WO2025059831A1

WO2025059831A1 - U2n relay

Info

Publication number: WO2025059831A1
Application number: PCT/CN2023/119576
Authority: WO
Inventors: Xiang Xu; Ling Yu; Vinh Van Phan; Faranaz SABOURI-SICHANI; Saubhagya Baliarsingh; Sayed Ali MARANDI
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2023-09-19
Filing date: 2023-09-19
Publication date: 2025-03-27
Anticipated expiration: 2026-03-19

Abstract

Example embodiments of the present disclosure relate to devices, methods, apparatuses, and computer readable storage medium for user equipment (UE) -to-network (U2N) relay. In a method, a first device transmits, to a second device, information related to congestion of a link between the first device and a third device. The first device discards at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device. The at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.

Description

U2N RELAY

FIELDS

Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to devices, methods, apparatuses, and computer readable storage medium for user equipment (UE) -to-network (U2N) relay.

BACKGROUND

Sidelink (SL) based U2N relay in current releases, e.g., Release 17 (Rel-17) and Release 18 (Rel-18) , is a single-hop (SH) U2N relay where a remote UE is connected to a single U2N relay UE directly over SL and uses the U2N relay UE to connect to a serving network. The third-generation partnership project (3GPP) Rel-18 is discussing XR awareness NG-RAN when an Extended Reality (XR) UE directly connects with a base station or a serving cell. There is no detailed technical discussion to support an XR UE indirectly connecting with the base station or the serving cell via a U2N relay UE.

SUMMARY

In a first aspect of the present disclosure, there is provided a first device. The first device includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first device at least to: transmit, to a second device, information related to congestion of a link between the first device and a third device; and discard at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.

In a second aspect of the present disclosure, there is provided a second device. The second device includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second device at least to: receive, from a first device, information related to congestion of a link between a first device and a third device; and discard at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.

In a third aspect of the present disclosure, there is provided a method. The method includes: transmitting, to a second device, information related to congestion of a link between the first device and a third device; and discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.

In a fourth aspect of the present disclosure, there is provided a method. The method includes: receiving, from a first device, information related to congestion of a link between a first device and a third device; and discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.

In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus includes means for transmitting, to a second device, information related to congestion of a link between the first device and a third device; and means for discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.

In a sixth aspect of the present disclosure, there is provided a second apparatus. The second apparatus includes means for receiving, from a first device, information related to congestion of a link between a first device and a third device; and means for discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.

In a seventh aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium includes instructions stored thereon for causing an apparatus to perform at least the method according to the third aspect.

In an eighth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium includes instructions stored thereon for causing an apparatus to perform at least the method according to the fourth aspect.

It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

FIG. 1A illustrates an example communication environment in which example embodiments of the present disclosure may be implemented;

FIG. 1B illustrates a signaling diagram for an example process of discarding buffered PDU (s) according to some example embodiments of the present disclosure;

FIGS. 2A and 2B illustrate signaling flowcharts of example processes for Uu congestion in accordance with some example embodiments of the present disclosure;

FIGS. 3A and 3B illustrate signaling flowcharts of example processes for PC5 congestion in accordance with some example embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of an example method in accordance with some example embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of another example method in accordance with some other example embodiments of the present disclosure;

FIG. 6 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

FIG. 7 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein may be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first, ” “second, ” …, etc. in front of noun (s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun (s) . For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or” , mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting 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 “includes” , “including” , “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.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

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

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR) , Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) , the sixth generation (6G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , an NR NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) may be based on a split architecture, which a RAN node (for example, a gNB) includes a Centralized Unit (CU) and one or more Distributed Units (DUs) connected with the CU.

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

As used herein, the term “resource, ” “transmission resource, ” “resource block, ” “physical resource block” (PRB) , “uplink resource, ” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and/or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

As used herein, the term “Extended Reality” or “XR” refers to real-and-virtual combined environments where human-machine interactions are generated by computers and wearables. XR is an umbrella term for different types of realities, e.g., Virtual Reality (VR) , Augmented Reality (AR) , Mixed Reality (MR) , and/or the like.

As used herein, the term “packet data unit set” or “PDU set” refers to one or more packet data units (PDUs) carrying payload of one unit of information generated at an application level (e.g., frame (s) , video slice (s) , and/or the like for XR services) . The PDUs of a PDU set are transmitted within the same quality of service (QoS) Flow. A data burst may include one or more PDU sets.

The PDU set based QoS handling by a next generation radio access network (NG-RAN) is determined by PDU set QoS parameters, such as a PDU set Delay Budget (PSDB) , a PDU set Error Rate (PSER) and PDU set Integrated Handling Information (PSIHI) . PSIHI indicates whether all PDUs of the PDU set are needed for the usage of the PDU set by the application layer in a receiver side. When the PSIHI is set for a QoS flow, if one PDU of a PDU set is known to be lost, the remaining PDUs of that PDU set may be considered as no longer needed by the application layer and may be subject to the discarding operation.

To support the PDU set based QoS handling, a PDU session anchor (PSA) user plane function (UPF) identifies PDUs that belong to PDU sets and determines the following PDU set information which it sends to the NG-RAN in a General Packet Radio Service (GPRS) Tunnel Protocol User Plane (GTP-U) header. The PDU set information is used by the NG-RAN for the PDU set based QoS handling. The PDU set information may include a sequence number for a PDU set (also called a PDU set sequence number) , indication of an end PDU of the PDU set, a sequence number for a PDU (also called a PDU sequence number) within a PDU set, and/or a size of PDU set (also called a PDU set size) in bytes.

PDU set importance (PSI) may identify the relative importance of a PDU set compared to other PDU sets within a QoS flow. As an example, I-frames do not depend on other frames while P-frames depend on previous I-frames and P-frames. B-frames depend on both I-frames and P-frames. Thus, in terms of transmission priority, I-frames are prioritized over P-frames, and P-frames are prioritized over B-frames. In this case, PDU sets that belong to I-frames have higher PSI than PDU sets that belong to P-frames, and PDU sets that belong to P-frames have higher PSI than PDU sets that belong to B-frames. The NG-RAN may use the priority level across QoS flows and PSI within a QoS flow for packet discarding at a PDU set level in presence of congestion.

As mentioned above, for SL based U2N relay, 3GPP Rel-18 is discussing XR awareness NG-RAN when an XR UE directly connects with a base station or a serving cell. However, there is no detailed technical discussion to support an XR UE indirectly connecting with the base station or the serving cell via a U2N relay UE.

Current Rel-18 XR discussions in NG-RAN is mainly for a downlink (DL) direction. For example, a gNB may discard the DL data belonging to a PDU set with lower PDU set importance in case of a DL congestion. When an XR UE connects with the network via a L2 U2N relay, congestion may happen in a PC5 relay radio link control (RLC) channel (CH) between a remote UE and a relay UE or a Uu relay RLC channel (CH) between a gNB or a distributed unit of the gNB (also called a gNB-DU) and the relay UE. When the PC5 relay RLC CH is congested, the relay UE may need to discard some buffered DL data received from the gNB or gNB-DU for the remote UE. When the Uu relay RLC CH is congested, the relay UE may need to discard some buffered uplink (UL) data received from the Remote UE.

