hop is between two adjacent U2U relay UEs, so the Tx UE of the intermediate hop is a U2U relay UE, and the exit hop of the U2U relay UE on the intermediate hop is considered to be the entry hop of its adjacent U2U relay UE.

[0051] Figure 2b Examples of communication settings in which some embodiments can be implemented are shown. For example, in Figure 2b In the setup, a user equipment 204 acts as a relay between one or more other user equipments 206, 208, and 212.

[0052] exist Figure 2b In the illustration, user equipment 204 acts as a component in two or more other UEs (such as...). Figure 2b The U2U relay UE provides a communication connection between user equipment 206, 208, and 212. Figure 2b In the exemplary illustration, these user equipments 206, 208 and 212 are labeled as terminal UE1, terminal UE2 and terminal UE3, respectively.

[0053] According to an embodiment, U2U relay UE 204 can configure the first-hop Tx-end UE (which can be the source UE or the target UE in bidirectional E2E communication) to have a maximum number of SL relay RLC channels. The Tx-end UE can be allowed to perform E2E RB transmissions to the U2U relay UE on the first hop. For example, the first-hop Tx-end UE can be terminal UE1206, which can also be referred to as the source UE, where the first hop is between terminal UE1206 and U2U relay UE 204. Terminal UE2208 and / or terminal UE3212 can be Rx-end UEs, which can also be referred to as the target UE. In one example, where both unacknowledged mode (UM) and acknowledged mode (AM) are supported on the SL, the maximum number of SL relay RLC channels can include a first maximum number of UM SL relay RLC channels and a second maximum number of AM SL relay RLC channels. In another example, the maximum number of SL Relay RLC channels may include a first maximum number of SL Relay RLC channels for SRBs in the control plane and a second maximum number of SL Relay RLC channels for DBRs in the user plane. In yet another example, the maximum number of SL Relay RLC channels may be configured jointly for both the control plane and the user plane. This configuration may be based on the SL RRC reconfiguration process.

[0054] According to the embodiment, the Tx-end UE 206 determines how many fewer SL Relay RLC channels than the maximum number of configured SL Relay RLC channels should be established for the first hop, and how to map E2ERBs on the established SL Relay RLC channels. The E2E RBs from the Tx-end UE 206 can be for different Rx-end UEs 208 and 212, because the Tx-end UE 206 can establish different E2E connections with different Rx-end UEs 208 and 212 via the same U2U Relay UE 204.

[0055] According to an embodiment, the U2U relay UE 204 can reconfigure (increase or decrease) the maximum number of allowed SL relay RLC channels during the lifetime of the relay connection. For example, when the U2U relay UE 204 begins to act as a relay for an additional relay connection, it may be necessary to reduce the maximum number of SL relay RLC channels that a single Tx-end UE 206 can use. The U2U relay UE 204 can decide to increase or decrease the maximum number of SL relay RLC channels based on factors such as load and available battery capacity.

[0056] According to an embodiment, if the U2U relay UE 204 has not configured the maximum number of allowed SL relay RLC channels to the Tx-end UE 206, then if, for example, a first request from the Tx-end UE 206 to the U2U relay UE 204 to establish an additional SL relay RLC channel for a new E2E RB is rejected by the U2U relay UE 204, then the Tx-end UE 206 may perform one of the following options: - The Tx-end UE 206 may receive an indication from the U2U relay UE 204, as well as a rejection of the Tx-end UE 206 being denied permission to request an additional SL relay RLC channel for a specified time interval, which begins when the indication is sent at the U2U relay UE 204 or received at the Tx-end UE 206, or until further notification from the U2U relay UE 204; -Tx-end UE 206 can map the new E2E RB to one of the existing (multiple) RLC channels and indicate this to U2U relay UE 204; or -Tx-side UE 206 may initiate a second request to U2U relay UE 204 to reconfigure one of the selected existing SL relay RLC channels to accommodate the new E2E RB or map it to the selected SL relay RLC channel. If the second request is also rejected, the new E2E RB is released by Tx-side UE 206, and at Tx-side UE 206, the AS layer may indicate to the NAS layer that the corresponding QoS flow is temporarily unavailable.

