WO2023169511A1

WO2023169511A1 - Sidelink (sl) buffer status report (bsr) handling for ue-to-network (u2n) relay based communication

Info

Publication number: WO2023169511A1
Application number: PCT/CN2023/080476
Authority: WO
Inventors: Zhang Zhang; Min Wang
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2022-03-10
Filing date: 2023-03-09
Publication date: 2023-09-14

Abstract

The present disclosure is related to UEs and methods performed by the UEs for handling SL BSR for U2N relay based communication. A method at a UE for SL communication comprises: determining whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node; and determining whether an SL BSR associated with the SL data to be transmitted is prioritized or not at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node.

Description

SIDELINK (SL) BUFFER STATUS REPORT (BSR) HANDLING FOR UE-TO-NETWORK (U2N) RELAY BASED COMMUNICATION

CROSS-REFERENCE TO RELATED APPLICATION (S)

This application claims priority to the PCT International Application No. PCT/CN2022/080124, entitled "SIDELINK (SL) BUFFER STATUS REPORT (BSR) HANDLING FOR UE-TO-NETWORK (U2N) RELAY BASED COMMUNICATION" , filed on March 10, 2022, which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure is related to the field of telecommunications, and in particular, to user equipments (UEs) and methods performed by the UEs for handling sidelink (SL) buffer status report (BSR) for UE-to-Network (U2N) relay based communication.

Background

Networks have always been hierarchical in nature. Devices have connected to and communicated with one or more base stations ever since the birth of cellular communications. However, new technology enablers in 5G New Radio (NR) will allow devices to connect directly to one another using a technique called sidelink communications. Sidelink is the new communication paradigm in which cellular devices are able to communicate without relaying their data via the network. That means vehicles, robots, and even consumer gadgets could create their own ad hoc networks without using the radio access network as an intermediary.

In the past decade new types of cellular services that go beyond traditional mobile broadband have had a strong impact on the scoping and development of the 5G NR standard. These new cellular services were motivated by the business and economic needs of making the 3^rd Generation Partnership Project (3GPP) ecosystem capable of supporting industrial requirements ranging from direct automotive communication between vehicles to industrial automation with Ultra-Reliable Low-Latency Communication (URLLC) for mission-and business-critical applications. But these same technologies can also be used for consumers to enhance their communication experience. For instance, sidelink proximity services would allow devices to discover and communicate with one another at extremely high data rates and low latency, making them ideal for peer-to-peer gaming and streaming services as well as enhanced Augmented Reality (AR) , Virtual Reality (VR) and other wearable device communications.

In contrast with uplink and downlink between a UE and a base station, where resource allocation and link adaptation are controlled by the network, in sidelink the device may perform both functions autonomously. In other words, the device gains more control of how to use network resources. At the same time, it is expected that 3GPP upcoming Release will introduce support for sidelink-based relaying and that in future releases multi-link relay will also be considered. Sidelink is also a candidate for future releases as an Industrial Internet of Things (IoT) enabler. By restricting the communication link to one hop, latency is greatly reduced, which is key to mission-critical industrial applications. Furthermore, sidelink is a potential solution for public safety ensuring direct communication or relayed communication between devices.

Another potential use case is multi-hop relaying where multiple sidelink connections are used to leap from/to device to achieve less power consumption, overcome link budget constraints, and enhance latency and reliability. Gaming and entertainment services with AR/VR can also take advantage of sidelink, as will body networks, using direct 5G connections to replace the Bluetooth and eventually Wi-Fi links that currently connect these devices. The result could be a revolutionary change in the communication architecture for many consumer devices. Instead of providing a different radio interface for every use case, device vendors could rely solely on 5G as the link for wide-area, local-area and personal-area communications.

Summary

In a sidelink based relaying scenario, a UE to NW (U2N) relay UE and/or a remote UE may transmit either relayed Uu traffic or PC5 traffic (or both) on the PC5 interface. In this case, an SL BSR may contain buffer status of SL Logical Channel (s) (LCH (s) ) carrying relayed Uu traffic and/or SL LCH (s) carrying PC5 traffic. Whether an SL BSR should be prioritized over a Uu BSR is determined based on a priority handling rule, i.e., comparison of highest SL LCH priority versus slP-rioritizationThres and comparison of highest UL LCH priority versus ul-PrioritizationThres. Such prioritization handling is designed based on an assumption that the SL LCH (s) only carry PC5 traffic, and SL LCH (s) are prioritized over Uu LCH (s) only in case the SL LCH (s) carry PC5 traffic which is sufficiently important while Uu LCH (s) carry Uu traffic which is not sufficiently important. Such prioritization rule is not efficient in UE to NW relay scenario as an SL BSR may contain buffer status of SL LCH (s) carrying relayed Uu traffic. Besides, it is difficult to set a proper slP-rioritizationThres, if the threshold is set only considering SL LCH(s) carrying PC5 traffic, the SL LCH (s) carrying relayed Uu traffic may be down-prioritized than expected. If the threshold is set only considering SL LCH (s) carrying relayed Uu traffic, the SL LCH (s) carrying PC5 traffic may be over-prioritized than expected.

Further, please note that in 3GPP Rel. 18 a remote UE may adopt mode 1 scheduling and send SL BSR over direct path when communicating over multi-paths with one path via a relay UE, in which case the above issues also exist at remote UE.

Therefore, to address or at least partially alleviate the above issues, some embodiments of the present disclosure are provided.

According to a first aspect of the present disclosure, a method at a UE for SL communication is provided. The method comprises: determining whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node; and determining whether an SL BSR associated with the SL data to be transmitted is prioritized or not at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node.

In some embodiments, the method further comprises: allocating resources to a logical channel (LCH) carrying Medium Access Control (MAC) Control Element (CE) for the SL BSR at least based on the determination of whether the SL BSR is prioritized or not; and transmitting, to a network node serving the UE, the logical channel by using the allocated resources. In some embodiments, the Uu data to be relayed over SL from/to a network node comprises at least one of: data that is received from the network node over a Uu interface and to be transmitted to another UE over a direct communication interface; and data that is to be transmitted to one or more other UEs over a direct communication interface and will be transmitted by the one or more other UEs to the network node over a Uu interface. In some embodiments, the step of determining whether the SL BSR is prioritized or not comprises: in response to determining that the SL data is PC5 data targeting the one or more other UEs: determining whether the highest priority value of one or more SL logical channels with the SL data is lower than a first threshold or not; and determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more SL logical channels with the SL data is lower than the first threshold or not.

In some embodiments, the step of determining whether the SL BSR is prioritized or not comprises: in response to determining that the SL data is Uu data to be relayed over SL from/to a network node: determining whether the highest priority value of one or more SL logical channels with the SL data is lower than a second threshold or not; and determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more SL logical channels with the SL data is lower than the second threshold or not, wherein the second threshold is configured separately from the first threshold. In some embodiments, the step of determining whether the SL BSR is prioritized or not further comprises: determining whether the highest priority value of one or more uplink (UL) logical channels with UL data available is equal to or higher than a third threshold or not; and determining whether the SL BSR is prioritized or not at least further based on the determination of whether the highest priority value of the one or more UL logical channels with the UL data is equal to or higher than the third threshold or not, wherein the third threshold is configured separately from the first threshold and/or the second threshold.

In some embodiments, the step of determining whether the SL BSR is prioritized or not comprises: determining whether the highest priority value of one or more UL logical channels with UL data available is equal to or higher than the highest priority value of one or more SL logical channels with the SL data plus a configured offset in response to determining that the SL data is Uu data to be relayed over SL from/to a network node; and determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more UL logical channels with the UL data is equal to or higher than the highest priority value of the one or more SL logical channels with the SL data plus the configured offset or not.

In some embodiments, the step of determining whether the SL BSR is prioritized or not further comprises at least one of: determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, determining that the SL data is PC5 data targeting one or more other UEs, and determining that the highest priority value of one or more SL logical channels with the SL data is lower than the first threshold; determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, determining that the SL data is Uu data to be relayed over SL from/to a network node, and determining that the highest priority value of one or more SL logical channels with the SL data is lower than the second threshold; determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than the highest priority value of one or more SL logical channels with the SL data plus a configured offset and determining that the SL data is Uu data to be relayed over SL from/to a network node; and determining that the SL BSR is not prioritized otherwise.

In some embodiments, when the SL BSR is prioritized and when the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, one or more prioritized SL BSR entries comprised in the SL BSR indicate at least one of: one or more SL Logical Channel Groups (LCGs) , for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry PC5 data targeting one or more other UEs, is lower than a first threshold; one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than a second threshold; and one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset.

In some embodiments, when the SL BSR is prioritized and when the highest priority value of one or more UL LCHs with UL data available is lower than a third threshold, one or more prioritized SL BSR entries comprised in the SL BSR indicate: one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset. In some embodiments, when a truncated SL BSR is to be reported, one or more SL BSR entries are comprised in the truncated SL BSR in an order listed below until a corresponding UL grant is exhausted: if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than a second threshold, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible; if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry PC5 data targeting one or more other UEs, is lower than a first threshold, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible; and if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible.

In some embodiments, a condition for determining whether an SL BSR is prioritized or not are regarded as being not met when at least one threshold used in the first condition is not configured. In some embodiments, a condition for determining whether an SL BSR is prioritized or not are regarded as being met when at least one threshold used in the second condition is not configured. In some embodiments, whether a condition is regarded as being met or not when at least one threshold used in the third condition is not configured is configured by a network node serving the UE. In some embodiments, whether a condition is regarded as being met or not when a threshold used in the condition is not configured is configured separately from whether another condition is regarded as being met or not when another threshold used in the other condition is not configured.

In some embodiments, the method further comprises: prioritizing or de-prioritizing an SL BSR over an UL BSR at least based on one or more factors related to the SL BSR and/or the UL BSR. In some embodiments, the one or more factors comprise at least one of: whether the SL BSR indicates buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node; a priority value associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; a packet delay budget (PDB) associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; a packet bit rate associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; a packet loss ratio associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; and a packet error ratio associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR. In some embodiments, a priority value and/or one or more thresholds used for determining whether the SL BSR is to be prioritized or not can be adjusted at least based on the one or more factors. In some embodiments, the method further comprises: determining a priority of an SL BSR to be equal to that of an UL BSR when the SL BSR indicates buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node. In some embodiments, the method further comprises: selecting one out of the SL BSR and the UL BSR, which have the same priority, to be transmitted with a same probability.