Current data discarding in the relay UE is mainly up to the relay UE's implementation. It does not consider the characteristics of XR traffic. For example, for a QoS flow when PSIHI is set, in case the relay UE discards one PDU from a PDU set, there is no need for the relay UE (or the remote UE or the gNB) to keep other PDUs belonging to the same PDU set.

Example embodiments of the present disclosure propose a scheme to coordinate PDU discard between multiple parties. With this scheme, a first device (such as a relay UE) transmits, to a second device (which may be one of a remote UE and a gNB) , information related to congestion of a link between the device and a third device (which may be the other of the remote UE and the gNB) . Due to the congestion, both the first device and the second device discards at least one buffered PDU of a PDU set. In this way, congestion and discard may be managed efficiently, especially, when an XR UE is accessing the network via a L2 U2N relay UE. Thus, SL based U2N relay for XR may be further enhanced.

FIG. 1A illustrates an example communication environment 100 in which example embodiments of the present disclosure may be implemented.

In the communication environment 100, which is a part of a communication network, a remote terminal device 110 may communicate with a relay terminal device 120 directly and communicate with a network device 130 via the relay terminal device 120. In some example embodiments, the network device 130 may be deployed in a distributed mode. For example, the network device 130 may include a part of a base station, e.g., at least one of a distributed unit (DU) or a centralized unit (CU) of the base station.

The relay terminal device 120 acts as an intermediary device between the remote terminal device 110 and the network device 130. For example, the relay terminal device 120 may communicate with the remote terminal device 110 via a PC5 interface and communicate with the network device 130 via a Uu interface to forward communications between the remote terminal device 110 and the network device 130.

A communication link or link between the remote terminal device 110 and the relay terminal device 120 is referred to as a sidelink (SL) . In SL mode, one of the remote terminal device 110 and the relay terminal device 120 is a TX device (or a transmitter) , and the other of the remote terminal device 110 and the relay terminal device 120 is a RX device (or a receiver) . A communication link or link from the network device 130 to the relay terminal device 120 is referred to as a DL while a communication link or link from the relay terminal device 120 to the network device 130 is referred to as an uplink (UL) . In DL, the network device 130 is a transmitting (TX) device (or a transmitter) , and the relay terminal device 120 is a receiving (RX) device (or a receiver) . In UL, the relay terminal device 120 is a TX device (or a transmitter) , and the network device 130 is a RX device (or a receiver) .

Communications in the communication environment 100 may be implemented according to any proper communication protocol (s) , including, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) , the fifth generation (5G) , the sixth generation (6G) , and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, including but not limited to: Code Division Multiple Access (CDMA) , Frequency Division Multiple Access (FDMA) , Time Division Multiple Access (TDMA) , Frequency Division Duplex (FDD) , Time Division Duplex (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Division Multiple (OFDM) , Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

It is to be understood that the type and the number of devices is shown in FIG. 1A only for the purpose of illustration without suggesting any limitation. The communication environment 100 may include any type and any number of devices configured to implement example embodiments of the present disclosure. In some example embodiments, the relay operation may implemented among any combination of terminal devices and network devices.

In the communication environment 100, when the relay terminal device 120 is forwarding the communications between the remote terminal device 110 and the network device 130, congestion may occur in a link between the relay terminal device 120 and the remote terminal device 110 and/or in a link between the relay terminal device 120 and the network device 130. In various example embodiments, the relay terminal device 120 may coordinate the discard of buffered PDUs with the remote terminal device 110 and the network device 130.

Some example implementations of how to handle the buffered PDUs will be discussed below with reference to FIG. 1B.

FIG. 1B illustrates a signaling diagram for an example process 140 of discarding buffered PDU (s) according to some example embodiments of the present disclosure. In the process 140, a first device 145 acts as a relay between a second device 150 and a third device 155. The first, second and third devices 145, 150 and 155 may be any combination of terminal devices and network devices.

In the following, for the purpose of illustration, some example embodiments are described with the first device 145 operating as a relay terminal device, the second device 150 operating as one of a remote terminal device and a network device and the third device 155 operating as the other of the remote terminal device and the network device. However, in some example embodiments, operations described with respect to a terminal device may be implemented at a network device or other devices, and operations described with respect to a network device may be implemented at a terminal device or other devices.

As shown in FIG. 1B, the first device 145 transmits (160) , to the second device 150, information related to congestion of a link between the first device 145 and the third device 155. Correspondingly, the second device 150 receives (162) the information from the first device 145. In some example embodiments, the first device 145 operates as the relay terminal device 120, the second device 150 may operate as either the remote terminal device 110 or the network device 130. In some example embodiments, the network device 130 may include at least one of a distributed unit (DU) or a centralized unit (CU) of a base station. Accordingly, as an example, the congestion may be either congestion in a PC5 interface (also called PC5 congestion) or congestion in a Uu interface (also called Uu congestion) .

The first device 145 may know the congestion based on its own detection. In some example embodiments, the first device 145 may detect the congestion of the link between the first device 145 and the third device 155. Based on the detection, the first device 145 may transmit (160) the information related to the congestion to the second device 150.

The first device 145 may determine that the link between the first device 145 and the third device 155 is congested, based on at least one condition being met. In some example embodiments, the at least one condition may include a condition that the amount of data in a buffer exceeds threshold amount where the data is received by the first device 145 from the second device 150 and to be transmitted to the third device 155. Based on this condition, the first device 145 may indicate the congestion to the second device 150 if the amount of buffered data exceeds the threshold amount. The threshold amount may be configured by the network or set by the first device 145 itself. For example, the network may send information about the threshold amount to the first device 145. In this case, the first device 145 may use the received threshold amount. If no threshold amount is received, the first device 145 itself may set threshold amount. The first device 145 may set the threshold amount by considering the PDU Set QoS parameters, for example, the PDU set delay budget.

Alternatively, or in addition, the at least one condition may include a condition that a channel busy ratio (CBR) exceeds a threshold ratio. The CBR may be used to represent a level of congestion (also called a congestion level) . For example, if the CBR for a relay radio link control (RLC) channel exceeds the threshold ratio, the first device 145 may determine that the congestion is detected. The threshold ratio may be configured by the network or set by the first device 145 itself. For instance, the first device 145 may set the threshold ratio to a value where the first device 145 may successfully perform the relay between the second device 150 and the third device 155.

In some example embodiments, the first device 145 may know the congestion based on an indication from the third device 155. As shown in FIG. 1B, the third device 155 may transmit (157) an indication that the link between the first device 145 and the third device 155 is congested. After the first device 145 receives (159) the indication from the third device 155, the first device 145 may transmit (160) , to the second device 150, the information related to the congestion of the link between the first device 145 and the third device 155.