[0057] In the example above, U2U relay UE 204 rejects Tx-end UE 206's request for an additional SL relay RLC channel and sends a rejection message to Tx-end UE 206 indicating that Tx-end UE 206 is not allowed to request an additional SL relay RLC channel. This is to prevent Tx-end UE 206 from re-initiating the request when U2U relay UE 204 cannot accept it, thus wasting resources. Typically, the U2U relay UE can determine and send an indication to the Tx UE whether it is allowed to request an additional SL relay RLC channel during or after the establishment of at least one SL relay RLC channel for the Tx UE on the ingress hop or communication link between the Tx UE and the U2U relay UE.

[0058] According to the embodiment, considering that the Tx-end UE 206 or U2U relay UE 204 can be in an RRC connected state and use mode 1 resource allocation, when using mode 1, the Tx-end UE 206 or U2U relay UE 204 can send data to the serving gNB 200 ( Figure 2aThis indicates, for example, the maximum number of allowed SL trunk RLC channels and / or whether the Tx-end UE 206 is allowed to request the establishment of additional SL trunk RLC channels. The Tx-end UE 206 may also indicate to the serving gNB 200 that a new E2E RB should be mapped to the selected SL trunk RLC channel due to a rejection of the first request or a positive result for the second request. If the Tx-end UE 206 or U2U trunk UE 204 is not allowed to have a separate SL trunk RLC channel for the identified E2E RB, the Tx-end UE 206 or U2U trunk UE 204 can be configured by the serving gNB to perform SL buffer status reports (SL-BSR) on an E2E RB-by-E2E RB basis for one or more identified E2E RBs of the Tx-end UE 206. In this case, the configuration of the Logical Channel Group (LCG) mapping for the identified E2E RBs from the gNB can be explicit or implicit. The latter, based on the priority of the E2E RB and the priorities of the SL trunk RLC channel carrying the E2E RB and the corresponding LC, applies an E2ERB-based SL BRS for E2E RBs whose priority is higher than the LC priority of the SL trunk RLC channel carrying the E2E RB. The effect is a new UE behavior for SL BSR: if multiple E2E RBs with different priorities are mapped to the same SL trunk RLC channel, the UE is allowed to use different LCGs to report the SL BSR or one-to-one corresponding LC for the same SL trunk RLC channel. For example, for all existing E2E RBs mapped to an SL trunk RLC channel, the LC one-to-one with the existing SL trunk RLC channel is configured with LCG1. Then, when a new E2E RB with an LCG2 configured with a priority higher than LCG1 is added to the same SL trunk RLC channel, the buffer size of the LC is reported based on the buffer sizes of LCG1 and LCG2, and these are distinguished.

[0059] In the following text, reference is made to the embodiments. Figure 4 Explain the signaling procedure for configuring the maximum number of SL trunk RLC channels for U2U trunk UE 204 to Tx terminal UE 206.

[0060] It can be assumed that a U2U trunk connection has already been established between the source UE and the destination UE via U2U trunk UE 204. Therefore, Figure 4 Step 401 described in the text may have been performed in a previous stage, or just before the U2U relay UE 204 decides to determine, for example, the maximum number of SL relay RL channels.

[0061] The U2U relay UE determines the maximum number of 402 SL relay RLC channels. This can be left to the UE to decide how to implement specifically; however, the U2U relay UE 204 can consider one or more of the following options. One option is that the U2U relay UE 204 considers the number of E2E RBs and their QoS requirements when communicating with the Tx-end UE 206. The U2U relay UE 204 can also consider the type of service provided by the U2U relay UE 204 (e.g., based on the relay service code) and / or the number of E2E connections made by the Tx-end UE 206 to different Rx-end UEs 208, 212 via the U2U relay UE 204. Another option is that the U2U relay UE 204 considers the total number of remaining SL relay RLC channels that can be allocated to the different Tx-end UEs 206 that the U2U relay UE 204 is serving. This can be considered as the SL relay RLC channel capacity of the U2U relay UE 204. According to an embodiment, a fixed number of U2U relay UEs 204 can be used, which is higher than the minimum constraint required for the maximum number of SL relay RLC channels to be configured for each Tx-end UE 206, regardless of how many E2E RBs and their QoS requirements the Tx-end UE 206 has, and / or how many E2E connections the Tx-end UE 206 has made with different Rx-end UEs 208, 212 via the U2U relay UE 204. An option also includes that the U2U relay UE 204 takes into account the resource allocation mode (mode 1 or mode 2) being used by the Tx-end UE 206 and / or the serving PLMN ID or cell ID of the Tx-end UE 206, taking into account inter-carrier policies or rules.