In some embodiments, the SL BSR indicates one of: buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only; and buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node only. In some embodiments, the method further comprises: prioritizing between a first SL BSR indicating buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only and a second SL BSR indicating buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node only in a same manner as prioritizing between an SL BSR and an UL BSR, with one or more thresholds for prioritizing between the first SL BSR and the second SL BSR that are configured separately from those for prioritizing between the SL BSR and the UL BSR. In some embodiments, a first SL BSR indicating buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only and a second SL BSR indicating buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node only are distinguished from each other by their LCH IDs or indicators in their MAC headers. In some embodiments, signaling between the UE and a network node comprises at least one of: system information; dedicated Radio Resource Control (RRC) signaling; paging message; MAC CE; and L1 signaling on physical channels.

According to a second aspect of the present disclosure, a UE is provided. The UE comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform any of the methods of the first aspect.

According to a third aspect of the present disclosure, a UE is provided. The UE comprises: a first determining module configured to determine whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node; and a second determining module configured to determine whether an SL BSR associated with the SL data to be transmitted is prioritized or not at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node. In some embodiments, the UE comprises one or more further modules configured to perform any of the methods of the first aspect.

According to a fourth aspect of the present disclosure, a method at a UE, which is connected to a network node via a direct path and an indirect path, is provided. The method comprises: determining a priority order between an SL BSR and an UL BSR at least based on one or more configured conditions related to the direct path and/or the indirect path.

In some embodiments, the SL BSR at least indicates buffer statuses for Uu data to be relayed over SL to the network node. In some embodiments, the method further comprises: allocating resources to logical channels carrying MAC CE for the SL BSR and/or the UL BSR at least based on the determined priority order; and transmitting, to a network node serving the UE, the logical channels by using the allocated resources. In some embodiments, the one or more configured conditions are related to at least one of: whether a transmission delay of the indirect path is lower than a transmission delay of the direct path; whether a radio channel quality of the indirect path is better than a radio channel quality of the direct path; and whether a traffic load of the indirect path is lower than a traffic load of the direct path. In some embodiments, the step of determining the priority order comprises at least one of: prioritizing the SL BSR over the UL BSR in response to determining that the indirect path can provide a lower transmission delay than that can be provided by the direct path; and prioritizing the UL BSR over the SL BSR in response to determining that the indirect path cannot provide a lower transmission delay than that can be provided by the direct path.

In some embodiments, a transmission delay is determined in at least one of: a Radio Link Control (RLC) layer; a Packet Data Convergence Protocol (PDCP) layer; and a MAC layer. In some embodiments, a PDCP status report is transmitted in response to at least one of: an upper layer requesting a PDCP entity re-establishment; an upper layer requesting a PDCP data recovery; an upper layer requesting an uplink data switching; an upper layer reconfiguring a PDCP entity to release Dual Active Protocol Stack (DAPS) and daps-SourceRelease being configured in the upper layer; an upper layer determining that a PDCP status report needs to be triggered; an expired periodic timer; and for a split Uu radio bearer (RB) , at least one of paths associated with the RB being changed and/or updated. In some embodiments, the at least one path is changed and/or updated in at least one way of: a path is replaced by another path; a path is removed; a new path is added for the RB; and the path used for data transmission is changed from a currently used path to a different path when only one path is used for data transmission at a time.

In some embodiments, a transmission delay is determined as follows:

where T_d is the transmission delay, T₁ is the time when a PDCP Protocol Data Unit (PDU) is transmitted by the UE, and T₂ is the time when a corresponding status report is received by the UE.

In some embodiments, a transmission delay is determined as follows:

where T_d is the transmission delay, T₃ is the time when a MAC PDU or transport block (TB) is transmitted by the UE, and T₄ is the time when a corresponding hybrid automatic repeat request (HARQ) feedback is received by the UE.

In some embodiments, a transmission delay for a path is determined at least based on an average transmission delay that is calculated based on multiple PDCP PDUs or multiple MAC PDUs or TBs. In some embodiments, the step of determining the priority order comprises at least one of: prioritizing the SL BSR over the UL BSR in response to determining that the indirect path has a better radio channel quality and/or a lower traffic load than that of the direct path; and prioritizing the UL BSR over the SL BSR in response to determining that the indirect path does not have a better radio channel quality and/or a lower traffic load than that of the direct path. In some embodiments, a radio channel quality indicates at least one of: Reference Signal Received Power (RSRP) ; Reference Signal Received Quality (RSRQ) ; Received Signal Strength Indication (RSSI) ; Signal to Interference plus Noise Ratio (SINR) ; Signal to Interference Ratio (SIR) ; and HARQ Block Error Rate (BLER) . In some embodiments, a traffic load indicates at least one of: a congestion level; and available resources.

In some embodiments, a radio channel quality and/or traffic load for the indirect path is determined as follows: measuring a first radio channel quality and/or traffic load for an SL hop between the UE and a relay UE; receiving, from the relay UE, a second radio channel quality and/or traffic load for an Uu hop between the relay UE and its serving network node; and determining the radio channel quality and/or traffic load for the indirect path at least based on the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load. In some embodiments, the radio channel quality and/or traffic load for the indirect path is determined as at least one of: a maximum value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; a minimum value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; an averaged value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; and a sum of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load. In some embodiments, signaling between the UE and a network node comprises at least one of: system information; dedicated RRC signaling; paging message; MAC CE; and L1 signaling on physical channels.

According to a fifth aspect of the present disclosure, a UE is provided. The UE comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform any of the methods of the fourth aspect.

According to a sixth aspect of the present disclosure, a UE that is connected to a network node via a direct path and an indirect path is provided. The UE comprises: a determining module configured to determine a priority order between an SL BSR and an UL BSR at least based on one or more configured conditions related to the direct path and/or the indirect path. In some embodiments, the UE comprises one or more further modules configured to perform any of the methods of the fourth aspect.

According to a seventh aspect of the present disclosure, a computer program comprising instructions is provided. The instructions, when executed by at least one processor, cause the at least one processor to carry out the method of any of the first and fourth aspects.

According to an eighth aspect of the present disclosure, a carrier containing the computer program of the seventh aspect is provided. In some embodiments, the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

With some embodiments of the present disclosure, SL-BSR can be prioritized properly and payload of a truncated SL-BSR can be generated properly when the SL BSR contains buffer status of SL LCH (s) carrying relayed Uu traffic, and this facilitates the gNB to obtain a timely and accurate buffer status information of relayed Uu traffic and ensures the performance of relayed Uu communication.

Brief Description of the Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and therefore are not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Fig. 1 is a diagram illustrating an exemplary network in which SL BSR handling for U2N relay based communication may be applicable according to an embodiment of the present disclosure.

Fig. 2 is a flow chart of an exemplary method at a UE for SL communication according to an embodiment of the present disclosure.

Fig. 3 is a flow chart of another exemplary method at a UE that is connected to a network node via a direct path and an indirect path according to another embodiment of the present disclosure.

Fig. 4 schematically shows an embodiment of an arrangement which may be used in a UE according to an embodiment of the present disclosure.

Fig. 5 is a block diagram illustrating an exemplary UE according to an embodiment of the present disclosure.

Fig. 6 is a block diagram illustrating another exemplary UE according to another embodiment of the present disclosure.

Fig. 7 schematically illustrates a telecommunication network connected via an intermediate network to a host computer according to an embodiment of the present disclosure.

Fig. 8 is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection according to an embodiment of the present disclosure.

Fig. 9 to Fig. 12 are flowcharts illustrating methods implemented in a communication system including a host computer, a base station, and a user equipment according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, the present disclosure is described with reference to embodiments shown in the attached drawings. However, it is to be understood that those descriptions are just provided for illustrative purpose, rather than limiting the present disclosure. Further, in the following, descriptions of known structures and techniques are omitted so as not to unnecessarily obscure the concept of the present disclosure.

Those skilled in the art will appreciate that the term "exemplary" is used herein to mean "illustrative, " or "serving as an example, " and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms "first" and "second, " and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term "step, " as used herein, is meant to be synonymous with "operation" or "action. " Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.

Conditional language used herein, such as "can, " "might, " "may, " "e.g., " and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment. Also, the term "or" is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Further, the term "each, " as used herein, in addition to having its ordinary meaning, can mean any subset of a set of elements to which the term "each" is applied.

The term "based on" is to be read as "based at least in part on. " The term "one embodiment" and "an embodiment" are to be read as "at least one embodiment. " The term "another embodiment" is to be read as "at least one other embodiment. " Other definitions, explicit and implicit, may be included below. In addition, language such as the phrase "at least one of X, Y and Z, " unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limitation of example embodiments. As used herein, the singular forms "a" , "an" , and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" , "comprising" , "has" , "having" , "includes" and/or "including" , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. It will be also understood that the terms "connect (s) , " "connecting" , "connected" , etc. when used herein, just mean that there is an electrical or communicative connection between two elements and they can be connected either directly or indirectly, unless explicitly stated to the contrary.

Of course, the present disclosure may be carried out in other specific ways than those set forth herein without departing from the scope and essential characteristics of the disclosure. One or more of the specific processes discussed below may be carried out in any electronic device comprising one or more appropriately configured processing circuits, which may in some embodiments be embodied in one or more application-specific integrated circuits (ASICs) . In some embodiments, these processing circuits may comprise one or more microprocessors, microcontrollers, and/or digital signal processors programmed with appropriate software and/or firmware to carry out one or more of the operations described above, or variants thereof. In some embodiments, these processing circuits may comprise customized hardware to carry out one or more of the functions described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Although multiple embodiments of the present disclosure will be illustrated in the accompanying Drawings and described in the following Detailed Description, it should be understood that the disclosure is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications, and substitutions without departing from the present disclosure that as will be set forth and defined within the claims.