In some example embodiments, the information may include an indication that the links between the first device 145 and the third device 155 is congested. In some other example embodiments, the information may include a second request to discard a PDU set. For example, after the first device 145 detects the congestion, e.g., Uu Relay RLC CH congestion or PC5 RLC CH congestion, or the first device 145 receives the indication of the congestion (also called a congestion indication) from the third device 155 when the third device 155 performs the congestion detection, the first device 145 may determine which PDU set is to be discarded and then transmit (160) to the second device 150 the information to request discarding of a PDU set.

The first device 145 may determine the PDU set based on PDU set importance (PSI) of the PDU set within at least one or more of a relay radio link control (RLC) channel, a radio bearer (RB) such as a data radio bearer (DRB) , or a quality of service (QoS) flow. For example, if the PSI of the PDU set is equal to or lower than threshold PSI, the first device 145 may determine that the PDU set is to be discarded. The threshold PSI may be dependent on a level of congestion (or a congestion level) which may be measured as a value of CBR, for example.

As an example, one or more PDU sets with corresponding one or more PSI values may be subject to discarding. The congestion level may be considered to determine which PDU sets have ongoing transmission to be interrupted and buffered PDUs to be discarded. For example, the following criterion may be (pre) configured: if thr1 < CBR ≤ thr2, PDU set (s) with PSI lower than X are discarded; else if thr2 < CBR, PDU set (s) with PSI lower than Y are discarded. X and Y represent different threshold PSI depending on values of CBR where Y > X. thr1 and thr2 represent threshold ratios for CBR.

In some example embodiments, a priority level of the QoS flow may also be considered by the first device 145 to determine the PDU set to be discarded. For example, before determining the PDU set based on the PSI of the PDU set within the QoS flow, the first device 145 may determine the QoS flow based on a priority level of the QoS flow. In an example, in the case that a plurality of QoS flows are multiplexed over the same Relay RLC channel, the first device 145 may determine a QoS flow to be discarded based on the priority of the QoS flow.

In some example embodiments, the first device 145 may transmit (160) to the second device 150 the second request to discard the PDU set, based on at least one condition being met. For the purpose of discussion, the at least one condition for triggering the transmission of the second request will be referred to as at least one first condition, and the at least one condition for detecting the link congestion as described above will be referred to as at least one second condition.

In some example embodiments, the at least one first condition may include a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number. For example, if the first device 145 determines that the number of packets (carrying the PDU) to be discarded is above a threshold number, the first device 145 may transmit (160) the second request to the second device 150. If the first device 145 determines the number of packets is to be discarded, which is below a threshold number, the first device 145 may not transmit (160) the second request to the second device 150. Alternatively, or in addition, the at least one first condition may include a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow. For example, if PSIHI is set, the first device 145 may request the second device 150 to discard the PDU set (s) .

In some example embodiments, to determine the PDU set to be discarded, the first device 145 may obtain at least one of the PSI of the PDU set, an identification (ID) of the QoS flow, or the PSIHI from a header of a received packet carrying the PDU of the PDU set.

In some example embodiments, the third device 155 may transmit, to the first device 145, an indication of a PDU set affected by the congestion, for example, when the third device 155 transmits (157) the indication of the congestion. Correspondingly, the first device 145 may receive the indication of the PDU set affected by the congestion. The affected PDU set may be indicated in any suitable way. In an example, the affected PDU set may be indicated by a sequence number for the PDU. After the first device 145 receives the indication of the PDU set affected by the congestion, the first device 145 may know that all PDUs belonging to the indicated PDU set need to be discarded.

In some example embodiments, the second request sent by the first device 145 to the second device 150 may include a sequence number (SN) for the PDU set. An RLC SN may be used to indicate the discarded PDU set. Alternatively, an SN may be introduced in Sidelink Relay Adaptation Protocol (SRAP) to indicate the discarding of PDU sets using an SRAP SN.

Alternatively, or in addition, the second request may include at least one SN for at least one PDU of the PDU set and/or at least one of a start SN or an end SN for PDUs of the PDU set. For example, the first device 145 may request the second device 150 to discard PDUs with e.g., up to SN X or within a SN window. Alternatively, or in addition, the second request may include PDU set importance (PSI) of the PDU set to indicate that the PDU set (s) with the PSI is to be discarded.

After the first device 145 determines the PDU set to be discarded, the first device 145 discards (168) at least one PDU of a PDU set. The at least one PDU of the PDU set is received from the second device 150 and buffered at the first device 145 and to be transmitted to the third device 155. In some example embodiments, the discarding (168) may be performed after transmitting (160) the second request to the second device 150. It is also possible that the discarding (168) and the transmitting (160) are performed concurrently or in a reversed order. For example, the first device 145 may first discard (168) the PDU set and then transmit (160) to the second device 150 the second request to discard the PDU set.

After the second device 150 receives (162) the information related to the congestion of the link between the first device 145 and the third device 155, the second device 150 discards (170) at least one PDU of the PDU set which is buffered at the second device 150 and to be transmitted to the third device 155 via the first device 145. For example, after the second device 150 receives (162) the second request to discard a PDU set, the second device 150 discards (170) at least one PDU of the PDU set.

In some example embodiments, the discarding (168) may be performed by the first device 145 in response to a first request from the second device 150 to discard a PDU set. For example, in the example embodiments where the information related to the congestion of the link between the first device 145 and the third device 155 includes an indication that the link between the first device 145 and the third device 155 is congested, the second device 150 may transmit (164) to the first device 145 a first request to discard the PDU set. After the first device 145 receives (166) the first request, the first device 145 may discard (168) at least one PDU of the PDU set. The second device 150 may also discard (170) at least one PDU of a PDU set.

The operations and algorithms to determine the PDU set to be discarded as described for the first device 145 may also be employed by the second device 150, and the detailed thereof will be omitted.

In some example embodiments, the information transmitted (160) by the first device 145 to the second device 150 may further include assistance information for determining a PDU set to be discarded. In some example embodiments, the assistance information includes at least one of: a relay radio link control (RLC) channel affected by the congestion, a radio bearer (RB) affected by the congestion, an identification of a quality of service (QoS) flow affected by the congestion, a sequence number for the PDU set affected by the congestion, or an available size of a buffer of the first device 145. The relay radio link control (RLC) channel affected by the congestion may be a PC5 relay RLC channel or a Uu relay RLC channel. This additional information may assist the second device 150 in determining the number of PDUs to be discarded.

In some example embodiments, the second device 150 may operate as a network device which is a base station (for example, a gNB, or a gNB-DU in distributed architecture) . In this example, if the PDU set to be discarded is determined by the second device 150, the second device 150 may transmit, to a CU of the base station, a third request to discard the PDU set. As such, the CU of the base station may discard the PDU (s) of the PDU set which have already been received from the DU, thereby further improving the data relay efficiency.