[0062] U2U relay UE 204 can configure the maximum number of SL relay RLC channels to Tx-end UE 206, for example, by sending at least one SL-RRC reconfiguration message (403) to Tx-end UE 206. The SL-RRC reconfiguration message can be a control message as used herein or an example of at least one control message. This may occur, for example, once a unicast SL connection is established between U2U relay UE 204 and Tx-end UE 206, or when the first E2E RB is established between Tx-end UE 206 and Rx-end UEs 208, 212. The maximum number of SL relay RLC channels and, for example, the local ID allocation, can be configured when U2U relay UE 204 assigns a local ID to Tx-end UE 206 for SRAP operation.

[0063] U2U relay UE 204 can also configure the maximum number of SL relay RLC channels to (multiple) other UEs 208 and 212, for example, by sending the SL-RRC reconfiguration message corresponding to 404 to (multiple) other UEs 208 and 212, because (multiple) other UEs 208 and 212 can also be Tx UEs in bidirectional communication, and also Rx UEs of Tx UE 206.

[0064] If needed, U2U relay UE 204 can reconfigure the maximum number of SL relay RLC channels to Tx-end UE 206. In one example, reconfiguration may depend on the addition or release of E2E RBs based on their QoS requirements. Note that Tx-end UE 206 may need to communicate with U2U relay UE 204 to perform QoS processing on each E2E RB that Tx-end UE 206 has, because the QoS segmentation of at least the packet delay budget for the first-hop and second-hop E2E RBs can be controlled by U2U relay UE 204. In another example, reconfiguration may depend on the addition or release of E2E connections between the same Tx-end UE 206 and Rx-end UEs 208, 212 via the same U2U relay UE 204. In this case, the maximum number of SL relay RLC channels can be (re)configured for each E2E connection, or for all E2E connections made by Tx UE 206 via U2U relay UE 204 to different Rx UEs 208 and 212.

[0065] The SL RRC reconfiguration process can be used to reconfigure the maximum number of SL relay RLC channels to the Tx-end UE 206 (re)configuration, but is not limited to this.

[0066] The Tx-side UE 206 determines whether an additional SL trunk RLC channel needs to be established for the additional E2ERB and U2U trunk UE 204 based on QoS requirements and available SL trunk RLC channels. For example, if the maximum number of SL trunk RLC channels has been reached, the Tx-side UE 206 will map the additional E2ERB to one of the existing SL trunk RLC channels.

[0067] To support multi-hop U2U relay, the maximum number of SL relay RLC channels can be (re)configured hop-by-hop, or that is, configured by a U2U relay UE 204 acting as an exit hop for a Tx-end UE from U2U relay UE 204 to Tx-end UE 206, or by another U2U relay UE acting as an ingress hop for a Tx-end UE to U2U relay UE 204.

[0068] Figure 5aA flowchart illustrating a method according to an embodiment is provided. A 502 U2U relay connection is established between a source UE 206 and one or more target UEs 208, 212 via a U2U relay UE for bidirectional communication. It should be noted that, from the perspective of communication toward the target UEs 208, 212, the source UE 206 may be a Tx-end UE, where the target UEs 208, 212 are Rx-end UEs. Correspondingly, from the perspective of communication from the target UEs 208, 212 to the source UE 206, the target UEs 208, 212 are Tx-end UEs, and the source UE 206 is an Rx-end UE.

[0069] In step 504, the U2U relay UE 204 determines and (re)configures the maximum number of SL relay RLC channels that the Tx-end UE is allowed to establish and use toward the U2U relay UE on the first hop.

[0070] In step 506, U2U relay UE 204 sends SL-RRC reconfiguration messages to (multiple) Rx-end UEs 208 and 212. The SL-RRC reconfiguration message indicates the maximum number of SL relay RLC channels determined by U2U relay UE 204 for bidirectional relay-side link communication between source UE 206 and target UEs 208 and 212.