Further, please note that although the following description of some embodiments of the present disclosure is given in the context of 5^th Generation New Radio (5G NR) , the present disclosure is not limited thereto. In fact, as long as SL BSR handling for U2N relay based communication is involved, the inventive concept of the present disclosure may be applicable to any appropriate communication architecture, for example, to Global System for Mobile Communications (GSM) /General Packet Radio Service (GPRS) , Enhanced Data Rates for GSM Evolution (EDGE) , Code Division Multiple Access (CDMA) , Wideband CDMA (WCDMA) , Time Division -Synchronous CDMA (TD-SCDMA) , CDMA2000, Worldwide Interoperability for Microwave Access (WiMAX) , Wireless Fidelity (Wi-Fi) , Long Term Evolution (LTE) , etc. Therefore, one skilled in the arts could readily understand that the terms used herein may also refer to their equivalents in any other infrastructure. For example, the term "User Equipment" or "UE" used herein may refer to a mobile device, a mobile terminal, a mobile station, a user device, a user terminal, a wireless device, a wireless terminal, an IoT device, a vehicle, or any other equivalents. For another example, the term "gNB" used herein may refer to a base station, a base transceiver station, an access point, a hot spot, a NodeB (NB) , an evolved NodeB (eNB) , a network element, a network node, an access network (AN) node, or any other equivalents.

Further, following 3GPP documents are incorporated herein by reference in their entireties:

- 3GPP Technical Specification Group (TSG) RAN Meeting #91e, RP-210893, Electronic Meeting, March 16 -26, 2021, "New WID on NR Sidelink Relay" ;

- 3GPP TSG RAN Meeting #94e, RP-213585, Electronic Meeting, Dec. 6 -17, 2021 (revision of RP-213548) , "New WID on NR sidelink relay enhancements" ;

- 3GPP TR 23.752 V2.0.0 (2021-03) , Technical Report, 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on system enhancement for Proximity based Services (ProSe) in the 5G System (5GS) (Release 17) ;

- 3GPP TS 38.321 V16.2.1 (2020-09) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Medium Access Control (MAC) protocol specification (Release 16) ; and

- 3GPP TS 38.331 V16.2.0 (2020-09) , Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification (Release 16) .

Fig. 1 is a diagram illustrating an exemplary network 10 in which SL BSR handling for U2N relay based communication may be applicable according to an embodiment of the present disclosure. Although the network 10 is a network defined in the context of 5G NR, the present disclosure is not limited thereto.

As shown in Fig. 1, the network 10 may comprise one or more UEs 100-1, 100-2, and 100-3 (collectively, UE (s) 100) and optionally a Radio Access Network (RAN) node 110, which could be a base station, a Node B, an evolved NodeB (eNB) , a gNB, or an Access Network (AN) node which provides the UEs 100 with access to the network 10. Further, the network 10 may comprise other nodes and/or entities that are not shown in Fig. 1, for example (but not limited to) an Access &Mobility Management Function (AMF) , a Session Management Function (SMF) , a Policy Control Function (PCF) , and/or a User Plane Function (UPF) . Further, as shown in Fig. 1, the UEs 100 may communicate with each other via sidelinks over the reference point PC5, and the UE 100-1 and the UE 100-3 may communicate with the gNB 110 over the reference point Uu.

However, the present disclosure is not limited thereto. In some other embodiments, the network 10 may comprise additional network functions, less network functions, or some variants of the existing network functions shown in Fig. 1. For example, in a network with the 4G architecture, the entities which perform these functions may be different from those shown in Fig. 1. For another example, in a network with a mixed 4G/5G architecture, some of the entities may be same as those shown in Fig. 1, and others may be different. Further, the functions shown in Fig. 1 are not essential to the embodiments of the present disclosure. In other words, some of them may be missing from some embodiments of the present disclosure. For example, in some embodiments, there is no gNB 110 or there are one or more gNBs that serve some or all of the UEs 100, respectively.

As shown in Fig. 1, the UE 100-1 in the coverage of the gNB 110 may function as a relay UE for the UE #2 100-2 that may function as a remote UE due to it is out of coverage of the gNB 110. Further, the UE 100-3 may also function as a remote UE even if it is in the coverage of the gNB 110, for example, due to a poor link quality or low transmission rate that can be offered by the gNB 110 to the UE 100-3. In other words, the UE #3 may have a direct path to the gNB 110 over the Uu link therebetween, and also an indirect path to the gNB 110 via the UE 100-1 over the PC5 link between the UE 100-3 and UE 100-1 and also over the Uu link between UE 100-1 and gNB 110. However, the present disclosure is not limited thereto. In other embodiments, the UE 100-1 may communicate with the gNB 110 via the UE 100-3, and in this case, the UE 100-1 is a remote UE and the UE 100-3 is a relay UE. Further, in some other embodiments, the UE 100-2 may communicate with the UE 100-3 via the UE 100-1, and in this case, the UE 100-1 functions as a UE-to-UE (U2U) relay UE. In yet some other embodiments, the UE 100-2 may communicate with the gNB 110 via the UE 100-1 and the UE 100-3, and in this case, the UE 100-1 and the UE 100-3 function as multi-hop UE-to-Network (U2N) relay UEs.

3GPP specified the LTE D2D (device-to-device) technology, also known as sidelink (SL) or the PC5 interface, as part of Release 12 (Rel-12) . The target use case (UC) was the Proximity Services (communication and discovery) . Support was enhanced during Rel-13. In Rel-14, the LTE sidelink was extensively redesigned to support vehicular communications (commonly referred to as Vehicle-to-Anything (V2X) or Vehicle-to-Vehicle (V2V) ) . Support was again enhanced during Rel-15. From the point of view of the lowest radio layers, the LTE SL uses broadcast communication. That is, transmission from a UE targets any receiver that is in range.

ProSe (Proximity Services) was specified in the Release 12 and 13 of LTE. Later in Rel. 14 and 15, LTE V2X related enhancements targeting the specific characteristics of vehicular communications were specified. In LTE V2X only broadcast is supported over sidelink.

In Rel-16, 3GPP introduced the sidelink for the 5G new radio (NR) . The driving UC was vehicular communications with more stringent requirements than those typically served using the LTE SL. To meet these requirements, the NR SL is capable of broadcast, groupcast, and unicast communications. In groupcast communication, the intended receivers of a message are typically a subset of the vehicles near the transmitter, whereas in unicast communication, there is a single intended receiver.

Both the LTE SL and the NR SL can operate with and without network coverage and with varying degrees of interaction between the UEs (user equipment) and the NW (network) , including support for standalone, network-less operation.

In 3GPP Rel. 17, National Security and Public Safety (NSPS) is considered to be one important use case, which can benefit from the already developed NR sidelink features in Rel. 16. Therefore, 3GPP will specify enhancements related to NSPS use case taking NR Rel. 16 sidelink as a baseline. Besides, in some scenarios NSPS services need to operate with partial or without NW coverage, such as indoor firefighting, forest firefighting, earthquake rescue, sea rescue, etc. where the infrastructure is (partially) destroyed or not available, therefore, coverage extension is a crucial enabler for NSPS, for both NSPS services communicated between UE and cellular NW and that communicated between UEs over sidelink. In Rel. 17, a Study Item Description (SID) on NR sidelink relay (RP-193253) was launched which aims to further explore coverage extension for sidelink-based communication, including both UE to NW relay for cellular coverage extension and UE to UE relay for sidelink coverage extension. Now the work has proceeded to normative phase and in the WID, "RP-210893" , only UE to NW relay is considered, including both layer 2 (L2) based and layer 3 (L3) based UE to NW relay. For L2 UE to NW relay, the two endpoints of the PDCP link are the remote UE and the gNB. The relay function is performed below PDCP. This means that data security is ensured between the remote UE and the gNB without exposing raw data at the UE to NW relay UE. For L3 UE to NW relay, remote UE is invisible to gNB and core NW, i.e., it does not have its own context and PDU session in gNB and core NW, its traffic is forwarded in relay UE's PDU session.

A remote UE and a UE to Network Relay shall set up a separate PC5 unicast link if an existing unicast link (s) was established with a different Relay Service Code or without a Relay Service Code.

An L2 UE to Network Relay UE in RRC_CONNECTED may report its source L2 ID to the serving gNB.

There are two different resource allocation (RA) procedures for sidelink, i.e., NW controlled RA (so called "mode 3" in LTE and "mode 1" in NR) and UE autonomous RA (so called "mode 4" in LTE and "mode 2" in NR) . The transmission resources are selected within a resource pool which is predefined or configured by the network (NW) .

With NW controlled RA, the sidelink radio resource for data transmission may be scheduled/allocated by the NW. The UE sends sidelink BSR to the NW to inform sidelink data available for transmission in the sidelink buffers associated with the MAC entity, and the NW signals the resource allocation to the UE using Downlink Control Information (DCI) . With autonomous RA, each device independently decides which radio resources to use for its transmission based on e.g. sensing.

A specific scheduling request (SR) configuration (i.e. sidelink SR) is introduced to indicate the NW that sidelink BSR is triggered.

In Rel. 17 a remote UE can only adopt mode 2 RA when connected to a UE to NW relay. In Rel. 18 a new work item on NR Sidelink Relay will be started including support of multi-path with UE to NW relay, i.e., a remote UE could connect to NW via one direct path and one indirect path, in this case the remote UE could adopt mode 1 RA and be scheduled by the gNB via the direct path.

The logical channel prioritization (LCP) procedure is applied when a new UL transmission is performed. In short, resources are allocated to the logical channels (LCHs) with data available in a decreasing priority order, i.e., high priority logical channel is served first.