In some example embodiments, if the congestion is solved, the first device 145 may transmit, to the second device 150, an indication that the congestion of the link between the first device 145 and the third device 155 is absent. Then, normal relay of the first device 145 between the second and third devices 150 and 155 may be recovered.

Some example embodiments of discard of the PDU (s) will be described below with reference to FIGS. 2A to 3B. In these embodiments, it may be considered to discard buffered PDUs related to a given PSI. In some example embodiments, the PSI levels for which the corresponding PDU sets may be discarded may be proportional to the corresponding congestion levels. For example, the affected PDU set (s) may be determined as below. One or more PDU sets with corresponding one or more PSI values may be subject to discarding. Determination of PDU sets with ongoing transmission to be interrupted and buffered PDUs to be discarded may be dependent on the congestion level measured as a CBR value. CBR represents Uu congestion as shown in FIGS. 2A and 2B and PC5 congestion as shown in FIGS. 3A and 3B.

FIGS. 2A and 2B illustrate signaling flowcharts of example processes for Uu congestion in accordance with some example embodiments of the present disclosure. In these examples, a remote UE 202 may operate as an example implementation of the second device 150, a relay UE 204 may operate as an example implementation of the first device 145, and a gNB 206 may operate as an example implementation of the third device 155.

When Uu congestion happens, it is assumed the remote UE 202 (which may be an XR UE) has a PDU set with lower PSI that has 5 PDUs. It is to be noted that 5 PDUs are selected as an example for the purpose of discussion. As shown in FIGS. 2A and 2B, 3 PDUs are buffered (216, 236) in the remote UE 202, waiting for UL transmission to the relay UE 204. The other 2 PDUs are already received and buffered (217, 237) in the relay UE 204 waiting for UL transmission to the gNB 206.

In a process 208 as shown in FIG. 2A, no XR information such as PSIHI and PSI is transferred to the relay UE 204 over PC5. The relay UE 204 detects (220) Uu Relay RLC CH congestion. Alternatively, the relay UE 204 may receive (224) the congestion indication from the gNB 206 when the gNB 206 performs (222) Uu congestion detection.

In some example embodiments, in case the relay UE 204 detects the Uu congestion, the relay UE 204 may be configured with threshold amount for the data buffer on each Relay RLC CH basis. If the amount of data in the data buffer exceeds the configured threshold amount, the relay UE 204 may consider the Uu is congested and may be triggered to send (226) the Uu congestion indication.

In some other example embodiments, in case the gNB 206 determines (222) the Uu congestion, the gNB 206 may be able to determine the PDU set to be discarded. The gNB 206 may inform (224) the relay UE 204 for "Uu is congested" and the PDU set Sequence Number indicating the affected PDU set (i.e., all PDUs belonging to the indicated PDU set need to be discarded) .

The relay UE 204 informs (226) the remote UE 202 that Uu Relay RLC CH is congested. The relay UE 204 may indicate the PC5 RLC CH (s) or the remote UE 202's end to end (E2E) RB to be affected.

The threshold for detecting (220) the congestion as mentioned above may be used to determine whether the relay UE 204 informs the remote UE of its Uu congestion or not. It means that, when the relay UE 204 detects (220) the Uu congestion, the relay UE 204 indicates (226) to the remote UE 202 that the Uu is congested if the amount of buffered data exceeds the configured threshold. This allows the discard of the buffered PDUs only when the gain, i.e., minimizing waste of resources in the uplink, by discard of the buffered PDUs in the side of the relay UE 204 is expected to be large. The relay UE 204 may provide the remote UE 202 with additional information, e.g., the size of the available buffer in the relay UE 204, that may assist the remote UE 202 in determining the number of PDUs to be discarded.

The remote UE 202 determines the PDUs to be discarded. The determination may be based on the priority of the QoS flow (in case multiple QoS flows are multiplexed over the same PC5 Relay RLC channel) , and the PSI of a QoS flow. In this example, the buffered 3 PDUs of this PDU set are discarded (228) .

In case the gNB 206 detects (222) the Uu congestion, the remote UE 202 may consider the decision of the gNB 206 for PDU discard, and may determine the additional PDUs, e.g., PDUs belonging to a not-yet-transmitted PDU set (s) to be discarded. The affected PDU set (s) may be determined based on the rules and conditions as described above.

In case PSIHI is set and some PDUs belonging to the affected PDU set are already transmitted to the relay UE 204, the remote UE 202 informs (230) the relay UE 204 to discard the PDUs belonging to the affected PDU set. Each UL PDU has a SRAP SN. The remote UE 202 indicates (230) the specific SRAP SN or a SRAP SN window, including a start SN and an end SN, indicating the PDUs to be discarded.

The relay UE 204 discards (232) the 2 buffered PDUs related to the affected PDU set in this example. Later, when the Uu Relay RLC CH is not congested, the relay UE 204 informs (233) the remote UE 202.

In a process 210 as shown in FIG. 2B, the SRAP header is enhanced to include XR related information over PC5. When the remote UE 202 sends (235) UL data to the relay UE 204, the PC5 SRAP header may include additional XR related information, e.g., PSI. The XR related information may also include 1) a flag to indicate whether it is sending the last PDU of the PDU set; 2) a PDU SN within the PDU set.

In case there are multiple QoS flows of the remote UE 202 mapped to the same E2E (or e2e) data radio bearers (DRBs) or the same PC5 Relay RLC CH, the PSI indicated in the PC5 SRAP header may be derived from the PSI of the PDU set within each relevant QoS flow, and the priority level across the relevant QoS flows that are mapped to the same E2E DRBs or the same PC5 Relay RLC CH. In this way, the PSI in PC5 SRAP may indicate the "relative importance information" among the PDU set of all relevant QoS flows.

It is noted that a Uu Relay RLC CH (or PC5 Relay RLC CH) may carry PDUs from multiple QoS flows, but PSI is per QoS flow. Accordingly, an SRAP header may need to indicate the ID of the QoS flow. In addition, the priority level across QoS flows and PDU set Importance within a QoS flow may be used for PDU set level packet discarding in the presence of congestion. Thus, the PC5 SRAP header may need to include the priority level of QoS flows.

As shown in FIG. 2B, the relay UE 204 detects (238) the Uu is congested. In some example embodiments, similar to the process 208 as shown in FIG. 2A, the gNB 206 may determine the Uu congestion and then determine the PDU set to be discarded. The gNB 206 may inform the relay UE 204 for "Uu is congested" and the PDU set Sequence Number indicating the affected PDU set.

When the relay UE 204 needs to discard the buffered UL data due to congestion in Uu, the relay UE 204 may consider the PSI within a QoS flow to determine the buffered UL PDUs to be discarded. As the PSI indicated in PC5 SRAP header involves the PSI of each QoS flow and the priority level across QoS flows, the relay UE 204 may determine to discard first the PDU set with the least importance and lowest priority level across QoS flows mapped to the same e2e DRB or PC5 Relay RLC CH. The relay UE 204 determines the PDU set (s) to be discarded and discards all PDUs belonging to the affected PDU set (s) . In this example, the buffered 2 UL PDUs are discarded (240) . The affected PDU set (s) may be determined based on the approaches described above.