[0071] Figure 5b A flowchart illustrating a method for a relay user equipment 204 according to an embodiment is provided. The relay user equipment 204 determines 512 whether a transmitting user equipment 206 is permitted to request the establishment of at least one relay channel on a communication link used for user equipment-to-user equipment relay communication between the relay user equipment and the transmitting user equipment. Based on this determination, the relay user equipment 204 generates 514 at least one control message to indicate the result of the determination to the transmitting user equipment 206, and sends 516 the at least one control message to the transmitting user equipment.

[0072] According to an embodiment, the relay channel is a side-link relay radio link control channel.

[0073] The determined result can indicate whether the transmitting user equipment 206 is permitted to request relay user equipment 204 to establish at least one relay channel on the communication link (e.g., the ingress hop of relay user equipment 204). In one example, the determined result could be that the transmitting user equipment 206 is permitted to request relay user equipment 204 to establish at least one relay channel on the communication link. Therefore, at least one control message can be generated such that it indicates the transmitting user equipment 206 is permitted to request relay user equipment 204 to establish at least one relay channel on the communication link. In another example, the determined result could be that the transmitting user equipment 206 is not permitted to request relay user equipment 204 to establish at least one relay channel on the communication link. Therefore, at least one control message can be generated such that it indicates the transmitting user equipment 206 is not permitted to request relay user equipment 204 to establish at least one relay channel on the communication link. In yet another example, the determined result could be that the transmitting user equipment 206 is permitted to request relay user equipment 204 to establish up to a maximum allowed number of relay channels on the communication link. Therefore, at least one control message can be generated, which indicates the maximum allowed number of relay channels that the sending user equipment 206 is permitted to request the relay user equipment 204 to establish on the communication link.

[0074] Figure 5c A flowchart illustrating a method for transmitting user equipment 206 according to an embodiment is provided. Transmitting user equipment 206 receives at least one control message 522 from relay user equipment 204. This control message indicates whether transmitting user equipment 206, for user equipment-to-user equipment relay communication, is permitted to request relay user equipment 204 to establish at least one relay channel on a communication link for user equipment-to-user equipment relay communication between relay user equipment 204 and transmitting user equipment 206. Then, based on the control message, transmitting user equipment 206 determines whether relay user equipment 204 requests relay user equipment 206 to establish at least one relay channel on the communication link for user equipment-to-user equipment relay communication. Based on this determination, transmitting user equipment 206 requests relay user equipment 204 to establish at least one relay channel on the communication link for user equipment-to-user equipment relay communication.

[0075] For example, transmitting user equipment 206 may determine to request relay user equipment 204 to establish at least one relay channel on the communication link based on at least one control message indicating that the transmitting user equipment is permitted to request the establishment of at least one relay channel. Additionally, if the request is permitted, transmitting user equipment 206 may use further information (e.g., information regarding the need to establish at least one relay channel) to determine whether it should request the establishment of at least one relay channel. In another example, transmitting user equipment 206 may determine not to request relay user equipment 204 to establish at least one relay channel on the communication link based on at least one control message indicating that the transmitting user equipment is not permitted to request the establishment of at least one relay channel.

[0076] In the case where a communication link for user equipment-to-user equipment relay communication has already been established, at least one relay channel can be referred to as at least one additional relay channel, because in this case, at least one relay channel may already exist in the communication link. Therefore, at least one control message can indicate whether the request to establish (multiple) additional relay channels for the communication link is permitted.

[0077] As described herein, in some embodiments, at least one control message may indicate the maximum number of relay channels(s) for a communication link (meaning the total maximum value for the communication link), or the maximum number of additional relay channels that can be requested to be established.

[0078] In embodiments, the maximum number of relay channels or additional relay channels can be indicated separately for the control plane and the user plane. Therefore, for example, two maximum numbers can be indicated, one indicating the maximum number of relay channels or additional relay channels for the control plane, and the other indicating the maximum number of relay channels or additional relay channels for the user plane. This approach can further enhance the flexibility of the solution.

[0079] In embodiments, the maximum number of relay channels or additional relay channels can be indicated jointly for both the control plane and the user plane. Therefore, only one maximum number can be indicated, which is the same quota for both the control plane and the user plane relay channels(s). Alternatively, the maximum number can indicate a separate quota of the same size for both the control plane and the user plane.

[0080] According to an embodiment, at least one control message indicates that the sending user equipment 206 is permitted to request the relay user equipment 204 to establish a maximum number of relay channels on a communication link used for user equipment-to-user equipment relay communication, or indicates the maximum number of relay channels on the communication link for both the user plane and the control plane.