Logical channels shall be prioritized in accordance with the following order (highest priority listed first) :

- C-RNTI MAC CE or data from UL-CCCH;

- Configured Grant Confirmation MAC CE or BFR MAC CE or Multiple Entry Configured Grant Confirmation MAC CE;

- Sidelink Configured Grant Confirmation MAC CE;

- LBT failure MAC CE;

- MAC CE for prioritized SL-BSR;

- MAC CE for BSR, with exception of BSR included for padding;

- Single Entry PHR MAC CE or Multiple Entry PHR MAC CE;

- MAC CE for the number of Desired Guard Symbols;

- MAC CE for Pre-emptive BSR;

- MAC CE for SL-BSR, with exception of prioritized SL-BSR and SL-BSR included for padding;

- data from any Logical Channel, except data from UL-CCCH;

- MAC CE for Recommended bit rate query;

- MAC CE for BSR included for padding;

- MAC CE for SL-BSR included for padding.

An SL-BSR (except SL-BSR included for padding) is prioritized if sl-PrioritizationThres is configured and the value of the highest priority of the SL logical channels with SL data available is lower than slP-rioritizationThres (a lower priority value corresponds to higher priority) ; and if ul-PrioritizationThres is configured and the value of the highest priority of the UL logical channels with UL data available is equal to or higher than ul-PrioritizationThres.

If SL-BSR is prioritized, and if the UL-grant size is not enough to carry the buffer status of all prioritized SL-BSR entries in the prioritized SL-BSR and UL-BSR, truncated SL-BSR containing buffer status for as many prioritized SL-BSR entries as possible is reported.

A UE to NW relay UE and/or a remote UE may transmit either relayed Uu traffic or PC5 traffic (or both) on the PC5 interface, in this case an SL BSR may contain buffer status of SL LCH (s) carrying relayed Uu traffic and/or SL LCH (s) carrying PC5 traffic. As described above, whether an SL BSR should be prioritized over a Uu BSR is determined based on a priority handling rule, i.e., comparison of highest SL LCH priority versus sl-PrioritizationThresand comparison of highest UL LCH priority. Such prioritization handling is designed based on an assumption that the SL LCH (s) only carry PC5 traffic, and SL LCH (s) are prioritized over Uu LCH (s) only in case the SL LCH (s) carry PC5 traffic which is sufficiently important while Uu LCH (s) carry Uu traffic which is not sufficiently important. Such prioritization rule is not efficient in UE to NW relay scenario as an SL BSR may contain buffer status of SL LCH (s) carrying relayed Uu traffic. Besides, it is difficult to set a proper slP-rioritizationThres, if the threshold is set only considering SL LCH (s) carrying PC5 traffic, the SL LCH (s) carrying relayed Uu traffic may be down-prioritized than expected, If the threshold is set only considering SL LCH (s) carrying relayed Uu traffic, the SL LCH (s) carrying PC5 traffic may be over-prioritized than expected.

Note that in Rel. 18 a remote UE may adopt mode 1 scheduling and send SL BSR over direct path when communicating over multi-paths with one path via a relay UE, in which case the above issues also exist at remote UE.

Therefore, it is necessary to study the above issues and develop corresponding solutions.

Some embodiments of the present disclosure propose mechanisms to properly determine when an SL-BSR should be prioritized and what prioritized SL-BSR entries should be included in a truncated SL-BSR in case the SL BSR includes buffer status of SL LCH (s) carrying relayed Uu traffic.

Some embodiments of the present disclosure may include:

- Take into account whether an SL BSR containing buffer status of SL LCH (s) carrying relayed Uu traffic when determining whether the SL BSR should be prioritized.

- Prioritize SL BSR as long as the highest priority value of SL LCH (s) carrying relayed Uu traffic is lower than the highest priority value of UL LCH (s) plus (or minus) an offset, regardless of the comparison to the priority threshold.

- Criteria to determine the prioritized SL-BSR entries in a prioritized SL-BSR.

- Criteria to determine what prioritized SL-BSR entries should be included in a truncated SL-BSR.

- Determine priority order between SL BSR containing buffer status of SL LCH (s) carrying relayed Uu traffic and Uu BSR based on performance comparison between direct path and indirect path.

- SL BSR for SL LCHs carrying relayed Uu traffic and SL BSR for SL LCHs carrying PC5 traffic are sent separately.

With some embodiments of the present disclosure, SL-BSR can be prioritized properly and payload of a truncated SL-BSR can be generated properly when the SL BSR contains buffer status of SL LCH (s) carrying relayed Uu traffic, and this facilitates the gNB to obtain a timely and accurate buffer status info of relayed Uu traffic and ensures the performance of relayed Uu communication.

In some embodiments of the present disclosure, a term "node" may be used which can be a network node or a UE. Examples of network nodes may be NodeB, base station (BS) , multi-standard radio (MSR) radio node such as MSR BS, eNodeB (or eNB) , gNodeB (or gNB) , MeNB, SeNB, 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 (BBU) , Centralized Baseband, C-RAN, access point (AP) , transmission points, transmission nodes, Remote Radio Unit (RRU) , Remote Radio Head (RRH) , nodes in distributed antenna system (DAS) , core network node (e.g. Mobile Switching Center (MSC) , Mobility Management Entity (MME) etc. ) , Operation &Maintenance (O&M) , Operations Support System (OSS) , Self-Organizing Network (SON) , positioning node (e.g. Evolved-Serving Mobile Location Center (E-SMLC) ) , etc.

Another example of a node is user equipment (UE) , which is a non-limiting term and may refer 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, vehicle to vehicle (V2V) , machine type UE, MTC UE or UE capable of machine to machine (M2M) communication, Personal Digital Assistant (PDA) , Tablet, mobile terminals, smart phone, laptop embedded equipment (LEE) , laptop mounted equipment (LME) , Universal Serial Bus (USB) dongles etc.

The term "radio access technology" or "RAT" may refer to any RAT e.g. Universal Terrestrial Radio Access (UTRA) , Evolved UTRA (E-UTRA) , narrow band internet of things (NB-IoT) , Wi-Fi, 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.

Further, the term "direct path" is used to stand for a direct connection from a remote UE to a gNB (e.g., via NR air interface) and the term "indirect path" is used to stand for an indirect connection between a remote UE and a gNB via an intermediate node also known as relay UE. In the below embodiments, assuming an indirect path contains two hops i.e., PC5 hop between remote UE and relay UE, and Uu hop between relay UE and gNB. However, the present disclosure is not limited to two hops. For an indirect path containing more than two hops, the embodiments are also applicable. In the embodiments, the term "path" is used interchangeably with the other term "connection" without losing the meaning.

Some embodiments of the present disclosure are described in the context of NR, i.e., remote UE and relay UE are deployed in a same or different NR cell. The embodiments are applicable to relay scenarios including UE to network (U2N) relay where the link between remote UE and relay UE may be based on LTE sidelink or NR sidelink, the Uu connection between relay UE and base station may be LTE Uu or NR Uu. The connection between remote UE and relay UE is also not limited to sidelink. Any short-range communication technology such as Wi-Fi is equally applicable. The embodiments are applicable to both L2 based and L3 based U2N relay. Some embodiments are not relevant for SL BSR and Uu BSR included for padding.

Embodiments applicable to both relay UE and remote UE.

In some embodiments, an SL BSR may be prioritized if both of the following conditions are met:

- The highest priority value of the UL logical channels with UL data available is equal to or higher than ul-PrioritizationThres (if ul-PrioritizationThres is configured) ,

- The highest priority value of the SL logical channels with SL data available is lower than slP-rioritizationThres (if slP-rioritizationThres is configured) , wherein the SL data is PC5 traffic transmitted between UEs (which is denoted PC5 traffic hereafter) , or the highest priority value of the SL logical channels with SL data available is lower than slrelay-PrioritizationThres (if slrelay-PrioritizationThres is configured) , wherein the SL data is relayed Uu traffic between the remote UE and the gNB (which is denoted relayed Uu traffic hereafter) .

However, the present disclosure is not limited thereto. In some other embodiments, an SL BSR may be prioritized if one of the conditions can be met.

In some embodiments, in a U2N relay scenario, an SL BSR may be prioritized if the highest priority value of the UL logical channels with UL data available is higher than (or equal to) the highest priority value of the SL logical channels with relayed Uu data plus a (pre) configured offset (denoted offset_UL2SL) , regardless of the priority comparison results in the above embodiment. Please note that, in the embodiments, a higher priority value corresponds to a lower priority. However, the present disclosure is not limited thereto. In some other embodiments, a higher priority value corresponds to a higher priority, and in such a case, necessary modifications of the embodiments may be applicable and can be contemplated by those skilled in the art based on the teaching of the present disclosure.

In some embodiments, for a prioritized SL-BSR, when the condition "highest priority value of the UL logical channels with UL data available is equal to or higher than ul-PrioritizationThres" is met, the prioritized SL-BSR entries may include SL LCG (s) where for each LCG the highest priority value of the LCH (s) belonging to the LCG and carrying PC5 traffic (the SL LCG (s) are denoted high priority nonU2N SL LCG (s) hereafter) is lower than sl-PrioritizationThres (if sl-PrioritizationThres is configured) and also SL LCG (s) where for each LCG the highest priority value of the LCH (s) belonging to the LCG and carrying relayed Uu traffic (the SL LCG (s) are denoted high priority U2N SL LCG (s) hereafter) is lower than slrelay-Prioritization Thres (if slrelay-Prioritization Thres is configured) or lower than the highest priority value of the UL logical channels with UL data available plus (or minus) offset_UL2SL, otherwise the prioritized SL-BSR entries may include only high priority U2N SL LCG (s) where the priority value of the LCG (s) (which is the highest priority value of the LCH (s) belonging to the LCG and having data) is lower than the highest priority value of the UL logical channels with UL data available plus (or minus) offset_UL2SL.

In some embodiments, when reporting truncated SL-BSR containing buffer status for part of prioritized SL-BSR entries, and the prioritized SL-BSR entries include both high priority U2N SL LCG (s) and high priority nonU2N SL LCG (s) , the SL-BSR entries may be included in the following order until the UL grant is exhausted:

- if there exist high priority U2N SL LCG (s) whose priority value is lower than slrelay-PrioritizationThres (if slrelay-PrioritizationThres is configured) , include such SL LCG (s) in the truncated SL-BSR as many as possible.