In case the relay UE 204 has not received all PDUs belonging to the affected PDU set (e.g., the relay UE 204 has not received the last PDU of the PDU set) , the relay UE 204 informs the remote UE 202 about the QoS flow to be affected by the Uu congestion, and the PDU set (s) discarded in the relay UE 204. To enable this, the SRAP SN may be introduced over PC5 and the relay UE 204 may inform (242) the remote UE 202 on the discarded PDUs by indicating the SRAP SN. As another example, if the relay UE 204 discards all the PDUs having the lowest importance indicated by PSI in case of Uu congestion detected, the relay UE 204 may also indicate the PSI to be discarded to the remote UE 202 instead of SRAP SN.

In case the remote UE 202 has the not-yet-transmitted PDUs belonging to the affected PDU set (s) , the remote UE 202 discards (244) the buffered UL PDUs. If the relay UE 204 indicates the PSI to be discarded instead of the specific PDU set, the remote UE 202 may discard all the not-yet-transmitted PDUs that belong to the PDU sets with the indicated PSI, and some of the PDUs in the PDU sets have been transmitted to the relay UE 204. As another example, the remote UE 202 may also discard the buffered PDU (s) belonging to other PDU set (s) which has a lower PSI than the PSI indicated by the relay UE 204.

FIGS. 3A and 3B illustrate signaling flowcharts of example processes for PC5 congestion in accordance with some example embodiments of the present disclosure. In these examples, a gNB (for example, the gNB 206 in FIG. 2A) may be deployed in a distributed mode and includes a DU (or gNB-DU) 305 and a CU (or a gNB-CU) 307. The Remote UE (or Remote terminal device) 202 connects with the network via the Relay UE (or Relay terminal device) 204. The connected network includes a gNB-DU 305, a gNB-CU 307 and Core Network (CN) 308. The Remote UE 202 has a QoS flow with the PDU Set QoS Parameters, for example, to be used for XR traffic. When the CN 308 sends a downlink data packet to the gNB-CU 307, the GTP-U header includes a PDU set information, for example, PSI.

In this example, when PC5 congestion happens, it is assumed the remote UE 202 (which may be an XR UE) has a PDU set with lower PSI that has 10 PDUs, and the gNB-CU 307, the gNB-DU 305, and the relay UE 204 all buffer some PDUs of the same PDU set.

As shown in FIGS. 3A and 3B, in this example, 5 PDUs are buffered (316, 334) in the gNB-CU 307, waiting for DL transmission to the gNB-DU 305. The other 3 PDUs are already received and buffered (317, 335) in the gNB-DU 305, waiting for DL transmission to the relay UE 204. The other 2 PDUs are already received and buffered (318, 336) in the relay UE 204, waiting for DL transmission to the remote UE 202. In this example, as described below, all DL data (belonging to the same PDU set) buffered in the gNB-CU 307, the gNB-DU 305, and the relay UE 204 need to be discarded (324, 328, 332, 338, 342, 346) due to PC5 congestion.

In a process 300 as shown in FIG. 3A, no XR information is transferred to the relay UE 204 over Uu. In this case, the gNB-DU 305 determines the DL packets to be discarded and then informs (326, 330) the relay UE and the gNB-CU 307 to discard the related DL packets.

As shown in FIG. 3A, the relay UE 204 detects (320) PC5 congestion. The PC5 congestion may be detected by configuring the CBR threshold and/or by configuring the buffer threshold for the PC5 Relay RLC channel. The relay UE 204 informs (322) the gNB-DU 305 about PC5 congestion. The relay UE 204 may also inform the gNB-DU 305 about the affected Uu Relay RLC CH.

The gNB-DU 305 determines the DL packets to be discarded, e.g., based on the priority level across QoS flows and PDU set Importance within a QoS flow for PDU set level packet discarding. In this example, 3 buffered PDUs are discarded (324) . The gNB-DU 305 may also perform following. If the gNB-DU 305 determines M number of packets to discard which is above a threshold number, or PSIHI is set, the gNB-DU 305 request (326) the relay UE 204 to discard PDUs, e.g., up to SN X or a SN window. M represent any positive integer. Herein, either the RLC SN may be used to indicate the discarded PDU, or the SN may be introduced in Uu SRAP to allow the gNB-DU 305 to indicate the discard of PDUs using SRAP SN. If DU 305 determines M number of packets to discard, which is below a threshold, DU 305 does not indicate relay or CU.

If it is needed to inform the relay UE 204, the gNB-DU 305 request (326) the relay UE 204 to discard the buffered DL PDUs of the affected PDU set. Since a Uu/PC5 RLC CH may multiplex PDUs from different QoS flows, Uu SRAP header may need to be enhanced to indicate the SN per QoS flow. Based on the request from the gNB-DU 305, the relay UE 204 discards (328) the buffered 2 PDUs of the affected PDU set, in this example.

If needed (e.g., the received DL PDU is not the last PDU of the affected PDU set) , the gNB-DU 305 requests (330) the gNB-CU 307 to discard the PDUs of the affected PDU set buffered in the gNB-CU 307. Based on the request from the gNB-DU 305, the gNB-CU 307 discards (332) the buffered 5 DUs of the affected PDU set, in this example.

In another example embodiment that is not shown in FIG. 3A, the gNB-DU 305 informs the gNB-CU 307 for the PC5 congestion. The gNB-CU 307 determines the DL packets to be discarded, e.g., based on the priority level across QoS flows and PDU set Importance within a QoS flow for PDU set level packet discarding. Then the gNB-CU 307 requests the relay UE 204 and the gNB-DU 305 to discard the buffered DL PDUs of the affected PDU set.

In a process 310 as shown in FIG. 3B, XR information is transferred to the relay UE 204 over Uu. In this case, after the relay UE 204 detects (337) PC5 congestion, the relay UE 204 determines the DL packets to be discarded and informs (340) the gNB-DU 305 to discard the related DL PDUs. The gNB-DU 305 further informs (344) the gNB-CU 307 to discard the related DL PDUs.

In order to enable the relay UE 204 to make the discard decision, the Uu SRAP header received (333) from the gNB-DU 305 is enhanced to include the XR related parameters, e.g., PSI, flag to indicate last PDU of a PDU set, PDU SN within a PDU set, ID of QoS flow (in case multiple QoS flows are multiplexed over one Uu Relay RLC CH) .

In this way, the proposed scheme mitigates the issue due to pending of the buffered data at a U2N relay UE (such as the relay UE 204) serving a remote UE with data transmissions for XR applications when congestion occurs at Uu or PC5 link. The proposed scheme may support use cases where XR information (e.g., PSI information) may be available at the relay UE or not.