[0081] According to an embodiment, at least one control message indicates that the transmitting user equipment 206 is permitted to request the relay user equipment to establish a maximum number of relay channels on a communication link used for user equipment-to-user equipment relay communication, or jointly indicates the maximum number of relay channels on the communication link for both the user plane and the control plane.

[0082] The above presents some examples of at least one such control message.

[0083] In an embodiment, the communication link used for user equipment to user equipment relay communication is referred to as the entry hop of the relay user equipment 204 for user equipment to user equipment relay communication.

[0084] In an embodiment, the communication link used for user equipment to user equipment relay communication is referred to as the entry hop of the relay user equipment 204 for user equipment to user equipment relay communication.

[0085] In the embodiments, in the case of single-hop relay, relay user equipment 204 is another transmitting user equipment for another communication link between the relay user equipment and Rx-end UE 206, 208, or 212; or in the case of multi-hop relay, relay user equipment 204 is another relay user equipment for user equipment-to-user equipment relay communication. The other communication link is referred to as the egress hop of relay user equipment 204 for user equipment-to-user equipment relay communication.

[0086] According to the embodiments, in order to maximize simplicity and scalability, for all end-to-end (E2E) SL radio bearers (RBs) between the transmitting UE (Tx end UE) and the receiving UE (Rx end UE) at each hop from one entity to another in a U2U relay, a single side link (SL) relay radio link control (RLC) channel can be used to provide Layer 2 (L2) user equipment to user equipment (U2U) relay.

[0087] Alternatively, if a clear distinction between control plane and user plane radio bearers is required, two SL relay RLC channels can be used, one for all E2E SL signaling radio bearers (SRB) and the other for all E2E SL data radio bearers (DRB).

[0088] The hop from the Tx-side UE to the next (second) entity can be called the first hop, the hop from the second entity to the next entity can be called the second hop, and so on.

[0089] According to an embodiment, for scheduling operations that maximize QoS differentiation in terms of quality of service (QoS) support between different E2E RBs, a one-to-one (1:1) mapping between E2E RBs and SL relay RLC channels may be preferred.

[0090] A U2U relay UE can provide multiple E2E connections for different pairs of source and destination UEs. However, there is a limitation on the total number of different SL relay RLC channels or SL non-relay RLC channels (commonly referred to as SL RLC channels) that a U2U relay UE can handle. This limitation stems from, for example, some hardware or software constraints. Note that, taking the case of U2U relaying via a single U2E relay UE as an example, to maintain unicast SL for the first and second hops of each E2E connection, it may be necessary to configure at least all the required SL SBRs for each hop, and these SL SBRs are mapped one-to-one with the SL non-relay RLC channels. Therefore, a significant portion of the total SL RLC channels of the U2U relay UE needs to be used to maintain unicast SL connections with each source and destination UE. The remaining portion of the total SL RLC channels can be (re)distributed to serve E2E SL RBs for different E2E connections.

[0091] Taking single-hop U2U relay as an example, since the U2U relay UE uses a unicast direct SL connection for each hop to serve both the Tx-end UE and the Rx-end UE, the U2U relay UE may need to have decision-making power over the content and manner of services it can provide to the source and destination UEs. Note that a U2U relay UE can serve more than one pair of Tx-end and Rx-end UEs, and has its own SL communication with other UEs. It should also be noted that current direct SL communication is Tx-oriented, meaning that the Tx UE can control its own SL transmissions when operating in autonomous resource allocation or (i.e.) Mode 2 in NR SL. Tx UE control includes establishing a non-relay RLC channel with the Rx UE for the unicast SL connection between them. If this control applies to the first hop in the U2U relay, the U2U relay UE may have to react to anything initiated by the Tx-end UE. This may be feasible because the U2U relay UE can reject reconfiguration initiated by the Tx-end UE. However, it is desirable to avoid faulty operations as much as possible to prevent wasting resources, especially when the U2U relay UE, as the responder, is fully aware of the potential for faulty operations.

[0092] When the Tx-end UE or U2U relay UE is in RRC connection state and uses NR SL mode 1 resource allocation for SL transmission, the serving gNB is responsible for configuring the SL relay RLC channel to the Tx-end UE or U2U relay UE.