- Else if there exist high priority nonU2N SL LCG (s) whose priority value is lower than sl-PrioritizationThres (if sl-PrioritizationThres is configured) , include such SL LCG (s) in the truncated SL-BSR as many as possible.

- Else if there exist high priority U2N SL LCG (s) whose priority value is lower than the highest priority value of the UL logical channels with UL data available plus (or minus) offset_UL2SL, include such SL LCG (s) in the truncated SL-BSR as many as possible.

In some embodiments, for any of the above embodiments, the conditions may be regarded as not met if the relevant threshold is not configured. In some embodiments, the conditions may be regarded as met if the relevant threshold is not configured. In some embodiments, which option to apply may be configured by the gNB and different options may be applied to the different conditions.

In some embodiments, the priority order between SL BSR and Uu BSR may be (pre) configured. For instance:

- The SL BSR may be always (de-) prioritized over the Uu BSR in case the SL BSR contains buffer status of SL LCH (s) carrying relayed Uu traffic.

- The SL BSR may be prioritized over the Uu BSR considering also factors other than LCH priority in case the SL BSR contains buffer status of SL LCH (s) carrying relayed Uu traffic. Such factors may comprise at least one of:

- Packet delay budget (PDB) ;

- Packet bit rate;

- Packet loss ratio;

- Packet error ratio.

In some embodiments, the priority value and/or the thresholds used in determining whether to prioritize SL BSR may be adjusted based on one or more of these factors.

- The SL BSR may have equal priority as Uu BSR in case the SL BSR contains buffer status of SL LCH (s) carrying relayed Uu traffic. In some embodiments, it is up to the UE to choose which BSR to send, and the UE should guarantee that the SL BSR and Uu BSR may be sent with equal probability.

In some embodiments, SL BSR for SL LCHs carrying relayed Uu traffic and SL BSR for SL LCHs carrying PC5 traffic may be sent separately. In this way, an SL BSR would only contain buffer status of SL LCHs carrying relayed Uu traffic or PC5 traffic, but not both. In some embodiments, prioritization between the two kinds of SL BSR could be according to state of art prioritization rule between SL BSR and Uu BSR but with different thresholds. In some embodiments, prioritization between SL BSR containing only buffer status of SL LCHs carrying relayed Uu traffic and UL BSR could be according to rules described in the above embodiments. In some embodiments, the two kinds of SL BSR may be differentiated by different LCH IDs or an indication in MAC header.

Embodiments applicable to remote UE.

In some embodiments, for a remote UE connecting to a gNB via both a direct path and an indirect path (i.e., via a relay UE) , the remote UE may determine the priority order between SL BSR and Uu BSR depending on at least one of the following (pre) configured conditions 1 and 2.

Condition 1: whether the indirect path can provide a faster transmission in terms of transmission delay than the direct path:

- The SL BSR may be prioritized over the Uu BSR if the indirect path can provide a faster transmission than the direct path;

- The Uu BSR may be prioritized over the SL BSR if the indirect path cannot provide a faster transmission than the direct path.

The transmission delay of a path can be measured in different options, for example Option 1 and Option 2 listed below. However, the present disclosure is not limited thereto.

As Option 1, transmission delay of a path may be measured at upper layer e.g., RLC layer or PDCP layer. Transmission delay of the path can be measured via the transmission delay of upper layer PDU (e.g., RLC PDU or PDCP PDU) which may be a time duration from the time when the PDU is started to be generated at the remote UE to the time when the PDU is received at the relay UE or gNB. In order to estimate transmission delay of one or multiple PDCP PDUs, the remote UE needs to receive PDCP status report from the gNB in case of L2 U2N relay. In addition to the following existing trigger conditions for PDCP status report (as captured in clause 5.4.1 of TS 38.323 v16.6.0)

- upper layer requests a PDCP entity re-establishment;

- upper layer requests a PDCP data recovery;

- upper layer requests a uplink data switching;

- upper layer reconfigures the PDCP entity to release DAPS and daps-SourceRelease is configured in upper layer (i.e., RRC) .

At least one of the following new conditions may be configured to PDCP receiving entity (e.g., gNB in this case) :

- Upper layer (i.e., RRC) determines that a PDCP status report needs to be triggered, e.g., it is necessary for PDCP receiving entity to provide a PDCP status report to PDCP transmitting entity;

- A periodic timer is expired;

- For a split Uu RB, among the paths associated with the RB (i.e., the paths on which data of the RB is transmitted) , at least one of the paths has been changed/updated

- In an example, one of the paths has been replaced by another path;

- In an example, one of the paths has been removed;

- In an example, a new additional path has been added for the RB;

- In an example, although multiple paths are associated with the RB, but the UE only uses one path to transmit data for the RB at a time, in this case, the UE has changed to a different path among all paths from the currently using path for data transmission.

Upon reception of a PDCP status report from the gNB on the path, the remote UE can estimate the transmission delay of a corresponding PDCP PDU based on the following formula:

Transmission delay of PDCP PDU M =

(the time when the corresponding status report is received from the gNB

- the time when PDCP PDU M is transmitted by the UE) /2 (1)

For the path, the remote UE may calculate an average transmission delay of PDCP PDU based on which the remote UE can estimate the transmission delay of the path.

As Option 2, transmission delay of the path may be measured by the remote UE at lower layer e.g., MAC layer. The UE may determine transmission delay of a MAC PDU/HARQ TB based on which the remote UE estimates transmission delay for the path.

After transmission of a MAC PDU/HARQ TB on the lower layer, the UE may wait for the corresponding HARQ feedback from the gNB. Upon reception of the corresponding HARQ feedback from the gNB, the remote UE can estimate the transmission delay of the MAC PDU/HARQ TB based on the following formula

Transmission delay of the MAC PDU/TB =

(the time when the corresponding HARQ feedback is received from the gNB

- the time when the MAC PDU/TB is transmitted by the UE) /2 (2)

For the path, the remote UE may calculate an average transmission delay of MAC PDU based on which the UE can estimate the transmission delay of the path.

This option is more applicable to direct path or indirect path when the relay UE performs relaying at L1.

Condition 2: whether the indirect path has better radio channel quality and/or a lower traffic load than the direct path

- The SL BSR may be prioritized over the Uu BSR if the indirect path has better radio channel quality and/or a lower traffic load than the direct path,

- Otherwise the Uu BSR may be prioritized over the SL BSR.

In some embodiments, the radio channel quality for a path may be measured in terms of metrics including RSRP, RSRQ, RSSI, SINR, SIR, HARQ BLER, etc. In some embodiments, the traffic load for a path may be measured in terms of congestion level, available resources, etc.

In some embodiments, it is straightforward for the remote UE to measure the direct path. However, the indirect path may contain two hops including the SL hop and the Uu hop. The Uu hop radio channel quality and/or traffic load may be obtained from the relay UE. After the remote UE has collected measurement results of both hops, it can derive end to end (E2E) measurements of the path by combining measurement results of both hops using one of the following options:

- Maximum value of measurement results between two hops;

- Minimum value of measurement results between two hops;

- Averaged value of measurement results of two hops;

- Sum of measurement results of two hops.

In some embodiments, the gNB may signal the relevant configurations mentioned in all the above embodiments to the UE via one of the following signaling alternatives:

- System information;

- Dedicated RRC signaling;

- Paging message;

- MAC CE;

- L1 signaling on physical channels including Physical Downlink Control Channel (PDCCH) , Physical Downlink Shared Channel (PDSCH) etc.

With some of the embodiments of the present disclosure, SL-BSR can be prioritized properly and payload of a truncated SL-BSR can be generated properly when the SL BSR contains buffer status of SL LCH (s) carrying relayed Uu traffic, and this facilitates the gNB to obtain a timely and accurate buffer status info of relayed Uu traffic and ensures the performance of relayed Uu communication.

Fig. 2 is a flow chart of an exemplary method 200 at a UE for SL communication according to an embodiment of the present disclosure. The method 200 may be performed at a UE (e.g., the UE 100-1, 100-2, or 100-3) for SL BSR handling for U2N relay based communication. The method 200 may comprise steps S210 and S220. However, the present disclosure is not limited thereto. In some other embodiments, the method 200 may comprise more steps, less steps, different steps, or any combination thereof. Further the steps of the method 200 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 200 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 200 may be combined into a single step.

The method 200 may begin at step S210 where whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node may be determined.

At step S220, whether an SL BSR associated with the SL data to be transmitted is prioritized or not may be determined at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node.

In some embodiments, the method 200 may further comprise: allocating resources to an LCH carrying MlAC CE for the SL BSR at least based on the determination of whether the SL BSR is prioritized or not; and transmitting, to a network node serving the UE, the logical channel by using the allocated resources. In some embodiments, the Uu data to be relayed over SL from/to a network node may comprise at least one of: data that is received from the network node over a Uu interface and to be transmitted to another UE over a direct communication interface; and data that is to be transmitted to one or more other UEs over a direct communication interface and will be transmitted by the one or more other UEs to the network node over a Uu interface. In some embodiments, the step of determining whether the SL BSR is prioritized or not may comprise: in response to determining that the SL data is PC5 data targeting the one or more other UEs: determining whether the highest priority value of one or more SL logical channels with the SL data is lower than a first threshold or not; and determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more SL logical channels with the SL data is lower than the first threshold or not.

In some embodiments, the step of determining whether the SL BSR is prioritized or not may comprise: in response to determining that the SL data is Uu data to be relayed over SL from/to a network node: determining whether the highest priority value of one or more SL logical channels with the SL data is lower than a second threshold or not; and determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more SL logical channels with the SL data is lower than the second threshold or not, wherein the second threshold is configured separately from the first threshold. In some embodiments, the step of determining whether the SL BSR is prioritized or not may further comprise: determining whether the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold or not; and determining whether the SL BSR is prioritized or not at least further based on the determination of whether the highest priority value of the one or more UL logical channels with the UL data is equal to or higher than the third threshold or not, wherein the third threshold is configured separately from the first threshold and/or the second threshold.