For example, as shown in FIGS. 2A and 3A, in case the XR related information (e.g., PSI) is not available at the relay UE 204, the relay UE 204 is configured to notify at least one of the remote UE 202 or the gNB 206 (or the gNB-DU 305 and gNB-CU 307 in FIGS. 3A and 3B) as soon as a packet of the target E2E RB is dropped by the relay UE 204. The relay UE 204 may receive a packet discarding command from at least one of the remote UE 202 and the gNB 206 (or the gNB-DU 305 and gNB-CU 307 in FIGS. 3A and 3B) and discard buffered packets of the target E2E RB according to the received command. Upon the reception of the congestion indication for, e.g., Uu congestion as shown in FIG. 2A or PC5 congestion as shown in FIG. 3A, the remote UE 202 or the gNB-DU 305 determines the PDU set (s) to be discarded and commands the relay UE 204 to discard the PDUs belonging to the affected PDU set (s) .

In case the XR related information (e.g., PSI) is available at the relay UE 204 as shown in FIGS. 2B and 3B, the relay UE 204 knows the congestion (e.g., Uu congestion in FIG. 2B, or PC5 congestion in FIG. 3B) , either based on its own detection or based on the indication from the gNB 206. Based on the XR information in the SRAP header of the received data packet, the relay UE 204 determines the PDU set (s) to be discarded, and notifies at least one of the remote UE 202 or the gNB-DU 305 or the gNB-CU 307 to discard the PDUs of the related PDU set (s) . In this case, no discarding command is expected.

Some example implementations of a use case of Uu congestion are shown in Table 1 as below.

Table 1: Use Case of Uu Congestion

Some example implementations of a use case of PC5 Congestion are shown in Table 2 as below.

Table 2: Use Case of PC5 Congestion

Example Methods

FIG. 4 shows a flowchart of an example method 400 implemented at a first device in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the first device 145 in FIG. 1B.

At block 410, the first device 145 transmits, to a second device, information related to congestion of a link between the first device and a third device. At block 420, the first device 145 discards at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device. The at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.

In some example embodiments, the information includes an indication that the link between the first device and the third device is congested.

In some example embodiments, the first device 145 may receive, from the second device, a first request to discard the PDU set; and in response to receiving the first request, discard the at least one PDU of the PDU set.

In some example embodiments, the information further includes assistance information for determining a PDU set to be discarded.

In some example embodiments, the assistance information includes at least one of: a PC5 relay radio link control (RLC) channel affected by the congestion, a Uu relay RLC channel affected by the congestion, a radio bearer (RB) affected by the congestion, an identification of a quality of service (QoS) flow affected by the congestion, a sequence number for the PDU set affected by the congestion, or an available size of a buffer of the first device.

In some example embodiments, the information includes a second request to discard the PDU set.

In some example embodiments, the first device 145 may determine the PDU set based on PDU set importance (PSI) of the PDU set within at least one or more of a relay radio link control (RLC) channel, a radio bearer (RB) , or a quality of service (QoS) flow.

In some example embodiments, based on the PSI of the PDU set being equal to or lower than threshold PSI, the first device 145 may determine that the PDU set is to be discarded.

In some example embodiments, the threshold PSI is dependent on a level of the congestion.

In some example embodiments, before determining the PDU set based on the PSI of the PDU set within the QoS flow, the first device 145 may determine the QoS flow based on a priority level of the QoS flow.

In some example embodiments, the first device 145 may transmit the second request to the second device based on at least one first condition being met. The at least one first condition may include at least one of: a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number; or a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow.

In some example embodiments, from a header of a received packet carrying the PDU of the PDU set, the first device 145 may obtain at least one of the PSI of the PDU set, an identification of the QoS flow, or the PSIHI.

In some example embodiments, the first request or the second request includes at least one of: a sequence number (SN) for the PDU set, at least one SN for at least one PDU of the PDU set, at least one of a start SN or an end SN for PDUs of the PDU set, or PDU set importance (PSI) of the PDU set.

In some example embodiments, the first device 145 may detect the congestion of the link between the first device and the third device; and based on the detecting, transmit the information to the second device.

In some example embodiments, based on at least one second condition being met, the first device 145 may determine that the link between the first device and the third device is congested. The at least one second condition includes at least one of: a condition that the amount of data in a buffer exceeds threshold amount, the data being received from the second device and to be transmitted to the third device; or a condition that a channel busy ratio (CBR) exceeds a threshold ratio.

In some example embodiments, the first device 145 may receive, from the third device, an indication that the link between the first device and the third device is congested; and transmit the information to the second device.

In some example embodiments, the first device 145 may receive, from the third device, an indication of a PDU set affected by the congestion.

In some example embodiments, the first device 145 may transmit, to the second device, an indication that the congestion of the link between the first device and the third device is absent.

In some example embodiments, the first device includes a relay terminal device, the second device includes one of a remote terminal device and a network device, and the third device includes the other of the remote terminal device and the network device.

In some example embodiments, the network device includes at least one of a distributed unit or a centralized unit of a base station.

FIG. 5 shows a flowchart of an example method 500 implemented at a second device in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of the second device 150 in FIG. 1B.

At block 510, the second device 150 receives, from a first device, information related to congestion of a link between a first device and a third device. At block 520, the second device 150 discards at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device. The at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.

In some example embodiments, the second device 150 may transmit, to the first device, a first request to discard the PDU set.

In some example embodiments, the second device 150 may determine the PDU set based on PDU set importance (PSI) of the PDU set within at least one or more of a relay radio link control (RLC) channel, a radio bearer (RB) , or a quality of service (QoS) flow.

In some example embodiments, based on the PSI of the PDU set being equal to or lower than threshold PSI, the second device 150 may determine that the PDU set is to be discarded.

In some example embodiments, before determining the PDU set based on the PSI of the PDU set within the QoS flow, the second device 150 may determine the QoS flow based on a priority level of the QoS flow.

In some example embodiments, the second device 150 may transmit the first request to the first device based on at least one first condition being met. The at least one first condition includes at least one of: a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number; or a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow.

In some example embodiments, the assistance information includes at least one of: a PC5 relay radio link control (RLC) channel affected by the congestion, a Uu relay RLC channel affected by the congestion, a radio bearer (RB) affected by the congestion, an identification of a quality of service (QoS) flow affected by the congestion, a sequence number for the PDU set affected by the congestion, or an available size of a buffer of the first device 145.

In some example embodiments, a header of a packet carrying the PDU of the PDU set transmitted to the first device carries at least one of the PSI of the PDU set, an identification of the QoS flow, or the PSIHI.

In some example embodiments, the first request or the second request includes at least one of: a sequence number (SN) for the PDU set, at least one SNs for at least one PDU of the PDU set, at least one of a start SN or an end SN for PDUs of the PDU set, or PDU set importance (PSI) of the PDU set.

In some example embodiments, the second device 150 may detect congestion of a link between the second device and the first device; and based on the detecting, transmit to the first device, an indication that the link between the second device and the first device is congested.

In some example embodiments, the second device 150 may transmit, to the first device, an indication of a PDU set affected by the congestion of the link between the second device and the first device.