[0093] For forward compatibility with multi-hop U2U relay support, hop-by-hop control is preferred. Therefore, 1:n (a pair of n, n∈Z) between the SL relay RLC channel and the SL RLC relay channel and the E2E SL RB should be avoided. + Centralized control of mapping. Furthermore, signaling overhead and the impact of standardization should be kept as low as possible.

[0094] According to the embodiments, the mechanism presented in this specification does not require configuration and control of the mapping between the E2E RB and the SL trunk RLC channel in L2 U2U trunking. Instead, the mapping is determined by the hop-based Tx UE based on any factors the UE implementation is willing to consider, such as QoS requirements, the maximum number of SL trunk RLC channels, etc. It is also a future proof, as multi-hop U2U trunking can implement this solution in a hop-by-hop manner.

[0095] Therefore, to avoid a situation where the Tx UE (i.e., the transmitting UE) continuously initiates requests to establish new SL trunk RLC channels while the U2U relay UE continuously rejects requests from the Tx UE, the U2U relay UE can control whether to allow the Tx UE to request the establishment of new SL trunk RLC channels. In one option, the U2U relay UE can pre-configure the maximum number of SL trunk RLC channels that the Tx UE can be allowed to establish. In another option, the U2U relay UE can indicate to the Tx UE immediately whether the Tx UE is allowed to request the establishment of new SL trunk RLC channels. For example, this indication can be sent along with an acceptance or initial rejection of the request from the Tx UE. Thus, for example, the provided solution improves communication efficiency because if not allowed, the Tx UE does not need to request the establishment of one or more trunk channels.

[0096] Figure 6 Examples of apparatuses according to at least some embodiments of the present invention are shown. The apparatus may be a wireless device, such as a user wireless device. The apparatus may perform one or more functions according to the examples described herein.

[0097] The device includes a processor 604 and a transceiver 606. The processor is operatively connected to the transceiver to control the transceiver. The device may include a memory 602. The memory may be operatively connected to the processor. It should be understood that the memory may be a separate memory or may be included in the processor and / or the transceiver.

[0098] According to an embodiment, the processor is configured to control the transceiver to perform one or more functions as described in the embodiment.

[0099] The memory can be a non-transitory computer-readable medium. The memory can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. As a non-limiting example, the data processor can be of any type suitable for the local technical environment and can include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture.

[0100] Implementations may be carried out in the form of software, hardware, application logic, or a combination of software, hardware, and application logic. The software, application logic, and / or hardware may reside on memory or any computer medium. In exemplary embodiments, the application logic, software, or instruction set is maintained on any of a variety of conventional computer-readable media. In the context of this document, "memory" or "computer-readable medium" can be any medium or apparatus capable of containing, storing, communicating, propagating, or transmitting instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0101] In relevant contexts, references to "computer-readable storage medium," "computer program product," "tangible computer program," or "processor" or "processing circuitry" should be understood to encompass not only computers with different architectures (such as single-processor / multi-processor architectures and sequential / parallel architectures) but also special-purpose circuits (such as field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), signal processing devices, and other devices). References to computer-readable program code devices, computer programs, computer instructions, computer code, etc., should be understood to express software (such as programmable content of hardware devices) used for programmable processor firmware as instructions for the processor, or as configured settings or configuration settings for fixed-function devices, gate arrays, programmable logic devices, etc. While the foregoing examples describe embodiments of the invention operating within a user radio equipment, UE, radio access equipment, or gNB, it should be understood that the invention described above can be implemented as part of any apparatus including circuitry for transmitting and / or receiving radio frequency signals. Therefore, for example, embodiments of the invention can be implemented in mobile phones, base stations, radio stations, user radio equipment, or computers such as desktop or tablet computers that include radio frequency communication components (e.g., wireless LAN, cellular radio, etc.).

[0102] Generally, various embodiments of the present invention can be implemented in hardware or dedicated circuitry or any combination thereof. While various aspects of the invention may be illustrated and described as block diagrams or using some other graphical representation, it should be understood that, by way of non-limiting example, the blocks, devices, systems, techniques or methods described herein can be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers, or other computing devices or some combination thereof.