In some embodiments, the step of determining whether the SL BSR is prioritized or not may comprise: determining whether the highest priority value of one or more UL logical channels with UL data available is equal to or higher than the highest priority value of one or more SL logical channels with the SL data plus a configured offset in response to determining that the SL data is Uu data to be relayed over SL from/to a network node; and determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more UL logical channels with the UL data is equal to or higher than the highest priority value of the one or more SL logical channels with the SL data plus the configured offset or not.

In some embodiments, the step of determining whether the SL BSR is prioritized or not may further comprise at least one of: determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, determining that the SL data is PC5 data targeting one or more other UEs, and determining that the highest priority value of one or more SL logical channels with the SL data is lower than the first threshold; determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, determining that the SL data is Uu data to be relayed over SL from/to a network node, and determining that the highest priority value of one or more SL logical channels with the SL data is lower than the second threshold; determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than the highest priority value of one or more SL logical channels with the SL data plus a configured offset and determining that the SL data is Uu data to be relayed over SL from/to a network node; and determining that the SL BSR is not prioritized otherwise.

In some embodiments, when the SL BSR is prioritized and when the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, one or more prioritized SL BSR entries comprised in the SL BSR may indicate at least one of: one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry PC5 data targeting one or more other UEs, is lower than a first threshold; one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than a second threshold; and one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset.

In some embodiments, when the SL BSR is prioritized and when the highest priority value of one or more UL LCHs with UL data available is lower than a third threshold, one or more prioritized SL BSR entries comprised in the SL BSR may indicate: one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset. In some embodiments, when a truncated SL BSR is to be reported, one or more SL BSR entries may be comprised in the truncated SL BSR in an order listed below until a corresponding UL grant is exhausted: if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than a second threshold, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible; if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry PC5 data targeting one or more other UEs, is lower than a first threshold, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible; and if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node, is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible.

In some embodiments, a condition for determining whether an SL BSR is prioritized or not may be regarded as being not met when at least one threshold used in the first condition is not configured. In some embodiments, a condition for determining whether an SL BSR is prioritized or not may be regarded as being met when at least one threshold used in the second condition is not configured. In some embodiments, whether a condition is regarded as being met or not when at least one threshold used in the third condition is not configured may be configured by a network node serving the UE. In some embodiments, whether a condition is regarded as being met or not when a threshold used in the condition is not configured may be configured separately from whether another condition is regarded as being met or not when another threshold used in the other condition is not configured.

In some embodiments, the method 200 may further comprise: prioritizing or de-prioritizing an SL BSR over an UL BSR at least based on one or more factors related to the SL BSR and/or the UL BSR. In some embodiments, the one or more factors may comprise at least one of: whether the SL BSR indicates buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node; a priority value associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; a PDB associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; a packet bit rate associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; a packet loss ratio associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; and a packet error ratio associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR. In some embodiments, a priority value and/or one or more thresholds used for determining whether the SL BSR is to be prioritized or not can be adjusted at least based on the one or more factors. In some embodiments, the method 200 may further comprise: determining a priority of an SL BSR to be equal to that of an UL BSR when the SL BSR indicates buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node. In some embodiments, the method 200 may further comprise: selecting one out of the SL BSR and the UL BSR, which have the same priority, to be transmitted with a same probability.

In some embodiments, the SL BSR may indicate one of: buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only; and buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node only. In some embodiments, the method 200 may further comprise: prioritizing between a first SL BSR indicating buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only and a second SL BSR indicating buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node only in a same manner as prioritizing between an SL BSR and an UL BSR, with one or more thresholds for prioritizing between the first SL BSR and the second SL BSR that are configured separately from those for prioritizing between the SL BSR and the UL BSR. In some embodiments, a first SL BSR indicating buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only and a second SL BSR indicating buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node only may be distinguished from each other by their LCH IDs or indicators in their MAC headers. In some embodiments, signaling between the UE and a network node may comprise at least one of: system information; dedicated RRC signaling; paging message; MAC CE; and L1 signaling on physical channels.

Fig. 3 is a flow chart of an exemplary method 300 at a UE that is connected to a network node via a direct path and an indirect path according to an embodiment of the present disclosure. The method 300 may be performed at a UE (e.g., the UE 100-1, 100-2, or 100-3) for SL BSR handling for U2N relay based communication. The method 300 may comprise a step S310. However, the present disclosure is not limited thereto. In some other embodiments, the method 300 may comprise more steps, different steps, or any combination thereof. Further the steps of the method 300 may be performed in a different order than that described herein. Further, in some embodiments, a step in the method 300 may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method 300 may be combined into a single step.

The method 300 may begin at step S310 where a priority order between an SL BSR and an UL BSR may be determined at least based on one or more configured conditions related to the direct path and/or the indirect path.

In some embodiments, the SL BSR may at least indicate buffer statuses for Uu data to be relayed over SL to the network node. In some embodiments, the method 300 may further comprise: allocating resources to logical channels carrying MAC CE for the SL BSR and/or the UL BSR at least based on the determined priority order; and transmitting, to a network node serving the UE, the logical channels by using the allocated resources. In some embodiments, the one or more configured conditions may be related to at least one of: whether a transmission delay of the indirect path is lower than a transmission delay of the direct path; whether a radio channel quality of the indirect path is better than a radio channel quality of the direct path; and whether a traffic load of the indirect path is lower than a traffic load of the direct path. In some embodiments, the step of determining the priority order may comprise at least one of: prioritizing the SL BSR over the UL BSR in response to determining that the indirect path can provide a lower transmission delay than that can be provided by the direct path; and prioritizing the UL BSR over the SL BSR in response to determining that the indirect path cannot provide a lower transmission delay than that can be provided by the direct path.

In some embodiments, a transmission delay may be determined in at least one of: an RLC layer; a PDCP layer; and a MAC layer. In some embodiments, a PDCP status report may be transmitted in response to at least one of: an upper layer requesting a PDCP entity re-establishment; an upper layer requesting a PDCP data recovery; an upper layer requesting an uplink data switching; an upper layer reconfiguring a PDCP entity to release DAPS and daps-SourceRe/ease being configured in the upper layer; an upper layer determining that a PDCP status report needs to be triggered; an expired periodic timer; and for a split Uu radio bearer (RB) , at least one of paths associated with the RB being changed and/or updated. In some embodiments, the at least one path may be changed and/or updated in at least one way of: a path is replaced by another path; a path is removed; a new path is added for the RB; and the path used for data transmission is changed from a currently used path to a different path when only one path is used for data transmission at a time.

In some embodiments, a transmission delay may be determined as follows:

where T_d is the transmission delay, T₃ is the time when a MAC PDU or TB is transmitted by the UE, and T₄ is the time when a corresponding HARQ feedback is received by the UE.

In some embodiments, a transmission delay for a path may be determined at least based on an average transmission delay that is calculated based on multiple PDCP PDUs or multiple MAC PDUs or TBs. In some embodiments, the step of determining the priority order may comprise at least one of: prioritizing the SL BSR over the UL BSR in response to determining that the indirect path has a better radio channel quality and/or a lower traffic load than that of the direct path; and prioritizing the UL BSR over the SL BSR in response to determining that the indirect path does not have a better radio channel quality and/or a lower traffic load than that of the direct path. In some embodiments, a radio channel quality may indicate at least one of: RSRP; RSRQ; RSSI; SINR; SIR; and HARQ BLER. In some embodiments, a traffic load may indicate at least one of: a congestion level; and available resources.

In some embodiments, a radio channel quality and/or traffic load for the indirect path may be determined as follows: measuring a first radio channel quality and/or traffic load for an SL hop between the UE and a relay UE; receiving, from the relay UE, a second radio channel quality and/or traffic load for an Uu hop between the relay UE and its serving network node; and determining the radio channel quality and/or traffic load for the indirect path at least based on the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load. In some embodiments, the radio channel quality and/or traffic load for the indirect path may be determined as at least one of: a maximum value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; a minimum value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; an averaged value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; and a sum of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load. In some embodiments, signaling between the UE and a network node may comprise at least one of: system information; dedicated RRC signaling; paging message; MAC CE; and L1 signaling on physical channels.

Fig. 4 schematically shows an embodiment of an arrangement which may be used in a UE according to an embodiment of the present disclosure. Comprised in the arrangement 400 are a processing unit 406, e.g., with a Digital Signal Processor (DSP) or a Central Processing Unit (CPU) . The processing unit 406 may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement 400 may also comprise an input unit 402 for receiving signals from other entities, and an output unit 404 for providing signal (s) to other entities. The input unit 402 and the output unit 404 may be arranged as an integrated entity or as separate entities.

Furthermore, the arrangement 400 may comprise at least one computer program product 408 in the form of a non-volatile or volatile memory, e.g., an Electrically Erasable Programmable Read-Only Memory (EEPROM) , a flash memory and/or a hard drive. The computer program product 408 comprises a computer program 410, which comprises code/computer readable instructions, which when executed by the processing unit 406 in the arrangement 400 causes the arrangement 400 and/or the UE in which it is comprised to perform the actions, e.g., of the procedure described earlier in conjunction with Fig. 2 through Fig. 3 or any other variant.

The computer program 410 may be configured as a computer program code structured in computer program modules 410A and 410B. Hence, in an exemplifying embodiment when the arrangement 400 is used in a UE, the code in the computer program of the arrangement 400 includes: a module 410A configured to determine whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node; and a module 410B configured to determine whether an SL BSR associated with the SL data to be transmitted is prioritized or not at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node.

Additionally or alternatively, the computer program 410 may be configured as a computer program code structured in a computer program module 410C. Hence, in an exemplifying embodiment when the arrangement 400 is used in a UE, the code in the computer program of the arrangement 400 includes: a module 410C configured to determine a priority order between an SL BSR and an UL BSR at least based on one or more configured conditions related to the direct path and/or the indirect path.

The computer program modules could essentially perform the actions of the flow illustrated in Fig. 2 through Fig. 3, to emulate the UE. In other words, when the different computer program modules are executed in the processing unit 406, they may correspond to different modules in the UE.

Although the code means in the embodiments disclosed above in conjunction with Fig. 4 are implemented as computer program modules which when executed in the processing unit causes the arrangement to perform the actions described above in conjunction with the figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.