In some example embodiments, the second device 150 may receive, from the first device, an indication that the congestion of the link between the first device and the third device is absent.

In some example embodiments, the second device includes a remote terminal device, the first device includes a relay terminal device, and the third device includes a network device.

In some example embodiments, the third device includes a remote terminal device, the first device includes a relay terminal device, and the second device includes a network device.

In some example embodiments, the second device 150 may transmit, to the centralized unit of the base station, a third request to discard the PDU set.

Example Apparatus, Device and Medium

In some example embodiments, a first apparatus capable of performing the method 400 (for example, the first device 145 in FIG. 1B) may include means for performing the respective operations of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first device 145 in FIG. 1B.

In some example embodiments, the first apparatus includes means for transmitting, to a second device, information related to congestion of a link between the first device and a third device; and means for discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.

In some example embodiments, the first apparatus includes: means for receiving, from the second device, a first request to discard the PDU set; and means for in response to receiving the first request, discarding the at least one PDU of the PDU set.

In some example embodiments, the first apparatus includes: means for determining the PDU set based on PDU set importance (PSI) of the PDU set within at least one or more of a relay radio link control (RLC) channel, a radio bearer (RB) , or a quality of service (QoS) flow.

In some example embodiments, the means for determining the PDU set includes: means for based on the PSI of the PDU set being equal to or lower than threshold PSI, determining that the PDU set is to be discarded.

In some example embodiments, the first apparatus further includes: means for before determining the PDU set based on the PSI of the PDU set within the QoS flow, determining the QoS flow based on a priority level of the QoS flow.

In some example embodiments, the means for transmitting the information includes: means for transmitting the second request to the second device based on at least one first condition being met, the at least one first condition including at least one of: a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number; or a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow.

In some example embodiments, the first apparatus further includes: means for obtaining, from a header of a received packet carrying the PDU of the PDU set, at least one of the PSI of the PDU set, an identification of the QoS flow, or the PSIHI.

In some example embodiments, the first apparatus includes: means for detecting the congestion of the link between the first device and the third device; and means for based on the detecting, transmitting the information to the second device.

In some example embodiments, the means for detecting the congestion includes: means for based on at least one second condition being met, determining that the link between the first device and the third device is congested, the at least one second condition including at least one of: a condition that the amount of data in a buffer exceeds threshold amount, the data being received from the second device and to be transmitted to the third device; or a condition that a channel busy ratio (CBR) exceeds a threshold ratio.

In some example embodiments, the first apparatus includes means for receiving, from the third device, an indication that the link between the first device and the third device is congested. The means for transmitting the information includes means for in response to receiving the indication, transmitting the information to the second device.

In some example embodiments, the first apparatus further includes: means for receiving, from the third device, an indication of a PDU set affected by the congestion.

In some example embodiments, the first apparatus further includes: means for transmitting, to the second device, an indication that the congestion of the link between the first device and the third device is absent.

In some example embodiments, the first apparatus further includes means for performing other operations in some example embodiments of the method 400 or the first device 145. In some example embodiments, the means includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the first apparatus.

In some example embodiments, a second apparatus capable of performing the method 500 (for example, the second device 150 in FIG. 1B) may include means for performing the respective operations of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second device 150 in FIG. 1B.

In some example embodiments, the second apparatus includes means for receiving, from a first device, information related to congestion of a link between a first device and a third device; and means for discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device, wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.

In some example embodiments, the second apparatus includes: means for transmitting, to the first device, a first request to discard the PDU set.

In some example embodiments, the second apparatus includes: means for determining the PDU set based on PDU set importance (PSI) of the PDU set within at least one or more of a relay radio link control (RLC) channel, a radio bearer (RB) , or a quality of service (QoS) flow.

In some example embodiments, the second apparatus further includes: means for before determining the PDU set based on the PSI of the PDU set within the QoS flow, determining the QoS flow based on a priority level of the QoS flow.

In some example embodiments, the means for transmitting the first request includes: means for transmitting the first request to the first device based on at least one first condition being met, the at least one first condition including at least one of: a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number; or a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow.

In some example embodiments, the second apparatus further includes: means for detecting congestion of a link between the second device and the first device; and means for based on the detecting, transmitting, to the first device, an indication that the link between the second device and the first device is congested.

In some example embodiments, the second apparatus further includes: means for transmitting, to the first device, an indication of a PDU set affected by the congestion of the link between the second device and the first device.

In some example embodiments, the second apparatus further includes: means for receiving, from the first device, an indication that the congestion of the link between the first device and the third device is absent.

In some example embodiments, the second device is the distributed unit of the base station, and the second apparatus further includes: means for transmitting, to the centralized unit of the base station, a third request to discard the PDU set.

In some example embodiments, the second apparatus further includes means for performing other operations in some example embodiments of the method 500 or the second device 150. In some example embodiments, the means includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the second apparatus.

FIG. 6 is a simplified block diagram of a device 600 that is suitable for implementing example embodiments of the present disclosure. The device 600 may be provided to implement a communication device, for example, the first device 145 or the second device 150 as shown in FIG. 1B. As shown, the device 600 includes one or more processors 610, one or more memories 620 coupled to the processor 610, and one or more communication modules 640 coupled to the processor 610.

The communication module 640 is for bidirectional communications. The communication module 640 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 640 may include at least one antenna.

The processor 610 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 600 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 620 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 624, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , an optical disk, a laser disk, and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 622 and other volatile memories that will not last in the power-down duration.

A computer program 630 includes computer executable instructions that are executed by the associated processor 610. The instructions of the program 630 may include instructions for performing operations/acts of some example embodiments of the present disclosure. The program 630 may be stored in the memory, e.g., the ROM 624. The processor 610 may perform any suitable actions and processing by loading the program 630 into the RAM 622.

The example embodiments of the present disclosure may be implemented by means of the program 630 so that the device 600 may perform any process of the disclosure as discussed with reference to FIG. 1B to FIG. 5. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some example embodiments, the program 630 may be tangibly contained in a computer readable medium which may be included in the device 600 (such as in the memory 620) or other storage devices that are accessible by the device 600. The device 600 may load the program 630 from the computer readable medium to the RAM 622 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