[0103] As used in this application, the term "circuit" may refer to one or more of the following: (a) Hardware circuit implementation only, such as implementation only in analog and / or digital circuits, and (b) A combination of hardware circuitry and software, such as (where applicable): (i) A combination of analog and / or digital hardware circuitry with software / firmware, and (ii) Any part of a hardware processor with software that works together to enable a device (such as a mobile phone or server) to perform various functions, including digital signal processors, software, and memory, and (c) Hardware circuitry and processors that require software (e.g., firmware) to operate (but the software may not exist when operation is not required), such as microprocessors or portions thereof.

[0104] This definition of "circuit" applies to all uses of the term in this application (including any claim). As another example, as used in this application, the term "circuit" also covers only hardware circuitry or processors (or processors), or a portion thereof, and their accompanying software and / or firmware implementations. The term "circuit" also covers, for example (and if applicable to a particular claim element), baseband integrated circuits or processor integrated circuits used in mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or networking devices.

[0105] According to an embodiment, an apparatus for user equipment-to-user equipment relay communication is provided, comprising: at least one processor; and at least one memory including computer program code; said at least one memory and said computer program code are configured to, together with said at least one processor, enable the apparatus to: Determine whether the transmitting user equipment in the user equipment-to-user equipment relay communication is permitted to request the device to establish at least one relay channel on the communication link used for the user equipment-to-user equipment relay communication, the communication link being between the device and the transmitting user equipment; Based on the determination, at least one control message is generated to indicate the result of the determination to the sending user equipment; Send the at least one control message to the sending user equipment.

[0106] According to an embodiment, the at least one memory includes computer program code configured to, together with the at least one processor, cause the device to: transmit the at least one control message during or after establishing the user equipment to user equipment relay communication.

[0107] According to an embodiment, the at least one memory includes computer program code configured, together with the at least one processor, to cause the device to transmit the at least one control message during or after the establishment of at least one relay channel on the communication link for user equipment-to-user equipment relay communication.

[0108] According to an embodiment, the at least one memory includes computer program code configured to, together with the at least one processor, cause the device to: indicate in the at least one control message that the transmitting user equipment is permitted to request the relay user equipment to establish a maximum number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or a maximum number of relay channels for the communication link.

[0109] According to an embodiment, the at least one memory includes computer program code configured to, together with the at least one processor, cause the means to: indicate in the at least one control message that the transmitting user equipment is permitted to request the relay user equipment to establish a maximum number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or indicate, for the user plane and for the control plane respectively, the maximum number of relay channels for the communication link.

[0110] According to an embodiment, the at least one memory includes computer program code configured, together with the at least one processor, to cause the means to: indicate in the at least one control message that the transmitting user equipment is permitted to request the relay user equipment to establish a maximum number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or to jointly indicate, for the user plane and control plane, the maximum number of relay channels for the communication link.

[0111] According to an embodiment, the at least one memory includes computer program code configured to, together with the at least one processor, cause the device to: indicate in the at least one control message whether the transmitting user equipment is permitted to request the relay user equipment to establish an additional relay channel.

[0112] According to an embodiment, the at least one memory includes computer program code configured to, together with the at least one processor, cause the device to: transmit the at least one control message during or after establishing the user equipment to user equipment relay communication.

[0113] According to an embodiment, the at least one memory includes computer program code configured, together with the at least one processor, to cause the device to transmit the at least one control message during or after the establishment of at least one relay channel on the communication link for user equipment-to-user equipment relay communication.

[0114] The foregoing description has provided a complete and informative description of exemplary embodiments of the invention through exemplary and non-limiting examples. However, various modifications and adjustments may become apparent to those skilled in the art when read in conjunction with the accompanying drawings and appended claims, given the foregoing description. Nevertheless, all such and similar modifications to the teachings of the invention will still fall within the scope of the invention.

Claims

1. A relay user equipment for user equipment-to-user equipment relay communication, comprising components for: Determine whether the transmitting user equipment in the user equipment-to-user equipment relay communication is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for the user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the transmitting user equipment; Based on the determination, at least one control message is generated to indicate the result of the determination to the sending user equipment; Send the at least one control message to the sending user equipment.

2. The relay user equipment according to claim 1, wherein the transmitting user equipment is a terminal user equipment or another relay user equipment in the user equipment-to-user equipment relay communication.