The processor may be a single CPU (Central processing unit) , but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs) . The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM) , a Read-Only Memory (ROM) , or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the UE.

Correspondingly to the method 200 as described above, an exemplary UE is provided. Fig. 5 is a block diagram of an exemplary UE 500 according to an embodiment of the present disclosure. The UE 500 may be, e.g., the UE 100-1, 100-2, or 100-3 in some embodiments.

The UE 500 may be configured to perform the method 200 as described above in connection with Fig. 2. As shown in Fig. 5, the UE 500 may comprise a first determining module 510 configured to determine whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node; and a second determining module 520 configured to determine whether an SL BSR associated with the SL data to be transmitted is prioritized or not at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node.

The above modules 510 and 520 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a Programmable Logic Device (PLD) or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 2. Further, the UE 500 may comprise one or more further modules, each of which may perform any of the steps of the method 200 described with reference to Fig. 2.

Correspondingly to the method 300 as described above, an exemplary UE is provided. Fig. 6 is a block diagram of an exemplary UE 600 according to an embodiment of the present disclosure. The relay UE 600 may be, e.g., the UE 100-1, 100-2, or 100-3 in some embodiments.

The UE 600 may be configured to perform the method 300 as described above in connection with Fig. 3. As shown in Fig. 6, the UE 600 may be connected to a network node via a direct path and an indirect path, and may comprise a determining module 610 configured to determine a priority order between an SL BSR and an UL BSR at least based on one or more configured conditions related to the direct path and/or the indirect path.

The above module 610 may be implemented as a pure hardware solution or as a combination of software and hardware, e.g., by one or more of: a processor or a micro-processor and adequate software and memory for storing of the software, a PLD or other electronic component (s) or processing circuitry configured to perform the actions described above, and illustrated, e.g., in Fig. 3. Further, the UE 600 may comprise one or more further modules, each of which may perform any of the steps of the method 300 described with reference to Fig. 3.

With reference to Fig. 7, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211, such as a radio access network, and a core network 3214. The access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first UE 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of UEs 3291, 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private, or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more sub-networks (not shown) .

The communication system of Fig. 7 as a whole enables connectivity between one of the connected UEs 3291, 3292 and the host computer 3230. The connectivity may be described as an over-the-top (OTT) connection 3250. The host computer 3230 and the connected UEs 3291, 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211, the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Fig. 8. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311, which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Fig. 8) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Fig. 8) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to set up and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331, which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides.

It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Fig. 8 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291, 3292 of Fig. 7, respectively. This is to say, the inner workings of these entities may be as shown in Fig. 8 and independently, the surrounding network topology may be that of Fig. 7.

In Fig. 8, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the use equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network) .

The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the latency and power consumption and thereby provide benefits such as reduced user waiting time, better responsiveness, extended battery lifetime.

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 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 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 3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc. ; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer′s 3310 measurements of throughput, propagation times, latency, and the like. The measurements may be implemented in that the software 3311, 3331 causes messages to be transmitted, in particular empty or ′dummy′ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

Fig. 9 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 7 and Fig. 8. For simplicity of the present disclosure, only drawing references to Fig. 9 will be included in this section. In a first step 3410 of the method, the host computer provides user data. In an optional substep 3411 of the first step 3410, the host computer provides the user data by executing a host application. In a second step 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 3440, the UE executes a client application associated with the host application executed by the host computer.

Fig. 10 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 7 and Fig. 8. For simplicity of the present disclosure, only drawing references to Fig. 10 will be included in this section. In a first step 3510 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 3530, the UE receives the user data carried in the transmission.

Fig. 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 7 and Fig. 8. For simplicity of the present disclosure, only drawing references to Fig. 11 will be included in this section. In an optional first step 3610 of the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second step 3620, the UE provides user data. In an optional substep 3621 of the second step 3620, the UE provides the user data by executing a client application. In a further optional substep 3611 of the first step 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third substep 3630, transmission of the user data to the host computer. In a fourth step 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Fig. 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig. 7 and Fig. 8. For simplicity of the present disclosure, only drawing references to Fig. 12 will be included in this section. In an optional first step 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second step 3720, the base station initiates transmission of the received user data to the host computer. In a third step 3730, the host computer receives the user data carried in the transmission initiated by the base station.

The present disclosure is described above with reference to the embodiments thereof. However, those embodiments are provided just for illustrative purpose, rather than limiting the present disclosure. The scope of the disclosure is defined by the attached claims as well as equivalents thereof. Those skilled in the art can make various alternations and modifications without departing from the scope of the disclosure, which all fall into the scope of the disclosure.

Abbreviation    Explanation
CA              Carrier Aggregation
CBR            Channel Busy Ratio
CQI             Channel Quality Indicator
CSI             Channel State Information
DFN             Direct Frame Number
DL              Downlink
DRX            Discontinuous Reception
FDD            Frequency Division Duplex
GNSS           Global Navigation Satellite System
HARQ           Hybrid automatic repeat request
IE              Information Element
MAC            Medium Access Control
MIB             Master Information Block
NSPS            National Security and Public Safety
OoC            Out-of-Coverage
PDCCH          Physical Downlink Control Channel
PDCP            Packet Data Convergence Protocol
PDU            Protocol Data Unit
PHY             Physical (layer)
PL             Path Loss
PMI             Precoding Matrix Indicator
ProSe           Proximity Services
PSCCH           Physical Sidelink Control Channel
PSSCH           Physical Sidelink Shared Channel
RI              Rank Indicator
RL             Relay
RLC             Radio link control
RM             Remote
RRC             Radio Resource Control
RSRP            Reference Signal Received Power
RSSI            Received Signal Strength Indicator
RX              Receive, receiver
SFN             System Frame Number
SIB             System Information Block
SINR            Signal to interference noise ration
SL              Sidelink
SLRB            Sidelink Radio Bearer
SLSS            Sidelink Synchronization Signals
SMF            Session Management Function
SynchUE         Synchronization UE
TDD            Time Division Duplex
TETRA          Terrestrial Trunked Radio
TX              Transmit, transmitter
UE              User Equipment
UL              Uplink
UPF             User Plane Function
V2V             Vehicle-to-vehicle
V2X             Vehicle-to-anything

Claims

A method (200) at a User Equipment (UE) (100-1, 100-2, 100-3, 400, 500) for sidelink (SL) communication, the method (200) comprising:

determining (S210) whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node (110) ; and

determining (S220) whether an SL buffer status report (BSR) associated with the SL data to be transmitted is prioritized or not at least based on the determination of whether SL data to be transmitted is PC5 data targeting one or more other UEs or Uu data to be relayed over SL from/to a network node (110) .
The method (200) of claim 1, further comprising:

allocating resources to a logical channel (LCH) carrying Medium Access Control (MAC) Control Element (CE) for the SL BSR at least based on the determination of whether the SL BSR is prioritized or not; and

transmitting, to a network node (110) serving the UE (100-1, 100-2, 100-3, 400, 500) , the logical channel by using the allocated resources.
The method (200) of claim 1 or 2, wherein the Uu data to be relayed over SL from/to a network node (110) comprises at least one of:

- data that is received from the network node (110) over a Uu interface and to be transmitted to another UE over a direct communication interface; and

- data that is to be transmitted to one or more other UEs over a direct communication interface and will be transmitted by the one or more other UEs to the network node (110) over a Uu interface.
The method (200) of any of claims 1 to 3, wherein the step of determining (S220) whether the SL BSR is prioritized or not comprises:

in response to determining that the SL data is PC5 data targeting the one or more other UEs:

determining whether the highest priority value of one or more SL logical channels with the SL data is lower than a first threshold or not; and

determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more SL logical channels with the SL data is lower than the first threshold or not.
The method (200) of any of claims 1 to 4, wherein the step of determining (S220) whether the SL BSR is prioritized or not comprises:

in response to determining that the SL data is Uu data to be relayed over SL from/to a network node (110) :

determining whether the highest priority value of one or more SL logical channels with the SL data is lower than a second threshold or not; and

determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more SL logical channels with the SL data is lower than the second threshold or not,

wherein the second threshold is configured separately from the first threshold.
The method (200) of claim 4 or 5, wherein the step of determining (S220) whether the SL BSR is prioritized or not further comprises:

determining whether the highest priority value of one or more uplink (UL) logical channels with UL data available is equal to or higher than a third threshold or not; and

determining whether the SL BSR is prioritized or not at least further based on the determination of whether the highest priority value of the one or more UL logical channels with the UL data is equal to or higher than the third threshold or not,

wherein the third threshold is configured separately from the first threshold and/or the second threshold.
The method (200) of any of claims 1 to 6, wherein the step of determining (S220) whether the SL BSR is prioritized or not comprises:

determining whether the highest priority value of one or more UL logical channels with UL data available is equal to or higher than the highest priority value of one or more SL logical channels with the SL data plus a configured offset in response to determining that the SL data is Uu data to be relayed over SL from/to a network node (110) ; and

determining whether the SL BSR is prioritized or not at least based on the determination of whether the highest priority value of the one or more UL logical channels with the UL data is equal to or higher than the highest priority value of the one or more SL logical channels with the SL data plus the configured offset or not.
The method (200) of any of claims 1 to 7, wherein the step of determining (S220) whether the SL BSR is prioritized or not further comprises at least one of:

determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, determining that the SL data is PC5 data targeting one or more other UEs, and determining that the highest priority value of one or more SL logical channels with the SL data is lower than the first threshold;

determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, determining that the SL data is Uu data to be relayed over SL from/to a network node (110) , and determining that the highest priority value of one or more SL logical channels with the SL data is lower than the second threshold;

determining that the SL BSR is prioritized in response to determining that the highest priority value of one or more UL logical channels with UL data available is equal to or higher than the highest priority value of one or more SL logical channels with the SL data plus a configured offset and determining that the SL data is Uu data to be relayed over SL from/to a network node (110) ; and

determining that the SL BSR is not prioritized otherwise.
The method (200) of any of claims 1 to 8, wherein when the SL BSR is prioritized and when the highest priority value of one or more UL logical channels with UL data available is equal to or higher than a third threshold, one or more prioritized SL BSR entries comprised in the SL BSR indicate at least one of:

- one or more SL Logical Channel Groups (LCGs) , for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry PC5 data targeting one or more other UEs, is lower than a first threshold;

- one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node (110) , is lower than a second threshold; and

- one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node (110) , is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset.
The method (200) of any of claims 1 to 9, wherein when the SL BSR is prioritized and when the highest priority value of one or more UL LCHs with UL data available is lower than a third threshold, one or more prioritized SL BSR entries comprised in the SL BSR indicate:

- one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node (110) , is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset.
The method (200) of any of claims 1 to 10, wherein when a truncated SL BSR is to be reported, one or more SL BSR entries are comprised in the truncated SL BSR in an order listed below until a corresponding UL grant is exhausted:

- if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node (110) , is lower than a second threshold, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible;

- if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry PC5 data targeting one or more other UEs, is lower than a first threshold, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible; and

- if there are one or more SL LCGs, for each of which, the highest priority value of one or more LCHs, which belong to the corresponding SL LCG and carry Uu data to be relayed over SL from/to a network node (110) , is lower than the highest priority value of one or more UL LCHs with UL data available minus a configured offset, then the one or more SL LCGs are indicated in the truncated SL BSR as many as possible.
The method (200) of any of claims 1 to 11, wherein a condition for determining whether an SL BSR is prioritized or not are regarded as being not met when at least one threshold used in the condition is not configured.
The method (200) of any of claims 1 to 11, wherein a condition for determining whether an SL BSR is prioritized or not are regarded as being met when at least one threshold used in the condition is not configured.
The method (200) of any of claims 1 to 11, wherein whether a condition is regarded as being met or not when at least one threshold used in the condition is not configured is configured by a network node (110) serving the UE (100-1, 100-2, 100-3, 400, 500) .
The method (200) of claim 14, wherein whether a condition is regarded as being met or not when a threshold used in the condition is not configured is configured separately from whether another condition is regarded as being met or not when another threshold used in the other condition is not configured.
The method (200) of any of claims 1 to 15, further comprising:

prioritizing or de-prioritizing an SL BSR over an UL BSR at least based on one or more factors related to the SL BSR and/or the UL BSR.
The method (200) of claim 16, wherein the one or more factors comprise at least one of:

- whether the SL BSR indicates buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node (110) ;

- a priority value associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR;

- a packet delay budget (PDB) associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR;

- a packet bit rate associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR;

- a packet loss ratio associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR; and

- a packet error ratio associated with an LCH whose buffer status is indicated by the SL BSR or the UL BSR.
The method (200) of claim 16 or 17, wherein a priority value and/or one or more thresholds used for determining whether the SL BSR is to be prioritized or not can be adjusted at least based on the one or more factors.
The method (200) of any of claims 1 to 15, further comprising:

determining a priority of an SL BSR to be equal to that of an UL BSR when the SL BSR indicates buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node (110) .
The method (200) of claim 19, further comprising:

selecting one out of the SL BSR and the UL BSR, which have the same priority, to be transmitted with a same probability.
The method (200) of any of claims 1 to 20, wherein the SL BSR indicates one of:

- buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only; and

- buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node (110) only.
The method (200) of claim 21, further comprising:

prioritizing between a first SL BSR indicating buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only and a second SL BSR indicating buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node (110) only in a same manner as prioritizing between an SL BSR and an UL BSR, with one or more thresholds for prioritizing between the first SL BSR and the second SL BSR that are configured separately from those for prioritizing between the SL BSR and the UL BSR.
The method (200) of claim 21 or 22, wherein a first SL BSR indicating buffer statuses of one or more SL LCHs carrying PC5 data targeting one or more other UEs only and a second SL BSR indicating buffer statuses of one or more SL LCHs carrying Uu data to be relayed over SL from/to a network node (110) only are distinguished from each other by their LCH IDs or indicators in their MAC headers.
The method (200) of any of claims 1 to 23, wherein signaling between the UE (100-1, 100-2, 100-3, 400, 500) and a network node (110) comprises at least one of:

- system information;

- dedicated Radio Resource Control (RRC) signaling;

- paging message;

- MAC CE; and

- L1 signaling on physical channels.
A method (300) at a UE (100-1, 100-2, 100-3, 400, 600) , which is connected to a network node (110) via a direct path and an indirect path, the method (300) comprising:

determining (S310) a priority order between an SL BSR and an UL BSR at least based on one or more configured conditions related to the direct path and/or the indirect path.
The method (300) of claim 25, wherein the SL BSR at least indicates buffer statuses for Uu data to be relayed over SL to the network node (110) .
The method (300) of claim 25 or 26, further comprising:

allocating resources to logical channels carrying MAC CE for the SL BSR and/or the UL BSR at least based on the determined priority order; and

transmitting, to a network node (110) serving the UE (100-1, 100-2, 100-3, 400, 600) , the logical channels by using the allocated resources.
The method (300) of any of claims 25 to 27, wherein the one or more configured conditions are related to at least one of:

- whether a transmission delay of the indirect path is lower than a transmission delay of the direct path;

- whether a radio channel quality of the indirect path is better than a radio channel quality of the direct path; and

- whether a traffic load of the indirect path is lower than a traffic load of the direct path.
The method (300) of any of claims 25 to 28, wherein the step of determining (S310) the priority order comprises at least one of:

prioritizing the SL BSR over the UL BSR in response to determining that the indirect path can provide a lower transmission delay than that can be provided by the direct path; and

prioritizing the UL BSR over the SL BSR in response to determining that the indirect path cannot provide a lower transmission delay than that can be provided by the direct path.
The method (300) of any of claims 25 to 29, wherein a transmission delay is determined in at least one of:

- a Radio Link Control (RLC) layer;

- a Packet Data Convergence Protocol (PDCP) layer; and

- a MAC layer.
The method (300) of any of claims 25 to 30, wherein a PDCP status report is transmitted in response to at least one of:

- an upper layer requesting a PDCP entity re-establishment;

- an upper layer requesting a PDCP data recovery;

- an upper layer requesting an uplink data switching;

- an upper layer reconfiguring a PDCP entity to release Dual Active Protocol Stack (DAPS) and daps-SourceRelease being configured in the upper layer;

- an upper layer determining that a PDCP status report needs to be triggered;

- an expired periodic timer; and

- for a split Uu radio bearer (RB) , at least one of paths associated with the RB being changed and/or updated.
The method (300) of claim 31, wherein the at least one path is changed and/or updated in at least one way of:

- a path is replaced by another path;

- a path is removed;

- a new path is added for the RB; and

- the path used for data transmission is changed from a currently used path to a different path when only one path is used for data transmission at a time.
The method (300) of any of claims 25 to 32, wherein a transmission delay is determined as follows:

where T_d is the transmission delay, T₁ is the time when a PDCP Protocol Data Unit (PDU) is transmitted by the UE (100-1, 100-2, 100-3, 400, 600) , and T₂ is the time when a corresponding status report is received by the UE (100-1, 100-2, 100-3, 400, 600) .
The method (300) of any of claims 25 to 32, wherein a transmission delay is determined as follows:

where T_d is the transmission delay, T₃ is the time when a MAC PDU or transport block (TB) is transmitted by the UE (100-1, 100-2, 100-3, 400, 600) , and T₄ is the time when a corresponding hybrid automatic repeat request (HARQ) feedback is received by the UE (100-1, 100-2, 100-3, 400, 600) .
The method (300) of any of claims 25 to 34, wherein a transmission delay for a path is determined at least based on an average transmission delay that is calculated based on multiple PDCP PDUs or multiple MAC PDUs or TBs.
The method (300) of any of claims 25 to 35, wherein the step of determining (S310) the priority order comprises at least one of:

prioritizing the SL BSR over the UL BSR in response to determining that the indirect path has a better radio channel quality and/or a lower traffic load than that of the direct path; and

prioritizing the UL BSR over the SL BSR in response to determining that the indirect path does not have a better radio channel quality and/or a lower traffic load than that of the direct path.
The method (300) of any of claims 25 to 36, wherein a radio channel quality indicates at least one of:

- Reference Signal Received Power (RSRP) ;

- Reference Signal Received Quality (RSRQ) ;

- Received Signal Strength Indication (RSSI) ;

- Signal to Interference plus Noise Ratio (SINR) ;

- Signal to Interference Ratio (SIR) ; and

- HARQ Block Error Rate (BLER) .
The method (300) of any of claims 25 to 37, wherein a traffic load indicates at least one of:

- a congestion level; and

- available resources.
The method (300) of any of claims 25 to 38, wherein a radio channel quality and/or traffic load for the indirect path is determined as follows:

measuring a first radio channel quality and/or traffic load for an SL hop between the UE (100-1, 100-2, 100-3, 400, 600) and a relay UE;

receiving, from the relay UE, a second radio channel quality and/or traffic load for an Uu hop between the relay UE and its serving network node (110) ; and

determining the radio channel quality and/or traffic load for the indirect path at least based on the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load.
The method (300) of claim 39, wherein the radio channel quality and/or traffic load for the indirect path is determined as at least one of:

- a maximum value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load;

- a minimum value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load;

- an averaged value of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load; and

- a sum of the first radio channel quality and/or traffic load and the second radio channel quality and/or traffic load.
The method (300) of any of claims 25 to 40, wherein signaling between the UE and a network node (110) comprises at least one of:

- system information;

- dedicated RRC signaling;

- paging message;

- MAC CE; and

- L1 signaling on physical channels.
A UE (100-1, 100-2, 100-3, 400, 500, 600) , comprising:

a processor (406) ;

a memory (408) storing instructions which, when executed by the processor (406) , cause the processor (406) to perform any of the methods (200, 300) of claims 1 to 41.
A computer program (410) comprising instructions which, when executed by at least one processor (406) , cause the at least one processor (406) to carry out the method (200, 300) of any of claims 1 to 41.
A carrier (408) containing the computer program (410) of claim 43, wherein the carrier (408) is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.