FIG. 7 shows an example of the computer readable medium 700 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 700 has the program 630 stored thereon.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non-transitory computer readable medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A first device comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the first device at least to:

transmit, to a second device, information that includes an indication related to a congestion of a link between the first device and a third device; and

discard at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device,

wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device, and is to be transmitted to the third device.
The first device of claim 1, wherein the information includes an indication that the link between the first device and the third device is congested.
The first device of claim 2, wherein the at least one memory and the at least one processor cause the first device to:

receive, from the second device, a first request to discard the at least one PDU of the PDU set; and

in response to receiving the request, discard the at least one PDU of the PDU set.
The first device of claim 2 or 3, wherein the information further includes assistance information for determining a PDU set to be discarded, wherein the assistance information includes at least one of:

a PC5 relay radio link control (RLC) channel affected by the congestion,

a Uu relay RLC channel affected by the congestion,

a radio bearer (RB) affected by the congestion,

an identification of a quality of service (QoS) flow affected by the congestion,

a sequence number for the PDU set affected by the congestion, or

an available size of a buffer of the first device.
The first device of claim 1, wherein the information includes a second request to discard the PDU set.
The first device of claim 5, wherein the at least one memory and the at least one processor cause the first device to:

determine the PDU set based on a PDU set importance (PSI) of the PDU set within at least one or more of a PC5 relay radio link control (RLC) channel, a Uu RLC channel, a radio bearer (RB) , or a quality of service (QoS) flow.
The first device of claim 6, wherein the at least one memory and the at least one processor cause the first device to:

based on the PSI of the PDU set being equal to or lower than a threshold PSI, determine that the PDU set is to be discarded.
The first device of claim 7, wherein the threshold PSI is dependent on a level of the congestion.
The first device of any of claims 6-8, wherein the at least one memory and the at least one processor cause the first device to:

before determining the PDU set based on the PSI of the PDU set within the QoS flow, determine the QoS flow based on a priority level of the QoS flow.
The first device of any of claims 6-9, wherein the at least one memory and the at least one processor cause the first device to:

transmit the second request to the second device based on at least one first condition being met, the at least one first condition including at least one of:

a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number; or

a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow.
The first device of claim 10, wherein the at least one memory and the at least one processor further cause the first device to:

obtain, from the second device, a header of a received packet carrying the PDU of the PDU set, at least one of the PSI of the PDU set, an identification of the QoS flow, or the PSIHI.
The first device of claim 3 or 5, wherein the first request or the second request includes at least one of:

a sequence number (SN) for the PDU set,

at least one SN for at least one PDU of the PDU set,

at least one of a start SN or an end SN for PDUs of the PDU set, or

PDU set importance (PSI) of the PDU set.
The first device of any of claims 1-12, wherein the at least one memory and the at least one processor cause the first device to detect the congestion of the link between the first device and the third device as follows:

based on at least one second condition being met, determine that the link between the first device and the third device is congested, the at least one second condition including at least one of:

a condition that the amount of data in a buffer exceeds threshold amount, the data being received from the second device and to be transmitted to the third device; or

a condition that a channel busy ratio (CBR) exceeds a threshold ratio.
The first device of any of claims 1-12, wherein an indication that the link between the first device and the third device is congested is received from the third device; and

in response to receiving the indication, the first device transmits the information to the second device to discard the PDU set of the second device.
The first device of any of claims 1-14, wherein the first device includes a relay terminal device, the second device includes one of a remote terminal device and a network device, and the third device includes the other of the remote terminal device and the network device, and wherein the network device includes at least one of a distributed unit or a centralized unit of a base station.
A second device comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the second device at least to:

receive, from a first device, information related to congestion of a link between a first device and a third device; and

discard at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device,

wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.
The second device of claim 16, wherein the information includes an indication that the link between the first device and the third device is congested.
The second device of claim 17, wherein the at least one memory and the at least one processor cause the second device to:

transmit, to the first device, a first request to discard the PDU set.
The second device of claim 18, wherein the at least one memory and the at least one processor cause the second device to:

determine the PDU set based on PDU set importance (PSI) of the PDU set within at least one or more of a PC5 relay radio link control (RLC) channel, a Uu relay RLC channel, a radio bearer (RB) , or a quality of service (QoS) flow.
The second device of claim 19, wherein the at least one memory and the at least one processor cause the second device to:

based on the PSI of the PDU set being equal to or lower than threshold PSI, determine that the PDU set is to be discarded.
The second device of claim 20, wherein the threshold PSI is dependent on a level of the congestion.
The second device of any of claims 19-21, wherein the at least one memory and the at least one processor cause the second device to:

before determining the PDU set based on the PSI of the PDU set within the QoS flow, determine the QoS flow based on a priority level of the QoS flow.
The second device of any of claims 18-22, wherein the at least one memory and the at least one processor cause the second device to:

transmit the first request to the first device based on at least one first condition being met, the at least one first condition including at least one of:

a condition that the number of PDUs of the PDU set to be discarded is equal to or greater than a threshold number; or

a condition that PDU set integrated handling information (PSIHI) is set for the QoS flow.
The second device of any of claims 17-23, wherein the information further includes assistance information for determining a PDU set to be discarded, wherein the assistance information includes at least one of:

a PC5 relay radio link control (RLC) channel affected by the congestion,

a Uu relay RLC channel affected by the congestion,

a radio bearer (RB) affected by the congestion,

an identification of a quality of service (QoS) flow affected by the congestion,

a sequence number for the PDU set affected by the congestion, or

an available size of a buffer of the first device.
The second device of claim 16, wherein the information includes a second request to discard the PDU set.
The second device of claim 25, wherein a header of a packet carrying the PDU of the PDU set transmitted to the first device carries at least one of the PSI of the PDU set, an identification of the QoS flow, or the PSIHI.
The second device of claim 18 or 25, wherein the first request or the second request includes at least one of:

a sequence number (SN) for the PDU set,

at least one SNs for at least one PDU of the PDU set,

at least one of a start SN or an end SN for PDUs of the PDU set, or

PDU set importance (PSI) of the PDU set.
The second device of any of claims 16-27, wherein the at least one memory and the at least one processor further cause the second device to:

detect congestion of a link between the second device and the first device; and

based on the detecting, transmit, to the first device, an indication that the link between the second device and the first device is congested.
The second device of any of claims 16-28, wherein the second device includes a remote terminal device, the first device includes a relay terminal device, and the third device includes a network device.
The second device of any of claims 16-28, wherein the third device includes a remote terminal device, the first device includes a relay terminal device, and the second device includes a network device, wherein the network device includes at least one of a distributed unit or a centralized unit of a base station.
The second device of claim 30, wherein the second device is the distributed unit of the base station, and the at least one memory and the at least one processor further cause the second device to:

transmit, to the centralized unit of the base station, a third request to discard the PDU set.
A method comprising:

transmitting, to a second device, information related to congestion of a link between the first device and a third device; and

discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device,

wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.
A method comprising:

receiving, from a first device, information related to congestion of a link between a first device and a third device; and

discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device,

wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.
A first apparatus comprising:

means for transmitting, to a second device, information related to congestion of a link between the first device and a third device; and

means for discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device,

wherein the at least one PDU of the PDU set is received from the second device and buffered at the first device and to be transmitted to the third device.
A second apparatus comprising:

means for receiving, from a first device, information related to congestion of a link between a first device and a third device; and

means for discarding at least one protocol data unit (PDU) of a PDU set according to the information related to the congestion of the link between the first device and the third device,

wherein the at least one PDU of the PDU set is buffered at the second device and to be transmitted to the third device via the first device.
A computer readable medium including instructions stored thereon for causing an apparatus at least to perform the method of claim 32 or the method of claim 33.