3. The relay user equipment according to claim 1 or 2, wherein the at least one control message indicates that the transmitting user equipment is permitted to request the relay user equipment to establish a maximum number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or indicates a maximum number of relay channels for the communication link.

4. The relay user equipment of claim 3, wherein the at least one control message indicates that the transmitting user equipment is permitted to request the relay user equipment to establish the maximum allowed number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or indicates the maximum allowed number of relay channels for the communication link for both the user plane and the control plane.

5. The relay user equipment of claim 3, wherein the at least one control message indicates that the transmitting user equipment is permitted to request the relay user equipment to establish the maximum allowed number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or jointly indicates the maximum allowed number of relay channels for the communication link for both the user plane and the control plane.

6. The relay user equipment according to any one of claims 1 to 5, wherein the relay user equipment comprises components for: The at least one control message is sent during or after the establishment of the user equipment to user equipment relay communication.

7. The relay user equipment according to any one of claims 1 to 5, wherein the relay user equipment comprises components for: The at least one control message is sent during or after the establishment of at least one relay channel on the communication link used for the user equipment to user equipment relay communication.

8. The relay user equipment according to any one of claims 1 to 7, wherein the communication link for the user equipment to user equipment relay communication is referred to as the ingress hop of the relay user equipment for the user equipment to user equipment relay communication.

9. The relay user equipment according to any one of claims 1 to 8, wherein the at least one control message includes an indication for indicating whether the transmitting user equipment is permitted to request the relay user equipment to establish an additional relay channel.

10. The relay user equipment according to any one of claims 1 to 9, wherein the relay channel is a sidelink relay radio link control channel.

11. The relay user equipment according to any one of claims 1 to 10, wherein the at least one control message is a sidelink radio resource control message.

12. A relay user equipment according to claim 8 or any one of claims 9 to 11 when dependent on claim 8, wherein the relay user equipment is another transmitting user equipment for an exit hop to another terminal user equipment or yet another relay user equipment in a user equipment-to-user equipment relay communication, and the exit hop from the relay user equipment to the yet another relay user equipment is another ingress hop of the yet another relay user equipment.

13. A method for user equipment-to-user equipment relay communication, comprising: The relay user equipment determines whether the transmitting user equipment in the user equipment-to-user equipment relay communication is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for the user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the transmitting user equipment. Based on the determination, the relay user equipment generates at least one control message to indicate the result of the determination to the sending user equipment; as well as The relay user equipment sends the at least one control message to the transmitting user equipment.

14. A transmitting user equipment for user equipment-to-user equipment relay communication, comprising components for: A relay user equipment (SUE) receiving at least one control message from the user equipment used for user equipment-to-user equipment relay communication, the at least one control message indicating whether the transmitting user equipment is permitted to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication, the communication link being between the relay user equipment and the transmitting user equipment; and Based on the control message, determine whether to request the relay user equipment to establish at least one relay channel on the communication link used for user equipment-to-user equipment relay communication.

15. The transmitting user equipment according to claim 14, wherein the transmitting user equipment is a terminal user equipment or another relay user equipment in user equipment-to-user equipment relay communication.

16. The transmitting user equipment according to claim 14 or 15, wherein the at least one control message indicates that the transmitting user equipment is permitted to request the relay user equipment to establish a maximum number of relay channels on the communication link used for user equipment-to-user equipment relay communication, or indicates a maximum number of relay channels for the communication link.

17. The transmitting user equipment of claim 16, wherein the at least one control message indicates that the transmitting user equipment is permitted to request the relay user equipment to establish the maximum allowed number of relay channels on the communication link for user equipment-to-user equipment relay communication, or indicates the maximum allowed number of relay channels for the communication link for both the user plane and the control plane.

18. The transmitting user equipment of claim 16, wherein the at least one control message indicates that the transmitting user equipment is permitted to request the relay user equipment to establish the maximum allowed number of relay channels on the communication link for user equipment-to-user equipment relay communication, or jointly indicates the maximum allowed number of relay channels for the communication link for both the user plane and the control plane.

19. The transmitting user equipment according to any one of claims 14 to 18, comprising components for: The at least one control message is received during or after the establishment of the user equipment to user equipment relay communication.

20. The transmitting user equipment according to any one of claims 14 to 18, comprising components for: The at least one control message is received during or after the establishment of at least one relay channel on the communication link used for the user equipment to user equipment relay communication.

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